publicationDate,title,abstract,id
2008-04-26,Origin of resistivity minima at low temperature in ferromagnetic metallic manganites,"The resistivity and magnetoresistance measurements were carried out on thin
film of La0.7Ca0.3MnO3 to investigate the possible origin of low temperature
resistivity minimum observed in these samples. We observed large hysteresis in
the magnetoresistance at low temperature; 5K and the sample current I has large
effect on resistivity minima temperature. The observation of hysteresis at low
temperatures suggests the presence of inhomogeneity at low temperatures. These
in-homogeneities consist of regions of different resistive phases. It appears
that the high resistive phase prevents the tunneling of charge carriers between
two low resistive regions and thus giving rise to the resistivity minimum in
these samples.",0804.4247v1
2015-08-05,The universal influence of contact resistance on the efficiency of a thermoelectric generator,"The influence of electrical and thermal contact resistance on the efficiency
of a segmented thermoelectric generator is investigated. We consider 12
different segmented $p$-legs and 12 different segmented $n$-legs, using 8
different $p$-type and 8 different $n$-type thermoelectric materials. For all
systems a universal influence of both the electrical and thermal contact
resistance is observed on the leg's efficiency, when the systems are analyzed
in terms of the contribution of the contact resistance to the total resistance
of the leg. The results are compared with the analytical model of Min and Rowe
(1992). In order for the efficiency not to decrease more than 20%, the contact
electrical resistance should be less than 30% of the total leg resistance for
zero thermal contact resistance, while the thermal contact resistance should be
less than 20% for zero electrical contact resistance. The universal behavior
also allowed the maximum tolerable contact resistance for a segmented system to
be found, i.e. the resistance at which a leg of only the high temperature
thermoelectric material has the same efficiency as the segmented leg with a
contact resistance at the interface. If e.g. segmentation increases the
efficiency by 30% then an electrical contact resistance of 30% or a thermal
contact resistance of 20% can be tolerated.",1508.01153v1
2018-02-10,Electroforming Free Controlled Bipolar Resistive Switching in Al/CoFe2O4/FTO device with Self-Compliance Effect,"Controlled bipolar resistive switching (BRS) has been observed in
nanostructured CoFe2O4 films using Al(aluminum)/CoFe2O4/FTO(fluorine-doped tin
oxide) device. The fabricated device shows electroforming-free uniform BRS with
two clearly distinguished and stable resistance states without any application
of compliance current (CC), with a resistance ratio of high resistance state
(HRS) and low resistance state (LRS) > 102. Small switching voltage (< 1 volt)
and lower current in both the resistance states confirms the fabrication of low
power consumption device. In the LRS, the conduction mechanism was found to be
of Ohmic in nature, while the high-resistance state (HRS/OFF state) was
governed by space charge-limited conduction mechanism, which indicates the
presence of an interfacial layer with imperfect microstructure near the top
Al/CFO interface. The device shows nonvolatile behavior with good endurance
properties, acceptable resistance ratio, uniform resistive switching due to
stable, less random filament formation/rupture and a control over the resistive
switching properties by choosing different stop voltages, which makes the
device suitable for its application in future nonvolatile resistive random
access memory (ReRAM).",1802.03643v1
2021-08-20,Understanding grain boundary electrical resistivity in Cu: the effect of boundary structure,"Grain boundaries (GBs) in metals usually increase electrical resistivity due
to their distinct atomic arrangement compared to the grain interior. While the
GB structure has a crucial influence on the electrical properties, its
relationship with resistivity is poorly understood. Here, we perform a
systematic study on the resistivity and structure relationship in Cu tilt GBs,
employing high resolution in-situ electrical measurements coupled with atomic
structure analysis of the GBs. Excess volume and energies of selected GBs are
calculated using molecular dynamics simulations. We find a consistent relation
between the coincidence site lattice (CSL) type of the GB and its resistivity.
The most resistive GBs are high range of low-angle GBs (misorientation 14 to 18
degrees) with twice the resistivity of high angle tilt GBs, due to the high
dislocation density and corresponding strain fields. Regarding the atomistic
structure, GB resistivity approximately correlates with the GB excess volume.
Moreover, we show that GB curvature increases resistivity by about 80%, while
phase variations and defects within the same CSL type do not considerably
change it.",2108.09148v1
2003-12-07,Temperature-dependent contact resistances in high-quality polymer field-effect transistors,"Contact resistances between organic semiconductors and metals can dominate
the transport properties of electronic devices incorporating such materials. We
report measurements of the parasitic contact resistance and the true channel
resistance in bottom contact poly(3-hexylthiophene) (P3HT) field-effect
transistors with channel lengths from 400 nm up to 40 $\mu$m, from room
temperature down to 77 K. For fixed gate voltage, the ratio of contact to
channel resistance decreases with decreasing temperature. We compare this
result with a recent model for metal-organic semiconductor contacts. Mobilities
corrected for this contact resistance can approach 1 cm$^{2}$/Vs at room
temperature and high gate voltages.",0312183v1
2024-02-26,A novel method for determining the resistivity of compressed superconducting materials,"The resistivity of a superconductor in its normal state plays a critical role
in determining its superconducting ground state. However, measuring the
resistivity of a material under high pressure has long presented a significant
technical challenge due to pressure-induced changes in the crystallographic
directions, especially for samples with anisotropic layered structures like
high-Tc superconductors and other intriguing quantum materials. Here, we are
the first to propose a novel and effective method for determining high-pressure
resistivity, which relies on the ambient-pressure resistivity, initial sample
sizes, lattice parameters, high-pressure resistance, and lattice parameters
measured from the same sample. Its validity has been confirmed through our
investigations of pressurized copper-oxide superconductors, which demonstrates
that this method provides new possibilities for researchers conducting
high-pressure studies related to resistivity of these materials.",2402.16257v1
2021-09-14,Internal reverse-biased p-n junctions: a possible origin of the high resistance in phase change superlattice,"Phase change superlattice is one of the emerging material technologies for
ultralow-power phase change memories. However, the resistance switching
mechanism of phase change superlattice is still hotly debated. Early electrical
measurements and recent materials characterizations have suggested that the
Kooi phase is very likely to be the as-fabricated low-resistance state. Due to
the difficulty in in-situ characterization at atomic resolution, the structure
of the electrically switched superlattice in its high-resistance state is still
unknown and mainly investigated by theoretical modellings. So far, there has
been no simple model that can unify experimental results obtained from
device-level electrical measurements and atomic-level materials
characterizations. In this work, we carry out atomistic transport modellings of
the phase change superlattice device and propose a simple mechanism accounting
for its high resistance. The modeled high-resistance state is based on the
interfacial phase changed superlattice that has previously been mistaken for
the low-resistance state. This work advances the understanding of phase change
superlattice for emerging memory applications.",2109.06376v1
2018-04-23,Magnetic field-induced resistivity upturn and exceptional magneto-resistance in Weyl semimetal TaSb2,"We study magneto-transport properties in single crystals of TaSb_2, which is
a recently discovered topological semimetal. In the presence of magnetic field,
the electrical resistivity shows onset of insulating behaviour followed by
plateau at low temperature. Such resistivity plateau is generally assigned to
topological surface states. TaSb2 exhibits extremely high magneto-resistance
with non-saturating field dependence. We find that aspects of extremely large
magneto resistance and resistivity plateau are well accounted by classical
Kohler scaling. Unambiguous evidence for anomalous Chiral transport is provided
with observation of negative longitudinal magneto-resistance. Shubnikov-de Haas
oscillations reveal two dominating frequencies, 201 T and 455 T. These aspects
categorize TaSb2 as a Type-II Weyl semimetal. At low temperature, the field
dependence of Hall resistivity shows non-linear behaviour that indicates the
presence of two types of charge carriers in consonance with reported electronic
band structure. Analysis of Hall resistivity imply very high electron
mobilities.",1804.08434v1
2023-07-12,Machine learning accelerated discovery of corrosion-resistant high-entropy alloys,"Corrosion has a wide impact on society, causing catastrophic damage to
structurally engineered components. An emerging class of corrosion-resistant
materials are high-entropy alloys. However, high-entropy alloys live in
high-dimensional composition and configuration space, making materials designs
via experimental trial-and-error or brute-force ab initio calculations almost
impossible. Here we develop a physics-informed machine-learning framework to
identify corrosion-resistant high-entropy alloys. Three metrics are used to
evaluate the corrosion resistance, including single-phase formability, surface
energy and Pilling-Bedworth ratios. We used random forest models to predict the
single-phase formability, trained on an experimental dataset. Machine learning
inter-atomic potentials were employed to calculate surface energies and
Pilling-Bedworth ratios, which are trained on first-principles data fast
sampled using embedded atom models. A combination of random forest models and
high-fidelity machine learning potentials represents the first of its kind to
relate chemical compositions to corrosion resistance of high-entropy alloys,
paving the way for automatic design of materials with superior corrosion
protection. This framework was demonstrated on AlCrFeCoNi high-entropy alloys
and we identified composition regions with high corrosion resistance. Machine
learning predicted lattice constants and surface energies are consistent with
values by first-principles calculations. The predicted single-phase formability
and corrosion-resistant compositions of AlCrFeCoNi agree well with experiments.
This framework is general in its application and applicable to other materials,
enabling high-throughput screening of material candidates and potentially
reducing the turnaround time for integrated computational materials
engineering.",2307.06384v3
2014-08-26,Enhancement in Quality Factor of SRF Niobium Cavities by Material Diffusion,"An increase in the quality factor of superconducting radiofrequency cavities
is achieved by minimizing the surface resistance during processing steps. The
surface resistance is the sum of temperature independent residual resistance
and temperature/material dependent Bardeen-Cooper-Schrieffer (BCS) resistance.
High temperature heat treatment usually reduces the impurities concentration
from the bulk niobium, lowering the residual resistance. The BCS part can be
reduced by selectively doping non-magnetic impurities. The increase in quality
factor, termed as Q-rise, was observed in cavities when titanium or nitrogen
thermally diffused in the inner cavity surface.",1408.6245v1
2015-12-15,A Graphene-Carbon Nanotube Hybrid Material for Photovoltaic Applications,"Large area graphene sheets grown by chemical vapor deposition can potentially
be employed as a transparent electrode in photovoltaics if their sheet
resistance can be significantly lowered, without any loss in transparency.
Here, we report the fabrication of a graphene-conducting-carbon-nanotube (CCNT)
hybrid material with a sheet resistance considerably lower than neat graphene,
and with the requisite small reduction in transparency. Graphene is deposited
on top of a a self-assembled CCNT monolayer which creates parallel conducting
paths on the graphene surface. The hybrid thereby circumvents electron
scattering due to defects in the graphene sheet, and reduces the sheet
resistance by a factor of two. The resistance can be further reduced by
chemically doping the hybrid. Moreover, the chemically doped hybrid is more
stable than a standalone chemically doped graphene sheet, as the CCNT network
enhances the dopant binding. In order to understand the results, we develop a
2D resistance network model in which we couple the CCNT layer to the graphene
sheet and demonstrate the model accounts quantitatively for the resistance
decrease. Our results show that a graphene-CCNT hybrid system has high
potential for use as a transparent electrode with high transparency and low
sheet resistance.",1512.04617v1
2022-06-11,Modeling of High and Low Resistant States in Single Defect Atomristors,"Resistance-change random access memory (RRAM) devices are nanoscale
metal-insulator-metal structures that can store information in their resistance
states, namely the high resistance (HRS) and low resistance (LRS) states. They
are a potential candidate for a universal memory as these non-volatile memory
elements can offer fast-switching, long retention and switching cycles, and
additionally, are also suitable for direct applications in neuromorphic
computing. In this study, we first present a model to analyze different
resistance states of RRAM devices or so-called ""atomristors"" that utilize novel
2D materials as the switching materials instead of insulators. The developed
model is then used to study the electrical characteristics of a single defect
monolayer MoS$_{2}$ memristor. The change in the device resistance between the
HRS and LRS is associated to the change in the tunneling probability when the
vacancy defects in the 2D material are substituted by the metal atoms from the
electrodes. The distortion due to defects and substituted metal atom is
captured in the 1D potential energy profile by averaging the effect along the
transverse direction. This simplification enables us to model single defect
memristors with a less extensive quantum transport model while taking into
account the presence of defects.",2206.05504v1
2011-06-06,Efficient resistive memory effect on SrTiO3 by ionic-bombardment,"SrTiO3 is known to exhibit resistive memory effect either with cation-doping
or with high-temperature thermal reduction. Here, we add another scheme,
ionic-bombardment, to the list of tools to create resistive memory effect on
SrTiO3 (STO). In an Ar-bombarded STO crystal, two orders of resistance
difference was observed between the high and low resistive states, which is an
order of magnitude larger than those achieved by the conventional thermal
reduction process. One of the advantages of this new scheme is that it can be
easily combined with lithographic processes to create spatially-selective
memory effect.",1106.1203v1
2006-02-21,Evidance for an Oxygen Diffusion Model for the Electric Pulse Induced Resistance Change Effect in Oxides,"Electric pulse induced resistance (EPIR) switching hysteresis loops for
Pr0.7Ca0.7MnO3 (PCMO) perovskite oxide films were found to exhibit an
additional sharp ""shuttle peak"" around the negative pulse maximum for films
deposited in an oxygen deficient ambient. The device resistance hysteresis loop
consists of stable high resistance and low resistance states, and transition
regions between them. The resistance relaxation of the ""shuttle peak"" and its
temperature behavior as well as the resistance relaxation in the transition
regions were studied, and indicate that the resistance switching relates to
oxygen diffusion with activation energy about 0.4eV. An oxygen diffusion model
with the oxygen ions (vacancies) as the active agent is proposed for the
non-volatile resistance switching effect in PCMO.",0602507v2
2014-06-16,Degenerate Resistive Switching and Ultrahigh Density Storage in Resistive Memory,"We show that, in tantalum oxide resistive memories, activation power provides
a multi-level variable for information storage that can be set and read
separately from the resistance. These two state variables (resistance and
activation power) can be precisely controlled in two steps: (1) the possible
activation power states are selected by partially reducing resistance, then (2)
a subsequent partial increase in resistance specifies the resistance state and
the final activation power state. We show that these states can be precisely
written and read electrically, making this approach potentially amenable for
ultra-high density memories. We provide a theoretical explanation for
information storage and retrieval from activation power and experimentally
demonstrate information storage in a third dimension related to the change in
activation power with resistance.",1406.4033v1
2020-06-10,Positive versus negative resistance response to hydrogenation in palladium and its alloys,"Resistive solid state sensors are widely used in multiple applications,
including molecular and gas detection. Absorption or intercalation of the
target species varies the lattice parameters and an effective thickness of thin
films, which is usually neglected in analyzing their transport properties in
general and the sensor response in particular. Here, we explore the case of
palladium-based thin films absorbing hydrogen and demonstrate that expansion of
thickness is an important mechanism determining the magnitude and the very
polarity of the resistance response to hydrogenation in high resistivity films.
The model of the resistance response that takes into account modifications of
thickness was tested and confirmed in three Pd-based systems with variable
resistivity: thin Pd films above and below the percolation threshold, thick
Pd-SiO2 granular composite films with different content of silica, and Pd-rich
CoPd alloys where resistivity depends on Co concentration. Superposition of the
bulk resistivity increase due to hydride formation and decrease of film
resistance due to thickness expansion provides a consistent explanation of the
hydrogenation response in both continuous and discontinuous films with
different structures and compositions.",2006.05801v1
2021-06-04,Noncured Graphene Thermal Interface Materials: Minimizing the Thermal Contact Resistance,"We report on experimental investigation of thermal contact resistance of the
noncuring graphene thermal interface materials with the surfaces characterized
by different degree of roughness. It is found that the thermal contact
resistance depends on the graphene loading non-monotonically, achieving its
minimum at the loading fraction of ~15 wt.%. Increasing the surface roughness
by ~1 micrometer results in approximately the factor of x2 increase in the
thermal contact resistance for this graphene loading. The obtained dependences
of the thermal conductivity, thermal contact resistance, and the total thermal
resistance of the thermal interface material layer on the graphene loading and
surface roughness indicate the need for optimization of the loading fraction
for specific materials and roughness of the connecting surfaces. Our results
are important for developing graphene technologies for thermal management of
high-power-density electronics.",2106.02180v1
2002-10-24,Violation of Ioffe-Regel condition but saturation of resistivity of the high Tc cuprates,"We demonstrate that the resistivity data of a number of high Tc cuprates, in
particular La(2-x)SrxCuO4, are consistent with resistivity saturation, although
the Ioffe-Regel condition is strongly violated. By using the f-sum rule
together with calculations of the kinetic energy in the t-J model, we show that
the saturation resistivity is unusually large. This is related to the strong
reduction of the kinetic energy due to strong correlation effects. The
fulfilment of the Ioffe-Regel condition for conventional transition metal
compounds is found to be somewhat accidental.",0210543v1
2023-04-26,Theoretical Puncture Mechanics of Soft Compressible Solids,"Accurate prediction of the force required to puncture a soft material is
critical in many fields like medical technology, food processing, and
manufacturing. However, such a prediction strongly depends on our understanding
of the complex nonlinear behavior of the material subject to deep indentation
and complex failure mechanisms. Only recently we developed theories capable of
correlating puncture force with material properties and needle geometry.
However, such models are based on simplifications that seldom limit their
applicability to real cases. One common assumption is the incompressibility of
the cut material, albeit no material is truly incompressible. In this paper we
propose a simple model that accounts for linearly elastic compressibility, and
its interplay with toughness, stiffness, and elastic strain-stiffening.
Confirming previous theories and experiments, materials having high-toughness
and low-modulus exhibit the highest puncture resistance at a given needle
radius. Surprisingly, in these conditions, we observe that incompressible
materials exhibit the lowest puncture resistance, where volumetric
compressibility can create an additional (strain) energy barrier to puncture.
Our model provides a valuable tool to assess the puncture resistance of soft
compressible materials and suggests new design strategies for sharp needles and
puncture-resistant materials.",2304.13838v1
2008-05-23,Non-hysteretic branches inside the hysteresis loop in VO2 films for focal plane array imaging bolometers,"In the resistive phase transition in VO2, temperature excursions from points
on the major hysteresis loop produce minor loops. We have found that for
sufficiently small excursions these minor loops degenerate into single-valued,
non-hysteretic branches (NHBs) having essentially the same or even higher
temperature coefficient of resistance (TCR) as the semiconducting phase at room
temperature. We explain this behavior and discuss the opportunities it presents
for infrared imaging technology based on resistive microbolometers. It is
possible to choose a NHB with 100 to 1000 times smaller resistivity than in a
pure semiconducting phase, thus providing a microbolometer with low tunable
resistivity and high TCR.",0805.3566v1
2021-05-26,Investigation of Forming Free Bipolar Resistive Switching Characteristics in Al/Mn3O4/FTO RRAM Device,"Bipolar resistive switching (BRS) phenomenon has been demonstrated in Mn3O4
using Al (Aluminum)/Mn3O4/FTO (Fluorine doped Tin Oxide) Resistive Random
Access Memory (RRAM) device. The fabricated RRAM device shows good retention,
non volatile behavior and forming free BRS. The Current-Voltage (I-V)
characteristics and the temperature dependence of the resistance (R-T)
measurements were used to explore conduction mechanisms and the thermal
activation energy (Ea). The resistance ratio of high resistance state (HRS) to
low resistance state (LRS) is ~102. The fabricated RRAM device shows different
conduction mechanisms in LRS and HRS state such as ohmic conduction and space
charge limited conduction (SCLC). The rupture and formation of conducting
filaments (CF) of oxygen vacancies take place by changing the polarity of
external voltage, which may be responsible for resistive switching
characteristics in the fabricated RRAM device. This fabricated RRAM device is
suitable for application in future high density non-volatile memory (NVM) RRAM
devices.",2105.12390v1
1998-08-18,Resistivity saturation revisited: results from a dynamical mean field theory,"We use the dynamical mean field method to study the high-temperature
resistivity of electrons strongly coupled to phonons. The results reproduce the
qualtiative behavior of the temperature and disorder dependence of the
resistivity of the 'A-15' materials, which is commonly described in terms of
saturation, but imply that the resistivity does not saturate. Rather, a change
in temperature dependence occurs when the scattering becomes strong enough to
cause a breakdown of the Migdal approximation.",9808188v2
2018-07-13,A new type of RPC with very low resistive material,"There are several working groups that are currently working on high rate
RPC's using different materials such as Si-based Ceramics, Low-resistive Glass,
low-resistive bakelite etc. A new type of single gap RPC has been fabricated
using very low-resistive carbon-loaded PTFE material to compete with all these
other groups and materials. In terms of bulk resistivity, this material is the
lowest and should in principle be able to work at the highest rates, provided
the material can withstand working bias and radiation. The efficiency and noise
rate of the RPC are measured with cosmic rays. The detail method of fabrication
and first experimental results are presented.",1807.04984v1
2013-04-20,Electric-Field-Induced Resistive Switching in a Family of Mott Insulators : towards Non-Volatile Mott-RRAM Memories,"The fundamental building blocks of modern silicon-based microelectronics,
such as double gate transistors in non-volatile Flash memories, are based on
the control of electrical resistance by electrostatic charging. Flash memories
could soon reach their miniaturization limits mostly because reliably keeping
enough electrons in an always smaller cell size will become increasingly
difficult . The control of electrical resistance at the nanometer scale
therefore requires new concepts, and the ultimate resistance-change device is
believed to exploit a purely electronic phase change such as the Mott insulator
to insulator transition [2]. Here we show that application of short electric
pulses allows to switch back and forth between an initial high-resistance
insulating state (""0"" state) and a low-resistance ""metallic"" state (""1"" state)
in the whole class of Mott Insulator compounds AM4X8 (A = Ga, Ge; M= V, Nb, Ta;
X = S, Se). We found that electric fields as low as 2 kV/cm induce an
electronic phase change in these compounds from a Mott insulating state to a
metallic-like state. Our results suggest that this transition belongs to a new
class of resistive switching and might be explained by recent theoretical works
predicting that an insulator to metal transition can be achieved by a simple
electric field in a Mott Insulator. This new type of resistive switching has
potential to build up a new class of Resistive Random Access Memory (RRAM) with
fast writing/erasing times (50 ns to 10 {\mu}s) and resistance ratios \Delta
R/R of the order of 25% at room temperature.",1304.5607v1
2012-06-26,Measurement of electrical properties of electrode materials for the bakelite Resistive Plate Chambers,"Single gap (gas gap 2 mm) bakelite Resistive Plate Chamber (RPC) modules of
various sizes from 10 cm \times 10 cm to 1 m \times 1 m have been fabricated,
characterized and optimized for efficiency and time resolution. Thin layers of
different grades of silicone compound are applied to the inner electrode
surfaces to make them smooth and also to reduce the surface resistivity. In the
silicone coated RPCs an efficiency > 90% and time resolution \sim 2 ns (FWHM)
have been obtained for both the streamer and the avalanche mode of operation.
Before fabrication of detectors the electrical properties such as bulk
resistivity and surface resistivity of the electrode materials are measured
carefully. Effectiveness of different silicone coating in modifying the surface
resistivity was evaluated by an instrument developed for monitoring the I-V
curve of a high resistive surface. The results indicate definite correlation of
the detector efficiency for the atmospheric muons and the RPC noise rates with
the surface resistivity and its variation with the applied bias voltage. It was
also found that the surface resistivity varies for different grades of silicone
material applied as coating, and the results are found to be consistent with
the detector efficiency and noise rate measurements done with these RPCs.",1206.5894v1
2015-09-21,Resistive Switching in Nanodevices,"Passing current at given threshold voltages through a metal/insulator/metal
sandwich structure device may change its resistive state. Such resistive
switching is unique to nanoscale devices, but its underlying physical mechanism
remains unknown. We show that the different resistive states are due to
different spontaneously charged states, characterized by different `band
bending' solutions of Poisson's equation. For an insulator with mainly donor
type defects, the low-resistivity state is characterized by a negatively
charged insulator due to convex band bending, and the high-resistivity state by
a positively charged insulator due to concave band bending; vice versa for
insulators with mainly acceptor type defects. These multiple solutions coexist
only for nanoscale devices and for bias voltages limited by the switching
threshold values, where the system charge spontaneously changes and the system
switches to another resistive state. We outline the general principles how this
functionality depends on material properties and defect abundance of the
insulator `storage medium', and propose a new magnetic memristor device with
increased storage capacity.",1509.06169v1
2018-06-30,Nanoscale compositional evolution in complex oxide based resistive memories,"Functional oxides based resistive memories are recognized as potential
candidate for the next-generation high density data storage and neuromorphic
applications. Fundamental understanding of the compositional changes in the
functional oxides is required to tune the resistive switching characteristics
for enhanced memory performance. Herein, we present the micro/nano-structural
and compositional changes induced in a resistive oxide memory during resistive
switching. Oxygen deficient amorphous chromium doped strontium titanate
(Cr:$a$-SrTiO$_{3-x}$) based resistance change memories are fabricated in a
Ti/Cr:$a$-SrTiO$_{3-x}$ heterostructure and subjected to different biasing
conditions to set memory states. Transmission electron microscope based
cross-sectional analyses of the memory devices in different memory states shows
that the micro/nano-structural changes in amorphous complex oxide and
associated redox processes define the resistive switching behavior. These
experimental results provide insights and supporting material for Ref. [1].",1807.00185v1
2018-06-04,"Atomistic Study of the Electronic Contact Resistivity Between the Half-Heusler Alloys (HfCoSb, HfZrCoSb, HfZrNiSn) and the Metal Ag","Half-Heusler(HH) alloys have shown promising thermoelectric properties in the
medium and high temperature range. To harness these material properties for
thermoelectric applications, it is important to realize electrical contacts
with low electrical contact resistivity. However, little is known about the
detailed structural and electronic properties of such contacts, and the
expected values of contact resistivity. Here, we employ atomistic ab initio
calculations to study electrical contacts in a subclass of HH alloys consisting
of the compounds HfCoSb, HfZrCoSb, and HfZrNiSn. By using Ag as a prototypical
metal, we show that the termination of the HH material critically determines
the presence or absence of strong deformations at the interface. Our study
includes contacts to doped materials, and the results indicate that the p-type
materials generally form ohmic contacts while the n-type materials have a small
Schottky barrier. We calculate the temperature dependence of the contact
resistivity in the low to medium temperature range and provide quantitative
values that set lower limits for these systems.",1806.01375v1
2009-01-28,Carbon Based Resistive Memory,"We propose carbon as new resistive memory material for non-volatile memories
and compare three allotropes of carbon, namely carbon nanotubes, graphene-like
conductive carbon and insulating carbon for their possible application as
resistance-change material in high density non-volatile memories. Repetitive
high-speed switching and the potential for multi-level programming have been
successfully demonstrated.",0901.4439v1
2016-01-31,Josephson-like Colossal Resistive Switching in Nanocrystalline Y-Ba-Cu-O at Room Temperature,"In this paper, we present data for two nanocrystalline YBa2Cu3O7-x (YBCO)
samples which both exhibit Josephson-like Colossal Resistive Switching (JCRS)
in voltage-current (V-I) traces from 4.2 K up to room temperature, in magnetic
fields up to 8 T. We report Josephson-like hysteresis for both positive and
negative current that has not been observed before in colossal resistive
switching materials. Non-zero resistance was measured in transport measurements
at all temperatures. At low temperatures (< 90 K), we also observed the usual
properties for YBCO including weak superconducting and paramagnetic behavior,
measured using ac susceptibility and magnetization measurements. The
resistivity of these nanocrystalline samples is 3 orders of magnitude higher
than standard polycrystalline materials at 300 K and the temperature dependence
semiconductor-like. We cannot rule out the possibility that these materials
contain a superconducting component responsible for the JCRS behavior at room
temperature.",1602.00271v3
2013-08-28,First studies with the Resistive-Plate WELL gaseous multiplier,"We present the results of first studies of the Resistive Plate WELL (RPWELL):
a single-faced THGEM coupled to a copper anode via a resistive layer of high
bulk resistivity. We explored various materials of different bulk resistivity
(10^9 - 10^12 Ohm cm) and thickness (0.4 - 4 mm). Our most successful
prototype, with a 0.6 mm resistive plate of ~10^9 Ohm cm, achieved gains of up
to 10^5 with 8 keV x-ray in Ne/5%CH4; a minor 30% gain drop occurred with a
rate increase from 10 to 10^4 Hz/mm^2. The detector displayed a full
""discharge-free"" operation--even when exposed to high primary ionization
events. We present the RPWELL detector concept and compare its performance to
that of other previously explored THGEM configurations--in terms of gain, its
curves, dependence on rate, and the response to high ionization. The robust
Resistive Plate WELL concept is a step forward in the Micro-Pattern
Gas-Detector family, with numerous potential applications.",1308.6152v1
2021-02-07,Quantum Conductors Formation and Resistive Switching Memory Effects in Zirconia Nanotubes,"The development prospects of memristive elements for non-volatile memory with
use of the metal-dielectric-metal sandwich structures with a thin oxide layer
are due to the possibility of reliable forming the sustained functional states
with quantized resistance. In the paper we study the properties of fabricated
memristors based on the non-stoichiometric $ZrO_2$ nanotubes in different
resistive switching modes. Anodic oxidation of the $Zr$ foil has been used to
synthesize a zirconia layer of $1.7$ $\mu$$m$ thickness, consisting of an
ordered array of vertically oriented nanotubes with outer diameter of 75 nm.
$Zr/ZrO_2/Au$ sandwich structures have been fabricated by mask magnetron
deposition. The effects of resistive switching in the $Zr/ZrO_2/Au$ memristors
in unipolar and bipolar modes have been investigated. The resistance ratios
$\geq3\cdot10^4$ between high-resistance (HRS) and low-resistance (LRS) states
have been evaluated. It has been founded the conductivity of LRS is quantized
in a wide range with minimum value of $0.5G_0=38.74$ $\mu$$S$ due to the
formation of quantum conductors based on oxygen vacancies ($V_O$). Resistive
switching mechanisms of $Zr/ZrO_2/Au$ memristors with allowing for migration of
$V_O$ in an applied electric field have been proposed. It has been shown that
the ohmic type and space charge limited conductivities are realized in the LRS
and HRS, correspondingly. We present the results which can be used for
development of effective memristors based on functional $Zr/ZrO_2/Au$
nanolayered structure with multiple resistive states and high resistance ratio.",2102.03764v1
2004-07-16,Negative Differential Resistivity and Positive Temperature Coefficient of Resistivity effect in the diffusion limited current of ferroelectric thin film capacitors,"We present a model for the leakage current in ferroelectric thin- film
capacitors which explains two of the observed phenomena that have escaped
satisfactory explanation, i.e. the occurrence of either a plateau or negative
differential resistivity at low voltages, and the observation of a Positive
Temperature Coefficient of Resistivity (PTCR) effect in certain samples in the
high-voltage regime. The leakage current is modelled by considering a
diffusion-limited current process, which in the high-voltage regime recovers
the diffusion-limited Schottky relationship of Simmons already shown to be
applicable in these systems.",0407428v1
2015-05-18,Nonpolar resistive memory switching with all four possible resistive switching modes in amorphous ternary rare earth LaHoO3 thin films,"We studied the resistive memory switching in pulsed laser deposited amorphous
LaHoO3 (LHO) thin films for non-volatile resistive random access memory (RRAM)
applications. Nonpolar resistive switching (RS) was achieved in PtLHOPt memory
cells with all four possible RS modes ( positive unipolar, positive bipolar,
negative unipolar, and negative bipolar) having high RON and ROFF ratios (in
the range of 104 to 105) and non-overlapping switching voltages (set voltage,
VON 3.6 to 4.2 V and reset voltage, VOFF 1.3 to 1.6 V) with a small variation
of about 5 to 8 percent. X ray photoelectron spectroscopic studies together
with temperature dependent switching characteristics revealed the formation of
metallic holmium (Ho) and oxygen vacancies (VO) constituted conductive
nanofilaments (CNFs) in the low resistance state (LRS). Detailed analysis of
current versus voltage characteristics further corroborated the formation of
CNFs based on metal like (Ohmic) conduction in LRS. Simmons Schottky emission
was found to be the dominant charge transport mechanism in the high resistance
state.",1505.04690v1
2019-07-23,Electron transport in high-entropy alloys: Al$_{x}$CrFeCoNi as a case study,"The high-entropy alloys Al$_{x}$CrFeCoNi exist over a broad range of Al
concentrations ($0 < x < 2$). With increasing Al content their structure is
changed from the fcc to bcc phase. We investigate the effect of such structural
changes on transport properties including the residual resistivity and the
anomalous Hall resistivity. We have performed a detailed comparison of the
first-principles simulations with available experimental data. We show that the
calculated residual resistivities for all studied alloy compositions are in a
fair agreement with available experimental data as concerns both the
resistivity values and concentration trends. We emphasize that a good agreement
with experiment was obtained also for the anomalous Hall resistivity. We have
completed study by estimation of the anisotropic magnetoresistance,
spin-disorder resistivity, and Gilbert damping. The obtained results prove that
the main scattering mechanism is due to the intrinsic chemical disorder whereas
the effect of spin polarization on the residual resistivity is appreciably
weaker.",1907.09731v1
2018-04-14,Investigating the Composite/Metal Interface and its Influence on the Electrical Resistance Measurement,"The advantages introduced by carbon fiber reinforced polymer (CFRP)
composites has made them an appropriate choice in many applications and an
ideal replacement for conventional materials. The benefits using CFRP
composites are due to their lightweight, high stiffness, as well as corrosion
resistance. For this reason, there is a fast growing trend in using CFRP
composites for aircraft and wind turbine structural applications. The
replacement of the conventional aerospace-grade metal alloys (aluminum,
titanium, magnesium, etc.) with CFRP composites results in new challenges. For
example, an aircraft during flight is prone to be struck by lightning. To
withstand the injection of such massive amount of energy, adequate electrical
properties, mainly electrical conductivity, is required. In fact, electrical
conductance (or its reciprocal, resistance) is a critical parameter
representing any material change and it can be considered an index for health
monitoring. In this paper, AS4/8552 carbon/epoxy laminated composites were
injected with two types of electrical currents, impulse current and direct
current. The change in measured electrical resistance was recorded. A
significant resistance drop occurred after electrical current injections.
Furthermore, four-point flexural tests were performed on these composites to
correlate an electrical resistance change with a potential flexural property
change. There was no clear trend between a resistance change and flexural
strength/modulus change of the test coupons, regardless of current injection.
However, it was observed that the injection of the current affects the contact
resistance such that its resistance decreases.",1804.06246v1
2018-08-09,Underlying burning resistant mechanisms for titanium alloy,"The ""titanium fire"" as produced during high pressure and friction is the
major failure scenario for aero-engines. To alleviate this issue, Ti-V-Cr and
Ti-Cu-Al series burn resistant titanium alloys have been developed. However,
which burn resistant alloy exhibit better property with reasonable cost needs
to be evaluated. This work unveils the burning mechanisms of these alloys and
discusses whether burn resistance of Cr and V can be replaced by Cu, on which
thorough exploration is lacking. Two representative burn resistant alloys are
considered, including Ti14(Ti-13Cu-1Al-0.2Si) and
Ti40(Ti-25V-15Cr-0.2Si)alloys. Compared with the commercial non-burn resistant
titanium alloy, i.e., TC4(Ti-6Al-4V)alloy, it has been found that both Ti14 and
Ti40 alloys form ""protective"" shields during the burning process. Specifically,
for Ti14 alloy, a clear Cu-rich layer is formed at the interface between
burning product zone and heat affected zone, which consumes oxygen by producing
Cu-O compounds and impedes the reaction with Ti-matrix. This work has
established a fundamental understanding of burning resistant mechanisms for
titanium alloys. Importantly, it is found that Cu could endow titanium alloys
with similar burn resistant capability as that of V or Cr, which opens a
cost-effective avenue to design burn resistant titanium alloys.",1808.02976v1
2005-10-03,Buffer-Enhanced Electrical-Pulse-Induced-Resistive Memory Effect in Thin Film Perovskites,"A multilayer perovskite thin film resistive memory device has been developed
comprised of: a Pr0.7Ca0.3MnO3 (PCMO) perovskite oxide epitaxial layer on a
YBCO bottom thin film electrode; a thin yttria stabilized zirconia (YSZ) buffer
layer grown on the PCMO layer, and a gold thin film top electrode. The
multi-layer thin film lattice structure has been characterized by XRD and TEM
analyses showing a high quality heterostructure. I-AFM analysis indicated nano
granular conductivity distributed uniformly throughout the PCMO film surface.
With the addition of the YSZ buffer layer, the pulse voltage needed to switch
the device is significantly reduced and the resistance-switching ratio is
increased compared to a non-buffered resistance memory device, which is very
important for the device fabrication. The magnetic field effect on the
multilayer structure resistance at various temperatures shows CMR behavior for
both high and low resistance states implying a bulk material component to the
switch behavior.",0510060v1
2020-04-24,Solution-processed silver sulphide nanocrystal film for resistive switching memories,"Resistive switching memories allow electrical control of the conductivity of
a material, by inducing a high resistance (OFF) or a low resistance (ON) state,
using electrochemical and ion transport processes. As alternative to high
temperature and vacuum-based physical sulphurization methods of silver (Ag),
here we propose, as resistive switching medium, a layer built from colloidal
Ag$_{2-x}$S nanocrystals -compatible with solution-processed approaches. The
effect of the electrode size (from macro- to micro-scale), composition (Ag, Ti
and Pt) and geometry on the device performance together with the
electrochemical mechanisms involved are evaluated. We achieved an optimized
Ag/Ti bowtie proof-of-concept configuration by e-beam lithography, which
fulfils the general requirements for ReRAM devices in terms of low power
consumption and reliable $I_{ON}/I_{OFF}$ ratio. This configuration
demonstrates reproducible switching between ON and OFF states with data
endurance of at least 20 cycles; and an $I_{ON}/I_{OFF}$ ratio up to 10$^3$ at
low power consumption (0.1V readout), which outperforms previous results in
literature for devices with resistive layers fabricated from silver
chalcogenide nanoparticles.",2004.11875v1
2005-12-22,Measurement of Local Reactive and Resistive Photoresponse of a Superconducting Microwave Device,"We propose and demonstrate a spatial partition method for the high-frequency
photo-response of superconducting devices correlated with inductive and
resistive changes in microwave impedance. Using a laser scanning microscope, we
show that resistive losses are mainly produced by local defects at microstrip
edges and by intergrain weak links in the high-temperature superconducting
material. These defects initiate nonlinear high-frequency response due to
overcritical current densities and entry of vortices.",0512572v1
2002-10-28,Nanometer-Scale Metallic Grains Connected with Atomic-Scale Conductors,"We describe a technique for connecting a nanometer-scale gold grain to leads
by atomic-scale gold point contacts. These devices differ from previous
metallic quantum dots in that the conducting channels are relatively
well-transmitting. We investigate the dependence of the Coulomb blockade on
contact resistance. The high-resistance devices display Coulomb blockade and
the low-resistance devices display a zero-bias conductance dip, both in
quantitative agreement with theory. We find that in the intermediate regime,
where the sample resistance is close to $h/e^2$, the I-V curve displays a
Coulomb staircase with symmetric contact capacitances.",0210620v1
2004-08-05,Influence of Grain size on the Electrical Properties of ${\rm Sb_2Te_3}$ Polycrystalline Films,"Resistance of vacuum deposited ${\rm Sb_2Te_3}$ films of thickness between
100-500nm has been measured in vacuum. It is found that the resistance of the
polycrystalline films strongly depends on the grain size and inter-granular
voids. The charge carrier are shown to cross this high resistivity inter-
granular void by ohmic conduction. The barrier height as well as temperature
coefficient of resistance are also shown to depend on the grain size and inter-
grain voids.",0408116v1
2008-05-03,Resistance Quenching in Graphene Interconnects,"We investigated experimentally the high-temperature electrical resistance of
graphene interconnects. The test structures were fabricated using the focused
ion beam from the single and bi-layer graphene produced by mechanical
exfoliation. It was found that as temperature increases from 300 to 500K the
resistance of the single- and bi-layer graphene interconnects drops down by 30%
and 70%, respectively. The quenching and temperature dependence of the
resistance were explained by the thermal generation of the electron-hole pairs
and acoustic phonon scattering. The obtained results are important for the
proposed applications of graphene as interconnects in integrated circuits.",0805.0334v1
2008-05-12,Negative differential resistance and pulsed current induced multi-level resistivity switching in charge ordered and disordered manganites,"We have investigated direct and pulsed current induced electroresistance in
two manganites with different electronic and magnetic ground states:
charge-orbital ordered 50 % Ca doped NdMnO3 and 50 % Mn doped LaNiO3. It has
been shown that negative differential resistance observed at high current
density in these compounds is related to Joule heating. However, bi-level and
multi-level resistivity switching induced by variations in pulse width and
pulse period at low current density can not be attributable to Joule heating
alone. We discuss possible origins.",0805.1643v1
2012-07-13,Enhanced Resolution of Poly-(Methyl Methacrylate) Electron Resist by Thermal Processing,"Granular nanostructure of electron beam resist had limited the ultimate
resolution of electron beam lithography. We report a thermal process to achieve
a uniform and homogeneous amorphous thin film of poly methyl methacrylate
electron resist. This thermal process consists of a short time-high temperature
backing process in addition to precisely optimized development process
conditions. Using this novel process, we patterned arrays of holes in a metal
film with diameter smaller than 5nm. In addition, line edge roughness and
surface roughness of the resist reduced to 1nm and 100pm respectively.",1207.3183v1
2016-11-12,Anomalous resistivity upturn in epitaxial L21-Co2MnAl films,"We report the controllable growth and the intriguing transport behavior of
high-spin-polarization epitaxial L21-Co2MnAl films, which exhibit a
low-temperature (T) resistivity upturn with pronounced T1/2 dependence, close
relevance to structural disorder, and robust independence of magnetic fields.
The resistivity upturn turns out to be qualitatively contradictory to weak
localization, particle-particle channel electron-electron interaction (EEI),
and orbital two-channel Kondo effect, leaving a three-dimensional particle-hole
channel EEI the most likely physical source. Our result highlights a
considerable tunability of the structural and electronic disorder of magnetic
films by varying growth temperature, affording unprecedented insights into the
spin polarization and the resistivity upturn.",1611.04013v2
2011-04-06,Temperature dependence of contact resistance of Au-Ti-Pd2Si-n+-Si ohmic contacts,"We investigated temperature dependence of contact resistance of an
Au-Ti-Pd2Si ohmic contact to heavily doped n+-Si. The contact resistance
increases with temperature owing to conduction through the metal shunts. In
this case, the limiting process is diffusion input of electrons to the metal
shunts. The proposed mechanism of contact resistance formation seems to realize
also in the case of wide-gap semiconductors with high concentration of surface
states and dislocation density in the contact.",1104.1030v1
2021-04-25,Electrical resistivity in 2d Kondo lattice systems,"I extend the calculations represented in \cite{konav} regarding the
resistivity in Kondo lattice materials from $3d$ syatem to $2d$ systems. In the
present work I consider a 2d system, and memory function is computed. However,
results found in 2d case are different from 3d system . I find that in $2d$ in
low temperature regime($ k_{B}T\ll \mu_d$) resistivity shows power
law($\frac{1}{T}$) behaviour and in the high temeprature regime($
k_{B}T\gg\mu_d$) resistivity varies linearly with temperature. In $3d$ these
behaviours are as $\frac{1}{T}$ and as $T^{\frac{3}{2}}$ respectively.",2104.12129v1
2008-01-22,Abnormal Resistance Switching Behaviors of NiO Thin Films: Possible Occurrence of Simultaneous Formation and Rupture of Conducting Channels,"We report the detailed current-voltage (I-V) characteristics of resistance
switching in NiO thin films. In unipolar resistance switching, it is commonly
believed that conducting filaments will rupture when NiO changes from a low
resistance to a high resistance state. However, we found that this resistance
switching can sometimes show abnormal behavior during voltage- and
current-driven I-V measurements. We used the random circuit breaker network
model to explain how abnormal switching behaviors could occur. We found that
this resistance change can occur via a series of avalanche processes, where
conducting filaments could be formed as well as ruptured.",0801.3323v1
2009-08-12,Large 1/f noise of unipolar resistance switching and its percolating nature,"We investigated the 1/f noise of Pt/NiO/Pt capacitors that show unipolar
resistance switching. When they were switched from the low to high resistance
states, the power spectral density of the voltage fluctuation was increased by
approximately five orders of magnitude. At 100 K, the relative resistance
fluctuation, SR/R2, in the low resistance state displayed a power law
dependence on the resistance R with exponent w = 1.6. This behavior can be
explained by percolation theory; however, at higher temperatures or near the
switching voltage, SR/R2 becomes enhanced further. This large 1/f noise can be
therefore an important problem in the development of resistance random access
memory devices.",0908.1606v1
2017-04-11,Scalability of Voltage-Controlled Filamentary and Nanometallic Resistance Memories,"Much effort has been devoted to device and materials engineering to realize
nanoscale resistance random access memory (RRAM) for practical applications,
but there still lacks a rational physical basis to be relied on to design
scalable devices spanning many length scales. In particular, the critical
switching criterion is not clear for RRAM devices in which resistance changes
are limited to localized nanoscale filaments that experience concentrated heat,
electric current and field. Here, we demonstrate voltage-controlled resistance
switching for macro and nano devices in both filamentary RRAM and nanometallic
RRAM, the latter switches uniformly and does not require forming. As a result,
using a constant current density as the compliance, we have achieved
area-scalability for the low resistance state of the filamentary RRAM, and for
both the low and high resistance states of the nanometallic RRAM. This finding
will help design area-scalable RRAM at the nanoscale.",1704.03415v1
2021-10-07,A Modern-day Alchemy: Double Glow Plasma Surface Metallurgy Technology,"In the long history of science and technology development, one goal is to
diffuse solid alloy elements into the surface of steel materials to form
surface alloys with excellent physical and chemical properties. On the basis of
plasma nitriding technology, double glow plasma surface metallurgy technology
has answered this challenge. This technology, which seems to be a modern-day
alchemy, can use any element in the periodic table of chemical elements,
including solid metal elements and their combinations, to form many types of
surface alloyed layers with high hardness, wear resistance, corrosion
resistance and high temperature oxidation resistance on various metal
materials. For examples, nickel base alloys, stainless steels and high speed
steels are formed on the surfaces of ordinary carbon steels; and high hardness,
wear resistance and high temperature oxidation resistance alloy are formed on
the surface of titanium alloy.This article briefly introduces the formation and
principle of double glow plasma surface metallurgy technology, and summarizes
the experimental results and industry application. The significance and
development prospect of this technology are discussed.",2110.03236v1
2019-09-15,Large Resistivity Reduction in Mixed-Valent CsAuBr$_3$ Under Pressure,"We report on high-pressure $p \leq 45$ GPa resistivity measurements on the
perovskite-related mixed-valent compound CsAuBr$_3$. The compounds
high-pressure resistivity can be classified into three regions: For low
pressures ($p < 10$ GPa) an insulator to metal transition is observed; between
$p= 10$ GPa and 14 GPa the room temperature resistivity goes through a minimum
and increases again; above $p = 14$ GPa a semiconducting state is observed.
From this pressure up to the highest pressure of $p = 45$ GPa reached in this
experiment, the room-temperature resistivity remains nearly constant. We find
an extremely large resistivity reduction between ambient pressure and 10 GPa by
more than 6 orders of magnitude. This decrease is among the largest reported
changes in the resistivity for this narrow pressure regime. We show - by an
analysis of the electronic band structure evolution of this material - that the
large change in resistivity under pressure in not caused by a crossing of the
bands at the Fermi level. We find that it instead stems from two bands that are
pinned at the Fermi level and that are moving towards one another as a
consequence of the mixed-valent to single-valent transition. This mechanism
appears to be especially effective for the rapid buildup of the density of
states at the Fermi level.",1909.06874v1
2023-02-25,"Peculiarities of electron transport and resistive switching in point contacts on TiSe2, TiSeS and CuxTiSe2","TiSe2 has received much attention among the transition metals chalcogenides
because of its thrilling physical properties concerning atypical resistivity
behavior, emerging of charge density wave (CDW) state, induced
superconductivity etc. Here, we report discovery of new feature of TiSe2,
namely, observation of resistive switching in voltage biased point contacts
(PCs) based on TiSe2 and its derivatives doped by S and Cu (TiSeS, CuxTiSe2).
The switching is taking place between a low resistive mainly metallic-type
state and a high resistive semiconducting-type state by applying bias voltage
(usually below 0.5V), while reverse switching takes place by applying voltage
of opposite polarity (usually below 0.5V). The difference in resistance between
these two states can reach up to two orders of magnitude at the room
temperature. The origin of the effect can be attributed to the variation of
stoichiometry in PC core due to drift/displacement of Se/Ti vacancies under
high electric field. Additionally, we demonstrated, that heating takes place in
PC core, which can facilitate the electric field induced effect. At the same
time, we did not found any evidence for CDW spectral features in our PC spectra
for TiSe2. The observed resistive switching allows to propose TiSe2 and their
derivatives as the promising materials, e.g., for non-volatile resistive random
access memory (ReRAM) engineering.",2302.13085v1
2021-04-21,A First-Principles-Based Approach to The High-Throughput Screening of Corrosion-Resistant High Entropy Alloys,"The design of corrosion-resistant high entropy alloys (CR-HEAs) is
challenging due to the alloys' virtually astrological composition space. To
facilitate this, efficient and reliable high-throughput exploratory approaches
are needed. Toward this end, the current work reports a first-principles-based
approach exploiting the correlations between work function, surface energy, and
corrosion resistance (i.e., work function and surface energy are, by
definitions, proportional and inversely proportional to an alloy's inherent
corrosion resistance, respectively). Two Bayesian CALPHAD models (or databases)
of work function and surface energy of FCC Co-Cr-Fe-Mn-Mo-Ni are assessed using
discrete surface energies and work functions derived by density-functional
theory (DFT) calculations. The models are then used to rank different
Co-Cr-Fe-Mn-Mo-Ni alloy compositions. It is observed that the ranked alloys
possess chemical traits similar to previously studied corrosion-resistance
alloys, suggesting that the proposed approach can be used to reliably screen
HEAs with potentially good inherent corrosion resistance.",2104.10590v1
2023-04-02,Percolation-induced resistivity drop in cold-pressed LuH2,"The stoichiometric bulk LuH2 is a paramagnetic metal with high electrical
conductivity comparable to simple metals. Here we show that the resistivity of
cold-pressed (CP) LuH2 samples varies sensitively upon modifying the grain size
or surface conditions via the grinding process, i.e., the CP pellets made of
commercially purchased LuH2 powder remain metallic but exhibit thousands of
times higher resistivity, while additional grinding of LuH2 powders in air
further enhances the resistivity and even results in weakly localized
behaviors. For these CP samples, interestingly, we can occasionally observe
abrupt resistivity drops at high temperatures, which also show dependences on
magnetic fields and electrical current. Measurements of variable-temperature
XRD, magnetic susceptibility, and specific heat exclude the possibilities of
structural, magnetic, and superconducting transitions for the observed
resistivity drops. Instead, we tentatively attribute these above observations
to the presence of insulating layers on the grain surface due to the
modification of hydrogen stoichiometry or the pollution by oxygen/nitrogen.
Percolation of the metallic grains through the insulating surfaces can explain
the sudden drop in resistivity. The present results thus call for caution in
asserting the resistivity drops as superconductivity and invalidate the
background subtraction in analyzing the resistivity data.",2304.00558v1
2017-07-28,High-temperature quantum oscillations of the Hall resistance in bulk Bi$_2$Se$_3$,"Helically spin-polarized Dirac fermions (HSDF) in protected topological
surface states (TSS) are of high interest as a new state of quantum matter. In
three-dimensional (3D) materials with TSS, electronic bulk states often mask
the transport properties of HSDF. Recently, the high-field Hall resistance and
low-field magnetoresistance indicate that the TSS may coexist with a layered
two-dimensional electronic system (2DES). Here, we demonstrate quantum
oscillations of the Hall resistance at temperatures up to 50 K in bulk
Bi$_2$Se$_3$ with a high electron density $n$ of about $2\!\cdot\!10^{19}$
cm$^{-3}$. From the angular and temperature dependence of the Hall resistance
and the Shubnikov-de Haas oscillations we identify 3D and 2D contributions to
transport. Angular resolved photoemission spectroscopy proves the existence of
TSS. We present a model for Bi$_2$Se$_3$ and suggest that the coexistence of
TSS and 2D layered transport stabilizes the quantum oscillations of the Hall
resistance.",1707.09181v1
2005-11-15,Unconventional Hall effect in oriented Ca$_3$Co$_4$O$_9$ thin films,"Transport properties of the good thermoelectric misfit oxide
Ca$_3$Co$_4$O$_9$ are examined. In-plane resistivity and Hall resistance
measurements were made on epitaxial thin films which were grown on {\it c}-cut
sapphire substrates using the pulsed laser deposition technique. Interpretation
of the in-plane transport experiments relates the substrate-induced strain in
the resulting film to single crystals under very high pressure ($\sim$ 5.5 GPa)
consistent with a key role of strong electronic correlation. They are confirmed
by the measured high temperature maxima in both resistivity and Hall
resistance. While hole-like charge carriers are inferred from the Hall effect
measurements over the whole investigated temperature range, the Hall resistance
reveals a non monotonic behavior at low temperatures that could be interpreted
with an anomalous contribution. The resulting unconventional temperature
dependence of the Hall resistance seems thus to combine high temperature
strongly correlated features above 340 K and anomalous Hall effect at low
temperature, below 100 K.",0511374v1
2013-10-21,Micro Pixel Chamber with resistive electrodes for spark reduction,"The Micro Pixel Chamber (mu-PIC) using resistive electrodes has been
developed and tested. The surface cathodes are made from resistive material, by
which the electrical field is reduced when large current is flowed.
Two-dimensional readouts are achieved by anodes and pickup electrodes, on which
signals are induced. High gas gain (> 60000) was measured using 55Fe (5.9 keV)
source, and very intensive spark reduction was attained under fast neutron. The
spark rate of resistive mu-PIC was only 10^-4 times less than that of
conventional mu-PIC at the gain of 10^4. With these developments, a new MPGD
with no floating structure is achieved, with enough properties of both high
gain and good stability to detect MIP particles. In addition, mu-PIC can be
operated with no HV applied on anodes by using resistive cathodes. Neither AC
coupling capacitors nor HV pull up resisters are needed for any anode
electrode. Signal readout is drastically simplified by that configuration.",1310.5550v1
2023-11-28,Quantifying the contribution of material and junction resistances in nano-networks,"Networks of nanowires and nanosheets are important for many applications in
printed electronics. However, the network conductivity and mobility are usually
limited by the inter-particle junction resistance, a property that is
challenging to minimise because it is difficult to measure. Here, we develop a
simple model for conduction in networks of 1D or 2D nanomaterials, which allows
us to extract junction and nanoparticle resistances from
particle-size-dependent D.C. resistivity data of conducting and semiconducting
materials. We find junction resistances in porous networks to scale with
nanoparticle resistivity and vary from 5 Ohm for silver nanosheets to 25 GOhm
for WS2 nanosheets. Moreover, our model allows junction and nanoparticle
resistances to be extracted from A.C. impedance spectra of semiconducting
networks. Impedance data links the high mobility (~7 cm2/Vs) of aligned
networks of electrochemically exfoliated MoS2 nanosheets to low junction
resistances of ~670 kOhm. Temperature-dependent impedance measurements allow us
to quantitatively differentiate intra-nanosheet phonon-limited band-like
transport from inter-nanosheet hopping for the first time.",2311.16740v1
2016-02-04,"Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe2, MoS2, and MoSe2 Transistors","We report a new strategy for fabricating 2D/2D low-resistance ohmic contacts
for a variety of transition metal dichalcogenides (TMDs) using van der Waals
assembly of substitutionally doped TMDs as drain/source contacts and TMDs with
no intentional doping as channel materials. We demonstrate that few-layer WSe2
field-effect transistors (FETs) with 2D/2D contacts exhibit low contact
resistances of ~ 0.3 k ohm.um, high on/off ratios up to > 109, and high drive
currents exceeding 320 uA um-1. These favorable characteristics are combined
with a two-terminal field-effect hole mobility ~ 2x102 cm2 V-1 s-1 at room
temperature, which increases to >2x103 cm2 V-1 s-1 at cryogenic temperatures.
We observe a similar performance also in MoS2 and MoSe2 FETs with 2D/2D drain
and source contacts. The 2D/2D low-resistance ohmic contacts presented here
represent a new device paradigm that overcomes a significant bottleneck in the
performance of TMDs and a wide variety of other 2D materials as the channel
materials in post-silicon electronics.",1602.01790v1
2013-12-30,Deviations from Matthiessen rule and resistivity saturation effects in Gd and Fe,"According to earlier first-principles calculations, the spin-disorder
contribution to the resistivity of rare-earth metals in the paramagnetic state
is strongly underestimated if Matthiessen's rule is assumed to hold. To
understand this discrepancy, the resistivity of paramagnetic Fe and Gd is
evaluated by taking into account both spin and phonon disorder. Calculations
are performed using the supercell approach within the linear muffin-tin orbital
method. Phonon disorder is modeled by introducing random displacements of the
atomic nuclei, and the results are compared with the case of fictitious
Anderson disorder. In both cases the resistivity shows a nonlinear dependence
on the square of the disorder potential, which is interpreted as a resistivity
saturation effect. This effect is much stronger in Gd than in Fe. The
non-linearity makes the phonon and spin-disorder contributions to the
resistivity non-additive, and the standard procedure of extracting the
spin-disorder resistivity by extrapolation from high temperatures becomes
ambiguous. An ""apparent"" spin-disorder resistivity obtained through such
extrapolation is in much better agreement with experiment compared to the
results obtained by considering only spin disorder. By analyzing the spectral
function of the paramagnetic Gd in the presence of Anderson disorder, the
resistivity saturation is explained by the collapse of a large area of the
Fermi surface due to the disorder-induced mixing between the electronic and
hole sheets.",1312.7802v1
2016-11-08,Controlling friction in a manganite surface by resistive switching,"We report a significant change in friction of a $\rm La_{0.55}Ca_{0.45}MnO_3$
thin film measured as a function of the materials resistive state under
ultrahigh vacuum conditions at room temperature by friction force microscopy.
While friction is high in the insulating state, it clearly changes to lower
values if the probed local region is switched to the conducting state via
nanoscale resistance switching. Thus we demonstrate active control of friction
without having to change the temperature or pressure. Upon switching back to an
insulating state the friction increases again. The results are discussed in the
framework of electronic friction effects and electrostatic interactions.",1611.02684v1
2019-10-05,Metamaterial insertions for resistive-wall beam-coupling impedance reduction,"Resistive-wall impedance usually constitutes a significant percentage of the
total beamcoupling impedance budget of an accelerator. Reduction techniques
often entail high electrical-conductivity coatings. This paper investigates the
use of negative-permittivity or negative-permeability materials for sensibly
reducing or theoretically nearly cancelling resistive-wall impedance. The
proposed approach is developed by means of an equivalent transmission-line
model. The effectiveness of such materials is benchmarked for the negative
permeability case with experimental measurements in two frequency bandwidths.
This first-stage study opens the possibility of considering metamaterials for
impedance mitigation.",1910.02246v1
2020-07-07,Resistivity saturation in an electron-doped cuprate,"We report the observation of resistivity saturation in lightly doped ($x\sim
0.10)$ as-grown samples of the electron-doped cuprate La$_{2-x}$Ce$_x$CuO$_4$
(LCCO). The saturation occurs at resistivity values roughly consistent with the
phenomenological Mott-Ioffe-Regel criterion once the low effective carrier
density of these materials is included in the analysis. These results imply
that, at least for light doping, the high-temperature metallic phase of these
materials is not necessarily strange and may be understood as simply a
low-density metal.",2007.03685v1
2015-06-24,Resonant tunneling in a quantum oxide superlattice,"Resonant tunnelling is a quantum mechanical process that has long been
attracting both scientific and technological attention owing to its intriguing
underlying physics and unique applications for high-speed electronics. The
materials system exhibiting resonant tunnelling, however, has been largely
limited to the conventional semiconductors, partially due to their excellent
crystalline quality. Here we show that a deliberately designed transition metal
oxide superlattice exhibits a resonant tunnelling behaviour with a clear
negative differential resistance. The tunnelling occurred through an atomically
thin, lanthanum {\delta}-doped SrTiO3 layer, and the negative differential
resistance was realized on top of the bipolar resistance switching typically
observed for perovskite oxide junctions. This combined process resulted in an
extremely large resistance ratio (~10^5) between the high and low-resistance
states. The unprecedentedly large control found in atomically thin
{\delta}-doped oxide superlattices can open a door to novel oxide-based
high-frequency logic devices.",1506.07583v1
2021-08-26,An investigation of high entropy alloy conductivity using first-principles calculations,"The Kubo-Greenwood equation, in combination with the first-principles
Korringa-Kohn-Rostoker Coherent Potential Approximation (KKR-CPA) can be used
to calculate the DC residual resistivity of random alloys at T = 0 K. We
implemented this method in a multiple scattering theory based ab initio
package, MuST, and applied it to the ab initio study of the residual
resistivity of the high entropy alloy Al$_x$CoCrFeNi as a function of $x$. The
calculated resistivities are compared with experimental data. We also predict
the residual resistivity of refractory high entropy alloy MoNbTaV$_x$W. The
calculated resistivity trends are also explained using theoretical arguments.",2108.11739v1
2024-01-27,Influence od the process parameters on the quality a efficiency of the resistance spot welding process of advanced high strength complex phase stells,"The effects of electrical characteristics of an inverter combined with main
welding parameters on the resistance spot weldability of advanced high strength
steels AHSS CP1000 is investigated.",2401.15457v1
2016-02-22,"The effect of Ta oxygen scavenger layer on HfO$_2$-based resistive switching behavior: thermodynamic stability, electronic structure, and low-bias transport","Reversible resistive switching between high-resistance and low-resistance
states in metal-oxide-metal heterostructures makes them very interesting for
applications in random access memories. While recent experimental work has
shown that inserting a metallic ""oxygen scavenger layer"" between the positive
electrode and oxide improves device performance, the fundamental understanding
of how the scavenger layer modifies heterostructure properties is lacking. We
use density functional theory to calculate thermodynamic properties and
conductance of TiN/HfO$_2$/TiN heterostructures with and without Ta scavenger
layer. First, we show that Ta insertion lowers the formation energy of
low-resistance states. Second, while the Ta scavenger layer reduces the
Schottky barrier height in the high-resistance state by modifying the interface
charge at the oxide-electrode interface, the heterostructure maintains a high
resistance ratio between high- and low-resistance states. Finally, we show that
the low-bias conductance of device on-states becomes much less sensitive to the
spatial distribution of oxygen removed from the HfO$_2$ in the presence of the
Ta layer. By providing fundamental understanding of the observed improvements
with scavenger layers, we open a path to engineer interfaces with oxygen
scavenger layers to control and enhance device performance. In turn, this may
enable the realization of a non-volatile low-power memory technology with
concomitant reduction in energy consumption by consumer electronics and
significant benefits to society.",1602.06793v1
2002-09-04,Electrical resistivity at large temperatures: Saturation and lack thereof,"Many transition metal compounds show saturation of the resistivity at high
temperatures, T, while the alkali-doped fullerenes and the high-Tc cuprates are
usually considered to show no saturation. We present a model of transition
metal compounds, showing saturation, and a model of alkali-doped fullerenes,
showing no saturation. To analyze the results we use the f-sum rule, which
leads to an approximate upper limit for the resistivity at large T. For some
systems and at low T, the resistivity increases so rapidly that this upper
limit is approached for experimental T. The resistivity then saturates. For a
model of transition metal compounds with weakly interacting electrons, the
upper limit corresponds to a mean free path consistent with the Ioffe-Regel
condition. For a model of the high Tc cuprates with strongly interacting
electrons, however, the upper limit is much larger than the Ioffe-Regel
condition suggests. Since this limit is not exceeded by experimental data, the
data are consistent with saturation also for the cuprates. After ""saturation""
the resistivity usually grows slowly. For the alkali-doped fullerenes,
""saturation"" can be considered to have happened already for T=0, due to
orientational disorder. For these systems, however, the resistivity grows so
rapidly after ""saturation"" that this concept is meaningless. This is due to the
small band width and to the coupling to the level energies of the important
phonons.",0209099v1
2023-12-26,Corrosion-resistant aluminum alloy design through machine learning combined with high-throughput calculations,"Efficiently designing lightweight alloys with combined high corrosion
resistance and mechanical properties remains an enduring topic in materials
engineering. To this end, machine learning (ML) coupled ab-initio calculations
is proposed within this study. Due to the inadequate accuracy of conventional
stress-strain ML models caused by corrosion factors, a novel reinforcement
self-learning ML algorithm (accuracy R2 >0.92) is developed. Then, a strategy
that integrates ML models, calculated energetics and mechanical moduli is
implemented to optimize the Al alloys. Next, this Computation Designed
Corrosion-Resistant Al alloy is fabricated that verified the simulation. The
performance (elongation reaches ~30%) is attributed to the H-captured Al-Sc-Cu
phases (-1.44 eV H-1) and Cu-modified {\eta}/{\eta}' precipitation inside the
grain boundaries (GBs). The developed Al-Mg-Zn-Cu interatomic potential (energy
accuracy 6.50 meV atom-1) proves the cracking resistance of the GB region
enhanced by Cu-modification. Conceptually, our strategy is of practical
importance for designing new alloys exhibiting corrosion resistance and
mechanical properties.",2312.15899v1
2001-03-01,Properties of Pt Schottky Type Contacts On High-Resistivity CdZnTe Detectors,"In this paper we present studies of the I-V characteristics of CdZnTe
detectors with Pt contacts fabricated from high-resistivity single crystals
grown by the high-pressure Brigman process. We have analyzed the experimental
I-V curves using a model that approximates the CZT detector as a system
consisting of a reversed Schottky contact in series with the bulk resistance.
Least square fits to the experimental data yield 0.78-0.79 eV for the Pt-CZT
Schottky barrier height, and <20 V for the voltage required to deplete a 2 mm
thick CZT detector. We demonstrate that at high bias the thermionic current
over the Schottky barrier, the height of which is reduced due to an interfacial
layer between the contact and CZT material, controls the leakage current of the
detectors. In many cases the dark current is not determined by the resistivity
of the bulk material, but rather the properties of the contacts; namely by the
interfacial layer between the contact and CZT material.",0103005v1
2010-01-27,"An anomalous butterfly-shaped magnetoresistance loop in an alloy, Tb4LuSi3","Magnetic-field (H) induced first-order magnetic transition and the assiciated
electronic phase-separation phenomena are active topics of research in
magnetism. Magnetoresistance (MR) is a key property to probe these phenomena
and, in literature, a butterfly-shaped MR loop has been noted while cycling the
field, with the envelope curve lying below the virgin curve in MR versus H
plots of such materials. Here, we report an opposite behavior of MR loop for an
alloy, Tb4LuSi3, at low temperatures (<<20 K) in the magnetically ordered
state. Such an anomalous curve reveals unexpected domination of higher
resistive high-field phase in electronic conduction, unlike in other materials
where conducion is naturally by low-resistive high-field phase that follows
first-order transition. The observed features reveal an unusual electronic
phase separation, namely involving high-resistive high-field phase and
low-resistive virgin phase.",1001.4942v1
2006-03-31,Clustering of vacancy defects in high-purity semi-insulating SiC,"Positron lifetime spectroscopy was used to study native vacancy defects in
semi-insulating silicon carbide. The material is shown to contain (i) vacancy
clusters consisting of 4--5 missing atoms and (ii) Si vacancy related
negatively charged defects. The total open volume bound to the clusters
anticorrelates with the electrical resistivity both in as-grown and annealed
material. Our results suggest that Si vacancy related complexes compensate
electrically the as-grown material, but migrate to increase the size of the
clusters during annealing, leading to loss of resistivity.",0603849v3
2024-01-26,New perspectives of Hall effects from first-principles calculations,"The Hall effect has been a fascinating topic ever since its discovery,
resulting in exploration of entire family of this intriguing phenomena. As the
field of topology develops and novel materials emerge endlessly over the past
few decades, researchers have been passionately debating the origins of various
Hall effects. Differentiating between the ordinary Hall effect and
extraordinary transport properties, like the anomalous Hall effect, can be
quite challenging, especially in high-conductivity materials, including those
with topological origins. In this study, we conduct a systematic and
comprehensive analysis of Hall effects by combining the semiclassical Boltzmann
transport theory with first principles calculations within the relaxation time
approximation. We first highlight some striking similarities between the
ordinary Hall effect and certain anomalous Hall effects, such as nonlinear
dependency on magnetic field and potential sign reversal of the Hall
resistivity. We then demonstrate that the Hall resistivity can be scaled with
temperature and magnetic field as well, analogue to the Kohler's rule which
scales the longitudinal resistivity under the relaxation time approximation. We
then apply this Kohler's rule for Hall resistivity to two representative
materials: ZrSiS and PtTe$_2$ with reasonable agreement with experimental
measurement. Moreover, our methodology has been proven to be applicable to the
planar Hall effects of bismuth, of perfect agreements with experimental
observations. Our research on the scaling behavior of Hall resistivity
addresses a significant gap in this field and provides a comprehensive
framework for a deeper understanding of the Hall resistance family, and thus
has potential to propel the field forward and spark further investigations into
the fascinating world of Hall effects.",2401.15150v1
2012-04-12,Effect of crystallographic anisotropy on the resistance switching phenomenon in perovskites,"Resistance switching effects in metal/perovskite contacts based on epitaxial
c-axis oriented Y-Ba-Cu-O (YBCO) thin films with different crystallographic
orientations have been studied. Three types of Ag/YBCO junctions with the
contact restricted to (i) c-axis direction, (ii) ab-plane direction, and (iii)
both were designed and fabricated, and their current-voltage characteristics
have been measured. The type (i) junctions exhibited conventional bipolar
resistance switching behavior, whereas in other two types the low-resistance
state was unsteady and their resistance quickly relaxed to the initial
high-resistance state. Physical mechanism based on the oxygen diffusion
scenario, explaining such behavior, is discussed.",1204.2598v1
2013-04-07,Characterization and simulation of resistive-MPGDs with resistive strip and layer topologies,"The use of resistive technologies to MPGD detectors is taking advantage for
many new applications, including high rate and energetic particle flux
scenarios. The recent use of these technologies in large area detectors makes
necessary to understand and characterize the response of this type of detectors
in order to optimize or constrain the parameters used in its production,
material resistivity, strip width, or layer thickness. The values to be chosen
will depend on the environmental conditions in which the detector will be
placed, and the requirements in time resolution and gain, improving the
detector performance for each given application. We present two different
methods to calculate the propagation of charge diffusion through different
resistive topologies; one is based on a FEM of solving the telegraph equation
in our particular strip detector scheme, the other is based on a
semi-analytical approach of charge diffusion and is used to determine the
charge evolution in a resistive layer.",1304.2057v1
2014-07-31,Compact chromium oxide thin film resistors for use in nanoscale quantum circuits,"We report on the electrical characterisation of a series of thin chromium
oxide films, grown by dc sputtering, to evaluate their suitability for use as
on-chip resistors in nanoelectronics. By increasing the level of oxygen doping,
the room-temperature sheet resistance of the chromium oxide films was varied
from 28$\Omega / \square$ to 32.6k$\Omega / \square$. The variation in
resistance with cooling to 4.2K in liquid helium was investigated; the sheet
resistance at 4.2K varied with composition from 65$\Omega / \square$ to above
20G$\Omega / \square$. All of the films measured displayed ohmic behaviour at
all measured temperatures. For on-chip devices for quantum phase-slip
measurements using niobium-silicon nanowires, interfaces between
niobium-silicon and chromium oxide are required. By characterising the
interface contact resistance, we found that a gold intermediate layer is
favourable: the specfic contact resistivity of chromium-oxide-to-gold
interfaces was 0.15 m$\Omega$cm$^2$, much lower than the value for direct
chromium-oxide to niobium-silicon interfaces, 65m$\Omega$cm$^2$. We conclude
that these chromium oxide films are suitable for use in nanoscale circuits as
high-value resistors, with resistivity tunable by oxygen content.",1407.8467v1
2016-06-12,Interlayer Resistance of Misoriented MoS2,"Interlayer misorientation in transition metal dichalcogenides alters the
interlayer distance, the electronic band structure, and the vibrational modes,
but, its effect on the interlayer resistance is not known. This work analyzes
the coherent interlayer resistance of misoriented 2H-MoS2 for low energy
electrons and holes as a function of the misorientation angle. The electronic
interlayer resistance monotonically increases with the supercell lattice
constant by several orders of magnitude similar to that of misoriented bilayer
graphene. The large hole coupling gives low interlayer hole resistance that
weakly depends on the misorientation angle. Interlayer rotation between an
n-type region and a p-type region will suppress the electron current with
little effect on the hole current. We estimate numerical bounds and explain the
results in terms of the orbital composition of the bands at high symmetry
points. Density functional theory calculations provide the interlayer coupling
used in both a tunneling Hamiltonian and a non-equilibrium Green function
calculation of the resistivity.",1606.03682v1
2017-11-30,Universal Scaling in Intrinsic Resistivity of Two-Dimensional Metal Borophene,"Two-dimensional boron sheets (borophenes) have been successfully synthesized
in experiments and are expected to exhibit intriguing transport properties such
as the emergence of superconductivity and Dirac Fermions. However, quantitative
understanding of intrinsic electrical transport of borophene has not been
achieved. Here, we report a comprehensive first-principles study on
electron-phonon driven intrinsic electrical resistivity (\r{ho}) of emerging
borophene structures. We find that the resistivity is highly dependent on the
atomic structures and electron density of borophene. Low-temperature
resistivity of borophene \r{ho} exhibits a universal scaling behavior, which
increases rapidly with temperature T (\r{ho}~T^4), while \r{ho} increases
linearly for a large temperature window T > 100 K. It is observed that this
universal behavior of intrinsic resistivity is well described by
Bloch-Gr\""unesisen model. Different from graphene and conventional
three-dimensional metals, the intrinsic resistivity of borophenes can be easily
tuned by adjusting carrier densities while the Bloch-Gr\""unesisen temperature
is nearly fixed at ~100 K. Our work suggests monolayer boron can serve as an
intriguing platform for realizing high-tunable two-dimensional electronic
devices.",1711.11186v1
2018-05-05,Tetrahedral amorphous carbon resistive memories with graphene-based electrodes,"Resistive-switching memories are alternative to Si-based ones, which face
scaling and high power consumption issues. Tetrahedral amorphous carbon (ta-C)
shows reversible, non-volatile resistive switching. Here we report polarity
independent ta-C resistive memory devices with graphene-based electrodes. Our
devices show ON/OFF resistance ratios$\sim$4x$10^5$, ten times higher than with
metal electrodes, with no increase in switching power, and low power
density$\sim$14$\mu$W/$\mu$m$^2$. We attribute this to a suppressed tunneling
current due to the low density of states of graphene near the Dirac point,
consistent with the current-voltage characteristics derived from a quantum
point contact model. Our devices also have multiple resistive states. This
allows storing more than one bit per cell. This can be exploited in a range of
signal processing/computing-type operations, such as implementing logic,
providing synaptic and neuron-like mimics, and performing analogue signal
processing in non-von-Neumann architectures",1805.02100v1
2017-03-10,Unipolar resistive switching in cobalt titanate thin films,"We report giant resistive switching of an order of 104, long-time charge
retention characteristics up to 104 s, non-overlapping SET and RESET voltages,
ohmic in low resistance state (LRS) and space charge limited current (SCLC)
mechanism in high resistance state (HRS) properties in polycrystalline
perovskite Cobalt Titanate (CoTiO3 ~ CTO) thin films. Impedance spectroscopy
study was carried out for both LRS and HRS states which illustrates that only
bulk resistance changes after resistance switching, however, there is a small
change (<10% which is in pF range) in the bulk capacitance value in both
states. These results suggest that in LRS state current filaments break the
capacitor in many small capacitors in a parallel configuration which in turn
provides the same capacitance in both states even there was 90 degree changes
in phase-angle and an order of change in the tangent loss.",1703.03662v1
2015-04-21,The question of intrinsic origin of the metal-insulator transition in i-AlPdRe quasicrystal,"The icosahedral (i-) AlPdRe is the most resistive quasicrystalline alloy
discovered so far. Resistivities ($\rho$) of $1\Omega cm$ at 4K and correlated
resistance ratios ($RRR = \rho_{4K}/\rho_{300K}$) of more than 200 are observed
in polycrystalline samples. These values are two orders of magnitude larger
than for the isomorphous i-AlPdMn phase. We discuss here the controversial
microscopic origin of the i-AlPdRe alloy electrical specificity. It has been
proposed that the high resistivity values are due to extrinsic parameters, such
as secondary phases or oxygen contamination. From comprehensive measurements
and data from the literature including electronic transport correlated with
micro structural and micro chemical analysis, we show that on the contrary
there is mounting evidence in support of an origin intrinsic to the i-phase.
Similarly to the other quasicrystalline alloys, the electrical resistivity of
the i-AlPdRe samples depends critically on minute changes in the structural
quality and chemical composition. The low resistivity in i-AlPdRe single-grains
compared to polycrystaline samples can be explained by difference in chemical
composition, heterogeneity and thermal treatment.",1504.05464v1
2023-04-08,Novel resistive charge-multipliers for dual-phase LAr-TPCs: towards stable operation at higher gains,"Cryogenic versions of Resistive WELL (RWELL) and Resistive Plate WELL
(RPWELL) detectors have been developed, aimed at stable avalanche
multiplication of ionization electrons in dual-phase TPCs. In the RWELL, a thin
resistive layer deposited on top of an insulator is inserted in between the
electron multiplier (THGEM) and the readout anode; in the RPWELL, a resistive
plate is directly coupled to the THGEM. Radiation-induced ionization electrons
in the liquid are extracted into the gaseous phase. They drift into the THGEM's
holes where they undergo charge multiplication. Embedding resistive materials
into the multiplier proved to enhance operation stability due to the mitigation
of electrical discharges - thus allowing operation at higher charge gain
compared to standard THGEM (a.k.a. LEM) multipliers. We present the detector
concepts and report on the main preliminary results.",2304.04044v4
2012-02-10,What Causes High Resistivity in CdTe,"CdTe can be made semi-insulating by shallow donor doping. This is routinely
done to obtain high resistivity in CdTe-based radiation detectors. However, it
is widely believed that the high resistivity in CdTe is due to the Fermi level
pinning by native deep donors. The model based on shallow donor compensation of
native acceptors was dismissed based on the assumption that it is practically
impossible to control the shallow donor doping level so precisely that the free
carrier density can be brought below the desired value suitable for radiation
detection applications. In this paper, we present our calculations on carrier
statistics and energetics of shallow donors and native defects in CdTe. Our
results show that the shallow donor can be used to reliably obtain high
resistivity in CdTe. Since radiation detection applications require both high
resistivity and good carrier transport, one should generally use shallow donors
and shallow acceptors for carrier compensation and avoid deep centers that are
effective carrier traps.",1202.2255v1
2003-05-17,Saturation of electrical resistivity,"Resistivity saturation is observed in many metallic systems with a large
resistivity, i.e., when the resistivity has reached a critical value, its
further increase with temperature is substantially reduced. This typically
happens when the apparent mean free path is comparable to the interatomic
separations - the Ioffe-Regel condition. Recently, several exceptions to this
rule have been found. Here, we review experimental results and early theories
of resistivity saturation. We then describe more recent theoretical work,
addressing cases both where the Ioffe-Regel condition is satisfied and where it
is violated. In particular we show how the (semiclassical) Ioffe-Regel
condition can be derived quantum-mechanically under certain assumptions about
the system and why these assumptions are violated for high-Tc cuprates and
alkali-doped fullerides.",0305412v1
2004-07-06,"High pressure effects on the electrical resistivity behavior of the Kondo lattice, YbPd2Si2","We report the influence of external pressure (P= up to 8 GPa) on the
temperature dependence of electrical resistivity of a Yb-based Kondo lattice,
YbPd2Si2, which does not undergo magnetic ordering under ambient pressure
condition. There are qualitative changes in the temperature dependence of
electrical resistivity due to the application of external pressure. While the
resistivity is found to vary quadratically below 15 K (down to 45 mK)
characteristic of Fermi-liquids, a drop is observed below 0.5 K for P= 1 GPa.
Since the resistance values do not attain zero, we are attempted to attribute
this drop to magnetic ordering, rather than to superconductivity. The
temperature at which this fall occurs goes through a peak as a function of P (8
K for2 GPa and about 5 K at higher pressures). mimicking Doniach's magnetic
phase diagram. We conclude that this is one of the few Yb-based stoichiometric
materials, in which one can travers from valence fluctuation to magnetic
ordering by the application of external pressure.",0407125v1
2014-08-19,Effect of silicon resistivity on its porosification using metal induced chemical etching,"A comparison of porous structures formed from silicon (Si) wafers with
different resistivities has been reported here based on the morphological
studies carried out using scanning electron microscope (SEM). The porous Si
samples have been prepared using metal induced etching (MIE) technique from two
different Si wafers having two different resistivities. It is observed that
porous Si containing well aligned Si nanowires are formed from high resistivity
(1-20 $\Omega$cm) Si wafer whereas interconnected pores or cheese like
structures are formed from low resistivity (0.02 $\Omega$cm ) Si wafers after
MIE. An explanation for the different porosification processes has also been
proposed based on the initial doping level where number of dopants seems to be
playing an important role on the etching process. Visible photoluminescence
have been observed from all the porous samples possibly due to quantum
confinement effect.",1408.4314v1
2020-09-07,Tuneable Magneto-Resistance by Severe Plastic Deformation,"Bulk metallic samples were synthesized from different binary powder mixtures
consisting of elemental Cu, Co, and Fe using severe plastic deformation. Small
particles of the ferromagnetic phase originate in the conductive Cu phase,
either by incomplete dissolution or by segregation phenomena during the
deformation process. These small particles are known to give rise to granular
giant magnetoresistance. Taking advantage of the simple production process, it
is possible to perform a systematic study on the influence of processing
parameters and material compositions on the magneto-resistance. Furthermore, it
is feasible to tune the magnetoresistive behavior as a function of the
specimens chemical composition. It was found that specimens of low
ferromagnetic content show an almost isotropic drop in resistance in a magnetic
field. With increasing ferromagnetic content, percolating ferromagnetic phases
cause an anisotropy of the magnetoresistance. By changing the parameters of the
high pressure torsion process, i.e., sample size, deformation temperature, and
strain rate, it is possible to tailor the magnitude of giant
magneto-resistance. A decrease in room temperature resistivity of approx. 3.5%
was found for a bulk specimen containing an approximately equiatomic fraction
of Co and Cu.",2009.02952v1
2017-11-22,High Efficiency Thin Film Superlattice Thermoelectric Cooler Modules Enabled by Low Resistivity Contacts,"V-telluride superlattice thin films have shown promising performance for
on-chip cooling devices. Recent experimental studies have indicated that device
performance is limited by the metal/semiconductor electrical contacts. One
challenge in realizing a low resistivity contacts is the absence of fundamental
knowledge of the physical and chemical properties of interfaces between metal
and V-telluride materials. Here we present a combination of experimental and
theoretical efforts to understand, design and harness low resistivity contacts
to V-tellurides. Ab initio calculations are used to explore the effects of
interfacial structure and chemical compositions on the electrical contacts, and
an ab initio based macroscopic model is employed to predict the fundamental
limit of contact resistivity as a function of both carrier concentration and
temperature. Under the guidance of theoretical studies, we develop an
experimental approach to fabricate low resistivity metal contacts to
V-telluride thin film superlattices, achieving a 100-fold reduction compared to
previous work. Interfacial characterization and analysis using both scanning
transmission electron microscopy and energy-dispersive x-ray spectroscopy show
the unusual interfacial morphology and the potential for further improvement in
contact resistivity. Finally, we harness the improved contacts to realize an
improved high-performance thermoelectric cooling module.",1711.08481v1
2000-02-17,Ion-Beam Induced Current in High-Resistance Materials,"The peculiarities of electric current in high-resistance materials, such as
semiconductors or semimetals, irradiated by ion beams are considered. It is
shown that after ion--beam irradiation an unusual electric current may arise
directed against the applied voltage. Such a negative current is a transient
effect appearing at the initial stage of the process. The possibility of using
this effect for studying the characteristics of irradiated materials is
discussed. A new method for defining the mean projected range of ions is
suggested.",0002264v1
2021-11-15,Resistive-nanoindentation on gold: Experiments and modeling of the electrical contact resistance,"This paper reports the experimental, analytical, and numerical study of
resistive-nanoindentation tests performed on gold samples (bulk and thin film).
First, the relevant contributions to electrical contact resistance are
discussed and analytically described. A brief comparison of tests performed on
gold and on natively oxidized metals highlights the high reproducibility and
the voltage-independence of experiments on gold(thanks to its oxide-free
surface). Then, the evolution of contact resistance during nanoindentation is
fully explained in terms of electronic transport regimes: starting from
tunneling, electronic transport is then driven by ballistic conduction before
ending with pure diffusive conduction. The corresponding analytical
expressions, as well as their validity domains, are determined and compared
with experimental data,showing excellent agreement. From there, focus is made
on the diffusive regime. Resistive-nanoindentation outputs are fully described
by analytical and finite-element modeling. The developed numerical framework
allows a better understanding of the main parameters: it first assesses the
technique capabilities (validity domains, sensitivity to tip defect,
sensitivity to rheology, effect of an oxide layer, and so on), butit also
validates the different assumptions made on current line distribution. Finally,
it is shown that a simple calibration procedure allows a well-resolved
monitoring of the contact area during resistive-nanoindentation performed on
samples with complex rheologies (ductile thin film on an elastic substrate).
Comparison to analytical and numerical approaches highlights the strength of
resistive-nanoindentation for continuous area monitoring.",2111.15474v1
2023-08-09,Observation of abnormal resistance-temperature behavior along with diamagnetic transition in Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O-based composite,"Recently, Sukbae Lee et al.reported that material
Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O (LK-99) has a series of characteristics of room
temperature superconductors, including diamagnetic transition, resistance jump,
nearly zero-resistance, magnetic field-dependent IV characteristics and so on
(10.6111/JKCGCT.2023.33.2.061, arXiv:2307.12008, arXiv:2307.12037). However,
whether LK-99 is really a room temperature superconductor is still
controversial. On the one hand, some people think that the relatively weak
diamagnetism of LK-99 reported by Sukbae Lee et al. is not the Meissner effect.
On the other hand, there are doubts about the authenticity of its
zero-resistance test results. Global replication studies have shown that LK-99
does have a large diamagnetic (arXiv:2308.01516), and also found a
zero-resistance behavior at a low temperature of 110 $^\circ$K
(arXiv:2308.01192). However, up to now, there is still no direct reproducible
evidence to support Sukbae Lee et al.'s conclusion that LK-99 is a room
temperature superconductor. Here, a distinct resistance jump was observed at
about 387 $^\circ$K under ambient pressure in our experiment for unclear reason
including possible impurity's contribution. The overall resistance of the test
LK-99 sample still shows semiconductivity, and the resistance cannot really
drop to zero. Our findings indicate that to identify the true potential of
LK-99, high quality crystals without impurity are very important.",2308.05001v1
1995-12-14,Vortex structure and resistive transitions in high-Tc superconductors,"The nature of the resistive transition for a current applied parallel to the
magnetic field in high-Tc materials is investigated by numerical simulation on
the three dimensional Josephson junction array model. It is shown by using
finite size scaling that for samples with disorder the critical temperature Tp
for the c axis resistivity corresponds to a percolation phase transition of
vortex lines perpendicularly to the applied field. The value of Tp is higher
than the critical temperature for j perpendicular to H, but decreases with the
thickness of the sample and with anisotropy. We predict that critical behavior
around Tp should reflect in experimentally accessible quantities, as the I-V
curves.",9512003v1
2010-06-26,Stabilizing the forming process in unipolar resistance switching using an improved compliance current limiter,"The high reset current IR in unipolar resistance switching now poses major
obstacles to practical applications in memory devices. In particular, the first
IR-value after the forming process is so high that the capacitors sometimes do
not exhibit reliable unipolar resistance switching. We found that the
compliance current Icomp is a critical parameter for reducing IR-values. We
therefore introduced an improved, simple, easy to use Icomp-limiter that
stabilizes the forming process by drastically decreasing current overflow, in
order to precisely control the Icomp- and subsequent IR-values.",1006.5132v1
2011-07-06,Hysteretic magnetic pinning and reversible resistance switching in High-Tc superconductor/ferromagnet multilayers,"We study a high-TC superconducting (YBa2Cu3O7-d) / ferromagnetic (Co/Pt
multilayer) hybrid which exhibits resistance switching driven by the magnetic
history: depending on the direction of the external field, a pronounced
decrease or increase of the mixed-state resistance is observed as magnetization
reversal occurs within the Co/Pt multilayer. We demonstrate that stray magnetic
fields cause these effects via i) creation of vortices/antivortices and ii)
magnetostatic pinning of vortices that are induced by the external field.",1107.1122v1
2017-05-11,The role of contact resistance in graphene field-effect devices,"The extremely high carrier mobility and the unique band structure, make
graphene very useful for field-effect transistor applications. According to
several works, the primary limitation to graphene based transistor performance
is not related to the material quality, but to extrinsic factors that affect
the electronic transport properties. One of the most important parasitic
element is the contact resistance appearing between graphene and the metal
electrodes functioning as the source and the drain. Ohmic contacts to graphene,
with low contact resistances, are necessary for injection and extraction of
majority charge carriers to prevent transistor parameter fluctuations caused by
variations of the contact resistance. The International Technology Roadmap for
Semiconductors, toward integration and down-scaling of graphene electronic
devices, identifies as a challenge the development of a CMOS compatible process
that enables reproducible formation of low contact resistance. However, the
contact resistance is still not well understood despite it is a crucial barrier
towards further improvements. In this paper, we review the experimental and
theoretical activity that in the last decade has been focusing on the reduction
of the contact resistance in graphene transistors. We will summarize the
specific properties of graphene-metal contacts with particular attention to the
nature of metals, impact of fabrication process, Fermi level pinning, interface
modifications induced through surface processes, charge transport mechanism,
and edge contact formation.",1705.04025v1
2022-09-13,Unconventional Resistivity Scaling in Topological Semimetal CoSi,"Nontrivial band topologies in semimetals lead to robust surface states that
can contribute dominantly to the total conduction. This may result in reduced
resistivity with decreasing feature size contrary to conventional metals, which
may highly impact the semiconductor industry. Here we study the resistivity
scaling of a representative topological semimetal CoSi using realistic band
structures and Green's function methods. We show that there exists a critical
thickness d_c dividing different scaling trends. Above d_c, when the defect
density is low such that surface conduction dominates, resistivity reduces with
decreasing thickness; when the defect density is high such that bulk conduction
dominates, resistivity increases in as conventional metals. Below d_c, the
persistent remnants of the surface states give rise to decreasing resistivity
down to the ultrathin limit, unlike in topological insulators. The observed
CoSi scaling can apply to broad classes of topological semimetals, providing
guidelines for materials screening and engineering. Our study shows that
topological semimetals bear the potential of overcoming the resistivity scaling
challenges in back-end-of-line interconnect applications.",2209.06135v1
2019-10-31,Tackling Challenges in Seebeck Coefficient Measurement of Ultra-High Resistance Samples with an AC Technique,"Seebeck coefficient is a widely-studied semiconductor property. Conventional
Seebeck coefficient measurements are based on DC voltage measurement. Normally
this is performed on samples with low resistances below a few Mohm level.
Meanwhile, certain semiconductors are highly intrinsic and resistive, many
examples can be found in optical and photovoltaic materials. The hybrid halide
perovskites that have gained extensive attention recently are a good example.
Few credible studies exist on the Seebeck coefficient of, CH3NH3PbI3, for
example. We report here an AC technique based Seebeck coefficient measurement,
which makes high quality voltage measurement on samples with resistances up to
100Gohm. This is achieved through a specifically designed setup to enhance
sample isolation and reduce meter loading. As a demonstration, we performed
Seebeck coefficient measurement of a CH3NH3PbI3 thin film at dark and found S =
+550 microV/K. Such property of this material has not been successfully studied
before.",1910.14205v1
2021-04-03,Resistive switching of tetraindolyl derivative in ultrathin films: A potential candidate for non-volatile memory applications,"Bipolar resistive switching using organic molecule is very promising for
memory application owing to their advantages like simple device structure, low
manufacturing cost, their stability and flexibility etc. Herein we report
Langmuir-Blodgett and spin-coated film based bipolar resistive switching
devices using organic material indole derivative. Pressure - area per molecule
isotherm, Brewster Angle Microscopy, Atomic Force Microscopy and Scanning
Electron Microscopy were used to have an idea about organization and morphology
of the organic material onto thin film. Based on device structure and
measurement protocol it is observed that the device made up of 1 shows
non-volatile Resistive Random Access Memory behaviour with very high memory
window, data sustainability and repeatability.Oxidation-reduction process as
well as electric field driven conduction are the key behind such switching
behaviour.Due to very good data retention, repeatability, stability and high
device yield the switching device designed using compound 1may be a potential
candidate for memory applications.",2104.01298v1
2021-06-05,On the anomalous low-resistance state and exceptional Hall component in hard-magnetic Weyl nanoflakes,"Magnetic topological materials, which combine magnetism and topology, are
expected to host emerging topological states and exotic quantum phenomena. In
this study, with the aid of greatly enhanced coercive fields in high-quality
nanoflakes of the magnetic Weyl semimetal Co3Sn2S2, we investigate anomalous
electronic transport properties that are difficult to reveal in bulk Co3Sn2S2
or other magnetic materials. When the magnetization is antiparallel to the
applied magnetic field, the low longitudinal resistance state occurs, which is
in sharp contrast to the high resistance state for the parallel case.
Meanwhile, an exceptional Hall component that can be up to three times larger
than conventional anomalous Hall resistivity is also observed for transverse
transport. These anomalous transport behaviors can be further understood by
considering nonlinear magnetic textures and the chiral magnetic field
associated with Weyl fermions, extending the longitudinal and transverse
transport physics and providing novel degrees of freedom in the spintronic
applications of emerging topological magnets.",2106.02906v1
2023-08-30,Chemical heterogeneity enhances hydrogen resistance in high-strength steels,"When H, the lightest, smallest and most abundant atom in the universe, makes
its way into a high-strength alloy (>650 MPa), the material's load-bearing
capacity is abruptly lost. This phenomenon, known as H embrittlement, was
responsible for the catastrophic and unpredictable failure of large engineering
structures in service. The inherent antagonism between high strength
requirements and H embrittlement susceptibility strongly hinders the design of
lightweight yet reliable structural components needed for carbon-free
hydrogen-propelled industries and reduced-emission transportation solutions.
Inexpensive and scalable alloying and microstructural solutions that enable
both, an intrinsically high resilience to H and high mechanical performance,
must be found. Here we introduce a counterintuitive strategy to exploit
typically undesired chemical heterogeneity within the material's microstructure
that allows the local enhancement of crack resistance and local H trapping,
thereby enhancing the resistance against H embrittlement. We deploy this
approach to a lightweight, high-strength steel and produce a high-number
density Mn-rich zones dispersed within the microstructure. These solute-rich
buffer regions allow for local micro-tuning of the phase stability, arresting
H-induced microcracks thus interrupting the H-assisted damage evolution chain,
regardless of how and when H is introduced and also regardless of the
underlying embrittling mechanisms. A superior H embrittlement resistance,
increased by a factor of two compared to a reference material with a
homogeneous solute distribution within each microstructure constituent, is
achieved at no expense of the material's strength and ductility.",2308.16048v1
2021-01-29,Novel design strategies for modulating conductive stretchable system response based on periodic assemblies,"Soft electronics have recently gathered considerable interest thanks to their
bio-mechanical compatibility. An important feature of such deformable
conductors is their electrical response to strain. While development of
stretchable materials with high gauge factors has attracted considerable
attention, there is a growing need for stretchable conductors whose response to
deformation can be accurately engineered to provide arbitrary resistance-strain
relationships. The rare studies addressing this issue have focused on
deterministic geometries of single rigid materials, limiting the scope of such
strategies. Herein, we introduce the novel concept of periodic stretchable
patterns combining multiple conductive materials to produce tailored responses.
Using shortest-path algorithms, we establish a computationally efficient
selection method to obtain required resistance-strain relationship. Using this
algorithm, we identify and experimentally demonstrate constant
resistance-strain responses up to 50% elongation using a single micro-textured
material. Finally, we demonstrate counter-intuitive sinusoidal responses by
integrating three materials, with interesting applications in sensing and soft
robotics.",2101.12600v1
2009-03-07,Correlation between resistance fluctuations and temperature dependence of conductivity in graphene,"The weak temperature dependence of the resistance R(T) of monolayer
graphene1-3 indicates an extraordinarily high intrinsic mobility of the charge
carriers. Important complications are the presence of mobile scattering centres
that strongly modify charge transport, and the presence of strong mesoscopic
conductance fluctuations that, in graphene, persist to relatively high
temperatures4,5. In this Letter, we investigate the surprisingly varied changes
in resistance that we find in graphene flakes as temperature is lowered below
70 K. We propose that these changes in R(T) arise from the temperature
dependence of the scattered electron wave interference that causes the
resistance fluctuations. Using the field effect transistor configuration, we
verify this explanation in detail from measurements of R(T) by tuning to
different gate voltages corresponding to particular features of the resistance
fluctuations. We propose simple expressions that model R(T) at both low and
high charge carrier densities.",0903.1334v1
2021-04-20,Accelerated Discovery of Molten Salt Corrosion-resistant Alloy by High-throughput Experimental and Modeling Methods Coupled to Data Analytics,"Insufficient availability of molten salt corrosion-resistant alloys severely
limits the fruition of a variety of promising molten salt technologies that
could otherwise have significant societal impacts. To accelerate alloy
development for molten salt applications and develop fundamental understanding
of corrosion in these environments, here we present an integrated approach
using a set of high-throughput alloy synthesis, corrosion testing, and modeling
coupled with automated characterization and machine learning. By using this
approach, a broad range of Cr-Fe-Mn-Ni alloys were evaluated for their
corrosion resistances in molten salt simultaneously demonstrating that
corrosion-resistant alloy development can be accelerated by thousands of times.
Based on the obtained results, we unveiled a sacrificial mechanism in the
corrosion of Cr-Fe-Mn-Ni alloys in molten salts which can be applied to protect
the less unstable elements in the alloy from being depleted, and provided new
insights on the design of high-temperature molten salt corrosion-resistant
alloys.",2104.10235v1
2014-12-05,Resistance switching devices based on amorphous insulator-metal thin films,"Nanometallic devices based on amorphous insulator-metal thin films are
developed to provide a novel non-volatile resistance-switching random-access
memory (RRAM). In these devices, data recording is controlled by a bipolar
voltage, which tunes electron localization length, thus resistivity, through
electron trapping/detrapping. The low-resistance state is a metallic state
while the high-resistance state is an insulating state, as established by
conductivity studies from 2K to 300K. The material is exemplified by a Si3N4
thin film with randomly dispersed Pt or Cr. It has been extended to other
materials, spanning a large library of oxide and nitride insulator films,
dispersed with transition and main-group metal atoms. Nanometallic RRAMs have
superior properties that set them apart from other RRAMs. The critical
switching voltage is independent of the film thickness/device
area/temperature/switching speed. Trapped electrons are relaxed by
electron-phonon interaction, adding stability which enables long-term memory
retention. As electron-phonon interaction is mechanically altered, trapped
electron can be destabilized, and sub-picosecond switching has been
demonstrated using an electromagnetically generated stress pulse. AC impedance
spectroscopy confirms the resistance state is spatially uniform, providing a
capacitance that linearly scales with area and inversely scales with thickness.
The spatial uniformity is also manifested in outstanding uniformity of
switching properties. Device degradation, due to moisture, electrode oxidation
and dielectrophoresis, is minimal when dense thin films are used or when a
hermetic seal is provided. The potential for low power operation, multi-bit
storage and complementary stacking have been demonstrated in various RRAM
configurations.",1412.2083v1
2003-11-05,"Thermoelectric power of Bi and Bi(1-x)Te(x), x=0.0014,in porous Vycor glass","Semiconductor quantum wires constitute a promising thermoelectric material
because of the increase of the electronic density of states in low-dimensional
materials. We studied the magnetic-field-dependent resistance and Seebeck
coefficient of a high-density network of 6-nm-diameter wires of Bi and of
Bi(1-x)Te(x), x=0.0014, in porous Vycor glass. The resistance R increases as
temperature decreases from 300 K down to 0.3 K for both composites. However, in
contrast to recent results that demonstrate the semiconducting behavior of the
resistance and very large enhancements of the thermoelectric power of
composites containing Bi nanowires with diameters of 9 and 15 nm, we find that
the resistance is not thermally activated and that the thermoelectric power of
the composites is of the same order of magnitude as the thermoelectric power of
bulk Bi. Our results are consistent with the nanowires having carrier density
that is enhanced by surface effects.",0311112v1
2009-06-27,Resistive switching in nanogap systems on SiO2 substrates,"Voltage-controlled resistive switching is demonstrated in various gap systems
on SiO2 substrate. The nanosized gaps are made by different means using
different materials including metal, semiconductor, and metallic nonmetal. The
switching site is further reduced by using multi-walled carbon nanotubes and
single-walled carbon nanotubes. The switching in all the gap systems shares the
same characteristics. This independence of switching on the material
compositions of the electrodes, accompanied by observable damage to the SiO2
substrate at the gap region, bespeaks the intrinsic switching from
post-breakdown SiO2. It calls for caution when studying resistive switching in
nanosystems on oxide substrates, since oxide breakdown extrinsic to the
nanosystem can mimic resistive switching. Meanwhile, the high ON/OFF ratio
(10E5), fast switching time (2 us, test limit), durable cycles demonstrated
show promising memory properties. The intermediate states observed reveal the
filamentary conduction nature.",0906.5100v1
2010-02-12,Experimental Study of Resistive Bistability in Metal Oxide Junctions,"We have studied resistive bistability (memory) effects in junctions based on
metal oxides, with a focus on sample-to-sample reproducibility which is
necessary for the use of such junctions as crosspoint devices of hybrid
CMOS/nanoelectronic circuits. Few-nm-thick layers of NbOx, CuOx and TiOx have
been formed by thermal and plasma oxidation, at various deposition and
oxidation conditions, both with or without rapid thermal post-annealing (RTA).
The resistive bistability effect has been observed for all these materials,
with particularly high endurance (over 1000 switching cycles) obtained for
single-layer TiO2 junctions, and the best reproducibility reached for
multi-layer junctions of the same material. Fabrication optimization has
allowed us to improve the OFF/ON resistance ratio to about 1000, but the
sample-to-sample reproducibility is so far lower than that required for large
scale integration.",1002.2650v1
2018-03-30,Reliability assessment in advanced nanocomposite materials for orthopaedic applications,"Alumina-zirconia nano-composites were recently developed as alternative
bearing materials for orthopedics. Previous, preliminary reports show that such
alumina-zirconia nanocomposites exhibit high crack resistance and low wear
rate. In this paper, additional information is given in terms of wear, crack
resistance and ageing behaviour: femoral heads are inspected after 7 million
cycles of wear testing on a hip simulator, crack resistance is measured and
compared to other ceramics used today in orthopedics, slow crack growth is
reported under static and cyclic fatigue, and aging resistance is assessed. We
also report on the load to failure of femoral heads prototypes during
compression tests. This overall reliability assessment ensures a potential
future development for these kinds of new nanocomposites in the orthopedic
field.",1804.08702v1
2018-10-18,Topological Hall effect in thin films of Mn$_{1.5}$PtSn,"Spin chirality in metallic materials with non-coplanar magnetic order can
give rise to a Berry phase induced topological Hall effect. Here, we report the
observation of a large topological Hall effect in high-quality films of
Mn$_{1.5}$PtSn that were grown by means of magnetron sputtering on MgO(001).
The topological Hall resistivity is present up to $\mu_{0}H \approx 4~$T below
the spin reorientation transition temperature, $T_{s}=185$~K. We find, that the
maximum topological Hall resistivity is of comparable magnitude as the
anomalous Hall resistivity. Owing to the size, the topological Hall effect is
directly evident prior to the customarily performed subtraction of magnetometry
data. Further, we underline the robustness of the topological Hall effect in
Mn\textsubscript{2-x}PtSn by extracting the effect for multiple stoichiometries
(x~=~0.5, 0.25, 0.1) and film thicknesses (t = 104, 52, 35~nm) with maximum
topological Hall resistivities between $0.76~\mu\Omega$cm and
$1.55~\mu\Omega$cm at 150~K.",1810.08232v1
2019-06-19,Origin of current-controlled negative differential resistance modes and the emergence of composite characteristics with high complexity,"Current-controlled negative differential resistance has significant potential
as a fundamental building block in brain-inspired neuromorphic computing.
However, achieving desired negative differential resistance characteristics,
which is crucial for practical implementation, remains challenging due to
little consensus on the underlying mechanism and unclear design criteria. Here,
we report a material-independent model of current-controlled negative
differential resistance to explain a broad range of characteristics, including
the origin of the discontinuous snap-back response observed in many transition
metal oxides. This is achieved by explicitly accounting for a non-uniform
current distribution in the oxide film and its impact on the effective circuit
of the device, rather than a material-specific phase transition. The
predictions of the model are then compared with experimental observations to
show that the continuous S-type and discontinuous snap-back characteristics
serve as fundamental building blocks for composite behaviour with higher
complexity. Finally, we demonstrate the potential of our approach for
predicting and engineering unconventional compound behaviour with novel
functionality for emerging electronic and neuromorphic computing applications.",1907.02651v1
2022-05-06,Interfacial resistive switching by multiphase polarization in ion-intercalation nanofilms,"Nonvolatile resistive-switching (RS) memories promise to revolutionize
hardware architectures with in-memory computing. Recently, ion-interclation
materials have attracted increasing attention as potential RS materials for
their ion-modulated electronic conductivity. In this Letter, we propose RS by
multiphase polarization (MP) of ion-intercalated thin films between
ion-blocking electrodes, in which interfacial phase separation triggered by an
applied voltage switches the electron-transfer resistance. We develop an
electrochemical phase-field model for simulations of coupled ion-electron
transport and ion-modulated electron-transfer rates and use it to analyze the
MP switching current and time, resistance ratio, and current-voltage response.
The model is able to reproduce the complex cyclic voltammograms of lithium
titanate (LTO) memristors, which cannot be explained by existing models based
on bulk dielectric breakdown. The theory predicts the achievable switching
speeds for multiphase ion-intercalation materials and could be used to guide
the design of high-performance MP-based RS memories.",2205.02980v2
2023-09-13,Amorphous VO$_x$ films with high temperature coefficient of the resistivity grown by reactive e-beam evaporation of V metal,"Amorphous VO$_x$ films without a hysteretic phase transition are stable with
respect to thermal cycling and highly demanded as sensitive elements of the
resistive thermometers and microbolometers. In this paper we present simple and
low-temperature growth of amorphous vanadium oxide films by reactive electron
beam evaporation of vanadium metal in $\sim 10^{-4}$ mBar oxygen atmosphere.
The temperature coefficient of the resistivity (TCR) of the films is weakly
sensitive to substrate material and temperature and could be tuned by oxygen
pressure in the growth chamber up to -2.2\% /K. The resistivity value is stable
for months. It depends on the substrate material and substrate temperature
during the evaporation. Simplicity and controllability of the method should
lead to various laboratory and industrial applications.",2309.07036v1
2007-01-02,Negative Differential Resistance of Electrons in Graphene Barrier,"The graphene is a native two-dimensional crystal material consisting of a
single sheet of carbon atoms. In this unique one-atom-thick material, the
electron transport is ballistic and is described by a quantum relativistic-like
Dirac equation rather than by the Schrodinger equation. As a result, a graphene
barrier behaves very differently compared to a common semiconductor barrier. We
show that a single graphene barrier acts as a switch with a very high on-off
ratio and displays a significant differential negative resistance, which
promotes graphene as a key material in nanoelectronics.",0701011v1
2019-10-07,Growth and Characterization of Polycrystalline NbO2 Thin Films on Crystalline and Amorphous Substrates,"NbO2 is a potential material for nanometric memristor devices, both in the
amorphous and the crystalline form. We fabricated NbO2 thin films using
RF-magnetron sputtering from a stoichiometric target. The as-deposited films
were amorphous regardless of the sputtering parameters. Post deposition vacuum
annealing of the films was necessary to achieve crystallinity. A high degree of
crystallinity was obtained by optimizing annealing duration and temperature.
The resistivity of the material increases as it undergoes a structural
transition from amorphous to crystalline with the crystalline films being one
order of magnitude more resistive.",1910.02824v1
2004-04-18,Anisotropy of superconductivity of as-grown MgB$_2$ thin films by molecular beam epitaxy,"Superconducting thin films of magnesium diboride (MgB$_2$) were prepared on
MgO (001) substrate by a molecular beam epitaxy (MBE) method with the
co-evaporation conditions of low deposition rate in ultra-high vacuum. The
structural and physical properties of the films were studied by RHEED, XRD,
XPS, resistivity and magnetization measurements.All films demonstrated
superconductivity without use of any post-annealing process.The highest {\it
T}$_{c,onset}$ determined by resistivity measurement was about 33K in the
present samples.Anisotropic superconducting properties were evaluated by the
resistivity and magnetic measurements.We will discuss the anisotropy of
superconductivity for as-grown MgB$_2$ thin films.",0404415v1
2005-08-02,Epitaxial growth and transport properties of Nb-doped SrTiO$_{3}$ thin films,"Nb-doped SrTiO$_{3}$ epitaxial thin films have been prepared on (001)
SrTiO$_{3}$ substrates using pulsed laser deposition. A high substrate
temperature ($>1000^{\circ}{C}$) was found to be necessary to achieve
2-dimensional growth. Atomic force microscopy reveals atomically flat surfaces
with 3.9 \AA $ $ steps. The films show a metallic behavior, residual
resistivity ratios between 10 and 100, and low residual resistivity of the
order of 10$^{-4}$$\Omega$cm. At 0.3 K, a sharp superconducting transition,
reaching zero resistance, is observed.",0508073v1
2011-11-07,Monte Carlo Study of Magnetic Resistivity in Semiconducting MnTe,"We investigate in this paper properties of the spin resistivity in the
magnetic semiconducting MnTe of NiAs structure. MnTe is a crossroad
semiconductor with a large band gap. It is an antiferromagnet with the N\'eel
temperature around 310K. Due to this high N\'eel temperature, there are many
applications using its magnetic properties. The method we use here is the Monte
Carlo simulation in which we take into account the interaction between
itinerant spins and lattice Mn spins. Our results show a very good agreement
with experiments on the shape of the spin resistivity near the N\'eel
temperature.",1111.1507v1
2016-11-21,Ramsey Interferometry of Particle-Hole Pairs in Tunnel Junctions,"We present a method to probe real-time dynamics in quantum mesoscopic systems
using Ramsey interferometry. This allows us to explore the effect of
interactions on quasi-particles in the time domain. We investigate the
dephasing effects of an ohmic environment on an electron-hole pair in a tunnel
junction. We show that dynamical Coulomb blockade phenomena can be observed for
resistances much smaller than the quantum of resistance. Moreover, the
crossover between high and low impedance limits can be probed for a constant
resistance by a proper control of the voltage modulation.",1611.06738v1
2010-11-08,Normal state resistivity of Ba$_{1-x}$K$_x$Fe$_2$As$_2$: evidence for multiband strong-coupling behavior,"We present theoretical analysis of the normal state resistivity in multiband
superconductors in the framework of Eliashberg theory. The results are compared
with measurements of the temperature dependence of normal state resistivity of
high-purity Ba$_{0.68}$K$_{0.32}$Fe$_{2}$As$_{2}$ single crystals with the
highest reported transition temperature $T_c$ = 38.5 K. The experimental data
demonstrate strong deviations from the Bloch-Gr\""{u}neisen behavior, namely the
tendency to saturation of the resistivity at high temperatures. The observed
behavior of the resistivity is explained within the two band scenario when the
first band is strongly coupled and relatively clean, while the second band is
weakly coupled and is characterized by much stronger impurity scattering.",1011.1900v3
2014-03-18,Electron-Phonon Interactions and the Intrinsic Electrical Resistivity of Graphene,"We present a first-principles study of the temperature- and density-dependent
intrinsic electrical resistivity of graphene. We use density-functional theory
and density-functional perturbation theory together with very accurate Wannier
interpolations to compute all electronic and vibrational properties and
electron-phonon coupling matrix elements; the phonon-limited resistivity is
then calculated within a Boltzmann-transport approach. An effective
tight-binding model, validated against first-principles results, is also used
to study the role of electron-electron interactions at the level of many-body
perturbation theory. The results found are in excellent agreement with recent
experimental data on graphene samples at high carrier densities and elucidate
the role of the different phonon modes in limiting electron mobility. Moreover,
we find that the resistivity arising from scattering with transverse acoustic
phonons is 2.5 times higher than that from longitudinal acoustic phonons. Last,
high-energy, optical, and zone-boundary phonons contribute as much as acoustic
phonons to the intrinsic electrical resistivity even at room temperature and
become dominant at higher temperatures.",1403.4603v1
2018-06-03,Influence of hydrogen on electron-phonon coupling and intrinsic electrical resistivity in zirconium: a first-principles study,"The paper presents the first-principle calculation of the electron-phonon
coupling and the temperature dependence of the intrinsic electrical resistivity
of the zirconium-hydrogen system with various hydrogen concentrations. The
nature of the anomalous decrease in the electrical resistivity of the Zr-H
system with the increase of hydrogen concentration (at the high concentrations
of H/Zr$>$1.5) was studied. It was found that the hydrogen concentration, where
the resistivity starts to decrease, is very close to the critical concentration
of the $\delta-\varepsilon$ phase transition. It was shown that the tetragonal
lattice distortion due to the $\delta-\varepsilon$ phase transition of the Zr-H
system eliminates imaginary phonon frequencies and the strong electron-phonon
coupling of the $\delta$ phase and, as a result, leads to the reduction of the
electrical resistivity of the Zr-H system at a high hydrogen concentration.",1806.00847v3
2021-12-29,Significant reduction in semiconductor interface resistance via interfacial atomic mixing,"The contact resistance between two dissimilar semiconductors is determined by
the carrier transmission through their interface. Despite the ubiquitous
presence of interfaces, quantitative simulation of charge transport across such
interfaces is difficult, limiting the understanding of interfacial charge
transport. This work employs Green's functions to study the charge transport
across representative Si/Ge interfaces. For perfect interfaces, it is found
that the transmittance is small and the contact resistance is high, not only
because the mismatch of carrier pockets makes it hard to meet the momentum
conservation requirement, but also because of the incompatible symmetries of
the Bloch wave functions of the two sides. In contrast, atomic mixing at the
interface increases the carrier transmittance as the interface roughness opens
many nonspecular transmission channels, which greatly reduces the contact
resistance compared with the perfect interface. Specifically, we show that
disordered interfaces with certain symmetries create more nonspecular
transmission. The insights from our study will benefit the future design of
high-performance heterostructures with low contact resistance.",2112.14400v2
2005-02-26,Josephson junction decoupling is the main origin of AC resistivity in the superconducting state,"The origin of AC resistivity in the high Tc superconductors is not addressed
adequately in literature. We found out, Josephson Junction (JJ) decoupling is
the main origin of the AC resistivity in high Tc superconductors. We have
measured the AC resistivity in the superconductors in the low frequency range
by measuring the complex AC impedance of superconducting YBa2Cu3O7 (YBCO)
polycrystalline samples. Our data shows that under certain conditions when the
number density of Josephson Junctions (JJ) present in the sample and the JJ
critical current crosses a threshold value, AC resistivity in the
superconducting state keeps on increasing with lowering temperature. The
underlying mechanism is an interesting interplay of JJ coupling energy,
amplitude of the supply AC voltage and the current applied to the
superconducting sample. The effect of the applied AC current of different
frequencies and the variation of temperature were studied in detail. To find
out the exact relation between the JJ coupling energy, JJ number density,
applied AC frequency, the amplitude of AC current and the AC resistivity in the
superconductors, we have studied samples of different grain sizes, pressurized
with different pressure and sintered at different physical situations. These
results have important implications for the understanding of the origin of AC
resistivity and characterization of superconducting samples. In this paper we
also extend the capability of the AC impedance studies in superconductors for
the characterization of materials for device applications.",0502639v1
2022-08-03,Low Resistance Ohmic Contact On Epitaxial MOVPE-grown $β$-Ga$_2$O$_3$ and $β$-(Al$_x$Ga$_1-x$)$_2$ O$_3$ Films,"We report on the realization of record low resistance Ohmic contacts to
MOVPE-grown heavily Si-doped $\beta$-Ga$_2$O$_3$ and
$\beta$-(Al$_x$Ga$_1-x$)$_2$ O$_3$ epitaxial films. Transfer length measurement
(TLM) patterns were fabricated on the heavily Si-doped homoepitaxial
$\beta$-Ga$_2$O$_3$ films with electron concentration (n) ranging from 1.77 to
3.23e20 cm^-3. Record low specific contact resistance and total contact
resistance (Rc) of 1.62e-7 Ohm.cm^2 and 0.023 Ohm.mm were realized for
$\beta$-Ga$_2$O$_3$: Si films with n > 3e20 cm^-3. TLM structures were also
fabricated on heavily Si doped coherently strained $\beta$-(Al$_x$Ga$_1-x$)$_2$
O$_3$ (x=12%, 17% and 22%) films. The film with 12% Al composition (n=1.23e20
cm^-3) showed \r{ho}c of 5.85e-6 Ohm.cm^2, but it increased to 2.19e-4 Ohm.cm^2
for a layer with a 22% Al composition. Annealing the samples post metal
deposition has generally led to a decrease in contact resistance, but for high
Al content $\beta$-(Al$_x$Ga$_1-x$)$_2$ O$_3$, the contact resistance did not
change significantly after the annealing process. The low contact resistance
values measured in this work are very promising for the fabrication of high
frequency power devices.",2208.02322v1
2022-11-30,High-efficiency energy harvesting based on nonlinear Hall rectifier,"Noncentrosymmetric quantum materials can convert AC input current into DC
transverse current through the nonlinear Hall effect at zero magnetic field. We
analyze the AC-DC power conversion efficiency of such ``Hall rectifier'' and
suggest its application in wireless charging and energy harvesting. Our key
observation is that the development of Hall voltage results in a change of
longitudinal resistance, resulting in a violation of Ohm's law due to the
nonlinear Hall effect. This feedback mechanism balances the input power and the
output power and hence is crucial to understanding the power transfer from
source to load. We derive a general expression for the power conversion
efficiency in terms of material parameters, external load resistance, and input
power. As the Hall current is perpendicular to the electric field and does not
generate Joule heating by itself, we obtain high power conversion efficiency
when the Hall angle (which increases with the input power) is large and the
load resistance is optimized. Promising materials for high-efficiency Hall
rectifiers are also discussed.",2211.17219v2
2011-02-28,Introduction to bulk metallic glass composite and its recent applications,"Bulk metallic glass (BMG) materials are hot topics in recent years, not to
mention BMG matrix composites, which further improve the magnetic and
mechanical properties of BMG materials. BMG and BMG matrix materials are fast
developing and promising materials in modern industry due to their
extraordinary properties such as high strength, low density, excellent
resistibility to high temperature and corrosion. In this paper, I reviewed
processing and application of several recently developed BMG and BMG matrix
materials.",1102.5758v1
2008-05-04,Increase of the wear resistance of carbide layers deposited by Pulsed Laser Deposition in addition with an auxiliary laser,"Carbides stand out because of their high hardness and wear-resistance. Thus
these materials are often discussed for coatings of machine tools etc. Within
this work Boron Carbide (B4C) and Carbide (C) thin films were deposited on Si
(100) substrates by pulsed-laser deposition technique. In order to improve the
wear-resistance of the deposited films, we introduced a new working technique
including the application of a second excimer laser in a special working mode.
Thereby one laser was used to ablate the carbide material from a target and to
deposit the material on the substrate. The light of the second laser was
directed directly onto the substrate in order to modify the ablated material.
We report on details for film deposition and film properties determined by
Scanning Electron Microscope, Energy Dispersive X-Ray Spectroscopy, X-Ray
Diffraction, Rutherford Backscattering, Raman Spectroscopy and tribological
experiments.",0805.0430v1
2017-10-24,Lithographic performance of ZEP520A and mr-PosEBR resists exposed by electron beam and extreme ultraviolet lithography,"Pattern transfer by deep anisotropic etch is a well-established technique for
fabrication of nanoscale devices and structures. For this technique to be
effective, the resist material plays a key role and must have high resolution,
reasonable sensitivity and high etch selectivity against the conventional
silicon substrate or underlayer film. In this work, the lithographic
performance of two high etch resistance materials was evaluated: ZEP520A
(Nippon Zeon Co.) and mr-PosEBR (micro resist technology GmbH). Both materials
are positive tone, polymer-based and non-chemically amplified resists. Two
exposure techniques were used: electron beam lithography (EBL) and extreme
ultraviolet (EUV) lithography. These resists were originally designed for EBL
patterning, where high quality patterning at sub-100 nm resolution was
previously demonstrated. In the scope of this work, we also aim to validate
their extendibility to EUV for high resolution and large area patterning. To
this purpose, the same EBL process conditions were employed at EUV. The figures
of merit, i.e. dose to clear, dose to size, and resolution, were extracted and
these results are discussed systematically. It was found that both materials
are very fast at EUV (dose to clear lower than 12 mJ/cm2) and are capable of
resolving dense lines/space arrays with a resolution of 25 nm half-pitch. The
quality of patterns was also very good and the sidewall roughness was below 6
nm. Interestingly, the general-purpose process used for EBL can be extended
straightforwardly to EUV lithography with comparable high quality and yield.
Our findings open new possibilities for lithographers who wish to devise novel
fabrication schemes exploiting EUV for fabrication of nanostructures by deep
etch pattern transfer.",1710.08733v1
2016-04-14,Study of Glass and Bakelite properties as electrodes in RPCs,"India-based Neutrino Observatory (INO) collaboration is planning to build a
magnetized Iron-CALorimeter detector (ICAL) for the study of atmospheric
neutrinos. ICAL detector will be a stack of 151 layers of magnetized iron
plates interleaved with Resistive Plate Chambers (RPCs) as active detector
elements with a total mass of 50 kton. Resistive Plate Chambers are gaseous
detectors made up of two parallel electrodes of high bulk resistivity like
float glass and bakelite. These detectors are extensively used in several high
energy physics experiments since 1980s because of high count rate, excellent
time as well as spatial resolutions, simple to fabricate and operate. Due to
detector aging issue, it is necessary to characterize electrode material so as
to select appropriate electrode material before fabricating the detector. In
the present studies, we measured bulk resistivity and surface current of glass
as well as bakelite. Bulk resistivity of bakelite is ~ 100 times less than that
of glass and surface current of bakelite is higher than that of glass. Also
glass does not need any kind of surface treatment to achieve better surface
uniformity. Therefore, glass electrodes are preferred over bakelite electrodes
in most of the cases. Locally manufactured Asahi glass of ~2 mm thickness and
bakelite sheets were tested during the studies as reported in this paper before
the various stages of detector fabrication.",1604.04130v2
2023-01-11,Resistive Switching and Current Conduction Mechanisms in Hexagonal Boron Nitride Threshold Memristors with Nickel Electrodes,"The two-dimensional (2D) insulating material hexagonal boron nitride (h BN)
has attracted much attention as the active medium in memristive devices due to
its favorable physical properties, among others, a wide bandgap that enables a
large switching window. Metal filament formation is frequently suggested for
h-BN devices as the resistive switching (RS) mechanism, usually supported by
highly specialized methods like conductive atomic force microscopy (C-AFM) or
transmission electron microscopy (TEM). Here, we investigate the switching of
multilayer hexagonal boron nitride (h-BN) threshold memristors with two nickel
(Ni) electrodes through their current conduction mechanisms. Both the high and
the low resistance states are analyzed through temperature-dependent
current-voltage measurements. We propose the formation and retraction of nickel
filaments along boron defects in the h-BN film as the resistive switching
mechanism. We corroborate our electrical data with TEM analyses to establish
temperature-dependent current-voltage measurements as a valuable tool for the
analysis of resistive switching phenomena in memristors made of 2D materials.
Our memristors exhibit a wide and tunable current operation range and low
stand-by currents, in line with the state of the art in h-BN-based threshold
switches, a low cycle-to-cycle variability of 5%, and a large On/Off ratio of
10${^7}$.",2301.10158v2
2021-08-21,Resistivity size effect due to surface steps on ruthenium thin films computed with a realistic tight-binding model,"A realistic tight-binding model is developed and employed to elucidate the
resistivity size effect due to steps on Ru thin films. The resistivity of two
different film orientations, $(0001)$ and $(1 \bar{1}00)$, is computed for
transport along a $[1 1 \bar{2} 0]$ direction both for smooth surfaces and for
surfaces with monolayer-high steps. In the case of smooth films, the systems
are also studied using solutions to the Boltzmann transport equation (BTE).
Interestingly, the resistivity of $(1 \bar{1}00)$ surfaces exhibits a
significant size effect even in the absence of surface steps. When
monolayer-high steps are spaced $\sim 10$ nm apart, the resistivity is shown to
increase due to scattering from the steps. However, only a small increase was
found which cannot explain the large effect seen in recent experiments with Ru
thin films. This highlights the need for further elucidation of the resistivity
size effect. Theoretical analysis suggest that films made from materials with a
relatively large ballistic conductance per area like Ru should exhibit a
reduced resistivity size effect. This result points to Ru as a promising
interconnect material. Finally, because a very efficient algorithm for
computing resistivity based on the kernel polynomial method (KPM) is used, the
approach fulfills a need for realistic models that can span length scales
directly relevant to experimental results. The calculations described here
include films approaching $5$ nm in thickness, with in-plane distances up to
$\sim 160$ nm and $3.8\times10^{5}$ atomic sites.",2108.09424v7
2018-11-14,Linear-in-T resistivity in dilute metals: A Fermi liquid perspective,"We consider a short-range deformation potential scattering model of
electron-acoustic phonon interaction to calculate the resistivity of an ideal
metal as a function of temperature (T) and electron density (n). We consider
both 3D metals and 2D metals, and focus on the dilute limit, i.e., low
effective metallic carrier density of the system. The main findings are: (1) a
phonon scattering induced linear-in-T resistivity could persist to arbitrarily
low T in the dilute limit independent of the Debye temperature ($T_D$) although
eventually the low-T resistivity turns over to the expected Bloch-Gruneisen
(BG) behavior with $T^5$ ($T^4$) dependence, in 3D (2D) respectively; (2)
because of low values of n, the phonon-induced resistivity could be very high
in the system; (3) the resistivity shows an intrinsic saturation effect at very
high temperatures (for $T>T_D$), and in fact, decreases with increasing T above
a high crossover temperature with this crossover being dependent on both $T_D$
and n in a non-universal manner. We also provide high-T linear-in-T resistivity
results for 2D and 3D Dirac materials. Our work brings out the universal
features of phonon-induced transport in dilute metals, and we comment on
possible implications of our results for strange metals, emphasizing that the
mere observation of a linear-in-T metallic resistivity at low temperatures or a
very high metallic resistivity at high temperatures is not necessarily a reason
to invoke an underlying quantum critical strange metal behavior. We discuss the
temperature variation of the effective transport scattering rate showing that
the scattering rate could be below or above $k_BT$, and in particular, purely
coincidentally, the calculated scattering rate happens to be $k_BT$ in normal
metals with no implications for the so-called Planckian behavior.",1811.05862v2
2012-04-10,Challenges for RPCs and resistive micropattern detectors in the next few years,"Nowadays RPCs are in a booming phase: they are successfully used in many
experiments, including LHC; there are ambitious plans to use them in several
upgrade detectors and in some new experiments as well as in various
applications. The aim of this paper is to highlight the main challenges which
the RPC community may face in the next few years and which were addressed in
talks presented at this conference. Examples could be: new and difficult
requirements from experiments (and their upgrades) and applications,
optimization and improvements of the existing traditional detector designs,
improvement of their characteristics (timing /rate performance, aging, dark
current and so on), implementation of new more sensitive electronics,
investigation of new materials, development of large- area detectors. We will
also review the fast and very promising developments of another type of
resistive electrode gaseous detector -micropattern detectors having at least
one of their electrodes made of resistive materials. These innovative detectors
combine in one design the best features of RPC (spark protection) and
micropattern detectors (high granularity-high position resolution).",1204.2144v1
2021-01-28,Magnetic Field Effects on the Transport Properties of High-Tc Cuprates,"Starting from a recently proposed comprehensive theory for the high-Tc
superconductivity in cuprates, we derive a general analytic expression for the
planar resistivity, in the presence of an applied external magnetic field
$\textbf{H}$ and explore its consequences in the different phases of these
materials. As an initial probe of our result, we show it compares very well
with experimental data for the resistivity of LSCO at different values of the
applied field. We also apply our result to Bi2201 and show that the
magnetoresistivity in the strange metal phase of this material, exhibits the
$H^2$ to $H$ crossover, as we move from the weak to the strong field regime.
Yet, despite of that, the magnetoresistivity does not present a quadrature
scaling. Remarkably, the resistivity H-field derivative does scale as a
function of $\frac{H}{T}$, in complete agreement with recent magneto-transport
measurements made in the strange metal phase of cuprates \cite{Hussey2020}. We,
finally, address the issue of the $T$-power-law dependence of the resistivity
of overdoped cuprates and compare our results with experimental data for
Tl2201. We show that this provides a simple method to determine whether the
quantum critical point associated to the pseudogap temperature $T^*(x)$ belongs
to the SC dome or not.",2101.11969v1
2022-09-08,Dominance of Electron-Magnon Scattering in Itinerant Ferromagnet Fe3GeTe2,"Fe3GeTe2 is a 2-dimensional van der Waals material exhibiting itinerant
ferromagnetism upto 230 K. Here, we study aspects of scattering mechanism in
Fe3Ge2Te2 single crystals via resistivity, magneto-transport and Hall effect
measurements. The quadratic temperature dependence of electrical resistivity
below the Curie temperature hints towards the dominance of electron-magnon
scattering. A non-saturating positive magnetoresistance (MR) is observed at low
temperatures when the magnetic field is applied parallel to the sample plane.
The linear negative MR at high fields for T < TC corroborates to the
suppression in magnon population due to the damping of spin waves. In the high
temperature regime T > TC,MR can be described by the scattering from spin
fluctuations using the model described by Khosla and Fischer. Isothermal Hall
resistivity curves unveil the presence of anomalous Hall resistivity.
Correlation between MR and side jump mechanism further reveals that the
electron-magnon scattering is responsible for the side jump contribution to the
anomalous Hall effect. Our results provide a clear understanding of the role of
electron-magnon scattering on anomalous Hall effect that rules out its origin
to be the topological band structure.",2209.03555v1
2014-12-01,Novel experimental design for high pressure - high temperature electrical resistance measurements in a 'Paris-Edinburgh' large volume press,"We present a novel experimental design for high sensitivity measurements of
the electrical resistance of samples at high pressures (0-6GPa) and high
temperatures (300-1000K) in a 'Paris-Edinburgh' type large volume press.
Uniquely, the electrical measurements are carried out directly on a small
sample, thus greatly increasing the sensitivity of the measurement. The
sensitivity to even minor changes in electrical resistance can be used to
clearly identify phase transitions in material samples. Electrical resistance
measurements are relatively simple and rapid to execute and the efficacy of the
present experimental design is demonstrated by measuring the electrical
resistance of Pb, Sn and Bi across a wide domain of temperature-pressure phase
space and employing it to identify the loci of phase transitions. Based on
these results, the phase diagrams of these elements are reconstructed to high
accuracy and found to be in excellent agreement with previous studies. In
particular, by mapping the locations of several well-studied reference points
in the phase diagram of Sn and Bi, it is demonstrated that a standard
calibration exists for the temperature and pressure, thus eliminating the need
for direct or indirect temperature and pressure measurements. The present
technique will allow simple and accurate mapping of phase diagrams under
extreme conditions and may be of particular importance in advancing studies of
liquid state anomalies.",1412.0613v2
2010-05-13,Gravitational-wave spin-down and stalling lower limits on the electrical resistivity of the accreted mountain in a millisecond pulsar,"The electrical resistivity of the accreted mountain in a millisecond pulsar
is limited by the observed spin-down rate of binary radio millisecond pulsars
(BRMSPs) and the spins and X-ray fluxes of accreting millisecond pulsars
(AMSPs). We find $\eta \ge 10^{-28}\,\mathrm{s}\,
(\tau_\mathrm{SD}/1\,\mathrm{Gyr})^{-0.8}$ (where $\tau_\mathrm{SD}$ is the
spin-down age) for BRMSPs and $\eta \ge
10^{-25}\,\mathrm{s}\,(\dot{M}_\mathrm{a}/\dot{M}_\mathrm{E})^{0.6}$ (where
$\dot{M}_\mathrm{a}$ and $\dot{M}_\mathrm{E}$ are the actual and Eddington
accretion rates) for AMSPs. These limits are inferred assuming that the
mountain attains a steady state, where matter diffuses resistively across
magnetic flux surfaces but is replenished at an equal rate by infalling
material. The mountain then relaxes further resistively after accretion ceases.
The BRMSP spin-down limit approaches the theoretical electron-impurity
resistivity at temperatures $\ga 10^5$ K for an impurity concentration of $\sim
0.1$, while the AMSP stalling limit falls two orders of magnitude below the
theoretical electron-phonon resistivity for temperatures above $10^8$ K. Hence
BRMSP observations are already challenging theoretical resistivity calculations
in a useful way. Next-generation gravitational-wave interferometers will
constrain $\eta$ at a level that will be competitive with electromagnetic
observations.",1005.2257v1
2017-01-23,Crystal Growth and Magneto-transport of Bi2Se3 Single crystals,"In this letter, we report growth and characterization of bulk Bi2Se3 single
crystals. The studied Bi2Se3 crystals are grown by self flux method through
solid state reaction from high temperature (950C) melt of constituent elements
and slow cooling (2C/hour). The resultant crystals are shiny and grown in [00l]
direction, as evidenced from surface XRD. Detailed Reitveld analysis of PXRD
(powder x-ray diffraction) of the crystals showed that these are crystallized
in rhombohedral crystal structure with space group of R3m (D5) and the lattice
parameters are a = 4.14(2)A, b = 4.14 (2) A and c = 28.7010(7) A. Temperature
versus resistivity (R-T) plots revealed metallic conduction down to 2K, with
typical room temperature resistivity (R300K) of around 0.53 mohm-cm and
residual resistivity of 0.12 mohm-cm. Resistivity under magnetic field ]
measurements exhibited large +Ve magneto resistance right from 2K to 200K.
Isothermal magneto resistance [RH] measurements at 2K, 100K and 200K exhibited
magneto resistance (MR) of up to 240, 130 and 60 percent respectively at 14
Tesla. Further the MR plots are non saturating and linear with field at all
temperature. At 2K the MR plots showed clear quantum oscillations at above say
10 Tesla applied field. Also the Kohler plots i.e., were seen consolidating on
one plot. Interestingly, the studied Bi2Se3 single crystal exhibited the
Shubnikov-de Haas oscillations (SdH) at 2K under different applied magnetic
fields ranging from 4Tesla to 14 Tesla",1701.06280v2
2020-06-24,Conductive filament evolution dynamics revealed by cryogenic (1.5 K) multilevel switching of CMOS-compatible Al2O3/TiO2 resistive memories,"This study demonstrates multilevel switching at 1.5 K of Al2O3/TiO2-x
resistive memory devices fabricated with CMOS-compatible processes and
materials. The I-V characteristics exhibit a negative differential resistance
(NDR) effect due to a Joule-heating-induced metal-insulator transition of the
Ti4O7 conductive filament. Carrier transport analysis of all multilevel
switching I-V curves show that while the insulating regime follows the space
charge limited current (SCLC) model for all resistance states, the conduction
in the metallic regime is dominated by SCLC and trap-assisted tunneling (TAT)
for low- and high-resistance states respectively. A non-monotonic conductance
evolution is observed in the insulating regime, as opposed to the continuous
and gradual conductance increase and decrease obtained in the metallic regime
during the multilevel SET and RESET operations. Cryogenic transport analysis
coupled to an analytical model accounting for the
metal-insulator-transition-induced NDR effects and the resistance states of the
device provide new insights on the conductive filament evolution dynamics and
resistive switching mechanisms. Our findings suggest that the non-monotonic
conductance evolution in the insulating regime is due to the combined effects
of longitudinal and radial variations of the Ti4O7 conductive filament during
the switching. This behavior results from the interplay between temperature-
and field-dependent geometrical and physical characteristics of the filament.",2006.13394v1
2002-04-23,"Effects of stoichiometry, purity, etching and distilling on resistance of MgB2 pellets and wire segments","We present a study of the effects of non-stoichiometry, boron purity, wire
diameter and post-synthesis treatment (etching and Mg distilling) on the
temperature dependent resistance and resistivity of sintered MgB2 pellets and
wire segments. Whereas the residual resistivity ratio (RRR) varies between RRR
\~ 4 to RRR > 20 for different boron purity, it is only moderately affected by
non-stoichiometry (from 20% Mg deficiency to 20% Mg excess) and is apparently
independent of wire diameter and presence of Mg metal traces on the wire
surface. The obtained set of data indicates that RRR values in excess of 20 and
residual resistivities as low as rho{0} ~ 0.4 mu Ohm cm are intrinsic material
properties of high purity MgB2.",0204510v1
2007-01-19,Resistance Anomaly in Disordered Superconducting Films,"We report on a resistance anomaly in disordered superconducting films
containing arrays of irregularly distributed nanoscale holes. At high driving
currents, peaks appear in the resistance as a function of temperature, with
peak values up to 2% above the classic normal-state resistance. We attribute
the observed resistance anomaly to dissipation-induced granularity which
enhances the contributions from fluctuation-induced reduction of the density of
states of the quasiparticles. The granular feature of a disordered
superconducting film originates from the inhomogeneous temperature distribution
caused by the variation of the local dissipation and/or heat transfer.",0701483v1
2007-07-28,Giant Magneto-impedance in stress-annealed Finemet/Copper/Finemet based trilayer structures,"The resistive and reactive components of magneto-impedance (MI) for
Finemet/Copper/Finemet sandwiched structures based on stress-annealed
nanocrystalline Fe75Si15B6Cu1Nb3 ribbons as functions of different fields
(longitudinal and perpendicular) and frequencies have been measured and
analyzed. Maximum magneto-resistance and magneto-inductance ratios of 700% and
450% have been obtained in 30-600 kHz frequency range respectively. These large
magneto-resistance and magneto-inductive ratios are a direct consequence of the
large effective relative permeability due to the closed magnetic flux path in
the trilayer structure. The influence of perpendicular bias fields (Hper) in
the Longitudinal Magneto-impedance (LMI) configuration greatly improves the MI
ratios and sensitivities. The maximum MI ratio for the resistive part increases
to as large as 2500% for Hper ~ 1 Oe. The sensitivity of the magneto-resistance
increases from 48%/Oe to 288%/Oe at 600 kHz frequency with the application of
Hper ~ 30 Oe. Such high increase in MI ratios and sensitivities with
perpendicular bias fields are due to the formation the favourable (transverse)
domain structures.",0707.4229v1
2010-04-12,Systematic Investigation of the Intrinsic Channel Properties and Contact Resistance of Monolayer and Multilayer Graphene FET,"The intrinsic channel properties of monolayer and multilayer graphene were
systematically investigated as a function of layer number by the exclusion of
contact resistance using four-probe measurements. We show that the continuous
change in normalized sheet resistivity from graphite to a bilayer graphene is
governed by one unique property, i.e., the band overlap, which markedly
increases from 1 meV for a bilayer graphene to 11 meV for eight layers and
eventually reaches 40 meV for graphite. The monolayer graphene, however, showed
a deviation in temperature dependence due to a peculiar linear dispersion.
Additionally, contact resistivity was extracted for the case of typical Cr/Au
electrodes. The observed high contact resistivity, which varies by three orders
of magnitude (from ~103 to 106 Ohm micron), might significantly mask the
outstanding performance of the monolayer graphene channel, suggesting its
importance in future research.",1004.2074v1
2010-09-02,Kondo and charge fluctuation resistivity due to Anderson impurities in graphene,"Motivated by experiments on ion irradiated graphene, we compute the
resistivity of graphene with dilute impurities. In the local moment regime we
employ the perturbation theory up to third order in the exchange coupling to
determine the behavior at high temperatures within the Kondo model. Resistivity
due to charge fluctuations is obtained within the mean field approach on the
Anderson impurity model. Due to the linear spectrum of the graphene the Kondo
behavior is shown to depend on the gate voltage applied. The location of the
impurity on the graphene sheet is an important variable determining its effect
on the Kondo scale and resistivity. Our results show that for chemical
potential nearby the node the charge fluctuations is responsible for the
observed temperature dependence of resistivity while away from the node the
spin fluctuations take over. Quantitative agreement with experimental data is
achieved if the energy of the impurity level varies linearly with the chemical
potential.",1009.0551v3
2017-10-05,Electric field Control of Exchange Bias by Resistive Switching,"We demonstrated an electric field controlled exchange bias (EB) effect
accompanied with unipolar resistive switching behavior in the
Si/SiO2/Pt/Co/NiO/Pt device. By applying certain voltages, the device displays
obvious EB in high-resistance-state while negligible EB in
low-resistance-state. Conductive filaments forming and rupture in the NiO layer
but near the Co-NiO interface are considered to play dominant roles in
determining the combined resistive switching and EB phenomena. This work paves
a new way for designing multifunctional and nonvolatile magnetic-electrical
random access memory devices.",1710.01865v1
2018-06-11,Conductivity and Resistivity of Dirac Electrons in Single-Component Molecular Conductor [Pd(dddt)_2],"Dirac electrons, which have been found in the single-component molecular
conductor [Pd(dddt)_2] under pressure, are examined by calculating the
conductivity and resistivity in terms of a tight-binding model for several
pressures of P GPa, which give a nodal line semimetal or insulator. The
temperature (T) dependence of the conductivity shows that the conductivity
increases linearly under pressure at low T due to the Dirac cone but stays
almost constant at high T. Further, at lower pressures, the conductivity is
suppressed due to an unconventional gap, which is examined by calculating the
resistivity. The resistivity exhibits a pseudogap-like behavior even in the
case described by the Dirac cone. Such behavior originates from a novel role of
the nodal line semimetal followed by a pseudogap that is different from a band
gap. The present result reasonably explains the resistivity observed in the
experiment.",1806.03819v2
2019-05-29,Intrinsic resistance peaks in AB-stacked multilayer graphene with odd number of layers,"The intrinsic resistance peak (ridge) structures were recently found to
appear in the carrier density dependence plot of the resistance of the
AB-stacked multilayer graphene with even numbers of layers.The ridges are due
to topological changes in the Fermi surface. Here, these structures were
studied in AB-stacked multilayer graphene with odd numbers of layers (5 and 7
layers) by performing experiments using encapsulated high-quality graphene
samples equipped with top and bottom gate electrodes.The intrinsic resistance
peaks that appeared on maps plotted with respect to the carrier density and
perpendicular electric field showed particular patterns depending on graphene's
crystallographic structure, and were qualitatively different from those of
graphene with even numbers of layers. Numerical calculations of the dispersion
relation and semi-classical resistivity using information based on the Landau
level structure determined by the magnetoresistance oscillations, revealed that
the difference stemmed from the even-odd layer number effect on the electronic
band structure.",1905.12193v2
2014-08-01,Resistive switching in ultra-thin La0.7Sr0.3MnO3 / SrRuO3 superlattices,"Superlattices may play an important role in next generation electronic and
spintronic devices if the key-challenge of the reading and writing data can be
solved. This challenge emerges from the coupling of low dimensional individual
layers with macroscopic world. Here we report the study of the resistive
switching characteristics of a of hybrid structure made out of a superlattice
with ultrathin layers of two ferromagnetic metallic oxides, La0.7Sr0.3MnO3
(LSMO) and SrRuO3 (SRO). Bipolar resistive switching memory effects are
measured on these LSMO/SRO superlattices, and the observed switching is
explainable by ohmic and space charge-limited conduction laws. It is evident
from the endurance characteristics that the on/off memory window of the cell is
greater than 14, which indicates that this cell can reliably distinguish the
stored information between high and low resistance states. The findings may
pave a way to the construction of devices based on nonvolatile resistive memory
effects.",1408.0103v1
2019-07-19,Niobium nitride thin films for very low temperature resistive thermometry,"We investigate thin film resistive thermometry based on
metal-to-insulator-transition (niobium nitride) materials down to very low
temperature. The variation of the NbN thermometer resistance have been
calibrated versus temperature and magnetic field. High sensitivity in
tempertaure variation detection is demonstrated through efficient temperature
coefficient of resistance. The nitrogen content of the niobium nitride thin
films can be tuned to adjust the optimal working temperature range. In the
present experiment, we show the versatility of the NbN thin film technology
through applications in very different low temperature use-cases. We
demonstrate that thin film resistive thermometry can be extended to
temperatures below 30 mK with low electrical impedance.",1907.08443v1
2018-07-23,Coexistence of Diamagnetism and Vanishingly Small Electrical Resistance at Ambient Temperature and Pressure in Nanostructures,"The great practical utility has motivated extensive efforts to discover
ultra-low resistance electrical conductors and superconductors in ambience.
Here we report the observation of vanishingly small electrical resistance at
the ambient temperature and pressure conditions in films and pellets of a
nanostructured material that is composed of silver particles embedded into a
gold matrix. Upon cooling below a sample-specific temperature scale ($T_{C}$)
as high as $286$ K, the film resistance drops below $\sim 2\mu\Omega$, being
limited by measurement uncertainty. The corresponding resistivity ($\sim
10^{-12}$ $\Omega$.m) is at least four orders of magnitude below that of
elemental noble metals, such as gold, silver or copper. Furthermore, the
samples become strongly diamagnetic below $T_{C}$, with volume susceptibilities
as low as -0.056. We additionally describe methods to tune $T_{C}$ to
temperatures much higher than room temperature.",1807.08572v3
2022-11-22,Contact Resistance Study of Various Metal Electrodes with CVD Graphene,"In this study, the contact resistance of various metals to chemical vapour
deposited (CVD) monolayer graphene is investigated. Transfer length method
(TLM) structures with varying widths and separation between contacts have been
fabricated and electrically characterized in ambient air and vacuum condition.
Electrical contacts are made with five metals: gold, nickel, nickel/gold,
palladium and platinum/gold. The lowest value of 92 {\Omega}{\mu}m is observed
for the contact resistance between graphene and gold, extracted from back-gated
devices at an applied back-gate bias of -40 V. Measurements carried out under
vacuum show larger contact resistance values when compared with measurements
carried out in ambient conditions. Post processing annealing at 450{\deg}C for
1 hour in argon-95% / hydrogen-5% atmosphere results in lowering the contact
resistance value which is attributed to the enhancement of the adhesion between
metal and graphene. The results presented in this work provide an overview for
potential contact engineering for high performance graphene-based electronic
devices.",2211.12415v1
2023-03-06,Quantum Acoustics Spawns Planckian Resistivity,"Strange metals exhibit universal linear-in-temperature resistivity described
by a Planckian scattering rate, the origin of which remains elusive. By
employing a novel approach inspired by quantum optics, we arrive at the
coherent state limit of lattice vibrations: quantum acoustics. Utilizing this
nonperturbative framework, we demonstrate that lattice vibrations are active
drivers in the Planckian resistivity phenomenon, challenging prevailing
theories. Treating charge carriers as quantum wave packets negotiating the
dynamic acoustic field, competition ensues between localization and
delocalization, settling on the conjectured universal quantum bound of
diffusion and capturing the enigmatic $T$-linear resistivity over hundreds of
degrees. Our research not only elucidates the critical role of phonons in
Planckian resistivity but also redefines their significance in the broader
landscape of high-temperature superconductivity and condensed matter physics.",2303.06077v3
2011-04-11,DOS-limited contact resistance in graphene FETs,"Graphene has attracted much attention as one of promising candidates of
future high-speed transistor materials because of its high carrier mobility of
more than 10,000 cm2 V-1 s-1. Up to this point, we have focused on the contact
properties as performance killers, as a very small density of states in
graphene might suppress the current injection from metal to graphene. This
paper systematically reviews the metal/graphene contact properties and
discusses the present status and future requirements of the specific contact
resistivity.",1104.1818v1
2006-07-28,Contact effects in polymer field-effect transistors,"Contact resistances often contribute significantly to the overall device
resistance in organic field-effect transistors (OFETs). Understanding charge
injection at the metal-organic interface is critical to optimizing OFET device
performance. We have performed a series of experiments using bottom-contact
poly(3-hexylthiophene) (P3HT) OFETs in the shallow channel limit to examine the
injection process. When contacts are ohmic we find that contact resistivity is
inversely proportional to carrier mobility, consistent with diffusion-limited
injection. However, data from devices with other electrode materials indicate
that this simple picture is inadequate to describe contacts with significant
barriers. A generalized transmission line method allows the analysis of
nonohmic contacts, and we find reasonable agreement with a model for injection
that accounts for the hopping nature of conduction in the polymer. Variation of
the (unintentional) dopant concentration in the P3HT can significantly alter
the injection process via changes in metal-organic band alignment. At very low
doping levels, transport suggests the formation of a barrier at the Au/P3HT
interface, while Pt/P3HT contacts remain ohmic with comparatively low
resistance. We recently observed that self-assembled monolayers on the metal
source/drain electrodes can significantly decrease contact resistance and
maintain ohmic conduction under conditions that would result in nonohmic, high
resistance contacts to untreated electrodes. Finally, we discuss measurements
on extremely short channel devices, in the initial steps toward examining
transport through individual polymer chains.",0607744v1
2008-11-21,Tuning the Correlation Decay in the Resistance Fluctuations of Multi-Species Networks,"A new network model is proposed to describe the $1/f^\alpha$ resistance noise
in disordered materials for a wide range of $\alpha$ values ($0< \alpha < 2$).
More precisely, we have considered the resistance fluctuations of a thin
resistor with granular structure in different stationary states: from nearly
equilibrium up to far from equilibrium conditions. This system has been
modelled as a network made by different species of resistors, distinguished by
their resistances, temperature coefficients and by the energies associated with
thermally activated processes of breaking and recovery. The correlation
behavior of the resistance fluctuations is analyzed as a function of the
temperature and applied current, in both the frequency and time domains. For
the noise frequency exponent, the model provides $0< \alpha < 1$ at low
currents, in the Ohmic regime, with $\alpha$ decreasing inversely with the
temperature, and $1< \alpha <2$ at high currents, in the non-Ohmic regime.
Since the threshold current associated with the onset of nonlinearity also
depends on the temperature, the proposed model qualitatively accounts for the
complicate behavior of $\alpha$ versus temperature and current observed in many
experiments. Correspondingly, in the time domain, the auto-correlation function
of the resistance fluctuations displays a variety of behaviors which are tuned
by the external conditions.",0811.3565v2
2023-07-01,"The near room-temperature upsurge of electrical resistivity in Lu-H-N is not superconductivity, but a metal-to-poor-conductor transition","Since the discovery of superconductivity in mercury at 4 K in 1911, searching
for materials with superconductivity at higher temperatures towards practical
conditions has been a primary enduring goal. The recent report of
room-temperature superconductivity at near-ambient pressure in nitrogen-doped
lutetium hydride (Lu-H-N) by Dasenbrock-Gammon et al. (Hereafter referred as
D-G) seems a great step approaching the ultimate goal. Specifically, they
claimed evidence of superconductivity on Lu-H-N with a maximum Tc of 294 K at 1
GPa. However, the failure to observe the drastic temperature-dependent
resistance change above 200 K in high-pressure synthesized Lu-H-N compounds, a
prerequisite for superconductivity, by researchers worldwide in all independent
follow-up studies casts a heavy shadow on the authenticity of the claims. The
sober questions are: what is the sample that produces the sharp resistance jump
near room temperature? What are the reasons for the non-reproducibility of
others who follow the D-G method of synthesis and the inscrutable low success
rate (35%) in synthesizing the right sample even for the authors in Ref. 1?
What causes the observed sharp resistance jump? Here, with a well-controlled
experiment protocol, we repeatedly reproduced the near room-temperature sudden
change of electrical resistance in the Lu-H-N sample, and we could
quantitatively compare its behavior with the initial pure Lu in a normal
metallic state. These results enable us to scrutinize the origin for the
near-room temperature sharp resistance change, which is attributed to a
metal-to-poor-conductor transition rather than superconductivity.",2307.00201v1
2020-01-17,"Magnetic, magnetoelastic and corrosion resistant properties of (Fe-Ni) based metallic glasses for structural health monitoring applications","We have performed a study of the magnetic, magnetoelastic, and corrosion
resistance properties of seven different composition magnetoelastic-resonant
platforms. For some applications, such as structural health monitoring, these
materials must have not only good magnetomechanical properties, but also a high
corrosion resistance. In the fabricated metallic glasses of composition
Fe(73-x)NixCr5Si10B12, the Fe/Ni ratio was varied (Fe + Ni = 73% at.) thus
changing the magnetic and magnetoelastic properties. A small amount of chromium
(Cr5) was added in order to achieve the desired good corrosion resistance. As
expected, all the studied properties change with the composition of the
samples. Alloys containing a higher amount of Ni than Fe do not show magnetic
behavior at room temperature, while iron-rich alloys have demonstrated not only
good magnetic properties, but also good magnetoelastic ones, with
magnetoelastic coupling coefficient as high as 0.41 for x=0 in the
Fe73Ni0Cr5Si10B12 (the sample containing only Fe but not Ni). Concerning
corrosion resistance, we have found a continuous degradation of these
properties as the Ni content increases in the composition. Thus, the corrosion
potential decreases monotonously from 46.74 mV for the x=0 composition,
Fe73Ni0Cr5Si10B12 to -239.47 mV for the x=73 composition Fe0Ni73Cr5Si10B12.",2001.06283v1
2014-05-08,Controlling boron redistribution in CoFeB/MgO magnetic tunnel junctions during annealing by variation of cap layer materials and MgO deposition methods,"Magnetic tunnel junctions with crystalline MgO tunnel barrier and amorphous
CoFeB electrodes received much attention due to their high tunnel magneto
resistance ratio at room temperature. One important parameter for achieving
high tunnel magneto resistance ratios is to control the boron diffusion from
the electrodes especially during post growth annealing. By high resolution
transmission electron microscopy and electron energy loss spectroscopy
techniques we show that the cap layer material adjacent to the electrodes and
the MgO deposition method are crucial to control boron redistribution. It is
pointed out, that Ta cap layers acts as sinks for boron during annealing in
contrast to Ru layers. Furthermore, radio frequency sputtered MgO tunneling
barriers contain a rather high concentraion of boron in trigonal
[BO$_3$]$^{3-}$ - environment after annealing in contrast to electron beam
evaporated MgO which is virtually free from any boron. Our data further
indicate that neither boron nor oxygen-vacancy-related gap states in the bulk
of MgO barriers affect spin polarized transport for tunnel magneto resistance
ratios at the level of 200%.",1405.1907v1
2021-10-20,Materials and possible mechanisms of extremely large magnetoresistance: A review,"Magnetoresistance (MR) is a characteristic that the resistance of a substance
changes with the external magnetic field, reflecting various physical origins
and microstructures of the substance. A large MR, namely a huge response to a
low external field, has always been a useful functional feature in industrial
technology and a core goal pursued by physicists and materials scientists.
Conventional large MR materials are mainly manganites, whose colossal MR (CMR)
can be as high as -90%. The dominant mechanism is attributed to spin
configuration aligned by the external field, which reduces magnetic scattering
and thus resistance. In recent years, some new systems have shown an extremely
large unsaturated MR (XMR). Unlike ordinary metals, the positive MR of these
systems can reach 103-108% and is persistent under super high magnetic fields.
The XMR materials are mainly metals or semimetals, distributed in high-mobility
topological or non-topological systems, and some are magnetic, which suggests a
wide range of application scenarios. Various mechanisms have been proposed for
the potential physical origin of XMR, including electron-hole compensation,
steep band, ultrahigh mobility, high residual resistance ratio, topological
fermions, etc. It turns out that some mechanisms play a leading role in certain
systems, while more are far from clearly defined. In addition, the researches
on XMR are largely overlapped or closely correlated with other recently rising
physics and materials researches, such as topological matters and
two-dimensional (2D) materials, which makes elucidating the mechanism of XMR
even more important. Moreover, the disclosed novel properties will lay a broad
and solid foundation for the design and development of functional devices. In
this review, we will discuss several aspects in the following order: ...",2110.10454v1
2024-05-09,Extreme high lattice-misfit superalloys with regular cubic L12 particles and excellent creep resistance,"In novel Co and CoNi based superalloys, the creep resistance is limited at
high temperatures due to low lattice misfit and solvus temperature. In this
study, we combined the advantages of Co-Ti (high lattice misfit and solvus
temperature) and Co-Al based superalloys (cuboidal precipitates) by using Ti to
substitute Al in alloys of Co-30Ni-(12.5-x)Al-xTi-2.5Mo-2.5W (at.%)
composition. With high Ti content, the alloys obtained extreme high lattice
misfit (bigger than 1.3 %) and solvus temperature (bigger than 1150 degree).
During aging at 900 degree, alloys with high Ti/Al ratio exhibited a lower
gamma prime precipitate coarsening rate resulting from their lower gamma prime
and gamma interfacial energy and higher lattice misfit. In addition, high Ti/Al
ratio brought higher gamma prime volume fraction and excellent mechanical
properties, such as higher yield stress and better creep resistance. However,
at high temperature of 1100 degree, the cubic gamma prime phase was decomposed
into deleterious Eta phase with D024 structure if the Ti/Al ratio exceeded 1.
Based on this, we outreached new alloys design with a high content of Cr and Ta
and appropriate Ti/Al ratio, i.e., Ti/Al ratio is smaller than 1. The newly
designed alloys still have high solvus temperature (bigger than 1200 degree)
and exhibit high lattice misfit (bigger than 1.2 %) as Co-12Ti (at.%)
superalloys but more regular cubic gamma prime precipitates and significantly
better creep resistance than superalloys Co-9Al-9W and Co-9Al-9W-2Ti at 850 and
950 degree. Nevertheless, compared with creep resistance of Ni based
superalloys, our newly designed alloys still need to be further improved,
especially in the 1000 and 1050 degree range.",2405.05851v1
2019-01-28,Strong damping-like spin-orbit torque and tunable Dzyaloshinskii-Moriya interaction generated by low-resistivity Pd$_{1-x}$Pt$_x$ alloys,"Despite their great promise for providing a pathway for very efficient and
fast manipulation of magnetization at the nanoscale, spin-orbit torque (SOT)
operations are currently energy inefficient due to a low damping-like SOT
efficiency per unit current bias, and/or the very high resistivity of the spin
Hall materials. Here, we report an advantageous spin Hall material, Pd1-xPtx,
which combines a low resistivity with a giant spin Hall effect as evidenced
through the use of three independent SOT ferromagnetic detectors. The optimal
Pd0.25Pt0.75 alloy has a giant internal spin Hall ratio of >0.47 (damping-like
SOT efficiency of ~ 0.26 for all three ferromagnets) and a low resistivity of
~57.5 {\mu}{\Omega} cm at 4 nm thickness. Moreover, we find the
Dzyaloshinskii-Moriya interaction (DMI), the key ingredient for the
manipulation of chiral spin arrangements (e.g. magnetic skyrmions and chiral
domain walls), is considerably strong at the Pd1-xPtx/Fe0.6Co0.2B0.2 interface
when compared to that at Ta/Fe0.6Co0.2B0.2 or W/Fe0.6Co0.2B0.2 interfaces and
can be tuned by a factor of 5 through control of the interfacial spin-orbital
coupling via the heavy metal composition. This work establishes a very
effective spin current generator that combines a notably high energy efficiency
with a very strong and tunable DMI for advanced chiral spintronics and spin
torque applications.",1901.09954v1
2014-10-29,Contact Research Strategy for Emerging Molybdenum Disulfide and Other Two-Dimensional Field-effect Transistors,"Layered two-dimensional (2D) semiconducting transition metal dichalcogenides
(TMD) have been widely isolated, synthesized, and characterized recently.
Numerous 2D materials are identified as the potential candidates as channel
materials for future thin film technology due to their high mobility and the
exhibiting bandgaps. While many TMD filed-effect transistors (FETs) have been
widely demonstrated along with a significant progress to clearly understand the
device physics, large contact resistance at metal/semiconductor interface still
remain a challenge. From 2D device research point of view, how to minimize the
Schottky barrier effects on contacts thus reduce the contact resistance of
metals on 2D materials is very critical for the further development of the
field. Here, we present a review of contact research on molybdenum disulfide
and other TMD FETs from the fundamental understanding of metal-semiconductor
interfaces on 2D materials. A clear contact research strategy on 2D
semiconducting materials is developed for future high-performance 2D FETs with
aggressively scaled dimensions.",1410.8201v1
2023-06-29,Speeding up high-throughput characterization of materials libraries by active learning: autonomous electrical resistance measurements,"High-throughput experimentation enables efficient search space exploration
for the discovery and optimization of new materials. However, large search
spaces of, e.g., compositionally complex materials, require decreasing
characterization times significantly. Here, an autonomous measurement algorithm
was developed, which leverages active learning based on a Gaussian process
model capable of iteratively scanning a materials library based on the highest
uncertainty. The algorithm is applied to a four-point probe electrical
resistance measurement device, frequently used to obtain indications for
regions of interest in materials libraries. Ten materials libraries with
different complexities of composition and property trends are analyzed to
validate the model. By stopping the process before the entire library is
characterized and predicting the remaining measurement areas, the measurement
efficiency can be improved drastically. As robustness is essential for
autonomous measurements, intrinsic outlier handling is built into the model and
a dynamic stopping criterion based on the mean predicted covariance is
proposed. A measurement time reduction of about 70-90% was observed while still
ensuring an accuracy of above 90%.",2306.17277v1
2013-03-29,An operational window for radiation-resistant materials based on sequentially healing grain interiors and boundaries,"Design of nuclear materials with high radiation-tolerance has great
significance1, especially for the next generation of nuclear energy systems2,3.
Response of nano- and poly-crystals to irradiation depends on the radiation
temperature, dose-rate and grain size4-13. However the dependencies had been
studied and interpreted individually, and thus severely lacking is the ability
to predict radiation performance of materials in extreme environments. Here we
propose an operational window for radiation-resistant materials, which is based
on a perspective of interactions among irradiation-induced interstitials,
vacancies, and grain boundaries. Using atomic simulations, we find that healing
grain boundaries needs much longer time than healing grain interiors. Not been
noticed before, this finding suggests priority should be thereafter given to
recovery of the grain boundary itself. This large disparity in healing time is
reflected in the spectra of defects-recombination energy barriers by the
presence of one high-barrier peak in addition to the peak of low barriers. The
insight gained from the study instigates new avenues for examining the role of
grain boundaries in healing the material. In particular, we sketch out the
radiation-endurance window in the parameter space of temperature, dose-rate and
grain size. The window helps evaluate material performance and develop
resistant materials against radiation damage.",1303.7316v1
2004-09-08,Magnetic and electronic phase transformations in (Sm0.65Sr0.35)MnO3 induced by temperature and magnetic field,"Temperature (4.2-260 K) and magnetic field (0-50 kOe) dependencies of the dc
electrical resistance, dc magnetization, and ac magnetic susceptibility of
(Sm0.65Sr0.35)MnO3 prepared from high purity components have been studied.",0409213v1
2015-11-19,High performance sensors based on resistance fluctuations of single layer graphene transistors,"One of the most interesting predicted applications of graphene monolayer
based devices is as high quality sensors. In this letter we show, through
systematic experiments, a chemical vapor sensor based on the measurement of low
frequency resistance fluctuations of single layer graphene
field-effect-transistor (SLG-FET) devices. The sensor has extremely high
sensitivity, very high specificity, high fidelity and fast response times. The
performance of the device using this scheme of measurement (which uses
resistance fluctuations as the detection parameter) is more than two orders of
magnitude better than a detection scheme where changes in the average value of
the resistance is monitored. We propose a number-density fluctuation based
model to explain the superior characteristics of noise measurement based
detection scheme presented in this article.",1511.06213v1
2014-08-19,Aluminium-oxide wires for superconducting high kinetic inductance circuits,"We investigate thin films of conducting aluminium-oxide, also known as
granular aluminium, as a material for superconducting high quality, high
kinetic inductance circuits. The films are deposited by an optimised reactive
DC magnetron sputter process and characterised using microwave measurement
techniques at milli-Kelvin temperatures. We show that, by precise control of
the reactive sputter conditions, a high room temperature sheet resistance and
therefore high kinetic inductance at low temperatures can be obtained. For a
coplanar waveguide resonator with 1.5\,k$\Omega$ sheet resistance and a kinetic
inductance fraction close to unity, we measure a quality factor in the order of
700\,000 at 20\,mK. Furthermore, we observe a sheet resistance reduction by
gentle heat treatment in air. This behaviour is exploited to study the kinetic
inductance change using the microwave response of a coplanar wave guide
resonator. We find the correlation between the kinetic inductance and the sheet
resistance to be in good agreement with theoretical expectations.",1408.4347v3
2013-05-05,Resistance of High-Temperature Cuprate Superconductors,"Cuprate superconductors have many different atoms per unit cell. A large
fraction of cells (5-25%) must be modified (""doped"") before the material
superconducts. Thus it is not surprising that there is little consensus on the
superconducting mechanism, despite almost 200,000 papers. Most astonishing is
that for the simplest electrical property, the resistance, ""despite sustained
theoretical efforts over the past two decades, its origin and its relation to
the superconducting mechanism remain a profound, unsolved mystery."" Currently,
model parameters used to fit normal state properties are experiment specific
and vary arbitrarily from one doping to the other. Here, we provide a
quantitative explanation for the temperature and doping dependence of the
resistivity, Hall effect, and magnetoresistance in one self-consistent model by
showing that cuprates are intrinsically inhomogeneous with a percolating
metallic region and insulating regions. Using simple counting of dopant-induced
plaquettes, we show that the superconducting pairing and resistivity are due to
phonons.",1305.1058v1
2013-12-18,Cyclic electric field stress on bipolar resistive switching devices,"We have studied the effects of accumulating cyclic electrical pulses of
increasing amplitude on the non-volatile resistance state of interfaces made by
sputtering a metal (Au, Pt) on top of the surface of a cuprate superconductor
YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO). We have analyzed the influence of the
number of applied pulses $N$ on the relative amplitude of the remnant
resistance change between the high ($R_H$) and the low ($R_L$) state
[$\alpha=(R_{H}-R_{L})/R_{L}$] at different temperatures ($T$). We show that
the critical voltage ($V_c$) needed to produce a resistive switching (RS, i.e.
$\alpha >0$) decreases with increasing $N$ or $T$. We also find a power law
relation between the voltage of the pulses and the number of pulses
$N_{\alpha_0}$ required to produce a RS of $\alpha=\alpha_0$. This relation
remains very similar to the Basquin equation used to describe the
stress-fatigue lifetime curves in mechanical tests. This points out to the
similarity between the physics of the RS, associated with the diffusion of
oxygen vacancies induced by electrical pulses, and the propagation of defects
in materials subjected to repeated mechanical stress.",1312.5338v1
2014-06-13,Subcoercive and multilevel ferroelastic remnant states with resistive readout,"Ferroelectric devices use their electric polarization ferroic order as the
switching and storage physical quantity for memory applications. However,
additional built-in physical quantities and memory paradigms are requested for
applications. We propose here to take advantage of the multiferroic properties
of ferroelectrics, using ferroelasticity to create a remnant strain, persisting
after stressing the material by converse piezoelectricity means. While large
electric fields are needed to switch the polarization, here writing occurs at
subcoercive much lower field values, which can efficiently imprint multiple
remnant strain states. A proof-of-principle device, with the simplest and
non-optimized resistance strain detection design, is shown here to exhibit
13-memory states of high reproducibility and reliability. The related
advantages in lower power consumption and limited device fatigue make our
approach relevant for applications.",1406.3457v1
2023-03-08,Encoding multistate charge order and chirality in endotaxial heterostructures,"High-density phase change memory (PCM) storage is proposed for materials with
multiple intermediate resistance states, which have been observed in
1$T$-TaS$_2$ due to charge density wave (CDW) phase transitions. However, the
metastability responsible for this behavior makes the presence of multistate
switching unpredictable in TaS$_2$ devices. Here, we demonstrate the
fabrication of nanothick verti-lateral $H$-TaS$_2$/1$T$-TaS$_2$
heterostructures in which the number of endotaxial metallic $H$-TaS$_2$
monolayers dictates the number of resistance transitions in 1$T$-TaS$_2$
lamellae near room temperature. Further, we also observe optically active
heterochirality in the CDW superlattice structure, which is modulated in
concert with the resistivity steps, and we show how strain engineering can be
used to nucleate these polytype conversions. This work positions the principle
of endotaxial heterostructures as a promising conceptual framework for
reliable, non-volatile, and multi-level switching of structure, chirality, and
resistance.",2303.04387v3
2021-05-13,Interaction Effects and Viscous Magneto-Transport in a Strongly Correlated 2D Hole System,"Fermi liquid theory has been a foundation in understanding the electronic
properties of materials. For weakly interacting two-dimensional (2D) electron
or hole systems, electron-electron interactions are known to introduce quantum
corrections to the Drude conductivity in the FL theory, giving rise to
temperature dependent conductivity and magneto-resistance. Here we study the
magneto-transport in a strongly interacting 2D hole system over a broad range
of temperatures ($T$ = 0.09 to $>$1K) and densities $p=1.98-0.99\times10^{10}$
cm$^{-2}$ where the ratio between Coulomb energy and Fermi energy $r_s$ = 20 -
30. We show that while the system exhibits a negative parabolic
magneto-resistance at low temperatures ($\lesssim$ 0.4K) characteristic of an
interacting FL, the FL interaction corrections represent an insignificant
fraction of the total conductivity. Surprisingly, a positive magneto-resistance
emerges at high temperatures and grows with increasing temperature even in the
regime $T \sim E_F$, close to the Fermi temperature. This unusual positive
magneto-resistance at high temperatures is attributed to the collective viscous
transport of 2D hole fluid in the hydrodynamic regime where holes scatter
frequently with each other. These findings highlight the collective transport
in a strongly interacting 2D system in the $r_s\gg 1$ regime and the
hydrodynamic transport induced magneto-resistance opens up possibilities to new
routes of magneto-resistance at high temperatures.",2105.06502v1
2015-04-29,Gate-Tunable Tunneling Resistance in Graphene/Topological Insulator Vertical Junctions,"Graphene-based vertical heterostructures, particularly stacks incorporated
with other layered materials, are promising for nanoelectronics. The stacking
of two model Dirac materials, graphene and topological insulator, can
considerably enlarge the family of van der Waals heterostructures. Despite well
understanding of the two individual materials, the electron transport
properties of a combined vertical heterojunction are still unknown. Here we
show the experimental realization of a vertical heterojunction between Bi2Se3
nanoplate and monolayer graphene. At low temperatures, the electron transport
through the vertical heterojunction is dominated by the tunneling process,
which can be effectively tuned by gate voltage to alter the density of states
near the Fermi surface. In the presence of a magnetic field, quantum
oscillations are observed due to the quantized Landau levels in both graphene
and the two-dimensional surface states of Bi2Se3. Furthermore, we observe an
exotic gate-tunable tunneling resistance under high magnetic field, which
displays resistance maxima when the underlying graphene becomes a quantum Hall
insulator.",1504.07780v3
2022-03-31,Towards automated design of corrosion resistant alloy coatings with an autonomous scanning droplet cell,"We present an autonomous scanning droplet cell platform designed for
on-demand alloy electrodeposition and real-time electrochemical
characterization for investigating the corrosion-resistance properties of
multicomponent alloys. Automation and machine learning are currently driving
rapid innovation in high throughput and autonomous materials design and
discovery. We present two alloy design case studies: one focusing on a
multi-objective corrosion resistant alloy optimization, and a case study
highlighting the complexity of the multimodal characterization needed to
provide insight into the underlying structural and chemical factors that drive
observed material behavior. This motivates a close coupling between autonomous
research platforms and scientific machine learning methodology that blends
mechanistic physical models and black box machine learning models. This
emerging research area presents new opportunities to accelerate materials
synthesis, evaluation, and hence discovery and design.",2203.17049v1
2019-06-10,Quantum oscillation of thermal conductivity and violation of Weidemann-Franz law in TaAs$_2$ and NbAs$_2$,"We report a study of thermal conductivity and resistivity at ultra-low
temperatures and in high magnetic fields for semi-metal materials TaAs$_2$ and
NbAs$_2$ by using single crystal samples. The thermal conductivity is strongly
suppressed in magnetic fields, having good correspondence with the large
positive magnetoresistance, which indicates a dominant electronic contribution
to thermal conductivity. In addition, not only the resistivity but also the
thermal conductivity display clear quantum oscillations behavior at subKelvin
temperatures and in magnetic fields up to 14 T. The most striking phenomenon is
that the thermal conductivity show a $T^4$ behavior at very low temperatures,
while the resistivity show a $T$-independent behavior. This indicates a strong
violation of the Weidemann-Franz law and points to a non-Feimi liquid state of
these materials.",1906.03961v3
2022-01-09,Resistivity testing of palladium dilution limits in CoPd alloys for hydrogen storage,"Palladium satisfies most of the requirements for an effective hydrogen
storage material with two major drawbacks: it has a relatively low gravimetric
hydrogen density and is prohibitively expensive for large-scale applications.
Pd-based alloys should be considered as possible alternatives to a pure Pd. The
question is how much one can dilute the Pd concentration in a variety of
candidate materials while preserving hydrogen absorption capability. We
demonstrate that the resistivity measurements of thin-film alloy samples can be
used for a qualitative high-throughput screening and study of the
hydrogen-absorbing properties over the entire range of palladium
concentrations. Contrary to palladium-rich alloys where additional hydrogen
scattering indicates a degree of hydrogen content, the diluted alloy films
respond by a decrease of resistance due to their thickness expansion. Evidence
of significant hydrogen absorption was found in thin CoPd films diluted to just
20% of Pd.",2201.02974v1
2023-05-26,Ferroelectricity driven-resistive switching and Schottky barrier modulation at CoPt/MgZnO interface for non-volatile memories,"Ferroelectric memristors have attracted much attention as a type of
nonvolatile resistance switching memories in neuromorphic computing, image
recognition, and information storage. Their resistance switching mechanisms
have been studied several times in perovskite and complicated materials
systems. It was interpreted as the modulation of carrier transport by
polarization control over Schottky barriers. Here, we experimentally report the
isothermal resistive switching across a CoPt/MgZnO Schottky barrier using a
simple binary semiconductor. The crystal and texture properties showed
high-quality and single-crystal Co$_{0.30}$Pt$_{0.70}$/Mg$_{0.20}$Zn$_{0.80}$O
hetero-junctions. The resistive switching was examined by an electric-field
cooling method that exhibited a ferroelectric T$_C$ of MgZnO close to the bulk
value. The resistive switching across CoPt/MgZnO Schottky barrier was
accompanied by a change in the Schottky barrier height of 26.5 meV due to an
interfacial charge increase and/or orbital hybridization induced reversal of
MgZnO polarization. The magnitude of the reversed polarization was estimated to
be a reasonable value of 3.0 (8.25) $\mu$ C/cm$^2$ at 300 K (2 K). These
findings demonstrated the utilities of CoPt/MgZnO interface as a potential
candidate for ferroelectric memristors and can be extended to probe the
resistive switching of other hexagonal ferroelectric materials.",2305.16563v3
2016-08-04,Bulk Superconductivity Induced by In-plane Chemical Pressure Effect in Eu0.5La0.5FBiS2-xSex,"We have investigated Se substitution effect to superconductivity of an
optimally-doped BiS2-based superconductor Eu0.5La0.5FBiS2. Eu0.5La0.5FBiS2-xSex
samples with x = 0-1 were synthesized. With increasing x, in-plane chemical
pressure is enhanced. For x = 0.6, 0.8, and 1, superconducting transitions with
a large shielding volume fraction are observed in magnetic susceptibility
measurements, and the highest Tc is 3.8 K for x = 0.8. From low-temperature
electrical resistivity measurements, a zero-resistivity state is observed for
all the samples, and the highest Tc is observed for x = 0.8. With increasing Se
concentration, characteristics of electrical resistivity changes from
semiconducting-like to metallic, suggesting that the emergence of bulk
superconductivity is linked with the enhanced metallicity. A superconductivity
phase diagram of the Eu0.5La0.5FBiS2-xSex superconductor is established.
Temperature dependences of electrical resistivity show an anomalous two-step
transition under high magnetic fields. Hence, the resistivity data are analyzed
with assuming in-plane anisotropy of upper critical field.",1608.01470v2
2018-11-03,Carbon nanotube/metal corrosion issues for nanotube coatings and inclusions in a matrix,"Corrosion is an inevitable phenomenon that is inherent in metals and even
though there has been significant research on this subject, no ideal protection
has been discovered to fully prevent corrosion. However, methods such as using
protective coatings, and modifying the structure or composition of the material
have been used to slow down gradual corrosion and fortunately they proved to be
quite beneficial. The research focus has shifted to integrating novel materials
and structures to improve the corrosion resistance of composites. Carbon
nanotubes (CNTs) are an attractive and promising filler due to their chemical
inertness and high mechanical, electrical, and thermal properties. CNTs can
fill the gaps of metals and polymer-based composites by forming a passive layer
on metals and promoting sacrificial protection in zinc rich polymer (ZRP)
coatings, and can therefore function as an anti-corrosion filler. This paper
reviews the research that has been performed to better understand the influence
of CNTs on corrosion resistance in composites. Accordingly, in metal matrix
composites (MMCs), most of the work has been carried out on electrodeposited
coatings, namely Ni-based-CNT composites, which show improved corrosion
resistance by CNT addition. On the other hand, there are a few papers that have
studied the corrosion resistance of Mg-based-CNT composites and their corrosion
results contradict those obtained from other metal-CNT composites. For ZRPs or
polymer-based coatings there are a few papers that studied the effect of CNTs
on the corrosion of said composites. It is believed that CNTs can strengthen
the adhesion between the coating and the substrate and facilitate sacrificial
protection by Zn particles by forming a conductive network, hence the improved
corrosion resistance.",1812.03815v1
1997-04-29,Normal state c-axis resistivity of high T_c cuprate superconductors,"It is shown that a strong intraplanar incoherent scattering can effectively
block the interplanar coherent tunneling between the weakly coupled planes of
the highly anisotropic but clean (intrinsic) materials such as the optimally
doped high-T_c layered cuprate superconductors. The calculated normal-state
C-axis resistivity \rho_c(T) then follows the metal-like temperature dependence
of the ab-plane resistivity \rho_{ab}(T) at high temperatures. At low enough
temperatures, however, \rho_c(T) exhibits a non-metal like upturn even as
\rho_{ab}(T) remains metallic. Moreover, in the metallic regime, \rho_c(T) is
not limited by the maximum metallic resistivity of Mott-Ioffe-Regel. This
correlation between the intrinsic \rho_c(T) and \rho_{ab}(T) is observed in the
normal state of the high-T_c stoichiometric cuprates.",9704242v1
1997-09-24,Radiation Induced Damage in GaAs Particle Detectors,"The motivation for investigating the use of GaAs as a material for detecting
particles in experiments for High Energy Physics (HEP) arose from its perceived
resistance to radiation damage. This is a vital requirement for detector
materials that are to be used in experiments at future accelerators where the
radiation environments would exclude all but the most radiation resistant of
detector types.",9709034v1
2017-07-05,Effects of Temperature and Near Ultraviolet Light on Current-Voltage Characteristics of Colemanite,"We investigate current-voltage (I-V) characteristics of the ferroelectric
material colemanite at room temperature, at a high temperature, and also under
the influence of near ultraviolet light. We demonstrate that all three I-V
plots exhibit hysteresis effects, and these new results shed new light on the
resistance of colemanite. These novel properties are explained on the basis of
its microstructure indicating potential applications in devices with negative
resistance as well as in photovoltaic devices.",1707.01194v1
2023-08-23,Verification of Wiedemann-Franz law in silver with moderate residual resistivity ratio,"Electrical and thermal transport were studied in a vacuum-annealed
polycrystalline silver wire with residual resistivity ratio 200-400, in the
temperature range 0.1-1.2K and in magnetic fields up to 5T. Both at zero field
and at 5T the wire exhibits the Wiedemann-Franz law with the fundamental Lorenz
number, contrary to an earlier report [Gloos, K. et al, Cryogenics 30, 14
(1990)]. Our result demonstrates that silver is an excellent material for
thermal links in ultra-low-temperature experiments operating at high magnetic
fields.",2308.12349v1
2016-02-02,Coexistence of magneto-resistance and -capacitance tunability in Sm2Ga2Fe2O9,"We propose that charge gradient resulting in the coexisting
magneto-resistance and-capacitance tunability in material systems. We have
experimentally observed coexisting of tunable magneto-resistance and
-capacitance in Sm2Ga2Fe2O9. Our model fits well with the experimental result.",1602.01136v1
2013-03-06,Nonlinear Surface Resistance of YBa2Cu3O7-x Superconducting Thin Films on MgO Substrates in Dielectric Resonator at Ultra High Frequencies,"The nonlinear surface resistance Rs of the YBa2Cu3O7-x superconducting thin
films on the MgO substrates was researched in the Hakki-Coleman dielectric
resonator at the microwave signal powers from -18 dBm to +30 dBm at the ultra
high frequency of 25 GHz in the range of temperatures from 12 K to 85 K. The
dependences of the surface resistance on the temperature RS(T) in the
YBa2Cu3O7-x superconducting thin films at the microwaves were measured. The
dependence of the surface resistance on the microwave power RS(P) in the
YBa2Cu3O7-x superconducting thin films at the microwaves were found at the two
temperatures T = 25 K and T = 50 K. The full expression for the estimation of
the measurements accuracy of the surface resistance RS was derived, and the
measurements accuracy was set at 1 %. The physical mechanisms, which can be
used to explain the experimental results, were discussed. It is shown that the
surface resistance Rs can nonlinearly increase as a result of the transition by
the sub-surface layer of the HTS thin film in a mixed state with the Abricosov
and Josephson magnetic vortices generation at an increase of the microwave
signal power P above the magnitude of 8 dBm. It is assumed that some additional
energy losses have place, because of the microwave power dissipation on the
normal metal cores of the magnetic vortices.",1303.1276v2
2019-12-13,Picosecond Multilevel Resistive Switching in Tantalum Oxide Thin Films,"The increasing demand for high-density data storage leads to an increasing
interest in novel memory concepts with high scalability and the opportunity of
storing multiple bits in one cell. A promising candidate is the redox-based
resistive switch repositing the information in form of different resistance
states. For reliable programming, the underlying physical parameters need to be
understood. We reveal that the programmable resistance states are linked to
internal series resistances and the fundamental nonlinear switching kinetics.
The switching kinetics of Ta$_{2}$O$_{5}$-based cells was investigated in a
wide range over 15 orders of magnitude from 250 ps to 10$^{5}$ s. We found
strong evidence for a switching speed of 10 ps which is consistent with analog
electronic circuit simulations. On all time scales, multi-bit data storage
capabilities were demonstrated. The elucidated link between fundamental
material properties and multi-bit data storage paves the way for designing
resistive switches for memory and neuromorphic applications.",2002.00700v1
2014-03-05,Strong Oxidation Resistance of Atomically Thin Boron Nitride Nanosheets,"Investigation on oxidation resistance of two-dimensional (2D) materials is
critical for many of their applications, because 2D materials could have higher
oxidation kinetics than their bulk counterparts due to predominant surface
atoms and structural distortions. In this study, the oxidation behavior of
high-quality boron nitride (BN) nanosheets of 1-4 layer thick has been examined
by heating in air. Atomic force microscopy and Raman spectroscopy analyses
reveal that monolayer BN nanosheets can sustain up to 850 {\deg}C and the
starting temperature of oxygen doping/oxidation of BN nanosheets only slightly
increases with the increase of nanosheet layer and depends on heating
conditions. Elongated etch lines are found on the oxidized monolayer BN
nanosheets, suggesting that the BN nanosheets are first cut along the
chemisorbed oxygen chains and then the oxidative etching grows perpendicularly
to these cut lines. The stronger oxidation resistance of BN nanosheets suggests
that they are more preferable for high-temperature applications than graphene.",1403.1002v1
2016-08-30,Design and Demonstration of Ultra Wide Bandgap AlGaN Tunnel Junctions,"Ultra violet light emitting diodes (UV LEDs) face critical limitations in
both the injection efficiency and light extraction efficiency due to the
resistive and absorbing p-type contact layers. In this work, we investigate the
design and application of polarization engineered tunnel junctions for
ultra-wide bandgap AlGaN (Al mole fraction higher than 50%) materials towards
highly efficient UV LEDs. We demonstrate that polarization-induced 3D charge is
beneficial in reducing tunneling barriers especially for high composition AlGaN
tunnel junctions. The design of graded tunnel junction structures could lead to
low tunneling resistance below 10-3 Ohm cm2 and low voltage consumption below 1
V (at 1 kA/cm2) for high composition AlGaN tunnel junctions. Experimental
demonstration of 292 nm emission was achieved through non-equilibrium hole
injection into wide bandgap materials with bandgap energy larger than 4.7 eV,
and detailed modeling of tunnel junctions shows that they can be engineered to
have low resistance, and can enable efficient emitters in the UV-C wavelength
range.",1608.08653v1
2010-02-10,"Strain, magnetic anisotropy, and anisotropic magnetoresistance in (Ga,Mn)As on high-index substrates: application to (113)A-oriented layers","Based on a detailed theoretical examination of the lattice distortion in
high-index epilayers in terms of continuum mechanics, expressions are deduced
that allow the calculation and experimental determination of the strain tensor
for (hhl)-oriented (Ga,Mn)As layers. Analytical expressions are derived for the
strain-dependent free-energy density and for the resistivity tensor for
monoclinic and orthorhombic crystal symmetry, phenomenologically describing the
magnetic anisotropy (MA) and anisotropic magnetoresistance (AMR) by appropriate
anisotropy and resistivity parameters, respectively. Applying the results to
(113)A orientation with monoclinic crystal symmetry, the expressions are used
to determine the strain tensor and the shear angle of a series of
(113)A-oriented (Ga,Mn)As layers by high-resolution x-ray diffraction and to
probe the MA and AMR at 4.2 K by means of angle-dependent magnetotransport.
Whereas the transverse resistivity parameters are nearly unaffected by the
magnetic field, the parameters describing the longitudinal resistivity are
strongly field dependent.",1002.2179v2
2011-08-08,Beam screen issues,"In the High Energy LHC (HE-LHC), a beam energy of about 16.5 TeV is currently
contemplated. The beam screen issues linked to the use of 20 T dipole magnets
instead of 8.33 T are discussed, with a particular emphasis on two mechanisms,
the magneto-resistance and the anomalous skin effect, assuming the nominal
machine and beam parameters. The magneto-resistance effect always leads to an
increase of the material resistivity (as the mean free path in the presence of
a transverse magnetic field becomes smaller). As concerns the anomalous skin
effect, the anomalous increase of surface resistance of metals at low
temperatures and high frequencies is attributed to the long mean free path of
the conduction electrons: when the skin depth becomes much smaller than the
mean free path, only a fraction of the conduction electrons moving almost
parallel to the metal surface is effective in carrying the current and the
classical theory breaks down.",1108.1643v1
2012-04-15,A Structural Phase Transition in Ca3Co4O9 Associated with Enhanced High Temperature Thermoelectric Properties,"Temperature dependent electrical resistivity, crystal structure and heat
capacity measurements reveal a resistivity drop and metal to semiconductor
transition corresponding to first order structural phase transition near 400 K
in Ca3Co4O9. The lattice parameter c varies smoothly with increasing
temperature, while anomalies in the a, b1 and b2 lattice parameters occur at ~
400 K. Both Ca2CoO3 and CoO2 layers become distorted above ~ 400 K associated
with the metal to semiconductor transport behavior change. Resistivity and heat
capacity measurements as a function of temperature under magnetic field
indicates low spin contribution to this transition. Reduced resistivity
associated with this first order phase transition from metallic to
semiconducting behavior enhances the thermoelectric properties at high
temperatures and points to the metal to semiconductor transition as a mechanism
for improved ZT in high temperature thermoelectric oxides.",1204.3231v1
2015-10-07,Fabrication and Characterisation of Oil-Free Large High Pressure Laminate Resistive Plate Chamber,"A large (240 cm $\times$ 120 cm $\times$ 0.2 cm) oil-free High Pressure
Laminate (HPL), commonly referred as ""bakelite"", Resistive Plate Chamber (RPC)
has been developed at VECC-Kolkata using locally available P-302 OLTC grade
HPL. The chamber has been operated in streamer mode using Argon, Freon(R134a)
and Iso-butane in a ratio of 34:57:9 by volume. The electrodes and glue samples
have been characterised by measuring their electrical parameters like bulk
resistivity and surface resistivity. The performance of the chamber has been
studied by measuring the efficiency, its uniformity and stability in detection
of cosmic muons. Timing measurement has been performed at a central location of
the chamber. The chamber showed an efficiency $>$95$\%$ and time resolution
($\sigma$), at the point of measurement, $\sim$0.83 ns at 9000V. Details of the
material characterisation, fabrication procedure and performance studies have
been discussed.",1510.02028v4
2016-11-22,CSAR 62 as negative-tone resist for high-contrast e-beam lithography at temperatures between 4 K and room temperature,"The temperature dependence of the electron-beam sensitive resist CSAR 62 is
investigated in its negative-tone regime. The writing temperatures span a wide
range from 4 K to room temperature with the focus on the liquid helium
temperature regime. The importance of low temperature studies is motivated by
the application of CSAR 62 for deterministic nanophotonic device processing by
means of in-situ electron-beam lithography. At low temperature, CSAR 62
exhibits a high contrast of 10.5 and a resolution of 49 nm. The etch stability
is almost temperature independent and it is found that CSAR 62 does not suffer
from peeling which limits the low temperature application of the standard
electron-beam resist PMMA. As such, CSAR 62 is a very promising negative-tone
resist for in-situ electron-beam lithography of high quality nanostructures at
low temperature.",1611.07266v1
2017-07-24,Advancement in the understanding of the field and frequency dependent microwave surface resistance of niobium,"The radio-frequency surface resistance of niobium resonators is incredibly
reduced when nitrogen impurities are dissolved as interstitial in the material,
conferring ultra-high Q-factors at medium values of accelerating field. This
effect has been observed in both high and low temperature nitrogen treatments.
As a matter of fact, the peculiar anti Q-slope observed in nitrogen doped
cavities, i.e. the decreasing of the Q-factor with the increasing of the
radio-frequency field, come from the decreasing of the BCS surface resistance
component as a function of the field. Such peculiar behavior has been
considered consequence of the interstitial nitrogen present in the niobium
lattice after the doping treatment. The study here presented show the field
dependence of the BCS surface resistance of cavities with different resonant
frequencies, such as: 650 MHz, 1.3 GHz, 2.6 GHz and 3.9 GHz, and processed with
different state-of-the-art surface treatments. These findings show for the
first time that the anti Q-slope might be seen at high frequency even for clean
Niobium cavities, revealing useful suggestion on the physics underneath the
anti Q-slope effect.",1707.07582v1
2022-09-29,"Magnetic properties, electrical resistivity, and hardness of high-entropy alloys FeCoNiPd and FeCoNiPt","We report the magnetic properties, electrical resistivity, and Vickers
microhardness of as-cast and annealed high-entropy alloys (HEAs) FeCoNiPd and
FeCoNiPt with the face-centered cubic structure. The heat treatment at 800
$^{\circ}$C does not largely affect the physical properties in each HEA. The
values of the Curie temperature and the saturation moment at 50 K are 955 K and
1.458 $\mu_\mathrm{B}$/f.u. for the annealed FeCoNiPd, and 851 K and 1.456
$\mu_\mathrm{B}$/f.u. for the annealed FeCoNiPt, respectively. Each HEA is a
soft ferromagnet and shows metallic resistivity. The electronic structure
calculations of both HEAs support the ferromagnetic ground states. The
comparisons between experimental and theoretical values are made for the Curie
temperature, the saturation moment, and the residual resistivity. The Vickers
microhardness of annealed FeCoNiPd and FeCoNiPt are both 188 HV. The hardness
vs. valence electron count (VEC) per atom plot of these HEAs does not largely
deviate from an expected universal relation forming a broad peak at
VEC$\sim$6.8. This study would give some hints on designing a soft
ferromagnetic HEA with high hardness.",2209.14506v1
2018-11-29,Logarithmic Upturn in Low-Temperature Electronic Transport as a Signature of d-Wave Order in Cuprate Superconductors,"In cuprate superconductors, high magnetic fields have been used extensively
to suppress superconductivity and expose the underlying normal state. Early
measurements revealed insulating-like behavior in underdoped material versus
temperature $T$, in which resistivity increases on cooling with a puzzling
$\log(1/T)$ form. We instead use microwave measurements of flux-flow
resistivity in YBa$_2$Cu$_3$O$_{6+y}$ and Tl$_2$Ba$_2$CuO$_{6+\delta}$ to study
charge transport deep inside the superconducting phase, in the low temperature
and low field regime. Here, the transition from metallic low-temperature
resistivity ($d\rho/dT>0$) to a $\log(1/T)$ upturn persists throughout the
superconducting doping range, including a regime at high carrier dopings in
which the field-revealed normal-state resistivity is Fermi-liquid-like. The
$\log(1/T)$ form is thus likely a signature of $d$-wave superconducting order,
and the field-revealed normal state's $\log(1/T)$ resistivity may indicate the
free-flux-flow regime of a phase-disordered $d$-wave superconductor.",1811.12348v1
2019-05-31,Pressure-Induced Structural Phase Transition and a Special Amorphization Phase of Two-Dimensional Ferromagnetic Semiconductor Cr2Ge2Te6,"Layered transition-metal trichalcogenides have become one of the research
frontiers as two-dimensional magnets and candidate materials used for
phase-change memory devices. Herein we report the high-pressure synchrotron
X-ray diffraction and resistivity measurements on Cr2Ge2Te6 (CGT) single
crystal by using diamond anvil cell techniques, which reveal a mixture of
crystalline-to-crystalline and crystalline-to-amorphous transitions taking
place concurrently at 18.3-29.2 GPa. The polymorphic transition could be
interpreted by atomic layer reconstruction and the amorphization could be
understood in connection with randomly flipping atoms into van der Waals gaps.
The amorphous (AM) phase is quenchable to ambient conditions. The electrical
resistance of CGT shows a bouncing point at ~ 18 GPa, consistent with the
polymorphism phase transition. Interestingly, the high-pressure AM phase
exhibits metallic resistance with the magnitude comparable to that of
high-pressure crystalline phases, whereas the resistance of the AM phase at
ambient pressure fails to exceed that of the crystalline phase, indicating that
the AM phase of CGT appeared under high pressure is quite unique and similar
behavior has never been observed in other phase-change materials. The results
definitely would have significant implications for the design of new functional
materials.",1905.13603v1
2018-08-23,Evidence for superconductivity above 260 K in lanthanum superhydride at megabar pressures,"Recent predictions and experimental observations of high Tc superconductivity
in hydrogen-rich materials at very high pressures are driving the search for
superconductivity in the vicinity of room temperature. We have developed a
novel preparation technique that is optimally suited for megabar pressure
syntheses of superhydrides using pulsed laser heating while maintaining the
integrity of sample-probe contacts for electrical transport measurements to 200
GPa. We detail the synthesis and characterization, including four-probe
electrical transport measurements, of lanthanum superhydride samples that
display a significant drop in resistivity on cooling beginning around 260 K and
pressures of 190 GPa. Additional measurements on two additional samples
synthesized the same way show resistance drops beginning as high as 280 K at
these pressures. The loss of resistance at these high temperatures is not
observed in control experiments on pure La as well as in partially transformed
samples at these pressures, and x-ray diffraction as a function of temperature
on the superhydride reveal no structural changes on cooling. We infer that the
resistance drop is a signature of the predicted room-temperature
superconductivity in LaH10, in good agreement with density functional structure
search and BCS theory calculations.",1808.07695v3
2021-02-04,Enhancing plasticity in high-entropy refractory ceramics via tailoring valence electron concentration,"Bottom-up design of high-entropy ceramics is a promising approach for
realizing materials with unique combination of high hardness and
fracture-resistance at elevated temperature. This work offers a simple yet
fundamental design criterion - valence electron concentration (VEC) > ~9.5
e-/f.u. to populate bonding metallic states at the Fermi level - for selecting
elemental compositions that may form rocksalt-structure (B1) high-entropy
ceramics with enhanced plasticity (reduced brittleness). Single-phase B1
(HfTaTiWZr)C and (MoNbTaVW)C, chosen as representative systems due to their
specific VEC values, are here synthesized and tested. Nanoindentation arrays at
various loads and depths statistically show that (HfTaTiWZr)C (VEC=8.6 e-/f.u.)
is hard but brittle, whilst (MoNbTaVW)C (VEC=9.4 e-/f.u.) is hard and
considerably more resistant to fracture than (HfTaTiWZr)C. Ab initio molecular
dynamics simulations and electronic-structure analysis reveal that the improved
fracture-resistance of (MoNbTaVW)C subject to tensile and shear deformation may
originate from the intrinsic material's ability to undergo local lattice
transformations beyond tensile yield points, as well as from relatively facile
activation of lattice slip. Additional simulations, carried out to follow the
evolution in mechanical properties as a function of temperature, suggest that
(MoNbTaVW)C may retain good resistance to fracture up to ~900-1200K, whereas
(HfTaTiWZr)C is predicted to remain brittle at all investigated temperatures.",2102.02455v2
2020-09-08,High-Pressure Torsion Deformation Induced Phase Transformations and Formations: New Material Combinations and Advanced Properties,"Heavy plastic shear deformation at relatively low homologous temperatures is
called high-pressure torsion (HPT) deformation, which is one method of severe
plastic deformation (SPD). The aim of the paper is to give an overview of a new
processing approach which permits the generation of innovative metastable
materials and novel nanocomposites by HPT deformation. Starting materials can
be either coarse-grained multi-phase alloys, a mixture of different elemental
powders or any other combination of multiphase solid starting materials. After
HPT processing, the achievable microstructures are similar to the ones
generated by mechanical alloying. Nevertheless, one advantage of the HPT
process is that bulk samples of the different types of metastable materials and
nanocomposites are obtained directly during HPT deformation. It will be shown
that different material combinations can be selected and materials with
tailored properties, or in other words, materials designed for specific
applications and the thus required properties, can be synthesized. Areas of
application for these new materials range from hydrogen storage to materials
resistant to harsh radiation environments.",2009.03531v1
2023-12-08,Low Resistance Ohmic Contact to P-type Monolayer WSe2,"Advanced microelectronics in the future may require semiconducting channel
materials beyond silicon. Two-dimensional (2D) semiconductors, characterized by
their atomically thin thickness, hold immense promise for high-performance
electronic devices at the nanometer scale with lower heat dissipation. One
challenge for achieving high-performance 2D semiconductor field effect
transistors (FET), especially for p-type materials, is the high electrical
contact resistance present at the metal-semiconductor interface. In
conventional bulk semiconductors, low resistance ohmic contact is realized
through heavy substitutional doping with acceptor or donor impurities at the
contact region. The strategy of substitutional doping, however, does not work
for p-type 2D semiconductors such as monolayer tungsten diselenide (WSe$_2$).In
this study, we developed highly efficient charge-transfer doping with
WSe$_2$/$\alpha$-RuCl$_3$ heterostructures to achieve low-resistance ohmic
contact for p-type WSe$_2$ transistors. We show that a hole doping as high as
3$\times$10$^{13}$ cm$^{-2}$ can be achieved in the WSe$_2/\alpha$-RuCl$_3$
heterostructure due to its type-III band alignment. It results in an Ohmic
contact with resistance lower than 4 k Ohm $\mu$m at the p-type monolayer
WSe$_2$/metal junction. at room temperature. Using this low-resistance contact,
we demonstrate high-performance p-type WSe$_2$ transistors with a saturation
current of 35 $\mu$A$\cdot$ $\mu$m$^{-1}$ and an I$_{ON}$/I$_{OFF}$ ratio
exceeding 10$^9$ It could enable future microelectronic devices based on 2D
semiconductors and contribute to the extension of Moore's law.",2312.04849v1
2022-01-06,Model-based quantitative methods to predict irradiation-induced swelling in alloys,"Predicting volume swelling of structural materials in nuclear reactors under
high-dose neutron irradiations based on existing low-dose experiments or
irradiation data with high-dose-rate energetic particles has been a
long-standing challenge for safety evaluation and rapidly screening
irradiation-resistant materials in nuclear energy systems. Here, we build an
Additional Defect Absorption Model that describes the irradiation-induced
swelling effects produced by energetic electrons, heavy-ions, and neutrons by
considering additional defect sinks inherent in the irradiation process. Based
on this model, we establish quantitative methods to predict high-dose swelling
from low-dose behavior and obtain the equivalent irradiation dose for different
energetic particles when the dose rates differ by several orders of magnitude.
Furthermore, we propose a universal parameter to characterize the swelling
resistance of various alloys and predict their radiation tolerances under
different radiation conditions. This work provides quantitative prediction
methods for evaluating irradiation-induced swelling effects of structural
materials, which is critical to the safety and material development for
advanced nuclear reactors.",2201.04958v1
2022-10-28,An innovative materials design protocol for the development of novel refractory high-entropy alloys for extreme environments,"In the quest of new materials that can withstand severe irradiation and
mechanical extremes for advanced applications (e.g. fission reactors, fusion
devices, space applications, etc), design, prediction and control of advanced
materials beyond current material designs become a paramount goal. Here, though
a combined experimental and simulation methodology, the design of a new
nanocrystalline refractory high entropy alloy (RHEA) system is established.
Compositions of this alloy, assessed under extreme environments and in situ
electron-microscopy, revealed both high mechanical strength and thermal
stability, grain refinement under heavy ion irradiation and outstanding
irradiation resistance to dual-beam irradiation and helium implantation, marked
by remarkable resistance to defect generation, growth and coalescence. The
experimental and modeling results, which demonstrated notable agreement, can be
applied to design and rapidly assess other alloys subjected to extreme
environmental conditions.",2210.16409v1
2023-02-07,Effect of ZrB$_2$ additions on the thermal stability of polycrystalline diamond,"This study investigates the effect of ZrB$_2$ additions on the
microstructure, thermal stability, and thermo-mechanical wear behaviour of
polycrystalline diamond. Following high-pressure high-temperature (HPHT)
sintering, the ZrB$_2$-PCD material showed a full conversion of the binder
phase to cobalt-boride (Co2B and Co$_{23}$B$_6$) phases. In-situ PXRD and TEM
vacuum annealing experiments observed that the onset of bulk graphitisation
occurred above $1000^{\circ}C$ for the ZrB$_2$-PCD material, compared to
$850^{\circ}C$ for the STD-PCD material. The ZrB$_2$-PCD tools showed excellent
thermo-mechanical wear behaviour, exhibiting increased durability and a steady
wear scar progression during high-temperature dry-VTL testing. However, lowered
abrasion wear resistance was observed for the ZrB2-PCD tools during
low-temperature wet-VTL testing, probably due the reduced diamond contiguity in
the ZrB2 additive sample. Further optimisation of the ZrB$_2$ additive phase
content, mixing methodology, or sintering conditions could be explored to
improve the abrasive wear resistance of this novel PCD material.",2302.03464v1
2016-06-14,Origin of the metal-to-insulator crossover in cuprate superconductors,"Superconductivity in cuprates peaks in the doping regime between a metal at
high p and an insulator at low p. Understanding how the material evolves from
metal to insulator is a fundamental and open question. Early studies in high
magnetic fields revealed that below some critical doping an insulator-like
upturn appears in the resistivity of cuprates at low temperature, but its
origin has remained a puzzle. Here we propose that this 'metal-to-insulator
crossover' is due to a drop in carrier density n associated with the onset of
the pseudogap phase at a critical doping p*. We use high-field resistivity
measurements on LSCO to show that the upturns are quantitatively consistent
with a drop from n=1+p above p* to n=p below p*, in agreement with high-field
Hall data in YBCO. We demonstrate how previously reported upturns in the
resistivity of LSCO, YBCO and Nd-LSCO are explained by the same universal
mechanism: a drop in carrier density by 1.0 hole per Cu atom.",1606.04491v1
2020-05-30,Linearity and rate capability measurements of RPC with semi-insulating crystalline electrodes operating in avalanche mode,"The intrinsic rate capability and the ageing properties of the Resistive
Plate Chambers are closely related to the electrodes material and to the
front-end electronics threshold. The development of a low noise pre-amplifier
led us to improve the intrinsic rate capability of High Pressure Laminate
(bakelite) up to $\sim10\;kHz/cm^2$, nevertheless the effective rate is
significantly limited by electrodes ageing. To further improve the effective
rate capability new materials are investigated. A Resistive Plate Chamber with
crystalline semi-insulating Gallium Arsenide electrodes has been characterized
with high energy electrons beam at the Beam Test Facility (BFT), (INFN National
Laboratory of Frascati, Italy). The response of the Resistive Plate Chamber to
multiple bunched electrons was measured operating the detector in avalanche
mode. The intrinsic rate capability has been also measured operating the
detector in a uniform high energy gamma radiation field at the GIF++ facility
(EHN1 of SPS, CERN).",2006.00306v1
2016-06-17,Manganite-based three level memristive devices with self-healing capability,"We report on non-volatile memory devices based on multifunctional manganites.
The electric field induced resistive switching of
Ti/$La_{1/3}$$Ca_{2/3}$Mn$O_3$/n-Si devices is explored using different
measurement protocols. We show that using current as the electrical stimulus
(instead of standard voltage-controlled protocols) improves the electrical
performance of our devices and unveils an intermediate resistance state. We
observe three discrete resistance levels (low, intermediate and high), which
can be set either by the application of current-voltage ramps or by means of
single pulses. These states exhibit retention and endurance capabilities
exceeding $10^4$ s and 70 cycles, respectively. We rationalize our experimental
observations by proposing a mixed scenario were a metallic filament and a
Si$O_x$ layer coexist, accounting for the observed resistive switching. Overall
electrode area dependence and temperature dependent resistance measurements
support our scenario. After device failure takes place, the system can be
turned functional again by heating up to low temperature (120 C), a feature
that could be exploited for the design of memristive devices with self-healing
functionality. These results give insight into the existence of multiple
resistive switching mechanisms in manganite-based memristive systems and
provide strategies for controlling them.",1606.05401v1
2019-07-25,Extraction of the short-range defect potential parameters from available experimental data on the graphene resistance,"We consider a problem of obtaining information about the scattering
potentials of the monolayer graphene sample using available experimental data
on its resistance. We have in mind a development of the study describing
super-high mobility electrons in suspended samples without chemical doping. As
far as practical absence of the doping impurities in this case makes the
Coulomb scattering negligible, we consider models of the short-range scattering
potentials. The model of short-range potential is assumed to be supported by
the close vicinity of the ring or the circumference of a circle. The diameter
of circles is supposed to be of the order of the crystal lattice spacing. The
empty core of the model potential guarantees the suppression of nonphysical
shortwave modes. Two models are investigated: the delta function on the
circumference of a circle (delta shell) and the annual well. An advantage of
the former is simplicity, while a virtue of the latter is regularity. We
consider scattering of electrons by these potentials and obtain exact explicit
formulae for the scattering data. We here discuss application of these formulae
for calculation of observables. Namely, we analyze the contribution of this
scattering into the graphene resistance and plot the resistivity as a function
of the Fermi energy according to our theoretical formulae. The obtained results
are consistent with experiment, where the resistance was measured as a function
of the Fermi momentum on the suspended annealed graphene. This fact gives a
possibility to find parameters of the modeled potential on the base of the
available experimental data on resistance of the suspended graphene sample with
the gate voltage controlled Fermi level position. It is clear to be very
important for applications.",1907.10894v1
2021-08-23,Polarization and resistive switching in epitaxial 2 nm Hf$_{0.5}$Zr$_{0.5}$O$_2$ tunnel junctions,"In the quest for reliable and power-efficient memristive devices,
ferroelectric tunnel junctions are being investigated as potential candidates.
CMOS-compatible ferroelectric hafnium oxides are at the forefront. However, in
epitaxial tunnel devices with thicknesses around ${\approx}$ 4 - 6 nm, the
relatively high tunnel energy barrier produces a large resistance that
challenges their implementation. Here, we show that ferroelectric and
electroresistive switching can be observed in ultrathin 2 nm epitaxial
Hf$_{0.5}$Zr$_{0.5}$O$_2$ (HZO) tunnel junctions in large area capacitors
(${\approx} 300{\mu}m^2$). We observe that the resistance area product is
reduced to about 160 ${\Omega}{\cdot}$cm$^2$ and 65 ${\Omega}{\cdot}$cm$^2$ for
OFF and ON resistance states, respectively. These values are two orders of
magnitude smaller than those obtained in equivalent 5 nm HZO tunnel devices
while preserving a similar OFF/ON resistance ratio (210 ${\%}$). The devices
show memristive and spike-timing-dependent plasticity (STDP) behavior and good
retention. Electroresistance and ferroelectric loops closely coincide,
signaling ferroelectric switching as a driving mechanism for resistance change.",2108.10373v1
2002-08-18,Synthesis and physical properties of LiBC intermetallics,"Polycrystalline samples of LiBC compounds, which were predicted as possible
candidate for high-Tc superconductivity, have been synthesised by a flux method
and investigated by means of electrical resistivity and magnetic
susceptibility. Scanning electron microscopy and X-ray diffraction patterns
showed a plate-like morphology and a single-phase nature of LiBC samples for
starting composition of Li1.25BC (flux composition). The lattice constants a, c
display a systematic variation with x and has maximum volume of the hexagonal
unit cell at x = 1.25. Electrical resistivity measurements revealed an
extrinsic semi-conducting behaviour of the single-phase LiBC with an activation
energy of 18 meV and a maximum specific resistivity of 2.5 Wcm at 300 K. In
contrast to the theoretical prediction of high Tc, no superconducting features
were detected down to 2 K both, by measurements of electrical resistivity and
magnetic susceptibility.",0208346v2
2008-10-22,Quantum resistance metrology in graphene,"We have performed a metrological characterization of the quantum Hall
resistance in a 1 $\mu$m wide graphene Hall-bar. The longitudinal resistivity
in the center of the $\nu=\pm 2$ quantum Hall plateaus vanishes within the
measurement noise of 20 m$\Omega$ upto 2 $\mu$A. Our results show that the
quantization of these plateaus is within the experimental uncertainty (15 ppm
for 1.5$ \mu$A current) equal to that in conventional semiconductors. The
principal limitation of the present experiments are the relatively high contact
resistances in the quantum Hall regime, leading to a significantly increased
noise across the voltage contacts and a heating of the sample when a high
current is applied.",0810.4064v1
2011-02-14,"Coexistence of superconductivity and antiferromagnetism in single crystals $A_{0.8}Fe_{2-y}Se_2$ (A= K, Rb, Cs, Tl/K and Tl/Rb): evidence from magnetization and resistivity","We measure the resistivity and magnetic susceptibility in the temperature
range from 5 K to 600 K for the single crystals $A$Fe$_{2-y}$Se$_2$ ($A$ =
K$_{0.8}$, Rb$_{0.8}$, Cs$_{0.8}$, Tl$_{0.5}$K$_{0.3}$ and
Tl$_{0.4}$Rb$_{0.4}$). A sharp superconducting transition is observed in low
temperature resistivity and susceptibility, and susceptibility shows 100%
Meissner volume fraction for all crystals, while an antiferromagnetic
transition is observed in susceptibility at Neel temperature ($T_N$) as high as
500 K to 540 K depending on A. It indicates the coexistence of
superconductivity and antiferromagnetism. A sharp increase in resistivity
arises from the structural transition due to Fe vacancy ordering at the
temperature slightly higher than $T_{\rm N}$. Occurrence of superconductivity
in an antiferromagnetic ordered state with so high $T_{\rm N}$ may suggest new
physics in this type of unconventional superconductors.",1102.2783v1
2012-08-15,Two-dimensional electron-gas-like charge transport at magnetic Heusler alloy-SrTiO$_3$ interface,"We report remarkably low residual resistivity, giant residual resistivity
ratio, free-electron-like Hall resistivity and high mobility ($\approx$ 10$^4$
cm$^2$V$^{-1}$s$^{-1}$) charge transport in epitaxial films of Co$_2$MnSi and
Co$_2$FeSi grown on (001) SrTiO$_3$. This unusual behavior is not observed in
films deposited on other cubic oxide substrates of comparable lattice
parameters. The scaling of the resistivity with thickness of the films allow
extraction of interface conductance, which can be attributed to a layer of
oxygen vacancies confined within 1.9 nm of the interface as revealed by
atomically resolved electron microscopy and spectroscopy. The high mobility
transport observed here at the interface of a fully spin polarized metal is
potentially important for spintronics applications.",1208.3099v2
2014-10-29,Large time-dependent coercivity and resistivity modification under sustained voltage application in a Pt/Co/AlOx/Pt junction,"The coercivity and resistivity of a Pt/Co/AlOx/Pt junction are measured under
sustained voltage application. High bias voltages of either polarity are
determined to cause a strongly enhanced, reversible coercivity modification
compared to low voltages. Time-resolved measurements show a logarithmic
development of the coercive field in this regime, which continues over a period
as long as thirty minutes. Furthermore, the resistance of the dielectric
barrier is found to change strongly and reversibly on the same time scale,
suggesting an electrochemical process is taking place within the dielectric. It
is argued that the migration of oxygen vacancies at the magnet/oxide interface
could explain both the resistance variation and the enhanced electric field
effect at high voltages. A thermal fluctuation aftereffect model is applied to
account for the observed logarithmic dependence.",1410.8018v1
2017-06-29,Effect of Anodizing Parameters on Corrosion Resistance of Coated Purified Magnesium,"Magnesium and its alloys are being considered for biodegradable biomaterials.
However, high and uncontrollable corrosion rates have limited the use of
magnesium and its alloys in biological environments. In this research, high
purified magnesium (HP-Mg) was coated with stearic acid in order to improve the
corrosion resistance of magnesium. Anodization and immersion in stearic acid
were used to form a hydrophobic layer on magnesium substrate. Different DC
voltages, times, electrolytes, and temperatures were tested. Electrochemical
impedance spectroscopy and potentiodynamic polarization were used to measure
the corrosion rates of the coated HP-Mg. The results showed that optimum
corrosion resistance occurred for specimens anodized at +4 volts for 4 minutes
at 70{\deg}C in borate benzoate. The corrosion resistance was temporarily
enhanced by 1000x.",1706.09547v1
2017-12-08,Selective etching of PDMS: etching as a negative tone resist,"In this work authors present for the first time how to apply the
additive-free, cured PDMS as a negative tone resist material, demonstrate the
creation of PDMS microstructures and test the solvent resistivity of the
created microstructures. The PDMS layers were 45 um and 100 um thick, the
irradiations were done with a focused proton microbeam with various fluences.
After irradiation, the samples were etched with sulfuric acid that removed the
unirradiated PDMS completely but left those structures intact that received
high enough fluences. The etching rate of the unirradiated PDMS was also
determined. Those structures that received at least 7.5*10^15 ion*cm-2 fluence
did not show any signs of degradation even after 19 hours of etching. As a
demonstration, 45 um and 100 um tall, high aspect ratio, good quality,
undistorted microstructures were created with smooth and vertical sidewalls.
The created microstructures were immersed into numerous solvents and some acids
to test their compatibility. It was found that the unirradiated PDMS cannot,
while the irradiated PDMS microstructures can resist to chloroform, n-hexane,
toluene and sulfuric acid. Hydrogen fluoride etches both the unirradiated and
the irradiated PDMS.",1712.03119v1
2018-06-28,Band-edge quasiparticles from electron phonon coupling and resistivity saturation,"We address the problem of resistivity saturation observed in materials such
as the A-15 compounds. To do so, we calculate the resistivity for the
Hubbard-Holstein model in infinite spatial dimensions to second order in
on-site repulsion $U\leq D$ and to first order in (dimensionless)
electron-phonon coupling strength $\lambda\leq0.5$, where $D$ is the
half-bandwidth. We identify a unique mechanism to obtain two parallel quantum
conducting channels: low-energy and band-edge high-energy quasi-particles. We
identify the source of the hitherto unremarked high-energy quasi-particles as a
positive slope in the frequency-dependence of the real part of the electron
self-energy. In the presence of phonons, the self-energy grows linearly with
the temperature at high-$T$, causing the resistivity to saturate. As $U$ is
increased, the saturation temperature is pushed to higher values, offering a
mechanism by which electron-correlations destroy saturation.",1806.11227v2
2019-06-15,Unidirectional Synapse-Like Behavior of Zr/ZrO2-NT/Au Layered Structure,"Zirconia nanotubular layer with an outer tube diameter 25 nm was synthesized
by potentiostatic anodization. The Zr/ZrO2-NT/Au memristive structure is
fabricated using stencil mask and magnetron sputtering techniques.
Current-voltage characteristics are measured in full cycles of resistive
switching with varying parameters of the applied harmonic voltage. An
equivalent circuit with unidirectional electrical conductivity for the studied
structure is proposed. Estimates of the electrical resistance of memristors in
high-and intermediate resistivity states are performed. The high synaptic
plasticity of memristors based on the Zr/ZrO2-NT/Au structure is shown.",1906.06549v1
2019-06-25,Compositionally graded contact layers for MOCVD grown high Al-content AlGaN transistors,"In this letter, we design and demonstrate an improved MOCVD grown reverse
Al-composition graded contact layer to achieve low resistance contact to MOCVD
grown ultra-wide bandgap (UWBG) Al0.70Ga0.30N channel metal semiconductor
field-effect transistors (MESFETs). Increasing the thickness of the reverse
graded layer was found to improve contact layer resistance significantly,
leading to contact resistance of 3.3x10^-5 Ohm.cm2. Devices with gate length,
LG, of 0.6 microns and source-drain spacing, LSD, of 1.5 microns displayed a
maximum current density, IDSMAX, of 635 mA/mm with an applied gate voltage,
VGS, of +2 V. Breakdown measurements on transistors with gate to drain spacing,
LGD, of 770 nm had breakdown voltage greater than 220 , corresponding to
minimum breakdown field of 2.86 MV/cm. This work provides a framework for the
design of low resistance contacts to MOCVD grown high Al-content AlxGa1-xN
channel transistors.",1906.10270v2
2021-02-05,Formation of Ultra-High-Resistance Au/Ti/p-GaN Junctions and the Applications in AlGaN/GaN HEMTs,"We report a dramatic current reduction, or a resistance increase, by a few
orders of magnitude of two common-anode Au/Ti/pGaN Schottky junctions annealed
within a certain annealing condition window (600 - 700 oC, 1 - 4 min). Results
from similar common-anode Schottky junctions made of Au/p-GaN, Al/Ti/p-GaN and
Au/Ti/graphene/p-GaN junctions demonstrated that all the three layers (Au, Ti
and p-GaN) are essential for the increased resistance. Raman characterization
of the p-GaN showed a decrease of the Mg-N bonding, i.e., the deactivation of
Mg, which is consistent with the Hall measurement results. Moreover, this
high-resistance junction structure was employed in p-GaN gate AlGaN/GaN HEMTs.
It was shown to be an effective gate technology that was capable to boost the
gate breakdown voltage from 9.9 V to 13.8 V with a negligible effect on the
threshold voltage or the sub-threshold slope.",2102.03418v1
2021-12-02,Homes' law in holographic superconductor with linear-$T$ resistivity,"Homes' law, $\rho_{s} = C \, \sigma_{DC} \, T_{c}$, is a universal relation
of superconductors between the superfluid density $\rho_{s}$ at zero
temperature, the critical temperature $T_{c}$ and the electric DC conductivity
$\sigma_{DC}$ at $T_c$. Experimentally, Homes' law is observed in high $T_c$
superconductors with linear-$T$ resistivity in the normal phase, giving a
material independent universal constant $C$. By using holographic models
related to the Gubser-Rocha model, we investigate how Homes' law can be
realized together with linear-$T$ resistivity in the presence of momentum
relaxation. We find that strong momentum relaxation plays an important role to
exhibit Homes' law with linear-$T$ resistivity.",2112.01153v2
2004-02-02,Universal charge transport of the Mn oxides in the high temperature limit,"We have found that various Mn oxides have the universal resistivity and
thermopower in the high temperature limit. The resistivities and thermopowers
of all the samples go toward constant values of 7$\pm$1 m$\Omega$cm and
$-79\pm$3 $\mu$V/K, which are independent of carrier density and crystal
structures. We propose that the electric conduction occurs in a highly
localized way in the high temperature limit, where the exchange of entropy and
charge occurs in the neighboring Mn$^{3+}$ and Mn$^{4+}$ ions.",0402032v1
2009-05-19,Boosting electronic transport in carbon nanotubes by isotopic disorder,"The current/voltage curve of metallic carbon nanotubes (CNTs) displays at
high bias a sudden increase of the resistivity due to the scattering of
electrons with phonons having an anomalously-high population (hot phonons).
Here, we show that it is possible to improve the electrical performances of
metallic CNTs by C13 isotope enrichment. In fact, isotopic disorder creates
additional channels for the hot-phonon deexcitation, reduces their population
and, thus, the nanotube high-bias differential-resistance. This is an
extraordinary case where disorder improves the electronic transport.",0905.3034v1
2011-04-05,Effect of uniaxial stress on low-frequency dispersion of dielectric constant in high-resistivity GaSe crystals,"Low-frequency dielectric spectra of high-resistivity GaSe layered crystals
have been studied on the samples clamped between two insulating parallel plates
at frequencies up to 100 kHz. The measurements have been carried out at
different uniaxial stresses up to $2.4\times10^5$ Pa applied along the c-axis
normal to crystal layer's plane. It is revealed that the dielectric spectra of
high-resistivity GaSe layered crystals with insulating plates obey a universal
power law ${\sim}\omega^{n-1}$, where ${\omega}$ is the angular frequency and
$n\approx 0.8$, earlier observed on high-resistivity GaSe crystals with
indium-soldered contacts. The same type of spectra on the crystals with
different types of contacts (insulating and ohmic) confirms the bulk character
of the observed polarization caused by hopping charge carriers. It is shown
that the frequency-dependent dielectric constant increases linearly with the
uniaxial stress characterized by the coefficient
${\Delta}{\epsilon}/({\epsilon}{\Delta}{p})=8{\times}10^{-7}$ Pa$^{-1}$. A
slight increase of power $1-n$ with the stress is observed, that leads to a
stronger dielectric dispersion. The strong stress dependence of the
low-frequency dielectric constant in high-resistivity GaSe crystals may be
referred to the presence of the formations of elementary dipoles, rotations of
which correspond to hops of localized charge carriers.",1104.0801v1
2017-12-08,Selective etching of PDMS: etching as positive resist,"Although, poly(dimethylsiloxane) (PDMS) is a widely used material in numerous
applications, such as micro- or nanofabrication, the method of its selective
etching has not been known up to now. In this work authors present two methods
of etching the pure, additive-free and cured PDMS as a positive resist
material.
  To achieve the chemical modification of the polymer necessary for selective
etching, energetic ions were used. We created 7 um and 45 um thick PDMS layers
and patterned them by a focused proton microbeam with various, relatively large
fluences. In this paper authors demonstrate that 30 wt% Potassium Hydroxide
(KOH) or 30 wt% sodium hydroxide (NaOH) at 70 oC temperature etch proton
irradiated PDMS selectively, and remove the chemically sufficiently modified
areas. In case of KOH development, the maximum etching rate was approximately
3.5 um/minute and it occurs at about 7.5*10^15 ion*cm-2. In case of NaOH
etching the maximum etching rate is slightly lower, 1.75 um/minute and can be
found at the slightly higher fluence of 8.75*10^15 ion*cm-2.
  These results are of high importance since up to this time it has not been
known how to develop the additive-free, cross-linked poly(dimethylsiloxane) in
lithography as a positive tone resist material.",1712.03125v1
2021-04-14,Inverse design of glass structure with deep graph neural networks,"Directly manipulating the atomic structure to achieve a specific property is
a long pursuit in the field of materials. However, hindered by the disordered,
non-prototypical glass structure and the complex interplay between structure
and property, such inverse design is dauntingly hard for glasses. Here,
combining two cutting-edge techniques, graph neural networks and swap Monte
Carlo, we develop a data-driven, property-oriented inverse design route that
managed to improve the plastic resistance of Cu-Zr metallic glasses in a
controllable way. Swap Monte Carlo, as ""sampler"", effectively explores the
glass landscape, and graph neural networks, with high regression accuracy in
predicting the plastic resistance, serves as ""decider"" to guide the search in
configuration space. Via an unconventional strengthening mechanism, a
geometrically ultra-stable yet energetically meta-stable state is unraveled,
contrary to the common belief that the higher the energy, the lower the plastic
resistance. This demonstrates a vast configuration space that can be easily
overlooked by conventional atomistic simulations. The data-driven techniques,
structural search methods and optimization algorithms consolidate to form a
toolbox, paving a new way to the design of glassy materials.",2104.06632v3
2021-05-07,Integrating superconducting van der Waals materials on paper substrates,"Paper has the potential to dramatically reduce the cost of electronic
components. In fact, paper is 10 000 times cheaper than crystalline silicon,
motivating the research to integrate electronic materials on paper substrates.
Among the different electronic materials, van der Waals materials are
attracting the interest of the scientific community working on paper-based
electronics because of the combination of high electrical performance and
mechanical flexibility. Up to now, different methods have been developed to
pattern conducting, semiconducting and insulating van der Waals materials on
paper but the integration of superconductors remains elusive. Here, the
deposition of NbSe2, an illustrative van der Waals superconductor, on standard
copy paper is demonstrated. The deposited NbSe2 films on paper display
superconducting properties (e.g. observation of Meissner effect and resistance
drop to zero-resistance state when cooled down below its critical temperature)
similar to those of bulk NbSe2.",2105.03487v1
2016-01-17,Resistivity plateau and extremely large magnetoresistance in NbAs2 and TaAs2,"In topological insulators (TIs), metallic surface conductance saturates the
insulating bulk resistance with de- creasing temperature, resulting in
resistivity plateau at low temperatures as a transport signature originating
from metallic surface modes protected by time reversal symmetry (TRS). Such
characteristic has been found in several materials including Bi2Te2Se, SmB6
etc. Recently, similar behavior has been observed in metallic com- pound LaSb,
accompanying an extremely large magetoresistance (XMR). Shubnikov-de Hass (SdH)
oscillation at low temperatures further confirms the metallic behavior of
plateau region under magnetic fields. LaSb[1] has been proposed by the authors
as a possible topological semimetal (TSM), while negative magnetoresistance is
absent at this moment. Here, high quality single crystals of NbAs2/TaAs2 with
inversion symmetry have been grown and the resistivity under magnetic field is
systematically investigated. Both of them exhibit metallic behavior under zero
magnetic field, and a metal-to-insulator transition occurs when a nonzero
magnetic field is applied, resulting in XMR (1.0*105% for NbAs2 and 7.3*105%
for TaAs2 at 2.5 K & 14 T). With tempera- ture decreased, a resistivity plateau
emerges after the insulator-like regime and SdH oscillation has also been
observed in NbAs2 and TaAs2.",1601.04239v1
2018-09-26,Changes in the near edge X-ray absorption fine structure of hybrid organic-inorganic resists upon exposure,"We report on the near edge X-ray absorption fine structure (NEXAFS)
spectroscopy of hybrid organic-inorganic resists. These materials are
nonchemically amplified systems based on Si, Zr, and Ti oxides, synthesized
from organically modified precursors and transition metal alkoxides by a
sol-gel route and designed for ultraviolet, extreme ultraviolet and electron
beam lithography. The experiments were conducted using a scanning transmission
X-ray microscope (STXM) which combines high spatial-resolution microscopy and
NEXAFS spectroscopy. The absorption spectra were collected in the proximity of
the carbon edge (~ 290 eV) before and after in situ exposure, enabling the
measurement of a significant photo-induced degradation of the organic group
(phenyl or methyl methacrylate, respectively), the degree of which depends on
the configuration of the ligand. Photo-induced degradation was more efficient
in the resist synthesized with pendant phenyl substituents than it was in the
case of systems based on bridging phenyl groups. The degradation of the methyl
methacrylate group was relatively efficient, with about half of the initial
ligands dissociated upon exposure. Our data reveal that the such dissociation
can produce different outcomes, depending on the structural configuration.
While all the organic groups were expected to detach and desorb from the resist
in their entirety, a sizeable amount of them remain and form undesired
byproducts such as alkene chains. In the framework of the materials synthesis
and engineering through specific building blocks, these results provide a
deeper insight into the photochemistry of resists, in particular for extreme
ultraviolet lithography.",1809.09916v1
2022-04-30,A simple strategy to measure the contact resistance between metals and doped organic films,"Charge injection from electrodes into doped organic films is a widespread
technology used in the majority of state-of-the-art organic semiconductor
devices. Although such interfaces are commonly considered to form Ohmic
contacts via strong band bending, an experiment that directly measures the
contact resistance has not yet been demonstrated. In this study, we use a
simple metal/doped organic semiconductor/metal stack and study its
voltage-dependent resistance. A transport layer thickness variation proves that
the presented experiment gains direct access to the contact resistance of the
device. We can quantify that for an operating current density of 10mA/cm2 the
investigated material system exhibits a voltage drop over the metal/organic
interface of about 200mV, which can be reduced by more than one order of
magnitude when employing an additional injection layer. The presented
experiment proposes a simple strategy to measure the contact resistance between
any metal and doped organic film without applying numerical tools or elaborate
techniques. Furthermore, the simplistic device architecture allows for very
high, homogeneous, and tunable electric fields within the organic layer, which
enables a clear investigation of the Poole-Frenkel effect.",2205.00261v1
2018-01-30,Novel circuit design for high-impedance and non-local electrical measurements of two-dimensional materials,"Two-dimensional materials offer a novel platform for the development of
future quantum technologies. However, the electrical characterisation of
topological insulating states, non-local resistance and bandgap tuning in
atomically-thin materials, can be strongly affected by spurious signals arising
from the measuring electronics. Common-mode voltages, dielectric leakage in the
coaxial cables and the limited input impedance of alternate-current amplifiers
can mask the true nature of such high-impedance states. Here, we present an
optical isolator circuit which grants access to such states by electrically
decoupling the current-injection from the voltage-sensing circuitry. We
benchmark our apparatus against two state-of-the-art measurements: the
non-local resistance of a graphene Hall bar and the transfer characteristic of
a WS2 field-effect transistor. Our system allows the quick characterisation of
novel insulating states in two-dimensional materials with potential
applications in future quantum technologies.",1801.10135v1
2013-08-31,Origin of defects responsible for charge transport in resistive random access memory based on hafnia,"A promising candidate for universal memory, which would involve combining the
most favourable properties of both high-speed dynamic random access memory
(DRAM) and non-volatile flash memory, is resistive random access memory
(ReRAM). ReRAM is based on switching back and forth from a high-resistance
state (HRS) to a low-resistance state (LRS). ReRAM cells are small, allowing
for the creation of memory on the scale of terabits. One of the most promising
materials for use as the active medium in resistive memory is hafnia (HfO$_2$).
  However, an unresolved physics is the nature of defects and traps that are
responsible for the charge transport in HRS state of resistive memory.
  In this study, we demonstrated experimentally and theoretically that oxygen
vacancies are responsible for the HRS charge transport in resistive memory
elements based on HfO$_2$. We also demonstrated that LRS transport occurs
through a mechanism described according to percolation theory.
  Based on the model of multiphonon tunneling between traps, and assuming that
the electron traps are oxygen vacancies, good quantitative agreement between
the experimental and theoretical data of current-voltage characteristics were
achieved. The thermal excitation energy of the traps in hafnia was determined
based on the excitation spectrum and luminescence of the oxygen vacancies.
  The findings of this study demonstrate that in resistive memory elements
using hafnia, the oxygen vacancies in hafnia play a key role in creating
defects in HRS charge transport.",1309.0071v2
2020-09-26,Optical imaging of strain-mediated phase coexistence during electrothermal switching in a Mott insulator,"Resistive-switching -- the current-/voltage-induced electrical resistance
change -- is at the core of memristive devices, which play an essential role in
the emerging field of neuromorphic computing. This study is about resistive
switching in a Mott-insulator, which undergoes a thermally driven
metal-to-insulator transition. Two distinct switching mechanisms were reported
for such a system: electric-field-driven resistive switching and electrothermal
resistive switching. The latter results from an instability caused by Joule
heating. Here, we present the visualization of the reversible resistive
switching in a planar V$_2$O$_3$ thin-film device using high-resolution
wide-field microscopy in combination with electric transport measurements. We
investigate the interaction of the electrothermal instability with the
strain-induced spontaneous phase-separation in the V$_2$O$_3$ thin film at the
Mott-transition. The photomicrographs show the formation of a narrow metallic
filament with a minimum width $\lesssim$ 500\,nm. Although the filament
formation and the overall shape of the current-voltage characteristics (IVCs)
are typical of an electrothermal breakdown, we also observe atypical effects
like oblique filaments, filament splitting, and hysteretic IVCs with
sawtooth-like jumps at high currents in the low-resistance regime. We were able
to reproduce the experimental results in a numerical model based on a
two-dimensional resistor network. This model demonstrates that resistive
switching, in this case, is indeed electrothermal and that the intrinsic
heterogeneity is responsible for the atypical effects. This heterogeneity is
strongly influenced by strain, thereby establishing a link between switching
dynamics and structural properties.",2009.12536v2
2023-10-01,Elucidating Dynamic Conductive State Changes in Amorphous Lithium Lanthanum Titanate for Resistive Switching Devices,"Exploration of novel resistive switching materials attracts attention to
replace conventional Si-based transistors and to achieve neuromorphic computing
that can surpass the limit of the current Von-Neumann computing for the time of
Internet of Things (IoT). Materials priorly used to serve in batteries have
demonstrated metal-insulator transitions upon an electrical biasing due to
resulting compositional change. This property is desirable for future resistive
switching devices. Amorphous lithium lanthanum titanate (a-LLTO) was originally
developed as a solid-state electrolyte with relatively high lithium ionic
conductivity and low electronic conductivity among oxide-type solid
electrolytes. However, it has been suggested that electric conductivity of
a-LLTO changes depending on oxygen content. In this work, the investigation of
switching behavior of a-LLTO was conducted by employing a range of voltage
sweep techniques, ultimately establishing a stable and optimal operating
condition within the voltage window of -3.5 V to 3.5 V. This voltage range
effectively balances the desirable trait of a substantial resistance change by
three orders of magnitude with the imperative avoidance of LLTO decomposition.
This switching behavior is also confirmed at nanodevice of Ni/LLTO/Ni through
in-situ biasing inside focused-ion beam/scanning electron microscope (FIB-SEM).
Experiment and computation with different LLTO composition shows that LLTO has
two distinct conductivity states due to Ti reduction. The distribution of these
two states is discussed using simplified binary model, implying the conductive
filament growth during low resistance state. Consequently, our study deepens
understanding of LLTO electronic properties and encourages the
interdisciplinary application of battery materials for resistive switching
devices.",2310.00543v1
2019-03-28,First Operation of a Resistive Shell Liquid Argon Time Projection Chamber -- A new Approach to Electric-Field Shaping,"We present a new technology for the shaping of the electric field in Time
Projection Chambers (TPCs) using a carbon-loaded polyimide foil. This
technology allows for the minimisation of passive material near the active
volume of the TPC and thus is capable to reduce background events originating
from radioactive decays or scattering on the material itself. Furthermore, the
high and continuous electric resistivity of the foil limits the power
dissipation per unit area and minimizes the risks of damages in the case of an
electric field breakdown. Replacing the conventional field cage with a
resistive plastic film structure called 'shell' decreases the number of
components within the TPC and therefore reduces the potential points of failure
when operating the detector. A prototype liquid argon (LAr) TPC with such a
resistive shell and with a cathode made of the same material was successfully
tested for long term operation with electric field values up to about 1.5
kV/cm. The experiment shows that it is feasible to successfully produce and
shape the electric field in liquefied noble-gas detectors with this new
technology.",1903.11858v2
2023-02-24,Antiferromagnetism of CeCd$_{0.67}$As$_{2}$ existing deep inside the narrow gap semiconducting state,"Single crystals of $R$Cd$_{0.67}$As$_2$ ($R$ = La and Ce) have been
synthesized by high temperature ternary melt and their physical properties have
been explored by means of magnetization, specific heat, electrical resistivity,
Hall coefficient, and thermoelectric power measurements. $R$Cd$_{0.67}$As$_2$
compounds indicate a (structural) phase transition at high temperatures,
accompanied by a remarkable increase of the electrical resistivity with an
extremely low carrier concentration. CeCd$_{0.67}$As$_2$ exhibits a large
magnetic anisotropy and an antiferromagnetic (AFM) order below $T_{N} = 4$~K.
Magnetic susceptibility curves, together with magnetization isotherms and
specific heat, are analyzed by the point charge model of crystalline electric
field (CEF). In the paramagnetic state, the observed magnetic properties can be
well explained by the CEF effects, implying that the 4$f$ moments remain
localized. Electrical resistivity measurements, together with Hall resistivity
and thermoelectric power, also suggest highly localized 4$f$ electrons, where
Kondo contributions are negligible. The low temperature physical properties
manifest strong magnetic field dependencies. For $H \perp c$, $T_{N}$ shifts to
lower temperature as magnetic field increases, and eventually disappears at
$H_{c} \sim 60$~ kOe. Inside the AFM state, three metamagnetic transitions are
clearly evidenced from the magnetization isotherms. The RKKY interaction may be
responsible for the AFM ordering in CeCd$_{0.67}$As$_2$, however it would have
to be mediated by extremely low charge carriers. Although the AFM ordering
temperature in CeCd$_{0.67}$As$_2$ can be continuously suppressed to zero, no
AFM quantum phase transition is expected due to the lack of conduction electron
clouds to screen the 4$f$ moments.",2302.12451v1
2003-05-06,High Magnetic Field Sensor Using LaSb2,"The magnetotransport properties of single crystals of the highly anisotropic
layered metal LaSb2 are reported in magnetic fields up to 45 T with fields
oriented both parallel and perpendicular to the layers. Below 10 K the
perpendicular magnetoresistance of LaSb2} becomes temperature independent and
is characterized by a 100-fold linear increase in resistance between 0 and 45 T
with no evidence of quantum oscillations down to 50 mK. The Hall resistivity is
hole-like and gives a high field carrier density of n ~ 3x10^20 cm^-3. The
feasibility of using LaSb2 for magnetic field sensors is discussed.",0305116v1
2016-12-30,CdTe and CdZnTe Crystal Growth and Production of Gamma Radiation Detectors,"Bridgman CdTe and CdZnTe crystal growth, with cadmium vapor pressure control,
is applied to production of semiconductor gamma radiation detectors. Crystals
are highly donor doped and highly electrically conducting. Annealing in
tellurium vapors transforms them into a highly compensated state of high
electrical resistance and high sensitivity to gamma radiation. N-type
detectors, equipped with ohmic contacts, and a grounded guard ring around the
positive contact, are not sensitive to hole trapping. Conductivity control, by
the doping level, optimizes the detector operation by trade-off between
electrons' lifetime and electrical resistance. Gamma spectra of single
detectors and detector arrays are presented. Detector optimization and gamma
detection mechanisms are discussed.",1612.09571v1
2015-06-25,Metallic multilayers for X-band Bragg reflector applications,"We present a structural and high frequency (8.72GHz) electrical
characterization of sputter deposited Ti/W, Ti/Ru and Mo/Ti metallic
multilayers for potential application as acoustic Bragg reflectors. We prove
that all metallic multilayers comprised of different acoustic impedance metals
such as Ti, W, Mo are promising candidates for Bragg reflector/bottom electrode
in full X-band thin film acoustic resonators. Values for high frequency
resistivity of the order of $10^{-8} ohm.m$ are measured by use of a
contact-free/non-invasive sheet resistance method.",1506.07702v1
2014-06-11,Very high thermoelectric power factor in a Fe3O4/SiO2/p-type Si(100)heterostructure,"The thermoelectric and transport properties of a Fe3O4/SiO2/p-Si(100)
heterostructure have been investigated between 100 and 300 K. Both Hall and
Seebeck coefficients change sign from negative to positive with increasing
temperature while the resistivity drops sharply due to tunneling of carriers
into the p-Si(100). The low resistivity and large Seebeck coefficient of Si
give a very high thermoelectric power factor of 25.5mW/K2m at 260K which is an
underestimated, lower limit value and is related to the density of states and
difference in the work functions of Fe3O4 and Si(100) that create an
accumulation of majority holes at the p-Si/SiO2 interface",1406.2814v1
2002-10-10,Effects of Pressure on Electron Transport and Local Structure of Manganites: Low to High Pressure Regime,"The pressure dependence of the resistivity and structure of
La0.60Y0.07Ca0.33MnO3 has been explored in the pressure range from 1 atm to ~7
GPa. The metal to insulator transition temperature (TMI) was found to reach a
maximum and the resistivity achieves a minimum at ~3.8 GPa. Beyond this
pressure, TMI is reduced with a concomitant increase in the resistivity.
Structural measurements at room temperature show that at low pressure (below 2
GPa) the Mn-O bond lengths are compressed. Between ~2 and ~4 GPa, a pressure
induced enhancement of the Jahn-Teller (JT) distortion occurs in parallel with
an increase in Mn-O1-Mn bond angle to ~180 (degree). Above ~4 GPa, the Mn-O1-Mn
bond angle is reduced while the JT distortion appears to remain unchanged. The
resistivity above TMI is well modeled by variable range hopping. The pressure
dependence of the localization length follows the behavior of TMI.",0210220v2
2003-07-31,Is Room Temperature Superconductivity in Carbon Nanotubes Too Wonderful to Believe?,"It is well known that copper-based perovskite oxides rightly enjoy consensus
as high-temperature superconductors on the basis of two signatures: Meissner
effect and zero resistance. In contrast, I provide over twenty signatures for
room temperature superconductivity in carbon nanotubes. The one-dimensionality
of the nanotubes complicates the right-of-passage for prospective
quasi-one-dimensional superconductors. The Meissner effect is less visible
because the diameters of nanotubes are much smaller than the penetration depth.
Zero resistance is less obvious because of the quantum contact resistance and
significant quantum phase slip, both of which are associated with a finite
number of transverse conduction channels. Nonetheless, on-tube resistance at
room temperature has been found to be indistinguishable from zero for many
individual multi-walled nanotubes. On the basis of more than twenty arguments,
I suggest that carbon nanotubes deserve to be classified as room temperature
superconductors. The mechanism for room-temperature superconductivity may arise
from strong electron-phonon and electron-plasmon coupling.",0307770v3
2003-09-24,High critical fields in MgB2 thin films with various resistivity values,"In this paper, we analyze the upper critical field of four MgB2 thin films,
with different resistivity (between 5 to 50 mWcm) and critical temperature
(between 29.5 to 38.8 K), measured up to 28 Tesla. In the perpendicular
direction the critical fields vary from 13 to 24 T and we can estimate 42-57 T
range in other direction. We observe linear temperature dependence even at low
temperatures without saturation, in contrast to BCS theory. Considering the
multiband nature of the superconductivity in MgB2, we conclude that two
different scattering mechanisms influence separately resistivity and critical
field. In this framework, resistivity values have been calculated from Hc2(T)
curves and compared with the measured ones.",0309543v1
2004-11-18,Hysteretic current-voltage characteristics and resistance switching at an epitaxial oxide Schottky junction SrRuO$_{3}$/SrTi$_{0.99}$Nb$_{0.01}$O$_{3}$,"Transport properties have been studied for a perovskite heterojunction
consisting of SrRuO$_{3}$ (SRO) film epitaxially grown on
SrTi$_{0.99}$Nb$_{0.01}$O$_{3}$ (Nb:STO) substrate. The SRO/Nb:STO interface
exhibits rectifying current-voltage ($I$-$V$) characteristics agreeing with
those of a Schottky junction composed of a deep work-function metal (SRO) and
an $n$-type semiconductor (Nb:STO). A hysteresis appears in the $I$-$V$
characteristics, where high resistance and low resistance states are induced by
reverse and forward bias stresses, respectively. The resistance switching is
also triggered by applying short voltage pulses of 1 $\mu$s - 10 ms duration.",0411474v1
2005-09-13,Evidence for High-Temperature Superconductivity in Doped Laser-Processed Sr-Ru-O,"We have discovered that samples of a new material produced by special
processing of crystals of Sr2RuO4 (which is known to be a triplet
superconductor with Tc values ~1.0-1.5K) exhibit signatures of
superconductivity (zero DC resistance and expulsion of magnetic flux) at
temperatures exceeding 200K. The special processing includes deposition of a
silver coating and laser micromachining; Ag doping and enhanced oxygen are
observed in the resultant surface layer. The transition, whether measured
resistively or by magnetic field expulsion, is broad. When the transition is
registered by resistive methods, the critical temperature is markedly reduced
when the measuring current is increased. The resistance disappears by about
190K. The highest value of Tc registered by magneto-optical visualization is
about 220K and even higher values (up to 250K) are indicated from the
SQUID-magnetometer measurements.",0509313v1
2006-05-04,Threshold Resistance in the DC Josephson Effect,"We show that SIS Josephson junctions have a threshold resistance, above which
the Josephson coupling and the supercurrents become extremely small, due to the
shrinking of the Cooper pair size during the Josephson tunneling. Accordingly,
the threshold resistance is smaller for higher Tc superconductors with small
Cooper pair size and for the insulating barrier with higher resistance. This
understanding agrees with the observations in SIS junctions of low Tc
superconductors, such as Sn, Pb, and Nb. For MgB2 it explains why the big gap
does not show the supercurrents, unlike the small gap. Furthermore, it is
consistent with the fact that high Tc cuprates show the Josephson effects only
for SNS type junctions, including the intrinsic Josephson effects.",0605122v1
2007-04-03,Scaling of Resistance and Electron Mean Free Path of Single-Walled Carbon Nanotubes,"We present an experimental investigation on the scaling of resistance in
individual single walled carbon nanotube devices with channel lengths that vary
four orders of magnitude on the same sample. The electron mean free path is
obtained from the linear scaling of resistance with length at various
temperatures. The low temperature mean free path is determined by impurity
scattering, while at high temperature the mean free path decreases with
increasing temperature, indicating that it is limited by electron-phonon
scattering. An unusually long mean free path at room temperature has been
experimentally confirmed. Exponentially increasing resistance with length at
extremely long length scales suggests anomalous localization effects.",0704.0300v2
2007-09-12,Thermal Transient Characterization of Packaged Thin Film Microcoolers,"A network identification by deconvolution (NID) method is applied to the
thermal transient response of packaged and unpackaged microcoolers. A thin film
resistor on top of the device is used as the heat source and the temperature
sensor. The package and the bonding thermal resistances can be easily
identified by comparing structure functions. High-speed coplanar probes are
used to achieve a short time resolution of roughly 100ns in the transient
temperature response. This is used to separate the thermal properties of the
thin film from the substrate. The obtained thermal resistances of the buffer
layer and Silicon substrate are consistent with the theoretical calculations.
In order to estimate the superlattice thermal resistance and separate it from
the thin SiNx layer deposited underneath the thin film resistive sensor, an
order of magnitude faster thermal transient response is needed.",0709.1817v1
2007-12-09,Interplay between carrier localization and magnetism in diluted magnetic and ferromagnetic semiconductors,"The presence of localized spins exerts a strong influence on quantum
localization in doped semiconductors. At the same time carrier-mediated
interactions between the localized spins are modified or even halted by
carriers' localization. The interplay of these effects is discussed for II-VI
and III-V diluted magnetic semiconductors. This insight is exploited to
interpret the complex dependence of resistance on temperature, magnetic field,
and concentration of valence-band holes in (Ga,Mn)As. In particular, high field
negative magnetoresistance results from the orbital weak localization effect.
The resistance maximum and the associated negative magnetoresistance near the
Curie temperature are assigned to the destructive influence of preformed
ferromagnetic bubbles on the ""antilocalization"" effect driven by
disorder-modified carrier-carrier interactions. These interactions account also
for the low-temperature increase of resistance. Furthermore, the sensitivity of
conductance to spin splitting and to scattering by spin disorder may explain
resistance anomalies at coercive fields, where relative directions of external
and molecular fields change.",0712.1293v2
2009-08-25,Bipolar resistive switching in amorphous titanium oxide thin films,"Using isothermal and temperature-dependent electrical measurements, we
investigated the resistive switching mechanism of amorphous titanium oxide thin
films deposited by a plasma-enhanced atomic layer deposition method between two
aluminum electrodes. We found a bipolar resistive switching behavior in the
high temperature region (> 140 K), and two activation energies of shallow
traps, 0.055 eV and 0.126 eV in the ohmic current regime. We also proposed that
the bipolar resistive switching of amorphous TiO2 thin films is governed by the
transition of conduction mode from a bulk-limited SCLC model (Off state) to an
interface-limited Schottky emission (On state), generated by the ionic movement
of oxygen vacancies.",0908.3525v1
2009-12-09,Scaling Properties of Ge-SixGe1-x Core-Shell Nanowire Field Effect Transistors,"We demonstrate the fabrication of high-performance Ge-SixGe1-x core-shell
nanowire field-effect transistors with highly doped source and drain, and
systematically investigate their scaling properties. Highly doped source and
drain regions are realized by low energy boron implantation, which enables
efficient carrier injection with a contact resistance much lower than the
nanowire resistance. We extract key device parameters, such as intrinsic
channel resistance, carrier mobility, effective channel length, and external
contact resistance, as well as benchmark the device switching speed and ON/OFF
current ratio.",0912.1827v1
2010-07-21,The effects of superconductor-stabilizer interfacial resistance on quench of a pancake coil made out of coated conductor,"We present the results of numerical analysis of normal zone propagation in a
stack of $YBa_2Cu_3O_{7-x}$ coated conductors which imitates a pancake coil.
Our main purpose is to determine whether the quench protection quality of such
coils can be substantially improved by increased contact resistance between the
superconducting film and the stabilizer. We show that with increased contact
resistance the speed of normal zone propagation increases, the detection of a
normal zone inside the coil becomes possible earlier, when the peak temperature
inside the normal zone is lower, and stability margins shrink. Thus, increasing
contact resistance may become a viable option for improving the prospects of
coated conductors for high $T_c$ magnets applications.",1007.3768v2
2012-10-15,Bi2Te_xSe_y series studied by resistivity and thermopower,"We study the detailed temperature and composition dependence of the
resistivity, $\rho(T)$, and thermopower, $S(T)$, for a series of layered
bismuth chalcogenides Bi$_2$Te$_{3-x}$Se$_x$, and report the stoichiometry
dependence of the optical band gap. In the resistivity of the most compensated
member, Bi$_2$Te$_{2.1}$Se$_{0.9}$, we find a low-temperature plateau whose
onset temperature correlates with the high-temperature activation energy. For
the whole series $S(T)$ can be described by a simple model for an extrinsic
semiconductor. By substituting Se for Te, the Fermi level is tuned from the
valence band into the conduction band. The maximum values of $S(T)$, bulk band
gap as well the activation energy in the resistivity are found for $x \approx
0.9$.",1210.3901v3
2014-07-14,Multistate nonvolatile straintronics controlled by a lateral electric field,"We present a multifunctional and multistate permanent memory device based on
lateral electric field control of a strained surface. Sub-coercive electrical
writing of a remnant strain of a PZT substrate imprints stable and rewritable
resistance changes on a CoFe overlayer. A proof-of-principle device, with the
simplest resistance strain gage design, is shown as a memory cell exhibiting
17-memory states of high reproducibility and reliability for nonvolatile
operations. Magnetoresistance of the film also depends on the cell state, and
indicates a rewritable change of magnetic properties persisting in the remnant
strain of the substrate. This makes it possible to combine strain, magnetic and
resistive functionalities in a single memory element, and suggests that
sub-coercive stress studies are of interest for straintronics applications.",1407.3651v2
2015-10-29,"Resistive superconducting transition and effects of atmospheric exposure in the intercalation superconductor Ax(C2H8N2)yFe2-zSe2 (A = Li, Na)","We have succeeded in observing zero-resistivity in newly discovered
intercalation superconductors Ax(C2H8N2)yFe2-zSe2 (A = Li, Na) with Tc = 45 K,
using the sintered pellet samples. The electrical resistivity, \r{ho}, in the
normal state is metallic and Tconset defined in the $\rho$ measurements, is as
high as ~ 57 K. We have also investigated effects of the atmospheric exposure
in Lix(C2H8N2)yFe2-zSe2. It has been found that both the crystal structure and
superconductivity are maintained at least up to several days, indicating this
material is comparatively resistant to the atmospheric exposure.",1510.08629v1
2016-05-19,Resistive Switching Characteristics of Al/Si3N4/p-Si MIS-Based Resistive Switching Memory Devices,"In this study, we proposed and demonstrated a self-rectifying property of
silicon nitride (Si3N4)-based resistive random access memory device by
employing p-type silicon (p-Si) as bottom electrode. The RRAM devices consisted
of Al/Si3N4/p-Si are fabricated by a low presure chemical vapor deposition and
exhibited an intrinsic diode property with non-linear current-voltage (I-V)
behavior. In addition, compared to conventional metal/insulator/metal (MIM)
structure of Al/Si3N4/Ti RRAM cells, operating current in whole bias regions
for proposed metal/insulator/semiconductor (MIS) cells has been dramatically
lowered because introduced p-Si bottom electrode efficiently suppresses the
current in both low and high resistive states. As a result, the results mean
that by employing p-Si as bottom electrode the Si3N4-based RRAM cells can be
applied to selector-free RRAM cells.",1605.06006v1
2016-06-25,Transport mechanism through metal-cobaltite interfaces,"The resistive switching (RS) properties as a function of temperature were
studied for Ag/La$_{1-x}$Sr$_x$CoO$_3$ (LSCO) interfaces. The LSCO is a
fully-relaxed 100 nm film grown by metal organic deposition on a LaAlO$_3$
substrate. Both low and a high resistance states were set at room temperature
and the temperature dependence of their current-voltage (IV) characteristics
was mea- sured taking care to avoid a significant change of the resistance
state. The obtained non-trivial IV curves of each state were well reproduced by
a circuit model which includes a Poole-Frenkel element and two ohmic
resistances. A microscopic description of the changes produced by the RS is
given, which enables to envision a picture of the interface as an area where
conductive and insulating phases are mixed, producing Maxwell-Wagner
contributions to the dielectric properties.",1606.07974v1
2016-07-19,Non-quasiparticle transport and resistivity saturation: A view from the large-N limit,"The electron dynamics in metals are usually well described by the
semiclassical approximation for long-lived quasiparticles. However, in some
metals, the scattering rate of the electrons at elevated temperatures becomes
comparable to the Fermi energy; then, this approximation breaks down, and the
full quantum-mechanical nature of the electrons must be considered. In this
work, we study a solvable, large-$N$ electron-phonon model, which at high
temperatures enters the non-quasiparticle regime. In this regime, the model
exhibits ""resistivity saturation"" to a temperature-independent value of the
order of the quantum of resistivity - the first analytically tractable model to
do so. The saturation is not due to a fundamental limit on the electron
lifetime, but rather to the appearance of a second conductivity channel. This
is suggestive of the phenomenological ""parallel resistor formula"", known to
describe the resistivity of a variety of saturating metals.",1607.05725v1
2016-11-04,Origin of multistate resistive switching in Ti/manganite/Si$O_x$/Si heterostructures,"We report on the growth and characterization of
Ti/$La_{1/3}$$Ca_{2/3}$Mn$O_3$/Si$O_x$/n-Si memristive devices. We demonstrate
that using current as electrical stimulus unveils an intermediate resistance
state, in addition to the usual high and low resistance states that are
observed in standard voltage controlled experiments. Based on thorough
electrical characterization (impedance spectroscopy, current-voltage curves
analysis), we disclose the contribution of three different microscopic regions
of the device to the transport properties: an ohmic incomplete metallic
filament, a thin manganite layer below the filament tip exhibiting
Poole-Frenkel like conduction, and the SiOx layer with an electrical response
well characterized by a Child-Langmuir law. Our results suggest that the
existence of the SiOx layer plays a key role in the stabilization of the
intermediate resistance level, indicating that the combination of two or more
active RS oxides adds functionalities in relation to single-oxide devices. We
understand that these multilevel devices are interesting and promising as their
fabrication procedure is rather simple and they are fully compatible with
standard Si-based electronics.",1611.01552v2
2017-06-07,Spatially Resolved Thermometry of Resistive Memory Devices,"The operation of resistive and phase-change memory (RRAM and PCM) is
controlled by highly localized self-heating effects, yet detailed studies of
their temperature are rare due to challenges of nanoscale thermometry. Here we
show that the combination of Raman thermometry and scanning thermal microscopy
(SThM) can enable such measurements with high spatial resolution. We report
temperature-dependent Raman spectra of HfO$_2$, TiO$_2$ and Ge$_2$Sb$_2$Te$_5$
(GST) films, and demonstrate direct measurements of temperature profiles in
lateral PCM devices. Our measurements reveal that electrical and thermal
interfaces dominate the operation of such devices, uncovering a thermal
boundary resistance of 30 m$^2$K$^{-1}$GW$^{-1}$ at GST-SiO$_2$ interfaces and
an effective thermopower 350 $\mu$V/K at GST-Pt interfaces. We also discuss
possible pathways to apply Raman thermometry and SThM techniques to nanoscale
and vertical resistive memory devices.",1706.02318v1
2017-12-03,Microstructure and properties of Cu-Sn-Zn-TiO2 Nano-composite coatings on mild steel,"Cu-Sn-Zn coatings have been widely used in industry for their unique
properties, such as good conductivity, high corrosion resistance and excellent
solderability. To further improve the mechanical performance of Cu-Sn-Zn
coatings, powder-enhanced method was applied in the current study and
Cu-Sn-Zn-TiO2 nano-composite coatings with different TiO2 concentration were
fabricated. The microstructure of Cu-Sn-Zn-TiO2 nano-composite coatings were
investigated by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM).
The mechanical properties of coatings including microhardness and wear
resistance were studied. The results indicate that the incorporation of TiO2
nanoparticle can significantly influence the properties of Cu-Sn-Zn coatings.
The microhardness of Cu-Sn-Zn coating was increased to 383 HV from 330 HV with
1g/L TiO2 addition. Also, the corrosion resistance of coating was enhanced. The
effects of TiO2 nanoparticle concentration on the microstructure, mechanical
properties and corrosion resistance of Cu-Sn-Zn-TiO2 nano-composite coatings
were discussed.",1712.00853v1
2022-02-11,Comparison of the charge-crystal and charge-glass state in geometrically frustrated organic conductors studied by fluctuation spectroscopy,"We present a systematic investigation of the low-frequency charge carrier
dynamics in different charge states of the organic conductors
$\theta$-(BEDT-TTF)$_2$$M$Zn(SCN)$_4$ with $M$=Rb,Tl, which result from
quenching or relaxing the charge degrees of freedom on a geometrically
frustrated triangular lattice. Due to strong electronic correlations these
materials exhibit a charge-ordering transition, which can be kinetically
avoided by rapid cooling resulting in a so-called charge-glass state without
long-range order. The combination of fluctuation spectroscopy and a heat pulse
method allows us to study and compare the resistance fluctuations in the
low-resistive quenched and the high-resistive charge-ordered state, revealing
striking differences in the respective noise magnitudes. For both compounds, we
find strongly enhanced resistance fluctuations right at the metal-insulator
transition and a broad noise maximum in the slowly cooled charge-crystal state
with partly dominating two-level processes revealing characteristic activation
energies.",2202.05602v1
2007-10-09,Strong reduction of field-dependent microwave surface resistance in YBa$_{2}$Cu$_{3}$O$_{7-δ}$ with sub-micrometric BaZrO$_3$ inclusions,"We observe a strong reduction of the field induced thin film surface
resistance measured at high microwave frequency ($\nu=$47.7 GHz) in
YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin films grown on SrTiO$_3$ substrates, as a
consequence of the introduction of sub-micrometric BaZrO$_3$ particles. The
field increase of the surface resistance is smaller by a factor of $\sim$3 in
the film with BaZrO$_3$ inclusions, while the zero-field properties are not
much affected. Combining surface resistance and surface reactance data we
conclude (a) that BaZrO$_3$ inclusions determine very deep and steep pinning
wells and (b) that the pinning changes nature with respect to the pure film.",0710.1754v1
2017-08-04,Tunable Spin-Orbit Torques in Cu-Ta Binary Alloy Heterostructures,"The spin Hall effect (SHE) is found to be strong in heavy transition metals
(HM), such as Ta and W, in their amorphous and/or high resistivity form. In
this work, we show that by employing a Cu-Ta binary alloy as buffer layer in an
amorphous Cu$_{100-x}$Ta$_{x}$-based magnetic heterostructure with
perpendicular magnetic anisotropy (PMA), the SHE-induced damping-like
spin-orbit torque (DL-SOT) efficiency $|\xi_{DL}|$ can be linearly tuned by
adjusting the buffer layer resistivity. Current-induced SOT switching can also
be achieved in these Cu$_{100-x}$Ta$_{x}$-based magnetic heterostructures, and
we find the switching behavior better explained by a SOT-assisted domain wall
propagation picture. Through systematic studies on Cu$_{100-x}$Ta$_{x}$-based
samples with various compositions, we determine the lower bound of spin Hall
conductivity
$|\sigma_{SH}|\approx2.02\times10^{4}[\hbar/2e]\Omega^{-1}\cdot\operatorname{m}^{-1}$
in the Ta-rich regime. Based on the idea of resistivity tuning, we further
demonstrate that $|\xi_{DL}|$ can be enhanced from 0.087 for pure Ta to 0.152
by employing a resistive TaN buffer layer.",1708.01356v1
2019-03-29,Effect of synthesis conditions on the electrical resistivity of TiSe$_2$,"Dilute impurities and growth conditions can drastically affect the transport
properties of TiSe$_2$, especially below the charge density wave transition. In
this paper, we discuss the effects of cooling rate, annealing time and
annealing temperature on the transport properties of TiSe$_2$: slow cooling of
polycrystalline TiSe$_2$ post-synthesis drastically increases the low
temperature resistivity, which is in contrast to the metallic behavior of
single-crystalline TiSe$_2$ due to charge doping from the residual iodine
transport agent. A logarithmic increase of resistivity upon cooling and
negative magnetoresistance with a sharp cusp around zero field are observed for
the first time for the polycrystalline TiSe$_2$ samples, pointing to
weak-localization effects due to low dimensionality. Annealing at low
temperatures has a similar, but less drastic effect. Furthermore, rapid
quenching of the polycrystalline samples from high temperatures freezes in
disorder, leading to a decrease in the low temperature resistivity.",1903.12375v3
2019-12-18,A theory of resistivity in Kondo lattice materials: the memory function approach,"We theoretically analyse D.C. resistivity($\rho$) in the Kondo-lattice model
using the powerful memory function approach. The complete temperature evolution
of $\rho$ is investigated using the W\""{o}lfle-G\""{o}tze expansion of the
memory function. The resistivity in this model originates due to spin-flip
magnetic scattering of conduction $s$-electron off the quasi-localized $d$ or
$f$ electron spins. We find the famous resistivity upturn at lower temperature
regime ($k_B T<<\mu_d$), where $\mu_d$ is the effective chemical potential of
$d$-electrons. In the high temperature regime $(\mu_d<<k_B T)$ we discover that
$\rho \propto T^{\frac{3}{2}}$. The worked out theory is quantitatively
compared with experimental data and reasonably good agreement is found.",1912.08407v1
2019-06-15,Oxide layer thickness effects on the resistance switching characteristics of Ti/TiO2-NT/Au structure,"Self-ordered nanotubular titania TiO2-NT with outer tube diameter of 45 nm
are synthesized using the anodic oxidation of titanium foil. Four sets of
memristors with 100 ${\mu}m$ diameter based on Ti/TiO2-NT/Au sandwich
structures with an oxide layer thickness of 80, 120, 160 and 200 nm are
fabricated. Current-voltage (CV) characteristics for the obtained samples in
the static and dynamic operation modes are studied. Resistance in high and low
resistance states is estimated. Basing on the analysis of the CV
characteristics in dynamic mode (> 14 000 switchings) a prospective of use for
synthesized Ti/TiO2-NT/Au micromemristors with oxide layer thickness of 160 nm
in non-volatile memory is shown.
  Keywords: anodic titania, titanium dioxide nanotubes, nanotubular structure,
memristor, resistive switching",1906.06555v1
2019-11-28,Tailored joint fabrication process derived ultra-low resistance MgB2 superconducting joint,"We report an ultra-low resistance superconducting joint using unreacted
multifilament MgB2 wires produced by tailoring the powder compaction pressure
within the joint with heat treatment conditions. The joint demonstrated an
ultra-low resistance of 5.48 x 10^-15 ohms and critical current (Ic) of 91.3 A
at 20 K in self-field. The microstructural and composition studies of the joint
revealed cracks and a high amount of MgO, respectively. These two features
reduced the Ic of the joint to some extent; nevertheless, the joint resistance
was not affected by it. Our tailored joining process will play a pivotal role
in superconducting joint development.",1911.12645v1
2020-10-23,Improvement of HRS Variability in OxRRAM by Tailored Metallic Liner,"In this work, we propose a novel integration in order to significantly reduce
the High Resistance State vari-ability and to improve thermal stability in
Oxide-based Resistive Random Access Memory (OxRRAM) devices. A novel device
featuring a metallic liner, acting as a parallel resistance, is presented. To
assess the effect of this solution, we compare the results with a standard
OxRRAM cell structure. A very good stability of the resistive states, both in
endurance and temperature, is highlighted and explained thanks to a conductive
fila-ment based model.",2010.12210v1
2020-11-01,Light induced resistive switching in copper oxide thin films,"Copper oxide thin film based metal-insulator-metal structures were subjected
to white light irradiation.The top electrodes included Al, Cr and Ni while the
bottom electrode was either Au or Pt. A white light pulse controls the set
process and this light induced set (LIS) can be performed at very low voltages
(tens of milli volts) which is not possible in the normal set process. The LIS
is initiated at the positive edge of the pulse and there is no effect of the
falling edge of the light. In most cases the high resistance state (HRS) to low
resistance state (LRS) transition is irreversible i.e.the devices continue to
remain in the LRS even after the light pulse is switched off. Light induced
reset (LIR) is achieved in only one device structure Al/CuxO/Au. By using LIS
and LIR, set and reset power of the device can be reduced to a great extent and
the set and reset parameters variation also reduces. The current work, thus,
points to the possibility of formation and compliance-free resistive random
access memory devices.",2011.00423v1
2021-04-05,Charge density wave and finite-temperature transport in minimally twisted bilayer graphene,"We study phenomena driven by electron-electron interactions in the minimally
twisted bilayer graphene (mTBLG) with a perpendicular electric field. The
low-energy degrees of freedom in mTBLG are governed by a network of
one-dimensional domain-wall states, described by two channels of
one-dimensional linearly dispersing spin-1/2 fermions. We show that the
interaction can realize a spin-gapped inter-channel charge density wave (CDW)
state at low temperatures, forming a ""Coulomb drag"" between the channels and
leaving only one charge conducting mode. For sufficiently high temperatures,
power-law-in-temperature resistivity emerges from the charge umklapp
scatterings within a domain wall. Remarkably, the presence of the CDW states
can strengthen the charge umklapp scattering and induce a resistivity minimum
at an intermediate temperature corresponding to the CDW correlation energy. We
further discuss the conditions that resistivity of the network is dominated by
the domain walls. In particular, the power-law-in-temperature resistivity
results can apply to other systems that manifest topological domain-wall
structures.",2104.02084v2
2021-05-14,Mechanical Response of Mesoporous Amorphous NiTi Alloy to External Deformations,"The porous titanium nickelide is very popular in various industries due to
unique combination of physical and mechanical properties such as shape memory
effect, high corrosion resistance, and biocompatibility. The non-equilibrium
molecular dynamics simulation was applied to study the influence of porosity
degree on mechanical properties of porous amorphous titanium nickelide at
uniaxial tension, uniaxial compression, and uniform shear. We have found that
the porous amorphous alloy is characterized by a relatively large value of
Young's modulus in comparison to its crystalline analogue. It has been found
that the system with a percolated network of pores exhibits improved elastic
characteristics associated with resistance to tensile and shear. The system
contained isolated spherical pores is more resistant to compression and less
resistant to tensile and shear. These results can be applied to develop and
improve the methods for making amorphous metal foams.",2105.06693v1
2021-08-01,Sb concentration dependent Structural and Transport properties of Polycrystalline (Bi1-xSbx)2Te3 Mixed crystal,"(Bi1-xSbx)2Te3 (x=0.60, 0.65, 0.68, 0.70, 0.75 and 0.80) mixed crystals have
been synthesized by solid state reaction. In depth structural, thermal,
transport and electronic properties are reported. Defect and disorder play a
crucial role in structural and transport behaviour. Disorder induced
iso-structural phase transition is observed at x=0.70, which is supported by
the structural and transport properties data. Debye temperature has been
estimated from the powder diffraction data. Differential scanning calorimetry
(DSC) data confirms the glass transition in the material. Low temperature
resistivity data shows Variable range hopping mechanism whereas high
temperature data follows activated behaviour. Activation energy is calculated
from the semiconducting region of resistivity data. Both Hall measurement and
temperature dependent thermopower data (S(T)) confirms that samples are p-type
in nature. Density of state effective mass has been estimated from Pisarenko
relation and corroborated with resistivity data. Thermal conductivity (k) is
estimated using experimentally obtained data. Figure of Merit (ZT) of the
synthesized samples are calculated using resistivity, S(T) and k. Structural
and transport properties are correlated, confirms the transition from disorder
to order state. Defect and disorder are corroborated with structural and
Thermoelectric properties of the synthesized samples.",2108.00525v1
2021-10-16,Topological phonons in an inhomogeneously strained silicon-6: Possible evidence of the high temperature spin superfluidity and the second sound of topological phonons,"The superposition of topological phonons and flexoelectronic charge
separation in an inhomogeneously strain Si give rise to topological electronic
magnetism of phonons. The topological electronic magnetism of phonons is also
expected to give rise to stationary spin current or spin superfluidity. In this
experimental study, we present possible evidence of spin superfluidity in an
inhomogeneously strained p-Si thin films samples. The spin superfluidity is
uncovered using non-local resistance measurement. A resonance behavior is
observed in a non-local resistance measurement at 10 kHz and between 270 K and
281.55 K, which is attributed to the second sound. The observation of second
sound and spatially varying non-local resistance phase are the evidences for
spin superfluidity. The spatially varying non-local resistance with opposite
phase are also observed in Pt/MgO/p-Si sample. The overall non-local responses
can be treated as a standing waveform from temporal magnetic moments of the
topological phonons.",2110.08431v1
2021-12-10,"Transport in the emergent Bose liquid: Bad metal, strange metal, and weak insulator, all in one system","Non-saturating high-temperature resistivity (""bad metal""), T-linear
low-temperature resistivity (""strange metal""), and a crossover to
activation-free growth of the resistivity in the low-temperature limit (""weak
insulator"") are among the most exotic behaviors widely observed in many
strongly correlated materials for decades that defy the standard Fermi liquid
description of solids. Here we investigate these puzzling behaviors by
computing temperature-dependent optical conductivity of an emergent Bose liquid
and find that it reproduces all the unexplained features of the experiments,
including a featureless continuum and a well-known mid-infrared peak. Amazingly
and with physically intuitive mechanisms, the corresponding doping- and
temperature-dependent resistivity displays the bad metal and strange metal
simultaneously and sometimes weak insulating behaviors as well. The unification
of all these non-Fermi liquid behaviors in a single model suggests that a new
quantum state of matter, namely the emergent Bose liquid, will guide the
development of the next generation of solid state physics.",2112.05747v1
2022-04-20,Electrical breakdown in Thick-GEM based WELL detectors,"The occurrence of electrical discharges in gas detectors restricts their
dynamic range and degrades their performance. Among the different methods
developed to mitigate discharge effects, the use of resistive materials in the
detector assembly was found to be very effective. In this work, we present the
results of a comparative study of electrical discharges in Thick-GEM-based
WELL-type detectors - with and without resistive elements. We present a new
method to measure discharges in the resistive-detector configurations; it
allows demonstrating, for the first time, the occurrence of discharges also in
the Resistive-Plate WELL detector configuration. It also provides direct
evidence for the Raether limit.",2204.09445v2
2022-11-27,Evolution of Resistive Switching Characteristics in WO3-x-based MIM Devices by Tailoring Oxygen Deficiency,"We report on resistive switching (RS) characteristics of W/WO3-x/Pt-based
thin film memristors modulated by precisely controlled oxygen
non-stoichiometry. RS properties of the devices with varied oxygen vacancy (VO)
concentration have been studied by measuring their DC current voltage
properties. Switchability of the resistance states in the memristors have been
found to depend strongly on the VOs concentration in the WO3-x layer. Depending
on x, the memristors exhibited forming-free bipolar, forming-required bipolar
and non-formable characteristics. Devices with high VOs concentration (~1*1021
cm-3) exhibited lower initial resistance and memory window of only 15, which
has been increased to ~6500 with reducing VOs concentration to ~5.8*1020 cm-3.
Forming-free, stable RS with memory window of ~2000 have been realized for a
memristor possessing VOs concentration of ~6.2*1020 cm-3. Investigation of the
conduction mechanism suggests that tailoring VOs concentration modifies the
formation and dimension of the conducting filaments as well as the Schottky
barrier height at WO3-x/Pt interface which deterministically modulates RS
characteristics of the WO3-x based memristors.",2211.14809v1
2024-05-13,Durability of MgO/hydromagnesite mortars -- Resistance to chlorides and corrosion,"The durability of MgO/hydromagnesite mortars was studied with respect to
their corrosion performance and resistance to chloride attack and moisture.
MgO/hydromagnesite pastes were cured in chloride solution to induce potential
formation of Mg-chlorides; however, no such phases were observed. Rapid
chloride ingress measurements demonstrated high penetration resistance and low
chloride migration coefficients, i.e. D_Cl = 1e-13 to 1e-12 m^2/s. The
corrosion rate of carbon steel embedded in MgO/HY mortars, as determined by
linear polarization resistance measurements, was in the range icorr = 1e-9
A/cm^2 in dry and 1e-7 A/cm^2 in wet conditions, irrespective of the mortar
composition or curing condition.These findings corroborate the hypothesis that,
in the absence of chlorides, the moisture condition is the primary predictor of
corrosion rate of carbon steel in the MgO/hydromagnesite binder. These
accelerated, short-term experiments suggest that the binder may be suited to
protect embedded carbon steel from corrosion under specific exposure conditions
of practical relevance.",2405.08164v1
2024-05-27,Electronic thermal resistivity and quasi-particle collision cross-section in semi-metals,"Electron-electron collisions lead to a T-square component in the electrical
resistivity of Fermi liquids. The case of liquid $^3$He illustrates that the
\textit{thermal} resitivity of a Fermi liquid has a T-square term, expressed in
m$\cdot$W$^{-1}$. Its natural units are $\hbar/k_FE_F^2$. Here, we present a
high-resolution study of the thermal conductivity in bismuth, employing
magnetic field to extract the tiny electronic component of the total thermal
conductivity and resolving signals as small as $\approx 60 \mu$K. We find that
the electronic thermal resistivity follows a T-square temperature dependence
with a prefactor twice larger than the electric T-square prefactor. Adding this
information to what has been known for other semi-metals, we find that the
prefactor of the T-square thermal resistivity scales with the square of the
inverse of the Fermi temperature, implying that the dimensionless
fermion-fermion collision cross-section is roughly proportional to the Fermi
wavelength, indicating that it is not simply set by the strength of the Coulomb
interaction.",2405.16984v2
2017-10-02,Anomalous magnetotransport properties of high-quality single crystals of Weyl semimetal WTe2: Sign change of Hall resistivity,"We report on a systematic study of Hall effect using high quality single
crystals of type-II Weyl semimetal WTe2 with the applied magnetic field B//c.
The residual resistivity ratio of 1330 and the large magnetoresistance of
1.5\times10^6 % in 9 T at 2 K, being in the highest class in the literature,
attest to their high quality. Based on a simple two-band model, the densities
(n_e and n_h) and mobilities (\mu_e and \mu_h) for electron and hole carriers
have been uniquely determined combining both Hall- and electrical-resistivity
data. The difference between ne and nh is ~1% at 2 K, indicating that the
system is in an almost compensated condition. The negative Hall resistivity
growing rapidly below ~20 K is due to a rapidly increasing \mu_h/\mu_e
approaching one. Below 3 K in a low field region, we found the Hall resistivity
becomes positive, reflecting that \mu_h/\mu_e finally exceeds one in this
region. These anomalous behaviors of the carrier densities and mobilities might
be associated with the existence of a Lifshitz transition and/or the spin
texture on the Fermi surface.",1710.00570v1
2021-10-14,Superconductor-insulator transitions in three-dimensional indium-oxide at high pressures,"Experiments investigating magnetic-field-tuned superconductor-insulator
transition (HSIT) mostly focus on two-dimensional material systems where the
transition and its proximate ground-state phases, often exhibit features that
are seemingly at odds with the expected behavior. Here we present a
complementary study of a three-dimensional pressure-packed amorphous
indium-oxide (InOx) powder where granularity controls the HSIT. Above a low
threshold pressure of ~0.2 GPa, vestiges of superconductivity are detected,
although neither a true superconducting transition nor insulating behavior are
observed. Instead, a saturation at very high resistivity at low pressure is
followed by saturation at very low resistivity at higher pressure. We identify
both as different manifestations of anomalous metallic phases dominated by
superconducting fluctuations. By analogy with previous identification of the
low resistance saturation as a ""failed superconductor"", our data suggests that
the very high resistance saturation is a manifestation of a ""failed insulator"".
Above a threshold pressure of ~6 GPa, the sample becomes fully packed, and
superconductivity is robust, with TC tunable with pressure. A quantum critical
point at PC~25 GPa marks the complete suppression of superconductivity. For a
finite pressure below PC, a magnetic field is shown to induce a HSIT from a
true zero-resistance superconducting state to a weakly insulating behavior.
Determining the critical field, HC, we show that similar to the 2D behavior,
the insulating-like state maintains a superconducting character, which is
quenched at higher field, above which the magnetoresistance decreases to its
fermionic normal state value.",2110.07251v3
2012-07-26,High pressure transport studies of the LiFeAs analogues CuFeTe2 and Fe2As,"We have synthesized two iron-pnictide/chalcogenide materials, CuFeTe2 and
Fe2As, which share crystallographic features with known iron-based
superconductors, and carried out high-pressure electrical resistivity
measurements on these materials to pressures in excess of 30 GPa. Both
compounds crystallize in the Cu2Sb-type crystal structure that is
characteristic of LiFeAs (with CuFeTe2 exhibiting a disordered variant). At
ambient pressure, CuFeTe2 is a semiconductor and has been suggested to exhibit
a spin-density-wave transition, while Fe2As is a metallic antiferromagnet. The
electrical resistivity of CuFeTe2, measured at 4 K, decreases by almost two
orders of magnitude between ambient pressure and 2.4 GPa. At 34 GPa, the
electrical resistivity decreases upon cooling the sample below 150 K,
suggesting the proximity of the compound to a metal-insulator transition.
Neither CuFeTe2 nor Fe2As superconduct above 1.1 K throughout the measured
pressure range.",1207.6272v1
2012-10-12,Pressure Induced Superconductivity in Ba0.5Sr0.5Fe2As2,"High-pressure electrical resistance measurements have been performed on
single crystal Ba0.5Sr0.5Fe2As2 platelets to pressures of 16 GPa and
temperatures down to 10 K using designer diamond anvils under quasi-hydrostatic
conditions with an insulating steatite pressure medium. The resistance
measurements show evidence of pressure-induced superconductivity with an onset
transition temperature at ~31 K and zero resistance at ~22 K for a pressure of
3.3 GPa. The transition temperature decreases gradually with increasing in
pressure before completely disappearing for pressures above 12 GPa. The present
results provide experimental evidence that a solid solution of two 122-type
materials, e.g., Ba1-x.SrxFe2As2 (0 < x <1), can also exhibit superconductivity
under high pressure",1210.3603v1
2012-12-03,Observation of Resistively Detected Hole Spin Resonance and Zero-field Pseudo-spin Splitting in Epitaxial Graphene,"Electronic carriers in graphene show a high carrier mobility at room
temperature. Thus, this system is widely viewed as a potential future
charge-based high-speed electronic-material to complement- or replace- silicon.
At the same time, the spin properties of graphene have suggested improved
capability for spin-based electronics or spintronics, and spin-based quantum
computing. As a result, the detection, characterization, and transport of spin
have become topics of interest in graphene. Here we report a microwave
photo-excited transport study of monolayer and trilayer graphene that reveals
an unexpectedly strong microwave-induced electrical-response and dual
microwave-induced resonances in the dc-resistance. The results suggest the
resistive detection of spin resonance, and provide a measurement of the
g-factor, the spin relaxation time, and the sub-lattice degeneracy-splitting at
zero-magnetic-field.",1212.0329v1
2013-04-09,Upper critical field of high quality single crystals of KFe$_2$As$_2$,"Measurements of temperature-dependent in-plane resistivity, $\rho(T)$, were
used to determine the upper critical field and its anisotropy in high quality
single crystals of stoichiometric iron arsenide superconductor KFe$_2$As$_2$.
The crystals were characterized by residual resistivity ratio,
$\rho(300K)/\rho(0)$ up to 3000 and resistive transition midpoint temperature,
$T_c$=3.8 K, significantly higher than in previous studies on the same
material. We find increased $H_{c2}(T)$ for both directions of the magnetic
field, which scale with the increased $T_c$. This unusual linear $H_{c2}(T_c)$
scaling is not expected for orbital limiting mechanism of the upper critical
field in clean materials.",1304.2689v1
2017-10-10,Thermal conductivity and electrical resistivity of solid iron at Earth's core conditions from first-principles,"We compute the thermal conductivity and electrical resistivity of solid hcp
Fe to pressures and temperatures of Earth's core. We find significant
contributions from electron-electron scattering, usually neglected at high
temperatures in transition metals. Our calculations show a quasi-linear
relation between electrical resistivity and temperature for hcp Fe at extreme
high pressures. We obtain thermal and electrical conductivities that are
consistent with experiments considering reasonable error. The predicted thermal
conductivity is reduced from previous estimates that neglect electron-electron
scattering. Our estimated thermal conductivity for the outer core is 77$\pm$10
W/m/K, and is consistent with a geodynamo driven by thermal convection.",1710.03564v6
2014-08-20,Carbon Memory Assessment,"The geometrical and performance scaling of silicon CMOS integrated circuit
technology over the past 50 years has enabled many affordable new products for
business and consumer applications. Recognizing that Flash is approaching its
ultimate physical scaling limits within the next 10 years or so, the global
electronics research community has begun an intense search for a new paradigm
and technology for extending the functional scaling of memory technologies.
Several promising nonvolatile memory concepts have emerged, based on different
switching and retention mechanisms from those of Flash memory, e.g., STTRAM,
RRAM, PCM and more recently, resistive memories based on carbon, which are the
topic of this paper. This paper will introduce into the diverse field of carbon
materials by recollecting some effects in carbon that can be used to produce a
multiple time switchable, non-volatile unipolar resistive memory with potential
high scalability down to atomic dimensions. Carbon-based memory is a
non-volatile resistive memory, therefore, the same architectures, circuits,
select transistor or diodes like in ReRAM or PCRAM can be considered as
implementation. The big advantage of carbon memory might be the high
temperature retention of 250 C, which makes it attractive for automotive and
harsh conditions. This is a white paper for the ITRS meeting on emerging
research devices (ERD) in Albuquerque, New Mexico, on August 25-26, 2014.",1408.4600v1
2003-11-06,"Violation of the Mott-Ioffe-Regel Limit: High-temperature Resistivity of Itinerant Magnets Srn+1RunO3n+1 (n=2,3,infinity) and CaRuO3","Srn+1RunO3n+1 represents a class of layered materials whose physical
properties are a strong function of the number of Ru-O layers per unit cell, n.
This series includes the p-wave superconductor Sr2RuO4 (n=1), enhanced
paramagnetic Sr3Ru2O7 (n=2), nearly ferromagnetic Sr4Ru3O10 (n=3) and itinerant
ferromagnetic SrRuO3 (n=infinity). In spite of a wide spectrum of physical
phenomena, this series of materials along with paramagnetic CaRuO3 shares two
major characteristics, namely, robust Fermi liquid behavior at low temperatures
and anomalous transport behavior featured by linear temperature dependence of
resistivity at high temperature where electron wavepackets are no longer
clearly defined. There is no crossover separating such two fundamentally
different states. In this paper, we report results of our study that
systematically addresses anisotropy and temperature dependence of basal-plane
and c-axis resistivity as a function of n for the entire Srn+1RunO3n+1 series
and CaRuO3 and for a wide temperature range of 1.7 K<T<900 K. It is found that
the anomalous transport behavior correlates with magnetic susceptibility and
becomes stronger with decreasing dimensionality. Implications of these results
are discussed.",0311142v1
2022-03-09,"Vanadium doped beta-Ga2O3 single crystals: Growth, Optical and Terahertz characterization","We report the growth of electrically-resistive vanadium-doped beta-Ga2O3
single crystals via the optical floating zone technique. By carefully
controlling the growth parameters V-doped crystals with very high electrical
resistivity compared to the usual n-type V-doped beta-Ga2O3 (ne~10^(18)/cm^3)
can be synthesized. The optical properties of such high resistive V-doped
b-Ga2O3 are significantly different compared to the undoped and n-doped
crystals. We study the polarization-dependent Raman spectra,
polarization-dependent transmission, temperature-dependent photoluminescence in
the optical wavelength range and the THz transmission properties in the 0.2 -
2.6 THz range. The V-doped insulating Ga2O3 crystals show strong birefringence
with refractive index contrast Dn of 0.3+-0.02 at 1 THz, suggesting it to be an
ideal material for optical applications in the THz region.",2203.04941v1
2017-05-08,Systematic efficiency study of line-doubled zone plates,"Line-doubled Fresnel zone plates provide nanoscale, high aspect ratio
structures required for efficient high resolution imaging in the multi-keV
x-ray range. For the fabrication of such optics a high aspect ratio HSQ resist
template is produced by electron-beam lithography and then covered with Ir by
atomic layer deposition (ALD).",1705.02807v1
2020-03-23,Plasma Surface Metallurgy of Materials Based on Double Glow Discharge Phenomenon,"Plasma Surface Metallurgy/Alloying is a kind of surface metallurgy/alloying
to employ low temperature plasma produced by glow discharge to diffuse alloying
elements into the surface of substrate material to form an alloy layer. The
first plasma surface metallurgy technology is plasma nitriding invented by
German scientist Dr. Bernard Berghuas in 1930. He was the first person to apply
glow discharge to realize the surface alloying. In order to break the
limitation of plasma nitriding technology, which can only be applied to a few
non-metallic gaseous elements such as nitrogen, carbon, sulfur, the ""Double
Glow Discharge Phenomenon""was found in 1978. Based on this phenomenon the
""Double Glow Plasma Surface Metallurgy Technology"", also known as the ""Xu-Tec
Process"" was invented in 1980. It can utilize any chemical elements in the
periodic table including solid metallic, gas non-metallic elements and their
combination to realize plasma surface alloying, hence greatly expanded the
field of surface alloying. Countless surface alloys with high hardness, wear
resistance and corrosion resistance, such as high speed steels, nickel base
alloys and burn resistant alloys have been produced on the surfaces of a
variety of materials. This technology may greatly improve the surface
properties of metal materials, comprehensively improve the quality of
mechanical products, save a lot of precious alloy elements for human beings.
Based on the plasma nitriding technology, the Xu-Tec Process has opened up a
new material engineering field of ""Plasma Surface Metallurgy"". This Review
Article briefly presents the history of glow discharge and surface alloying,
double glow discharge phenomenon, basic principle and current status of Double
Glow Plasma Surface Metallurgy/Alloying. Industrial applications, advantages
and future potential of the Xu-Tec process are also presented.",2003.10250v1
2024-05-23,Concurrence of directional Kondo transport and incommensurate magnetic order in the layered material AgCrSe$_2$,"In this work, we report on the concurrent emergence of the directional Kondo
behavior and incommensurate magnetic ordering in a layered material. We employ
temperature- and magnetic field-dependent resistivity measurements,
susceptibility measurements, and high resolution wavelength X-ray diffraction
spectroscopy to study the electronic properties of AgCrSe$_2$. Impurity Kondo
behavior with a characteristic temperature of $T_\text K$ = 32 K is identified
through quantitative analysis of the in-plane resistivity, substantiated by
magneto-transport measurements. The agreement between our experimental data and
the Schlottmann's scaling theory allows us to determine the impurity spin as
$S$ = 3/2. Furthermore, we discuss the origin of the Kondo behavior and its
relation to the material's antiferromagnetic transition. Our study uncovers an
unusual phenomenon -- the equivalence of the N\'eel temperature and the Kondo
temperature -- paving the way for further investigations into the intricate
interplay between impurity physics and magnetic phenomena in quantum materials,
with potential applications in advanced electronic and magnetic devices.",2405.14541v1
2013-04-11,Resistance switching in oxides with inhomogeneous conductivity,"Electric-field-induced resistance switching (RS) phenomena have been studied
for over 60 years in metal/dielectrics/metal structures. In these experiments a
wide range of dielectrics have been studied including binary transition metal
oxides, perovskite oxides, chalcogenides, carbon- and silicon-based materials,
as well as organic materials. RS phenomena can be used to store information and
offer an attractive performance, which encompasses fast switching speeds, high
scalability, and the desirable compatibility with Si-based
complementary-metal-oxide-semiconductor fabrication. This is promising for
nonvolatile memory technology, i.e. resistance random access memory (RRAM).
However, a comprehensive understanding of the underlying mechanism is still
lacking. This impedes a faster product development as well as an accurate
assessment of the device performance potential. Generally speaking, RS occurs
not in the entire dielectric but only a small, confined region, which results
from the local variation of conductivity in dielectrics. In this review, we
focus on the RS in oxides with such an inhomogeneous conductivity. According to
the origin of the conductivity inhomogeneity, the RS phenomena and their
working mechanism are reviewed by dividing them into two aspects: interface RS,
based on the change of contact resistance at metal/oxide interface due to the
change of Schottky barrier and interface chemical layer, and bulk RS, realized
by the formation, connection, and disconnection of conductive channels in the
oxides. Finally the current challenges of RS investigation and the potential
improvement of the RS performance for the nonvolatile memories are discussed.",1304.3290v1
2018-01-11,Modeling the Oblique Spin Precession in Lateral Spin Valves for Accurate Determination of Spin Lifetime Anisotropy: Effect of Finite Contact Resistance and Channel Length,"The spin lifetime anisotropy is an important quantity for investigating the
spin relaxation mechanisms in graphene and in heterostructures of
two-dimensional materials. We generalize the diffusive spin transport equations
of oblique spin precession in a lateral spin valve with finite contact
resistance. This yields a method to determine the spin lifetime anisotropy
ratio {\xi}={\tau}$_{\perp}$/{\tau}$_{\parallel}$, which is the ratio between
lifetimes of spin polarized perpendicular and parallel to the graphene surface.
By solving the steady-state Bloch equations, we show that the line-shape of the
oblique spin precession signal can be described with six dimensionless
parameters, which can be solved analytically. We demonstrate that the
anisotropic spin precession characteristics can be strongly suppressed by
contact induced spin relaxation originating from conductance mismatch between
the channel material and electrodes. To extract the spin lifetime anisotropy
ratio accurately, we develop a closed form equation that includes the effect of
finite contact resistance. Furthermore, we demonstrate that in the high contact
resistance regime, the minimum channel length required for accurately
determining the spin lifetime anisotropy for a sufficiently low external
magnetic field is only determined by the diffusion coefficient of the channel
material, as opposed to the spin diffusion length. Our work provides an
accurate model to extract the spin lifetime anisotropy ratio from the oblique
spin precession measurement, and can be used to guide the device design for
such measurements.",1801.03606v1
2019-03-14,Low Resistivity and High Breakdown Current Density of 10-nm Diameter van der Waals TaSe3 Nanowires by Chemical Vapor Deposition,"Micron-scale single-crystal nanowires of metallic TaSe3, a material that
forms -Ta-Se3-Ta-Se3- stacks separated from one another by a tubular van der
Waals (vdW) gap, have been synthesized using chemical vapor deposition (CVD) on
a SiO2/Si substrate, in a process compatible with semiconductor industry
requirements. Their electrical resistivity was found unaffected by downscaling
from the bulk to as little as 7 nm in width and height, in striking contrast to
the resistivity of copper for the same dimensions. While the bulk resistivity
of TaSe3 is substantially higher than that of bulk copper, at the nanometer
scale the TaSe3 wires become competitive to similar-sized copper ones.
Moreover, we find that the vdW TaSe3 nanowires sustain current densities in
excess of 108 A/cm2 and feature an electromigration energy barrier twice that
of copper. The results highlight the promise of quasi-one-dimensional
transition metal trichalcogenides for electronic interconnect applications and
the potential of van der Waals materials for downscaled electronics.",1903.06227v1
2019-09-01,"Low activation, refractory, high entropy alloys for nuclear applications","Two new, low activation high entropy alloys (HEAs) TiVZrTa and TiVCrTa are
studied for use as in-core, structural nuclear materials for in-core nuclear
applications. Low-activation is a desirable property for nuclear reactors, in
an attempt to reduce the amount of high level radioactive waste upon
decommissioning, and for consideration in fusion applications.The alloy TiVNbTa
is used as a starting composition to develop two new HEAs; TiVZrTa and TiVCrTa.
The new alloys exhibit comparable indentation hardness and modulus, to the
TiVNbTa alloy in the as-cast state. After heavy ion implantation the new alloys
show an increased irradiation resistance.",1909.00373v1
2019-08-07,Part I: Theoretical Predictions of Preferential Oxidation in Refractory High Entropy Materials,"High entropy materials, which include high entropy alloys, carbides, and
borides, are a topic of substantial research interest due to the possibility of
a large number of new material compositions that could fill gaps in application
needs. There is a current need for materials exhibiting high temperature
stability, particularly oxidation resistance. A systematic understanding of the
oxidation behavior in high entropy materials is therefore required. Prior work
notes large differences in the thermodynamic favorability between oxides formed
upon oxidation of high entropy materials. This work uses both analytical and
computational thermodynamic approaches to investigate and quantify the effects
of this large variation and the resulting potential for preferential component
oxidation in refractory high entropy materials including group IV-, V- and
VI-element based alloys and ceramics. Thermodynamic calculations show that a
large tendency towards preferential oxidation is expected in these materials,
even for elements whose oxides exhibit a small difference in thermodynamic
favorability. The effect is reduced in carbides, compared to their alloy
counterparts. Further, preferential oxidation in high entropy refractory
materials could result in possible destabilization of the solid solution or
formation of other, competing phases, with corresponding changes in bulk
material properties.",1908.02654v2
2011-03-30,The efficient spin injector scheme based on Heusler materials,"We present the rational design scheme intended to provide the stable high
spin-polarization at the interfaces of the magneto-resistive junctions by
fulfilling the criteria of structural and chemical compatibilities at the
interface. This can be realized by joining the semiconducting and half-metallic
Heusler materials with similar structures. The present first-principal
calculations verify that interface remains half-metallic if the nearest
interface layers effectively form a stable Heusler material with the properties
intermediate between the surrounding bulk parts. This leads to a simple rule
for selecting the proper combinations.",1103.5928v1
2005-07-19,Resistance profile measurements on a symmetric electrical pulse induced resistance change device,"We report the first direct measurements of the micro scale resistance profile
between the terminals of a two terminal symmetric thin film Pr0.7Ca0.3MnO3
electrical pulse induced resistance change device composed of a Pr0.7Ca0.3MnO3
active layer. The symmetric device is one in which the electrode shape, size,
composition, and deposition processing are identical. We show that under
certain limitations of pulse switching voltage, such a symmetric electrical
pulse induced resistance change device can exhibit either no net device
resistance switching at room temperature, or bipolar switching with the
resistance hysteresis curve exhibiting a ""table leg"" structure. The resistance
measurements are made using surface scanning Kelvin probe microscopy, which
allows for the measurement of the profile of resistance from one electrode,
across the Pr0.7Ca0.3MnO3 material and into the second electrode, both before
resistance switching and after switching. The results show that resistance
switching in the symmetric device occurs primarily in the interface region
within about 1 to 3 micron of the electrical contact surface. Resistance
switching is also observed in the bulk Pr0.7Ca0.3MnO3 material although at a
lower level. Symmetry considerations for a two terminal symmetric device that
can switch resistance are discussed, and the data reported here is consistent
with the symmetric model previously developed.",0507432v2
2019-07-03,Suppression of the antiferromagnetic metallic state in the pressurized MnBi2Te4 single crystal,"MnBi2Te4 has attracted tremendous research interest recently as the first
intrinsic antiferromagnetic (AF) topological insulator. It undergoes a
long-range AF order at TN = 24 K accompanied with a cusp-like anomaly in the
metallic resistivity. Here, we studied the effect of hydrostatic pressure on
its electrical transport properties up to 12.5 GPa by using a cubic anvil cell
apparatus. We find that TN determined from the resistivity anomaly first
increases slightly with pressure and then decreases until vanished completely
at ~7 GPa. Intriguingly, its resistivity rho(T) is enhanced gradually by
pressure, and evolves from metallic to activated behavior as the AF order is
suppressed. From the Hall resistivity measurements, we confirm that the n-type
carriers dominate the transport properties and the carrier density is raised by
pressure. In addition, the critical magnetic field Hc1 ~3.3 T at 0 GPa for the
spin-flop transition to the canted AF state is found to increase to ~ 5 T and
7.5 T at 1 and 3 GPa. High-pressure XRD evidenced no structural transition up
to 12.8 GPa. Based on the Hall resistivity results and first-principles
calculations, we proposed that the intralayer direct AF interactions are
strengthened by pressure and the competition between AF and FM interactions not
only prevents long-range magnetic order but also promotes charge carrier
localizations through enhance magnetic fluctuations at high pressures.",1907.01760v1
2020-09-02,Understanding modes of negative differential resistance in amorphous and polycrystalline vanadium oxides,"Metal-oxide-metal devices based on amorphous VOx are shown to exhibit one of
two distinct negative differential resistance (NDR) characteristics depending
on the maximum current employed for electroforming. For low compliance currents
they exhibit a smooth S-type characteristic and have a temperature-dependent
device resistance characterised by an activation energy of 0.25 eV, consistent
with conduction in polycrystalline VO2, while for high-compliance currents they
exhibit an abrupt snap-back characteristic and a resistance characterised by an
activation energy of 0.025 eV, consistent with conduction in oxygen deficient
VOx. In both cases, the temperature dependence of the switching voltage implies
that the conductivity change is due to the insulator-metal transition in VO2.
From this analysis it is concluded that electroforming at low currents creates
a conductive filament comprised largely of polycrystalline VO2, while
electroforming at high currents creates a composite structure comprised of VO2
and a conductive halo of oxygen deficient VOx. The effect of electroforming on
the NDR mode is then explained with reference to a lumped element model of
filamentary conduction that includes the effect of a parallel resistance
created by the halo. These results provide new insight into the NDR response of
vanadium-oxide-based devices and a basis for designing devices with specific
characteristics.",2009.00810v1
2022-03-31,Atomic-scale origin of the low grain-boundary resistance in perovskite solid electrolytes,"Oxide solid electrolytes (OSEs) have the potential to achieve improved safety
and energy density for lithium-ion batteries, but their high grain-boundary
(GB) resistance is a general bottleneck. In the most well studied perovskite
OSE, Li3xLa2/3-xTiO3 (LLTO), the ionic conductivity of GBs is about three
orders of magnitude lower than that of the bulk. In contrast, the related
Li0.375Sr0.4375Ta0.75Zr0.25O3 (LSTZ0.75) perovskite exhibits low GB resistance
for reasons yet unknown. Here, we used aberration-corrected scanning
transmission electron microscopy and spectroscopy, along with an active
learning moment tensor potential, to reveal the atomic scale structure and
composition of LSTZ0.75 GBs. Vibrational electron energy loss spectroscopy is
applied for the first time to characterize the otherwise unmeasurable Li
distribution in GBs of LSTZ0.75. We found that Li depletion, which is a major
reason for the low GB ionic conductivity of LLTO, is absent for the GBs of
LSTZ0.75. Instead, the low GB resistivity of LSTZ0.75 is attributed to the
formation of a unique defective cubic perovskite interfacial structure that
contained abundant vacancies. Our study provides insights into the atomic scale
mechanisms of low GB resistivity and sheds light on possible paths for
designing OSEs with high total ionic conductivity.",2204.00091v1
2008-03-29,Superconductivity at 52 K in iron-based F-doped layered quaternary compound Pr[O1-xFx]FeAs,"Since the discovery of copper oxide superconductor in 1986 [1], extensive
efforts have been devoted to the search of new high-Tc superconducting
materials, especially high-Tc systems other than cuprates. The recently
discovered quaternary superconductor La[O1-xFx]FeAs with the superconducting
critical transition Tc of 26 K [2], which has a much simple layered structure
compared with cuprates, has attracted quick enthusiasm and is going to become a
new high-Tc system [3-6]. Here we report the discovery of bulk
superconductivity in the praseodymium-arsenide oxides Pr[O1-xFx]FeAs with an
onset drop of resistivity as high as 52 K, and the unambiguous zero-resistivity
and Meissner transition at low temperature, which will place these quaternary
compounds to another high-Tc superconducting system explicitly.",0803.4283v1
2017-01-14,Systematic comprehension the metal phase of Pr0.7(CaxSr1-x)0.3MnO3 via temperature and magnetic induction,"Temperature, magnetic induction and substitution dependent resistivity are a
crucial factor in determining the physical properties of magneto-resistive
materials. The first objective of this work was to find out an applicable
method of using temperature to predict the resistivity of
Pr0.7(CaxSr1-x)0.3MnO3 in the metal phase within the transition area. Based on
non-linear curve fitting, a typical numerical method is used to quantitatively
analyze the temperature-dependent resistivity within temperatures lower than
the metal-insulator transition temperature (Tp). The simulations agree very
well with the observed curves (resistivity versus temperature). The second
objective of this work is to search for the applicable method to link
magneto-resistivity to magnetic induction, calculation on the principle of
non-linear curve fitting, four typical numerical methods are highlighted
because the magnetic induction-dependent magneto-resistivity are quantitatively
analyzed by these methods. The observed effects of magnetic induction on the
shift of temperature-resistive curve should be more essential in physics and
are quantitatively discussed in magneto-resistive materials. Lastly, the
influences of Ca substitution on magneto-resistivity are detected.",1701.04688v1
1999-04-23,Shot noise in ferromagnetic single electron tunneling devices,"Frequency dependent current noise in ferromagnetic double junctions with
Coulomb blockade is studied theoretically in the limit of sequential tunneling.
Two different relaxation processes are found in the correlations between spin
polarized tunneling currents; low frequency spin fluctuations and high
frequency charge fluctuations. Spin accumulation in strongly asymmetric
junctions is shown to lead to a negative differential resistance. We also show
that large spin noise activated in the range of negative differential
resistance gives rise to a significant enhancement of the current noise.",9904341v1
2001-02-28,Pressure dependence of Tc in the MgB2 superconductor as probed by resistivity measurements,"High-pressure resistivity experiments were performed on the recently
discovered superconductor, MgB2. Tc decreases quasi-linearly with applied
pressure to 1.4 GPa at a rate of -2.0(1) K/GPa, which is somewhat larger than
that derived from recently-reported ac susceptibility measurements. The
reduction of Tc is consistent with the BCS picture, in a similar way to the
C60-based superconductors. Taking into account the pressure dependence of the
unit cell volume, V, the volume coefficient of Tc, d(lnTc)/dV is significantly
large.",0102511v1
2003-03-11,Microscopic origin of collective exponentially small resistance states,"The formation of ""zero"" (exponentially small) resistance states (ESRS) in
high mobility two-dimensional electron systems (2DES) in a static magnetic
field B and subjected to strong microwave (MW) radiation has attracted great
theoretical interest. These states appear to be associated with a new kind of
energy gap $\Delta$. Here I show that the energy gap $\Delta$ is explained by a
microscopic quantum model that involves the Prime Number Theorem, hitherto
reserved for only mathematical contexts.",0303184v2
2003-11-03,Inverted current-driven switching in Fe(Cr)/Cr/Fe(Cr) nanopillars,"From both theory and experiment, scattering of minority electrons is expected
to be weaker than scattering of majority electrons in both dilute Fe(Cr) alloys
and at Fe(Cr)/Cr interfaces. We show that Fe(Cr)/Cr/Fe(Cr) trilayer nanopillars
display a normal magnetoresistance--i.e., largest resistance at low magnetic
fields and smallest at high fields, but an inverted current-driven
switching--i.e., positive current flowing from the fixed to the reversing layer
switches the trilayer from higher to lower resistance, and negative current
switches it from lower to higher.",0311047v1
2004-04-06,Superconductivity in diamond,"We report the discovery of superconductivity in boron-doped diamond
synthesized at high pressure (8-9 GPa) and temperature (2,500-2,800 K).
Electrical resistivity, magnetic susceptibility, specific heat, and
field-dependent resistance measurements show that boron-doped diamond is a
bulk, type-II superconductor below the superconducting transition temperature
Tc=4 K; superconductivity survives in a magnetic field up to Hc2(0)=3.5 T. The
discovery of superconductivity in diamond-structured carbon suggests that Si
and Ge, which also form in the diamond structure, may similarly exhibit
superconductivity under the appropriate conditions.",0404156v1
2007-03-21,Electronic Properties of the Semiconductor RuIn$_3$,"Temperature dependent measurements of the resistivity on RuIn$_3$ single
crystals show a semiconducting behaviour, in contrast to previously published
results. In the high temperature range the semiconducting gap was measured to
be $0.4-0.5$eV. We observe an anisotropy of the resistivity along [110] and
[001] orientations of the tetragonal single crystals. At low temperatures two
activation energies of impurities were estimated to 1meV and 10meV. The
temperature dependence of the specific heat and the band structure calculations
provide also a semiconducting behaviour of RuIn$_3$.",0703563v1
2002-06-13,Potential of RPCs for tracking,"We have demonstrated that small gap (0.1 to 0.4 mm) RPCs made of low
resistivity materials (less than 1E8 Ohm.cm) can operate at counting rates of
up to 1E5 Hz/mm2 with position resolutions better than 50 micrometer. Results
of preliminary tests allow us to suggest a possible application of this new
type of RPC for tracking.",0206039v1
2008-03-31,Percolation Model Explaining Both Unipolar Memory and Threshold Resistance Switchings in NiO Film,"We observed two types of unipolar resistance switching (RS) in NiO film:
memory RS at low temperature and threshold RS at high temperature. We explain
these phenomena using a bond percolation model that describes the forming and
rupturing of conducting filaments. Assuming Joule heating and thermal
dissipation processes in the bonds, we explain how both RS types could occur
and be controlled by temperature. We show that these unipolar RS are closely
related and can be explained by a simple unified percolation picture.",0803.4258v1
2009-08-21,Measuring Charge Transport in an Amorphous Semiconductor Using Charge Sensing,"We measure charge transport in hydrogenated amorphous silicon (a-Si:H) using
a nanometer scale silicon MOSFET as a charge sensor. This charge detection
technique makes possible the measurement of extremely large resistances. At
high temperatures, where the a-Si:H resistance is not too large, the charge
detection measurement agrees with a direct measurement of current. The device
geometry allows us to probe both the field effect and dispersive transport in
the a-Si:H using charge sensing and to extract the density of states near the
Fermi energy.",0908.3181v2
2010-04-22,Small gap semiconducting organic charge-transfer interfaces,"We investigated transport properties of organic heterointerfaces formed by
single-crystals of two organic donor-acceptor molecules,
tetramethyltetraselenafulvalene (TMTSF) and 7,7,8,8-tetracyanoquinodimethane
(TCNQ). Whereas the individual crystals have un-measurably high resistance, the
interface exhibits a resistivity of few tens of MegaOhm with a temperature
dependence characteristic of a small gap semiconductor. We analyze the
transport properties based on a simple band-diagram that naturally accounts for
our observations in terms of charge transfer between two crystals. Together
with the recently discovered tetrathiafulvalene (TTF)-TCNQ interfaces, these
results indicate that single-crystal organic heterostructures create new
electronic systems with properties relevant to both fundamental and applied
fields.",1004.3927v1
2011-05-26,Coulomb Drag and High Resistivity Behavior in Double Layer Graphene,"We show that Coulomb drag in ultra-clean graphene double layers can be used
for controlling the on/off ratio for current flow by tunning the external gate
voltage. Hence, although graphene remains semi-metallic, the double layer
graphene system can be tuned from conductive to a highly resistive state. We
show that our results explain previous data of Coulomb drag in double layer
graphene samples in disordered SiO2 substrates.",1105.5399v2
2013-09-04,Low temperature magnetic transitions of single crystal HoBi,"We present resistivity, specific heat and magnetization measurements in high
quality single crystals of HoBi, with a residual resistivity ratio of 126. We
find, from the temperature and field dependence of the magnetization, an
antiferromagnetic transition at 5.7 K, which evolves, under magnetic fields,
into a series of up to five metamagnetic phases.",1309.1113v1
2018-02-25,Field-effect-driven half-metallic multilayer graphene,"Rhombohedral stacked multilayer graphene displays the occurrence of a
magnetic surface state at low temperatures. Recent angular resolved
photoemission experiments demonstrate the robustness of the magnetic state in
long sequences of ABC graphene. Here, by using first-principles calculations,
we show that field-effect doping of these graphene multilayers induces a
perfect half-metallic behaviour with 100% of spin current polarization already
at dopings attainable in conventional field effect transistors with solid state
dielectrics. Our work demonstrates the realisability of a new kind of
spintronic devices where the transition between the low resistance and the high
resistance state is driven only by electric fields.",1802.09028v1
2020-06-04,Materials & Properties: Thermal & Electrical Characteristics,"This lecture gives an introduction to the basic physics of the electrical
conductivity of metals, its temperature dependence and its limiting factors. We
will then introduce the concept of surface resistance, of high relevance in
accelerators for its link with beam impedance and for RF applications,
including notions related to the anomalous skin effect. The surface resistance
will help establishing a link to heat exchanges between bodies by radiation,
and to the concept of emissivity. Thermal conductivity will then be introduced,
discussing both its electron and phonon exchange components, and the relevant
limiting factors.",2006.02842v1
2020-09-10,Solid-state Li-ion batteries operating at room temperature using new borohydride argyrodite electrolytes,"Using a new class of (BH4)- substituted argyrodite Li6PS5Z0.83(BH4)0.17, (Z =
Cl, I) solid electrolyte, Li-metal solid-state batteries operating at room
temperature have been developed. The cells were made by combining the modified
argyrodite with an In-Li anode and two types of cathode: an oxide, LixMO2 (M =
1/3Ni, 1/3Mn, 1/3Co; so called NMC) and a titanium disulfide, TiS2. The
performance of the cells was evaluated through galvanostatic cycling and
Alternating Current AC electrochemical impedance measurements. Reversible
capacities were observed for both cathodes for at least tens of cycles.
However, the high-voltage oxide cathode cell shows lower reversible capacity
and larger fading upon cycling than the sulfide one. The AC impedance
measurements revealed an increasing interfacial resistance at the cathode side
for the oxide cathode inducing the capacity fading. This resistance was
attributed to the intrinsic poor conductivity of NMC and interfacial reactions
between the oxide material and the argyrodite electrolyte. On the contrary, the
low interfacial resistance of the TiS2 cell during cycling evidences a better
chemical compatibility between this active material and substituted
argyrodites, allowing full cycling of the cathode material, 240 mAhg-1, for at
least 35 cycles with a coulombic efficiency above 97%.",2009.04779v1
2000-04-08,Electrical Conductivity in Magnesium-Doped Al_2 O_3 Crystal at Moderate Temperatures,"AC and DC electrical measurements between 273 and 800 K were used to
characterize the electrical conductivity of Al_2 O_3:Mg single crystals
containing [Mg]^{0} center. At low fields contacts are blocking. At high
fields, electrical current flows steadily through the sample and the I-V
characteristic corresponds to a directly biased barrier whit a series
resistance (bulk resistance). AC measurements yield values for the junction
capacitance as well as for the sample resistance, and provide perfectly
reproducible conductivity values. The conductivity varies linearly whit the
[Mg]^{0} concentration and a thermal activation energy of 0.68 eV was obtained,
which agrees very well with the activation energy previously reported for
motion of free holes.",0004123v1
2001-07-13,Superconductivity in the Correlated Pyrochlore Cd_2Re_2O_7,"We report the observation of superconductivity in high-quality
Cd$_2$Re$_2$O$_7$ single crystals with room-temperature pyrochlore structure.
Resistivity and ac susceptibility measurements establish an onset transition
temperature T$_c^{onset}$ = 1.47 K with transition width $\Delta$T$_c$ = 0.25
K. In applied magnetic field, the resistive transition shows a type-II
character, with an approximately linear temperature-dependence of the upper
critical field H$_{c2}$. The bulk nature of the superconductivity is confirmed
by the specific heat jump with $\Delta$C = 37.9 mJ/mol-K. Using the $\gamma$
value extracted from normal-state specific heat data, we obtain
$\Delta$C/$\gamma$T$_c$ = 1.29, close to the weak coupling BCS value. In the
normal state, a negative Hall coefficient below 100 K suggests electron-like
conduction in this material. The resistivity exhibits a quadratic T-dependence
between 2 and 60 K, i.e., $\rho =\rho_0$+AT$^2$, indicative of Fermi-liquid
behavior. The values of the Kadowaki-Woods ratio A/$\gamma^2$ and the Wilson
ratio are comparable to that for strongly correlated materials.",0107309v3
2002-03-12,Magnetoresistances observed by decomposition of the magnetic moment in La1-xCaxMnO3 films,"A ferromagnetic phase, characterized by electron carriers and a high
temperature colossal magnetoresistance (HTCMR) dependent on the magnetic
moment, and a semiconducting phase, characterized by hole carriers and a low
temperature CMR (LTCMR), are observed in La$_{1-x}$Ca$_{x}$MnO$_3$ thin films
by the van der Pauw method. The LTCMR is much more sensitive to the magnetic
field than the HTCMR. In the ferromagnetic phase for films with anisotropic
moments in two dimensions, a remnant resistivity of the order of 10$^{-8}
\~{\Omega}m$ is observed up to 100 K and increases exponentially with both a
temperature up to $T_c$ and a magnetic field above one Tesla (a positive
magnetoresistivity). We found that the ferromagnetic phase below $T_c$ is in a
polaronic state with a polaronic mobile conduction, and the carrier density
dips near $T_c$. For resistances measured by the four-probe method with line
electrodes, low temperature information of the HTCMR is not revealed. The van
der Pauw method is more effective for the resistance measurement of a magnetic
material than the four-probe method.",0203245v2
2004-01-20,A New Approach to the Josephson Effect,"We introduce a new approach to the Josephson effect in SIS tunnel junctions.
The Josephson coupling energy is calculated from the overlap of real space
Cooper pair wavefunctions in two superconductors through an insulating barrier.
It is shown that the Josephson tunneling is limited by the size of the Cooper
pair and its shrinking during the tunneling. Therefore, the Josephson coupling
energy and the critical current become extremely small in high $T_{c}$
superconductors, including $MgB_{2}$. This shrinking also causes the observed
DC supercurrent in low $T_{c}$ superconductors, such as Pb and Sn, to fall off
much faster than $1/R_{n}$ for tunneling resistance $R_{n}$ above several ohms.
Consequently there is a material-dependent threshold resistance, above which
the supercurrent decreases much faster with increasing resistance. The
impurity-induced shrinking is also shown to limit the critical current.
Furthermore, the (weak) temperature dependence of the Cooper pair size is found
to contribute to the temperature dependence of the DC supercurrent.",0401374v2
2008-05-12,"Influence of sintering temperature on resistivity, magnetoresistance and thermopower of La0.67Ca0.33MnO3","A systematic investigation of La0.67Ca0.33MnO3 manganites has been
undertaken, mainly to understand the influence of varying crystallite size
(nanometer range) on electrical resistivity, magnetic susceptibility and
thermoelectric power. The materials were prepared by the sol-gel method of
sintering at four different temperatures between 800 and 1100 degrees C. The
samples were characterized by X-ray diffraction and data were analyzed using
Rietveld refinement. The metal-insulator transition temperatures (TP) are found
to increase with increasing sintering temperatures, while the magnetic
transition temperatures (TC) decrease. The electrical resistivity and
thermoelectric power data at low temperatures (T < TP) have been analyzed by
considering various scattering phenomena, while the high temperature (T > TP)
data were analyzed with Mott's small polaron hopping conduction mechanisms.
PACS Codes: 73.50.Lw, 75.47.Gk, 75.47.Lx",0805.1663v1
2008-09-12,Two insulating phases in compressed Pr1-xCaxMnO3 thin films,"The temperature dependent resistivity of two Pr1-xCaxMnO3 (x=0.5 and 0.4)
thin films grown on LaAlO3 has been studied as a function of hydrostatic
pressure (up to 2.5 GPa) and magnetic field (up to 9T). Both samples show a
monotonic decrease in the resistivity with an increase in pressure,
corresponding to a change of -35% at 2.5 GPa. No pressure induced
metal-to-insulator transition was observed in the temperature-dependent
resistivity. The non-trivial interaction between high pressure and magnetic
field reveals that the effect of pressure cannot be simply rescaled to that of
a specific field, as has been reported for the corresponding bulk material. We
propose an interpretation of the data based on phase separation, where two
different insulating phases coexist: the charge ordered phase, which is
sensitive to both magnetic field and pressure, and a second insulating phase
that can be tuned by magnetic field. Such a result demonstrates that phase
separation can be manipulated in thin films by independent application of
magnetic field and/or external pressure.",0809.2184v1
2008-10-28,Electrical properties of boron-doped MWNTs synthesized by hot-filament chemical vapor deposition,"We have synthesized a large amount of boron-doped multiwalled carbon
nanotubes (MWNTs) by hot-filament chemical vapor deposition. The synthesis was
carried out in a flask using a methanol solution of boric acid as a source
material. The scanning electron microscopy, transmission electron microscopy,
and micro-Raman spectroscopy were performed to evaluate the structural
properties of the obtained MWNTs. In order to evaluate the electrical
properties, temperature dependence of resistivity was measured in an individual
MWNTs with four metal electrodes. The Ramman shifts suggest carrier injection
into the boron-doped MWNTs, but the resistivity of the MWNTs was high and
increased strongly with decreasing temperature. Defects induced by the plasma
may cause this enhanced resistivity.",0810.4971v1
2011-06-15,An Analytical Approach for Memristive Nanoarchitectures,"As conventional memory technologies are challenged by their technological
physical limits, emerging technologies driven by novel materials are becoming
an attractive option for future memory architectures. Among these technologies,
Resistive Memories (ReRAM) created new possibilities because of their
nano-features and unique $I$-$V$ characteristics. One particular problem that
limits the maximum array size is interference from neighboring cells due to
sneak-path currents. A possible device level solution to address this issue is
to implement a memory array using complementary resistive switches (CRS).
Although the storage mechanism for a CRS is fundamentally different from what
has been reported for memristors (low and high resistances), a CRS is simply
formed by two series bipolar memristors with opposing polarities. In this paper
our intention is to introduce modeling principles that have been previously
verified through measurements and extend the simulation principles based on
memristors to CRS devices and hence provide an analytical approach to the
design of a CRS array. The presented approach creates the necessary design
methodology platform that will assist designers in implementation of CRS
devices in future systems.",1106.2927v2
2013-02-05,Graphene-Ferroelectric Hybrid Structure for Flexible Transparent Electrodes,"Graphene has exceptional optical, mechanical and electrical properties,
making it an emerging material for novel optoelectronics, photonics and for
flexible transparent electrode applications. However, the relatively high sheet
resistance of graphene is a major constrain for many of these applications.
Here we propose a new approach to achieve low sheet resistance in large-scale
CVD monolayer graphene using non-volatile ferroelectric polymer gating. In this
hybrid structure, large-scale graphene is heavily doped up to 3{\times}1013
cm-2 by non-volatile ferroelectric dipoles, yielding a low sheet resistance of
120 {\Omega}{\Box} at ambient conditions. The graphene-ferroelectric
transparent conductors (GFeTCs) exhibit more than 95% transmittance from the
visible to the near infrared range owing to the highly transparent nature of
the ferroelectric polymer. Together with its excellent mechanical flexibility,
chemical inertness and the simple fabrication process of ferroelectric
polymers, the proposed GFeTCs represent a new route towards large-scale
graphene based transparent electrodes and optoelectronics.",1302.0993v1
2013-03-11,"Crystals, magnetic and electronic properties of a new ThCr2Si2-type BaMn2Bi2 and K-doped compositions","This is a report on the new 122 ternary transition-metal pnictide of
BaMn2Bi2, which is crystallized from bismuth flux. BaMn2Bi2 adopts
ThCr2Si2-type structure (I4/mmm) with a = 4.4902(3) {\AA} and c = 14.687(1)
{\AA}; it is antiferromagnetic with anisotropic magnetic susceptibility and
semiconducting with a band gap of Eg = 6 meV. Heat capacity result confirms the
insulating ground state in BaMn2Bi2 with the electronic residual Sommerfeld
coefficient of {\gamma} ~ 0. The high temperature magnetization results show
that magnetic ordering temperature is TN ~ 400 K. Hole-doping in BaMn2Bi2 via
potassium in Ba1-xKxMn2Bi2 results in metallic behavior for x = 0.10(1),
0.32(1) and 0.36(1). With K-doping, more magnetically anisotropic behavior is
observed. Although there is a downturn in electrical resistivity and low-field
magnetization data below 4 K in > 30%-doped crystals, there is no sign of zero
resistance or diamagnetism. This manuscript is a report on new materials of
BaMn2Bi2 and Ba1-xKxMn2Bi2 (0 < x < 0.4). Results from powder X-ray
diffraction, anisotropic temperature- and field-dependent magnetization,
temperature-and field-dependent electrical resistivity, and heat capacity are
presented.",1303.2695v2
2015-02-09,Surface-state-dominated transport in crystals of the topological crystalline insulator In-doped Pb$_{1-x}$Sn$_x$Te,"Three-dimensional topological insulators and topological crystalline
insulators represent new quantum states of matter, which are predicted to have
insulating bulk states and spin-momentum-locked gapless surface states.
Experimentally, it has proven difficult to achieve the high bulk resistivity
that would allow surface states to dominate the transport properties over a
substantial temperature range. Here we report a series of indium-doped
Pb$_{1-x}$Sn$_x$Te compounds that manifest huge bulk resistivities together
with strong evidence of topological surface states, based on
thickness-dependent transport studies and magnetoresistance measurements. For
these bulk-insulating materials, the surface states determine the resistivity
for temperatures approaching 30 K.",1502.02696v1
2016-04-20,Magnetoresistance and Shubnikov-de Hass oscillation in YSb,"YSb crystals are grown and the transport properties under magnetic field are
measured. The resistivity exhibits metallic behavior under zero magnetic field
and the low temperature resistivity shows a clear upturn once a moderate
magnetic field is applied. The upturn is greatly enhanced by increasing
magnetic field, finally resulting in a metal-to-insulator-like transition. With
temperature further decreased, a resistivity plateau emerges after the
insulator-like regime. At low temperature (2.5 K) and high field (14 T), the
transverse magnetoresistance (MR) is quite large (3.47 $\times 10^4\%$ ). In
addition, Shubnikov-de Haas (SdH) oscillation has also been observed in YSb.
Periodic behavior of the oscillation amplitude reveals the related information
about Fermi surface and two major oscillation frequencies can be obtained from
the FFT spectra of the oscillations. The trivial Berry phase extracted from SdH
oscillation, band structure revealed by angle-resolved photoemission
spectroscopy (ARPES) and first-principles calculations demonstrate that YSb is
a topologically trivial material.",1604.05912v2
2016-04-06,Structural characterization of APPJ treated Bismaleimide coatings and heat treated Titania-BMI,"Bismaleimide (BMI) are thermosetting polymers mainly used in aerospace
applications having properties of dimensional stability, low shrinkage,
chemical resistance, fire resistance, good mechanical properties and high
resistance against various solvents, acids, and water. BMI is commercially
available as Homide 250. BMI coating has also been used for the corrosion
protection. Metallization (AL) of BMI using vacuum evaporation was done which
serves the purpose of prevention of space charge accumulation in aircraft
bodies. Addition of inorganic materials like metal oxides can influence the
properties of the polymer as an inorganic-organic composite. The
organic-ionorganic composites have wide applications in electronics, optics,
chemistry and medicine. Titanium dioxide (TiO2, Titania) has a wide range of
applications starting from photocatalysis, dye-sensitized solar cells to
optical coatings and electronics. A BMI-TiO2 composite was prepared by chemical
route. Atmospheric Plasma Jet (APPJ) using Helium gas was also treated on BMI.
XRD and FTIR studies of the composite system prepared at different temperatures
showed its crystalline and structural configuration.",1604.07297v1
2016-06-27,Structural and electrical properties of Sn substituted double sintering derived Ni-Zn ferrite,"The Sn substituted Ni-Zn ferrites were synthesized by the standard double
sintering technique using nano powders of nickel oxide (NiO), zinc oxide (ZnO),
iron oxide (Fe2O3) and tin oxide (SnO2). The structural and electrical
properties have been investigated by the X-ray diffraction, scanning electron
microscopy, DC resistivity and dielectric measurements. Extra intermediate
phase has been detected along with the inverse cubic spinel phase of Ni-Zn
ferrite. Enhancement of grain size is observed in Sn substituted Ni-Zn
ferrites. DC resistivity as a function of temperature has been investigated by
two probe method. The DC resistivity was found to decrease whereas the
dielectric constants increase with increasing Sn content in Ni-Zn ferrites. The
dielectric constant of the as prepared samples is high enough to use these
materials in miniaturized memory devices based capacitive components or energy
storage principles.",1606.08118v1
2017-02-18,Scaling limits of graphene nanoelectrodes,"Graphene is an ideal material for fabricating atomically thin nanometre
spaced electrodes. Recently, carbon-based nanoelectrodes have been employed to
create single-molecule transistors and phase change memory devices. In spite of
the significant recent interest in their use in a range of nanoscale devices
from phase change memories to molecular electronics, the operating and scaling
limits of these electrodes are completely unknown. In this paper, we report on
our observations of consistent voltage driven resistance switching in sub-5 nm
graphene nanogaps. We find that we are able to reversibly cycle between a low
and a high resistance state using feedback-controlled voltage ramps.We
attribute this unexplained switching in the gap to the formation and breakdown
of carbon filaments.By increasing the gap, we find that such intrinsic
resistance switching of graphene nanogaps imposes a scaling limit of 10 nm
(approx.) on the gap-size for devices with operating voltages of 1 to 2 volts.",1702.05668v1
2019-09-23,Nanoscale ballistic diodes made of polar materials for amplification and generation of radiation in 10 THz-range,"We investigate ultra-high frequency electrical properties of nanoscale
$n^+$-$i$-$n^+$ diodes made of polar semiconductors. The calculations show that
the coupling between optical vibrations of the lattice and the ballistic
electrons strongly modifies and enhances the time-of-flight effects giving rise
to narrow resonances of the diode impedance in the reststrahlen frequency
range. Particularly, negative dynamic resistance is induced in close proximity
to the optical phonon frequency. The resonant effects in the dynamic resistance
of nanoscale GaAs and InP diodes are studied in detail. The obtained magnitudes
of the negative dynamic resistance effect indicate that the nanoscale diodes
are capable of generating electromagnetic radiation in far-infrared spectral
range under electric pumping.",1909.10185v1
2019-12-20,Electron-phonon interaction and zero-field charge carrier transport in the nodal-line semimetal ZrSiS,"We study electron-phonon interaction and related transport properties of
nodal-line semimetal ZrSiS using first-principles calculations. We find that
ZrSiS is characterized by a weak electron-phonon coupling on the order of 0.1,
which is almost energy independent. The main contribution to the
electron-phonon coupling originates from long-wavelength optical phonons,
causing no significant renormalization of the electron spectral function. At
the charge neutrality point, we find that electrons and holes provide a
comparable contribution to the scattering rate. The phonon-limited resistivity
calculated within the Boltzmann transport theory is found to be strongly
direction-dependent with the ratio between out-of-plane and in-plane directions
being $\rho_{zz}/\rho_{xx}\sim 7.5$, mainly determined by the anisotropy of
carrier velocities. We estimate zero-field resistivity to be
$\rho_{xx}\approx12$ $\mu\Omega$ cm at 300 K, which is in good agreement with
experimental data. Relatively small resistivity in ZrSiS can be attributed to a
combination of weak electron-phonon coupling and high carrier velocities.",1912.09832v2
2015-04-06,Gate-tunable Memristive Phenonmena Mediated by Grain Boundaries in Single Layer MoS2,"Continued progress in high speed computing depends on breakthroughs in both
materials synthesis and device architectures. The performance of logic and
memory can be enhanced significantly by introducing a memristor, a two terminal
device with internal resistance that depends on the history of the external
bias voltage. State of the art memristors, based on metal insulator metal (MIM)
structures with insulating oxides, such as TiO2, are limited by a lack of
control over the filament formation and external control of the switching
voltage. Here, we report a class of memristors based on grain boundaries (GBs)
in single-layer MoS2 devices. Specifically, the resistance of GBs emerging from
contacts can be easily and repeatedly modulated, with switching ratios up to
1000 and a dynamic negative differential resistance (NDR). Furthermore, the
atomically thin nature of MoS2 enables tuning of the set voltage by a third
gate terminal in a field-effect geometry, which provides new functionality that
is not observed in other known memristive devices.",1504.01416v1
2020-12-09,"Potassium-Doped Para-Terphenyl: Structure, Electrical Transport Properties and Possible Signatures of a Superconducting Transition","Preliminary evidence for the occurrence of high-Tc superconductivity in
alkali-doped organic materials, such as potassium-doped p-terphenyl (KPT), were
recently obtained by magnetic susceptibility measurements and by the opening of
a large superconducting gap as measured by ARPES and STM techniques. In this
work, KPT samples have been synthesized by a chemical method and characterized
by low-temperature Raman scattering and resistivity measurements. Here, we
report the occurrence of a resistivity drop of more than 4 orders of magnitude
at low temperatures in KPT samples in the form of compressed powder. This fact
was interpreted as a possible sign of a broad superconducting transition taking
place below 90 K in granular KPT. The granular nature of the KPT system appears
to be also related to the 20 K broadening of the resistivity drop around the
critical temperature.",2012.04899v1
2020-12-23,Direct observation of the electrically triggered Insulator-Metal transition in V3O5 far below the transition temperature,"Resistive switching is one of the key phenomena for applications such as
nonvolatile memories or neuromorphic computing. V3O5, a compound of the
vanadium oxide Magn\'eli series, is one of the rare materials to exhibit an
insulator-metal transition (IMT) above room temperature (Tc ~ 415 K). Here we
demonstrate both static dc resistive switching (RS) and fast oscillatory
spiking regimes in V3O5 devices at room temperature (120 K below the phase
transition temperature) by applying an electric field. We use operando optical
imaging to track a reflectivity change during the RS and find that a
percolating high temperature metallic phase filament is formed. This
demonstrates that the electrically induced RS triggers the phase transition.
Furthermore, we optically capture the spiking oscillations that we link to the
negative differential resistance regime and find the filament forms and
dissolves via a periodic spatio-temporal instability that we describe by
numerical simulations.",2012.13009v1
2021-02-10,Current-limiting amplifier for high speed measurement of resistive switching data,"Resistive switching devices, important for emerging memory and neuromorphic
applications, face significant challenges related to control of delicate
filamentary states in the oxide material. As a device switches, its rapid
conductivity change is involved in a positive feedback process that would lead
to runaway destruction of the cell without current, voltage, or energy
limitation. Typically, cells are directly patterned on MOS transistors to limit
the current, but this approach is very restrictive as the necessary integration
limits the materials available as well as the fabrication cycle time. In this
article we propose an external circuit to cycle resistive memory cells,
capturing the full transfer curves while driving the cells in such a way to
suppress runaway transitions. Using this circuit, we demonstrate the
acquisition of $10^5$ I-V loops per second without the use of on-wafer current
limiting transistors. This setup brings voltage sweeping measurements to a
relevant timescale for applications, and enables many new experimental
possibilities for device evaluation in a statistical context.",2102.05770v1
2021-04-13,Negative Differential Resistance in Carbon-Based Nanostructures,"Nonlinear electrical properties, such as negative differential resistance
(NDR), are essential in numerous electrical circuits, including memristors.
Several physical origins have been proposed to lead to the NDR phenomena in
semiconductor devices in the last more than half a century. Here, we report NDR
behavior formation in randomly oriented graphene-like nanostructures up to 37 K
and high on-current density up to 10^5 A/cm^2. Our modeling of the
current-voltage characteristics, including the self-heating effects, suggests
that strong temperature dependence of the low-bias resistance is responsible
for the nonlinear electrical behavior. Our findings open opportunities for the
practical realization of the on-demand NDR behavior in nanostructures of 2D and
3D material-based devices via heat management in the conducting films and the
underlying substrates.",2104.06337v2
2021-05-17,Enhancement of the superconductivity and quantum metallic state in the thin film of superconducting Kagome metal KV$_3$Sb$_5$,"Recently V-based Kagome metal attracted intense attention due to the
emergence of superconductivity in the low temperature. Here we report the
fabrication and physical investigations of the high quality single-crystalline
thin films of the Kagome metal KV$_3$Sb$_5$. For the sample with the thickness
of about 15 nm, the temperature dependent resistance reveals a
Berezinskii-Kosterlitz-Thouless (BKT) type behavior, indicating the presence of
two-dimensional superconductivity. Compared with the bulk sample, the onset
transition temperature $T^{onset}_{c}$ and the out-of-plane upper critical
field $H_{c2}$ are enhanced by 15\% and more than 10 times respectively.
Moreover, the zero-resistance state is destroyed by a magnetic field as low as
50 Oe. Meanwhile, the temperature-independent resistance is observed in a wide
field region, which is the hallmark of quantum metallic state. Our results
provide evidences for the existence of unconventional superconductivity in this
material.",2105.07732v1
2021-06-28,Superconductivity in an extreme strange metal,"Some of the highest-transition-temperature superconductors across various
materials classes exhibit linear-in-temperature `strange metal' or `Planckian'
electrical resistivities in their normal state. It is thus believed by many
that this behavior holds the key to unlock the secrets of high-temperature
superconductivity. However, these materials typically display complex phase
diagrams governed by various competing energy scales, making an unambiguous
identification of the physics at play difficult. Here we use electrical
resistivity measurements into the micro-Kelvin regime to discover
superconductivity condensing out of an extreme strange metal state -- with
linear resistivity over 3.5 orders of magnitude in temperature. We propose that
the Cooper pairing is mediated by the modes associated with a recently
evidenced dynamical charge localization-delocalization transition, a mechanism
that may well be pertinent also in other strange metal superconductors.",2106.14849v2
2022-01-28,"Factors that control stability, variability, and reliability issues of endurance cycle in ReRAM devices: a phase field study","The morphological evolution of the conducting filament (CF) predominantly
controls the electric response of the resistive random access memory (ReRAM)
devices. However, the parameters -- in terms of the material and the processing
-- which control the growth of such CF are plenty. Extending the phase field
technique for ReRAM systems presented by Roy and Cha [J. Appl. Phys. 128,
205102 (2020)], we could successfully model the complete SET (low resistance
state) and RESET (high resistance state) sates due to the application of
sweeping voltage. The key parameters that influence the stability of the
multi-cycle \emph{I-V} response or the endurance behavior are identified. The
computational findings of the presented model ReRAM system are practical in
correlating the multi-parametric influence with the stability, variability, and
reliability of the endurance cycle that affect the device performance and also
lead to the device failure. We believe that our computational approach of
connecting the morphological changes of the CF with the electrical response,
has the potential to further understand and optimize the performance of the
ReRAM devices.",2201.12304v2
2022-07-03,An Atomistic Modelling Framework for Valence Change Memory Cells,"We present a framework dedicated to modelling the resistive switching
operation of Valence Change Memory (VCM) cells. The method combines an
atomistic description of the device structure, a Kinetic Monte Carlo (KMC)
model for the creation and diffusion of oxygen vacancies in the central oxide
under an external field, and an ab-initio quantum transport method to calculate
electrical current and conductance. As such, it reproduces a realistically
stochastic device operation and its impact on the resulting conductance. We
demonstrate this framework by simulating a switching cycle for a
TiN/HfO$_2$/TiN VCM cell, and see a clear current hysteresis between high/low
resistance states, with a conductance ratio of one order of magnitude.
Additionally, we observe that the changes in conductance originate from the
creation and recombination of vacancies near the active electrode, effectively
modulating a tunnelling gap for the current. This framework can be used to
further investigate the mechanisms behind resistive switching at an atomistic
scale and optimize VCM material stacks and geometries.",2207.01095v1
2023-06-16,Piezo-resistive pressure sensor based on CVD-grown ZnO nanowires on Polyethylene Tetrathalate substrate,"Recent developments in the domain of electronic materials and devices have
attracted the interest of researchers toward flexible and printable electronic
components like organic transistors, printable electrodes and sensors. Zinc
Oxide (ZnO) nanowires (NWs) possess a number of excellent properties like high
mobility, large exciton binding energy and the direct-band gap in addition to
large piezoelectric coefficients. Here, we report on flexible piezo-resistive
sensor based on Indium tin oxide (ITO)-coated Polyethylene tetrathalate (PET)
substrate. The device shows sensitivity in terms of change in resistance from
100 {\Omega} to 2.4 K{\Omega} at an applied potential of 5V upon bending from
flat to 95 degrees. The 1-D nanowire flexible device in its flat state shows
saturated output current. We observed ten folds enhanced variation as compared
to previous reports. Improved sensitivity was observed in our experiments due
to fewer defects in CVD-grown NWs as compared to others where hydrothermally
grown nanowires were used. The methodology of device fabrication reported here
requires less time and enables efficient devices for the realization of
flexible and wearable technology.",2307.13805v1
2023-10-22,Microstructure evolution and characteristics of laser-clad lightweight refractory NbxMo$_{0.5}$Ti$_{1.5}$Ta$_{0.2}$Cr high-entropy alloy,"Lightweight refractory high-entropy alloy coatings (RHEAcs) of
NbxMo$_{0.5}$Ti$_{1.5}$Ta$_{0.2}$Cr (where $x=$ 1, 1.3, 1.5, and 2) were
fabricated on the surface of 316L stainless steel using laser cladding (LC)
technology. A comprehensive study was conducted to elucidate the effect of Nb
content on the microstructure, microhardness and wear resistance of
NbxMo$_{0.5}$Ti$_{1.5}$Ta$_{0.2}$Cr RHEAcs before and after annealing at 900
for 10 h. The results show that the grains are gradually refined with the
increase of Nb content. The coating consists mainly of a body-centered cubic
(BCC) solid solution, C15-Laves phase, and a small amount of hexagonal
close-packed (HCP) solid solution containing Ti. The microhardness of RHEAcs is
significantly higher compared to the base material. Notably, at Nb1.3, due to
the influence of lattice dislocations, the microhardness reaches a peak of
1066.5 HV, which is about 7.11 times higher than that of the base material. On
the contrary, at Nb$_2$, the microhardness is at its lowest point, averaging
709.31 HV, but 4.72 times that of the base material. After annealing, an
increase in microhardness is observed at all Nb concentrations, up to 31.2% at
Nb$_2$. Before annealing, the wear resistance of RHEAcs was slightly better
than that of 316L stainless steel at different Nb contents. However, after
annealing, the coefficient of friction (COF) and wear rate of the coatings are
lower than those of annealed 316L stainless steel, highlighting their excellent
wear resistance. It is noteworthy that the loss of wear properties after
annealing at Nb1 is at a minimum, obtaining the most balanced wear resistance
before and after annealing. The enhanced wear resistance after annealing can be
attributed to the presence of ultra-fine grain oxide friction layers, mainly
composed of TiO2 and Ta2O5 . The main mode of wear is oxidative wear, with a
small amount of wear from abrasive wear.",2310.14223v1
2019-08-16,Scaling Analysis of Anomalous Hall Resistivity in the Co$_{2}$TiAl Heusler Alloy,"A comprehensive magnetotransport study including resistivity ($\rho_{xx}$) at
various fields, isothermal magnetoresistance and Hall resistivity ($\rho_{xy}$)
has been carried out at different temperatures on the Co$_{2}$TiAl Heusler
alloy. Co$_{2}$TiAl alloy shows a paramagnetic (PM) to ferromagnetic (FM)
transition below the curie temperature (T$_{C}$) $\sim$ 125 K. In the FM
region, resistivity and magnetoresistance reveals a spin flip electron-magnon
scattering and the Hall resistivity unveils the anomalous Hall resistivity
($\rho_{xy}^{AH}$). Scaling of anomalous Hall resistivity with resistivity
establishes the extrinsic scattering process responsible for the anomalous hall
resistivity; however Skew scattering is the dominant mechanism compared to the
side-jump contribution. A one to one correspondence between magnetoresistance
and side-jump contribution to anomalous Hall resistivity verifies the
electron-magnon scattering being the source of side-jump contribution to the
anomalous hall resistivity.",1908.05974v1
2009-08-20,"Magnetism, Superconductivity and Stoichiometry in Single Crystals of Fe1+y(Te1-xSx)z","We report synthesis of high quality Fe1+y(Te1-xSx)z single crystals and a
comprehensive study of structural, magnetic and transport properties. There is
high sensitivity to material stoichiometry which includes vacancies on the
Te(S) site. Our results reveal competition and coexistence of magnetic order
and percolative superconductivity for x >= 0.03, while zero resistivity is
acheived for x >= 0.1.",0908.3011v1
2020-11-20,"Phonons, electrons and thermal transport in Planckian high T$_c$ materials","The room temperature thermal diffusivity of high T$_c$ materials is dominated
by phonons. This allows the scattering of phonons by electrons to be discerned.
We argue that the measured strength of this scattering suggests a converse
Planckian scattering of electrons by phonons across the room temperature phase
diagram of these materials. Consistent with this conclusion, the temperature
derivative of the resistivity of strongly overdoped cuprates is noted to show a
kink at a little below 200 K that we argue should be understood as the onset of
a high temperature Planckian $T$-linear scattering of electrons by classical
phonons. This kink continuously disappears towards optimal doping, even while
strong scattering of phonons by electrons remains visible in the thermal
diffusivity, sharpening the long-standing puzzle of the lack of a feature in
the $T$-linear resistivity at optimal doping associated to onset of phonon
scattering.",2011.10466v2
2017-08-10,Zero resistance from one atmosphere to the pressure of earth's outer core in a superconducting high entropy alloy,"We report the observation of extraordinarily robust zero-resistance
superconductivity in the pressurized (TaNb)0.67(HfZrTi)0.33 high entropy alloy
- a new kind of material with a body-centered cubic crystal structure made from
five randomly distributed transition metal elements. The transition to
superconductivity (TC) increases from an initial temperature of 7.7 K at
ambient pressure to 10 K at ~ 60 GPa, and then slowly decreases to 9 K by 190.6
GPa, a pressure that falls within that of the outer core of the earth. We infer
that the continuous existence of the zero-resistance superconductivity from one
atmosphere up to such a high pressure requires a special combination of
electronic and mechanical characteristics. This high entropy alloy
superconductor thus may have a bright future for applications under extreme
conditions, and also poses a challenge for understanding the underlying quantum
physics.",1708.03146v2
2020-05-16,Electric-field induced strange metal states and possible high-temperature superconductivity in hydrogenated graphitic fibers,"In this work, we have studied the effects from increasing the strength of the
applied electric field on the charge transport of hydrogenated graphitic
fibers. Resistivity measurements were carried out for direct currents in the nA
- mA range and for temperatures from 1.9 K to 300 K. The high-temperature
non-ohmic voltage-current dependence is well described by the nonlinear random
resistor network model applied to systems that are disordered at all scales.
The temperature-dependent resistivity shows linear, step-like transitions from
insulating to metallic states as well as plateau features. As more current is
being sourced, the fiber becomes more conductive and thus the current density
goes up. The most interesting features is observed in high electric fields. As
the fiber is cooled, the resistivity first decreases linearly with the
temperature and then enters a plateau region at a temperature T ? 260 ? 280 K
that is field-independent. These observations on a system made out of carbon,
hydrogen, nitrogen, and oxygen atoms suggest possible electric-field induced
superconductivity with a high critical temperature that was predicted from
studying the role of chirality on the origin of life [1].",2005.07885v1
2021-09-28,Development of high-rate capable and ultra-low mass Resistive Plate Chamber with Diamond-Like Carbon,"A new type of resistive plate chamber (RPC) is under development using
thin-film resistive electrodes based on diamond-like carbon (DLC). Planned to
be put on the path of high-intensity low-momentum muon beam of the MEG II
experiment, this detector is required to be high-rate capable and ultra-low
mass. Using a prototype detector with 2 cm $\times$ 2 cm size and 0.1 % $X_0$
material budget, performance studies were conducted for MIP detection
efficiency, timing resolution and high rate capability in low-momentum muon
beam. In this paper, the measured performance is presented including the result
with low-momentum muon beam at rate up to 1 $\mathrm{MHz/cm^2}$. Based on the
result, the expected performance of the full-scale detector in the MEG~II
experiment is also discussed.",2109.13525v1
2014-02-06,High-performance ferroelectric memory based on fully patterned tunnel junctions,"In tunnel junctions with ferroelectric barriers, switching the polarization
direction modifies the electrostatic potential profile and the associated
average tunnel barrier height. This results in strong changes of the tunnel
transmission and associated resistance. The information readout in
ferroelectric tunnel junctions (FTJs) is thus resistive and non-destructive,
which is an advantage compared to the case of conventional ferroelectric
memories (FeRAMs). Initially, endurance limitation (i.e. fatigue) was the main
factor hampering the industrialization of FeRAMs. Systematic investigations of
switching dynamics for various ferroelectric and electrode materials have
resolved this issue, with endurance now reaching $10^{14}$ cycles. Here we
investigate data retention and endurance in fully patterned submicron
Co/BiFeO$_3$/Ca$_{0.96}$Ce$_{0.04}$MnO$_3$ FTJs. We report good reproducibility
with high resistance contrasts and extend the maximum reported endurance of
FTJs by three orders of magnitude ($4\times10^6$ cycles). Our results indicate
that here fatigue is not limited by a decrease of the polarization or an
increase of the leakage but rather by domain wall pinning. We propose
directions to access extreme and intermediate resistance states more reliably
and further strengthen the potential of FTJs for non-volatile memory
applications.",1402.1289v1
2021-07-02,Topological surface conduction in Kondo insulator YbB$_{12}$,"Kondo insulators have recently aroused great interest because they are
promising materials that host a topological insulator state caused by the
strong electron interactions. Moreover, recent observations of the quantum
oscillations in the insulating state of Kondo insulators have come as a great
surprise. Here, to investigate the surface electronic state of a prototype
Kondo insulator YbB$_{12}$, we measured transport properties of single crystals
and microstructures. In all samples, the temperature dependence of the
electrical resistivity is insulating at high temperatures and the resistivity
exhibits a plateau at low temperatures. The magnitude of the plateau value
decreases with reducing sample thickness, which is quantitatively consistent
with the surface electronic conduction in the bulk insulating YbB$_{12}$.
Moreover, the magnetoresistance of the microstructures exhibits a
weak-antilocalization effect at low field. These results are consistent with
the presence of topologically protected surface state, suggesting that
YbB$_{12}$ is a candidate material of the topological Kondo insulator. The high
field resistivity measurements up to $\mu_0H$ = 50 T of the microstructures
provide supporting evidence that the quantum oscillations of the resistivity in
YbB$_{12}$ occurs in the insulating bulk.",2107.00912v2
2021-07-22,Quantum oscillations in 2D insulators induced by graphite gates,"We demonstrate a mechanism for magnetoresistance oscillations in insulating
states of two-dimensional (2D) materials arising from the interaction of the 2D
layer and proximal graphite gates. We study a series of devices based on
different two-dimensional systems, including mono- and bilayer Td-WTe2,
angle-aligned MoTe2/WSe2 heterobilayers and Bernal-stacked bilayer graphene,
which all share a similar graphite-gated geometry. We find that the resistivity
of the 2D system generically shows quantum oscillations as a function of
magnetic field corresponding to a high-density Fermi surface when they are
tuned near an insulating state, in contravention of na\""ive band theory.
Simultaneous measurement of the resistivity of the graphite gates show that
these oscillations are precisely correlated with quantum oscillations in the
resistivity of the graphite gates themselves. Further supporting this
connection, the oscillations are quenched when the graphite gate is replaced by
TaSe2, a high-density metal that does not show quantum oscillations. The
observed phenomenon arises from the oscillatory behavior of graphite density of
states, which modulates the device capacitance and, as a consequence, the
carrier density in the sample layer even when a constant electrochemical
potential is maintained between the sample and the gate electrode. Oscillations
are most pronounced near insulating states where the resistivity is strongly
density dependent. Our study suggests a unified mechanism for quantum
oscillations in graphite-gated 2D insulators based on sample-gate coupling.",2107.10430v2
2014-11-10,Low carrier concentration crystals of the topological insulator Bi$_{2-x}$Sb$_{x}$Te$_{3-y}$Se$_{y}$: a magnetotransport study,"In 3D topological insulators achieving a genuine bulk-insulating state is an
important research topic. Recently, the material system
(Bi,Sb)$_{2}$(Te,Se)$_{3}$ (BSTS) has been proposed as a topological insulator
with high resistivity and a low carrier concentration (Ren \textit{et al.}
\cite{Ren2011}). Here we present a study to further refine the bulk-insulating
properties of BSTS. We have synthesized Bi$_{2-x}$Sb${_x}$Te$_{3-y}$Se$_{y}$
single crystals with compositions around $x = 0.5$ and $y = 1.3$. Resistance
and Hall effect measurements show high resistivity and record low bulk carrier
density for the composition Bi$_{1.46}$Sb$_{0.54}$Te$_{1.7}$Se$_{1.3}$. The
analysis of the resistance measured for crystals with different thicknesses
within a parallel resistor model shows that the surface contribution to the
electrical transport amounts to 97% when the sample thickness is reduced to $1
\mu$m. The magnetoconductance of exfoliated BSTS nanoflakes shows 2D weak
antilocalization with $\alpha \simeq -1$ as expected for transport dominated by
topological surface states.",1411.2479v2
2022-05-20,Resistivity and Thermal Conductivity of an Organic Insulator beta'-EtMe3Sb[Pd(dmit)2]2,"A finite residual linear term in the thermal conductivity at zero temperature
in insulating magnets indicates the presence of gapless excitations of
itinerant quasiparticles, which has been observed in some candidate materials
of quantum spin liquids (QSLs). In the organic triangular insulator
beta'-EtMe3Sb[Pd(dmit)2]2, a QSL candidate material, the low-temperature
thermal conductivity depends on the cooling process and the finite residual
term is observed only in samples with large thermal conductivity. Moreover, the
cooling rate dependence is largely sample dependent. Here we find that, while
the low-temperature thermal conductivity significantly depends on the cooling
rate, the high-temperature resistivity is almost perfectly independent of the
cooling rate. These results indicate that in the samples with the finite
residual term, the mean free path of the quasiparticles that carry the heat at
low temperatures is governed by disorders, whose characteristic length scale of
the distribution is much longer than the electron mean free path that
determines the high-temperature resistivity. This explains why recent X-ray
diffraction and nuclear magnetic resonance measurements show no cooling rate
dependence. Naturally, these measurements are unsuitable for detecting
disorders of the length scale relevant for the thermal conductivity, just as
they cannot determine the residual resistivity of metals. Present results
indicate that very careful experiments are needed when discussing itinerant
spin excitations in beta'-EtMe3Sb[Pd(dmit)2]2.",2205.10039v1
2022-09-17,Superfunctional high-entropy alloys and ceramics by severe plastic deformation,"High-entropy alloys and ceramics containing at least five principal elements
have recently received high attention for various mechanical and functional
applications. The application of severe plastic deformation (SPD), particularly
the high-pressure torsion (HPT) method, combined with the CALPHAD and
first-principles calculations resulted in the development of numerous
superfunctional high-entropy materials with superior properties compared to the
normal functions of engineering materials. This article reviews the recent
advances in the application of SPD to developing superfunctional high-entropy
materials. These superfunctional properties include (i) ultrahigh hardness
levels comparable to the hardness of ceramics in high-entropy alloys, (ii) high
yield strength and good hydrogen embrittlement resistance in high-entropy
alloys; (iii) high strength, low elastic modulus, and high biocompatibility in
high-entropy alloys, (iv) fast and reversible hydrogen storage in high-entropy
hydrides, (v) photovoltaic performance and photocurrent generation on
high-entropy semiconductors, (vi) photocatalytic oxygen and hydrogen production
from water splitting on high-entropy oxides and oxynitrides, and (vii) CO2
photoreduction on high-entropy ceramics. These findings introduce SPD as not
only a processing tool to improve the properties of existing high-entropy
materials but also as a synthesis tool to produce novel high-entropy materials
with superior properties compared with conventional engineering materials.",2209.08291v3
2016-06-10,Short channel effects in graphene-based field effect transistors targeting radio-frequency applications,"Channel length scaling in graphene field effect transistors (GFETs) is key in
the pursuit of higher performance in radio frequency electronics for both rigid
and flexible substrates. Although two-dimensional (2D) materials provide a
superior immunity to Short Channel Effects (SCEs) than bulk materials, they
could dominate in scaled GFETs. In this work, we have developed a model that
calculates electron and hole transport along the graphene channel in a
drift-diffusion basis, while considering the 2D electrostatics. Our model
obtains the self-consistent solution of the 2D Poisson's equation coupled to
the current continuity equation, the latter embedding an appropriate model for
drift velocity saturation. We have studied the role played by the
electrostatics and the velocity saturation in GFETs with short channel lengths
L. Severe scaling results in a high degradation of GFET output conductance. The
extrinsic cutoff frequency follows a 1/L^n scaling trend, where the index n
fulfills n < 2. The case n = 2 corresponds to long-channel GFETs with low
source/drain series resistance, that is, devices where the channel resistance
is controlling the drain current. For high series resistance, n decreases down
to n= 1, and it degrades to values of n < 1 because of the SCEs, especially at
high drain bias. The model predicts high maximum oscillation frequencies above
1 THz for channel lengths below 100 nm, but, in order to obtain these
frequencies, it is very important to minimize the gate series resistance. The
model shows very good agreement with experimental current voltage curves
obtained from short channel GFETs and also reproduces negative differential
resistance, which is due to a reduction of diffusion current.",1606.03264v2
2007-01-29,Long-term Correlations and 1/f^alpha Noise in the Steady States of Multi-Species Resistor Networks,"We introduce a multi-species network model which describes the resistance
fluctuations of a resistor in a non-equilibrium stationary state. More
precisely, a thin resistor characterized by a 1/f^alpha resistance noise is
described as a two-dimensional network made by different species of elementary
resistors. The resistor species are distinguished by their resistances and by
their energies associated with thermally activated processes of breaking and
recovery. Depending on the external conditions, stationary states of the
network can arise as a result of the competition between these processes. The
properties of the network are studied as a function of the temperature by Monte
Carlo simulations carried out in the temperature range 300 \div 800 K. At low
temperatures, the resistance fluctuations display long-term correlations
expressed by a power-law behavior of the auto-correlation function and by a
value approx 1 of the alpha-exponent of the spectral density. On the contrary,
at high temperatures the resistance fluctuations exhibit a finite and
progressively smaller correlation time associated with a non-exponential decay
of correlations and with a value of the alpha-exponent smaller than one. This
temperature dependence of the alpha coefficient reproduces qualitatively well
the experimental findings.",0701712v1
2008-06-26,Different resistivity response to spin density wave and superconductivity at 20 K in $Ca_{1-x}Na_xFe_2As_2$,"We report that intrinsic transport and magnetic properties, and their
anisotropy from high quality single crystal $CaFe_2As_2$. The resistivity
anisotropy ($\rho_c/\rho_{ab}$) is $\sim 50 $, and less than 150 of
$BaFe_2As_2$, which arises from the strong coupling along c-axis due to an
apparent contraction of about 0.13 nm compared to $BaFe_2As_2$. Temperature
independent anisotropy indicates that the transport in ab plane and along
c-axis direction shares the same scattering mechanism. In sharp contrast to the
case of parent compounds $ROFeAs$ (R=rare earth) and $MFe_2As_2$ (M=Ba and Sr),
spin-density-wave (SDW) ordering (or structural transition) leads to a steep
increase of resistivity in $CaFe_2As_2$. Such different resistivity response to
SDW ordering is helpful to understand the role played by SDW ordering in
Fe-based high-$T_c$ superconductors. The susceptibility behavior is very
similar to that observed in single crystal $BaFe_2As_2$. A linear temperature
dependent susceptibility occurs above SDW transition of about 165 K. Partial
substitution of Na for Ca suppresses the SWD ordering (anomaly in resistivity)
and induces occurrence of superconductivity at $\sim 20$ K.",0806.4279v1
2014-02-25,Measurement of junction conductance and proximity effect at superconductor/semiconductor junctions,"The superconducting proximity effect has played an important role in recent
work searching for Majorana modes in thin semiconductor devices. Using
transport measurements to quantify the changes in the semiconductor caused by
the proximity effect provides a measure of dynamical processes such as
screening and scattering. However, in a two terminal measurement the resistance
due to the interface conductance is in series with resistance of transport in
the semiconductor. Both of these change, and it is impossible to separate them
without more information. We have devised a new three terminal device that
provides two resistance measurements that are sufficient to extract both the
junction conductance and the two dimensional sheet resistance under the
superconducting contact. We have compared junctions between Nb and InAs and Nb
and 30% InGaAs all grown before being removed from the ultra high vacuum
molecular beam epitaxy growth system. The most transparent junctions are to
InAs, where the transmission coefficient per Landauer mode is greater than 0.6.
Contacts made with ex-situ deposition are substantially more opaque. We find
that for the most transparent junctions, the largest fractional change as the
temperature is lowered is to the resistance of the semiconductor.",1402.6055v1
2018-08-14,Impurities and Defects in Mott Systems,"Disorder has intriguing consequences for correlated electronic materials,
which include several families of high-temperature superconductors and
resistive switching systems. We address the question of why strongly correlated
d-wave superconductors, such as the cuprates, prove to be surprisingly robust
against the introduction of non-magnetic impurities. We show that, very
generally, both the pair-breaking and the normal state transport scattering
rates are significantly suppressed by strong correlations effects arising in
the proximity to a Mott insulating state. We also show that the
correlation-renormalized scattering amplitude is generically enhanced in the
forward direction, an effect which was previously often ascribed to the
specific scattering by charged impurities outside the copper-oxide planes. We
provide the theoretical insights for resistive switching systems and show how
impurities and underlying correlations can play significant roles in practical
devices. We report the striking result of a connection between the resistive
switching and shock wave formation, a classic topic of non-linear dynamics. We
argue that the profile of oxygen vacancies that migrate during the commutation
forms a shock wave that propagates through a highly resistive region of the
device. We validate the scenario by means of model simulations and experiments
in a manganese-oxide based memristor device and we extend our theory to the
case of binary oxides. The shock wave scenario brings unprecedented physical
insight and enables to rationalize the process of oxygen-vacancy-driven
resistive change with direct implications for a key technological aspect- the
commutation speed.",1808.04767v1
2023-01-10,Microstructuring YbRh2Si2 for resistance and noise measurements down to ultra-low temperatures,"The discovery of superconductivity in the quantum critical Kondo-lattice
system YbRh2Si2 at an extremely low temperature of 2 mK has inspired efforts to
perform high-resolution electrical resistivity measurements down to this
temperature range in highly conductive materials. Here we show that control
over the sample geometry by microstructuring using focused-ion-beam (FIB)
techniques allows to reach ultra-low temperatures and increase signal-to-noise
ratios (SNR) tenfold, without adverse effects to sample quality. In five
experiments we show four-terminal sensing resistance and magnetoresistance
measurements which exhibit sharp phase transitions at the N\'eel temperature,
and Shubnikov-de-Haas (SdH) oscillations between 13 T and 18 T where we
identified a new SdH frequency of 0.39 kT. The increased SNR allowed resistance
fluctuation (noise) spectroscopy that would not be possible for bulk crystals,
and confirmed intrinsic 1/f-type fluctuations. Under controlled strain, two
thin microstructured samples exhibited a large increase of T_N from 67 mK up to
188 mK while still showing clear signatures of the phase transition and SdH
oscillations. SQUID-based thermal noise spectroscopy measurements in a nuclear
demagnetisation refrigerator down to 0.95 mK, show a sharp superconducting
transition at T_c = 1.2 mK. These experiments demonstrate microstructuring as a
powerful tool to investigate the resistance and the noise spectrum of highly
conductive correlated metals over wide temperature ranges.",2301.03928v1
2024-05-06,Bayesian optimization for stable properties amid processing fluctuations in sputter deposition,"We introduce a Bayesian optimization approach to guide the sputter deposition
of molybdenum thin films, aiming to achieve desired residual stress and sheet
resistance while minimizing susceptibility to stochastic fluctuations during
deposition. Thin films are pivotal in numerous technologies, including
semiconductors and optical devices, where their properties are critical.
Sputter deposition parameters, such as deposition power, vacuum chamber
pressure, and working distance, influence physical properties like residual
stress and resistance. Excessive stress and high resistance can impair device
performance, necessitating the selection of optimal process parameters.
Furthermore, these parameters should ensure the consistency and reliability of
thin film properties, assisting in the reproducibility of the devices. However,
exploring the multidimensional design space for process optimization is
expensive. Bayesian optimization is ideal for optimizing inputs/parameters of
general black-box functions without reliance on gradient information. We
utilize Bayesian optimization to optimize deposition power and pressure using a
custom-built objective function incorporating observed stress and resistance
data. Additionally, we integrate prior knowledge of stress variation with
pressure into the objective function to prioritize films least affected by
stochastic variations. Our findings demonstrate that Bayesian optimization
effectively explores the design space and identifies optimal parameter
combinations meeting desired stress and resistance specifications.",2405.03092v1
2023-04-06,Performance Analysis of DNA Crossbar Arrays for High-Density Memory Storage Applications,"Deoxyribonucleic acid (DNA) has emerged as a promising building block for
next-generation ultra-high density storage devices. Although DNA has high
durability and extremely high density in nature, its potential as the basis of
storage devices is currently hindered by limitations such as expensive and
complex fabrication processes and time-consuming read-write operations. In this
article, we propose the use of a DNA crossbar array architecture for an
electrically readable Read-Only Memory (DNA-ROM). While information can be
written error-free to a DNA-ROM array using appropriate sequence encoding, its
read accuracy can be affected by several factors such as array size,
interconnect resistance, and Fermi energy deviations from HOMO levels of DNA
strands employed in the crossbar. We study the impact of array size and
interconnect resistance on the bit error rate of a DNA-ROM array through
extensive Monte Carlo simulations. We have also analyzed the performance of our
proposed DNA crossbar array for an image storage application, as a function of
array size and interconnect resistance. While we expect that future advances in
bioengineering and materials science will address some of the fabrication
challenges associated with DNA crossbar arrays, we believe that the
comprehensive body of results we present in this paper establishes the
technical viability of DNA crossbar arrays as low-power, high-density storage
devices. Finally, our analysis of array performance vis-a-vis interconnect
resistance should provide valuable insights into aspects of the fabrication
process such as the proper choice of interconnects necessary for ensuring high
read accuracies.",2304.14269v1
2023-11-09,Signature of superconductivity in pressurized La$_4$Ni$_3$O$_{10}$,"The discovery of high-temperature superconductivity near 80 K in bilayer
nickelate La$_3$Ni$_2$O$_7$ under high pressures has renewed the exploration of
superconducting nickelate in bulk materials. The extension of superconductivity
in other nickelates in a broader family is also essential. Here, we report the
experimental observation of superconducting signature in trilayer nickelate
La$_4$Ni$_3$O$_{10}$ under high pressures. By using a modified sol-gel method
and post-annealing treatment under high oxygen pressure, we successfully
obtained polycrystalline La$_4$Ni$_3$O$_{10}$ samples with different transport
behaviors at ambient pressure. Then we performed high-pressure electrical
resistance measurements on these samples in a diamond-anvil-cell (DAC)
apparatus. Surprisingly, the signature of possible superconducting transition
with a maximum transition temperature ($T_\text{c}$) of about 20 K under high
pressures is observed, as evidenced by a clear drop of resistance and the
suppression of resistance drops under magnetic fields. Although the resistance
drop is sample-dependent and relatively small, it appears in all of our
measured samples. We argue that the observed superconducting signal is most
likely to originate from the main phase of La$_4$Ni$_3$O$_{10}$. Our findings
will motivate the exploration of superconductivity in a broader family of
nickelates and shed light on the understanding of the underlying mechanisms of
high-$T_\text{c}$ superconductivity in nickelates.",2311.05453v1
2024-04-29,Thermoelectric transport properties of the quasi-one-dimensional dimer-Mott insulator $β'$-(BEDT-TTF)$_2$ICl$_2$,"Low-dimensional materials, in which the electronic and transport properties
are drastically modified in comparison to those of three-dimensional bulk
materials, yield a key class of thermoelectric materials with high conversion
efficiency. Among such materials, the organic compounds may serve peculiar
properties owing to their unique molecular-based low-dimensional structures
with highly anisotropic molecular orbitals. Here we present the thermoelectric
transport properties of the quasi-one-dimensional dimer-Mott insulator
$\beta'$-(BEDT-TTF)$_2$ICl$_2$, where BEDT-TTF stands for
bis(ethylenedithio)-tetrathiafulvalene. We find that the thermopower exhibits
typical activation-type temperature variation expected for insulators but its
absolute value is anomalously large compared to the expected value from the
activation-type temperature dependence of the electrical resistivity.
Successively, the Jonker-plot analysis, in which the thermopower is usually
scaled by the logarithm of the resistivity, shows an unusual relation among
such transport quantities. We discuss a role of the low dimensionality for the
enhanced thermopower along with recent observations of such a large thermopower
in several low-dimensional materials.",2404.19137v1
2021-12-28,Review of Transition-Metal Diboride Thin Films,"We review the thin film growth, chemistry, and physical properties of Group
4-6 transition-metal diboride (TMB2) thin films with AlB2-type crystal
structure (Strukturbericht designation C32). Industrial applications are
growing rapidly as TMB2 begin competing with conventional refractory ceramics
like carbides and nitrides, including pseudo-binaries such as Ti1-xAlxN. The
TMB2 crystal structure comprises graphite-like honeycombed atomic sheets of B
interleaved by hexagonal close-packed TM layers. From the C32 crystal structure
stems unique properties including high melting point, hardness, and corrosion
resistance, yet limited oxidation resistance, combined with high electrical
conductivity. We correlate the underlying chemical bonding, orbital overlap,
and electronic structure to the mechanical properties, resistivity, and
high-temperature properties unique to this class of materials. The review
highlights the importance of avoiding contamination elements (like oxygen) and
boron segregation on both the target and substrate sides during sputter
deposition, for better-defined properties, regardless of the boride system
investigated. This is a consequence of the strong tendency for B to segregate
to TMB2 grain boundaries for boron-rich compositions of the growth flux. It is
judged that sputter deposition of TMB2 films is at a tipping point towards a
multitude of applications for TMB2 not solely as bulk materials, but also as
protective coatings and electrically conducting high-temperature stable thin
films.",2112.14099v1
2016-06-10,On the search for the chiral anomaly in Weyl semimetals: The negative longitudinal magnetoresistance,"Recently, the existence of massless chiral (Weyl) fermions has been
postulated in a class of semi-metals with a non-trivial energy dispersion.These
materials are now commonly dubbed Weyl semi-metals (WSM).One predicted property
of Weyl fermions is the chiral or Adler-Bell-Jackiw anomaly, a chirality
imbalance in the presence of parallel magnetic and electric fields. In WSM, it
is expected to induce a negative longitudinal magnetoresistance (NMR), the
chiral magnetic effect.Here, we present experimental evidence that the
observation of the chiral magnetic effect can be hindered by an effect called
""current jetting"". This effect also leads to a strong apparent NMR, but it is
characterized by a highly non-uniform current distribution inside the sample.
It appears in materials possessing a large field-induced anisotropy of the
resistivity tensor, such as almost compensated high-mobility semimetals due to
the orbital effect.In case of a non-homogeneous current injection, the
potential distribution is strongly distorted in the sample.As a consequence, an
experimentally measured potential difference is not proportional to the
intrinsic resistance.Our results on the MR of the WSM candidate materials NbP,
NbAs, TaAs, TaP exhibit distinct signatures of an inhomogeneous current
distribution, such as a field-induced ""zero resistance' and a strong dependence
of the `measured resistance"" on the position, shape, and type of the voltage
and current contacts on the sample. A misalignment between the current and the
magnetic-field directions can even induce a ""negative resistance"".
Finite-element simulations of the potential distribution inside the sample,
using typical resistance anisotropies, are in good agreement with the
experimental findings. Our study demonstrates that great care must be taken
before interpreting measurements of a NMR as evidence for the chiral anomaly in
putative Weyl semimetals.",1606.03389v1
2011-10-07,Overlapping-gate architecture for silicon Hall bar MOSFET devices in the low electron density and high magnetic field regime,"A common issue in low temperature measurements of enhancement-mode
metal-oxide-semiconductor (MOS) field-effect transistors (FETs) in the low
electron density regime is the high contact resistance dominating the device
impedance. In that case a voltage bias applied across the source and drain
contact of a Hall bar MOSFET will mostly fall across the contacts (and not
across the channel) and therefore magneto-transport measurements become
challenging. However, from a physical point of view, the study of MOSFET
nanostructures in the low electron density regime is very interesting (impurity
limited mobility [1], carrier interactions [2,3] and spin-dependent transport
[4]) and it is therefore important to come up with solutions [5,6] that work
around the problem of a high contact resistance in such devices (c.f. Fig. 1
(a)).",1110.1418v1
2013-04-01,"Novel Bismaleimide Resin/Silsesquioxane and Titania Nanocomposites by the Sol-Gel Process: the Preparation, Morphology, Thermal and Thermo-mechanical Properties","Bismaleimide(BMI) resin/silsesquioxane or titania nanocomposites were
synthesized from bismaleimide resin and SiO3/2 or TiO2 via the sol-gel process
of N-{\gamma}-triethoxylsilylpropyl-maleamic acid (TESPMA) or
tetrabutyltitanate (Ti(OnBu)4, TBT), respectively, in the presence of the
AP-BMI prepolymers. These nanocomposite materials were characterized by FT-IR,
FE-SEM, TGA and DMA. It was found that the nano-scale SiO3/2 or TiO2 particles
were formed in the AP-BMI resin matrix and the average original particle size
of the dispersed phase in the nanocomposites was less than 100nm, but the
particle aggregates with bigger size existed. Obvious improvements of Tg and
the heat resistance of the AP-BMI resin were achieved by introduction of the
nano-sized SiO3/2 inorganic phase, and the modulus at high temperatures was
improved too. The incorporation of nano-scale TiO2 particles into the AP-BMI
resin improved the Tg of the polymer, but lowered the thermal resistance of the
material, and improved the modulus of the material at lower temperatures, but
lowered the modulus at higher temperatures.",1304.0288v1
2016-04-19,Observation of spin Seebeck contribution to the transverse thermopower in Ni-Pt and MnBi-Au bulk nanocomposites,"Transverse thermoelectric devices produce electric fields perpendicular to an
incident heat flux. Classically, this process is driven by the Nernst effect in
bulk solids, wherein a magnetic field generates a Lorentz force on thermally
excited electrons. The spin Seebeck effect (SSE) also produces
magnetization-dependent transverse electric fields. SSE is traditionally
observed in thin metallic films deposited on electrically insulating
ferromagnets, but the films' high resistance limits thermoelectric conversion
efficiency. Combining Nernst and SSE in bulk materials would enable devices
with simultaneously large transverse thermopower and low electrical resistance.
Here we demonstrate experimentally this is possible in composites of conducting
ferromagnets (Ni or MnBi) containing metallic nanoparticles with strong
spin-orbit interactions (Pt or Au). These materials display positive shifts in
transverse thermopower attributable to inverse spin Hall electric fields in the
nanoparticles. This more than doubles the power output of the Ni-Pt materials,
establishing proof-of-principle that SSE persists in bulk nanocomposites.",1604.05626v3
2016-01-18,Large magnetoresistance in LaBi: origin of field-induced resistivity upturn and plateau in compensated semimetals,"The discovery of non-magnetic extreme magnetoresistance (XMR) materials has
induced great interests because the XMR phenomenon challenges our understanding
of how a magnetic field can alter electron transport in semimetals. Among XMR
materials, the LaSb shows XMR and field-induced exotic behaviors but it seems
to lack the essentials for these properties. Here, we study the
magnetotransport properties and electronic structure of LaBi, isostructural to
LaSb. LaBi exhibits large MR as in LaSb, which can be ascribed to the nearly
compensated electron and hole with rather high mobilities. More importantly,
our analysis suggests that the XMR as well as field-induced resistivity upturn
and plateau observed in LaSb and LaBi can be well explained by the two-band
model with the compensation situation. We present the critical conditions
leading to these field-induced properties. It will contribute to understanding
the XMR phenomenon and explore novel XMR materials.",1601.04618v2
2003-03-14,Microwave performance of high-density bulk MgB2,"We have performed microwave measurements on superconducting
hot-isostatically- pressed (HIPed) bulk MgB2 using a parallel-plate resonator
technique. The high density and strength of the HIPed material allowed
preparation of samples with mirror-like surfaces for microwave measurements.
The microwave surface resistance decreased by about 40% at 20 K when the
root-mean-square surface roughness was reduced from 220 nm to 110 nm through
surface-polishing and ion-milling. The surface resistance was independent of
surface microwave magnetic field at least up to 4 Oe and below 30 K. We
attribute this behavior, and the overall low surface resistance (~0.8 mOhms at
10 GHz and 20 K), to the high density of our samples and the absence of weak
links between grains.",0303283v1
2006-02-23,Quantum Metallicity on the High-Field Side of the Superconductor-Insulator Transition,"We investigate ultrathin superconducting TiN films, which are very close to
the localization threshold. Perpendicular magnetic field drives the films from
the superconducting to an insulating state, with very high resistance. Further
increase of the magnetic field leads to an exponential decay of the resistance
towards a finite value. In the limit of low temperatures, the saturation value
can be very accurately extrapolated to the universal quantum resistance h/e^2.
Our analysis suggests that at high magnetic fields a new ground state, distinct
from the normal metallic state occurring above the superconducting transition
temperature, is formed. A comparison with other studies on different materials
indicates that the quantum metallic phase following the magnetic-field-induced
insulating phase is a generic property of systems close to the disorder-driven
superconductor-insulator transition.",0602557v2
2013-09-18,Pressure-Induced Superconductivity in Mineral Calaverite AuTe2,"The pressure dependences of resistivity and ac susceptibility have been
measured in the mineral calaverite AuTe$_2$. Resistivity clearly shows a
first-order phase transition into a high-pressure phase, consistent with the
results of a previous structural analysis. We found zero resistivity and a
diamagnetic shielding signal at low temperatures in the high-pressure phase,
which clearly indicates the appearance of superconductivity. Our experimental
results suggest that bulk superconductivity appears only in the high-pressure
phase. For AuTe$_2$, the highest superconducting transition temperature under
pressure is $T_{\rm c}$ = 2.3 K at 2.34 GPa; it was $T_{\rm c}$ = 4.0 K for
Pt-doped (Au$_{0.65}$Pt$_{0.35}$)Te$_2$. The difference in $T_{\rm c}$ between
the two systems is discussed on the basis of the results obtained using the
band calculations and McMillan's formula.",1309.4827v2
2018-03-07,Saturation and negative temperature coefficient of electrical resistivity in liquid iron-sulfur alloys at high densities from first principles calculations,"We report results on electronic transport properties of liquid Fe-S alloys at
conditions of planetary cores, computed by first-principle techniques in the
Kubo-Greenwood formalism. We describe a combined effect of resistivity
saturation due to temperature, compression, and chemistry by comparing the
electron mean free path from the Drude response of optical conductivity to the
mean interatomic distance. At high compression and high sulfur concentration
the Ioffe-Regel condition is satisfied, and the temperature coefficient of
resistivity changes sign from positive to negative. We show that this happens
due to a decrease of the $d$-density of states at the Fermi level in response
to thermal broadening.",1803.02649v1
2018-10-03,On the temperature scaling behaviour of the linear magnetoresistance observed in high-temperature superconductors,"An analytical model invoking variations in the charge-carrier density is used
to generate magnetoresistance curves that are almost indistinguishable from
those produced by sophisticated numerical models. This demonstrates that,
though disorder is pivotal in causing linear magnetoresistance, the form of the
magnetoresistance thus generated is insensitive to details of the disorder.
Taken in conjunction with the temperature ($T$) dependence of the zero-field
resistivity, realistic levels of disorder are shown to be sufficient to explain
the linear magnetoresistance and field-$T$ resistance scaling observed in
high-temperature pnictide and cuprate superconductors. Hence, though the
$T$-linear zero-field resistance is a definite signature of the ""strange metal""
state of high-temperature superconductors, their linear magnetoresistance and
its scaling is unlikely to be so.",1810.01998v3
2020-04-17,High-pressure characterization of multifunctional CrVO4,"The structural stability and physical properties of CrVO4 under compression
were studied by X-ray diffraction, Raman spectroscopy, optical absorption,
resistivity measurements, and ab initio calculations up to 10 GPa.
High-pressure X-ray diffraction and Raman measurements show that CrVO4
undergoes a phase transition from the ambient pressure orthorhombic CrVO4-type
structure (Cmcm space group, phase III) to the high-pressure monoclinic CrVO4-V
phase, which is isomorphic to the wolframite structure. Such a phase transition
(CrVO4-type - wolframite), driven by pressure, also was previously observed in
indium vanadate. The crystal structure of both phases and the pressure
dependence in unit-cell parameters, Raman-active modes, resistivity, and
electronic band gap, is reported. Vanadium atoms are sixth-fold coordinated in
the wolframite phase, which is related to the collapse in the volume at the
phase transition. Besides, we also observed drastic changes in the phonon
spectrum, a drop of the band-gap, and a sharp decrease of resistivity. All the
observed phenomena are explained with the help of first-principles
calculations.",2004.08072v1
2020-08-28,"High-Bandwidth, Variable-Resistance Differential Noise Thermometry","We develop Johnson noise thermometry applicable to mesoscopic devices with
variable source impedance with high bandwidth for fast data acquisition. By
implementing differential noise measurement and two-stage impedance matching,
we demonstrate noise measurement in the frequency range 120-250 MHz with a wide
sample resistance range 30 {\Omega}-100 k{\Omega} tuned by gate voltages and
temperature. We employ high-frequency, single-ended low noise amplifiers
maintained at a constant cryogenic temperature in order to maintain the desired
low noise temperature. We achieve thermometer calibration with temperature
precision up to 650 mK on a 10 K background with 30 s of averaging. Using this
differential noise thermometry technique, we measure thermal conductivity on a
bilayer graphene sample spanning the metallic and semiconducting regimes in a
wide resistance range, and we compare it to the electrical conductivity.",2008.12739v1
2014-09-19,Fluorine doping: A feasible solution to enhancing the conductivity of high-resistance wide bandgap Mg0.51Zn0.49O active components,"N-type doping of high-resistance wide bandgap semiconductors, wurtzite
high-Mg-content MgxZn1-xO for instance, has always been a fundamental
application-motivated research issue. Herein, we report a solution to enhancing
the conductivity of high-resistance Mg0.51Zn0.49O active components, which has
been reliably achieved by fluorine doping via radio-frequency plasma assisted
molecular beam epitaxial growth. Fluorine dopants were demonstrated to be
effective donors in Mg0.51Zn0.49O single crystal film having a solar-blind 4.43
eV bandgap, with an average concentration of 1.0E19 F/cm3.The dramatically
increased carrier concentration (2.85E17 cm-3 vs ~1014 cm-3) and decreased
resistivity (129 ohm.cm vs ~10E6 ohm cm) indicate that the electrical
properties of semi-insulating Mg0.51Zn0.49O film can be delicately regulated by
F doping. Interestingly, two donor levels (17 meV and 74 meV) associated with F
were revealed by temperature-dependent Hall measurements. A Schottky type
metal-semiconductor-metal ultraviolet photodetector manifests a remarkably
enhanced photocurrent, two orders of magnitude higher than that of the undoped
counterpart. The responsivity is greatly enhanced from 0.34 mA/W to 52 mA/W
under 10 V bias. The detectivity increases from 1.89E9 cm Hz1/2/W to 3.58eE10
cm Hz1/2/W under 10 V bias at room temperature.These results exhibit F doping
serves as a promising pathway for improving the performance of high-Mg-content
MgxZn1-xO-based devices.",1409.5657v2
2021-11-03,Resistive switching in HfO2-x/La0.67Sr0.33MnO3 heterostructure: An intriguing case of low H-field susceptibility of an E-field controlled active interface,"High-performance non-volatile resistive random access memories (ReRAM) and
their small stimuli control are of immense interest for high-speed computation
and big-data processing in the emergent Internet of Things (IOT) arena. Here,
we examine the resistive switching (RS) behavior in growth controlled
HfO2/La0.67Sr0.33MnO3 heterostructures and their tunability under low magnetic
field. It is demonstrated that oxygen-deficient HfO2 films show bipolar
switching with high on/off ratio, stable retention, as well as good endurance
owing to the orthorhombic-rich phase constitution and charge
(de)-trapping-enabled Schottky-type conduction. Most importantly, we have
demonstrated that, the RS can be tuned by a very low externally applied
magnetic field (0-30 mT). Remarkably, application of a magnetic field of 30 mT
causes the RS to be fully quenched and frozen in the high resistance state
(HRS) even after the removal of magnetic field. However, the quenched state
could be resurrected by applying higher bias voltage than the one for initial
switching. This is argued to be a consequence of the electronically and
ionically active nature of the HfO2-x/LSMO interface on both sides, and its
susceptibility to the electric and low magnetic field effects. This result
could pave the way for new designs of interface engineered high-performance
oxitronic ReRAM devices.",2111.02476v1
2002-09-26,Kapitza resistance at the liquid solid interface,"Using equilibrium and nonequilibrium molecular dynamics simulations, we
determine the Kapitza resistance (or thermal contact resistance) at a model
liquid solid interface. The Kapitza resistance (or the associated Kapitza
length) can reach appreciable values when the liquid does not wet the solid.
The analogy with the hydrodynamic slip length is discussed.",0209607v1
2008-02-06,On the calculation of Schottky contact resistivity,"This numerical study examines the importance of self-consistently accounting
for transport and electrostatics in the calculaiton of semiconductor/metal
Schottky contact resistivity. It is shown that ignoring such self-consistency
results in significant under-estimation of the contact resistivity. An explicit
numerical method has also been proposed to efficiently improve contact
resistivity calculations.",0802.0729v1
2016-12-17,"Upper critical field, pressure-dependent superconductivity and electronic anisotropy of Sm$_4$Fe$_2$As$_2$Te$_{1-x}$O$_{4-y}$F$y$","We present a detailed study of the electrical transport properties of a
recently discovered iron-based superconductor:
Sm$_4$Fe$_2$As$_2$Te$_{0.72}$O$_{2.8}$F$_{1.2}$. We followed the temperature
dependence of the upper critical field by resistivity measurement of single
crystals in magnetic fields up to 16 T, oriented along the two main
crystallographic directions. This material exhibits a zero-temperature upper
critical field of 90 T and 65 T parallel and perpendicular to the Fe$_2$As$_2$
planes, respectively. An unprecedented superconducting magnetic anisotropy
$\gamma_H=H_{c2}^{ab}/H_{c2}^c \sim 14$ is observed near Tc, and it decreases
at lower temperatures as expected in multiband superconductors. Direct
measurement of the electronic anisotropy was performed on microfabricated
samples, showing a value of $\rho_c/\rho_{ab}(300K) \sim 5$ that raises up to
19 near Tc. Finally, we have studied the pressure and temperature dependence of
the in-plane resistivity. The critical temperature decreases linearly upon
application of hydrostatic pressure (up to 2 GPa) similarly to overdoped
cuprate superconductors. The resistivity shows saturation at high temperatures,
suggesting that the material approaches the Mott-Ioffe-Regel limit for metallic
conduction. Indeed, we have successfully modelled the resistivity in the normal
state with a parallel resistor model that is widely accepted for this state.
All the measured quantities suggest strong pressure dependence of the density
of states.",1612.05792v1
2019-07-28,Field-dependent nonlinear surface resistance and its optimization by surface nano-structuring in superconductors,"We propose a theory of nonlinear surface resistance of a dirty superconductor
in a strong radio-frequency (RF) field, taking into account magnetic and
nonmagnetic impurities, finite quasiparticle lifetimes, and a thin
proximity-coupled normal layer characteristic of the oxide surface of many
materials. The Usadel equations were solved to obtain the quasiparticle density
of states (DOS) and the low-frequency surface resistance $R_s$ as functions of
the RF field amplitude $H_0$. It is shown that the interplay of the broadening
of the DOS peaks and a decrease of a quasiparticle gap caused by the RF
currents produces a minimum in $R_s(H_0)$ and an extended rise of the quality
factor $Q(H_0)$ with the RF field. Paramagnetic impurities shift the minimum in
$R_s(H_0)$ to lower fields and can reduce $R_s(H_0)$ in a wide range of $H_0$.
Subgap states in the DOS can give rise to a residual surface resistance while
reducing $R_s$ at higher temperatures. A proximity-coupled normal layer at the
surface can shift the minimum in $R_s(H_0)$ to either low and high fields and
can reduce $R_s$ below that of an ideal surface. The theory shows that the
behavior of $R_s(H_0)$ changes as the temperature and the RF frequency are
increased, and the field dependence of $Q(H_0)$ can be very sensitive to the
materials processing. Our results suggest that the nonlinear RF losses can be
minimized by tuning pairbreaking effects at the surface using impurity
management or surface nanostructuring.",1907.12040v1
2019-08-08,Substrate induced nanoscale resistance variation in epitaxial graphene,"Graphene, the first true two-dimensional material still reveals the most
remarkable transport properties among the growing class of two-dimensional
materials. Although many studies have investigated fundamental scattering
processes, the surprisingly large variation in the experimentally determined
resistances associated with a localized defect is still an open issue. Here, we
quantitatively investigate the local transport properties of graphene prepared
by polymer assisted sublimation growth (PASG) using scanning tunneling
potentiometry. PASG graphene is characterized by a spatially homogeneous
current density, which allows to analyze variations in the local
electrochemical potential with high precision. We utilize this possibility by
examining the local sheet resistance finding a significant variation of up to
270% at low temperatures. We identify a correlation of the sheet resistance
with the stacking sequence of the 6H-SiC substrate as well as with the distance
between the graphene sheet and the substrate. Our results experimentally
quantify the strong impact of the graphene-substrate interaction on the local
transport properties of graphene.",1908.02956v2
2021-01-16,Optical Tuning of Resistance Switching in Polycrystalline Gallium Phosphide Thin Films,"The nanoscale resistive switching characteristics of gallium phosphide (GaP)
thin films directly grown on Si are investigated as a function of incident
light. Firstly, as-grown GaP films show a high RON/ROFF (~10^4), shown to arise
from the formation of conductive channels along the grain boundaries. It is
proposed that point defects (most likely Ga interstitials) and structural
disorder at the grain boundaries provide the ideal environment to enable the
filamentary switching process. Next, we explored if such defects can give rise
to mid-gap states, and if so could they be activated by photonic excitation.
Both first-principles calculations as well as UV-vis and photoluminescence
spectroscopy strongly point to the possibility of mid-gap electronic states in
the polycrystalline GaP film. Photoconductive atomic force microscopy (phAFM),
a scanning probe technique, is used to image photocurrents generated as a
function of incident photon energy (ranging from sub band-gap to above
band-gap) on the GaP film surface. We observe photocurrents even for incident
photon energies lower than the band-gap, consistent with the presence of
mid-gap electronic states. Moreover the photocurrent magnitude is found to be
directly proportional to the incident photon energy with a concomitant decrease
in the filament resistance. This demonstrates GaP directly integrated on Si can
be a promising photonic resistive switching materials system.",2101.06538v1
2020-11-03,Switchable domains in point contacts based on transition metal tellurides,"We report resistive switching in voltage biased point contacts (PCs) based on
series of van der Waals transition metals tellurides (TMTs) such as MeTe2
(Me=Mo, W) and TaMeTe4 (Me= Ru, Rh, Ir). The switching occurs between a low
resistive ""metallic-type"" state, which is the ground state, and a high
resistive ""semiconducting-type"" state by applying certain bias voltage (<1V),
while reverse switching takes place by applying voltage of opposite polarity.
The origin of the effect can be formation of domain in PC core by applying a
bias voltage, when a strong electric field (about 10kV/cm) modifies the crystal
structure and controls its polarization. In addition to the discovery of the
switching effect in PCs, we also suggest a simple method of material testing
before functionalizing them, which offers a great advantage in finding suitable
novel substances. The new functionality of studied TMTs arising from switchable
domains in submicron hetero-structures that are promising, e.g., for
non-volatile resistive random access memory (RRAM) engineering.",2011.01569v2
2020-11-30,Above-room-temperature giant thermal conductivity switching in spintronic multilayer,"Thermal switching provides an effective way for active heat flow control,
which has recently attracted increasing attention in terms of nanoscale thermal
management technologies. In magnetic and spintronic materials, the thermal
conductivity depends on the magnetization configuration: this is the
magneto-thermal resistance effect. Here we show that an epitaxial
Cu/Co$_{50}$Fe$_{50}$ multilayer film exhibits giant magnetic-field-induced
modulation of the cross-plane thermal conductivity. The magneto-thermal
resistance ratio for the Cu/Co$_{50}$Fe$_{50}$ multilayer reaches 150% at room
temperature, which is much larger than the previous record high. Although the
ratio decreases with increasing the temperature, the giant magneto-thermal
resistance effect of ~100% still appears up to 400 K. The magnetic field
dependence of the thermal conductivity of the Cu/Co$_{50}$Fe$_{50}$ multilayer
was observed to be about twice greater than that of the cross-plane electrical
conductivity. The observation of the giant magneto-thermal resistance effect
clarifies a potential of spintronic multilayers as thermal switching devices.",2011.14558v1
2022-03-01,Cu-doping effects on the ferromagnetic semimetal CeAuGe,"We present a study of Cu-substitution effects in 4f-Ce intermetallic compound
CeAu1-xCuxGe, with potentially unusual electronic states, in the whole
concentration range (x = 0.0 - 1.0). The parent CeAuGe compound, crystallizing
in a non-centrosymmetric hexagonal structure, is a ferromagnetic semimetal with
Curie temperature 10 K. Cu-doping on Au-site of CeAuGe, CeAu1-xCuxGe, changes
the crystal structure from the non-centrosymmetric (P63mc) to centrosymmetric
(P63/mmc) space group at the concentration x ~ 0.5, where the c-lattice
constant has a maximum value. Magnetic susceptibility and electrical
resistivity measurements reveal that all Cu-doped compounds undergo magnetic
phase transition near 10 K, with the maximum transition temperature of 12 K for
x = 0.5. The neutron powder diffraction experiments show the ferromagnetic
ordering of Ce3+ magnetic moments with a value of ~ 1.2 Bohr magneton at 1.8 K,
oriented perpendicular to the hexagonal c-axis. By using symmetry analysis, we
have found the solutions for the magnetic structure in the ferromagnetic
Shubnikov space groups Cmc'21' and P21'/m' for x < 0.5 and x >= 0.5,
respectively. Electrical resistivity exhibits a metallic temperature behaviour
in all compounds. The resistivity has a local minimum in the paramagnetic state
due to Kondo effects at high doping x = 0.8 and 1.0. At the small Cu-doping
level, x = 0.2, the resistivity shows a broad feature at the ferromagnetic
transition temperature and an additional transition-like peculiarity at 2.5 K
in the ferromagnetic state.",2203.00335v1
2022-06-13,The two-dimensional metallic triangular lattice antiferromagnet CeCd3P3,"Single crystals of $R$Cd$_{3}$P$_{3}$ ($R$ = La and Ce) have been
investigated by magnetization, electrical resistivity, Hall coefficient, and
specific heat. Magnetization measurements of CeCd$_{3}$P$_{3}$ demonstrate
clear quasi-2D magnetic behavior. Electrical resistivity and Hall coefficient
measurements suggest that $R$Cd$_{3}$P$_{3}$ compounds are low carrier density
metallic systems, in strong contrast to an earlier study of polycrystalline
material. Specific heat and electrical resistivity measurements of
CeCd$_{3}$P$_{3}$ reveal a high temperature (structural) phase transition at
$T_{s} = 127$~K and antiferromagnetic ordering below $T_{N} = 0.41$~K. Upon
applying magnetic field in the easy-plane ($H {\parallel} ab$) the magnetic
ordering temperature increases to 0.43~K at $H \sim 15$~kOe, demonstrating
partial lifting of the magnetic frustration. The large electronic specific heat
persists in an unusually wide range of temperature above $T_{N}$, due to the
frustrated spins. The observation of conventional metallic behavior in the
electrical resistivity suggests that the $f$-electrons in CeCd$_{3}$P$_{3}$
undergo negligible hybridization with the conduction electrons. Thus,
CeCd$_{3}$P$_{3}$ may be a model system for exploring the complex interplay
between magnetic frustration and RKKY physics on a low carrier density Ce
triangular lattice.",2206.06366v1
2023-01-13,Image-Force Barrier Lowering of Schottky Barriers in Two-Dimensional Materials as a Function of Metal Contact Angle,"Two-dimensional (2D) semiconductors are a promising solution for the
miniaturization of electronic devices and for the exploration of novel physics.
However, practical applications and demonstrations of physical phenomena are
hindered by high Schottky barriers at the contacts to 2D semiconductors. While
the process of image-force barrier lowering (IFBL) can considerably decrease
the Schottky barrier, IFBL is not fully understood for the majority of
prevalent contact geometries. We introduce a novel technique to determine the
IFBL potential energy with application spanning far beyond that of any existing
method. We do so by solving Poisson's equation with the boundary conditions of
two metal surfaces separated by an angle Omega. We then prove that our result
can also be obtained with the method of images provided a non-Euclidean,
cone-manifold space is used. The resulting IFBL is used to calculate the
expected contact resistance of the most prevalent geometric contacts. Finally,
we investigate contact resistance and show how the stronger IFBL counteracts
the effect of larger depletion width with increasing contact angle. We find
that top contacts experience lower contact resistance than edge contacts.
Remarkably, our results identify tunable parameters for reducing Schottky
barriers and likewise contact resistance to edge-contacted 2D materials,
enhancing potential applications.",2301.05373v2
2023-12-07,Demonstration of high-impedance superconducting NbRe Dayem bridges,"Here we demonstrate superconducting Dayem-bridge weak-links made of different
stoichiometric compositions of NbRe. Our devices possess a relatively high
critical temperature, normal-state resistance, and kinetic inductance. In
particular, the high kinetic inductance makes this material a good alternative
to more conventional niobium-based superconductors (e.g., NbN or NbTiN) for the
realization of superinductors and high-quality factor resonators, whereas the
high normal-state resistance yields a large output voltage in superconducting
switches and logic elements realized upon this compound. Moreover, out-of-plane
critical magnetic fields exceeding 2 T ensure that possible applications
requiring high magnetic fields can also be envisaged. Altogether, these
features make this material appealing for a number of applications in the
framework of quantum technologies.",2312.04331v2
2019-01-11,"A Piezoelectric, Strain-Controlled Antiferromagnetic Memory Insensitive to Magnetic Fields","Spintronic devices based on antiferromagnetic (AFM) materials hold the
promise of fast switching speeds and robustness against magnetic fields.
Different device concepts have been predicted and experimentally demonstrated,
such as low-temperature AFM tunnel junctions that operate as spin-valves, or
room-temperature AFM memory, for which either thermal heating in combination
with magnetic fields, or N\'eel spin-orbit torque is used for the information
writing process. On the other hand, piezoelectric materials were employed to
control magnetism by electric fields in multiferroic heterostructures, which
suppresses Joule heating caused by switching currents and may enable low
energy-consuming electronic devices. Here, we combine the two material classes
to explore changes of the resistance of the high-N\'eel-temperature
antiferromagnet MnPt induced by piezoelectric strain. We find two non-volatile
resistance states at room temperature and zero electric field, which are stable
in magnetic fields up to 60 T. Furthermore, the strain-induced resistance
switching process is insensitive to magnetic fields. Integration in a tunnel
junction can further amplify the electroresistance. The tunneling anisotropic
magnetoresistance reaches ~11.2% at room temperature. Overall, we demonstrate a
piezoelectric, strain-controlled AFM memory which is fully operational in
strong magnetic fields and has potential for low-energy and high-density memory
applications.",1901.03551v1
2020-07-09,Frequency domain measurements of thermal properties using 3omega-Scanning Thermal Microscope in a vacuum environment,"Material thermal properties characterization at nanoscales remains a
challenge even if progresses were done in developing specific characterization
techniques like the Scanning Thermal Microscopy (SThM). In the present work, we
propose a detailed procedure based on the combined use of a SThM probe
characterization and its Finite Element Modeling (FEM) to recover in-operando
3omega measurements achieved under high vacuum. This approach is based on a
two-step methodology: (i) a fine description of the probe s electrical and
frequency behaviors in out of contact mode to determine intrinsic parameters of
the SThM tip, (b) a minimization of the free parameter of our model, i.e. the
contact thermal resistance, by comparing 3omega measurements to our simulations
of the probe operating in contact mode. Such an approach allows us to
accurately measure thermal interface resistances of the probe as a function of
the strength applied between the tip and the surface for three different
materials (silicon, silica and gold). In addition, FEM modeling provides
insights about the 3omega-SThM technique sensitivity, as a function of probe /
sample interface resistance to measure material thermal conductivity, paving
the way to quantitative SThM measurements.",2007.04632v1
2022-04-02,Traction of Interlocking Spikes on a Granular Material,"The interlock drive system generates traction by inserting narrow articulated
spikes into the ground and by leveraging the soil's strength to resist
horizontal draft forces. The system promises high tractive performance in low
gravity environments where tires have little traction for lack of weight. At
Earth and Space 2021 we reported the performance of such spikes on a silty clay
loam, a cohesive soil. We found that in such soil, traction below a critical
depth is provided by a zone of lateral soil failure. We also found that the
articulation translates a horizontal draft force into a vertical penetration
force strong enough to penetrate a narrow spike to a depth where the soil can
sustain the draft force, in a self-regulating way. It is conceivable that a
granular material like regolith or sand with little to no cohesive strength
provides less vertical penetration resistance and less resistance to a
horizontal draft force than a cohesive soil, which leads to the question of
whether and how much tractive force an interlocking spike can generate on a
granular material. Here we report on field trials that study different spike
designs in dry and unsaturated moist sand. The results demonstrate that a loose
granular material requires larger spikes than a cohesive soil, that these
larger spikes penetrate dry and moist sand reliably, and that they promise good
tractive efficiency. The trials indicate that on sand, a larger spike diameter
can improve the pull/weight ratio without a loss of tractive performance.",2205.00840v2
2015-02-12,RF Transport Electromagnetic Properties of CVD Graphene from DC to 110 MHz,"We report measurement of the radio-frequency (RF) transport electromagnetic
properties of chemical vapour deposition (CVD) graphene over the DC to 110 MHz
frequency range at room temperature. Graphene on Si/SiO2 substrate was mounted
in a shielded four terminal-pair (4TP) adaptor which enabled direct connection
to a calibrated precision impedance analyser for measurements. Good agreement
is observed for the DC four-probe resistance and the 4TP resistance at 40 Hz,
both yielding R ~ 104 {\Omega}. In general the apparent graphene channel
electromagnetic properties are found to be strongly influenced by the substrate
parasitic capacitance and resistance, particularly for high-frequencies f > 1
MHz. A phenomenological lumped-parameter equivalent circuit model is presented
which matches the frequency response of the graphene 4TP impedance device over
approximately seven decades of the frequency range of the applied transport
alternating current. Based on this model, it is shown for the first time, that
the intrinsic graphene channel resistance of the 4TP device is
frequency-independent (i.e. dissipationless) with RG ~ 105 {\Omega} or sheet
resistance of approximately 182 {\Omega} / sq. The parasitic substrate
impedance of the device is found shunt RG with RP ~ 2.2 {\Omega} in series with
CP ~ 600 pF. These results suggest that our new RF 4TP method is in good
agreement with the conventional DC four-probe method for measuring the
intrinsic sheet resistance of single-atom thick materials and could potentially
open up new applications in RF electronics, AC quantum Hall effect metrology
and sensors based on graphene 4TP devices operating over broad range of
frequencies.",1502.03835v1
2015-12-11,Intrinsic high electrical conductivity of stoichiometric SrNbO3 epitaxial thin films,"SrVO3 and SrNbO3 are perovskite-type transition-metal oxides with the same d1
electronic configuration. Although SrNbO3 (4d1) has a larger d orbital than
SrVO3 (3d1), the reported electrical resistivity of SrNbO3 is much higher than
that of SrVO3, probably owing to nonstoichiometry. In this paper, we grew
epitaxial, high-conductivity stoichiometric SrNbO3 using pulsed laser
deposition. The growth temperature strongly affected the Sr/Nb ratio and the
oxygen content of the films, and we obtained stoichiometric SrNbO3 at a very
narrow temperature window around 630 ${\deg}$C. The stoichiometric SrNbO3
epitaxial thin films grew coherently on KTaO3 (001) substrates with high
crystallinity. The room-temperature resistivity of the stoichiometric film was
$2.82 {\times} 10^{-5} {\Omega}$cm, one order of magnitude lower than the
lowest reported value of SrNbO3 and comparable with that of SrVO3. We observed
a T-square dependence of resistivity below $T^{\ast}$ = 180 K and non-Drude
behavior in near-infrared absorption spectroscopy, attributable to the
Fermi-liquid nature caused by electron correlation. Analysis of the T-square
coefficient A of resistivity experimentally revealed that the 4d orbital of Nb
that is larger than the 3d ones certainly contributes to the high electrical
conduction of SrNbO3.",1512.03588v1
2020-08-22,Indium-Tin-Oxide Transistors with One Nanometer Thick Channel and Ferroelectric Gating,"In this work, we demonstrate high performance indium-tin-oxide (ITO)
transistors with the channel thickness down to 1 nm and ferroelectric
Hf0.5Zr0.5O2 as gate dielectric. On-current of 0.243 A/mm is achieved on
sub-micron gate-length ITO transistors with a channel thickness of 1 nm, while
it increases to as high as 1.06 A/mm when the channel thickness increases to 2
nm. A raised source/drain structure with a thickness of 10 nm is employed,
contributing to a low contact resistance of 0.15 {\Omega}mm and a low contact
resistivity of 1.1{\times}10-7 {\Omega}cm2. The ITO transistor with a recessed
channel and ferroelectric gating demonstrates several advantages over 2D
semiconductor transistors and other thin film transistors, including large-area
wafer-size nanometer thin film formation, low contact resistance and contact
resistivity, atomic thin channel being immunity to short channel effects, large
gate modulation of high carrier density by ferroelectric gating, high-quality
gate dielectric and passivation formation, and a large bandgap for the
low-power back-end-of-line (BEOL) CMOS application.",2008.09881v1
2022-12-13,Collapse of Metallicity and High-$T_c$ Superconductivity in the High-Pressure phase of FeSe$_{0.89}$S$_{0.11}$,"We investigate the high-pressure phase of the iron-based superconductor
FeSe$_{0.89}$S$_{0.11}$ using transport and tunnel diode oscillator studies. We
construct detailed pressure-temperature phase diagrams that indicate that
outside of the nematic phase, the superconducting critical temperature reaches
a minimum before it is quickly enhanced towards 40 K above 4 GPa. The
resistivity data reveal signatures of a fan-like structure of non-Fermi liquid
behaviour which could indicate the existence of a putative quantum critical
point buried underneath the superconducting dome around 4.3 GPa. Further
increasing the pressure, the zero-field electrical resistivity develops a
non-metallic temperature dependence and the superconducting transition broadens
significantly. Eventually, the system fails to reach a fully zero-resistance
state despite a continuous finite superconducting transition temperature, and
any remaining resistance at low temperatures becomes strongly
current-dependent. Our results suggest that the high-pressure, high-$T_c$ phase
of iron chalcogenides is very fragile and sensitive to uniaxial effects of the
pressure medium, cell design and sample thickness which can trigger a
first-order transition. These high-pressure regions could be understood
assuming a real-space phase separation caused by concomitant electronic and
structural instabilities.",2212.06824v1
2023-03-30,Highly tunable NbTiN Josephson junctions fabricated with focused helium ion beam,"We demonstrate a ""direct writing"" method for the fabrication of planar
Josephson junctions from high quality superconducting niobium titanium nitride
(NbTiN) thin films using focused He-ion beam irradiation. Compared to the
materials previously used in such processing, YBCO and MgB$_2$, NbTiN has much
better mechanical and electrical properties, as well as good corrosion
resistance. We show that we can control the suppression of superconductivity in
NbTiN as a function of the helium ion beam fluence, and that this controllable
critical temperature suppression combined with the high spatial resolution and
position control of the He-ion beam in a helium ion microscope enables us to
successfully fabricate Josephson junctions with highly tunable weak links.
Because of the continuous nature of the disorder-induced metal-insulator
transition, this method allows the creation of barriers with wide range of
resistivities ranging from the metallic to the insulating state, with the
critical current and the junction resistance varying over two orders of
magnitude. Electrical transport measurements show that junctions follow closely
the ideal resistively and capacitively shunted junction behavior, have high
characteristic voltages ($0.2-1.4$ mV) and show Shapiro steps up to very high
orders. This suggests that these type of junctions are suitable for a wide
range of applications in superconducting electronics and quantum information
technology, with the bonus that a whole device can be fabricated from just a
single thin film, with the excellent electrical and microwave characteristics
offered by NbTiN.",2303.17348v1
2020-09-05,Corrosion Resistance of Sulfur-Selenium Alloy Coatings,"Despite decades of research, metallic corrosion remains a long-standing
challenge in many engineering applications. Specifically, designing a material
that can resist corrosion both in abiotic as well as biotic environments
remains elusive. Here we design a lightweight sulfur-selenium (S-Se) alloy with
high stiffness and ductility that can serve as a universal corrosion-resistant
coating with protection efficiency of ~99.9% for steel in a wide range of
diverse environments. S-Se coated mild steel shows a corrosion rate that is 6-7
orders of magnitude lower than bare metal in abiotic (simulated seawater and
sodium sulfate solution) and biotic (sulfate-reducing bacterial medium)
environments. The coating is strongly adhesive and mechanically robust. We
attribute the high corrosion resistance of the alloy in diverse environments to
its semi-crystalline, non-porous, anti-microbial, and viscoelastic nature with
superior mechanical performance, enabling it to successfully block a variety of
diffusing species.",2009.02451v1
2006-09-08,Peak resistance temperature and low temperature resistivity in thin film $La_{1-x} Ca_x Mn O_3$ mixtures for x <= 1/3,"The electrical resistivity of La$_{1-x}$Ca$_{x}$MnO$_{3}$ thin films grown on
(001) NdGaO$_{3}$ and (100) SrTiO$_{3}$ substrates by off-axis sputtering has
been studied as a function of the Calcium doping level. The samples have very
narrow rocking curves and excellent in plane registry with the substrate. A
strong correlation between the peak resistance temperature and the polaronic
hopping energy is seen which is not simply linear. The low temperature
resistivity is seen to be fit better by a model of single magnon scattering,
and a near linear correlation between the resistivity due to magnon scattering
and static impurities is observed.",0609206v1
2011-10-18,Superior performance of multilayered fluoropolymer films in low voltage electrowetting,"The requirement for low operational voltage in electrowetting devices, met
using thin dielectrics, is usually connected with serious material failure
issues. Dielectric breakdown (visible as electrolysis) is frequently evident
slightly beyond the onset of the contact angle saturation. Here, plasma
enhanced chemical vapor deposition (PECVD) is used to deposit thin fluorocarbon
films prior to the spin-coating of Teflon\textregistered amorphous
fluoropolymer on tetraethoxysilane (TEOS) substrates. The resulting
multilayered hydrophobic top coating improves the electrowetting performance of
the stack, by showing high resistance to dielectric breakdown at high applied
voltages and for continuous long term application of DC and AC voltage. Leakage
current measurements during electrowetting experiments with the proposed
composite coating showed that current remains fairly constant at consecutive
electrowetting tests in contrast to plain Teflon\textregistered coating in
which material degradation is evident by a progressive increase of the leakage
current after multiple electrowetting tests. Since the proposed composite
coating demonstrates increased resistance to material failure and to dielectric
breakdown even at thin configurations, its integration in electrowetting
devices may impact their reliability, robustness and lifetime.",1110.4075v1
2023-12-11,High-speed sensing of RF signals with phase change materials,"RF radiation spectrum is central to wireless and radar systems among numerous
high-frequency device technologies. Here, we demonstrate sensing of RF signals
in the technologically relevant 2.4 GHz range utilizing vanadium dioxide (VO2),
a quantum material that has garnered significant interest for its
insulator-to-metal transition. We find the electrical resistance of both
stoichiometric as well as off-stoichiometric vanadium oxide films can be
modulated with RF wave exposures from a distance. The response of the materials
to the RF waves can be enhanced by either increasing the power received by the
sample or reducing channel separation. We report a significant ~73% drop in
resistance with a 5 {\mu}m channel gap of the VO2 film at a characteristic
response time of 16 microseconds. The peak sensitivity is proximal to the phase
transition temperature boundary that can be engineered via doping and crystal
chemistry. Dynamic sensing measurements highlight the films' rapid response and
broad-spectrum sensitivity. Engineering electronic phase boundaries in
correlated electron systems could offer new capabilities in emerging
communication technologies.",2312.06459v1
2015-09-14,Torsional chiral magnetic effect in Weyl semimetal with topological defect,"We propose a torsional response raised by lattice dislocation in Weyl
semimetals akin to chiral magnetic effect; i.e. a fictitious magnetic field
arising from screw or edge dislocation induces charge current. We demonstrate
that, in sharp contrast to the usual chiral magnetic effect which vanishes in
real solid state materials, the torsional chiral magnetic effect exists even
for realistic lattice models, which implies the experimental detection of the
effect via SQUID or nonlocal resistivity measurements in Weyl semimetal
materials.",1509.03981v3
2016-05-02,Study of glass properties as electrode for RPC,"Operation and performance of the Resistive Plate Chambers (RPCs) mostly
depend on the quality and characteristics of the electrode materials. The
India-based Neutrino Observatory collaboration has chosen glass RPCs as the
active detector elements for its Iron Calorimeter detector and is going to
deploy RPCs in an unprecedented scale. Therefore, it is imperative that we
study the electrode material aspects in detail. We report here, systematic
characterization studies on the glasses from two manufacturers. RPC detectors
were built using these glasses and performances of the same were compared with
their material properties.",1605.01044v1
2010-07-06,Effects of chemical substitution on transport properties of Bi-based high temperature superconductors,"This report describes some transport and magnetic properties of doped Bi2212
and Bi2223 superconducting whiskers. These materials have advantages over
polycrystalline sample as well as large bulk crystals in that they provide
narrow transitions in resistance versus temperature as well as in magnetization
versus temperature curves. In addition they are easy to grow and and have short
oxygen annealing times. Here Data on transport and magnetic properties of these
superconducting whiskers are presented.",1007.0971v1
2021-07-03,Thin film of Al-Ga-Pd-Mn quasicrystalline alloy,"Thin film quasicrystal coatings have unique properties such as very high
electrical and thermal resistivity and very low surface energy. A nano
quasicrystalline thin film of icosahedral Al-Ga-Pd-Mn alloy, has produced by
flash evaporation followed by annealing. Attempts will be made to discuss the
micromechanisms for the formation of quasicrystalline thin film in Al-Ga-Pd-Mn
alloys",2107.01478v1
2014-03-06,"Normalized Contact Force to Minimize ""Electrode-Lead"" Resistance in a Nanodevice","In this report, the contact resistance between ""electrode"" and ""lead"" is
investigated for reasonable measurements of samples' resistance in a
polypyrrole (PPy) nanowire device. The sample's resistance, including
""electrode-lead"" contact resistance, shows a decrease as force applied to the
interface increases. Moreover, the sample's resistance becomes reasonably
similar to, or lower than, values calculated by resistivity of PPy reported in
previous studies. The decrease of electrode-lead contact resistance by
increasing the applying force was analyzed by using Holm theory: the general
equation of relation between contact resistance ($R_H$) of two-metal thin films
and contact force ($R_H$ $\propto$ $1/\sqrt{F}$). The present investigation can
guide a reliable way to minimize electrode-lead contact resistance for
reasonable characterization of nanomaterials in a microelectrode device.",1403.1357v1
2004-11-12,Microwave induced resistance oscillations on a high-mobility 2DEG: absorption/reflection and temperature damping experiments,"In this work we address experimentally a number of unresolved issues related
to microwave induced resistance oscillations (MIRO) and the zero-resistance
states observed recently on very high-mobility 2D electron gases in GaAs/AlGaAs
heterostructures. In particular, we examine electrodynamic effects via
reflection/absorption experiments and study the exact waveform of MIRO and
their damping due to temperature. It is shown that electrodynamic effects due
to metallic-like reflection and plasmons are important producing a wide
cyclotron resonance line and a number of oscillations which do not coincide
with the MIRO. To describe the MIRO waveform a simple model was employed
involving radiation-induced scattering with displacement. A very good
correlation was found between the temperature dependencies of the quantum
lifetime from MIRO and the transport scattering time from the electron
mobility. The results are compared with measurements of Shubnikov-de Haas
oscillations down to 30 mK on the same sample.",0411338v1
2007-04-20,Photoelectric phenomena in structures based on high-resistivity semiconductor crystals with a thin insulator layer at the semiconductor-metal boundary,"A previously unknown effect-giant spatial redistribution of the electric
field strength in a crystal under illumination of the structure - was
discovered and investigated in real photoresistors on high-resistivity
(semi-insulating) semiconductor CdTe crystals (in metal-thin insulator-
semiconductor-thin insulator -metal structures).
  A new concept is proposed for photoelectric phenomena in high- resistivity
semiconductor crystals. The concept is based on the idea that the
redistribution of the field under such conditions that the carrier lifetime
remains unchanged under illumination plays a determining role in these
phenomena. The nature of the effect is described, the dependence of the
characteristics of the structures on the parameters of the crystal and the
insulator layers is explained by the manifestation of this effect, and ways to
produce structures with prescribed photoelectric characteristics for new
devices and scientific methods are examined.",0704.2703v1
2009-03-15,Current-induced electroresistance in Nd0.5Ca0.5Mn0.95Ni0.05O3,"We have investigated the dc and pulsed current-induced electroresistance in
phase separated manganite Nd0.5Ca0.5Mn0.95Ni0.05O3 (NCMONi05) as a function of
temperature and magnetic field. It is shown that the negative differential
resistance which appears above a threshold current (Ic) and hysteresis in the
V-I progressively vanish with increasing period of the current pulses. However
a strong non-linearity in V-I exists even for a pulse period of 6s. The peak
voltage at Ic decreases in magnitude and shifts towards higher current values
with increasing strength of the magnetic field. The strong nonlinear behavior
and the negative differential resistance in the dc current sweep are
accompanied by a rapid increase of the sample surface temperature and therefore
primarily arise from the Joule heating in the sample. While the Joule heating
assists electroresistance in the high dc current regime, the nonlinearity in
the pulsed current sweep and the resistivity switching between a high and low
value induced by controlling the width and period of pulses can not be
explained solely on the basis of Joule heating.",0903.2616v2
2009-09-15,Broken symmetry states and divergent resistance in suspended bilayer graphene,"Graphene [1] and its bilayer have generated tremendous excitement in the
physics community due to their unique electronic properties [2]. The intrinsic
physics of these materials, however, is partially masked by disorder, which can
arise from various sources such as ripples [3] or charged impurities [4].
Recent improvements in quality have been achieved by suspending graphene flakes
[5,6], yielding samples with very high mobilities and little charge
inhomogeneity. Here we report the fabrication of suspended bilayer graphene
devices with very little disorder. We observe fully developed quantized Hall
states at magnetic fields of 0.2 T, as well as broken symmetry states at
intermediate filling factors $\nu = 0$, $\pm 1$, $\pm 2$ and $\pm 3$. The
devices exhibit extremely high resistance in the $\nu = 0$ state that grows
with magnetic field and scales as magnetic field divided by temperature. This
resistance is predominantly affected by the perpendicular component of the
applied field, indicating that the broken symmetry states arise from many-body
interactions.",0909.2883v1
2010-03-06,Reduction of high reset currents in unipolar resistance switching Pt/SrTiOx/Pt capacitors using acceptor doping,"The high reset current, IR, in unipolar resistance switching is an important
issue which should be resolved for practical applications in nonvolatile
memories. We showed that,during the forming and set processes, the compliance
current, Icomp, can work as a crucial parameter to reduce IR. Doping with Co or
Mn can significantly reduce the leakage current in capacitors made using SrTiOx
film, opening a larger operation window for Icomp. By decreasing Icomp with
acceptor doping, we could reduce IR in SrTiOx films by a factor of
approximately 20. Our work suggests that the decrease of Icomp by carrier
doping could be a viable alternative for reducing IR in unipolar resistance
switching.",1003.1390v1
2011-11-01,High pressure transport properties of the topological insulator Bi2Se3,"We report x-ray diffraction, electrical resistivity, and magnetoresistance
measurements on Bi2Se3 under high pressure and low temperature conditions.
Pressure induces profound changes in both the room temperature value of the
electrical resistivity as well as the temperature dependence of the
resistivity. Initially, pressure drives Bi2Se3 towards increasingly insulating
behavior and then, at higher pressures, the sample appears to enter a fully
metallic state coincident with a change in the crystal structure. Within the
low pressure phase, Bi2Se3 exhibits an unusual field dependence of the
transverse magnetoresistance that is positive at low fields and becomes
negative at higher fields. Our results demonstrate that pressures below 8 GPa
provide a non-chemical means to controllably reduce the bulk conductivity of
Bi2Se3.",1111.0098v1
2011-11-14,Study of Resistive Micromegas in a Mixed Neutron and Photon Radiation Field,"The Muon ATLAS Micromegas Activity (MAMMA) focuses on the development and
testing of large-area muon detectors based on the bulk-Micromegas technology.
These detectors are candidates for the upgrade of the ATLAS Muon System in view
of the luminosity upgrade of Large Hadron Collider at CERN (sLHC). They will
combine trigger and precision measurement capability in a single device. A
novel protection scheme using resistive strips above the readout electrode has
been developed. The response and sparking properties of resistive Micromegas
detectors were successfully tested in a mixed (neutron and gamma) high
radiation field supplied by the Tandem accelerator, at the N.C.S.R. Demokritos
in Athens. Monte-Carlo studies have been employed to study the effect of 5.5
MeV neutrons impinging on Micromegas detectors. The response of the Micromegas
detectors on the photons originating from the inevitable neutron inelastic
scattering on the surrounding materials of the experimental facility was also
studied.",1111.3185v1
2015-01-26,Linear magneto-resistance versus weak antilocalization effects in Bi$_2$Te$_3$ films,"In chalcogenide topological insulator materials, two types of
magneto-resistance (MR) effects are widely discussed: a positive MR dip around
zero magnetic field associated with the weak antilocalization (WAL) effect and
a linear MR effect which generally persists to high fields and high
temperatures. We have studied the MR of topological insulator Bi2Te3 films from
the metallic to semiconducting transport regime. While in metallic samples, the
WAL is difficult to identify due to the smallness of the WAL compared to the
samples' conductivity, the sharp WAL dip in the MR is clearly present in the
samples with higher resistivity. To correctly account for the low field MR by
the quantitative theory of WAL according to the Hikami-Larkin-Nagaoka (HLN)
model, we find that the classical (linear) MR effect should be separated from
the WAL quantum correction. Otherwise the WAL fitting alone yields an
unrealistically large coefficient $\alpha$ in the HLN analysis.",1501.06500v2
2018-04-05,Observation of transition from semiconducting to metallic ground state in high-quality single crystalline FeSi,"We report anomalous physical properties of single-crystalline FeSi over a
wide temperature range 1.8-400 K. X-ray diffraction, specific heat, and
magnetization measurements indicate that the FeSi crystals synthesized in this
study are of high quality with a very low concentration of magnetic impurities
($\sim$0.01$\%$). The electrical resistivity $\rho$($T$) can be described by
activated behavior with an energy gap $\Delta$ = 57 meV between 67 K and 150 K.
At temperatures below 67 K, $\rho$($T$) is significantly lower than an
extrapolation of the activated behavior, and the Hall coefficient and
magneto-resistivity undergo a sign change in this region. At $\sim$19 K, a
transition from semiconducting to metallic-like behavior is observed with
deceasing temperature. Whereas the transition temperature is very robust in a
magnetic field, the magnitude of the resistivity below $\sim$30 K is very
sensitive to magnetic field. There is no indication of a bulk phase transition
or onset of magnetic order in the vicinity of either 67 K or 19 K from specific
heat and magnetic susceptibility measurements. These measurements provide
evidence for a conducting surface state in FeSi at low temperatures.",1804.02036v1
2014-08-12,Nematic spin correlations in the tetragonal state of uniaxial strained BaFe2-xNixAs2,"Understanding the microscopic origins of electronic phases in high-transition
temperature (high-Tc) superconductors is important for elucidating the
mechanism of superconductivity. In the paramagnetic tetragonal phase of
BaFe2-xTxAs2 (where T is Co or Ni) iron pnictides, an in-plane resistivity
anisotropy has been observed. Here we use inelastic neutron scattering to show
that low-energy spin excitations in these materials change from four-fold
symmetric to two-fold symmetric at temperatures corresponding to the onset of
the in-plane resistivity anisotropy. Because resistivity and spin excitation
anisotropies both vanish near optimal superconductivity, we conclude that they
are likely intimately connected.",1408.2756v1
2017-07-01,Memory vs. irreversibility in thermal densification of amorphous glasses,"We report on dynamic effects associated with thermally-annealing amorphous
indium-oxide films. In this process the resistance of a given sample may
decrease by several orders of magnitude at room-temperatures, while its
amorphous structure is preserved. The main effect of the process is
densification - increased system density. The study includes the evolution of
the system resistivity during and after the thermal-treatment, the changes in
the conductance-noise, and accompanying changes in the optical properties. The
sample resistance is used to monitor the system dynamics during the annealing
period as well as the relaxation that ensues after its termination. These
reveal slow processes that fit well a stretched-exponential law, a behavior
that is commonly observed in structural glasses. There is an intriguing
similarity between these effects and those obtained in high-pressure
densification experiments. Both protocols exhibit the ""slow spring-back""
effect, a familiar response of memory-foams. A heuristic picture based on a
modified Lennard-Jones potential for the effective interparticle interaction is
argued to qualitatively account for these densification-rarefaction phenomena
in amorphous materials whether affected by thermal-treatment or by application
of high-pressure.",1707.00173v1
2021-05-24,Characterization of self-heating in cryogenic high electron mobility transistors using Schottky thermometry,"Cryogenic low noise amplifiers based on high electron mobility transistors
(HEMTs) are widely used in applications such as radio astronomy, deep space
communications, and quantum computing, and the physical mechanisms governing
the microwave noise figure are therefore of practical interest. In particular,
the contribution of thermal noise from the gate at cryogenic temperatures
remains unclear owing to a lack of experimental measurements of thermal
resistance under these conditions. Here, we report measurements of gate
junction temperature and thermal resistance in a HEMT at cryogenic and room
temperatures using a Schottky thermometry method. At temperatures $\sim 20$ K,
we observe a nonlinear trend of thermal resistance versus power that is
consistent with heat dissipation by phonon radiation. Based on this finding, we
consider heat transport by phonon radiation at the low-noise bias and liquid
helium temperatures and estimate that the thermal noise from the gate is
several times larger than previously assumed owing to self-heating. We conclude
that without improvements in thermal management, self-heating results in a
practical lower limit for microwave noise figure of HEMTs at cryogenic
temperatures.",2105.11571v1
2021-10-06,Temperature dependent striction effect in a single crystalline Nd2Fe14B revealed using a novel high temperature resistivity measurement technique,"We studied the temperature dependence of resistivity in a single crystalline
Nd2Fe14B using a newly developed high temperature probe. This novel probe uses
mechanical pin connectors instead of conducting glue/paste. From warming and
cooling curves, the Curie temperature was consistently measured around Tc = 580
K. In addition, anomalous discrete jumps were found only in cooling curves
between 400 and 500 K, but not shown in warming curves. More interestingly,
when the jumps occurred during cooling, the resistivity was increased. This
phenomenon can be understood in terms of temperature dependent striction effect
induced by the re-orientation of magnetic domains well below the Curie
temperature.",2110.02909v1
2022-11-15,Pressure-Induced Insulator-to-Metal Transition in van der Waals compound CoPS$_3$,"We have studied the insulator-to-metal transition and crystal structure
evolution under high pressure in the van der Waals compound CoPS$_3$ through
$\textit{in-situ}$ electrical resistance, Hall resistance, magnetoresistance,
X-ray diffraction, and Raman scattering measurements. CoPS$_3$ exhibits a
$C2/m$ $\rightarrow$ $P\overline{3}$ structural transformation at 7 GPa
accompanied by a 2.9$\%$ reduction in the volume per formula unit.
Concomitantly, the electrical resistance decreases significantly, and CoPS$_3$
becomes metallic. This metallic CoPS$_3$ is a hole-dominant conductor with
multiple conduction bands. The linear magnetoresistance and the small volume
collapse at the metallization suggest the incomplete high-spin $\rightarrow$
low-spin transition in the metallic phase. Thus, the metallic CoPS$_3$ possibly
possesses an inhomogeneous magnetic moment distribution and short-range
magnetic ordering. This report summarizes the comprehensive phase diagram of
$M$PS$_3$ ($M$ = V, Mn, Fe, Co, Ni, and Cd) that metalize under pressures.",2211.07925v4
2020-05-03,Resistive Switching Behaviour of Organic Molecules,"Organic electronics is very promising due to the flexibility, modifiability
as well as variety of the available organic molecules. Efforts are going on to
use organic materials for the realization of memory devices. In this regard
resistive switching devices surely will play a key role. In this paper an
effort has been made to illustrate the general information about resistive
switching devices as well as switching mechanisms involving organic materials.
As a whole a general overview of the emerging topic resistive switching has
been given.",2005.01033v1
2023-06-17,An account of Natural material based Non Volatile Memory Device,"The development in electronic sector has brought a remarkable change in the
life style of mankind. At the same time this technological advancement results
adverse effect on environment due to the use of toxic and non degradable
materials in various electronic devices. With the emergence of environmental
problems, the green, reprogrammable, biodegradable, sustainable and
environmental-friendly electronic devices have become one of the best solutions
for protecting our environment from hazardous materials without compromising
the growth of the electronic industry. Natural material has emerged as the
promising candidate for the next generation electronic devices due to its easy
processing, transparency, flexibility, abundant resources, sustainability,
recyclability, and simple extraction. This review targets the characteristics,
advancements, role, limitations, and prospects of using natural materials as
the functional layer of a resistive switching memory device with a primary
focus on the switching/memory properties. Among the available memory devices,
resistive random access memory (RRAM), write once read many (WORM) unipolar
memory etc. devices have a huge potential to become the non-volatile memory of
the next generation owing to their simple structure, high scalability, and low
power consumption. The motivation behind this work is to promote the use of
natural materials in electronic devices and attract researchers towards a green
solution of hazardous problems associated with the electronic devices.",2306.10382v1
2016-10-10,Determination of the resistivity anisotropy of orthorhombic materials via transverse resistivity measurements,"Measurements of the resistivity anisotropy can provide crucial information
about the electronic structure and scattering processes in anisotropic and
low-dimensional materials, but quantitative measurements by conventional means
often suffer very significant systematic errors. Here we describe a novel
approach to measuring the resistivity anisotropy of orthorhombic materials,
using a single crystal and a single measurement, that is derived from a
$\frac{\pi}{4}$ rotation of the measurement frame relative to the
crystallographic axes. In this new basis the transverse resistivity gives a
direct measurement of the resistivity anisotropy, which combined with the
longitudinal resistivity also gives the in-plane elements of the conventional
resistivity tensor via a 5-point contact geometry. This is demonstrated through
application to the charge-density wave compound ErTe$_3$, and it is concluded
that this method presents a significant improvement on existing techniques in
many scenarios.",1610.03122v1
2019-08-28,Temperature-dependent hardness of diamond-structured covalent materials,"Understanding temperature-dependent hardness of covalent materials is not
only of fundamental scientific interest, but also of crucial importance for
technical applications. In this work, a temperature-dependent hardness formula
for diamond-structured covalent materials is constructed on the basis of the
dislocation theory. Our results show that, at low temperature, the Vickers
hardness is mainly controlled by Poisson's ratio and shear modulus with the
latter playing a dominant role. With increasing temperature, the plastic
deformation mechanism undergoes a transition from shuffle-set dislocation
control to glide-set dislocation control, leading to a steeper drop of hardness
at high temperature. In addition, an intrinsic parameter, a3G, is revealed for
diamond-structured covalent materials, which measures the resistance to soften
at high temperature. Our hardness model shows remarkable agreement with
experimental data. Current work not only sheds lights on the physical origin of
hardness, but also provides a direct principle for superhard materials design.",1909.11032v2
2014-06-11,Evidence of surface transport and weak anti-localization in single crystal of Bi2Te2Se topological insulator,"Topological insulators are known to their metallic surface states, a result
of strong-spin-orbital coupling, that show unique surface transport phenomenon.
But these surface transports are buried in presence of metallic bulk
conduction. We synthesized very high quality Bi$_2$Te$_2$Se single crystals by
modified Bridgman method, that possess high bulk resistivity of
$>$20~$\Omega$cm below 20~K, whereas the bulk is mostly inactive and surface
transport dominates. Temperature dependence resistivity follows the activation
law like a gap semiconductor in temperature range 20-300~K. We designed a
special measurement geometry, which aims to extract the surface transport from
the bulk. This special geometry is applied to measure the resistance and found
that Bi$_2$Te$_2$Se single crystal exhibits a cross over from bulk to surface
conduction at 20~K. Simultaneously, the material also shows strong evidence of
weak anti-localization in magneto-transport due to the protection against
scattering by conducting surface states. This novel simple geometry is an easy
route to find the evidence of surface transport in topological insulators,
which are the promising materials for future spintronic applications.",1406.2879v1
2019-05-29,Growth of metallic delafossite PdCoO2 by molecular beam epitaxy,"The Pd, and Pt based ABO2 delafossites are a unique class of layered,
triangular oxides with 2D electronic structure and a large conductivity that
rivals the noble metals. Here, we report successful growth of the metallic
delafossite PdCoO2 by molecular beam epitaxy (MBE). The key challenge is
controlling the oxidation of Pd in the MBE environment where phase-segregation
is driven by the reduction of PdCoO2 to cobalt oxide and metallic palladium.
This is overcome by combining low temperature (300 {\deg}C) atomic
layer-by-layer MBE growth in the presence of reactive atomic oxygen with a
post-growth high-temperature anneal. Thickness dependence (5-265 nm) reveals
that in the thin regime (<75 nm), the resistivity scales inversely with
thickness, likely dominated by surface scattering; for thicker films the
resistivity approaches the values reported for the best bulk-crystals at room
temperature, but the low temperature resistivity is limited by structural
twins. This work shows that the combination of MBE growth and a post-growth
anneal provides a route to creating high quality films in this interesting
family of layered, triangular oxides.",1905.12549v2
2019-06-21,Current localisation and redistribution as the basis of discontinuous current controlled negative differential resistance in NbOx,"In-situ thermo-reflectance imaging is used to show that the discontinuous,
snap-back mode of current-controlled negative differential resistance (CC-NDR)
in NbOx-based devices is a direct consequence of current localization and
redistribution. Current localisation is shown to result from the creation of a
conductive filament either during electroforming or from current bifurcation
due to the super-linear temperature dependence of the film conductivity. The
snap-back response then arises from current redistribution between regions of
low and high current-density due to the rapid increase in conductivity created
within the high current density region. This redistribution is further shown to
depend on the relative resistance of the low current-density region with the
characteristics of NbOx cross-point devices transitioning between continuous
and discontinuous snap-back modes at critical values of film conductivity,
area, thickness and temperature, as predicted. These results clearly
demonstrate that snap-back is a generic response that arises from current
localization and redistribution within the oxide film rather than a
material-specific phase transition, thus resolving a long-standing controversy.",1906.08980v2
2017-12-03,Spin transport in two-layer-CVD-hBN/graphene/hBN heterostructures,"We study room temperature spin transport in graphene devices encapsulated
between a layer-by-layer-stacked two-layer-thick chemical vapour deposition
(CVD) grown hexagonal boron nitride (hBN) tunnel barrier, and a few-layer-thick
exfoliated-hBN substrate. We find mobilities and spin-relaxation times
comparable to that of SiO$_2$ substrate based graphene devices, and obtain a
similar order of magnitude of spin relaxation rates for both the Elliott-Yafet
and D'Yakonov-Perel' mechanisms. The behaviour of
ferromagnet/two-layer-CVD-hBN/graphene/hBN contacts ranges from transparent to
tunneling due to inhomogeneities in the CVD-hBN barriers. Surprisingly, we find
both positive and negative spin polarizations for high-resistance
two-layer-CVD-hBN barrier contacts with respect to the low-resistance contacts.
Furthermore, we find that the differential spin injection polarization of the
high-resistance contacts can be modulated by DC bias from -0.3 V to +0.3 V with
no change in its sign, while its magnitude increases at higher negative bias.
These features mark a distinctive spin injection nature of the
two-layer-CVD-hBN compared to the bilayer-exfoliated-hBN tunnel barriers.",1712.00815v1
2004-09-06,"Calculation of resistance for weak scattering, strong scattering and insulating quasi-one dimensional systems","A parameter free calculation of the resistivity is applied to liquid metals
near the melting point ranging from weak to strong scattering limit. The method
is based on length dependent resistance calculations for quasi-one dimensional
systems and was applied on structures with up to 10000 atoms. The calculated
value for conductance fluctuations is in good agreement with theoretical
predictions. The resistivities are compared with the Kubo-Greenwood and the
extended Ziman formula with the same scattering potential and similar
structure. The resistance calculation is applicable for insulating materials as
well, which is demonstrated for crystalline and amorphous silicon.",0409131v2
2012-07-02,Magneto-resistance in three-dimensional composites,"In this paper we study the magneto-resistance, i.e. the second-order term of
the resistivity perturbed by a low magnetic field, of a three-dimensional
composite material. Extending the two-dimensional periodic framework of [4], it
is proved through a H-convergence approach that the dissipation energy induced
by the effective magneto-resistance is greater or equal to the average of the
dissipation energy induced by the magneto-resistance in each phase of the
composite. This inequality validates for a composite material the Kohler law
which is known for a homogeneous conductor. The case of equality is shown to be
very sensitive to the magnetic fi eld orientation. We illustrate the result
with layered and columnar periodic structures.",1207.0468v1
2020-06-30,Roadmap for Gain-Bandwidth-Product Enhanced Photodetectors,"Photodetectors are key optoelectronic building blocks performing the
essential optical-to-electrical signal conversion, and unlike solar cells,
operate at a specific wavelength and at high signal or sensory speeds. Towards
achieving high detector performance, device physics, however, places a
fundamental limit of the achievable detector sensitivity, such as responsivity
and gain, when simultaneously aimed to increasing the detectors temporal
response, speed, known as the gain-bandwidth product (GBP). While detectors GBP
has been increasing in recent years, the average GBP is still relatively modest
(~10^6-10^7 Hz-A/W). Here we discuss photodetector performance limits and
opportunities based on arguments from scaling length theory relating
photocarrier channel length, mobility, electrical resistance with optical
waveguide mode constrains. We show that short-channel detectors are synergistic
with slot-waveguide approaches, and when combined, offer a high-degree of
detector design synergy especially for the class of nanometer-thin materials.
Indeed, we find that two dimensional material-based detectors are not limited
by their low mobility and can, in principle, allow for 100 GHz fast response
rates. However, contact resistance is still a challenge for such thin
materials, a research topic that is still not addressed yet. An interim
solution is to utilize heterojunction approaches for functionality separation.
Nonetheless, atomistically- and nanometer-thin materials used in such
next-generation scaling length theory based detectors also demand high material
quality and monolithic integration strategies into photonic circuits including
foundry-near processes. As it stands, this letter aims to guide the community
if achieving the next generation photodetectors aiming for a performance target
of GBP = 10^12 Hz-A/W.",2006.16937v1
2005-06-01,Insulator-metal transition in a conservative system: An evidence for mobility coalescence in island silver films,"Aging, which manifests itself as an irreversible increase in electrical
resistance in island metal films is of considerable interest from both academic
as well as applications point of view. Aging is attributed to various causes,
oxidation of islands and mobility of islands followed by coalescence (mobility
coalescence) being the main contenders. The effect of parameters like substrate
temperature, substrate cleaning, residual gases in the vacuum chamber,
ultrasonic vibration of the substrate, suggest that the mobility coalescence is
responsible for the aging in island metal films. Electron microscopy studies
show evidence for mobility of islands at high substrate temperatures. The
comparison of aging data of island silver films deposited on glass substrates
in ultra high vacuum and high vacuum suggests that the oxidation of islands, as
being responsible for aging in these films, can be ruled out. Further, under
certain conditions of deposition, island silver films exhibit a dramatic and
drastic fall in electrical resistance, marking the insulator-metal transition.
This interesting transition observed in a conservative system - after the
stoppage of deposition of the film- is a clear evidence for mobility
coalescence of islands even at room temperature. The sudden fall in resistance
is preceded by fluctuations in resistance with time and fluctuations are
attributed to the making and breaking of the percolation path in the film.",0506022v2
2010-09-22,Hall-effect and resistivity measurements in CdTe and ZnTe at high pressure: Electronic structure of impurities in the zincblende phase and the semi-metallic or metallic character of the high-pressure phases,"We carried out high-pressure resistivity and Hall-effect measurements in
single crystals of CdTe and ZnTe up to 12 GPa. Slight changes of transport
parameters in the zincblende phase of CdTe are consitent with the shallow
character of donor impurities. Drastic changes in all the transport parameters
of CdTe were found around 4 GPa, i.e. close to the onset of the cinnabar to
rock-salt transition. In particular, the carrier concentration increases by
more than five orders of magnitude. Additionally, an abrupt decrease of the
resistivity was detected around 10 GPa. These results are discussed in
comparison with optical, thermoelectric, and x-ray diffraction experiments. The
metallic character of the Cmcm phase of CdTe is confirmed and a semi-metallic
character is determined for the rock-salt phase. In zincblende ZnTe, the
increase of the hole concentration by more than two orders of magnitude is
proposed to be due to a deep-to-shallow transformation of the acceptor levels.
Between 9 and 11 GPa, transport parameters are consistent with the
semiconducting character of cinnabar ZnTe. A two orders of magnitude decrease
of the resistivity and a carrier-type inversion occurs at 11 GPa, in agreement
with the onset of the transition to the Cmcm phase of ZnTe. A metallic
character for this phase is deduced.",1009.4304v1
2019-10-18,Atomically Controlled Tunable Doping in High Performance WSe2 Devices,"Two-dimensional transitional metal dichalcogenide (TMD) field-effect
transistors (FETs) are promising candidates for future electronic applications,
owing to their excellent transport properties and potential for ultimate device
scaling. However, it is widely acknowledged that substantial contact resistance
associated with the contact-TMD interface has impeded device performance to a
large extent. It has been discovered that O2 plasma treatment can convert WSe2
into WO3-x and substantially improve contact resistances of p-type WSe2 devices
by strong doping induced thinner depletion width. In this paper, we carefully
study the temperature dependence of this conversion, demonstrating an oxidation
process with a precise monolayer control at room temperature and multilayer
conversion at elevated temperatures. Furthermore, the lateral oxidation of WSe2
under the contact revealed by HR-STEM leads to potential unpinning of the metal
Fermi level and Schottky barrier lowering, resulting in lower contact
resistances. The p-doping effect is attributed to the high electron affinity of
the formed WO3-x layer on top of the remaining WSe2 channel, and the doping
level is found to be dependent on the WO3-x thickness that is controlled by the
temperature. Comprehensive materials and electrical characterizations are
presented, with a low contact resistance of ~528 ohm-um and record high
on-state current of 320 uA/um at -1V bias being reported.",1910.08619v1
2004-03-23,Systematic approach to the growth of high-quality single-crystals of Sr3Ru2O7,"We describe a simple procedure for optimising the growth condition for high
quality single crystals of the strontium ruthenate perovskites using an image
furnace. The procedure involves carefully measuring the mass lost during
crystal growth in order to predict the optimal initial atomic ratio. Using this
approach we have succeeded in growing crystals of Sr3Ru2O7 with a residual
resistivity as low as 0.25 ??cm. The procedure we describe here is expected to
be useful for other systems when a standard travelling-solvent floating-zone
(TSFZ) method cannot be used because of high volatility of a constituent
material.",0403572v1
2022-03-22,High-field magnetoresistance of microcrystalline and nanocrystalline Ni metal at 3 K and 300 K,"The magnetoresistance (MR) and the magnetization isotherms were studied up to
high magnetic fields at T = 3 K and 300 K for a microcrystalline ($\mu$c) Ni
foil corresponding to bulk Ni and for a nanocrystalline (nc) Ni foil. At T = 3
K, for the $\mu$c-Ni sample with a residual resistivity ratio (RRR) of 331, the
field dependence of the resistivity was similar to what was reported previously
for high-purity ferromagnets whereas the MR(H) behavior for the nc-Ni sample
with RRR = 9 resembled that what was observed at low temperatures for Ni-based
alloys with low impurity concentration. In the magnetically saturated state,
the resistivity increased with magnetic field for both samples at T = 3 K and
the field dependence was dominated by the ordinary MR due to the Lorentz force
acting on the electron trajectories. However, the MR(H) curves were found to be
saturating for $\mu$c-Ni and non-saturating for nc-Ni, the difference arising
from their very different electron mean free paths. At T = 300 K, the MR(H)
curves of both Ni samples were very similar to those known for bulk Ni. After
magnetic saturation, the resistivity decreased nearly linearly with magnetic
field which behavior is due to the suppression of thermally-induced magnetic
disorder with increasing magnetic field. The MR(H) data were analyzed at both
temperatures with the help of Kohler plots from which the resistivity
anisotropy splitting ($\Delta\rho_{AMR}$) and the anisotropic magnetoresistance
(AMR) ratio were derived. It was demonstrated that at T = 300 K,
$\rho(H\rightarrow 0)=\rho(B\rightarrow 0)$ due to the negligible contribution
of the ordinary MR. The data for the two Ni samples at 3 K and 300 K were found
to indicate an approximately linear scaling of $\Delta\rho_{AMR}$ with the
zero-field resistivity. This implies that the AMR ratio does not vary
significantly with temperature in either microstructural state of Ni.",2203.11568v1
2023-09-18,Theoretical analysis on the possibility of superconductivity in a trilayer Ruddlesden-Popper nickelate La$_4$Ni$_3$O$_{10}$ under pressure and its experimental examination: comparison with La$_3$Ni$_2$O$_7$,"We study the possibility of superconductivity in a trilayer Ruddlesden-Popper
nickelate La$_4$Ni$_3$O$_{10}$ under pressure both theoretically and
experimentally, making comparison with the recently discovered high $T_c$
superconductor La$_3$Ni$_2$O$_7$, a bilayer nickelate. Through DFT
calculations, we find that a structural phase transition from monoclinic to
tetragonal takes place around 10 - 15 GPa. Using the tetragonal crystal
structure, we theoretically investigate the possibility of superconductivity,
where a combination of fluctuation exchange approximation and linearized
Eliashberg equation is applied to a six-orbital model constructed from first
principles band calculation. The obtained results suggests that
La$_4$Ni$_3$O$_{10}$ may also become superconducting under high pressure with
$T_c$ comparable to some cuprates, although it is not as high as
La$_3$Ni$_2$O$_7$. We also perform experimental studies using our
polycrystalline samples of La$_3$Ni$_2$O$_{7.01}$ and La$_4$Ni$_3$O$_{9.99}$.
The superconducting transition of La$_3$Ni$_2$O$_{7.01}$, with a maximum onset
$T_c$ of 67.0 K at a pressure of 26.5 GPa, is confirmed by a drop in the
electrical resistance, as well as the magnetic field dependence of the
resistance. Quite interestingly, similar temperature and magnetic field
dependencies of the resistance are observed also for La$_4$Ni$_3$O$_{9.99}$,
where a drop in the resistance is observed at lower temperatures compared to
La$_3$Ni$_2$O$_{7.01}$, under pressures of 32.8 GPa and above. Given the
theoretical expectation, the reduction in the resistance can most likely be
attributed to the occurrence of superconductivity in La$_4$Ni$_3$O$_{9.99}$.
The temperature at which the resistance deviates from a linear behavior,
considered as the onset $T_c$, monotonically increases up to 23 K at 79.2 GPa,
which is opposite to the pressure dependence of $T_c$ in La3Ni2O7.01.",2309.09462v4
2019-07-16,"Pressure-Induced Large Volume Collapse, Plane-to-Chain, Insulator to Metal Transition in CaMn$_2$Bi$_2$","In-situ high pressure single crystal X-ray diffraction study reveals that the
quantum material CaMn$_2$Bi$_2$ undergoes a unique plane to chain structural
transition between 2 and 3 GPa, accompanied by a large volume collapse.
CaMn2Bi2 displays a new structure type above 2.3 GPa, with the puckered Mn
honeycomb lattice of the trigonal ambient-pressure structure converting to
one-dimensional (1D) zigzag chains in the high-pressure monoclinic structure.
Single crystal measurements reveal that the pressure-induced structural
transformation is accompanied by a dramatic two order of magnitude drop of
resistivity; although the ambient pressure phase displays semiconducting
behavior at low temperatures, metallic temperature dependent resistivity is
observed for the high pressure phase, as, surprisingly, are two resistivity
anomalies with opposite pressure dependences. Based on the electronic structure
calculations, we hypothesized that the newly emerged electronic state under
high pressure is associated with a Fermi surface instability of the quasi-1D Mn
chains, while we infer that the other is a magnetic transition. Assessment of
the total energies for hypothetical magnetic structures for high pressure
CaMn$_2$Bi$_2$ indicates that ferrimagnetism is thermodynamically favored.",1907.07203v1
2014-10-09,Chloride Molecular Doping Technique on 2D Materials: WS2 and MoS2,"Low-resistivity metal-semiconductor (M-S) contact is one of the urgent
challenges in the research of 2D transition metal dichalcogenides (TMDs). Here,
we report a chloride molecular doping technique which greatly reduces the
contact resistance (Rc) in the few-layer WS2 and MoS2. After doping, the Rc of
WS2 and MoS2 have been decreased to 0.7 kohm*um and 0.5 kohm*um, respectively.
The significant reduction of the Rc is attributed to the achieved high electron
doping density thus significant reduction of Schottky barrier width. As a
proof-ofconcept, high-performance few-layer WS2 field-effect transistors (FETs)
are demonstrated, exhibiting a high drain current of 380 uA/um, an on/off ratio
of 4*106, and a peak field-effect mobility of 60 cm2/V*s. This doping technique
provides a highly viable route to diminish the Rc in TMDs, paving the way for
high-performance 2D nano-electronic devices.",1410.2563v1
2021-04-08,Electrical Properties of Selective-Area-Grown Superconductor-Semiconductor Hybrid Structures on Silicon,"We present a superconductor-semiconductor material system that is both
scalable and monolithically integrated on a silicon substrate. It uses
selective area growth of Al-InAs hybrid structures on a planar III-V buffer
layer, grown directly on a high resistivity silicon substrate. We characterized
the electrical properties of this material system at millikelvin temperatures
and observed a high average field-effect mobility of $\mu \approx
3200\,\mathrm{cm^2/Vs}$ for the InAs channel, and a hard induced
superconducting gap. Josephson junctions exhibited a high interface
transmission, $\mathcal{T} \approx 0.75 $, gate voltage tunable switching
current with a product of critical current and normal state resistance,
$I_{\mathrm{C}}R_{\mathrm{N}} \approx 83\,\mathrm{\mu V}$, and signatures of
multiple Andreev reflections. These results pave the way for scalable and high
coherent gate voltage tunable transmon devices and other
superconductor-semiconductor hybrids fabricated directly on silicon.",2104.03621v1
2021-09-21,Strain effects on the wear rate of severely deformed copper,"A variety of severe plastic deformation (SPD) techniques have been developed
to process materials to high strains and impart microstructural refinement.
High pressure torsion (HPT) is one technique that imparts inhomogeneous strain
to process discs with low strain in the center and high strain at the outer
edge. In the literature, this inhomogeneity is typically ignored when
characterizing wear properties after HPT. In this work, the wear rate of pure
copper discs processed by HPT was characterized by conducting dry sliding
reciprocating wear tests at a few judicious locations on the discs. From only
two discs, the wear resistance across many ranges of strains was captured.
These measurements agreed with the literature for other SPD processes at
varying strains. Wear rates dropped and plateaued at about 25% that of the
unprocessed state when processing past equivalent strains of around 15, after
which microstructural and microhardness saturation has also been observed. Some
indication of a relationship between the direction of the imposed SPD shearing
and the sliding wear direction was also observed. The incremental
microstructure, microhardness, and wear resistance evolution past equivalent
strains of ~15 indicate that for high purity copper these properties receive no
clear benefit from higher SPD strains.",2109.09907v1
2016-07-07,Lithium transport through Lithium-ion battery cathode coatings,"The surface coating of cathodes using insulator films has proven to be a
promising method for high-voltage cathode stabilization in Li-ion batteries.
However, there is still substantial uncertainty about how these films function,
specifically with regard to important coating design principles such as lithium
solubility and transport through the films. This study uses Density Functional
Theory to examine the diffusivity of interstitial lithium in crystalline
{\alpha}-$AlF_3$, {\alpha}-$Al_2O_3$, m-$ZrO_2$, c-MgO, and {\alpha}-quartz
$SiO_2$, which provide benchmark cases for further understanding of insulator
coatings in general. In addition, we propose an Ohmic electrolyte model to
predict resistivities and overpotential contributions under battery operating
conditions. For the crystalline materials considered we predict that Li+
diffuses quite slowly, with a migration barrier larger than 0.9 eV in all
crystalline materials except {\alpha}-quartz $SiO_2$, which is predicted to
have a migration barrier of 0.276 eV along <001>. These results suggest that
the stable crystalline forms of these insulator materials, except for oriented
{\alpha}-quartz $SiO_2$, are not practical for conformal cathode coatings.
Amorphous $Al_2O_3$ and $AlF_3$ have higher Li+ diffusivities than their
crystalline counterparts. Our predicted amorphous $Al_2O_3$ resistivity (1789
M{\Omega}m) is near the top of the range of fitted resistivities extracted from
previous experiments on nominal $Al_2O_3$ coatings (7.8 to 913 M{\Omega}m)
while our predicted amorphous $AlF_3$ resistivity (114 M{\Omega}m) is close to
the middle of the range. These comparisons support our framework for modeling
and understanding the impact on overpotential of conformal coatings in terms of
their fundamental thermodynamic and kinetic properties, and support that these
materials can provide practical conformal coatings in their amorphous form.",1607.02125v1
2023-04-20,An Origami-Inspired Design of Highly Efficient Cellular Cushion Materials,"Current architectured cellular cushion materials rely mainly on damage and/or
unpredictable collapse of their unit cells to absorb and dissipate energy under
impact. This prevents shape recovery and produces undesirable force
fluctuations that limit reusability and reduce energy absorption efficiency.
Here, we propose to combine advanced manufacturing technologies with Origami
principles to create a new class of architectured cellular viscoelastic cushion
material which combines low weight and high energy absorption efficiency with
damage resistance and full behavior customization. Each unit cell in the
proposed material is inspired by the Kresling Origami topology, which absorbs
impact energy by gracefully folding the different interfaces forming the cell
to create axial and rotational motions. A large part of the absorbed energy is
then dissipated through viscoelasticity and friction between the interfaces.
The result is a nearly ideal cushion material exhibiting high energy absorbing
efficiency (around 70%) combined with high energy dissipation (94% of the
absorbed energy). The material is also tunable for optimal performance,
reliable despite successive impact events, and achieves full shape recovery.",2304.10238v1
2024-01-28,"Discharge quenching mechanism and performance of RPWELL with tunable 3D printed resistive plates, charge evacuation in semiconductive glass RPWELL and discharge quenching for Cryogenic-RWELL over a wide range of resistivity","Resistive electrodes are used in gaseous detectors to quench electrical
discharges. This helps to protect delicate electrodes and readout electronics
and to improve the stability of the detector operation. An RPWELL is a
THGEM-based WELL detector with a resistive plate coupled to a conductive anode.
Till now, the choice of the resistive plate was limited to a few materials,
like LRS Glass and Semitron. These materials have fixed resistivities and,
sometimes, thickness and area limitations. This restricts the potential usage
of the detector to a rather small range of applications, as well as the
possibility of studying in depth the physics processes governing the discharge
quenching mechanism. In our present study, we used a new plastic material doped
with carbon nanotubes to produce resistive plates with a commercial 3D printer.
This method has the flexibility to produce samples of different thicknesses and
different resistivity values. We describe here the sample production and
characterize the RPWELL performance with different resistive plates. In
particular we show the dependence of discharge quenching on the thickness and
resistivity of the plate. The dynamics of the charge carriers in the material
is proposed as an explanation for the long gain recovery time after a
discharge.",2401.15611v2
2009-09-25,Electric field-induced colossal electroresistance and its relaxation in multiferroic La2NiMnO6,"In this work, we report direct as well as pulsed electric field-induced
resistivity switching and its relaxation in a multiferroic insulator La2NiMnO6.
At a fixed base temperature (Tb), the dc resistivity switches abruptly from a
high to a low value, which is manifested as an upward jump in the dc current
density (J) when the electric field (E) exceeds a threshold value Eth. The
fractional change in the resistance is as much as 70 % at room temperature for
Eth = 95 V/cm. The Eth increases with lowering Tb and follows the relation
Eth(Tb) = Eth(0)exp[-Tb/T0], as similar to the behavior found in charge density
wave systems. It is shown that the abrupt jump in J vanishes under pulsed
electric fields if the period between pulses is long enough. Surprisingly, a
step-like increase in J also occurs at a fixed dc electric field (Ec) and T =
Tb, above a threshold waiting time (tth). The tth decreases with increasing Ec
and Tb. Simultaneous measurement of surface temperature during the J-E sweep
and temporal studies suggest that conductive channels are created in an
insulating matrix due to the local self heating, and the coalescence of these
channels above a threshold E- field or time causes the observed anomalies in J.
However, the dissipated Joule power (P = Ith2R) at the transition from high to
low resistive state in the sample decreases with lowering temperature, which
suggests that the Joule heating is the consequence of transition from the high
to low resistance state rather than itself a driving force of the non linear
electrical transport. In addition, non linear J-E characteristics is also found
even with a pulsed voltage sweep, which suggests that intrinsic mechanisms
other than self heating is still active in this material.",0909.4612v1
2022-07-10,"Diffusion theory of electrical contact resistance of ""thermoelectric superlattice metal"" couple","The paper proposes a strict diffusion theory of the electrical contact
resistance of a thermoelectric superlattice (TES) - metal couple.The limits of
the contact resistance for traditional thermoeletric materials with parabolic
band spectrum and for superlattices described by Fivaz model are estimated.",2207.05065v1
2018-01-30,Open Material Property Library With Native Simulation Tool Integrations -- MASTO,"Reliable material property data is crucial for trustworthy simulations
throughout different areas of engineering. Special care must be taken when
materials at extreme conditions are under study. Superconductors and devices
assembled from superconductors and other materials, like superconducting
magnets, are often operated at such extreme conditions: at low temperatures
under high magnetic fields and stresses. Typically, some library or database is
used for getting the data. We have started to develop a database for storing
all kind of material property data online called Open Material Property Library
With Native Simulation Tool Integrations -- MASTO. The data that can be
imported includes, but is not limited to, anisotropic critical current surfaces
for high temperature superconducting materials, electrical resistivities as a
function of temperature, RRR and magnetic field, general fits for describing
material behaviour etc. Data can also depend on other data and it can be
versioned to guarantee permanent access. The guiding idea in MASTO is to build
easy-to-use integration for various programming languages, modelling frameworks
and simulation software. Currently, a full-fledged integration is built for
MATLAB to allow users to fetch and use data with one-liners. In this paper we
briefly review some of the material property databases commonly used in
superconductor modelling, present a case study showing how selection of the
material property data can influence the simulation results, and introduce the
principal ideas behind MASTO. This work serves as the reference document for
citing MASTO when it is used in simulations.",1801.09897v1
2018-11-22,Chemical vapor deposition of hexagonal boron nitride and its use in electronic devices,"Dielectrics are insulating materials used in many different electronic
devices and play an important role in all of them. Current advanced electronic
devices use dielectric materials with a high dielectric constant and avoid high
leakage currents. However, these materials show several intrinsic problems, and
also a bad interaction with adjacent materials. Therefore, the race for finding
a suitable dielectric material for current and future electronic devices is
still open. In this context two dimensional [2D] materials have become a
serious option, not only thanks to their advanced properties, but also to the
development of scalable synthesis methods. Graphene has been the most explored
2D material for electronic devices. However, graphene has no band gap, and
therefore it cannot be used as dielectric. MoS2 and other 2D transition metal
dichalcogenides (TMDs) are semiconducting 2D materials that can provide more
versatility in electronic devices. In this PhD thesis I have investigated the
use of monolayer and multilayer hexagonal boron nitride (h-BN) as dielectric
for electronic devices, as it is a 2D material with a band gap of ~5.9 eV. My
work has mainly focused on the synthesis of the h-BN using chemical vapor
deposition, the study of its intrinsic morphological and electrical properties
at the nanoscale, and its performance as dielectric in different electronic
devices, such as capacitors and memristors. Overall, our experiments indicate
that h-BN is a very reliable dielectric material, and that it can be
successfully used in capacitors and memristors. Moreover, h-BN shows additional
performances never observed in traditional dielectrics, such as volatile
resistive switching, which may also open the door for new applications.",1905.06938v1
2020-04-14,Materials Requirements of High-Speed and Low-Power Spin-Orbit-Torque Magnetic Random-Access Memory,"As spin-orbit-torque magnetic random-access memory (SOT-MRAM) is gathering
great interest as the next-generation low-power and high-speed on-chip cache
memory applications, it is critical to analyze the magnetic tunnel junction
(MTJ) properties needed to achieve sub-ns, and ~fJ write operation when
integrated with CMOS access transistors. In this paper, a 2T-1MTJ cell-level
modeling framework for in-plane type Y SOT-MRAM suggests that high spin Hall
conductivity and moderate SOT material sheet resistance are preferred. We
benchmark write energy and speed performances of type Y SOT cells based on
various SOT materials experimentally reported in the literature, including
heavy metals, topological insulators and semimetals. We then carry out detailed
benchmarking of SOT material Pt, beta-W, and BixSe(1-x) with different
thickness and resistivity. We further discuss how our 2T-1MTJ model can be
expanded to analyze other variations of SOT-MRAM, including perpendicular (type
Z) and type X SOT-MRAM, two-terminal SOT-MRAM, as well as spin-transfer-torque
(STT) and voltage-controlled magnetic anisotropy (VCMA)-assisted SOT-MRAM. This
work will provide essential guidelines for SOT-MRAM materials, devices, and
circuits research in the future.",2004.06268v2
2022-04-28,Degradation model of high-nickel positive electrodes: Effects of loss of active material and cyclable lithium on capacity fade,"Nickel-rich layered oxides have been widely used as positive electrode
materials for high-energy-density lithium-ion batteries, but their degradation
has severely affected cell performance, in particular at a high voltage and
temperature. However, the underlying degradation mechanisms have not been well
understood due to the complexity and lack of predictive models.Here we present
a model at the particle level to describe the structural degradation caused by
phase transition in terms of loss of active material (LAM), loss of lithium
inventory (LLI), and resistance increase. The particle degradation model is
then incorporated into a cell-level P2D model to explore the effects of LAM and
LLI on capacity fade in cyclic ageing tests. It is predicted that the loss of
cyclable lithium (trapped in the degraded shell) leads to a shift in the
stoichiometry range of the negative electrode but does not directly contribute
to the capacity loss, and that the loss of positive electrode active materials
dominates the fade of usable cell capacity in discharge. The available capacity
at a given current rate is further decreased by the additional resistance of
the degraded shell layer. The change pattern of the state-of-charge curve
provides information of more dimensions than the conventional capacity-fade
curve, beneficial to the diagnosis of degradation modes. The model has been
implemented into PyBaMM and made available as open source codes.",2204.13364v2
2019-02-26,Data-driven Exploration of Pressure-Induced Superconductivity in AgIn$_{5}$Se$_{8}$,"Candidates compounds for new thermoelectric and superconducting materials,
which have narrow band gap and flat bands near band edges, were exhaustively
searched by a high-throughput first-principles calculation from an inorganic
materials database named AtomWork. We focused on AgIn$_{5}$Se$_{8}$ which has
high density of state near the Fermi level. AgIn$_{5}$Se$_{8}$ was successfully
synthesized as single crystals using a melt and slow cooling method. The
single-crystal X-ray diffraction analysis revealed the obtained crystal is high
quality without deficiencies. The valence states in AgIn$_{5}$Se$_{8}$ were
determined to be Ag1+, In3+ and Se2- in accordance with a formal charge by the
core level X-ray photoelectron spectroscopy analysis. The electrical resistance
was evaluated under high pressure using a diamond anvil cell with boron-doped
diamond electrodes. Although the sample was insulator with a resistance of
above 40 M{\Omega} at ambient pressure, the resistance markedly decreased with
increase of the pressure, and a pressure-induced superconducting transition was
discovered at 3.4 K under 52.5 GPa. The transition temperature increased up to
3.7 K under further pressure of 74.0 GPa.",1902.09770v1
2020-06-25,"Influence of Yb3+on the structural, electrical and optical properties of sol-gel synthesized Ni-Zn nanoferrites","Polycrystalline Yb substituted NiZn nanoferrites with the compositions of
Ni0.5Zn0.5YbxFe2-xO4 (x= 0.00, 0.04, 0.08, 0.12, 0.16 and 0.20) have been
synthesized using sol gel auto combustion technique. Single phase cubic spinel
structure has been confirmed by the X ray diffraction (XRD) patterns. Larger
lattice constants of the compositions are found with increasing Yb3+
concentration while the average grain size (52 to 18 nm) has noticeable
decrease as Yb3+ content is increased. The presence of all existing elements as
well as the purity of the samples has also been confirmed from energy
dispersive X ray spectroscopic (EDS) analysis. Frequency dependent dielectric
constant, dielectric loss, dielectric relaxation time, AC and DC resistivity of
the compositions have also been examined at room temperature. The DC
resistivity value is found in the order of 10 to power 10 (omega-cm) which is
at least four orders greater than the ferrites prepared by conventional method.
This larger value of resistivity attributes due to very small grain size and
successfully explained using the Verwey and deBoer hopping conduction model.
The contribution of grain and grain boundary resistance has been elucidated
using Cole Cole plot. The study of temperature dependent DC resistivity
confirms the semiconducting nature of all titled compositions wherein bandgap
(optical) increases from 2.73 eV to 3.25 eV with the increase of Yb content.
The high value of resistivity is of notable achievement for the compositions
that make them a potential candidate for implication in the high frequency
applications where reduction of eddy current loss is highly required.",2006.14180v1
2024-04-12,"Electron-phonon interaction, magnetic phase transition, charge density waves and resistive switching in VS2 and VSe2 revealed by Yanson point contact spectroscopy","VS2 and VSe2 have attracted particular attention among the transition metals
dichalcogenides because of their promising physical properties concerning
magnetic ordering, charge density wave (CDW), emergent superconductivity, etc.,
which are very sensitive to stoichiometry and dimensionality reduction. Yanson
point contact (PC) spectroscopic study reveals metallic and nonmetallic states
in VS2 PCs, as well as a magnetic phase transition was detected below 25 K.
Analysis of PC spectra of VS2 testifies the realization of the thermal regime
in PCs. At the same time, rare PC spectra, where the magnetic phase transition
was not visible, shows a broad maximum of around 20 mV, likely connected with
electron-phonon interaction (EPI). On the other hand, PC spectra of VSe2
demonstrate metallic behavior, which allowed us to detect features associated
with EPI and CDW transition. The Kondo effect appeared for both compounds,
apparently due to interlayer vanadium ions. Besides, the resistive switching
was observed in PCs on VSe2 between a low resistive, mainly metallic-type
state, and a high resistive nonmetallic-type state by applying bias voltage
(about 0.4V). In contrast, reverse switching occurs by applying a voltage of
opposite polarity (about 0.4V). The reason may be the alteration of
stoichiometry in the PC core due to the displacement of V ions to interlayer
under a high electric field. The observed resistive switching characterize VSe2
as a potential material, e.g., for non-volatile resistive RAM, neuromorphic
engineering, and for other nanoelectronic applications. At the same time, VSe2
attracts attention as a rare layered van der Waals compound with magnetic
transition.",2404.08269v1
2010-11-12,Large bulk resistivity and surface quantum oscillations in the topological insulator Bi2Te2Se,"Topological insulators are predicted to present novel surface transport
phenomena, but their experimental studies have been hindered by a metallic bulk
conduction that overwhelms the surface transport. We show that a new
topological insulator, Bi2Te2Se, presents a high resistivity exceeding 1 Ohm-cm
and a variable-range hopping behavior, and yet presents Shubnikov-de Haas
oscillations coming from the surface Dirac fermions. Furthermore, we have been
able to clarify both the bulk and surface transport channels, establishing a
comprehensive understanding of the transport in this material. Our results
demonstrate that Bi2Te2Se is the best material to date for studying the surface
quantum transport in a topological insulator.",1011.2846v1
2017-02-14,Modelling electron-phonon interactions in graphene with curved space hydrodynamics,"We introduce a different perspective describing electron-phonon interactions
in graphene based on curved space hydrodynamics. Interactions of phonons with
charge carriers increase the electrical resistivity of the material. Our
approach captures the lattice vibrations as curvature changes in the space
through which electrons move following hydrodynamic equations. In this picture,
inertial corrections to the electronic flow arise naturally effectively
producing electron-phonon interactions. The strength of the interaction is
controlled by a coupling constant, which is temperature independent. We apply
this model to graphene and recover satisfactorily the linear scaling law for
the resistivity that is expected at high temperatures. Our findings open up a
new perspective of treating electron-phonon interactions in graphene, and also
in other materials where electrons can be described by the Fermi liquid theory.",1702.04156v1
2019-10-31,Vorticity of viscous electronic flow in graphene,"In ultra-pure materials electrons may exhibit a collective motion similar to
the hydrodynamic flow of a viscous fluid, the phenomenon with far reaching
consequences in a wide range of many body systems from black holes to
high-temperature superconductivity. Yet the definitive detection of this
intriguing behavior remains elusive. Until recently, experimental techniques
for observing hydrodynamic behavior in solids were based on measuring
macroscopic transport properties, such as the ""nonlocal"" (or ""vicinity"")
resistance, which may allow alternative interpretation. Earlier this year two
breakthrough experiments demonstrated two distinct imaging techniques making it
possible to ""observe"" the electronic flow directly. We demonstrate that a
hydrodynamic flow in a long Hall bar (in the absence of magnetic field)
exhibits a nontrivial vortex structure accompanied by a sign-alternating
nonlocal resistance. An experimental observation of such unique flow pattern
could serve a definitive proof of electronic hydrodynamics.",1910.14473v2
2021-11-09,Magnetotransport in ferromagnetic Fe$_2$Ge semimetallic thin films,"Thin films of the ferromagnet Fe$_2$Ge were grown via molecular beam epitaxy,
and their electrical and magneto-transport properties measured for the first
time. X-ray diffraction and vibrating sample magnetometry measurements
confirmed the crystalline ferromagnetic Fe$_2$Ge phase. The observed high
temperature maximum in the longitudinal resistivity, as well as the observed
suppression of electron-magnon scattering at low temperatures, point to the
presence of strong spin polarization in this material. Measurements of the Hall
resistivity, $\rho_{xy}$, show contributions from both the ordinary Hall effect
and anomalous Hall effect, $\rho_{xy}^{AH}$, from which we determined the
charge carrier concentration and mobility. Measurements also show a small
negative magnetoresistance in both the longitudinal and transverse geometries.
Fe$_2$Ge holds promise as a useful spintronic material, especially for its
semiconductor compatibility.",2111.05417v1
2022-01-18,In-plane magnetic structure and exchange interactions in the high-temperature antiferromagnet Cr2Al,"The ordered tetragonal intermetallic Cr$_2$Al forms the same structure type
as Mn$_2$Au, and the latter has been heavily investigated for its potential in
antiferromagnetic spintronics due to its degenerate in-plane N\'{e}el vector.
We present the single crystal flux growth of Cr$_2$Al and orientation-dependent
magnetic properties. Powder neutron diffraction of Cr$_2$Al and
first-principles simulations reveal that the magnetic ordering is likely
in-plane and therefore identical to Mn$_2$Au, providing a second material
candidate in the MoSi$_2$ structure type to evaluate the fundamental
interactions that govern spintronic effects. The single ordering transition
seen in thermal analysis and resistivity indicates that no canting of the
moments along the $c$ axis is likely. Magnetometry, resistivity, and
differential scanning calorimetry measurements confirm the N\'{e}el temperature
to be $634 \pm 2$ K. First-principles simulations indicate that the system has
a small density of states at the Fermi energy and confirm the lowest-energy
magnetic ground state ordering, while Monte Carlo simulations match the
experimental N\'{e}el temperature.",2201.07356v1
2024-03-26,Large topological Hall effect arising from spin reorientation in kagome magnet Fe3Ge,"Materials systems with spin chirality can provide ultra-high-density,
ultra-fast, and ultralow-power information carriers for digital transformation.
These material systems include magnetic skyrmions, chiral domain walls, spin
reorientation,and so on. The topological Hall effect (THE) has been identified
as the most convenient and effective tool for detecting the presence of spin
chirality in these systems. The research on the THE that may arise from spin
reorientation and specifically in Fe3Ge with spin reorientation remains an
unexplored area, so we study the THE in Fe3Ge Conduct systematic research.
X-Ray Diffraction (XRD) results indicate that our Fe3Ge ribbon sample has a
D019 structure. First-principles calculations and magnetic and electrical
testing confirm spin reorientation in the Fe3Ge ribbon sample at 350 K.The Hall
resistivity test results are consistent with our expectations, indicating the
presence of the THE in the Fe3Ge ribbon sample. The topological Hall
resistivity reaches a maximum value of 0.69 m{\Omega} cm at 400 K. For the
first time, a detailed experimental study of the THE in Fe3Ge with spin
reorientation has been conducted, introducing a new member to the family of
THE.",2403.17354v1
2022-08-23,Anomalous electrical transport and magnetic skyrmions in Mn-tuned Co9Zn9Mn2 single crystals,"\b{eta}-Mn-type CoxZnyMnz (x + y + z = 20) alloys have recently attracted
increasing attention as a new class of chiral magnets with skyrmions at and
above room temperature. However, experimental studies on the transport
properties of this material are scarce. In this work, we report the successful
growth of the \b{eta}-Mn-type Co9.24Zn9.25Mn1.51 and Co9.02Zn9.18Mn1.80 single
crystals and a systematic study on their magnetic and transport properties. The
skyrmion phase was found in a small temperature range just below the Curie
temperature. The isothermal ac susceptibility and dc magnetization as a
function of magnetic field confirm the existence of the skyrmion phase. A
negative linear magnetoresistance over a wide temperature range from 2 K to 380
K is observed and attributed to the suppression of the magnetic ordering
fluctuation under high fields. Both the magnetization and electrical
resistivity are almost isotropic. The quantitative analysis of the Hall
resistance suggests that the anomalous Hall effect of Co9.24Zn9.25Mn1.51 and
Co9.02Zn9.18Mn1.80 single crystals is dominated by the intrinsic mechanism. Our
findings contribute to a deeper understanding of the properties of CoxZnyMnz (x
+ y + z = 20) alloys material and advance their application in spintronic
devices.",2208.10955v1
2007-08-31,Fundamental Constants,"The notion of ``fundamental constant'' is heavily theory-laden. A natural,
fairly precise formulation is possible in the context of the standard model
(here defined to include gravity). Some fundamental constants have profound
geometric meaning. The ordinary gravitational constant parameterizes the
stiffness, or resistance to curvature, of space-time. The cosmological term
parameterizes space-time's resistance to expansion -- which may be, and
apparently is at present, a {\it negative} resistance, i.e. a tendency toward
expansion. The three gauge couplings of the strong, electromagnetic, and weak
interactions parameterize resistance to curvature in internal spaces. The
remaining fundamental couplings, of which there are a few dozen, supply an
ungainly accommodation of inertia. The multiplicity and variety of fundamental
constants are esthetic and conceptual shortcomings in our present understanding
of foundational physics. I discuss some ideas for improving the situation. I
then briefly discuss additional constants, primarily cosmological, that enter
into our best established present-day world model. Those constants presently
appear as macroscopic state parameters, i.e. as empirical ``material
constants'' of the Universe. I mention a few ideas for how they might become
fundamental constants in a future theory. In the course of this essay I've
advertised several of my favorite speculations, including a few that might be
tested soon.",0708.4361v1
2014-02-10,Tuning the band gap of PbCrO4 through high-pressure: Evidence of wide-to-narrow semiconductor transitions,"The electronic transport properties and optical properties of lead(II)
chromate (PbCrO4) have been studied at high pressure by means of resistivity,
Hall-effect, and optical-absorption measurements. Band-structure
first-principle calculations have been also performed. We found that the
low-pressure phase is a direct band-gap semiconductor (Eg = 2.3 eV) that shows
a high resistivity. At 3.5 GPa, associated to a structural phase transition, a
band-gap collapse takes place, becoming Eg = 1.8 eV. At the same pressure the
resistivity suddenly decreases due to an increase of the carrier concentration.
In the HP phase, PbCrO4 behaves as an n-type semiconductor, with a donor level
probably associated to the formation of oxygen vacancies. At 15 GPa a second
phase transition occurs to a phase with Eg = 1.2 eV. In this phase, the
resistivity increases as pressure does probably due to the self-compensation of
donor levels and the augmentation of the scattering of electrons with ionized
impurities. In the three phases the band gap red shifts under compression. At
20 GPa, Eg reaches a value of 0.8 eV, behaving PbCrO4 as a narrow-gap
semiconductor.",1402.2139v1
2015-08-11,Pressure induced electronic topological transition in Sb2S3,"Pressure induced electronic topological transitions in the wide band gap
semiconductor Sb2S3 (Eg = 1.7-1.8 eV) with similar crystal symmetry (SG: Pnma)
to its illustrious analog, Sb2Se3, has been studied using Raman spectroscopy,
resistivity and the available literature on the x-ray diffraction studies. In
this report, the vibrational and the transport properties of Sb2S3 have been
studied up to 22 GPa and 11 GPa, respectively. We observed the softening of
phonon modes Ag(2), Ag(3) and B2g and a sharp anomaly in their line widths at 4
GPa. The resistivity studies also shows an anomaly around this pressure. The
changes in resistivity as well as Raman line widths can be ascribed to the
changes in the topology of the Fermi surface which induces the electron-phonon
and the strong phonon-phonon coupling, indicating a clear evidence of the
electronic topological transition (ETT) in Sb2S3. The pressure dependence of
a/c ratio plot obtained from the literature showed a minimum at ~ 5 GPa, which
is consistent with our high pressure Raman and resistivity results. Finally, we
give the plausible reasons for the non-existence of a non-trivial topological
state in Sb2S3 at high pressures.",1508.02516v1
2018-11-19,Room-temperature Low-field Colossal Magneto-resistance in Double-perovskite Manganite,"The gigantic decrease of resistance by an applied magnetic field, which is
often referred to as colossal magnetoresistance (CMR), has been an attracting
phenomenon in strongly correlated electron systems. The discovery of CMR in
manganese oxide compounds has developed the science of strong coupling among
charge, orbital, and spin degrees of freedom. CMR is also attracting scientists
from the viewpoint of possible applications to sensors, memories, and so on.
However, no application using CMR effect has been achieved so far, partly
because the CMR materials which satisfy all of the required conditions for the
application, namely, high operating temperature, low operating magnetic field,
and sharp resistive change, have not been discovered. Here we report a
resistance change of more than two-orders of magnitude at a magnetic field
lower than 2 T near 300 K in an A-site ordered NdBaMn_2_O_6_ crystal. When
temperature and a magnetic field sweep from insulating (metallic) phase to
metallic (insulating) phase, the insulating (metallic) conduction changes to
the metallic (insulating) conduction within 1 K and 0.5 T, respectively. The
CMR is ascribed to the melting of the charge ordering. The entropy change which
is estimated from the B-T phase diagram is smaller than what is expected for
the charge and orbital ordering. The suppression of the entropy change is
attributable to the loss of the short range ferromagnetic fluctuation of Mn
spin moments, which an important key of the high temperature and low magnetic
field CMR effect.",1811.07596v1
2018-10-17,Perspectives of HgTe Topological Insulators for Quantum Hall Metrology,"We report the studies of high-quality HgTe/(Cd,Hg)Te quantum wells (QWs) with
a width close to the critical one $d_c$, corresponding to the topological phase
transition and graphene like band structure in view of their applications for
Quantum Hall Effect (QHE) resistance standards. We show that in the case of
inverted band ordering, the coexistence of conducting topological helical edge
states together with QHE chiral states degrades the precision of the resistance
quantization. By experimental and theoretical studies we demonstrate how one
may reach very favorable conditions for the QHE resistance standards: low
magnetic fields allowing to use permanent magnets ( B $\leq$ 1.4T) and
simultaneously realtively high teperatures (liquid helium, T $\geq$ 1.3K). This
way we show that HgTe QW based QHE resistance standards may replace their
graphene and GaAs counterparts and pave the way towards large scale fabrication
and applications of QHE metrology devices.",1810.07449v1
2019-07-25,Reducing sheet resistance of self-assembled transparent graphene films by defect patching and doping with UV/ozone treatment,"Liquid phase exfoliation followed by Langmuir-Blodgett self-assembly (LBSA)
is a promising method for scalable production of thin graphene films for
transparent conductor applications. However, monolayer assembly into thin films
often induces a high density of defects, resulting in a large sheet resistance
that hinders practical use. We introduce UV/ozone as a novel photochemical
treatment that reduces sheet resistance of LBSA graphene threefold, while
preserving the high optical transparency. The effect of such treatment on our
films is opposite to the effect it has on mechanically exfoliated or CVD films,
where UV/ozone creates additional defects in the graphene plane, increasing
sheet resistance. Raman scattering shows that exposure to UV/ozone reduces the
defect density in LBSA graphene, where edges are the dominant defect type. FTIR
spectroscopy indicates binding of oxygen to the graphene lattice during
exposure to ozone. In addition, work function measurements reveal that the
treatment dopes the LBSA film, making it more conductive. Such defect patching
paired with doping leads to an accessible way of improving the transparent
conductor performance of LBSA graphene, making solution-processed thin films a
candidate for industrial use.",1907.10916v2
2019-10-17,Link between magnetism and resistivity upturn in cuprates: a thermal conductivity study of La$_{2-x}$Sr$_x$CuO$_4$,"A key unexplained feature of cuprate superconductors is the upturn in their
normal state electrical resistivity $\rho(T)$ seen at low temperature inside
the pseudogap phase. We examined this issue via measurements of the thermal
conductivity $\kappa(T)$ down to 50 mK and in fields up to 17 T on the cuprate
La$_{2-x}$Sr$_x$CuO$_4$ at dopings $p = 0.13$, 0.136, 0.143 and 0.18. At $p$ =
0.136, 0.143, and 0.18, we observe an initial increase of the electronic
thermal conductivity $\kappa_0/T$ as a function of field, as expected in a
$d$-wave superconductor. For $p$ = 0.136 and 0.143, further increasing the
field then leads to a decrease of $\kappa_0/T$, which correlates with the onset
of spin density-wave order as observed in neutron scattering experiments on the
same samples. This decrease of $\kappa_0/T$ with field is imposed by the
Wiedemann-Franz law and the high value of the resistivity in the high-field
normal state of these samples. Our study therefore provides a direct link
between magnetism and the resistivity upturn in the pseudogap phase of
cuprates. We discuss this scenario in the broader context of other cuprates.",1910.08126v1
2021-08-18,High Entropy Alloy CrFeNiCoCu sputtered films,"High entropy alloy(HEA) films of CrFeCoNiCu were prepared by sputtering,
their structure was characterized, and their electric properties measured by
temperature dependent Hall and Seebeck measurement. The HEA films show a solid
solution with fcc structure, and a 111 texture with columnar grains of widths
15-30 nm extending through film thickness with very many twins. The residual
electrical resistivity of the films is around 140 {\mu}{\Omega}cm and the
temperature dependence of the resistivity is metal-like. The temperature
coefficient of resistivity (TCR) is small (2 ppm/K). The Hall coefficient is
positive while the Seebeck coefficients is negative. This is interpreted as
arising from an electronic structure where the Fermi level passes through band
states having both holes and electrons as indicated by band structure
calculations. The HEA structure appears stable for annealing in vacuum, while
annealing in an oxygen containing atmosphere causes the surface to oxidize and
grow a Cr-rich oxide on the surface. This is then accompanied by demixing of
the HEA solid solution and a decrease in residual resistance of the film.",2108.08373v2
2022-05-03,Structural and electronic phase transitions in Zr$_{1.03}$Se$_{2}$ at high pressure,"A detailed high pressure investigation is carried out using x-ray
diffraction, Raman spectroscopy and low temperature resistivity measurements on
hexagonal ZrSe$_{2}$ having an excess of 3 at.\% Zr. Structural studies show
that the sample goes through a gradual structural transition from hexagonal to
monoclinic phase, with a mixed phase in the pressure range 5.9 GPa to 14.8 GPa.
Presence of a minimum in the $c/a$ ratio in the hexagonal phase and a minimum
in the full width half maximum of the $A_{1g}$ mode at about the same pressure
indicates an electronic phase transition. The sample shows a metallic
characteristic in its low temperature resistivity data at ambient pressure,
which persist till about 5.1 GPa and can be related the presence of slight
excess Zr. At and above 7.3 GPa, the sample shows a metal to semiconductor
transition with the opening of a very small band gap, which increases with
pressure. The low temperature resistivity data show an upturn, which flattens
with an increase in pressure. The phenomenological analysis of the low
temperature resistivity data indicates the presence of Kondo effect in the
sample, which may be due to the excess Zr.",2205.01322v1
2022-06-08,Quantized anomalous Hall resistivity achieved in molecular beam epitaxy-grown MnBi2Te4 thin films,"The intrinsic magnetic topological insulator MnBi2Te4 provides a feasible
pathway to high temperature quantum anomalous Hall (QAH) effect as well as
various novel topological quantum phases. Although quantized transport
properties have been observed in exfoliated MnBi2Te4 thin flakes, it remains a
big challenge to achieve molecular beam epitaxy (MBE)-grown MnBi2Te4 thin films
even close to the quantized regime. In this work, we report the realization of
quantized anomalous Hall resistivity in MBE-grown MnBi2Te4 thin films with the
chemical potential tuned by both controlled in-situ oxygen exposure and top
gating. We find that elongated post-annealing obviously elevates the
temperature to achieve quantization of the Hall resistivity, but also increases
the residual longitudinal resistivity, indicating a picture of high-quality QAH
puddles weakly coupled by tunnel barriers. These results help to clarify the
puzzles in previous experimental studies on MnBi2Te4 and to find a way out of
the big difficulty in obtaining MnBi2Te4 samples showing quantized transport
properties.",2206.03773v2
2022-07-23,Anomalous resistivity upturn in the van der Waals ferromagnet Fe$_5$GeTe$_2$,"Fe$_5$GeTe$_2$ (n = 3, 4, 5) have recently attracted increasing attention due
to their two-dimensional van der Waals characteristic and high temperature
ferromagnetism, which make promises for spintronic devices. The Fe(1) split
site is one important structural characteristic of Fe$_5$GeTe$_2$ which makes
it very different from other Fe$_5$GeTe$_2$ (n = 3, 4) systems. The local
atomic disorder and short-range order can be induced by the split site. In this
work, the high-quality van der Waals ferromagnet Fe$_5$GeTe$_2$ were grown to
study the low-temperature transport properties. We found a resistivity upturn
below 10 K. The temperature and magnetic field dependence of the resistivity
are in good agreement with a combination of the theory of disorder-enhanced
three-dimensional electron-electron and single-channel Kondo effect. The Kondo
effect exists only at low magnetic field B < 3 T, while electron-electron
dominates the appearance for the low-temperature resistivity upturn. We believe
that the enhanced three-dimensional electron-electron interaction in this
system is induced by the local atomic structural disorder due to the split site
of Fe(1). Our results indicate that the split site of Fe plays an important
role for the exceptional transport properties.",2207.11383v1
2000-09-21,High-pressure study of the non-Fermi liquid material U_2Pt_2In,"The effect of hydrostatic pressure (p<= 1.8 GPa) on the non-Fermi liquid
state of U_2Pt_2In is investigated by electrical resistivity measurements in
the temperature interval 0.3-300 K. The experiments were carried out on
single-crystals with the current along (I||c) and perpendicular (I||a) to the
tetragonal axis. The pressure effect is strongly current-direction dependent.
For I||a we observe a rapid recovery of the Fermi-liquid T^2-term with
pressure. The low-temperature resistivity can be analysed satisfactorily within
the magnetotransport theory of Rosch, which provides strong evidence for the
location of U_2Pt_2In at an antiferromagnetic quantum critical point. For I||c
the resistivity increases under pressure, indicating the enhancement of an
additional scattering mechanism. In addition, we have measured the pressure
dependence of the antiferromagnetic ordering temperature (T_N= 37.6 K) of the
related compound U_2Pd_2In. A simple Doniach-type diagram for U_2Pt_2In and
U_2Pd_2In under pressure is presented.",0009324v1
2002-04-19,Spin-injection through an Fe/InAs Interface,"The spin-dependence of the interface resistance between ferromagnetic Fe and
InAs is calculated from first-principles for specular and disordered (001)
interfaces. Because of the symmetry mismatch in the minority-spin channel, the
specular interface acts as an efficient spin filter with a transmitted current
polarisation between 98 an 89%.
  The resistance of a specular interface in the diffusive regime is comparable
to the resistance of a few microns of bulk InAs.
  Symmetry-breaking arising from interface disorder reduces the spin asymmetry
substantially and we conclude that efficient spin injection from Fe into InAs
can only be realized using high quality epitaxial interfaces.",0204422v1
2002-10-01,Free and Trapped Injected Carriers in C60 Crystals,"We report on the conductance from two-contact carrier injection in C60 single
crystals. In the nonlinear regime, the current and voltage obey a power law, I
\~ V^m, where m can be as high as 10 at room temperature. This nonlinear
behavior - the resistance decreases by 6 orders of magnitude without saturation
- is among the highest reported for organic systems, and can be explained by
injection of free carriers into the trap-filling region. We find that H2
annealing suppresses shallow traps and enhances nonlinearity. Two limiting
types of temperature dependence of the nonlinear resistance are observed -
decreasing and increasing resistance at the orientational ordering temperature.
A simple model incorporating deep traps is presented to understand this
behavior and the impact of this model on possible field-effect transistor
action is discussed.",0210029v1
2003-02-03,Critical Current Density and Resistivity of MgB2 Films,"The high resistivity of many bulk and film samples of MgB2 is most readily
explained by the suggestion that only a fraction of the cross-sectional area of
the samples is effectively carrying current. Hence the supercurrent (Jc) in
such samples will be limited by the same area factor, arising for example from
porosity or from insulating oxides present at the grain boundaries. We suggest
that a correlation should exist, Jc ~ 1/{Rho(300K) - Rho(50K)}, where Rho(300K)
- Rho(50K) is the change in the apparent resistivity from 300 K to 50 K. We
report measurements of Rho(T) and Jc for a number of films made by hybrid
physical-chemical vapor deposition which demonstrate this correlation, although
the ""reduced effective area"" argument alone is not sufficient. We suggest that
this argument can also apply to many polycrystalline bulk and wire samples of
MgB2.",0302017v1
2003-03-19,Structural and Electronic Properties of Amorphous and Polycrystalline In2Se3 Films,"Structural and electronic properties of amorphous and single-phase
polycrystalline films of gamma- and kappa-In2Se3 have been measured. The stable
gamma phase nucleates homogeneously in the film bulk and has a high
resistivity, while the metastable kappa phase nucleates at the film surface and
has a moderate resistivity. The microstructures of hot-deposited and
post-annealed cold-deposited gamma films are quite different but the electronic
properties are similar. The increase in the resistivity of amorphous In2Se3
films upon annealing is interpreted in terms of the replacement of In-In bonds
with In-Se bonds during crystallization. Great care must be taken in the
preparation of In2Se3 films for electrical measurements as the presence of
excess chalcogen or surface oxidation may greatly affect the film properties.",0303369v1
2003-04-16,Initial dissipation and current-voltage characteristics of superconductors containing fractal clusters of a normal phase,"The influence of fractal clusters of a normal phase on distinctive features
of current-voltage characteristic of percolative type-II superconductors is
considered. The results of high-resolution measurements of the differential
resistance of BPSCCO/Ag composites are discussed in the context of magnetic
flux dynamics. The region of initial dissipation is observed on current-voltage
characteristics in the neighborhood of the transition into a resistive state.
In the course of this stage of resistive transition the vortices start to break
away from the normal-phase clusters, which act as pinning centers. The effect
of transport current on vortex depinning is investigated. A broad current range
of initial dissipation is considered as an evidence of fractal nature of the
normal-phase clusters.",0304354v2
2003-12-12,Electronic behavior in mats of single-walled carbon nanotubes under pressure,"Single-walled carbon nanotubes (SWNTs) have many interesting properties; they
may be metallic or semiconducting depending on their diameter and helicity of
the graphene sheet. Hydrostatic or quasi-hydrostatic high pressures can probe
many electronic features. Resistance - temperature measurements in SWNTs from
normal condition and under 0.4 GPa of quasi-hydrostatic pressures reveal a
semiconducting-like behavior. From 0.5 to about 2.0 GPa the resistance changes
to a Kondo-like feature due to magnetic impurities used to catalyse the
nanotube formation. Above 2.0 GPa, they become metallic and at about 2.4 GPa
the resistance decreases dramatically around 3 K suggesting a superconducting
transition.",0312307v1
2004-08-12,Impedance spectroscopy study on post-annealing-tuned polycrystalline CaCu3Ti4O12 films: Evidence of Barrier Layer Capacitor Effects,"In this paper, impedance spectroscopy study was performed to establish the
electrical property and microstructure relations of the as-deposited and
post-annealed polycrystalline CCTO films prepared on Pt/Ti/SiO2/Si (100)
substrates by pulsed-laser deposition (PLD). Our results demonstrated that the
as-deposited polycrystalline CCTO film was made of insulating grain boundaries
with semiconducting grains, indicating that the high-dielectric-constant is
attributed to the barrier layer capacitor (BLC) effects. The simple
resistor-capacitor (RC) equivalent circuit and the modified constant phase
element (CPE) circuit were used to describe the impedance spectroscopy, and
excellent agreement between the calculated and measured curves was obtained in
the CPE circuit. The resistance and capacitance of the grains and grain
boundaries can be tuned by changing the annealing atmosphere and temperature.
Under oxygen-absent annealing atmosphere, the electric resistances of the grain
boundaries changed greatly but the resistance of the grains has almost no
change. While under oxygen annealing atmosphere, the reverse happened. On the
basis of this result, it is demonstrated that the origin of the
semiconductivity of the grains in CCTO polycrystalline films arises from their
oxygen-loss, while the grain boundaries are close to oxygen- stoicheometry.",0408275v2
2004-12-03,Resistance noise scaling in a 2D system in GaAs,"The 1/f resistance noise of a two-dimensional (2D) hole system in a high
mobility GaAs quantum well has been measured on both sides of the 2D
metal-insulator transition (MIT) at zero magnetic field (B=0), and deep in the
insulating regime. The two measurement methods used are described: I or V
fixed, and measurement of resp. V or I fluctuations. The normalized noise
magnitude SR/R^2 increases strongly when the hole density is decreased, and its
temperature (T) dependence goes from a slight increase with T at the largest
densities, to a strong decrease at low density. We find that the noise
magnitude scales with the resistance, SR /R^2 ~ R^2.4. Such a scaling is
expected for a second order phase transition or a percolation transition. The
possible presence of such a transition is investigated by studying the
dependence of the conductivity as a function of the density. This dependence is
consistent with a critical behavior close to a critical density p* lower than
the usual MIT critical density pc.",0412084v1
2005-10-21,"Superconductivity mediated by a soft phonon mode: specific heat, resistivity, thermal expansion and magnetization of YB6","The superconductor YB6 has the second highest critical temperature Tc among
the boride family MBn. We report measurements of the specific heat,
resistivity, magnetic susceptibility and thermal expansion from 2 to 300 K,
using a single crystal with Tc = 7.2 K. The superconducting gap is
characteristic of medium-strong coupling. The specific heat, resistivity and
expansivity curves are deconvolved to yield approximations of the phonon
density of states, the spectral electron-phonon scattering function and the
phonon density of states weighted by the frequency-dependent Grueneisen
parameter respectively. Lattice vibrations extend to high frequencies >100 meV,
but a dominant Einstein-like mode at ~8 meV, associated with the vibrations of
yttrium ions in oversized boron cages, appears to provide most of the
superconducting coupling and gives rise to an unusual temperature behavior of
several observable quantities. A surface critical field Hc3 is also observed.",0510572v3
2006-03-31,Evidences of a consolute critical point in the Phase Separation regime of La(5/8-y)Pr(y)Ca(3/8)MnO(3) (y = 0.4) single crystals,"We report on DC and pulsed electric field sensitivity of the resistance of
mixed valent Mn oxide based La(5/8-y)Pr(y)Ca(3/8)MnO(3) (y = 0.4) single
crystals as a function of temperature. The low temperature regime of the
resistivity is highly current and voltage dependent. An irreversible transition
from high (HR) to a low resistivity (LR) is obtained upon the increase of the
electric field up to a temperature dependent critical value (V_c). The
current-voltage characteristics in the LR regime as well as the lack of a
variation in the magnetization response when V_c is reached indicate the
formation of a non-single connected filamentary conducting path. The
temperature dependence of V_c indicates the existence of a consolute point
where the conducting and insulating phases produce a critical behavior as a
consequence of their separation.",0603850v1
2007-06-29,NMR relaxation and resistivity from rattling phonons in pyrochlore superconductors,"We calculate the temperature dependence of NMR relaxation rate and electrical
resistivity for coupling to a local, strongly anharmonic phonon mode. We argue
that the two-phonon Raman process is dominating NMR relaxation. Due to the
strong anharmonicity of the phonon an unusual temperature dependence is found
having a low temperature peak and becoming constant towards higher
temperatures. The electrical resistivity is found to vary like T^2 at low
temperatures and following a sqrt{T} behavior at high temperatures. Both
results are in qualitative agreement with recent observations on
beta-pyrochlore oxide superconductors.",0706.4345v2
2007-07-04,NaV2O4: a Quasi-1D Metallic Antiferromagnet with Half-Metallic Chains,"NaV2O4 crystals were grown under high pressure using a NaCl flux, and the
crystals were characterized with X-ray diffraction, electrical resistivity,
heat capacity, and magnetization. The structure of NaV2O4 consists of double
chains of edge-sharing VO6 octahedra. The resistivity is highly anisotropic,
with the resistivity perpendicular to the chains more than 20 times greater
than that parallel to the chains. Magnetically, the intrachain interactions are
ferromagnetic and the interchain interactions are antiferromagnetic; 3D
antiferromagnetic order is established at 140 K. First principles electronic
structure calculations indicate that the chains are half metallic.
Interestingly, the case of NaV2O4 seems to be a quasi-1D analogue of what was
found for half-metallic materials.",0707.0519v3
2007-09-11,Transport properties and magnetic field induced localization in the misfit cobaltite [Bi$_2$Ba$_{1.3}$K$_{0.6}$Co$_{0.1}$]$^{RS}$[CoO$_2$]$_{1.97}$ single crystal,"Resistivity under magnetic field, thermopower and Hall coefficient are
systematically studied for
[Bi$_2$Ba$_{1.3}$K$_{0.6}$Co$_{0.1}$]$^{RS}$[CoO$_2$]$_{1.97}$ single crystal.
In-plane resistivity ($\rho_{ab}$(T)) shows metallic behavior down to 2 K with
a $T^2$ dependence below 30 K; while out-of-plane resistivity ($\rho_{c}(T)$)
shows metallic behavior at high temperature and a thermal activation
semiconducting behavior below about 12 K. Striking feature is that magnetic
field induces a ln(1/$T$) diverging behavior in both $\rho_{ab}$ and
$\rho_{c}(T)$ at low temperature. The positive magnetoresistance (MR) could be
well fitted by the formula based on multi-band electronic structure. The
ln(1/$T$) diverging behavior in $\rho_{ab}$ and $\rho_{c}(T)$ could arise from
the magnetic-field-induced 2D weak localization or spin density wave.",0709.1519v1
2007-11-29,Magnetoelectric Effects on Composite Nano Granular $Fe/TiO_{2-δ}$ Films,"Employing a new experimental technique to measure magnetoelectric response
functions, we have measured the magnetoelectric effect in composite films of
nano granular metallic iron in anatase titanium dioxide at temperatures below
50 K. A magnetoelectric resistance is defined as the ratio of a transverse
voltage to bias current as a function of the magnetic field. In contrast to the
anomalous Hall resistance measured above 50 K, the magnetoelectic resistance
below 50 K is significantly larger and exhibits an even symmetry with respect
to magnetic field reversal $H\to -H$. The measurement technique required
attached electrodes in the plane of the film composite in order to measure
voltage as a function of bias current and external magnetic field. To our
knowledge, the composite films are unique in terms of showing magnetoelectric
effects at low temperatures, $<$ 50 K, and anomalous Hall effects at high
temperatures, $>$ 50 K.",0711.4776v1
2009-04-23,Microscopic origin of bipolar resistive switching of nanoscale titanium oxide thin films,"We report a direct observation of the microscopic origin of the bipolar
resistive switching behavior in nanoscale titanium oxide films. Through a
high-resolution transmission electron microscopy, an analytical TEM technique
using energy-filtering transmission electron microscopy and an in situ x-ray
photoelectron spectroscopy, we demonstrated that the oxygen ions piled up at
top interface by an oxidation-reduction reaction between the titanium oxide
layer and the top Al metal electrode. We also found that the drift of oxygen
ions during the on/off switching induced the bipolar resistive switching in the
titanium oxide thin films.",0904.3628v2
2009-08-25,"Bipolar resistive switching characteristics of poly(3,4-ethylene-dioxythiophene): poly(styrenesulfonate) thin film","We investigated the reversible resistive switching of
poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) thin films
sandwiched between Al electrodes. The J-V sweep curve showed a hysteretic
behavior which depends on the polarity of the applied voltage bias. From the
analysis of I-V curves, it was revealed that the charge transport through the
junction was governed by the bulk space-charge-limited conduction (SCLC) model.
Using transmission electron microscopy (TEM) analysis, it was confirmed that
the initial high resistance state of PEDOT:PSS films is related with the
segregation of PSS- chains induced by redox reaction between a Al metal
electrode and PEDOT:PSS film. Positive space charges present on the top region
of PEDOT:PSS films can be proposed as a possible trap centers of electron
trapping and detrapping process.",0908.3527v1
2010-02-02,Memristor Behaviour in Nano-Sized Vertical Lsmo/Lsmo Tunnel Junctions,"We report a memory resistance (memristor) behavior with nonlinear
current-voltage characteristics and bipolar hysteretic resistance switching in
the nanocolumnar manganite (LSMO) films. The switching from a high (HRS) to a
low (LRS) resistance occurs at a bias field ~1 MV/cm. Applied electric field
drops mostly at the insulating interfacial LSMO layer and couples to correlated
polarons at the LSMO(111)/LSMO(111) vertical interfaces. The observed
memristance behaviour has an electronic (polaronic) origin and is caused by an
electric-field-controlled Jahn-Teller (JT) effect, followed by the orbital
reconstruction and formation of a metastable orbitally disordered interfacial
phase (LRS). Compared to the earlier reported ionic memristor in Ti-O films, an
electronic (polaronic) nano-sized LSMO memristor shows an additional
(re-entrant) LRS-HRS switching at higher fields because of the second minimum
in the elastic energy of a JT system.",1002.0495v1
2010-02-11,"Synthesis, anisotropy, and superconducting properties of LiFeAs single crystal","A LiFeAs single crystal with $T_c^{onset}$$\sim$19.7 K was grown successfully
in a sealed tungsten crucible using the Bridgeman method. The electrical
resistivity experiments revealed a ratio of room temperature to residual
resistivity (RRR) of approximately 46 and 18 for the in-plane and out-of plane
directions. The estimated anisotropic resistivity, $\gamma_\rho$=$\rho_c$ /
$\rho_{ab}$, was approximately 3.3 at $T_c^{onset}$. The upper critical fields
had large $H_{c2} ^{\shortparallel ab}$ and $H_{c2}^{\shortparallel c}$ values
of 83.4 T and 72.5 T, respectively, and an anisotropy ratio is
$\gamma_H$=$H_{c2}^{\shortparallel ab}$ / $H_{c2} ^{\shortparallel
c}$$\sim$1.15. The high upper critical field value and small anisotropy
highlight the potential use of LiFeAs in a variety of applications. The
calculated critical current density $(J_c)$ from the $M$-$H$ loop is
approximately 10$^3$ A/cm$^2$",1002.2249v1
2010-07-15,Role of interface reaction on resistive switching of Metal/a-TiO2/Al RRAM devices,"For the clear understanding of the role of interface reaction between top
metal electrode and titanium oxide layer, we investigated the effects of
various top metals on the resistive switching in Metal/a-TiO2/Al devices. The
top Al device with the highest oxygen affinity showed the best memory
performance, which is attributed to the fast formation of interfacial layer
(Al-Ti-O), as confirmed by high resolution transmission electron microscopy and
electron dispersive spectroscopy. Hence, we concluded that the interface layer,
created by the redox reaction between top metal electrode and TiO2 layer, plays
a crucial role in bipolar resistive switching behaviors of metal/TiO2/Al
systems.",1007.2463v1
2010-11-05,Interplay between the electrical transport properties of GeMn thin films and Ge substrates,"We present evidence that electrical transport studies of epitaxial p-type
GeMn thin films fabricated on high resistivity Ge substrates are severely
influenced by parallel conduction through the substrate, related to the large
intrinsic conductivity of Ge due to its small bandgap. Anomalous Hall
measurements and large magneto resistance effects are completely understood by
taking a dominating substrate contribution as well as the measurement geometry
into account. It is shown that substrate conduction persists also for well
conducting, degenerate, p-type thin films, giving rise to an effective
two-layer conduction scheme. Using n-type Ge substrates, parallel conduction
through the substrate can be reduced for the p-type epi-layers, as a
consequence of the emerging pn-interface junction. GeMn thin films fabricated
on these substrates exhibit a negligible magneto resistance effect. Our study
underlines the importance of a thorough characterization and understanding of
possible substrate contributions for electrical transport studies of GeMn thin
films.",1011.1450v1
2011-08-31,Local Tunneling Magnetoresistance probed by Low-Temperature Scanning Laser Microscopy,"Tunneling magnetoresistance (TMR) in a vertical manganite junction was
investigated by low-temperature scanning laser microscopy (LTSLM) allowing to
determine the local relative magnetization M orientation of the two electrodes
as a function of magnitude and orientation of the external magnetic field H.
Sweeping the field amplitude at fixed orientation revealed magnetic domain
nucleation and propagation in the junction electrodes. For the high-resistance
state an almost single-domain antiparallel magnetization configuration was
achieved, while in the low-resistance state the junction remained in a
multidomain state. Calculated resistance $R_\mathrm{calc}(H)$ based on the
local M configuration obtained by LTSLM is in quantitative agreement with R(H)
measured by magnetotransport.",1108.6159v1
2012-04-16,Experimental investigation of the magnetic field driven superconductor/ insulator transition in underdoped $La_{2-x}Sr_xCuO_4$ thin films,"The magnetic field driven superconductor/insulator transition is studied in a
large variety of $La_{2-x}Sr_xCuO_4$ thin films of various Sr dopings.
Temperature dependence of the resistivity down to 4.2 or 1.5 K under high
pulsed magnetic field (up to 57 T) is analyzed. In particular, the existence of
plateaus in the resistance versus temperature curves, in a limited range of
temperature, for given values of the magnetic field is carefully investigated.
It is shown to be associated to scaling behaviour of the resistance versus
magnetic field curves, evocative of the presence of a quantum critical point. A
three-dimensional (H,x,T) phase diagram is proposed, taking into account the
intrinsic lamellar nature of the materials by the existence of a temperature
crossover from quantum-two-dimensional to three-dimensional behavior.",1204.3493v1
2012-08-20,Universal linear in temperature resistivity from black hole superradiance,"Observations across many families of unconventional materials motivative the
search for robust mechanisms producing linear in temperature d.c. resistivity.
BKT quantum phase transitions are commonplace in holographic descriptions of
finite density matter, separating critical and ordered phases. We show that at
a holographic BKT critical point, if the unstable operator is coupled to the
current via irrelevant operators, then a linear contribution to the resistivity
is universally obtained. We also obtain broad power law tails in the optical
conductivity, that shift spectral weight from the Drude peak as well as
interband energy scales. We give a partial realization of this scenario using
an Einstein-Maxwell-pseudoscalar bulk theory. The instability is a vectorial
mode at nonzero wavevector, which is communicated to the homogeneous current
via irrelevant coupling to an ionic lattice.",1208.4102v1
2012-11-12,Magnetic and transport properties of tetragonal- or cubic-Heusler-type Co-substituted Mn-Ga epitaxial thin films,"The composition dependence of the structural, magnetic, and transport
properties of epitaxially grown Mn-Co-Ga films were investigated. The crystal
structure was observed to change from tetragonal to cubic as the Co content was
increased. In terms of the dependence of saturation magnetization on the Co
content, relatively small value was obtained for the
Mn$_{2.3}$Co$_{0.4}$Ga$_{1.3}$ film at a large {\it K}$_\textrm u$ value of 9.2
Merg/cm$^3$. Electrical resistivity of Mn-Co-Ga films was larger than that of
pure Mn-Ga film. The maximum value of the resistivity was 490 $\mu\Omega$cm for
Mn$_{2.2}$Co$_{0.6}$Ga$_{1.2}$ film. The high resistivity of Mn-Co-Ga might be
due to the presence of localized electron states in the films due to chemical
disordering caused by the Co substitution.",1211.2524v1
2013-03-19,Self-Formation of Sub-10-nm Nanogaps by Silicidation for Resistive Switch in Air,"We developed a simple and reliable method for the fabrication of sub-10-nm
wide nanogaps. The self-formed nanogap is based on the stoichiometric
solid-state reaction between metal and Si atoms during silicidation process.
The nanogap width is deter- mined by the metal layer thickness. Our proposed
method produces nanogaps either symmetric or asymmetric electrodes, as well as,
multiple nanogaps within one unique process step for application to complex
circuits. Therefore, this method provides high throughput and it is suitable
for large-scale production. To demonstrate the feasibil- ity of the proposed
fabrication method, nanogap resistive switches have been built and
characterized. They exhibit a pronounced hysteresis with up to 103 on/off
conductance ratios in air. Our results indicate that the voltages for initially
electroforming the de- vice to the switch state are determinated by the nanogap
sizes. However, the set and reset voltages of the device do not strongly
dependent on the nanogap widths. These phenomena could be helpful to understand
how the resistive switching is established.",1303.4586v1
2013-10-13,Origin of the energy gap in the narrow-gap semiconductor FeSb2 revealed by high-pressure magnetotransport measurements,"To elucidate an origin of the two energy gaps in the narrow-gap semiconductor
FeSb2, we have investigated the effects of hydrostatic pressure on the
resistivity, Hall resistance and magnetoresistance at low temperatures. The
larger energy gap evaluated from the temperature dependence of resistivity
above 100 K is enhanced from 30 to 40 meV with pressure from 0 to 1.8 GPa, as
generally observed in conventional semiconductors. In the low-temperature range
where a large Seebeck coefficient was observed, we evaluate the smaller energy
gap from the magnetotransport tensor using a two-carrier model and find that
the smaller gap exhibits a weak pressure dependence in contrast to that of the
larger gap. To explain the pressure variations of the energy gaps, we propose a
simple model that the smaller gap is a gap from the impurity level to the
conduction band and the larger one is a gap between the valence and conduction
bands, suggesting that the observed large Seebeck coefficient is not relevant
to electron correlation effects.",1310.3451v1
2013-10-30,Analysis of post wet chemistry heat treatment effects on Nb SRF surface resistance,"Most of the current research in superconducting radio frequency (SRF)
cavities is focused on ways to reduce the construction and operating cost of
SRF based accelerators as well as on the development of new or improved cavity
processing techniques. The increase in quality factors is the result of the
reduction of the surface resistance of the materials. A recent test on a 1.5
GHz single cell cavity made from ingot niobium of medium purity and heat
treated at 1400 C in a ultra-high vacuum induction furnace resulted in a
residual resistance of about 1nanoohm and a quality factor at 2.0 K increasing
with field up to 5x10^10 at a peak magnetic field of 90 mT. In this
contribution, we present some results on the investigation of the origin of the
extended Q0-increase, obtained by multiple HF rinses, oxypolishing and heat
treatment of all Nb cavities.",1310.8159v1
2014-02-04,Multilevel recording in Bi-deficient Pt/BFO/SRO heterostructures based on ferroelectric resistive switching targeting high-density information storage in nonvolatile memories,"We demonstrate the feasibility of multilevel recording in
Pt/Bi(1-d)FeO3/SrRuO3 capacitors using the ferroelectric resistive switching
phenomenon exhibited by the Pt/Bi(1-d)FeO3 interface. A tunable population of
up and down ferroelectric domains able to modulate the Schottky barrier height
at the Pt/Bi(1-d)FeO3 interface can be achieved by means of either a collection
of SET/RESET voltages or current compliances. This programming scheme gives
rise to well defined resistance states, which form the basis for a multilevel
storage nonvolatile memory.",1402.0739v1
2014-05-06,Effect of realistic metal electronic structure on the lower limit of contact resistivity of epitaxial metal-semiconductor contacts,"The effect of realistic metal electronic structure on the lower limit of
resistivity in [100] oriented n-Si is investigated using full band Density
Functional Theory and Semi-Empirical Tight Binding (TB) calculations. Using
simulation unit cells guided by the interface chemistry of epitaxial CoSi2 on
[100] oriented Si observed experimentally, it is shown that the 'ideal metal'
assumption fails in some situations and consequently underestimates the lower
limit of contact resistivity in n-Si by at least an order of magnitude at high
doping concentrations. The mismatch in transverse momentum space in the metal
and the semiconductor, the so-called 'valley filtering effect', is shown to be
dependent on the interface chemistry simulated. The results emphasize the need
for explicit inclusion of the metal atomic and electronic structure in the
atomistic modeling of transport across metal-semiconductor contacts",1405.1317v1
2014-11-16,Laser doping for ohmic contacts in n-type Ge,"We achieved ohmic contacts down to 5 K on standard n-doped Ge samples by
creating a strongly doped thin Ge layer between the metallic contacts and the
Ge substrate. Thanks to the laser doping technique used, Gas Immersion Laser
Doping, we could attain extremely large doping levels above the solubility
limit, and thus reduce the metal/doped Ge contact resistance. We tested
independently the influence of the doping concentration and doped layer
thickness, and showed that the ohmic contact improves when increasing the
doping level and is not affected when changing the doped thickness.
Furthermore, we characterised the doped Ge/Ge contact, showing that at high
doping its contact resistance is the dominant contribution to the total contact
resistance.",1411.4325v1
2015-02-19,Anomalous impact of hydrostatic pressure on superconductivity of polycrystalline LaO0.5F0.5BiSe2,"We report bulk superconductivity at 2.5K in LaO0.5F0.5BiSe2 compound through
the DC magnetic susceptibility and electrical resistivity measurements. The
synthesized LaO0.5F0.5BiSe2 compound is crystallized in tetragonal structure
with space group P4/nmm and Reitveld refined lattice parameters are a= 4.15(1)A
and c=14.02(2)A. The lower critical field of Hc1= 40Oe, at temperature 2K is
estimated through the low field magnetization measurements. The LaO0.5F0.5BiSe2
compound showed metallic normal state electrical resistivity with residual
resistivity value of 1.35m{\Omega}-cm. The compound is type-II superconductor,
and the estimated Hc2(0) value obtained by WHH formula is above 20kOe for
90percent Rn criteria. The superconducting transition temperature decreases
with applied pressure till around 1.68GPa and with further higher pressures a
high Tc phase emerges with possible onset Tc of above 5K for 2.5GPa.",1502.05502v3
2016-06-13,Performance studies of MRPC prototypes for CBM,"Multi-gap Resistive Plate Chambers (MRPCs) with multi-strip readout are
considered to be the optimal detector candidate for the Time-of-Flight (ToF)
wall in the Compressed Baryonic Matter (CBM) experiment. In the R&D phase MRPCs
with different granularities, low-resistive materials and high voltage stack
configurations were developed and tested. Here, we focus on two prototypes
called HD-P2 and THU-strip, both with strips of 27 cm$^2$ length and
low-resistive glass electrodes. The HD-P2 prototype has a single-stack
configuration with 8 gaps while the THU-strip prototype is constructed in a
double-stack configuration with 2 $\times$ 4 gaps. The performance results of
these counters in terms of efficiency and time resolution carried out in a test
beam time with heavy-ion beam at GSI in 2014 are presented in this proceeding.",1606.04917v1
2016-06-28,Observation of quantum Hall effect in a microstrained Bi$_2$Se$_3$ single crystal,"We report the observation of quantum Hall effect (QHE) in a Bi$_2$Se$_3$
single crystal having carrier concentration ($n$)
$\sim1.13\times10^{19}$cm$^{-3}$, three dimensional Fermi surface and bulk
transport characteristics. The plateaus in Hall resistivity coincide with
minima of Shubnikov de Haas oscillations in resistivity. Our results
demonstrate that the presence of perfect two dimensional transport is not an
essential condition for QHE in Bi$_2$Se$_3$. The results of high resolution
x-ray diffraction (HRXRD), energy-dispersive x-ray spectroscopy (EDX), and
residual resistivity measurements show the presence of enhanced crystalline
defects and microstrain. We propose that the formation of localized state at
the edge of each Landau level due to resonance between the bulk and defect band
of Bi$_2$Se$_3$ causes the quantum Hall effect.",1606.08576v1
2016-07-20,Nonlocal topological valley transport at large valley Hall angles,"Berry curvature hot spots in two-dimensional materials with broken inversion
symmetry are responsible for the existence of transverse valley currents, which
give rise to giant nonlocal dc voltages. Recent experiments in high-quality
gapped graphene have highlighted a saturation of the nonlocal resistance as a
function of the longitudinal charge resistivity $\rho_{{\rm c}, xx}$, when the
system is driven deep into the insulating phase. The origin of this saturation
is, to date, unclear. In this work we show that this behavior is fully
compatible with bulk topological transport in the regime of large valley Hall
angles (VHAs). We demonstrate that, for a fixed value of the valley diffusion
length, the dependence of the nonlocal resistance on $\rho_{{\rm c}, xx}$
weakens for increasing VHAs, transitioning from the standard $\rho^3_{{\rm c},
xx}$ power-law to a result that is independent of $\rho_{{\rm c}, xx}$.",1607.05902v1
2016-10-26,Resistive Switching and Voltage Induced Modulation of Tunneling Magnetoresistance in Nanosized Perpendicular Organic Spin Valves,"Nanoscale multifunctional perpendicular organic spin valves have been
fabricated. The devices based on an La$_{0.7}$Sr$_{0.3}$MnO$_3$/Alq$_3$/Co
trilayer show resistive switching of up to 4-5 orders of magnitude and
magnetoresistance as high as -70% the latter even changing sign when voltage
pulses are applied. This combination of phenomena is typically observed in
multiferroic tunnel junctions where it is attributed to magnetoelectric
coupling between a ferromagnet and a ferroelectric material. Modeling indicates
that here the switching originates from a modification of the
La$_{0.7}$Sr$_{0.3}$MnO$_3$ surface. This modification influences the tunneling
of charge carriers and thus both the electrical resistance and the tunneling
magnetoresistance which occurs at pinholes in the organic layer.",1610.08218v1
2016-11-03,Current crowding mediated large contact noise in graphene field-effect transistors,"The impact of the intrinsic time-dependent fluctuations in the electrical
resistance at the graphene-metal interface or the contact noise, on the
performance of graphene field effect transistors, can be as adverse as the
contact resistance itself, but remains largely unexplored. Here we have
investigated the contact noise in graphene field effect transistors of varying
device geometry and contact configuration, with carrier mobility ranging from
5,000 to 80,000$~$cm$^{2}$V$^{-1}$s$^{-1}$. Our phenomenological model for
contact noise due to current crowding in purely two dimensional conductors,
confirms that the contacts dominate the measured resistance noise in all
graphene field effect transistors in the two-probe or invasive four probe
configurations, and surprisingly, also in nearly noninvasive four probe (Hall
bar) configuration in the high mobility devices. The microscopic origin of
contact noise is directly linked to the fluctuating electrostatic environment
of the metal-channel interface, which could be generic to two dimensional
material-based electronic devices.",1611.01181v2
2017-09-02,Signatures of the Kondo effect in VSe2,"VSe2 is a transition metal dichaclogenide which has a charge-density wave
transition that has been well studied. We report on a low-temperature upturn in
the resistivity and, at temperatures below this resistivity minimum, an unusual
magnetoresistance which is negative at low fields and positive at higher
fields, in single crystals of VSe2. The negative magnetoresistance has a
parabolic dependence on the magnetic field and shows little angular dependence.
The magnetoresistance at temperatures above the resistivity minimum is always
positive. We interpret these results as signatures of the Kondo effect in VSe2.
An upturn in the susceptibility indicates the presence of interlayer V ions
which can provide the localized magnetic moments required for scattering the
conduction electrons in the Kondo effect. The low-temperature behaviour of the
heat capacity, including a high value of gamma, along with a deviation from a
Curie-Weiss law observed in the low-temperature magnetic susceptibility, are
consistent with the presence of magnetic interactions between the paramagnetic
interlayer V ions and a Kondo screening of these V moments.",1709.00594v1
2017-11-20,Computational analysis of short-range interactions between an edge dislocation and an array of equally-spaced identical shearable or non-shearable precipitates,"The interaction between dislocations and precipitates plays an important role
in the mechanical behavior of alloys. To provide more insight into the physics
of this interaction, this research analyzes short-range interactions of an edge
dislocation with an array of equally-spaced identical precipitates. We use a
modified dislocation dynamics approach accounting for penetrable and
impenetrable precipitates. This research quantifies the effects of precipitate
resistance on the geometry of the dislocation-precipitation interaction and the
local distribution of plastic strain near a precipitate. The results show that
a precipitate with a higher resistance causes an increase in the maximum value
of dislocation curvature during the bypass. In addition, a higher level of
precipitate resistance leads to a lower level of plastic deformation. Moreover,
we observed a high plastic strain gradient at the interface of non-shearable
precipitates.",1711.07428v2
2018-01-25,Non-volatile bipolar resistive switching in sol-gel derived BiFeO3 thin films,"BiFeO3 thin films are deposited on FTO coated glass substrates using a simple
sol-gel deposition technique, limiting thickness about 70 nm and Ag/BiFeO3/FTO
RRAM devices are prepared. The devices showed low-voltage bipolar switching
with the maximum Ion/Ioff ~ 450, and low set and reset voltages ~ 1.1 V and
-1.5 V, respectively. The devices are stable against on-off cycles with ~ 104 s
retention time without any significant degradation. The variations in the set
and reset voltages are 0.4 V and 0.6 V, respectively. We found that ohmic and
trap-controlled space charge limited conductions are responsible for low and
high resistance states, respectively. The resistive switching mechanism is
attributed to the formation and rupturing of the metal filament during the
oxidation and reduction of Ag ions for the set and reset states.",1801.08502v1
2017-03-22,A comparative study of resists and lithographic tools using the Lumped Parameter Model,"A comparison of the performance of high resolution lithographic tools is
presented here. We use extreme ultraviolet interference lithography, electron
beam lithography, and He ion beam lithography tools on two different resists
that are processed under the same conditions. The dose-to-clear and the
lithographic contrast are determined experimentally and are used to compare the
relative efficiency of each tool. The results are compared to previous studies
and interpreted in the light of each tool-specific secondary electron yield. In
addition, the patterning performance is studied by exposing dense line/spaces
patterns and the relation between critical dimension and exposure dose is
discussed. Finally, the Lumped Parameter Model is employed in order to
quantitatively estimate the critical dimension of line/spaces, using each tool
specific aerial image. Our implementation is then validated by fitting the
model to the experimental data from interference lithography exposures, and
extracting the resist contrast.",1703.08229v1
2020-04-15,Radiation reaction friction: Resistive material medium,"We explore a novel method of describing the radiation friction of particles
traveling through a mechanically resistive medium. We introduce a particle
motion induced matter warping along the path in a manner assuring that charged
particle dynamics occurs subject to radiative energy loss described by the
Larmor formula. We compare our description with the Landau-Lifshitz-like model
for the radiation friction and show that the established model exhibits
non-physical behavior. Our approach predicts in the presence of large
mechanical friction an upper limit on radiative energy loss being equal to the
energy loss due to the mechanical medium resistance. We demonstrate that
mechanical friction due to strong interactions, for example of quarks in
quark-gluon plasma, can induce significant soft photon radiation.",2004.09634v2
2020-04-28,Temperature-Dependent Resistivity of Alternative Metal Thin Films,"The temperature coefficients of the resistivity (TCR) of Cu, Ru, Co, Ir, and
W thin films have been investigated as a function of film thickness below 10
nm. Ru, Co, and Ir show bulk-like TCR values that are rather independent of the
thickness whereas the TCR of Cu increases strongly with decreasing thickness.
Thin W films show negative TCR values, which can be linked to high disorder.
The results are qualitatively consistent with a temperature-dependent
semiclassical thin film resistivity model that takes into account phonon,
surface, and grain boundary scattering.",2004.13854v3
2007-10-26,Transport and magnetic properties in YBaCo2O5.45: Focus on the high-temperature transition,"The electronic transport properties and the magnetic susceptibility were
measured in detail in $YBaCo_2O_{5.45}$. Close to the so-called metal-insulator
transition, strong effects of resistance relaxation, a clear thermal hysteresis
and a sudden increase of the resistance noise are observed. This is likely due
to the first order character of the transition and to the underlying phases
coexistence. Despite these out of equilibrium features, a positive and linear
magneto-resistance is also observed, possibly linked to the heterogeneity of
the state. From a magnetic point of view, the paramagnetic to ordered magnetic
state transition is observed using non linear susceptibilty. This transition
shows the characteristics of a continuous transition, and time dependent
effects can be linked with the dynamics of magnetic domains in presence of
disorder. Thus, when focusing on the order of the transitions, the electronic
one and the magnetic one can not be directly associated.",0710.5008v1
2017-04-24,Near-perfect spin filtering and negative differential resistance in an Fe(II)S complex,"Density functional theory and nonequilibrium Green's function calculations
have been used to explore spin-resolved transport through the high-spin state
of an iron(II)sulfur single molecular magnet. Our results show that this
molecule exhibits near-perfect spin filtering, where the spin-filtering
efficiency is above 99%, as well as significant negative differential
resistance centered at a low bias voltage. The rise in the spin-up conductivity
up to the bias voltage of 0.4 V is dominated by a conductive lowest unoccupied
molecular orbital, and this is accompanied by a slight increase in the magnetic
moment of the Fe atom. The subsequent drop in the spin-up conductivity is
because the conductive channel moves to the highest occupied molecular orbital
which has a lower conductance contribution. This is accompanied by a drop in
the magnetic moment of the Fe atom. These two exceptional properties, and the
fact that the onset of negative differential resistance occurs at low bias
voltage, suggests the potential of the molecule in nanoelectronic and
nanospintronic applications.",1704.07327v1
2017-07-08,Electron and thermal transport via Variable Range Hopping in MoSe$_{2}$ single crystals,"Bulk single crystal Molybdenum diselenide has been studied for its electronic
and thermal transport properties. We perform resistivity measurements with
current in-plane (CIP) and current perpendicular to plane (CPP) as a function
of temperature. The CIP measurements exhibit metal to semiconductor transition
at $\simeq 31$ K. In the semiconducting phase ($T > 31$ K), the transport is
best explained by variable range hopping (VRH) model. Large magnitude of
resistivity in CPP mode indicates strong structural anisotropy. Seebeck
coefficient as a function of temperature measured in the range $90 - 300$ K,
also agrees well with the VRH model. The room temperature Seebeck coefficient
is found to be $139$ $\mu$V/K. VRH fittings of the resistivity and Seebeck
coefficient data indicate high degree of localization.",1707.02426v1
2015-04-14,Voltage equilibration for reactive atomistic simulations of electrochemical processes,"We introduce EChemDID, a model to describe electrochemical driving force in
reactive molecular dynamics simulations. The method describes the equilibration
of external electrochemical potentials (voltage) within metallic structures and
their effect on the self consistent partial atomic charges used in reactive
molecular dynamics. An additional variable assigned to each atom denotes the
local potential in its vicinity and we use fictitious, but computationally
convenient, dynamics to describe its equilibration within not-simply connected
metallic structures on-the-fly during the molecular dynamics simulation. This
local electrostatic potential is used to dynamically modify the atomic
electronegativities used to compute partial atomic changes via charge
equilibration. Validation tests show that the method provides an accurate
description of the electric fields generated by the applied voltage and the
driving force for electrochemical reactions. We demonstrate EChemDID via
simulations of the operation of electrochemical metallization cells. The
simulations predict the switching of the device between a high-resistance to a
low-resistance state as a conductive metallic bridge is formed and resistive
currents that can be compared with experimental measurements. In addition to
applications in nanoelectronics, EChemDID could be useful to model
electrochemical energy conversion devices.",1504.03621v1
2016-09-29,Magnetotransport properties and evidence of topological insulating state in LaSbTe,"In this report, we present the magnetotransport and magnetization properties
of LaSbTe single crystals. Magnetic field-induced turn-on behavior and
low-temperature resistivity plateau have been observed. By adopting both
metal-semiconductor crossover and Kohler scaling analysis, we have discussed
the possible origin of the temperature and magnetic field dependence of
resistivity. At 5 K and 9 T, a large, non-saturating transverse
magnetoresistance (MR) $\sim$ 5$\times$10$^{3}$ \% has been obtained. The MR
shows considerable anisotropy, when the magnetic field is applied along
different crystallographic directions. The non-linear field dependence of the
Hall resistivity confirms the presence of two types of charge carriers. From
the semiclassical two-band fitting of Hall conductivity and longitudinal
conductivity, very high carrier mobilities and almost equal electron and hole
densities have been deduced, which result in large MR. The Fermi surface
properties have been analyzed from de Haas-van Alphen oscillation. From the
magnetization measurement, the signature of non-trivial surface state has been
detected, which confirms that LaSbTe is a topological insulator, consistent
with the earlier first-principles calculations.",1609.09397v3
2019-11-20,Investigation of the phase separation property in La$_{0.2}$Pr$_{0.4}$Ca$_{0.4}$MnO$_3$ manganite,"We report a comprehensive investigation of La0.2Pr0.4Ca0.4MnO3 to clarify the
micrometre scale phase separation phenomenon in the mixed valent manganite
(La,Pr,Ca)MnO3. The compound shows multiple magnetic transitions, in which the
charge-ordered state is converted into a ferromagnetic state in steps with the
application of a magnetic field. The ac susceptibility measurements show that
the glassy transition at low temperatures does not depend on the frequency,
thus indicating the absence of any spin glass behaviour. Magnetization as well
as heat capacity measurements indicate that this low temperature transition is
magnetic field dependent. The field dependent resistivity at 2K shows a sharp
drop indicating that the sample behaviour changes from a high resistive state
to a low resistive state, corroborating the conversion of charge-ordered
insulating (COI) phase to a ferromagnetic metallic (FMM) phase. Our results
point towards the existence of phase separation, rigidity of the low
temperature glassy-like phase as well as the conversion of COI phase to FMM
phase by the application of magnetic fields.",1911.08881v1
2021-02-01,Real-time Hall-effect detection of current-induced magnetization dynamics in ferrimagnets,"Measurements of the transverse Hall resistance are widely used to investigate
electron transport, magnetization phenomena, and topological quantum states.
Owing to the difficulty of probing transient changes of the transverse
resistance, the vast majority of Hall effect experiments are carried out in
stationary conditions using either dc or ac currents. Here we present an
approach to perform time-resolved measurements of the transient Hall resistance
during current-pulse injection with sub-nanosecond temporal resolution. We
apply this technique to investigate in real-time the magnetization reversal
caused by spin-orbit torques in ferrimagnetic GdFeCo dots. Single-shot Hall
effect measurements show that the current-induced switching of GdFeCo is widely
distributed in time and characterized by significant activation delays, which
limit the total switching speed despite the high domain-wall velocity typical
of ferrimagnets. Our method applies to a broad range of current-induced
phenomena and can be combined with non-electrical excitations to perform
pump-probe Hall effect measurements.",2102.00716v1
2021-04-23,Deformation and tearing of graphene-reinforced elastomer nanocomposites,"The resistance to failure through tearing is a crucial mechanical property
for the application of different elastomers. In this work, graphene
nanoplatelets (GNPs) were introduced into a fluoroelastomer (FKM) matrix with
the aim of improving its tear resistance. The fracture energy through tearing
was evaluated using the pure shear test. It was found that the tearing energy
increased linearly with the volume fraction of the GNPs. At the maximum GNP
content, the tearing resistance was 3 times higher, suggesting efficient
toughening from the GNPs. Theoretical analysis of the micromechanics was
conducted by considering debonding and pull-out of the nanoplatelets as
possible toughening mechanisms. It was determined quantitatively that the main
toughening mechanism was debonding of the interface rather than pull-out. The
formation of cavities at flake ends during the deformation, as confirmed by
scanning electron microscopy, was found to contribute to the remarkably high
interfacial debonding energy (~1 kJ/m2).",2104.11535v1
2021-04-27,Electronegative metal dopants improve switching consistency in Al2O3 resistive switching devices,"Resistive random access memories are promising for non-volatile memory and
brain-inspired computing applications. High variability and low yield of these
devices are key drawbacks hindering reliable training of physical neural
networks. In this study, we show that doping an oxide electrolyte, Al2O3, with
electronegative metals makes resistive switching significantly more
reproducible, surpassing the reproducibility requirements for obtaining
reliable hardware neuromorphic circuits. The underlying mechanism is the ease
of creating oxygen vacancies in the vicinity of electronegative dopants, due to
the capture of the associated electrons by dopant mid-gap states, and the
weakening of Al-O bonds. These oxygen vacancies and vacancy clusters also bind
significantly to the dopant, thereby serving as preferential sites and building
blocks in the formation of conducting paths. We validate this theory
experimentally by implanting multiple dopants over a range of
electronegativities, and find superior repeatability and yield with highly
electronegative metals, Au, Pt and Pd. These devices also exhibit a gradual SET
transition, enabling multibit switching that is desirable for analog computing.",2104.13301v2
2021-05-06,Contact resistance of various metallisation schemes to superconducting boron doped diamond between 1.9 and 300 K,"Diamond is a material that offers potential in numerous device applications.
In particular, highly boron doped diamond is attractive due to its
superconductivity and high Young's Modulus. The fabrication of stable, low
resistance, ohmic contacts is essential to ensure proper device function.
Previous work has established the efficacy of several methods of forming
suitable contacts to diamond at room temperature and above, including carbide
forming and carbon soluble metallisation schemes. Herein, the stability of
several contact schemes (Ti, Cr, Mo, Ta and Pd) to highly boron doped
nanocrystalline diamond was verified down to the cryogenic temperatures with
modified Transmission Line Model (TLM) measurements. While all contact schemes
remained ohmic, a significant temperature dependency is noted at Tc and at the
lowest temperatures the contact resistances ranged from Ti/Pt/Au with ${(8.83
\pm 0.10)\times 10^{-4} \:{\Omega}.cm}$ to Ta/Pt/Au with ${(8.07 \pm 0.62)
\times 10^{-6} \:{\Omega}.cm}$.",2105.02839v1
2021-08-10,Giant Piezospintronic Effect in a Noncollinear Antiferromagnetic Metal,"One of the main bottleneck issues for room-temperature antiferromagnetic
spintronic devices is the small signal read-out owing to the limited
anisotropic magnetoresistance in antiferromagnets. However, this could be
overcome by either utilizing the Berry-curvature-induced anomalous Hall
resistance in noncollinear antiferromagnets or establishing tunnel junction
devices based on effective manipulation of antiferromagnetic spins. In this
work, we demonstrate the giant piezoelectric strain control of the spin
structure and the anomalous Hall resistance in a noncollinear antiferromagnetic
metal - D019 hexagonal Mn3Ga. Furthermore, we built tunnel junction devices
with a diameter of 200 nm to amplify the maximum tunneling resistance ratio to
more than 10% at room-temperature, which thus implies significant potential of
noncollinear antiferromagnets for large signal-output and high-density
antiferromagnetic spintronic device applications.",2108.04439v1
2021-09-07,Strain-dependent resistance and giant gauge factor in monolayer WSe2,"We report the strong dependence of resistance on uniaxial strain in monolayer
WSe2 at various temperatures, where the gauge factor can reach as large as
2400. The observation of strain-dependent resistance and giant gauge factor is
attributed to the emergence of nonzero Berry curvature dipole. Upon increasing
strain, Berry curvature dipole can generate net orbital magnetization, which
would introduce additional magnetic scattering, decreasing the mobility and
thus conductivity. Our work demonstrates the strain engineering of Berry
curvature and thus the transport properties, making monolayer WSe2 potential
for the application in the high-performance flexible and transparent
electronics.",2109.02980v1
2021-09-12,Coexistence of resistance oscillations and the anomalous metal phase in a lithium intercalated TiSe$_2$ superconductor,"Superconductivity and charge density wave (CDW) appear in the phase diagram
of a variety of materials including the high - $T$$_c$ cuprate family and many
transition metal dichalcogenides (TMDs). Their interplay may give rise to
exotic quantum phenomena. Here, we show that superconducting arrays can
spontaneously form in TiSe$_2$ - a TMD with coexisting superconductivity and
CDW - after lithium ion intercalation. We induce a superconducting dome in the
phase diagram of Li$_x$TiSe$_2$ by using the ionic solid-state gating
technique. Around optimal doping, we observe magnetoresistance oscillations,
indicating the emergence of periodically arranged domains. In the same
temperature, magnetic field and carrier density regime where the resistance
oscillations occur, we observe signatures for the anomalous metal - a state
with a resistance plateau across a wide temperature range below the
superconducting transition. Our study not only sheds further insight into the
mechanism for the periodic electronic structure, but also reveals the interplay
between the anomalous metal and superconducting fluctuations.",2109.05450v1
2021-10-11,Observation of Exchange Bias in Antiferromagnetic Cr$_{0.79}$Se due to the Coexistence of Itinerant Weak Ferromagnetism at Low-temperatures,"We report on the structural, electrical transport, and magnetic properties of
antiferromagnetic transition-metal monochalcogenide Cr$_{0.79}$Se. Different
from the existing off-stoichiometric compositions, Cr$_{0.79}$Se is found to be
synthesised into the same NiAs-type hexagonal crystal structure of CrSe.
Resistivity data suggest Cr$_{0.79}$Se to be a Fermi-liquid-type metal at low
temperatures, while at intermediate temperatures the resistivity depends
sublinearly on the temperature. Eventually, at the elevated temperatures the
rate of change of resistivity rapidly decreases with increasing temperature.
Magnetic measurements suggest a transition from paramagnetic phase to an
antiferromagnetic phase at a N$\acute{e}$el temperature of 225 K. Further
reduction of the sample temperature results into coexistance of weak
ferromagnetism along with the antiferromagnetic phase below 100 K. As a result,
below 100 K, we identify significant exchange bias due to the interaction
between the ferro- and antiferromagnetic phases. In addition, from the
temperature dependent X-ray diffraction measurements we observe that the
NiAs-type structure is stable up to as high as 600$^o$C.",2110.05058v1
2022-06-16,Fill Factor Losses and Deviations from the Superposition Principle in Lead-Halide Perovskite Solar Cells,"The enhancement of the fill factor in the current generation of perovskite
solar cells is the key for further efficiency improvement. Thus, methods to
quantify the fill factor losses are urgently needed. A classical method to
quantify Ohmic and non-Ohmic resistive losses in solar cells is based on the
comparison between the voltage in the dark and under illumination analysed at
equal recombination current density. Applied to perovskite solar cells, we
observe a combination of an Ohmic series resistance with a voltage-dependent
resistance that is most prominent at short circuit and low forward bias. The
latter is most likely caused by the poor transport properties of the electron
and/or hole transport layers. By measuring the photoluminescence of perovskite
solar cells as a function of applied voltage, we provide direct evidence for a
high quasi-Fermi level splitting at low and moderate forward bias that
substantially exceeds the externally applied voltage. This quasi-Fermi level
splitting causes recombination losses and, thus, reduces both the short-circuit
current and the fill factor of the solar cell.",2207.02297v1
2022-12-07,Self-assembled neuromorphic networks at self-organized criticality in Ag-hBN platform,"Networks and systems which exhibit brain-like behavior can analyze
information from intrinsically noisy and unstructured data with very low power
consumption. Such characteristics arise due to the critical nature and complex
interconnectivity of the brain and its neuronal network. We demonstrate that a
system comprising of multilayer hexagonal Boron Nitride (hBN) films contacted
with Silver (Ag), that can uniquely host two different self-assembled networks,
which are self-organized at criticality (SOC). This system shows bipolar
resistive switching between high resistance (HRS) and low resistance states
(LRS). In the HRS, Ag clusters (nodes) intercalate in the van der Waals gaps of
hBN forming a network of tunnel junctions, whereas the LRS contains a network
of Ag filaments. The temporal avalanche dynamics in both these states exhibit
power-law scaling, long-range temporal correlation, and SOC. These networks can
be tuned from one to another with voltage as a control parameter. For the first
time, different neuron-like networks are realized in a single CMOS compatible,
2D materials platform.",2301.01619v1
2023-06-13,An Evaluation of Multi-Component Weft-Knitted Twill Structures for Sensing Tensile Force,"We present multi-component knitted resistive sensors for tracking tensile
force. The knits were fabricated using a Twill structure, which is a simple
pattern featuring anisotropic elastic behavior, providing high stability along
course-direction. Our sensors are made of two commercially available conductive
yarn types, with highly different linear resistance. We present a variety of
integration methods using the proposed Twill structure, all of which can be
easily replicated on a two-bed weft-knitting machine. We evaluate the
performance of the resulting sensor variations, with respect to consistency,
hysteresis, short-term and long-term relaxation and drift, among other metrics.
We found that particulars of the knit's loop composition have a crucial effect
on the consistency of the sensor readings. Furthermore, we show that knitting
resistive yarn more tightly than the substrate material gives superior results
and that improving elastic recoil by adding Lycra to the supporting substrate
can considerably improve performance.",2306.07612v1
2024-04-13,Combinatorial Printing of Functionally Graded Solid-State Electrolyte for High-Voltage Lithium Metal Batteries,"Heterogeneous multilayered solid-state electrolyte (HMSSE) has been widely
explored for their broadened working voltage range and compatibility with
electrodes. However, due to the limitations of traditional manufacturing
methods such as casting, the interface between electrolyte layers in HMSSE can
decrease the ionic conductivity severely. Here, a novel combinatory aerosol jet
printing (CAJP) is introduced to fabricate functionally graded solid-state
electrolyte (FGSSE) without sharp interface. Owing to the unique ability of
CAJP (in-situ mixing and instantaneous tuning of the mixing ratio), FGSSE with
smooth microscale compositional gradation is achieved. Electrochemical tests
show that FGSSE has excellent oxidative stability exceeding 5.5 V and improved
conductivity (>7 times of an analogous HMSSE). By decoupling the total
resistance, we show that the resistance from the electrolyte/electrolyte
interface of HMSSE is 5.7 times of the total resistance of FGSSE. The
Li/FGSSE/NCM622 cell can be stably run for more than 200 cycles along with
improved rate performance.",2404.09008v1
2024-05-29,Multipacting mitigation by atomic layer deposition: the case study of Titanium Nitride,"This study investigates the use of Atomic Layer deposition (ALD) to mitigate
multipacting phenomena inside superconducting radio frequency (SRF) cavities
used in particle accelerators. The unique ALD capability to control the film
thickness down to the atomic level on arbitrary complex shape objects enable
the fine tuning of TiN film resistivity and total electron emission yield
(TEEY) from coupons to devices. This level of control allows us to adequately
choose a TiN film thickness that provide both a high resistivity to prevent
Ohmic losses and low TEEY to mitigate multipacting for the application of
interest. The methodology presented in this work can be scaled to other domain
and devices subject to RF fields in vacuum and sensitive to multipacting or
electron discharge processes with their own requirements in resistivities and
TEEY values",2405.18949v1
2015-05-29,Few Layer HfS2 FET,"2D materials are expected to be favorable channel materials for field-effect
transistor (FET) with extremely short channel length because of their superior
immunity to short-channel effects (SCE). Graphene, which is the most famous 2D
material, has no bandgap without additional techniques and this property is
major hindrance in reducing the drain leakage. Therefore, 2D materials with
finite band gap, such as transition metal dichalcogenides (TMDs, e.g. MoS2
WSe2) or phosphorene, are required for the low power consumption FETs. Hafnium
disulfide (HfS2) is a novel TMD, which has not been investigated as channel
material. We focused on its potential for well-balanced mobility and bandgap
properties. The higher electron affinity of Hf dichalcogenides compared with Mo
or W chalcogenides facilitates the formation of low resistance contact and
staggered heterojunction with other 2D materials. Here we demonstrate the first
few layer HfS2 FET with robust current saturation and high current on/off ratio
of more than 10^4.",1505.07970v1
2011-10-29,From mixed valence to the Kondo lattice regime,"Many heavy fermion materials are known to crossover from the Kondo lattice
regime to the mixed-valent regime or vice-versa as a function of pressure or
doping. We study this crossover theoretically by employing the periodic
Anderson model within the framework of the dynamical mean field theory. Changes
occurring in the dynamics and transport across this crossover are highlighted.
As the valence is decreased (increased) relative to the Kondo lattice regime,
the Kondo resonance broadens significantly, while the lower (upper) Hubbard
band moves closer to the Fermi level. The resistivity develops a two peak
structure in the mixed valent regime: a low temperature coherence peak and a
high temperature 'Hubbard band' peak. These two peaks merge yielding a broad
shallow maximum upon decreasing the valence further. The optical conductivity,
likewise exhibits an unusual absorption feature (shoulder) in the deep
mid-infrared region, which grows in intensity with decreasing valence. The
involvement of the Hubbard bands in dc transport, and of the effective f-level
in the optical conductivity are shown to be responsible for the anomalous
transport properties. A two-band hybridization-gap model, which neglects
incoherent effects due to many-body scattering, commonly employed to understand
the optical response in these materials is shown to be inadequate, especially
in the mixed-valent regime. Comparison of theory with experiment carried out
for (a) dc resistivities of CeRhIn5, Ce2Ni3Si5, CeFeGe3 and YbIr2Si2; (b)
pressure dependent resistivity of YbInAu2 and CeCu6; and (c) optical
conductivity measurements in YbIr2Si2 yields excellent agreement.",1110.6498v1
2021-04-01,Enhanced spin injection in molecularly functionalized graphene via ultra-thin oxide barriers,"Realisation of practical spintronic devices relies on the ability to create
and detect pure spin currents. In graphene-based spin valves this is usually
achieved by injection of spin-polarized electrons from ferromagnetic contacts
via a tunnel barrier, with Al2O3 and MgO used most widely as barrier materials.
However, the requirement to make these barriers sufficiently thin often leads
to pinholes and low contact resistances which in turn results in low spin
injection efficiencies, typically 5% at room temperature, due to the so-called
resistance mismatch problem. Here we demonstrate an alternative approach to
fabricate ultra-thin tunnel barrier contacts to graphene. We show that
laser-assisted chemical functionalization of graphene with sp3-bonded phenyl
groups effectively provides a seed layer for growth of ultrathin Al2O3 films,
ensuring smooth, high quality tunnel barriers and an enhanced spin injection
efficiency. Importantly, the effect of functionalization on spin transport in
the graphene channel itself is relatively weak, so that the enhanced spin
injection dominates and leads to an order of magnitude increase in spin
signals. Furthermore, spatial control of functionalization using a focused
laser beam and lithographic techniques can in principle be used to limit
functionalization to contact areas only, further reducing the effect on the
graphene channel. Our results open a new route towards circumventing the
resistance mismatch problem in graphene-based spintronic devices based on the
easily available and highly stable Al2O3, and facilitate a step forward in the
development of their practical applications.",2104.00709v1
2017-05-16,Application of flash method in the measurements of interfacial thermal resistance in layered and particulate composite materials,"Presented study concerns the possibility of evaluation of interfacial thermal
resistance (ITR) between the constituents in composite materials with the use
of flash technique. Two variants of such measurement are considered, the first
of which is the measurement of ITR between two bonded layers of different
materials which had been studied before by various researchers. The second
tested measurement method is targeted at determination of ITR in particulate
composites with low and moderate filler content based on their effective
thermal conductivity. Method of such measurement is proposed and tested on two
cases of particle-filled polymer composites. Positive verification results were
obtained for polymer/glass composite in which the difference between thermal
conductivities of matrix and filler is low. For a polymer filled with aluminum
particles the evaluation of average ITR in the samples was impossible as the
effective medium models applied in the method strongly underestimated the
thermal conductivity of that material. The investigation confirmed the need for
more accurate methods of macroscopic thermal properties prediction for
composite media with high contrast of thermal conductivities of the
constituents. Extended literature study suggests that the method can be
applicable to selected classes of engineering materials.",1705.05621v1
1998-12-23,Temperature dependence of electric resistance and magnetoresistance of pressed nanocomposites of multilayer nanotubes with the structure of nested cones,"Bulk samples of carbon multilayer nanotubes with the structure of nested
cones (fishbone structure) suitable for transport measurements, were prepared
by compressing under high pressure (~25 kbar) a nanotube precursor synthesized
through thermal decomposition of polyethylene catalyzed by nickel. The
structure of the initial nanotube material was studied using high-resolution
transmission electron microscopy. In the low-temperature range (4.2 - 100 K)
the electric resistance of the samples changes according to the law ln \rho ~
(T_0/T)^{1/3}, where T_0 ~ 7 K. The measured magnetoresistance is quadratic in
the magnetic field and linear in the reciprocal temperature. The measurements
have been interpreted in terms of two-dimensional variable-range hopping
conductivity. It is suggested that the space between the inside and outside
walls of nanotubes acts as a two-dimensional conducting medium. Estimates
suggest a high value of the density of electron states at the Fermi level of
about 5 10^{21} eV^{-1} cm^{-3}.",9812384v1
2017-01-07,"Spatially uniform resistance switching of low current, high endurance titanium-niobium-oxide memristors","We analyzed micrometer-scale titanium-niobium-oxide prototype memristors,
which exhibited low write-power (<3 {\mu}W) and energy (<200 fJ/bit/{\mu}m2),
low read-power (~nW), and high endurance (>millions of cycles). To understand
their physico-chemical operating mechanisms, we performed in-operando
synchrotron x-ray transmission nanoscale spectromicroscopy using an
ultra-sensitive time-multiplexed technique. We observed only spatially uniform
material changes during cell operation, in sharp contrast to the frequently
detected formation of a localized conduction channel in transition-metal-oxide
memristors. We also associated the response of assigned spectral features
distinctly to non-volatile storage (resistance change) and writing of
information (application of voltage and Joule heating). These results provide
critical insights into high-performance memristors that will aid in device
design, scaling and predictive circuit-modeling, all of which are essential for
the widespread deployment of successful memristor applications.",1701.01784v1
2001-02-09,Superconducting Properties of MgB2 Bulk Materials Prepared by High Pressure Sintering,"High-density bulk materials of a newly discovered 40K intermetallic MgB2
superconductor were prepared by high pressure sintering. Superconducting
transition with the onset temperature of 39K was confirmed by both magnetic and
resistive measurements. Magnetization versus field (M-H) curve shows the
behavior of a typical Type II superconductor and the lower critical field
Hc1(0) estimated from M-H curve is 0.032T. The bulk sample shows good
connection between grains and critical current density Jc estimated from the
magnetization hysteresis using sample size was 2x104A/cm2 at 20K and 1T. Upper
critical field Hc2(0) determined by extrapolating the onset of resistive
transition and assuming a dirty limit is 18T.",0102167v1
2018-09-17,High quality factor graphene-based 2D heterostructure mechanical resonator,"Ultralight mechanical resonators based on low-dimensional materials are well
suited as exceptional transducers of minuscule forces or mass changes. However,
the low dimensionality also provides a challenge to minimize resistive losses
and heating. Here, we report on a novel approach that aims to combine different
2D materials to tackle this challenge. We fabricated a heterostructure
mechanical resonator consisting of few layers of niobium diselenide (NbSe$_2$)
encapsulated by two graphene sheets. The hybrid membrane shows high quality
factors up to 245'000 at low temperatures, comparable to the best few-layer
graphene mechanical resonators. In contrast to few-layer graphene resonators,
the device shows reduced electrical losses attributed to the lower resistivity
of the NbSe$_2$ layer. The peculiar low temperature dependence of the intrinsic
quality factor points to dissipation over two-level systems which in turn relax
over the electronic system. Our high sensitivity readout is enabled by coupling
the membrane to a superconducting cavity which allows for the integration of
the hybrid mechanical resonator as a sensitive and low loss transducer in
future quantum circuits.",1809.06169v1
2022-04-22,Comparison of different sensor thicknesses and substrate materials for the monolithic small collection-electrode technology demonstrator CLICTD,"Small collection-electrode monolithic CMOS sensors profit from a high
signal-to-noise ratio and a small power consumption, but have a limited active
sensor volume due to the fabrication process based on thin high-resistivity
epitaxial layers. In this paper, the active sensor depth is investigated in the
monolithic small collection-electrode technology demonstrator CLICTD. Charged
particle beams are used to study the charge-collection properties and the
performance of devices with different thicknesses both for perpendicular and
inclined particle incidence. In CMOS sensors with a high-resistivity
Czochralski substrate, the depth of the sensitive volume is found to increase
by a factor two in comparison with standard epitaxial material and leads to
significant improvements in the hit-detection efficiency and the spatial and
time resolution.",2204.10569v2
2021-11-01,A New Class of Alumina-Forming Superalloy for 3D Printing,"A new class of crack-resistant nickel-based superalloy containing high
$\gamma^\prime$ fraction is studied for the laser-powder bed fusion (L-PBF)
process. The effects of the (Nb+Ta)/Al ratio is emphasised, a strategy that is
shown to confer excellent low-temperature strength whilst maintaining oxidation
resistance at high temperatures via stable alumina scale formation. The
processability of the new alloys is characterised with respect to defect
assessment by micro-focus x-ray computed tomography; use is made of a prototype
turbine blade geometry and the heritage alloy CM247LC as a benchmark. In all
cases, some processing-related porosity is present in thin wall sections such
as the trailing edge, but this can be avoided by judicious processing. The
cracking seen in CM247LC -- in solid-state, liquation and solidification forms
-- is avoided. A novel sub-solvus heat treatment strategy is proposed which
takes advantage of AM not requiring solutioning; super-solvus heat treatment is
inappropriate since it embrittles the material by deterioration of the texture
and coarsening of grain boundary carbides. The tensile strength of the new
superalloy is greatest when the Nb+Ta content is highest and exceeds that of
CM247LC up to $\sim$900$\,$$^\circ$C. The oxidation resistance is best when Al
content is highest, and oxidation-assisted cracking resistance maximized when
the (Nb+Ta)/Al ratio is balanced. In all cases these are equivalent or superior
to that of CM247LC. Nevertheless, the creep resistance of the new alloys is
somewhat inferior to that of CM247LC for which the $\gamma^\prime$, C, and B
contents are higher; this implies a processing/property trade-off which
requires further clarification.",2111.01049v1
2005-11-08,Development of the Charge Particle Detector Based on CVD - Diamond,"High radiation hardness, chemical resistance, high temperature operation
capabilities stimulate a growing interest to use diamond materials as detectors
of ionizing radiation. Samples of CVD-diamond materials in sizes 12 square mm
and 4 square mm with thickness from 50 microns up to 500 microns have been
grown in INR RAS using a DC glow discharge in a mixture of gases CH4/H2 on
molybdenum substrates.",0511068v1
2018-10-24,High Strain Rate Behaviour of Nano-quasicrystalline Al93Fe3Cr2Ti2 Alloy and Composites,"In the present work, we demonstrate for the first time the outstanding
dynamic mechanical properties of nano-quasicrystalline Al93Fe3Cr2Ti2 at.% alloy
and composites. Unlike most crystalline aluminium-based alloys, this alloy and
composites exhibit substantial strain rate sensitivity and retain much of their
ductility at high rates of strain. This opens new pathways for use in
safety-critical materials where impact resistance is required.",1810.10476v2
2019-12-24,Large spin Hall angle and spin mixing conductance in highly resistive antiferromagnetic Mn2Au,"Antiferromagnetic (AFM) materials recently have shown interest in the
research in spintronics due to its zero stray magnetic field, high anisotropy,
and spin orbit coupling. In this context, the bi-metallic AFM Mn2Au has drawn
attention because it exhibits unique properties and its Neel temperature is
very high. Here, we report spin pumping and inverse spin Hall effect
investigations in Mn2Au and CoFeB bilayer system using ferromagnetic resonance.
We found large spin Hall angle {\theta}_SH = 0.22",1912.11522v2
2008-09-09,Printed Graphene Circuits,"we have fabricated transparent electronic devices based on graphene materials
with thickness down to one single atomic layer by the transfer printing method.
The resulting printed graphene devices retain high field effect mobility and
have low contact resistance. The results show that the transfer printing method
is capable of high-quality transfer of graphene materials from silicon dioxide
substrates, and the method thus will have wide applications in manipulating and
delivering graphene materials to desired substrate and device geometries. Since
the method is purely additive, it exposes graphene (or other functional
materials) to no chemical preparation or lithographic steps, providing greater
experimental control over device environment for reproducibility and for
studies of fundamental transport mechanisms. Finally, the transport properties
of the graphene devices on the PET substrate demonstrate the non-universality
of minimum conductivity and the incompleteness of the current transport theory.",0809.1634v1
2021-08-29,A graph based workflow for extracting grain-scale toughness from meso-scale experiments,"We introduce a novel machine learning computational framework that aims to
compute the material toughness, after subjected to a short training process on
a limited meso-scale experimental dataset. The three part computational
framework relies on the ability of a graph neural network to perform high
accuracy predictions of the micro-scale material toughness, utilizing a limited
size dataset that can be obtained from meso-scale fracture experiments. We
analyze the functionality of the different components of the framework, but the
focus is on the capabilities of the neural network. The minimum size of the
dataset required for the network training is investigated. The results
demonstrate the high efficiency of the algorithm in predicting the crack growth
resistance in micro-scale level, using a crack path trajectory limited to
200-300 grains for the network training. The merit of the proposed framework
arises from the capacity to enhance its performance in different material
systems with a limited additional training on data obtained from experiments
that do not require complex or cumbersome measurements. The main objective is
the development of an efficient computational tool that enables the study of a
wide range of material microstructure properties and the investigation of their
influence on the material toughness.",2108.12783v1
2022-08-25,Magnetoresistive behaviour of ternary Cu-based materials processed by high-pressure torsion,"Severe plastic deformation using high-pressure torsion of ternary Cu-based
materials (CuFeCo and CuFeNi) was used to fabricate bulk samples with a
nanocrystalline microstructure. The goal was to produce materials featuring the
granular giant magnetoresistance effect, requiring interfaces between ferro-
and nonmagnetic materials. This magnetic effect was found for both ternary
systems; adequate subsequent annealing had a positive influence. The
as-deformed states, as well as microstructural changes upon thermal treatments,
were studied using scanning electron microscopy and X-ray diffraction
measurements. Deducing from electron microscopy, a single-phase structure was
observed for all as-deformed samples, indicating the formation of a
supersaturated solid solution. However, judging from the presence of the
granular giant-magnetoresistive effect, small ferromagnetic particles have to
be present. The highest drop in room temperature resistivity (2.45% at 1790
kA/m) was found in Cu62Fe19Ni19 after annealing for 1 h at 400 {\deg}C.
Combining the results of classical microstructural studies and magnetic
measurements, insights into the evolution of ferromagnetic particles are
accessible.",2208.11895v1
2023-03-28,Electrolyte Coatings for High Adhesion Interfaces in Solid-state Batteries from First Principles,"We introduce an adhesion parameter that enables rapid screening for materials
interfaces with high adhesion. This parameter is obtained by density functional
theory calculations of individual single-material slabs rather than slabs
consisting of combinations of two materials, eliminating the need to calculate
all configurations of a prohibitively vast space of possible interface
configurations. Cleavage energy calculations are used as an upper bound for
electrolyte and coating energies and implemented in an adapted contact angle
equation to derive the adhesion parameter. In addition to good adhesion, we
impose further constraints in electrochemical stability window, abundance, bulk
reactivity, and stability to screen for coating materials for next-generation
solid-state batteries. Good adhesion is critical in combating delamination and
resistance to Lithium diffusivity in solid-state batteries. Here, we identify
several promising coating candidates for the Li7La3Zr2O12 and sulfide
electrolyte systems including the previously investigated electrode coating
materials LiAlSiO4 and Li5AlO8, making them especially attractive for
experimental optimization and commercialization.",2303.16350v1
2014-12-12,High-T_c superconductivity in ultrathin Bi_2Sr_2CaCu_2O_8+x down to halfunit-cell thickness by protection with graphene,"High-T_c superconductors confined to two dimension exhibit novel physical
phenomena, such as superconductor-insulator transition. In the
Bi_2Sr_2CaCu_2O_8+x (Bi2212) model system, despite extensive studies, the
intrinsic superconducting properties at the thinness limit have been difficult
to determine. Here we report a method to fabricate high quality single-crystal
Bi2212 films down to half-unit-cell thickness in the form of graphene/Bi2212
van der Waals heterostructure, in which sharp superconducting transitions are
observed. The heterostructure also exhibits a nonlinear current-voltage
characteristic due to the Dirac nature of the graphene band structure. More
interestingly, although the critical temperature remains essentially the same
with reduced thickness of Bi2212, the slope of the normal state T-linear
resistivity varies by a factor of 4-5, and the sheet resistance increases by
three orders of magnitude, indicating a surprising decoupling of the normal
state resistance and superconductivity. The developed technique is versatile,
applicable to investigate other two-dimensional (2D) superconducting materials.",1412.3896v1
2019-08-18,Maximizing the spin-orbit torque efficiency of Pt/Ti multilayers by optimization of the tradeoff between the intrinsic spin Hall conductivity and carrier lifetime,"We report a comprehensive study of the maximization of the spin Hall ratio
({\theta}SH) in Pt thin films by the insertion of sub-monolayer layers of Ti to
decrease carrier lifetime while minimizing the concurrent reduction in the spin
Hall conductivity. We establish that the intrinsic spin Hall conductivity of
Pt, while robust against the strain and the moderate interruption of crystal
order caused by these insertions, begins to decrease rapidly at high
resistivity level because of the shortening carrier lifetime. The unavoidable
trade-off between the intrinsic spin Hall conductivity and carrier lifetime
sets a practical upper bound of {\theta}SH >=0.8 for heterogeneous materials
where the crystalline Pt component is the source of the spin Hall effect and
the resistivity is increased by shortening carrier lifetime. This work also
establishes a very promising spin-Hall metal of [Pt 0.75 nm/Ti 0.2 nm]7/Pt 0.75
nm for energy-efficient, high-endurance spin-orbit torque technologies (e.g.,
memories, oscillators, and logic) due to its combination of a giant {\theta}SH
of 0.8, or equivalently a dampinglike spin torque efficiency per unit current
density of 0.35, with a relatively low resistivity (90 uOhm cm) and high
suitability for practical technology integration.",1908.06528v1
2019-10-22,Transverse Beam Stability with Low-Impedance Collimators in the High Luminosity Large Hadron Collider: Status and Challenges,"The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) will double
its beam intensity for the needs of High Energy Physics frontier. In order to
ensure coherent stability until the beams are put in collision, the transverse
impedance has to be reduced. As the major portion of the ring impedance is
supplied by its collimation system, several low resistivity jaw materials have
been proposed to lower the collimator impedance and a special collimator has
been built and installed in the machine to study their effect. The results show
a significant reduction of the resistive wall tune shift with novel materials,
in agreement with the impedance model and the bench impedance and resistivity
measurements. The largest improvement is obtained with a 5 {\mu}m Molybdenum
coating of a Molybdenum-Graphite jaw. This coating can lower the machine
impedance by up to 30% and the stabilizing Landau octupole threshold by up to
120 A. The collimators to be upgraded have been chosen based on the improvement
of the octupole threshold, as well as the tolerance to steady state losses and
failure scenarios. A half of the overall improvement can be obtained by coating
the jaws of a subset of 4 out of 11 collimators identified as the highest
contributors to machine impedance. This subset of low-impedance collimators is
being installed during the Long Shutdown 2 in 2019-2020.",1910.09974v2
2020-11-05,Preparation of the AlTiNiCuCox system high-entropy alloys and structural analysis,"This study aimed to explore and develop a new material with high
cost-effectiveness, excellent strength, light weight, high hardness, great wear
resistance, corrosion resistance, and favorable oxidation resistance.
Structural analysis suggested that, with the change in Co addition amount, the
surface morphology and structure of the alloy system changed. XRD analysis
indicated that, the alloy system was the FCC+BCC mixed structure. In addition,
metallographical demonstrated that, with the increase in Co content, the
dendritic crystal transformed from big block to dendritic structure, then to
snowflake, gradually to petal-like, and finally to petal shape. SEM-EDS
analysis revealed that, Cu element was enriched in interdendritic site, while
Ti, Ni, Al and Co elements were enriched in dendrite. Besides, TEM and TEM-EDS
analysis indicated that, there was nano-size precipitate of small particles in
the Cu-enriched block region, along with dislocation; further, there was twin
structure inside the dendrite, as well as the second phase with different
morphology, and the second phase showed coherency with the matrix. The above
analysis suggested that, the intercrystalline structure was the Cu-enriched
phase of FCC structure; the internal matrix of grain was the NiTi and TiCo
phases of BCC structure; and the second phases inside the grain were the
AlCu2Ti,AlNi2Ti,AlCo2Ti and CuNi phases of FCC structure. Taken together, the
AlTiNiCuCox system novel alloys have changed phase structures and phase types
of the alloy system.",2011.02799v1
2022-01-19,Secondary Phase Limited Metal-Insulator Phase Transition in Chromium Nitride Thin Films,"Chromium nitride (CrN) is a well-known hard coating material that has found
applications in abrasion and wear-resistant cutting tools, bearings, and
tribology applications due to its high hardness, high-temperature stability,
and corrosion-resistant properties. In recent years, CrN has also attracted
significant interest due to its high thermoelectric power factor, and for its
unique and intriguing metal-insulator phase transition. While CrN bulk
single-crystals exhibit the characteristic metal-insulator transition
accompanied with structural (orthorhombic-to-rocksalt) and magnetic
(antiferromagnetic-to-paramagnetic) transition at ~260-280K, observation of
such phase transition in thin-film CrN has been scarce and highly debated. In
this work, the formation of the secondary metallic Cr2N phase during the growth
is demonstrated to inhibit the observation of metal-insulator phase transition
in CrN thin films. When the Cr-flux during deposition is reduced below a
critical limit, epitaxial and stoichiometric CrN thin film is obtained that
reproducibly exhibits the phase transition. Annealing of the mixed-phase film
inside reducing NH3 environment converts the Cr2N into CrN, and a discontinuity
in the electrical resistivity at ~ 277 K appears which supports the underlying
hypothesis. A clear demonstration of the origin behind the controversy of the
metal-insulator transition in CrN thin films marks significant progress and
would enable its nanoscale device realization.",2201.07442v1
2022-01-22,High-throughput calculations combining machine learning to investigate the corrosion properties of binary Mg alloys,"Magnesium (Mg) alloys have shown great prospects as both structural and
biomedical materials, while poor corrosion resistance limits their further
application. In this work, to avoid the time-consuming and laborious experiment
trial, a high-throughput computational strategy based on first-principles
calculations is designed for screening corrosion-resistant binary Mg alloy with
intermetallics, from both the thermodynamic and kinetic perspectives. The
stable binary Mg intermetallics with low equilibrium potential difference with
respect to the Mg matrix are firstly identified. Then, the hydrogen adsorption
energies on the surfaces of these Mg intermetallics are calculated, and the
corrosion exchange current density is further calculated by a hydrogen
evolution reaction (HER) kinetic model. Several intermetallics, e.g. Y3Mg, Y2Mg
and La5Mg, are identified to be promising intermetallics which might
effectively hinder the cathodic HER. Furthermore, machine learning (ML) models
are developed to predict Mg intermetallics with proper hydrogen adsorption
energy employing work function (W_f) and weighted first ionization energy
(WFIE). The generalization of the ML models is tested on five new binary Mg
intermetallics with the average root mean square error (RMSE) of 0.11 eV. This
study not only predicts some promising binary Mg intermetallics which may
suppress the galvanic corrosion, but also provides a high-throughput screening
strategy and ML models for the design of corrosion-resistant alloy, which can
be extended to ternary Mg alloys or other alloy systems.",2201.09059v1
2019-10-17,High electrical conductivity in the epitaxial polar metals LaAuGe and LaPtSb,"Polar metals are an intriguing class of materials that simultaneously host
free carriers and polar structural distortions. Despite the name ""polar metal,""
however, most well-studied polar metals are poor electrical conductors. Here,
we demonstrate the molecular beam epitaxial (MBE) growth of LaPtSb and LaAuGe,
two polar metal compounds whose electrical resistivity is an order of magnitude
lower than the well studied oxide polar metals. These materials belong to a
broad family of $ABC$ intermetallics adopting the stuffed wurtzite structure,
also known as hexagonal Heusler compounds. Scanning transmission electron
microscopy (STEM) reveals a polar structure with unidirectionally buckled $BC$
(PtSb, AuGe) planes. Magnetotransport measurements demonstrate good metallic
behavior with low residual resistivity ($\rho_{LaAuGe}=59.05$
$\mu\Omega\cdot$cm and $\rho_{LaAPtSb}=27.81$ $\mu\Omega\cdot$cm at 2K) and
high carrier density ($n_h\sim 10^{21}$ cm$^{-3}$). Photoemission spectroscopy
measurements confirm the band metallicity and are in quantitative agreement
with density functional theory (DFT) calculations. Through DFT-Chemical
Pressure and Crystal Orbital Hamilton Population analyses, the atomic packing
factor is found to support the polar buckling of the structure, though the
degree of direct interlayer $B-C$ bonding is limited by repulsion at the $A-C$
contacts. When combined with insulating hexagonal Heuslers, these materials
provide a new platform for fully epitaxial, multiferroic heterostructures.",1910.07685v1
2024-02-06,Physics-based Modeling of Pulse and Relaxation of High-rate Li/CF$_{x}$-SVO batteries in Implantable Medical Devices,"We present a physics-based model that accurately predicts the performance of
Medtronic's implantable medical device battery lithium/carbon monofluoride
(CF$_x$) - silver vanadium oxide (SVO) under both low-rate background
monitoring and high-rate pulsing currents. The distinct properties of multiple
active materials are reflected by parameterizing their thermodynamics,
kinetics, and mass transport properties separately. Diffusion limitations of
Li$^+$ in SVO are used to explain cell voltage transient behavior during pulse
and post-pulse relaxation. We also introduce change in cathode electronic
conductivity, Li metal anode surface morphology, and film resistance buildup to
capture evolution of cell internal resistance throughout multi-year electrical
tests. We share our insights on how the Li$^+$ redistribution process between
active materials can restore pulse capability of the hybrid electrode, allow
CF$_x$ to indirectly contribute to capacity release during pulsing, and affect
the operation protocols and design principles of batteries with other hybrid
electrodes. We also discuss additional complexities in porous electrode model
parameterization and electrochemical characterization techniques due to
parallel reactions and solid diffusion pathways across active materials. We
hope our models implemented in the Hybrid Multiphase Porous Electrode Theory
(Hybrid-MPET) framework can complement future experimental research and
accelerate development of multi-active material electrodes with targeted
performance.",2402.03677v1
2020-04-25,Reconciliation of experiments and theory on transport properties of iron and the geodynamo,"The amount of heat transport from the core, which constrains the dynamics and
thermal evolution of the region, depends on the transport properties of iron.
Ohta et al.(2016) and Konopkova et al.(2016) measured electrical resistivity
and thermal conductivity of iron, respectively, in laser-heated diamond anvil
cells (DACs) at relevant Earth's core pressure-temperature (P-T) conditions,
and obtained dramatically contradictory results. Here we measure the electrical
resistivity of hcp-iron up to ~170 GPa and ~3,000 K using a four-probe van der
Pauw method coupled with homogeneous flat-top laser-heating in a DAC. We also
compute its electrical and thermal conductivity by first-principles methods
including electron-phonon and electron-electron scattering. We find that the
measured resistivity of hcp-iron increases almost linearly with increasing
temperature, and is consistent with current first-principles computations. The
proportionality coefficient between resistivity and thermal conductivity (the
Lorenz number) in hcp-iron differs from the ideal value (2.44*10^-8 W Omega
K^-2), so a non-ideal Lorenz number of ~(2.0-2.1)*10^-8 W Omega K^-2 is used to
convert the experimental resistivity to the thermal conductivity of hcp-Fe at
high P-T. The results constrain the resistivity and thermal conductivity of
hcp-iron to ~80(5) u Omega cm and ~100(10) W/mK, respectively, at conditions
near core-mantle boundary. Our results indicate an adiabatic heat flow of
~10(1) TW through the core-mantle boundary for a liquid Fe alloy outer core,
supporting a present-day geodynamo driven by thermal convection through the
core's secular cooling and by compositional convection through the latent heat
and gravitational energy during the inner core's solidification.",2004.12035v1
2020-08-26,"Understanding the role of Ca segregation on thermal stability, electrical resistivity and mechanical strength of nanostructured aluminum","Achieving a combination of high mechanical strength and high electrical
conductivity in low-weight Al alloys requires a full understanding of the
relationships between nanoscaled features and physical properties. Grain
boundary strengthening through grain size reduction offers some interesting
possibilities but is limited by thermal stability issues. Zener pinning by
stable nanoscaled particles or grain boundary segregation are well-known
strategies for stabilizing grain boundaries. In this study, the Al-Ca system
has been selected to investigate the way segregation affects the combination of
mechanical strength and electrical resistivity. For this purpose, an Al-Ca
composite material was severely deformed by high-pressure torsion to achieve a
nanoscaled structure with a mean grain size of only 25 nm. X-ray diffraction,
transmission electron microscopy and atom probe tomography data revealed that
the fcc Ca phase was dissolved for large levels of plastic deformation leading
mainly to Ca segregations along crystalline defects. The resulting
microhardness of about 300 HV is much higher than predictions based on Hall and
Petch Law and is attributed to limited grain boundary mediated plasticity due
to Ca segregation. The electrical resistivity is also much higher than that
expected for nanostructured Al. The main contribution comes from Ca
segregations that lead to a fraction of electrons reflected or trapped by grain
boundaries twice larger than in pure Al. The two-phase state was investigated
by in-situ and ex-situ microscopy after annealing at 200{\textdegree}C for 30
min, where precipitation of nanoscaled Al4Ca particles occurred and the mean
grain size reached 35 nm. Annealing also significantly decreased electrical
resistivity, but it remained much higher than that of nanostructured pure Al,
due to Al/Al4Ca interfaces that reflect or trap more than 85% of electrons.",2008.11405v1
2021-02-15,"High-entropy van der Waals materials formed from mixed metal dichalcogenides, halides and phosphorus trisulfides","The charge, spin, and composition degrees of freedom in high-entropy alloy
endow it with tunable valence and spin states, infinite combinations and
excellent mechanical performance. Meanwhile, the stacking, interlayer, and
angle degrees of freedom in van der Waals material bring it with exceptional
features and technological applications. Integration of these two distinct
material categories while keeping their merits would be tempting. Based on this
heuristic thinking, we design and explore a new range of materials (i.e.,
dichalcogenides, halides and phosphorus trisulfides) with multiple metallic
constitutions and intrinsic layered structure, which are coined as high-entropy
van der Waals materials. Millimeter-scale single crystals with homogeneous
element distribution can be efficiently acquired and easily exfoliated or
intercalated in this materials category. Multifarious physical properties like
superconductivity, magnetic ordering, metal-insulator transition and corrosion
resistance have been exploited. Further research based on the concept of
high-entropy van der Waals materials will enrich the high-throughput design of
new systems with intriguing properties and practical applications.",2102.07493v2
2014-12-01,Conventional superconductivity at 190 K at high pressures,"The highest critical temperature of superconductivity Tc has been achieved in
cuprates: 133 K at ambient pressure and 164 K at high pressures. As the nature
of superconductivity in these materials is still not disclosed, the prospects
for a higher Tc are not clear. In contrast the Bardeen-Cooper-Schrieffer (BCS)
theory gives a clear guide for achieving high Tc: it should be a favorable
combination of high frequency phonons, strong coupling between electrons and
phonons, and high density of states. These conditions can be fulfilled for
metallic hydrogen and covalent hydrogen dominant compounds. Numerous followed
calculations supported this idea and predicted Tc=100-235 K for many hydrides
but only moderate Tc~17 K has been observed experimentally. Here we found that
sulfur hydride transforms at P~90 GPa to metal and superconductor with Tc
increasing with pressure to 150 K at ~200 GPa. This is in general agreement
with recent calculations of Tc~80 K for H2S. Moreover we found
superconductivity with Tc~190 K in a H2S sample pressurized to P>150 GPa at
T>220 K. This superconductivity likely associates with the dissociation of H2S,
and formation of SHn (n>2) hydrides. We proved occurrence of superconductivity
by the drop of the resistivity at least 50 times lower than the copper
resistivity, the decrease of Tc with magnetic field, and the strong isotope
shift of Tc in D2S which evidences a major role of phonons in the
superconductivity. H2S is a substance with a moderate content of hydrogen
therefore high Tc can be expected in a wide range of hydrogen-contain
materials. Hydrogen atoms seem to be essential to provide the high frequency
modes in the phonon spectrum and the strong electron-phonon coupling.",1412.0460v1
2021-04-12,High-speed ionic synaptic memory based on two-dimensional titanium carbide MXene,"Synaptic devices with linear high-speed switching can accelerate learning in
artificial neural networks (ANNs) embodied in hardware. Conventional resistive
memories however suffer from high write noise and asymmetric conductance
tuning, preventing parallel programming of ANN arrays as needed to surpass
conventional computing efficiency. Electrochemical random-access memories
(ECRAMs), where resistive switching occurs by ion insertion into a redox-active
channel address these challenges due to their linear switching and low noise.
ECRAMs using two-dimensional (2D) materials and metal oxides suffer from slow
ion kinetics, whereas organic ECRAMs enable high-speed operation but face
significant challenges towards on-chip integration due to poor temperature
stability of polymers. Here, we demonstrate ECRAMs using 2D titanium carbide
(Ti3C2Tx) MXene that combines the high speed of organics and the integration
compatibility of inorganic materials in a single high-performance device. Our
ECRAMs combine the speed, linearity, write noise, switching energy and
endurance metrics essential for parallel acceleration of ANNs, and importantly,
they are stable after heat treatment needed for back-end-of-line integration
with Si electronics. The high speed and performance of these ECRAMs introduces
MXenes, a large family of 2D carbides and nitrides with more than 30
compositions synthesized to date, as very promising candidates for devices
operating at the nexus of electrochemistry and electronics.",2104.05396v4
2022-12-06,Novel superhard structures of high-pressure C-N compounds,"Through machine learning force field accelerated structure search combined
with first-principles calculations, we have studied the structures of new C-N
compounds with different stoichiometric ratios, and found twelve new superhard
C-N compounds, the energies of these structures are similar to c-C3N4 , which
is possibly synthesized by high pressure experiment, the XRD of Pa-3(C4N)
P3(C4N) and C2/m(C2N) are consistent with previous experimental data and can be
used as the structural candidate. According to the macro hardness model, they
are all superhard structures, with Vickers hardness over 40GPa, even, the
hardness of Pa-3 (C4N) as high as 82.2GPa, and Pa-3 (C4N) combines high tensile
and shear resistance. Compared with the hardness calculated by macro hardness
model and bond resistance model, we obtained the relationship between the
hardness and chemical concentration of C-N compounds under the two models,
besides that, we also calculated the fracture toughness of these structures.
According to Niu's model, P2_1/c(C4N) has the best fracture toughness, which is
higher than WC in calculation, This also indicated the superior mechanical
properties of the novel C-N compounds. Moreover, for nitrogen-rich structures,
they have the potential to be used as high energy density, the energy density
of Pa-3(CN3), P-3c1 (CN4), and I-42d (CN4) are 7.076kJ/g, 7.742kJ/g and
8.045kJ/g, which is close or higher than CL-20, therefore, the C-N compounds
synthesized under high pressure have great potential as ideally superhard
materials and high energy density materials(HEDMs).",2212.03009v3
2004-03-19,Influence of intermartensitic transitions on transport properties of Ni2.16Mn0.84Ga alloy,"Magnetic, transport, and x-ray diffraction measurements of ferromagnetic
shape memory alloy Ni$_{2.16}$Mn$_{0.84}$Ga revealed that this alloy undergoes
an intermartensitic transition upon cooling, whereas no such a transition is
observed upon subsequent heating. The difference in the modulation of the
martensite forming upon cooling from the high-temperature austenitic state
[5-layered (5M) martensite], and the martensite forming upon the
intermartensitic transition [7-layered (7M) martensite] strongly affects the
magnetic and transport properties of the alloy and results in a large thermal
hysteresis of the resistivity $\rho$ and magnetization $M$. The
intermartensitic transition has an especially marked influence on the transport
properties, as is evident from a large difference in the resistivity of the 5M
and 7M martensite, $(\rho_{\mathrm{5M}} - \rho_{\mathrm{7M}})/\rho
_{\mathrm{5M}} \approx 15%$, which is larger than the jump of resistivity at
the martensitic transition from the cubic austenitic phase to the monoclinic 5M
martensitic phase. We assume that this significant difference in $\rho$ between
the martensitic phases is accounted for by nesting features of the Fermi
surface. It is also suggested that the nesting hypothesis can explain the
uncommon behavior of the resistivity at the martensitic transition, observed in
stoichiometric and near-stoichiometric Ni-Mn-Ga alloys.",0403495v1
2004-10-10,Ultrathin epitaxial graphite: 2D electron gas properties and a route toward graphene-based nanoelectronics,"We have produced ultrathin epitaxial graphite films which show remarkable 2D
electron gas (2DEG) behavior. The films, composed of typically 3 graphene
sheets, were grown by thermal decomposition on the (0001) surface of 6H-SiC,
and characterized by surface-science techniques. The low-temperature
conductance spans a range of localization regimes according to the structural
state (square resistance 1.5 kOhm to 225 kOhm at 4 K, with positive
magnetoconductance). Low resistance samples show characteristics of
weak-localization in two dimensions, from which we estimate elastic and
inelastic mean free paths. At low field, the Hall resistance is linear up to
4.5 T, which is well-explained by n-type carriers of density 10^{12} cm^{-2}
per graphene sheet. The most highly-ordered sample exhibits Shubnikov - de Haas
oscillations which correspond to nonlinearities observed in the Hall
resistance, indicating a potential new quantum Hall system. We show that the
high-mobility films can be patterned via conventional lithographic techniques,
and we demonstrate modulation of the film conductance using a top-gate
electrode. These key elements suggest electronic device applications based on
nano-patterned epitaxial graphene (NPEG), with the potential for large-scale
integration.",0410240v1
2005-04-29,"Electromigration in thin tunnel junctions with ferromagnetic/nonmagnetic: nanoconstrictions, local heating, and direct and wind forces","Current Induced Resistance Switching (CIS) was recently observed in thin
tunnel junctions with ferromagnetic (FM) electrodes \emph{i.e} FM/I/FM. This
effect was attributed to electromigration of metallic atoms in
nanoconstrictions in the insulating barrier (I). Here we study how the CIS
effect is influenced by a thin non-magnetic (NM) Ta layer, deposited just below
the AlO$_x$ insulating barrier in tunnel junctions of the type FM/NM/I/FM
(FM=CoFe). Enhanced resistance switching occurs with increasing maximum applied
current ($\Imax$), until a plateau of constant CIS is reached for $\Imax\sim65$
mA (CIS$\sim$60%) and above. However, such high electrical currents also lead
to a large ($\sim$9%) irreversible resistance decrease, indicating barrier
degradation. Anomalous voltage-current characteristics with negative derivative
were also observed near $\pm\Imax$ and this effect is here attributed to
heating in the tunnel junction. One observes that the current direction for
which resistance switches in FM/NM/I/FM (clockwise) is opposite to that of
FM/I/FM tunnel junctions (anti-clockwise). This effect will be discussed in
terms of a competition between the electromigration contributions due to the so
called direct and wind forces. It will be shown that the direct force is likely
to dominate electromigration in the Ta (NM) layers, while the wind contribution
likely dominates in the CoFe (FM) layers.",0504772v6
2007-02-05,Effect of Ir substitution in the ferromagnetic superconductor RuSr2GdCu2O8,"A detailed study of the effect caused by the partial substitution of Ru by Ir
on the magnetic and superconducting properties of the ruthenocuprate
Ru(1-x)Ir(x)Sr2GdCu2o8; 0 <= x <= 0.10; is presented. The combined experimental
results of structural, electrical, and magnetic measurements indicate that Ir
substitutes Ru for x <= 0.10 with no significant structural distortions.
Ir-doping gradually suppresses both the magnetic and the superconducting
states. However, all samples were observed to attain the zero-resistance state
at temperatures >= 2 K up to the highest applied magnetic field of 18 T. The
resistive upper-critical field Hc2 as a function of temperature has been
determined for these polycrystalline samples. Values of Hc2(0) were found to be
\~ 52 T, and weakly dependent on the Ir concentration. We have also observed
that the superconducting transition width decreases and the slope of the
resistive transition increases with increasing Ir doping, a feature which is
much more pronounced at high applied magnetic fields. The double-peak structure
observed in the derivative of the resistive curves has been related to an
inhomogeneous nature of the physical grains which is enhanced due to the Ru
substitution by Ir. This indicates that the Josephson-junction-array (JJA)
model seems to be appropriated to describe the superconducting state in these
ruthenocuprates. The low temperature rho(T) data along with the determined
vortex thermal activation energy are consistent with a 2D vortex dynamics in
these materials.",0702078v1
1997-04-04,Radiation damage to neutron and proton irradiated GaAs particle detectors,"The radiation damage in 200 um thick Schottky diodes made on semi-insulating
(SI) undoped GaAs Liquid Encapsulated Czochralski (LEC) bulk material with
resistivities between 0.4 and 8.9*10E7 Ohm*cm were studied using
alpha-spectroscopy, signal response to minimum ionising particles (MIP), I-V
and CV-measurements. The results have been analysed to investigate the
influence of the substrate resistivity on the detector performance after
neutron and proton irradiation. The leakage current density, signal response to
alpha-particles and MIPs show a strong dependence on the resistivity before and
after irradiation. An observed decrease of the electron mean free drift length
before and after irradiation with increasing substrate resistivity can be
explained by a model involving the different ionisation ratios of defects,
which are introduced by the irradiation. Comparison of the radiation damage due
to neutrons and protons gives a hardness factor of 7+-0.9 for 24 GeV/c protons.
The best detectors show a response to MIPs of 5250 e- at 200 V reverse bias
after a irradiation level of 2*10E14 p/cm^2.",9704002v1
2003-04-10,Students' Understanding of Direct Current Resistive Electrical Circuits,"Research has shown that both high school and university students' reasoning
patterns regarding direct current resistive electric circuits often differ from
the currently accepted explanations. At present, there are no standard
diagnostic examinations in electric circuits. Two versions of a diagnostic
instrument called Determining and Interpreting Resistive Electric circuits
Concepts Tests (DIRECT) were developed, each consisting of 29 questions. The
information provided by the exam provides classroom instructors a means with
which to evaluate the progress and conceptual difficulties of their students
and their instructional methods. It can be used to evaluate curricular packages
and/or other supplemental materials for their effectiveness in overcoming
students' conceptual difficulties. The analyses indicate that students,
especially females, tend to hold multiple misconceptions, even after
instruction. During interviews, the idea that the battery is a constant source
of current was used most often in answering the questions. Students tended to
focus on current in solving the problems and to confuse terms, often assigning
the properties of current to voltage and/or resistance. Results indicated that
students do not have a clear understanding of the underlying mechanisms of
electric circuit phenomena. On the other hand, students were able to translate
easily from a ""realistic"" representation of a circuit to the corresponding
schematic diagram.",0304040v2
2013-05-15,"Structural ordering driven anisotropic magnetoresistance, anomalous Hall resistance and its topological overtones in full-Heusler Co2MnSi thin films","We report the evolution of crystallographic structure, magnetic ordering and
electronic transport in thin films of full-Heusler alloy Co$_2$MnSi deposited
on (001) MgO with annealing temperatures ($T_A$). By increasing the $T_A$ from
300$^\circ$C to 600$^\circ$C, the film goes from a disordered nanocrystalline
phase to $B2$ ordered and finally to the $L2_1$ ordered alloy. The saturation
magnetic moment improves with structural ordering and approaches the
Slater-Pauling value of $\approx 5.0 \mu_B$ per formula unit for $T_A$ =
600$^\circ$C. At this stage the films are soft magnets with coercive and
saturation fields as low as $\approx$ 7 mT and 350 mT, respectively. Remarkable
effects of improved structural order are also seen in longitudinal resistivity
($\rho_{xx}$) and residual resistivity ratio. A model based upon electronic
transparency of grain boundaries illucidates the transition from a state of
negative $d\rho/dT$ to positive $d\rho/dT$ with improved structural order. The
Hall resistivity ($\rho_{xy}$) derives contribution from the normal scattering
of charge carriers in external magnetic field, the anomalous effect originating
from built-in magnetization and a small but distinct topological Hall effect in
the disordered phase. The carrier concentration ($n$) and mobility ($\mu$) have
been extracted from the high field $\rho_{xy}$ data. The highly ordered films
are characterized by $n$ and $\mu$ of 1.19$\times$ 10$^{29}$ m$^{-3}$ and 0.4
cm$^2V^{-1}s^{-1}$ at room temperature. The dependence of $\rho_{xy}$ on
$\rho_{xx}$ indicates the dominance of skew scattering in our films, which
shows a monotonic drop on raising the $T_A$. The topological Hall effect is
analyzed for the films annealed at 300$^\circ$C. ......",1305.3453v1
2013-05-21,Observation of even denominator fractional quantum Hall effect in suspended bilayer graphene,"We investigate low-temperature magneto-transport in recently developed,
high-quality multi-terminal suspended bilayer graphene devices, enabling the
independent measurement of the longitudinal and transverse resistance. We
observe clear signatures of the fractional quantum Hall effect, with different
states that are either fully developed, and exhibit a clear plateau in the
transverse resistance with a concomitant dip in longitudinal resistance, or
incipient, and exhibit only a longitudinal resistance minimum. All observed
states scale as a function of filling factor nu, as expected. An unprecedented
even-denominator fractional state is observed at nu = -1/2 on the hole side,
exhibiting a clear plateau in Rxy quantized at the expected value of 2h/e^2
with a precision of ~0.5%. Many of our observations, together with a recent
electronic compressibility measurement performed in graphene bilayers on
hexagonal boron-nitride (hBN) substrates, are consistent with a recent theory
that accounts for the effect of the degeneracy between the N=0 and N=1 Landau
levels in the fractional quantum Hall effect, and predicts the occurrence of a
Moore-Read type nu = -1/2 state. Owing to the experimental flexibility of
bilayer graphene --which has a gate-dependent band structure, can be easily
accessed by scanning probes, and can be contacted with materials such as
superconductors--, our findings offer new possibilities to explore the
microscopic nature of even-denominator fractional quantum Hall effect.",1305.4761v3
2014-11-07,Resistance noise at the metal-insulator transition in thermochromic VO2 films,"Thermochromic VO2 films were prepared by reactive DC magnetron sputtering
onto heated sapphire substrates and were used to make 100-nm-thick samples that
were 10 {\mu}m wide and 100 micron long. The resistance of these samples
changed by a factor of about 2000 in the 50 < Ts < 70 C range of temperature Ts
around the ""critical"" temperature Tc between a low-temperature semiconducting
phase and a high-temperature metallic-like phase of VO2. Power density spectra
S(f) were extracted for resistance noise around Tc and demonstrated unambiguous
1/f behavior. Data on S(10Hz)/Rs^2 scaled as Rs^x, where Rs is sample
resistance; the noise exponent x was -2.6 for Ts < Tc and +2.6 for Ts > Tc.
These exponents can be reconciled with the Pennetta-Trefan-Reggiani theory [C.
Pennetta, G. Trefanan, and L. Reggiani, Phys. Rev. Lett. 85, 5238 (2000)] for
lattice percolation with switching disorder ensuing from random defect
generation and healing in steady state. Our work hence highlights the dynamic
features of the percolating semiconducting and metallic-like regions around Tc
in thermochromic VO2 films.",1411.2026v1
2015-02-18,Anomalous electrical conductivity in rapidly crystallized Cu${}_{50-x}$Zr${}_{x}$ (x = 50 - 66.6) alloys,"Cu${}_{50-x}$Zr${}_{x}$ (x = 50, 54, 60 and 66.6) polycrystalline alloys were
prepared by arc-melting. The crystal structure of the ingots has been examined
by X-ray diffraction. Non-equilibrium martensitic phases with monoclinic
structure were detected in all the alloys except Cu${}_{33.4}$Zr${}_{66.6}$.
Temperature dependencies of electrical resistivity in the temperature range of
T = 4 - 300 K have been measured as well as room temperature values of Hall
coefficients and thermal conductivity. Electrical resistivity demonstrates
anomalous behavior. At the temperatures lower than 20 K, their temperature
dependencies are non-monotonous with pronounced minima. At elevated
temperatures they have sufficiently non-linear character which cannot be
described within framework of the standard Bloch--Gr\""{u}neisen model. We
propose generalized Bloch--Gr\""{u}neisen model with variable Debye temperature
which describes experimental resistivity dependencies with high accuracy. We
found that both the electrical resistivity and the Hall coefficients reveal
metallic-type conductivity in the Cu-Zr alloys. The estimated values of both
the charge carrier mobility and the phonon contribution to thermal and electric
conductivity indicate the strong lattice defects and structure disorder.",1502.05297v1
2016-05-24,Thermoelectric transport in the layered Ca$_3$Co$_{4-x}$Rh$_x$O$_9$ single crystals,"We have examined an isovalent Rh substitution effect on the transport
properties of the thermoelectric oxide Ca$_3$Co$_{4}$O$_9$ using
single-crystalline form. With increasing Rh content $x$, both the electrical
resistivity and the Seebeck coefficient change systematically up to $x=0.6$ for
Ca$_3$Co$_{4-x}$Rh$_{x}$O$_9$ samples. In the Fermi-liquid regime where the
resistivity behaves as $\rho=\rho_0+AT^2$ around 120 K, the $A$ value decreases
with increasing Rh content, indicating that the correlation effect is weakened
by Rh $4d$ electrons with extended orbitals. We find that, in contrast to such
a weak correlation effect observed in the resistivity of Rh-substituted
samples, the low-temperature Seebeck coefficient is increased with increasing
Rh content, which is explained with a possible enhancement of a pseudogap
associated with the short-range order of spin density wave. In high-temperature
range above room temperature, we show that the resistivity is largely
suppressed by Rh substitution while the Seebeck coefficient becomes almost
temperature-independent, leading to a significant improvement of the power
factor in Rh-substituted samples. This result is also discussed in terms of the
differences in the orbital size and the associated spin state between Co $3d$
and Rh $4d$ electrons.",1605.07682v1
2017-10-25,Engineering physics of superconducting hot-electron bolometer mixers,"Superconducting hot-electron bolometers are presently the best performing
mixing devices for the frequency range beyond 1.2 THz, where good quality
superconductor-insulator-superconductor (SIS) devices do not exist. Their
physical appearance is very simple: an antenna consisting of a normal metal,
sometimes a normal metal-superconductor bilayer, connected to a thin film of a
narrow, short superconductor with a high resistivity in the normal state. The
device is brought into an optimal operating regime by applying a dc current and
a certain amount of local- oscillator power. Despite this technological
simplicity its operation has been found to be controlled by many different
aspects of superconductivity, all occurring simultaneously. A core ingredient
is the understanding that there are two sources of resistance in a
superconductor: a charge conversion resistance occurring at an
normal-metal-superconductor interface and a resistance due to time- dependent
changes of the superconducting phase. The latter is responsible for the actual
mixing process in a non-uniform superconducting environment set up by the
bias-conditions and the geometry. The present understanding indicates that
further improvement needs to be found in the use of other materials with a
faster energy-relaxation rate. Meanwhile several empirical parameters have
become physically meaningful indicators of the devices, which will facilitate
the technological developments.",1710.09136v1
2018-02-13,Multiple-Modes Scanning Probe Microscopy Characterization of Copper doped Zinc Oxide (ZnO:Cu) Thin Films,"This paper presents multiple-modes Scanning Probe Microscopy (SPM) studies on
characterize resistance switching (RS), polarization rotation (PO) and surface
potential changes in copper doped ZnO (ZnO:Cu) thin films. The bipolar RS
behavior is confirmed by conductive Atomic Force Microscopy (c-AFM). The PO
with almost 180{\deg} phase angle is confirmed by using the vertical and
lateral Piezoresponse Force Microscopy (PFM). In addition, it elucidates that
obvious polarization rotation behavior can be observed in the sample with
increasing Cu concentration. Furthermore, correlation of the RS behavior with
PO behavior has been studied by performing various mode SPM measurements on the
same location. The electric field resulted from the opposite polarization
orientation are corresponded to the different resistance states. It is found
that the region with the polarization in downward direction has low resistance
state (LRS), whereas the region with upward polarization has high resistance
state (HRS). In addition, the Piezoresponse Force Spectroscopy (PFS) and
Switching Spectroscopy PFM (SS-PFM) measurements further confirm that the
existence of the built-in field due to the uncomplemented polarization may
affect the depletion region and hence contribute to the RS behavior. In
addition, Kelvin Probe Force Microscopy (KPFM) results show that, when
ZnO-based thin films is subjected to negative and then followed by positive
sample bias, injection charge limit current is dominated.",1802.04494v1
2019-02-11,Electrical percolation in metal wire network based strain sensors,"Metal wire networks rely on percolation paths for electrical conduction, and
by suitably introducing break-make junctions on a flexible platform, a network
can be made to serve as a resistive strain sensor. Several experimental designs
have been proposed using networks made of silver nanowires, carbon nanotubes
and metal meshes with high sensitivities. However, there is limited theoretical
understanding; the reported studies have taken the numerical approach and only
consider rearrangement of nanowires with strain, while the critical break-make
property of the sensor observed experimentally has largely been ignored.
Herein, we propose a generic geometrical based model and study distortion,
including the break-make aspect, and change in electrical percolation of the
network on applying strain. The result shows that when a given strain is
applied, wire segments below a critical angle with respect to the applied
strain direction end up breaking, leading to increased resistance of the
network. The percolation shows interesting attributes; the calculated
resistance increases linearly in the beginning and at a higher rate for higher
strains, consistent with the experimental findings. In a real scenario, the
strain direction need not necessarily be in the direction of measurement, and
therefore, strain value and its direction both are incorporated into the
treatment. The study reveals interesting anisotropic conduction features;
strain sensitivity is higher parallel to the strain, while strain range is
wider for perpendicular measurement. The percolation is also investigated on
direct microscopic images of metal networks to obtain resistance-strain
characteristics and identification of current percolation pathways. The
findings will be important for electrical percolation in general, particularly
in predicting characteristics and improvising metal network-based strain
sensors.",1902.03746v1
2019-12-16,Electrical Characterization of CIGS Thin Film Solar Cells by Two and Four-Wires Probe Technique,"The characterization of thin film solar cells is of huge importance for
obtaining high open circuit voltage and low recombination rates from the
interfaces or within the bulk of the main materials. Among the many electrical
characterization techniques, the two and four wire probe using the Cascade
instrument is of interest since the resistance of the wires, and the electrical
contacts can be excluded by the additional two wires in 4 wire probe
configuration. In this paper, both two and four-point probes configuration are
employed to characterize the CIGS chalcogenide thin film solar cells. The two
wire probe has been used to measure the current-voltage characteristics of the
cell which results in a huge internal resistance. Therefore, the four wire
connection are also used to eliminate the lead resistance to enhance the
characterization accuracy. The load resistance in the twowire probe diminishes
the photogenerated current density at smaller voltage ranges. In contrast, the
proposed four wire probe collects more current at higher voltages due to
enhanced carrier collection efficiency from contact electrodes. The current
conduction mechanism is also identified at every voltage region represented by
the value of the ideality factor of that voltage region.",2002.07391v1
2020-03-31,Design and Simulation of Memristor-Based Artificial Neural Network for Bidirectional Adaptive Neural Interface,"This article proposes a general approach to the simulation and design of a
multilayer perceptron (MLP) network on the basis of cross-bar arrays of
metal-oxide memristive devices. The proposed approach uses the ANNM theory,
tolerance theory, simulation methodology and experiment design. The tolerances
analysis and synthesis process is performed for the ANNM hardware
implementation on the basis of two arrays of memristive microdevices in the
original 16x16 cross-bar topology being a component of bidirectional adaptive
neural interface for automatic registration and stimulation of bioelectrical
activity of a living neuronal culture used in robotics control system. The ANNM
is trained for solving a nonlinear classification problem of stable information
characteristics registered in the culture grown on a multi-electrode array.
Memristive devices are fabricated on the basis of a newly engineered
Au/Ta/ZrO2(Y)/Ta2O5/TiN/Ti multilayer structure, which contains self-organized
interface oxide layers, nanocrystals and is specially developed to obtain
robust resistive switching with low variation of parameters. An array of
memristive devices is mounted into a standard metal-ceramic package and can be
easily integrated into the neurointerface circuit. Memristive devices
demonstrate bipolar switching of anionic type between the high-resistance state
and low-resistance state and can be programmed to set the intermediate
resistive states with a desired accuracy. The ANNM tuning, testing and control
are implemented by the FPGA-based control subsystem. All developed models and
algorithms are implemented as Python-based software.",2004.00154v1
2017-04-29,Wear-resistant thin films of MRI-230D-Mg alloy using plasma-driven electrolytic oxidation,"Wear resistant coatings were produced on a permanent mould cast MRI 230D Mg
alloy by (a) PEO in silicate based electrolyte, (b) PEO in phosphate based
electrolyte, (c) hybrid coatings of silicate PEO followed by laser surface
alloying (LSA) with Al and Al2O3, and (d) hybrid coatings of phosphate PEO
followed by LSA with Al and Al2O3. Microstructural characterization of the
coatings was carried out by scanning electron microscopy (SEM) and X(ray
diffraction. The tribological behavior of the coatings was investigated under
dry sliding condition using linearly reciprocating ball-on-flat wear test. Both
the PEO coatings exhibited a friction coefficient of about 0.8 and hybrid
coatings exhibited a value of about 0.5 against the AISI 52100 steel ball as
the friction partner, which were slightly reduced with the increase in applied
load. The PEO coatings sustained the test without failure at 2 N load but
failed at 5 N load due to micro-fracture caused by high contact stresses. The
hybrid coatings did not get completely worn off at 2 N load but were completely
removed exposing the substrate at 5 N load. The PEO coatings exhibited better
wear resistance than the hybrid coatings and silicate PEO coatings exhibited
better wear resistance than the phosphate PEO coatings. Both the PEO coatings
melted/decomposed on laser irradiation and all the hybrid coatings exhibited
similar microstructure and wear behavior irrespective of the nature of the
primary PEO coating or laser energies. SEM examination of worn surfaces
indicated abrasive wear combined with adhesive wear for all the specimens. The
surface of the ball exhibited a discontinuous transfer layer after the wear
test.",1705.00116v1
2018-08-01,Effect of multiband transport on charge carrier density fluctuations at the LaAlO$_3$/SrTiO$_3$ interface,"Multiband transport in superconductors is interesting both from an academic
as well as an application point of view. It has been postulated that interband
scattering can significantly affect the carrier dynamics in these materials. In
this article we present a detailed study of the electrical transport properties
of the high-mobility two-dimensional electron gas residing at the interface of
LaAlO$_3$/SrTiO$_3$, a prototypical multi-band superconductor. We show, through
careful measurements of the gate dependence of the magnetoresistance and
resistance fluctuations at ultra-low temperatures, that transport in the
superconducting regime of this system has contributions from two bands which
host carriers of very different characters. We identify a gate-voltage tunable
Lifshitz transition in the system and show that the resistance fluctuations
have strikingly different features on either side of it. At low carrier
densities, resistance noise is dominated by number-density fluctuations arising
from trapping-detrapping of charge carriers from defects in the underlying
SrTiO$_3$ substrate, characteristic of a single-band semiconductor. Above the
Lifshitz transition, the noise presumably originates from inter-band
scattering. Our work highlights the importance of inter-band scattering
processes in determining the transport properties of low-dimensional systems
and projects resistance fluctuation spectroscopy as a viable technique for
probing the charge carrier dynamics across a Lifshitz transition.",1808.00246v1
2016-09-06,Interlayer Transport through a Graphene / Rotated-Boron-Nitride / Graphene Heterostructure,"Interlayer electron transport through a graphene / hexagonal boron-nitride
(h-BN) / graphene heterostructure is strongly affected by the misorientation
angle $\theta$ of the h-BN with respect to the graphene layers with different
physical mechanisms governing the transport in different regimes of angle,
Fermi level, and bias. The different mechanisms and their resulting signatures
in resistance and current are analyzed using two different models, a
tight-binding, non-equilibrium Green function model and an effective continuum
model, and the qualitative features resulting from the two different models
compare well. In the large-angle regime ($\theta > 4^\circ$), the change in the
effective h-BN bandgap seen by an electron at the $K$ point of the graphene
causes the resistance to monotonically increase with angle by several orders of
magnitude reaching a maximum at $\theta = 30^\circ$. It does not affect the
peak-to-valley current ratios in devices that exhibit negative differential
resistance. In the small-angle regime ($\theta < 4^\circ$), Umklapp processes
open up new conductance channels that manifest themselves as non-monotonic
features in a plot of resistance versus Fermi level that can serve as
experimental signatures of this effect. For small angles and high bias, the
Umklapp processes give rise to two new current peaks on either side of the
direct tunneling peak.",1609.01369v1
2018-12-13,Search for power-efficient wide-range reversible resistance modulation of $VO_2$ single crystals,"The abrupt metal insulator transition in $VO_2$ is attracting considerable
interest from both fundamental and applicative angles. We report on DC I-V
characteristics measured on $VO_2$ single crystals in the two-probe
configuration at several ambient temperatures below the insulator-metal
transition. The insulator-mixed-metal-insulator transition is induced by Joule
heating above ambient temperature in the range of negative differential
resistivity (NDR). In this range the stability of V(I) is governed by the load
resistance $R_L$. Steady state I(V) is obtained for $R_L> |dV/dI|_{max}$ in the
NDR regime. For $R_L< |dV/dI|_{max}$ there is switching between initial and
final steady states associated with peaks in the Joule power, that are higher
the lower $R_L$ is. The peaks caused by steep switching are superfluous and
damaging the samples. On the other hand, the large $R_L$ needed for steady
state is the main power consumer in the circuit at high currents. The present
work is motivated by the need to avoid damaging switching in the NDR regime
while reducing the power consumption in the circuit. It is shown here that
large resistance modulation can be obtained under steady state conditions with
reduced power consumption by increasing the ambient temperature of the device
above room temperature.",1812.05702v1
2020-01-28,Pressure tuning of structural and magnetic transitions in EuAg$_4$As$_2$,"We report temperature dependent measurements of ambient pressure specific
heat, magnetic susceptibility, anisotropic resistivity and thermal expansion as
well as in-plane resistivity under pressure up to 20.8 kbar on single crystals
of EuAg$_4$As$_2$. Based on thermal expansion and in-plane electrical transport
measurements at ambient pressure this compound has two, first order, structural
transitions in 80 - 120 K temperature range. Ambient pressure specific heat,
magnetization and thermal expansion measurements show a cascade of up to seven
transitions between 8 and 16 K associated with the ordering of the Eu$^{2+}$
moments. In-plane electrical transport is able to detect more prominent of
these transitions: at 15.5, 9.9, and 8.7 K as well as a weak feature at 11.8 K
at ambient pressure. Pressure dependent electrical transport data show that the
magnetic transitions shift to higher temperatures under pressure, as does the
upper structural transition, whereas the lower structural transition is
suppressed and ultimately vanishes. A jump in resistivity, associated with the
upper structural transition, decreases under pressure with an extrapolated
disappearance (or a change of sign) by 30-35 kbar. In the 10 - 15 kbar range a
kink in the pressure dependence of the upper structural transition temperature
as well as the high and low temperature in-plane resistivities suggest that a
change in the electronic structure may occur in this pressure range. The
results are compared with the literature data for SrAg$_4$As$_2$.",2001.10574v1
2020-08-07,Dependable contact related parameter extraction in graphene-metal junctions,"The accurate extraction and the reliable, repeatable reduction of graphene -
metal contact resistance (R$_{C}$) are still open issues in graphene
technology. Here, we demonstrate the importance of following clear protocols
when extracting R$_{C}$ using the transfer length method (TLM). We use the
example of back-gated graphene TLM structures with nickel contacts, a
complementary metal oxide semiconductor compatible metal. The accurate
extraction of R$_{C}$ is significantly affected by generally observable Dirac
voltage shifts with increasing channel lengths in ambient conditions. R$_{C}$
is generally a function of the carrier density in graphene. Hence, the position
of the Fermi level and the gate voltage impact the extraction of R$_{C}$.
Measurements in high vacuum, on the other hand, result in dependable extraction
of R$_{C}$ as a function of gate voltage owing to minimal spread in Dirac
voltages. We further assess the accurate measurement and extraction of
important parameters like contact-end resistance, transfer length, sheet
resistance of graphene under the metal contact and specific contact resistivity
as a function of the back-gate voltage. The presented methodology has also been
applied to devices with gold and copper contacts, with similar conclusions.",2008.03218v1
2021-05-18,"On the role of boron, carbon and zirconium on hot cracking and creep resistance of additively manufactured polycrystalline superalloys","We investigate the hot cracking susceptibility and creep resistance of three
versions of a nickel-based superalloy with different contents of boron, carbon
and zirconium fabricated by laser powder bed fusion. Crack-free and creep
resistant components are achieved for alloys with boron, carbon and no
zirconium. We then rationalize this result by evaluating how boron, carbon and
zirconium are distributed at grain boundaries in the as-built and heat-treated
microstructures of an alloy containing all these elements. Observations are
conducted by scanning and transmission electron microscopy, and atom probe
tomography. In the as-built microstructure, boron, carbon and zirconium
segregate at high-angle grain boundaries as a result of solute partitioning to
the liquid and limited solid-state diffusion during solidification and cooling.
After heat-treatment, the amount of boron and carbon segregating at grain
boundaries increases significantly. In contrast, zirconium is not found at
grain boundaries but it partitions at the gamma' precipitates formed during the
heat treatment. The presence of zirconium at grain boundaries in the as-built
condition is known to be susceptible to enhance hot cracking, while its absence
in the heat-treated microstructure strongly suggests that this element has no
major effect on the creep resistance. Based on our observations, we propose
alloy design guidelines to at the same time avoid hot cracking during
fabrication and achieve the required creep performance after heat-treatment.",2105.08307v1
2021-07-13,"Reactivity of the Si(100)-2$\times$1-Cl surface with respect to PH$_3$, PCl$_3$, and BCl$_3$: Comparison with PH$_3$ on Si(100)-2$\times$1-H","Despite the interest in a chlorine monolayer on Si(100) as an alternative to
hydrogen resist for atomic-precision doping, little is known about its
interaction with dopant-containing molecules. We used the density functional
theory to evaluate whether a chlorine monolayer on Si(100) is suitable as a
resist for \ce{PH3}, \ce{PCl3}, and \ce{BCl3} molecules. We calculated reaction
pathways for \ce{PH3}, \ce{PCl3}, and \ce{BCl3} adsorption on a bare and
Cl-terminated Si(100)-2$\times$1 surface, as well as for \ce{PH3} adsorption on
H-terminated Si(100)-2$\times$1, which is widely used in current technologies
for atomically precise doping of Si(100) with phosphorus. It was found that the
Si(100)-2$\times$1-Cl surface has a higher reactivity towards phosphine than
Si(100)-2$\times$1-H, and, therefore, unpatterned areas are less protected from
undesirable incorporation of \ce{PH3} fragments. On the contrary, the
resistance of the Si(100)-2$\times$1-Cl surface against the chlorine-containing
molecules turned out to be very high. Several factors influencing reactivity
are discussed. The results reveal that phosphorus and boron trichlorides are
well-suited for doping a patterned Cl-resist by donors and acceptors,
respectively.",2107.06168v1
2022-10-18,In-plane electronic anisotropy revealed by interlayer resistivity measurements on the iron-based superconductor parent compound CaFeAsF,"Both cuprates and iron-based superconductors demonstrate nematicity, defined
as the spontaneous breaking of rotational symmetry in electron systems. The
nematic state can play a role in the high-transition-temperature
superconductivity of these compounds. However, the microscopic mechanism
responsible for the transport anisotropy in iron-based compounds remains
debatable. Here, we investigate the electronic anisotropy of CaFeAsF by
measuring its interlayer resistivity under magnetic fields with varying field
directions. Counterintuitively, the interlayer resistivity was larger in the
longitudinal configuration ($B \parallel I \parallel c$) than in the transverse
one ($B \perp I \parallel c$). The interlayer resistivity exhibited a so-called
coherence peak under in-plane fields and was highly anisotropic with respect to
the in-plane field direction. At $T$ = 4 K and $B$ = 14 T, the
magnetoresistance $\Delta\rho/\rho_0$ was seven times larger in the $B
\parallel b_o$ than in the $B \parallel a_o$ configuration. Our theoretical
calculations of the conductivity based on the first-principles electronic band
structure qualitatively reproduced the above observations but underestimated
the magnitudes of the observed features. The proposed methodology can be a
powerful tool for probing the nematic electronic state in various materials.",2210.09533v2
2023-11-15,Transport properties of strongly correlated Fermi systems,"In our short review, we consider the transport properties of strongly
correlated Fermi systems like heavy fermion metals and high-$T_c$
superconductors. Their transport properties are defined by strong
inter-particle interaction forming flat bands in these compounds. Indeed, in
contrast to the behavior of the transport properties of conventional metals,
the strongly correlated compounds exhibit the linear in temperature
resistivity, $\rho(T)\propto T$. We analyze the magnetoresistance and show that
it under the application of magnetic field becomes negative. It is shown that
near a quantum phase transition, when the density of electronic states
diverges, semiclassical physics remains applicable to describe the resistivity
$\rho$ of strongly correlated metals due to the presence of a transverse
zero-sound collective mode, representing the phonon mode in solids. We
demonstrate that when $T$ exceeds the extremely low Debye temperature $T_D$,
the resistivity $\rho(T)$ changes linearly with $T$, since the mechanism of
formation of the $T$-dependence $\rho(T)$ is similar electron-phonon mechanism,
which predominates at high temperatures in ordinary metals. Thus, in the region
of $T$-linear resistance, electron-phonon scattering leads to a lifetime of
$\tau$ quasiparticles practically independent of the material, which is
expressed as the ratio of the Planck constant $\hbar$ to the Boltzmann constant
constant $k_B$, $T\tau\sim \hbar/k_B$. We explain that due to the
non-Fermi-liquid behavior the real part of the frequency-dependent optical
conductivity $\sigma^R_{opt}(\omega)$ exhibits a scaling behavior, and
demonstrates the unusual power law behavior
$\sigma^R_{opt}(\omega)\propto\omega^{-1}$, rather than the well-known one
shown by conventional metals, $\sigma^R_{opt}(\omega)\propto\omega^{-2}$.",2311.08974v1
2024-01-26,First-principles methodology for studying magnetotransport in narrow-gap semiconductors: an application to Zirconium Pentatelluride ZrTe5,"The origin of anomalous resistivity peak and accompanied sign reversal of
Hall resistivity of ZrTe$_5$ has been under debate for a long time. Although
various theoretical models have been proposed to account for these intriguing
transport properties, a systematic study from first principles view is still
lacking. In this work, we present a first principles calculation combined with
Boltzmann transport theory to investigate the transport properties in
narrow-gap semiconductors at different temperatures and doping densities within
the relaxation time approximation. Regarding the sensitive
temperature-dependent chemical potential and relaxation time of semiconductors,
we take proper approximation to simulate these two variables, and then
comprehensively study the transport properties of ZrTe$_5$ both in the absence
and presence of an applied magnetic field. Without introducing topological
phases and correlation interactions, we qualitatively reproduced crucial
features observed in experiments, including zero-field resistivity anomaly,
nonlinear Hall resistivity with sign reversal, and non-saturating
magnetoresistance at high temperatures. Our calculation allows a systematic
interpretation of the observed properties in terms of multi-carrier and Fermi
surface geometry. Our method can be extended to other narrow-gap semiconductors
and further pave the way to explore interesting and novel transport properties
of this field.",2401.15151v1
2016-12-09,Characterization of Fully Depleted CMOS Active Pixel Sensors on High Resistivity Substrates for Use in a High Radiation Environment,"Depleted CMOS active sensors (DMAPS) are being developed for high-energy
particle physics experiments in high radiation environments, such as in the
ATLAS High Luminosity Large Hadron Collider (HL-LHC). Since charge collection
by drift is mandatory for harsh radiation environment, the application of high
bias voltage to high resistive sensor material is needed. In this work, a
prototype of a DMAPS was fabricated in a 150nm CMOS process on a substrate with
a resistivity of >2 k{\Omega}cm that was thinned to 100 {\mu}m. Full depletion
occurs around 20V, which is far below the breakdown voltage of 110 V. A readout
chip has been attached for fast triggered readout. Presented prototype also
uses a concept of sub-pixel en/decoding three pixels of the prototype chip are
readout by one pixel of the readout chip. Since radiation tolerance is one of
the largest concerns in DMAPS, the CCPD_LF chip has been irradiated with X-rays
and neutrons up to a total ionization dose of 50 Mrad and a fluence of
10E15neq/cm2, respectively.",1612.03154v1
2022-03-14,Photomultipliers as High Rate Radiation-Resistant In-Situ Sensors in Future Experiments,"In the Energy Frontier we suggest developing high rate (100 MHz) finely
segmented forward calorimetry preradiators with time resolution <50 ps which
will survive the first 1-2 Lint of incident high radiation doses, protecting
forward calorimeters 3<y<6; less than 5 degrees to the beam behind them from
radiation damage, with high granularity, high rate capability and 30ps time
resolution (4D calorimetry) providing lepton and photon ID and measurement. In
the Intensity Frontier beam particle selection, such as tagged neutrino and
kaon beams, and lepton violation experiments with muons require very high
rates. Cosmic Frontiers requiring low power, non-cooled calorimetry or optical
detection that can keep track of particles or photons arriving at 100 MHz, and
survivable for years in space radiation may also benefit. The basic research is
to use compact channelized PMTs with quartz or other radiation resistant
windows with metal envelopes as an in-situ sensor, directly coupled to Cerenkov
(or radiation-resistant scintillator) tiles, utilizing the dynode signals as a
potentially compensating 2nd signal, and with no active electronics. If
successful, directions include proposals for high SE yield mesh dynode
activator materials such as GaP or B doped diamond films with 25 SEe at 300 eV
electron energies, and possibly for compact low cost tile SE sensors with no
photocathode, far easier to fabricate than PMTs with all metal final assembly
in air, brazed seals; bakeout 900 C; pump out with tipoff - vacuum 100x higher
than PMTs. Such sensors have many applications beyond HEP, in research,
medicine, industry and defense.",2203.09941v1
2019-01-25,Current-Induced Torques with Dresselhaus Symmetry Due to Resistance Anisotropy in 2D Materials,"We report measurements of current-induced torques in heterostructures of
Permalloy (Py) with TaTe$_2$, a transition-metal dichalcogenide (TMD) material
possessing low crystal symmetry, and observe a torque component with
Dresselhaus symmetry. We suggest that the dominant mechanism for this
Dresselhaus component is not a spin-orbit torque, but rather the Oersted field
arising from a component of current that flows perpendicular to the applied
voltage due to resistance anisotropy within the TaTe$_2$. This type of
transverse current is not present in wires made from a single uniform layer of
a material with resistance anisotropy, but will result whenever a material with
resistance anisotropy is integrated into a heterostructure with materials
having different resistivities, thereby producing a spatially non-uniform
pattern of current flow. This effect will therefore influence measurements in a
wide variety of heterostructures incorporating 2D TMD materials and other
materials with low crystal symmetries.",1901.08908v1
1999-08-13,Resistive upper critical fields and irreversibility lines of optimally-doped high-T_c cuprates,"We present the resistively-determined upper critical field H^{\rho}_{c2}(T)
and the irreversibility lines H^{\rho}_{irr}(T) of various high-T_c cuprates,
deduced from measurements in 61-T pulsed magnetic fields applied parallel to
the c-axis. The SHAPE of both H^{\rho}_{c2}(T) and H^{\rho}_{irr}(T) depends
monotonically on the anisotropy of the material and none of the samples show
saturation of H^{\rho}(T) at low temperatures. The anomalous positive
curvature, d^2 H^{\rho}/dT^2 > 0, is the strongest in materials with the
largest normal-state anisotropy, regardless of whether anisotropy is varied by
changing the carrier concentration or by comparing a variety of optimally-doped
compounds.",9908190v1
2009-04-10,Transition of stoichiometricSr2VO3FeAs to a superconducting state at 37.2 K,"The superconductor Sr4V2O6Fe2As2 with transition temperature at 37.2 K has
been fabricated. It has a layered structure with the space group of p4/nmm, and
with the lattice constants a = 3.9296Aand c = 15.6732A. The observed large
diamagnetization signal and zero-resistance demonstrated the bulk
superconductivity. The broadening of resistive transition was measured under
different magnetic fields leading to the discovery of a rather high upper
critical field. The results also suggest a large vortex liquid region which
reflects high anisotropy of the system. The Hall effect measurements revealed
dominantly electron-like charge carriers in this material. The
superconductivity in the present system may be induced by oxygen deficiency or
the multiple valence states of vanadium.",0904.1732v5
2014-12-25,Carbon Nanotube Based Delay Model For High Speed Energy Efficient on Chip Data Transmission Using: Current Mode Technique,"Speed is a major concern for high density VLSI networks. In this paper the
closed form delay model for current mode signalling in VLSI interconnects has
been proposed with resistive load termination. RLC interconnect line is
modelled using characteristic impedance of transmission line and inductive
effect. The inductive effect is dominant at lower technology node is modelled
into an equivalent resistance. In this model first order transfer function is
designed using finite difference equation, and by applying the boundary
conditions at the source and load termination. It has been observed that the
dominant pole determines system response and delay in the proposed model. Using
CNIA tool (carbon nanotube interconnect analyzer) the interconnect line
parameters has been estimated at 45nm technology node. The novel proposed
current mode model superiority has been validated for CNT type of material. It
superiority factor remains to 66.66% as compared to voltage mode signalling.
And current mode dissipates 0.015pJ energy where as VM consume 0.045pJ for a
single bit transmission across the interconnect over CNT material. Secondly the
damping factor of a lumped RLC circuit is shown to be a useful figure of merit.",1412.7818v1
2015-03-29,Edge-channel interferometer at the graphene quantum Hall pn junction,"We demonstrate a quantum Hall edge-channel interferometer in a high-quality
graphene pn junction under a high magnetic field. The co-propagating p and n
quantum Hall edge channels traveling along the pn interface functions as a
built-in Aharanov-Bohm-type interferometer, the interferences in which are
sensitive to both the external magnetic field and the carrier concentration.
The trajectories of peak and dip in the observed resistance oscillation are
well reproduced by our numerical calculation that assumes magnetic flux
quantization in the area enclosed by the co-propagating edge channels. Coherent
nature of the co-propagating edge channels are confirmed by the
checkerboard-like pattern in the dc-bias and magnetic-field dependences of the
resistance oscillations.",1503.08385v1
2017-11-16,Anisotropic magnetic properties of the ferromagnetic semiconductor CrSbSe$_3$,"Single crystals of CrSbSe$_3$, a structurally pseudo-one-dimensional
ferromagnetic semiconductor, were grown using a high-temperature solution
growth technique and were characterized by x-ray diffraction, anisotropic,
temperature- and field-dependent magnetization, temperature-dependent
resistivity and optical absorption measurements. A band gap of 0.7 eV was
determined from both resistivity and optical measurements. At high
temperatures, CrSbSe$_3$ is paramagnetic and isotropic with a Curie-Weiss
temperature of $\sim$145 K and an effective moment of $\sim$4.1 $\mu_B$/Cr. A
ferromagnetic transition occurs at $T_c$ = 71 K. The $a$-axis, perpendicular to
the chains in the structure, is the magnetic easy axis, while the chain axis
direction, along $b$, is the hard axis. Magnetic isotherms measured around
$T_c$ do not follow the behavior predicted by simple mean field critical
exponents for a second order phase transition. A tentative set of critical
exponents is estimated based on a modified Arrott plot analysis, giving
$\beta\sim$0.25, $\gamma\sim$1.38 and $\delta\sim$6.6.",1711.06342v1
2018-05-18,Search for alternative magnetic tunnel junctions based on all-Heusler stacks,"By imposing the constraints of structural compatibility, stability and a
large tunneling magneto-resistance, we have identified the
Fe$_3$Al/BiF$_3$/Fe$_3$Al stack as a possible alternative to the
well-established FeCoB/MgO/FeCoB in the search for a novel materials platform
for high-performance magnetic tunnel junctions. Various geometries of the
Fe$_3$Al/BiF$_3$/Fe$_3$Al structure have been analyzed, demonstrating that a
barrier of less than 2~nm yields a tunneling magneto-resistance in excess of
25,000~\% at low bias, without the need for the electrodes to be half-metallic.
Importantly, the presence of a significant spin gap in Fe$_3$Al for states with
$\Delta_1$ symmetry along the stack direction makes the TMR very resilient to
high voltages.",1805.08603v1
2019-09-23,High Throughput Production of Transparent Conductive Single-Walled Carbon Nanotube Films via Advanced Floating Catalyst Chemical Vapor Deposition,"Single-walled carbon nanotube (SWCNT) films are promising materials for
transparent conductive films (TCFs) with potential applications in flexible
displays, touch screens, solar cells and solid-state lighting1,2. However,
further reductions in resistivity and in cost of SWCNT films are necessary for
high quality TCF products3. Here, we report an improved floating catalyst
chemical vapor deposition method to directly and continuously produce ultrathin
and freestanding SWCNT films at the hundred meter-scale. Both carbon conversion
efficiency and SWCNT TCF yield are increased by three orders of magnitude
relative to the conventional floating catalyst chemical vapor deposition. After
doping, the film manifests a sheet resistance of 40 ohm/sq. at 90%
transmittance, representing record performance for large-scale SWCNT films. Our
work provides a new avenue to accelerate the industrialization of SWCNT films
as TCFs.",1909.10189v1
2020-03-24,XUV Induced Bleaching of a Tin Oxo Cage Photoresist Studied by High Harmonic Absorption Spectroscopy,"Inorganic molecular materials such as tin oxo cages are a promising
generation of photoresists compatible with the demands of the recently
developed Extreme UltraViolet (EUV) lithography technology. Therefore, a
detailed understanding of the photon-induced reactions which occur in
photoresists after exposure is important. We used XUV broadband laser pulses in
the range of 25-40 eV from a table-top high-harmonic source to expose thin
films of the tin oxo cage resist to shed light on some of the photo-induced
chemistry via XUV absorption spectroscopy. During the exposure, the transmitted
spectra were recorded and a noticeable absorbance decrease was observed in the
resist. Dill parameters were extracted to quantify the XUV induced conversion
and compared to EUV exposure results at 92 eV. Based on the absorption changes,
we estimate that approximately 60% of tin-carbon bonds are cleaved at the end
of the exposure.",2003.10961v1
2017-03-18,Discovering the Building Blocks of Atomic Systems using Machine Learning,"Machine learning has proven to be a valuable tool to approximate functions in
high-dimensional spaces. Unfortunately, analysis of these models to extract the
relevant physics is never as easy as applying machine learning to a large
dataset in the first place. Here we present a description of atomic systems
that generates machine learning representations with a direct path to physical
interpretation. As an example, we demonstrate its usefulness as a universal
descriptor of grain boundary systems. Grain boundaries in crystalline materials
are a quintessential example of a complex, high-dimensional system with broad
impact on many physical properties including strength, ductility, corrosion
resistance, crack resistance, and conductivity. In addition to modeling such
properties, the method also provides insight into the physical ""building
blocks"" that influence them. This opens the way to discover the underlying
physics behind behaviors by understanding which building blocks map to
particular properties. Once the structures are understood, they can then be
optimized for desirable behaviors.",1703.06236v1
2019-06-06,Modeling the effect of microstructure on elastic wave propagation in platelet-reinforced composites and ceramics,"Dense ceramics are irreplaceable in applications requiring high mechanical
stiffness, chemical and temperature resistance and low weight. To improve their
toughness, ceramics can be reinforced with elongated inclusions. Recent
manufacturing strategies have been developed to control the orientations of
disc-like micro-particles in polymeric and ceramic matrices and to build
periodic microstructures. Given the infinite number of possible microstructures
available, modeling tools are required to select the potentially best design.
Periodic microstructures can be involved in elastic wave scattering to
dissipate mechanical energy from vibrations. In this paper, a model is proposed
to determine the frequency bandgaps associated to periodic architectures in
composites and ceramics and the influence of microstructural parameters are
investigated. The results are used to define guidelines for the future
fabrication of hard bulk ceramic materials that combine traditional ceramic
properties with high vibration resistance.",1906.02582v1
2020-08-28,Tunnel magnetoresistance in scandium nitride magnetic tunnel junctions using first principles,"The magnetic tunnel junction is a cornerstone of spintronic devices and
circuits, providing the main way to convert between magnetic and electrical
information. In state-of-the-art magnetic tunnel junctions, magnesium oxide is
used as the tunnel barrier between magnetic electrodes, providing a uniquely
large tunnel magnetoresistance at room temperature. However, the wide bandgap
and band alignment of magnesium oxide-iron systems increases the
resistance-area product and causes challenges of device-to-device variability
and tunnel barrier degradation under high current. Here, we study using first
principles narrower-bandgap scandium nitride tunneling properties and transport
in magnetic tunnel junctions in comparison to magnesium oxide. These
simulations demonstrate a high tunnel magnetoresistance in Fe/ScN/Fe MTJs via
{\Delta}_1 and {\Delta}_2' symmetry filtering with low wavefunction decay
rates, allowing a low resistance-area product. The results show that scandium
nitride could be a new tunnel barrier material for magnetic tunnel junction
devices to overcome variability and current-injection challenges.",2008.12770v1
2020-11-07,Thickness-dependent quantum transport of Weyl fermions in ultra-high-quality SrRuO3 films,"The recent observation of Weyl fermions in the itinerant 4d ferromagnetic
perovskite SrRuO3 points to this material being a good platform for exploring
novel physics related to a pair of Weyl nodes in epitaxial heterostructures. In
this letter, we report the thickness-dependent magnetotransport properties of
ultra-high-quality epitaxial SrRuO3 films grown under optimized conditions on
SrTiO3 substrates. Signatures of Weyl fermion transport, i.e., unsaturated
linear positive magnetoresistance accompanied by a quantum oscillation having a
{\pi} Berry phase, were observed in films with thicknesses as small as 10 nm.
Residual resistivity increased with decreasing film thickness, indicating
disorder near the interface between SrRuO3 and the SrTiO3 substrate. Since this
disorder affects the magnetic and electrical properties of the films, the Curie
temperature decreases and the coercive field increases with decreasing
thickness. Thickness-dependent magnetotransport measurements revealed that the
threshold residual resistivity ratio (RRR) to observe Weyl fermion transport is
21. These results provide guidelines for realizing quantum transport of Weyl
fermions in SrRuO3 near heterointerfaces.",2011.03670v1
2021-05-11,Exploring the Correlation between Solvent Diffusion and Creep Resistance of Mg-Ga HCP Alloys from High Throughput Liquid-Solid Diffusion Couple,"The liquid-solid diffusion couple technique, supported by phenomenological
analysis and nano-indentation tests, is proposed on account of the relatively
low melting points of Mg to explore the diffusion mobility and creep
deformation. The potential of this strategy is demonstrated in Mg-Ga hcp alloys
where Ga solute (i.e. impurity) and Mg solvent diffusions in hcp Mg-Ga alloys
were both unveiled. It was followed by mapping the compressive creep behavior
via nanoindentation along the composition arrays within the same Mg-Ga couple
sample. The compressive creep resistance of Mg-Ga hcp alloys increased with the
Ga content, and this enhancement was similar to the one found in Mg-Zn alloys
and superior to the one reported in Mg-Al alloys though Al is a slower impurity
diffuser in hcp-Mg than Zn and Ga. Thereby, the solvent diffusion and its
variation with the composition, rather than the solute diffusion, was suggested
to govern the creep properties at high temperatures and low stresses.",2105.05096v1
2021-08-30,Out-of-Plane Resistance Switching of 2D Bi2O2Se at Nanoscale,"2D bismuth oxyselenide (Bi2O2Se) with high electron mobility shows great
potential for nanoelectronics. Although in-plane properties of Bi2O2Se have
been widely studied, its out-ofplane electrical transport behavior remains
elusive, despite its importance in fabricating devices with new functionality
and high integration density. Here, we study the out-of-plane electrical
properties of 2D Bi2O2Se at nanoscale by conductive atomic force microscope. We
find that hillocks with tunable heights and sizes are formed on Bi2O2Se after
applying vertical electrical field. Intriguingly, such hillocks are conductive
in vertical direction, resulting in a previously unknown out-of-plane
resistance switching in thick Bi2O2Se flakes while ohmic conductive
characteristic in thin ones. Furthermore, we observe the transformation from
bipolar to stable unipolar conduction in thick Bi2O2Se flake possessing such
hillocks, suggesting its potential to function as a selector in vertical
devices. Our work reveals unique out-of-plane transport behavior of 2D Bi2O2Se,
providing the basis for fabricating vertical devices based on this emerging 2D
material.",2108.13240v1
2004-07-07,Properties of MgB2 thin films with carbon doping,"We have studied structural and superconducting properties of MgB2 thin films
doped with carbon during the hybrid physical-chemical vapor deposition process.
A carbon-containing metalorganic precursor bis(cyclopentadienyl)magnesium was
added to the carrier gas to achieve carbon doping. As the amount of carbon in
the films increases, the resistivity increases, Tc decreases, and the upper
critical field increases dramatically as compared to the clean films. The
self-field Jc in the carbon-doped films is lower than that in the clean films,
but Jc remains relatively high to much higher magnetic fields, indicating
stronger pinning. Structurally, the doped films are textured with nano-grains
and highly resistive amorphous areas at the grain boundaries. The carbon doping
approach can be used to produce MgB2 materials for high magnetic field
applications.",0407146v1
2006-01-30,Growth of high quality large area MgB2 thin films by reactive evaporation,"We report a new in-situ reactive deposition thin film growth technique for
the production of MgB2 thin films which offers several advantages over all
existing methods and is the first deposition method to enable the production of
high-quality MgB2 films for real-world applications. We have used this growth
method, which incorporates a rotating pocket heater, to deposit MgB2 films on a
variety of substrates, including single-crystalline, polycrystalline, metallic,
and semiconductor materials up to 4"" in diameter. This technique allows growth
of double-sided, large-area films in the intermediate temperature range of 400
to 600 degrees C. These films are clean, well-connected, and consistently
display Tc values of 38 to 39 K with low resistivity and residual resistivity
values. They are also robust and uncommonly stable upon exposure to atmosphere
and water.",0601669v1
2017-03-27,"Machining of Spherical Component Fabricated by Selected Laser Melting, Part II: Application of Ti in Biomedical","Ti and Ti-Based alloys have unique properties such as high strength, low
density and excellent corrosion resistance. These properties are essential for
the manufacture of lightweight and high strength components for biomedical
applications. In this paper, Ti properties such as metallurgy, mechanical
properties, surface modification, corrosion resistance, biocompatibility and
osseointegration in biomedical applications have been discussed. This paper
also analyses the advantages and disadvantages of various Ti manufacturing
processes for biomedical applications such as casting, powder metallurgy, cold
and hot working, machining, laser engineering net shaping, superplastic
forming, forging and ring rolling. The contributions of this research are
twofold, firstly scrutinizing the behaviour of Ti and Ti-Based alloys in-vivo
and in-vitro experiments in biomedical applications to determine the factors
leading to failure, and secondly strategies to achieve desired properties
essential to improving the quality of patient outcomes after receiving surgical
implants. Future research will be directed toward manufacturing of Ti for
medical applications by improving the production process, for example using
optimal design approaches in additive manufacturing and investigating alloys
containing other materials in order to obtain better medical and mechanical
characteristics.",1703.10045v1
2021-10-28,Analysis of Prospective Elements and Crystal Lattice Structures via Computer Algorithms to Identify Standard Temperature Pressure (STP) Superconductors,"Superconductors have the potential to revolutionize technology due to their
ability to have zero electrical resistance. However, superconductor materials
require either low temperatures or high pressures to function in a
superconductive state. Thus, researchers are now on the search for the
first-ever room temperature, ambient pressure superconductor. Yet, recent
discoveries have only shown superconductors that work at low temperatures with
ambient pressure or room temperature with high pressures. The region between
these two extremes has not been identified due to the number of variables that
affect superconductivity. To reduce the number of permutations that need to be
tested to identify the first STP superconductor I propose the use of a computer
algorithm designed to test various crystal structures of superconducting
materials and combinations of elements that will have zero electrical
resistance and exhibit the Meisner effect. Some elemental superconductors that
have the highest critical temperature at standard pressure are V, Zr, La, Hf,
Re, Th, Pa, U, and Am. The elements once combined with other elements in the
right crystalline structure can produce a metastable state where the
superconductors will keep their physical characteristics once they form.",2110.15201v1
2022-07-28,Pressure induced 3D strain in 2D Graphene,"Two-dimensional (2D) materials such as graphene offer a variety of
outstanding properties for a wide range of applications. Their transport
properties in particular present a rich field of study. However, the studies of
transport properties of graphene under pressure are mostly limited to $\sim$1
GPa, largely due to the technical challenges and difficulties of placing
graphene inside a diamond anvil cell (DAC) and maintaining good electrical
contacts under pressure. We developed a novel technique allowing for direct
measurements of the transport properties of high quality chemical vapor
deposition (CVD) monolayer graphene under pressures. Combined Raman
spectroscopic and direct resistivity measurements on pure monolayer graphene up
to 40 GPa shows an effective out of plane stiffness of
$c_{33}$=0.26$\pm_{.09}^{.11}$ GPa, and observe relatively constant resistances
with pressure, suggesting high pressure as a useful technique for producing
large biaxial strains within graphene.",2207.14183v1
2023-07-12,The Collaborative Effects of Intrinsic and Extrinsic Impurities in Low RRR SRF Cavities,"The superconducting radio-frequency (SRF) community has shown that
introducing certain impurities into high-purity niobium can improve quality
factors and accelerating gradients. We question why some impurities improve RF
performance while others hinder it. The purpose of this study is to
characterize the impurity profile of niobium with a low residual resistance
ratio (RRR) and correlate these impurities with the RF performance of low RRR
cavities so that the mechanism of impurity-based improvements can be better
understood and improved upon. The combination of RF testing and material
analysis reveals a microscopic picture of why low RRR cavities experience low
temperature-dependent BCS resistance behavior more prominently than their high
RRR counterparts. We performed surface treatments, low temperature baking and
nitrogen-doping, on low RRR cavities to evaluate how the intentional addition
of oxygen and nitrogen to the RF layer further improves performance through
changes in the mean free path and impurity profile. The results of this study
have the potential to unlock a new understanding on SRF materials and enable
the next generation of SRF surface treatments.",2307.06259v1
2023-02-15,An experimental high-throughput to high-fidelity study towards discovering Al-Cr containing corrosion-resistant compositionally complex alloys,"Compositionally complex alloys hold the promise of simultaneously attaining
superior combinations of properties, such as corrosion resistance,
light-weighting, and strength. Achieving this goal is a challenge due in part
to a large number of possible compositions and structures in the vast alloy
design space. High-throughput methods offer a path forward, but a strong
connection between the synthesis of an alloy of a given composition and
structure with its properties has not been fully realized to date. Here, we
present the rapid identification of corrosion-resistant alloys based on
combinations of Al and Cr in a base Al-Co-Cr-Fe-Ni alloy. Previously unstudied
alloy stoichiometries were identified using a combination of high-throughput
experimental screening coupled with key metallurgical and electrochemical
corrosion tests, identifying alloys with excellent passivation behavior. The
alloy native oxide performance and its self-healing attributes were probed
using rapid tests in deaerated 0.1 mol/L H2SO4. Importantly, a correlation was
found between the electrochemical impedance modulus of the exposure-modified
air-formed film and self-healing rate of the CCAs. Multi-element extended x-ray
absorption fine structure analyses connected more ordered type chemical
short-range order in the Ni-Al 1st nearest-neighbor shell to poorer corrosion
resistance. This report underscores the utility of high throughput exploration
of compositionally complex alloys for the identification and rapid screening of
a vast stoichiometric space.",2302.07988v2
2021-04-06,"In-situ dispersion of electrospun nanofibers in PDMS for fabrication of high strength, transparent nanocomposites","The polymer nanocomposites find applications in diverse areas ranging from
smart materials to bioengineering. They are developed by dispersion of
nanomaterials in a bulk phase of a polymeric material. Although several methods
facilitate efficient dispersion of nanomaterials in a bulk polymer matrix to
create nanocomposites, majority of them follows heat, beat and treat processes.
These processes are high energy demanding processes. Moreover, the challenge
increases when nanomaterials need to be dispersed in a viscous polymeric
material. This results in spatial heterogeneity in the dispersion of
nanomaterials, eventually leading to compromised mechanical properties of a
nanocomposite. Therefore, in the current work, we propose an in-situ, on-step
fabrication process of polydimethylsiloxane (PDMS) nanocomposites. Electrospun
polyvinyl alcohol (PVA) nanofibers are homogenously dispersed in a PDMS matrix
to create a high strength, transparent PDMS nanocomposite. The homogenous
dispersion of nanofibers in PDMS matrix is characterised by scanning electron
microscopy (SEM), confocal imaging and rheological studies. Further, the
prepared PDMS nanocomposite exhibits improved mechanical strength and
comparable optical transparency in comparison to native PDMS. Hence, the
fabricated PDMS nanocomposites, being resistant to mechanical stress and
optically transparent, will find applications as transdermal patches, flexible
electronics, microfluidic devices and others.",2104.02418v1
2022-04-12,Bayesian optimization with experimental failure for high-throughput materials growth,"A crucial problem in achieving innovative high-throughput materials growth
with machine learning and automation techniques, such as Bayesian optimization
(BO) and robotic experimentation, has been a lack of an appropriate way to
handle missing data due to experimental failures. Here, we propose a new BO
algorithm that complements the missing data in the optimization of materials
growth parameters. The proposed method provides a flexible optimization
algorithm capable of searching a wide multi-dimensional parameter space. We
demonstrate the effectiveness of the method with simulated data as well as in
its implementation for actual materials growth, namely
machine-learning-assisted molecular beam epitaxy (ML-MBE) of SrRuO3, which is
widely used as a metallic electrode in oxide electronics. Through the
exploitation and exploration in a wide three-dimensional parameter space, while
complementing the missing data, we attained tensile-strained SrRuO3 film with a
high residual resistivity ratio of 80.1, the highest among tensile-strained
SrRuO3 films ever reported, in only 35 MBE growth runs.",2204.05452v1
2023-08-30,Target tests for the ILC positron source Talk presented at the International Workshop on Future Linear Colliders (LCWS2023),"The positron source is an essential component of the International Linear
Collider (ILC) and is an area that poses some design challenges. One
consideration is the material for the target, where the 1014 positrons per
second for the ILC are generated. The potential material would need to be able
to resist the high load created by the intense high energy photon beam. One of
such candidates is the titanium alloy Ti-6Al-4V, for which the results of
material tests with 3.5 MeV electrons are shown. The material was characterized
after the irradiation by high-energy X-ray diffraction (HE-XRD) and changes
caused by the irradiation to the crystal structure were studied. These tests
revealed there was only minimal change in the phase fractions and crystal
structure of the material under conditions as expected for the ILC.",2308.15916v1
2019-08-16,Ab initio phonon transport across grain boundaries in graphene using machine learning based on small dataset,"Establishing the structure-property relationship for grain boundaries (GBs)
is critical for developing next generation functional materials, but has been
severely hampered due to its extremely large configurational space. Atomistic
simulations with low computational cost and high predictive power are strongly
desirable, but the conventional simulations using empirical interatomic
potentials and density functional theory suffer from the lack of predictive
power and high computational cost, respectively. A machine learning interatomic
potential (MLIP) recently emerged but often requires an extensive size of the
training dataset, making it a less feasible approach. Here we demonstrate that
an MLIP trained with a rationally designed small training dataset can predict
thermal transport across GBs in graphene with ab initio accuracy at an
affordable computational cost. In particular, we employed a rational approach
based on the structural unit model to find a small set of GBs that can
represent the entire configurational space and thus can serve as a
cost-effective training dataset for the MLIP. Only 5 GBs were found to be
enough to represent the entire configurational space of graphene GBs. Using the
atomistic Green's function approach and the MLIP, we revealed that the
structure-thermal resistance relation in graphene does not follow the common
understanding that large dislocation density causes larger thermal resistance.
In fact, thermal resistance is nearly independent of dislocation density at
room temperature and is higher when the dislocation density is small at
sub-room temperature. We explain this intriguing behavior with the buckling
near a GB causing a strong scattering of flexural phonon modes.",1909.02386v3
2022-02-18,Synergism between B and Nb improves fire resistance in microalloyed steels,"The development of new fire-resistant steels represents a challenge in
materials science and engineering of utmost importance. Alloying elements such
as Nb and Mo are generally used to improve the strength at both room- and
high-temperatures due to, for example, the formation of precipitates and harder
microconstituents. In this study we show alternatively that the addition of
small amounts of boron in Nb-microalloyed steels may play a crucial role in
maintaining the mechanical properties at high temperatures. The 66\,\%
yield-strength criteria for fire resistance is achieved at $\approx
574$\,{\deg}C for a boron steel, whereas without boron this value reaches
$\approx 460$\,{\deg}C, a remarkable boron-induced mechanical strengthening
enhancement. DFT calculations show that boron additions can lower the vacancy
formation energy when compared to pure ferrite and, for Nb-B steels, there is a
further 24\,\% reduction, suggesting that the boron-niobium combination acts as
an effective pinning-based strengthening agent.",2202.09197v1
2020-07-28,Good Practice Guide on the electrical characterization of graphene using non-contact and high-throughput methods,"The electrical characterisation of graphene, either in plane sheets or in
properly geometrised form can be approached using non-contact methods already
employed for thin film materials. The extraordinary thinness (and,
correspondingly, the volume) of graphene, however, makes the proper application
of these methods difficult. The electrical properties of interest (sheet
electrical resistivity/conductivity, concentration and mobility of charge
carriers) must be indirectly derived from the measurement outcome by
geometrical and electrical modelling; the assumptions behind such models (e.g.,
uniformity and isotropy, effective value of the applied fields, etc.) require
careful consideration. The traceability of the measurement to the International
System of units and a proper expression of measurement uncertainty is an issue.
  This guide focuses on non-contact and high-throughput methods, that are
methods where the graphene sample surface is not physically contacted with any
metallic electrodes at any stage. A companion guide about contact methods is
also available. The methods discussed are:
  - Measurement of surface potential and work function using Scanning Kelvin
Probe Microscopy (SKPM); - Measurement of sheet resistance by Microwave
Resonant Cavity; - Measurement of sheet resistance by Terahertz time-domain
spectroscopy (THz-TDS); For each method, a corresponding measurement protocol
is discussed, which describes: - The measurement principle; - Sample
requirements and preparation; - A description of the measurement equipment /
apparatus; - Calibration standards and ways to achieve a traceable measurement;",2007.14047v1
2020-12-08,The Competing Effect of Initial Crack Depth Versus Chemical Strengthening Parameters on Apparent Fracture Toughness of Sodium Aluminosilicate Glass,"The widespread use of sodium aluminosilicate glass in many engineering
applications due to its mechanical and optical properties (transparency,
dielectric, etc.), has become common in recent years. However, glass, a brittle
material, has its vulnerability to fracture. Processes such as heat treatment
(heat tempering) or chemical strengthening through ion-exchange have been used
to create residual stress profiles on the glass, in a bid to improve its
fracture strength. However, failure still occurs, which is mostly catastrophic
and expensive to repair. Therefore understanding, predicting, and eventually
improving the resistance to damage or fracture of chemically strengthened glass
is important to designing new glasses that would be tougher while retaining
their transparency. The relationship between the glass residual stress
parameters such as the compressive stress (CS), depth of compression layer
(DOL), and central tension (CT) versus apparent (effective) fracture toughness
for different crack depth was investigated in this study using a Silicon
Carbide particle blast plus ring-on-ring (RoR) test method. The results also
showed that improving the fracture resistance of glass via chemical
strengthening requires a proper combination of CS, DOL, and CT, which is
particularly dependent on the initial/existing crack (flaw) depth. It was
determined that for a damage event involving the introduction of a shallow
crack depth, the criterion for optimal resistance to fracture, in terms of
apparent fracture toughness, is weighted more towards a high CS, than deep DOL
while for a deep flaw damage event, it is more weighted towards deep DOL, than
a high CS. These results provide a valuable piece of information in the design
of a more robust glass in engineering applications.",2012.04732v1
2021-04-07,Ultra-Thin Lubricant-Infused Vertical Graphene Nanoscaffolds for High-Performance Dropwise Condensation,"Lubricant-infused surfaces (LIS) are highly efficient in repelling water and
constitute a very promising family of materials for condensation processes
occurring in a broad range of energy applications. However, the performance of
LIS in such processes is limited by the inherent thermal resistance imposed by
the thickness of the lubricant and supporting surface structure, as well as by
the gradual depletion of the lubricant over time. Here we present a remarkable,
ultra-thin (~70 nm) and conductive LIS architecture, obtained by infusing
lubricant into a vertically grown graphene nanoscaffold on copper. The
ultra-thin nature of the scaffold, combined with the high in-plane thermal
conductivity of graphene, drastically minimize earlier limitations, effectively
doubling the heat transfer performance compared to a state-of-the-art CuO LIS
surface. We show that the effect of the thermal resistance to the heat transfer
performance of a LIS surface, although often overlooked, can be so detrimental
that a simple nanostructured CuO surface can outperform a CuO LIS surface,
despite film condensation on the former. The present vertical graphene LIS is
also found to be resistant to lubricant depletion, maintaining stable dropwise
condensation for at least ~7 hours with no significant change of advancing
contact angle and contact angle hysteresis. The lubricant consumed by the
vertical graphene LIS is 52.6% less than the existing state-of-the-art CuO LIS,
making also the fabrication process more economical.",2104.03091v1
2023-07-24,Large negative magnetoresistance and pseudogap phase in superconducting A15-type La$_4$H$_{23}$,"High pressure plays a crucial role in the field of superconductivity.
Compressed hydride superconductors are leaders in the race for a material that
can conduct electricity without resistance at high or even room temperature. In
the present work, we have discovered new lanthanum superhydride, cubic A15-type
La$_4$H$_{23}$, with lower stabilization pressure compared to the reported
$\textit{fcc}$ LaH$_{10}$. Superconducting La$_4$H$_{23}$ was obtained by laser
heating of LaH$_3$ with ammonia borane at about 120 GPa. Transport measurements
reveal the maximum critical temperature $\textit{T}$$_{C}$(onset) = 105 K and
the critical field $\textit{H}$$_{C2}$(0) = 32 T at 118 GPa, as evidenced by
the sharp drop of electrical resistance and the displacement of superconducting
transitions in applied magnetic fields. Moreover, we provide evidence for
unconventional transport associated with a pseudogap phase in La$_4$H$_{23}$
using pulsed magnetic fields up to 68 T. A large negative magnetoresistance in
the non-superconducting state below 40 K, quasi $\textit{T}$-linear electrical
resistance, and a sign-change of its temperature dependence mark the emergence
of pseudogap in this hydride. Discovered lanthanum hydride is a new member of
the A15 family of superconductors with $\textit{T}$$_C$ exceeding the boiling
point of liquid nitrogen.",2307.13067v3
2019-07-04,Contact Engineering High Performance n-Type MoTe2 Transistors,"Semiconducting MoTe2 is one of the few two-dimensional (2D) materials with a
moderate band gap, similar to silicon. However, this material remains
under-explored for 2D electronics due to ambient instability and predominantly
p-type Fermi level pinning at contacts. Here, we demonstrate unipolar n-type
MoTe2 transistors with the highest performance to date, including high
saturation current (>400 ${\mu}A/{\mu}m$ at 80 K and >200 ${\mu}A/{\mu}m$ at
300 K) and relatively low contact resistance (1.2 to 2 $k{\Omega}\cdot{\mu}m$
from 80 to 300 K), achieved with Ag contacts and AlOx encapsulation. We also
investigate other contact metals, extracting their Schottky barrier heights
using an analytic subthreshold model. High-resolution X-ray photoelectron
spectroscopy reveals that interfacial metal-Te compounds dominate the contact
resistance. Among the metals studied, Sc has the lowest work function but is
the most reactive, which we counter by inserting monolayer h-BN between MoTe2
and Sc. These metal-insulator-semiconductor (MIS) contacts partly de-pin the
metal Fermi level and lead to the smallest Schottky barrier for electron
injection. Overall, this work improves our understanding of n-type contacts to
2D materials, an important advance for low-power electronics.",1907.02587v1
2011-03-11,Optimized fabrication of high quality La0.67Sr0.33MnO3 thin films considering all essential characteristics,"In this article, an overview of the fabrication and properties of high
quality La0.67Sr0.33MnO3 (LSMO) thin films is given. A high quality LSMO film
combines a smooth surface morphology with a large magnetization and a small
residual resistivity, while avoiding precipitates and surface segregation. In
literature, typically only a few of these issues are adressed. We therefore
present a thorough characterization of our films, which were grown by pulsed
laser deposition. The films were characterized with reflection high energy
electron diffraction, atomic force microscopy, x-ray diffraction, magnetization
and transport measurements, x-ray photoelectron spectroscopy and scanning
transmission electron microscopy. The films have a saturation magnetization of
4.0 {\mu}B/Mn, a Curie temperature of 350 K and a residual resistivity of 60
{\mu}{\Omega}cm. These results indicate that high quality films, combining both
large magnetization and small residual resistivity, were realized. A comparison
between different samples presented in literature shows that focussing on a
single property is insufficient for the optimization of the deposition process.
For high quality films, all properties have to be adressed. For LSMO devices,
the thin film quality is crucial for the device performance. Therefore, this
research is important for the application of LSMO in devices.",1103.2267v1
2022-10-24,Nanomolding of Metastable Mo$_{4}$P$_{3}$,"Reduced dimensionality leads to emergent phenomena in quantum materials and
there is a need for accelerated materials discovery of nanoscale quantum
materials in reduced dimensions. Thermomechanical nanomolding is a rapid
synthesis method that produces high quality single-crystalline quantum
nanowires with controlled dimensions over wafer-scale sizes. Herein, we apply
nanomolding to fabricate nanowires from bulk feedstock of MoP, a triple-point
topological metal with extremely high conductivity that is promising for
low-resistance interconnects. Surprisingly, we obtained single-crystalline
Mo$_{4}$P$_{3}$ nanowires, a metastable phase at room temperature in
atmospheric pressure. We thus demonstrate nanomolding can create metastable
phases inaccessible by other nanomaterial syntheses and can explore a
previously inaccessible synthesis space at high temperatures and pressures.
Furthermore, our results suggest that the current understanding of interfacial
solid diffusion for nanomolding is incomplete, providing opportunities to
explore solid-state diffusion at high-pressure and high-temperature regimes in
confined dimensions.",2210.13392v1
2024-02-02,Nano-ironing van der Waals Heterostructures Towards Electrically Controlled Quantum Dots,"Assembling two-dimensional van der Waals layered materials into
heterostructures is an exciting development that sparked the discovery of rich
correlated electronic phenomena and offers possibilities for designer device
applications. However, resist residue from fabrication processes is a major
limitation. Resulting disordered interfaces degrade device performance and mask
underlying transport physics. Conventional cleaning processes are inefficient
and can cause material and device damage. Here, we show that thermal scanning
probe based cleaning can effectively eliminate resist residue to recover
pristine material surfaces. Our technique is compatible at both the material-
and device-level, and we demonstrate the significant improvement in the
electrical performance of 2D WS2 transistors. We also demonstrate the cleaning
of van der Waals heterostructures to achieve interfaces with low disorder. This
enables the electrical formation and control of quantum dots that can be tuned
from macroscopic current flow to the single-electron tunnelling regime. Such
material processing advances are crucial for constructing high-quality vdW
heterostructures that are important platforms for fundamental studies and
building blocks for quantum and nano-electronics applications.",2402.01185v1
2024-02-13,Plasma-wall interaction in laser inertial fusion reactors: novel proposals for radiation tests of first wall materials,"Dry-wall laser inertial fusion (LIF) chambers will have to withstand strong
bursts of fast charged particles which will deposit tens of kJ m$^{-2}$ and
implant more than 10$^{18}$ particles m$^{-2}$ in a few microseconds at a
repetition rate of some Hz. Large chamber dimensions and resistant
plasma-facing materials must be combined to guarantee the chamber performance
as long as possible under the expected threats: heating, fatigue, cracking,
formation of defects, retention of light species, swelling and erosion. Current
and novel radiation resistant materials for the first wall need to be validated
under realistic conditions. However, at present there is a lack of facilities
which can reproduce such ion environments.
  This contribution proposes the use of ultra-intense lasers and high-intense
pulsed ion beams (HIPIB) to recreate the plasma conditions in LIF reactors. By
target normal sheath acceleration, ultra-intense lasers can generate very short
and energetic ion pulses with a spectral distribution similar to that of the
inertial fusion ion bursts, suitable to validate fusion materials and to
investigate the barely known propagation of those bursts through background
plasmas/gases present in the reactor chamber. HIPIB technologies, initially
developed for inertial fusion driver systems, provide huge intensity pulses
which meet the irradiation conditions expected in the first wall of LIF
chambers and thus can be used for the validation of materials too.",2402.10235v1
2002-03-25,Photo-response of the conductivity in functionalized pentacene compounds,"We report the first investigation of the photo-response of the conductivity
of a new class of organic semiconductors based on functionalized pentacene.
These materials form high quality single crystals that exhibit a thermally
activated resistivity. Unlike pure pentacene, the functionalized derivatives
are readily soluble in acetone, and can be evaporated or spin-cast as thin
films for potential device applications. The electrical conductivity of the
single crystal materials is noticeably sensitive to ambient light changes. The
purpose, therefore, of the present study, is to determine the nature of the
photo-response in terms of carrier activation vs. heating effects, and also to
measure the dependence of the photo-response on photon energy. We describe a
new method, involving the temperature dependent photo-response, which allows an
unambiguous identification of the signature of heating effects in materials
with a thermally activated conductivity. We find strong evidence that the
photo-response in the materials investigated is predominantly a highly
localized heating mechanism. Wavelength dependent studies of the photo-response
reveal resonant features and cut-offs that indicate the photon energy
absorption is related to the electronic structure of the material.",0203522v1
2016-04-19,Tuning the work function in transition metal oxides and their heterostructures,"The development of novel functional materials in experimental labs combined
with computer-based compound simulation brings the vision of materials design
on a microscopic scale continuously closer to reality. For many applications
interface and surface phenomena rather than bulk properties are key. One of the
most fundamental qualities of a material-vacuum interface is the energy
required to transfer an electron across this boundary, i.e. the work function.
It is a crucial parameter for numerous applications, including organic
electronics, field electron emitters, and thermionic energy converters. Being
generally very resistant to degradation at high temperatures, transition metal
oxides present a promising materials class for such devices. We have performed
a systematic study for perovskite oxides that provides reference values and,
equally important, reports on materials trends and the tunability of work
functions. Our results identify and classify dependencies of the work function
on several parameters including specific surface termination, surface
reconstructions, oxygen vacancies, and heterostructuring.",1604.05615v1
2020-04-15,Featureless adaptive optimization accelerates functional electronic materials design,"Electronic materials exhibiting phase transitions between metastable states
(e.g., metal-insulator transition materials with abrupt electrical resistivity
transformations) are challenging to decode. For these materials, conventional
machine learning methods display limited predictive capability due to data
scarcity and the absence of features impeding model training. In this article,
we demonstrate a discovery strategy based on multi-objective Bayesian
optimization to directly circumvent these bottlenecks by utilizing latent
variable Gaussian processes combined with high-fidelity electronic structure
calculations for validation in the chalcogenide lacunar spinel family. We
directly and simultaneously learn phase stability and band gap tunability from
chemical composition alone to efficiently discover all superior compositions on
the design Pareto front. Previously unidentified electronic transitions also
emerge from our featureless adaptive optimization engine. Our methodology
readily generalizes to optimization of multiple properties, enabling co-design
of complex multifunctional materials, especially where prior data is sparse.",2004.07365v2
2022-11-08,Extraordinary magnetometry -- a review on extraordinary magnetoresistance,"Extraordinary magnetoresistance (EMR) is a geometric magnetoresistance effect
occurring in hybrid devices consisting of a high-mobility material joined by a
metal. The change in resistance can exceed 107% at room temperature when a
magnetic field of 5 T is applied. Magnetic field sensors based on EMR hold the
potential formeasuring weak magnetic fields with an unprecedented sensitivity,
yet, to date this potential is largely unmet. In this work, we provide an
extensive review of the current state-of-the-art in EMR sensors with a focus on
the hybrid device geometries, the constituent material properties and
applications of EMR. We present a direct comparison of the best devices in
literature across magnetoresistance, sensitivity and noise equivalent field for
different materials and geometric designs. The compilation of studies collected
in this review illustrates the extremely rich possibilities for tuning the
magnetoresistive behavior varying the device geometry and material properties.
In addition, we aim to improve the understanding of the EMR effect and its
interplay with geometry and material properties. Finally, we discuss recent
trends in the field and future perspectives for EMR.",2211.04308v1
2015-07-24,Measurements of the Rate Capability of Various Resistive Plate Chambers,"Resistive Plate Chambers (RPCs) exhibit a significant loss of efficiency for
the detection of particles, when subjected to high particle fluxes. This rate
limitation is related to the usually high resistivity of the resistive plates
used in their construction. This paper reports on measurements of the
performance of three different glass RPC designs featuring a different total
resistance of the resistive plates. The measurements were performed with 120
GeV protons at varying beam intensities",1507.06968v2
2006-06-17,Elastomeric carbon nanotube circuits for local strain sensing,"We use elastomeric polydimethylsiloxane substrates to strain single-walled
carbon nanotubes and modulate their electronic properties, with the aim of
developing flexible materials that can sense local strain. We demonstrate
micron-scale nanotube devices that can be cycled repeatedly through strains as
high as 20% while providing reproducible local strain transduction by via the
device resistance. We also compress individual nanotubes, and find they undergo
an undulatory distortion with a characteristic spatial period of 100-200 nm.
The observed period can be understood by the mechanical properties of nanotubes
and the substrate in conjunction with continuum elasticity theory. These could
potentially be used to create superlattices within individual nanotubes,
enabling novel devices and applications.",0606463v1
2007-06-12,Very large spontaneous electric polarization in BiFeO3 single crystals at room temperature and its evolution under cycling fields,"Electric polarization loops are measured at room temperature on highly pure
BiFeO3 single crystals synthesized by a flux growth method. Because the
crystals have a high electrical resistivity, the resulting low leakage currents
allow us to measure a large spontaneous polarization reaching 100
microC.cm^{-2}, a value never reported in the bulk. During electric cycling,
the slow degradation of the material leads to an evolution of the hysteresis
curves eventually preventing full saturation of the crystals.",0706.1681v1
2008-04-23,Giant Carrier Mobility in Single Crystals of FeSb2,"We report the giant carrier mobility in single crystals of FeSb2. Nonlinear
field dependence of Hall resistivity is well described with the two-carrier
model. Maximum mobility values in high mobility band reach ~10^5 cm^2/Vs at 8
K, and are ~10^2 cm^2/Vs at the room temperature. Our results point to a class
of materials with promising potential for applications in solid state
electronics.",0804.3625v1
2011-01-30,Thermodynamics of second phase conductive filaments,"We present a theory of second phase conductive filaments in phase
transformable systems; applications include threshold switches, phase change
memory, and shunting in thin film structures. We show that the average filament
parameters can be described thermodynamically. In agreement with the published
data, the predicted filament current voltage characteristics exhibit negative
differential resistance vanishing at high currents where the current density
becomes a bulk material property. Our description is extendible to filament
transients and allows for efficient numerical simulation.",1101.5737v2
2012-08-30,Calculation of thermal parameters of SiGe microbolometers,"The thermal parameters of a SiGe microbolometer were calculated using
numerical modeling. The calculated thermal conduction and thermal response time
are in good agreement with the values found experimentally and range between
2x10$^-7$ and 7x10$^-8$ W/K and 1.5 and 4.5 ms, respectively. High sensitivity
of microbolometer is achieved due to optimization of the thermal response time
and thermal conduction by fitting the geometry of supporting heat-removing legs
or by selection of a suitable material providing boundary thermal resistance
higher than 8x10$^-3$ cm$^2$K/W at the SiGe interface.",1208.6147v1
2022-02-22,Superconductivity and weak anti-localization in nodal-line semimetal SnTaS_2,"Topological semimetals with superconducting properties provide an emergent
platform to explore the properties of topological superconductors. We report
magnetization, and magneto-transport measurements on high quality single
crystals of transition metal dichalcogenide SnTaS2. It is a nodal line
semimetal with superconducting transition below Tc = 2.9 K. Moderate anisotropy
(3.1) is observed in upper critical fields along H||c and H||ab plane. In the
normal state we observe large magneto-resistance and weak anti-localization
effect that provide unambiguous confirmation of topological features in SnTaS2.
Therefore, genuine topological characteristics can be studied in this material,
particularly with regard to microscopic origin of order parameter symmetry.",2202.10711v1
2020-05-07,HVDC Surface Flashover in Compressed Air for Various Dielectrics,"This study measures the voltage at which flashover occurs in compressed air
for a variety of dielectric materials and lengths in a uniform field for DC
voltages up to 100 kV. Statistical time lag is recorded and characterized,
displaying a roughly exponential dependence on breakdown voltage. Of the
materials tested, acrylic is observed to be the most resistant to flashover.
These data are intended to facilitate the design of compressed-air insulated
high voltage systems as an alternative to SF6 insulated systems.",2006.12615v2
2023-07-30,Non-Equilibrium Nature of Fracture Determines the Crack Paths,"A high-fidelity neural network-based force field, NN-F$^{3}$, is developed to
cover the strain states up to material failure and the non-equilibrium,
intermediate nature of fracture. Simulations of fracture in 2D crystals using
NN-F$^{3}$ reveal spatial complexities from lattice-scale kinks to sample-scale
patterns. We find that the fracture resistance cannot be quantified by the
energy densities of relaxed edges as in the literature. Instead, the fracture
patterns, critical stress intensity factors at the kinks, and energy densities
of edges in the intermediate, unrelaxed states offer reasonable measures for
the fracture toughness and its anisotropy.",2307.16126v1
2004-09-30,Scaling theory of magneto-resistance in disordered local moment ferromagnets,"We present a scaling theory of magneto-transport in Anderson-localized
disordered ferromagnets. Within our framework a pronounced
magnetic-field-sensitive resistance peak emerges naturally for temperatures
near the magnetic phase transition. We find that the resistance anomaly is a
direct consequence of the change in localization length caused by the magnetic
transition. For increasing values of the external magnetic field, the
resistance peak is gradually depleted and pushed towards higher temperatures.
Our results are in good agreement with magneto-resistance measurements on a
variety of disordered magnets.",0410003v2
2009-02-08,Pulse width controlled resistivity switching at room temperature in Bi0.8Sr0.2MnO3,"We report pulsed as well as direct current/voltage induced electroresistance
in Bi0.8Sr0.2MnO3 at room temperature. It is shown that bi-level and
multi-level resistivity switching can be induced by a sequence of pulses of
varying pulse width at fixed voltage amplitude. Resistivity increases abruptly
(= 55 % at 300 K) upon reducing pulse width from 100 ms to 25 ms for a fixed
electric field (E = 2 V/cm2) of 200 ms pulse period. The resistivity switching
is accompanied by a periodic change in temperature which alone can not explain
the magnitude of the resistivity change.",0902.1281v1
2010-01-05,Mechanism for bipolar resistive switching in transition metal oxides,"We introduce a model that accounts for the bipolar resistive switching
phenomenom observed in transition metal oxides. It qualitatively describes the
electric field-enhanced migration of oxygen vacancies at the nano-scale. The
numerical study of the model predicts that strong electric fields develop in
the highly resistive dielectric-electrode interfaces, leading to a spatially
inhomogeneous oxygen vacancies distribution and a concomitant resistive
switching effect. The theoretical results qualitatively reproduce non-trivial
resistance hysteresis experiments that we also report, providing key validation
to our model.",1001.0703v1
2011-05-19,Nonvolatile bipolar resistive switching in Au/BiFeO3/Pt,"Nonvolatile bipolar resistive switching has been observed in an Au/BiFeO3/Pt
structure, where a Schottky contact and a quasi-Ohmic contact were formed at
the Au/BiFeO3 and BiFeO3/Pt interface, respectively. By changing the polarity
of the external voltage, the Au/BiFeO3/Pt is switched between two stable
resistance states without an electroforming process. The resistance ratio is
larger than two orders of magnitude. The resistive switching is understood by
the electric field - induced carriers trapping and detrapping, which changes
the depletion layer thickness at the Au/BiFeO3 interface.",1105.3827v1
2011-07-30,Polaronic transport in the ferromagnetic phase of Gd1-xCaxBaCo2O5.53,"Temperature dependent electrical resistivity and thermopower measurements
were carried out on Gd1-xCaxBaCo2O5.53 with x varying between 0 and 0.25. Ca
subsitution leads to the incorporation of holes (Co4+) into the system that
leads to a reduction in resistivity and a stabilisation of the ferromagnetic
phase at low temperatures. The temperature dependence of resistivity and
thermopower are markedly different in the Ca doped sample, with a dramatic
reduction in the resistivity, as compared to that in the pristine sample. The
variation in both the resistivity and thermopower with temperature is explained
in terms of the transport of polarons in the ferromagnetic phase of Ca doped
system.",1108.0059v1
2017-06-20,Scaling of the Hall effects beyond the quantum resistance threshold in oxidized CoFeB,"The ordinary and the extraordinary Hall effects were studied in gradually
oxidized amorphous CoFeB ferromagnets over six orders of resistivity from the
metallic to the strongly insulating regime. Polarity of the extraordinary Hall
effect reverses, and the amplitude of both the ordinary and the extraordinary
Hall effects increases quadratically with resistivity when resistance exceeds
the quantum resistance threshold. The absolute value of the extraordinary Hall
effect scales linearly with the ordinary one in the entire range over eight
orders of magnitude between the metallic and the insulating states. The
behavior differs qualitatively and quantitatively from theoretically predicted
and experimentally known in other materials.",1706.06392v1
2016-03-11,Measurement of the $B_{1g}$ and $B_{2g}$ components of the elastoresistivity tensor for tetragonal materials via transverse resistivity configurations,"The elastoresistivity tensor $m_{ij,kl}$ relates changes in resistivity to
strains experienced by a material. As a fourth-rank tensor, it contains
considerably more information about the material than the simpler (second-rank)
resistivity tensor; in particular, for a tetragonal material, the $B_{1g}$ and
$B_{2g}$ components of the elastoresistivity tensor ($m_{xx,xx}-m_{xx,yy}$ and
$2m_{xy,xy}$, respectively) can be related to its nematic susceptibility.
Previous experimental probes of this quantity have focused exclusively on
differential longitudinal elastoresistance measurements, which determine the
induced resistivity anisotropy arising from anisotropic in-plane strain based
on the difference of two longitudinal resistivity measurements. Here we
describe a complementary technique based on \textit{transverse}
elastoresistance measurements. This new approach is advantageous because it
directly determines the strain-induced resistivity anisotropy from a single
transverse measurement. To demonstrate the efficacy of this new experimental
protocol, we present transverse elastoresistance measurements of the
$2m_{xy,xy}$ elastoresistivity coefficient of BaFe$_2$As$_2$, a representative
iron-pnictide that has previously been characterized via differential
longitudinal elastoresistance measurements.",1603.03537v1
2017-04-13,Low temperature physical properties of Co-35Ni-20Mo-10Cr alloy MP35N,"Multiphase Co-35Ni-20Mo-10Cr alloy MP35N is a high strength alloy with
excellent corrosion resistance. Its applications span chemical, medical, and
food processing industries. Thanks to its high modulus and high strength, it
found applications in reinforcement of ultra-high field pulsed magnets.
Recently, it has also been considered for reinforcement in superconducting
wires used in ultra-high field superconducting magnets. For these applications,
accurate measurement of its physical properties at cryogenic temperatures is
very important. In this paper, physical properties including electrical
resistivity, specific heat, thermal conductivity, and magnetization of
as-received and aged samples are measured from 2 to 300 K. The electrical
resistivity of the aged sample is slightly higher than the as-received sample,
both showing a weak linear temperature dependence in the entire range of 2 -
300 K. The measured specific heat Cp of 0.43 J/g-K at 295 K agrees with a
theoretical prediction, but is significantly smaller than the values in the
literature. The thermal conductivity between 2 and 300 K is in good agreement
with the literature which is only available above 77 K. Magnetic property of
MP35N changes significantly with aging. The as-received sample exhibits Curie
paramagnetism with a Curie constant C = 0.175 K. While the aged sample contains
small amounts of a ferromagnetic phase even at room temperature. The measured
MP35N properties will be useful for the engineering design of pulsed magnets
and superconducting magnets using MP35N as reinforcement.",1704.04275v1
2024-02-20,Molten Salt Flux Liquid Transport Method for Ultra Clean Single Crystals UTe2,"Various single crystal growth techniques are presented for the unconventional
superconductor UTe2. The molten salt flux liquid transport (MSFLT) method is
employed to grow high-quality and large single crystals, exhibiting a high
residual resistivity ratio (RRR = 200-800). On the other hand, the Te self-flux
and chemical vapor transport (CVT) method produces samples of lower quality.
The MSFLT method is a hybrid approach that combines the molten salt flux (MSF)
and CVT methods. One significant advantage is that the materials gradually
crystallize at the relatively low temperature which is fixed during the main
process. This might be crucial for preventing U deficiency and obtaining
high-quality and large single crystals of UTe2. Many different single crystals
obtained by different technique were characterized by resistivity, specific
heat measurements. The superconducting transition temperature decreases with
the residual resistivity, followed by the Abrikosov-Gor'kov pair breaking
theory. The highest quality sample reaches Tc=2.1K. The residual gamma-value of
specific heat for the highest quality sample is only 3 percents of the normal
state gamma-value. The specific heat jump, Delta C/(gamma Tc) reaches about 2.7
for high quality samples, indicating a strong coupling superconductor.
Furthermore, the magnetic susceptibility for the field along a-axis in a high
quality single crystal does not show an up-turn behavior on cooling, which is
consistent with the results of NMR Knight shift and muSR experiments.",2402.12740v2
2023-12-29,Bilayer Vanadium Dioxide Thin Film with Elevated Transition Temperatures and High Resistance Switching,"Despite widespread interest in the phase-change applications of vanadium
dioxide (VO$_2$), the fabrication of high-quality VO$_2$ thin films with
elevated transition temperatures (TIMT) and high Insulator-Metal-Transition
resistance switching still remains a challenge. This study introduces a
two-step atmospheric oxidation approach to fabricate bilayer VO$_{2-x}$/VO$_2$
films on a c-plane sapphire substrate. To quantify the impact of the VO$_2$
buffer layer, a single-layer VO$_2$ film of the same thickness was also
fabricated. The bilayer VO$_{2-x}$/VO$_2$ films wherein the top VO$_{2-x}$ film
was under-oxidized demonstrated an elevation in TIMT reaching ~97 $^\circ$C,
one of the highest reported to date for VO$_2$ films and is achieved in a
doping-free manner. Our results also reveal a one-order increase in resistance
switching, with the optimum bilayer VO$_2$/VO$_2$ film exhibiting ~3.6 orders
of switching from 25 $^\circ$C to 110 $^\circ$C, compared to the optimum
single-layer VO$_2$ reference film. This is accompanied by a one-order decrease
in the on-state resistance in its metallic phase. The elevation in TIMT,
coupled with increased strain extracted from the XRD characterization of the
bilayer film, suggests the possibility of compressive strain along the c-axis.
These VO$_{2-x}$/VO$_2$ films also demonstrate a significant change in the
slope of their resistance vs temperature curves contrary to the conventional
smooth transition. This feature was ascribed to the rutile/monoclinic
quasi-heterostructure formed due to the top VO$_{2-x}$ film having a reduced
TIMT. Our findings carry significant implications for both the lucid
fabrication of VO$_2$ thin film devices as well as the study of phase
transitions in correlated oxides.",2312.17437v1
2024-01-31,Spark Plasma Sintering for high-speed diffusion welding of the ultrafine grained near-a Ti-5Al-2V alloy with high strength and corrosion resistance for nuclear engineering,"The paper demonstrates the prospects of Spark Plasma Sintering (SPS) for the
high-speed diffusion welding of the high-strength ultrafine-grained (UFG)
near-a Ti-5Al-2V alloy. The effect of increased diffusion welding intensity in
the UFG Ti alloys is discussed also. The welds of the UFG near-a-Ti-5Al-2V
alloy obtained by SPS are featured by high density, strength, and corrosion
resistance. The rate of weld sealing in the UFG alloys has been shown to depend
on the heating rate non-monotonously (with a pronounced maximum). At the stage
of continuous heating and isothermic holding, the kinetics of the weld sealing
was found to be determined by the exponential creep rate, the intensity of
which in the coarse-grained (CG) alloys is limited by the diffusion rate in the
crystal lattice whereas in the UFG alloys it is limited by the grain boundary
diffusion rate.",2401.17718v1
2018-01-29,Memristor properties of high temperature superconductors,"The review of studies on memristive properties or effect of resistive
switchings in four classes of high temperature superconductors is presented in
order to reveal functional properties of HTSCs which become apparent in the
effects under discussion, prospects of usage of high temperature
superconductors based memristors in applications and search for new mechanisms
of strongly correlated nature to realize new generation memristors. The
properties are: undergoing metal insulator transition at oxygen doping,
transport anisotropy, existence of charge reservoirs through which doping of
conductive copper oxygen layers is carried out. These are the main functional
properties of HTSCs which permit to use them in memristors. By the example of
study of bipolar effect of resistive switching in high temperature
superconductors based heterojunctions it is shown how one can form memristor
structures based on high temperature superconductors using their functional
properties.",1801.09428v1
2016-03-07,Prediction of a Two-dimensional Phosphorus Nitride Monolayer,"Today, 2D semiconductor materials have been extended into the nitrogen group:
phosphorene, arsenene, antimonene and even nitrogene. Motivated by them, based
upon first-principles density functional calculations, we propose a new
two-dimensional phosphorus nitride (PN) structure that is stable well above the
room temperature, due to its extremely high cohesive energy. Unlike
phosphorene, PN structure is resistant to high temperature oxidation. The
structure is predicted to be a semiconductor with a wide, indirect band gap of
2.64 eV. More interestingly, the phosphorus nitride monolayer experiences an
indirect-to-direct band-gap transition at a relatively small tensile strain.
Such dramatic transformation in the electronic structure combined with
structural stability and oxidation resistance at high temperature could pave
the way for exciting innovations in high-speed ultrathin transistors, power
electronic modules, ultra-high efficiency LEDs and semiconductor lasers.",1603.01957v2
2023-04-12,Crack-free high composition (>35%) thick (>30 nm) barrier AlGaN/AlN/GaN HEMT on sapphire with record low sheet resistance,"In this article, high composition (>35%) thick (>30 nm) barrier AlGaN/AlN/GaN
HEMT structure grown on a sapphire substrate with ultra-low sheet resistivity
(<250 \Omega / \Box ) is reported. Optimization of growth conditions, such as
reduced growth rate, low carbon incorporation, and thickness optimization of
different epitaxial layers allowed to grow a crack-free high composition and
thick AlGaN barrier layer HEMT structure. A significantly high two-dimensional
electron gas (2DEG) density of 1.46 \times 10^{13} cm^{-2} with a room
temperature mobility of 1710 cm^{2}/V.s is obtained by Hall measurement using
the Van-Der-Pauw method. These state-of-the-art results show great potential
for high-power Ga-polar HEMT design on the sapphire substrate.",2304.05593v1
2015-02-06,Long-term stability of phase-separated Half-Heusler compounds,"Half-Heusler (HH) compounds have shown high Figure of merits up to 1.5. The
key to these high thermoelectric efficiencies is an intrinsic phase separation,
which occurs in multicomponent Half-Heusler compounds and leads to an
significantly reduction of the thermal conductivity. For commercial
applications, compatible n- and p-type materials are essential and their
thermal stability under operating conditions, e.g. for an automotive up to 873
K, needs to be guaranteed. For the first time, the long-term stability of n-
and p-type HH materials is proved. We investigated HH materials based on the
Ti0.3Zr0.35Hf0.35NiSn-system after 500 cycles (1700 h) from 373 to 873 K. Both
compounds exhibit a maximum Seebeck coefficient of S around 210 muV/K and an
intrinsic phase separation into two HH phases. The dendritic microstructure is
temperature resistant and maintained the low thermal conductivity values (kappa
less than 4 W/Km). Our results emphasize that phase-separated HH compounds are
suitable low cost materials and can lead to enhanced thermoelectric
efficiencies beyond the set benchmark for industrial applications.",1502.01828v1
2020-08-12,Helium effects and bubbles formation in irradiated Ti3SiC2,"Ti3SiC2 is a potential structural material for nuclear reactor applications.
However, He irradiation effects in this material are not well understood,
especially at high temperatures. Here, we compare the effects of He irradiation
in Ti3SiC2 at room temperature (RT) and at 750 {\deg}C. Irradiation at 750
{\deg}C was found to lead to extremely elongated He bubbles that are
concentrated in the nano-laminate layers of Ti3SiC2, whereas the overall
crystal structure of the material remained intact. In contrast, at RT, the
layered structure was significantly damaged and highly disordered after
irradiation. Our study reveals that at elevated temperatures, the unique
structure of Ti3SiC2 can accommodate large amounts of He atoms in the
nano-laminate layer, without compromising the structural stability of the
material. The structure and the mechanical tests results show that the
irradiation induced swelling and hardening at 750 {\deg}C are much smaller than
those at RT. These results indicate that Ti3SiC2 has an excellent resistance to
accumulation of radiation-induced He impurities and that it has a considerable
tolerance to irradiation-induced degradation of mechanical properties at high
temperatures.",2008.05468v1
2023-09-05,"Control of Mechanical and Fracture Properties in Two-phase Materials Reinforced by Continuous, Irregular Networks","Composites with high strength and high fracture resistance are desirable for
structural and protective applications. Most composites, however, suffer from
poor damage tolerance and are prone to unpredictable fractures. Understanding
the behavior of materials with an irregular reinforcement phase offers
fundamental guidelines for tailoring their performance. Here, we study the
fracture nucleation and propagation in two phase composites, as a function of
the topology of their irregular microstructures. We use a stochastic algorithm
to design the polymeric reinforcing network, achieving independent control of
topology and geometry of the microstructure. By tuning the local connectivity
of isodense tiles and their assembly into larger structures, we tailor the
mechanical and fracture properties of the architected composites, at the local
and global scale. Finally, combining different reinforcing networks into a
spatially determined meso-scale assembly, we demonstrate how the spatial
propagation of fractures in architected composite materials can be designed and
controlled a priori.",2309.01888v1
2020-01-21,"Mechanical behavior, enhanced dc resistivity, energy band gap and high temperature magnetic properties of Y-substituted Mg-Zn ferrites","We report the synthesis of Y-substituted Mg-Zn ferrites using conventional
standard ceramic technique. XRD patterns confirm the single phase cubic spinel
structure up to x = 0.03 and appearance of a secondary phase of YFeO3for higher
Y contents. FESEM images depict the distribution of grains and EDS spectra
confirmed the absence of any unwanted element. Completion of solid state
reaction and formation of spinel structure has been revealed from FTIR spectra.
The FTIR data along with lattice constant, bulk density and porosity were
further used to calculate the stiffness constant (Cij), elastic constant and
Debye temperatures. Mechanical stability of all studied compositions is
confirmed from Cij using Born stability conditions. Brittleness and isotropic
nature are also confirmed using Poisson ratio and anisotropy constants,
respectively. The enhancement of dc electrical resistivity with Y content is
observed. The energy band gap (increased with Y contents) is found in good
agreement with dc electrical resistivity. Ferrimagnetic to paramagnetic phase
change has been observed from the field dependent high temperature
magnetization curves. The magnetic moments and saturation magnetization were
found to be decreased with increasing temperature. The Curie temperature (Tc)
has been measured from temperature dependent magnetic moment (M-T) and initial
permeability and found to be in good agreement with each other. Decrease in Tc
with Y content is due to redistribution of cations and weakening of the
exchange coupling constant. The magnetic phase transition has been analyzed by
Arrott plot and found to have second order phase transition. The dc resistivity
endorses the prepared ferrites are suitable for high frequency and high
temperature magnetic device applications as well.",2001.07313v1
2023-01-07,Impact of Severe Plastic Deformation on Kinetics and Thermodynamics of Hydrogen Storage in Magnesium and Its Alloys,"Magnesium and its alloys are the most investigated materials for solid-state
hydrogen storage in the form of metal hydrides, but there are still unresolved
problems with the kinetics and thermodynamics of hydrogenation and
dehydrogenation of this group of materials. Severe plastic deformation (SPD)
methods, such as equal-channel angular pressing (ECAP), high-pressure torsion
(HPT), intensive rolling and fast forging, have been widely used to enhance the
activation, air resistance, and hydrogenation/dehydrogenation kinetics of
Mg-based hydrogen storage materials by introducing ultrafine/nanoscale grains
and crystal lattice defects. These severely deformed materials, particularly in
the presence of alloying additives or second-phase nanoparticles, can show not
only fast hydrogen absorption/desorption kinetics but also good cycling
stability. It was shown that some materials that are apparently inert to
hydrogen can absorb hydrogen after SPD processing. Moreover, the SPD methods
were effectively used for hydrogen binding-energy engineering and synthesizing
new magnesium alloys with low thermodynamic stability for reversible
low/room-temperature hydrogen storage, such as nanoglasses, high-entropy
alloys, and metastable phases including the high-pressure {\gamma}-MgH2
polymorph. This article reviews recent advances in the development of Mg-based
hydrogen storage materials by SPD processing and discusses their potential in
future applications.",2301.05009v1
2021-07-26,Massive electrons and unconventional room-temperature superconductivity in superhydrides,"The search for room-temperature superconducting materials has been at the
center of modern research for decades. The recent discovery of high-temperature
superconductivity, under extreme pressure in hydrogen-rich materials, is a
tremendous achievement in this research front. This discovery offers a route in
the search for room temperature superconductivity at ambient pressure. The
superconductivity of these hydrogen-rich materials was confirmed by the
observation of zero-resistance, isotope effects, effect of magnetic field, and
other standard properties. However, some of the experimental features were
puzzling as they were not consistent with the known superconductivity theories.
These debatable features have lead to a series of recent publications
downplaying the existence of superconductivity in these superhydrides. Here we
propose a concept of massive electrons under pressure and successfully explain
all non-standard experimental observations. Our massive electron concept
explains the large effective mass of the quasiparticles, the reason for the
high critical temperatures for moderate electron-phonon couplings, and a 3-5
orders of magnitude larger conductivity causing a narrow resistivity broadening
at the transition in the presence of magnetic field. We anticipate our findings
will lead to a new directions and tweaks in current research in the search for
ambient-pressure, room-temperature superconductors.",2107.12255v1
2010-04-21,Superconductor-insulator quantum phase transition,"The current understanding of the superconductor-insulator transition is
discussed level by level in a cyclic spiral-like manner. At the first level,
physical phenomena and processes are discussed which, while of no formal
relevance to the topic of transitions, are important for their implementation
and observation; these include superconductivity in low electron density
materials, transport and magnetoresistance in superconducting island films and
in highly resistive granular materials with superconducting grains, and the
Berezinskii-Kosterlitz-Thouless transition. The second level discusses and
summarizes results from various microscopic approaches to the problem, whether
based on the Bardeen-Cooper-Schrieffer theory (the disorder-induced reduction
in the superconducting transition temperature; the key role of Coulomb blockade
in high-resistance granular superconductors; superconducting fluctuations in a
strong magnetic field) or on the theory of the Bose-Einstein condensation. A
special discussion is given to phenomenological scaling theories. Experimental
investigations, primarily transport measurements, make the contents of the
third level and are for convenience classified by the type of material used
(ultrathin films, variable composition materials, high-temperature
superconductors, superconductor-poor metal transitions). As a separate topic,
data on nonlinear phenomena near the superconductor-insulator transition are
presented. At the final, summarizing, level the basic aspects of the problem
are enumerated again to identify where further research is needed and how this
research can be carried out. Some relatively new results, potentially of key
importance in resolving the remaining problems, are also discussed.",1004.3761v1
2016-03-30,"Butterfly Magnetoresistance, Quasi-2D Dirac Fermi Surfaces, and a Topological Phase Transition in ZrSiS","Magnetoresistance (MR), the change of a material's electrical resistance in
response to an applied magnetic field, is a technologically important property
that has been the topic of intense study for more than a quarter century. Here
we report the observation of an unusual ""butterfly"" shaped titanic angular
magnetoresistance (AMR) in the non-magnetic, Dirac material, ZrSiS. The MR is
large and positive, reaching nearly 1.8 x 10^5 percent at 9 T and 2 K at an
angle of 45o between the applied current (along the a-axis) and the applied
field (90o is H parallel to the c-axis). Approaching 90o, a ""dip"" is seen in
the AMR which can be traced to an angle dependent deviation from the H^2 law.
By analyzing the SdH oscillations at different angles, we find that ZrSiS has a
combination of 2D and 3D Dirac pockets comprising its Fermi surface and that
the anomalous transport behavior coincides with a topological phase transition
whose robust signature is evident despite transport contributions from other
parts of the Fermi surface. We also find that as a function of angle, the
temperature dependent resistivity in high field displays a broad peak-like
behavior, unlike any known Dirac/Weyl material. The combination of very high
mobility carriers and multiple Fermi surfaces in ZrSiS allow for large bulk
property changes to occur as a function of angle between applied fields makes
it a promising platform to study the physics stemming from the coexistence of
2D and 3D Dirac electrons.",1603.09318v2
2020-08-27,Large-Scale and Robust Multifunctional Vertically-Aligned MoS$_2$ Photo-Memristors,"Memristive devices have drawn considerable research attention due to their
potential applications in non-volatile memory and neuromorphic computing. The
combination of resistive switching devices with light-responsive materials is
considered a novel way to integrate optical information with electrical
circuitry. On the other hand, 2D materials have attracted substantial
consideration thank to their unique crystal structure, as reflected in their
chemical and physical properties. Although not the major focus, van der Waals
solids were proven to be potential candidates in memristive devices. In this
scheme, the majority of the resistive switching devices were implemented on
planar flakes, obtained by mechanical exfoliation. Here we utilize a facile and
robust methodology to grow large-scale vertically aligned MoS$_2$ (VA-MoS$_2$)
films on standard silicon substrates. Memristive devices with the structure
silver/VA-MoS$_2$/Si are shown to have low set-ON voltages (<0.5V),
large-retention times ($>2\times10^4$ s) and high thermal stability (up to 350
$^\circ$C). The proposed memristive device also exhibits long term potentiation
/ depression (LTP/LTD) and photo-active memory states. The large-scale
fabrication, together with the low operating voltages, high thermal stability,
light-responsive behaviour and long-term potentiation/depression, makes this
approach very appealing for real-life non-volatile memory applications.",2008.11950v1
2002-08-15,High Ferromagnetic Transition Temperature (172K) in Mn delta-doped GaAs with p-type Selective Doping,"We have found high ferromagnetic transition temperature in Mn delta-doped
GaAs-based heterostructures grown on GaAs(001) substrates by molecular beam
epitaxy. A 0.3 ML Mn d-doped GaAs samples showed high resistivity at low
temperature and did not show a ferromagnetic behavior. However, in a
selectively doped heterostructure (Mn delta-doped GaAs / Be-doped AlGaAs),
where holes were supplied from the Be-doped AlGaAs layer, clear ferromagnetic
order was observed. The ferromagnetic transition temperature of the selectively
doped heterostructure was as high as 172K with suitable low-temperature (LT)
annealing treatment.",0208299v1
2013-10-30,"Large, high quality single-crystals of the new Topological Kondo Insulator, SmB6","SmB6 has recently been predicted to be a Topological Kondo Insulator, the
first strongly correlated heavy fermion material to exhibit topological surface
states. High quality crystals are necessary to investigate the topological
properties of this material. Single crystal growth of the rare earth
hexaboride, SmB6, has been carried out by the floating zone technique using a
high power xenon arc lamp image furnace. Large, high quality single-crystals
are obtained by this technique. The crystals produced by the floating zone
technique are free of contamination from flux materials and have been
characterised by resistivity and magnetisation measurements. These crystals are
ideally suited for the investigation of both the surface and bulk properties of
SmB6.",1310.8189v1
2019-11-05,Metal$/BaTiO_{3}/β-Ga_{2}O_{3}$ Dielectric Heterojunction Diode with 5.7 MV/cm Breakdown Field,"Wide and ultra-wide band gap semiconductors can provide excellent performance
due to their high energy band gap, which leads to breakdown electric fields
that are more than an order of magnitude higher than conventional silicon
electronics. In materials where p-type doping is not available, achieving this
high breakdown field in a vertical diode or transistor is very challenging. We
propose and demonstrate the use of dielectric heterojunctions that use extreme
permittivity materials to achieve high breakdown field in a unipolar device. We
demonstrate the integration of a high permittivity material BaTiO3 with n-type
$\beta$-Ga2O3 to enable 5.7 MV/cm average electric field and 7 MV/cm peak
electric field at the device edge, while maintaining forward conduction with
relatively low on-resistance and voltage loss. The proposed dielectric
heterojunction could enable new design strategies to achieve theoretical device
performance limits in wide and ultra-wide band gap semiconductors where bipolar
doping is challenging.",1911.02068v1
2009-03-17,In search for the superconducting spin-switch: Magnetization induced resistance switching effects in La$_{0.67}$Sr$_{0.33}$MnO$_3$/YBa$_2$Cu$_3$O$_{7-δ}$ bi- and trilayers,"We have studied the influence of the magnetization on the superconducting
transition temperature ($T_c$) in bi- and trilayers consisting of the
half-metallic ferromagnet La$_{0.67}$Sr$_{0.33}$MnO$_3$ (LSMO) and the
high-temperature superconductor YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO). We have
made use of tilted epitaxial growth in order to achieve contacts between the
two materials that are partly in the crystallographic $ab$-plane of the YBCO.
As a result of uniaxial magnetic anisotropy in the tilted structures, we
observe sharp magnetization switching behavior. At temperatures close to $T_c$,
the magnetization switching induces resistance jumps in trilayers, resulting in
a magnetization dependence of $T_c$. In bilayers, this switching effect can be
observed as well, provided that the interface to the ferromagnetic layer is
considerably rough. Our results indicate that the switching behavior arises
from magnetic stray fields from the ferromagnetic layers that penetrate into
the superconductor. A simple model describes the observed behavior well. We
find no evidence that the switching behavior is caused by a so-called
superconducting spin-switch, nor by accumulation of spin-polarized electrons.
Observation of magnetic coupling of the ferromagnetic layers, through the
superconductor, supports the idea of field induced resistance switching.",0903.2993v1
2016-12-13,Bad Metals from Fluctuating Density Waves,"Bad metals have a large resistivity without being strongly disordered. In
many bad metals the Drude peak moves away from zero frequency as the
resistivity becomes large at increasing temperatures. We catalogue the position
and width of the `displaced Drude peak' in the observed optical conductivity of
several families of bad metals, showing that $\omega_\text{peak} \sim \Delta
\omega \sim k_BT/\hbar$. This is the same quantum critical timescale that
underpins the $T$-linear dc resistivity of many of these materials. We provide
a unified theoretical description of the optical and dc transport properties of
bad metals in terms of the hydrodynamics of short range quantum critical
fluctuations of incommensurate density wave order. Within hydrodynamics, pinned
translational order is essential to obtain the nonzero frequency peak.",1612.04381v5
2017-03-11,On the isotope effect in compressed superconducting H$_\textrm{3}$S and D$_\textrm{3}$S,"A maximum superconductive transition temperature $T_\textrm{C}$ = 203.5 K has
recently been reported for a sample of the binary compound tri-hydrogen sulfide
(H$_\textrm{3}$S) prepared at high pressure and with room temperature
annealing. Measurements of $T_\textrm{C}$ for H$_\textrm{3}$S and its deuterium
counterpart D$_\textrm{3}$S have suggested a mass isotope effect exponent
${\alpha}$ with anomalous enhancements for reduced applied pressures. While
widely cited for evidence of phonon-based superconductivity, the measured
$T_\textrm{C}$ is shown to exhibit important dependences on the quality and
character of the H$_\textrm{3}$S and D$_\textrm{3}$S materials under study;
examination of resistance versus temperature data shows that variations in
$T_\textrm{C}$ and apparent ${\alpha}$ are strongly correlated with residual
resistance ratio, indicative of sensitivity to metallic order. Correlations
also extend to the fractional widths of the superconducting transitions. Using
resistance data to quantify and compensate for the evident materials
differences between H$_\textrm{3}$S and D$_\textrm{3}$S samples, a value of
${\alpha}$ = 0.043 $\pm$ 0.140 is obtained. Thus, when corrected for the
varying levels of disorder, the experimental upper limit ($\leq$0.183) lies
well below ${\alpha}$ derived in phonon-based theories.",1703.04034v1
2019-07-17,Quasi 2-D magnetism in the Kagome layer compound FeSn,"Single crystals of the single Kagome layer compound FeSn are investigated
using x-ray and neutron scattering, magnetic susceptibility and magnetization,
heat capacity, resistivity, Hall, Seebeck, thermal expansion, thermal
conductivity measurements and density functional theory (DFT). FeSn is a planar
antiferromagnet below TN = 365 K and exhibits ferromagnetic magnetic order
within each Kagome layer. The in-plane magnetic susceptibility is sensitive to
synthesis conditions. Resistivity, Hall and Seebeck results indicate multiple
bands near the Fermi energy. The resistivity of FeSn is about 3 times lower for
current along the stacking direction than in the plane, suggesting that
transport and the bulk electronic structure of FeSn is not quasi 2D. FeSn is an
excellent metal with Rho(300K)/Rho(2K) values about 100 in both directions.
While the ordered state is antiferromagnetic, high temperature susceptibility
measurements indicate a ferromagnetic Curie-Weiss temperature of 173 K,
reflecting the strong in-plane ferromagnetic interactions. DFT calculations
show a 3D electronic structure with the Dirac nodal lines along the K-H
directions in the magnetic Brillouin zone about 0.3 eV below the Fermi energy,
with the Dirac dispersions at the K points gapped by spin-orbit coupling except
at the H point. The magnetism, however, is highly 2D with
Jin-plane/Jout-of-plane = 10. The predicted spin-wave spectrum is presented.",1907.07719v1
2019-06-25,Spin-split band hybridization in graphene proximitized with $α$-RuCl$_3$ nanosheets,"Proximity effects induced in the 2D Dirac material graphene potentially open
access to novel and intriguing physical phenomena. Thus far, the coupling
between graphene and ferromagnetic insulators has been experimentally
established. However, only very little is known about graphene's interaction
with antiferromagnetic insulators. Here, we report a low temperature study of
the electronic properties of high quality van der Waals heterostructures
composed of a single graphene layer proximitized with $\alpha$-RuCl$_3$. The
latter is known to become antiferromagnetically ordered below 10 K. Shubnikov
de Haas oscillations in the longitudinal resistance together with Hall
resistance measurements provide clear evidence for a band realignment that is
accompanied by a transfer of electrons originally occupying the graphene's spin
degenerate Dirac cones into $\alpha$-RuCl$_3$ band states with in-plane spin
polarization. Left behind are holes in two separate Fermi pockets, only the
dispersion of one of which is distorted near the Fermi energy due to spin
selective hybridization with these spin polarized $\alpha$-RuCl$_3$ band
states. This interpretation is supported by our DFT calculations. An unexpected
damping of the quantum oscillations as well as a zero field resistance upturn
close to the N$\'e$el temperature of $\alpha$-RuCl$_3$ suggests the onset of
additional spin scattering due to spin fluctuations in the $\alpha$-RuCl$_3$.",1906.10405v1
2020-01-17,"A back-end, CMOS compatible ferroelectric Field Effect Transistor for synaptic weights","Neuromorphic computing architectures enable the dense co-location of memory
and processing elements within a single circuit. This co-location removes the
communication bottleneck of transferring data between separate memory and
computing units as in standard von Neuman architectures for data-critical
applications including machine learning. The essential building blocks of
neuromorphic systems are non-volatile synaptic elements such as memristors. Key
memristor properties include a suitable non-volatile resistance range,
continuous linear resistance modulation and symmetric switching. In this work,
we demonstrate voltage-controlled, symmetric and analog potentiation and
depression of a ferroelectric Hf$_{57}$Zr$_{43}$O$_{2}$ (HZO) field effect
transistor (FeFET) with good linearity. Our FeFET operates with a low writing
energy (fJ) and fast programming time (40 ns). Retention measurements have been
done over 4-bits depth with low noise (1%) in the tungsten oxide (WO$_{x}$)
read out channel. By adjusting the channel thickness from 15nm to 8nm, the
on/off ratio of the FeFET can be engineered from 1% to 200% with an
on-resistance ideally >100 kOhm, depending on the channel geometry. The device
concept is using earth-abundant materials, and is compatible with a back end of
line (BEOL) integration into complementary metal-oxidesemiconductor (CMOS)
processes. It has therefore a great potential for the fabrication of high
density, large-scale integrated arrays of artificial analog synapses.",2001.06475v1
2020-05-16,Switching friction at a manganite surface using electric fields,"We report active control of the friction force at the contact between a
nanoscale asperity and a La$_{0.55}$Ca$_{0.45}$MnO$_3$ (LCMO) thin film using
electric fields. We use friction force microscopy under ultrahigh vacuum
conditions to measure the friction force as we change the film resistive state
by electric field-induced resistive switching. Friction forces are high in the
insulating state and clearly change to lower values when the probed local
region is switched to the conducting state. Upon switching back to an
insulating state, the friction forces increase again. Thus, we demonstrate
active control of friction without having to change the contact temperature or
pressure. By comparing with measurements of friction at the metal-to-insulator
transition and with the effect of applied voltage on adhesion, we rule out
electronic excitations, electrostatic forces and changes in contact area as the
reasons for the effect of resistive switching on friction. Instead, we argue
that friction is limited by phonon relaxation times which are strongly coupled
to the electronic degrees of freedom through distortions of the MnO6 octahedra.
The concept of controlling friction forces by electric fields should be
applicable to any materials where the field produces strong changes in phonon
lifetimes.",2005.08949v1
2020-08-17,Enhancement of spin Hall conductivity in W-Ta alloy,"Generating pure spin currents via the spin Hall effect in heavy metals has
been an active topic of research in the last decade. In order to reduce the
energy required to efficiently switch neighbouring ferromagnetic layers for
applications, one should not only increase the charge- to-spin conversion
efficiency but also decrease the longitudinal resistivity of the heavy metal.
In this work, we investigate the spin Hall conductivity in W_{1-x}Ta_{x} /
CoFeB / MgO (x = 0 - 0.2) using spin torque ferromagnetic resonance
measurements. Alloying W with Ta leads to a factor of two change in both the
damping-like effective spin Hall angle (from - 0.15 to - 0.3) and longitudinal
resistivity (60 - 120 {\mu}W cm). At 11% Ta concentration, a remarkably high
spin Hall angle value of - 0.3 is achieved with a low longitudinal resistivity
100 {\mu}W cm, which could lead to a very low power consumption for this
W-based alloy. This work demonstrates sputter-deposited W-Ta alloys could be a
promising material for power-efficient spin current generation.",2008.07572v1
2020-12-23,"Resistivity, Hall effect, and anisotropic superconducting coherence lengths of HgBa$_2$CaCu$_2$O$_{6+δ}$ thin films with different morphology","Thin films of the high-temperature superconductor
HgBa$_2$CaCu$_2$O$_{6+\delta}$ have been prepared on SrTiO$_3$ substrates by
pulsed-laser deposition of precursor films and subsequent annealing in
mercury-vapor atmosphere. The microstructural properties of such films can vary
considerably and have been analyzed by x-ray diffraction and atomic force
microscopy. Whereas the resistivity is significantly enhanced in samples with
coarse-grained structure, the Hall effect shows little variation. This
disparity is discussed based on models for transport properties in granular
materials. We find that, despite of the morphological variation, all samples
have similar superconducting properties. The critical temperatures $T_c \sim
121.2$ K $\dots 122.0$ K, resistivity, and Hall data indicate that the samples
are optimally doped. The analyses of superconducting order parameter
fluctuations in zero and finite magnetic fields yield the in-plane $\xi_{ab}(0)
\sim 2.3$ nm $\dots 2.8$ nm and out-of-plane $\xi_{c}(0) \sim 0.17$ nm $ \dots
0.24$ nm Ginzburg-Landau coherence lengths at zero temperature. Hall
measurements provide estimates of carrier scattering defects in the normal
state and vortex pinning properties in the superconducting state inside the
grains.",2012.12539v1
2021-05-03,Fingerprints of quantum criticality in locally resolved transport,"Understanding electrical transport in strange metals, including the seeming
universality of Planckian $T$-linear resistivity, remains a longstanding
challenge in condensed matter physics. We propose that local imaging
techniques, such as nitrogen vacancy center magnetometry, can locally identify
signatures of quantum critical response which are invisible in measurements of
a bulk electrical resistivity. As an illustrative example, we use a minimal
holographic model for a strange metal in two spatial dimensions to predict how
electrical current will flow in regimes dominated by quantum critical dynamics
on the Planckian length scale. We describe the crossover between quantum
critical transport and hydrodynamic transport (including Ohmic regimes), both
in charge neutral and finite density systems. We compare our holographic
predictions to experiments on charge neutral graphene, finding quantitative
agreement with available data; we suggest further experiments which may
determine the relevance of our framework to transport on Planckian scales in
this material. More broadly, we propose that locally imaged transport be used
to test the universality (or lack thereof) of microscopic dynamics in the
diverse set of quantum materials exhibiting $T$-linear resistivity.",2105.01075v4
2022-06-16,Size-Dependent Grain Boundary Scattering in Topological Semimetals,"We assess the viability of topological semimetals for application in advanced
interconnect technology, where conductor size is on the order of a few
nanometers and grain boundaries are expected to be prevalent. We investigate
the electron transport properties and grain boundary scattering in thin films
of the topological semimetals CoSi and CoGe using first-principles calculations
combined with the Non-Equilibrium Green's Function (NEGF) technique. Unlike
conventional interconnect metals like Cu and Al, we find that CoSi and CoGe
conduct primarily through topologically-protected surface states in thin film
structures even in the presence of grain boundaries. The area-normalized
resistance decreases with decreasing film thickness for CoSi and CoGe thin
films both with and without grain boundaries; a trend opposite to that of the
conventional metals Cu and Al. The surface-dominated transport mechanisms in
thin films of topological semimetals with grain boundaries demonstrates a
fundamentally new paradigm of the classical resistivity size-effect, and
suggests that these materials may be promising candidates for applications as
nano-interconnects where high electrical resistivity acts as a major bottleneck
limiting semiconductor device performance.",2206.08214v2
2023-03-06,Thermal hysteretic behavior and negative magnetoresistance in an unusual charge-density-wave material EuTe4,"EuTe4 is a newly-discovered van der Waals material exhibiting a novel
charge-density wave (CDW) with a large thermal hysteresis in the resistivity
and CDW gap. In this work, we systematically study the electronic structure and
transport properties of EuTe4 using high-resolution angle-resolved
photoemission spectroscopy (ARPES), magnetoresistance measurements, and
scanning tunneling microscopy (STM). We observe a CDW gap of about 200 meV at
low temperatures that persists up to 400 K, suggesting that the CDW transition
occurs at a much higher temperature. We observe a large thermal hysteretic
behavior of the ARPES intensity near the Fermi level, consistent with the
resistivity measurement. The hysteresis in the resistivity measurement does not
change under a magnetic field up to 7 T, excluding the thermal magnetic
hysteresis mechanism. Instead, the surface topography measured with STM shows
surface domains with different CDW trimerization directions, which may be
important for the thermal hysteretic behavior of EuTe4. Interestingly, we
observe a large negative magnetoresistance at low temperatures that can be
associated with the canting of magnetically ordered Eu spins. Our work shed
light on the understanding of magnetic, transport, and electronic properties of
EuTe4.",2303.02848v1
2023-05-10,Doubling of the superconducting transition temperature in ultra-clean wafer-scale aluminum nanofilms,"Superconducting properties of thin films can be vastly different from those
of bulk materials. Seminal work has shown the critical temperature Tc of
elemental superconductors decreases with decreasing film thickness when the
normal-state sheet resistance is lower than the quantum resistance h/(4e2).
Sporadic examples on disordered films, however, hinted an enhancement in Tc
although, structural and strain characterization was not possible since samples
were prepared on a cold substrate in situ. To clarify the role of reduced
dimensionality and disorder on the superconducting properties of thin films we
employed molecular beam epitaxy to grow wafer-scale high-quality aluminum (Al)
nanofilms with normal-state sheet resistance at least 20 times lower than
h/(4e2) and investigated their electronic and structural properties ex situ.
Defying general expectations, Tc increases with decreasing Al film thickness,
reaching 2.4 K for 3.5-nm-thick Al film grown on GaAs: twice that of bulk Al
(1.2 K). DFT calculations indicate surface phonon softening impacts
superconductivity in pure ultra-thin films, offering a new route for materials
engineering in two dimensions.",2305.06084v1
1999-06-17,Anomalous c-axis charge dynamics in copper oxide materials,"Within the t-J model, the c-axis charge dynamics of the copper oxide
materials in the underdoped and optimally doped regimes is studied by
considering the incoherent interlayer hopping. It is shown that the c-axis
charge dynamics is mainly governed by the scattering from the in-plane
fluctuation. In the optimally doped regime, the c-axis resistivity is a linear
in temperatures, and shows the metallic-like behavior for all temperatures,
while the c-axis resistivity in the underdoped regime is characterized by a
crossover from the high temperature metallic-like behavior to the low
temperature semiconducting-like behavior, which are consistent with experiments
and numerical simulations.",9906260v2
2001-07-04,Crystal Growth and Characterization of Doped CZT Crystals,"Cd1-xZnxTe crystals with x in the range of 0.1-0.2 were grown by the
high-pressure vertical Bridgman method from pre-synthesized CZT. Resistive
graphite heaters were used to control the temperature profiles within the
furnaces, and an argon overpressure was used to reduce the cadmium loss. The
crystals were doped with either Al, Ni, In, Ga, Ge or Sn. The doping was
carried out by three different ways: 1) by adding of the pure metals during
growth runs; 2) by adding of the tellurides of the metals during growth runs;
or 3) by inserting of the metal tellurides during synthesis of the starting CZT
material. Some of the growth process parameters were also varied. The as-grown
CZT ingots had diameters of either 15 or 38 mm. The influence of the doping on
CZT properties, particularly the conductivity type and specific electrical
resistivity, will be discussed. Energy spectra from alpha particles (U-233,
Ra-226, and U-233+Pu-239+Pu-238) and from different gamma sources (Cs-137,
Co-60, Co-57, Am-241) will be reported.",0107081v1
2007-05-29,Sliding charge density wave in manganites,"The so-called stripe phase of the manganites is an important example of the
complex behaviour of metal oxides, and has long been interpreted as the
localisation of charge at atomic sites. Here, we demonstrate via resistance
measurements on La_{0.50}Ca_{0.50}MnO_3 that this state is in fact a
prototypical charge density wave (CDW) which undergoes collective transport.
Dramatic resistance hysteresis effects and broadband noise properties are
observed, both of which are typical of sliding CDW systems. Moreover, the high
levels of disorder typical of manganites result in behaviour similar to that of
well-known disordered CDW materials. Our discovery that the manganite
superstructure is a CDW shows that unusual transport and structural properties
do not require exotic physics, but can emerge when a well-understood phase (the
CDW) coexists with disorder.",0705.4310v2
2009-02-23,Superconductivity at 22.3 K in SrFe2-xIrxAs2,"By substituting the Fe with the 5d-transition metal Ir in SrFe2As2, we have
successfully synthesized the superconductor SrFe2-xIrxAs2 with Tc = 22.3 K at x
= 0.5. X-ray diffraction indicates that the material has formed the
ThCr2Si2-type structure with a space group I4/mmm. The temperature dependence
of resistivity and dc magnetization both reveal sharp superconducting
transitions at around 22 K. An estimate on the diamagnetization signal reveals
a high Meissner shielding volume. Interestingly, the normal state resistivity
exhibits a roughly linear behavior up to 300 K. The superconducting transitions
at different magnetic fields were also measured yielding a slope of -dHc2/dT =
3.8 T/K near Tc. Using the Werthamer-Helfand-Hohenberg (WHH) formula, the upper
critical field at zero K is found to be about 58 T. Counting the possible
number of electrons doped into the system in SrFe2-xIrxAs2, we argue that the
superconductivity in the Ir-doped system is different from the Co-doped case,
which should add more ingredients to the underlying physics of the iron
pnictide superconductors.",0902.3957v2
2009-09-07,SiC Graphene Suitable For Quantum Hall Resistance Metrology,"We report the first observation of the quantum Hall effect in epitaxial
graphene. The result described in the submitted manuscript fills the yawning
gap in the understanding of the electronic properties of this truly remarkable
material and demonstrate suitability of the silicon carbide technology for
manufactiring large area high quality graphene. Having found the quantum Hall
effect in several devices produced on distant parts of a single large-area
wafer, we can confirm that material synthesized on the Si-terminated face of
SiC promises a suitable platform for the implementations of quantum resistance
metrology at elevated temperatures and, in the longer term, opens bright
prospects for scalable electronics based on graphene.",0909.1193v1
2010-07-07,Unusual Resistance Hysteresis in n-Layer Graphene Field Effect Transistors Fabricated on Ferroelectric Pb(Zr_0.2Ti_0.8)O_3,"We have fabricated n-layer graphene field effect transistors on epitaxial
ferroelectric Pb(Zr_0.2Ti_0.8)O_3 (PZT) thin films. At low gate voltages, PZT
behaves as a high-k dielectric with k up to 100. An unusual resistance
hysteresis occurs in gate sweeps at high voltages, with its direction opposite
to that expected from the polarization switching of PZT. The relaxation of the
metastable state is thermally activated, with an activation barrier of 50-110
meV and a time constant of 6 hours at 300 K. We attribute its origin to the
slow dissociation/recombination dynamics of water molecules adsorbed at the
graphene-PZT interface. This robust hysteresis can potentially be used to
construct graphene-ferroelectric hybrid memory devices.",1007.1240v1
2011-01-15,Theory of anomalous Hall effect for type-II high-Tc and conventional superconductors,"The anomalous Hall effect for type-II superconductors is investigated by
random walk theorem. It is shown that the origin of Hall anomaly is induced by
the thermally activated vortex bundle flow (TAVBF) over the
directional-dependent energy barrier formed by the Magus force, random
collective pinning force, and strong pinning force inside the vortex bundles.
The directional-dependent potential barrier of the vortex bundles renormalizes
the Hall and longitudinal resistivities strongly. Under the framework of
present theory, it is also shown that the Hall anomaly is universal for type-II
superconductors, either high- or conventional as well as bulk materials or thin
films. The conditions for Hall anomaly and reentry phenomenon are derived, the
Hall and longitudinal resistivities as well as Hall angle for type-II
superconducting films and bulk materials versus temperature and applied
magnetic field are calculated. All the results are in agreement with the
experiments.",1101.2943v1
2011-12-08,Circuit Modeling of Tunneling Real-Space Transfer Transistors: Toward Terahertz Frequency Operation,"High frequency operation of tunneling real-space transfer transistor (TRSTT)
in the negative differential resistance (NDR) regime is assessed by calculating
the device common source unity current gain frequency (fT) range with a small
signal equivalent circuit model including tunneling. Our circuit model is based
on an In0.2Ga0.8As and delta-doped GaAs dual channel structure with various
gate lengths. The calculated TRSTT fT agrees very well with experimental data,
limiting factor being the resistance of the delta-doped GaAs layer. By
optimizing the gate dimensions and channel materials, we find fT in the NDR
region approaches terahertz range, which anticipates potential use of TRSTT as
terahertz sources.",1112.1980v1
2013-01-24,Spin transport parameters in metallic multilayers determined by ferromagnetic resonance measurements of spin pumping,"We measured spin transport in nonferromagnetic (NM) metallic multilayers from
the contribution to damping due to spin pumping from a ferromagnetic Co90Fe10
thin film. The multilayer stack consisted of NM1/NM2/Co90Fe10(2 nm)/NM2/NM3
with varying NM materials and thicknesses. Using conventional theory for one
dimensional diffusive spin transport in metals, we show that the effective
damping due to spin pumping can be strongly affected by the spin transport
properties of each NM in the multilayer, which permits the use of damping
measurements to accurately determine the spin transport properties of the
various NM layers in the full five-layer stack. We find that due to its high
electrical resistivity, amorphous Ta is a poor spin conductor, in spite of a
short spin-diffusion length of 1.0 nm, and that Pt is an excellent spin
conductor by virtue of its low electrical resistivity and a spin diffusion
length of only 0.5 nm. Spin Hall effect measurements may have underestimated
the spin Hall angle in Pt by assuming a much longer spin diffusion length.",1301.5861v1
2014-11-01,Manipulating electronic states at oxide interfaces using focused micro X-rays from standard lab-sources,"Recently, x-ray illumination, using synchrotron radiation, has been used to
manipulate defects, stimulate self-organization and to probe their structure.
Here we explore a method of defect-engineering low-dimensional systems using
focused laboratory-scale X-ray sources. We demonstrate an irreversible change
in the conducting properties of the 2-dimensional electron gas at the interface
between the complex oxide materials LaAlO3 and SrTiO3 by X-ray irradiation. The
electrical resistance is monitored during exposure as the irradiated regions
are driven into a high resistance state. Our results suggest attention shall be
paid on electronic structure modification in X-ray spectroscopic studies and
highlight large-area defect manipulation and direct device patterning as
possible new fields of application for focused laboratory X-ray sources.",1411.0177v1
2015-01-13,Phase-change memory function of correlated electrons in organic conductors,"Phase-change memory (PCM), a promising candidate for next-generation
non-volatile memories, exploits quenched glassy and thermodynamically stable
crystalline states as reversibly switchable state variables. We demonstrate PCM
functions emerging from a charge-configuration degree of freedom in strongly
correlated electron systems. Non-volatile reversible switching between a
high-resistivity charge-crystalline (or charge-ordered) state and a
low-resistivity quenched state, charge glass, is achieved experimentally via
heat pulses supplied by optical or electrical means in organic conductors
$\theta$-(BEDT-TTF)$_2$$X$. Switching that is one order of magnitude faster is
observed in another isostructural material that requires faster cooling to
kinetically avoid charge crystallization, indicating that the material's
critical cooling rate can be useful guidelines for pursuing a faster
correlated-electron PCM function.",1501.02873v2
2015-01-15,Optimizing the Optical and Electrical Properties of Graphene Ink Thin Films by Laser-annealing,"We demonstrate a facile fabrication technique for graphene-based transparent
conductive films. Highly flat and uniform graphene films are obtained through
the incorporation of an efficient laser annealing technique with one-time drop
casting of high-concentration graphene ink. The resulting thin films are
uniform and exhibit a transparency of more than 85% at 550 nm and a sheet
resistance of about 30 k{\Omega}/sq. These values constitute an increase of 45%
in transparency, a reduction of surface roughness by a factor of four and a
decrease of 70% in sheet resistance compared to unannealed films.",1501.03843v1
2015-02-18,The Role of Transport Agents in MoS2 Single Crystals,"We report resistivity, thermoelectric power and thermal conductivity of MoS2
single crystals prepared by chemical vapour transport (CVT) method using I2,
Br2 and TeCl4 as transport agents. The material presents low-lying donor and
acceptor levels, which dominate the in-plane charge transport. Intercalates
into the Van der Waals gap strongly influence the inter-plane resistivity.
Thermoelectric power displays the characteristics of strong electron-phonon
interaction. Detailed theoretical model of thermal conductivity reveals the
presence of high number of defects in the MoS2 structure. We show that these
defects are inherent to CVT growth method, coming mostly from the transport
agent molecules inclusion as identified by Total Reflection X-ray Fluorescence
analysis (TXRF) and in-beam activation analysis (IBAA).",1502.05161v1
2015-08-20,Transport Conductivity of Graphene at RF and Microwave Frequencies,"We measure graphene coplanar waveguides from direct current (DC) to 13.5GHz
and show that the apparent resistance (in the presence of parasitic impedances)
has an quadratic frequency dependence, but the intrinsic conductivity (without
the influence of parasitic impedances) is frequency-independent. Consequently,
in our devices the real part of the complex alternating current conductivity is
the same as the DC value and the imaginary part~0. The graphene channel is
modelled as a parallel resistive-capacitive network with a frequency dependence
identical to that of the Drude conductivity with momentum relaxation
time~2.1ps, highlighting the influence of alternating current (AC) electron
transport on the electromagnetic properties of graphene. This can lead to
optimized design of high-speed analogue field-effect transistors, mixers,
frequency doublers, low-noise amplifiers and radiation detectors.",1508.04984v1
2016-08-17,Nanocomposite si-c-n coatings,"Coatings of ternary nanocomposite Si-C-N ceramic coatings have shown newer
and improved mechanical and functional properties over the coarser and
monolithic coatings. Properties like high hardness, wear resistance, oxidation
resistance, tunable band gap and chemical inertness have been observed for
Si-C-N which makes its potential for numerous applications. Although lot of
research has taken place in Si-C-N coatings, proper understanding of the effect
of different parameters on the coating properties are still not resolved. The
changes occurring in fraction of Si, C and N and the phases forming in the
coatings with variation in deposition conditions require investigations. This
research paper gives a systematic study of the role of different deposition
parameters like substrate temperature, pressure, power on the nucleation and
growth, structure, microstructural bonding and mechanical properties of the
film deposited by magnetron sputtering which adds significantly to the
fundamental knowledge of nanocomposite Si-C-N coatings as well as its
applications.",1608.05667v1
2016-12-21,Correlation between battery material performance and cooperative electron-phonon interaction in LiCo$_y$Mn$_{2-y}$O$_{4}$,"Understanding the basic physics related to archetypal lithium battery
material (such as LiCo$_y$Mn$_{2-y}$O$_{4}$) is of considerable interest and is
expected to aid designing of cathodes of high capacity. The relation between
electrochemical performance, activated-transport parameters, thermal expansion,
and cooperativity of electron-phonon-interaction distortions in
LiCo$_y$Mn$_{2-y}$O$_{4}$ is investigated. The first order
cooperative-normal-mode transition, detected through coefficient of thermal
expansion, is found to disappear at a critical doping ($y \sim 0.16$);
interestingly, for $y \gtrsim 0.16$ the resistivity does not change much with
doping and the electrochemical capacity becomes constant over repeated cycling.
The critical doping $y \sim 0.16$ results in breakdown of the network of
cooperative/coherent normal-mode distortions; this leads to vanishing of the
first-order transition, establishment of hopping channels with lower
resistance, and enhancing lithiation and delithiation of the battery, thereby
minimizing electrochemical capacity fading.",1612.07092v1
2018-05-07,High-temperature thermoelectric properties of half-Heusler phases Er$_{1-x}$Ho$_x$NiSb,"Polycrystalline samples of Er$_{1-x}$Ho$_x$NiSb ($x$ = 0, 0.2, 0.3, 0.5, 0.7,
0.8, 1) were characterized by means of x-ray powder diffraction (XRD), scanning
electron microscopy (SEM), and optical metallography. The results proved the
formation of half-Heusler alloys in the entire composition range. Their
electrical transport properties (resistivity, thermoelectric power) were
studied in the temperature interval 350-1000 K. The measured electrical
resistivity spanned between 5 and 25 $\mu \Omega$m. The maximum thermopower of
50-65 $\mu$V/K was observed at temperatures 500-650 K. Replacing Ho for Er
resulted in a non-monotonous variation of the thermoelectric power factor ($PF
= S^2/\rho$). The largest $PF$ of 4.6 $\mu$WcmK$^{-2}$ was found at 660 K for
Er$_{0.5}$Ho$_{0.5}$NiSb. This value is distinctly larger than PF determined
for the terminal phases ErNiSb and HoNiSb.",1805.02435v1
2018-05-16,Magnetic properties of single crystalline itinerant ferromagnet AlFe2B2,"Single crystals of AlFe$_{2}$B$_{2}$ have been grown using the self flux
growth method and then measured the structural properties, temperature and
field dependent magnetization, and temperature dependent electrical resistivity
at ambient as well as high pressure. The Curie temperature of AlFe$_{2}$B$_{2}$
is determined to be $274$~K. The measured saturation magnetization and the
effective moment for paramagnetic Fe-ion indicate the itinerant nature of the
magnetism with a Rhode-Wohlfarth ratio $ \frac{M_{C}}{M_{sat}}\approx 1.14$.
Temperature dependent resistivity measurements under hydrostatic pressure shows
that transition temperature \textit{T$_C$} is suppressed down to 255 K for $p =
2.24$~GPa pressure with a suppression rate of $\sim -8.9$~K/GPa. The anisotropy
fields and magnetocrystalline anisotropy constants are in reasonable agreement
with density functional theory calculations.",1805.06373v1
2019-09-29,Structural and electrical properties of ceramic Li-ion conductors based on Li$_{1.3}$Al$_{0.3}$Ti$_{1.7}$(PO$_4$)$_3$-LiF,"The work presents the investigations of Li1.3Al0.3Ti1.7(PO4)3-xLiF Li-ion
conducting ceramics with 0 < x < 0.3 by means of X-ray diffractometry (XRD),
7Li, 19F, 27Al and 31P Magic Angle Spinning Nuclear Magnetic Resonance (MAS
NMR) spectroscopy, thermogravimetry (TG), scanning electron microscopy (SEM),
impedance spectroscopy (IS) and density method. It has been shown that the
total ionic conductivity of both as-prepared and ceramic Li1.3Al0.3Ti1.7(PO4)3
is low due to a grain boundary phase exhibiting high electrical resistance.
This phase consists mainly of berlinite crystalline phase as well as some
amorphous phase containing Al3+ ions. The electrically resistant phases of the
grain boundary decompose during sintering with LiF additive. The processes
leading to microstructure changes and their effect on the ionic properties of
the materials are discussed in the frame of the brick layer model (BLM). The
highest total ionic conductivity at room temperature was measured for
LATP-0.1LiF ceramic sintered at 800{\deg}C and was equal to {\sigma}tot = 1.1 x
10-4 Scm-1.",1909.13291v2
2017-03-19,A thermodynamic analysis of the spider silk and the importance of complexity,"The spider silk is one of the most interesting bio-materials investigated in
the last years. One of the main reasons that brought scientists to study this
organized system is its high level of resistance if compared to other
artificial materials characterized by higher density. Subsequently, researchers
discovered that the spider silk is a complex system formed by different kinds
of proteins, organized (or disorganized) to guarantee the required resistance,
which is function of the final application and of the environmental conditions.
Some spider species are able to make different silks, up to twelve, having a
composition that seems to be function of the final use (i.e. dragline web,
capture web, etc). The aim of this paper is to analyze the properties of the
spider silk by means of a thermodynamic approach, taking advantage of the
well-known theories applied to polymers, and to try to underline and develop
some intriguing considerations. Moreover, this study can be taken as an example
to introduce and discuss the importance of the concept of optionality and of
the anti-fragile systems proposed by N. N. Thaleb in his book ""Antifragile:
Things that gain from disorder"".",1703.06497v1
2019-07-31,Large spin Hall magnetoresistance in antiferromagnetic α-Fe2O3/Pt heterostructures,"We investigate the spin Hall magnetoresistance (SMR) at room temperature in
thin film heterostructures of antiferromagnetic, insulating, (0001)-oriented
alpha-Fe2O3 (hematite) and Pt. We measure their longitudinal and transverse
resistivities while rotating an applied magnetic field of up to 17T in three
orthogonal planes. For out-of-plane magnetotransport measurements, we find
indications for a multidomain antiferromagnetic configuration whenever the
field is aligned along the film normal. For in-plane field rotations, we
clearly observe a sinusoidal resistivity oscillation characteristic for the SMR
due to a coherent rotation of the Neel vector. The maximum SMR amplitude of
0.25% is, surprisingly, twice as high as for prototypical ferrimagnetic
Y3Fe5O12/Pt heterostructures. The SMR effect saturates at much smaller magnetic
fields than in comparable antiferromagnets, making the alpha-Fe2O3/Pt system
particularly interesting for room-temperature antiferromagnetic spintronic
applications.",1907.13393v4
2020-09-16,Properties and influence of microstructure and crystal defects in Fe$_2$VAl modified by laser surface remelting,"Laser surface remelting can be used to manipulate the microstructure of cast
material. Here, we present a detailed analysis of the microstructure of
Fe$_2$VAl following laser surface remelting. Within the melt pool, elongated
grains grow nearly epitaxially from the heat-affected zone. These grains are
separated by low-angle grain boundaries with 1{\deg}-5{\deg} misorientations.
Segregation of vanadium, carbon, and nitrogen at grain boundaries and
dislocations is observed using atom probe tomography. The local electrical
resistivity was measured by an in-situ four-point-probe technique. A smaller
increase in electrical resistivity is observed at these low-angle grain
boundaries compared to high-angle grain boundaries in a cast sample. This
indicates that grain boundary engineering could potentially be used to
manipulate thermoelectric properties.",2009.07685v2
2016-03-18,"Electronic Structure, Phase Stability and Resistivity of Hybrid Hexagonal C$_x$(BN)$_{1-x}$ Two-dimensional Nanomaterial: A First-principles Study","We use density functional theory based first-principles method to investigate
the bandstructure and phase stability in the laterally grown hexagonal
C$_x$(BN)$_{1-x}$, two-dimensional Graphene and $h$-BN hybrid nanomaterials,
which were synthesized by experimental groups recently (Liu $et al$, Nature
Nanotech, 8, 119 (2013)). Our detail electronic structure calculations on such
materials, with both armchair and zigzag interfaces between the Graphene and $
h$-BN domains, indicate that the band-gap decreases non-monotonically with the
concentration of Carbon. The calculated bandstructure shows the onset of Dirac
cone like features near the band-gap at high Carbon concentration ($x \sim
0.8$). From the calculated energy of formation, the phase stability of
C$_x$(BN)$_{1-x}$ was studied using a regular solution model and the system was
found to be in the ordered phase below a few thousand Kelvin. Furthermore,
using the Boltzmann transport theory we calculate the electrical resistivity
from the bandstrcture of C$_x$(BN)$_{1-x}$ at different temperature ($T$),
which shows a linear behaviour when plotted in the logarithmic scale against
$T^{-1}$, as observed experimentally",1603.05780v1
2017-08-25,Ballistic geometric resistance resonances in a single surface of a topological insulator,"Transport in topological matter has shown a variety of novel phenomena over
the last decade. Although numerous transport studies have been conducted on
three-dimensional topological insulators (3D-TIs), study of ballistic motion
and thus exploration of potential landscapes on a hundred nanometer scale is
for the prevalent TI materials almost impossible due to their low carrier
mobility. Therefore it is unknown whether helical Dirac electrons in TIs, bound
to interfaces between topologically distinct materials, can be manipulated on
the nanometer scale by local gates or locally etched regions. Here we impose a
submicron periodic potential onto a single surface of Dirac electrons in high
mobility strained mercury telluride (HgTe), which is a strong TI. Pronounced
geometric resistance resonances constitute the first observation of a ballistic
effect in 3D-TIs.",1708.07766v1
2018-08-22,Evidence for Undoped Weyl Semimetal Charge Transport in $Y_{2}Ir_{2}O_{7}$,"Weyl fermions scattering from a random Coulomb potential are predicted to
exhibit resistivity versus temperature $\rho \space \alpha \space T^{-4}$ in a
single particle model. Here we show that, in closed environment-grown
polycrystalline samples of $Y_{2}Ir_{2}O_{7}$, $\rho = \rho_{0} T^{-4}$ over
four orders of magnitude in $\rho$. While the measured prefactor, $\rho_{0}$,
is obtained from the model using reasonable materials parameters, the $T^{-4}$
behavior extends far beyond the model's range of applicability. In particular,
the behavior extends into the low-temperature, high-resistivity region where
the Ioffe-Regel parameter, $k_{T} \ell \ll 2\pi$. Strong on-site Coulomb
correlations, instrumental for predicting a Weyl semimetal state in
$Y_{2}Ir_{2}O_{7}$, are the possible origin of such ""bad"" Weyl semimetal
behavior.",1808.07583v4
2019-04-07,Restoration of long range order of Na ions in $Na_xCoO_2$ at high temperatures by sodium site doping,"We have systematically investigated the $Na_xCoO_2$ system doped with Cu, Y,
Sn, W, Au and Bi for $x$ = 0:5; 0:75 and 1.00 using density functional theory.
Sn, W, and Bi always substitute a Co while Au always substitutes a Na
regardless of Na concentration. However, for Cu and Y, the substitution site
depends on Na concentration. When compared to the available experimental data,
we find that thermoelectric performance is enhanced when the dopants substitute
a Na site. In this case, surprisingly, resistivity decreases despite the
reduced hole concentration caused by carrier recombination. We propose improved
carrier mobility to be the cause of observed reduced resistivity.",1904.03644v1
2019-08-07,Fast response of pulsed laser deposited Zinc ferrite thin film as a chemo-resistive gas sensor,"Thin films of ZnFe2O4 deposited by pulsed laser technique are here
demonstrated as one of the interesting materials for sensing of ethanol. The
response transients were fitted well to one-site Langmuir adsorption model.
Activation energies for (I) adsorption and reaction of ethanol and (II)
desorption (i.e. recovery process) of ethanol from zinc ferrite thin film
surface were obtained on the basis of this model. In this paper, we showed the
effect of operating temperature and gas-concentration on the response time of
thin film sensor materials. At the operating temperature 340oC, the ZnFe2O4
thin film showed high (84%) as well as immediate response to 500 ppm of
ethanol, with its resistance being saturated within ~12 seconds, which stands
far superior to the response time of nano crystalline powders. Those films were
also observed to have a good repeatability of their sensor response, thus
representing a major step towards low-cost large-scale production of this class
of devices.",1908.02780v1
2012-06-18,GdN Nanoisland-Based GaN Tunnel Junctions,"We show that GdN nanoislands can enhance inter-band tunneling in GaN PN
junctions by several orders of magnitude, enabling low optical absorption
low-resistance tunnel junctions (specific resistivity 1.3 X 10-3 {\Omega}-cm2)
for various optoelectronic applications. We exploit the ability to overgrow
high quality GaN over GdN nanoislands to create new nanoscale heterostructure
designs that are not feasible in planar epitaxy. GdN nanoisland assisted
inter-band tunneling was found to enhance tunneling in both of the polar
orientations of GaN. Tunnel injection of holes was confirmed by low temperature
operation of GaN p-n junction with a tunneling contact layer, showing strong
electroluminescence down to 20K. The availability of tunnel junctions with
negligible absorption could not only improve the efficiency of existing
optoelectronic devices significantly, but also enable new electronic and
optical devices based on wide band gap materials.",1206.3810v3
2015-07-01,Itinerant Antiferromagnetism in FeMnP0.8Si0.2 Single Crystals,"Compounds based on the Fe2P structure have continued to attract interest
because of the interplay between itinerant and localized magnetism in a
non-centrosymmetric crystal structure, and because of the recent developments
of these materials for magnetocaloric applications. Here we report the growth
and characterization of mm size single crystals of FeMnP0.8Si0.2. Single
crystal x-ray diffraction, magnetization, resistivity, Hall and heat capacity
data are reported. Surprisingly, the crystals exhibit itinerant
antiferromagnetic order below 158 K with no hint of ferromagnetic behavior in
the magnetization curves and with the spins ordered primarily in the ab plane.
The room temperature resistivity is close to the Ioffe-Regel limit for a metal.
Single crystal x-ray diffraction indicates a strong preference for Mn to occupy
the larger pyramidal 3g site. The cation site preference in the as-grown
crystals and the antiferromagnetism are not changed after high temperature
anneals and a rapid quench to room temperature.",1507.00275v1
2019-01-22,S-type Negative Differential Resistance in Semiconducting Transition-Metal Dichalcogenides,"Current-controlled (also known as ""S-type"") negative differential resistance
(NDR) is of crucial importance to many emerging applications including
neuromorphic computing and high-density memristors integration. However, the
experimental realization of S-type NDR based on conventional mechanisms poses
demanding requirements on materials, which greatly limits their potential
applications. Here, we experimentally identify that semiconducting transition
metal dichalcogenides (TMDs) can host a bipolar S-type NDR devices. Theoretical
simulations indicate that the origin of the NDR in these devices arises from a
thermal feedback mechanism. Furthermore, we demonstrate the potential
applications of TMDs based S-type NDR device in signal processing and
neuromorphic electronics.",1901.07161v1
2020-12-30,High Current Density in Monolayer MoS$_2$ Doped by AlO$_x$,"Semiconductors require stable doping for applications in transistors,
optoelectronics, and thermoelectrics. However, this has been challenging for
two-dimensional (2D) materials, where existing approaches are either
incompatible with conventional semiconductor processing or introduce
time-dependent, hysteretic behavior. Here we show that low temperature (<
200$^\circ$ C) sub-stoichiometric AlO$_x$ provides a stable n-doping layer for
monolayer MoS$_2$, compatible with circuit integration. This approach achieves
carrier densities > 2x10$^{13}$ 1/cm$^2$, sheet resistance as low as ~7
kOhm/sq, and good contact resistance ~480 Ohm.um in transistors from monolayer
MoS$_2$ grown by chemical vapor deposition. We also reach record current
density of nearly 700 uA/um (>110 MA/cm$^2$) in this three-atom-thick
semiconductor while preserving transistor on/off current ratio > $10^6$. The
maximum current is ultimately limited by self-heating and could exceed 1 mA/um
with better device heat sinking. With their 0.1 nA/um off-current, such doped
MoS$_2$ devices approach several low-power transistor metrics required by the
international technology roadmap",2012.15350v1
2021-06-09,Maximizing Spin-Orbit Torque Generated by the Spin Hall Effect of Pt,"Efficient generation of spin-orbit torques (SOTs) is central for the exciting
field of spin-orbitronics. Platinum, the archetypal spin Hall material, has the
potential to be an outstanding provider for spin-orbit torques due to its giant
spin Hall conductivity, low resistivity, high stabilities, and the ability to
be compatible with CMOS circuits. However, pure clean-limit Pt with low
resistivity still provides a low damping-like spin-orbit torque efficiency,
which limits its practical applications. The efficiency of spin-orbit torque in
Pt-based magnetic heterostructures can be improved considerably by increasing
the spin Hall ratio of Pt and spin transmissivity of the interfaces. Here we
reviews recent advances in understanding the physics of spin current
generation, interfacial spin transport, and the metrology of spin-orbit
torques, and summarize progress towards the goal of Pt-based spin-orbit torque
memories and logic that are fast, efficient, reliable, scalable, and
non-volatile.",2106.04992v2
2021-08-12,Revisiting the Reduction of Thermal Conductivity in Nano- to Micro-Grained Bismuth Telluride: The Importance of Grain-Boundary Thermal Resistance,"Nanograined bulk alloys based on bismuth telluride (Bi2Te3) are the dominant
materials for room-temperature thermoelectric applications. In numerous
studies, existing bulk phonon mean free path (MFP) spectra predicted by
atomistic simulations suggest sub-100 nm grain sizes are necessary to reduce
the lattice thermal conductivity by decreasing phonon MFPs. This is in contrast
with available experimental data, where a remarkable thermal conductivity
reduction is observed even for micro-grained Bi2Te3 samples. In this work,
first-principles phonon MFPs along both the in-plane and cross-plane directions
are re-computed for bulk Bi2Te3. These phonon MFPs can explain new and existing
experimental data on flake-like Bi2Te3 nanostructures with various thicknesses.
For polycrystalline Bi2Te3-based materials, a better explanation of the
experimental data requires further consideration of the grain-boundary thermal
resistance that can largely suppress the transport of high-frequency optical
phonons.",2108.05972v1
2022-12-02,Electric modulation of the Fermi arc spin transport via three-terminal configuration in the topological semimetal nanowires,"Spin momentum locking is a key feature of the topological surface state,
which plays an important role in spintronics. The electrical detection of
current-induced spin polarization protected by the spin momentum locking in
non-magnetic systems provides a new platform for developing spintronics while
previous studies were mostly based on magnetic materials. In this study, the
spin transport measurement of Dirac semimetal Cd3As2 was studied by the
three-terminal geometry, and a hysteresis loop signal with high resistance and
low resistance state was observed. The hysteresis was reversed by reversing the
current direction, which illustrates the spin-momentum locking feature of
Cd3As2. Furthermore, we realized the on-off states of the spin signals through
electric modulation of the Fermi arc via the three-terminal configuration,
which enables the great potential of Cd3As2 in spin field-effect transistors.",2212.01072v1
2023-08-02,Observation of zero resistance above 100$^\circ$ K in Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O,"Room-temperature superconductivity has always been regarded as the ultimate
goal in the fields of solid-state physics and materials science, with its
realization holding revolutionary significance, capable of triggering
significant changes in energy transmission and storage. However, achieving it
poses various challenges. Recent research revealed that material
Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O displays room-temperature superconductivity
under atmospheric pressure, sparking global interest in further exploration.
Here, we utilized solid-phase synthesis to obtain a polycrystalline sample of
Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O. X-ray diffraction confirmed its structural
consistency with referenced literature. Zero resistance, which is important
evidence for superconductivity, was observed above 100$^\circ$ K under ambient
pressure in our experiment. Our finding indicates that
Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O is a possible candidate for searching
high-temperature superconductors.",2308.01192v1
2024-04-13,Solution-Processed Inks with Fillers of NbS$_3$ Quasi-One-Dimensional Charge-Density-Wave Material,"We report on the solution processing and testing of electronic ink comprised
of quasi-one-dimensional NbS$_3$ charge-density-wave fillers. The ink was
prepared by liquid-phase exfoliation of NbS$_3$ crystals into high-aspect ratio
quasi-1D fillers dispersed in a mixture of isopropyl alcohol and ethylene
glycol solution. The results of the electrical measurements of two-terminal
electronic test structures printed on silicon substrates reveal resistance
anomalies in the temperature range of ~330 K to 370 K. It was found that the
changes in the temperature-dependent resistive characteristics of the test
structures originate from the charge-density-wave phase transition of
individual NbS$_3$ fillers. The latter confirms that the exfoliated NbS$_3$
fillers preserve their intrinsic charge-density-wave quantum condensate states
and can undergo phase transitions above room temperature even after chemical
exfoliation processes and printing. These results are important for developing
""quantum inks"" with charge-density-wave fillers for the increased functionality
of future solution-processed electronics.",2404.09038v1
2024-02-16,Cycling on rough roads: A model for resistance and vibration,"Minimising opposing forces is a matter of interest to most cyclists. These
forces arise from passage through air (""drag"") and interaction with the road
surface (""resistance""). Recent work recognises that resistance forces arise not
only from the deformation of the tyre (""rolling resistance"") but also from
irregularities in the road surface (""roughness resistance""), which lead to
power dissipation in the body of the rider through vibration. The latter effect
may also have an adverse impact on human health. In this work we offer a
quantitative theory of roughness resistance and vibration that links these
effects to a surface characterisation in terms of the International Roughness
Index (IRI). We show that the roughness resistance and the Vibration Dose Value
(or VDV, the usual vibration dosage metric) can be expressed in terms of
elementary formulae. The roughness resistance depends only on the vertical
stiffness of the bicycle and the roughness index. Surprisingly, other
apparently relevant parameters, such as physiological characteristics of the
bicycle rider and other features of the bicycle, do not enter. For roads of
moderate roughness, roughness resistance is larger than rolling resistance. For
very rough roads, roughness resistance is larger than aerodynamic drag. So only
on roads of high quality (in most jurisdictions, accounting for less than 10~\%
of the total) can roughness resistance be ignored. Roughness resistance can be
mitigated by reducing the vertical stiffness of the bicycle. In common with
other recent reports, we find that almost any cycling activity will breach
public health guidelines relating to Vibration Dose Value.",2405.00019v1
2015-05-11,Pressure-induced semimetal to superconductor transition in a three-dimensional topological material ZrTe5,"As a new type of topological materials, ZrTe5 shows many exotic properties
under extreme conditions. Utilizing resistance and ac magnetic susceptibility
measurements under high pressure, while the resistance anomaly near 128 K is
completely suppressed at 6.2 GPa, a fully superconducting transition emerges
surprisingly. The superconducting transition temperature Tc increases with
applied pressure, and reaches a maximum of 4.0 K at 14.6 GPa, followed by a
slight drop but remaining almost constant value up to 68.5 GPa. At pressures
above 21.2 GPa, a second superconducting phase with the maximum Tc of about 6.0
K appears and coexists with the original one to the maximum pressure studied in
this work. In situ high-pressure synchrotron X-ray diffraction and Raman
spectroscopy combined with theoretical calculations indicate the observed
two-stage superconducting behavior is correlated to the structural phase
transition from ambient Cmcm phase to high-pressure C2/m phase around 6 GPa,
and to a mixture of two high-pressure phases of C2/m and P-1 above 20 GPa. The
combination of structure, transport measurement and theoretical calculations
enable a complete understanding of the emerging exotic properties in
three-dimensional topological materials happened under extreme environments.",1505.02658v2
2015-08-05,Screening and transport in 2D semiconductor systems at low temperatures,"Low temperature carrier transport properties in two-dimensional (2D)
semiconductor systems can be theoretically well-understood within a mean-field
type RPA-Boltzmann theory as being limited by scattering from screened Coulomb
disorder arising from random quenched charged impurities in the environment. In
the current work, we derive a number of simple analytical formula, supported by
realistic numerical calculations, for the relevant density, mobility, and
temperature range where 2D transport should manifest strong intrinsic (i.e.,
arising purely from electronic effects and not from phonon scattering) metallic
temperature dependence in different semiconductor materials arising entirely
from the 2D screening properties, thus providing an explanation for why the
strong temperature dependence of the 2D resistivity can only be observed in
high-quality and low-disorder (i.e., high-mobility) 2D samples and also why
some high-quality 2D materials (i.e., n-GaAs) manifest much weaker metallicity
than other materials. We also discuss effects of interaction and disorder on
the 2D screening properties in this context as well as compare 2D and 3D
screening functions to comment why such a strong intrinsic temperature
dependence arising from screening cannot occur in 3D metallic carrier
transport. Experimentally verifiable predictions are made about the
quantitative magnitude of the maximum possible low-temperature metallicity in
2D systems and the scaling behavior of the temperature scale controlling the
quantum to classical crossover where the system reverses the sign of the
temperature derivative of the 2D resistivity at high temperatures.",1508.01195v1
2007-07-04,Role of oxygen vacancies in Cr-doped SrTiO3 for resistance-change memory,"Transition-metal oxides exhibiting a bistable resistance state are attractive
for non-volatile memory applications. The relevance of oxygen vacancies (VO)
for the resistance-change memory was investigated with x-ray fluorescence,
infrared microscopy, and x-ray absorption spectroscopy using Cr-doped SrTiO3 as
example. We propose that the microscopic origin of resistance switching in this
class of materials is due to an oxygen-vacancy drift occurring in close
proximity to one of the electrodes.",0707.0563v1
2012-12-17,Measurement of specific contact resistivity using scanning voltage probes,"Specific contact resistivity measurements have conventionally been heavy in
both fabrication and simulation/calculation in order to account for complicated
geometries and other effects such as parasitic resistance. We propose a simpler
geometry to deliver current, and the use of a scanning voltage probe to sense
the potential variation along the sample surface, from which the specific
contact resistivity can be straightforwardly deduced. We demonstrate an
analytical example in the case where both materials are thin films.
Experimental data with a scanning Kelvin probe measurement on graphene from the
literature corroborates our model calculation.",1212.4182v2
2013-11-04,Surface resistivity of hydrogenated amorphous carbon films: Existence of intrinsic graphene on its surface,"Surface resistivity of hydrogenated amorphous carbon films was measured as a
function of the applied electrical field. The measured dependence shows a sharp
ambipolar peak near zero gate voltage. Furthermore, we found that in some
samples sheet resistance at the peak is as low as 7.5 k{\Omega}/sq. This value
is the same order of magnitude as the sheet resistance of a defect free
graphene monolayer. Therefore a conclusion is made that an intrinsic graphene
with dimensions of at least millimeters exist on the surface of amorphous
carbon films. These results can open new perspectives not only for graphene
applications, but also for better understanding of this unique material.",1311.0605v2
2014-06-17,High-Performance MoS2 Field-Effect Transistors Enabled by Chloride Doping: Record Low Contact Resistance (0.5 kohm*um) and Record High Drain Current (460 uA/um),"In this paper, we report a novel chemical doping technique to reduce the
contact resistance (Rc) of transition metal dichalcogenides (TMDs) -
eliminating two major roadblocks (namely, doping and high Rc) towards
demonstration of high-performance TMDs field-effect transistors (FETs). By
using 1,2 dichloroethane (DCE) as the doping reagent, we demonstrate an active
n-type doping density > 2*1019 cm-3 in a few-layer MoS2 film. This enabled us
to reduce the Rc value to a record low number of 0.5 kohm*um, which is ~10x
lower than the control sample without doping. The corresponding specific
contact resistivity (pc) is found to decrease by two orders of magnitude. With
such low Rc, we demonstrate 100 nm channel length (Lch) MoS2 FET with a drain
current (Ids) of 460 uA/um at Vds = 1.6 V, which is twice the best value
reported so far on MoS2 FETs.",1406.4492v1
2015-04-14,Thermal boundary resistance at Si/Ge interfaces determined by approach-to-equilibrium molecular dynamics simulations,"The thermal boundary resistance of Si/Ge interfaces as been determined using
approach-to-equilibrium molecular dynamics simulations. Assuming a reciprocal
linear dependence of the thermal boundary resistance, a length-independent bulk
thermal boundary resistance could be extracted from the calculation resulting
in a value of 3.76x10$^{-9}$ m$^2$ K/W for a sharp Si/Ge interface and thermal
transport from Si to Ge. Introducing an interface with finite thickness of 0.5
nm consisting of a SiGe alloy, the bulk thermal resistance slightly decreases
compared to the sharp Si/Ge interface. Further growth of the boundary leads to
an increase in the bulk thermal boundary resistance. When the heat flow is
inverted (Ge to Si), the thermal boundary resistance is found to be higher.
From the differences in the thermal boundary resistance for different heat flow
direction, the rectification factor of the Si/Ge has been determined and is
found to significantly decrease when the sharp interface is moderated by
introduction of a SiGe alloy in the boundary layer.",1504.03613v1
2019-06-12,Kapitza resistance in basic chain models with isolated defects,"Kapitza thermal resistance is a common feature of material interfaces. It is
defined as the ratio of the thermal drop at the interface to the heat flux
flowing across the interface. One expects that this resistance will depend on
the structure of the interface and on the temperature. We address the heat
conduction in one-dimensional chain models with isotopic and/or coupling
defects and explore the relationship between the interaction potentials and
simulated properties of the Kapitza resistance. It is revealed that in linear
models the Kapitza resistance is well-defined and size-independent (contrary to
the bulk heat conduction coefficient), but depends on the parameters of
thermostats used in the simulation. For $\beta$-FPU model one also encounters
the dependence on the thermostats; in addition, the simulated boundary
resistance strongly depends on the total system size. Finally, in the models
characterized by convergent bulk heat conductivity (chain of rotators,
Frenkel-Kontorova model) the boundary resistance is thermostat- and
size-independent, as one expects. In linear chains, the Kapitza resistance is
temperature-independent; thus, its temperature dependence allows one to judge
on significance of the nonlinear interactions in the phonon scattering
processes at the interface.",1906.05152v1
2022-09-22,Computational Design of Corrosion-resistant and Wear-resistant Titanium Alloys for Orthopedic Implants,"Titanium alloys are promising candidates for orthopedic implants due to their
mechanical resilience and biocompatibility. Current titanium alloys in
orthopedic implants still suffer from low wear and corrosion resistance. Here,
we present a computational method for optimizing the composition of titanium
alloys for enhanced corrosion and wear resistance without compromising on other
aspects such as phase stability, biocompatibility, and strength. We use the
cohesive energy, oxide formation energy, surface work function, and the elastic
shear modulus of pure elements as proxy descriptors to guide us towards alloys
with enhanced wear and corrosion resistance. For the best-selected candidates,
we then use the CALPHAD approach, as implemented in the Thermo-Calc software,
to calculate the phase diagram, yield strength, hardness, Pourbaix diagram, and
the Pilling-Bedworth (PB) ratio. These calculations are used to assess the
thermodynamic stability, biocompatibility, corrosion resistance, and wear
resistance of the selected alloys. Additionally, we provide insights about the
role of silicon on improving the corrosion and wear resistance of alloys.",2210.00845v1
2021-08-17,"Superconducting-like and magnetic transitions in oxygen-implanted diamond-like and amorphous carbon films, and in highly oriented pyrolytic graphite","In our previously published work, we have reported colossal
magnetoresistance, Andreev oscillations, ferromagnetism, and granular
superconductivity in oxygen-implanted carbon fibers, graphite foils, and highly
oriented pyrolytic graphite. In this follow-up research, more results on these
oxygen-implanted graphite samples are presented. We show results from transport
measurements on oxygen-implanted diamond-like carbon thin coatings, amorphous
carbon films, and highly oriented pyrolytic graphite. Significantly, a
three-order magnitude drop in the electrical resistance of the oxygen-implanted
diamond-like carbon films is observed at the 50 K temperature that we have
previously reported for the transition to the superconducting state. Below 50
K, the films resistance oscillates between the high and low resistance states,
less when the sample is under a transverse magnetic field. This metastability
between the insulating and superconducting-like states possibly reflects the
evolution of the amplitude for the superconducting order parameter also known
as the longitudinal Higgs mode. Transitions to low resistance state and
metastability are also observed for amorphous carbon films. Finally, the highly
oriented pyrolytic graphite samples resistance have a thermally activated term
that can be understood on the basis of the LAMH model applied to narrow SC
channels in which thermal fluctuations can cause phase slips. We also find that
in oxygen-implanted carbon materials, the electron charge and spin correlations
do not compete and their interplay rather facilitates the emergence of
high-temperature superconductivity, and thus, additional unexpected effects
like Heisenberg spin waves and magneto-structural transitions are observed.",2108.07417v1
2019-11-20,Aspects of the Normal State Resistivity of Cuprate Superconductors,"Planar normal state resistivity data taken from three families of cuprate
superconductors are compared with theoretical calculations from the recent
extremely correlated Fermi liquid theory (ECFL). The two hole doped cuprate
materials $LSCO$ and $BSLCO$ and the electron doped material $LCCO$ have
yielded rich data sets at several densities $\delta$ and temperatures T,
thereby enabling a systematic comparison with theory. The recent ECFL
resistivity calculations for the highly correlated $t$-$t'$-$J$ model by us
give the resistivity for a wide set of model parameters. After using X-ray
diffraction and angle resolved photoemission data to fix parameters appearing
in the theoretical resistivity, only one parameter, the magnitude of the
hopping $t$, remains undetermined. For each data set, the slope of the
experimental resistivity at a single temperature-density point is sufficient to
determine $t$, and hence the resistivity on absolute scale at all remaining
densities and temperatures. This procedure is shown to give a fair account of
the entire data.",1911.09119v3
2005-10-20,Dependence of tunnel magnetoresistance in MgO based magnetic tunnel junctions on Ar pressure during MgO sputtering,"We investigated dependence of tunnel magnetoresistance effect in
CoFeB/MgO/CoFeB magnetic tunnel junctions on Ar pressure during MgO-barrier
sputtering. Sputter deposition of MgO-barrier at high Ar pressure of 10 mTorr
resulted in smooth surface and highly (001) oriented MgO. Using this MgO as a
tunnel barrier, tunnel magnetoresistance (TMR) ratio as high as 355% at room
temperature (578% at 5K) was realized after annealing at 325 C or higher, which
appears to be related to a highly (001) oriented CoFeB texture promoted by the
smooth and highly oriented MgO. Electron-beam lithography defined
deep-submicron MTJs having a low-resistivity Au underlayer with the
high-pressure deposited MgO showed high TMR ratio at low resistance-area
product (RA) below 10 ohm-um^2 as 27% at RA = 0.8 ohm-um^2, 77% at RA = 1.1
ohm-um^2, 130% at RA = 1.7 ohm-um^2, and 165% at RA = 2.9 ohm-um^2.",0510531v1
2014-09-23,Fabrication of Flexible Super Capacitor Using Laser Lightscribe Technique,"Super capacitors are promising energy storage devices due to their capability
of delivering high peak current and storing high amount of energy in a short
time with very low internal power loss. We fabricated the graphene or graphite
oxide super-capacitor using laser Lightscribe technique. We prepared graphite
oxide by modified hummers method and used PET film as a flexible substrate on
which graphite oxide (GO) was coated. Using Lightscribe drive and software, the
super-capacitor configuration was patterned on the GO coated PET film. During
the writing process, the laser converts GO into graphene. We characterized the
fabricated flexible super-capacitor which exhibits high resistance of 20KOhm
with applied voltage of 10V and further increase of voltage (20V) decreases the
resistance to 8KOhm. We also analyzed the frequency response of the capacitor
using impedance measurement which shows high frequency response and estimated
capacitance is 120nF. We optimized the patterns by running the Lightscribe
repeatedly on the GO coated PET substrate.",1409.6396v1
2019-09-20,Extraordinary high room-temperature carrier mobility in graphene-WSe$_2$ heterostructures,"High carrier mobilities play a fundamental role for high-frequency
electronics, integrated optoelectronics as well as for sensor and spintronic
applications, where device performance is directly linked to the magnitude of
the carrier mobility. Van der Waals heterostructures formed by graphene and
hexagonal boron nitride (hBN) already outperform all known materials in terms
of room temperature mobility. Here, we show that the mobility of today's best
graphene/hBN devices can be surpassed by more than a factor of three by
heterostructures formed by tungsten diselenide (WSe$_2$), graphene and hBN,
which can have mobilities as high as 350,000 cm$^2$/(Vs) at room temperature,
and resistivities as low as 15 Ohm. The resistivity of these devices shows a
much weaker temperature dependence than the one of graphene on any other known
substrate. The origin of this behaviour points to modified acoustic phonon
bands in graphene and questions our understanding of electron-phonon scattering
in van der Waals heterostructures.",1909.09523v1
2015-06-29,High quality monolayer graphene synthesized by resistive heating cold wall chemical vapour deposition,"Emerging flexible and wearable technologies such as healthcare electronics
and energy-harvest devices could be transformed by the unique properties of
graphene. The vision for a graphene-driven industrial revolution is motivating
intensive research on the synthesis of (1) high quality and (2) low cost
graphene. Hot-wall chemical vapour deposition (CVD) is one of the most
competitive growth methods, but its long processing times are incompatible with
production lines. Here we demonstrate the growth of high quality monolayer
graphene using a technique that is 100 times faster than standard hot-wall CVD,
resulting in 99% reduction in production costs. A thorough complementary study
of Raman spectroscopy, atomic force microscopy, scanning electron microscopy
and electrical magneto-transport measurements shows that our cold wall
CVD-grown graphene is of comparable quality to that of natural graphene.
Finally, we demonstrate the first transparent and flexible graphene capacitive
touch-sensor that could enable the development of artificial skin for robots.",1506.08569v1
2015-09-29,A Nonlinear HP-Type Complementary Resistive Switch,"Resistive Switching (RS) is the change in resistance of a dielectric under
the influence of an external current or electric field. This change is
non-volatile, and the basis of both the memristor and resistive random access
memory. In the latter, high integration densities favor the anti-serial
combination of two RS-elements to a single cell, termed the complementary
resistive switch (CRS). Motivated by the irregular shape of the filament
protruding into the device, we suggest a nonlinearity in the
resistance-interpolation function, and thereby expand the original
HP-memristor. We numerically simulate and analytically solve this model.
Further, the nonlinearity allows for its application to the CRS.",1509.08885v1
2003-08-14,Resistivity Ratio of Niobium Superconducting Cavities,"Resistivity measurements have been made on Nb cavities, as well as on Pb and
Cu, at 296, 77, and 4.2 K by means of a contactless induced-current method. For
superconductors, a constant magnetic field drives the material normal below the
transition temperature. These measurements provide a simple means for initial
material evaluation as well as a direct means of monitoring the effects of
material parameters (purity, heat treatment, gas incorporation, etc.) on the
electron mean free path. Approximate determinations of Hc, Hc1, and Hc2 can
also be derived from these measurements. Normal-state thermal conductivity and
the Ginzburg-Landau parameter kappa are calculated from the resistivity
measurements.",0308266v1
2014-01-09,Rapid Embedded Wire Heating via Resistive Guiding of Laser-Generated Fast Electrons as a Hydrodynamic Driver,"Resistively guiding laser-generated fast electron beams in targets consisting
of a resistive wire embedded in lower $Z$ material should allow one to rapidly
heat the wire to over 100eV over a substantial distance without strongly
heating the surrounding material. On the multi-ps timescale this can drive
hydrodynamic motion in the surrounding material. Thus ultra-intense laser solid
interactions have the potential as a controlled driver of radiation
hydrodynamics in solid density material. In this paper we assess the laser and
target parameters needed to achieve such rapid and controlled heating of the
embedded wire.",1401.1998v1
2002-07-19,Spin Injection: Interface Resistance in Fe/Semiconductor Junctions Calculated from First Principles,"We calculate the current spin polarisation and the interface resistance of
Fe/GaAs and Fe/ZnSe (001) spin injection junctions from first principles,
including also the possibility of a Schottky barrier. From our results of
interface resistance we estimate the barrier thickness needed for efficient
spin injection if the process is non-ballistic.",0207492v1
2007-08-01,Resistance noise in Bi_2Sr_2CaCu_2O$_{8+δ}$,"The resistance noise in a Bi_2Sr_2CaCu_2O$_{8+\delta}$ thin film is found to
increase strongly in the underdoped regime. While the increase of the raw
resistance noise with decreasing temperature appears to roughly track the
previously reported pseudogap temperature for this material, standard noise
analysis rather suggests that the additional noise contribution is driven by
the proximity of the superconductor-insulator transition.",0708.0117v1
2010-06-14,A conjecture of Biggs concerning the resistance of a distance-regular graph,"Previously, Biggs has conjectured that the resistance between any two points
on a distance-regular graph of valency greater than 2 is bounded by twice the
resistance between adjacent points. We prove this conjecture, give the sharp
constant for the inequality, and display the graphs for which the conjecture
most nearly fails. Some necessary background material is included, as well as
some consequences.",1006.2687v1
2019-06-13,"Comment on arXiv:1807.08572, ""Coexistence of Diamagnetism and Vanishingly Small Electrical Resistance at Ambient Temperature and Pressure in Nanostructures""","A recent preprint arXiv:1807.08572 reported the observation of a transition
in Ag/Au nanoparticle composites near room temperature and at ambient pressure,
to a vanishingly small four-probe resistance, which was tentatively identified
as a percolating superconducting transition. In this brief comment, I point out
that a vanishing four-probe resistance may also emerge in non-superconducting
systems near conductance percolation threshold.",1906.05742v1
2017-08-18,A New Method for Characterizing Bulk and Surface Conductivities of Three-Dimensional Topological Insulators: Inverted Resistance Measurements,"We introduce a new resistance measurement method that is useful in
characterizing materials with both surface and bulk conduction, such as
three-dimensional topological insulators. The transport geometry for this new
resistance measurement configuration consists of one current lead as a closed
loop that fully encloses the other current lead on the surface, and two voltage
leads that are both placed outside the loop. We show that in the limit where
the transport is dominated by the surface conductivity of the material, the
four-terminal resistance measured from such a transport geometry is
proportional to $\sigma_b/\sigma_s^2$, where $\sigma_b$ and $\sigma_s$ are the
bulk and surface conductivities of the material, respectively. We call this new
type of measurement \textit{inverted resistance measurement}, as the resistance
scales inversely with the bulk resistivity. We discuss possible implementations
of this new method by performing numerical calculations on different geometries
and introduce strategies to extract the bulk and surface conductivities. We
also demonstrate inverted resistance measurements on SmB$_6$, a topological
Kondo insulator, using both single-sided and coaxially-aligned double-sided
Corbino disk transport geometries. Using this new method, we are able to
measure the bulk conductivity, even at low temperatures, where the bulk
conduction is much smaller than the surface conduction in this material.",1708.05762v2
2007-11-02,Effects of carbon nanotubes on grain boundary sliding in zirconia polycrystals,"Mechanical properties of zirconia polycrystals decrease drastically at high
temperature due to thermally activated grain boundary (GB) sliding, leading to
plastic or even super-plastic deformation. As GB sliding is a source of energy
dissipation in the material, mechanical loss measurements are well suited to
study such a mechanism. They reveal, in general, a mechanical loss peak, which
evolves into an exponential increase at higher temperature. When intergranular
glassy films or/and amorphous pockets are presented in polycrystalline
ceramics, the mechanical loss is globally higher and so is the creep rate. Here
we show that introducing carbon nanotubes in zirconia, in particular, reduces
drastically GB sliding and consequently the mechanical loss at high
temperature. The nanotubes were observed at the grain boundaries by
high-resolution transmission electron microscopy and were related to the
reduction of superplasic flow through the boundaries, which should improve the
material creep resistance.",0711.0381v1
2010-01-25,"High-pressure synthesis, crystal and electronic structures of a new scandium tungstate, Sc0.67WO4","Negative thermal expansion (NTE) materials possess a low-density, open
structure which can respond to high pressure conditions, leading to new
compounds and/or different physical properties. Here we report that one such
NTE material -- white, insulating, orthorhombic Sc2W3O12 -- transforms into a
black compound when treated at 4 GPa and 1400 oC. The high pressure phase,
Sc0.67WO4, crystallizes in a defect-rich wolframite-type structure, a dense,
monoclinic structure (space group P2/c) containing 1-D chains of edge-sharing
WO6 octahedra. The chemical bonding of Sc0.67WO4 vis-a-vis the ambient pressure
Sc2W3O12 phase can be understood on the basis of the Sc defect structure.
Magnetic susceptibility, resistivity, thermoelectric power and IR spectroscopic
measurements reveal that Sc0.67WO4 is a paramagnet whose conductivity is that
of a metal in the presence of weak localization and electron-electron
interactions. Oxygen vacancies are suggested as a potential mechanism for
generating the carriers in this defective wolframite material.",1001.4561v1
2016-10-18,Low Temperature Thermoelectric Properties of Co- and Cr- doped CuAgSe,"High mobility phonon-glass semimetal $CuAgSe$ has shown promise in recent
years as a potential low-temperature thermoelectric material. It exhibits
reasonably strong thermoelectric performance as well as an extremely high
carrier mobility, both of which are enhanced when the material is doped with Ni
at the Cu sites. The exact mechanism by which these enhancements result;
however, is unclear. In order to further investigate the effects of chemical
substitution on the material's thermoelectric properties, we have prepared and
performed various measurements on $CuAgSe$ samples doped with Co and Cr
according to the following compositional formulas: $Cu_{1-x}Co_{x}AgSe$
$(x=0.02, 0.05, 0.10)$ and $Cu_{1-x}Cr_{x}AgSe$ $(x=0.02, 0.05)$. Measurements
of temperature and magnetic field dependent thermal conductivity, electrical
resistivity, and Seebeck coefficient will be discussed. Our results reveal a
remarkable sensitivity of $CuAgSe$'s thermoelectric properties to chemical
doping in general as well as a particular sensitivity to specific dopants. This
demonstrated tunability of $CuAgSe$'s various properties furthers the case that
high mobility phonon glass-semimetals are strong candidates for potential low
temperature thermoelectric applications.",1610.05634v1
2018-03-14,Ultra High Molecular Weight Polyethylene: optical features at millimeter wavelengths,"The next generation of experiments for the measurement of the Cosmic
Microwave Background (CMB) requires more and more the use of advanced
materials, with specific physical and structural properties. An example is the
material used for receiver's cryostat windows and internal lenses. The large
throughput of current CMB experiments requires a large diameter (of the order
of 0.5m) of these parts, resulting in heavy structural and optical requirements
on the material to be used. Ultra High Molecular Weight (UHMW) polyethylene
(PE) features high resistance to traction and good transmissivity in the
frequency range of interest. In this paper, we discuss the possibility of using
UHMW PE for windows and lenses in experiments working at millimeter
wavelengths, by measuring its optical properties: emissivity, transmission and
refraction index. Our measurements show that the material is well suited to
this purpose.",1803.05228v1
2019-08-02,Machine-learning-assisted thin-film growth: Bayesian optimization in molecular beam epitaxy of SrRuO3 thin films,"Materials informatics exploiting machine learning techniques, e.g., Bayesian
optimization (BO), has the potential to offer high-throughput optimization of
thin-film growth conditions through incremental updates of machine learning
models in accordance with newly measured data. Here, we demonstrated BO-based
molecular beam epitaxy (MBE) of SrRuO3, one of the most-intensively studied
materials in the research field of oxide electronics, mainly owing to its
unique nature as a ferromagnetic metal. To simplify the intricate search space
of entangled growth conditions, we ran the BO for a single condition while
keeping the other conditions fixed. As a result, high-crystalline-quality
SrRuO3 film exhibiting a high residual resistivity ratio (RRR) of over 50 as
well as strong perpendicular magnetic anisotropy was developed in only 24 MBE
growth runs in which the Ru flux rate, growth temperature, and
O3-nozzle-to-substrate distance were optimized. Our BO-based search method
provides an efficient experimental design that is not as dependent on the
experience and skills of individual researchers, and it reduces experimental
time and cost, which will accelerate materials research.",1908.00739v1
2002-04-08,Pressure Effect on the Superconducting and Magnetic Transitions of the Superconducting Ferromagnet RuSr2GdCu2O8,"The superconducting ferromagnet RuSr2GdCu2O8 was investigated at high
pressure. The intra-grain superconducting transition temperature, Tc, is
resolved in ac-susceptibility as well as resistivity measurements. It is shown
that the pressure shift of Tc is much smaller than that of other high-Tc
compounds in a similar doping state. In contrast, the ferromagnetic transition
temperature, Tm, increases with pressure at a relative rate that is about twice
as large as that of Tc. The high-pressure data indicate a possible competition
of the ferromagnetic and superconducting states in RuSr2GdCu2O8.",0204185v1
2004-09-23,Superconducting and Normal State Properties of Heavily Hole-Doped Diamond,"We report measurements of the specific heat, Hall effect, upper critical
field and resistivity on bulk, B-doped diamond prepared by reacting amorphous B
and graphite under high-pressure/high-temperature conditions. These experiments
establish unambiguous evidence for bulk superconductivity and provide a
consistent set of materials parameters that favor a conventional, weak coupling
electron-phonon interpretation of the superconducting mechanism at high hole
doping.",0409624v1
2000-04-10,Systematic evolution of the magnetotransport properties of Bi_{2}Sr_{2-x}La_{x}CuO_{6} in a wide doping range,"Recently we have succeeded in growing a series of high-quality
Bi_{2}Sr_{2-x}La_{x}CuO_{6} crystals in a wide range of carrier concentrations.
The data of \rho_{ab}(T) and R_H(T) of those crystals show behaviors that are
considered to be ""canonical"" to the cuprates. The optimum zero-resistance T_c
has been raised to as high as 38 K, which is almost equal to the optimum T_c of
La_{2-x}Sr_{x}CuO_{4}.",0004134v1
2005-07-20,Superconductivity in Polycrystalline Diamond Thin Films,"Superconductivity was discovered in heavily boron-doped diamond thin films
deposited by the microwave plasma assisted chemical vapor deposition (MPCVD)
method. Advantages of the MPCVD deposited diamond are the controllability of
boron concentration in a wide range, and a high boron concentration, especially
in (111) oriented films, compared to that of the high-pressure high-temperature
method. The superconducting transition temperatures are determined to be 8.7K
for Tc onset and 5.0K for zero resistance by transport measurements. And the
upper critical field is estimated to be around 7T.",0507476v2
2006-11-15,"Silicon detectors: damage, modelling and expected long-time behaviour in physics experiments at ultra high energy","In this contribution, the structural modifications of the material and the
degradation of devices is modelled and compared with experimental data for more
resistivities, temperatures, crystal orientations and oxygen concentrations,
considering the existence of the new primary fourfold coordinated defect,
besides the vacancy and the interstitial. Some estimations of the behaviour of
detectors in concrete environments at the next generations of high energy
physics experiments as LHC, SLHC, VLHC, or ULHC are done.",0611142v1
2008-01-07,High pressure-high temperature phase diagram of ammonia,"The high pressure(P)-high temperature(T) phase diagram of solid ammonia has
been investigated using diamond anvil cell and resistive heating techniques.
The III-IV transition line has been determined up to 20 GPa and 500 K both on
compression and decompression paths. No discontinuity is observed at the
expected location for the III-IV-V triple point. The melting line has been
determined by visual observations of the fluid-solid equilibrium up to 9 GPa
and 900 K. The experimental data is well fitted by a Simon-Glatzel equation in
the covered P-T range. These transition lines and their extrapolations are
compared with reported calculations.",0801.0913v1
2008-07-16,High-Temperature Superconductivity in Eu0.5K0.5Fe2As2,"Subsequent to our recent report of SDW type transition at 190 K and
antiferromagnetic order below 20 K in EuFe2As2, we have studied the effect of
K-doping on the SDW transition at high temperature and AF order at low
temperature. 50% K doping suppresses the SDW transition and in turn gives rise
to high-temperature superconductivity below T_c = 32 K, as observed in the
electrical resistivity, AC susceptibility as well as magnetization. A well
defined anomaly in the specific heat provides additional evidence for bulk
superconductivity.",0807.2530v2
2017-09-08,Room temperature ferromagnetism in transparent and conducting Mn-doped $SnO_{2}$ thin films,"The magnetization as a function of magnetic field showed hysteretic behavior
at room temperature. According to the temperature dependence of the
magnetization, the Curie temperature $(T_{C})$ is higher than 350 K.
Ferromagnetic Mn-doped tin oxide thin films exhibited low electrical
resistivity and high optical transmittance in the visible region (400-800 nm).
The coexistence of ferromagnetism, high visible transparency and high
electrical conductivity in the Mn-doped $SnO_{2}$ films is expected to be a
desirable trait for spintronics devices.",1709.05930v1
2020-11-18,The CLICTD Monolithic CMOS Sensor,"CLICTD is a monolithic silicon pixel sensor fabricated in a modified 180 nm
CMOS imaging process with a small collection electrode design and a
high-resistivity epitaxial layer. It features an innovative sub-pixel
segmentation scheme and is optimised for fast charge collection and high
spatial resolution. The sensor was developed to target the requirements for the
tracking detector of the proposed future Compact Linear Collider (CLIC). Most
notably, a temporal resolution of a few nanoseconds and a spatial resolution
below 7 microns are demanded. In this contribution, the sensor performance
measured in beam tests is presented with emphasis on recent studies using
assemblies with different thicknesses (down to 50 microns to minimize the
material budget) and inclined particle tracks.",2011.09389v1
2023-11-28,A Brief Review and Perspective on the Functional Biodegradable Films for Food Packaging,"High-performance, environmentally-friendly biodegradable packaging as
substitutes for conventional plastics becomes severe demand to nowadays economy
and society. As an aliphatic aromatic copolyester PBAT is recognized as the
preferred alternative to traditional plastics. However, the relatively high
cost and weak properties obstacles the widespread adoption of PBAT.
Modification pertaining to improve the properties, lower the cost, and include
the functional additives of PBAT is a continuous effort to meet the needs of
food accessibility, antibacterial properties, oxygen resistance, high
mechanical strength, stable size, low moisture absorption, and various gas
permeability for commercial competitiveness.",2311.16932v1
2023-05-18,Indium-Tin-Oxide for High-performance Electro-optic Modulation,"Advances in opto-electronics are often led by discovery and development of
materials featuring unique properties. Recently the material class of
transparent conductive oxides (TCO) has attracted attention for active photonic
devices on-chip. In particular Indium Tin Oxide (ITO) is found to have
refractive index changes on the order of unity. This property makes it possible
to achieve electro-optic modulation of sub-wavelength device scales, when thin
ITO films are interfaced with optical light confinement techniques such as
found in plasmonics; optical modes are compressed to nanometer scale to create
strong light-matter-interactions. Here we review efforts towards utilizing this
novel material for high-performance and ultra-compact modulation. While high
performance metrics are achieved experimentally, there are open questions
pertaining the permittivity modulation mechanism of ITO. Furthermore, we show
that a footprint-saving waveguide inline cavity can enhance obtainable
extinction-ratio to insertion-loss ratios by about one order of magnitude over
non-cavity based version. Moreover, we offer a speed analysis that shows that
the device is resistance limited, but not capacitance or drift-carrier limited.
Interestingly, two bias options exist for ITO and we find that a
side-connection enables devices that should in principle enable several hundred
of GHz fast devices, using our routinely achievable ITO film resistivities.
Finally, we offer a brief discuss about footprint savings of compact ITO
modulators showing a 3-orders of magnitude smaller footprint over Silicon
photonic MZI-based modulators.",2305.10639v1
2024-03-14,"Magnetotransport properties in van-der-Waals \textit{\textbf{R}}Te$_{3}$ (\textit{\textbf{R}} = La, Ce, Tb)","Rare-earth tritellurides are van-der-Waals antiferromagnets which have been
attracting attention as materials not only with high mobility, but also with
various states such as superconductivity under high pressure, incommensurate
charge-density-wave (CDW) phase, and multiple antiferromagnetic phases. In this
work, we performed longitudinal resistivity and Hall resistivity measurements
simultaneously in exfoliated $R$Te$_{3}$ ($R$ =La, Ce, Tb) thin film devices,
in order to investigate the influence of magnetic ordering on transport
properties in van-der-Waals magnetic materials. We have obtained carrier
mobility and concentration using a two-band model, and have observed an
increase in carrier mobility in the antiferromagnets CeTe$_{3}$ and TbTe$_{3}$
due to the magnetic transition. Especially in CeTe$_{3}$, the carrier
concentration has changed drastically below the magnetic transition
temperature, suggesting the interaction between the CDW and antiferromagnetic
phases. In addition, the analysis of the Shubnikov-de Haas oscillations in
CeTe$_{3}$ supports the possibility of Fermi surface modulation by magnetic
ordering. This research will pave the way not only for spintronic devices that
take advantage of high mobility, but also for the study of the correlation
between CDW and magnetism states in low-dimensional materials.",2403.09250v2
2016-02-19,Magnetic effects in sulfur-decorated graphene,"The interaction between two different materials can present novel phenomena
that are quite different from the physical properties observed when each
material stands alone. Strong electronic correlations, such as magnetism and
superconductivity, can be produced as the result of enhanced Coulomb
interactions between electrons. Two-dimensional materials are powerful
candidates to search for the novel phenomena because of the easiness of
arranging them and modifying their properties accordingly. In this work, we
report magnetic effects of graphene, a prototypical non-magnetic
two-dimensional semi-metal, in the proximity with sulfur, a diamagnetic
insulator. In contrast to the well-defined metallic behaviour of clean
graphene, an energy gap develops at the Fermi energy for the graphene/sulfur
compound with decreasing temperature. This is accompanied by a steep increase
of the resistance, a sign change of the slope in the magneto-resistance between
high and low fields, and magnetic hysteresis. A possible origin of the observed
electronic and magnetic responses is discussed in terms of the onset of
low-temperature magnetic ordering. These results provide intriguing insights on
the search for novel quantum phases in graphene-based compounds.",1602.06214v2
2020-09-27,Non-equilibrium Effects in Dissipative Strongly Correlated Systems,"Novel physics arises when strongly correlated system is driven out of
equilibrium by external fields. Dramatic changes in physical properties, such
as conductivity, are empirically observed in strongly correlated materials
under high electric field. In particular, electric-field driven metal-insulator
transitions are well-known as the resistive switching effect in a variety of
materials, such as VO$_2$, V$_2$O$_3$ and other transition metal oxides. To
satisfactorily explain both the phenomenology and its underlying mechanism, it
is required to model microscopically the out-of-equilibrium dissipative lattice
system of interacting electrons. In this thesis, we developed a systematic
method of modeling non-equilibrium steady states for dissipative lattice
systems by means of Non-equilibrium Green's function and Dynamical Mean Field
Theory. We firstly establish a ""minimum model"" to formulate the strong-field
transport in non-interacting dissipative electron lattice. This model is
exactly soluble and convenient for discussing energy dissipation and
steady-state properties. The formalism is then combined with Dynamical Mean
Field Theory to provide a systematic framework describing the nonequilibrium
steady-state of correlated materials. We use the formalism to study the
strong-field transport properties of correlated materials, Mott insulators and
Dirac electrons in graphene. We concentrate on the microscopic description of
resistive switching. Of particular interest is the filament formation during
the dynamical phase transition, which has been interpreted as a result of the
delicate interplay between dissipation and Mott physics. We will also examine
$IV$ characteristics and particularly the current saturation of Dirac electrons
in graphene. The arXiv version has been updated with minor modifications and
corrections.",2009.12865v1
2020-09-28,A hybrid optoelectronic Mott insulator,"The coupling of electronic degrees of freedom in materials to create
hybridized functionalities is a holy grail of modern condensed matter physics
that may produce novel mechanisms of control. Correlated electron systems often
exhibit coupled degrees of freedom with a high degree of tunability which
sometimes lead to hybridized functionalities based on external stimuli.
However, the mechanisms of tunability and the sensitivity to external stimuli
are determined by intrinsic material properties which are not always
controllable. A Mott metal-insulator transition, which is technologically
attractive due to the large changes in resistance, can be tuned by doping,
strain, electric fields, and orbital occupancy but cannot be, in and of itself,
controlled externally with light. Here we present a new approach to produce
hybridized functionalities using a properly engineered
photoconductor/strongly-correlated hybrid heterostructure, showing control of
the Metal-to-Insulator transition (MIT) using optical means. This approach
combines a photoconductor, which does not exhibit an MIT, with a strongly
correlated oxide, which is not photoconducting. Due to the close proximity
between the two materials, the heterostructure exhibits large volatile and
nonvolatile, photoinduced resistivity changes and substantial photoinduced
shifts in the MIT transition temperatures. This approach can potentially be
extended to other judiciously chosen combinations of strongly correlated
materials with systems which exhibit optically, electrically or magnetically
controllable behavior.",2009.13606v1
2020-01-02,Thermal Conductivity Measurements in Nanosheets via Bolometric Effect,"Thermal conductivity measurement techniques for materials with nanoscale
dimensions require fabrication of very complicated devices or their
applicability is limited to a class of materials. Discovery of new methods with
high thermal sensitivity are required for the widespread use of thermal
conductivity measurements in characterizing materials properties. We propose
and demonstrate a simple non-destructive method with superior thermal
sensitivity to measure the in-plane thermal conductivity of nanosheets and
nanowires using the bolometric effect. The method utilizes laser beam heating
to create a temperature gradient, as small as a fraction of a Kelvin, over the
suspended section of the nanomaterial with electrical contacts. Local
temperature rise due to the laser irradiation alters the electrical resistance
of the device, which can be measured precisely. This resistance change is then
used to extract the temperature profile along the nanomaterial using thermal
conductivity as a fitting parameter. We measured the thermal conductivity of
V2O3 nanosheets to validate the applicability of the method and found an
excellent agreement with the literature. Further, we measured the thermal
conductivity of metallic 2H-TaS2 for the first time and performed ab initio
calculations to support our measurements. Finally, we discussed the
applicability of the method on semiconducting nanosheets and performed
measurements on WS2 and MoS2 thin flakes.",2001.00368v1
2020-11-01,Bipolar Magnetic Semiconducting Behavior in VNbRuAl: A New Spintronic Material for Spin Filters,"We report the theoretical prediction of a new class of spintronic materials,
namely bipolar magnetic semiconductor (BMS), which is also supported by our
experimental data. BMS acquires a unique band structure with unequal band gaps
for spin up and down channels, and thus are useful for tunable spin transport
based applications such as spin filters. The valence band (VB) and conduction
band (CB) in BMS approach the Fermi level through opposite spin channels, and
hence facilitate to achieve reversible spin polarization which are controllable
via applied gate voltage. We report the quaternary Heusler alloy VNbRuAl to
exactly possess the band structure of BMS. The alloy is found to crystallize in
LiMgPdSn prototype structure (space group $F\bar{4}3m$) with B$2$ disorder and
lattice parameter 6.15 \AA . The resistivity and Hall measurements show a two
channel semiconducting behavior and a quasi linear dependence of negative
magneto resistance (MR) indicating the possible semiconducting nature.
Interestingly, VNbRuAl also shows a fully compensated ferrimagnetic (FCF)
behavior with vanishing net magnetization (m$_s$$\sim$ $10^{-3}$ $\mu_B/f.u.$)
and significantly high ordering temperature ($> 900$ K). Unlike conventional
FCF, vanishing moment in this case appears to be the result of a combination of
long range antiferromagnetic (AFM) ordering and the inherent B2 disorder of the
crystal. This study opens up the possibility of finding a class of materials
for AFM spintronics, with great significance both from fundamental and applied
fronts.",2011.00533v1
2021-10-26,Wet Scandium Etching for hard mask formation on a silicon substrate,"Nowadays, microelectronics and nanoelectronics require the search for new
materials, including masks for creating structures. Today, the intermediate
hard mask strategy is one of the key issues in achieving a good balance between
lithography and etching at the microelectronic fabrication. One of the
interesting challenges in microelectronics and photovoltaics is the creation of
interspacing, vertically oriented silicon arrays on Si substrate for
semiconductor devices with multi-function. The fabrication of such structures
is still a serious technological problem and requires searching for new
approaches and materials. In this work, we propose using scandium as a new hard
mask material over silicon due to its high resistance to plasma chemical
etching and low sputtering coefficient. We have shown that a wet etching of the
scandium layer with a thickness of several nanometers can be used to obtain
pattern structures with a resolution of up to 4 microns, which is a good result
for the wet etching approach. Scandium metal was found to be an excellent
resistant mask over silicon under the selected plasma etching conditions.
Therefore, a scandium hard mask can open up new possibilities for the formation
of different microscale topographical patterns.",2110.13639v3
2007-01-03,Two-dimensional Vortices in Superconductors,"Superconductors have two key characteristics. They expel magnetic field and
they conduct electrical current with zero resistance. However, both properties
are compromised in high magnetic fields which can penetrate the material and
create a mixed state of quantized vortices. The vortices move in response to an
electrical current dissipating energy which destroys the zero resistance
state\cite{And64}. One of the central problems for applications of high
temperature superconductivity is the stabilization of vortices to ensure zero
electrical resistance. We find that vortices in the anisotropic superconductor
Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ (Bi-2212) have a phase transition from
a liquid state, which is inherently unstable, to a two-dimensional vortex
solid. We show that at high field the transition temperature is independent of
magnetic field, as was predicted theoretically for the melting of an ideal
two-dimensional vortex lattice\cite{Fis80,Gla91}. Our results indicate that the
stable solid phase can be reached at any field as may be necessary for
applications involving superconducting magnets\cite{Has04,Sca04,COHMAG}. The
vortex solid is disordered, as suggested by previous studies at lower
fields\cite{Lee93,Cub93}. But its evolution with increasing magnetic field
displays unexpected threshold behavior that needs further investigation.",0701059v1
2007-11-01,Point-contact search for antiferromagnetic giant magnetoresistance,"We report the first measurements of effects of large current densities on
current-perpendicular-to-plane magnetoresistance (MR) of magnetic multilayers
containing two antiferromagnetic layers separated by a non-magnetic layer.
These measurements were intended to search for a recently predicted
antiferromagnetic giant magnetoresistance (AGMR) similar to GMR seen in
multilayers containing two ferromagnetic layers separated by a non-magnetic
layer. We report on MR measurements for current injected from point contacts
into sandwiches containing different combinations of layers of F = CoFe and AFM
= FeMn. In addition to: AFM/N/AFM, F/AFM/N/AFM, and F/AFM/N/AFM/F structures,
initial results led us to examine also AFM/F/N/AFM, F/AFM, and single F- and
AFM-layer structures. At low currents, no MR was observed in any samples, and
no MR was observed at any current densities in samples containing only AFMs.
Together, these results indicate that no AGMR is present in these samples. In
samples containing F-layers, high current densities sometimes produced a small
positive MR - largest resistance at high fields. For a given contact
resistance, this MR was usually larger for thicker F-layers, and for a given
current, it was usually larger for larger contact resistances (smaller
contacts). We tentatively attribute this positive MR to suppression at high
currents of spin accumulation induced around and within the F-layers.",0711.0059v3
2008-06-18,Linear-T resistivity and change in Fermi surface at the pseudogap critical point of a high-Tc superconductor,"A fundamental question of high-temperature superconductors is the nature of
the pseudogap phase which lies between the Mott insulator at zero doping and
the Fermi liquid at high doping p. Here we report on the behaviour of charge
carriers near the zero-temperature onset of that phase, namely at the critical
doping p* where the pseudogap temperature T* goes to zero, accessed by
investigating a material in which superconductivity can be fully suppressed by
a steady magnetic field. Just below p*, the normal-state resistivity and Hall
coefficient of La1.6-xNd0.4SrxCuO4 are found to rise simultaneously as the
temperature drops below T*, revealing a change in the Fermi surface with a
large associated drop in conductivity. At p*, the resistivity shows a linear
temperature dependence as T goes to zero, a typical signature of a quantum
critical point. These findings impose new constraints on the mechanisms
responsible for inelastic scattering and Fermi surface transformation in
theories of the pseudogap phase.",0806.2881v2
2016-06-07,Spin-Orbit Interaction and Kondo Scattering at the PrAlO$_3$/SrTiO$_3$ Interface: Effects of Oxygen Content,"We report the effect of oxygen pressure during growth ($P_{O_{2}}$) on the
electronic and magnetic properties of PrAlO$_3$ films grown on $\rm
TiO_{2}$-terminated SrTiO$_3$ substrates. Resistivity measurements show an
increase in the sheet resistance as $P_{O_{2}}$ is increased. The temperature
dependence of the sheet resistance at low temperatures is consistent with Kondo
theory for $P_{O_{2}} \ge 10^{-5}$ torr. Hall effect data exhibit a complex
temperature dependence that suggests a compensated carrier density. We observe
behavior consistent with two different types of carriers at interfaces grown at
$P_{O_{2}} \ge 10^{-4}$ torr. For these interfaces, we measured a moderate
positive magnetoresistance (MR) due to a strong spin-orbit (SO) interaction at
low magnetic fields that evolves into a larger negative MR at high fields.
Positive high MR values are associated with samples where a fraction of
carriers are derived from oxygen vacancies. Analysis of the MR data permitted
the extraction of the SO interaction critical field ( e.g. $ H_{SO}=$1.25 T for
$P_{O_{2}}=10^{-5}$ torr). The weak anti-localization effect due to a strong SO
interaction becomes smaller for higher $P_{O_{2}}$ grown samples, where MR
values are dominated by the Kondo effect, particularly at high magnetic fields.",1606.02308v1
2016-07-20,Magnetotransport properties of the type II Weyl semimetal candidate Ta3S2,"We have investigated the magnetoresistance (MR) and Hall resistivity
properties of the single crystals of tantalum sulfide, Ta3S2, which was
recently predicted to be a new type II Weyl semimetal. Large MR (up to ~8000%
at 2 K and 16 T), field-induced metal-insulator-like transition and nonlinear
Hall resistivity are observed at low temperatures. The large MR shows a strong
dependence on the field orientation, leading to a giant anisotropic
magnetoresistance (AMR) effect. For the field applied along the b-axis (B//b),
MR exhibits quadratic field dependence at low fields and tends towards
saturation at high fields; while for B//a, MR presents quadratic field
dependence at low fields and becomes linear at high fields without any trend
towards saturation. The analysis of the Hall resistivity data indicates the
coexistence of a large number of electrons with low mobility and a small number
of holes with high mobility. Shubnikov-de Haas (SdH) oscillation analysis
reveals three fundamental frequencies originated from the three-dimensional
(3D) Fermi surface (FS) pockets. We find that the semi-classical multiband
model is sufficient to account for the experimentally observed MR in Ta3S2.",1607.05798v2
2017-10-25,Device model for pixelless infrared image up-converters based on polycrystalline graphene heterostructures,"We develop a device model for pixelless converters of far/mid-infrared
radiation (FIR/MIR) images into near-infrared/visible (NIR/VIR) images. These
converters use polycrystalline graphene layers (PGLs) immersed in the van der
Waals (vdW) materials integrated with light emitting diode (LED). The PGL
serves as an element of the PGL infrared photodetector (PGLIP) sensitive to the
incoming FIR/MIR due to the interband absorption. The spatially non-uniform
photocurrent generated in the PGLIP repeats (mimics) the non-uniform
distribution (image) created by the incident FIR/MIR. The injection of the
nonuniform photocurrent into the LED active layer results in the nonuniform
NIR/VIR image reproducing the FIR/MIR image. The PGL and the entire layer
structure are not deliberately partitioned into pixels. We analyze the
characteristics of such pixelless PGLIP-LED up-converters and show that their
image contrast transfer function and the up-conversion efficiency depend on the
PGL lateral resistivity. The up-converter exhibits high photoconductive gain
and conversion efficiency when the lateral resistivity is sufficiently high.
Several teams have successfully demonstrated the large area PGLs with the
resistivities varying in a wide range. Such layers can be used in the pixelless
PGLIP-LED image up-converters. The PGLIP-LED image up-converters can
substantially surpass the image up-converters based on the quantum-well
infrared photodetector (QWIP) integrated with the LED. These advantages are due
to the use of the interband FIR/NIR absorption and a high photoconductive gain
in the GLIPs.",1710.09060v1
2018-06-18,Electroluminescence on-off ratio control of n-i-n GaAs/AlGaAs-based resonant tunneling structures,"We explore the nature of the electroluminescence (EL) emission of purely
n-doped GaAs/AlGaAs resonant tunneling diodes (RTDs) and the EL evolution with
voltage. A singular feature of such a device is unveiled when the electrical
output current changes from high to low and the EL on-off ratio is enhanced by
2 orders of magnitude compared to the current on-off ratio. By combining the EL
and current properties, we are able to identify two independent impact
ionization channels associated with the coherent resonant tunneling current and
the incoherent valley current. We also perform the same investigation with an
associated series resistance, which induces a bistable electrical output in the
system. By simulating a resistance variation for the current-voltage and the
EL, we are able to tune the EL on-off ratio by up to 6 orders of magnitude. We
further observe that the EL on and off states can be either direct or inverted
compared to the tunneling current on and off states. This electroluminescence,
combined with the unique RTD properties such as the negative differential
resistance (NDR) and high frequency operation, enables the development of high
speed functional opto-electronic devices and optical switches.",1806.06757v1
2012-01-19,Magnetic Field Effects on Transport Properties of PtSn4,"The anisotropic physical properties of single crystals of orthorhombic PtSn4
are reported for magnetic fields up to 140 kOe, applied parallel and
perpendicular to the crystallographic b-axis. The magnetic susceptibility has
an approximately temperature independent behavior and reveals an anisotropy
between ac-plane and b-axis. Clear de Haas-van Alphen oscillations in fields as
low as 5 kOe and at temperatures as high as 30 K were detected in magnetization
isotherms. The thermoelectric power and resistivity of PtSn4 show the strong
temperature and magnetic field dependencies. A change of the thermoelectric
power at H = 140 kOe is observed as high as ~ 50 mu-V/K. Single crystals of
PtSn4 exhibit very large transverse magnetoresistance of ~ 5x10^5% for the
ac-plane and of ~ 1.4x10^5% for the b-axis resistivity at 1.8 K and 140 kOe, as
well as pronounced Shubnikov-de Haas oscillations. The magnetoresistance of
PtSn4 appears to obey Kohler's rule in the temperature and field range
measured. The Hall resistivity shows a linear temperature dependence at high
temperatures followed by a sign reversal around 25 K which is consistent with
thermoelectric power measurements. The observed quantum oscillations and band
structure calculations indicate that PtSn4 has three dimensional Fermi
surfaces.",1201.4091v1
2020-10-23,"Air-stable, earth-abundant molten chlorides and corrosion-resistant containment for chemically-robust, high-temperature thermal energy storage for concentrated solar power","A dramatic reduction in man-made CO2 emissions could be achieved if the cost
of electricity generated from concentrated solar power (CSP) plants could
become competitive with fossil-fuel-derived electricity. The solar
heat-to-electricity conversion efficiency of CSP plants may be significantly
increased (and the associated electricity cost decreased) by operating CSP
turbines with inlet temperatures >750 C instead of <550 C, and by using thermal
energy storage (TES) at >750 C to allow for rapidly dispatchable and/or
continuous electricity production. Unfortunately, earth-abundant
MgCl2-KCl-based liquids currently being considered as low-cost media for
large-scale, high-temperature TES are susceptible to oxidation in air, with
associated undesired changes in liquid composition and enhanced corrosion of
metal alloys in pipes and tanks containing such liquids. In this paper,
alternative high-temperature, earth-abundant molten chlorides that are stable
in air are identified via thermodynamic calculations. The oxidation resistance,
and corrosion-resistant containment, of such molten chlorides at 750 C are then
demonstrated. Such chemically-robust, low-cost TES media and effective
containment provide critical advances towards the higher-temperature operation
of, and lower-cost electricity generation from, CSP plants.",2010.12476v1
2023-03-03,Anomalous Random Telegraphy Signal in Suspended Graphene with Oxygen Adsorption,"Graphene is a promising material for sensing applications because of its
large specific surface area and low noise. In many applications, graphene will
inevitably be in contact with oxygen since it is the second most abundant gas
in the atmosphere. Therefore, it is of interest to understand how this gas
affects the sensor properties. In this work, the effect of oxygen on the
low-frequency noise of suspended graphene is demonstrated. Devices with
suspended graphene nanoribbons with a width (W) and length (L) of 200 nm were
fabricated. The resistance as a function of time was measured in a vacuum and
pure oxygen atmosphere through an ac lock-in method. After signal processing
with wavelet denoising and analysis, it is demonstrated that oxygen causes
random telegraphy signal (RTS) in the millisecond scale, with an average dwell
time of 2.9 milliseconds in the high-resistance state, and 2 milliseconds in
the low-resistance state. It is also shown that this RTS occurs only at some
periods, which indicates that, upon adsorption, the molecules take some time
until they find the most energetically favorable adsorption state. Also, a
slow-down in the RTS time constants is observed, which infers that less active
sites are available as time goes on because of oxygen adsorption. Therefore, it
is very important to consider these effects to guarantee high sensitivity and
high durability for graphene-based sensors that will be exposed to oxygen
during their lifetime.",2303.01649v2
2007-09-12,Characterization of Thermal Interface Materials to Support Thermal Simulation,"In this paper new characterization equipment for thermal interface materials
is presented. Thermal management of electronic products relies on the
effec-tive dissipation of heat. This can be achieved by the optimization of the
system design with the help of simulation methods. The precision of these
models relies also on the used material data. For the determi-nation of this
data an experimental set-up for a static measurement is presented, which
evaluates thermal conductivity and interface resistance of thermal inter-face
materials (e.g. adhesive, solder, pads, or pastes). A qualitative
structure-property correlation is pro-posed taking into account particle size,
filler content and void formation at the interface based on high resolution FIB
imaging. The paper gives an overview over the set-up and the measurement
technique and discusses experimental and simulation results.",0709.1849v1
2016-02-29,A Solid-State Dielectric Elastomer Switch for Soft Logic,"In this paper we describe a stretchable solid-state electronic switching
material that operates at high voltage potentials, as well as a switch material
benchmarking technique that utilizes a modular dielectric elastomer (artificial
muscle) ring oscillator. The solid-state switching material was integrated into
our oscillator, which self-started after 16s and performed 5 oscillations at a
frequency of 1.05Hz with 3.25kV DC input. Our materials-by-design approach for
the nickel filled polydimethysiloxane (Ni-PDMS) based switch has resulted in
significant improvements over previous carbon-grease based switches in four key
areas, namely sharpness of switching behavior upon applied stretch, magnitude
of electrical resistance change, ease of manufacture, and rate of production.
Switch lifetime was demonstrated to be in the range of tens to hundreds of
cycles with the current process. An interesting and potentially useful
strain-based switching hysteresis behavior is also presented.",1602.08988v1
2019-03-15,An efficient phase-field model for fatigue fracture in ductile materials,"Fatigue fracture in ductile materials, e. g. metals, is caused by cyclic
plasticity. Especially regarding the high numbers of load cycles, plastic
material models resolving the full loading path are computationally very
demanding. Herein, a model with particularly small computational effort is
presented. It provides a macroscopic, phenomenological description of fatigue
fracture by combining the phase-field method for brittle fracture with a
classic durability concept. A local lifetime variable is obtained, which
degrades the fracture resistance progressively. By deriving the stress-strain
path from cyclic material characteristics, only one increment per load cycle is
needed at maximum. The model allows to describe fatigue crack initiation,
propagation and residual fracture and can reproduce Paris behaviour.",1903.06465v3
2021-10-21,Structures and physical properties of V-based kagome metals CsV$_{6}$Sb$_{6}$ and CsV$_{8}$Sb$_{12}$,"We report two new members of V-based kagome metals CsV$_{6}$Sb$_{6}$ and
CsV$_{8}$Sb$_{12}$. The most striking structural feature of CsV$_{6}$Sb$_{6}$
is the V kagome bilayers. For CsV$_{8}$Sb$_{12}$, there is an intergrowth of
two-dimensional V kagome layers and one-dimensional V chains and the latter
lead to the orthorhombic symmetry of this material. Further measurements
indicate that these two materials exhibit metallic and Pauli paramagnetic
behaviors. More importantly, different from CsV$_{3}$Sb$_{5}$, the charge
density wave state and superconductivity do not emerge in CsV$_{6}$Sb$_{6}$ and
CsV$_{8}$Sb$_{12}$ when temperature is above 2 K. Small magnetoresistance with
saturation behavior and linear field dependence of Hall resistivity at high
field and low temperature suggest that the carriers in both materials should be
uncompensated with much different concentrations. The discovery of these two
new V-based kagome metals sheds light on the exploration of correlated
topological materials based on kagome lattice.",2110.11452v2
2022-05-17,The Highly Disordered Zintl Phase Ca$_{10}$GdCdSb$_9$ -- New Example of a p-type Semiconductor with Remarkable Thermoelectric Properties,"Ca$_{10}$GdCdSb$_9$ is a new Zintl phase with a large unit cell volume (~2500
{\AA}3) and a very complex, disordered structure, which can drive the
realization of ultralow thermal conductivity in this material. The measured
Seebeck coefficient, $\alpha$, for single-crystalline Ca$_{10}$GdCdSb$_9$
approaches 350 $\mu$V/K at 600 K. The experimentally determined electrical
resistivity of Ca$_{10}$GdCdSb$_9$ is very low, leading to a remarkably
high-power factor PF of 23.2 $\mu$W/cm.K$^2$ at 460 K. The extraordinary PF
value in this material, higher than those of the currently known
state-of-the-art materials within the same temperature range, suggests that the
Ca$_{10}$RECdSb$_9$ material system (RE = rare earth metal) could serve as a
viable playground to harnessing new efficient thermoelectric generators.",2205.08559v1
2022-10-12,Experimental data management platform for data-driven investigation of combinatorial alloy thin films,"Experimental materials data are heterogeneous and include a variety of
metadata for processing and characterization conditions, making the
implementation of data-driven approaches for developing novel materials
difficult. In this paper, we introduce the Thin-Film Alloy Database (TFADB), a
materials data management platform, designed for combinatorially investigated
thin-film alloys through various experimental tools. Using TFADB, researchers
can readily upload, edit, and retrieve multidimensional experimental alloy
data, such as composition, thickness, X-ray Diffraction, electrical
resistivity, nanoindentation, and image data. Furthermore,
composition-dependent properties from the database can easily be managed in a
format adequate to be preprocessed for machine learning analyses. High
flexibility of the software allows management of new types of materials data
that can be potentially acquired from new combinatorial experiments.",2210.06027v1
2022-10-18,Reaction-diffusion pathways for a programmable nanoscale texture of diamond-SiC composite,"The diamond-SiC composite has a low density and the highest possible speed of
sound among existing materials except for the diamond. The composite is
synthesized by a complex exothermic chemical reaction between diamond powder
and liquid Si. This makes it an ideal material for protection against impact
loading. Experiments show that a system of patterns is formed at the
diamond-SiC interface. Modeling of reaction-diffusion processes of composite
synthesis proves a formation of ceramic materials with a regular (periodic)
interconnected microstructure in a given system. Composite material with
interconnected structures at the interface has very high mechanical properties
and resistance to impact since its fractioning is intercrystallite.",2210.10021v1
2023-11-02,Machine Learning Design of Perovskite Catalytic Properties,"Discovering new materials that efficiently catalyze the oxygen reduction and
evolution reactions is critical for facilitating the widespread adoption of
solid oxide fuel cell and electrolyzer (SOFC/SOEC) technologies. Here, we
develop machine learning (ML) models to predict perovskite catalytic properties
critical for SOFC/SOEC applications, including oxygen surface exchange, oxygen
diffusivity, and area specific resistance (ASR). The models are based on
trivial-to-calculate elemental features and are more accurate and dramatically
faster than the best models based on ab initio-derived features, potentially
eliminating the need for ab initio calculations in descriptor-based screening.
Our model of ASR enables temperature-dependent predictions, has well calibrated
uncertainty estimates and online accessibility. Use of temporal
cross-validation reveals our model to be effective at discovering new promising
materials prior to their initial discovery, demonstrating our model can make
meaningful predictions. Using the SHapley Additive ExPlanations (SHAP)
approach, we provide detailed discussion of different approaches of model
featurization for ML property prediction. Finally, we use our model to screen
more than 19 million perovskites to develop a list of promising cheap,
earth-abundant, stable, and high performing materials, and find some top
materials contain mixtures of less-explored elements (e.g., K, Bi, Y, Ni, Cu)
worth exploring in more detail.",2311.01401v1
2024-01-22,Order induces toughness in anisotropic colloidal crystal composites,"Spatial ordering of matter elicits exotic properties sometimes absent from a
material's constituents. A few highly mineralised natural materials achieve
high toughness through delocalised damage, whereas synthetic particulate
composites must trade toughness for mineral content. We test whether ordering
the mineral phase in particulate composites through the formation of
macroscopic colloidal crystals can trigger the same damage resistance found in
natural materials. Our macroscopic silica rod based anisotropic colloidal
crystal composites are processed fully at room temperature and pressure, reach
volume fraction of mineral higher than 80%, and aided by a ductile interface,
unveil plastic strain reaching 10% through the collective movement of rods and
damage delocalisation over millimetres. These composites demonstrate key design
rules to break free from conventionally accepted structural materials
properties trade-off.",2401.11727v1
2016-10-24,Probing Intrinsic Material Conductivity in Two-Terminal Devices: A Resistance-Difference Method,"It is generally impossible to separately measure the resistance of the
functional component (i.e., the intrinsic device materials) and the parasitic
component (i.e., terminals, interfaces and serial loads) in a two-terminal
device. Yet such knowledge is important for understanding device physics and
designing device systems. Here, we consider a case where an electric current,
temperature, or magnetic field causes a small but identical relative
conductivity change of the device materials. We find an exact solution to this
relative change by a simple resistance-data analysis of similarly configured
two-terminal devices. The solution is obtainable even if the change is quite
small, say, less than 0.1%. In special cases of small relative changes in
parasitic resistance, the absolute parasitic resistance is also obtainable. Our
method is especially useful for studying the switching and transport
characteristics of the emergent non-volatile resistance memory.",1610.07666v2
2018-03-22,Status and update of the RaDIATE Collaboration R&D Program,"The Radiation Damage In Accelerator Target Environments (RaDIATE)
collaboration was founded in 2012 and currently consists of over 50
participants and 11 institutions globally. Due to the increasing power of
future proton accelerator sources in target facilities, there is a critical
need to further understand the physical and thermo-mechanical radiation
response of target facility materials. Thus, the primary objective of the
RaDIATE collaboration is to draw on existing expertise in the nuclear materials
and accelerator targets fields to generate new and useful materials data for
application within the accelerator and fission/fusion communities. Current
research activities of the collaboration include post irradiation examination
(PIE) of decommissioned components from existing beamlines such as the NuMI
beryllium beam window and graphite NT-02 target material. PIE of these
components includes advanced microstructural analyses (SEM/TEM, EBSD, EDS) and
micro-mechanics technique such as nano-indentation, to help characterize any
microstructural radiation damage incurred during operation. New irradiation
campaigns of various candidate materials at both low and high energy beam
facilities are also being pursued. Beryllium helium implantation studies at the
University of Surrey as well as high energy proton irradiation of various
materials at Brookhaven National Laboratory's BLIP facility have been
initiated. The program also extends to beam-induced thermal shock experiments
using high intensity beam pulses at CERN's HiRadMat facility, followed by
advanced PIE activities to evaluate thermal shock resistance of the materials.
Preliminary results from ongoing research activities, as well as the future
plans of the RaDIATE collaboration R&D program will be discussed.",1803.08563v1
2021-12-22,Self-repairing high entropy oxides,"All biological organisms, from plants to living creatures, can heal minor
wounds and damage. The realization of a similar self-healing capacity in
inorganic materials has been a design target for many decades. This would
represent a breakthrough in materials engineering, enabling many novel
technological applications, since such materials would be able to resist damage
caused by electromagnetic irradiation and/or mechanical impact. Here we
demonstrate that a high-entropy oxide is intrinsically capable of undergoing an
autonomous self-repairing process. Transmission electron microscopy revealed
that the spinel structure of (AlCoCrCu0.5FeNi)3O4 can regrow and repair itself
at the atomic level when damaged. Density functional theory calculations reveal
that the extra enthalpy stored in the high entropy material during fabrication
can be released to effectively heal macroscopic defects by regrowing into a
partially ordered state. This extraordinary self-repairing phenomenon makes
this new material highly desirable as a coating, enabling structures used in
harsh environments to better withstand damage, such as cosmic irradiation in
space, nuclear irradiation in nuclear power facilities, or tribological damage.
Most importantly, our results set the general design principles for the
synthesis of self-repairing materials.",2112.11747v1
2004-01-23,"Crystal growth and anisotropic transport properties of high-Tc superconductors Bi2Sr2Can-1CunO2n+4+d (n = 2, 3)","Large high-quality single crystals of Bi2Sr2Can-1CunO2n+4+d (n = 2, 3) were
successfully grown using an improved traveling solvent floating zone (TSFZ)
method, which features a slow growth rate and steep temperature gradient along
the melting zone. By measuring anisotropic resistivities and susceptibilities
of Bi2Sr2CaCu2O8+d, the characteristic pseudogap temperature T* was studied as
a function of doping. The T* suggest that the pseudogap is not simply a
precursor of high-Tc superconductivity, but that the pseudogap and the
superconducting gap compete with each other. The anisotropic resistivities of
Bi2Sr2Ca2Cu3O10+d were also measured, revealing that the Tc remains fixed in
the overdoped region while anisotropy decreases continuously. This anomalous
behavior will be discussed in terms of the inequivalent hole doping, which
occurs between two inequivalent CuO2 planes in the triple-layer system.",0401448v3
2010-04-28,Conductivity states changes in plasticized PVC films near breakdown threshold voltages values,"The near threshold ""soft breakdown"" measurements of PVC films conductivity
are investigated. In a wide range of external electric field strength for
various rather thick (>20 mkm) PVC films the resistance shows strong
nonlinearity and seems to enter high conductive state close to the breakdown
threshold. For our ""thick"" films boundary conditions electrode surface
specifics should not be so important as in thin polymer films experiments. Both
fast, instant mechanisms of nonlinearity, and effects of accumulation and delay
responce were observed. The phenomena corresponding to reversible transitions
in a state with rather high conductivity, seems to be similar to ones
registered earlier in thin layers of some broad-bandgap polymers. In a range of
relatively low field intensity, far from a threshold breakdown, as a result of
reversible switches between normal and high resistivity states a polymer film
in a standard measuring cell formed a relaxation generator giving a loud enough
sound signal with frequency increasing with the increase of external field.",1004.4972v1
2010-12-27,Superconductivity and Magnetic Properties of high-quality single crystals of $A_{x}$Fe$_2$Se$_2$ ($A$ = K and Cs),"We successfully grew the high-quality single crystals of $A_{x}$Fe$_2$Se$_2$
($A$ = K and Cs) by self-flux method. Sharp superconducting transition was
observed for both types of crystals. The crystals show the onset
superconducting transition temperatures ($T_{\rm c}$) of 31 K and 30 K for K-
and Cs-compounds, respectively, with nearly 100% shielding fraction. The
crystals show quite high resistivity in the normal state of more than 160
m$\Omega$ cm and 1300 m$\Omega$ cm maximum resistivity for
$K_{0.86}Fe_2Se_{1.82}$ and $Cs_{0.86}Fe_{1.66}Se_{2}$ single crystals,
respectively. Much larger upper critical field $H_{\rm c2}$ is inferred from
low-temperature iso-magnetic-field magnetoresistance in these crystals than in
FeSe. The anisotropy $H^{ab}_{\rm c2}$(0)/$H^{c}_{\rm c2}$(0) is around 3 for
both of the two materials. Anisotropic peculiar magnetic behavior in normal
state has been found for $Cs_{0.86}Fe_{1.66}Se_{2}$",1012.5552v1
2015-09-15,Epitaxial graphene quantum dots for high-performance THz bolometers,"Light absorption in graphene causes a large change in electron temperature,
due to low electronic heat capacity and weak electron phonon coupling [1-3],
making it very attractive as a hot-electron bolometer material. Unfortunately,
the weak variation of electrical resistance with temperature has substantially
limited the responsivity of graphene bolometers. Here we show that quantum dots
of epitaxial graphene on SiC exhibit an extraordinarily high variation of
resistance with temperature due to quantum confinement, higher than 430 Mohm/K
at 2.5 K, leading to responsivities for absorbed THz power above 10^10 V/W.
This is five orders of magnitude higher than other types of graphene hot
electron bolometers. The high responsivity combined with an extremely low
noise-equivalent power, about 0.2 fW/Hz^0.5 at 2.5K, place the performance of
graphene quantum dot bolometers well above commercial cooled bolometers.
Additionally, these quantum dot bolometers have the potential for superior
performance for operation above 77K.",1509.04646v1
2016-11-15,Linear magnetoresistance in a quasi-free two dimensional electron gas in an ultra-high mobility GaAs quantum well,"We report a magnetotransport study of an ultra-high mobility
($\bar{\mu}\approx 25\times 10^6$\,cm$^2$\,V$^{-1}$\,s$^{-1}$) $n$-type GaAs
quantum well up to 33 T. A strong linear magnetoresistance (LMR) of the order
of 10$^5$ % is observed in a wide temperature range between 0.3 K and 60 K. The
simplicity of our material system with a single sub-band occupation and free
electron dispersion rules out most complicated mechanisms that could give rise
to the observed LMR. At low temperature, quantum oscillations are superimposed
onto the LMR. Both, the featureless LMR at high $T$ and the quantum
oscillations at low $T$ follow the empirical resistance rule which states that
the longitudinal conductance is directly related to the derivative of the
transversal (Hall) conductance multiplied by the magnetic field and a constant
factor $\alpha$ that remains unchanged over the entire temperature range. Only
at low temperatures, small deviations from this resistance rule are observed
beyond $\nu=1$ that likely originate from a different transport mechanism for
the composite fermions.",1611.04857v1
2017-02-24,Elemental Analysis of Glass and Bakelite Electrodes Using PIXE Facility,"The evolution of particle detectors dates back to the discovery of X-rays and
radioactivity in 1890s. In detector history, the Resistive Plate Chambers
(RPCs) are introduced in early 1980s. An RPC is a gaseous detector made up of
two parallel electrodes having high resistivity like that of glass and
bakelite. Currently several high energy physics experiments are using RPC-based
detector system due to robustness and simplicity of construction. In each and
every experiment, RPCs have to run continuously for several years. So, it
demands an in-depth characterization of the electrode materials. In the present
study, an elemental analysis of locally available glass and bakelite samples is
done using PIXE facility available at Panjab University Cyclotron, Chandigarh.
PIXE measurements are done using 2.7 MeV proton beam incident on the electrode
sample target. The constituent elements present in these electrode samples are
reported.",1702.08480v3
2014-08-12,Collapse of CuO Double Chains and Suppression of Superconductivity in High-Pressure Phase of YBa$_2$Cu$_4$O$_8$,"The crystal structure and electrical resistivity of YBa$_2$Cu$_4$O$_8$ (Y124)
were studied under high pressure up to 18 GPa using diamond-anvil cells,
respectively, in order to clarify its conduction mechanism. Y124 causes the
first-order phase-transition into the orthorhombic Immm at pressure around 11
GPa. The high-pressure phase (HPP) also shows the superconductivity, while the
manner of temperature dependence of electrical resistance and the pressure
dependence of transition temperature, Tc, drastically change above 11 GPa. The
CuO$_2$ plane persists in HPP but the CuO double chains collapse with the phase
transition and transform into three-dimensional Cu-O network, resulting in the
renewal of conduction system.",1408.2613v1
2019-02-11,Improved oxidation resistance of high emissivity coatings on fibrous ceramic for reusable space system,"To develop high emissivity coatings on fibrous ceramic substrates with
improved thermal resistance for reusable space systems,
WSi2-MoSi2-Si-SiB6-borosilicate glass coatings were prepared on fibrous ZrO2 by
slurry dipping and subsequent high temperature rapid sintering. A coating with
50 wt% WSi2 and 50 wt% MoSi2 presents optimal thermal stability with only 10.06
mg/cm2 mass loss and 4.0 % emissivity decrease in the wavelength regime of 1.27
to 1.73 microns after 50 h oxidation at 1773 K. The advantages of double phase
metal silicide coatings combining WSi2 and MoSi2 include improved thermal
compatibility with the substrate and an enhanced glass mediated self healing
ability.",1902.03943v2
2018-08-16,Investigating Unipolar Switching in Niobium Oxide Resistive Switches: Correlating Quantized Conductance and Mechanism,"Memory devices based on resistive switching (RS) have not been fully realised
due to lack of understanding of the underlying switching mechanisms. Nature of
ion transport responsible for switching and growth of conducting filament in
transition metal oxide based RS devices is still in debate. Here, we
investigated the mechanism in Niobium oxide based RS devices, which shows
unipolar switching with high ON/OFF ratio, good endurance cycles and high
retention times. We controlled the boundary conditions between low-conductance
insulating and a high-conductance metallic state where conducting filament (CF)
can form atomic point contact and exhibit quantized conductance behaviour.
Based on the statistics generated from quantized steps data, we demonstrated
that the CF is growing atom by atom with the applied voltage sweeps. We also
observed stable quantized states, which can be utilized in multistate
switching.",1808.05600v1
2019-12-19,A high-throughput structural and electrochemical study of metallic glass formation in Ni-Ti-Al,"Based on a set of machine learning predictions of glass formation in the
Ni-Ti-Al system, we have undertaken a high-throughput experimental study of
that system. We utilized rapid synthesis followed by high-throughput structural
and electrochemical characterization. Using this dual-modality approach, we are
able to better classify the amorphous portion of the library, which we found to
be the portion with a full-width-half-maximum (FWHM) of 0.42 A$^{-1}$ for the
first sharp x-ray diffraction peak. We demonstrate that the FWHM and corrosion
resistance are correlated but that, while chemistry still plays a role, a large
FWHM is necessary for the best corrosion resistance.",1912.09330v1
2011-04-22,High purity semi-insulating 4H-SiC epitaxial layers by Defect-Competition Epitaxy,"Thick, high-purity semi-insulating (SI)homoepitaxial layers on Si-face 4H-SiC
weregrownsystematically, with resistivity \geq 109{\Omega}-cmby maintaining
high C/Si ratios 1.3-15 during growth.Comparison of secondary ion mass spectra
betweenlow-dopedepilayers grown at C/Si ratio<1.3andSI-epilayers grown at C/Si
ratio>1.3 showed little difference in residual impurity concentrations. A
reconciliation of impurity concentration with measured resistivity indicated a
compensating trap concentration of ~1015cm-3present only in the SI-epilayers.
High- resolution photo induced transient spectroscopy (HRPITS) identified
themas Si-vacancy related deep centers, with no detectable EH6/7 and
Z1/2levels. Recombination lifetimes ~5ns suggest application in fast-switching
power devices.",1104.4509v1
2020-05-22,Sharp negative differential resistance from vibrational mode softening in molecular junctions,"We unravel the critical role of vibrational mode softening in single-molecule
electronic devices at high bias. Our theoretical analysis is carried out with a
minimal model for molecular junctions, with mode softening arising due to
quadratic electron-vibration couplings, and by developing a mean-field
approach. We discover that the negative sign of the quadratic
electron-vibration coupling coefficient can realize at high voltage a sharp
negative differential resistance (NDR) effect with a large peak-to-valley
ratio. Calculated current-voltage characteristics, obtained based on ab initio
parameters for a nitro-substituted oligo(phenylene ethynylene) junction, agree
very well with measurements. Our results establish that vibrational mode
softening is a crucial effect at high voltage, underlying NDR, a substantial
diode effect, and the breakdown of current-carrying molecular junctions.",2005.11365v1
2023-02-28,ZrNb(CO) RF superconducting thin film with high critical temperature in the theoretical limit,"Superconducting radio-frequency (SRF) resonators are critical components for
particle accelerator applications, such as free-electron lasers, and for
emerging technologies in quantum computing. Developing advanced materials and
their deposition processes to produce RF superconductors that yield nanoohms
surface resistances is a key metric for the wider adoption of SRF technology.
Here we report ZrNb(CO) RF superconducting films with high critical
temperatures (Tc) achieved for the first time under ambient pressure. The
attainment of a Tc near the theoretical limit for this material without applied
pressure is promising for its use in practical applications. A range of Tc,
likely arising from Zr doping variation, may allow a tunable superconducting
coherence length that lowers the sensitivity to material defects when an
ultra-low surface resistance is required. Our ZrNb(CO) films are synthesized
using a low-temperature (100 - 200 C) electrochemical recipe combined with
thermal annealing. The phase transformation as a function of annealing
temperature and time is optimized by the evaporated Zr-Nb diffusion couples.
Through phase control, we avoid hexagonal Zr phases that are equilibrium-stable
but degrade Tc. X-ray and electron diffraction combined with photoelectron
spectroscopy reveal a system containing cubic ZrNb mixed with rocksalt NbC and
low-dielectric-loss ZrO2. We demonstrate proof-of-concept RF performance of
ZrNb(CO) on an SRF sample test system. BCS resistance trends lower than
reference Nb, while quench fields occur at approximately 35 mT. Our results
demonstrate the potential of ZrNb(CO) thin films for particle accelerator and
other SRF applications.",2302.14410v2
2020-01-07,First principles evaluation of fcc ruthenium for use in advanced interconnects,"As the semiconductor industry turns to alternate conductors to replace Cu for
future interconnect nodes, much attention as been focused on evaluating the
electrical performance of Ru. The typical hexagonal close-packed (hcp) phase
has been extensively studied, but relatively little attention has been paid to
the face-centered cubic (fcc) phase, which has been shown to nucleate in
confined structures and may be present in tight-pitch interconnects. Using
\emph{ab initio} techniques, we benchmark the performance of fcc Ru. We find
that the phonon-limited bulk resistivity of the fcc Ru is less than half of
that of hcp Ru, a feature we trace back to the stronger electron-phonon
coupling elements that are geometrically inherited from the modified Fermi
surface shape of the fcc crystal. Despite this benefit of the fcc phase, high
grain boundary scattering results in increased resistivity compared to Cu-based
interconnects with similar average grain size. We find, however, that the line
resistance of fcc Ru is lower than that of Cu below 21 nm line width due to the
conductor volume lost to adhesion and wetting liners. In addition to studying
bulk transport properties, we evaluate the performance of adhesion liners for
fcc Ru. We find that it is energetically more favorable for fcc Ru to bind
directly to silicon dioxide than through conventional adhesion liners such as
TaN and TiN. In the case that a thin liner is necessary for the Ru deposition
technique, we find that the vertical resistance penalty of a liner for fcc Ru
can be up to eight times lower than that calculated for conventional liners
used for Cu interconnects. Our calculations, therefore, suggest that the
formation of the fcc phase of Ru may be a beneficial for advanced,
low-resistance interconnects.",2001.02216v3
2021-12-12,Electric-field-driven resistive transition in multiferroic SrCo$_2$Fe$_{16}$O$_{27}$/Sr$_3$Co$_2$Fe$_{24}$O$_{41}$composite,"We report observation of electric-field-driven resistive transition at a
characteristic threshold field $E_{th}(T)$ across a temperature range 10-200 K
in an off-stoichiometric composite of (~80 vol%) W- and (~20 vol%) Z-type
hexaferrites. The dielectric constant $\epsilon$ and the relaxation time
constant $\tau$ too exhibit anomalous jump at $E_{th}(T)$. The $E_{th}(T)$, the
extent of jump in resistivity ($\Delta\rho$), and the hysteresis associated
with the jump [$\Delta E_{th}(T)$] are found to decrease systematically with
the increase in temperature ($T$). Several temperature-driven phase transitions
have also been noticed in low and high resistive states (LRS and HRS). The
temperature-driven conduction turns out to be governed by activated hopping of
small polarons at all the phases with electric ($E$) and magnetic ($H$) field
dependent activation energy $U(E,H)$. Interestingly, as the temperature is
raised, the $E$-driven conduction at a fixed temperature evolves from
$\textit{Ohmic}$ to $\textit{non-Ohmic}$ across 10-200 K and within 110-200 K,
$\rho$ follows three-dimensional variable range hopping (3D-VRH) with stretched
exponential $\sim$ $exp[(E_0/E)^4]$ or power law $\sim$ $(E_0/E)^m$ ($m$ varies
within $\sim$0.6-0.7 and $\sim$0.6-0.8 at LRS and HRS, respectively) dependence
depending on the localization length ($\zeta_E$) to diffusion length ($d_E$)
ratio associated with $E$-driven conduction. The $\rho(E,T)$ follows universal
scaling only at LRS within 10-110 K but not at higher temperature or at HRS.
The entire set of observations has been discussed within the framework of
structural evolution of the point-defect (cation vacancies or oxygen excess)
network. This comprehensive map of esoteric $\rho-E-T-H$ and $\epsilon-E-T-H$
patterns provides insights on defect driven effects in a composite useful for
tuning both the resistive transition and multiferroicity.",2112.06246v1
2023-02-20,Observation of near room temperature thin film superconductivity of atmospherically stable Ag-Au mesoscopic thin film,"An environmentally stable mesoscopic thin film of Au of certain thickness has
been deposited thermally on top of a Ag+ implanted oxide substrate to develop a
close to room temperature superconductor. This thin film has been deposited in
two different stages. Initially, a sol-gel derived ion conducting metal oxide
(ICMO) thin film has been deposited by spin coating. Afterward, Ag+ has been
introduced inside ICMO thin film by a chemical method. Following this, a thin
layer of Au has been deposited on top of that Ag ion-implanted oxide via
thermal evaporation. The temperature dependent resistivity (R-T) has been
studied by four probe method. During high-to-low temperature sweep, around 240
K this thin film sample shows a sudden drop of resistance from 0.7 Ohm to 0.1
micro-Ohm. This 6-7 orders drop of resistance has been observed instantly
within <0.1 K temperature variation of the sample. This transition temperature
(TC) has been shifted toward the higher temperature by 5-6 degrees when
temperature has been increased from low to the higher side. During 2nd and 3rd
temperature cycling, both these transitions have been shifted by ~10 K towards
room temperature w.r.t the earlier. However, after three successive temperature
cycles, TC becomes stable and transitions occur close to 0 oC repeatedly. At
the low resistance phase, current level has been varied from +100 mA to -100 mA
which shows a random fluctuation of voltage drop within 10 nV range, indicating
resistance under such circumstance is too low to measure by Delta mode
electrical measurement (0.1 micro-Ohm). Besides, transition temperature reduces
to lower temperature by 4 K, after applying 1 tesla magnetic field
perpendicular to the thin film. Few YouTube video links of temperature
dependent electrical characterization of such a thin film is given next to the
acknowledgement section.",2302.09974v3
2023-10-11,Absence of topological Hall effect in Fe$_x$Rh$_{100-x}$ epitaxial films: revisiting their phase diagram,"A series of Fe$_x$Rh$_{100-x}$ ($30 \leq x \leq 57$) films were epitaxially
grown using magnetron sputtering, and were systematically studied by
magnetization-, electrical resistivity-, and Hall resistivity measurements.
After optimizing the growth conditions, phase-pure Fe$_{x}$Rh$_{100-x}$ films
were obtained, and their magnetic phase diagram was revisited. The
ferromagnetic (FM) to antiferromagnetic (AFM) transition is limited at narrow
Fe-contents with $48 \leq x \leq 54$ in the bulk Fe$_x$Rh$_{100-x}$ alloys. By
contrast, the FM-AFM transition in the Fe$_x$Rh$_{100-x}$ films is extended to
cover a much wider $x$ range between 33 % and 53 %, whose critical temperature
slightly decreases as increasing the Fe-content. The resistivity jump and
magnetization drop at the FM-AFM transition are much more significant in the
Fe$_x$Rh$_{100-x}$ films with $\sim$50 % Fe-content than in the Fe-deficient
films, the latter have a large amount of paramagnetic phase. The
magnetoresistivity (MR) is rather weak and positive in the AFM state, while it
becomes negative when the FM phase shows up, and a giant MR appears in the
mixed FM- and AFM states. The Hall resistivity is dominated by the ordinary
Hall effect in the AFM state, while in the mixed state or high-temperature FM
state, the anomalous Hall effect takes over. The absence of topological Hall
resistivity in Fe$_{x}$Rh$_{100-x}$ films with various Fe-contents implies that
the previously observed topological Hall effect is most likely extrinsic. We
propose that the anomalous Hall effect caused by the FM iron moments at the
interfaces nicely explains the hump-like anomaly in the Hall resistivity. Our
systematic investigations may offer valuable insights into the spintronics
based on iron-rhodium alloys.",2310.07140v1
2022-06-22,Thermoelectric properties of high-entropy rare-earth cobaltates,"High-entropy concept introduced with a promising paradigm to obtain exotic
physical properties has motivated us to explore the thermoelectric properties
of Sr-substituted high-entropy rare-earth cobaltates i.e.,
(LaNdPrSmEu)$_{1-x}$Sr$_x$CoO3 (0 \leq x \leq 0.10). The structural analysis of
the samples synthesized using the standard solid-state route, confirms the
orthorhombic structure with the Pbnm space group. The Seebeck coefficient and
electrical resistivity decrease with rising Sr concentration as well as with an
increase in temperature. The multiple A-site ions in high-entropy rare-earth
cobaltates result in an improved Seebeck coefficient ({\alpha}) compared to
La$_{0.95}$Sr$_{0.05}$CoO$_3$, associated with a decrease in the Co-O-Co bond
angle, which further enhances the power factor. The random distribution of
cations at the rare-earth site results in a significant lowering of phonon
thermal conductivity. As a result, a maximum figure of merit (zT) of 0.23 is
obtained at 350K for (LaNdPrSmEu)$_{0.95}$Sr$_{0.05}$CoO$_3$, which is one of
the highest values of zT reported at this temperature for oxide materials. This
study shows promise to decouple thermoelectric parameters using the
high-entropy concept in several materials.",2206.11106v1
2005-12-15,The WHO surveillance threshold and the emergence of drug-resistant HIV strains in Botswana,"Background: Approximately 40% of adults in Botswana are HIV-infected. The
Botswana antiretroviral program began in 2002 and currently treats 34,000
patients with a goal of treating 85,000 patients (~30% of HIV-infected adults)
by 2009. We predict the evolution of drug-resistant strains of HIV that may
emerge as a consequence of this treatment program. We discuss the implications
of our results for the World Health Organization's (WHO's) proposed
surveillance system for detecting drug-resistant strains of HIV in Africa.
Methods: We use a mathematical model of the emergence of drug resistance. We
incorporate demographic and treatment data to make specific predictions as to
when the WHO surveillance threshold is likely to be exceeded. Results: Our
results show - even if rates of acquired resistance are high, but the
drug-resistant strains that evolve are only half as transmissible as wild-type
strains - that transmission of drug-resistant strains will remain low (< 5% by
2009) and are unlikely to exceed the WHO's surveillance threshold. However,our
results show that transmission of drug-resistant strains in Botswana could
increase to ~15% by 2009 if resistant strains are as transmissible as wild-type
strains. Conclusion: The WHO's surveillance system is designed to detect
transmitted resistance that exceeds a threshold level of 5%. Whether this
system will detect drug-resistant strains in Botswana by 2009 will depend upon
the transmissibility of the strains that emerge. Our results imply that it
could be many years before the WHO detects transmitted resistance in other
sub-Saharan African countries with less ambitious treatment programs than
Botswana.",0512032v1
2020-04-10,Strain-engineering the Schottky barrier and electrical transport on MoS2,"Strain provides an effective means to tune the electrical properties while
retaining the native chemical composition of the material. Unlike
three-dimensional solids, two-dimensional materials withstand higher levels of
elastic strain making it easier to tune various electrical properties to suit
the technology needs. In this work we explore the effect of uniaxial
tensile-strain on the electrical transport properties of bi- and few-layered
MoS2, a promising 2D semiconductor. Raman shifts corresponding to the in-plane
vibrational modes show a redshift with strain indicating a softening of the
in-plane phonon modes. Photo luminescence measurements reveal a redshift in the
direct and the indirect emission peaks signalling a reduction in the material
bandgap. Transport measurements show a substantial enhancement in the
electrical conductivity with a high piezoresistive gauge factor of ~ 321
superior to that for Silicon for our bi-layered device. The simulations
conducted over the experimental findings reveal a substantial reduction of the
Schottky barrier height at the electrical contacts in addition to the
resistance of MoS2. Our studies reveal that strain is an important and
versatile ingredient to tune the electrical properties of 2D materials and also
can be used to engineer high-efficiency electrical contacts for future device
engineering.",2004.05061v1
2011-08-25,"Synthesis, Crystal Growth and Epitaxial Layer Deposition of FeSe0.88 Superconductor and Other Poison Materials by Use of High Gas Pressure Trap System","The FeSe samples in the form of polycrystals, single crystals and thin films
have been prepared and characterized. The synthesized material has been hot
isostatically pressed under pressure of 0.45 GPa of 5N purity argon with the
use of the high gas pressure trap system (HGPTS). Thin films have been
fabricated by the mixed procedures with the use of DC sputtering from various
types of targets and processed employing the HGPTS. The used HGPTS assures a
full separation of the active volume for synthesis or crystal growth of
material and the inert gas medium. The obtained FeSe0.88 samples have Tc
between 8 and 12 K. The samples have been characterized by SEM, EDX, XRD,
magnetic susceptibility and resistivity measurements.",1108.5069v1
2021-07-19,Making high-quality quantum microwave devices with van der Waals superconductors,"Ultra low-loss microwave materials are crucial for enhancing quantum
coherence and scalability of superconducting qubits. Van der Waals (vdW)
heterostructure is an attractive platform for quantum devices due to the
single-crystal structure of the constituent two-dimensional (2D) layered
materials and the lack of dangling bonds at their atomically sharp interfaces.
However, new fabrication and characterization techniques are required to
determine whether these structures can achieve low loss in the microwave
regime. Here we report the fabrication of superconducting microwave resonators
using NbSe$_2$ that achieve a quality factor $Q > 10^5$. This value sets an
upper bound that corresponds to a resistance of $\leq 192 \mu\Omega$ when
considering the additional loss introduced by integrating NbSe$_2$ into a
standard transmon circuit. This work demonstrates the compatibility of 2D
layered materials with high-quality microwave quantum devices.",2107.09147v3
2021-10-21,Phonon anharmonicity: a pertinent review of recent progress and perspective,"Anharmonic lattice vibrations govern the thermal dynamics in materials and
present how the atoms interact and how they conduct heat. An indepth
understanding of the microscopic mechanism of phonon anharmonicity in condensed
systems is critical for developing better functional and energy materials. In
recent years, a variety of novel behaviors in condense matters are driven by
phonon anharmonic effects in some way or another, such as soft mode phase
transition, negative thermal expansion, multiferroicity, ultralow thermal
conductivity or high thermal resistance, and high-temperature
superconductivity, etc. All these properties have endowed anharmonicity with
many promising applications and provided remarkable opportunities for
developing anharmonicity engineering, regulating heat transport towards
excellent performance in materials. In this work, we review the recent
development of the study on phonon anharmonic effect and summarize its
origination, influence and mechanism, research methods, and applications.
Besides, the remaining challenges, future trends, and prospects of phonon
anharmonicity are also put forward.",2110.11094v1
2023-01-16,Nonlinear transport in a photo-induced superconductor,"Optically driven quantum materials exhibit a variety of non-equilibrium
functional phenomena [1-11], which are potentially associated with unique
transport properties. However, these transient electrical responses have
remained largely unexplored, primarily because of the challenges associated
with integrating quantum materials into ultrafast electrical devices. Here,
thin films of K3C60 grown by Molecular Beam Epitaxy were connected by coplanar
terahertz waveguides to a series of photo-conductive switches. This geometry
enabled ultrafast transport measurements at high current densities, providing
new information on the photo-induced phase created in the high temperature
metal by mid-infrared excitation [12-16]. Nonlinearities in the current-voltage
charactersitics of the transient state validate the assignment of transient
superconductivity, and point to an inhomogeneous phase in which superconducting
regions of the sample are connected by resistive weak links [17-23]. This work
opens up the possibility of systematic transport measurements in driven quantum
materials, both to probe their properties and to integrate them into ultrafast
optoelectronic platforms.",2301.06425v1
2015-09-03,On the Concept of Cryptographic Quantum Hashing,"In the paper we define a notion of quantum resistant
($(\epsilon,\delta)$-resistant) hash function which combine together a notion
of pre-image (one-way) resistance ($\epsilon$-resistance) property we define in
the paper and the notion of collision resistance ($\delta$-resistance)
properties.
  We show that in the quantum setting a one-way resistance property and
collision resistance property are correlated: the ""more"" a quantum function is
one-way resistant the ""less"" it collision resistant and vice versa. We present
an explicit quantum hash function which is ""balanced"" one-way resistant and
collision resistant and demonstrate how to build a large family quantum hash
functions. Balanced quantum hash functions need a high degree of entanglement
between the qubits. We use a ""phase constructions"" technique to express quantum
hashing constructions, which is good to map hash states to coherent states in a
superposition of time-bin modes. The later is ready to be implemented with
current optical technology.",1509.01268v2
2019-12-11,Observation of excess resistance anomaly at resistive transitions in Ag/Au nanostructures,"The resistive transition in nanocomposite films of silver (Ag) nanoclusters
of ~ 1 nm diameter embedded in gold (Au) matrix exhibits an anomalous
resistance peak at the onset of the transition, even for transition
temperatures as high as 260 K. The maximum value of the resistance ranges
between ~ 30% - 300% above that of the normal state depending on devices as
well as lead configuration within a single device. The excess resistance regime
was observed in about 10% of the devices, and extends from ~ 10 - 100 K.
Application of magnetic field of 9 T was found to partially suppress the excess
resistance. From the critical current behavior, as well as negative
differential resistance in the current-voltage characteristics, we discuss the
possibility of interacting phase slip centers and alternate physical scenarios
that may cause the excess resistance in our system.",1912.05428v1
2020-08-13,Properties of materials considered for improvised masks,"During a pandemic in which aerosol and droplet transmission is possible, the
demand for masks that meet medical or workplace standards can prevent most
individuals or organizations from obtaining suitable protection. Cloth masks
are widely believed to impede droplet and aerosol transmission but most are
constructed from materials with unknown filtration efficiency, airflow
resistance and water resistance. Further, there has been no clear guidance on
the most important performance metrics for the materials used by the general
public (as opposed to high-risk healthcare settings). Here we provide data on a
range of common fabrics that might be used to construct masks. None of the
materials were suitable for masks meeting the N95 NIOSH standard, but many
could provide useful filtration (>90%) of 3 micron particles (a plausible
challenge size for human generated aerosols), with low pressure drop. These
were: nonwoven sterile wraps, dried baby wipes and some double-knit cotton
materials. Decontamination of N95 masks using isopropyl alcohol produces the
expected increase in particle penetration, but for 3 micron particles,
filtration efficiency is still well above 95%. Tightly woven thin fabrics,
despite having the visual appearance of a good particle barrier, had remarkably
low filtration efficiency and high pressure drop. These differences in
filtration performance can be partly explained by the material structure; the
better structures expose individual fibers to the flow while the poor materials
may have small fundamental fibers but these are in tightly bundled yarns. The
fit and use of the whole mask are critical factors not addressed in this work.
Despite the complexity of the design of a very good mask, it is clear that for
the larger aerosol particles, any mask will provide substantial protection to
the wearer and those around them.",2008.06001v1
2022-06-01,A Pseudo-Two-Dimensional (P2D) Model for FeS2 Conversion Cathode Batteries,"Conversion cathode materials are gaining interest for secondary batteries due
to their high theoretical energy and power density. However, practical
application as a secondary battery material is currently limited by practical
issues such as poor cyclability. To better understand these materials, we have
developed a pseudo-two-dimensional model for conversion cathodes. We apply this
model to FeS2 - a material that undergoes intercalation followed by conversion
during discharge. The model is derived from the half-cell Doyle-Fuller-Newman
model with additional loss terms added to reflect the converted shell
resistance as the reaction progresses. We also account for polydisperse active
material particles by incorporating a variable active surface area and
effective particle radius. Using the model, we show that the leading loss
mechanisms for FeS2 are associated with solid-state diffusion and electrical
transport limitations through the converted shell material. The polydisperse
simulations are also compared to a monodisperse system, and we show that
polydispersity has very little effect on the intercalation behavior yet leads
to capacity loss during the conversion reaction. We provide the code as an
open-source Python Battery Mathematical Modelling (PyBaMM) model that can be
used to identify performance limitations for other conversion cathode
materials.",2206.00647v2
2024-03-12,Physics-Transfer Learning for Material Strength Screening,"The strength of materials, like many problems in the natural sciences, spans
multiple length and time scales, and the solution has to balance accuracy and
performance. Peierls stress is one of the central concepts in crystal
plasticity that measures the strength through the resistance of a dislocation
to plastic flow. The determination of Peierls stress involves a multiscale
nature depending on both elastic lattice responses and the energy landscape of
crystal slips. Material screening by strength via the Peierls stress from
first-principles calculations is computationally intractable for the nonlocal
characteristics of dislocations, and not included in the state-of-the-art
computational material databases. In this work, we propose a physics-transfer
framework to learn the physics of crystal plasticity from empirical atomistic
simulations and then predict the Peierls stress from chemically accurate
density functional theory-based calculations of material parameters. Notably,
the strengths of single-crystalline metals can be predicted from a few
single-point calculations for the deformed lattice and on the {\gamma} surface,
allowing efficient, high-throughput screening for material discovery.
Uncertainty quantification is carried out to assess the accuracy of models and
sources of errors, showing reduced physical and system uncertainties in the
predictions by elevating the fidelity of training models. This physics-transfer
framework can be generalized to other problems facing the accuracy-performance
dilemma, by harnessing the hierarchy of physics in the multiscale models of
materials science.",2403.07526v1
2016-06-25,Observation of Optical and Electrical In-plane Anisotropy in High-mobility Few-layer ZrTe5,"Transition metal pentatelluride ZrTe5 is a versatile material in
condensed-matter physics and has been intensively studied since the 1980s. The
most fascinating feature of ZrTe5 is that it is a 3D Dirac semimetal which has
linear energy dispersion in all three dimensions in momentum space.
Structure-wise, ZrTe5 is a layered material held together by weak interlayer
van der Waals force. The combination of its unique band structure and 2D atomic
structure provides a fertile ground for more potential exotic physical
phenomena in ZrTe5 related to 3D Dirac semimentals. However the physical
properties of its few-layer form have yet to be thoroughly explored. Here we
report strong optical and electrical in-plane anisotropy of mechanically
exfoliated few-layer ZrTe5. Raman spectroscopy shows significant intensity
change with sample orientations, and the behavior of angle-resolved phonon
modes at the gamma point is explained by theoretical calculation. DC
conductance measurement indicates a 50% of difference along different in-plane
directions. The diminishing of resistivity anomaly in few-layer samples
indicates the evolution of band structure with reduced thickness.
Low-temperature Hall experiment sheds lights on more intrinsic anisotropic
electrical transport, with hole mobility of 3,000 and 1,500 cm2/Vs along a-axis
and c-axis respectively. Pronounced quantum oscillations in magneto-resistance
are observed at low temperatures with highest electron mobility up to 44,000
cm2/Vs.",1606.07960v2
2018-09-25,Intrinsic Insulating Ground State in Transition Metal Dichalcogenide TiSe2,"The transition metal dichalcogenide TiSe$_2$ has received significant
research attention over the past four decades. Different studies have presented
ways to suppress the 200~K charge density wave transition, vary low temperature
resistivity by several orders of magnitude, and stabilize magnetism or
superconductivity. Here we give the results of a new synthesis technique
whereby samples were grown in a high pressure environment with up to 180~bar of
argon gas. Above 100~K, properties are nearly unchanged from previous reports,
but a hysteretic resistance region that begins around 80~K, accompanied by
insulating low temperature behavior, is distinct from anything previously
observed. An accompanying decrease in carrier concentration is seen in Hall
effect measurements, and photoemission data show a removal of an electron
pocket from the Fermi surface in an insulating sample. We conclude that high
inert gas pressure synthesis accesses an underlying nonmetallic ground state in
a material long speculated to be an excitonic insulator.",1809.09467v2
2018-08-24,Data-driven Exploration of New Pressure-induced Superconductivity in PbBi$_2$Te$_4$ with Two Transition Temperatures,"Candidates compounds for new thermoelectric and superconducting materials,
which have narrow band gap and flat bands near band edges, were exhaustively
searched by the high-throughput first-principles calculation from an inorganic
materials database named AtomWork. We focused on PbBi$_2$Te$_4$ which has the
similar electronic band structure and the same crystal structure with those of
a pressure-induced superconductor SnBi2Se4 explored by the same data-driven
approach. The PbBi$_2$Te$_4$ was successfully synthesized as single crystals
using a melt and slow cooling method. The core level X-ray photoelectron
spectroscopy analysis revealed Pb2+, Bi3+ and Te2- valence states in
PbBi$_2$Te$_4$. The thermoelectric properties of the PbBi$_2$Te$_4$ sample were
measured at ambient pressure and the electrical resistivity was also evaluated
under high pressure using a diamond anvil cell with boron-doped diamond
electrodes. The resistivity decreased with increase of the pressure, and two
pressure-induced superconducting transitions were discovered at 3.4 K under
13.3 GPa and at 8.4 K under 21.7 GPa. The data-driven approach shows promising
power to accelerate the discovery of new thermoelectric and superconducting
materials.",1808.07973v1
2021-03-17,Multi-level resistance switching and random telegraph noise analysis of nitride based memristors,"Resistance switching devices are of special importance because of their
application in resistive memories (RRAM) which are promising candidates for
replacing current nonvolatile memories and realize storage class memories.
These devices exhibit usually memristive properties with many discrete
resistance levels and implement artificial synapses. The last years,
researchers have demonstrated memristive chips as accelerators in computing,
following new in-memory and neuromorphic computational approaches. Many
different metal oxides have been used as resistance switching materials in MIM
or MIS structures. Understanding of the mechanism and the dynamics of
resistance switching is very critical for the modeling and use of memristors in
different applications. Here, we demonstrate the bipolar resistance switching
of silicon nitride thin films using heavily doped Si and Cu as bottom and
top-electrodes, respectively. Analysis of the current-voltage characteristics
reveal that under space-charge limited conditions and appropriate current
compliance setting, multi-level resistance operation can be achieved.
Furthermore, a flexible tuning protocol for multi-level resistance switching
was developed applying appropriate SET/RESET pulse sequences. Retention and
random telegraph noise measurements performed at different resistance levels.
The present results reveal the attractive properties of the examined devices.",2103.09931v1
2021-10-28,Spread and erase -- How electron hydrodynamics can eliminate the Landauer-Sharvin resistance,"It has long been realized that even a perfectly clean electronic system
harbors a Landauer-Sharvin resistance, inversely proportional to the number of
its conduction channels. This resistance is usually associated with voltage
drops on the system's contacts to an external circuit. Recent theories have
shown that hydrodynamic effects can reduce this resistance, raising the
question of the lower bound of resistance of hydrodynamic electrons. Here we
show that by a proper choice of device geometry, it is possible to spread the
Landauer-Sharvin resistance throughout the bulk of the system, allowing its
complete elimination by electron hydrodynamics. We trace the effect to the
dynamics of electrons flowing in channels that terminate within the sample. For
ballistic systems this termination leads to back-reflection of the electrons
and creates resistance. Hydrodynamically, the scattering of these electrons off
other electrons allows them to transfer to transmitted channels and avoid the
resistance. Counter-intuitively, we find that in contrast to the ohmic regime,
for hydrodynamic electrons the resistance of a device with a given width can
decrease with its length, suggesting that a long enough device may have an
arbitrarily small total resistance.",2110.15369v2
2005-08-04,Subharmonic gap structures and Josephson effect in MgB2/Nb micro-constrictions,"Superconducting micro-constrictions between Nb tips and high quality
MgB$_{2}$ pellets have been realized by means of a point-contact inset, driven
by a micrometric screw. Measurements of the current-voltage characteristics and
of the dynamical conductance versus bias have been performed in the temperature
range between 4.2 K and 500 K. Above the Nb critical temperature T$_{C}^{Nb}$,
the conductance of the MgB$_2$/normal-metal constrictions behaves as predicted
by the BTK model for low resistance contacts while high resistance junctions
show quasiparticle tunneling characteristics. Consistently, from the whole set
of data we infer the value $\Delta_{\pi} = 2.5 \pm 0.2$ meV for the
three-dimensional gap of MgB$_2$. Below T$_{C}^{Nb}$, low resistance contacts
show Josephson current and subharmonic gap structures (SGS), due to multiple
Andreev reflections. Simultaneous observations of both features, unambiguously
indicate coupling of the 3D band of MgB$_2$ with the Nb superconducting order
parameter. We found that the temperature dependence of the Josephson critical
current follows the classical Ambegaokar-Baratoff behavior with a value
$I_CR_N=(2.1 \pm 0.1)$ meV at low temperatures.",0508137v2
2007-02-02,Dependence of electronic structure of SrRuO3 and the degree of correlation on cation off-stoichiometry,"We have grown and studied high quality SrRuO3 films grown by MBE as well as
PLD. By changing the oxygen activity during deposition we were able to make
SrRuO3 samples that were stoichiometric (low oxygen activity) or with ruthenium
vacancies (high oxygen activity). Samples with strontium vacancies were found
impossible to produce since the ruthenium would precipitate out as RuO2. The
volume of the unit cell of SrRuO3 becomes larger as more ruthenium vacancies
are introduced. The residual resistivity ratio (RRR) and room temperature
resistivity were found to systematically depend on the volume of the unit cell
and therefore on the amount of ruthenium vacancies. The RRR varied from ~30 for
stoichiometric samples to less than two for samples that were very ruthenium
poor. The room temperature resistivity varied from 190 microOhm cm for
stoichoimetric samples to over 300 microOhm cm for very ruthenium poor samples.
UPS spectra show a shift of weight from the coherent peak to the incoherent
peak around the Fermi level when samples have more ruthenium vacancies. Core
level XPS spectra of the ruthenium 3d lines show a strong screened part in the
case of stoichiometric samples. This screened part disappears when ruthenium
vacancies are introduced. Both the UPS and the XPS results are consistent with
the view that correlation increases as the amount of ruthenium vacancies
increase.",0702050v1
2007-11-17,Development of New Hole-Type Avalanche Detectors and the First Results of their Applications,"We have developed a new detector of photons and charged particles- a
hole-type structure with electrodes made of a double layered resistive
material: a thin low resistive layer coated with a layer having a much higher
resistivity. One of the unique features of this detector is its capability to
operate at high gas gains (up to 10E4) in air or in gas mixtures with air. They
can also operate in a cascaded mode or be combined with other detectors, for
example with GEM. This opens new avenues in their applications. Several
prototypes of these devices based on new detectors and oriented on practical
applications were developed and successfully tested: a detector of soft X-rays
and alpha particles, a flame sensor, a detector of dangerous gases. All of
these detectors could operate stably even in humid air and/or in dusty
conditions. The main advantages of these detectors are their simplicity, low
cost and high sensitivity. For example, due to the avalanche multiplication,
the detectors of flames and dangerous gases have a sensitivity of 10-100 times
higher than commercial devices. We therefore believe that new detectors will
have a great future.",0711.2747v1
2010-10-29,Analytical method for parameterizing the random profile components of nanosurfaces imaged by atomic force microscopy,"The functional properties of many technological surfaces in biotechnology,
electronics, and mechanical engineering depend to a large degree on the
individual features of their nanoscale surface texture, which in turn are a
function of the surface manufacturing process. Among these features, the
surface irregularities and self-similarity structures at different spatial
scales, especially in the range of 1 to 100 nm, are of high importance because
they greatly affect the surface interaction forces acting at a nanoscale
distance. An analytical method for parameterizing the surface irregularities
and their correlations in nanosurfaces imaged by atomic force microscopy (AFM)
is proposed. In this method, flicker noise spectroscopy - a statistical physics
approach - is used to develop six nanometrological parameters characterizing
the high-frequency contributions of jump- and spike-like irregularities into
the surface texture. These contributions reflect the stochastic processes of
anomalous diffusion and inertial effects, respectively, in the process of
surface manufacturing. The AFM images of the texture of corrosion-resistant
magnetite coatings formed on low-carbon steel in hot nitrate solutions with
coating growth promoters at different temperatures are analyzed. It is shown
that the parameters characterizing surface spikiness are able to quantify the
effect of process temperature on the corrosion resistance of the coatings. It
is suggested that these parameters can be used for predicting and
characterizing the corrosion-resistant properties of magnetite coatings.",1010.6232v1
2013-04-04,Non-contact method for measurement of the microwave conductivity of graphene,"We report a non-contact method for conductivity and sheet resistance
measurements of graphene samples using a high Q microwave dielectric resonator
perturbation technique, with the aim of fast and accurate measurement of
microwave conductivity and sheet resistance of monolayer and few layers
graphene samples. The dynamic range of the microwave conductivity measurements
makes this technique sensitive to a wide variety of imperfections and
impurities and can provide a rapid non-contacting characterisation method.
Typically the graphene samples are supported on a low-loss dielectric
substrate, such as quartz, sapphire or SiC. This substrate is suspended in the
near-field region of a small high Q sapphire puck microwave resonator. The
presence of the graphene perturbs both centre frequency and Q value of the
microwave resonator. The measured data may be interpreted in terms of the real
and imaginary components of the permittivity, and by calculation, the
conductivity and sheet resistance of the graphene. The method has great
sensitivity and dynamic range. Results are reported for graphene samples grown
by three different methods: reduced graphene oxide (GO), chemical vapour
deposition (CVD) and graphene grown epitaxially on SiC. The latter method
produces much higher conductivity values than the others.",1304.1304v1
2016-02-03,"Robust tunability of magnetorestance in Half-Heusler RPtBi (R = Gd, Dy, Tm, and Lu) compounds","We present the magnetic field dependencies of transport properties for
$R$PtBi ($R$ = Gd, Dy, Tm, and Lu) half-Heusler compounds. Temperature and
field dependent resistivity measurements of high quality $R$PtBi single
crystals reveal an unusually large, non-saturating magnetoresistance (MR) up to
300 K under a moderate magnetic field of $H$ = 140 kOe. At 300 K, the large MR
effect decreases as the rare-earth is traversed from Gd to Lu and the magnetic
field dependence of MR shows a deviation from the conventional $H^{2}$
behavior. The Hall coefficient ($R_{H}$) for $R$ = Gd indicates a sign change
around 120 K, whereas $R_{H}$ curves for $R$ = Dy, Tm, and Lu remain positive
for all measured temperatures. At 300 K, the Hall resistivity reveals a
deviation from the linear field dependence for all compounds. Thermoelectric
power measurements on this family show strong temperature and magnetic field
dependencies which are consistent with resistivity measurements. A highly
enhanced thermoelectric power under applied magnetic field is observed as high
as $\sim$100 $\mu$V/K at 140 kOe. Analysis of the transport data in this series
reveals that the rare-earth-based Half-Husler compounds provide opportunities
to tune MR effect through lanthanide contraction and to elucidate the mechanism
of non-trivial MR.",1602.01194v1
2018-06-07,A Timing RPC with low resistive ceramic electrodes,"For precise start time determination a Beam Fragmentation T$_0$ Counter
(BFTC) is under development for the Time-of-Flight Wall of the Compressed
Baryonic Matter Spectrometer (CBM) at the Facility for Antiproton and Ion
Research (FAIR) at Darmstadt/Germany. This detector will be located around the
beam pipe, covering the front area of the Projectile Spectator Detector. The
fluxes at this region are expected to exceed 10$^5$cm$^{-2}$s$^{-1}$. Resistive
plate chambers (RPC) with ceramic composite electrodes could be use because of
their high rate capabilities and radiation hardness of material. Efficiency
$\ge$ 97\%, time resolution $\le$ 90 ps and rate capability $\ge$
10$^5$cm$^{-2}$s$^{-1}$ were confirmed during many tests with high beam fluxes
of relativistic electrons. We confirm the stability of these characteristics
with low resistive Si$_3$N$_4$/SiC floating electrodes for a prototype of eight
small RPCs, where each of them contains six gas gaps. The active RPC size
amounts 20$\times$20 mm$^2$ produced on basis of Al$_3$O$_2$ and
Si$_3$N$_4$/SiC ceramics. Recent test results obtained with relativistic
electrons at the linear accelerator ELBE of the Helmholtz-Zentrum
Dresden-Rossendorf with new PADI-10 Front-end electronic will be presented.",1806.02629v2
2019-05-07,Single-parameter scaling in the magnetoresistance of optimally doped La$_{2-x}$Sr$_{x}$CuO$_4$,"We show that the recent magnetoresistance data on thin-film
La$_{2-x}$Sr$_{x}$CuO$_4$ (LSCO) in strong magnetic fields ($B$) obeys a
single-parameter scaling of the form MR$(B,T)=f(\mu_H(T)B)$, where
$\mu_H^{-1}(T)\sim T^{\alpha}$ ($1\le\alpha\le2$), from $T=180$K until
$T\sim20$K, at which point the single-parameter scaling breaks down. The
functional form of the MR is distinct from the simple quadratic-to-linear
quadrature combination of temperature and magnetic field found in the optimally
doped iron superconductor BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$. Further,
low-temperature departure of the MR in LSCO from its high-temperature scaling
law leads us to conclude that the MR curve collapse is not the result of
quantum critical scaling. We examine the classical effective medium theory
(EMT) previously used to obtain the quadrature resistivity dependence on field
and temperature for metals with a $T$-linear zero-field resistivity. It appears
that this scaling form results only for a binary, random distribution of
metallic components. More generally, we find a low-temperature, high-field
region where the resistivity is simultaneously $T$ and $B$ linear when multiple
metallic components are present. Our findings indicate that if mesoscopic
disorder is relevant to the magnetoresistance in strange metal materials, the
binary-distribution model which seems to be relevant to the iron pnictides is
distinct from the more broad-continuous distributions relevant to the cuprates.
Using the latter, we examine the applicability of classical effective medium
theory to the MR in LSCO and compare calculated MR curves with the experimental
data.",1905.02737v1
2021-01-18,Intrinsic hysteresis in the presumed superconducting transition of hydrides under high pressure,"Superconducting transitions in the absence of magnetic field should be
non-hysteretic. Here we address the fact that the drops in electrical
resistance that have been interpreted as evidence of superconductivity in
several hydrides under high pressure (so-called ""superhydrides"") show
hysteresis. We argue that the experimental evidence shows that the observed
hysteresis cannot be attributed to experimental artifacts but is intrinsic to
the samples. Assuming that the drops in resistance signal a thermodynamic phase
transition, we argue that the presence of intrinsic thermal hysteresis
indicates that these are first order transitions, whereas for standard
superconductors the transition in the absence of applied magnetic field is
always second order. We conclude that this is another feature that
qualitatively distinguishes superhydrides from standard superconductors, in
addition to the ones that have been pointed out earlier [1,2], $assuming$ these
materials are superconductors. Alternatively and more likely, whether or not
the drops in resistance signal a thermodynamic phase transition, our analysis
indicates that superhydrides are not superconductors.",2101.07208v4
2021-03-27,Tesla's fluidic diode and the electronic-hydraulic analogy,"Reasoning by analogy is powerful in physics for students and researchers
alike, a case in point being electronics and hydraulics as analogous studies of
electric currents and fluid flows. Around 100 years ago, Nikola Tesla proposed
a flow control device intended to operate similarly to an electronic diode,
allowing fluid to pass easily in one direction but providing high resistance in
reverse. Here we use experimental tests of Tesla's diode to illustrate
principles of the electronic-hydraulic analogy. We design and construct a
differential pressure chamber (akin to a battery) that is used to measure flow
rate (current) and thus resistance of a given pipe or channel (circuit
element). Our results prove the validity of Tesla's device, whose anisotropic
resistance derives from its asymmetric internal geometry interacting with
high-inertia flows, as quantified by the Reynolds number (here, Re ~ 1e3).
Through the design and testing of new fluidic diodes, we explore the
limitations of the analogy and the challenges of shape optimization in fluid
mechanics. We also provide materials that may be incorporated into lesson plans
for fluid dynamics courses, laboratory modules and further research projects.",2103.14813v1
2021-08-19,Measurement of the Low-temperature Loss Tangent of High-resistivity Silicon with a High Q-factor Superconducting Resonator,"In this letter, we present the direct loss tangent measurement of a
high-resistivity intrinsic (100) silicon wafer in the temperature range from ~
70 mK to 1 K, approaching the quantum regime. The measurement was performed
using a technique that takes advantage of a high quality factor superconducting
niobium resonator and allows to directly measure the loss tangent of insulating
materials with high level of accuracy and precision. We report silicon loss
tangent values at the lowest temperature and for electric field amplitudes
comparable to those found in planar transmon devices one order of magnitude
larger than what was previously estimated. In addition, we discover a
non-monotonic trend of the loss tangent as a function of temperature that we
describe by means of a phenomenological model based on variable range hopping
conduction between localized states around the Fermi energy. We also observe
that the dissipation increases as a function of the electric field and that
this behavior can be qualitatively described by the variable range hopping
conduction mechanism as well. This study lays the foundations for a novel
approach to investigate the loss mechanisms and accurately estimate the loss
tangent in insulating materials in the quantum regime, leading to a better
understanding of coherence in quantum devices.",2108.08894v5
2007-06-01,High-Tc superconductivity originated from strong spin-charge correlation: indication from linear temperature dependence of resistivity,"Both the highest- and the linear temperature dependence of the resistivity in
wide temperature range appear at the optimally doped regions of Cu-based
superconductors1,2,3,4,5, and the highest- of Fe-based superconductors6,7 are
also associated with the linear temperature dependence of the resistivity in
normal states near superconducting states. This means that the high temperature
superconductivity and the linear temperature dependence of the resistivity
should be dominated by the same mechanism. This letter on theoretic calculation
clearly shows that strong spin-charge correlation dominated resistivity behaves
the linear temperature dependence, thus high-temperature superconductivity
should be induced by strong spin-charge correlation.",0706.0059v2
2023-08-30,Investigation of W-SiC compositionally graded films as a divertor material,"W-SiC composite material is a promising plasma-facing material candidate
alternative to pure W due to the low neutron activation, low impurity
radiation, and low tritium diffusivity of SiC while leveraging the high erosion
resistance of the W armor. Additionally, W and SiC have high thermomechanical
compatibility given their similar thermal expansion rates. The present study
addresses the synthesis and performance of compositionally graded W-SiC films
fabricated by pulsed-DC magnetron sputtering. Compositional gradients were
characterized using transmission electron microscopy (TEM) and
energy-dispersive X-ray spectroscopy (EDS), and crystallographic information
was obtained using electron diffraction and X-ray diffraction (XRD). Samples
were exposed to L-mode deuterium plasma discharges in the DIII-D tokamak using
the Divertor Material Evaluation System (DiMES). Post-mortem characterizations
were performed using scanning electron microscopy (SEM) and XRD. Electron
diffraction and XRD showed that the compositionally graded W-SiC films were
composed of polycrystalline W and amorphous SiC with amorphous W+SiC
interlayers. No macroscopic delamination or microstructural changes were
observed under mild exposure conditions. This study serves as a preliminary
examination of W-SiC compositionally graded composites as a potential candidate
divertor material in future tokamak devices.",2308.16358v2
1999-09-28,"Magnetotransport properties of (Ga,Mn)As investigated at low temperature and high magnetic field","Magnetotransport properties of ferromagnetic semiconductor (Ga,Mn)As have
been investigated. Measurements at low temperature (50 mK) and high magnetic
field (<= 27 T) have been employed in order to determine the hole concentration
p = 3.5x10^20 cm ^-3 of a metallic (Ga0.947Mn0.053)As layer. The analysis of
the temperature and magnetic field dependencies of the resistivity in the
paramagnetic region was performed with the use of the above value of p, which
gave the magnitude of p-d exchange energy |N0beta | ~ 1.5 eV.",9909393v1
2003-09-28,Electron-Phonon Scattering in Metallic Single-Walled Carbon Nanotubes,"Electron scattering rates in metallic single-walled carbon nanotubes are
studied using an atomic force microscope as an electrical probe. From the
scaling of the resistance of the same nanotube with length in the low and high
bias regimes, the mean free paths for both regimes are inferred. The observed
scattering rates are consistent with calculations for acoustic phonon
scattering at low biases and zone boundary/optical phonon scattering at high
biases.",0309641v1
1998-10-26,High frequency magneto-impedance of double perovskite $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$: secondary transitions at high temperatures,"Radio frequency magneto-impedance measurements clearly reveal a pronounced
anomaly at 260K besides the main MI transition at 125K in the double perovskite
material $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$. This feature is not seen clearly in
static resistivity and magnetization measurements. We suggest that this anomaly
represents short range magnetic correlations enhanced at radio frequencies,
with the easy axis along the c-axis .",9810351v2
1999-04-29,Consilience of High-Tc Theories,"Improvements both in the quality and in the variety of experiments on
high-temperature superconductors have yielded new insights into the microscopic
origins of pairing. A number of competing theories have already been ruled out.
Some of the more promising descriptions -- gauge theories, coupled-chains,
nesting instabilities, nodal liquids, and stripes -- share features in common.
A unified picture of the cuprates is beginning to emerge.",9904437v1
1999-09-03,A thermostable trilayer resist for niobium lift-off,"We have developped a novel lift-off process for fabrication of high quality
superconducting submicron niobium structures. The process makes use of a
thermostable polymer with a high transition temperature T_{g}= 235 C and an
excellent chemical stability. The superconducting critical temperature of 100
nm wide niobium lines is above 7 K. An example of shadow evaporation of a Nb-Cu
submicron hybrid structure is given. A potential application of this process is
the fabrication of very small single electron devices using refratory metals.",9909053v1
2003-10-29,Ultrasonic Defect Modification in Irradiated Silicon,"It is shown for the first time, that room temperature Ultrasonic Defect
Manipulation (UDM) can significantly reduce the concentration of radiation
defects in high resistivity silicon. Secondary Ion Mass Spectroscopy revealed
that oxygen- and hydrogen- related chemical reactions in silicon are likely to
occur under UDM at room temperature. Ultrasonically stimulated chemical
reactions in solids can be an important source of energy, which is required for
UDM.",0310675v1
2004-08-24,Barrier layer formation and PTCR effect in (1-x) Pb(Fe1/2Nb1/2)O3]-xPbTiO3 (x = 0.13) ceramics,"(1-x)Pb(Fe1/2Nb1/2)O3-PbTiO3(PFN-xPT)Ceramics with x = 0.13 sintered at 1473K
show diffuse phase transition and very high dielectric constant at lower
frequencies.The high value of dielectric constant at lower frequencies is shown
to be due to the barrier layer formation.The resistivity of the PFN-xPT
ceramics, obtained by complex impedance analysis, initially decreases with
temperature and then shows an upward trend beyond the ferroelectric Curie point
reminiscent of BaTiO3 based thermistors with PTCR effect.",0408509v1
2005-02-06,Model for a Macroscopically Disordered Conductor with an Exactly Linear High-Field Magnetoresistance,"We calculate the effective resistivity of a macroscopically disordered two
dimensional conductor consisting of two components in a perpendicular magnetic
field. When two components have equal area fractions, we use a duality theorem
to show that the magnetoresistance is non-saturating and at high fields varies
exactly linearly with magnetic field. At other compositions, an effective
medium calculation leads to a saturating magnetoresistance. We briefly discuss
possible connections between these results and magnetoresistance measurements
on heavily disordered chalconide semiconductors.",0502162v2
2007-07-28,Performances of a Newly High Sensitive Trilayer F/Cu/F GMI Sensor,"We have selected stress-annealed nanocrystalline Fe-based ribbons for
ferromagnetic/copper/ferromagnetic sensors exhibiting high magneto-impedance
ratio. Longitudinal magneto-impedance reaches 400% at 60 kHz and longitudinal
magneto-resistance increases up to 1300% around 200 kHz.",0707.4232v2
2009-09-25,Spin Injection Enhancement Through Schottky Barrier Superlattice Design,"We predict it is possible to achieve high-efficiency room-temperature spin
injection from a mag- netic metal into InAs-based semiconductors using an
engineered Schottky barrier based on an InAs/AlSb superlattice. The Schottky
barrier with most metals is negative for InAs and positive for AlSb. For such
metals there exist InAs/AlSb superlattices with a conduction band edge
perfectly aligned with the metal's Fermi energy. The initial AlSb layer can be
grown to the thickness required to produce a desired interface resistance. We
show that the conductivity and spin lifetimes of such superlattices are
sufficiently high to permit efficient spin injection from ferromagnetic metals.",0909.4594v1
2009-11-29,Current driven discontinuous insulator-metal transition and colossal low-field magnetoresistance in Sm0.6Sr0.4MnO3,"It is shown that with increasing magnitude of current (I), resistivity of
Sm0.6Sr0.4MnO3 transforms from a smooth to a discontinuous insulator-metal
transition which is also accompanied by an abrupt decrease in temperature of
the sample. We report colossal low-field magnetoresistance under a high current
bias (-99% at H = 0.5 T and 70 K) and electroresistance (-8000 % at H = 0 T and
60 K) for I = 11 mA. We interpret our observations in terms of current induced
supercooling of the high temperature paramagnetic phase and enlargement of
volume fraction of the ferromagnetic phase under a magnetic field.",0911.5491v1
2010-03-26,Superconductor terahertz metamaterial,"We characterize the behaviour of split ring resonators made up of
high-transition temperature YBCO superconductor using terahertz time domain
spectroscopy. The superconductor metamaterial shows sharp change in the
transmission spectrum at the fundamental inductive-capacitive resonance and the
dipole resonance as the temperature dips below the transition temperature. Our
results reveal that the high performance of such a metamaterial is limited by
material imperfections and defects such as cracks, voids and secondary phases
which play dominant role in partially impeding the flow of current causing
dissipation of energy and electrical resistance to appear in the superconductor
film.",1003.5169v1
2013-08-15,Low Temperature Nanoscale Electronic Transport on the MoS_2 surface,"Two-probe electronic transport measurements on a Molybdenum Disulphide
(MoS_2) surface were performed at low temperature (30K) under ultra-high vacuum
conditions. Two scanning tunneling microscope tips were precisely positioned in
tunneling contact to measure the surface current-voltage characteristics. The
separation between the tips is controllably varied and measured using a high
resolution scanning electron microscope. The MoS_2 surface shows a surface
electronic gap (E_S) of 1.4eV measured at a probe separation of 50nm.
Furthermore, the two- probe resistance measured outside the electronic gap
shows 2D-like behavior with the two-probe separation.",1308.3299v1
2014-02-27,Nonlinear conductivity in CaRuO3 thin films measured by short current pulses,"Metals near quantum critical points have been predicted to display universal
out-of equilibrium behavior in the steady current-carrying state. We have
studied the non-linear conductivity of high-quality CaRuO$_3$ thin films with
residual resistivity ratio up to 57 using micro-second short, high-field
current pulses at low temperatures. Even for the shortest pulses of $5\mu$s,
Joule heating persists, making it impossible to observe a possible universal
non-linearity. Much shorter pulses are needed for the investigation of
universal non-linear conductivity.",1402.6845v1
2015-02-02,Electrical and magnetic properties of La$_{0.5}$Rh$_4$Sb$_{12}$ filled skutterudite synthesized at high pressure,"A filled skutterudite, La$_{0.5}$Rh$_4$Sb$_{12}$, with a lattice constant of
9.284(2) {\AA} was synthesized using a high-pressure technique. The electrical
resistivity showed semiconducting behavior and the energy gap was estimated to
be more than 0.08 eV. Magnetic susceptibility measurements indicated
temperature-independent diamagnetism, which originates from Larmor
diamagnetism. The electrical properties of this compound are more similar to
those of the La$_{0.5}$Rh$_4$As$_{12}$ semiconductor with an energy gap of 0.03
eV than to those of the La$_{0.6}$Rh$_4$P$_{12}$ superconductor.",1502.00337v2
2016-01-12,Melting of B12P2 boron subphosphide under pressure,"Melting of boron subphosphide (B12P2) to 26 GPa has been studied by in situ
synchrotron X-ray powder diffraction in a laser-heated diamond anvil cell, and
by quenching and electrical resistance measurements in a toroid-type
high-pressure apparatus. B12P2 melts congruently, and the melting curve has a
positive slope of 23(6) K/GPa. No solid-state phase transition was observed up
to the melting in the whole pressure range under study.",1601.02930v1
2016-02-23,Preparation of Silver and Silver-backing self-supported thin targets by high vacuum evaporation,"We have produced in the Nuclear Physics Center in Lisbon thin film
self-supported targets of Ag, LiF/Ag and CaF$_2$/Ag by a high vacuum resistance
evaporation method. The production setup, materials, methods, characterization
and results are described.",1602.07172v2
2016-05-09,Highly Non-linear and Reliable Amorphous Silicon Based Back-to-Back Schottky Diode as Selector Device for Large Scale RRAM Arrays,"In this work we present silicon process compatible, stable and reliable
($>10^{8}$cycles), high non-linearity ratio at half-read voltage ($>5\times
10^{5}$), high speed ($<60ns$) low operating voltage ($<2V$) back-to-back
Schottky diodes. Materials choice of electrode, thickness of semiconductor
layer and doping level are investigated by numerical simulation, experiments
and current-voltage equations to give a general design consideration when
back-to-back Schottky diodes are used as selector device for Resistive Random
Access Memory(RRAM) arrays.",1605.02757v1
2016-07-19,Performance Enhancement of Black Phosphorus Field-Effect Transistors by Chemical Doping,"In this letter, a new approach to chemically dope black phosphorus (BP) is
presented, which significantly enhances the device performance of BP
field-effect transistors for an initial period of 18 h, before degrading to
previously reported levels. By applying
2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), low ON-state
resistance of 3.2 ohm.mm and high field-effect mobility of 229 cm2/Vs are
achieved with a record high drain current of 532 mA/mm at a moderate channel
length of 1.5 {\mu}m.",1607.05760v1
2018-04-04,Ultra-high Vacuum Deposition of Higher Manganese Silicide Mn4Si7 Thin Films,"We have successfully grown one of the higher manganese silicides, Mn4Si7 thin
films on silicon (100) substrates using an ultra-high vacuum deposition with a
base pressure of 1x10-9 torr. The thickness of the film was varied from 65-100
nm. These films exhibit a tetragonal crystal structure and display paramagnetic
behavior as predicted for the stoichiometric Mn4Si7 system. They have a
resistivity of 3.321 x 10-5 ohm-m at room temperature and show a semi-metallic
nature.",1804.01604v1
2018-04-09,Superconductivity in REO0.5F0.5BiS2 with high-entropy-alloy-type blocking layers,"We synthesized new REO0.5F0.5BiS2 (RE: rare earth) superconductors with the
high-entropy-alloy-type (HEA-type) REO blocking layers. According to the RE
concentration and the RE ionic radius, the lattice constant of a systematically
changed in the HEA-type samples. A sharp superconducting transition was
observed in the resistivity measurements for all the HEA-type samples, and the
transition temperature of the HEA-type samples was higher than that of typical
REO0.5F0.5BiS2. The sharp superconducting transition and the enhanced
superconducting properties of the HEA-type samples may indicate the
effectiveness of the HEA states of the REO blocking layers in the
REO0.5F0.5BiS2 system.",1804.02880v2
2020-09-01,Solute softening and vacancy generation by diffusion-less climb in magnesium alloys,"Active room temperature diffusion-less climb of the <a> edge dislocations in
model Mg-Al alloys was observed using molecular dynamics simulations.
Dislocations on prismatic and pyramidal I planes climb through the basal plane
to overcome solute obstacles. This out-of-plane dislocation motion softens the
high resistance pyramidal I glide and significantly reduces the anisotropy of
dislocation mobility, and could help improve the ductility of Mg. The flow
stress scales linearly with solute concentration, cAl. Dislocations climb
predominantly in the negative direction, with climb angle on the order of
0.01cAl, producing very high vacancy concentration on the order of 10-4.",2009.00656v1
2020-06-20,Can an amorphous crystallize into a high entropy alloy?,"On the premise that amorphous-HEA composites could demonstrate high toughness
and resistance to embrittlement akin to the phase separating glassy-solid
solution composites, we develop a thermodynamics based approach to identify
chemical compositions capable of undergoing the amorphous to HEA
transformation. We introduce two new parameters called phase selection value
(PSV) and molar volume dispersity parameter. Using this thermodynamic approach
seven multi-component compositions were proposed and the general guidelines for
identifying such compositions was established. The approach also reveals that
BMGs may not be as such amenable to undergo an amorphous to HEA transformation.",2006.11579v1
2015-03-20,Bottom-up assembly of metallic germanium,"Extending chip performance beyond current limits of miniaturisation requires
new materials and functionalities that integrate well with the silicon
platform. Germanium fits these requirements and has been proposed as a
high-mobility channel material,[1] a light emitting medium in
silicon-integrated lasers,[2,3] and a plasmonic conductor for bio-sensing.[4,5]
Common to these diverse applications is the need for homogeneous, high electron
densities in three-dimensions (3D). Here we use a bottom-up approach to
demonstrate the 3D assembly of atomically sharp doping profiles in germanium by
a repeated stacking of two-dimensional (2D) high-density phosphorus layers.
This produces high-density (10^19 to 10^20 cm-3) low-resistivity (10^-4 Ohmcm)
metallic germanium of precisely defined thickness, beyond the capabilities of
diffusion-based doping technologies.[6] We demonstrate that free electrons from
distinct 2D dopant layers coalesce into a homogeneous 3D conductor using
anisotropic quantum interference measurements, atom probe tomography, and
density functional theory.",1503.05994v1
2014-08-06,Permanent magnet with MgB2 bulk superconductor,"Superconductors with persistent zero-resistance currents serve as permanent
magnets for high-field applications requiring a strong and stable magnetic
field, such as magnetic resonance imaging (MRI). The recent global helium
shortage has quickened research into high-temperature superconductors (HTSs)
materials that can be used without conventional liquid-helium cooling to 4.2 K.
Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB2)
makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week
with an extremely high stability (<0.1 ppm/h). The magnetic field trapped in
this magnet is uniformly distributed, as for single-crystalline
neodymium-iron-boron. Magnetic hysteresis loop of the MgB2 permanent bulk
magnet was detrmined. Because MgB2 is a simple-binary-line compound that does
not contain rare-earth metals, polycrystalline bulk material can be
industrially fabricated at low cost and with high yield to serve as strong
magnets that are compatible with conventional compact cryocoolers, making MgB2
bulks promising for the next generation of Tesla-class permanent-magnet
applications.",1408.1277v1
2014-08-20,In-situ hydrogen charging of zirconium powder to study isothermal percipitation of hydrides and determination of Zr-hydride crystal structure,"Zirconium alloys are widely used in the nuclear industry because of their
high strength, good corrosion resistance and low neutron absorption
cross-section. However, zirconium has strong affinity for hydrogen which leads
to hydrogen concentration build-up over time. It is well known that the
formation of hydrides will degrade the material and leads to, for example,
delayed hydride cracking during high burn up. Even though zirconium hydrides
have been studied for several decades, there still remain some controversies
regarding the formation mechanisms, exact crystal structure, and stability of
various hydride phases. This study uses high resolution synchrotron radiation
as a probing tool to observe the precipitation and dissolution of hydrides in
highly pure zirconium powder during in-situ hydrogen charging. The experiment
enabled the direct observation of the hydride formation and phase
transformations. It, also, provided high quality data for crystal structure
determination.",1408.4665v1
2022-12-02,Ablation threshold and temperature dependent thermal conductivity of high entropy carbide thin films,"High entropy carbides (HECs) are a promising new class of ultra-high
temperature ceramics that could provide novel material solutions for leading
edges of hypersonic vehicles, which can reach temperatures above 3500C and
experience extreme thermal gradients. Although the mechanical and thermal
properties of HECs have been studied extensively at room temperature, few works
have examined HEC properties at high temperatures or considered these
materials' responses to thermal shock. In this work, we measure the thermal
conductivity of a five-cation HEC up to 1200C. We find that thermal
conductivity increases with temperature, consistent with trends demonstrated in
single-metal carbides. We also measure thermal conductivity of an HEC deposited
with varying CH4 flow rate, and find that although thermal conductivity is
reduced when carbon content surpasses stoichiometric concentrations, the films
all exhibited the same temperature dependent trends regardless of carbon
content. To compare the thermal shock resistance of HECs with a refractory
carbide, we conduct pulsed laser ablation measurements to determine the fluence
threshold the HECs can withstand before damaging. We find that this metric for
the average bond strength trends with the theoretical hardness of the HECs as
expected.",2212.01238v1
2023-10-18,A New Class of Materials Based on Nanoporous High Entropy Alloys with Outstanding Properties,"Nanoporous metals with a random, bicontinuous structure of both pores and
ligaments exhibit many unique mechanical properties, but their technical
applications are often limited by their intrinsic brittleness under tensile
strain triggered by fracture of the weakest ligaments. Here, we use molecular
dynamics simulations to study the mechanical behavior and thermal stability of
two different bicontinuous nanoporous high entropy alloys, Al0.1CoCrFeNi and
NbMoTaW. To isolate the properties related to the nanoporous nature of our
samples, we also studied the corresponding bulk and nanocrystalline systems.
The results demonstrate that the specific modulus of nanoporous HEAs are 2 to 3
times greater than that of single element nanoporous materials with specific
strength reaching values 5 to 10 times higher, comparable to bulk metals with
the highest specific strength. Bicontinuous HEAs also displayed excellent
resistance to thermal degradation as evidenced by the absence of coarsening
ligaments up to temperatures of 1273 K which ensures the durability and
reliability in high-temperature applications. The findings uncover
unprecedented mechanical and thermal properties of bicontinuous nanoporous high
entropy alloys, paving the way for their promising utilization in advanced
engineering and structural applications.",2310.11937v1
1996-09-20,High Temperature Thermopower in La_{2/3}Ca_{1/3}MnO_3 Films: Evidence for Polaronic Transport,"Thermoelectric power, electrical resistivity and magnetization experiments,
performed in the paramagnetic phase of La_{2/3}Ca_{1/3}MnO_3, provide evidence
for polaron-dominated conduction in CMR materials. At high temperatures, a
large, nearly field-independent difference between the activation energies for
resistivity (rho) and thermopower (S), a characteristic of Holstein Polarons,
is observed, and ln(rho) ceases to scale with the magnetization. On approaching
T_c, both energies become field-dependent, indicating that the polarons are
magnetically polarized. Below T_c, the thermopower follows a law S(H) prop.
1/rho (H) as in non saturated ferromagnetic metals.",9609212v1
2000-01-25,Influence of high-energy electron irradiation on the transport properties of La_{1-x}Ca_{x}MnO_{3} films (x \approx 1/3),"The effect of crystal lattice disorder on the conductivity and colossal
magnetoresistance in La_{1-x}Ca_{x}MnO_{3} (x \approx 0.33) films has been
examined. The lattice defects are introduced by irradiating the film with
high-energy (\simeq 6 MeV) electrons with a maximal fluence of about 2\times
10^{17} cm^{-2}. This comparatively low dose of irradiation produces rather
small radiation damage in the films. The number of displacements per atom (dpa)
in the irradiated sample is about 10^{-5}. Nethertheless, this results in an
appreciable increase in the film resistivity. The percentage of resistivity
increase in the ferromagnetic metallic state (below the Curie tempetature
T_{c}) was much greater than that observed in the insulating state (above
T_{c}). At the same time irradiation has much less effect on T_{c} or on the
magnitude of the colossal magnetoresistance. A possible explanation of such
behavior is proposed.",0001372v1
2001-07-27,Lattice coupled first order magnetoresistance transition in an A-type antiferromagnet: Pr$_{0.46}$Sr$_{0.54}$MnO$_3$,"We investigated magnetic, magnetotransport and magnetostriction properties of
the A-type antiferromagnet Pr$_{0.46}$Sr$_{0.54}$MnO$_3$ which undergoes a
first order paramagnetic-antiferromagnetic transition below T$_N$ = 210 K while
cooling and T$_N$ = 215 K while warming. The zero field ($\mu_0$H = 0 T)
resistivity shows a sudden jump at T$_N$ and a small bump around T$_{max}$ =
220 K (\TEXTsymbol{>} T$_N$). T$_N$ shifts down and T$_{max}$ shifts up with
increasing $\mu_0$H. Magnetoresistance as high as -45-57 % at 7 T is found in
the temperature range 180 K-230 K. Isothermal measurements indicate that the
field induced antiferromagnetic to ferromagnetic transition below T$_N$ is
accompanied by a rapid decrease of the resistivity but increase of volume
($\Delta $V/V = +0.25 % at 180 K and 13.7 T). This lattice coupled
magnetoresistance transition is suggested due to the field induced structural
transition from the low volume orthorhombic to the high volume tetragonal
structure.",0107560v1
2001-09-04,Magnetotransport in a bi-crystal film of La_0.7Sr_0.3MnO_3,"Transport properties of an epitaxial film of La_0.7Sr_0.3MnO_3 (LSMO),
deposited epitaxially on a LaAlO_3 bi-crystal substrate having a misorientation
angle of 9.2 deg., have been studied.
  The film was patterned into a meander containing 100 grain boundaries. The
resistivity of the sample exhibits two components; one originating from the
grain boundary regions, and one from the LSMO elements in the meander; the
latter contribution is similar to the resistivity of a reference epitaxial LSMO
film. The low (<0.5 T) and high (up to 6 T) field magnetoresistance was also
studied. The meander show a large low field magnetoresistance, increasing with
decreasing temperature, and a constant high field slope of the
magnetoconductance, results that are well explained by a two-step spin
polarized tunneling model.",0109052v1
2002-08-20,Fabrication and properties of gallium metallic photonic crystals,"Gallium metallic photonic crystals with 100% filling factor have been
fabricated via infiltration of liquid gallium into opals of 300-nm silica
spheres using a novel high pressure-high temperature technique. The electrical
resistance of the Ga-opal crystals was measured at temperatures from 10 to 280
K. The data obtained show that Ga-opal crystals are metallic network with
slightly smaller temperature coefficient of resistivity than that for bulk
gallium. Optical reflectivity of bulk gallium, plain opal and several Ga-opal
crystals were measured at photon energies from 0.3 to 6 eV. A pronounced
photonic stop band in the visible spectral range was found in both the plain
and Ga infiltrated opals. The reflectivity spectra also show increase in
reflectivity below 0.6 eV; which we interpret as a significantly lower
effective plasma frequency of the metallic mesh in the infiltrated opal compare
to the plasma frequency in the pure metal.",0208392v1
2002-09-24,High Curie temperature GaMnAs obtained by resistance-monitored annealing,"We show that by annealing Ga1-xMnxAs thin films at temperatures significantly
lower than in previous studies, and monitoring the resistivity during growth,
an unprecedented high Curie temperature Tc and conductivity can be obtained. Tc
is unambiguously determined to be 118 K for Mn concentration x=0.05, 140 K for
x=0.06, and 120 K for x=0.08. We also identify a clear correlation between Tc
and the room temperature conductivity. The results indicate that Curie
temperatures significantly in excess of the current values are achievable with
improvements in growth and post-growth annealing conditions.",0209554v1
2003-10-09,RF Surface Resistance of a HIPped MgB2 Sample at 21 GHz,"Magnesium diboride (MgB2) is attractive for RF cavity application for
particle accelerators because it might not show an increase of RF surface
losses at high magnetic surface fields, a phenomenon that has prevented high-Tc
superconducting materials such as YBCO from being used for this application. We
have measured the RF surface resistance (Rs) at 21 GHz of a MgB2 sample
fabricated using Hot Isostatic Press (HIP) at 200 MPa and 1000 C. The results
show that polishing with 0.1-micron diamond lapping film followed by a 1500-psi
DI water rinse in a clean room reduced the Rs by a factor of 6.2 at 15 K and it
is the lowest compared to other published data. The Rs data near the lowest
temperature (~13 K) scatter between 0.6 and 1.3 mOhm. The penetration depth and
energy gap were estimated to be 263 nm and 1.9-2.7, respectively, for the
polished surface.",0310213v1
2004-08-31,"Normal state properties of high angle grain boundaries in (Y,Ca)Ba2Cu3O7-delta","By lithographically fabricating an optimised Wheatstone bridge geometry, we
have been able to make accurate measurements of the resistance of grain
boundaries in Y1-xCaxBa2Cu3O7-d between the superconducting transition
temperature, Tc, and room temperature. Below Tc the normal state properties
were assessed by applying sufficiently high currents. The behaviour of the
grain boundary resistance versus temperature and of the conductance versus
voltage are discussed in the framework charge transport through a tunnel
barrier. The influence of misorientation angle, oxygen content, and calcium
doping on the normal state properties is related to changes of the height and
shape of the grain boundary potential barrier.",0409004v1
2005-07-06,"Oxidation Resistant Germanium Nanowires: Bulk Synthesis, Long Chain Alkanethiol Functionalization and Langmuir-Blodgett Assembly","A simple method is developed to synthesize gram quantities of uniform Ge
nanowires (GeNWs) by chemical vapor deposition on preformed, monodispersed
seed-particles loaded onto high surface area silica support. Various chemical
functionalization schemes are investigated to passivate the GeNW surfaces using
alkanethiols and alkyl Grignard reactions. The stability of functionalization
against oxidation of germanium for various alkyl chain lengths is elucidated by
X-ray photoelectron spectroscopy. Among all schemes tested, long chain
alkanethiols (>=C12) are found to impart the most stable GeNW passivation
against oxidation upon extended exposure to ambient air. Further, the
chemically functionalized oxidation-resistant nanowires are soluble in organic
solvents and can be readily assembled into close-packed Langmuir-Blodgett films
potentially useful for future high performance electronic devices.",0507145v2
2006-03-08,Nanoscopic processes of Current Induced Switching in thin tunnel junctions,"In magnetic nanostructures one usually uses a magnetic field to commute
between two resistance (R) states. A less common but technologically more
interesting alternative to achieve R-switching is to use an electrical current,
preferably of low intensity. Such Current Induced Switching (CIS) was recently
observed in thin magnetic tunnel junctions, and attributed to electromigration
of atoms into/out of the insulator. Here we study the Current Induced
Switching, electrical resistance, and magnetoresistance of thin
MnIr/CoFe/AlO$_x$/CoFe tunnel junctions. The CIS effect at room temperature
amounts to 6.9% R-change between the high and low states and is attributed to
nanostructural rearrangements of metallic ions in the electrode/barrier
interfaces. After switching to the low R-state some electro-migrated ions
return to their initial sites through two different energy channels. A low
(high) energy barrier of $\sim$0.13 eV ($\sim$0.85 eV) was estimated. Ionic
electromigration then occurs through two microscopic processes associated with
different types of ions sites/defects. Measurements under an external magnetic
field showed an additional intermediate R-state due to the simultaneous
conjugation of the MR (magnetic) and CIS (structural) effects.",0603208v1
2007-04-13,Counting and manipulating single electrons using a carbon nanotube transistor,"We report on the electric measurements of an individual Au nanoparticle with
an ultra-high contact resistance of about $10^{19} \Omega$. The high-impedance
measurements have been carried out by counting the electrons that are
transferred onto the particle. In order to do this, a carbon nanotube is used
as the electrode for the supply of electrons but also as the detector of the
charge transfer. Measurements using single-electron detection allow us to
determine the separation between the electron states in the Au nanoparticle,
which is about 4 meV, consistent with the charging energy of the particle.
Single-electron detection with nanotubes offers great promise for the study of
electron transfer in highly resistive molecular systems.",0704.1794v1
2007-07-17,Positive and negative pressure effects on the magnetic ordering and the Kondo effect in the compound Ce2RhSi3,"The competition between magnetic ordering and the Kondo effect in Ce2RhSi3,
ordering antiferromagnetically at 7 K, is investigated by the measurements of
magnetization, heat capacity and electrical resistivity on the solid solutions,
Ce(2-x)La(x)RhSi3, Ce(2-y)Y(y)RhSi3, and Ce2RhSi(3-z)Ge(z), as well as by high
pressure studies on this compound. The trends in the Kondo and Neel temperature
variations among these alloys are compared to infer the roles of unit-cell
volume and electronic structure changes. On the basis of the results, we infer
that this compound lies at the peak of Doniach-magnetic-phase-diagram. The high
pressure electrical resistivity data indicate that the quantum critical point
for this compound is in the vicinity of 4 GPa.",0707.2518v1
2007-09-05,Thickness-dependence of the electronic properties in V2O3 thin films,"High quality vanadium sesquioxide V2O3 films (170-1100 {\AA}) were grown
using the pulsed laser deposition technique on (0001)-oriented sapphire
substrates, and the effects of film thickness on the lattice strain and
electronic properties were examined. X-ray diffraction indicates that there is
an in-plane compressive lattice parameter (a), close to -3.5% with respect to
the substrate and an out-of-plane tensile lattice parameter (c) . The thin film
samples display metallic character between 2-300 K, and no metal-to-insulator
transition is observed. At low temperature, the V2O3 films behave as a strongly
correlated metal, and the resistivity (\rho) follows the equation \rho =\rho_0
+ A T^2, where A is the transport coefficient in a Fermi liquid. Typical values
of A have been calculated to be 0.14 \mu\Omega cm K^{-2}, which is in agreement
with the coefficient reported for V2O3 single crystals under high pressure.
Moreover, a strong temperature-dependence of the Hall resistance confirms the
electronic correlations of these V2O3 thin films samples.",0709.0692v1
2008-06-09,Superconductivity in single crystals of LaFePO,"Single crystals of the compound LaFePO were prepared using a flux growth
technique at high temperatures. Electrical resistivity measurements reveal
metallic behavior and a resistive transition to the superconducting state at a
critical temperature T_c ~ 6.6 K. Magnetization measurements also show the
onset of superconductivity near 6 K. In contrast, specific heat measurements
manifest no discontinuity at T_c. These results lend support to the conclusion
that the superconductivity is associated with oxygen vacancies that alter the
carrier concentration in a small fraction of the sample, although
superconductivity characterized by an unusually small gap value can not be
ruled-out. Under applied magnetic fields, T_c is suppressed anisotropically for
fields perpendicular and parallel to the ab-plane, suggesting that the
crystalline anisotropy strongly influences the superconducting state.
Preliminary high-pressure measurements show that T_c passes through a maximum
of nearly 14 K at ~ 110 kbar, demonstrating that significantly higher T_c
values may be achieved in the phosphorus-based oxypnictides.",0806.1265v2
2009-08-23,Superconductivity at high Tc in neodymium-doped 1111-SrFeAsF system,"Polycrystalline Sr1-xNdxFeAsF samples were prepared at various Nd-doping
levels using both a stoichiometric mixture of the starting materials and in
slight excess amounts of FeAs. Susceptibility and resistivity of the samples
were studied down to 4 K revealing a probable coexistence of superconductivity
and a magnetic ordering. Temperature dependence of resistivity for all the
Nd-doped samples shows the presence of a transition below 15 K most likely
originating from the magnetic ordering of Nd moments, while the
spin-density-wave anomaly at 175 K survives up to 0.35 Nd-doping.
Superconductivity only occurs above 0.40 Nd-doping with onset maximum Tc
reaching as high as 52 K.",0908.3285v3
2011-06-29,Hysteretic magnetoresistance and thermal bistability in a magnetic two-dimensional hole system,"Colossal negative magnetoresistance and the associated field-induced
insulator-to-metal transition, the most characteristic features of magnetic
semiconductors, are observed in n-type rare earth oxides and chalcogenides,
p-type manganites, n-type and p-type diluted magnetic semiconductors (DMS) as
well as in quantum wells of n-type DMS. Here, we report on magnetostransport
studies of Mn modulation-doped InAs quantum wells, which reveal a magnetic
field driven and bias voltage dependent insulator-to-metal transition with
abrupt and hysteretic changes of resistance over several orders of magnitude.
These phenomena coexist with the quantised Hall effect in high magnetic fields.
We show that the exchange coupling between a hole and the parent Mn acceptor
produces a magnetic anisotropy barrier that shifts the spin relaxation time of
the bound hole to a 100 s range in compressively strained quantum wells. This
bistability of the individual Mn acceptors explains the hysteretic behaviour
while opening prospects for information storing and processing. At high bias
voltage another bistability, caused by the overheating of electrons10, gives
rise to abrupt resistance jumps.",1106.5832v1
2011-09-06,Evolution of transport properties of BaFe2-xRuxAs2 in a wide range of isovalent Ru substitution,"The effects of isovalent Ru substitution at the Fe sites of BaFe2-xRuxAs2 are
investigated by measuring resistivity and Hall coefficient on high-quality
single crystals in a wide range of doping (0 < x < 1.4). Ru substitution
weakens the antiferromagnetic (AFM) order, inducing superconductivity for
relatively high doping level of 0.4 < x < 0.9. Near the AFM phase boundary, the
transport properties show non-Fermi-liquid-like behaviors with a
linear-temperature dependence of resistivity and a strong temperature
dependence of Hall coefficient with a sign change. Upon higher doping, however,
both of them recover conventional Fermi-liquid behaviors. Strong doping
dependence of Hall coefficient together with a small magnetoresistance suggest
that the anomalous transport properties can be explained in terms of
anisotropic charge carrier scattering due to interband AFM fluctuations rather
than a conventional multi-band scenario.",1109.1083v1
2012-09-06,High-temperature thermoelectric properties of the double-perovskite ruthenium oxide (Sr$_{1-x}$La$_x$)$_2$ErRuO$_6$,"We have prepared polycrystalline samples of (Sr$_{1-x}$La$_x$)$_2$ErRuO$_6$
and (Sr$_{1-x}$La$_x$)$_2$YRuO$_6$, and have measured the resistivity, Seebeck
coefficient, thermal conductivity, susceptibility and x-ray absorption in order
to evaluate the electronic states and thermoelectric properties of the doped
double-perovskite ruthenates. We have observed a large Seebeck coefficient of
-160 $\mu$V/K and a low thermal conductivity of 7 mW/cmK for $x$=0.1 at 800 K
in air. These two values are suitable for efficient oxide thermoelectrics,
although the resistivity is still as high as 1 $\Omega$cm. From the
susceptibility and x-ray absorption measurements, we find that the doped
electrons exist as Ru$^{4+}$ in the low spin state. On the basis of the
measured results, the electronic states and the conduction mechanism are
discussed.",1209.1250v1
2012-10-12,Simultaneous measurement of pressure evolution of crystal structure and superconductivity in FeSe0.92 using designer diamonds,"Simultaneous high pressure x-ray diffraction and electrical resistance
measurements have been carried out on a PbO type {\alpha}-FeSe0.92 compound to
a pressure of 44 GPa and temperatures down to 4 K using designer diamond anvils
at synchrotron source. At ambient temperature, a structural phase transition
from a tetragonal (P4/nmm) phase to an orthorhombic (Pbnm) phase is observed at
11 GPa and the Pbnm phase persists up to 74 GPa. The superconducting transition
temperature (TC) increases rapidly with pressure reaching a maximum of ~28 K at
~ 6 GPa and decreases at higher pressures, disappearing completely at 14.6 GPa.
Simultaneous pressure-dependent x-ray diffraction and resistance measurements
at low temperatures show superconductivity only in a low pressure orthorhombic
(Cmma) phase of the {\alpha}-FeSe0.92. Upon increasing pressure at 10 K near
TC, crystalline phases change from a mixture of orthorhombic (Cmma) and
hexagonal (P63/mmc) to a high pressure orthorhombic (Pbnm) phase near 6.4 GPa
where TC is maximum.",1210.3645v1
2012-11-20,Optically excited multi-band conduction in LaAlO3/SrTiO3 heterostructures,"The low-temperature resistance of a conducting LaAlO3/SrTiO3 interface with a
10 nm thick LaAlO3 film decreases by more than 50% after illumination with
light of energy higher than the SrTiO3 band-gap. We explain our observations by
optical excitation of an additional high mobility electron channel, which is
spatially separated from the photo-excited holes. After illumination, we
measure a strongly non-linear Hall resistance which is governed by the
concentration and mobility of the photo-excited carriers. This can be explained
within a two-carrier model where illumination creates a high-mobility electron
channel in addition to a low-mobility electron channel which exists before
illumination.",1211.4778v1
2013-12-04,Physical characteristics and cation distribution of NiFe2O4 thin films with high resistivity prepared by reactive co-sputtering,"We fabricated NiFe2O thin films on MgAl2O4 (001) substrates by reactive dc
magnetron co-sputtering in a pure oxygen atmosphere at different substrate
temperatures. The film properties were investigated by various techniques with
a focus on their structure, surface topography, magnetic characteristics, and
transport properties. Structural analysis revealed a good crystallization with
epitaxial growth and low roughness and a similar quality as in films grown by
pulsed laser deposition. Electrical conductivity measurements showed high room
temperature resistivity (12 Ohmm), but low activation energy, indicating an
extrinsic transport mechanism. A band gap of about 1.55 eV was found by optical
spectroscopy. Detailed x-ray spectroscopy studies confirmed the samples to be
ferrimagnetic with fully compensated Fe moments. By comparison with multiplet
calculations of the spectra we found that the cation valencies are to a large
extent Ni2+ and Fe3+.",1312.1086v1
2013-12-13,Low-energy electronic properties of clean CaRuO$_3$: elusive Landau quasiparticles,"We have prepared high-quality epitaxial thin films of CaRuO$_3$ with residual
resistivity ratios up to 55. Shubnikov-de Haas oscillations in the
magnetoresistance and a $T^2$ temperature dependence in the electrical
resistivity only below 1.5 K, whose coefficient is substantially suppressed in
large magnetic fields, establish CaRuO$_3$ as a Fermi liquid (FL) with
anomalously low coherence scale. Non-Fermi liquid (NFL) $T^{3/2}$ dependence is
found between 2 and 25 K. The high sample quality allows access to the
intrinsic electronic properties via THz spectroscopy. For frequencies below 0.6
THz, the conductivity is Drude-like and can be modeled by FL concepts, while
for higher frequencies non-Drude behavior, inconsistent with FL predictions, is
found. This establishes CaRuO$_3$ as a prime example of optical NFL behavior in
the THz range.",1312.3809v1
2017-10-18,Near-thermal limit gating in heavily-doped III-V semiconductor nanowires using polymer electrolytes,"Doping is a common route to reducing nanowire transistor on-resistance but
has limits. High doping level gives significant loss in gate performance and
ultimately complete gate failure. We show that electrolyte gating remains
effective even when the Be doping in our GaAs nanowires is so high that
traditional metal-oxide gates fail. In this regime we obtain a combination of
sub-threshold swing and contact resistance that surpasses the best existing
p-type nanowire MOSFETs. Our sub-threshold swing of 75 mV/dec is within 25% of
the room-temperature thermal limit and comparable with n-InP and n-GaAs
nanowire MOSFETs. Our results open a new path to extending the performance and
application of nanowire transistors, and motivate further work on improved
solid electrolytes for nanoscale device applications.",1710.06950v2
2018-02-02,Magneto-transport properties of proposed triply degenerate topological semimetal Pd$_{3}$Bi$_{2}$S$_{2}$,"We report transport properties of single-crystalline Pd$_{3}$Bi$_{2}$S$_{2}$,
which has been predicted to host an unconventional electronic phase of matter
beyond three-dimensional Dirac and Weyl semimetals. Similar to several
topological systems, the resistivity shows field induced
metal-semiconductor-like crossover at low temperature. Large, anisotropic and
non-saturating magnetoresistance (MR) has been observed in transverse
experimental configuration. At 2 K and 9 T, the MR value reaches as high as
$\sim$1.1$\times$10$^{3}$ \%. Hall resistivity reveals the presence of two
types of charge carriers and has been analyzed using two-band model. In spite
of the large density ($>$ 10$^{21}$ cm$^{-3}$), the mobility of charge carriers
is found to be quite high ($\sim$ 0.75$\times$10$^{4}$ cm$^{2}$ V$^{-1}$
s$^{-1}$ for hole and $\sim$ 0.3$\times$10$^{4}$ cm$^{2}$ V$^{-1}$ s$^{-1}$ for
electron). The observed magneto-electrical properties indicate that
Pd$_{3}$Bi$_{2}$S$_{2}$ may be a new member of the topological semimetal
family, which can have a significant impact in technological applications.",1802.00712v2
2019-09-17,Spin-Orbit-Torque Field-Effect Transistor (SOTFET): Proposal for a New Magnetoelectric Memory,"Spin-based memories are attractive for their non-volatility and high
durability but provide modest resistance changes, whereas semiconductor logic
transistors are capable of large resistance changes, but lack memory function
with high durability. The recent availability of multiferroic materials
provides an opportunity to directly couple the change in spin states of a
magnetic memory to a charge change in a semiconductor transistor. In this work,
we propose and analyze the spin-orbit torque field-effect transistor (SOTFET),
a device with the potential to significantly boost the energy efficiency of
spin-based memories, and to simultaneously offer a palette of new
functionalities.",1909.08133v3
2017-03-09,Transport properties of iron at the Earth's core conditions: the effect of spin disorder,"The electronic and thermal transport properties of the Earth's core are
crucial for many geophysical models such as the geodynamo model of the Earth's
magnetic field and of its reversals. Here we show, by considering bcc-iron and
iron-rich iron-silicon alloy as a representative of the Earth's core
composition and applying the first-principles modeling that the spin disorder
at the Earth's core conditions provides an essential contribution, of order
20~$\mu\Omega$\,cm, to the electrical resistivity. This value is comparable in
magnitude with the electron-phonon and with the recently estimated
electron-electron scattering contributions. The origin of the spin-disorder
resistivity (SDR) consists in the existence of fluctuating local moments that
are stabilized at high temperatures by the magnetic entropy even at pressures
at which the ground state of iron is non-magnetic. We find that electron-phonon
and SDR contributions are not additive at high temperatures. We thus observe a
large violation of the Matthiessen rule, not common in conventional metallic
alloys at ambient conditions.",1703.03205v3
2020-04-07,Large-scalable fabrication of improved Bi-Te-based flexible thermoelectric modules using a semiconductor manufacturing process,"Among the several flexible thermoelectric modules in existence, sintered
Bi-Te-based modules represent a viable option because of their high output
power density and flexibility, which enables the use of arbitrary heat sources.
We have fabricated Bi-Te-based modules with a large-scalable fabrication
process and improved their output performance. The reduction in the
interconnection resistance, using thick electrodes of the flexible printed
circuit, significantly improves the module's output power to 87 mW/cm$^{2}$ at
$\Delta T$ = 70 K, which is 1.3-fold higher than a previous prototype module.
Furthermore, the establishment of the fabrication for the top electrodes by
using the surface mount technology makes it possible to realize a
high-throughput manufacturing of the module. Our durability tests reveal that
there is no significant change in the internal resistance of the module during
10000 cycles of mechanical bending test and 1000 cycles of thermal stress test.",2004.03068v1
2020-09-24,Pressure-Temperature Phase Diagram of $α$-Mn,"Electrical resistivity and ac-susceptibility measurements under high pressure
were carried out in high-quality single crystals of $\alpha$-Mn. The
pressure-temperature phase diagram consists of an antiferromagnetic ordered
phase (0<$P$<1.4 GPa, $T<T_{\rm N}$), a pressure-induced ordered phase
(1.4<$P$<4.2-4.4 GPa, $T<T_{\rm A}$), and a paramagnetic phase. A significant
increase was observed in the temperature dependence of ac-susceptibility at
$T_{\rm A}$, indicating that the pressure-induced ordered phase has a
spontaneous magnetic moment. Ferrimagnetic order and parasitic ferromagnetism
are proposed as candidates for a possible magnetic structure. At the critical
pressure, where the pressure-induced ordered phase disappears, the temperature
dependence of the resistivity below 10 K is proportional to $T^{5/3}$. This
non-Fermi liquid behavior suggests the presence of pronounced magnetic
fluctuation.",2009.11488v1
2012-01-09,"Physical properties of $A_x$Fe$_{2-y}$S$_2$ ($A$=K, Rb and Cs) single crystals","We successfully synthesized two new compounds Rb$_x$Fe$_{2-y}$S$_2$ and
Cs$_x$Fe$_{2-y}$S$_2$ which were isostructural with K$_x$Fe$_{2-y}$Se$_2$
superconductor. We systematically investigated the resistivity, magnetism and
thermoelectric power of $A_x$Fe$_{2-y}$S$_2$ ($A$=K, Rb and Cs) single
crystals. High temperature resistivity and magnetic measurements show anomalies
above 500 K depending on $A$ which are similar to $A_x$Fe$_{2-y}$Se$_2$.
Discrepancy between ZFC and FC curves was observed in K$_x$Fe$_{2-y}$S$_2$ and
Rb$_x$Fe$_{2-y}$S$_2$, while it disappears in Cs$_x$Fe$_{2-y}$S$_2$. Our
results indicate the similar magnetism between $A_x$Fe$_{2-y}$S$_2$ and
$A_x$Fe$_{2-y}$Se$_2$ at high temperature.",1201.1709v1
2019-03-12,Single-crystal growth and extremely high H_c2 of 12442-type Fe-based superconductor KCa_2Fe_4As_4F_2,"Millimeter sized single crystals of KCa_2Fe_4As_4F_2 were grown using a
self-flux method. The chemical compositions and crystal structure were
characterized carefully. Superconductivity with the critical transition T_c =
33.5 K was confirmed by both the resistivity and magnetic susceptibility
measurements. Moreover, the upper critical field H_c2 was studied by the
resistivity measurements under different magnetic fields. A rather steep
increase for the in-plane H_c2^ab with cooling, d\mu_0H_c2^a/dT|T_c = -50.9
T/K, was observed, indicating an extremely high upper critical field. Possible
origins for this behavior were discussed. The findings in our work is a great
promotion both for understanding the physical properties and applications of
12442-type Fe-based superconductors.",1903.04822v1
2020-06-28,Design of a $β$-Ga$_2$O$_3$ Schottky Barrier Diode With p-type III-Nitride Guard Ring for Enhanced Breakdown,"This work presents the electrostatic analysis of a novel Ga$_2$O$_3$ vertical
Schottky diode with three different guard ring configurations to reduce the
peak electric field at the metal edges. Highly doped p-type GaN, p-type
nonpolar AlGaN and polarization doped graded p-AlGaN are simulated and analyzed
as the guard ring material, which forms a heterojunction with the Ga$_2$O$_3$
drift layer. Guard ring with non-polar graded p-AlGaN with a bandgap larger
than Ga$_2$O$_3$ is found to show the best performance in terms of screening
the electric field at the metal edges. The proposed guard ring configuration is
also compared with a reported Ga$_2$O$_3$ Schottky diode with no guard ring and
a structure with a high resistive Nitrogen-doped guard ring. The optimized
design is predicted to have breakdown voltage as high as 5.3 kV and a specific
on-resistance of 3.55 m$\Omega$-cm$^2$ which leads to an excellent power figure
of merit of 7.91 GW/cm$^2$.",2006.15645v1
2020-10-01,Impurity Band Conduction in Si-doped \b{eta}-Ga2O3 Films,"By combining temperature-dependent resistivity and Hall effect measurements,
we investigate donor state energy in Si-doped \b{eta}-Ga2O3 films grown using
metal-organic vapor phase epitaxy (MOVPE). High magnetic field Hall effect
measurements (H = +/-90 kOe) showed non-linear Hall resistance for T < 150 K
revealing two-band conduction. Further analyses revealed carrier freeze-out
characteristics in both bands yielding donor state energies of ~ 33.7 and ~
45.6 meV. The former is consistent with the donor energy of Si in \b{eta}-Ga2O3
whereas the latter suggests a residual donor state, likely associated with a DX
center. This study provides a critical insight into the impurity band
conduction and the defect energy states in \b{eta}-Ga2O3 using high-field
magnetotransport measurements.",2010.00193v1
2021-03-31,Slip band interactions and GND latent hardening in a galling resistant stainless steel,"Slip activation, slip band interactions, and GND densities in iron-base,
galling resistant alloy Nitronic 60 have been characterised at the grain length
scale using small-scale mechanical testing with high resolution digital image
correlation and high-angular resolution electron backscatter diffraction. By
correlating the two measurement techniques, new insight into slip band
interactions, the generation of lattice curvature and the corresponding
accumulation of geometrically necessary dislocations (GNDs) is provided.
Multiple discrete slip bands are typically active within single grains,
resulting in significant slip band interactions. Crossing slip bands were found
to generate accumulations of GNDs. Regions where slip bands block other slip
bands were associated with the highest GND densities, in excess of three time
the densities of crossing slip bands. Representative crystal plasticity
modelling investigations have demonstrated that discrete slip blocking events
are responsible for locally elevated GND density. This behaviour is
rationalised in terms of lattice curvature associated with the differing levels
of constraint provided by the crossing or blocking-type behaviours. Ferrite
grains are also found to contribute to the generation of GNDs. Together, these
two effects provide significant work hardening mechanisms, likely to be key to
the development of future iron-base hard facing alloys.",2103.16864v1
2021-06-10,Anomalous charge transport of superconducting Cu$_{x}$PdTe$_2$ under high pressure,"By means of high-pressure resistivity measurements on single crystals, we
investigate the charge transport properties of Cu$_x$PdTe$_2$, notable for the
combination of topological type-II Dirac semimetallic properties with
superconductivity up to $T_c = 2.5$ K. In both cases of pristine ($x = 0$) and
intercalated ($x=0.05$) samples, we find an unconventional $T^4$ power law
behavior of the low-temperature resistivity visible up to $\sim$40 K and
remarkably stable under pressure up to 8.2 GPa. This observation is explained
by the low carrier density $n$, which strongly reduces the $k$-region available
for electron-phonon scattering, as previously reported in other low-$n$
two-dimensional systems, such as multilayer graphene and semiconductor
heterostructures. Our data analysis complemented by specific heat measurements
and supported by previous quantum oscillation studies and \textit{ab initio}
calculations suggests a scenario of one-band charge transport. Within this
scenario, our analysis yields a large value of transport electron-phonon
coupling constant $\lambda_{tr} = 1.2$ at ambient pressure that appears to be
strongly enhanced by pressure assuming a constant effective mass.",2106.05613v1
2021-06-18,Coulomb Drag between a Carbon Nanotube and Monolayer Graphene,"We have measured Coulomb drag between an individual single-walled carbon
nanotube (SWNT) as a one-dimensional (1D) conductor and the two-dimensional
(2D) conductor monolayer graphene, separated by a few-atom-thick boron nitride
layer. The graphene carrier density is tuned across the charge neutrality point
(CNP) by a gate, while the SWNT remains degenerate. At high temperatures, the
drag resistance changes sign across the CNP, as expected for momentum transfer
from drive to drag layer, and exhibits layer exchange Onsager reciprocity. We
find that layer reciprocity is broken near the graphene CNP at low temperatures
due to nonlinear drag response associated with temperature dependent drag and
thermoelectric effects. The drag resistance shows power-law dependences on
temperature and carrier density characteristic of 1D Fermi liquid-2D Dirac
fluid drag. The 2D drag signal at high temperatures decays with distance from
the 1D source slower than expected for a diffusive current distribution,
suggesting additional interaction effects in the graphene in the hydrodynamic
transport regime.",2106.10246v2
2021-06-25,Direct microscopic evidence of shear induced graphitization of ultrananocrystalline diamond films,"The origin of ultralow friction and high wear resistance in
ultrananocrystalline diamond (UNCD) films is still under active debate because
of the perplexed tribochemistry at the sliding interface. Herein, we report a
comparative study on surface topography and nanoscale friction of tribofilms,
in wear tracks of two sets of UNCD films having different structural
characteristics. Despite both the films display ultralow coefficient of
friction, the UNCD films grown under Ar atmosphere (UNCDAr) exhibit a high wear
resistance while the wear rate is higher for the films grown in N2 (UNCDN).
Frictional force microscopic (FFM) investigations clearly reveal the
manifestation of shear induced graphitization on both the films. However, the
wear track of UNCDAr films have a large network of a few layer graphene (FLG)
structures over the amorphous carbon tribofilms while only isolated clusters of
FLG structures are present in the wear track of UNCDN films. Here, we
demonstrate the direct micro-/nanoscopic evidence for the formation of large
network of ~ 0.8 - 6 nm thick FLG structures, as a consequence of shear induced
graphitization and discuss their decisive role in ultralow friction and wear.",2106.13778v1
2023-02-15,Metal-bonded Atomic Layers of Transition Metal Carbides (MXenes),"Although two-dimensional transition metal carbides and nitrides (MXenes) have
fantastic physical and chemical properties as well as wide applications, it
remains challenging to produce stable MXenes due to their rapid structural
degradation. Here, unique metal-bonded atomic layers of transition metal
carbides with high stabilities are produced via a simple topological reaction
between chlorine-terminated MXenes and selected metals, where the metals enable
to not only remove Cl terminations, but also efficiently bond with adjacent
atomic MXene slabs, driven by the symmetry of MAX phases. The films constructed
from Al-bonded Ti$_3$C$_2$Cl$_x$ atomic layers show high oxidation resistance
up to 400 degrees centigrade and low sheet resistance of 9.3 ohm per square.
Coupled to the multi-layer structure, the Al-bonded Ti$_3$C$_2$Cl$_x$ film
displays a significantly improved EMI shielding capability with a total
shielding effectiveness value of 39 dB at a low thickness of 3.1 micron,
outperforming pure Ti$_3$C$_2$Cl$_x$ film.",2302.07720v1
2023-03-22,A mixed-dimensional model for direct current simulations in presence of a thin high-resistivity liner,"In this work we present a mixed-dimensional mathematical model to obtain the
electric potential and current density in direct current simulations when a
thin liner is included in the modelled domain. The liner is used in landfill
management to prevent leakage of leachate from the waste body into the
underground and is made of a highly-impermeable high-resistivity plastic
material. The electrodes and the liner have diameters and thickness
respectively that are much smaller than their other dimensions, thus their
numerical simulation might be too costly in an equi-dimensional setting. Our
approach is to approximate them as objects of lower dimension and derive the
corresponding equations. The obtained mixed-dimensional model is validated
against laboratory experiments of increasing complexity showing the reliability
of the proposed mathematical model.",2303.12469v1
2006-02-03,Frequency quenching of microwave induced resistance oscillations in a high mobility two-dimensional electron gas,"The frequency dependence of microwave-induced resistance oscillations (MIROs)
has been studied experimentally in high-mobility electron GaAs/AlGaAs
structures to explore the limits at which these oscillations can be observed.
It is found that in dc transport experiments at frequencies above 120 GHz,
MIROs start to quench, while above 230 GHz, they completely disappear. The
results will need to be understood theoretically but are qualitatively
discussed within a model in which forced electronic charge oscillations
(plasmons) play an intermediate role in the interaction process between the
radiation and the single-particle electron excitations between Landau levels.",0602079v2
2010-09-15,Controlling electron-phonon interactions in graphene at ultra high carrier densities,"We report on the temperature dependent electron transport in graphene at
different carrier densities $n$. Employing an electrolytic gate, we demonstrate
that $n$ can be adjusted up to 4$\times10^{14}$cm$^{-2}$ for both electrons and
holes. The measured sample resistivity $\rho$ increases linearly with
temperature $T$ in the high temperature limit, indicating that a
quasi-classical phonon distribution is responsible for the electron scattering.
As $T$ decreases, the resistivity decreases more rapidly following $\rho (T)
\sim T^{4}$. This low temperature behavior can be described by a
Bloch-Gr\""{u}neisen model taking into account the quantum distribution of the
2-dimensional acoustic phonons in graphene. We map out the density dependence
of the characteristic temperature $\Theta_{BG}$ defining the cross-over between
the two distinct regimes, and show, that for all $n$, $\rho(T)$ scales as a
universal function of the normalized temperature $T/\Theta_{BG}$.",1009.2988v1
2010-11-02,Chirality-dependent phonon-limited resistivity in multiple layers of graphene,"We develop a theory for the temperature and density dependence of
phonon-limited resistivity $\rho(T)$ in bilayer and multilayer graphene, and
compare with the corresponding monolayer result. For the unscreened case, we
find $\rho \approx C T$ with $C \propto v_{\rm F}^{-2}$ in the high-temperature
limit, and $\rho \approx A T^4$ with $A \propto v_{\rm F}^{-2} k_{\rm F}^{-3}$
in the low-temperature Bloch-Gr\""uneisen limit, where $v_{\rm F}$ and $k_{\rm
F}$ are Fermi velocity and Fermi wavevector, respectively. If screening effects
are taken into account, $\rho \approx C T$ in the high-temperature limit with a
renormalized $C$ which is a function of the screening length, and $\rho \approx
A T^6$ in the low-temperature limit with $A \propto k_{\rm F}^{-5}$ but
independent of $v_{\rm F}$. These relations hold in general with $v_{\rm F}$
and a chiral factor in $C$ determined by the specific chiral band structure for
a given density.",1011.0741v2
2011-07-21,Observations of two-dimensional quantum oscillations and ambipolar transport in the topological insulator Bi2Se3 achieved by Cd doping,"We present a defect-engineering strategy to optimize the transport properties
of the topological insulator Bi2Se3 to show a high bulk resistivity and clear
quantum oscillations. Starting with a p-type Bi2Se3 obtained by combining Cd
doping and a Se-rich crystal-growth condition, we were able to observe a
p-to-n-type conversion upon gradually increasing the Se vacancies by post
annealing. With the optimal annealing condition where a high level of
compensation is achieved, the resistivity exceeds 0.5 Ohmcm at 1.8 K and we
observed two-dimensional Shubnikov-de Haas oscillations composed of multiple
frequencies in magnetic fields below 14 T.",1107.4178v2
2016-04-13,Long Term Performance Studies of Large Oil-Free Bakelite Resistive Plate Chamber,"Several high energy physics and neutrino physics experiments worldwide
require large-size RPCs to cover wide acceptances. The muon tracking systems in
the Iron calorimeter (ICAL) in the INO experiment, India and the near detector
in DUNE at Fermilab are two such examples. A (240 cm $\times$ 120 cm $\times$
0.2 cm) bakelite RPC has been built and tested at Variable Energy Cyclotron
Centre, Kolkata, using indigenous materials procured from the local market. No
additional lubricant, like oil has been used on the electrode surfaces for
smoothening. The chamber is in operation for $>$ 365 days. We have tested the
chamber for its long term operation. The leakage current, bulk resistivity,
efficiency, noise rate and time resolution of the chamber have been found to be
quite stable during the testing peroid. It showed an efficiency $>$ 95$\%$ with
an average time resolution of $\sim$0.83 ns at the point of measurement at 9000
V throughout the testing period. Details of the long term performance of the
chamber have been discussed.",1604.03668v2
2016-07-25,Influencia del potencial de polarización en la deposición de películas delgadas de NiO,"Nickel oxide (NiO) is a binary compound with a lot of applications in the
present technology. NiO thin films were deposited by reactive sputtering
magnetron under several voltage biases applied in the glass substrates (0, 50,
100, 200, 300, 400 and 500 V). Films were characterized by profilometry, X-ray
diffraction, elemental composition and electrical resistivity at room
temperature and at low temperatures. The present work showed that despite the
insulating behavior of substrate the residual stress was reduced at high biases
and the (111) texture was promoted. Electrical resistivity was reduced at high
bias and at low temperatures thermal activation of p-type conduction was
detected.",1607.07391v1
2017-01-29,Built-in Homojunction Dominated Intrinsically Rectifying-Resistive Switching in NiO Nanodots for Selection Device-Free Memory Application,"The intrinsically rectifying-resistive switching (IR-RS) has been regarded as
an effective way to address the crosstalk issue, due to the Schottky diodes
formed at the metal/oxide interfaces in the ON states to suppress the sneak
current at reverse biases. In this letter, we report for the first time another
type of IR-RS that is related to the built-in homojunction. The IR-RS study was
usually limited to macroscopic samples with micron-order pad-type electrodes,
while this work is on NiO nanodots fabricated with ultrathin
anodic-aluminum-oxide templates and acting as nanoscaled analogs of real
devices. The NiO nanodots show high storage density and high uniformity, and
the IR-RS behaviors are of good device performances in terms of retention,
endurance, switching ratio and rectification ratio. The feasibility of the
IR-RS for selection device-free memory application has been demonstrated, by
calculating the maximum crossbar array size under the worst-case scenario to be
3 Mbit.",1702.05665v1
2018-02-20,Perturbation theories behind thermal mode spectroscopy for high-accuracy measurement of thermal diffusivity of solids,"Thermal mode spectroscopy (TMS) has been recently proposed for accurately
measuring thermal diffusivity of solids from a temperature decay rate of a
specific thermal mode selected by three- dimensional (anti)nodal information
[Phys. Rev. Lett., 117, 195901 (2016)]. In this paper, we find out the
following advantages of TMS by use of perturbation analyses. First, TMS is
applicable to the measurement of high thermal diffusivity with a small size
specimen. Second, it is less affected by thermally resistive films on a
specimen in the sense that the resistance at the interface does not affect the
first-order correction of thermal diffusivity. Third, it can perform doubly
accurate measurement of the thermal diffusivity specified at a thermal
equilibrium state even if the diffusivity depends on temperature in the sense
that the measurement can be performed within tiny temperature difference from
the given state and that the decay rate of the slowest decaying mode is not
affected by the dependence.",1802.07378v2
2020-02-28,Hydrodynamic and ballistic transport over large length scales in GaAs/AlGaAs,"We study hydrodynamic and ballistic transport regimes through nonlocal
resistance measurements and high-resolution kinetic simulations in a mesoscopic
structure on a high-mobility two-dimensional electron system in a GaAs/AlGaAs
heterostructure. We evince the existence of collective transport phenomena in
both regimes and demonstrate that negative nonlocal resistances and current
vortices are not exclusive to only the hydrodynamic regime. The combined
experiments and simulations highlight the importance of device design,
measurement schemes and one-to-one modeling of experimental devices to
demarcate various transport regimes.",2002.12806v3
2019-03-07,Fe-Sn nanocrystalline films for flexible magnetic sensors with high thermal stability,"The interplay of magnetism and spin-orbit coupling on an Fe kagome lattice in
Fe3Sn2 crystal produces a unique band structure leading to an order of
magnitude larger anomalous Hall effect than in conventional ferromagnetic
metals. In this work, we demonstrate that Fe-Sn nanocrystalline films also
exhibit a large anomalous Hall effect, being applicable to magnetic sensors
that satisfy both high sensitivity and thermal stability. In the films prepared
by a co-sputtering technique at room temperature, the partial development of
crystalline lattice order appears as nanocrystals of Fe-Sn kagome layer. The
tangent Hall angle, the ratio of Hall resistivity to longitudinal resistivity,
is largely enhanced in the optimal alloy composition of close to Fe3Sn2,
exemplifying the kagome origin even though the films are composed of
nanocrystal and amorphous-like domains. These ferromagnetic Fe-Sn films possess
great advantages as a Hall sensor over semiconductors in thermal stability
owing to the weak temperature dependence of the anomalous Hall responses.
Moreover, the room-temperature fabrication enables us to develop a mechanically
flexible Hall sensor on an organic substrate. These demonstrations manifest the
potential of kagome metal as an untapped reservoir for designing new functional
devices.",1903.02689v1
2021-01-25,Statics and Dynamics of Space-Charge-Layers in Polarized Inorganic Solid Electrolytes,"The quest for safe high-energy batteries with ""5V-class"" cathodes and lithium
metal anodes drives research into solid electrolytes. However, reasons for the
large charge transfer resistances -- the major bottleneck of all-solid-state
batteries -- are still debated. In this article, we explore the processes in
incompressible solid electrolytes between blocking electrodes by theory-based
continuum modeling and numerical simulations. We investigate the experimentally
observed wide space-charge-zones in solid electrolytes, which are a possible
cause for the high interfacial resistances. On time scales relevant for battery
applications, we reduce our model equations. Analytic and numeric calculations
predict and study the actual structure of space-charge-layers in solid
electrolytes. To illustrate these dynamics and validate our model,
computational results are presented and compared with experimental
observations. Analog to semiconductors, we determine the material dependent,
asymmetric space-charge-layer width in the low temperature limit approximately.
This allows us to make an explicit statement about the influence of defect
concentrations and dielectric properties on the width of the
space-charge-layers in homogeneous solid electrolytes.",2101.10294v1
2015-06-01,High-pressure study of the Weyl semimetal NbAs,"We performed a series of high-pressure synchrotron X-ray diffraction (XRD)
and resistance measurements on the Weyl semimetal NbAs. The crystal structure
remains stable up to 26 GPa according to the powder XRD data. The resistance of
NbAs single crystal increases monotonically with pressure at low temperature.
Up to 20 GPa, no superconducting transition is observed down to 0.3 K. These
results show that the Weyl semimetal phase is robust in NbAs, and applying
pressure is not a good way to get a topological superconductor from a Weyl
semimetal.",1506.00374v2
2020-08-14,High-Mobility Carriers Induced by Chemical Doping in the Candidate Nodal-Line Semimetal CaAgP,"We report the electronic properties of single crystals of candidate
nodal-line semimetal CaAgP. The transport properties of CaAgP are understood
within the framework of a hole-doped nodal-line semimetal. In contrast,
Pd-doped CaAgP shows a drastic increase of magnetoresistance at low magnetic
fields and a strong decrease of electrical resistivity at low temperatures
probably due to weak antilocalization. Hall conductivity data indicated that
the Pd-doped CaAgP has not only hole carriers induced by the Pd doping, but
also high-mobility electron carriers in proximity of the Dirac point.
Electrical resistivity of Pd-doped CaAgP also showed a superconducting
transition with onset temperature of 1.7-1.8 K.",2008.06188v1
2020-12-19,Anomalous behavior in high-pressure carbonaceous sulfur hydride,"A new experimental study by Snider et al. [Nature 586, 373-377 (2020)]
reported behavior in a high-pressure carbon-sulfur-hydrogen system that has
been interpreted by the authors as superconductivity at room temperature. The
sudden drop of electrical resistance at a critical temperature and the change
of the R vs. T behavior with an applied magnetic field point to
superconductivity. This is a very exciting study in one of the most important
areas of science, hence, it is crucial for the community to investigate these
findings and hopefully reproduce these results. In this comment, we present
calculations that expand upon the arguments put forth by Hirsch and Marsiglio
[arXiv:2010.10307], and offer some speculations about physical mechanisms that
might explain the observed data. In agreement with Hirsch and Marsiglio, we
show that there are errors in the analysis presented in the experimental paper,
and with the correct analysis, the reported R vs. T data significantly deviate
from the expected behavior. In particular, the extremely sharp change in
resistance at the superconducting transition is not consistent with a strongly
type II superconductor.",2012.10771v3
2021-02-23,High magnetic field induced crossover from the Kondo to Fermi liquid behavior in 1$T$-VTe$_{2}$ single crystals,"The magnetic and magnetotransport properties of metallic 1$T$-VTe$_{2}$
single crystals were investigated at temperatures from 1.3 to 300 K and in
magnetic fields up to 35 T. Upon applying a high magnetic field, it is found
that the electrical resistivity displays a crossover from the logarithmic
divergence of the single-impurity Kondo effect to the Fermi liquid behavior at
low temperatures. The Brillouin scale of the negative magnetoresistivity above
the Kondo temperature $T_{\rm{K}}$ = 12 K indicates that the Kondo features
originate from intercalated V ions, with $S$ = 1/2. Both magnetic
susceptibility and Hall effect show an anomaly around $T_{\rm{K}}$. By using
the modified Hamann expression we successfully describe the
temperature-dependent resistivity under various magnetic fields, which shows
the characteristic peak below $T_{\rm{K}}$ due to the splitting of the Kondo
resonance.",2102.11444v1
2021-02-26,Crossover from itinerant to localized states in the thermoelectric oxide [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$],"The layered cobaltite [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$], often expressed as
the approximate formula Ca$_3$Co$_4$O$_9$, is a promising candidate for
efficient oxide thermoelectrics but an origin of its unusual thermoelectric
transport is still in debate. Here we investigate \textit{in-plane} anisotropy
of the transport properties in a broad temperature range to examine the
detailed conduction mechanism. The in-plane anisotropy between $a$ and $b$ axes
is clearly observed both in the resistivity and the thermopower, which is
qualitatively understood with a simple band structure of the triangular lattice
of Co ions derived from the angle-resolved photoemission spectroscopy
experiments. On the other hand, at high temperatures, the anisotropy becomes
smaller and the resistivity shows a temperature-independent behavior, both of
which indicate a hopping conduction of localized carriers. Thus the present
observations reveal a crossover from low-temperature itinerant to
high-temperature localized states, signifying both characters for the enhanced
thermopower.",2102.13250v1
2021-11-03,Devices for Thermal Conductivity Measurements of Electroplated Bi for X-ray TES Absorbers,"Electroplated Bismuth (Bi) is commonly used in Transition-Edge Sensors (TESs)
for X-rays because of its high stopping power and low heat capacity.
Electroplated Bi is usually grown on top of another metal that acts as seed
layer, typically gold (Au), making it challenging to extrapolate its
thermoelectric properties. In this work, we present four-wire resistance
measurement structures that allow us to measure resistance as a function of
temperature of electroplated Bi independently of Au. The results show that the
thermal conductivity of the Bi at 3 K is high enough to guarantee the correct
thermalization of X-ray photons when used as an absorber for TESs.",2111.02503v1
2021-11-09,Absence of decoherence in the electron-wall system,"Decoherence is associated with a dissipative environment as described by the
Caldeira-Leggett equation. Anglin and Zurek predicted that a resistive surface
could act as such a dissipative environment for a free electron wave passing
close to it. We scrutinize Zurek's and other promising decoherence theoretical
models by observing electrons passing by an optically excited GaAs surface and
through a gold channel. The high resistivity of the GaAs surface and close
proximity to the gold surface leads to strong decoherence within these
decoherence models. In contradistinction, the observed contrast is high in our
electron diffraction patterns. This implies lower decoherence rates than
suggested by these models, making electron-matter-wave-guides and other
technologies, where quantum coherence of electrons close to materials is
important, a possibility",2111.05246v1
2022-06-10,Fabrication of uniformly doped graphene quantum Hall arrays with multiple quantized resistance outputs,"In this work, limiting factors for developing metrologically useful arrays
from epitaxial graphene on SiC are lifted with a combination of
centimeter-scale, high-quality material growth and the implementation of
superconducting contacts. Standard devices for metrology have been restricted
to having a single quantized value output based on the $\nu$ = 2 Landau level.
With the demonstrations herein of devices having multiple outputs of quantized
values available simultaneously, these versatile devices can be used to
disseminate the ohm globally. Such devices are designed to give access to
quantized resistance values over the range of three orders of magnitude,
starting as low as the standard value of approximately 12.9 k$\Omega$ and
reaching as high as 1.29 M$\Omega$. Several experimental methods are used to
assess the quality and versatility of the devices, including standard lock-in
techniques and Raman spectroscopy.",2206.05098v1
2022-06-29,On the depletion behaviour of low-temperature covalently bonded silicon sensor diodes,"Low temperature covalent direct wafer-wafer bonding allows for the fusion of
multiple semiconductor wafers without any additional material at the bonding
interface. In the context of particle pixel detectors this might provide an
alternative to bump-bonding for joining sensors to readout chips. Previous
investigations have shown that the amorphous layer formed at the interface
during bonding is detrimental to charge propagation. To investigate the
influence of the bonding interface on signal collection we have fabricated
custom test structures by bonding high-resistivity N to high-resistivity P-type
silicon wafers thus forming P-N junctions. Scanning transmission electron
microscopy shows indeed the formation of ca. 3nm wide amorphous layer at the
interface. Using a scanning transient current technique (TCT) setup we were
able to record generated signals. Illuminating our sample with light of
different wavelengths and from different sides, indicates that the P side of
the bonded structures can be fully depleted, but not the N side. This indicates
a strongly asymmetric depletion behaviour which we attribute to the presence of
the bonding interface.",2206.14717v2
2022-07-26,Engineering Surface Oxygen Vacancies in $\mathrm{SrTiO_3}$ to Form a High Mobility and Transparent Quasi Two dimensional Electron System,"Quasi-two-dimensional electron systems (q-2DES) are formed in various
hetero-structures, including oxide interfaces. Oxygen vacancies (OVs) in oxides
like $\mathrm{SrTiO_3}$ are known to produce electronic carriers. A novel way
to produce $\mathrm{SrTiO_{3-\delta}}$ on the surface using a low-energy
$\mathrm{H_2}$ plasma is shown here. It results in a q-2DES with mobility as
high as $\mu \sim 20,000 \; cm^2V^{-1}s^{-1}$, displaying quantum oscillations
in magneto-resistance. We can achieve a sharper or weaker confinement potential
by adjusting the process pressure. The system with sharper confinement displays
clearer quantum oscillations and Kondo-like temperature dependence of
resistance. OVs close to the surface behaving like a correlated Anderson
impurity is responsible for the Kondo behaviour. Quantum oscillations are less
prominent in the weakly confined system. A cross-over from weak-localization to
anti-localization with temperature is seen, but no Kondo behavior. The process
also results in a transparent conductor amenable to lithographic patterning.
This conductor's standard figure of merit is comparable to poly-crystalline ITO
films in the visible regime and extends with similar performance into the
$\lambda$ $\sim 1.5$ $\mu m$ telecommunication wavelength.",2207.12933v1
2022-09-05,Growth of rare-earth monopnictide DySb single crystal by novel Self-flux method,"This report presents a new synthesis protocol for the single crystal growth
of rare earth monopnictide DySb by self-flux technique. A detailed structural,
transport and magnetic characterization have been done using X-Ray diffraction
(XRD), High resolution X-Ray diffraction (HRXRD), resistivity and magnetization
measurements respectively. The Rietveld refinement of powder XRD pattern
confirms that the grown crystal is in single phase and crystallizes in space
group Fm3m(225) of rock-salt type crystal structure. HRXRD on cleaved crystal
confirms the single crystalline nature while rocking curve analysis reveals the
high quality of the grown crystal. Temperature dependent resistivity and
magnetization measurements show a transition at 9.7K from paramagnetic (PM) to
antiferromagnetic (AFM) state.",2209.01930v1
2022-10-27,Single photon detection performance of highly disordered NbTiN thin films,"We experimentally investigated the detection performance of highly disordered
NbxTi1-xN based superconducting nanowire single photon detectors (SNSPDs). The
dependence on the composition of the transition temperature Tc for NbxTi1-xN
films show a dome-like behavior on the Nb content, with a maximal Tc at
xNb~0.65 , and the Nb0.65Ti0.35N films also combine relatively large sheet
resistance and intermediate residual resistivity ratio. Moreover, 60-nm-wide
and 7-nm-thick Nb0.65Ti0.35N nanowires show a switching current as high as 14.5
uA, and saturated intrinsic detection efficiency with a plateau of more than 2
uA at 2.4 K. Finally, the corresponding SNSPDs on an alternative SiO2/Ta2O5
dielectric mirror showed a system detection efficiency of approximately 92% for
1550 nm photons, and the timing jitter is around 26 ps. Our results demonstrate
that the highly disordered NbxTi1-xN films are promising for fabricating SNSPDs
for near- and middle-infrared single photons with high detection efficiency and
low timing jitter.",2210.15215v1
2022-11-24,Development of Hybrid Resistive Plate Chambers,"Resistive Plate Chambers (RPCs) are essential active media of large-scale
experiments as part of the muon systems and (semi-)digital hadron calorimeters.
Among the several outstanding issues associated with the RPCs, the loss of
efficiency for the detection of particles when subjected to high particle
fluxes, and the limitations associated with the common RPC gases can be listed.
In order to address the latter issue, we developed novel RPC designs with
special anode plates coated with high secondary electron emission yield
materials such as Al$_2$O$_3$ and TiO$_2$. The proof of principle was obtained
for various designs and is in progress for the rest. The idea was initiated
following the achievements on the development of the novel 1-glass RPCs.
  Here we report on the construction of various different RPC designs, and
their performance measurements in laboratory tests and with particle beams; and
discuss the future test plans.",2211.13796v2
2023-09-11,Experimental realization of a high Curie temperature CoFeRuSn quaternary Heusler alloy for spintronic applications,"We synthesize CoFeRuSn equiatomic quaternary Heusler alloy using arc-melt
technique and investigate its structural, magnetic and transport properties.
The room temperature powder X-ray diffraction analysis reveals that CoFeRuSn
crystallizes in cubic crystal structure with small amount of DO3 - disorder.
The field dependence of magnetization shows non-zero but small hysteresis and
saturation behavior up to room temperature, indicating soft ferromagnetic
nature of CoFeRuSn. The magnetic moment estimated from the magnetization data
is found to be 4.15 {\mu}B / f.u., which is slightly less than the expected
Slater-Pauling rule. The deviation in the value of experimentally observed
moment from the theoretical value might be due to small disorder in the
crystal. The low temperature fit to electrical resistivity data show absence of
quadratic temperature dependence of resistivity, suggesting half-metallic
behavior of CoFeRuSn. The high Curie temperature and possible half-metallic
behavior of CoFeRuSn make it a highly promising candidate for room temperature
spintronic applications.",2309.05493v1
2018-04-11,Extremely large magnetoresistance in topologically trivial semimetal $α$-WP$_2$,"Extremely large magnetoresistance (XMR) was recently discovered in many
non-magnetic materials, while its underlying mechanism remains poorly
understood due to the complex electronic structure of these materials. Here, we
report an investigation of the $\alpha$-phase WP$_2$, a topologically trivial
semimetal with monoclinic crystal structure (C2/m), which contrasts to the
recently discovered robust type-II Weyl semimetal phase in $\beta$-WP$_2$. We
found that $\alpha$-WP$_2$ exhibits almost all the characteristics of XMR
materials: the near-quadratic field dependence of MR, a field-induced up-turn
in resistivity following by a plateau at low temperature, which can be
understood by the compensation effect, and high mobility of carriers confirmed
by our Hall effect measurements. It was also found that the normalized MRs
under different magnetic fields has the same temperature dependence in
$\alpha$-WP$_2$, the Kohler scaling law can describe the MR data in a wide
temperature range, and there is no obvious change in the anisotropic parameter
$\gamma$ value with temperature. The resistance polar diagram has a peanut
shape when field is rotated in $\textit{ac}$ plane, which can be understood by
the anisotropy of Fermi surface. These results indicate that both
field-induced-gap and temperature-induced Lifshitz transition are not the
origin of up-turn in resistivity in the $\alpha$-WP$_2$ semimetal. Our findings
establish $\alpha$-WP$_2$ as a new reference material for exploring the XMR
phenomena.",1804.03879v1
2019-05-02,Robust axion insulator and Chern insulator phases in a two-dimensional antiferromagnetic topological insulator,"The intricate interplay between nontrivial topology and magnetism in
two-dimensional (2D) materials has led to the emergence of many novel phenomena
and functionalities. An outstanding example is the quantum anomalous Hall (QAH)
effect, which was realized in magnetically doped topological insulators (TIs)
in the absence of magnetic field. Recently, the layered van der Waals compound
MnBi2Te4 has been theoretically predicted and experimentally verified to be a
TI with interlayer antiferromagnetic (AFM) order. It is a rare stoichiometric
material with coexisting topology and magnetism, thus represents a perfect
building block for complex topological-magnetic structures. Here we investigate
the quantum transport behaviors of both bulk crystal and exfoliated MnBi2Te4
flakes in a field effect transistor geometry. In the 6 septuple layers (SLs)
device tuned into the insulating regime, we observe a large longitudinal
resistance and zero Hall plateau, which are characteristic of the axion
insulator state. The robust axion insulator state occurs in zero magnetic
field, over a wide magnetic field range, and at relatively high temperatures.
Moreover, a moderate magnetic field drives a quantum phase transition from the
axion insulator phase to a Chern insulator phase with zero longitudinal
resistance and quantized Hall resistance h/e2 (h is the Plank constant and e is
the elemental charge). These results pave the road for using even-number-SL
MnBi2Te4 to realize the quantized topological magnetoelectric effect and axion
electrodynamics in condensed matter systems.",1905.00715v2
2019-04-24,Antisymmetric magnetoresistance in van der Waals Fe3GeTe2/graphite/Fe3GeTe2 tri-layer heterostructures,"Van der Waals (vdW) ferromagnetic materials are rapidly establishing
themselves as effective building blocks for next generation spintronic devices.
When layered with non-magnetic vdW materials, such as graphene and/or
topological insulators, vdW heterostructures can be assembled (with no
requirement for lattice matching) to provide otherwise unattainable device
structures and functionalities. We report a hitherto rarely seen antisymmetric
magnetoresistance (MR) effect in van der Waals heterostructured
Fe3GeTe2/graphite/Fe3GeTe2 devices. Unlike conventional giant magnetoresistance
(GMR) which is characterized by two resistance states, the MR in these vdW
heterostructures features distinct high, intermediate and low resistance
states. This unique characteristic is suggestive of underlying physical
mechanisms that differ from those observed before. After theoretical
calculations, the three resistance behavior was attributed to a spin momentum
locking induced spin polarized current at the graphite/FGT interface. Our work
reveals that ferromagnetic heterostructures assembled from vdW materials can
exhibit substantially different properties to those exhibited by similar
heterostructures grown in vacuum. Hence, it highlights the potential for new
physics and new spintronic applications to be discovered using vdW
heterostructures.",1904.10588v2
2007-03-09,Nanometer-Scale Materials Contrast Imaging with a Near-Field Microwave Microscope,"We report topography-free materials contrast imaging on a nano-fabricated
Boron-doped Silicon sample measured with a Near-field Scanning Microwave
Microscope over a broad frequency range. The Boron doping was performed using
the Focus Ion Beam technique on a Silicon wafer with nominal resistivity of 61
Ohm.cm. A topography-free doped region varies in sheet resistance from
1000Ohm/Square to about 400kOhm/Square within a lateral distance of 4
micrometer. The qualitative spatial-resolution in sheet resistance imaging
contrast is no worse than 100 nm as estimated from the frequency shift signal.",0703241v1
2010-03-15,A Memadmittance Systems Model for Thin Film Memory Materials,"In 1971 the memristor was originally postulated as a new non-linear circuit
element relating the time integrals of current and voltage. More recently
researchers at HPLabs have linked the theoretical memristor concept to
resistance switching behavior of TiO(2-x) thin films. However, a variety of
other thin film materials exhibiting memory resistance effects have also been
found to exhibit a memory capacitance effect. This paper proposes a
memadmittance (memory admittance) systems model which attempts to consolidate
the memory capacitance effects with the memristor model. The model produces
equations relating the cross-sectional area of conductive bridges in resistive
switching films to shifts in capacitance.",1003.2842v1
2018-09-06,Estimation of the electrical and thermal contact resistances and thermoemf of thermoelectric material-metal transient contact layer due to semiconductor surface rougness,"The impact of semiconductor surface roughness on the electrical and thermal
contact resistances and thermoEMF of thermoelectric material (TEM)-metal
transient contact layer is studied theoretically. The distribution of hollows
and humps on the rough surface is simulated by the truncated Gaussian
distribution. The impact of distribution parameters on the electrical contact
resistance and thermoEMF of thermoelectric material-metal contact is studied.",1809.02504v1
2022-03-30,STeP-CiM: Strain-enabled Ternary Precision Computation-in-Memory based on Non-Volatile 2D Piezoelectric Transistors,"We propose 2D Piezoelectric FET (PeFET) based compute-enabled non-volatile
memory for ternary deep neural networks (DNNs). PeFETs consist of a material
with ferroelectric and piezoelectric properties coupled with Transition Metal
Dichalcogenide channel. We utilize (a) ferroelectricity to store binary bits
(0/1) in the form of polarization (-P/+P) and (b) polarization dependent
piezoelectricity to read the stored state by means of strain-induced bandgap
change in Transition Metal Dichalcogenide channel. The unique read mechanism of
PeFETs enables us to expand the traditional association of +P (-P) with low
(high) resistance states to their dual high (low) resistance depending on read
voltage. Specifically, we demonstrate that +P (-P) stored in PeFETs can be
dynamically configured in (a) a low (high) resistance state for positive read
voltages and (b) their dual high (low) resistance states for negative read
voltages, without afflicting a read disturb. Such a feature, which we name as
Polarization Preserved Piezoelectric Effect Reversal with Dual Voltage Polarity
(PiER), is unique to PeFETs and has not been shown in hitherto explored
memories. We leverage PiER to propose a Strain-enabled Ternary Precision
Computation-in-Memory (STeP-CiM) cell with capabilities of computing the scalar
product of the stored weight and input, both of which are represented with
signed ternary precision. Further, using multi word-line assertion of STeP-CiM
cells, we achieve massively parallel computation of dot products of signed
ternary inputs and weights. Our array level analysis shows 91% lower delay and
improvements of 15% and 91% in energy for in-memory multiply-and-accumulate
operations compared to near-memory design approaches based on SRAM and PeFET
respectively. STeP-CiM exhibits upto 8.91x improvement in performance and 6.07x
average improvement in energy over SRAM/PeFET based near-memory design.",2203.16416v1
2013-01-28,Can high risk fungicides be used in mixtures without selecting for fungicide resistance?,"Fungicide mixtures produced by the agrochemical industry often contain
low-risk fungicides, to which fungal pathogens are fully sensitive, together
with high-risk fungicides known to be prone to fungicide resistance. Can these
mixtures provide adequate disease control while minimizing the risk for the
development of resistance? We present a population dynamics model to address
this question. We found that the fitness cost of resistance is a crucial
parameter to determine the outcome of competition between the sensitive and
resistant pathogen strains and to assess the usefulness of a mixture. If
fitness costs are absent, then the use of the high-risk fungicide in a mixture
selects for resistance and the fungicide eventually becomes nonfunctional. If
there is a cost of resistance, then an optimal ratio of fungicides in the
mixture can be found, at which selection for resistance is expected to vanish
and the level of disease control can be optimized.",1301.6561v2
2005-12-15,Introduction to tensorial resistivity probability tomography,"The probability tomography approach developed for the scalar resistivity
method is here extended to the 2D tensorial apparent resistivity acquisition
mode. The rotational invariant derived from the trace of the apparent
resistivity tensor is considered, since it gives on the datum plane anomalies
confined above the buried objects. Firstly, a departure function is introduced
as the difference between the tensorial invariant measured over the real
structure and that computed for a reference uniform structure. Secondly, a
resistivity anomaly occurrence probability (RAOP) function is defined as a
normalised crosscorrelation involving the experimental departure function and a
scanning function derived analytically using the Frechet derivative of the
electric potential for the reference uniform structure. The RAOP function can
be calculated in each cell of a 3D grid filling the investigated volume, and
the resulting values can then be contoured in order to obtain the 3D
tomographic image. Each non-vanishing value of the RAOP function is interpreted
as the probability which a resistivity departure from the reference resistivity
obtain in a cell as responsible of the observed tensorial apparent resistivity
dataset on the datum plane. A synthetic case shows that the highest RAOP values
correctly indicate the position of the buried objects and a very high spacial
resolution can be obtained even for adjacent objects with opposite resistivity
contrasts with respect to the resistivity of the hosting matrix. Finally, an
experimental field case dedicated to an archaeological application of the
resistivity tensor method is presented as a proof of the high resolution power
of the probability tomography imaging, even when the data are collected in
noisy open field conditions.",0512147v1
2014-07-24,Macro- and microscopic properties of strontium doped indium oxide,"Solid state synthesis and physical mechanisms of electrical conductivity
variation in polycrystalline, strontium doped indium oxide In2O3:(SrO)x were
investigated for materials with different doping levels at different
temperatures (T=20-300 C) and ambient atmosphere content including humidity and
low pressure. Gas sensing ability of these compounds as well as the sample
resistance appeared to increase by 4 and 8 orders of the magnitude,
respectively, with the doping level increase from zero up to x=10%. The
conductance variation due to doping is explained by two mechanisms:
acceptor-like electrical activity of Sr as a point defect and appearance of an
additional phase of SrIn2O4. An unusual property of high level (x=10%) doped
samples is a possibility of extraordinarily large and fast oxygen exchange with
ambient atmosphere at not very high temperatures (100-200 C). This peculiarity
is explained by friable structure of crystallite surface. Friable structure
provides relatively fast transition of samples from high to low resistive state
at the expense of high conductance of the near surface layer of the grains.
Microscopic study of the electro-diffusion process at the surface of oxygen
deficient samples allowed estimation of the diffusion coefficient of oxygen
vacancies in the friable surface layer at room temperature as 3x10^(-13)
cm^2/s, which is by one order of the magnitude smaller than that known for
amorphous indium oxide films.",1407.6471v1
2015-03-29,Universal low-temperature Ohmic contacts for quantum transport in transition metal dichalcogenides,"Low carrier mobility and high electrical contact resistance are two major
obstacles prohibiting explorations of quantum transport in TMDCs. Here, we
demonstrate an effective method to establish low-temperature Ohmic contacts in
boron nitride encapsulated TMDC devices based on selective etching and
conventional electron-beam evaporation of metal electrodes. This method works
for most extensively studied TMDCs in recent years, including MoS2, MoSe2,
WSe2, WS2, and 2H-MoTe2. Low electrical contact resistance is achieved at 2 K.
All of the few-layer TMDC devices studied show excellent performance with
remarkably improved field-effect mobilities ranging from 2300 cm2/V s to 16000
cm2/V s, as verified by the high carrier mobilities extracted from Hall effect
measurements. Moreover, both high-mobility n-type and p-type TMDC channels can
be realized by simply using appropriate contact metals. Prominent Shubnikov-de
Haas oscillations have been observed and investigated in these high-quality
TMDC devices.",1503.08427v2
2017-04-13,"High-pressure phase diagram, structural transitions, and persistent non-metallicity of BaBiO$_3$: theory and experiment","BaBiO$_3$ is a mixed-valence perovskite which escapes the metallic state
through a Bi valence (and Bi-O bond) disproportionation or CDW distortion,
resulting in a semiconductor with a gap of 0.8 eV at zero pressure. The
evolution of structural and electronic properties at high pressure is, however,
largely unknown. Pressure, one might have hoped, could reduce the
disproportionation, making the two Bi ions equivalent and bringing the system
closer to metallicity or even to superconductivity, such as is attained at
ambient pressure upon metal doping. We address the high-pressure phase diagram
of pristine BaBiO$_3$ by ab initio DFT calculations based on GGA and hybrid
functionals in combination with crystal structure prediction methods based on
evolutionary algorithms, molecular dynamics and metadynamics. The calculated
phase diagram from 0 to 50 GPa indicates that pristine BaBiO$_3$ resists
metallization under pressure, undergoing instead at room temperature structural
phase transitions from monoclinic \textit{I2/m} to nearly tetragonal
\textit{P-1} at 7 GPa, possibly to monoclinic \textit{C2/m} at 27 GPa, and to
triclinic \textit{P1} at 43 GPa. Remarkably, all these phases sustain and in
fact increase the inequivalence of two Bi neighboring sites and of their Bi-O
bonds and, in all cases except semimetallic \textit{C2/m}, the associated
insulating character. We then present high-pressure resistivity data which
generally corroborate these results, and show that the insulating character
persists at least up to 80 GPa, suggesting that the \textit{C2/m} phase is
probably an artifact of the small computational cell.",1704.04098v1
2019-11-18,Effect of particle contact on the electrical performance of NTC-epoxy composite thermistors,"As demand rises for flexible electronics, traditionally prepared sintered
ceramic sensors must be transformed into fully new sensor materials that can
bend and flex in use and integration. Negative temperature coefficient of
resistance (NTC) ceramic thermistors are preferred temperature sensors for
their high accuracy and excellent stability, yet their high stiffness and high
temperature fabrication process limits their use in flexible electronics. Here,
a low stiffness thermistor based on NTC ceramic particles of micron size
embedded in an epoxy polymer matrix is reported. The effect of
particle-to-particle contact on electrical performance is studied by arranging
the NTC particles in the composite films in one of three ways: 1) Low particle
contact, 2) Improved particle contact perpendicular to the electrodes and 3)
dispersing high particle contact agglomerated clumps throughout the polymer. At
50 vol.\% of agglomerated NTC particles, the composite films exhibit a
$\beta$-value of 2069 K and a resistivity, $\rho$, of 3.3$\cdot 10^5$
$\Omega$m, 4 orders of magnitude lower than a randomly dispersed composite at
identical volume. A quantitative analysis shows that attaining a predominantly
parallel connectivity of the NTC particles and polymer is a key parameter in
determining the electrical performance of the composite film.",1911.07468v2
2021-03-11,Review on quasi-2D square planar nickelates,"In strongly correlated materials, lattice, charge, spin and orbital degrees
of freedom interact with each other, leading to emergent physical properties
such as superconductivity, colossal magnetic resistance and metal-insulator
transition. Quasi-2D square planar nickelates, Rn+1NinO2n+2 (R=rare earth, n=2,
3...), are of significant interest and long sought for cuprate analogue due to
the 3d9 electronic configuration of Ni+, the same as the active ion Cu2+ in the
high-Tc superconducting cuprates. The field has attracted intense attention
since 2019 due to the discovery of superconductivity in thin films of
Nd0.8Sr0.2NiO2, although no superconductivity has been reported in bulk
polycrystalline powders. Herein, we review the synthesis of polycrystalline
powders of quasi-2D square planar nickelates through topotactic reduction of
parent compounds that are synthesized via solid state reaction, precursor
method, high pressure floating zone method and high-pressure flux method. We
emphasize single crystal preparation using the high-pressure floating zone
techniques. We discuss their crystal structure and physical properties
including resistivity, magnetic susceptibility and heat capacity. We highlight
the cuprate-like physics, including charge/spin stripes and large orbital
polarization, identified in single crystals of R4Ni3O8 (R=La and Pr) combining
synchrotron X-ray/neutron single crystal diffraction and density functional
theory calculations. Furthermore, the challenges and possible research
directions of this fast-moving field in the future are briefly discussed.",2103.06674v1
2022-05-25,Stranger than Metals,"Although the resistivity in traditional metals increases with temperature,
its $T$ dependence vanishes at low or high temperature, albeit for different
reasons. Here, we review a class of materials, known as \lq strange' metals,
that can violate both principles. In materials exhibiting such behavior, the
change in slope of the resistivity as the mean free path drops below the
lattice constant, or as $T \rightarrow 0$, can be imperceptible, suggesting
complete continuity between the charge carriers at low and high $T$. Since
particles cannot scatter at length scales shorter than the interatomic spacing,
strange metallicity calls into question the relevance of locality and a
particle picture of the underlying current. This review focuses on transport
and spectroscopic data on candidate strange metals with an eye to isolate and
identify a unifying physical principle. Special attention is paid to quantum
criticality, Planckian dissipation, Mottness, and whether a new gauge
principle, which has a clear experimental signature, is needed to account for
the non-local transport seen in strange metals. For the cuprates, strange
metallicity is shown to track the superfluid density, thereby making a theory
of this state the primary hurdle in solving the riddle of high-temperature
superconductivity.",2205.12979v1
2024-03-08,Experimental set-up for thermal measurements at the nanoscale using an SThM probe with niobium nitride thermometer,"Scanning Thermal Microscopy (SThM) has become an important measurement tool
for characterizing the thermal properties of materials at the nanometer scale.
This technique requires a SThM probe that combines an Atomic Force Microscopy
(AFM) probe and a very sensitive resistive thermometry; the thermometer being
located at the apex of the probe tip allows the mapping of temperature or
thermal properties of nanostructured materials with very high spatial
resolution. The high interest of the SThM technique in the field of thermal
nanoscience currently suffers from a low temperature sensitivity despite its
high spatial resolution. To address this challenge, we developed a high
vacuum-based AFM system hosting a highly sensitive niobium nitride (NbN) SThM
probe to demonstrate its unique performance. As a proof of concept, we utilized
this custom-built system to carry out thermal measurements using the 3$\omega$
method. By measuring the $V_{3\omega}$ voltage on the NbN resistive thermometer
in vacuum conditions we were able to determine the SThM probe's thermal
conductance and thermal time constant. The performance of the probe is
demonstrated by doing thermal measurements in-contact with a sapphire sample.",2403.05405v2
2015-12-17,A Novel Material for In Situ Construction on Mars: Experiments and Numerical Simulations,"A significant step in space exploration during the 21st century will be human
settlement on Mars. Instead of transporting all the construction materials from
Earth to the red planet with incredibly high cost, using Martian soil to
construct a site on Mars is a superior choice. Knowing that Mars has long been
considered a ""sulfur-rich planet"", a new construction material composed of
simulated Martian soil and molten sulfur is developed. In addition to the raw
material availability for producing sulfur concrete and a strength reaching
similar or higher levels of conventional cementitious concrete, fast curing,
low temperature sustainability, acid and salt environment resistance, 100%
recyclability are appealing superior characteristics of the developed Martian
Concrete. In this study, different percentages of sulfur are investigated to
obtain the optimal mixing proportions. Three point bending, unconfined
compression and splitting tests were conducted to determine strength
development, strength variability, and failure mechanisms. The test results
show that the strength of Martian Concrete doubles that of sulfur concrete
utilizing regular sand. It is also shown that the particle size distribution
plays an important role in the mixture's final strength. Furthermore, since
Martian soil is metal rich, sulfates and, potentially, polysulfates are also
formed during high temperature mixing, which might contribute to the high
strength. The optimal mix developed as Martian Concrete has an unconfined
compressive strength of above 50 MPa. The formulated Martian Concrete is
simulated by the Lattice Discrete Particle Model (LDPM), which exhibits
excellent ability in modeling the material response under various loading
conditions.",1512.05461v3
1998-09-07,Metallic temperature dependence of resistivity in perchlorate doped polyacetylene,"We have measured the electrical resistivity ($\rho$) and the thermoelectric
power (TEP) of the perchlorate (ClO4^-) doped stretch oriented polyacetylene
(PA) film. For the highly conducting samples ($\sigma_{RT} > 41000 S/cm$), the
temperature dependence of the 4-probe resistivity shows positive temperature
coefficient of resistivity (TCR) from T=1.5K to 300K. For the less conducting
samples, the 4-probe resistivity data show the crossover of TCR with a broad
minimum peak at T=T* > 200K. For samples of $\sigma_{RT}$$>$20000 S/cm, the
$\rho (1.5K)/\rho (300K) <1$, i.e., the resistivity at 1.5K is lower than the
room temperature resistivity value. The temperature dependence of the TEP shows
diffusive linear metallic TEP becoming temperature independent below 40K.
Unlike the others who used Cu(ClO_4)_2 for the ClO_4^- doping, the initial
doping material we used is anhydrous Fe(ClO_4)_3 which is crucial to obtain the
positive TCR from T=1.5K to 300K.",9809106v1
2006-11-20,Using Cluster Dynamics to Model Electrical Resistivity Measurements in Precipitating Al-Sc Alloys,"Electrical resistivity evolution during precipitation in Al-Sc alloys is
modeled using cluster dynamics. This mesoscopic modeling has already been shown
to correctly predict the time evolution of the precipitate size distribution.
In this work, we show that it leads too to resistivity predictions in
quantitative agreement with experimental data. We only assume that all clusters
contribute to the resistivity and that each cluster contribution is
proportional to its area. One interesting result is that the resistivity excess
observed during coarsening mainly arises from large clusters and not really
from the solid solution. As a consequence, one cannot assume that resistivity
asymptotic behavior obeys a simple power law as predicted by LSW theory for the
solid solution supersaturation. This forbids any derivation of the precipitate
interface free energy or of the solute diffusion coefficient from resistivity
experimental data in a phase-separating system like Al-Sc supersaturated
alloys.",0611524v1
2008-10-06,Strong resistance nonlinearity and third harmonic generation in the unipolar resistance switching of NiO thin films,"We investigated third harmonic generation in NiO thin films, which exhibit
unipolar resistance switching behavior. We found that the low resistance states
of the films were strongly nonlinear, with variations in the resistance R as
large as 60%. This strong nonlinear behavior was most likely caused by Joule
heating of conducting filaments inside the films. By carefully controlling the
applied dc bias, we obtained several low resistance states, whose values of the
third harmonic coefficient B3f were proportional to R2+w (with w = 2.07). This
suggested that the resistance changes of the NiO films were accompanied by
connectivity changes of the conducting filaments, as observed in classical
percolating systems.",0810.0886v1
2009-07-19,Current Driven tri-stable Resistance States in Magnetic Point Contacts,"Point contacts between normal and ferromagnetic metals are investigated using
magneto-resistance and transport spectroscopy measurements combined with
micromagnetic simulations. Pronounced hysteresis in the point-contact
resistance versus both bias current and external magnetic field are observed.
It is found that such hysteretic resistance can exhibit, in addition to
bi-stable resistance states found in ordinary spin valves, tri-stable
resistance states with a middle resistance level. We interpret these
observation in terms of surface spin-valve and spin-vortex states, originating
from a substantially modified spin structure at the ferromagnetic interface in
contact core. We argue that these surface spin states, subject to a weakened
exchange interaction, dominate the effects of spin transfer torques on the
nanometer scale.",0907.3286v1
2014-03-25,Electric-Field-Modulated Nonvolatile Resistance Switching in VO2/PMN-PT(111) Heterostructures,"The electric-field-modulated resistance switching in VO2 thin films grown on
piezoelectric (111)-0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (PMN-PT) substrates has
been investigated. Large relative change in resistance (10.7%) was observed in
VO2/PMN-PT(111) hererostructures at room temperature. For a substrate with a
given polarization direction, stable resistive states of VO2 films can be
realized even when the applied electric fields are removed from the
heterostructures. By sweeping electric fields across the heterostructure
appropriately, multiple resistive states can be achieved. These stable
resistive states result from the different stable remnant strain states of
substrate, which is related to the rearrangements of ferroelectric domain
structures in PMN-PT(111) substrate. The resistance switching tuned by electric
field in our work may have potential applications for novel electronic devices.",1403.6388v2
2015-02-23,Phonon residual resistance of pure crystals,"Using the Boltzmann transport equation, we study phonon residual resistance
of perfect metallic crystals of a finite thickness $d$ along which a weak
constant electric field $E$ is applied. This resistance which is $\propto
d^{-5}E^{-3}$, is due to scattering of electric field-heated electrons with
emission of long-wave acoustic phonons. This electron-phonon interaction is
caused by zero-point vibrations of the atoms in the perfect crystal lattice
sites. Consideration is carried out for Cu, Ag and Au single crystals with the
thickness of about 1 cm, in the fields of the order of 1 mV/cm. Following the
Matthiessen rule, the resistance of the pure crystals the thicknesses of which
are much larger than the electron mean free path, is represented as the sum of
the impurity and phonon residual resistances. The condition on the thickness
$d$ and the field $E$ is found at which the phonon scattering of the
field-heated electrons dominates. Under this condition, the low-temperature
resistances of pure crystals do not depend on the their purity and determine
the phonon residual resistivity of the ideal crystals. The calculations are
performed for Cu with a purity of at least 99.9999%.",1502.06486v2
2016-02-25,"Electric fields, weighting fields, signals and charge diffusion in detectors including resistive materials","In this report we discuss static and time dependent electric fields in
detector geometries with an arbitrary number of parallel layers of a given
permittivity and weak conductivity. We derive the Green's functions i.e. the
field of a point charge, as well as the weighting fields for readout pads and
readout strips in these geometries. The effect of 'bulk' resistivity on
electric fields and signals is investigated. The spreading of charge on thin
resistive layers is also discussed in detail, and the conditions for allowing
the effect to be described by the diffusion equation is discussed. We apply the
results to derive fields and induced signals in Resistive Plate Chambers,
Micromega detectors including resistive layers for charge spreading and
discharge protection as well as detectors using resistive charge division
readout like the MicroCAT detector. We also discuss in detail how resistive
layers affect signal shapes and increase crosstalk between readout electrodes.",1602.07949v1
2016-02-26,Investigating the Temperature Effects on Resistive Random Access Memory (RRAM) Devices,"In this paper, we report the effect of filament radius and filament
resistivity on the saturated temperature of ZnO, TiO2, WO3 and HfO2 Resistive
Random Access Memory (RRAM) devices. We resort to the thermal reaction model of
RRAM for the present analysis. The results substantiate decrease in saturated
temperature with increase in the radius and resistivity of filament for the
investigated RRAM devices. Moreover, a sudden change in the saturated
temperature at a lower value of filament radius and resistivity is observed as
against the steady change at the medium and higher value of the filament radius
and resistivity. Results confirm the dependence of saturated temperature on the
filament size and resistivity in RRAM.",1602.08262v1
2017-11-02,Resistivity scaling model for metals with conduction band anisotropy,"It is generally understood that the resistivity of metal thin films scales
with film thickness mainly due to grain boundary and boundary surface
scattering. Recently, several experiments and ab initio simulations have
demonstrated the impact of crystal orientation on resistivity scaling. The
crystal orientation cannot be captured by the commonly used resistivity scaling
models and a qualitative understanding of its impact is currently lacking. In
this work, we derive a resistivity scaling model that captures grain boundary
and boundary surface scattering as well as the anisotropy of the band
structure. The model is applied to Cu and Ru thin films, whose conduction bands
are (quasi-)isotropic and anisotropic respectively. After calibrating the
anisotropy with ab initio simulations, the resistivity scaling models are
compared to experimental resistivity data and a renormalization of the fitted
grain boundary reflection coefficient can be identified for textured Ru.",1711.00796v3
2021-02-05,Does Non-Genetic Heterogeneity Facilitate the Development of Genetic Drug Resistance?,"Non-genetic forms of antimicrobial drug resistance can result from
cell-to-cell variability that is not encoded in the genetic material. Data from
recent studies also suggest that non-genetic mechanisms can facilitate the
development of genetic drug resistance. In this Perspective article, we
speculate on how the interplay between non-genetic and genetic mechanisms may
affect microbial adaptation and evolution during drug treatment. We argue that
cellular heterogeneity arising from fluctuations in gene expression, epigenetic
modifications, as well as genetic changes contributes to drug resistance at
different timescales, and that the interplay between these mechanisms may
influence the evolutionary dynamics of pathogen resistance. Accordingly,
developing a better understanding of non-genetic mechanisms in drug resistance
and how they interact with genetic mechanisms will enhance our ability to
combat antimicrobial resistance.",2102.03276v1
2023-04-10,T-square dependence of the electronic thermal resistivity in metallic strontium titanate,"The temperature dependence of the phase space for electron-electron (e-e)
collisions leads to a T-square contribution to electrical resistivity of
metals. Umklapp scattering are identified as the origin of momentum loss due to
e-e scattering in dense metals. However, in dilute metals like lightly doped
strontium titanate, the origin of T-square electrical resistivity in absence of
Umklapp events is yet to be pinned down. Here, by separating electron and
phonon contributions to heat transport, we extract the electronic thermal
resistivity in niobium-doped strontium titanate and show that it also displays
a T-square temperature dependence. Its amplitude correlates with the T-square
electrical resistivity. The Wiedemann-Franz law strictly holds in the
zero-temperature limit, but not at finite-temperature, because the two T-square
prefactors are different by a factor of $\approx 3$, like in other Fermi
liquids. Recalling the case of $^3$He, we argue that T-square thermal
resistivity does not require Umklapp events. The approximate recovery of the
Wiedemann-Franz law in presence of disorder would account for a T-square
electrical resistivity without Umklapp.",2304.04841v2
2001-07-03,Low temperature resistance minimum in non-superconducting 3R-Nb_{1+x}S_2 and 3R-Ga_xNbS_2,"We report the structural and electron transport properties of 3R-Nb_{1+x}S_2
(x >= .07) and 3R-Ga_xNbS_2 (.1 <= x <= .33) prepared as polycrystalline
pellets as well as single crystals grown by vapour transport. We observe a
resistance minimum in these compounds between 20-60 K, with the T_min
proportional to x. The resistance scales as rho/rho_min(T/T_min) between .2 <
T/T_min < 2 for different phases with x <= .25 whose resistivity differs by an
order of magnitude. Powder X-ray diffraction (XRD) also shows progressively
increasing intensity of superlattice lines with cation concentration. The
thermopower changes sign around the resistance minimum. The explanation of the
resistance minimum and the simultaneous rapid suppression of superconductivity
is sought in e-e scattering effects in the presence of cation disorder in these
narrow band anisotropic materials.",0107067v1
2006-08-11,Fracture resistance via topology optimisation,"The fracture resistance of structures is optimised using the level-set
method. Fracture resistance is assumed to be related to the elastic energy
released by a crack propagating in a normal direction from parts of the
boundary which are in tension, and is calculated using the virtual crack
extension technique. The shape derivative of the fracture-resistance objective
function is derived. Two illustrative two-dimensional case studies are
presented: a hole in a plate subjected to biaxial strain; and a bridge fixed at
both ends subjected to a single load in which the compliance and fracture
resistance are jointly optimised. The structures obtained have rounded corners
and more material at places where they are in tension. Based on the results, we
propose that fracture resistance may be modelled more easily but less directly
by including a term proportional to surface area in the objective function, in
conjunction with non-linear elasticity where the Young's modulus in tension is
lower than in compression.",0608260v1
2016-05-19,Resistive Switching Phenomena of HfO2 Films Grown by MOCVD for Resistive Switching Memory Devices,"The resistive switching phenomena of HfO2 films grown by metalorganic
chemical vapor deposition was studied for the application of ReRAM devices. In
the fabricated Pt/HfO2/TiN memory cells, the bipolar resistive switching
characteristics were observed, and the set and reset states were measured to be
as low as 7 uA and 4 uA, respectively, at VREAD = 1 V. Regarding the resistive
switching performance, the stable RS performance was observed under 40
repetitive dc cycling test with the small variations of set/reset voltages and
currents, and good retention characteristics over 105 s in both LRS and HRS.
These results show the possibility of MOCVD grown HfO2 films as a promising
resistive switching materials for ReRAM applications.",1605.06014v1
2020-02-10,Resistivity minimum in diluted metallic magnets,"Resistivity minima are commonly seen in itinerant magnets and they are often
attributed to the Kondo effect. However, recent experiments are revealing an
increasing number of materials showing resistivity minima in the absence of
indications of Kondo singlet formation. In a previous work [Z. Wang, K. Barros,
G.-W. Chern, D. L. Maslov, and C. D. Batista, Phys. Rev. Lett. 117, 206601
(2016)], we demonstrated that the Ruderman-Kittel-Kasuya-Yosida (RKKY)
interaction can produce a classical spin liquid state at finite temperature,
whose resistivity increases with decreasing temperature. The classical spin
liquid exists over a relatively large temperature window because of the
frustrated nature of the RKKY interaction produced by a 2D electron gas. In
this work, we investigate the robustness of the RKKY-induced resistivity upturn
against site dilution, which provides an alternative, and more robust, way of
stabilizing the classical spin liquid state down to T=0. By using series
expansions and stochastic Landau-Lifshitz dynamics simulation, we show that
site dilution competes with thermal fluctuations and further stabilizes the
resistivity upturn, which is accompanied by a negative magnetoresistivity due
to suppression of the electron-spin scattering.",2002.03858v2
2021-10-06,Pinpointing the Dominant Component of Contact Resistance to Atomically Thin Semiconductors,"Achieving good electrical contacts is one of the major challenges in
realizing devices based on atomically thin two-dimensional (2D) semiconductors.
Several studies have examined this hurdle, but a universal understanding of the
contact resistance and an underlying approach to its reduction are currently
lacking. In this work we expose the shortcomings of the classical contact
resistance model in describing contacts to 2D materials, and offer a correction
based on the addition of a lateral pseudo-junction resistance component (Rjun).
We use a combination of unique contact resistance measurements to
experimentally characterize Rjun for Ni contacts to monolayer MoS2. We find
that Rjun is the dominating component of the contact resistance in undoped 2D
devices and show that it is responsible for most of the back-gate bias and
temperature dependence. Our corrected model and experimental results help
understand the underlying physics of state-of-the-art contact engineering
approaches in the context of minimizing Rjun.",2110.02563v1
2023-11-14,Giant Resistance Switch in Twisted Transition Metal Dichalcogenide Tunnel Junctions,"Resistance switching in multilayer structures are typically based on
materials possessing ferroic orders. Here we predict an extremely large
resistance switching based on the relative spin-orbit splitting in twisted
transition metal dichalcogenide (TMD) monolayers tunnel junctions. Because of
the valence band spin splitting which depends on the valley index in the
Brillouin zone, the perpendicular electronic transport through the junction
depends on the relative reciprocal space overlap of the spin-dependent Fermi
surfaces of both layers, which can be tuned by twisting one layer. Our quantum
transport calculations reveal a switching resistance of up to $10^6 \%$ when
the relative alignment of TMDs goes from $0^{\circ}$ to $60^{\circ}$ and when
the angle is kept fixed at $60^{\circ}$ and the Fermi level is varied. By
creating vacancies, we evaluate how inter-valley scattering affects the
efficiency and find that the resistance switching remains large ($10^4 \%$) for
typical values of vacancy concentration. Not only this resistance switching
should be observed at room temperature due to the large spin splitting, but our
results show how twist angle engineering and control of van der Waals
heterostructures could be used for next-generation memory and electronic
applications.",2311.08397v1
2000-10-24,Slater Transition in the Pyrochlore Cd2Os2O7,"Cd2Os2O7 crystallizes in the pyrochlore structure and undergoes a
metal-insulator transition (MIT) near 226 K. We have characterized the MIT in
Cd2Os2O7 using X-ray diffraction, resistivity at ambient and high pressure,
specific heat, magnetization, thermopower, Hall coefficient, and thermal
conductivity. Both single crystals and polycrystalline material were examined.
The MIT is accompanied by no change in crystal symmetry and a change in unit
cell volume of less than 0.05%. The resistivity shows little temperature
dependence above 226 K, but increases by 3 orders of magnitude as the sample is
cooled to 4 K. The specific heat anomaly resembles a mean-field transition and
shows no hysteresis or latent heat. Cd2Os2O7 orders magnetically at the MIT.
The magnetization data is consistent with antiferromagnetic order, with a small
parasitic ferromagnetic component. The Hall and Seebeck coefficients are
consistent with a semiconducting gap opening at the Fermi energy at the MIT. We
have also performed electronic structure calculations on Cd2Os2O7. These
calculations indicate that Cd2Os2O7 is metallic, with a sharp peak in the
density of states at the Fermi energy. We intepret the data in terms of a
Slater transition. In this scenario, the MIT is produced by a doubling of the
unit cell due to the establishment of antiferromagnetic order. A Slater
transition-unlike a Mott transition-is predicted to be continuous, with a
semiconducting energy gap opening much like a BCS gap as the material is cooled
below $T_{MIT}$.",0010364v1
2004-12-17,Origin of Colossal Dielectric Response of Pr(0.6)Ca(0.4)MnO(3),"We report the detailed study of dielectric response of Pr(0.6)Ca(0.4)MnO(3)
(PCMO), member of manganite family showing colossal magnetoresistance.
Measurements have been performed on four polycrystalline samples and four
single crystals, allowing us to compare and extract the essence of dielectric
response in the material. High frequency dielectric function is found to be 30,
as expected for the perovskite material. Dielectric relaxation is found in
frequency window of 20Hz-1MHz at temperatures of 50-200K that yields to
colossal low-frequency dielectric function, i.e. static dielectric constant.
Static dielectric constant is always colossal, but varies considerably in
different samples from 1000 until 100000. The measured data can be simulated
very well by blocking (surface barrier) capacitance in series with sample
resistance. This indicates that the large dielectric constant in PCMO arises
from the Schottky barriers at electrical contacts. Measurements in magnetic
field and with d.c. bias support this interpretation. Weak anomaly at the
charge ordering temperature can also be attributed to interplay of sample and
contact resistance. We comment our results in the framework of related studies
by other groups.",0412473v3
2012-05-14,Bi2Te1.6S1.4 - a Topological Insulator in the Tetradymite Family,"We describe the crystal growth, crystal structure, and basic electrical
properties of Bi2Te1.6S1.4, which incorporates both S and Te in its Tetradymite
quintuple layers in the motif -[Te0.8S0.2]-Bi-S-Bi-[Te0.8S0.2]-. This material
differs from other Tetradymites studied as topological insulators due to the
increased ionic character that arises from its significant S content.
Bi2Te1.6S1.4 forms high quality crystals from the melt and is the S-rich limit
of the ternary Bi-Te-S {\gamma}-Tetradymite phase at the melting point. The
native material is n-type with a low resistivity; Sb substitution, with
adjustment of the Te to S ratio, results in a crossover to p-type and resistive
behavior at low temperatures. Angle resolved photoemission study shows that
topological surface states are present, with the Dirac point more exposed than
it is in Bi2Te3 and similar to that seen in Bi2Te2Se. Single crystal structure
determination indicates that the S in the outer chalcogen layers is closer to
the Bi than the Te, and therefore that the layers supporting the surface states
are corrugated on the atomic scale.",1205.2924v1
2015-05-26,"Transport, Magnetic and Vibrational Properties of Chemically Exfoliated Few Layer Graphene","We study the vibrational, magnetic and transport properties of Few Layer
Graphene (FLG) using Raman and electron spin resonance spectroscopy and
microwave conductivity measurements. FLG samples were produced using wet
chemical exfoliation with different post-processing, namely ultrasound
treatment, shear mixing, and magnetic stirring. Raman spectroscopy shows a low
intensity D mode which attests a high sample quality. The G mode is present at
$1580$ cm$^{-1}$ as expected for graphene. The 2D mode consists of 2 components
with varying intensities among the different samples. This is assigned to the
presence of single and few layer graphene in the samples. ESR spectroscopy
shows a main line in all types of materials with a width of about $1$ mT and
and a $g$-factor in the range of $2.005-2.010$. Paramagnetic defect centers
with a uniaxial $g$-factor anisotropy are identified, which shows that these
are related to the local sp$^2$ bonds of the material. All kinds of
investigated FLGs have a temperature dependent resistance which is compatible
with a small gap semiconductor. The difference in resistance is related to the
different grain size of the samples.",1505.06857v1
2017-02-10,Highly wear-resistant and low-friction Si3N4 composites by addition of graphene nanoplatelets approaching the 2D limit,"Graphene nanoplatelets (GNPs) have emerged as one of the most promising
filler materials for improving the tribological performance of ceramic
composites due to their outstanding solid lubricant properties as well as
mechanical and thermal stability. Yet, the addition of GNPs has so far provided
only a very limited improvement in the tribological properties of ceramics,
particularly concerning the reduction of their friction coefficient. This is
most likely due to the challenges of achieving a lubricating and protecting
tribo-film through a high GNP coverage of the exposed surfaces. Here we show
that this can be achieved by efficiently increasing the exfoliation degree of
GNPs down to the few-layer (FL) range. By employing FL-GNPs as filler material,
the wear resistance of Si3N4 composites can be increased by about twenty times,
the friction coefficient reduced to nearly its half, while the other mechanical
properties are also preserved or improved. Using confocal Raman microscopy, we
were able to demonstrate the formation of a continuous FL- GNP tribo-film,
already at 5wt% FL-GNP content.",1702.03153v1
2017-12-16,Stress-dependent electrical transport and its universal scaling in granular materials,"We experimentally and numerically examine stress-dependent electrical
transport in granular materials to elucidate the origins of their universal
dielectric response. The ac responses of granular systems under varied
compressive loadings consistently exhibit a transition from a resistive plateau
at low frequencies to a state of nearly constant loss at high frequencies. By
using characteristic frequencies corresponding to the onset of conductance
dispersion and measured direct-current resistance as scaling parameters to
normalize the measured impedance, results of the spectra under different stress
states collapse onto a single master curve, revealing well-defined
stress-independent universality. In order to model this electrical transport, a
contact network is constructed on the basis of prescribed packing structures,
which is then used to establish a resistor-capacitor network by considering
interactions between individual particles. In this model the
frequency-dependent network response meaningfully reproduces the experimentally
observed master curve exhibited by granular materials under various normal
stress levels indicating this universal scaling behaviour is found to be
governed by i) interfacial properties between grains and ii) the network
configuration. The findings suggest the necessity of considering contact
morphologies and packing structures in modelling electrical responses using
network-based approaches.",1712.05938v2
2020-04-06,Spin Hall magnetoresistance in antiferromagnetic insulators,"Antiferromagnetic materials promise improved performance for spintronic
applications, as they are robust against external magnetic field perturbations
and allow for faster magnetization dynamics compared to ferromagnets. The
direct observation of the antiferromagnetic state, however, is challenging due
to the absence of a macroscopic magnetization. Here, we show that the spin Hall
magnetoresistance (SMR) is a versatile tool to probe the antiferromagnetic spin
structure via simple electrical transport experiments by investigating the
easy-plane antiferromagnetic insulators $\alpha$-Fe2O3 (hematite) and NiO in
bilayer heterostructures with a Pt heavy metal top electrode. While rotating an
external magnetic field in three orthogonal planes, we record the longitudinal
and the transverse resistivities of Pt and observe characteristic resistivity
modulations consistent with the SMR effect. We analyze both their amplitude and
phase and compare the data to the results from a prototypical collinear
ferrimagnetic Y3Fe5O12/Pt bilayer. The observed magnetic field dependence is
explained in a comprehensive model, based on two magnetic sublattices and
taking into account magnetic field-induced modifications of the domain
structure. Our results show that the SMR allows us to understand the spin
configuration and to investigate magnetoelastic effects in antiferromagnetic
multi-domain materials. Furthermore, in $\alpha$-Fe2O3/Pt bilayers, we find an
unexpectedly large SMR amplitude of $2.5 \times 10^{-3}$, twice as high as for
prototype Y3Fe5O12/Pt bilayers, making the system particularly interesting for
room-temperature antiferromagnetic spintronic applications.",2004.02639v2
2017-04-11,Transfer of Vertical Graphene Nanosheets onto Flexible Substrates towards Supercapacitor Application,"Vertical graphene nanosheets (VGNs) are the material of choice for
next-generation electronic device applications. The growing demand for flexible
devices in electronic industry brings in restriction on growth temperature of
the material of interest. However, VGNs with better structural quality is
usually achieved at high growth temperatures. The difficulty associated with
the direct growth on flexible substrates can overcome by adopting an effective
strategy of transferring the well grown VGNs onto arbitrary flexible substrates
through soft chemistry route. Hence, we demonstrated a simple, inexpensive and
scalable technique for the transfer of VGNs onto arbitrary substrates without
disrupting its morphology and structural properties. After transfer, the
morphology, chemical structure and electronic properties are analyzed by
scanning electron microscopy, Raman spectroscopy and four probe resistive
methods, respectively. Associated characterization investigation indicates the
retention of morphological, structural and electrical properties of transferred
VGNs compared to as-grown one. Furthermore the storage capacity of the VGNs
transferred onto flexible substrates is also examined. A very lower sheet
resistance of 0.67 kOhm/sq. and excellent supercapacitance of 158
micro-Farrad/cm2 with 91.4% retention after 2000 cycles confirms the great
prospective of this damage-free transfer approach of VGNs for flexible
nanoelectronic device applications",1704.03227v1
2019-03-26,Isostructural Mott Transition in 2D honeycomb antiferromagnet V$_{0.9}$PS$_3$,"We present the observation of an isostructural Mott insulator-metal
transition in van-der-Waals honeycomb antiferromagnet V$_{0.9}$PS$_3$ through
high-pressure x-ray diffraction and transport measurements. The MPX$_3$ family
of magnetic van-der-Waals materials (M denotes a first row transition metal and
X either S or Se) are currently the subject of broad and intense attention, but
the vanadium compounds have until this point not been studied beyond their
basic properties. We observe insulating variable-range-hopping type resistivity
in V$_{0.9}$PS$_3$, with a gradual increase in effective dimensionality with
increasing pressure, followed by a transition to a metallic resistivity
temperature dependence between 112 and 124 kbar. The metallic state
additionally shows a low-temperature upturn we tentatively attribute to the
Kondo Effect. A gradual structural distortion is seen between 26-80 kbar, but
no structural change at higher pressures corresponding to the insulator-metal
transition. We conclude that the insulator-metal transition occurs in the
absence of any distortions to the lattice - an isostructural Mott transition in
a new class of two-dimensional material, and in strong contrast to the behavior
of the other MPX$_3$ compounds.",1903.10971v1
2019-03-29,Substrate Mediated Synthesis of Ti-Si-N Nano-and-Micro Structures for Optoelectronic Applications,"Being one of the strongest materials, ternary TiSiN exhibits a very
interesting family of binary transition metal nitride and silicide systems. A
novel technique to fabricate morphologically fascinating nano and micro
structures of TiSiN is reported here. The referred TiSiN films, majorly
constituted with cubic TiN phase, are enriched with crystalline nanoparticles,
micro-flowers and faceted micro-crystals which possess attractive
functionalities towards plasmon mediated optoelectronic applications.
Reactivity of titanium to silicon nitride based dielectric topping on the
substrate at high temperature plays the key role in nitride formation for the
demonstrated protocol. The optoelectronic response for these morphologically
enriched composite films indicates an influential role of photo-induced surface
plasmon polaritons on their dc transport properties. A plasmonically tuned
resistive switching, controlled by the surface morphology in association with
the film thickness, is observed under light illumination. Using Drudes modified
frequency dependent bulk electron scattering rates and surface mediated
SPPs-electron scattering rates, a generic model is proposed for addressing
unambiguously the increased device resistance in response to light. The
featured synthesis process opens a new direction towards the growth of
transition metal nitrides while the proposed model serves as a basic platform
to understand photo-induced electron scattering mechanisms in metal.",1903.12376v1
2020-01-06,Controlled introduction of defects to delafossite metals by electron irradiation,"The delafossite metals PdCoO$_{2}$, PtCoO$_{2}$ and PdCrO$_{2}$ are among the
highest conductivity materials known, with low temperature mean free paths of
tens of microns in the best as-grown single crystals. A key question is whether
these very low resistive scattering rates result from strongly suppressed
backscattering due to special features of the electronic structure, or are a
consequence of highly unusual levels of crystalline perfection. We report the
results of experiments in which high energy electron irradiation was used to
introduce point disorder to the Pd and Pt layers in which the conduction
occurs. We obtain the cross-section for formation of Frenkel pairs in absolute
units, and cross-check our analysis with first principles calculations of the
relevant atomic displacement energies. We observe an increase of resistivity
that is linear in defect density with a slope consistent with scattering in the
unitary limit. Our results enable us to deduce that the as-grown crystals
contain extremely low levels of in-plane defects of approximately $0.001\%$.
This confirms that crystalline perfection is the most important factor in
realizing the long mean free paths, and highlights how unusual these
delafossite metals are in comparison with the vast majority of other
multi-component oxides and alloys. We discuss the implications of our findings
for future materials research.",2001.01471v1
2020-01-17,Wettability and surface energy of parylene F,"Parylenes are barrier materials employed as protective layers. However, many
parylenes are unsuitable for applications under harsh conditions. A new
material, parylene F, demonstrates considerable potential for a wide range of
applications due to its high temperature and UV resistance. For the first time,
the wettability and surface energy of parylene F were investigated to determine
the feasibility of parylene F as an alternative to the commonly employed
parylene C. The results show that parylene F has a hydrophobic surface with a
water contact angle of 109.63 degrees. We found that 3.5 ul probe liquid is an
optimal value for the contact angle measurement of parylene F. Moreover, we
found that the Owens-Wendt-Kaelble and the Lifshitz-van der Waals/acid-base
approaches are unsuitable for determining the surface energy of parylene F,
whereas an approach based on the limitless liquid-solid interface wetting
system is compatible. Furthermore, the results show that parylene F has a
surface energy of 39.05 mJ/m2. Considering the improved resistance, relatively
low cost, and the desirable properties, parylene F can replace parylene C for
applications under harsh conditions.",2001.06146v2
2020-01-24,Adaptive hard and tough mechanical response in single-crystal B1 VNx ceramics via control of anion vacancies,"High hardness and toughness are generally considered mutually exclusive
properties for single-crystal ceramics. Combining experiments and ab initio
molecular dynamics (AIMD) atomistic simulations at room temperature, we
demonstrate that both the hardness and toughness of single-crystal
NaCl-structure VNx/MgO(001) thin films are simultaneously enhanced through the
incorporation of anion vacancies. Nanoindentation results show that VN0.8, here
considered as representative understoichiometric VNx system, is ~20% harder, as
well as more resistant to fracture than stoichiometric VN samples. AIMD
modeling of VN and VN0.8 supercells subjected to [001] and [110] elongation
reveal that the tensile strengths of the two materials are similar.
Nevertheless, while the stoichiometric VN phase systematically cleaves in a
brittle manner at tensile yield points, the understoichiometric compound
activates transformation-toughening mechanisms that dissipate accumulated
stresses. AIMD simulations also show that VN0.8 exhibits an initially greater
resistance to both {110}<1-10> and {111}<1-10> shear deformation than VN.
However, for progressively increasing shear strains, the VN0.8 mechanical
behavior gradually evolves from harder to more ductile than VN. The transition
is mediated by anion vacancies, which facilitate {110}<1-10> and {111}<1-10>
lattice slip by reducing activation shear stresses by as much as 35%.
Electronic-structure analyses show that the two-regime hard/tough mechanical
response of VN0.8 primarily stems from its intrinsic ability to transfer d
electrons between 2nd-neighbor and 4th-neighbor (i.e., across vacancy sites)
V-V metallic states. Our work offers a route for electronic-structure design of
hard materials in which a plastic mechanical response is triggered with
loading.",2001.08933v2
2020-05-14,Gate- and Light-Tunable Negative Differential Resistance with High Peak Current Density in 1T-TaS$_2$/2H-MoS$_2$ T-Junction,"Metal-based electronics is attractive for fast and radiation-hard electronic
circuits and remains one of the longstanding goals for researchers. The
emergence of 1T-TaS$_2$, a layered material exhibiting strong charge density
wave (CDW) driven resistivity switching that can be controlled by an external
stimulus such as electric field and optical pulses, has triggered a renewed
interest in metal-electronics. Here we demonstrate a negative differential
resistor (NDR) using electrically driven CDW phase transition in an
asymmetrically designed T-junction made up of 1T-TaS$_2$/2H-MoS$_2$ van der
Waals heterostructure. The principle of operation of the proposed device is
governed by majority carrier transport and is distinct from usual NDR devices
employing tunneling of carriers, thus avoids the bottleneck of weak tunneling
efficiency in van der Waals heterojunctions. Consequently, we achieve a peak
current density in excess of $10^5$ nA$\mu$m$^{-2}$, which is about two orders
of magnitude higher than that obtained in typical layered material based NDR
implementations. The peak current density can be effectively tuned by an
external gate voltage as well as photo-gating. The device is robust against
ambiance-induced degradation and the characteristics repeat in multiple
measurements over a period of more than a month. The findings are attractive
for the implementation of active metal-based functional circuits.",2005.07146v2
2021-05-23,"Substrate-Versatile Direct-Write Printing of Carbon Nanotube-Based Flexible Conductors, Circuits, and Sensors","Printed electronics rely on the deposition of conductive liquid inks,
typically onto polymeric or paper substrates. Among available conductive
fillers for use in electronic inks, carbon nanotubes (CNTs) have high
conductivity, low density, processability at low temperatures, and intrinsic
mechanical flexibility. However, the electrical conductivity of printed CNT
structures has been limited by CNT quality and concentration, and by the need
for nonconductive modifiers to make the ink stable and extrudable. This study
introduces a polymer-free, printable aqueous CNT ink, and presents the
relationships between printing resolution, ink rheology, and ink-substrate
interactions. A model is constructed to predict printed feature sizes on
impermeable substrates based on Wenzel wetting. Printed lines have conductivity
up to 10,000 S/m. The lines are flexible, with < 5% change in DC resistance
after 1,000 bending cycles, and <3% change in DC resistance with a bending
radius down to 1 mm. Demonstrations focus on (i) conformality, via printing
CNTs onto stickers that can be applied to curved surfaces, (ii) interactivity
using a CNT-based button printed onto folded paper structure, and (iii)
capacitive sensing of liquid wicking into the substrate itself. Facile
integration of surface mount components on printed circuits is enabled by the
intrinsic adhesion of the wet ink.",2105.10942v1
2021-10-05,Nanoscale devices with superconducting electrodes to locally channel current in 3D Weyl semimetals,"We report on the fabrication of nano-devices on the \hkl[-1 0 1] surface of a
Weyl semimetal, a macroscopic crystal of TaAs, and low-temperature transport
measurements. We can implement electron beam lithography by peeling off and
transferring the resist for nanofabrication onto the irregular crystal. We
fabricate the device electrodes with superconducting Niobium nitride (NbN) to
control the current flow through the intended active area of the devices. Our
device structure enables the reduction of the current jetting effect, and we
demonstrate the negative magnetoresistance measurement as a function of angle.
The high field magnetotransport show three distinct oscillation frequencies
corresponding to the three bands at the Fermi level. Resistance measured in the
low magnetic field shows the usual weak anti-localization dip near the
zero-field -- a signature of a Weyl material. Our method of fabricating devices
with superconducting electrodes provides a way to probe the electrical
properties of macroscopic single crystals at the nanoscale. As we use
conventional lithographic techniques for patterning, this method can be
extended to a wide gamut of electrode materials and a large class of 3D quantum
materials.",2110.01793v1
2021-11-29,Doped graphene/carbon black hybrid catalyst giving enhanced oxygen reduction reaction activity with high resistance to corrosion in proton exchange membrane fuel cells,"Nitrogen doping of the carbon is an important method to improve the
performance and durability of catalysts for proton exchange membrane fuel cells
by platinum-nitrogen and carbon-nitrogen bonds. This study shows that p-phenyl
groups and graphitic N acting bridges linking platinum and the graphene/carbon
black (the ratio graphene/carbon black=2/3) hybrid support materials achieved
the average size of platinum nanoparticles with (4.88 +/- 1.79) nm. It improved
the performance of the lower-temperature hydrogen fuel cell up to 0.934 W cm-2
at 0.60 V, which is 1.55 times greater than that of commercial Pt/C. Doping
also enhanced the interaction between Pt and the support materials, and the
resistance to corrosion, thus improving the durability of the low-temperature
hydrogen fuel cell with a much lower decay of 10 mV at 0.80 A cm-2 after 30k
cycles of an in-situ accelerated stress test of catalyst degradation than that
of 92 mV in Pt/C, which achieves the target of Department of Energy (<30 mV).
Meanwhile, Pt/NrEGO2-CB3 remains 78% of initial power density at 1.5 A cm-2
after 5k cycles of in-situ accelerated stress test of carbon corrosion, which
is more stable than the power density of commercial Pt/C, keeping only 54%
after accelerated stress test.",2111.14648v1
2022-03-22,Traps and transport resistance: the next frontier for stable state-of-the-art non-fullerene acceptor solar cells,"Stability is one of the most important challenges facing organic solar cells
(OSC) on their path to commercialization. In the high-performance material
system PM6:Y6 studied here, investigate degradation mechanisms of inverted
photovoltaic devices. We have identified two distinct degradation pathways: one
requires presence of both illumination and oxygen and features a short-circuit
current reduction, the other one is induced thermally and marked by severe
losses of open-circuit voltage and fill factor. We focus our investigation on
the thermally accelerated degradation. Our findings show that bulk material
properties and interfaces remain remarkably stable, however, aging-induced
defect state formation in the active layer remains the primary cause of thermal
degradation. The increased trap density leads to higher non-radiative
recombination, which limits open-circuit voltage and lowers charge carrier
mobility in the photoactive layer. Furthermore, we find the trap-induced
transport resistance to be the major reason for the drop in fill factor. Our
results suggest that device lifetimes could be significantly increased by
marginally suppressing trap formation, leading to a bright future for OSC.",2203.11905v1
2022-07-05,Phonons behave like Electrons in the Thermal Hall Effect of the Cuprates,"The thermal Hall effect, which arises when heat flows transverse to an
applied thermal gradient, has become an important observable in the study of
quantum materials. Recent experiments found a large thermal Hall conductivity
$\kappa_{xy}$ in many high-temperature cuprate superconductors, including deep
inside the Mott insulator, but the underlying mechanism remains unknown. Here,
we uncover a surprising linear temperature dependence for the inverse thermal
Hall resistivity, $1/\rho_H=-\kappa_{xx}^2/\kappa_{xy}$, in the Mott insulating
cuprates $\mathrm{La_2CuO_4}$ and $\mathrm{Sr_2CuO_2Cl_2}$. We also find this
linear scaling in the pseudogap state of Nd-LSCO in the out-of-plane direction,
highlighting the importance of phonons. On the electron-doped side, the linear
inverse thermal Hall signal emerges in NCCO and PCCO at various dopings,
including in the strange metal. Although such dependence arises in the simple
Drude model for itinerant electrons, its origin is unclear in strongly
correlated Mott insulating or pseudogap states. We perform a Boltzmann analysis
for phonons that incorporates skew-scattering, and we are able to identify
regimes where a linear $T$ inverse Hall resistivity appears. Finally, we
suggest future experiments that would further our fundamental understanding of
heat transport in the cuprates, and other quantum materials.",2207.02240v3
2022-08-28,Multiferroic Ti$_3$C$_2$T$_x$ MXene with Tunable Ferroelectric-controlled High Performance Resistive Memory Devices,"Multiferroic (MF) devices based on simultaneous ferroelectric and
ferromagnetic phenomena are considered to be promising candidates for future
bi-functional micro/nano-electronics. The multiferroic phenomena in
two-dimensional materials is rarely reported in literature. We reported a
simple approach to reveal frequency-dependent ferroelectricity and
mutiferroicity in Ti$_3$C$_2$T$_x$ MXene film at room-temperature. To study the
frequency and poling effect on ferroelectricity as well as multiferroicity, we
performed electric polarization vs. electric field measurement at different
external frequencies measured under zero and non-zero static magnetic fields.
In order to further investigate this effect, the magneto-electric (ME) coupling
was also performed to confirm the multiferroic nature of our synthesized
Ti$_3$C$_2$T$_x$ MXene film. The ferroelectric hysteresis effect was attributed
to the switching of electric domain walls under low frequencies that continue
to respond to at much extent to the higher frequencies. The coupling between
disordered electric dipoles with local spin moments could cause presence of
strong magneto-electric coupling. Moreover, the bipolar resistive switching in
trilayer memory devices also supports the ferroelectric behavior of HT-
Ti$_3$C$_2$T$_x$ MXene film and showed uniform repeatability in switching
behavior due to minimum dielectric loss inside ferroelectric
HT-Ti$_3$C$_2$T$_x$ MXene along with improved on/off ratio in comparison to
non-ferroelectric Ti$_3$C$_2$T$_x$ MXene. The unique multiferroic behavior
along with ferroelectric-tuned memristor devices reported here at room
temperature will help understand the intrinsic nature of 2D materials and will
establish novel data storage devices.",2208.13128v1
2023-08-05,Graphene-based RRAM devices for neural computing,"Resistive random access memory (RRAM) is very well known for its potential
application in in-memory and neural computing. However, they often have
different types of device-to-device and cycle-to-cycle variability. This makes
it harder to build highly accurate crossbar arrays.Traditional RRAM designs
make use of various filament-based oxide materials for creating a channel which
is sandwiched between two electrodes to form a two-terminal structure. They are
often subjected to mechanical and electrical stress over repeated
read-and-write cycles. The behavior of these devices often varies in practice
across wafer arrays over these stress when fabricated. The use of emerging 2D
materials is explored to improve electrical endurance, long retention In review
time, high switching speed, and fewer power losses. This study provides an
in-depth exploration of neuro-memristive computing and its potential
applications, focusing specifically on the utilization of graphene and 2D
materials in resistive random-access memory (RRAM) for neural computing. The
paper presents a comprehensive analysis of the structural and design aspects of
graphene-based RRAM, along with a thorough examination of commercially
available RRAM models and their fabrication techniques. Furthermore, the study
investigates the diverse range of applications that can benefit from
graphene-based RRAM devices.",2308.02767v1
2023-08-06,Mechanically exfoliated low-layered [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$]: A single-crystalline p-type transparent conducting oxide,"Transparent conducting oxides (TCOs) are essential components of
optoelectronic devices and various materials have been explored for highly
efficient TCOs having a combination of high transmittance and low sheet
resistance. Here, we focus on a misfit thermoelectric oxide
[Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$] and fabricate the transparent low-layered
crystals by a mechanical tape-peeling method using the single-crystalline
samples. From the transmittance measurement, we find that the thickness of
low-layered samples is several orders of hundred nanometers, which is
comparable with the estimation from the scanning electron microscopy images.
Compared to the previous results on the polycrystalline and $c$-axis oriented
transparent films, the electrical resistivity is reduced owing to the
single-crystalline nature. The figure of merit for the transparent conducting
materials in the present low-layered samples is then evaluated to be higher
than the values in the previous reports. The present results on the low-layered
single-crystalline [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$] may offer a unique class
of multi-functional transparent thermoelectric oxides.",2308.03221v1
2023-09-06,Robust Sandwiched B/TM/B Structures by Metal Intercalating into Bilayer Borophene Leading to Excellent Hydrogen Evolution Reaction,"Bilayer borophene, very recently synthesized on Ag and Cu, possesses
extremely flat large surface and excellent conductivity. Besides, the van der
Waals gap of bilayer borophene can be intercalated by metal atoms, thereby
tailoring the properties of bilayer borophene. Herein, we propose that
sandwiched B/TM/B (TM=Co, Ni, Cu, Pd) could be a new 2D formation by transiton
metal atoms intercalated into bilayer borophene network, it is quiet robust
with both energetic, structural and thermal stability, and exhibits heat
resistance of at least 1300 K. Besides, it is novel platform for
electrocatalytic hydrogen evolution reaction (HER). The interecalation metal
atom serves as single-atomic catalyst, which acting the nonmetal boron layers.
Beyond that, the transtion metal is protected by outside boron layers from
being corroded by acidic/alkaline solution. B/Cux/B, B/Pdx/B and B/Alx/B with
different metal coverage exhibit defect-independent extremely low HER free
energy in the range of -0.162 ~ 0.179 eV, -0.134 ~ 0.183 eV and -0.082 ~ 0.086
eV which are comparable to noble metal Pt. Combining excellent conduction, high
structural and thermal stability, low resistance to intercalated behaviour,
effortless water splitting process, excellent defect-independent catalytic
performance, cheapness and abundance of raw materials, free of corrodation, 2D
sandwiched B/TM/B (TM=Co, Ni, Cu, Pd) is believed to promising for
electrocatalytic HER applications.",2309.02963v1
2023-11-22,Rashba-splitting-induced topological flat band detected by anomalous resistance oscillations beyond the quantum limit in ZrTe$_5$,"Topological flat band, on which the kinetic energy of topological electrons
is quenched, represents a platform for investigating the topological properties
of correlated systems. Recent experimental studies on flattened electronic
bands have mainly concentrated on 2-dimensional materials created by van der
Waals heterostructure-based engineering. Here, we report the observation of a
topological flat band formed by polar-distortion-assisted Rashba splitting in a
3-dimensional Dirac material ZrTe$_5$. The polar distortion and resulting
Rashba splitting on the band are directly detected by torque magnetometry and
the anomalous Hall effect, respectively. The local symmetry breaking further
flattens the band, on which we observe resistance oscillations beyond the
quantum limit. These oscillations follow the temperature dependence of the
Lifshitz-Kosevich formula but are evenly distributed in B instead of 1/B in
high magnetic fields. Furthermore, the cyclotron mass anomalously gets enhanced
about 10$^2$ times at field ~20 T. These anomalous properties of oscillations
originate from a topological flat band with quenched kinetic energy. The
topological flat band, realized by polar-distortion-assisted Rashba splitting
in the 3-dimensional Dirac system ZrTe$_5$, signifies an intrinsic platform
without invoking moir\'e or order-stacking engineering, and also opens the door
for studying topologically correlated phenomena beyond the dimensionality of
two.",2311.13346v2
2024-04-19,Machine Learning-guided accelerated discovery of structure-property correlations in lean magnesium alloys for biomedical applications,"Magnesium alloys are emerging as promising alternatives to traditional
orthopedic implant materials thanks to their biodegradability,
biocompatibility, and impressive mechanical characteristics. However, their
rapid in-vivo degradation presents challenges, notably in upholding mechanical
integrity over time. This study investigates the impact of high-temperature
thermal processing on the mechanical and degradation attributes of a lean
Mg-Zn-Ca-Mn alloy, ZX10. Utilizing rapid, cost-efficient characterization
methods like X-ray diffraction and optical, we swiftly examine microstructural
changes post-thermal treatment. Employing Pearson correlation coefficient
analysis, we unveil the relationship between microstructural properties and
critical targets (properties): hardness and corrosion resistance. Additionally,
leveraging the least absolute shrinkage and selection operator (LASSO), we
pinpoint the dominant microstructural factors among closely correlated
variables. Our findings underscore the significant role of grain size
refinement in strengthening and the predominance of the ternary Ca2Mg6Zn3 phase
in corrosion behavior. This suggests that achieving an optimal blend of
strength and corrosion resistance is attainable through fine grains and reduced
concentration of ternary phases. This thorough investigation furnishes valuable
insights into the intricate interplay of processing, structure, and properties
in magnesium alloys, thereby advancing the development of superior
biodegradable implant materials.",2404.13022v1
2010-02-08,Processing and Characterization of Multiferroic Bi-relaxors,"We compare chemical solution deposition (CSD), and pulsed-laser-deposition
(PLD), specimens of the new room-temperature, single-phase, multiferroic
magnetoelectric, [PbFe2/3W1/3O3]x[PbZr0.53Ti0.47O3]1-x (PZTFWx ~ 0.40<x<0.20)
with polarization, loss (<1%), and resistivity (typically 108 ohm.cm) equal to
or superior to BiFeO3. Single phase polycrystalline multiferroics PZTFWx thin
films were fabricated on platinized silicon substrate by CSD and as epitaxial
single-crystal films on MgO substrate by PLD. High dielectric constants (1200-
3000), high polarization (30 - 60 micro C/cm2), weak saturation magnetization
(0.48 - 4.53 emu/cm3), a broad dielectric temperature peak, high-frequency
dispersion, low dielectric loss and low leakage current were observed in these
materials, suggesting the family as candidates for room-temperature
multiferroic devices. The ferroelectric switching in these materials can be
suppressed or quenched with applied magnetic field.",1002.1637v1
2012-08-20,Topological insulator Bi2Te3 films synthesized by metal organic chemical vapor deposition,"Topological insulator (TI) materials such as Bi2Te3 and Bi2Se3 have attracted
strong recent interests. Large scale, high quality TI thin films are important
for developing TI-based device applications. In this work, structural and
electronic properties of Bi2Te3 thin films deposited by metal organic chemical
vapor deposition (MOCVD) on GaAs (001) substrates were characterized via X-ray
diffraction (XRD), Raman spectroscopy, angle-resolved photoemission
spectroscopy (ARPES), and electronic transport measurements. The characteristic
topological surface states (SS) with a single Dirac cone have been clearly
revealed in the electronic band structure measured by ARPES, confirming the TI
nature of the MOCVD Bi2Te3 films. Resistivity and Hall effect measurements have
demonstrated relatively high bulk carrier mobility of ~350 cm^2/Vs at 300K and
~7,400 cm^2/Vs at 15 K. We have also measured the Seebeck coefficient of the
films. Our demonstration of high quality topological insulator films grown by a
simple and scalable method is of interests for both fundamental research and
practical applications of thermoelectric and TI materials.",1208.4071v1
2017-10-03,Large thermoelectric figure of merit in graphene layered devices at low temperature,"Nanostructured materials have emerged as an alternative to enhance the figure
of merit (ZT) of thermoelectric (TE) devices. Graphene exhibits a high
electrical conductivity (in-plane) that is necessary for a high ZT; however,
this effect is countered by its impressive thermal conductivity. In this work
TE layered devices composed of electrochemically exfoliated graphene (EEG) and
a phonon blocking material such as poly (3,4-ethylenedioxythiophene)polystyrene
sulfonate (PEDOT:PSS), polyaniline (PANI) and gold nanoparticles (AuNPs) at the
interface were prepared. The figure of merit, ZT, of each device was measured
in the cross-plane direction using the Transient Harman Method (THM) and
complemented with AFM-based measurements. The results show remarkable high ZT
values (0.81 < ZT < 2.45) that are directly related with the topography,
surface potential, capacitance gradient and resistance of the devices at the
nanoscale.",1710.01152v1
2014-08-07,A broadband silicon quarter-wave retarder for far-infrared spectroscopic circular dichroism,"The high brightness, broad spectral coverage and pulsed characteristics of
infrared synchrotron radiation enable time-resolved spectroscopy under
throughput-limited optical systems, as can occur with the high-field magnet
cryostat systems used to study electron dynamics and cyclotron resonance by
far-infrared techniques. A natural extension for magnetospectroscopy is to
sense circular dichroism, i.e. the difference in a material's optical response
for left and right circularly polarized light. A key component for
spectroscopic circular dichroism is an achromatic 1/4 wave retarder functioning
over the spectral range of interest. We report here the development of an
in-line retarder using total internal reflection in high-resistivity silicon.
We demonstrate its performance by distinguishing electronic excitations of
different handednesses for GaAs in a magnetic field. This 1/4 wave retarder is
expected to be useful for far-infrared spectroscopy of circular dichroism in
many materials.",1408.1650v1
2018-09-05,Improving the performance of Ge$_2$Sb$_2$Te$_5$ materials via nickel doping: Towards RF-compatible phase-change devices,"High-speed electrical switching of Ge2Sb2Te5 (GST) remains a challenging task
due to the large impedance mismatch between the low-conductivity amorphous
state and the high-conductivity crystalline state. In this letter, we
demonstrate an effective doping scheme using nickel to reduce the resistivity
contrast between the amorphous and crystalline states by nearly three orders of
magnitude. Most importantly, our results show that doping produces the desired
electrical performance without adversely affecting the film's optical
properties. The nickel doping level is approximately 2% and the lattice
structure remains nearly unchanged when compared with undoped-GST. The
refractive indices at amorphous and crystalline states were obtained using
ellipsometry which echoes the results from XRD. The material's thermal
transport properties are measured using time-domain thermoreflectance (TDTR),
showing no change upon doping. The advantages of this doping system will open
up new opportunities for designing electrically reconfigurable high speed
optical elements in the near-infrared spectrum.",1810.01964v1
2012-01-04,Graphene -- Based Nanocomposites as Highly Efficient Thermal Interface Materials,"We found that an optimized mixture of graphene and multilayer graphene -
produced by the high-yield inexpensive liquid-phase-exfoliation technique - can
lead to an extremely strong enhancement of the cross-plane thermal conductivity
K of the composite. The ""laser flash"" measurements revealed a record-high
enhancement of K by 2300 % in the graphene-based polymer at the filler loading
fraction f =10 vol. %. It was determined that a relatively high concentration
of single-layer and bilayer graphene flakes (~10-15%) present simultaneously
with thicker multilayers of large lateral size (~ 1 micrometer) were essential
for the observed unusual K enhancement. The thermal conductivity of a
commercial thermal grease was increased from an initial value of ~5.8 W/mK to
K=14 W/mK at the small loading f=2%, which preserved all mechanical properties
of the hybrid. Our modeling results suggest that graphene - multilayer graphene
nanocomposite used as the thermal interface material outperforms those with
carbon nanotubes or metal nanoparticles owing to graphene's aspect ratio and
lower Kapitza resistance at the graphene - matrix interface.",1201.0796v1
2016-03-07,"High-pressure melt growth and transport properties of SiP, SiAs, GeP, and GeAs 2D layered semiconductors","Silicon and Germanium monopnictides SiP, SiAs, GeP and GeAs form a family of
2D layered semiconductors. We have succeeded in growing bulk single crystals of
these compounds by melt-growth under high pressure (0.5-1 GPa) in a cubic anvil
hot press. Large (mm-size), shiny, micaceous crystals of GeP, GeAs and SiAs
were obtained, and could be exfoliated into 2D flakes. Small and brittle
crystals of SiP were yielded by this method. High-pressure sintered
polycrystalline SiP and GeAs have also been successfully used as a precursor in
the Chemical Vapor Transport growth of these crystals in the presence of
I$_{2}$ as a transport agent. All compounds are found to crystallize in the
expected layered structure and do not undergo any structural transition at low
temperature, as shown by Raman spectroscopy down to T=5K. All materials exhibit
a semiconducting behavior. The electrical resistivity of GeP, GeAs and SiAs is
found to depend on temperature following a 2D-Variable Range Hopping conduction
mechanism. The availability of bulk crystals of these compounds opens new
perspectives in the field of 2D semiconducting materials for device
applications.",1603.02134v1
2017-05-01,High pressure floating-zone growth of perovskite nickelate LaNiO3 single crystals,"We report the first single crystal growth of the correlated metal LaNiO3
using a high-pressure optical-image floating zone furnace. The crystals were
studied using single crystal/powder x-ray diffraction, resistivity, specific
heat, and magnetic susceptibility. The availability of bulk LaNiO3 crystals
will (i) promote deep understanding in this correlated material, including the
mechanism of enhanced paramagnetic susceptibility, and (ii) provide rich
opportunities as a substrate for thin film growth such as important
ferroelectric and/or multiferroic materials. This study demonstrates the power
of high pO2 single crystal growth of nickelate perovskites and correlated
electron oxides more generally.",1705.00570v1
2018-07-18,2D Tunnel Field Effect Transistors (FETs) with a Stable Charge-Transfer-Type p$^+$-WSe$_2$ Source,"Two-dimensional (2D) materials are highly promising for tunnel field effect
transistors (TFETs) with low subthreshold swing and high drive current because
the shorter tunnel distance and strong gate controllability can be expected
from the van der Waals gap distance and the atomically sharp heterointerface
formed independently of lattice matching. However, the common problem for 2D-2D
TFETs is the lack of highly doped 2D materials with the high process stability
as the sources. In this study, we have found that p+-WSe2 doped by charge
transfer from a WOx surface oxide layer can be stabilized by transferring it
onto a h-BN substrate. Using this p$^+$-WSe$_2$ as a source, we fabricate
all-solid-state 2D-2D heterostructure TFETs with an Al2O3 top gate insulator,
i.e., type-II p$^+$-WSe$_2$ /MoS$_2$ and type-III p$^+$-WSe$_2$ /WSe$_2$. The
band-to-band tunneling and negative differential resistance trends are clearly
demonstrated at low temperatures. This work suggests that high doped 2D crystal
of the charge transfer type is an excellent choice as sources for TFETs.",1807.06762v1
2019-10-14,Plasmonic Titanium Nitride via Atomic Layer Deposition: A Low-Temperature Route,"To integrate plasmonic devices into industry, it is essential to develop
scalable and CMOS compatible plasmonic materials. In this work, we report high
plasmonic quality titanium nitride (TiN) on c-plane sapphire by plasma enhanced
atomic layer deposition (PE-ALD). TiN with low losses and high metallicity was
achieved at temperatures below 500{\deg}C, by exploring the effects of
chemisorption time, substrate temperature and plasma exposure time on material
properties. Reduction in chemisorption time mitigates premature precursor
decomposition at T_S > 375{\deg}C , and a trade-off between reduced impurity
concentration and structural degradation caused by plasma bombardment is
achieved for 25s plasma exposure. 85 nm thick TiN films grown at a substrate
temperature of 450{\deg}C, compatible with CMOS processes, with 0.5s
chemisorption time and 25s plasma exposure exhibited a high plasmonic figure of
merit (|{\epsilon}^'/{\epsilon}^''|) of 2.8 and resistivity of 31
{\mu}{\Omega}-cm. These TiN thin films fabricated with subwavelength apertures
were shown to exhibit extraordinary transmission.",2001.05063v1
2021-06-26,High Infrared Reflectance Modulation in VO2 Films Synthesized on Glass and ITO coated Glass substrates using Atmospheric Oxidation of Vanadium,"Vanadium Dioxide (VO2) is a strongly correlated material, which exhibits
insulator to metal transition at ~68 C along with large resistivity and
infrared optical reflectance modulation. In this work, we use atmospheric
pressure thermal oxidation of Vanadium to synthesize VO2 films on glass and ITO
coated glass substrates. With the optimized short oxidation durations of 2 min
and 4 min, the synthesized VO2 film shows high optical reflectance switching in
long-wavelength infrared on glass substrates and mid-wavelength infrared on ITO
coated glass substrates, respectively. Peak reflectance switching values of
~76% and ~79% are obtained on the respective substrates, which are among the
highest reported values. Using the reflectance data, we extract VO2 complex
refractive index in infrared wavelengths, in both the insulating and metallic
phases. The extracted refractive index shows good agreement with VO2
synthesized using other methods. This demonstration of high optical reflectance
switching in VO2 thin films, grown on low cost glass and ITO coated glass
substrates, using a simple low thermal budget process will aid in enhancing VO2
applications in the optical domain.",2106.14006v1
2022-04-11,Emergent superconductivity in van der Waals Kagome material Pd3P2S8 under high pressure,"Kagome lattice systems have been proposed to host rich physics, which provide
an excellent platform to explore unusual quantum states. Here, we report on the
discovery of superconductivity in van der Waals material Pd3P2S8 under
pressure. The superconductivity is observed in Pd3P2S8 for those pressures
where the temperature dependence of the resistivity changes from a
semiconducting-like behavior to that of a normal metal. The superconducting
transition temperature Tc increases with applied pressure and reaches ~ 6.83 K
at 79.5 GPa. Combining high-pressure XRD, Raman spectroscopy and theoretical
calculations, our results demonstrate that the observed superconductivity
induced by high pressure in Pd3P2S8 is closely related to the formation of
amorphous phase, which results from the structural instability due to the
enhanced coupling between interlayer Pd and S atoms upon compression.",2204.05179v1
2001-07-21,Distinct origins of magnetic -field -induced resistivity irreversibility in two manganites with similar ground states : Pr$_{0.5}$Sr$_{0.41}$Ca$_{0.09}$MnO$_{3}$ and La$_{0.5}$Ca$_{0.5}$MnO$_{3}$,"Our investigation of the magnetotransport in two charge ordered manganites
with similar magnetic ground states reveals that the origin of
magnetoresistance can not be concluded from the isofield resistivity, $\rho
$(T, constant H), measurements alone. Both
Pr$_{0.5}$Sr$_{0.41}$Ca$_{0.09}$MnO$_{3}$ (PrSrCa) and
La$_{0.5}$Ca$_{0.5}$MnO$_{3}$ (LaCa) show a ferromagnetic transition (T$_{C}$ =
260 K for PrSrCa, 230 K for LaCa) followed by an antiferromagnetic transition
(T$_{N}$ = 170 K for PrSrCa, 140 K for LaCa). These compounds show
qualitatively similar magnetotransport : Below the irreversibility temperature
T$_{IR}$, field cooled (FC) resistivity is lower than zero field cooled (ZFC)
and decreases continuously with T, whereas the ZFC $\rho $(T, H) resembles $\
$the behavior of $\rho $(T, H = 0 T). The value of $\rho $(ZFC)/$\rho $(FC) is
$\approx $ 10$^{4}$ at 5 K and $\mu_{0}$H = 7 T in both compounds. However,
isothermal magnetic measurements suggest distinct origins of magnetoresistance
: Field cooling enhances ferromagnetic phase fraction in LaCa whereas it drives
PrSrCa into a metastable state with high magnetization. The distinct origins of
magnetotransport is also reflected in other magnetic history dependent
properties.",0107448v1
2006-09-15,Magneto Transport of high TCR (temperature coefficient of resistance) La2/3Ca1/3MnO3: Ag Polycrystalline Composites,"We report the synthesis, (micro)structural, magneto-transport and
magnetization of polycrystalline La2/3Ca1/3MnO3:Agx composites with x = 0.0,
0.1, 0.2, 0.3 and 0.4. The temperature coefficient of resistance (TCR) near
ferromagnetic (FM) transition is increased significantly with addition of Ag.
The FM transition temperature (TFM) is also increased slightly with Ag
addition. Magneto-transport measurements revealed that magneto-resistance MR is
found to be maximum near TFM. Further the increased MR of up to 60% is seen
above 300 K for higher silver added samples in an applied field of 7 Tesla.
Sharp TCR is seen near TFM with highest value of up to 15 % for Ag (0.4)
sample, which is an order of magnitude higher than as for present pristine
sample and best value yet reported for any polycrystalline LCMO compound.
Increased TCR, TFM and significant above room temperature MR of
La2/3Ca1/3MnO3:Agx composites is explained on the basis of improved grains size
and connectivity with silver addition in the matrix. Better coupled FM domains
and nearly conducting grain boundaries give rise to improved physical
properties of the La2/3Ca1/3MnO3 manganites.",0609364v1
2007-09-05,Microwave surface resistance of pristine and neutron-irradiated MgB2 samples in magnetic field,"We report on the microwave surface resistance of two polycrystalline Mg11B2
samples; one consists of pristine material, the other has been irradiated at
very high neutron fluence. It has already been reported that in the strongly
irradiated sample the two gaps merge into a single value. The mw surface
resistance has been measured in the linear regime as a function of the
temperature and the DC magnetic field, at increasing and decreasing fields. The
results obtained in the strongly irradiated sample are quite well justified in
the framework of a generalized Coffey and Clem model, in which we take into
account the field distribution inside the sample due to the critical state. The
results obtained in the pristine sample show several anomalies, especially at
low temperatures, which cannot be justified in the framework of standard models
for the fluxon dynamics. Only at temperatures near Tc and for magnetic fields
greater than 0.5Hc2(T) the experimental data can quantitatively be accounted
for by the Coffey and Clem model, provided that the upper-critical-field
anisotropy is taken into due account.",0709.0618v2
2008-02-12,Two-Fluid Behaviour at the Origin of the Resistivity Peak in Doped Manganites,"We report a series of magnetic and transport measurements on high-quality
single crystal samples of colossal magnetoresistive manganites, La_{0.7}
Ca_{0.3} Mn O_3 and Pr_{0.7} Sr_{0.3} Mn O_3. 1 % Fe doping allows a Moessbauer
spectroscopy study, which shows (i) unusual line broadening within the
ferromagnetic phase and (ii) a coexistence of ferro- and paramagnetic
contributions in a region, T_1<T<T_2, around the Curie point T_C. In the case
of Pr_{0.7} Sr_{0.3} Mn O_3, the resistivity peak occurs at a considerably
higher temperature, T_{MI}>T_2. This shows that phase separation into metallic
(ferromagnetic) and insulating (paramagnetic) phases cannot be generally
responsible for the resistivity peak (and hence for the associated colossal
magnetoresistance). Our results can be understood phenomenologically within the
two-fluid approach, which also allows for a difference between T_C and T_{MI}.
Our data indeed imply that while magnetic and transport properties of the
manganites are closely interrelated, the two transitions at T_C and T_{MI} can
be viewed as distinct phenomena.",0802.1664v3
2008-06-15,Anisotropy in the electrical resistivity and susceptibility of superconducting BaFe$_{2}$As$_{2}$ single crystals,"Sizable single crystals of $BaFe_2As_2$ have been grown with self-flux
method. The crystals are plate-like with c-axis perpendicular to the plane. The
size can be as large as 3 x 5 x 0.2 $mm^3$. The resistivity anisotropy
($\rho_c/\rho_{ab}$) is as large as about 150, and independent of temperature.
The transport in ab plane and along c-axis direction shares the same scattering
mechanism. In contrast to the magnetic behavior of polycrystalline samples, no
Curie-Weiss behavior are observed, a temperature linear dependent
susceptibility occurs above spin-density-wave (SDW) transition. The
susceptibility behavior is very similar to that of antiferromagnetic SDW
chromium. Magnetic behavior of single crystal definitely gives evidence for
existence of local moment except for the contribution to susceptibility from
itinerant electrons. A resistivity minimum strongly dependent on magnetic field
is observed. A log(1/T) divergency, similar to that of the underdoped cuprates,
happens at low temperature. Here we first present intrinsic transport and
magnetic properties, and their anisotropy from high quality single crystal.",0806.2452v2
2008-10-01,Qualitative explanation of the temperature behaviors of the transport properties and magnetic susceptibility of high-temperature superconductors in the normal state,"A model based on the alternating structure of the imbedded conduction layers
(the Cu-O2 planes) with the charge-transfer-insulator (CTI) layers is proposed.
There are three kinds of carriers, each with a different behavior:
conduction-like holes in the Cu-O2 layers and electrons and normal holes in the
CTI matrix between the Cu-O2 layers. This structure explains the strong
anisotropies. The relationship is obtained between the concentration nq of
conduction-like holes in the Cu-O2 layers and the temperature T. The anomalous
temperature behavior of the resistivity as well as the Hall constant also
follows. We give the hole density in ab plane a definite physical meaning, and
also define explicitly optimal doping, overdoping and underdoping. Our model
gives the correct temperature dependence of the resistivity and the hole
constant on optimal doping, overdoping and underdoping, and it predicts the
temperature behavior of the cotangent of the Hall angle quite well. Based on
this model, we can also understand that the HiTc materials become ""Fermi
Liquids"" in the extremely overdoped region, and the dR/dT becomes negative
below some temperature T<1.211T0 in the underdoped case. Based on this model,
the thermal behaviors of the magnetic susceptibility in different doping can
also be easily explained. The resistivity along c-axis is discussed.",0810.0169v2
2011-01-29,"Crystal structure, physical properties and superconductivity in $A_{x}$Fe$_2$Se$_2$ single crystals","We studied the correlation among structure and transport properties and
superconductivity in the different $A_x$Fe$_2$Se$_2$ single crystals ($A$ = K,
Rb, and Cs). Two sets of (00$l$) reflections are observed in the X-ray single
crystal diffraction patterns, and arise from the intrinsic inhomogeneous
distribution of the intercalated alkali atoms. The occurrence of
superconductivity is closely related to the {\sl c}-axis lattice constant, and
the $A$ content is crucial to superconductivity. The hump observed in
resistivity seems to be irrelevant to superconductivity. There exist many
deficiencies within the FeSe layers in $A_x$Fe$_2$Se$_2$, while their $T_{\rm
c}$ does not change so much. In this sense, superconductivity is robust to the
Fe and Se vacancies. Very high resistivity in the normal state should arise
from such defects in the conducting FeSe layers. $A_x$Fe$_2$Se$_2$ ($A$ = K,
Rb, and Cs) single crystals show the same susceptibility behavior in the normal
state, and no anomaly is observed in susceptibility at the hump temperature in
resistivity. The clear jump in specific heat for Rb$_x$Fe$_2$Se$_2$ and
K$_x$Fe$_2$Se$_2$ single crystals shows the good bulk superconductivity in
these crystals.",1101.5670v1
2011-03-04,Measurements of thermodynamic and transport properties of EuC$_2$: a low-temperature analogue of EuO,"EuC$_2$ is a ferromagnet with a Curie-temperature of $T_C \simeq 15\,$K. It
is semiconducting with the particularity that the resistivity drops by about 5
orders of magnitude on cooling through $T_C$, which is therefore called a
metal-insulator transition. In this paper we study the magnetization, specific
heat, thermal expansion, and the resistivity around this ferromagnetic
transition on high-quality EuC$_2$ samples. At $T_C$ we observe well defined
anomalies in the specific heat $c_p(T)$ and thermal expansion $\alpha(T)$ data.
The magnetic contributions of $c_p(T)$ and $\alpha(T)$ can satisfactorily be
described within a mean-field theory, taking into account the magnetization
data. In zero magnetic field the magnetic contributions of the specific heat
and thermal expansion fulfill a Gr\""uneisen-scaling, which is not preserved in
finite fields. From an estimation of the pressure dependence of $T_C$ via
Ehrenfest's relation, we expect a considerable increase of $T_C$ under applied
pressure due to a strong spin-lattice coupling. Furthermore the influence of
weak off stoichiometries $\delta$ in EuC$_{2 \pm \delta}$ was studied. It is
found that $\delta$ strongly affects the resistivity, but hardly changes the
transition temperature. In all these aspects, the behavior of EuC$_2$ strongly
resembles that of EuO.",1103.0980v1
2012-07-13,Synthesis and acid resistance of maya blue pigment,"Maya blue is an organo-clay artificial pigment composed of indigo and
palygorskite. It was invented and frequently used in Mesoamerica in ancient
times (eighth to 16th centuries). We analyse in this paper one of the
characteristics of Maya blue that has attracted the attention of scientists
since its rediscovery in 1931: its high stability against chemical aggression
(acids, alkalis, solvents, etc.) and biodegradation, which has permitted the
survival of many works of art for centuries in hostile environments, such as
the tropical forest. We have reproduced the different methods proposed to
produce a synthetic pigment with the characteristics of the ancient Maya blue.
The stability of the pigments produced using either palygorskite or sepiolite
has been analysed by performing acid attacks of different intensities. The
results are analysed in terms of pigment decolouration and destruction of the
clay lattice, revealed by X-ray diffraction. Palygorskite pigments are much
more resistant than sepiolite pigments. It is shown that indigo does not
protect the clay lattice against acid aggression. We show that Maya blue is an
extremely resistant pigment, but it can be destroyed using very intense acid
treatment under reflux.",1207.3229v1
2013-04-07,Quasi-classical physics and T-linear resistivity in both strongly correlated and ordinary metals,"We show that near a quantum critical point generating quantum criticality of
strongly correlated metals where the density of electron states diverges, the
quasi-classical physics remains applicable to the description of the
resistivity \rho of strongly correlated metals due to the presence of a
transverse zero-sound collective mode, reminiscent of the phonon mode in
solids. We demonstrate that at T, being in excess of an extremely low Debye
temperature T_D, the resistivity \rho(T) changes linearly with T, since the
mechanism, forming the T dependence of \rho(T), is the same as the
electron-phonon mechanism that prevails at high temperatures in ordinary
metals. Thus, electron-phonon scattering leads to near material-independence of
the lifetime \tau of quasiparticles that is expressed as the ratio of the
Planck constant \hbar to the Boltzmann constant k_B, T\tau\sim \hbar/k_B. We
find that at T<T_D there exists a different mechanism, maintaining the T-linear
dependence of \rho(T), and making the constancy of \tau fail in spite of the
presence of T-linear dependence. Our results are in good agreement with
exciting experimental observations.",1304.2068v4
2013-09-13,1/f noise in graphene,"We present a novel and comprehensive model of 1/f noise in nanoscale graphene
devices that accounts for the unusual and so far unexplained experimental
characteristics. We find that the noise power spectral density versus carrier
concentration of single-layer sheet devices has a behavior characterized by a
shape going from the M to the Gamma type as the material inhomogeneity
increases, whereas the shape becomes of V type in bilayer sheet devices for any
inhomogeneity, or of M type at high carrier concentration. In single-layer
nanoribbons, instead, the ratio of noise to resistance versus the latter
quantity is approximately constant, whereas in the bilayer case it exhibits a
linear decrease on a logarithmic scale as resistance increases and its limit
for zero resistance equals the single-layer value. Noise at the Dirac point is
much greater in single-layer than in bilayer devices and it increases with
temperature. The origin of 1/f noise is attributed to the traps in the device
and to their relaxation time dispersion. The coupling of trap charge
fluctuations with the electrode current is computed according to the
electrokinematics theorem, by taking into account their opposite effects on
electrons and holes as well as the device inhomogeneities. The results agree
well with experiments.",1309.3420v1
2014-09-19,Absence of a quantum limit to charge diffusion in bad metals,"Good metals are characterised by diffusive transport of coherent
quasi-particle states and the resistivity is much less than the
Mott-Ioffe-Regel (MIR) limit, $\frac{ha}{e^{2}}$, where $a$ is the lattice
constant. In bad metals, such as many strongly correlated electron materials,
the resistivity exceeds the Mott-Ioffe-Regel limit and the transport is
incoherent in nature. Hartnoll, loosely motivated by holographic duality
(AdS/CFT correspondence) in string theory, recently proposed a lower bound to
the charge diffusion constant, $D \gtrsim \hbar v_{F}^{2}/(k_{B}T)$, in the
incoherent regime of transport, where $v_F$ is the Fermi velocity and $T$ the
temperature. Using dynamical mean field theory (DMFT) we calculate the charge
diffusion constant in a single band Hubbard model at half filling. We show that
in the strongly correlated regime the Hartnoll's bound is violated in the
crossover region between the coherent Fermi liquid region and the incoherent
(bad metal) local moment region. The violation occurs even when the bare Fermi
velocity $v_F$ is replaced by its low temperature renormalised value,
$v_F^*$.The bound is satisfied at all temperatures in the weakly and moderately
correlated systems as well as in strongly correlated systems in the high
temperature region where the resistivity is close to linear in temperature. Our
calculated charge diffusion constant, in the incoherent regime of transport,
also strongly violates a proposed quantum limit of spin diffusion, $D_{s} \sim
1.3 \hbar/m$, where $m$ is the fermion mass, experimentally observed and
theoretically calculated in a cold degenerate Fermi gas in the unitary limit of
scattering.",1409.5662v2
2016-05-26,"Fast suppression of superconductivity with Fe site Ni substitution in Fe1-xNixSe0.5Te0.5 (x=0.0, 0.01, 0.03, 0.05, 0.07, 0.10 and 0.20) single crystals","We report the effect of Ni doping on superconductivity of FeSe0.5Te0.5. The
single crystal samples of series Fe1-xNixSe0.5Te0.5 (x=0.0, 0.01, 0.03, 0.05,
0.07, 0.10 and 0.20) are synthesized via vacuum shield solid state reaction
route and high temperature heating followed by slow cooling. All the crystals
of Fe1-xNixSe0.5Te0.5 series with x up to 0.20, i.e., 20% substitution of Ni at
Fe site are crystallized in single phase tetragonal structure with space group
P4/nmm. The electrical resistivity measurements revealed that Tc decreases fast
with increase of Ni concentration in Fe1-xNixSe0.5Te0.5. Namely the
superconducting transition temperature (Tc) being defined as resistivity =0
decrease from 12K to around 4K and 2K for x=0.01 and 0.03 samples respectively.
For x=0.05 (5at% Ni at Fe site) though Tconset is observed in resistivity
measurements but \r{ho}=0 is not seen down to 2K. For x more than 0.07, neither
the Tconset nor Tc\r{ho}=0 is seen down 2K in R-T measurements. It is
demonstrated that Ni doping at Fe site in FeSe0.5Te0.5 superconductor
suppresses superconductivity fast. The rate of Tc depression is albeit non
monotonic. Summarily, a systematic study on suppression of superconductivity
with Fe site Ni doping in flux free gown FeSe0.5Te0.5 single crystals is
presented in the current communication.",1605.08217v2
2016-06-23,Resistive properties and phase diagram of the organic antiferromagnetic metal $κ$-(BETS)$_2$FeCl$_4$,"The low-temperature electronic state of the layered organic charge-transfer
salt $\kappa$-(BETS)$_2$FeCl$_4$ was probed by interlayer electrical resistance
measurements under magnetic field. Both above and below
$T_{\mathrm{N}}=0.47\,$K, the temperature of antiferromagnetic ordering of
$3d$-electron spins of Fe$^{3+}$ localized in the insulating anion layers, a
non-saturating linear $R(T)$ dependence has been observed. A weak
superconducting signal has been detected in the antiferromagnetic state, at
temperatures $\leq 0.2\,$K. Despite the very high crystal quality, only a tiny
fraction of the sample appears to be superconducting. Besides a small kink
feature in the resistivity, the impact of the antiferromagnetic ordering of
localized Fe$^{3+}$ spins on the conduction $\pi$-electron system is clearly
manifested in the Fermi surface reconstruction, as evidenced by Shubnikov-de
Haas oscillations. The ""magnetic field -- temperature"" phase diagrams for the
field directions parallel to each of the three principal crystal axes have been
determined. For magnetic field along the easy axis a spin-flop transition has
been found. Similarities and differences between the present material and the
sister compound $\kappa$-(BETS)$_2$FeBr$_4$ are discussed.",1606.07331v3
2016-10-28,Asymmetric pentagonal metal meshes for flexible transparent electrodes and heaters,"Metal meshes have emerged as an important class of flexible transparent
electrodes. We report on the characteristics of a new class of asymmetric
meshes, tiled using a recently-discovered family of pentagons. Micron-scale
meshes were fabricated on flexible polyethylene terephthalate substrates via
optical lithography, metal evaporation (Ti 10 nm, Pt 50 nm) and lift-off. Three
different designs were assessed, each with the same tessellation pattern and
linewidth (5 micron), but with different sizes of the fundamental pentagonal
unit. The designs corresponded to areal coverage of the metal patterns of 27%
(Design#1), 14% (Design#2) and 9% (Design#3), respectively. Good mechanical
stability was observed for both tensile strain and compressive strain. After
1,000 bending cycles, devices subjected to tensile strain showed fractional
resistance increases in the range 8% to 17% with the lowest changes observed
for Design#2. Devices subjected to compressive strain showed fractional
resistance increases in the range 0% to 7% with best results observed for
Design#1. The performance of the pentagonal metal mesh devices as visible
transparent heaters via Joule heating was also assessed. A saturation
temperature of 88 +/- 1 degrees C was achieved at low voltage (5 V) with a fast
response time (~ 20 s) and a high thermal resistance (168 +/- 6 degrees C
cm2/W). Finally, de-icing was successfully demonstrated (45 s at 5 V) for an
ice layer on a glass coupon placed on top of the PET substrate.",1611.02744v1
2018-11-06,Metallic surface states in a correlated d-electron topological Kondo insulator candidate FeSb2,"The resistance of a conventional insulator diverges as temperature approaches
zero. The peculiar low temperature resistivity saturation in the 4f Kondo
insulator (KI) SmB6 has spurred proposals of a correlation-driven topological
Kondo insulator (TKI) with exotic ground states. However, the scarcity of model
TKI material families leaves difficulties in disentangling key ingredients from
irrelevant details. Here we use angle-resolved photoemission spectroscopy
(ARPES) to study FeSb2, a correlated d-electron KI candidate that also exhibits
a low temperature resistivity saturation. On the (010) surface, we find a rich
assemblage of metallic states with two-dimensional dispersion. Measurements of
the bulk band structure reveal band renormalization, a large
temperature-dependent band shift, and flat spectral features along certain high
symmetry directions, providing spectroscopic evidence for strong correlations.
Our observations suggest that exotic insulating states resembling those in SmB6
and YbB12 may also exist in systems with d instead of f electrons.",1811.02183v3
2016-03-09,Quantization of Hall Resistance at the Metallic Interface between an Oxide Insulator and SrTiO$_{3}$,"The two-dimensional metal forming at the interface between an oxide insulator
and SrTiO3 provides new opportunities for oxide electronics. However, the
quantum Hall effect, one of the most fascinating effects of electrons confined
in two dimensions, remains underexplored at these complex oxide
heterointerfaces. Here, we report the experimental observation of quantized
Hall resistance in a SrTiO3 heterointerface based on the modulation-doped
amorphous-LaAlO$_{3}$/SrTiO$_{3}$ heterostructure, which exhibits both high
electron mobility exceeding 10000 cm$^{2}$/Vs and low carrier density on the
order of ~10$^{12}$ cm$^{-2}$. Along with unambiguous Shubnikov-de Haas
oscillations, the spacing of the quantized Hall resistance suggests that the
interface is comprised of a single quantum well with ten parallel conducting
two-dimensional subbands. This provides new insight into the electronic
structure of conducting oxide interfaces and represents an important step
towards designing and understanding advanced oxide devices.",1603.02850v2
2017-07-21,Electrical characterization of structured platinum diselenide devices,"Platinum diselenide (PtSe2) is an exciting new member of the two-dimensional
(2D) transition metal dichalcogenide (TMD) family. it has a semimetal to
semiconductor transition when approaching monolayer thickness and has already
shown significant potential for use in device applications. Notably, PtSe2 can
be grown at low temperature making it potentially suitable for industrial
usage. Here, we address thickness dependent transport properties and
investigate electrical contacts to PtSe2, a crucial and universal element of
TMD-based electronic devices. PtSe2 films have been synthesized at various
thicknesses and structured to allow contact engineering and the accurate
extraction of electrical properties. Contact resistivity and sheet resistance
extracted from transmission line method (TLM) measurements are compared for
different contact metals and different PtSe2 film thicknesses. Furthermore, the
transition from semimetal to semiconductor in PtSe2 has been indirectly
verified by electrical characterization of field-effect devices. Finally, the
influence of edge contacts at the metal - PtSe2 interface has been studied by
nanostructuring the contact area using electron beam lithography. By increasing
the edge contact length, the contact resistivity was improved by up to 70%
compared to devices with conventional top contacts. The results presented here
represent crucial steps towards realizing high-performance nanoelectronic
devices based on group-10 TMDs.",1707.06824v1
2017-08-06,Electric-field-induced extremely large change in resistance in graphene ferromagnets,"A colossal magnetoresistance ($\sim 100\times10^3\%$) and an extremely large
magnetoresistance ($\sim 1\times10^6\%$) have been previously explored in
manganite perovskites and Dirac materials, respectively. However, the
requirement of an extremely strong magnetic field (and an extremely low
temperature) makes them not applicable for realistic devices. In this work, we
propose a device that can generate even larger changes in resistance in a
zero-magnetic field and at a high temperature. The device is composed of a
graphene under two strips of yttrium iron garnet (YIG), where two gate voltages
are applied to cancel the heavy charge doping in the YIG-induced half-metallic
ferromagnets. By calculations using the Landauer-B\""{u}ttiker formalism, we
demonstrate that, when a proper gate voltage is applied on the free
ferromagnet, changes in resistance up to $305\times10^6\%$ ($16\times10^3\%$)
can be achieved at the liquid helium (nitrogen) temperature and in a zero
magnetic field. We attribute such a remarkable effect to a gate-induced
full-polarization reversal in the free ferromagnet, which results in a
metal-state to insulator-state transition in the device. We also find that, the
proposed effect can be realized in devices using other magnetic insulators such
as EuO and EuS. Our work should be helpful for developing a realistic switching
device that is energy saving and CMOS-technology compatible.",1708.01858v2
2018-08-30,Metallic glasses for spintronics: anomalous temperature dependence and giant enhancement of inverse spin Hall effect,"Spin-charge conversion via inverse spin Hall effect (ISHE) is essential for
enabling various applications of spintronics. The spin Hall response usually
follows a universal scaling relation with longitudinal electric resistivity and
has mild temperature dependence because elementary excitations play only a
minor role in resistivity and hence ISHE. Here we report that the ISHE of
metallic glasses shows nearly two orders of magnitude enhancements with
temperature increase from a threshold of 80-100 K to glass transition points.
As electric resistivity changes only marginally in the temperature range, the
anomalous temperature dependence is in defiance of the prevailing scaling law.
Such a giant temperature enhancement can be well described by a two-level
thermal excitation model of glasses and disappears after crystallization,
suggesting a new mechanism which involves unique thermal excitations of
glasses. This finding may pave new ways to achieve high spin-charge conversion
efficiency at room and higher temperatures for spintronic devices and to detect
structure and dynamics of glasses using spin currents.",1808.10371v1
2018-07-06,MRPC3b mass production for CBM-TOF and eTOF at STAR,"The Compressed Baryonic Matter (CBM) spectrometer aims to study strongly
interacting matter under extreme conditions. The key element providing hadron
identification at incident energies between 2 and 11 AGeV in heavy-ion
collisions at the SIS100 accelerator is a Time-of-Flight (TOF) wall covering
the polar angular range from $2.5^0$ --$25^0$ and full azimuth. CBM is expected
to be operational in the year 2024 at the Facility for Anti-proton and Ion
Research (FAIR) in Darmstadt, Germany. The existing conceptual design foresees
a 120 m^2 TOF-wall composed of Multi-gap Resistive Plate Chambers (MRPC) which
is subdivided into a high rate region, a middle rate region and a low rate
region. The MRPC3b Multistrip-MRPCs, foreseen to be integrated in the low rate
region, have to cope with charged particle fluxes up to 1 kHz/cm2 and therefore
will be constructed with thin float glass (0.28 mm thickness) as resistive
electrode material. In the scope of the FAIR phase 0 program it is planned to
install about 36 \% of the MRPC3b counters in the east endcap region of the
STAR experiment at BNL as an upgrade for the Beam Energy Scan campaign (BESII)
in 2019/2020.",1807.02452v1
2019-01-03,Study of electrostatic septum design and its high-voltage discharge protection,"In this paper, we introduce the design of electrostatic septum (ESS) for the
accelerator of Shanghai Advanced Proton Therapy (SAPT), and discuss its
mechanical structure and the material selection of the electrode. The beam loss
on the septum is studied, and the calculation results are given by the particle
simulation and by the formula which is related to the placement angle and the
divergence angle in the horizontal direction. Considering the thermal effect of
the beam loss on the head of the septum, the equilibrium temperature at work is
calculated. In addition, the distribution of the electric field and the
trajectory of the particles are also simulated. The phenomenon of vacuum
discharge in the working ESS is analyzed in detail on the relationship between
the working current and the enhancement factor of the electric field on the
electrode surface. Based on the discharge mechanism, the importance of
degassing and cleaning of ESS is analyzed. We also analyzed the effect of
external series resistance from circuit and discharge mechanism. It is
considered that series resistance within a certain range can increase the
breakdown voltage between vacuum electrodes and reduce the irreversible damage
to the surface of the electrode system caused by the discharge process. The
formula for the value of the resistance is given.",1901.00646v3
2020-05-17,Remarkable low-energy properties of the pseudogapped semimetal Be$_5$Pt,"We report measurements and calculations on the properties of the
intermetallic compound Be$_5$Pt. High-quality polycrystalline samples show a
nearly constant temperature dependence of the electrical resistivity over a
wide temperature range. On the other hand, relativistic electronic structure
calculations indicate the existence of a narrow pseudogap in the density of
states arising from accidental approximate Dirac cones extremely close to the
Fermi level. A small true gap of order 3 meV is present at the Fermi level, yet
the measured resistivity is nearly constant from low to room temperature. We
argue that this unexpected behavior can be understood by a cancellation of the
energy dependence of density of states and relaxation time due to disorder, and
discuss a model for electronic transport. With applied pressure, the
resistivity becomes semiconducting, consistent with theoretical calculations
that show that the band gap increases with applied pressure. We further discuss
the role of Be inclusions in the samples.",2005.08327v2
2021-04-19,Various magnetism of the compressed antiferromagnetic topological insulator EuSn2As2,"We report a comprehensive high-pressure study on the antiferromagnetic
topological insulator EuSn2As2 up to 21.1 GPa through measurements of
synchrotron x-ray diffraction, electrical resistance, magnetic resistance, and
Hall transports combined with first-principles calculations. No evident trace
of a structural phase transition is detected. The Neel temperatures determined
from resistance are increased from 24 to 77 K under pressure, which is resulted
from the enhanced magnetic exchange couplings between Eu2+ ions yielded by our
first-principles calculations. The negative magnetoresistance of EuSn2As2
persists to higher temperatures accordantly. However, the enhancement of the
observed N\'eel temperatures deviates from the calculations obviously above
10.0 GPa. In addition, the magnitude of the magnetoresistance, the Hall
coefficients, and the charge carrier densities show abrupt changes between 6.9
to 10.0 GPa. The abrupt changes probably originate from a pressure induced
valence change of Eu ions from a divalent state to a divalent and trivalent
mixed state. Our results provide insights into variation of the magnetism of
EuSn2As2 and similar antiferromagnetic topological insulators under pressure.",2104.09412v1
2021-04-20,Properties of MoO2 and MoO3 Films Prepared from the Chemically Driven Isothermal Close Space Vapor Transport Technique,"Chemically _ driven isothermal close space vapour transport was used to
prepare pure MoO2 films which were eventually converted to MoO3 by annealing in
air. According to temperature_dependent Raman measurements, the MoO2/MoO3 phase
transformation was found to occur in the 225 _ 350 oC range; no other phases
were detected during the transition. A clear change in composition and Raman
spectra, as well as noticeable modifications of the band gap and the absorption
coefficient confirmed the conversion from MoO2 to MoO3. An extensive
characterization of films of both pure phases was carried out. In particular, a
procedure was developed to determine the dispersion relation of the refractive
index of MoO2 from the shift of the interference fringes the used SiO2/Si
substrate. The obtained refractive index was corrected taking into account the
porosity calculated from elastic backscattering spectrometry. The Debye
temperature and the residual resistivity were extracted from the electrical
resistivity temperature dependence using the Bloch _ Gruneisen equation. MoO3
converted samples presented very high resistivity and a typical semiconducting
behaviour. They also showed intense and broad luminescence spectra, which were
deconvoluted considering several contributions; and its behaviour with
temperature was examined. Furthermore, surface photovoltage spectra were taken
and the relation of these spectra with the photoluminescence is discussed.",2104.10245v1
2021-08-21,Evolution of superconductivity and charge order in pressurized RbV$_3$Sb$_5$,"The kagome metals $A$V$_3$Sb$_5$ ($A=$ K, Rb, Cs) under ambient pressure
exhibit an unusual charge order, from which superconductivity emerges. In this
work, by applying hydrostatic pressure using a liquid pressure medium and
carrying out electrical resistance measurements for RbV$_3$Sb$_5$, we find the
charge order becomes suppressed under a modest pressure $p_{\rm c}$
($1.4<p_{\rm c}<1.6$ GPa), while the superconducting transition temperature
$T_{\rm c}$ is maximized. $T_{\rm c}$ is then gradually weakened with further
increase of pressure and reaches a minimum around 14.3 GPa, before exhibiting
another maximum around 22.8 GPa, signifying the presence of a second
superconducting dome. Distinct normal state resistance anomalies are found to
be associated with the second superconducting dome, similar to KV$_3$Sb$_5$.
Our findings point to qualitatively similar temperature-pressure phase diagrams
in KV$_3$Sb$_5$ and RbV$_3$Sb$_5$, and suggest a close link between the second
superconducting dome and the high-pressure resistance anomalies.",2108.09434v2
2021-08-22,"Explainable Machine Learning using Real, Synthetic and Augmented Fire Tests to Predict Fire Resistance and Spalling of RC Columns","This paper presents the development of systematic machine learning (ML)
approach to enable explainable and rapid assessment of fire resistance and
fire-induced spalling of reinforced concrete (RC) columns. The developed
approach comprises of an ensemble of three novel ML algorithms namely; random
forest (RF), extreme gradient boosted trees (ExGBT), and deep learning (DL).
These algorithms are trained to account for a wide collection of geometric
characteristics and material properties, as well as loading conditions to
examine fire performance of normal and high strength RC columns by analyzing a
comprehensive database of fire tests comprising of over 494 observations. The
developed ensemble is also capable of presenting quantifiable insights to ML
predictions; thus, breaking free from the notion of 'blackbox' ML and
establishing a solid step towards transparent and explainable ML. Most
importantly, this work tackles the scarcity of available fire tests by
proposing new techniques to leverage the use of real, synthetic and augmented
fire test observations. The developed ML ensemble has been calibrated and
validated for standard and design fire exposures and for one, two, three and
four-sided fire exposures thus; covering a wide range of practical scenarios
present during fire incidents. When fully deployed, the developed ensemble can
analyze over 5,000 RC columns in under 60 seconds thus, providing an attractive
solution for researchers and practitioners. The presented approach can also be
easily extended for evaluating fire resistance and spalling of other structural
members and under varying fire scenarios and loading conditions and hence paves
the way to modernize the state of this research area and practice.",2108.09862v1
2021-11-27,Antiferromagnetism and large magnetoresistance in GdBi single crystal,"Single crystal of the binary equi-atomic compound GdBi crystallizing in the
rock salt type cubic crystal structure with the space group $Fm\bar{3}m$ has
been grown by flux method. The electrical and magnetic measurements have been
performed on well oriented single crystals. The antiferromagnetic ordering of
the Gd moments is confirmed at $T_{\rm N} = 27.5$~K. The magnetization
measurement performed at $2$~K along the principal crystallographic direction
[100] did not show any metamagnetic transition and no sign of saturation up to
$7$~T. Zero field electrical resistivity reveals a sharp drop at $27.5$~K
suggesting a reduction in the spin disorder scattering due to the
antiferromagnetic alignment of the Gd moments. The residual resistivity at
$2$~K is 390~n$\Omega$cm suggesting a good quality of the grown crystal. The
magneto resistance attains a value of $1.0~\times~10^{4}\%$ with no sign of
saturation, in a field of $14$~T, at $T = 2$~K. Shubnikov de Hass (SdH)
oscillations have been observed in the high field range of the
magnetoresistance with five different frequencies corresponding to the extremal
areas of the Fermi surface. Analysis of the Hall data revealed a near
compensation of the charge carriers accounting for the extremely large
magnetoresistance.",2111.13836v1
2022-06-13,Ultra-High-Precision Detection of Single Microwave Photons based on a Hybrid System between Majorana Zero Mode and a Quantum Dot,"The ability to detect single photons has become increasingly essential due to
the rise of photon-based quantum computing. In this theoretical work, we
propose a system consisting of a quantum dot (QD) side-coupled to a
superconducting nanowire. The coupling opens a gap in both the QD mode and the
Majorana zero mode (MZM) at the nanowire edge, enabling photon absorption in
the system. We show that the absorbed photoelectron decays via rapid
(sub-nanosecond to nanosecond) nonradiative heat transfer to the nanowire
phonon modes rather than by spontaneous emission. Furthermore, we calculate the
temperature increase and associated resistance increase induced by the
absorption of a photon for a given appropriate set of material and
environmental parameters, yielding a temperature increase in the millikelvin
range and a resistance increase in the kiloohm range, vastly exceeding the
photon-absorption-induced temperature and resistance increases for competing
2D-3D hybrid systems by 5 and 9 orders of magnitude, respectively. Lastly, we
determine the detector efficiency and discuss the system density required for
deterministic photon number measurement, demonstrating that a photon absorption
probability of over 99.9 percent can be achieved for an integrated system
consisting of an array of nanowire-QD complexes on-chip inside a cavity. Our
results thus provide a basis for a deterministic microwave photon number
detector with an unprecedented photon-number-detection resolution.",2206.06521v4
2022-11-02,Beta-Ga2O3 MOSFETs with near 50 GHz fMAX and 5.4 MV/cm average breakdown field,"This letter reports high-performance $\mathrm{\beta} Ga2O3 thin channel
MOSFETs with T-gate and degenerately doped source/drain contacts regrown by
MOCVD. Gate length scaling (LG= 160-200 nm) leads to a peak drain current
(ID,MAX) of 285 mA/mm and peak trans-conductance (gm) of 52 mS/mm at 10 V drain
bias with 23.5 Ohm mm on resistance (Ron). A low metal/n+ contact resistance of
0.078 Ohm mm was extracted from TLM measurement. Ron is dominated by interface
resistance between channel and regrown layer. A gate-to-drain breakdown voltage
of 192 V is measured for LGD = 355 nm resulting in average breakdown field
(E_AVG) of 5.4 MV/cm. This E_AVG is the highest reported among all sub-micron
gate length lateral FETs. RF measurements on 200 nm Silicon Nitride (Si3N4)
passivated device shows a current gain cut off frequency (f_T) of 11 GHz and
record power gain cut off frequency (f_MAX) of 48 GHz. The f_T.V_Br product is
2.11 THz.V for 192 V breakdown voltage. The switching figure of merit exceeds
that of silicon and is comparable to mature wide-band gap devices.",2211.01088v1
2023-04-06,All-electrical operation of a Curie-switch at room temperature,"We present all-electrical operation of a Fe$_x$Cr$_{1-x}$-based Curie switch
at room temperature. More specifically, we study the current-induced
thermally-driven transition from ferromagnetic to antiferromagnetic
Ruderman-Kittel-Kasuya-Yosida (RKKY) indirect coupling in a
Fe/Cr/Fe$_{17.5}$Cr$_{82.5}$/Cr/Fe multilayer. Magnetometry measurements at
different temperatures show that the transition from the ferromagnetic to the
antiferromagnetic coupling at zero field is observed at $\sim$325K. Analytical
modelling confirms that the observed temperature-dependent transition from
indirect ferromagnetic to indirect antiferromangetic interlayer exchange
coupling originates from the modification of the effective interlayer exchange
constant through the ferromagnetic-to-paramagnetic transition in the
Fe$_{17.5}$Cr$_{82.5}$ spacer with minor contributions from the
thermally-driven variations of the magnetization and magnetic anisotropy of the
Fe layers. Room-temperature current-in-plane magnetotransport measurements on
the patterned Fe/Cr/Fe$_{17.5}$Cr$_{82.5}$/Cr/Fe strips show the transition
from the 'low-resistance' parallel to the 'high-resistance' antiparallel
remanent magnetization configuration, upon increased probing current density.
Quantitative comparison of the switching fields, obtained by magnetometry and
magnetotransport, confirms that the Joule heating is the main mechanism
responsible for the observed current-induced resistive switching.",2304.03040v2
2023-05-14,Response of the Verwey transition in magnetite to a controlled point-like disorder induced by 2.5 MeV electron irradiation,"A controlled point-like disorder induced by low temperature 2.5 MeV electron
irradiation was used to probe the nature of the Verwey transition in magnetite,
$\text{Fe}_{3}\text{O}_{4}$. Two large single crystals, one with optimal
transition temperature, $T_{V}\approx121$ K, and another with $T_{V}\approx109$
K, as well as biogenic nanocrystals, $T_{V}\approx110$ K, were examined.
Temperature-dependent resistivity is consistent with the
semiconductor-to-semiconductor sharp, step-like Verwey transition from a state
with a small bandgap of around 60 meV to a state with a larger bandgap of about
300 meV. The irradiation causes an up-shift of the resistivity curves above the
transition without transition smearing or broadening. It also causes an
apparent down-shift of the resistivity maximum at high temperatures. In the
lower $T_{V}$ crystal, the electron irradiation drives the transition
temperature into a ``forbidden"" regime believed to separate the first order
from the second order phase transition. Contrary to this belief, the transition
itself remains sharp and hysteretic without a significant change in the
hysteresis width. We conclude that the sudden change of the bandgap accompanied
by the monoclinic distortion and the change of magnetic anisotropy is the
reason for the Verwey transition in magnetite and the effect of additional
disorder is mostly in the smearing of the sharp gap edges near the Fermi level.",2305.08276v1
2023-09-12,Numerical study on the effects of fluid properties in electrohydrodynamic pulsating jet under constant voltage,"Pulsating jet is one of the common working modes in electrohydrodynamic
printing (EHDP) that process is highly affected by operating parameters and
material properties. In this paper, the processes of pulsating jet for liquids
with different physical properties were investigated using numerical
simulation. An electrohydrodynamic solver was established, and a charge flux
restricting step was adopted to ensure a realistic distribution of free
charges. Three various ejection regimes were observed in our simulations:
oscillating cone (OC), choked jet (CJ), and stable cone-jet (SJ). We found that
three dimensionless numbers relating to liquid properties determined the
ejection regime: the Ohnesorge number, Q0{\epsilon}r/Q, and Q0/(QRe). Based on
those dimensionless numbers, the roles of liquid properties on pulsating jet
(OC and CJ) were analyzed. In OC, the break of the jet is due to the
significant oscillation of the Taylor cone, which is mainly affected by
viscosity and conductivity. In CJ, the jet emission is terminated by the
excessive resistant force in the cone-jet transition region. For liquids with
low and medium viscosity, the dominant resistant force is the polarization
force or viscous force when {\epsilon}rRe is larger or smaller than 1,
respectively. For high viscosity liquids, the viscous force always becomes the
major resistance. These results further reveal the physical mechanism of
pulsating jet and can be used to guide its application.",2309.06277v1
2023-10-13,Controlling Umklapp scattering in bilayer graphene moir'e superlattice,"In this Letter, we present experimental findings on electron-electron
scattering in a two-dimensional moir'e heterostructure with tunable Fermi wave
vector, reciprocal lattice vector, and band gap. We achieve this in
high-mobility aligned heterostructures of bilayer graphene (BLG) and hBN.
Around half-filling, the primary contribution to the resistance of BLG/hBN
aligned superlattices arises from electron-electron Umklapp (Uee) scattering,
making the resistance of graphene/hBN moir'e devices significantly larger than
that of non-aligned devices (where Uee is forbidden). We quantify the strength
of the Uee scattering and find that it follows a universal scaling with Fermi
energy and has a non-monotonic dependence on the charge carrier density. The
Uee scattering is strongly electric field tunable and affected by
layer-polarization of BLG. It has a strong particle-hole asymmetry - the
resistance when the chemical potential is in the conduction band is
significantly lesser than when it is in the valence band, making the
electron-doped regime more practical for potential applications.",2310.08906v2
2023-11-20,Absence of metallicity and bias-dependent resistivity in low-carrier-density EuCd2As2,"EuCd2As2 was theoretically predicted to be a minimal model of Weyl semimetals
with a single pair of Weyl points in the ferromagnet state. However, the
heavily p-doped EuCd2As2 crystals in previous experiments prevent direct
identification of the semimetal hypothesis. Here we present a comprehensive
magneto-transport study of high-quality EuCd2As2 crystals with ultralow bulk
carrier density (10^13 cm-3). In contrast to the general expectation of a Weyl
semimetal phase, EuCd2As2 shows insulating behavior in both antiferromagnetic
and ferromagnetic states as well as surface-dominated conduction from band
bending. Moreover, the application of a dc bias current can dramatically
modulate the resistance by over one order of magnitude, and induce a periodic
resistance oscillation due to the geometric resonance. Such nonlinear transport
results from the highly nonequilibrium state induced by electrical field near
the band edge. Our results suggest an insulating phase in EuCd2As2 and put a
strong constraint on the underlying mechanism of anomalous transport properties
in this system.",2311.11515v1
2024-01-15,Alternating Bias Assisted Annealing of Amorphous Oxide Tunnel Junctions,"We demonstrate a transformational technique for controllably tuning the
electrical properties of fabricated thermally oxidized amorphous aluminum-oxide
tunnel junctions. Using conventional test equipment to apply an alternating
bias to a heated tunnel barrier, giant increases in the room temperature
resistance, greater than 70%, can be achieved. The rate of resistance change is
shown to be strongly temperature-dependent, and is independent of junction size
in the sub-micron regime. In order to measure their tunneling properties at mK
temperatures, we characterized transmon qubit junctions treated with this
alternating-bias assisted annealing (ABAA) technique. The measured frequencies
follow the Ambegaokar-Baratoff relation between the shifted resistance and
critical current. Further, these studies show a reduction of
junction-contributed loss on the order of $\approx 2 \times10^{-6}$, along with
a significant reduction in resonant- and off-resonant-two level system defects
when compared to untreated samples. Imaging with high-resolution TEM shows that
the barrier is still predominantly amorphous with a more uniform distribution
of aluminum coordination across the barrier relative to untreated junctions.
This new approach is expected to be widely applicable to a broad range of
devices that rely on amorphous aluminum oxide, as well as the many other
metal-insulator-metal structures used in modern electronics.",2401.07415v2
2024-01-22,Self-pulsing of Dielectric Barrier Discharges at Low Driving Frequencies,"This paper investigates the self-pulsing of Dielectric Barrier Discharges
(DBDs) at low driving frequencies. In particular, (a) the dependence of current
on the product pd of gas pressure p and the gas gap length d, (b) the effects
of lossy dielectrics (in resistive discharges) and large dielectric
permittivity (in ferroelectrics) on current dynamics, (c) the transition from
Townsend to a dynamic Capacitively Coupled Plasma (CCP) discharge with changing
pd values, and (d) the transition from Townsend to a high-frequency CCP regime
with increasing the driving frequency. A one-dimensional fluid model of Argon
plasma is coupled to an equivalent RC circuit for lossy dielectrics. Our
results show multiple current pulses per AC period in Townsend and CCP
discharge modes which are explained by uncoupled electron-ion transport in the
absence of quasineutrality and surface charge deposition at dielectric
interfaces. The number of current pulses decreases with an increasing applied
frequency when the Townsend discharge transforms into the CCP discharge. The
resistive barrier discharge with lossy dielectrics exhibits Townsend and glow
modes for the same pd value (7.6 Torr cm) for higher and lower resistances,
respectively. Finally,we show that ferroelectric materials can amplify
discharge current in DBDs. Similarities between current pulsing in DBD, Trichel
pulses in corona discharges, and subnormal oscillations in DC discharges are
discussed. 1",2401.12410v3
2015-06-26,Conventional superconductivity at 203 K at high pressures,"A superconductor is a material that can conduct electricity with no
resistance below its critical temperature (Tc). The highest Tc that has been
achieved in cuprates1 is 133 K at ambient pressure2 and 164 K at high
pressures3. As the nature of superconductivity in these materials has still not
been explained, the prospects for a higher Tc are not clear. In contrast, the
Bardeen-Cooper-Schrieffer (BCS) theory gives a guide for achieving high Tc and
does not put bounds on Tc, all that is needed is a favorable combination of
high frequency phonons, strong electron-phonon coupling, and a high density of
states. These conditions can be fulfilled for metallic hydrogen and covalent
compounds dominated by hydrogen4,5. Numerous calculations support this idea and
predict Tc of 50-235 K for many hydrides6 but only moderate Tc=17 K has been
observed experimentally7. Here we studied sulfur hydride8 where a Tc~80 K was
predicted9. We found that it transforms to a metal at pressure ~90 GPa. With
cooling superconductivity was found deduced from a sharp drop of the
resistivity to zero and a decrease of Tc with magnetic field. The pronounce
isotope shift of Tc in D2S is evidence of an electron-phonon mechanism of
superconductivity that is consistent with the BCS scenario. The
superconductivity has been confirmed by magnetic susceptibility measurements
with Tc=203K. The high Tc superconductivity most likely is due to H3S which is
formed from H2S under its decomposition under pressure. Even higher Tc, room
temperature superconductivity, can be expected in other hydrogen-based
materials since hydrogen atoms provide the high frequency phonon modes as well
as the strong electron-phonon coupling.",1506.08190v1
2014-05-01,Effect of Electrical Properties on Gd modified BiFeO3-PbZrO3,"The 0.5(BiGdxFe1-xO3)-0.5(PbZrO3) composite was synthesized using a high
temperature solid-state reaction technique. Preliminary X-ray structural
analysis confirms the formation of the composite. The dielectric constant and
loss tangent have been studied. The hysteresis loop suggest that the material
is lossy. The impedance parameters were studied using an impedance analyzer in
a wide range of frequency (102-106 Hz) at different temperatures for all
samples. The Nyquist plot suggests the contribution of bulk effect as well as
grain boundary effect and the bulk resistance deceases with rise in temperature
for all samples. The electrical transport confirms the presence of hopping
mechanism in the material. The dc conductivity increases with rise in
temperature. The frequency variation of ac conductivity shows that the compound
obeys Jonschers universal power law and confirms the Small Polaron (SP)
tunneling effect due to low activation energy for all samples. Temperature
dependence of dc and ac conductivity indicates that electrical conduction in
the materials are thermally activated process.",1405.0104v1
2019-02-13,Cu-substituted Fe2P: An emerging candidates for magnetic RAM application,"We propose that Cu-substituted Fe$_2$P, (Fe$_{1-x}$Cu$_x$)$_2$P ($x\sim
0.16$), to be an outstanding contender for the STT-MRAM application. Using
first principles based calculations in the framework of density functional
theory and through Monte Carlo simulations, we demonstrate that this material
can be used as ferromagnetic electrode in the magnetic tunnel junction (MTJ) of
STT-MRAM due to its moderate perpendicular magnetic anisotropy (PMA), large
tunnel magneto-resistance (TMR), good thermal stability and high ferromagnetic
transition temperature. We point out that the simplicity in the synthesis, huge
abundance, and non-toxicity make this material a very good candidate to replace
the current MTJ materials for STT-MRAM such as FePt,~FeCo or FeCoB.",1902.04876v1
2012-06-01,Novel highly conductive and transparent graphene based conductors,"Future wearable electronics, displays and photovoltaic devices rely on highly
conductive, transparent and yet mechanically flexible materials. Nowadays
indium tin oxide (ITO) is the most wide spread transparent conductor in
optoelectronic applications, however the mechanical rigidity of this material
limits its use for future flexible devices. Here we report novel transparent
conductors based on few layer graphene (FLG) intercalated with ferric chloride
(FeCl3) with an outstandingly high electrical conductivity and optical
transparency. We show that upon intercalation a record low sheet resistance of
8.8 Ohm/square is attained together with an optical transmittance higher than
84% in the visible range. These parameters outperform the best values of ITO
and of other carbon-based materials, making these novel transparent conductors
the best candidates for future flexible optoelectronics.",1206.0001v1
2020-11-16,"First-principles study of the electronic, magnetic, and crystal structure of perovskite molybdates","The molybdate oxides SrMoO$_3$, PbMoO$_3$, and LaMoO$_3$ are a class of
metallic perovskites that exhibit interesting properties including high
mobility, and unusual resistivity behavior. We use first-principles methods
based on density functional theory to explore the electronic, crystal, and
magnetic structure of these materials. In order to account for the electron
correlations in the partially-filled Mo $4d$ shell, a local Hubbard $U$
interaction is included. The value of $U$ is estimated via the constrained
random-phase approximation approach, and the dependence of the results on the
choice of $U$ are explored. For all materials, GGA+$U$ predicts a metal with an
orthorhombic, antiferromagnetic structure. For LaMoO$_3$, the $Pnma$ space
group is the most stable, while for SrMoO$_3$ and PbMoO$_3$, the $Imma$ and
$Pnma$ structures are close in energy. The $R_4^+$ octahedral rotations for
SrMoO$_3$ and PbMoO$_3$ are found to be overestimated compared to the
experimental low-temperature structure.",2011.08323v2
2020-11-21,Flash microwave pressing of zirconia,"Microwave Pressing is a promising way to reduce microwave sintering
temperatures and stabilize microwave powder materials processing. A
multi-physics simulation was conducted of the regulated pressure-assisted
microwave cavity. This simulation took into consideration resonance phenomena
and the nonlinear temperature-dependent material parameters of zirconia. The
intrinsic behaviors of microwave systems and zirconia make the regulation of
the microwave pressing difficult. However, the same phenomena can be used to
activate flash sintering. Flash microwave sintering uses high electric fields
of the resonant microwave profile, the Negative Temperature Behavior (NTC) of
zirconia resistivity, and the mechanical pressure applied to the powder via a
die compaction configuration. The resulting flash microwave pressing still
needs improvement in terms of the processed material structure homogeneity, but
it has the capacity to become the fastest sintering treatment as it allows room
temperature activation where the total process time only takes a few seconds.
In addition, this 10-20s processing technique has shown good potential for
improving the transparency of alumina pre-sintered specimens.",2011.14009v1
2021-03-28,Acoustic-pressure-assisted engineering of aluminium foams,"Foaming metals modulates their physical properties, enabling attractive
applications where lightweight, low thermal conductivity or acoustic isolation
are desirable. Adjusting the size of the bubbles in the foams is particularly
relevant for targeted applications. Here we provide a method with a detailed
theoretical understanding how to tune the size of the bubbles in aluminium
melts in-situ via acoustic pressure. Our description is in full agreement with
the high-rate three-dimensional X-Ray radioscopy of the bubble formation. We
complement our study with the intriguing results on the effect of foaming on
electrical resistivity, Seebeck coefficient and thermal conductivity from
cryogenic to room temperature. Compared to bulk materials the investigated foam
shows an enhancement in the thermoelectric figure of merit. These results
herald promising application of foaming in thermoelectrics materials and
devices for thermal energy conversion.",2103.15225v1
2023-04-21,Probabilistic selection and design of concrete using machine learning,"Development of robust concrete mixes with a lower environmental impact is
challenging due to natural variability in constituent materials and a multitude
of possible combinations of mix proportions. Making reliable property
predictions with machine learning can facilitate performance-based
specification of concrete, reducing material inefficiencies and improving the
sustainability of concrete construction. In this work, we develop a machine
learning algorithm that can utilize intermediate target variables and their
associated noise to predict the final target variable. We apply the methodology
to specify a concrete mix that has high resistance to carbonation, and another
concrete mix that has low environmental impact. Both mixes also fulfill targets
on the strength, density, and cost. The specified mixes are experimentally
validated against their predictions. Our generic methodology enables the
exploitation of noise in machine learning, which has a broad range of
applications in structural engineering and beyond.",2304.11226v1
2024-03-08,Superconductivity of the New Medium-Entropy Alloy V4Ti2W with a Body-Centered Cubic Structure,"Medium- and high-entropy alloy (MEA and HEA) superconductors have attracted
considerable interest since their discovery. This paper reports the
superconducting properties of ternary tungsten-containing MEA V4Ti2W for the
first time. V4Ti2W is a type II superconductor with a body-centered cubic (BCC)
structure. Experimental results of resistivity, magnetization, and heat
capacity indicate that the superconducting transition temperature of the MEA
V4Ti2W is roughly 5.0 K. The critical magnetic fields at the upper and lower
ends are 9.93(2) T and 40.7(3) mT, respectively. Interestingly, few BCC MEA
superconductors with VEC greater than 4.8 have been found. The addition of
tungsten leads to a VEC of 4.83 e/a for V4Ti2W, which is rarely higher than the
4.8 value. Adding tungsten element expands the variety of MEA alloys, which may
improve the microstructure and mechanical properties of materials and even
superconducting properties. This material could potentially offer a new
platform for the investigation of innovative MEA and HEA superconductors.",2403.05115v1
2024-03-28,Challenges in extracting nonlinear current-induced phenomena in Ca2RuO4,"An appealing direction to change the properties of strongly correlated
materials is to induce nonequilibrium steady states by the application of a
direct current. While access to these novel states is of high scientific
interest, Joule heating due to current flow often constitutes a hurdle to
identify nonthermal effects. The biggest challenge usually resides in measuring
accurately the temperature of a sample subjected to direct current, and to use
probes that give direct information of the material. In this work, we exploit
the simultaneous measurement of electrical transport and magnetisation to probe
non-equilibrium steady states in Ca2RuO4. In order to reveal non-thermal
current-induced effects, we employ a simple model of Joule self-heating to
remove the effects of heating and discuss the importance of temperature
inhomogeneity within the sample. Our approach provides a solid basis for
investigating current-induced phenomena in highly resistive materials.",2403.19210v1
2000-01-07,Near-Field Microwave Microscopy of Materials Properties,"Near-field microwave microscopy has created the opportunity for a new class
of electrodynamics experiments of materials. Freed from the constraints of
traditional microwave optics, experiments can be carried out at high spatial
resolution over a broad frequency range. In addition, the measurements can be
done quantitatively so that images of microwave materials properties can be
created. We review the five major types of near-field microwave microscopes and
discuss our own form of microscopy in detail. Quantitative images of microwave
sheet resistance, dielectric constant, and dielectric tunability are presented
and discussed. Future prospects for near-field measurements of microwave
electrodynamic properties are also presented.",0001075v2
2010-08-18,A Stepped Oxide Hetero-Material Gate Trench Power MOSFET for Improved Performance,"In this work, we propose a new Stepped Oxide Hetero-Material Trench (SOHMT)
power MOSFET with three sections in the trench gate (an N+ poly gate sandwiched
between two P+ poly gates) and having different gate oxide thicknesses
(increasing from source side to drain side). The different gate oxide thickness
serves the purpose of simultaneously achieving (i) a good gate control on the
channel charge and (ii) a lesser gate to drain capacitance. As a result, we
obtain higher transconductance as well as reduced switching delays, making the
proposed device suitable for both RF amplification and high speed switching
applications. In addition, the sandwiched gate with different work function
gate materials modifies the electric field profile in the channel resulting in
an improved breakdown voltage. Using two-dimensional simulations, we have shown
that the proposed device structure exhibits about 32% enhancement in breakdown
voltage, 25% reduction in switching delays, 20% enhancement in peak
transconductance and 10% reduction in figure of merit (product of ON-resistance
and gate charge) as compared to the conventional trench gate MOSFET.",1008.3022v1
2016-10-05,A Novel Nanoporous Graphite Based on Graphynes: First Principles Structure and Carbon Dioxide Preferential Physisorption,"Ubiquitous graphene is a stricly 2D material representing an ideal adsorbing
platform due to its large specific surface area as well as its mechanical
strength and resistance to both thermal and chemical stresses. However,
graphene as a bulk material has the tendency to form irreversible agglomerates
leading to 3D graphitic structures with a significant decrease of the area
available for adsorption and no room for gas intercalation. In this paper a
novel nanoporous graphite formed by graphtriyne sheets is introduced: its 3D
structure is theoretically assessed by means of electronic structure and
molecular dynamics computations within the DFT level of theory. It is found
that the novel layered carbon allotrope is almost as compact as pristine
graphite but the inherent porosity of the 2D graphyne sheets and its relative
stacking leads to nanochannels that cross the material and whose sub-nanometer
size could allow the diffusion and storage of gas species. A molecular
prototype of the nanochannel is used to accurately determine first principles
adsorption energies and enthalpies for CO2, N2, H2O and H2 within the pores.
The proposed porous graphite presents no significant barrier for gas diffusion
and it shows a high propensity for CO2 physisorption with respect to the other
relevant components in both pre- and post-combustion gas streams.",1610.01313v1
2017-06-30,Role of anisotropy in determining stability of electrodeposition at solid-solid interfaces,"We investigate the stability of electrodeposition at solid-solid interfaces
for materials exhibiting an anisotropic mechanical response. The stability of
electrodeposition or resistance to the formation of dendrites is studied within
a linear stability analysis. The deformation and stress equations are solved
using the Stroh formalism and faithfully recover the boundary conditions at the
interface. The stability parameter is used to quantify the stability of
different solid-solid interfaces incorporating the full anisotropy of the
elastic tensor of the two materials. Results show a high degree of variability
in the stability parameter depending on the crystallographic orientation of the
solids in contact, and point to opportunities for exploiting this effect in
developing Li metal anodes.",1707.00064v3
2021-02-27,van der Waals heterostructures based on atomically-thin superconductors,"Van der Waals heterostructures (vdWHs) allow the assembly of high-crystalline
two-dimensional (2D) materials in order to explore dimensionality effects in
strongly correlated systems and the emergence of potential new physical
scenarios. In this work, it is illustrated the feasibility to integrate 2D
materials in-between 2D superconductors. Particularly, it is presented the
fabrication and electrical characterization of vertical vdWHs based on
air-unstable atomically-thin transition metal dichalcogenides formed by
NbSe2/TaS2/NbSe2 stacks, with TaS2 being the insulator 1T-TaS2 or the metal
2H-TaS2. Phase transitions as 1T-TaS2 charge density wave and NbSe2
superconductivity are detected. An enhancement of the vdWH resistance due to
Andreev reflections is observed below the superconducting transition
temperature of the NbSe2 flakes. Moreover, in the NbSe2 superconducting state,
the field and temperature dependence of the normalized conductance is analyzed
within the Dynes' model and the overall behavior is consistent with the
Bardeen-Cooper-Schrieffer theory. This vdWH approach can be extended to other
2D materials, such as 2D magnets or topological insulators, with the aim of
exploring the new emergent properties that may arise from such combinations.",2103.00203v1
2022-11-18,Pressure-Tuning Superconductivity in Noncentrosymmetric Topological Materials ZrRuAs,"Recently, the hexagonal phase of ternary transition metal pnictides TT'X (T =
Zr, Hf; T'= Ru; X = P, As), which are well-known noncentrosymmetric
superconductors, were predicted to host nontrivial bulk topology. In this work,
we systematically investigate the electronic responses of ZrRuAs to external
pressure. At ambient pressure, ZrRuAs show superconductivity with Tc ~ 7.74 K,
while a large upper critical field ~ 13.03 T is obtained for ZrRuAs, which is
comparable to the weak-coupling Pauli limit. The resistivity of ZrRuAs exhibits
a non-monotonic evolution with increasing pressure. The superconducting
transition temperature Tc increases with applied pressure and reaches a maximum
value of 7.93 K at 2.1 GPa, followed by a decrease. The nontrivial topology is
robust and persists up to the high-pressure regime. Considering both robust
superconductivity and intriguing topology in this material, our results could
contribute to studies of the interplay between topological electronic states
and superconductivity.",2211.10289v1
2023-03-28,On optimization of heterogeneous materials for enhanced resistance to bulk fracture,"We propose a novel approach to optimize the design of heterogeneous
materials, with the goal of enhancing their effective fracture toughness under
mode-I loading. The method employs a Gaussian processes-based Bayesian
optimization framework to determine the optimal shapes and locations of stiff
elliptical inclusions within a periodic microstructure in two dimensions. To
model crack propagation, the phase-field fracture method with an efficient
interior-point monolithic solver and adaptive mesh refinement, is used. To
account for the high sensitivity of fracture properties to initial crack
location with respect to heterogeneities, we consider multiple cases of initial
crack and optimize the material for the worst-case scenario. We also impose a
minimum clearance constraint between the inclusions to ensure design
feasibility. Numerical experiments demonstrate that the method significantly
improves the fracture toughness of the material compared to the homogeneous
case.",2303.15801v1
2024-01-23,Electronic Noise Spectroscopy of Quasi-2D van der Waals Antiferromagnetic Semiconductors,"We investigated low-frequency current fluctuations, i.e. electronic noise, in
FePS3 van der Waals, layered antiferromagnetic semiconductor. The noise
measurements have been used as noise spectroscopy for advanced materials
characterization of the charge carrier dynamics affected by spin ordering and
trapping states. Owing to the high resistivity of the material, we conducted
measurements on vertical device configuration. The measured noise spectra
reveal pronounced Lorentzian peaks of two different origins. One peak is
observed only near the Neel temperature and it is attributed to the
corresponding magnetic phase transition. The second Lorentzian peak, visible in
the entire measured temperature range, has the characteristics of the
trap-assisted generation-recombination processes similar to those in
conventional semiconductors but shows a clear effect of the spin order
reconfiguration near the Neel temperature. The obtained results contribute to
understanding the electron and spin dynamics in this type of antiferromagnetic
semiconductors and demonstrate the potential of electronic noise spectroscopy
for advanced materials characterization.",2401.12432v1
2015-04-24,Graphene surpasses GaAs/AlGaAs for the application of the quantum Hall effect in metrology,"The quantum Hall effect (QHE) theoretically provides a universal standard of
electrical resistance in terms of the Planck constant $h$ and the electron
charge $e$. In graphene, the spacing between the lowest discrete energy levels
occupied by the charge carriers under magnetic field is exceptionally large.
This is promising for a quantum Hall resistance standard more practical in
graphene than in the GaAs/AlGaAs devices currently used in national metrology
institutes. Here, we demonstrate that large QHE devices, made of high quality
graphene grown by propane/hydrogen chemical vapour deposition on SiC
substrates, can surpass state-of-the-art GaAs/AlGaAs devices by considerable
margins in their required operational conditions. In particular, in the device
presented here, the Hall resistance is accurately quantized within $1\times
10^{-9}$ over a 10-T wide range of magnetic field with a remarkable lower bound
at 3.5 T, temperatures as high as 10 K, or measurement currents as high as 0.5
mA. These significantly enlarged and relaxed operational conditions, with a
very convenient compromise of 5 T, 5.1 K and 50 $\mu$A, set the superiority of
graphene for this application and for the new generation of versatile and
user-friendly quantum standards, compatible with a broader industrial use. We
also measured an agreement of the quantized Hall resistance in graphene and
GaAs/AlGaAs with an ultimate relative uncertainty of $8.2\times 10^{-11}$. This
supports the universality of the QHE and its theoretical relation to $h$ and
$e$, essential for the application in metrology, particularly in view of the
forthcoming Syst\`eme International d'unit\'es (SI) based on fundamental
constants of physics, including the redefinition of the kilogram in terms of
$h$.",1504.06511v1
2009-12-24,Nanostructural Superconducting Materials for Fault Current Limiters and Cryogenic Electrical Machines,"Materials of the Y-Ba-Cu-O (melt-textured YBa2Cu3O7-d-based materials or
MT-YBCO) and Mg-B-O (MgB2-based materials) systems with high superconducting
performance, which can be attained due to the formation of regularly
distributed nanostructural defects and inhomogenities in their structure can be
effectively used in cryogenic technique, in particular in fault current
limiters and electrical machines (electromotors, generators, pumps for liquid
gases, etc.). The developed processes of high-temperature (900-800 oC)
oxygenation under elevated pressure (16 MPa) of MT-YBCO and high-pressure (2
GPa) synthesis of MgB2-based materials allowed us to attain high SC (critical
current densities, upper critical fields, fields of irreversibility, trapped
magnetic fields) and mechanical (hardness, fracture toughness, Young modulus)
characteristics. It has been shown that the effect of materials properties
improvement in the case of MT-YBCO was attained due to the formation of high
twin density (20-22 micron-1), prevention of macrockracking and reduction (by a
factor of 4.5) of microcrack density, and in the case of MgB2-based materials
due to the formation of oxygen-enriched as compared to the matrix phase
fine-dispersed Mg-B-O inhomogenities as well as inclusions of higher borides
with near-MgB12 stoichiometry in the Mg-B-O matrix (with 15-37 nm average grain
sizes). The possibility is shown to obtain the rather high Tc (37 K) and
critical current densities in materials with MgB12 matrix (with 95 percent of
shielding fraction as calculated from the resistant curve).",0912.4899v1
2010-11-01,Modeling materials with optimized transport properties,"Following demands for materials with peculiar transport properties, e.g. in
magnetoelectronics or thermoelectrics, there is a need for materials modeling
at the quantum-mechanical level. We combine density-functional with various
scale-bridging tools to establish correlations between the macroscopic
properties and the atomic structure of materials. For examples, magnetic memory
devices exploiting the tunneling magneto-resistance (TMR) effect depend
crucially on the spin polarization of the electrodes. Heusler alloys, e.g.
Co2MnSi, if perfectly ordered, are ferromagnetic half-metals with (ideally)
100% spin polarization. Their performance as electrodes in TMR devices is
limited by atomic disorder and deviations from perfect stoichiometry, but also
by interface states at the tunneling barrier. We use ab initio thermodynamics
in conjunction with the cluster expansion technique to show that excess
manganese in the alloy and at the interface helps to preserve the desired
half-metallic property. As another example, nanostructured materials with a
reduced thermal conductivity but good electrical conductivity are sought for
applications in thermoelectrics. Semiconductor heterostructures with a regular
arrangement of nanoscale inclusions ('quantum dot superlattices') hold the
promise of a high thermoelectric figure of merit. Our theoretical analysis
reveals that an increased figure of merit is to be expected if the quantum dot
size, the superlattice period and the doping level are all suitably fine-tuned.
Such a superlattice thus constitutes a material whose transport properties are
controlled by geometrical features at the nanoscale.",1011.0324v1
2023-05-15,Thermal conductivity of macroporous graphene aerogel measured using high resolution comparative infrared thermal microscopy,"Graphene aerogel (GA) is a promising material for thermal management
applications across many fields due to its lightweight and thermally insulative
properties. However, standard values for important thermal properties, such as
thermal conductivity, remain elusive due to the lack of reliable
characterization techniques for highly porous materials. Comparative infrared
thermal microscopy (CITM) is an attractive technique to obtain thermal
conductance values of porous materials like GA, due to its non-invasive
character, which requires no probing of, or contact with, the often-delicate
structures and frameworks. In this study, we improve upon CITM by utilizing a
higher resolution imaging setup and reducing the need for pore-filling coating
of the sample (previously used to adjust for emissivity). This upgraded setup,
verified by characterizing porous silica aerogel, allows for a more accurate
confirmation of the fundamental thermal conductivity value of GA while still
accounting for the thermal resistance at material boundaries. Using this
improved method, we measure a thermal conductivity below 0.036 W/m$\cdot$K for
commercial GA using multiple reference materials. These measurements
demonstrate the impact of higher resolution thermal imaging to improve accuracy
in low density, highly porous materials characterization. This study also
reports thermal conductivity for much lower density (less than 15 mg/cm$^3$) GA
than previously published studies while maintaining the robustness of the CITM
technique.",2305.09033v3
2024-04-18,Assessing the Risk of Proliferation via Fissile Material Breeding in ARC-class Fusion Reactors,"Construction of a nuclear weapon requires access to kilogram-scale quantities
of fissile material, which can be bred from fertile material like U-238 and
Th-232 via neutron capture. Future fusion power plants, with total neutron
source rates in excess of $10^{20}$ n/s, could breed weapons-relevant
quantities of fissile material on short timescales, posing a breakout
proliferation risk. The ARC-class fusion reactor design is characterized by
demountable high temperature superconducting magnets, a FLiBe liquid immersion
blanket, and a relatively small size ($\sim$ 4 m major radius, $\sim$ 1 m minor
radius). We use the open-source Monte Carlo neutronics code OpenMC to perform
self-consistent time-dependent simulations of a representative ARC-class
blanket to assess the feasibility of a fissile breeding breakout scenario. We
find that a significant quantity of fissile material can be bred in less than
six months of full power operation for initial fertile inventories ranging from
5 to 50 metric tons, representing a non-negligible proliferation risk. We
further study the feasibility of this scenario by examining other consequences
of fissile breeding such as reduced tritium breeding ratio, extra heat from
fission and decay heat, isotopic purity of bred material, and self-protection
time of irradiated blanket material. We also examine the impact of Li-6
enrichment on fissile breeding and find that it substantially reduces breeding
rate, motivating its use as a proliferation resistance tool.",2404.12451v1
2022-01-10,A theory for anisotropic magnetoresistance in materials with two vector order parameters,"Anisotropic magnetoresistance (AMR) and related planar Hall resistance (PHR)
are ubiquitous phenomena of magnetic materials. Although the universal angular
dependences of AMR and PHR in magnetic polycrystalline materials with one order
parameter are well known, no similar universal relation for other class of
magnetic materials are known to date. Here I present a general theory of
galvanomagnetic effects in magnetic materials with two vector order parameters,
such as magnetic single crystals with a dominated crystalline axis or
polycrystalline non-collinear ferrimagnetic materials. It is shown that AMR and
PHR have a universal angular dependence. In general, both longitudinal and
transverse resistivity are non-reciprocal in the absence of inversion symmetry:
Resistivity takes different value when the current is reversed. Different from
simple magnetic polycrystalline materials where AMR and PHR have the same
magnitude, and $\pi/4$ out of phase, the magnitude of AMR and PHR of materials
with two vector order parameters are not the same in general, and the phase
difference is not $\pi/4$. Instead of $\pi$ periodicity of the usual AMR and
PHR, the periodicities of materials with two order parameters are $2\pi$.",2201.03316v1
2003-11-04,Resistive transition in $π$-junction superconductors,"The resistivity behavior of inhomogeneous superconductors with random $\pi$
junctions, as in high-$T_c$ materials with d-wave symmetry, is studied by
numerical simulation of a three-dimensional XY spin glass model. Above a
concentration threshold of antiferromagnetic couplings, a resistive transition
is found in the chiral-glass phase at finite temperatures and the critical
exponents are determined from dynamic scaling analysis. The power-law exponent
for the nonlinear contribution found in recent resistivity measurements is
determined by the dynamic critical exponent of this transition.",0311083v1
2004-07-28,Universal behavior of giant electroresistance in epitaxial La0.67Ca0.33MnO3 thin films,"We report a giant resistance drop induced by dc electrical currents in
La0.67Ca0.33MnO3 epitaxial thin films. Resistance of the patterned thin films
decreases exponentially with increasing current and a maximum drop shows at the
temperature of resistance peak Tp. Variation of resistance with current
densities can be scaled below and above Tp, respectively. This work can be
useful for the future applications of electroresistance.",0407719v2
2005-06-17,Experimental Evidence for Zero DC Resistance of Superconductors,"Even after nearly a century of discovery of superconductivity, there has been
no direct experimental proof of the expected zero resistance of
superconductors. Indeed, it has been believed that it is impossible to
experimentally show that the resistance has fallen exactly to zero. In this
work we demonstrate that the dc resistivity of a superconducting material below
the transition temperature has to be exactly zero.",0506426v2
2007-11-29,Increase of Thermal Resistance Between a Nanostructure and a Surface due to Phonon Multireflections,"The thermal resistance between a nanostructure and a half-body is calculated
in the framework of particle-phonons physics. The current models approximate
the nanostructure as a thermal bath. We prove that the multireflections of heat
carriers in the nanostructure significantly increase resistance in
contradiction with former predictions. This increase depends on the shape of
the nanostructure and the heat carriers mean free path only. We provide a
general and simple expression for the contact resistance and examine the
specific cases of nanowires and nanoparticles.",0711.4718v1
2009-09-07,Low-Temperature Resistivity Anomalies in Periodic Curved Surfaces,"Effects of periodic curvature on the the electrical resistivity of corrugated
semiconductor films are theoretically considered. The presence of a
curvature-induced potential affects the motion of electrons confined to the
thin curved film, resulting in a significant resistivity enhancement at
specific values of two geometric parameters: the amplitude and period of the
surface corrugation. The maximal values of the two parameters in order to
observe the corrugation-induced resistivity enhancement in actual experiments
are quantified by employing existing material constants.",0909.1135v1
2011-02-23,Pt/Ti/Al2O3/Al tunnel junctions showing electroforming-free bipolar resistive switching behavior,"We investigated electroforming-free bipolar resistive switching behavior in
Pt/Ti/Al2O3/Al tunnel junctions where the Al2O3 tunnel barrier was naturally
formed on Al in air. Various compliance current values for the junction's set
switching successfully lead to various resistance values in its low resistance
state, suggesting the possibility for multi-level-operation. A mechanism for
the bipolar switching is qualitatively discussed in terms of the modulation of
the tunnel barrier by the reactive Ti layer on top of the barrier.",1102.4720v1
2013-05-09,Electrostatic gating of metallic and insulating phases in SmNiO3 ultrathin films,"The correlated electron system SmNiO3 exhibits a metal-insulator phase
transition at 130 {\deg}C. Using an ionic liquid as an electric double layer
(EDL) gate on three-terminal ultrathin SmNiO3 devices, we investigate gate
control of the channel resistance and transition temperature. Resistance
reduction is observed across both insulating and metallic phases with ~25%
modulation at room temperature. We show that resistance modulation is
predominantly due to electrostatic charge accumulation and not electrochemical
doping by control experiments in inert and air en-vironments. We model the
resistance behavior and estimate the accumulated sheet density (~1-2 x 10^14
cm^-2) and EDL capacitance (~12 {\mu}F/cm^2).",1305.2111v1
2013-06-18,Some features of anomalous conductivity of vinylene and vinyl chloride copolymer films,"Manifestations of anomalous conductivity in polar dielectric films is
demonstrated for the first time on samples of copolymer of vinylene and vinyl
chloride, as was previously observed on modified PVC samples. On the base of
these experimental results important new insights into the physical sense of
traditionally used in these conditions specific resistivity indicators, both
volume and surface, should be replaced by transverse and longitudinal
resistance (according to polymer film surface) respectively, because the
specific resistivity of polymer composite does not permits to calculate as
usual the resistance of sample of arbitrary form..",1306.4127v1
2013-07-02,The density of states of graphene underneath a metal electrode and its correlation with the contact resistivity,"The density of states (DOS) of graphene underneath a metal is estimated
through a quantum capacitance measurement of the metal/graphene/SiO2/n+-Si
contact structure fabricated by a resist-free metal deposition process.
Graphene underneath Au maintains a linear DOS - energy relationship except near
the Dirac point, whereas the DOS of graphene underneath Ni is broken and
largely enhanced around the Dirac point, resulting in only a slight modulation
of the Fermi energy. Moreover, the DOS of graphene in the contact structure is
correlated with the contact resistivity measured using devices fabricated by
the resist-free process.",1307.0690v1
2013-08-06,"Correct nonlinearity and hysteresis of volt-ampere characteristics of spin valves, magnetic tunnel junctions and memristors","There are essential achievements in synthesis of interesting for creation of
compact electronic memory switched by own current structures of spin valves and
magnetic tunnel junctions with hysteretic current dependences of resistance. In
the offered message the attention to discrepancy to physical principles of a
hysteresis of resistance represented in publications is paid. It is
schematically presented how the dependences of resistance on current should
look not contradicting the energy conservation law for hysteresis dependence of
resistance on current and corresponding volt-ampere characteristic.",1308.1220v1
2015-09-28,Multi-level Resistive Switching Characteristics of W/Co:TiO2/FTO Structures,"In the present work, multi-level resistive switching (RS) in W/Co:TiO2/FTO
structures induced by a multi-mixed mechanism was studied. It was found that
the devices could be reproducibly programmed into three nonvolatile resistance
states. And the directly switching between any resistance states was realized.
This increases the operation speed and lowers the complexity of control circuit
of multi-state nonvolatile memory.",1509.08211v1
2020-09-16,The electric pulses induced multi-resistance states in the hysteresis temperature range of 1T-TaS2 and 1T-TaS1.6Se0.4,"The electric pulse-induced responses of 1T-TaS2 and 1T-TaS1.6Se0.4 crystals
in the commensurate charge-density-wave (CCDW) phase in the hysteresis
temperature range have been investigated. We observed that abrupt multiple
steps of the resistance are excited by electric pulses at a fixed temperature
forming multi metastable like states. We propose that the response of the
system corresponds to the rearrangements of the textures of CCDW domains and
the multi-resistance states or the nonvolatile resistance properties excited
simply by electric pulses have profound significance for the exploration of
solid-state devices.",2009.07587v1
2012-01-26,Resistive switching effects on the spatial distribution of phases in metal-complex oxide interfaces,"In order to determine the key parameters that control the resistive switching
mechanism in metal-complex oxides interfaces, we have studied the electrical
properties of metal / YBa2Cu3O7-d (YBCO) interfaces using metals with different
oxidation energy and work function (Au, Pt, Ag) deposited by sputtering on the
surface of a YBCO ceramic sample. By analyzing the IV characteristics of the
contact interfaces and the temperature dependence of their resistance, we
inferred that ion migration may generate or cancel conducting filaments, which
modify the resistance near the interface, in accordance with the predictions of
a recent model.",1201.5670v1
2019-08-21,Artificial Spin Ice Phase-Change Memory Resistors,"We study the implications of the anisotropic magnetic resistance on permalloy
nanowires, and in particular on the property of the resistance depending on the
type of lattice. We discuss how the internal spin configuration of artificial
spin ice nanowires can affect their effective resistive state, and which
mechanisms can introduce a current-dependent effect dynamic resistive state. We
discuss a spin-induced thermal phase-change mechanism, and an athermal
domain-wall spin inversion. In both cases we observe memory behavior
reminiscent of a memristor, with an I-V hysteretic pinched behavior.",1908.08073v1
2020-07-09,Modeling Resistive Switching in Nanogranular Metal Films,"Films produced by assembling bare gold clusters well beyond the electrical
percolation threshold show a resistive switching behavior whose investigation
has started only recently. Here we address the challenge to charaterize the
resistance of a nanogranular film starting from limited information on the
structure at the microscopic scale by the means of Bruggeman's approach to
multicomponent media, within the framework of Effective Medium Approximations.
The approach is used to build a model that proves that the observed resistive
switching can be explained by thermally regulated local structural
rearrangements.",2007.04710v2
2019-01-12,Development of the Micro Pixel Chamber with resistive electrodes,"We developed a novel design of a Micro Pixel Chamber ($\mu$-PIC) with
resistive electrodes for a charged-particle-tracking detector in high-rate
applications. Diamond-Like Carbon (DLC) thin film is used for the cathodes. The
resistivity can be controlled flexibly ($\mathrm{10^{5-7}k\Omega/sq.}$) at high
uniformity. The fabrication-process was greatly improved and the resistive
$\mu$-PIC could be operated at 10$\times$10 $\mathrm{cm^2}$. Resistors for the
HV bias and capacitors for the AC coupling were completely removed by applying
PCB and carbon-sputtering techniques, and the resistive $\mu$-PIC became a very
compact detector. The performances of our new resistive $\mu$-PIC were measured
in various ways. Consequently, it was possible to attain high gas gains
($\mathrm{> 10^{4}}$), high detection efficiency, and position resolution
exceeding 100 $\mu$m. The spark current was suppressed, and the new resistive
$\mu$-PIC was operated stably under fast-neutrons irradiation. These features
offer solutions for a charged-particle-tracking detector in future high-rate
applications.",1901.03836v1
2015-10-13,Interface-mediated thermomechanical effects during high velocity impact between monocrystalline surfaces,"High velocity impact between crystalline surfaces is important for a range of
material phenomena, yet a fundamental understanding of the effect of surface
structure, energetics and kinetics on the underlying thermo-mechanical response
remains elusive. Here, we employ non-equilibrium molecular dynamics (NEMD)
simulations to describe the nanoscale dynamics of the high velocity impact
between commensurate and incommensurate monocrystalline (001) copper surfaces.
For impact velocities in the range 100-1200 m/s, the kinetic energy dissipation
involves nucleation and emission of dislocation loops from defective sites
within the rapidly forming interface, well below the bulk single-crystal yield
point. At higher velocities, adiabatic dissipation occurs via
plasticity-induced heating as the interface structurally melts following the
impact. The adhesive strength of the reformed interface is controlled by the
formation and nucleation of dislocations and point defects as they modify the
interfacial energy relative to the deformed bulk. As confirmation, the excess
interface energy decreases monotonically with increasing impact velocity. The
relative crystal orientation of the surfaces equally important; the grain
boundaries formed following incommensurate impact exhibit higher impact
resistance, with smaller defect densities and interfacial enthalpies,
suggesting an enhanced ability of the grain boundaries to absorb the
non-equilibrium damage and therefore facilitate particle bonding. Our study
highlights the key role played by the atomic-scale surface structure in
determining the impact resistance and adhesion of crystalline surfaces.",1510.03775v1
2007-10-03,Directional-dependent thermally activated motion of vortex bundles and theory of anomalous Hall effect in type-II conventional and high-Tc superconductors,"The anomalous Hall effect for type-II conventional and high-Tc
superconductors is studied based upon the theory of thermally activated motion
of vortex bundles jumping over the directional-dependent energy barrier. It is
shown that the Hall anomaly is universal for type-II conventional and high-Tc
superconductors as well as for superconducting bulk materials and thin films,
provided certain conditions are satisfied. We find that the
directional-dependent potential barrier of the vortex bundles renormalizes the
Hall and longitudinal resistivities, and Hall anomaly for superconductors is
induced by the competition between the Magnus force and the random collective
pinning force of the vortex bundle. We also find that the domain of anomalous
Hall effect includes two regions: the region of thermally activated motion of
the small vortex bundles and that of the large vortex bundles separated by the
contour of the quasiorder-disorder first-order phase transition, or the peak
effect of the vortex system. The Hall and longitudinal resistivities as
functions of temperature as well as applied magnetic field have been calculated
for type-II superconducting films and bulk materials. The conditions for
occurring the double sign reversal or reentry phenomenon is also investigated.
All the results are in agreement with the experiments.",0710.0700v2
2022-04-20,Superconducting bimodal ionic photo-memristor,"Memristive circuit elements constitute a cornerstone for novel electronic
applications, such as neuromorphic computing, called to revolutionize
information technologies. By definition, memristors are sensitive to the
history of electrical stimuli, to which they respond by varying their
electrical resistance across a continuum of nonvolatile states. Recently, much
effort has been devoted to developing devices that present an analogous
response to optical excitation. Here we realize a new class of device, a
tunnelling photo-memristor, whose behaviour is bimodal: both electrical and
optical stimuli can trigger the switching across resistance states in a way
determined by the dual optical-electrical history. This unique behaviour is
obtained in a device of ultimate simplicity: an interface between a
high-temperature superconductor and a transparent semiconductor. The
microscopic mechanism at play is a reversible nanoscale redox reaction between
both materials, whose oxygen content determines the electron tunnelling rate
across their interface. Oxygen exchange is controlled here via illumination by
exploiting a competition between electrochemistry, photovoltaic effects and
photo-assisted ion migration. In addition to their fundamental interest, the
unveiled electro-optic memory effects have considerable technological
potential. Especially in combination with high-temperature superconductivity
which, beyond facilitating the high connectivity required in neuromorphic
circuits, brings photo-memristive effects to the realm of superconducting
electronics.",2204.09255v1
2018-11-03,Modern Data Analytics Approach to Predict Creep of High-Temperature Alloys,"A breakthrough in alloy design often requires comprehensive understanding in
complex multi-component/multi-phase systems to generate novel material
hypotheses. We introduce a modern data analytics workflow that leverages
high-quality experimental data augmented with advanced features obtained from
high-fidelity models. Herein, we use an example of a consistently-measured
creep dataset of developmental high-temperature alloy combined with scientific
alloy features populated from a high-throughput computational thermodynamic
approach. Extensive correlation analyses provide ranking insights for most
impactful alloy features for creep resistance, evaluated from a large set of
candidate features suggested by domain experts. We also show that we can
accurately train machine learning models by integrating high-ranking features
obtained from correlation analyses. The demonstrated approach can be extended
beyond incorporating thermodynamic features, with input from domain experts
used to compile lists of features from other alloy physics, such as diffusion
kinetics and microstructure evolution.",1811.01239v1
2021-01-24,Electronic structure and transport properties of sol-gel-derived high-entropy Ba(Zr0.2Sn0.2Ti0.2Hf0.2Nb0.2)O3 thin films,"High-entropy perovskite thin films, as the prototypical representative of the
high-entropy oxides with novel electrical and magnetic features, have recently
attracted great attention. Here, we reported the electronic structure and
charge transport properties of sol-gel-derived high-entropy
Ba(Zr0.2Sn0.2Ti0.2Hf0.2Nb0.2)O3 thin films annealed at various temperatures. By
means of X-ray photoelectron spectroscopy and absorption spectrum, it is found
that the conduction-band-minimum shifts downward and the valence-band-maximum
shifts upward with the increase of annealing temperature, leading to the
narrowed band gap. Electrical resistance measurements confirmed a
semiconductor-like behavior for all the thin films. Two charge transport
mechanisms, i.e., the thermally-activated transport mechanism at high
temperatures and the activation-less transport mechanism at low temperatures,
are identified by a self-consistent analysis method. These findings provide a
critical insight into the electronic band structure and charge transport
behavior of Ba(Zr0.2Sn0.2Ti0.2Hf0.2Nb0.2)O3, validating it as a compelling
high-entropy oxide material for future electronic/energy-related technologies.",2101.09633v2
2015-06-16,Unforeseen high temperature and humidity stability of FeCl$_3$ intercalated few layer graphene,"We present the first systematic study of the stability of the structure and
electrical properties of FeCl$_3$ intercalated few-layer graphene to high
levels of humidity and high temperature. Complementary experimental techniques
such as electrical transport, high resolution transmission electron microscopy
and Raman spectroscopy conclusively demonstrate the unforeseen stability of
this transparent conductor to a relative humidity up to $100 \%$ at room
temperature for 25 days, to a temperature up to $150\,^\circ$C in atmosphere
and up to a temperature as high as $620\,^\circ$C in vacuum, that is more than
twice higher than the temperature at which the intercalation is conducted. The
stability of FeCl$_3$ intercalated few-layer graphene together with its unique
values of low square resistance and high optical transparency, makes this
material an attractive transparent conductor in future flexible electronic
applications.",1506.04907v1
2009-12-24,Properties of MgB2 bulk,"The review considers bulk MgB2-based materials in terms of their structure,
superconducting and mechanical properties. Superconducting transition
temperatures of 34.5-39.4 K, critical current densities of 1.8-1.0 x E6 A/sq.cm
in self field and 103 in 8 T field at 20 K, 3-1.5xE5 A/sq. cm in self field at
35 K, HC2 15 T at 22 K and Hirr 13 T at 20 K have been registered for
polycrystalline materials. As TEM and SEM study show, dispersed higher borides
and rather big amount (5-14 percents) of oxygen (bonded simultaneously with Mg
and B) can be present in the structure even if X-ray pattern contains only
reflexes of well crystallized MgB2 with traces of MgO. Materials with such a
rather high oxygen content demonstrated high superconducting characteristics.
At present it is established that nanosized MgB12 grains provide effective
pinning in polycrystalline material. Besides, additions can introduce the MgB2
structure inducing disorder in lattice sites (for example, C substitution for
B). The disorder increases the normal state resistivity, magnetic penetration
depth, and the upper critical field, but reduces the transition temperature and
anisotropy. It is highly probable that the additives (Ti, Ta, Zr, SiC) together
with synthesis or sintering temperature can affect the distribution of oxygen
and hydrogen in the material structure as well as the formation of grains of
higher borides, thus influencing superconducting properties. The
superconductivity of materials with matrix close to MgB12 in stoichiometry
(Tc=37 K) has been defined.",0912.4906v1
2017-10-23,Realization of a hole-doped Mott insulator on a triangular silicon lattice,"The physics of doped Mott insulators is at the heart of some of the most
exotic physical phenomena in materials research including insulator-metal
transitions, colossal magneto-resistance, and high-temperature
superconductivity in layered perovskite compounds. Advances in this field would
greatly benefit from the availability of new material systems with similar
richness of physical phenomena, but with fewer chemical and structural
complications in comparison to oxides. Using scanning tunneling microscopy and
spectroscopy, we show that such a system can be realized on a silicon platform.
Adsorption of one-third monolayer of Sn atoms on a Si(111) surface produces a
triangular surface lattice with half-filled dangling bond orbitals. Modulation
hole-doping of these dangling bonds unveils clear hallmarks of Mott physics,
such as spectral weight transfer and the formation of quasi-particle states at
the Fermi level, well-defined Fermi contour segments, and a sharp singularity
in the density of states. These observations are remarkably similar to those
made in complex oxide materials, including high-temperature superconductors,
but highly extraordinary within the realm of conventional sp-bonded
semiconductor materials. It suggests that exotic quantum matter phases can be
realized and engineered on silicon-based materials platforms.",1710.08065v1
2020-04-12,Investigation on the Mechanical Properties of Functionally Graded Nickel and Aluminium Alloy by Molecular Dynamics Study,"Functionally graded materials (FGMs), have drawn considerable attention of
the worldwide researchers and scientific community because of its unique
mechanical, thermal and electrical properties which may be exploited by varying
the compositions gradually over volume. This makes FGM multifunctional material
(properties changing continuously in a certain direction) for specific purpose
without creating any phase interface thus making it superior to its composite
counterparts. In this paper, we applied Molecular Dynamics (MD) approach to
investigate the mechanical properties of functional graded Ni-Al alloy with Ni
coating by applying uniaxial tension. Nickel-Aluminum (Ni-Al) alloy has been
used extensively in the industry due to its remarkable mechanical and thermal
properties. Our aim is to find the difference in material behavior when we
change the grading function (linear, elliptical and parabolic), temperature and
crystallographic direction. We also observe distinct type of failure mechanism
for different grading function at different temperature. Close observation
reveals that elliptically graded Ni-Al alloy has high tensile strength at low
temperature whereas at high temperature, the highest tensile strength is found
for parabolic grading. Besides, at any temperature, the parabolically graded
Ni-Al alloy shows superior elasticity than its elliptical and linear
counterpart. Moreover, it is also observed that [111] crystallographic
direction for this alloy demonstrates more resistivity towards failure than any
other crystallographic direction. It is found that lattice disorder plays a
significant role on the mechanical properties of Functionally Graded Materials
(FGMs). This paper details a pathway to tune the mechanical properties like
Young's Modulus, plasticity and yield strength at molecular level by varying
the composition of materials along different grading functions.",2004.05651v1
1997-03-03,Longitudinal and transverse dissipation in a simple model for the vortex lattice with screening,"Transport properties of the vortex lattice in high temperature
superconductors are studied using numerical simulations in the case in which
the non-local interactions between vortex lines are dismissed. The results
obtained for the longitudinal and transverse resistivities in the presence of
quenched disorder are compared with the results of experimental measurements
and other numerical simulations where the full interaction is considered. This
work shows that the dependence on temperature of the resistivities is well
described by the model without interactions, thus indicating that many of the
transport characteristics of the vortex structure in real materials are mainly
a consequence of the topological configuration of the vortex structure only. In
addition, for highly anisotropic samples, a regime is obtained where
longitudinal coherence is lost at temperatures where transverse coherence is
still finite. I discuss the possibility of observing this regime in real
samples.",9703035v1
1997-08-19,Metallization of Fluid Hydrogen,"The electrical resistivity of liquid hydrogen has been measured at the high
dynamic pressures, densities and temperatures that can be achieved with a
reverberating shock wave. The resulting data are most naturally interpreted in
terms of a continuous transition from a semiconducting to a metallic, largely
diatomic fluid, the latter at 140 GPa, (ninefold compression) and 3000 K. While
the fluid at these conditions resembles common liquid metals by the scale of
its resistivity of 500 micro-ohm-cm, it differs by retaining a strong pairing
character, and the precise mechanism by which a metallic state might be
attained is still a matter of debate. Some evident possibilities include (i)
physics of a largely one-body character, such as a band-overlap transition,
(ii) physics of a strong-coupling or many-body character,such as a Mott-Hubbard
transition, and (iii) processes in which structural changes are paramount.",9708144v1
1997-09-16,The Metallic-Like Conductivity of a Two-Dimensional Hole System,"We report on a zero magnetic field transport study of a two-dimensional,
variable-density, hole system in GaAs. As the density is varied we observe, for
the first time in GaAs-based materials, a crossover from an insulating behavior
at low-density, to a metallic-like behavior at high-density, where the metallic
behavior is characterized by a large drop in the resistivity as the temperature
is lowered. These results are in agreement with recent experiments on Si-based
two-dimensional systems by Kravchenko et al. and others. We show that, in the
metallic region, the resistivity is dominated by an exponential
temperature-dependence with a characteristic temperature which is proportional
to the hole density, and appear to reach a constant value at lower
temperatures.",9709184v3
1998-04-23,Hysteretic behavior and evidence for domain formation in a double-layer quantum Hall system at total filling factor 2,"We report anomalous behavior in a double-layer two dimensional hole gas
(2DHG) at even integer filling factors which includes hysteresis in the
longitudinal and Hall resistances and a very weak temperature dependence of the
resistance minima. All anomalies disappear and the conventional quantum Hall
effect behavior recovers when a thin metal film is placed on top of the 2DHG.
The behavior is attributed to presence of the theoretically predicted magnetic
ordering at even integer filling factors which causes the formation of
macroscopic spin-charge domains.",9804256v2
1998-11-18,Hall-effect in LuNi_2B_2C in normal and superconducting mixed states,"The Hall resistivity rho_{xy} of LuNi_2B_2C is negative in the normal as well
as in the mixed state and has no sign reversal typical for high-T_c
superconductors. A distinct nonlinearity in the rho_{xy} dependence on field H
was found in the normal state for T < 40K, accompanied by a large
magnetoresistance reaching +90% for mu_0H=16T at T=20K. The scaling relation
rho_{xy} ~ \rho_{xx}^\beta (\rho_{xx} is the longitudinal resistivity) was
found in the mixed state, the value of \beta being dependent on the degree of
disorder.",9811273v1
1999-07-22,Charge carrier density collapse in La_0.67Ca_0.33MnO_3 and La_0.67Sr_0.33MnO_3 epitaxial thin films,"We measured the temperature dependence of the linear high field Hall
resistivity of La_0.67Ca_0.33MnO_3 (T_C=232K) and La_0.67Sr_0.33MnO_3
(T_C=345K) thin films in the temperature range from 4K up to 360K in magnetic
fields up to 20T. At low temperatures we find a charge carrier density of 1.3
and 1.4 holes per unit cell for the Ca- and Sr-doped compound, respectively. In
this temperature range electron-magnon scattering contributes to the
longitudinal resistivity. At the ferromagnetic transition temperature T_C a
dramatic drop in the number of current carriers $n$ down to 0.6 holes per unit
cell, accompanied by an increase in unit cell volume, is observed. Corrections
of the Hall data due to a non saturated magnetic state will lead a more
pronounced charge carrier density collapse.",9907346v1
1999-08-05,Fermi-level alignment at metal-carbon nanotube interfaces: application to scanning tunneling spectroscopy,"At any metal-carbon nanotube interface there is charge transfer and the
induced interfacial field determines the position of the carbon nanotube band
structure relative to the metal Fermi-level. In the case of a single-wall
carbon nanotube (SWNT) supported on a gold substrate, we show that the charge
transfers induce a local electrostatic potential perturbation which gives rise
to the observed Fermi-level shift in scanning tunneling spectroscopy (STS)
measurements. We also discuss the relevance of this study to recent experiments
on carbon nanotube transistors and argue that the Fermi-level alignment will be
different for carbon nanotube transistors with low resistance and high
resistance contacts.",9908073v3
1999-08-25,Hall effect of epitaxial double-perovskite Sr_2FeMoO_6 thin films,"We prepared high epitaxial thin films of the compound Sr_2FeMoO_6 with narrow
rocking curves by pulsed laser deposition. The diagonal and nondiagonal
elements of the resistivity tensor were investigated at temperatures from 4 K
up to room temperature in magnetic fields up to 8 T. An electronlike ordinary
Hall effect and a holelike anomalous Hall contribution are observed. Both
coefficients have reversed sign compared to the colossal magnetoresistive
manganites. We found at 300 K an ordinary Hall coefficent of -1.87x10^{-10}
m^3/As, corresponding to a nominal charge carrier density of four electrons per
formula unit. At low temperature only a small negative magnetoresistance is
observed which vanishes at higher temperatures. The temperature coefficient of
the resistivity is negative over the whole temperature range. A Kondo like
behavior is observed below 30 K while above 100 K variable range hopping like
transport occurs.",9908361v2
1999-10-15,Electronic Transport in a Three-dimensional Network of 1-D Bismuth Quantum Wires,"The resistance R of a high density network of 6 nm diameter Bi wires in
porous Vycor glass is studied in order to observe its expected semiconductor
behavior. R increases from 300 K down to 0.3 K. Below 4 K, where R varies
approximately as ln(1/T), the order-of-magnitude of the resistance rise, as
well as the behavior of the magnetoresistance are consistent with localization
and electron-electron interaction theories of a one-dimensional disordered
conductor in the presence of strong spin-orbit scattering. We show that this
behaviour and the surface-enhanced carrier density may mask the proposed
semimetal-to-semiconductor transition for quantum Bi wires.",9910241v1
2000-01-25,Pressure Induced Quantum Critical Point and Non-Fermi-Liquid Behavior in BaVS3,"The phase diagram of BaVS3 is studied under pressure using resistivity
measurements. The temperature of the metal to nonmagnetic Mott insulator
transition decreases under pressure, and vanishes at the quantum critical point
p_cr=20kbar. We find two kinds of anomalous conducting states. The
high-pressure metallic phase is a non-Fermi liquid described by Delta rho = T^n
where n=1.2-1.3 at 1K < T < 60K. At p<p_cr, the transition is preceded by a
wide precursor region with critically increasing resistivity which we ascribe
to the opening of a soft Coulomb gap.",0001371v2
2000-03-14,"Magnetic and electrical resistance behaviour of the oxides, Ca$_{3-x}$Y$_x$LiRuO$_6$ (x= 0.0, 0.5 and 1.0)","We have investigated the magnetic and electrical resistance behaviour of
  Ca$_{3-x}$Y$_x$LiRuO$_6$. The parent compound exhibits magnetic ordering from
Ru sublattice at a rather high temperature, 113 K. Though the paramagnetic
  Curie temperature ($\theta$$_p$) is negative indicative of antiferromagnetic
ordering, the large magnitude (-250 K) of $\theta$$_p$ reveals complex nature
of the magnetism in this compound. Ru ions appear to be in the pentavalent
state. We note that the N\'eel temperature undergoes only a marginal reduction
by Y substitution. All these compositions are found to be insulators and thus
the electron doping does not result in metallicity. Thus the overall magnetic
and transport behaviour are found to be essentially insensitive to Y
substitution for Ca, a finding which may favour the idea of
quasi-one-dimensional magnetism in these compounds.",0003227v1
2001-03-26,Superconducting Mg-B films by pulsed laser deposition in an in-situ two-step process using multi-component targets,"Superconducting thin films have been prepared in a two-step in-situ process,
using the Mg-B plasma generated by pulsed laser ablation. The target was
composed of a mixture of Mg and MgB2 powders to compensate for the volatility
of Mg and therefore to ensure a high Mg content in the film. The films were
deposited at temperatures ranging from room temperature to 300 degrees C
followed by a low-pressure in-situ annealing procedure. Various substrates have
been used and diverse ways to increase the Mg content into the film were
applied. The films show a sharp transition in the resistance and have a zero
resistance transition temperature of 22-24 K.",0103543v1
2001-05-29,"Growth, structure analysis and anisotropic superconducting properties of MgB2 single crystals","Here we report the growth of sub-millimeter MgB2 single crystals of various
shapes under high pressure in Mg-B-N system. Structure refinement using a
single-crystal X-ray diffraction analysis gives lattice parameters a=3.0851(5)
A and c=3.5201(5) A with small reliability factors (Rw =0.025, R=0.018), which
enables us to analyze the Fourier and Fourier difference maps. The maps clearly
show the B sp2 orbitals and covalency of the B-B bonds. The sharp
superconducting transitions at Tc =38.1-38.3K were obtained in both
magnetization (DTc =0.6K) and resistivity (DTc <0.3K) measurements. Resistivity
measurements with magnetic fields applied parallel and perpendicular to the Mg
and B sheets reveal the anisotropic nature of this compound, with upper
critical field anisotropy ratio of about 2.7.",0105545v2
2001-10-18,Strong Quasiparticle Trapping In A 6x6 Array Of Vanadium-Aluminum Superconducting Tunnel Junctions,"A 6x6 array of symmetrical V/Al/AlOx/Al/V Superconducting Tunnel Junctions
(STJs) was fabricated. The base electrode is a high quality epitaxial film with
a residual resistance ratio (RRR) of ~30. The top film is polycrystalline with
an RRR of ~10. The leakage currents of the 25x25 mm^2 junctions are of the
order of 0.5 pA/mm^2 at a bias voltage of 100 mV, which corresponds to a
dynamical resistance of ~ 3 10^5 ohms. When the array was illuminated by 6 keV
X-ray photons from a 55Fe radioactive source the single photon charge output
was found to be low and strongly dependent on the temperature of the devices.
This temperature dependence at X-ray energies can be explained by the existence
of a very large number of quasiparticle (QP) traps in the Vanadium. QPs are
confined in these traps, having a lower energy gap than the surrounding
material, and are therefore not available for tunneling. The number of traps
can be derived from the energy dependence of the responsivity of the devices
(charge output per electron volt of photon input energy).",0110374v1
2001-10-18,Magnetic and transport properties of the new antiferromagnetic Kondo-lattice CeNiBi2,"We report results of the first studies on the magnetic and transport
properties of a new material CeNiBi_2. The magnetic susceptibility exhibits a
sharp peak at T_N = 6K, indicating an antiferromagnetic phase transition. This
antiferromagnetic order below T_N is confirmed by magnetization measurement,
which displays a metamagnetic-like transition at H_m = 5 T. Both
low-temperature susceptibility and high-field magnetization are suggestive of
strong crystalline-electric-field effect in CeNiBi_2. The electrical
resistivity shows the presence of Kondo and crystal-field effects with a sharp
drop below TN due to the antiferromagnetic ordering. This sharp drop below T_N
in the electrical resistivity is suppressed slightly to higher temperatures by
an applied magnetic field to 18 T. With increasing magnetic field, the slope of
magnetoresistance changes from positive to negative, being indicative of the
transition to a ferromagnetic state.",0110380v1
2002-03-08,Strain effect on electronic transport and ferromagnetic transition temperature in La$_{0.9}$Sr$_{0.1}$MnO$_{3}$ thin films,"We report on a systematic study of strain effects on the transport properties
and the ferromagnetic transition temperature $T_{c}$ of high-quality
La$_{0.9}$Sr$_{0.1}$MnO$_{3}$ thin films epitaxially grown on (100) SrTiO$_{3}$
substrates. Both the magnetization and the resistivity are critically dependent
on the film thickness. $T_{c}$ is enhanced with decreasing the film thickness
due to the compressive stain produced by lattice mismatch. The resistivity
above 165 K of the films with various thicknesses is consistent with small
polaronic hopping conductivity. The polaronic formation energy $E_{P}$ is
reduced with the decrease of film thickness. We found that the strain
dependence of $T_{c}$ mainly results from the strain-induced electron-phonon
coupling. The strain effect on $E_{P}$ is in good agreement with the
theoretical predictions.",0203196v1
2002-04-22,Role of Umklapp Processes in Conductivity of Doped Two-Leg Ladders,"Recent conductivity measurements performed on the hole-doped two-leg ladder
material $\mathrm{Sr_{14-x}Ca_xCu_{24}O_{41}}$ reveal an approximately linear
power law regime in the c-axis DC resistivity as a function of temperature for
$x=11$. In this work, we employ a bosonic model to argue that umklapp processes
are responsible for this feature and for the high spectral weight in the
optical conductivity which occurs beyond the finite frequency Drude-like peak.
Including quenched disorder in our model allows us to reproduce experimental
conductivity and resistivity curves over a wide range of energies. We also
point out the differences between the effect of umklapp processes in a single
chain and in the two-leg ladder.",0204485v1
2002-07-02,"Comment to the paper : Collapse of the vortex-lattice inductance and shear modulus at the melting transition in untwinned YBa$_2$Cu$_3$O$_7$, by Matl \QTR{em}{et al.}","In a recent paper, Matl et al present a high-frequency study of the complex
resistivity of a pinned vortex lattice in YBaCuO . They focus on the
inductive-to-resistive transition which is investigated as a function of
temperature at a constant field $B_0=2$ T, so that the transition is associated
with the vanishing of vortex pinning strength. To our view, their conclusions
rely on a rather brittle experimental body and the collapse of C66 results from
an involved analysis of the finite frequency corrections to $\rho (\omega)$.
These corrections are not necessary since the complex frequency spectrum has
been previously interpreted by the two modes model, first proposed for low Tc
materials. We think that it is more adequate to interpret the present data and
should be at least considered.",0207074v1
2003-05-21,Carbon-substituted MgB2 single crystals,"Carbon-substituted MgB2 single crystals, Mg(B_1-xC_x)_2 of 0.3-1.0 mm size
were grown for x=0.02-0.15 by a high-pressure technique. The doping dependence
of lattice constants studied in a range of x=0.0-0.2 shows a monotonic decrease
in a, while the c parameter remains almost invariant. Using X-ray diffraction
and Auger electron spectroscopy, the solubility limit of C in MgB2 was
estimated to be about 15(+/-)1%,which is substantially larger than that
reported for the polycrystalline samples synthesized by encapsulation
techniques. Measurements of temperature dependence of magnetization and
resistivity showed a dramatic decrease in Tc with C-substitution, followed by
complete suppression of superconductivity for x>0.125. Resistivity measurements
in magnetic fields parallel and perpendicular to the basal plane of the
crystals showed a nearly isotropic state in the heavily-doped crystals (x>0.1).",0305485v1
2003-07-01,Efficient nonlinear room-temperature spin injection from ferromagnets into semiconductors through a modified Schottky barrier,"We suggest a consistent microscopic theory of spin injection from a
ferromagnet (FM) into a semiconductor (S). It describes tunneling and emission
of electrons through modified FM-S Schottky barrier with an ultrathin heavily
doped interfacial S layer . We calculate nonlinear spin-selective properties of
such a reverse-biased FM-S junction, its nonlinear I-V characteristic, current
saturation, and spin accumulation in S. We show that the spin polarization of
current, spin density, and penetration length increase with the total current
until saturation. We find conditions for most efficient spin injection, which
are opposite to the results of previous works, since the present theory
suggests using a lightly doped resistive semiconductor. It is shown that the
maximal spin polarizations of current and electrons (spin accumulation) can
approach 100% at room temperatures and low current density in a nondegenerate
high-resistance semiconductor.",0307030v4
2003-12-23,1-D Simulation of the Electron Density Distribution in a Novel Nonvolatile Resistive Random Access Memory Device,"The operation of a novel nonvolatile memory device based on a conductive
ferroelectric/non-ferroelectric thin film multilayer stack is simulated
numerically. The simulation involves the self-consistent steady state solution
of Poisson's equation and the transport equation for electrons assuming a
Drift-Diffusion transport mechanism. Special emphasis is put on the screening
of the spontaneous polarization by conduction electrons as a function of the
applied voltage. Depending on the orientation of the polarization in the
ferroelectric layer, a high and a low resistive state are found giving rise to
a hysteretic I-V characteristic. The R_high to R_low ratio ranging from > 50%
to several orders of magnitude is calculated as a function of the dopant
content.",0312609v1
2004-03-08,"Hole mobility in organic single crystals measured by a ""flip-crystal"" field-effect technique","We report on single crystal high mobility organic field-effect transistors
(OFETs) prepared on prefabricated substrates using a ""flip-crystal"" approach.
This method minimizes crystal handling and avoids direct processing of the
crystal that may degrade the FET electrical characteristics. A chemical
treatment process for the substrate ensures a reproducible device quality. With
limited purification of the starting materials, hole mobilities of 10.7, 1.3,
and 1.4 cm^2/Vs have been measured on rubrene, tetracene, and pentacene single
crystals, respectively. Four-terminal measurements allow for the extraction of
the ""intrinsic"" transistor channel resistance and the parasitic series contact
resistances. The technique employed in this study shows potential as a general
method for studying charge transport in field-accumulated carrier channels near
the surface of organic single crystals.",0403210v1
2004-04-11,Synthesis of as-grown superconducting MgB_2 thin films by molecular beam epitaxy in UHV conditions,"As-grown superconducting MgB_2 thin films have been grown on SrTiO_3(001),
MgO(001), and Al_2O_3(0001) substrates by a molecular beam epitaxy (MBE) method
with novel co-evaporation conditions of low deposition rate in ultra-high
vacuum. The structural and physical properties of the films were studied by
RHEED, XRD, electrical resistivity measurements, and SQUID magnetometer. The
RHEED patterns indicate three-dimensional growth for MgB_2. The highest T_c
determined by resistivity measurement was about 36K in these samples. And a
clear Meissner effect below T_c was observed using magnetic susceptibility
measurement. We will discuss the influence of B buffer layer on the structural
and physical properties.",0404252v1
2004-08-20,Anomalous Hall effect in insulating Ga1-xMnxAs,"We have investigated the effect of doping by Te on the anomalous Hall effect
in Ga1-xMnxAs (x = 0.085). For this relatively high value of x the temperature
dependence of resistivity shows an insulating behavior. It is well known that
in Ga1-xMnxAs the Mn ions naturally act as acceptors. Additional doping by Te
donors decreases the Curie temperature and increases the anomalous Hall
resistivity. With increasing Te concentration the long-range ferromagnetic
order in Ga1-xMnxAs eventually disappears, and paramagnetic-to-spin glass
transition is observed instead. The critical concentration of holes required
for establishing ferromagnetic order in Ga1-xMnxAs (x = 0.085) has been
estimated by using the magnetic polaron percolation theory proposed by Kaminski
and Das Sarma [Phys.Rev.Lett. 88, 247202 (2002)].",0408446v1
2005-01-14,Magnetization and magnetoresistance in insulating phases of SrFeO3-d,"We report the synthesis and properties of two new insulating phases of
SrFeO3-d with introduction of oxygen deficiencies in metallic SrFeO3 ; one with
0.15 < d < 0.19 (sample A)and the other above d = 0.19 (sample B). Sample A
shows large negative magnetoresistance around the charged ordering (CO)
temperature with magnetic anomalies seen in the temperature dependent
resistivity,magnetization and M-H hysteresis loops. Sample B shows a smooth
insulating behavior with no thermal hysteresis in the resistivity and with a
small positive magnetoresistance. cac and cdc show multiple features associated
with a frustrated magnetic order (helical) due to competing ferro- and
antiferromagnetic interactions. The competing effects of ferro- and
antiferromagnetic phases extend up to T ~ 230 K revealing a new high
temperature scale in this system. These observations are discussed in the
context of magnetic interactions associated with the varying Fe4+/Fe3+ ratio.",0501352v1
2005-07-14,Field-Dependent Hall Effect in Single Crystal Heavy Fermion YbAgGe below 1K,"We report the results of a low temperature (T >= 50 mK) and high field (H <=
180 kOe) study of the Hall resistivity in single crystals of YbAgGe, a heavy
fermion compound that demonstrates field-induced non-Fermi-liquid behavior near
its field-induced quantum critical point. Distinct features in the anisotropic,
field-dependent Hall resistivity sharpen on cooling down and at the base
temperature are close to the respective critical fields for the field-induced
quantum critical point. The field range of the non-Fermi-liquid region
decreases on cooling but remains finite at the base temperature with no
indication of its conversion to a point for T -> 0. At the base temperature,
the functional form of the field-dependent Hall coefficient is field direction
dependent and complex beyond existing simple models thus reflecting the
multi-component Fermi surface of the material and its non-trivial modification
at the quantum critical point.",0507338v1
2005-10-20,Stick slip motion in grain grain friction in a humid atmosphere,"We set up an original apparatus to measure the grain grain friction stress
inside a granular medium composed of sodo-silicate-glass beads surrounded by a
water vapor atmosphere.We analyze here the influence of the physico chemistry
of water on our glass beads and its consequences on our shear experiment. We
found two scales in the analysis of the shear stress signal. On the microscopic
scale of one bead, the experimental results show a dependence on the size of
beads, on the shear rate and on humidity for the resulting stick slip signal.
On the macroscopic scale of the whole assembly of beads, the behavior of the
total amplitude of the shear stress depends on the size of the beads and is
humidity dependent only for relative humidity larger than 80%. For high degrees
of humidity, on the microscopic scale, water lubricates the surface of the
beads leading to a decrease in the microscopic resistance to shear while on the
macroscopic scale the resistance to shear is increased: the assembly of very
humid grains behaves as a non Newtonian fluid.",0510532v1
2006-06-23,Electronic transport in Si nanowires: Role of bulk and surface disorder,"We calculate the resistance and mean free path in long metallic and
semiconducting silicon nanowires (SiNWs) using two different numerical
approaches: A real space Kubo method and a recursive Green's function method.
We compare the two approaches and find that they are complementary: depending
on the situation a preferable method can be identified. Several numerical
results are presented to illustrate the relative merits of the two methods. Our
calculations of relaxed atomic structures and their conductance properties are
based on density functional theory without introducing adjustable parameters.
Two specific models of disorder are considered: Un-passivated, surface
reconstructed SiNWs are perturbed by random on-site (Anderson) disorder whereas
defects in hydrogen passivated wires are introduced by randomly removed H
atoms. The un-passivated wires are very sensitive to disorder in the surface
whereas bulk disorder has almost no influence. For the passivated wires, the
scattering by the hydrogen vacancies is strongly energy dependent and for
relatively long SiNWs (L>200 nm) the resistance changes from the Ohmic to the
localization regime within a 0.1 eV shift of the Fermi energy. This high
sensitivity might be used for sensor applications.",0606600v1
2006-07-18,Dielectric breakdown in underoxidized magnetic tunnel junctions: Dependence on oxidation time and area,"Magnetic tunnel junctions (MTJs) with partially oxidized 9 \AA
AlO$_x$-barriers were recently shown to have the necessary characteristics to
be used as magnetoresistive sensors in high-density storage devices. Here we
study dielectric breakdown in such underoxidized magnetic tunnel junctions,
focusing on its dependence on tunnel junction area and oxidation time. A clear
relation between breakdown mechanism and junction area is observed for the MTJs
with the highest studied oxidation time: samples with large areas fail usually
due to extrinsic causes (characterized by a smooth resistance decrease at
dielectric breakdown). Small area junctions fail mainly through an intrinsic
mechanism (sharp resistance decrease at breakdown). However, this dependence
changes for lower oxidation times, with extrinsic breakdown becoming dominant.
In fact, in the extremely underoxidized magnetic tunnel junctions, failure is
exclusively related with extrinsic causes, independently of MTJ-area. These
results are related with the presence of defects in the barrier (weak spots
that lead to intrinsic breakdown) and of metallic unoxidized Al
nanoconstrictions (leading to extrinsic breakdown).",0607452v1
2007-01-20,Fabrication and Low Temperature Thermoelectric Properties of Na_xCoO_2 (x = 0.68 and 0.75) Epitaxial Films by the Reactive Solid-Phase Epitaxy,"We have fabricated Na_xCoO_2 thin films via lateral diffusion of sodium into
Co_3O_4 (111) epitaxial films (reactive solid-phase epitaxy: Ref. 4). The
environment of thermal diffusion is key to the control of the sodium content in
thin films. From the results of x-ray diffraction and in-plane resistivity, the
epitaxial growth and the sodium contents of these films were identified. The
thermoelectric measurements show a large thermoelectric power similar to that
observed in single crystals. The quasiparticle scattering rate is found to
approach zero at low temperatures, consistent with the small residual
resistivity, indicating high quality of the Na_xCoO_2 thin films.",0701492v1
2007-02-05,Existence of two electronic states in Sr4Ru3O10 at low temperatures,"We report measurements on in-plane resistivity, thermopower, and
magnetization as a function of temperature and magnetic fields on single
crystalline Sr4Ru3O10 grown by the floating zone method. As the temperature was
lowered to below around 30 K, the in-plane and c-axis resistivities and the
thermopower were found to exhibit a step feature accompanied by hysteresis
behavior when the in-plane field was swept up and down from below 10 kOe to
above 20 kOe. The sharp increase in the thermopower with increasing in-plane
magnetic field at low temperatures has not been observed previously in layered
transition metal oxides. Comparing with magnetization data, we propose that the
step feature marks the transition between the two different electronic states
in Sr4Ru3O10. We propose that the alignment of domains by the in-plane magnetic
field is responsible to the emergence of the new electronic states in high
applied in-plane magnetic field.",0702093v1
2007-05-02,Comment on ``Collapse of Coherent Quasiparticle States in $θ$-(BEDT-TTF)$_2$I$_3$ Observed by Optical Spectroscopy'',"Recently, Takenaka et al. reported that the resistivity rho(T) of
theta-(BEDT-TTF)_2I_3 (theta-ET) exceeds the Ioffe-Regel resistivity by a
factor of 50 at large temperatures T (``bad metal''). This was ascribed to
strong correlation. We argue that the optical conductivity sigma(omega) implies
that correlation is not very strong, and that correlation gives no general
strong suppression of sigma(omega). The large rho(T) is primarily due to a
downturn in sigma(omega) at small omega, earlier emphasized by Takenaka et al.
as the explanation for bad metal behavior of high-T_c cuprates. We argue,
however, that for cuprates strong correlation is the main effect. The data of
Takenaka et al. puts theta-ET in a new class of bad metals.",0705.0230v1
2007-07-15,Physical properties of a new cuprate superconductor Pr_2Ba_4Cu_7O_{15-δ},"We present studies of the thermal, magnetic and electrical transport
properties of reduced polycrystalline Pr_2Ba_4Cu_7O_{15-\delta} (Pr247) showing
a superconducting transition at Tc = 10 - 16 K and compare them with those of
as-sintered non-superconducting Pr247. The electrical resistivity in the normal
state exhibited T2 dependence up to approximately 150 K. A clear specific heat
anomaly was observed at Tc for Pr247 reduced in a vacuum for 24 hrs, proving
the bulk nature of the superconducting state. By the reduction treatment, the
magnetic ordering temperature TN of Pr moments decreased from 16 to 11 K, and
the entropy associated with the ordering increased, while the effective
paramagnetic moments obtained from the DC magnetic susceptibility varied from
2.72 to 3.13 mB. The sign of Hall coefficient changed from positive to negative
with decreasing temperature in the normal state of a superconducting Pr247,
while that of as-sintered one was positive down to 5 K. The electrical
resistivity under high magnetic fields was found to exhibit T^a dependence (a =
0.08 - 0.4) at low temperatures. A possibility of superconductivity in the
so-called CuO double chains is discussed.",0707.2180v1
2007-07-30,Intrinsic tunneling in phase separated manganites,"We present evidence of direct electron tunneling across intrinsic insulating
regions in sub-micrometer wide bridges of the phase separated ferromagnet
(La,Pr,Ca)MnO$_3$. Upon cooling below the Curie temperature, a predominantly
ferromagnetic supercooled state persists where tunneling across the intrinsic
tunnel barriers (ITBs) results in metastable, temperature-independent,
high-resistance plateaus over a large range of temperatures. Upon application
of a magnetic field, our data reveal that the ITBs are extinguished resulting
in sharp, colossal, low-field resistance drops. Our results compare well to
theoretical predictions of magnetic domain walls coinciding with the intrinsic
insulating phase.",0707.4411v2
2008-01-09,Impact of in-plane currents on magnetoresistance properties of an exchange-biased spin-valve with insulating antiferromagnetic layer,"The impact of in-plane alternating currents on the exchange bias, resistance,
and magnetoresistance of a CoFe/NiCoO/CoFe/Cu/CoFe spin-valve is studied. With
increasing current, the resistance is increased while the maximum
magnetoresistance ratio decreases. Noticeably, the reversal of the pinned layer
is systematically suppressed in both field sweeping directions. Since the NiCoO
oxide is a good insulator, it is expected that the ac current flows only in the
CoFe/Cu/CoFe top layers, thus ruling out any presence of spin-transfer torque
acting on the spins in the antiferromagnetic layer. Instead, our measurements
show clear evidences for the influence of Joule heating caused by the current.
Moreover, results from temperature-dependent measurements very much resemble
those of the current dependence, indicating that the effect of Joule heating
plays a major role in the current-in-plane spin-valve configurations. The
results also suggest that spin-transfer torques between ferromagnetic layers
might still exist and compete with the exchange bias at sufficiently high
currents.",0801.1515v1
2008-04-09,"Curie point singularity in the temperature derivative of resistivity in (Ga,Mn)As","We observe a singularity in the temperature derivative $d\rho/dT$ of
resistivity at the Curie point of high-quality (Ga,Mn)As ferromagnetic
semiconductors with $T_c$'s ranging from approximately 80 to 185 K. The
character of the anomaly is sharply distinct from the critical contribution to
transport in conventional dense-moment magnetic semiconductors and is
reminiscent of the $d\rho/dT$ singularity in transition metal ferromagnets.
Within the critical region accessible in our experiments, the temperature
dependence on the ferromagnetic side can be explained by dominant scattering
from uncorrelated spin fluctuations. The singular behavior of $d\rho/dT$ on the
paramagnetic side points to the important role of short-range correlated spin
fluctuations.",0804.1578v2
2008-06-24,Low temperature thermal resistance for a new design of silver sinter heat exchanger,"We have developed a novel procedure for constructing high surface area silver
sinter heat exchangers. Our recipe incorporates nylon fibers having a diameter
of ~ 50 microns and thin wires of bulk silver in the heat exchanger. In order
to increase the thermal conductance of liquid helium within the heat exchanger,
prior to sintering, the nylon fibers are dissolved with an organic acid leaving
a network of channels. In addition, the silver wires reinforce the structural
integrity, and reduce the resistance, of the silver sinter. We have constructed
a 3-He melting curve thermometer (MCT) with this type of heat exchanger and
measured the thermal time response of the liquid 3-He inside the MCT in the
temperature range T = 2-150 mK. We find a thermal relaxation time of ~ 490 s at
T ~ 1 mK. We have used scanning electron microscopy (SEM) to characterize the
heat exchanger and BET absorption for determination of the specific surface
area.",0806.3930v1
2008-08-09,Transport and Magnetic properties of Fe1/3VSe2,"Electrical conductivity, thermopower and magnetic properties of
Fe-intercalated Fe0.33VSe2 has been reported between 4.2K - 300K. We observe a
first order transition in the resistivity of the sintered pellets around 160K
on cooling. The electronic properties including the transitional hysteresis in
the resistance anomaly (from 80K-160K) are found to be very sensitive to the
structural details of the samples, which were prepared in different annealing
conditions. The thermopower results on the sintered pellets are reported
between 10K - 300K. The magnetic measurements between 2K - 300K and up to 14
Tesla field show the absence of any magnetic ordering in Fe0.33VSe2. The
magnetic moment per Fe -atom at room temperature (between 1.4 to 1.7 Bohr
Magneton) is much lower than in previously reported anti-ferromagnetic FeV2Se4.
Furthermore, the Curie constant shows a rapid and continuous reduction and
combined with the high field magnetization result at 2K suggests a rapid
decrease in the paramagnetic moments on cooling to low temperatures and the
absence of any magnetic order in Fe0.33VSe2 at low temperatures.",0808.1334v1
2008-08-28,Giant frictional drag in strongly interacting bilayers near filling factor one,"We study the frictional drag in high mobility, strongly interacting GaAs
bilayer hole systems in the vicinity of the filling factor $\nu=1$ quantum Hall
state (QHS), at the same fillings where the bilayer resistivity displays a
reentrant insulating phase. Our measurements reveal a very large longitudinal
drag resistivity ($\rho^{D}_{xx}$) in this regime, exceeding 15 k$\Omega/\Box$
at filling factor $\nu=1.15$. $\rho^{D}_{xx}$ shows a weak temperature
dependence and appears to saturate at a finite, large value at the lowest
temperatures. Our observations are consistent with theoretical models positing
a phase separation, e.g. puddles of $\nu=1$ QHS embedded in a different state,
when the system makes a transition from the coherent $\nu=1$ QHS to the weakly
coupled $\nu=2$ QHS.",0808.3807v1
2008-10-26,Development of Glass Resistive Plate Chambers for INO,"The India-based Neutrino Observatory (INO) collaboration is planning to build
a massive 50kton magnetised Iron Calorimeter (ICAL) detector, to study
atmospheric neutrinos and to make precision measurements of the parameters
related to neutrino oscillations. Glass Resistive Plate Chambers (RPCs) of
about 2m X 2m in size are going to be used as active elements for the ICAL
detector. We have fabricated a large number of glass RPC prototypes of 1m X 1m
in size and have studied their performance and long term stability. In the
process, we have developed and produced a number of materials and components
required for fabrication of RPCs. We have also designed and optimised a number
of fabrication and quality control procedures for assembling the gas gaps. In
this paper we will review our activities towards development of glass RPCs for
the INO ICAL detector and will present results of the characterisation studies
of the RPCs.",0810.4693v1
2009-02-01,"Enhancement of positive magnetoresistance following a magnetic-field-induced ferromagnetic transition in an intermetallic compound, Tb5Si3","We report the existence of a field-induced ferromagnetic transition in the
magnetically ordered state (<69 K) of an intermetallic compound, Tb5Si3, and
this transition is distinctly first-order at 1.8 K (near 60 kOe), whereas it
appears to become second order near 20 K. The finding we stress is that the
electrical resistivity becomes suddenly large in the high-field state after
this transition and this is observed in the entire temperature range in the
magnetically ordered state. Such an enhancement of 'positive' magnetoresistance
(below 100 kOe) at the metamagnetic transition field is unexpected on the basis
that the application of magnetic field should favor a low-resistive state due
to alignment of spins.",0902.0153v1
2009-06-08,Tunneling Electroresistance in Ferroelectric Tunnel Junctions with a Composite Barrier,"Tunneling electroresistance (TER) effect is the change in the electrical
resistance of a ferroelectric tunnel junction (FTJ) associated with
polarization reversal in the ferroelectric barrier layer. Here we predict that
a FTJ with a composite barrier that combines a functional ferroelectric film
and a thin layer of a non-polar dielectric can exhibit a significantly enhanced
TER. Due to the change in the electrostatic potential with polarization
reversal the non-polar dielectric barrier acts as a switch that changes its
barrier height from a low to high value. The predicted values of TER are giant
and indicate that the resistance of the FTJ can be changed by many orders in
magnitude at the coercive electric field of ferroelectric.",0906.1524v1
2009-08-11,Contrasting Pressure Effects in Sr2VFeAsO3 and Sr2ScFePO3,"We report the resistivity measurements under pressure of two Fe-based
superconductors with a thick perovskite oxide layer, Sr2VFeAsO3 and Sr2ScFePO3.
The superconducting transition temperature Tc of Sr2VFeAsO3 markedly increases
with increasing pressure. Its onset value, which was Tc{onset}=36.4 K at
ambient pressure, increases to Tc{onset}=46.0 K at ~4 GPa, ensuring the
potential of the ""21113"" system as a high-Tc material. However, the
superconductivity of Sr2ScFePO3 is strongly suppressed under pressure. The
Tc{onset} of ~16 K decreases to ~5 K at ~4 GPa, and the zero-resistance state
is almost lost. We discuss the factor that induces this contrasting pressure
effect.",0908.1469v2
2010-03-11,Nonlinear response and two stable electrical conductivity levels measured in plasticized PVC thin film samples,"The electrical conductivity of PVC films prepared with a patented plasticizer
of type ""A"" was measured with high precision automated setup, based on standard
ring sell with a voltage range much less than breakdown voltage. Continual
voltage-current measurements permit to take into account Debay relaxation
process and clearly distinguish specific polymer film conductivity effects,
connected with continuous current-stabilization behavior and transitions
between two stable (long-living) states with several order magnitude different
conductivities. Spontaneous reversible and non-destructive transitions of
resistance levels was observed. For 30 mkm polymer films the values of sample
resistance was measured equal to: high- 106 Ohm and low -103 Ohm.",1003.2331v1
2010-09-13,Non-monotonic temperature dependent transport in graphene grown by Chemical Vapor Deposition,"Temperature-dependent resistivity of graphene grown by chemical vapor
deposition (CVD) is investigated. We observe in low mobility CVD graphene
device a strong insulating behavior at low temperatures and a metallic behavior
at high temperatures manifesting a non-monotonic in the temperature dependent
resistivity.This feature is strongly affected by carrier density modulation. To
understand this anomalous temperature dependence, we introduce thermal
activation of charge carriers in electron-hole puddles induced by randomly
distributed charged impurities. Observed temperature evolution of resistivity
is then understood from the competition among thermal activation of charge
carriers, temperature-dependent screening and phonon scattering effects. Our
results imply that the transport property of transferred CVD-grown graphene is
strongly influenced by the details of the environment",1009.2506v2
2010-10-14,Viscous corrections to the resistance of nano-junctions: a dispersion relation approach,"It is well known that the viscosity of a homogeneous electron liquid diverges
in the limits of zero frequency and zero temperature. A nanojunction breaks
translational invariance and necessarily cuts off this divergence. However, the
estimate of the ensuing viscosity is far from trivial. Here, we propose an
approach based on a Kramers-Kr\""onig dispersion relation, which connects the
zero-frequency viscosity, $\eta(0)$, to the high-frequency shear modulus,
$\mu_{\infty}$, of the electron liquid via $\eta(0) =\mu_{\infty} \tau$, with
$\tau$ the junction-specific momentum relaxation time. By making use of a
simple formula derived from time-dependent current-density functional theory we
then estimate the many-body contributions to the resistance for an integrable
junction potential and find that these viscous effects may be much larger than
previously suggested for junctions of low conductance.",1010.2959v2
2011-05-18,Multiple photoexcitation of two-dimensional electron systems: bichromatic magnetoresistance oscillations revisited,"We analyze theoretically magnetoresistance of high mobility two-dimensional
electron systems being illuminated by multiple radiation sources. In
particular, we study the influence on the striking effect of microwave-induced
resistance oscillations. We consider moderate radiation intensities without
reaching the zero resistance states regime. We use the model of
radiation-driven Larmor orbits extended to several light sources. First, we
study the case of two different radiations polarized in the same direction with
different or equal frequencies. For both cases we find a regime of
superposition or interference of harmonic motions. When the frequencies are
different, we obtain a modulated magnetoresistance response with pulses and
beats. On the other hand, when the frequencies are the same, we find that the
final result will depend on the phase difference between both radiation fields
going from an enhanced response to a total collapse of oscillations, reaching
an outcome similar to darkness. Finally, we consider a multiple photoexcitation
case (three different frquencies) where we propose the two-dimensional electron
system as a potential nanoantenna device for microwaves.",1105.3592v1
2011-07-11,Impairment of double exchange mechanism in electron transport of iron pnictides,"Double exchange mechanism is believed to favor transport along ferromagnetic
directions, the failure of which in explaining the unusual resistivity
anisotropy in iron pnictides is investigated. Several factors intrinsic to the
microscopic mechanism of transport in iron pnictides are identified and
analyzed, including the moderate Hund's coupling, low local moment, and
presence of two anisotropic degenerate orbitals xz and yz. In particular, the
substantial second neighbor hoppings are found to be decisive in giving results
opposite to the double exchange picture. In high temperature nonmagnetic phase,
orbital ordering is shown to give the right trend of resistivity anisotropy as
observed experimentally, advocating its essential role in electron transport of
iron pnictides.",1107.1952v1
2011-10-24,Anisotropy of upper critical fields and thermally-activated flux flow of quenched KxFe2-ySe2 single crystals,"We report the anisotropy of the upper critical fields mu0Hc2(T) and
thermally-activated flux flow (TAFF) behavior of quenched KxFe2-ySe2. Even
though the post-annealing and quenching process enhances the superconducting
volume fraction, it has a minor effect on the upper critical fields for H//c
and H//ab. Analysis of the angular-dependence of resistivity rho_ab(theta,H)
indicates that it follows the scaling law based on the anisotropic
Ginzburg-Landau (GL) theory and the anisotropy Gamma(T) increases with
decreasing temperature with Gamma(T) ~ 3.6 at 27 K. The resistivity of quenched
sample exhibits an Arrhenius TAFF behavior for both field directions. Field
dependence of thermally activated energy U0(H) implies that the collective flux
creep is dominant in high fields and point defects are the main pinning source
in this regime.",1110.5316v1
2011-10-26,Mg substitution in CuCrO2 delafossite compounds,"A detailed investigation of the series CuCr(1-x)MgxO2 (x = 0.0 - 0.05) has
been performed by making high-temperature resistivity and thermopower
measurements, and by performing a theoretical analysis of the latter.
Microstructure characterization has been carried out as well. Upon Mg2+ for
Cr3+ substitution, a concomitant decrease in the electrical resistivity and
thermopower values is found, up to x ~ 0.02 - 0.03, indicating a low solubility
limit of Mg in the structure. This result is corroborated by scanning electron
microscopy observations, showing the presence of MgCr2O4 spinels as soon as x =
0.005. The thermopower is discussed in the temperature-independent correlation
functions ratio approximation as based on the Kubo formalism, and the
dependence of the effective charge carrier density on the nominal Mg
substitution rate is addressed. This leads to a solubility limit of 1.1% Mg in
the delafossite, confirmed by energy dispersive X-ray spectroscopy analysis.",1110.5730v2
2011-11-09,Insulator-to-metal transition and large thermoelectric effect in La$_{1-x}$Sr$_{x}$MnAsO,"We report the Sr substitution effect in an antiferromagnetic insulator
LaMnAsO. The Sr doping limit is $x\sim$ 0.10 under the synthesis conditions, as
revealed by x-ray diffractions indicate. Upon Sr doping, the room-temperature
resistivity drops by five orders of magnitude down to $\sim$0.01
$\Omega\cdot$cm, and the temperature dependence of resistivity shows
essentially metallic behavior for $x\geq$0.08. Hall and Seebeck measurements
confirm consistently that the insulator-to-metal transition is due to hole
doping. Strikingly, the room-temperature Seebeck coefficient for the metallic
samples is as high as $\sim240 \mu$V/K, making the system as a possible
candidate for thermoelectric applications.",1111.2232v1
2011-11-23,Magneto-Electric Effects on Sr Z-type Hexaferrite at Room Temperature,"In this paper, magnetoelectric effects of Sr Z-type hexaferrite,
Sr3Fe24Co2O41, at room temperature is measured. The change in remanence
magnetization was measured by applying a DC voltage or electric field across a
slab of hexaferrite. Changes of ~ 18% in remanence was observed in an electric
field of 10,000V/cm implying a similar change in the microwave permeability at
frequencies below 3GHz. Also, a change in dielectric constant at 1 GHz of ~16%
in a magnetic field of only 320 Oe was measured. In these types of measurements
high resistivity is critical in order to reduce current flow in the
hexaferrite. The resistivity of the hexaferrite was raised to 4.28x10^8 ohm-cm
by annealing under oxygen pressure. The measurements indicate that indeed
electric polarization and magnetization changes were induced by the application
of magnetic and electric fields, respectively. The implications for microwave
applications appear to be very promising at room temperature.",1111.5555v1
2011-11-23,Room Temperature Magnetoelectric Effects on Single Slabs of Z-type Hexaferrites,"In this paper, magnetoelectric effects of Sr Z-type hexaferrite,
Sr3Fe24Co2O41, at room temperature is measured. The change in remanence
magnetization was measured by applying a DC voltage or electric field across a
slab of hexaferrite. Changes of ~ 18% in remanence was observed in an electric
field of 10,000V/cm implying a similar change in the microwave permeability at
frequencies below 3GHz. In these types of measurements high resistivity is
critical in order to reduce current flow in the hexaferrite. The resistivity of
the hexaferrite was raised to 4.28x10^8 ohm?-cm by annealing under oxygen
pressure. The measurements indicate that indeed electric polarization and
magnetization changes were induced by the application of magnetic and electric
fields, respectively. The implications for microwave applications appear to be
very promising at room temperature.",1111.5556v1
2012-02-05,Temperature dependent elastic constants and ultimate strength of graphene and graphyne,"Based on the first principles calculation combined with quasi-harmonic
approximation, in this work we focus on the analysis of temperature dependent
lattice geometries, thermal expansion coefficients, elastic constants and
ultimate strength of graphene and graphyne. For the linear thermal expansion
coefficient, both graphene and graphyne show a negative region in the low
temperature regime. This coefficient increases up to be positive at high
temperatures. Graphene has superior mechanical properties, with Young modulus
E11=371.0 N/m, E22=378.2 N/m and ultimate tensile strength of 119.2 GPa at room
temperature. Based on our analysis, it is found that graphene's mechanical
properties have strong resistance against temperature increase up to 1200 K.
Graphyne also shows good mechanical properties, with Young modulus E11=224.7
N/m, E22=223.9 N/m and ultimate tensile strength of 81.2 GPa at room
temperature, but graphyne's mechanical properties have a weaker resistance with
respect to the increase of temperature than that of graphene.",1202.0933v1
2012-02-08,Coexisting Holes and Electrons in High-Tc Materials: Implications from Normal State Transport,"Normal state resistivity and Hall effect are shown to be successfully modeled
by a two-band model of holes and electrons that is applied self-consistently to
(i) DC transport data reported for eight bulk-crystal and six oriented-film
specimens of YBa2Cu3O7-{\delta}, and (ii) far-infrared Hall angle data reported
for YBa2Cu3O7-{\delta} and Bi2Sr2CaCu2O8+{\delta}. The electron band exhibits
extremely strong scattering; the extrapolated DC residual resistivity of the
electronic component is shown to be consistent with the previously observed
excess thermal conductivity and excess electrodynamic conductivity at low
temperature. Two-band hole-electron analysis of Hall angle data suggest that
the electrons possess the greater effective mass.",1202.1792v1
2012-07-25,Superconductivity at 5.4 K in $β$-Bi$_2$Pd,"We investigate bulk superconductivity in a high-quality single crystal of
Bi$_2$Pd ($\beta$-Bi$_2$Pd, space group; I4/mmm) at temperatures less than 5.4
K by exploring its electrical resistivity, magnetic susceptibility, and
specific heat. The temperature dependence of the electrical resistivity shows
convex-upward behaviors at temperatures greater than 40-50 K, which can be
explained by a parallel-resistor model. In addition, we demonstrate that this
material is a multiple-band/multiple-gap superconductor based on the
temperature dependences of the specific heat and the upper critical field.",1207.5905v3
2012-10-09,Giant exchange bias and ferromagnetism in the CoO shell of Co/CoO-MgO core-shell nanoparticles,"Using magnetron sputtering, we produced a series of Co/CoO-MgO nanoparticles
on Si(100) substrates. High-resolution transmission electron microscopy (HRTEM)
image shows that small isolated Co-clusters (core) covered with CoO (shells)
with a size of a few nm embedded in a MgO matrix. Resistivity as a function of
Co atomic ratio exhibits a distinct percolation threshold with a sharp decrease
around 69% Co content. Across the threshold, the resistivity drops about 7
orders of magnitude. For a sample at this percolation critical threshold, we
have observed a giant exchange bias field HE=2460 Oe at T= 2K, and using soft
x-ray magnetic circular dichroism at the Co-L2,3 edge, we have detected a
ferromagnetic (FM) signal originating from the antiferromagnetic CoO shell.
Moreover, decreasing the Mg-impurities will reduce the FM signal from CoO shell
(namely the uncompensated spin density) and the size of HE, thus directly
support the uncompensated spin model.",1210.2510v1
2012-11-12,Density dependent electrical conductivity in suspended graphene: Approaching the Dirac point in transport,"We theoretically consider, comparing with the existing experimental
literature, the electrical conductivity of gated monolayer graphene as a
function of carrier density, temperature, and disorder in order to assess the
prospects of accessing the Dirac point using transport studies in high-quality
suspended graphene. We show that the temperature dependence of graphene
conductivity around the charge neutrality point provides information about how
close the system can approach the Dirac point although competition between
long-range and short-range disorder as well as between diffusive and ballistic
transport may considerably complicate the picture. We also find that acoustic
phonon scattering contribution to the graphene resistivity is always relevant
at the Dirac point in contrast to higher density situations where the acoustic
phonon contribution to the resistivity is strongly suppressed at the low
temperature Bloch-Gr\""{u}neisen regime. We provide detailed numerical results
for temperature and density dependent conductivity for suspended graphene.",1211.2845v2
2012-12-26,Molybdenum sputtering film characterization for high gradient accelerating structures,"Technological advancements are strongly required to fulfill the demands of
new accelerator devices with the highest accelerating gradients and operation
reliability for the future colliders. To this purpose an extensive R&D
regarding molybdenum coatings on copper is in progress. In this contribution we
describe chemical composition, deposition quality and resistivity properties of
different molybdenum coatings obtained via sputtering. The deposited films are
thick metallic disorder layers with different resistivity values above and
below the molibdenum dioxide reference value. Chemical and electrical
properties of these sputtered coatings have been characterized by Rutherford
backscattering, XANES and photoemission spectroscopy. We will also present a
three cells standing wave section coated by a molybdenum layer $\sim$ 500 nm
thick designed to improve the performance of X-Band accelerating systems.",1212.6203v1
2012-12-28,Magneto-resistance up to 60 Tesla in Topological Insulator Bi2Te3 Thin Films,"We report magneto-transport studies of topological insulator Bi_{2}Te_{3}
thin films grown by pulsed laser deposition. A non-saturating linear-like
magneto-resistance (MR) is observed at low temperatures in the magnetic field
range from a few Tesla up to 60 Tesla. We demonstrate that the strong
linear-like MR at high field can be well understood as the weak
antilocalization phenomena described by Hikami-Larkin-Nagaoka theory. Our
analysis suggests that in our system, a topological insulator, the elastic
scattering time can be longer than the spin-orbit scattering time. We briefly
discuss our results in the context of Dirac Fermion physics and 'quantum linear
magnetoresistance'.",1212.6464v1
2013-01-02,Visualizing Atomic-Scale Negative Differential Resistance in Bilayer Graphene,"We investigate the atomic-scale tunneling characteristics of bilayer graphene
on silicon carbide using the scanning tunneling microscopy. The high-resolution
tunneling spectroscopy reveals an unexpected negative differential resistance
(NDR) at the Dirac energy, which spatially varies within the single unit cell
of bilayer graphene. The origin of NDR is explained by two near-gap van Hove
singularities emerging in the electronic spectrum of bilayer graphene under a
transverse electric field, which are strongly localized on two sublattices in
different layers. Furthermore, defects near the tunneling contact are found to
strongly impact on NDR through the electron interference. Our result provides
an atomic-level understanding of quantum tunneling in bilayer graphene, and
constitutes a useful step towards graphene-based tunneling devices.",1301.0270v1
2013-04-01,Pressure Induced Superconductivity and Structural Transitions in Ba(Fe0.9Ru0.1)2As2,"High pressure electrical resistance and x-ray diffraction measurements have
been performed on ruthenium-doped Ba(Fe0.9Ru0.1)2As2, up to pressures of 32 GPa
and down to temperatures of 10 K, using designer diamond anvils under
quasi-hydrostatic conditions. At 3.9 GPa, there is an evidence of
pressure-induced superconductivity with Tc onset of 24 K and zero resistance at
Tc zero of ~14.5 K. The superconducting transition temperature reaches maximum
at ~5.5 GPa and then decreases gradually with increase in pressure before
completely disappearing above 11.5 GPa. Upon increasing pressure at 200 K, an
isostructural phase transition from a tetragonal (I4/mmm) phase to a collapsed
tetragonal phase is observed at 14 GPa and the collapsed phase persists up to
at least 30 GPa. The changes in the unit cell dimensions are highly anisotropic
across the phase transition and are qualitatively similar to those observed in
undoped BaFe2As2 parent.",1304.0298v2
2013-04-10,Charge Kondo Effect in Thermoelectric Properties of Lead Telluride doped with Thallium Impurities,"We investigate the thermoelectric properties of PbTe doped with a small
concentration $x$ of Tl impurities acting as acceptors and described by
Anderson impurities with negative on-site (effective) interaction. The
resulting charge Kondo effect naturally accounts for a number of the low
temperature anomalies in this system, including the unusual doping dependence
of the carrier concentration, the Fermi level pinning and the self-compensation
effect. The Kondo anomalies in the low temperature resistivity at temperatures
$T\leq 10\, {\rm K}$ and the $x$-dependence of the residual resistivity are
also in good agreement with experiment. Our model also captures the qualitative
aspects of the thermopower at higher temperatures $T>300\, {\rm K}$ for high
dopings ($x>0.6%$) where transport is expected to be largely dominated by
carriers in the heavy hole band of PbTe.",1304.3026v1
2013-04-22,Modeling Composites of Multi-Walled Carbon Nanotubes in Polycarbonate,"High strain rate experiments performed on multi-walled carbon nanotubes and
polycarbonate composites (MWCNT-PC) have exhibited enhanced impact resistance
under a dynamic strain rate of nearly 2500/s with composition of only 0.5 to
2.0 percent of Multi walled carbon nanotubes(MWCNTs) in pure polycarbonate(PC).
Similarly, hardness and elastic modulus under static loads resulted in
significant increase depending upon the composition of MWCNTs in PC.The present
work aims to analyze these results by correlating the data to fit expressions
in generalizing the behavior of MWCNTs composition for MWCNT-PC composites
under both static and impact loads. As a result we found that an optimum
composition of 2.1 percent of MWCNTs exhibits maximum stress resistance within
elastic range under strain rates of nearly 2500/s for MWCNT-PC composites.The
results are critically dependent on the composition of MWCNTs and significantly
deteriorate below and above a threshold composition. A simple model based on
Lennard-Jones atom-atom based potential is formulated to compute static
properties of pure as well as composites of PC.",1304.5979v1
2013-08-15,Suppression of bulk conductivity in InAs/GaSb broken gap composite quantum wells,"The two-dimensional topological insulator state in InAs/GaSb quantum wells
manifests itself by topologically protected helical edge channel transport
relying on an insulating bulk. This work investigates a way of suppressing bulk
conductivity by using gallium source materials of different degrees of impurity
concentrations. While highest-purity gallium is accompanied by clear conduction
through the sample bulk, intentional impurity incorporation lead to a bulk
resistance over 1 M\Omega. This resistance was found to be independent of
applied magnetic fields. Ultra high electron mobilities for GaAs/AlGaAs
structures fabricated in a molecular beam epitaxy system used for the growth of
Sb-based samples are reported.",1308.3375v2
2013-09-06,Heteroepitaxy of Group IV-VI Nitrides by Atomic Layer Deposition,"Heteroepitaxial growth of selected group IV-VI nitrides on various
orientations of sapphire (\alpha-Al2O3) is demonstrated using atomic layer
deposition. High quality, epitaxial films are produced at significantly lower
temperatures than required by conventional deposition methods. Characterization
of electrical and superconducting properties of epitaxial films reveals a
reduced room temperature resistivity and increased residual resistance ratio
(RRR) for films deposited on sapphire compared to polycrystalline samples
deposited concurrently on fused quartz substrates.",1309.1789v1
2013-10-31,Single crystal growth and characterization of the large-unit-cell compound Cu13Ba,"Single crystals of Cu$_{13}$Ba were successfully grown out of Ba-Cu self
flux. Temperature dependent magnetization, $M(T)$, electrical resistivity,
$\rho(T)$, and specific heat, $C_p(T)$, data are reported. Isothermal
magnetization measurements, $M(H)$, show clear de Haas-van Alphen oscillations
at $T$ = 2 K for applied fields as low as $\mu_0H$ = 1T. An anomalous behavior
of the magnetic susceptibility is observed up to $T$ ~ 50K reflecting the
effect of de Haas-van Alphen oscillations at fairly high temperatures. The
field- and temperature-dependencies of the magnetization indicate the presence
of diluted magnetic impurities with a concentration of the order of 0.01at.%.
Accordingly, the minimum and lower temperature rise observed in the electrical
resistivity at and below $T$ = 15K is attributed to the Kondo impurity effect.",1311.0027v1
2013-11-22,Thermally excited multi-band conduction in LaAlO3/SrTiO3 heterostructures exhibiting magnetic scattering,"Magnetotransport measurements of charge carriers at the interface of a
LaAlO3/SrTiO3 heterostructure with 26 unit cells of LaAlO3 show Hall resistance
and magnetoresistance which at low and high temperatures is described by a
single channel of electron-like charge carriers. At intermediate temperatures,
we observe non-linear Hall resistance and positive magnetoresistance,
establishing the presence of at least two electron-like channels with
significantly different mobilities and carrier concentrations. These channels
are separated by 6 meV in energy and their temperature dependent occupation and
mobilities are responsible for the observed transport properties of the
interface. We observe that one of the channels has a mobility that decreases
with decreasing temperature, consistent with magnetic scattering in this
channel.",1311.5807v1
2014-04-18,Systematic control of carrier concentration and resisitivity in RF sputtered Zinc oxide thin films,"RF sputtered ZnO and Al:ZnO films are attractive transparent conductive
oxides for fabrication of opto-electronic devices. In this paper we present
efforts to control carrier concentration and mobility of ZnO/Al:ZnO thin films
by controlling deposition parameters (RF power, pressure and substrate
temperature. Al:ZnO thin film with resistivity as low as $\rho$ = $3.8\times
10^{-4}$ $\Omega$.cm at deposition temperature of 250{\deg}C has been achieved.
Zinc oxide thin film with low resistivity of $\rho$ = $3.7\times 10^{-2}$
$\Omega$.cm and high electron mobility of $30$ $\mathrm{cm^{-2}V^{-1}s^{-1}}$
at deposition temperature of 250{\deg}C with acceptable electronic parameters
stability has been obtained.Light transmission of Al:ZnO and ZnO samples
deposited on glass at different substrate temperature has been studied.
Investigation were made to assess the effect of deposition temperature on the
photoluminescence spectra (PL) of ZnO/Al:ZnO sputtered on silicon and glass
substrate. The evolution of near band edge (NBE) and deep level emission (DLE)
photoluminescence peaks with deposition temperature in ZnO/Al:ZnO sputtered on
Silicon and glass substrate have been studied.",1404.4902v1
2014-04-17,Caracterización de austenita expandida generada por cementación iónica de aceros inoxidables. Estudio de la estabilidad frente a la irradiación con haces de iones ligeros energéticos,"This thesis was focused on the surface modification with plasma discharge.
Austenitic AISI 316L stainless steel sample was carburised under different
experimental conditions and mechanical properties have been studied (thickness,
lattice parameter, elemental composition, hardness, wear resistance and
corrosion resistance). After that, steel substrates have been nitrided or
carburised in order to analyse their stability under ion bombardment using a
plasma focus device. Helium and deuterium were the gases used in 0, 1, 5, and
10 discharges. Optical and X-ray characterisations were used. Finally, using
magnetron sputtering nitrided/carburised samples were coated with an AlN thin
film in order to study their stability under long treatments at high
temperatures.",1404.5204v1
2014-05-05,Controllable growth of Al nanorods for inexpensive and degradation-resistant surface enhanced Raman spectroscopy,"Surface enhanced Raman spectroscopy (SERS) has the capacity of detecting
trace amount of biological or chemical matter, even single molecules, through
the use of metallic nanostructures such as nanorods. Silver (Ag) and gold (Au)
nanorods have led to the impressive enhancement of Raman signals, but they are
either expensive, degrade fast over time, or suffer from poor sample
repeatability. In contrast, Al is much less expensive, and Al nanorods could
potentially be resistant to degradation over time due to the protection from
native aluminum-oxide layers. Unfortunately, the controllable growth of Al
nanorods has not been reported so far. This Letter reports, for the first time,
the controllable growth of Al nanorods using physical vapor deposition (PVD);
through the use of oxygen (O) surfactants. The enhancement factor of the Al
nanorods in SERS is as high as 1250, and shows nearly no degradation after
storage in ambient for 30 days or annealing at 475 K for one day.",1405.1009v1
2014-06-27,Simulation of Non-linear SRF losses derived from characteristic topography of etched and electropolished niobium surfaces,"A simplified numerical model has been developed to simulate non-linear
superconducting radiofrequency (SRF) losses on Nb surfaces. This study focuses
exclusively on excessive surface resistance (Rs) losses due to the microscopic
topographical magnetic field enhancements. When the enhanced local surface
magnetic field exceeds the superconducting critical transition magnetic field
Hc, small volumes of surface material may become normal conducting and increase
the effective surface resistance without inducing a quench. Using topographic
data from typical Buffered Chemical Polish (BCP) and Electropolish (EP) treated
fine grain niobium , we have estimated the resulting field-dependent losses and
extrapolated this model to the implications for cavity performance. The model
predictions correspond well to the characteristic BCP versus EP high field Q0
performance differences for fine grain niobium. We describe the algorithm of
the model, its limitations, and the effects of this non-linear loss
contribution on SRF cavity performance.",1406.7276v4
2015-01-25,Superconductivity in Dense Rashba Semiconductor BiTeCl,"Layered non-centrosymmetric bismuth tellurohalides are being examined as
candidates for topological insulators. Pressure is believed to be essential for
inducing and tuning topological order in these systems. Through electrical
transport and Raman scattering measurements, we find superconductivity in two
high-pressure phases of BiTeCl with the different normal state features,
carrier characteristics, and upper critical field behaviors. Superconductivity
emerges when the resistivity maximum or charge density wave is suppressed by
the applied pressure and then persists till the highest pressure of 51 GPa
measured. The huge enhancement of the resistivity with three magnitude of
orders indicates the possible achievement of the topological order in the dense
insulating phase. These findings not only enrich the superconducting family
from topological insulators but also pave the road on the search of topological
superconductivity in bismuth tellurohalides.",1501.06203v1
2015-02-04,Topological Insulator Thin Films Starting from the Amorphous Phase - Bi$_2$Se$_3$ as Example,"We present a new method to obtain topological insulator Bi$_2$Se$_3$ thin
films with a centimeter large lateral length. To produce amorphous Bi$_2$Se$_3$
thin films we have used a sequential flash-evaporation method at room
temperature. Transmission electron microscopy has been used to verify that the
prepared samples are in a pure amorphous state. During annealing the samples
transform into the rhombohedral Bi$_2$Se$_3$ crystalline strcuture which was
confirmed using X-ray diffraction and Raman spectroscopy. Resistance
measurements of the amorphous films show the expected Mott variable range
hopping conduction process with a high specific resistance compared to the one
obtained in the crystalline phase (metallic behavior). We have measured the
magnetoresistance (MR) and the Hall effect (HE) at different temperatures
between 2 K and 275 K. At temperatures $T \lesssim 50$ K and fields $B \lesssim
1$ T we observe weak anti-localization in the MR; the Hall measurements confirm
the n-type character of the samples. All experimental results of our films are
in quantitative agreement with results from samples prepared using more
sophisticated methods.",1502.01135v1
2015-03-13,Suspended graphene devices with local gate control on an insulating substrate,"We present a fabrication process for graphene-based devices where a graphene
monolayer is suspended above a local metallic gate placed in a trench. As an
example we detail the fabrication steps of a graphene field-effect transistor.
The devices are built on a bare high-resistivity silicon substrate. At
temperatures of 77~K and below, we observe the field-effect modulation of the
graphene resistivity by a voltage applied to the gate. This fabrication
approach enables new experiments involving graphene-based superconducting
qubits and nano-electromechanical resonators. The method is applicable to other
two-dimensional materials.",1503.04147v2
2015-03-18,A novel fast timing micropattern gaseous detector: FTM,"In recent years important progress in micropattern gaseous detectors has been
achieved in the use of resistive material to build compact spark-protected
devices. The novel idea presented here consists of the polarisation of WELL
structures using only resistive coating. This allows a new device to be built
with an architecture based on a stack of several coupled layers where drift and
WELL multiplication stages alternate in the structure. The signals from each
multiplication stage can be read out from any external readout boards through
the capacitive couplings. Each layer provides a signal with a gain of
10^4-10^5. The main advantage of this new device is the dramatic improvement of
the timing provided by the competition of the ionisation processes in the
different drift regions, which can be exploited for fast timing at the high
luminosity accelerators (e.g. HL-LHC upgrade) as well as far applications like
medical imaging.",1503.05330v1
2015-10-19,High resolution Hall measurements across the VO2 metal-insulator transition reveal impact of spatial phase separation,"Many strongly correlated transition metal oxides exhibit a metal-insulator
transition (MIT), the manipulation of which is essential for their application
as active device elements. However, such manipulation is hindered by lack of
microscopic understanding of mechanisms involved in these transitions. A
prototypical example is VO2, where previous studies indicated that the MIT
resistance change correlate with changes in carrier density and mobility. We
studied the MIT using Hall measurements with unprecedented resolution and
accuracy, simultaneously with resistance measurements. Contrast to prior
reports, we find that the MIT is not correlated with a change in mobility, but
rather, is a macroscopic manifestation of the spatial phase separation which
accompanies the MIT. Our results demonstrate that, surprisingly, properties of
the nano-scale spatially-separated metallic and semiconducting domains actually
retain their bulk properties. This study highlights the importance of taking
into account local fluctuations and correlations when interpreting transport
measurements in highly correlated systems.",1510.05414v1
2016-02-12,Relaxation of the resistive superconducting state in boron-doped diamond films,"We report a study of the relaxation time of the restoration of the resistive
superconducting state in single crystalline boron-doped diamond using
amplitude-modulated absorption of (sub-)THz radiation (AMAR). The films grown
on an insulating diamond substrate have a low carrier density of about
2.5x10^{21} cm^{-3} and a critical temperature of about 2 K. By changing the
modulation frequency we find a high-frequency rolloff which we associate with
the characterstic time of energy relaxation between the electron and the phonon
systems or the relaxation time for nonequilibrium superconductivity. Our main
result is that the electron-phonon scattering time varies clearly as T^{-2},
over the accessible temperature range of 1.7 to 2.2 K. In addition, we find,
upon approaching the critical temperature T_c, evidence for an increasing
relaxation time on both sides of T_c.",1602.04046v1
2016-05-12,"Scalable, ultra-resistant structural colors based on network metamaterials","Structural colours have drawn wide attention for their potential as a future
printing technology for various applications, ranging from biomimetic tissues
to adaptive camouflage materials. However, an efficient approach to realise
robust colours with a scalable fabrication technique is still lacking,
hampering the realisation of practical applications with this platform. Here we
develop a new approach based on large scale network metamaterials, which
combine dealloyed subwavelength structures at the nanoscale with loss-less,
ultra-thin dielectrics coatings. By using theory and experiments, we show how
sub-wavelength dielectric coatings control a mechanism of resonant light
coupling with epsilon-near-zero (ENZ) regions generated in the metallic
network, manifesting the formation of highly saturated structural colours that
cover a wide portion of the spectrum. Ellipsometry measurements report the
efficient observation of these colours even at angles of $70$ degrees. The
network-like architecture of these nanomaterials allows for high mechanical
resistance, which is quantified in a series of nano-scratch tests. With such
remarkable properties, these metastructures represent a robust design
technology for real-world, large scale commercial applications.",1605.03700v1
2016-08-02,Low-energy electron-irradiation effect on transport properties of graphene field effect transistor,"We study the effects of low-energy electron beam irradiation up to 10 keV on
graphene based field effect transistors. We fabricate metallic bilayer
electrodes to contact mono- and bi-layer graphene flakes on SiO$_2$, obtaining
specific contact resistivity $\rho_c \simeq 19 k\Omega \mu m^2$ and carrier
mobility as high as 4000 cm$^2$V$^{-1}$s$^{-1}$. By using a highly doped
p-Si/SiO$_2$ substrate as back gate, we analyze the transport properties of the
device and the dependence on the pressure and on the electron bombardment. We
demonstrate that low energy irradiation is detrimental on the transistor
current capability, resulting in an increase of the contact resistance and a
reduction of the carrier mobility even at electron doses as low as 30
$e^-/nm^2$. We also show that the irradiated devices recover by returning to
their pristine state after few repeated electrical measurements.",1608.00716v1
2016-08-23,Disorder effect on the anisotropic resistivity of phosphorene determined by a tight-binding model,"In this work we develop a compact multi-orbital tight-binding model for
phosphorene that accurately describes states near the main band gap. The model
parameters are adjusted using as reference the band structure obtained by a
density-functional theory calculation with the hybrid HSE06 functional. We use
the optimized tight-binding model to study the effects of disorder on the
anisotropic transport properties of phosphorene. In particular, we evaluate how
the longitudinal resistivity depends on the lattice orientation for two typical
disorder models: dilute scatterers with high potential fluctuation amplitudes,
mimicking screened charges in the substrate, and dense scatterers with lower
amplitudes, simulating weakly bounded adsorbates. We show that the intrinsic
anisotropy associated to the band structure of this material, although
sensitive to the type and intensity of the disorder, is robust.",1608.06633v2
2016-10-21,Giant Positive Magnetoresistance and field-induced metal insulator transition in Cr2NiGa,"We report here the magneto-transport properties of the newly synthesized
Heusler compound Cr2NiGa which crystallizes in a disordered cubic B2 structure
belonging to Pm-3m space group. The sample is found to be paramagnetic down to
2 K with metallic character. On application of magnetic field, a significantly
large increase in resistivity is observed which corresponds to
magnetoresistance as high as 112% at 150 kOe of field at the lowest
temperature. Most remarkably, the sample shows negative temperature coefficient
of resistivity below about 50 K under the application of field gretare than or
equal to 80 kOe, signifying a field-induced metal to `insulating' transition.
The observed magnetoresistance follows Kohler's rule below 20 K indicating the
validity of the semiclassical model of electronic transport in metal with a
single relaxation time. A multi-band model for electronic transport, originally
proposed for semimetals, is found to be appropriate to describe the
magneto-transport behavior of the sample.",1610.06771v1
2017-02-08,Hall field-induced resistance oscillations in MgZnO/ZnO heterostructures,"We report on nonlinear magnetotransport in a two-dimensional electron gas
hosted in a MgZnO/ZnO heterostructure. Upon application of a direct current, we
observe pronounced Hall field-induced resistance oscillations (HIRO) which are
well known from experiments on high-mobility GaAs/AlGaAs quantum wells. The
unique sensitivity of HIRO to the short-range component of the disorder
potential allows us to unambiguously establish that the mobility of our
MgZnO/ZnO heterostructure is limited by impurities residing within or near the
2D channel. Demonstration that HIRO can be realized in a system with a much
lower mobility, much higher density, and much larger effective mass than in
previously studied systems, highlights remarkable universality of the
phenomenon and its great promise to be used in studies of a wide variety of
emerging 2D materials.",1702.02557v1
2017-02-22,Variable-range-hopping conduction processes in oxygen deficient polycrystalline ZnO films,"We have fabricated oxygen deficient polycrystalline ZnO films by the rf
sputtering deposition method. To systematically investigate the charge
transport mechanisms in these samples, the electrical resistivities have been
measured over a wide range of temperature from 300 K down to liquid-helium
temperatures. We found that below about 100 K, the variable-range-hopping (VRH)
conduction processes govern the charge transport properties. In particular, the
Mott VRH conduction process dominates at higher temperatures, while crossing
over to the Efros-Shklovskii (ES) VRH conduction process at lower temperatures.
The crossover occurred at temperatures as high as a few tens degrees Kelvin.
Moreover, the temperature behavior of resistivity over the entire VRH
conduction regime from the Mott-type to the ES-type process can be well
described by a universal scaling law.",1702.06729v1
2017-06-25,Coherent Interlayer Tunneling and Negative Differential Resistance with High Current Density in Double Bilayer Graphene-WSe2 Heterostructures,"We demonstrate gate-tunable resonant tunneling and negative differential
resistance between two rotationally aligned bilayer graphene sheets separated
by bilayer WSe2. We observe large interlayer current densities of 2 uA/um2 and
2.5 uA/um2, and peak-to-valley ratios approaching 4 and 6 at room temperature
and 1.5 K, respectively, values that are comparable to epitaxially grown
resonant tunneling heterostructures. An excellent agreement between theoretical
calculations using a Lorentzian spectral function for the two-dimensional (2D)
quasiparticle states, and the experimental data indicates that the interlayer
current stems primarily from energy and in-plane momentum conserving 2D-2D
tunneling, with minimal contributions from inelastic or non-momentum-conserving
tunneling. We demonstrate narrow tunneling resonances with intrinsic
half-widths of 4 and 6 meV at 1.5 K and 300 K, respectively.",1706.08034v1
2017-09-08,Coulomb drag and counterflow Seebeck coefficient in bilayer-graphene double layers,"We have fabricated bilayer-graphene double layers separated by a thin
($\sim$20 nm) boron nitride layer and performed Coulomb drag and counterflow
thermoelectric transport measurements. The measured Coulomb drag resistivity is
nearly three orders smaller in magnitude than the intralayer resistivities. The
counterflow Seebeck coefficient is found to be well approximated by the
difference between Seebeck coefficients of individual layers and exhibit a peak
in the regime where two layers have opposite sign of charge carriers. The
measured maximum counterflow power factor is $\sim$ 700 $\mu$W/K$^2$cm at room
temperature, promising high power output per mass for lightweight
thermoelectric applications. Our devices open a possibility for exploring the
novel regime of thermoelectrics with tunable interactions between n-type and
p-type channels based on graphene and other two-dimensional materials and their
heterostructures.",1709.02778v1
2017-11-05,Synthesis of sodium cobaltate Na$_{x}$CoO$_{2}$ single crystals with controlled Na ordering,"In this study, we synthesized single crystals of Na$_{x}$CoO$_{2}$ with
$x\sim0.8$ using the optical floating zone technique. A thorough
electrochemical treatment of the samples permitted us to control the
de-intercalation of Na to obtain single crystal samples of stable Na ordered
phases with $x=0.5-0.8$. Comparisons of the bulk magnetic properties with those
observed in the Na ordered powder samples confirmed the high quality of these
single crystal phases. The ab plane resistivity was measured for the Na ordered
samples and it was quite reproducible for different sample batches. The data
were analogous to those found in previous initial experimental studies on
single crystals, but the lower residual resistivity and sharper
anti-ferromagnetic transitions determined for our samples confirmed their
higher quality.",1711.01611v2
2018-01-19,Nontrivial Metallic State of Molybdenum Disulfide,"The electrical conductivity and Raman spectroscopy measurements have been
performed on MoS$_2$ at high pressures up to 90 GPa and variable temperatures
down to 5 K. We find that the temperature dependence of the resistance in a
metallic 2H$_a$ phase has an anomaly (a hump) which shifts with pressure to
higher temperature. Concomitantly, a new Raman phonon mode appears in the
metallic state suggesting that the electrical resistance anomaly may be related
to a structural transformation. We suggest that this anomalous behavior is due
to a charge density wave state, the presence of which is indicative for a
possibility for an emergence of superconductivity at higher pressures.",1801.06351v1
2019-05-23,Laser machined ultrathin microscale platinum thermometers on transparent oxide substrates,"Ultrathin microscale resistive thermometers are of key value to many
applications. Here we have fabricated a laser machined 50 ${\mu}$m wide and 50
nm thick serpentine Pt thin film sensor capable of sensing temperatures up to
650 ${^\circ}$ C over multiple heating and cooling cycles. Various materials
and associated processing conditions were studied, including both sapphire and
silica as transparent substrates, alumina and TiO2 as adhesion layers, and
lastly alumina and silicon oxide as capping layer. In-situ resistance
monitoring helps to verify the multi-cycle stability of the sensor and guide
the optimization. 10 ${\mu}$m sized sensors can be laser machined but will not
survive multiple heating and cooling cycles. We demonstrate that the sensors
with amorphous Ge thin layers can also repeatably measure temperatures up to
650 ${^\circ}$ C. It is anticipated that this sensor can be used for fast and
high spatial resolution temperature probing for laser processing applications.",1905.09812v1
2014-08-06,Desarrollo de capas de AlN sobre aleaciones de aluminio como protección superficial contra la corrosión y el desgaste,"Aluminum and their alloys, after careful treatments, can develop excellent
mechanical, tribological, electrical and chemical (high corrosion resistance)
properties. However, 7000 series, with Cu in the alloy, have a poor corrosion
resistance. On the other hand, aluminum nitride (AlN) has a wurtzitic phase and
good thermal stability, optical, electric, piezoelectric, mechanical,
tribological, and chemical properties, so the application range is huge. In
this paper, AlN deposition on Al 7075 was done using the reactive magnetron
sputtering technique in order to verify the aluminum nitride performance as an
Al alloy protective film under wear and corrosive processes.",1408.1378v1
2014-08-28,Magneto-Dielectric Behavior in $La_{0.53}Ca_{0.47}MnO_{3}$,"We prospect magneto-dielectricity in $La_{0.53}Ca_{0.47}MnO_{3}$ across its
paramagnetic (PMI) to ferromagnetic (FMM) isostructural transition at $T_{C}
\sim 253K$, by magnetic ($(M)$), caloric ($(W)$), dielectric ($(\epsilon')$),
magneto-resistive (MR), and magneto-capacitance (MC) investigations.
Skew-broadened first-order transition character is confirmed via
heating/cooling hystereses in $(M)(T)$ and $(W)(T)$, with superheating
temperature $T**$ almost next to $T_C$ and supercooling temperature $T*$
exhibiting kinetics. Above $T_C$, linearly-related MC and MR reflect purely
magneto-resistance effect. Near $T_C$, the high-frequency MC(5T) much exceeds
the magneto-losses, and is uncorrelated with dc MR(5T) in the FM-ordered state.
The intrinsic magneto-dielectricity manifest below $T_C$ and above ~kHz is
traced to an intra-granular Maxwell-Wagner-type effect at the interface-region
of PMI-FMM phase-coexistence.",1408.6640v2
2017-03-02,Thermal conduction across a boron nitride and silicon oxide interface,"The needs for efficient heat removal and superior thermal conduction in
nano/micro devices have triggered tremendous studies in low-dimensional
materials with high thermal conductivity. Hexagonal boron nitride (h-BN) is
believed to be one of the candidates for thermal management and heat
dissipation due to its novel physical properties, i.e. thermal conductor and
electrical insulator. Here we reported interfacial thermal resistance between
few-layer h-BN and its silicon oxide substrate using differential 3 omega
method. The measured interfacial thermal resistance is around ~1.6*10-8 m2K/W
for monolayer h-BN and ~3.4*10-8 m2K/W for 12.8nm-thick h-BN in metal/h-BN/SiO2
interfaces. Our results suggest that the voids and gaps between substrate and
thick h-BN flakes limit the interfacial thermal conduction. This work provides
a deeper understanding of utilizing h-BN flake as lateral heat spreader in
electronic and optoelectronic nano/micro devices with further miniaturization
and integration.",1703.00669v1
2019-02-10,The role of plastic strain gradients in the crack growth resistance of metals,"Crack advance from short or long pre-cracks is predicted by the progressive
failure of a cohesive zone in a strain gradient, elasto-plastic solid. The
presence of strain gradients leads to the existence of an elastic zone at the
tip of a stationary crack, for both the long crack and the short crack cases.
This is in sharp contrast with previous asymptotic analyses of gradient solids,
where elastic strains were neglected. The presence of an elastic singularity at
the crack tip generates stresses which are sufficiently high to activate
quasi-cleavage. For the long crack case, crack growth resistance curves are
predicted for a wide range of ratios of cohesive zone strength to yield
strength. Remarkably, this feature of an elastic singularity is preserved for
short cracks, leading to a severe reduction in tensile ductility. In
qualitative terms, these predictions resemble those of discrete dislocation
calculations, including the concept of a dislocation-free zone at the crack
tip.",1902.03664v1
2019-07-11,Impurity concentration dependent electrical conduction in germanium crystal at low temperatures,"Germanium single crystal having 45 mm diameter and 100 mm length of 7N+
purity has been grown by Czochralski method. Structural quality of the crystal
has been characterized by Laue diffraction. Electrical conduction and Hall
measurements are carried out on samples retrieved from different parts of the
crystal along the growth axis. Top part of the crystal exhibits lowest impurity
concentration (~10^12/cm3) that gradually increases towards the bottom
(10^13/cm3). The crystal is n-type at room temperature and the resistivity
shows non-monotonic temperature dependence. There is a transition from n-type
to p-type conductivity below room temperature at which bulk resistivity shows
maximum and dip in carrier mobility. This intrinsic to extrinsic transition
regions shift towards room temperature as the impurity concentration increases
and reflects the purity level of the crystal. Similar trend is observed in
boron implanted high purity germanium (HPGe) crystal at different doping level.
The phenomena can be understood as a result of interplay between temperature
dependent conduction mechanism driven by impurity band and intrinsic carrier in
Ge crystals having fairly low acceptor concentrations (<10^12/cm3).",1907.05067v1
2020-02-25,Non-invasive nanoscale potentiometry and ballistic transport in epigraphene nanoribbons,"The recent observation of non-classical electron transport regimes in
two-dimensional materials has called for new high-resolution non-invasive
techniques to locally probe electronic properties. We introduce a novel hybrid
scanning probe technique to map the local resistance and electrochemical
potential with nm- and $\mu$V resolution, and we apply it to study epigraphene
nanoribbons grown on the sidewalls of SiC substrate steps. Remarkably, the
potential drop is non uniform along the ribbons, and $\mu$m-long segments show
no potential variation with distance. The potential maps are in excellent
agreement with measurements of the local resistance. This reveals ballistic
transport in ambient condition, compatible with micrometer-long
room-temperature electronic mean free paths.",2002.11024v1
2020-04-07,Multi-terminal electronic transport in boron nitride encapsulated TiS$_3$ nanosheets,"We have studied electrical transport as a function of carrier density,
temperature and bias in multi-terminal devices consisting of hexagonal boron
nitride (h-BN) encapsulated titanium trisulfide (TiS$_3$) sheets. Through the
encapsulation with h-BN, we observe metallic behavior and high electron
mobilities. Below $\sim$60 K an increase in the resistance, and non-linear
transport with plateau-like features in the differential resistance are
present, in line with the expected charge density wave (CDW) formation.
Importantly, the critical temperature and the threshold field of the CDW phase
can be controlled through the back-gate.",2004.03687v1
2020-04-09,Magnetic field-dependent resistance crossover and logarithmic to non-saturating magnetoresistance in topological insulator Bi$_2$Te$_3$,"We report a metal-insulator like transition in single crystalline 3D
topological insulator Bi2Te3 at a temperature of 230K in presence of an
external magnetic field applied normal to the surface. This transition becomes
more prominent at larger magnetic field strength with the residual resistance
value increasing linearly with the magnetic field. At low temperature, the
magnetic field dependence of the magnetoresistance shows a transition from
logarithmic to linear behavior and the onset magnetic field value for this
transition decreases with increasing temperature. The logarithmic
magnetoresistance indicates the weak anti-localization of the surface Dirac
electrons while the high temperature behavior originates from the bulk carriers
due to intrinsic impurities. At even higher temperatures beyond~230 K, a
completely classical Lorentz model type quadratic behavior of the
magnetoresistance is observed. We also show that the experimentally observed
anomalies at ~230K in the magneto-transport properties do not originate from
any stacking fault in Bi2Te3.",2004.04375v2
2012-01-02,Magnetodielectric behavior in La2CoMnO6 nanoparticles,"We have investigated magnetic, dielectric and magnetodielectric properties of
La2CoMnO6 nanoparticles prepared by sol-gel method. Magnetization measurements
revealed two distinct ferromagnetic transitions at 218 K and 135 K that can be
assigned to ordered and disordered magnetic phases of the La2CoMnO6
nanoparticles. Two dielectric relaxations culminating around the magnetic
transitions were observed with a maximum magnetodielectric response reaching
10% and 8% at the respective relaxation peaks measured at 100 kHz under 5T
magnetic field. The dc electrical resistivity followed an insulating behavior
and showed a negative magnetoresistance; there was no noticeable anomaly in
resistivity or magnetoresistance near the magnetic ordering temperatures.
Complex impedance analysis revealed a clear intrinsic contribution to the
magnetodielectric response; however, extrinsic contribution due to
Maxwell-Wagner effect combined with magnetoresistance property dominated the
magnetodielectric effect at high temperatures.",1201.0448v1
2012-01-30,Unusual size effects on thermoelectricity in a strongly correlated oxide,"We investigated size effects on thermoelectricity in thin films of a strongly
correlated layered cobaltate. At room temperature, the thermopower is
independent of thickness down to 6 nm. This unusual behavior is inconsistent
with the Fuchs-Sondheimer theory, which is used to describe conventional metals
and semiconductors, and is attributed to the strong electron correlations in
this material. Although the resistivity increases, as expected, below a
critical thickness of $\sim$ 30 nm. The temperature dependent thermopower is
similar for different thicknesses but resistivity shows systematic changes with
thickness. Our experiments highlight the differences in thermoelectric behavior
of strongly correlated and uncorrelated systems when subjected to finite size
effects. We use the atomic limit Hubbard model at the high temperature limit to
explain our observations. These findings provide new insights on decoupling
electrical conductivity and thermopower in correlated systems.",1201.6274v1
2016-03-05,MIRO-like oscillations of magneto-resistivity in GaAs heterostructures induced by THz radiation,"We report on the study of terahertz radiation induced MIRO-like oscillations
of magneto-resistivity in GaAs heterostructures. Our experiments provide an
answer on two most intriguing questions - effect of radiation helicity and the
role of the edges - yielding crucial information for understanding of the MIRO
origin. Moreover, we demonstrate that the range of materials exhibiting
radiation-induced magneto-oscillations can be largely extended by using
high-frequency radiation.",1603.01760v1
2017-05-17,Epitaxial electrical contact to graphene on SiC,"Establishing good electrical contacts to nanoscale devices is a major issue
for modern technology and contacting 2D materials is no exception to the rule.
One-dimensional edge-contacts to graphene were recently shown to outperform
surface contacts but the method remains difficult to scale up. We report a
resist-free and scalable method to fabricate few graphene layers with
electrical contacts in a single growth step. This method derives from the
discovery reported here of the growth of few graphene layers on a metallic
carbide by thermal annealing of a carbide forming metallic film on SiC in high
vacuum. We exploit the combined effect of edge-contact and partially-covalent
surface epitaxy between graphene and the metallic carbide to fabricate devices
in which low contact-resistance and Josephson effect are observed. Implementing
this approach could significantly simplify the realization of large-scale
graphene circuits.",1705.08257v2
2017-07-10,Phonon-Driven Electron Scattering and Magnetothermoelectric Effect in Two-Dimensional Tin Selenide,"The bulk tin selenide (SnSe) is the best thermoelectric material currently
with the highest figure-of-merit due to the strong phonon-phonon interactions.
We investigate the effect of electron-phonon coupling (EPC) on the transport
properties of two-dimensional (2D) SnSe sheet. We demonstrate that EPC plays a
key role in the scattering rate where the constant relaxation time
approximation is deficient. The EPC strength is especially large in contrast to
that of pristine graphene. The scattering rate depends sensitively on the
system temperatures and the carrier densities when the Fermi energy approaches
the band edge. We also investigate the magnetothermoelectric effect of the 2D
SnSe. It is found that at low temperatures there are enormous magnetoelectrical
resistivity and magnetothermal resistivity above 500\%, suggesting the high
potential for device applications. Our results agree reasonably well with the
experimental data.",1707.02737v1
2019-03-05,Development of a time projection chamber with a sheet-resistor field cage,"A new-concept time projection chamber (TPC) using a commercial resistive
sheet, sheet-resistor micro-TPC SR-microPIC, was developed and its performance
was measured. SR-microTPC has the potential to create a more uniform electric
field than conventional TPCs with resistor-chains owing to its continuous sheet
resistivity, and its production would be easier than that of conventional TPCs.
The material used in this study, Achilles-Vynilas, was found to be thin,
transparent, and low-radioactive. The performance test with cosmic muons showed
very promising results, including the demonstration of a good
tracking-performance. This type of TPC field cage can offer an alternative for
the widely used conventional field cages",1903.01663v3
2019-03-30,Disentangling spin-orbit coupling and local magnetism in a quasi-two-dimensional electron system,"Quantum interference between time-reversed electron paths in two dimensions
leads to the well-known weak localization correction to resistance. If
spin-orbit coupling is present, the resistance correction is negative, termed
weak anti-localization (WAL). Here we report the observation of WAL coexisting
with exchange coupling between itinerant electrons and localized magnetic
moments. We use low-temperature magneto-transport measurements to investigate
the quasi-two-dimensional, high-electron-density interface formed between
SrTiO$_3$ (STO) and the anti-ferromagnetic Mott insulator NdTiO$_3$ (NTO). As
the magnetic field angle is gradually tilted away from the sample normal, the
data reveals the interplay between strong $k$-cubic Rashba-type spin-orbit
coupling and a substantial magnetic exchange interaction from local magnetic
regions. The resulting quantum corrections to the conduction are in excellent
agreement with existing models and allow sensitive determination of the small
magnetic moments (22 $\mu_B$ on average), their magnetic anisotropy and mutual
coupling strength. This effect is expected to arise in other 2D magnetic
materials systems.",1904.00295v2
2019-08-27,Large surface conductance and two-dimensional superconductivity in microstructured crystalline topological insulators,"Controllable geometric manipulation via micromachining techniques provides a
promising tool for enhancing useful topological electrical responses relevant
to future applications such as quantum information science. Here we present
microdevices fabricated with focused ion beam from indium-doped topological
insulator Pb1-xSnxTe. With device thickness on the order of 1 {\mu}m and an
extremely large bulk resistivity, we achieve an unprecedented enhancement of
the surface contribution to about 30% of the total conductance near room
temperature. The surface contribution increases as the temperature is reduced,
becoming dominant below approximately 180 K, compared to 30 K in mm-thickness
crystals. In addition to the enhanced surface contribution to normal-state
transport, we observe the emergence of a two-dimensional superconductivity
below 6 K. Measurements of magnetoresistivity at high magnetic fields reveal a
weak antilocalization behavior in the normal-state magnetoconductance at low
temperature and a variation in the power-law dependence of resistivity on
temperature with field. These results demonstrate that interesting electrical
response relevant to practical applications can be achieved by suitable
engineering of single crystals.",1908.10427v1
2019-12-11,Pressure-induced superconductivity and structural transition in ferromagnetic Cr2Si2Te6,"The discovery of intrinsic magnetism in atomically thin two-dimensional
transition-metal trichalcogenides has attracted intense research interest due
to the exotic properties of magnetism and potential applications in devices.
Pressure has proven to be an effective tool to manipulate the crystal and
electronic structures of the materials. Here, we report investigations on
ferromagnetic van der Waals Cr2Si2Te6 via high-pressure synchrotron x-ray
diffraction, electrical resistance, Hall resistance, and magnetoresistance
measurements. Under compression, Cr2Si2Te6 simultaneously undergoes a
structural transition, emergence of superconductivity at 3 K, sign change of
the magnetoresistance, and dramatic change of the Hall coefficient at ~8 GPa.
The superconductivity persists up to the highest measured pressure of 47.1 GPa
with a maximum Tc = 4.5 K at ~30 GPa. The discovery of superconductivity in the
two-dimensional van der Waals ferromagnetic Cr-based Cr2Si2Te6 provides new
perspectives to explore superconductivity and the interplay between
superconductivity and magnetism.",1912.05166v1
2012-06-23,Molecular-beam epitaxial growth of a far-infrared transparent electrode for extrinsic Germanium photoconductors,"We have evaluated the optical and electrical properties of a far-infrared
(IR) transparent electrode for extrinsic germanium (Ge) photoconductors at 4 K,
which was fabricated by molecular beam epitaxy (MBE). As a far-IR transparent
electrode, an aluminum (Al)-doped Ge layer is formed at well-optimized doping
concentration and layer thickness in terms of the three requirements: high
far-IR transmittance, low resistivity, and excellent ohmic contact. The
Al-doped Ge layer has the far-IR transmittance of >95 % within the wavelength
range of 40--200 microns, while low resistivity (~5 ohm-cm) and ohmic contact
are ensured at 4 K. We demonstrate the applicability of the MBE technology in
fabricating the far-IR transparent electrode satisfying the above requirements.",1206.5368v1
2015-04-08,Post-growth purification of Co nanostructures prepared by focused electron beam induced deposition,"In the majority of cases nanostructures prepared by focused electron beam
induced deposition (FEBID) employing an organometallic precursor contain
predominantly carbon-based ligand dissociation products. This is unfortunate
with regard to using this high-resolution direct-write approach for the
preparation of nanostructures for various fields, such as mesoscopic physics,
micromagnetism, electronic correlations, spin-dependent transport and numerous
applications. Here we present an in-situ cleaning approach to obtain pure
Co-FEBID nanostructures. The purification procedure lies in the exposure of
heated samples to a H$_2$ atmosphere in conjunction with the irradiation by
low-energy electrons. The key finding is that the combination of annealing at
$300^\circ$C, H$_2$ exposure and electron irradiation leads to compact, carbon-
and oxygen free Co layers down to a thickness of about 20\,nm starting from
as-deposited Co-FEBID structures. In addition to this, in temperature-dependent
electrical resistance measurements on post-processed samples we find a typical
metallic behavior. In low-temperature magneto-resistance and Hall effect
measurements we observe ferromagnetic behavior.",1504.01945v1
2015-06-22,"Preparation, characterization, and electrical properties of epitaxial NbO2 thin film lateral devices","Epitaxial NbO2 (110) films, 20 nm thick, were grown by pulsed laser
deposition on Al2O3 (0001) substrates. The Ar/O2 total pressure during growth
was varied to demonstrate the gradual transformation between NbO2 and Nb2O5
phases, which was verified using x-ray diffraction, x-ray photoelectron
spectroscopy, and optical absorption measurements. Electric resistance
threshold switching characteristics were studied in a lateral geometry using
interdigitated Pt top electrodes in order to preserve the epitaxial crystalline
quality of the films. Volatile and reversible transitions between high and low
resistance states were observed in epitaxial NbO2 films, while irreversible
transitions were found in case of Nb2O5 phase. Electric field pulsed current
measurements confirmed thermally-induced threshold switching.",1506.06640v2
2018-07-25,Galvanomagnetic properties of the putative type-II Dirac semimetal PtTe$_2$,"Platinum ditelluride has recently been characterized, based on angle-resolved
photoemission spectroscopy data and electronic band structure calculations, as
a possible representative of type-II Dirac semimetals. Here, we report on the
magnetotransport behavior (electrical resistivity, Hall effect) in this
compound, investigated on high-quality single-crystalline specimens. The
magnetoresistance (MR) of PtTe$_2$ is large (over $3000\%$ at $T=1.8$ K in
$B=9$ T) and unsaturated in strong fields in the entire temperature range
studied. The MR isotherms obey a Kohler's type scaling with the exponent $m$ =
1.69, different from the case of ideal electron-hole compensation. In applied
magnetic fields, the resistivity shows a low-temperature plateau,
characteristic of topological semimetals. In strong fields, well-resolved
Shubnikov - de Haas (SdH) oscillations with two principle frequencies were
found, and their analysis yielded charge mobilities of the order of
$10^3\,\rm{cm^2V^{-1}s^{-1}}$ and rather small effective masses of charge
carriers, $0.11m_e$ and $0.21m_e$. However, the extracted Berry phases point to
trivial character of the electronic bands involved in the SdH oscillations. The
Hall effect data corroborated a multi-band character of the electrical
conductivity in PtTe$_2$, with moderate charge compensation.",1807.09876v1
2018-12-18,An application of extensions of the Ramo-Shockley theorem to signals in silicon sensors,"We discuss an extension of the Ramo-Shockley theorem that allows the
calculation of signals in detectors that contain non-linear materials of
arbitrary permittivity and finite conductivity (volume resistivity) as well as
a static space-charge. The readout-electrodes can be connected by an arbitrary
impedance network. This formulation is useful for the treatment of
semiconductor sensors where the finite volume resistivity in the sensitive
detector volume cannot be neglected. The signals are calculated by means of
time dependent weighting fields and weighting vectors. These are calculated by
adding voltage or current signals to the electrodes in question, which has a
very practical application when using semiconductor device simulation programs.
An analytic example for an un-depleted silicon sensor is given.",1812.07570v2
2018-12-19,"Blue (In,Ga)N Light-Emitting Diodes with Buried n+-p+ Tunnel Junctions by Plasma-Assisted Molecular Beam Epitaxy","Blue light-emitting diodes (LEDs) consisting of a buried n+-p+ GaN tunnel
junction, (In,Ga)N multiple quantum wells (MQWs) and a n+-GaN top layer are
grown on single-crystal Ga-polar n+-GaN bulk wafers by plasma-assisted
molecular beam epitaxy. The (In,Ga)N MQW active regions overgrown on the p+-GaN
show chemically abrupt and sharp interfaces in a wide range of compositions and
are seen to have high structural and optical properties as verified by X-ray
diffraction and spatially resolved cathodoluminescence measurements. The
processed LEDs reveal clear rectifying behavior with a low contact and buried
tunnel junction resistivity. By virtue of the top n+-GaN layer with a low
resistance, excellent current spreading in the LEDs is observed at low currents
in this device structure. A few of new device possibilities based on this
unique design are discussed.",1812.07708v1
2019-01-07,Growth and Characterization of Fe0.95Se0.6Te0.4 Single Crystal,"In this paper we present the single crystal growth of Fe0.95Se0.6Te0.4 high
TC superconducting sample by the modified Bridgman technique. The x-ray
diffraction pattern shows the single crystal nature of the sample, as only
(00l) peaks are detectable. The stoichiometric composition has been verified by
energy dispersive x-ray analysis. The superconducting transition temperature at
14 K was confirmed through DC magnetization (ZFC-FC) and resistivity
measurements. By analyzing the isothermal M-H curves, we determined the value
of H_c1 (0) ~360 Oe by extrapolating the data. The temperature coefficient of
resistivity obtained using the power law fitting was found to be 0.6. The
obtained Raman spectra at room temperature can be interpreted with the
tetragonal crystal structure and space group P4/nmm.",1901.01955v1
2019-11-06,Low frequency imaginary impedance at the superconducting transition of 2H-NbSe$_2$,"The superconducting transition leads to a sharp resistance drop in a
temperature interval that can be a small fraction of the critical temperature
T$_c$. A superconductor exactly at T$_c$ is thus very sensitive to all kinds of
thermal perturbations, including the heat dissipated by the measurement
current. We show that the interaction between electrical and thermal currents
leads to a sizeable imaginary impedance at frequencies of order of tens of Hz
at the resistive transition of single crystals of the layered material
2H-NbSe$_2$. We explain the result using models developed for transition edge
sensors. By measuring under magnetic fields and at high currents, we find that
the imaginary impedance is strongly influenced by the heat associated with
vortex motion and out-of-equilibrium quasiparticles.",1911.02340v2
2020-01-15,Enhanced Carrier Transport by Transition Metal Doping in WS2 Field Effect Transistors,"High contact resistance is one of the primary concerns for electronic device
applications of two-dimensional (2D) layered semiconductors. Here, we explore
the enhanced carrier transport through metal-semiconductor interfaces in WS2
field effect transistors (FETs) by introducing a typical transition metal, Cu,
with two different doping strategies: (i) a ""generalized"" Cu doping by using
randomly distributed Cu atoms along the channel and (ii) a ""localized"" Cu
doping by adapting an ultrathin Cu layer at the metal-semiconductor interface.
Compared to the pristine WS2 FETs, both the generalized Cu atomic dopant and
localized Cu contact decoration can provide a Schottky-to-Ohmic contact
transition owing to the reduced contact resistances by 1 - 3 orders of
magnitude, and consequently elevate electron mobilities by 5 - 7 times higher.
Our work demonstrates that the introduction of transition metal can be an
efficient and reliable technique to enhance the carrier transport and device
performance in 2D TMD FETs.",2001.05105v1
2020-01-20,Electrical conduction mechanisms of metal / high-Tc superconductor (YBCO) interfaces,"Current-voltage characteristics of Au~/~YBa$_2$Cu$_3$O$_{7-\delta}$
interfaces (Au/YBCO), built on optimally-doped YBCO thin films, grown by pulsed
laser deposition, were measured as a function of temperature in the 50 K to 270
K range, for two different resistance states. A non-trivial equivalent circuit
model is proposed, which reveals the existence of a highly inhomogeneous
scenario composed by two complex layers: one presenting both a non-linear
Poole-Frenkel conduction as well as Variable Range Hopping localization effects
(probably associated with YBa$_2$Cu$_3$O$_{6}$) mixed with a minor metallic
phase, while the other is also composed by a mixture of YBCO with different
oxygen contents, where a metallic ohmic phase still percolates. A microscopic
description of the effects produced by the resistance switching is given,
showing the evolution of carrier traps, localization effects and dielectric
behavior for each state. The dielectric behavior is interpreted in terms of a
Maxwell-Wagner scenario.",2001.07237v1
2020-06-09,Fluctuations superconductivity and giant negative magnetoresistance in a gate voltage tuned 2D electron liquid with strong spin-orbit impurity scattering,"We present a quantitative theory of the gate-voltage tuned
superconductor-to-insulator transition (SIT) observed experimentally in the 2D
electron liquid created in the (111) interface between crystalline SrTiO_3 and
LaAlO_3 . Considering two fundamental opposing effects of Cooper-pair
fluctuations; the critical conductivity enhancement, known as
para-conductivity, and its suppression associated with the loss of unpaired
electrons due to Cooper-pairs formation, we employ the standard thermal
fluctuations theory, modified to include quantum fluctuations within a novel
phenomenological approach. Relying on the quantitative agreement found between
our theory and a large body of experimental sheet-resistance data, we conclude
that spin-orbit scatterings, via significant enhancement of the interaction
between fluctuations, strongly enhance the sheet resistance peak at high
fields, and reveal anomalous metallic behavior at low fields, due to mixing of
relatively heavy electron bands with a light electron band near a Lifshitz
point.",2006.05098v3
2020-08-15,Ultrahigh Doping of Graphene Using Flame-Deposited MoO3,"The expected high performance of graphene-based electronics is often hindered
by lack of adequate doping, which causes low carrier density and large sheet
resistance. Many reported graphene doping schemes also suffer from instability
or incompatibility with existing semiconductor processing. Here we report
ultrahigh and stable p-type doping up to ~7x10^13 1/cm^2 (~2x10^21 1/cm^3}) of
monolayer graphene grown by chemical vapor deposition. This is achieved by
direct polycrystalline MoO3 growth on graphene using a rapid flame synthesis
technique. With this approach, the metal-graphene contact resistance for holes
is reduced to ~200 Ohm-um. We also demonstrate that flame-deposited MoO3
provides over 5x higher doping of graphene, as well as superior thermal and
long-term stability, compared to electron-beam deposited MoO3.",2008.06794v1
2020-11-13,Large anomalous Hall angle in a topological semimetal candidate TbPtBi,"The magnetotransport properties in antiferromagnetic half-Heusler single
crystals of TbPtBi, a magnetic-field-induced topological semimetal with simple
band structure, are investigated. We found that a nonmonotonic magnetic field
dependence of the anomalous Hall resistivity in a high magnetic field (B>7T),
which come from the change of band structure induced by the Zeeman-like
splitting when applying the external magnetic field. The experiment results
show that credible anomalous Hall resistivity and conductivity reach up to
0.6798m{\Omega}cm and 125{\Omega}-1cm-1, respectively. A large AHA up to 33% is
obtained in TbPtBi, which is comparable to typical ferromagnetic Weyl
semimetal. The analysis of results show it should be attributed to topological
band around EF and low carrier density.",2011.06864v1
2021-03-09,Anisotropy of the In-Plane and Out-of-Plane Resistivity and the Hall Effect in the Normal State of Vicinal-Grown YBa$_{2}$Cu$_{3}$O$_{7-δ}$ Thin Films,"The resistivity and the Hall effect in the copper-oxide high-temperature
superconductor YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ (YBCO) are remarkably
anisotropic. Using a thin film of YBCO grown on an off-axis cut SrTiO$_3$
substrate allows one to investigate these anisotropic transport properties in a
planar and well-defined sample geometry employing a homogeneous current
density. In the normal state, the Hall voltage probed parallel to the
copper-oxide layers is positive and strongly temperature dependent, whereas the
out-of-plane Hall voltage is negative and almost temperature independent. The
results confirm previous measurements on single crystals by an entirely
different measurement method and demonstrate that vicinal thin films might be
also useful for investigations of other layered nanomaterials.",2103.05511v1
2021-06-24,Erasable superconductivity in topological insulator Bi2Se3 induced by voltage pulse,"Three-dimensional topological insulators (TIs) attract much attention due to
its topologically protected Dirac surface states. Doping into TIs or their
proximity with normal superconductors can promote the realization of
topological superconductivity(SC) and Majorana fermions with potential
applications in quantum computations. Here, an emergent superconductivity was
observed in local mesoscopic point-contacts on the topological insulator Bi2Se3
by applying a voltage pulse through the contacts, evidenced by the Andreev
reflection peak in the point-contact spectra and a visible resistance drop in
the four-probe electrical resistance measurements. More intriguingly, the
superconductivity can be erased with thermal cycles by warming up to high
temperatures (300 K) and induced again by the voltage pulse at the base
temperature (1.9 K), suggesting a significance for designing new types of
quantum devices. Nematic behaviour is also observed in the superconducting
state, similar to the case of CuxBi2Se3 as topological superconductor
candidates.",2106.13207v1
2021-06-29,Low Resistance III-V Hetero-contacts to N-Ge,"We experimentally study III-V/Ge heterostructure and demonstrate InGaAs
hetero-contacts to n-Ge with a wide range of In % and achieve low contact
resistivity ($\rho_C$) of $5\times10^{-8} \Omega\cdot cm^2$ for Ge doping of $3
\times 10^{19} cm^{-3}$. This results from re-directing the charge neutrality
level (CNL) near the conduction band and benefiting from low effective mass for
high electron transmission. For the first time, we observe that the
heterointerface presents no temperature dependence despite the two different
conduction minimum valley locations of III-V ($\Gamma$-valley) and Ge
(L-valley), which potentially stems from elastic trap-assisted tunneling
through defect states at the interface generated by dislocations. The
hetero-interface plays a dominant role in the overall $\rho_C$ below $\approx 1
\times 10^{-7} \Omega \cdot cm^2$, which can be further improved with large
active dopant concentration in Ge by co-doping.",2106.15099v1
2021-09-08,Unusual Magnetic Properties in Layered Magnetic Topological Insulator EuSn2As2,"EuSn2As2 with layered rhombohedral crystal structure is proposed to be a
candidate of intrinsic antiferromagnetic (AFM) topological insulator. Here, we
have investigated systematic magnetoresistance (MR) and magnetization
measurements on the high quality EuSn2As2 single crystal with the magnetic
field both parallel and perpendicular to (00l) plane. Both the kink of magnetic
susceptibility and longitudinal resistivity reveal that EuSn2An2 undergoes an
AFM transition at TN = 21 K. At T = 2 K, the magnetization exhibits two
successive plateaus of ~ 5.6 {\mu}B/Eu and ~ 6.6 {\mu}B/Eu at the corresponding
critical magnetic fields. Combined with the negative longitudinal MR and
abnormal Hall resistance, we demonstrate that EuSn2An2 undergoes complicated
magnetic transitions from an AFM state to a canted ferromagnetic (FM) state at
Hc and then to a polarized FM state at Hs as the magnetic field increase.",2109.03414v1
2022-05-12,Shubnikov-de Haas and de Haas-van Alphen oscillation in Czochralski grown CoSi single crystal,"Anisotropic transport, Shubnikov-de Haas (SdH), and de Haas-van Alphen (dHvA)
quantum oscillations studies are reported on a high-quality CoSi single crystal
grown by the Czochralski method. Temperature-dependent resistivities indicate
the dominating electron-electron scattering. Magnetoresistance (MR) at 2 K
reaches 610% for I||[111] and B||[01-1], whereas it is 500% for I||[01-1] and
B||[111]. A negative slope in field-dependent Hall resistivity suggests
electrons are the majority carriers. The carrier concentration extracted from
Hall conductivity indicates no electron-hole compensation. In 3D CoSi, the
electron transport lifetime is found to be approximately in the same order as
quantum lifetime, whereas in 2D electron gas the long-range scattering drives
the transport life much larger than the quantum lifetime. From linear and Hall
SdH oscillations the effective masses and Dingle temperatures have been
calculated. The dHvA oscillation reveals three frequencies at 18 ($\gamma$),
558 ($\alpha$) and 663 T ($\beta$)), whereas, SdH oscillation results in only
two frequencies $\alpha$ and $\beta$. The $\gamma$ frequency observed in dHvA
oscillation is a tiny hole pocket at the $\Gamma$ point.",2205.05881v1
2022-07-05,Anderson localization crossover in 2D Si systems: The past and the present,"Using Ioffe-Regel-Mott (IRM) criterion for strong localization crossover in
disordered doped 2D electron systems, we theoretically study the relationships
among the three key experimentally determined localization quantities: critical
density ($n_\mathrm{c}$), critical resistance ($\rho_\mathrm{c}$), and sample
quality defined by the effective impurity density (as experimentally diagnosed
by the sample mobility, $\mu_\mathrm{m}$, at densities much higher than
critical densities). Our results unify experimental results for 2D
metal-insulator transitions (MIT) in Si systems over a 50-year period
(1970-2020), showing that $n_\mathrm{c}$ ($\rho_\mathrm{c}$) decrease
(increase) with increasing sample quality, explaining why the early experiments
in the 1970s, using low-quality samples ($\mu_\mathrm{m} \sim 10^3
\mathrm{cm}^2/Vs$) reported strong localization crossover at $n_c \sim 10^{12}
\mathrm{cm}^{-2}$ with $\rho_c \sim 10^3\Omega$ whereas recent experiments
(after 1995), using high-quality samples ($\mu_\mathrm{m} >10^4
\mathrm{cm}^2/Vs$), report $n_c \sim 10^{11} \mathrm{cm}^{-2}$ with
$\rho_c>10^4\Omega$. Our theory establishes the 2D MIT to be primarily a
screened Coulomb disorder-driven strong localization crossover phenomenon,
which happens at different sample-dependent critical density and critical
resistance, thus unifying Si 2D MIT phenomena over a 50-year period.",2207.02220v1
2022-08-22,Electronic structure and physical properties of EuAuAs single crystal,"High-quality single crystals of EuAuAs were studied by means of powder x-ray
diffraction, magnetization, magnetic susceptibility, heat capacity, electrical
resistivity and magnetoresistance measurements. The compound crystallizes with
a hexagonal structure of the ZrSiBe type (space group $P6_3/mmc$). It orders
antiferromagnetically below 6 K due to the magnetic moments of divalent Eu
ions. The electrical resistivity exhibits metallic behavior down to 40 K,
followed by a sharp increase at low temperatures. The magnetotransport
isotherms show a distinct metamagnetic-like transition in concert with the
magnetization data. The antiferromagnetic ground state in \mbox{EuAuAs} was
corroborated in the \textit{ab initio} electronic band structure calculations.
Most remarkably, the calculations revealed the presence of nodal line without
spin-orbit coupling and Dirac point with inclusion of spin-orbit coupling. The
\textit{Z}$_2$ invariants under the effective time reversal and inversion
symmetries make this system nontrivial topological material. Our findings,
combined with experimental analysis, makes EuAuAs a plausible candidate for an
antiferromagnetic topological nodal-line semimetal.",2208.10405v1
2022-09-18,Superparamagnetic and metal-like Ru2TiGe: a propitious thermoelectric material,"We report a study of structural, magnetic, heat capacity and thermoelectric
properties of a Rubased Heusler alloy, Ru2TiGe. The magnetic measurements
reveal that at higher temperatures, diamagnetic and Pauli paramagnetic
contributions dominate the magnetic behaviour whereas, at lower temperatures
(T<= 20 K), superparamagnetic interaction among clusters is observed. Effect of
such magnetic defects is also evident in the electrical resistivity behaviour
at lower temperatures. Though the temperature dependence of resistivity
exhibits a metal-like nature, the large value of Seebeck coefficient leads to
an appreciable power factor of the order of 1 mW/mK2 at 300 K. Large power
factor as well as low thermal conductivity results in a value of ZT = 0.025 at
390 K for Ru2TiGe that is orders of magnitude higher than that of the other
pure Heusler alloys and point towards its high potential for practical
thermoelectric applications.",2209.08474v1
2022-11-02,Umklapp electron-electron scattering in bilayer graphene moiré superlattice,"Recent experimental advances have been marked by the observations of
ballistic electron transport in moir\'e superlattices in highly aligned
heterostructures of graphene and hexagonal boron nitride (hBN). Here, we
predict that a high-quality graphene bilayer aligned with an hBN substrate
features $T^2$-dependent resistivity caused by umklapp electron-electron (Uee)
scattering from the moir\'e superlattice, that is, a momentum kick by Bragg
scattering experienced by a pair of electrons. Substantial Uee scattering
appears upon $p$-doping of the bilayer above a threshold density, which depends
on the twist angle between graphene and hBN, and its contribution towards the
resistivity grows rapidly with hole density until it reaches a peak value,
whose amplitude changes non-monotonically with the superlattice period. We also
analyse the influence of an electrostatically induced bandgap in the bilayer
and trigonal warping it enhances in the electron dispersion on the
electron-electron umklapp scattering.",2211.01005v1
2023-01-11,Application of the partial Dirichlet-Neumann contact algorithm to simulate low-velocity impact events on composite structures,"Impact simulations for damage resistance analysis are computationally
intensive due to contact algorithms and advanced damage models. Both methods,
which are the main ingredients in an impact event, require refined meshes at
the contact zone to obtain accurate predictions of the contact force and damage
onset and propagation through the material. This work presents the application
of the partial Dirichlet-Neumann contact algorithm to simulate low-velocity
impact problems on composite structures using High-Performance Computing. This
algorithm is devised for parallel finite element codes running on
supercomputers, and it is extended to explicit time integration schemes to
solve impact problems including damage. The proposed framework is validated
with a standard test for damage resistance on fiber-reinforced polymer matrix
composites. Moreover, the parallel performance of the proposed algorithm has
been evaluated in a mesh of 74M of elements running with 2400 processors.",2301.05552v2
2023-01-19,Unusual anisotropic magnetoresistance due to magnetization-dependent spin-orbit interactions,"One of recent surprising discoveries is the unusual anisotropic
magnetoresistance (UAMR) that depends on two magnetization components
perpendicular to the current differently, in contrast to the conventional
anisotropic magnetoresistance (AMR) that predicts no change in resistance when
the magnetization varies in the plane perpendicular to the current. Using
density functional theory and Boltzmann transport equation calculations for bcc
Fe, hcp Co, and bcc FeCo alloys, we show that UAMR can be accounted by the
magnetization-dependent spin-orbit interactions (SOI): Magnetization-dependent
SOI modifies electron energy bands that, in turn, changes resistance. A
phenomenological model reveals the intrinsic connection between SOI and
order-parameters. Such a mechanism is confirmed by the strong biaxial stain
effect on UAMR. Our findings provide an efficient way of searching and
optimizing materials with large UAMR, important in the design of
high-performance spintronic devices.",2301.07886v1
2023-03-06,Timing resistive plate chambers for thermal neutron detection with 3D position sensitivity,"An optimized design of a neutron detector based on timing RPCs (Resistive
Plate Chambers) with boron-10 neutron converters is presented. The detector is
composed of a stack of ten double gap RPCs with aluminium cathode plates coated
on both sides with $^{10}B_{4}C$. This design enables simultaneous
determination with high accuracy of both the neutron time-of-flight (down to ns
resolution) and the interaction position in 3D (down to 0.25 mm resolution
across and ~1 mm along the beam). It is shown that the detection efficiency can
approach 60% for neutrons with $\lambda$ = 4.7 \.A. A new geometry with less
material budget is introduced for the signal pick-up strip arrays. The results
of simulation-based optimization of the design are reported considering the
trade-off between the detection efficiency, the count rate capability and the
amount of elastic scattering on the detector components.",2303.03461v1
2023-03-22,Effect of gamma radiation on electrical properties of diffusive memristor devices,"Diffusive memristors continue to receive tremendous interest due to their
ability to emulate biological neurons and thus aid the development of
bio-inspired computation technology. A major issue with the diffusive memristor
is the inability to reliably control the formation of the conduction filaments
which affects both the device functionality and reproducibility of regimes
after each application of voltage. Here we investigate the effect of gamma
radiation on the electrical properties of the diffusive memristors based on
metallic nanoparticles in dielectric matrix. Our experiments show that after
exposing to radiation, the memristors demonstrate much sharper (and less noisy)
hysteresis in the current-voltage characteristics while preserving the same
low- and high-resistive states as in the pristine samples. Additionally, the
radiation lowers both threshold and hold voltages that correspond to onset of
low- and high- resistive states, respectively. The proposed mechanism involves
radiation-induced defects in the silica matrix which help to establish dominant
pathways for nanoparticles to form conduction filaments. Our findings suggest
an efficient way to enhance working characteristics of diffusive memristors and
to improve their reproducibility.",2303.12762v1
2023-07-18,Universal scaling near band-tuned metal-insulator phase transitions,"We present a theory for band-tuned metal-insulator transitions based on the
Kubo formalism. Such a transition exhibits scaling of the resistivity curves,
in the regime where $T\tau >1$ or $\mu \tau>1$, where $\tau$ is the scattering
time and $\mu$ the chemical potential. At the critical value of the chemical
potential, the resistivity diverges as a power law, $R_c \sim 1/T$.
Consequently, on the metallic side there is a regime with negative $dR/dT$,
which is often misinterpreted as insulating. We show that scaling and this
`fake insulator' regime is observed in a wide range of experimental systems. In
particular, we show that Mooij correlations in high-temperature metals with
negative $dR/dT$ can be quantitatively understood with our scaling theory in
the presence of $T$-linear scattering.",2307.09292v1
2023-10-10,The black hole to black hole phase transition probed by the D3-D7 model fermionic spectral functions,"We consider the D3-D7 model and analyze the phase transition from the
black-hole phase to another black-hole phase using the spectral function of a
probe fermion on D7 in the presence of the finite density and temperature. From
the fermionic spectral functions, we study the temperature dependence of the
decay rate and we observe a jump in it at the critical temperature that
corresponds to the first order phase transition. We found that if we assume
that the Drude model works in this case so that the resistivity is proportional
to the fermion decay rate, the jump matches the resistivity data in a heavy
fermion material.",2310.06317v1
2023-10-22,Electrical conductivity enhancement of epitaxially grown TiN thin films,"Titanium nitride (TiN) presents superior electrical conductivity with
mechanical and chemical stability and compatibility with the semiconductor
fabrication process. Here, we fabricated epitaxial and polycrystalline TiN
(111) thin films on MgO (111), sapphire (001), and mica substrates at 640oC and
room temperature by using a DC sputtering, respectively. The epitaxial films
show less amount of surface oxidation than the polycrystalline ones grown at
room temperature. The epitaxial films show drastically reduced resistivity (~30
micro-ohm-cm), much smaller than the polycrystalline films.
Temperature-dependent resistivity measurements show a nearly monotonic
temperature slope down to low temperature. These results demonstrate that high
temperature growth of TiN thin films leads to significant enhancement of
electrical conductivity, promising for durable and scalable electrode
applications.",2310.14208v1
2023-11-20,Magnetic-field-induced nonlinear transport in HfTe5,"The interplay of electron correlations and topological phases gives rise to
various exotic phenomena including fractionalization, excitonic instability,
and axionic excitation. Recently-discovered transition-metal pentatellurides
can reach the ultra-quantum limit in low magnetic fields and serve as good
candidates for achieving such a combination. Here, we report evidences of
density wave and metal-insulator transition in HfTe5 induced by intense
magnetic fields. Using the nonlinear transport technique, we detect a distinct
nonlinear conduction behavior in the longitudinal resistivity within the a-c
plane, corresponding to the formation of a density wave induced by magnetic
fields. In high fields, the onset of the nonlinear conduction in the Hall
resistivity indicates an impurity-pinned magnetic freeze-out as the possible
origin of the insulating behavior. These frozen electrons can be gradually
re-activated into mobile states above a threshold electric field. These
experimental evidences call for further investigations into the underlying
mechanism for the bulk quantum Hall effect and field-induced phase transtions
in pentatellurides.",2311.11517v1
2023-11-29,Lateral NbS$_2$/MoS$_2$/NbS$_2$ transistors: physical modeling and performance assessment,"Reducing the contact resistance of field-effect transistors based on
two-dimensional materials is one of the key improvements required to to enable
the integration of such transistors in an industrially relevant process.
Suitably designed lateral heterojunctions provide an opportunity to
independently tailor the contact and channel properties and to mitigate the
problem of high contact resistance. Inspired by the recent experimental
demonstration of a two-dimensional $p$-type Schottky barrier, here we use
quantum transport simulations to estimate the performance of $p$-type
transistors in which the channel consists of a lateral heterostructure of
NbS$_2$/MoS$_2$/NbS$_2$ (semimetal-semiconductor-semimetal). We find that the
gate alignment with the channel is a critical design parameter, strongly
influencing the capability of the gate to modulate the Schottky barrier at the
MoS$_2$/NbS$_2$ interfaces. This effect is also found to significantly affect
the scaling behavior of the device.",2311.18031v1
2024-02-23,Electrical Scanning Probe Microscope Measurements Reveal Surprisingly High Dark Conductivity in Y6 and PM6:Y6 and Non-Langevin Recombination in PM6:Y6,"We used broadband local dielectric spectroscopy (BLDS), an electric force
microscopy technique, to make non-contact measurements of conductivity in the
dark and under illumination of PM6:Y6 and Y6 prepared on ITO and PEDOT:PSS/ITO.
Over a range of illumination intensities, BLDS spectra were acquired and fit to
an impedance model of the tip-sample interaction to obtain a sample resistance
and capacitance. By comparing two descriptions of cantilever friction, an
impedance model and a microscopic model, we connected the sample resistance
inferred from impedance modeling to a microscopic sample conductivity. A charge
recombination rate was estimated from plots of the conductivity versus light
intensity and found to be sub-Langevin. The dark conductivity was orders of
magnitude higher than expected from Fermi-level equilibration of the PM6:Y6
with the substrate, suggesting that dark carriers may be a source of
open-circuit voltage loss in PM6:Y6.",2402.15501v1
2021-05-07,Integrating van der Waals materials on paper substrates for electrical and optical applications,"Paper holds the promise to replace silicon substrates in applications like
internet of things or disposable electronics that require ultra-low-cost
electronic components and an environmentally friendly electronic waste
management. In the last years, spurred by the abovementioned properties of
paper as a substrate and the exceptional electronic, mechanical and optical
properties of van der Waals (vdW) materials, many research groups have worked
towards the integration of vdW materials-based devices on paper. Recently, a
method to deposit a continuous film of densely packed interconnects of vdW
materials on paper by simply rubbing the vdW crystals against the rough surface
of paper has been presented. This method utilizes the weak interlayer vdW
interactions and allows cleaving of the crystals into micro platelets through
the abrasion against the paper. Here, we aim to illustrate the general
character and the potential of this technique by fabricating films of 39
different vdW materials (including superconductors, semi-metals,
semiconductors, and insulators) on standard copier paper. We have thoroughly
characterized their optical properties showing their high optical quality: one
can easily resolve the absorption band edge of semiconducting vdW materials and
even the excitonic features present in some vdW materials with high exciton
binding energy. We also measured the electrical resistivity for several vdW
materials films on paper finding exceptionally low values, which are in some
cases, orders of magnitude lower than those reported for analogous films
produced by inkjet printing. We finally demonstrate the fabrication of
field-effect devices with vdW materials on paper using the paper substrate as
an ionic gate.",2105.03486v1
2017-06-29,Origin of Contact Resistance at Ferromagnetic Metal-Graphene Interfaces,"Edge contact geometries are thought to yield ultralow contact resistances in
most non-ferromagnetic metal-graphene interfaces owing to their large
metal-graphene coupling strengths. Here, we examine the contact resistance of
edge- versus surface-contacted ferromagnetic metal-graphene interfaces (i.e.
nickel- and cobalt-graphene interfaces) using both single-layer and few-layer
graphene. Good qualitative agreement is obtained between theory and experiment.
In particular, in both theory and experiment, we observe that the contact
resistance of edge-contacted ferromagnetic metal-graphene interfaces is much
lower than that of surface-contacted ones, for all devices studied and
especially for the single-layer graphene systems. We show that this difference
in resistance is not due to differences in the metal-graphene coupling
strength, which we quantify using Hamiltonian matrix elements. Instead, the
larger contact resistance in surface contacts results from spin filtering at
the interface, in contrast to the edge-contacted case where both spins are
transmitted. Temperature-dependent resistance measurements beyond the Curie
temperature TC show that the spin degree of freedom is indeed important for the
experimentally measured contact resistance. These results show that it is
possible to induce a large change in contact resistance by changing the
temperature in the vicinity of TC, thus paving the way for
temperature-controlled switches based on spin.",1706.09591v1
2023-09-22,Non-equilibrium Thermal Resistance of Interfaces Between III-V Compounds,"Interfacial thermal resistance has been often estimated and understood using
the Landauer formalism that assumes incident phonons with equilibrium
distribution. However, previous studies suggest that phonons are
out-of-equilibrium near the interface because of the heat flow through the
leads and the scattering of phonons by the interface. In this paper, we report
a systematic study on how vibrational spectra mismatch affects the degree of
phonon non-equilibrium near an interface, how fast it is relaxed as the phonons
diffuse into a lead, and the overall interfacial thermal resistance from the
non-equilibrium phonons. Our discussion is based on the solution of the
Peierls-Boltzmann transport equation with ab initio inputs for 36 interfaces
between semi-infinite group-III (Al, Ga, In) and group-V (P, As, Sb) compound
semiconductor leads. The simulation reveals that the non-equilibrium phonons
cause significant interfacial thermal resistance for all 36 interfaces, making
the overall interfacial thermal resistance two to three times larger than that
predicted by the Landauer formalism. We observe a clear trend that the degree
of phonon non-equilibrium near an interface and the interfacial thermal
resistance from the non-equilibrium phonons increase as the mismatch of the
Debye temperature of two lead materials increases. This contrasts with Landauer
formalism's predictions, which show no correlation with the Debye temperature
mismatch. The relaxation length of the phonon non-equilibrium varies
significantly from 50nm to 1.5um depending on the combination of the lead
materials. The relaxation length is proportional to the phonon mean free path
of the corresponding lead material but also largely depends on the material in
the opposite lead. This suggests the relaxation length cannot be considered an
intrinsic property of the corresponding lead material.",2309.13187v1
2003-10-28,On magnetic field generation in Kolmogorov turbulence,"We analyze the initial, kinematic stage of magnetic field evolution in an
isotropic and homogeneous turbulent conducting fluid with a rough velocity
field, v(l) ~ l^alpha, alpha<1. We propose that in the limit of small magnetic
Prandtl number, i.e. when ohmic resistivity is much larger than viscosity, the
smaller the roughness exponent, alpha, the larger the magnetic Reynolds number
that is needed to excite magnetic fluctuations. This implies that numerical or
experimental investigations of magnetohydrodynamic turbulence with small
Prandtl numbers need to achieve extremely high resolution in order to describe
magnetic phenomena adequately.",0310780v2
1999-08-04,Polarization fields in nitride nanostructures: ten points to think about,"Macroscopic polarization, both of intrinsic and piezoelectric nature, is
unusually strong in III-V nitrides, and the built in electric fields in the
layers of nitride-based nanostructures, stemming from polarization changes at
heterointerfaces, have a major impact on the properties of single and multiple
quantum wells, high mobility transistors, and thin films. The concepts involved
in the theory and applications of polarization in nitrides have encountered
some resistance in the field. Here we discuss critically ten ``propositions''
aimed at clarifying the main controversial issues.",9908060v1
2001-02-06,"Observation of superconductivity in Y$_2$PdGe$_3$, structurally same as MgB$_2$","The results of electrical resistance (1.4 - 300 K), magnetization (2-300 K)
and heat-capacity (2 - 50 K) measurements in Y$_2$PdGe$_3$, found to
crystallize in a AlB$_2$-derived hexagonalstructure, are reported. The results
establish that this compound is superconducting below 3 K. This obervation is
interesting considering that this compound is the first superconductor among
the ternary members derived from the hexagonal AlB$_2$ structure. With
superconductivity being uncommon even among binary alloys derived from AlB$_2$
structure and with recent excitement on the observation of high temperature
superconductivity in Mg$B_2$, this finding gains importance.",0102110v1
2002-05-08,Complex Quantum Phenomena in a Bilayered Calcium Ruthenate,"Ca$_3$Ru$_2$O$_7$ undergoes an antiferromagnetic transition at
$T_{\text{N}}=56 $K, followed by a Mott-like (MI) transition at
$T_{\text{MI}}=48$ K. This nonmetallic ground state, with a charge gap of 0.1
eV, is suppressed by a highly anisotropic metamagnetic transition that leads to
a fully spin-polarized metallic state. We report the observation of
Shubnikov-de Haas oscillations in the \textit{gapped} state, colossal
magnetoresistance in the inter-plane resistivity with a large anisotropy
different from that observed in the magnetization, and non-Fermi liquid
behavior in the metallic state at high magnetic fields.",0205151v1
2002-06-10,Realization of La2MnVO6: Search for half-metallic antiferromagnetism?,"Single-phase polycrystalline La2MnVO6 samples were synthesized by arc melting
and characterized by X-ray diffraction, magnetization and resistivity
measurements. We find that the compound has cubic (space group), partly ordered
double perovskite structure. The sample exhibits ferrimagnetic behavior and
variable-range hopping conductivity. We conclude based on the magnetic
properties that both Mn and V ions are trivalent; moreover, the Mn3+ ions are
in a high-spin state, which is the reason that the compound is not a
half-metallic antiferromagnet.",0206146v1
2002-07-09,Perspectives of superconducting MgB2 for microwave applications,"We discuss the temperature, frequency, and power-dependent surface resistance
of the boride superconductor MgB2 in relation to possible applications for
passive microwave devices. The data available in the literature are compared
with results for polycrystalline Nb3Sn and epitaxial YBa2Cu3O7-x, which are
representative of the classical and cuprate superconductors. MgB2 displays all
specific features that make superconductors attractive for high-performance
devices, even though the fabrication technology is not yet mature. We attempt
to identify promising areas of applications, as well as material requirements,
which could further promote the attractiveness of the new superconductor in
this field.",0207226v1
2002-08-15,Superconductivity in Ba_2Sn_3Sb_6 and SrSn_3Sb_4,"Resistivity and ac magnetic susceptibility measurements on Ba2Sn3Sb6 and
SrSn3Sb4 indicate that these Zintl compounds display a transition to a
superconducting phase at Tc = 3.9 K. The Meissner effect was observed for
Ba2Sn3Sb6 under an applied field of 25 Oe. The signatures for
superconductivity, such as high and low velocity conduction electrons and lone
pairs, are present for both of these compounds.",0208313v1
2002-11-22,Correlations and Semimetallic Behaviors in Pyrochlore Oxide Cd2Re2O7,"Electronic properties of the metallic pyrochlore oxide Cd2Re2O7 are studied
by means of electrical resistivity and Hall measurements. Semimetallic band
structures are revealed as expected from band structure calculations. It is
found that large changes in carrier density and mass occur at the structural
phase transition at Ts1 = 200 K. A large mass enhancement is observed,
particularly for the high-temperature phase with the ideal pyrochlore
structure, suggesting that an anomalous correlation has an important effect on
the itinerant electrons in the pyrochlore lattice.",0211517v1
2004-02-02,Dielectric responses of the layered cobalt oxysulfide Sr_2Cu_2CoO_2S_2 with CoO_2 square-planes,"We have studied the dielectric responses of the layered cobalt oxysulfide
Sr$_2$Cu$_2$CoO$_2$S$_2$ with the CoO$_2$ square-planes. With decreasing
temperature below the N\'eel temperature, the resistivity increases like a
semiconductor, and the thermopower decreases like a metal. The dielectric
constant is highly dependent on temperature, and the dielectric relaxation is
systematically changed with temperature, which is strongly correlated to the
magnetic states. These behaviors suggest that carriers distributed
homogeneously in the paramagnetic state at high temperatures are expelled from
the antiferromagnetically ordered spin domain below the N\'eel temperature.",0402034v1
2005-01-28,Ce doping in T-La2CuO4 films: Broken electron-hole symmetry for high-Tc superconductivity,"We attempted Ce doping in La2CuO4 with the K2NiF4 (T) structure by molecular
beam epitaxy. At low growth temperature and with an appropriate substrate
choice, we found that Ce can be incorporated into the K2NiF4 lattice up to x ~
0.06, which had not yet been realized in bulk synthesis. The doping of Ce makes
T-La2-xCexCuO4 more insulating, which is in sharp contrast to Ce doping in
La2CuO4 with the Nd2CuO4 structure, which makes the compounds superconducting.
The observed smooth increase in resistivity from hole-doped side
(T-La2-xSrxCuO4) to electron-doped side (T-La2-xCexCuO4) indicates that
electron-hole symmetry is broken in the T-phase materials.",0501703v1
2005-09-05,"Large magnetoresistance and magnetocaloric effect above 70 K in Gd2Co2Al, Gd2Co2Ga and Gd7Rh3","The electrical resistivity, magnetization and heat-capacity behavior of the
Gd-based compounds, Gd2Co2Al, Gd2Co2Ga and Gd7Rh3, ordering magnetically at TC=
78 K, TC= 76 K and TN= 140 K have been investigated as a function of
temperature and magnetic field. All these compounds are found to show large
magnetoresistance (with a negative sign) in the paramagnetic state at rather
high temperatures with the magnitude peaking at respective magnetic ordering
temperatures. There is a corresponding behavior in the magnetocaloric effect as
inferred from the entropy derived from these data.",0509107v1
2006-10-11,"Intergrain connectivity and resistive broadening in vortex state: a comparison between MgB2, NbSe2 and Bi2Sr2Ca2Cu3O10 superconductors","Magnetoresistance and radio frequency penetration depth techniques are used
to study grain connectivity and broadening of superconducting transition. We
study and compare these issues in clean polycrytalline samples of three
different superconducting systems e.g. MgB2, NbSe2 and Bi2Sr2Ca2Cu3O10. From
the rf response, the bulk pinning force constant is evaluated. From high field
transport measurements, H-T phase diagram is ascertained for the three systems
with varying degrees of fluctuation and connectivity.",0610295v1
2007-03-25,Novel dynamical effects and glassy response in strongly correlated electronic system,"We find an unconventional nucleation of low temperature paramagnetic metal
(PMM) phase with monoclinic structure from the matrix of high-temperature
antiferromagnetic insulator (AFI) phase with tetragonal structure in strongly
correlated electronic system $BaCo_{0.9}Ni_{0.1}S_{1.97}$. Such unconventional
nucleation leads to a decease in resistivity by several orders with relaxation
at a fixed temperature without external perturbation. The novel dynamical
process could arise from the competition of strain fields, Coulomb
interactions, magnetic correlations and disorders. Such competition may
frustrate the nucleation, giving rise to a slow, nonexponential relaxation and
""physical aging"" behavior.",0703647v1
2007-07-05,Anomalous exchange coupling in transition-metal-oxide based superlattices with antiferromagnetic spacer layers,"A direct correlation is seen between the coercive field (HC) and the
magnetic-field-dependent resistivity (MR) in SrMnO3/SrRuO3 superlattices of
perpendicular magnetic anisotropy. The magnetoresistance shows a sharp jump at
Hc for in-plane current and the out-of-plane magnetic field. Both HC and
high-field MR also oscillate with the thickness of the SrMnO3 spacer layers
separating the metallic ruthenate. Since the spacer in these superlattices has
no mobile carriers to facilitate an oscillatory coupling, we attribute the
observed behavior to the spin-polarized quantum tunneling of electrons between
the ferromagnetic layers and antiferromagnetically ordered t2g spins of SrMnO3.",0707.0768v1
2007-08-10,Coherent quasiparticle transport in grain boundary junctions employing high-Tc superconductors,"Magneto-fluctuations of the normal resistance RN have been reproducibly
observed in YBa2Cu3O7-d biepitaxial grain boundary junctions at low
temperatures. We attribute them to mesoscopic transport in narrow channels
across the grain boundary line, occurring in an unusual energy regime. The
Thouless energy appears to be the relevant energy scale. Possible implications
on the understanding of coherent transport of quasiparticles in HTS and of the
dissipation mechanisms are discussed.",0708.1448v1
2007-09-26,Single crystal growth and anisotropy of CeRuPO,"We report on the single crystal growth of the ferromagnetic Kondo lattice
system CeRuPO using a Sn flux method. Magnetic susceptibility and electrical
resistivity measurements indicate strong anisotropy of this structurally
layered compound. They evidence that the magnetic moments order
ferromagnetically along the c-direction of the tetragonal unit cell, whereas
the crystal electric field (CEF) anisotropy favors the ab-plane. Therefore,
CeRuPO presents the unusual case within rare earth systems, where the
anisotropy of the interionic exchange interaction overcomes the single ion
anisotropy due to the CEF interaction.",0709.4144v2
2007-11-30,Large voltage from spin pumping in magnetic tunnel junctions,"We studied the response of a ferromagnet-insulator-normal metal tunnel
structure under an external oscillating radio frequency (R.F.) magnetic field.
The D. C. voltage across the junction is calculated and is found not to
decrease despite the high resistance of the junction; instead, it is of the
order of $\mu V$ to $100\mu V$, much larger than the experimentally observed
value (100 nano-V) in the ""strong coupled"" ohmic ferromagnet-normal metal
bilayers. This is consistent with recent experimental results in tunnel
structures, where the voltage is larger than $\mu V$s. The damping and loss of
an external RF field in this structure is calculated.",0711.4939v1
2008-01-07,High Performance Thermal Interface Technology Overview,"An overview on recent developments in thermal interfaces is given with a
focus on a novel thermal interface technology that allows the formation of 2-3
times thinner bondlines with strongly improved thermal properties at lower
assembly pressures. This is achieved using nested hierarchical surface channels
to control the particle stacking with highly particle-filled materials.
Reliability testing with thermal cycling has also demonstrated a decrease in
thermal resistance after extended times with longer overall lifetime compared
to a flat interface.",0801.1046v1
2008-01-17,Stability of RVB hole stripes in high-temperature superconductors,"Indications of density-wave states in underdoped cuprates, coming from recent
STM (scanning tunneling microscopy) and Hall-resistance measurements, have
raised new concerns whether stripes could be stabilized in the superconducting
phase of cuprate materials, even in the absence of antiferromagnetism. Here, we
investigate this issue using state-of-the-art quantum Monte Carlo calculations
of a $t-J$ model. In particular we consider the stability of unidirectional
hole domains in a modulated superconducting background, by taking into account
the effect of tetragonal-lattice distortions, next-nearest neighbor hopping and
long-range Coulomb repulsion.",0801.2722v2
2008-08-03,Superconductivity in Yttrium Iron Oxyarsenide System,"Iron-based oxypnictides substituted with yttrium have been prepared via a
conventional solid state reaction. The product after first 50 hours of reaction
showed diamagnetic-like transition at around 10 K but was not superconducting,
while additional 72 hours of high temperature heat treatment was required to
yield superconducting sample which was doped with fluoride. Temperature
dependence of the susceptibility shows both screening and Meissner effect at
around 10 K, while resistance as a function of temperature displayed a drop at
around the same temperature.",0808.0288v2
2008-09-16,"Interface heat transfer between crossing carbon nanotubes, and the thermal conductivity of nanotube pellets","We theoretically compute the interface thermal resistance between crossing
single walled carbon nanotubes of various chiralities, using an atomistic
Green's function approach with semi-empirical potentials. The results are then
used to model the thermal conductivity of three dimensional nanotube pellets in
vacuum. For an average nanotube length of 1 $\mu$m, the model yields an upper
bound for the thermal conductivity of densely compacted pellets, of the order
of a few W/m-K. This is in striking contrast with the ultra-high thermal
conductivity reported on individually suspended nanotubes. The results suggest
that nanotube pellets might have an application as thermal insulators.",0809.2660v1
2008-10-29,High-Mobility Few-Layer Graphene Field Effect Transistors Fabricated on Epitaxial Ferroelectric Gate Oxides (Supplementary Information),"Supplementary Information to arXiv:0810.4466: 1. Characterizations of
Pb(Zr_0.2Ti_0.8)O_3 (PZT) films. 2. Substrate preparation before the
exfoliation of graphene. 3. The band structure of FLG. 4. Dielectric constant
measurements of PZT. 5. rho(V_g) and R_H(V_g) fitting inside the band overlap
regime. 6. The deformation potential of longitudinal acoustic (LA) phonons in
graphene. 7. Resistivity and Hall measurements of a SiO_2-gated FLG.",0810.5339v1
2008-12-20,Mobility Extraction and Quantum Capacitance Impact in High Performance Graphene Field-effect Transistor Devices,"The field-effect mobility of graphene devices is discussed. We argue that the
graphene ballistic mean free path can only be extracted by taking into account
both, the electrical characteristics and the channel length dependent mobility.
In doing so we find a ballistic mean free path of 300nm at room-temperature for
a carrier concentration of ~1e12/cm2 and that a substantial series resistance
of around 300ohmum has to be taken into account. Furthermore, we demonstrate
first quantum capacitance measurements on single-layer graphene devices.",0812.3927v1
2009-01-07,Electrically Controlled Magnetic Memory and Programmable Logic based on Graphene/Ferromagnet Hybrid Structures,"It has been shown that the combining of the electrical effect on the exchange
bias field with giant magneto-resistance effect of the graphene/ferromagnet
hybrid structures reveals a new non-volatile magnetic random access memory
device conception. In such device an electric bias realizes the writing bits
instead a magnetic field of remote word line with high energy consumption.
Interplay of two graphene mediated exchange bias fields applied to different
sides of free ferromagnet results in programable logic operations that depends
on specific realization of the structure.",0901.0926v1
2009-03-21,Graphite in the bi-layer regime: in-plane transport,"An interplay between the increase in the number of carriers and the decrease
in the scattering time is expected to result in a saturation of the in-plane
resistivity, $\rho_{ab}$, in graphite above room temperature. Contrary to this
expectation, we observe a pronounced increase in $\rho_{ab}$ in the interval
between 300 and 900 K. We provide a theory of this effect based on intervalley
scattering of charge carriers by high-frequency, graphene-like optical phonons.",0903.3646v2
2009-04-22,Emergence of dissipative structures in current-carrying superconducting wires,"We discuss the emergence of a spontaneous temperature and critical current
spatial modulation in current-carrying high temperature superconducting wire.
The modulation of the critical current along the wire on a scale of 3 - 10 mm
forces a fraction of the transport current to crisscross the resistive
interface between the superconducting film and normal metal stabilizer attached
to it. This generates additional heat that allows such a structure to be self
sustainable. Stability and the conditions for experimental observation of this
phenomenon are also discussed.",0904.3474v1
2009-04-23,"Crystal growth, structure and ferromagnetic properties of a Ce3Pt23Si11 single crystal","A high-quality single crystal of Ce3Pt23Si11 has been grown using the
Czochralski method. The crystal structure is presented and the chemical
composition has been checked using an electron microprobe analyzer.
Measurements of the electrical resistivity and magnetic susceptibility
performed at low temperature show a ferromagnetic transition at Tc = 0.44 K.",0904.3720v1
2009-05-29,Growth of Sr1-xCaxRuO3 thin films by metalorganic aerosol deposition,"We report the growth of thin films of Sr1-xCaxRuO3 on SrTiO3 and MgO
substrates by metalorganic aerosol deposition. The structure and microstructure
is characterized by X-ray diffraction and room-temperature scanning tunnelling
microscopy (STM), respectively. STM indicates in-plane epitaxy and a small
surface roughness for films on SrTiO3. The high-quality of the films is
supported by large residual resistivity ratios up to 29.",0905.4896v2
2009-09-07,Anomalous magnetotransport and cyclotron resonance of high mobility magnetic 2DHGs in the quantum Hall regime,"Low temperature magnetotransport measurements and far infrared transmission
spectroscopy are reported in molecular beam epitaxial grown two-dimensional
hole systems confined in strained InAs quantum wells with magnetic impurities
in the channel. The interactions of the free holes spin with the magnetic
moment of 5/2 provided by manganese features intriguing localization phenomena
and anomalies in the Hall and the quantum Hall resistance. In magnetic field
dependent far infrared spectroscopy measurements well pronounced cyclotron
resonance and an additional resonance are found that indicates an anticrossing
with the cyclotron resonance.",0909.1124v1
2010-08-15,Unconventional Anomalous Hall Effect in the Metallic Triangular-Lattice Magnet PdCrO2,"We experimentally reveal an unconventional anomalous Hall effect (UAHE) in a
quasi-two-dimensional triangular-lattice antiferromagnet PdCrO2. Using high
quality single crystals of PdCrO2, we found that the Hall resistivity deviates
from the conventional behavior below T* = 20 K, noticeably lower than TN = 37.5
K, at which Cr^{3+} (S=3/2) spins order in a 120 degree structure. In view of
the theoretical expectation that the spin chirality cancels out in the simplest
120 degree spin structure, we discuss required conditions for the emergence of
UAHE within Berry-phase mechanisms.",1008.2503v1
2010-08-27,Metal-nonmetal transition in LixCoO2 thin film and thermopower enhancement at high Li concentration,"We investigate the transport properties of LixCoO2 thin films whose
resistivities are nearly an order of magnitude lower than those of the bulk
polycrystals. A metal-nonmetal transition occurs at ~0.8 in a biphasic domain,
and the Seebeck coefficient (S) is drastically increased at ~140 K (= T*) with
increasing the Li concentration to show a peak of magnitude ~120 \muV/K in the
S-T curve of x = 0.87. We show that T* corresponds to a crossover temperature
in the conduction, most likely reflecting the correlation-induced temperature
dependence in the low-energy excitations.",1008.4635v1
2010-10-21,Atomistic quantum transport modeling of metal-graphene nanoribbon heterojunctions,"We calculate quantum transport for metal-graphene nanoribbon heterojunctions
within the atomistic self-consistent Schr\""odinger/Poisson scheme. Attention is
paid on both the chemical aspects of the interface bonding as well the
one-dimensional electrostatics along the ribbon length. Band-bending and doping
effects strongly influence the transport properties, giving rise to conductance
asymmetries and a selective suppression of the subband formation. Junction
electrostatics and p-type characteristics drive the conduction mechanism in the
case of high work function Au, Pd and Pt electrodes, while contact resistance
becomes dominant in the case of Al.",1010.4393v1
2010-11-02,Spin connection and boundary states in a topological insulator,"We study the surface resistivity of a three-dimensional topological insulator
when the boundaries exhibit a non trivial curvature. We obtain an analytical
solution for a spherical topological insulator, and we show that a non trivial
quantum spin connection emerges from the three dimensional band structure. We
analyze the effect of the spin connection on the scattering by a bump on a flat
surface. Quantum effects induced by the geometry lead to resonances when the
electron wavelength is comparable to the size of the bump.",1011.0565v1
2010-11-20,Imaging Dissipation and Hot Spots in Carbon Nanotube Network Transistors,"We use infrared thermometry of carbon nanotube network (CNN) transistors and
find the formation of distinct hot spots during operation. However, the average
CNN temperature at breakdown is significantly lower than expected from the
breakdown of individual nanotubes, suggesting extremely high regions of power
dissipation at the nanotube junctions. Statistical analysis and comparison with
a thermal model allow the extraction of the average tube-tube junction thermal
resistance, ~4.4x10^11 K/W (thermal conductance ~2.27 pW/K). This indicates
that nanotube junctions have a much greater impact on CNN transport,
dissipation, and reliability than extrinsic factors such as low substrate
thermal conductivity.",1011.4551v2
2011-05-16,Coulomb drag in graphene,"We calculate theoretically the Coulomb drag resistivity for two graphene
monolayers spatially separated by a distance ""$d$"". We show that the frictional
drag induced by inter-layer electron-electron interaction goes asymptotically
as $T^2/n^3$ and $T^2 \ln(n)/n$ in the high-density ($k_F d \gg 1$) and
low-density ($k_F d \ll 1$) limits, respectively.",1105.3203v2
2011-07-23,Modified exponential I(U) dependence and optical efficiency of AlGaAs SCH lasers in computer modeling with Synopsys TCAD,"Optical and electrical characteristics of AlGaAs lasers with separate
confinement heterostructures are modeled by using Synopsys's Sentaurus TCAD,
and open source software. We propose a modified exponential $I-V$ dependence to
describe electrical properties. A simple analytical, phenomenological model is
found to describe optical efficiency, $\eta$, with a high accuracy, by using
two parameters only. A link is shown between differential electrical
resistivity $r=dU/dI$ just above the lasing offset voltage, and the functional
$\eta(U)$ dependence.",1107.4668v1
2011-08-20,Demonstration of Forward Inter-band Tunneling in GaN by Polarization Engineering,"We report on the design, fabrication, and characterization of GaN interband
tunnel junction showing forward tunneling characteristics. We have achieved
very high forward tunneling currents (153 mA/cm2 at 10 mV, and 17.7 A/cm2 peak
current) in polarization-engineered GaN/InGaN/GaN heterojunction diodes grown
by plasma assisted molecular beam epitaxy. We also report the observation of
repeatable negative differential resistance in interband III-Nitride tunnel
junctions, with peak-valley current ratio (PVCR) of 4 at room temperature. The
forward current density achieved in this work meets the typical current drive
requirements of a multi-junction solar cell.",1108.4075v1
2012-04-10,Tunneling conduction in graphene/(poly)vinyl alcohol composites,"Graphene/(Poly)vinyl alcohol (PVA) composite film with thickness $60 \mu m$
were synthesized by solidification of a PVA solution comprising of dispersed
graphene nanosheets. The close proximity of the graphene sheets enables the
fluctuation induced tunneling of electrons to occur from one sheet to another.
The dielectric data show that the present system can be simulated to a parallel
resistance-capacitor network. The high frequency exponent of the frequency
variation of the ac conductivity indicates that the charge carriers move in a
two-dimensional space. The sample preparation technique will be helpful for
synthesizing flexible conductors.",1204.2126v2
2012-07-27,Theoretical model of structure-dependent conductance crossover in disordered carbon,"We analyze the effects of sp^2/sp^3 bond-aspect ratio on the transport
properties of amorphous carbon quasi-1D structures where structural disorder
varies in a very non-linear manner with the effective bandgap. Using a
tight-binding approach the calculated electron transmission showed a high
probability over a wide region around the Fermi-level for sp^2-rich carbon and
also distinct peaks close to the band edges for sp^3-rich carbon structures.
This model shows a sharp rise of the structure resistance with the increase of
sp^3C % followed by saturation in the wide bandgap regime for carbon
superlattice-like structures and suggests the tuneable characteristic time of
carbon-based devices.",1207.6478v1
2012-11-22,Physical properties and band structure of reactive molecular beam epitaxy grown oxygen engineered HfO$_{2\pm x}$,"We have conducted a detailed thin film growth structure of oxygen engineered
monoclinic HfO$_{2\pm x}$ grown by reactive molecular beam epitaxy (MBE). The
oxidation conditions induce a switching between ($\bar{1}11$) and (002) texture
of hafnium oxide. The band gap of oxygen deficient hafnia decreases with
increasing amount of oxygen vacancies by more than 1 eV. For high oxygen
vacancy concentrations, defect bands form inside the band gap that induce
optical transitions and $p$-type conductivity. The resistivity changes by
several orders of magnitude as a function of oxidation conditions. Oxygen
vacancies do not give rise to ferromagnetic behavior.",1211.5215v1
2013-05-21,High sensitive quasi freestanding epitaxial graphene gassensor on 6H-SiC,"We have measured the electrical response to NO$_2$, N$_2$, NH$_3$ and CO for
epitaxial graphene and quasi freestanding epitaxial graphene on 6H-SiC
substrates. Quasi freestanding epitaxial graphene shows a 6 fold increase in
NO2 sensitivity compared to epitaxial graphene. Both samples show a sensitivity
better than the experimentally limited 1 ppb. The strong increase in
sensitivity of quasi freestanding epitaxial graphene can be explained by a
Fermi-energy close to the Dirac Point leading to a strongly surface doping
dependent sample resistance. Both sensors show a negligible sensitivity to
N$_2$, NH$_3$ and CO.",1305.4737v1
2013-09-04,Enhancing high-temperature thermoelectric properties of PtAs2 by Rh doping,"The effects of Rh doping on the thermoelectric properties of Pt1-xRhxAs2 (x =
0, 0.005, and 0.01) with pyrite structure were studied by conducting
measurements of electrical resistivity rho, Seebeck coefficient S, and thermal
conductivity kappa. The sample with x = 0.005 exhibited large S and low rho,
resulting in a maximum power factor (S^2/rho) of 65 muW/cmK^2 at 440 K. The
peculiarly shaped ""corrugated flat band"" predicted for PtSb2 might explain the
enhanced thermoelectric properties of doped PtAs2.",1309.0939v1
2013-10-06,Charge transport through graphene junctions with wetting metal leads,"Graphene is believed to be an excellent candidate material for
next-generation electronic devices. However, one needs to take into account the
nontrivial effect of metal contacts in order to precisely control the charge
injection and extraction processes. We have performed transport calculations
for graphene junctions with wetting metal leads (metal leads that bind
covalently to graphene) using nonequilibrium Green's functions and density
functional theory. Quantitative information is provided on the increased
resistance with respect to ideal contacts and on the statistics of current
fluctuations. We find that charge transport through the studied two-terminal
graphene junction with Ti contacts is pseudo-diffusive up to surprisingly high
energies.",1310.1640v1
2013-11-17,Giant magnetothermopower in charge ordered Nd0.75Na0.25MnO3,"We report magnetization, resistivity and thermopower in the charge-orbital
ordered antiferromagnet Nd0.75Na0.25MnO3. Magnetic-field induced collapse of
antiferromagnetism is found to be accompanied by a giant negative
magnetothermopower (= 80-100% for a field change of 5T) over a wide temperature
(T = 60-225K) and giant magnetoresistance. While the field-induced metamagnetic
transition in magnetization is reversible upon field-cycling at T > 40 K, it is
irreversible at lower temperatures and this has impact on magnetoresistance,
magnetothermopower as well as change in the temperature of the sample. Our
results indicate high sensitivity of thermopower to changes in the magnetic
state of the sample.",1311.4165v1
2014-02-05,Selective molecular capture mechanism in carbon nanotube networks,"Recent air pollution issues have raised significant attention to develop
efficient air filters, and one of the most promising candidates is that enabled
by nanofibers. We explore here selective molecular capture mechanism for
volatile organic compounds in carbon nanotube networks by performing atomistic
simulations. The results are discussed with respect to the two key parameters
that define the performance of nanofiltration, i.e. the capture efficiency and
flow resistance, which validate the advantage of carbon nanotube networks with
high surface-to-volume ratio and atomistically smooth surfaces. We also reveal
the important roles of interfacial adhesion and diffusion that govern selective
gas transport through the network.",1402.1011v1
2016-01-06,Effect of SW defect on structural and transport properties of silicene nanoribbons,"Using density functional theory and non-equilibrium Greens function
technique, we performed theoretical investigations on the structural and
transport properties of zigzag silicene nanoribbons with Stone-Wales defect.
The calculated formation energy is significantly lower than that of graphene
and silicene, which implies the high stability of such defect in SiNRs.
Negative differential resistance can be observed within certain bias voltage
range in both perfect and SW defected SiNRs. In order to elucidate the
mechanism the NDR behavior,the transmission spectra and molecular projected
self-consistent Hamiltonian states are discussed in details.",1601.01053v1
2016-01-30,Slippery but tough - the rapid fracture of lubricated frictional interfaces,"We study the onset of friction for rough contacting blocks whose interface is
coated with a thin lubrication layer. High speed measurements of the real
contact area and stress fields near the interface reveal that propagating shear
cracks mediate lubricated frictional motion. While lubricants reduce interface
resistances, surprisingly, they significantly increase energy dissipated,
$\Gamma$, during rupture. Moreover, lubricant viscosity affects the onset of
friction but has no effect on $\Gamma$. Fracture mechanics provide a new way to
view the otherwise hidden complex dynamics of the lubrication layer.",1602.00085v2
2016-10-09,Physical properties of KMgBi single crystals,"KMgBi single crystals are grown by using the Bi flux successfully. KMgBi
shows semiconducting behavior with a metal-semiconductor transition at high
temperature region and a resistivity plateau at low temperature region,
suggesting KMgBi could be a topological insulator with a very small band gap.
Moreover, KMgBi exhibits multiband feature with strong temperature dependence
of carrier concentrations and mobilities.",1610.02699v2
2017-06-27,Influence of Heat Treatment on the Corrosion Behavior of Purified Magnesium and AZ31 Alloy,"Magnesium and its alloys are ideal for biodegradable implants due to their
biocompatibility and their low-stress shielding. However, they can corrode too
rapidly in the biological environment. The objective of this research was to
develop heat treatments to slow the corrosion of high purified magnesium and
AZ31 alloy in simulated body fluid at 37{\deg}C. Heat treatments were performed
at different temperatures and times. Hydrogen evolution, weight loss, PDP, and
EIS methods were used to measure the corrosion rates. Results show that heat
treating can increase the corrosion resistance of HP-Mg by 2x and AZ31 by 10x.",1706.08663v1
2017-12-06,Superconductivity in the ternary compound SrPt$_{10}$P$_4$ with complex new structure,"We report superconductivity at 1.4K in the ternary SrPt$_{10}$P$_4$ with a
complex new structure. SrPt$_{10}$P$_4$ crystallizes in a monoclinic
space-group C2/c (\#15) with lattice parameters a= 22.9151(9)$\AA$, b=
13.1664(5)$\AA$, c=13.4131(5)$\AA$, and $\beta$= 90.0270(5)${^\circ}$. Bulk
superconductivity in the samples has been demonstrated through resistivity, ac
susceptibility, and heat capacity measurements. High pressure measurements have
shown that the superconducting T$_C$ is systematically suppressed upon
application of pressure, with a dT$_C$/dP coefficient of -0.016 K/GPa.",1712.02010v1
2018-03-06,Comparative study on magnetoresistance of carbon-cobalt nanocomposite thin films grown by pulsed laser deposition,"We present a comparative study on the influence of applied magnetic field on
the resistance of $C_{1-x}Co_x$ thin films (with $x=0.1$, $0.15$ and $0.2$)
grown on $Si$ substrate by pulsed laser deposition technique. It is found that
the behavior of magnetoresistance (MR) drastically depends on the temperature.
Namely, at low temperatures MR is positive and its behavior is governed by the
field mediated weak localization scenario. While at high temperatures MR turns
negative and its behavior is dominated by electron scattering on ferromagnetic
cobalt atoms.",1803.02064v1
2018-04-27,Emergent antiferromagnetism of YTiO3 in YTiO3-CaTiO3 superlattices,"Transport and magnetoresistance measurements are performed on metallic,
high-carrier density YTiO3-CaTiO3 superlattices as a probe towards the
investigation of an emergent magnetic order of YTiO3. On varying the thickness
of YTiO3 while keeping the CaTiO3 layer thickness constant in the
superlattices, a low-temperature upturn in sheet-resistance, a non-Fermi
liquid-like charge transport and positive magnetoresistance are observed.
Analyses of the origin of such effects suggest that a unique antiferromagnetic
order is realized in the ultra-thin, epitaxially strained YTiO3 layers, which
corroborates well with some recent theoretical predictions in this regard.",1804.10333v1
2018-10-01,Poly(ionic liquid)-Derived Carbon with Site-Specific N-Doping and Biphasic Heterojunction for Enhanced CO2 Capture and Sensing,"CO2 capture is a pressing global environmental issue that drives scientists
to develop creative strategies for tackling this challenge. The concept in this
contribution is to produce site specific nitrogen doping in microporous carbon
fibers. It creates a carbon/carbon heterojunction by using poly(ionic liquid)
(PIL) as soft activation agent that deposits nitrogen species exclusively on
the skin of commercial microporous carbon fibers. Such carbon-based biphasic
heterojunction amplifies the interaction between carbon fiber and CO2 molecule
for unusually high CO2 uptake and resistive sensing.",1810.06418v1
2020-09-13,Adiabatic theory of SET and RESET transitions,"We develop a phenomenological theory of pulse induced phase transformations
behind the SET (from high to low resistive state) and RESET (backward)
processes in nonvolatile memory. We show that in modern era devices, both
evolve in the adiabatic regime with energy deposition time much shorter than
that of thermalization. They are however different by the operating modes:
voltage source driven for SET and current source driven for RESET. The
characteristic temperatures and transition rates are expressed through material
and process parameters.",2009.06057v2
2007-10-29,Thermoelectrical manipulation of nano-magnets,"We propose a device that can operate as a magneto-resistive switch or
oscillator. The device is based on a spin-thermo-electronic control of the
exchange coupling of two strong ferromagnets through a weakly ferromagnetic
spacer. We show that the local Joule heating due to a high concentration of
current in a magnetic point contact or a nanopillar can be used to reversibly
drive the weak ferromagnet through its Curie point and thereby
exchange-decouple the strongly ferromagnetic layers, which have an antiparallel
ground state. Such a spin-thermionic parallel-to-antiparallel switching causes
magnetoresistance oscillations where the frequency can be controlled by proper
biasing from essentially DC to GHz.",0710.5477v1
2007-10-30,Devitrification of a glass-like arrested ferromagnetic phase in La0.5Ca0.5MnO3,"Magnetization measurements in La0.5Ca0.5MnO3 manganite show that the
high-temperature long-range ferromagnetic-metallic phase transforms to
antiferromagnetic-insulating phase, although a fraction of
ferromagnetic-metallic phase undergoes glass-like kinetic arrest and coexists
at low temperature with the equilibrium antiferromagnetic-insulating phase. We
show here through resistivity measurements that the residual arrested
ferromagnetic-metallic fraction can be converted to the equilibrium
antiferromagnetic-insulating phase by successive annealing at higher
temperatures, possibly through heterogeneous nucleation of equilibrium phase.
Significantly, larger fractions of this glassy ferromagnetic-metallic phase can
be obtained by cooling in higher fields and larger conversion to equilibrium
antiferromagnetic-insulating phase results.",0710.5585v1
2019-03-26,Patterning of diamond with 10 nm resolution by electron-beam-induced etching,"We report on mask-less, high resolution etching of diamond surfaces,
featuring sizes down to 10 nm. We use a scanning electron microscope (SEM)
together with water vapor, which was injected by a needle directly onto the
sample surface. Using this versatile and low-damage technique, trenches with
different depths were etched. Cross sections of each trench were obtained by
focused ion beam milling and used to calculate the achieved aspect ratios. The
developed technique opens up the possibility of mask- and resist-less
patterning of diamond for nano-optical and electronic applications.",1903.10824v1
2015-07-11,Insulator/metal phase transition and colossal magnetoresistance in holographic model,"Within massive gravity, we construct a gravity dual for insulator/metal phase
transition and colossal magnetoresistance (CMR) effect found in some manganese
oxides materials. In heavy graviton limit, a remarkable
magnetic-field-sensitive DC resistivity peak appears at the Curie temperature,
where an insulator/metal phase transition happens and the magnetoresistance is
scaled with the square of field-induced magnetization. We find that metallic
and insulating phases coexist below the Curie point and the relation with the
electronic phase separation is discussed.",1507.03105v2
2019-10-23,Percolation with plasticity for neuromorphic computing,"We introduce the percolation with plasticity (PWP) systems that exhibit
neuromorphic functionalities including multi-valued memory, random number
generation, matrix-vector multiplication, and associative learning. PWP systems
have multiple (N >> 1) interfaces with external circuitry (electrodes) allowing
N! >> 1 measurable interelectrode resistances. Due to the underlying material
properties, they undergo successive nonvolatile modifications in response to
electric pulses. PWP networks offer some advantages over the existing neural
network architectures. Overall, random self-tuning PWP systems with high degree
of parallelism, multiple inputs and outputs present close similarities to the
cortex of mammalian brain. Understanding their topology, electrodynamics, and
statistics opens a field of its own calling upon new theoretical and
experimental insights.",1910.10535v1
2019-11-04,Closed-loop electric currents and non-local resistance measurements with wide F/I/N tunnel contacts,"Lateral spin valves are used to generate and characterize pure spin currents.
Non-local voltage measured in such structures provides information about spin
polarization and spin decay rates. For wide high-transparency F/N contacts it
was shown that the Johnson-Silsbee non-local effect is substantially enriched
by closed-loop electric currents driven by local spin injection in the
electrically dangling part of the valve. For valves with low-transparency F/I/N
tunnel contacts such circular currents are strongly suppressed, yet we show
that the voltage modifications persist, may be significant, and must be
accounted for in the data analysis.",1911.01034v1
2020-01-08,Electrical and optical properties of hydrated amorphous vanadium oxide,"Electrical and optical properties of amorphous vanadium oxide thin films
obtained by electrochemical anodic oxidation are studied. It is shown that
under cathodic polarization the hydrogen insertion into vanadium oxide from an
electrolyte occurs. Metal-insulator transition in amorphous HxVO2 is found to
be preserved up to high concentration (x ~ 1.5) of hydrogen. Memory switching
with the N-type negative differential resistance, associated with the H+ ionic
transfer, is observed in ""V/hydrated amorphous vanadium oxide/Au"" sandwich
structures.",2001.02418v1
2020-01-08,Electrical conductivity of vanadium dioxide switching channel,"The electrical conductivity of the switching channel of vanadium dioxide
thin-film sandwich structures is studied over a wide temperature range (15-300
K). It is shown that the electrical resistance of the channel varies with
temperature as R~exp(aT-b/T) in the high-temperature region (above 70 K). The
experimental results are discussed from the viewpoint of the small polaron
hopping conduction theory which takes into account the influence of thermal
lattice vibrations onto the resonance integral.",2001.03053v1
2021-03-19,Side-leakage of facemask,"Face masks are used to trap particles (or fluid drops) in a porous material
(filter) in order to avoid or reduce the transfer of particles between the
human lungs (or mouth and nose) and the external environment. The air exchange
between the lungs and the environment is assumed to occur through the facemask
filter. However, if the resistance to air flow through the filter is high some
air (and accompanied particles) will leak through the filter-skin interface. In
this paper I will present a model study of the side-leakage problem.",2103.10970v1
2021-04-25,High Pressure RTSC-Hydrides are Extreme Hard Type-II Superconductors,"It is argued that most of the RTSC hydrides are intrinsic hard type-II
superconductors with strong pinning effects. The pinning centers are long
columnar-like defects, with the radius of the order of the superconducting
coherence length. The core and electromagnetic pinning are both equally
operative, thus giving maximal pinning potential when vortices are oriented
along the columnar axis. The theory predicts: (i) large critical currents, (ii)
huge decrease of the temperature broadening of the resistance in magnetic field
compared with standard superconductors, (iii) large magnetization hysteresis,
(iv) the magnetic irreversible line is pushed toward the second critical field
and magnetization relaxation is much slower. That the RTSC-hydrides are hard
type-II SC can give rise to new physics in these materials.",2104.12214v1
2022-11-19,A Large-Area RPC Detector for Muography,"A muon telescope equipped with four Resistive Plate Chambers of 2 m$^{2}$ per
plane was tested with the muon scattering tomography technique. The telescope
was operated during several hours with high atomic number materials located at
its center with two detector planes on each side. With an intrinsic efficiency
above 98%, spatial resolution around 1 cm and detector planes spaced by 45 cm,
it was possible to identify the presence of a 5 cm thick tungsten block in 10
minutes of acquisition. The results obtained after five hours of acquisition
are also presented in this communication.",2211.10795v1
2023-05-22,Microcontroller Based AVR Hazardous Gas Detection System using IoT,"MQ-6 Semiconductor Sensor for Combustible Gas detection is a Sensitive Gas
sensor. The sensitive material of this MQ-6 gas sensor is SnO2, which works
with lower conductivity in clean air. When the target combustible gas exist,
the sensors conductivity is higher along with the gas concentration rising. As
the conductivity increases the current in the circuit of the sensor increases
which results in lower sensor resistance. This change is used to correspond,
the output signal of gas concentration. MQ-6 gas sensor has high sensitivity to
Methane, Propane and Butane and could be used to detect both Methane and
Propane. The sensor could be used to detect different combustible gas
especially Methane, it is with low cost and suitable for different application.",2305.12855v1
2017-10-25,High-temperature cyclic oxidation kinetics and microstructural transition mechanisms of Ti-6Al-4V composites reinforced with hybrid (TiC+TiB) networks,"The microstructural features and high-temperature oxidation resistance of
hybrid (TiC+TiB) networks reinforced Ti-6Al-4V composites were investigated
after fabricated with reaction hot pressing technique. The inhomogeneous
distribution of hybrid reinforcers resulted in a sort of stress-induced grain
refinement for {\alpha}-Ti matrix phase, which was further facilitated by
heterogeneous nucleation upon additive interfaces. HRTEM analyses revealed the
crystallographic orientation relation between TiB and alpha-Ti phases as
(201)TiB//(-1100)alpha-Ti plus [11-2]//[0001] alpha-Ti, while TiC and
{\alpha}-Ti phases maintained the interrelation of (-200)TiC//(-2110)
{\alpha}-Ti and [001]TiC//[01-10] alpha-Ti. The hybridly reinforced
Ti-6Al-4V/(TiC+TiB) composites displayed superior oxidation resistance to both
the sintered matrix alloy and the two composites reinforced solely with TiC or
TiB addition during the cyclic oxidation at 873, 973 and 1073 K respectively
for 100 h. The hybrid reinforcers volume fraction was a more influential factor
to improve oxidation resistance than the matrix alloy powder size. As
temperature rose from 873 to 1073 K, the oxidation kinetics transferred from
the nearly parabolic type through qusilinear tendency into the finally linear
mode. This corresponded to the morphological transition of oxide scales from a
continuous protective film to a partially damaged layer and ended up with the
complete spallation of alternating alumina and rutile multilayers. A
phenomenological model was proposed to elucidate the growth process of oxides
scales. The release of thermal stress, the suppression of oxygen diffusion and
the fastening of oxide adherence were found as the three major mechanisms to
enhance the oxidation resistance of hybrid reinforced composites.",1710.09315v1
2007-07-20,A mechanism for unipolar resistance switching in oxide non-volatile memory devices,"Building on a recently introduced model for non-volatile resistive switching,
we propose a mechanism for unipolar resistance switching in
metal-insulator-metal sandwich structures. The commutation from the high to low
resistance state and back can be achieved with successive voltage sweeps of the
same polarity. Electronic correlation effects at the metal-insulator interface
are found to play a key role to produce a resistive commutation effect in
qualitative agreement with recent experimental reports on binary transition
metal oxide based sandwich structures.",0707.3077v1
2013-08-02,Precision Quantum Hall Resistance Measurement on Epitaxial Graphene Device in Low Magnetic Field,"Precision quantum Hall resistance (QHR) measurements were performed on
large-area epitaxial graphene device at low magnetic fields (B = 2 T - 8 T) at
temperature T = 1.5 K. Hall resistance was measured using Cryogenic Current
Comparator resistance bridge with high biasing current Isd = 40 micro ampere.
The results showed that at B = 8 T the relative deviation of Hall resistance
from the expected quantized value h/2e2 is within experimental uncertainty of
3.5 parts in 108 and remained below 0.35 parts per million (ppm) down to B = 3
T.",1308.0456v1
2011-01-30,Spin transport in magnetically ordered systems: effect of the lattice relaxation time,"Spin resistivity $R$ has been shown to result mainly from the scattering of
itinerant spins with magnetic impurities and lattice spins. $R$ is proportional
to the spin-spin correlation so that its behavior is very complicated near and
at the magnetic phase transition of the lattice spins. For the time being there
are many new experimental data on the spin resistivity going from
semiconductors to superconductors. Depending on materials, various behaviors
have been observed. There is however no theory so far which gives a unified
mechanism for spin resistivity in magnetic materials. Recently, we have showed
Monte Carlo results for different systems. We found that the spin resistivity
is very different from one material to another. In this paper, we show for the
first time how the dynamic relaxation time of the lattice spins affects the
resistivity of itinerant spins observed in Monte Carlo simulation.",1101.5789v1
2020-09-16,Resistive switching in reverse: voltage driven formation of a transverse insulating barrier,"Application of an electric stimulus to a material with a metal-insulator
transition can trigger a large resistance change. Resistive switching from an
insulating into a metallic phase, which typically occurs by the formation of
conducting filaments parallel to the current flow, has been an active research
topic. Here we present the discovery of an opposite, metal-to-insulator
switching that proceeds via nucleation and growth of an insulating barrier
perpendicular to the driving current. The barrier formation leads to an unusual
N-type negative differential resistance in the current-voltage characteristics.
Electrically inducing a transverse barrier enables a novel approach to
voltage-controlled magnetism. By triggering a metal-to-insulator resistive
switching in a magnetic material, local on/off control of ferromagnetism can be
achieved by a global voltage bias applied to the whole device.",2009.07412v1
2021-08-14,Voltage-controlled magnetism enabled by resistive switching,"The discovery of new mechanisms of controlling magnetic properties by
electric fields or currents furthers the fundamental understanding of magnetism
and has important implications for practical use. Here, we present a novel
approach of utilizing resistive switching to control magnetic anisotropy. We
study a ferromagnetic oxide that exhibits an electrically triggered
metal-to-insulator phase transition producing a volatile resistive switching.
This switching occurs in a characteristic spatial pattern: the formation of a
transverse insulating barrier inside a metallic matrix resulting in an unusual
ferromagnetic/paramagnetic/ferromagnetic configuration. We found that the
formation of this voltage-driven paramagnetic insulating barrier is accompanied
by the emergence of a strong uniaxial magnetic anisotropy that overpowers the
intrinsic material anisotropy. Our results demonstrate that resistive switching
is an effective tool for manipulating magnetic properties. Because resistive
switching can be induced in a very broad range of materials, our findings could
enable a new class of voltage-controlled magnetism systems.",2108.06445v1
2022-08-02,Investigating thermal transport in knotted graphene nanoribbons using non-equilibrium molecular dynamics,"In this work, we investigated the effect of knots in the thermal transport of
graphene nanoribbons through non-equilibrium molecular dynamics simulations. We
considered the cases of one, two, and three knots are present. Temperature
jumps appear in the temperature profile where the knots are located, which
indicates that they introduce thermal resistances in the system, similar to
interfacial Kapitza resistance present between two different materials and/or
single materials with defects and/or lattice distortions. We found that the
thermal resistance introduced by each individual knot is essentially the same
as the overall resistance increase linearly with the number of knots, as they
behave as thermal resistances associated in series. Also, the relative position
between each knot in the arrangement does not strongly affect the thermal
current produced by the temperature gradient, showing a weak thermal
rectification effect.",2208.01751v1
2010-05-21,Effect of Heterogeneous Mixing and Vaccination on the Dynamics of Anthelmintic Resistance: A Nested Model,"Anthelmintic resistance is a major threat to current measures for helminth
control in humans and animals. The introduction of anthelmintic vaccines, as a
complement to or replacement for drug treatments, has been advocated as a
preventive measure. Here, a computer-based simulation, tracking the dynamics of
hosts, parasites and parasite-genes, shows that, depending on the degree of
host-population mixing, the frequency of totally recessive autosomes associated
with anthelmintic resistance can follow either a fast dynamical regime with a
low equilibrium point or a slow dynamical regime with a high equilibrium point.
For fully dominant autosomes, only one regime is predicted. The effectiveness
of anthelminthic vaccines against resistance is shown to be strongly influenced
by the underlying dynamics of resistant autosomes. Vaccines targeting adult
parasites, by decreasing helminth fecundity or lifespan, are predicted to be
more effective than vaccines targeting parasite larvae, by decreasing host
susceptibility to infection, in reducing the spread of resistance. These
results may inform new strategies to prevent, monitor and control the spread of
anthelmintic resistance, including the development of viable anthelmintic
vaccines.",1005.3891v1
2018-06-20,Modeling continuous levels of resistance to multidrug therapy in cancer,"Multidrug resistance consists of a series of genetic and epigenetic
alternations that involve multifactorial and complex processes, which are a
challenge to successful cancer treatments. Accompanied by advances in
biotechnology and high-dimensional data analysis techniques that are bringing
in new opportunities in modeling biological systems with continuous phenotypic
structured models, we study a cancer cell population model that considers a
multi-dimensional continuous resistance trait to multiple drugs to investigate
multidrug resistance. We compare our continuous resistance trait model with
classical models that assume a discrete resistance state and classify the cases
when the continuum and discrete models yield different dynamical patterns in
the emerging heterogeneity in response to drugs. We also compute the maximal
fitness resistance trait for various continuum models and study the effect of
epimutations. Finally, we demonstrate how our approach can be used to study
tumor growth regarding the turnover rate and the proliferating fraction, and
show that a continuous resistance level may result in a different dynamics when
compared with the predictions of other discrete models.",1806.07557v1
2021-01-18,Hubs-biased resistance distances on graphs and networks,"We define and study two new kinds of ""effective resistances"" based on
hubs-biased -- hubs-repelling and hubs-attracting -- models of navigating a
graph/network. We prove that these effective resistances are squared Euclidean
distances between the vertices of a graph. They can be expressed in terms of
the Moore-Penrose pseudoinverse of the hubs-biased Laplacian matrices of the
graph. We define the analogous of the Kirchhoff indices of the graph based of
these resistance distances. We prove several results for the new resistance
distances and the Kirchhoff indices based on spectral properties of the
corresponding Laplacians. After an intensive computational search we conjecture
that the Kirchhoff index based on the hubs-repelling resistance distance is not
smaller than that based on the standard resistance distance, and that the last
is not smaller than the one based on the hubs-attracting resistance distance.
We also observe that in real-world brain and neural systems the efficiency of
standard random walk processes is as high as that of hubs-attracting schemes.
On the contrary, infrastructures and modular software networks seem to be
designed to be navigated by using their hubs.",2101.07103v2
2021-10-18,Low-Frequency 1/f Noise Characteristics of Ultra-Thin AlO$_{x}$-Based Resistive Switching Memory Devices with Magneto-Resistive Responses,"Low-frequency 1/f voltage noise has been employed to probe stochastic charge
dynamics in AlO$_{x}$-based non-volatile resistive memory devices exhibiting
both resistive switching (RS) and magneto-resistive (MR) effects. A
1/f$^{\gamma}$ noise power spectral density is observed in a wide range of
applied voltage biases. By analyzing the experimental data within the framework
of Hooge's empirical relation, we found that the Hooge's parameter $\alpha$ and
the exponent $\gamma$ exhibit a distinct variation upon the resistance
transition from the low resistance state (LRS) to the high resistance state
(HRS), providing strong evidence that the electron trapping/de-trapping
process, along with the electric field-driven oxygen vacancy migration in the
AlO$_x$ barrier, plays an essential role in the charge transport dynamics of
AlO$_x$-based RS memory devices.",2110.09331v1
2023-07-24,Clustering MIC data through Bayesian mixture models: an application to detect M. Tuberculosis resistance mutations,"Antimicrobial resistance is becoming a major threat to public health
throughout the world. Researchers are attempting to contrast it by developing
both new antibiotics and patient-specific treatments. In the second case,
whole-genome sequencing has had a huge impact in two ways: first, it is
becoming cheaper and faster to perform whole-genome sequencing, and this makes
it competitive with respect to standard phenotypic tests; second, it is
possible to statistically associate the phenotypic patterns of resistance to
specific mutations in the genome. Therefore, it is now possible to develop
catalogues of genomic variants associated with resistance to specific
antibiotics, in order to improve prediction of resistance and suggest
treatments. It is essential to have robust methods for identifying mutations
associated to resistance and continuously updating the available catalogues.
This work proposes a general method to study minimal inhibitory concentration
(MIC) distributions and to identify clusters of strains showing different
levels of resistance to antimicrobials. Once the clusters are identified and
strains allocated to each of them, it is possible to perform regression method
to identify with high statistical power the mutations associated with
resistance. The method is applied to a new 96-well microtiter plate used for
testing M. Tuberculosis.",2307.12603v1
2023-06-19,On the Active Components in Crystalline Li-Nb-O and Li-Ta-O Coatings from First Principles,"Layered-oxide $\mathrm{LiNi_xMn_yCo_{1-x-y}O_2}$ (NMC) positive electrodes
with high Nickel content, deliver high voltages and energy densities. However,
a high nickel content, e.g., $x$ = 0.8 (NMC 811), can lead to high surface
reactivity, which can trigger thermal runaway and gas generation. While claimed
safer, all-solid-state batteries still suffer from high interfacial resistance.
Here, we investigate niobate and tantalate coating materials, which can
mitigate the interfacial reactivities in Li-ion and all-solid-state batteries.
First-principles calculations reveal the multiphasic nature of Li-Nb-O and
Li-Ta-O coatings, containing mixtures of $\mathrm{LiNbO_3}$ and
$\mathrm{Li_3NbO_4}$, or of $\mathrm{LiTaO_3}$ and $\mathrm{Li_3TaO_4}$. The
concurrence of several phases in Li-Nb-O or Li-Ta-O modulates the type of
stable native defects in these coatings. Li-Nb-O and Li-Ta-O coating materials
can form favorably lithium vacancies $\mathrm{Vac^{'}_{Li}}$ and antisite
defects $\mathrm{Nb^{\bullet \bullet \bullet \bullet}_{Li}}$
($\mathrm{Ta^{\bullet \bullet \bullet \bullet}_{Li}}$) combined into
charge-neutral defect complexes. Even in defective crystalline
$\mathrm{LiNbO_3}$ (or $\mathrm{LiTaO_3}$), we reveal poor Li-ion conduction
properties. In contrast, $\mathrm{Li_3NbO_4}$ and $\mathrm{Li_3TaO_4}$ that are
introduced by high-temperature calcinations can provide adequate Li-ion
transport in these coatings. Our in-depth investigation of the
structure-property relationships in the important Li-Nb-O and Li-Ta-O coating
materials helps to develop more suitable calcination protocols to maximize the
functional properties of these niobates and tantalates.",2306.10716v1
2020-01-23,Large Enhancement of Thermoelectric Efficiency Due to a Pressure-Induced Lifshitz Transition in SnSe,"Lifshitz transition, a change in Fermi surface topology, is likely to greatly
influence exotic correlated phenomena in solids, such as high-temperature
superconductivity and complex magnetism. However, since the observation of
Fermi surfaces is generally difficult in the strongly correlated systems, a
direct link between the Lifshitz transition and quantum phenomena has been
elusive so far. Here, we report a marked impact of the pressure-induced
Lifshitz transition on thermoelectric performance for SnSe, a promising
thermoelectric material without strong electron correlation. By applying
pressure up to 1.6 GPa, we have observed a large enhancement of thermoelectric
power factor by more than 100% over a wide temperature range (10-300 K).
Furthermore, the high carrier mobility enables the detection of quantum
oscillations of resistivity, revealing the emergence of new Fermi pockets at
~0.86 GPa. The observed thermoelectric properties linked to the multi-valley
band structure are quantitatively reproduced by first-principles calculations,
providing novel insight into designing the SnSe-related materials for potential
valleytronic as well as thermoelectric applications.",2001.08674v1
2009-07-10,Cellulose-Bound Magnesium Diboride Superconductivity,"Two-phase superconductor tapes were produced by blending high purity
magnesium diboride powder with a liquid ethylcellulose-based polymeric binder.
This procedure produced a material which is easily formable with a high
superconducting transition temperature (38K). We show that the bulk
superconducting properties are not affected by the presence of the binder, nor
is there any evidence of a chemical reaction between the superconducting
particles and the binder. However, the transport properties of the material are
strongly affected by the presence of the binder, which leads to a seven order
of magnitude increase of the normal state resistance along with a seven order
of magnitude decrease of the transport critical current density. This new
material is shown to be equivalent to a system of coupled Josephson junctions.",0907.1744v1
2010-06-27,Soft capacitor fibers using conductive polymers for electronic textiles,"A novel, highly flexible, conductive polymer-based fiber with high electric
capacitance is reported. In its crossection the fiber features a periodic
sequence of hundreds of conductive and isolating plastic layers positioned
around metallic electrodes. The fiber is fabricated using fiber drawing method,
where a multi-material macroscopic preform is drawn into a sub-millimeter
capacitor fiber in a single fabrication step. Several kilometres of fibers can
be obtained from a single preform with fiber diameters ranging between 500um
-1000um. A typical measured capacitance of our fibers is 60-100 nF/m and it is
independent of the fiber diameter. For comparison, a coaxial cable of the
comparable dimensions would have only ~0.06nF/m capacitance. Analysis of the
fiber frequency response shows that in its simplest interrogation mode the
capacitor fiber has a transverse resistance of 5 kOhm/L, which is inversely
proportional to the fiber length L and is independent of the fiber diameter.
Softness of the fiber materials, absence of liquid electrolyte in the fiber
structure, ease of scalability to large production volumes, and high
capacitance of our fibers make them interesting for various smart textile
applications ranging from distributed sensing to energy storage.",1006.5221v1
2015-03-06,Conductivity of a Weyl semimetal with donor and acceptor impurities,"We study transport in a Weyl semimetal with donor and acceptor impurities.
  At sufficiently high temperatures transport is dominated by electron-electron
interactions, while the low-temperature resistivity comes from the scattering
of quasiparticles on screened impurities.
  Using the diagrammatic technique, we calculate the conductivity
$\sigma(T,\omega,n_A,n_D)$ in the impurities-dominated regime as a function of
temperature $T$, frequency $\omega$, and the concentrations $n_A$ and $n_D$ of
donors and acceptors and discuss the crossover behaviour between the regimes of
low and high temperatures and impurity concentrations.
  In a sufficiently compensated material [$|n_A-n_D|\ll(n_A+n_D)$] with a small
effective fine structure constant $\alpha$, $\sigma(\omega,T)\propto
T^2/(T^{-2}-i\omega\cdot\text{const})$ in a wide interval of temperatures.
  For very low temperatures or in the case of an uncompensated material the
transport is effectively metallic. We discuss experimental conditions necessary
for realising each regime.",1503.02078v2
2015-10-31,High-performance Thermal Interface Material Based on Few-layer Graphene Composite,"We developed high-performance thermal interface materials (TIMs) based on
few-layer graphene (FLG) composite, where FLG was prepared by the interlayer
catalytic exfoliation (ICE) method. We experimentally demonstrated feasibility
of FLG composites as TIMs by investigating their thermal and mechanical
properties, and reliability. We measured the thermal interface resistance
($R_{int}$) between FLG composite TIMs (FLGTs) and copper and to be 3.2$\pm$1.7
and 4.3$\pm$1.4 $mm^2$K/W for 5 vol.% and 10 vol.% FLGTs at 330 K,
respectively, comparable to or even lower than that of many commercial TIMs. In
addition, the thermal conductivity ($\kappa_{TIM}$) of FLGTs is increased by an
enhancement factor ($\beta$) of ~17 as the FLG concentration increases from 0
to 10 vol.%. We also characterized Vickers hardness and glass transition
temperature ($T_g$) of our FLGTs. We find that our FLGTs are thermally and
mechanically reliable within practical operating temperature and pressure
ranges.",1511.00076v2
2016-02-16,Perfect charge compensation in extremely large magnetoresistance materials LaSb and LaBi revealed by the first-principles calculations,"By the first-principles electronic structure calculations, we have
systematically studied the electronic structures of recently discovered
extremely large magnetoresistance (XMR) materials LaSb and LaBi. We find that
both LaSb and LaBi are semimetals with the electron and hole carriers in
perfect balance. The calculated carrier densities in the order of $10^{20}$
cm$^{-3}$ are in good agreement with the experimental values, implying long
mean free time of carriers and thus high carrier mobilities. With a
semiclassical two-band model, the perfect charge compensation and high carrier
mobilities naturally explain (i) the XMR observed in LaSb and LaBi; (ii) the
non-saturating quadratic dependence of XMR on external magnetic field; and
(iii) the resistivity plateau in the turn-on temperature behavior at very low
temperatures. The explanation of these features without resorting to the
topological effect indicates that they should be the common characteristics of
all perfectly electron-hole compensated semimetals.",1602.05061v1
2016-06-17,"Homogeneously bright, flexible and foldable lighting devices with functionalised graphene electrodes","Alternating current electroluminescent technology allows the fabrication of
large area, flat and flexible lights. Presently the maximum size of a
continuous panel is limited by the high resistivity of available transparent
electrode materials causing a visible gradient of brightness. Here, we
demonstrate that the use of the best known transparent conductor
FeCl$_{3}$-intercalated few-layer graphene boosts the brightness of
electroluminescent devices by 49$\%$ compared to pristine graphene. Intensity
gradients observed for high aspect ratio devices are undetectable when using
these highly conductive electrodes. Flat lights on polymer substrates are found
to be resilient to repeated and flexural strains.",1606.05482v1
2017-10-27,The Quantum Hall Effect with Wilczek's charged magnetic flux tubes instead of electrons,"Composites formed from charged particles and magnetic flux tubes, proposed by
Wilczek, are one model for anyons - particles obeying fractional statistics.
Here we propose a scheme for realizing charged flux tubes, in which a charged
object with an intrinsic magnetic dipole moment is placed between two
semi-infinite blocks of a high permeability ($\mu_r$) material, and the images
of the magnetic moment create an effective flux tube. We show that the scheme
can lead to a realization of Wilczek's anyons, when a two-dimensional electron
system, which exhibits the integer quantum Hall effect (IQHE), is sandwiched
between two blocks of the high-$\mu_r$ material with a temporally fast response
(in the cyclotron and Larmor frequency range). The signature of Wilczek's
anyons is a slight shift of the resistivity at the plateau of the IQHE. Thus,
the quest for high-$\mu_r$ materials at high frequencies, which is underway in
the field of metamaterials, and the quest for anyons, are here found to be on
the same avenue.",1710.10108v2
2020-03-03,Chemical sensing with atomically-thin metals templated by a two-dimensional insulator,"Boosting the sensitivity of solid-state gas sensors by incorporating
nanostructured materials as the active sensing element can be complicated by
interfacial effects. Interfaces at nanoparticles, grains, or contacts may
result in non-linear current-voltage response, high electrical resistance, and
ultimately, electric noise that limits the sensor read-out. Here we report the
possibility to prepare nominally one atom thin, electrically continuous metals,
by straightforward physical vapor deposition on the carbon zero-layer grown
epitaxially on silicon carbide. With platinum as the metal, its electrical
conductivity is strongly modulated when interacting with chemical analytes, due
to charges being transferred to/from Pt. This, together with the scalability of
the material, allows us to microfabricate chemiresistor devices for electrical
read-out of chemical species with sub part-per-billion detection limits. The
two-dimensional system formed by atomically-thin metals open up a route for
resilient and high sensitivity chemical detection, and could be the path for
designing new heterogeneous catalysts with superior activity and selectivity.",2003.01594v1
2020-04-27,Runaway dynamics in the DT phase of ITER operations in the presence of massive material injection,"A runaway avalanche can result in a conversion of the initial plasma current
into a relativistic electron beam in high current tokamak disruptions. We
investigate the effect of massive material injection of deuterium-noble gas
mixtures on the coupled dynamics of runaway generation, resistive diffusion of
the electric field, and temperature evolution during disruptions in the DT
phase of ITER operations. We explore the dynamics over a wide range of injected
concentrations and find substantial runaway currents, unless the current quench
time is intolerably long. The reason is that the cooling associated with the
injected material leads to high induced electric fields that, in combination
with a significant recombination of hydrogen isotopes, leads to a large
avalanche generation. Balancing Ohmic heating and radiation losses provides
qualitative insights into the dynamics, however, an accurate modeling of the
temperature evolution based on energy balance appears crucial for quantitative
predictions.",2004.12861v3
2020-09-04,Magnon-induced Giant Anomalous Nernst Effect in Single Crystal MnBi,"Thermoelectric modules are a promising approach to energy harvesting and
efficient cooling. In addition to the longitudinal Seebeck effect, recently
transverse devices utilizing the anomalous Nernst effect (ANE) have attracted
interest. For high conversion efficiency, it is required that the material
should have a large ANE thermoelectric power and low electrical resistance, the
product of which is the ANE conductivity. ANE is usually explained in terms of
intrinsic contributions from Berry curvature. Our observations suggest that
extrinsic contributions also matter. Studying single-crystal MnBi, we find a
very high ANE thermopower (~10 $\mu$V/K) under 0.6 T at 80 K, and a transverse
thermoelectric conductivity of over 40 A/Km. With insight from theoretical
calculations, we attribute this large ANE predominantly to a new advective
magnon contribution arising from magnon-electron spin-angular momentum
transfer. We propose that introducing large spin-orbit coupling into
ferromagnetic materials may enhance the ANE through the extrinsic contribution
of magnons.",2009.02211v3
2022-02-10,Nanostructured transition metal dichalcogenide multilayers for advanced nanophotonics,"Transition metal dichalcogenides (TMDs) attract significant attention due to
their exceptional optical, excitonic, mechanical, and electronic properties.
Nanostructured multilayer TMDs were recently shown to be highly promising for
nanophotonic applications, as motivated by their exceptionally high refractive
indexes and optical anisotropy. Here, we extend this vision to more
sophisticated structures, such as periodic arrays of nanodisks and nanoholes,
as well as proof-of-concept waveguides and resonators. We specifically focus on
various advanced nanofabrication strategies, including careful selection of
resists for electron beam lithography and etching methods. The specific
materials studied here include semiconducting WS$_2$, in-plane anisotropic
ReS$_2$, and metallic TaSe$_2$, TaS$_2$ and NbSe$_2$. The resulting
nanostructures can potentially impact several nanophotonic and optoelectronic
areas, including high-index nanophotonics, plasmonics and on-chip optical
circuits. The knowledge of TMD material-dependent nanofabrication parameters
developed here will help broaden the scope of future applications of these
materials in all-TMD nanophotonics.",2202.04898v1
2021-01-20,Electrically-Insulating Flexible Films with Quasi-One-Dimensional van-der-Waals Fillers as Efficient Electromagnetic Shields,"We report polymer composite films containing fillers comprised of
quasi-one-dimensional (1D) van der Waals materials, specifically transition
metal trichalcogenides containing 1D structural motifs that enable their
exfoliation into bundles of atomic threads. These nanostructures are
characterized by extremely large aspect ratios of up to 10^6. The polymer
composites with low loadings of quasi-1D TaSe3 fillers (below 3 vol. %)
revealed excellent electromagnetic interference shielding in the X-band GHz and
EHF sub-THz frequency ranges, while remaining DC electrically insulating. The
unique electromagnetic shielding characteristics of these films are attributed
to effective coupling of the electromagnetic waves to the high-aspect-ratio
electrically-conductive TaSe3 atomic-thread bundles even when the filler
concentration is below the electrical percolation threshold. These novel films
are promising for high-frequency communication technologies, which require
electromagnetic shielding films that are flexible, lightweight, corrosion
resistant, electrically insulating and inexpensive.",2101.08239v1
2020-05-07,Understanding cooperative loading in carbon nanotube fibres through in-situ structural studies during stretching,"Carbon nanotube (CNT) fibres are firmly established as a new high-performance
fibre, but their tensile mechanical properties remain a relatively small
fraction of those of the constituent CNTs. Clear structure-property relations
and accurate mechanical models are pressing requirements to bridge this gap. In
this work we analyse the structural evolution and molecular stress transfer in
CNT fibres by performing in-situ synchrotron wide- and small-angle X-ray
scattering and Raman spectroscopy during tensile deformation. The results show
that CNT fibres can be accurately described as network of bundles that slide
progressively according to the initial orientation distribution function of the
material following a Weibull distribution. This model decouples the effects of
CNT alignment and degree of cooperative loading, as demonstrated for fibres
produced at different draw ratios. It also helps explain the unusually high
toughness (fracture energy) of CNT fibres produced by the direct spinning
method, a key property for impact resistance in structural materials, for
example.",2005.03305v2
2020-12-02,Crystallographic Reconstruction Driven Modified Mechanical Properties in Anisotropic Rhenium Disulfides,"Atomic-scale investigation on mechanical behaviors is highly necessary to
fully understand the fracture mechanics especially of brittle materials, which
are determined by atomic-scale phenomena (e.g., lattice trapping). Here,
exfoliated anisotropic rhenium disulfide (ReS2) flakes are used to investigate
atomic-scale crack propagation depending on the propagation directions. While
the conventional strain-stress curves exhibit a strong anisotropy depending on
the cleavage direction of ReS2, but our experimental results show a reduced
cleavage anisotropy due to the lattice reconstruction in [100] cracking with
high resistance to fracture. In other words, [010] and [110] cracks with low
barriers to cleavage exhibit the ultimate sharpness of the crack tip without
plastic deformation, whereas [100] cracks drive lattice rotation on one side of
the crack, leading to a non-flat grain boundary formation. Finally,
crystallographic reconstruction associated with the high lattice randomness of
two-dimensional materials drives to a modified cleavage tendency, further
indicating the importance of atomic-scale studies for a complete understanding
of the mechanics.",2012.01045v1
2021-03-04,Observation of an Unusual Colossal Anisotropic Magnetoresistance Effect in an Antiferromagnetic Semiconductor,"Searching for novel antiferromagnetic materials with large magnetotransport
response is highly demanded for constructing future spintronic devices with
high stability, fast switching speed, and high density. Here we report a
colossal anisotropic magnetoresistance effect in an antiferromagnetic binary
compound with layered structure rare-earth dichalcogenide EuTe2. The AMR
reaches 40000%, which is 4 orders of magnitude larger than that in conventional
antiferromagnetic alloys. Combined magnetization, resistivity, and theoretical
analysis reveal that the colossal AMR effect is attributed to a novel mechanism
of vector-field tunable band structure, rather than the conventional spin-orbit
coupling mechanism. Moreover, it is revealed that the strong hybridization
between orbitals of Eu-layer with localized spin and Te-layer with itinerant
carriers is extremely important for the large AMR effect. Our results suggest a
new direction towards exploring AFM materials with prominent magnetotransport
properties, which creates an unprecedented opportunity for AFM spintronics
applications.",2103.02818v1
2023-01-17,Comparing Methods of Characterizing Energetic Disorder in Organic Solar Cells,"Energetic disorder has been known for decades to limit the performance of
structurally disordered semiconductors such as amorphous silicon and organic
semiconductors. However, in the past years, high performance organic solar
cells have emerged showing a continuously reduced amount of energetic disorder.
While searching for future high efficiency material systems, it is therefore
important to correctly characterize this energetic disorder. While there are
several techniques in literature, the most common approaches to probe the
density of defect states are using optical excitation as in external quantum
efficiency measurements or sequential filling of the tail states by applying an
external voltage as in admittance spectroscopy. A metanalysis of available
literature as well as our experiments using four characterization techniques on
two material systems reveal that electrical, voltage-dependent measurements
frequently yield higher values of energetic disorder than optical measurements.
With drift-diffusion simulations, we demonstrate that the approaches probe
different energy ranges of the subband-gap density of states. We further
explore the limitations of the techniques and find that extraction of
information from a capacitance-voltage curve can be inhibited by an internal
series resistance. Thereby, we explain the discrepancies between measurements
techniques with sensitivity to different energy ranges and electronic
parameters.",2301.06792v1
2023-06-12,Significant improvement of the lower critical field in Y doped Nb: potential replacement of basic material for the radio-frequency superconducting cavity,"The research of high energy and nuclear physics requires high power
accelerators, and the superconducting radio-frequency (SRF) cavity is regarded
as their engine. Up to now, the widely used practical and effective material
for making the SRF cavity is pure Nb. The key parameter that governs the
efficiency and the accelerating field (E_acc) of a SRF cavity is the lower
critical field Hc1. Here, we report a significant improvement of Hc1 for a new
type of alloy, Nb_{1-x}Y_x fabricated by the arc melting technique.
Experimental investigations with multiple tools including x-ray diffraction,
scanning electron microscopy, resistivity and magnetization are carried out,
showing that the samples have good quality and a 30%-60% enhancement of Hc1.
First principle calculations indicate that this improvement is induced by the
delicate tuning of a Lifshitz transition of a Nb derivative band near the Fermi
energy, which increases the Ginzburg-Landau parameter and Hc1. Our results may
trigger a replacement of the basic material and thus a potential revolution for
manufacturing the SRF cavity.",2306.06915v1
2023-07-18,Observation of giant two-level systems in a granular superconductor,"Disordered thin films are a common choice of material for superconducting,
high impedance circuits used in quantum information or particle detector
physics. A wide selection of materials with different levels of granularity are
available, but, despite low microwave losses being reported for some, the high
degree of disorder always implies the presence of intrinsic defects.
Prominently, quantum circuits are prone to interact with two-level systems
(TLS), typically originating from solid state defects in the dielectric parts
of the circuit, like surface oxides or tunneling barriers. We present an
experimental investigation of TLS in granular aluminum thin films under applied
mechanical strain and electric fields. The analysis reveals a class of strongly
coupled TLS having electric dipole moments up to 30 eA, an order of magnitude
larger than dipole moments commonly reported for solid state defects. Notably,
these large dipole moments appear more often in films with a higher
resistivity. Our observations shed new light on granular superconductors and
may have implications for their usage as a quantum circuit material.",2307.09078v2
2024-03-01,First-principles Investigation of Thermodynamic Properties of CrNbO4 and CrTaO4,"In the present study, the DFT+U method was employed to predict the
thermodynamic properties of Cr2O3, Nb2O5, and Ta2O5. Results were benchmarked
with experimental data showing high accuracy, except for the negative thermal
expansion (NTE) of Nb2O5, which is attributed to its polymorphic complexity.
Additionally, we extended our analysis to rutile-type oxides CrNbO4 and CrTaO4,
examining their entropy and heat capacity at finite temperatures. CrNbO4
displayed slightly higher entropy and heat capacity at high temperatures. The
mean linear thermal expansion coefficients for CrNbO4 and CrTaO4 from 500 K to
2000 K were predicted to be 6.00*10-6/K and 13.49*10-6/K, respectively,
corroborating with DFT predictions and experimental evidence. Our research
highlights the precision of the DFT+U and phonon methods in predicting the
thermodynamic properties of oxide materials, offering insights into the design
of corrosion-resistant materials.",2403.00705v1
2017-03-05,Response to Comment on 'Spin-Orbit Logic with Magnetoelectric Nodes: A Scalable Charge Mediated Nonvolatile Spintronic Logic' (arXiv:1607.06690),"In this technical note, we address the comments on the energy estimates for
Magnetoelectric Spin-orbit (MESO) Logic, a new logic device proposed by the
authors. We provide an analytical derivation of the switching energy, and
support it with time-domain circuit simulations using a self-consistent
ferroelectric (FE) compact model. While the energy to charge a capacitor is
dissipated in the interconnect and transistor resistance, we note that the
energy to switch a capacitor and a FE is independent of the interconnect
resistance value to the first order. Also device design can mitigate the
parasitic energy losses. We further show the circuit simulations for a sub 10
aJ switching operation of a MESO logic device comprehending: a) Energy stored
in multiferroic; b) Energy dissipation in the resistance of the interconnect,
Ric ; c) Energy dissipation in the inverse spin-orbit coupling (ISOC) spin to
charge converter Risoc; d) Supply, ground resistance, and transistor losses. We
also identify the requirements for the resistivity of the spin-orbit coupling
materials and address the effect of internal resistance of the spin to charge
conversion layer. We provide the material parameter space where MESO (with a
fan-out of 1 and interconnect) achieves sub 10 aJ switching energy with path
for scaling via ferroelectric/magnetoelectric/spin-orbit materials development.",1703.01559v1
2014-11-05,Modeling of High Composition AlGaN Channel HEMTs with Large Threshold Voltage,"We report on the potential of high electron mobility transistors (HEMTs)
consisting of high composition AlGaN channel and barrier layers for power
switching applications. Detailed 2D simulations show that threshold voltages in
excess of 3 V can be achieved through the use of AlGaN channel layers. We also
calculate the two-dimensional electron gas (2DEG) mobility in AlGaN channel
HEMTs and evaluate their power figures of merit as a function of device
operating temperature and Al mole fraction in the channel. Our models show that
power switching transistors with AlGaN channels would have comparable
on-resistance to GaN-channel based transistors for the same operation voltage.
The modeling in this paper shows the potential of high composition AlGaN as a
channel material for future high threshold enhancement mode transistors.",1411.1447v1
2016-11-10,Ultra-high vacuum compatible preparation chain for intermetallic compounds,"We report the development of a versatile material preparation chain for
intermetallic compounds that focuses on the realization of a high-purity growth
environment. The preparation chain comprises of an argon glovebox, an
inductively heated horizontal cold boat furnace, an arc melting furnace, an
inductively heated rod casting furnace, an optically heated floating-zone
furnace, a resistively heated annealing furnace, and an inductively heated
annealing furnace. The cold boat furnace and the arc melting furnace may be
loaded from the glovebox by means of a load-lock permitting to synthesize
compounds starting with air-sensitive elements while handling the constituents
exclusively in an inert gas atmosphere. All furnaces are all-metal sealed,
bakeable, and may be pumped to ultra-high vacuum. We find that the latter
represents an important prerequisite for handling compounds with high vapor
pressure under high-purity argon atmosphere. We illustrate operational aspects
of the preparation chain in terms of the single-crystal growth of the
heavy-fermion compound CeNi2Ge2.",1611.03392v1
2020-08-06,Granular superconductors for high kinetic inductance and low loss quantum devices,"Granular aluminum is a promising material for high kinetic inductance devices
such as qubit circuits. It has the advantage over atomically disordered
materials such as NbN_x, to maintain a high kinetic inductance concomitantly
with a high quality factor. We show that high quality nano-scale granular
aluminum films having a sharp superconducting transition with normal state
resistivity values of the order of 1x10^5 \mu\Omega cm and kinetic inductance
values of the order of 10 nH/sq can be obtained, surpassing state of the art
values. We argue that this is a result of the different nature of the
metal-to-insulator transition, being electronic correlations driven (Mott type)
in the former and disorder driven (Anderson type) in the latter.",2008.02860v1
2023-11-14,A calculation method to estimate thermal conductivity of high entropy ceramic for thermal barrier coatings,"High entropy ceramics are highly promising as next generation thermal barrier
coatings due to their unique disorder structure, which imparts ultra-low
thermal conductivity and good high temperature stability. Unlike traditional
ceramic materials, the thermal resistance in high entropy ceramics
predominantly arises from phonon-disorder scattering rather than phonon-phonon
interactions. In this study, we propose a calculation method based on the
supercell phonon unfolding (SPU) technique to predict the thermal conductivity
of high entropy ceramics, specially focusing on rocksalt oxides structures. Our
prediction method relies on using the reciprocal value of SPU phonon spectra
linewidth as an indicator of phonon lifetime. The obtained results demonstrate
a strong agreement between the predicted thermal conductivities and the
experimental measurements, validating the feasibility of our calculation
method. Furthermore, we extensively investigate and discuss the atomic
relaxation and lattice distortion effects in 5-dopants and 6-dopants rocksalt
structures during the process.",2311.08246v1
2022-04-14,Non-equilibrium Phonon Thermal Resistance at MoS2/Oxide and Graphene/Oxide Interfaces,"Accurate measurements and physical understanding of thermal boundary
resistance (R) of two-dimensional (2D) materials are imperative for effective
thermal management of 2D electronics and photonics. In previous studies, heat
dissipation from 2D material devices was presumed to be dominated by phonon
transport across the interfaces. In this study, we find that in addition to
phonon transport, thermal resistance between non-equilibrium phonons in the 2D
materials could play a critical role too when the 2D material devices are
internally self-heated, either optically or electrically. We accurately measure
R of oxide/MoS2/oxide and oxide/graphene/oxide interfaces for three oxides
(SiO2, HfO2, Al2O3) by differential time-domain thermoreflectance (TDTR). Our
measurements of R across these interfaces with external heating are 2-to-4
times lower than previously reported R of the similar interfaces measured by
Raman thermometry with internal self-heating. Using a simple model, we show
that the observed discrepancy can be explained by an additional internal
thermal resistance (Rint) between non-equilibrium phonons present during Raman
measurements. We subsequently estimate that for MoS2 and graphene, Rint is
about 31 and 22 m2 K/GW, respectively. The values are comparable to the thermal
resistance due to finite phonon transmission across interfaces of 2D materials
and thus cannot be ignored in the design of 2D material devices. Moreover, the
non-equilibrium phonons also lead to a different temperature dependence than
that by phonon transport. As such, our work provides important insights into
physical understanding of heat dissipation in 2D material devices.",2204.06975v1
1996-08-24,Band Structure and Transport Properties of CrO_2,"Local Spin Density Approximation (LSDA) is used to calculate the energy bands
of both the ferromagnetic and paramagnetic phases of metallic CrO_2. The Fermi
level lies in a peak in the paramagnetic density of states, and the
ferromagnetic phase is more stable. As first predicted by Schwarz, the magnetic
moment is 2 \mu_B per Cr atom, with the Fermi level for minority spins lying in
an insulating gap between oxygen p and chromium d states (""half-metallic""
behavior.) The A_1g Raman frequency is predicted to be 587 cm^{-1}. Drude
plasma frequencies are of order 2eV, as seen experimentally by Chase. The
measured resistivity is used to find the electron mean-free path l, which is
only a few angstroms at 600K, but nevertheless, resistivity continues to rise
as temperature increases. This puts CrO_2 into the category of ""bad metals"" in
common with the high T_c superconductors, the high T metallic phase of VO_2,
and the ferromagnet SrRuO_3. In common with both SrRuO_3 and Sr_2RuO_4, the
measured specific heat \gamma is higher than band theory by a renormalization
factor close to 4.",9608006v1
2013-01-13,A new lower limit for the bond breaking strains of defect-free carbon nanotubes: Tight binding MD simulation study,"The Order (N) Tight Binding Molecular Dynamics (TBMD) algorithms applied to
simulate the tensile elongations of short (2-2.5 nm) armchair and zigzag Single
Walled Carbon Nanotubes (SWCNTs) without bond breakings or defect formation.
Simulations are repeated at high temperatures. We fix the lower limit of
breaking strains to short SWCNTs without bond breaking or 5-7 defects
formation. At room temperature, the simulated (4,4) SWCNT is able to carry the
strain up to 130% of the relaxed tube length without bond breaking or 5-7
defects formation. This value is 127% for (11,0) SWCNT, 125% for (17,0) SWCNT,
123% for (10,10) SWCNT. In defect free, short nanotubes as the nanotube's
radius increase the bond-breakings occur at lower strain values regardless of
their chirality. This is true when we heat the tubes to higher temperatures.
Bond breaking strain values, tensile strength, Young's modulus of the SWCNTs
are obtained as functions of temperature. Defect free zigzag nanotubes exhibit
higher tensile strength than armchaired ones. Young's modulus of defect free
individual singlewall nanotubes is found to be in the range of 0.400 TPa within
the elastic limit. At room temperature and experimentally realizable strain
values, thinner tubes are more resistant to bond breaking and zigzag tubes over
armchair ones. At high temperatures although the resistance to strain drops the
same trend still holds. We observe a slight decrease of the tensile strength
with increasing temperatures. The same trend is also observed in the Young's
modulus. Results are important in determining a true breaking strains of
SWCNTs.",1301.2786v1
2013-01-28,"Structural disorder, magnetism, and electrical and thermoelectric properties of pyrochlore Nd2Ru2O7","Polycrystalline Nd2Ru2O7 samples have been prepared and examined using a
combination of structural, magnetic, and electrical and thermal transport
studies. Analysis of synchrotron X-ray and neutron diffraction patterns
suggests some site disorder on the A-site in the pyrochlore sublattice: Ru
substitutes on the Nd-site up to 7.0(3)%, regardless of the different
preparative conditions explored. Intrinsic magnetic and electrical transport
properties have been measured. Ru 4d spins order antiferromagnetically at 143 K
as seen both in susceptibility and specific heat, and there is a corresponding
change in the electrical resistivity behaviour. A second antiferromagnetic
ordering transition seen below 10 K is attributed to ordering of Nd 4f spins.
Nd2Ru2O7 is an electrical insulator, and this behaviour is believed to be
independent of the Ru-antisite disorder on the Nd site. The electrical
properties of Nd2Ru2O7 are presented in the light of data published on all
A2Ru2O7 pyrochlores, and we emphasize the special structural role that Bi3+
ions on the A-site play in driving metallic behaviour. High-temperature
thermoelectric properties have also been measured. When considered in the
context of known thermoelectric materials with useful figures-of-merit, it is
clear that Nd2Ru2O7 has excessively high electrical resistivity which prevents
it from being an effective thermoelectric. A method for screening candidate
thermoelectrics is suggested.",1301.6661v1
2015-01-06,Coexistence of Electron-Glass Phase and Persistent Photoconductivity in GeSbTe Compounds,"It is demonstrated that persistent-photoconductivity (PPC), well-studied in
lightly-doped semiconductors, is observable in GeSbTe compounds using infrared
excitation at cryogenic temperatures. The low level of energy-flux necessary to
induce an appreciable effect seems surprising given the high
carrier-concentration n of these ternary alloys. On the other hand, their high
density of carriers makes GeSbTe films favorable candidates for exhibiting
intrinsic electron-glass effects with long relaxation times. These are indeed
observed in GeSbTe thin-films that are Anderson-localized. In particular, a
memory-dip is observed in samples with sheet resistances larger than app. 100
kOhms at T=4K with similar characteristics as in other systems that exhibit
intrinsic electron-glass effects. Persistent-photoconductivity however is
observable in GeSbTe films even for sheet resistances of the order of 1 kOhm,
well below the range of disorder required for observing electron-glass effects.
These two non-equilibrium phenomena, PPC and electron-glass, are shown to be of
different nature in terms of other aspects as well. In particular, their
relaxation dynamics is qualitatively different; the excess conductance dG/G
associated with PPC decays with time as a stretched exponential whereas a
logarithmic relaxation law characterizes dG(t) of all electron-glasses studied
to date. Surprisingly, the magnitude of the memory-dip is enhanced when the
system is in the PPC state. This counter-intuitive result may be related to the
compositional disorder in these materials extending over mesoscopic scales.
Evidence in support of this scenario is presented and discussed.",1501.01163v2
2018-11-05,Outstanding Radiation Resistance of Tungsten-based High Entropy Alloys,"A novel W-based refractory high entropy alloy with outstanding radiation
resistance has been developed. The alloy was grown as thin films showing a
bimodal grain size distribution in the nanocrystalline and ultrafine regimes
and a unique 4 nm lamella-like structure revealed by atom probe tomography
(APT). Transmission electron microscopy (TEM) and X-ray diffraction show an
underlying body-centered cubic crystalline structure with certain black spots
appearing after thermal annealing at elevated temperatures. Thorough analysis
based on TEM and APT correlated the black spots with second phase particles
rich in Cr and V. After both in situ and ex situ irradiation, these
precipitates evolve to quasi-spherical particles with no sign of
irradiation-created dislocation loops even after 8 dpa at either room
temperature or 1073 K. Furthermore, nanomechanical testing shows a large
hardness of 14 GPa in the as-deposited samples, with a slight increase after
thermal annealing and almost negligible irradiation hardening. Theoretical
modeling based on ab initio methodologies combined with Monte Carlo techniques
predicts the formation of Cr and V rich second phase particles and points at
equal mobilities of point defects as the origin of the exceptional radiation
tolerance. The fact that these alloys are suitable for bulk production coupled
with the exceptional radiation and mechanical properties makes them ideal
structural materials for applications requiring extreme conditions.",1811.01915v1
2017-04-05,Cubic lead perovskite PbMoO3 with anomalous metallic behavior,"A previously unreported Pb-based perovskite PbMoO$_3$ is obtained by
high-pressure and high-temperature synthesis. This material crystallizes in the
$Pm\bar{3}m$ cubic structure at room temperature, making it distinct from
typical Pb-based perovskite oxides with a structural distortion. PbMoO$_3$
exhibits a metallic behavior down to 0.1 K with an unusual $T$-sub linear
dependence of the electrical resistivity. Moreover, a large specific heat is
observed at low temperatures accompanied by a peak in $C_P/T^3$ around 10 K, in
marked contrast to the isostructural metallic system SrMoO$_3$. These transport
and thermal properties for PbMoO$_3$, taking into account anomalously large Pb
atomic displacements detected through diffraction experiments, are attributed
to a low-energy vibrational mode, associated with incoherent off-centering of
lone pair Pb$^{2+}$ cations. We discuss the unusual behavior of the electrical
resistivity in terms of a polaron-like conduction, mediated by the strong
coupling between conduction electrons and optical phonons of the local
low-energy vibrational mode.",1704.01270v1
2018-12-18,Hidden kagome-lattice picture and origin of high conductivity in delafossite PtCoO$_2$,"We study the electronic structure of delafossite PtCoO$_2$ to elucidate its
extremely small resistivity and high mobility. The band exhibits steep
dispersion near the Fermi level despite the fact that it is formed mainly by Pt
$d$ orbitals that are typically localized. We propose a picture based on two
hidden kagome-lattice-like electronic structure: one originating from Pt
$s+p_x/p_y$ orbitals, and the other from Pt $d_{3z^2-r^2}+d_{xy}/d_{x^2-y^2}$
orbitals, each placed on the bonds of the triangular lattice. In particular, we
find that the underlying Pt $s+p_x/p_y$ bands actually determine the steepness
of the original dispersion, so that the large Fermi velocity can be attributed
to the large width of the Pt $s+p_x/p_y$ band. More importantly, the
kagome-like electronic structure gives rise to ""orbital-momentum locking"" on
the Fermi surface, which reduces the electron scattering by impurities. We
conclude that the combination of the large Fermi velocity and the
orbital-momentum locking is likely to be the origin of the extremely small
resistivity in PtCoO$_2$.",1812.07213v2
2019-10-29,Multi-frequency Shubnikov-de Haas oscillations in topological semimetal Pt$_2$HgSe$_3$,"Monolayer jacutingaite (Pt$_2$HgSe$_3$) has been recently identified as a
candidate quantum spin Hall system with a 0.5 eV band gap, but no transport
measurements have been performed so far on this material, neither in monolayer
nor in the bulk. By using a dedicated high-pressure technique, we grow crystals
enabling the exfoliation of 50-100 nm thick layers and the realization of
devices for controlled transport experiments. Magnetoresistance measurements
indicate that jacutingaite is a semimetal, exhibiting Shubnikov-de Haas (SdH)
resistance oscillations with a multi-frequency spectrum. We adapt the
Lifshitz-Kosevich formula to analyze quantitatively the SdH resistance
oscillations in the presence of multiple frequencies, and find that the
experimental observations are overall reproduced well by band structure
ab-initio calculations for bulk jacutingaite. Together with the relatively high
electron mobility extracted from the experiments ($\approx 2000$ cm$^2$/Vs,
comparable to what is observed in WTe$_2$ crystals of the same thickness), our
results indicate that monolayer jacutingaite should provide an excellent
platform to investigate transport in 2D quantum spin Hall systems.",1910.13228v2
2020-10-11,Observation of Josephson-like tunneling junction characteristics and positive magnetoresistance in Oxygen deficient Nickelate films of $Nd_{0.8}Sr_{0.2}NiO_{3-δ}$,"Nickelate films have recently attracted broad attention due to the
observation of superconductivity in the infinite layer phase of
$Nd_{0.8}Sr_{0.2}NiO_2$ (obtained by reducing Sr doped $NdNiO_3$ films) and
their similarity to the cuprates high temperature superconductors. Here we
report on the observation of a new type of transport in oxygen poor
$Nd_{0.8}Sr_{0.2}NiO_{3-\delta}$ films. At high temperatures, variable range
hopping is observed while at low temperatures a novel tunneling behavior is
found where Josephson-like tunneling junction characteristic with serial
resistance is revealed. We attribute this phenomenon to coupling between
superconductive (S) surfaces of the grains in our Oxygen poor films via the
insulating (I) grain boundaries, which yields SIS junctions in series with the
normal (N) resistance of the grains themselves. The similarity of the observed
conductance spectra to tunneling junction characteristic with Josephson-like
current is striking, and seems to support the existence of superconductivity in
our samples.",2010.05277v2
2021-04-04,Mesoporous silica nanoparticles containing silver as novel antimycobacterial agents against Mycobacterium tuberculosis,"Tuberculosis remains today a major public health issue with a total of 9
million new cases and 2 million deaths annually. The lack of an effective
vaccine and the increasing emergence of new strains of Mycobacterium
tuberculosis (Mtb) highly resistant to antibiotics, anticipate a complicated
scenario in the near future. The use of nanoparticles features as an
alternative to antibiotics in tackling this problem due to their potential
effectiveness in resistant bacterial strains. In this context, silver
nanoparticles have demonstrated high bactericidal efficacy, although their use
is limited by their relatively high toxicity, which calls for the design of
nanocarriers that allow silver based nanoparticles to be safely delivered to
the target cells or tissues. In this work mesoporous silica nanoparticles are
used as carriers of silver based nanoparticles as antimycobacterial agent
against Mtb. Two different synthetic approaches have been used to afford, on
the one hand, a 2D hexagonal mesoporous silica nanosystem which contains silver
bromide nanoparticles distributed all through the silica network and, on the
other hand, a core@shell nanosystem with metallic silver nanoparticles as core
and mesoporous silica shell in a radial mesoporous rearrangement. Both
materials have demonstrated good antimycobacterial capacity in in vitro test
using Mtb, being lower the minimum inhibitory concentration for the nanosystem
which contains silver bromide. Therefore, the interaction of this material with
the mycobacterial cell has been studied by cryo-electron microscopy,
establishing a direct connection between the antimycobactericidal effect
observed and the damage induced in the cell envelope.",2104.01649v1
2021-04-29,The dominance of non-electron-phonon charge carrier interaction in highly-compressed superhydrides,"The primary mechanism governing the emergence of near-room-temperature
superconductivity in superhydrides is widely accepted to be the electron-phonon
interaction. If so, the temperature dependent resistance, R(T), in these
materials should obey the Bloch-Gr\""uneisen equation, where the power-law
exponent, p, should be equal to the exact integer value of p=5. On the other
hand, there is a well-established theoretical result that pure electron-magnon
interaction should be manifested by p=3, and p=2 is the value for pure
electron-electron interaction. Here we aimed to reveal the type of charge
carrier interaction in the layered transition metal dichalcogenides PdTe2,
high-entropy alloy (ScZrNb)0.65[RhPd]0.35, and highly-compressed elemental
boron and superhydrides H3S, LaHx, PrH9 and BaH12 by fitting the temperature
dependent resistance of these materials to the Bloch-Gr\""uneisen equation where
the power-law exponent, p, is a free-fitting parameter. In the result, we
showed that the high-entropy alloy (ScZrNb)0.65[RhPd]0.35 exhibited pure
electron-phonon mediated superconductivity with p = 4.9. Unexpectedly we
revealed that all studied superhydrides exhibit 1.8 < p < 3.2. This implies
that it is unlikely that the electron-phonon interaction is the primary
mechanism for the Cooper pairs formation in highly-compressed superhydrides and
alternative pairing mechanisms, for instance, the electron-magnon, the
electron-polaron, the electron-electron or other, should be considered as the
origin for the emergence of near-room-temperature superconductivity in these
compounds.",2104.14145v3
2021-09-30,Physical and Mechanical Properties of Cu-Fe System Functionally Graded and Multimaterial Structures after the DED,"This paper is devoted to experimental characterisation of linear thermal
expansion coefficient (LTEC) and mechanical characteristics of the laser
deposited Cu-Fe system multilayer functionally graded (FG) structures and
binary Cu-Fe alloys, fabricated from the tin, aluminium, and chromium bronze
with 89-99 wt.% of copper and stainless steel (SS) AISI 316L with 1:1 and 3:1
bronze-to-steel ratio. The best tensile mechanical strength of as-built parts
is demonstrated by the aluminium bronze-stainless steel 1:1 alloy and reaches
876.4 MPa along with low elasticity modulus (11.2 GPa) and 1.684 1/K LTEC.
Contrarily, the worst values of the mechanical characteristics are exhibited by
parts created from the chromium bronze and SS, which failed at 294.0-463.3 MPa
ultimate stress, showed the highest elasticity modulus (up to 42.4 GPa) and
comparatively high average LTEC (up to 1.878 1/K). The aluminium
bronze-stainless steel binary and FG alloys are discussed in the light of
prospective application as the part of gradient materials, created by additive
manufacturing (AM) technologies via the gradient path method and the
alternating layers technique, with expected possibility of application in
aerospace, nuclear, and electronic industry due to advantageous combination of
the antifrictionality, heat conductivity, and oxidation resistance of the
bronze, and the high mechanical strength, corrosion and creep resistance of the
stainless steel.",2110.00103v1
2021-10-26,Temperature induced first order electronic topological transition in $β$-Ag$_2$Se,"$\beta$-Ag$_2$Se is a promising material for room temperature thermoelectric
applications and magneto-resistive sensors. However, no attention was paid
earlier to the hysteresis in the temperature dependence of resistivity
($\rho$($T$)). Here, we show that a broad hysteresis above 35 K is observed not
only in $\rho$($T$), but also in other electronic properties such as Hall
coefficient ($R_H$($T$)), Seebeck coefficient, thermal conductivity and
ultraviolet photoelectron spectra (UPS). We also show that the hysteresis is
not associated with a structural transition. The $\rho$($T$) and $R_H$($T$)
show that $\beta$-Ag$_2$Se is semiconducting above 300 K, but metallicity is
retained below 300 K. While electronic states are absent in the energy range
from the Fermi level ($E_F$) to 0.4 eV below the $E_F$ at 300 K, a distinct
Fermi edge is observed in the UPS at 15 K suggesting that the $\beta$-Ag$_2$Se
undergoes an electronic topological transition from a high temperature
semiconducting state to a low temperature metallic state. Our study reveals
that a constant and moderately high thermoelectric figure of merit ($ZT$) in
the range 300-395 K is observed due to the broad semiconductor to metal
transition in $\beta$-Ag$_2$Se.",2110.13554v1
2021-11-11,Current-induced superconducting anisotropy of Sr$\mathsf{_2}$RuO$\mathsf{_4}$,"In the unconventional superconductor Sr$\mathsf{_2}$RuO$\mathsf{_4}$, unusual
first-order superconducting transition has been observed in the low-temperature
and high-field region, accompanied by a four-fold anisotropy of the in-plane
upper critical magnetic field $H_{c2}$. The origin of such unusual $H_{c2}$
behavior should be closely linked to the debated superconducting symmetry of
this oxide. Here, toward clarification of the unusual $H_{c2}$ behavior, we
performed the resistivity measurements capable of switching in-plane current
directions as well as precisely controlling the field directions. Our results
reveal that resistive $H_{c2}$ under the in-plane current exhibits an
additional two-fold anisotropy. By systematically analyzing $H_{c2}$ data taken
under various current directions, we succeeded in separating the two-fold
$H_{c2}$ component into the one originating from applied current and the other
originating from certain imperfection in the sample. The former component,
attributable to vortex flow effect, is weakened at low temperatures where
$H_{c2}$ is substantially suppressed. The latter component is enhanced in the
first order transition region, possibly reflecting a change in the nature of
the superconducting state under high magnetic field.",2111.06097v1
2022-03-08,Electronic effects on the radiation damage in high-entropy alloys,"High-entropy alloys (HEAs) are exceptional candidates for radiation-resistant
materials due to their complex local chemical environment and slow defect
migration. Despite commonly overlooked, electronic effects on defects evolution
in radiation environments also play a crucial role by dissipating excess energy
through electron-phonon coupling and electronic heat conduction during cascade
events. We present a systematic study on electronic properties in random-solid
solutions (RSS) in four and five principal elements HEAs and their effect on
defect formation, clustering, and recombination. Electronic properties,
including electron-phonon coupling factor, the electronic specific heat, and
the electronic thermal conductivity, are computed within first-principles
calculations. Using the two-temperature molecular dynamics simulations, we show
that the electron-phonon coupling factor and electronic specific heat play a
critical role in Frenkel pairs formation. Specifically, the electron-phonon
coupling factor quickly dissipates the kinetic energy during primary knock-on
atom events via plasmon excitations and is subsequently dissipated via the
free-electrons conduction. We show that these effects are more critical than
the elastic distortion effects produced by the atomic mismatch. Of tremendous
interest, we show that including lighter elements helps to increase the
electron-phonon coupling factor, suggesting the possibility to improve
radiation resistance in HEA through optimal composition.",2203.03779v2
2019-07-29,Linear-$T$ resistivity from low to high temperature: axion-dilaton theories,"The linear-$T$ resistivity is one of the hallmarks of various strange metals
regardless of their microscopic details. Towards understanding this universal
property, the holographic method or gauge/gravity duality has made much
progress. Most holographic models have focused on the low temperature limit,
where the linear-$T$ resistivity has been explained by the infrared geometry.
We extend this analysis to high temperature and identify the conditions for a
robust linear-$T$ resistivity up to high temperature. This extension is
important because, in experiment, the linear-$T$ resistivity is observed in a
large range of temperatures, up to room temperature. In the axion-dilaton
theories we find that, to have a robust linear-$T$ resistivity, the strong
momentum relaxation is a necessary condition, which agrees with the previous
result for the Guber-Rocha model. However, it is not sufficient in the sense
that, among large range of parameters giving a linear-$T$ resistivity in low
temperature limit, only very limited parameters can support the linear-$T$
resistivity up to high temperature even in strong momentum relaxation. We also
show that the incoherent term in the general holographic conductivity formula
or the coupling between the dilaton and Maxwell term is responsible for a
robust linear-$T$ resistivity up to high temperature.",1907.12168v3
2015-01-16,Phonon transmission across Mg2Si/Mg2Si1-xSnx interfaces: A first-principles-based atomistic Green's function study,"Phonon transmission across interfaces of dissimilar materials has been
studied intensively in the recent years by using atomistic simulation tools
owing to its importance in determining the effective thermal conductivity of
nanostructured materials. Atomistic Green's function (AGF) method with
interatomic force constants from the first-principles (FP) calculations has
evolved to be a promising approach to study phonon transmission in many not
well-studied material systems. However, the direct FP calculation for
interatomic force constants becomes infeasible when the system involves atomic
disorder. Mass approximation is usually used, but its validity has not been
tested. In this paper, we employ the higher-order force constant model to
extract harmonic force constants from the FP calculations, which originates
from the virtual crystal approximation but considers the local force-field
difference. As a feasibility demonstration of the proposed method that
integrates higher-order force constant model from the FP calculations with the
AGF, we study the phonon transmission in the Mg2Si/Mg2Si1-xSnx systems. When
integrated with the AGF, the widely-used mass approximation is found to
overpredict phonon transmission across Mg2Si/Mg2Sn interface. The difference
can be attributed to the absence of local strain field-induced scattering in
the mass approximation, which makes the high-frequency phonons less scattered.
The frequency-dependent phonon transmission across an interface between a
crystal and an alloy, which often appears in high efficiency ""nanoparticle in
alloy"" thermoelectric materials, is studied. The interfacial thermal resistance
across Mg2Si/Mg2Si1-xSnx interface is found to be weakly dependent on the
composition of Sn when the composition x is less than 40%, but increases
rapidly when it is larger than 40% due to the transition of high-frequency
phonon DOS in Mg2Si1-xSnx alloys.",1501.04084v1
2020-06-19,Dionysian Hard Sphere Packings are Mechanically Stable at Vanishingly Low Densities,"High strength-to-weight ratio materials can be constructed by either
maximizing strength or minimizing weight. Tensegrity structures and aerogels
take very different paths to achieving high strength-to-weight ratios but both
rely on internal tensile forces. In the absence of tensile forces, removing
material eventually destabilizes a structure. Attempts to maximize the
strength-to-weight ratio with purely repulsive spheres have proceeded by
removing spheres from already stable crystalline structures. This results in a
modestly low density and a strength-to-weight ratio much worse than can be
achieved with tensile materials. Here, we demonstrate the existence of a
packing of hard spheres that has asymptotically zero density and yet maintains
finite strength, thus achieving an unbounded strength-to-weight ratio. This
construction, which we term Dionysian, is the diametric opposite to the
Apollonian sphere packing which completely and stably fills space. We create
tools to evaluate the stability and strength of compressive sphere packings.
Using these we find that our structures have asymptotically finite bulk and
shear moduli and are linearly resistant to every applied deformation, both
internal and external. By demonstrating that there is no lower bound on the
density of stable structures, this work allows for the construction of
arbitrarily lightweight high-strength materials.",2006.11415v3
2020-06-30,Electrothermal Transport Induced Material Re Configuration and Performance Degradation of CVD Grown Monolayer MoS2 Transistors,"We report, for CVD-grown monolayer MoS2, the very first results on temporal
degradation of material and device performance under electrical stress. Both
low and high field regimes of operation are explored at different temperatures,
gate bias and stress cycles. During low field operation, current is found to
saturate after hundreds of seconds of operation with the current decay time
constant being a function of temperature and stress cycle. Current saturation
after several seconds during low field operation occurs when a thermal
equilibrium is established. However, high field operation, especially at low
temperature, leads to impact ionization assisted material and device
degradation. It is found that high field operation at low temperature results
in amorphization of the channel and is verified by device and Kelvin Probe
Force Microscopy (KPFM) analyses. In general, a prolonged room temperature
operation of CVD-grown MoS2 transistors lead to degraded gate control, higher
OFF state current and negative shift in threshold voltage (VT). This is further
verified, through micro-Raman and Photoluminescence spectroscopy, which suggest
that a steady state DC electrical stress leads to the formation of localized
low resistance regions in the channel and a subsequent loss of transistor
characteristics. Our findings unveil unique mechanism by which CVD MoS2
undergoes material degradation under electrical stress and subsequent breakdown
of transistor behavior. Such an understanding of material and device
reliability helps in determining the safe operating regime from device as well
as circuit perspective.",2006.16952v1
2020-08-12,High Rate Hybrid MnO2@CNT Fabric Anode for Li-Ion Batteries: Properties and Lithium Storage Mechanism by In-Situ Synchrotron X-Ray Scattering,"High-performance anodes for rechargeable Li-ion battery are produced by
nanostructuring of the transition metal oxides on a conductive support. Here,
we demonstrate a hybrid material of MnO2 directly grown onto fabrics of carbon
nanotube fibres, which exhibits notable specific capacity over 1100 and 500
mAh/g at a discharge current density of 25 mA/g and 5 A/g, respectively, with
coulombic efficiency of 97.5 %. Combined with 97 % capacity retention after
1500 cycles at a current density of 5 A/g, both capacity and stability are
significantly above literature data. Detailed investigations involving
electrochemical and in situ synchrotron X-ray scattering study reveal that
during galvanostatic cycling, MnO2 undergoes an irreversible phase transition
to LiMnO2, which stores lithium through an intercalation process, followed by
conversion mechanism and pseudocapacitive processes. This mechanism is further
confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy. The
fraction of pseudocapacitive charge storage ranges from 27% to 83%, for current
densities from 25 mA/g to 5 A/g. Firm attachment of the active material to the
built-in current collector makes the electrodes flexible and mechanically
robust, and ensures that the low charge transfer resistance and the high
electrode surface area remain after irreversible phase transition of the active
material and extensive cycling.",2008.05169v1
2021-12-01,Unraveling diffusion kinetics of honeycomb structured Na$_2$Ni$_2$TeO$_6$ as a high-potential and stable electrode for sodium-ion batteries,"In search of the potential cathode materials for sodium-ion batteries and to
understand the diffusion kinetics, we report the detailed analysis of
electrochemical investigation of honeycomb structured Na$_{2}$Ni$_{2}$TeO$_{6}$
material using cyclic voltammetry (CV), electrochemical impedance spectroscopy
(EIS), galvanostatic charge-discharge (GCD) and galvanostatic intermittent
titration technique (GITT). We found the discharge capacities of 82 and 77
mAhg$^{-1}$ at 0.05~C and 0.1~C current rates, respectively, and the
mid-working potential of $\approx$3.9~V at 1~C and high capacity retention of
80\% after 500 cycles at 0.5~C as well as excellent rate capability. The
analysis of CV data at different scan rates reveals the pseudo-capacitive
mechanism of sodium-ion storage. Interestingly, the {\it in-situ} EIS
measurements show a systematic change in the charge-transfer resistance at
different charge/discharge stages as well as after different number of cycles.
The diffusion coefficient extracted using CV, EIS and GITT lies mainly in the
range of 10$^{-10}$ to 10$^{-12}$ cm$^{2}$s$^{-1}$ and the
de-insertion/insertion of Na$^+$-ion concentration during electrochemical
cycling is consistent with the ratio of Ni$^{3+}$/Ni$^{2+}$ valence state
determined by photoemission study. Moreover, the post-cyclic results of
retrieved active material show very stable structure and morphology even after
various charge-discharge cycles. Our detailed electrochemical investigation and
diffusion kinetics studies establish the material as a high working potential
and long life electrode for sodium-ion batteries.",2112.00536v1
2000-04-19,Role of in-plane dissipation in dynamics of Josephson lattice in high-temperature superconductors,"We calculate the flux-flow resistivity of the Josephson vortex lattice in a
layered superconductor taking into account both the inter-plane and in-plane
dissipation channels. We consider the limiting cases of small fields (isolated
vortices) and high fields (overlapping vortices). In the case of the dominating
in-plane dissipation, typical for high-temperature superconductors, the field
dependence of flux-flow resistivity is characterized by {\it three} distinct
regions. As usual, at low fields the flux-flow resistivity grows linearly with
field. When the Josephson vortices start to overlap the flux-flow resistivity
crosses over to the regime of {\it quadratic} field dependence. Finally, at
very high fields the flux-flow resistivity saturates at the c-axis
quasiparticle resistivity. The intermediate quadratic regime indicates dominant
role of the in-plane dissipation mechanism. Shape of the field dependence of
the flux-flow resistivity can be used to extract both components of the
quasiparticle",0004337v2
2014-11-24,Spatial heterogeneity in drug concentrations can facilitate the emergence of resistance to cancer therapy,"Acquired resistance is one of the major barriers to successful cancer
therapy. The development of resistance is commonly attributed to genetic
heterogeneity. However, heterogeneity of drug penetration of the tumor
microenvironment both on the microscopic level within solid tumors as well as
on the macroscopic level across metastases may also contribute to acquired drug
resistance. Here we use mathematical models to investigate the effect of drug
heterogeneity on the probability of escape from treatment and time to
resistance. Specifically we address scenarios with sufficiently efficient
therapies that suppress growth of all preexisting genetic variants in the
compartment with highest drug concentration. To study the joint effect of drug
heterogeneity, growth rate, and evolution of resistance we analyze a multitype
stochastic branching process describing growth of cancer cells in two
compartments with different drug concentration and limited migration between
compartments. We show that resistance is more likely to arise first in the low
drug compartment and from there populate the high drug compartment. Moreover,
we show that only below a threshold rate of cell migration does spatial
heterogeneity accelerate resistance evolution, otherwise deterring drug
resistance with excessively high migration rates. Our results provide new
insights into understanding why cancers tend to quickly become resistant, and
that cell migration and the presence of sanctuary sites with little drug
exposure are essential to this end.",1411.6684v1
2018-10-23,Relativistic resistive magnetohydrodynamic reconnection and plasmoid formation in merging flux tubes,"We apply the general relativistic resistive magnetohydrodynamics code {\tt
BHAC} to perform a 2D study of the formation and evolution of a reconnection
layer in between two merging magnetic flux tubes in Minkowski spacetime.
Small-scale effects in the regime of low resistivity most relevant for dilute
astrophysical plasmas are resolved with very high accuracy due to the extreme
resolutions obtained with adaptive mesh refinement. Numerical convergence in
the highly nonlinear plasmoid-dominated regime is confirmed for a sweep of
resolutions. We employ both uniform resistivity and non-uniform resistivity
based on the local, instantaneous current density. For uniform resistivity we
find Sweet-Parker reconnection, from $\eta = 10^{-2}$ down to $\eta = 10^{-4}$,
for a reference case of magnetisation $\sigma = 3.33$ and plasma-$\beta = 0.1$.
{For uniform resistivity $\eta=5\times10^{-5}$ the tearing mode is recovered,
resulting in the formation of secondary plasmoids. The plasmoid instability
enhances the reconnection rate to $v_{\rm rec} \sim 0.03c$ compared to $v_{\rm
rec} \sim 0.01c$ for $\eta=10^{-4}$.} For non-uniform resistivity with a base
level $\eta_0 = 10^{-4}$ and an enhanced current-dependent resistivity in the
current sheet, we find an increased reconnection rate of $v_{\rm rec} \sim
0.1c$. The influence of the magnetisation $\sigma$ and the plasma-$\beta$ is
analysed for cases with uniform resistivity $\eta=5\times10^{-5}$ and
$\eta=10^{-4}$ in a range $0.5 \leq \sigma \leq 10$ and $0.01 \leq \beta \leq
1$ in regimes that are applicable for black hole accretion disks and jets. The
plasmoid instability is triggered for Lundquist numbers larger than a critical
value of $S_{\rm c} \approx 8000$.",1810.10116v2
2023-11-06,Quantification of spin-charge interconversion in highly resistive sputtered Bi$_x$Se$_{1-x}$ with non-local spin valves,"The development of spin-orbitronic devices, such as magneto-electric
spin-orbit logic devices, calls for materials with a high resistivity and a
high spin-charge interconversion efficiency. One of the most promising
candidates in this regard is sputtered Bi$_x$Se$_{1-x}$. Although there are
several techniques to quantify spin-charge interconversion, to date reported
values for sputtered Bi$_x$Se$_{1-x}$ have often been overestimated due to
spurious effects related to local currents combined with a lack of
understanding of the effect of the interfaces and the use of approximations for
unknown parameters, such as the spin diffusion length. In the present study,
non-local spin valves are used to inject pure spin currents into
Bi$_x$Se$_{1-x}$, allowing us to directly obtain its spin diffusion length as
well as its spin Hall angle, from 10 K up to 300 K. These values, which are
more accurate than those previously reported in sputtered Bi$_x$Se$_{1-x}$,
evidence that the efficiency of this material is not exceptional. Indeed, the
figure of merit for spin-charge interconversion, given by the product of these
two parameters, is slightly under 1 nm. Our work demonstrates the importance of
considering all material parameters and interfaces when quantifying the spin
transport properties of materials with strong spin-orbit coupling.",2311.03598v1
2015-02-10,Dichotomy between the hole and electrons behavior in the multiband FeSe probed by ultra high magnetic fields,"Magnetoresistivity \r{ho}xx and Hall resistivity \r{ho}xy in ultra high
magnetic fields up to 88T are measured down to 0.15K to clarify the multiband
electronic structure in high-quality single crystals of superconducting FeSe.
At low temperatures and high fields we observe quantum oscillations in both
resistivity and Hall effect, confirming the multiband Fermi surface with small
volumes. We propose a novel and independent approach to identify the sign of
corresponding cyclotron orbit in a compensated metal from magnetotransport
measurements. The observed significant differences in the relative amplitudes
of the quantum oscillations between the \r{ho}xx and \r{ho}xy components,
together with the positive sign of the high-field \r{ho}xy , reveal that the
largest pocket should correspond to the hole band. The low-field
magnetotransport data in the normal state suggest that, in addition to one hole
and one almost compensated electron bands, the orthorhombic phase of FeSe
exhibits an additional tiny electron pocket with a high mobility.",1502.02922v1
2023-10-31,Unlocking ultrastrong high-temperature ceramics: Beyond Equimolar Compositions in High Entropy Nitrides,"Traditionally, increasing compositional complexity and chemical diversity of
high entropy alloy ceramics whilst maintaining a stable single-phase solid
solution has been a primary design strategy for the development of new
ceramics. However, only a handful have shown properties that justify the
increased alloying content. Here, we unveil a groundbreaking strategy based on
deviation from conventional equimolar composition towards non-equimolar
composition space, enabling tuning the metastability level of the
supersaturated single-phase solid solution. By employing high-temperature
micromechanical testing of refractory metal-based high entropy nitrides, we
found that the activation of an additional strengthening mechanism upon
metastable phase decomposition propels the yield strength of a non-equimolar
nitride at 1000 C to a staggering 6.9 GPa, that is 40 % higher than the most
robust equimolar nitride. We show that the inherent instability triggers the
decomposition of the solid solution with non-equimolar composition at high
temperatures, inducing strengthening due to the coherency stress of a
spinodally modulated structure, combined with the lattice resistance of the
product solid solution phase. In stark contrast, the strength of equimolar
systems, boasting diverse chemical compositions, declines as a function of
temperature due to the weakening of the lattice resistance and the absence of
other strengthening mechanisms.",2310.20441v2
2010-09-21,Large yield production of high mobility freely suspended graphene electronic devices on a PMGI based organic polymer,"The recent observation of fractional quantum Hall effect in high mobility
suspended graphene devices introduced a new direction in graphene physics, the
field of electron-electron interaction dynamics. However, the technique used
currently for the fabrication of such high mobility devices has several
drawbacks. The most important is that the contact materials available for
electronic devices are limited to only a few metals (Au, Pd, Pt, Cr and Nb)
since only those are not attacked by the reactive acid (BHF) etching
fabrication step. Here we show a new technique which leads to mechanically
stable suspended high mobility graphene devices which is compatible with almost
any type of contact material. The graphene devices prepared on a
polydimethylglutarimide based organic resist show mobilities as high as 600.000
cm^2/Vs at an electron carrier density n = 5.0 10^9 cm^-2 at 77K. This
technique paves the way towards complex suspended graphene based spintronic,
superconducting and other types of devices.",1009.4213v2
2024-02-04,"High temperature internal friction in a Ti-46Al-1Mo-0.2Si intermetallic, comparison with creep behaviour","Advanced g-TiAl based intermetallics Mo-bearing have been developed to obtain
the fine-grained microstructure required for superplastic deformation to be
used during further processing. In the present work we have studied an alloy of
Ti-46Al-1Mo-0.2Si (at%) with two different microstructures, as-cast material
with a coarse grain size above 300 mm, and the hot extruded material exhibiting
a grain size smaller than 20 mm. We have used a mechanical spectrometer
especially developed for high temperature internal friction measurements to
study the defect mobility processes taking place at high temperature. The
internal friction spectra at different frequencies has been studied and
analyzed up to 1360 K in order to characterize the relaxation processes
appearing in this temperature range. A relaxation peak, with a maximum in
between 900 K and 1080 K, depending on the oscillating frequency, has been
attributed to Ti-atoms diffusion by the stress-induced reorientation of
Al-VTi-Al elastic dipoles. The high temperature background in both
microstructural states, as-cast and extruded, has been analyzed, measuring the
apparent activation parameters, in particular the apparent energies of
Ecast(IF) 4.4 +- 0.05 eV and Eext(IF) 4.75 +- 0.05 eV respectively. These
results have been compared to those obtained on the same materials by creep
deformation. We may conclude that the activation parameters obtained by
internal friction analysis, are consistent with the ones measured by creep.
Furthermore, the analysis of the high temperature background allows establish
the difference on creep resistance for both microstructural states",2402.03389v1
1997-03-03,Evidence for Kondo Effect in Au80Co20 Ribbons,"A minimum in resistivity as a function of temperature for an as-quenched
Au80Co20 ribbon prepared by melt-spinning using a wheel surface speed of 20 m
s^{-1} is found at 25 K. No resistivity minimum is found for an as-quenched
ribbon using a wheel surface speed of 60 m s^{-1}, however, upon heat treatment
of this ribbon a resistivity minimum is recovered. The temperature of the
minimum decreases with increasing total time of heat treatment. These
observations are interpretted as evidence for the microstructural control of
the Kondo effect typically found in dilute magnetic alloys in a giant
magnetoresistance granular material.",9703030v1
2006-05-18,Intrinsic inhomogeneities and effects of resistive switching in doped manganites,"The effect of resistive switching in doped manganites being in the
ferromagnetic state has been studied using resistive and magneto-optic methods.
The visualization of magnetic structure of La0.75Sr0.25MnO3-x single crystals,
and its transformation under electric current proposed local superheating of
the material above the Curie temperature, which was supported by numerical
calculation. The obtained results suggest a significant role of
micrometer-scale inhomogeneity of manganites in phase separation, magnetic and
transport properties of the material.",0605457v1
2008-04-29,Resistivity reduction of boron-doped multi-walled carbon nanotubes synthesized from a methanol solution containing a boric acid,"Boron-doped multi-walled carbon nanotubes (MWNTs) were synthesized using a
methanol solution of boric acid as a source material. Accurate measurements of
the electrical resistivity of an individual boron-doped MWNT was performed with
a four-point contact, which was fabricated using an electron beam lithography
technique. The doped boron provides conduction carriers, which reduces the
resistivity of the MWNT.",0804.4514v1
2018-12-20,"Layer-by-layer resistive switching: multi-state functionality due to electric-field-induced healing of ""dead"" layers","Materials exhibiting reversible resistive switching in electrical fields are
highly demanded for functional elements in oxide electronics. In particular,
multilevel switching effects allow for advanced applications like neuromorphic
circuits. Here we report on a structurally driven switching mechanism involving
the so-called `dead layers' of perovskite manganite surfaces. Forming a tunnel
barrier whose thickness can be changed in monolayer steps by electrical fields,
the switching effect exhibits well-defined and robust resistive states.",1812.08563v1
2019-10-29,Improvement in corrosion resistance and biocompatibility of AZ31 magnesium alloy by NH+2 ions,"Magnesium alloys have been considered to be favorable biodegradable metallic
materials used in orthopedic and cardiovascular applications. We introduce NH+2
to the AZ31 Mg alloy surface by ion implantation at the energy of 50 KeV with
doses ranging from 1e16 ions/cm2 to 1e17 ions/cm2 to improve its corrosion
resistance and biocompatibility. Surface morphology, mechanical properties,
corrosion behavior and biocompatibility are studied in the experiments. The
analysis confirms that the modified surface with smoothness and hydrophobicity
significantly improves the corrosion resistance and biocompatibility while
maintaining the mechanical property of the alloy.",1910.13265v1
2020-01-08,UV-laser modification and selective ion-beam etching of amorphous vanadium pentoxide thin films,"We present the results on excimer laser modification and patterning of
amorphous vanadium pentoxide films. Wet positive resist-type and Ar ion-beam
negative resist-type etching techniques were employed to develop UV-modified
films. V2O5 films were found to possess sufficient resistivity compared to
standard electronic materials thus to be promising masks for sub-micron
lithog-raphy",2001.03054v1
2006-06-20,Phase study of oscillatory resistances in high mobility GaAs/AlGaAs devices: Indications of a new class of integral quantum Hall effect,"An experimental study of the high mobility GaAs/AlGaAs system at large-$\nu$
indicates several distinct phase relations between the oscillatory diagonal-
and Hall- resistances, and suggests a new class of integral quantum Hall
effect, which is characterized by ""anti-phase"" Hall- and diagonal- resistance
oscillations.",0606517v1
2017-09-15,Spontaneous surface reserve formation in wicked membranes bestow extreme stretchability,"Soft stretchable materials are key for arising technologies such as
stretchable electronics or batteries, smart textiles, biomedical devices,
tissue engineering and soft robotics. Recent attempts to design such materials,
via e.g. micro-patterning of wavy fibres on soft substrates, polymer
engineering at the molecular level or even kirigami techniques, provide
appealing prospects but suffer drawbacks impacting the material viability:
complexity of manufacturing, fatigue or failure upon cycling, restricted range
of materials or biological incompatibility. Here, we report a universal
strategy to design highly stretchable, self-assembling and fatigue-resistant
synthetic fabrics. Our approach finds its inspiration in the mechanics of
living animal cells that routinely encounter and cope with extreme
deformations, e.g. with the engulfment of large intruders by macrophages,
squeezing and stretching of immune cells in tiny capillaries or
shrinking/swelling of neurons upon osmotic stimuli. All these large instant
deformations are actually mediated and buffered by membrane reserves available
in the form of microvilli, membrane folds or endomembrane that can be recruited
on demand. We synthetically mimicked this behavior by creating nanofibrous
liquid-infused tissues spontaneously forming surface reserves whose unfolding
fuels any imposed shape change. Our process, relying only on geometry,
elasticity and capillarity, allows to endow virtually any material with high
stretchability and reversibility, making it straightforward to implement
additional mechanical, electrical or chemical functions. We illustrate this
with proof-of-concept activable capillary muscles, adaptable slippery liquid
infused porous surfaces and stretchable basic printed electronic circuits.",1709.05228v1
2018-02-26,Trilayer TMDC Heterostructures for MOSFETs and Nanobiosensors,"Two dimensional materials such as Transition Metal Dichalcogenides (TMDC) and
their bi-layer/tri-layer heterostructures have become the focus of intense
research and investigation in recent years due to their promising applications
in electronics and optoelectronics. In this work, we have explored device level
performance of trilayer TMDC heterostructure (MoS2/MX2/MoS2; M=Mo or, W and X=S
or, Se) Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) in the
quantum ballistic regime. Our simulation shows that device 'on' current can be
improved by inserting a WS2 monolayer between two MoS2 monolayers. Application
of biaxial tensile strain reveals a reduction in drain current which can be
attributed to the lowering of carrier effective mass with increased tensile
strain. In addition, it is found that gate underlap geometry improves
electrostatic device performance by improving sub-threshold swing. However,
increase in channel resistance reduces drain current. Besides exploring the
prospect of these materials in device performance, novel trilayer TMDC
heterostructure double gate Field Effect Transistors (FETs) are proposed for
sensing Nano biomolecules as well as for pH sensing. Bottom gate operation
ensures these FETs operating beyond Nernst limit of 59 mV/pH. Simulation
results found in this work reveal that scaling of bottom gate oxide results in
better sensitivity while top oxide scaling exhibits an opposite trend. It is
also found that, for identical operating conditions, proposed TMDC FET pH
sensors show super-Nernst sensitivity indicating these materials as potential
candidates in implementing such sensor. Besides pH sensing, all these materials
show high sensitivity in the sub-threshold region as a channel material in
nanobiosensor while MoS2/WS2/MoS2 FET shows the least sensitivity among them.",1802.09141v1
2018-06-07,Plasmonics in Argentene,"Two-dimensional materials exhibit a fascinating range of electronic and
photonic properties vital for nanophotonics, quantum optics and emerging
quantum information technologies. Merging concepts from the fields of ab initio
materials science and nanophotonics, there is now an opportunity to engineer
new photonic materials whose optical, transport, and scattering properties are
tailored to attain thermodynamic and quantum limits. Here, we present
first-principles calculations predicting that Argentene, a single-crystalline
hexagonal close-packed monolayer of Ag, can dramatically surpass the optical
properties and electrical conductivity of conventional plasmonic materials. In
the low-frequency limit, we show that the scattering rate and resistivity
reduce by a factor of three compared to the bulk three-dimensional metal. Most
importantly, the low scattering rate extends to optical frequencies in sharp
contrast to e.g. graphene, whose scattering rate increase drastically in the
near-infrared range due to optical-phonon scattering. Combined with an
intrinsically high carrier density, this facilitates highly-confined surface
plasmons extending to visible frequencies. We evaluate Argentene across three
distinct figures of merit, spanning the spectrum of typical plasmonic
applications; in each, Argentene outperforms the state-of-the-art. This unique
combination of properties will make Argentene a valuable addition to the
two-dimensional heterostructure toolkit for quantum electronic and photonic
technologies.",1806.02672v1
2023-03-22,Enhanced functional reversibility in lead-free ferroelectric material over long cycle pyroelectric energy conversion,"The ferroelectric material usually exhibits temperature dependent spontaneous
polarization, known as pyroelectricity, which can be used to directly convert
thermal energy to electricity from ambient low-grade waste heat. When utilizing
the structural phase transformations of the material, the conversion capability
can be magnified, consequently the device performance can be strongly boosted
by orders of magnitude. However, common ferroelectric oxides suffer the
mechanical fatigue and functional degradation over cyclic phase
transformations, hindering widespread applications of the energy conversion
device. In this paper, we investigate the mechanical and functional
reversibility of the material by lattice tuning and grain coarsening. We
discover the lead-free compound
Ba(Ce$_{0.005}$Zr$_{0.005}$)Ti$_{0.99}$O3-0.10(Ba$_{0.7}$Ca$_{0.3}$)TiO$_3$
(BCZT-0.10BCT) satisfying the compatibility condition among all present phases
by its lattice parameters, making the phase transformations highly reversible.
We demonstrated that the energy conversion device with the equiaxial coarse
grains exhibits exceptional fatigue-resistance, with stable pyroelectric
current output at 4$\mu$A/cm$^2$ over 3,000 energy conversion cycles. Our work
opens a new way to fabricate high-performance material that advances the
pyroelectric energy conversion for practical application in engineering.",2303.12583v1
2023-04-28,Computational study of III-V direct-gap semiconductors for thermoradiative cell applications,"We investigate the performance of thermoradiative (TR) cells using the III-V
group of semiconductors, which include GaAs, GaSb, InAs, and InP, with the aim
of determining their efficiency and finding the best TR cell materials among
the III-V group. The TR cells generate electricity from thermal radiation, and
their efficiency is influenced by several factors such as the bandgap,
temperature difference, and absorption spectrum. To create a realistic model,
we incorporate sub-bandgap and heat losses in our calculations and utilize
density-functional theory to determine the energy gap and optical properties of
each material. Our findings suggest that the effect of absorptivity on the
material, especially when the sub-bandgap and heat losses are considered, can
decrease the efficiency of TR cells. However, careful treatment of the
absorptivity indicates that not all materials have the same trend of decrease
in the TR cell efficiency when taking the loss mechanisms into account. We
observe that GaSb exhibits the highest power density, while InP demonstrates
the lowest one. Moreover, GaAs and InP exhibit relatively high efficiency
without the sub-bandgap and heat losses, whereas InAs display lower efficiency
without considering the losses, yet exhibit higher resistance to sub-bandgap
and heat losses compared to the other materials, thus effectively becoming the
best TR cell material in the III-V group of semiconductors.",2304.14917v1
2005-12-21,"Poly-MTO, {(CH_3)_{0.92} Re O_3}_\infty, a Conducting Two-Dimensional Organometallic Oxide","Polymeric methyltrioxorhenium, {(CH_{3})_{0.92}ReO_{3}}_{\infty} (poly-MTO),
is the first member of a new class of organometallic hybrids which adopts the
structural pattern and physical properties of classical perovskites in two
dimensions (2D). We demonstrate how the electronic structure of poly-MTO can be
tailored by intercalation of organic donor molecules, such as
tetrathiafulvalene (TTF) or bis-(ethylendithio)-tetrathiafulvalene (BEDT-TTF),
and by the inorganic acceptor SbF$_3$. Integration of donor molecules leads to
a more insulating behavior of poly-MTO, whereas SbF$_3$ insertion does not
cause any significant change in the resistivity. The resistivity data of pure
poly-MTO is remarkably well described by a two-dimensional electron system.
Below 38 K an unusual resistivity behavior, similar to that found in doped
cuprates, is observed: The resistivity initially increases approximately as
$\rho \sim$ ln$(1/T$) before it changes into a $\sqrt{T}$ dependence below 2 K.
As an explanation we suggest a crossover from purely two-dimensional
charge-carrier diffusion within the \{ReO$_2$\}$_{\infty}$ planes at high
temperatures to three-dimensional diffusion at low temperatures in a
disorder-enhanced electron-electron interaction scenario (Altshuler-Aronov
correction). Furthermore, a linear positive magnetoresistance was found in the
insulating regime, which is caused by spatial localization of itinerant
electrons at some of the Re atoms, which formally adopt a $5d^1$ electronic
configuration. X-ray diffraction, IR- and ESR-studies, temperature dependent
magnetization and specific heat measurements in various magnetic fields suggest
that the electronic structure of poly-MTO can safely be approximated by a
purely 2D conductor.",0512544v1
2017-10-10,Clustered vacancies in ZnO: Chemical aspects and consequences on physical properties,"Chemical nature of point defects, their segregation, cluster or complex
formation in ZnO is an important area of investigation. In this report, 1.2 MeV
Ar ion beam is used to incorporate defects in granular ZnO. Evolution of
defective state with irradiation fluence 1 x 10^14 and 1 x 10^16 ions/cm2 has
been monitored using XPS, PL and Raman spectroscopic study. XPS study shows
presence of oxygen vacancies (VO) in the Ar ion irradiated ZnO. Zn(LMM) Auger
spectra clearly identifies transition involving metallic zinc in the irradiated
samples. Intense PL emission from IZn related shallow donor bound excitons
(DBX) is visible in the 10 K spectra for all samples. Although overall PL is
largely reduced with irradiation disorder, DBX intensity is increased for the
highest fluence irradiated sample. Raman study indicates damage in both zinc
and oxygen sub-lattice by energetic ion beam. Representative Raman modes from
defect complexes involving VO, IZn and IO are visible after irradiation with
intermediate fluence. Further increase of fluence shows, to some extent, a
homogenization of disorder. Huge reduction of resistance is also noted for this
sample. Certainly, high irradiation fluence induces a qualitative modification
of the conventional (and highly resistive) grain boundary (GB) structure of
granular ZnO. Low resistive path, involving IZn related shallow donors, across
the GB can be presumed to explain resistance reduction. Open volumes (VZn and
VO) agglomerate more and more with increasing irradiation fluence and finally
get transformed to voids. Results as a whole have been elucidated with a model
which emphasizes possible evolution of new defect microstructure that is
distinctively different from the GB related disorder. Based on the model,
qualitative explanations of commonly observed radiation hardness, colouration
and ferromagnetism in disordered ZnO have been put forward.",1710.03696v1
2021-09-23,Zero Magnetic Field Plateau Phase Transition in Higher Chern Number Quantum Anomalous Hall Insulators,"The plateau-to-plateau transition in quantum Hall effect under high magnetic
fields is a celebrated quantum phase transition between two topological states
through either sweeping the magnetic field or tuning the carrier density. The
recent realization of the quantum anomalous Hall (QAH) insulators with tunable
Chern numbers introduces the channel degree of freedom to the dissipation-free
chiral edge transport and makes the study of the quantum phase transition
between two topological states under zero magnetic field possible. Here, we
synthesized the magnetic topological insulator (TI)/TI penta-layer
heterostructures with different Cr doping concentrations in the middle magnetic
TI layers using molecular beam epitaxy (MBE). By performing transport
measurements, we found a zero magnetic field quantum phase transition between
the C = 1 and C = 2 QAH states. In tuning the transition, the Hall resistance
monotonically decreases from h/e2 to h/2e2, concurrently, the longitudinal
resistance exhibits a maximum at the critical point. Our results show that the
ratio between the Hall resistance and the longitudinal resistance is greater
than 1 at the critical point, which indicates that the original chiral edge
channel from the C = 1 QAH state coexists with the dissipative bulk conduction
channels. Subsequently, these bulk conduction channels appear to self-organize
and form the second chiral edge channel in completing the plateau phase
transition. Our study will motivate further investigations of this novel Chern
number change-induced quantum phase transition and advance the development of
the QAH chiral edge current-based electronic and spintronic devices.",2109.11382v1
2023-07-15,Planar Hall effect and Anisotropic Magnetoresistance in Thin Films of Chiral Antiferromagnet Mn3Sn,"Antiferromagnetic Weyl semimetals with spin chirality offer excellent
platforms to address the Berry phase physics, which manifests prominently in
several of their electro-optical and electro-magnetic responses including as a
large anomalous Hall effect (AHE) and spin Hall conductivity. Here, we report
measurements of magneto-transport in c-axis textured Mn3Sn thin films grown on
the [111] plane of single crystal MgO. At room temperature, these films display
a weak uncompensated magnetic moment of \approx 0.12 \micro_{B}/f.u. in the
basal plane and a longitudinal resistivity (\rho_{xx}) close to \approx 3.8
\micro\Omega.m. A residual resistivity ration (\rho_{xx} (300 K)/\rho_{xx} (2
K)) of \approx 3.92 further indicates the high quality of the films. While at
300 K a weak AHE together with field-linear Hall resistivity (\rho_{xy}) is
observed in magnetic fields (H) applied perpendicular to the Kagome planes, the
temperature (T) dependence of \rho_{xy} shows prominent signatures of three
magnetic phases in the temperature regime of 2 to 300 K. The \rho_{xy} also
derives a non-trivial topological contribution (\r{ho}THE \approx 1n\Omega.m)
in the spin glass phase which appears at T \geq 100 K. Our measurements of
anisotropic magnetoresistance (AMR) and planar Hall effect (PHE) over a wide
H-T phase space reveal the hitherto unseen effects in the three magnetic phases
of Mn3Sn. While the AMR and PHE are negative in the inverse triangular spin
phase (250 K \geq T \geq TN), the helical phase (100 \geq T \geq 250 K) is
devoid of anisotropic in-plane resistivity, and the spin glass phase shows a
sign reversal of AMR with the increasing magnetic field. The origin of this
sign change in AMR/PHE is attributed to the emergence of topologically
protected spin textures like skyrmions where the fictitious effective magnetic
field is estimated to be \approx 4.4 tesla.",2307.07795v1
2024-02-27,"Field, frequency and temperature dependence of the surface resistance of nitrogen diffused niobium superconducting radio frequency cavities","We report the RF performance of several single-cell superconducting
radio-frequency cavities subjected to low temperature heat treatment in
nitrogen environment. The cavities were treated at temperature 120 - 165
$^{\circ}$C for an extended period of time (24 - 48 hours) either in high
vacuum or in a low partial pressure of ultra-pure nitrogen. The improvement in
$Q_0$ with a Q-rise was observed when nitrogen gas was injected at $\sim$300
$^{\circ} $C during the cavity cooldown from 800 $^{\circ}$C and held at 165
$^{\circ}$C, without any degradation in accelerating gradient over the baseline
performance. The treatment was applied to several elliptical cavities with
frequency ranging from 0.75 GHz to 3.0 GHz, showing an improved quality factor
as a result of low temperature nitrogen treatments. The Q-rise feature is
similar to that achieved by nitrogen alloying Nb cavities at higher
temperature, followed by material removal by electropolishing. The surface
modification was confirmed by the change in electronic mean free path and tuned
with the temperature and duration of heat treatment. The decrease of the
temperature-dependent surface resistance with increasing RF field, resulting in
a Q-rise, becomes stronger with increasing frequency and decreasing
temperature. The data suggest a crossover frequency of $\sim 0.95$~GHz above
which the Q-rise phenomenon occurs at 2~K. Some of these results can be
explained qualitatively with an existing model of intrinsic field-dependence of
the surface resistance with both equilibrium and nonequilibrium quasiparticle
distribution functions. The change in the Q-slope below 0.95 GHz may result
from masking contribution of trapped magnetic flux to the residual surface
resistance.",2402.17458v3
2010-05-10,Advances in the Development of Micropattern Gaseous Detectors with Resistive Electrodes,"We describe the most recent efforts made by various groups in implementing
resistive electrodes in micropattern gaseous detectors with the aim to combine
in the same design the best features of RPCs (for the example, their robustness
and spark protection property) with the high granularity and thus the good
position resolution offered by microelectronic technology. In the stream of
this activity, we have recently developed two novel detectors with resistive
electrodes: one was based on resistive micromeshes and the second one is a MSGC
with resistive electrodes. We have demonstrated that the resistive meshes are a
convenient construction element for various designs of spark protective
detectors: RPCs type, GEM type and MICROMEGAS type. These new detectors enable
to considerably enhance the RPC and micropattern detectors applications since
they feature not only a high position resolution but also a relatively good
energy resolution (25-30 persent FWHM at 6 keV) and, if necessary, they can
operate in cascaded mode allowing the achievement of a high overall gas gain.
The main conclusion from these studies is that the implementation of resistive
electrodes in micropattern detectors makes them fully spark protected; on this
basis we consider this direction very promising.",1005.1477v1
2020-03-03,Filled Carbon Nanotubes as Anode Materials for Lithium-Ion Batteries,"Downsizing well-established materials to the nanoscale is a key route to
novel functionalities, in particular if different functionalities are merged in
hybrid nanomaterials. Hybrid carbon-based hierarchical nanostructures are
particularly promising for electrochemical energy storage since they combine
benefits of nanosize effects, enhanced electrical conductivity and integrity of
bulk materials. We show that endohedral multiwalled carbon nanotubes (CNT)
encapsulating high-capacity (here: conversion and alloying) electrode materials
have a high potential for use in anode materials for lithium-ion batteries
(LIB). There are two essential characteristics of filled CNT relevant for
application in electrochemical energy storage: (1) rigid hollow cavities of the
CNT provide upper limits for nanoparticles in their inner cavities which are
both separated from the fillings of other CNT and protected against
degradation. In particular, the CNT shells resist strong volume changes of
encapsulates in response to electrochemical cycling, which in conventional
conversion and alloying materials hinders application in energy storage
devices. (2) Carbon mantles ensure electrical contact to the active material as
they are unaffected by potential cracks of the encapsulate and form a stable
conductive network in the electrode compound. Our studies confirm that
encapsulates are electrochemically active and can achieve full theoretical
reversible capacity. The results imply that encapsulating nanostructures inside
CNT can provide a route to new high-performance nanocomposite anode materials
for LIB.",2003.01379v1
2014-10-16,Electron beam induced current in the high injection regime,"Electron beam induced current (EBIC) is a powerful technique which measures
the charge collection efficiency of photovoltaics with sub-micron spatial
resolution. The exciting electron beam results in a high generation rate
density of electron-hole pairs, which may drive the system into nonlinear
regimes. An analytic model is presented which describes the EBIC response when
the {\it total} electron-hole pair generation rate exceeds the rate at which
carriers are extracted by the photovoltaic cell, and charge accumulation and
screening occur. The model provides a simple estimate of the onset of the high
injection regime in terms of the material resistivity and thickness, and
provides a straightforward way to predict the EBIC lineshape in the high
injection regime. The model is verified by comparing its predictions to
numerical simulations in 1 and 2 dimensions. Features of the experimental data,
such as the magnitude and position of maximum collection efficiency versus
electron beam current, are consistent with the 3 dimensional model.",1410.4435v1
2018-04-09,Self-Modulation Doping Effect in the High-Mobility Layered Semiconductor Bi2O2Se,"Recently an air-stable layered semiconductor Bi2O2Se was discovered to
exhibit an ultrahigh mobility in transistors fabricated with its thin layers.
In this work, we explored the mechanism that induces the high mobility and
distinguishes Bi2O2Se from other semiconductors. We found that the electron
donor states lie above the lowest conduction band. Thus, electrons get
spontaneously ionized from donor sites (e.g., Se vacancies) without involving
the thermal activation, different from the donor ionization in conventional
semiconductors. Consequently, the resistance decreases as reducing the
temperature as observed in our measurement, which is similar to a metal but
contrasts to a usual semiconductor. Furthermore, the electron conduction
channels locate spatially away from ionized donor defects (Se vacancies) in
different van der Waals layers. Such a spatial separation can strongly suppress
the scattering caused by donor sites and subsequently increase the electron
mobility, especially at the low temperature. We call this high-mobility
mechanism self-modulation doping, i.e. the modulation doping spontaneously
happening in a single-phase material without requiring a heterojunction. Our
work paves a way to design novel high-mobility semiconductors with layered
materials.",1804.03186v1
2019-05-21,Persistent antiferromagnetic order in heavily overdoped Ca$_{1-x}$La$_x$FeAs$_2$,"In the Ca$_{1-x}$La$_x$FeAs$_2$ (112) family of pnictide superconductors, we
have investigated a highly overdoped composition (x = 0.56), prepared by
high-pressure, high-temperature synthesis. Magnetic measurements show an
antiferromagnetic transition at TN = 120K, well above the one at lower doping
(0.15 < x < 0.27). Below the onset of long-range magnetic order at TN, the
electrical resistivity is strongly reduced and is dominated by
electron-electron interactions, as evident from its temperature dependence. The
Seebeck coefficient shows a clear metallic behavior as in narrow band
conductors. The temperature dependence of the Hall coefficient and the
violation of Kohler's rule agree with the multiband character of the material.
No superconductivity was observed down to 1.8 K. The success of the
high-pressure synthesis encourages further investigations of the so far only
partially explored phase diagram in this family of Iron-based high temperature
superconductors.",1905.08640v1
2019-09-10,"Low temperature deformation of MoSi$_2$ and the effect of Ta, Nb and Al as alloying elements","Molybdenum disilicide (MoSi$_2$) is a very promising material for high
temperature structural applications due to its high melting point (2030
{\deg}C), low density, high thermal conductivity and good oxidation resistance.
However, MoSi$_2$ has limited ductility below 900 {\deg}C due to its
anisotropic plastic deformation behaviour and high critical resolved shear
stresses on particular slip systems. Nanoindentation of MoSi$_2$ microalloyed
with aluminium, niobium or tantalum showed that all alloying elements cause a
decrease in hardness. Analysis of surface slip lines indicated the activation
of the additional {1 1 0}<1 1 1> slip system in microalloyed MoSi$_2$, which is
not active below 300 {\deg}C in pure MoSi$_2$. This was confirmed by TEM
dislocation analysis of the indentation plastic zone. Further micropillar
compression experiments comparing pure MoSi$_2$ and the Ta-alloyed sample
enabled the determination of the critical resolved shear stresses of individual
slip systems even in the most brittle [0 0 1] crystal direction.",1909.04707v1
2017-07-06,A General Perspective of Fe-Mn-Al-C Steels,"During the last years, the scientific and industrial community has focused on
the astonishing properties of Fe-Mn-Al-C steels. These high advanced steels
allow high-density reductions about ~15% lighter than conventional steels, high
corrosion resistance, high strength (ultimate tensile strength (UTS) ~1 Gpa)
and at the same time ductilities above 60%. The increase of the tensile or
yield strength and the ductility at the same time is almost a special feature
of this kind of new steels, which makes them so interesting for many
applications such as in the automotive, armor and mining industry. The control
of these properties depends on a complex relationship between the chemical
composition of the steel, the test temperature, the external loads and the
processing parameters of the steel. This review has been conceived to tried to
elucidate these complex relations and gather the most important aspects of
Fe-Mn-Al-C steels developed so far.",1707.01920v2
2022-01-11,Fishtail effect and the vortex phase diagram of high-entropy alloy superconductor,"High-entropy alloy (HEA) is an attracting topic raising in materials science
and condensed matter physics. Although several types of superconductors have
been discovered in HEAs, the critical currents (Jc) of HEA superconductors
remain uncharacterized up to now. Here, we systematically study the
current-carrying ability of (TaNb)0.7(HfZrTi)0.5 HEA at various heat treatment
conditions. We obtained the high upper critical field and large current
carrying ability, which point to optimistic applications. Interestingly, the
fishtail or second peak effect was found for the first time in HEA
superconductors, and the position of the vortex pinning force shows a maximum
at 0.72 of the reduced field, which is quite different from the cuprates and
iron-based high-Tc superconductors. Together with the resistive measurements,
the vortex phase diagram is obtained for HEA superconductor.",2201.03994v1
2023-01-12,Non-centrosymmetric Sr$_{2}$IrO$_{4}$ obtained under High Pressure,"Sr$_{2}$IrO$_{4}$ with strong spin-orbit coupling (SOC) and Hubbard repulsion
(U) hosts Mott insulating states. The similar crystal structure, magnetic and
electronic properties, particularly the $d$-wave gap observed in
Sr$_{2}$IrO$_{4}$ enhanced the analogies to cuprate high-$T_{c}$
superconductor, La$_{2}$CuO$_{4}$. The incomplete analogy was due to the lack
of broken inversion symmetry phases observed in Sr$_{2}$IrO$_{4}$. Here, under
high pressure and high temperature conditions, we report a non-centrosymmetric
Sr$_{2}$IrO$_{4}$. The crystal structure and its noncentrosymmetric character
were determined by single crystal X-ray diffraction and high-resolution
scanning transmission electron microscopy (HR-STEM). The magnetic
characterization confirms the Ir$^{4+}$ with $S$ = 1/2 at low temperature in
Sr$_{2}$IrO$_{4}$ with magnetic ordering occurred at around 86 K, where a
larger moment is observed than the ambient pressure Sr$_{2}$IrO$_{4}$.
Moreover, the resistivity measurement shows three-dimensional Mott
variable-range hopping existed in the system. This non-centrosymmetric
Sr$_{2}$IrO$_{4}$ phase appears to be a unique material to offer further
understanding of high-$T_{c}$ superconductivity.",2301.05282v1
2010-12-31,Processing and study of the composite CdS/Bi-Pb-Sr-Ca-Cu-O,"We have fabricated and characterized samples of the superconducting-
semiconducting Bi-Pb-Sb-Sr-Ca-Cu-O/CdS composite. Nano-size particles of CdS
were deposited and introduced into the porosities of the Bi-Pb-Sb-Sr-Ca-Cu-O
material by the spray pyrolysis technique. The morphology and hollow size in
the porous superconducting material as well as the grain size in CdS and the
morphology of the surface of the composite were obtained by Scanning Electron
Microscopy. We obtained the critical superconducting temperature of both the
Bi-Pb-Sb-Sr-Ca-Cu-O and the Bi-Pb-Sb-Sr-Ca-Cu-O/CdS composite measuring the
resistivity. Both show a metallic behaviour just above the superconducting
transition. For the superconductor alone, resistivity starts falling at Tc,on
sup = 99,9 K and reaches zero at Tc,sup=76,3 K. The behaviour of the composite
is different. The transition starts at Tc,on comp = 65,3 K and reaches zero
resistance at Tc,comp = 56,5 K. This seems to indicate that the semiconductor
penetrates the whole superconducting Bi-Pb-Sb-Sr-Ca-Cu-O sample so that there
is no region of pure superconducting material left. Since the materials do not
actually mix (see text) the behaviour might be attributable to the interface.
Also the resistivity curves present a very interesting feature, i.e., below the
temperature at which the composite attains zero-resistivity, a re-entrant
behaviour manifests itself and a finite resistivity peak appears. It increases
to a certain value to drop back to zero at some temperature below. We comment
further on this feature in the text.",1101.0277v1
2009-02-02,"Single crystals of LnFeAsO1-xFx (Ln=La, Pr, Nd, Sm, Gd) and Ba1-xRbxFe2As2: growth, structure and superconducting properties","A review of our investigations on single crystals of LnFeAsO1-xFx (Ln=La, Pr,
Nd, Sm, Gd) and Ba1-xRbxFe2As2 is presented. A high pressure technique has been
applied for the growth of LnFeAsO1-xFx crystals, while Ba1-xRbxFe2As2 crystals
were grown using quartz ampoule method. Single crystals were used for
electrical transport, structure, magnetic torque and spectroscopic studies.
Investigations of the crystal structure confirmed high structural perfection
and show less than full occupation of the (O, F) position in superconducting
LnFeAsO1-xFx crystals. Resistivity measurements on LnFeAsO1-xFx crystals show a
significant broadening of the transition in high magnetic fields, whereas the
resistive transition in Ba1 xRbxFe2As2 simply shifts to lower temperature.
Critical current density for both compounds is relatively high and exceeds
2x109 A/m2 at 15 K in 7 T. The anisotropy of magnetic penetration depth,
measured on LnFeAsO1-xFx crystals by torque magnetometry is temperature
dependent and apparently larger than the anisotropy of the upper critical
field. Ba1-xRbxFe2As2 crystals are electronically significantly less
anisotropic. Point-Contact Andreev-Reflection spectroscopy indicates the
existence of two energy gaps in LnFeAsO1-xFx. Scanning Tunneling Spectroscopy
reveals in addition to a superconducting gap, also some feature at high energy
(~20 meV).",0902.0224v2
2020-03-20,"Anisotropy of the transport properties of NdFeAs(O,F) thin films grown on vicinal substrates","NdFeAs(O,F) thin films having different fluorine contents were grown on 5
deg. or 10 deg. vicinal cut MgO and CaF2 single crystalline substrates by
molecular beam epitaxy. Structural characterisations by reflection high-energy
electron diffraction and x-ray diffraction confirmed the epitaxial growth of
NdFeAs(O,F). The resistivities of the ab-plane and along the c-axis were
derived from the resistivity measurements in the longitudinal and transversal
directions. The c-axis resistivity was always higher than the ab-plane
resistivity, resulting from the anisotropic electronic structure. The
resistivity anisotropy at 300 K was almost constant in the range of 50-90
irrespective of the F content. On the other hand, the resistivity anisotropy at
56 K showed a strong fluorine dependence: the resistivity anisotropy was over
200 for the films with optimum F contents (superconducting transition
temperature Tc around 50 K), whereas the resistivity anisotropy was around 70
for the films in the under-doped regime (Tc between 35 and 45 K). The mass
anisotropy are the effective masses along the c-axis and on the ab-plane) close
to Tc derived from the anisotropic Ginzburg-Landau approach using the
angular-dependency of the ab-plane resistivity was in the range from 2 to 5. On
the assumption that the square of the mass anisotropy is equal to the
resistivity anisotropy, those values are small compared to the normal state
anisotropy.",2003.09105v1
2017-03-23,Development and characterization of Brassica juncea fruticulosa introgression lines exhibiting resistance to mustard aphid,"Background: Mustard aphid is a major pest of Brassica oilseeds. No source for
aphid resistance is presently available in Brassica juncea . A wild crucifer,
Brassica fruticulosa is known to be resistant to mustard aphid. An artificially
synthesized amphiploid, AD-4 (B. fruticulosa x B. rapa var. brown sarson) was
developed for use as a bridge species to transfer fruticulosa resistance to B.
juncea. Using the selfed backcross we could select a large number of lines with
resistance to mustard aphid. This paper reports cytogenetic stability of
introgression lines, molecular evidence for alien introgression and their
reaction to mustard aphid infestation. Results: Majority of introgression lines
had expected euploid chromosome number(2n= 36), showed normal meiosis and high
pollen grain fertility. Well-distributed and transferable simple-sequence
repeats (SSR) markers for all the 18 B. juncea chromosomes helped to
characterize introgression events. Average proportions of recipient and donor
genome in the substitution lines were 49.72 and 35.06%, respectively. Minimum
alien parent genome presence (27.29%) was observed in the introgression line,
Ad3K-280 . Introgressed genotypes also varied for their resistance responses to
mustard aphid infestations under artificial release conditions for two
continuous seasons. Some of the test genotypes showed consistent resistant
reaction. Conclusions: B.juncea-fruticulosa introgression set may prove to be a
very powerful breeding tool for aphid resistance related QTL/gene discovery and
fine mapping of the desired genes/QTLs to facilitate marker assisted transfer
of identified gene(s) for mustard aphid resistance in the background of
commercial mustard genotypes.",1703.07987v1
2020-09-21,Chaos-induced resistivity in different magnetic configurations,"It is widely believed that magnetic reconnection plays an important role in
various eruptive phenomena of space and astrophysical plasmas. The mechanism of
anomalous resistivity, however, has been an open and unsolved problem. The
chaos-induced resistivity proposed by Yoshida (1998) is one of possible
mechanisms for anomalous resistivity. By use of the test particle simulation,
the present work studies the chaos-induced resistivity for different
configurations of reconnection magnetic fields and its distribution in
different chaos regions of reconnection current sheets. The results show that
the chaos-induced resistivity can be 6-7 orders of magnitude higher than the
classical Spitzer resistivity in the X-type chaos regions and 5 orders of
magnitude in the O-type chaos regions. Moreover, in the X-type chaos regions
the chaos-induced resistivity of the magnetized case is higher by a factor of 2
to 3 times than that of the unmagnetized case, but in the O-type chaos regions
the chaos-induced resistivity of the magnetized case is close to or lower than
that of the unmagnetized case. The present work is helpful to the understanding
of the dynamics of reconnection current sheets, especially of the generation
mechanism of the anomalous resistivity of collisionless reconnection regions.",2009.09745v1
2019-12-10,Temperature and gate effects on contact resistance and mobility in graphene transistors by TLM and Y-function methods,"The metal-graphene contact resistance is one of the major limiting factors
toward the technological exploitation of graphene in electronic devices and
sensors. A high contact resistance can be detrimental to device performance and
spoil the intrinsic great properties of graphene. In this paper, we fabricate
graphene field-effect transistors with different geometries to study the
contact and channel resistance as well as the carrier mobility as a function of
gate voltage and temperature. We apply the transfer length method and the
y-function method showing that the two approaches can complement each other to
evaluate the contact resistance and prevent artifacts in the estimation of the
gate-voltage dependence of the carrier mobility. We find that the gate voltage
modulates the contact and the channel resistance in a similar way but does not
change the carrier mobility. We also show that the raising temperature lowers
the carrier mobility, has negligible effect on the contact resistance, and can
induce a transition from a semiconducting to a metallic behavior of the
graphene sheet resistance, depending on the applied gate voltage. Finally we
show that eliminating the detrimental effects of the contact resistance on the
transistor channel current almost doubles the carrier field-effect mobility and
that a competitive contact resistance an be achieved by the zig-zag shaping of
the Ni contact.",1912.04623v1
2019-12-17,Mitigate Parasitic Resistance in Resistive Crossbar-based Convolutional Neural Networks,"Traditional computing hardware often encounters on-chip memory bottleneck on
large scale Convolution Neural Networks (CNN) applications. With its unique
in-memory computing feature, resistive crossbar-based computing attracts
researchers' attention as a promising solution to the memory bottleneck issue
in von Neumann architectures. However, the parasitic resistances in the
crossbar deviate its behavior from the ideal weighted summation operation. In
large-scale implementations, the impact of parasitic resistances must be
carefully considered and mitigated to ensure circuits' functionality. In this
work, we implemented and simulated CNNs on resistive crossbar circuits with
consideration of parasitic resistances. Moreover, we carried out a new mapping
scheme for high utilization of crossbar arrays on convolution, and a mitigation
algorithm to mitigate parasitic resistances in CNN applications. The mitigation
algorithm considers parasitic resistances as well as data/kernel patterns of
each layer to minimize the computing error in crossbar-based convolutions of
CNNs. We demonstrated the proposed methods with implementations of a 4-layer
CNN on MNIST and ResNet(20, 32, and 56) on CIFAR-10. Simulation results show
the proposed methods well mitigate the parasitic resistances in crossbars. With
our methods, modern CNNs on crossbars can preserve ideal(software) level
classification accuracy with 6-bit ADCs and DACs implementation.",1912.08716v1
2017-03-23,Influence of material parameters on the performance of niobium based superconducting RF cavities,"A detailed thermal analysis of a Niobium (Nb) based superconducting radio
frequency (SRF) cavity in a liquid helium bath is presented, taking into
account the temperature and magnetic field dependence of the surface resistance
and thermal conductivity in the superconducting state of the starting Nb
material (for SRF cavity fabrication) with different impurity levels. The drop
in SRF cavity quality factor (Q_0) in the high acceleration gradient regime
(before ultimate breakdown of the SRF cavity) is studied in details. It is
argued that the high field Q_0-drop in SRF cavity is considerably influenced by
the intrinsic material parameters such as electrical conductivity, and thermal
diffusivity. The detail analysis also shows that the current specification on
the purity of niobium material for SRF cavity fabrication is somewhat over
specified. Niobium material with a relatively low purity can very well serve
the purpose for the accelerators dedicated for spallation neutron source (SNS)
or accelerator driven sub-critical system (ADSS) applications, where the
required accelerating gradient is typically up to 20 MV/m,. This information
will have important implication towards the cost reduction of superconducting
technology based particle accelerators for various applications.",1703.07985v3
2015-01-09,Superconductivity in quasi-one-dimensional Cs2Cr3As3 with large interchain distance,"Since the discovery of high-temperature superconductivity (SC) in
quasi-two-dimensional copper oxides, a few layered compounds, which bear
similarities to the cuprates, have also been found to host unconventional SC.
Our recent observation of SC at 6.1 K in correlated electron material K2Cr3As3
(J. K. Bao et al., arXiv: 1412.0067) represents an obviously different
paradigm, primarily because of its quasi-one-dimensional (Q1D) nature. The new
material is structurally featured by the (Cr3As3)2- double-walled subnano-tubes
composed of face-sharing Cr6/2 (As6/2) octahedron linear chains, which are well
separated by columns of K+ counterions. Later, an isostructural superconducting
Rb2Cr3As3 was synthesized, thus forming a new superconducting family. Here we
report the third member, Cs2Cr3As3, which possesses the largest interchain
distance. SC appears below 2.2 K. Similar to the former two sister compounds,
Cs2Cr3As3 exhibits a non-Fermi liquid behavior with a linear temperature
dependence of resistivity in the normal state, and a high upper critical field
beyond the Pauli limit as well, suggesting common unconventional SC in the Q1D
Cr-based material.",1501.02065v1
2018-03-05,Simulation study of ballistic spin-MOSFET devices with ferromagnetic channels based on some Heusler and oxide compounds,"Newly emerged materials from the family of Heuslers and complex oxides
exhibit finite bandgaps and ferromagnetic behavior with Curie temperatures much
higher than even room temperature. In this work, using the semiclassical
top-of-the-barrier FET model, we explore the operation of a spin-MOSFET that
utilizes such ferromagnetic semiconductors as channel materials, in addition to
ferromagnetic source/drain contacts. Such a device could retain the spin
polarization of injected electrons in the channel, the loss of which limits the
operation of traditional spin transistors with non-ferromagnetic channels. We
examine the operation of four material systems that are currently considered
some of the most prominent known ferromagnetic semiconductors, three
Heusler-type alloys (Mn2CoAl, CrVZrAl, CoVZrAl) and one from the oxide family
(NiFe2O4). We describe their bandstructures by using data from DFT
calculations. We investigate under which conditions high spin polarization and
significant ION/IOFF ratio, two essential requirements for the spin-MOSFET
operation, are both achieved. We show that these particular Heusler channels,
in their bulk form, do not have adequate bandgap to provide high ION/IOFF
ratios, and have small magnetoconductance compared to state-of-the-art devices.
However, with confinement into ultra-narrow sizes down to a few nanometers, and
by engineering their spin dependent contact resistances, they could prove
promising channel materials for the realization of spin-MOSFET transistor
devices that offer combined logic and memory functionalities. Although the main
compounds of interest in this paper are Mn2CoAl, CrVZrAl, CoVZrAl, and NiFe2O4
alone, we expect that the insight we provide is relevant to other classes of
such materials as well.",1803.01789v1
2022-03-14,HDPView: Differentially Private Materialized View for Exploring High Dimensional Relational Data,"How can we explore the unknown properties of high-dimensional sensitive
relational data while preserving privacy? We study how to construct an
explorable privacy-preserving materialized view under differential privacy. No
existing state-of-the-art methods simultaneously satisfy the following
essential properties in data exploration: workload independence, analytical
reliability (i.e., providing error bound for each search query), applicability
to high-dimensional data, and space efficiency. To solve the above issues, we
propose HDPView, which creates a differentially private materialized view by
well-designed recursive bisected partitioning on an original data cube, i.e.,
count tensor. Our method searches for block partitioning to minimize the error
for the counting query, in addition to randomizing the convergence, by choosing
the effective cutting points in a differentially private way, resulting in a
less noisy and compact view. Furthermore, we ensure formal privacy guarantee
and analytical reliability by providing the error bound for arbitrary counting
queries on the materialized views. HDPView has the following desirable
properties: (a) Workload independence, (b) Analytical reliability, (c) Noise
resistance on high-dimensional data, (d) Space efficiency. To demonstrate the
above properties and the suitability for data exploration, we conduct extensive
experiments with eight types of range counting queries on eight real datasets.
HDPView outperforms the state-of-the-art methods in these evaluations.",2203.06791v3
2024-01-23,Integration of High-Tc Superconductors with High Q Factor Oxide Mechanical Resonators,"Micro-mechanical resonators are building blocks of a variety of applications
in basic science and applied electronics. This device technology is mainly
based on well-established and reproducible silicon-based fabrication processes
with outstanding performances in term of mechanical Q factor and sensitivity to
external perturbations. Broadening the functionalities of MEMS by the
integration of functional materials is a key step for both applied and
fundamental science. However, combining functional materials and silicon-based
compounds is challenging. An alternative approach is fabricating MEMS based on
complex heterostructures made of materials inherently showing a variety of
physical properties such as transition metal oxides. Here, we report on the
integration of a high-Tc superconductor YBa2Cu3O7 (YBCO) with high Q factor
micro-bridge resonator made of a single-crystal LaAlO3 (LAO) thin film. LAO
resonators are tensile strained, with a stress of 345 MPa, show Q factor in the
range of tens of thousands, and have low roughness. The topmost YBCO layer
deposited by Pulse Laser Deposition shows a superconducting transition starting
at 90 K with zero resistance below 78 K. This result opens new possibilities
towards the development of advanced transducers, such as bolometers or magnetic
field detectors, as well as basic science experiments in solid state physics,
material science, and quantum opto-mechanics.",2401.12758v1
2004-06-25,Resistance Noise Near to Electrical Breakdown: Steady State of Random Networks as a Function of the Bias,"A short review is presented of a recently developed computational approach
which allows the study of the resistance noise over the full range of bias
values, from the linear regime up to electrical breakdown. Resistance noise is
described in terms of two competing processes in a random resistor network. The
two processes are thermally activated and driven by an electrical bias. In the
linear regime, a scaling relation has been found between the relative variance
of resistance fluctuations and the average resistance. The value of the
critical exponent is significantly higher than that associated with 1/f noise.
In the nonlinear regime, occurring when the bias overcomes the threshold value,
the relative variance of resistance fluctuations scales with the bias. Two
regions can be identified in this regime: a moderate bias region and a
pre-breakdown one. In the first region, the scaling exponent has been found
independent of the values of the model parameters and of the bias conditions. A
strong nonlinearity emerges in the pre-breakdown region which is also
characterized by non-Gaussian noise. The results compare well with measurements
of electrical breakdown in composites and with electromigration experiments in
metallic lines.",0406648v1
2010-11-29,"Contact effects on transport in magnetite, an archetypal correlated transition metal oxide","Multiterminal measurements have typically been employed to examine electronic
properties of strongly correlated electronic materials such as transition metal
oxides without the influence of contact effects. In contrast, in this work we
investigate the interface properties of Fe$_3$O$_4$ with different metals, with
the contact effects providing a window on the physics at work in the correlated
oxide. Contact resistances are determined by means of four-terminal electrical
measurements as a function of source voltage and temperature. Contact
resistances vary systematically with the work function of the electrode metal,
$\phi(M)$, $M=$Cu, Au and Pt, with higher work function yielding lower contact
resistance. This trend and the observation that contact resistances are
directly proportional to the Fe$_3$O$_4$ resistivity are consistent with
modeling the oxide as an effective $p$-type semiconductor with hopping
transport. The jumps in contact resistance values at the bias-driven
insulator-metal transition have a similar trend with $\phi$($M$), consistent
with the transition mechanism of charge gap closure by electric field.",1011.6407v1
2012-10-01,Thermal Contact Resistance Across Nanoscale Silicon Dioxide and Silicon Interface,"Silicon dioxide and silicon (SiO$_{2}$/Si) interface plays a very important
role in semiconductor industry. However, at nanoscale, its interfacial thermal
properties haven't been well understood so far. In this paper, we
systematically study the interfacial thermal resistance (Kapitza resistance) of
a heterojunction composed of amorphous silicon dioxide and crystalline silicon
by using molecular dynamics simulations. Numerical results have shown that
Kapitza resistance at SiO$_{2}$/Si interface depends on the interfacial
coupling strength remarkably. In the weak interfacial coupling limit, Kapitza
resistance depends on both the detailed interfacial structure and the length of
the heterojunction, showing large fluctuation among different samples. In
contrast, it is almost insensitive to the detailed interfacial structure or the
length of the heterojunction in the strong interfacial coupling limit, giving
rise to a nearly constant value around 0.9 $\times10^{-9}$ m$^{2}$KW$^{-1}$ at
room temperature. Moreover, the temperature dependent Kapitza resistance in the
strong interfacial coupling limit has also been examined. Our study provides
useful guidance to the thermal management and heat dissipation across nanoscale
SiO$_{2}$/Si interface, in particular for the design of silicon nanowire based
nano electronics and photonics devices.",1210.0354v1
2013-02-19,Local breakdown of the quantum Hall effect in narrow single layer graphene Hall devices,"We have analyzed the breakdown of the quantum Hall effect in 1 micrometer
wide Hall devices fabricated from an exfoliated monolayer graphene transferred
on SiOx. We have observed that the deviation of the Hall resistance from its
quantized value is weakly dependent on the longitudinal resistivity up to
current density of 5 A/m, where the Hall resistance remains quantized even when
the longitudinal resistance increases monotonously with the current. Then a
collapse in the quantized resistance occurs while longitudinal resistance keeps
its gradual increase. The exponential increase of the conductivity with respect
to the current suggests impurity mediated inter-Landau level scattering as the
mechanism of the breakdown. The results are interpreted as the strong variation
of the breakdown behavior throughout the sample due to the randomly distributed
scattering centers that mediates the breakdown.",1302.4729v1
2016-01-17,Low-resistance GaN tunnel homojunctions with 150 kA/cm^2 current and repeatable negative differential resistance,"We report GaN n++/p++ interband tunnel junctions with repeatable negative
differential resistance and low resistance. Reverse and forward tunneling
current densities were observed to increase as Si and Mg doping concentrations
were increased. Hysteresis-free, bidirectional negative differential resistance
was observed at room temperature from these junctions at a forward voltage of
~1.6-2 V. Thermionic PN junctions with tunnel contact to the p-layer exhibited
forward current density of 150 kA/cm^2 at 7.6 V, with a low series device
resistance of 1 x 10^-5 ohm.cm^2.",1601.04353v2
2017-02-13,Deconstructing temperature gradients across fluid interfaces: the structural origin of the thermal resistance of liquid-vapor interfaces,"The interfacial thermal resistance determines condensation-evaporation
processes and thermal transport across material-fluid interfaces. Despite its
importance in transport processes, the interfacial structure responsible for
the thermal resistance is still unknown. By combining non-equilibrium molecular
dynamics simulations and interfacial analyses that remove the interfacial
thermal fluctuations we show that the thermal resistance of liquid-vapor
interfaces is connected to a low density fluid layer that is adsorbed at the
liquid surface. This thermal resistance layer (TRL) defines the boundary where
the thermal transport mechanism changes from that of gases (ballistic) to that
characteristic of dense liquids, dominated by frequent particle collisions
involving very short mean free paths. We show that the thermal conductance is
proportional to the number of atoms adsorbed in the TRL, and hence we explain
the structural origin of the thermal resistance in liquid-vapor interfaces.",1702.03896v2
2018-03-21,Measuring the thermal conductivity and interfacial thermal resistance of suspended MoS2 using electron beam self-heating technique,"Establishment of a new technique or extension of an existing technique for
thermal and thermoelectric measurements to a more challenging system is an
important task to explore the thermal and thermoelectric properties of various
materials and systems. The bottleneck lies in the challenges in measuring the
thermal contact resistance. In this work, we applied electron beam self-heating
technique to derive the intrinsic thermal conductivity of suspended Molybdenum
Disulfide (MoS2) ribbons and the thermal contact resistance, with which the
interfacial thermal resistance between few-layer MoS2 and Pt electrodes was
calculated. The measured room temperature thermal conductivity of MoS2 is
around 30 W/mK, while the estimated interfacial thermal resistance is around
2*10-6 m2K/W. Our experiments extend a useful branch in application of this
technique for studying thermal properties of suspended layered ribbons and have
potential application in investigating the interfacial thermal resistance of
different 2D heterojunctions.",1803.07757v1
2019-09-16,An experimental proof that resistance-switching memories are not memristors,"It has been suggested that all resistive-switching memory cells are
memristors. The latter are hypothetical, ideal devices whose resistance, as
originally formulated, depends only on the net charge that traverses them.
Recently, an unambiguous test has been proposed [J. Phys. D: Appl. Phys. {\bf
52}, 01LT01 (2019)] to determine whether a given physical system is indeed a
memristor or not. Here, we experimentally apply such a test to both in-house
fabricated Cu-SiO2 and commercially available electrochemical metallization
cells. Our results unambiguously show that electrochemical metallization memory
cells are not memristors. Since the particular resistance-switching memories
employed in our study share similar features with many other memory cells, our
findings refute the claim that all resistance-switching memories are
memristors. They also cast doubts on the existence of ideal memristors as
actual physical devices that can be fabricated experimentally. Our results then
lead us to formulate two memristor impossibility conjectures regarding the
impossibility of building a model of physical resistance-switching memories
based on the memristor model.",1909.07238v2
2014-08-22,"Resistance and lifetime measurements of polymer solar cells using glycerol doped poly[3,4-ethylenedioxythiophene]: poly[styrenesulfonate] hole injection layers","We have performed resistivity measurements of
poly[3,4-ethylenedioxythiophene]: poly[styrenesulfonate] (PEDOT:PSS) films with
varying concentrations of glycerol. Resistivity is seen to decrease
exponentially from roughly 3 ohm-cm for pure PEDOT:PSS to 3x10-2 ohm-cm for 35
mg/cm3 glycerol in PEDOT:PSS. Beyond this concentration adding glycerol does
not significantly change resistivity. Bulk heterojunction polymer solar cells
using these variously doped PEDOT:PSS layers as electrodes were studied to
characterize the effects on efficiency and lifetime. Although our data display
significant scatter, lowering the resistance of the PEDOT:PSS layers results in
lower device resistance and higher efficiency as expected. We also note that
the lifetime of the devices tends to be reduced as the glycerol content of
PEDOT:PSS is increased. Many devices show an initial increase in efficiency
followed by a roughly exponential decay. This effect is explained based on
concomitant changes in the zero bias conductance of the samples under dark
conditions.",1408.5199v2
2017-01-17,Grain Boundary Resistance in Copper Interconnects from an Atomistic Model to a Neural Network,"Orientation effects on the resistivity of copper grain boundaries are studied
systematically with two different atomistic tight binding methods. A
methodology is developed to model the resistivity of grain boundaries using the
Embedded Atom Model, tight binding methods and non-equilibrum Green's functions
(NEGF). The methodology is validated against first principles calculations for
small, ultra-thin body grain boundaries (<5nm) with 6.4% deviation in the
resistivity. A statistical ensemble of 600 large, random structures with grains
is studied. For structures with three grains, it is found that the distribution
of resistivities is close to normal. Finally, a compact model for grain
boundary resistivity is constructed based on a neural network.",1701.04897v3
2015-07-20,Effect of Covalent Functionalisation on Thermal Transport Across Graphene-Polymer Interfaces,"This paper is concerned with the interfacial thermal resistance for polymer
composites reinforced by various covalently functionalised graphene. By using
molecular dynamics simulations, the obtained results show that the covalent
functionalisation in graphene plays a significant role in reducing the
graphene-paraffin interfacial thermal resistance. This reduction is dependent
on the coverage and type of functional groups. Among the various functional
groups, butyl is found to be the most effective in reducing the interfacial
thermal resistance, followed by methyl, phenyl and formyl. The other functional
groups under consideration such as carboxyl, hydroxyl and amines are found to
produce negligible reduction in the interfacial thermal resistance. For
multilayer graphene with a layer number up to four, the interfacial thermal
resistance is insensitive to the layer number. The effects of the different
functional groups and the layer number on the interfacial thermal resistance
are also elaborated using the vibrational density of states of the graphene and
the paraffin matrix. The present findings provide useful guidelines in the
application of functionalised graphene for practical thermal management.",1507.05397v1
2020-12-05,Machine Learning and Data Analytics for Design and Manufacturing of High-Entropy Materials Exhibiting Mechanical or Fatigue Properties of Interest,"This chapter presents an innovative framework for the application of machine
learning and data analytics for the identification of alloys or composites
exhibiting certain desired properties of interest. The main focus is on alloys
and composites with large composition spaces for structural materials. Such
alloys or composites are referred to as high-entropy materials (HEMs) and are
here presented primarily in context of structural applications. For each output
property of interest, the corresponding driving (input) factors are identified.
These input factors may include the material composition, heat treatment,
manufacturing process, microstructure, temperature, strain rate, environment,
or testing mode. The framework assumes the selection of an optimization
technique suitable for the application at hand and the data available.
Physics-based models are presented, such as for predicting the ultimate tensile
strength (UTS) or fatigue resistance. We devise models capable of accounting
for physics-based dependencies. We factor such dependencies into the models as
a priori information. In case that an artificial neural network (ANN) is deemed
suitable for the applications at hand, it is suggested to employ custom kernel
functions consistent with the underlying physics, for the purpose of attaining
tighter coupling, better prediction, and for extracting the most out of the -
usually limited - input data available.",2012.07583v1
2000-11-10,The origin of high transport spin polarization in La$_{0.7}$Sr$_{0.3} $MnO$_{3}$: direct evidence for minority spin states,"Using the point contact Andreev reflection technique, we have carried out a
systematic study of the spin polarization in the colossal magnetoresistive
manganite, La$_{0.7}$Sr$_{0.3}$MnO$_{3}$} (LSMO). Surprisingly, we observed a
significant increase in the current spin polarization with the residual
resistivity. This counterintuitive trend can be understood as a transition from
ballistic to diffusive transport in the contact. Our results strongly suggest
that LSMO does have minority spin states at the Fermi level. However, since its
current spin polarization is much higher than that of the density of states,
this material can mimic the behavior of a true half-metal in transport
experiments. Based on our results we call this material a {\it transport}
half-metal.",0011198v1
2006-05-30,Complex Precipitation Pathways in Multi-Component Alloys,"One usual way to strengthen a metal is to add alloying elements and to
control the size and the density of the precipitates obtained. However,
precipitation in multicomponent alloys can take complex pathways depending on
the relative diffusivity of solute atoms and on the relative driving forces
involved. In Al-Zr-Sc alloys, atomic simulations based on first-principle
calculations combined with various complementary experimental approaches
working at different scales reveal a strongly inhomogeneous structure of the
precipitates: owing to the much faster diffusivity of Sc compared with Zr in
the solid solution, and to the absence of Zr and Sc diffusion inside the
precipitates, the precipitate core is mostly Sc-rich, whereas the external
shell is Zr-rich. This explains previous observations of an enhanced nucleation
rate in Al-Zr-Sc alloys compared with binary Al-Sc alloys, along with much
higher resistance to Ostwald ripening, two features of the utmost importance in
the field of light high-strength materials.",0605738v1
2006-11-06,Coexisting tuneable fractions of glassy and equilibrium long-range-order phases in manganites,"Antiferromagnetic-insulating(AF-I) and the ferromagnetic-metallic(FM-M)
phases coexist in various half-doped manganites over a range of temperature and
magnetic field, and this is often believed to be an essential ingredient to
their colossal magnetoresistence. We present magnetization and resistivity
measurements on Pr(0.5)Ca(0.5)Mn(0.975)Al(0.025)O(3) and Pr(0.5)Sr(0.5)MnO(3)
showing that the fraction of the two coexisting phases at low-temperature in
any specified measuring field H, can be continuously controlled by following
designed protocols traversing field-temperature space; for both materials the
FM-M fraction rises under similar cooling paths. Constant-field temperature
variations however show that the former sample undergoes a 1st order transition
from AF-I to FM-M with decreasing T, while the latter undergoes the reverse
transition. We suggest that the observed path-dependent phase-separated states
result from the low-T equilibrium phase coexisting with supercooled glass-like
high temperature phase, where the low-T equilibrium phases are actually
homogeneous FM-M and AF-I phases respectively for the two materials.",0611152v1
2008-05-27,Colossal electroresistance effect around room temperature in LuFe2O4,"A colossal electroresistance effect is observed around room temperature in a
transition metal oxide LuFe2O4. The measurements of resistance under various
applied voltages as well as the highly nonlinear current-voltage
characteristics reveal that a small electric field is able to drive the
material from the insulating state to a metallic state. The threshold field at
which the insulating-metallic transition occurs, decreases exponentially with
increasing temperature. We interpret this transition as a consequence of the
breakdown of the charge-ordered state triggered by applied electric field,
which is supported by the dramatic dielectric response in a small electric
field. This colossal electroresistance effect as well as the high dielectric
tunability around room temperature in low applied fields makes LuFe2O4 a very
promising material for many applications.",0805.4042v1
2008-07-21,Superconducting and thermal properties of ex-situ Glidcop sheathed multifilamentary MgB2 wires,"In DC and AC practical applications of MgB2 superconducting wires an
important role is represented by the material sheath which has to provide,
among other things, a suitable electrical and thermal stabilization. A way to
obtain a large enough amount of low resistivity material in to the conductor
architecture is to use it as external sheath. In this paper we study ex-situ
multifilamentary MgB2 wires using oxide-dispersion-strengthened copper
(GlidCop) as external sheath in order to reach a good compromise between
critical current density and thermal properties. We prepared three GlidCop
samples differing by the content of dispersed sub-microscopic Al2O3 particles.
We characterized the superconducting and thermal properties and we showed that
the good thermal conductivity together the good mechanical properties and a
reasonable critical current density make of GlidCop composite wire a useful
conductor for applications where high thermal conductivity is request at
temperature above 30K, such as Superconducting-FCL.",0807.3259v1
2012-12-14,Using metallic photonic crystals as visible light sources,"In this paper we study numerically and experimentally the possibility of
using metallic photonic crystals (PCs) of different geometries (log-piles,
direct and inverse opals) as visible light sources. It is found that by tuning
geometrical parameters of a direct opal PC one can achieve substantial
reduction of the emissivity in the infrared along with its increase in the
visible. We take into account disorder of the PC elements in their sizes and
positions, and get quantitative agreement between the numerical and
experimental results. We analyze the influence of known temperature-resistant
refractory host materials necessary for fixing the PC elements, and find that
PC effects become completely destroyed at high temperatures due to the host
absorption. Therefore, creating PC-based visible light sources requires that
low-absorbing refractory materials for embedding medium be found.",1212.3451v1
2013-01-10,Weak antilocalization in topological insulator Bi$_{2}$Te$_{3}$ microflakes,"We have studied the carrier transport in two topological insulator (TI)
Bi$_{2}$Te$_{3}$ microflakes between 0.3 and 10 K and under applied backgate
voltages ($V_{\rm BG}$). Logarithmic temperature dependent resistance
corrections due to the two-dimensional electron-electron interaction effect in
the presence of weak disorder were observed. The extracted Coulomb screening
parameter is negative, which is in accord with the situation of strong
spin-orbit scattering as is inherited in the TI materials. In particular,
positive magnetoresistances (MRs) in the two-dimensional weak-antilocalization
(WAL) effect were measured in low magnetic fields, which can be satisfactorily
described by a multichannel-conduction model. Both at low temperatures of $T <
1$ K and under high positive $V_{\rm BG}$, signatures of the presence of two
coherent conduction channels were observed, as indicated by an increase by a
factor of $\approx$ 2 in the prefactor which characterizes the WAL MR
magnitude. Our results are discussed in terms of the (likely) existence of the
Dirac fermion surface states, in addition to the bulk states, in the
three-dimensional TI Bi$_2$Te$_3$ material.",1301.2023v1
2013-12-12,Niobium Silicon alloys for Kinetic Inductance Detectors,"We are studying the properties of Niobium Silicon amorphous alloys as a
candidate material for the fabrication of highly sensitive Kinetic Inductance
Detectors (KID), optimized for very low optical loads. As in the case of other
composite materials, the NbSi properties can be changed by varying the relative
amounts of its components. Using a NbSi film with T_c around 1 K we have been
able to obtain the first NbSi resonators, observe an optical response and
acquire a spectrum in the band 50 to 300 GHz. The data taken show that this
material has very high kinetic inductance and normal state surface resistivity.
These properties are ideal for the development of KID. More measurements are
planned to further characterize the NbSi alloy and fully investigate its
potential.",1312.3588v1
2014-07-05,Approaching the Limits of Transparency and Conductivity in Graphitic Materials through Lithium Intercalation,"Various bandstructure engineering methods have been studied to improve the
performance of graphitic transparent conductors; however none demonstrated an
increase of optical transmittance in the visible range. Here we measure in situ
optical transmittance spectra and electrical transport properties of
ultrathin-graphite (3-60 graphene layers) simultaneously via electrochemical
lithiation/delithiation. Upon intercalation we observe an increase of both
optical transmittance (up to twofold) and electrical conductivity (up to two
orders of magnitude), strikingly different from other materials. Transmission
as high as 91.7% with a sheet resistance of 3.0 {\Omega} per square is achieved
for 19-layer LiC6, which corresponds to a figure of merit
{\sigma}_dc/{\sigma}_opt = 1400, significantly higher than any other continuous
transparent electrodes. The unconventional modification of ultrathin-graphite
optoelectronic properties is explained by the suppression of interband optical
transitions and a small intraband Drude conductivity near the interband edge.
Our techniques enable the investigation of other aspects of intercalation in
nanostructures.",1407.1416v1
2014-10-02,Absence of the Ordinary and Extraordinary Hall effects scaling in granular ferromagnets at metal-insulator transition,"Universality of the extraordinary Hall effect scaling was tested in granular
three-dimensional Ni-SiO2 films across the metal-insulator transition. Three
types of magnetotransport behavior have been identified: metallic, weakly
insulating and strongly insulating. Scaling between both the ordinary and
extraordinary Hall effects and material resistivity is absent in the weakly
insulating range characterized by logarithmic temperature dependence of
conductivity. The results provide compelling experimental confirmation to
recent models of granular metals predicting transition from logarithmic to
exponential conductivity temperature dependence when inter-granular conductance
drops below the quantum conductance value and loss of Hall effect scaling when
inter-granular conductance is higher than the quantum one. The effect was found
at high temperatures and reflects the granular structure of material rather
than low temperature quantum corrections.",1410.0491v1
2014-11-04,Self-consistent modelling of nonlinear dynamic ESM microscopy in mixed ionic-electronic conductors,"Dynamic Electrochemical Strain Microscopy (ESM) response of mixed
ionic-electronic conductors is analysed in the framework of the Thomas-Fermi
screening theory and Vegard law with accounting of the steric effects. The
emergence of dynamic charge waves and nonlinear deformation of the surface as
result of applying probing voltage is numerically explored. 2D maps of the
strain and concentration distribution across the mixed ionic-electronic
conductor and bias-induced surface displacements for ESM microscopy were
calculated. Obtained numerical results can be of applied to quantify ESM
response of Li-based solid electroytes, materials with resistive switching and
electroactive ferroelectric polymers, which are of potential interest for
flexible and high-density non-volatile memory devices.",1411.0966v1
2015-06-03,Stable room-temperature ferromagnetic phase at the FeRh(100) surface,"Interfaces and low dimensionality are sources of strong modifications of
electronic, structural, and magnetic properties of materials. FeRh alloys are
an excellent example because of the first-order phase transition taking place
at $\sim$400 K from an antiferromagnetic phase at room temperature to a high
temperature ferromagnetic one. It is accompanied by a resistance change and
volume expansion of about 1\%. We have investigated the electronic and magnetic
properties of FeRh(100) epitaxially grown on MgO by combining spectroscopies
characterized by different probing depths, namely X-ray magnetic circular
dichroism and photoelectron spectroscopy. We thus reveal that the symmetry
breaking induced at the Rh-terminated surface stabilizes a surface
ferromagnetic layer involving five planes of Fe and Rh atoms in the nominally
antiferromagnetic phase at room temperature. First-principles calculations
provide a microscopic description of the structural relaxation and the electron
spin-density distribution that fully support the experimental findings.",1508.01777v1
2015-09-10,Three-Dimensional Stateful Material Implication Logic,"Monolithic three-dimensional integration of memory and logic circuits could
dramatically improve performance and energy efficiency of computing systems.
Some conventional and emerging memories are suitable for vertical integration,
including highly scalable metal-oxide resistive switching devices (memristors),
yet integration of logic circuits proves to be much more challenging. Here we
demonstrate memory and logic functionality in a monolithic three-dimensional
circuit by adapting recently proposed memristor-based stateful material
implication logic. Though such logic has been already implemented with a
variety of memory devices, prohibitively large device variability in the most
prospective memristor-based circuits has limited experimental demonstrations to
simple gates and just a few cycles of operations. By developing a
low-temperature, low-variability fabrication process, and modifying the
original circuit to increase its robustness to device imperfections, we
experimentally show, for the first time, reliable multi-cycle multi-gate
material implication logic operation within a three-dimensional stack of
monolithically integrated memristors. The direct data manipulation in three
dimensions enables extremely compact and high-throughput logic-in-memory
computing and, remarkably, presents a viable solution for the Feynman grand
challenge of implementing an 8-bit adder at the nanoscale.",1509.02986v1
2018-01-19,"Superconductivity in potassium-doped 2,2$'$-bipyridine","Organic compounds are always promising candidates of superconductors with
high transition temperatures. We examine this proposal by choosing
2,2$'$-bipyridine solely composed by C, H, and N atoms. The presence of
Meissner effect with a transition temperature of 7.2 K in this material upon
potassium doping is demonstrated by the $dc$ magnetic susceptibility
measurements. The real part of the $ac$ susceptibility exhibits the same
transition temperature as that in $dc$ magnetization, and a sharp peak appeared
in the imaginary part indicates the formation of the weakly linked
superconducting vortex current. The occurence of superconductivity is further
supported by the resistance drop at the transition together with its
suppression by the applied magnetic fields. The superconducting phase is
identified to be K$_3$-2,2$'$-bipyridine from the analysis of Raman scattering
spectra. This work not only opens an encouraging window for finding
superconductivity after optoelectronics in 2,2$'$-bipyridine-based materials
but also offers an example to realize superconductivity from conducting
polymers and their derivatives.",1801.06320v2
2018-05-07,The Role of Grain Boundaries under Long-Time Radiation,"Materials containing a high proportion of grain boundaries offer significant
potential for the development of radiation-resistent structural materials.
However, a proper understanding of the connection between the radiation-induced
microstructural behaviour of grain boundary and its impact at long natural time
scales is still missing. In this letter, point defect absorption at interfaces
is summarised by a jump Robin-type condition at a coarse-grained level, wherein
the role of interface microstructure is effectively taken into account. Then a
concise formula linking the sink strength of a polycrystalline aggregate with
its grain size is introduced, and is well compared with experimental
observation. Based on the derived model, a coarse-grained formulation
incorporating the coupled evolution of grain boundaries and point defects is
proposed, so as to underpin the study of long-time morphological evolution of
grains induced by irradiation. Our simulation results suggest that the presence
of point defect sources within a grain further accelerates its shrinking
process, and radiation tends to trigger the extension of twin boundary
sections.",1805.02360v1
2019-09-19,Low compressible BP$_3$N$_6$,"Using first principles calculation, the structural and mechanical properties
of BP$_3$N$_6$ which adopts an orthorhombic structure with space group Pna2$_1$
(no. 33), were determined at three different pressure values (0, 20 and
42.4~GPa). The nine independent elastic constants meet all necessary and
sufficient conditions for mechanical stability criteria for an orthorhombic
crystal. BP$_3$N$_6$ show strong resistance to volume change hence a potential
low compressible material. The Vicker's hardness of BP$_3$N$_6$ was found to
range between 49-51~GPa for different external pressures imposed on the
crystal. These high values of Vicker's hardness implies that BP$_3$N$_6$ is a
potential superhard material.",1909.08879v2
2014-08-06,Crystal structure and electronic structure of CePt2In7,"We report a corrected crystal structure for the CePt2In7 superconductor,
refined from single crystal x-ray diffraction data. The corrected crystal
structure shows a different Pt-In stacking along the c-direction in this
layered material than was previously reported. In addition, all the atomic
sites are fully occupied with no evidence of atom site mixing, resolving a
discrepancy between the observed high resistivity ratio of the material and the
atomic disorder present in the previous structural model The Ce-Pt distance and
coordination is typical of that seen in all other reported Ce_nM_mIn_3n+2m
compounds. Our band structure calculations based on the correct structure
reveal three bands at the Fermi level that are more three dimensional than
those previously proposed, and Density functional theory (DFT) calculations
show that the new structure has a significantly lower energy.",1408.1246v1
2017-01-30,Pressure-induced superconductivity and topological quantum phase transitions in a quasi-one-dimensional topological insulator: Bi4I4,"Superconductivity and topological quantum states are two frontier fields of
research in modern condensed matter physics. The realization of
superconductivity in topological materials is highly desired, however,
superconductivity in such materials is typically limited to two- or
three-dimensional materials and is far from being thoroughly investigated. In
this work, we boost the electronic properties of the quasi-one-dimensional
topological insulator bismuth iodide \b{eta}-Bi4I4 by applying high pressure.
Superconductivity is observed in \b{eta}-Bi4I4 for pressures where the
temperature dependence of the resistivity changes from a semiconducting-like
behavior to that of a normal metal. The superconducting transition temperature
Tc increases with applied pressure and reaches a maximum value of 6 K at 23
GPa, followed by a slow decrease. Our theoretical calculations suggest the
presence of multiple pressure-induced topological quantum phase transitions as
well as a structural-electronic instability.",1701.08860v1
2019-03-12,Structural and electronic properties of the spin-filter material CrVTiAl with disorder,"The effects of chemical disorder on the transport properties of the
spin-filter material CrVTiAl are investigated experimentally and theoretically.
Synchrotron X-ray diffraction experiments on bulk CrVTiAl and the associated
Rietveld analysis indicate that the crystal structure consists primarily of a
mixture of a partially ordered B2 phase, a fully disordered A2 phase and a
small component of an ordered L2\textsubscript{1} or Y phase. High temperature
resistivity measurements confirm the existence of a band gap. First-principles,
all-electron, self-consistent electronic structure computations show that the
chemically disordered A2 and B2 phases are metallic, while the spin-filter
properties of the ideal Y-type phase are preserved in the presence of
L2\textsubscript{1} disorder. The Hall coefficient is found to decrease with
increasing temperature, similar to the measured increase in the conductivity,
indicating the presence of thermally activated semiconductor-like carriers.",1903.05004v1
2019-01-28,Effect of Bi Substitution on Thermoelectric Properties of SbSe2-based Layered Compounds NdO$_{0.8}$F$_{0.2}$Sb$_{1-x}$Bi$_x$Se$_2$,"Although SbSe2-based layered compounds have been predicted to be
high-performance thermoelectric materials and topological materials, most of
these compounds obtained experimentally have been insulators so far. Here, we
present the effect of Bi substitution on the thermoelectric properties of
SbSe2-based layered compounds NdO0.8F0.2Sb1-xBixSe2 (x = 0-0.4). The room
temperature electrical resistivity is decreased to 8.0 * 10^-5 ohmm for x =
0.4. The electrical power factor is calculated to be 1.4 * 10^-4 W/mK^2 at 660
K, which is in reasonable agreement with combined Jonker and Ioffe analysis.
The room-temperature lattice thermal conductivity of less than 1 W/mK is almost
independent of x, in contrast to the point-defect scattering model for
conventional alloys. The present work provides an avenue for exploring
SbSe2-based insulating and BiSe2-based conducting systems.",1901.09909v1
2020-08-21,An unexplored MBE growth mode reveals new properties of superconducting NbN,"Accessing unexplored conditions in crystal growth often reveals remarkable
surprises and new regimes of physical behavior. In this work, performing
molecular beam epitaxy of the technologically important superconductor NbN at
temperatures greater than 1000$^\circ$C, higher than in the past, is found to
reveal persistent RHEED oscillations throughout the growth, atomically smooth
surfaces, normal metal resistivities as low as 37$\mu\Omega$-cm and
superconducting critical temperatures in excess of 15 K. Most remarkably, a
reversal of the sign of the Hall coefficient is observed as the NbN films are
cooled, and the high material quality allows the first imaging of Abrikosov
vortex lattices in this superconductor.",2008.09596v3
2020-09-25,A Possible Method of Carbon Deposit Mapping on Plasma Facing Components Using Infrared Thermography,"The material eroded from the surface of plasma facing components is
redeposited partly close to high heat flux areas. At these locations, the
deposit is heated by the plasma and the deposition pattern evolves depending on
the operation parameters. The mapping of the deposit is still a matter of
intense scientific activity, especially during the course of experimental
campaigns. A method based on the comparison of surface temperature maps,
obtained in situ by infrared cameras and by theoretical modelling is proposed.
The difference between the two is attributed to the thermal resistance added by
deposited material, and expressed as a deposit thickness. The method benefits
of elaborated imaging techniques such as possibility theory and fuzzy logics.
The results are consistent with deposit maps obtained by visual inspection
during shutdowns.",2010.06374v1
2020-10-29,Nature of native atomic defects in ZrTe$_5$ and their impact on the low-energy electronic structure,"Over the past decades, investigations of the anomalous low-energy electronic
properties of ZrTe$_5$ have reached a wide array of conclusions. An open
question is the growth method's impact on the stoichiometry of ZrTe$_5$
samples, especially given the very small density of states near its chemical
potential. Here we report on high resolution scanning tunneling microscopy and
spectroscopy measurements performed on samples grown via different methods.
Using density functional theory calculations, we identify the most prevalent
types of atomic defects on the surface of ZrTe$_5$, namely Te vacancies and
intercalated Zr atoms. Finally, we precisely quantify their density and outline
their role as ionized defects in the anomalous resistivity of this material.",2010.15513v1
2021-11-17,Anisotropic superconductivity and unusually robust electronic critical field in single crystal La$_{7}$Ir$_{3}$,"Polycrystalline La$_{7}$Ir$_{3}$ is reported to show superconductivity
breaking time-reversal symmetry while also having an isotropic $s$-wave gap.
Single crystals of this noncentrosymmetric superconductor are highly desirable
to understand the nature of the electron pairing mechanism in this system. Here
we report the growth of high-quality single crystals of La$_{7}$Ir$_{3}$ by the
Czochralski method. The structural and superconducting properties of these
large crystals have been investigated using x-rays, magnetization, resistivity
and heat capacity measurements. We observe a clear anisotropy in the lower and
upper critical fields for magnetic fields applied parallel and perpendicular to
the hexagonal $c$ axis. We also report the presence of a robust electronic
critical field, that diverges from the upper critical field derived from heat
capacity, which is the hallmark of surface superconductivity.",2111.09239v2
2022-01-09,Phase field fracture predictions of microscopic bridging behaviour of composite materials,"We investigate the role of microstructural bridging on the fracture toughness
of composite materials. To achieve this, a new computational framework is
presented that integrates phase field fracture and cohesive zone models to
simulate fibre breakage, matrix cracking and fibre-matrix debonding. The
composite microstructure is represented by an embedded cell at the vicinity of
the crack tip, whilst the rest of the sample is modelled as an anisotropic
elastic solid. The model is first validated against experimental data of
transverse matrix cracking from single-notched three-point bending tests. Then,
the model is extended to predict the influence of grain bridging,
brick-and-mortar microstructure and 3D fibre bridging on crack growth
resistance. The results show that these microstructures are very efficient in
enhancing the fracture toughness via fibre-matrix debonding, fibre breakage and
crack deflection. In particular, the 3D fibre bridging effect can increase the
energy dissipated at failure by more than three orders of magnitude, relative
to that of the bulk matrix; well in excess of the predictions obtained from the
rule of mixtures. These results shed light on microscopic bridging mechanisms
and provide a virtual tool for developing high fracture toughness composites.",2201.03066v1
2022-10-30,Linear nonsaturating magnetoresistance in kagome superconductor CsV3Sb5 thin flakes,"Linear nonsaturating magnetoresistance (LMR) represents a class of anomalous
resistivity response to external magnetic field that has been observed in a
variety of materials including but not limited to topological semi-metals,
high-Tc superconductors and materials with charge/spin density wave (CDW/SDW)
orders. Here we report the observation of LMR in layered kagome superconductor
and CDW material CsV3Sb5 thin flakes, as well as the dimensional crossover and
temperature (T) crossover of such LMR. Specifically, in ultrathin CsV3Sb5
crystals, the magnetoresistance (MR) exhibits a crossover from LMR at low T to
quadratic B dependence above the CDW transition temperature; the MR also
exhibits a crossover from LMR to sublinear MR for sample thickness at around
~20 nm at low T. We discuss several possible origins of the LMR and attribute
the effect to two-dimensional (2D) CDW fluctuations. Our results may provide a
new perspective for understanding the interactions between competing orders in
kagome superconductors.",2210.16890v1
2023-08-09,Superionic phase transition of copper(I) sulfide and its implication for purported superconductivity of LK-99,"Lee, Kim, and coworkers have recently claimed room-temperature and
ambient-pressure superconductivity in a copper-doped lead apatite material
named LK-99. However, the polycrystalline material synthesized has a
significant fraction of copper(I) sulfide. Copper(I) sulfide has a known phase
transition at 104 degrees C from an ordered low-temperature phase to a
high-temperature superionic phase. As a result of this phase transition,
copper(I) sulfide exhibits sharp transitions in electrical resistivity and heat
capacity, which are expected to coincide with the temperature-induced
transitions reported for LK-99. This implies that LK-99 must be synthesized
without any copper(I) sulfide to allow unambiguous validation of the
superconducting properties of LK-99.",2308.05222v3
2023-11-15,Strongly pinned skyrmionic bubbles and higher-order nonlinear Hall resistances at the interface of Pt/FeSi bilayer,"Engineering of magnetic heterostructures for spintronic applications has
entered a new phase, driven by the recent discoveries of topological materials
and exfoliated van der Waals materials. Their low-dimensional properties can be
dramatically modulated in designer heterostructures via proximity effects from
adjacent materials, thus enabling the realization of diverse quantum states and
functionalities. Here we investigate spin-orbit coupling (SOC) proximity
effects of Pt on the recently discovered quasi-two-dimensional ferromagnetic
state at FeSi surface. Skyrmionic bubbles (SkBs) are formed as a result of the
enhanced interfacial Dzyloshinskii-Moriya interaction. The strong pinning
effects on the SkBs are evidenced from the significant dispersion in size and
shape of the SkBs and are further identified as a greatly enhanced threshold
current density required for depinning of the SkBs. The robust integrity of the
SkB assembly leads to the emergence of higher-order nonlinear Hall effects in
the high current density regime, which originate from nontrivial Hall effects
due to the noncollinearity of the spin texture, as well as from the
current-induced magnetization dynamics via the augmented spin-orbit torque.",2311.08730v1
2023-11-21,Reliable lift-off patterning of graphene dispersions for humidity sensors,"Dispersion-based graphene materials are promising candidates for various
sensing applications. They offer the advantage of relatively simple and fast
deposition via spin-coating, Langmuir-Blodgett deposition, or inkjet printing.
Film uniformity and reproducibility remain challenging in all of these
deposition methods. Here, we demonstrate, characterize, and successfully apply
a scalable structuring method for graphene dispersions. The method is based on
a standard lift-off process, is simple to implement, and increases the film
uniformity of graphene devices. It is also compatible with standard
semiconductor manufacturing methods. We investigate two different graphene
dispersions via Raman spectroscopy and Atomic Force Microscopy and observe no
degradation of the material properties by the structuring process. Furthermore,
we achieve high uniformity of the structured patterns and homogeneous graphene
flake distribution. Electrical characterizations show reproducible sheet
resistance values correlating with material quantity and uniformity. Finally,
repeatable humidity sensing is demonstrated with van der Pauw devices, with
sensing limits of less than 1% relative humidity.",2311.12650v2
2024-04-10,Optimal Matching of Thermal Vibrations into Carbon Nanotubes,"Carbon nanotubes (CNTs) are promising candidates to improve the thermal
conductivity of nano-composites. The main obstacle to these applications is the
extremely high thermal boundary (Kapitza) resistance between the CNTs and their
matrix. In this theoretical work our goal is to maximize the heat flux through
the CNT by functionalizing the CNT ends. We use a Landauer approach to
calculate and optimize the energy flux from a soft to a hard material in one
dimension through a connecting continuous medium of varying elasticity and
density. The transmission probability of phonons through the system is
calculated both numerically and analytically. We find that over 90% of the
maximum heat flux into CNT is possible for 1nm length of the intermediate
material at room temperature (300K).",2404.06938v1
2010-11-12,Suspension and Measurement of Graphene and Bi2Se3 Atomic Membranes,"Coupling high quality, suspended atomic membranes to specialized electrodes
enables investigation of many novel phenomena, such as spin or Cooper pair
transport in these two dimensional systems. However, many electrode materials
are not stable in acids that are used to dissolve underlying substrates. Here
we present a versatile and powerful multi-level lithographical technique to
suspend atomic membranes, which can be applied to the vast majority of
substrate, membrane and electrode materials. Using this technique, we
fabricated suspended graphene devices with Al electrodes and mobility of 5500
cm^2/Vs. We also demonstrate, for the first time, fabrication and measurement
of a free-standing thin Bi2Se3 membrane, which has low contact resistance to
electrodes and a mobility of >~500 cm^2/Vs.",1011.2837v1
2011-11-04,Dual-gated bilayer graphene hot electron bolometer,"Detection of infrared light is central to diverse applications in security,
medicine, astronomy, materials science, and biology. Often different materials
and detection mechanisms are employed to optimize performance in different
spectral ranges. Graphene is a unique material with strong, nearly
frequency-independent light-matter interaction from far infrared to
ultraviolet, with potential for broadband photonics applications. Moreover,
graphene's small electron-phonon coupling suggests that hot-electron effects
may be exploited at relatively high temperatures for fast and highly sensitive
detectors in which light energy heats only the small-specific-heat electronic
system. Here we demonstrate such a hot-electron bolometer using bilayer
graphene that is dual-gated to create a tunable bandgap and
electron-temperature-dependent conductivity. The measured large electron-phonon
heat resistance is in good agreement with theoretical estimates in magnitude
and temperature dependence, and enables our graphene bolometer operating at a
temperature of 5 K to have a low noise equivalent power (33 fW/Hz1/2). We
employ a pump-probe technique to directly measure the intrinsic speed of our
device, >1 GHz at 10 K.",1111.1202v1
2012-11-08,Structural phase transformations in metallic grain boundaries,"Structural transformations at interfaces are of profound fundamental interest
as complex examples of phase transitions in low-dimensional systems. Despite
decades of extensive research, no compelling evidence exists for structural
transformations in high-angle grain boundaries in elemental systems. Here we
show that the critical impediment to observations of such phase transformations
in atomistic modeling has been rooted in inadequate simulation methodology. The
proposed new methodology allows variations in atomic density inside the grain
boundary and reveals multiple grain boundary phases with different atomic
structures. Reversible first-order transformations between such phases are
observed by varying temperature or injecting point defects into the boundary
region. Due to the presence of multiple metastable phases, grain boundaries can
absorb significant amounts of point defects created inside the material by
processes such as irradiation. We propose a novel mechanism of radiation damage
healing in metals which may guide further improvements in radiation resistance
of metallic materials through grain boundary engineering.",1211.1756v2
2014-10-10,Topological Origin of Fracture Toughening in Complex Solids: the Viewpoint of Rigidity Theory,"In order to design tougher materials, it is crucial to understand the
relationship between their composition and their resistance to fracture. To
this end, we investigate the fracture toughness of usual sodium silicate
glasses (NS) and complex calcium--silicate--hydrates (CSH), the binding phase
of cement. Their atomistic structure is described in the framework of the
topological constraints theory, or rigidity theory. We report an analogous
rigidity transition, driven by pressure in NS and by composition in CSH.
Relying both on simulated and available experimental results, we show that
optimally constrained isostatic systems show improved fracture toughness. The
flexible to stressed--rigid transition is shown to be correlated to a
ductile-to-brittle transition, with a local minimum of the brittleness for
isostatic system. This fracture toughening arises from a reversible molecular
network, allowing optimal stress relaxation and crack blunting behaviors. This
opens the way to the discovery of high-performance materials, designed at the
molecular scale.",1410.2916v1
2015-02-09,Pressure-induced superconductivity in the three-dimensional Dirac semimetal Cd3As2,"The recently discovered Dirac and Weyl semimetals are new members of
topological materials. Starting from them, topological superconductivity may be
achieved, e.g. by carrier doping or applying pressure. Here we report
high-pressure resistance and X-ray diffraction study of the three-dimensional
topological Dirac semimetal Cd3As2. Superconductivity with Tc ~ 2.0 K is
observed at 8.5 GPa. The Tc keeps increasing to about 4.0 K at 21.3 GPa, then
shows a nearly constant pressure dependence up to the highest pressure 50.9
GPa. The X-ray diffraction measurements reveal a structure phase transition
around 3.5 GPa. Our observation of superconductivity in pressurized topological
Dirac semimetal Cd3As2 provides a new candidate for topological superconductor,
as argued in a recent point contact study and a theoretical work.",1502.02509v2
2017-06-19,Electrical and Thermal Transport at the Planckian Bound of Dissipation in the Hydrodynamic Electron Fluid of WP2,"Materials with strongly-correlated electrons exhibit interesting phenomena
such as metal-insulator transitions and high-temperature superconductivity. In
stark contrast to ordinary metals, electron transport in these materials is
thought to resemble the flow of viscous fluids. Despite their differences, it
is predicted that transport in both, conventional and correlated materials, is
fundamentally limited by the uncertainty principle applied to energy
dissipation. Here we discover hydrodynamic electron flow in the Weyl-semimetal
tungsten phosphide (WP2). Using thermal and magneto-electric transport
experiments, we observe the transition from a conventional metallic state, at
higher temperatures, to a hydrodynamic electron fluid below 20 K. The
hydrodynamic regime is characterized by a viscosity-induced dependence of the
electrical resistivity on the square of the channel width, and by the
observation of a strong violation of the Wiedemann-Franz law. From
magneto-hydrodynamic experiments and complementary Hall measurements, the
relaxation times for momentum and thermal energy dissipating processes are
extracted. Following the uncertainty principle, both are limited by the
Planckian bound of dissipation, independent of the underlying transport regime.",1706.05925v2
2017-09-22,On Extracting Mechanical Properties from Nanoindentation at Temperatures up to 1000$^{\circ}$C,"Alloyed MCrAlY bond coats, where M is usually cobalt and/or nickel, are
essential parts of modern turbine blades, imparting environmental resistance
while mediating thermal expansivity differences. Nanoindentation allows the
determination of their properties without the complexities of traditional
mechanical tests, but was not previously possible near turbine operating
temperatures.
  Here, we determine the hardness and modulus of CMSX-4 and an Amdry-386 bond
coat by nanoindentation up to 1000$^{\circ}$C. Both materials exhibit a
constant hardness until 400$^{\circ}$C followed by considerable softening,
which in CMSX-4 is attributed to the multiple slip systems operating underneath
a Berkovich indenter.
  The creep behaviour has been investigated via the nanoindentation hold
segments. Above 700$^{\circ}$C, the observed creep exponents match the
temperature-dependence of literature values in CMSX-4. In Amdry-386,
nanoindentation produces creep exponents very close to literature data,
implying high-temperature nanoindentation may be powerful in characterising
these coatings and providing inputs for material, model and process
optimisations.",1709.07714v1
2017-03-16,Equivalence of Effective Medium and Random Resistor Network models for disorder-induced unsaturating linear magnetoresistance,"A linear unsaturating magnetoresistance at high perpendicular magnetic
fields, together with a quadratic positive magnetoresistance at low fields, has
been seen in many different experimental materials, ranging from silver
chalcogenides and thin films of InSb to topological materials like graphene and
Dirac semimetals. In the literature, two very different theoretical approaches
have been used to explain this classical magnetoresistance as a consequence of
sample disorder. The phenomenological Random Resistor Network model constructs
a grid of four-terminal resistors, each with a varying random resistance. The
Effective Medium Theory model imagines a smoothly varying disorder potential
that causes a continuous variation of the local conductivity. Here, we
demonstrate numerically that both models belong to the same universality class
and that a restricted class of the Random Resistor Network is actually
equivalent to the Effective Medium Theory. Both models are also in good
agreement with experiments on a diverse range of materials. Moreover, we show
that in both cases, a single parameter, i.e. the ratio of the fluctuations in
the carrier density to the average carrier density, completely determines the
magnetoresistance profile.",1703.05478v1
2017-08-24,Probing the Fermi surface and magnetotransport properties in MoAs$_{2}$,"Transition metal dipnictides (TMDs) have recently been identified as possible
candidates to host topology protected electronic band structure. These
materials belong to an isostructural family and show several exotic transport
properties. Especially, the large values of magnetoresistance (MR) and carrier
mobility have drawn significant attention from the perspective of technological
applications. In this report, we have investigated the magnetotransport and
Fermi surface properties of single crystalline MoAs$_{2}$, another member of
this group of compounds. Field induced resistivity plateau and a large MR have
been observed, which are comparable to several topological systems.
Interestingly, in contrast to other isostructural materials, the carrier
density in MoAs$_{2}$ is quite high and shows single-band dominated transport.
The Fermi pockets, which have been identified from the quantum oscillation, are
largest among the members of this group and have significant anisotropy with
crystallographic direction. Our first-principles calculations reveal a
substantial difference between the band structures of MoAs$_{2}$ and other
TMDs. The calculated Fermi surface consists of one electron pocket and another
'open-orbit' hole pocket, which has not been observed in TMDs so far.",1708.07294v1
2019-03-18,Zirconia UV-curable colloids for additive manufacturing via hybrid inkjet printing-stereolithography,"Currently, additive manufacturing of ceramics by stereolithography (SLA) is
limited to single materials and by a poor thickness resolution that strongly
depends on the ceramic particles-UV light interaction. Combining selective
laser curing with inkjet printing represents a novel strategy to overcome these
constrains. Nonetheless, this approach requires UV-curable inks that allow
hardening of the printed material and sintering to high density. In this work,
we report how to design an ink for inkjet printing of yttria stabilized
zirconia (YSZ) which can be impressed by addition of UV-curable monomers. We
especially show how the formulation of the inks and particularly the UV-monomer
concentration impacts the printability and the UV-curing. This leads to prints
that are resistant to solvent washing first and densify to 96% dense YSZ layers
after sintering.",1903.07731v1
2019-12-23,Large $d_{33}$ Piezoelectric-Polymer Composites For RF Acoustic Resonators,"While piezoelectric transduction enables designing acoustic resonators
operating at multi-GHz frequencies, the deposition of piezoelectric materials
typically requires high temperature processes and specific crystallographic
orientation of substrates, thus imposing a limitation on materials that could
be used. In this paper we present a piezoelectrically transduced thickness mode
acoustic resonator that employs piezoelectric (PMNPT) nanoparticles embedded in
a polymer (SU8) matrix. This composite material is deposited using standard
resist-spin coaters and is thus compatible with a variety of substrates. The
device presented here uses a double side polished single crystal silicon wafer
as the low loss acoustic substrate for the resonator and $1.7\mu m$ thick
SU8-PMNPT composite film as the actuator, and exhibits large effective
piezoelectric coefficient $(d_{33})$ of $216pm/V$, and we experimentally
demonstrate efficient transduction of acoustic resonances at frequencies up to
$1.5GHz$.",1912.10713v1
2021-01-25,Polycaprolactone/graphite nanoplates composite nanopapers,"Nanopapers based on graphene and related materials were recently proposed for
application in heat spreader applications. To overcome typical limitations in
brittleness of such materials, this work addressed the combination of graphite
nanoplatelets (GNP) with a soft, tough and crystalline polymer, acting as an
efficient binder between nanoplates. With this aim, polycaprolactone (PCL) was
selected and exploited in this paper. The crystalline organization of PCL
within the nanopaper was studied to investigate the effect of polymer
confinement between GNP. Thermomechanical properties were studied by dynamic
mechanical analyses at variable temperature and creep measurements at high
temperature, demonstrating superior resistance at temperatures well above PCL
melting. Finally, the heat conduction properties on the nanopapers were
evaluated, resulting in outstanding values above 150 Wm-1K-1.",2101.10283v1
2019-11-13,Portable and wireless signal transducer for field testing of environmental sensors based on 2D materials,"In this paper we present the design and fabrication of a portable device for
environmental monitoring applications. This novel hand-held apparatus monitors
the changes in the resistance of a sensing surface with a high accuracy and
resolution and transmits the recorded data wirelessly to a cellphone. Such a
design offers a solution for field testing of environmental sensors. The tested
sensing surface in this study is based on an ultrathin material: graphene,
which is placed on the surface of a Si/SiO2 wafer. This signal transducer and
wireless communication system form together an ideal platform to harvest the
sensitivity and selectivity of 2D materials for gas sensing applications.",1911.05764v2
2022-01-08,Dynamical Mean Field Studies of Infinite Layer Nickelates: Physics Results and Methodological Implications,"This article summarizes recent work on the many-body (beyond density
functional theory) electronic structure of layered rare-earth nickelates, both
in the context of the materials themselves and in comparison to the
high-temperature superconducting (high-$T_c$) layered copper-oxide compounds.
It aims to outline the current state of our understanding of layered nickelates
and to show how the analysis of these fascinating materials can shed light on
fundamental questions in modern electronic structure theory. A prime focus is
determining how the interacting physics defined over a wide energy range can be
estimated and ""downfolded"" into a low energy theory that would describe the
relevant degrees of freedom on the $\sim 0.5$ eV scale and that could be solved
to determine superconducting and spin and charge density wave phase boundaries,
temperature-dependent resistivities, and dynamical susceptibilities.",2201.02852v1
2022-03-04,Broadband Cross-Circular Polarization Carpet Cloaking based on a Phase Change Material Metasurface in the Mid-infrared Region,"In view of the fact that most invisibility devices focus on linear
polarization cloaking and that the characteristics of mid infrared cloaking are
rarely studied, we propose a cross circularly polarized invisibility carpet
cloaking device in the mid infrared band. Based on the Pancharatnam Berry phase
principle, the unit cells with the cross circular polarization gradient phase
were carefully designed and constructed into a metasurface. In order to achieve
tunable cross circular polarization carpet cloaks, a phase change material is
introduced into the design of the unit structure. When the phase change
material is in amorphous and crystalline states, the proposed metasurface unit
cells can achieve high efficiency cross polarization conversion and reflection
intensity can be tuned. According to the phase compensation principle of carpet
cloaking, we construct a metasurface cloaking device with a phase gradient
using the designed unit structure. From the near and far field distributions,
the cross circular polarization cloaking property is confirmed in the broadband
wavelength range. The proposed cloaking device can effectively resist detection
of cross-circular polarization.",2203.02222v1
2022-03-06,Scaled indium oxide transistors fabricated using atomic layer deposition,"In order to continue to improve integrated circuit performance and
functionality, scaled transistors with short channel lengths and low thickness
are needed. But the further scaling of silicon-based devices and the
development of alternative semiconductor channel materials that are compatible
with current fabrication processes is challenging. Here we report
atomic-layer-deposited indium oxide transistors with channel lengths down to 8
nm, channel thicknesses down to 0.5 nm and equivalent dielectric oxide
thickness down to 0.84 nm. Due to the scaled device dimensions and low contact
resistance, the devices exhibit high on-state currents of 3.1 A/mm at a drain
voltage of 0.5 V and a transconductance of 1.5 S/mm at a drain voltage 1 V. Our
devices are a promising alternative channel material for scaled transistors
with back-end-of-line processing compatibility.",2203.02869v1
2022-10-18,Nanoscale friction controlled by top layer thickness in [LaMnO$_{3}$]$_{m}$/[SrMnO$_{3}$]$_{n}$ superlattices,"We conducted lateral force microscopy measurements on seven
[LaMnO$_{3}$]$_{m}$/[SrMnO$_{3}$]$_{n}$ superlattices with varied layer
thicknesses. We observe that the friction forces and the friction coefficients
initially increase with increasing LaMnO3 top layer thickness, followed by
saturation when the top layer thickness exceeds a few nanometers. These
observations clearly demonstrate that sliding friction is affected by
sub-surface material properties to a depth of several nanometers and is not
just determined by dynamics in the contact interface. We argue that the
sub-surface dissipated energy is governed by damping in the elastically
strained volume below the AFM tip, an effect which we estimate via
thermoelasticity. The absence of a correlation between friction and the thermal
resistivity of our superlattices shows furthermore that high-frequency phonons
and heat conduction do not play a role in determining friction. Our
observations thus demonstrate that friction can be tailored by sub-surface
material properties.",2210.09677v1
2023-05-15,Superconductivity at epitaxial LaTiO3-KTaO3 interfaces,"Design of epitaxial interfaces is a pivotal way to engineer artificial
structures where new electronic phases can emerge. Here we report a systematic
emergence of interfacial superconducting state in epitaxial heterostructures of
LaTiO3 and KTaO3. The superconductivity transition temperature increases with
decreasing the thickness of LaTiO3. Such behavior is observed for both (110)
and (111) crystal oriented structures. For thick samples, the finite resistance
developing below the superconducting transition temperature increases with
increasing LaTiO3 thickness. Consistent with previous reports, the (001)
oriented heterointerface features high electron mobility of 250 cm2/Vs and
shows no superconducting transition down to 40 mK. Our results imply a
non-trivial impact of LaTiO3 on the superconducting state and indicate how
superconducting KTaO3 interfaces can be integrated with other oxide materials.",2305.08304v1
2024-02-16,Erosion Study of Tungsten Carbide films under 100 keV Kr+ ion irradiation,"Tungsten carbide (WC) stands out as a crucial material for exploration in
extreme environments due to its resistance to radiation and impressive
mechanical strength. Widely utilized in cutting tools, high-wear components,
and as a potential contender for plasma-facing material in nuclear reactors,
WC's erosion behavior under surrogate irradiations is a subject of
investigation. In the present work, WC films were synthesized at two different
substrate temperatures of 400 K and 600 K using RF sputtering and were then
irradiated with 100 keV Kr1+ ions at a fluence of 1x1017 ions/cm2. The
crystalline phases of as deposited WC films were confirmed by glancing
incidence X-ray diffraction (GIXRD) measurements. Rutherford Backscattering
Spectrometry (RBS) was employed to determine the thicknesses of pristine
samples and the sputtering rate by measuring the difference in the areal
densities of the pristine and irradiated films. The erosion rate of both types
of films was found to be ~ 1.6 atoms per incident Kr+ ion. These findings
contribute to a foundational comprehension of the radiation tolerance behavior
of WC thin films, crucial for their performance in the demanding conditions of
extreme radiation.",2402.10461v1
2001-05-22,Infrared optical properties of Pr2CuO4,"The ab-plane reflectance of a Pr2CuO4 single crystal has been measured over a
wide frequency range at a variety of temperatures, and the optical properties
determined from a Kramers-Kronig analysis. Above ~ 250 K, the low frequency
conductivity increases quickly with temperature; the resistivity follows the
form e^(E_a/k_BT), where E_a ~ 0.17 eV is much less than the inferred optical
gap of ~ 1.2 eV. Transport measurements show that at low temperature the
resistivity deviates from activated behavior and follows the form
e^[(T_0/T)^1/4], indicating that the dc transport in this material is due to
variable-range hopping between localized states in the gap. The four
infrared-active Eu modes dominate the infrared optical properties. Below ~ 200
K, a striking new feature appears near the low-frequency Eu mode, and there is
additional new fine structure at high frequency. A normal coordinate analysis
has been performed and the detailed nature of the zone-center vibrations
determined. Only the low-frequency Eu mode has a significant Pr-Cu interaction.
Several possible mechanisms related to the antiferromagnetism in this material
are proposed to explain the sudden appearance of this and other new spectral
features at low temperature.",0105445v2
2006-11-29,What is the valence of a correlated solid? The double life of delta-plutonium,"Plutonium displays phase transitions with enormous volume differences among
its phases and both its Pauli like magnetic susceptibility and resistivity are
an order of magnitude larger than those of simple metals. Curium is also highly
resistive but its susceptibility is Curie-like at high temperatures and orders
antiferromagnetically at low temperatures. The anomalous properties of the late
actinides stem from the competition between the itinerancy and localization of
its f electrons, which makes the late actinides elemental strongly correlated
materials. A central problem in this field is to understand the mechanism by
which these materials resolve these conflicting tendencies. In this letter we
identify the electronic mechanisms responsible for the anomalous behaviour of
late actinides. We revisit the concept of valence using theoretical approach
that treats magnetism, Kondo screening, atomic multiplet effects, spin orbit
coupling and crystal field splitting on the same footing. Plutonium is found to
be in a rare mixed valent state, namely its ground state is a superposition of
two distinct valencies. Curium settles in a single valence magnetically ordered
state at low temperatures. The f7 atomic configuration of Curium is contrasted
with the multiple configuration manifolds present in Plutonium ground state
which we characterize by a valence histogram. The balance between the Kondo
screening and magnetism is determined by the competition between spin orbit
coupling and the strength of atomic multiplets which is in turn regulated by
the degree of itinerancy. The approach presented here, highlights the
electronic origin of the bonding anomalies in plutonium and can be applied to
predict generalized valences and the presence or absence of magnetism in other
compounds starting from first principles.",0611760v1
2009-05-08,Magnetotransport in polycrystalline La$_{2/3}$Sr$_{1/3}$MnO$_{3}$ thin films of controlled granularity,"Polycrystalline La$_{2/3}$Sr$_{1/3}$MnO$_{3}$ (LSMO) thin films were
synthesized by pulsed laser ablation on single crystal (100) yttria-stabilized
zirconia (YSZ) substrates to investigate the mechanism of magneto-transport in
a granular manganite. Different degrees of granularity is achieved by using the
deposition temperature (T$_{D}$) of 700 and 800 $^{0}$C. Although no
significant change in magnetic order temperature (T$_C$) and saturation
magnetization is seen for these two types of films, the temperature and
magnetic field dependence of their resistivity ($\rho$(T, H)) is strikingly
dissimilar. While the $\rho$(T,H) of the 800 $^{0}$C film is comparable to that
of epitaxial samples, the lower growth temperature leads to a material which
undergoes insulator-to-metal transition at a temperature (T$_{P}$ $\approx$ 170
K) much lower than T$_C$. At T $\ll$ T$_P$, the resistivity is characterized by
a minimum followed by ln $\emph{T}$ divergence at still lower temperatures. The
high negative magnetoresistance ($\approx$ 20$%$) and ln $\emph{T}$ dependence
below the minimum are explained on the basis of Kondo-type scattering from
blocked Mn-spins in the intergranular material. Further, a striking feature of
the T$_D$ = 700 $^{0}$C film is its two orders of magnitude larger anisotropic
magnetoresistance (AMR) as compared to the AMR of epitaxial films. We attribute
it to unquenching of the orbital angular momentum of 3d electrons of Mn ions in
the intergranular region where crystal field is poorly defined.",0905.1306v1
2009-12-27,Topological Insulator Nanowires and Nanoribbons,"Recent theoretical calculations and photoemission spectroscopy measurements
on the bulk Bi2Se3 material show that it is a three-dimensional topological
insulator possessing conductive surface states with nondegenerate spins,
attractive for dissipationless electronics and spintronics applications.
Nanoscale topological insulator materials have a large surface-to-volume ratio
that can manifest the conductive surface states and are promising candidates
for devices. Here we report the synthesis and characterization of high quality
single crystalline Bi2Se3 nanomaterials with a variety of morphologies. The
synthesis of Bi2Se3 nanowires and nanoribbons employs Au-catalyzed
vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces,
are formed by stacking nanoplatelets along the axial direction of the wires.
Nanoribbons are grown along [11-20] direction with a rectangular cross-section
and have diverse morphologies, including quasi-one-dimensional, sheetlike,
zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on
nanoribbons show atomically smooth surfaces with ~ 1 nm step edges, indicating
single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb
atomic lattice, suggesting that the STM tip couples not only to the top Se
atomic layer, but also to the Bi atomic layer underneath, which opens up the
possibility to investigate the contribution of different atomic orbitals to the
topological surface states. Transport measurements of a single nanoribbon
device (four terminal resistance and Hall resistance) show great promise for
nanoribbons as candidates to study topological surface states.",0912.5045v1
2010-06-02,Antiferromagnetic Mott insulating state in single crystals of the hexagonal lattice material Na2IrO3,"We have synthesized single crystals of Na_2IrO_3 and studied their structure,
transport, magnetic, and thermal properties using powder x-ray diffraction
(PXRD), electrical resistivity, isothermal magnetization M versus magnetic
field H, magnetic susceptibility \chi versus temperature T, and heat capacity C
versus T measurements. Na_2IrO_3 crystallizes in the monoclinic \emph{C2/c}
(No. 15) type structure which is made up of Na and NaIr_2O_6 layers alternately
stacked along the c axis. The \chi(T) data show Curie-Weiss behavior at high T
> 200K with an effective moment \mu_eff = 1.82(1) \mu_B indicating an effective
spin S_eff = 1/2 on the Ir^4+ moments. A large Weiss temperature \theta = -
116(3)K indicates substantial antiferromagnetic interactions between these
S_eff = 1/2, Ir^4+ moments. Sharp anomalies in \chi(T) and C(T) data indicate
that Na_2IrO_3 undergoes a transition into a long-range antiferromagnetically
ordered state below T_N = 15 K. The magnetic entropy at T_N is only about 20%
of what is expected for S_eff = 1/2 moment ordering. The reduced entropy and
the small ratio T_N/\theta \approx 0.13 suggest geometrical magnetic
frustration and/or low-dimensional magnetic interactions in Na_2IrO_3. In plane
resistivity measurements show insulating behavior. This together with the local
moment magnetism indicates that bulk Na_2IrO_3 is a Mott insulator.",1006.0437v1
2010-11-02,Graphene: from materials science to particle physics,"Since its discovery in 2004, graphene, a two-dimensional hexagonal carbon
allotrope, has generated great interest and spurred research activity from
materials science to particle physics and vice versa. In particular, graphene
has been found to exhibit outstanding electronic and mechanical properties, as
well as an unusual low-energy spectrum of Dirac quasiparticles giving rise to a
fractional quantum Hall effect when freely suspended and immersed in a magnetic
field. One of the most intriguing puzzles of graphene involves the
low-temperature conductivity at zero density, a central issue in the design of
graphene-based nanoelectronic components. While suspended graphene experiments
have shown a trend reminiscent of semiconductors, with rising resistivity at
low temperatures, most theories predict a constant or even decreasing
resistivity. However, lattice field theory calculations have revealed that
suspended graphene is at or near the critical coupling for excitonic gap
formation due to strong Coulomb interactions, which suggests a simple and
straightforward explanation for the experimental data. In this contribution we
review the current status of the field with emphasis on the issue of gap
formation, and outline recent progress and future points of contact between
condensed matter physics and Lattice QCD.",1011.0643v1
2013-03-04,Statistical Study of Deep Sub-Micron Dual-Gated Field-Effect Transistors on Monolayer CVD Molybdenum Disulfide Films,"Monolayer Molybdenum Disulfide (MoS2) with a direct band gap of 1.8 eV is a
promising two-dimensional material with a potential to surpass graphene in next
generation nanoelectronic applications. In this letter, we synthesize monolayer
MoS2 on Si/SiO2 substrate via chemical vapor deposition (CVD) method and
comprehensively study the device performance based on dual-gated MoS2
field-effect transistors. Over 100 devices are studied to obtain a statistical
description of device performance in CVD MoS2. We examine and scale down the
channel length of the transistors to 100 nm and achieve record high drain
current of 62.5 mA/mm in CVD monolayer MoS2 film ever reported. We further
extract the intrinsic contact resistance of low work function metal Ti on
monolayer CVD MoS2 with an expectation value of 175 {\Omega}.mm, which can be
significantly decreased to 10 {\Omega}.mm by appropriate gating. Finally,
field-effect mobilities ({\mu}FE) of the carriers at various channel lengths
are obtained. By taking the impact of contact resistance into account, an
average and maximum intrinsic {\mu}FE is estimated to be 13.0 and 21.6 cm2/Vs
in monolayer CVD MoS2 films, respectively.",1303.0776v1
2014-10-17,Anisotropic strain in SmSe and SmTe: implications for electronic transport,"Mixed valence rare-earth samarium compounds SmX (X=Se,Te) have been recently
proposed as candidate materials for use in high-speed, low-power digital
switches driven by stress induced changes of resistivity. At room temperature
these materials exhibit a pressure driven insulator-to-metal transition with
resistivity decreasing by up to 7 orders of magnitude over a small pressure
range. Thus, the application of only a few GPa's to the piezoresistor (SmX)
allows the switching device to perform complex logic. Here we study from first
principles the electronic properties of these compounds under uniaxial strain
and discuss the consequences on carrier transport. The changes in the band
structure show that the piezoresistive response is mostly governed by the
reduction of band gap with strain. Furthermore, it becomes optimal when the
Fermi level is pinned near the localized valence band. The piezoresistive
effect under uniaxial strain which must be taken into account in thin films and
other systems with reduced dimensionality is also quantified. Under uniaxial
strain we find that the piezoresistive response can be substantially larger
than in the isotropic case. Analysis of complex band structure of SmSe yields a
tunneling length of the order of 1 nm. The results suggest that the conduction
mechanism governing the piezoresistive effect in bulk, i.e.~thermal promotion
of electrons, should still be dominant in few-nanometer-thick films.",1410.4740v1
2015-08-19,Independent tuning of electronic properties and induced ferromagnetism in topological insulators with heterostructure approach,"The quantum anomalous Hall effect (QAHE) has been recently demonstrated in
Cr- and V-doped three-dimensional topological insulators (TIs) at temperatures
below 100 mK. In those materials, the spins of unfilled d-electrons in the
transition metal dopants are exchange coupled to develop a long-range
ferromagnetic order, which is essential for realizing QAHE. However, the
addition of random dopants does not only introduce excess charge carriers that
require readjusting the Bi/Sb ratio, but also unavoidably introduces
paramagnetic spins that can adversely affect the chiral edge transport in QAHE.
In this work, we show a heterostructure approach to independently tune the
electronic and magnetic properties of the topological surface states in
(BixSb1-x)2Te3 without resorting to random doping of transition metal elements.
In heterostructures consisting of a thin (BixSb1-x)2Te3 TI film and yttrium
iron garnet (YIG), a high Curie temperature (~ 550 K) magnetic insulator, we
find that the TI surface in contact with YIG becomes ferromagnetic via
proximity coupling which is revealed by the anomalous Hall effect (AHE). The
Curie temperature of the magnetized TI surface ranges from 20 to 150 K but is
uncorrelated with the Bi fraction x in (BixSb1-x)2Te3. In contrast, as x is
varied, the AHE resistivity scales with the longitudinal resistivity. In this
approach, we decouple the electronic properties from the induced ferromagnetism
in TI. The independent optimization provides a pathway for realizing QAHE at
higher temperatures, which is important for novel spintronic device
applications.",1508.04719v1
2016-11-08,Superconductivity Induced by High Pressure in Weyl Semimetal TaP,"Weyl semimetal defines a material with three dimensional Dirac cones which
appear in pair due to the breaking of spatial inversion or time reversal
symmetry. Superconductivity is the state of quantum condensation of paired
electrons. Turning a Weyl semimetal into superconducting state is very
important in having some unprecedented discoveries. In this work, by doing
resistive measurements on a recently recognized Weyl semimetal TaP under
pressure up to about 100 GPa, we observe superconductivity at about 70 GPa. The
superconductivity retains when the pressure is released. The systematic
evolutions of resistivity and magnetoresistance with pressure are well
interpreted by the relative shift between the chemical potential and paired
Weyl points. Calculations based on the density functional theory also
illustrate the structure transition at about 70GPa, the phase at higher
pressure may host superconductivity. Our discovery of superconductivity in TaP
by pressure will stimulate further study on superconductivity in Weyl
semimetals.",1611.02548v1
2017-02-15,On Ni-Sb-Sn based skutterudites,"Novel filled skutterudites EpyNi4Sb12-xSnx (Ep = Ba and La) have been
prepared by arc melting followed by annealing at 250C, 350C and 450C up to 30
days in sealed quartz vials. A maximum filling level of y = 0.93 and y = 0.65
was achieved for the Ba and La filled skutterudite, respectively. Single-phase
samples with the composition Ni4Sb8.2Sn3.8, Ba0.42Ni4Sb8.2Sn3.8 and
Ba0.92Ni4Sb6.7Sn5.3 were employed for measurements of the physical properties
i.e. temperature dependent electrical resistivity, Seebeck coefficient and
thermal conductivity.
  Resistivity data showed a crossover from metallic to semiconducting
behaviour. The corresponding gap width was extracted from maxima in the Seebeck
coefficient data as a function of temperature. Temperature dependent single
crystal X-ray structure analyses (at 100 K, 200 K and 300 K) revealed the
thermal expansion coefficients, Einstein and Debye temperatures for two
selected samples Ba0.73Ni4Sb8.1Sn3.9 and Ba0.95Ni4Sb6.1Sn5.9. These data
compare well with Debye temperatures from measurements of specific heat (4.4 K
< T < 200 K).
  Several mechanical properties were measured and evaluated. Thermal expansion
coefficients are 11.8.10-6 K-1 for Ni4Sb8.2Sn3.8 to 13.8.10-6 K-1 for
Ba0.92Ni4Sb6.7Sn5.3. Room temperature Vicker's hardness values (up to a load of
24.5 mN) vary within the range of 2.6 GPa to 4.7 GPa. Severe plastic
deformation (SPD) via high-pressure torsion (HPT) was used to introduce
nanostructuring. Physical properties before and after HPT were compared,
showing no significant effect on the material's thermoelectric behaviour.",1702.04654v1
2018-04-13,Tuning spin one channel to exotic orbital two-channel Kondo effect in ferrimagnetic composites of LaNiO3 and CoFe2O4,"We report the tuning from spin one channel (1CK) to orbital two-channel Kondo
(2CK) effect by varying CoFe2O4 (CFO) content in the composites with LaNiO3
(LNO) along with the presence of ferrimagnetism. Although there is no signature
of resistivity upturn in case of pure LNO, all the composites exhibit a
distinct upturn in the temperature range 30-80 K. For composite with lower
percentage of CFO (10 %), the electron spin plays the key role in the emergence
of resistivity upturn which is affected by external magnetic field. On the
other hand, when the CFO content is increased (15%), the upturn shows strong
robustness against high magnetic field (14 T) and a crossover in temperature
variation from lnT to T^1/2 at the Kondo temperature, indicating the appearance
of orbital 2CK effect. The orbital 2CK effect is originated due to the
scattering of conduction electrons from the structural two-level systems which
is created at the interfaces between the two phases (LNO and CFO) of different
crystal structures as well as inside the crystal planes. A negative
magnetoresistance (MR) is observed at low temperature (< 30 K) for composites
containing both lower (10 %) and higher percentage (15 %) of CFO. We have
analyzed the negative MR using Khosla and Fisher semi-empirical model based on
spin dependent scattering of conduction electrons from localized spins.",1804.04796v1
2018-06-20,Tunable disorder and localization in the rare-earth nickelates,"The rare-earth nickelates are a rich playground for transport properties,
known to host non-Fermi liquid character, resistance saturation and
metal-insulator transitions. We report a study of transport in LaNiO3 in the
presence of tunable disorder induced by irradiation. While pristine LaNiO3
samples are metallic, highly irradiated samples show insulating behaviour at
all temperatures. Using irradiation fluence as a tuning handle, we uncover an
intermediate region hosting a metal-insulator transition. This transition falls
within the Mott-Ioffe-Regel regime wherein the mean free path is comparable to
lattice spacing. In the high temperature metallic regime, we find a transition
from non-Fermi liquid to a Fermi-liquid-like character. On the insulating side
of the metal-insulator transition, we find behaviour that is consistent with
weak localization. This is reflected in magnetoresistance that scales with the
square of the field and in resistivity. In the highly irradiated insulating
samples, we find good agreement with variable range hopping, consistent with
Anderson localization. We find qualitatively similar behaviour in thick PrNiO3
films as well. Our results demonstrate that ion irradiation can be used to
tailor transport, serving as an excellent tool to study the physics of
localization.",1806.07986v1
2019-09-04,Exploring Disorder in the Spin Gapless Semiconductor Mn$_2$CoAl,"Since the prediction of spin-gapless semiconducting behaviour in the Heusler
compound Mn$_2$CoAl, evidence of spin-gapless behaviour in thin films has
typically been inferred from magnetotransport measurements. The spin gapless
state is however fragile, and further, band structure calculations indicate
that even a small amount of atomic disorder may destroy it. To explore the
impact of disorder on the properties of Mn$_2$CoAl, we have undertaken an
experimental study of the structural, magnetotransport and optical properties
from the far infrared to the UV, on DC magnetron sputtered Mn$_2$CoAl thin
films. A very short mean free path, of the order of a lattice spacing, is
extracted from the DC transport data. A room temperature resistivity of 200
$\mu$$\Omega$cm along with a small and negative temperature coefficient of
resistance between 4 and 400 K was measured. We note that parameters of this
magnitude are often observed in disordered metals. We find this behaviour is
well described by a weak localisation model, a result that is supported by a
large Drude contribution to the optical response, where a high scattering rate
is derived, which is equal to the value derived from the DC conductivity and
Hall effect data. We also note the strong similarities between the
magnetotransport behaviour reported for Mn$_2$CoAl films in the literature,
including ours. We conclude that, based on comparisons between the experimental
data, and recent band structure calculations that explicitly include disorder,
as-prepared Mn$_2$CoAl films are best described as a disordered metal, rather
than a spin gapless semiconductor.",1909.02153v1
2019-07-10,Electronic Transport Evidence for Topological Nodal-Line Semimetals of ZrGeSe single crystals,"Although the band topology of ZrGeSe has been studied via magnetic torque
technique, the electronic transport behaviors related to the relativistic
Fermions in ZrGeSe are still unknown. Here, we first report systematic
electronic transport properties of high-quality ZrGeSe single crystals under
magnetic fields up to 14 T. Resistivity plateaus of temperature dependent
resistivity curves both in the presence and absence of magnetic fields as well
as large, non-saturating magnetoresistance in low-temperature region were
observed. By analyzing the temperature- and angular-dependent Shubnikov-de Haas
oscillations and fitting it via the Lifshitz-Kosevich (LK) formula with the
Berry phase being taken into account, we proved that Dirac fermions dominate
the electronic transport behaviors of ZrGeSe and the presence of non-trivial
Berry phase. First principles calculations demonstrate that ZrGeSe possesses
Dirac bands and normal bands near Fermi surface, resulting in the observed
magnetotransport phenomena. These results demonstrate that ZrGeSe is a
topological nodal-line semimetal, which provides a fundamentally important
platform to study the quantum physics of topological semimetals.",1907.04762v1
2019-12-06,Correlated Insulating States and Transport Signature of Superconductivity in Twisted Trilayer Graphene Moiré of Moiré Superlattices,"Layers of two-dimensional materials stacked with a small twist-angle give
rise to beating periodic patterns on a scale much larger than the original
lattice, referred to as a moir\'e superlattice. When the stacking involves more
than two layers with independent twist angles between adjacent layers, it
generates moir\'e of moir\'e superlattices, with multiple length scales that
control the system's behavior. Here we demonstrate these effects of a
high-order moir\'e superlattice in twisted trilayer graphene with two
consecutive small twist angles. We report correlated insulating states near the
half filling of the moir\'e of moir\'e superlattice at an extremely low carrier
density (~1010 cm-2), near which we also report a zero-resistance transport
behavior typically expected in a 2D superconductor. Moreover, the temperature
dependence of the measured resistances at full-occupancy (v = -4 and v = 4)
states are semi-metallic, distinct from the insulating behavior of twisted
bilayer systems, providing the first demonstration of emergent correlated
transport behaviors from continuous, non-isolated higher-order moir\'e flat
bands. Our findings shed new insights into the microscopic mechanisms of
moir\'e correlated states and provide the impetus for future studies on this
material platform, such as the demonstration of phase coherence and
Meissner-like effect.",1912.03375v2
2020-01-14,Heavy non-degenerate electrons in doped strontium titanate,"Room-temperature metallicity of lightly doped SrTiO$_3$ is puzzling, because
the combination of mobility and the effective mass would imply a mean-free-path
(mfp) below the Mott Ioffe Regel (MIR) limit and a scattering time shorter than
the Planckian time ($\tau_P=\hbar/k_BT$). We present a study of electric
resistivity, Seebeck coefficient and inelastic neutron scattering extended to
very high temperatures, which deepens the puzzle. Metallic resistivity persists
up to 900 K and is accompanied by a large Seebeck coefficient whose magnitude
(as well as its temperature and doping dependence) indicates that carriers are
becoming heavier with rising temperature. Combining this with neutron
scattering data, we find that between 500 K and 900 K, the Bohr radius and the
electron wave-length become comparable to each other and twice the lattice
parameter. According to our results, between 100 K and 500 K, metallicity is
partially driven by temperature-induced amplification of the carrier mass. We
contrast this mass amplification of non-degenerate electrons with the
better-known case of heavy degenerate electrons. Above 500 K, the
mean-free-path continues to shrink with warming in spite of becoming shorter
than both the interatomic distance and the thermal wavelength of the electrons.
The latter saturates to twice the lattice parameter. Available theories of
polaronic quasi-particles do not provide satisfactory explanation for our
observations.",2001.04668v4
2021-06-21,Three-dimensional quasi-quantized Hall insulator phase in SrSi2,"In insulators, the longitudinal resistivity becomes infinitely large at zero
temperature. For classic insulators, the Hall conductivity becomes zero at the
same time. However, there are special systems, such as two-dimensional quantum
Hall isolators, in which a more complex scenario is observed at high magnetic
fields. Here, we report experimental evidence for a quasi-quantized Hall
insulator in the quantum limit of the three-dimensional semimetal SrSi2. Our
measurements reveal a magnetic field-range, in which the longitudinal
resistivity diverges with decreasing temperature, while the Hall conductivity
approaches a quasi-quantized value that is given only by the conductance
quantum and the Fermi wave vector in the field-direction. The quasi-quantized
Hall insulator appears in a magnetic-field induced insulating ground state of
three-dimensional materials and is deeply rooted in quantum Hall physics.",2106.11329v1
2021-07-05,Quantum anomalous Hall effect from intertwined moiré bands,"Electron correlation and topology are two central threads of modern condensed
matter physics. Semiconductor moir\'e materials provide a highly tunable
platform for studies of electron correlation. Correlation-driven phenomena,
including the Mott insulator, generalized Wigner crystals, stripe phases and
continuous Mott transition, have been demonstrated. However, nontrivial band
topology has remained elusive. Here we report the observation of a quantum
anomalous Hall (QAH) effect in AB-stacked MoTe2/WSe2 moir\'e heterobilayers.
Unlike in the AA-stacked structures, an out-of-plane electric field controls
not only the bandwidth but also the band topology by intertwining moir\'e bands
centered at different high-symmetry stacking sites. At half band filling,
corresponding to one particle per moir\'e unit cell, we observe quantized Hall
resistance, h/e2 (with h and e denoting the Planck's constant and electron
charge, respectively), and vanishing longitudinal resistance at zero magnetic
field. The electric-field-induced topological phase transition from a Mott
insulator to a QAH insulator precedes an insulator-to-metal transition;
contrary to most known topological phase transitions, it is not accompanied by
a bulk charge gap closure. Our study paves the path for discovery of a wealth
of emergent phenomena arising from the combined influence of strong correlation
and topology in semiconductor moir\'e materials.",2107.01796v1
2021-10-01,Gate-tunable Intrinsic Anomalous Hall Effect in Epitaxial MnBi2Te4 Films,"Anomalous Hall effect (AHE) is an important transport signature revealing
topological properties of magnetic materials and their spin textures. Recently,
antiferromagnetic MnBi2Te4 has been demonstrated to be an intrinsic magnetic
topological insulator that exhibits quantum AHE in exfoliated nanoflakes.
However, its complicated AHE behaviors may offer an opportunity for the
unexplored correlation between magnetism and band structure. Here, we show the
Berry curvature dominated intrinsic AHE in wafer-scale MnBi2Te4 thin films. By
utilizing a high-dielectric SrTiO3 as the back-gate, we unveil an ambipolar
conduction and electron-hole carrier (n-p) transition in ~7 septuple layer
MnBi2Te4. A quadratic relation between the saturated AHE resistance and
longitudinal resistance suggests its intrinsic AHE mechanism. For ~3 septuple
layer MnBi2Te4, however, the AHE reverses its sign from pristine negative to
positive under the electric-gating. The first-principles calculations
demonstrate that such behavior is due to the competing Berry curvature between
polarized spin-minority-dominated surface states and spin-majority-dominated
inner-bands. Our results shed light on the physical mechanism of the
gate-tunable intrinsic AHE in MnBi2Te4 thin films and provide a feasible
approach to engineering its AHE.",2110.00540v1
2021-12-23,Impact of the superconductors properties on the measurement sensitivity of resonant-based axion detectors,"Axions, hypothetical particles theorized to solve the strong CP-problem, are
presently being considered as strong candidates as cold dark matter
constituents. The signal power of resonant-based axion detectors, known as
haloscopes, is directly proportional to their quality factor $Q$. In this
paper, the impact of the use of superconductors in the performances of the
haloscopes is studied by evaluating the obtainable $Q$. In particular, the
surface resistance $R_s$ of NbTi, Nb$_3$Sn, YBa$_2$Cu$_3$O$_{7-\delta}$ and
FeSe$_{0.5}$Te$_{0.5}$ is computed in the frequency, magnetic field and
temperature ranges of interest, starting from the measured vortex motion
complex resistivity and screening lengths of these materials. From $R_s$ the
quality factor $Q$ of a cylindrical haloscope with copper conical bases and
superconductive lateral wall, operating with the TM$_{010}$ mode, is evaluated
and used to perform a comparison of the performances of the different
materials. Both YBa$_2$Cu$_3$O$_{7-\delta}$ and FeSe$_{0.5}$Te$_{0.5}$ are
shown to improve the measurement sensitivity by almost an order of magnitude
with respect to a whole Cu cavity, while NbTi is shown to be suitable only at
lower frequencies (<10 GHz). Nb$_3$Sn can give an intermediate improvement in
the whole spectrum of interest.",2112.12775v1
2022-01-28,Substitutional Doped GeSe: Tunable Oxidative States with Strain Engineering,"Layered chalcogenide materials have a wealth of nanoelectronics applications
like resistive switching and energy-harvesting such as photocatalyst owing to
rich electronic, orbital, and lattice excitations. In this work, we explore
monochalcogenide germanium selenide GeSe with respect to substitutional doping
with 13 metallic cations by using first-principles calculations. Typical
dopants including s-shell (alkali elements Li and Na), p-shell (Al, Pb and Bi),
3d (Fe, Cu, Co and Ni), 4d (Pd and Ag) and 5d (Au and Pt) elements are
systematically examined. Amongst all the cationic dopants, Al with the highest
oxidation states, implying a high mobility driven by electric field, and
Al-doped GeSe may be a promising candidate for novel resistive switching
devices. We show that there exist many localized induced states in the band gap
of GeSe upon doping Fe, Co, or Ni, while for Cu, Ag, and Au cases there is no
such states in the gap. The Ag and Cu are + 0.27 and + 0.35 charged
respectively and the positive charges are beneficial for field-driven motion in
GeSe. In contrast, Au is slightly negatively charged renders Au-doped GeSe a
promising photocatalyst and enhanced surface plasmon. Moreover, we explore the
coexistence of dopant and strain in GeSe and find dynamical adjustments of
localized states in GeSe with levels successive shifting upward/downward with
strain. This induces dynamic oxidative states of the dopants under strain which
should be quite popular in composites where motion of metal adatoms causes
significant deformation.",2201.11890v1
2022-05-24,Quantum hybridization negative differential resistance from non-toxic halide perovskite nanowire heterojunctions and its strain control,"While low-dimensional organometal halide perovskites are expected to open up
new opportunities for a diverse range of device applications, like in their
bulk counterparts, the toxicity of Pb-based halide perovskite materials is a
significant concern that hinders their practical use. We recently predicted
that lead triiodide (PbI$_3$) columns de-rived from trimethylsulfonium (TMS)
lead triiodide (CH$_3$)$_3$SPbI$_3$ (TMSPbI$_3$) by stripping off TMS ligands
should be semimetallic, and additionally ultrahigh negative differential
resistance (NDR) can arise from the heterojunction composed of a TMSPbI$_3$
channel sandwiched by PbI$_3$ electrodes. Herein, we computationally explore
whether similar material and device characteristics can be obtained from other
one-dimensional halide perovskites based on non-Pb metal elements, and in doing
so deepen the understanding of their mechanistic origins. First, scanning
through several candidate metal halide inorganic frameworks as well as their
parental form halide perovskites, we find that the germanium triiodide
(GeI$_3$) column also assumes a semimetallic character by avoiding the Peierls
distortion. Next, adopting the bundled nanowire GeI$_3$-TMSGeI$_3$-GeI$_3$
junction configuration, we obtain a drastically high peak current density and
ultrahigh NDR at room temperature. Furthermore, the robustness and
controllability of NDR signals under strain are revealed, establishing its
potential for flexible electronics applications. It will be emphasized that,
despite the performance metrics notably enhanced over those from the
PbI$_3$-TMSPbI$_3$-PbI$_3$ case, these device characteristics still arise from
the identical quantum hybridization NDR mechanism.",2205.11689v1
2022-06-06,"Anisotropic magnetic property of single crystals $R$V$_6$Sn$_6$ ($R$ = Y, Gd - Tm, Lu)","$R$V${_6}$Sn${_6}$ ($R$ = Y, Gd - Tm, Lu) single crystals are synthesized by
Sn-flux method and their physical properties are characterized by
magnetization, resistivity, and specific heat measurements. Powder X-ray
diffraction patterns of all samples can be well indexed with the hexagonal
HfFe$_6$Ge$_6$-type structure, where rare-earth atoms form hexagonal layers and
vanadium atoms form Kagome layers. At high temperatures, magnetic
susceptibility measurements of moment bearing rare-earths ($R$ = Gd - Tm)
follow Curie-Weiss behavior. Effective moments estimated from the
polycrystalline average of magnetic susceptibility curves are consistent with
the values for free $R^{3+}$ ion. Strong magnetic anisotropy due to crystalline
electric field effects is observed for moment bearing rare-earths, except
GdV$_6$Sn$_6$. The easy magnetization direction is determined to be $c$-axis
for $R$ = Tb - Ho and $ab$-plane for $R$ = Er, and Tm. The vanadium ions in
$R$V${_6}$Sn${_6}$ possess no magnetic moment. The compounds for $R$ = Y and Lu
exhibit typical characteristics of paramagnetic metals. At low temperatures,
the magnetic ordering is confirmed from magnetization, specific heat, and
resistivity: the highest $T_{N} = 4.9$~K for GdV$_6$Sn$_6$ and the lowest
$T_{N} = 2.3$~K for HoV$_6$Sn$_6$. No magnetic ordering is observed down to
1.8~K for $R$ = Er and Tm. A slight deviation of the magnetic ordering
temperature from the de Gennes scaling suggests the dominant
Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange interaction between rare-earth
moments in metallic $R$V${_6}$Sn${_6}$ compounds.",2206.02924v1
2022-09-21,Optical properties and carrier localization in the layered phosphide EuCd$_\mathbf{2}$P$_\mathbf{2}$,"The temperature dependence of the complex optical properties of the layered
phosphide material EuCd$_2$P$_2$ have been measured over a wide frequency range
above and below $T_{\rm N} \simeq 11.5$ K for light polarized in the $a-b$
planes. At room temperature, the optical conductivity is well described by a
weak free-carrier component with a Drude plasma frequency of $\simeq 1100$
cm$^{-1}$ and a scattering rate of $1/\tau_D\simeq 700$ cm$^{-1}$, with the
onset of interband absorptions above $\simeq 2000$ cm$^{-1}$. Two
infrared-active $E_u$ modes are observed at $\simeq\,$89 and 239 cm$^{-1}$. As
the temperature is reduced the scattering rate decreases and the low-frequency
conductivity increases slightly; however, below $\simeq 50$ K the conductivity
decreases until at the resistivity maximum at $\simeq 18$ K (just below
$2T_{\rm N}$) the spectral weight associated with free carriers is transferred
to a localized excitation at $\simeq 500$ cm$^{-1}$. Below $T_{\rm N}$,
metallic behavior is recovered. Interestingly, the $E_u$ modes are largely
unaffected by these changes, with only the position of the high-frequency mode
showing any signs of anomalous behavior. While several scenarios are
considered, the prevailing view is that the resistivity maximum and subsequent
carrier localization is due to the formation of ferromagnetic domains below
$\simeq 2T_{\rm N}$ that result in spin-polarized clusters due to spin-carrier
coupling [1].",2209.10606v2
2022-10-14,Anti-site disorder and Berry curvature driven anomalous Hall effect in spin gapless semiconducting Mn2CoAl Heusler compound,"Spin gapless semiconductors exhibit a finite band gap for one spin channel
and closed gap for other spin channel, emerged as a new state of magnetic
materials with a great potential for spintronic applications. The first
experimental evidence for the spin gapless semiconducting behavior was observed
in an inverse Heusler compound Mn2CoAl. Here, we report a detailed
investigation of the crystal structure and anomalous Hall effect in the Mn2CoAl
using experimental and theoretical studies. The analysis of the high-resolution
synchrotron x-ray diffraction data shows anti-site disorder between Mn and Al
atoms within the inverse Heusler structure. The temperature-dependent
resistivity shows semiconducting behavior and follows Mooijs criteria for
disordered metal. Scaling behavior of the anomalous Hall resistivity suggests
that the anomalous Hall effect in the Mn2CoAl is primarily governed by
intrinsic mechanism due to the Berry curvature in momentum space. The
experimental intrinsic anomalous Hall conductivity (AHC) is found to be 35
S/cm, which is considerably larger than the theoretically predicted value for
ordered Mn2CoAl. Our first-principle calculations conclude that the anti-site
disorder between Mn and Al atoms enhances the Berry curvature and hence the
value of intrinsic AHC, which is in a very well agreement with the experiment.",2210.07668v1
2022-12-02,FeRhCrSi: A new spin semimetal with room temperature spin-valve behavior,"Spin semimetals are a recently discovered new class of spintronic materials,
which exhibit a band gap in one spin channel while a semimetallic feature in
the other and thus allows for tunable spin transport. Here, we present
experimental verification of spin semimetallic behavior in FeRhCrSi, a
quaternary Heusler alloy with saturation moment 2 $\mu_B$ and Curie temperature
$>$ 400 K. It crystallises in the L2$_1$ structure with 50$\%$ antisite
disorder between Fe and Rh. Below 300 K, it shows a weakly temperature
dependent electrical resistivity with negative temperature coefficient,
indicating the normal semimetal or spin semimetal behavior. Anomalous
magnetoresistance data reveals dominant contribution from asymmetric part, a
clear signature of spin-valve nature, which is retained even at room
temperature. \textcolor{black}{The asymmetric part of magneto-resistance shows
an unusual increase with increasing temperature.} Hall measurements confirm the
anomalous nature of conductivity originating from the intrinsic Berry
curvature, with holes being the majority carriers. Ab-initio simulation
confirms a unique long-range ferrimagnetic ordering to be the ground state,
explaining the origin behind the unexpected low saturation moment. The
ferrimagnetic disordered structure confirms the spin semimetallic feature of
FeRhCrSi, as observed experimentally.",2212.00924v2
2023-01-11,Domain Wall-Magnetic Tunnel Junction Analog Content Addressable Memory Using Current and Projected Data,"With the rise in in-memory computing architectures to reduce the
compute-memory bottleneck, a new bottleneck is present between analog and
digital conversion. Analog content-addressable memories (ACAM) are being
recently studied for in-memory computing to efficiently convert between analog
and digital signals. Magnetic memory elements such as magnetic tunnel junctions
(MTJs) could be useful for ACAM due to their low read/write energy and high
endurance, but MTJs are usually restricted to digital values. The spin orbit
torque-driven domain wall-magnetic tunnel junction (DW-MTJ) has been recently
shown to have multi-bit function. Here, an ACAM circuit is studied that uses
two domain wall-magnetic tunnel junctions (DW-MTJs) as the analog storage
elements. Prototype DW-MTJ data is input into the magnetic ACAM (MACAM) circuit
simulation, showing ternary CAM function. Device-circuit co-design is carried
out, showing that 8-10 weight bits are achievable, and that designing
asymmetrical spacing of the available DW positions in the device leads to
evenly spaced ACAM search bounds. Analyzing available spin orbit torque
materials shows platinum provides the largest MACAM search bound while still
allowing spin orbit torque domain wall motion, and that the circuit is
optimized with minimized MTJ resistance, minimized spin orbit torque material
resistance, and maximized tunnel magnetoresistance. These results show the
feasibility of using DW-MTJs for MACAM and provide design parameters.",2301.04598v1
2023-04-26,Microbial Corrosion Prevention by Citrobacter sp. Biofilms,"Microbiologically influenced corrosion (MIC) compromises the integrity of
many technologically relevant metals. Protective coatings based on synthetic
materials pose potential environmental impacts. Here, we report a MIC resistant
coating based on a biofilm matrix of Citrobacter sp. strain MIC21 on underlying
copper (Cu) surfaces. Three identical corrosion cells varying in the type of
working electrode (annealed Cu, 29.5% coldworked, and 56.2% coldworked Cu) were
used. Graphite plate and Ag/AgCl served as counter and reference electrodes,
respectively. The working electrolyte was based on lactate-C media along with
an inocula consisting of Oleidesulfovibrio alaskensis strain G20 and
Citrobacter sp. strain MIC21. Passivating effect of the co-cultured biofilm
matrix was observed in the form of an ennoblement effect. Tests based on
sequencing, microscopy, and spectroscopy revealed the formation of a compact
biofilm matrix dominated by strain MIC21 cells, exopolymers, and insoluble
precipitates. This matrix displayed elastic modulus (a measure of rigidity) as
high as 0.8 Gpa and increased corrosion resistance by ~10-fold. Interestingly,
strain MIC21 has the capacity to inhibit the undesirable growth of aggressive
strain G20. Additional corrosion tests also substantiated the passivation
effects of strain MIC21. We provide mechanistic insight into the underlying
reasons responsible for corrosion prevention behavior of the biofilm matrix.",2304.13862v1
2023-06-01,Bulk conducting states of intrinsically doped Bi$_2$Se$_3$,"With a large band gap and a single Dirac cone responsible for the topological
surface states, Bi2Se3 is widely regarded as a prototypical 3D topological
insulator. Further applications of the bulk material has, however, been
hindered by inherent structural defects that donate electrons and make the bulk
conductive. Consequently, controlling these defects is of great interest for
future technological applications, and while past literature has focused on
adding external doping elements to the mixture, a complete study on undoped
Bi2Se3 was still lacking. In this work, we use the self-flux method to obtain
high-quality Bi2Se3 single-crystals in the entire concentration range available
on the phase-diagram for the technique. By combining basic structural
characterization with measurements of the resistivity, Hall effect and
Shubnikov-de Haas (SdH) quantum oscillations, the effects of these impurities
on the bulk transport are investigated in samples with electron densities
ranging from 10^17 cm^-3 to 10^19 cm^-3, from Se-rich to Bi-rich mixtures,
respectively, evidencing the transition into a degenerate semiconductor regime.
We find that electron-donor impurities, likely Se vacancies, unavoidably shift
the Fermi level up to 200 meV inside the conduction band. Other impurities,
like interstitial Bi and Se, are shown to play a significant role as scattering
centres, specially at low temperatures and in the decoherence of the SdH
oscillations. Previous open questions on Bi2Se3, such as the upturn in
resistivity below 30 K, the different scattering times in transport and quantum
oscillations, and the presence of additional low mobility bands, are addressed.
The results outlined here provide a concise picture on the bulk conducting
states in flux-grown Bi2Se3 single crystals, enabling better control of the
structural defects and electronic properties.",2306.00827v1
2023-07-06,"Tunable magnetism and electron correlation in Titanium-based Kagome metals RETi3Bi4 (RE = Yb, Pr, and Nd) by rare-earth engineering","Rare-earth engineering is an effective way to introduce and tune the
magnetism in topological Kagome magnets, which has been acting as a fertile
platform to investigate the quantum interactions between geometry, topology,
spin, and correlation. Here we report the structure and properties of three
newly discovered Titanium-based Kagome metals RETi3Bi4 (RE = Yb, Pr, and Nd)
with various magnetic states. They crystalize in the orthogonal space group
Fmmm (No.69), where slightly distorted Ti Kagome lattice, RE triangular
lattice, Bi honeycomb and triangular lattices stack along the a axis. By
changing the rare earth atoms on RE zag-zig chains, the magnetism can be tuned
from nonmagnetic YbTi3Bi4 to short-range ordered PrTi3Bi4 (Tanomaly ~ 8.2 K),
and finally to ferromagnetic NdTi3Bi4 (Tc ~ 8.5 K). The measurements of
resistivity and specific heat capacity demonstrate an evolution of electron
correlation and density of states near the Fermi level with different rare
earth atoms. In-situ resistance measurements of NdTi3Bi4 under high pressure
further reveal a potential relationship between the electron correlation and
ferromagnetic ordering temperature. These results highlight RETi3Bi4 as another
family of topological Kagome magnets to explore nontrivial band topology and
exotic phases in Kagome materials.",2307.02942v1
2023-09-23,Three-dimensional graphene on a nano-porous 4H-SiC backbone: a novel material for food sensing applications,"Sensors which are sensitive to volatile organic compounds and thus able to
monitor the conservation state of food, are precious because they work
non-destructively and allow to avoid direct contact with the food, ensuring
hygienic conditions. In particular, the monitoring of rancidity would solve a
widespread issue in food storage. The sensor discussed here is produced
utilizing a novel three-dimensional arrangement of graphene, which is grown on
a crystalline silicon carbide (SiC) wafer previously porousified by chemical
etching. This approach allows a very high surface-to.volume ratio. Furthermore,
the structure of the sensor surface features a large amount of edges, dangling
bounds, and active sites, which make the sensor, on a chemically robust
skeleton, chemically active, particularly to hydrogenated molecules. The
interaction of the sensor with such compounds is read out by measuring the
sensor resistance in a four wire configuration. The sensor performance has been
assessed on three hazelnut samples: sound hazelnuts, spoiled hazelnuts, and
stink bug hazelnuts. A resistance variation of about DeltaR = 0.13 (0.02) Ohm
between sound and damaged hazelnuts has been detected. Our measurements confirm
the ability of the sensor to discriminate between sound and damaged hazelnuts.
The sensor signal is stable for days, providing the possibility to use this
sensor for the monitoring of the storage state of fats and foods in general.",2309.13431v1
2023-09-26,On Hyperelastic Crease,"We present analyses of crease-formation and stability criteria for
incompressible hyperelastic solids. A generic singular perturbation over a
laterally compressed half-space creates a far-field eigenmode of three
energy-release angular sectors separated by two energy-elevating sectors of
incremental deformation. The far-field eigenmode braces the energy-release
field of the surface flaw against the transition to a self-similar crease
field, and the braced-incremental-deformation (bid) field has a unique shape
factor that determines the creasing stability. The shape factor, which is
identified by two conservation integrals that represent a subsurface
dislocation in the tangential manifold, is a monotonically increasing function
of compressive strain. For Neo-Hookean material, when the shape factor is below
unity, the bid field is configurationally stable. When the compressive strain
is 0.356, the shape factor becomes unity, and the bid field undergoes a
higher-order transition to a crease field. At the crease-limit point, we have
two asymptotic solutions of the crease-tip folding field and the leading-order
far field with two scaling parameters, the ratio of which is determined by
matched asymptotes. Our analyses show that the surface is stable against
singular perturbation up to the crease limit point and becomes unstable beyond
the limit. However, the flat state is metastable against a regular perturbation
between the crease limit point and wrinkle critical point, which is a
first-order instability point. We introduced a novel finite element method for
simulating the bid field with a finite domain size. For Gent model, the
strain-stiffening alters the shape factor dependence on the compressive strain,
raising crease resistance. The new findings in crease mechanisms will help
study ruga mechanics of self-organization and design soft-material structures
for high crease resistance.",2309.14626v1
2024-02-15,Quantum Linear Magnetoresistance and Fermi Liquid Behavior in Kagome Metal Ni3In2S2,"Kagome metals gain attention as they manifest a spectrum of quantum
phenomena, including superconductivity, charge order, frustrated magnetism, and
intertwined correlated states of condensed matter. With regard to electronic
band structure, several of the them exhibit non-trivial topological
characteristics. Here, we present a thorough investigation on the growth and
the physical properties of single crystals of Ni3In2S2 which is established to
be a Dirac nodal line Kagome metal. Extensive characterization is attained
through temperature and field-dependent resistivity, angle-dependent
magnetoresistance and specific heat measurements. In most metals, the Fermi
liquid behaviour is mostly restricted to a narrow range of temperature. In
Ni3In2S2, this characteristic feature has been observed for an extensive
temperature range of 82 K. This is attributed to the strong electron-electron
correlation in the material. Specific heat measurements reveal a high
Kadowaki-Woods ratio which is in good agreement with strongly correlated
systems. Almost linear positive magnetoresistance follows the conventional
Kohler scaling which depicts the applicability of semi-classical theories. The
angle-dependent magneto-resistance been explained using the Voigt-Thomson
formula. Furthermore, de-Haas van Alphen oscillations are observed in
magnetization vs. magnetic field measurement which shed light on the
topological features in the Shandite Ni3In2S2.",2402.10096v1
2022-11-28,On the energy conversion efficiency of the bulk photovoltaic effect,"The bulk photovoltaic effect (BPVE) leads to directed photo-currents and
photo-voltages in bulk materials. Unlike photo-voltages in p-n junction solar
cells that are limited by carrier recombination to values below the bandgap
energy of the absorbing material, the BPVE photo-voltages have been shown to
greatly exceed the bandgap energy. Therefore the BPVE is not subject to the
Shockley-Queisser limit for sunlight to electricity conversion in single
junction solar cells and experimental claims of efficiencies beyond this limit
have been made. Here, we show that BPVE energy conversion efficiencies are, in
practice, orders of magnitude below the Shockley-Queisser limit of single
junction solar cells and are subject to different, more stringent limits. The
name BPVE stands for two different fundamental effects, the shift current and
the injection current. In both of these, the voltage bias necessary to produce
electrical energy, accelerates both, intrinsic and photo-generated, carriers.
We discuss how energy conservation alone fundamentally limits the BPVE to a
bandgap-dependent value that exceeds the Shockley Queisser limit only for very
small bandgaps. Yet, small bandgap materials have a large number of intrinsic
carriers, leading to high conductivity which suppresses the photo-voltage. We
discuss further how slightly more stringent fundamental limits for injection
(ballistic) currents may be derived from the trade-off between high
resistivity, needed for a high voltage, and long ballistic transport length,
needed for a high current. We also explain how erroneous experimental and
theoretical claims of high efficiency have arisen. Finally, we calculate the
energy conversion efficiency for an example 2D material that has been suggested
as candidate material for high efficiency BPVE based solar cells and show that
the efficiency is very similar to the efficiency of known 3D materials.",2211.15124v2
2016-07-06,Thermal Resistances of Thin-Films of Small Molecule Organic Semiconductors,"We have measured the thermal resistances of thin films of the small molecule
organic semiconductors bis(triisopropylsilylethynyl) pentacene (TIPS-pn),
bis(triethylsilylethynyl) anthradithiophene (TES-ADT) and difluoro
bis(triethylsilylethynyl) anthradithiophene (diF-TES-ADT). For each material,
several films of different thicknesses have been measured to separate the
effects of intrinsic thermal conductivity from interface thermal resistance.
For non-crystalline films of all three materials, with thicknesses ranging from
< 100 nm to > 4 microns, the thermal conductivities are similar to that of
polymers and over an order of magnitude smaller than that of the crystals,
reflecting the large reduction in phonon mean-free path in the films. Thin (<
205 nm) crystalline films of TES-ADT, prepared by vapor-annealing spin-cast
films, have also been measured, but for these the thermal resistances are
dominated by interface scattering.",1607.01712v2
2012-06-11,Thermal Stability of Thermoelectric Materials via In Situ Resistivity Measurements,"An experimental setup for determining the electrical resistivity of several
types of thermoelectric materials over the temperature range 20 < T < 550 C is
described in detail. One resistivity measurement during temperature cycling is
also explained for Cu0.01Bi2Te2.7Se0.3 while a second measurement is made on
Yb0.35Co4Sb12 as a function of time at 400 C. Both measurements confirm that
the materials are thermally stable for the temperature range and time period
measured. Measurements made during temperature cycling show an irreversible
decrease in the electrical resistivity of Cu0.01Bi2Te2.7Se0.3 when the
measuring temperature exceeds the pressing temperature. Several other possible
uses of such a system include but are not limited to studying the effects of
annealing and/or oxidation as a function of both temperature and time.",1206.2094v1
2022-07-27,Terahertz microresonators for material characterisation,"Terahertz (THz) technology is rapidly evolving, and the advancement of data
and information processing devices is essential. Silicon THz microresonators
provide perfect platforms to develop compact and integrated devices that could
transform THz technology. Here we present a systematic study on the key figure
of merit of silicon THz disc microresonators - the quality factor (Q-factor) -
in dependence on the substrate's resistivity. Our results show that the
Q-factor depends linearly on the resistivity and a variation in resistivity
from 10k$\Omega$cm to 15k$\Omega$cm changes the Q-factor from 50k to 76k at
0.6THz. Moreover, we experimentally determine that the silicon material
absorption is inversely proportional to the substrate's resistivity. In
general, the presented methodology is ideally suited to precisely measure the
material absorption of low-loss materials in the THz domain, which is
challenging using conventional THz spectroscopy.",2207.13818v1
2023-03-24,Charge-density-wave resistive switching and voltage oscillations in ternary chalcogenide BaTiS3,"Phase change materials, which show different electrical characteristics
across the phase transitions, have attracted considerable research attention
for their potential electronic device applications. Materials with
metal-to-insulator or charge density wave (CDW) transitions such as VO2 and
1T-TaS2 have demonstrated voltage oscillations due to their robust bi-state
resistive switching behavior with some basic neuronal characteristics. BaTiS3
is a small bandgap ternary chalcogenide that has recently reported the
emergence CDW order below 245 K. Here, we report on the discovery of DC voltage
/ current-induced reversible threshold switching in BaTiS3 devices between a
CDW phase and a room temperature semiconducting phase. The resistive switching
behavior is consistent with a Joule heating scheme and sustained voltage
oscillations with a frequency of up to 1 kHz has been demonstrated by
leveraging the CDW phase transition and the associated negative differential
resistance. Strategies of reducing channel sizes and improving thermal
management may further improve the device performance. Our findings establish
BaTiS3 as a promising CDW material for future energy-efficient electronics,
especially for neuromorphic computing.",2303.14169v1
2016-02-24,Design and optimization of resistive anode for a two-dimensional imaging triple-GEM detector,"The optimization of resistive anode for two dimensional imaging detectors
which consists of a series of high resistive square pads surrounding by low
resistive strips has been studied by both numerical simulations and
experimental tests. It has been found that to obtain good detector performance,
the resistance ratio of the pad to the strip should be larger than 5, the
nonuniformity of the pad surface resistivity had better be less than $20\%$, a
smaller pad width leads to a smaller spatial resolution and when the pad width
is $6mm$, the spatial resolution ($\sigma$) can reach about $105{\mu}m$. Based
on the study results, a 2-D GEM detector prototype with the optimized resistive
anode is constructed and a good imaging performance is achieved.",1602.07438v1
2017-09-19,Considering non-uniform current distributions in magnetoresistive sensor designs and their implications for the resistance transfer function,"Non-uniform current distributions of spin valves with disk shaped free layers
are investigated. In the context of spin valves, the vortex state, which is the
ground-state in many disk shaped magnetic bodies, allows for distinct parallel
channels of high and low resistivity. The readout current is thus able to evade
high resistivity regions in favor of low resistivity regions, giving rise to
'conductive inhomogeneities'. Therefore, the total resistance of the spin valve
does not always correspond exactly to the total average magnetization of the
free layer. In addition, the resistance transfer function can be significantly
influenced by the spatial placement of the electrodes, giving rise to
'geometric inhomogeneities'. The resulting deviations from resistance to
magnetization transfer function are investigated for different spin valve
geometries and compared to measurements of comparable devices.",1709.06394v1
2023-09-19,Effects of plasma resistivity in three-dimensional full-F gyro-fluid turbulence simulations,"A full-F, isothermal, electromagnetic, gyro-fluid model is used to simulate
plasma turbulence in a COMPASS-sized, diverted tokamak. A parameter scan
covering three orders of magnitude of plasma resistivity and two values for the
ion to electron temperature ratio with otherwise fixed parameters is setup and
analysed. Simulations are performed with a new version of the FELTOR code,
which is fully parallelized on GPUs. Each simulation covers a couple of
milliseconds.
  Two transport regimes for high and low plasma resistivities are revealed.
Beyond a critical resistivity the mass and energy confinement reduces with
increasing resistivity. Further, for high plasma resistivity the direction of
parallel acceleration is swapped compared to low resistivity.
  The integration of exact conservation laws over the closed field line region
allows for an identification of numerical errors within the simulations. The
electron force balance and energy conservation show relative errors on the
order of $10^{-3}$ while the particle conservation and ion momentum balance
show errors on the order of $10^{-2}$.
  Relative fluctuations amplitudes increase from below $1\%$ in the core to
$15\%$ in the edge and up to $40\%$ in the scrape-off layer.
  Finally, three-dimensional visualisations using ray tracing techniques are
displayed and discussed. The field-alignment of turbulent fluctuations in
density and parallel current becomes evident.",2309.10414v1
2016-11-09,"TiO$_2$-based Memristors and ReRAM: Materials, Mechanisms and Models (a Review)","The memristor is the fundamental non-linear circuit element, with uses in
computing and computer memory. ReRAM (Resistive Random Access Memory) is a
resistive switching memory proposed as a non-volatile memory. In this review we
shall summarise the state of the art for these closely-related fields,
concentrating on titanium dioxide, the well-utilised and archetypal material
for both. We shall cover material properties, switching mechanisms and models
to demonstrate what ReRAM and memristor scientists can learn from each other
and examine the outlook for these technologies.",1611.04456v1
2018-10-30,An alternative to the topological interpretation of the transverse resistivity anomalies in SrRuO3,"We clarify the physical origin of anomalies in transverse resistivity often
observed in exotic materials, such as SrRuO3, in which the Berry curvature is
manifested in the transport properties. The previously attributed mechanism for
the anomalies, the topological Hall effect (THE), is refuted by our thorough
investigations as well as formulation of a model considering inhomogeneous
magnetoelectric properties in the material. Our analyses fully explain every
feature of the anomalies without resorting to the THE. The present results
establish a fundamental understanding, which was previously overlooked, of
magneto-transport properties in such exotic materials.",1810.12529v1
2004-11-26,The Acceleration Mechanism of Resistive MHD Jets Launched from Accretion Disks,"We analyzed the results of non-linear resistive magnetohydrodynamical (MHD)
simulations of jet formation to study the acceleration mechanism of
axisymmetric, resistive MHD jets. The initial state is a constant angular
momentum, polytropic torus threaded by weak uniform vertical magnetic fields.
The time evolution of the torus is simulated by applying the CIP-MOCCT scheme
extended for resistive MHD equations. We carried out simulations up to 50
rotation period at the innermost radius of the disk created by accretion from
the torus. The acceleration forces and the characteristics of resistive jets
were studied by computing forces acting on Lagrangian test particles. Since the
angle between the rotation axis of the disk and magnetic field lines is smaller
in resistive models than in ideal MHD models, magnetocentrifugal acceleration
is smaller. The effective potential along a magnetic field line has maximum
around $z \sim 0.5r_0$ in resistive models, where $r_0$ is the radius where the
density of the initial torus is maximum. Jets are launched after the disk
material is lifted to this height by pressure gradient force. Even in this
case, the main acceleration force around the slow magnetosonic point is the
magnetocentrifugal force. The power of the resistive MHD jet is comparable to
the mechanical energy liberated in the disk by mass accretion. Joule heating is
not essential for the formation of jets.",0411712v1
2016-10-30,Temperature and Humidity Dependence of Resistance in Nano-Diamond Powder,"The electrical resistance of detonation nano-diamond powders was measured
from liquid nitrogen temperature to room temperature and in relative humidity
environments from around 10% to 100%. After sample exposures of several hours
at 100% relative humidity at room temperature (around 295 K), when the
temperature was reduced, the resistance increased to the upper measurement
limit of our apparatus (120 M{\Omega}) at around 240 K. Upon warming, the
resistance dropped back to the room temperature value, with some hysteresis.
For sample exposures after several hours at 100% relative humidity at room
temperature, as the relative humidity was reduced, the sample resistance
increased to the upper range limit of the apparatus. As the relative humidity
was then increased (all at room temperature), the resistance dropped. For
samples exposed to low (~10%) relative humidity for several hours at room
temperature, as the humidity was increased (at room temperature), the
resistance decreased, and then increased when the humidity was reduced. The
temperature behavior was markedly differ from that of powdered graphite and
multi-walled carbon nano tubes.",1611.02242v2
2018-07-04,Gate controlled large resistance switching driven by charge density wave in 1T-TaS2/2H-MoS2 heterojunction,"1T-TaS2 is a layered material that exhibits charge density wave (CDW) induced
distinct electrical resistivity phases and has attracted a lot of attention for
interesting device applications. However, such resistivity switching effects
are often weak, and cannot be modulated by an external gate voltage - limiting
their widespread usage. Using a back-gated 1T-TaS2/2H-MoS2 heterojunction, here
we show that the usual resistivity switching in TaS2 due to different phase
transitions is accompanied with a surprisingly strong modulation in the
Schottky barrier height (SBH) at the TaS2/MoS2 interface - providing an
additional knob to control the degree of the phase-transition-driven
resistivity switching by an external gate voltage. In particular, the
commensurate (C) to triclinic (T) phase transition results in an increase in
the SBH owing to a collapse of the Mott gap in TaS2. The change in SBH allows
us to estimate an electrical Mott gap opening of ~71 +/- 7 meV in the C phase
of TaS2. On the other hand, the nearly-commensurate (NC) to incommensurate (IC)
phase transition results in a suppression in the SBH, and the heterojunction
shows a gate-controlled resistivity switching up to 17.3, which is ~14.5 times
higher than that of standalone TaS2. The findings mark an important step
forward showing a promising pathway to externally control as well as amplify
the CDW induced resistivity switching. This will boost device applications that
exploit these phase transitions, such as ultra-broadband photodetection,
negative differential conductance, fast oscillator and threshold switching in
neuromorphic circuits.",1807.01652v2
2008-10-08,Performance Analysis of 60nm gate length III-V InGaAs HEMTs: Simulations vs. experiments,"An analysis of recent experimental data for high-performance In0.7Ga0.3As
high electron mobility transistors (HEMTs) is presented. Using a fully quantum
mechanical, ballistic model, we simulate In0.7Ga0.3As HEMTs with gate lengths
of LG = 60nm, 85, and 135 nm and compare the result to the measured I-V
characteristics including draininduced barrier lowering, sub-threshold swing,
and threshold voltage variation with gate insulator thickness, as well as
on-current performance. To first order, devices with three different oxide
thicknesses and channel lengths can all be described by our ballistic model
with appropriate values of parasitic series resistance. For high gate voltages,
however, the ballistic simulations consistently overestimate the measured
on-current, and they do not show the experimentally observed decrease in
on-current with increasing gate length. With no parasitic series resistance at
all, the simulated on-current of the LG = 60 nm device is about twice the
measured current. According to the simulation, the estimated ballistic carrier
injection velocity for this device is about 2.7 x 10^7 cm/s. Because of the
importance of the semiconductor capacitance, the simulated gate capacitance is
about 2.5 times less than the insulator capacitance. Possible causes of the
transconductance degradation observed under high gate voltages in these devices
are also explored. In addition to a possible gate-voltage dependent scattering
mechanism, the limited ability of the source to supply carriers to the channel,
and the effect of nonparabolicity are likely to play a role. The drop in
on-current with increasing gate length is an indication that the devices
operate below the ballistic limit.",0810.1540v1
2008-12-26,Flux quanta driven by high-density currents in low-impurity V3Si and LuNi2B2C: free flux flow and flux-core size effect,"High density direct currents (DC) are used to drive flux quanta via the
Lorentz force towards a highly ordered ""free flux flow"" (FFF) dynamic state,
made possible by the weak-pinning environment of high-quality, single-crystal
samples of two low-Tc superconducting compounds, V3Si and LuNi2B2C. We report
the effect of the magnetic field-dependent fluxon core size on flux flow
resistivity rho_f. Much progress has been made in minimizing the technical
challenges associated with the use of high currents. Attainment of a FFF phase
is indicated by the saturation at highest currents of flux-flow dissipation
levels that are well below the normal state resistance and have field-dependent
values. The field dependence of the corresponding rho_f is shown to be
consistent with a prediction based on a model for the decrease of flux core
size at higher fields in weak-coupling BCS s-wave materials.",0812.4715v4
2020-06-01,Radiation hardness of GaAs: Cr and Si sensors irradiated by electron beam,"The interest in using the radiation detectors based on high resistive
chromium-compensated GaAs (GaAs:Cr) in high energy physics and others applied
fields has been growing steadily due to its numerous advantages over others
classical materials. High radiation hardness at room temperature stands out and
needs to be systematically investigated. In this paper an experimental study of
the effect of 20.9 MeV electrons generated by the LINAC-200 accelerator on some
properties of GaAs:Cr based sensors is presented. In parallel, Si sensors were
irradiated at the same conditions, measured and analyzed in order to perform a
comparative study. The target sensors were irradiated with the dose up to 1.5
MGy. The current-voltage characteristics, resistivity, charge collection
efficiency and their dependences on the bias voltage and temperature were
measured at different absorbed doses. An analysis of the possible microscopic
mechanisms leading to the observed effects in GaAs:Cr sensors is presented in
the article.",2006.01254v1
2021-02-04,Quantum Transport in Two-Dimensional WS$_2$ with High-Efficiency Carrier Injection Through Indium Alloy Contacts,"Two-dimensional transition metal dichalcogenides (TMDCs) have properties
attractive for optoelectronic and quantum applications. A crucial element for
devices is the metal-semiconductor interface. However, high contact resistances
have hindered progress. Quantum transport studies are scant as low-quality
contacts are intractable at cryogenic temperatures. Here, temperature-dependent
transfer length measurements are performed on chemical vapour deposition grown
single-layer and bilayer WS$_2$ devices with indium alloy contacts. The devices
exhibit low contact resistances and Schottky barrier heights (\sim10
k$\Omega$\si{\micro\metre} at 3 K and 1.7 meV). Efficient carrier injection
enables high carrier mobilities ($\sim$190 cm$^2$V$^{-1}$s$^{-1}$) and
observation of resonant tunnelling. Density functional theory calculations
provide insights into quantum transport and properties of the WS$_2$-indium
interface. Our results reveal significant advances towards high-performance
WS$_2$ devices using indium alloy contacts.",2102.02489v1
2021-08-11,Single-domain perpendicular magnetization induced by the coherent O 2p-Ru 4d hybridized state in an ultra-high-quality SrRuO3 film,"We investigated the Ru 4d and O 2p electronic structure and magnetic
properties of an ultra-high-quality SrRuO3 film on SrTiO3 grown by
machine-learning-assisted molecular beam epitaxy. The high itinerancy and long
quantum lifetimes of the quasiparticles in the Ru 4d t2g-O 2p hybridized
valence band are confirmed by observing the prominent well-screened peak in the
Ru 3d core-level photoemission spectrum, the coherent peak near the Fermi
energy in the valence band spectrum, and quantum oscillations in the
resistivity. The element-specific magnetic properties and the hybridization
between the Ru 4d and O 2p orbitals were characterized by Ru M2,3-edge and O
K-edge soft X-ray absorption spectroscopy and X-ray magnetic circular dichroism
measurements. The ultra-high-quality SrRuO3 film with the residual resistivity
ratio of 86 shows the large orbital magnetic moment of oxygen ions induced by
the strong orbital hybridization of the O 2p states with the spin-polarized Ru
4d t2g states. The film also shows single-domain perpendicular magnetization
with an almost ideal remanent magnetization ratio of 0.97. These results
provide detailed insights into the relevance between orbital hybridization and
the perpendicular magnetic anisotropy in SrRuO3/SrTiO3 systems.",2108.04980v1
2009-08-03,Resistivity of Mn$_{1-x}$Fe$_x$Si single crystals: Evidence for quantum critical behavior,"Resistivity measurements have been made on Mn$_{1-x}$Fe$_x$Si single crystals
between 2 and 300K for $x$ = 0, 0.05, 0.08, 0.12 and 0.15. Fe doping is found
to depress the magnetic ordering temperature from 30K for $x$ = 0 to below 2K
for $x$ = 0.15. Although Fe doping results in a large increase of the
low-temperature residual resistivity, the temperature dependence of the
resistivity above the magnetic transition remains practically unaffected by
increasing Fe content. An analysis of the temperature derivative of the
resistivity provides strong evidence for the existence of a non-Fermi-liquid
ground state near $x$ = 0.15 and thus for a quantum critical point tuned by Fe
content.",0908.0294v1
2012-10-09,Effect of back-gate on contact resistance and on channel conductance in graphene-based field-effect transistors,"We study the contact resistance and the transfer characteristics of
back-gated field effect transistors of mono- and bi-layer graphene. We measure
specific contact resistivity of ~7kohm*um2 and ~30kohm*um2 for Ni and Ti,
respectively. We show that the contact resistance is a significant contributor
to the total source-to-drain resistance and it is modulated by the back-gate
voltage. We measure transfer characteristics showing double dip feature that we
explain as the effect of doping due to charge transfer from the contacts
causing minimum density of states for graphene under the contacts and in the
channel at different gate voltage.",1210.2531v1
2013-07-01,Magnetic and transport parameters of LSMO and YBCO/LSMO films deposited on sapphire substrates,"The La0.7Sr0.3MnO3 (LSMO) layers and YBa2Cu3O7-{\delta}/La0.7Sr0.3MnO3
(YBCO/LSMO) bilayers were grown by magnetron sputtering on sapphire (Al2O3 or
ALO) substrates. Temperature dependences of resistance of single LSMO films,
grown on ALO substrates were typical for polycrystalline manganite materials
and the resistance decreased with decrease of the temperature at medium
temperatures and increased at lower and higher temperatures. Deposition of a
top YBCO layer led to a drastic increase of the sample resistance. These
bilayers did not demonstrate a decreasing of the resistance with decrease of
temperature. Temperature dependence of the resistance of these samples was
interpreted in the framework of a phenomenological model of two intergrain
conduction channels. In framework of this model, parameters of the samples were
determined and discussed.",1307.0302v1
2015-01-27,Realization of a reversible switching in TaO2 polymorphs via Peierls distortion for resistance random access memory,"Transition-metal-oxide based resistance random access memory is a promising
candidate for next-generation universal non-volatile memories. Searching and
designing appropriate new materials used in the memories becomes an urgent
task. Here, a new structure with the TaO2 formula was predicted using
evolutionary algorithms in combination with first-principles calculations. This
new structure having a triclinic symmetry (T-TaO2) is both energetically and
dynamically more favorable than the commonly believed rutile structure
(R-TaO2). Our hybrid functional calculations show that T-TaO2 is a
semiconductor with a band gap of 1.0 eV, while R-TaO2 is a metallic conductor.
This large difference in electrical property makes TaO2 a potential candidate
for resistance random access memory (RRAM). Furthermore, we have shown that
T-TaO2 is actually a Peierls distorted R-TaO2 phase and the transition between
these two structures is via a directional displacement of Ta atoms. The energy
barrier for the reversible phase transition from R-TaO2 to T-TaO2 is 0.19
eV/atom and the other way around is 0.23 eV/atom, suggesting low power
consumption for the resistance switch. The present findings provide a new
mechanism for the resistance switch and will also stimulate experimental work
to fabricate tantalum oxides based RRAM.",1501.06632v1
2015-02-09,Four-Probe Methods for Measuring the Resistivity of Samples in the Form of Rectangular Parallelepipeds,"The problem of measuring the resistivity of isotropic samples of finite
dimensions in the form of rectangular parallelepipeds using the four-probe
technique was considered. Two variants of contact arrangements were studied:
(1) four collinear probes are positioned on one side of a sample symmetrically
with respect to the other sides, and (2) two probes on one side of a sample and
two on the opposite side are placed precisely in opposite positions and
symmetrically with respect to the other sides of the sample (the Schnabel
method). Solutions of the problem of the electric field potential distribution
in a sample for different positions of the current contacts were found. The
solutions were obtained in the form of double series and methods of their
summation are presented. The obtained results are extended to the case of
measuring the resistivity of anisotropic samples when the resistivity tensor
has two independent components. The results of using the developed technique
for measuring the resistivity of such a highly anisotropic material as highly
oriented pyrolitic graphite using the Schnabel method are presented.",1502.02600v1
2019-12-10,Resistance Drift in Ge2Sb2Te5 Phase Change Memory Line Cells at Low Temperatures and Its Response to Photoexcitation,"Resistance drift in phase change materials is characterized in amorphous
phase change memory line-cells from 300 K to 125 K range and is observed to
follow the previously reported power-law behavior with drift coefficients in
the 0.07 to 0.11 range in dark. While these drift coefficients measured in dark
are similar to commonly observed drift coefficients (~0.1) at and above room
temperature, measurements under light show a significantly lower drift
coefficient (0.05 under illumination versus 0.09 in dark at 150K). Periodic
on/off switching of light shows sudden decrease/increase of resistance,
attributed to photo-excited carriers, followed by a very slow response (~30
minutes at 150 K) attributed to contribution of charge traps. Continuation of
the resistance drift at low temperatures and the observed photo-response
suggest that resistance drift in amorphous phase change materials is
predominantly an electronic process.",1912.04480v2
2022-04-04,"Inter- to Intra-Layer Resistivity Anisotropy of NdFeAs(O,H) with Various Hydrogen Concentrations","With molecular beam epitaxy and topotactic chemical reaction, we prepared
NdFeAs(O,H) epitaxial thin films with various hydrogen concentrations on
5{\deg} vicinal cut MgO substrates. By measuring the resistivities along the
longitudinal and transversal directions, the ab plane and the c axis
resistivities (\{rho}_ab and \{rho}_c) were obtained. The resistivity
anisotropy {\gamma}_\{rho}=\{rho}_c \ \{rho}_ab of NdFeAs(O,H) with various
hydrogen concentrations was compared with that of NdFeAs(O,F). At the H
concentrations which led to superconducting transition temperatures Tc over 40
K, {\gamma}_\r{ho} recorded ~100-150 at 50 K. On the other hand, a low
{\gamma}_\{rho} value of 9 was observed with the mostly doped sample. The
exponent \{beta} of the ab plane resistivity obtained by fitting a power law
expression \{rho}_{ab}(T)=\{rho}_0+AT^\{beta} to the data was close to unity
down to low temperature in the vicinity where the second antiferromagnetic
phase locates, which may be related to the quantum critical point discussed at
the over-doped side of the phase diagram.",2204.01554v1
2020-04-28,A Route to High-Toughness Battery Electrodes,"There is increasing interest in materials that combine energy-storing
functions with augmented mechanical properties, ranging from flexibility in
bending to stretchability to structural properties. In the case of lithium-ion
batteries, these mechanical functions could enable their integration in
emerging technologies such as wearable, free-form electronics and ultimately as
structural elements, for example, in transport applications. This work presents
a method to produce flexible LiFePO4 LFP electrodes with an extraordinary
combination of electrochemical and mechanical performance. Such electrodes
exhibit an exceptionally high specific toughness, combined with superior rate
capability and energy density, with respect to reference electrodes with
typical metallic current collectors. These properties are a result of the
strong adhesion of the active material particles to the high surface area
carbon nanotube fiber fabric, used as a lightweight, tough, and highly
conducting current collector. This strong adherence minimizes electrical
resistance, mitigates interfacial failure, and increases ductility through
heterogeneous strain after cohesive failure of the inorganic phase. As a
result, these electrodes can withstand large deformations before fracture, and,
even after fracture, they retain excellent electrochemical performance,
approximately double that of unstretched, Al-supported LFP electrodes with
equivalent loading.",2004.13350v1
2023-02-02,High-entropy silicide superconductors with W$_{5}$Si$_{3}$-type structure,"We report the synthesis, crystal structure and physical properties of two new
high-entropy silicides (HESs), namely
(Nb$_{0.1}$Mo$_{0.3}$W$_{0.3}$Re$_{0.2}$Ru$_{0.1}$)$_{5}$Si$_{3}$ and
(Nb$_{0.2}$Mo$_{0.3}$W$_{0.3}$Re$_{0.1}$Ru$_{0.1}$)$_{5}$Si$_{3}$. Structural
analysis indicates that both HESs consist of a (nearly) single tetragonal
W$_{5}$Si$_{3}$-type phase (space group $I$4/$mcm$) with a disordered cation
distribution. Electrical resistivity, magnetic susceptibility and specific heat
measurements show that
(Nb$_{0.1}$Mo$_{0.3}$W$_{0.3}$Re$_{0.2}$Ru$_{0.1}$)$_{5}$Si$_{3}$ and
(Nb$_{0.2}$Mo$_{0.3}$W$_{0.3}$Re$_{0.1}$Ru$_{0.1}$)$_{5}$Si$_{3}$ are weakly
coupled bulk superconductors, which represent the first superconducting
high-entropy nonoxide ceramics. In particular, these HESs have higher $T_{\rm
c}$ values (3.2-3.3 K) compared with those of the binary counterparts, and
their $B_{\rm c2}$(0)/$T_{\rm c}$ ratios are the largest among superconductors
of the same structural type.",2302.00844v1
2024-01-15,Fatigue Behavior of High-Entropy Alloys,"High-entropy alloys (HEAs) refer to alloys composed of five or more elements
in equal or near-equal amounts or in an atomic concentration range of 5 to 35
atomic percent (at%). Different elemental ratios will affect the
microstructures of HEAs and provide them with unique properties. Based on past
research, HEAs have exhibited superior performance, relative to most
conventional alloys, with respect to many properties, such as strength,
toughness, corrosion resistance, magnetic behavior, etc. Among them, fatigue
behavior has been a topic of focus, due to its importance in industrial
applications. In this article, we summarized the research progress in the
HEA-fatigue behavior in the past ten years, including experimental results and
theoretical studies in subdivisions, such as high-cycle fatigue, low-cycle
fatigue, fatigue-crack growth, fatigue mechanisms, etc. The influence of the
processing and test methods on HEAs is described. The accuracy of several
commonly used prediction models is also outlined. Finally, unresolved issues
and suggestions on the direction of future research efforts are presented.",2401.07418v1
2024-01-26,Accelerated intermetallic phase amorphization in a Mg-based high-entropy alloy powder,"We describe a novel mechanism for the synthesis of a stable high-entropy
alloy powder from an otherwise immiscible Mg-Ti rich metallic mixture by
employing high-energy mechanical milling. The presented methodology expedites
the synthesis of amorphous alloy powder by strategically injecting entropic
disorder through the inclusion of multi-principal elements in the alloy
composition. Predictions from first principles and materials theory corroborate
the results from microscopic characterizations that reveal a transition of the
amorphous phase from a precursor intermetallic structure. This transformation,
characterized by the emergence of antisite disorder, lattice expansion, and the
presence of nanograin boundaries, signifies a departure from the precursor
intermetallic structure. Additionally, this phase transformation is accelerated
by the presence of multiple principal elements that induce severe lattice
distortion and a higher configurational entropy. The atomic size mismatch of
the dissimilar elements present in the alloy produces a stable amorphous phase
that resists reverting to an ordered lattice even on annealing.",2401.15197v2
2024-03-28,High Mobility Charge Transport in a Multicarrier Altermagnet CrSb,"A newly identified magnetic phase called altermagnet is being actively
studied because of its unprecedented spin-dependent phenomena. Among the
candidate materials, CrSb has a particularly high transition temperature and a
large spin-splitting energy, but its transport properties have remained
unexplored. In this study, we report the magnetotransport properties of CrSb
measured on single crystals. We found that the Hall resistivity shows a
nonlinear dependence on the magnetic field at low temperatures. From
symmetry-based considerations, however, this behavior can not be attributed to
an anomalous Hall effect, but to a multicarrier effect. A multicarrier fitting
to the in-plane conductivity tensor revealed that there are carriers with high
mobilities in CrSb, probably because of the presence of Weyl points in the
electronic structure.",2403.19233v1
2014-02-26,MoS2 P-type Transistors and Diodes Enabled by High Workfunction MoOx Contacts,"The development of low-resistance source/drain contacts to transition metal
dichalcogenides (TMDCs) is crucial for the realization of high-performance
logic components. In particular, efficient hole contacts are required for the
fabrication of p-type transistors with MoS2, a model TMDC. Previous studies
have shown that the Fermi level of elemental metals is pinned close to the
conduction band of MoS2, thus resulting in large Schottky barrier heights for
holes with limited hole injection from the contacts. Here, we show that
substoichiometric molybdenum trioxide (MoOx, x<3), a high workfunction
material, acts as an efficient hole injection layer to MoS2 and WSe2. In
particular, we demonstrate MoS2 p-type field-effect transistors and diodes by
using MoOx contacts. We also show drastic on-current improvement for p-type
WSe2 FETs with MoOx contacts over devices made with Pd contacts, which is the
prototypical metal used for hole injection. The work presents an important
advance in contact engineering of TMDCs and will enable future exploration of
their performance limits and intrinsic transport properties.",1402.6632v1
2015-03-23,Electron-Irradiation Induced Nanocrystallization of Pb(II) in Silica Gels Prepared in High Magnetic Field,"In a previous study, structure of silica gels prepared in a high magnetic
field was investigated. While a direct application of such anisotropic silica
gels is for an optical anisotropic medium possessing chemical resistance, we
show here their possibility of medium in materials processing. In this
direction, for example, silica hydrogels have so far been used as media of
crystal growth. In this paper, as opposed to the soft-wet state, dried silica
gels have been investigated. We have found that lead (II) nanocrystallites were
formed induced by electron irradiation to lead (II)-doped dried silica gels
prepared in a high magnetic field such as B = 10 T. Hydrogels made from a
sodium metasilicate solution doped with lead (II) acetate were prepared. The
dried specimens were irradiated by electrons in a transmission electron
microscope environment. Electron diffraction patterns indicated the
crystallinity of lead (II) nanocrystallites depending on B. An advantage of
this processing technique is that the crystallinity can be controlled through
the strength of magnetic field B applied during gel preparation. Specific
skills are not required to control the strength of magnetic field.",1503.06863v1
2017-04-07,Thermopower and thermal conductivity in the Weyl semimetal NbP,"The Weyl semimetal NbP exhibits an extremely large magnetoresistance (MR) and
an ultra-high mobility. The large MR originates from a combination of the
nearly perfect compensation between electron- and hole-type charge carriers and
the high mobility, which is relevant to the topological band structure. In this
work we report on temperature- and field-dependent thermopower and thermal
conductivity experiments on NbP. Additionally, we carried out complementary
heat capacity, magnetization, and electrical resistivity measurements. We found
a giant adiabatic magnetothermopower with a maximum of 800 $\mu$V/K at 50 K in
a field of 9 T. Such large effects have been observed rarely in bulk materials.
We suggest that the origin of this effect might be related to the high
charge-carrier mobility. We further observe pronounced quantum oscillations in
both thermal conductivity and thermopower. The obtained frequencies compare
well with our heat capacity and magnetization data.",1704.02241v2
2020-10-29,Two-dimensional hole gas in organic semiconductors,"A highly conductive metallic gas that is quantum mechanically confined at a
solid-state interface is an ideal platform to explore nontrivial electronic
states that are otherwise inaccessible in bulk materials. Although
two-dimensional electron gas (2DEG) has been realized in conventional
semiconductor interfaces, examples of two-dimensional hole gas (2DHG), which is
the counter analogue of 2DEG, are still limited. Here, we report the
observation of a 2DHG in solution-processed organic semiconductors in
conjunction with an electric double-layer using ionic liquids. A molecularly
flat single crystal of high mobility organic semiconductors serves as a
defect-free interface that facilitates two-dimensional confinement of
high-density holes. Remarkably low sheet resistance of 6 k$\Omega$ and high
hole gas density of 10$^{14}$ cm$^{-2}$ result in a metal-insulator transition
at ambient pressure. The measured degenerated holes in the organic
semiconductors provide a broad opportunity to tailor low-dimensional electronic
states using molecularly engineered heterointerfaces.",2010.15883v1
2021-07-29,Synergetic enhancement of power factor and suppression of lattice thermal conductivity via electronic structure modification and nanostructuring on Ni and B co-doped p-type Si-Ge alloy,"For simultaneously achieving the high-power factor and low lattice thermal
conductivity of Si-Ge based thermoelectric materials, we employed, in this
study, constructively modifying the electronic structure near the chemical
potential and nano-structuring by low temperature and high-pressure sintering
on nano-crystalline powders. Nickel was doped to create the impurity states
near the edge of the valence band for enhancing the power factor with boron for
tuning the carrier concentration. The nanostructured samples with the nominal
composition of Si0.65-xGe0.32Ni0.03Bx (x = 0.01, 0.02, 0.03, and 0.04) were
synthesized by the mechanical alloying followed low-temperature and
high-pressure sintering process. A large magnitude of Seebeck coefficient
reaching 321 {\mu}VK-1 together with a small electrical resistivity of 4.49
m{\Omega}cm, leads to a large power factor of 2.3 Wm-1K-2 at 1000 K. With
successfully reduced thermal conductivity down to 1.47 Wm-1K-1, a large value
of ZT ~1.56 was obtained for Si0.65-xGe0.32Ni0.03B0.03 at 1000 K",2107.13778v1
2021-09-03,Growth and characterization of high-quality single-crystalline SnTe retaining cubic symmetry down to the lowest temperature studied,"SnTe, an archetypical topological crystalline insulator, often shows a
transition from a highly symmetric cubic phase to a rhombohedral structure at
low temperatures. In order to achieve the highly symmetric cubic phase at low
temperatures suitable for quantum behaviour, we have employed the modified
Bridgman method to grow a high-quality single-crystalline sample of SnTe.
Analysis of the crystal structure using Laue diffraction and rocking curve
measurements show a very high degree of single crystallinity of the sample.
Resistivity and the specific heat data do not show the signature of structural
transition down to the lowest temperature studied. The magnetic susceptibility
shows diamagnetic behaviour. All these properties manifest the behaviour of a
typical bulk semiconductor with conducting surface states as expected in a
topological material. Detailed powder x-ray diffraction measurements show cubic
structure in the whole temperature range studied.",2109.01420v2
2021-11-22,High-entropy ceramics: propelling applications through disorder,"Disorder enhances desired properties, as well as creating new avenues for
synthesizing materials. For instance, hardness and yield stress are improved by
solid-solution strengthening, a result of distortions and atomic size
mismatches. Thermo-chemical stability is increased by the preference of
chemically disordered mixtures for high-symmetry super-lattices. Vibrational
thermal conductivity is decreased by force-constant disorder without
sacrificing mechanical strength and stiffness. Thus, high-entropy ceramics
propel a wide range of applications: from wear resistant coatings and thermal
and environmental barriers to catalysts, batteries, thermoelectrics and nuclear
energy management. Here, we discuss recent progress of the field, with a
particular emphasis on disorder-enhanced properties and applications.",2111.11519v1
2022-11-08,Observation of room-temperature ferroelectricity in elemental Te nanowires,"Ferroelectrics are essential in low-dimensional memory devices for multi-bit
storage and high-density integration. A polar structure is a necessary premise
for ferroelectricity, mainly existing in compounds. However, it is usually rare
in elemental materials, causing a lack of spontaneous electric polarization.
Here, we report an unexpected room-temperature ferroelectricity in few-chain Te
nanowires. Out-of-plane ferroelectric loops and domain reversal are observed by
piezoresponse force microscopy. Through density functional theory, we attribute
the ferroelectricity to the ion-displacement created by the interlayer
interaction between lone pair electrons. Ferroelectric polarization can induce
a strong field effect on the transport along the Te chain, supporting a
self-gated field-effect transistor. It enables a nonvolatile memory with high
in-plane mobility, zero supply voltage, multilevel resistive states, and a high
on/off ratio. Our work provides new opportunities for elemental ferroelectrics
with polar structures and paves a way towards applications such as low-power
dissipation electronics and computing-in-memory devices.",2211.04066v1
2009-07-17,Study of timing properties of single gap high-resistive bakelite RPC,"The time resolution for several single gap (2 mm) prototype Resistive Plate
Chambers (RPC) made of high resistive (bulk resistivity ~ 10^10 - 10^12 ohm
cm), 2 mm thick matt finished bakelite paper laminates with silicone coating on
the inner surfaces, has been measured. The time resolution for all the modules
has been found to be ~ 2 ns at the plateau region.",0907.2982v1
2003-09-16,Metal-insulator transition in EuO,"It is shown that the spectacular metal-insulator transition in Eu-rich EuO
can be simulated within an extended Kondo lattice model. The different orders
of magnitude of the jump in resistivity in dependence on the concentration of
oxygen vacancies as well as the low-temperature resistance minimum in
high-resistivity samples are reproduced quantitatively. The huge colossal
magnetoresistance (CMR) is calculated and discussed.",0309369v2
2016-08-08,Quantum Criticality and DBI Magneto-resistance,"We use the DBI action from string theory and holography to study the
magneto-resistance at quantum criticality with hyperscaling violation. We find
and analyze a rich class of scaling behaviors for the magneto-resistance. A
special case describes the scaling results found in pnictides by Hayers et al.
in~\cite{analytis}.",1608.02598v2
2023-09-19,Resistivity of the two-dimensional Bose-Hubbard model at weak coupling,"We calculate the weak-coupling resistivity of the two-dimensional Bose
Hubbard model, comparing with the more familiar fermionic case. At high
temperature the resistivity is linear in $T$, while in the low temperature
normal state it is exponentially suppressed. We explore the density dependence
and calculate the momentum relaxation rate.",2309.10782v1
2018-09-24,Ionic Tuning of Cobaltites at the Nanoscale,"Control of materials through custom design of ionic distributions represents
a powerful new approach to develop future technologies ranging from spintronic
logic and memory devices to energy storage. Perovskites have shown particular
promise for ionic devices due to their high ion mobility and sensitivity to
chemical stoichiometry. In this work, we demonstrate a solid-state approach to
control of ionic distributions in (La,Sr)CoO$_{3}$ thin films. Depositing a Gd
capping layer on the perovskite film, oxygen is controllably extracted from the
structure, up-to 0.5 O/u.c. throughout the entire 36 nm thickness. Commensurate
with the oxygen extraction, the Co valence state and saturation magnetization
show a smooth continuous variation. In contrast, magnetoresistance measurements
show no-change in the magnetic anisotropy and a rapid increase in the
resistivity over the same range of oxygen stoichiometry. These results suggest
significant phase separation, with metallic ferromagnetic regions and
oxygen-deficient, insulating, non-ferromagnetic regions, forming percolated
networks. Indeed, X-ray diffraction identifies oxygen-vacancy ordering,
including transformation to a brownmillerite crystal structure. The unexpected
transformation to the brownmillerite phase at ambient temperature is further
confirmed by high-resolution scanning transmission electron microscopy which
shows significant structural - and correspondingly chemical - phase separation.
This work demonstrates room-temperature ionic control of magnetism, electrical
resistivity, and crystalline structure in a 36 nm thick film, presenting new
opportunities for ionic devices that leverage multiple material
functionalities.",1809.08728v1
2020-02-17,Ductile and brittle crack-tip response in equimolar refractory high-entropy alloys,"Understanding the strengthening and deformation mechanisms in refractory
high-entropy alloys (HEAs), proposed as new high-temperature material, is
required for improving their typically insufficient room-temperature ductility.
Here, density-functional theory simulations and a continuum mechanics analysis
were conducted to systematically investigate the competition between cleavage
decohesion and dislocation emission from a crack tip in the body-centered cubic
refractory HEAs HfNbTiZr, MoNbTaVW, MoNbTaW, MoNbTiV, and NbTiVZr. This
crack-tip competition is evaluated for tensile loading and a totality of 15
crack configurations and slip systems. Our results predict that dislocation
plasticity at the crack tip is generally unfavorable -- although the
competition is close for some crack orientations, suggesting intrinsic
brittleness and low crack-tip fracture toughness in these five HEAs at zero
temperature. Fluctuations in local alloy composition, investigated for
HfNbTiZr, can locally reduce the resistance to dislocation emission for a slip
system relative to the configuration average of that slip system, but do not
change the dominant crack-tip response. In the case of single-crystal MoNbTaW,
where an experimental, room-temperature fracture-toughness value is available
for a crack on a \{100\} plane, theoretical and experimental results agree
favorably. Factors that may limit the agreement are discussed. We survey the
effect of material anisotropy on preferred crack tip orientations, which are
found to be alloy specific. Mixed-mode loadings are found to shift the
competition in favor of cleavage or dislocation nucleation, depending on crack
configuration and amplified by the effect of material anisotropy on crack tip
stresses.",2002.07013v1
2019-08-22,Non-localized states and high hole mobility in amorphous germanium,"Covalent amorphous semiconductors, such as amorphous silicon (a-Si) and
germanium (a-Ge), are commonly believed to have localized electronic states at
the top of the valence band and the bottom of the conduction band. Electrical
conductivity is thought to be by the hopping mechanism through localized
states. The carrier mobility of these materials is usually very low, in the
order of ~10^-3 - 10^-2 cm^2/(Vs) at room temperature. In this study, we
present the Hall effect characterization of a-Ge prepared by self-ion
implantation of Ge ions. The a-Ge prepared by this method is highly homogenous
and has a mass density within 98.5% of the crystalline Ge. The material
exhibits an exceptionally high electrical conductivity and carrier mobility
(~100 cm^2/(Vs)) for an amorphous semiconductor. The temperature-dependent
resistivity of the material is very-well defined with two distinctive regions,
extrinsic and intrinsic conductivity, as in crystalline Ge. These results are
direct evidence for a largely-preserved band structure and non-localized states
of the valence band in a-Ge, as proposed by Tauc et al. from optical
characterization alone. This finding is not only significant for the
understanding of electrical conductivity in covalent disordered semiconductors,
but the exceptionally high mobility we have observed in amorphous Ge opens up
device applications not previously considered for amorphous semiconductors.",1908.08246v1
2020-11-20,StressNet: Deep Learning to Predict Stress With Fracture Propagation in Brittle Materials,"Catastrophic failure in brittle materials is often due to the rapid growth
and coalescence of cracks aided by high internal stresses. Hence, accurate
prediction of maximum internal stress is critical to predicting time to failure
and improving the fracture resistance and reliability of materials. Existing
high-fidelity methods, such as the Finite-Discrete Element Model (FDEM), are
limited by their high computational cost. Therefore, to reduce computational
cost while preserving accuracy, a novel deep learning model, ""StressNet,"" is
proposed to predict the entire sequence of maximum internal stress based on
fracture propagation and the initial stress data. More specifically, the
Temporal Independent Convolutional Neural Network (TI-CNN) is designed to
capture the spatial features of fractures like fracture path and spall regions,
and the Bidirectional Long Short-term Memory (Bi-LSTM) Network is adapted to
capture the temporal features. By fusing these features, the evolution in time
of the maximum internal stress can be accurately predicted. Moreover, an
adaptive loss function is designed by dynamically integrating the Mean Squared
Error (MSE) and the Mean Absolute Percentage Error (MAPE), to reflect the
fluctuations in maximum internal stress. After training, the proposed model is
able to compute accurate multi-step predictions of maximum internal stress in
approximately 20 seconds, as compared to the FDEM run time of 4 hours, with an
average MAPE of 2% relative to test data.",2011.10227v1
2022-05-16,Single Crystalline 2D Material Nanoribbon Networks for Nanoelectronics,"The last decade has seen a flurry of studies related to graphene nanoribbons
owing to their potential applications in the quantum realm. However, little
experimental work has been reported towards nanoribbons of other 2D materials
due to the absence of synthesis routes. Here, we propose a universal approach
to synthesize high-quality networks of nanoribbons from arbitrary 2D materials
while maintaining high crystallinity, sufficient yield, narrow size
distribution, and straight-forward device integrability. The wide applicability
of this technique is demonstrated by fabricating MoS2, WS2, WSe2, and graphene
nanoribbon field effect transistors that inherently do not suffer from
interconnection resistances. By relying on self-assembled and self-aligned
organic nanostructures as masks, we demonstrate the possibility of controlling
the predominant crystallographic direction of the nanoribbon's edges.
Electrical characterization shows record mobilities and very high ON currents
for various TMDCs despite extreme width scaling. Lastly, we explore decoration
of nanoribbon edges with plasmonic particles paving the way towards the
development of nanoribbon-based plasmonic sensing and opto-electronic devices.",2205.09507v1
2023-04-18,Controllable Strain-driven Topological Phase Transition and Dominant Surface State Transport in High-Quality HfTe5 Samples,"Controlling materials to create and tune topological phases of matter could
potentially be used to explore new phases of topological quantum matter and to
create novel devices where the carriers are topologically protected. It has
been demonstrated that a trivial insulator can be converted into a topological
state by modulating the spin-orbit interaction or the crystal lattice. However,
there are limited methods to controllably and efficiently tune the crystal
lattice and at the same time perform electronic measurements at cryogenic
temperatures. Here, we use large controllable strain to demonstrate the
topological phase transition from a weak topological insulator phase to a
strong topological insulator phase in high-quality HfTe5 samples. After
applying high strain to HfTe5 and converting it into a strong topological
insulator, we found that the sample's resistivity increased by more than two
orders of magnitude (24,000%) and that the electronic transport is dominated by
the topological surface states at cryogenic temperatures. Our findings show
that HfTe5 is an ideal material for engineering topological properties, and it
could be generalized to study topological phase transitions in van der Waals
materials and heterostructures. These results can pave the way to create novel
devices with applications ranging from spintronics to fault-tolerant
topologically protected quantum computers.",2304.09072v1
2016-12-17,Electric Properties of Dirac Fermions Captured into 3D Nanoporous Graphene Networks,"Graphene, as a promising material of post-silicon electronics, opens a new
paradigm for the novel electronic properties and device applications. On the
other hand, the 2D feature of graphene makes it technically challenging to be
integrated into 3D transistors with a sufficient processor capacity. Although
there are many attempts to assemble 2D graphene into 3D structures, the
characteristics of massless Dirac fermions cannot be well preserved in these
materials for transistor applications. Here we report a high-performance
graphene transistor by utilizing 3D nanoporous graphene which is comprised of
an interconnected single graphene sheet and a commodious open porosity to
infuse an ionic liquid for a tunable electronic state by applying electric
fields. The 3D nanoporous graphene transistor, with high carrier mobility of
5000-7500 cm$^2$V$^{-1}$s$^{-1}$, exhibits two to three orders of magnitude
higher electric conductance and capacitance than those of 2D graphene devices,
along with preserved ambipolor electronic nature of Dirac cones. Moreover, the
3D graphene networks with Dirac fermions turn out to exhibit a unique nonlinear
Hall resistance in a wide range of the gate voltages. The high quality 3D
nanoporous graphene EDLT may open a new field for utilizing Dirac fermions in
3D network structures for various fundamental and practical applications.",1612.05716v1
2017-11-24,Stability of Thin Film Refractory Plasmonic Materials Taken to High Temperatures in Air,"Materials such as W, TiN, and SrRuO3 (SRO) have been suggested as promising
alternatives to Au and Ag in plasmonic applications owing to their refractory
properties. However, investigation of the reproducibility of the optical
properties after thermal cycling at high operational temperatures is so far
lacking. Here, thin films of W, Mo, Ti, TiN, TiON, Ag, Au, and SrRuO3 are
investigated to assess their viability for robust refractory plasmonic
applications. Films ranging in thickness from 50 - 180 nm are deposited on MgO
and Si substrates by RF magnetron sputtering and, in the case of SrRuO3, pulsed
laser deposition, prior to characterisation by means of AFM, XRD, spectroscopic
ellipsometry, and DC resistivity. Measurements are conducted before and after
annealing in air at temperatures ranging from 300 - 1000{\deg} C for one hour,
to establish the maximum cycling temperature and potential longevity at
temperature for each material. It is found that SrRuO3 retains metallic
behaviour after annealing at 800{\deg} C, however, importantly, the optical
properties of TiN and TiON are degraded as a result of oxidation. Nevertheless,
both TiN and TiON may be better suited than Au or SRO for high temperature
applications operating under vacuum conditions.",1711.08923v1
2016-03-17,Transport evidence for the three-dimensional Dirac semimetal phase in ZrTe5,"Topological Dirac semimetal is a newly discovered class of materials and has
attracted intense attentions. This material can be viewed as a
three-dimensional (3D) analogue of graphene and has linear energy dispersion in
bulk, leading to a range of exotic transport properties. Here we report direct
quantum transport evidence of 3D Dirac semimetal phase of layered material
ZrTe5 by angular dependent magnetoresistance measurements under high magnetic
fields up to 31 Tesla. We observed very clear negative longitudinal
magnetoresistance induced by chiral anomaly under the condition of the magnetic
field aligned only along the current direction. Pronounced Shubnikov-de Hass
(SdH) quantum oscillations in both longitudinal magnetoresistance and
transverse Hall resistance were observed, revealing anisotropic light cyclotron
masses and high mobility of the system. In particular, a nontrivial {\pi}-Berry
phase in the SdH gives clear evidence for 3D Dirac semimetal phase.
Furthermore, we observed clear Landau Level splitting under high magnetic
field, suggesting possible splitting of Dirac point into Weyl points due to
broken time reversal symmetry. Our results indicate that ZrTe5 is an ideal
platform to study 3D massless Dirac and Weyl fermions in a layered compound.",1603.05351v2
2022-06-16,Scalable Composites Benefiting from Transition-Metal Oxides as Cathode Materials for Efficient Lithium-Sulfur Batteries,"Composite materials achieved by including transition-metal oxides with
different structures and morphologies in sulfur are suggested as scalable
cathodes for high-energy lithium-sulfur (Li-S) batteries. The composites
contain 80 wt.% sulfur and 20 wt.% of either MnO2 or TiO2, leading to a sulfur
content in the electrode of 64 wt.% and revealing a reversible, fast, and lowly
polarized conversion process in the cell with limited interphase resistance.
The S-TiO2 composite exhibits an excellent rate capability between C/10 and 2C,
and a cycle life extended over 400 cycles at 2C, owing to the effects of the
nanometric TiO2 additive in boosting the reaction kinetics. Instead, the
micrometric sized particles of MnO2 partially limit the electrochemical
activity of S-MnO2 to the current rate of 1C. Nevertheless, both S-MnO2 and
S-TiO2 withstand a sulfur loading up to values approaching 6 mgcm-2, and
deliver an areal capacit ranging from about 4.5 to 5.5 mAhcm-2 at C/5. The
excellent performances of the metal oxide-sulfur electrodes, even at high
active material loading, and the possible scalability of the synthetic pathway
adopted in the work suggest that the composites are viable cathodes for
next-generation Li-S batteries with high energy density and efficient
electrochemical process.",2206.14569v1
2024-01-25,Spatially Resolved High Voltage Kelvin Probe Force Microcopy: A Novel Avenue for Examining Electrical Phenomena at Nanoscale,"Kelvin probe microscopy (KPFM) is a well-established scanning probe
technique, used to measure surface potential accurately; it has found extensive
use in the study of a range of materials phenomena. In its conventional form,
KPFM frustratingly precludes imaging samples or scenarios where large surface
potential exists or large surface potential gradients are created outside the
typical +/-10V window. If the potential regime measurable via KPFM could be
expanded, to enable precise and reliable metrology, through a high voltage KPFM
(HV-KPFM) adaptation, it could open up pathways towards a range of novel
experiments, where the detection limit of regular KPFM has so far prevented the
use of the technique. In this work, HV-KPFM has been realised and shown to be
capable of measuring large surface potential and potential gradients with
accuracy and precision. The technique has been employed to study a range of
materials (positive temperature coefficient of resistivity ceramics, charge
storage fluoropolymers and pyroelectrics) where accurate spatially resolved
mapping of surface potential within high voltage regime facilitates novel
physical insight. The results demonstrate that HV-KPFM can be used as an
effective tool to fill in existing gaps in surface potential measurements while
also opening routes for novel studies in materials physics.",2401.14124v1
2024-02-05,High Strain Engineering of a Suspended WSSe Monolayer Membrane by Indentation and Measured by Tip-enhanced Photoluminescence,"Straintronics involves the manipulation and regulation of the electronic
characteristics of 2D materials through the use of macro- and nano-scale strain
engineering. In this study, we utilized an atomic force microscope (AFM)
coupled with an optical system to perform indentation measurements and
tip-enhanced photoluminescence (TEPL), allowing us to extract the local optical
response of a suspended monolayer membrane of ternary WSSe at various levels of
deformation, up to strains of 10%. The photoluminescence signal is modelled
considering the deformation, stress distribution and strain dependence of the
WSSe band structure. We observe an additional TEPL signal that exhibits
significant variation under strain, with 64 meV per percent of elongation. This
peak is linked to the highly strained 2D material lying right underneath the
tip. We discuss the amplification of the signal and its relation to the
excitonic funnelling effect in a more comprehensive model. We will also compare
the diffusion caused by Auger recombination against the radiative excitonic
decay. We use TEPL to examine and comprehend the local physics of 2D
semi-conducting materials subjected to extreme mechanical strain. Chemical
vapour deposition-fabricated 2D ternaries possess high strain resistance,
comparable to the benchmark MoS2, and a high Young's modulus of 273 GPa.",2402.03061v1
2019-08-11,Magnetotransport as diagnostic of spin reorientation: kagome ferromagnet as a case study,"While in most ferro or antiferromagnetic materials there is a unique
crystallographic direction, including crystallographically equivalent
directions, in which the moments like to point due to spin-orbit coupling, in
some, the direction of the spin reorients as a function of a certain physical
parameter such as temperature, pressure etc. Fe3Sn2 is a kagome ferromagnet
with an onset of ferromagnetism below 650 K, and undergoes a spin reorientation
near 150 K. While it is known that the moments in Fe3Sn2 point perpendicular to
the kagome plane at high temperatures and parallel to the kagome plane at low
temperatures, how the distribution of the magnetic domains in the two different
spin orientations evolve throughout the spin reorientation is not well known.
Furthermore, while there have been various reports on the magnetotransport
properties in the Hall configuration, the angular dependence of
magnetoresistance has not been studied so far. In this paper, we have examined
the spin reorientation by using anisotropic magnetoresistivity in detail,
exploiting the dependence of the resistivity on the direction between
magnetization and applied current. We are able to determine the distribution of
the magnetic domains as a function of temperature between 360 K to 2 K and the
reorientation transition to peak at 120 K. We discover that both out of plane
and in plane phases coexist at temperatures around the spin reorientation,
indicative of a first order transition. Although the volume of the magnetic
domains in the different phases sharply changes at the spin reorientation
transition, the electronic structure for a specific magnetization is not
influenced by the spin reorientation. In contrast, we observe an electronic
transition around 40 K, hitherto unreported, and reflected in both the
zero-field resistivity and anisotropic resistivity.",1908.03927v1
2021-11-22,Shape-Dependent Multi-Weight Magnetic Artificial Synapses for Neuromorphic Computing,"In neuromorphic computing, artificial synapses provide a multi-weight
conductance state that is set based on inputs from neurons, analogous to the
brain. Additional properties of the synapse beyond multiple weights can be
needed, and can depend on the application, requiring the need for generating
different synapse behaviors from the same materials. Here, we measure
artificial synapses based on magnetic materials that use a magnetic tunnel
junction and a magnetic domain wall. By fabricating lithographic notches in a
domain wall track underneath a single magnetic tunnel junction, we achieve 4-5
stable resistance states that can be repeatably controlled electrically using
spin orbit torque. We analyze the effect of geometry on the synapse behavior,
showing that a trapezoidal device has asymmetric weight updates with high
controllability, while a straight device has higher stochasticity, but with
stable resistance levels. The device data is input into neuromorphic computing
simulators to show the usefulness of application-specific synaptic functions.
Implementing an artificial neural network applied on streamed Fashion-MNIST
data, we show that the trapezoidal magnetic synapse can be used as a
metaplastic function for efficient online learning. Implementing a
convolutional neural network for CIFAR-100 image recognition, we show that the
straight magnetic synapse achieves near-ideal inference accuracy, due to the
stability of its resistance levels. This work shows multi-weight magnetic
synapses are a feasible technology for neuromorphic computing and provides
design guidelines for emerging artificial synapse technologies.",2111.11516v2
2014-11-04,Tackling drug resistant infection outbreaks of global pandemic Escherichia coli ST131 using evolutionary and epidemiological genomics,"High-throughput molecular screening is required to investigate the origin and
diffusion of antimicrobial resistance in pathogen outbreaks. The most frequent
cause of human infection is Escherichia coli, which is dominated by sequence
type 131 (ST131), a set of rapidly radiating pandemic clones. The highly
infectious clades of ST131 originated firstly by a mutation enhancing virulence
and adhesion. Secondly, single-nucleotide polymorphisms occurred enabling
fluoroquinolone-resistance, which is near-fixed in all ST131. Thirdly, broader
resistance through beta-lactamases has been gained and lost frequently,
symptomatic of conflicting environmental selective effects. This flexible
approach to gene exchange is worrying and supports the proposition that ST131
will develop an even wider range of plasmid and chromosomal elements promoting
antimicrobial resistance. To stymie ST131, deep genome sequencing is required
to understand the origin, evolution and spread of antimicrobial resistance
genes. Phylogenetic methods that decipher past events can predict future
patterns of virulence and transmission based on genetic signatures of
adaptation and gene exchange. Both the effect of partial antimicrobial exposure
and cell dormancy caused by variation in gene expression may accelerate the
development of resistance. High-throughput sequencing can decode measurable
evolution of cell populations within patients associated with systems-wide
changes in gene expression during treatments. A multi-faceted approach can
enhance assessment of antimicrobial resistance in E. coli ST131 by examining
transmission dynamics between hosts to achieve a goal of pre-empting resistance
before it emerges by optimising antimicrobial treatment protocols.",1411.0905v3
2014-09-25,Recycled nylon fibers as cement mortar reinforcement,"We investigate engineering applications of recycled nylon fibers obtained
from waste fishing nets, focusing our attention on the use of recycled nylon
fibers as tensile reinforcement of cementitious mortars. We begin by
characterizing the tensile behavior of both unconditioned and alkali-cured
recycled nylon fibers obtained through manual cutting of waste fishing net
filaments, with the aim of assessing the resistance of such materials to
chemical attacks. Special attention is also given to evaluating the workability
of fresh mortar and the possible impacts of contaminants released by waste
fishing nets into the environment. Next, we deal with compression and bending
tests on cementitious mortars reinforced with recycled nylon fibers, and
establish comparisons with the experimental behavior of the unreinforced
material and with results given in existing literature. In our analysis of
different weight fractions and aspect ratios of the reinforcing fibers, we
observe marked increases in the tensile strength (up to +35%) and toughness (up
to 13 times greater) of the nylon reinforced mortar, as compared with the
unreinforced material. The presented results emphasize the high environmental
and mechanical potential of recycled nylon fibers for the reinforcement of
sustainable cement mortars.",1409.7258v4
2019-05-14,Ohmic contact engineering in few-layer black Phosphorus field effect transistors,"Achieving good quality Ohmic contacts to van der Waals materials is a
challenge, since at the interface between metal and van der Waals material,
different conditions can occur, ranging from the presence of a large energy
barrier between the two materials to the metallization of the layered material
below the contacts. In black phosphorus (bP), a further challenge is its high
reactivity to oxygen and moisture, since the presence of uncontrolled oxidation
can substantially change the behavior of the contacts. In this study, we
investigate the influence of the metal used for the contacts to bP against the
variability between different flakes and different samples, using three of the
most used metals as contacts: Chromium, Titanium, and Nickel. Using the
transfer length method, from an analysis of ten devices, both at room
temperature and at low temperature, Ni results to be the best metal for Ohmic
contacts to bP, providing the lowest contact resistance and minimum scattering
between different devices. Moreover, we investigate the gate dependence of the
current-voltage characteristics of these devices. In the accumulation regime,
we observe good linearity for all metals investigated.",1905.05649v1
2019-06-24,Conductivity of Dirac-like surface states in correlated honeycomb transition metal oxide Mott insulators,"The search for materials with novel and unusual electronic properties is at
the heart of condensed matter physics as well as the basis to develop
conceptual new technologies. In this context, the correlated honeycomb
transition metal oxides attract large attention for both, being a possible
experimental realization of the theoretically predicted magnetic Kitaev
exchange and the theoretical prospect of topological nontriviality. The Mott
insulating sodium iridate is prototypical among these materials with the
promising prospect to bridge the field of strongly correlated systems with
topology, finally opening a path to a wide band gap material with exotic
surface properties. Here, we report a profound study of the electronic
properties of ultra-high-vacuum cleaved surfaces combining transport
measurements with scanning tunneling techniques, showing that multiple
conductive channels with differing nature are simultaneously apparent in this
material. Most importantly, a V-shaped density of states and a low sheet
resistance, in spite of a large defect concentration, point towards a
topologically protected surface conductivity contribution. By incorporating the
issue of the addressability of electronic states in the tunneling process, we
develop a framework connecting previous experimental results as well as
theoretical considerations.",1906.09809v2
2020-07-22,Impact of Li$_{2.9}$B$_{0.9}$S$_{0.1}$O$_{3.1}$ glass additive on the structure and electrical properties of the LATP-based ceramics,"The existing solid electrolytes for lithium ion batteries suffer from low
total ionic conductivity, which restricts its usefulness for the lithium-ion
battery technology. Among them, the NASICON-based materials, such as
Li1.3Al0.3Ti1.7(PO4)3 (LATP) exhibit low total ionic conductivity due to highly
resistant grain boundary phase. One of the possible approaches to efficiently
enhance their total ionic conductivity is the formation of a composite
material. Herein, the Li2.9B0.9S0.1O3.1 glass, called LBSO hereafter, was
chosen as an additive material to improve the ionic properties of the ceramic
Li1.3Al0.3Ti1.7(PO4)3 base material. The properties of this
Li1.3Al0.3Ti1.7(PO4)3-xLi2.9B0.9S0.1O3.1 (0 < x < 0.3) system have been studied
by means of high temperature X-ray diffractometry (HTXRD), 7Li, 11B, 27Al and
31P magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR),
thermogravimetry (TG), scanning electron microscopy (SEM), impedance
spectroscopy (IS) and density methods. We show here that the introduction of
the foreign LBSO phase enhances their electric properties. This study reveals
several interesting correlations between the apparent density, the
microstructure, the composition, the sintering temperature and the ionic
conductivity. Moreover, the electrical properties of the composites will be
discussed in the terms of the brick-layer model (BLM). The highest value of
{\sigma}tot = 1.5 x 10-4 Scm-1 has been obtained for LATP-0.1LBSO material
sintered at 800{\deg}C.",2007.11244v2
2020-12-16,Anisotropic phonon-mediated electronic transport in chiral Weyl semimetals,"Discovery and observations of exotic, quantized optical and electrical
responses have sparked renewed interest in nonmagnetic chiral crystals. Within
this class of materials, six group V transition metal ditetrelides, that is,
XY$_2$ (X = V, Nb, Ta and Y = Si, Ge), host composite Weyl nodes on
high-symmetry lines, with Kramers-Weyl fermions at time-reversal invariant
momenta. In addition, at least two of these materials, NbGe$_2$ and NbSi$_2$,
exhibit superconducting transitions at low temperatures. The interplay of
strong electron-phonon interaction and complex Fermi surface topology present
an opportunity to study both superconductivity and hydrodynamic electron
transport in these systems. Towards this broader question, we present an ab
initio theoretical study of the electronic transport and electron-phonon
scattering in this family of materials, with a particular focus on NbGe$_2$ vs.
NbSi$_2$, and the other group V ditetrelides. We shed light on the microscopic
origin of NbGe$_2$'s large and anisotropic room temperature resistivity and
contextualize its strong electron-phonon scattering with a presentation of
other relevant scattering lifetimes, both momentum-relaxing and
momentum-conserving. Our work explores the intriguing possibility of observing
hydrodynamic electron transport in these chiral Weyl semimetals.",2012.09207v1
2022-08-15,Valley-coherent quantum anomalous Hall state in AB-stacked MoTe2/WSe2 bilayers,"Moir\'e materials provide fertile ground for the correlated and topological
quantum phenomena. Among them, the quantum anomalous Hall (QAH) effect, in
which the Hall resistance is quantized even under zero magnetic field, is a
direct manifestation of the intrinsic topological properties of a material and
an appealing attribute for low-power electronics applications. The QAH effect
has been observed in both graphene and transition metal dichalcogenide (TMD)
moir\'e materials. It is thought to arise from the interaction-driven valley
polarization of the narrow moir\'e bands. Here, we show surprisingly that the
newly discovered QAH state in AB-stacked MoTe2/WSe2 moir\'e bilayers is not
valley-polarized but valley-coherent. The layer- and helicity-resolved optical
spectroscopy measurement reveals that the QAH ground state possesses
spontaneous spin (valley) polarization aligned (anti-aligned) in two TMD
layers. In addition, saturation of the out-of-plane spin polarization in both
layers occurs only under high magnetic fields, supporting a canted spin
texture. Our results call for a new mechanism for the QAH effect and highlight
the potential of TMD moir\'e materials with strong electronic correlations and
spin-orbit interactions for exotic topological states.",2208.07452v1
2022-09-26,Evaluating Effects of Geometry and Material Composition on Production of Transversely Shaped Beams from Diamond Field Emission Array Cathodes,"Field emission cathodes (FECs) are attractive for the next generation of
injectors due to their ability to provide high current density bright beams
with low intrinsic emittance. One application of FECs worthy of special
attention is to provide transversely shaped electron beams for emittance
exchange that translates a transverse electron beam pattern into a longitudinal
pattern. FECs can be fabricated in a desired pattern and produce transversely
shaped beams without the need for complex masking or laser schemes. However,
reliable and consistent production of transversely shaped beams is affected by
material properties of the FEC. This paper reports the results of testing two
diamond field emitter array (DFEA) FECs with the same lithography pattern and
emitter geometry but different material and tip characteristics. Although both
cathodes were able to sustain gradients of 44 MV/m and produce maximum output
integral charge of 0.5 nC per radiofrequency (rf) pulse, their emission
patterns were quite different. One cathode did not produce a patterned beam
while the other one did. Differences in field emission characteristics and
patterned beam production were explained by the differences in the tip geometry
and the cathode material properties. The main practical takeaway was found to
be that the tip sharpness was not a prerequisite for good patterned beam
production. Instead, other material characteristics, such as the ballast
resistance, determined cathode performance.",2209.13047v1
2023-04-13,Effect of hirtisation on the roughness and fatigue performance of porous titanium lattice structures,"Additive manufacturing (AM) has enabled the fabrication of extremely complex
components such as porous metallic lattices, which have applications in
aerospace, automotive, and in particular biomedical devices. The fatigue
resistance of these materials is currently an important limitation however, due
to manufacturing defects such as semi-fused particles and weld lines. Here
Hirtisation$^\circledR$ is used for post-processing of Ti-6Al-4V lattices,
reducing the strut surface roughness (Sa) from 12 to 6 $\mu$m, removing all
visible semi-fused particles. The evenness of this treatment in lattices with
$\rho /\rho_{s}$ up to 18.3% and treatment depth of 6.5 mm was assessed,
finding no evidence of reduced effectiveness on internal surfaces. After
normalising to quasi-static mechanical properties to account for material
losses during hirtisation (34-37% reduction in strut diameter), the fatigue
properties show a marked improvement due to the reduction in surface roughness.
Normalised high cycle fatigue strength ($\sigma_{f,10^{6}}/\sigma_{y}$)
increased from around 0.1 to 0.16-0.21 after hirtisation, an average increase
of 80%. For orthopaedic implant devices where matching the stiffness of
surrounding bone is crucial, the $\sigma_{f}/E$ ratio is a key metric. After
hirtisation the $\sigma_{f}/E$ ratio increased by 90%, enabling design of
stiffness matched implant materials with greater fatigue strength. This work
demonstrates that hirtisation is an effective method for improving the surface
roughness of porous lattice materials, thereby enhancing their fatigue
performance.",2304.06621v1
2024-03-15,An inflated dynamic Laplacian to track the emergence and disappearance of semi-material coherent sets,"Lagrangian methods continue to stand at the forefront of the analysis of
time-dependent dynamical systems. Most Lagrangian methods have criteria that
must be fulfilled by trajectories as they are followed throughout a given
finite flow duration. This key strength of Lagrangian methods can also be a
limitation in more complex evolving environments. It places a high importance
on selecting a time window that produces useful results, and these results may
vary significantly with changes in the flow duration. We show how to overcome
this drawback in the tracking of coherent flow features. Finite-time coherent
sets (FTCS) are material objects that strongly resist mixing in complicated
nonlinear flows. Like other materially coherent objects, by definition they
must retain their coherence properties throughout the specified flow duration.
Recent work [Froyland and Koltai, CPAM, 2023] introduced the notion of
semi-material FTCS, whereby a balance is struck between the material nature and
the coherence properties of FTCS. This balance provides the flexibility for
FTCS to come and go, merge and separate, or undergo other changes as the
governing unsteady flow experiences dramatic shifts. The purpose of this work
is to illustrate the utility of the inflated dynamic Laplacian introduced in
[Froyland and Koltai, CPAM, 2023] in a range of dynamical systems that are
challenging to analyse by standard Lagrangian means, and to provide an
efficient meshfree numerical approach for the discretisation of the inflated
dynamic Laplacian.",2403.10360v1
2024-03-20,Tailoring Physical Properties of Crystals through Synthetic Temperature Control: A Case Study for new Polymorphic NbFeTe2 phases,"Growth parameters play a significant role in the crystal quality and physical
properties of layered materials. Here we present a case study on a van der
Waals magnetic NbFeTe2 material. Two different types of polymorphic NbFeTe2
phases, synthesized at different temperatures, display significantly different
behaviors in crystal symmetry, electronic structure, electrical transport, and
magnetism. While the phase synthesized at low temperature showing behavior
consistent with previous reports, the new phase synthesized at high
temperature, has completely different physical properties, such as metallic
resistivity, long-range ferromagnetic order, anomalous Hall effect, negative
magnetoresistance, and distinct electronic structures. Neutron diffraction
reveals out-of-plane ferromagnetism below 70K, consistent with the electrical
transport and magnetic susceptibility studies. Our work suggests that simply
tuning synthetic parameters in a controlled manner could be an effective route
to alter the physical properties of existing materials potentially unlocking
new states of matter, or even discovering new materials.",2403.13596v1
2022-07-06,Proposal for semiconductor-free negative differential resistance tunnel diode with ultra-high peak-to-valley current ratio,"The negative differential resistance (NDR) tunnel diodes are promising
alternative devices for beyond-CMOS computing as they offer several potential
applications when integrated with transistors. We propose a novel
semiconductor-free NDR tunnel diode concept that exhibits an ultra-high
peak-to-valley current ratio (PVCR) value. Our proposed NDR diode consists of
two cold metal electrodes separated by a thin insulating tunnel barrier. The
NDR effect stems from the unique electronic band structure of the cold metal
electrodes, i.e., the width of the isolated metallic bands around the Fermi
level as well as the energy gaps separating higher- and lower-lying bands
determine the current-voltage ($I$-$V$) characteristics and the PVCR value of
the tunnel diode. By proper choice of the cold metal electrode materials,
either a conventional N-type or ${\Lambda}$-type NDR effect can be obtained.
Two-dimensional (2D) materials offer a unique platform for the realization of
proposed NDR tunnel diodes. To demonstrate the proof of concept we employ the
nonequilibrium Green function method combined with density functional theory to
calculate the $I$-$V$ characteristic of the lateral (AlI$_2$/MgI$_2$/AlI$_2$)
and vertical (NbS$_2$/h-BN/NbS$_2$) heterojunction tunnel diodes based on 2D
cold metals. For the lateral tunnel diode, we obtain a ${\Lambda}$-type NDR
effect with an ultra-high PVCR value of 10$^{16}$ at room temperature, while
the vertical tunnel diode exhibits a conventional N-type NDR effect with a
smaller PVCR value of about 10$^4$. The proposed concept provides a
semiconductor-free solution for NDR devices to achieve desired $I$-$V$
characteristics with ultra-high PVCR values for memory and logic applications.",2207.02593v2
2001-02-12,Temperature- and magnetic-field-dependent resistivity of MgB2 sintered at high temperature and high pressure condition,"We report the temperature- and magnetic-field-dependent resistivity of MgB2
sintered at high temperature and high pressure condition. The superconducting
transition width for the resistivity measurement was about 0.4 K, and the
low-field magnetization showed a sharp superconducting transition with a
transition width of about 1 K. The resistivity in the normal state roughly
followed T^2 behavior with smaller residual resistivity ratio (RRR) of 3 over
broad temperature region above 100 K rather than reported T^3 behavior with
larger RRR value of ~ 20 in the samples made at lower pressures. Also, the
resistivity did not change appreciably with the applied magnetic field, which
was different from previous report. These differences were discussed with the
microscopic and structural change due to the high-pressure sintering.",0102215v4
2017-03-01,Size Dependence of Nanoscale Wear of Silicon Carbide,"Nanoscale, single-asperity wear of single-crystal silicon carbide (sc-SiC)
and nanocrystalline silicon carbide (nc-SiC) is investigated using
single-crystal diamond nanoindenter tips and nanocrystalline diamond atomic
force microscopy (AFM) tips under dry conditions, and the wear behavior is
compared to that of single-crystal silicon with both thin and thick native
oxide layers. We discovered a transition in the relative wear resistance of the
SiC samples compared to that of Si as a function of contact size. With larger
nanoindenter tips (tip radius around 370 nm), the wear resistances of both
sc-SiC and nc-SiC are higher than that of Si. This result is expected from the
Archard's equation because SiC is harder than Si. However, with the smaller AFM
tips (tip radius around 20 nm), the wear resistances of sc-SiC and nc-SiC are
lower than that of Si, despite the fact that the contact pressures are
comparable to those applied with the nanoindenter tips, and the plastic zones
are well-developed in both sets of wear experiments. We attribute the decrease
in the relative wear resistance of SiC compared to that of Si to a transition
from a wear regime dominated by the materials' resistance to plastic
deformation (i.e., hardness) to a regime dominated by the materials' resistance
to interfacial shear. This conclusion is supported by our AFM studies of
wearless friction, which reveal that the interfacial shear strength of SiC is
higher than that of Si. The contributions of surface roughness and surface
chemistry to differences in interfacial shear strength are also discussed.",1703.01181v1
2022-02-09,Scalable $\rm Al_2O_3-TiO_2$ Conductive Oxide Interfaces as Defect Reservoirs for Resistive Switching Devices,"Resistive switching devices herald a transformative technology for memory and
computation, offering considerable advantages in performance and energy
efficiency. Here we employ a simple and scalable material system of conductive
oxide interfaces and leverage their unique properties for a new type of
resistive switching device. For the first time, we demonstrate an $\rm
Al_2O_3-TiO_2$ based valence-change resistive switching device, where the
conductive oxide interface serves both as the back electrode and as a reservoir
of defects for switching. The amorphous-polycrystalline $\rm Al_2O_3-TiO_2$
conductive interface is obtained following the technological path of
simplifying the fabrication of the two-dimensional electron gases (2DEGs),
making them more scalable for practical mass integration. We combine physical
analysis of the device chemistry and microstructure with comprehensive
electrical analysis of its switching behavior and performance. We pinpoint the
origin of the resistive switching to the conductive oxide interface, which
serves as the bottom electrode and as a reservoir of oxygen vacancies. The
latter plays a key role in valence-change resistive switching devices. The new
device, based on scalable and complementary metal-oxide-semiconductor (CMOS)
technology-compatible fabrication processes, opens new design spaces towards
increased tunability and simplification of the device selection challenge.",2202.04477v2
2019-04-07,Phase field modelling of crack propagation in functionally graded materials,"We present a phase field formulation for fracture in functionally graded
materials (FGMs). The model builds upon homogenization theory and accounts for
the spatial variation of elastic and fracture properties. Several paradigmatic
case studies are addressed to demonstrate the potential of the proposed
modelling framework. Specifically, we (i) gain insight into the crack growth
resistance of FGMs by conducting numerical experiments over a wide range of
material gradation profiles and orientations, (ii) accurately reproduce the
crack trajectories observed in graded photodegradable copolymers and
glass-filled epoxy FGMs, (iii) benchmark our predictions with results from
alternative numerical methodologies, and (iv) model complex crack paths and
failure in three dimensional functionally graded solids. The suitability of
phase field fracture methods in capturing the crack deflections intrinsic to
crack tip mode-mixity due to material gradients is demonstrated. Material
gradient profiles that prevent unstable fracture and enhance crack growth
resistance are identified: this provides the foundation for the design of
fracture resistant FGMs. The finite element code developed can be downloaded
from www.empaneda.com/codes.",1904.08749v1
2009-05-13,Reliability of resistivity quantification for shallow subsurface water processes,"The reliability of surface-based electrical resistivity tomography (ERT) for
quantifying resistivities for shallow subsurface water processes is analysed. A
method comprising numerical simulations of water movement in soil and
forward-inverse modeling of ERT surveys for two synthetic data sets is
presented. Resistivity contrast, e.g. by changing water content, is shown to
have large influence on the resistivity quantification.
  An ensemble and clustering approach is introduced in which ensembles of 50
different inversion models for one data set are created by randomly varying the
parameters for a regularisation based inversion routine. The ensemble members
are sorted into five clusters of similar models and the mean model for each
cluster is computed. Distinguishing persisting features in the mean models from
singular artifacts in individual tomograms can improve the interpretation of
inversion results.
  Especially in the presence of large resistivity contrasts in high sensitivity
areas, the quantification of resistivities can be unreliable. The ensemble
approach shows that this is an inherent problem present for all models inverted
with the regularisation based routine. The results also suggest that the
combination of hydrological and electrical modeling might lead to better
results.",0905.2117v1
2009-06-17,Resistive MHD jet simulations with large resistivity,"Axisymmetric resistive MHD simulations for radially self-similar initial
conditions are performed, using the NIRVANA code. The magnetic diffusivity
could occur in outflows above an accretion disk, being transferred from the
underlying disk into the disk corona by MHD turbulence (anomalous turbulent
diffusivity), or as a result of ambipolar diffusion in partially ionized flows.
We introduce, in addition to the classical magnetic Reynolds number Rm, which
measures the importance of resistive effects in the induction equation, a new
number Rb, which measures the importance of the resistive effects in the energy
equation. We find two distinct regimes of solutions in our simulations. One is
the low-resistivity regime, in which results do not differ much from ideal-MHD
solutions. In the high-resistivity regime, results seem to show some
periodicity in time-evolution, and depart significantly from the ideal-MHD
case. Whether this departure is caused by numerical or physical reasons is of
considerable interest for numerical simulations and theory of astrophysical
outflows and is currently investigated.",0906.3254v1
2011-12-29,Magnetospheric Accretion and Ejection of Matter in Resistive Magnetohydrodynamic Simulations,"The ejection of matter in the close vicinity of a young stellar object is
investigated, treating the accretion disk as a gravitationally bound reservoir
of matter. By solving the resistive MHD equations in 2D axisymmetry using our
version of the Zeus-3D code with newly implemented resistivity, we study the
effect of magnetic diffusivity in the magnetospheric accretion-ejection
mechanism. Physical resistivity was included in the whole computational domain
so that reconnection is enabled by the physical as well as the numerical
resistivity. We show, for the first time, that quasi-stationary fast ejecta of
matter, which we call {\em micro-ejections}, of small mass and angular momentum
fluxes, can be launched from a purely resistive magnetosphere. They are
produced by a combination of pressure gradient and magnetic forces, in presence
of ongoing magnetic reconnection along the boundary layer between the star and
the disk, where a current sheet is formed. Mass flux of micro-ejection
increases with increasing magnetic field strength and stellar rotation rate,
and is not dependent on the disk to corona density ratio and amount of
resistivity.",1112.6226v2
2016-10-17,Nonlinear Resistivity for Magnetohydrodynamical Models,"A new formulation of the plasma resistivity that arises from the collisional
momentum-transfer rate between electrons and ions is presented. The resistivity
computed herein is shown to depend not only on the temperature and density but
also on all other polynomial velocity-space moments of the distribution
function, such as the pressure tensor and heat flux vector. The exact
expression for the collisional momentum-transfer rate is determined, and is
used to formulate the nonlinear anisotropic resistivity. The new formalism
recovers the Spitzer resistivity, as well as the concept of thermal force if
the heat flux is assumed to be proportional to a temperature gradient.
Furthermore, if the pressure tensor is related to viscous stress, the latter
enters the expression for the resistivity. The relative importance of the
nonlinear term(s) with respect to the well-established electron inertia and
Hall terms is also examined. The subtle implications of the nonlinear
resistivity, and its dependence on the fluid variables, are discussed in the
context of magnetized plasma environments and phenomena such as magnetic
reconnection.",1610.05193v2
2020-03-09,Quantum mechanical current-to-voltage conversion with quantum Hall resistance array,"Accurate measurement of the electric current requires a stable and calculable
resistor for an ideal current to voltage conversion. However, the temporal
resistance drift of a physical resistor is unavoidable, unlike the quantum Hall
resistance directly linked to the Planck constant h and the elementary charge
e. Lack of an invariant high resistance leads to a challenge in making small
current measurements below 1 muA with an uncertainty better than one part in
106. In this work, we demonstrate a current to voltage conversion in the range
from a few nano amps to one microamp with an invariant quantized Hall array
resistance. The converted voltage is directly compared with the Josephson
voltage reference in the framework of Ohm's law. Markedly distinct from the
classical conversion, which relies on an artifact resistance reference, this
current-to-voltage conversion does not demand timely resistance calibrations.
It improves the precision of current measurement down to 8 10 -8 at 1 muA.",2003.04464v1
2021-02-11,Suppressing evolution through environmental switching,"Ecology and evolution under changing environments are important in many
subfields of biology with implications for medicine. Here, we explore an
example: the consequences of fluctuating environments on the emergence of
antibiotic resistance, which is an immense and growing problem. Typically, high
doses of antibiotics are employed to eliminate the infection quickly and
minimize the time under which resistance may emerge. However, this strategy may
not be optimal. Since competition can reduce fitness and resistance typically
has a reproductive cost, resistant mutants' fitness can depend on their
environment. Here we show conditions under which environmental varying fitness
can be exploited to prevent the emergence of resistance. We develop a
stochastic Lotka-Volterra model of a microbial system with competing
phenotypes: a wild strain susceptible to the antibiotic, and a mutant strain
that is resistant. We investigate the impact of various pulsed applications of
antibiotics on population suppression. Leveraging competition, we show how a
strategy of environmental switching can suppress the infection while avoiding
resistant mutants. We discuss limitations of the procedure depending on the
microbe and pharmacodynamics and methods to ameliorate them.",2102.05813v2
2023-12-08,Electron-hole collision-limited resistance of gapped graphene,"Collisions between electrons and holes can dominate the carrier scattering in
clean graphene samples in the vicinity of charge neutrality point. While
electron-hole limited resistance in pristine gapless graphene is well-studied,
its evolution with induction of band gap $E_g$ is less explored. Here, we
derive the functional dependence of electron-hole limited resistance of gapped
graphene $\rho_{eh}$ on the ratio of gap and thermal energy $E_g/kT$. At low
temperatures and large band gaps, the resistance grows linearly with $E_g/kT$,
and possesses a minimum at $E_g \approx 2.5 kT$. This contrast to the Arrhenius
activation-type behaviour for intrinsic semiconductors. Introduction of
impurities restores the Arrhenius law for resistivity at low temperatures
and/or high doping densities. The hallmark of electron-hole collision effects
in graphene resistivity at charge neutrality is the crossover between
exponential and power-law resistivity scalings with temperature.",2312.05066v1
2019-03-18,"Experimental and Theoretical Investigation on the Possible Half-metallic Behaviour of Equiatomic Quaternary Heusler Alloys: CoRuMnGe and CoRuVZ (Z = Al, Ga)","In this report, structural, electronic, magnetic and transport properties of
quaternary Heusler alloys CoRuMnGe and CoRuVZ (Z = Al, Ga) are investigated.
All the three alloys are found to crystallize in cubic structure. CoRuMnGe
exhibits L2$_1$ structure whereas, the other two alloys have B2-type disorder.
For CoRuMnGe and CoRuVGa, the experimental magnetic moments are in close
agreement with the theory as well as those predicted by the Slater-Pauling
rule, while for CoRuVAl, a relatively large deviation is seen. The reduction in
the moment in case of CoRuVAl possibly arises due to the anti-site disorder
between Co and Ru sites as well as V and Al sites. Among these alloys, CoRuMnGe
has the highest T$\mathrm{_C}$ of 560 K. Resistivity variation with temperature
reflects the half-metallic nature in CoRuMnGe alloy. CoRuVAl shows metallic
character in both paramagnetic and ferromagnetic states, whereas the
temperature dependence of resistivity for CoRuVGa is quite unusual. In the last
system, $\rho$ vs. T curve shows an anomaly in the form of a maximum and a
region of negative temperature coefficient of resistivity (TCR) in the
magnetically ordered state. The ab initio calculations predict nearly
half-metallic ferromagnetic state with high spin polarization of 91, 89 and 93
\% for CoRuMnGe, CoRuVAl and CoRuVGa respectively. To investigate the
electronic properties of the experimentally observed structure, the Co-Ru swap
disordered structures of CoRuMnGe alloy are also simulated and it is found that
the disordered structures retain half-metallic nature, high spin polarization
with almost same magnetic moment as in the ideal structure. Nearly
half-metallic character, high T$\mathrm{_C}$ and high spin polarization make
CoRuMnGe alloy promising for room temperature spintronic applications.",1903.07265v2
2021-05-06,High-sensitivity of initial SrO growth on the residual resistivity in epitaxial thin films of SrRuO$_3$ on SrTiO$_3$ (001),"The growth of SrRuO$_3$ (SRO) thin film with high-crystallinity and low
residual resistivity (RR) is essential to explore its intrinsic properties.
Here, utilizing the adsorption-controlled growth technique, the growth
condition of initial SrO layer on TiO$_2$-terminated SrTiO$_3$ (STO) (001)
substrate was found to be crucial for achieving a low RR in the resulting SRO
film grown afterward. The optimized initial SrO layer shows a $c$(2 x 2)
superstructure that was characterized by electron diffraction, and a series of
SRO films with different thicknesses ($t$s) were then grown. The resulting SRO
films exhibit excellent crystallinity with orthorhombic-phase down to $t
\approx$ 4.3 nm, which was confirmed by high resolution X-ray measurements.
From azimuthal X-ray scan for SRO orthorhombic (021) reflection, we uncover
four structural domains with a dominant domain of orthorhombic SRO [001] along
cubic STO [010] direction. The dominant domain population depends on $t$, STO
miscut angle (${\alpha}$), and miscut direction (${\beta}$), giving a volume
fraction of about 92 $\%$ for $t \approx$ 26.6 nm and (${\alpha}$, ${\beta}$) ~
(0.14$^{\rm o}$, 5$^{\rm o}$). On the other hand, metallic and ferromagnetic
properties were well preserved down to $t \approx$ 1.2 nm. Residual resistivity
ratio (RRR = ${\rho}$(300 K)/${\rho}$(5 K)) reduces from 77.1 for $t \approx$
28.5 nm to 2.5 for $t \approx$ 1.2 nm, while ${\rho}$(5 K) increases from 2.5
$\mu\Omega$cm for $t \approx$ 28.5 nm to 131.0 $\mu\Omega$cm for $t \approx$
1.2 nm. The ferromagnetic onset temperature ($T_c\prime$) of around 151 K
remains nearly unchanged down to $t \approx$ 9.0 nm and decreases to 90 K for
$t \approx$ 1.2 nm. Our finding thus provides a practical guideline to achieve
high crystallinity and low RR in ultra-thin SRO films by simply adjusting the
growth of initial SrO layer.",2105.02404v1
2021-12-01,"Synthesis and study of (Na, Zr) and (Ca, Zr) phosphate-molybdates and phosphate-tungstates: Thermal expansion behavior, radiation test and hydrolytic stability","Thermal expansion behavior at high temperatures of synthesized
Na$_{1-x}$Zr$_2$(PO$_4$)$_{3-x}$(XO$_4$)$_x$, and
Ca$_{1-x}$Zr$_2$(PO$_4$)$_{3-x}$(XO$_4$)$_x$, X = Mo, W compounds has been
investigated. Ceramics with relatively high density (more than 97.5%) were
produced by Spark Plasma Sintering (SPS) of submicron powders obtained by
sol-gel synthesis. The study of strength characteristics has revealed that
hardness the ceramics are greater than 5 GPa, and minimum fracture toughness
factor was 1 MPa*m$^{1/2}$. It was found that ceramics have a high hydrolytic
resistance in the static regime -- the minimum leaching rates for the Mo- and
W-containing specimens were $31\times10^{-6}$ and $3.36\times 10^{-6}$
g/(cm$^2$*day), respectively. The ceramics had a high resistance to the
irradiation by Xe$^{+26}$ multiple-charged ions with the energy 167 MeV up to
the fluences in the range 1*10$^{12}$ - 6*10$^{13}$ cm$^{-2}$. The
Mo-containing Na$_{0.5}$Zr$_2$(PO$_4$)$_{2.5}$(XO$_4$)$_{0.5}$ ceramics were
shown to have a higher radiation resistance that the phosphate-tungstates.",2112.00373v1
2021-02-22,High T$_C$ ferromagnetic inverse Heusler alloys: A comparative study of Fe$_2$RhSi and Fe$_2$RhGe,"We report the results of experimental investigations on structural, magnetic,
resistivity, caloric properties of Fe$_2$RhZ (Z=Si,Ge) along with
\textit{ab-initio} band structure calculations using first principle
simulations. Both these alloys are found to crystallize in inverse Heusler
structure but with disorder in tetrahedral sites between Fe and Rh. Fe$_2$RhSi
has saturation moment of 5.00 $\mu_B$ and while its counterpart has 5.19
$\mu_B$. Resistivity measurement reveals metallic nature in both of them.
Theoretical simulations using generalized gradient approximation(GGA) predict
inverse Heusler structure with ferromagnetic ordering as ground state for both
the alloys. However it underestimates the experimentally observed moments.
GGA+$U$ approach, with Hubbard $U$ values estimated from density functional
perturbation theory helps to improve the comparison of the experimental
results. Fe$_2$RhSi is found to be half metallic ferromagnet while Fe$_2$RhGe
is not. Varying $U$ values on Fe and Rh sites does not change the net moment
much in Fe$_2$RhSi, unlike in Fe$_2$RhGe. Relatively small exchange splitting
of orbitals in Fe$_2$RhGe compared to that of Fe$_2$RhSi is the reason for not
opening the band gap in the minority spin channel in the former. High ordering
temperature and moment make Fe$_2$RhSi useful for spintronics applications.",2102.10967v1
1995-11-10,Contrasting Dynamic Spin Susceptibility Models and their Relation to High Temperature Superconductivity,"We compare the normal-state resistivities $\rho$ and the critical
temperatures $T_c$ for superconducting $d_{x^2-y^2}$ pairing due to
antiferromagnetic (AF) spin fluctuation exchange in the context of the two
phenomenological dynamical spin susceptibility models, recently proposed by
Millis, Monien, and Pines (MMP) and Monthoux and Pines (MP) and, respectively,
by Radtke, Ullah, Levin, and Norman (RULN), for the cuprate high-$T_c$
materials. Assuming comparable electronic bandwidths and resistiviies in both
models, we show that the RULN model gives a much lower d-wave $T_c$
($\lsim20$K) than the MMP model (with $T_c\sim100$K). We demonstrate that these
profound differences in the $T_c$'s arise from fundamental differences in the
spectral weight distributions of the two model susceptibilities and are
{\it{not}} primarily caused by differences in the calculational techniques
employed by MP and RULN. The MMP model, claimed to fit NMR data in YBCO,
exhibits substantial amounts of spin fluctuation spectral weight up to an
imposed cut-off of 400meV, whereas, in the RULN model, claimed to fit YBCO
neutron scattering data, the weight is narrowly peaked and effectively cut-off
by 100meV. Further neutron scattering experiments, to explore the spectral
weight distribution at all wavevectors over a sufficiently large excitation
energy range, will thus be of crucial importance to resolve the question
whether AF spin fluctuation exchange provides a viable mechanism to account for
high-$T_c$ superconductivity. The large high-frequency boson spectral weight,
needed to generate both a high d-wave $T_c$ and a low normal-state resistivity,
also implies large values, of order unity, for the Migdal smallness parameter,
thus casting serious doubt on the validity of the very",9511051v1
2011-11-14,High Field (14Tesla) Magneto Transport of Sm/PrFeAsO,"We report high field magneto transport of Sm/PrFeAsO. Below spin density wave
transition (TSDW), the magneto-resistance (MR) of Sm/PrFeAsO is positive and
increasing with decreasing temperature. The MR of SmFeAsO, is found 16%,
whereas the same is 21.5% in case of PrFeAsO, at 2.5 K under applied magnetic
field of 14 Tesla (T). In case of SmFeAsO, the variation of isothermal MR with
field below 20 K is nonlinear at lower magnetic fields (< 2 Tesla) and the same
is linear at moderately higher magnetic fields (H \geq 3.5 T). On the other
hand PrFeAsO shows almost linear MR at all temperatures below 20 K. The
anomalous behavior of MR being exhibited in PrFeAsO is originated from Dirac
cone states. The stronger interplay of Fe and Pr ordered moments is responsible
for this distinct behavior. PrFeAsO also shows a hump in resistivity (R-T) with
possible conduction band (FeAs) mediated ordering of Pr moments at around 12 K.
However the same is absent in SmFeAsO even down to 2 K. Our results of high
field magneto-transport of up to 14 Tesla brings about clear distinction
between ground states of SmFeAsO and PrFeAsO.",1111.3143v2
2013-02-25,On the specifics of the electrical conductivity anomalies in PVC nanocomposites,"A qualitative model describing the ""anomalous"" features of the conductivity
of polymer nanocomposites, in particular, switching to the conducting state in
relatively thick (tens of microns or more) of flexible PVC films is considered.
In previously published experimental results, change of conductivity by 10 or
more orders of magnitude occurred both in the absence of external influences
(spontaneously), and under the influence of an applied electric field, as well
as other initiating factors (such as uniaxial pressure) . In a model of hopping
conduction mechanism it is shown, that switching in the conduction states under
the action of external field significantly (by orders of magnitude) below
threshold can be associated with a high-resistance state instability that
results from the sequence of ""shorting"" (reversible soft breakdown) of narrow
insulating gaps between regions with relatively high conductivity. Increasing
the field strength in the remaining insulating gaps ultimately leads to the
formation of a conducting channel between the external electrodes and switching
conductivity of the composite film sample in a state of high conductivity. This
cascade model is essentially based on the transition from the usual description
of the charge tunneling through single independent insulating gap to take into
account correlations between adjacent gaps. In the frame of developed model
other ""anomalies"" such as exponential dependence of the resistance on the
sample thickness, pressure, and other influences can be qualitative explained.
An analogy of the model with a cascading breakdown of avalanche transistors is
also considered.",1302.5993v1
2016-12-15,The properties of ultrapure delafossite metals,"Although they were first synthesized in chemistry laboratories nearly fifty
years ago, the physical properties of the metals PdCoO2, PtCoO2 and PdCrO2 have
only more recently been studied in detail. The delafossite structure contains
triangular co-ordinated atomic layers, and electrical transport in the
delafossite metals is strongly two-dimensional. Their most notable feature is
their in-plane conductivity, which is amazingly high for oxide metals. At room
temperature, the conductivity of non-magnetic PdCoO2 and PtCoO2 is higher per
carrier than those of any alkali metal and even the most conductive elements,
copper and silver. At low temperatures the best crystals have resistivities of
a few n{\Omega}cm, corresponding to mean free paths of tens of microns. PdCrO2
is a frustrated antiferromagnetic metal, with magnetic scattering contributing
to the resistivity at high temperatures and small gaps opening in the Fermi
surface below the N\'eel temperature. There is good evidence that electronic
correlations are weak in the Pd/Pt layers but strong in the Co/Cr layers;
indeed the Cr layer in PdCrO2 is thought to be a Mott insulator. The
delafossite metals therefore act like natural heterostructures between strongly
correlated and nearly free electron sub-systems. Combined with the extremely
high conductivity, they provide many opportunities to study electrical
transport and other physical properties in new regimes. The purpose of this
review is to describe current knowledge of these fascinating materials and set
the scene for what is likely to be a considerable amount of future research.",1612.04948v1
2017-10-05,Dual-wavelength Photo-Hall effect spectroscopy of deep levels in high resistive CdZnTe with negative differential photoconductivity,"Photo-Hall effect spectroscopy was used in the study of deep levels in high
resistive CdZnTe. The monochromator excitation in the photon energy range
0.65-1.77 eV was complemented by a laser diode high-intensity excitation at
selected photon energies. A single sample characterized by multiple unusual
features like negative differential photoconductivity and anomalous depression
of electron mobility was chosen for the detailed study involving measurements
at both the steady and dynamic regimes. We revealed that the Hall mobility and
photoconductivity can be both enhanced and suppressed by an additional
illumination at certain photon energies. The anomalous mobility decrease was
explained by an excitation of the inhomogeneously distributed deep level at the
energy Ev+1.0 eV enhancing thus potential non-uniformities. The appearance of
negative differential photoconductivity was interpreted by an intensified
electron occupancy of that level by a direct valence band-to-level excitation.
Modified Shockley-Read-Hall theory was used for fitting experimental results by
a model comprising five deep levels. Properties of the deep levels and their
impact on the device performance were deduced.",1710.01945v1
2020-02-25,"Hydrogenated amorphous silicon detectors for particle detection, beam flux monitoring and dosimetry in high-dose radiation environment","Hydrogenated amorphous silicon (a-Si:H) has remarkable radiation resistance
properties and can be deposited on a lot of different substrates. A-Si:H based
particle detectors have been built since mid 1980s as planar p-i-n or Schottky
diode structures; the thickness of these detectors ranged from 1 to 50 micron.
However MIP detection using planar structures has always been problematic due
to the poor S/N ratio related to the high leakage current at high depletion
voltage and the low charge collection efficiency. The usage of 3D detector
architecture can be beneficial for the possibility to reduce inter-electrode
distance and increase the thickness of the detector for larger charge
generation compared to planar structures. Such a detector can be used for
future hadron colliders for its radiation resistance and also for X-ray
imaging. Furthermore the possibility of a-Si:H deposition on flexible materials
(like kapton) can be exploited to build flexible and thin beam flux measurement
detectors and x-ray dosimeters.",2002.10848v1
2021-01-29,Wide-range epitaxial strain control of electrical and magnetic properties in high-quality SrRuO3 films,"Epitaxial strain in 4d ferromagnet SrRuO3 films is directly linked to the
physical properties through the strong coupling between lattices, electrons,
and spins. It provides an excellent opportunity to tune the functionalities of
SrRuO3 in electronic and spintronic devices. However, a thorough understanding
of the epitaxial strain effect in SrRuO3 has remained elusive due to the lack
of systematic studies. This study demonstrates wide-range epitaxial strain
control of electrical and magnetic properties in high-quality SrRuO3 films. The
epitaxial strain was imposed by cubic or pseudocubic perovskite substrates
having a lattice mismatch of -1.6 to 2.3% with reference to bulk SrRuO3. The
Poisson ratio, which describes the two orthogonal distortions due to the
substrate clamping effect, is estimated to be 0.33. The Curie temperature (TC)
and residual resistivity ratios of the series of films are higher than or
comparable to the highest reported values for SrRuO3 on each substrate,
confirming the high crystalline quality of the films. A TC of 169 K is achieved
in a tensile-strained SrRuO3 film on the DyScO3 (110) substrate, which is the
highest value ever reported for SrRuO3. The TC (146-169 K), magnetic anisotropy
(perpendicular or in-plane magnetic easy axis), and metallic conduction
(residual resistivity at 2 K of 2.10 - 373 {\mu}{\Omega}cm) of SrRuO3 are
widely controlled by epitaxial strain. These results provide guidelines to
design SrRuO3-based heterostructures for device applications.",2101.12376v1
2020-05-16,Pressure-induced Topological and Structural Phase Transitions in an Antiferromagnetic Topological Insulator,"Recently, natural van der Waals heterostructures of (MnBi2Te4)m(Bi2Te3)n have
been theoretically predicted and experimentally shown to host tunable magnetic
properties and topologically nontrivial surface states. In this work, we
systematically investigate both the structural and electronic responses of
MnBi2Te4 and MnBi4Te7 to external pressure. In addition to the suppression of
antiferromagnetic order, MnBi2Te4 is found to undergo a
metal-semiconductor-metal transition upon compression. The resistivity of
MnBi4Te7 changes dramatically under high pressure and a non-monotonic evolution
of \r{ho}(T) is observed. The nontrivial topology is proved to persists before
the structural phase transition observed in the high-pressure regime. We find
that the bulk and surface states respond differently to pressure, which is
consistent with the non-monotonic change of the resistivity. Interestingly, a
pressure-induced amorphous state is observed in MnBi2Te4, while two high
pressure phase transitions are revealed in MnBi4Te7. Our combined theoretical
and experimental research establishes MnBi2Te4 and MnBi4Te7 as highly tunable
magnetic topological insulators, in which phase transitions and new ground
states emerge upon compression.",2005.08015v1
2020-08-03,Solute hydrogen and deuterium observed at the near atomic scale in high-strength steel,"Observing solute hydrogen (H) in matter is a formidable challenge, yet,
enabling quantitative imaging of H at the atomic-scale is critical to
understand its deleterious influence on the mechanical strength of many
metallic alloys that has resulted in many catastrophic failures of engineering
parts and structures. Here, we report on the APT analysis of hydrogen (H) and
deuterium (D) within the nanostructure of an ultra-high strength steel with
high resistance to hydrogen embrittlement. Cold drawn, severely deformed
pearlitic steel wires (Fe-0.98C-0.31Mn-0.20Si-0.20Cr-0.01Cu-0.006P-0.007S wt.%,
{\epsilon}=3.1) contains cementite decomposed during the pre-deformation of the
alloy and ferrite. We find H and D within the decomposed cementite, and at some
interfaces with the surrounding ferrite. To ascertain the origin of the H/D
signal obtained in APT, we explored a series of experimental workflows
including cryogenic specimen preparation and cryogenic-vacuum transfer from the
preparation into a state-of-the-art atom probe. Our study points to the
critical role of the preparation, i.e. the possible saturation of H-trapping
sites during electrochemical polishing, how these can be alleviated by the use
of an outgassing treatment, cryogenic preparation and transfer prior to
charging. Accommodation of large amounts of H in the under-stoichiometric
carbide likely explains the resistance of pearlite against hydrogen
embrittlement.",2008.00684v1
2021-07-01,"Singular angular magnetoresistance and sharp resonant features in a high-mobility metal with open orbits, ReO3","We report high-resolution angular magnetoresistance (AMR) experiments
performed on crystals of ReO$_3$ with high mobility (90,000 cm$^2$/Vs at 2 K)
and extremely low residual resistivity (5-8 n$\Omega$cm). The Fermi surface,
comprised of intersecting cylinders, supports open orbits. The resistivity
$\rho_{xx}$ in a magnetic field $B$ = 9 T displays a singular pattern of
behavior. With $\bf E\parallel \hat{x}$ and $\bf B$ initially
$\parallel\bf\hat{z}$, tilting $\bf B$ in the longitudinal $k_z$-$k_x$ plane
leads to a steep decrease in $\rho_{xx}$ by a factor of 40. However, if $\bf B$
is tilted in the transverse $k_y$-$k_z$ plane, $\rho_{xx}$ increases steeply by
a factor of 8. Using the Shockley tube integral approach, we show that, in
ReO$_3$, the singular behavior results from the rapid conversion of closed to
open orbits, resulting in opposite signs for AMR in orthogonal planes. The
floor values of $\rho_{xx}$ in both AMR scans are identified with specific sets
of open and closed orbits. Also, the ""completion angle"" $\gamma_c$ detected in
the AMR is shown to be an intrinsic geometric feature that provides a new way
to measure the Fermi radius $k_F$. However, additional sharp resonant features
which appear at very small tilt angles in the longitudinal AMR scans are not
explained by the tube integral approach.",2107.00742v1
2021-07-07,Development and validation of electrical-insulating Al2O3 coatings for high-temperature liquid PbLi applications,"Electrical-insulating coatings are of great importance for liquid-metal
breeder/coolant based systems relevant to fusion power plants. In specific to
Pb-16Li eutectic, a candidate breeder material, such coatings are being
actively investigated for their criticality in addressing various
functionalities. For such applications, a candidate coating must be
demonstrated for its compatibility with corrosive media, high operational
temperatures and integrity of electrical-insulation over long durations without
substantial degradation. At present, no relevant in-situ insulation resistance
(IR) data is available for performance assessment of coated substrates within
PbLi environment. To address this shortfall, an experimental study was
performed at IPR towards application of high-purity alumina coatings on SS-316L
substrates and further rigorous validation in static PbLi environment. The
adopted coating process required a low-temperature heat treatment (< 430C) and
could yield average coating thicknesses in the range of 100-500 micron. Coated
samples were validated for their electrical insulation integrity in static PbLi
over two test campaigns for continuous durations of over 700 h and 1360 h,
including thermal cycling, at operational temperature between 300C-400C.
Estimated volumetric electrical-resistivity remained of the order of 109-1011
ohm-cm without significant degradation. In-situ estimations of thermal derating
factors establish excellent electrical-insulation characteristics after long
term exposure to liquid PbLi. This paper presents details of utilized coating
application methods, coating thickness estimations, liquid-metal test set-up,
insulation performance and critical observations from SEM/EDX and XRD analysis
on the tested samples.",2107.03244v1
2021-09-26,Tomographic Volumetric Additive Manufacturing of Silicon Oxycarbide Ceramics,"Ceramics are highly technical materials with properties of interest for
multiple industries. Precisely because of their high chemical, thermal, and
mechanical resistance, ceramics are difficult to mold into complex shapes. A
possibility to make convoluted ceramic parts is to use preceramic polymers
(PCP) in liquid form. The PCP resin is first solidified in a desired geometry
and then transformed into ceramic compounds through a pyrolysis step that
preserves the shape. Light-based additive manufacturing (AM) is a promising
route to achieve solidification of the PCP resin. Different approaches, such as
stereolithography, have already been proposed but they all rely on a
layer-by-layer printing process which sets limitations on the printing speed
and object geometry. Here, we report on the fabrication of complex 3D
centimeter-scale ceramic parts by using tomographic volumetric printing which
is fast, high resolution and offers a lot of freedom in terms of geometrical
design compared to state-of-the-art AM techniques. First, we formulated a
photosensitive preceramic resin that was solidified by projecting light
patterns from multiple angles. Then, the obtained 3D printed parts were
converted into ceramics by pyrolyzing them in a furnace. We demonstrate the
strength of this approach through the fabrication of dense microcomponents
exhibiting overhangs and hollow geometries without the need of supporting
structures, and characterize their resistance to high heat and harsh chemical
treatments.",2109.12680v1
2022-11-16,Characterisation of Gamma-irradiated MCz-Silicon Detectors with a High-$K$ Negative Oxide as Field Insulator,"The high-luminosity operation of the Tracker in the Compact Muon Solenid
(CMS) detector at the Large Hadron Collider (LHC) experiment calls for the
development of silicon-based sensors. This involves implementation of
AC-coupling to micro-scale pixel sensor areas to provide enhanced isolation of
radiation-induced leakage currents. The motivation of this study is the
development of AC-pixel sensors with negative oxides (such as aluminium oxide -
Al$_2$O$_3$ and hafnium oxide - HfO$_2$) as field insulators that possess good
dielectric strength and provide radiation hardness. Thin films of Al$_2$O$_3$
and HfO$_2$ grown by atomic layer deposition (ALD) method were used as
dielectrics for capacitive coupling. A comparison study based on dielectric
material used in MOS capacitors indicate HfO$_2$ as a better candidate since it
provides higher sensitivity (where, the term sensitivity is defined as the
ratio of the change in flat-band voltage to dose) to negative charge
accumulation with gamma irradiation.
  Further, space charge sign inversion was observed for sensors processed on
high resistivity p-type Magnetic Czochralski silicon (MCz-Si) substrates that
were irradiated with gamma rays up to a dose of 1 MGy. The inter-pixel
resistance values of heavily gamma irradiated AC-coupled pixel sensors suggest
that high-$K$ negative oxides as field insulators provide a good electrical
isolation between the pixels.",2211.09158v2
2023-07-12,Extrinsic Anomalous Hall effect in Mn Doped GeSnTe Semiconductors in the Bad Metal Hopping Regime,"We present high field magnetotransport studies of Ge1-x-y(SnxMny)Te bulk
multiferroics with diamagnetic Sn and paramagnetic Mn concentration x = 0.38 to
0.79 and y = 0.02 to 0.086, respectively. The zero field resistivity, {\rho}(T)
takes significant contribution from defects below T = 20 K however, a mixed
scattering contribution from dynamic disorder and unusual sources is estimated
from T = 20 K to 300 K. The carrier mobility shows anomalous temperature
dependence from T0.2 to T0.5 which hints towards possible presence of polaronic
effects resulting from coupling of holes with phonons. This anomalous behavior
cannot be understood in terms of pure phononic scattering mechanism at high
temperature. From point of view of high field results, the transverse component
of magnetoresistivity manifests anomalous Hall effect originating from
extrinsic scattering sources, particularly the side jump mechanism reveals a
larger contribution. We also find that the correlation between the transverse
and longitudinal conductivities follow the universal scaling law {\sigma}xy ~
{\sigma}xxn where n = 1.6 in the low conductivity limit. The values n = 1.5 to
1.8 obtained for the present GSMT alloys justify the bad metal hopping regime
since the results fall in the low conductivity ferromagnetic family with
{\sigma}xx ~ 104 ohmcm-1. The interpretation of the n = 1.6 scaling in the low
conductivity regime is thus far not fully understood. However, the anomalous
Hall resistivity scaling with modified relation by Tian et al is indicative of
the dominant side jump scattering along with noticeable role of skew
scattering.",2307.06271v1
2012-10-07,Tailoring Magnetism of Perpendicularly Magnetized MnxGa Epitaxial Films on GaAs for Practical Applications,"MnxGa films with high perpendicular anisotropy, coercivity and energy product
have great application potential in ultrahigh-density perpendicular recording,
permanent magnets, spin-transfer-torque memory and oscillators,
magneto-resistance sensors and ferromagnetic metal/semiconductor
heterostructure devices. Here we present a comprehensive diagram of effective
magnetism-tailoring of perpendicularly magnetized MnxGa films grown on III-V
semiconductor GaAs by using molecular-beam epitaxy for the first time, by
systematically investigating the wide-range composition and detailed
post-growth annealing effects. We show that the (001)-orientated MnxGa films
with L10 or D022 ordering could be crystallized on GaAs in a very wide
composition range from x=0.76 to 2.6. L10-ordered MnxGa films show robust
magnetization, high remanent ratio, giant perpendicular anisotropy, high
intrinsic and extrinsic coercivity, and large energy product, which make this
kind of material favorable for perpendicular magnetic recording,
high-performance spintronic devices and permanent magnet applications. In
contrast, D022-ordered films exhibit lower perpendicular anisotropy and weaker
magnetism. Post-growth annealing MnxGa films studies reveal high
thermal-stability up to 450 oC, and effective tailoring of magnetic properties
can be realized by prolonging annealing at 450 oC. These results would be
helpful for understanding this kind of material and designing new spintronic
devices for specific practical applications.",1210.2062v3
2012-11-14,The Critical Current Density of an SNS Josephson-Junction,"The critical current density (Jc) through a superconductor in high magnetic
fields is controlled by the inclusions and microstructure of the material that
hold fluxons stationary to keep the resistance zero and is described using
Ginzburg-Landau (G-L) theory. Although the functional form of Jc for
superconducting-normal-superconducting (SNS) Josephson-Junctions (J-Js) is
known in the low field limit, includes the local properties of the junctions
and has been confirmed experimentally in many systems, there are no general
solutions for Jc of J-Js in high fields. Scaling laws describe the functional
form (magnetic field, temperature and strain dependence) of Jc for
polycrystalline superconductors in high fields but do not include local grain
boundary properties. They are derived by considering isolated pinning sites
where at criticality fluxons either depin or free fluxons shear past pinned
fluxons as part of the flux line lattice. However, visualisation of solutions
to the Time Dependent Ginzburg-Landau (TDGL) equations for polycrystalline
materials have shown that fluxons cross the superconductor by flowing along the
grain boundaries. Here we derive clean- and dirty- limit analytic equations for
of SNS J-Js in high fields and verify them using computational solutions to
TDGL theory. We consider SNS J-Js to be the basic building blocks for grain
boundaries in polycrystalline materials since they provide flux-flow channels.
The J-Js description provides a mathematical framework that includes the
utility of scaling laws together with our microscopic understanding of barriers
to supercurrent flow and helps identify the grain boundary engineering that can
improve in low temperature polycrystalline superconductors used in high
magnetic field applications.",1211.3255v2
2013-09-08,Nanoscale resolution scanning thermal microscopy with thermally conductive nanowire probes,"Scanning thermal microscopy (SThM) - a type of scanning probe microscopy that
allows mapping thermal transport and temperatures in nanoscale devices, is
becoming a key approach that may help to resolve heat dissipation problems in
modern processors and develop new thermoelectric materials. Unfortunately,
performance of current SThM implementations in measurement of high thermal
conductivity materials continues to me limited. The reason for these
limitations is two-fold - first, SThM measurements of high thermal conductivity
materials need adequate high thermal conductivity of the probe apex, and
secondly, the quality of thermal contact between the probe and the sample
becomes strongly affected by the nanoscale surface corrugations of the studied
sample. In this paper we develop analytical models of the SThM approach that
can tackle these complex problems - by exploring high thermal conductivity
nanowires as a tip apex, and exploring contact resistance between the SThM
probe and studied surface, the latter becoming particularly important when both
tip and surface have high thermal conductivities. We develop analytical model
supported by the finite element analysis simulations and by the experimental
tests of SThM prototype using carbon nanotube (CNT) at the tip apex as a heat
conducting nanowire. These results elucidate vital relationships between the
performance of the probe in SThM from one side and thermal conductivity,
geometry of the probe and its components from the other, providing pathway for
overcoming current limitations of SThM.",1309.2010v1
2019-09-13,Electric field and current induced electroforming modes in NbOx,"Electroforming is used to initiate the memristive response in
metal/oxide/metal devices by creating a filamentary conduction path in the
oxide film. Here we use a simple photoresist-based detection technique to map
the spatial distribution of conductive filaments formed in Nb/NbOx/Pt devices,
and correlate these with current-voltage characteristics and in-situ
thermoreflectance measurements to identify distinct modes of electroforming in
low and high conductivity NbOx films. In low conductivity films the filaments
are randomly distributed within the oxide film, consistent with a field-induced
weakest-link mechanism, while in high conductivity films they are concentrated
in the center of the film. In the latter case the current-voltage
characteristics and in-situ thermoreflectance imaging show that electroforming
is associated with current bifurcation into regions of low and high current
density. This is supported by finite element modelling of the current
distribution and shown to be consistent with predictions of a simple core-shell
model of the current distribution. These results clearly demonstrate two
distinct modes of electroforming in the same materials system and show that the
dominant mode depends on the conductivity of the film, with field-induced
electroforming dominant in low conductivity films and current-bifurcation
induced electroforming dominant in high conductivity films. Finally, we
demonstrate S-type and snap-back negative differential resistance in the high
conductivity films and explain this behavior in terms of two-zone model.",1909.06443v2
2000-05-25,Critical Resistivity along the Quantum Hall Liquid--Insulator Transition Line,"The critical resistivity measured along the quantum Hall liquid--insulator
transition line indicates a pronounced peak at a critical filling factor close
to 1, which marks the crossover from the high to low magnetic field regime in
the phase diagram. The origin of this behavior is explained in the framework of
classical transport in a puddle network model. The proposed scenario is also
consistent with the behavior of the critical Hall resistance along the
transition line. In addition, a formula is suggested as a fit for isotherms
($\rho_{xx}$ vs. $\nu$) in the moderately high field regime, which exhibits a
violation of duality symmetry as the critical resistivity is evelated from the
`universal' value $h/e^2$.",0005436v1
2018-03-20,HPL-GEM: Controlling High Pressure Laminates bulk resistivity with GEMs,"We succeeded in modifying and controlling the electrical resistance of a
standard High Pressure Laminate (HPL) panel through the use of a Gas Electron
Multiplier (GEM) foil that has been embedded into the bulk of the HPL plate
itself. Electrical characterizations were made and preliminary data show that
this HPL-GEM embedded system can easily vary its bulk resistance by more than
one order of magnitude. Data show that the bulk resistance change is
exponential with the applied voltage to the embedded GEM.",1803.07675v1
2024-02-22,Auxiliary Calculations for Graphene-Based Quantum Hall Arrays Using Partially Recursive Star-Mesh Transformations,"A previous mathematical approach adopted for optimizing the number of total
device elements required for obtaining high effective quantized resistances in
graphene-based quantum Hall array devices (QHARS) has been further explored
with partial recursion patterns. Designs would assume the use of epitaxial
graphene elements, whose quantized Hall resistance at the {\nu}=2 plateau (R_H
\approx 12906.4 \Ohm) becomes the building block for larger effective,
quantized resistances. Auxiliary calculations suggest the importance of
applying full recursions at least once to maximize the reduction of total QHARS
elements needed for high resistances.",2402.14520v1
2005-03-31,Tuning Negative Differential Resistance in a Molecular Film,"We have observed tunable negative differential resistance (NDR) in scanning
tunneling spectroscopy measurements of a double layer of C60 molecules on a
metallic surface. Using a simple model we show that the observed NDR behavior
is explained by voltage-dependent changes in the tunneling barrier height.",0503765v1
2006-10-10,Residual resistivity due to wedge disclination dipoles in metals with rotational plasticity,"The residual resistivity $\rho $ in metals caused by wedge disclination
dipoles is studied in the framework of the Drude formula. It is shown that
$\rho\sim L^{-p}$ with $p=3$ for biaxial and $p=2$ for uniaxial dipoles ($L$ is
a size of dipole arm)",0610258v1
2006-10-26,Two years later--lessons from vortex dynamics in super media,"Two years ago the reasons for resistance to the fundamental vortex dynamics
in super media emerged in 1990's were analyzed (cond-mat/0407007). Five
""mistakes"" were identified to explain this resistance. Given the current
tremendous interest in vortex dynamics, it would be desirable to provide a
progress report: A survey of literature reveals that 3 out 5 ""mistakes"" has in
fact been confirmed by other researchers.",0610753v1
2008-12-16,Electrical properties of vanadium oxide subject to hydrogen plasma treatment,"The effect of doping with hydrogen on the electrical properties of vanadium
oxide is studied. For vanadium oxide films, subject to cold hydrogen plasma
treatment, the temperature dependence of resistance with a maximum at T ~ 100 K
is observed. Also, the dependence of the a.c. resistance on frequency is
studied. A strategy for fabrication new superconducting materials is discussed.",0812.2973v1
2011-02-07,Direct correlation between strengthening mechanisms and electrical noise in strained copper wires,"We have measured the resistance noise of copper metallic wires during a
tensile stress. The time variation of the main resistance is continuous up to
the wire breakdown, but its fluctuations reveal the intermittent and
heterogeneous character of plastic flow. We show in particular direct
correlations between strengthening mechanisms and noise spectra
characteristics.",1102.1253v1
2011-09-05,Mesoscopic Thermovoltage Measurement Design,"Quantitative thermoelectric measurements in the mesoscopic regime require
accurate knowledge of temperature, thermovoltage, and device energy scales. We
consider the effect of a finite load resistance on thermovoltage measurements
of InAs/InP heterostructure nanowires. Load resistance and ac attenuation
distort the measured thermovoltage therefore complicating the evaluation of
device performance. Understanding these effects improves experimental design
and data interpretation.",1109.1009v1
2016-07-20,MegaOhm Extraordinary Hall effect in oxidized CoFeB,"We report on development of controllably oxidized CoFeB ferromagnetic films
demonstrating the extraordinary Hall effect (EHE) resistivity exceeding 1 Ohmcm
and magnetic field sensitivity up to 10^6 Ohm/T. Such EHE resistivity is four
orders of magnitude higher than previously observed in ferromagnetic materials,
while sensitivity is two orders larger than the best of semiconductors",1607.05923v1
1995-12-18,Anisotropic Localization Effect in Layered Materials,"We investigate localization properties in the highly anisotropic and
intrinsically disordered layered material, which is analogous to high-Tc
cuprates. By varying the anisotropy of the system which is parameterized by the
interlayer hopping $tp$, we find a crossover from two-dimensional (2D) to
three-dimensional (3D) behavior at a critical hopping amplitude $tp_c$, where a
mobility edge starts to appear. We show that below the mobility edge,
anisotropic localization effect may exist for a finite size system, when the
$ab$-plane localization length is longer than the system size and the $c$-axis
localization length is shorter than the system size. Nevertheless, we argue
that such anisotropic localization can not account for the ``semiconductor''
like behavior of the $c$-axis resistivity of high $\Tc$ cuprates.",9512133v1
2008-03-20,Graphene-Based Liquid Crystal Device,"Graphene is only one atom thick, optically transparent, chemically inert and
an excellent conductor. These properties seem to make this material an
excellent candidate for applications in various photonic devices that require
conducting but transparent thin films. In this letter we demonstrate liquid
crystal devices with electrodes made of graphene which show excellent
performance with a high contrast ratio. We also discuss the advantages of
graphene compared to conventionally-used metal oxides in terms of low
resistivity, high transparency and chemical stability.",0803.3031v1
2008-10-02,Carrier doping to pseudo-low-dimensional compound La2RuO5,"Hole carrier doping has been tried to pseudo-low-dimensional material La2RuO5
by substituting La3+ with Cd2+. Single phased samples of La2-xCdxRuO5 with x up
to 0.5 have been successfully obtained and also high pressure O2 annealing has
been performed to the x=0.5 sample. Although the formal ionic state of Ru is
expected to increase from 4+ (at x=0) to 4.5+ (at x=0.5), the magnetic and
electrical properties show no significant changes in as-sintered samples. In
contrast, high pressure O2 annealed x=0.5 samples show a little reduction of
electrical resistivity and the decrease of thermoelectric power at 260 K. From
these results, it can be speculated that the doped carriers are mostly
compensated by oxygen deficiency in as-sintered samples.",0810.0350v1
2008-12-15,"High-temperature oxygen non-stoichiometry, conductivity and structure in strontium-rich nickelates La2-xSrxNiO4-δ(x = 1 and 1.4)","Oxygen nonstoichiometry, electrical conductivity and thermal expansion of La2
xSrxNiO4-\delta phases with high levels of strontium substitution (1 =< x =<
1.4) have been investigated in air and oxygen atmosphere in the temperature
range 20-1050 degrees C. These phases retain the K2NiF4-type structure of
La2NiO4 (tetragonal, space group I4/mmm). The oxygen vacancy fraction was
determined independently from thermogravimetric and neutron diffraction
experiments, and is found to increase considerably on heating. The electrical
resistivity, thermal expansion and cell parameters with temperature show
peculiar variations with temperature, and differ notably from
La2NiO4$\pm$\delta in this respect. These variations are tentatively correlated
with the evolution of nickel oxidation state, which crosses from a Ni3+/Ni4+ to
a Ni2+/Ni3+ equilibrium on heating.",0812.2747v1
2009-12-08,The Deposition of High-Quality HfO2 on Graphene and the Effect of Remote Oxide Phonon Scattering,"We demonstrate the atomic layer deposition of high-quality HfO2 film on
graphene and report the magnitude of remote oxide phonon (ROP) scattering in
dual-oxide graphene transistors. Top gates with 30 nm HfO2 oxide layer exhibit
excellent doping capacity of greater than 1.5x10^(13)/cm^(2). The carrier
mobility in HfO2-covered graphene reaches 20,000 cm^(2)/Vs at low temperature,
which is the highest among oxide-covered graphene and compares to that of
pristine samples. The temperature-dependent resistivity exhibits the effect of
ROP scattering from both the SiO2 substrate and the HfO2 over-layer. At room
temperature, surface phonon modes of the HfO2 film centered at 54 meV dominate
and limit the carrier mobility to ~20,000 cm^(2)/Vs. Our results highlight the
important choice of oxide in graphene devices.",0912.1378v2
2013-12-21,Near-Field Microwave Magnetic Nanoscopy of Superconducting Radio Frequency Cavity Materials,"A localized measurement of the RF critical field on superconducting radio
frequency (SRF) cavity materials is a key step to identify specific defects
that produce quenches of SRF cavities. Two new measurements are performed to
demonstrate these capabilities with a novel near-field scanning probe microwave
microscope. The first is a third harmonic nonlinear measurement on a high
Residual- Resistance-Ratio bulk Nb sample showing strong localized nonlinear
response for the first time, with surface RF magnetic field $B_{surface} \sim
10^{2}$ $mT$. The second is a raster scanned harmonic response image on a high
quality $MgB_{2}$ thin film demonstrating a quench defect-free surface over
large areas.",1312.6257v1
2014-11-14,"Characterization of TiAlSiON Coatings Deposited by Plasma Enhanced Magnetron Sputtering: XRD, XPS, and DFT Studies","The results of characterization of TiAlSiON hard coatings deposited on
ferric-chromium AISI 430 stainless steel by plasma enhanced magnetron
sputtering are presented. The coating with maximum hardness (of 45 GPa) was
obtained at the following optimal values of elemental concentrations: Si ~5
at.%, Al ~15 at.%, and Ti ~27 at.%. The elastic modulus of the coating was 590
GPa. The reading of gaseous mixture (Ar-N2) pressure was 1*10-3 Torr and the
reading of partial pressure of oxygen (O2) was 1*10-5 Torr. The X-ray
diffraction (XRD) measurements showed the presence of Ti(Al)N. High-energy
resolved XPS spectra of core levels revealed the formation of Ti-N, Ti-O-N,
Si-N and Al-O-N bonds. Comparison of XPS valence band spectra with specially
performed density functional theory calculations for two ordered and few
disordered TiN1-xOx (0 =< x <= 1) demonstrates that a Ti(Al)OxNy phase is
formed on the surface of AISI430 steel upon the plasma enhanced magnetron
sputtering, which provides this material with a good combination of high
hardness and improved oxidation resistance.",1411.3859v1
2015-05-25,Cluster spin-glass ground state in quasi-one-dimensional KCr$_{3}$As$_{3}$,"We report structural and physical properties of a new quasi-one-dimensional
Cr-based compound, KCr$_{3}$As$_{3}$, which is prepared by potassium
deintercalation from the superconductive K$_{2}$Cr$_{3}$As$_{3}$.
KCr$_{3}$As$_{3}$ adopts the TlFe$_{3}$Te$_{3}$-type structure with space group
$P6_{3}$/$m$ (No. 176). The high-temperature magnetic susceptibility obeys the
Curie-Weiss law with an effective magnetic moment of 0.68
$\mu_{\mathrm{B}}$/Cr. Below 56 K the susceptibility deviates from the
high-temperature Curie-Weiss behavior, coinciding with the rapid increase in
resistivity, which suggests formation of spin clusters. The short-range spin
correlations are also supported by the specific-heat data. The title material
does not exhibit bulk superconductivity; instead, it shows a cluster spin-glass
state below $\sim$ 5 K.",1505.06525v1
2017-12-29,Structural transformations in porous glasses under mechanical loading. II. Compression,"The role of porous structure and glass density in response to compressive
deformation of amorphous materials is investigated via molecular dynamics
simulations. The disordered, porous structures were prepared by quenching a
high-temperature binary mixture below the glass transition into the phase
coexistence region. With decreasing average glass density, the pore morphology
in quiescent samples varies from a random distribution of compact voids to a
porous network embedded in a continuous glass phase. We find that during
compressive loading at constant volume, the porous structure is linearly
transformed in the elastic regime and the elastic modulus follows a power-law
increase as a function of the average glass density. Upon further compression,
pores deform significantly and coalesce into large voids leading to formation
of domains with nearly homogeneous glass phase, which provides an enhanced
resistance to deformation at high strain.",1712.10265v1
2018-02-07,"Stability of boron-doped graphene/copper interface: DFT, XPS and OSEE studies","Two different types of boron-doped graphene/copper interfaces synthesized
using two different flow rates of Ar through the bubbler containing the boron
source were studied. X-ray photoelectron spectra (XPS) and optically stimulated
electron emission (OSEE) measurements have demonstrated that boron-doped
graphene coating provides a high corrosion resistivity of Cu-substrate with the
light traces of the oxidation of carbon cover. The density functional theory
calculations suggest that for the case of substitutional (graphitic)
boron-defect only the oxidation near boron impurity is energetically favorable
and creation of the vacancies that can induce the oxidation of copper substrate
is energetically unfavorable. In the case of non-graphitic boron defects
oxidation of the area, a nearby impurity is metastable that not only prevent
oxidation but makes boron-doped graphene. Modeling of oxygen reduction reaction
demonstrates high catalytic performance of these materials.",1802.02345v1
2018-06-11,Uncovering electron scattering mechanisms in NiFeCoCrMn derived concentrated solid solution and high entropy alloys,"Whilst it has long been known that disorder profoundly affects transport
properties, recent measurements on a series of solid solution 3d-transition
metal alloys reveal two orders of magnitude variations in the residual
resistivity. Using ab-initio methods, we demonstrate that, while the carrier
density of all alloys is as high as in normal metals, the electron
mean-free-path can vary from ~10 {\AA} (strong scattering limit) to ~10$^3$
{\AA} (weak scattering limit). Here, we delineate the underlying electron
scattering mechanisms responsible for this disparate behavior. While spin
dependent site-diagonal disorder is always dominant, for alloys containing only
Fe, Co, and Ni the majority spin channel experiences negligible disorder
scattering, thereby providing a short circuit, while for Cr/Mn containing
alloys both spin channels experience strong disorder scattering due to an
electron filling effect. Unexpectedly, other scattering mechanisms (e.g.
displacement scattering) are found to be relatively weak in most cases.",1806.03785v2
2018-11-26,Engineering Large Anisotropic Magnetoresistance in La0.7Sr0.3MnO3 Films at Room Temperature,"The magnetoresistance (MR) effect is widely employed in technologies that
pervade our world from magnetic reading heads to sensors. Diverse contributions
to MR, such as anisotropic, giant, tunnel, colossal, and spin-Hall, are
revealed in materials depending on the specific system and measuring
configuration. Half-metallic manganites hold promise for spintronic
applications but the complexity of competing interactions has not permitted the
understanding and control of their magnetotransport properties to enable the
realization of their technological potential. Here we report on the ability to
induce a dominant switchable magnetoresistance in La0.7Sr0.3MnO3 epitaxial
films, at room temperature (RT). By engineering an extrinsic magnetic
anisotropy, we show a large enhancement of anisotropic magnetoresistance (AMR)
which leads to, at RT, signal changes much larger than the other contributions
such as the colossal magnetoresistance (CMR). The dominant extrinsic AMR
exhibits large variation in the resistance in low field region, showing high
sensitivity to applied low magnetic fields. These findings have a strong impact
on the real applications of manganite based devices for the high-resolution low
field magnetic sensors or spintronics.",1811.10301v1
2017-03-23,Unconventional Large Linear Magnetoresistance in Cu$_{2-x}$Te,"We report a large linear magnetoresistance in Cu$_{2-x}$Te, reaching
$\Delta\rho/\rho(0)$ = 250\% at 2 K in a 9 T field. This is observed for
samples with $x$ in the range 0.13 to 0.22, and the results are comparable to
the effects observed in Ag$_2 X$ materials, although in this case the results
appear for a much wider range of bulk carrier density. Examining the magnitude
vs. crossover field from low-field quadratic to high-field linear behavior, we
show that models based on classical transport behavior best explain the
observed results. The effects are traced to misdirected currents due to
topologically inverted behavior in this system, such that stable surface states
provide the high mobility transport channels. The resistivity also crosses over
to a $T^2$ dependence in the temperature range where the large linear MR
appears, an indicator of electron-electron interaction effects within the
surface states. Thus this is an example of a system in which these interactions
dominate the low-temperature behavior of the surface states.",1703.07945v1
2019-02-14,One-dimensional edge contacts to a monolayer semiconductor,"Integration of electrical contacts into van der Waals (vdW) heterostructures
is critical for realizing electronic and optoelectronic functionalities.
However, to date no scalable methodology for gaining electrical access to
buried monolayer two-dimensional (2D) semiconductors exists. Here we report
viable edge contact formation to hexagonal boron nitride (hBN) encapsulated
monolayer MoS$_2$. By combining reactive ion etching, in situ Ar$^+$ sputtering
and annealing, we achieve a relatively low edge contact resistance, high
mobility (up to ~30 cm$^2$/Vs) and high on-current density (>50 uA/um at
V$_{\rm DS}$ = 3V), comparable to top contacts. Furthermore, the atomically
smooth hBN environment also preserves the intrinsic MoS$_2$ channel quality
during fabrication, leading to a steep subthreshold swing of 116 mV/dec with a
negligible hysteresis. Hence, edge contacts are highly promising for
large-scale practical implementation of encapsulated heterostructure devices,
especially those involving air sensitive materials, and can be arbitrarily
narrow, which opens the door to further shrinkage of 2D device footprint.",1902.05506v3
2019-02-20,Vortex pinning and flux flow microwave studies of coated conductors,"Demanding microwave applications in a magnetic field require the material
optimization not only in zero-field but, more important, in the in-field flux
motion dominated regime. However, the effect of artificial pinning centers
(APC) remains unclear at high frequency. Moreover, in coated conductors the
evaluation of the high frequency material properties is difficult due to the
complicated electromagnetic problem of a thin superconducting film on a
buffered metal substrate. In this paper we present an experimental study at 48
GHz of 150-200 nm YBa$_2$Cu$_3$O$_{7-x}$ coated conductors, with and without
APCs, on buffered Ni-5at%W tapes. By properly addressing the electromagnetic
problem of the extraction of the superconductor parameters from the measured
overall surface impedance $Z$, we are able to extract and to comment on the
London penetration depth, the flux flow resistivity and the pinning constant,
highlighting the effect of artificial pinning centers in these samples.",1902.07589v1
2020-02-25,"Shear thickening and jamming of dense suspensions: the ""roll"" of friction","Particle-based simulations of discontinuous shear thickening (DST) and shear
jamming (SJ) suspensions are used to study the role of stress-activated
constraints, with an emphasis on resistance to gear-like rolling. Rolling
friction decreases the volume fraction required for DST and SJ, in quantitative
agreement with real-life suspensions with adhesive surface chemistries and
""rough"" particle shapes. It sets a distinct structure of the frictional force
network compared to only sliding friction, and from a dynamical perspective
leads to an increase in the velocity correlation length, in part responsible
for the increased viscosity. The physics of rolling friction is thus a key
element in achieving a comprehensive understanding of strongly shear-thickening
materials.",2002.10996v2
2020-09-16,Superconductivity in CuAl2-type Co0.2Ni0.1Cu0.1Rh0.3Ir0.3Zr2 with a high-entropy-alloy transition metal site,"Research on high-entropy-alloy (HEA) superconductors is a growing field in
material science. In this study, we explored new HEA-type superconductors and
discovered a CuAl2-type superconductor Co0.2Ni0.1Cu0.1Rh0.3Ir0.3Zr2 with a
HEA-type transition metal site. A superconducting transition was observed at
8.0 K after electrical resistivity, magnetization, and specific heat
measurements. The bulk characteristics of the superconductivity were confirmed
through the specific heat measurements. The discovery of superconductivity in
HEA-type Co0.2Ni0.1Cu0.1Rh0.3Ir0.3Zr2 will provide a novel pathway to explore
new HEA-type superconductors and investigate the relationship between the
mixing entropy and superconductivity of HEA-type compounds.",2009.07548v3
2017-05-17,High Thermoelectric Figure of Merit by Resonant Dopant in Half-Heusler Alloys,"Half-Heusler alloys have been one of the benchmark high temperature
thermoelectric materials owing to their thermal stability and promising figure
of merit ZT. Simonson et al. early showed that small amounts of vanadium doped
in Hf0.75Zr0.25NiSn enhanced the Seebeck coefficient and correlated the change
with the increased density of states near the Fermi level. We herein report a
systematic study on the role of vanadium (V), niobium (Nb), and tantalum (Ta)
as prospective resonant dopants in enhancing the ZT of n-type half-Heusler
alloys based on Hf0.6Zr0.4NiSn0.995Sb0.005. The V doping was found to increase
the Seebeck coefficient in the temperature range 300-1000 K, consistent with a
resonant doping scheme. In contrast, Nb and Ta act as normal n-type dopants, as
evident by the systematic decrease in electrical resistivity and Seebeck
coefficient. The combination of enhanced Seebeck coefficient due to the
presence of V resonant states and the reduced thermal conductivity has led to a
state-of-the-art ZT of 1.3 near 850 K in n-type
(Hf0.6Zr0.4)0.99V0.01NiSn0.995Sb0.005 alloys.",1705.06100v1
2019-03-12,Superconductivity behavior in epitaxial TiN films points at surface magnetic disorder,"We analyze the evolution of the normal and superconducting electronic
properties in epitaxial TiN films, characterized by high Ioffe-Regel parameter
values, as a function of the film thickness. As the film thickness decreases,
we observe an increase of in the residual resistivity, which becomes dominated
by diffusive surface scattering for $d\leq20\,$nm. At the same time, a
substantial thickness-dependent reduction of the superconducting critical
temperature is observed compared to the bulk TiN value. In such a high quality
material films, this effect can be explained by a weak magnetic disorder
residing in the surface layer with a characteristic magnetic defect density of
$\sim10^{12}\,\mathrm{cm}^{-2}$. Our results suggest that surface magnetic
disorder is generally present in oxidized TiN films.",1903.05009v3
2019-12-30,Pinning Dislocations in Colloidal Crystals with Active Particles that Seek Stacking Faults,"There is growing interest in functional, adaptive devices built from
colloidal subunits of micron size or smaller. A colloidal material with dynamic
mechanical properties could facilitate such microrobotic machines. Here we
study via computer simulation how active interstitial particles in small
quantities can be used to modify the bulk mechanical properties of a colloidal
crystal. Passive interstitial particles are known to pin dislocations in
metals, thereby increasing resistance to plastic deformation. We extend this
tactic by employing anisotropic active interstitials that travel
super-diffusively and bind strongly to stacking faults associated with partial
dislocations. We find that: 1) interstitials that are effective at reducing
plasticity compromise between strong binding to stacking faults and high
mobility in the crystal bulk. 2) Reorientation of active interstitials in the
crystal depends upon rotational transitions between high-symmetry crystal
directions. 3) The addition of certain active interstitial shapes at
concentrations as low as $60$ per million host particles ($0.006\%$) can create
a shear threshold for dislocation migration.",1912.12792v1
2015-06-16,Correlation of Crystal Quality and Extreme Magnetoresistance of WTe$_2$,"High quality single crystals of WTe$_2$ were grown using a Te flux followed
by a cleaning step involving self-vapor transport. The method is reproducible
and yields consistently higher quality single crystals than are typically
obtained via halide assisted vapor transport methods. Magnetoresistance
(MR)values at 9 Tesla and 2 Kelvin as high as 1.75 million \%, nearly an order
of magnitude higher than previously reported for this material, were obtained
on crystals with residual resistivity ratio (RRR) of approximately 1250. The MR
follows a near B$^2$ law (B = 1.95(1)) and, assuming a semiclassical model, the
average carrier mobility for the highest quality crystal was found to be
~167,000 cm$^2$/Vs at 2 K. A correlation of RRR, MR ratio and average carrier
mobility ($\mu_{avg}$) is found with the cooling rate during the flux growth.",1506.04823v1
2018-12-18,The role of β-titanium ligaments in the deformation of dual phase titanium alloys,"Multiphase titanium alloys are critical materials in high value engineering
components, for instance in aero engines. Microstructural complexity is
exploited through interface engineering during mechanical processing to realise
significant improvements in fatigue and fracture resistance and strength. In
this work, we explore the role of select interfaces using in-situ
micromechanical testing with concurrent observations from high angular
resolution electron backscatter diffraction (HR-EBSD). Our results are
supported with post mortem transmission electron microscopy (TEM). Using
micro-pillar compression, we performed in-depth analysis of the role of select
{\beta}-titanium (body centred cubic) ligaments which separate neighbouring
{\alpha}-titanium (hexagonal close packed) regions and inhibit the dislocation
motion and impact strength during mechanical deformation. These results shed
light on the strengthening mechanisms and those that can lead to strain
localisation during fatigue and failure.",1812.07250v2
2019-10-14,Investigation of nitrogen polar p-type doped GaN/AlxGa(1-x)N superlattices for applications in wide-bandgap p-type field effect transistors,"In this study the MOCVD growth and electrical properties of N-polar
modulation doped p-AlGaN/GaN superlattices (SLs) were investigated. Hole sheet
charge density and mobility were studied as a function of the concentration of
the p-type dopant Mg in the SL and the number of SL periods. Room temperature
Hall measurements were carried out to determine the hole mobility and the sheet
charge density. While the hole density increased with increasing number of SL
periods, the hole mobility was largely unaffected.Hole mobilities as high as
18cm2/Vs at a simultaneous high hole density of 6.5e13 cm-2 were observed for
N-polar SLs with a Mg modulation doping of 7.5e18 cm-3. For comparable
uniformly doped Ga-polar SL samples, a mobility of 11cm2/Vs was measured.
Lowest sheet resistance in the GaN/AlGaN materials system of 5kOhm/sq is also
reported. Test-structure transistors were also fabricated to investigate the
applicability of these SL structures, with planar device resulting in a current
of 5mA/mm, and a FinFET structure resulting in a current of over 100mA/mm.",1910.06421v1
2019-11-27,Enhancement of the electronic thermoelectric properties of bulk strained silicon-germanium alloys using the scattering relaxation times from first principles,"We use first-principles electronic structure methods to calculate the
electronic thermoelectric properties (i.e. due to electronic transport only) of
single-crystalline bulk $n$-type silicon-germanium alloys vs Ge composition,
temperature, doping concentration and strain. We find excellent agreement to
available experiments for the resistivity, mobility and Seebeck coefficient.
These results are combined with the experimental lattice thermal conductivity
to calculate the thermoelectric figure of merit $ZT$, finding very good
agreement with experiment. We predict that 3% tensile hydrostatic strain
enhances the $n$-type $ZT$ by 50% at carrier concentrations of $n=10^{20}$
cm$^{-3}$ and temperature of $T=1200K$. These enhancements occur at different
alloy compositions due to different effects: at 50% Ge composition the
enhancements are achieved by a strain induced decrease in the Lorenz number,
while the power factor remains unchanged. These characteristics are important
for highly doped and high temperature materials, in which up to 50% of the heat
is carried by electrons. At 70% Ge the increase in $ZT$ is due to a large
increase in electrical conductivity produced by populating the high mobility
$\Gamma$ conduction band valley, lowered in energy by strain.",1911.12149v1
2020-10-01,High magnetic field spin-valley-split Shubnikov-de Haas oscillations in a WSe$_2$ monolayer,"We study Shubnikov-de Haas oscillations in a p-type WSe$_2$ monolayer under
very high magnetic field. The oscillation pattern is complex due to a large
spin and valley splitting, in the non-fully-resolved Landau level regime. Our
experimental data can be reproduced with a model in which the main parameter is
the ratio between the Zeeman energy and the cyclotron energy. The model takes
into account the Landau levels from both valleys with the same Gaussian
broadening, which allows to predict the relative amplitude of the resistance
oscillation originating from each valley. The Zeeman energy is found to be
several times larger than the cyclotron energy. It translates into a large and
increasing effective Land\'e factor as the hole density decreases, in the
continuity of the values reported in the literature at lower carrier density.",2010.00510v1
2020-11-27,High-pressure effects on superconducting properties and crystal structure of Bi-based layered superconductor La2O2Bi3Ag0.6Sn0.4S6,"The effects of pressure on the superconducting properties of a Bi-based
layered superconductor La2O2Bi3Ag0.6Sn0.4S6, which possesses a four-layer-type
conducting layer, have been studied through the electrical resistance and
magnetic susceptibility measurements. The crystal structure under pressure was
examined using synchrotron X-ray diffraction at SPring-8. In the low-pressure
regime, bulk superconductivity with a transition temperature Tc of ~ 4.5 K was
induced by pressure, which was achieved by in-plane chemical pressure effect
owing to the compression of the tetragonal structure. In the high-pressure
regime above 6.4 GPa, a structural symmetry lowering was observed, and
superconducting transitions with a Tc ~ 8 K were observed. Our results suggest
the possible commonality on the factor essential for Tc in Bi-based
superconductors with two-layer-type and four-layer-type conducting layers.",2011.13532v1
2021-02-01,Liquefaction-induced Plasticity from Entropy-boosted Amorphous Ceramics,"Ceramics are easy to break, and very few generic mechanisms are available for
improving their mechanical properties, e.g., the 1975-discovered anti-fracture
mechanism is strictly limited to zirconia and hafnia. Here we report a general
mechanism for achieving high plasticity through liquefaction of ceramics. We
further disclose the general material design strategies to achieve this
difficult task through entropy-boosted amorphous ceramics (EBACs), enabling
fracture-resistant properties that can withstand severe plastic deformation
(e.g., over 95%, deformed to a thickness of a few nanometers) while maintaining
high hardness and reduced modulus. The findings reported here open a new route
to ductile ceramics and many applications.",2102.00802v1
2021-02-13,Mechanical Performance of 3D Printed Interpenetrating Phase Composites with Spinodal Topologies,"The mechanical response of interpenetrating phase composites (IPCs) with
stochastic spinodal topologies is investigated experimentally and numerically.
Model polymeric systems are fabricated by Polyjet multi-material printing, with
the reinforcing phase taking the topology of a spinodal shell, and the
remaining volume filled by a softer matrix. We show that spinodal shell IPCs
have comparable compressive strength and stiffness to IPCs with two
well-established periodic reinforcements, the Schwarz P triply periodic minimal
surface (TPMS) and the octet truss-lattice, while exhibiting far less
catastrophic failure and greater damage resistance, particularly at high volume
fraction of reinforcing phase. The combination of high stiffness and strength
and a long flat plateau after yielding makes spinodal shell IPCs a promising
candidate for energy absorption and impact protection applications, where the
lack of material softening upon large compressive strains can prevent sudden
collapse. Importantly, in contrast with all IPCs with periodic reinforcements,
spinodal shell IPCs are amenable to scalable manufacturing via self-assembly
techniques.",2102.06707v1
2021-07-22,Anomalous High-Field Magnetotransport in CaFeAsF due to the Quantum Hall Effect,"CaFeAsF is an iron-based superconductor parent compound whose Fermi surface
is quasi-two dimensional, composed of Dirac-electron and Schr\""odinger-hole
cylinders elongated along the $c$ axis. We measured the longitudinal and Hall
resistivities in CaFeAsF with the electrical current in the $ab$ plane in
magnetic fields up to 45 T applied along the $c$ axis and obtained the
corresponding conductivities via tensor inversion. We found that both the
longitudinal and Hall conductivities approached zero above $\sim$40 T as the
temperature was lowered to 0.4 K. Our analysis indicates that the Landau-level
filling factor is $\nu$ = 2 for both electrons and holes at these high field
strengths, resulting in a total filling factor $\nu$ = $\nu_{hole} -
\nu_{electron}$ = 0. We therefore argue that the $\nu$ = 0 quantum Hall state
emerges under these conditions.",2107.10460v4
2022-01-08,Atomic disorder and Berry phase driven anomalous Hall effect in Co2FeAl Heusler compound,"Co2-based Heusler compounds are the promising materials for the spintronics
application due to their high Curie temperature, large spin-polarization, large
magnetization density, and exotic transport properties. In the present
manuscript, we report the anomalous Hall effect (AHE) in a polycrystalline
Co2FeAl Heusler compound using combined experimental and theoretical studies.
The Rietveld analysis of high-resolution synchrotron x-ray diffraction data
reveals a large degree (~50 %) of antisite disorder between Fe and Al atoms.
The analysis of anomalous transport data provides the experimental anomalous
Hall conductivity (AHC) about 227 S/cm at 2 K with an intrinsic contribution of
155 S/cm, which has nearly constant variation with temperature. The detailed
scaling analysis of anomalous Hall resistivity suggests that the AHE in Co2FeAl
is governed by the Berry phase driven intrinsic mechanism. Our theoretical
calculations reveal that the disorder present in Co2FeAl compound enhances the
Berry curvature induced intrinsic AHC.",2201.02864v1
2022-07-15,High power density energy harvesting devices based on the anomalous Nernst effect of Co/Pt magnetic multilayers,"The anomalous Nernst effect (ANE) is a thermomagnetic phenomenon with
potential applications in thermal energy harvesting. While many recent works
studied the approaches to increase the ANE coefficient of materials, relatively
little effort was devoted to increasing the power supplied by the effect. Here
we demonstrate a nanofabricated device with record power density generated by
the ANE. To accomplish this, we fabricate micrometer-sized devices in which the
thermal gradient is three orders of magnitude higher than conventional
macroscopic devices. In addition, we use Co/Pt multilayers, a system
characterized by a high ANE thermopower (~1 microV/K), low electrical
resistivity, and perpendicular magnetic anisotropy. These innovations allow us
to obtain power densities of around 13 W/cm3. We believe that this design may
find uses in harvesting wasted energy in e.g. electronic devices.",2207.07526v2
2023-02-20,A High Throughput Aqueous Passivation Testing Methodology for Compositionally Complex Alloys using Scanning Droplet Cell,"Compositionally complex alloy systems containing more than five principal
elements allow exploring a wide range of compositions, processing, and
structural variables with the hope for identifying unique properties. Such
opportunities also apply to designing materials for improved corrosion
resistance, regulated by a self-healing passive film. Such a rich landscape in
reactivity and protectivity demands the search for high-throughput experimental
testing workflows to uncover key metrics, indicative of superior properties. In
this communication, one such methodology is demonstrated for evaluating
passivation performance of a combinatorial library of
Al0.7-x-yCoxCryFe0.15Ni0.15 thin film alloys in deaerated 0.1 mol/L H2SO4(aq),
using a scanning droplet cell.",2302.09804v4
2023-09-29,Transforming Materials Discovery for Artificial Photosynthesis: High-Throughput Screening of Earth-Abundant Semiconductors,"We present a highly efficient workflow for designing semiconductor structures
with specific physical properties, which can be utilized for a range of
applications, including photocatalytic water splitting. Our algorithm generates
candidate structures composed of earth-abundant elements that exhibit optimal
light-trapping, high efficiency in \ce{H2} and/or \ce{O2} production, and
resistance to reduction and oxidation in aqueous media. To achieve this, we use
an ionic translation model trained on the Inorganic Crystal Structure Database
(ICSD) to predict over thirty thousand undiscovered semiconductor compositions.
These predictions are then screened for redox stability under Hydrogen
Evolution Reaction (HER) or Oxygen Evolution Reaction (OER) conditions before
generating thermodynamically stable crystal structures and calculating accurate
band gap values for the compounds. Our approach results in the identification
of dozens of promising semiconductor candidates with ideal properties for
artificial photosynthesis, offering a significant advancement toward the
conversion of sunlight into chemical fuels.",2310.00118v1
2023-10-28,Ultralong-term high-density data storage with atomic defects in SiC,"There is an urgent need to increase the global data storage capacity, as
current approaches lag behind the exponential growth of data generation driven
by the Internet, social media and cloud technologies. In addition to increasing
storage density, new solutions should provide long-term data archiving that
goes far beyond traditional magnetic memory, optical disks and solid-state
drives. Here, we propose a concept of energy-efficient, ultralong, high-density
data archiving based on optically active atomic-size defects in a radiation
resistance material, silicon carbide (SiC). The information is written in these
defects by focused ion beams and read using photoluminescence or
cathodoluminescence. The temperature-dependent deactivation of these defects
suggests a retention time minimum over a few generations under ambient
conditions. With near-infrared laser excitation, grayscale encoding and
multi-layer data storage, the areal density corresponds to that of Blu-ray
discs. Furthermore, we demonstrate that the areal density limitation of
conventional optical data storage media due to the light diffraction can be
overcome by focused electron-beam excitation.",2310.18843v1
2003-04-30,Pulsed Laser Deposition of epitaxial titanium diboride thin films,"Epitaxial titanium diboride thin films have been deposited on sapphire
substrates by Pulsed Laser Ablation technique. Structural properties of the
films have been studied during the growth by Reflection High Energy Electron
Diffraction (RHEED) and ex-situ by means of X-ray diffraction techniques; both
kinds of measurements indicate a good crystallographic orientation of the TiB2
film both in plane and along the c axis. A flat surface has been observed by
Atomic Force Microscopy imaging. Electrical resistivity at room temperature
resulted to be five times higher than the value reported for single crystals.
The films resulted to be also very stable at high temperature, which is very
promising for using this material as a buffer layer in the growth of magnesium
diboride thin films.",0304680v1
2016-02-19,Magnetic anisotropy of large floating-zone-grown single-crystals of SrRuO3,"SrRuO3 is a highly interesting material due to its anomalous-metal properties
related with ferromagnetism and its relevance as conductive perovskite layer or
substrate in heterostructure devices. We have used optical floating zone
technique in an infrared image furnace to grow large single crystals of SrRuO3
with volumes attaining several hundred mm3. Crystals obtained for optimized
growth parameters exhibit a high ferromagnetic Curie temperature of 165 K and a
low-temperature magnetization of 1.6 muB at a magnetic field of 6 T. The high
quality of the crystals is further documented by large residual resistance
ratios of 75 and by crystal structure and chemical analyzes. With these
crystals the magnetic anisotropy could be determined.",1602.06171v2
2014-08-11,High spin polarization in CoFeMnGe quaternary Heusler alloy,"We report the structure, magnetic property and spin polarization of CoFeMnGe
equiatomic quaternary Heusler alloy. The alloy was found to exist in the L21
structure with considerable amount of DO3 disorder. Thermal analysis result
indicated the Curie temperature is about 711K without any other phase
transformation up to melting temperature. The magnetization value was close to
that predicted by the Slater-Pauling curve. Current spin polarization of P =
0.70 {plus/minus}0.1 was deduced using point contact Andreev reflection (PCAR)
measurements. Half-metallic trend in the resistivity has also been observed in
the temperature range of 5 K to 300 K. Considering the high spin polarization
and Curie temperature, this material appears to be promising for spintronic
applications.",1408.2408v2
2019-04-01,Quantum transport in high-quality shallow InSb quantum wells,"InSb is one of the promising candidates to realize a topological state
through proximity induced superconductivity in a material with strong
spin-orbit interactions. In two-dimensional systems, thin barriers are needed
to allow strong coupling between superconductors and semiconductors. However,
it is still challenging to obtain a high-quality InSb two-dimensional electron
gas in quantum wells close to the surface. Here we report on a molecular beam
epitaxy grown heterostructure of InSb quantum wells with substrate-side
Si-doping and ultra-thin InAlSb (5 nm, 25 nm, and 50 nm) barriers to the
surface. We demonstrate that the carrier densities in these quantum wells are
gate-tunable and electron mobilities up to 350,000 $\rm{cm^2(Vs)^{-1}}$ are
extracted from magneto-transport measurements. Furthermore, from
temperature-dependent magneto-resistance measurements, we extract an effective
mass of 0.02 $m_0$ and find a Zeeman splitting compatible with the expected
g-factor.",1904.00828v2
2021-06-28,Topological Anderson Insulator in cation-disordered Cu2ZnSnS4,"Abstract: Using ab initio calculations supported by experimental transport
measurements, we present the first credible candidate for the realization of a
disorder-induced Topological Anderson Insulator in a real material system. High
energy reactive ball-milling produces a polymorph of Cu2ZnSnS4 with high cation
disorder, which shows an inverted ordering of bands at the Brillouin zone
center, in contrast to its ordered phase. Adiabatic continuity arguments
establish that this disordered Cu2ZnSnS4 can be connected to the closely
related Cu2ZnSnSe4, previously predicted to be a 3D topological insulator. Band
structure calculations with a slab geometry reveal the presence of robust
surface states, while impedance spectroscopy coupled with resistivity
measurements point to the surface-dominated transport which such states would
imply; thus making a strong case in favor of a novel topological phase. As
such, this study opens up a window to understanding and potentially exploiting
topological behavior in a rich class of easily-synthesized multinary,
disordered compounds.",2106.14714v1
2023-12-11,"Impersonating a Superconductor: High-Pressure BaCoO$_3$, an Insulating Ferromagnet","We report the high-pressure synthesis (6 GPa, 1200 $^{\circ}$C) and ambient
pressure characterization of hexagonal HP-BaCoO$_3$. The material (with the 2H
crystal structure) has a short intrachain Co-Co distance of about 2.07
$\text{\r{A}}$. Our magnetization investigation revealed robust diamagnetic
behavior below approximately 130 K when exposed to weak applied magnetic fields
(10 Oe) and a distinct half-levitation phenomenon below that temperature, such
as is often observed for superconductors. Its field-dependent magnetization
profile, however, unveils the characteristics of ferromagnetism, marked by a
substantial magnetic retentivity of 0.22(1) ${\mu}_B$/Co at a temperature of 2
K. Electrical resistivity measurements indicate that HP-BaCoO$_3$ is a
ferromagnetic insulator, not a superconductor.",2312.14955v1
2022-10-03,The impact of resistive electric fields on particle acceleration in reconnection layers,"In the context of particle acceleration in high-energy astrophysical
environments featuring magnetic reconnection, the importance of the resistive
term of the electric field compared to the convective one is still under
debate. In this work, we present a quantitative analysis through 2D
magnetohydrodynamic numerical simulations of tearing-unstable current sheets
coupled to a test-particles approach, performed with the PLUTO code. We find
that the resistive field plays a significant role in the early-stage
energization of high-energy particles. Indeed, these particles are firstly
accelerated due to the resistive electric field when they cross an X-point,
created during the fragmentation of the current sheet. If this preliminary
particle acceleration mechanism dominated by the resistive field is neglected,
particles cannot reach the same high energies. Our results support therefore
the conclusion that the resistive field is not only non-negligible but it does
actually play an important role in the particle acceleration mechanism.",2210.01113v1
2024-01-31,Investigation of Microstructure and Corrosion Resistance of Ti-Al-V Titanium Alloys Obtained by Spark Plasma Sintering,"The research results of the microstructure and corrosion resistance of Ti and
Ti-Al-V Russian industrial titanium alloys obtained by spark plasma sintering
(SPS) are described. Investigations of the microstructure, phase composition,
hardness, tensile strength, electrochemical corrosion resistance and hot salt
corrosion of Ti-Al-V titanium alloy specimens were carried out. It was shown
that the alloy specimens have a uniform highly dense microstructure and high
hardness values. The studied alloys also have high resistance to
electrochemical corrosion during tests in acidic aqueous solution causing the
intergranular corrosion as well as high resistance to the hot salt corrosion.
The assumption that the high hardness of the alloys as well as the differences
in the corrosion resistance of the central and lateral parts of the specimens
are due to the diffusion of carbon from the graphite mold into the specimen
surface was suggested.",2401.17941v1
2003-02-01,High-Temperature Hall Effect in Ga(1-x)Mn(x)As,"The temperature dependence of the Hall coefficient of a series of
ferromagnetic Ga(1-x)Mn(x)As samples is measured in the temperature range 80K <
T < 500K. We model the Hall coefficient assuming a magnetic susceptibility
given by the Curie-Weiss law, a spontaneous Hall coefficient proportional to
rho_xx^2(T), and including a constant diamagnetic contribution in the
susceptibility. For all low resistivity samples this model provides excellent
fits to the measured data up to T=380K and allows extraction of the hole
concentration (p). The calculated p are compared to alternative methods of
determining hole densities in these materials: pulsed high magnetic field (up
to 55 Tesla) technique at low temperatures (less than the Curie temperature),
and electrochemical capacitance- voltage profiling. We find that the Anomalous
Hall Effect (AHE) contribution to rho_xy is substantial even well above the
Curie temperature. Measurements of the Hall effect in this temperature regime
can be used as a testing ground for theoretical descriptions of transport in
these materials. We find that our data are consistent with recently published
theories of the AHE, but they are inconsistent with theoretical models
previously used to describe the AHE in conventional magnetic materials.",0302013v2
2007-06-15,Growth mechanisms and structure of fullerene-like carbon-based thin films: superelastic materials for tribological applications,"In this chapter we review our findings on the bonding structure and growth
mechanisms of carbon-based thin solid films with fullerene-like (FL)
microstructure. The so-called FL arrangements arise from the curvature and
cross-linking of basal planes in graphitic-like structures, partially
resembling that of molecular fullerenes. This three-dimensional superstructure
takes advantage of the strength of planar pi bonds in sp2 hybrids and confers
the material interesting mechanical properties, such as high hardness, high
elastic recovery, low-friction and wear-resistance. These properties can be
tailored by controlling the curvature, size and connectivity of the FL
arrangements, making these materials promising coatings for tribological
applications. We have focused our interest mostly on carbon nitride (CNx) since
nitrogen promotes the formation of FL arrangements at low substrate
temperatures and they are emerging over pure carbon coatings in tribological
applications such as protective overcoats in magnetic hard disks. We address
structural issues such as origin of plane curvature, nature of the
cross-linking sites and sp2 clustering, together with growth mechanisms based
on the role of film-forming precursors, chemical re-sputtering or concurrent
ion assistance during growth.",0706.2258v1
2013-07-08,"Significant ZT Enhancement in p-type Ti(Co,Fe)Sb-InSb Nanocomposites via a Synergistic High Mobility Electron Injection Energy filtering and Boundary Scattering Approach","It has been demonstrated that InSb nanoinclusions, which are formed in situ,
can simultaneously improve all three individual thermoelectric properties of
the n-type half Heusler compound (Ti,Zr,Hf)(Co,Ni)Sb [Xie et al., Acta Mater.
58, 4795 (2010)]. In the work presented herein, we have adopted the same
approach to the p-type half Heusler compound Ti(Co,Fe)Sb. The results of
resistivity, Seebeck coefficient, thermal conductivity, and Hall coefficient
measurements indicate that the combined high mobility electron injection, low
energy electron filtering, and boundary scattering, again, lead to a
simultaneous improvement of all three individual thermoelectric properties:
enhanced Seebeck coefficient and electrical conductivity as well as reduced
lattice thermal conductivity. A figure of merit of ZT=0.33 was attained at 900
K for the sample containing 1 atomic percent InSb nanoinclusions, a 450 percent
improvement over the nanoinclusion-free sample. This represents a rare case
that the same nanostructuring approach successfully works for both p-type and
n-type thermoelectric materials of the same class, hence pointing to a
promising materials design route for higher performance half-Heusler materials
in the future and hopefully will realize similar improvement in TE devices
based on such half Heusler alloys.",1307.2160v1
2018-06-21,Planar Hall effect in type II Dirac semimetal VAl$_{3}$,"The study of electronic properties in topological systems is one of the most
fascinating topics in condensed matter physics, which has generated enormous
interests in recent times. New materials are frequently being proposed and
investigated to identify their non-trivial band structure. While sophisticated
techniques such as angle-resolved photoemission spectroscopy have become
popular to map the energy-momentum relation, the transport experiments lack any
direct confirmation of Dirac and Weyl fermions in a system. From band structure
calculations, VAl$_{3}$ has been proposed to be a type II topological Dirac
semimetal. This material represents a large family of isostructural compounds,
all having similar electronic band structure and is an ideal system to explore
the rich physics of Lorentz symmetry violating Dirac fermions. In this work, we
present a detailed analysis on the magnetotransport properties of VAl$_{3}$. A
large, non-saturating magnetoresistance has been observed. Hall resistivity
reveals the presence of two types of charge carriers with high mobility. Our
measurements show a large planar Hall effect in this material, which is robust
and can be easily detectable up to high temperature. This phenomenon originates
from the relativistic chiral anomaly and non-trivial Berry curvature, which
validates the theoretical prediction of the Dirac semimetal phase in VAl$_{3}$.",1806.08287v1
2017-08-17,Separation of Electron and Hole Dynamics in the Semimetal LaSb,"We report investigations on the magnetotransport in LaSb, which exhibits
extremely large magnetoresistance (XMR). Foremost, we demonstrate that the
resistivity plateau can be explained without invoking topological protection.
We then determine the Fermi surface from Shubnikov - de Haas (SdH) quantum
oscillation measurements and find good agreement with the bulk Fermi pockets
derived from first principle calculations. Using a semiclassical theory and the
experimentally determined Fermi pocket anisotropies, we quantitatively describe
the orbital magnetoresistance, including its angle dependence. We show that the
origin of XMR in LaSb lies in its high mobility with diminishing Hall effect,
where the high mobility leads to a strong magnetic field dependence of the
longitudinal magnetoconductance. Unlike a one-band material, when a system has
two or more bands (Fermi pockets) with electron and hole carriers, the added
conductance arising from the Hall effect is reduced, hence revealing the latent
XMR enabled by the longitudinal magnetoconductance. With diminishing Hall
effect, the magnetoresistivity is simply the inverse of the longitudinal
magnetoconductivity, enabling the differentiation of the electron and hole
contributions to the XMR, which varies with the strength and orientation of the
magnetic field. This work demonstrates a convenient way to separate the
dynamics of the charge carriers and to uncover the origin of XMR in multi-band
materials with anisotropic Fermi surfaces. Our approach can be readily applied
to other XMR materials.",1708.05416v2
2019-01-21,Solid-State Thermal Energy Storage Using Reversible Martensitic Transformations,"The identification and use of reversible Martensitic transformations,
typically described as shape memory transformations, as a new class of
solid-solid phase change material is experimentally demonstrated here for the
first time. To prove this claim, time-domain thermoreflectance,
frequency-domain thermoreflectance, and differential scanning calorimetry
studies were conducted on commercial NiTi alloys to quantify thermal
conductivity and latent heat. Additional Joule-heating experiments demonstrate
successful temperature leveling during transient heating and cooling in a
simulated environment. Compared to standard solid-solid materials and
solid-liquid paraffin, these experimental results show that shape memory alloys
provide up to a two order of magnitude higher Figure of Merit. Beyond these
novel experimental results, a comprehensive review of >75 binary NiTi and
NiTi-based ternary and quaternary alloys in the literature shows that shape
memory alloys can be tuned in a wide range of transformation temperatures (from
-50 to 330{deg}C), latent heats (from 9.1 to 35.1 J/g), and thermal
conductivities (from 15.6 to 28 W/mK). This can be accomplished by changing the
Ni and Ti balance, introducing trace elements, and/or by thermomechanical
processing. Combining excellent corrosion resistance, formability, high
strength and ductility, high thermal performance, and tunability, SMAs
represent an exceptional phase change material that circumvents many of the
scientific and engineering challenges hindering progress in this field.",1901.06990v1
2020-11-30,Discovery of carbon-based strongest and hardest amorphous material,"Carbon is likely the most fascinating element of the periodic table because
of the diversity of its allotropes stemming from its variable (sp, sp2, and
sp3) bonding motifs. Exploration of new forms of carbon has been an eternal
theme of contemporary scientific research. Here we report on novel amorphous
carbon phases containing high fraction of sp3 bonded atoms recovered after
compressing fullerene C60 to previously unexplored high pressure and
temperature. The synthesized carbons are the hardest and strongest amorphous
materials known to date, capable of scratching diamond crystal and approaching
its strength which is evidenced by complimentary mechanical tests.
Photoluminescence and absorption spectra of the materials demonstrate they are
semiconductors with tunable bandgaps in the range of 1.5-2.2 eV, comparable to
that of amorphous silicon. A remarkable combination of the outstanding
mechanical and electronic properties makes this class of amorphous carbons an
excellent candidate for photovoltaic applications demanding ultrahigh strength
and wear resistance.",2011.14819v2
2021-12-20,Ultrafast Multi-Shot Ablation and Defect Generation in Monolayer Transition Metal Dichalcogenides,"Transition metal dichalcogenides are known to possess large optical
nonlinearities and driving these materials at high intensities is desirable for
many applications. Understanding their optical responses under repetitive
intense excitation is essential to improve the performance limit of these
strong-field devices and to achieve efficient laser patterning. Here, we report
the incubation study of monolayer MoS${}_{2}$ and WS${}_{2}$ induced by 160 fs,
800 nm pulses in air to examine how their ablation threshold scales with the
number of admitted laser pulses. Both materials were shown to outperform
graphene and most bulk materials; specifically, MoS${}_{2}$ is as resistant to
radiation degradation as the best of the bulk thin films with a record fast
saturation. Our modeling provides convincing evidence that the small reduction
in threshold and fast saturation of MoS${}_{2}$ originates in its excellent
bonding integrity against radiation-induced softening. Sub-ablation damages, in
the forms of vacancies, lattice disorder, and nano-voids, were revealed by
transmission electron microscopy, photoluminescence, Raman, and second harmonic
generation studies, which were attributed to the observed incubation. For the
first time, a sub-ablation damage threshold is identified for monolayer
MoS${}_{2}$ to be 78% of single-shot ablation threshold, below which
MoS${}_{2}$ remains intact for many laser pulses. Our results firmly establish
MoS${}_{2}$ as a robust material for strong-field devices and for
high-throughput laser patterning.",2112.10743v1
2024-03-19,Electrical transport crossover and large magnetoresistance in selenium deficient van der Waals HfSe2-x,"Transition metal dichalcogenides have received much attention in the past
decade not only due to the new fundamental physics, but also due to the
emergent applications in these materials. Currently chalcogenide deficiencies
in TMDs are commonly believed either during the high temperature growth
procedure or in the nanofabrication process resulting significant changes of
their reported physical properties in the literature. Here we perform a
systematic study involving pristine stochiometric HfSe2, Se deficient HfSe1.9
and HfSe1.8. Stochiometric HfSe2 transport results show semiconducting behavior
with a gap of 1.1eV. Annealing HfSe2 under high vacuum at room temperature
causes the Se loss resulting in HfSe1.9, which shows unconventionally large
magnetoresistivity following the extended Kohler's rule at low temperatures
below 50 K. Moreover, a clear electrical resistivity crossover, mimicking the
metal-insulator transition, is observed in the HfSe1.9 single crystal. Further
increasing the degree of deficiency in HfSe1.8 results in complete metallic
electrical transport at all temperatures down to 2K. Such a drastic difference
in the transport behaviors of stoichiometric and Se-deficient HfSe2 further
emphasizes that defect control and engineering could be an effective method
that could be used to tailor the electronic structure of 2D materials,
potentially unlock new states of matter, or even discover new materials.",2403.12430v1
2018-09-27,Granular aluminum: A superconducting material for high impedance quantum circuits,"Superconducting quantum information processing machines are predominantly
based on microwave circuits with relatively low characteristic impedance, of
about 100 Ohm, and small anharmonicity, which can limit their coherence and
logic gate fidelity. A promising alternative are circuits based on so-called
superinductors, with characteristic impedances exceeding the resistance quantum
$R_Q = 6.4$ k$\Omega$. However, previous implementations of superinductors,
consisting of mesoscopic Josephson junction arrays, can introduce unintended
nonlinearity or parasitic resonant modes in the qubit vicinity, degrading its
coherence. Here we present a fluxonium qubit design using a granular aluminum
(grAl) superinductor strip. Granular aluminum is a particularly attractive
material, as it self-assembles into an effective junction array with a
remarkably high kinetic inductance, and its fabrication can be in-situ
integrated with standard aluminum circuit processing. The measured qubit
coherence time $T_2^R$ up to 30 $\mu$s illustrates the potential of grAl for
applications ranging from protected qubit designs to quantum limited amplifiers
and detectors.",1809.10646v1
2012-11-29,Effects of Resistivity on Magnetized Core-Collapse Supernovae,"We studied roles of a turbulent resistivity in the core-collapse of a
strongly magnetized massive star, carrying out 2D-resistive-MHD simulations.
The three cases with different initial strengths of magnetic field and rotation
are investigated; 1. strongly magnetized rotating core; 2.moderately magnetized
rotating core; 3. very strongly magnetized non-rotating core. In each case,
both an ideal-MHD model and resistive-MHD models are computed. As a result of
computations, each model shows a matter eruption helped by a magnetic
acceleration (and also by a centrifugal acceleration in the rotating cases). We
found that a resistivity attenuates the explosion in case~1 and 2, while it
enhances the explosion in case~3. We also found that in the rotating cases,
main mechanisms for the amplification of a magnetic field in the post-bounce
phase are an outward advection of magnetic field and a winding of poloidal
magnetic field-lines by differential rotation, which are somewhat dampened down
with the presence of a resistivity. Although the magnetorotational instability
seems to occur in the rotating models, it will play only a minor role in a
magnetic field amplification. Another impact of resistivity is that on the
aspect ratio. In the rotating cases, a large aspect ratio of the ejected
matters, $> 2.5$, attained in a ideal-MHD model is reduced to some extent in a
resistive model. These results indicate that a resistivity possibly plays an
important role in the dynamics of strongly magnetized supernovae.",1211.6817v2
2019-04-18,Scaling-up atomically thin coplanar semiconductor-metal circuitry via phase engineered chemical assembly,"Two-dimensional (2D) layered semiconductors, with their ultimate atomic
thickness, have shown promise to scale down transistors for modern integrated
circuitry. However, the electrical contacts that connect these materials with
external bulky metals are usually unsatisfactory, which limits the transistor
performance. Recently, contacting 2D semiconductors using coplanar 2D
conductors has shown promise in reducing the problematic high resistance
contacts. However, many of these methods are not ideal for scaled production.
Here, we report on the large-scale, spatially controlled chemical assembly of
the integrated 2H-MoTe2 field-effect transistors (FETs) with coplanar metallic
1T' MoTe2 contacts via phase engineered approaches. We demonstrate that the
heterophase FETs exhibit ohmic contact behavior with low contact resistance,
resulting from the coplanar seamless contact between 2H and 1T' MoTe2 confirmed
by transmission electron microscopy characterizations. The average mobility of
the heterophase FETs was measured to be as high as 23 cm2 V-1 s-1 (comparable
with those of exfoliated single crystals), due to the large 2H MoTe2
single-crystalline domain (486{\mu}m). By developing a patterned growth method,
we realize the 1T' MoTe2 gated heterophase FET array whose components of
channel, gate, and contacts are all 2D materials. Finally, we transfer the
heterophase device array onto a flexible substrate and demonstrate the
near-infrared photoresponse with high photoresponsivity (~1.02 A/W). Our study
provides a basis for the large-scale application of phase-engineered coplanar
MoTe2 semiconductors-meter structure in advanced electronics and
optoelectronics.",1904.08545v1
2023-09-27,High-Resolution Full-field Structural Microscopy of the Voltage Induced Filament Formation in Neuromorphic Devices,"Neuromorphic functionalities in memristive devices are commonly associated
with the ability to electrically create local conductive pathways by resistive
switching. The archetypal correlated material, VO2, has been intensively
studied for its complex electronic and structural phase transition as well as
its filament formation under applied voltages. Local structural studies of the
filament behavior are often limited due to time-consuming rastering which makes
impractical many experiments aimed at investigating large spatial areas or
temporal dynamics associated with the electrical triggering of the phase
transition. Utilizing Dark Field X-ray Microscopy (DFXM), a novel full-field
x-ray imaging technique, we study this complex filament formation process
in-operando in VO2 devices from a structural perspective. We show that prior to
filament formation, there is a significant gain of the metallic rutile phase
beneath the metal electrodes that define the device. We observed that the
filament formation follows a preferential path determined by the nucleation
sites within the device. These nucleation sites are predisposed to the phase
transition and can persistently maintain the high-temperature rutile phase even
after returning to room temperature, which can enable a novel training/learning
mechanism. Filament formation also appears to follow a preferential path
determined by a nucleation site within the device which is predisposed to the
rutile transition even after returning to room temperature. Finally, we found
that small isolated low-temperature phase clusters can be present inside the
high-temperature filaments indicating that the filament structure is not
uniform. Our results provide a unique perspective on the electrically induced
filament formation in metal-insulator transition materials, which further the
basic understanding of this resistive switching.",2309.15712v1
2020-12-23,"Separated transport relaxation scales and interband scattering in SrRuO$_3$, CaRuO$_3$, and Sr$_2$RuO$_4$ thin films","The anomalous charge transport observed in some strongly correlated metals
raises questions as to the universal applicability of Landau Fermi liquid
theory. The coherence temperature $T_{FL}$ for normal metals is usually taken
to be the temperature below which $T^2$ is observed in the resistivity. Below
this temperature, a Fermi liquid with well-defined quasiparticles is expected.
However, metallic ruthenates in the Ruddlesden-Popper family, frequently show
non-Drude low-energy optical conductivity and unusual $\omega/T$ scaling,
despite the frequent observation of $T^2$ dc resistivity. Herein we report
time-domain THz spectroscopy measurements of several different high-quality
metallic ruthenate thin films and show that the optical conductivity can be
interpreted in more conventional terms. In all materials, the conductivity has
a two-Drude peak lineshape at low temperature and a crossover to a one-Drude
peak lineshape at higher temperatures. The two-component low-temperature
conductivity is indicative of two well-separated current relaxation rates for
different conduction channels. We discuss three particular possibilities for
the separation of rates: (a) Strongly energy-dependent inelastic scattering;
(b) an almost-conserved pseudomomentum operator that overlaps with the current,
giving rise to the narrower Drude peak; (c) the presence of multiple conduction
channels that undergoes a crossover to stronger interband scattering at higher
temperatures. None of these scenarios require the existence of exotic
quasiparticles. The results may give insight into the possible significance of
Hund's coupling in determining interband coupling in these materials. Our
results also show a route towards understanding the violation of Matthiessen's
rule in this class of materials and deviations from the ""Gurzhi"" scaling
relations in Fermi liquids.",2012.12800v1
2016-05-09,An analytical model for the influence of contact resistance on thermoelectric efficiency,"An analytical model is presented that can account for both electrical and hot
and cold thermal contact resistances when calculating the efficiency of a
thermoelectric generator. The model is compared to a numerical model of a
thermoelectric leg, for 16 different thermoelectric materials, as well as the
analytical models of Ebling et. al. (2010) and Min \& Rowe (1992). The model
presented here is shown to accurately calculate the efficiency for all systems
and all contact resistances considered, with an average difference in
efficiency between the numerical model and the analytical model of
$-0.07\pm0.35$ pp. This makes the model more accurate than previously published
models. The maximum absolute difference in efficiency between the analytical
model and the numerical model is 1.14 pp for all materials and all contact
resistances considered.",1605.03565v1
2017-12-22,Magnetoresistance in YBi and LuBi semimetals due to nearly perfect carrier compensation,"Monobismuthides of yttrium and lutetium are shown as new representatives of
materials which exhibit extreme magnetoresistance and magnetic-field-induced
resistivity plateau. At low temperatures and in magnetic field of 9T the
magnetoresistance attains the order of magnitude of 10,000% and 1,000%, on YBi
and LuBi, respectively. Our thorough examination of electron transport
properties of both compounds show that observed features are the consequence of
nearly perfect carrier compensation rather than of possible nontrivial topology
of electronic states. The field-induced plateau of electrical resistivity can
be explained with Kohler scaling. Anisotropic multi-band model of electronic
transport describes very well the magnetic field dependence of electrical
resistivity and Hall resistivity. Data obtained from the Shubnikov-de Haas
oscillations analysis also confirm that Fermi surface of each compound contains
almost equal amounts of holes and electrons. First-principle calculations of
electronic band structure are in a very good agreement with the experimental
data.",1712.08433v3
2020-05-07,Origin of the Significant Impact of Ta on the Creep Resistance of FeCrNi Alloys,"Heat resistant FeCrNi alloys are widely used in the petrochemical industry
because they exhibit a unique combination of creep and oxidation resistance at
temperatures exceeding 900$^\circ$C. Their creep properties are often optimized
by micro-additions of carbide forming elements. In the present work, the
influence of Ta micro-additions has been experimentally investigated both on
as-cast and aged microstructures to understand the origin of the significant
impact of this element on the creep resistance. Calculations with thermocal
software were also carried out to support experimental data. It is shown that a
small addition of Ta is beneficial as it increases the volume fraction of
stable MC carbides. We demonstrate also that additions of Ta may have a
dramatic effect on the thermal stability of microstructures. This is attributed
to a smaller equilibrium volume fraction of M23C6 and more pronounced
heterogeneous precipitation at MC/matrix interfaces. The influence on the creep
properties in then discussed.",2005.03309v1
2022-10-07,Radiation-resistant aluminium alloy for space missions in the extreme environment of the solar system,"Future human-based exploration of our solar system requires the invention of
materials that can resist harsh environments. Age-hardenable aluminium alloys
would be attractive candidates for structural components in long-distance
spacecrafts, but their radiation resistance to solar energetic particles is
insufficient. Common hardening phases dissolve and displacement damage occurs
in the alloy matrix, which strongly degrades properties. Here we present an
alloy where hardening is achieved by T-phase, featuring a giant unit cell and
highly-negative enthalpy of formation. The phase shows record radiation
survivability and can stabilize an ultrafine-grained structure upon temperature
and radiation in the alloy, therby successfully preventing displacement damage
to occur. Such concept can be considered ideal for the next-generation space
materials and the design of radiation resistant alloy.",2210.03397v3
2022-11-22,"Optical properties and corrosion resistance of Ti2AlC, Ti3AlC2, and Cr2AlC as candidates for Concentrated Solar Power receivers","New generation concentrated solar power (CSP) plants require new solar
receiver materials with selective optical properties and excellent corrosion
resistance against molten salts. MAX phases are promising materials for CSP
applications due to their optical properties and resistance to thermal shocks.
Herein, we report a solar absorptance >/= 0.5 and a thermal emittance of
0.17-0.31 between 600 and 1500 K for Cr2AlC, Ti2AlC, and Ti3AlC2. These
compositions were also exposed to solar salt corrosion at 600{\deg}C for up to
4 weeks. Cr2AlC exhibited superior corrosion resistance due to the formation of
a protective nanometric layer.",2211.12251v2
2020-01-16,Social Engineering Resistant 2FA,"Attackers increasingly, and with high success rates, use social engineering
techniques to circumvent second factor authentication (2FA) technologies,
compromise user accounts and sidestep fraud detection technologies. We
introduce a social engineering resistant approach that we term device-aware
2FA, to replace the use of traditional security codes.",2001.06075v1
2019-01-12,Surface impedance measurements on Nb$_{3}$Sn at high magnetic fields,"Nb$_{3}$Sn is a superconductor of great relevance for perspective RF
applications. We present for the first time surface impedance $Z_s$
measurements at 15 GHz and low RF field amplitude on Nb$_{3}$Sn in high
magnetic fields up to 12 T, with the aim of increasing the knowledge of
Nb$_{3}$Sn behavior in such conditions. $Z_s$ is a fundamental material
parameter that directly gives useful information about the dissipative and
reactive phenomena when the superconductor is subjected to high-frequency
excitations. Therefore, we present an analysis of the measured $Z_s$ with the
aim of extracting interesting data about pinning in Nb$_{3}$Sn at high
frequencies. From $Z_s$ we extract the vortex motion complex resistivity to
obtain the $r$-parameter and the depinning frequency $\nu_p$ in high magnetic
fields. The comparison of the results with the literature shows that the
measured $\nu_p$ on bulk Nb$_{3}$Sn is several times greater than that of pure
Nb. This demonstrates how Nb$_{3}$Sn can be a good candidate for RF
technological applications, also in high magnetic fields.",1901.03819v1
2020-08-25,Observation of High Harmonics of the Cyclotron Resonance in Microwave Transmission of a High-Mobility Two-Dimensional Electron System,"We report an observation of magnetooscillations of the microwave power
transmitted through the high mobility two-dimensional electron system hosted by
a GaAs quantum well. The oscillations reflect an enhanced absorption of
radiation at high harmonics of the cyclotron resonance and follow
simultaneously measured microwave-induced resistance oscillations (MIRO) in the
dc transport. While the relative amplitude (up to 1%) of the transmittance
oscillations appears to be small, they represent a significant (>50%)
modulation of the absorption coefficient. The analysis of obtained results
demonstrates that the low-B decay, magnitude, and polarization dependence of
the transmittance oscillations accurately follow the theory describing
photon-assisted scattering between distant disorder-broadened Landau levels.
The extracted sample parameters reasonably well describe the concurrently
measured MIRO. Our results provide an insight into the MIRO polarization
immunity problem and pave the way to probe diverse high-frequency transport
properties of high-mobility systems using precise transmission measurements.",2008.11114v1
2021-09-20,Giant anomalous Nernst signal in the antiferromagnet YbMnBi2,"Searching for a high anomalous Nernst effect (ANE) is crucial for
thermoelectric energy conversion applications because the associated unique
transverse geometry facilitates module fabrication. Topological ferromagnets
with large Berry curvatures show high ANEs; however, they face drawbacks such
as strong magnetic disturbances and low mobility due to high magnetization.
Herein, we demonstrate that YbMnBi2, a canted antiferromagnet, has a large ANE
conductivity of ~10 Am-1K-1 that surpasses the common high values (i.e. 3-5
Am-1K-1) observed so far in ferromagnets. The canted spin structure of Mn
guarantees a nonzero Berry curvature but generates only a weak magnetization
three orders of magnitude lower than that of general ferromagnets. The heavy Bi
with a large spin-orbit coupling enables a high ANE and low thermal
conductivity, whereas its highly dispersive px/y orbitals ensure low
resistivity. The high anomalous transverse thermoelectric performance and
extremely small magnetization makes YbMnBi2 an excellent candidate for
transverse thermoelectrics.",2109.09382v1
2022-02-09,Low energy switching of phase change materials using a 2D thermal boundary layer,"The switchable optical and electrical properties of phase change materials
(PCMs) are finding new applications beyond data storage in reconfigurable
photonic devices. However, high power heat pulses are needed to melt-quench the
material from crystalline to amorphous. This is especially true in silicon
photonics, where the high thermal conductivity of the waveguide material makes
heating the PCM energy inefficient. Here, we improve the energy efficiency of
the laser-induced phase transitions by inserting a layer of two-dimensional
(2D) material, either MoS2 or WS2, between the silica or silicon and the PCM.
The 2D material reduces the required laser power by at least 40% during the
amorphization (RESET) process, depending on the substrate. Thermal simulations
confirm that both MoS2 and WS2 2D layers act as a thermal barrier, which
efficiently confines energy within the PCM layer. Remarkably, the thermal
insulation effect of the 2D layer is equivalent to a ~100 nm layer of SiO2. The
high thermal boundary resistance induced by the van der Waals (vdW)-bonded
layers limits the thermal diffusion through the layer interfaces. Hence, 2D
materials with stable vdW interfaces can be used to improve the thermal
efficiency of PCM-tuned Si photonic devices. Furthermore, our waveguide
simulations show that the 2D layer does not affect the propagating mode in the
Si waveguide, thus this simple additional thin film produces a substantial
energy efficiency improvement without degrading the optical performance of the
waveguide. Our findings pave the way for energy-efficient laser-induced
structural phase transitions in PCM-based reconfigurable photonic devices.",2202.04699v1
2008-06-27,Electron pockets in the Fermi surface of hole-doped high-Tc superconductors,"High-temperature superconductivity occurs as copper oxides are chemically
tuned to have a carrier concentration intermediate between their metallic state
at high doping and their insulating state at zero doping. The underlying
evolution of the electron system in the absence of superconductivity is still
unclear and a question of central importance is whether it involves any
intermediate phase with broken symmetry. The Fermi surface of underdoped
YBa2Cu3Oy and YBa2Cu4O8 was recently shown to include small pockets in contrast
with the large cylinder characteristic of the overdoped regime1, pointing to a
topological change in the Fermi surface. Here we report the observation of a
negative Hall resistance in the magnetic field-induced normal state of
YBa2Cu3Oy and YBa2Cu4O8, which reveals that these pockets are electron-like. We
propose that electron pockets arise most likely from a reconstruction of the
Fermi surface caused by the onset of a density-wave phase, as is thought to
occur in the electron-doped materials near the onset of antiferromagnetic order
Comparison with materials of the La2CuO4 family that exhibit spin/charge
density-wave order suggests that a Fermi surface reconstruction also occurs in
those materials, pointing to a generic property of high-Tc superconductors.",0806.4621v1
2008-11-19,Elucidation of the origins of HTSC transport behaviour and quantum oscillations,"A detailed exposition is made of recent transport and 'quantum oscillation'
results from HTSC systems covering the full range from overdoped to underdoped
material. This now very extensive and high quality data set is interpreted here
within the framework developed by the author of local pairs and boson-fermion
resonance, arising in the context of negative-U behaviour in an inhomogeneous
electronic environment. The strong inhomogeneity comes with the mixed-valent
condition of these materials, which when underdoped lie in close proximity to
the Mott-Anderson transition. The observed intense scattering is presented as
resulting from pair formation and electron-boson collisions in the resonant
crossover circumstance. The high level of scattering brings the systems to
incoherence in the pseudogapped state, p < pc (= 0.183). In a high magnetic
field the striped partition of the inhomogeneous charge distribution is much
strengthened and regularized. Magnetization and resistance oscillations, of
period dictated by the favoured positioning of the square fluxon array within
the real space environment of the diagonal 2D charge striping array, are
demonstrated to be responsible for the recently reported behaviour hitherto
widely attributed to the quantum oscillation response of a much more standard
Fermi liquid condition. A detailed analysis embracing all the experimental data
serves to indicate that in the given conditions of very high field, low
temperature, 2D-striped, underdoped, d-wave superconducting, HTSC material the
flux quantum becomes doubled to h/e.",0811.3096v2
2011-11-04,Local Structure of the Superconductor K0.8Fe1.6+xSe2: Evidence of Large Structural Disorder,"The local structure of superconducting single crystals of K0.8Fe1.6+xSe2 with
Tc = 32.6 K was studied by x-ray absorption spectroscopy. Near-edge spectra
reveal that the average valence of Fe is 2+. The room temperature structure
about the Fe, K and Se sites was examined by iron, selenium and potassium
K-edge measurements. The structure about the Se and Fe sites shows a high
degree of order in the nearest neighbor Fe-Se bonds. On the other hand, the
combined Se and K local structure measurements reveal a very high level of
structural disorder in the K layers. Temperature dependent measurements at the
Fe sites show that the Fe-Se atomic correlation follows that of the Fe-As
correlation in the superconductor LaFeAsO0.89F0.11 - having the same effective
Einstein temperature (stiffness). In K0.8Fe1.6+xSe2, the nearest neighbor Fe-Fe
bonds has a lower Einstein temperature and higher structural disorder than in
LaFeAsO0.89F0.11. The moderate Fe site and high K site structural disorder is
consistent with the high normal state resistivity seen in this class of
materials. For higher shells, an enhancement of the second nearest neighbor
Fe-Fe interaction is found just below Tc and suggests that correlations between
Fe magnetic ion pairs beyond the first neighbor are important in models of
magnetic order and superconductivity in these materials.",1111.1026v1
2017-02-14,Pressure-induced metallization and superconducting phase in ReS2,"Among the family of TMDs, ReS2 takes a special position, which crystalizes in
a unique distorted low-symmetry structure at ambient conditions. The interlayer
interaction in ReS2 is rather weak, thus its bulk properties are similar to
that of monolayer. However, how does compression change its structure and
electronic properties is unknown so far. Here using ab initio crystal structure
searching techniques, we explore the high-pressure phase transitions of ReS2
extensively and predict two new high-pressure phases. The ambient pressure
phase transforms to a ""distorted-1T"" structure at very low pressure and then to
a tetragonal I41/amd structure at around 90 GPa. The ""distorted-1T"" structure
undergoes a semiconductor-metal transition (SMT) at around 70 GPa with a band
overlap mechanism. Electron-phonon calculations suggest that the I41/amd
structure is superconducting and has a critical superconducting temperature of
about 2 K at 100 GPa. We further perform high-pressure electrical resistance
measurements up to 102 GPa. Our experiments confirm the SMT and the
superconducting phase transition of ReS2 under high pressure. These
experimental results are in good agreement with our theoretical predictions.",1702.04061v1
2018-05-04,Silicon Oxide Electron-Emitting Nanodiodes,"Electrically driven on-chip electron sources that do not need to be heated
have been long pursued because the current thermionic electron sources show the
problems of high power consumption, slow temporal response, bulky size, etc.,
but their realization remains challenging. Here we show that a nanogap formed
by two electrodes on a silicon oxide substrate functions as an
electron-emitting nanodiode after the silicon oxide in the nanogap is
electrically switched to a high-resistance conducting state. A nanodiode based
on graphene electrodes can be turned on by a voltage of ~7 V in ~100 ns and
show an emission current of up to several microamperes, corresponding to an
emission density of ~10^6 A cm^-2 and emission efficiency as high as 16.6%. We
attribute the electron emission to be generated from a metal-insulator-metal
tunneling diode on the substrate surface formed by the rupture of conducting
filaments in silicon oxide. An array of 100 nanodiodes exhibits a global
emission density of 5 A cm^-2 and stable emission with negligible current
degradation over tens of hours under modest vacuum. The combined advantages of
a low operating voltage, fast temporal response, high emission density and
efficiency, convenient fabrication and integration, and stable emission in
modest vacuum make silicon oxide electron-emitting nanodiodes a promising
on-chip alternative to thermionic emission sources.",1805.01602v1
2019-11-04,Enhanced upper critical field in Co-doped Ba122 superconductors by lattice defect tuning,"Nanoscale defects in superconductors play a dominant role in enhancing
superconducting properties through electron scattering, modulation of coherence
length, and correlation with quantized magnetic flux. For iron-based
superconductors (IBSCs) that are expected to be employed in high-field magnetic
applications, a fundamental question is whether such defects develop an upper
critical field (Hc2) similar to that of conventional BCS-type superconductors.
Herein, we report the first demonstration of a significantly improved Hc2 in a
122-phase IBSC by introducing defects through high-energy milling. Co-doped
Ba122 polycrystalline bulk samples (Ba(Fe,Co)2As2) were prepared by sintering
powder which was partially mechanically alloyed through high-energy milling. A
remarkable increase in full-width at half maximum of X-ray powder diffraction
peaks, anomalous shrinkage in the a-axis, and elongation in the c-axis were
observed. When lattice defects are introduced into the grains, semiconductor
behavior of the electric resistivity at low temperature (T < 100 K), slight
decrease in transition temperature (Tc), upturn of Hc2(T) near Tc, and a large
increase in Hc2(T) slope were observed. The slope of Hc2(T) increased
approximately by 50%, i.e., from 4 to 6 T/K, and exceeded that of single
crystals and thin films. Defect engineering through high-energy milling is
expected to facilitate new methods for the designing and tuning of Hc2 in
122-phase IBSCs.",1911.01080v1
2019-11-07,Chemical manipulation of hydrogen induced high p-type and n-type conductivity in Ga2O3,"Advancement of optoelectronic and high-power devices is tied to the
development of wide band gap materials with excellent transport properties.
However, bipolar doping (n-type and p-type doping) and realizing high carrier
density while maintaining good mobility have been big challenges in wide band
gap materials. Here P-type and n-type conductivity was introduced in
beta-Ga2O3, an ultra-wide band gap oxide, by controlling hydrogen incorporation
in the lattice without further doping. Hydrogen induced a 9-order of magnitude
increase of n-type conductivity with donor ionization energy of 20 meV and
resistivity of 10-4 Ohm.cm. The conductivity was switched to p-type with
acceptor ionization energy of 42 meV by altering hydrogen incorporation in the
lattice. Density functional theory calculations were used to examine hydrogen
location in the Ga2O3 lattice and identified a new donor type as the source of
this remarkable n-type conductivity. Positron annihilation spectroscopy
confirmed this finding and the interpretation of the results. This work
illustrates a new approach that allows a tunable and reversible way of
modifying the conductivity of semiconductors and it is expected to have
profound implications on semiconductor field. At the same time it demonstrates
for the first time p-type and remarkable n-type conductivity in Ga2O3 which
should usher in the development of Ga2O3 devices and advance optoelectronics
and high-power devices",1911.02717v1
2021-03-01,Absence of magnetic evidence for superconductivity in hydrides under high pressure,"It is generally believed that magnetization measurements on sulfur hydride
under high pressure performed in 2015 [1] provided ""final convincing evidence
of superconductivity"" [2] in that material, in agreement with theoretical
predictions [3,4]. Supported by this precedent, drops in resistance that were
later observed in several other hydrides under high pressure [2,5] have been
generally accepted as evidence of superconductivity without corroborating
evidence from magnetic measurements. In this paper we challenge the original
interpretation that the magnetic measurements on sulfur hydride performed in
2015 were evidence of superconductivity. We point out that a large paramagnetic
contribution to the magnetic susceptibility was detected below Tc and argue
that its temperature dependence rules out the possibility that it would be a
background signal; instead the temperature dependence indicates that the
paramagnetic behavior originated in the sample. We discuss possible
explanations for this remarkable behavior and conclude that standard
superconductors would not show such behavior. We also survey all the other
published data from magnetic measurements on this class of materials and
conclude that they do not provide strong evidence for superconductivity.
Consequently, we call into question the generally accepted view that
conventional superconductivity in hydrogen-rich materials at high temperature
and pressure is a reality, and discuss the implications if it is not.",2103.00701v3
2021-08-15,"High power Figure-of-Merit, 10.6-kV AlGaN/GaN lateral Schottky barrier diode with single channel and sub-100-μm anode-to-cathode spacing","GaN-based lateral Schottky diodes (SBDs) have attracted great attention for
high-power applications due to its combined high electron mobility and large
critical breakdown field. However, the breakdown voltage (BV) of the SBDs are
far from exploiting the material advantages of GaN at present, limiting the
desire to use GaN for ultra-high voltage (UHV) applications. Then, a golden
question is whether the excellent properties of GaN-based materials can be
practically used in the UHV field? Here we demonstrate UHV AlGaN/GaN SBDs on
sapphire with a BV of 10.6 kV, a specific on-resistance of 25.8 m{\Omega}.cm2,
yielding a power figure of merit of more than 3.8 GW/cm2. These devices are
designed with single channel and 85-{\mu}m anode-to-cathode spacing, without
other additional electric field management, demonstrating its great potential
for the UHV application in power electronics.",2108.06679v1
2023-11-14,A New Look at Calcium Digermanide CaGe$_2$: A High-Performing Semimetal Transparent Conducting Material for Ge Optoelectronics,"Following a recently manifested guide of how to team up infrared transparency
and high electrical conductivity within semimetal materials [C. Cui $et$ $al.$
Prog. Mater. Sci. 2023, 136, 101112], we evaluate an applicability of the
calcium digermanide (CaGe$_2$) thin film electrodes for the advanced Ge-based
optical devices. Rigorous growth experiments were conducted to define the
optimal annealing treatment and thickness of the Ca-Ge mixture for producing
stable CaGe$_2$ layers with high figure of merit (FOM) as transparent
conducting material. Ab-initio electronic band structure calculations and
optical modeling confirmed CaGe$_2$ semimetal nature, which is responsible for
a demonstrated high FOM. To test CaGe$_2$ electrodes under actual conditions, a
planar Ge photodetector (PD) with metal-semiconductor-metal structure was
fabricated, where CaGe$_2$/Ge interface acts as Schottky barrier. The resulting
Ge PD with semimetal electrodes outperformed commercially available Ge devices
in terms of both photoresponse magnitude and operated spectral range. Moreover,
by using femtosecond-laser projection lithography, a mesh CaGe$_2$ electrode
with the relative broadband transmittance of 90\% and sheet resistance of 20
$\Omega$/sq. was demonstrated, which further enhanced Ge PD photoresponse.
Thus, obtained results suggest that CaGe$_2$ thin films have a great potential
in numerous applications promoting the era of advanced Ge optoelectronics.",2311.07903v1
2023-12-14,"Unlocking High Performance, Ultra-Low Power Van der Waals Transistors: Towards Back-End-of-Line In-Sensor Machine Vision Applications","Recent reports on machine learning (ML) and machine vision (MV) devices have
demonstrated the potentials of 2D materials and devices. Yet, scalable 2D
devices are being challenged by contact resistance and Fermi Level Pinning
(FLP), power consumption, and low-cost CMOS compatible lithography processes.
To enable CMOS+2D, it is essential to find a proper lithography strategy that
can fulfill these requirements. Here, we explore modified van der Waals (vdW)
deposition lithography and demonstrate a relatively new class of
van-der-Waals-Field-Effect-Transistors (vdW-FETs) based on 2D materials. This
lithography strategy enables us to unlock high performance devices evident by
high current on-off ratio (Ion/Ioff), high turn-on current density (Ion), and
weak Fermi Level Pinning (FLP). We utilize this approach to demonstrate a
gate-tunable near-ideal diode using MoS2/WSe2 heterojunction with an ideality
factor of ~1.65 and current rectification of 102. We finally demonstrate a
highly sensitive, scalable, and ultra-low power phototransistor using MoS2/
WSe2 vdW-FET for Back-End-of-Line (BEOL) integration. Our phototransistor
exhibits the highest gate-tunable photoresponsivity achieved to date for white
light detection with ultra-low power dissipation, enabling ultra-sensitive,
ultra-fast, and efficient optoelectronic applications such as in-sensor
neuromorphic machine vision. Our approach shows the great potential of modified
vdW deposition lithography for back-end-of-line CMOS+2D applications.",2312.08634v1
2006-08-31,Systematic study of disorder induced by neutron irradiation in MgB2 thin films,"The effects of neutron irradiation on normal state and superconducting
properties of epitaxial magnesium diboride thin films are studied up to
fluences of 1020 cm-2. All the properties of the films change systematically
upon irradiation. Critical temperature is suppressed and, at the highest
fluence, no superconducting transition is observed down to 1.8 K. Residual
resistivity progressively increases from 1 to 190 microohmcm; c axis expands
and then saturates at the highest damage level. We discuss the mechanism of
damage through the comparison with other damage procedures. The normal state
magnetoresistivity of selected samples measured up to high fields (28 and 45T)
allows to determine unambiguously the scattering rates in each band; the
crossover between the clean and dirty limit in each sample can be monitored.
This set of samples, with controlled amount of disorder, is suitable to study
the puzzling problem of critical field in magnesium diboride thin films. The
measured critical field values are extremely high (of the order of 50T in the
parallel direction at low fluences) and turns out to be rather independent on
the experimental resistivity, at least at low fluences. A simple model to
explain this phenomenology is presented.",0608706v2
2001-11-30,Effects of Bulk and Surface Conductivity on the Performance of CdZnTe Pixel Detectors,"We studied the effects of bulk and surface conductivity on the performance of
high-resistivity CdZnTe (CZT) pixel detectors with Pt contacts. We emphasize
the difference in mechanisms of the bulk and surface conductivity as indicated
by their different temperature behaviors. In addition, the existence of a thin
(10-100 A) oxide layer on the surface of CZT, formed during the fabrication
process, affects both bulk and surface leakage currents. We demonstrate that
the measured I-V dependencies of bulk current can be explained by considering
the CZT detector as a metal-semiconductor-metal system with two back-to-back
Schottky-barrier contacts. The high surface leakage current is apparently due
to the presence of a low-resistivity surface layer that has characteristics
which differ considerably from those of the bulk material. This surface layer
has a profound effect on the charge collection efficiency in detectors with
multi-contact geometry; some fraction of the electric field lines originated on
the cathode intersects the surface areas between the pixel contacts where the
charge produced by an ionizing particle gets trapped. To overcome this effect
we place a grid of thin electrodes between the pixel contacts; when the grid is
negatively biased, the strong electric field in the gaps between the pixels
forces the electrons landing on the surface to move toward the contacts,
preventing the charge loss. We have investigated these effects by using CZT
pixel detectors indium bump bonded to a custom-built VLSI readout chip.",0112001v1
2008-10-23,Thermopower across the pseudogap critical point of La(1.6-x)Nd(0.4)Sr(x)CuO(4): Evidence for a quantum critical point in a hole-doped high-Tc superconductor,"The thermopower S of the high-Tc superconductor La(1.6-x)Nd(0.4)Sr(x)CuO(4)
was measured as a function of temperature T near its pseudogap critical point,
the critical hole doping p* where the pseudogap temperature T* goes to zero.
Just above p*, S/T varies as ln(1/T) over a decade of temperature. Below p*,
S/T undergoes a large increase below T*. As with the temperature dependence of
the resistivity, which is linear just above p* and undergoes a large upturn
below T*, these are typical signatures of a quantum phase transition. This
suggests that p* is a quantum critical point below which some order sets in,
causing a reconstruction of the Fermi surface, whose fluctuations are
presumably responsible for the linear-T resistivity and logarithmic
thermopower. We discuss the possibility that this order is the ""stripe"" order
known to exist in this material.",0810.4280v2
2009-09-23,Zooming on the Quantum Critical Point in Nd-LSCO,"Recent studies of the high-Tc superconductor La_(1.6-x)Nd_(0.4)Sr_(x)CuO_(4)
(Nd-LSCO) have found a linear-T in-plane resistivity rho_(ab) and a logarithmic
temperature dependence of the thermopower S / T at a hole doping p = 0.24, and
a Fermi-surface reconstruction just below p = 0.24 [1, 2]. These are typical
signatures of a quantum critical point (QCP). Here we report data on the c-axis
resistivity rho_(c)(T) of Nd-LSCO measured as a function of temperature near
this QCP, in a magnetic field large enough to entirely suppress
superconductivity. Like rho_(ab), rho_(c) shows an upturn at low temperature, a
signature of Fermi surface reconstruction caused by stripe order. Tracking the
height of the upturn as it decreases with doping enables us to pin down the
precise location of the QCP where stripe order ends, at p* = 0.235 +- 0.005. We
propose that the temperature T_(rho) below which the upturn begins marks the
onset of the pseudogap phase, found to be roughly twice as high as the stripe
ordering temperature in this material.",0909.4218v1
2009-12-30,30 inch Roll-Based Production of High-Quality Graphene Films for Flexible Transparent Electrodes,"We report that 30-inch scale multiple roll-to-roll transfer and wet chemical
doping considerably enhance the electrical properties of the graphene films
grown on roll-type Cu substrates by chemical vapor deposition. The resulting
graphene films shows a sheet resistance as low as ~30 Ohm/sq at ~90 %
transparency which is superior to commercial transparent electrodes such as
indium tin oxides (ITO). The monolayer of graphene shows sheet resistances as
low as ~125 Ohm/sq with 97.4% optical transmittance and half-integer quantum
Hall effect, indicating the high-quality of these graphene films. As a
practical application, we also fabricated a touch screen panel device based on
the graphene transparent electrodes, showing extraordinary mechanical and
electrical performances.",0912.5485v3
2013-10-03,Aharonov-Bohm resistance magneto-oscillations on single-nanohole graphite and graphene structures,"Graphene is a stable single atomic layer material exhibiting two-dimensional
electron gas of massless Dirac fermions of high mobility. One of the intriguing
properties of graphene is a possibility of realization of the Tamm-type edge
states. These states differ from the usual surface states caused by defects,
impurities and other imperfections at the edge of the system, as well as they
differ from the magnetic edge states caused by skipping cyclotron orbits. The
Tamm states result from breaking of periodic crystal potential at the edge,
they can exist even at zero magnetic field and form a conducting band. Until
recently those states have been observed in graphene only by local STM
technique and there were no direct experiments on their contribution to
transport measurements. Here we present the experiments on Aharonov-Bohm (AB)
oscillations of resistance in a single-nanohole graphite and graphene
structures, it indicates the presence of conducting edge states cycling around
nanohole. An estimation show the penetration depth of the edge states to be as
short as about 2 nm. The oscillations persist up to temperature T=115 K and the
T-range of their existence increases with a decrease of the nanohole diameter.
The proposed mechanism of the AB oscillations based on the resonant intervalley
backscattering of the Dirac fermions by the nanohole via the Tamm states. The
experimental results are consistent with such a scenario. Our findings show a
way towards interference devices operating at high temperatures on the edge
states in graphene",1310.0991v1
2014-02-27,"Spin-charge interplay in antiferromagnetic La$_{2-x}$Sr$_{x}$CuO$_{4}$ studied by the muons, neutrons, and ARPES techniques","Exploring whether a spin density wave (SDW) is responsible for the charge
excitations gap in the high-temperature superconducting cuprates is difficult,
since the region of the phase diagram where the magnetic properties are clearly
exposed is different from the region where the band dispersion is visible. On
the one hand, long range magnetic order disappears as doping approaches 2% from
below, hindering our ability to perform elastic neutron scattering (ENS). On
the other hand, cuprates become insulating at low temperature when the doping
approaches 2% from above, thus restricting angle-resolved photoemission
spectroscopy (ARPES). In fact, ARPES data for samples with doping lower than 3%
are rare and missing the quasiparticle peaks in the energy distribution curves
(EDCs). The main problem is the high resistivity of extremely underdoped
samples, which is detrimental to ARPES due to charging effects. Nevertheless,
the resistivity of La$_{2-x}$Sr$_{x}$CuO$_{4}$ as a function of temperature, at
2% doping, has a broad minimum around 100K. This minimum opens a window for
both experiments. By preparing a series of LSCO single crystals with $\sim
$0.2-0.3% doping steps around 2%, we managed to find one to which both
techniques apply. This allows us to explore the cross talk between the magnetic
and electronic properties of the material.",1402.6936v1
2014-05-21,High Mobility WSe2 p- and n-Type Field Effect Transistors Contacted by Highly Doped Graphene for Low-Resistance Contacts,"We report the fabrication of both n-type and p-type WSe2 field effect
transistors with hexagonal boron nitride passivated channels and ionic-liquid
(IL)-gated graphene contacts. Our transport measurements reveal intrinsic
channel properties including a metal-insulator transition at a characteristic
conductivity close to the quantum conductance e2/h, a high ON/OFF ratio of >107
at 170 K, and large electron and hole mobility of ~200 cm2V-1s-1 at 160 K.
Decreasing the temperature to 77 K increases mobility of electrons to ~330
cm2V-1s-1 and that of holes to ~270 cm2V-1s-1. We attribute our ability to
observe the intrinsic, phonon limited conduction in both the electron and hole
channels to the drastic reduction of the Schottky barriers between the channel
and the graphene contact electrodes using IL gating. We elucidate this process
by studying a Schottky diode consisting of a single graphene/WSe2 Schottky
junction. Our results indicate the possibility to utilize chemically or
electrostatically highly doped graphene for versatile, flexible and transparent
low-resistance Ohmic contacts to a wide range of quasi-2D semiconductors.
  KEYWORDS: MoS2, WSe2, field-effect transistors, graphene, Schottky barrier,
ionic-liquid gate",1405.5437v1
2015-01-07,Angle dependence of the orbital magnetoresistance in bismuth,"We present an extensive study of angle-dependent transverse magnetoresistance
in bismuth, with a magnetic field perpendicular to the applied electric current
and rotating in three distinct crystallographic planes. The observed angular
oscillations are confronted with the expectations of semi-classic transport
theory for a multi-valley system with anisotropic mobility and the agreement
allows us to quantify the components of the mobility tensor for both electrons
and holes. A quadratic temperature dependence is resolved. As Hartman argued
long ago, this indicates that inelastic resistivity in bismuth is dominated by
carrier-carrier scattering. At low temperature and high magnetic field, the
threefold symmetry of the lattice is suddenly lost. Specifically, a $2\pi/3$
rotation of magnetic field around the trigonal axis modifies the amplitude of
the magneto-resistance below a field-dependent temperature. By following the
evolution of this anomaly as a function of temperature and magnetic field, we
mapped the boundary in the (field, temperature) plane separating two electronic
states. In the less-symmetric state, confined to low temperature and high
magnetic field, the three Dirac valleys cease to be rotationally invariant. We
discuss the possible origins of this spontaneous valley polarization, including
a valley-nematic scenario.",1501.01584v2
2015-02-26,First principles design of divacancy defected graphene nanoribbon based rectifying and negative differential resistance device,"We have elaborately studied the electronic structure of 555-777 divacancy
(DV) defected armchair edged graphene nanoribbon (AGNR) and transport
properties of AGNR based two-terminal device constructed with one defected
electrode and one N doped electrode, by using density functional theory and
non-equilibrium Green's function based approach. The introduction of 555-777 DV
defect into AGNRs, results in a shifting of the {\pi} and {\pi}* bands towards
the higher energy value which indicates a shifting of the Fermi level towards
the lower energy. Formation of a potential barrier, very similar to that of
conventional p-n junction, has been observed across the junction of defected
and N doped AGNR. The prominent asymmetric feature of the current in the
positive and negative bias indicates the diode like property of the device with
high rectifying efficiency within wide range of bias voltages. The device also
shows robust negative differential resistance (NDR) with very high
peak-to-valley ratio. The analysis of the shifting of the energy states of the
electrodes and the modification of the transmission function with applied bias
provides an insight into the nonlinearity and asymmetry observed in the I-V
characteristics. Variation of the transport properties on the width of the
ribbon has also been discussed.",1502.07465v1
2016-06-07,Superconductivity and Charge Density Wave in ZrTe$_{3-x}$Se$_{x}$,"Charge density wave (CDW), the periodic modulation of the electronic charge
density, will open a gap on the Fermi surface that commonly leads to decreased
or vanishing conductivity. On the other hand superconductivity, a commonly
believed competing order, features a Fermi surface gap that results in infinite
conductivity. Here we report that superconductivity emerges upon Se doping in
CDW conductor ZrTe$_{3}$ when the long range CDW order is gradually suppressed.
Superconducting critical temperature $T_c(x)$ in ZrTe$_{3-x}$Se$_x$
(${0\leq}x\leq0.1$) increases up to 4 K plateau for
$0.04$$\leq$$x$$\leq$$0.07$. Further increase in Se content results in
diminishing $T_{c}$ and filametary superconductivity. The CDW modes from Raman
spectra are observed in $x$ = 0.04 and 0.1 crystals, where signature of
ZrTe$_{3}$ CDW order in resistivity vanishes. The electronic-scattering for
high $T_{c}$ crystals is dominated by local CDW fluctuations at high
temperures, the resistivity is linear up to highest measured $T=300K$ and
contributes to substantial in-plane anisotropy.",1606.02284v1
2016-07-15,Effect of interface on mid-infrared photothermal response of MoS2 thin film grown by pulsed laser deposition,"Here we report mid infrared (mid-IR) photothermal response of multi layer
MoS2 thin film grown on crystalline (p-type silicon and c-axis oriented single
crystal sapphire) and amorphous substrates (Si/SiO2 and Si/SiN) by pulsed laser
deposition (PLD) technique. The photothermal response of the MoS2 films was
measured as changes in the resistance of MoS2 films when irradiated with mid IR
(7 to 8.2 {\mu}m) source. We show that it is possible to enhance the
temperature coefficient of resistance (TCR) of the MoS2 thin film by
controlling the interface through proper choice of substrate and growth
conditions. The thin films grown by PLD were characterized using XRD, Raman,
AFM, XPS and TEM. High-resolution transmission electron microscopy (HRTEM)
images show that the MoS2 films grow on sapphire substrate in a layer-by-layer
manner with misfit dislocations. Layer growth morphology is disrupted when
grown on substrates with diamond cubic structure such as silicon due to growth
twin formation. The growth morphology is very different on amorphous substrates
such as Si/SiO2 or Si/SiN. The MoS2 film grown on silicon shows a very high TCR
(-2.9% K-1), mid IR sensitivity (delR/R=5.2 %) and responsivity (8.7 V/W) as
compared to films on other substrates.",1607.04682v1
2016-11-10,Pressure-induced quantum phase transition in the itinerant ferromagnet UCoGa,"In this paper, we report the results of a high pressure study of the
itinerant 5f-electron ferromagnet UCoGa. The work is focused on probing the
expected ferromagnet-to-paramagnet quantum phase transition induced by high
pressure and on the general features of the P-T(-H) phase diagram. Diamond
anvil cells were employed to measure the magnetization and electrical
resistivity under pressures up to ~ 10 GPa.At ambient pressure, UCoGa exhibits
collinear ferromagnetic ordering of uranium magnetic moments {\mu}U ~ 0.74
{\mu}B (at 2 K) aligned along the c-axis of the hexagonal crystal structure
below Curie temperature TC = 48K. With the application of pressure, gradual
decrease of both, TC and the saturated magnetic moment, has been observed up to
pressures ~ 6 GPa. This is followed by a sharp drop of magnetic moment and a
sudden disappearance of the magnetic order at the pressure of 6.5 GPa,
suggesting a first-order phase transition, as expected for a clean system. The
low temperature power law dependence of the electrical resistivity shows
distinct anomalies around the ~ 6 GPa, consistent with the pressure evolution
of the magnetic moment and the ordering temperature. The tricritical point of
the UCoGa phase diagram is located at approximately ~ 30 K and ~ 6 GPa.",1611.03276v1
2016-11-14,Two-carrier analyses of the transport properties of black phosphorus under pressure,"We report on the electronic transport properties of black phosphorus and
analyze them using a two-carrier model in a wide range of pressure up to 2.5
GPa. In semiconducting state at 0.29 GPa, the remarkable non-linear behavior in
the Hall resistance is reasonably reproduced by assuming the coexistence of two
kinds of hole with different densities and mobilities. On the other hand,
two-carrier analyses of the magnetotransport properties above 1.01 GPa suggest
the coexistence of high mobility electron and hole carriers that have almost
the same densities, i.e., nearly compensated semimetallic nature of black
phosphorus. In the semimetallic state, analyses of both the two-carrier model
and quantum oscillations indicate a systematic increase in the carrier
densities as pressure increases. An observed sign inversion of Hall resistivity
at low magnetic fields suggests the existence of high mobility electrons
(\sim105 cm2 V-1 s-1) that is roughly ten times larger than that of holes, in
the semimetallic black phosphorus. We conclude that the extremely large
positive magnetoresistance that has been observed in semimetallic state cannot
be reproduced by a conventional two-carrier model.",1611.04277v2
2017-06-23,Fabrication of highly dense isotropic Nd-Fe-B bonded magnets via extrusion-based additive manufacturing,"Isotropic bonded magnets with a high loading fraction of 70 vol.% Nd-Fe-B are
fabricated via an extrusion-based additive manufacturing, or 3D printing system
that enables rapid production of large parts for the first time. The density of
the printed magnet is 5.15 g/cm3. The room temperature magnetic properties are:
intrinsic coercivity Hci = 8.9 kOe (708.2 kA/m), remanence Br = 5.8 kG (0.58
Tesla), and energy product (BH)max = 7.3 MGOe (58.1 kJ/m3). The as-printed
magnets are then coated with two types of polymers, both of which improve the
thermal stability at 127 {\deg}C as revealed by flux aging loss measurements.
Tensile tests performed at 25 {\deg}C and 100 {\deg}C show that the ultimate
tensile stress (UTS) increases with increasing loading fraction of the magnet
powder, and decreases with increasing temperature. AC magnetic susceptibility
and resistivity measurements show that the 3D printed Nd-Fe-B bonded magnets
exhibit extremely low eddy current loss and high resistivity. Finally, we show
that through back electromotive force measurements that motors installed with
3D printed Nd-Fe-B magnets exhibit similar performance as compared to those
installed with sintered ferrites.",1706.07792v1
2017-10-11,Pressure Induced Superconductivity in the New Compound ScZrCo1-$δ$,"It is widely perceived that the correlation effect may play an important role
in several unconventional superconducting families, such as cuprate, iron-based
and heavy-fermion superconductors. The application of high pressure can tune
the ground state properties and balance the localization and itineracy of
electrons in correlated systems, which may trigger unconventional
superconductivity. Moreover, non-centrosymmetric structure may induce the spin
triplet pairing which is very rare in nature. Here, we report a new compound
ScZrCo1-${\delta}$ crystallizing in the Ti2Ni structure with the space group of
FD3-MS without a spatial inversion center. The resistivity of the material at
ambient pressure shows a bad metal and weak semiconducting behavior.
Furthermore, specific heat and magnetic susceptibility measurements yield a
rather large value of Wilson ratio ~4.47. Both suggest a ground state with
correlation effect. By applying pressure, the up-going behavior of resistivity
in lowering temperature at ambient pressure is suppressed and gradually it
becomes metallic. At a pressure of about 19.5 GPa superconductivity emerges. Up
to 36.05 GPa, a superconducting transition at about 3.6 K with a quite high
upper critical field is observed. Our discovery here provides a new platform
for investigating the relationship between correlation effect and
superconductivity.",1710.04047v1
2019-05-07,Nonsaturating magnetoresistance and nontrivial band topology of type-II Weyl semimetal NbIrTe4,"Weyl semimetals, characterized by nodal points in the bulk and Fermi arc
states on the surface, have recently attracted extensive attention due to the
potential application on low energy consumption electronic materials. In this
report, the thermodynamic and transport properties of a theoretically predicted
Weyl semimetal NbIrTe4 is measured in high magnetic fields up to 35 T and low
temperatures down to 0.4 K. Remarkably, NbIrTe4 exhibits a nonsaturating
transverse magnetoresistance which follows a power-law dependence in B.
Low-field Hall measurements reveal that hole-like carriers dominate the
transport for T $>$ 80 K, while the significant enhancement of electron
mobilities with lowering T results in a non-negligible contribution from
electron-like carriers which is responsible for the observed non-linear Hall
resistivity at low T. The Shubnikov-de Haas oscillations of the Hall
resistivity under high B give the light effective masses of charge carriers and
the nontrivial Berry phase associated with Weyl fermions. Further
first-principles calculations confirm the existence of 16 Weyl points located
at kz = 0, $\pm$0.02 and $\pm$0.2 planes in the Brillouin zone.",1905.02455v1
2014-08-29,Exotic Kondo crossover in a wide temperature region in the topological Kondo insulator SmB6 revealed by high-resolution ARPES,"Temperature dependence of the electronic structure of SmB6 is studied by
high-resolution ARPES down to 1 K. We demonstrate that there is no essential
difference for the dispersions of the surface states below and above the
resistivity saturating anomaly (~ 3.5 K). Quantitative analyses of the surface
states indicate that the quasi-particle scattering rate increases linearly as a
function of temperature and binding energy, which differs from Fermi-Liquid
behavior. Most intriguingly, we observe that the hybridization between the d
and f states builds gradually over a wide temperature region (30 K < T < 110
K). The surface states appear when the hybridization starts to develop. Our
detailed temperature-dependence results give a complete interpretation of the
exotic resistivity result of SmB6, as well as the discrepancies among
experimental results concerning the temperature regions in which the
topological surface states emerge and the Kondo gap opens, and give new
insights into the exotic Kondo crossover and its relationship with the
topological surface states in the topological Kondo insulator SmB6.",1408.7090v1
2018-10-08,Correlation between scale-invariant normal state resistivity and superconductivity in an electron-doped cuprate,"An understanding of the normal state in the high-temperature superconducting
cuprates is crucial to the ultimate understanding of the long-standing problem
of the origin of the superconductivity itself. This so-called strange metal
state is thought to be associated with a quantum critical point (QCP) hidden
beneath the superconductivity(1,2). In electron-doped cuprates in contrast to
hole-doped cuprates it is possible to access the normal state at very low
temperatures and low magnetic fields to study this putative QCP and to probe
the T~0 K state of these materials(3,4). We report measurements of the low
temperature normal state magnetoresistance (MR) of the n-type cuprate system
La2-xCexCuO4 (LCCO) and find that it is characterized by a linear-in-field
behavior, which follows a scaling relation with applied field and temperature,
for doping (x) above the putative QCP (x= 0.14)(5). This unconventional
behavior suggests that magnetic fields probe the same physics that gives rise
to the anomalous low-temperature linear-in-T resistivity(4). The magnitude of
the linear MR decreases as Tc decreases and goes to zero at the end of the
superconducting dome (x ~0.175) above which a conventional quadratic MR is
found. These results show that there is a strong correlation between the
quantum critical excitations of the strange metal state and the high-Tc
superconductivity.",1810.03499v1
2017-04-12,Fabrication of Simple Apparatus for Resistivity Measurement in High Temperature Range 300-620 K,"A simple and low cost apparatus has been designed and built to measure the
electrical resistivity, ($\rho$), of metal and semiconductors in 300-620 K
temperature range. The present design is suitable to do measurement on
rectangular bar sample by using conventional four-probe dc method. A small
heater is made on the sample mounting copper block to achieve the desired
temperature. Heat loss from sample holder is minimize by using very low thermal
conductive insulator block. This unique design of heater and minimized heat
loss from sample platform provide uniform sample temperature and also have very
good thermal stability during the measurement. The electrical contacts of
current leads and potential probes on the sample are done by using very thin
(42 SWG) copper wires and high temperature silver paste. The use of limited
components and small heater design make present instrument very simple, light
weight, easy to sample mount, small in size, and low cost. To calibrate the
instrument pure nickel sample was used, and two other materials
La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) and LaCoO$_{3}$ (LCO) were also
characterized to demonstrate the accuracy of this set-up. $\rho$(T) behavior on
these samples were found to be in good agreement with the reported data. The
metal-insulator transition for LSMO (T$_{MI}$ = $\sim$358 K) and the
insulator-metal transition for LCO (T$_{IM}$ = $\sim$540 K) were clearly
observed and these transitions temperature were also consistent with those
reported in literature.",1704.04122v1
2019-03-15,Enhanced Tunnelling in a Hybrid of Single-Walled Carbon Nanotubes and Graphene,"Transparent and conductive films (TCFs) are of great technological
importance. The high transmittance, electrical conductivity and mechanical
strength make single-walled carbon nanotubes (SWCNTs) a good candidate for
their raw material. Despite the ballistic transport in individual SWCNTs,
however, the electrical conductivity of their networks is limited by low
efficiency of charge tunneling between the tube elements. Here, we demonstrate
that the nanotube network sheet resistance at high optical transmittance is
decreased by more than 50% when fabricated on graphene and thus provides a
comparable improvement as widely adopted gold chloride ($\mathrm{AuCl_3}$)
doping. However, while Raman spectroscopy reveals substantial changes in
spectral features of doped nanotubes, no similar effect is observed in presence
of graphene. Instead, temperature dependent transport measurements indicate
that graphene substrate reduces the tunneling barrier heights while its
parallel conductivity contribution is almost negligible. Finally, we show that
combining the graphene substrate and $\mathrm{AuCl_3}$ doping, the SWCNT thin
films can exhibit sheet resistance as low as 36 $\Omega$/sq. at 90%
transmittance.",1903.06449v1
2019-04-04,Anomalous high-magnetic field electronic state of the nematic superconductors FeSe$_{1-x}$S$_x$,"Understanding superconductivity requires detailed knowledge of the normal
electronic state from which it emerges. A nematic electronic state that breaks
the rotational symmetry of the lattice can potentially promote unique
scattering relevant for superconductivity. Here, we investigate the normal
transport of superconducting FeSe$_{1-x}$S$_x$ across a nematic phase
transition using high magnetic fields up to 69 T to establish the temperature
and field-dependencies. We find that the nematic state is an anomalous
non-Fermi liquid, dominated by a linear resistivity at low temperatures that
can transform into a Fermi liquid, depending on the composition $x$ and the
impurity level. Near the nematic end point, we find an extended temperature
regime with $T^{1.5}$ resistivity. The transverse magnetoresistance inside the
nematic phase has as a $H^{1.55}$ dependence over a large magnetic field range
and it displays an unusual peak at low temperatures inside the nematic phase.
Our study reveals anomalous transport inside the nematic phase, driven by the
subtle interplay between the changes in the electronic structure of a
multi-band system and the unusual scattering processes affected by large
magnetic fields and disorder",1904.02522v1
2019-08-13,Magnetization Current Simulation of High Temperature Bulk Superconductors Using A-V-A Formulation and Iterative Algorithm Method: Critical State Model and Flux Creep Model,"In this work we will introduce the A-V-A formulation based iterative
algorithm method (IAM) for simulating the magnetization current of high
temperature superconductors. This new method embedded in ANSYS can simulate the
critical state model by forcing the trapped current density to the critical
current density Jc for all meshed superconducting elements after each iterative
load step, as well as simulate the flux creep model by updating the E-J power
law based resistivity values. The simulation results of a disk-shaped ReBCO
bulk during zero field cooling (ZFC) or field cooling (FC) magnetization agree
well with the simulation results from using the H-formulation in COMSOL. The
computation time is shortened by using the A-V formulation in superconductor
areas and the A-formulation in non-superconductor areas. This iterative method
is further proved friendly for adding ferromagnetic materials into the FEA
model or taking into account the magnetic field-dependent or mechanical
strain-related critical current density of the superconductors. The influence
factors for the magnetization simulation, including the specified iterative
load steps, the initial resistivity, the ramping time and the updating
coefficient, are discussed in detail. The A-V-A formulation based IAM,
implemented in ANSYS, shows its unique advantages in adjustable computation
time, multi-frame restart analysis and easy-convergence.",1908.04640v2
2015-07-17,Study of the Effects of High-Energy Proton Beams on Escherichia Coli,"Antibiotic-resistant bacterial infection becomes one of the most serious
risks to public health care today. However, discouragingly, the development of
new antibiotics has been little progressed over the last decade. There is an
urgent need of the alternative approaches to treat the antibiotic-resistant
bacteria. The novel methods, which include photothermal therapy based on gold
nano-materials and ionizing radiation such as X-rays and gamma rays, have been
reported. Studies of the effects of high-energy proton radiation on bacteria
are mainly focused on Bacillus species and its spores. The effect of proton
beams on Escherichia coli (E. coli) has been limitedly reported. The
Escherichia coli is an important biological tool to obtain the metabolic and
genetic information and also a common model microorganism for studying toxicity
and antimicrobial activity. In addition, E. coli is a common bacterium in the
intestinal tract of mammals. Herein, the morphological and physiological
changes of E. coli after proton irradiation were investigated. The diluted
solutions of the cells were used for proton beam radiation. LB agar plates were
used to count the number of colonies formed. The growing profile of the cells
was monitored by optical density at 600 nm. The morphology of the irradiated
cells was analyzed with optical microscope. Microarray analysis was performed
to examine the gene expression changes between irradiated samples and control
samples without irradiation.",1507.04863v1
2020-12-02,Incoherent transport across the strange metal regime of highly overdoped cuprates,"Strange metals possess highly unconventional transport characteristics, such
as a linear-in-temperature ($T$) resistivity, an inverse Hall angle that varies
as $T^2$ and a linear-in-field ($H$) magnetoresistance. Identifying the origin
of these collective anomalies has proved profoundly challenging, even in
materials such as the hole-doped cuprates that possess a simple band structure.
The prevailing dogma is that strange metallicity in the cuprates is tied to a
quantum critical point at a doping $p*$ inside the superconducting dome. Here,
we study the high-field in-plane magnetoresistance of two superconducting
cuprate families at doping levels beyond $p*$. At all dopings, the
magnetoresistance exhibits quadrature scaling and becomes linear at high $H/T$
ratios. Moreover, its magnitude is found to be much larger than predicted by
conventional theory and insensitive to both impurity scattering and magnetic
field orientation. These observations, coupled with analysis of the zero-field
and Hall resistivities, suggest that despite having a single band, the cuprate
strange metal phase hosts two charge sectors, one containing coherent
quasiparticles, the other scale-invariant `Planckian' dissipators.",2012.01208v2
2021-11-16,Orbital Selective Kondo Effect in Heavy Fermion Superconductor UTe$_{2}$,"It has been a great challenge to explore many-body effects in heavy fermion
systems with $ab$-$initio$ approaches. We computed the electronic structure of
UTe$_{2}$ without purposive judgements, such as intentional selection of
on-site Coulomb interaction and disregarding spin-orbit coupling. We show that
U-5$f$ electrons are highly localized in the paramagnetic normal state, giving
rise to the Kondo effect. It is also found that the hybridization between
U-5$f$ and U-6$d$ predominantly in the orthorhombic $ab$-plane is responsible
for the high-temperature Kondo effect. In contrast, the hybridization between
U-5$f$ and Te-5$p$ along the $c$-axis manifests the Kondo scattering at a much
lower temperature, which could be responsible for the low-temperature upturn of
the $c$-axis resistivity. Our results show that the electron correlation in
UTe$_2$ is orbital selective, which naturally elucidates the recent
experimental observations of anomalous temperature dependence of resistivity.
Furthermore, we suggest that the Kondo effect is suppressed at high pressure
owing to weak localization of magnetic moments, which results from enhanced
U-5$f$ electron hopping.",2111.08800v4
2022-07-10,Engineering underdoped CuO$_2$ nanoribbons in nm-thick $a$-axis YBa$_2$Cu$_3$O$_{7-δ}$ films,"In underdoped cuprate high $T_{\mathrm{c}}$ superconductors, various local
orders and symmetry breaking states, in addition to superconductivity, reside
in the CuO$_2$ planes. The confinement of the CuO$_2$ planes can therefore play
a fundamental role in modifying the hierarchy between the various orders and
their intertwining with superconductivity. Here we present the growth of
$a$-axis oriented YBa$_2$Cu$_3$O$_{7-\delta}$ films, spanning the whole
underdoped side of the phase diagram. In these samples, the CuO$_2$ planes are
confined by the film thickness, effectively forming unit-cell-thick
nanoribbons. The unidirectional confinement at the nanoscale enhances the
in-plane anisotropy of the films. By X-ray diffraction and resistance vs
temperature measurements, we have discovered the suppression of the
orthorhombic-to-tetragonal transition at low dopings, and a very high
anisotropy of the normal state resistance in the $b$-$c$ plane, the latter
being connected to a weak coupling between adjacent CuO$_2$ nanoribbons. These
findings show that the samples we have grown represent a novel system,
different from the bulk, where future experiments can possibly shed light on
the rich and mysterious physics occurring within the CuO$_2$ planes.",2207.04541v3
2022-12-11,Strain induced variations in transport and optical properties of SrVO$_3$: a DFT+U study,"First-principles calculations based on density functional theory + Hubbard U
(DFT+U) approach have been carried out to study the strain induced variations
in the optical and transport properties of the correlated perovskite SrVO$_3$.
By virtue of its conductivity, high carrier mobility and optical transparency,
SrVO$_3$ can be used as a potential replacement of indium tin oxide (ITO) as a
transparent conductor. As strain tuning is an effective way to tune the
electron-electron correlations in correlated oxides, the epitaxial strain
induced variations in V-3d bandwidth, band center shift and band splitting at
high symmetry points (${\Gamma}$, R) in SrVO$_3$ are investigated. The
alterations in resistivity, carrier concentration, Hall coefficient and plasma
frequency with applied strain are also elucidated. Our calculations revealed
that under tensile strain, the lifting of the threefold degeneracy of
3d-t$_{2g}$ orbital and d-band narrowing reinforces a relatively less
conducting state thus limiting the $\omega_P$ to lower frequencies. On the
contrary, in case of compressive strain the d-band widening predominates
leading to an increase in carrier concentration and decrease in resistivity
enhancing the metallic state. As a result, $\omega_P$ is increased to higher
frequencies which decreases the optical transparency window. Hence, our results
and findings clearly demonstrate the interdependence between the optical and
transport properties, and provides a detailed mechanism to tune the
optoelectronic properties of SrVO$_3$ for its applications as a transparent
conducting oxide.",2212.05449v1
2022-12-19,Optical Switching in Tb/Co-Multilayer Based Nanoscale Magnetic Tunnel Junctions,"Magnetic tunnel junctions (MTJs) are elementary units of magnetic memory
devices. For high-speed and low-power data storage and processing applications,
fast reversal by an ultrashort laser pulse is extremely important. We
demonstrate optical switching of Tb/Comultilayer-based nanoscale MTJs by
combining optical writing and electrical read-out methods. A 90 fs-long laser
pulse switches the magnetization of the storage layer (SL). The change in
magnetoresistance between the SL and a reference layer (RL) is probed
electrically across the tunnel barrier. Single-shot switching is demonstrated
by varying the cell diameter from 300 nm to 20 nm. The anisotropy,
magnetostatic coupling, and switching probability exhibit cell-size dependence.
By suitable association of laser fluence and magnetic field, successive
commutation between high-resistance and low-resistance states is achieved. The
switching dynamics in a continuous film is probed with the magneto-optical Kerr
effect technique. Our experimental findings provide strong support for the
growing interest in ultrafast spintronic devices.",2212.10361v1
2023-02-02,Controlling the Skyrmion Density and Size for Quantized Convolutional Neural Networks,"Skyrmion devices show energy efficient and high integration data storage and
computing capabilities. Herein, we present the results of experimental and
micromagnetic investigations of the creation and stability of magnetic
skyrmions in the Ta/IrMn/CoFeB/MgO thin film system. We investigate the
magnetic-field dependence of the skyrmion density and size using polar magneto
optical Kerr effect MOKE microscopy supported by a micromagnetic study. The
evolution of the topological charge with time under a magnetic field is
investigated, and the transformation dynamics are explained. Furthermore,
considering the voltage control of these skyrmion devices, we evaluate the
dependence of the skyrmion size and density on the Dzyaloshinskii Moriya
interaction and the magnetic anisotropy. We furthermore propose a skyrmion
based synaptic device based on the results of the MOKE and micromagnetic
investigations. We demonstrate the spin-orbit torque controlled discrete
topological resistance states with high linearity and uniformity in the device.
The discrete nature of the topological resistance makes it a good candidate to
realize hardware implementation of weight quantization in a quantized neural
network (QNN). The neural network is trained and tested on the CIFAR10 dataset,
where the devices act as synapses to achieve a recognition accuracy of 87%,
which is comparable to the result of ideal software-based methods.",2302.01390v1
2023-03-04,High pressure ferroelectric-like semi-metallic state in $Eu-$doped $BaTiO_3$,"We have conducted a detailed high-pressure (HP) investigation on $Eu-$doped
$BaTiO_3$ using angle-resolved x-ray diffraction, Raman spectroscopy,
dielectric permittivity and dc resistance measurements. The x-ray diffraction
data analysis shows a pressure-induced structural phase transition from the
ambient tetragonal to the mixed cubic and tetragonal phase above 1.4 GPa. The
tetragonality of the sample due to the internal deformation of the $TiO_6$
octahedra caused by charge difference from Eu doping cannot be lifted upon by
pressure. Softening, weakening, and disappearance of low-frequency Raman modes
indicate ferroelectric tetragonal to the paraelectric cubic phase transition.
But the pressure-induced increase in the intensity of [E(LO), A1(LO)] and the
octahedral breathing modes indicate the local structural inhomogeneity remains
in the crystal and is responsible for spontaneous polarization in the sample.
Low-frequency electronic scattering response suggests the pressure-induced
carrier delocalization, leading to a semi-metallic state in the system. Our HP
dielectric constant and dc resistance data can be explained by the presence of
pressure-induced localized clusters of microscopic ferroelectric ordering. Our
results suggest HP phase coexistence leads to a ferroelectric-like
semi-metallic state in $Eu-$doped $BaTiO_3$ under the extreme quantum limit.",2303.02329v2
2023-09-21,"High-Conductance, Ohmic-like HfZrO$_4$ Ferroelectric Memristor","The persistent and switchable polarization of ferroelectric materials based
on HfO$_2$-based ferroelectric compounds, compatible with large-scale
integration, are attractive synaptic elements for neuromorphic computing. To
achieve a record current density of 0.01 A/cm$^2$ (at a read voltage of 80 mV)
as well as ideal memristive behavior (linear current-voltage relation and
analog resistive switching), devices based on an ultra-thin (2.7 nm thick),
polycrystalline HfZrO$_4$ ferroelectric layer are fabricated by Atomic Layer
Deposition. The use of a semiconducting oxide interlayer (WO$_{x<3}$) at one of
the interfaces, induces an asymmetric energy profile upon ferroelectric
polarization reversal and thus the long-term potentiation / depression
(conductance increase / decrease) of interest. Moreover, it favors the stable
retention of both the low and the high resistive states. Thanks to the low
operating voltage (<3.5 V), programming requires less than 10${^-12}$ J for 20
ns long pulses. Remarkably, the memristors show no wake-up or fatigue effect.",2309.12070v1
2023-12-27,"Inkjet-Printed High-Yield, Reconfigurable, and Recyclable Memristors on Paper","Reconfigurable memristors featuring neural and synaptic functions hold great
potential for neuromorphic circuits by simplifying system architecture, cutting
power consumption, and boosting computational efficiency. Their additive
manufacturing on sustainable substrates offers unique advantages for future
electronics, including low environmental impact. Here, exploiting
structure-property relationship of MoS2 nanoflake-based resistive layer, we
present paper-based, inkjet-printed, reconfigurable memristors. With >90% yield
from a 16x65 device array, our memristors demonstrate robust resistive
switching, with $>10^5$ ON-OFF ratio and <0.5 V operation in non-volatile
state. Through modulation of compliance current, the devices transition into
volatile state, with only 50 pW switching power consumption, rivalling
state-of-the-art metal oxide-based counterparts. We show device recyclability
and stable, reconfigurable operation following disassembly, material collection
and re-fabrication. We further demonstrate synaptic plasticity and neuronal
leaky integrate-and-fire functionality, with disposable applications in smart
packaging and simulated medical image diagnostics. Our work shows a sustainable
pathway towards printable, high-yield, reconfigurable neuromorphic devices,
with minimal environmental footprint.",2312.16501v1
2018-06-20,Linear-$T$ resistivity at high temperature,"The linear-$T$ resistivity is one of the characteristic and universal
properties of strange metals. There have been many progress in understanding it
from holographic perspective (gauge/gravity duality). In most holographic
models, the linear-$T$ resistivity is explained by the property of the infrared
geometry and valid at low temperature limit. On the other hand, experimentally,
the linear-$T$ resistivity is observed in a large range of temperatures, up to
room temperature. By using holographic models related to the Gubser-Rocha
model, we investigate how much the linear-$T$ resistivity is robust at higher
temperature above the superconducting phase transition temperature. We find
that strong momentum relaxation plays an important role to have a robust
linear-$T$ resistivity up to high temperature.",1806.07739v2
2018-07-18,Multi-band effects in in-plane resistivity anisotropy of strain-detwinned disordered Ba(Fe$_{1-x}$Ru$_{x}$)$_{2}$As$_{2}$,"In-plane resistivity anisotropy was measured in strain-detwinned as-grown and
partially annealed samples of isovalently-substituted
$\mathrm{Ba(Fe_{1-x}Ru_{x})_{2}As_{2}}$ ($0<x \leq 0.125$) and the results were
contrasted with previous reports on anneal samples with low residual
resistivity. In samples with high residual resistivity, detwinned with
application of strain, the difference of the two components of in-plane
resistivity in the orthorhombic phase, $\rho_a -\rho_b$, was found to obey
Matthiessen rule irrespective of sample composition, which is in stark contrast
with observations on annealed samples. Our findings are consistent with
two-band transport model in which contribution from high mobility carriers of
small pockets of the Fermi surface has negligible anisotropy of residual
resistivity and is eliminated by disorder. Our finding suggests that
magnetic/nematic order has dramatically different effect on different parts of
the Fermi surface. It predominantly affects inelastic scattering for small
pocket high mobility carriers and elastic impurity scattering for larger sheets
of the Fermi surface.",1807.07130v1
2022-07-21,Energy-scale competition in the Hall resistivity of a strange metal,"Anomalous transport behavior -- both longitudinal and Hall -- is the defining
characteristic of the strange-metal state of High-Tc cuprates. The temperature,
frequency, and magnetic field dependence of the resistivity is understood
within strange metal phenomenology as resulting from energy-scale competition
to set the inelastic relaxation rate. The anomalously strong temperature
dependence of the Hall coefficient, however, is at odds with this
phenomenology. Here we report measurements of the Hall resistivity in the
strange metal state of cuprates over a broad range of magnetic fields and
temperatures. The observed field and temperature dependent Hall resistivity at
very high magnetic fields reveals a distinct high-field regime which is
controlled by energy-scale competition. This extends the strange metal
phenomenology in the cuprates to include the Hall resistivity and suggests, in
particular, that the direct effect of magnetic field on the relaxation dynamics
of quantum fluctuations may be at least partially responsible for the anomalous
Hall resistivity of the strange metal state.",2207.10244v1
2022-04-26,Flexibility of Fluorinated Graphene-Based Materials,"The resistivity of different films and structures containing fluorinated
graphene (FG) flakes and chemical vapor deposition (CVD) grown graphene of
various fluorination degrees under tensile and compressive strains due to
bending deformations was studied. Graphene and multilayer graphene films grown
by means of the CVD method were transferred onto the flexible substrate by
laminating and were subjected to fluorination. They demonstrated a weak
fluorination degree (F/C lower 20%). Compressive strains led to a strong
(one-two orders of magnitude) decrease in the resistivity in both cases, which
was most likely connected with the formation of additional conductive paths
through fluorinated graphene. Tensile strain up to 3% caused by the bending of
both types of CVD-grown FG led to a constant value of the resistivity or to an
irreversible increase in the resistivity under repeated strain cycles. In the
case of the structures with the FG thin film printed on polyvinyl alcohol, a
stable bipolar resistive switching was observed up to 6.5% of the tensile
strain (bending radius was 2 mm). The excellent performance of the crossbar
memristor structures under tensile strain shows that the FG films and
structures created from suspension are especially promising for flexible
electronics.",2204.12596v1
2021-03-18,Topological Semimetals for Scaled Back-End-Of-Line Interconnect Beyond Cu,"The resistance bottleneck in metal-interconnect scaling calls for new
interconnect materials. This paper explores topological semimetals as a
potential solution. After reviewing the desirable properties of topological
semimetals for back-end-of-line (BEOL) interconnects, we use CoSi as an example
to demonstrate the decreasing resistance-area product with scaling and provide
material-search guidelines.",2103.10505v1
2021-08-31,Magnetoresistance and Scaling Laws in Type-II Weyl Semimetal WP_2,"Topological materials with extremely large magnetoresistance exhibit a
prognostic feature of resistivity turn-on behaviour. This occurs when the
temperature dependence of resistivity changes from metallic to semiconducting
characteristics on application of external magnetic field above a threshold
value. Here, we study the magneto-transport properties of type-II Weyl
Semimetal WP2. We find that semi-classical theories of magnetoresistance are
consistent with our data without the need to invoke topological surface states.
Our findings in this work provides an alternative basis to understand the
temperature dependence of magnetoresistance in topological materials.",2108.13981v1
2017-11-29,Coexistence of superconductivity and charge-density wave in the quasi-one-dimensional material HfTe3,"We present the first experimental evidence for metallicity, superconductivity
(SC) and the co-existence of charge density waves (CDW) in the
quasi-one-dimensional material HfTe3. The existence of such phenomena is a
typical characteristic of the transition metal chalcogenides however, without
the application of hydrostatic pressure/chemical doping, it is rare for a
material to exhibit the co-existence of both states. Materials such as HfTe3
can therefore provide us with a unique insight into the relationship between
these multiple ordered states. By improving on the original synthesis
conditions, we have successfully synthesised single phase HfTe3 and confirmed
the resultant structure by performing Rietveld refinement. Using low
temperature resistivity measurements, we provide the first experimental
evidence of SC at ~1.4 K as well as a resistive anomaly indicative of a CDW
formation at ~82 K. By the application of hydrostatic-pressure, the resistivity
anomaly shifts to higher temperature. The results show that HfTe3 is a
promising new material to help study the relationship between SC and CDW.",1711.10628v1
1995-03-08,Model of C-Axis Resistivity of High-$\Tc$ Cuprates,"We propose a simple model which accounts for the major features and
systematics of experiments on the $c$-axis resistivity, $\rho_c$, for $\lsco$,
$\ybco$ and $\bsco $. We argue that the $c$-axis resistivity can be separated
into contributions from in-plane dephasing and the $c$-axis ``barrier''
scattering processes, with the low temperature semiconductor-like behavior of
$\rho_c$ arising from the suppression of the in-plane density of states
measured by in-plane magnetic Knight shift experiments. We report on
predictions for $\rho_c$ in impurity-doped $\ybco$ materials.",9503044v1
1998-09-29,Point contact spectroscopy and temperature dependence of resistivity of metallic sodium tungsten bronzes -Role of optical phonons,"In this paper we report the results of electrical resistivity (1.5K < T
<300K) and point contact spectroscopy (PCS) measurements on single crystals of
metallic sodium tungsten bronze with varying sodium content. We have shown that
the electron-phonon coupling function as measured through PCS can explain
quantitatively the large temperature dependence of resistivity $\rho$ seen in
these materials over the entire temperature range. The electron-phonon coupling
function shows predominatly large peaks for phonon frequency range of 30meV <
$\omega$ 100meV which match well with the calculated optical phonon modes for
WO$_6$ octahedra. The integrated electron-phonon coupling constant $\lambda$
from this data is $\approx$ 0.25-0.45.",9809393v1
1998-11-24,Ac transport studies in polymers by a resistor network and transfer matrix approaches: application to polyaniline,"A statistical model of resistor network is proposed to describe a polymer
structure and to simulate the real and imaginary components of its ac
resistivity. It takes into account the polydispersiveness of the material as
well as intrachain and interchain charge transport processes. By the
application of a transfer matrix technique, it reproduces ac resistivity
measurements carried out with polyaniline films in different doping degrees and
at different temperatures. Our results indicate that interchain processes
govern the resistivity behavior in the low frequency region while, for higher
frequencies, intrachain mechanisms are dominant.",9811335v1
1999-02-22,"La substitution induced linear temperature dependence of electrical resistivity and Kondo behavior in the alloys, Ce_{2-x}La_{x}CoSi_{3}","The results of electrical resistivity, heat capacity and magnetic
susceptibility behavior of new class of alloys, Ce_{2-x}La_{x}CoSi_{3}, are
reported. The x= 0.0 alloy is mixed valent and La substitution for Ce (x= 0.25)
induces linear temperature dependence of resistivity at low temperatures, an
observation of relevance to the topic of non-Fermi liquid behavior. The
modifications of Kondo effect for all the alloys are also presented.",9902298v1
1999-04-06,Conductance of Distorted Carbon Nanotubes,"We have calculated the effects of structural distortions of armchair carbon
nanotubes on their electrical transport properties. We found that the bending
of the nanotubes decreases their transmission function in certain energy ranges
and leads to an increased electrical resistance. Electronic structure
calculations show that these energy ranges contain localized states with
significant $\sigma$-$\pi$ hybridization resulting from the increased curvature
produced by bending. Our calculations of the contact resistance show that the
large contact resistances observed for SWNTs are likely due to the weak
coupling of the NT to the metal in side bonded NT-metal configurations.",9904083v1
1999-07-31,"Characterisation, Raman, Magnetic and Resistivity measurements in polycrystalline samples of LaMnO3 doped with Cd","We report a study of polycrystalline samples of the family La1-xCdxMnO3+dwith
different percentage of Mn4+ ions. X-rays diffraction, Iodometric titration,
Raman, Magnetic and Electrical Resistivity measurements provide a general
characterisation of the physical properties. Results are qualitatively similar
to the ones found in Ca doped manganese perovskites.
  Key words: Cd, manganese perovskites, magnetoresistance, Raman, magnetic,
resistivity",9908006v2
2000-05-19,Interface resistance of disordered magnetic multilayers,"We study the effect of interface disorder on the spin-dependent interface
resistances of Co/Cu, Fe/Cr and Au/Ag multilayers using a newly developed
method for calculating transmission matrices from first-principles. The
efficient implementation using tight-binding linear-muffin-tin orbitals allows
us to model interface disorder using large lateral supercells whereby specular
and diffuse scattering are treated on an equal footing. Without introducing any
free parameters, quantitative agreement with experiment is obtained. We predict
that disorder {\it reduces} the majority-spin interface resistance of
Fe/Cr(100) multilayers by a factor 3.",0005314v1
2000-09-04,Magnon scattering processes and low temperature resistivity in CMR manganites,"Low temperature resistivity of CMR manganites is investigated. At the ground
state, conduction electrons are perfectly spin polarized, which is called
half-metallic. From one-magnon scattering processes, it is discussed that the
resistivity of a half metal as a function of temperature scales as rho(T) -
rho(0) propto T^3. We take (Nd,Tb,Sr)MnO_3 as an example to compare theory and
experiments. The result is in a good agreement.",0009036v1
2000-10-26,Magnetic-history-dependent nanostructural and resistivity changes in Pr0.5Ca0.5Mn0.98Cr0.02O3,"We show that nanostructure and resistivity of Pr0.5Ca0.5Mn0.98Cr0.02O3 are
sensitive to whether the sample is zero-field-cooled (ZFC) of field-cooled (FC)
either in the 'self magnetic field (H = 2 T)' of the electron microscope or
under the external magnetic field of 2 T. FC resistivity at H = 2 T is lower
than ZFC values below 140 K. The average value of the chare-orbital modulation
vector (q = 0.44) of the FC crystallites is lower than that of the ZFC
cystallites (q = 0.48) and the FC crystallites exhibit numerous defects like
discommensuration, dislocations and regios with loss of superstructures
compared to the ZFC crystallites.",0010427v1
2000-10-30,Theory of electrical spin injection: Tunnel contacts as a solution of the conductivity mismatch problem,"Theory of electrical spin injection from a ferromagnetic (FM) metal into a
normal (N) conductor is presented. We show that tunnel contacts (T) can
dramatically increase spin injection and solve the problem of the mismatch in
the conductivities of a FM metal and a semiconductor microstructure. We also
present explicit expressions for the spin-valve resistance of FM-T-N- and
FM-T-N-T-FM-junctions with tunnel contacts at the interfaces and show that the
resistance includes both positive and negative contributions (Kapitza
resistance and injection conductivity, respectively).",0010473v1
2001-11-09,"A common origin for the resistivity of Cd$_2$Re$_2$O$_7$, the cuprates, and Sr$_2$RuO$_4$?","We propose an explanation for the temperature dependence of the resistivity
of Cd$_2$Re$_2$O$_7$, including the regime above the structural phase
transition at $T$=200 $^o$K. The mechanism involved relies on the existence of
a strong van Hove singularity close to the Fermi surface, which is evidenced by
relevant band structure calculations. The same mechanism has successfully
described the $T$-linear resistivity of the cuprates and Sr$_2$RuO$_4$, and the
one-particle scattering rate in the former materials, as corroborated by recent
experiments. We describe a few predictions for Cd$_2$Re$_2$O$_7$ and
Cd$_2$Os$_2$O$_7$.",0111166v1
2002-04-09,"Electrical transport properties of bulk MgB2 materials synthesized by the electrolysis on fused mixtures of MgCl2, NaCl, KCl and MgB2O4","Electrolysis was carried out on fused mixtures of MgCl2, NaCl, KCl and MgB2O4
under an Ar flow at 600C. Electrical resistivity measurements for the grown
deposits show an onset of superconducting transition at 37 K in the absence of
applied magnetic field. The resistivity decreases down to zero below 32 K. From
an applied-field dependence of resistivity, an upper critical field and a
coherence length were calculated to be 9.7 T and 5.9 nm at 0 K, respectively.",0204208v1
2002-05-22,Scattering theory of interface resistance in magnetic multilayers,"The scattering theory of transport has to be applied with care in a diffuse
environment. Here we discuss how the scattering matrices of heterointerfaces
can be used to compute interface resistances of dirty magnetic multilayers.
First principles calculations of these interface resistances agree well with
experiments in the CPP (current perpendicular to the interface plane)
configuration.",0205452v1
2002-09-05,Magnetoresistance and Hall Effect in the Ferromagnetic Semiconductor GaMnAs,"The resistivity, temperature, and magnetic field dependence of the anomalous
Hall effect in a series of metallic Ga1-xMnxAs thin films with 0.015=<x=<0.08
is presented. A quadratic dependence of the anomalous Hall resistance on the
resistivity is observed, with a magnitude which is in agreement with Berry
phase theories of the anomalous Hall effect in dilute magnetic semiconductors.",0209123v1
2003-04-06,Microwave Residual Surface Resistance of Superconductors,"Two distinct models account for the microwave residual surface resistance of
superconducting cavities with equally good agreement with the measured
temperature and frequency dependence. In presenting his phonon-generation
model, Passow claimed that Rabinowitz' fluxoid power-loss model of residual
resistance does not fit the experimental data, whereas his does. In fact, the
two models have essentially the same temperature and frequency dependence.
Furthermore, Passow's phonon-generation model cannot explain the observed
sensitivity to details of sample preparation and history, while the fluxoid
model can.",0304139v1
2004-02-17,Peculiarities of the resistive transition in fractal superconducting structures,"The influence of fractal clusters of a normal phase on the current-voltage
characteristics of a percolation superconductor in the region of a resistive
transition has been studied. The clusters represent the aggregates of columnar
defects, which give rise to a correlated microscopic disorder in the system.
Dependencies of the static and dynamic resistance on the transport current are
obtained for an arbitrary fractal dimension of the cluster boundaries. It is
revealed that a mixed state of the vortex glass type is realized in the
superconducting system involved.",0402437v2
2005-04-08,Temperature dependent asymmetry of the nonlocal spin-injection resistance: evidence for spin non-conserving interface scattering,"We report nonlocal spin injection and detection experiments on mesoscopic
Co-Al2O3-Cu spin valves. We have observed a temperature dependent asymmetry in
the nonlocal resistance between parallel and antiparallel configurations of the
magnetic injector and detector. This strongly supports the existence of a
nonequilibrium resistance that depends on the relative orientation of the
detector magnetization and the nonequilibrium magnetization in the normal metal
providing evidence for increasing interface spin scattering with temperature.",0504201v2
2005-09-29,Charge-transfer polaron induced negative differential resistance and giant magnetoresistance in organic spintronics: A Su-Schrieffer-Heeger model study,"Combining the Su-Schrieffer-Heeger model and the non-equilibrium Green's
function formalism, we investigate the negative differential resistance effect
in organic spintronics at low temperature and interprete it with a self-doping
picture. A giant negative magnetoresistance exceeding 300% is theoretically
predicted as the results of the negative differential resistance effects.",0509761v2
2005-12-30,A Tunable Anomalous Hall Effect in a Non-Ferromagnetic System,"We measure the low-field Hall resistivity of a magnetically-doped
two-dimensional electron gas as a function of temperature and
electrically-gated carrier density. Comparing these results with the carrier
density extracted from Shubnikov-de Haas oscillations reveals an excess Hall
resistivity that increases with decreasing temperature. This excess Hall
resistivity qualitatively tracks the paramagnetic polarization of the sample,
in analogy to the ferromagnetic anomalous Hall effect. The data are consistent
with skew-scattering of carriers by disorder near the crossover to
localization.",0512730v1
2006-01-30,Magnetic Moment Softening and Domain Wall Resistance in Ni Nanowires,"Magnetic moments in atomic scale domain walls formed in nanoconstrictions and
nanowires are softened which affects dramatically the domain wall resistance.
We perform ab initio calculations of the electronic structure and conductance
of atomic-size Ni nanowires with domain walls only a few atomic lattice
constants wide. We show that the hybridization between noncollinear spin states
leads to a reduction of the magnetic moments in the domain wall. This magnetic
moment softening strongly enhances the domain wall resistance due to scattering
produced by the local perturbation of the electronic potential.",0601662v1
2006-08-10,"Friedel oscillations, impurity scattering and temperature dependence of resistivity in graphene","We show that Friedel oscillations (FO) in grapehene are strongly affected by
the chirality of electrons in this material. In particular, the FO of the
charge density around an impurity show a faster, $1/r^3$, decay than in
conventional 2D electron systems and do not contribute to a linear
temperature-dependent correction to the resistivity. In contrast, the FO of the
exchange field which surrounds atomically sharp defects breaking the hexagonal
symmetry of the honeycomb lattice lead to a negative linear T dependence of the
resistivity.",0608228v2
2006-10-19,"Magneto-resistive memory in ferromagnetic (Ga,Mn)As nanostructures","We show a novel magneto-resistive effect that appears in lithographically
shaped, three-arm nanostructure, fabricated from ferromagnetic (Ga,Mn)As
layers. The effect, related to a rearrangement of magnetic domain walls between
different pairs of arms in the structure, reveals as a dependence of zero-field
resistance on the direction of previously applied magnetic field. This effect
could allow designing devices with unique switching and memory properties.",0610535v1
2006-11-06,Unusual field and temperature dependence of Hall effect in graphene,"We calculate the classic Hall conductivity and mobility of the undoped and
doped (or in the gate voltage) graphene as a function of temperature, magnetic
field, and carrier concentration. Carrier collisions with defects and acoustic
phonons are taken into account. The Hall resistivity varies almost linearly
with temperature. The magnetic field dependence of resistivity and mobility is
anomalous in weak magnetic fields. There is the square root contribution from
the field in the resistivity. The Hall mobility diverges logarithmically with
the field for low doping.",0611147v2
2006-11-30,"Anisotropic magnetoresistance contribution to measured domain wall resistances of in-plane magnetised (Ga,Mn)As","We demonstrate the presence of an important anisotropic magnetoresistance
contribution to the domain wall resistance recently measured in thin-film
(Ga,Mn)As with in-plane magnetic anisotropy. Analytic results for simple domain
wall orientations supplemented by numerical results for more general cases show
this previously omitted contribution can largely explain the observed negative
resistance.",0611780v1
2006-12-16,Transmission Line Impedance of Carbon Nanotube Thin Films for Chemical Sensing,"We measure the resistance and frequency-dependent gate capacitance of carbon
nanotube (CNT) thin films in ambient, vacuum, and under low-pressure (10E-6
torr) analyte environments. We model the CNT film as an RC transmission line
and show that changes in the measured capacitance as a function of gate bias
and analyte pressure are consistent with changes in the transmission line
impedance due to changes in the CNT film resistivity alone; the electrostatic
gate capacitance of the CNT film does not depend on gate voltage or chemical
analyte adsorption. However, the CNT film resistance is enormously sensitive to
low pressure analyte exposure.",0612432v1
2007-03-01,Bias-dependent Contact Resistance in Rubrene Single-Crystal Field-Effect Transistors,"We report a systematic study of the bias-dependent contact resistance in
rubrene single-crystal field-effect transistors with Ni, Co, Cu, Au, and Pt
electrodes. We show that the reproducibility in the values of contact
resistance strongly depends on the metal, ranging from a factor of two for Ni
to more than three orders of magnitude for Au. Surprisingly, FETs with Ni, Co,
and Cu contacts exhibits an unexpected reproducibility of the bias-dependent
differential conductance of the contacts, once this has been normalized to the
value measured at zero bias. This reproducibility may enable the study of
microscopic carrier injection processes into organic semiconductors.",0703029v1
2004-02-14,Theory of resistor networks: The two-point resistance,"The resistance between arbitrary two nodes in a resistor network is obtained
in terms of the eigenvalues and eigenfunctions of the Laplacian matrix
associated with the network. Explicit formulas for two-point resistances are
deduced for regular lattices in one, two, and three dimensions under various
boundary conditions including that of a Moebius strip and a Klein bottle. The
emphasis is on lattices of finite sizes. We also deduce summation and product
identities which can be used to analyze large-size expansions of two-and-higher
dimensional lattices.",0402038v2
2004-12-17,Introductory physics: The new scholasticism,"Most introductory physics textbooks neglect air resistance in situations
where an astute student can observe that it dominates the dynamics. We give
examples from many books. Using dimensional analysis we discuss how to estimate
the relative importance of air resistance and gravity. The discussion can be
used to mitigate the baleful influence of these textbooks. Incorrectly
neglecting air resistance is one of their many unphysical teachings. Shouldn't
a physics textbook teach correct physics?",0412107v2
2008-10-22,Scaling behaviors of RESET voltages and currents in unipolar resistance switching,"Unipolar switching phenomena have attracted a great deal of recent attention,
but the wide distributions of switching voltages still pose major obstacles for
scientific advancement and practical applications. Using NiO capacitors, we
investigated the distributions of the RESET voltage and current. We found that
they scaled with the resistance value Ro in the low resistance state, and that
the scaling exponents varied at Ro = 30 Ohm. We explain these intriguing
scaling behaviors and their crossovers by analogy with percolation theory. We
show that the connectivity of conducting filaments plays a crucial role in the
RESET process.",0810.4043v1
2008-10-29,FeTe as a candidate material for new iron-based superconductor,"Tetragonal FeSe is a superconductor with a transition temperature Tc of 8 K
and shows a huge enhancement of Tc with applying pressure. Tetragonal FeTe has
a structure very analogous to superconducting FeSe, but does not show
superconducting transition. We investigated the pressure effect of resistivity
on FeTe. The resistivity at room temperature decreased with increasing
pressure. An anomaly in resistivity around 80 K shifted towards a lower
temperature with increasing pressure.",0810.5191v1
2008-11-27,Electrical resistance of Ni nanowires (diameter greater than or equal to 20 nm) near the Curie Temperatures,"In this letter we report electrical transport measurements on nickel
nanowires of diameters down to 20 nm in the region close to its
paramagnetic-ferromagnetic transition temperature T_C (reduced temperature|t|
less than or equal to 0.001). The data analysis done in the frame work of
critical behavior of resistance near TC shows that the critical behavior
persists even down to the lowest diameter wire of 20 nm. However, there is a
suppression of the critical behavior of the resistivity as measured by the
critical exponents and the parameters quantifying the anomaly. The spin system
shows approach to a quasi one-dimensional spin system.",0811.4544v1
2009-01-04,Current Oscillations and Negative Resistances in Crossed Carbon Nanotubes Suspended Over a Dielectric Trench,"An oscillatory dependence of the drain current on the drain voltage is found
in a nanostructure consisting of two crossing semiconductor carbon nanotubes
that are suspended over a dielectric trench, which is backed by a doped silicon
substrate that acts as a gate. Alternating positive and negative differential
resistance regions are generated as a function of the drain source values and
can be slightly shifted by the gate voltage. Moreover, the negative
differential resistance is retrieved in a large bandwidth, of up to 100 MHz,
when the structure is excited with ac signals.",0901.0363v1
2009-01-05,Contact resistance in graphene-based devices,"We report a systematic study of the contact resistance present at the
interface between a metal (Ti) and graphene layers of different, known
thickness. By comparing devices fabricated on 11 graphene flakes we demonstrate
that the contact resistance is quantitatively the same for single-, bi-, and
tri-layer graphene ($\sim800 \pm 200 \Omega \mu m$), and is in all cases
independent of gate voltage and temperature. We argue that the observed
behavior is due to charge transfer from the metal, causing the Fermi level in
the graphene region under the contacts to shift far away from the charge
neutrality point.",0901.0485v1
2009-03-09,Predictability of reset switching voltages in unipolar resistance switching,"In unipolar resistance switching of NiO capacitors, Joule heating in the
conducting channels should cause a strong nonlinearity in the low resistance
state current-voltage (I-V) curves. Due to the percolating nature of the
conducting channels, the reset current IR, can be scaled to the nonlinear
coefficient Bo of the I-V curves. This scaling relationship can be used to
predict reset voltages, independent of NiO capacitor size; it can also be
applied to TiO2 and FeOy capacitors. Using this relation, we developed an error
correction scheme to provide a clear window for separating reset and set
voltages in memory operations.",0903.1490v1
2009-03-17,Electronic transport in ferromagnetic conductors with inhomogeneous magnetic order parameter -- domain-wall resistance,"We microscopically derive transport equations for the conduction electrons in
ferromagnetic materials with an inhomogeneous magnetization profile. Our
quantum kinetic approach includes elastic scattering and anisotropic spin-flip
scattering at magnetic impurities. In the diffusive limit, we calculate the
resistance through a domain wall and find that the domain-wall resistance can
be positive or negative. In the limit of long domain walls we derive analytical
expressions and compare them with existing works, which used less general
models or different theoretical frameworks.",0903.3033v2
2009-06-02,Effect of annealing on the magnetic and superconducting properties of single-crystalline UCoGe,"Single-crystals of the new ferromagnetic superconductor UCoGe have been
grown. The quality of as-grown samples can be significantly improved by a
heat-treatment procedure, which increases the residual resistance ratio (RRR)
from ~5 to ~30. Magnetization and resistivity measurements show the annealed
samples have a sharp ferromagnetic transition with a Curie temperature T_C is
2.8 K. The ordered moment of 0.06 mu_B is directed along the orthorhombic
c-axis. Superconductivity is found below a resistive transition temperature T_s
= 0.65 K.",0906.0497v1
2009-07-21,Memristive switching of MgO based magnetic tunnel junctions,"Here we demonstrate that both, tunnel magneto resistance (TMR) and resistive
switching (RS), can be observed simultaneously in nano-scale magnetic tunnel
junctions. The devices show bipolar RS of 6 % and TMR ratios of about 100 %.
For each magnetic state, multiple resistive sates are created depending on the
bias history which provides a method for multi-bit data storage and logic. The
electronic transport measurements are discussed in the framework of a
memristive system. Differently prepared MgO barriers are compared to gain
insight into the switching mechanism.",0907.3684v1
2010-03-03,In-situ direct visualization of irradiated e-beam patterns on unprocessed resists using atomic force microscopy,"We introduce an in-situ characterization method of resists used for e-beam
lithography. The technique is based on the application of an atomic force
microscope which is directly mounted below the cathode of an electron-beam
lithography system. We demonstrate that patterns irradiated by the e-beam can
be efficiently visualized and analyzed in surface topography directly after the
e-beam exposure. This in-situ analysis takes place without any development or
baking steps, and gives access to the chemical (or latent) image of the
irradiated resist.",1003.0796v1
2010-06-06,Spin Resistivity in Frustrated Antiferromagnets,"In this paper we study the spin transport in frustrated antiferromagnetic FCC
films by Monte Carlo simulation. In the case of Ising spin model, we show that
the spin resistivity versus temperature exhibits a discontinuity at the phase
transition temperature: an upward jump or a downward fall, depending on how
many parallel and antiparallel localized spins interacting with a given
itinerant spin. The surface effects as well as the difference of two degenerate
states on the resistivity are analyzed. Comparison with non frustrated
antiferromagnets is shown to highlight the frustration effect. We also show and
discuss the results of the Heisenberg spin model on the same lattice.",1006.1081v2
2010-07-20,First-principles studies on electrical resistivity of iron under pressure,"We investigate the temperature and pressure dependences of the electrical
resistivity for bcc and hcp Fe using the low-order variational approximation
and theoretical transport spectral functions calculated from first principles
linear response linear-muffin-tin-orbital method in the generalized-gradient
approximation. The calculated values are in close agreement with available
experimental data, and show strong increase with temperature and decrease with
pressure. We also discuss the behavior of the electrical resistivity for the
bcc -> hcp phase transition.",1007.3423v1
2010-08-11,Contact resistivity and current flow path at metal/graphene contact,"The contact properties between metal and graphene were examined. The
electrical measurement on a multiprobe device with different contact areas
revealed that the current flow preferentially entered graphene at the edge of
the contact metal. The analysis using the cross-bridge Kelvin structure (CBK)
suggested that a transition from the edge conduction to area conduction
occurred for a contact length shorter than the transfer length of ~1 micron.
The contact resistivity for Ni was measured as ~5*10-6 Ohmcm2 using the CBK. A
simple calculation suggests that a contact resistivity less than 10-9 Ohmcm2 is
required for miniaturized graphene field effect transistors.",1008.1826v1
2010-12-05,Snake States in Graphene p-n Junctions,"We investigate transport in locally-gated graphene devices, where carriers
are injected and collected along, rather than across, the gate edge. Tuning
densities into the p-n regime significantly reduces resistance along the p-n
interface, while resistance across the interface increases. This provides an
experimental signature of snake states, which zig-zag along the p-n interface
and remain stable as applied perpendicular magnetic field approaches zero.
Snake states appear as a peak in transverse resistance measured along the p-n
interface. The generic role of snake states disordered graphene is also
discussed.",1012.0959v2
2011-08-18,Non-volatile Complementary Resistive Switch-based Content Addressable Memory,"This paper presents a novel resistive-only Binary and Ternary Content
Addressable Memory (B/TCAM) cell that consists of two Complementary Resistive
Switches (CRSs). The operation of such a cell relies on a logic$\rightarrow$ON
state transition that enables this novel CRS application.",1108.3716v2
2012-11-16,Universal scaling of resistivity in bilayer graphene,"We report the temperature dependent electrical transport properties of gated
bilayer graphene devices. We see a clear evidence of insulating behavior due to
electron-hole charge puddles. The electrical resistivity increases while the
mobility decreases with decreasing temperature, a characteristic due to carrier
inhomogeneity in graphene. The theoretical fittings using an empirical formula
of single electron tunneling indicate that electrical resistivity follows a
universal curve with a scaling parameter. The scaling parameter is determined
to be a measure of the fluctuations in the electron-hole puddle distribution.",1211.3807v1
2013-04-15,Many Topological Insulators Fail the Surface Conduction Test,"In this report, we scrutinize the thickness dependent resistivity data from
the recent literature on electrical transport measurements in topological
insulators. A linear increase in resistivity with increase in thickness is
expected in the case of these materials since they have an insulating bulk and
conducting surface. However, such a trend is not seen in the resistivity versus
thickness data for all the cases examined, except for some samples, where it
holds for a narrow range of thickness.",1304.4037v2
2014-04-14,Giant generic topological Hall resistivity of MnSi under pressure,"We report detailed low temperature magnetotransport and magnetization
measurements in MnSi under pressures up to $\sim12\,{\rm kbar}$. Tracking the
role of sample quality, pressure transmitter, and field and temperature history
allows us to link the emergence of a giant topological Hall resistivity
$\sim50\,{\rm n\Omega cm}$ to the skyrmion lattice phase at ambient pressure.
We show that the remarkably large size of the topological Hall resistivity in
the zero-temperature limit must be generic. We discuss various mechanisms which
can lead to the much smaller signal at elevated temperatures observed at
ambient pressure.",1404.3734v1
2015-01-27,The Vacancy Effect on Thermal Interface Resistance between Aluminum and Silicon by Molecular Dynamics,"Thermal transport across interfaces is an important issue for
microelectronics, photonics, and thermoelectric devices and has been studied
both experimentally and theoretically in the past. In this paper, thermal
interface resistance (1/G) between aluminum and silicon with nanoscale
vacancies was calculated using non-equilibrium molecular dynamics (NEMD). Both
phonon-phonon coupling and electron-phonon coupling are considered in
calculations. The results showed that thermal interface resistance increased
largely due to vacancies. The effect of both the size and the type of vacancies
is studied and compared. And an obvious difference is found for structures with
different type/size vacancies.",1501.06666v1
2015-03-12,"Comment on ""Correlation between Bulk Thermodynamic Measurements and the Low-Temperature-Resistance Plateau in SmB6""","Low-temperature-resistivity plateau observed in $\rm SmB_6$ single
crystal,which is due to surface, not bulk, conduction has been confirmed from
electrical transport measurements. Recently, the correlation between bulk
thermodynamic measurements and the low-temperature-resistance plateau in $\rm
SmB_6$ have been investigated and a change in Sm valence at the surface has
been obtained from x-ray absorption spectroscopy and x-ray magnetic circular
dichroism. Here we show that the statement of the report are not supported by
the results from x-ray absorption spectroscopy and x-ray magnetic circular
dichroism.",1503.03901v1
2015-05-14,On the vanishing resistivity limit and the magnetic boundary-layers for one-dimensional compressible magnetohydrodynamics,"We consider an initial-boundary value problem for the one-dimensional
equations of compressible isentropic viscous and non-resistive
magnetohydrodynamic flows. The global well-posedness of strong solutions with
general large data is established. Moreover, the vanishing resistivity limit is
justified and the thickness of magnetic boundary layers is analyzed. The proofs
of these results are based on a full use of the so-called ""effective viscous
flux"", the material derivative and the structure of the equations.",1505.03596v1
2017-02-06,A thermodynamic theory of filamentary resistive switching,"We present a phenomenological theory of filamentary resistive random access
memory (RRAM) describing the commonly observed features of their
current-voltage characteristics. Our approach follows the approach of
thermodynamic theory developed earlier for chalcogenide memory and threshold
switches and largely independent of their microscopic details. It explains,
without adjustable parameters, such features as the domains of filament
formation and switching, voltage independent current in SET and current
independent voltage in RESET regimes, the relation between the set and reset
voltages, filament resistance independent of its length, etc. Furthermore, it
expresses the observed features through the material and circuitry parameters
thus paving a way to device improvements.",1702.01480v1
2017-10-02,Electrical resistivity across the tricriticality in itinerant ferromagnet,"We investigate the discontinuous ferromagnetic phase diagram near tricritical
point in UCo 1-x Ru x Al compounds by electrical resistivity measurements.
Separation of phases in UCo 0.995 Ru 0.005 Al at ambient pressure and in UCo
0.990 Ru 0.010 Al at pressure of 0.2 GPa and disappearance of ferromagnetism at
0.4 GPa is confirmed. The exponent of temperature dependence of electrical
resistivity implies change from Fermi liquid behavior to non-Fermi liquid at
0.2 GPa and reaches minimum at 0.4 GPa. Our results are compared to results
obtained on the pure UCoAl and explanation for different exponents is given.",1710.00860v1
2017-10-04,Towards Replacing Resistance Thermometry with Photonic Thermometry,"Resistance thermometry provides a time-tested method for taking temperature
measurements that has been painstakingly developed over the last century.
However, fundamental limits to resistance-based approaches along with a desire
to reduce the cost of sensor ownership and increase sensor stability has
produced considerable interest in developing photonic temperature sensors. Here
we demonstrate that silicon photonic crystal cavity-based thermometers can
measure temperature with uncertainities of 175 mK (k = 1), where uncertainties
are dominated by ageing effects originating from the hysteresis in the device
packaging materials. Our results, a 4-fold improvement over recent
developments, clearly demonstate the rapid progress of silicon photonic sensors
in replacing legacy devices.",1710.01704v1
2018-09-28,Thermal resistance of GaN/AlN graded interfaces,"Compositionally graded interfaces in power electronic devices eliminate
dislocations, but they can also decrease thermal conduction, leading to
overheating. We quantify the thermal resistances of GaN/AlN graded interfaces
of varying thickness using ab initio Green's functions, and compare them with
the abrupt interface case. A non-trivial power dependence of the thermal
resistance versus interface thickness emerges from the interplay of alloy and
mismatch scattering mechanisms. We show that the overall behavior of such
graded interfaces is very similar to that of a thin-film of an effective alloy
in the length scales relevant to real interfaces.",1809.11046v2
2017-03-08,Resistive Switching in Memristive Electrochemical Metallization Devices,"We report on resistive switching of memristive electrochemical metallization
devices using 3D kinetic Monte Carlo simulations describing the transport of
ions through a solid state electrolyte of an Ag/TiO$_{\text{x}}$/Pt thin layer
system. The ion transport model is consistently coupled with solvers for the
electric field and thermal diffusion. We show that the model is able to
describe not only the formation of conducting filaments but also its
dissolution. Furthermore, we calculate realistic current-voltage
characteristics and resistive switching kinetics. Finally, we discuss in detail
the influence of both the electric field and the local heat on the switching
processes of the device.",1703.02946v2
2012-01-31,"Magnetoresistance, noise properties and the Koshino-Taylor effect in the quasi-1D oxide KRu_4O_8","The low temperature electronic and galvanomagnetic transport properties of
the low dimensional oxide KRu_4O_8 are experimentally considered. A quadratic
temperature variation of the resistivity is observed to be proportional to the
residual resistivity. It shows the role of inelastic electron scattering
against impurities, i.e. a large Koshino-Taylor effect, rather than a
consequence of strong electronic correlations. In the same temperature range,
the Kohler rule is not fulfilled. The resistance noise increases also sharply,
possibly due to a strong coupling of carriers with lattice fluctuations in this
low dimensional compound.",1201.6474v1
2022-07-12,A Simple and Precise Way to Determine Electrical Resistivity of Isotropic Conductors: Simplifying the Four-Probe Method,"COMSOL Multiphysics software is used to describe the behavior of the
electrical resistivity of several samples with rectangular shape typically used
in the Montgomery method. The simulation data obtained using four isotropic
conductors allowed us to understand in detail the behavior of the electric
potential and electric field of the samples. The results provide an analytical
method which can substitute the four-probe method with much more simplicity and
precision.",2207.05863v1
2022-11-08,Role of the annealing parameters on the resistance of indium tin oxide nanocrystalline films,"The optical and electrical properties of films made of nanoparticles of
indium tin oxide (ITO) are widely studied because of the significance of this
material for transparent electrodes, smart windows, and nonlinear optics
components. In this work, a systematic study of the resistance in ITO
nanocrystalline films, as a function of post-fabrication parameters, such as
the temperature and time of annealing, has been performed. A tunability of the
resistance with the annealing parameters, in a range of three orders of
magnitude, has been demonstrated.",2211.04144v2
2023-11-16,Measuring the Kapitza Resistance between a Passivated Semiconductor and Liquid Helium,"In this paper, we describe an experimental investigation into the effect of
passivation layer thickness on heat dissipation between a quartz substrate and
liquid helium. We have observed that by depositing SiN from 0 to 240 nm, the
Kapitza resistance increases by 0.0365 m^2.K/W per nanometer more than for an
unpassivated semiconductor. We hypothesize that this increase in Kapitza
resistance represents an additional barrier to the cooling of semiconductor
devices in liquid helium.",2312.03713v1
2021-07-26,Laser-equipped gas reaction chamber for probing environmentally sensitive materials at near atomic scale,"Numerous metallurgical and materials science applications depend on
quantitative atomic-scale characterizations of environmentally-sensitive
materials and their transient states. Studying the effect upon materials
subjected to thermochemical treatments in specific gaseous atmospheres is of
central importance for specifically studying a material's resistance to certain
oxidative or hydrogen environments. It is also important for investigating
catalytic materials, direct reduction of an oxide, particular surface science
reactions or nanoparticle fabrication routes. This manuscript realizes such
experiments upon a thermochemical reaction chamber called the Reacthub and
allows for transferring treated materials under cryogenic & ultrahigh vacuum
workflow conditions for characterisation by either atom probe or scanning
Xe+/electron microscopies. Two examples are discussed in the present study. One
protocol was in the deuterium gas charging (25 kPa D2 at 200 {\deg}C) of a
high-manganese twinning-induced-plasticity steel and characterization of the
ingress and trapping of hydrogen at various features (grain boundaries in
particular) in efforts to relate this to the steel's hydrogen embrittlement
susceptibility. Deuterium was successfully detected after gas charging but most
contrast originated from the complex ion FeOD+ signal and the feature may be an
artefact. The second example considered the direct deuterium reduction (5 kPa
D2 at 700 {\deg}C) of a single crystal wuestite sample, demonstrating that
under a standard thermochemical treatment causes rapid reduction upon the
nanoscale. Further studies are required for complete confidence about these
phenomena, but these experiments successfully demonstrate that how an ex-situ
thermochemical treatment can be realised that captures
environmentally-sensitive transient states that can be analysed by atomic-scale
by atom probe microscope.",2107.11987v2
2023-03-19,2D MXene Electrochemical Transistors,"In the past two decades another transistor based on conducting polymers,
called the organic electrochemical transistor (ECT) was shown and largely
studied. The main difference between organic ECTs and FETs is the mode and
extent of channel doping: while in FETs the channel only has surface doping
through dipoles, the mixed ionic-electronic conductivity of the channel
material in Organic ECTs enables bulk electrochemical doping. As a result, the
organic ECT maximizes conductance modulation at the expense of speed. Until now
ECTs have been based on conducting polymers, but here we show that MXenes, a
class of 2D materials beyond graphene, have mixed ionic-electronic properties
that enable the realization of electrochemical transistors (ECTs). We show that
the formulas for organic ECTs can be applied to these 2D ECTs and used to
extract parameters like mobility. These MXene ECTs have high transconductance
values but low on-off ratios. We further show that conductance switching data
measured using ECT, in combination with other in-situ ex-situ electrochemical
measurements, is a powerful tool for correlating the change in conductance to
that of redox state: to our knowledge, this is the first report of this
important correlation for MXene films. Many future possibilities exist for
MXenes ECTs, and we think other 2D materials with bandgaps can also form ECTs
with single or heterostructured 2D materials. 2D ECTs can draw great
inspiration and theoretical tools from the field of organic ECTs and have the
potential to considerably extend the capabilities of transistors beyond that of
conducting polymer ECTs, with added properties such as extreme heat resistance,
tolerance for solvents, and higher conductivity for both electrons and ions
than conducting polymers.",2303.10768v2
2016-02-10,Electronic Evidence of Temperature-Induced Lifshitz Transition and Topological Nature in ZrTe5,"The topological materials have attracted much attention recently. While
three-dimensional topological insulators are becoming abundant, two-dimensional
topological insulators remain rare, particularly in natural materials. ZrTe5
has host a long-standing puzzle on its anomalous transport properties; its
underlying origin remains elusive. Lately, ZrTe5 has ignited renewed interest
because it is predicted that single-layer ZrTe5 is a two-dimensional
topological insulator and there is possibly a topological phase transition in
bulk ZrTe5. However, the topological nature of ZrTe5 is under debate as some
experiments point to its being a three-dimensional or quasi-two-dimensional
Dirac semimetal. Here we report high-resolution laser-based angle-resolved
photoemission measurements on ZrTe5. The electronic property of ZrTe5 is
dominated by two branches of nearly-linear-dispersion bands at the Brillouin
zone center. These two bands are separated by an energy gap that decreases with
decreasing temperature but persists down to the lowest temperature we measured
(~2 K). The overall electronic structure exhibits a dramatic temperature
dependence; it evolves from a p-type semimetal with a hole-like Fermi pocket at
high temperature, to a semiconductor around ~135 K where its resistivity
exhibits a peak, to an n-type semimetal with an electron-like Fermi pocket at
low temperature. These results indicate a clear electronic evidence of the
temperature-induced Lifshitz transition in ZrTe5. They provide a natural
understanding on the underlying origin of the resistivity anomaly at ~135 K and
its associated reversal of the charge carrier type. Our observations also
provide key information on deciphering the topological nature of ZrTe5 and
possible temperature-induced topological phase transition.",1602.03576v1
2010-11-11,Nonlinear Insulator in Complex Oxides,"The insulating state is one of the most basic electronic phases in condensed
matter. This state is characterised by an energy gap for electronic excitations
that makes an insulator electrically inert at low energy. However, for complex
oxides, the very concept of an insulator must be re-examined. Complex oxides
behave differently from conventional insulators such as SiO2, on which the
entire semiconductor industry is based, because of the presence of multiple
defect levels within their band gap. As the semiconductor industry is moving to
such oxides for high-dielectric (high-k) materials, we need to truly understand
the insulating properties of these oxides under various electric field
excitations. Here we report a new class of material called nonlinear insulators
that exhibits a reversible electric-field-induced metal-insulator transition.
We demonstrate this behaviour for an insulating LaAlO3 thin film in a
metal/LaAlO3/Nb-SrTiO3 heterostructure. Reproducible transitions were observed
between a low-resistance metallic state and a high-resistance non-metallic
state when applying suitable voltages. Our experimental results exclude the
possibility that diffusion of the metal electrodes or oxygen vacancies into the
LaAlO3 layer is occurring. Instead, the phenomenon is attributed to the
formation of a quasi-conduction band (QCB) in the defect states of LaAlO3 that
forms a continuum state with the conduction band of the Nb-SrTiO3. Once this
continuum (metallic) state is formed, the state remains stable even when the
voltage bias is turned off. An opposing voltage is required to deplete the
charges from the defect states. Our ability to manipulate and control these
defect states and, thus, the nonlinear insulating properties of complex oxides
will open up a new path to develop novel devices.",1011.2629v1
2022-08-31,CeFe$_2$Al$_{10}$: a Correlated Metal with a Fermi Surface Exhibiting Nonmetallic Conduction,"Metals can be defined as materials with a Fermi surface or as materials
exhibiting metallic conduction (i.e., $\mathrm{d} \rho / \mathrm{d}T > 0$).
Usually, these definitions both hold at low temperatures, such as liquid-helium
temperatures, as the Fermi energy is sufficiently larger than the thermal
energy. However, they may not both hold in correlated electron systems where
the Fermi energy is reduced by renormalization. In this paper, we demonstrate
that although the resistivity of CeFe$_2$Al$_{10}$ increases with decreasing
temperature below $\sim20$ K, CeFe$_2$Al$_{10}$ is a metal with a Fermi
surface. This assertion is based on the observation of Shubnikov--de Haas
oscillations and a Hall resistivity that changes sign with the magnetic field,
which requires the coexistence of electron and hole carriers. Our analysis of
Shubnikov--de Haas and magnetotransport data indicates that the Fermi energies
are as small as $\sim$30 K and that, despite the increasing carrier mobility
with decreasing temperature as in conventional metals, the loss of thermally
excited carriers leads to nonmetallic conduction ($\mathrm{d} \rho /
\mathrm{d}T < 0$) below $\sim20$ K. Furthermore, we investigate how this
anomalous metal transforms to a more conventional metal with metallic
conduction by the application of high pressure and a high magnetic field. This
study illustrates the subtle distinction between semimetals and semiconductors
in correlated electron systems. This distinction is relevant to investigations
of correlated topological insulators and semimetals.",2208.14630v4
2011-08-08,KEK effort for high field magnets,"KEK has emphasized efforts to develop the RHQNb3Al superconductor and a
sub-scale magnet reaching 13 T towards the HL-LHC upgrade in last years. In
addition, relevant R&D regarding radiation resistance has been carried out. For
higher field magnets beyond 15 T, HTS in combination with A15 superconductors
should be one of baseline materials. However, all these superconductors are
very sensitive to stress and strain and thorough understanding of behaviour is
truly desired for realization of high field magnets. KEK has launched a new
research subject on stress/strain sensitivity of HTS and A15 superconductors in
collaboration with the neutron diffraction facility at J-PARC and High Field
Laboratory in Tohoku University. Present activity for high field magnets at KEK
is reported.",1108.1626v1
2013-10-29,Fabrication of single-walled carbon nanotube/Si heterojunction solar cell with high photovoltaic conversion efficiency and stability,"The photovoltaic properties of carbon nanotube/Si heterojunction solar cells
were investigated using network films of high quality single-walled carbon
nanotubes (SWNTs) grown by atmospheric-pressure floating-catalyst chemical
vapor deposition. Because of the optimization of the device window size and the
utilization of SWNT thin films with both low resistivity and high transparency,
a high photovoltaic conversion efficiency of greater than 12% was achieved for
SWNTs/Si heterojunction solar cells without any post processing, such as
carrier doping treatment. In addition, the high stability and reproducibility
of the photovoltaic performance of these devices in air was demonstrated.",1310.7783v2
2021-02-15,Fermi-surface reconstruction at the metamagnetic high-field transition in uranium mononitride,"We report on the electronic and thermodynamic properties of the
antiferromagnetic metal uranium mononitride with a N\'eel temperature
$T_N\approx 53\,$K. The fabrication of microstructures from single crystals
enables us to study the low-temperature metamagnetic transition at
approximately $58\,$T by high-precision magnetotransport, Hall-effect, and
magnetic-torque measurements. We confirm the evolution of the high-field
transition from a broad and complex behavior to a sharp first-order-like step,
associated with a spin flop at low temperature. In the high-field state, the
magnetic contribution to the temperature dependence of the resistivity is
suppressed completely. It evolves into an almost quadratic dependence at low
temperatures indicative of a metallic character. Our detailed investigation of
the Hall effect provides evidence for a prominent Fermi-surface reconstruction
as the system is pushed into the high-field state.",2102.07512v2
2020-06-17,Electrical transport measurements for superconducting sulfur hydrides using boron-doped diamond electrodes on beveled diamond anvil,"A diamond anvil cell (DAC) which can generate extremely high pressure of
multi-megabar is promising tool to develop a further physics such a
high-transition temperature superconductivity. However, electrical transport
measurements, which is one of the most important properties of such functional
materials, using the DAC is quite difficult because the sample space is very
small and a deformation of electrodes under extreme condition. In this study,
we fabricated a boron-doped diamond micro-electrode and an undoped diamond
insulation on a beveled culet surface of the diamond anvil. By using the
developed DAC, we demonstrated the electrical transport measurements for sulfur
hydride H$_2$S which known as a pressure-induced high-transition temperature
superconducting H$_3$S at high pressure. The measurements were successfully
conducted under high pressure up to 192 GPa, and then a multi-step
superconducting transition composed from pure sulfur and some kinds of surfer
hydrides, which is possible HS$_2$, was observed with zero resistance.",2006.09671v1
2023-10-02,Thermoelectric properties of high-entropy wolframite oxide: (CoCuNiFeZn)$_{1-x}$Ga$_x$WO$_4$,"In this report, the synthesis of high-entropy wolframite oxide
(CoCuNiFeZn)$_{1-x}$Ga$_x$WO$_4$ through standard solid-state route followed by
spark plasma sintering (SPS) and their structural, microstructural, and
thermoelectric properties are investigated. X-ray diffraction pattern followed
by pattern matching refinement shows monoclinic structure with volume of the
unit cell decreasing with increasing Ga content. The optical band gap for these
oxides shows a cocktail effect in high entropy configuration. The Seebeck
coefficient indicates electrons as dominating charge carriers with a
non-degenerate behavior. The electrical resistivity decreases with increasing
temperature depicting a semiconducting nature. Thermal conductivity in
high-entropy samples ($\kappa\sim$2.1 W/mK @ 300\,K) is significantly lower as
compared to MgWO$_4$ ($\kappa\sim$11.5 W/mK @ 300\,K), which can be explained
by the strong phonon scattering due to large lattice disorder in high entropy
configuration. The thermoelectric figure of merit zT increases with Ga doping
via modifying all three thermoelectric parameters positively.",2310.00930v1
1999-03-01,Anisotropic resistivity of the antiferromagnetic insulator Bi_2Sr_2ErCu_2O_8,"Anisotropic resistivities of Bi_2Sr_2Ca_{1-x}Er_xCu_2O_8 single crystals were
measured and analyzed from 4.2 to 500 K with special interest in the parent
antiferromagnetic insulator of x=1.0. Although the resistivity is
semiconducting along both the in- and out-of-plane directions, the temperature
dependence is found to be significantly different. As a result, the resistivity
ratio for x=1.0 takes a broad maximum near room temperature. The electric
conduction in parent antiferromagnetic insulators is different from other
semiconductors, and is as unconventional as that in high-temperature
superconductors.",9903023v2
2002-11-18,Transverse voltages and reciprocity theorem in magnetic fields for high T_c superconductors,"We have tested four-point methods of the Hall effect measurement on BiSrCaCuO
(2223) polycrystal and also the validity of the magnetic field form of the
reciprocity theorem. We found that different types of determination of the Hall
resistance using various combination of measured resistances provide different
value of it. We have separated two parts of the resistance combinations, which
are even and odd in magnetic field, respectively. The odd part, which is
equivalent to the Hall effect, is equal for all formulae used. The even part of
transverse resistance varies in different formulae. The magnetic field form of
the reciprocity theorem is not valid. Models for explanation of this violation
are also discussed.",0211370v1
2003-06-03,Anomalous Flux Flow Resistivity in Two Gap Superconductor MgB_2,"The flux flow resistivity associated with purely viscous motion of vortices
in high-quality MgB_2 was measured by microwave surface impedance. Flux flow
resistivity exhibits unusual field dependence with strong enhancement at low
field, which is markedly different to conventional s-wave superconductors. A
crossover field which separates two distinct flux flow regimes having different
flux flow resistivity slopes was clearly observed in H//ab-plane. The unusual
H-dependence indicates that two very differently sized superconducting gaps in
MgB_2 manifest in the vortex dynamics and almost equally contribute to energy
dissipation. The carrier scattering rate in two different bands is also
discussed with the present results, compared to heat capacity and thermal
conductivity results.",0306057v1
2005-09-30,Valence fluctuation mediated superconductivity in CeCu2Si2,"It has been proposed that there are two types of superconductivity in
CeCu2Si2, mediated by spin fluctuations at ambient pressure, and by critical
valence fluctuations around a charge instability at a pressure P_v \simeq 4.5
GPa. We present in detail some of the unusual features of this novel type of
superconducting state, including the coexistence of superconductivity and huge
residual resistivity of the order of the Ioffe-Regel limit, large and pressure
dependent resistive transition widths in a single crystal measured under
hydrostatic conditions, asymmetric pressure dependence of the specific heat
jump shape, unrelated to the resistivity width, and negative temperature
dependence of the normal state resistivity below 10 K at very high pressure.",0509787v1
2007-06-05,Hall magnetoresistivity response under Microwave excitation revisited,"We theoretically analyzed the microwave-induced modification of the Hall
magnetoresistivity in high mobility two-dimensional electron systems. These
systems present diagonal magnetoresistivity oscillations and zero-resistance
states when are subjected to microwave radiation. The most surprising
modification of the Hall magnetoresistivity is a periodic reduction which
correlates with a periodic increase in the diagonal resistivity. We present a
model that explains the experimental results considering that radiation affects
directly only the diagonal resistivity and the observed Hall resistivity
changes are coming from the tensor relationship between both of them.",0706.0588v1
2009-06-22,Temperature dependent electrical resistivity of a single strand of ferromagnetic single crystalline nanowire,"We have measured the electrical resistivity of a single strand of a
ferromagnetic Ni nanowire of diameter 55 nm using a 4-probe method in the
temperature range 3 K-300 K. The wire used is chemically pure and is a high
quality oriented single crystalline sample in which the temperature independent
residual resistivity is determined predominantly by surface scattering. Precise
evaluation of the temperature dependent resistivity ($\rho$) allowed us to
identify quantitatively the electron-phonon contribution (characterized by a
Debye temperature $\theta_R$) as well as the spin-wave contribution which is
significantly suppressed upon size reduction.",0906.3903v1
2010-07-01,"First tests of ""bulk"" MICROMEGAS with resistive cathode mesh","We present the first results from tests of a MICROMEGAS detector manufactured
using the so-called ""bulk"" technology and having a resistive cathode mesh
instead of the conventional metallic one. This detector operates as usual
MICROMEGAS, but in the case of sparks, which may appear at high gas gains, the
resistive mesh reduces their current and makes the sparks harmless. This
approach could be complementary to the ongoing efforts of various groups to
develop spark-protected MICROMEGAS with resistive anode planes.",1007.0211v1
2010-07-08,Microwave zero-resistance states in a bilayer electron system,"Magnetotransport measurements on a high-mobility electron bilayer system
formed in a wide GaAs quantum well reveal vanishing dissipative resistance
under continuous microwave irradiation. Profound zero-resistance states (ZRS)
appear even in the presence of additional intersubband scattering of electrons.
We study the dependence of photoresistance on frequency, microwave power. and
temperature. Experimental results are compared with a theory demonstrating that
the conditions for absolute negative resistivity correlate with the appearance
of ZRS.",1007.1393v1
2011-05-17,Microwave-induced Hall resistance in bilayer electron systems,"The influence of microwave irradiation on dissipative and Hall resistance in
high-quality bilayer electron systems is investigated experimentally. We
observe a deviation from odd symmetry under magnetic field reversal in the
microwave-induced Hall resistance $\Delta R_{xy}$ whereas the dissipative
resistance $\Delta R_{xx}$ obeys even symmetry. Studies of $\Delta R_{xy}$ as a
function of the microwave electric field and polarization exhibit a strong and
non-trivial power and polarization dependence. The obtained results are
discussed in connection to existing theoretical models of microwave-induced
photoconductivity.",1105.3362v1
2011-12-02,Mooij Rule and Weak Localization,"It has been shown that the observed correlation between the resistivity
$\rho$ of high-resistive metallic alloys and the sign of the temperature
derivative $d\rho/dT$ can be explained by taking into account the weak
localization. This correlation is known as Mooij rule: the derivative
$d\rho/dT$ is negative for alloys with resistivity in the range of
$300\div150\,\mu\Omega\cdot$cm, which corresponds to the electron mean free
path about the interatomic distance; however, this derivative is positive for
alloys with lower resistivity.",1112.0429v1
2015-03-16,"High pressure investigation of superconducting signatures in CeCu$_{2}$Si$_{2}$ : ac- magnetic susceptibility and heat capacity, resistivity and thermopower","Taking advantage of a novel multiprobe setup we have measured, on a unique
sample, the ac-magnetic susceptibility, the resistivity, the ac-specific heat
and the thermopower of the superconductor heavy fermion CeCu$_{2}$Si$_{2}$
under pressure up to 5.1 GPa. At the superconducting transition temperature
$T_c$, the Meissner signal corresponds to that expected for the sample volume
and coincides with the specific heat jump and the resistive transition
completion temperatures. Differing from previous observations, here the
susceptibility measurements did not reveal any anomaly in the vicinity of the
resistive transition onset.",1503.04861v2
2024-05-14,Experimental Demonstration of Turbulence-resistant Lidar via Quantum Entanglement,"We report a proof-of-principle experimental demonstration of a
turbulence-resistant quantum Lidar system. As a key technology for sensing and
ranging, Lidar has drawn considerable attention for a study from quantum
perspective, in search of proven advantages complementary to the capabilities
of conventional Lidar technologies. Environmental factors such as strong
atmospheric turbulence can have detrimental effects on the performance of these
systems. We demonstrate the possibility of turbulence-resistant operation of a
quantum Lidar system via two-photon interference of entangled photon pairs.
Additionally, the reported quantum Lidar also demonstrates the expected noise
resistance. This study suggests a potential high precision timing-positioning
technology operable under turbulence and noise.",2405.08916v1
2020-11-26,Systematic study of nonmagnetic resistance changes due to electrical pulsing in single metal layers and metal/antiferromagnet bilayers,"Intense current pulses are often required to operate microelectronic and
spintronic devices. Notably, strong current pulses have been shown to induce
magnetoresistance changes attributed to domain reorientation in
antiferromagnet/heavy metal bilayers and non-centrosymmetric antiferromagnets.
In such cases, nonmagnetic resistivity changes may dominate over signatures of
antiferromagnetic switching. We report systematic measurements of the
current-induced changes of the transverse and longitudinal resistance of Pt and
Pt/NiO layers deposited on insulating substrates, namely Si/SiO$_2$,
Si/Si$_3$N$_4$, and Al$_2$O$_3$. We identify the range of pulse amplitude and
length that can be used without affecting the resistance and show that it
increases with the device size and thermal diffusivity of the substrate. No
significant difference is observed in the resistive response of Pt and NiO/Pt
devices, thus precluding evidence on the switching of antiferromagnetic domains
in NiO. The variation of the transverse resistance is associated to a
thermally-activated process in Pt that decays following a double exponential
law with characteristic timescales of a few minutes to hours. We use a
Wheatstone bridge model to discriminate between positive and negative
resistance changes, highlighting competing annealing and electromigration
effects. Depending on the training of the devices, the transverse resistance
can either increase or decrease between current pulses. Further, we elucidate
the origin of the nonmonotonic resistance baseline, which we attribute to
training effects combined with the asymmetric distribution of the current.
These results provide insight into the origin of current-induced resistance
changes in metal layers and a guide to minimize nonmagnetic artifacts in
switching experiments of antiferromagnets.",2011.13413v1
2013-04-17,Universal density scaling of disorder-limited low-temperature conductivity in high-mobility two-dimensional systems,"We theoretically consider the carrier density dependence of low-temperature
electrical conductivity in high-quality and low-disorder two-dimensional (2D)
`metallic' electronic systems such as 2D GaAs electron or hole quantum wells or
gated graphene. Taking into account resistive scattering by Coulomb disorder
arising from quenched random charged impurities in the environment, we show
that the 2D conductivity \sigma(n) varies as \sigma ~ n^{\beta(n)} as a
function of the 2D carrier density n where the exponent \beta(n) is a smooth,
but non-monotonic, function of density with possible nontrivial extrema. In
particular, the density scaling exponent \beta(n) depends qualitatively on
whether the Coulomb disorder arises primarily from remote or background charged
impurities or short-range disorder, and can, in principle, be used to
characterize the nature of the dominant background disorder. A specific
important prediction of the theory is that for resistive scattering by remote
charged impurities, the exponent \beta can reach a value as large as 2.7 for
k_F d ~ 1, where k_F ~\sqrt{n} is the 2D Fermi wave vector and d is the
separation of the remote impurities from the 2D layer. Such an exponent \beta
(>5/2) is surprising because unscreened Coulomb scattering by remote impurities
gives a limiting theoretical scaling exponent of \beta = 5/2, and naively one
would expect \beta(n) \le 5/2 for all densities since unscreened Coulomb
scattering should nominally be the situation bounding the resistive scattering
from above. We find numerically and show theoretically that the maximum value
of \alpha (\beta), the mobility (conductivity) exponent, for 2D semiconductor
quantum wells is around 1.7 (2.7) for all values of d (and for both electrons
and holes) with the maximum \alpha occurring around k_F d ~ 1. We discuss
experimental scenarios for the verification of our theory.",1304.4668v1
2014-03-16,Comparison of Sn-doped and nonstoichiometric vertical-Bridgman-grown crystals of the topological insulator Bi2Te2Se,"A comparative study of the properties of topological insulator Bi2Te2Se (BTS)
crystals grown by the vertical Bridgeman method is described. Two defect
mechanisms that create acceptor impurities to compensate for the native n-type
carriers are compared: Bi excess, and light Sn doping. Both methods yield low
carrier concentrations and an n-p crossover over the length of the grown
crystal boules, but lower carrier concentrations and higher resistivities are
obtained for the Sn-doped crystals, which reach carrier concentrations as low
as 8 x 1014 cm-3. Further, the temperature dependent resistivities for the
Sn-doped crystals display strongly activated behavior at high temperatures,
with a characteristic energy of half the bulk band gap. The (001) cleaved
Sn-doped BTS crystals display high quality Shubnikov de Haas (SdH) quantum
oscillations due to the topological surface state electrons. Angle resolved
photoelectron spectroscopy (ARPES) characterization shows that the Fermi energy
(EF) for the Sn-doped crystals falls cleanly in the surface states with no
interference from the bulk bands, that the Dirac point for the surface states
lies approximately 60 meV below the top of the bulk valence band maximum, and
allows for a determination of the bulk and surface state carrier concentrations
as a function of Energy near EF. Electronic structure calculations that compare
Bi excess and Sn dopants in BTS demonstrate that Sn acts as a special impurity,
with a localized impurity band that acts as a charge buffer occurring inside
the bulk band gap. We propose that the special resonant level character of Sn
in BTS gives rise to the exceptionally low carrier concentrations and activated
resistivities observed.",1403.3870v1
2015-02-13,Epitaxial graphene on SiC: Modification of structural and electron transport properties by substrate pretreatment,"The electrical transport properties of epitaxial graphene layers are
correlated with the SiC surface morphology. In this study we show by atomic
force microscopy and Raman measurements that the surface morphology and the
structure of the epitaxial graphene layers change significantly when different
pretreatment procedures are applied to nearly on-axis 6H-SiC(0001) substrates.
It turns out that the often used hydrogen etching of the substrate is
responsible for undesirable high macro steps evolving during graphene growth. A
more advantageous type of sub-nanometer stepped graphene layers is obtained
with a new method: a high-temperature conditioning of the SiC surface in argon
atmosphere. The results can be explained by the observed graphene buffer layer
domains after the conditioning process which suppress giant step bunching and
graphene step flow growth. The superior electronic quality is demonstrated by a
less extrinsic resistance anisotropy obtained in nano-probe transport
experiments and by the excellent quantization of the Hall resistance in
low-temperature magneto-transport measurements. The quantum Hall resistance
agrees with the nominal value (half of the von Klitzing constant) within a
standard deviation of 4.5*10(-9) which qualifies this method for the
fabrication of electrical quantum standards.",1502.03927v3
2020-07-09,"Growth, Properties, and Applications of Pulsed Laser Deposited Nanolaminate Ti3AlC2 Thin Films","Recently, nanolaminated ternary carbides have attracted immense interest due
to the concomitant presence of both ceramic and metallic properties. Here, we
grow nanolaminate Ti3AlC2 thin films by pulsed laser deposition on
c-axis-oriented sapphire substrates and, surprisingly, the films are found to
be highly oriented along the (103) axis normal to the film plane, rather than
the (000l) orientation. Multiple characterization techniques are employed to
explore the structural and chemical quality of these films, the electrical and
optical properties, and the device functionalities. The 80-nm thick Ti3AlC2
film is highly conducting at room temperature (resistivity of 50 micro ohm-cm),
and a very-low-temperature coefficient of resistivity. The ultrathin (2 nm)
Ti3AlC2 film has fairly good optical transparency and high conductivity at room
temperature (sheet resistance of 735 ohm). Scanning tunneling microscopy
reveals the metallic characteristics (with finite density of states at the
Fermi level) at room temperature. The metal-semiconductor junction of the
p-type Ti3AlC2 film and n-Si show the expected rectification (diode)
characteristics, in contrast to the ohmic contact behavior in the case of
Ti3AlC2 on p-Si. A triboelectric-nanogenerator-based touch-sensing device,
comprising of the Ti3AlC2 film, shows a very impressive peak-to-peak
open-circuit output voltage of 80 V. These observations reveal that pulsed
laser deposited Ti3AlC2 thin films have excellent potential for applications in
multiple domains, such as bottom electrodes, resistors for high-precision
measurements, Schottky diodes, ohmic contacts, fairly transparent ultrathin
conductors, and next-generation biomechanical touch sensors for energy
harvesting.",2007.04798v1
2022-01-19,Tearing instability and current-sheet disruption in the turbulent dynamo,"Turbulence in a conducting plasma can amplify seed magnetic fields in what is
known as the turbulent, or small-scale, dynamo. The associated growth rate and
emergent magnetic-field geometry depend sensitively on the material properties
of the plasma, in particular on the Reynolds number ${\rm Re}$, the magnetic
Reynolds number ${\rm Rm}$, and their ratio ${\rm Pm}\equiv{\rm Rm}/{\rm Re}$.
For ${\rm Pm} > 1$, the amplified magnetic field is gradually arranged into a
folded structure, with direction reversals at the resistive scale and field
lines curved at the larger scale of the flow. As the mean magnetic energy grows
to come into approximate equipartition with the fluid motions, this folded
structure is thought to persist. Using analytical theory and high-resolution
MHD simulations with the Athena++ code, we show that these magnetic folds
become unstable to tearing during the nonlinear stage of the dynamo for ${\rm
Rm}\gtrsim 10^4$ and ${\rm Re}\gtrsim 10^3$. An ${\rm Rm}$- and ${\rm
Pm}$-dependent tearing scale, at and below which folds are disrupted, is
predicted theoretically and found to match well the characteristic
field-reversal scale measured in the simulations. The disruption of folds by
tearing increases the ratio of viscous-to-resistive dissipation. In the
saturated state, the magnetic-energy spectrum exhibits a sub-tearing-scale
steepening to a slope consistent with that predicted for tearing-mediated
Alfv\'enic turbulence. Its spectral peak appears to be independent of the
resistive scale and comparable to the driving scale of the flow, while the
magnetic energy resides in a broad range of scales extending down to the
field-reversal scale set by tearing. Emergence of a degree of large-scale
magnetic coherence in the saturated state of the turbulent dynamo may be
consistent with observations of magnetic-field fluctuations in galaxy clusters
and recent laboratory experiments.",2201.07757v2
2014-04-10,Metal-insulator transition upon heating and negative-differential-resistive-switching induced by self-heating in BaCo0.9Ni0.1S1.8,"The layered compound BaCo1-xNixS2-y (0.05<x<0.2 and 0.05<y<0.2) exhibits an
unusual first-order structural and electronic phase transition from a low-T
monoclinic paramagnetic metal to a high-T tetragonal antiferromagnetic
insulator around 200 K with huge hysteresis (~ 40 K) and large volume change
(~0.01). Here we report on unusual voltage-controlled resistive switching
followed by current-controlled resistive switching induced by self-heating in
polycrystalline BaCo1-xNixS2-y (nominal x=0.1 and y=0.2). These were due to the
steep metal to insulator transition upon heating followed by the activated
behavior of the resistivity above the transition. The major role of Joule
heating in switching is supported by the absence of nonlinearity in the current
as function of voltage, I(V), obtained in pulsed measurements, in the range of
electric fields relevant to d.c. measurements. The voltage-controlled negative
differential resistance around the threshold for switching was explained by a
simple model of self-heating. The main difficulty in modeling I(V) from the
samples resistance as function of temperature R(T) was the progressive increase
of R(T), and to a lesser extend the decrease of the resistance jumps at the
transitions, caused by the damage induced by cycling through the transitions by
heating or self-heating. This was dealt with by following systematically R(T)
over many cycles and by using the data of R(T) in the heating cycle closest to
that of the self-heating one.",1404.2773v1
2014-07-17,Robust recipe for low-resistance ohmic contacts to a two-dimensional electron gas in a GaAs/AlGaAs heterostructure,"The study of electron transport in low-dimensional systems is of importance,
not only from a fundamental point of view, but also for future electronic and
spintronic devices. In this context heterostructures containing a
two-dimensional electron gas (2DEG) are a key technology. In particular
GaAs/AlGaAs heterostructures, with a 2DEG at typically 100 nm below the
surface, are widely studied. In order to explore electron transport in such
systems, low-resistance ohmic contacts are required that connect the 2DEG to
macroscopic measurement leads at the surface. Here we report on designing and
measuring a dedicated device for unraveling the various resistance
contributions in such contacts, which include pristine 2DEG series resistance,
the 2DEG resistance under a contact, the contact resistance itself, and the
influence of pressing a bonding wire onto a contact. We also report here a
robust recipe for contacts with very low resistance, with values that do not
change significantly for annealing times between 20 and 350 sec, hence
providing the flexibility to use this method for materials with different 2DEG
depths. The type of heating used for annealing is found to strongly influence
the annealing process and hence the quality of the resulting contacts.",1407.4781v1
2017-03-10,Contact resistance at planar metal contacts on bilayer graphene and effects of molecular insertion layers,"The possible origins of metal-bilayer graphene (BLG) contact resistance are
investigated by taking into consideration the bandgap formed by interfacial
charge transfer at the metal contacts. Our results show that a charge injection
barrier (Schottky barrier) does not contribute to the contact resistance
because the BLG under the contacts is always degenerately doped. We also showed
that the contact-doping-induced increase in the density of states (DOS) of BLG
under the metal contacts decreases the contact resistance owing to enhanced
charge carrier tunnelling at the contacts. The contact doping can be enhanced
by inserting molecular dopant layers into the metal contacts. However, carrier
tunnelling through the insertion layer increases the contact resistance, and
thus, alternative device structures should be employed. Finally, we showed that
the inter-band transport by variable range hopping via in-gap states is the
largest contributor to contact resistance when the carrier type of the gated
channel is opposite to the contact doping carrier type. This indicates that the
strategy of contact resistance reduction by the contact-doping-induced increase
in the DOS is effective only for a single channel transport branch (n- or
p-type) depending on the contact doping carrier type.",1703.03521v1
2018-12-04,On the extraction of resistivity and area of nanoscale interconnect lines by temperature-dependent resistance measurements,"Several issues concerning the applicability of the temperature coefficient of
the resistivity (TCR) method to scaled interconnect lines are discussed. The
central approximation of the TCR method, the substitution of the interconnect
wire TCR by the bulk TCR becomes doubtful when the resistivity of the conductor
metal is strongly increased by finite size effects. Semiclassical calculations
for thin films show that the TCR deviates from bulk values when the surface
roughness scattering contribution to the total resistivity becomes significant
with respect to grain boundary scattering, an effect that might become even
more important in nanowires due to their larger surface-to-volume ration. In
addition, the TCR method is redeveloped to account for line width roughness. It
is shown that for rough wires, the TCR method yields the harmonic average of
the cross-sectional area as well as, to first order, the accurate value of the
resistivity at the extracted area. Finally, the effect of a conductive barrier
or liner layer on the TCR method is discussed. It is shown that the liner or
barrier parallel conductance can only be neglected when it is lower than about
5 to 10% of the total conductance. It is furthermore shown that neglecting the
liner/barrier parallel conductance leads mainly to an overestimation of the
cross-sectional area of the center conductor whereas its resistivity is less
affected.",1812.01379v1
2021-12-21,On the origin and the amplitude of T-square resistivity in Fermi liquids,"In 1937, Baber, Landau and Pomeranchuk postulated that collisions between
electrons generates a contribution to the electric resistivity of metals with a
distinct T$^2$ temperature dependence. The amplitude of this term is small in
common metals, but dominant in metals hosting either heavy carriers or a low
concentration of them. The link between the temperature dependence and the size
of the scattering phase space is straightforward, but not the microscopic
source of dissipation. To explain how electron-electron collisions lead to
momentum leak, Umklapp events or multiple electron reservoirs have been
invoked. This interpretation is challenged by a number of experimental
observations: the persistence of T-square resistivity in dilute metals (in
which the two mechanisms are irrelevant), the successful extension of
Kadowaki-Woods scaling to dilute metals, and the observation of a
size-dependent T-square thermal resistivity ($T/\kappa$) and its
Wiedemann-Franz (WF) correlation with T-square electrical resistivity. This
paper argues that much insight is provided by the case of normal liquid $^3$He
where the T-square temperature dependence of energy and momentum diffusivity is
driven by fermion-fermion collisions. The amplitude of T-square resistivity in
$^3$He and in metals share a common scaling. Thus, the ubiquitous T-square
electrical resistivity ultimately stems from the Fermi-liquid temperature
dependence of momentum diffusivity.",2112.11092v3
2022-03-30,One Dimensional Wormhole Corrosion in Metals,"Corrosion is a ubiquitous failure mode of materials in extreme environments.
The more localized it is, the more difficult it is to detect and more
deleterious its effects. Often, the progression of localized corrosion is
accompanied by the evolution of porosity in materials, creating internal
void-structures that facilitate the ingress of the external environment into
the interior of the material, further accelerating the internal corrosion.
Previously, the dominant morphology of such void-structures has been reported
to be either three-dimensional (3D) or two-dimensional (2D). Here, we report a
more localized form of corrosion, which we call 1D wormhole corrosion. Using
electron tomography, we show multiple examples of this 1D and percolating
morphology that manifests a significantly high aspect ratio differentiable from
2D and 3D corrosion. To understand the origin of this mechanism in a Ni-Cr
alloy corroded by molten salt, we combined energy-filtered four-dimensional
scanning transmission electron microscopy (EF-4D-STEM) and ab initio density
functional theory (DFT) calculations to develop a vacancy mapping method with
nanometer-resolution, identifying a remarkably high vacancy concentration in
the diffusion-induced grain boundary migration (DIGM) zone, up to 100 times the
equilibrium value at the melting point. These vacancy supersaturation regions
act as the precursors of wormholes, and lead to the asymmetrical growth of
voids along GBs. We show that similar 1D penetrating corrosion morphologies
could also occur in other materials or corrosion conditions, implying the broad
impact of this extremely localized corrosion mechanism. Deciphering the origins
of 1D corrosion is an important step towards designing structural materials
with enhanced corrosion resistance, and also offers new pathways to create
ordered-porous materials for functional applications.",2203.16312v1
2018-06-28,Thermomechanical response of thickly tamped targets and diamond anvil cells under pulsed hard x-ray irradiation,"In the laboratory study of extreme conditions of temperature and density, the
exposure of matter to high intensity radiation sources has been of central
importance. Here we interrogate the performance of multi-layered targets in
experiments involving high intensity, hard x-ray irradiation, motivated by the
advent of extremely high brightness hard x-ray sources, such as free electron
lasers and 4th-generation synchrotron facilities. Intense hard x-ray beams can
deliver significant energy in targets having thick x-ray transparent layers
(tampers) around samples of interest, for the study of novel states of matter
and materials' dynamics. Heated-state lifetimes in such targets can approach
the microsecond level, regardless of radiation pulse duration, enabling the
exploration of conditions of local thermal and thermodynamic equilibrium at
extreme temperature in solid density matter. The thermal and mechanical
response of such thick layered targets following x-ray heating, including
hydrodynamic relaxation and heat flow on picosecond to millisecond timescales,
is modelled using radiation hydrocode simulation, finite element analysis, and
thermodynamic calculations. Assessing the potential for target survival over
one or more exposures, and resistance to damage arising from heating and
resulting mechanical stresses, this study doubles as an investigation into the
performance of diamond-anvil high pressure cells under high x-ray fluences.
Long used in conjunction with synchrotron x-ray radiation and high power
optical lasers, the strong confinement afforded by such cells suggests novel
applications at emerging high intensity x-ray facilities and new routes to
studying thermodynamic equilibrium states of warm, very dense matter.",1806.10893v2
2021-01-13,Fermi Level Engineering and Mechanical Properties of High Entropy Carbides,"Fermi level engineering and mechanical properties evolution in high entropy
carbides are investigated by theoretical and experimental means. Massive
elemental diversity in high entropy ceramics broadens the compositional space
but imposes great challenges in composition selection and property
investigation. We have utilized the valence electron concentration (VEC)
descriptor to design and predict properties of high entropy carbides. The VEC
regulates the Fermi energy and systematically alters the bonding
characteristics of materials. As a result, mechanical properties evolve as
function of the VEC. At VEC 8.4, the strong {\sigma} bonding states stem from
filled overlapping metal d and carbon p orbitals, which results in maximum
resistance to shear deformation and highest hardness. Beyond or below the
optimum VEC point of 8.4, mechanical response degrades due to filling or
emptying of energy orbitals that facilitates shear deformation. Furthermore,
the optimum VEC point can shift based on the constituent metals that formulate
the high entropy carbide. Our analyses demonstrate strong correlation between
calculated hardness and shear modulus. As an experimental complement, a set of
high entropy carbides are synthesized, and mechanical properties investigated.
The measured hardness follows theoretical predictions and the highest hardness
of ~30 GPa is achieved at VEC 8.4. In contrast, hardness decreases by 50% when
VEC is 9.4. Designing high entropy carbides based on VEC and understanding
mechanical properties at an electronic level enables one to manipulate the
composition spectrum to procure a desired mechanical response from a chemically
disordered crystal.",2101.04885v1
2022-12-01,Magnetic and Electrical Properties of high-entropy rare-earth manganites,"Detailed investigations of structural, magnetic and electronic transport
properties of hole-doped high-entropy rare-earth manganites are presented. The
high-entropy samples (LaNdPrSmEu)$_{1-x}$Sr$_x$MnO$_3$
(0$\leq$\textit{x}$\leq$0.5), synthesized using the solid-state technique, show
a change in the crystal structure from \textit{Pbnm} to \textit{R-3c} with
increasing Sr substitution, attributed to the change in the tolerance factor.
Prominent ferromagnetic ordering is observed in the sample with a rhombohedral
structure (\textit{x}$\geq$0.3), originating from the dominant double exchange
mechanism mediated by itinerant electrons. Further, the Curie temperature is
smaller for the high-entropy sample with \textit{x}=0.3, as compared to
La$_{0.7}$Sr$_{0.3}$MnO$_3$, suggesting a strong relation between the Curie
temperature and the Mn-O-Mn bond angle associated with the reduced ionic radii
at the rare-earth site. The electrical resistivity of the high-entropy samples
is larger than those of La$_{1-x}$Sr$_x$MnO$_3$, which can be ascribed to the
reduced bandwidth due to the enhanced structural distortion. A concomitant rise
in magnetoresistance is observed for high-entropy samples with the increase in
Sr concentration. These findings considering the configurational complexity of
different rare-earths advance the understanding of high-entropy rare earth
manganites.",2212.00819v1
2018-03-02,Tuning thermal transport in graphene via combinations of molecular antiresonances,"We propose a method to engineer the phonon thermal transport properties of
low dimensional systems. The method relies on introducing a predetermined
combination of molecular adsorbates, which give rise to antiresonances at
frequencies specific to the molecular species. Despite their dissimilar
transmission spectra, thermal resistances due to individual molecules remain
almost the same for all species. On the other hand, thermal resistance due to
combinations of different species are not additive and show large differences
depending on the species. Using a toy model, the physics underlying the
violation of resistance summation rule is investigated. It is demonstrated that
equivalent resistance of two scatterers having the same resistances can be
close to the sum of the constituents or $\sim$70\% of it depending on the
relative positions of the antiresonances. The relative positions of the
antiresonances determine the net change in transmission, therefore the
equivalent resistance. Since the entire spectrum is involved in phonon spectrum
changes in different parts of the spectrum become important. Performing
extensive first-principles based computations, we show that these distinctive
attributes of phonon transport can be useful to tailor the thermal transport
through low dimensional materials, especially for thermoelectric and thermal
management applications.",1803.01029v2
2017-01-15,Thickness dependence of the resistivity of Platinum group metal thin films,"We report on the thin film resistivity of several platinum-group metals (Ru,
Pd, Ir, Pt). Platinum-group thin films show comparable or lower resistivities
than Cu for film thicknesses below about 5\,nm due to a weaker thickness
dependence of the resistivity. Based on experimentally determined mean linear
distances between grain boundaries as well as ab initio calculations of the
electron mean free path, the data for Ru, Ir, and Cu were modeled within the
semiclassical Mayadas--Shatzkes model [Phys. Rev. B 1, 1382 (1970)] to assess
the combined contributions of surface and grain boundary scattering to the
resistivity. For Ru, the modeling results indicated that surface scattering was
strongly dependent on the surrounding material with nearly specular scattering
at interfaces with SiO2 or air but with diffuse scattering at interfaces with
TaN. The dependence of the thin film resistivity on the mean free path is also
discussed within the Mayadas--Shatzkes model in consideration of the
experimental findings.",1701.04124v3
2022-08-04,Topological Metal MoP Nanowire for Interconnect,"The increasing resistance of Cu interconnects for decreasing dimensions is a
major challenge in continued downscaling of integrated circuits beyond the 7-nm
technology node as it leads to unacceptable signal delays and power consumption
in computing. The resistivity of Cu increases due to electron scattering at
surfaces and grain boundaries of the interconnects at the nanoscale.
Topological semimetals, owing to their topologically protected surface states
and suppressed electron backscattering, are promising material candidates to
potentially replace current Cu interconnects as low-resistance interconnects.
Here, we report the attractive resistivity scaling of topological metal MoP
nanowires and show that the resistivity values are comparable to those of Cu
interconnects below 500 nm$^2$ cross-section areas. More importantly, we
demonstrate that the dimensional scaling of MoP nanowires, in terms of line
resistance versus total cross-sectional area, is superior to those of effective
Cu and barrier-less Ru interconnects, suggesting MoP is an attractive solution
to the current scaling challenge of Cu interconnects.",2208.02784v1
2008-04-04,Magnetic Order versus superconductivity in the Iron-based layered La(O1-xFx)FeAs systems,"In high-transition temperature (high-Tc) copper oxides, it is generally
believed that antiferromagnetism plays a fundamental role in the
superconducting mechanism because superconductivity occurs when mobile
electrons or holes are doped into the antiferromagnetic parent compounds. The
recent discovery of superconductivity in the rare-earth (R) iron-based oxide
systems [RO1-xFxFeAs] has generated enormous interest because these materials
are the first noncopper oxide superconductors with Tc exceeding 50 K. The
parent (nonsuperconducting) LaOFeAs material is metallic but shows anomalies
near 150 K in both resistivity and dc magnetic susceptibility. While optical
conductivity and theoretical calculations suggest that LaOFeAs exhibits a
spin-density-wave (SDW) instability that is suppressed with doping electrons to
form superconductivity, there has been no direct evidence of the SDW order.
Here we use neutron scattering to demonstrate that LaOFeAs undergoes an abrupt
structural distortion below ~150 K, changing the symmetry from tetragonal
(space group P4/nmm) to monoclinic (space group P112/n) at low temperatures,
and then followed with the development of long range SDW-type antiferromagnetic
order at ~134 K with a small moment but simple magnetic structure. Doping the
system with flourine suppresses both the magnetic order and structural
distortion in favor of superconductivity. Therefore, much like high-Tc copper
oxides, the superconducting regime in these Fe-based materials occurs in close
proximity to a long-range ordered antiferromagnetic ground state. Since the
discovery of long",0804.0795v1
2012-12-11,Characterization of thin-film NbN superconductor for single-photon detection by transport measurements,"The fabrication of high-quality thin superconducting films is essential for
single-photon detectors. Their device performance is crucially affected by
their material parameters, thus requiring reliable and nondestructive
characterization methods after the fabrication and patterning processes.
Important material parameters to know are the resistivity, superconducting
transition temperature, relaxation time of quasiparticles, and uniformity of
patterned wires. In this work, we characterize micro-patterned thin NbN films
by using transport measurements in magnetic fields. We show that from the
instability of vortex motion at high currents in the flux-flow state of the
$IV$ characteristic, the inelastic life time of quasiparticles can be
determined to be about 2 ns. Additionally, from the depinning transition of
vortices at low currents, as a function of magnetic field, the size
distribution of grains can be extracted. This size distribution is found to be
in agreement with the film morphology obtained from scanning electron
microscopy and high-resolution transmission electron microscopy images.",1212.2258v2
2014-12-11,High-precision realization of robust quantum anomalous Hall state in a hard ferromagnetic topological insulator,"The discovery of the quantum Hall (QH) effect led to the realization of a
topological electronic state with dissipationless currents circulating in one
direction along the edge of a two dimensional electron layer under a strong
magnetic field. The quantum anomalous Hall (QAH) effect shares a similar
physical phenomenon as the QH effect, whereas its physical origin relies on the
intrinsic spin-orbit coupling and ferromagnetism.Here we report the
experimental observation of the QAH state in V-doped (Bi,Sb)2Te3 films with the
zero-field longitudinal resistance down to 0.00013+-0.00007h/e2 (~3.35+-1.76
ohm), Hall conductance reaching 0.9998+-0.0006e2/h and the Hall angle becoming
as high as 89.993+-0.004degree at T=25mK. Further advantage of this system
comes from the fact that it is a hard ferromagnet with a large coercive field
(Hc>1.0T) and a relative high Curie temperature. This realization of robust QAH
state in hard FMTIs is a major step towards dissipationless electronic
applications without external fields.",1412.3758v2
2015-01-22,High spin polarization and large spin splitting in equiatomic quaternary CoFeCrAl Heusler alloy,"In this paper, we investigate CoFeCrAl alloy by means of various experimental
techniques and ab-initio calculations to look for half-metallic nature. The
alloy is found to exist in the cubic Heusler structure, with presence of B2
ordering. Saturation magnetization (MS) value of about 2 Bohr magneton/f.u. is
observed at 8 K under ambient pressure, which is in good agreement with the
Slater-Pauling rule. MS values are found to be independent of pressure, which
is a prerequisite for half-metals. The ab-initio electronic structure
calculations predict half-metallic nature for the alloy with a spin slitting
energy of 0.31 eV. Importantly, this system shows a high current spin
polarization value of 0.67 [with error of 0.02], as deduced from the point
contact Andreev reflection (PCAR) measurements. Linear dependence of electrical
resistivity with temperature indicates the possibility of reasonably high spin
polarization at elevated temperatures (~150 K) as well. All these suggest that
CoFeCrAl is a promising material for the spintronic devices.",1501.05599v1
2015-12-08,A Two-Temperature Model of Magnetized Protostellar Outflows,"We explore kinematics and morphologies of molecular outflows driven by young
protostars using magnetohydrodynamic simulations in the context of the unified
wind model of Shang et al. The model explains the observed high-velocity jet
and low-velocity shell features. In this work we investigate how these
characteristics are affected by the underlying temperature and magnetic field
strength. We study the problem of a warm wind running into a cold ambient
toroid by using a tracer field that keeps track of the wind material. While an
isothermal equation of state is adopted, the effective temperature is
determined locally based on the wind mass fraction. In the unified wind model,
the density of the wind is cylindrically stratified and highly concentrated
toward the outflow axis. Our simulations show that for a sufficiently
magnetized wind, the jet identity can be well maintained even at high
temperatures. However, for a high temperature wind with low magnetization, the
thermal pressure of the wind gas can drive material away from the axis, making
the jet less collimated as it propagates. We also study the role of the
poloidal magnetic field of the toroid. It is shown that the wind-ambient
interface becomes more resistant to corrugation when the poloidal field is
present, and the poloidal field that bunches up within the toroid prevents the
swept-up material from being compressed into a thin layer. This suggests that
the ambient poloidal field may play a role in producing a smoother and thicker
swept-up shell structure in the molecular outflow.",1512.02609v1
2017-10-25,Small-mass atomic defects enhance vibrational thermal transport at disordered interfaces with ultrahigh thermal boundary conductance,"The role of interfacial nonidealities and disorder on thermal transport
across interfaces is traditionally assumed to add resistance to heat transfer,
decreasing the thermal boundary conductance (TBC).$^1$ However, recent
computational works have suggested that interfacial defects can enhance this
thermal boundary conductance through emergence of unique vibrations that are
intrinsic to the material interface and defect atoms,$^{2-6}$ a finding that
contradicts traditional theory and conventional understanding. By manipulating
the local heat flux of atomic vibrations that comprise these interfacial modes,
in principle, the TBC can be increased. In this work, we provide evidence that
interfacial defects can enhance the TBC across interfaces through the emergence
of unique high frequency vibrational modes that arise from atomic mass defects
at the interface with relatively small masses. We demonstrate ultrahigh TBC at
amorphous SiOC:H/SiC:H interfaces, approaching 1 GW m$^{-2}$ K$^{-1}$, that is
further increased through the introduction of nitrogen defects. The fact that
disordered interfaces can exhibit such high conductances, which can be further
increased with additional defects offers a unique direction in controlling
interfacial thermal transport that becomes important in manipulating heat
transfer across materials with high densities of interfaces.",1710.09440v1
2019-03-14,Nonsaturating large magnetoresistance in the high carrier density nonsymmorphic metal CrP,"The band structure of high carrier density metal CrP features an interesting
crossing at the Y point of the Brillouin zone. The crossing, which is protected
by the nonsymmorphic symmetry of the space group, results in a hybrid,
semi-Dirac-like energy-momentum dispersion relation near Y. The linear
energy-momentum dispersion relation along Y-$\Gamma$ is reminiscent of the
observed band structure in several semimetallic extremely large
magnetoresistance (XMR) materials. We have measured the transverse
magnetoresistance of CrP up to 14 T at temperatures as low as $\sim$ 16 mK. Our
data reveal a nonsaturating, quadratic magnetoresistance as well as the
behaviour of the so-called `turn-on' temperature in the temperature dependence
of resistivity. Despite the difference in the magnitude of the
magnetoresistance and the fact that CrP is not a semimetal, these features are
qualitatively similar to the observations reported for XMR materials. Thus, the
high-field electrical transport studies of CrP offer the prospect of
identifying the possible origin of the nonsaturating, quadratic
magnetoresistance observed in a wide range of metals.",1903.05914v1
2018-07-03,An Inside Look at the Ti-MoS2 Contact in Ultra-thin Field Effect Transistor with Atomic Resolution,"Two-dimensional molybdenum disulfide (MoS2) is an excellent channel material
for ultra-thin field effect transistors. However, high contact resistance
across the metal-MoS2 interface continues to limit its widespread realization.
Here, using atomic-resolution analytical scanning transmission electron
microscopy (STEM) together with first principle calculations, we show that this
contact problem is a fundamental limitation from the bonding and interactions
at the metal-MoS2 interface that cannot be solved by improved deposition
engineering. STEM analysis in conjunction with theory shows that when MoS2 is
in contact with Ti, a metal with a high affinity to form strong bonds with
sulfur, there is a release of S from Mo along with the formation of small
Ti/TixSy clusters. A destruction of the MoS2 layers and penetration of metal
can also be expected. The design of true high-mobility metal-MoS2 contacts will
require the optimal selection of the metal or alloy based on their bonding
interactions with the MoS2 surface. This can be advanced by evaluation of
binding energies with increasing the number of atoms within metal clusters.",1807.01377v1
2021-02-03,Novel drying additives and their evaluation for self-flowing refractory castables,"The drying step of dense refractory castables containing hydraulic binders is
a critical process, which usually requires using slow heating rates due to the
high explosion trend of such materials during their first thermal treatment.
Thus, this work investigated the performance of alternative additives to induce
faster and safer drying of self-flowing high-alumina refractory castables
bonded with calcium aluminate cement (CAC) or hydratable alumina (HA). The
following materials were analyzed for this purpose: polymeric fibers, a
permeability enhancing compound (RefPac MIPORE 20) and an organic additive
(aluminum salt of 2-hydroxypropanoic acid). The drying behavior and explosion
resistance of the cured samples were evaluated when subjecting the prepared
castables to heating rates of 2, 5 or 20C/min and the obtained data were then
correlated to the potential of the drying agents to improve the permeability
and mechanical strength level of the refractories at different temperatures.
The collected results attested that the selected additives were more efficient
in optimizing the drying behavior of the CAC-bonded compositions, whereas the
HA-containing castables performed better when the aluminum-based salt was
blended with a small amount of CAC (0.5 wt.%), which changed the binders
hydration reaction sequence and optimized the permeability level of the
resulting microstructure. Consequently, some of the designed compositions
evaluated in this work showed improved drying behavior and no explosion was
observed even during the tests carried out under a high heating rate (20C/min).",2102.02008v1
2021-02-06,"Contact-Barrier Free, High Mobility, Dual-Gated Junctionless Transistor Using Tellurium Nanowire","Gate-all-around nanowire transistor, due to its extremely tight electrostatic
control and vertical integration capability, is a highly promising candidate
for sub-5 nm technology node. In particular, the junctionless nanowire
transistors are highly scalable with reduced variability due to avoidance of
steep source/drain junction formation by ion implantation. Here we demonstrate
a dual-gated junctionless nanowire \emph{p}-type field effect transistor using
tellurium nanowire as the channel. The dangling-bond-free surface due to the
unique helical crystal structure of the nanowire, coupled with an integration
of dangling-bond-free, high quality hBN gate dielectric, allows us to achieve a
phonon-limited field effect hole mobility of $570\,\mathrm{cm^{2}/V\cdot s}$ at
270 K, which is well above state-of-the-art strained Si hole mobility. By
lowering the temperature, the mobility increases to
$1390\,\mathrm{cm^{2}/V\cdot s}$ and becomes primarily limited by Coulomb
scattering. \txc{The combination of an electron affinity of $\sim$4 eV and a
small bandgap of tellurium provides zero Schottky barrier height for hole
injection at the metal-contact interface}, which is remarkable for reduction of
contact resistance in a highly scaled transistor. Exploiting these properties,
coupled with the dual-gated operation, we achieve a high drive current of
$216\,\mathrm{\mu A/\mu m}$ while maintaining an on-off ratio in excess of
$2\times10^4$. The findings have intriguing prospects for alternate channel
material based next-generation electronics.",2102.03507v1
2021-05-27,Route to High-Performance Micro-solid Oxide Fuel Cells on Metallic Substrates,"Micro-solid oxide fuel cells based on thin films have strong potential for
use in portable power devices. However, devices based on silicon substrates
typically involve thin-film metallic electrodes which are unstable at high
temperatures. Devices based on bulk metal substrates overcome these
limitations, though performance is hindered by the challenge of growing
state-of-the-art epitaxial materials on metals. Here, we demonstrate for the
first time the growth of epitaxial cathode materials on metal substrates
(stainless steel) commercially supplied with epitaxial electrolyte layers (1.5
{um (Y2O3)0.15(ZrO2)0.85 (YSZ) + 50 nm CeO2). We create epitaxial mesoporous
cathodes of (La0.60Sr0.40)0.95Co0.20Fe0.80O3 (LSCF) on the substrate by growing
LSCF/MgO vertically aligned nanocomposite films by pulsed laser deposition,
followed by selectively etching out the MgO. To enable valid comparison with
the literature, the cathodes are also grown on single-crystal substrates,
confirming state-of-the-art performance with an area specific resistance of
100ohmegacm2 at 500dC and activation energy down to 0.97 eV. The work marks an
important step toward the commercialization of high-performance micro-solid
oxide fuel cells for portable power applications.",2105.13117v1
2023-03-15,Characterization of local deformation around hydrides in Zircaloy-4 using conventional and high angular resolution electron backscatter diffraction,"Zircaloy-4 is used as a fuel cladding material for water reactors, as it has
good mechanical properties, corrosion resistance, and a low thermal neutron
absorption cross section. However, the mechanical performance of Zircaloy-4 can
be reduced during service due to hydrogen uptake and hydride formation. These
hydrides are brittle, and often reduce the strength and toughness of materials
as well as increase susceptibility to delayed hydride cracking (DHC). In this
work, large grain Zircaloy-4 with hydrides was prepared and then cross
sectioned using cryo-ion beam polishing, using plasma focused ion beam (pFIB)
and broad ion beam (BIB) approaches to enable the preparation of a very high
quality flat surface with no preferential etching of either the hydride or
zirconium metal (typically metallographic polishing preferentially removes
hydrides). Conventional and high angular resolution electron backscatter
diffraction (EBSD) analysis were then used to explore morphology, deformation
fields, and orientation relationships between the zirconium matrix and
hydrides. Four maps were collected for analysis which included hydrides near
grain boundaries: (a) where the hydride smoothly decorates across two of the
connecting boundaries near a triple junction; (b) where the hydride smoothly
decorates the boundary; (c) a mixture of smooth decoration of the interface and
protrusion into the grains; (d) fine scale hydride that protrudes into one
grain. This work highlights that incompatibility of the hydride within the
zirconium matrix is strongly linked to the orientation relationship of the
hydride and matrix, and the grain boundary character. These results may enable
enhanced understanding of the role of hydrides in fracture as well as
stress-induced hydride reorientation and DHC susceptibility.",2303.08311v1
2014-10-15,Cyclic Strength and Nonlinear Material Fracture Mechanics (by the example of steels),"It was shown that a material fatigue fracture diagram can be viewed as a
locus of points with $\sigma $ and $\sqrt l$ coordinates' product equal to
$K_{1c}/2$, and $\sigma $ and $l$ product -- to $G_{1c}/2$, where $K_{1c}$ and
$G_{1c}$ are non-linear fracture mechanics force and energy criteria. It was
established that the average number of interatomic bonds destroyed within one
alternate stress $\nabla_{1cs}$ cycle is directly proportional to $\sigma $
that is twice as large as a peak value of $\sigma^a$. It was found that
low-cycle fatigue is characterized by $\sigma >\sigma_{0.2}$ and $\sigma_{1cs}>
1$, high-cycle fatigue -- by $\sigma = \sigma_{0.2}$ and $\nabla_{1cs} = 1$,
and giga-cycle fatigue -- by $\sigma < \sigma_{0.2}$ and $\nabla_{1cs} < 1$. An
individual interatomic bond cannot be destroyed part by part but as a single
unit. The latter means that in giga-cycle fatigue a single interatomic bond is
destroyed within several cycles rather than within a single cycle. The factors
$F$ (collapsibility) and $R$ (resistibility) were proposed and mentioned as
essential material physical constants. The introduced notion $\nabla_{1cs}$ and
the established linear nature of $\nabla_{1cs}$ relationship allow to: a)
clarify the fatigue crack growth physical nature in low-, high- and giga-cycle
fracture zones; b) determine the nature of a fatigue fracture diagram
disruption; c) plot the fatigue fracture diagram using the results obtained in
a single specimen cyclic strength test with a selected value of $\sigma \ge
\sigma_{0.2}$. For giga-cycle fatigue it is important (with similar purpose in
mind) to determine this dependence for $\sigma < \sigma_{0.2}$. It is
recommended to use $G_{1c}$ criterion to find the $l_{cr}$ length value which
in contrast to $K_{1c}$ has a clear physical nature.",1410.4177v2
2014-12-14,Gate-tunable quantum oscillations in ambipolar Cd3As2 thin films,"Electrostatic doping in materials can lead to various exciting electronic
properties, such as metal-insulator transition and superconductivity, by
altering the Fermi level position or introducing exotic phases. Cd3As2, a
three-dimensional (3D) analog of graphene with extraordinary carrier mobility,
was predicted to be a 3D Dirac semimetal, a feature confirmed by recent
experiments. However, most research so far has been focused on metallic bulk
materials that are known to possess ultra-high mobility and giant
magnetoresistance but limited carrier transport tunability. Here, we report on
the first observation of a gate-induced transition from band conduction to
hopping conduction in single-crystalline Cd3As2 thin films via electrostatic
doping by solid electrolyte gating. The extreme charge doping enables the
unexpected observation of p-type conductivity in a 50 nm-thick Cd3As2 thin film
grown by molecular beam epitaxy. More importantly, the gate-tunable
Shubnikov-de Haas (SdH) oscillations and the temperature-dependent resistance
reveal a unique band structure and bandgap opening when the dimensionality of
Cd3As2 is reduced. This is also confirmed by our first-principles calculations.
The present results offer new insights towards nanoelectronic and
optoelectronic applications of Dirac semimetals in general, and provide new
routes in the search for the intriguing quantum spin Hall effect in
low-dimension Dirac semimetals, an effect that is theoretically predicted but
not yet experimentally realized.",1412.4380v2
2016-05-15,Nearly massless Dirac fermions hosted by Sb square net in BaMnSb2,"Layered compounds AMnBi2 (A=Ca, Sr, Ba, or rare earth element) have been
established as Dirac materials. Dirac electrons generated by the
two-dimensional (2D) Bi square net in these materials are normally massive due
to the presence of a spin-orbital coupling (SOC) induced gap at Dirac nodes.
Here we report that the Sb square net in an isostructural compound BaMnSb2 can
host nearly massless Dirac fermions. We observed strong Shubnikov-de Haas (SdH)
oscillations in this material. From the analyses of the SdH oscillations, we
find key signatures of Dirac fermions, including light effective mass
(~0.052m0; m0, mass of free electron), high quantum mobility (1280 cm2V-1S-1)
and a Pi Berry phase accumulated along cyclotron orbit. Compared with AMnBi2,
BaMnSb2 also exhibits much more significant quasi two-dimensional (2D)
electronic structure, with the out-of-plane transport showing nonmetallic
conduction below 120K and the ratio of the out-of-plane and in-plane
resistivity reaching ~670. Additionally, BaMnSb2 also exhibits an
antiferromagnetic order with a weak ferromagnetic component. The combination of
nearly massless Dirac fermions on quasi-2D planes with a magnetic order makes
BaMnSb2 an intriguing platform for seeking novel exotic phenomena of massless
Dirac electrons.",1605.04613v2
2017-10-09,Huge magnetoresistance and ultra-sharp metamagnetic transition in polycrystalline ${Sm_{0.5}Ca_{0.25}Sr_{0.25}MnO_3}$,"Large magnetoresistive materials are of immense interest for a number of
spintronic applications by developing high density magnetic memory devices,
magnetic sensors and magnetic switches. Colossal magnetoresistance, for which
resistivity changes several order of magnitude (${\sim10^4 \%}$) in an external
magnetic field, occurs mainly in phase separated oxide materials, namely
manganites, due to the phase competition between the ferromagnetic metallic and
the antiferromagnetic insulating regions. Can one further enhance the
magnetoresistance by tuning the volume fraction of the two phases? In this
work, we report a huge colossal magnetoresistance along with the ultra-sharp
metamagnetic transition in half doped ${Sm_{0.5}Ca_{0.25}Sr_{0.25}MnO_3}$
manganite compound by suitably tuning the volume fraction of the competing
phases. The obtained magnetoresistance value at 10 K is as large as
$\sim10^{13}\%$ in a 30 kOe external magnetic field and $\sim10^{15}\%$ in 90
kOe external magnetic field and is several orders of magnitude higher than any
other observed magnetoresistance value reported so far. Using model Hamiltonian
calculations we have shown that the inhomogeneous disorder, deduced from
tunneling electron microscopy, suppresses the CE-type phase and seeds the
ferromagnetic metal in an external magnetic field.",1710.03007v2
2018-09-12,V$_5$S$_8$: a Kondo lattice based on intercalation of van der Waals layered transition metal dichalcogenide,"Since the discovery of graphene, a tremendous amount of two dimensional (2D)
materials have surfaced. Their electronic properties can usually be well
understood without considering correlations between electrons. On the other
hand, strong electronic correlations are known to give rise to a variety of
exotic properties and new quantum phases, for instance, high temperature
superconductivity, heavy fermions and quantum spin liquids. The study of these
phenomena has been one of the main focuses of condensed matter physics. There
is a strong incentive to introduce electronic correlations into 2D materials.
Via intercalating a van der Waals layered compound VS$_2$, we show an emergence
of a Kondo lattice, an extensively studied strongly correlated system, by
magnetic, specific heat, electrical and thermoelectric transport studies. In
particular, an exceptionally large Sommerfeld coefficient, 440
mJ$\cdot$K$^{-2}\cdot$mol$^{-1}$, indicates a strong electron correlation. The
obtained Kadowaki-Woods ratio, $2.7\times 10^{-6}$
$\mu\Omega\cdot$cm$\cdot$mol$^2\cdot$K$^2\cdot$mJ$^{-2}$, also supports the
strong electron-electron interaction. The temperature dependence of the
resistivity and thermopower corroborate the Kondo lattice picture. The
intercalated compound is one of a few rare examples of $d$-electron Kondo
lattices. We further show that the Kondo physics persists in ultra-thin films.
This work thus demonstrates a route to generate strong correlations in 2D
materials.",1809.04213v1
2014-08-03,"Carrier screening, transport, and relaxation in 3D Dirac semimetals","A theory is developed for the density and temperature dependent carrier
conductivity in doped three-dimensional (3D) Dirac materials focusing on
resistive scattering from screened Coulomb disorder due to random charged
impurities (e.g., dopant ions and unintentional background impurities). The
theory applies both in the undoped intrinsic (""high-temperature"", $T \gg T_F$)
and the doped extrinsic (""low-temperature"", $T \ll T_F$) limit with analytical
scaling properties for the carrier conductivity obtained in both regimes, where
$T_F$ is the Fermi temperature corresponding to the doped free carrier density
(electrons or holes). The scaling properties describing how the conductivity
depends on the density and temperature can be used to establish the Dirac
nature of 3D systems through transport measurements. We also consider the
temperature dependent conductivity limited by the acoustic phonon scattering in
3D Dirac materials. In addition, we theoretically calculate and compare the
single particle relaxation time $\tas$, defining the quantum level broadening,
and the transport scattering time $\tat$, defining the conductivity, in the
presence of screened charged impurity scattering. A critical quantitative
analysis of the $\tat/\tas$ results for 3D Dirac materials in the presence of
long-range screened Coulomb disorder is provided.",1408.0518v2
2017-03-28,Metallic vanadium disulfide nanosheets as a platform material for multifunctional electrode applications,"Nano-thick metallic transition metal dichalcogenides such as VS$_{2}$ are
essential building blocks for constructing next-generation electronic and
energy-storage applications, as well as for exploring unique physical issues
associated with the dimensionality effect. However, such 2D layered materials
have yet to be achieved through either mechanical exfoliation or bottom-up
synthesis. Herein, we report a facile chemical vapor deposition route for
direct production of crystalline VS$_{2}$ nanosheets with sub-10 nm thicknesses
and domain sizes of tens of micrometers. The obtained nanosheets feature
spontaneous superlattice periodicities and excellent electrical conductivities
(~3$\times$10$^{3}$ S cm$^{-1}$), which has enabled a variety of applications
such as contact electrodes for monolayer MoS$_{2}$ with contact resistances of
~1/4 to that of Ni/Au metals, and as supercapacitor electrodes in aqueous
electrolytes showing specific capacitances as high as 8.6$\times$10$^{2}$ F
g$^{-1}$. This work provides fresh insights into the delicate
structure-property relationship and the broad application prospects of such
metallic 2D materials.",1703.09582v1
2019-02-26,Superconductivity at 161 K in Thorium Hydride $ThH_{10}$: Synthesis and Properties,"Here we report targeted high-pressure synthesis of two novel high-$T_C$
hydride superconductors, $P6_3/mmc$-$ThH_9$ and $Fm\bar{3}m$-$ThH_{10}$, with
the experimental critical temperatures ($T_C$) of 146 K and 159-161 K and upper
critical magnetic fields ($\mu$$H_C$) 38 and 45 Tesla at pressures 170-175
Gigapascals, respectively. Superconductivity was evidenced by the observation
of zero resistance and a decrease of $T_C$ under external magnetic field up to
16 Tesla. This is one of the highest critical temperatures that has been
achieved experimentally in any compounds, along with such materials as
$LaH_{10}$, $H_3S$ and $HgBa_2Ca_xCu_2O_{6+z}$. Our experiments show that
$fcc$-$ThH_{10}$ has stabilization pressure of 85 GPa, making this material
unique among all known high-$T_C$ metal polyhydrides. Two recently predicted
Th-H compounds, $I4/mmm$-$ThH_4$ (> 86 GPa) and $Cmc2_1$-$ThH_6$ (86-104 GPa),
were also synthesized. Equations of state of obtained thorium polyhydrides were
measured and found to perfectly agree with the theoretical calculations. New
phases were examined theoretically and their electronic, phonon, and
superconducting properties were calculated.",1902.10206v4
2022-02-10,"Giant magnetoresistance, Fermi surface topology, Shoenberg effect and vanishing quantum oscillations in type-II Dirac semimetal candidates MoSi$_2$ and WSi$_2$","We performed comprehensive theoretical and experimental studies of the
electronic structure and the Fermi surface topology of two novel quantum
materials, MoSi$_2$ and WSi$_2$. The theoretical predictions of the electronic
structure in the vicinity of the Fermi level was verified experimentally by
thorough analysis of the observed quantum oscillations in both electrical
resistivity and magnetostriction. We established that the Fermi surface sheets
in MoSi$_2$ and WSi$_2$ consist of 3D dumbbell-shaped hole-like pockets and
rosette-shaped electron-like pockets, with nearly equal volumes. Based on this
finding, both materials were characterized as almost perfectly compensated
semimetals. In conjunction, the magnetoresistance attains giant values of
$10^4$ and $10^5\,\%$ for WSi$_2$ and MoSi$_2$, respectively. In turn, the
anisotropic magnetoresistance achieves $-95$ and $-98\,\%$ at $T=2\,$K and in
$B=14\,$T for WSi$_2$ and MoSi$_2$, respectively. Furthermore, for both
compounds we observed the Shoenberg effect in their Shubnikov-de Haas
oscillations that persisted at as high temperature as $T=25\,$K in MoSi$_2$ and
$T=12\,$K in WSi$_2$. In addition, we found for MoSi$_2$ a rarely observed
spin-zero phenomenon. Remarkably, the electronic structure calculations
revealed type-II Dirac cones located near 480 meV and 710 meV above the Fermi
level in MoSi$_2$ and WSi$_2$, respectively.",2202.05362v1
2017-04-24,1D van der Waals Material Tellurium: Raman Spectroscopy under Strain and Magneto-transport,"Experimental demonstrations of 1D van der Waals material tellurium have been
presented by Raman spectroscopy under strain and magneto-transport. Raman
spectroscopy measurements have been performed under strains along different
principle axes. Pronounced strain response along c-axis is observed due to the
strong intra-chain covalent bonds, while no strain response is obtained along
a-axis due to the weak inter-chain van der Waals interaction. Magneto-transport
results further verify its anisotropic property, resulting in dramatically
distinct magneto-resistance behaviors in terms of three different magnetic
field directions. Specifically, phase coherence length extracted from weak
antilocalization effect, L$_{\Phi}$ ~ T$^{-0.5}$, claims its 2D transport
characteristics when an applied magnetic field is perpendicular to the thin
film. In contrast, L$_{\Phi}$ ~ T$^{-0.33}$ is obtained from universal
conductance fluctuations once the magnetic field is along c-axis of Te,
indicating its nature of 1D transport along the helical atomic chains. Our
studies, which are obtained on high quality single crystal tellurium thin film,
appear to serve as strong evidences of its 1D van der Waals structure from
experimental perspectives. It is the aim of this paper to address this special
concept that differs from the previous well-studied 1D nanowires or 2D van der
Waals materials.",1704.07020v1
2019-03-09,A New Magnetic Topological Quantum Material Candidate by Design,"Magnetism, when combined with an unconventional electronic band structure,
can give rise to forefront electronic properties such as the quantum anomalous
Hall effect, axion electrodynamics, and Majorana fermions. Here we report the
characterization of high-quality crystals of EuSn$_2$P$_2$, a new quantum
material specifically designed to engender unconventional electronic states
plus magnetism. EuSn$_2$P$_2$ has a layered, Bi$_2$Te$_3$-type structure.
Ferromagnetic interactions dominate the Curie-Weiss susceptibility, but a
transition to antiferromagnetic ordering occurs near 30 K. Neutron diffraction
reveals that this is due to two-dimensional ferromagnetic spin alignment within
individual Eu layers and antiferromagnetic alignment between layers - this
magnetic state surrounds the Sn-P layers at low temperatures. The bulk
electrical resistivity is sensitive to the magnetism. Electronic structure
calculations reveal that EuSn$_2$P$_2$ might be a strong topological insulator,
which can be a new magnetic topological quantum material (MTQM) candidate. The
calculations show that surface states should be present, and they are indeed
observed by ARPES measurements.",1903.03888v1
2019-01-23,Enhancing Interconnect Reliability and Performance by Converting Tantalum to 2D Layered Tantalum Sulfide at Low Temperature,"The interconnect half-pitch size will reach ~20 nm in the coming sub-5 nm
technology node. Meanwhile, the TaN/Ta (barrier/liner) bilayer stack has to be
> 4 nm to ensure acceptable liner and diffusion barrier properties. Since
TaN/Ta occupy a significant portion of the interconnect cross-section and they
are much more resistive than Cu, the effective conductance of an ultra-scaled
interconnect will be compromised by the thick bilayer. Therefore, two
dimensional (2D) layered materials have been explored as diffusion barrier
alternatives. However, many of the proposed 2D barriers are prepared at too
high temperatures to be compatible with the back-end-of-line (BEOL) technology.
In addition, as important as the diffusion barrier properties, the liner
properties of 2D materials must be evaluated, which has not yet been pursued.
Here, a 2D layered tantalum sulfide (TaSx) with ~1.5 nm thickness is developed
to replace the conventional TaN/Ta bilayer. The TaSx ultra-thin film is
industry-friendly, BEOL-compatible, and can be directly prepared on
dielectrics. Our results show superior barrier/liner properties of TaSx
compared to the TaN/Ta bilayer. This single-stack material, serving as both a
liner and a barrier, will enable continued scaling of interconnects beyond 5 nm
node.",1901.08143v1
2020-08-31,Enhanced fracture toughness in ceramic superlattice thin films: on the role of coherency stresses and misfit dislocations,"Superlattice (SL) thin films composed of refractory ceramics unite extremely
high hardness and enhanced fracture toughness; a material combination often
being mutually exclusive. While the hardness enhancement obtained whentwo
materials form a superlattice is well described by existing models based on
dislocation mobility, the underlying mechanisms behind the increase in fracture
toughness are yet to be unraveled. Here we provide a model based on linear
elasticity theory to predict the fracture toughness enhancement in
(semi-)epitaxial nanolayers due to coherency stresses and formation of misfit
dislocations. We exemplarily study a superlattice structure composed of two
cubic transition metal nitrides (TiN, CrN) on a MgO (100) single-crystal
substrate. Minimization of the overall strain energy, each time a new layer is
added on the nanolayered stack, allows estimating the density of misfit
dislocations formed at the interfaces. The evolving coherency stresses, which
are partly relaxed by the misfit dislocations, are then used to calculate the
apparent fracture toughness of respective SL architectures by applying the
weight function method. The results show that the critical stress intensity
increases steeply with increasing bilayer period for very thin (essentially
dislocation-free) SLs, before the K_IC values decline more gently along with
the formation of misfit dislocations. The characteristic K_IC vs.
bilayer-period-dependence nicely matches experimental trends. Importantly, all
critical stress intensity values of the superlattice films clearly exceed the
intrinsic fracture toughness of the constituting layer materials, evincing the
importance of coherency stresses for increasing the crack growth resistance.",2008.13652v1
2020-12-10,Evidence of non-trivial Berry phase and Kondo physics in SmBi,"Realization of semimetals with non-trivial topologies such as Dirac and Weyl
semimetals, have provided a boost in the study of these quantum materials.
Presence of electron correlation makes the system even more exotic due to
enhanced scattering of charge carriers, Kondo screening etc. Here, we studied
the electronic properties of single crystalline, SmBi employing varied state of
the art bulk measurements. Magnetization data reveals two magnetic transitions;
an antiferromagnetic order with a Neel temperature of ~ 9 K and a second
magnetic transition at a lower temperature (= 7 K). The electrical resistivity
data shows an upturn typical of a Kondo system and the estimated Kondo
temperature is found to be close to the Neel temperature. High quality of the
crystal enabled us to discover signature of quantum oscillation in the
magnetization data even at low magnetic field. Using a Landau level fan diagram
analysis, a non-trivial Berry phase is identified for a Fermi pocket revealing
the topological character in this material. These results demonstrate an unique
example of the Fermiology in the antiferromagnetic state and opens up a new
paradigm to explore the Dirac fermion physics in correlated topological metal
via interplay of Kondo interaction, topological order and magnetism.",2012.05459v1
2021-03-25,Bonding nature and optical contrast of $TiTe_2$/$Sb_2Te_3$ phase-change heterostructure,"Chalcogenide phase-change materials (PCMs) are regarded as the leading
candidate for storage-class non-volatile memory and neuro-inspired computing.
Recently, using the $TiTe_2$/$Sb_2Te_3$ material combination, a new framework -
phase-change heterostructure (PCH), has been developed and proved to
effectively suppress the noise and drift in electrical resistance upon memory
programming, largely reducing the inter-device variability. However, the
atomic-scale structural and chemical nature of PCH remains to be fully
understood. In this work, we carry out thorough ab initio simulations to assess
the bonding characteristics of the PCH. We show that the $TiTe_2$ crystalline
nanolayers do not chemically interact with the surrounding $Sb_2Te_3$, and are
stabilized by strong covalent and electrostatic Ti-Te interactions, which
create a prohibitively high barrier for atomic migrations along the pulsing
direction. We also find significant contrast in computed dielectric functions
in the PCH, suggesting possible optical applications of this class of devices.
With the more confined space and therefore constrained phase transition
compared to traditional PCM devices, the recently introduced class of PCH-based
devices may lead to improvements in phase-change photonic and optoelectronic
applications with much lower stochasticity during programming.",2103.13583v2
2021-06-30,Classifying charge carrier interaction in highly-compressed elements and silane,"Since pivotal experimental discovery of the near-room-temperature
superconductivity (NRTS) in highly-compressed sulphur hydride by Drozdov et al
(2015 Nature 525 73-76), more than a dozen of binary and of ternary
hydrogen-rich phases exhibited superconducting transition above 100 K have been
discovered to date. There is a widely accepted theoretical point of view that
primary mechanism governing the emergence of superconductivity in hydrogen-rich
phases is the electron-phonon pairing. However, our recent analysis of
experimental temperature dependent resistance in $H_{3}S$, $LaH_{x}$, $PrH_{9}$
and $BaH_{12}$ (arXiv: 2104.14145) showed that these compounds exhibit the
dominance of non-electron-phonon charge carrier interaction and, thus, it is
unlikely that the electron-phonon pairing is the primary mechanism for the
emergence of superconductivity in these materials. Here we use the same
approach to reveal charge carrier interaction in highly-compressed lithium,
black phosphorous, sulfur, and silane. We found that all these superconductors
exhibit the dominance of non-electron-phonon charge carrier interaction. This
explains the failure of high-Tc values predicted for these materials by the
first-principles calculations which utilized the electron-phonon pairing as the
mechanism for the emergence of superconductivity in these materials. Our result
implies that alternative pairing mechanisms (i.e., electron-magnon,
electron-polaron, electron-electron, etc.) should be tested within
first-principles calculations approach as possible mechanisms for the emergence
of superconductivity in highly-compressed superconductors.",2106.15873v1
2021-09-08,Coherent spin rotation-induced zero thermal expansion in MnCoSi-based spiral magnets,"Materials exhibiting zero thermal expansion (ZTE), namely, volume invariance
during temperature change, can resist thermal shock and are highly desired in
modern industries as high-precision components. However, pure ZTE materials are
rare, especially those that are metallic. Here, we report the discovery of a
pure metallic ZTE material: an orthorhombic Mn1-xNixCoSi spiral magnet. The
introduction of Ni can efficiently enhance the ferromagnetic exchange
interaction and construct the transition from a spiral magnetic state to a
ferromagnetic-like state in MnCoSi-based alloys. Systematic in situ neutron
powder diffraction revealed a new cycloidal spiral magnetic structure in bc
plane at ground state which would transform to the helical spiral in the ab
plane with increasing temperature. Combined with Lorentz transmission electron
microscopy techniques, the cycloidal and helical spin order coherently rotated
at varying periods along the c axis during the magnetic transition. This spin
rotation drove the continuous movement of the coupled crystalline lattice and
induced a large negative thermal expansion along the a axis, eventually leading
to a wide-temperature ZTE effect. Our work not only introduces a new ZTE alloy
but also presents a new mechanism by which to discover or design ZTE magnets.",2109.03557v1
2022-04-09,Role of substrate surface morphology on the performance of graphene inks for flexible electronics,"Two-dimensional (2D) materials, such as graphene, are seen as potential
candidates for fabricating electronic devices and circuits on flexible
substrates. Inks or dispersions of 2D materials can be deposited on flexible
substrates by large-scale coating techniques, such as inkjet printing and spray
coating. One of the main issues in coating processes is nonuniform deposition
of inks, which may lead to large variations of properties across the
substrates. Here, we investigate the role of surface morphology on the
performance of graphene ink deposited on different paper substrates with
specific top coatings. Substrates with good wetting properties result in
reproducible thin films and electrical properties with low sheet resistance.
The correct choice of surface morphology enables high-performance films without
postdeposition annealing or treatment. Scanning terahertz time-domain
spectroscopy (THz-TDS) is introduced to evaluate both the uniformity and the
local conductivity of graphene inks on paper. A paper-based strain gauge is
demonstrated and a variable resistor acts as an on-off switch for operating an
LED. Customized surfaces can thus help in unleashing the full potential of
ink-based 2D materials.",2204.04503v1
2023-04-28,"First-principles Prediction of Potential Candidate Materials MCu$_3$X$_4$ (M = V, Nb, Ta; X = S, Se, Te) for Neuromorphic Computing","Inspired by the neuro-synaptic frameworks in the human brain, neuromorphic
computing is expected to overcome the bottleneck of traditional von-Neumann
architecture and be used in artificial intelligence. Here, we predict a class
of potential candidate materials, MCu$_3$X$_4$ (M = V, Nb, Ta; X = S, Se, Te),
for neuromorphic computing applications through first-principles calculations
based on density functional theory. We find that when MCu$_3$X$_4$ are inserted
with Li atom, the systems would transform from semiconductors to metals due to
the considerable electron filling [~0.8 electrons per formula unit (f.u.)] and
still maintain well structural stability. Meanwhile, the inserted Li atom also
has a low diffusion barrier (~0.6 eV/f.u.), which ensures the feasibility to
control the insertion/extraction of Li by gate voltage. These results establish
that the system can achieve the reversible switching between two stable memory
states, i.e., high/low resistance state, indicating that it could potentially
be used to design synaptic transistor to enable neuromorphic computing. Our
work provides inspiration for advancing the search of candidate materials
related to neuromorphic computing from the perspective of theoretical
calculations.",2304.14897v1
2023-06-26,Microscopic conductivity of passive films on ferritic stainless steel for hydrogen fuel cells,"Hydrogen fuel cells offer a clean and sustainable energy conversion solution.
The bipolar separator plate, a critical component in fuel cells, plays a vital
role in preventing reactant gas cross-contamination and facilitating efficient
ion transport in a fuel cell. High chromium ferritic stainless steel with an
artificially formed thin chromium oxide passive film has recently gained
attention due to its superior electrical conductivity and corrosion resistance,
making it a suitable material for separators. In this study, we investigate the
microscopic electrical conductivity of the intrinsic passive oxide film on such
ferritic stainless steel. Through advanced surface characterization techniques
such as current sensing atomic force microscopy and scanning tunneling
microscopy/spectroscopy, we discover highly conductive regions within the film
that vary depending on location. These findings provide valuable insights into
the behavior of the passive oxide film in fuel cells. By understanding the
microscopic electrical properties, we can enhance the design and performance of
separator materials in hydrogen fuel cells. Ultimately, this research
contributes to a broader understanding of separator materials and supports the
wider application of hydrogen fuel cells.",2306.14513v1
2003-10-20,Radiation induced oscillatory Hall effect in high mobility GaAs/AlGaAs devices,"We examine the radiation induced modification of the Hall effect in high
mobility GaAs/AlGaAs devices that exhibit vanishing resistance under microwave
excitation. The modification in the Hall effect upon irradiation is
characterized by (a) a small reduction in the slope of the Hall resistance
curve with respect to the dark value, (b) a periodic reduction in the magnitude
of the Hall resistance, $R_{xy}$, that correlates with an increase in the
diagonal resistance, $R_{xx}$, and (c) a Hall resistance correction that
disappears as the diagonal resistance vanishes.",0310474v2
2015-09-03,A simple model for in- and out-of-plane resistivities of hole doped cuprates,"The highly anisotropic and qualitatively different nature of in- and
out-of-plane charge dynamics in high-Tc cuprates cannot be accommodated within
the conventional Boltzmann transport theory. The variation of in- and
out-of-plane resistivities with temperature and hole content are also anomalous
and cannot be explained by Fermi-liquid theory. In this study we have proposed
a simple phenomenological model for the dc resistivity of cuprates by
incorporating two firmly established generic features of all hole doped cuprate
superconductors- (1) the pseudogap in the quasiparticle energy spectrum and (2)
the T-linear resistivity at high temperatures. This T-linear behavior over an
extended temperature range can be attributed to a quantum criticality,
affecting the electronic phase diagram of cuprates. Experimental in-plane and
out-of-plane resistivities of double layer Y(Ca)123 have been analyzed using
the proposed model. This phenomenological model describes the temperature and
hole content dependent resistivity over a wide range of temperature and hole
content.",1509.01107v2
2015-10-12,The Mott-Ioffe-Regel limit and resistivity crossover in a tractable electron-phonon model,"Many metals display resistivity saturation - a substantial decrease in the
slope of the resistivity as a function of temperature, that occurs when the
electron scattering rate $\tau^{-1}$ becomes comparable to the Fermi energy
$E_F/\hbar$ (the Mott-Ioffe-Regel limit). At such temperatures, the usual
description of a metal in terms of ballistically propagating quasiparticles is
no longer valid. We present a tractable model of a large $N$ number of
electronic bands coupled to $N^2$ optical phonon modes, which displays a
crossover behavior in the resistivity at temperatures where $\tau^{-1}\sim
E_F/\hbar$. At low temperatures, the resistivity obeys the familiar linear
form, while at high temperatures, the resistivity still increases linearly, but
with a modified slope (that can be either lower or higher than the
low-temperature slope, depending on the band structure). The high temperature
non-Boltzmann regime is interpreted by considering the diffusion constant and
the compressibility, both of which scale as the inverse square root of the
temperature.",1512.00041v2
2022-02-13,Information Density in Multi-Layer Resistive Memories,"Resistive memories store information in a crossbar arrangement of
two-terminal devices that can be programmed to patterns of high or low
resistance. While extremely compact, this technology suffers from the
""sneak-path"" problem: certain information patterns cannot be recovered, as
multiple low resistances in parallel make a high resistance indistinguishable
from a low resistance. In this paper, a multi-layer device is considered, and
the number of bits it can store is derived exactly and asymptotic bounds are
developed. The information density of a series of isolated arrays with extreme
aspect ratios is derived in the single- and multi-layer cases with and without
peripheral selection circuitry. This density is shown to be non-zero in the
limit, unlike that of the arrays with moderate aspect ratios previously
considered. A simple encoding scheme that achieves capacity asymptotically is
presented.",2202.06367v1
2023-09-27,Fractal-like star-mesh transformations using graphene quantum Hall arrays,"A mathematical approach is adopted for optimizing the number of total device
elements required for obtaining high effective quantized resistances in
graphene-based quantum Hall array devices. This work explores an analytical
extension to the use of star-mesh transformations such that fractal-like, or
recursive, device designs can yield high enough resistances (like 1 E{\Omega},
arguably the highest resistance with meaningful applicability) while still
being feasible to build with modern fabrication techniques. Epitaxial graphene
elements are tested, whose quantized Hall resistance at the nu=2 plateau (R_H =
12906.4 {\Omega}) becomes the building block for larger effective, quantized
resistances. It is demonstrated that, mathematically, one would not need more
than 200 elements to achieve the highest pertinent resistances",2309.15813v1
1999-01-25,Charge Transport in Synthetic Metals,"The phenomenology of charge transport in synthetic metals is reviewed. It is
argued that the conventional quasiparticle picture and Boltzmann transport
theory do not apply to these materials. The central ideas of Fermi liquid
theory are reviewed, and the significant corrections produced by quasiparticle
scattering from ferromagnetic spin fluctuations in liquid $^3$He are described.
It is shown that Sr$_2$RuO$_4$ does not display the symptoms of a
nearly-ferromagnetic Fermi liquid, so the source of its odd angular momentum
pairing remains to be understood. The solution of an assisted-tunneling model
of charge transport in quasi-one dimensional materials is described. This model
has a quantum critical point and gives a resistivity that is linear in
temperature or frequency, whichever is greater.",9901270v1
2000-01-11,Interpretation of a microwave induced current step in a single intrinsic Josephson junction on a Bi-2223 thin film,"Thin stacks consisting of a single intrinsic Josephson junction on
(Bi,Pb)-Sr-Ca-Cu-O thin films are investigated under the influence of external
microwave fields. The $I$-$V$-characteristic shows a single resistive branch, a
clear superconducting gap edge structure and a pronounced current step in
external microwave fields. With increasing irradiation power it shifts to
higher voltages, while the height of the step remains practically unchanged. In
a numerical simulation including an ac-magnetic field parallel to the
superconducting layers the experimental features of the structure can be
explained by a collective motion of Josephson fluxons.",0001152v2
2000-12-07,Superconductivity on the threshold of magnetism in CePd2Si2 and CeIn3,"The magnetic ordering temperature of some rare earth based heavy fermion
compounds is strongly pressure-dependent and can be completely suppressed at a
critical pressure, p$_c$, making way for novel correlated electron states close
to this quantum critical point. We have studied the clean heavy fermion
antiferromagnets CePd$_2$Si$_2$ and CeIn$_3$ in a series of resistivity
measurements at high pressures up to 3.2 GPa and down to temperatures in the mK
region. In both materials, superconductivity appears in a small window of a few
tenths of a GPa on either side of p$_c$. We present detailed measurements of
the superconducting and magnetic temperature-pressure phase diagram, which
indicate that superconductivity in these materials is enhanced, rather than
suppressed, by the closeness to magnetic order.",0012118v1
2002-02-03,Giant change in IR light transmission in La_{0.67}Ca_{0.33}MnO_{3} film near the Curie temperature: promising application in optical devices,"Transport, magnetic, magneto-optical (Kerr effect) and optical (light
absorption) properties have been studied in an oriented polycrystalline
La_{0.67}Ca_{0.33}MnO_{3} film which shows colossal magneto-resistance. The
correlations between these properties are presented. A giant change in IR light
transmission (more than a 1000-fold decrease) is observed on crossing the Curie
temperature (about 270 K) from high to low temperature. Large changes in
transmittance in a magnetic field were observed as well. The giant changes in
transmittance and the large magneto-transmittance can be used for development
of IR optoelectronic devices controlled by thermal and magnetic fields.
Required material characteristics of doped manganites for these devices are
discussed.",0202041v1
2002-07-10,Crystal growth and characterization of MgB2: Relation between structure and superconducting properties,"We discuss the important aspects of synthesis and crystal growth of MgB2
under high pressure (P) and temperature (T) in Mg-B-N system, including the
optimisation of P-T conditions for reproducible crystal growth, the role of
liquid phases in this process, the temperature dependence of crystal size and
the effect of growing instabilities on single crystals morphology. Extensive
experiments have been carried out on single crystals with slightly different
lattice constants and defects concentration, which revealed and possible
effects of Mg-deficiency and lattice strain on the superconducting properties
of MgB2 (Tc, Jc, residual resistivity ratio, anisotropy etc.).",0207247v1
2002-07-10,Synthesis effects on the magnetic and superconducting properties of RuSr2GdCu2O8,"A systematic study on the synthesis of the Ru-1212 compound by preparing a
series of samples that were annealed at increasing temperatures and then
quenched has been performed. It results that the optimal temperature for the
annealing lies around 1060-1065 C; a further temperature increase worsens the
phase formation. Structural order is very important and the subsequent grinding
and annealing improves it. Even if from the structural point of view the
samples appear substantially similar, the physical characterization highlight
great differences both in the electrical and magnetic properties related to
intrinsic properties of the phase as well as to the connection between the
grains as inferred from the resistive and the Curie Weiss behaviour at high
temperature as well as in the visibility of ZFC anf FC magnetic signals.",0207265v1
2002-08-02,Transport spin polarisation in SrRuO3 measured through Point Contact Andreev reflection,"We report a study in which Andreev reflection using a Nb point contact is
used to measure the transport spin polarisation of the 4d itinerant ferromagnet
SrRuO3. By performing the study in high quality thin films with residual
resistivities less than 7micro-ohm-cm, we ensure that the study is done in the
ballistic limit, a regime which is difficult to reach in oxide ferromagnets.
The degree of transport spin polarisation that we find is comparable to that of
the hole doped rare-earth manganites. We conclude that the large transport spin
polarisation results mainly from a difference in the Fermi velocities between
the majority and minority spin channels in this material.",0208044v3
2002-08-23,Superconductivity in molecular solids with Jahn-Teller phonons,"We analyze fulleride superconductivity at experimental doping levels,
treating the electron-electron and electron-phonon interactions on an equal
footing, and establish the existence of novel physics which helps explain the
unusually high superconducting transition temperatures in these systems. The
Jahn-Teller phonons create a local (intramolecular) pairing that is
surprisingly resistant to the Coulomb repulsion, despite the weakness of
retardation in these low-bandwidth systems. The requirement for coherence
throughout the solid to establish superconductivity then yields a very strong
doping dependence to Tc, one consistent with experiment and much stronger than
expected from standard Eliashberg theory.",0208454v1
2003-08-13,Physical properties of single-crystalline fibers of the colossal-magnetoresistance manganite La0.7Ca0.3MnO3,"We have grown high-quality single crystals of the colossal-magnetoresistance
(CMR) material La0.7Ca0.3MnO3 by using the laser heated pedestal growth (LHPG)
method. Samples were grown as fibers of different diameters, and with lengths
of the order of centimeters. Their composition and structure were verified
through X-ray diffraction, scanning electron microcopy with EDX (Energy
Dispersive X-ray Analysis) and by Rietveld analysis. The quality of the
crystalline fibers was confirmed by Laue and EBSD (Electron Backscatter
Diffraction) patterns. Rocking curves performed along the fiber axis revealed a
half-height width of 0.073 degrees. The CMR behavior was confirmed by
electrical resistivity and magnetization measurements as a function of
temperature.",0308245v1
2004-07-22,Real Space Imaging of the Microscopic Origins of the Ultrahigh Dielectric Constant in Polycrystalline CaCu3Ti4O12,"The origins of an ultrahigh dielectric constant in polycrystalline
CaCu3Ti4O12 (CCTO) was studied using the combination of impedance spectroscopy,
electron microscopy, and scanning probe microscopy (SPM). Impedance spectra
indicate that the transport properties in the 0.1 Hz .. 1 MHz frequency range
are dominated by a single parallel resistive-capacitive (RC) element with a
characteristic relaxation frequency of 16 Hz. Dc potential distributions
measurements by SPM illustrate that significant potential drops occur at the
grain boundaries, which thus can be unambiguously identified as the dominant RC
element. High frequency ac amplitude and phase distributions illustrate very
weak contrast at the interfaces, which is indicative of strong capacitive
coupling. These results demonstrate that the ultrahigh dielectric constant
reported for polycrystalline CCTO materials are related to the grain boundary
behavior.",0407608v1
2004-07-28,Room temperature tunneling magnetoresistance in magnetite based junctions: Influence of tunneling barrier,"Magnetite (Fe3O4) based tunnel junctions with turret/mesa structure have been
investigated for different barrier materials (SrTiO3, NdGaO3, MgO, SiO2, and
Al2O(3-x)). Junctions with a Ni counter electrode and an aluminium oxide
barrier showed reproducibly a tunneling magnetoresistance (TMR) effect at room
temperature of up to 5% with almost ideal switching behavior. This number only
partially reflects the intrinsic high spin polarization of Fe3O4. It is
considerably decreased due to an additional series resistance within the
junction. Only SiO2 and Al2O(3-x) barriers provide magnetically decoupled
electrodes as necessary for sharp switching. The observed decrease of the TMR
effect as a function of increasing temperature is due to a decrease in spin
polarization and an increase in spin-scattering in the barrier. Among the oxide
half-metals magnetite has the potential to enhance the performance of TMR based
devices.",0407725v1
2005-05-04,Tunable charge carriers and thermoelectricity of single-crystal Ba8Ga16Sn30,"We have grown single crystals of the type-VIII intermetallic clathrate
Ba8Ga16Sn30 from both Sn and Ga flux, evaluated their compositions through
electron microprobe analysis and studied their transport properties through
measurements on temperature dependent resistivity, thermopower and Hall
coefficient. Crystals grown in Sn flux show n-type carriers and those from Ga
flux show p-type carriers, whereas all measured compositions remain very close
to the stoichiometric 8:16:30 proportion of Ba:Ga:Sn, expected from
charge-balance principles. Our results indicate a very high sensitivity of the
charge carrier nature and density with respect to the growth conditions,
leading to relevant differences in transport properties which point to the
importance of tuning this material for optimal thermoelectric performance.",0505095v2
2005-05-14,"Surface morphology, structure and transport property of NaxCoO2 thin films grown by pulsed laser deposition","In this paper, we report the growth of NaxCoO2 thin films by pulsed-laser
deposition (PLD). It is shown that the concentration of sodium is very
sensitive to the substrate temperature and the target-substrate distance due to
the evaporation of sodium during the deposition. alpha prime-phase Na0.75CoO2
and gamma- phase Na0.71CoO2 thin films can be obtained with different
conditions. Correspondingly, the surface morphology of the films changes from
flake-like to particle-like. The temperature dependence of resistivity for the
films prepared with the optimal condition shows metallic behavior, consistent
with the data of NaxCoO2 single crystals. This work demonstrates that PLD is a
promising technique to get high quality NaxCoO2 thin films.",0505360v1
2005-10-19,Oxygen Isotope Effect on the Spin State Transition in (Pr$_{0.7}$Sm$_{0.3}$)$_{0.7}$Ca$_{0.3}$CoO${_3}$,"Oxygen isotope substitution is performed in the perovskite cobalt oxide
(Pr$_{0.7}$Sm$_{0.3}$)$_{0.7}$Ca$_{0.3}$CoO${_3}$ which shows a sharp spin
state transition from the intermediate spin (IS) state to the low spin (LS)
state at a certain temperature. The transition temperature of the spin state
up-shifts with the substitution of $^{16}O$ by $^{18}$O from the resistivity
and magnetic susceptibility measurements. The up-shift value is 6.8 K and an
oxygen isotope exponent ($\alpha_S$) is about -0.8. The large oxygen isotope
effect indicates strong electron-phonon coupling in this material. The
substitution of $^{16}$O by $^{18}$O leads to a decrease in the frequency of
phonon and an increase in the effective mass of electron ($m$$^\ast$), so that
the bandwidth W is decreased and the energy difference between the different
spin states is increased. This is the reason why the $T_s$ is shifted to high
temperature with oxygen isotopic exchange.",0510499v1
2005-10-24,Combining half-metals and multiferroics into epitaxial heterostructures for spintronics,"We report on the growth of epitaxial bilayers of the La2/3Sr1/3MnO3 (LSMO)
half-metallic ferromagnet and the BiFeO3 (BFO) multiferroic, on SrTiO3(001) by
pulsed laser deposition. The growth mode of both layers is two-dimensional,
which results in unit-cell smooth surfaces. We show that both materials keep
their properties inside the heterostructures, i.e. the LSMO layer (11 nm thick)
is ferromagnetic with a Curie temperature of ~330K, while the BFO films shows
ferroelectricity down to very low thicknesses (5 nm). Conductive-tip atomic
force microscope mappings of BFO/LSMO bilayers for different BFO thicknesses
reveal a high and homogeneous resistive state for the BFO film that can thus be
used as a ferroelectric tunnel barrier in tunnel junctions based on a
half-metal.",0510625v1
2006-05-22,Dissipative Van der Waals interaction between a small particle and a metal surface,"We use a general theory of the fluctuating electromagnetic field to calculate
the friction force acting on a small neutral particle, e.g., a physisorbed
molecule, or a nanoscale object with arbitrary dispersive and absorptive
dielectric properties, moving near a metal surface. We consider the dependence
of the electromagnetic friction on the temperature $T$, the separation $d$, and
discuss the role of screening, non-local and retardation effects. We find that
for high resistivity materials, the dissipative van der Waals interaction can
be an important mechanism of vibrational energy relaxation of physisorbed
molecules, and friction for microscopic solids. Several controversial topics
related to electromagnetic dissipative shear stress is considered. The problem
of local heating of the surface by an STM tip is also briefly commented on.",0605525v1
1999-04-15,Comparative Energy Dependence of Proton and Pion Degradation in Diamond,"A comparative theoretical study of the damages produced by protons and pions,
in the energy range 50 MeV - 50 GeV, in diamond, is presented. The
concentration of primary defects (CPD) induced by hadron irradiation is used to
describe material degradation. The CPD has very different behaviours for
protons and pions: the proton degradation is important at low energies and is
higher than the pion one in the whole energy range investigated, with the
exception of the Delta33 resonance region, where a large maximum of the
degradation exists for pions. In comparison with silicon, the most investigated
and the most studied material for detectors, diamond theoretically proves to be
one order of magnitude more resistant, both to proton and pion irradiation.",9904342v1
2008-10-06,Theory of the spontaneous buckling of doped graphene,"Graphene is a realization of an esoteric class of materials -- electronic
crystalline membranes. We study the interplay between the free electrons and
the two-dimensional crystal, and find that it induces a substantial effect on
the elastic structure of the membrane. For the hole-doped membrane, in
particular, we predict a spontaneous buckling. In addition, attenuation of
elastic waves is expected, due to the effect of corrugations on the bulk
modulus. These discoveries have a considerable magnitude in graphene, affecting
both its mesoscopic structure, and its electrical resistivity, which has an
inherent asymmetry between hole- and electron-doped graphene.",0810.1062v4
2009-06-12,Giant magnetic anisotropy changes in Sr2CrReO6 thin films on BaTiO3,"The integration of ferromagnetic and ferroelectric materials into hybrid
heterostructures yields multifunctional systems with improved or novel
functionality. We here report on the structural, electronic and magnetic
properties of the ferromagnetic double perovskite Sr2CrReO6, grown as epitaxial
thin film onto ferroelectric BaTiO3. As a function of temperature, the
crystal-structure of BaTiO3 undergoes phase transitions, which induce
qualitative changes in the magnetic anisotropy of the ferromagnet. We observe
abrupt changes in the coercive field of up to 1.2T along with resistance
changes of up to 6.5%. These results are attributed to the high sensitivity of
the double perovskites to mechanical deformation.",0906.2276v1
2010-01-22,Conducting interfaces between band insulating oxides: the LaGaO3/SrTiO3,"We show that the growth of the heterostructure LaGaO3/SrTiO3 yields the
formation of a highly conductive interface. Our samples were carefully analyzed
by high resolution electron microscopy, in order to assess their crystal
perfection and to evaluate the abruptness of the interface. Their carrier
density and sheet resistance are compared to the case of LaAlO3/SrTiO3 and a
superconducting transition is found. The results open the route to widening the
field of polar-non polar interfaces, pose some phenomenological constrains to
their underlying physics and highlight the chance of tailoring their properties
for future applications by adopting suitable polar materials.",1001.3956v2
2010-06-15,Fluorographene: Two Dimensional Counterpart of Teflon,"We report a stoichiometric derivative of graphene with a fluorine atom
attached to each carbon. Raman, optical, structural, micromechanical and
transport studies show that the material is qualitatively different from the
known graphene-based nonstoichiometric derivatives. Fluorographene is a
high-quality insulator (resistivity >10^12 Ohm per square) with an optical gap
of 3 eV. It inherits the mechanical strength of graphene, exhibiting Young's
modulus of 100 N/m and sustaining strains of 15%. Fluorographene is inert and
stable up to 400C even in air, similar to Teflon.",1006.3016v2
2010-10-26,Graphene to Graphane: Novel Electrochemical Conversion,"A novel electrochemical means to generate atomic hydrogen, simplifying the
synthesis and controllability of graphane formation on graphene is presented.
High quality, vacuum grown epitaxial graphene (EG) was used as starting
material for graphane conversion. A home-built electrochemical cell with Pt
wire and exposed graphene as the anode and cathode, respectively, was used to
attract H+ ions to react with the exposed graphene. Cyclic voltammetry of the
cell revealed the potential of the conversion reaction as well as oxidation and
reduction peaks, suggesting the possibility of electrochemically reversible
hydrogenation. A sharp increase in D peak in the Raman spectra of EG, increase
of D/G ratio, introduction of a peak at ~2930 cm-1 and respective peak shifts
as well as a sharp increase in resistance showed the successful hydrogenation
of EG. This conversion was distinguished from lattice damage by thermal
reversal back to graphene at 1000{\deg}C.",1010.5458v1
2010-11-15,Transfer Printing Approach to All-Carbon Nanoelectronics,"Transfer printing methods are used to pattern and assemble monolithic carbon
nanotube (CNT) thin-film transistors on large-area transparent, flexible
substrates. Airbrushed CNT thin-films with sheet resistance 1kOhmsquare^{-1} at
80% transparency were used as electrodes, and high quality chemical vapor
deposition (CVD)-grown CNT networks were used as the semiconductor component.
Transfer printing was used to pre-pattern and assemble thin film transistors on
polyethylene terephthalate (PET) substrates which incorporated
Al_{2}O_{3}/poly-methylmethacrylate (PMMA) dielectric bi-layer. CNT-based
ambipolar devices exhibit field-effect mobility in range 1 - 33 cm^{2}/Vs and
on/off ratio ~10^{3}, comparable to the control devices fabricated using Au as
the electrode material.",1011.3269v1
2011-07-05,Hidden spin liquid in an antiferromagnet: Applications to FeCrAs,"The recently studied material FeCrAs exhibits a surprising combination of
experimental signatures, with metallic, Fermi liquid like specific heat but
resistivity showing strong non-metallic character. The Cr sublattice posseses
local magnetic moments, in the form of stacked (distorted) Kagome lattices.
Despite the high degree of magnetic frustration, anti-ferromagnetic order
develops below ~125K suggesting the non-magnetic Fe sublattice may play a role
in stabilizing the ordering. From the material properties we propose a
microscopic Hamiltonian for the low energy degrees of freedom, including the
non-magnetic Fe sublattice, and study its properties using slave-rotor mean
field theory. Using this approach we find a spin liquid phase on the Fe
sublattice, which survives even in the presence of the magnetic Cr sublattice.
Finally, we suggest that the features of FeCrAs can be qualitatively explained
by critical fluctuations in the non-magnetic sublattice Fe due to proximity to
a metal-insulator transition.",1107.1002v1
2011-11-16,Infrared Spectroscopy of Wafer-Scale Graphene,"We report on spectroscopy results from the mid- to far-infrared on
wafer-scale graphene, grown either epitaxially on silicon carbide, or by
chemical vapor deposition. The free carrier absorption (Drude peak) is
simultaneously obtained with the universal optical conductivity (due to
interband transitions), and the wavelength at which Pauli blocking occurs due
to band filling. From these the graphene layer number, doping level, sheet
resistivity, carrier mobility, and scattering rate can be inferred. The mid-IR
absorption of epitaxial two-layer graphene shows a less pronounced peak at
0.37\pm0.02 eV compared to that in exfoliated bilayer graphene. In heavily
chemically-doped single layer graphene, a record high transmission reduction
due to free carriers approaching 40% at 250 \mum (40 cm-1) is measured in this
atomically thin material, supporting the great potential of graphene in
far-infrared and terahertz optoelectronics.",1111.3714v1
2011-12-22,Single crystal growth of YbRh2Si2 and YbIr2Si2,"We report on the single crystal growth of the heavy-fermion compounds
YbRh2Si2 and YbIr2Si2 using a high-temperature indium-flux technique. The
optimization of the initial composition and the temperature-time profile lead
to large (up to 100 mg) and clean (\rho_0=0.5 \mu\Omega cm) single crystals of
YbRh2Si2. Low-temperature resistivity measurements revealed a sample dependent
temperature exponent below 10 K, which for the samples with highest quality
deviates from a linear-in-T behaviour. Furthermore, we grew single crystals of
the alloy series Yb(Rh_(1-x)Ir_x)2Si2 with 0<x<0.23 and report the structural
details. For pure YbIr2Si2, we establish the formation of two crystallographic
modifications, where the magnetic 4f-electrons have different physical ground
states.",1112.5251v1
2012-02-11,Observation of Andreev bound state and multiple energy gaps in the non-centrosymmetric superconductor BiPd,"We report directional point contact Andreev reflection (PCAR) measurements on
high-quality single crystals of the non-centrosymmetric superconductor, BiPd.
The PCAR spectra measured on different crystallographic faces of the single
crystal clearly show the presence of multiple superconducting energy gaps. For
point contacts with low resistance, in addition to the superconducting gap
feature, a pronounced zero bias conductance peak is observed. These
observations provide strong evidence of the presence of unconventional order
parameter in this material.",1202.2454v2
2012-08-09,Frictional characteristics of exfoliated and epitaxial graphene,"To determine the friction coefficient of graphene, micro-scale scratch tests
are conducted on exfoliated and epitaxial graphene at ambient conditions. The
experimental results show that the monolayer, bilayer, and trilayer graphene
all yield friction coefficients of approximately 0.03. The friction coefficient
of pristine graphene is less than that of disordered graphene, which is treated
by oxygen plasma. Ramping force scratch tests are performed on graphene with
various numbers of layers to determine the normal load required for the probe
to penetrate graphene. A very low friction coefficient and also its high
pressure resistance make graphene a promising material for antiwear coatings.",1208.1830v1
2012-10-05,A study of gas contaminants and interaction with materials in RPC closed loop systems,"Resistive Plate Counters (RPC) detectors at the Large Hadron Collider (LHC)
experiments use gas recirculation systems to cope with large gas mixture
volumes and costs. In this paper a long-term systematic study about gas
purifiers, gas contaminants and detector performance is discussed. The study
aims at measuring the lifetime of purifiers with unused and used cartridge
material along with contaminants release in the gas system. During the
data-taking the response of several RPC double-gap detectors was monitored in
order to characterize the correlation between dark currents, filter status and
gas contaminants.",1210.1819v1
2013-01-22,Thermoelectric Properties of Intermetallic Semiconducting RuIn3 and Metallic IrIn3,"Low temperature (<400 K) thermoelectric properties of semiconducting RuIn3
and metallic IrIn3 are reported. RuIn3 is a narrow band gap semiconductor with
a large n-type Seebeck coefficient at room temperature (S(290K)~400 {\mu}V/K),
but the thermoelectric Figure of merit (ZT(290K) = 0.007) is small because of
high electrical resistivity and thermal conductivity ({\kappa}(290 K) ~ 2.0 W/m
K). IrIn3 is a metal with low thermopower at room temperature (S(290K)~20
{\mu}V/K) . Iridium substitution on the ruthenium site has a dramatic effect on
transport properties, which leads to a large improvement in the power factor
and corresponding Figure of merit (ZT(380 K) = 0.053), improving the efficiency
of the material by an over of magnitude.",1301.5353v1
2013-02-21,Study of gas contaminants and interaction with materials in RPC closed loop system,"Resistive Plate Counters (RPC) detectors at the Large Hadron Collider (LHC)
experiments use gas recirculation systems to cope with large gas mixture
volumes and costs. In this paper a long-term systematic study about gas
purifiers, gas contaminants and detector performance is discussed. The study
aims at measuring the lifetime of purifiers with new and used cartridge
material along with contaminants release in the gas system. During the
data-taking the response of several RPC double-gap detectors was monitored in
order to characterize the correlation between dark currents, filter status and
gas contaminants.",1302.5225v2
2013-04-24,High sensitivity measurements of thermal properties of textile fabrics,"A new testing apparatus is proposed to measure the thermal properties of
fabrics made from polymeric materials. The calibration of the apparatus and the
data acquisition procedure are considered in detail in order to measure thermal
conductivity, resistance, absorption and diffusivity constants of the tested
fabric samples. Differences between dry and wet fabrics have been carefully
detected and analyzed. We have developed a new measurement protocol, the
""ThermoTex"" protocol, which agrees with the UNI EN 31092 standard and entails
an accurate quantification of the experimental errors according to a standard
statistical analysis, thus allowing a rigorous investigation of the physical
behavior of the phenomena involved. As a consequence, our machinery exhibits
great potentialities for optimizing the thermal comfort of fabrics, according
to the market demand, thanks to the possible development of a predictive
phenomenological theory of the effects involved.",1304.6714v1
2013-07-12,High-energy radiation damage in zirconia: modeling results,"Zirconia is viewed as a material of exceptional resistance to amorphization
by radiation damage, and consequently proposed as a candidate to immobilize
nuclear waste and serve as an inert nuclear fuel matrix. Here, we perform
molecular dynamics simulations of radiation damage in zirconia in the range of
0.1-0.5 MeV energies with full account of electronic energy losses. We find
that the lack of amorphizability co-exists with a large number of point defects
and their clusters. These, importantly, are largely isolated from each other
and therefore represent a dilute damage that does not result in the loss of
long-range structural coherence and amorphization. We document the nature of
these defects in detail, including their sizes, distribution and morphology,
and discuss practical implications of using zirconia in intense radiation
environments.",1307.3380v4
2013-08-16,Quantum Criticality in Electron-doped BaFe_{2-x}Ni_xAs_2,"A quantum critical point (QCP) is a point in a system's phase diagram at
which an order is completely suppressed at absolute zero temperature (T). The
presence of a quantum critical point manifests itself in the finite-T physical
properties, and often gives rise to new states of matter. Superconductivity in
the cuprates and in heavy fermion materials is believed by many to be mediated
by fluctuations associated with a quantum critical point. In the
recently-discovered iron-pnictide high temperature superconductors, it is
unknown whether a QCP exists or not in a carrier-doped system. Here we report
transport and nuclear magnetic resonance (NMR) measurements on
BaFe_{2-x}Ni_xAs_2 (0 =< x =< 0.17). We find two critical points at x_{c1} =
0.10 and x_{c2} = 0.14. The electrical resistivity follows \rho = \rho_0 +
A*T^n, with n = 1 around x_{c1} and another minimal n = 1.1 at x_{c2}. By NMR
measurements, we identity x_{c1} to be a magnetic QCP and suggest that x_{c2}
is a new type of QCP associated with a nematic structural phase transition. Our
results suggest that the superconductivity in carrier-doped pnictides is
closely linked to the quantum criticality.",1308.3539v1
2013-11-07,Helium Ion Microscopy,"Helium Ion Microcopy (HIM) based on Gas Field Ion Sources (GFIS) represents a
new ultra high resolution microscopy and nano-fabrication technique. It is an
enabling technology that not only provides imagery of conducting as well as
uncoated insulating nano-structures but also allows to create these features.
The latter can be achieved using resists or material removal due to sputtering.
The close to free-form sculpting of structures over several length scales has
been made possible by the extension of the method to other gases such as Neon.
A brief introduction of the underlying physics as well as a broad review of the
applicability of the method is presented in this review.",1311.1711v2
2014-04-08,Fingerprints of Inelastic Transport at the Surface of the Topological Insulator Bi2Se3: Role of Electron-Phonon Coupling,"We report on electric-field and temperature dependent transport measurements
in exfoliated thin crystals of Bi$_{2}$Se$_{3}$ topological insulator. At low
temperatures ($< 50$ K) and when the chemical potential lies inside the bulk
gap, the crystal resistivity is strongly temperature dependent, reflecting
inelastic scattering due to the thermal activation of optical phonons. A linear
increase of the current with voltage is obtained up to a threshold value at
which current saturation takes place. We show that the activated behavior, the
voltage threshold and the saturation current can all be quantitatively
explained by considering a single optical phonon mode with energy $\hbar \Omega
\approx 8$ meV. This phonon mode strongly interacts with the surface states of
the material and represents the dominant source of scattering at the surface at
high electric fields.",1404.2198v1
2014-09-03,Significant reduction of lattice thermal conductivity by electron-phonon interaction in silicon with high carrier concentrations: a first-principles study,"Electron-phonon interaction has been well known to create major resistance to
electron transport in metals and semiconductors, whereas less studies were
directed to its effect on the phonon transport, especially in semiconductors.
We calculate the phonon lifetimes due to scattering with electrons (or holes),
combine them with the intrinsic lifetimes due to the anharmonic phonon-phonon
interaction, all from first-principles, and evaluate the effect of the
electron-phonon interaction on the lattice thermal conductivity of silicon.
Unexpectedly, we find a significant reduction of the lattice thermal
conductivity at room temperature as the carrier concentration goes above 1e19
cm-3 (the reduction reaches up to 45% in p-type silicon at around 1e21 cm-3), a
range of great technological relevance to thermoelectric materials.",1409.1268v1
2015-01-16,Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy,"Chalcogen-hyperdoped silicon shows potential applications in silicon-based
infrared photodetectors and intermediate band solar cells. Due to the low solid
solubility limits of chalcogen elements in silicon, these materials were
previously realized by femtosecond or nanosecond laser annealing of implanted
silicon or bare silicon in certain background gases. The high energy density
deposited on the silicon surface leads to a liquid phase and the fast
recrystallization velocity allows trapping of chalcogen into the silicon
matrix. However, this method encounters the problem of surface segregation. In
this paper, we propose a solid phase processing by flash-lamp annealing in the
millisecond range, which is in between the conventional rapid thermal annealing
and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon
shows a substitutional fraction of around 70% with an implanted concentration
up to 2.3%. The resistivity is lower and the carrier mobility is higher than
those of nanosecond pulsed laser annealed samples. Our results show that
flash-lamp annealing is superior to laser annealing in preventing surface
segregation and in allowing scalability.",1501.03953v1
2015-03-20,Strong charge ordering above room temperature in B-site disordered electron-doped manganite SrMn0.875Mo0.125O3-δ,"Low as well as high-temperature electron and x-ray diffraction studies have
been carried out on a rare-earth free B-site disordered electron-doped
manganite SrMn0.875.Mo0.125O3-{\delta} in the temperature range of 83K to 637K.
These studies reveal the occurrence of strong charge ordering (CO) at room
temperature in a pseudo tetragonally distorted perovskite phase with
space-group Pmmm. Non integral modulation vector of 8.95 times along [-110]
indicates a charge density wave type modulation. The CO phase with basic
perovskite structure Pmmm transforms to a charge disorder cubic phase through a
first order phase transition at 355K. Supporting temperature dependent
measurements of resistance and magnetization show a metal-insulator and
antiferromagnetic transitions across 355K with a wide hysterisis ranging from
150K to 365K. The occurrence of pseudo tetragonality of the basic perovskite
lattice with c/a < 1 together with charge-ordered regions with 2-dimensional
modulation have been analyzed as the coexistence of two CO phases with
3dx2/3dy2 type and 3dx2-y2 type orbital ordering.",1503.06000v1
2015-08-28,Does a dissolution-precipitation mechanism explain concrete creep in moist environments?,"Long-term creep (i.e., deformation under sustained load) is a significant
material response that needs to be accounted for in concrete structural design.
However, the nature and origin of creep remains poorly understood, and
controversial. Here, we propose that concrete creep at RH (relative humidity) >
50%, but fixed moisture-contents (i.e., basic creep), arises from a
dissolution-precipitation mechanism, active at nanoscale grain contacts, as is
often observed in a geological context, e.g., when rocks are exposed to
sustained loads, in moist environments. Based on micro-indentation and vertical
scanning interferometry experiments, and molecular dynamics simulations carried
out on calcium-silicate-hydrates (C-S-H's), the major binding phase in
concrete, of different compositions, we show that creep rates are well
correlated to dissolution rates - an observation which supports the
dissolution-precipitation mechanism as the origin of concrete creep. C-S-H
compositions featuring high resistance to dissolution, and hence creep are
identified - analysis of which, using topological constraint theory, indicates
that these compositions present limited relaxation modes on account of their
optimally connected (i.e., constrained) atomic networks.",1508.07082v1
2015-09-11,High thermoelectric performance and low thermal conductivity of densified LaOBiSSe,"In this study, we examined the thermoelectric properties of the layered
bismuth-chalcogenide-based (BiCh2-based) compound LaOBiSSe, which is expected
to be a new candidate material for thermoelectric applications. Densified
samples were obtained with a hot-press method. The results of the X-ray
diffraction measurements showed that the samples obtained were weakly oriented.
This affected the resistivity (r) and Seebeck coefficient (S) of the samples
because they are dependent upon the orientation of the crystal structure. The
values obtained for the power factor (S2/r) when measured perpendicular to the
pressing direction (P1) were higher than that when measured parallel to the
pressing direction (P2). The thermal conductivity (k) of the samples was also
sensitive to the orientation. The values of k measured along P2 were lower than
that measured along P1. The highest figure-of-merit (approximately 0.36) was
obtained at around 650 K in both directions, i.e., P1 and P2.",1509.03387v1
2016-04-22,Thermoelectric Properties of Antiperovskite Calcium Oxides Ca3PbO and Ca3SnO,"We report the thermoelectric properties of polycrystalline samples of
Ca3Pb1-xBixO (x = 0, 0.1, 0.2) and Ca3SnO, both crystallizing in a cubic
antiperovskite-type structure. The Ca3SnO sample shows metallic resistivity and
its thermoelectric power approaches 100 uV K-1 at room temperature, resulting
in the thermoelectric power factor of Ca3SnO being larger than that of
Ca3Pb1-xBixO. On the basis of Hall and Sommerfeld coefficients, the Ca3SnO
sample is found to be a p-type metal with a carrier density of ~1019 cm-3, a
mobility of ~80 cm2 V-1 s-1, both comparable to those in degenerated
semiconductors, and a moderately large hole carrier effective mass. The
coexistence of moderately high mobility and large effective mass observed in
Ca3SnO, as well as possible emergence of a mutivalley electronic structure with
a small band gap at low-symmetry points in k-space, suggests that the
antiperovskite Ca oxides have strong potential as a thermoelectric material.",1604.06541v2
2016-04-26,A Sinusoidally-Architected Helicoidal Biocomposite,"A fibrous herringbone-modified helicoidal architecture is identified within
the exocuticle of an impact-resistant crustacean appendage. This previously
unreported composite microstructure, which features highly textured apatite
mineral templated by an alpha-chitin matrix, provides enhanced stress
redistribution and energy absorption over the traditional helicoidal design
under compressive loading. Nanoscale toughening mechanisms are also identified
using high load nanoindentation and in-situ TEM picoindentation.",1604.07798v2
2016-05-04,Atomically Thin Boron Nitride: Unique Properties and Applications,"Atomically thin boron nitride (BN) is an important two-dimensional (2D)
nanomaterial, with many properties distinct from graphene. In this feature
article, these unique properties and associated applications often not possible
from graphene are outlined. The article starts with characterization and
identification of atomically thin BN. It is followed by demonstrating their
strong oxidation resistance at high temperatures and applications in protecting
metals from oxidation and corrosion. As flat insulators, BN nanosheets are
ideal dielectric substrates for surface enhanced Raman spectroscopy (SERS) and
electronic devices based on 2D heterostructures. The light emission of BN
nanosheets in the deep ultraviolet (DUV) and ultraviolet (UV) regions are also
included for its scientific and technological importance. The last part is
dedicated to synthesis, characterization, and optical properties of BN
nanoribbons, a special form of nanosheets.",1605.01136v1
2016-05-06,Superconducting gap structure of FeSe,"The microscopic mechanism governing the zero-resistance flow of current in
some iron-based, high-temperature superconducting materials is not well
understood up to now. A central issue concerning the investigation of these
materials is their superconducting gap symmetry and structure. Here we present
a combined study of low-temperature specific heat and scanning tunnelling
microscopy measurements on single crystalline FeSe. The results reveal the
existence of at least two superconducting gaps which can be represented by a
phenomenological two-band model. The analysis of the specific heat suggests
significant anisotropy in the gap magnitude with deep gap minima. The tunneling
spectra display an overall ""U""-shaped gap close to the Fermi level away as well
as on top of twin boundaries. These results are compatible with the anisotropic
nodeless models describing superconductivity in FeSe.",1605.01908v2
2016-05-24,Pressure-Induced Confined Metal from the Mott Insulator Sr3Ir2O7,"The spin-orbit Mott insulator Sr3Ir2O7 provides a fascinating playground to
explore insulator-metal transition driven by intertwined charge, spin, and
lattice degrees of freedom. Here, we report high pressure electric resistance
and resonant inelastic x ray scattering measurements on single crystal Sr3Ir2O7
up to 63 65 GPa at 300 K. The material becomes a confined metal at 59.5 GPa,
showing metallicity in the ab plane but an insulating behavior along the c
axis. Such an unusual phenomenon resembles the strange metal phase in cuprate
superconductors. Since there is no sign of the collapse of spin orbit or
Coulomb interactions in x-ray measurements, this novel insulator metal
transition is potentially driven by a first-order structural change at nearby
pressures. Our discovery points to a new approach for synthesizing functional
materials.",1605.07582v1
2016-11-08,Valley Hall Effect and Nonlocal Transport in Strained Graphene,"Graphene subject to high levels of shear strain leads to strong
pseudo-magnetic fields resulting in the emergence of Landau levels. Here we
show that, with modest levels of strain, graphene can also sustain a classical
valley hall effect (VHE) that can be detected in nonlocal transport
measurements. We provide a theory of the strain-induced VHE starting from the
quantum Boltzmann equation. This allows us to show that, averaging over
short-range impurity configurations destroys quantum coherence between valleys,
leaving the elastic scattering time and inter-valley scattering rate as the
only parameters characterizing the transport theory. Using the theory, we
compute the nonlocal resistance of a Hall bar device in the diffusive regime.
Our theory is also relevant for the study of moderate strain effects in the
(nonlocal) transport properties of other two-dimensional materials and van der
Walls heterostructures.",1611.02382v2
2016-11-11,Microfluidization of graphite and formulation of graphene-based conductive inks,"We report the exfoliation of graphite in aqueous solutions under high shear
rate [$\sim10^8s^{-1}$] turbulent flow conditions, with a 100\% exfoliation
yield. The material is stabilized without centrifugation at concentrations up
to 100 g/L using carboxymethylcellulose sodium salt to formulate conductive
printable inks. The sheet resistance of blade coated films is
below$\sim2\Omega/\square$. This is a simple and scalable production route for
graphene-based conductive inks for large area printing in flexible electronics.",1611.04467v1
2016-12-26,Observation of quantum oscillations in FIB fabricated nanowires of topological insulator (Bi2Se3),"Since last few years, research based on topological insulators (TI) is in
great interests due to intrinsic exotic fundamental properties and future
potential applications such as quantum computers or spintronics. The
fabrication of TI nanodevices and study on their transport properties mostly
focused on high quality crystalline nanowires or nanoribbons. Here we report
robust approach of Bi2Se3 nanowire formation from deposited flakes using ion
beam milling method. The fabricated Bi2Se3 nanowire devices have been employed
to investigate the robustness of topological surface state (TSS) to gallium ion
doping and any deformation in the material due to fabrication tools. We report
the quantum oscillations in magnetoresistance curves under the parallel
magnetic field. The resistance versus magnetic field curves have been studied
and compared with Aharonov-Bohm (AB) interference effects which further
demonstrate the transport through TSS. The fabrication route and observed
electronic transport properties indicate clear quantum oscillations and can be
exploited further in studying the exotic electronic properties associated with
TI based nanodevices.",1612.08353v1
2017-09-26,SnAs-based layered superconductor NaSn2As2,"Superconductivity with exotic properties has often been discovered in
materials with a layered (two-dimensional) crystal structure. The low
dimensionality affects the electronic structure of materials, which could
realize a high transition temperature (Tc) and/or unconventional pairing
mechanisms. Here, we report the superconductivity in a layered tin arsenide
NaSn2As2. The crystal structure consists of (Sn2As2)2- bilayers, which is bound
by van-der-Waals forces, separated by Na+ ions. Measurements of electrical
resistivity and specific heat confirm the bulk nature of superconductivity of
NaSn2As2 with Tc of 1.3 K. Our results propose that the SnAs layers will be a
basic structure providing another universality class of a layered
superconducting family, and it provides a new platform for the physics and
chemistry of low-dimensional superconductors with lone pair electrons.",1709.08899v2
2017-11-10,Giant anisotropic magnetoresistance and planar Hall effect in the Dirac semimetal Cd3As2,"Anisotropic magnetoresistance is the change tendency of resistance of a
material on the mutual orientation of the electric current and the external
magnetic field. Here, we report experimental observations in the Dirac
semimetal Cd3As2 of giant anisotropic magnetoresistance and its transverse
version, called the planar Hall effect. The relative anisotropic
magnetoresistance is negative and up to -68% at 2 K and 10 T. The high
anisotropy and the minus sign in this isotropic and nonmagnetic material are
attributed to a field-dependent current along the magnetic field, which may be
induced by the Berry curvature of the band structure. This observation not only
reveals unusual physical phenomena in Weyl and Dirac semimetals, but also finds
additional transport signatures of Weyl and Dirac fermions other than negative
magnetoresistance.",1711.03671v2
2017-11-15,Revisiting the electron-doped SmFeAsO: enhanced superconductivity up to 58.6 K by Th and F codoping,"In the iron-based high-Tc bulk superconductors, Tc above 50K was only
observed in the electron-doped 1111-type compounds. Here we revisit the
electron-doped SmFeAsO polycrystals to make a further investigation for the
highest T-c in these materials. To introduce more electron carriers and less
crystal lattice distortions, we study the Th and F codoping effects into the
Sm-O layers with heavy electron doping. Dozens of Sm1-x Th-x FeAsO1-y F-y
samples are synthesized through the solid state reaction method, and these
samples are carefully characterized by the structural, resistive, and magnetic
measurements. We find that the codoping of Th and F clearly enhances the
superconducting T-c more than the Th or F single-doped samples, with the
highest record T-c up to 58.6K when x= 0.2 and y= 0.225. Further element doping
causes more impurities and lattice distortions in the samples with a weakened
superconductivity.",1711.05440v1
2018-01-19,Observation of Meissner effect in potassium-doped \emph{p}-quinquephenyl},"The chain-like organic compounds with conjugated structure have the potential
to become high temperature superconductors. We examine this idea by choosing
p-quinquephenyl with five phenyl rings connected in para position. The dc
magnetic susceptibility measurements provide solid evidence for the presence of
Meissner effect when the compound is doped by potassium. The real part of the
ac susceptibility shows exactly same transition temperature as that in dc
magnetization, and the imaginary part of nearly zero value after transition
implies the realization of zero-resistivity. All these features support the
existence of superconductivity with a critical temperature of 7.3 K in this
material. The occurrence of bipolarons revealed by Raman spectra guarantees
potassium metal intercalated into p-quinquephenyl and suggests the important
role of this elementary excitation played on superconductivity.",1801.06324v2
2018-01-19,Pressure-induced superconductivity in palladium sulfide,"An extended study on PdS is carried out with the measurements of the
resistivity, Hall coefficient, Raman scattering, and X-ray diffraction at high
pressures up to 42.3 GPa. With increasing pressure, superconductivity is
observed accompanying with a structural phase transition at around 19.5 GPa.
The coexistence of semiconducting and metallic phases observed at normal state
is examined by the Raman scattering and X-ray diffraction between 19.5 and 29.5
GPa. After that, only the metallic normal state maintains with an almost
constant superconducting transition temperature. The similar evolution between
the superconducting transition temperature and carrier concentration with
pressure supports the phonon-mediated superconductivity in this material. These
results highlight the important role of pressure played in inducing
superconductivity from these narrow band-gap semiconductors.",1801.06330v1
2018-02-07,"Structure, magnetic and transport properties of epitaxial thin films of equiatomic CoFeMnGe quaternary Heusler alloy","Future spintronics requires the realization of thin film of half-metallic
ferromagnets having high Curie temperature and 100\% spin polarization at the
Fermi level for potential spintronics applications. In this paper, we report
the epitaxial thin films growth of half-metallic CoFeMnGe Heusler alloy on MgO
(001) substrate using pulsed laser deposition system, along with the study of
structural, magnetic and transport properties. The magnetic property
measurements of the thin film suggest a soft ferromagnetic state at room
temperature with an in-plane magnetic anisotropy and a Curie temperature well
above the room temperature. Anisotropic magnetoresistance (AMR) ratio and
temperature dependent electrical resistivity measurements of the thin film
indicate the compound to be half-metallic in nature and therefore suitable for
the fabrications of spintronics devices.",1802.02413v1
2018-03-12,Sub 20 meV Schottky barriers in metal/MoTe2 junctions,"The newly emerging class of atomically-thin materials has shown a high
potential for the realisation of novel electronic and optoelectronic
components. Amongst this family, semiconducting transition metal
dichalcogenides (TMDCs) are of particular interest. While their band gaps are
compatible with those of conventional solid state devices, they present a wide
range of exciting new properties that is bound to become a crucial ingredient
in the future of electronics. To utilise these properties for the prospect of
electronics in general, and long-wavelength-based photodetectors in particular,
the Schottky barriers formed upon contact with a metal and the contact
resistance that arises at these interfaces have to be measured and controlled.
We present experimental evidence for the formation of Schottky barriers as low
as 10 meV between MoTe2 and metal electrodes. By varying the electrode work
functions, we demonstrate that Fermi level pinning due to metal induced gap
states at the interfaces occurs at 0.14 eV above the valence band maximum. In
this configuration, thermionic emission is observed for the first time at
temperatures between 40 K and 75 K. Finally, we discuss the ability to tune the
barrier height using a gate electrode.",1803.04164v1
2018-04-09,Dislocation-induced thermal transport anisotropy in single-crystal group-III nitride films,"Dislocations, one-dimensional lattice imperfections, are common to
technologically important materials such as III-V semiconductors, and adversely
affect heat dissipation in e.g., nitride-based high-power electronic devices.
For decades, conventional models based on nonlinear elasticity theory have
predicted this thermal resistance is only appreciable when heat flux is
perpendicular to the dislocations. However, this dislocation-induced
anisotropic thermal transport has yet to be seen experimentally. In this study,
we measure strong thermal transport anisotropy governed by highly oriented
threading dislocation arrays along the cross-plane direction in micron-thick,
single-crystal indium nitride (InN) films. We find that the cross-plane thermal
conductivity is more than tenfold higher than the in-plane thermal conductivity
at 80 K when the dislocation density is on the order of ~3x10^10 cm^-2. This
large anisotropy is not predicted by the conventional models. With enhanced
understanding of dislocation-phonon interactions, our results open new regimes
for tailoring anisotropic thermal transport with line defects, and will
facilitate novel methods for directed heat dissipation in thermal management of
diverse device applications.",1804.02825v1
2018-05-01,Strongly correlated proton-doped perovskite nickelate memory devices,"We demonstrate memory devices based on proton doping and re-distribution in
perovskite nickelates (RNiO3, {R=Sm,Nd}) that undergo filling-controlled Mott
transition. Switching speeds as high as 30 ns in two-terminal devices patterned
by electron-beam lithography is observed. The state switching speed reported
here are 300X greater than what has been noted with proton-driven resistance
switching to date. The ionic-electronic correlated oxide memory devices also
exhibit multi-state non-volatile switching. The results are of relevance to use
of quantum materials in emerging memory and neuromorphic computing.",1805.00527v1
2018-06-21,Strange metallicity in the doped Hubbard model,"Strange or bad metallic transport, defined by its incompatibility with
conventional quasiparticle pictures, is a theme common to strongly correlated
materials and ubiquitous in many high temperature superconductors. The Hubbard
model represents a minimal starting point for modeling strongly correlated
systems. Here we demonstrate strange metallic transport in the doped
two-dimensional Hubbard model using determinantal quantum Monte Carlo
calculations. Over a wide range of doping, we observe resistivities exceeding
the Mott-Ioffe-Regel limit with linear temperature dependence. The temperatures
of our calculations extend to as low as 1/40 the non-interacting bandwidth,
placing our findings in the degenerate regime relevant to experimental
observations of strange metallicity. Our results provide a foundation for
connecting theories of strange metals to models of strongly correlated
materials.",1806.08346v2
2018-09-13,Superconductivity in LaPd2Bi2 with CaBe2Ge2-type structure,"Here we report the synthesis and superconductivity of a novel ternary
compound LaPd2Bi2. Shiny plate-like single crystals of LaPd2Bi2 were first
synthesized by high-temperature solution method with PdBi flux. X-ray
diffraction analysis indicates that LaPd2Bi2 belongs to the primitive
tetragonal CaBe2Ge2-type structure with the space group P4/nmm (No. 129), and
the refined lattice parameters are a = 4.717(2) {\AA}, c = 9.957(3) {\AA}.
Electrical resistivity and magnetic susceptibility measurements reveal that
LaPd2Bi2 undergoes a superconducting transition at 2.83 K and exhibits the
characteristics of type-II superconductivity. The discovery of
superconductivity in LaPd2Bi2 with CaBe2Ge2-type structure may help to further
understand the possible relationship between the occurrence of
superconductivity and the crystal structures in 122-type materials.",1809.04811v1
2019-05-08,Miniature Multi-Level Optical Memristive Switch Using Phase Change Material,"The optical memristive switches are electrically activated optical switches
that can memorize the current state. They can be used as optical latching
switches in which the switching state is changed only by applying an electrical
Write/Erase pulse and maintained without external power supply. We demonstrate
an optical memristive switch based on a silicon MMI structure covered with
nanoscale-size Ge2Sb2Te5 (GST) material on top. The phase change of GST is
triggered by resistive heating of the silicon layer beneath GST with an
electrical pulse. Experimental results reveal that the optical transmissivity
can be tuned in a controllable and repeatable manner with the maximum
transmission contrast exceeding 20 dB. Partial crystallization of GST is
obtained by controlling the width and amplitude of the electric pulses.
Crucially, we also demonstrate that both Erase and Write operations, to and
from any intermediate level, are possible with accurate control of the
electrical pulses. Our work marks a significant step forward towards realizing
photonic memristive switches without static power consumption, which are highly
demanded in high-density large-scale integrated photonics.",1905.03163v1
2020-03-02,Structural and Magnetic Properties of Molecular Beam Epitaxy Grown Chromium Selenide Thin Films,"Chromium selenide thin films were grown epitaxially on Al${_2}$O${_3}$(0001)
and Si(111)-(7${\times}$7) substrates using molecular beam epitaxy (MBE). Sharp
streaks in reflection high-energy electron diffraction and triangular
structures in scanning tunneling microscopy indicate a flat smooth film growth
along the c-axis, and is very similar to that from a hexagonal surface. X-ray
diffraction pattern confirms the growth along the c-axis with c-axis lattice
constant of 17.39 {\AA}. The grown film is semiconducting, having a small band
gap of about 0.034 eV, as calculated from the temperature dependent
resistivity. Antiferromagnetic nature of the film with a N\'eel temperature of
about 40 K is estimated from the magnetic exchange bias measurements. A larger
out-of-plane exchange bias, along with a smaller in-plane exchange bias is
observed below 40 K. Exchange bias training effects are analyzed based on
different models and are observed to be following a modified power-law decay
behavior.",2003.01199v1
2017-03-01,Chemical and Lattice Stability of the Tin Sulfides,"The tin sulfides represent a materials platform for earth-abundant
semiconductor technologies. We present a first-principles study of the five
known and proposed phases of SnS together with SnS2 and Sn2S3. Lattice-dynamics
techniques are used to evaluate the dynamical stability and
temperature-dependent thermodynamic free energy, and we also consider the
effect of dispersion forces on the energetics. The recently identified
{\pi}-cubic phase of SnS is found to be metastable with respect to the
well-known orthorhombic Pnma/Cmcm equilibrium. The Cmcm phase is a low-lying
saddle point between Pnma minima on the potential-energy surface, and is
observed as an average structure at high temperatures. Bulk rocksalt and
zincblende phases are found to be dynamically unstable, and we show that
whereas rocksalt SnS can potentially be stabilised under a reduction of the
lattice constant, the hypothetical zincblende phase proposed in several earlier
studies is extremely unlikely to form. We also investigate the stability of
Sn2S3 with respect to SnS and SnS2, and find that both dispersion forces and
vibrational contributions to the free energy are required to explain its
experimentally-observed resistance to decomposition.",1703.00361v2
2017-03-11,Sign reversal of magnetoresistance and p to n transition in Ni doped ZnO thin film,"We report the magnetoresistance and nonlinear Hall effect studies over a wide
temperature range in pulsed laser deposited Ni0.07Zn0.93O thin film. Negative
and positive contributions to magnetoresistance at high and low temperatures
have been successfully modeled by the localized magnetic moment and two band
conduction process involving heavy and light hole subbands, respectively.
Nonlinearity in the Hall resistance also agrees well with the two channel
conduction model. A negative Hall voltage has been found for T $\gte 50 K$,
implying a dominant conduction mainly by electrons whereas positive Hall
voltage for T less than 50 K shows hole dominated conduction in this material.
Crossover in the sign of magnetoresistance from negative to positive reveals
the spin polarization of the charge carriers and hence the applicability of Ni
doped ZnO thin film for spintronic applications.",1703.03942v1
2018-10-01,Quantum transport in a compensated semimetal W2As3 with nontrivial Z2 indices,"We report a topological semimetal W2As3 with a space group C2/m. Based on the
first-principles calculations, band crossings are partially gapped when
spin-orbit coupling is included. The Z2 indices at the electron filling are
[1;111], characterizing a strong topological insulator and topological surface
states. From the magnetotransport measurements, nearly quadratic field
dependence of magnetoresistance (MR) (B || [200]) at 3 K indicates an
electron-hole compensated compound whose longitudinal MR reaches 115 at 3 K and
15 T. In addition, multiband features are detected from the high-magnetic-field
Shubnikov-de Haas (SdH) oscillation, Hall resistivity, and band calculations. A
nontrivial pi Berry's phase is obtained, suggesting the topological feature of
this material. A two- band model can fit well the conductivity and Hall
coefficient. Our experiments manifest that the transport properties of W2As3
are in good agreement with the theoretical calculations.",1810.00665v1
2019-07-05,Giant enhancement of Piezo-resistance in ballistic graphene due to transverse electric fields,"We investigate the longitudinal and transverse piezoresistance effect in
suspended graphene in the ballistic regime. Utilizing parametrized tight
binding Hamiltonian from ab initio calculations along with Landauer quantum
transport formalism, we devise a methodology to evaluate the piezoresistance
effect in 2D materials especially in graphene. We evaluate the longitudinal and
transverse gauge factor of graphene along armchair and zigzag directions in the
linear elastic limit ($0\%$-$10\%$). The longitudinal and transverse gauge
factors are identical along armchair and zigzag directions. Our model predicts
a significant variation ($\approx 1000\% $ change) in transverse gauge factor
compared to longitudinal gauge factor along with sign inversion. The calculated
value of longitudinal gauge factor is $\approx 0.3$ whereas the transverse
gauge factor is $\approx -3.3$. We rationalize our prediction using deformation
of Dirac cone and change in separation between transverse modes due to
longitudinal and transverse strain, leading to an inverse change in gauge
factor. The results obtained herein may serve as a template for high strain
piezoresistance effect of graphene in nano electromechanical systems.",1907.02896v1
2020-04-23,Experimental evidence of monolayer AlB$_2$ with symmetry-protected Dirac cones,"Monolayer AlB$_2$ is composed of two atomic layers: honeycomb borophene and
triangular aluminum. In contrast with the bulk phase, monolayer AlB$_2$ is
predicted to be a superconductor with a high critical temperature. Here, we
demonstrate that monolayer AlB$_2$ can be synthesized on Al(111) via molecular
beam epitaxy. Our theoretical calculations revealed that the monolayer AlB$_2$
hosts several Dirac cones along the $\Gamma$--M and $\Gamma$--K directions;
these Dirac cones are protected by crystal symmetries and are thus resistant to
external perturbations. The extraordinary electronic structure of the monolayer
AlB$_2$ was confirmed via angle-resolved photoemission spectroscopy
measurements. These results are likely to stimulate further research interest
to explore the exotic properties arising from the interplay of Dirac fermions
and superconductivity in two-dimensional materials.",2004.10916v1
2020-09-13,Extreme softness of brain matter in simple shear,"We show that porcine brain matter can be modelled accurately as a very soft
rubber-like material using the Mooney-Rivlin strain energy function, up to
strains as high as 60\%. This result followed from simple shear experiments
performed on small rectangular fresh samples ($2.5$ cm$^3$ and $1.1$ cm$^3$) at
quasi-static strain rates. They revealed a linear shear stress--shear strain
relationship ($R^2> 0.97 $), characteristic of Mooney-Rivlin materials at large
strains. We found that porcine brain matter is about 30 times less resistant to
shear forces than a silicone gel. We also verified experimentally that brain
matter exhibits the positive Poynting effect of nonlinear elasticity, and
numerically that the stress and strain fields remain mostly homogeneous
throughout the thickness of the samples in simple shear.",2009.06102v1
2020-09-29,Dimensional Crossover Tuned by Pressure in Layered Magnetic NiPS3,"Layered magnetic transition-metal thiophosphate NiPS3 has unique
two-dimensional (2D) magnetic properties and electronic behavior. The
electronic band structure and corresponding magnetic state are expected to
sensitive to the interlayer interaction, which can be tuned by external
pressure. Here, we report an insulator-metal transition accompanied with
magnetism collapse during the 2D-3D crossover in structure induced by
hydrostatic pressure. A two-stage phase transition from monoclinic (C2=m) to
trigonal (P-31m) lattice is identified by ab initio simulation and confirmed by
high-pressure XRD and Raman data, corresponding to a layer by layer slip
mechanism along the a-axis. Temperature dependence resistance measurements and
room temperature infrared spectroscopy show that the insulator-metal transition
occurs near 20 GPa as well as magnetism collapse, which is further confirmed by
low temperature Raman measurement and theoretical calculation. These results
establish a strong correlation among the structural change, electric transport,
and magnetic phase transition and expand our understandings about the layered
magnetic materials.",2009.14051v1
2022-02-23,The honeycomb and hyperhoneycomb polymorphs of IrI$_3$,"The synthesis of IrI$_3$ at high pressure in its layered honeycomb polymorph
is reported. Its crystal structure is refined by single crystal X-ray
diffraction. Faults in the honeycomb layer stacking are observed by single
crystal diffraction, synchrotron powder diffraction, and transmission electron
microscopy. A previously unreported hyperhoneycomb polymorph of IrI$_3$
($\beta$-IrI$_3$), is also described. Its structure in space group Fddd is
determined by single crystal XRD. Both materials are highly-resistive
diamagnetic semiconductors, consistent with a low spin d$^6$ configuration for
Ir(III). The two- and three-dimensional Ir arrays in these polymorphs of
IrI$_3$ are analogous to those found in the $\alpha$- and $\beta$- polymorphs
of Li$_2$IrO$_3$, although the Ir electron configurations are different.",2202.11658v1
2014-01-10,Ferroelectric-like SrTiO3 surface dipoles probed by graphene,"The electrical transport properties of graphene are greatly influenced by its
environment. Owing to its high dielectric constant, strontium titanate (STO) is
expected to suppress the long-range charged impurity scattering and
consequently to enhance the mobility. However, the absence of such enhancement
has caused some controversies regarding the scattering mechanism. In graphene
devices transferred from SiO2 to STO using a newly developed technique, we
observe a moderate mobility enhancement near the Dirac point, which is the
point of charge neutrality achieved by adjusting the Fermi level. While bulk
STO is not known as a ferroelectric material, its surface was previously
reported to exhibit an outward displacement of oxygen atoms and
ferroelectric-like dipole moment. When placed on STO, graphene shows strong and
asymmetric hysteresis in resistivity, which is consistent with the dipole
picture associated with the oxygen displacement. The hysteretic response of the
surface dipole moment diminishes the polarizability, therefore weakens the
ability of STO to screen the Coulomb potential of the impurities.",1401.2222v1
2017-05-01,Large Thermoelectric Power Factor at Low Temperatures in One-Dimensional Telluride Ta4SiTe4,"We report the discovery of a very large thermoelectric power over -400 microV
K-1 in the whisker crystals of a one-dimensional telluride Ta4SiTe4, while
maintaining a low electrical resistivity of rho = 2 mohm cm, yielding a very
large power factor of P = 80 microW cm-1 K-2 at an optimum temperature of 130
K. This temperature is widely controlled from the cryogenic temperature of 50 K
to room temperature by chemical doping, resulting in the largest P of 170
microW cm-1 K-2 at 220-280 K. These P values far exceed those of the
Bi2Te3-Sb2Te3 alloys at around room temperature, offering an avenue for
realizing the practical-level thermoelectric cooling at low temperatures. The
coexistence of a one-dimensional electronic structure and a very small band gap
appearing in the vicinity of the Dirac semimetals probably causes the very
large power factors in Ta4SiTe4, indicating that the ""one-dimensional Dirac
semimetal"" is a promising way to find high-performance thermoelectric materials
for the low temperature applications.",1705.00404v1
2017-08-25,Spin torque control of antiferromagnetic moments in NiO,"For a long time, there have been no efficient ways of controlling
antiferromagnets. Quite a strong magnetic field was required to manipulate the
magnetic moments because of a high molecular field and a small magnetic
susceptibility. It was also difficult to detect the orientation of the magnetic
moments since the net magnetic moment is effectively zero. For these reasons,
research on antiferromagnets has not been progressed as drastically as that on
ferromagnets which are the main materials in modern spintronic devices. Here we
show that the magnetic moments in NiO, a typical natural antiferromagnet, can
indeed be controlled by the spin torque with a relatively small electric
current density (~5 x 10^7 A/cm^2) and their orientation is detected by the
transverse resistance resulting from the spin Hall magnetoresistance . The
demonstrated techniques of controlling and detecting antiferromagnets would
outstandingly promote the methodologies in the recently emerged
""antiferromagnetic spintronics"". Furthermore, our results essentially lead to a
spin torque antiferromagnetic memory.",1708.07682v1
2019-03-13,"Hydrodynamic Phonon Transport: Past, Present, and Prospect","The hydrodynamic phonon transport was studied several decades ago for
verifying the quantum theory of lattice thermal transport. Recent prediction of
significant hydrodynamic phonon transport in graphitic materials shows its
practical importance for high thermal conductivity materials and brought a
renewed attention. As the study on this topic has been inactive to some extent
for several decades, we aim at providing a brief overview of the past studies
as well as very recent studies. The topics we discuss in this chapter include
the collective motion of phonons, several approaches to solve the
Peierls-Boltzmann transport equation for hydrodynamic phonon transport, the
role of normal scattering for thermal resistance, and the propagation of second
sound. Then, we close this chapter with our perspectives for the future studies
and the practical implication of hydrodynamic phonon transport.",1903.05731v1
2019-04-12,Synthesis of anti-perovskite-type carbides and nitrides from metal oxides and melamine,"Four anti-perovskite-type compounds, ZnNNi3, ZnCNi3, SnNCo3, and SnCCo3, are
synthesised through reactions between ingredient metal oxides and organic
compound melamine (C3H6N6). ZnNNi3 and ZnCNi3 are selectively synthesised by
choosing different reaction temperatures and nominal oxide-to-melamine ratios.
SnNCo3 is synthesised for the first time by this melamine method. Resistivity,
magnetisation, and heat capacity measurements reveal that SnNCo3 is a
correlated metal with a high density of states at the Fermi level. Our results
demonstrate that this feasible synthetic route using melamine is useful in the
search for complex metal carbides and nitrides toward novel functional
materials.",1904.06103v1
2019-12-23,Hydride Vapor-Phase Epitaxy Reactor for Bulk GaN Growth,"An HVPE reactor for the growth of bulk GaN crystals with a diameter of 50 mm
was developed. Growth rate non-uniformity of 1% was achieved using an
axisymmetric vertical gas injector with stagnation point flow.
Chemically-resistant refractory materials were used instead of quartz in the
reactor hot zone. High-capacity external gallium precursor sources were
developed for the non-stop growth of the bulk GaN layers. A load-lock vacuum
chamber and a dry in-situ growth chamber cleaning were implemented to improve
the growth process reproducibility. Freestanding GaN crystals with a diameter
of 50 mm were grown with the reactor.",1912.11010v1
2012-03-27,Shadow evaporation of epitaxial Al/Al2O3/Al tunnel junctions on sapphire utilizing an inorganic bilayer mask,"This letter describes a new inorganic shadow mask that has been employed for
the evaporation of all-epitaxial Al/Al2O3/Al superconducting tunnel junctions.
Organic resists that are commonly used for shadow masks and other lift-off
processes are not compatible with ultra-high vacuum deposition systems, and
they can break down at even moderately elevated temperatures. The inorganic
mask described herein does not suffer these same shortcomings. It was
fabricated from a Ge/Nb bilayer, comprising suspended Nb bridges supported by
an undercut Ge sacrificial layer. Utilizing such a bilayer mask on C-plane
sapphire, the growth of epitaxial Al tunnel junctions was achieved using
molecular beam epitaxy. Crystalline Al2O3 was grown diffusively at 300 C in a
molecular oxygen background of 2.0 utorr, while amorphous oxide was grown at
room temperature and 25 mtorr. A variety of analysis techniques were employed
to evaluate the materials, and tunnel junction current-voltage characteristics
were measured at millikelvin temperatures.",1203.6007v1
2012-06-14,Conduction in jammed systems of tetrahedra,"Control of transport processes in composite microstructures is critical to
the development of high performance functional materials for a variety of
energy storage applications. The fundamental process of conduction and its
control through the manipulation of granular composite attributes (e.g., grain
shape) are the subject of this work. We show that athermally jammed packings of
tetrahedra with ultra-short range order exhibit fundamentally different
pathways for conduction than those in dense sphere packings. Highly resistive
granular constrictions and few face-face contacts between grains result in
short-range distortions from the mean temperature field. As a consequence,
'granular' or differential effective medium theory predicts the conductivity of
this media within 10% at the jamming point; in contrast, strong enhancement of
transport near interparticle contacts in packed-sphere composites results in
conductivity divergence at the jamming onset. The results are expected to be
particularly relevant to the development of nanomaterials, where nanoparticle
building blocks can exhibit a variety of faceted shapes.",1206.2990v1
2016-09-06,Effect of morphology and defectiveness of graphene-related materials on the electrical and thermal conductivity of their polymer nanocomposites,"In this work, electrically and thermally conductive poly (butylene
terephthalate) nanocomposites were prepared by in-situ ring-opening
polymerization of cyclic butylene terephthalate (CBT) in presence of a
tin-based catalyst. One type of graphite nanoplatelets (GNP) and two different
grades of reduced graphene oxide (rGO) were used. Furthermore, high temperature
annealing treatment under vacuum at 1700{\deg}C was carried out on both RGO to
reduce their defectiveness and study the correlation between the
electrical/thermal properties of the nanocomposites and the nanoflakes
structure/defectiveness. The morphology and quality of the nanomaterials were
investigated by means of electron microscopy, x-ray photoelectron spectroscopy,
thermogravimetry and Raman spectroscopy. Thermal, mechanical and electrical
properties of the nanocomposites were investigated by means of rheology,
dynamic mechanical thermal analysis, volumetric resistivity and thermal
conductivity measurements. Physical properties of nanocomposites were
correlated with the structure and defectiveness of nanoflakes, evidencing a
strong dependence of properties on nanoflakes structure and defectiveness. In
particular, a significant enhancement of both thermal and electrical
conductivities was demonstrated upon the reduction of nanoflakes defectiveness.",1609.01581v2
2016-09-22,Crystal structure and low-energy Einstein mode in ErV$_2$Al$_{20}$ intermetallic cage compound,"Single crystals of a new ternary aluminide ErV$_2$Al$_{20}$ were grown using
a self-flux method. The crystal structure was determined by powder X-ray
diffraction measurements and Rietveld refinement, and physical properties were
studied by means of electrical resistivity, magnetic susceptibility and
specific heat measurements. These measurements reveal that ErV$_2$Al$_{20}$ is
a Curie-Weiss paramagnet down to 1.95 K with an effective magnetic moment
$\mu_{eff}$ = 9.27(1) $\mu_B$ and Curie-Weiss temperature $\Theta_{CW}$ =
-0.55(4) K. The heat capacity measurements show a broad anomaly at low
temperatures that is attributed to the presence of a low-energy Einstein mode
with characteristic temperature $\Theta_E$ = 44 K, approximately twice as high
as in the isostructural 'Einstein solid' VAl$_{10.1}$.",1609.07161v1
2020-05-11,Crystal Structure and Thermoelectric Transport Properties of As-Doped Layered Pnictogen Oxyselenides NdO0.8F0.2Sb1-xAsxSe2,"We report the synthesis and thermoelectric transport properties of As-doped
layered pnictogen oxyselenides NdO0.8F0.2Sb1-xAsxSe2 (x < 0.7), which are
predicted to show high-performance thermoelectric properties based on
first-principles calculation. The crystal structure of these compounds belongs
to the tetragonal P4/nmm space group (No. 129) at room temperature. The lattice
parameter c decreases with increasing x, while a remains almost unchanged among
the samples. Despite isovalent substitution of As for Sb, electrical
resistivity significantly rises with increasing x. Very low thermal
conductivity of less than 0.8 W/mK is observed at temperatures between 300 and
673 K for all the examined samples. For As-doped samples, the thermal
conductivity further decreases above 600 K. Temperature-dependent synchrotron
X-ray diffraction indicates that an anomaly also occurs in the c-axis length at
around 600 K, which may relate to the thermal transport properties.",2005.04836v1
2020-05-17,Paramagnetic resonance in La2NiMnO6 probed by impedance and lock-in detection techniques,"We report the detection of paramagnetic resonance in the double perovskite
La2NiMnO6 at room temperature for microwave magnetic fields with frequencies, f
= 1 GHz to 5 GHz, using two cavity-less methods. We use an indirect impedance
method which makes use of a radio frequency impedance analyzer and a folded
copper strip coil for the frequency range f = 1 to 2.2 GHz. In this method,
when an applied dc magnetic field is swept, high-frequency resistance of the
strip coil exhibits a sharp peak and the reactance curve crosses zero
exhibiting resonance. A lock-in based broadband setup using a coplanar
waveguide for microwave excitation was used for f = 2 to 5 GHz The resonance
fields (Hr) obtained from both the techniques increase linearly with frequency
and a large spectroscopic g-factor, equal to 2.1284, which supports the
presence of Ni2+ cation with strong spin-orbit coupling. Line shape analysis
and analytical fitting were performed to characterize the material in terms of
its initial susceptibility and damping parameters.",2005.08142v1
2020-05-19,Molecular beam epitaxy growth of nonmagnetic Weyl semimetal LaAlGe thin film,"Here, we report a detailed method of growing LaAlGe, a non-magnetic Weyl
semimetal, thin film on silicon(100) substrates by molecular beam epitaxy and
their structural and electrical characterizations. 50 nm thick LaAlGe films
were deposited and annealed for 16 hours in situ at a temperature 793 K.
As-grown high-quality films showed uniform surface topography and near ideal
stoichiometry with a body-centered tetragonal crystal structure.
Temperature-dependent longitudinal resistivity can be understood with dominant
interband s-d electron-phonon scattering in the temperature range 5-40 K. Hall
measurements confirmed the semimetallic nature of the films with electron
dominated charge carrier density near 7.15*10^21 cm^-3 at 5 K.",2005.09695v1
2020-07-13,One nanometer HfO$_2$-based ferroelectric tunnel junctions on silicon,"In ferroelectric materials, spontaneous symmetry breaking leads to a
switchable electric polarization, which offers significant promise for
nonvolatile memories. In particular, ferroelectric tunnel junctions (FTJs) have
emerged as a new resistive switching memory which exploit
polarization-dependent tunnel current across a thin ferroelectric barrier. Here
we demonstrate FTJs with CMOS-compatible Zr-doped HfO$_2$ (Zr:HfO$_2$)
ferroelectric barriers of just 1 nm thickness, grown by atomic layer deposition
on silicon. These 1 nm Zr:HfO$_2$ tunnel junctions exhibit large
polarization-driven electroresistance (19000$\%$), the largest value reported
for HfO$_2$-based FTJs. In addition, due to just a 1 nm ferroelectric barrier,
these junctions provide large tunnel current (> 1 A/cm$^2$) at low read
voltage, orders of magnitude larger than reported thicker HfO$_2$-based FTJs.
Therefore, our proof-of-principle demonstration provides an approach to
simultaneously overcome three major drawbacks of prototypical FTJs: a
Si-compatible ultrathin ferroelectric, large electroresistance, and large read
current for high-speed operation.",2007.06182v1
2020-08-03,Energy gap tuning and gate-controlled topological phase transition in InAs/In$_{x}$Ga$_{1-x}$Sb composite quantum wells,"We report transport measurements of strained InAs/In$_{x}$Ga$_{1-x}$Sb
composite quantum wells (CQWs) in the quantum spin Hall phase, focusing on the
control of the energy gap through structural parameters and an external
electric field. For highly strained CQWs with $x = 0.4$, we obtain a gap of 35
meV, an order of magnitude larger than that reported for binary InAs/GaSb CQWs.
Using a dual-gate configuration, we demonstrate an electrical-field-driven
topological phase transition, which manifests itself as a re-entrant behavior
of the energy gap. The sizeable energy gap and high bulk resistivity obtained
in both the topological and normal phases of a single device open the
possibility of electrical switching of the edge transport.",2008.00664v1
2020-08-15,Microwave AC voltage induced phase change in Sb$_2$Te$_3$ nanowires,"Scaling information bits to ever smaller dimensions is a dominant drive for
information technology (IT). Nanostructured phase change material emerges as a
key player in the current green-IT endeavor with low power consumption,
functional modularity and promising scalability. In this work, we present the
demonstration of microwave AC voltage induced phase change phenomenon at 3 GHz
in single Sb$_2$Te$_3$ nanowires. The resistance change by a total of 6 - 7
orders of magnitude is evidenced by a transition from the crystalline metallic
to the amorphous semiconducting phase, which is cross-examined by temperature
dependent transport measurement and high-resolution electron microscopy
analysis. This discovery could potentially tailor multi-state information bit
encoding and discrimination along a single nanowire, rendering technology
advancement for neuro-inspired computing devices.",2008.06666v1
2020-10-23,Observation of photoelectric nonvolatile memory and oscillations in VO2 at room temperature,"Vanadium dioxide (VO2) is a phase change material that can reversibly change
between high and low resistivity states through electronic and structural phase
transitions. Thus far, VO2 memory devices have essentially been volatile at
room temperature, and nonvolatile memory has required non-ambient surroundings
(e.g., elevated temperatures, electrolytes) and long write times. Here, we
report the first observation of optically addressable nonvolatile memory in VO2
at room temperature with a readout by voltage oscillations. The read and write
times had to be kept shorter than about 150 {\mu}s. The writing of the memory
and onset of the voltage oscillations had a minimum optical power threshold.
This discovery demonstrates the potential of VO2 for new computing devices and
architectures, such as artificial neurons and oscillatory neural networks.",2010.12531v1
2020-11-17,Effect of Surface Treatment on High-Temperature Oxidation Behavior of IN 713C,"The effects of surface preparations on oxidation kinetics and oxide scale
morphology for the commercially available Ni-based superalloy IN 713C have been
investigated. The ground and polished samples were exposed in air at 800-1100C.
The ground specimens were found to demonstrate lower oxidation kinetics
compared to those after polishing. The grinding also affected the oxide scale
morphology, resulting in a protective alumina scale, while the polished samples
developed Ni-/Cr-rich mixed oxides on the surface. Better oxidation resistance
of the ground surfaces is related to a higher concentration of defects in the
nearsurface region introduced by cold working. These defects facilitate the
outward transport of the scaleforming element Al and thus are beneficial for
protective oxidation. The oxidation mechanism at lower temperatures was
introduced. The model based on the generalized Darken method and multiphase
approximation was proposed.",2011.08910v1
2021-02-01,Resistive transition of hydrogen-rich superconductors,"Critical temperature, $T_c$, and the transition width, $\Delta$$T_c$, are two
primary parameters of the superconducting transition. The latter parameter
reflects the superconducting state disturbance originating from the
thermodynamic fluctuations, atomic disorder, applied magnetic field, the
presence of secondary crystalline phases, applied pressure, etc. Recently,
Hirsch and Marsiglio (2020 arXiv:2012.12796) performed an analysis of the
transition width in several near-room-temperature superconductors (NRTS) and
reported that the reduced transition width, $\Delta$$T_c$$/$$T_c$, in these
materials does not follow a conventional trend of transition width broadening
on applied magnetic field observed in low- and high-$T_c$ superconductors. Here
we present thorough mathematical analysis of the magnetoresistive data,
$\it{R(T,B)}$, for the high-entropy alloy $(ScZrNb)_{0.65}$$[RhPd]_{0.35}$ and
hydrogen-rich superconductors of Im-3m-$H_{3}S$, C2/m-$LaH_{10}$ and
P63/mmc-$CeH_9$. We found that the reduced transition width,
$\Delta$$T_c$$/$$T_c$, in these materials does follow a conventional broadening
trend on applied magnetic field.",2102.00946v3
2021-02-10,Evidence of damage in carbon fibre composite tiles joined to a metallic heat sink under high heat flux fatigue,"The two years experience with Active Metal Casting flat bonds shows that this
technology is suitable for the heat fluxes expected in Tore Supra (10
MW/m${}^2$). Tests were pursued up to 3330 cycles, with elements still
functional. At higher heat fluxes, fatigue damage is observed, but the bond
resists remarkably well with no tile detachment. Examination of such
deliberately damaged bonds showed distributed cracking, proving the absence of
any weak link. The limitations to those higher heat fluxes are more related to
the design and the base materials than to the bond itself.",2102.05316v1
2021-03-14,Electron-beam Floating-zone Refined UCoGe,"The interplay between unconventional superconductivity and quantum critical
ferromagnetism in the U-Ge compounds represents an open problem in strongly
correlated electron systems. Sample quality can have a strong influence on both
of these ordered states in the compound UCoGe, as is true for most
unconventional superconductors. We report results of a new approach at UCoGe
crystal growth using a floating-zone method with potential for improvements of
sample quality and size as compared with traditional means such as Czochralski
growth. Single crystals of the ferromagnetic superconductor UCoGe were produced
using an ultra-high vacuum electron-beam floating-zone refining technique.
Annealed single crystals show well-defined signatures of bulk ferromagnetism
and superconductivity at $T_c \sim$2.6 K and $T_s \sim$0.55 K, respectively, in
the resistivity and heat capacity. Scanning electron microscopy of samples with
different surface treatments shows evidence of an off-stoichiometric uranium
rich phase of UCoGe collected in cracks and voids that might be limiting sample
quality.",2103.08000v1
2021-03-24,Large Nernst effect and field enhanced transversal ZT in ZrTe5,"Thermoelectric materials can recover electrical energy from waste heat and
vice versa, which are of great significance in green energy harvesting and
solid state refrigerator. The thermoelectric figure of merit (zT) quantifies
the energy conversion efficiency, and a large Seebeck or Nernst effect is
crucial for the development of thermoelectric devices. Here we present a
significantly large Nernst thermopower in topological semimetal ZrTe5, which is
attributed to both strong Berry curvature and bipolar transport. The largest
in-plane S_xy (when B//b) approaches 1900 {\mu}V/K at T=100K and B=13T, and the
out-of-plane S_xz (when B//c) reaches 5000 {\mu}V/K. As a critical part of z_N
T, the linearly increased in-plane S_xy and resistivity \r{ho}_yy regard to B
induces an almost linear increasing transversal z_N T without saturate under
high fields. The maximum z_N T of 0.12 was obtained at B=13 T and T= 120K,
which significantly surmounts its longitudinal counterpart under the same
condition.",2103.13069v1
2021-03-26,Large Microwave Inductance of Granular Boron-Doped Diamond Superconducting Films,"Boron-doped diamond granular thin films are known to exhibit
superconductivity with an optimal critical temperature of Tc = 7.2K. Here we
report the measured complex surface impedance of Boron-doped diamond films in
the microwave frequency range using a resonant technique. Experimentally
measured inductance values are in good agreement with estimates obtained from
the normal state sheet resistance of the material. The magnetic penetration
depth temperature dependence is consistent with that of a fully-gapped s-wave
superconductor. Boron-doped diamond films should find application where high
kinetic inductance is needed, such as microwave kinetic inductance detectors
and quantum impedance devices.",2103.14738v3
2021-06-25,An estimate for thermal diffusivity in highly irradiated tungsten using Molecular Dynamics simulation,"The changing thermal conductivity of an irradiated material is among the
principal design considerations for any nuclear reactor, but at present few
models are capable of predicting these changes starting from an arbitrary
atomistic model. Here we present a simple model for computing the thermal
diffusivity of tungsten, based on the conductivity of the perfect crystal and
resistivity per Frenkel pair, and dividing a simulation into perfect and
athermal regions statistically. This is applied to highly irradiated
microstructures simulated with Molecular Dynamics. A comparison to experiment
shows that simulations closely track observed thermal diffusivity over a range
of doses from the dilute limit of a few Frenkel pairs to the high dose
saturation limit at 3 displacements per atom (dpa).",2106.13666v2
2021-07-15,Microstructure manipulation by laser-surface remelting of a full-Heusler compound to enhance thermoelectric properties,"There is an increasing reckoning that the thermoelectric performance of a
material is dependent on its microstructure. However, the
microstructure-properties relationship often remains elusive, in part due to
the complexity of the hierarchy and scales of features that influence transport
properties. Here, we focus on the promising Heusler-Fe2VAl compound. We
directly correlate microstructure and local properties, using advanced scanning
electron microscopy methods including in-situ four-point-probe technique for
electron transport measurements. The local thermal conductivity is investigated
by scanning thermal microscopy. Finally, atom probe tomography provides
near-atomic scale compositional analysis. To locally manipulate the
microstructure, we use laser surface remelting. The rapid quenching creates a
complex microstructure with a high density of dislocations and small, elongated
grains. We hence showcase that laser surface remelting can be employed to
manipulate the microstructure to reduce the thermal conductivity and electrical
resistivity, leading to a demonstrated enhancement of the thermoelectric
performance at room temperature.",2107.07327v1
2021-07-29,Breakdown of the topological protection by cavity vacuum fields in the integer quantum Hall effect,"The control of the electronic properties of materials via the vacuum fields
of cavity electromagnetic resonators is one of the emerging frontiers of
condensed matter physics. We show here that the enhancement of vacuum field
fluctuations in subwavelength split-ring resonators dramatically affects
arguably one of the most paradigmatic quantum protectorates, namely the quantum
Hall electron transport in high-mobility 2D electron gases. The observed
breakdown of the topological protection of the integer quantum Hall effect is
interpreted in terms of a long-range cavity-mediated electron hopping where the
anti-resonant terms of the light-matter coupling finally result into a finite
resistivity induced by the vacuum fluctuations. The present experimental
platform can be used for any 2D material and provides new ways to manipulate
electron phases in matter thanks to vacuum-field engineering",2107.14145v1
2021-09-03,Quantum anomalous Hall edge channels survive up to the Curie temperature,"Achieving metrological precision of quantum anomalous Hall resistance
quantization at zero magnetic field so far remains limited to temperatures of
the order of 20 mK, while the Curie temperature in the involved material is as
high as 20 K. The reason for this discrepancy remains one of the biggest open
questions surrounding the effect, and is the focus of this article. Here we
show, through a careful analysis of the non-local voltages on a multi-terminal
Corbino geometry, that the chiral edge channels continue to exist without
applied magnetic field up to the Curie temperature of bulk ferromagnetism of
the magnetic topological insulator, and that thermally activated bulk
conductance is responsible for this quantization breakdown. Our results offer
important insights on the nature of the topological protection of these edge
channels, provide an encouraging sign for potential applications, and establish
the multi-terminal Corbino geometry as a powerful tool for the study of edge
channel transport in topological materials.",2109.01463v1
2021-11-03,Insulator-to-superconductor transition in quasi-one-dimensional HfS3 under pressure,"Various transition metal trichalcogenides (TMTC) show the charge-density-wave
and superconductivity, which provide an ideal platform to study the correlation
between these two orderings and the mechanism of superconductivity. Currently,
almost all metallic TMTC compounds can show superconductivity either at ambient
pressure or at high pressure. However, most TMTC compounds are semiconductors
and even insulators. Does the superconductivity exist in any non-metal TMTC
compound? In this work, we managed to manipulate the electronic behavior of
highly insulating HfS3 in term of pressure. HfS3 underwent an
insulator-semiconductor transition near 17 GPa with a band gap reduce of ~1 eV.
The optical absorption and Raman measurement provide the consistent results,
suggesting the structural origin of the electronic transition. Upon further
compression, HfS3 becomes a superconductor. The superconducting transition was
initialized as early as 50.6 GPa and the zero-resistance is reached above 91.2
GPa. The superconducting behavior is further confirmed by both the magnetic
field effect and current effect. This work sheds the light that all TMTC may be
superconductors, and opens a new avenue to explore the abundant emergence
phenomena in TMTC material family.",2111.02060v1
2021-11-16,Ultrathin ferrimagnetic GdFeCo films with very low damping,"Ferromagnetic materials dominate as the magnetically active element in
spintronic devices, but come with drawbacks such as large stray fields, and low
operational frequencies. Compensated ferrimagnets provide an alternative as
they combine the ultrafast magnetization dynamics of antiferromagnets with a
ferromagnet-like spin-orbit-torque (SOT) behavior. However to use ferrimagnets
in spintronic devices their advantageous properties must be retained also in
ultrathin films (t < 10 nm). In this study, ferrimagnetic Gdx(Fe87.5Co12.5)1-x
thin films in the thickness range t = 2-20 nm were grown on high resistance
Si(100) substrates and studied using broadband ferromagnetic resonance
measurements at room temperature. By tuning their stoichiometry, a nearly
compensated behavior is observed in 2 nm Gdx(Fe87.5Co12.5)1-x ultrathin films
for the first time, with an effective magnetization of Meff = 0.02 T and a low
effective Gilbert damping constant of {\alpha} = 0.0078, comparable to the
lowest values reported so far in 30 nm films. These results show great promise
for the development of ultrafast and energy efficient ferrimagnetic spintronic
devices.",2111.08768v1
2021-12-06,Sliding Ferroelectric Tunnel Junctions,"Very recently, ferroelectric polarization in staggered bilayer hexagonal
boron nitride (BBN) and its novel sliding inversion mechanism was reported
experimentally (Science 2021, 372, 1458; 2021, 372, 1462), which paves a new
way to realize van der Waals (vdW) ferroelectric devices with new
functionalities. Here, we develop vdW sliding ferroelectric tunnel junctions
(FTJs) using the sliding ferroelectric BBN unit as ultrathin barriers and
explore their transport properties with different ferroelectric states and
metal contacts via the first principles. It is found that the electrode/BBN
contact electric field quenches the ferroelectricity in the staggered BBN,
resulting a very small tunnelling electroresistance (TER). Inserting
high-mobility 2D materials between Au and BN can restore the BBN
ferroelectricity, reaching a giant TER of ~10,000% in sliding FTJs. We finally
investigate the metal-contact and thickness effect on the tunnelling property
of sliding FTJs. The giant TER and multiple non-volatile resistance states in
vdW sliding FTJs show the promising applications in voltage-controlled
nano-memories with ultrahigh storage density.",2112.02886v1
2022-06-06,Enhancement of superconductivity on the verge of a structural instability in isovalently doped $β$-ThRh$_{1-x}$Ir$_{x}$Ge,"$\beta$-ThRhGe, the high-temperature polymorph of ThRhGe, is isostructural to
the well-known ferromagnetic superconductor URhGe. However, contrary to URhGe,
$\beta$-ThRhGe is nonmagnetic and undergoes an incomplete structural phase
transition at 244 K, followed by a superconducting transition below 3.36 K.
Here we show that the isovalent substitution of Ir for Rh leads to a strong
enhancement of superconductivity by suppressing the structural transition. At
$x$ = 0.5, where the structural transition disappears, $T_{\rm c}$ reaches a
maximum of 6.88 K. The enhancement of superconductivity is linked to the
proximity to a structural quantum critical point at this Ir concentration, as
suggested by the analysis of thermodynamic as well as resistivity data. First
principles calculations indicate that the Ir doping has little effect on the
electronic band dispersion near the Fermi level. $\beta$-ThRh$_{1-x}$Ir$_{x}$Ge
thus provides an excellent platform to study the interplay between
superconductivity and structural quantum criticality in actinide-containing
compounds.",2206.02364v1
2022-06-21,HR-EBSD analysis of in situ stable crack growth at the micron scale,"Understanding the local fracture resistance of microstructural features. such
as brittle inclusions, coatings, and interfaces at the microscale under complex
loading conditions is critical for microstructure-informed design of materials.
In this study, a novel approach has been formulated to decompose the J-integral
evaluation of the elastic energy release rate to the three-dimensional stress
intensity factors directly from experimental measurements of the elastic
deformation gradient tensors of the crack field by in situ high (angular)
resolution electron backscatter diffraction (HR-EBSD). An exemplar study is
presented of a quasi-static crack, inclined to the observed surface,
propagating on low index {hkl} planes in a (001) single crystal silicon wafer.",2206.10243v2
2022-10-01,Surface modulation of metal-organic frameworks for on-demand photochromism in the solid state,"Organic photoswitchable molecules have struggled in solid state form to
fulfill their remarkable potential, in terms of photoswitching performance and
long-term stability when compared to their inorganic counterparts. We report
the concept of non-electron deficient host's surface with optimal porosity and
hydrophobicity, as a priori strategy to design photoefficient organic
solid-state photochromic materials with outstanding mechanical robustness. When
exposed to a light stimulus including natural sunlight, the photoswitchable
nanocomposite changes color promptly and reversibly, in a matter of seconds
along with excellent photo-fatigue resistance, which are on a par with
inorganic photochromes. Exemplars of commercially viable prototypes that are
optically clear, comprising smart windows, complex photochromic sculptures, and
self-erasing rewritable devices, were engineered by direct blending with
resilient polymers; particularly, the use of high-stiffness polymer (> 2 GPa)
is no longer an insurmountable challenge. Finally, photochromic films with
anticounterfeiting features could be manufactured through precision inkjet
printing of nanocrystals.",2210.00241v1
2022-10-06,Fracture behavior of MOF monoliths revealed by nanoindentation and nanoscratch,"Monolithic metal-organic frameworks (MOFs) represent a promising solution for
the industrial implementation of this emerging class of multifunctional
materials, due to their structural stability. When compared to MOF powders,
monoliths exhibit other intriguing properties like hierarchical porosity, that
significantly improves volumetric adsorption capacity. The mechanical
characterization of MOF monoliths plays a pivotal role in their industrial
expansion, but so far, several key aspects remain unclear. In particular, the
fracture behavior of MOF monoliths has not been explored. In this work, we
studied the initiation and propagation of cracks in four prototypical MOF
monoliths, namely ZIF-8, HKUST-1, MIL-68 and MOF-808. We observed that shear
faults inside the contact area represent the main failure mechanism of MOF
monoliths and are the source of radial cracks. MIL-68 and MOF-808 showed a
remarkably high resistance to cracking, which can be ascribed to their
consolidated nanostructure.",2210.03219v1
2022-10-26,Thermoelectric properties in semimetals with inelastic electron-hole scattering,"We present systematic theoretical results on thermoelectric effects in
semimetals based on the variational method of the linearized Boltzmann
equation. Inelastic electron-hole scattering is known to play an important role
in the unusual transport of semimetals, including the broad $T^2$ temperature
dependence of the electrical resistivity and the strong violation of the
Wiedemann-Franz law. By treating the inelastic electron-hole scattering more
precisely beyond the relaxation time approximation, we show that the Seebeck
coefficient when compensated depends on the screening length of the Coulomb
interaction as well as the Lorenz ratio (the ratio of thermal to electric
conductivity due to electrons divided by temperature). It is found that
deviations from the compensation condition significantly increase the Seebeck
coefficient, along with crucial suppressions of the Lorenz ratio. The result
indicates that uncompensated semimetals with the electron-hole scattering have
high thermoelectric efficiency when the phonon contribution to thermal
conductivity is suppressed.",2210.14825v2
2023-01-10,Depolarization Induced III-V Triatomic Layers with Tristable Polarization States,"The integration of ferroelectrics that exhibit high dielectric,
piezoelectric, and thermal susceptibilities with the mainstream semiconductor
industry will enable novel device types for widespread applications, and yet
there are few silicon-compatible ferroelectrics suitable for device
downscaling. We demonstrate with first-principles calculations that the
enhanced depolarization field at the nanoscale can be utilized to soften
unswitchable wurtzite III-V semiconductors, resulting in ultrathin
two-dimensional (2D) sheets possessing reversible polarization states. A 2D
sheet of AlSb consisting of three atomic planes is identified to host both
ferroelectricity and antiferroelectricity, and the tristate switching is
accompanied by a metal-semiconductor transition. The thermodynamics stability
and potential synthesizability of the triatomic layer are corroborated with
phonon spectrum calculations, ab initio molecular dynamics, and
variable-composition evolutionary structure search. We propose a 2D AlSb-based
homojunction field effect transistor that supports three distinct and
nonvolatile resistance states. This new class of III-V semiconductor-derived 2D
materials with dual ferroelectricity and antiferroelectricity opens up the
possibility for nonvolatile multibit-based integrated nanoelectronics.",2301.03876v1
2023-01-11,Direct imaging of local atomic structures in zeolite using novel low-dose scanning transmission electron microscopy,"Zeolites have been used in industrial applications such as catalysts, ion
exchangers, and molecular sieves because of their unique porous atomic
structures. However, the direct observation of zeolitic local atomic structures
via electron microscopy is difficult owing to their low resistance to electron
irradiation. Subsequently, the fundamental relationships between these
structures and their properties remain unclear. A novel low-electron-dose
imaging technique, optimum bright-field scanning transmission electron
microscopy (OBF STEM) has recently been developed. It reconstructs images with
a high signal-to-noise ratio and a dose efficiency approximately two orders of
magnitude higher than that of conventional methods. Herein, we performed
low-dose atomic-resolution OBF STEM observations of an FAU-type zeolite,
effectively visualizing all the atomic sites in its framework. Additionally,
the complex local atomic structure of the twin boundaries in the zeolite was
directly characterized. The results of this study facilitate the
characterization of the local atomic structures in many electron-beam-sensitive
materials.",2301.04377v1
2023-04-25,Simulations of Magnetization Reversal in FM/AFM Bilayers With THz Frequency Pulses,"It is widely known that antiferromagnets (AFMs) display a high frequency
response in the terahertz (THz) range, which opens up the possibility for
ultrafast control of their magnetization for next generation data storage and
processing applications. However, because the magnetization of the different
sublattices cancel, their state is notoriously difficult to read. One way to
overcome this is to couple AFMs to ferromagnets - whose state is trivially read
via magneto-resistance sensors. Here we present conditions, using theoretical
modelling, that it is possible to switch the magnetization of an AFM/FM bilayer
using THz frequency pulses with moderate field amplitude and short durations,
achievable in experiments. Consistent switching is observed in the phase
diagrams for an order of magnitude increase in the interface coupling and a
tripling in the thickness of the FM layer. We demonstrate a range of reversal
paths that arise due to the combination of precession in the materials and the
THz-induced fields. Our analysis demonstrates that the AFM drives the switching
and results in a much higher frequency dynamics in the FM due to the exchange
coupling at the interface. The switching is shown to be robust over a broad
range of temperatures relevant for device applications.",2304.12969v1
2023-05-24,A new class of carbon stabilized austenitic steels resistant to hydrogen embrittlement,"High strength steels are susceptible to H-induced failure, which is typically
caused by the presence of diffusible H in the microstructure. The diffusivity
of H in austenitic steels with fcc crystal structure is slow. The austenitic
steels are hence preferred for applications in the hydrogen-containing
atmospheres. However, the fcc structure of austenitic steels is often
stabilized by the addition of Ni, Mn or N, which are relatively expensive
alloying elements to use. Austenite can kinetically also be stabilized by using
C. Here, we present an approach applied to a commercial cold work tool steel,
where we use C to fully stabilize the fcc phase. This results in a
microstructure consisting of only austenite and an M7C3 carbide. An exposure to
H by cathodic hydrogen charging exhibited no significant influence on the
strength and ductility of the C stabilized austenitic steel. While this
material is only a prototype based on an existing alloy of different purpose,
it shows the potential for low-cost H-resistant steels based on C stabilized
austenite.",2305.15290v3
2023-06-17,Pseudogap behavior in charge density wave kagome material ScV$_6$Sn$_6$ revealed by magnetotransport measurements,"Over the last few years, significant attention has been devoted to studying
the kagome materials AV$_3$Sb$_5$ (A = K, Rb, Cs) due to their unconventional
superconductivity and charge density wave (CDW) ordering. Recently
ScV$_6$Sn$_6$ was found to host a CDW below $\approx$90K, and, like
AV$_3$Sb$_5$, it contains a kagome lattice comprised only of V ions. Here we
present a comprehensive magnetotransport study on ScV$_6$Sn$_6$. We discovered
several anomalous transport phenomena above the CDW ordering temperature,
including insulating behavior in interlayer resistivity, a strongly
temperature-dependent Hall coefficient, and violation of Kohler's rule. All
these anomalies can be consistently explained by a progressive decrease in
carrier densities with decreasing temperature, suggesting the formation of a
pseudogap. Our findings suggest that high-temperature CDW fluctuations play a
significant role in determining the normal state electronic properties of
ScV$_6$Sn$_6$.",2306.10230v1
2023-07-12,Monolithic Selenium/Silicon Tandem Solar Cells,"Selenium is experiencing renewed interest as a promising candidate for the
wide bandgap photoabsorber in tandem solar cells. However, despite the
potential of selenium-based tandems to surpass the theoretical efficiency limit
of single junction devices, such a device has never been demonstrated. In this
study, we present the first monolithically integrated selenium/silicon tandem
solar cell. Guided by device simulations, we investigate various
carrier-selective contact materials and achieve encouraging results, including
an open-circuit voltage of V$_\text{oc}$=1.68 V from suns-V$_\text{oc}$
measurements. The high open-circuit voltage positions selenium/silicon tandem
solar cells as serious contenders to the industrially dominant single junction
technologies. Furthermore, we quantify a pseudo fill factor of more than 80%
using injection-level-dependent open-circuit voltage measurements, indicating
that a significant fraction of the photovoltaic losses can be attributed to
parasitic series resistance. This work provides valuable insights into the key
challenges that need to be addressed for realizing higher efficiency
selenium/silicon tandem solar cells.",2307.05996v1
2023-10-09,Colossal c-axis response and lack of rotational symmetry breaking within the kagome plane of the CsV$_3$Sb$_5$ superconductor,"The kagome materials AV4$_3$Sb$_5$ (A = K, Rb, Cs) host an intriguing
interplay between unconventional superconductivity and charge-density-waves.
Here, we investigate CsV$_3$Sb$_5$ by combining high-resolution
thermal-expansion, heat-capacity and electrical resistance under strain
measurements. We directly unveil that the superconducting and charge-ordered
states strongly compete, and that this competition is dramatically influenced
by tuning the crystallographic c-axis. In addition, we report the absence of
additional bulk phase transitions within the charge-ordered state, notably
associated with rotational symmetry-breaking within the kagome planes. This
suggests that any breaking of the C$_6$ invariance occurs via different
stacking of C$_6$-symmetric kagome patterns. Finally, we find that the
charge-density-wave phase exhibits an enhanced A$_{1g}$-symmetric
elastoresistance coefficient, whose large increase at low temperature is driven
by electronic degrees of freedom.",2310.06102v1
2023-10-15,Parabolic Vector Focus Wave Modes,"Weber-type parabolic beams have a transverse intensity profile, which is
parabolically-shaped and can be flexibly controlled. On the other hand, this
type of beams belongs to the family of the so-called nondiffracting beams and
have properties, promising for applications where the shape of the beam is of
an importance. Vector electromagnetic theory has to be introduced in order to
fully describe optical beams inside a high numerical aperture system, where the
angles of the spatial spectra are large. We introduce here parabolic vector
focus wave modes (FWM), which are both resistant to diffraction and to material
dispersion. We employ here a spectral approach and investigate durations of
parabolic vector FWMs in the femtosecond region. Two cases of transverse
electric and transverse magnetic modes are introduced and both standing and
traveling types of waves are considered. We demonstrate how the angular
dispersion affects the pulse shape and its properties. Parabolic vector FWMs
are studied in a transparent dielectric media (sapphire), which is widely used
as laser processed material.",2310.09896v1
2023-11-09,Single-Atom Control of Arsenic Incorporation in Silicon for High-Yield Artificial Lattice Fabrication,"Artificial lattices constructed from individual dopant atoms within a
semiconductor crystal hold promise to provide novel materials with tailored
electronic, magnetic, and optical properties. These custom engineered lattices
are anticipated to enable new, fundamental discoveries in condensed matter
physics and lead to the creation of new semiconductor technologies including
analog quantum simulators and universal solid-state quantum computers. In this
work, we report precise and repeatable, substitutional incorporation of single
arsenic atoms into a silicon lattice. We employ a combination of scanning
tunnelling microscopy hydrogen resist lithography and a detailed statistical
exploration of the chemistry of arsine on the hydrogen terminated silicon (001)
surface, to show that single arsenic dopants can be deterministically placed
within four silicon lattice sites and incorporated with 97$\pm$2% yield. These
findings bring us closer to the ultimate frontier in semiconductor technology:
the deterministic assembly of atomically precise dopant and qubit arrays at
arbitrarily large scales.",2311.05752v1
2023-11-26,"Quantum oscillations in kagome metals (Ti, Zr, Hf)V6Sn6 at Van Hove filling","Kagome materials have recently drawn great attention due to the interplay
between nontrivial band topology, electron correlations, and Van Hove
singularities related many-body orders. Here we report three new vanadium-based
kagome metals, TiV6Sn6, ZrV6Sn6, and HfV6Sn6, and conduct a comprehensive
investigation of their structural, magnetic, and electrical transport
properties. All three compounds exhibit large unsaturated magnetoresistances
and multiband Hall effects at low temperatures, indicating the existence of
multiple highly mobile carriers. Both the diagonal and off-diagonal resistivity
show quantum oscillations with nontrivial Berry phases and high quantum
mobilities. First-principles calculations together with quantum oscillation
analyses suggest the Van Hove singularities at the M point for the three
compounds all located in close vicinity of the Fermi level, and there also
exist multiple topological nontrivial band crossings, including a nodal ring
and a massive Dirac cone. Our work extends the kagome AM6X6 family and paves
the way for searching possible Van Hove physics in the V kagome lattice.",2311.15239v2
2023-12-14,Long-Range Structural Order in a Hidden Phase of Ruddlesden-Popper Bilayer Nickelate La$_3$Ni$_2$O$_7$,"The recent discovery of superconductivity in Ruddlesden-Popper bilayer
nickelate, specifically La$_3$Ni$_2$O$_7$, has generated significant interest
in the exploration of high-temperature superconductivity within this material
family. In this study, we present the crystallographic and electrical
resistivity properties of two distinct Ruddlesden-Popper nickelates: the
bilayer La$_3$Ni$_2$O$_7$ (referred to as 2222-phase) and a previously
uncharacterized phase, La$_3$Ni$_2$O$_7$ (1313-phase). The 2222-phase is
characterized by a pseudo $F$-centered orthorhombic lattice, featuring bilayer
perovskite [LaNiO$_3$] layers interspaced by rock salt [LaO] layers, forming a
repeated ...2222... sequence. Intriguingly, the 1313-phase, which displays
semiconducting properties, crystallizes in the $Cmmm$ space group and exhibits
a pronounced predilection for a $C$-centered orthorhombic lattice. Within this
structure, the perovskite [LaNiO$_3$] layers exhibit a distinctive long-range
ordered arrangement, alternating between single- and trilayer configurations,
resulting in a ...1313... sequence. This report contributes to novel insights
into the crystallography and the structure-property relationship of
Ruddlesden-Popper nickelates, paving the way for further investigations into
their unique physical properties.",2312.09200v2
2024-03-11,Active Control of Bound States in the Continuum in Toroidal Metasurfaces,"The remarkable properties of toroidal metasurfaces, featuring ultrahigh-Q
bound states in the continuum (BIC) resonances and nonradiating anapole modes,
have garnered significant attention. The active manipulation of toroidal
resonance characteristics offers substantial potential for advancing tunable
metasurfaces. Our study specifically explores the application of vanadium
dioxide, a widely used phase change material in active photonics and
room-temperature bolometric detectors, to control BIC resonances in toroidal
metasurfaces. The phase change transition of vanadium dioxide occurs in a
narrow temperature range providing a large variation in material resistivity.
Through heating thin film patches of vanadium dioxide integrated into a
metasurface comprising gold split-ring resonators on a sapphire substrate, we
achieve remarkable control over the amplitude and frequency of toroidal dipole
BIC resonances due to their high sensitivity to losses present in the system.
Breaking the symmetry of meta-atoms reveals enhanced tunability. The predicted
maximum change in the amplitude of toroidal dipole BIC resonances reaches 14 dB
with a temperature variation of approximately 10oC. The proposed tunable
metasurface holds promise for various applications, including active photonic
systems and room temperature bolometers.",2403.06345v1
2024-04-11,Hydrogen Trapping and Embrittlement in Metals -- A Review,"Hydrogen embrittlement in metals (HE) is a serious challenge for the use of
high strength materials in engineering practice and a major barrier to the use
of hydrogen for global decarbonization. Here we describe the factors and
variables that determine HE susceptibility and provide an overview of the
latest understanding of HE mechanisms. We discuss hydrogen uptake and how it
can be managed. We summarize hydrogen trapping and the techniques used for its
characterization. We also review literature that argues that hydrogen trapping
can be used to decrease HE susceptibility. We discuss the future research that
is required to advance the understanding of HE and hydrogen trapping and to
develop HE-resistant alloys.",2404.07736v1
1999-07-23,Unconventional one-magnon scattering resistivity in half metals,"Low-temperature resistivity of half-metals is investigated. To date it has
been discussed that the one-magnon scattering process in half-metals is
irrelevant for low-temperature resistivity, due to the fully spin-polarized
electronic structure at the ground state. If one takes into account the
non-rigid-band behavior of the minority band due to spin fluctuations at finite
temperatures, however, the unconventional one-magnon scattering process is
shown to be most relevant and gives T^3 dependence in resistivity. This
behavior may be used as a crucial test in the search for half-metallic
materials which are potentially important for applications. Comparison with
resistivity data of
  La_1-x Sr_x MnO_3 as candidates for half-metals shows good agreement.",9907363v2
2002-05-27,Superconductivity of epsilon-Fe: complete resistive transition,"Last year, iron was reported to become superconducting at temperatures below
2K and pressures between 15 and 30 GPa. The evidence presented was a weak
resistivity drop, suppressed by a magnetic field above 0.2 T, and a small
Meissner signal. However, a compelling demonstration, such as the occurrence of
zero resistance, was lacking. Here we report the measurement of a complete
resistive transition at 22.2 GPa with an onset slightly above 2 K in two very
pure samples of iron, of different origins. The superconductivity appears
unusually sensitive to disorder, developing only when the electronic mean free
path is above a threshold value, while the normal state resistivity is
characteristic of a nearly ferromagnetic metal.",0205557v1
2002-06-08,Diffusion theory of spin injection through resistive contacts,"Insertion of a resistive contact between a ferromagnetic metal and a
semiconductor microstructure is of critical importance for achieving efficient
spin injection into a semiconductor. However, the equations of the diffusion
theory are rather cumbersome for the junctions including such contacts. A
technique based on deriving a system of self-consistent equations for the
coefficients of spin injection, ""gamma"", through different contacts are
developed. These equations are concise when written in the proper notations.
Moreover, the resistance of a two-contact junction can be expressed in terms of
""gamma""'s of both contacts. This equation makes calculating the spin valve
effect straightforward, allows to find an explicit expression for the junction
resistance and to prove that its nonequilibrium part is positive. Relation of
these parameters to different phenomena like spin-e.m.f. and the junction
transients is established. Comparative effect of the Coulomb screening on
different parameters is clarified. It is also shown that the spin
non-conservation in a contact can have a dramatic effect on the non-equilibrium
resistance of the junction.",0206129v2
2002-08-13,Resistance of multilayers with long length scale interfacial roughness,"The resistance of multilayers with interface roughness on a length scale
which is large compared to the atomic spacing is computed in several cases via
the Boltzmann equation. This type of roughness is common in magnetic
multilayers. When the electronic mean free paths are small compared to the
layer thicknesses, the current flow is non-uniform, and the resistance
decreases in the Current-Perpendicular-to-Plane (CPP) configuration and
increases in the Current-In-Plane (CIP) configuration. For mean free paths much
longer than the layer thicknesses, the current flow is uniform, and the
resistance increases in both the CPP and CIP configurations due to enhanced
surface scattering. In both the CPP and CIP geometries, the giant
magnetoresistance can be either enhanced or reduced by the presence of long
length scale interface roughness depending on the parameters. Finally, the
changes in the CPP and CIP resistivities due to increasing interface roughness
are estimated using experimentally determined parameters.",0208251v1
2004-02-13,Superconducting Properties under Magnetic Field in Na$_{0.35}$CoO$_{2}{\cdot}1.3$H$_{2}$O Single Crystal,"We report the in-plane resistivity and magnetic susceptibility of the layered
cobalt oxide Na$_{0.35}$CoO$_{2}{\cdot}1.3$H$_{2}$O single crystal. The
temperature dependence of the resistivity shows metallic behavior from room
temperature to the superconducting transition temperature $T_{c}$ of 4.5 K.
Sharp resistive transition, zero resistivity and almost perfect superconducting
volume fraction below $T_{c}$ indicate the good quality and the bulk
superconductivity of the single crystal. The upper critical field $H_{c2}$ and
the coherence length $\xi$ are obtained from the resistive transitions in
magnetic field parallel to the c-axis and the $ab$-plane. The anisotropy of
$\xi$, $\xi_{ab} / \xi_{c} =$ 12 nm/1.3 nm $\simeq$ 9.2, suggests that this
material is considered to be an anisotropic three dimensional superconductor.
In the field parallel to the $ab$-plane, $H_{c2}$ seems to be suppressed to the
value of Pauli paramagnetic limit. It may indicate the spin singlet
superconductivity in the cobalt oxide.",0402355v1
2004-03-22,"Electrical Transport Across an Individual Magnetic Domain Wall in (Ga,Mn)As Microdevices","Recent studies demonstrate that an individual magnetic domain wall (DW) can
be trapped and reproducibly positioned within multiterminal (Ga,Mn)As
microdevices. The electrical resistance obtained from such measurements is
found to be measurably altered by the presence of this single entity. To
elucidate these observations we develop a simple model for the electrical
potential distribution along a multiterminal device in the presence of a single
DW. This is employed to calculate the effect of a single DW upon the
longitudinal and transverse resistance. The model provides very good agreement
with experimental observations, and serves to highlight important deviations
from simple theory. We show that measurements of transverse resistance along
the channel permits establishing the position and the shape of the DW contained
within it. An experimental scheme is developed that enables unambiguous
extraction of the intrinsic DW resistivity. This permits the intrinsic
contribution to be differentiated from resistivities originating from the bulk
and from magnetic anisotropy - effects that are generally manifested as large
backgrounds in the experiments.",0403547v1
2004-07-30,Occurrence of Hysteresis like behavior of resistance of $Sb_2 Te_3$ film in heating-cooling cycle,"Experimental observations of a peculiar behavior observed on heating and
cooling ${\rm Sb_2Te_3}$ films at different heating and cooling rate are
detailed. The film regained its original resistance, forming a closed loop, on
the completion of the heating-cooling cycle which was reproducible for
identical conditions of heating and cooling. The area enclosed by the loop was
found to depend on (i) the thickness of the film, (ii) the heating rate, (iii)
the maximum temperature to which film was heated and (iv) the cooling rate. The
observations are explained on basis of model which considers the film to be a
resultant of parallel resistances. The film's finite thermal conductivity gives
rise to a temperature gradient along the thickness of the film, due to this and
the temperature coefficient of resistance, the parallel combination of
resistance changes with temperature. Difference in heating and cooling rates
give different temperature gradient, which explains the observed hysteresis.",0407796v1
2004-08-03,Non-Gaussian Resistance Fluctuations in Disordered Materials,"We study the distribution of resistance fluctuations of conducting thin films
with different levels of internal disorder. The film is modeled as a resistor
network in a steady state determined by the competition between two biased
processes, breaking and recovery of the elementary resistors. The fluctuations
of the film resistance are calculated by Monte Carlo simulations which are
performed under different bias conditions, from the linear regime up to the
threshold for electrical breakdown. Depending on the value of the external
current, on the level of disorder and on the size of the system, the
distribution of the resistance fluctuations can exhibit significant deviations
from Gaussianity. As a general trend, a size dependent, non universal
distribution is found for systems with low and intermediate disorder. However,
for strongly disordered systems, close to the critical point of the
conductor-insulator transition, the non-Gaussianity persists when the size is
increased and the distribution of resistance fluctuations is well described by
the universal Bramwell-Holdsworth-Pinton distribution.",0408057v1
2007-02-26,Nonpolar resistance switching of metal/binary-transition-metal oxides/metal sandwiches: homogeneous/inhomogeneous transition of current distribution,"Exotic features of a metal/oxide/metal (MOM) sandwich, which will be the
basis for a drastically innovative nonvolatile memory device, is brought to
light from a physical point of view. Here the insulator is one of the
ubiquitous and classic binary-transition-metal oxides (TMO), such as Fe2O3,
NiO, and CoO. The sandwich exhibits a resistance that reversibly switches
between two states: one is a highly resistive off-state and the other is a
conductive on-state. Several distinct features were universally observed in
these binary TMO sandwiches: namely, nonpolar switching, non-volatile threshold
switching, and current--voltage duality. From the systematic sample-size
dependence of the resistance in on- and off-states, we conclude that the
resistance switching is due to the homogeneous/inhomogeneous transition of the
current distribution at the interface.",0702564v1
2007-11-02,Effects of Ferromagnetic Magnetic Ordering and Phase Transition on the Resistivity of Spin Current,"It has been shown experimentally a long time ago that the magnetic ordering
causes an anomalous behavior of the electron resistivity in ferromagnetic
crystals. Phenomenological explanations based on the interaction between
itinerant electron spins and lattice spins have been suggested to explain these
observations. We show by extensive Monte Carlo simulation that this behavior is
also observed for the resistivity of the spin current calculated as a function
of temperature ($T$) from low-$T$ ordered phase to high-$T$ paramagnetic phase
in a ferromagnet. We show in particular that across the critical region, the
spin resistivity undergoes a huge peak. The origin of this peak is shown to
stem from the formation of magnetic domains near the phase transition. The
behavior of the resistivity obtained here is compared to experiments and
theories. A good agreement is observed.",0711.0298v1
2008-01-29,Temperature Dependence of the Spin Resistivity in Ferromagnetic Thin Films,"The magnetic phase transition is experimentally known to give rise to an
anomalous temperature-dependence of the electron resistivity in ferromagnetic
crystals. Phenomenological theories based on the interaction between itinerant
electron spins and lattice spins have been suggested to explain these
observations. In this paper, we show by extensive Monte Carlo (MC) simulation
the behavior of the resistivity of the spin current calculated as a function of
temperature ($T$) from low-$T$ ordered phase to high-$T$ paramagnetic phase in
a ferromagnetic film. We analyze in particular effects of film thickness,
surface interactions and different kinds of impurities on the spin resistivity
across the critical region. The origin of the resistivity peak near the phase
transition is shown to stem from the existence of magnetic domains in the
critical region. We also formulate in this paper a theory based on the
Boltzmann's equation in the relaxation-time approximation. This equation can be
solved using numerical data obtained by our simulations. We show that our
theory is in a good agreement with our MC results. Comparison with experiments
is discussed.",0801.4444v1
2008-02-19,"Advanced resistivity model for arbitrary magnetization orientation applied to a series of compressive- to tensile-strained (Ga,Mn)As layers","The longitudinal and transverse resistivities of differently strained
(Ga,Mn)As layers are theoretically and experimentally studied as a function of
the magnetization orientation. The strain in the series of (Ga,Mn)As layers is
gradually varied from compressive to tensile using (In,Ga)As templates with
different In concentrations. Analytical expressions for the resistivities are
derived from a series expansion of the resistivity tensor with respect to the
direction cosines of the magnetization. In order to quantitatively model the
experimental data, terms up to the fourth order have to be included. The
expressions derived are generally valid for any single-crystalline cubic and
tetragonal ferromagnet and apply to arbitrary surface orientations and current
directions. The model phenomenologically incorporates the longitudinal and
transverse anisotropic magnetoresistance as well as the anomalous Hall effect.
The resistivity parameters obtained from a comparison between experiment and
theory are found to systematically vary with the strain in the layer.",0802.2635v1
2008-07-28,Current induced resistance change of magnetic tunnel junctions with ultra-thin MgO tunnel barriers,"Ultra-thin magnetic tunnel junctions with low resistive MgO tunnel barriers
are prepared to examine their stability under large current stress. The devices
show magnetoresistance ratios of up to 110 % and an area resistance product of
down to 4.4 ohm micrometer squared. If a large current is applied, a reversible
resistance change is observed, which can be attributed to two different
processes during stressing and one relaxation process afterwards. Here, we
analyze the time dependence of the resistance and use a simple model to explain
the observed behavior. The explanation is further supported by numerical fits
to the data in order to quantify the timescales of the involved phenomena.",0807.4422v1
2009-05-15,First-principles analysis of spin-disorder resistivity of Fe and Ni,"Spin-disorder resistivity of Fe and Ni and its temperature dependence are
analyzed using noncollinear density functional calculations within the
supercell method. Different models of thermal spin disorder are considered,
including the mean-field approximation and the nearest-neighbor Heisenberg
model. Spin-disorder resistivity is found to depend weakly on magnetic
short-range order. If the local moments are kept frozen at their
zero-temperature values, very good agreement with experiment is obtained for
Fe, but for Ni the resistivity at elevated temperatures is significantly
overestimated. Agreement with experiment for Fe is improved if the local
moments are iterated to self-consistency. The overestimation of the resistivity
for paramagnetic Ni is attributed to the reduction of the local moments down to
0.35 Bohr magnetons. Overall, the results suggest that low-energy spin
fluctuations in Fe and Ni are better viewed as classical rotations of local
moments rather than quantized spin fluctuations that would require an (S+1)/S
correction.",0905.2606v1
2009-06-04,Resistivity of Graphene Nanoribbon Interconnects,"Graphene nanoribbon interconnects are fabricated, and the extracted
resistivity is compared to that of Cu. It is found that the average resistivity
at a given line-width (18nm<W<52nm) is about 3X that of a Cu wire, whereas the
best GNR has a resistivity comparable to that of Cu. The conductivity is found
to be limited by impurity scattering as well as LER scattering; as a result,
the best reported GNR resistivity is 3X the limit imposed by substrate phonon
scattering. This study reveals that even moderate-quality graphene nanowires
have the potential to outperform Cu for use as on-chip interconnects.",0906.0924v1
2009-08-17,Unipolar Resistance Switching in Amorphous High-k dielectrics Based on Correlated Barrier Hopping Theory,"We have proposed a kind of nonvolatile resistive switching memory based on
amorphous LaLuO3, which has already been established as a promising candidate
of high-k gate dielectric employed in transistors. Well-developed unipolar
switching behaviors in amorphous LaLuO3 make it suited for not only logic but
memory applications using the conventional semiconductor or the emerging
nano/CMOS architectures. The conduction transition between high- and low-
resistance states is attributed to the change in the separation between oxygen
vacancy sites in the light of the correlated barrier hopping theory. The mean
migration distances of vacancies responsible for the resistive switching are
demonstrated in nanoscale, which could account for the ultrafast programming
speed of 6 ns. The origin of the distributions in switching parameters in
oxides can be well understood according to the switching principle.
Furthermore, an approach has also been developed to make the operation voltages
predictable for the practical applications of resistive memories.",0908.2379v2
2010-05-21,Highly anisotropic resistivities in the double-exchange model for strained manganites,"The highly anisotropic resistivities in strained manganites are theoretically
studied using the two-orbital double-exchange model. At the nanoscale, the
anisotropic double-exchange and Jahn-Teller distortions are found to be
responsible for the robust anisotropic resistivities observed here via Monte
Carlo simulations. An unbalanced in the population of orbitals caused by strain
is responsible for these effects. In contrast, the anisotropic superexchange is
found to be irrelevant to explain our results. Our model study suggests that
highly anisotropic resistivities could be present in a wide range of strained
manganites, even without (sub)micrometer-scale phase separation. In addition,
our calculations also confirm the formation of anisotropic clusters in
phase-separated manganites, which magnifies the anisotropic resistivities.",1005.3865v1
2010-06-28,Random barrier double-well model for resistive switching in tunnel barriers,"The resistive switching phenomenon in MgO-based tunnel junctions is
attributed to the effect of charged defects inside the barrier. The presence of
electron traps in the MgO barrier, that can be filled and emptied, locally
modifies the conductance of the barrier and leads to the resistive switching
effects. A double-well model for trapped electrons in MgO is introduced to
theoretically describe this phenomenon. Including the statistical distribution
of potential barrier heights for these traps leads to a power-law dependence of
the resistance as a function of time, under a constant bias voltage. This model
also predicts a power-law relation of the hysteresis as a function of the
voltage sweep frequency. Experimental transport results strongly support this
model and in particular confirm the expected power laws dependencies of
resistance. They moreover indicate that the exponent of these power laws varies
with temperature as theoretically predicted.",1006.5329v2
2010-12-08,Measuring sheet resistance of CIGS solar cell's window layer by spatially resolved electroluminescence imaging,"A spatially resolved electroluminescence (EL) imaging experiment is developed
to measure the local sheet resistance of the window layer, directly on the
completed CIGS cell. Our method can be applied to the EL imaging studies that
are made in fundamental studies as well as in in-line process inspection (1-3).
The EL experiment consists in using solar cell as a light emitting device : a
voltage is applied to the cell and its luminescence is detected. We develop an
analytical and quantitative model to simulate the behavior of CIGS solar cells
based on the spread sheet resistance effect in the window layer. We determine
the repartition of the electric potential on the ZnO, for given cell's
characteristics such as sheet resistance and contact geometries. Knowing the
repartition of the potential, the EL intensity is estimated and the
experimental EL signal is fitted, which allows the determination of the window
layer sheet resistance.",1012.1693v1
2011-02-11,Pressure cycle of superconducting Cs0.8Fe2Se2: a transport study,"We report measurements of the temperature and pressure dependence of the
electrical resistivity of single crystalline iron-based chalcogenide
Cs0.8Fe2Se2. In this material superconductivity Tc~30K develops from a normal
state with extremely large resistivity. At ambient pressure a large ""hump"" in
the resistivity is observed around 200K. Under pressure, the resistivity
decreases by two orders of magnitude, concomitant with a sudden Tc suppression
around p~8GPa. Even at 9GPa a metallic resistivity state is not recovered, and
the {\rho}(T) ""hump"" is still detected. A comparison of the data measured upon
increasing and decreasing the external pressure leads us to suggest that
superconductivity is not related to this hump.",1102.2464v2
2011-12-06,Tunable resistivity of individual magnetic domain walls,"Despite the relevance of current-induced magnetic domain wall (DW) motion for
new spintronics applications, the exact details of the current-domain wall
interaction are not yet understood. A property intimately related to this
interaction is the intrinsic DW resistivity. Here, we investigate
experimentally how the resistivity inside a DW depends on the wall width D,
which is tuned using focused ion beam irradiation of Pt/Co/Pt strips. We
observe the nucleation of individual DWs with Kerr microscopy, and measure
resistance changes in real-time. A 1/D^2 dependence of DW resistivity is found,
compatible with Levy-Zhang theory. Also quantitative agreement with theory is
found by taking full account of the current flowing through each individual
layer inside the multilayer stack.",1112.1239v1
2012-04-16,Complementary Resistive Switching in Tantalum Oxide-Based Resistive Memory Devices,"Complementary resistive switches (CRS) are considered as a potential solution
for the sneak path problem in large-scale integration of passive crossbar
resistive memory arrays. A typical CRS is composed of two bipolar memory cells
that are connected anti-serially. Here we report a tantalum-oxide based
resistive memory that achieves the complementary switching functionality within
a single memory cell. The complementary switching effect is accompanied by
switching polarity reversal in different voltage bias regimes. These effects
were explained by the redistribution of oxygen vacancies inside the
tantalum-oxide layers. The effects of symmetry breaking on bipolar switching
and complementary switching were also discussed.",1204.3515v2
2014-03-16,InGaN/GaN Tunnel Junctions For Hole Injection in GaN Light Emitting Diodes,"InGaN/GaN tunnel junction contacts were grown on top of an InGaN/GaN blue
(450 nm) light emitting diode wafer using plasma assisted molecular beam
epitaxy. The tunnel junction contacts enable low spreading resistance n-GaN top
contact layer thereby requiring less top metal contact coverage on the surface.
A voltage drop of 5.3 V at 100 mA, forward resistance of 2 x 10-2 ohm cm2 and a
higher light output power are measured in tunnel junction LED. A low resistance
of 5 x 10-4 ohm cm2 was measured in a MBE grown tunnel junction on GaN PN
junction device, indicating that the tunnel junction LED device resistance is
limited by the regrowth interface and not by the intrinsic tunneling
resistance.",1403.3932v1
2014-12-01,Resistivity minimum in strongly phase separated manganite thin films: impact of intrinsic and extrinsic perturbations,"The origin of the resistivity minimum observed in strongly phase separated
manganites has been investigated in single crystalline thin films of LPCMO
(x~0.42, y~0.40). The antiferromagnetic/charge ordered insulator
(AFM/COI)-ferromagnetic metal (FMM) phase transition, coupled with the colossal
hysteresis between the field cool cooled and field cooled warming magnetization
demonstrates strongly phase separated nature, which gives rise to
non-equilibrium magnetic liquid state that freezes into a magnetic glass. The
thermal cycling and magnetic field dependence of the resistivity unambiguously
shows that the pronounced resistivity minimum observed during warming is a
consequence non-equilibrium states resulting from the magnetic frustration
created by the delicate coexistence of the FMM and AFM/COI phases. The
non-equilibrium states and hence the resistivity minimum is extremely sensitive
to the relative fraction of the coexisting phases and can be tuned by intrinsic
and extrinsic perturbations like the defect density, thermal cycling and
magnetic field.",1412.0418v1
2015-01-05,Reversed anisotropy of the in-plane resistivity in the antiferromagnetic phase of iron tellurides,"We systematically investigated the anisotropic in-plane resistivity of the
iron telluride including three kinds of impurity atoms: excess Fe, Se
substituted for Te, and Cu substituted for Fe. Sizable resistivity anisotropy
was found in the magneto-structurally ordered phase whereas the sign is
opposite ($\rho_a$ $>$ $\rho_b$, where the $b$-axis parameter is shorter than
the $a$-axis one) to that observed in the transition-metal doped iron arsenides
($\rho_a$ $<$ $\rho_b$). On the other hand, our results demonstrate that the
magnitude of the resistivity anisotropy in the iron tellurides is correlated
with the amount of impurities, implying that the resistivity anisotropy
originates from an exotic impurity effect like that in the iron arsenides. This
suggests that the anisotropic carrier scattering by impurities is a universal
phenomenon in the magneto-structurally ordered phase of the iron-based
materials.",1501.00774v1
2015-05-21,Resistance minimum and electrical conduction mechanism in polycrystalline CoFeB thin films,"The temperature dependent resistance $R$($T$) of polycrystalline
ferromagnetic CoFeB thin films of varying thickness are analyzed considering
various electrical scattering processes. We observe a resistance minimum in
$R$($T$) curves below $\simeq$ 29 K, which can be explained as an effect of
intergranular Coulomb interaction in a granular system. The structural and
Coulomb interaction related scattering processes contribute more as the film
thickness decreases implying the role of disorder and granularity. Although the
magnetic contribution to the resistance is the weakest compared to these two,
it is the only thickness independent process. On the contrary, the negative
coefficient of resistance can be explained by electron interaction effect in
disordered amorphous films.",1505.05711v2
2015-10-29,Magneto-transport behaviour of Bi2Se3-xTex: Role of disorder,"Magnetoresistance and Hall resistance measurements have been carried out in
fastcooled single crystals of Bi2Se3-xTex (x: 0 to 2) in 4 to 300 K temperature
range, under magnetic fields up to 15 T. The variation of resistivity with
temperature that points to a metallic behaviour in Bi2Se3, shows an upturn at
low temperatures in the Te doped samples. Magnetoresistance measurements in
Bi2Se3 show clear signatures of Shubnikov de Hass oscillations that gets
suppressed in the Te doped samples. In the Bi2SeTe2 sample, the
magneto-resistance shows a cusp like positive magneto-resistance at low
magnetic fields and low temperatures, a feature associated with weak
antilocalisation (WAL), that crosses over to negative magneto-resistance at
higher fields. The qualitatively different magnetotransport behaviour seen in
Bi2SeTe2 as compared to Bi2Se3 is rationalised in terms of the disorder,
through an estimate of the carrier density, carrier mobility and an analysis in
terms of the Ioffe Regel criterion with support from Hall Effect measurements.",1510.08561v1
2015-12-10,Mini array of quantum Hall devices based on epitaxial graphene,"Series connection of four quantum Hall effect (QHE) devices based on
epitaxial graphene films was studied for realization of a quantum resistance
standard with an up-scaled value. The tested devices showed quantum Hall
plateaux RH,2 at filling factor i = 2 starting from relatively low magnetic
field (between 4 T and 5 T) when temperature was 1.5 K. Precision measurements
of quantized Hall resistance of four QHE devices connected by triple series
connections and external bonding wires were done at B = 7 T and T = 1.5 K using
a commercial precision resistance bridge with 50 microA current through the QHE
device. The results showed that the deviation of the quantized Hall resistance
of the series connection of four graphene-based QHE devices from the expected
value of 4*RH,2 = 2h/e^2 was smaller than the relative standard uncertainty of
the measurement (< 1*10^-7) limited by the used resistance bridge.",1512.03163v2
2016-01-04,Making Consistent Contacts to Graphene: Effect of Architecture and Growth Induced Defects,"The effect of contact architecture, graphene defect density and
metal-semiconductor work function difference on resistivity of metal-graphene
contacts have been investigated. An architecture with metal on the bottom of
graphene is found to yield resistivities that are lower, by a factor of 4, and
most consistent as compared to metal on top of graphene. Growth defects in
graphene film were found to further reduce resistivity by a factor of 2. Using
a combination of method and metal used, the contact resistivity of graphene has
been decreased by a factor of 10 to 1200 +- 250 Ohm-um using Palladium as the
contact metal. While the improved consistency is due to the metal being able to
contact uncontaminanted graphene in the metal on the bottom architecture, lower
contact resistivities observed on defective graphene with the same metal is
attributed to the increased number of modes of quantum transport in the
channel.",1601.00429v1
2016-06-13,Effect of interstitial impurities on the field dependent microwave surface resistance of niobium,"Previous work has demonstrated that the radio frequency surface resistance of
niobium resonators is dramatically reduced when nitrogen impurities are
dissolved as interstitial in the material. The origin of this effect is
attributed to the lowering of the Mattis and Bardeen surface resistance
contribution with increasing accelerating field. Meanwhile, an enhancement of
the sensitivity to trapped magnetic field is typically observed for such
cavities. In this paper we conduct the first systematic study on these
different components contributing to the total surface resistance as a function
of different levels of dissolved nitrogen, in comparison with standard surface
treatments for niobium resonators. Adding these results together we are able to
show for the first time which is the optimum surface treatment that maximizes
the Q-factor of superconducting niobium resonators as a function of expected
trapped magnetic field in the cavity walls. These results also provide new
insights on the physics behind the change in the field dependence of the Mattis
and Bardeen surface resistance, and of the trapped magnetic vortex induced
losses in superconducting niobium resonators.",1606.04174v1
2016-10-18,Dichotomy between in-plane magnetic susceptibility and resistivity anisotropies in extremely strained $BaFe_{2}As_{2}$,"The in-plane resistivity and uniform magnetic susceptibility anisotropies of
$BaFe_{2}As_{2}$ are obtained with a new method, in which a large
symmetry-breaking uniaxial strain is applied using a substrate with a very
anisotropic thermal expansion. The resistivity anisotropy and its corresponding
elastoresistivity exhibit very similar diverging behavior as those obtained
from piezo-stack experiments. This suggests that the resistivity anisotropy is
more a direct measure of magnetism than of nematicity, since the nematic
transition is no longer well-defined under a large strain. In strong contrast
to the large resistivity anisotropy above $T_{N}$, the anisotropy of the
in-plane magnetic susceptibility develops largely below $T_{N}$. Using an
itinerant model, we show that the observed anisotropy ($\chi_{b}>\chi_{a}$) is
determined by spin-orbit coupling and the orientation of the magnetic moments
in the antiferromagnetic phase, and that the anisotropy is dominated by
intra-orbital ($yz,yz$) contributions of the Umklapp susceptibility.",1610.05575v2
2016-12-15,Reaction-Drift Model for Switching Transients in Pr$_{0.7}$Ca$_{0.3}$MnO$_3$ Based Resistive RAM,"Earlier, the DC hole-current modeling of PCMO RRAM by drift-diffusion (DD)
including self-heating (SH) in TCAD (but without ionic transport) was able to
explain the experimentally observed SCLC characteristics, prior to resistive
switching. Further, transient analysis using DD+SH model was able to reproduce
the experimentally observed fast current increase at ~100ns timescale followed
by saturation increases, prior to resistive switching. However, resistive
switching requires the inclusion of ionic transport. We propose a
Reaction-Drift (RD) model of oxide ions, which is combined with the DD+SH
model. Experimentally, SET operations consist of 3 stages and RESET operations
consists of 4 stages. The DD+SH+RD model is able to reproduce the entire
transient behavior over 10$^{-8}$-1s range in timescale for both SET and RESET
operations for a range of bias, temperature. Remarkably, a universal RESET
behaviour of $log(I)\propto m*log(t)$, where $m\approx -1/10$, is reproduced.
The quantitatively different voltage time dilemma for SET and RESET is also
replicated for a range of ambient temperature. This demonstrates a
comprehensive model for resistance switching in PCMO based RRAM.",1612.05293v2
2018-06-20,Domain wall resistance in CoFeB-based heterostructures with interface Dzyaloshinskii-Moriya interaction,"We have studied the domain wall resistance in W/Ta/CoFeB/MgO
heterostructures. The Ta layer thickness is varied to control the type of
domain walls via changes in the interfacial Dzyaloshinskii Moriya interaction.
We find a nearly constant domain wall resistance against the Ta layer
thickness. Adding contributions from the anisotropic magnetoresistance, spin
Hall magnetoresistance and anomalous Hall effect describe well the domain wall
resistance of the thick Ta layer films. However, a discrepancy remains for the
thin Ta layer films wherein chiral N\'eel-like domain walls are found. These
results show the difficulty of studying the domain wall type from resistance
measurements.",1806.07750v1
2019-02-12,Designing multi-level resistance states for multi-bit storage using half doped manganites,"Designing nonvolatile multi-level resistive devices is the necessity of time
to go beyond traditional one-bit storage systems, thus enhancing the storage
density. Here, we explore the electronic phase competition scenario to design
multi-level resistance states using a half doped CE-type charge ordered
insulating bulk manganite, $Sm_{0.5}Ca_{0.25}Sr_{0.25}MnO_3$ (SCSMO). By
introducing electronic phase coexistence in a controllable manner in SCSMO, we
show that the system can be stabilized into several metastable states, against
thermal cycling, up to 62 K. As a result the magnetization (and the
resistivity) remains unaltered during the thermal cycling. Monte Carlo
calculations using two-band double exchange model, including super-exchange,
electron-phonon coupling, and quenched disorder, show that the system freezes
into a phase coexistence metastable state during the thermal cycling due to the
chemical disorder in SCSMO. Using the obtained insights we outline a pathway by
utilizing four reversible metastable resistance states to design a prototype
multi-bit memory device.",1902.04377v1
2019-03-02,On the origin of the anomalous peak in the resistivity of TiSe$_2$,"Resistivity measurements of TiSe$_2$ typically show only a weak change in
gradient at the charge density wave transition at $T_{CDW}\approx$ 200~K, but
more prominently feature a broad peak at a lower $T_{peak}\sim$ 165~K, which
has remained poorly understood despite decades of research on the material.
Here we present quantitative simulations of the resistivity using a simplified
parametrization of the normal state band structure, based on recent
photoemission data. Our simulations reproduce the overall profile of the
resistivity of TiSe$_2$, including its prominent peak, without implementing the
CDW at all. We find that the peak in resistivity corresponds to a crossover
between a low temperature regime with electron-like carriers only, to a regime
around room temperature where thermally activated and highly mobile hole-like
carriers dominate the conductivity. Even when implementing substantial
modifications to model the CDW below the transition temperature, we find that
these thermal population effects still dominate the transport properties of
TiSe$_2$.",1903.00756v1
2012-06-13,Modelling of Current Percolation Channels in Emerging Resistive Switching Elements,"Metallic oxides encased within Metal-Insulator-Metal (MIM) structures can
demonstrate both unipolar and bipolar switching mechanisms, rendering them the
capability to exhibit a multitude of resistive states and ultimately function
as memory elements. Identifying the vital physical mechanisms behind resistive
switching can enable these devices to be utilized more efficiently, reliably
and in the long-term. In this paper, we present a new approach for analysing
resistive switching by modelling the active core of two terminal devices as 2D
and 3D grid circuit breaker networks. This model is employed to demonstrate
that substantial resistive switching can only be supported by the formation of
continuous current percolation channels, while multi-state capacity is ascribed
to the establishment and annihilation of multiple channels.",1206.2746v1
2019-06-07,Extended Nyquist formula for a resistance subject to a heat flow,"The Nyquist formula quantifies the thermal noise driven fluctuations of
voltage across a resistance in equilibrium. We deal here with the case of a
resistance driven out of equilibrium by putting it in contact with two
thermostats at different temperatures. We reach a non-equilibrium steady state
where a heat flux is flowing through the resistance. Our measurements
demonstrate anyway that a simple extension of the Nyquist formula to the non
uniform temperature field describes with an excellent precision the thermal
noise. For a metallic ohmic material, the fluctuations are actually equivalent
to those of a resistance in equilibrium with a single thermostat at the mean
temperature between the hot and cold sources.",1906.02974v2
2020-06-22,Optimal design of a bilayer for the highest thermal resistance: A lesson learned from the shells of snails from hydrothermal extreme environment,"Inspired by the unique design of the shells of snails inhabiting the deep-sea
hydrothermal environment, here we theoretically study the temperature response
of a bilayer to an external thermal impulse. A semi-analytical solution to the
temperature field in the bilayer is obtained, allowing us to assess the peak
temperature that occurs on the inner wall as a quantitative indicator of the
thermal resistance of the bilayer. The structural determining factors of the
thermal resistance of a bilayer are then investigated by examining the effects
of the stacking sequence and volume fractions of the constitutive layers on the
peak temperature on the inner wall. Our results indicate that the stacking
sequence of the two layers in a bilayer, as well as their volume fractions,
play important roles in determining the thermal resistance. For two layers with
given materials, there exists an optimal stacking sequence and thickness ratio
giving rise to the best thermal resistance. The results of our work not only
account for the unique laminated design of the snail shells from hydrothermal
environments but also provide practical guidelines for the design of multilayer
thermal barriers in engineering.",2006.11987v1
2020-11-01,Reduction of interfacial thermal resistance of overlapped graphene by bonding carbon chains,"Exploring the mechanism of interfacial thermal transport and reducing the
interfacial thermal resistance is of great importance for thermal management
and modulation. Herein, the interfacial thermal resistance between overlapped
graphene nanoribbons is largely reduced by adding bonded carbon chains by
performing molecular dynamics simulations. And the analytical model
(cross-interface model, CIM) is utilized to analyze and explain the
two-dimensional thermal transport mechanism at cross-interface. An order of
magnitude reduction in interfacial thermal resistance is found as the graphene
nanoribbons are bonded by just one carbon chain. Interestingly, the decreasing
rate of interfacial thermal resistance slows down gradually with the increasing
of the number of carbon chains, which can be explained by the proposed
theoretical relationship based on CIM. Moreover, by the comparison of CIM and
traditional simplified model, the accuracy of CIM is verified and demonstrated
in overlapped graphene nanoribbons. This work provides a new way to improve the
interfacial thermal transport and reveal the essential mechanism for
low-dimensional materials applied in thermal management.",2011.00494v1
2021-04-15,Origins of anisotropic transport in electrically-switchable antiferromagnet $\mathrm{Fe_1/3NbS_2}$,"Recent experiments on the antiferromagnetic intercalated transition metal
dichalcogenide $\mathrm{Fe_{1/3}NbS_2}$ have demonstrated reversible
resistivity switching by application of orthogonal current pulses below its
magnetic ordering temperature, making $\mathrm{Fe_{1/3}NbS_2}$ promising for
spintronics applications. Here, we perform density functional theory
calculations with Hubbard U corrections of the magnetic order, electronic
structure, and transport properties of crystalline $\mathrm{Fe_{1/3}NbS_2}$,
clarifying the origin of the different resistance states. The two
experimentally proposed antiferromagnetic ground states, corresponding to
in-plane stripe and zigzag ordering, are computed to be nearly degenerate.
In-plane cross sections of the calculated Fermi surfaces are anisotropic for
both magnetic orderings, with the degree of anisotropy sensitive to the Hubbard
U value. The in-plane resistance, computed within the Kubo linear response
formalism using a constant relaxation time approximation, is also anisotropic,
supporting a hypothesis that the current-induced resistance changes are due to
a repopulating of AFM domains. Our calculations indicate that the transport
anisotropy of $\mathrm{Fe_{1/3}NbS_2}$ in the zigzag phase is reduced relative
to stripe, consistent with the relative magnitudes of resistivity changes in
experiment. Finally, our calculations reveal the likely directionality of the
current-domain response, specifically, which domains are energetically
stabilized for a given current direction.",2104.07591v1
2021-08-01,First-principles study on the electrical resistivity in zirconium dichalcogenides with multi-valley bands: mode-resolved analysis of electron-phonon scattering,"Based on the first-principles calculations, we study the electron-phonon
scattering effect on the resistivity in the zirconium dichalcogenides,
$\text{Zr}_{}\text{S}_{2}$ and $\text{Zr}_{}\text{Se}_{2}$, whose electronic
band structures possess multiple valleys at conduction band minimum. The
computed resistivity exhibits non-linear temperature dependence, especially for
$\text{Zr}_{}\text{S}_{2}$, which is also experimentally observed on some TMDCs
such as $\text{Ti}_{}\text{S}_{2}$ and $\text{Zr}_{}\text{Se}_{2}$. By
performing the decomposition of the contributions of scattering processes, we
find that the intra-valley scattering by acoustic phonons mainly contributes to
the resistivity around 50 K. Moreover, the contribution of the intra-valley
scattering by optical phonons becomes dominant even above 80 K, which is a
sufficiently low temperature compared with their frequencies. By contrast, the
effect of the inter-valley scattering is found to be not significant. Our study
identifies the characteristic scattering channels in the resistivity of the
zirconium dichalcogenides, which provides critical knowledge to microscopically
understand electron transport in systems with multi-valley band structure.",2108.00474v1
2024-02-15,What can we learn from nonequilibrium response of a strange metal?,"We critically address the recent experiment [Science 382, 907 (2023)] on
nonequilibrium transport and noise in a strange metal YbRh2Si2 patterned into
the nanowire shape. In the long device, resistivity, differential resistance
and current noise data seem to be consistent allowing us to extract
electron-phonon coupling and the temperature dependence of electron-phonon
scattering length. The obtained values can be reconciled with the experimental
data for the short device only assuming the significant contact resistance. We
discuss its possible origin as due to the current redistribution between
YbRh2Si2 and its gold covering, and reveal that this redistribution contact
resistance should be proportional to the YbRh2Si2 resistivity. We also discuss
some subtleties of the noise measurements. Overall, neglecting electron-phonon
energy relaxation even in the shortest devices is arguable so that the observed
shot noise suppression can hardly be attributed to the failure of quasiparticle
concept.",2402.09946v1
2023-07-27,Reduced stress propagation leads to increased mechanical failure resistance in auxetic materials,"Materials with negative Poisson ratio have the counter-intuitive property of
expanding laterally when they are stretched longitudinally. They are
accordingly termed auxetic, from the Greek auxesis meaning to increase.
Experimental studies have demonstrated auxetic materials to have superior
material properties, compared with conventional ones. These include synclastic
curvature, increased acoustic absorption, increased resilience to material
fatigue, and increased resistance to mechanical failure. Until now, the latter
observations have remained poorly understood theoretically. With this
motivation, the contributions of this work are twofold. First, we elucidate
analytically the way in which stress propagates spatially across a material
following a localised plastic failure event, finding a significantly reduced
stress propagation in auxetic materials compared with conventional ones. In
this way, a plastic failure event occurring in one part of a material has a
reduced tendency to trigger knock-on plastic events in neighbouring regions.
Second, via the numerical simulation of a lattice elastoplastic model, we
demonstrate a key consequence of this reduced stress propagation to be an
increased resistance to mechanical failure. This is seen not only via an
increase in the externally measured yield strain, but also via a decreased
tendency for plastic damage to percolate internally across a sample in
catastrophic system-spanning clusters.",2307.14914v2
2014-11-28,Signature of high Tc around 25K in higher quality heavily boron-doped diamond,"Diamond has outstanding physical properties: the hardest known material, a
wide band gap, the highest thermal conductivity, and a very high Debye
temperature. In 2004, Ekimov et al. discovered that heavily boron-doped
(B-doped) diamond becomes a superconductor around 4 K. Our group successfully
controlled the boron concentration and synthesized homoepitaxially grown
superconducting diamond films by a CVD method. By CVD method, we found that
superconductivity appears when the boron concentration (nB) exceeds a
metal-insulator transition concentration of 3.0x10^20 cm^-3 and its Tczero
increases up to 7.4 K with increasing nB. We additionally elucidated that the
holes formed at the valence band are responsible for the metallic states
leading to superconductivity. The calculations predicted that the hole doping
into the valence band induces strong attractive interaction and a rapid
increase in Tc with increasing boron concentration. According to the
calculations, if substitutional doped boron could be arranged periodically or
the degree of disorder is reduced, a Tc of approximately 100 K could be
achieved via minimal percent doping. In this work, we have successfully
observed zero resistivity above 10 K and an onset of resistivity reduction at
25.2 K in heavily B-doped diamond film. However, the effective carrier
concentration is similar to that of superconducting diamond with a lower Tc. We
found that the carrier has a longer mean free path and lifetime than previously
reported, indicating that this highest Tc diamond has better crystallinity
compared to that of other superconducting diamond films. In addition, the
susceptibility shows a small transition above 20 K in the high quality diamond,
suggesting a signature of superconductivity above 20 K. These results strongly
suggest that heavier carrier doped defect-free crystalline diamond could give
rise to high Tc diamond.",1411.7752v1
2019-08-21,Fatigue-resistant high-performance elastocaloric materials via additive manufacturing,"Elastocaloric cooling, which exploits the latent heat released and absorbed
as stress-induced phase transformations are reversibly cycled in shape memory
alloys, has recently emerged as a frontrunner in non-vapor-compression cooling
technologies. The intrinsically high thermodynamic efficiency of elastocaloric
materials is limited only by work hysteresis. Here, we report on creating
high-performance low-hysteresis elastocaloric cooling materials via additive
manufacturing of Titanium-Nickel (Ti-Ni) alloys. Contrary to established
knowledge of the physical metallurgy of Ti-Ni alloys, intermetallic phases are
found to be beneficial to elastocaloric performances when they are combined
with the binary Ti-Ni compound in nanocomposite configurations. The resulting
microstructure gives rise to quasi-linear stress-strain behaviors with
extremely small hysteresis, leading to enhancement in the materials efficiency
by a factor of five. Furthermore, despite being composed of more than 50%
intermetallic phases, the reversible, repeatable elastocaloric performance of
this material is shown to be stable over one million cycles. This result opens
the door for direct implementation of additive manufacturing to elastocaloric
cooling systems where versatile design strategy enables both topology
optimization of heat exchangers as well as unique microstructural control of
metallic refrigerants.",1908.07900v1
2019-07-31,Quantum oscillations in diamond field effect transistors with a h-BN gate dielectric,"Diamond has attracted attention as a next-generation semiconductor because of
its various exceptional properties such as a wide bandgap and high breakdown
electric field. Diamond field effect transistors, for example, have been
extensively investigated for high-power and high-frequency electronic
applications. The quality of their charge transport (i.e., mobility), however,
has been limited due to charged impurities near the diamond surface. Here, we
fabricate diamond field effect transistors by using a monocrystalline hexagonal
boron nitride as a gate dielectric. The resulting high mobility of charge
carriers allows us to observe quantum oscillations in both the longitudinal and
Hall resistivities. The oscillations provide important information on the
fundamental properties of the charge carriers, such as effective mass,
lifetime, and dimensionality. Our results indicate the presence of a
high-quality two-dimensional hole gas at the diamond surface and thus pave the
way for studies of quantum transport in diamond and the development of low-loss
and high-speed devices.",1907.13500v2
2021-12-08,High-Mg Calcite Nanoparticles Within a Low-Mg Calcite Matrix via Spinodal Decomposition: A Widespread Phenomenon in Biomineralization,"During the process of biomineralization, organisms utilize various
biostrategies to enhance the mechanical durability of their skeletons. In this
work, we establish that the presence of high-Mg nanoparticles embedded within
lower Mg calcite matrices is a widespread strategy utilized by various
organisms from different kingdoms and phyla to improve the mechanical
properties of their high Mg calcite skeletons. We show that such phase
separation and the formation of high-Mg nanoparticles are achieved through
spinodal decomposition of an amorphous Mg calcite precursor. Such decomposition
is independent of the biological characteristics of the studied organisms
belonging to different phyla and even kingdoms, but rather originates from
their similar chemical composition and a specific Mg content within their
skeletons, which generally ranges from 14 to 48 mol percent of Mg. We show
evidence of high Mg calcite nanoparticles in the cases of 6 biologically
different organisms all demonstrating more than 14 mol percent Mg calcite, and
consider it likely that this phenomenon is immeasurably more prevalent in
nature. We also establish the absence of these high Mg nanoparticles in
organisms whose Mg content is lower than 14 mol percent, providing further
evidence that whether or not spinodal decomposition of an amorphous Mg calcite
precursor takes place is determined by the amount of Mg it contains. The
valuable knowledge gained from this biostrategy significantly impacts the
understanding of how biominerals, though comprised of intrinsically brittle
materials, can effectively resist fracture.",2112.04141v1
2022-08-11,Superconductivity above 80 K in polyhydrides of hafnium,"Studies on polyhydrides are attracting growing attentions recently due to
their potential high temperature superconductivity (SC). We here report the
discovery of SC in hafnium polyhydrides at high pressures. The hafnium
superhydrides are synthesized at high pressure and high temperature conditions
using diamond anvil cell in combination with in-situ high pressure laser
heating technique. The SC was investigated by in-situ high pressure resistance
measurements in applied magnetic fields. A superconducting transition with
onset Tc ~83 K was observed at 243 GPa. The upper critical field Hc2(0) was
estimated to be 24 Tesla by GL theory and the consequent superconducting
coherent length to be ~37 angstrom. Our results suggest that the
superconducting phase is from C2/m-HfH14. This is the first 5d transition metal
polyhydride superconductor with Tc above the liquid nitrogen temperature.",2208.05816v2
2001-05-16,Superconducting properties of well-shaped MgB2 single crystal,"We report measurements of the transport and the magnetic properties of
high-quality, sub-millimeter-sized MgB2 single crystals with clear
hexagonal-plate shapes. The low-field magnetization and the magnetic hysteresis
curves show the vortex pinning of these crystals to be very weak. The Debye
temperature of $\Theta_{D}\sim 1100$ K, obtained from the zero-field resistance
curve, suggests that the normal-state transport properties are dominated by
electron-phonon interactions. The resistivity ratio between 40 K and 300 K was
about 5, and the upper critical field anisotropy ratio was 3 $\pm$ 0.2 at
temperatures around 32 K.",0105330v7
2003-09-24,Quantum Effects in Thermal Conductivity of Solid Krypton - Methane Solutions,"The dynamic interaction of a quantum rotor with its crystalline environment
has been studied by measurement of the thermal conductivity of solid
Kr1_c(CH4)_c solutions at c = 0.05-0.75 in the temperature region from 2 up to
40K. The thermal resistance of the solutions was mainly determined by the
resonance scattering of phonons by CH4 molecules with the nuclear spin I=1 (the
nuclear spin of T-species). The influence of the nuclear spin conversion on the
temperature dependence of the thermal conductivity k(T) was found: a clearly
defined minimum on k(T), its temperature position depending on the CH4
concentration. It was shown that the anisotropy molecular field not increase
monotonously with the CH4 concentration. A compensation effect in the mutual
orientation arrangement of the neighboring rotors is observed at c > 0.5. The
temperature dependence of Kr1_c(CH4)_c is described within the Debye model of
thermal conductivity taking into account the lower limit of the phonon mean
free path. The anomalous temperature dependence of the thermal resistance shows
the evolution of the phonon-rotation coupling at varying temperature. It
increases strongly when the character of CH4 rotation changes from the quantum
at low temperatures to classical at high temperatures. Also, a jump of thermal
conductivity (a sharp increase in k(T) within a narrow temperature range) was
observed, whose position varies from 9.7 K to 8.4 K when the CH4 concentration
changes from 0.25 to 0.45.",0309542v1
2005-05-19,Strongly correlated properties of the thermoelectric cobalt oxide Ca3Co4O9,"We have performed both in-plane resistivity, Hall effect and specific heat
measurements on the thermoelectric cobalt oxide Ca$_{3}$Co$_{4}$O$_{9}$. Four
distinct transport regimes are found as a function of temperature,
corresponding to a low temperature insulating one up to $T_{min}\approx $63 K,
a strongly correlated Fermi liquid up to $T^*\approx $140 K, with
$\rho=\rho_0+AT^2$ and $A\approx 3.63$ $10^{-2} \mu \Omega cm/K^{2}$, followed
by an incoherent metal with $k_Fl\leq 1$ and a high temperature insulator above
T$^{**}\approx $510 K . Specific heat Sommerfeld coefficient $\gamma = 93$
mJ/(mol.K$^{2}$) confirms a rather large value of the electronic effective mass
and fulfils the Kadowaki-Woods ratio $A/\gamma^2 \approx 0.45$ 10$^{-5}$ $\mu
\Omega cm.K^2/(mJ^2mol^{-2})$. Resistivity measurements under pressure reveal a
decrease of the Fermi liquid transport coefficient A with an increase of $T^*$
as a function of pressure while the product $A(T^*)^2/a$ remains constant and
of order $h/e^2$. Both thermodynamic and transport properties suggest a strong
renormalization of the quasiparticles coherence scale of order $T^*$ that seems
to govern also thermopower.",0505464v1
2005-10-03,New Misfit-Layered Cobalt Oxide (CaOH)1.14CoO2,"We found a new cobalt oxide (CaOH)1.14CoO2 by utilizing the high-pressure
technique. X-ray and electron diffraction studies revealed that the compound
has layer structure which consists of CdI2-type CoO2 layers and rock-salt-type
double CaOH atomic layers. The two subcells have incommensurate periodicity
along the a-axis, resulting in modulated crystal structure due to the
inter-subcell interaction. The structural modulation affects carrier conduction
through the potential randomness. We found that the two-dimensional (2-D)
variable-range hopping (VRH) regime with hole conduction is dominant at low
temperature for this compound, and that the conduction mechanism undergoes
crossover from the 2-D VRH regime to thermal activation-energy type one with
increasing temperature. Based on the experimental results of resistivity,
thermoelectric power, magnetic susceptibility and specific heat measurements,
we suggested a possible electronic-band structure model to explain these
results. The cobalt t2g-derivative band crosses Fermi energy level near the
band edge, yielding small finite density of localized states at the Fermi level
in the band. The observed resistivity, Seebeck coefficient, large Pauli
paramagnetic component in the magnetic susceptibility and comparatively small
Sommerfeld constant in the specific heat are principally attributed to the
holes in the t2g-derivative band. We estimated the Wilson ratio to be about
2.8, suggesting the strong electron correlation realized in this compound.",0510031v1
2007-09-12,The Hot-Spot Phenomenon and its Countermeasures in Bipolar Power Transistors by Analytical Electro-Thermal Simulation,"This communication deals with a theoretical study of the hot spot onset (HSO)
in cellular bipolar power transistors. This well-known phenomenon consists of a
current crowding within few cells occurring for high power conditions, which
significantly decreases the forward safe operating area (FSOA) of the device.
The study was performed on a virtual sample by means of a fast, fully
analytical electro-thermal simulator operating in the steady state regime and
under the condition of imposed input base current. The purpose was to study the
dependence of the phenomenon on several thermal and geometrical factors and to
test suitable countermeasures able to impinge this phenomenon at higher biases
or to completely eliminate it. The power threshold of HSO and its localization
within the silicon die were observed as a function of the electrical bias
conditions as for instance the collector voltage, the equivalent thermal
resistance of the assembling structure underlying the silicon die, the value of
the ballasting resistances purposely added in the emitter metal
interconnections and the thickness of the copper heat spreader placed on the
die top just to the aim of making more uniform the temperature of the silicon
surface.",0709.1831v1
2007-09-14,An inhomogeneous Josephson phase in thin-film and High-Tc superconductors,"In many cases inhomogeneities are known to exist near the metal (or
superconductor)-insulator transition, as follows from well-known domain-wall
arguments. If the conducting regions are large enough (i.e. when the T=0
superconducting gap is much larger than the single-electron level spacing), and
if they have superconducting correlations, it becomes energetically favorable
for the system to go into a Josephson-coupled zero-resistance state before
(i.e. at higher resistance than) becoming a ""real"" metal. We show that this is
plausible by a simple comparison of the relevant coupling constants. For small
grains in the above sense, the electronic grain structure is washed out by
delocalization and thus becomes irrelevant. When the proposed ""Josephson state""
is quenched by a magnetic field, an insulating, rather then a metallic, state
should appear. This has been shown to be consistent with the existing data on
oxide materials as well as ultra-thin films. We discuss the Uemura correlations
versus the Homes law, and derive the former for the large-grain Josephson array
(inhomogenous superconductor) model. The small-grain case behaves like a dirty
homogenous metal. It should obey the Homes law provided that the system is in
the dirty supeconductivity limit. A speculation why that is typically the case
for d-wave superconductors is presented.",0709.2321v1
2009-03-18,Two-dimensional electrochemical model for mixed conductors: a study of ceria,"A two-dimensional small bias model has been developed for a patterned metal
current collector $|$ mixed oxygen ion and electronic conductor (MIEC) $|$
patterned metal current collector electrochemical cell in a symmetric gas
environment. Specifically, we compute the electrochemical potential
distributions of oxygen vacancies and electrons in the bulk and near the
surface for $\text{Pt} | \text{Sm}_{0.15}\text{Ce}_{0.85}\text{O}_{1.925} |
\text{Pt}$ symmetric cell in a $\text{H}_2-\text{H}_2\text{O}-\text{Ar}$
(reducing) atmosphere from 500 to $650^o C$. Using a two-dimensional
finite-element model, we show that two types of electronic current exist within
the cell: an in-plane drift-diffusion current that flows between the gas $|$
ceria chemical reaction site and the metal current collector, and a cross-plane
current that flows between the two metal electrodes on the opposite side of the
cell. By fitting the surface reaction constant $\tilde k_f^0$ to experimental
electrode resistance values while fixing material properties such as bulk ionic
and electronic equilibrium defect concentrations and mobilities, we are able to
separate the electrode polarization into the surface reaction component and the
in-plane electron drift-diffusion component. We show that for mixed conductors
with a low electronic conductivity (a function of oxygen partial pressure) or a
high surface reaction rate constant, the in-plane electron drift-diffusion
resistance can become rate-limiting in the electrode reaction.",0903.3250v1
2009-11-11,The pseudogap behavior in the stoichiometric FeSe superconductor (Tc~9.4 K),"This paper reports the synthesis and superconducting behaviors of the
tetragonal iron-chalcogenide superconductor FeSe. The electrical resistivity
and magnetic moment measurements confirmed its superconductivity with a
$T_c^{zero}$ and $T_c^{mag}$ at 9.4 K under ambient pressure. EPMA indicated
the sample to have a stoichiometric Fe:Se ratio of 1:1 ($\pm$0.02). The Seebeck
coefficient which was 12.3 $\mu$V/K at room temperature, changed to a negative
value near 200 K, indicating it to be a two carriers material. Above $T_c$, the
$\rho(T)$ curve revealed an 'S' shape. Hence $d\rho(T)/dT$, and
$d^2\rho(T)/dT^2$ showed pseudogap-like behavior at $T^*$=110 K according to
the resistivity curvature mapping (RCM) method for high $T_c$ cuprates.
Moreover, the magnetoresistance $\rho_H(T)/\rho_{H=0}$ under a magnetic field
and the Seebeck coefficient $S(T)$ revealed revealed pseudogap-like behavior
near $T^*$. Interestingly, at the same temperature, 30 K, the sign of $S(T)$
and all signs of $d^2\rho(T)/dT^2$ changed from negative to positive above
$T_c$.",0911.2045v2
2010-07-22,Anisotropic fluctuations and quasiparticle excitations in FeSe_0.5Te_0.5,"We present data for the temperature dependence of the magnetic penetration
depth lambda(T), heat capacity C(T), resistivity R(T) and magnetic torque ?tau
for highly homogeneous single crystal samples of Fe1:0Se0:44(4)Te0:56(4).
lambda(T) was measured down to 200mK in zero field. We find lambda(T) follows a
power law lambda~T^n with n = 2.2 +/- 0.1. This is similar to some 122
iron-arsenides and likely results from a sign-changing pairing state combined
with strong scattering. Magnetic fields of up to B =55T or 14T were used for
the ? tau(B) and C(T)/R(T) measurements respectively. The specific heat,
resistivity and torque measurements were used to map out the (H,T) phase
diagram in this material. All three measurements were conducted on exactly the
same single crystal sample so that the different information revealed by these
probes is clearly distinguished. Heat capacity data strongly resemble those
found for the high Tc cuprates, where strong fluctuation effects wipe-out the
phase transition at Hc2. Unusually, here we find the fluctuation effects appear
to be strongly anisotropic.",1007.3914v2
2010-11-09,Frustrated Metastable Behavior of Magnetic and Transport Properties in Charge Ordered La1-xCaxMnO3+d Manganites,"We have studied the effect of metastable, irreversibility induced by repeated
thermal cycles on the electric transport and magnetization of polycrystalline
samples of La1-xCaxMnO3 (0.48\leq x \leq 0.55) close to charge ordering. With
time and thermal cycling (T<300 K) there is an irreversible transformation of
the low-temperature phase from a partially ferromagnetic and metallic to one
that is less ferromagnetic and highly resistive for the composition close to
charge ordering (x=050 and 0.52). Irrespective of the actual ground state of
the compound, the effect of thermal cycling is towards an increase of the
amount of the insulating phase. We have observed the magnetic relaxation in the
metastable state and also the revival of the metastable state (in a relaxed
sample) due to high temperature thermal treatment. We observed changes in the
resistivity and magnetization as the revived metastable state is cycled. The
time changes in the magnetization are logarithmic in general and activation
energies are consistent with those expected for electron transfer between Mn
ions. Changes induced by thermal cycling can be inhibited by applying magnetic
field. These results suggest that oxygen non-stoichiometry results in
mechanical strains in this two-phase system, leading to the development of
frustrated metastable states which relax towards the more stable charge-ordered
and antiferromagnetic microdomains. Our results also suggest that the growth
and coexistence of phases gives rise to microstructural tracks and strain
accommodation, producing the observed irreversibility.",1011.2179v1
2011-05-17,The metallic transport of (TMTSF)_2X organic conductors close to the superconducting phase,"Comparing resistivity data of quasi-one dimensional superconductors
(TMTSF)_2PF_6 and (TMTSF)_2ClO_4 along the least conducting c*-axis and along
the high conductivity a -axis as a function of temperature and pressure, a low
temperature regime is observed in which a unique scattering time governs
transport along both directions of these anisotropic conductors. However, the
pressure dependence of the anisotropy implies a large pressure dependence of
the interlayer coupling. This is in agreement with the results of
first-principles DFT calculations implying methyl group hyperconjugation in the
TMTSF molecule. In this low temperature regime, both materials exhibit for rc a
temperature dependence aT + bT^2. Taking into account the strong pressure
dependence of the anisotropy, the T-linear rc is found to correlate with the
suppression of the superconducting Tc, in close analogy with ra data. This work
is revealing the domain of existence of the 3D coherent regime in the generic
(TMTSF)_2X phase diagram and provides further support for the correlation
between T-linear resistivity and superconductivity in non-conventional
superconductors.",1105.3323v2
2011-11-29,Towards the Realization of Higher Connectivity in MgB2 Conductors: In-situ or Sintered Ex-situ?,"The two most common types of MgB2 conductor fabrication technique - in-situ
and ex-situ - show increasing conflicts concerning the connectivity, an
effective current-carrying cross-sectional area. An in-situ reaction yields a
strong intergrain coupling with a low packing factor, while an ex-situ process
using pre-reacted MgB2 yields tightly packed grains, however, their coupling is
much weaker. We studied the normal-state resistivity and microstructure of
ex-situ MgB2 bulks synthesized with varied heating conditions under ambient
pressure. The samples heated at moderately high temperatures of ~900{\deg}C for
a long period showed an increased packing factor, a larger intergrain contact
area and a significantly decreased resistivity, all of which indicate the
solid-state self-sintering of MgB2. Consequently the connectivity of the
sintered ex-situ samples exceeded the typical connectivity range 5-15% of the
in-situ samples. Our results show self-sintering develops the superior
connectivity potential of ex-situ MgB2, though its intergrain coupling is not
yet fulfilled, to provide a strong possibility of twice or even much higher
connectivity in optimally sintered ex-situ MgB2 than in in-situ MgB2.",1111.6767v2
2012-07-25,Metallic state in La-doped YBa$_2$Cu$_3$O$_y$ thin films with $n$-type charge carriers,"We report hole and electron doping in La-doped YBa$_2$Cu$_3$O$_y$(YBCO) thin
films synthesized by pulsed laser deposition technique and subsequent
\emph{in-situ} postannealing in oxygen ambient and vaccum. The $n$-type samples
show a metallic behavior below the Mott limit and a high carrier density of
$\sim2.8$ $\times$ 10$^{21}$ cm$^{-3}$ at room temperature (\emph{T}) at the
optimally reduced condition. The in-plane resistivity ($\rho$$_{ab}$) of the
$n$-type samples exhibits a quadratic \emph{T} dependence in the
moderate-\emph{T} range and shows an anomaly at a relatively higher \emph{T}
probably related to pseudogap formation analogous to underdoped
Nd$_{2-x}$Ce$_x$CuO$_4$ (NCCO). Furthermore, $\rho$$_{ab}$(T), \emph{T}$_c$ and
\emph{T} with minimum resistivity (\emph{T}$_{min}$) were investigated in both
$p$- and $n$-side. The present results reveal the $n$-$p$ asymmetry (symmetry)
within the metallic-state region in an underdoped cuprate and suggest the
potential toward ambipolar superconductivity in a single YBCO system.",1207.5914v1
2012-11-28,Photoconductivity effects in mixed-phase BSCCO whiskers,"We report on combined photoconductivity and annealing experiments in
whisker-like crystals of the Bi-Sr-Ca-Cu-O (BSCCO) high-Tc superconductor. Both
single-phase Bi2Sr2CaCu2O8+\delta (Bi-2212) samples and crystals of the mixed
phases Bi2Sr2Ca2Cu3O10+x (Bi-2223)/Bi-2212 have been subjected to annealing
treatments at 90{\deg}C in air in a few hours steps, up to a maximum total
annealing time of 47 h. At every step, samples have been characterized by means
of electrical resistance vs temperature (R vs T) and resistance vs time at
fixed temperature (R vs t) measurements, both in the dark and under
illumination with a UV-VIS halogen arc lamp. A careful comparison of the
results from the two techniques has shown that, while for single-phase samples
no effect is recorded, for mixed-phase samples an enhancement in the
conductivity that increases with increasing the annealing time is induced by
the light at the nominal temperature T = 100 K, i.e. at an intermediate
temperature between the critical temperatures of the two phases. A simple
pseudo-1D model based on the Kudinov's scheme [Kudinov et al., Phys. Rev. B 47,
9017-28, (1993)] has been developed to account for the observed effects, which
is based on the existence of Bi-2223 filaments embedded in the Bi-2212 matrix
and on the presence of electronically active defects at their interfaces. This
model reproduces fairly well the photoconductive experimental results and shows
that the length of the Bi-2223 filaments decreases and the number of defects
increases with increasing the annealing time.",1211.6594v1
2013-01-03,Studies of YBa2Cu3O6+x degradation and surface conductivity properties by Scanning Spreading Resistance Microscopy,"Local surface conductivity properties and surface degradation of c-axis
oriented YBa2Cu3O6+x (YBCO) thin films were studied by Scanning Spreading
Resistance Microscopy (SSRM). For the surface degradation studies, the YBCO
surface was cleaned by ion beam etching and the SSRM surface conductivity map
has been subsequently repeatedly measured over several hours in air and pure
nitrogen. Average surface conductivity of the scanned area was gradually
decreasing over time in both cases, faster in air. This was explained by oxygen
out-diffusion in both cases and chemical reactions with water vapor in air. The
obtained surface conductivity images also revealed its high inhomogenity on
micrometer and nanometer scale with numerous regions of highly enhanced
conductivity compared to the surroundings. Furthermore, it has been shown that
the size of these conductive regions considerably depends on the applied
voltage. We propose that such inhomogeneous surface conductivity is most likely
caused by varying thickness of degraded YBCO surface layer as well as varying
oxygen concentration (x parameter) within this layer, what was confirmed by
scanning Auger electron microscopy (SAM). In our opinion the presented findings
might be important for analysis of current-voltage and differential
characteristics measured on classical planar junctions on YBCO as well as other
perovskites.",1301.0397v1
2013-02-21,Electronic transport on carbon nanotube networks: a multiscale computational approach,"Carbon nanotube networks are one of the candidate materials to function as
malleable, transparent, conducting films, with the technologically promising
application of being used as flexible electronic displays. Nanotubes disorderly
distributed in a film offers many possible paths for charge carriers to travel
across the entire system, but the theoretical description of how this charge
transport occurs is rather challenging for involving a combination of intrinsic
nanotube properties with network morphology aspects. Here we attempt to
describe the transport properties of such films in two different length scales.
Firstly, from a purely macroscopic point of view we carry out a geometrical
analysis that shows how the network connectivity depends on the nanotube
concentration and on their respective aspect ratio. Once this is done, we are
able to calculate the resistivity of a heavily disordered networked film.
Comparison with experiment offers us a way to infer about the junction
resistance between neighbouring nanotubes. Furthermore, in order to guide the
frantic search for high-conductivity films of nanotube networks, we turn to the
microscopic scale where we have developed a computationally efficient way for
calculating the ballistic transport across these networks. While the ballistic
transport is probably not capable of describing the observed transport
properties of these films, it is undoubtedly useful in establishing an upper
value for their conductivity. This can serve as a guideline in how much room
there is for improving the conductivity of such networks.",1302.5379v1
2013-12-05,Giant topological Hall effect in strained Fe$_{0.7}$Co$_{0.3}$Si epilayers,"The coupling of electron spin to real-space magnetic textures leads to a
variety of interesting magnetotransport effects. The skyrmionic spin textures
often found in chiral B20-lattice magnets give rise, via real-space Berry
phases, to the topological Hall effect, but it is typically rather small. Here,
B20-ordered Fe$_{0.7}$Co$_{0.3}$Si epilayers display a giant topological Hall
effect due to the combination of three favourable properties: they have a high
spin-polarisation, a large ordinary Hall coefficient, and dense chiral spin
textures. The topological Hall resistivity is as large as 820 n$\Omega$cm at
helium temperatures. Moreover, we observed a drop in the longitudinal
resistivity of 100 n$\Omega$cm at low temperatures in the same field range,
suggesting that it is also of topological origin. That such strong effects can
be found in material grown in thin film form on commercial silicon wafer bodes
well for skyrmion-based spintronics.",1312.1722v1
2013-12-23,Signatures of electronic phase separation in the Hall effect of anisotropically strained La0.67Ca0.33MnO3 films,"Systematic transport measurements have been performed on a series of
La0.67Ca0.33MnO3 (LCMO) thin films with varying degrees of anisotropic strain.
The strain is induced via epitaxial growth on NdGaO3(001) substrates and varied
by controlling the thermal annealing time. An antiferromagnetic insulating
(AFI) state, possibly associated with charge ordering, emerges upon thermal
annealing. The Hall effect in these materials exhibits features that are
indicative of a percolative phase transition and correlate closely with the
emergence of the AFI state. In the paramagnetic phase, the Hall resistivity
takes on two slopes in all samples: a decreasing negative slope with increasing
temperature at low fields, which is attributed to the carrier hopping motion,
and an almost temperature independent positive slope at high fields due to
diffusive transport of holes. Significantly, the crossover fields of the Hall
resistivity slope at different temperatures correspond to the same
magnetization, which is interpreted as the critical point of a magnetic
field-driven percolative phase transition. At lower temperatures near the
zero-field metal-insulator transition, pronounced enhancement of the Hall
coefficient with the development of the AFI state is observed. The enhancement
peaks near the magnetic field-driven percolation; its magnitude correlates with
the strength of the AFI state and is suppressed with the melting of the AFI
state by an in-plane magnetic field. The observations resemble many features of
the enhancement of the Hall coefficient in granular metal films near the
composition-driven percolation.",1312.6670v1
2014-04-16,Origin of High Temperature Oxidation Resistance of Ti-Al-Ta-N Coatings,"Alloying Ti-Al-N coatings with Ta has proven to enhance their hardness,
thermal stability, and oxidation resistance. However, especially for
arc-evaporated Ti-Al-Ta-N coatings only limited information on the detailed
influence of the elements on various properties is available. Therefore, we
have developed arc-evaporated Ti1-x-yAlxTayN coatings with various Al (x = 0.50
- 0.65) and Ta (y = 0.00 - 0.15) contents. While the thermal stability of our
coatings during annealing in inert He atmosphere increases with increasing Ta
content, best results are obtained for specific Ta-Al ratios during oxidation.
Single phase cubic Ti0.32Al0.60Ta0.08N yields a mass-gain of only ~5 % after 5
h at 950 {\deg}C in synthetic air, whereas Ti0.35Al0.65N is completely oxidized
after 15 min. This is in part based on the suppressed anatase and direct rutile
TiO2 formation at a defined Ta-Al content. Consequently, the anatase-to-rutile
transformation, generally observed for Ti1-xAlxN, is absent. This reduces the
generation of pores and cracks within the oxide scale and especially at the
nitride-oxide interface, leading to the formation of a protective rutile and
corundum based oxide scale. This is also reflected in the pronounced decrease
in activation energy for the protective scale formation from 232 kJ/mol for
Ti0.35Al0.65N down to 14.5 kJ/mol for Ti0.32Al0.60Ta0.08N. Based on our results
we can conclude that especially phase transformations within the oxide scale
need to be suppressed, as the connected volume changes lead to the formation of
cracks and pores.",1404.4345v1
2014-12-02,Effect of phase separation induced supercooling on magnetotransport properties of epitaxial La5/8-yPryCa3/8MnO3 (y~0.4) thin film,"Thin films of La5/8-yPryCa3/8MnO3 (y~0.4) have been grown on single crystal
SrTiO3 (001) by RF sputtering. The structural and surface characterizations
confirm the epitaxial nature of these film. However, the difference between the
rocking curve of the (002) and (110) peaks and the presence of pits/holes in
the step-terrace type surface morphology suggests high density of defect in
these films. Pronounced hysteresis between the field cool cooled (FCC) and
field cooled warming (FCW) magnetization measurements suggest towards the
non-ergodic magnetic state. The origin of this nonergodicity could be traced to
the magnetic liquid like state arising from the delicacy of the coexisting
magnetic phases, viz., ferromagnetic and antiferromagnetic-charge ordered
(FM/AFM-CO). The large difference between the insulator metal transitions
during cooling and warming cycles (TIMC~64 K and TIMW~123 K) could be regarded
as a manifestation of the nonergodicity leading to supercooling of the magnetic
liquid while cooling. The nonergodicity and supercooling are weakened by the
AFM-FM phase transition induced by an external magnetic field. TIM and small
polaron activation energy corresponding the magnetic liquid state (cooling
cycle) vary nonlinearly with the applied magnetic field but become linear in
the crystalline solid state (warming cycle). The analysis of the low
temperature resistivity data shows that electron-phonon interaction is
drastically reduced by the applied magnetic field. The resistivity minimum in
the lower temperature region of the self-field warming curve has been explained
in terms of the Kondo like scattering in the magnetically inhomogeneous regime.",1412.0862v1
2016-11-09,Unusual non saturating Giant Magneto-resistance in single crystalline Bi2Te3 topological insulator,"We report synthesis, structural details and electrical transport properties
of topological insulator Bi2Te3. The single crystalline specimens of Bi2Te3 are
obtained from high temperature (950C) melt and slow cooling (2C/hour). The
resultant crystals were shiny, one piece (few cm) and of bright silver color.
The Bi2Te3 crystal is found to be perfect with clear [00l] alignment. The
powder XRD pattern being carried out on crushed crystals showed that Bi2Te3
crystallized in R3m symmetry with a = b = 4.3866(2) A, c = 30.4978(13) A and
Gamma = 120degree. The Bi position is refined to (0, 0, 0.4038 (9)) at Wyckoff
position 6c and of Te are (0, 0, 0) at Wyckoff position 3a and at (0, 0,
0.2039(8)) at 6c. Ambient pressure and low temperature (down to 2K) electrical
transport measurements revealed metallic behavior. Magneto transport
measurements under magnetic field showed huge non saturating magneto resistance
(MR) reaching up to 250% at 2.5K and under 50KOe field. Summarily, the short
communication clearly demonstrates that Bi2Te3 topological insulator exhibit
non-saturating large positive MR at low temperature of say below 10K. The non
saturating MR is seen right up to room temperature albeit with much decreased
magnitude. Worth mentioning is the fact that these crystals are bulk in nature
and hence the anomalous MR is clearly an intrinsic property and not due to the
size effect as reported for nano-wires or thin films of the same.",1611.02859v2
2016-11-28,Grand Design Spiral Arms in A Young Forming Circumstellar Disk,"We study formation and long-term evolution of a circumstellar disk in a
collapsing molecular cloud core using a resistive magnetohydrodynamic
simulation. While the formed circumstellar disk is initially small, it grows as
accretion continues and its radius becomes as large as 200 AUs toward the end
of the Class-I phase. A pair of grand-design spiral arms form due to
gravitational instability in the disk, and they transfer angular momentum in
the highly resistive disk. Although the spiral arms disappear in a few
rotations as expected in a classical theory, new spiral arms form recurrently
as the disk soon becomes unstable again by gas accretion. Such recurrent spiral
arms persist throughout the Class-0 and I phase. We then perform synthetic
observations and compare our model with a recent high-resolution observation of
a young stellar object Elias 2-27, whose circumstellar disk has grand design
spiral arms. We find good agreement between our theoretical model and the
observation. Our model suggests that the grand design spiral arms around Elias
2-27 are consistent with material arms formed by gravitational instability. If
such spiral arms commonly exist in young circumstellar disks, it implies that
young circumstellar disks are considerably massive and gravitational
instability is the key process of angular momentum transport.",1611.09361v2
2017-09-27,Pressure induced spin crossover in disordered α-LiFeO2,"Structural, magnetic and electrical-transport properties of {\alpha}-LiFeO2,
crystallizing in the rock salt structure with random distribution of Li and Fe
ions, have been studied by synchrotron X-ray diffraction, 57Fe M\""ossbauer
spectroscopy and electrical resistance measurements at pressures up to 100 GPa
using diamond anvil cells. It was found that the crystal structure is stable at
least to 82 GPa, though a significant change in compressibility has been
observed above 50 GPa. The changes in the structural properties are found to be
on a par with a sluggish Fe3+ high- to low-spin (HS-LS) transition (S=5/2 to
S=1/2) starting at 50 GPa and not completed even at ~100 GPa. The HS-LS
transition is accompanied by an appreciable resistance decrease remaining a
semiconductor up to 115 GPa and is not expected to be metallic even at about
200 GPa. The observed feature of the pressure-induced HS-LS transition is not
an ordinary behavior of ferric oxides at high pressures. The effect of Fe3+
nearest and next nearest neighbors on the features of the spin crossover is
discussed.",1709.09680v1
2018-03-24,Ion implantation in nanodiamonds: size effect and energy dependence,"Nanoparticles are ubiquitous in nature and are increasingly important for
technology. They are subject to bombardment by ionizing radiation in a diverse
range of environments. In particular, nanodiamonds represent a variety of
nanoparticles of significant fundamental and applied interest. Here we present
a combined experimental and computational study of the behaviour of
nanodiamonds under irradiation by xenon ions. Unexpectedly, we observed a
pronounced size effect on the radiation resistance of the nanodiamonds:
particles larger than 8 nm behave similarly to macroscopic diamond (i.e.
characterized by high radiation resistance) whereas smaller particles can be
completely destroyed by a single impact from an ion in a defined energy range.
This latter observation is explained by extreme heating of the nanodiamonds by
the penetrating ion. The obtained results are not limited to nanodiamonds,
making them of interest for several fields, putting constraints on processes
for the controlled modification of nanodiamonds, on the survival of dust in
astrophysical environments, and on the behaviour of actinides released from
nuclear waste into the environment.",1803.09081v1
2020-09-14,Memristive control of mutual SHNO synchronization for neuromorphic computing,"Synchronization of large spin Hall nano-oscillators (SHNO) arrays is an
appealing approach toward ultra-fast non-conventional computing based on
nanoscale coupled oscillator networks. However, for large arrays, interfacing
to the network, tuning its individual oscillators, their coupling, and
providing built-in memory units for training purposes, remain substantial
challenges. Here, we address all these challenges using memristive gating of
W/CoFeB/MgO/AlOx based SHNOs. In its high resistance state (HRS), the memristor
modulates the perpendicular magnetic anisotropy (PMA) at the CoFeB/MgO
interface purely by the applied electric field. In its low resistance state
(LRS), and depending on the voltage polarity, the memristor adds/subtracts
current to/from the SHNO drive. The operation in both the HRS and LRS affects
the SHNO auto-oscillation mode and frequency, which can be tuned up to 28
MHz/V. This tuning allows us to reversibly turn on/off mutual synchronization
in chains of four SHNOs. We also demonstrate two individually controlled
memristors to tailor both the coupling strength and the frequency of the
synchronized state. Memristor gating is therefore an efficient approach to
input, tune, and store the state of the SHNO array for any non-conventional
computing paradigm, all in one platform.",2009.06594v1
2022-02-09,Electron-Electron Interaction and Weak Antilocalization Effect in a Transition Metal Dichalcogenide Superconductor,"In disordered transition-metal dichalcogenide (TMD) superconductor, both the
strong spin-orbit coupling (SOC) and disorder show remarkable effects on
superconductivity. However, the features of SOC and disorder were rarely
detected directly. Here we report the quantum transport behaviors arising from
the interplay of SOC and disorder in the TMD superconductor 1T-NbSeTe. Before
entering the superconducting state, the single crystal at low temperature shows
a resistivity upturn, which is T1/2 dependent and insensitive to the applied
magnetic fields. The magnetoresistance (MR) at low temperatures shows a H1/2
dependence at high magnetic fields. The characteristics are in good agreement
with the electron-electron interaction (EEI) in a disordered conductor. In
addition, the upturn changes and MR at low magnetic fields suggest the
contribution of weak antilocalization (WAL) effect arising from the strong SOC
in the material. Moreover, the quantitative analyses of the transport features
in different samples imply anomalous disorder-enhanced superconductivity that
needs to be further understood. The results reveal the disorder enhanced EEI
and the strong SOC induced WAL effect in 1T-NbSeTe, which illustrate the
resistivity minimum in the widely studied doped superconductors. The work also
provides insights into the disorder effect on the superconductivity.",2202.04338v1
2016-03-21,Measurement of Characteristic Impedance of Silicon Fiber Sheet based readout strips panel for RPC detector in INO,"The India based Neutrino Observatory (INO) is a mega science project of
India, which is going to use near about 30, 000 Resistive Plate Chambers (RPC)
as active detector elements for the study of atmospheric neutrino oscillations.
Each RPC detector will consist of two orthogonally placed readout strips panel
for picking the signals generated in the gas chamber. The area of RPC detector
in INO-ICAL (Iron Calorimeter) experiment will be 2m x 2m, therefore the
dimension of readout strips panel will also be of 2m x 2m. To get undistorted
signals pass through the readout strips panel to frontend electronics, their
Characteristic Impedance should be matched with each other. For the matching of
Characteristic Impedance we have used the principle of termination. In the
present paper we will describe the need and search of new dielectric material
for the fabrication of flame resistant, waterproof and flexible readout pickup
strips panel. We will also describe the measurement of Characteristic Impedance
of plastic honeycomb based readout strips panel and Silicon Fiber sheet based
readout strips panel in a comparative way, and its variation under loading and
with time.",1603.06334v1
2017-04-18,Extruded Mg based hybrid composite alloys studied by longitudinal impression creep,"The creep behaviour of a creep-resistant AE42 magnesium alloy reinforced with
Saffil short fibres and SiC particulates in various combinations has been
examined in the longitudinal direction, i.e., the plane containing random fibre
orientation was parallel to the loading direction, in the temperature range of
175-300 C at the stress levels ranging from 60 to 140 MPa using impression
creep test technique. At 175 C, normal creep behaviour, i.e., strain rate
decreasing with strain and then reaching a steady state, is observed at all the
stresses employed. At 240 C, normal creep behaviour is observed up to 80 MPa
and reverse creep behaviour, i.e., strain rate increasing with strain, then
reaching a steady state and again decreasing, is observed above that stress. At
300 C, reverse creep behaviour is observed at all the stresses employed. This
pattern remains the same for all the composites. The reverse creep behaviour is
found to be associated with the fibre breakage. The stress exponent is found to
be very high for all the composites. However, after taking the threshold stress
into account, the stress exponent varies from 3.9 to 7.0, which suggests
viscous glide and dislocation climb being the dominant creep mechanisms. The
apparent activation energy Qc was not calculated due to insufficient data at
any stress level either for normal or reverse creep behaviour. The creep
resistance of the hybrid composites is found to be comparable to that of the
composite reinforced with 20% Saffil short fibres at all the temperatures and
stress levels investigated.",1704.06563v2
2018-08-12,High-pressure polymorphism of BaFe2Se3,"BaFe2Se3 is a potential superconductor material exhibiting transition at 11 K
and ambient pressure. Here we extended the structural and performed electrical
resistivity measurements on this compound up to 51 GPa and 20 GPa,
respectively, in order to distinguish if the superconductivity in this sample
is intrinsic to the BaFe2Se3 phase or if it is originating from minor FeSe
impurities that show a similar superconductive transition temperature. The
electrical resistance measurements as a function of pressure show that at 5 GPa
the superconducting transition is observed at around 10 K, similar to the one
previously observed for this sample at ambient pressure. This indicates that
the superconductivity in this sample is intrinsic to the BaFe2Se3 phase and not
to FeSe with Tc > 20 K at these pressures. Further increase in pressure
suppressed the superconductive signal and the sample remained in an insulating
state up to the maximum achieved pressure of 20 GPa. Single-crystal and powder
X-ray diffraction measurements revealed two structural transformations in
BaFe2Se3: a second order transition above 3.5 GPa from Pnma (CsAg2I3-type
structure) to Cmcm (CsCu2Cl3-type structure) and a first order transformation
at 16.6 GPa. Here, {\gamma}-BaFe2Se3 transforms into {\delta}-BaFe2Se3 (Cmcm,
CsCu2Cl3-type average structure) via a first order phase transition mechanism.
This transitions is characterized by a significant shortening of the b lattice
parameter of {\gamma}-BaFe2Se3 (17%) and accompanied by an anisotropic
expansion in the orthogonal ac plane at the transition point.",1808.03952v1
2019-03-14,Electric Switching of the Charge-Density-Wave and Normal Metallic Phases in Tantalum Disulfide Thin-Film Devices,"We report on switching among three charge-density-wave phases - commensurate,
nearly commensurate, incommensurate - and the high-temperature normal metallic
phase in thin-film 1T-TaS2 devices induced by application of an in-plane
electric field. The electric switching among all phases has been achieved over
a wide temperature range, from 77 K to 400 K. The low-frequency electronic
noise spectroscopy has been used as an effective tool for monitoring the
transitions, particularly the switching from the incommensurate
charge-density-wave phase to the normal metal phase. The noise spectral density
exhibits sharp increases at the phase transition points, which correspond to
the step-like changes in resistivity. Assignment of the phases is consistent
with low-field resistivity measurements over the temperature range from 77 K to
600 K. Analysis of the experimental data and calculations of heat dissipation
suggest that Joule heating plays a dominant role in the electric-field induced
transitions in the tested 1T-TaS2 devices on Si/SiO2 substrates. The
possibility of electrical switching among four different phases of 1T-TaS2 is a
promising step toward nanoscale device applications. The results also
demonstrate the potential of noise spectroscopy for investigating and
identifying phase transitions in materials.",1903.06050v1
2015-06-26,Negative Differential Resistance in Boron Nitride Graphene Heterostructures: Physical Mechanisms and Size Scaling Analysis,"Hexagonal boron nitride (hBN) is drawing increasing attention as an insulator
and substrate material to develop next generation graphene-based electronic
devices. In this paper, we investigate the quantum transport in
heterostructures consisting of a few atomic layers thick hBN film sandwiched
between graphene nanoribbon electrodes. We show a gate-controllable vertical
transistor exhibiting strong negative differential resistance (NDR) effect with
multiple resonant peaks, which stay pronounced for various device dimensions.
We find two distinct mechanisms that are responsible for NDR, depending on the
gate and applied biases, in the same device. The origin of first mechanism is a
Fabry-P\'e like interference and that of the second mechanism is an in-plane
wave vector matching when the Dirac points of the electrodes align. The hBN
layers can induce an asymmetry in the current-voltage characteristics which can
be further modulated by an applied bias. We find that the electron-phonon
scattering introduces the decoherence and therefore suppresses first mechanism
whereas second mechanism remains relatively unaffected. We also show that the
NDR features are tunable by varying device dimensions. The NDR feature with
multiple resonant peaks, combined with the ultrafast tunneling speed provides
prospect for the graphene-hBN-graphene heterostructure in the high-performance
electronics.",1506.08207v1
2015-07-02,Massive $2$-form field and holographic ferromagnetic phase transition,"In this paper, we investigate in some detail the holographic ferromagnetic
phase transition in an AdS${_4}$ black brane background by introducing a
massive 2-form field coupled to the Maxwell field strength in the bulk. In the
two probe limits, one is to neglect the back reaction of the 2-form field to
the background geometry and to the Maxwell field, and the other to neglect the
back reaction of both the Maxwell field and the 2-form field, we find that the
spontaneous magnetization and the ferromagnetic phase transition always happen
when the temperature gets low enough with similar critical behavior. We
calculate the DC resistivity in a semi-analytical method in the second probe
limit and find it behaves as the colossal magnetic resistance effect in some
materials. In the case with the first probe limit, we obtain the off-shell free
energy of the holographic model near the critical temperature and compare with
the Ising-like model. We also study the back reaction effect and find that the
phase transition is always second order. In addition, we find an analytical
Reissner-Norstr\""om-like black brane solution in the Einstein-Maxwell-2-form
field theory with a negative cosmological constant.",1507.00546v2
2018-12-31,"Growth, Characterization and High Field Magneto-Conductivity of Co0.1Bi2Se3 Topological Insulator","We report the crystal growth as well as transport properties of Co added
Bi2Se3 single crystals. The values of the lattice parameters a and b for Co
added sample were observed to increase as compared to the pure Bi2Se3. The
Raman spectroscopy displayed higher Raman shift of corresponding vibrational
modes for Co0.1Bi2Se3, and the resistivity curves with and without applied
magnetic field shows a metallic behaviour. Both the crystals were subjected to
magneto-resistance (MR) measurements under applied fields of 14Tesla. The value
of MR is found to decrease from about 380 (5K, 14 Tesla) for Bi2Se3 to 200
degree for Co0.1Bi2Se3. To elaborate the transport properties of pure and Co
added Bi2Se3 crystals, the magneto-conductivity is fitted to the HLN (Hikami
Larkin Nagaoka) equation and it is found that the charge conduction is mainly
dominated by surface driven WAL (weak anti-localization) with negligible bulk
WL (weak localization) contribution in both crystals alike. The MH curves of
Co0.1Bi2Se3 crystal at different temperatures displayed a combination of both
ferromagnetic and diamagnetic behaviour. On the other hand, the Electron
Paramagnetic Resonance (EPR) revealed that pure Bi2Se3 is diamagnetic whereas,
Co orders ferro-magnetically with resonating field around 3422Oe at room
temperature.",1812.11713v1
2019-11-28,"Low-friction, wear-resistant, and electrically homogeneous multilayer graphene grown by chemical vapor deposition on molybdenum","Chemical vapour deposition (CVD) is a promising method for producing
large-scale graphene (Gr). Nevertheless, microscopic inhomogeneity of Gr grown
on traditional metal substrates such as copper or nickel results in a spatial
variation of Gr properties due to long wrinkles formed when the metal substrate
shrinks during the cooling part of the production cycle. Recently, molybdenum
(Mo) has emerged as an alternative substrate for CVD growth of Gr, mainly due
to a better matching of the thermal expansion coefficient of the substrate and
Gr. We investigate the quality of multilayer Gr grown on Mo and the relation
between Gr morphology and nanoscale mechanical and electrical properties, and
spatial homogeneity of these parameters. With atomic force microscopy (AFM)
based scratching, Kelvin probe force microscopy, and conductive AFM, we measure
friction and wear, surface potential, and local conductivity, respectively. We
find that Gr grown on Mo is free of large wrinkles that are common with growth
on other metals, although it contains a dense network of small wrinkles. We
demonstrate that as a result of this unique and favorable morphology, the Gr
studied here has low friction, high wear resistance, and excellent homogeneity
of electrical surface potential and conductivity.",1911.12653v1
2021-02-23,Strain-tuning of nematicity and superconductivity in single crystals of FeSe,"Strain is a powerful experimental tool to explore new electronic states and
understand unconventional superconductivity. Here, we investigate the effect of
uniaxial strain on the nematic and superconducting phase of single crystal FeSe
using magnetotransport measurements. We find that the resistivity response to
the strain is strongly temperature dependent and it correlates with the sign
change in the Hall coefficient being driven by scattering, coupling with the
lattice and multiband phenomena. Band structure calculations suggest that under
strain the electron pockets develop a large in-plane anisotropy as compared
with the hole pocket. Magnetotransport studies at low temperatures indicate
that the mobility of the dominant carriers increases with tensile strain. Close
to the critical temperature, all resistivity curves at constant strain cross in
a single point, indicating a universal critical exponent linked to a
strain-induced phase transition. Our results indicate that the superconducting
state is enhanced under compressive strain and suppressed under tensile strain,
in agreement with the trends observed in FeSe thin films and overdoped
pnictides, whereas the nematic phase seems to be affected in the opposite way
by the uniaxial strain. By comparing the enhanced superconductivity under
strain of different systems, our results suggest that strain on its own cannot
account for the enhanced high $T_c$ superconductivity of FeSe systems.",2102.11984v1
2021-02-24,Calibration of manganin pressure gauge for diamond-anvil cells,"Pressure calibration for most diamond-anvil cell (DAC) experiments is mainly
based on the ruby scale, which is key to implement this powerful tool for
high-pressure study. However, the ruby scale can often hardly be used for
programmably-controlled DAC devices, especially the piezoelectric-driving
cells, where a continuous pressure calibration is required. In this work, we
present an effective pressure gauge for DACs made of manganin metal, based on
the four-probe resistivity measurements. Pressure dependence of its resistivity
is well established and shows excellent linear relations in the 0 - 30 GPa
pressure range with a slope of 23.4 (9) GPa for the first-cycle compression, in
contrast to that of multiple-cycle compression and decompression having a
nearly identical slope of 33.7 (4) GPa likely due to the strain effect. In
addition, such-established manganin scale can be used for continuously
monitoring the cell pressure of piezoelectric-driving DACs, and the reliability
of this method is also verified by the fixed-point method with a Bi pressure
standard. Realization of continuous pressure calibration for
programmably-controlled DACs would offer many opportunities for study of
dynamics, kinetics, and critical behaviors of pressure-induced phase
transitions.",2102.12125v1
2021-03-19,A Robust nitridation technique for fabrication of disordered superconducting TiN thin films featuring phase slip events,"Disorder induced phase slip (PS) events appearing in the current voltage
characteristics (IVCs) are reported for two-dimensional TiN thin films produced
by a robust substrate mediated nitridation technique. Here, high temperature
annealing of Ti/Si3N4 based metal/substrate assembly is the key to produce
majority phase TiN accompanied by TiSi2 and elemental Si as minority phases.
The method itself introduces different level of disorder intrinsically by
tuning the amount of the non-superconducting minority phases that are
controlled by annealing temperature (Ta) and the film thickness. The
superconducting critical temperature (Tc) strongly depends on Ta and the
maximum Tc obtained from the demonstrated technique is about 4.8 K for the
thickness range of about 12 nm and above. Besides, the dynamics of IVCs get
modulated by the appearance of intermediated resistive steps for decreased Ta
and the steps get more prominent for reduced thickness. Further, the deviation
in the temperature dependent critical current (Ic) from the Ginzburg-Landau
theoretical limit varies strongly with the thickness. Finally, the Tc,
intermediate resistive steps in the IVCs and the depairing current are observed
to alter in a similar fashion with Ta and the thickness indicating the
robustness of the synthesis process to fabricate disordered nitride-based
superconductor.",2103.10751v2
2021-07-22,Temperature dependence of on-state inter-terminal capacitances (Cgd and Cgs) of SiC MOSFETs and frequency limitations of their measurements,"Inter-terminal capacitances (ITCs) have major influence on the dynamic
performance of power SiC MOSFETs. Knowledge of the exact values for the ITCs is
required in order to perform accurate and predictive compact model simulations
of their dynamic performance. Since commercial SiC MOSFETs are capable of
operating in a wide range of temperatures, it is important to know the values
of ITCs in the whole temperature range of operation. Direct measurements of the
ITCs with standard equipment is possible only at low current levels (i.e. in
the off-state (Vgs < Vth) for Vds > 0 V), however their values in the on-state
(Vgs>Vth) also influence the MOSFETs switching performance. In this work, ITCs
of a planar SiC MOSFET in the on-state are studied by the means of a calibrated
TCAD model, revealing substantial temperature dependence in the range of
300-450 K. In the first approximation, this temperature dependence of the ITCs
can be explained by a weaker temperature dependence of the MOSFET channel
resistance in comparison to its JFET and epitaxial layer resistances. In
addition, it is shown that at high frequencies stray inductances of the
TO-247-3 package result in a change of the extracted values of the on-state
ITCs. This effect is already notable at 1 MHz.",2107.10408v1
2021-07-24,Anomalous Nernst thermopower and giant magnetostriction in microwave synthesized La0.5Sr0.5CoO3,"Ferromagnetic metallic oxides have potential applications in spincaloric
devices which utilize the spin property of charge carriers for interconversion
of heat and electricity through the spin Seebeck or the anomalous Nernst effect
or both. In this work, we synthesized polycrystalline La0.5S0.5CoO3 by
microwave irradiation method and studied its transverse thermoelectric voltage
(Nernst thermopower) and change in the linear dimension of the sample (Joule
magnetostriction) in response to external magnetic fields. In addition,
magnetization, temperature dependences of electrical resistivity, and
longitudinal Seebeck coefficient (Sxx) in absence of an external magnetic field
were also measured. The sample is ferromagnetic with a Curie temperature of TC
= 247 K and shows a metal-like resistivity above and below TC with a negative
sign of Sxx suggesting charge transport due to electrons. Magnetic field
dependence of the Nernst thermopower (Sxy) at a fixed temperature shows a rapid
increase at low fields and a tendency to saturate at high fields as like the
magnetization. Anomalous contribution to Sxy was extracted from total Sxy
measured and it exhibits a maximum value of ~ 0.21 microV/K at 180 K for H = 50
kOe, which is comparable to the value found in a single crystal for a lower Sr
content. The Joule magnetostriction is positive, i.e., the length of the sample
expands along the direction of the magnetic field and it does not saturate even
at 50 kOe. The magnetostriction increases with decreasing temperature below TC
and reaches a maximum value of 500 ppm at T = 40 K and below. Coexistence of
the anomalous Nernst thermopower and giant magnetostriction in a single
compound has potential applications for thermal energy harvesting and
low-temperature actuators, respectively.",2107.11535v1
2022-01-15,Fabrication and micro-Raman spectroscopy of arrays of copper phthalocyanine molecular-magnet microdisks,"Phthalocyanines as organic semiconductors and molecular magnets provide
plenty of industrial or high-tech applications from dyes and pigments up to gas
sensors, molecular electronics, spintronics and quantum computing. Copper
phthalocyanine (CuPc) belongs among the most used phthalocyanines, typically in
the form of powder or films but self-grown nanowires are also known. Here we
describe an opposite, i.e., top-down approach based on fabrication of ordered
arrays of CuPc microstructures (microdisks) using electron beam lithography and
other steps. Among critical points of this approach belongs a choice of a
proper resist and a solvent. Fabricated CuPc microdisks have a diameter of 5
${\mu}$m and heights from 7 up to 70 nm. Micro-Raman spectroscopy of the films
and microdisks reveals a crystalline ${\beta}$ phase associated with a
paramagnetic form. Additional measurements with an increasing laser power show
a significant shift (${\Delta}{\omega}$ ~ 7.1 cm$^{-1}$ ) and broadening of a
peak at 1532 rel$\cdot$cm$^{-1}$ corresponding to the phonon B1g mode. The
observed smooth changes exclude a phase transition and confirm the thermally
stable polymorph. Our versatile fabrication technique using the common
lithographic resist brings new possibilities for the fabrication of various
micro/nanostructures such as micromagnets, heterostructures or organic
electronic devices.",2201.08235v1
2022-07-06,Mechanism of the Resistivity Switching Induced by the Joule Heating in Crystalline NbO$_2$,"Recently the memristive electrical transport properties in NbO$_2$ have
attracted much attention for their promising application to the neuromorphic
computation. At the center of debates is whether the metal-to-insulator
transition (MIT) originates from the structural distortion (Peierls) or the
electron correlation (Mott). With inputs from experiments and first principles
calculations, we develop a thermodynamical model rooted in the scenario of the
MIT driven by a $2^{nd}$ order Peierls instability. We find that the
temperature dependence of the electrical conductivity can be accurately fit by
the band gap varying with temperature due to the gradual weakening of the Nb-Nb
dimers. The resistivity switching can consequently be understood by dimer-free
metallic domains induced by local Joule heating. In solving the heat equation,
we find that the steady state can not be reached if the applied voltage exceeds
a threshold, resulting in the chaotic behavior observed in the high voltage and
current states. With the Ginzburg-Landau theory and the Joule heating equation,
the evolution of the metallic domains under bias voltage can be simulated and
directly verified by experiments.",2207.02682v2
2022-12-13,Deep multilevel wet etching of fused silica glass microstructures in BOE solution,"Fused silica glass is a material of choice for micromechanical, microfluidic,
and optical devices due to its ultimate chemical resistance, optical,
electrical, and mechanical performance. Wet etching in hydrofluoric solutions
especially a buffered oxide etching (BOE) solution is still the key method for
fabricating fused silica glass-based microdevices. It is well known that
protective mask integrity during deep fused silica wet etching is a big
challenge due to chemical stability of fused glass and extremely aggressive BOE
properties. Here, we propose a multilevel fused silica glass microstructures
fabrication route based on deep wet etching through a stepped mask with just a
one grayscale photolithography step. First, we provide a deep comprehensive
analysis of a fused quartz dissolution mechanism in BOE solution and calculate
the main fluoride fractions like $HF^-_2$, $F^-$, $(HF)_2$ components in a BOE
solution as a function of pH and $NH_4F:HF$ ratio at room temperature. Then, we
experimentally investigate the influence of BOE concentration ($NH_4F:HF$ from
1:1 to 14:1) on the mask resistance, etch rate and profile isotropy during
fused silica 60 minutes etching through a metal/photoresist mask. Finally, we
demonstrate a high-quality multilevel over-200 um isotropic wet etching process
with the rate up to 3 um/min, which could be of a great interest for advanced
fused silica microdevices with flexure suspensions, inertial masses,
microchannels, and through-wafer holes.",2212.06699v1
2023-03-02,Evolution of complex magnetic phases and metal-insulator transition through Nb substitution in La$_{0.5}$Sr$_{0.5}$Co$_{1-x}$Nb$_x$O$_3$,"We report the evolution of structural, magnetic, transport, and electronic
properties of bulk polycrystalline La$_{0.5}$Sr$_{0.5}$Co$_{1-x}$Nb$_x$O$_3$
($x =$ 0.025--0.25) samples. The Rietveld refinement of the x-ray diffraction
patterns with R$\bar3$c space group reveals that the lattice parameters and
rhombohedral distortion monotonously increase with the Nb$^{5+}$(4$d^0$)
substitution ($x$). The magnetic susceptibility exhibits a decrease in the
magnetic ordering temperature and net magnetization with $x$, which manifests
that the Nb substitution dilutes the ferromagnetic (FM) double exchange
interaction and enhances the antiferromagnetic (AFM) super-exchange
interaction. Interestingly, for the $x>$ 0.1 samples the FM order is completely
suppressed and the emergence of a glassy state is clearly evident. Moreover,
the decrease in the coercivity (H$\rm_{C}$) and remanence (M$\rm_{r}$) with $x$
in the magnetic isotherms measured at 5~K further confirms the dominance of AFM
interactions and reduction of FM volume fraction for the $x>$ 0.1 samples. More
interestingly, we observe resistivity minima for the $x=$ 0.025 and 0.05
samples, which are analyzed using the quantum corrections in the conductivity,
and found that the weak localization effect dominates over the renormalized
electron-electron interactions in the 3D limit. Further, a semiconducting
resistivity behavior is obtained for $x>$ 0.05, which follows the Arrhenius law
at high temperatures ($\sim$160--320~K), and the 3D-variable range hopping
prevails in the low-temperature region ($<$160~K). The core-level photoemission
spectra confirm the valence state of constituent elements and the absence of
Co$^{2+}$ is discernible.",2303.01108v1
2023-10-18,Electrically-driven amplification of terahertz acoustic waves in graphene,"In graphene devices, the electronic drift velocity can easily exceed the
speed of sound in the material at moderate current biases. Under this
condition, the electronic system can efficiently amplify acoustic phonons,
leading to the exponential growth of sound waves in the direction of the
carrier flow. Here, we demonstrate that such phonon amplification can
significantly modify the electrical properties of graphene devices. We observe
a super-linear growth of the resistivity in the direction of the carrier flow
when the drift velocity exceeds the speed of sound, causing up to a 7 times
increase over 8 micrometers. The resistance growth is observable for carrier
densities away from the Dirac point and is enhanced at cryogenic temperatures.
These observations are explained by a theoretical model for the
electrical-amplification of acoustic phonons, which reach frequencies up to 2.2
terahertz with the nanoscale wavelength set by gate-tunable ~kF transitions
across the Fermi surface. These findings offer a route to high-frequency
on-chip sound generation and detection, which can be used to modulate and probe
electronic physics in van der Waals heterostructures in the terahertz frequency
range.",2310.12225v1
2024-04-24,Structural investigation of the quasi-one-dimensional topological insulator Bi$_4$I$_4$,"The bismuth-halide Bi$_4$I$_4$ undergoes a structural transition around
$T_P\sim 300$K, which separates a high-temperature $\beta$ phase ($T>T_P$) from
a low-temperature $\alpha$ phase ($T<T_P$). $\alpha$ and $\beta$ phases are
suggested to host electronic band structures with distinct topological
classifications. Rapid quenching was reported to stabilize a metastable
$\beta$-Bi$_4$I$_4$ at $T<T_P$, making possible a comparative study of the
physical properties of the two phases in the same low-temperature range. In
this work, we present a structural investigation of the Bi$_4$I$_4$ before and
after quenching together with electrical resistivity measurements. We found
that rapid cooling does not consistently lead to a metastable
$\beta$-Bi$_4$I$_4$, and a quick transition to $\alpha$-Bi$_4$I$_4$ is
observed. As a result, the comparison of putative signatures of different
topologies attributed to a specific structural phase should be carefully
considered. The observed phase instability is accompanied by an increase in
iodine vacancies and by a change in the temperature dependence of electrical
resistivity, pointing to native defects as a possible origin of our finding.
Density functional theory (DFT) calculations support the scenario that iodine
vacancies, together with bismuth antisites and interstitials, are among the
defects that are more likely to occur in Bi$_4$I$_4$ during the growth.",2404.16194v1
1998-12-22,Theory of Colossal Magnetoresistance in Doped Manganites,"The exchange interaction of polaronic carriers with localized spins leads to
a ferromagnetic/paramagnetic transition in doped charge-transfer insulators
with strong electron-phonon coupling. The relative strength of the exchange and
electron-phonon interactions determines whether the transition is first or
second order. A giant drop in the number of current carriers during the
transition, which is a consequence of local bound pair (bipolaron) formation in
the paramagnetic phase, is extremely sensitive to an external magnetic field.
Below the critical temperature of the transition, $T_c$, the binding of the
polarons into immobile pairs competes with the ferromagnetic exchange between
polarons and the localized spins on Mn ions, which tends to align the polaron
moments and, therefore, breaks up those pairs. The number of carriers abruptly
increases below $T_c$ leading to a sudden drop in resistivity. We show that the
carrier density collapse describes the colossal magnetoresistance of doped
manganites close to the transition.
  Below $T_c$, transport occurs by polaronic tunneling, whereas at high
temperatures the transport is by hopping processes. The transition is
accompanied by a spike in the specific heat, as experimentally observed. The
gap feature in tunneling spectroscopy is related to the bipolaron binding
energy, which depends on the ion mass. This dependence explains the giant
isotope effect of the magnetization and resistivity upon substitution of
$^{16}$O by $^{18}$O. It is shown also that the localization of polaronic
carriers by disorder {\em cannot} explain the observed huge sensitivity of the
transport properties to the magnetic field in doped manganites.",9812355v1
1999-02-22,Hall-effect in LuNi_2B_2C and YNi_2B_2C borocarbides: a comparative study,"The Hall effect in LuNi_2B_2C and YNi_2B_2C borocarbides has been
investigated in normal and superconducting mixed states. The Hall resistivity
rho_{xy} for both compounds is negative in the normal as well as in the mixed
state and has no sign reversal below T_c typical for high-T_c superconductors.
In the mixed state the behavior of both systems is quite similar. The scaling
relation rho_{xy}\sim\rho_{xx}^\beta (\rho_{xx} is the longitudinal
resistivity) was found with \beta=2.0 and 2.1 for annealed Lu- and Y-based
compounds, respectively. The scaling exponent \beta decreases with increasing
degree of disorder and can be varied by annealing. This is attributed to a
variation of the strength of flux pinning. In the normal state weakly
temperature dependent Hall coefficients were observed for both compounds. A
distinct nonlinearity in the \rho_{xy} dependence on field H was found for
LuNi_2B_2C in the normal state below 40K, accompanied by a large
magnetoresistance (MR) reaching +90% for H=160kOe at T=20K. At the same time
for YNi_2B_2C only linear \rho_{xy}(H) dependences were observed in the normal
state with an approximately three times lower MR value. This difference in the
normal state behavior of the very similar Lu- and Y-based borocarbides seems to
be connected with the difference in the topology of the Fermi surface of these
compounds.",9902299v1
2000-07-21,Effect of γ-irradiation on superconductivity in polycrystalline YBa_{2}Cu_{3}O_{7-δ},"A bulk polycrystalline sample of YBa_{2}Cu_{3}O_{7-\delta} (\delta \approx
0.1) has been irradiated by \gamma-rays with ^{60}Co source. Non-monotonic
behavior of T_c (defined as the temperature at which normal resistance is
halved) with increasing irradiation dose \Phi (up to about 220 MR) is observed:
T_c decreases at low doses (\Phi \leq 50 MR) from initial value (\approx 93 K)
by about 2 K and then rises, forming minimum. At highest doses (\Phi \geq 120
MR) T_c goes down again. The temperature width, \delta T_c, of resistive
transition increases rather sharp with dose below 75 MR and somewhat drops at
higher dose. We believe that this effect is revealed for the first time at
\gamma-irradiation of high-T_c superconductor. The cross section for the
displacement of lattice atoms in YBCO by \gamma-rays due to the Compton process
were calculated, and possible dpa values were estimated. The results obtained
are discussed taking into account that the sample is granular superconductor
and, hence, the observed variations of superconducting properties should be
connected primarily with the influence of \gamma-rays on intergrain Josephson
coupling.",0007345v1
2004-08-13,The effect of oxygen stoichiometry on electrical transport and magnetic properties of La0.9Te0.1MnOy,"The effect of the variation of oxygen content on structural, magnetic and
transport properties in the electron-doped manganites La0.9Te0.1MnOy has been
investigated. All samples show a rhombohedral structure with the space group .
The Curie temperature decreases and the paramagnetic-ferromagnetic (PM-FM)
transition becomes broader with the reduction of oxygen content. The
resistivity of the annealed samples increases slightly with a small reduction
of oxygen content. Further reduction in the oxygen content, the resistivity
maximum increases by six orders of magnitude compared with that of the
as-prepared sample, and the r(T) curves of samples with y = 2.86 and y = 2.83
display the semiconducting behavior () in both high-temperature PM phase and
low-temperature FM phase, which is considered to be related to the appearance
of superexchange ferromagnetism (SFM) and the localization of carriers. The
results are discussed in terms of the combined effects of the increase in the
Mn2+/(Mn2++Mn3+) ratio, the partial destruction of double exchange (DE)
interaction, and the localization of carriers due to the introduction of oxygen
vacancies in the Mn-O-Mn network.",0408302v1
2007-09-14,"Crystallography, magnetic susceptibility, heat capacity, and electrical resistivity of heavy fermion LiV$_2$O$_4$ single crystals grown using a self-flux technique","Magnetically pure spinel compound ${\rm LiV_2O_4}$ is a rare $d$-electron
heavy fermion. Measurements on single crystals are needed to clarify the
mechanism for the heavy fermion behavior in the pure material. In addition, it
is known that small concentrations ($< 1$ mol%) of magnetic defects in the
structure strongly affect the properties, and measurements on single crystals
containing magnetic defects would help to understand the latter behaviors.
Herein, we report flux growth of ${\rm LiV_2O_4}$ and preliminary measurements
to help resolve these questions. The magnetic susceptibility of some as-grown
crystals show a Curie-like upturn at low temperatures, showing the presence of
magnetic defects within the spinel structure. The magnetic defects could be
removed in some of the crystals by annealing them at 700 $^\circ$C\@. A very
high specific heat coefficient $\gamma$ = 450 mJ/(mol K${^2}$\@) was obtained
at a temperature of 1.8 K for a crystal containing a magnetic defect
concentration $n$${\rm_{defect}}$ = 0.5 mol%. A crystal with $n$${\rm
_{defect}}$ = 0.01 mol% showed a residual resistivity ratio of 50.",0709.2387v3
2009-08-26,On the strong impact of doping in the triangular antiferromagnet CuCrO2,"Electronic band structure calculations using the augmented spherical wave
method have been performed for CuCrO2. For this antiferromagnetic (T_N = 24 K)
semiconductor crystallizing in the delafossite structure, it is found that the
valence band maximum is mainly due to the t_2g orbitals of Cr^3+ and that spin
polarization is predicted with 3 mu_B per Cr^3+. The structural
characterizations of CuCr1-xMgxO2 reveal a very limited range of Mg^2+
substitution for Cr^3+ in this series. As soon as x = 0.02, a maximum of 1% Cr
ions substituted by Mg site is measured in the sample. This result is also
consistent with the detection of Mg spinel impurities from X-ray diffraction
for x = 0.01. This explains the saturation of the Mg^2+ effect upon the
electrical resistivity and thermoelectric power observed for x > 0.01. Such a
very weak solubility limit could also be responsible for the discrepancies
found in the literature. Furthermore, the measurements made under magnetic
field (magnetic susceptibility, electrical resistivity and Seebeck coefficient)
support that the Cr^4+ ""holes"", created by the Mg^2+ substitution, in the
matrix of high spin Cr^3+ (S = 3/2) are responsible for the transport
properties of these compounds.",0908.3828v1
2009-12-02,Magnetotransport of La0.70ca0.3-xsrxmno3 (Ag): A Potential Room Temperature Bolometer and Magnetic Sensor,"Here we report the optimized magneto-transport properties of polycrystalline
La0.70Ca0.3-xSrxMnO3 and their composites with Ag. The optimization was carried
out by varying the Sr and Ag contents simultaneously to achieve large
temperature coefficient of resistance (TCR) as well as low field
magneto-resistance (MR) at room temperature. Sharpest paramagnetic
(PM)-ferromagnetic (FM) and insulator-metal (IM) transition is observed in the
vicinity of the room temperature (TC=300 K=TIM) for the composition
La0.70Ca0.20Sr00.10MnO3:Ag0.20. Partial substitution of larger Sr2+ ions at the
Ca2+ ions sites controls the magnitude of the FM and IM transition
temperatures, while the Ag induces the desired sharpness in these transitions.
For the optimized composition, maximum TCR and MR are tuned to room temperature
(300 K) with the former being as high as 9% and the later being 20 and 30
percent at 5 and 10 kOe magnetic fields respectively. Such sharp single peak
(TCR= 9 percent) at room temperature can be used for the bolometric and
infrared detector applications. The achievement of large TCR and low field MR
at T~300K in polycrystalline samples is encouraging and we believe that further
improvements can be achieved in thin films, which, by virtue of their low
conduction noise, are more suitable for device applications.",0912.0347v2
2012-08-16,Gate tunable quantum transport in double layer graphene,"We analyze the effect of screening provided by the additional graphene layer
in double layer graphene heterostructures (DLGs) on transport characteristics
of DLG devices in the metallic regime. The effect of gate-tunable charge
density in the additional layer is two-fold: it provides screening of the
long-range potential of charged defects in the system, and screens out Coulomb
interactions between charge carriers. We find that the efficiency of defect
charge screening is strongly dependent on the concentration and location of
defects within the DLG. In particular, only a moderate suppression of
electron-hole puddles around the Dirac point induced by the high concentration
of remote impurities in the silicon oxide substrate could be achieved. A
stronger effect is found on the elastic relaxation rate due to charged defects
resulting in mobility strongly dependent on the electron denisty in the
additional layer of DLG. We find that the quantum interference correction to
the resistivity of graphene is also strongly affected by screening in DLG. In
particular, the dephasing rate is strongly suppressed by the additional
screening that supresses the amplitude of electron-electron interaction and
reduces the diffusion time that electrons spend in proximity of each other. The
latter effect combined with screening of elastic relaxation rates results in a
peculiar gate tunable weak-localization magnetoresistance and quantum
correction to resistivity. We propose suitable experiments to test our theory
and discuss the possible relevance of our results to exisiting data.",1208.3470v2
2012-10-20,Tunable spin reorientation transition and magnetocaloric effect in Sm0.7-xLaxSr0.3MnO3 series,"We report electrical resistivity, magnetic and magnetocaloric properties in
Sm0.7-xLaxSr0.3MnO3 series for x= 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.65, and
0.7. All the compounds show second order paramagnetic to ferromagnetic
transition at T = Tc which is tunable anywhere between 83 K and 373 K with a
proper choice of the doping level (x). The insulating ferromagnet x= 0
transforms to ferromagnetic metal below Tc for x= 0.1 and the insulator-metal
transition temperature shifts up with increasing x. The magnetization (M)
exhibits an interesting behavior as a function of temperature and doping level.
The field-cooled M(T) of all but x= 0.7 compound show a cusp at a temperature
T* much below Tc. While the Tc increases monotonically with increasing x, T*
increases gradually, attains a maximum value (T*= 137 K) for x= 0.6 and
decreases rapidly thereafter. It is suggested that the decrease of M(T) below
T* is due to ferrimagnetic interaction between Sm(4f) and Mn(3d) sublattices
that promotes spin-reorientation transition of the Mn-sublattice. The observed
anomalous feature in M(T) does not have impact on the dc resistivity. Magnetic
entropy change (delta Sm) was estimated from magnetization isotherms. The sign
of delta Sm is found to change from negative above T* to positive below T*
indicating the coexistence of normal and inverse magnetocaloric effects. delta
Sm is nearly composition independent (-delta Sm is about 1.5 J/Kg K for delta H
= 1 Tesla) and refrigeration capacity lies between 50 and 80 J/kg K for x =
0.1-0.6. The tunability of Curie temperature with a nearly constant delta Sm
value along with high refrigeration capacity makes this series of compounds
interesting for magnetic refrigeration over a wide temperature range.",1210.5595v1
2012-11-27,"Anisotropic Impurity-States, Quasiparticle Scattering and Nematic Transport in Underdoped Ca(Fe1-xCox)2As2","Iron-based high temperature superconductivity develops when the `parent'
antiferromagnetic/orthorhombic phase is suppressed, typically by introduction
of dopant atoms. But their impact on atomic-scale electronic structure, while
in theory quite complex, is unknown experimentally. What is known is that a
strong transport anisotropy with its resistivity maximum along the crystal
b-axis, develops with increasing concentration of dopant atoms; this
`nematicity' vanishes when the `parent' phase disappears near the maximum
superconducting Tc. The interplay between the electronic structure surrounding
each dopant atom, quasiparticle scattering therefrom, and the transport
nematicity has therefore become a pivotal focus of research into these
materials. Here, by directly visualizing the atomic-scale electronic structure,
we show that substituting Co for Fe atoms in underdoped Ca(Fe1-xCox)2As2
generates a dense population of identical anisotropic impurity states. Each is
~8 Fe-Fe unit cells in length, and all are distributed randomly but aligned
with the antiferromagnetic a-axis. By imaging their surrounding interference
patterns, we further demonstrate that these impurity states scatter
quasiparticles in a highly anisotropic manner, with the maximum scattering rate
concentrated along the b-axis. These data provide direct support for the recent
proposals that it is primarily anisotropic scattering by dopant-induced
impurity states that generates the transport nematicity; they also yield simple
explanations for the enhancement of the nematicity proportional to the dopant
density and for the occurrence of the highest resistivity along the b-axis.",1211.6454v1
2013-05-16,Different routes to pressure-induced volume collapse transitions in gadolinium and terbium metals,"The sudden decrease in molar volume exhibited by most lanthanides under high
pressure is often attributed to changes in the degree of localization of their
4f-electrons. We give evidence, based on electrical resistivity measurements of
dilute Y(Gd) and Y(Tb) alloys to 120 GPa, that the volume collapse transitions
in Gd and Tb metals have different origins, despite their being neighbors in
the periodic table. Remarkably, the change under pressure in the magnetic state
of isolated Pr or Tb impurity ions in the nonmagnetic Y host appears to closely
mirror corresponding changes in pure Pr or Tb metals. The collapse in Tb
appears to be driven by an enhanced negative exchange interaction between 4f
and conduction electrons under pressure (Kondo resonance) which, in the case of
Y(Tb), dramatically alters the superconducting properties of the Y host, much
like previously found for Y(Pr). In Gd our resistivity measurements suggest
that a Kondo resonance is not the main driver for its volume collapse. X-ray
absorption and emission spectroscopies clearly show that 4f local moments
remain largely intact across both volume collapse transitions ruling out 4f
band formation (delocalization) and valence transition models as possible
drivers. The results highlight the richness of behavior behind the volume
collapse transition in lanthanides and demonstrate the stability of the 4f
level against band formation to extreme pressure.",1305.3852v4
2014-04-09,Quantum transport evidence for a three-dimensional Dirac semimetal phase in Cd3As2,"The material termed three-dimensional (3D) Dirac semimetal has attracted
great interests recently, since it is an electronic analogue to two-dimensional
graphene. Starting from this novel phase, various topologically distinct phases
may be obtained, such as topological insulator, Weyl semimetal, quantum spin
Hall insulator, and topological superconductor. Soon after the theoretical
predictions, the angle-resolve photoemission spectroscopy and scanning
tunnelling microscopy experiments gave evidences for 3D Dirac points in Na3Bi
and Cd3As2. Here we report quantum transport properties of Cd3As2 single
crystal in magnetic field. A sizable linear quantum magnetoresistance is
observed at high temperature. With decreasing temperature, the Shubnikov-de
Haas oscillations appear in both longitudinal resistance Rxx and transverse
Hall resistance Rxy. From the strong oscillatory component \Delta Rxx, the
linear dependence of Landau index n on 1/B gives an n-axis intercept 0.58. Our
quantum transport result clearly reveals a nontrivial \pi\ Berry's phase, thus
provides strong bulk evidence for a 3D Dirac semimetal phase in Cd3As2. This
may open new perspectives for its use in electronic devices.",1404.2557v3
2014-04-15,Formation of a topological non-Fermi liquid in MnSi,"Fermi liquid theory provides a remarkably powerful framework for the
description of the conduction electrons in metals and their ordering phenomena,
such as superconductivity, ferromagnetism, and spin- and charge-density-wave
order. A different class of ordering phenomena of great interest concerns spin
configurations that are topologically protected, that is, their topology can be
destroyed only by forcing the average magnetization locally to zero. Examples
of such configurations are hedgehogs (points at which all spins are either
pointing inwards or outwards) or vortices. A central question concerns the
nature of the metallic state in the presence of such topologically distinct
spin textures. Here we report a high-pressure study of the metallic state at
the border of the skyrmion lattice in MnSi, which represents a new form of
magnetic order composed of topologically non-trivial vortices. When long-range
magnetic order is suppressed under pressure, the key characteristic of the
skyrmion lattice - that is, the topological Hall signal due to the emergent
magnetic flux associated with their topological winding - is unaffected in sign
or magnitude and becomes an important characteristic of the metallic state. The
regime of the topological Hall signal in temperature, pressure and magnetic
field coincides thereby with the exceptionally extended regime of a pronounced
non-Fermi-liquid resistivity. The observation of this topological Hall signal
in the regime of the NFL resistivity suggests empirically that spin
correlations with non-trivial topological character may drive a breakdown of
Fermi liquid theory in pure metals.",1404.4050v1
2014-09-12,Observation of topological surface state quantum Hall effect in an intrinsic three-dimensional topological insulator,"A three-dimensional (3D) topological insulator (TI) is a quantum state of
matter with a gapped insulating bulk yet a conducting surface hosting
topologically-protected gapless surface states. One of the most distinct
electronic transport signatures predicted for such topological surface states
(TSS) is a well-defined half-integer quantum Hall effect (QHE) in a magnetic
field, where the surface Hall conductivities become quantized in units of
(1/2)e2/h (e being the electron charge, h the Planck constant) concomitant with
vanishing resistance. Here, we observe well-developed QHE arising from TSS in
an intrinsic TI of BiSbTeSe2. Our samples exhibit surface dominated conduction
even close to room temperature, while the bulk conduction is negligible. At low
temperatures and high magnetic fields perpendicular to the top and bottom
surfaces, we observe well-developed integer quantized Hall plateaus, where the
two parallel surfaces each contributing a half integer e2/h quantized Hall (QH)
conductance, accompanied by vanishing longitudinal resistance. When the bottom
surface is gated to match the top surface in carrier density, only odd integer
QH plateaus are observed, representing a half-integer QHE of two degenerate
Dirac gases. This system provides an excellent platform to pursue a plethora of
exotic physics and novel device applications predicted for TIs, ranging from
magnetic monopoles and Majorana particles to dissipationless electronics and
fault-tolerant quantum computers.",1409.3778v2
2014-12-23,Magnetic and structural transitions in La$_{0.4}$Na$_{0.6}$Fe$_2$As$_2$ single crystals,"La$_{0.4}$Na$_{0.6}$Fe$_2$As$_2$ single crystals have been grown out of an
NaAs flux in an alumina crucible and characterized by measuring magnetic
susceptibility, electrical resistivity, specific heat, as well as single
crystal x-ray and neutron diffraction. La$_{0.4}$Na$_{0.6}$Fe$_2$As$_2$ single
crystals show a structural phase transition from a high temperature tetragonal
phase to a low-temperature orthorhombic phase at T$_s$\,=\,125\,K. This
structural transition is accompanied by an anomaly in the temperature
dependence of electrical resistivity, anisotropic magnetic susceptibility, and
specific heat. Concomitant with the structural phase transition, the Fe moments
order along the \emph{a} direction with an ordered moment of
0.7(1)\,$\mu_{\textup{B}}$ at \emph{T}\,=\,5 K. The low temperature stripe
antiferromagnetic structure is the same as that in other
\emph{A}Fe$_{2}$As$_{2}$ (\emph{A}\,=\,Ca, Sr, Ba) compounds.
La$_{0.5-x}$Na$_{0.5+x}$Fe$_2$As$_2$ provides a new material platform for the
study of iron-based superconductors where the electron-hole asymmetry could be
studied by simply varying La/Na ratio.",1412.7447v1
2015-01-08,Structure and bonding in amorphous iron carbide thin films,"We investigate the amorphous structure, chemical bonding, and electrical
properties of magnetron sputtered Fe1-xCx (0.21<x<0.72) thin films. X-ray,
electron diffraction and transmission electron microscopy show that the Fe1-xCx
films are amorphous nanocomposites, consisting of a two-phase domain structure
with Fe-rich carbidic FeCy, and a carbon-rich matrix. Pair distribution
function analysis indicates a close-range order similar to those of crystalline
Fe3C carbides in all films with additional graphene-like structures at high
carbon content (71.8 at% C). From X-ray photoelectron spectroscopy
measurements, we find that the amorphous carbidic phase has a composition of
15-25 at% carbon that slightly increases with total carbon content. X-ray
absorption spectra exhibit increasing number of unoccupied 3d states and
decreasing number of C 2p states as a function of carbon content. These changes
signify a systematic redistribution in orbital occupation due to
charge-transfer effects at the domain-size dependent carbide/matrix interfaces.
Four-point probe resistivity of the Fe1-xCx films increases exponentially with
carbon content from 200 mu-Ohm-cm (x=0.21) to 1200 mu-Ohm-cm (x=0.72), and is
found to depend on the total carbon content rather than the composition of the
carbide. Our findings open new possibilities for modifying the resistivity of
amorphous thin film coatings based on transition metal carbides by control of
amorphous domain structures.",1501.01839v1
2015-09-09,Controlling the Electrical Properties of Undoped and Ta-doped TiO2 Polycrystalline Films via Ultra-Fast Annealing Treatments,"We present a study on the crystallization process of undoped and Ta doped
TiO2 amorphous thin films. In particular, the effect of ultra-fast annealing
treatments in environments characterized by different oxygen concentrations is
investigated via in-situ resistance measurements. The accurate examination of
the key parameters involved in this process allows us to reduce the time needed
to obtain highly conducting and transparent polycrystalline thin films
(resistivity about $6 \times 10^{-4}$ {\Omega}cm, mean transmittance in the
visible range about $81\%$) to just 5 minutes (with respect to the 180 minutes
required for a standard vacuum annealing treatment) in nitrogen atmosphere (20
ppm oxygen concentration) at ambient pressure. Experimental evidence of
superficial oxygen incorporation in the thin films and its detrimental role for
the conductivity are obtained by employing different concentrations of
traceable 18O isotopes during ultra-fast annealing treatments. The results are
discussed in view of the possible implementation of the ultra-fast annealing
process for TiO2-based transparent conducting oxides as well as electron
selective layers in solar cell devices; taking advantage of the high control of
the ultra-fast crystallization processes which has been achieved, these two
functional layers are shown to be obtainable from the crystallization of a
single homogeneous thin film.",1509.02744v1
2016-10-14,rHARM: Accretion and Ejection in Resistive GR-MHD,"Turbulent magnetic diffusivity plays an important role for accretion disks
and the launching of disk winds. We have implemented magnetic diffusivity,
respective resistivity in the general relativistic MHD code HARM. This paper
describes the theoretical background of our implementation, its numerical
realization, our numerical tests and preliminary applications. The test
simulations of the new code rHARM are compared with an analytic solution of the
diffusion equation and a classical shock tube problem. We have further
investigated the evolution of the magneto-rotational instability (MRI) in tori
around black holes for a range of magnetic diffusivities. We find indication
for a critical magnetic diffusivity (for our setup) beyond which no MRI
develops in the linear regime and for which accretion of torus material to the
black hole is delayed. Preliminary simulations of magnetically diffusive thin
accretion disks around Schwarzschild black holes that are threaded by a
large-scale poloidal magnetic field show the launching of disk winds with mass
fluxes of about 50% of the accretion rate. The disk magnetic diffusivity allows
for efficient disk accretion that replenishes the mass reservoir of the inner
disk area and thus allows for long-term simulations of wind launching for more
than 5000 time units.",1610.04445v1
2016-10-26,Doping of Ga in antiferromagnetic semiconductor alpha-Cr2O3oxide and its effects on modified magnetic and electronic properties,"The samples of Ga doped Cr2O3 oxide have been prepared using chemical
co-precipitation route. X-ray diffraction pattern and Raman spectra have
confirmed rhombohedral crystal structure with space group R3-C. Magnetic
measurement has indicated the dilution of antiferromagnetic (AFM) spin order in
Ga doped alpha-Cr2O3 system oxide, where the AFM transition temperature of bulk
alpha-Cr2O3 oxide at about 320 K has been suppressed and ferrimagnetic behavior
is observed from the analysis of the temperature dependence of magnetization
data below 350 K. Apart from Ga doping effect, the spin freezing (50 K-70 K)
and superparamagnetic behavior of the surface spins at lower temperatures,
typically below 50 K, have been exhibited due to nano-sized grains of the
samples. All the samples showed non-linear current-voltage (I-V)
characteristics. However, I-V characteristics of the Ga doped samples are
remarkably different from alpha-Cr2O3 sample. The I-V curves of Ga doped
samples have exhibited many unique electronic properties, e.g., bi-stable (low
resistance- LR and high resistance-HR) electronic states and negative
differential resistance (NDR). Optical absorption spectra revealed three
electronic transitions in the samples associated with band gap energy at about
2.67-2.81 eV, 1.91-2.11 eV, 1.28-1.35 eV, respectively.",1610.08426v1
2018-02-21,Multi-Terminal Memtransistors from Polycrystalline Monolayer MoS2,"In the last decade, a 2-terminal passive circuit element called a memristor
has been developed for non-volatile resistive random access memory and has more
recently shown promise for neuromorphic computing. Compared to flash memory,
memristors have higher endurance, multi-bit data storage, and faster read/write
times. However, although 2-terminal memristors have demonstrated basic neural
functions, synapses in the human brain outnumber neurons by more than a factor
of 1000, which implies that multiterminal memristors are needed to perform
complex functions such as heterosynaptic plasticity. Previous attempts to move
beyond 2-terminal memristors include the 3-terminal Widrow-Hoff memistor and
field-effect transistors with nanoionic gates or floating gates, albeit without
memristive switching in the transistor. Here, we report the scalable
experimental realization of a multi-terminal hybrid memristor and transistor
(i.e., memtransistor) using polycrystalline monolayer MoS2. Two-dimensional
(2D) MoS2 memtransistors show gate tunability in individual states by 4 orders
of magnitude in addition to large switching ratios with high cycling endurance
and long-term retention of states. In addition to conventional neural learning
behavior of long-term potentiation/depression, 6-terminal MoS2 memtransistors
possess gate-tunable heterosynaptic functionality that is not achievable using
2-terminal memristors. For example, the conductance between a pair of two
floating electrodes (pre-synaptic and post-synaptic neurons) is varied by 10X
by applying voltage pulses to modulatory terminals. In situ scanning probe
microscopy, cryogenic charge transport measurements, and device modeling reveal
that bias-induced MoS2 defect motion drives resistive switching by dynamically
varying Schottky barrier heights.",1802.07783v1
2019-02-20,Effect of the temperature and magnetic field induced martensitic transformation in bulk Fe$_{45}$Mn$_{26}$Ga$_{29}$ alloy on its electronic structure and physical properties,"Effect of the temperature and magnetic field induced martensitic
transformation (MT) on the electronic structure and some physical properties of
bulk Fe$_{45.2}$Mn$_{25.9}$Ga$_{28.9}$ Heusler alloy has been investigated.
{According to the experimental results of DSC, magnetic and transport
measurements direct and reverse martensitic transformation without external
magnetic field takes place within 194 $\leq T \leq$ 328 K temperature range
with a hysteresis up to $\Delta T \approx$ 100 K defined as $\Delta T$ =
$A_{f,s}$ - $M_{s,f}$, where $A_{f,s}$ and $M_{s,f}$ are the critical
temperatures of direct and reverse martensitic transformation. External
magnetic field of $\mu_{0}H$ = 5 T causes a high-temperature shift of MT
temperatures.} MT from parent austenite L2$_{1}$ phase to martensitic
tetragonally distorted L2$_{1}$ one (i. e. to L1$_{0}$) causes significant
changes in the electronic structure of alloy, a drastic increase in alloy
magnetization, a decrease in the alloy resistivity, and a reversal of the sign
of the temperature coefficient of resistivity from negative to positive. At the
same time experimentally determined optical properties of
Fe$_{45.6}$Mn$_{25.9}$Ga$_{28.9}$ Heusler alloy in austenitic and martensitic
states look visually rather similar being noticeable different in microscopic
nature as can be concluded from first-principle calculations. Experimentally
observed changes in the physical properties of the alloy are discussed in terms
of the electronic structures of an austenite and martensite phases.",1902.07462v1
2020-02-04,Single-defect Memristor in MoS$_2$ Atomic-layer,"Non-volatile resistive switching, also known as memristor effect in two
terminal devices, has emerged as one of the most important components in the
ongoing development of high-density information storage, brain-inspired
computing, and reconfigurable systems. Recently, the unexpected discovery of
memristor effect in atomic monolayers of transitional metal dichalcogenide
sandwich structures has added a new dimension of interest owing to the
prospects of size scaling and the associated benefits. However, the origin of
the switching mechanism in atomic sheets remains uncertain. Here, using
monolayer MoS$_2$ as a model system, atomistic imaging and spectroscopy reveal
that metal substitution into sulfur vacancy results in a non-volatile change in
resistance. The experimental observations are corroborated by computational
studies of defect structures and electronic states. These remarkable findings
provide an atomistic understanding on the non-volatile switching mechanism and
open a new direction in precision defect engineering, down to a single defect,
for achieving optimum performance metrics including memory density, switching
energy, speed, and reliability using atomic nanomaterials.",2002.01574v1
2020-04-07,Temperature dependence of transport mechanisms in organic multiferroic tunnel junctions,"Organic multiferroic tunnel junctions (OMFTJs) with multi-resistance states
have been proposed and drawn intensive interests due to their potential
applications, for examples of memristor and spintronics based synapse devices.
The ferroelectric control of spin-polarization at ferromagnet
(FM)/ferroelectric organic (FE-Org) interface by electrically switching the
ferroelectric polarization of the FE-Org has been recently realized. However,
there is still a lack of understanding of the transport properties in OMFTJs,
especially the interplay between the ferroelectric domain structure in the
organic barrier and the spin-polarized electron tunneling through the barrier.
Here, we report on a systematic study of the temperature dependent transport
behavior in La0.6Sr0.4MnO3/PVDF/Co OMFTJs. It is found that the thermal
fluctuation of the ferroelectric domains plays an important role on the
transport properties. When T>120K, the opposite temperature dependence of
resistance for in up and down ferroelectric polarization states results in a
rapid diminishing of tunneling electroresistance (TER). These results
contribute to the understanding of the transport properties for designing high
performance OMFTJs for memristor and spintronics applications.",2004.03284v1
2020-09-16,"High Field Magneto-Transport of Mixed Topological Insulators Bi2Se3-xTex (x = 0, 1, 2 & 3)","The article comprises structural, microstructural, and physical properties
analysis of Bi2Se3-xTex (x= 0, 1, 2 and 3) mixed topological insulator (MTI)
single crystals. All the crystals were grown through a well-optimized
solid-state reaction route via the self-flux method. These MTI are well
characterized through XRD (X-ray Diffraction), SEM (Scanning Electron
Microscopy), EDAX (Energy Dispersive spectroscopy), and thereby, the physical
properties are analyzed through the RT (Resistance vs temperature) down to 10K
as well as the magneto-resistance (MR) measurements (at 5K) in a magnetic field
of up to 10 Tesla. The MR drastically varies from x=0 to x=3 in MTI, from a
huge 400 percent, it goes down to 20 percent and 5 percent and eventually back
to 315 percent. This fascinated behaviour of MR is explained in this article
through HLN (Hikami-Larkin-Nagaoka) equation and an additional term. This
article not only proposed the mesmerizing behavior of MR in MTI but also
explains the reason through competing WAL (Weak Anti-Localization) and WL (Weak
Localization) conduction processes.",2009.07757v1
2016-03-05,Development and characterization of single gap glass RPC,"India-based Neutrino Observatory (INO) facility is going to have a 50 kton
magnetized Iron CALorimeter (ICAL) detector for precision measurements of
neutrino oscillations using atmospheric neutrinos. The proposed ICAL detector
will be a stack of magnetized iron plates (acting as target material)
interleaved with glass Resistive Plate Chambers (RPCs) as the active detector
elements. An RPC is a gaseous detector made up of two parallel electrode plates
having high bulk resistivity like that of float glass and bakelite. For the
ICAL detector, glass is preferred over bakelite as it does not need any kind of
surface treatment to achieve better surface uniformity and also the cost of
associated electronics is reduced. Under the detector R&D efforts for the
proposed glass RPC detector, a few glass RPCs of 1m X 1m dimension are
fabricated procuring glass of ~ 2 mm thickness from one of the Indian glass
manufacturers (Asahi). In the present paper, we report the characterization of
RPC based on leakage current study, muon detection efficiency and noise rate
studies with varying gas compositions.",1603.01719v5
2017-08-08,High Surface Conductivity of Fermi Arc Electrons in Weyl semimetals,"Weyl semimetals (WSMs), a new type of topological condensed matter, are
currently attracting great interest due to their unusual electronic states and
intriguing transport properties such as chiral anomaly induced negative
magnetoresistance, a semi--quantized anomalous Hall effect and the debated
chiral magnetic effect. These systems are close cousins of topological
insulators (TIs) which are known for their disorder tolerant surface states.
Similarly, WSMs exhibit unique topologically protected Fermi arcs surface
states. Here we analyze electron--phonon scattering, a primary source of
resistivity in metals at finite temperatures, as a function of the shape of the
Fermi arc where we find that the impact on surface transport is significantly
dependent on the arc curvature and disappears in the limit of a straight arc.
Next, we discuss the effect of strong surface disorder on the resistivity by
numerically simulating a tight binding model with the presence of quenched
surface vacancies using the Coherent Potential Approximation (CPA) and
Kubo--Greenwood formalism. We find that the limit of a straight arc geometry is
remarkably disorder tolerant, producing surface conductivity that is a factor
of 50 larger of a comparable set up with surface states of TI. Finally, a
simulation of the effects of surface vacancies on TaAs is presented,
illustrating the disorder tolerance of the topological surface states in a
recently discovered WSM material.",1708.02415v1
2019-08-21,Half-metallic ferromagnetism and Ru-induced localization in quaternary Heusler alloy CoRuMnSi,"We report a combined theoretical and experimental investigation of
half-metallic ferromagnetism in equiatomic quaternary Heusler alloy CoRuMnSi.
Room temperature XRD analysis reveals that the alloy crystallizes in L21
disorder instead of pristine Y-type structure due to 50% swap disorder between
the tetrahedral sites, i.e., Co and Ru atoms. Magnetization measurements reveal
a net magnetization of 4 $\mu_B$ with Curie temperature of ~780 K. Resistivity
measurement reveals the presence of localization effect below 35 K while above
100 K, a linear dependence is observed. Resistivity behavior indicates the
absence of single magnon scattering, which indirectly supports the
half-metallic nature. The majority spin band near the Fermi level clearly
indicates the overlap of flat eg bands with sharply varying conduction bands
that are responsible for the localization. In-depth analysis of the projected
atomic d-orbital character of band structure reveals unusual bonding, giving
rise to the flat eg bands purely arising out of Ru ions. Co-Ru swap disorder
calculations indicate the robustness of half-metallic nature, even when the
structure changes from Y-type to L21-type, with no major change in the net
magnetization of the system. Thus, robust half-metallic nature, stable
structure, and high Curie temperature make this alloy quite a promising
candidate to be used as a source of highly spin-polarized currents in
spintronic applications.",1908.07804v1
2012-03-10,How local is the Phantom Force?,"The phantom force is an apparently repulsive force, which can dominate the
atomic contrast of an AFM image when a tunneling current is present. We
described this effect with a simple resistive model, in which the tunneling
current causes a voltage drop at the sample area underneath the probe tip.
Because tunneling is a highly local process, the areal current density is quite
high, which leads to an appreciable local voltage drop that in turn changes the
electrostatic attraction between tip and sample. However, Si(111)-7\times7 has
a metallic surface-state and it might be proposed that electrons should instead
propagate along the surface-state, as through a thin metal film on a
semiconducting surface, before propagating into the bulk. In this article, we
investigate the role of the metallic surface-state on the phantom force. First,
we show that the phantom force can be observed on H/Si(100), a surface without
a metallic surface-state. Furthermore, we investigate the influence of the
surface-state on our phantom force observations of Si(111)-7\times7 by
analyzing the influence of the macroscopic tip radius R on the strength of the
phantom force, where a noticeable effect would be expected if the local voltage
drop would reach extensions comparable to the tip radius. We conclude that a
metallic surface-state does not suppress the phantom force, but that the local
resistance Rs has a strong effect on the magnitude of the phantom force.",1203.2258v1
2012-06-14,Influence of the substrate and precursor on the magnetic and magneto-transport properties in magnetite films,"We have investigated the magnetic and transport properties of nanoscaled
Fe3O4 films obtained from Chemical Vapor Deposition (CVD) technique using
[FeIIFe2III(OBut)8] and [Fe2III(OBut)6] precursors. Samples were deposited on
different substrates (i.e., MgO (001), MgAl2O4 (001) and Al2O3 (0001)) with
thicknesses varying from 50 to 350 nm. Atomic Force Microscopy analysis
indicated a granular nature of the samples, irrespective of the synthesis
conditions (precursor and deposition temperature, Tpre) and substrate. Despite
the similar morphology of the films, magnetic and transport properties were
found to depend on the precursor used for deposition. Using [FeIIFe2III(OBut)8]
as precursor resulted in lower resistivity, higher MS and a sharper
magnetization decrease at the Verwey transition (TV). The temperature
dependence of resistivity was found to depend on the precursor and Tpre. We
found that the transport is dominated by the density of antiferromagnetic
antiphase boundaries (AF-APB's) when [FeIIFe2III(OBut)8] precursor and Tpre =
363 K are used. On the other hand, grain boundary-scattering seems to be the
main mechanism when [Fe2III(OBut)6] is used. The Magnetoresistance (MR(H))
displayed an approximate linear behavior in the high field regime (H > 796
kA/m), with a maximum value at room-temperature of \sim2-3% for H = 1592 kA/m,
irrespective from the transport mechanism.",1206.3158v1
2015-07-23,Percolative Metal-Insulator Transition in LaMnO$_3$,"We show that the pressure-induced metal-insulator transition (MIT) in
LaMnO$_3$ is fundamentally different from the Mott-Hubbard transition and is
percolative in nature, with the measured resistivity obeying the percolation
scaling laws. Using the Gutzwiller method to treat correlation effects in a
model Hamiltonian that includes both Coulomb and Jahn-Teller interactions, we
show, One, that the MIT is driven by a competition between electronic
correlation and the electron-lattice interaction, an issue that has been long
debated, and Two, that with compressed volume, the system has a tendency
towards phase separation into insulating and metallic regions, consisting,
respectively, of Jahn-Teller distorted and undistorted octahedra. This tendency
manifests itself in a mixed phase of intermixed insulating and metallic regions
in the experiment. Conduction in the mixed phase occurs by percolation and the
MIT occurs when the metallic volume fraction, steadily increasing with
pressure, exceeds the percolation threshold $v_c \approx 0.29$. Measured
high-pressure resistivity follows the percolation scaling laws quite well,
establishing the percolative nature of conduction, and the temperature
dependence follows the Efros-Shklovskii variable-range hopping behavior for
granular materials.",1507.06592v2
2019-06-20,On the interaction of precipitates and tensile twins in magnesium alloys,"Although magnesium alloys deform extensively through shear strains and
crystallographic re-orientations associated with the growth of twins, little is
known about the strengthening mechanisms associated with this deformation mode.
A crystal plasticity based phase field model for twinning is employed in this
work to study the strengthening mechanisms resulting from the interaction
between twin growth and precipitates. The full-field simulations reveal in
great detail the pinning and de-pinning of a twin boundary at individual
precipitates, resulting in a maximum resistance to twin growth when the
precipitate is partially embedded in the twin. Furthermore, statistically
representative precipitate distributions are used to systematically investigate
the influence of key microstructural parameters such as precipitate
orientation, volume fraction, size, and aspect ratio on the resistance to twin
growth. The results indicate that the effective critical resolved shear stress
(CRSS) for twin growth increases linearly with precipitate volume fraction and
aspect ratio. For a constant volume fraction of precipitates, reduction of the
precipitate size below a critical level produces a strong increase in the CRSS
due to the Orowan-like strengthening mechanism between the twin interface and
precipitates. Above this level the CRSS is size independent. The results are
quantitatively and qualitatively comparable with experimental measurements and
predictions of mean-field strengthening models. Based on the results,
guidelines for the design of high strength magnesium alloys are discussed.",1906.08736v2
2020-01-15,Ohmic contacts on n-type and p-type cubic silicon carbide (3C-SiC) grown on silicon,"This paper is a report on Ohmic contacts on n-type and p-type type cubic
silicon carbide (3C-SiC) layers grown on silicon substrates. In particular, the
morphological, electrical and structural properties of annealed Ni and Ti/Al/Ni
contacts has been studied employing several characterization techniques. Ni
films annealed at 950{\deg}C form Ohmic contacts on moderately n-type doped
3C-SiC (ND ~ 1x1017cm-3), with a specific contact resistance of 3.7x10-3
{\Omega}cm2. The main phase formed upon annealing in this contact was nickel
silicide (Ni2Si), with randomly dispersed carbon in the reacted layer. In the
case of a p-type 3C-SiC with a high doping level (NA ~ 5x1019cm-3), Ti/Al/Ni
contacts were preferable to Ni ones, as they gave much lower values of the
specific contact resistance (1.8x10-5 {\Omega}cm2). Here, an Al3Ni2 layer was
formed in the uppermost part of the contact, while TiC was detected at the
interface. For this system, a temperature dependent electrical characterization
allowed to establish that the thermionic field emission rules the current
transport at the interface. All these results can be useful for the further
development of a devices technology based on the 3C-SiC polytype.",2001.05159v4
2020-01-22,Correlation between crystal purity and the charge density wave in 1$T$-VSe$_2$,"We examine the charge density wave (CDW) properties of 1$T$-VSe$_{2}$
crystals grown by chemical vapour transport (CVT) under varying conditions.
Specifically, we find that by lowering the growth temperature ($T_{\mathrm{g}}$
$<$ 630$^{\circ}$C), there is a significant increase in both the CDW transition
temperature and the residual resistance ratio (RRR) obtained from electrical
transport measurements. Using x-ray photoelectron spectroscopy (XPS), we
correlate the observed CDW properties with stoichiometry and the nature of
defects. In addition, we have optimized a method to grow ultra-high purity
1$T$-VSe$_{2}$ crystals with a CDW transition temperature, $T_{\mathrm{CDW}}$ =
(112.7 $\pm$ 0.8) K and maximum residual resistance ratio (RRR) $\approx$ 49,
which is the highest reported thus far. This work highlights the sensitivity of
the CDW in 1$T$-VSe$_{2}$ to defects and overall stoichiometry, and the
importance of controlling the crystal growth conditions of strongly-correlated
transition metal dichalcogenides.",2001.08020v2
2020-06-29,Tuning Chern Number in Quantum Anomalous Hall Insulators,"The quantum anomalous Hall (QAH) state is a two-dimensional topological
insulating state that has quantized Hall resistance of h/Ce2 and vanishing
longitudinal resistance under zero magnetic field, where C is called the Chern
number. The QAH effect has been realized in magnetic topological insulators
(TIs) and magic-angle twisted bilayer graphene. Despite considerable
experimental efforts, the zero magnetic field QAH effect has so far been
realized only for C = 1. Here we used molecular beam epitaxy to fabricate
magnetic TI multilayers and realized the QAH effect with tunable Chern number C
up to 5. The Chern number of these QAH insulators is tuned by varying the
magnetic doping concentration or the thickness of the interior magnetic TI
layers in the multilayer samples. A theoretical model is developed to
understand our experimental observations and establish phase diagrams for QAH
insulators with tunable Chern numbers. The realization of QAH insulators with
high tunable Chern numbers facilitates the potential applications of
dissipationless chiral edge currents in energy-efficient electronic devices and
opens opportunities for developing multi-channel quantum computing and
higher-capacity chiral circuit interconnects.",2006.16215v3
2021-02-08,"Structural, magnetic, thermodynamic and electrical transport properties of a new compound $\mbox{Pr}_2\mbox{Rh}_{2}\mbox{Ga}$","A new ternary intermetallic compound $\mathrm{Pr_2Rh_2Ga}$ was synthesized by
arc-melting and was characterized by powder X-ray diffraction (PXRD),
magnetization, heat capacity $\mathrm{C}_p(\textit{T})$, and electrical
resistivity $\rho(T)$ measurements. PXRD patterns revealed that
$\mathrm{Pr_2Rh_2Ga}$ crystallizes in the $\rm{La_2Ni_3}$-type of orthorhombic
structure with the space group $Cmca$. The temperature variation of magnetic
susceptibility, $\mathrm {C}_p(\textit{T})$ and $\rho(T)$ confirmed that
$\mathrm{Pr_2Rh_2Ga}$ exhibits a ferromagnetic behavior with the transition
temperature of 18 K. The estimated Sommerfeld coefficient $\gamma$ = 640
mJ/($\mathrm{Pr.mole.K^2}$) from the $\mathrm {C}_p(\textit{T})$ results in the
paramagnetic region just above $T_{C}$~was large in comparison to ordinary
metals. In the paramagnetic region $\rho(T)$ data showed a metallic behavior
characteristic of electron - phonon scattering. The maximum negative
magneto-resistance at high field occurs in the region near the magnetic phase
transition temperature. The maximum value of magnetic entropy change ($\rm
-\Delta \textit{S}_{M}$) and adiabatic temperature change ($\rm \Delta
\textit{T}_{ad}$) are $\rm8.2~J/kg.K$ and $\rm3.6~K$, respectively, around the
transition temperature for the change of magnetic field 0-9 T. The calculated
refrigerant capacity is $\rm70~J/kg$, and $\rm135~J/kg$ for a change of
magnetic field 0-5 T and 0-9 T, respectively. Arrott plot derived from
isothermal magnetization and the universal scaling plot by normalizing $\rm
-\Delta \textit{S}_{M}$ confirm that the compound undergoes a second order
ferromagnetic to paramagnetic phase transition.",2102.04106v2
2021-10-09,Topologically Protected Ferroelectric Domain Wall Memory with Large Readout Current,"The discovery and precise manipulation of atomic-size conductive
ferroelectric domain defects, such as geometrically confined walls, offer new
opportunities for a wide range of prospective electronic devices, and the
so-called walltronics is emerging consequently. Here we demonstrate the highly
stable and fatigue-resistant nonvolatile ferroelectric memory device based on
deterministic creation and erasure of conductive domain wall geometrically
confined inside a topological domain structure. By introducing a pair of
delicately designed co-axial electrodes onto the epitaxial BiFeO3 film, one can
easily create quadrant center topological polar domain structure. More
importantly, a reversible switching of such center topological domain structure
between the convergent state with highly conductive confined wall and the
divergent state with insulating confined wall can be realized, hence resulting
in an apparent resistance change with a large On/Off ratio > 104 and a
technically preferred readout current (up to 40 nA). Owing to the topological
robustness of the center domain structure, the device exhibits the excellent
restoration repeatability over 106 cycles and a long retention over 12 days (>
106 s). This work demonstrates a good example for implementing the exotic polar
topologies in high-performance nanoscale devices, and would spur more interest
in exploring the rich emerging applications of these exotic topological states.",2110.04530v1
2021-12-05,Insights into Cold Source MOSFETs with Sub-60 mV/decade and Negative Differential Resistance Effect,"To extend the Moores law in the 5 nm node, a large number of two dimensional
(2D) materials and devices have been thoroughly researched, among which the
cold metals 2H MS2 (M = Nb, Ta) with unique band structures are expected to
achieve the sub-60 mV/dec subthreshold swing (SS). The studied cold metal
field-effect transistors (CM-FETs) based on the cold metals are capable to
fulfill the high-performance (HP) and low-dissipation (LP) goals
simultaneously, as required by the International Technology Roadmap for
Semiconductors (ITRS). Moreover, gaps of cold metals also enable the CM-FETs to
realize negative differential resistance (NDR) effect. Owing to the wide
transmission path in the broken gap structure of NbS2/MoS2 heterojunction, the
recording 4110 A/m peak current, several orders of magnitude higher than the
tunneling current of the Esaki diode, is achieved by NbS2/MoS2 CM-FET. The
largest peak-valley ratio (PVR) is obtained by TaS2/MoS2 CM-FET with VGS = -1V
at room temperature. Our results claim that the superior on-state current, SS,
cut-off frequency and NDR effect can be obtained by CM-FETs simultaneously. The
study of CM-FETs provides a practicable solution for state-of-the-art logic
device in sub 5 nm node for both more Moore roadmap and more than Moore roadmap
applications.",2112.02578v1
2021-12-13,Tunneling Magnetoresistance in Noncollinear Antiferromagnetic Tunnel Junctions,"Antiferromagnetic (AFM) spintronics has emerged as a subfield of spintronics
driven by the advantages of antiferromagnets producing no stray fields and
exhibiting ultrafast magnetization dynamics. The efficient method to detect an
AFM order parameter, known as the N\'eel vector, by electric means is critical
to realize concepts of AFM spintronics. Here, we demonstrate that non-collinear
AFM metals, such as Mn3Sn, exhibit a momentum dependent spin polarization which
can be exploited in AFM tunnel junctions to detect the N\'eel vector. Using
first-principles calculations based on density functional theory, we predict a
tunneling magnetoresistance (TMR) effect as high as 300% in AFM tunnel
junctions with Mn3Sn electrodes, where the junction resistance depends on the
relative orientation of their N\'eel vectors and exhibits four non-volatile
resistance states. We argue that the spin-split band structure and the related
TMR effect can also be realized in other non-collinear AFM metals like Mn3Ge,
Mn3Ga, Mn3Pt, and Mn3GaN. Our work provides a robust method for detecting the
N\'eel vector in non-collinear antiferromagnets via the TMR effect, which may
be useful for their application in AFM spintronic devices.",2112.06568v2
2022-01-26,A new quasi-one-dimensional superconductor parent compound NaMn$_6$Bi$_5$ with lower antiferromagnetic transition temperatures,"Mn-based superconductor is rare and recently reported in
quasi-one-dimensional KMn$_6$Bi$_5$ with [Mn$_6$Bi$_5$]-columns under high
pressure. Here we report the synthesis, magnetic properties, electrical
resistivity, and specific heat capacity of the newly-discovered
quasi-one-dimensional NaMn$_6$Bi$_5$ single crystal. Compared with other
AMn$_6$Bi$_5$ (A = K, Rb, and Cs), NaMn$_6$Bi$_5$ has larger intra-column Bi-Bi
bond length, which may result in the two decoupled antiferromagnetic
transitions at 47.3 K and 52.3 K. The relatively lower antiferromagnetic
transition temperatures make NaMn$_6$Bi$_5$ a more suitable platform to explore
Mn-based superconductors. Anisotropic resistivity and non-Fermi liquid behavior
at low temperature are observed. Heat capacity measurement reveals that
NaMn$_6$Bi$_5$ has similar Debye temperature with those of AMn$_6$Bi$_5$ (A = K
and Rb), whereas the Sommerfeld coefficient is unusually large. Using
first-principles calculations, the quite different density of states and an
unusual enhancement near the Fermi level are observed for NaMn$_6$Bi$_5$, when
compared with those of other AMn$_6$Bi$_5$ (A = K, Rb, and Cs) compounds.",2201.10719v1
2022-09-30,Charge Transport in Ba$_{1-x}$Rb$_{x}$Fe$_{2}$As$_{2}$ Single Crystals,"Recent studies in heavily hole-doped iron-based superconductor RbFe$_2$As$_2$
have suggested the emergence of novel electronic nematicity directed along the
Fe-As direction, 45$^\circ$ rotated from the usual nematicity ubiquitously
found in BaFe$_2$As$_2$ and related materials. This motivates us to study the
physical properties of Ba$_{1-x}$Rb$_{x}$Fe$_{2}$As$_{2}$, details of which
remain largely unexplored. Here we report on the normal-state charge transport
in Ba$_{1-x}$Rb$_{x}$Fe$_{2}$As$_{2}$ superconductors by using high-quality
single crystals in the range of Rb concentration $0.14\le x \le 1.00$. From the
systematic measurements of the temperature dependence of electrical resistivity
$\rho(T)$, we find a signature of a deviation from the Fermi liquid behavior
around the optimal composition, which does not seem related to the
antiferromagnetic quantum criticality but has a potential link to hidden
nematic quantum criticality. In addition, electron correlations derived from
the coefficient of $T^2$ resistivity show a marked increase with Rb content
near the heavily hole-doped end, consistent with the putative Mott physics near
the $3d^5$ electron configuration in iron-based superconductors.",2209.15526v1
2022-10-14,Physical properties of the layered $f$-electron van der Waals magnet Ce$_2$Te$_5$,"We report a detailed study of the magnetic, transport, and thermodynamic
properties of Ce$_2$Te$_5$ single crystals, a layered $f$-electron van der
Waals magnet. Four consecutive transitions at $\sim$ 5.2, 2.1, 0.9, and 0.4 K
were observed in the $ac$-plane electrical resistivity $\rho$(T), which were
further confirmed in specific heat $C_\textrm{p}$(T) measurements. Analysis of
the magnetic susceptibility $\chi$(T), the magnetic-field variation of
$\rho$(T), and the increase of the first transition temperature ($T_\textrm{c}
\sim$ 5.2 K) with applied magnetic field indicates ferromagnetic order, while
the decrease of the other transitions with field suggests different states with
dominant antiferromagnetic interactions below $T_2 \sim$ 2.1 K, $T_3 \sim$ 0.9
K, and $T_4$ = 0.4 K. Critical behavior analysis around $T_\textrm{c}$ that
gives critical exponents $\beta = 0.31(2)$, $\gamma = 0.99(2)$, $\delta =
4.46(1)$, $T_\textrm{c} = 5.32(1)$ K indicates that Ce$_2$Te$_5$ shows a
three-dimensional magnetic critical behavior. Moreover, the Hall resistivity
$\rho_{\textrm{xy}}$ indicates that Ce$_2$Te$_5$ is a multi-band system with a
relatively high electron mobility $\sim 2900$ cm$^2$ V$^{-1}$ s$^{-1}$ near
$T_\textrm{c}$, providing further opportunities for future device applications.",2210.07507v1
2023-07-10,Inability of linear axion holographic Gubser-Rocha model to capture all the transport anomalies of strange metals,"In the last decade, motivated by the concept of Planckian relaxation and the
possible existence of a quantum critical point in cuprate materials,
holographic techniques have been extensively used to tackle the problem of
strange metals and high-$T_c$ superconductors. Among the various setups, the
linear axion Gubser-Rocha model has often been considered as a promising
holographic model for strange metals since endowed with the famous linear in
$T$ resistivity property. As fiercely advocated by Phil Anderson, beyond
$T$-linear resistivity, there are several additional anomalies unique to the
strange metal phase, as for example a Fermi liquid like Hall angle -- the
famous problem of the two relaxation scales. In this short note, we show that
the linear axion holographic Gubser-Rocha model, which presents a single
momentum relaxation time, fails in this respect and therefore is not able to
capture the transport phenomenology of strange metals. We prove our statement
by means of a direct numerical computation, a previously demonstrated scaling
analysis and also a hydrodynamic argument. Finally, we conclude with an
optimistic discussion on the possible improvements and generalizations which
could lead to a holographic model for strange metals in all their glory.",2307.04433v2
2023-08-20,Pressure-induced double-dome superconductivity in kagome metal CsTi3Bi5,"We present high-pressure resistance measurements up to 40 GPa on recently
discovered titanium-based kagome metal CsTi$_3$Bi$_5$. At ambient pressure,
CsTi$_3$Bi$_5$ shows no evidence of superconductivity in resistivity and
specific heat. By applying pressure, superconductivity emerges and the
superconducting transition temperature ${\it T}_{\rm c}$ reaches its first
maximum of 1.2 K at $\sim$5 GPa. Then the ${\it T}_{\rm c}$ is suppressed by
pressure and cannot be detected around 10 GPa, manifesting as a superconducting
dome. Remarkably, upon further increasing pressure above $\sim$13 GPa, another
superconducting dome shows up, with the maximum ${\it T}_{\rm c}$ of 0.6 K and
ending pressure at $\sim$36 GPa. The variation of ${\it T}_{\rm c}$ displays a
clear double-dome shape in the superconducting phase diagram. Our work
demonstrates the similarity between CsTi$_3$Bi$_5$ and CsV$_3$Sb$_5$, providing
valuable insights into the rich physics of these novel kagome metals.",2308.10129v1
2023-09-20,Highly Conductive RuO$_2$ Thin Films from Novel Facile Aqueous Chemical Solution Deposition,"Ruthenium dioxide (RuO$_2$) thin films were synthesized by Chemical Solution
Deposition (CSD) on silicon substrates using only water and acetic acid as
solvents. The microstructure, phase-purity, electrical and optical properties
as well as the thermal stability of the thin films have been characterized. The
microstructure of the thin films strongly depends on the annealing temperature:
A smooth thin film was achieved at an annealing temperature of 600$^\circ$C.
Higher annealing temperatures (800$^\circ$C) led to radial grain growth and an
inhomogeneous thin film. A very low resistivity of 0.89 {\Omega}m was measured
for a 220 nm-thick thin film prepared at 600$^\circ$. The resistivity of the
thin films increases with temperature, which indicates metallic behavior.
Phase-purity of the thin films was confirmed with X-ray Diffraction (XRD)
measurements, X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy.
Transmission and reflectivity measurements indicate that RuO$_2$ efficiently
blocks the UV-VIS and IR wavelengths. The optical constants determined via
spectroscopic ellipsometry show high absorption in the near-IR region as well
as a lower one in the UV-VIS region. The thermal stability was investigated by
post-annealing, confirming that the thin films are stable up to 750$^\circ$C in
synthetic air.",2310.18319v1
2023-12-31,Structural deformation and irreversible magnetic properties of flexible Co/Pt and Co/Pd thin films,"The successful commercialization of flexible spintronic devices requires a
complete understanding of the impact of external strain on the structural,
electronic, and magnetic properties of a system. The impact of bending-induced
strain on flexible films is studied quite well. However, little is known about
the effect of other modes of flexibility, e.g., wrinkling, twisting, peeling,
and stretching on the functional properties of flexible films. In this context,
perpendicular magnetic anisotropic Co/Pt and Co/Pd thin films are prepared on
flexible Kapton substrates, and the impact of the peeling mode is studied in
detail. The peeling method generates numerous cracks, and buckling in the thin
film, along with localized blister formation imaged by scanning electron
microscopy. Further, the resistivity measurement confirms a significant
enhancement in sample resistance owing to the severe damage of the films. The
structural discontinuities strongly affect the magnetization reversal phenomena
as measured by the magneto-optic Kerr effect (MOKE)-based microscopy. The
bubble domains got converted to elongated-shaped domains due to several
hindrances to the wall motion after strain application. Further, the relaxation
measurements reveal that the thermal energy is insufficient to switch the
magnetization at a few areas due to their high pinning potential associated
with the damages. In contrast to bending-induced strain, here, all the
modifications in the functional properties are found to be irreversible in
nature.",2401.00482v1
2024-04-09,Thin Accretion disks in GR-MHD simulations,"We review some recent results of general relativistic magnetohydrodynamic
(GR-MHD) simulations considering the evolution of geometrically thin disks
around a central black hole. Thin disk GR-MHD simulations complement the widely
used MAD (Magnetically Arrested Disk) or SANE (Standard And Normal Evolution)
approaches of evolving from an initial disk torus. In particular, we discuss
the dynamical evolution of the disk, its role in the formation of disk winds or
jets, the impact of disk resistivity, and its potential role in generating
magnetic flux by an internal disk dynamo. The main characteristics of a thin
disk in our approach are the Keplerian rotation of the disk material, which
allows to launch disk outflows by the Blandford-Payne magneto-centrifugal
effect, in addition to the Blandford-Znajek-driven spine jet from the black
hole ergosphere. Thus, for this approach, we neglect disk thermodynamics and
radiative effects, concentrating predominantly on the dynamical evolution of
the system. Resistive MHD further allows the investigation of physical
reconnection and also dynamo action. Magnetic reconnection may generate
magnetic islands of plasmoids that are ejected from the disk along with the
outflow. We also discussed potential applications of thin disk in explaining
the decaying phase of an outburst in black hole X-ray binaries (BH-XRBs).
Post-processing of radiation using the simulated dynamical data allows to
derive spectra or fluxes, e.g., in the X-ray band, and to derive potential
variability characteristics.",2404.06140v1
2002-06-26,Comparative Study of Dense Bulk MgB$_2$ Materials Prepared by Different Methods,"We report on the results of a comparative investigation of highly dense bulk
MgB$_2$ samples prepared by three methods: (i) hot deformation; (ii) high
pressure sintering; and (iii) mechanical alloying of Mg and B powders with
subsequent hot compaction. All types of samples were studied by
ac-susceptibility, dc-magnetization and resistivity measurements in magnetic
fields up to $\mu_0H=160$ kOe. A small but distinct anisotropy of the upper
critical field $H_{c2}^{a,b}/H_{c2}^{c}\sim1.2$ connected with some texture of
MgB$_2$ grains was found for the hot deformed samples. The samples prepared by
high pressure sintering as well as by mechanical alloying show improved
superconducting properties, including high upper critical fields $H_{c2}$
($\mu_0H_{c2}(0)\sim23$ T), irreversibility fields $H_{irr}$ which are strongly
shifted towards higher values $H_{irr}(T)\sim0.8H_{c2}(T)$ and high critical
current $J_c$ ($J_c=10^5$ A/cm$^2$ at 20 K and 1 T).",0206513v1
2007-03-06,$t-J$ model one-electron renormalizations: high energy features in photoemission experiments of high-$T_c$ cuprates,"Recent angle-resolved photoemission experiments in hole doped cuprates
reported new and interesting high energy features which may be useful for
understanding the electronic properties of these materials. Using a
perturbative approach, which allows the calculation of dynamical properties in
the $t-J$ model, one-electron spectral properties were calculated. A strongly
renormalized quasiparticle band near the Fermi surface and incoherent spectra
at high energy were obtained. Among different current experimental
interpretations, the obtained results are closer to the interpretation given by
Pan {\it et al.}\cite{pan}. The self-energy shows large high energy
contributions which are responsible for the incoherent structures showed by the
spectral functions and the reduction of the quasiparticle weight and bandwidth.
According to the calculation, collective charge fluctuations are the main
source for the self-energy renormalizations. For testing if the obtained
self-energy is compatible with transport measurement the resistivity versus
temperature was estimated.",0703152v1
2011-05-31,Multiband Transport in Bilayer Graphene at High Carrier Densities,"We report a multiband transport study of bilayer graphene at high carrier
densities. Employing a poly(ethylene)oxide-CsClO$_4$ solid polymer electrolyte
gate we demonstrate the filling of the high energy subbands in bilayer graphene
samples at carrier densities $|n|\geq2.4\times 10^{13}$ cm$^{-2}$. We observe a
sudden increase of resistance and the onset of a second family of Shubnikov de
Haas (SdH) oscillations as these high energy subbands are populated. From
simultaneous Hall and magnetoresistance measurements together with SdH
oscillations in the multiband conduction regime, we deduce the carrier
densities and mobilities for the higher energy bands separately and find the
mobilities to be at least a factor of two higher than those in the low energy
bands.",1106.0035v1
2012-04-30,High Mobility in a Stable Transparent Perovskite Oxide,"We discovered that La-doped BaSnO3 with the perovskite structure has an
unprecedentedly high mobility at room temperature while retaining its optical
transparency. In single crystals, the mobility reached 320 cm^2(Vs)^-1 at a
doping level of 8x10^19 cm^-3, constituting the highest value among
wide-band-gap semiconductors. In epitaxial films, the maximum mobility was 70
cm^2(Vs)^-1 at a doping level of 4.4x10^20 cm^-3. We also show that resistance
of (Ba,La)SnO3 changes little even after a thermal cycle to 530 Deg. C in air,
pointing to an unusual stability of oxygen atoms and great potential for
realizing transparent high-frequency, high-power functional devices.",1204.6702v3
2013-01-25,All-Heusler giant-magnetoresistance junctions with matched energy bands and Fermi surfaces,"We present an all-Heusler architecture which could be used as a rational
design scheme for achieving high spin-filtering efficiency in the
current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices. A
Co2MnSi/Ni2NiSi/Co2MnSi trilayer stack is chosen as the prototype of such an
architecture, of which the electronic structure and magnetotransport properties
are systematically investigated by first principles approaches. Almost
perfectly matched energy bands and Fermi surfaces between the all-Heusler
electrode-spacer pair are found, indicating large interfacial spin-asymmetry,
high spin-injection efficiency, and consequently high GMR ratio. Transport
calculations further confirms the superiority of the all-Heusler architecture
over the conventional Heusler/transition-metal(TM) structure by comparing their
transmission coefficients and interfacial resistances of parallel conduction
electrons, as well as the macroscopic current-voltage (I-V) characteristics. We
suggest future theoretical and experimental efforts in developing novel
all-Heusler GMR junctions for the read heads of the next generation
high-density hard disk drives (HDDs).",1301.6106v1
2013-05-02,Optimisation of CMOS pixel sensors for high performance vertexing and tracking,"CMOS Pixel Sensors tend to become relevant for a growing spectrum of charged
particle detection instruments. This comes mainly from their high granularity
and low material budget. However, several potential applications require a
higher read-out speed and radiation tolerance than those achieved with
available devices based on a 0.35 micrometers feature size technology. This
paper shows preliminary test results of new prototype sensors manufactured in a
0.18 micrometers process based on a high resistivity epitaxial layer of
sizeable thickness. Grounded on these observed performances, we discuss a
development strategy over the coming years to reach a full scale sensor
matching the specifications of the upgraded version of the Inner Tracking
System (ITS) of the ALICE experiment at CERN, for which a sensitive area of up
to about 10 square meters may be equipped with pixel sensors.",1305.0531v2
2014-05-05,High Precision Measurements Using High Frequency Signals,"Generalized lock-in amplifiers use digital cavities with Q-factors as high as
5X10^8. In this letter, we show that generalized lock-in amplifiers can be used
to analyze microwave (giga-hertz) signals with a precision of few tens of
hertz. We propose that the physical changes in the medium of propagation can be
measured precisely by the ultra-high precision measurement of the signal. We
provide evidence to our proposition by verifying the Newton's law of cooling by
measuring the effect of change in temperature on the phase and amplitude of the
signals propagating through two calibrated cables. The technique could be used
to precisely measure different physical properties of the propagation medium,
for example length, resistance, etc. Real time implementation of the technique
can open up new methodologies of in-situ virtual metrology in material design.",1405.0853v1
2014-12-03,High-field thermal transport properties of REBCO coated conductors,"The use of REBCO coated conductors is envisaged for many applications,
extending from power cables to high-field magnets. Whatever the case, thermal
properties of REBCO tapes play a key role for the stability of superconducting
devices. In this work, we present the first study on the longitudinal thermal
conductivity ($\kappa$) of REBCO coated conductors in magnetic fields up to 19
T applied both parallelly and perpendicularly to the thermal-current direction.
Copper-stabilized tapes from six industrial manufacturers have been
investigated. We show that zero-field $\kappa$ of coated conductors can be
calculated with an accuracy of $\pm 15%$ from the residual resistivity ratio of
the stabilizer and the Cu/non-Cu ratio. Measurements performed at high fields
have allowed us to evaluate the consistency of the procedures generally used
for estimating in-field $\kappa$ in the framework of the Wiedemann-Franz law
from an electrical characterization of the materials. In-field data are
intended to provide primary ingredients for the thermal stability analysis of
high-temperature superconductor-based magnets.",1412.1328v1
2015-10-19,Simulating feedback from nuclear clusters: the impact of multiple sources,"Nuclear star clusters (NCs) are found to exist in the centres of many
galaxies and appear to follow scaling relations similar to those of
super-massive black holes. Previous analytical work has suggested that such
relations are a consequence of feedback regulated growth. We explore this idea
using high resolution hydrodynamical simulations, focusing on the validity of
the simplifying assumptions made in analytical models. In particular, we
investigate feedback emanating from multiple stellar sources rather than from a
single source, as is usually assumed, and show that collisions betweens shells
of gas swept up by feedback leads to momentum cancellation and the formation of
high density clumps and filaments. This high density material is resistant both
to expulsion from the galaxy potential and to disruption by feedback; if it
falls back onto the NC, we expect the gas to be available for further star
formation or for feeding a central black hole. We also note our results may
have implications for the evolution of globular clusters and stellar clusters
in high redshift dark matter halos.",1510.05697v1
2016-06-21,Mobility induced unsaturated high linear magnetoresistance in transition-metal monopnictides Weyl semimetals,"Discovery of Weyl fermions in semimetallic tansition-metal monopnictides is a
major breakthrough in condensed matter physics. A Weyl semimetal is
characterized by the existence of robust Weyl points and unclosed topological
surface states in the form of Fermi arc. All the four compounds of the Weyl
semimetal transition monopnictide family i.e. NbP, TaP, NbAs and TaAs exhibit
extremely high mobility and unsaturated high magnetoresistance (MR). For
example, MR values are 8.5x10^5% at 1.85 K for NbP and 1.5x10^5% at 3 K in 9 T
for TaAs. NbP also achieves very low value of residual resistivity 0.63
micro-ohm cm at 2 K due to suppression of scattering resulting in ultra-high
mobility 5x10^6 cm^2/Vs, Interestingly, we find that the mobility of these
compounds play an important role for such a large MR.",1606.06649v1
2017-06-28,First-principles prediction of high-entropy-alloy stability,"High entropy alloys (HEAs) are multicomponent compounds whose high
configurational entropy allows them to solidify into a single phase, with a
simple crystal lattice structure. Some HEA's exhibit desirable properties, such
as high specific strength, ductility, and corrosion resistance, while
challenging the scientist to make confident predictions in the face of multiple
competing phases. We demonstrate phase stability in the multicomponent alloy
system of Cr-Mo-Nb-V, for which some of its binary subsystems are subject to
phase separation and complex intermetallic-phase formation. Our
first-principles calculation of free energy predicts that the configurational
entropy stabilizes a single body-centered cubic (BCC) phase from T = 1,700K up
to melting, while precipitation of a complex intermetallic is favored at lower
temperatures. We form the compound experimentally and confirm that it forms as
a single BCC phase from the melt, but that it transforms reversibly at lower
temperatures.",1706.09282v1
2018-05-15,"Unprecedented High Irreversibility Line in Nontoxic Cuprate Superconductor (Cu,C)Ba2Ca3Cu4O11+delta","One of the key factors limiting the high power applications for a type-II
superconductor is the irreversibility line Hirr(T) which reflects the very
boundary of resistive dissipation in the phase diagram of magnetic field versus
temperature. In cuprate family, the Y-, Bi-, Hg- and Tl-based systems have
superconducting transition temperatures exceeding the liquid nitrogen boiling
temperature (~77K). However, the toxic elements Hg and Tl in the latter two
systems strongly constrain the possible applications. The Bi-based (2223)
system is nontoxic, but the irreversibility magnetic field is strongly
suppressed in the liquid nitrogen temperature region. For this purpose, the
best perspective so far is relying on the YBa2Cu3O7 (Tc~90 K) system which is
nontoxic and has a relatively high irreversibility magnetic field. Here we
report the study of a nontoxic superconductor (Cu,C)Ba2Ca3Cu4O11+{\delta} with
Tc = 116K. It is found that the irreversibility magnetic field is
unprecedentedly high among all superconductors and it thus provides a great
potential of applications in the liquid nitrogen temperature region.",1805.05830v1
2018-11-04,Grain growth in Pt microheaters subjected to high current density under constant power,"When $50$ nm thick Pt microheaters of lateral dimensions $1\times10$
$\mu$m$^2$ are subjected to high electric power their resistance $R$ rises, as
expected. Following an initial rise however there is a gradual decrement in $R$
while constant electric power dissipation is maintained. We find that this
lowering in $R$ is accompanied by grain growth in the polycrystalline thin Pt
film of our heaters. This is confirmed by XRD measurements and SEM imaging.
Similar growth in grain size is observed in thin Pt films that are
oven-annealed at high temperatures. Thus we argue that maintaining high power
dissipation in a microheater has the same effect on its material structure as
post-annealing. We observe the in-plane grain size of a $50$ nm thick as-grown
Pt film/heater to be $D_\parallel=15$ nm. When post-annealed at a temperature
of $T=600^\circ$C for 30 min, $D_\parallel=30$ nm, compared with when electric
current is run through a heater we estimate the mean crystalline length to be
$D_\parallel=35$ nm.",1811.01434v1
2011-04-15,Structural and Magnetic Phase Transitions in NdCoAsO under High Pressures,"We have investigated structural and magnetic phase transitions under high
pressures in a quaternary rare earth transition metal arsenide oxide NdCoAsO
compound that is isostructural to high temperature superconductor NdFeAsO.
Four-probe electrical resistance measurements carried out in a designer diamond
anvil cell show that the ferromagnetic Curie temperature and anti-ferromagnetic
Neel temperature increase with an increase in pressure. High pressure x-ray
diffraction studies using a synchrotron source show a structural phase
transition from a tetragonal phase to a new crystallographic phase at a
pressure of 23 GPa at 300 K. The NdCoAsO sample remained anti-ferromagnetic and
non-superconducting to temperatures down to 10 K and to the highest pressure
achieved in this experiment of 53 GPa. A P-T phase diagram for NdCoAsO is
presented to a pressure of 53 GPa and low temperatures of 10 K.",1104.3172v1
2012-06-21,High Performance Single Layered WSe2 p-FETs with Chemically Doped Contacts,"We report high performance p-type field-effect transistors based on single
layered (thickness, ~0.7 nm) WSe2 as the active channel with chemically doped
source/drain contacts and high-{\kappa} gate dielectrics. The top-gated
monolayer transistors exhibit a high effective hole mobility of ~250 cm2/Vs,
perfect subthreshold swing of ~60 mV/dec, and ION/IOFF of >10^6 at room
temperature. Special attention is given to lowering the contact resistance for
hole injection by using high work function Pd contacts along with degenerate
surface doping of the contacts by patterned NO2 chemisorption on WSe2. The
results here present a promising material system and device architecture for
p-type monolayer transistors with excellent characteristics.",1206.4776v1
2020-08-26,Microwave measurements of the high magnetic field vortex motion pinning parameters in Nb$_3$Sn,"The high frequency vortex motion in Nb$_3$Sn was analyzed in this work up to
12 T. We used a dielectric loaded resonator tuned at 15 GHz to evaluate the
surface impedance $Z$ of a Nb$_3$Sn bulk sample (24.8 at.\%Sn). From the field
induced variation of $Z$, the high frequency vortex parameters (the pinning
constant $k_p$, the depinning frequency $\nu_p$ and the flux flow resistivity
$\rho_{ff}$) were obtained over a large temperature and field range; their
field and temperature dependence were analyzed. Comparison with other
superconducting materials shows that high frequency applications in strong
magnetic fields are also feasible with Nb$_3$Sn. In the present work, we report
the first measurements about the microwave response in Nb$_3$Sn in strong
magnetic fields.",2008.11656v3
2021-05-05,High Permittivity Dielectric Field-Plated Vertical (001) $β$-Ga$_2$O$_3$ Schottky Barrier Diode with Surface Breakdown Electric Field of 5.45 MV/cm and BFOM of $>$ 1 GW/cm$^{2}$,"This paper presents vertical (001) oriented $\beta$-Ga$_2$O$_3$ field plated
(FP) Schottky barrier diode (SBD) with a novel extreme permittivity dielectric
field oxide. A thin drift layer of 1.7 $\mu m$ was used to enable a
punch-through (PT) field profile and very low differential specific
on-resistance (R$_{on-sp}$) of 0.32 m$\Omega$-cm$^{2}$. The extreme
permittivity field plate oxide facilitated the lateral spread of the electric
field profile beyond the field plate edge and enabled a breakdown voltage
($V_{br}$) of 687 V. The edge termination efficiency increases from 13.5 $\%$
for non-field plated structure to 63 $\%$ for high permittivity field plate
structure. The surface breakdown electric field was extracted to be 5.45 MV/cm
at the center of the anode region using TCAD simulations. The high permittivity
field plated SBD demonstrated a record high Baliga figure of merit (BFOM) of
1.47 GW/cm$^{2}$ showing the potential of Ga$_2$O$_3$ power devices for
multi-kilovolt class applications.",2105.04413v1
2021-06-24,GaN HEMT based high energy particles detection preamplifier,"GaN high electron mobility transistors (HEMT) have gained some foothold in
the power electronics industry due to wide frequency bandwidth and power
handling. The material offers a wide bandgap and higher critical field strength
compared to most wide bandgap semiconductors, resulting in better radiation
resistance and theoretically higher speeds as the devices dimensions could be
reduced without suffering voltage breakdown. This work consists of the
underlying simulation work intended to examine the response of the GaN HEMTs
preamlifying circuits for high resolution high energy radiation detectors. The
simulation and experimental results illustrate the superior performance of the
GaN HEMT in an amplifying circuit. Using a spice model for a commercially
available GaN HEMT non distorted output to an input signal of 200 ps was
displayed. Real world measurements underscore the fast response of the GaN HEMT
with its measured slew rate at approximately 3000 V /{\mu}s a result only 17%
lower than the result obtained from the simulation.",2106.12703v1
2022-06-20,Effect of Heat Treatment Mode and Aggressive Media on Mechanical Properties of Porous Polytetrafluoroethylene Membranes Fabricated via Electrospinning,"Electrospinning is a modern alternative to the expanded method for producing
porous polytetrafluoroethylene membranes. High strength and relative
elongation, as well as the ability to maintain these properties for a long time
when exposed to aggressive media at high temperatures, determine the
application scope of the electrospun polytetrafluoroethylene membranes. Herein,
we report the effect of polytetrafluoroethylene suspension content in the
spinning solution, heat treatment mode (quenching and annealing) and aggressive
media at high temperatures on the tensile strength and relative elongation of
electrospun polytetrafluoroethylene membranes. Membranes fabricated from
spinning solutions with 50 to 60 wt % polytetrafluoroethylene suspension
content that underwent quenching were characterized by the highest tensile
strength and relative elongation. Electrospun polytetrafluoroethylene membranes
also demonstrated high chemical resistance to concentrated mineral acids and
alkalis, a bipolar aprotic solvent, engine oil and deionized water at 100 deg
for 48 hours.",2206.09739v1
2023-01-02,Non-Equilibrium Spark Plasma Reactive Doping Enables Highly Adjustable Metal to Insulator Transitions and Improved Mechanical Stability for VO2,"Although vanadium dioxide (VO2) exhibits the most abrupt metal to insulator
transition (MIT) properties near room-temperature, the present regulation of
their MIT functionalities is insufficient owing to the high complexity and
susception associated with V4+. Herein, we demonstrate a spark plasma assisted
reactive sintering (SPARS) approach to simultaneously achieve in situ doping
and sintering of VO2 within largely short period (~10 minutes). This enables
high convenience and flexibility in regulating the electronic structure of VO2
via dopant elements covering Ti, W, Nb, Mo, Cr and Fe, leading to a wide
adjustment in their metal to insulator transition temperature (TMIT) and basic
resistivity. Furthermore, the mechanical strengths of the doped-VO2 were
meanwhile largely improved via the compositing effect of high melting-point
dopant oxide. The high adjustability in MIT properties and improved mechanical
properties further paves the way towards practical applications of VO2 in power
electronics, thermochromism and infrared camouflage.",2301.00634v1
2024-01-15,High entropy alloys and their affinity to hydrogen: from Cantor to platinum group elements alloys,"Properties of high entropy alloys are currently in the spotlight due to their
promising applications. One of the least investigated aspects is the affinity
of these alloys to hydrogen, its diffusion and reactions. In this study we
apply high-pressure at ambient temperature and investigate stress-induced
diffusion of hydrogen into the tructure of high entropy alloys HEA including
the famous Cantor alloy as well as less known, but nevertheless important
platinum group PGM alloys. By applying X-ray diffraction to samples loaded into
diamond anvil cells we perform a comparative investigation of these HEA alloys
in Ne and H2 pressure-transmitting media. Surprisingly, even under stresses far
exceeding conventional industrial processes both Cantor and PGM alloys show
exceptional resistance to hydride formation, on par with widely used industrial
grade CuBe alloys. Our observations inspire optimism for practical HEA
applications in hydrogen-relevant industry and technology e.g. coatings, etc,
particularly those related to transport and storage.",2401.07802v1
2019-10-06,Patterning Sn-based EUV resists with low-energy electrons,"Extreme Ultraviolet (EUV) lithography is the newest technology that will be
used in the semiconductor industry for printing circuitry in the sub-20 nm
scale. Low-energy electrons (LEEs) produced upon illumination of resist
materials with EUV photons (92 eV) play a central role in the formation of the
nanopatterns. However, up to now the details of this process are not well
understood. In this work, a novel experimental approach that combines
Low-Energy Electron Microscopy (LEEM), Electron Energy Loss Spectroscopy
(EELS), and Atomic Force Microscopy (AFM) is used to study changes induced by
electrons in the 0-40 eV range in thin films of molecular organometallic EUV
resists known as tin-oxo cages. LEEM-EELS spectroscopic experiments were used
to detect surface charging upon electron exposure and to estimate the electron
landing energy. AFM post-exposure analyses revealed that irradiation of the
resist with LEEs leads to the densification of the resist layer associated to
carbon loss. The same chemical processes that yield densification render the
solubility change responsible for the pattern formation in the lithographic
application. Remarkably, electrons as low as 1.2 eV are able to induce chemical
reactions in the Sn-based resist. Based on the thickness profiles resulting
from LEE exposures in the 3-48 mC/cm 2 dose range, a simplified reaction model
is proposed where the resist undergoes sequential chemical reactions, yielding
first a sparsely cross-linked network, followed by the formation of a denser
cross-linked network. This model allows us to estimate a maximum reaction
volume on the initial material of 0.15 nm 3 per incident electron in the energy
range studied, which means that less than 10 LEEs per molecule on average are
needed to turn the material insoluble and thus render a pattern.",1910.02511v1
2010-01-07,Phase change memory technology,"We survey the current state of phase change memory (PCM), a non-volatile
solid-state memory technology built around the large electrical contrast
between the highly-resistive amorphous and highly-conductive crystalline states
in so-called phase change materials. PCM technology has made rapid progress in
a short time, having passed older technologies in terms of both sophisticated
demonstrations of scaling to small device dimensions, as well as integrated
large-array demonstrators with impressive retention, endurance, performance and
yield characteristics.
  We introduce the physics behind PCM technology, assess how its
characteristics match up with various potential applications across the
memory-storage hierarchy, and discuss its strengths including scalability and
rapid switching speed. We then address challenges for the technology, including
the design of PCM cells for low RESET current, the need to control
device-to-device variability, and undesirable changes in the phase change
material that can be induced by the fabrication procedure. We then turn to
issues related to operation of PCM devices, including retention,
device-to-device thermal crosstalk, endurance, and bias-polarity effects.
Several factors that can be expected to enhance PCM in the future are
addressed, including Multi-Level Cell technology for PCM (which offers higher
density through the use of intermediate resistance states), the role of coding,
and possible routes to an ultra-high density PCM technology.",1001.1164v2
2023-04-28,Structural and Optoelectronic Properties of Thin Film LaWN$_3$,"Nitride perovskites are an emerging class of materials that have been
predicted to display a range of interesting physics and functional properties,
but they are under-explored due to the difficulty of synthesizing oxygen-free
nitrides. LaWN3, recently reported as the first oxygen-free nitride perovskite,
exhibited polar symmetry and a large piezoelectric coefficient. However, the
predicted ferroelectric switching was hindered by large leakage current, which
motivates better understanding of its electronic structure and optical
properties. Here, we study the structure and optoelectronic properties of thin
film LaWN3 in greater detail, employing combinatorial techniques to correlate
these properties with cation stoichiometry. We report a two-step synthesis that
utilizes a more common RF substrate bias instead of a nitrogen plasma source,
yielding nanocrystalline films that are crystallized by ex-situ annealing. We
investigate the structure and composition of these films, finding
polycrystalline La-rich and highly textured W-rich films. The optical
absorption onset and temperature- and magnetic field-dependent resistivity are
consistent with semiconducting behavior and are highly sensitive to cation
stoichiometry, which may be related to amorphous impurities: metallic W or WNx
in W-rich samples and insulating La2O3 in La-rich samples. The fractional
magnetoresistance is linear and small, consistent with defect scattering, and a
W-rich sample has n-type carriers with high densities and low mobilities. We
demonstrate a photoresponse in LaWN3: the resistivity of a La-rich sample is
enhanced by 28% at low temperature, likely due to a defect trapping mechanism.
The physical properties of LaWN3 are highly sensitive to cation stoichiometry,
like many oxide perovskites, which therefore calls for precise composition
control to utilize the interesting properties observed in this nitride
perovskite.",2305.00098v1
2007-03-12,"Metal-insulator (fermion-boson)-crossover origin of pseudogap phase of cuprates I: anomalous heat conductivity, insulator resistivity boundary, nonlinear entropy","Among all experimental observations of cuprate physics, the
metal-insulator-crossover (MIC), seen in the pseudogap (PG) region of the
temperature-doping phase diagram of copper-oxides under a strong magnetic
field, when the superconductivity is suppressed, is most likely the most
intriguing one. Since it was expected that the PG-normal state for these
materials, as for conventional superconductors, is conducting. This MIC,
revealed in such phenomena as heat conductivity downturn, anomalous Lorentz
ratio, insulator resistivity boundary, nonlinear entropy, resistivity
temperature upturn, insulating ground state, nematicity- and stripe-phases and
Fermi pockets, unambiguously indicates on the insulating normal state, from
which the high-temperature superconductivity (HTS) appears. In the present work
(article I), we discuss the MIC phenomena mentioned in the title of article.
The second work (article II) will be devoted to discussion of other listed
above MIC phenomena and also to interpretation of the recent observations in
the hidden magnetic order and scanning tunneling microscopy (STM) experiments
spin and charge fluctuations as the intra PG and HTS pair ones. We find that
all these MIC (called in the literature as non-Fermi liquid) phenomena can be
obtained within the Coulomb single boson and single fermion two liquid model,
which we recently developed, and the MIC is a crossover of single fermions into
those of single bosons. We show that this MIC originates from bosons of Coulomb
two liquid model and fermions, whose origin is these bosons. At an increase of
doping up to critical value or temperature up to PG boundary temperature, the
boson system undegoes bosonic insulator - bosonic metal - fermionic metal
transitions.",0703290v3
2009-05-11,"The characteristics of the superconducting and magnetic phases in the polycrystalline samples of ruthenocuprates of nominal compositions RuSr2GdCu2O8, Ru0.98Sr2GdCu2O8 and Ru0.5Sr2GdCu2.5O8-d","The temperature dependencies of the resistivity for the superconducting
ruthenocuprates of nominal compositions RuSr2GdCu2O8, Ru0.98Sr2GdCu2O8 and
Ru0.5Sr2GdCu2.5O8-d were examined for the magnetic field dependent
characteristics of the superconducting transitions. The effect of the
insignificant diminishing of the Ru/Cu ratio in parent RuSr2GdCu2O8 was
confirmed as relevant for the stabilisation of the superconducting phase. Noted
differences in the compared characteristics are interpreted for possible
inhomogeneous nucleation of the superconducting phase in the parent
ruthenocuprate. The phase anisotropy in RuSr2GdCu2O8 and Ru0.98Sr2GdCu2O8 , in
presence of the compounds Ru magnetism, appears to be a cause of a significant
softening of the Hc2(T) phase line. An anomalous lowering of the
magneto-resistivity was observed in the approx. 10 K range above the onset of
the superconducting transition, which may suggest the presence of enhanced
superconducting fluctuations in the samples. The positive magnetic field shift
of the temperatures, which limit the magneto-resistivity and the specific heat
signatures of the magnetic ordered state of the Ru sub-lattice, suggests
probing the influence of the ferromagnetic Ru interactions in an effective
metallic-like conduction channel present in the samples. Superconducting
characteristics of the Ru0.5Sr2GdCu2.5O8-d reveal a significant contribution of
the Gd paramagnetic signal at low temperatures, interpreted for the presence of
a significant anisotropy of the superconducting phase. It is concluded that the
Ru-Cu substituted phases of ruthenocuprates may present an opportunity to
investigate the effectively anisotropic superconducting phase despite its
comparatively high Tc in the compounds related to the 123-type cuprate
superconductor.",0905.1721v4
2014-04-14,"Interplane resistivity of underdoped single crystals (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$, $0 \leq x<0.34$","Temperature-dependent inter-plane resistivity, $\rho _c(T)$, was measured in
hole-doped iron-arsenide superconductor (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$ over a
doping range from parent compound to optimal doping $T_c\approx 38~K$, $0\leq x
\leq 0.34$. Measurements were undertaken on high-quality single crystals grown
from FeAs flux. The coupled magnetic/structural transition at $T_{SM}$ leads to
clear accelerated decrease of $\rho_c(T)$ on cooling in samples with $T_c
<$26~K ($x <0.25$). This decrease in hole-doped material is in notable contrast
to an increase in $\rho_c(T)$ in the electron-doped Ba(Fe$_{1-x}$Co$_x$)Fe
$_2$As$_2$ and iso-electron substituted BaFe$_2$(As$_{1-x}$P$_x$)$_2$. The
$T_{SM}$ decreases very sharply with doping, dropping from $T_s$=71~K to zero
on increase of $T_c$ from approximately 25 to 27~K. The $\rho_c(T)$ becomes
$T$-linear close to optimal doping. The broad crossover maximum in $\rho_c(T)$,
found in the parent BaFe$_2$As$_2$ at around $T_{max} \sim$200~K, shifts to
higher temperature $\sim$250~K with doping $x$=0.34. The maximum shows clear
correlation with the broad crossover feature found in the temperature-dependent
in-plane resistivity $\rho_a(T)$. The doping evolution of $T_{max}$ in
(Ba$_{1-x}$K$_x$)Fe$_2$As$_2$ is in notable contrast with both rapid
suppression of $T_{max}$ found in Ba(Fe$_{1-x}TM_x$)$_2$As$_2$
($TM$=Co,Rh,Ni,Pd) and its rapid increase BaFe$_2$(As$_{1-x}$P$_x$)$_2$. This
observation suggest that pseudogap features are much stronger in hole-doped
than in electron-doped iron-based superconductors, revealing significant
electron-hole doping asymmetry similar to the cuprates. This paper replaces:
cond-mat:1106.0533.",1404.3664v1
2016-02-02,Field-insensitive heavy fermion features and phase transition in the caged-structure quasi-skutterudite Sm$_3$Ru$_4$Ge$_{13}$,"The robust field-insensitive heavy fermion features in Sm$_3$Ru$_4$Ge$_{13}$
and the magnetic phase transition at $T_N \approx$ 5~K are studied using
magnetization $M(T)$, specific heat $C_p(T)$, resistivity $\rho(T)$ and thermal
conductivity $\kappa_T(T)$. The average crystal structure of
Sm$_3$Ru$_4$Ge$_{13}$ conforms to the cubic space group $Pm\bar{3}n$ however,
signatures of subtle structural distortions are obtained from the x ray data.
The magnetic susceptibility, $\chi(T)$, follows a modified Curie-Weiss law
indicating the presence of crystal fields of Sm$^{3+}$ and the significance of
van Vleck terms. No sign of ferromagnetism is observed in $M(H)$ of
Sm$_3$Ru$_4$Ge$_{13}$ which yields only 0.025~$\mu_\mathrm{B}$/f.u.-Sm at 2~K,
7~T. The Sommerfeld coefficient, $\gamma \approx$ 220~mJ/mol-Sm K$^2$,
estimated from the analysis of low temperature specific heat suggests the
formation of heavy quasi particles at low temperature. Though a ln$T$
dependence of $\rho(T)$ is observed till 60~K, the resistivity behavior is
accounted for by assuming a two-band model for activated behavior of charge
carriers. The field scans of resistivity, $\rho(H)$, below $T_N$ display
significant nonlinearity while those above the $T_N$ are more metal-like. Low
values of thermal conductivity, $\kappa_T(T)$, are observed in
Sm$_3$Ru$_4$Ge$_{13}$ however, displaying an anomaly at $T_N$ which signifies
magnetoelastic coupling. A fairly high value of Seebeck coefficient, $S
\approx$ 40~$\mu$V/K is observed at 300~K. We identify Sm$_3$Ru$_4$Ge$_{13}$ as
a low charge carrier density system with unusual field-insensitive heavy
fermion features very similar to the filled skutterudites.",1602.00957v1
2018-03-11,Anomalous metamagnetism in the low carrier density Kondo lattice YbRh3Si7,"We report complex metamagnetic transitions in single crystals of the new low
carrier Kondo antiferromagnet YbRh3Si7. Electrical transport, magnetization,
and specific heat measurements reveal antiferromagnetic order at T_N = 7.5 K.
Neutron diffraction measurements show that the magnetic ground state of
YbRh3Si7 is a collinear antiferromagnet where the moments are aligned in the ab
plane. With such an ordered state, no metamagnetic transitions are expected
when a magnetic field is applied along the c axis. It is therefore surprising
that high field magnetization, torque, and resistivity measurements with H||c
reveal two metamagnetic transitions at mu_0H_1 = 6.7 T and mu_0H_2 = 21 T. When
the field is tilted away from the c axis, towards the ab plane, both
metamagnetic transitions are shifted to higher fields. The first metamagnetic
transition leads to an abrupt increase in the electrical resistivity, while the
second transition is accompanied by a dramatic reduction in the electrical
resistivity. Thus, the magnetic and electronic degrees of freedom in YbRh3Si7
are strongly coupled. We discuss the origin of the anomalous metamagnetism and
conclude that it is related to competition between crystal electric field
anisotropy and anisotropic exchange interactions.",1803.04013v2
2021-01-28,Direct Opto-Electronic Imaging of 2D Semiconductor - 3D Metal Buried Interfaces,"The semiconductor-metal junction is one of the most critical factors for high
performance electronic devices. In two-dimensional (2D) semiconductor devices,
minimizing the voltage drop at this junction is particularly challenging and
important. Despite numerous studies concerning contact resistance in 2D
semiconductors, the exact nature of the buried interface under a
three-dimensional (3D) metal remains unclear. Herein, we report the direct
measurement of electrical and optical responses of 2D semiconductor-metal
buried interfaces using a recently developed metal-assisted transfer technique
to expose the buried interface which is then directly investigated using
scanning probe techniques. We characterize the spatially varying electronic and
optical properties of this buried interface with < 20 nm resolution. To be
specific, potential, conductance and photoluminescence at the buried
metal/MoS$_2$ interface are correlated as a function of a variety of metal
deposition conditions as well as the type of metal contacts. We observe that
direct evaporation of Au on MoS$_2$ induces a large strain of ~5% in the
MoS$_2$ which, coupled with charge transfer, leads to degenerate doping of the
MoS$_2$ underneath the contact. These factors lead to improvement of contact
resistance to record values of 138 kohm-um, as measured using local conductance
probes. This approach was adopted to characterize MoS$_2$-In/Au alloy
interfaces, demonstrating contact resistance as low as 63 kohm-um. Our results
highlight that the MoS$_2$/Metal interface is sensitive to device fabrication
methods, and provides a universal strategy to characterize buried contact
interfaces involving 2D semiconductors.",2101.12203v1
2016-09-12,"Magnetic, specific heat and electrical transport properties of Frank-Kasper cage compounds RTM$_2$Al$_{20}$ [R = Eu,Gd and La ; TM = V,Ti]","Single crystals of Frank-Kasper compounds RTM$_2$Al$_{20}$ (R = Eu, Gd and
La; TM = V and Ti) were grown by self-flux method and their physical properties
were investigated through magnetization ($M$), magnetic susceptibility
($\chi$), specific heat ($C_P$) and electrical resistivity ($\rho$)
measurements. Powder x-ray diffraction studies and structural analysis showed
that these compounds crystallize in the cubic crystal structure with the space
group $Fd\overline{3}m$. The magnetic susceptibility for the compounds
EuTi$_2$Al$_{20}$ and GdTi$_2$Al$_{20}$ showed a sudden jump below the N{\'e}el
temperature $T_N$ indicative of plausible double magnetic transition. Specific
heat ($C_P$) and electrical resistivity ($\rho$) measurements also confirm the
first-order magnetic transition (FOMT) and possible double magnetic
transitions. Temperature variation of heat capacity showed a sharp phase
transition and huge $C_P$ value for the (Eu/Gd)Ti$_2$Al$_{20}$ compounds Full
width at half-maximum (FWHM) $<$ 0.2 K) which is reminiscent of a first-order
phase transition and a unique attribute among RTM$_2$Al$_{20}$ compounds. We
observed clear anomaly between heating and cooling cycle in temperature-time
relaxation curve for the compounds GdTi$_2$Al$_{20}$ (2.38 $K$) and
EuTi$_2$Al$_{20}$ (3.2 $K$) which is indicating a thermal arrest due to the
latent heat. The temperature variation of $S_{mag}$ for GdTi$_2$Al$_{20}$
saturates to a value $0.95R\ln8$ while the other magnetic systems exhibited
still lower entropy saturation values in the high temperature limit.
Resistivity measurements showed that all the samples behave as normal Fermi
liquid type compounds and $\rho(T)$ due to electron-phonon scattering follows
Bloch-Gr$\ddot{\textrm u}$neisen-Mott relation in the paramagnetic region.",1609.03458v1
2019-01-25,Insulator-like behavior coexisting with metallic electronic structure in strained FeSe thin films grown by molecular beam epitaxy,"This paper reports that ~10-nm-thick FeSe thin films exhibit insulator-like
behavior in terms of the temperature dependence of their electrical resistivity
even though bulk FeSe has a metallic electronic structure that has been
confirmed by photoemission spectroscopy and first-principles calculations. This
apparent contradiction is explained by potential barriers formed in the
conduction band. Very thin FeSe epitaxial films with various [Fe]/[Se] were
fabricated by molecular beam epitaxy and classified into two groups with
respect to lattice strain and electrical properties. Lattice parameter a
increased and lattice parameter c decreased with increasing [Fe]/[Se] up to 1.1
and then a levelled off and c began to decrease at higher [Fe]/[Se].
Consequently, the FeSe films had the most strained lattice when [Fe]/[Se] was
1.1, but these films had the best quality with respect to crystallinity and
surface flatness. All the FeSe films with [Fe]/[Se] of 0.8-1.9 exhibited
insulator-like behavior, but the temperature dependences of their electrical
resistivities exhibited different activation energies Ea between the Se-rich
and Fe-rich regions; i.e., Ea were small (a few meV) up to [Fe]/[Se]=1.1 but
jumped up to ~25 meV at higher [Fe]/[Se]. The film with [Fe]/[Se]=1.1 had the
smallest Ea of 1.1 meV and exhibited an insulator-superconducting transition at
35 K with zero resistance under gate bias. The large Ea of the Fe-rich films
was attributed to the unusual lattice strain with tensile in-plane and relaxed
out-of-plane strains. The large Ea of films with [Fe]/[Se]>1.1 resulted in low
mobility with a high potential barrier of ~50 meV in the conduction band for
percolation carrier conduction compared with that of the [Fe]/[Se]=1.1 film
(~17 meV). Therefore, the Fe-rich films exhibited remarkable insulator-like
behavior similar to a semiconductor despite their metallic electronic
structure.",1901.08780v1
2019-10-23,Persistent Insulator: Avoidance of Metallization at Megabar Pressures in Strongly Spin-Orbit-Coupled Sr2IrO4,"It is commonly anticipated that an insulating state collapses in favor of an
emergent metallic state at high pressures as the unit cell shrinks and the
electronic bandwidth broadens to fill the insulating energy band gap. Here we
report a rare insulating state that persists up to at least 185 GPa in the
antiferromagnetic iridate Sr2IrO4, which is the archetypical spin-orbit-driven
Jeff = 1/2 insulator. This study shows the electrical resistance of
single-crystal Sr2IrO4 initially decreases with applied pressure, reaches a
minimum in the range, 32 - 38 GPa, then abruptly rises to fully recover the
insulating state with further pressure increases up to 185 GPa. Our synchrotron
x-ray diffraction and Raman scattering data show the onset of the rapid
increase in resistance is accompanied by a structural phase transition from the
native tetragonal I41/acd phase to an orthorhombic Pbca phase (with much
reduced symmetry) at 40.6 GPa. The clear-cut correspondence of these two
anomalies is key to understanding the stability of the insulating state at
megabar pressures: Pressure-induced, severe structural distortions prevent the
expected metallization, despite the 26% volume compression attained at the
highest pressure accessed in this study. Moreover, the resistance of Sr2IrO4
remains stable while the applied pressure is tripled from 61 GPa to 185 GPa.
These results suggest that a novel type of electronic Coulomb correlation
compensates the anticipated band broadening in strongly spin-orbit-coupled
materials at megabar pressures.",1910.10291v1
2020-06-19,Synthesis and study of highly dense and smooth TiN thin films,"This study aims towards a systematic reciprocity of the tunable synthesis
parameters - partial pressure of N$_2$ gas, ion energy (\Ei) and Ti interface
in TiN thin film samples deposited using ion beam sputtering at ambient
temperature (300\,K). At the optimum partial pressure of N$_2$ gas, samples
were prepared with or without Ti interface at \Ei~=~1.0 or 0.5\,keV. They were
characterized using x-ray reflectivity (XRR) to deduce thickness, roughness and
density. The roughness of TiN thin films was found to be below 1\,nm, when
deposited at the lower \Ei~of 0.5\,keV and when interfaced with a layer of Ti.
Under these conditions, the density of TiN sample reaches to
5.80($\pm$0.03)\,g~cm$^{-3}$, a value highest hitherto for any TiN sample.
X-ray diffraction and electrical resistivity measurements were performed. It
was found that the cumulative effect of the reduction in \Ei~from 1.0 to
0.5\,keV and the addition of Ti interface favors (111) oriented growth leading
to dense and smooth TiN films and a substantial reduction in the electrical
resistivity. The reduction in \Ei~has been attributed to the surface kinetics
mechanism (simulated using SRIM) where the available energy of the sputtered
species (\Esp) leaving the target at \Ei~= 0.5\,keV is the optimum value
favoring the growth of defects free homogeneously distributed films. The
electronic structure of samples was probed using N K-edge absorption
spectroscopy and the information about the crystal field and spin-orbit
splitting confirmed TiN phase formation. In essence, through this work, we
demonstrate the role of \Esp~and Ti interface in achieving highly dense and
smooth TiN thin films with low resistivity without the need of a high
temperature or substrate biasing during the thin film deposition process.",2006.11055v1
2020-12-31,Room-temperature superconductivity in an artificial 2D Mott-insulating square lattice and its advanced condensed phase that generates a low-loss current in the atmosphere: A possible perpetual motion machine,"A 2D metallic phononic crystal (PnC), which is fabricated by drilling
periodic holes in a suspended niobium (Nb) film, is repeatedly cooled and
warmed in the temperature range of 2--300 K. During the first five temperature
cycles, the resistance of the metallic PnC gradually increases in accordance
with the Friedel sum rule, indicating that narrow Nb bridges between adjacent
thru-holes are converted into $d$-orbital-filled Mott insulators. The
consequent 2D Mott-insulating square lattice is a crystallographic analog of a
copper oxide layer in high-temperature superconductors such as YBCO and BSCCO.
Subsequent temperature cycles of the thus produced ideal Hubbard crystal
realize zero resistance at 60 K, and the zero-resistance state remains up to
300 K, being retained in the atmosphere (i.e., at room temperature, in a
terrestrial magnetic field, and under atmospheric pressure). The necessity of
the latter temperature cycles remains unclear in this study; however, a
possible transition mechanism involving the combined Josephson and charging
effects is discussed. The critical current and critical field of the
room-temperature superconductor (RTSC) are $I_{C}$ = 18.8 mA and
$\mu_{0}H_{\perp}$ = 12 T, respectively. Once a large current exceeding $I_{C}$
is applied to the RTSC, some of the $d$ electrons are forced out, and a special
interface consisting of the p-type semiconducting and superconducting states is
formed. Carriers diffuse because of the nonequilibrium charge concentration,
but they are Andreev-reflected back. In the reversible, thermally isolated
system, the entropy never increases, and a simple experiment confirms a
low-loss current generated from the interface spontaneously. That is, this
study challenges the forbidden perpetual motion machine which can be a solution
to the World energy crisis.",2012.15858v1
2021-03-25,Distinct quantum anomalous Hall ground states induced by magnetic disorders,"The quantum anomalous Hall (QAH) effect in magnetic topological insulator
(TI) represents a new state of matter originated from the interplay between
topology and magnetism. The defining characteristics of the QAH ground state
are the quantized Hall resistivity ($\rho_{yx}$) and vanishing longitudinal
resistivity ($\rho_{xx}$) in the absence of external magnetic field. A
fundamental question concerning the QAH effect is whether it is merely a
zero-magnetic-field quantum Hall (QH) effect, or if it can host unique quantum
phases and phase transitions that are unavailable elsewhere. The most dramatic
departure of the QAH systems from other QH systems lies in the strong magnetic
disorders that induce spatially random magnetization. Because disorder and
magnetism play pivotal roles in the phase diagram of two-dimensional electron
systems, the high degree of magnetic disorders in QAH systems may create novel
phases and quantum critical phenomena. In this work, we perform systematic
transport studies of a series of magnetic TIs with varied strength of magnetic
disorders. We find that the ground state of QAH effect can be categorized into
two distinct classes: the QAH insulator and anomalous Hall (AH) insulator
phases, as the zero-magnetic-field counterparts of the QH liquid and Hall
insulator in the QH systems. In the low disorder limit of the QAH insulator
regime, we observe a universal quantized longitudinal resistance $\rho_{xx} =
h/e^{2}$ at the coercive field. In the AH insulator regime, we find that a
magnetic field can drive it to the QAH insulator phase through a quantum
critical point with distinct scaling behaviors from that in the QH phase
transition. We propose that the transmission between chiral edge states at
domain boundaries, tunable by disorder and magnetic fields, is the key for
determining the QAH ground state.",2103.13783v1
2021-04-08,"Extremely large magnetoresistance in the ""ordinary"" metal ReO3","The extremely large magnetoresistance (XMR) observed in many topologically
nontrivial and trivial semimetals has attracted much attention in relation to
its underlying physical mechanism. In this paper, by combining the band
structure and Fermi surface (FS) calculations with the Hall resistivity and de
Haas-Van Alphen (dHvA) oscillation measurements, we studied the anisotropy of
magnetoresistance (MR) of ReO$_3$ with a simple cubic structure, an ""ordinary""
nonmagnetic metal considered previously. We found that ReO$_3$ exhibits almost
all the characteristics of XMR semimetals: the nearly quadratic field
dependence of MR, a field-induced upturn in resistivity followed by a plateau
at low temperatures, high mobilities of charge carriers. It was found that for
magnetic field \emph{H} applied along the \emph{c} axis, the MR exhibits an
unsaturated \emph{H}$^{1.75}$ dependence, which was argued to arise from the
complete carrier compensation supported by the Hall resistivity measurements.
For \emph{H} applied along the direction of 15$^\circ$ relative to the \emph{c}
axis, an unsaturated \emph{H}$^{1.90}$ dependence of MR up to
9.43~$\times$~$10^3$$\%$ at 10~K and 9~T was observed, which was explained by
the existence of electron open orbits extending along the $k_{x}$ direction.
Two mechanisms responsible for XMR observed usually in the semimetals occur
also in the simple metal ReO$_3$ due to its peculiar FS (two closed electron
pockets and one open electron pocket), once again indicating that the details
of FS topology are a key factor for the observed XMR in materials.",2104.03799v1
2021-05-06,A strange metal in a bosonic system,"Fermi liquid theory forms the basis for our understanding of the majority of
metals, which is manifested in the description of transport properties that the
electrical resistivity goes as temperature squared in the limit of zero
temperature. However, the observations of strange metal states in various
quantum materials, notably high-temperature superconductors, bring this
spectacularly successful theoretical framework into crisis. When electron
scattering rate 1/{\tau} hits its limit, kBT/{\hbar} where {\hbar} is the
reduced Planck's constant, T represents absolute temperature and kB denotes
Boltzmann's constant, Planckian dissipation occurs and lends strange metals a
surprising link to black holes, gravity, and quantum information theory. Here,
we show the characteristic signature of strange metallicity arising
unprecedentedly in a bosonic system. Our nanopatterned YBa2Cu3O7-{\delta}(YBCO)
film arrays reveal T-linear resistance as well as B-linear magnetoresistance
over an extended temperature and magnetic field range in a quantum critical
region in the phase diagram. Moreover, the slope of the T-linear resistance
{\alpha}_cp appears bounded by {\alpha}_cp {\approx} h/2e^2 [1/T]_c^onset where
T_c^onset is the temperature at which Cooper pairs form, intimating a common
scale-invariant transport mechanism corresponding to Planckian dissipation.In
contrast to fermionic systems where the temperature and magnetic field
dependent scattering rates combine in quadrature of {\hbar}/{\tau} {\approx}
{\sqrt} (((k_B T)^2+({\mu}_B B)^2)), both terms linearly combine in the present
bosonic system, i.e. {\hbar}/{\tau} {\approx} (k_B T+[{\gamma}{\mu}]_B B),
where {\gamma} is a constant. By extending the reach of strange metal
phenomenology to a bosonic system, our results suggest that there is a
fundamental principle governing their transport which transcends particle
statistics.",2105.02654v1
2021-09-22,Discs and outflows in the early phases of massive star formation: influence of magnetic fields and ambipolar diffusion,"We study mass accretion and ejection in the vicinity of massive star forming
cores using high-resolution (5 au) 3D AMR numerical simulations. We investigate
the mechanisms at the origin of outflows and characterise the properties of the
disc forming around massive protostars. We include both protostellar radiative
feedback via PMS evolutionary tracks and magnetic ambipolar diffusion. We
studied 3 different cases: purely hydrodynamical, ideal MHD, and ambipolar
diffusion. In the resistive models, we investigate the effects the initial
amplitude of both magnetic field and rotation have on the properties of the
massive protostellar system. We use simple criteria to identify the outflow and
disc material and follow their evolution as the central star accretes mass up
to 20 solar mass. The outflow is completely different when magnetic fields are
introduced, so that magnetic processes are the main driver of the outflow up to
stellar masses of ~20 solar mass. The disc properties depend on the physics
included. The disc formed in the ideal and resistive runs show opposite
properties in terms of plasma beta and of magnetic fields topology. While the
disc in the ideal case is dominated by the magnetic pressure and the toroidal
magnetic fields, the one formed in the resistive runs is dominated by the
thermal pressure and has essentially vertical magnetic fields in the inner
regions (R<200 au). We find that magnetic processes dominate the early
evolution of massive protostellar systems (<20 solar mass) and shapes the
accretion/ejection as well as the disc formation. Ambipolar diffusion is mainly
at work at disc scales and regulates its properties. Our finding for the
outflow and disc properties are reminiscent of low-mass star formation,
suggesting that accretion and ejection in young massive and low-mass protostars
are regulated by the same physical processes at the early stages.",2109.10580v1
2022-05-03,The Resistive Nature of Decomposing Interfaces of Solid Electrolytes with Alkali Metal Electrodes,"A crucial ingredient in lithium (Li) and sodium (Na)-ion batteries (LIBs and
NIBs) is the electrolytes. The use of Li-metal (Na-metal) as anode in liquid
electrolyte LIBs (NIBs) is constrained by several issues including thermal
runway and flammability, electrolyte leakage, and limited chemical stability.
Considerable effort has been devoted toward the development of solid
electrolytes (SEs) and all-solid-state batteries, which are presumed to
mitigate some of the issues of Li-metal(Na-metal) in contact with flammable
liquid electrolytes. However, most SEs, such as Li$_3$PS$_4$, Li$_6$PS$_5$Cl
and Na$_3$PS$_4$ readily decompose against the highly reducing Li-metal and
Na-metal anodes. Using first-principles calculations we elucidate the stability
of more than 20 solid$||$solid interfaces formed between the decomposition
products of Li$_3$PS$_4$, Li$_6$PS$_5$Cl (and Na$_3$PS$_4$) against the
Li-metal (Na-metal) electrode. We suggest that the work of adhesion needed to
form a hetereogenous interfaces is an important descriptor to quantify the
stability of interfaces. Subsequently, we clarify the atomistic origins of the
resistance to Li-ion transport at interfaces of the Li-metal anode and selected
decomposition products (Li$_3$P, Li$_2$S} and LiCl) of SEs, via a high-fidelity
machine learned potential (MLP). Utilising an MLP enables nano-second-long
molecular dynamics simulations on `large' interface models (here with 8320
atoms), but with similar accuracy to first-principles approaches. Our
simulations demonstrate that the interfaces formed between Li-metal and
argyrodite (e.g., Li$_6$PS$_5$Cl) decomposition products are resistive to
Li-ion transport. The implications of this study are important since binary
compounds are commonly found in the vicinity of Li(Na)-metal upon chemical
and/or electrochemical decomposition of ternary and quaternary SEs.",2205.01264v1
2015-09-22,Stability and scalability of piezoelectric flags,"We investigate the effect of piezoelectric (PZT) material on the flutter
speed, vibration mode and frequency, and energy harvesting power and efficiency
of a flexible flag in various fluids. We develop a fully coupled
fluid-solid-electric model by combining the inviscid vortex sheet model with a
linear electro-mechanical coupling model. A resistance only circuit and a
resonant resistance-inductance (RL) circuit are considered. For a purely
resistive circuit, an increased electro-mechanical coupling factor results in
an increased flutter speed, vibration frequency, averaged electric power and
efficiency. A consistent optimal resistance is found that maximizes the flutter
speed and the energy harvesting power. For a resonant RL circuit, by tuning the
inductance to match the circuit frequency to the flag's vibration frequency,
the flutter speed can be greatly decreased, and a larger averaged power and
efficiency are obtained. We also consider a model scale set-up with several
commonly used commercial materials for operating in air and water. Typical
ranges of dimensionless parameters are obtained for four types of material that
span a wide range of solid density and rigidity values. We find that the
resistance only circuit is more effective when the flag is placed in a lighter
fluid (e.g. air), while the RL circuit is able to reduce the flutter speed when
the flag is placed in a heavier fluid (e.g. water).",1509.06726v1
2019-09-25,Phonon Scattering at Kinks in Suspended Graphene,"Recent experiments have shown surprisingly large thermal time constants in
suspended graphene ranging from 10 to 100 ns in drums with a diameter ranging
from 2 to 7 microns. The large time constants and their scaling with diameter
points towards a thermal resistance at the edge of the drum. However, an
explanation of the microscopic origin of this resistance is lacking. Here, we
show how phonon scattering at a kink in the graphene, e.g. formed by sidewall
adhesion at the edge of the suspended membrane, can cause a large thermal time
constant. This kink strongly limits the fraction of flexural phonons that cross
the suspended graphene edge, which causes a thermal interface resistance at its
boundary. Our model predicts thermal time constants that are of the same order
of magnitude as experimental data, and shows a similar dependence on the
circumference. Furthermore, the model predicts the relative in-plane and
out-of-plane phonon contributions to graphene's thermal expansion force, in
agreement with experiments. We thus show, that in contrast to conventional
thermal (Kapitza) resistance which occurs between two different materials, in
2D materials another type of thermal interface resistance can be geometrically
induced in a single material.",1909.11615v1
2019-12-24,Tunable Contact Resistance in Transition Metal Dichalcogenide Lateral Heterojunctions,"Contact resistance of semiconducting transition metal dichalcogenides has
been shown to decrease in lateral heterojunctions formed with their metallic
phases but its origins remain elusive. Here we combine first principles and
quantum transport calculations to rationalize the contact resistance of these
structures in terms of phase, composition (WTe2, MoTe2, WSe2, and MoSe2), and
length of the channel. We find that charge injection in metallic
1T'-WTe2/1T'-MoTe2 junctions is nearly ideal as electrode Bloch states remain
delocalized through the channel. Mixtures of 1T' selenides and tellurides
depart from this scenario due to the momentum mismatch between states in the
lead and channel. In semiconducting channels, the large Schottky barriers
degrade the electrical contacts. Around band edges, contact resistance values
are about an order of magnitude lower than those obtained experimentally
suggesting that doping and phase-engineering could be employed to overcome this
issue. We predict that transport regime in these junctions shifts from
thermionic emission to tunneling for channels shorter than 3 nm at room
temperature. We also discuss the presence of states at the metal/semiconductor
interfaces. By underpinning mechanisms to control the contact resistance in
heterogeneous two-dimensional materials, this work proves valuable towards the
development of devices suitable for optoelectronics and phase-change materials
applications.",1912.13500v1
2022-05-12,Chromium-Doped Bismuth Antimony Telluride for Future Quantum Hall Resistance Standards,"Since 2017, epitaxial graphene has been the base material for the US national
standard for resistance. A future avenue of research within electrical
metrology is to remove the need for strong magnetic fields, as is currently the
case for devices exhibiting the quantum Hall effect. The quantum Hall effect is
just one of many research endeavours that revolve around recent quantum
physical phenomena like composite fermions, charge density waves, and
topological properties [1-2]. New materials, like magnetically doped
topological insulators (MTIs), offer access to the quantum anomalous Hall
effect, which in its ideal form, could become a future resistance standard
needing only a small permanent magnet to activate a quantized resistance value
[3-5]. Furthermore, these devices could operate at zero-field for measurements,
making the dissemination of the ohm more economical and portable. Here we
present results on precision measurements of the h/e2 quantized plateau of
Cr-Doped (BixSb1-x)2Te3 and give them context by comparing them to modern
graphene-based resistance standards. Ultimately, MTI-based devices could be
combined in a single system with magnetic-field-averse Josephson voltage
standards to obtain an alternative quantum current standard.",2205.06077v1
2024-01-23,Wide-range resistivity characterization of semiconductors with terahertz time-domain spectroscopy,"Resistivity is one of the most important characteristics in the semiconductor
industry. The most common way to measure resistivity is the four-point probe
method, which requires physical contact with the material under test. Terahertz
time domain spectroscopy, a fast and non-destructive measurement method, is
already well established in the characterization of dielectrics. In this work,
we demonstrate the potential of two Drude model-based approaches to extract
resistivity values from terahertz time-domain spectroscopy measurements of
silicon in a wide range from about 10$^{-3}$ $\Omega$cm to 10$^{2}$ $\Omega$cm.
One method is an analytical approach and the other is an optimization approach.
Four-point probe measurements are used as a reference. In addition, the spatial
resistivity distribution is imaged by X-Y scanning of the samples to detect
inhomogeneities in the doping distribution.",2401.12787v1
2005-04-13,Growth Mechanisms and Oxidation-Resistance of Gold-Coated Iron Nanoparticles,"We report the chemical synthesis of Fe-core/Au-shell nanoparticles by a
reverse micelle method, and the investigation of their growth mechanisms and
oxidation-resistant characteristics. The core-shell structure and the presence
of the Fe & Au phases have been confirmed by transmission electron microscopy,
energy dispersive spectroscopy, X-ray diffraction, Mossbauer spectroscopy, and
inductively coupled plasma techniques. Additionally, atomic-resolution
Z-contrast imaging and electron energy loss spectroscopy (EELS) in a scanning
transmission electron microscope (STEM) have been used to study details of the
growth processes. The Au-shell grows by nucleating on the Fe-core surface
before coalescing. The magnetic moments of such nanoparticles, in the loose
powder form, decrease over time due to oxidation. The less than ideal
oxidation-resistance of the Au shell may have been caused by the rough Au
surfaces. However, in the pressed pellet form, electrical transport
measurements show that the particles are fairly stable, as the resistance of
the pellet does not change appreciably over time.",0504314v1
2005-11-14,Reproducible Low Contact Resistance in Rubrene Single-Crystal Field-Effect Transistors with Nickel Source and Drain Electrodes,"We have investigated the contact resistance of rubrene single-crystal
field-effect transistors (FETs) with Nickel electrodes by performing scaling
experiments on devices with channel length ranging from 200 nm up to 300
$\mu$m. We find that the contact resistance can be as low as 100 $\Omega$cm
with narrowly spread fluctuations. For comparison, we have also performed
scaling experiments on similar Gold-contacted devices, and found that the
reproducibility of FETs with Nickel electrodes is largely superior. These
results indicate that Nickel is a very promising electrode material for the
reproducible fabrication of low resistance contacts in organic FETs.",0511333v1
2005-11-23,Tuning the conductance of single-walled carbon nanotubes by ion irradiation in the Anderson localization regime,"Carbon nanotubes are a good realization of one-dimensional crystals where
basic science and potential nanodevice applications merge. Defects are known to
modify the electrical resistance of carbon nanotubes. They can be present in
as-grown carbon nanotubes, but controlling externally their density opens a
path towards the tuning of the nanotube electronic characteristics. In this
work consecutive Ar+ irradiation doses are applied to single-walled nanotubes
(SWNTs) producing a uniform density of defects. After each dose, the room
temperature resistance versus SWNT-length [R(L)] along the nanotube is
measured. Our data show an exponential dependence of R(L) indicating that the
system is within the strong Anderson localization regime. Theoretical
simulations demonstrate that mainly di-vacancies contribute to the resistance
increase induced by irradiation and that just a 0.03% of di-vacancies produces
an increase of three orders of magnitude in the resistance of a 400 nm SWNT
length.",0511585v1
2009-07-13,Enhanced Room Temperature Coefficient of Resistance and Magneto-resistance of Ag-added La0.7Ca0.3-xBaxMnO3 Composites,"In this paper we report an enhanced temperature coefficient of resistance
(TCR) close to room temperature in La0.7Ca0.3-xBaxMnO3 + Agy (x = 0.10, 0.15
and y = 0.0 to 0.40) (LCBMO+Ag) composite manganites. The observed enhancement
of TCR is attributed to the grain growth and opening of new conducting channels
in the composites. Ag addition has also been found to enhance intra-granular
magneto-resistance. Inter-granular MR, however, is seen to decrease with Ag
addition. The enhanced TCR and MR at / near room temperature open up the
possibility of the use of such materials as infrared bolometric and magnetic
field sensors respectively.",0907.2134v2
2009-09-21,Spin torque and charge resistance of ferromagnetic semiconductor $2π$ and $π$ domain walls,"Charge resistance and spin torque are generated by coherent carrier transport
through ferromagnetic 360 degree domain walls, although they follow
qualitatively different trends than for 180 degree domain walls. The charge
resistance of 360 degree domain walls reaches a maximum at an intermediate wall
thickness, unlike 180 degree domain walls, whose resistance decreases
monotonically with wall thickness. The peak amplitude of the spin torque and
the optimal thickness of the domain wall to maximize torque for a 360 degree
wall are more than twice as large as found for a 180 degree domain wall in the
same material, producing a larger domain wall velocity for the 360 degree wall
and suggesting unexpected nonlinearities in magnetoelectronic devices
incorporating domain wall motion.",0909.3831v1
2010-08-07,Extending Electrical Resistivity Measurements in Micro-scratching of Silicon to Determine Thermal Conductivity of the Metallic Phase Si-II,"Ductile Regime Machining of semiconductors (DRM) offers higher quality of the
resulting surfaces. To optimize this process, it is required to understand the
thermal kinetics of silicon metallization under pressure. Such understanding is
not yet possible since the metallic phases of silicon aren't readily amenable
to thermal characterization through direct measurements. This being the case,
one has to rely on processing indirect measurement data to deduce refined
estimates of the thermal transport properties of pressurized Silicon. A
feasible measurement of this sort is the electrical resistivity, since its'
variation during indentation and consider is often an indicator of the
formation of the metallic silicon phase Si-II under the indenter. This paper,
therefore, describes a procedure by which the average thermal conductivity of
the metallic phase of silicon, Si-II is extracted from electrical resistivity
measurements taken in real time. The procedure is based on teaming a
temperature evaluation code to the resistivity measurements thus allowing the
extraction of the conductivity as a function of temperature.",1008.1363v1
2013-03-15,Quantum resistance metrology using graphene,"In this paper we review the recent extraordinary progress in the development
of a new quantum standard for resistance based on graphene. We discuss the
unique properties of this material system relating to resistance metrology and
discuss results of the recent highest-ever precision direct comparison of the
Hall resistance between graphene and traditional GaAs. We mainly focus our
review on graphene expitaxially grown on SiC, a system which so far resulted in
the best results. We also brie y discuss progress in the two other graphene
material systems, exfoliated graphene and chemical vapour deposition graphene,
and make a critical comparison with SiC graphene. Finally we discuss other
possible applications of graphene in metrology.",1303.3749v2
2013-07-02,Periodic steps in the resistance vs. temperature characteristics of doped graphite and graphene: evidence of superconductivity?,"We have observed periodically repeated steps in the resistance vs.
temperature characteristics of doped Highly Oriented Pyrolytic Graphite and
exfoliated doped multi-layer graphene. The observations consist of a series of
regularly spaced steps in the resistance vs. temperature curves. The lowest
step is observed at a temperature of from 50 to 60 K. Additional steps are
observed at multiples of that basic temperature with the highest step
temperature being at approximately 270 K. Quenching by a modest applied
magnetic field has been observed. The sizes and widths of the observed steps
appear to vary and may be related to some sort of aggregation reminiscent of
flux vortex pinning. An additional argon ion implantation at reduced energy was
done to see if additional defects in the material would yield additional
structure. This was observed to yield much sharper resistance steps at
temperatures in excess of 200 K in thin exfoliated peels from the implanted
surface of the sample and would support the possibility of the steps being
related to pancake vortex pinning in a layered superconductor. Unfortunately,
as yet, there has been no direct measurement of either the superconducting
energy gap nor has a definitive Meissner effect been observed.",1307.0581v1
2014-04-08,Ferromagnetic resonance spin pumping in CoFeB with highly resistive non-magnetic electrodes,"The relative contribution of spin pumping and spin rectification from the
ferromagnetic resonance of CoFeB/non-magnetic bilayers was investigated as a
function of non-magnetic electrode resistance. Samples with highly resistive
electrodes of Ta or Ti exhibit a stronger spin rectification signal, which may
result in over-(or under-)estimation of the spin Hall angle of the materials,
while those with low resistive electrodes of Pt or Pd show the domination of
the inverse spin Hall effect from spin pumping. By comparison with samples of
single FM layer and an inverted structure, we provide a proper analysis method
to extract spin pumping contribution.",1404.1993v1
2014-10-08,Resistive switching phenomena in TiOx nanoparticle layers for memory applications,"Electrical characteristics of a Co/TiO_x/Co resistive memory device,
fabricated by two different methods are reported. In addition to crystalline
TiO_2 layers fabricated via conventional atomic layer deposition (ALD), an
alternative method has been examined, where TiO_x nanoparticle layers were
fabricated via sol-gel. The different devices have shown different hysteresis
loops with a unique crossing point for the sol-gel devices. A simple
qualitative model is introduced to describe the different current-voltage
behaviours by suggesting only one active metal-oxide interface for the ALD
devices and two active metal-oxide interfaces for the sol-gel devices.
Furthermore, we show that the resistive switching behaviour could be easily
tuned by proper interface engineering and that despite having a similar active
material, different fabrication methods can lead to dissimilar resistive
switching properties.",1410.2019v1
2014-12-19,The Effect of Varying Co layer thickness on the Time-Temperature Characteristics of Co/Sb Semimetal Embedded Magnetic Nanoparticles,"We report the effect of varying cobalt thickness on the temperature-dependent
time decay of the electrical resistance of Co/Sb multilayer samples. We find
that for a given temperature, a five fold change in the Co thickness produces a
100 fold change in the characteristic decay time of the resistance. We find
that the characteristic decay time, as a function of temperature, follows an
Arrhenius law. During deposition, the Co evolves single domain magnetic
nanoparticles, on the Sb, in either a Volmer-Weber or Stranski-Krastanov growth
mode. This metastable state is then encased in 2.5 nm of Sb producing an
embedded nanoparticle system. Scanning Tunneling Microscopy (STM) measurements
taken before sample aging (annealing at a given temperature for enough time to
complete the resistance decay) and after aging show that these nanoparticles
undergo morphological transformations during aging. These transformations lead
to well defined time dependent decays in both the magnetization and the
electrical resistance, making this material an excellent candidate for an
electronic time-temperature sensor.",1412.6436v1
2016-07-07,Low temperature Hall effect in bismuth chalcogenides thin films,"Bismuth chalcogenides are the most studied 3D topological insulators. As a
rule, at low temperatures thin films of these materials demonstrate positive
magnetoresistance due to weak antilocalization. Weak antilocalization should
lead to resistivity decrease at low temperatures; in experiments, however,
resistivity grows as temperature decreases. From transport measurements for
several thin films (with various carrier density, thickness, and carrier
mobility), and by using purely phenomenological approach, with no microscopic
theory, we show that the low temperature growth of the resistivity is
accompanied by growth of the Hall coefficient, in agreement with diffusive
electron-electron interaction correction mechanism. Our data reasonably explain
the low-temperature resistivity upturn.",1607.02034v2
2017-11-05,Quantification of Dislocation-Precipitate Interactions,"The present research is the first attempt to systematically quantify the
dislocation-precipitate interaction in terms of applied shear stress,
precipitate resistance, and the required time to reach the critical state of
dislocation-precipitate interaction when a dislocation line is about to pass
through precipitates. To model the dislocation-precipitate interaction, we
adopt a modified three-dimensional dislocation dynamics. Using the present
modeling approach, which employs three-dimensional dislocation dynamics
simulations, we obtain thousands of data points, accounting for various
precipitate resistances, applied shear stresses, and precipitate spacing. The
material of reference is Copper (Cu). From the simulations, which quantify the
dislocation-precipitate interaction in terms of the applied shear stress,
precipitate resistance scale, and dislocation-precipitate interaction time, we
found a universal equation. The dislocation-precipitate interaction time versus
precipitate resistance and stress, referred to as the ""dislocation-precipitate
interaction map,"" determines the ""pass"" or ""no-pass"" state of the interaction.
Using this map, we incorporate the dislocation-precipitate interaction time in
a two-dimensional multiscale framework which adopts the dislocation dynamics
approach at the micro-scale and the finite element method at the macro-scale.
We use this framework to model the mechanical behavior of free-standing copper
thin films. The results show a dual effect of the dislocation-precipitate
interaction time on the hardening level.",1711.01556v1
2018-04-09,Superconductivity from Meissner Effect and Zero Resistivity in a Phenyl Molecule,"Recently, phenyl molecules have been reported to exhibit Meissner effect
mainly from magnetization measurements. Realizing zero-resistivity state in
these materials seems a challenge due to many practical difficulties but is
required to characterize the existence of superconductivity. By choosing
potassium-doped tris(2-methylphenyl)bismuthine as an example, we perform
temperature-dependent magnetic susceptibility and resistivity measurements at
different magnetic fields and pressures. The solid evidence for supporting
superconductivity is achieved from the obtained Meissner effect and zero
resistivity with the critical temperature ($T_c$) of 3.6 K at atmosphere
pressure. Upon compression, we observe the gradual evolution of
superconductivity from its initial phase with a parabolic behavior of $T_{c}$
to the second one with almost constant value of $T_{c}$ of 7 K. The 7 K phase
seems a common feature for these newly discovered phenyl-based superconductors.",1804.03060v1
2018-09-17,Tetragonal CuMnAs alloy: role of defects,"The antiferromagnetic (AFM) CuMnAs alloy with tetragonal structure is a
promising material for the AFM spintronics. The resistivity measurements
indicate the presence of defects about whose types and concentrations is more
speculated as known. We confirmed vacancies on Mn or Cu sublattices and
Mn$_{\rm Cu}$ and Cu$_{\rm Mn}$ antisites as most probable defects in CuMnAs by
our new ab initio total energy calculations. We have estimated resistivities of
possible defect types as well as resistivities of samples for which the X-ray
structural analysis is available. In the latter case we have found that samples
with Cu- and Mn-vacancies with low formation energies have also resistivities
which agree well with the experiment. Finally, we have also calculated exchange
interactions and estimated the N\'eel temperatures by using the Monte Carlo
approach. A good agreement with experiment was obtained.",1809.06239v1
2022-02-13,Slow electron-phonon relaxation controls the dynamics of the superconducting resistive transition,"We investigate the temporal and spatial scales of resistance fluctuations
(R-fluctuations) at the superconducting resistive transition accessed through
voltage fluctuations measurements in thin epitaxial TiN films. This material is
characterized by a record slow electron-phonon relaxation, which puts it far
beyond the applicability range of the textbook scenario of superconducting
fluctuations. The measured Lorentzian spectrum of the R-fluctuations identifies
their correlation time, which is nearly constant across the transition region
and has no relation to the conventional Ginzburg-Landau time scale. Instead,
the correlation time coincides with the energy relaxation time determined by a
combination of the electron-phonon relaxation and the diffusion in reservoirs.
Our data is quantitatively consistent with the model of spontaneous temperature
fluctuations and highlight important caveats in the accepted physical picture
of the resistive transition in materials with slow electron-phonon relaxation.",2202.06309v2
2015-07-30,A physics based model of gate tunable metal-graphene contact resistance benchmarked against experimental data,"The metal-graphene contact resistance is a technological bottleneck for the
realization of viable graphene based electronics. We report a useful model to
find the gate tunable components of this resistance determined by the
sequential tunneling of carriers between the 3D-metal and 2D-graphene
underneath followed by Klein tunneling to the graphene in the channel. This
model quantifies the intrinsic factors that control that resistance, including
the effect of unintended chemical doping. Our results agree with experimental
results for several metals.",1507.08412v1
2018-07-12,Ultra Low Specific Contact Resistivity in Metal-Graphene Junctions via Atomic Orbital Engineering,"A systematic investigation of graphene edge contacts is provided.
Intentionally patterning monolayer graphene at the contact region creates
well-defined edge contacts that lead to a 67% enhancement in current injection
from a gold contact. Specific contact resistivity is reduced from 1372
{\Omega}m for a device with surface contacts to 456 {\Omega}m when contacts are
patterned with holes. Electrostatic doping of the graphene further reduces
contact resistivity from 519 {\Omega}m to 45 {\Omega}m, a substantial decrease
of 91%. The experimental results are supported and understood via a multi-scale
numerical model, based on density-functional-theory calculations and transport
simulations. The data is analyzed with regards to the edge perimeter and
hole-to-graphene ratio, which provides insights into optimized contact
geometries. The current work thus indicates a reliable and reproducible
approach for fabricating low resistance contacts in graphene devices. We
provide a simple guideline for contact design that can be exploited to guide
graphene and 2D material contact engineering.",1807.04772v1
2019-10-18,Resistive contribution in electrical switching experiments with antiferromagnets,"Recent research demonstrated the electrical switching of antiferromagnets via
intrinsic spin-orbit torque or the spin Hall effect of an adjacent heavy metal
layer. The electrical readout is typically realized by measuring the transverse
anisotropic magnetoresistance at planar cross- or star-shaped devices with four
or eight arms, respectively. Depending on the material, the current density
necessary to switch the magnetic state can be large, often close to the
destruction threshold of the device. We demonstrate that the resulting
electrical stress changes the film resistivity locally and thereby breaks the
fourfold rotational symmetry of the conductor. This symmetry breaking due to
film inhomogeneity produces signals, that resemble the anisotropic
magnetoresistance and is experimentally seen as a ""saw-tooth""-shaped transverse
resistivity. This artifact can persist over many repeats of the switching
experiment and is not easily separable from the magnetic contribution. We
discuss the origin of the artifact, elucidate the role of the film
crystallinity, and propose approaches how to separate the resistive
contribution from the magnetic contribution.",1910.08576v1
2020-12-11,Anomalous Hall resistivity and possible topological Hall effect in the EuAl$_4$ antiferromagnet,"We report the observation of anomalous Hall resistivity in single crystals of
EuAl$_4$, a centrosymmetric tetragonal compound, which exhibits coexisting
antiferromagnetic (AFM) and charge-density-wave (CDW) orders with onset at
$T_\mathrm{N} \sim 15.6$ K and $T_\mathrm{CDW} \sim 140$ K, respectively. In
the AFM state, when the magnetic field is applied along the $c$-axis direction,
EuAl$_4$ undergoes a series of metamagnetic transitions. Within this field
range, we observe a clear hump-like anomaly in the Hall resistivity,
representing part of the anomalous Hall resistivity. By considering different
scenarios, we conclude that such a hump-like feature is most likely a
manifestation of the topological Hall effect, normally occurring in
noncentrosymmetric materials known to host nontrivial topological spin
textures. In view of this, EuAl$_4$ would represent a rare case where the
topological Hall effect not only arises in a centrosymmetric structure, but it
also coexists with CDW order.",2012.06088v1
2021-05-11,Lattice contraction induced by resistive switching in chromium-doped V2O3: a hallmark of Mott physics,"Since the beginnings of the electronic age, a quest for ever faster and
smaller switches has been initiated, since this element is ubiquitous and
foundational in any electronic circuit to regulate the flow of current. Mott
insulators are promising candidates to meet this need as they undergo extremely
fast resistive switching under electric field. However the mechanism of this
transition is still under debate. Our spatially-resolved {\mu}-XRD imaging
experiments carried out on the prototypal Mott insulator (V0.95Cr0.05)2O3 show
that the resistive switching is associated with the creation of a conducting
filamentary path consisting in an isostructural compressed phase without any
chemical nor symmetry change. This clearly evidences that the resistive
switching mechanism is inherited from the bandwidth-controlled Mott transition.
This discovery might hence ease the development of a new branch of electronics
dubbed Mottronics.",2105.05093v2
2021-06-21,Unique Temperature Distribution and Explicit Efficiency Formula for One-Dimensional Thermoelectric Generators under Constant Seebeck Coefficients,"A thermoelectric generator converts a temperature difference into electrical
energy. Its energy conversion efficiency is determined by the steady-state
temperature distribution inside the generator. By assuming the thermoelectric
material in the generator has a temperature-independent Seebeck coefficient and
the generator is one-dimensional, we show that the second-order
integro-differential equation describing the inside temperature distribution
has a unique solution for any given ratio of external load resistance to the
internal resistance. Hence the efficiency is well defined. Furthermore, we show
the efficiency has an explicit formula in terms of the temperature-dependent
thermal conductivity and electrical resistivity of the thermoelectric material.
On the other hand, if we impose an external load resistance value, not the
ratio, then the integro-differential equation can have multiple solutions.",2106.10957v1
2022-05-02,Recent advances in inorganic oxides-based resistive random-access memory devices,"Memory has always been a building block element for information technology.
Emerging technologies such as artificial intelligence, big data, the internet
of things, etc., require a novel kind of memory technology that can be energy
efficient and have an exception data retention period. Among several existing
memory technologies, resistive random-access memory (RRAM) is an answer to the
above question as it is necessary to possess the combination of speed of RAM
and nonvolatility, thus proving to be one of the most promising candidates to
replace flash memory in next-generation non-volatile RAM applications. This
review discusses the existing challenges and technological advancements made
with RRAM, including switching mechanism, device structure, endurance, fatigue
resistance, data retention period, and mechanism of resistive switching in
inorganic oxides material used as a dielectric layer. Finally, a summary and a
perspective on future research are presented.",2205.05537v1
2023-01-06,"Spin Transport in Magnetically Ordered Systems: Ferromagnets, Antiferromagnets and Frustrated Systems","In this review, we outline the important results on the resistivity
encountered by an electron in magnetically ordered materials. The mechanism of
the collision between the electron and the lattice spins is shown. Experiments
on the spin resistivity in various magnetic materials as well as theoretical
background are recalled. We focus on our works since 15 years using principally
Monte Carlo simulations. In these works, we have studied the spin resistivity
in various kinds of magnetic systems ranging from ferromagnets and
antiferromagnets to frustrated spin systems. It is found that the spin
resistivity shows a broad peak at the transition temperature in systems with a
second-order phase transition, while it undergoes a discontinuous jump at the
transition temperature of a first-order transition. New results on the
hexagonal-close-packed (HCP) antiferromagnet are also shown in extended details
for the Ising case in both the frustrated and non-frustrated parameter regions.",2301.02689v1
2023-02-27,Analytical expression of negative differential thermal resistance in a macroscopic heterojunction,"Heat flux ($J$) generally increases with temperature difference in a
material. A differential coefficient of $J$ against temperature ($T$) is called
differential thermal conductance ($k$), and an inverse of $k$ is differential
thermal resistance ($r$). Although $k$ and $r$ are generally positive, they can
be negative in a macroscopic heterojunction with positive $T$-dependent
interfacial thermal resistance (ITR). The negative differential thermal
resistance (NDTR) effect is an important effect that can realize thermal
transistor, thermal memory, and thermal logic gate. In this paper, we examine
analytical expressions of $J$, $k$, $r$, and other related quantities as a
function of parameters related to thermal conductivity ($\kappa$) and ITR in a
macroscopic heterojunction to precisely describe the NDTR effect.",2302.14065v3
2017-01-18,Role of Thermal Resistance on the Performance of Superconducting Radio Frequency Cavities,"Thermal stability is an important parameter for the operation of the
superconducting radio frequency (SRF) cavities used in particle accelerators.
The rf power dissipated on the inner surface of the cavities is conducted to
the helium bath cooling the outer cavity surface and the equilibrium
temperature of the inner surface depends on the thermal resistance. In this
manuscript, we present the results of direct measurements of thermal resistance
on 1.3 GHz single cell SRF cavities made from high purity large grain and fine
grain niobium as well as their rf performance for different treatments applied
to outer cavity surface in order to investigate the role of the Kapitza
resistance to the overall thermal resistance and to the SRF cavity performance.
The results show no significant impact of the thermal resistance to the SRF
cavity performance after chemical polishing, mechanical polishing or
anodization of the outer cavity surface. Temperature maps taken during the rf
test show non-uniform heating of the surface at medium rf fields. Calculations
of Q0(Bp) curves using the thermal feedback model show good agreement with
experimental data at 2 K and 1.8 K when a pair-braking term is included in the
calculation of the BCS surface resistance. These results indicate local
intrinsic non-linearities of the surface resistance, rather than purely thermal
effects, to be the main cause for the observed field dependence of Q0(Bp).",1701.05097v1
2019-04-13,Quantum Point Contact Parameter Extraction of Carbon-based Resistive Memory using Hybrid Genetic Algorithm,"Resistive switching phenomenon in carbon film is associated with formation
and annihilation of low resistance sp2 nanochannels within the amorphous sp3
matrix. The thinnest point of these graphitic nanochannels behaves like quantum
wire (QW) and limits current flow. Transport mechanism at these bottlenecks can
be described within the framework of quantum point contact (QPC) model. The
model applies mesoscopic Landauer formalism and correlates device resistance
state with the density of the nanochannels as well as lateral area of its
constriction. However, QPC model parameter extraction from macroscopic I-V
characteristic is not feasible due to multiple nonlinear and closely coupled
parameters, e.g. barrier height ({\Phi}), barrier curvature ({\alpha}) and
voltage drop ratio (\b{eta}). In this work, a hybrid genetic algorithm (GA)
based parameter extraction flow is proposed and is applied to extract
parameters from experimental result of carbon-based resistive memories. In this
proposed flow, the number of single subband channels for low resistance state
(NLRS) and barrier curvature parameter at high resistance state ({\alpha}HRS)
were first derived by exploring boundary conditions at low voltage. The four
remaining parameters ({\Phi}HRS, {\Phi}LRS, {\alpha}LRS, and \b{eta}) were then
extracted from experimental I-V characteristic by leveraging hybrid GA. Mean
absolute percentage error (MAPE) of fitted QPC models is only 3.7% and the
extracted parameters are within reasonable range. Hereby, we regard the QPC
model as a viable model to describe conduction mechanism of graphitic
nanochannels in carbon-based resistive memories.",1904.06542v1
2022-11-16,Unconventional charge-to-spin conversions in graphene/MoTe2 van der Waals heterostructures,"Spin-charge interconversion (SCI) is a central phenomenon to the development
of spintronic devices from materials with strong spin-orbit coupling (SOC). In
the case of materials with high crystal symmetry, the only allowed SCI
processes are those where the spin current, charge current and spin
polarization directions are orthogonal to each other. Consequently, standard
SCI experiments are designed to maximize the signals arising from the SCI
processes with conventional mutually orthogonal geometry. However, in
low-symmetry materials, certain non-orthogonal SCI processes are also allowed.
Since the standard SCI experiment is limited to charge current flowing only in
one direction in the SOC material, certain allowed SCI configurations remain
unexplored. In this work, we performed a thorough SCI study in a graphene-based
lateral spin valve combined with low-symmetry MoTe$_2$. Due to a very low
contact resistance between the two materials, we could detect SCI signals using
both a standard configuration, where the charge current is applied along the
MoTe$_2$, and a recently introduced (3D-current) configuration, where the
charge current flow can be controlled in three directions within the
heterostructure. As a result, we observed three different SCI components, one
orthogonal and two non-orthogonal, giving new insight into the SCI processes in
low-symmetry materials. The large SCI signals obtained at room temperature,
along with the versatility of the 3D-current configuration, provide feasibility
and flexibility to the design of the next generation of spin-based devices.",2211.09095v1
2001-06-27,Planar Superconductor-Normal-Superconductor Josephson Junctions in MgB2,"Since the discovery of superconductivity in MgB2 considerable progress has
been made in determining the physical properties of the material, which are
promising for bulk conductors. Tunneling studies show that the material is
reasonably isotropic and has a well-developed s-wave energy gap (&#8710;),
implying that electronic devices based on MgB2 could operate close to 30K.
Although a number of groups have reported the formation of thin films by
post-reaction of precursors, heterostructure growth is likely to require
considerable technological development, making single-layer device structures
of most immediate interest. MgB2 is unlike the cuprate superconductors in that
grain boundaries do not form good Josephson junctions, and although a SQUID
based on MgB2 nanobridges has been fabricated, the nanobridges themselves do
not show junction-like properties. Here we report the successful creation of
planar MgB2 junctions by localised ion damage in thin films. The critical
current (IC) of these devices is strongly modulated by applied microwave
radiation and magnetic field. The product of the critical current and normal
state resistance (ICRN) is remarkably high, implying a potential for very high
frequency applications.",0106562v1
2008-04-02,Anomalously large measured thermoelectric power factor in Sr$_{1-x}$La$_x$TiO$_3$ thin films due to SrTiO$_3$ substrate reduction,"We report the observation that thermoelectric thin-films of La-doped SrTiO3
grown on SrTiO3 substrates yield anomalously high values of thermopower to give
extraordinary values of power factor at 300K. Thin-films of Sr0.98La0.02TiO3,
grown via pulsed laser deposition at low temperature and low pressure (450C,
10-7Torr), do not yield similarly high values when grown on other substrates.
The thin-film growth induces oxygen reduction in the SrTiO3 crystals, doping
the substrate n-type. It is found that the backside resistance of the SrTiO3
substrates is as low (~12ohm/square) as it is on the film-side after film
growth.",0804.0443v3
2014-06-13,Superconductivity in single-layer films of FeSe with a transition temperature above 100 K,"Recently, interface has been employed to enhance superconductivity in the
single-layer FeSe films grown on SrTiO3(001)(STO) with a possible Tc of ~ 80 K,
which is nearly ten times of the Tc of bulk FeSe and is above the Tc record of
56 K for the bulk Fe-based superconductors. This work together with those on
superconducting oxides interfaces revives the long-standing idea that electron
pairing at a two-dimensional (2D) interface between two different materials is
a potential path to high transition temperature (Tc) superconductivity.
Subsequent angle-resolved photoemission spectroscopy (ARPES) measurements
revealed different electronic structure from those of bulk FeSe with a
superconducting-like energy gap closing at around 65K. However, previous ex
situ electrical transport measurements could only detect the zero-resistance
below ~30 K. Here we report the observation of high Tc superconductivity in the
FeSe/STO system. By in situ 4-point probe (4PP) electrical transport
measurement that can be conducted at an arbitrary position of the FeSe film on
STO, we detected superconductivity above 100 K. Our finding makes FeSe/STO the
exciting and ideal research platform for higher Tc superconductivity.",1406.3435v1
2019-05-23,Lattice frustration in spin-orbit Mott insulator Sr3Ir2O7 at high pressure,"The intertwined charge, spin, orbital, and lattice degrees of freedom could
endow 5d compounds with exotic properties. Current interest is focused on
electromagnetic interactions in these materials, whereas the important role of
lattice geometry remains to be fully recognized. For this sake, we investigate
pressure-induced phase transitions in the spin-orbit Mott insulator Sr3Ir2O7
with Raman, electrical resistance, and x-ray diffraction measurements. We
reveal an interesting magnetic transition coinciding with a structural
transition at 14.4 GPa, but without a concurrent insulator-metal transition.
The conventional correlation between magnetic and Mott insulating states is
thereby absent. The observed softening of the one-magnon mode can be explained
by a reduced tetragonal distortion, while the actual magnetic transition is
associated with tilting of the IrO6 octahedra. This work highlights the
critical role of lattice frustration in determining the high-pressure phases of
Sr3Ir2O7. The ability to control electromagnetic properties via manipulating
the crystal structure with pressure promises a new way to explore new quantum
states in spin-orbit Mott insulators.",1905.09637v1
2019-09-13,Monolayer MoS2 field effect transistor with low Schottky barrier height with ferromagnetic metal contacts,"Two-dimensional MoS2 has emerged as promising material for nanoelectronics
and spintronics due to its exotic properties. However, high contact resistance
at metal semiconductor MoS2 interface still remains an open issue. Here, we
report electronic properties of field effect transistor devices using monolayer
MoS2 channels and permalloy (Py) as ferromagnetic (FM) metal contacts.
Monolayer MoS2 channels were directly grown on SiO2/Si substrate via chemical
vapor deposition technique. The increase in current with back gate voltage
shows the tunability of FET characteristics. The Schottky barrier height (SBH)
estimated for Py/MoS2 contacts is found to be +28.8 meV (zero-bias), which is
the smallest value reported so-far for any direct metal (magnetic or
non-magnetic)/monolayer MoS2 contact. With the application of gate voltage (+10
V), SBH shows a drastic reduction down to a value of -6.8 meV. The negative SBH
reveals ohmic behavior of Py/MoS2 contacts. Low SBH with controlled ohmic
nature of FM contacts is a primary requirement for MoS2 based spintronics and
therefore using directly grown MoS2 channels in the present study can pave a
path towards high performance devices for large scale applications.",1909.06014v1
2017-03-10,Extremely high conductivity observed in the triple point topological metal MoP,"Weyl and Dirac fermions have created much attention in condensed matter
physics and materials science. Recently, several additional distinct types of
fermions have been predicted. Here, we report ultra-high electrical
conductivity in MoP at low temperature, which has recently been established as
a triple point Fermion material. Here we show that the electrical resistivity
is 6 n-ohm cm at 2 K with a large mean free path of 11 microns. de Haas-van
Alphen oscillations reveal spin splitting of the Fermi surfaces. In contrast to
noble metals with similar conductivity and number of carriers, the
magnetoresistance in MoP does not saturate up to 9 T at 2 K. Interestingly, the
momentum relaxing time of the electrons is found to be more than 15 times
larger than the quantum coherence time. This difference between the scattering
scales shows that momentum conserving scattering dominates in MoP at low
temperatures.",1703.03736v2
2020-09-13,Topologically-Driven Linear Magnetoresistance in Helimagnetic FeP,"The helimagnet FeP is part of a family of binary pnictide materials with the
MnP-type structure which share a nonsymmorphic crystal symmetry that preserves
generic band structure characteristics through changes in elemental
composition. It shows many similarities, including in its magnetic order, to
isostructural CrAs and MnP, two compounds that are driven to superconductivity
under applied pressure. Here we present a series of high magnetic field
experiments on high quality single crystals of FeP, showing that the resistance
not only increases without saturation by up to several hundred times its zero
field value by 35 T, but that it also exhibits an anomalously linear field
dependence over the entire field range when the field is aligned precisely
along the crystallographic c-axis. A close comparison of quantum oscillation
frequencies to electronic structure calculations links this orientation to a
semi-Dirac point in the band structure which disperses linearly in a single
direction in the plane perpendicular to field, a symmetry-protected feature of
this entire material family. We show that the two striking features of MR-large
amplitude and linear field dependence-arise separately in this system, with the
latter likely due to a combination of ordered magnetism and topological band
structure.",2009.05984v2
2017-04-28,Optimization of the Crystal Growth of the Superconductor CaKFe$_{4}$As$_{4}$ from Solution in the FeAs-CaFe$_{2}$As$_{2}$-KFe$_{2}$As$_{2}$ System,"Measurements of the anisotropic properties of single crystals play a crucial
role in probing the physics of new materials. Determining a growth protocol
that yields suitable high-quality single crystals can be particularly
challenging for multi-component compounds. Here we present a case study of how
we refined a procedure to grow single crystals of CaKFe$_{4}$As$_{4}$ from a
high temperature, quaternary liquid solution rich in iron and arsenic (""FeAs
self-flux""). Temperature dependent resistance and magnetization measurements
are emphasized, in addition to the x-ray diffraction, to detect inter-grown
CaKFe$_{4}$As$_{4}$, CaFe$_{2}$As$_{2}$ and KFe$_{2}$As$_{2}$ within, what
appear to be, single crystals. Guided by the rules of phase equilibria and
these data, we adjusted growth parameters to suppress formation of the impurity
phases. The resulting optimized procedure yielded phase-pure single crystals of
CaKFe$_{4}$As$_{4}$. This optimization process offers insight into the growth
of quaternary compounds and a glimpse of the four-component phase diagram in
the pseudo-ternary FeAs-CaFe$_{2}$As$_{2}$-KFe$_{2}$As$_{2}$ system.",1704.09025v2
2020-08-15,Low Dimensional Material based Electro-Optic Phase Modulation Performance Analysis,"Electro-optic modulators are utilized ubiquitously ranging from applications
in data communication to photonic neural networks. While tremendous progress
has been made over the years, efficient phase-shifting modulators are
challenged with fundamental tradeoffs, such as voltage-length, index
change-losses or energy-bandwidth, and no single solution available checks all
boxes. While voltage-driven phase modulators, such as based on lithium niobate,
offer low loss and high speed operation, their footprint of 10's of cm-scale is
prohibitively large, especially for density-critical applications, for example
in photonic neural networks. Ignoring modulators for quantum applications,
where loss is critical, here we distinguish between current versus
voltage-driven modulators. We focus on the former, since current-based schemes
of emerging thin electro-optical materials have shown unity-strong index
modulation suitable for heterogeneous integration into foundry waveguides.
Here, we provide an in-depth ab-initio analysis of obtainable modulator
performance based on heterogeneously integrating low-dimensional materials,
i.e. graphene, thin films of indium tin oxide, and transition metal
dichalcogenide monolayers into a plurality of optical waveguide designs atop
silicon photonics. Using the fundamental modulator tradeoff of
energy-bandwidth-product as a design-quality quantifier, we show that a small
modal cross section, such as given by plasmonic modes, enables high-performance
operation, physically realized by arguments on charge-distribution and low
electrical resistance. An in-depth design understanding of phase-modulator
performance, beyond doped-junctions in silicon, offers opportunities for
micrometer-compact yet energy-bandwidth-ratio constrained modulators with
timely opportunities to hardware-accelerate applications beyond data
communication towards photonic machine intelligence.",2008.06792v1
2021-03-30,Magnetic Texture in Insulating Single Crystal High Entropy Oxide Spinel Films,"Magnetic insulators are important materials for a range of next generation
memory and spintronic applications. Structural constraints in this class of
devices generally require a clean heterointerface that allows effective
magnetic coupling between the insulating layer and the conducting layer.
However, there are relatively few examples of magnetic insulators which can be
synthesized with surface qualities that would allow these smooth interfaces and
precisely tuned interfacial magnetic exchange coupling which might be
applicable at room temperature. In this work, we demonstrate an example of how
the configurational complexity in the magnetic insulator layer can be used to
realize these properties. The entropy-assisted synthesis is used to create
single crystal (Mg0.2Ni0.2Fe0.2Co0.2Cu0.2)Fe2O4 films on substrates spanning a
range of strain states. These films show smooth surfaces, high resistivity, and
strong magnetic responses at room temperature. Local and global magnetic
measurements further demonstrate how strain can be used to manipulate magnetic
texture and anisotropy. These findings provide insight into how precise
magnetic responses can be designed using compositionally complex materials that
may find application in next generation magnetic devices.",2103.16722v1
2022-08-03,"Reactive Laser Synthesis of Ultra-high-temperature Ceramics HfC, ZrC, TiC, HfN, ZrN, and TiN for Additive Manufacturing","Ultra-high-temperature ceramics (UHTCs) are optimal structural materials for
applications that require extreme temperature resilience, resistance to
chemically aggressive environments, wear, and mechanical stress. Processing
UHTCs with laser-based additive manufacturing (AM) has not been fully realized
due to a variety of obstacles. In this work, selective laser reaction sintering
(SLRS) techniques were investigated for the production of near net-shape UHTC
ceramics such as HfC, ZrC, TiC, HfN, ZrN, and TiN. Group IV transition metal
and metal oxide precursor materials were chemically converted and
reaction-bonded into layers of UHTCs using single-step selective laser
processing in CH4 or NH3 gas that might be compatible with prevailing powder
bed fusion techniques. Conversion of either metals (Hf, Zr and Ti) or metal
oxides (HfO2, ZrO2, and TiO2) particles was first investigated to examine
reaction mechanisms and volume changes associated with SLRS of single-component
precursor systems. SLRS processing of metal or metal oxide alone produced near
stoichiometric UHTC phases with yields up to 100 wt% total for carbides and
nitrides. However, for single component precursors, gas-solid reactivity
induced volumetric changes resulted in residual stresses and cracking in the
product layer. To mitigate conversion-induced stresses, composite metal/metal
oxide precursors were employed to compensate for the volume changes of either
the metal (which expands during conversion) or the metal oxide precursor (which
contracts).",2208.02041v2
2023-04-24,Absolute radiation tolerance of amorphous alumina coatings at room temperature,"In this study structural and mechanical properties of a 1 um thick Al2O3
coating, deposited on 316L stainless steel by Pulsed Laser Deposition (PLD),
subjected to high energy ion irradiation were assessed. Mechanical properties
of pristine and ion-modified specimens were investigated using the
nanoindentation technique. A comprehensive characterization combining
Transmission Electron Microscopy and Grazing-Incidence X-ray Diffraction
provided deep insight into the structure of the tested material at the nano-
and micro- scale. Variation in the local atomic ordering of the irradiated zone
at different doses was investigated using a reduced distribution function
analysis obtained from electron diffraction data. Findings from nanoindentation
measurements revealed a slight reduction in hardness of all irradiated layers.
At the same time TEM examination indicated that the irradiated layer remained
amorphous over the whole dpa range. No evidence of crystallization, void
formation or element segregation was observed up to the highest implanted dose.
Reported mechanical and structural findings were critically compared with each
other pointing to the conclusion that under given irradiation conditions, over
the whole range of doses used, alumina coatings exhibit excellent radiation
resistance. Obtained data strongly suggest that investigated material may be
considered as a promising candidate for next-generation nuclear reactors,
especially LFR-type, where high corrosion protection is one of the highest
prerogatives to be met.",2304.11973v1
2023-06-01,"Nonlinear characteristics of Ti, Nb, and NbN superconducting resonators for parametric amplifiers","Superconducting resonators and parametric amplifiers are important components
in scientific systems such as kinetic inductance detector arrays,
frequency-domain multiplexers for other superconducting bolometers,
spin-ensemble based memories, and circuit quantum electrodynamics
demonstrators. In this paper, we report microwave measurements of
superconducting Ti, Nb, and NbN resonators and their use as parametric
amplifiers. These half-wave resonators were fabricated under near identical
sputtering and lithographic conditions to ensure a like-for-like comparison of
material properties. We report a wide range of properties and behaviours in
terms of transition temperatures, resistivities, rate-limiting nonlinear
response times, nonlinear dissipation, signs of the nonlinear inductances and
their dependences on temperature and resonance harmonic. We have successfully
operated Nb and NbN resonators as high gain parametric amplifiers, achieving
greater than $20\,\mathrm{dB}$ of power amplification. We have shown that for a
half-wave resonator, amplification can be realised not only in the fundamental
resonance but also in the higher harmonic resonances. Further, for materials
with high transition temperatures, e.g. Nb and NbN, amplification can be
achieved at $\sim4\,\mathrm{K}$, i.e. a temperature maintained by a pulse tube
cooler. Finally, in materials systems that have very fast response times, e.g.
NbN, we have found that a cross-harmonic type of amplification can be achieved
by placing pump tone in a different resonant mode as the signal and the idler.
This wide range of observations will have important implications on the design
and application of superconducting parametric amplifiers.",2306.00685v2
2023-07-17,MBE growth of axion insulator candidate EuIn2As2,"The synthesis of thin films of magnetic topological materials is necessary to
achieve novel quantized Hall effects and electrodynamic responses. EuIn2As2 is
a recently predicted topological axion insulator that has an antiferromagnetic
ground state and an inverted band structure, but that has only been synthesized
and studied as a single crystal. We report on the synthesis of c-axis oriented
EuIn2As2 films on sapphire substrates by molecular beam epitaxy. By carefully
tuning the substrate temperature during growth, we stabilize the Zintl phase of
EuIn2As2 expected to be topologically non-trivial. The magnetic properties of
these films reproduce those seen in single crystals, but their resistivity is
enhanced when grown at lower temperatures. We additionally find that the
magnetoresistance of EuIn2As2 is negative even up to fields as high as 31T.
while it is highly anisotropic at low fields, it becomes nearly isotropic at
high magnetic fields above 5T. Overall, the transport characteristics of
EuIn2As2 appear similar to those of chalcogenide topological insulators,
motivating the development of devices to gate tune the Fermi energy and reveal
topological features in quantum transport.",2307.08831v2
2023-12-20,Singular Hall response from a correlated ferromagnetic flat nodal-line semimetal,"Topological quantum phases have been largely understood in weakly correlated
systems, which have identified various quantum phenomena such as spin Hall
effect, protected transport of helical fermions, and topological
superconductivity. Robust ferromagnetic order in correlated topological
materials particularly attracts attention, as it can provide a versatile
platform for novel quantum devices. Here, we report singular Hall response
arising from a unique band structure of flat topological nodal lines in
combination with electron correlation in an itinerant, van der Waals
ferromagnetic semimetal, Fe3GaTe2, with a high Curie temperature of Tc=360 K.
High anomalous Hall conductivity violating the conventional scaling,
resistivity upturn at low temperature, and a large Sommerfeld coefficient are
observed in Fe3GaTe2, which implies heavy fermion features in this
ferromagnetic topological material. Our circular dichroism in angle-resolved
photoemission spectroscopy and theoretical calculations support the original
electronic features in the material. Thus, low-dimensional Fe3GaTe2 with
electronic correlation, topology, and room-temperature ferromagnetic order
appears to be a promising candidate for robust quantum devices.",2312.12889v1
2024-02-28,Multifunctional composite magnet for practical transverse thermoelectrics,"Permanent magnets are used in various products and essential for human
society. If omnipresent permanent magnets could directly convert heat into
electricity, they would lead to innovative energy harvesting and thermal
management technologies. However, achieving such ""multifunctionality"" has been
difficult because of the poor thermoelectric performance of conventional
magnets. Here, we develop a multifunctional composite magnet that enables giant
transverse thermoelectric conversion. The proposed composite material,
comprising alternately and obliquely stacked
SmCo$_5$/Bi$_{0.2}$Sb$_{1.8}$Te$_3$ multilayers, exhibits large remanent
magnetization and coercivity as well as an excellent figure of merit of 0.32
for transverse thermoelectric conversion around room temperature. While having
versatile transverse geometry and high mechanical durability, the thermopile
module based on these composite magnets generates 204 mW at a temperature
difference of 152 K owing to extremely low interfacial electrical and thermal
resistances. The corresponding power density per heat transfer area of 56.7
mW/cm$^2$ is not only record-high among all the transverse thermoelectric
modules but also comparable to those of commercial longitudinal thermoelectric
modules based on the Seebeck effect. The novel functional material enables the
integration of thermoelectric conversion capabilities wherever permanent
magnets are currently used.",2402.18019v1
1996-06-05,Hall Resistivity in Ferromagnetic Manganese-Oxide Compounds,"Temperature-dependence and magnetic field-dependence of the Hall effect and
the magnetic property in manganese-oxide thin films are studied. The
spontaneous magnetization and the Hall resistivity are obtained for a various
of magnetic fields over all the temperature. It is shown that the Hall
resistivity in small magnetic field is to exhibit maximum near the Curie point,
and strong magnetic field moves the position of the Hall resistivity peak to
much high temperature and suppresses the peak value. The change of the Hall
resistance in strong magnetic field may be larger than that of the diagonal
ones. The abnormal Hall resistivity in the ferromagnetic manganese-oxide
thin-films is attributed to the spin-correlation fluctuation scattering.",9606030v1
2002-06-04,Free flux flow resistivity in strongly overdoped high-T_c cuprate; purely viscous motion of the vortices in semiclassical d-wave superconductor,"We report the free flux flow (FFF) resistivity associated with a purely
viscous motion of the vortices in moderately clean d-wave superconductor
Bi:2201 in the strongly overdoped regime (T_c=16K) for a wide range of the
magnetic field in the vortex state. The FFF resistivity is obtained by
measuring the microwave surface impedance at different microwave frequencies.
It is found that the FFF resistivity is remarkably different from that of
conventional s-wave superconductors. At low fields (H<0.2H_c2) the FFF
resistivity increases linearly with H with a coefficient which is far larger
than that found in conventional s-wave superconductors. At higher fields, the
FFF resistivity increases in proportion to \sqrt H up to H_c2. Based on these
results, the energy dissipation mechanism associated with the viscous vortex
motion in ""semiclassical"" d-wave superconductors with gap nodes is discussed.
Two possible scenarios are put forth for these field dependence; the
enhancement of the quasiparticle relaxation rate and the reduction of the
number of the quasiparticles participating the energy dissipation in d-wave
vortex state.",0206031v1
2003-06-14,Radiation induced zero-resistance states in GaAs/AlGaAs heterostructures: Voltage-current characteristics and intensity dependence at the resistance minima,"High mobility two-dimensional electron systems exhibit vanishing resistance
over broad magnetic field intervals upon excitation with microwaves, with a
characteristic reduction of the resistance with increasing radiation intensity
at the resistance minima. Here, we report experimental results examining the
voltage - current characteristics, and the resistance at the minima vs. the
microwave power. The findings indicate that a non-linear V-I curve in the
absence of microwave excitation becomes linearized under irradiation, unlike
expectations, and they suggest a similarity between the roles of the radiation
intensity and the inverse temperature.",0306388v2
2007-05-12,Effects of electromagnetic waves on the electrical properties of contacts between grains,"A DC electrical current is injected through a chain of metallic beads. The
electrical resistances of each bead-bead contacts are measured. At low current,
the distribution of these resistances is large and log-normal. At high enough
current, the resistance distribution becomes sharp and Gaussian due to the
creation of microweldings between some beads. The action of nearby
electromagnetic waves (sparks) on the electrical conductivity of the chain is
also studied. The spark effect is to lower the resistance values of the more
resistive contacts, the best conductive ones remaining unaffected by the spark
production. The spark is able to induce through the chain a current enough to
create microweldings between some beads. This explains why the electrical
resistance of a granular medium is so sensitive to the electromagnetic waves
produced in its vicinity.",0705.1775v2
2009-12-10,Dichotomy in the $T$-linear resistivity in hole-doped cuprates,"From analysis of the in-plane resistivity $\rho_{ab}(T)$ of
La$_{2-x}$Sr$_x$CuO$_4$, we show that normal state transport in overdoped
cuprates can be delineated into two regimes in which the electrical resistivity
varies approximately linearly with temperature. In the low temperature limit,
the $T$-linear resistivity extends over a very wide doping range, in marked
contrast to expectations from conventional quantum critical scenarios. The
coefficient of this $T$-linear resistivity scales with the superconducting
transition temperature $T_c$, implying that the interaction causing this
anomalous scattering is also associated with the superconducting pairing
mechanism. At high temperatures, the coefficient of the $T$-linear resistivity
is essentially doping independent beyond a critical doping $p_{\rm crit}$ =
0.19 at which the ratio of the two coefficients is maximal. Taking our cue from
earlier thermodynamic and photoemission measurements, we conclude that the
opening of the normal state pseudogap at $p_{\rm crit}$ is driven by the loss
of coherence of anti-nodal quasiparticles at low temperatures.",0912.2001v1
2010-05-25,Resistive Magnetohydrodynamic Simulations of Relativistic Magnetic Reconnection,"Resistive relativistic magnetohydrodynamic (RRMHD) simulations are applied to
investigate the system evolution of relativistic magnetic reconnection. A
time-split Harten--Lan--van Leer method is employed. Under a localized
resistivity, the system exhibits a fast reconnection jet with an Alfv\'{e}nic
Lorentz factor inside a narrow Petschek-type exhaust. Various shock structures
are resolved in and around the plasmoid such as the post-plasmoid vertical
shocks and the ""diamond-chain"" structure due to multiple shock reflections.
Under a uniform resistivity, Sweet--Parker-type reconnection slowly evolves.
Under a current-dependent resistivity, plasmoids are repeatedly formed in an
elongated current sheet. It is concluded that the resistivity model is of
critical importance for RRMHD modeling of relativistic magnetic reconnection.",1005.4485v2
2013-12-18,Magneto-transport characteristics of a 2D electron system driven to negative magneto-conductivity by microwave photoexcitation,"Negative diagonal magneto-conductivity/resistivity is a spectacular- and
thought provoking- property of driven, far-from-equilibrium, low dimensional
electronic systems. The physical response of this exotic electronic state is
not yet fully understood since it is rarely encountered in experiment. The
microwave-radiation-induced zero-resistance state in the high mobility
GaAs/AlGaAs 2D electron system is believed to be an example where negative
magneto-conductivity/resistivity is responsible for the observed phenomena.
Here, we examine the magneto-transport characteristics of this negative
conductivity/resistivity state in the microwave photo-excited two-dimensional
electron system (2DES) through a numerical solution of the associated boundary
value problem. The results suggest, surprisingly, that a bare negative diagonal
conductivity/resistivity state in the 2DES under photo-excitation should yield
a positive diagonal resistance with a concomitant sign reversal in the Hall
voltage.",1312.5026v1
2014-12-19,Nano-artifact metrics based on random collapse of resist,"Artifact metrics is an information security technology that uses the
intrinsic characteristics of a physical object for authentication and clone
resistance. Here, we demonstrate nano-artifact metrics based on silicon
nanostructures formed via an array of resist pillars that randomly collapse
when exposed to electron-beam lithography. The proposed technique uses
conventional and scalable lithography processes, and because of the random
collapse of resist, the resultant structure has extremely fine-scale morphology
with a minimum dimension below 10 nm, which is less than the resolution of
current lithography capabilities. By evaluating false match, false non-match
and clone-resistance rates, we clarify that the nanostructured patterns based
on resist collapse satisfy the requirements for high-performance security
applications.",1412.6271v1
2015-07-15,ERK/p38 MAPK inhibition reduces radio-resistance to pulsed proton beam in breast cancer stem cells cells,"Recent studies have identified highly tumorigenic cells with stem cell-like
characteristics in human cancers, termed cancer stem cells (CSCs). CSCs are
resistant to conventional radiotherapy and chemotherapy owing to their high DNA
repair ability and oncogene overexpression. However, the mechanisms regulating
CSC radio-resistance, particularly proton beam resistance, remain unclear. We
isolated CSCs from the breast cancer cell lines MCF-7 and MDA-MB-231, which
expressed the characteristic breast CSC membrane protein markers
CD44+/CD24-/low, and irradiated the CSCs with pulsed proton beams. We confirmed
that CSCs are resistant to pulsed proton beams and showed that treatment with
p38 and ERK inhibitors reduced CSC radioresistance. Based on these results,
BCSC radio-resistance can be reduced during proton beam therapy by co-treatment
with ERK1/2 or p38 inhibitors, representing a novel approach for breast cancer
therapy.",1509.02377v1
2017-06-23,Investigating prescriptions for artificial resistivity in smoothed particle magnetohydrodynamics,"In numerical simulations, artificial terms are applied to the evolution
equations for stability. To prove their validity, these terms are thoroughly
tested in test problems where the results are well known. However, they are
seldom tested in production-quality simulations at high resolution where they
interact with a plethora of physical and numerical algorithms. We test three
artificial resistivities in both the Orszag-Tang vortex and in a star formation
simulation. From the Orszag-Tang vortex, the Price et. al. (2017) artificial
resistivity is the least dissipative thus captures the density and magnetic
features; in the star formation algorithm, each artificial resistivity
algorithm interacts differently with the sink particle to produce various
results, including gas bubbles, dense discs, and migrating sink particles. The
star formation simulations suggest that it is important to rely upon physical
resistivity rather than artificial resistivity for convergence.",1706.07721v1
2019-07-05,Impurity scattering induced carrier transport in twisted bilayer graphene,"We theoretically calculate the impurity-scattering induced resistivity of
twisted bilayer graphene at low twist angles where the graphene Fermi velocity
is strongly suppressed. We consider, as a function of carrier density, twist
angle, and temperature, both long-ranged Coulomb scattering and short-ranged
defect scattering within a Boltzmann theory relaxation time approach. For
experimentally relevant disorder, impurity scattering contributes a resistivity
comparable to (much larger than) the phonon scattering contribution at high
(low) temperatures. Decreasing twist angle leads to larger resistivity, and in
general, the resistivity increases (decreases) with increasing temperature
(carrier density). Inclusion of the van Hove singularity in the theory leads to
a strong increase in the resistivity at higher densities, where the chemical
potential is close to a van Hove singularity, leading to an apparent
density-dependent plateau type structure in the resistivity, which has been
observed in recent transport experiments. We also show that the Matthissen's
rule is strongly violated in twisted bilayer graphene at low twist angles.",1907.02856v3
2021-01-28,Contagion-Preserving Network Sparsifiers: Exploring Epidemic Edge Importance Utilizing Effective Resistance,"Network epidemiology has become a vital tool in understanding the effects of
high-degree vertices, geographic and demographic communities, and other
inhomogeneities in social structure on the spread of disease. However, many
networks derived from modern datasets are quite dense, such as mobility
networks where each location has links to a large number of potential
destinations. One way to reduce the computational effort of simulating
epidemics on these networks is sparsification, where we select a representative
subset of edges based on some measure of their importance. Recently an approach
was proposed using an algorithm based on the effective resistance of the edges.
We explore how effective resistance is correlated with the probability that an
edge transmits disease in the SI model. We find that in some cases these two
notions of edge importance are well correlated, making effective resistance a
computationally efficient proxy for the importance of an edge to epidemic
spread. In other cases, the correlation is weaker, and we discuss situations in
which effective resistance is not a good proxy for epidemic importance.",2101.11818v1
2023-02-22,Drugs Resistance Analysis from Scarce Health Records via Multi-task Graph Representation,"Clinicians prescribe antibiotics by looking at the patient's health record
with an experienced eye. However, the therapy might be rendered futile if the
patient has drug resistance. Determining drug resistance requires
time-consuming laboratory-level testing while applying clinicians' heuristics
in an automated way is difficult due to the categorical or binary medical
events that constitute health records. In this paper, we propose a novel
framework for rapid clinical intervention by viewing health records as graphs
whose nodes are mapped from medical events and edges as correspondence between
events in given a time window. A novel graph-based model is then proposed to
extract informative features and yield automated drug resistance analysis from
those high-dimensional and scarce graphs. The proposed method integrates
multi-task learning into a common feature extracting graph encoder for
simultaneous analyses of multiple drugs as well as stabilizing learning. On a
massive dataset comprising over 110,000 patients with urinary tract infections,
we verify the proposed method is capable of attaining superior performance on
the drug resistance prediction problem. Furthermore, automated drug
recommendations resemblant to laboratory-level testing can also be made based
on the model resistance analysis.",2302.11231v2
2023-11-03,Resistive Diffusion in Magnetized ICF Implosions: Reduced Magnetic Stabilization of the Richtmyer Meshkov Instability,"Resistive diffusion is typically regarded to be negligible in magnetized ICF
experiments, with magnetic flux effectively compressed during the implosion. In
this work the Richtmyer Meshkov instability at the ice-ablator interface is
taken as an example for investigating resistive effects. For a high temperature
(approximately 100eV) interface with magnetic field applied perpendicular to
shock propagation, perturbation growth is suppressed by magnetic tension.
However, for lower temperature interfaces the resistive diffusion prevents
substantial magnetic field twisting at small scales. ICF implosion simulations
are then used to assess magnetic diffusivity at different interfaces; the
ice-ablator interface is found to be too resistive for the magnetic fields to
enhance stability. For Rayleigh-Taylor growth at the hot-spot edge, on the
other hand, resistivity is estimated to only be a secondary effect, as seen in
previous simulation studies.",2311.01645v2
2024-03-14,Role of many phonon modes on the high-temperature linear-in-$T$ electronic resistivity,"We theoretically consider the possibility that phonons may be playing a role
in the observed linear-in-$T$ resistivity in cuprates by focusing on the
obvious question: How can phonon scattering be consistent with a linear-in-$T$
resistivity with a constant slope given that cuprates have many phonon modes
with different energies and electron-phonon couplings (e.g. 21 phonon modes for
LSCO)? We show using an arbitrarily large number of independent phonon modes
that, within a model Boltzmann transport theory, the emergent high-$T$
linear-in-$T$ resistivity manifests an approximately constant slope independent
of the number of phonon modes except in some fine-tuned narrow temperature
regimes. We also comment on the quantitative magnitude of the linear-in-$T$
resistivity in cuprates pointing out the constraints on the effective
electron-phonon coupling necessary to produce the observed resistivity.",2403.09890v1
2017-02-16,Anomalous Nonlocal Resistance and Spin-charge Conversion Mechanisms in Two-Dimensional Metals,"We uncover two anomalous features in the nonlocal transport behavior of
two-dimensional metallic materials with spin-orbit coupling. Firstly, the
nonlocal resistance can have negative values and oscillate with distance, even
in the absence of a magnetic field. Secondly, the oscillations of the nonlocal
resistance under an applied in-plane magnetic field (Hanle effect) can be
asymmetric under field reversal. Both features are produced by direct
magnetoelectric coupling, which is possible in materials with broken inversion
symmetry but was not included in previous spin diffusion theories of nonlocal
transport. These effects can be used to identify the relative contributions of
different spin-charge conversion mechanisms. They should be observable in
adatom-functionalized graphene, and may provide the reason for discrepancies in
recent nonlocal transport experiments on graphene.",1702.04955v3
2018-06-23,Crack growth resistance in metallic alloys: the role of isotropic versus kinematic hardening,"The sensitivity of crack growth resistance to the choice of isotropic or
kinematic hardening is investigated. Monotonic mode I crack advance under small
scale yielding conditions is modelled via a cohesive zone formulation endowed
with a traction-separation law. R-curves are computed for materials that
exhibit linear or power law hardening. Kinematic hardening leads to an enhanced
crack growth resistance relative to isotropic hardening. Moreover, kinematic
hardening requires greater crack extension to achieve the steady state. These
differences are traced to the non-proportional loading of material elements
near the crack tip as the crack advances. The sensitivity of the R-curve to the
cohesive zone properties and to the level of material strain hardening is
explored for both isotropic and kinematic hardening.",1806.08986v1
2020-01-08,Novel hypostasis of old materials in oxide electronics: metal oxides for resistive random access memory applications,"Transition-metal oxide films, demonstrating the effects of both threshold and
nonvolatile memory resistive switching, have been recently proposed as
candidate materials for storage-class memory. In this work we describe some
experimental results on threshold switching in a number of various transition
metal (V, Ti, Fe, Nb, Mo, W, Hf, Zr, Mn, Y, and Ta) oxide films obtained by
anodic oxidation. Then, the results concerning the effects of bistable
resistive switching in MOM and MOS structures on the basis of such oxides as
V2O5, Nb2O5, and NiO are presented. It is shown that sandwich structures on the
basis of the Au/V2O5/SiO2/Si, Nb/Nb2O5/Au, and Pt/NiO/Pt can be used as memory
elements for ReRAM applications. Finally, model approximations are developed in
order to describe theoretically the effect of nonvolatile unipolar switching in
Pt NiO-Pt structures.",2001.03026v1
2022-04-28,Ultralow Electron-Surface Scattering in Nanoscale Metals Leveraging Fermi Surface Anisotropy,"Increasing resistivity of metal wires with reducing nanoscale dimensions is a
major performance bottleneck of semiconductor computing technologies. We show
that metals with suitably anisotropic Fermi velocity distributions can strongly
suppress electron scattering by surfaces and outperform isotropic conductors
such as copper in nanoscale wires. We derive a corresponding descriptor for the
resistivity scaling of anisotropic conductors, screen thousands of metals using
first-principles calculations of this descriptor and identify the most
promising materials for nanoscale interconnects. Previously-proposed layered
conductors such as MAX phases and delafossites show promise in thin films, but
not in narrow wires due to increased scattering from side walls. We find that
certain intermetallics (notably CoSn) and borides (such as YCo$_3$B$_2$) with
one-dimensionally anisotropic Fermi velocities are most promising for narrow
wires. Combined with first-principles electron-phonon scattering predictions,
we show that the proposed materials exhibit 2-3x lower resistivity than copper
at 5 nm wire dimensions.",2204.13458v1
2022-07-20,Optimal Structures for Failure Resistance Under Impact,"The complex physics and numerous failure modes of structural impact creates
challenges when designing for impact resistance. While simple geometries of
layered material are conventional, advances in 3D printing and additive
manufacturing techniques have now made tailored geometries or integrated
multi-material structures achievable. Here, we apply gradient-based topology
optimization to the design of such structures. We start by constructing a
variational model of an elastic-plastic material enriched with gradient
phase-field damage, and present a novel method to efficiently compute its
transient dynamic time evolution. We consider a finite element discretization
with explicit updates for the displacements. The damage field is solved through
an augmented Lagrangian formulation, splitting the operator coupling between
the nonlinearity and non-locality. Sensitivities over this trajectory are
computed through the adjoint method, resulting in an adjoint problem which we
solve in a similar manner to the forward dynamics. We demonstrate this
formulation by studying the optimal design of 2D solid-void structures
undergoing blast loading. Then, we explore the trade-offs between strength and
toughness in the design of a spall-resistant structure composed of two
materials of differing properties undergoing dynamic impact.",2207.09678v1
1998-05-11,"Two-dimensional arrays of low capacitance tunnel junctions: general properties, phase transitions and Hall effect","We describe transport properties of two-dimensional arrays of low capacitance
tunnel junctions, such as the current voltage characteristic and its dependence
on external magnetic field and temperature. We discuss several experiments in
which the small capacitance of the junctions plays an important role. In arrays
where the junctions have a relatively large charging energy, (i.e. when they
have a low capacitance) and a high normal state resistance, the low bias
resistance increases with decreasing temperature and eventually at very low
temperature the array becomes insulating even though the electrodes in the
array are superconducting. This transition to the insulating state can be
described by thermal activation. In an intermediate region where the junction
resistance is of the order of the quantum resistance and the charging energy is
of the order of the Josephson coupling energy, the arrays can be tuned between
a superconducting and an insulating state with a magnetic field. We describe
measurements of this magnetic-field-tuned superconductor insulator transition,
and we show that the resistance data can be scaled over several orders of
magnitude. Four arrays follow the same universal function. At the transition
the transverse (Hall) resistance is found to be very small in comparison with
the longitudinal resistance. However, for magnetic field values larger than the
critical value.we observe a substantial Hall resistance. The Hall resistance of
these arrays oscillates with the applied magnetic field. features in the
magnetic field dependence of the Hall resistance can qualitatively be
correlated to features in the derivative of the longitudinal resistance,
similar to what is found in the quantum Hall effect.",9805121v1
2020-07-03,First-principles study of electronic transport and structural properties of Cu$_{12}$Sb$_4$S$_{13}$ in its high-temperature phase,"We present an ab initio study of the structural and electronic transport
properties of tetrahedrite, Cu$_{12}$Sb$_4$S$_{13}$, in its high-temperature
phase. We show how this complex compound can be seen as the outcome of an
ordered arrangement of S-vacancies in a semiconducting fematinite-like
structure (Cu3SbS4). Our calculations confirm that the S-vacancies are the
natural doping mechanism in this thermoelectric compound and reveal a similar
local chemical environment around crystallographically inequivalent Cu atoms,
shedding light on the debate on XPS measurements in this compound. To access
the electrical transport properties as a function of temperature we use the
Kubo-Greenwood formula applied to snapshots of first-principles molecular
dynamics simulations. This approach is essential to effectively account for the
interaction between electrons and lattice vibrations in such a complex crystal
structure where a strong anharmonicity plays a key role in stabilising the
high-temperature phase. Our results show that the Seebeck coeffcient is in good
agreement with experiments and the phonon-limited electrical resistivity
displays a temperature trend that compares well with a wide range of
experimental data. The predicted lower bound for the resistivity turns out to
be remarkably low for a pristine mineral in the Cu-Sb-S system but not too far
from the lowest experimental data reported in literature. The Lorenz number
turns out to be substantially lower than what expected from the free-electron
value in the Wiedemann-Franz law, thus providing an accurate way to estimate
the electronic and lattice contributions to the thermal conductivity in
experiments, of great significance in this very low thermal conductivity
crystalline material.",2007.01809v2
2015-03-25,Anisotropy of Thermal Conductivity of Free-Standing Reduced Graphene Oxide Films Annealed at High Temperature,"We investigated thermal conductivity of free-standing reduced graphene oxide
films subjected to a high-temperature treatment of up to 1000 C. It was found
that the high-temperature annealing dramatically increased the in-plane thermal
conductivity, K, of the films from 3 W/mK to 61 W/mK at room temperature. The
cross-plane thermal conductivity, Kc, revealed an interesting opposite trend of
decreasing to a very small value of 0.09 W/mK in the reduced graphene oxide
films annealed at 1000 C. The obtained films demonstrated an exceptionally
strong anisotropy of the thermal conductivity, K/Kc ~ 675, which is
substantially larger even than in the high-quality graphite. The electrical
resistivity of the annealed films reduced to 1 - 19 Ohms/sq. The observed
modifications of the in-plane and cross-plane thermal conductivity components
resulting in an unusual K/Kc anisotropy were explained theoretically. The
theoretical analysis suggests that K can reach as high as ~500 W/mK with the
increase in the sp2 domain size and further reduction of the oxygen content.
The strongly anisotropic heat conduction properties of these films can be
useful for applications in thermal management.",1503.07239v1
2017-03-07,Thermodynamic Stabilization of Precipitates through Interface Segregation: Chemical Effects,"Precipitation hardening, which relies on a high density of intermetallic
precipitates, is a commonly utilized technique for strengthening structural
alloys. Structural alloys are commonly strengthened through a high density of
small size intermetallic precipitates. At high temperatures, however, the
precipitates coarsen to reduce the excess energy of the interface, resulting in
a significant reduction in the strengthening provided by the precipitates. In
certain ternary alloys, the secondary solute segregates to the interface and
results in the formation of a high density of nanosize precipitates that
provide enhanced strength and are resistant to coarsening. To understand the
chemical effects involved, and to identify such systems, we develop a
thermodynamic model using the framework of the regular nanocrystalline solution
model. For various global compositions, temperatures and thermodynamic
parameters, equilibrium configuration of Mg-Sn-Zn alloy is evaluated by
minimizing the Gibbs free energy function with respect to the region-specific
(bulk solid-solution, interface and precipitate) concentrations and sizes. The
results show that Mg$_2$Sn precipitates can be stabilized to nanoscale sizes
through Zn segregation to Mg/Mg$_2$Sn interface, and the precipitates can be
stabilized against coarsening at high-temperatures by providing a larger Zn
concentration in the system. Together with the inclusion of elastic strain
energy effects and the input of computationally informed interface
thermodynamic parameters in the future, the model is expected to provide a more
realistic prediction of segregation and precipitate stabilization in ternary
alloys of structural importance.",1703.02621v2
2020-09-29,High open-circuit voltage in transition metal dichalcogenide solar cells,"The conversion efficiency of ultra-thin solar cells based on layered
materials has been limited by their open-circuit voltage, which is typically
pinned to a value under 0.6 V. Here we report an open-circuit voltage of 1.02 V
in a 120 nm-thick vertically stacked homojunction fabricated with
substitutionally doped MoS2. This high open-circuit voltage is consistent with
the band alignment in the MoS2 homojunction, which is more favourable than in
widely-used TMDC heterostructures. It is also attributed to the high
performance of the substitutionally doped MoS2, in particular the p-type
material doped with Nb, which is demonstrated by the observation of
electroluminescence from tunnelling graphene/BN/MoS2 structures in spite of the
indirect nature of bulk MoS2. We find that illuminating the TMDC/metal contacts
decreases the measured open-circuit voltage in MoS2 van der Waals homojunctions
because they are photoactive, which points to the need of developing
low-resistance, ohmic contacts to doped MoS2 in order to achieve high
efficiency in practical devices. The high open-circuit voltage demonstrated
here confirms the potential of layered transition-metal dichalcogenides for the
development of highly efficient, ultra-thin solar cells.",2009.13911v1
2019-11-25,Natural-mixing guided design of refractory high-entropy alloys with as-cast tensile ductility,"Multi-principal-element metallic alloys have created a growing interest that
is unprecedented in metallurgical history, in exploring the property limits of
metals and the governing physical mechanisms. Refractory high-entropy alloys
(RHEAs) have drawn particular attention due to their (i) high melting points
and excellent softening-resistance, which are the two key requirements for
high-temperature applications; and (ii) compositional space, which is immense
even after considering cost and recyclability restrictions. However, RHEAs also
exhibit intrinsic brittleness and oxidation-susceptibility, which remain as
significant challenges for their processing and application. Here, utilizing
natural-mixing characteristics amongst refractory elements, we designed a
Ti38V15Nb23Hf24 RHEA that exhibits >20% tensile ductility already at the
as-cast state, and physicochemical stability at high-temperatures. Exploring
the underlying deformation mechanisms across multiple length-scales, we observe
that a rare beta prime precipitation strengthening mechanism governs its
intriguing mechanical response. These results also reveal the effectiveness of
natural-mixing tendencies in expediting HEA discovery.",1911.10975v1
2021-12-23,Record High Tc Element Superconductivity Achieved In Titanium,"It is challenging to search for high Tc superconductivity (SC) in transition
metal elements wherein d electrons are usually not favored by conventional BCS
theory. Here we report discovery of surprising SC up to 310 GPa with Tc above
20 K in wide pressure range from 108 GPa to 240 GPa in titanium. The maximum
Tc^onset above 26 K and zero resistance Tc^zero of 21 K are record high values
hitherto achieved among element superconductors. The Hc2(0) is estimated to be
about 32 Tesla with coherence length 32 angstrom. The results show strong s-d
transfer and d-band dominance, indicating correlation driven contributions to
high Tc SC in dense titanium. This finding is in sharp contrast to the
theoretical predications based on pristine electron-phonon coupling scenario.
The study opens a fresh promising avenue for rational design and discovery of
high Tc superconductors among simple materials via pressure tuned
unconventional mechanism.",2112.12396v3
2022-01-12,Emergence of superconducting dome in insulating ZrNx films via nitrogen manipulation,"Reproducing the electronic phase diagram of strongly correlated
high-transition-temperature (high-Tc) superconductors in materials other than
Cu-, Fe-, and Ni-based compounds has been a challenging task. Only very
recently, a few material systems have partially achieved this goal by band
engineering. In this work, we combine film growth, charge transport,
magnetometry, Terahertz Spectroscopy, Raman scattering, and Scanning
Transmission Electron Microscopy to investigate superconductivity and the
normal state of ZrNx, which reveals a phase diagram that bears extraordinary
similarities to those of high-Tc superconductors. Remarkably, even though
superconductivity of ZrNx can be characterized within the
Bardeen-Cooper-Schrieffer paradigm and its normal state can be understood
within the Fermi liquid framework, by tunning the N chemical concentration, we
observe the evolution of a superconducting dome in the close vicinity of a
strongly insulating state and a normal state resistivity mimics its counterpart
of the high-Tc superconductors.",2201.04340v2
2023-06-22,Scalable Electrodeposition of Eutectic Indium Gallium from an Acetonitrile-Based Electrolyte for Integrated Stretchable Electronics,"For the advancement of highly-integrated stretchable electronics, the
development of scalable sub-micrometer conductor patterning is required.
Eutectic gallium indium EGaIn is an attractive conductor for stretchable
electronics, as its liquid metallic character grants it high electrical
conductivity upon deformation. However, its high surface energy precludes
patterning it with (sub)-micron resolution. Herein, we overcome this limitation
by reporting for the first time the electrodeposition of EGaIn. We use a
non-aqueous acetonitrile-based electrolyte that exhibits high electrochemical
stability and chemical orthogonality. The electrodeposited material led to
low-resistance lines that remained stable upon (repeated) stretching to a 100
percent strain. Because electrodeposition benefits from the resolution of
mature nanofabrication methods used to pattern the base metal, the proposed
bottom-up approach achieved a record-high density integration of EGaIn regular
lines of 300 nm half-pitch on an elastomer substrate by plating on a gold seed
layer pre-patterned by nanoimprinting. Moreover, vertical integration was
enabled by filling high aspect ratio vias. This capability was conceptualized
by the fabrication of an omnidirectionally stretchable 3D electronic circuit,
and demonstrates a soft-electronic analogue of the stablished damascene process
used to fabricate microchip interconnects. Overall, this work proposes a simple
route to address the challenge of metallization in highly integrated (3D)
stretchable electronics.",2306.12781v2
2020-05-28,High-temperature and Abrasion Resistant Selective Solar Absorber under Ambient Environment,"Selective solar absorbers (SSAs) with high performance are the key to
concentrated solar power systems. Optical metamaterials are emerging as a
promising strategy to enhance selective photon absorption, however, the
high-temperature resistance (>500C) remains as one of the main challenges for
their practical applications. Here, a multilayered metamaterial system
(Al2O3/W/SiO2/W) based on metal-insulator-metal (MIM) resonance effect has been
demonstrated with high solar absorptance over 92%, low thermal emittance loss
below 6%, and significant high-temperature resistance: it has been proved that
the optical performance remains 93.6% after 1-hour thermal annealing under
ambient environment up to 500C, and 94.1% after 96-hour thermal cycle test at
400C, which is also confirmed by the microscopic morphology characterization.
The spectral selectivity of fabricated SSAs is angular independent and
polarization insensitive. Outdoor tests demonstrate that a peak temperature
rise (193.5C) can be achieved with unconcentrated solar irradiance and surface
abrasion resistance test yields that SSAs have a robust resistance to abrasion
attack for engineering applications.",2005.14305v1
2015-11-22,On materials destruction criteria,"In terms of nonlinear material fracture mechanics, the real
(discrete)-structure material fracture model has been developed. The model
rests on the demonstration of the fact that crack resistance $K_{1c}=2\sigma
\sqrt l$ and fracture toughness are $G_{1c}=J_{1c}=2\sigma l$ obtained on the
basis of energy conservation law and derived without linear material fracture
mechanics assumptions can be respectively taken as force and energy criteria
for non-linear fracture mechanics. It is shown that $G_{1c}=K_{1c}^2/E$ is the
energy criterion of linear fracture mechanics of material and it is
sufficiently less than $G_{1c} = J_{1c}=2\sigma l$.",1511.07037v1
2021-01-31,"Origin of high hardness and optoelectronic and thermo-physical properties of boron-rich compounds B6X (X = S, Se): a comprehensive study via DFT approach","In the present study, the structural and hitherto uninvestigated mechanical
(elastic stiffness constants, machinability index, Cauchy pressure, anisotropy
indices, brittleness/ductility, Poissons ratio), electronic, optical, and
thermodynamic properties of novel boron-rich compounds B6X (X = S, Se) have
been explored using density functional theory. The estimated structural lattice
parameters were consistent with the prior report. The mechanical and dynamical
stability of these compounds have been established theoretically. The materials
are brittle in nature and elastically anisotropic. The value of fracture
toughness, KIC for the B6S and B6Se are ~ 2.07 MPam0.5, evaluating the
resistance to limit the crack propagation inside the materials. Both B6S and
B6Se compounds possess high hardness values in the range 31-35 GPa, and have
the potential to be prominent members of the class of hard compounds. Strong
covalent bonding and sharp peak at low energy below the Fermi level confirmed
by partial density of states (PDOS) resulted in the high hardness. The profile
of band structure, as well as DOS, assesses the indirect semiconducting nature
of the titled compounds. The comparatively high value of Debye temperature
({\Theta}D), minimum thermal conductivity (Kmin), lattice thermal conductivity
(kph), low thermal expansion coefficient, and low density suggest that both
boron-rich chalcogenides might be used as thermal management materials. Large
absorption capacities in the mid ultraviolet region (3.2-15 eV) of the studied
materials and low reflectivity (~16 %) are significantly noted. Such favorable
features give promise to the compounds under investigation to be used in UV
surface-disinfection devices as well as medical sterilizer equipment
applications. Excellent correlations are found among all the studied physical
properties of these compounds.",2102.00446v1
2022-10-09,High-performance non-Fermi-liquid metallic thermoelectric materials,"Searching for high-performance thermoelectric (TE) materials in the paradigm
of narrow-bandgap semiconductors has lasted for nearly 70 years and is
obviously hampered by a bottleneck of research now. Here we report on the
discovery of a few metallic compounds, TiFexCu2x-1Sb and TiFe1.33Sb, showing
the thermopower exceeding many TE semiconductors and the dimensionless figure
of merits comparable with the state-of-the-art TE materials. A quasi-linear
temperature (T) dependence of electrical resistivity in 2 K - 700 K and the
logarithmic T-dependent electronic specific heat at low temperature are also
observed to coexist with the high thermopower, highlighting the strong
intercoupling of the non-Fermi-liquid (NFL) quantum critical behavior of
electrons with TE transports. Electronic structure analysis reveals the
existence of fluctuating Fe-eg-related local magnetic moments, Fe-Fe
antiferromagnetic (AFM) interaction at the nearest 4c-4d sites, and two-fold
degenerate eg orbitals antiferromagnetically coupled with the dual-type
itinerant electrons close to the Fermi level, all of which infer to a
competition between the AFM ordering and Kondo-like spin compensation as well
as a parallel two-channel Kondo effect. These effects are both strongly
meditated by the structural disorder due to the random filling of Fe/Cu at the
equivalent 4c/4d sites of the Heusler crystal lattice. The magnetic
susceptibility deviates from ideal antiferromagnetism but can be fitted well by
x(T) = 1/({\theta} + BT{\alpha}), seemingly being consistent with the quantum
critical scenario of strong local correlation as discussed before. Our work not
only breaks the dilemma that the promising TE materials should be heavily-doped
semiconductors, but also demonstrates the correlation among high TE
performance, NFL quantum criticality, and magnetic fluctuation, which opens up
new directions for future research.",2210.04201v1
1997-01-06,The role of intermediate layers in the c-axis conductivity of layered superconductors,"A simplified model of c axis transport in the high T_c superconductors is
presented. Expressions are found for the c axis optical conductivity, the d.c.
resistivity, and the c axis penetration depth. Within the framework of this
model, the pseudogap in the optical conductivity arises naturally as a result
of the layered band structure of the high T_c materials. We discuss the
occurence of the pseudogap in terms of three parameters: a band gap Delta_{ps},
a temperature dependent scattering rate Gamma(T), and the strength of the
interlayer coupling t_{perp}. We are also able to find analytic expressions for
the d.c. conductivity and the low temperature penetration depth in terms of
these three parameters. This work is an attempt to present a simple, unified
picture of c axis properties in the high T_c cuprates.",9701029v2
1999-06-01,Current dependence of grain boundary magnetoresistance in La_0.67Ca_0.33MnO_3 films,"We prepared epitaxial ferromagnetic manganite films on bicrystal substrates
by pulsed laser ablation. Their low- and high-field magnetoresistance (MR) was
measured as a function of magnetic field, temperature and current. At low
temperatures hysteretic changes in resistivity up to 70% due to switching of
magnetic domains at the coercitive field are observed. The strongly non-ohmic
behavior of the current-voltage leads to a complete suppression of the MR
effect at high bias currents with the identical current dependence at low and
high magnetic fields. We discuss the data in view of tunneling and mesoscale
magnetic transport models and propose an explicit dependence of the spin
polarization on the applied current in the grain boundary region.",9906007v1
2001-04-02,Antiferromagnetic vortex state in a high-temperature superconductor,"There is strong evidence that magnetic interactions play a crucial role in
the mechanism driving high-temperature superconductivity in cuprate
superconductors. To investigate this further we have done neutron scattering
experiments on the simplest high-temperature superconductor La(2-x)Sr(x)CuO(4)
(LSCO) in an applied magnetic field. Below the superconducting transition
temperature (Tc), the field penetrates the material via an array of normal
state inclusions or vortices while phase coherent superconductivity
characterized by zero resistance is suppressed to the lower field-dependent
irreversibility temperature. The measurements described here were performed on
underdoped LSCO (x=0.10), which develops static incommensurate order below Tc
in zero field. Our results show that application of a magnetic field enhances
this response without changing the onset temperature. For H=5T the
field-induced signal saturates to three times the zero-field signal and phase
coherent superconductivity is established within the antiferromagnetic phase.",0104026v1
2004-02-13,High performance n-doped carbon nanotube field-effect transistors,"We describe a robust technique for the fabrication of high performance
vertically scaled n-doped field-effect transistors from large band gap carbon
nanotubes. These devices have a tunable threshold voltage in the
technologically relevant range (-1.3V < V_th < 0.5V) and can carry up to 5-6
muA of current in the on-state. We achieve such performance by exposure to
potassium (K) vapor and device annealing in high vacuum. The treatment has a
two-fold effect to: (i) controllably shift V_th toward negative gate biases via
bulk doping of the nanotube (up to about 0.6e/nm), and (ii) increase the
on-current by 1-2 orders of magnitude. This current enhancement is achieved by
lowering external device resistance due to more intimate contact between K
metal and doped nanotube channel in addition to potential reduction of the
Schottky barrier height at the contact.",0402350v1
2005-04-03,Dependence of Giant Tunnel Magnetoresistance of Sputtered CoFeB/MgO/CoFeB Magnetic Tunnel Junctions on MgO Barrier Thickness and Annealing Temperatur,"We investigated the dependence of giant tunnel magnetoresistance (TMR) on the
thickness of an MgO barrier and on the annealing temperature of sputtered
CoFeB/MgO/CoFeB magnetic tunnel junctions deposited on SiO2/Si wafers. The
resistance-area product exponentially increases with MgO thickness, indicating
that the quality of MgO barriers is high in the investigated thickness range of
1.15-2.4 nm. High-resolution transmission electron microscope images show that
annealing at 375 C results in the formation of crystalline CoFeB/MgO/CoFeB
structures, even though CoFeB electrodes are amorphous in the as-sputtered
state. The TMR ratio increases with annealing temperature and is as high as
260% at room temperature and 403% at 5 K.",0504051v1
2006-05-09,Subgap conductivity in SIN-junctions of high barrier transparency,"We investigate the current-voltage characteristics of high-transparency
superconductor-insulator-normal metal (SIN) junctions with the specific tunnel
resistance below 30 kOhm per square micron. The junctions were fabricated from
different superconducting and normal conducting materials, including Nb, Al,
AuPd and Cu. The subgap leakage currents were found to be appreciably larger
than those given by the standard tunnelling model. We explain our results using
the model of two-electron tunnelling in the coherent diffusive transport
regime. We demonstrate that even in the high-transparency SIN-junctions, a
noticeable reduction of the subgap current can be achieved by splitting a
junction into several submicron sub-junctions. These structures can be used as
nonlinear low-noise shunts in Rapid-Single-Flux-Quantum (RSFQ) circuitry for
controlling Josephson qubits.",0605237v2
2002-09-09,Long-term damage induced by hadrons in silicon detectors for uses at the LHC-accelerator and in space missions,"In the present paper, the phenomenological model developed by the authors in
previous papers has been used to evaluate the degradation induced by hadron
irradiation at the future accelerator facilities or by cosmic protons in high
resistivity silicon detectors. The damage has been analysed at the microscopic
(defects production and their evolution toward equilibrium) and at the
macroscopic level (changes in the leakage current of the p-n junction). The
rates of production of primary defects, as well as their evolution toward
equilibrium have been evaluated considering explicitly the type of the
projectile particle and its energy. Vacancy-interstitial annihilation,
interstitial migration to sink, complex (VP, VO, CiOi, CiCs) and divacancy
formation are taken into account for different initial silicon material. The
influence of these defects on the leakage detector current has been calculated
in the frame of the Schokley-Read-Hall model.",0209086v2
2006-11-20,Correlation between radiation processes in silicon and long-time degradation of detectors for high energy physics experiments,"In this contribution, the correlation between fundamental interaction
processes induced by radiation in silicon and observable effects which limit
the use of silicon detectors in high energy physics experiments is investigated
in the frame of a phenomenological model which includes: generation of primary
defects at irradiation starting from elementary interactions in silicon;
kinetics of defects, effects at the p-n junction detector level. The effects
due to irradiating particles (pions, protons, neutrons), to their flux, to the
anisotropy of the threshold energy in silicon, to the impurity concentrations
and resistivity of the starting material are investigated as time, fluence and
temperature dependences of detector characteristics. The expected degradation
of the electrical parameters of detectors in the complex hadron background
fields at LHC & SLHC are predicted.",0611185v1
2008-07-11,Electronic liquid crystal state in the high-temperature superconductor YBCO(6.45),"Electronic phases with symmetry properties matching those of conventional
liquid crystals have recently been discovered in transport experiments on
semiconductor heterostructures and metal oxides at milli-Kelvin temperatures.
We report the spontaneous onset of a onedimensional, incommensurate modulation
of the spin system in the high-temperature superconductor YBa2Cu3O6.45 upon
cooling below ~150 K, while static magnetic order is absent above 2 K. The
evolution of this modulation with temperature and doping parallels that of the
in-plane anisotropy of the resistivity, indicating an electronic nematic phase
that is stable over a wide temperature range. The results suggest that soft
spin fluctuations are a microscopic route towards electronic liquid crystals,
and nematic order can coexist with high-temperature superconductivity in
underdoped cuprates.",0807.1861v1
2009-08-20,"Scaling relation of the anomalous Hall effect in (Ga,Mn)As","We present magnetotransport studies performed on an extended set of (Ga,Mn)As
samples at 4.2 K with longitudinal conductivities sigma_{xx} ranging from the
low- to the high-conductivity regime. The anomalous Hall conductivity
sigma_{xy}^(AH) is extracted from the measured longitudinal and Hall
resistivities. A transition from sigma_{xy}^(AH)=20 Omega^{-1}cm^{-1} due to
the Berry phase effect in the high-conductivity regime to a scaling relation
sigma_{xy}^(AH) proportional to sigma_{xx}^{1.6} for low-conductivity samples
is observed. This scaling relation is consistent with a recently developed
unified theory of the anomalous Hall effect in the framework of the Keldysh
formalism. It turns out to be independent of crystallographic orientation,
growth conditions, Mn concentration, and strain, and can therefore be
considered universal for low-conductivity (Ga,Mn)As. The relation plays a
crucial role when deriving values of the hole concentration from
magnetotransport measurements in low-conductivity (Ga,Mn)As. In addition, the
hole diffusion constants for the high-conductivity samples are determined from
the measured longitudinal conductivities.",0908.2935v1
2009-11-11,Temperature dependent nucleation and annihilation of individual magnetic vortices,"We studied the temperature dependence of the magnetization reversal in
individual submicron permalloy disks with micro-Hall and bend-resistance
magnetometry. The nucleation field exhibits a nonmonotonic dependence with
positive and negative slopes at low and high temperatures, respectively, while
the annihilation field monotonically decreases with increasing temperature, but
with distinctly different slopes at low and high temperatures. Our analysis
suggests that at low temperatures vortex nucleation and annihilation proceeds
via thermal activation over an energy barrier, while at high temperatures they
are governed by a temperature dependence of the saturation magnetization.",0911.2267v1
2009-12-08,Correlating the nanostructure and electronic properties of InAs nanowires,"The electronic properties and nanostructure of InAs nanowires are correlated
by creating multiple field effect transistors (FETs) on nanowires grown to have
low and high defect density segments. 4.2 K carrier mobilities are ~4X larger
in the nominally defect-free segments of the wire. We also find that dark field
optical intensity is correlated with the mobility, suggesting a simple route
for selecting wires with a low defect density. At low temperatures, FETs
fabricated on high defect density segments of InAs nanowires showed transport
properties consistent with single electron charging, even on devices with low
resistance ohmic contacts. The charging energies obtained suggest quantum dot
formation at defects in the wires. These results reinforce the importance of
controlling the defect density in order to produce high quality electrical and
optical devices using InAs nanowires.",0912.1511v2
2012-05-30,A Path to Higher Q0 with Large Grain Niobium Cavities,"The improvement of the quality factor Q0 of superconducting radio-frequency
(SRF) cavities at medium accelerating gradients (20-25 MV/m) is important in
order to reduce the cryogenic losses in continuous wave (CW) accelerators used
for a variety of applications. In recent years, SRF cavities fabricated from
ingot niobium have become a viable alternative to standard high-purity
fine-grain Nb for the fabrication of high-performing SRF cavities with the
possibility of significant cost reduction. Recent studies demonstrated the
improvement of Q0 at medium field in cavities heat treated at 800-1200 {\deg}C
without subsequent chemical etching [ ]. To further explore this treatment
procedure, a new induction furnace with an all-niobium hot-zone was
commissioned [ ]. A single-cell 1.5 GHz cavity fabricated from ingot material
from CBMM, Brazil, with RRR 200, was heat treated in the new furnace in the
temperature range 800-1400 {\deg}C for several hours. Residual resistance value
of 1 - 5 n\Omega have been consistently achieved on this cavity Q0-values as
high as 4.6\times1010 at 90 mT peak surface magnetic field at 2 K. Q0 values of
about ~2\times1011 have been measured at 1.5 K.",1205.6736v1
2013-01-23,Superconductivity of interface layer at contact between normal metal and high temperature superconductor,"In this research, it is shown that there are the necessary physical
conditions to originate the returning superconductivity in the thin interface
layer at the contact between the normal metal and the high temperature
superconductor (N-S contact). The influences by the temperature T, magnetic
field H and direct current I on the electrical resistance RG of the thin
interface layer G in the multilayered system N-G-S, where N can be one the
normal metal layers of Argentum (Ag), Indium (In), Gallium-Indium (Ga-50%In), G
is the thin interface layer, S is the high temperature superconductor (HTS)
layer of YBa2Cu3O7-x, are researched experimentally.",1301.5542v2
2015-03-23,Gate-tunable high mobility remote-doped InSb/In_{1-x}Al_{x}Sb quantum well heterostructures,"Gate-tunable high-mobility InSb/In_{1-x}Al_{x}Sb quantum wells (QWs) grown on
GaAs substrates are reported. The QW two-dimensional electron gas (2DEG)
channel mobility in excess of 200,000 cm^{2}/Vs is measured at T=1.8K. In
asymmetrically remote-doped samples with an HfO_{2} gate dielectric formed by
atomic layer deposition, parallel conduction is eliminated and complete 2DEG
channel depletion is reached with minimal hysteresis in gate bias response of
the 2DEG electron density. The integer quantum Hall effect with Landau level
filling factor down to 1 is observed. A high-transparency non-alloyed Ohmic
contact to the 2DEG with contact resistance below 1{\Omega} \cdot mm is
achieved at 1.8K.",1503.06710v1
2015-09-10,Crystal Structure of 200 K-Superconducting Phase of Sulfur Hydride System,"This article reports the experimentally clarified crystal structure of a
recently discovered sulfur hydride in high temperature superconducting phase
which has the highest critical temperature Tc over 200 K which has been ever
reported. For understanding the mechanism of the high superconductivity, the
information of its crystal structure is very essential. Herein we have carried
out the simultaneous measurements electrical resistance and synchrotron x-ray
diffraction under high pressure, and clearly revealed that the hydrogen
sulfide, H2S, decomposes to H3S and its crystal structure has body-centered
cubic symmetry in the superconducting phase.",1509.03156v1
2015-09-13,High-Mobility Holes in Dual-Gated WSe$_2$ Field-Effect Transistors,"We demonstrate dual-gated $p$-type field-effect transistors (FETs) based on
few-layer tungsten diselenide (WSe$_2$) using high work-function platinum
source/drain contacts, and a hexagonal boron nitride top-gate dielectric. A
device topology with contacts underneath the WSe$_2$ results in $p$-FETs with
$I_{ON}$/$I_{OFF}$ ratios exceeding 10$^7$, and contacts that remain Ohmic down
to cryogenic temperatures. The output characteristics show current saturation
and gate tunable negative differential resistance. The devices show intrinsic
hole mobilities around 140 cm$^2$/Vs at room temperature, and approaching 4,000
cm$^2$/Vs at 2 K. Temperature-dependent transport measurements show a
metal-insulator transition, with an insulating phase at low densities, and a
metallic phase at high densities. The mobility shows a strong temperature
dependence consistent with phonon scattering, and saturates at low
temperatures, possibly limited by Coulomb scattering, or defects.",1509.03896v1
2016-08-02,High Current Density and Low Thermal Conductivity of Atomically Thin Semimetallic WTe2,"Two-dimensional (2D) semimetals beyond graphene have been relatively
unexplored in the atomically-thin limit. Here we introduce a facile growth
mechanism for semimetallic WTe2 crystals, then fabricate few-layer test
structures while carefully avoiding degradation from exposure to air. Low-field
electrical measurements of 80 nm to 2 um long devices allow us to separate
intrinsic and contact resistance, revealing metallic response in the thinnest
encapsulated and stable WTe2 devices studied to date (3 to 20 layers thick).
High-field electrical measurements and electro-thermal modeling demonstrate
that ultra-thin WTe2 can carry remarkably high current density (approaching 50
MA/cm2, higher than most common interconnect metals) despite a very low thermal
conductivity (of the order ~3 W/m/K). These results suggest several pathways
for air-stable technological viability of this layered semimetal.",1608.00988v1
2016-10-25,Pressure-induced superconductivity in the giant Rashba system BiTeI,"At ambient pressure, BiTeI is the first material found to exhibit a giant
Rashba splitting of the bulk electronic bands. At low pressures, BiTeI
undergoes a transition from trivial insulator to topological insulator. At
still higher pressures, two structural transitions are known to occur. We have
carried out a series of electrical resistivity and AC magnetic susceptibility
measurements on BiTeI at pressure up to ~40 GPa in an effort to characterize
the properties of the high-pressure phases. A previous calculation found that
the high-pressure orthorhombic P4/nmm structure BiTeI is a metal. We find that
this structure is superconducting with Tc values as high as 6 K. AC magnetic
susceptibility measurements support the bulk nature of the superconductivity.
Using electronic structure and phonon calculations, we compute Tc and find that
our data is consistent with phonon-mediated superconductivity.",1610.08038v1
2016-11-27,Strained GaN Quantum-Well FETs on Single Crystal Bulk AlN Substrates,"We report the first realization of molecular beam epitaxy grown strained GaN
quantum well field-effect transistors on single-crystal bulk AlN substrates.
The fabricated double heterostructure FETs exhibit a two- dimensional electron
gas (2DEG) density in excess of 2x10^13/cm2. Ohmic contacts to the 2DEG channel
were formed by n+ GaN MBE regrowth process, with a contact resistance of 0.13
Ohm-mm. Raman spectroscopy using the quantum well as an optical marker reveals
the strain in the quantum well, and strain relaxation in the regrown GaN
contacts. A 65-nm-long rectangular-gate device showed a record high DC drain
current drive of 2.0 A/mm and peak extrinsic transconductance of 250 mS/mm.
Small-signal RF performance of the device achieved current gain cutoff
frequency fT~120 GHz. The DC and RF performance demonstrate that bulk AlN
substrates offer an attractive alternative platform for strained quantum well
nitride transistors for future high-voltage and high-power microwave
applications.",1611.08914v1
2017-09-19,Design parameter space for a High Pressure Optimized Dense Plasma Focus operating with Deuterium,"The potential of the Dense Plasma Focus (DPF) for industrial applications in
many fields is well recognized, although yet to be realized in practice.
Particularly attractive is the possibility of its use as inexpensive industrial
source of nuclear reactions for diverse high value applications such as fast
pulsed neutron radiography of hydrogenous materials, non-intrusive neutron
interrogation of concealed organic contraband and rapid production of short
lived radioisotopes for medical diagnostics and therapy. Recently, it has been
suggested that it may be possible to operate the DPF efficiently in a
High-Pressure-Optimized (HPO) mode. This paper explores the design parameter
space for such HPO-DPF based on the revised Resistive Gratton-Vargas (RGV)
model with a view to identify a practicable set of system parameters and their
scaling. The current waveform predicted by the revised RGV model for the chosen
set of parameters is fitted to the Lee model to estimate the likely neutron
yield.",1709.06243v1
2017-12-09,Extremely large magnetoresistance and high-density Dirac-like fermions in ZrB2,"We report the detailed study on transport properties of ZrB2 single crystal,
a predicted topological nodal-line semimetal. ZrB2 exhibits extremely large
magnetoresistance as well as field-induced resistivity upturn and plateau.
These behaviors can be well understood by the two-band model with the perfect
electron - hole compensation and high carrier mobilities. More importantly, the
electrons with small effective masses and nontrivial Berry phase have
significantly high density when compared to those in known topological
semimetals. It strongly suggests that ZrB2 hosts Dirac-like nodal-line
fermions.",1712.03362v1
2018-11-01,Ultra-thin low frequency perfect sound absorber with high ratio of active area,"A concept of ultra-thin low frequency perfect sound absorber is proposed and
demonstrated experimentally. To minimize non-linear effects, an high ratio of
active area to total area is used to avoid large localized amplitudes. The
absorber consists of three elements: a mass supported by a very flexible
membrane, a cavity and a resistive layer. The resonance frequency of the sound
absorber can be easily adjusted just by changing the mass or thickness of the
cavity. A very large ratio between wavelength and material thickness is
measured for a manufactured perfect absorber (ratio = 201) . It is shown that
this high sub-wavelength ratio is associated with narrowband effects and that
the increase in the sub-wavelength ratio is limited by the damping in the
system.",1811.00897v1
2019-06-28,High pO2 Floating Zone Crystal Growth of the Perovskite Nickelate PrNiO3,"Single crystals of PrNiO3 were grown under an oxygen pressure of 295 bar
using a unique high-pressure optical-image floating zone furnace. The crystals,
with volume in excess of 1 mm3, were characterized structurally using single
crystal and powder X-ray diffraction. Resistivity, specific heat, and magnetic
susceptibility were measured, all of which evidenced an abrupt, first order
metal-insulator transition (MIT) at ~130 K, in agreement with previous
literature reports on polycrystalline specimens. Temperature-dependent single
crystal diffraction was performed to investigate changes through the MIT. Our
study demonstrates the opportunity space for high fugacity, reactive
environments for single crystal growth specifically of perovskite nickelates
but more generally to correlated electron oxides.",1907.00078v1
2020-02-17,Characterization of High-Purity Germanium (Ge) Crystals for Developing Novel Ge Detectors,"High-purity germanium (HPGe) crystals are required to be well-characterized
before being fabricated into Ge detectors. The characterization of HPGe
crystals is often performed with the Hall Effect system, which measures the
carrier concentration, the Hall mobility, and the electrical resistivity. The
reported values have a strong dependence on the size of the ohmic contacts and
the geometry of the samples used in conducting the Hall Effect measurements. We
conduct a systematic study using four samples cut from the same location in a
HPGe crystal made into different sized ohmic contacts or different geometries
to study the variation of the measured parameters from the Hall Effect system.
The results are compared to the C-V measurements provided by the Ge detector
made from the same crystal. We report the systematic errors involved with the
Hall Effect system and find a reliable technique that minimizes the systematic
error to be only a few percent from the Hall Effect measurements.",2002.07706v2
2016-03-13,A sub-1-volt analog metal oxide memristive-based synaptic device for energy-efficient spike-based computing systems,"Nanoscale metal oxide memristors have potential in the development of
brain-inspired computing systems that are scalable and efficient1-3. In such
systems, memristors represent the native electronic analogues of the biological
synapses. However, the characteristics of the existing memristors do not fully
support the key requirements of synaptic connections: high density, adjustable
weight, and low energy operation. Here we show a bilayer memristor that is
forming-free, low-voltage (~|0.8V|), energy-efficient (full On/Off switching at
~2pJ), and reliable. Furthermore, pulse measurements reveal the analog nature
of the memristive device, that is it can be directly programmed to intermediate
resistance states. Leveraging this finding, we demonstrate
spike-timing-dependent plasticity (STDP), a spike-based Hebbian learning rule4.
In those experiments, the memristor exhibits a marked change in the normalized
synaptic strength (>30 times) when the pre- and post-synaptic neural spikes
overlap. This demonstration is an important step towards the physical
construction of high density and high connectivity neural networks.",1603.03979v1
2017-07-24,Probing local lattice distortion in medium- and high-entropy alloys,"The atomic-level tunability that results from alloying multiple transition
metals with d electrons in concentrated solid solution alloys (CSAs), including
high-entropy alloys (HEAs), has produced remarkable properties for advanced
energy applications, in particular, damage resistance in high-radiation
environments. The key to understanding CSAs radiation performance is
quantitatively characterizing their complex local physical and chemical
environments. In this study, the local structure of a FeCoNiCrPd HEA is
quantitatively analyzed with X-ray total scattering and extended X-ray
absorption fine structure methods. Compared to FeCoNiCr and FeCoNiCrMn,
FeCoNiCrPd with a quasi-random alloy structure has a strong local lattice
distortion, which effectively pins radiation-induced defects. Distinct from a
relaxation behavior in FeCoNiCr and FeCoNiCrMn, ion irradiation further
enhanced the local lattice distortion in FeCoNiCrPd due to a preference for
forming Pd-Pd atomic pairs.",1707.07745v1
2019-12-02,Probing intraband excitations in ZrTe$_5$: a high-pressure infrared and transport study,"Zirconium pentatetelluride, ZrTe5, shows remarkable sensitivity to
hydrostatic pressure. In this work we address the high-pressure transport and
optical properties of this compound, on samples grown by flux and charge vapor
transport. The high-pressure resistivity is measured up to 2 GPa, and the
infrared transmission up to 9 GPa. The dc conductivity anisotropy is determined
using a microstructured sample. Together, the transport and optical
measurements allow us to discern band parameters with and without the
hydrostatic pressure, in particular the Fermi level, and the effective mass in
the less conducting, out-of-plane direction. The results are interpreted within
a simple two-band model characterized by a Dirac-like, linear in-plane band
dispersion, and a parabolic out-of-plane dispersion.",1912.00942v2
2019-12-23,Change of electronic properties on transition from high-entropy to Ni-rich (TiZrNbCu)(1-x)Ni(x) alloys,"We present results of comprehensive study of electronic properties of
(TiZrNbCu)(1-x)Ni(x) metallic glasses performed in broad composition range x
encompassing both, high entropy (HE) range, and conventional Ni-base alloy
concentration range, x >= 0.35. The electronic structure studied by
photoemission spectroscopy and low temperature specific heat (LTSH) reveal a
split-band structure of density of states inside valence band with d-electrons
of Ti, Zr, Nb and also Ni present at Fermi level N(E_F), whereas LTSH and
magnetoresistivity results show that variation of N(E_F) with x changes in
Ni-base regime. The variation of superconducting transition temperatures with x
closely follows that of N(E_F). The electrical resistivities of all alloys are
high and decrease with increasing temperature over most of explored temperature
range, and their temperature dependence seems dominated by weak localization
effects over a broad temperature range (10-300 K). The preliminary study of
Hall effect shows positive Hall coefficient that decreases rapidly in Ni-base
alloys.",1912.11133v1
2012-03-27,Graphene-Graphite Quilts for Thermal Management of High-Power GaN Transistors,"Self-heating is a severe problem for high-power GaN electronic and
optoelectronic devices. Various thermal management solutions, e.g. flip-chip
bonding or composite substrates have been attempted. However, temperature rise
still limits applications of the nitride-based technology. Here we demonstrate
that thermal management of GaN transistors can be substantially improved via
introduction of the alternative heat-escaping channels implemented with
few-layer graphene - an excellent heat conductor. We have transferred few-layer
graphene to AlGaN/GaN heterostructure field-effect transistors on SiC
substrates to form the ""graphene-graphite quilts"" - lateral heat spreaders,
which remove heat from the channel regions. Using the micro-Raman spectroscopy
for in-situ monitoring we have shown that temperature can be lowered by as much
as ~ 20oC in such devices operating at ~13-W/mm power density. The simulations
suggest that the efficiency of the ""graphene quilts"" can be made even higher in
GaN devices on thermally resistive sapphire substrates and in the designs with
the closely located heat sinks. Our results open a novel application niche for
few-layer graphene in high-power electronics.",1203.6099v1
2018-12-06,Technologies for Future Vertex and Tracking Detectors at CLIC,"CLIC is a proposed linear $e^{+}e^{-}$ collider with center-of-mass energies
of up to $3\,\textrm{TeV}$. Its main objectives are precise top quark and Higgs
boson measurements, as well as searches for Beyond Standard Model physics. To
meet the physics goals, the vertex and tracking detectors require not only a
spatial resolution of a few micrometers and a very low material budget, but
also timing capabilities with a precision of a few nanoseconds to allow
suppression of beam-induced backgrounds.
  Different technologies using hybrid silicon detectors are explored for the
vertex detectors, such as dedicated readout ASICs, small-pitch active edge
sensors as well as capacitively coupled High-Voltage CMOS sensors. Monolithic
sensors are considered as an option for the tracking detector, and a prototype
using a CMOS process with a high-resistivity epitaxial layer is being designed.
Different designs using a silicon-on-insulator process are under investigation
for both vertex and tracking detector.
  All prototypes are evaluated in laboratory and beam tests, and newly
developed simulation tools combining Geant4 and TCAD are used to assess and
optimize their performance. This contribution gives an overview of the R&D
program for the CLIC vertex and tracking detectors, highlighting new results
from the prototypes.",1812.02625v1
2019-06-22,Dynamic enlargement of a hole in a sheet: crater formation and propagation of cylindrical shock waves,"Predicting the shape of a crater formed by high velocity impact is of
interest in several fields. It can aid in design of more efficient protective
structures, in forensic analysis of bullet holes, and in understanding the
effects of meteorite impact in both space systems and in extreme geological
events. In this paper we present, for the first time, a complete theoretical
solution of the dynamic plane-stress problem. We consider the steady-state
expansion of a cylindrical hole in a strain hardening elastoplastic sheet and
find that a self-similar field emerges if the `specific cavitation energy' is
constant. It is shown that at the quasistatic limit this solution reduces to
available classical solutions, while at high expansion velocities shock waves
can appear. Investigation of the constitutive sensitivities of the expansion
field is conducted and compared with available results for the spherical field
which is commonly applied to predict resistance to high velocity penetration.
It is shown that shock waves appear at significantly lower expansion
velocities, in the plane-stress deformation pattern, for which material
compressibility is found to have a negligible effect. This insensitivity can be
taken advantage of in the future for design of light weight protective layers
by incorporating porosity.",1906.09514v1
2019-10-08,Visualizing dissipative charge carrier dynamics at the nanoscale with superconducting charge qubit microscopy,"The investigation of novel electronic phases in low-dimensional quantum
materials demands for the concurrent development of new measurement techniques
that combine surface sensitivity with high spatial resolution and high
measurement accuracy. We propose a new quantum sensing imaging modality based
on superconducting charge qubits to study dissipative charge carrier dynamics
with nanometer spatial and high temporal resolution. Using analytical and
numerical calculations we show that superconducting charge qubit microscopy
(SCQM) has the potential to resolve temperature and resistivity changes in a
sample as small as $\Delta T\leq0.1\;$mK and $\Delta\rho\leq1\cdot10^{4}
\,\Omega\cdot$cm, respectively. Among other applications, SCQM will be
especially suited to study the microscopic mechanisms underlying interaction
driven quantum phase transitions, to investigate the boundary modes found in
novel topological insulators and, in a broader context, to visualize the
dissiaptive charge carrier dynamics occurring in mesoscopic and nanoscale
devices.",1910.03583v2
2020-06-05,Anomalous dependence of thermoelectric parameters on carrier concentration and electronic structure in Mn-substituted Fe2CrAl Heusler alloy,"We investigate the high temperature thermoelectric properties of Heusler
alloys Fe2-xMnxCrAl (0<x<1). Substitution of 12.5% Mn at Fe-site (x = 0.25)
causes a significant increase in high temperature resistivity (\r{ho}) and an
enhancement in the Seebeck coefficient (S), as compared to the parent alloy.
However, as the concentration of Mn is increased above 0.25, a systematic
decrement in the magnitude of both parameters is noted. These observations have
been ascribed (from theoretical analysis) to a change in band gap and
electronic structure of Fe2CrAl with Mn-substitution. Due to absence of mass
fluctuations and lattice strain, no significant change in thermal conductivity
is seen across this series of Heusler alloys. Additionally, S drastically
changes its magnitude along with a crossover from negative to positive above
900 K, which has been ascribed to the dominance of holes over electrons in high
temperature regime. In this series of alloys, S and \r{ho} shows a strong
dependence on the carrier concentration and strength of d-d hybridization
between Fe/Mn and Cr atoms.",2006.03234v2
2020-06-24,Tip-induced oxidation of silicene nano-ribbons,"We report on the oxidation of self-assembled silicene nanoribbons grown on
the Ag(110) surface using Scanning Tunneling Microscopy and High-Resolution
Photoemission Spectroscopy. The results show that silicene nanoribbons present
a strong resistance towards oxidation using molecular oxygen. This can be
overcome by increasing the electric field in the STM tunnel junction above a
threshold of +2.6 V to induce oxygen dissociation and reaction. The higher
reactivity of the silicene nanoribbons towards atomic oxygen is observed as
expected. The HR-PES confirm these observations: Even at high exposures of
molecular oxygen, the Si 2p core-level peaks corresponding to pristine silicene
remain dominant, reflecting a very low reactivity to molecular oxygen. Complete
oxidation is obtained following exposure to high doses of atomic oxygen; the Si
2p core level peak corresponding to pristine silicene disappears.",2006.13780v1
2020-08-06,Melting and decomposition of orthorhombic B6Si under high pressure,"Melting of orthorhombic boron silicide B6Si has been studied at pressures up
to 8 GPa using in situ electrical resistivity measurements and quenching. It
has been found that in the 2.6-7.7 GPa range B6Si melts congruently, and the
melting curve exhibits negative slope of -31(2) K/GPa that points to a higher
density of the melt as compared to the solid phase. At very high temperatures
B6Si melt appears to be unstable and undergoes disproportionation into silicon
and boron-rich silicides. The onset temperature of disproportionation strongly
depends on pressure, and the corresponding low-temperature boundary exhibits
negative slope of -92(3) K/GPa which is indicative of significant volume
decrease in the course of B6Si melt decomposition.",2008.02739v1
2020-11-02,GaN/AlGaN 2DEGs in the quantum regime: Magneto-transport and photoluminescence to 60 tesla,"Using high magnetic fields up to 60 T, we report magneto-transport and
photoluminescence (PL) studies of a two-dimensional electron gas (2DEG) in a
GaN/AlGaN heterojunction grown by molecular-beam epitaxy. Transport
measurements demonstrate that the quantum limit can be exceeded (Landau level
filling factor $\nu < 1$), and show evidence for the $\nu =2/3$ fractional
quantum Hall state. Simultaneous optical and transport measurements reveal
synchronous quantum oscillations of both the PL intensity and longitudinal
resistivity in the integer quantum Hall regime. PL spectra directly reveal the
dispersion of occupied Landau levels in the 2DEG and therefore the electron
mass. These results demonstrate the utility of high (pulsed) magnetic fields
for detailed measurements of quantum phenomena in high-density 2DEGs.",2011.01365v1
2021-05-31,Effect of Zr and Al Addition on Nanocluster Formation in Oxide Dispersion Strenghthened Steel-an ab initio Study,"Conventional Oxide dispersion strengthened steels are characterized by
thermally stable, high density of Y-Ti-O nanoclusters, which are responsible
for their high creep strength. Ti plays a major role in obtaining a high
density of ultrafine particles of optimum size range of 2-10 nm. In
Al-containing ODS steels developed for corrosion resistance, Y-Al-O clusters
formed are of size range 20 -100 nm, and Ti fails in making dispersions finer
in the presence of Al. Usage of similar alloying elements like Zr in place of
Ti is widely considered. In this study, binding energies of different stages of
Y-Zr-O-Vacancy and Y-Al-O-Vacancy complexes in the bcc Iron matrix are studied
by first-principle calculations. It is shown that in all the stages of
formation, Y-Zr-O-Vacancy clusters have higher binding energy than
Y-Al-O-Vacancy clusters and hence in ferritic steel containing both Zr and Al,
Y-Zr-O-Vacancy clusters are more stable and more favored to nucleate than
Y-Al-O-Vacancy clusters. The bonding nature in each stage is analyzed using
charge density difference plots for the plausible reason for higher stability
of Y-Zr-O-Vacancy clusters.",2105.15063v1
2021-06-07,Accelerated Corrosion of High Entropy Alloys under Tensile Stress,"High entropy alloys are finding significant scientific interest due to their
exotic microstructures and exceptional properties resulting thereof. These
alloys have excellent corrosion resistance and may find broad range of
applications from bio-implants, aerospace components and nuclear industry. A
critical performance metric that determines the application worthiness of the
alloys is the resilience of stressed structural members in a corrosive
environment. This study reports the results from a novel experimental setup to
quantify the corrosion rate under uniaxial tensile stress in a single phase fcc
Al0.1CoCrFeNi high entropy alloy rods. Under a uniform uniaxial applied stress
of 600 MPa, the corrosion current density was observed to increase by three
orders of magnitude and ~150 mV drop in corrosion potential. The mechanism of
accelerated corrosion is identified as surface passivation layer breakdown, pit
initiation on un-passivated surface and rapid pit-propagation along the loading
direction.",2106.03690v1
2021-07-09,Excavation Learning for Rigid Objects in Clutter,"Autonomous excavation for hard or compact materials, especially irregular
rigid objects, is challenging due to high variance of geometric and physical
properties of objects, and large resistive force during excavation. In this
paper, we propose a novel learning-based excavation planning method for rigid
objects in clutter. Our method consists of a convolutional neural network to
predict the excavation success and a sampling-based optimization method for
planning high-quality excavation trajectories leveraging the learned prediction
model. To reduce the sim2real gap for excavation learning, we propose a
voxel-based representation of the excavation scene. We perform excavation
experiments in both simulation and real world to evaluate the learning-based
excavation planners. We further compare with two heuristic baseline excavation
planners and one data-driven scene-independent planner. The experimental
results show that our method can plan high-quality excavations for rigid
objects in clutter and outperforms the baseline methods by large margins. As
far as we know, our work presents the first learning-based excavation planner
for cluttered and irregular rigid objects.",2107.04171v1
2021-07-17,Vacancy tuned thermoelectric properties and high spin filtering performance in graphene/silicene heterostructures,"The main contribution of this paper is to study the spin caloritronic effects
in defected graphene/silicene nanoribbon (GSNR) junctions. Each step-like GSNR
is subjected to the ferromagnetic exchange and local external electric fields,
and their responses are determined using the nonequilibrium Greens function
(NEGF) approach. To further study the thermoelectric (TE) properties of the
GSNRs, three defect arrangements of divacancies (DVs) are also considered for a
larger system, and their responses are re-evaluated. The results demonstrate
that the defected GSNRs with the DVs can provide an almost perfect thermal spin
filtering effect (SFE), and spin switching. A negative differential
thermoelectric resistance (NDTR) effect and high spin polarization efficiency
(SPE) larger than 99.99 percent are obtained. The system with the DV defects
can show a large spin-dependent Seebeck coefficient, equal to 1.2 mV/K, which
is relatively large and acceptable. Appropriate thermal and electronic
properties of the GSNRs can also be obtained by tuning up the DV orientation in
the device region. Accordingly, the step-like GSNRs can be employed to produce
high efficiency spin caloritronic devices with various features in practical
applications.",2107.08240v1
2021-12-24,Anisotropic thermal expansion and electronic transitions in the Co$_3$BO$_5$ ludwigite,"The investigations of the crystal structure, magnetic and electronic
properties of the Co$_3$BO$_5$ at high temperatures were carried out using
powder x-ray diffraction, magnetic susceptibility, electrical resistivity, and
thermopower measurements. The orthorhombic symmetry (Sp.gr. Pbam) was
established at 300 K and no evidence of structural phase transitions was found
up to 1000 K. The thermal expansion of the crystal lattice is strongly
anisotropic. At $T<T_c=550$ K, a large thermal expansion along the c-axis is
observed with simultaneous contraction along a-axis. The activation energy of
the conductivity decreases significantly at high temperatures and follows the
thermal expansion variation, that exhibits two electronic transitions at ~500
and ~700 K, in coincidence with the anomalies of the heat capacity. Electronic
transport was found to be a dominant conduction mechanism in the entire
temperature range. The temperature dependence of the effective magnetic moment
reflects the evolution of the spin state of Co$^{3+}$ ions towards the spin
crossover to a high spin state. The interrelation between the crystal structure
and electronic properties is discussed.",2112.12941v1
2022-01-03,Deep-potential enabled multiscale simulation of gallium nitride devices on boron arsenide cooling substrates,"High-efficient heat dissipation plays critical role for high-power-density
electronics. Experimental synthesis of ultrahigh thermal conductivity boron
arsenide (BAs, 1300 W m-1K-1) cooling substrates into the wide-bandgap
semiconductor of gallium nitride (GaN) devices has been realized. However, the
lack of systematic analysis on the heat transfer across the BAs-GaN interface
hampers the practical applications. In this study, by constructing the accurate
and high-efficient machine learning interatomic potentials, we performed
multiscale simulations of the BAs-GaN heterostructures. Ultrahigh interfacial
thermal conductance (ITC) of 265 MW m-2K-1 is achieved, which lies in the
well-matched lattice vibrations of BAs and GaN. Moreover, the competition
between grain size and boundary resistance was revealed with size increasing
from 1 nm to 100 {\mu}m. Such deep-potential equipped multiscale simulations
not only promote the practical applications of BAs cooling substrates in
electronics, but also offer new approach for designing advanced thermal
management systems.",2201.00516v3
2022-04-01,Tuning of Carrier Concentration and Superconductivity in High-Entropy-Alloy-Type Metal Telluride (AgSnPbBi)(1-x)/4InxTe,"High-entropy-alloy-type (HEA-type) compound superconductors have been drawing
much attention as a new class of exotic superconductors with local structural
inhomogeneity. NaCl-type (Ag,In,Sn,Pb,Bi)Te is a typical HEA-type
superconductor, but the carrier doping mechanism had been unclear. In this
study, we synthesized (Ag,In,Sn,Pb,Bi)Te with various In concentration using
high-pressure synthesis: the studied system is (AgSnPbBi)(1-x)/4InxTe (x =
0-0.4). Single-phase samples were obtained for x = 0-0.3. A semiconductor-like
temperature dependence of resistivity was observed for x = 0, while
superconductivity appeared for the In-doped samples. The highest transition
temperature (Tc) was 3.0 K for x = 0.3. The Seebeck coefficient decreases with
increase of x, which suggests that In3+ generates electron carriers in
(AgSnPbBi)(1-x)/4InxTe. Tuning of carrier concentration and superconducting
properties of (Ag,In,Sn,Pb,Bi)Te would be useful for further investigation of
exotic superconductivity in the HEA-type compound.",2204.00407v1
2022-04-30,Fluorinated graphene films with graphene quantum dots for electronic applications,"This work analyzes carrier transport, the relaxation of non-equilibrium
charge, and the electronic structure of fluorinated graphene (FG) films with
graphene quantum dots (GQDs). The FG films with GQDs were fabricated by means
of chemical functionalization in an aqueous solution of hydrofluoric acid. High
fluctuations of potential relief inside the FG barriers have been detected in
the range of up to 200 mV. A phenomenological expression that describes the
dependence of the time of non-equilibrium charge emission from GQDs on quantum
confinement levels and film thickness (potential barrier parameters between
GQDs) is suggested. An increase in the degree of functionalization leads to a
decrease in GQD size, the removal of the GQD effect on carrier transport, and
the relaxation of non-equilibrium charge. The study of the electronic
properties of FG films with GQDs has revealed a unipolar resistive switching
effect in the films with a relatively high degree of fluorination and a high
current modulation in transistorlike structures with a lower degree of
fluorination. 2D films with GQDs are believed to have considerable potential
for various electronic applications (nonvolatile memory, 2D connections with
optical control and logic elements).",2205.00205v1
2022-06-09,Field-tunable Weyl points and large anomalous Hall effects in degenerate magnetic semiconductor EuMg$_2$Bi$_2$,"Magnets, with topologically-nontrivial Dirac/Weyl points, have recently
attracted significant attention owing to the unconventional physical
properties, such as large anomalous Hall effects. However, they typically have
a high carrier density and complicated band structure near the Fermi energy. In
this study, we report degenerate magnetic semiconductor EuMg$_2$Bi$_2$, which
exhibits a single valley at the $\Gamma$ point, where the field-tunable Weyl
points form via the magnetic exchange interaction with the local Eu spins. By
the high-field measurements on high-quality single crystals, we observed the
quantum oscillations in resistivity, elastic constant, and surface impedance,
which enabled us to determine the position of the Fermi energy. In combination
with the first-principles calculation, we revealed that the Weyl points are
located in the vicinity of the Fermi energy when the Eu spins are fully
polarized. Furthermore, we observed large anomalous Hall effect (Hall angle
$\Theta_{\mathrm{AH}}\sim0.07$) in the forced ferromagnetic phase, which is
consistent with this field variation of band structure.",2206.04577v1
2023-09-12,High-pressure hydrothermal growth and characterization of Sr3Os4O14 single crystals,"Single crystals of the novel strontium osmate Sr3Os4O14 have been grown by
the hydrothermal method using opposed anvil high-pressure and high-temperature
technique. The reaction took place in sealed gold capsules at 3 GPa and a
temperature of 1100 C, with water acting as a solvent. The employed method
yields up to 1 mm crystals with quite uncommon double-terminated morphologies.
The crystal structure was identified as tetragonal by single-crystal X-ray
diffraction, with lattice parameters a = 12.2909(8) A and c = 7.2478(5) A. The
structural analysis suggests P42nm or P42/mnm as a possible space group. In
general, the structure belongs to the pyrochlore type and is composed of a
network of symmetrically arranged OsO6 octahedra. Resistivity measurements
evidence a metallic behavior, accompanied by a temperature-independent
paramagnetism. Heat capacity measurements reveal a slightly enhanced value of
the Sommerfeld coefficient 34 mJ/mol K2. Superconductivity has not been
observed down to 2 K.",2309.06138v1
2024-02-04,Comparative study on high temperature mechanical behavior in 3YTZP containing SWCNTs or MWCNTs,"Effects on mechanical properties of the presence of either single-walled
carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) in a 3YTZP
matrix have been investigated in this work. Thus, monolithic 3YTZP and 3YTZP
containing 2.5 vol% either SWCNTs or MWCNTs were fabricated by Spark Plasma
Sintering (SPS) at 1250 C. Samples were crept at temperatures between 1100 and
1200 C and stresses between 5 and 230 MPa. Raman spectroscopy measurements
indicate the absence of severe damages in the CNTs structure after sintering
and testing. Scanning electron microscopy studies show that microstructures do
not evolve during creep tests. Mechanical results point out that monolithic
3YTZP exhibits a higher creep resistance than composites since CNTs facilitate
grain boundary sliding during high-temperature deformation. SWCNTs and MWCNTs
have a similar effect on the high temperature mechanical behavior in 3YTZP
where the bundle length and the level of dispersion of CNTs play a crucial
role.",2402.08130v1
2024-03-29,Synthesis of CaKFe$_4$As$_4$ bulk samples with high critical current density using a spark plasma sintering technique,"A high density CaKFe$_4$As$_4$ bulk sample was successfully synthesized using
a spark plasma sintering (SPS) technique. The density of the synthesized sample
was 5.02 g cm$^{-3}$, corresponding to 96.2% of the theoretical density of
CaKFe$_4$As$_4$. Moreover, a reasonably high Vickers hardness of 1 GPa was
measured. The electrical resistivity of the SPS bulk sample was as low as
approximately 600 $\mu\Omega$ cm at 300 K, which is smaller than that of the
ordinary sintered polycrystalline sample by nearly one order of magnitude, and
exhibited a sharp superconducting transition, with the transition width
$\Delta\textit{T}_c$ less than 2 K, indicating an improved grain connectivity.
The critical current density of the SPS bulk sample, as calculated from the
magnetization hysteresis loops (magnetic $\textit{J}_c$), reached 18 kA
cm$^{-2}$ at 4.2 K under 5 T, which is the highest among the iron-based
superconductor polycrystalline samples reported thus far.",2403.19981v1
2016-07-11,Role of carbon nanotube diameter on thermal interfacial resistance through the analysis of vibrational mismatch: A Molecular Dynamics approach,"Carbon nanotube (CNT) have been known to increase the heat transfer at the
solid-liquid interfaces, but have a limitation due to the interfacial thermal
resistance. Vibrational mismatch at the interface leads to this interfacial
thermal resistance, which plays an important role in energy transfer at the
boundary. Negligible work has been reported on the influence of CNT diameter on
the resistance through the vibrational mismatch study. Molecular dynamics
simulations have been performed to investigate the effect of CNT diameter on
interfacial resistance between carbon nanotube (CNT) and water molecules. This
work is an effort to understand the heat transfer phenomenon at the interface
by quantifying the vibrational mismatch. Analysis of the vibrational spectra of
CNT and water molecules is done to study the effect of CNT diameter on
interfacial resistance. Starting with the initial configuration, and
equilibrating the system of CNT and water molecules at 300 K and 1 atm, the CNT
temperature is raised to 700 K by velocity rescaling. This system is now
allowed to relax as a micro-canonical ensemble. Based on the lumped capacitance
analysis, the time constant of the CNT temperature response is determined,
which is then used to compute the interfacial thermal resistance. The
interfacial thermal resistance is observed to be relatively higher for the
larger diameter nanotube. This is attributed to the higher vibrational mismatch
existing for larger diameter CNT as a result of low overlapping region between
vibrational density states of CNT and water molecules. For smaller diameter
CNT, the interfacial thermal resistance is low which results in the efficient
heat transfer at the interface thus, emphasizing the indispensable role of
larger diameter CNTs in the cooling applications.",1607.03379v2
2016-07-22,Using machine learning to identify factors that govern amorphization of irradiated pyrochlores,"Structure-property relationships is a key materials science concept that
enables the design of new materials. In the case of materials for application
in radiation environments, correlating radiation tolerance with fundamental
structural features of a material enables materials discovery. Here, we use a
machine learning model to examine the factors that govern amorphization
resistance in the complex oxide pyrochlore ($A_2B_2$O$_7$). We examine the
fidelity of predictions based on cation radii and electronegativities, the
oxygen positional parameter, and the energetics of disordering and amorphizing
the material. No one factor alone adequately predicts amorphization resistance.
We find that, when multiple families of pyrochlores (with different B cations)
are considered, radii and electronegativities provide the best prediction but
when the machine learning model is restricted to only the $B$=Ti pyrochlores,
the energetics of disordering and amorphization are optimal. This work provides
new insight into the factors that govern the amorphization susceptibility and
highlights the ability of machine learning approaches to generate that insight.",1607.06789v1
2018-11-25,Electrical and Thermal Properties of SnTe/Sb2Te3 Superlattice Phase Change Materials,"The fundamental electrical and thermal properties of the devices consisting
of SnxTe1-x/Sb2Te3 superlattice (SnTeSL) materials have been investigated and
compared with those of the conventional Ge2Sb2Te5 (GST225) and GeTe/Sb2Te3
superlattice (GeTeSL) in terms of their resistance switching characteristics. A
significant reduction in the switching power of SnTeSL is demonstrated by
conducting a proper initialization procedure, varying x in SnxTe1-x/Sb2Te3, and
applying short electric pulses. It is found that the observed drastic power
reduction occurs due to the exponential decrease in the electric current under
the pulse incidence. On the other hand, the thermal properties of the studied
SL materials are very similar to those of the conventional phase change
materials. The obtained transmission electron micrographs and results of
multilevel-cell recording in GeTeSL and SnTeSL via multi-pulse incidence are
totally different from the properties of the phase change materials along the
GeTe-Sb2Te3 pseudo-binary tie line. Two different models (the partial switching
and electric field-induced one) are proposed to elucidate the mechanism of the
resistance switching in the SL materials.",1811.09969v2
2018-12-11,Thermal resistance by transition between collective and non-collective phonon flows in graphitic materials,"Phonons in graphitic materials exhibit strong normal scattering
(N-scattering) compared to umklapp scattering (U-scattering). The strong
N-scattering cause collective phonon flow, unlike the relatively common cases
where U-scattering is dominant. If graphitic materials have finite size and
contact with hot and cold reservoirs emitting phonons with non-collective
distribution, N-scattering change the non-collective phonon flow to the
collective phonon flow near the interface between graphitic material and a heat
reservoir. We study the thermal resistance by N-scattering during the
transition between non-collective and collective phonon flows. Our Monte Carlo
solution of Peierls-Boltzmann transport equation shows that the N-scattering in
graphitic materials reduce heat flux from the ballistic case by around 15%,
30%, and 40% at 100, 200, and 300 K, respectively. This is significantly larger
than ~ 5% reduction of Debye crystal with similar Debye temperature (~ 2300 K).
We associate the large reduction of heat flux by N-scattering with the
non-linear dispersion and multiple phonon branches with different group
velocities of graphitic materials.",1812.04703v1
2021-04-15,Gas Sensing Properties of single-material SnP3 logical junction via Negative Differential Resistance: Theoretical Study,"The field of 2D materials has gained a lot of attention for vast range of
applications. Amongst others, the sensing ability towards harmful gases is the
application, which we explored in the present work using quantum-mechanical
simulations for the SnP3 material. Its electronic properties, namely 1 and 2
layers being semiconducting, while multilayers being metallic, offer a
possibility to build a single-material logical junction. In addition, the
harmful gases studied here show physical adsorption with charge transfer from
the substrate to the gas molecules. Calculated recovery times show promise of a
good sensing material. The I-V characteristics calculated for all cases
indicates that SnP3 could be a viable sensing material towards NO gas via
negative differential resistance.",2104.07702v1
2022-05-23,Absorption bias: An ideal descriptor for radiation tolerance of nanocrystalline BCC metals,"To evaluate the radiation tolerance of nanocrystalline (NC) materials, the
damage effects of Fe and W as typical body-centered cubic (BCC) metals under
uniform irradiation are studied by a sequential multi-scale modelling
framework. An ideal descriptor, the absorption bias (the ratio of the
absorption abilities of grain boundaries (GBs) to interstitials (I) and
vacancies (V)), is proposed to characterize the radiation tolerance of
materials with different grain sizes. Low absorption bias promotes defects
annihilation through enhancing I-V recombination and optimally tuning its
competition with GB absorption. Thus, the lower absorption bias, the higher
anti-irradiation performance of NC BCC metals is. Furthermore, by
comprehensively considering the mechanical property, thermal stability and
radiation resistance, nano-crystals are recommended for Fe-based structural
materials but coarse crystals for W-based plasma-facing materials. This work
reevaluates the radiation resistance of NC materials, resulting in new
strategies for designing structural materials of nuclear devices through
manipulating grain sizes.",2205.11050v1
2009-04-20,Successive phase transitions under high pressure in FeTe0.92,"We performed magnetization and electrical resistivity measurements under high
pressures of up to 19 GPa for FeTe0.92. The compound shows an anomaly in
magnetization and resistivity at atmospheric pressure due to a structural
distortion accompanied by a magnetic transition. We also observed magnetic and
resistive anomalies under high pressure, suggesting that two pressure-induced
phases exist at a low temperature. Unlike in FeAs-based compounds, no
superconductivity was detected under high pressures of up to 19 GPa, although
the anomaly at atmospheric pressure was suppressed by applying pressure.",0904.2945v2
2012-11-24,High Rate Resistive Plate Chamber for LHC detector upgrades,"The limitation of the detection rate of standard bakelite resistive plate
chambers (RPC) used as muon detectors in the LHC experiments has prevented the
use of such detectors in the high rate regions in both CMS and ATLAS detectors.
One alternative to these detectors are RPCs made with low resistivity glass
plates ($10^{10} {\rm \Omega .cm}$), a beam test at DESY has shown that such
detectors can operate at few thousand Hz/cm$^2$ with high efficiency(> 90%)",1211.5698v1
2018-06-21,Mutation rate variability as a driving force in adaptive evolution,"Mutation rate is a key determinant of the pace as well as outcome of
evolution, and variability in this rate has been shown in different scenarios
to play a key role in evolutionary adaptation and resistance evolution under
stress caused by selective pressure. Here we investigate the dynamics of
resistance fixation in a bacterial population with variable mutation rates and
show that evolutionary outcomes are most sensitive to mutation rate variations
when the population is subject to environmental and demographic conditions that
suppress the evolutionary advantage of high-fitness subpopulations. By directly
mapping a biophysical fitness function to the system-level dynamics of the
population we show that both low and very high, but not intermediate, levels of
stress in the form of an antibiotic result in a disproportionate effect of
hypermutation on resistance fixation. We demonstrate how this behavior is
directly tied to the extent of genetic hitchhiking in the system, the
propagation of high-mutation rate cells through association with high-fitness
mutations. Our results indicate a substantial role for mutation rate
flexibility in the evolution of antibiotic resistance under conditions that
present a weak advantage over wildtype to resistant cells.",1806.08454v2
2015-03-13,Paper-based spintronics: magneto-resistivity of permalloy deposited onto paper substrates,"Driven by low-cost, resource abundance and distinct material properties, the
use of paper in electronics, optics and fluidics is under investigation.
Considering sensor systems based on magneto-resistance principles (anisotropic,
giant, tunnel) that are conventionally manufactured onto inorganic
semiconductor materials, we propose the use of paper substrates for cost
reduction purposes primarily. In particular, we studied the magneto-resistance
sensitivity of permalloy (Py:Ni81Fe19) onto paper substrates. In this work, we
report on our findings with clean room paper (80 g/m2, Rrms = 2.877 {\mu}m, 23%
surface porosity, latex impregnation, no embossed macro-structure). Here, the
Py:Ni81Fe19 coating was manufactured by means of a dry process, sputter
deposition, and spans an area of 10x10 mm2 and a thickness of 70 nm. Employing
a four-point-probe DC resistivity measurement setup, we investigated the change
of electrical resistance of Py:Ni81Fe19 under the presence of an oriented
external magnetic field. In particular, we investigate the magneto-resistive
change at two configurations: (1) the direction of the magnetic field is
parallel to the nominal induced electric current and (2) the direction of the
magnetic field is perpendicular to the electric current. Due to the stochastic
orientation of the fibers interplaying with the Py:Ni81Fe19 coating, the change
in magneto-resistance of the overall system at both measurement configurations
closely corresponds to the classical response of Py:Ni81Fe19 at a +/-45{\deg}
angle between the direction of electrical current and magnetic field. Using the
magneto-optic kerr effect, we observed the formation of domain walls at the
fiber bending locations. Future work will focus on the impact of layer
thickness, fiber dimensions and structure of magnetic coating on the
performance of the paper-based Py:Ni81Fe19 magneto-resistors.",1503.04853v2
2002-12-16,"Effects of Boron Purity, Mg Stoichiometry and Carbon Substitution on Properties of Polycrystalline MgB$_{2}$","By synthesizing MgB$_{2}$ using boron of different nominal purity we found
values of the residual resistivity ratio ($RRR = R(300 K) / R(42 K)$) from 4 to
20, which covers almost all values found in literature. To obtain high values
of $RRR$, high purity reagents are necessary. With the isotopically pure boron
we obtained the highest $RRR \sim$ 20 for the stoichiometric compound. We also
investigated Mg$_{x}$$^{11}$B$_{2}$ samples with 0.8 $< x <$ 1.2. For the range
Mg$_{0.8}$$^{11}$B$_{2}$ up to Mg$_{1.2}$$^{11}$B$_{2}$ we found average values
of $RRR$ between 14 and 24. For smaller variations in stoichiometry ($x=1\pm
0.1$) $RRR = 18 \pm 3$. All of our data point to the conclusion that high $RRR$
($\sim 20$) and low $\rho_{0}$ ($\leq 0.4 \mu \Omega cm$) are intrinsic
material properties associated with high purity MgB$_{2}$. In addition we have
performed initial work on optimizing the formation of carbon doped MgB$_{2}$
via the use of B$_{4}$C. Nearly single phase material can be formed by reaction
of nominal Mg(B$_{0.8}$C$_{0.2}$)$_{2}$ for 24 hours at $1200^{\circ}C$. The
$T_{c}$ for this composition is between $21.9 K$ and $22.7 K$ (depending on
criterion).",0212385v1
2012-04-24,Microstructural analysis of phase separation in iron chalcogenide superconductors,"The interplay between superconductivity, magnetism and crystal structure in
iron-based superconductors is a topic of great interest amongst the condensed
matter physics community as it is thought to be the key to understanding the
mechanisms responsible for high temperature superconductivity. Alkali metal
doped iron chalcogenide superconductors exhibit several unique characteristics
which are not found in other iron-based superconducting materials such as
antiferromagnetic ordering at room temperature, the presence of ordered iron
vacancies and high resistivity normal state properties. Detailed
microstructural analysis is essential in order to understand the origin of
these unusual properties. Here we have used a range of complementary scanning
electron microscope based techniques, including high-resolution electron
backscatter di raction mapping, to assess local variations in composition and
lattice parameter with high precision and sub-micron spatial resolution. Phase
separation is observed in the Csx Fe2-ySe2 crystals, with the minor phase
distributed in a plate-like morphology throughout the crystal. Our results are
consistent with superconductivity occurring only in the minority phase.",1204.5472v4
2017-08-16,"Single-nanowire, low-bandgap hot carrier solar cells with tunable open-circuit voltage","Compared to traditional pn-junction photovoltaics, hot carrier solar cells
offer potentially higher efficiency by extracting work from the kinetic energy
of photogenerated ""hot carriers"" before they cool to the lattice temperature.
Hot carrier solar cells have been demonstrated in high-bandgap ferroelectric
insulators and GaAs/AlGaAs heterostructures, but so far not in low-bandgap
materials, where the potential efficiency gain is highest. Recently, a high
open-circuit voltage was demonstrated in an illuminated wurtzite InAs nanowire
with a low bandgap of 0.39 eV, and was interpreted in terms of a
photothermoelectric effect. Here, we point out that this device is a hot
carrier solar cell and discuss its performance in those terms. In the
demonstrated devices, InP heterostructures are used as energy filters in order
to thermoelectrically harvest the energy of hot electrons photogenerated in
InAs absorber segments. The obtained photovoltage depends on the
heterostructure design of the energy filter and is therefore tunable. By using
a high-resistance, thermionic barrier an open-circuit voltage is obtained that
is in excess of the Shockley-Queisser limit. These results provide
generalizable insight into how to realize high voltage hot carrier solar cells
in low-bandgap materials, and therefore are a step towards the demonstration of
higher efficiency hot carrier solar cells.",1708.04848v1
2019-11-11,Mechanical properties of VMoNO as a function of oxygen concentration: toward development of hard and tough refractory oxynitrides,"Improved toughness is a central goal in the development of wear-resistant
refractory ceramic coatings. Extensive theoretical and experimental research
has revealed that NaCl structure VMoN alloys exhibit surprisingly high
ductility combined with high hardness and toughness. However, during operation,
protective coatings inevitably oxidize, a problem which may compromise material
properties and performance. Here, we explore the role of oxidation in altering
VMoN properties. Density functional theory and theoretical intrinsic hardness
models are used to investigate the mechanical behavior of cubic V0.5Mo0.5N1-xOx
solid solutions as a function of the oxygen concentration x. Elastic-constant
and intrinsic hardness calculations show that oxidation does not degrade the
mechanical properties of V0.5Mo0.5N. Electronic structure analyses indicate
that the presence of oxygen reduces the covalent bond character, which slightly
lowers the alloy strength and intrinsic hardness. Nevertheless, the character
of metallic d-d states, which are crucial for allowing plastic deformation and
enhancing toughness, remains unaffected. Overall, our results suggest that
VMoNO oxynitrides, with oxygen concentrations as high as 50%, possess high
intrinsic hardness, while still being ductile.",1911.04165v1
2020-12-25,Superconductivity to 262 kelvin via catalyzed hydrogenation of yttrium at high pressures,"Room temperature superconductivity has been achieved under high pressure in
an organically derived carbonaceous sulfur hydride with a critical
superconducting transition temperature (Tc) of 288 kelvin. This development is
part of a new class of dense, hydrogen rich materials with remarkably high
critical temperatures. Metal superhydrides are a subclass of these materials
that provide a different and potentially more promising route to very high Tc
superconductivity. The most promising binary metal superhydrides contain
alkaline or rare earth elements, and recent experimental observations of LaH10
have shown them capable of Tc s up to 250 to 260 kelvin. Predictions have shown
yttrium superhydrides to be the most promising with an estimated Tc in excess
of 300 kelvin for YH10. Here we report the synthesis of an yttrium superhydride
that exhibits superconductivity at a critical temperature of 262 kelvin at 182
gigapascal. A palladium thin film assists the synthesis by protecting the
sputtered yttrium from oxidation and promoting subsequent hydrogenation. Phonon
mediated superconductivity is established by the observation of zero
resistance, an isotope effect and the reduction of Tc under an external
magnetic field. The upper critical magnetic field is 103 tesla at zero
temperature. We suggest YH9 is the synthesized product based on comparison of
the measured Raman spectra and Tc to calculated Raman results.",2012.13627v1
2021-08-25,A Stable High-Capacity Lithium-Ion Battery Using a Biomass-Derived Sulfur-Carbon Cathode and Lithiated Silicon Anode,"A full lithium-ion-sulfur cell with a remarkable cycle life was achieved by
combining an environmentally sustainable biomass-derived sulfur-carbon cathode
and a pre-lithiated silicon oxide anode. X-ray diffraction, Raman spectroscopy,
energy dispersive spectroscopy, and thermogravimetry of the cathode evidenced
the disordered nature of the carbon matrix in which sulfur was uniformly
distributed with a weight content as high as 75%, while scanning and
transmission electron microscopy revealed the micrometric morphology of the
composite. The sulfur-carbon electrode in the lithium half-cell exhibited a
maximum capacity higher than 1200 mAhgS-1, reversible electrochemical process,
limited electrode/electrolyte interphase resistance, and a rate capability up
to C/2. The material showed a capacity decay of about 40% with respect to the
steady-state value over 100 cycles, likely due to the reaction with the lithium
metal of dissolved polysulfides or impurities including P detected in the
carbon precursor. Therefore, the replacement of the lithium metal with a less
challenging anode was suggested, and the sulfur-carbon composite was
subsequently investigated in the full lithium-ion-sulfur battery employing a
Li-alloying silicon oxide anode. The full-cell revealed an initial capacity as
high as 1200 mAhgS-1, a retention increased to more than 79% for 100
galvanostatic cycles, and 56% over 500 cycles. The data reported herein well
indicated the reliability of energy storage devices with extended cycle life
employing high-energy, green, and safe electrode materials.",2108.11284v1
2023-09-07,Enhanced strength-ductility combination by introducing bimodal grains structures in high-density oxide dispersion strengthened FeCrAl alloys fabricated by spark plasma sintering technology,"Oxide dispersion strengthened FeCrAl alloys dispersed high-density
nano-oxides in the matrix show outstanding corrosion resistance and mechanical
properties. However, ODS FeCrAl alloys achieve the high strength generally at
the expense of ductility in some way. Here, a method by introducing a bimodal
grain structure was designed to overcome the strength-ductility tradeoff. In
this work, ODS FeCrAl alloys were successfully fabricated through various
mechanical alloying time, combined with spark plasma sintering under the vacuum
of less than 4Pa. Microstructural characterization showed that the average
grains size and nano-oxides size decrease gradually, and the density of
nano-oxides increases, as the milling time increases. Mechanical properties
revealed that both the strength and ductility were significantly synergistic
enhanced with increasing milling time. The bimodal grain distribution
characterized by electron backscatter diffraction (EBSD) (vacuum degree was
less than 5E-5pa) was beneficial for the activation of the back stress
strengthening and the annihilation of these microcracks, thus achieving the
excellent ductility (27.65%). In addition, transmission electron microscope
(TEM) characterization under the vacuum degree of less than 10-6pa illustrated
that ultra-high-density nano-oxides (9.61E22/m3) was crucial for enhancing the
strength of ODS FeCrAl alloys (993MPa). The strengthening mechanism
superposition, based on the model of nano-oxides interrelated with the
dislocation, illustrated an excellent agreement with experimental results from
yield strength strengthening mechanisms. To our best knowledge, H40 (milled for
40h, and sintered at 1100C) alloy presents the outstanding strength with the
exceptional ductility among all studied ODS FeCrAl alloys, which makes it the
promising cladding materials for the accident tolerant fuel cladding.",2309.03703v1
2017-11-14,The Dominant Role of Critical Valence Fluctuations on High $T_{\rm c}$ Superconductivity in Heavy Fermions,"Despite almost 40 years of research, the origin of heavy-fermion
superconductivity is still strongly debated. Especially, the pressure-induced
enhancement of superconductivity in CeCu$_2$Si$_2$ away from the magnetic
breakdown is not sufficiently taken into consideration. As recently reported in
CeCu$_2$Si$_2$ and several related compounds, optimal superconductivity occurs
at the pressure of a valence crossover, which arises from a virtual critical
end point at negative temperature $T_{\rm cr}$. In this context, we did a
meticulous analysis of a vast set of top-quality high-pressure electrical
resistivity data of several Ce-based heavy fermion compounds. The key novelty
is the salient correlation between the superconducting transition temperature
$T_{\rm c}$ and the valence instability parameter $T_{\rm cr}$, which is in
line with theory of enhanced valence fluctuations. Moreover, it is found that,
in the pressure region of superconductivity, electrical resistivity is governed
by the valence crossover, which most often manifests in scaling behavior. We
develop the new idea that the optimum superconducting $T_{\rm c}$ of a given
sample is mainly controlled by the compound's $T_{\rm cr}$ and limited by
non-magnetic disorder. In this regard, the present study provides compelling
evidence for the crucial role of critical valence fluctuations in the formation
of Cooper pairs in Ce-based heavy fermion superconductors besides the
contribution of spin fluctuations near magnetic quantum critical points, and
corroborates a plausible superconducting mechanism in strongly correlated
electron systems in general.",1711.05145v2
2017-05-09,Universal experimental test for the role of free charge carriers in thermal Casimir effect within a micrometer separation range,"We propose a universal experiment to measure the differential Casimir force
between a Au-coated sphere and two halves of a structured plate covered with a
P-doped Si overlayer. The concentration of free charge carriers in the
overlayer is chosen slightly below the critical one, f or which the phase
transition from dielectric to metal occurs. One ha f of the structured plate is
insulating, while its second half is made of gold. For the former we consider
two different structures, one consisting of bulk high-resistivity Si and the
other of a layer of silica followed by bulk high-resistivity Si. The
differential Casimir force is computed within the Lifshitz theory using four
approaches that have been proposed in the literature to account for the role of
free charge carriers in metallic and dielectric materials interacting with
quantum fluctuations. According to these approaches, Au at low frequencies is
described by either the Drude or the plasma model, whereas the free charge
carriers in dielectric materials at room temperature are either taken into
account or disregarded. It is shown that the values of differential Casimir
forces, computed in the micrometer separation range using these four
approaches, are widely distinct from each other and can be easily discriminated
experimentally. It is shown that for all approaches the thermal component of
the differential Casimir force is sufficiently large for direct observation.
The possible errors and uncertainties in the proposed experiment are estimated
and its importance for the theory of quantum fluctuations is discussed.",1705.03223v2
2021-03-10,Solid phase epitaxial growth of the correlated-electron transparent conducting oxide SrVO3,"SrVO3 thin films with a high figure of merit for applications as transparent
conductors were crystallized from amorphous layers using solid phase epitaxy
(SPE). Epitaxial SrVO3 films crystallized on SrTiO3 using SPE exhibit a room
temperature resistivity of 2.5 x 10-5 Ohms cm, a residual resistivity ratio of
3.8, and visible light transmission above 0.5 for a 60 nm-thick film. SrVO3
layers were deposited at room temperature using radio-frequency sputtering in
an amorphous form and subsequently crystallized by heating in controlled gas
environment. The lattice parameters and mosaic angular width of x-ray
reflections from the crystallized films are consistent with partial relaxation
of the strain resulting from the epitaxial mismatch between SrVO3 and SrTiO3. A
reflection high-energy electron diffraction study of the kinetics of SPE
indicates that crystallization occurs via the thermally activated propagation
of the crystalline/amorphous interface, similar to SPE phenomena in other
perovskite oxides. Thermodynamic calculations based on density functional
theory predict the temperature and oxygen partial pressure conditions required
to produce the SrVO3 phase and are consistent with the experiments. The
separate control of deposition and crystallization conditions in SPE presents
new possibilities for the crystallization of transparent conductors in complex
geometries and over large areas.",2103.05797v2
2023-11-13,Superconductivity in trilayer nickelate La$_4$Ni$_3$O$_{10}$ single crystals,"The pursuit of discovering new high-temperature superconductors that diverge
from the copper-based paradigm carries profound implications for elucidating
mechanisms behind superconductivity and may also enable new applications. Here,
our investigation reveals that application of pressure effectively suppresses
the spin and charge order in trilayer nickelate La$_4$Ni$_3$O$_{10}$ single
crystals, leading to the emergence of superconductivity with a maximum critical
temperature (Tc) of around 30 K. In the normal state, we observe a ""strange
metal"" behavior, characterized by a linear temperature-dependent resistance
extending up to 300 K. These results could be interpreted as the pressure's
influence, inducing damping on the density-wave gap and spin order, while
promoting spin fluctuations and bringing the associated flat dz2 band into
close proximity with the Fermi surface. This, in turn, fosters strong
correlations and ""strange metal"" behavior, thus setting the stage for the
eventual emergence of superconductivity. Furthermore, the layer-dependent
superconductivity observed hints at a unique interlayer coupling mechanism
specific to nickelates, setting them apart from cuprates in this regard. Our
findings provide crucial insights into the fundamental mechanisms underpinning
superconductivity, while also introducing a new material platform to explore
the intricate interplay between the spin/charge order, flat band structures,
interlayer coupling, strange metal behavior and high-temperature
superconductivity.",2311.07353v2
2019-02-28,3D quench modeling based on T-A formulation for high temperature superconductor CORC cables,"High temperature superconductor (HTS) (RE)Ba2Cu3Ox (REBCO) conductor on round
core cable (CORC) has high current carrying capacity for high field magnet and
power applications. In REBCO CORC cables, current redistribution occurs among
tapes through terminal contact resistances when a local quench occurs.
Therefore, the quench behaviour of CORC cable is different from single tape
situation, for it is significantly affected by terminal contact resistances. To
better understand the underlying physical process of local quenches in CORC
cables, a new 3D multi-physics modelling tool for CORC cables is developed and
presented in this paper. In this model, the REBCO tape is treated as a thin
shell without thickness, and four models are coupled: T-formulation model,
A-formulation model, a heat transfer model and an equivalent circuit model. The
current redistribution, temperature and tape voltage of CORC cable during hot
spot induced quenches are analysed using this model. The results show that the
thermal stability of CORC cable can be considerably improved by reducing
terminal contact resistance. The minimum quench energy (MQE) increases rapidly
with the reduction of terminal contact resistance when the resistance is in a
middle range. When the terminal contact resistance is too low or too high, the
MQE shows no obvious variation with terminal contact resistances. With a low
terminal contact resistance, a hot spot in one tape may induce an over-current
quench on the other tapes without hot spots. This will not happen in a cable
with high terminal contact resistance. In this case, the tape with hot spot
will quench and burn out before inducing a quench on other tapes. The modelling
tool developed can be used to design CORC cables with improved thermal
stability.",1902.11055v1
2001-06-20,Saturation of electrical resistivity in metals at large temperatures,"We present a microscopic model for systems showing resistivity saturation. An
essentially exact quantum Monte-Carlo calculation demonstrates that the model
describes saturation. We give a simple explanation for saturation, using charge
conservation and considering the limit where thermally excited phonons have
destroyed the periodicity. Crucial model features are phonons coupling to the
hopping matrix elements and a unit cell with several atoms. We demonstrate the
difference to a model of alkali-doped C60 with coupling to the level positions,
for which there is no saturation.",0106397v2
2002-05-13,Pseudogap effects on the charge dynamics in the underdoped copper oxide materials,"Within the t-J model, the charge dynamics of copper oxide materials in the
underdoped regime is studied based on the fermion-spin theory. It is shown that
both in-plane charge dynamics and c-axis charge dynamics are mainly governed by
the scattering from the in-plane fluctuation, which would be suppressed when
the holon pseudogap opens at low temperatures, leading to the temperature
linear to the nonlinear range in the in-plane resistivity and crossovers to the
semiconducting-like range in the c-axis resistivity.",0205248v1
2004-05-26,An Inhomogeneous Josephson Phase Near the (Super) Conductor-Insulator Transition,"In many cases inhomogeneities are known to exist near the metal (or
superconductor)- insulator transition, as follows from well-known domain-wall
arguments. If the conducting regions are large enough, and if they have
superconducting correlations, it becomes energetically favorable for the system
to go into a Josephson- coupled zero-resistance state before (i.e. at higher
resistance than) the material becomes a real metal. We show that this is
plausible by a simple comparison of the relevant coupling constants. We also
illustrate using data in the literature on oxide materials as well as
ultra-thin films, that when this proposed Josephson state is quenched by a
magnetic field, an insulating, rather then a metallic, state indeed appears.",0405625v1
2005-08-15,Electronic structure and anisotropic transport properties in hexagonal YPtIn and LuAgGe ternary compounds,"We present anisotropic, zero applied magnetic field, temperature dependent
resistivity measurements on hexagonal, non-magnetic, YPtIn and LuAgGe single
crystals. For these materials the in-plane resistivity, $\rho_{ab}$, is
significantly higher than the $c$ - axis one, $\rho_c$, with $\rho_{ab}/\rho_c
\approx 1.4$ for YPtIn and $\approx 4.2 - 4.7$ for LuAgGe. The connection
between the electronic structure and the anisotropic transport properties is
discussed using density functional calculations that link the observed
anisotropy with a specific shape of Fermi surface and anisotropy of the Fermi
velocities.",0508346v1
2010-11-12,Microwave inductance of thin metal strips,"We have measured the frequency-dependent, complex impedance of thin metal
strips in a broad range of microwave frequencies (45~MHz to 20~GHz). The
spectra are in good agreement with theoretical predictions of an RCL model. The
resistance, inductance, and capacitance, which govern the microwave response,
depend on the strip width and thickness as well as on the strip and substrate
materials. While the strip resistance scales inversely with the cross section,
the inductance depends on the width of the strip, but not on the thickness (in
the limit of small thickness).",1011.2913v1
2011-01-24,Graded anharmonic crystals as genuine thermal diodes: Analytical description of rectification and negative differential thermal resistance,"We address the heat flow study starting from microscopic models of matter: we
develop an approach and investigate some anharmonic graded mass crystals, with
weak interparticle interactions. We calculate the thermal conductivity, and
show the existence of rectification and negative differential thermal
resistance. Our formalism allows us to understand the mechanism behind the
phenomena, and shows that the properties of graded materials make them genuine
thermal diodes.",1101.4589v1
2011-07-15,Enhanced Gas-Flow-Induced Voltage in Graphene,"We show by systemically experimental investigation that gas-flow-induced
voltage in monolayer graphene is more than twenty times of that in bulk
graphite. Examination over samples with sheet resistances ranging from 307 to
1600 {\Omega}/sq shows that the induced voltage increase with the resistance
and can be further improved by controlling the quality and doping level of
graphene. The induced voltage is nearly independent of the substrate materials
and can be well explained by the interplay of Bernoulli's principle and the
carrier density dependent Seebeck coefficient. The results demonstrate that
graphene has great potential for flow sensors and energy conversion devices.",1107.3049v1
2016-02-17,On the analysis of stage I in the resistivity recovery of electron irradiated iron,"The experimental results of Takaki et al. [1] on the stage I resistivity
recovery of electron irradiated iron are analyzed using the analytical theory
of diffusion annealing formulated by Simpson & Sossin [2] and Schroeder [3]
taking into account the recent first-principles calculations of Fu et al. [4]
regarding the mobility of interstitials. Excellent agreement between theory and
experiment is obtained by a minimal set of adjustable parameters. The results
show that the diffusion annealing equations can be successfully employed for
the analysis of recovery experiments in iron.",1602.05449v2
2016-04-18,Large thermopower in the antiferromagnetic semiconductor BaMn$_2$Bi$_2$,"We report electrical and thermal transport properties of Mn-based material
BaMn$_2$Bi$_2$ with ThCr$_2$Si$_2$ structure. The resistivity of the
antiferromagnetic BaMn$_2$Bi$_2$ shows a metal-semiconductor transition at
$\sim 80$ K with decreasing temperature. Correspondingly, the thermopower $S$
shows a peak at the same temperature, approaching ~150 $\mu$V/K. With
increasing temperature $S$ decreases to about 125 $\mu$V/K at the room
temperature. The magnetic field enhances the peak value to 210 $\mu$V/K. The
Hall resistivity reveals an abrupt change of the carrier density close to the
metal-semiconductor transition temperature.",1604.05296v1
2016-06-20,Resistivity scaling in metallic thin films and nanowires due to grain boundary and surface roughness scattering,"A modeling approach, based on an analytical solution of the semiclassical
multi-subband Boltzmann transport equation, is presented to study resistivity
scaling in metallic thin films and nanowires due to grain boundary and surface
roughness scattering. While taking into account the detailed statistical
properties of grains, roughness and barrier material as well as the metallic
band structure and quantum mechanical aspects of scattering and confinement,
the model does not rely on phenomenological fitting parameters.",1606.05972v2
2016-07-27,Alloy-like behaviour of the thermal conductivity of non-symmetric superlattices,"In this work, we show a phenomenological alloy-like fit of the thermal
conductivity of (A)d1:(B)d2 superlattices with d1 /= d2, i.e. non-symmetric
structure. The presented method is a generalization of the Norbury rule of the
summation of thermal resistivities in alloy compounds. Namely, we show that
this approach can be also extended to describe the thermal properties of
crystalline and ordered-system composed by two or more elements, and, has a
potentially much wider application range. Using this approximation we estimate
that the interface thermal resistance depends on the period and the ratio of
materials that form the superlattice structure",1607.08017v2
2018-03-30,Nanostructured Ceramic Oxides with a Slow Crack Growth Resistance Close to Covalent Materials,"Oxide ceramics are sensitive to slow crack growth because adsorption of water
can take place at the crack tip, leading to a strong decrease of the surface
energy in humid (or air) conditions. This is a major drawback concerning
demanding, long-term applications such as orthopaedic implants. Here we show
that a specific nanostructuration of ceramic oxides can lead to a crack
resistance never reached before, similar to that of covalent ceramics.",1804.01393v1
2018-05-30,Interface thermal behavior in nanomaterials by thermal grating relaxation,"We study the relaxation of a thermal grating in multilayer materials with
interface thermal resistances. The analytical development allows for the nu-
merical determination of this thermal property in Approach to Equilibrium
Molecular Dynamics and suggests an experimental setup for its measurement.
Possible non-diffusive effects at the nanoscale are take into consideration by
a non-local formulation of the heat equation. As a case study, we numerically
apply the present approach to silicon grain boundary thermal resistance",1805.12086v1
2019-07-04,Pressure-induced superconductivity in SnSb2Te4,"We report the discovery of a new superconductor from phase change materials
SnSb2Te4. Single crystals of SnSb2Te4 were grown using a conventional
melting-growth method. The sample resistance under pressure was measured using
an originally designed diamond anvil cell with boron-doped diamond electrodes.
The pressure dependence of the resistance has been measured up to 32.6 GPa. The
superconducting transition of SnSb2Te4 appeared at 2.1 K(Tconset) under 8.1
GPa, which was further increased with applied pressure to a maximum onset
transition temperature 7.4K under 32.6 GPa.",1907.02381v1
2019-04-13,Giant Interfacial Thermal Resistance Arising From Materials With Mismatched Phonon Structures,"Previous researches only reported very small interfacial thermal resistances
at room temperature due to limitations in sample combinations and methods.
Taking cognizance of the importance of mismatched phonon structures, we report
values up to $2*10^{-4}W^{-1}m^{2}K$, thousand times larger than highest values
reported to date. This enables substantial tuning of the thermal conductivity
in composites, and does not constrain other characteristics. Our findings
inspire new design strategies, for heat control in integrated circuits and
thermoelectric composites, that harness thermal transport at interfaces.",1904.06540v2
2020-01-26,Pulse percolation conduction and multi-value memory,"We develop a theory of pulse conduction in percolation type of materials such
as noncrystalline semiconductors and nano-metal compounds. For short voltage
pulses, the corresponding electric currents are inversely proportional to the
pulse length and exhibit significant nonohmicity due to strong local fields in
resistive regions of the percolation bonds. These fields can trigger local
switching events incrementally changing bond resistances in response to pulse
trains. Our prediction opens a venue to a class of multi-value nonvolatile
memory implementable with a variety of materials.",2001.09512v3
2020-08-27,Nitrobenzene as Additive to Improve Reproducibility and Degradation Resistance of Highly Efficient Methylammonium-Free Inverted Perovskite Solar Cells,"We show that the addition of 1 % (v/v) nitrobenzene within the perovskite
formulation can be used as a method to improve the power conversion efficiency
and reliability performance of methylammonium-free (CsFA) inverted perovskite
solar cells. Addition of nitrobenzene increased PCE due to defect passivation
and provides smoother films resulting in PVSCs with narrower PCE distribution.
Moreover, the nitrobenzene additive methylammonium-free hybrid PVSCs exhibit
prolonged lifetime compare to additive free PVSCs due to enhanced air and
moisture degradation resistance.",2008.12041v1
2021-10-27,Planar Hall effect in Cu intercalated PdTe$_2$,"We present the Planar Hall effect studies on the Cu intercalated type-II
Dirac semimetal PdTe$_{2}$. The electrical resistivity exhibits a positive
field dependence both in perpendicular and parallel field directions, causing
non-zero anisotropy. The longitudinal magnetoresistance shows almost linear
field dependence at low temperatures. A tilted prolate spheroid shaped orbits
are observed in parametric plot between transverse and longitudinal
resistivities. Our study suggest that for the type-II Dirac semimetal materials
with positive longitudinal magnetoresistance, the origin of Planar Hall effect
cannot be asserted with certainty to the topological or non-topological without
taking into account the anisotropy of Fermi surface.",2110.14251v1
2023-10-04,Anisotropic transport and Negative Resistance in a polycrystalline metal-semiconductor (Ni-TiO2) hybrid,"We investigate anomalous electrical transport properties of a Ni-TiO2 hybrid
system displaying a unique nanostructured morphology. The system undergoes an
insulator to metal transition below 150 K with a low temperature metallic phase
that shows negative resistance in a four-probe configuration. Temperature
dependent transport measurements and numerical modelling show that the
anomalies originate from the dendritic architecture of the TiO2 backbone
interspersed with Ni nanoparticles that paradoxically renders this
polycrystalline, heterogeneous system highly anisotropic. The study critiques
inferences that may be drawn from four-probe transport measurements and offers
valuable insights into modelling conductivity of anisotropic hybrid materials.",2310.02976v1
2024-02-21,Nonlinear longitudinal current of band-geometric origin in wires of finite thickness,"The miniaturization of integrated circuits is facing an obstruction due to
the escalating electrical resistivity of conventional copper interconnects. The
underlying reason for this problem was unveiled by Fuchs and Sondheimer, who
showed that thinner wires are more resistive because current-carrying electrons
encounter the rough surfaces of the wire more frequently therein. Here, we
present a generalization of the Fuchs-Sondheimer theory to Dirac and Weyl
materials, which are candidates for next-generation interconnects. We predict a
nonlinear longitudinal electric current originating from the combined action of
the Berry curvature and non-specular surface-scattering.",2402.14112v1
2007-09-25,Quantum to Classical Transition of the Charge Relaxation Resistance of a Mesoscopic Capacitor,"We present an analysis of the effect of dephasing on the single channel
charge relaxation resistance of a mesoscopic capacitor in the linear low
frequency regime. The capacitor consists of a cavity which is via a quantum
point contact connected to an electron reservoir and Coulomb coupled to a gate.
The capacitor is in a perpendicular high magnetic field such that only one
(spin polarized) edge state is (partially) transmitted through the contact. In
the coherent limit the charge relaxation resistance for a single channel
contact is independent of the transmission probability of the contact and given
by half a resistance quantum. The loss of coherence in the conductor is modeled
by attaching to it a fictitious probe, which draws no net current. In the
incoherent limit one could expect a charge relaxation resistance that is
inversely proportional to the transmission probability of the quantum point
contact. However, such a two terminal result requires that scattering is
between two electron reservoirs which provide full inelastic relaxation. We
find that dephasing of a single edge state in the cavity is not sufficient to
generate an interface resistance. As a consequence the charge relaxation
resistance is given by the sum of one constant interface resistance and the
(original) Landauer resistance. The same result is obtained in the high
temperature regime due to energy averaging over many occupied states in the
cavity. Only for a large number of open dephasing channels, describing
spatially homogenous dephasing in the cavity, do we recover the two terminal
resistance, which is inversely proportional to the transmission probability of
the QPC. We compare different dephasing models and discuss the relation of our
results to a recent experiment.",0709.3956v1
2007-01-23,Silicon Sensors implemented on p-type substrates for high radiation resistance applications,"Silicon based micropattern detectors are essential elements of modern high
energy physics experiments. Cost effectiveness and high radiation resistance
are two important requirements for technologies to be used in inner tracking
devices. Processes based on p-type substrates have very strong appeal for these
applications. Recent results and prototype efforts under way are reviewed.",0701270v1
2021-05-01,Ultra-stable shear jammed granular material,"Dry granular materials such as sand, gravel, pills, or agricultural grains,
can become rigid when compressed or sheared. At low density, one can distort
the shape of a container of granular material without encountering any
resistance. Under isotropic compression, the material will reach a certain {\it
jamming} density and then resist further compression. {\em Shear jamming}
occurs when resistance to shear emerges in a system at a density lower than the
jamming density, and the elastic properties of such states have important
implications for industrial and geophysical processes. We report on
experimental observations of changes in the mechanical properties of a
shear-jammed granular material subjected to small-amplitude, quasi-static
cyclic shear. We study a layer of plastic discs confined to a shear cell, using
photoelasticimetry to measure all inter-particle vector forces. For
sufficiently small cyclic shear amplitudes and large enough initial shear, the
material evolves to an unexpected ""ultra-stable"" state in which all the
particle positions and inter-particle contact forces remain unchanged after
each complete shear cycle for thousands of cycles. The stress response of these
states to small imposed shear is nearly elastic, in contrast to the original
shear jammed state.",2105.00313v3
2014-09-05,"Thermalization and possible quantum relaxation times in ""classical"" fluids: theory and experiment","Quantum effects in material systems are often pronounced at low energies and
become insignificant at high temperatures. We find that, perhaps
counterintuitively, certain quantum effects may follow the opposite route and
become sharp when extrapolated to high temperature within a ""classical"" liquid
phase. In the current work, we suggest basic quantum bounds on relaxation (and
thermalization) times, examine kinetic theory by taking into account such
possible fundamental quantum time scales, find new general equalities
connecting semi-classical dynamics and thermodynamics to Planck's constant, and
compute current correlation functions. Our analysis suggests that, on average,
the extrapolated high temperature dynamical viscosity of general liquids may
tend to a value set by the product of the particle number density ${\sf n}$ and
Planck's constant $h$. We compare this theoretical result with experimental
measurements of an ensemble of 23 metallic fluids where this seems to indeed be
the case. The extrapolated high temperature viscosity of each of these liquids
$\eta$ divided (for each respective fluid by its value of ${\sf n} h$) veers
towards a Gaussian with an ensemble average value that is close to unity up to
an error of size $0.6 \%$. Inspired by the Eigenstate Thermalization
Hypothesis, we suggest a relation between the lowest equilibration temperature
to the melting or liquidus temperature and discuss a possible corollary
concerning the absence of finite temperature ""ideal glass"" transitions. We
suggest a general quantum mechanical derivation for the viscosity of glasses at
general temperatures. We invoke similar ideas to discuss other transport
properties and demonstrate how simple behaviors including resistivity
saturation and linear $T$ resistivity may appear very naturally. Our approach
suggests that minimal time lags may be present in fluid dynamics.",1409.1915v14
2002-02-15,Resistance and Resistance Fluctuations in Random Resistor Networks Under Biased Percolation,"We consider a two-dimensional random resistor network (RRN) in the presence
of two competing biased percolations consisting of the breaking and recovering
of elementary resistors. These two processes are driven by the joint effects of
an electrical bias and of the heat exchange with a thermal bath. The electrical
bias is set up by applying a constant voltage or, alternatively, a constant
current. Monte Carlo simulations are performed to analyze the network evolution
in the full range of bias values. Depending on the bias strength, electrical
failure or steady state are achieved. Here we investigate the steady-state of
the RRN focusing on the properties of the non-Ohmic regime. In constant voltage
conditions, a scaling relation is found between $<R>/<R>_0$ and $V/V_0$, where
$<R>$ is the average network resistance, $<R>_0$ the linear regime resistance
and $V_0$ the threshold value for the onset of nonlinearity. A similar relation
is found in constant current conditions. The relative variance of resistance
fluctuations also exhibits a strong nonlinearity whose properties are
investigated. The power spectral density of resistance fluctuations presents a
Lorentzian spectrum and the amplitude of fluctuations shows a significant
non-Gaussian behavior in the pre-breakdown region. These results compare well
with electrical breakdown measurements in thin films of composites and of other
conducting materials.",0202268v1
2007-03-29,Magnetic-field cycling induced anomalous irreversibility in resistivity of charge-ordered manganites,"The rare-earth ions (RE = Eu, Dy Ho, Tm, Y) substituted charge-ordered
antiferromagnetic manganites, Pr0.45RE0.05Ca0.5MnO3, were studied for the
magnetic and the transport properties in the presence of external
magnetic-fields of up to 14 Tesla. Regardless of the intrinsic magnetic
property of RE ions, all the compounds exhibit successive step-like
metamagnetic transitions at low temperatures, which are strongly correlated to
their electronic transitions. At any fixed temperature in two different
temperature-regimes, we observed contrary effects of the magnetic-field cycling
on the resistivity of these manganites, namely, i) in the low temperature
regime (<70 K), the resistivity was irreversible showing lower values than
initial after a magnetic-field cycle was over, which is consistent with the
irreversible magnetization, and ii) in a temperature regime above 70 K, the
resistivity is irreversible with noticeably higher values than initial, whereas
the magnetization was found to be reversible. For the latter case, we further
show that this irreversibility of resistivity systematically depends on the
temperature and the magnitude of applied magnetic-field. These results suggest
that the observed resistivity behavior originated from the magnetic-field
induced metamagnetic transitions and training effect.",0703771v1
2011-06-02,"Anisotropic resistivity in underdoped single crystals (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$, $0 \leq x<0.35$","Temperature-dependent in-plane, $\rho_a(T)$, and inter-plane, $\rho_c(T)$,
resistivities were measured for the iron-arsenide superconductor
(Ba$_{1-x}$K$_x$)Fe $_2$As$_2$ over a broad doping range from parent compound
to optimal doping $T_c\approx 38 K$, $0\leq x \leq 0.35$. The coupled
magnetic/structural transition at $T_{SM}$ is clearly observed for samples with
$T_c <$26 K ($x <0.25$), however its effect on resistivity is much weaker than
in the electron-doped Ba(Fe$_{1-x}$Co$_x$)Fe $_2$As$_2$, and the transition
leads only to a decrease of resistivity. In addition to the feature at
$T_{SM}$, the inter-plane resistivity shows a maximum at $T^*\sim$200 K, which
moves slightly to higher temperature with doping, revealing a trend opposite to
the electron-doped materials. A smeared feature at about the same temperature
is seen in $\rho_a(T)$. For $T<T^*$, the temperature dependence of resistivity
shows systematic evolution and is close to linear at optimal doping. This
feature, being most pronounced for $\rho_c(T)$, suggests the existence of a
quantum critical point close to optimal doping.",1106.0533v1
2012-02-15,Noise studies of magnetization dynamics in dilute magnetic semiconductor heterostructures,"We study theoretically and experimentally the frequency and temperature
dependence of resistivity noise in semiconductor heterostructures delta-doped
by Mn. The resistivity noise is observed to be non-monotonous as a function of
frequency. As a function of temperature, the noise increases by two orders of
magnitude for a resistivity increase of about 50%. We study two possible
sources of resistivity noise -- dynamic spin fluctuations and charge
fluctuations, and find that dynamic spin fluctuations are more relevant for the
observed noise data. The frequency and temperature dependence of resistivity
noise provide important information on the nature of the magnetic interactions.
In particular, we show how noise measurements can help resolve a long standing
debate on whether the Mn-doped GaAs is an p-d Zener/RKKY or double exchange
ferromagnet. Our analysis includes the effect of different kinds of disorder
such as spin-glass type of interactions and a site-dilution type of disorder.
We find that the resistivity noise in these structures is well described by a
disordered RKKY ferromagnet model dynamics with a conserved order parameter.",1202.3207v2
2016-12-02,"Structural, Morphological and Electrical Properties of Porous Silicon Prepared Under Laser Illumination","Porous silicon (PSi) layers has been prepared in this work via
photoelectrochemical (PEC) etching process of an n type silicon wafers of two
resistivities (3.5 ohm.cm and 0.02 ohm.cm) in hydrofluoric (HF) acid of 24.5
precent concentration at different etching times (5 to 25 min). The irradiation
has been achieved using laser beam of 2W power and 810 nm wavelength. We have
studied the morphological and structural properties of PSi layers using the
techniques of Xray Diffraction (XRD) and Scanning Electron Microscopy (SEM) and
Gravimetric method. The Xray Diffraction data shows that the structure aspect
of PSi layers remains crystalline as well as the decreasing of diffraction
angle (thetaB) of Xray from PSi layers (29 to 26 degree) and increasing of the
lattice parameter values of PSi structures with increasing of etching times
from 5 to 25 min., and the resistivity of silicon substrates from 0.02 to 3.5
ohm.cm. The nanocrystallite size is decreasing from (20.72 to 5.13 nm) with
increasing of etching times, and the resistivity of silicon substrates. The SEM
images shows that the values of pore width and PSi layer thickness increases
from (0.5 to 6.25 micrometer) and (6.7 to 47 micrometer) respectively with
increasing of etching times and silicon substrates resistivities, while the
values of the thickness of walls between pores has been varied from (1.25 to
0.03 micrometer) with increasing of etching times and silicon substrates
resistivities. The pore shape of pores has been varied from Cylindrical to
Rectangular and to Starful with varied of etching conditions. Further the
measured specific surface area of PSi layers has been increased from (7.43 to
235.35 m2/cm3) with increasing of etching times and silicon substrates
resistivities.",1612.04865v1
2017-11-20,Anomalous transport properties in Nb/Bi1.95Sb0.05Se3 hybrid structure,"We report the proximity induced anomalous transport behavior in a Nb
Bi1.95Sb0.05Se3 heterostructure. Mechanically Exfoliated single crystal of
Bi1.95Sb0.05Se3 topological insulator (TI) is partially covered with a 100 nm
thick Niobium superconductor using DC magnetron sputtering by shadow masking
technique. The magnetotransport (MR) measurements have been performed
simultaneously on the TI sample with and without Nb top layer in the
temperature,T, range of 3 to 8 K, and a magnetic field B up to 15 T. MR on TI
region shows Subnikov de Haas oscillation at fields greater than 5 T. Anomalous
linear change in resistance is observed in the field range of negative 4T to
positive 4T at which Nb is superconducting. At 0 T field, the temperature
dependence of resistance on the Nb covered region revealed a superconducting
transition (TC) at 8.2 K, whereas TI area showed similar TC with the absence of
zero resistance states due to the additional resistance from superconductor
(SC) TI interface. Interestingly below the TC the R vs T measured on TI showed
an enhancement in resistance for positive field and prominent fall in
resistance for negative field direction. This indicates the directional
dependent scattering of the Cooper pairs on the surface of the TI due to the
superposition of spin singlet and triplet states in the superconductor and TI
respectively.",1711.07147v1
2017-03-02,Nature of carrier injection in metal/2D semiconductor interface and its implications to the limits of contact resistance,"Monolayers of transition metal dichalcogenides (TMDCs) exhibit excellent
electronic and optical properties. However, the performance of these
two-dimensional (2D) devices are often limited by the large resistance offered
by the metal contact interface. Till date, the carrier injection mechanism from
metal to 2D TMDC layers remains unclear, with widely varying reports of
Schottky barrier height (SBH) and contact resistance (Rc), particularly in the
monolayer limit. In this work, we use a combination of theory and experiments
in Au and Ni contacted monolayer MoS2 device to conclude the following points:
(i) the carriers are injected at the source contact through a cascade of two
potential barriers - the barrier heights being determined by the degree of
interaction between the metal and the TMDC layer; (ii) the conventional
Richardson equation becomes invalid due to the multi-dimensional nature of the
injection barriers, and using Bardeen-Tersoff theory, we derive the appropriate
form of the Richardson equation that describes such composite barrier; (iii) we
propose a novel transfer length method (TLM) based SBH extraction methodology,
to reliably extract SBH by eliminating any confounding effect of temperature
dependent channel resistance variation; (iv) we derive the Landauer limit of
the contact resistance achievable in such devices. A comparison of the limits
with the experimentally achieved contact resistance reveals plenty of room for
technological improvements.",1703.00671v2
2017-05-08,The influence of magnetic order on the magnetoresistance anisotropy of Fe$_{1+δ-x}$Cu$_{x}$Te,"We performed resistance measurements on Fe$_{1+\delta-x}$Cu$_{x}$Te with
$x_{EDX}\leq 0.06$ in the presence of in-plane applied magnetic fields,
revealing a resistance anisotropy that can be induced at a temperature far
below the structural and magnetic zero-field transition temperatures. The
observed resistance anisotropy strongly depends on the field orientation with
respect to the crystallographic axes, as well as on the field-cooling history.
Our results imply a correlation between the observed features and the
low-temperature magnetic order. Hysteresis in the angle-dependence indicates a
strong pinning of the magnetic order within a temperature range that varies
with the Cu content. The resistance anisotropy vanishes at different
temperatures depending on whether an external magnetic field or a remnant field
is present: the closing temperature is higher in the presence of an external
field. For $x_{EDX} = 0.06$ the resistance anisotropy closes above the
structural transition, at the same temperature at which the zero-field
short-range magnetic order disappears and the sample becomes paramagnetic. Thus
we suggest that under an external magnetic field the resistance anisotropy
mirrors the magnetic order parameter. We discuss similarities to nematic order
observed in other iron pnictide materials.",1705.02849v1
2019-06-21,A Two Dimensional Tunneling Resistance Transmission Line Model for Nanoscale Parallel Electrical Contacts,"Contact resistance and current crowding are important to nanoscale electrical
contacts. In this paper, we present a self-consistent model to characterize
partially overlapped parallel contacts with varying specific contact
resistivity along the contact length. For parallel tunneling contacts formed
between contacting members separated by a thin insulating gap, we examine the
local voltage-dependent variation of potential barrier height and tunneling
current along the contact length, by solving the lumped circuit transmission
line model (TLM) equations coupled with the tunneling current self
consistently. The current and voltage distribution along the parallel tunneling
contacts and their overall contact resistance are analyzed in detail, for
various input voltage, electrical contact dimension, and material properties
(i.e. work function, sheet resistance of the contact members, and permittivity
of the insulating layer). It is found the existing one-dimensional (1D)
tunneling junction models become less reliable when the tunneling layer
thickness becomes smaller or the applied voltage becomes larger. In these
regimes, the proposed self-consistent model may provide a more accurate
evaluation of the parallel tunneling contacts. This work provides insights on
the design, and potential engineering, of nanoscale electrical contacts with
controlled current distribution and contact resistance via engineered spatially
varying contact layer properties and geometry.",1906.09188v2
2020-11-25,Linear-in temperature resistivity from an isotropic Planckian scattering rate,"A variety of ""strange metals"" exhibit resistivity that decreases linearly
with temperature as $T\rightarrow 0$, in contrast with conventional metals
where resistivity decreases as $T^2$. This $T$-linear resistivity has been
attributed to charge carriers scattering at a rate given by $\hbar/\tau=\alpha
k_{\rm B} T$, where $\alpha$ is a constant of order unity. This simple
relationship between the scattering rate and temperature is observed across a
wide variety of materials, suggesting a fundamental upper limit on
scattering---the ""Planckian limit""---but little is known about the underlying
origins of this limit. Here we report a measurement of the angle-dependent
magnetoresistance (ADMR) of Nd-LSCO---a hole-doped cuprate that displays
$T$-linear resistivity down to the lowest measured temperatures. The ADMR
unveils a well-defined Fermi surface that agrees quantitatively with
angle-resolved photoemission spectroscopy (ARPES) measurements and reveals a
$T$-linear scattering rate that saturates the Planckian limit, namely $\alpha =
1.2 \pm 0.4$. Remarkably, we find that this Planckian scattering rate is
isotropic, i.e. it is independent of direction, in contrast with expectations
from ""hot-spot"" models. Our findings suggest that $T$-linear resistivity in
strange metals emerges from a momentum-independent inelastic scattering rate
that reaches the Planckian limit.",2011.13054v2
2023-05-10,Voltage-tunable giant nonvolatile multiple-state resistance in sliding-interlayer ferroelectric h-BN van der Waals multiferroic tunnel junction,"Multiferroic tunnel junctions (MFTJs) based on two-dimensional (2D) van der
Waals heterostructures with sharp and clean interfaces at the atomic scale are
crucial for applications in nanoscale multi-resistive logic memory devices. The
recently discovered sliding ferroelectricity in 2D van der Waals materials has
opened new avenues for ferroelectric-based devices. Here, we theoretically
investigate the spin-dependent electronic transport properties of
Fe$_3$GeTe$_2$/graphene/bilayer-$h$-BN/graphene/CrI$_3$ (FGT/Gr-BBN-Gr/CrI)
all-vdW MFTJs by employing the nonequilibrium Green's function combined with
density functional theory. We demonstrate that such FGT/Gr-BBN-Gr/CrI MFTJs
exhibit four non-volatile resistance states associated with different staking
orders of sliding ferroelectric BBN and magnetization alignment of
ferromagnetic free layer CrI$_3$, with a maximum tunnel magnetoresistance
(electroresistance) ratio, i.e., TMR (TER) up to $\sim$$3.36\times10^{4}$\%
($\sim$$6.68\times10^{3}$\%) at a specific bias voltage. Furthermore, the
perfect spin filtering and remarkable negative differential resistance effects
are evident in our MFTJs. We further discover that the TMR, TER, and spin
polarization ratio under an equilibrium state can be enhanced by the
application of in-plane biaxial strain. This work shows that the giant
tunneling resistance ratio, multiple resistance states, and excellent
spin-polarized transport properties of sliding ferroelectric BBN-based MFTJs
indicate its significant potential in nonvolatile memories.",2305.06126v2
1999-08-17,Experiments on Ladders Reveal a Complex Interplay between a Spin-Gapped Normal State and Superconductivity,"In recent years, the study of ladder materials has developed into a
well-established area of research within the general context of Strongly
Correlated Electrons. This effort has been triggered by an unusual
cross-fertilization between theory and experiments. In this paper, the main
experimental results obtained in the context of ladders are reviewed from the
perspective of a theorist. Emphasis is given to the many similarities between
the two-dimensional high-$\rm T_c$ cuprates and the two-leg ladder compounds,
including Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$ (14-24-41) which has a
superconducting phase at high pressure and a small hole density. Examples of
these similarities include regimes of linear resistivity vs temperature in
metallic ladders and a normal state with spin-gap or pseudogap characteristics.
Some controversial results in this context are also discussed. It is remarked
that the ladder 14-24-41 is the first superconducting copper-oxide material
with a non-square-lattice layered arrangement, and certainly much can be
learned from a careful analysis of this compound. A short summary of the main
theoretical developments in this field is also included, as well as a brief
description of the properties of non-copper-oxide ladders. Suggestions by the
author on possible experiments are described in the text. Overall, it is
concluded that the enormous experimental effort carried out on ladders has
already unveiled quite challenging and interesting physics that adds to the
rich behavior of electrons in transition-metal-oxides, and in addition
contributes to the understanding of the two-dimensional cuprates. However,
still considerable work needs to be carried out to fully understand the
interplay between charge and spin degrees of freedom in these materials.",9908250v1
2001-03-03,Magnetic properties of magnetically textured Bi-2212 ceramics,"This paper aims at reporting magnetic properties of bulk polycrystalline
Bi2Sr2Ca0.8Dy0.2Cu2O8-y samples textured under a magnetic field. The
microstructure of these materials is highly anisotropic and exhibits particular
features needed to be taken into account in order to interpret their magnetic
and electrical properties. First the AC magnetic susceptibility c = c ' - j c""
has been measured for several magnetic fields (H // ab and H // c) and compared
to the electrical resistivity data. The structure of the c"" peak is shown to be
related to the chemical content distribution of the superconducting grains.
Next, the magnetic flux profiles have been extracted from the magnetic
measurements using the Campbell - Rollins procedure. The anisotropy of the flux
profiles and their peculiar curvature behaviour for H // c point out the role
of both grain platelet structure and the presence of secondary phases. From
these results, we conclude that the magnetic properties of such magnetically
textured materials do not allow for a reliable extraction of the critical
current density Jc but essentially probe geometric effects. Such effects have
to be taken into account for improving the manufacture of attractive high-Tc
materials.",0103081v2
2005-02-16,Abrupt metal-insulator transition observed in VO2 thin films induced by a switching voltage pulse,"An abrupt metal-insulator transition (MIT) was observed in VO2 thin films
during the application of a switching voltage pulse to two-terminal devices.
Any switching pulse over a threshold voltage for the MIT of 7.1 V enabled the
device material to transform efficiently from an insulator to a metal. The
characteristics of the transformation were analyzed by considering both the
delay time and rise time of the measured current response. The extrapolated
switching time of the MIT decreased down to 9 ns as the external load
resistance decreased to zero. Observation of the intrinsic switching time of
the MIT in the correlated oxide films is impossible because of the
inhomogeneity of the material; both the metallic state and an insulating state
co-exist in the measurement volume. This indicates that the intrinsic switching
time is in the order of less than a nanosecond. The high switching speed might
arise from a strong correlation effect (Coulomb repulsion) between the
electrons in the material.",0502375v4
2006-05-19,"Magnetic unipolar features in con- ductivity of point contacts between normal and ferromagnetic d-metals (Co, Ni, Fe)","In nanocontacts between normal and ferromagnetic metals (N--F) abrupt changes
of the order of 1% are detected in differential resistance, dV/dI(V), versus
bias voltage, V, on achieving of high current densities, ~10^9 A/cm^2. These
features in dV/dI(V) are observed when the electron flow is directed from the
nonmagnetic metal into the ferromagnet and connected with magnetization
excitations in the ferromagnet induced by the current. Applying an external
magnetic field leads to a shift of the observed features to higher biasing
current, confirming the magnetic nature of the effect. Such effects are
observed for the non-ballistic (not spectral) regime of current flow in the
nanocontacts. Thus, the current induced magneto-conductance effects in
multilayered N--F structures (nanopillars) extensively studied in the recent
literature have much more general character and can be stimulated by elastic
electron scattering at single N--F interfaces.",0605485v1
2007-08-14,"Landscape phage, phage display, stripped phage, biosensors, detection, affinity reagent, nanotechnology, Salmonella typhimurium, Bacillus anthracis","Filamentous phage, such as fd used in this study, are thread-shaped bacterial
viruses. Their outer coat is a tube formed by thousands equal copies of the
major coat protein pVIII. We constructed libraries of random peptides fused to
all pVIII domains and selected phages that act as probes specific for a panel
of test antigens and biological threat agents. Because the viral carrier is
infective, phage borne bio-selective probes can be cloned individually and
propagated indefinitely without needs of their chemical synthesis or
reconstructing. We demonstrated the feasibility of using landscape phages and
their stripped fusion proteins as new bioselective materials that combine
unique characteristics of affinity reagents and self assembling membrane
proteins. Biorecognition layers fabricated from phage-derived probes bind
biological agents and generate detectable signals. The performance of
phage-derived materials as biorecognition films was illustrated by detection of
streptavidin-coated beads, Bacillus anthracis spores and Salmonella typhimurium
cells. With further refinement, the phage-derived analytical platforms for
detecting and monitoring of numerous threat agents may be developed, since the
biodetector films may be obtained from landscape phages selected against any
bacteria, virus or toxin. As elements of field-use detectors, they are superior
to antibodies, since they are inexpensive, highly specific and strong binders,
resistant to high temperatures and environmental stresses.",0708.1823v1
2010-01-28,A simple kinetic sensor to structural transitions,"Driven non-equilibrium structural phase transformation has been probed using
time varying resistance fluctuations or noise. We demonstrate that the
non-Gaussian component (NGC) of noise obtained by evaluating the higher order
statistics of fluctuations, serves as a simple kinetic detector of these phase
transitions. Using the martensite transformation in free-standing wires of
nickel-titanium binary alloys as a prototype, we observe clear deviations from
the Gaussian background in the transformation zone, indicative of the long
range correlations in the system as the phase transforms. The viability of non-
Gaussian statistics as a robust probe to structural phase transition was also
confirmed by comparing the results from differential scanning calorimetry
measurements. We further studied the response of the NGC to the modifications
in the microstructure on repeated thermal cycling, as well as the variations in
the temperature drive rate, and explained the results using established
simplistic models based on the different competing time scales. Our experiments
(i) suggest an alternative method to estimate the transformation temperature
scales with high accuracy, and (ii) establish a connection between the
material-specific evolution of microstructure to the statistics of its linear
response. Since the method depends on an in-built long-range correlation during
transformation, it could be portable to other structural transitions, as well
as to materials of different physical origin and size.",1001.5137v1
2010-03-04,Spin glass like behavior in the novel layered material Na_2IrO_3,"We have synthesized the novel material Na_2IrO_3 and studied its structure,
transport, magnetic, and thermal properties using powder x-ray diffraction
(PXRD), electrical resistivity, isothermal magnetization M versus magnetic
field H, static \chi and dynamic \chi_ac magnetic susceptibility versus
temperature T, and heat capacity C versus T measurements. Na_2IrO_3
crystallizes in the monoclinic C2/c (No. 15) structure which is made up of Na
and NaIr_2O_6 layers alternately stacked along the c axis. From a Rietveld
refinement of the PXRD pattern we identify atomic disorder arising from a
mixing of Ir and Na sites within the NaIr_2O_6 layers. The \chi data in H = 1 T
shows Curie-Weiss behavior at high T > 100 K with an effective moment \mu_eff =
1.82(1) \mu_B indicating an effective spin S_eff = 1/2 on the Ir^{4+} moments.
A Weiss temperature \theta = - 62(1) K indicates substantial antiferromagnetic
interactions between these S_eff = 1/2, Ir^{4+} moments. The \chi data in low
field show a sharp cusp at T_g = 5.5 K and there is a bifurcation between
zero-field-cooled (ZFC) and field-cooled (FC) data below this T. The \chi_ac
data also show a sharp cusp at T_g = 5.5 K at a frequency f = 1 Hz which moves
to higher temperatures with increasing f. We did not observe any anomaly at T_g
in our C measurements and only a broad shoulder was observed at a much higher T
= 12 K. Our results indicate that in Na_2IrO_3, a spin-glass like state occurs
below the freezing temperature T_g = 5.5 K and this freezing most likely arises
either from structural disorder or geometrical magnetic frustration.",1003.0973v2
2013-01-10,Micro-branching in mode-I fracture in a randomly perturbed lattice,"We study mode-I fracture in lattices with noisy bonds. In contrast to
previous attempts, by using a small parameter that perturbs the force-law
between the atoms in perfect lattices and using a 3-body force law, simulations
reproduce the qualitative behavior of the beyond steady-state cracks in the
high velocity regime, including reasonable micro-branching. As far as the
physical properties such as the structure factor $g(r)$, the radial or angular
distributions, these lattices share the physical properties of perfect lattices
rather than that of an amorphous material (e.g., the continuous random network
model). A clear transition can be seen between steady-state cracks, where a
single crack propagates in the midline of the sample and the regime of unstable
cracks, where micro-branches start to appear near the main crack, in line with
previous experimental results. This is seen both in a honeycomb lattice and a
fully hexagonal lattice. This model reproduces the main physical features of
propagating cracks in brittle materials, including the behavior of velocity as
a function of driving displacement and the increasing amplitude of oscillations
of the electrical resistance. In addition, preliminary indications of power-law
behavior of the micro-branch shapes can be seen, potentially reproducing one of
the most intriguing experimental results of brittle fracture.",1301.2143v1
2013-04-24,Supramolecular Spin Valves,"Magnetic molecules possess a high potential as building blocks for the design
of spintronic devices. Moreover, the use of molecular materials opens the way
for the controlled use of bottom-up, e.g. supramolecular, processing techniques
combining massively parallel self-fabrication with conventional top-down
nanostructuring techniques. The development of solid state spintronic devices
based on the giant magnetoresistance (GMR), tunnel magnetoresistance (TMR), and
spin valve effects has revolutionized the field of magnetic memory
applications. Recently, organic semiconductors were inserted into nanometer
sized tunnel junctions allowing enhancement of spin reversal, giant
magneto-resistance behaviour was observed in single non-magnetic molecules
coupled to magnetic electrodes, and the use of the quantum tunnelling
properties of single-molecule magnets (SMMs) in hybrid devices was proposed.
Herein, we present an original device in which a non-magnetic molecular quantum
dot, made of a single-wall carbon nanotube (SWCNT) contacted with non-magnetic
electrodes, is laterally coupled via supramolecular interactions to a TbPc2-SMM
(Pc = phthalocyanine), which provides a localized magnetic moment. The
conductance through the SWCNT is modulated by sweeping the magnetic field,
exhibiting magnetoresistance ratios up to 300% between fully polarized and
non-polarized SMMs below 1 K. We thus demonstrate the functionality of a
supramolecular spin valve without magnetic leads. Our results open up prospects
of circuit-integration and implementation of new device capabilities.",1304.6543v1
2014-09-10,Controlling and distinguishing electronic transport of topological and trivial surface states in a topological insulator,"Topological insulators (TI), with characteristic Dirac-fermion topological
surface states (TSS), have emerged as a new class of electronic materials with
rich potentials for both novel physics and device applications. However, a
major challenge with realistic TI materials is to access, distinguish and
manipulate the electronic transport of TSS often obscured by other possible
parallel conduction channels that include the bulk as well as a two-dimensional
electron gas (2DEG) formed near the surface due to bending of the bulk bands.
Such a (Schrodinger-fermion) 2DEG represents topologically-trivial surface
states, whose coexistence with the TSS has been revealed by angle resolved
photoemission spectroscopy. Here we show that simple manipulations of surface
conditions can be used to access and control both types of surface states and
their coexistence in bulk-insulating Bi2Te2Se, whose surface conduction is
prominently manifested in temperature dependent resistance and nonlocal
transport. The trivial 2DEG and TSS can both exhibit clear Shubnikov-de Haas
oscillations in magnetoresistance, with different Berry phases ~0 and ~pi that
distinguish their different topological characters. We also report a deviation
from the typical weak antilocalization behavior, possibly due to high mobility
TSS. Our study enables distinguishing, controlling and harnessing electronic
transport of TI surface carriers with different topological natures.",1409.3217v1
2014-09-12,Fast non-thermal switching between macroscopic charge-ordered quantum states induced by charge injection,"The functionality of logic and memory elements in current electronics is
based on multi-stability, driven either by manipulating local concentrations of
electrons in transistors, or by switching between equivalent states of a
material with a degener- ate ground state in magnetic or ferroelectric
materials. Another possibility is offered by phase transitions with switching
between metallic and insulating phases, but classical phase transitions are
limited in speed by slow nucleation, proliferation of domains and hysteresis.
We can in principle avoid these problems by using quantum states for switching,
but microscopic systems suffer from decoherence which prohibits their use in
everyday devices. Macroscopic quantum states, such as the superconducting
ground state have the advantage that on a fundamental level they do not suffer
from decoherence plaguing microscopic systems. Here we demonstrate for the
first time ultrafast non-thermal switching between different metastable
electronically ordered states by pulsed electrical charge injection. The
macroscopic nature of the many-body quantum states(1-4) - which are not part of
the equilibrium phase diagram - gives rise to unprecedented stability and
remarka- bly sharp switching thresholds. Fast sub-50 ps switching, large
associated re- sistance changes, 2-terminal operation and demonstrable high
fidelity of bi-stability control suggest new opportunities for the use of
macroscopic quantum states in electronics, particularly for an ultrafast
non-volatile quantum charge-order resistive random access memory (QCOR-RAM).",1409.3794v1
2014-10-19,Enabling microstructural changes of FCC/BCC alloys in 2D dislocation dynamics,"Dimension reduction procedure is the recipe to represent defects in two
dimensional dislocation dynamics according to the changes in the geometrical
properties of the defects triggered by different conditions such as radiation,
high temperature, or pressure. In the present study, this procedure is extended
to incorporate further features related to the presence of defects with a
special focus on face-centered cubic/body-centered cubic alloys used for
diverse engineering purposes. In order to reflect the microstructural state of
the alloy on the computational cell of two dimensional dislocation dynamics,
the distribution of the multi-type defects over slip lines is implemented by
using corresponding strength and line spacing for each type of defect.
Additionally, a simple recursive incremental relation is set to count the loop
accumulation on the precipitates. In the case of continuous resistance against
the motion of edge dislocations on the slip lines, an expression of friction is
introduced to see its contribution on the yield strength. Each new property is
applied independently on a different material by using experimental information
about defect properties and grain sizes under the condition of plain strain
deformation: both constant and dynamically increasing obstacle strength for
precipitate coarsening in prime-aged and heat-treated
copper-chromium-zirconium, internal friction in tantalum-2.5tungsten, and mixed
hardening due to the presence of precipitates and prismatic loops in irradiated
oxide dispersion strengthened EUROFER with 0.3% yttria.",1410.5094v2
2015-10-22,Thermal conductivity of III-V semiconductor superlattices,"This paper presents a semiclassical model for the anisotropic thermal
transport in III-V semiconductor superlattices (SLs). An effective interface
rms roughness is the only adjustable parameter. Thermal transport inside a
layer is described by the Boltzmann transport equation in the relaxation time
approximation and is affected by the relevant scattering mechanisms
(three-phonon, mass-difference, and dopant and electron scattering of phonons),
as well as by diffuse scattering from the interfaces captured via an effective
interface scattering rate. The in-plane thermal conductivity is obtained from
the layer conductivities connected in parallel. The cross-plane thermal
conductivity is calculated from the layer thermal conductivities in series with
one another and with thermal boundary resistances (TBRs) associated with each
interface; the TBRs dominate cross-plane transport. The TBR of each interface
is calculated from the transmission coefficient obtained by interpolating
between the acoustic mismatch model (AMM) and the diffuse mismatch model (DMM),
where the weight of the AMM transmission coefficient is the same
wavelength-dependent specularity parameter related to the effective interface
rms roughness that is commonly used to describe diffuse interface scattering.
The model is applied to multiple III-arsenide superlattices, and the results
are in very good agreement with experimental findings. The method is both
simple and accurate, easy to implement, and applicable to complicated SL
systems, such as the active regions of quantum cascade lasers. It is also valid
for other SL material systems with high-quality interfaces and predominantly
incoherent phonon transport.",1510.06725v1
2016-08-22,Superconducting Order from Disorder in 2H-TaSe$_{2-x}$S$_{x}$ (0$\leq$x$\leq$2),"We report on the emergence of robust superconducting order in single crystal
alloys of 2H-TaSe$_{2-x}$S$_{x}$ (0$\leq$x$\leq$2) . The critical temperature
of the alloy is surprisingly higher than that of the two end compounds
TaSe$_{2}$ and TaS$_{2}$. The evolution of superconducting critical temperature
T$_{c} (x)$ correlates with the full width at half maximum of the Bragg peaks
and with the linear term of the high temperature resistivity. The conductivity
of the crystals near the middle of the alloy series is higher or similar than
that of either one of the end members 2H-TaSe$_{2}$ and/or 2H-TaS$_{2}$. It is
known that in these materials superconductivity (SC) is in close competition
with charge density wave (CDW) order. We interpret our experimental findings in
a picture where disorder tilts this balance in favor of superconductivity by
destroying the CDW order.",1608.06275v2
2017-02-07,Quantitative Nanoscale Mapping of Three-Phase Thermal Conductivities in Filled Skutterudites via Scanning Thermal Microscopy,"In the last two decades, a nanostructuring paradigm has been successfully
applied in a wide range of thermoelectric materials, resulting in significant
reduction in thermal conductivity and superior thermoelectric performance.
These advances, however, have been accomplished without directly investigating
the local thermoelectric properties, even though local electric current can be
mapped with high spatial resolution. In fact, there still lacks an effective
method that links the macroscopic thermoelectric performance to the local
microstructures and properties. Here, we show that local thermal conductivity
can be mapped quantitatively with good accuracy, nanometer resolution, and
one-to-one correspondence to the microstructure using a three-phase
skutterudite as a model system. Scanning thermal microscopy combined with
finite element simulations demonstrate close correlation between sample
conductivity and probe resistance, enabling us to distinguish thermal
conductivities spanning orders of magnitude, yet resolving thermal variation
across a phase interface with small contrast. The technique thus provides a
powerful tool to correlate local thermal conductivities, microstructures, and
macroscopic properties for nanostructured materials in general, and
nanostructured thermoelectrics in particular.",1702.01895v3
2017-06-24,Probing nanocrystalline grain dynamics in nanodevices,"Dynamical structural defects exist naturally in a wide variety of solids.
They fluctuate temporally, and hence can deteriorate the performance of many
electronic devices. Thus far, the entities of such dynamic objects have been
identified to be individual atoms. On the other hand, it is a long-standing
question whether a nanocrystalline grain constituted of a large number of atoms
can switch, as a whole, reversibly like a dynamical atomic defect (i.e., a
two-level system). This is an emergent issue considering the current
development of nanodevices with ultralow electrical noise, qubits with long
quantum coherence time, and nanoelectromechanical system (NEMS) sensors with
ultrahigh resolution. Here we demonstrate experimental observations of dynamic
nanocrystalline grains which repeatedly switch between two or more metastable
coordinate states. We study temporal resistance fluctuations in thin ruthenium
dioxide (RuO2) metal nanowires and extract microscopic parameters including
relaxation time scales, mobile grain sizes, and the bonding strengths of
nanograin boundaries. Such material parameters are not obtainable by other
experimental approaches. When combined with previous in-situ high-resolution
transmission electron microscopy (HRTEM), our electrical method can be used to
infer rich information about the structural dynamics of a wide variety of
nanodevices and new 2D materials.",1706.07887v1
2017-12-27,Controlled synthesis of the antiperovskite oxide superconductor Sr$_{3-x}$SnO,"A large variety of perovskite oxide superconductors are known, including some
of the most prominent high-temperature and unconventional superconductors.
However, superconductivity among the oxidation state inverted material class,
the antiperovskite oxides, was reported just recently for the first time. In
this superconductor, Sr$_{3-x}$SnO, the unconventional ionic state Sn$^{4-}$ is
realized and possible unconventional superconductivity due to a band inversion
has been discussed. Here, we discuss an improved facile synthesis method,
making it possible to control the strontium deficiency in Sr$_{3-x}$SnO.
Additionally, a synthesis method above the melting point of Sr$_{3}$SnO is
presented. We show temperature dependence of magnetization and electrical
resistivity for superconducting strontium deficient Sr$_{3-x}$SnO
($T_{\mathrm{c}}$ ~ 5 K) and for Sr$_{3}$SnO without a superconducting
transition down to 0.15 K. Further, we reveal a significant effect of strontium
raw material purity on the superconductivity and achieve 40% increased
superconducting volume fraction (~100%) compared to the highest value reported
so far. More detailed characterisation utilising powder X-ray diffraction and
energy-dispersive X-ray spectroscopy show that a minor cubic phase, previously
suggested to be a Sr$_{3-x}$SnO, is SrO. The improved characterization and
controlled synthesis reported herein enable detailed investigations on the
superconducting nature and its dependency on the strontium deficiency in
Sr$_{3-x}$SnO.",1712.09484v1
2018-04-11,NMR and the antiferromagnetic crystal phase regions in rapidly quenched ribbons and in alloys of the type $Cu-Mn-Al$,"It was shown that anomalous resistivity behavior of the $Cu-Mn-Al$ ribbons is
explained by the s-d interaction between conduction electrons and the clustered
Mn atoms. While nuclear magnetic resonance measurements show the
antiferromagnetic and ferromagnetic clusters of Mn atom coexisting without
long-range order, it is an interesting problem to study magnetic resonance
properties also for the antiferromagnetic crystal phase regions (which have
long-range order for larger regions) and which may also occur in these ribbons.
The Heusler Type $Cu-Mn-Al$ Alloy has a composition half way between
$Cu_{2}MnAl$ and $Cu_{3}Al$. Electron microscopy of the premartensitic $\beta
Cu-Zn-Al$ alloy has shown that the $\beta Cu-Zn-Al$ alloy quenched from high
temperature has the electron diffraction patterns of this alloy well explained
by the model with the existence of small particles with an orthorhombic
structure. It was noted that an important aspect of improvement in the material
properties is to create a nanostructured state in matrix, which has significant
advantages in magnetic and mechanical characteristics in contrast to the bulk
materials in crystalline or amorphous state. It is an interesting problem to
study magnetic resonance properties not only for the Mn atoms and clusters
without long-range order but also for the antiferromagnetic crystal phase
regions (which have long-range order for larger regions) which may also occur
in ribbons. This is the aim of our paper.",1804.04196v1
2020-03-25,Magnetic-field-induced FM-AFM metamagnetic transition and strong negative magnetoresistance in Mn$_{1/4}$NbS$_2$ under pressure,"Transition metal dichalcogenides (TMDC) stand out with their high chemical
stability and the possibility to incorporate a wide range of magnetic species
between the layers. The behavior of conduction electrons in such materials
intercalated by 3d-elements is closely related to their magnetic properties and
can be sensitively controlled by external magnetic fields. Here, we study the
magnetotransport properties of NbS$_2$ intercalated with Mn, Mn$_{1/4}$NbS$_2$,
demonstrating a complex behavior of the magnetoresistance and of the ordinary
and anomalous Hall resistivities. Application of pressure as tuning parameter
leads to the drastic changes of the magnetotransport properties of
Mn$_{1/4}$NbS$_2$ exhibiting large negative magnetoresistance up to $65 \%$ at
7.1 GPa. First-principles electronic structure calculations indicates
pressure-induced transition from ferromagnetic to antiferromagnetic state.
Theoretical calculations accounting for the finite temperature magnetic
properties of Mn$_{1/4}$NbS$_2$ suggest a field-induced metamagnetic
ferromagnetic-antiferromagnetic transition as an origin of the large negative
magentoresistance. These results inspire the development of materials for
spintronic applications based on intercalated TMDC with a well controllable
metamagnetic transition.",2003.11678v1
2017-03-16,Elemental Phosphorus: structural and superconducting phase diagram under pressure,"Pressure-induced superconductivity and structural phase transitions in
phosphorous (P) are studied by resistivity measurements under pressures up to
170 GPa and fully $ab-initio$ crystal structure and superconductivity
calculations up to 350 GPa. Two distinct superconducting transition temperature
(T$_{c}$) vs. pressure ($P$) trends at low pressure have been reported more
than 30 years ago, and for the first time we are able to reproduce them and
devise a consistent explanation founded on thermodynamically metastable phases
of black-phosphorous. Our experimental and theoretical results form a single,
consistent picture which not only provides a clear understanding of elemental P
under pressure but also sheds light on the long-standing and unsolved
$anomalous$ superconductivity trend. Moreover, at higher pressures we predict a
similar scenario of multiple metastable structures which coexist beyond their
thermodynamical stability range. Metastable phases of P experimentally
accessible at pressures above 240 GPa should exhibit T$_{c}$'s as high as 15 K,
i.e. three times larger than the predicted value for the ground-state crystal
structure. We observe that all the metastable structures systematically exhibit
larger transition temperatures than the ground-state ones, indicating that the
exploration of metastable phases represents a promising route to design
materials with improved superconducting properties.",1703.05694v1
2018-10-08,Monte Carlo phonon transport simulations in hierarchically disordered silicon nanostructures,"Hierarchical material nanostructuring is considered to be a very promising
direction for high performance thermoelectric materials. In this work we
investigate thermal transport in hierarchically nanostructured silicon. We
consider the combined presence of nanocrystallinity and nanopores, arranged
under both ordered and randomized positions and sizes, by solving the Boltzmann
transport equation using the Monte Carlo method. We show that nanocrystalline
boundaries degrade the thermal conductivity more drastically when the average
grain size becomes smaller than the average phonon mean free path. The
introduction of pores degrades the thermal conductivity even further. Its
effect, however, is significantly more severe when the pore sizes and positions
are randomized, as randomization results in regions of higher porosity along
the phonon transport direction, which introduce significant thermal resistance.
We show that randomization acts as a large increase in the overall effective
porosity. Using our simulations, we show that existing compact nanocrystalline
and nanoporous theoretical models describe thermal conductivity accurately
under uniform nanostructured conditions, but overestimate it in randomized
geometries. We propose extensions to these models that accurately predict the
thermal conductivity of randomized nanoporous materials based solely on a few
geometrical features. Finally, we show that the new compact models introduced
can be used within Matthiessens rule to combine scattering from different
geometrical features within approximately 10 per cent accuracy.",1810.03334v1
2020-09-22,A cracking oxygen story: a new view of stress corrosion cracking in titanium alloys,"Titanium alloys can suffer from halide-associated stress corrosion cracking
at elevated temperatures e.g., in jet engines, where chlorides and Ti-oxide
promote the cracking of water vapour in the gas stream, depositing embrittling
species at the crack tip. Here we report, using isotopically-labelled
experiments, that crack tips in an industrial Ti-6Al-2Sn-4Zr-6Mo alloy are
strongly enriched (>5 at.%) in oxygen from the water vapour, far greater than
the amounts (0.25 at.%) required to embrittle the material. Surprisingly,
relatively little hydrogen (deuterium) is measured, despite careful preparation
and analysis. Therefore, we suggest that a combined effect of O and H leads to
cracking, with O playing a vital role, since it is well-known to cause
embrittlement of the alloy. In contrast it appears that in alpha+beta Ti
alloys, it may be that H may drain away into the bulk owing to its high
solubility in beta-Ti, rather than being retained in the stress field of the
crack tip. Therefore, whilst hydrides may form on the fracture surface,
hydrogen ingress might not be the only plausible mechanism of embrittlement of
the underlying matrix. This possibility challenges decades of understanding of
stress-corrosion cracking as being related solely to the hydrogen enhanced
localised plasticity (HELP) mechanism, which explains why H-doped Ti alloys are
embrittled. This would change the perspective on stress corrosion embrittlement
away from a focus purely on hydrogen to also consider the ingress of O
originating from the water vapour, insights critical for designing corrosion
resistant materials.",2009.10567v2
2017-05-08,"Casimir free energy of dielectric films: Classical limit, low-temperature behavior and control","The Casimir free energy of dielectric films, both free-standing in vacuum and
deposited on metallic or dielectric plates, is investigated. It is shown that
the values of the free energy depend considerably on whether the calculation
approach used neglects or takes into account the dc conductivity of film
material. We demonstrate that there are the material-dependent and universal
classical limits in the former and latter cases, respectively. The analytic
behavior of the Casimir free energy and entropy for a free-standing dielectric
film at low temperature in found. According to our results, the Casimir entropy
goes to zero when the temperature vanishes if the calculation approach with
neglected dc conductivity of a film is employed. If the dc conductivity is
taken into account, the Casimir entropy takes the positive value at zero
temperature, depending on the parameters of a film, i.e., the Nernst heat
theorem is violated. By considering the Casimir free energy of silica and
sapphire films deposited on a Au plate in the framework of two calculation
approaches, we argue that physically correct values are obtained by
disregarding the role of dc conductivity. A comparison with the well known
results for the configuration of two parallel plates is made. Finally, we
compute the Casimir free energy of silica, sapphire and Ge films deposited on
high-resistivity Si plates of different thicknesses and demonstrate that it can
be positive, negative and equal to zero. Possible applications of the obtained
results to thin films used in microelectronics are discussed.",1705.02897v1
2017-07-17,Realizing Thermoelectric and Thermistor Bi-functionalities via Triggering Electron Correlations with Lattice-dipole,"Establishing strong electron-correlations not only shed lights on overcoming
the trade-off limitations for optimizing thermoelectric materials, but can also
introduce new functionalities that extend the vision of conventional
thermoelectric applications. Here, we demonstrate that the high thermoelectric
and thermistor functionalities coexist in lattice distorted SrNbxTi1-xO3 films
with electron correlations between carriers and ordering aligned lattice
dipoles. As-grown SrNbxTi1-xO3/SrTiO3 with effectively preserved interfacial
strains exhibits cross-plane charge ordering and orbital anisotropy, as
indicated by the polarization dependent near edge X-ray absorption fine
structures. The resultant coulomb-correlations regulate the carrier transport
and enhance the Seebeck coefficient more independently via enlarging the system
vibration entropy. As-achieved maximum thermoelectric power factor exceeds 100
uWcm-1K-2 measured in the bulk performance of SrNb0.2Ti0.8O3 (2.2 um)/SrTiO3
(100 um), which is comparable to the best thermoelectric materials for low
temperature applications. In addition, the strong temperature dependence of the
carrier scattering aroused by the lattice dipoles introduces a positive
temperature dependent thermistor transportation behavior with large temperature
coefficient of resistance ranging from 30 to 300 K, which is rarely seen in
conventional thermistors. Combining both functionalities largely extend the
horizon in exploring new Joule sensors for detection of temperature and thermal
perturbations across a broad temperature range.",1707.04988v2
2017-08-17,Tailoring tricolor structure of magnetic topological insulator for robust axion insulator,"Exploration of novel electromagnetic phenomena is a subject of great interest
in topological quantum materials. One of the unprecedented effects to be
experimentally verified is topological magnetoelectric (TME) effect originating
from an unusual coupling of electric and magnetic fields in materials. A
magnetic heterostructure of topological insulator (TI) hosts such an exotic
magnetoelectric coupling and can be expected to realize the TME effect as an
axion insulator. Here we designed a magnetic TI with tricolor structure where a
non-magnetic layer of (Bi, Sb)2Te3 is sandwiched by a soft ferromagnetic
Cr-doped (Bi, Sb)2Te3 and a hard ferromagnetic V-doped (Bi, Sb)2Te3.
Accompanied by the quantum anomalous Hall (QAH) effect, we observe zero Hall
conductivity plateaus, which are a hallmark of the axion insulator state, in a
wide range of magnetic field between the coercive fields of Cr- and V-doped
layers. The resistance of the axion insulator state reaches as high as 10^9
ohm, leading to a gigantic magnetoresistance ratio exceeding 10,000,000% upon
the transition from the QAH state. The tricolor structure of TI may not only be
an ideal arena for the topologically distinct phenomena, but also provide
magnetoresistive applications for advancing dissipationless topological
electronics.",1708.05387v1
2019-03-02,AC Elastocaloric effect as a probe for thermodynamic signatures of continuous phase transitions,"Studying the response of materials to strain can elucidate subtle properties
of electronic structure in strongly correlated materials. So far, mostly the
relation between strain and resistivity, the so called elastoresistivity, has
been investigated. The elastocaloric effect is a second rank tensor quantity
describing the relation between entropy and strain. In contrast to the
elastoresistivity, the elastocaloric effect is a thermodynamic quantity.
Experimentally, elastocaloric effect measurements are demanding since the
thermodynamic conditions during the measurement have to be well controlled.
Here we present a technique to measure the elastocaloric effect under quasi
adiabatic conditions. The technique is based on oscillating strain, which
allows for increasing the frequency of the elastocaloric effect above the
thermal relaxation rate of the sample. We apply the technique to Co-doped iron
pnictide superconductors and show that the thermodynamic signatures of second
order phase transitions in the elastocaloric effect closely follow those
observed in calorimetry experiments. In contrast to the heat capacity, the
electronic signatures in the elastocaloric effect are measured against a small
phononic background even at high temperatures, establishing this technique as a
powerful complimentary tool for extracting the entropy landscape proximate to a
continuous phase transition.",1903.00791v1
2019-03-27,Investigation of Room Temperature Ferroelectricity and Ferrimagnetism in Multiferroic AlxFe2-xO3 Epitaxial Thin Films,"Multiferroic materials open up the possibility to design novel functionality
in electronic devices, with low energy consumption. However, there are very few
materials that show multiferroicity at room temperature, which is essential to
be practically useful. AlxFe2-xO3 (x-AFO) thin films, belonging to the k-Al2O3
family are interesting because they show room temperature ferrimagnetism and
have a polar crystal structure. However, it is difficult to realise its
ferroelectric properties at room temperature, due to low resistivity of the
films. In this work, we have deposited x-AFO (0.5 <= x <= 1) epitaxial thin
films with low leakage, on SrTiO3<111> substrates by Pulsed Laser Deposition.
Magnetic measurements confirmed room temperature ferrimagnetism of the films,
however the Curie temperature was found to be influenced by deposition
conditions. First principle calculations suggested that ferroelectric domain
switching occurs through shearing of in-plane oxygen layers, and predicted a
high polarization value of 24 uC/cm2. However, actual ferroelectric
measurements showed the polarization to be two order less. Presence of multiple
in-plane domains which oppose polarization switching of adjacent domains, was
found to be the cause for the small observed polarization. Comparing dielectric
relaxation studies and ferroelectric characterization showed that
oxygen-vacancy defects assist domain wall motion, which in turn facilitates
polarization switching.",1903.11422v1
2016-09-09,Extremely large magnetoresistance in a topological semimetal candidate pyrite PtBi2,"While pyrite-type PtBi2 with face-centered cubic structure has been predicted
to be a three-dimensional (3D) Dirac semimetal, experimental study on its
physical properties remains absent. Here we report the angular-dependent
magnetoresistance (MR) measurements of PtBi2 single-crystal under high magnetic
fields. We observed extreme large unsaturated magnetoresistance (XMR) up to
11.2 million percent at T = 1.8 K in a magnetic field of 33 T, which surpasses
the previously reported Dirac materials, such as WTe2, LaSb and NbP. The
crystals exhibit an ultrahigh mobility and significant Shubnikov-de Hass (SdH)
quantum oscillations with nontrivial Berry's phase. Analysis of Hall
resistivity indicates that the XMR can be ascribed to the nearly compensated
electron and hole. Our experimental results associated with the ab initio
calculations suggest that pyrite PtBi2 is a topological semimetal candidate
which might provide a platform for exploring topological materials with XMR in
noble metal alloys.",1609.02626v2
2019-06-19,"Apparatus for Seebeck coefficient measurement of wire, thin film and bulk materials in the wide temperature range (80-650K)","A Seebeck coefficient measurement apparatus has been designed and developed,
which is very effective for accurate characterization of different type of
samples in a wide temperature range (80 - 650K) simultaneously covering low as
well as the high-temperature regime. Reducing the complexity of the technical
design of sample holder and data collections has always been challenging to
implement in a single instrument when samples are in different geometrical
shape and electronic structure. Our unique design of sample holder with
pressure probes covers measurements of different samples shapes (wires, thin
films and pellets) as well as different resistivity ranges (metals,
semiconductors and insulators). It is suitable for characterization of
different samples sizes (3-12 mm). A double heater configuration powered by a
dual channel source meter is employed for maintaining a desired constant
temperature difference across the sample for the whole temperature range. Two
K-type thermocouples are used for simultaneously reading of temperatures and
Seebeck voltages by utilizing different channels of a multichannel digital
multimeter. Calibration of the system has been carried out using constantan,
chromel and alumel materials and recorded data is found to be very accurate and
consistent with earlier reports. The Seebeck coefficients of standard samples
of constantan (wire) and GaN (thin film) have been reported, which shows the
measurement capability of designed setup with versatile samples.",1906.08023v2
2019-11-20,Piezoelectricity in monolayer hexagonal boron nitride,"Two-dimensional (2D) hexagonal boron nitride (hBN) is a wide-bandgap van der
Waals crystal with a unique combination of properties, including exceptional
strength, large oxidation resistance at high temperatures and optical
functionalities. Furthermore, in recent years hBN crystals have become the
material of choice for encapsulating other 2D crystals in a variety of
technological applications, from optoelectronic and tunnelling devices to
composites. Monolayer hBN, which has no center of symmetry, has been predicted
to exhibit piezoelectric properties, yet experimental evidence is lacking.
Here, by using electrostatic force microscopy, we observed this effect as a
strain-induced change in the local electric field around bubbles and creases,
in agreement with theoretical calculations. No piezoelectricity was found in
bilayer and bulk hBN, where the centre of symmetry is restored. These results
add piezoelectricity to the known properties of monolayer hBN, which makes it a
desirable candidate for novel electromechanical and stretchable optoelectronic
devices, and pave a way to control the local electric field and carrier
concentration in van der Waals heterostructures via strain. The experimental
approach used here also shows a way to investigate the piezoelectric properties
of other materials on the nanoscale by using electrostatic scanning probe
techniques.",1911.09134v1
2020-07-16,The influence of material properties and process parameters on the spreading process in additive manufacturing,"Laser powder bed fusion (LPBF) is an additive manufacturing (AM) technology.
To achieve high product quality, the powder is best spread as a uniform, dense
layer. The challenge for LPBF manufacturers is to develop a spreading process
that can produce a consistent layer quality for the many powders used, which
show considerable differences in spreadability. Therefore, we investigate the
influence of material properties, process parameters and the type of spreading
tool on the layer quality. The discrete particle method is used to simulate the
spreading process and to define metrics to evaluate the powder layer
characteristics. We found that particle shape and surface roughness in terms of
rolling resistance and interparticle sliding friction as well as particle
cohesion all have a major (sometimes surprising) influence on the powder layer
quality: more irregular shaped particles, rougher particle surfaces and/or
higher interfacial cohesion usually, but not always, lead to worse
spreadability. Our findings illustrate that there is a trade-off between
material properties and process parameters. Increasing the spreading speed
decreases layer quality for non- and weakly cohesive powders, but improves it
for strongly cohesive ones. Using a counter-clockwise rotating roller as a
spreading tool improves the powder layer quality compared to spreading with a
blade. Finally, for both geometries, a unique correlation between the quality
criteria uniformity and mass fraction is reported and some of the findings are
related to size-segregation during spreading.",2007.10125v1
2021-03-12,Nanodevices engineering and spin transport properties of MnBi2Te4 monolayer,"Two-dimensional (2D) magnetic materials are essential for the development of
the next-generation spintronic technologies. Recently, layered van der Waals
(vdW) compound MnBi2Te4 (MBT) has attracted great interest, and its 2D
structure has been reported to host coexisting magnetism and topology. Here, we
design several conceptual nanodevices based on MBT monolayer (MBT-ML) and
reveal their spin-dependent transport properties by means of the
first-principles calculations. The pn-junction diodes and sub-3-nm pin-junction
field-effect transistors (FETs) show a strong rectifying effect and a spin
filtering effect, with an ideality factor n close to 1 even at a reasonably
high temperature. In addition, the pip- and nin-junction FETs give an
interesting negative differential resistive (NDR) effect. The gate voltages can
tune currents through these FETs in a large range. Furthermore, the MBT-ML has
a strong response to light. Our results uncover the multifunctional nature of
MBT-ML, pave the road for its applications in diverse next-generation
semiconductor spin electric devices.",2103.07025v1
2021-04-12,Fiber Packing and Morphology Driven Moisture Diffusion Mechanics in Reinforced Composites,"Fiber reinforced polymer composite (FRPC) materials are extensively used in
lightweight applications due to their high specific strength and other
favorable properties including enhanced endurance and corrosion resistance.
However, these materials are inevitably exposed to moisture, which is known to
drastically reduce their mechanical properties caused by moisture absorption
and often accompanied with plasticization, weight gain, hygrothermal swelling,
and de-bonding between fiber and matrix. Hence, it is vital to understand
moisture diffusion mechanics into FRPCs. The presence of fibers, especially
impermeable like Carbon fibers, introduce tortuous moisture diffusion pathways
through polymer matrix. In this paper, we elucidate the impact of fiber packing
and morphology on moisture diffusion in FRPC materials. Computational models
are developed within a finite element framework to evaluate moisture kinetics
in impermeable FRPCs. We introduce a tortuosity factor for measuring the extent
of deviation in moisture diffusion pathways due to impermeable fiber
reinforcements. Two-dimensional micromechanical models are analyzed with
varying fiber volume fractions, spatial distributions and morphology to
elucidate the influence of internal micromechanical fiber architectures on
tortuous diffusion pathways and corresponding diffusivities. Finally, a
relationship between tortuosity and diffusivity is established such that
diffusivity can be calculated using tortuosity for a given micro-architecture.
Tortuosity can be easily calculated for a given architecture by solving steady
state diffusion governing equations, whereas time-dependent transient diffusion
equations need to be solved for calculating moisture diffusivity. Hence,
tortuosity, instead of diffusivity, can be used in future composites designs,
multi-scale analyses, and optimization for enabling robust structures in
moisture environments.",2104.05180v2
2021-05-01,Anisotropy and Current Control of Magnetization in SrRuO$_3$ SrTiO$_3$ Heterostructures for Spin-Memristors,"Spintronics-based nonvolatile components in neuromorphic circuits offer the
possibility of realizing novel functionalities at low power. Current-controlled
electrical switching of magnetization is actively researched in this context.
Complex oxide heterostructures with perpendicular magnetic anisotropy (PMA),
consisting of SrRuO$_3$ (SRO) grown on SrTiO$_3$ (STO) are strong material
contenders. Utilizing the crystal orientation, magnetic anisotropy in such
simple heterostructures can be tuned to either exhibit a perfect or slightly
tilted PMA. Here, we investigate current-induced magnetization modulation in
such tailored ferromagnetic layers with a material with strong spin-orbit
coupling (Pt), exploiting the spin Hall effect. We find significant differences
in the magnetic anisotropy between the SRO/STO heterostructures, as manifested
in the first and second harmonic magnetoresistance measurements.
Current-induced magnetization switching can be realized with spin-orbit
torques, but for systems with perfect PMA this switching is probabilistic as a
result of the high symmetry. Slight tilting of the PMA can break this symmetry
and allow the realization of deterministic switching. Control over the magnetic
anisotropy of our heterostructures therefore provides control over the manner
of switching. Based on our findings, we propose a three-terminal spintronic
memristor, with a magnetic tunnel junction design, that shows several resistive
states controlled by electric charge. Non-volatile states can be written
through SOT by applying an in-plane current, and read out as a tunnel current
by applying a small out-of-plane current. Depending on the anisotropy of the
SRO layer, the writing mechanism is either deterministic or probabilistic
allowing for different functionalities to emerge. We envisage that the
probabilistic MTJs could be used as synapses while the deterministic devices
can emulate neurons",2105.00269v1
2021-05-05,Ni$_{80}$Fe$_{20}$ Nanotubes with Optimized Spintronic Functionalities Prepared by Atomic Layer Deposition,"Permalloy Ni$_{80}$Fe$_{20}$ is one of the key magnetic materials in the
field of magnonics. Its potential would be further unveiled if it could be
deposited in three dimensional (3D) architectures of sizes down to the
nanometer. Atomic Layer Deposition, ALD, is the technique of choice for
covering arbitrary shapes with homogeneous thin films. Early successes with
ferromagnetic materials include nickel and cobalt. Still, challenges in
depositing ferromagnetic alloys reside in the synthesis via decomposing the
consituent elements at the same temperature and homogeneously. We report
plasma-enhanced ALD to prepare permalloy Ni$_{80}$Fe$_{20}$ thin films and
nanotubes using nickelocene and iron(III) tert-butoxide as metal precursors,
water as the oxidant agent and an in-cycle plasma enhanced reduction step with
hydrogen. We have optimized the ALD cycle in terms of Ni:Fe atomic ratio and
functional properties. We obtained a Gilbert damping of 0.013, a resistivity of
28 $\mu\Omega$cm and an anisotropic magnetoresistance effect of 5.6 $\%$ in the
planar thin film geometry. We demonstrate that the process also works for
covering GaAs nanowires, resulting in permalloy nanotubes with high aspect
ratios and diameters of about 150 nm. Individual nanotubes were investigated in
terms of crystal phase, composition and spin-dynamic response by microfocused
Brillouin Light Scattering. Our results enable NiFe-based 3D spintronics and
magnonic devices in curved and complex topology operated in the GHz frequency
regime.",2105.01969v1
2021-09-17,Towards replacing physical testing of granular materials with a Topology-based Model,"In the study of packed granular materials, the performance of a sample (e.g.,
the detonation of a high-energy explosive) often correlates to measurements of
a fluid flowing through it. The ""effective surface area,"" the surface area
accessible to the airflow, is typically measured using a permeametry apparatus
that relates the flow conductance to the permeable surface area via the
Carman-Kozeny equation. This equation allows calculating the flow rate of a
fluid flowing through the granules packed in the sample for a given pressure
drop. However, Carman-Kozeny makes inherent assumptions about tunnel shapes and
flow paths that may not accurately hold in situations where the particles
possess a wide distribution in shapes, sizes, and aspect ratios, as is true
with many powdered systems of technological and commercial interest. To address
this challenge, we replicate these measurements virtually on micro-CT images of
the powdered material, introducing a new Pore Network Model based on the
skeleton of the Morse-Smale complex. Pores are identified as basins of the
complex, their incidence encodes adjacency, and the conductivity of the
capillary between them is computed from the cross-section at their interface.
We build and solve a resistive network to compute an approximate laminar fluid
flow through the pore structure. We provide two means of estimating
flow-permeable surface area: (i) by direct computation of conductivity, and
(ii) by identifying dead-ends in the flow coupled with isosurface extraction
and the application of the Carman-Kozeny equation, with the aim of establishing
consistency over a range of particle shapes, sizes, porosity levels, and void
distribution patterns.",2109.08777v1
2021-11-11,Tuning the Room Temperature Ferromagnetism in Fe5GeTe2 by Arsenic Substitution,"In order to tune the magnetic properties of the cleavable high-Curie
temperature ferromagnet Fe$_{5-x}$GeTe$_2$, the effect of increasing the
electron count through arsenic substitution has been investigated. Small
additions of arsenic (2.5 and 5%) seemingly enhance ferromagnetic order in
polycrystalline samples by quenching fluctuations on one of the three magnetic
sublattices, whereas larger As concentrations decrease the ferromagnetic Curie
temperature ($T_{\rm C}$) and saturation magnetization. This work also
describes the growth and characterization of Fe$_{4.8}$AsTe$_2$ single crystals
that are structurally analogous to Fe$_{5-x}$GeTe$_2$ but with some phase
stability complications. Magnetization measurements reveal dominant
antiferromagnetic behavior in Fe$_{4.8}$AsTe$_2$ with a N\'{e}el temperature of
$T_{\rm N}$ $\approx$42K. A field-induced spin-flop below $T_{\rm N}$ results
in a switch from negative to positive magnetoresistance, with significant
hysteresis causing butterfly-shaped resistance loops. In addition to reporting
the properties of Fe$_{4.8}$AsTe$_2$, this work shows the importance of
manipulating the individual magnetic sublattices in Fe$_{5-x}$GeTe$_2$ and
motivates further efforts to control the magnetic properties in related
materials by fine tuning of the Fermi energy or crystal chemistry.",2111.06439v1
2022-01-11,Antiferromagnetic Excitonic Insulator State in Sr3Ir2O7,"Excitonic insulators are usually considered to form via the condensation of a
soft charge mode of bound electron-hole pairs. This, however, presumes that the
soft exciton is of spin-singlet character. Early theoretical considerations
have also predicted a very distinct scenario, in which the condensation of
magnetic excitons results in an antiferromagnetic excitonic insulator state.
Here we report resonant inelastic x-ray scattering (RIXS) measurements of
Sr3Ir2O7. By isolating the longitudinal component of the spectra, we identify a
magnetic mode that is well-defined at the magnetic and structural Brillouin
zone centers, but which merges with the electronic continuum in between these
high-symmetry points and which decays upon heating concurrent with a decrease
in the material's resistivity. We show that a bilayer Hubbard model, in which
electron-hole pairs are bound by exchange interactions, consistently explains
all the electronic and magnetic properties of Sr3Ir2O7 indicating that this
material is a realization of the long-predicted antiferromagnetic excitonic
insulators phase.",2201.04030v1
2022-03-18,Surface temperature and emissivity measurement for materials exposed to a flame through two-color IR-thermography,"Two-color (2C) pyrometry has long been used for flame temperature and soot
concentration studies and is now becoming more widely used to measure surface
temperatures of burning materials. With the obvious advantage of being a
contact-free method that requires only minimal optical access, 2C pyrometry
combined with high-speed acquisition is a promising diagnostic tool to obtain
exceptional temporal and spatial resolution of thermally degrading samples.
However, its conceptual simplicity relies on a set of basic assumptions that
when violated can result in large errors. In this work, we use an experimental
configuration representative for fire resistance testing for aerospace and
naval applications to analyze the impact of camera parameters and test setup on
the accuracy of the surface temperature results obtained. Two types of fibre
reinforced polymer composites and a steel plate are used to investigate
material specific aspects that effect the measurements. An improved workflow
for camera calibration is presented that takes the actual experimental setup
into account. The temperature and emissivity mapping obtained trough in-situ IR
measurements is compared against data acquired trough thermocouples and
post-fire hemispherical directional reflectance measurements at room
temperature. This comparison illustrates the necessity for proper
post-processing and demonstrates that emissivity values obtained from pristine
or burnt samples are not well suited to obtain accurate surface temperatures
through conventional (single color) IR thermography. We also present a detailed
error budget and suggestions for calibration measurements to keep the overall
error well below 50 K in a temperature range from 673 K - 1473 K.",2203.09689v1
2022-04-11,A-type antiferromagnetic order in semiconducting EuMg$_2$Sb$_2$ single crystals,"Eu-based Zintl-phase materials EuA$_2$Pn$_2$ (A = Mg, In, Cd, Zn; Pn = Bi,
Sb, As, P) have generated significant recent interest owing to the complex
interplay of magnetism and band topology. Here, we investigated the electronic,
magnetic, and electronic properties of the layered Zintl-phase single crystals
of EuMg$_2$Sb$_2$ with the trigonal CaAl$_2$Si$_2$ crystal structure (space
group $P\bar{3}m1$). Electrical resistivity measurements complemented with
angle-resolved photoemission spectroscopy (ARPES) studies find an activated
behavior with the intrinsic conductivity at high temperatures indicating a
semiconducting electronic ground state with a narrow energy gap of 370 meV.
Magnetic susceptibility and zero-field heat-capacity measurements indicate that
the compound undergoes antiferromagnetic (AFM) ordering at the Neel temperature
$T_{\rm N}$ = 8.0(2) K. Zero-field neutron-diffraction measurements reveal that
the AFM ordering is A-type where the Eu ordered moments (Eu$^{2+}$, S= 7/2)
arranged in ab-plane layers are aligned ferromagnetically in the ab plane with
the Eu moments in adjacent layers aligned antiferromagnetically. We also find
that Eu-moment reorientation in the trigonal AFM domains within the ab planes
occurs below $T_{\rm N}$ at low fields < 0.05 T due to very small in-plane
anisotropy. Although isostructural semimetallic EuMg$_2$Bi$_2$ is reported to
host Dirac surface states, the observation of narrow-gap semiconducting
behavior in EuMg$_2$Sb$_2$ implies a strong role of spin-orbit coupling in
tuning the electronic states of these materials.",2204.05261v1
2022-05-11,Tunable photochemical deposition of silver nanostructures on layered ferroelectric CuInP$_2$S6,"2D layered ferroelectric materials such as CuInP$_2$S6 (CIPS) are promising
candidates for novel and high-performance photocatalysts, owning to their
ultrathin layer thickness, strong interlayer coupling, and intrinsic
spontaneous polarization, while how to control the photocatalytic activity in
layered CIPS remains unexplored. In this work, we report for the first time the
photocatalytic activity of ferroelectric CIPS for the chemical deposition of
silver nanostructures (AgNSs). The results show that the shape and spatial
distribution of AgNSs on CIPS are tunable by controlling layer thickness,
environmental temperature, and light wavelength. The ferroelectric polarization
in CIPS plays a critical role in tunable AgNS photodeposition, as evidenced by
layer thickness and temperature dependence experiments. We further reveal that
AgNS photodeposition process starts from the active site creation, selective
nanoparticle nucleation/aggregation, to the continuous film formation.
Moreover, AgNS/CIPS heterostructures prepared by photodeposition exhibit
excellent resistance switching behavior and good surface enhancement Raman
Scattering activity. Our findings provide new insight into the photocatalytic
activity of layered ferroelectrics and offer a new material platform for
advanced functional device applications in smart memristors and enhanced
chemical sensors.",2205.05385v2
2022-06-23,Superconductivity in the crystallogenide LaFeSiO$_{1-δ}$ with squeezed FeSi layers,"Pnictogens and chalcogens are both viable anions for promoting Fe-based
superconductivity and intense research activity in the related families has
established systematic correlation between the Fe-anion height and the
superconducting critical temperature $T_c$, with an optimum Fe-anion height of
$\sim$ 1.38 \r{A}. Here, we report the discovery of superconductivity in a
novel compound LaFeSiO$_{1-\delta}$ that incorporates a crystallogen element,
Si, and challenges the above picture: considering the strongly squeezed Fe-Si
height of 0.94 \r{A}, the superconducting transition at $T_{c}$ = 10 K is
unusually high. In the normal state, the resistivity displays non-Fermi-liquid
behavior while NMR experiments evidence weak antiferromagnetic fluctuations.
According to first-principles calculations, the Fermi surface of this material
is dominated by hole pockets without nesting properties, which explains the
strongly suppressed tendency towards magnetic order and suggests that the
emergence of superconductivity materializes in a distinct set-up, as compared
to the standard $s_\pm$- and $d$-wave electron-pocket-based situations. These
properties and its simple-to-implement synthesis make LaFeSiO$_{1-\delta}$ a
particularly promising platform to study the interplay between structure,
electron correlations and superconductivity.",2206.11690v1
2022-10-18,All-electrical spin-to-charge conversion in sputtered Bi$_x$Se$_{1-x}$,"One of the major obstacles to realizing spintronic devices such as MESO logic
devices is the small signal magnitude used for magnetization readout, making it
important to find materials with high spin-to-charge conversion efficiency.
Although intermixing at the junction of two materials is a widely occurring
phenomenon, its influence on material characterization and the estimation of
spin-to-charge conversion efficiencies is easily neglected or underestimated.
Here, we demonstrate all electrical spin-to-charge conversion in
Bi$_x$Se$_{1-x}$ nanodevices and show how the conversion efficiency can be
overestimated by tens of times depending on the adjacent metal used as a
contact. We attribute this to the intermixing-induced compositional change and
the properties of a polycrystal that lead to drastic changes in resistivity and
spin Hall angle. Strategies to improve the spin-to-charge conversion signal in
similar structures for functional devices are discussed.",2210.09792v1
2023-09-09,Intrinsic magnetic properties of the layered antiferromagnet CrSBr,"Van der Waals magnetic materials are an ideal platform to study
low-dimensional magnetism. Opposed to other members of this family, the
magnetic semiconductor CrSBr is highly resistant to degradation in air, which,
besides its exceptional optical, electronic, and magnetic properties, is the
reason the compound is receiving considerable attention at the moment. For many
years, its magnetic phase diagram seemed to be well-understood. Recently,
however, several groups observed a magnetic transition in magnetometry
measurements at temperatures of around 40 K that is not expected from
theoretical considerations, causing a debate about the intrinsic magnetic
properties of the material. In this letter, we report the absence of this
particular transition in magnetization measurements conducted on high-quality
CrSBr crystals, attesting to the extrinsic nature of the low-temperature
magnetic phase observed in other works. Our magnetometry results obtained from
large bulk crystals are in very good agreement with the magnetic phase diagram
of CrSBr previously predicted by the mean-field theory; A-type
antiferromagnetic order is the only phase observed below the N\'eel temperature
at TN = 131 K. Moreover, numerical fits based on the Curie-Weiss law confirm
that strong ferromagnetic correlations are present within individual layers
even at temperatures much larger than TN.",2309.04778v1
2024-01-25,Threshold displacement energy map of Frenkel pair generation in $\rm Ga_2O_3$ from machine-learning-driven molecular dynamics simulations,"$\beta$ phase gallium oxide ($\beta$-$\rm Ga_2O_3$) demonstrates tremendous
potential for electronics applications and offers promising prospects for
integration into future space systems with the necessity of high radiation
resistance. Therefore, a comprehensive understanding of the threshold
displacement energy (TDE) and the radiation-induced formation of Frenkel pairs
(FPs) in this material is vital but has not yet been thoroughly studied. In
this work, we performed over 5,000 molecular dynamics simulations using our
machine-learning potentials to determine the TDE and investigate the formation
of FPs. The average TDEs for the two Ga sites, Ga1 (tetrahedral site) and Ga2
(octahedral site), are 22.9 and 20.0 eV, respectively. While the average TDEs
for the three O sites are nearly uniform, ranging from 17.0 to 17.4 eV. The
generated TDE maps reveal significant differences in displacement behavior
between these five atomic sites. Our developed defect identification methods
successfully categorize various types of FPs in this material, with more than
ten types of Ga FPs being produced during our simulations. O atoms are found to
form two main types of FPs and the O split interstitial site on O1 site is most
common. Finally, the recombination behavior and barriers of Ga and O FPs
indicate that the O FP has a higher possibility of recovery upon annealing. Our
findings provide important insights into the studies of radiation damage and
defects in $\rm Ga_2O_3$ and can contribute to the design and development of
$\rm Ga_2O_3$-based devices",2401.14039v2
2024-03-06,Collision Cascade-Driven Evolution of Vacancy Defects in Ni-Based Concentrated Solid-Solution Alloys,"Concentrated solid--solution alloys (CSAs) in single--phase form have
recently garnered considerable attention owing to their potential for
exceptional irradiation resistance. This computational study delves into the
intricate interplay of alloying elements on the generation, recombination, and
evolution of irradiation-induced defects. Molecular dynamics simulations were
conducted for collision cascades at room temperature, spanning a range of
primary knock-on atom energies from 1 to 10 keV. The investigation encompasses
a series of model crystals, progressing from pure Ni to binary CSAs such as
NiFe$_{20}$, NiFe, NiCr$_{20}$, and culminating in the more intricate
NiFeCr$_{20}$ CSA. We observe that materials rich in chromium actively
facilitate dislocation emissions and induce the nucleation of stacking fault
tetrahedra in the proximity of nanovoids, owing to Shockley partial
interactions. This result is validated by molecular static simulations, which
calculate the surface, vacancy, and defect formation energies. Among various
shapes considered, the spherical void proves to be the most stable, followed by
the truncated octahedron and octahedron shapes. On the other hand, the
tetrahedron cubic shape is identified as the most unstable, and stacking fault
tetrahedra exhibit the highest formation energy. Notably, among the materials
studied, NiCr$_{20}$ and NiFeCr$_{20}$ CSAs stood out as the sole alloys
capable of manifesting this mechanism, mainly observed at high impact energies.",2403.03922v1
2024-05-08,Pressure induced metallization and loss of surface magnetism in FeSi,"Single crystalline FeSi samples with a conducting surface state (CSS) were
studied under high pressure ($\textit{P}$) and magnetic field ($\textit{B}$) by
means of electrical resistance ($\textit{R}$) measurements to explore how the
bulk semiconducting state and the surface state are tuned by the application of
pressure. We found that the energy gap ($\Delta$) associated with the
semiconducting bulk phase begins to close abruptly at a critical pressure
($P_{cr}$) of ~10 GPa and the bulk material becomes metallic with no obvious
sign of any emergent phases or non-Fermi liquid behavior in
$\textit{R}$($\textit{T}$) in the neighborhood of $P_{cr}$ above 3 K. Moreover,
the metallic phase appears to remain at near-ambient pressure upon release of
the pressure. Interestingly, the hysteresis in the $\textit{R}$($\textit{T}$)
curve associated with the magnetically ordered CSS decreases with pressure and
vanishes at $P_{cr}$, while the slope of the $\textit{R}$($\textit{B}$) curve,
d$\textit{R}$/d$\textit{B}$, which has a negative value for $\textit{P}$ <
$P_{cr}$, decreases in magnitude with $\textit{P}$ and changes sign at
$P_{cr}$. Thus, the CSS and the corresponding two-dimensional magnetic order
collapse at $P_{cr}$ where the energy gap $\Delta$ of the bulk material starts
to close abruptly, revealing the connection between the CSS and the
semiconducting bulk state in FeSi.",2405.04739v1
2024-05-09,Controlled Fabrication of Native Ultra-Thin Amorphous Gallium Oxide from 2D Gallium Sulfide for Emerging Electronic Applications,"Oxidation of two-dimensional (2D) layered materials has proven advantageous
in creating oxide/2D material heterostructures, opening the door for a new
paradigm of low-power electronic devices. Gallium (II) sulfide ($\beta$-GaS), a
hexagonal phase group III monochalcogenide, is a wide bandgap semiconductor
with a bandgap exceeding 3 eV in single and few layer form. Its oxide, gallium
oxide (Ga$_2$O$_3$), combines large bandgap (4.4-5.3 eV) with high dielectric
constant (~10). Despite the technological potential of both materials,
controlled oxidation of atomically-thin $\beta$-GaS remains under-explored.
This study focuses into the controlled oxidation of $\beta$-GaS using oxygen
plasma treatment, achieving ultrathin native oxide (GaS$_x$O$_y$, ~4 nm) and
GaS$_x$O$_y$/GaS heterostructures where the GaS layer beneath remains intact.
By integrating such structures between metal electrodes and applying electric
stresses as voltage ramps or pulses, we investigate their use for resistive
random-access memory (ReRAM). The ultrathin nature of the produced oxide
enables low operation power with energy use as low as 0.22 nJ per operation
while maintaining endurance and retention of 350 cycles and 10$^4$ s,
respectively. These results show the significant potential of the
oxidation-based GaS$_x$O$_y$/GaS heterostructure for electronic applications
and, in particular, low-power memory devices.",2405.05632v1
2013-06-04,Constitutive Model for Material Comminuting at High Shear Rate,"The modeling of high velocity impact into brittle or quasibrittle solids is
hampered by the unavailability of a constitutive model capturing the effects of
material comminution into very fine particles. The present objective is to
develop such a model, usable in finite element programs. The comminution at
very high strain rates can dissipate a large portion of the kinetic energy of
an impacting missile. The spatial derivative of the energy dissipated by
comminution gives a force resisting the penetration, which is superposed on the
nodal forces obtained from the static constitutive model in a finite element
program. The present theory is inspired partly by Grady's model for comminution
due to explosion inside a hollow sphere, and partly by analogy with turbulence.
In high velocity turbulent flow, the energy dissipation rate is enhanced by the
formation of micro-vortices (eddies) which dissipate energy by viscous shear
stress. Similarly, here it is assumed that the energy dissipation at fast
deformation of a confined solid gets enhanced by the release of kinetic energy
of the motion associated with a high-rate shear strain of forming particles.
For simplicity, the shape of these particles in the plane of maximum shear rate
is considered to be regular hexagons. The rate of release of free energy
density consisting of the sum of this energy and the fracture energy of the
interface between the forming particle is minimized. The particle sizes are
assumed to be distributed according to Schuhmann's power law. It is concluded
that the minimum particle size is inversely proportional to the (2/3)-power of
the shear strain rate, that the kinetic energy release is to proportional to
the (2/3)-power, and that the dynamic comminution creates an apparent material
viscosity inversely proportional to the (1/3)-power of the shear strain rate.",1306.1120v1
2005-10-03,A Study of Apparent Symmetry Breakdown in Perovskite Oxide-based Symmetric RRAM Devices,"A new model of a symmetric two-terminal non-volatile RRAM device based on
Perovskite oxide thin film materials, specifically Pr1-xCaxMnO3 (PCMO), is
proposed and analyzed. The model consists of two identical half-parts, which
are completely characterized by the same resistance verses pulse voltage
hysteresis loop, connected together in series. Even though the modeled device
is physically symmetric with respect to the direction of current, it is found
to exhibit switching of the resistance with the application of voltage pulses
of sufficient amplitude and of different polarities. The apparent breakdown of
parity conservation of the device is attributed to changes in resistance of the
active material layer near the electrodes during switching. Thus the switching
is history dependent, a feature that can be very useful for the construction of
real non-volatile memory devices. An actual symmetric device, not previously
reported in the literature and based on the proposed model, is fabricated in
the PCMO material system. Measurements of the resistance of this new device
generated an experimental hysteresis curve that matches well the calculated
hysteresis curve of the model, thus confirming the features predicated by the
new symmetric model.",0510059v1
2009-02-20,Lattice Resistance to Dislocation Motion : Singularity Distribution Approach,This paper has been withdrawn.,0902.3505v3
2015-03-03,Negative differential resistance and characteristic nonlinear electromagnetic response of a Topological Insulator,"Materials exhibiting negative differential resistance have important
applications in technologies involving microwave generation, which range from
motion sensing to radio astronomy. Despite their usefulness, there has been few
physical mechanisms giving rise to materials with such properties, i.e. GaAs
employed in the Gunn diode. In this work, we show that negative differential
resistance also generically arise in Dirac ring systems, an example of which
has been experimentally observed in the surface states of Topological
Insulators. This novel realization of negative differential resistance is based
on a completely different physical mechanism from that of the Gunn effect,
relying on the characteristic non-monotonicity of the response curve that
remains robust in the presence of nonzero temperature, chemical potential, mass
gap and impurity scattering. As such, it opens up new possibilities for
engineering applications, such as frequency upconversion devices which are
highly sought for terahertz signal generation. Our results may be tested with
thin films of Bi2Se3 Topological Insulators, and are expected to hold
qualitatively even in the absence of a strictly linear Dirac dispersion, as
will be the case in more generic samples of Bi2Se3 and other materials with
topologically nontrivial Fermi sea regions.",1503.01097v4
2016-01-09,Flux trapping in superconducting accelerating cavities during cooling down with a spatial temperature gradient,"During the cool-down of a superconducting accelerating cavity, a magnetic
flux is trapped as quantized vortices, which yield additional dissipation and
contribute to the residual resistance. Recently, cooling down with a large
spatial temperature gradient attracts much attention for successful reductions
of trapped vortices. The purpose of the present paper is to propose a model to
explain the observed efficient flux expulsions and the role of spatial
temperature gradient during the cool-down of cavity. In the vicinity of a
region with a temperature close to the critical temperature Tc,the critical
fields are strongly suppressed and can be smaller than the ambient magnetic
field. A region with a lower critical field smaller than the ambient field is
in the vortex state. As a material is cooled down, a region with a temperature
close Tc associating the vortex state domain sweeps and passes through the
material. In this process, vortices contained in the vortex state domain are
trapped by pinning centers that randomly distribute in the material. A number
of trapped vortices can be naively estimated by using the analogy with the
beam-target collision event. Based on this result, the residual resistance is
evaluated. We find that a number of trapped vortices and the residual
resistance are proportional to the strength of the ambient magnetic field and
the inverse of the temperature gradient. The obtained residual resistance
agrees well with experimental results. A material property dependence of a
number of trapped vortices is also discussed.",1601.02118v2
2018-01-08,Magnetoresistance when Spin Effects on Conduction are Weak,"This paper considers certain materials, including topological insulators,
where spin rotation symmetry is broken much more strongly than time reversal
symmetry. When these materials are in the diffusive regime, i.e. when they have
disorder that is strong enough to cause an electron to scatter many times while
crossing a sample, electrons and holes move in pairs that have zero spin and
are insensitive to spin physics. Working within this spinless scenario, we show
that Fourier transforming the magnetoconductance with respect to external
magnetic field obtains a curve describing the area distribution of loops traced
by electrons and holes within the sample. We present loop area distributions of
Landau levels, weak (anti)localization, conduction governed by Levy flights,
and linear-in-field resistance. Of these four the last two are new results.
Comparing these distributions, we argue that the linear-in-field resistance
seen in some topological insulators is caused by the same diffusive scattering
that causes weak antilocalization. The difference is that linear-in-field
resistance materials retain a level of quantum coherence that is usually seen
only on the surface of 2-D wires or in ring geometries. In an appendix we
include some speculative material about linear-in-temperature resistance.",1801.02663v6
2020-09-04,Thermal conductivity of PbTe-CoSb3 bulk polycrystalline composite: the role of microstructure and interface thermal resistance,"Systematic experimental and theoretical research on the role of
microstructure and interface thermal resistance on the thermal conductivity of
the PbTe-CoSb3 bulk polycrystalline composite is presented. In particular, the
correlation between the particle size of the dispersed phase and interface
thermal resistance (R_{int}) on the phonon thermal conductivity (\kappa_{ph})
is discussed. With this aim, a series of PbTe-CoSb_3 polycrystalline composite
materials with the different particle sizes of CoSb_3 was prepared. The
structural (XRD) and microstructural analysis (SEM/EDXS) confirmed assumed
chemical and phase compositions. The acoustic impedance difference (\Delta Z)
was determined from measured sound velocities in PbTe and CoSb_3 phases. The
interface thermal resistance (R_{int}) was calculated using the Debye model and
agrees with the experimental R_{int}. It is shown that the \kappa_{ph} of the
composite may be reduced when the particle size of the dispersed phase (CoSb_3)
is smaller than the critical value of ~230nm. This relationship was concluded
to be crucial for controlling the heat transport phenomena in composite
thermoelectric materials. The selection of the components with different
elastic properties (acoustic impedance) and particle size smaller than the
Kapitza radius leads to a new direction in the engineering of composite TE
materials with designed thermal properties",2009.02190v2
2020-09-20,"Development of a computational software in Python, used to study the materials resistance in beams","In this research, we do a software writing in Python to calculate the
efforts, bending moments and deformations in beams of different materials. This
computational tool, that we developed, is of great help in area of
computational physical, more exactly in resistance of materials, which serves
as support for researchers and teachers especially in physics and civil
engineering, of the part of statics, who wish to carry out the modeling of the
functions, involved in the calculation of resistance in beams in a practical
and simple way, using the software presented in this article. In order to carry
out this software, we are going to use the following methods: the
double-integration method and the conjugate-beam method, which will serve as
the basis of calculation to find the mathematical expressions involved in the
analysis of resistance in beams, then we will perform the implementation of the
aforementioned methods, using Python as the programming language. As a final
step in this project, the graphical interface of said calculation tool will be
made using the Python 3.0 Tkinter library. In this work, we show the results of
the graphs of the stress profiles, bending moments and deformations, for the
case of different types of beams, load and force distributions applied to them.
Where we were also able to conclude that a calculation software was
successfully built, dedicated to the analysis of efforts and deformations in
beams made of different materials.",2009.09448v2
2022-07-01,High-throughput analysis of Fröhlich-type polaron models,"The electronic structure of condensed matter can be significantly affected by
the electron-phonon interaction, leading to important phenomena such as
electrical resistance, superconductivity or the formation of polarons. This
interaction is often neglected in band structure calculations but can have a
strong impact on band gaps or optical spectra. Commonly used frameworks for
electron-phonon energy corrections are the Allen-Heine-Cardona theory and the
Fr\""ohlich model. While the latter shows qualitative agreement with experiment
for many polar materials, its simplicity should bring hard limits to its
applicability in real materials. Improvements can be made by introducing a
generalized version of the model, which considers anisotropic and degenerate
electronic bands, and multiple phonon branches. In this work, we search for
trends and outliers on over a thousand materials in existing databases of
phonon and electron band structures. We use our results to identify the limits
of applicability of the standard Fr\""olich model by comparing to the
generalized version, and by testing its basic hypothesis of a large radius for
the polaronic wavefunction and the corresponding atomic displacement cloud.
Among our extended set of materials, most exhibit large polaron behavior as
well as validity of the perturbative treatment. For the valence band, there is
also a significant fraction of the materials for which the perturbative
treatment cannot be applied and/or for which the size of the self-trapping
region is close to the atomic repetition distance. We find a large variety of
behaviors, and employ much more accurate, fully ab initio Allen-Heine-Cardona
calculations to understand extreme cases, where the Fr\""ohlich model should
fail and unusually large zero-point renormalization energies occur.",2207.00364v1
2013-03-26,Molecular Memory with Atomically-Smooth Graphene Contacts,"We report the use of bilayer graphene as an atomically-smooth contact for
nanoscale devices. A two-terminal Bucky ball (C60) based molecular memory is
fabricated with bilayer graphene as a contact on the polycrystalline nickel
electrode. Graphene provides an atomically-smooth covering over an otherwise
rough metal surface. The use of graphene additionally prohibits the
electromigration of nickel atoms into the C60 layer. The devices exhibit a
low-resistance state in the first sweep cycle and irreversibly switch to a high
resistance state at 0.8-1.2 V bias. The reverse sweep has a hysteresis behavior
as well. In the subsequent cycles, the devices retain the high-resistance
state, thus making it write-once read-many memory (WORM). The ratio of current
in low-resistance to high-resistance state is lying in 20-40 range for various
devices with excellent retention characteristics. Control sample without the
bilayer graphene shows random hysteresis and switching.",1303.6603v1
2020-04-10,Vortex Dynamics and Dissipation Under High-amplitude Microwave Drive,"In this paper, we describe the vortex dynamics under high-amplitude microwave
drive and its effect on the surface resistance of superconductors. The vortex
surface resistance is calculated with a Montecarlo approach, where the vortex
motion equation is solved for a collection of vortex flux lines each
oscillating within a random pinning landscape. This approach is capable of
providing a detailed description of the microscopic vortex dynamics and in turn
important insights into the microwave field amplitude dependence of the vortex
surface resistance. The numerical simulations are compared against experimental
data of vortex surface resistance at high microwave amplitude measured by means
of bulk niobium superconducting-radio frequency cavities operating at 1.3 GHz.
The good qualitative agreement of simulations and experiments suggests that the
non-linear dependence of the trapped flux surface resistance with the microwave
field amplitude is generated by progressive microwave depinning and vortex
jumps.",2004.05083v2
2015-07-17,Resistive thrust production can be as crucial as added mass mechanisms for inertial undulatory swimmers,"In this paper, we address a crucial point regarding the description of
moderate to high Reynolds numbers aquatic swimmers. For decades, swimming
animals have been classified in two different families of propulsive mechanisms
based on the Reynolds number: the ""resistive"" swimmers, using local friction to
produce the necessary thrust force for locomotion at low Reynolds number and
the ""reactive"" swimmers, lying in the high Reynolds range, and using added mass
acceleration (described by perfect fluid theory). However, inertial swimmers
are also systems that dissipate energy, due to their finite size, therefore
involving strong resistive contributions, even for high Reynolds numbers. Using
a complete model for the hydrodynamic forces, involving both reactive and
resistive contributions, we revisit here the physical mechanisms responsible
for the thrust production of such swimmers. We show, for instance, that the
resistive part of the force balance is as crucial as added mass effects in the
modeling of the thrust force, especially for elongated species. The conclusions
brought by this work may have significant contributions to the understanding of
complex swimming mechanisms, especially for the future design of artificial
swimmers.",1507.04952v1
2022-07-13,Memristive and tunneling effects in 3D interconnected silver nanowires,"Due to their memristive properties nanowire networks are very promising for
neuromorphic computing applications. Indeed, the resistance of such systems can
evolve with the input voltage or current as it confers a synaptic behaviour to
the device. Here, we propose a network of silver nanowires (Ag-NWs) which are
grown in a nanopourous membrane with interconnected nanopores by
electrodeposition. This bottom-up approach fabrication method gives a
conducting network with a 3D architecture and a high density of Ag-NWs. The
resulting 3D interconnected Ag-NW network exhibits a high initial resistance as
well as a memristive behavior. It is expected to arise from the creation and
the destruction of conducting silver filaments inside the Ag-NW network.
Moreover, after several cycles of measurement, the resistance of the network
switches from a high resistance regime, in the GOhm range, with a tunnel
conduction to a low resistance regime, in the kOhm range.",2207.06338v1
2011-05-06,Giant microwave photoresistivity in a high-mobility quantum Hall system,"We report the observation of a remarkably strong microwave photoresistivity
effect in a high-mobility two-dimensional electron system subject to a weak
magnetic field and low temperature. The effect manifests itself as a giant
microwave-induced resistivity peak which, in contrast to microwave-induced
resistance oscillations, appears only near the second harmonic of the cyclotron
resonance and only at sufficiently high microwave frequencies. Appearing in the
regime linear in microwave intensity, the peak can be more than an order of
magnitude stronger than the microwave-induced resistance oscillations and
cannot be explained by existing theories.",1105.1390v1
2014-11-19,Towards pristine graphene-metal interface and microstructures: Laser assisted direct patterning on Epitaxial graphene,"Graphene-metal contact resistance is governed by both intrinsic and extrinsic
factors. Intrinsically, both the density of states bottleneck near the Dirac
point and carrier reflection at the graphene-metal interface lead to a high
contact resistance. Moreover, graphene exhibits insulating behavior for
out-of-the-plane conduction. Extrinsically, surface contamination introduced by
photoresist residue or different adsorbed species during standard lithography
processing alters graphene's intrinsic properties by uncontrolled doping and
increased scattering which results in high and inconsistent contact resistance.
Here we demonstrate a femto-second laser assisted direct patterning of graphene
microstructures that enables us to study both intrinsic and extrinsic effects
on the graphene-metal interface. We show that a clean graphene-metal interface
is not sufficient to obtain contact resistance approaching the intrinsic limit
set by the quantum resistance. We also demonstrated that unlike CVD graphene,
edge state conduction (or end-contact) is not spontaneously formed by metal
deposition in case of graphene grown on SiC(0001). We conclude that for
epitaxial graphene, intentional end-contact formation is necessary to obtain
contact resistance near the quantum contact resistance limit.",1411.5114v1
2023-11-08,An attention-based deep learning network for predicting Platinum resistance in ovarian cancer,"Background: Ovarian cancer is among the three most frequent gynecologic
cancers globally. High-grade serous ovarian cancer (HGSOC) is the most common
and aggressive histological type. Guided treatment for HGSOC typically involves
platinum-based combination chemotherapy, necessitating an assessment of whether
the patient is platinum-resistant. The purpose of this study is to propose a
deep learning-based method to determine whether a patient is platinum-resistant
using multimodal positron emission tomography/computed tomography (PET/CT)
images. Methods: 289 patients with HGSOC were included in this study. An
end-to-end SE-SPP-DenseNet model was built by adding Squeeze-Excitation Block
(SE Block) and Spatial Pyramid Pooling Layer (SPPLayer) to Dense Convolutional
Network (DenseNet). Multimodal data from PET/CT images of the regions of
interest (ROI) were used to predict platinum resistance in patients. Results:
Through five-fold cross-validation, SE-SPP-DenseNet achieved a high accuracy
rate and an area under the curve (AUC) in predicting platinum resistance in
patients, which were 92.6% and 0.93, respectively. The importance of
incorporating SE Block and SPPLayer into the deep learning model, and
considering multimodal data was substantiated by carrying out ablation studies
and experiments with single modality data. Conclusions: The obtained
classification results indicate that our proposed deep learning framework
performs better in predicting platinum resistance in patients, which can help
gynecologists make better treatment decisions. Keywords: PET/CT, CNN, SE Block,
SPP Layer, Platinum resistance, Ovarian cancer",2311.04769v1
2000-08-17,Development of Gold Contacted Flip-chip Detectors with IMARAD CZT,"We present initial results from our evaluation of a gold-contacted pixellated
detector using cadmium zinc telluride substrate produced by IMARAD Imaging
Systems. The Horizontal Bridgman (HB) grown crystals from IMARAD have been
shown to produce high resolution photopeaks, but they are also seen to have
large leakage current. Our previous tests with IMARAD CZT showed that the use
of indium anodes and gold cathode improved the resistivity compared to the
standard indium-contacted detectors. We seek to test whether simple evaporated
gold contacts alone could also reduce the leakage current and thus improve the
spectral resolution, especially in the 10-100 keV energy range. We have
fabricated several metal-semiconductor-metal (MSM) detectors with a 4x4 array
of pixels on 10x10 mm substrates. Measurements of the detectors' leakage
current, spectral response, and temperature sensitivity are presented and
compared to IMARAD's ohmic contact detector and gold contact MSM detectors made
of High Pressure Bridgman (HPB) material. Finally, we show preliminary results
from a tiled flip-chip pixellated detector made using the IMARAD detectors.",0008275v1
1997-09-21,Microwave properties of $(Pr_xY_{1-x})Ba_2Cu_3O_{7-δ}$ : Influence of magnetic scattering,"We report measurements of the surface impedance $Z_s=R_s+iX_s$ of
$(Pr_xY_{1-x})Ba_2Cu_3O_{7-\delta}$, $(x=0,0.15,0.23,0.3,0.4,0.5)$. Increasing
$Pr$ concentration leads to some striking results not observed in samples doped
by non-magnetic constituents. The three principal features of the $R_s(T)$ data
- multiple structure in the transition, a high residual resistance and, at high
$Pr$ concentrations, an upturn of the low $T$ data, are all characteristic of
the influence of magnetic scattering on superconductivity, and appear to be
common to materials where magnetism and superconductivity coexist. The low $T$
behavior of $\lambda (T)$ appears to change from $T$ to $T^4$ at large $Pr$
doping, and provides evidence of the influence of magnetic pairbreaking of the
$Pr$.",9709232v1
1997-12-08,High frequency magneto-electrodynamics of La_(1-x)Sr_xMnO3 single crystals,"The radio frequency (RF) response of La1-xSrxMnO3 single crystals reveal a
variety of features associated with the structural, electronic and magnetic
properties of the system. The resonance technique operating at ~ 4 MHz employed
in this study is sensitive to small changes in both the magnetic susceptibility
and resistivity of the samples. Very sharp changes in frequency are observed at
the ferromagnetic (FM) and structural phase transitions in both the metallic (x
= 0.175) and insulating (0.125) crystals studied. In addition to the known
transitions identified as FM and orthorhombic distortions, our experiments show
rich structures which are not observed in conventional DC magnetization and
transport experiments. Our results demonstrate that RF experiments are ideally
suited to investigate the complex phase diagram in the manganites. The colossal
frequency change that we observe at the FM transition in the La1-xSrxMnO3
crystals is indicative of the enormous potential for using these materials in
high frequency switching applications.",9712093v1
1999-04-28,Structure and properties of a novel fulleride Sm6C60,"A novel fulleride Sm6C60 has been synthesized using high temperature solid
state reaction. The Rietveld refinement on high resolution synchrotron X-ray
powder diffraction data shows that Sm6C60 is isostructural with body-centered
cubic A6C60 (A=K, Ba). Raman spectrum of Sm6C60 is similar to that of Ba6C60,
and the frequencies of two Ag modes in Sm6C60 are nearly the same as that of
Ba6C60, suggesting that Sm is divalent and hybridization between C60 molecules
and the Sm atom could exist in Sm6C60. Resistivity measurement shows a weak
T-linear behavior above 180 K, the transport at low temperature is mainly
dominated by granular-metal theory.",9904404v1
2000-04-10,Magnetotransport study of the charged stripes in high-T_c cuprates,"We present a study of the in-plane and out-of-plane magnetoresistance (MR) in
heavily-underdoped, antiferromagnetic YBa_{2}Cu_{3}O_{6+x}, which reveals a
variety of striking features. The in-plane MR demonstrates a ""d-wave""-like
anisotropy upon rotating the magnetic field H within the ab plane. With
decreasing temperature below 20-25 K, the system acquires memory: exposing a
crystal to the magnetic field results in a persistent in-plane resistivity
anisotropy. The overall features can be explained by assuming that the CuO_2
planes contain a developed array of stripes accommodating the doped holes, and
that the MR is associated with the field-induced topological ordering of the
stripes.",0004135v1
2000-07-11,Grain boundary effects on magnetotransport in bi-epitaxial films of La$_{0.7}$Sr$_{0.3}$MnO$_3$,"The low field magnetotransport of La$_{0.7}$Sr$_{0.3}$MnO$_3$ (LSMO) films
grown on SrTiO$_3$ substrates has been investigated. A high qualtity LSMO film
exhibits anisotropic magnetoresistance (AMR) and a peak in the
magnetoresistance close to the Curie temperature of LSMO. Bi-epitaxial films
prepared using a seed layer of MgO and a buffer layer of CeO$_2$ display a
resistance dominated by grain boundaries. One film was prepared with seed and
buffer layers intact, while a second sample was prepared as a 2D square array
of grain boundaries. These films exhibit i) a low temperature tail in the low
field magnetoresistance; ii) a magnetoconductance with a constant high field
slope; and iii) a comparably large AMR effect. A model based on a two-step
tunneling process, including spin-flip tunneling, is discussed and shown to be
consistent with the experimental findings of the bi-epitaxial films.",0007194v1
2001-02-23,Temperature Dependence of Low-Lying Electronic Excitations of LaMnO_3,"We report on the optical properties of undoped single crystal LaMnO_3, the
parent compound of the colossal magneto-resistive manganites. Near-Normal
incidence reflectance measurements are reported in the frequency range of
20-50,000 cm-1 and in the temperature range 10-300 K. The optical conductivity,
s_1(w), is derived by performing a Kramers-Kronig analysis of the reflectance
data. The far-infrared spectrum of s_1(w) displays the infrared active optical
phonons. We observe a shift of several of the phonon to high frequencies as the
temperature is lowered through the Neel temperature of the sample (T_N = 137
K). The high-frequency s_1(w) is characterized by the onset of absorption near
1.5 eV. This energy has been identified as the threshold for optical
transitions across the Jahn-Teller split e_g levels. The spectral weight of
this feature increases in the low-temperature state. This implies a transfer of
spectral weight from the UV to the visible associated with the paramagnetic to
antiferromagnetic state. We discuss the results in terms of the double exchange
processes that affect the optical processes in this magnetic material.",0102437v1
2001-02-27,Anisotropic three-dimentional magnetic fluctuations in heavy fermion CeRhIn5,"CeRhIn5 is a heavy fermion antiferromagnet that orders at 3.8 K. The
observation of pressure-induced superconductivity in CeRhIn5 at a very high Tc
of 2.1 K for heavy fermion materials has led to speculations regarding to its
magnetic fluctuation spectrum. Using magnetic neutron scattering, we report
anisotropic three-dimensional antiferromagnetic fluctuations with an energy
scale of less than 1.7 meV for temperatures as high as 3Tc. In addition, the
effect of the magnetic fluctuations on electrical resistivity is well described
by the Born approximation.",0102503v1
2001-12-21,First order transition from ferromagnetism to antiferromagnetism in Ce(Fe$_{0.96}$Al$_{0.04}$)$_2$: a magnetotransport study,"The magnetotransport behaviour is investigated in detail across the first
order magnetic phase transition from ferromagnetic to antiferromagnetic state
in polycrystalline Ce(Fe$_{0.96}$Al$_{0.04}$)$_2$ sample. The study clearly
brings out various generic features associated with a first order transition,
viz., hysteresis, phase coexistence, supercooling and superheating, presence
and limits of the metastable regimes. These results of magnetotransport study
exhibit and support all the interesting thermomagnetic history effects that
were observed in our earlier dc-magnetisation study on the same sample. Most
notable here is the initial (or virgin) resistivity vs. field curve lying
outside the hysteretic ""butterfly shaped"" magnetoresistivity loops obtained on
cyclying the magnetic field between high enough positive and negative
strengths. These findings, bearing one-to-one similarity with the data obtained
in their magnetic counterpart (i.e., dc-magnetisation), have been ascribed an
origin due to the arresting of this first order transition kinetics at low
temperature and high magnetic field.",0112408v1
2002-08-07,Transport critical current densities and n factors in mono- and multifilamentary MgB2/Fe tapes and wires using fine powders,"Mono- and multifilamentary MgB2/Fe tapes and wires with high transport
critical current densities have been prepared using the powder-in-tube (PIT)
process. The fabrication details are described. The effect of powder grain
sizes and recrystallization temperature on jc has been investigated. At 25K and
1 T, jc values close to 105 A/cm2 were measured, while jc of 106 A/cm2 were
extrapolated for 4.2K/0T in our monofilamentary tape. MgB2/Fe tapes exhibit
high exponential n factors for the resistive transition: n ~ 80 and 40 were
found at 5 T and 7 T, respectively. The highest transport jc values obtained so
far in MgB2/Fe wires with 7 filaments were 1.1 * 105 A/cm2 at 4.2 K and in a
field of 2 T, which is still lower than for monofilamentary tapes. Improved
deformation and recovering processing is expected to lead to higher jc values.",0208133v1
2004-02-20,Metal-insulator transition and glassy behavior in two-dimensional electron systems,"Studies of low-frequency resistance noise demonstrate that glassy freezing
occurs in a two-dimensional electron system in silicon in the vicinity of the
metal-insulator transition (MIT). The width of the metallic glass phase, which
separates the 2D metal and the (glassy) insulator, depends strongly on
disorder, becoming extremely small in high-mobility (low-disorder) samples. The
glass transition is manifested by a sudden and dramatic slowing down of the
electron dynamics, and by a very abrupt change to the sort of statistics
characteristic of complicated multistate systems. In particular, the behavior
of the second spectrum, an important fourth-order noise statistic, indicates
the presence of long-range correlations between fluctuators in the glassy
phase, consistent with the hierarchical picture of glassy dynamics.",0402535v1
2004-04-21,Formation and Thermal Stability of sub-10 nm Carbon Templates on Si(100),"We report a lithographic process for creating high-resolution (<10 nm) carbon
templates on Si(100). A scanning electron microscope, operating under low
vacuum (10E-6 mbar), produces a carbon-containing deposit (""contamination
resist"") on the silicon surface via electron-stimulated dissociation of ambient
hydrocarbons, water and other adsorbed molecules. Subsequent annealing at
temperatures up to 1320 K in ultra-high vacuum removes SiO2 and other
contaminants, with no observable change in dot shape. The annealed structures
are compatible with subsequent growth of semiconductors and complex oxides.
Carbon dots with diameter as low as 3.5 nm are obtained with a 200 us
electron-beam exposure time.",0404505v1
2005-04-19,High temperature magnetic ordering in La2RuO5,"Magnetic susceptibility, heat capacity and electrical resistivity
measurements have been carried out on a new ruthenate, La2RuO5 (monoclinic,
space group P21/c) which reveal that this compound is a magnetic semiconductor
with a high magnetic ordering temperature of 170K. The entropy associated with
the magnetic transition is 8.3 J/mole-K -close to that expected for the low
spin (S=1) state of Ru4+ ions. The low temperatures specific heat coefficient g
is found to be nearly zero consistent with the semiconducting nature of the
compound. The magnetic ordering temperature of La2RuO5 is comparable to the
highest known Curie temperature of another ruthenate, namely, metallic SrRuO3,
and in both these compounds the nominal charge state of Ru is 4+.",0504489v1
2006-05-11,Multifilament YBa2Cu3O6+x -coated conductors with minimized coupling losses,"We report an experimental approach to making multifilament coated conductors
with low losses in applied time-varying magnetic field. Previously, the
multifilament conductors obtained for that purpose by laser ablation suffered
from high coupling losses. Here we report how this problem can be solved. When
the substrate metal in the grooves segregating the filaments is exposed to
oxygen, it forms high resistivity oxides that electrically insulate the stripes
from each other and from the substrate. As the result, the coupling loss has
become negligible over the entire range of tested parameters (magnetic field
amplitudes B and frequencies f) available to us.",0605313v1
2006-06-17,The thermally activated motion of vortex bundles and the anomalous Hall effect in type-II conventional and high-Tc superconductors,"The anomalous Hall effect in type-II conventional and high-Tc superconductors
is investigated based on the proposed novel theory of the thermally activated
motion of vortex bundles over a directional-dependent energy barrier. Our
calculations demonstrate clearly that anomalous Hall effect is induced by the
competition between the Magnus force and the random collective pinning force of
the vortex bundle. The Hall as well as the longitudinal resistivity for
constant temperature and constant applied magnetic field of type-II
superconducting films and bulk materials are calculated. The reentry phenomenon
is also investigated. All the results are in good agreement with the
experiments.",0606464v2
1999-11-30,Analysis of trap spectra in LEC and epitaxial GaAs,"Different methods of trap parameter measurement are analysed. Transient
photoconductivity and thermally stimulated effects were used to investigate the
influence of traps in LEC SI-GaAs and high resistivity epitaxial GaAs. The
peculiarities of the TSC were analysed and shown to be related to the influence
of crystal micro-inhomogeneities.",9911048v1
2006-08-25,The Effects of Preheating of a Fine Tungsten Wire and the Polarity of a High-Voltage Electrode on the Energy Characteristics of an Electrically Exploded Wire in Vacuum,"Results obtained from experimental and numerical studies of tungsten wires
electrical explosion in vacuum are presented. The experiments were performed
both with and without preheating of the wires, using positive or negative
polarity of a high-voltage electrode. Preheating is shown to increase energy
deposition in the wire core due to a longer resistive heating stage. The effect
was observed both in single wire and wire array experiments. The evolution of
the phase state of the wire material during explosion was examined by means of
one-dimensional numerical simulation using a semiempirical wide-range equation
of state describing the properties of tungsten with allowance made for melting
and vaporization.",0608251v1
2007-03-11,A low-noise ferrite magnetic shield,"Ferrite materials provide magnetic shielding performance similar to commonly
used high permeability metals but have lower intrinsic magnetic noise generated
by thermal Johnson currents due to their high electrical resistivity.
Measurements inside a ferrite shield with a spin-exchange relaxation-free
atomic magnetometer reveal a noise level of 0.75 fT Hz^(-1/2), 25 times lower
than what would be expected in a comparable mu-metal shield. The authors
identify a 1/f component of the magnetic noise due to magnetization
fluctuations and derive general relationships for the Johnson current noise and
magnetization noise in cylindrical ferromagnetic shields in terms of their
conductivity and complex magnetic permeability.",0703115v2
2007-08-14,The zero-energy state in graphene in a high magnetic field,"The fate of the charge-neutral Dirac point in graphene in a high magnetic
field $H$ has been investigated at low temperatures ($T\sim$ 0.3 K). In samples
with small $V_0$ (the gate voltage needed to access the Dirac point), the
resistance $R_0$ at the Dirac point diverges steeply with $H$, signalling a
crossover to an insulating state in intense field. The approach to the
insulating state is highly unusual. Despite the steep divergence in $R_0$, the
profile of $R_0$ vs. $T$ in fixed $H$ saturates to a $T$-independent value
below 2 K, consistent with charge carrying gapless excitations.",0708.1959v2
2008-03-25,Superconductivity at 43 K in Samarium-arsenide Oxides $SmFeAsO_{1-x}F_x$,"Since the discovery of high-transition temperature ($T_c$) superconductivity
in layered copper oxides, extensive efforts have been devoted to explore the
higher $T_c$ superconductivity. However, the $T_c$ higher than 40 K can be
obtained only in the copper oxide superconductors so far. The highest reported
value of $T_c$ for non-copper-oxide bulk superconductivity is 39 K in
$MgB_2$.\cite{jun} The $T_c$ of about 40 K is close to or above the theoretical
value predicted from BCS theory.\cite{mcmillan} Therefore, it is very
significant to search for non-copper oxide superconductor with the transition
temperature higher than 40 K to understand the mechanism of high-$T_c$
superconductivity. Here we report the discovery of bulk superconductivity in
samarium-arsenide oxides $SmFeAsO_{1-x}F_x$ with ZrCuAiAs type structure.
Resistivity and magnetization measurements show strong evidences for transition
temperature as high as 43 K. $SmFeAsO_{1-x}F_x$ is the first non-copper oxide
superconductor with $T_c$ higher than 40 K. The $T_c$ higher than 40 K may be a
strong argument to consider $SmFeAsO_{1-x}F_x$ as an unconventional
superconductor.",0803.3603v2
2008-04-21,CeFePO: A Heavy Fermion Metal with Ferromagnetic Correlations,"The ground state properties of CeFePO, a homologue of the new high
temperature superconductors RFePnO(1-x)Fx, were studied by means of
susceptibility, specific heat, resistivity, and NMR measurements on
polycrystals. All the results demonstrate that this compound is a magnetically
non-ordered heavy Fermion metal with a Kondo temperature TK~10K, a Sommerfeld
coefficient gamma=700mJ/molK2 and a mass enhancement factor of the order of
200. The absence of a Fe-contribution to the effective moment at high
temperatures indicates that the magnetism in CeFePO is completely dominated by
the effect of Ce. Thus the strong electronic correlation effects originate from
the Ce-4f electrons rather than from the Fe-3d electrons. An enhanced
Sommerfeld-Wilson ratio R=5.5 as well as a Korringa product S0/T1TK2~0.065 well
below 1 indicate the presence of ferromagnetic correlations. Therefore, CeFePO
appears to be on the non-magnetic side of a ferromagnetic instability.",0804.3250v2
2008-07-05,"Growth and characterization of A_{1-x}K_xFe_2As_2 (A = Ba, Sr) single crystals with x=0 - 0.4","Single crystals of A$_{1-x}$K$_x$Fe$_2$As$_2$ (A=Ba, Sr) with high quality
have been grown successfully by FeAs self-flux method. The samples have sizes
up to 4 mm with flat and shiny surfaces. The X-ray diffraction patterns suggest
that they have high crystalline quality and c-axis orientation. The
non-superconducting crystals show a spin-density-wave (SDW) instability at
about 173 K and 135 K for Sr-based and Ba-based compound, respectively. After
doping K as the hole dopant into the BaFe$_2$As$_2$ system, the SDW transition
is smeared, and superconducting samples with the compound of
Ba$_{1-x}$K$_x$Fe$_2$As$_2$ (0 $< x \leqslant$ 0.4) are obtained. The
superconductors characterized by AC susceptibility and resistivity measurements
exhibit very sharp superconducting transition at about 36 K, 32 K, 27 K and 23
K for x= 0.40,0.28,0.25 and 0.23, respectively.",0807.0759v3
2008-08-18,A Ni-based Superconductor: the Heusler Compound ZrNi$_2$Ga,"This work reports on the novel Heusler superconductor ZrNi2Ga. Compared to
other nickel-based superconductors with Heusler structure, ZrNi2Ga exhibits a
relatively high superconducting transition temperature of Tc=2.9 K and an upper
critical field of 1.5 T. Electronic structure calculations show that this
relatively high transition temperature is caused by a van Hove singularity,
which leads to an enhanced density of states at the Fermi energy. The van Hove
singularity originates from a higher order valence instability at the L-point
in the electronic structure. The enhanced density of states at the Fermi level
was confirmed by specific heat and susceptibility measurements. Although many
Heusler compounds are ferromagnetic, our measurements of ZrNi2Ga indicate a
paramagnetic state above Tc and could not reveal any traces of magnetic order
down to temperatures of at least 0.35 K. We investigated in detail the
superconducting state with specific heat, magnetization, and resistivity
measurements. The resulting data show the typical behavior of a conventional,
weakly coupled BCS (s-wave) superconductor.",0808.2356v1
2008-10-03,"Small anisotropy, weak thermal fluctuations, and high field superconductivity in Co-doped iron pnictide Ba(Fe1-xCox)2As2","We performed high-field magnetotransport and magnetization measurements on a
single crystal of the 122-phase iron pnictide Ba(Fe1-xCox)2As2. Unlike the HTS
cuprates and 1111-phase oxypnictides, Ba(Fe1-xCox)2As2 showed practically no
broadening of the resistive transitions under magnetic fields up to 45 T. The
mass anisotropy gamma = Hc2ab/Hc2c deduced from the slopes of the upper
critical field dHc2ab/dT = 4.9T/K and dHc2c/dT = 2.5T/K decreases from ~2 near
Tc, to ~1.5 at lower temperatures. We observed the irreversibility field close
to Hc2, and a rather unusual symmetric volume pinning force curve Fp(H)
suggestive of strong pinning nano-structure.",0810.0699v2
2009-05-01,Highly segmented thin microstrip detector with data-driven fast readout,"In September 2008 the Slim5 collaboration submitted a low material budget
silicon demonstrator to test with 12 GeV/c protons, at the PS-T9 test-beam at
CERN. Inside the reference telescope, two different detectors were placed as
device under test (DUT). The first was a 4k-Pixel Matrix of Deep N Well MAPS,
developed in a 130 nm CMOS Technology, providing digital sparsified readout.
The other one was a high resistivity double sided silicon detector, with short
strips at 45-degree angle to the detector's edge, read out by the FSSR2 chip.
The FSSR2 is a 128 channel data-driven fast readout chip developed by Fermilab
and INFN. In this paper we describe the main features of latter sensor, the
striplet. The primary goal of the test was to measure the efficiency and the
resolution of the striplets. The data-driven approach of the FSSR2 readout
chips has been fully exploited by the DAQ system.",0905.0083v3
2009-10-08,Structural and transport properties of Sr2VO{3-delta}FeAs superconductors with different oxygen deficiencies,"Sr2VO{3-delta}FeAs superconductors with different oxygen deficiencies have
been successfully fabricated. It is found that the superconducting transition
temperature drops down monotonically with the increase of oxygen deficiency.
The diminishing of superconductivity is accompanied by the enhancement of
residual resistivity, indicating an unraveled scattering effect induced by the
oxygen deficiency. The highest superconducting transition temperature at about
40 K is achieved near the stoichiometrical sample Sr$_2$VO$_{3}$FeAs.
Surprisingly, the X-ray photoelectron spectroscopy (XPS) shows that the
vanadium has a ""5+"" valence state in the samples. The Hall effect measurements
reveal that the density of charge carriers (electron-like here) varies
qualitatively with the increase of oxygen deficiency. Magnetotransport
measurements show that the superconducting transition changes from
one-step-like shape at low fields to two-step-like one at high fields,
indicating a high anisotropy.",0910.1537v2
2010-04-22,Optimizing Transistor Performance of Percolating Carbon Nanotube Networks,"In percolating networks of mixed metallic and semiconducting CNTs, there is a
tradeoff between high on-current (dense networks) and high on/off ratio (sparse
networks in which the metallic CNT fraction is not percolating). Experiments on
devices in a transistor configuration and Monte Carlo simulations were
performed to determine the scaling behavior of device resistivity as a function
of channel length (L) for CNT density p in the range 0.04 - 1.29 CNT/{\mu}m^2
in the on- and off-states. Optimized devices with field-effect mobility up to
50 cm^2/Vs at on/off ratio > 10^3 were obtained at W = 50 {\mu}m, L > 70 {\mu}m
for p = 0.54 - 0.81 CNTs/{\mu}m^2.",1004.4009v1
2010-06-25,Spin and charge dynamics in [TbPc$_2$]$^0$ and [DyPc$_2$]$^0$ single molecule magnets,"Magnetization, AC susceptibility and $\mu$SR measurements have been performed
in neutral phthalocyaninato lanthanide ([LnPc$_2]^0$) single molecule magnets
in order to determine the low-energy levels structure and to compare the
low-frequency spin excitations probed by means of macroscopic techniques, such
as AC susceptibility, with the ones explored by means of techniques of
microscopic character, such as $\mu$SR. Both techniques show a high temperature
thermally activated regime for the spin dynamics and a low temperature
tunneling one. While in the activated regime the correlation times for the spin
fluctuations estimated by AC susceptibility and $\mu$SR basically agree, clear
discrepancies are found in the tunneling regime. In particular, $\mu$SR probes
a faster dynamics with respect to AC susceptibility. It is argued that the
tunneling dynamics probed by $\mu$SR involves fluctuations which do not yield a
net change in the macroscopic magnetization probed by AC susceptibiliy. Finally
resistivity measurements in [TbPc$_2]^0$ crystals show a high temperature
nearly metallic behaviour and a low temperature activated behaviour.",1006.4919v1
2010-09-17,Graphene Transport at High Carrier Densities using a Polymer Electrolyte Gate,"We report the study of graphene devices in Hall-bar geometry, gated with a
polymer electrolyte. High densities of 6 $\times 10^{13}/cm^{2}$ are
consistently reached, significantly higher than with conventional back-gating.
The mobility follows an inverse dependence on density, which can be correlated
to a dominant scattering from weak scatterers. Furthermore, our measurements
show a Bloch-Gr\""uneisen regime until 100 K (at 6.2 $\times10^{13}/cm^{2}$),
consistent with an increase of the density. Ubiquitous in our experiments is a
small upturn in resistivity around 3 $\times10^{13}/cm^{2}$, whose origin is
discussed. We identify two potential causes for the upturn: the renormalization
of Fermi velocity and an electrochemically-enhanced scattering rate.",1009.3367v2
2010-10-28,Poole-Frenkel Effect and Phonon-Assisted Tunneling in GaAs Nanowires,"We present electronic transport measurements of GaAs nanowires grown by
catalyst-free metal-organic chemical vapor deposition. Despite the nanowires
being doped with a relatively high concentration of substitutional impurities,
we find them inordinately resistive. By measuring sufficiently high
aspect-ratio nanowires individually in situ, we decouple the role of the
contacts and show that this semi-insulating electrical behavior is the result
of trap-mediated carrier transport. We observe Poole-Frenkel transport that
crosses over to phonon-assisted tunneling at higher fields, with a tunneling
time found to depend predominantly on fundamental physical constants as
predicted by theory. By using in situ electron beam irradiation of individual
nanowires we probe the nanowire electronic transport when free carriers are
made available, thus revealing the nature of the contacts.",1010.6086v1
2010-11-23,NaIrO3 - A pentavalent post-perovskite,"Sodium iridium(V) oxide, NaIrO3, was synthesized by a high pressure solid
state method and recovered to ambient conditions. It is found to be
isostructural with CaIrO3, the much-studied structural analogue of the
high-pressure post-perovskite phase of MgSiO3. Among the oxide
post-perovskites, NaIrO3 is the first example with a pentavalent cation. The
structure consists of layers of corner- and edge-sharing IrO6 octahedra
separated by layers of NaO8 bicapped trigonal prisms. NaIrO3 shows no magnetic
ordering and resistivity measurements show non-metallic behavior. The crystal
structure, electrical and magnetic properties are discussed and compared to
known post-perovskites and pentavalent perovskite metal oxides.",1011.5125v2
2010-12-11,Transport Spin Polarization of High-Curie Temperature MnBi Films,"We report on the study of the structural, magnetic and transport properties
of highly textured MnBi films with the Curie temperature of 628K. In addition
to detailed measurements of resistivity and magnetization, we measure transport
spin polarization of MnBi by Andreev reflection spectroscopy and perform fully
relativistic band structure calculations of MnBi. A spin polarization from
51\pm1 to 63\pm1% is observed, consistent with the calculations and with an
observation of a large magnetoresistance in MnBi contacts. The band structure
calculations indicate that, in spite of almost identical densities of states at
the Fermi energy, the large disparity in the Fermi velocities leads to high
transport spin polarization of MnBi. The correlation between the values of
magnetization and spin polarization is discussed.",1012.2486v1
2011-10-06,High-Precision Tuning of State for Memristive Devices by Adaptable Variation-Tolerant Algorithm,"Using memristive properties common for the titanium dioxide thin film
devices, we designed a simple write algorithm to tune device conductance at a
specific bias point to 1% relative accuracy (which is roughly equivalent to
7-bit precision) within its dynamic range even in the presence of large
variations in switching behavior. The high precision state is nonvolatile and
the results are likely to be sustained for nanoscale memristive devices because
of the inherent filamentary nature of the resistive switching. The proposed
functionality of memristive devices is especially attractive for analog
computing with low precision data. As one representative example we demonstrate
hybrid circuitry consisting of CMOS summing amplifier and two memristive
devices to perform analog multiply and accumulate computation, which is a
typical bottleneck operation in information processing.",1110.1393v1
2011-10-19,Evaluating the robustness of top coatings comprising plasma-deposited fluorocarbons in electrowetting systems,"Thin dielectric stacks comprising a main insulating layer and a hydrophobic
top coating are commonly used in low voltage electrowetting systems. However,
in most cases, thin dielectrics fail to endure persistent electrowetting
testing at high voltages, namely beyond the saturation onset, as electrolysis
indicates dielectric failure. Careful sample inspection via optical microscopy
revealed possible local delamination of the top coating under high electric
fields. Thus, improvement of the adhesion strength of the hydrophobic top
coating to the main dielectric is attempted through a plasma-deposited
fluorocarbon interlayer. Interestingly enough the proposed dielectric stack
exhibited a) resistance to dielectric breakdown, b) higher contact angle
modulation range, and c) electrowetting cycle reversibility. Appearance of
electrolysis in the saturation regime is inhibited, suggesting the use of this
hydrophobic dielectric stack for the design of more efficient electrowetting
systems. The possible causes of the improved performance are investigated by
nanoscratch characterization.",1110.4238v1
2011-10-21,P-T phase diagram of iron arsenide superconductor NdFeAsO0.88F0.12,"NdFeAsO0.88F0.12 belongs to the recently discovered family of high-TC
iron-based superconductors. The influence of high pressure on transport
properties of this material has been studied. Contrary to La-based compounds,
we did not observe a maximum in TC under pressure. Under compression, TC drops
rapidly as a linear function of pressure with the slope k = -2.8 \pm 0.1 K /
GPa. The extrapolated value of TC at zero pressure is about TC (0) = 51.7 \pm
0.4 K. At pressures higher than ~18.4 GPa, the superconducting state disappears
at all measured temperatures. The resistance changes slope and shows a turn-up
behavior, which may be related to the Kondo effect or a weak localization of
two-dimensional carriers below ~45 K that is above TC and thus competing with
the superconducting phase. The behavior of the sample is completely reversible
at the decompression. On the bases of our experimental data, we propose a
tentative P-T phase diagram of NdFeAsO0.88F0.12.",1110.4909v1
2011-11-20,Flame Synthesis of Graphene Films in Open Environments,"Few-layer graphene (FLG) is grown on copper and nickel substrates at high
rates using a novel flame synthesis method in open-atmosphere environments.
Transmittance and resistance properties of the transferred films are similar to
those grown by other methods, but the concentration of oxygen, as assessed by
XPS, is actually less than that for CVD-grown graphene under near vacuum
conditions. The method involves utilizing a multi-element
inverse-diffusion-flame burner, where post-flame species and temperatures are
radially-uniform upon deposition at a substrate. Advantages of the flame
synthesis method are scalability for large-area surface coverage, increased
growth rates, high purity and yield, continuous processing, and reduced costs
due to efficient use of fuel as both heat source and reagent. Additionally, by
adjusting local growth conditions, other carbon nanostructures (i.e. nanotubes)
are readily synthesized.",1111.4699v1
2012-07-25,Conductivity crossover in nano-crystalline diamond films: Realization of a disordered superlattice-like structure,"We present the electrical transport characteristics of a batch of
nano-crystalline diamond films of varying nitrogen concentrations and explain
the conduction mechanism by the disordered quasi-superlattice model applied to
semiconductor heterostructures. Synthesized by the hot filament chemical vapour
deposition technique, the degree of structural disorder in the films, confirmed
from Raman spectroscopy, is found to be controllable, resulting in the
transition of conduction mechanism from localized and activated to the metallic
conduction regime. Hence through high field magneto-resistance measurements at
low temperatures we firmly establish a conductivity crossover from hopping to
3D weak localization. The long electronic dephasing time and its weak
temperature dependence suggest the possibility for diamond-based high-speed
device applications.",1207.5916v1
2012-10-23,Impact of the various spin and orbital ordering processes on multiferroic properties of orthovanadate DyVO3,"The orthovanadate DyVO3 crystal, known to exhibit multiple structural, spin
and orbital ordering transitions, is presently investigated on the basis of
magnetization, heat capacity, resistivity, dielectric and polarization
measurements. Our main result is experimental evidence for the existence of
multiferroicity below a high TC of 108 K over a wide temperature range
including different spin-orbital ordered states. The onset of ferroelectricity
is found to coincide with the antiferromagnetic C-type spin ordering transition
taking place at 108 K, which indicates that DyVO3 belongs to type II
multiferroics exhibiting a coupling between magnetism and ferroelectricity.
Some anomalies detected on the temperature dependence of electric polarization
are discussed with respect to the nature of the spin-orbital ordered states of
the V sublattice and the degree of spin alignment in the Dy sublattice. The
orthovanadates RVO3 (R = rare earth or Y) form an important new category for
searching for high-TC multiferroics.",1210.6373v3
2013-04-04,Atomic Calligraphy: The Direct Writing of Nanoscale Structures using MEMS,"We present a micro-electromechanical system (MEMS) based method for the
resist free patterning of nano-structures. Using a focused ion beam (FIB) to
customize larger MEMS machines, we fabricate apertures as small as 50 nm on
plates that can be moved with nanometer precision over an area greater than
20x20 {\mu}m^2. Depositing thermally evaporated gold atoms though the apertures
while moving the plate results in the deposition of nanoscale metal patterns.
Adding a shutter only microns above the aperture, enables high speed control of
not only where but also when atoms are deposited. Using a shutter, different
sized apertures can be selectively opened and closed for nano-structure
fabrication with features ranging from nano- to micrometers in scale. The
ability to evaporate materials with high precision, and thereby fabricate
circuits and structures in situ, enables new kinds of experiments based on the
interactions of a small number of atoms and eventually even single atoms.",1304.1334v1
2013-04-04,Substrate-Independent Catalyst-Free Synthesis of High-Purity Bi2Se3 Nanostructures,"We describe a catalyst-free vapor-solid synthesis of bismuth selenide
(Bi2Se3) nanostructures at ambient pressure with hydrogen as a carrier gas. The
nanostructures were synthesized on glass, silicon and mica substrates and the
method yields a variety of nanostructures: nanowires, nanoribbons,
nanoplatelets and nanoflakes. The materials analysis shows high chemical purity
in all cases, without sacrificing the crystalline structure of Bi2Se3.
Low-temperature measurements of the nanostructures indicate contributions from
the surface states with a tunable carrier density. Samples synthesized on
flexible mica substrates show no significant change in resistance upon bending,
indicating robustness of as-grown Bi2Se3 nanostructures and their suitability
for device applications.",1304.1388v1
2013-07-14,Voltage-triggered Ultra-fast Metal-insulator Transition in Vanadium Dioxide Switches,"Electrically driven metal-insulator transition in vanadium dioxide (VO2) is
of interest in emerging memory devices, neural computation, and high speed
electronics. We report on the fabrication of out-of-plane VO2
metal-insulator-metal (MIM) structures and reproducible high-speed switching
measurements in these two-terminal devices. We have observed a clear
correlation between electrically-driven ON/OFF current ratio and
thermally-induced resistance change during metal-insulator transition. It is
also found that sharp metal-insulator transition could be triggered by external
voltage pulses within 2 ns at room temperature and the achieved ON/OFF ratio is
greater than two orders of magnitude with good endurance.",1307.3774v1
2013-07-17,Dielectric Coatings for IACT Mirrors,"Imaging Atmospheric Cherenkov Telescopes for very-high energy gamma-ray
astronomy need mirror with high reflectance roughly in the wavelength between
300 and 550 nm. The current standard reflective layer of such mirrors is
aluminum. Being permanently exposed to the environment they show a constant
degradation over the years. New and improved dielectric coatings have been
developed to enhance their resistance to environmental impact and to extend
their possible lifetime. In addition, these customized coatings have an
increased reflectance of over 95% and are designed to significantly lower the
night-sky background contribution. The development of such coatings for mirrors
with areas up to 2 m2 and low application temperatures to suite the composite
materials used for the new mirror susbtrates of the Cherenkov Telescope Array
(CTA) and the results of extensive durability tests are presented.",1307.4557v1
2013-08-14,Perspectives of Micro-Pattern Gaseous Detector Technologies for Future Physics Projects,"A centenary after the invention of the basic principle of gas amplification,
gaseous detectors - are still the first choice whenever the large area coverage
with low material budget is required. Advances in photo-lithography and
micro-processing techniques in the chip industry during the past two decades
triggered a major transition in the field of gas detectors from wire structures
to Micro-Pattern Gas Detector (MPGD) concepts, revolutionizing cell-size
limitations for many gas detector applications. The high radiation resistance
and excellent spatial and time resolution make them an invaluable tool to
confront future detector challenges at the frontiers of research. The design of
the new micro-pattern devices appears suitable for industrial production. In
2008, the RD51 collaboration at CERN has been established to further advance
technological developments of MPGDs and associated electronic-readout systems,
for applications in basic and applied research. This review provides an
overview of the state-of-the-art of the MPGD technologies and summarizes recent
activities for the next generation of colliders within the framework of the
RD51 collaboration.",1308.3047v2
2013-08-18,Pulsed Laser Deposition of High-Quality Thin Films of the Insulating Ferromagnet EuS,"High-quality thin films of the ferromagnetic-insulator europium(II) sulfide
(EuS) were fabricated by pulsed laser deposition on Al2O3 (0001) and Si (100)
substrates. A single orientation was obtained with the [100] planes parallel to
the substrates, with atomic-scale smoothness indicates a near-ideal surface
topography. The films exhibit uniform ferromagnetism below 15.9 K, with a
substantial component of the magnetization perpendicular to the plane of the
films. Optimization of the growth condition also yielded truly insulating films
with immeasurably large resistance. This combination of magnetic and electric
properties open the gate for novel devices that require a true ferromagnetic
insulator.",1308.3820v2
2014-02-19,Monte Carlo Simulation of RPC-based PET with GEANT4,"The Resistive Plate Chambers (RPC) are low-cost charged-particle detectors
with good timing resolution and potentially good spatial resolution. Using RPC
as gamma detector provides an opportunity for application in positron emission
tomography (PET). In this work, we use GEANT4 simulation package to study
various methods improving the detection efficiency of a realistic RPC-based PET
model for 511keV photons, by adding more detection units, changing the
thickness of each layer, choosing different converters and using multi-gaps RPC
(MRPC) technique. Proper balance among these factors are discussed. It's found
that although RPC with materials of high atomic number can reach a higher
efficiency, they may contribute to a poor spatial resolution and higher
background level.",1402.4544v1
2014-03-04,Molecular weight dependent bimolecular recombination in organic solar cells,"Charge carrier recombination is studied in operational organic solar cells
made from the polymer:fullerene system PCDTBT:PC71BM
(poly[N-9""-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]
: [6,6]-phenyl-C$_{70}$-butyric acid methyl ester). A newly developed technique
High Intensity Resistance dependent PhotoVoltage (HI-RPV) is presented for
reliably quantifying the bimolecular recombination coefficient independently of
variations in experimental conditions, thereby resolving key limitations of
previous experimental approaches. Experiments are performed on solar cells of
varying thicknesses and varying polymeric molecular weights. It is shown that
solar cells made from low molecular weight PCDTBT exhibit Langevin
recombination, whereas suppressed (non-Langevin) recombination is found in
solar cells made with high molecular weight PCDTBT.",1403.0972v2
2015-01-27,Transition from semiconducting to metallic-like conducting and weak antilocalization effect in single crystals of LuPtSb,"High quality half-Heusler single crystals of LuPtSb have been synthesized by
a Pb flux method. The temperature dependent resistivity and Hall effects
indicate that the LuPtSb crystal is a p-type gapless semiconductor showing a
transition from semiconducting to metallic conducting at 150 K. Moreover, a
weakly temperature-dependent positive magnetoresistance (MR) as large as 109 %
and high carrier mobility up to 2950 cm2/Vs are experimentally observed at
temperatures below 150 K. The low-field MR data shows evidence for weak
antilocalization (WAL) effect at temperatures even up to 150 K. Analysis of the
temperature and angle dependent magnetoconductance manifests that the WAL
effect originates from the bulk contribution owing to the strong spin-orbital
coupling.",1501.06714v1
2015-05-22,Synthesis of monoclinic IrTe2 under high pressure and its physical properties,"In a pressure-temperature (P-T) diagram for synthesizing IrTe2 compounds, the
well-studied trigonal (H) phase with the CdI2-type structure is stable at low
pressures. The superconducting cubic (C) phase can be synthesized under higher
temperatures and pressures. A rhombohedral phase with the crystal structure
similar to the C phase can be made at ambient pressure; but the phase contains
a high concentration of Ir deficiency. In this paper, we report that a rarely
studied monoclinic (M) phase can be stabilized in narrow ranges of pressure and
temperature in this P-T diagram. The peculiar crystal structure of the M-IrTe2
eliminates the tendency to form Ir-Ir dimers found in the H phase. The M phase
has been fully characterized by structural determination and measurements of
electrical resistivity, thermoelectric power, DC magnetization, and specific
heat. These physical properties have been compared with those in the H and C
phases of Ir1-xTe2. Moreover, magnetic and transport properties and specific
heat of the M-IrTe2 can be fully justified by calculations with the
density-functional theory presented in this paper.",1505.06124v1
2015-08-12,Direct Observation of Re-entrant Multiferroic CuO at High Pressures,"We have carried out a detailed experimental investigation on CuO using
dielectric constant, ac resistance, Raman spectroscopy and X-ray diffraction
measurements at high pressures and room temperature. Both dielectric constant
and dielectric loss show an anomalous peak in the pressure range 3.4-4 GPa
indicating a ferroelectric transition. Raman studies show anomalous behaviour
of the Ag mode with a slope change in the mode frequency and a minimum in the
mode FWHM at 3.4 GPa indicating a strong spin phonon coupling along [1 0 -1]
direction. A step like behaviour in the intensity of the Ag mode is observed at
3.4 GPa, indicating a change in the polarization of the mode. A maximum in the
intensity of (2,0,-2)Bragg peak at 3.4 GPa points the occurrence of critical
scattering due to emergence of magnetic exchange interaction. All our
experimental evidences show to the presence of re-entrant type-II multiferroic
behaviour in CuO at about 4 GPa.",1508.02874v1
2015-10-21,Titanium Nitride as a Seed Layer for Heusler Compounds,"Titanium nitride (TiN) shows low resistivity at room temperature, high
thermal stability and thus has the potential to serve as seed layer in magnetic
tunnel junctions. High quality TiN thin films with regard to the
crystallographic and electrical properties were grown and characterized by
X-ray diffraction and 4-terminal transport measurements. Element specific X-ray
absorption spectroscopy revealed pure TiN in the bulk. To investigate the
influence of a TiN seed layer on a ferro(i)magnetic bottom electrode, an
out-of-plane magnetized Mn2.45Ga as well as in- and out-of-plane magnetized
Co2FeAl thin films were deposited on a TiN buffer, respectively. The magnetic
properties were investigated using a superconducting quantum interference
device (SQUID) and anomalous Hall effect (AHE) for Mn2.45Ga. Magneto optical
Kerr effect (MOKE) measurements were carried out to investigate the magnetic
properties of Co2FeAl. TiN buffered Mn2.45Ga thin films showed higher
coercivity and squareness ratio compared to unbuffered samples. The Heusler
compound Co2FeAl showed already good crystallinity when grown at room
temperature.",1510.06256v3
2016-04-19,Insulating and metallic spin glass in K$_{x}$Fe$_{2-δ-y}$Ni$_{y}$Se$_{2}$ (0.06 $\leq$ $y$ $\leq$ 1.44) single crystals,"We report electron doping effects by Ni in
K$_{x}$Fe$_{2-\delta-y}$Ni$_{y}$Se$_{2}$ (0.06 $\leq$ $y$ $\leq$ 1.44) single
crystal alloys. A rich ground state phase diagram is observed. Small amount of
Ni ($\sim$ 4\%) suppressed superconductivity below 1.8 K, inducing insulating
spin glass magnetic ground state for higher Ni content. With further Ni
substitution, metallic resistivity is restored. For high Ni concentration in
the lattice the unit cell symmetry is high symmetry $I4/mmm$ with no phase
separation whereas both $I4/m + I4/mmm$ space groups were detected in the phase
separated crystals when concentration of Ni $<$ Fe. The absence of
superconductivity coincides with the absence of crystalline Fe vacancy order.",1604.05713v1
2016-05-16,Growth and characterization of CaFe$_{1-x}$Co$_x$AsF single crystals by CaAs flux method,"Millimeter sized single crystals of CaFe$_{1-x}$Co$_x$AsF were grown using a
self-flux method. It is found that high-quality single crystals can be grown
from three approaches with different initial raw materials. The chemical
compositions and crystal structure were characterized carefully. The c-axis
lattice constant is suppressed by the Co substitution. Superconductivity with
the critical transition $T_c$ as high as 21 K was confirmed by both the
resistivity and magnetic susceptibility measurements in the sample with $x$ =
0.12. Moreover, it is found that $T_c$ can be enhanced for about 1 K under the
very small hydrostatic pressure of 0.22 GPa, which is more quickly than that
reported in the polycrystalline samples. Our results is a promotion for the
physical investigations of 1111 phase iron-pnictide superconductors.",1605.04642v1
2016-06-02,High Current Density 2D/3D Esaki Tunnel Diodes,"The integration of two-dimensional materials such as transition metal
dichalcogenides with bulk semiconductors offer interesting opportunities for
2D/3D heterojunction-based novel device structures without any constraints of
lattice matching. By exploiting the favorable band alignment at the GaN/MoS2
heterojunction, an Esaki interband tunnel diode is demonstrated by transferring
large area, Nb-doped, p-type MoS2 onto heavily n-doped GaN. A peak current
density of 446 A/cm2 with repeatable room temperature negative differential
resistance, peak to valley current ratio of 1.2, and minimal hysteresis was
measured in the MoS2/GaN non-epitaxial tunnel diode. A high current density of
1 kA/cm2 was measured in the Zener mode (reverse bias) at -1 V bias. The
GaN/MoS2 tunnel junction was also modeled by treating MoS2 as a bulk
semiconductor, and the electrostatics at the 2D/3D interface was found to be
crucial in explaining the experimentally observed device characteristics.",1606.00509v1
2016-06-24,Thermal insulator transition induced by interface scattering,"We develop an effective medium model of thermal conductivity that accounts
for both percolation and interface scattering. This model accurately explains
the measured increase and decrease of thermal conductivity with loading in
composites dominated by percolation and interface scattering, respectively. Our
model further predicts that strong interface scattering leads to a sharp
decrease in thermal conductivity, or an insulator transition, at high loadings
when conduction through the matrix is restricted and heat is forced to diffuse
through particles with large interface resistance. The accuracy of our model
and its ability to predict transitions between insulating and conducting states
suggest it can be a useful tool for designing materials with low or high
thermal conductivity for a variety of applications.",1606.07851v2
2016-06-29,Large linear magnetoresistance from neutral defects in Bi$_2$Se$_3$,"The chalcogenide Bi$_2$Se$_3$ can attain the three dimensional (3D) Dirac
semimetal state under the influence of strain and microstrain. Here we report
the presnece of large linear magnetoresistance in such a Bi$_2$Se$_3$ crystal.
The magnetoresistance has quadratic form at low fields which crossovers to
linear above 4 T. The temperature dependence of magnetoresistance scales with
carrier mobility and the crossover field scales with inverse of mobility. Our
analysis suggest that the linear magnetoresistance in our system has a
classical origin and arises from the scattering of high mobility 3D Dirac
electrons from crystalline inhomogeneities. We observe that the charged
selenium vacancies are strongly screened by high mobility Dirac electrons and
the neutral crystalline defects are the main scattering center for transport
mechanism. Our analysis suggests that both the resistivity and the
magnetoresistance have their origin in scattering of charge carriers from
neutral defects.",1606.09059v1
2016-10-03,Thallium under extreme compression,"We present a combined theoretical and experimental study of the high-pressure
behavior of thallium. X-ray diffraction experiments have been carried out at
room temperature up to 125 GPa using diamond-anvil cells, nearly doubling the
pressure range of previous experiments. We have confirmed the hcp-fcc
transition at 3.5 GPa and determined that the fcc structure remains stable up
to the highest pressure attained in the experiments. In addition, HP-HT
experiments have been performed up to 8 GPa and 700 K by using a combination of
x-ray diffraction and a resistively heated diamond-anvil cell. Information on
the phase boundaries is obtained, as well as crystallographic information on
the HT bcc phase. The equation of state for different phases is reported. Ab
initio calculations have also been carried out considering several potential
high-pressure structures. They are consistent with the experimental results and
predict that, among the structures considered in the calculations, the fcc
structure of thallium is stable up to 4.3 TPa. Calculations also predict the
post-fcc phase to have a close-packed orthorhombic structure above 4.3 TPa.",1610.00435v1
2016-10-19,Applications and non-idealities of submicron Al-AlOx-Nb tunnel junctions,"We have developed a technique to fabricate sub-micron, 0.6 um x 0.6 um
Al-AlOx-Nb tunnel junctions using a standard e-beam resist, angle evaporation
and double oxidation of the tunneling barrier, resulting in high quality
niobium, as determined by the the high measured values of the critical
temperature TC 7.5 K and the gap 1.3 meV. The devices show great promise for
local nanoscale thermometry in the temperature range 1 - 7.5 K. Electrical
characterization of the junctions was performed at sub-Kelvin temperatures both
with and without an external magnetic field, which was used to suppress
superconductivity in Al and thus bring the junction into a
normal-metal-insulator-superconductor (NIS) configuration. We observed excess
sub-gap current, which could not be explained by the standard tunneling theory.
Evidence points towards materials science issues of the barrier or Nb/AlOx
interface as the culprit.",1610.05903v1
2017-06-28,Super-Hydrophobic Stearic Acid Layer Formed on Anodized High Purified Magnesium for Improving Corrosion Resistance of Biodegradable Implants,"Magnesium and its alloys are ideal candidates for biodegradable implants.
However, they can dissolve too rapidly in the human body for most applications.
In this research, high purified magnesium (HP-Mg) was coated with stearic acid
in order to slow the corrosion rate of magnesium in simulated body fluid at
37{\deg}C. HP-Mg was anodized to form an oxide/hydroxide layer, then it was
immersed in a stearic acid solution. Electrochemical impedance spectroscopy and
potentiodynamic polarization were used to estimate the corrosion rate of HP-Mg
specimens. The results confirm that the hydrophobic coating can temporarily
decrease the corrosion rate of HP-Mg by 1000x.",1706.09508v1
2017-10-19,Design of high-strength refractory complex solid-solution alloys,"Nickel-based superalloys and near-equiatomic high-entropy alloys containing
Molybdenum are known for higher temperature strength and corrosion resistance.
Yet, complex solid-solution alloys offer a huge design space to tune for
optimal properties at slightly reduced entropy. For refractory Mo-W-Ta-Ti-Zr,
we showcase KKR electronic-structure methods via the coherent-potential
approximation to identify alloys over 5-dimensional design space with improved
mechanical properties and necessary global (formation enthalpy) and local
(short-range order) stability. Deformation is modeled with classical molecular
dynamic simulations, validated from our first-principles data. We predict
complex solid-solution alloys of improved stability with greatly enhanced
modulus of elasticity ($3\times$ at 300 K) over near-equiatomic cases, as
validated experimentally, and with higher moduli above 500~K over commercial
alloys ($2.3\times$ at 2000 K). We also show that optimal complex
solid-solution alloys are not described well by classical potentials due to
critical electronic effects.",1710.06983v2
2017-11-16,Superconductivity at 7.3 K in the 133-type Cr-based RbCr3As3 single crystals,"Here we report the preparation and superconductivity of the 133-type Cr-based
quasi-one-dimensional (Q1D) RbCr3As3 single crystals. The samples were prepared
by the deintercalation of Rb+ ions from the 233-type Rb2Cr3As3 crystals which
were grown from a high-temperature solution growth method. The RbCr3As3
compound crystallizes in a centrosymmetric structure with the space group of
P63/m (No. 176) different with its non-centrosymmetric Rb2Cr3As3
superconducting precursor, and the refined lattice parameters are a = 9.373(3)
{\AA} and c = 4.203(7) {\AA}. Electrical resistivity and magnetic
susceptibility characterizations reveal the occurrence of superconductivity
with an interestingly higher onset Tc of 7.3 K than other Cr-based
superconductors, and a high upper critical field Hc2(0) near 70 T in this
133-type RbCr3As3 crystals.",1711.06133v1
2017-12-01,Radiation damage and thermal shock response of carbon-fiber-reinforced materials to intense high-energy proton beams,"A comprehensive study on the effects of energetic protons on carbon-fiber
composites and compounds under consideration for use as low-Z pion production
targets in future high-power accelerators and low-impedance collimating
elements for intercepting TeV-level protons at the Large Hadron Collider has
been undertaken addressing two key areas, namely, thermal shock absorption and
resistance to irradiation damage.",1712.00509v1
2018-01-08,Automated Instrumentation for the Determination of the High-Temperature Thermoelectric Figure-of-Merit,"In this work, we report the fabrication of a high temperature measurement
setup to measure Figure of merit (ZT). This setup facilitates the simultaneous
measurement of Seebeck coefficient ({\alpha}), thermal conductivity (\kappa),
and electrical resistivity (\rho) required to calculate ZT. Measurement of
temperature, as well as voltages using same thermocouples, simplified the
design of the setup by minimizing sensors and wires. Limited components used in
the sample holder further simplify the design and make it small in size and
lightweight. The dedicated thin heater is made, which minimizes the heat loss.
Further, low heat loss is achieved by optimizing the insulator dimension. To
measure power delivered to the heater, 4-wire technique is used. Low cost and
commonly available materials used in the fabrication of various components make
it more accessible to the user as any parts can be easily replaced in case of
any damage occurs. A dedicated program is built in the Python programming
language to automate the whole measurement process. p-type Bi0.36Sb1.45Te3
sample is used to calibrate this measurement setup. The data collected are
found to be in good agreement with the reported data.",1801.02360v1
2018-01-30,Structural and electronic phase transitions in FePS$_3$ under the application of pressure,"Two-dimensional materials have proven to be a prolific breeding ground of new
and unstudied forms of magnetism and unusual metallic states, particularly when
tuned between their insulating and metallic phases. In this paper we present
work on a new metal to insulator transition system FePS$_3$ . This compound is
a two-dimensional van-der-Waals antiferromagnetic Mott insulator. Here we
report the discovery of an insulator-metal transition in FePS$_3$, as evidenced
by x-ray diffraction and electrical transport measurements, using high pressure
as a tuning parameter. Two structural phase transitions are observed in the
x-ray diffraction data as a function of pressure and resistivity measurements
show evidence of onset of a metallic state at high pressures. We propose models
for the two new structures that can successfully explain the x-ray diffraction
patterns.",1801.10089v2
2018-03-14,A 1.6:1 Bandwidth Two-Layer Antireflection Structure for Silicon Matched to the 190-310 GHz Atmospheric Window,"Although high-resistivity, low-loss silicon is an excellent material for THz
transmission optics, its high refractive index necessitates antireflection
treatment. We fabricated a wide-bandwidth, two-layer antireflection treatment
by cutting subwavelength structures into the silicon surface using multi-depth
deep reactive ion etching (DRIE). A wafer with this treatment on both sides has
<-20 dB (<1%) reflectance over 190-310 GHz. We also demonstrated that bonding
wafers introduces no reflection features above the -20 dB level, reproducing
previous work. Together these developments immediately enable construction of
wide-bandwidth silicon vacuum windows and represent two important steps toward
gradient-index silicon optics with integral broadband antireflection treatment.",1803.05168v2
2018-04-26,Large effective mass and interaction-enhanced Zeeman splitting of $K$-valley electrons in MoSe$_2$,"We study the magnetotransport of high-mobility electrons in monolayer and
bilayer MoSe$_2$, which show Shubnikov-de Haas (SdH) oscillations and quantum
Hall states in high magnetic fields. An electron effective mass of 0.8$m_e$ is
extracted from the SdH oscillations' temperature dependence; $m_e$ is the bare
electron mass. At a fixed electron density the longitudinal resistance shows
minima at filling factors (FFs) that are either predominantly odd, or
predominantly even, with a parity that changes as the density is tuned. The SdH
oscillations are insensitive to an in-plane magnetic field, consistent with an
out-of-plane spin orientation of electrons at the $K$-point. We attribute the
FFs parity transitions to an interaction enhancement of the Zeeman energy as
the density is reduced, resulting in an increased Zeeman-to-cyclotron energy
ratio.",1804.10104v2
2018-05-31,Unusual magnetotransport in holmium monoantimonide,"We report the magnetotransport properties of HoSb, a semimetal with
antiferromagnetic ground state. HoSb shows extremely large magnetoresistance
(XMR) and Shubnikov-de Haas (SdH) oscillation at low temperature and high
magnetic field. Different from previous reports in other rare earth
monopnictides, kinks in $\rho(B)$ and $\rho_{xy}(B)$ curves and the field
dependent resistivity plateau are observed in HoSb, which result from the
magnetic phase transitions. The fast Fourier transform analysis of the SdH
oscillation reveals the split of Fermi surfaces induced by the nonsymmetric
spin-orbit interaction. The Berry phase extracted from SdH oscillation
indicates the possible nontrivial electronic structure of HoSb in the presence
of magnetic field. The Hall measurements suggest that the XMR originates from
the electron-hole compensation and high mobility.",1805.12496v1
2018-06-28,Tribological Properties of Ultrananocrystalline Diamond Nanowire Thin Film: Influence of Sliding Ball Counterbodies,"Ultrananocrystalline Diamond Nanowire (UNCD NW) thin film was deposited on
mirror polished silicon substrate (100) using Microwave Plasma Enhanced
Chemical Vapor Deposition (MPECVD) System with optimized deposition parameters
in CH4 (6%)/N2 plasma media. The film exhibited wire like morphology with
randomly oriented and homogeneously distributed ultranano diamond grains
separated by an interphase boundary of graphitic and amorphous carbon (a-C)
phases. Micro-tribological studies of film were carried out against Al2O3, SiC
and steel balls in ambient atmospheric conditions. Initially, the friction
coefficient was found to be high for UNCD NW/SiC and UNCD NW/Steel sliding
pairs which gradually decreased to low value. While, in UNCD NW/Al2O3 sliding
combination, the ultralow value of friction coefficient was maintained
throughout the whole sliding process. High wear resistant properties of the
film were observed in UNCD NW/SiC and UNCD NW/Steel pairs. In UNCD NW/Al2O3
case, ball counterbody showed negligible wear dimension. Such kind of
tribological behavior was attributed to the different type of mechanical and
chemical interactions of ball counterbodies with UNCD NW thin film.",1806.10765v1
2018-09-13,Anisotropic hybridization in a new Kondo lattice compound CeCoInGa$_3$,"We report a detailed and comparative study of the single crystal CeCoInGa$_3$
in both experiment and theory. Resistivity measurements reveal the typical
behavior of Kondo lattice with the onset temperature of coherence, $T^*\approx
50\,$K. The magnetic specific heat can be well fitted using a spin-fluctuation
model at low temperatures, yielding a large Sommerfeld coefficient,
$\gamma\approx172\,$mJ/mol K$^2$ at 6 K, suggesting that this is a
heavy-fermion compound with a pronounced coherence effect. The magnetic
susceptibility exhibits a broad field-independent peak at $T_{\chi}$ and shows
an obvious anisotropy within the $bc$ plane, reflecting the anisotropy of the
coherence effect at high temperatures. These are compared with strongly
correlated calculations combining first-principles band structure calculations
and dynamical mean-field theory. Our results confirm the onset of coherence at
about 50 K and reveal a similar anisotropy in the hybridization gap, pointing
to a close connection between the hybridization strength of the low-temperature
Fermi-liquid state and the high-temperature coherence effect.",1809.04735v1
2018-11-18,In situ high-cycle fatigue reveals the importance of grain boundary structure in nanocrystalline Cu-Zr,"Nanocrystalline metals typically have high fatigue strengths, but low
resistance to crack propagation. Amorphous intergranular films are disordered
grain boundary complexions that have been shown to delay crack nucleation and
slow crack propagation during monotonic loading by diffusing grain boundary
strain concentrations, suggesting they may also be beneficial for fatigue
properties. To probe this hypothesis, in situ transmission electron microscopy
fatigue cycling is performed on Cu-1 at.% Zr thin films thermally treated to
have either only ordered grain boundaries or to contain amorphous intergranular
films. The sample with only ordered grain boundaries experienced grain
coarsening at crack initiation followed by unsteady crack propagation and
extensive nanocracking, whereas the sample containing amorphous intergranular
films had no grain coarsening at crack initiation followed by steady crack
propagation and distributed plastic activity. Microstructural design for
control of these behaviors through simple thermal treatments can allow for the
improvement of nanocrystalline metal fatigue toughness.",1811.07263v1
2019-09-02,Thermoelastic equation of state and melting of Mg metal at high pressure and high temperature,"The p-V-T equation of state of magnesium metal has been measured up to 20 GPa
and 1500 K using both multianvil and opposite anvil techniques combined with
synchrotron X-ray diffraction. To fit the experimental data, the model of
Anderson-Gr\""uneisen has been used with fixed parameter {\delta}T. The 300-K
bulk modulus of B0 = 32.5(1) GPa and its first pressure derivative, B0' =
3.73(2), have been obtained by fitting available data up to 20 GPa to Murnaghan
equation of state. Thermal expansion at ambient pressure has been described
using second order polynomial with coefficients a = 25(2)x10-6 K-1 and b =
9.4(4)x10-9 K-2. The parameter describing simultaneous pressure and temperature
impact on thermal expansion coefficient (and, therefore, volume) is {\delta}T =
1.5(5). The good agreement between fitted and experimental isobars has been
achieved to relative volumes of 0.75. The Mg melting observed by X-ray
diffraction and in situ electrical resistivity measurements confirms previous
results and additionally confirms the p-T estimations in the vicinity of
melting.",1909.00645v1
2014-08-28,Crossover of conduction mechanism in Sr2IrO4 epitaxial thin films,"High quality epitaxial Sr2IrO4 thin films with various thicknesses (9-300 nm)
have been grown on SrTiO3 (001) substrates, and their electric transport
properties have been investigated. All samples showed the expected insulating
behavior with a strong resistivity dependence on film thickness, that can be as
large as three orders of magnitude at low temperature. A close examination of
the transport data revealed interesting crossover behaviors for the conduction
mechanism upon variation of thickness and temperature. While Mott variable
range hopping (VRH) dominated the transport for films thinner than 85 nm, high
temperature thermal activation behavior was observed for films with large
thickness, which was followed by a crossover from Mott to Efros-Shklovskii (ES)
VRH in the low temperature range. This low temperature crossover from Mott to
ES VRH indicates the presence of a Coulomb gap (~3 meV). Our results
demonstrate the competing and tunable conduction in Sr2IrO4 thin films, which
in turn would be helpful for understanding the insulating nature related to
strong spin-orbit-coupling of the 5d iridates.",1408.6798v1
2017-03-01,Tunnel-injected sub-260 nm ultraviolet light emitting diodes,"We report on tunnel-injected deep ultraviolet light emitting diodes (UV LEDs)
configured with a polarization engineered Al0.75Ga0.25N/ In0.2Ga0.8N tunnel
junction structure. Tunnel-injected UV LED structure enables n-type contacts
for both bottom and top contact layers. However, achieving Ohmic contact to
wide bandgap n-AlGaN layers is challenging and typically requires high
temperature contact metal annealing. In this work, we adopted a compositionally
graded top contact layer for non-alloyed metal contact, and obtained a low
contact resistance of Rc=4.8x10-5 Ohm cm2 on n-Al0.75Ga0.25N. We also observed
a significant reduction in the forward operation voltage from 30.9 V to 19.2 V
at 1 kA/cm2 by increasing the Mg doping concentration from 6.2x1018 cm-3 to
1.5x1019 cm-3. Non-equilibrium hole injection into wide bandgap Al0.75Ga0.25N
with Eg>5.2 eV was confirmed by light emission at 257 nm. This work
demonstrates the feasibility of tunneling hole injection into deep UV LEDs, and
provides a novel structural design towards high power deep-UV emitters.",1703.00117v1
2019-02-27,High-performance dendritic metamaterial absorber for broadband and near-meter wave radar,"Absorbing materials in ultra-high frequency (UHF) band has constantly been a
major challenge. The size of the absorber in UHF band is large, whereas the
resonant frequency band is narrow. According to Rozanov's theory, two kinds of
composite metamaterial absorbers are designed to realize the requirements of
low-frequency broadband metamaterial microwave absorber: the
magnetic-metamaterial composite absorber1 (MA1) and the dielectric-metamaterial
composite absorber 2 (MA2). In the range of approximately 300-1000MHz, both
absorbers achieve absorption of over 90% and feature good adaptability to the
incident angle of the incident wave. The absorbers also present good absorption
rate of over 80% in the range of 0-45 degree. Processing samples of indium tin
oxide (ITO) resistance film and polymethacrylimide (PMI) foam board feature
simple preparation and low cost, and the most important thing is to consider
the weight problem, which features certain advantages in terms of use.",1902.10398v1
2019-07-29,Mechanical Characterisation of the Protective Al$_2$O$_3$ Scale in Cr$_2$AlC MAX phases,"MAX phases have great potential under demands of both high-temperature and
high-stress performance, with their mixed atomic bonding producing the
temperature and oxidation resistance of ceramics with the mechanical resilience
of metals. Here, we measure the mechanical properties up to 980C by
nanoindentation on highly dense and pure Cr$_2$AlC, as well as after oxidation
with a burner rig at 1200C for more than 29 hours. Only modest reductions in
both hardness and modulus up to 980C were observed, implying no change in
deformation mechanism. Furthermore, micro-cantilever fracture tests were
carried out at the Cr$_2$AlC/Cr$_7$C$_3$ and Cr$_7$C$_3$/Al$_2$O$_3$ interfaces
after the oxidation of the Cr$_2$AlC substrates with said burner rig. The
values are typical of ceramic-ceramic interfaces, below 4 MPa/m, leading to the
hypothesis that the excellent macroscopic behaviour is due to a combination of
low internal strain due to the match in thermal expansion coefficient as well
as the convoluted interface.",1907.12341v1
2019-03-21,Stabilization and heteroepitaxial growth of metastable tetragonal FeS thin films by pulsed laser deposition,"Pulsed laser deposition, a non-equilibrium thin-film growth technique, was
used to stabilize metastable tetragonal iron sulfide (FeS), the bulk state of
which is known as a superconductor with a critical temperature of 4 K.
Comprehensive experiments revealed four important factors to stabilize
tetragonal FeS epitaxial thin films: (i) an optimum growth temperature of 300
{\deg}C followed by thermal quenching, (ii) an optimum growth rate of ~7
nm/min, (iii) use of a high-purity bulk target, and (iv) use of a
single-crystal substrate with small in-plane lattice mismatch (CaF2).
Electrical resistivity measurements indicated that none of all the films
exhibited superconductivity. Although an electric double-layer transistor
structure was fabricated using the tetragonal FeS epitaxial film as a channel
layer to achieve high-density carrier doping, no phase transition was observed.
Possible reasons for the lack of superconductivity include lattice strain,
off-stoichiometry of the film, electrochemical etching by the ionic liquid
under gate bias, and surface degradation during device fabrication.",1903.08820v1
2019-03-26,Gate tunable quantum Hall effects in defect-suppressed Bi2Se3 films,"Despite many years of efforts, attempts to reach the quantum regime of
topological surface states (TSS) on an electrically tunable topological
insulator (TI) platform have so far failed on binary TI compounds such as
Bi2Se3 due to high density of interfacial defects. Here, utilizing an optimal
buffer layer on a gatable substrate, we demonstrate the first electrically
tunable quantum Hall effects (QHE) on TSS of Bi2Se3. On the n-side,
well-defined QHE shows up, but it diminishes near the charge neutrality point
(CNP) and completely disappears on the p-side. Furthermore, around the CNP the
system transitions from a metallic to a highly resistive state as the magnetic
field is increased, whose temperature dependence indicates presence of an
insulating ground state at high magnetic fields.",1903.10945v2
2019-04-09,Alloy Design for Mechanical Properties: Conquering the Length Scales,"Predicting the structural response of advanced multiphase alloys and
understanding the underlying microscopic mechanisms that are responsible for it
are two critically important roles modeling plays in alloy development. An
alloys demonstration of superior properties, such as high strength, creep
resistance, high ductility, and fracture toughness, is not sufficient to secure
its use in widespread application. Still, a good model is needed, to take
measurable alloy properties, such as microstructure and chemical composition,
and forecast how the alloy will perform in specified mechanical deformation
conditions, including temperature, time, and rate. In this bulletin, we
highlight recent achievements by multiscale modeling in elucidating the coupled
effects of alloying, microstructure, and the dynamics of mechanisms on the
mechanical properties of polycrystalline alloys. Much of the understanding
gained by these efforts relied on integration of computational tools that
varied over many length and time scales, from first principles density
functional theory, atomistic simulation methods, dislocation and defect theory,
micromechanics, phase field modeling, single crystal plasticity, and
polycrystalline plasticity.",1904.04569v1
2019-08-13,Investigating the real-time dissolution of a compositionally complex alloy using inline ICP and correlation with XPS,"The real-time dissolution of the single-phase compositionally complex alloy
(CCA), Al1.5TiVCr, was studied using an inline inductively coupled plasma
method. Compositionally complex alloys (CCAs), a term encompassing high entropy
alloys (HEAs) or multi-principal element alloys (MPEAs), are - in general -
noted for their inherently high corrosion resistance. In order to gain an
insight into the dissolution of Al1.5TiVCr alloy, atomic emission
spectroelectrochemistry was utilised in order to measure the ion dissolution of
the alloy during anodic polarisation. It was revealed that incongruent
dissolution occurred, with preferential dissolution of Al, and essentially no
dissolution of Ti, until the point of alloy breakdown. Results were correlated
with X-ray photoelectron spectroscopy, which revealed a complex surface oxide
inclusive of unoxidised metal, and metal oxides in disproportion to the bulk
alloying element ratio.",1908.04493v1
2012-06-01,Quantum Superinductor with Tunable Non-Linearity,"We report on the realization of a superinductor, a dissipationless element
whose microwave impedance greatly exceeds the resistance quantum. The design of
the superinductor, implemented as a ladder of nanoscale Josephson junctions,
enables tuning of the inductance and its nonlinearity by a weak magnetic field.
The Rabi decay time of the superinductor-based qubit exceeds 1 microsecond. The
high kinetic inductance and strong nonlinearity offer new types of
functionality, including the development of qubits protected from both flux and
charge noises, fault tolerant quantum computing, and high-impedance isolation
for electrical current standards based on Bloch oscillations.",1206.0307v2
2015-07-10,Antibunched photons from inelastic Cooper-pair tunneling,"We demonstrate theoretically that charge transport across a Josephson
junction, voltage-biased through a resistive environment, produces antibunched
photons. We develop a continuous-mode description of the emitted radiation
field in a semi-infinite transmission line terminated by the Josephson
junction. Within a perturbative treatment in powers of the tunneling coupling
across the Josephson junction, we capture effects originating in charging
dynamics of consecutively tunneling Cooper pairs. We find that within a
feasible experimental setup the Coulomb blockade provided by high
zero-frequency impedance can be used to create antibunched photons at a very
high rate and in a very versatile frequency window ranging from a few GHz to a
THz.",1507.02885v1
2018-07-20,High-Pressure Phase Diagram of NdFeAsO$_{0.9}$F$_{0.1}$: Disappearance of superconductivity on the verge of ferromagnetism from nd moments,"We investigated transport and magnetic properties of NdFeAsO$_{0.9}$F$_{0.1}$
single crystal under hydrostatic pressures up to 50\,GPa. The ambient pressure
superconductivity at $T_{c} \sim$ 45.4\,K is fully suppressed at $P_{c} \sim$
21 GPa. Upon further increase of the pressure, the ferromagnetism associated
with the order of rare-earth subsystem is induced at the border of
superconductivity. Our finding is supported by the hysteresis in the
magnetization $M$($H$) loops and the strong increase in the field cooled data,
$M$($T$), toward low temperatures. We also show that the temperature evolution
of the electrical resistivity as a function of pressure is consistent with a
crossover from a Fermi-liquid to non-Fermi-liquid to Fermi-liquid. These
results give access to the high-pressure side of the superconducting phase
diagram in 1111 type of materials.",1807.07729v1
2018-12-19,Benchmarking vdW-DF first principle predictions against Coupled Electron-Ion Monte Carlo for high pressure liquid hydrogen,"We report first principle results for nuclear structure and optical responses
of high pressure liquid hydrogen along two isotherms in the region of molecular
dissociation. We employ Density Functional Theory with the vdW-DF approximation
(vdW) and we benchmark the results against existing predictions from Coupling
Electron-Ion Monte Carlo (CEIMC). At fixed density and temperature, we find
that pressure from vdW is higher than pressure from CEIMC by about 10 GPa in
the molecular insulating phase and about 20 GPa in the dissociated metallic
phase. Molecules are found to be overstabilized using vdW, with a slightly
shorter bond length, and with a stronger resistance to compression. As a
consequence, pressure dissociation along isotherms using vdW is more
progressive than computed with CEIMC. Below the critical point, the
liquid-liquid phase transition is observed with both theories in the same
density region but the one predicted by vdW has a smaller density
discontinuity, i.e. a smaller first order character. The optical conductivity
computed using Kubo-Greenwood is rather similar for the two systems and
reflects the slightly more pronounced molecular character of vdW.",1812.07818v1
2019-10-01,In-situ detection of nucleation in high temperature solutions,"The state of a sample during crystal growth from high temperature solutions
is not accessible in conventional furnace systems. An optimization of the
growth parameters often requires arduous trial and error procedures in
particular in case of novel multicomponent systems with unknown phase diagrams.
Here we present a measurement technique based on lock-in amplification that
allows for in-situ detection of the liquidus and solidus temperatures as well
as structural phase transitions. A thin, metallic measurement wire is mounted
in close vicinity to the melt. Characteristic anomalies in the time-dependent
electrical resistivity of this wire allow for the detection of latent heat
release without using a reference crucible. The method is implemented in a
'feedback furnace' and enables an adjustment of the temperature profile based
on the occurrence or absence of phase transitions. The absolute temperature
serves as an additional source of information. Obtained phase transition
temperatures are in good agreement with differential thermal analysis (DTA).",1910.00316v1
2019-10-04,Improvement of temperature uniformity of induction-heated T-shape susceptor for high-temperature MOVPE,"The induction heating is a common method applied in metalorganic vapor phase
epitaxy (MOVPE) especially for higher-temperature growth conditions. However,
compared to the susceptor heated by the multiple-zone resistant heater, the
inductive-heated susceptor could suffer from severe thermal non-uniformity
issue. In this simulation study, we propose to employ a T-shape susceptor
design with various geometric modifications to significantly improve the
substrate temperature uniformity by manipulating thermal transfer.
Specifically, the thermal profile can be tailored by horizontal expansion and
vertical elongation of the susceptor, or forming a cylindrical hollow structure
at the susceptor bottom cylinder. Three optimized designs are shown with
different temperature uniformity as well as various induction heating
efficiencies. The temperature variation of the entire substrate surface can be
less than 5 {\deg}C at ~1900 {\deg}C with high induction heating efficiency
after applying the proposed techniques.",1910.02024v1
2019-10-21,Harnessing energy landscape exploration to control the buckling of cylindrical shells,"The complexity and unpredictability of postbuckling responses in even simple
thin shells have raised great challenges to emerging technologies exploiting
buckling transitions. Here we comprehensively survey the buckling landscapes to
show the full complexity of the stable buckling states and the transition
mechanisms between each of them. This is achieved by combining a simple and
versatile triangulated lattice model for modelling the shell morphologies with
efficient high-dimensional free-energy minimisation and transition path finding
algorithms. We show how the simple free energy landscapes of short, lightly
compressed cylinders become vastly more complex at high compressive strains or
aspect ratios. We then exploit these landscapes to introduce an effective
method for targeted design - landscape biasing. This is used to inform
thickness modifications enabling landscape redesign, and the development of
structures which are highly resistant to lateral perturbations. Our methods are
general, and can be extended to studying postbuckling responses of other
geometries.",1910.09210v1
2019-11-07,Long- to short-junction crossover and field-reentrant critical current in Al/Ag-nanowires/Al Josephson junctions,"We have probed the superconducting proximity effect through long high-quality
monocrystalline Ag nanowires, by realizing Josephson junctions of different
lengths, with different superconducting materials. Thanks to the high number of
junctions probed, both the contact resistance and electron diffusion constant
could be determined, enabling a comparison of the measured critical current to
theoretical expectation, over the entire regime from short to long diffusive
junction. Although the length dependence of the critical current is as
expected, the amplitude of the $R_{N}I_c$ product is smaller than predicted by
theory. We also address the magnetic field dependence of the critical current.
The quasi-gaussian decay of the critical current with field expected of a long
narrow junction is observed for all superconducting contacts we used except for
aluminum. We present the striking non-monotonous effect of field on the
critical current of junctions with aluminum contacts, and analyze it in terms
of improved quasiparticle thermalization by a magnetic field.",1911.02962v1
2019-11-13,Giant enhancement of cryogenic thermopower by polar structural instability in the pressurized semimetal MoTe2,"We found that a high mobility semimetal 1T'-MoTe2 shows a significant
pressure-dependent change in the cryogenic thermopower in the vicinity of the
critical pressure, where the polar structural transition disappears. With the
application of a high pressure of 0.75 GPa, while the resistivity becomes as
low as 10 {\mu}{\Omega}cm, thermopower reached the maximum value of 60
{\mu}VK-1 at 25 K, leading to a giant thermoelectric power factor of 300
{\mu}WK-2cm-1. Based on semiquantitative analyses, the origin of this behavior
is discussed in terms of inelastic electron-phonon scattering enhanced by the
softening of zone center phonon modes associated with the polar structural
instability.",1911.05269v1
2019-11-26,One-directional thermal transport in densely aligned single-wall carbon nanotube films,"Individual carbon nanotubes (CNTs) possess extremely high thermal
conductivities. However, the thermal conductivities and their anisotropy of
macroscopic assemblies of CNTs have so far remained small. Here, we report
results of directional thermal transport measurements on a nearly-perfectly
aligned CNT film fabricated via controlled vacuum filtration. We found the
thermal conductivity to be 43 +- 2.2 W m^-1 K^-1 with a record-high thermal
anisotropy of 500. From the temperature dependence of the thermal conductivity
and its agreement with the atomistic phonon transport calculation, we conclude
that the effect of intertube thermal resistance on heat conduction in the
alignment direction is negligible because of the large contact area between
CNTs. These observations thus represent ideal unidirectional thermal transport,
i.e., the thermal conductivity of the film is determined solely by that of
individual CNTs.",1911.11340v1
2020-05-05,Nanofilm Materials for Devices of Magnetic Field Measurement in Radiation Environment,"The prospects of using nanofilms of indium-containing III-V semiconductors,
gold and single-layer graphene in magnetic field sensors, intended for
application in radiation environment were evaluated on the results of testing
in neutron fluxes. Semiconductor sensors are capable of withstanding radiation
levels typical for the ITER-type fusion reactors, while gold sensors are stable
even under environment expected in the first fusion power plant DEMO. Graphene
is promising for creating sensors that combine high magnetic field sensitivity
and high irradiation resistance.",2005.02075v1
2020-11-11,"Synthesis of high-entropy-alloy-type superconductors (Fe,Co,Ni,Rh,Ir)Zr2 with tunable transition temperature","We report on the synthesis and superconductivity of high-entropy-alloy-type
(HEA-type) compounds TrZr2 (Tr = Fe, Co, Ni, Rh, Ir), in which the Tr site
satisfies the criterion of HEA. Polycrystalline samples of HEA-type TrZr2 with
four different compositions at the Tr site were synthesized by arc melting
method. The phase purity and crystal structure were examined by Rietveld
refinement of X-ray diffraction profile. It has been confirmed that the
obtained samples have a CuAl2-type tetragonal structure. From analyses of
elemental composition and mixing entropy at the Tr site, the HEA state for the
Tr site was confirmed. The physical properties of obtained samples were
characterized by electrical resistivity and magnetization measurements. All the
samples show bulk superconductivity with various transition temperature (Tc).
The Tc varied according to the compositions and showed correlations with the
lattice constant c and Tr-Zr bond lengths. Introduction of an HEA site in TrZr2
is useful to achieve systematic tuning of Tc with a wide temperature range,
which would be a merit for superconductivity application.",2011.05590v1
2020-11-20,Large Thermoelectric Power Factor in Whisker Crystals of Solid Solutions of the One-Dimensional Tellurides Ta4SiTe4 and Nb4SiTe4,"One-dimensional tellurides Ta4SiTe4 and Nb4SiTe4 were found to show high
thermoelectric performance below room temperature. This study reported the
synthesis and thermoelectric properties of whisker crystals of
Ta4SiTe4-Nb4SiTe4 solid solutions and Mo- or Ti-doped (Ta0.5Nb0.5)4SiTe4.
Thermoelectric power of the solid solutions systematically increased with
increasing Ta content, while their electrical resistivity was unexpectedly
small. Mo- and Ti-doped (Ta0.5Nb0.5)4SiTe4 showed n- and p-type thermoelectric
properties with large power factors exceeding 40 microW cm-1 K-2, respectively.
The fact that not only Ta4SiTe4 and Nb4SiTe4 but also their solid solutions
showed high performance indicated that this system is a promising candidate for
thermoelectric applications at low temperatures.",2011.10162v1
2020-12-11,Absence of superconductivity in topological metal ScInAu$_2$,"The Heusler compound ScInAu$_2$ was previously reported to have a
superconducting ground state with a critical temperature of 3.0 K. Recent high
throughput calculations have also predicted that the material harbors a
topologically non-trivial band structure similar to that reported for
beta-PdBi$_2$. In an effort to explore the interplay between the
superconducting and topological properties properties, electrical resistance,
magnetization, and x-ray diffraction measurements were performed on
polycrystalline ScInAu$_2$. The data reveal that high-quality polycrystalline
samples lack the super-conducting transition present samples that have not been
annealed. These results indicate the earlier reported superconductivity is
non-intrinsic. Several compounds in the Au-In-Sc ternary phase space (ScAu$_2$,
ScIn$_3$, and ScInAu$_2$) were explored in an attempt to identify the secondary
phase responsible for the non-intrinsic superconductivity. The results suggest
that elemental In is responsible for the reported superconductivity in
ScInAu$_2$.",2012.06501v1
2021-02-24,"Synthesis of new high-entropy alloy-type Nb3 (Al, Sn, Ge, Ga, Si) superconductors","Studies on high-entropy alloy (HEA) superconductors have recently been
increasing, particularly in the fields of materials science and condensed
matter physics. To contribute to research on new HEA-type superconductors, in
our study we synthesized polycrystalline samples of A15-type superconductors of
Nb3Al0.2Sn0.2Ge0.2Ga0.2Si0.2 (#1) and Nb3Al0.3Sn0.3Ge0.2Ga0.1Si0.1 (#2) with an
HEA-type site by arc melting. Elemental and structural analyses revealed that
the compositions of the obtained samples satisfied the HEA state criteria.
Superconducting transitions were observed at 9.0 and 11.0 K for #1 and #2,
respectively, in the temperature dependence of magnetization and electrical
resistivity. Specific heat measurements revealed that the Sommerfeld
coefficient, Debye temperature, and {\Delta}C/{\gamma}Tc for the obtained
samples were close to those reported for conventional Nb3Sn family
superconductors.",2102.12271v1
2021-02-24,Spin waves and high-frequency response in layered superconductors with helical magnetic structure,"We evaluate the spin-wave spectrum and dynamic susceptibility in a layered
superconductors with helical interlayer magnetic structure. We especially focus
on the structure in which the moments rotate 90$^{\circ}$ from layer to layer
realized in the iron pnictide RbEuFe$_{4}$As$_{4}$. The spin-wave spectrum in
superconductors is strongly renormalized due to the long-range electromagnetic
interactions between the oscillating magnetic moments. This leads to strong
enhancement of the frequency of the mode coupled with uniform field and this
enhancement exists only within a narrow range of the c-axis wave vectors of the
order of the inverse London penetration depth. The key feature of materials
like RbEuFe$_{4}$As$_{4}$ is that this uniform mode corresponds to the maximum
frequency of the spin-wave spectrum with respect to c-axis wave vector. As a
consequence, the high-frequency surface resistance acquires a very distinct
asymmetric feature spreading between the bare and renormalized frequencies. We
also consider excitation of spin waves with Josephson effect in a tunneling
contact between helical-magnetic and conventional superconductors and study the
interplay between the spin-wave features and geometrical cavity resonances in
the current-voltage characteristics.",2102.12445v2
2021-06-08,High electrical conduction of Sb square net in anti-ThCr$_2$Si$_2$ type La$_2$O$_2$Sb thin film grown by multilayer solid-phase epitaxy,"Anti-ThCr$_2$Si$_2$ type $RE_2$O$_2$Sb ($RE$ = rare earth) with Sb square net
has shown insulating conduction so far. Here we report the synthesis of
La$_2$O$_2$Sb epitaxial thin films for the first time by multilayer solid-phase
epitaxy. The valence state of Sb was about -2 evaluated from X-ray
photoemission spectroscopy measurement, and the indirect band gap of 0.17 eV
was observed. The La$_2$O$_2$Sb epitaxial thin film showed unexpectedly high
electrical conduction as a narrow gap semiconductor, whose resistivity at room
temperature was approximately ten-thousand-fold lower than that of
La$_2$O$_2$Sb bulk polycrystal, attributed to increased carrier mobility
probably due to suppressed Sb dimerization.",2106.04713v1
2021-07-12,Hysteretic effects and magnetotransport of electrically switched CuMnAs,"Antiferromagnetic spintronics allows us to explore storing and processing
information in magnetic crystals with vanishing magnetization. In this
manuscript, we investigate magnetoresistance effects in antiferromagnetic
CuMnAs upon switching into high-resistive states using electrical pulses. By
employing magnetic field sweeps up to 14 T and magnetic field pulses up to
$\sim$ 60 T, we reveal hysteretic phenomena and changes in the
magnetoresistance, as well as the resilience of the switching signal in CuMnAs
to the high magnetic field. These properties of the switched state are
discussed in the context of recent studies of antiferromagnetic textures in
CuMnAs.",2107.05724v1
2021-08-20,Quantum oscillations in an optically-illuminated two-dimensional electron system at the LaAlO$_3$/SrTiO$_3$ interface,"We have investigated the illumination effect on the magnetotransport
properties of a two-dimensional electron system at the LaAlO$_3$/SrTiO$_3$
interface. The illumination significantly reduces the zero-field sheet
resistance, eliminates the Kondo effect at low-temperature, and switches the
negative magnetoresistance into the positive one. A large increase in the
density of high-mobility carriers after illumination leads to quantum
oscillations in the magnetoresistance originating from the Landau quantization.
The carrier density ($\sim 2 \times 10^{12}$ cm$^{-2}$) and effective mass
($\sim 1.7 ~m_e$) estimated from the oscillations suggest that the
high-mobility electrons occupy the d$_{xz/yz}$ subbands of Ti:t$_{2g}$ orbital
extending deep within the conducting sheet of SrTiO$_3$. Our results
demonstrate that the illumination which induces additional carriers at the
interface can pave the way to control the Kondo-like scattering and study the
quantum transport in the complex oxide heterostructures.",2108.09156v1
2021-11-27,Antiferromagnetic order in MnBi2Te4 films grown on Si(111) by molecular beam epitaxy,"MnBi2Te4 has recently been predicted and shown to be a magnetic topological
insulator with intrinsic antiferromagnetic order. However, it remains a
challenge to grow stoichiometric MnBi2Te4 films by molecular beam epitaxy (MBE)
and to observe pure antiferromagnetic order by magnetometry. We report on a
detailed study of MnBi2Te4 films grown on Si(111) by MBE with elemental
sources. Films of about 100 nm thickness are analyzed in stoichiometric,
structural, magnetic and magnetotransport properties with high accuracy.
High-quality MnBi2Te4 films with nearly perfect septuple-layer structure are
realized and structural defects typical for epitaxial van-der-Waals layers are
analyzed. The films reveal antiferromagnetic order with a Neel temperature of
19 K, a spin-flop transition at a magnetic field of 2.5 T and a resistivity of
1.6 mOhm cm. These values are comparable to that of bulk MnBi2Te4 crystals. Our
results provide an important basis for realizing and identifying single-phase
MnBi2Te4 films with antiferromagnetic order grown by MBE.",2111.13960v1
2021-12-04,Superconducting and normal state properties of high entropy alloy Nb-Re-Hf-Zr-Tiinvestigated by muon spin relaxation and rotation,"Superconducting high entropy alloy (HEA) are emerging as a new class of
superconducting materials. It provides a unique opportunity to understand the
complex interplay of disorder and superconductivity. We report the synthesis
and detail bulk and microscopic characterization of
Nb$_{60}$Re$_{10}$Zr$_{10}$Hf$_{10}$Ti$_{10}$ HEA alloy using transport,
magnetization, specific heat, and muon spin rotation/relaxation ($\mu$SR)
measurements. Bulk superconductivity with transition temperature $T_{C}$ = 5.7
K confirmed by magnetization, resistivity, and heat capacity measurements.
Zero-field $\mu$SR measurement shows that the superconducting state preserves
time-reversal symmetry, and transverse-field measurements of the superfluid
density are well described by an isotropic s-wave model.",2112.02388v1
2022-01-31,Disorder-mediated quenching of magnetization in NbVTiAl: Theory and Experiment,"In this paper, we present the structural, electronic, magnetic and transport
properties of a equiatomic quaternary alloy NbVTiAl. The absence of (111) and
(200) peaks in X-ray diffraction (XRD) data confirms the A2-type structure.
Magnetization measurements indicate a high Curie temperature and a negligibly
small magnetic moment ($\sim 10^{-3} \mu_B/f.u.$) These observations are
indicative of fully compensated ferrimagnetism in the alloy.
Temperature-dependent resistivity indicates metallic nature. Ab-initio
calculation of fully ordered NbVTiAl structure confirms a nearly half metallic
behavior with a high spin polarization ($\sim$ 90 \%) and a net magnetic moment
of 0.8 $\mu_B/f.u.$ (in complete contrast to the experimental observation). One
of the main objective of the present paper is to resolve and explain the
long-standing discrepancy between theoretical prediction and experimental
observation of magnetization for V-based quaternary Heusler alloys, in general.
To gain an in-depth understanding, we modelled various disordered states and
its subsequent effect on the magnetic and electronic properties. The
discrepancy is attributed to the A2 disorder present in the system, as
confirmed by our XRD data. The presence of disorder also causes the emergence
of finite states at the Fermi level, which impacts the spin polarization of the
system.",2201.13037v1
2022-03-12,Quantum transport evidence of the boundary states and Lifshitz transition in Bi$_4$Br$_4$,"The quasi-one-dimensional van der Waals compound Bi$_4$Br$_4$ was recently
found to be a promising high-order topological insulator with exotic electronic
states. In this paper, we study the electrical transport properties of
Bi$_4$Br$_4$ bulk crystals. Two electron-type samples with different electron
concentrations are investigated. Both samples have saturation resistivity
behavior in low temperature. In the low-concentration sample, two-dimensional
quantum oscillations are clearly observed in the magnetoresistance
measurements, which are attributed to the band-bending-induced surface state on
the (001) facet. In the high-concentration sample, the angular
magnetoresistance exhibits two pairs of symmetrical sharp valleys with an
angular difference close to the angle between the crystal planes (001) and
(100). The additional valley can be explained by the contribution of the
boundary states on the (100) facet. Besides, Hall measurements at low
temperatures reveal an anomalous decrease of electron concentration with
increasing temperature, which can be explained by the temperature-induced
Lifshitz transition. These results shed light on the abundant surface and
boundary state transport signals and the temperature-induced Lifshitz
transition in Bi$_4$Br$_4$.",2203.06529v1
2022-06-21,Second harmonic AC calorimetry technique within a diamond anvil cell,"Tuning the energy density of matter at high pressures gives rise to exotic
and often unprecedented properties, e.g., structural transitions,
insulator-metal transitions, valence fluctuations, topological order, and the
emergence of superconductivity. The study of specific heat has long been used
to characterize these kinds of transitions, but their application to the
diamond anvil cell (DAC) environment has proved challenging. Limited work has
been done on the measurement of specific heat within DACs, in part due to the
difficult experimental setup. To this end we have developed a novel method for
the measurement of specific heat within a DAC that is independent of the DAC
design and therefore readily compatible with any DACs already performing high
pressure resistance measurements. As a proof-of-concept, specific heat
measurements of the MgB2 superconductor were performed, showing a clear anomaly
at the transition temperature (Tc), indicative of bulk superconductivity. This
technique allows for specific heat measurements at higher pressure than
previously possible.",2206.10072v1
2022-08-10,Synthesis and Superconductivity in Yttrium-Cerium Hydrides at Moderate Pressures,"Inspired by the high critical temperature in yttrium superhydride and the low
stabilized pressure in superconducting cerium superhydride, we carry out four
independent runs to synthesize yttrium-cerium alloy hydrides. The phases
examined by the Raman scattering and x-ray diffraction measurements. The
superconductivity is detected with the zero-resistance state at the critical
temperature in the range of 97-140 K at pressures ranging from 114 GPa to
120$\pm$4 GPa. The maximum critical temperature of the synthesized hydrides is
larger than those reported for cerium hydrides, while the corresponding
stabilized pressure is much lower than those for superconducting yttrium
hydrides. The structural analysis and theoretical calculations suggest that the
phase of Y$_{0.5}$Ce$_{0.5}$H$_9$ has the space group $P6_3/mmc$ with the
calculated critical temperature of 119 K, in fair agreement with the
experiments. These results indicate that alloying superhydrides indeed can
maintain relatively high critical temperature at modest pressures accessible by
many laboratories.",2208.05191v1
2022-10-12,Field Induced Multiple Superconducting Phases in UTe2 along Hard Magnetic Axis,"The superconducting (SC) phase diagram in uranium ditelluride is explored
under magnetic fields ($H$) along the hard magnetic b-axis using a high-quality
single crystal with $T_{\rm c} = 2.1$ K. Simultaneous electrical resistivity
and AC magnetic susceptibility measurements discern low- and high-field SC
(LFSC and HFSC, respectively) phases with contrasting field-angular dependence.
Crystal quality increases the upper critical field of the LFSC phase, but the
$H^{\ast}$ of $\sim$15 T, at which the HFSC phase appears, is always the same
through the various crystals. A phase boundary signature is also observed
inside the LFSC phase near $H^{\ast}$, indicating an intermediate SC phase
characterized by small flux pinning forces.",2210.05909v2
2022-10-20,Nanowire bolometer using a 2D high-temperature superconductor,"Superconducting nanowires are very important due to their applications
ranging from quantum technology to astronomy. In this work, we implement a
non-invasive process to fabricate nanowires of high-$T_\text{c}$ superconductor
Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (BSCCO). We demonstrate that our nanowires
can be used as bolometers in the visible range with very high responsivity of
9.7 $\times$ 10$^{3}$ V/W. Interestingly, in a long (30 $\mu$m) nanowire of 9
nm thickness and 700 nm width, we observe bias current-dependent localized
spots of maximum photovoltage. Moreover, the scalability of the bolometer
responsivity with the normal state resistance of the nanowire could allow
further performance improvement by increasing the nanowire length in a meander
geometry. We observe phase slip events in nanowires with small cross-sections
(12 nm thick, 300 nm wide, and 3 $\mu$m long) at low temperatures. Our study
presents a scalable method for realizing sensitive bolometers working near the
liquid-nitrogen temperature.",2210.11254v2
2023-01-16,Role of disorder and strong 5$d$ electron correlation in the electronic structure of Sr2TiIrO6,"Transport and magnetic properties along with high resolution valence band
photoemission study of disordered double perovskite Sr$_{2}$TiIrO$_{6}$ has
been investigated. Insulator to insulator transition along with a magnetic
transition concurrently occurs at 240 K. Comparison of valence band
photoemission with band structure calculations suggests that the spin orbit
coupling as well as electron correlation are necessary to capture the line
shape and width of the Ir 5$d$ band. Room temperature valence band
photoemission spectra show negligibly small intensity at Fermi energy, $E_{F}$.
Fermi cut-off is observed at low temperatures employing high resolution. The
spectral density of states at room temperature exhibits $|E-E_{F}|^{2}$ energy
dependence signifying the role of electron-electron interaction. This energy
dependence changes to $|E-E_{F}|^{3/2}$ below the magnetic transition
evidencing the role of electron-magnon coupling in magnetically ordered state.
The evolution of pseudogap ($\pm$12 meV) explains the sudden increase in
resistivity ($\rho$) below 50 K in this disordered system. The temperature
dependent spectral density of states at $E_{F}$ exhibiting $T^{1/2}$ behaviour
verifies Altshuler-Aronov theory for correlated disordered systems.",2301.06275v1
2023-01-20,Giant resonant enhancement for photo-induced superconductivity in K$_3$C$_{60}$,"Photo-excitation at terahertz and mid-infrared frequencies has emerged as a
new way to manipulate functionalities in quantum materials, in some cases
creating non-equilibrium phases that have no equilibrium analogue. In
K$_3$C$_{60}$, a metastable zero-resistance phase was documented with optical
properties and pressure dependences compatible with non-equilibrium high
temperature superconductivity. Here, we report the discovery of a dominant
energy scale for this phenomenon, along with the demonstration of a giant
increase in photo-susceptibility near 10 THz excitation frequency. At these
drive frequencies a metastable superconducting-like phase is observed up to
room temperature for fluences as low as ~400 $\mu J/cm^2$. These findings shed
light on the microscopic mechanism underlying photo-induced superconductivity.
They also trace a path towards steady state operation, currently limited by the
availability of a suitable high-repetition rate optical source at these
frequencies.",2301.08633v2
2023-02-13,Superconductivity with large upper critical field in noncentrosymmetric Cr-bearing high-entropy alloys,"A series of new Cr$_{5+x}$Mo$_{35-x}$W$_{12}$Re$_{35}$Ru$_{13}$C$_{20}$
high-entropy alloys (HEAs) have been synthesized and characterized by x-ray
diffraction, scanning electron microscopy, electrical resistivity, magnetic
susceptibility and specific heat measurements. It is found that the HEAs adopt
a noncentrosymmetric cubic $\beta$-Mn type structure and exhibit bulk
superconductivity for 0 $\leq$ $x$ $\leq$ 9. With increasing $x$, the cubic
lattice parameter decreases from 6.7940(3) {\AA} to 6.7516(3) {\AA}. Meanwhile,
the superconducting transition temperature $T_{\rm c}$ is suppressed from 5.49
K to 3.35 K due to the magnetic pair breaking caused by Cr moments. For all
these noncentrosymmetric HEAs, the zero-temperature upper critical field
$B_{\rm c2}$(0) is comparable to Pauli paramagnetic limit $B_{\rm P}$(0) =
1.86$T_{\rm c}$. In particular, the $B_{\rm c2}$(0)/$B_{\rm P}$(0) ratio
reaches a maximum of $\sim$1.03 at $x$ = 6, which is among the highest for
$\beta$-Mn type superconductors.",2302.06036v1
2023-02-23,Pressure induced electride phase formation in calcium: A key to its strange high-pressure behavior,"Elemental calcium (Ca), a simple metal at ambient conditions, has attracted
huge interest because of its unusual high-pressure behavior in structural,
electrical, and melting properties whose origin remain unsolved. Here, using a
theoretical framework appropriate for describing electride phase formation,
i.e., the presence of anionic electrons, we establish electride formation in Ca
at a pressure as low as 8 GPa. Our analysis shows that under pressure the
valence electrons of Ca localize at octahedral holes and exhibit anionic
character which is responsible for its strange pressure behavior. Our
calculated enthalpy and electrical resistance indicate that Ca will directly
transform from an FCC-electride phase to an SC-electride phase near 30 GPa
thereby avoiding the intermediate BCC phase. These findings are not limited to
Ca but might hold a key to the understanding of host-guest type structures
which occur in other elemental solids though at much higher pressures.",2302.11833v1
2023-05-16,Ambient and high-pressure electrical transport and structural investigations of magnetic Weyl semimetal PrAlGe,"We present ambient and high-pressure electrical transport and structural
properties of recently discovered magnetic Weyl semimetal PrAlGe. Electrical
resistivity at ambient pressure shows an anomaly at $T_C$ = 15.1 K related to
the ferromagnetic transition. Anomalous Hall effect (AHE) is observed below
$T_C$. We observe a 1.4 K/GPa increase of $T_C$ with pressure, resulting in
$T_C$ $\approx$ 47 K at 23.0 GPa. Strong competition between Lorentz force and
spin-scattering mechanisms suppressed by magnetic field is deduced from the
magnetoresistance measurements under pressure. As in the ambient pressure case,
the AHE is found to be present below $T_C$ up to the highest applied pressure.
We observe a clear anomaly in the pressure dependence of $T_C$,
magnetoresistance and Hall effect at 12.5 GPa suggesting the occurrence of a
pressure-induced electronic transition at this pressure. X-ray diffraction
(XRD) experiment under pressure revealed the lattice structure to be stable up
to $\sim$19.6 GPa with the absence of any symmetry changing structural phase
transition from the initial $I4_1md$ structure. Careful analysis of the
pressure dependent XRD data reveal an isostructural transition near 11 GPa.
Observed isostructural transition may be related to the pressure-induced
electronic transition deduced from the magnetoresistance and Hall effect data.",2305.09298v1
2023-05-18,High-quality superconducting α-Ta film sputtered on heated silicon substrate,"Intrigued by the discovery of the long lifetime in the
{\alpha}-Ta/Al2O3-based Transmon qubit, researchers recently found {\alpha}-Ta
film is a promising platform for fabricating multi-qubits with long coherence
time. To meet the requirements for integrating superconducting quantum
circuits, the ideal method is to grow {\alpha}-Ta film on a silicon substrate
compatible with industrial manufacturing. Here we report the {\alpha}-Ta film
sputter-grown on Si (100) with a low-loss superconducting TiNx buffer layer.
The {\alpha}-Ta film with a large growth temperature window has a good
crystalline character. The superconducting critical transition temperature (Tc)
and residual resistivity ratio (RRR) in the {\alpha}-Ta film grown at 500
{\deg}C are higher than that in the {\alpha}-Ta film grown at room temperature
(RT). These results provide crucial experimental clues toward understanding the
connection between the superconductivity and the materials' properties in the
{\alpha}-Ta film and open a new route for producing a high-quality {\alpha}-Ta
film on silicon substrate for future industrial superconducting quantum
computers.",2305.10957v2
2023-05-20,A Computational Approach for Mapping Electrochemical Activity of Multi-Principal Element Alloys,"Multi principal element alloys (MPEAs) comprise a unique class of metal
alloys. MPEAs have been demonstrated to possess several exceptional properties,
including, as most relevant to the present study, a high corrosion resistance.
In the context of MPEA design, the vast number of potential alloying elements
and the staggering number of elemental combinations favours a computational
alloy design approach. In order to computationally assess the prospective
corrosion performance of MPEA, an approach was developed in this study. A
density functional theory (DFT) based Monte Carlo method was used for the
development of MPEA structure, with the AlCrTiV alloy used as a model.
High-throughput DFT calculations were performed to create training datasets for
surface activity towards different adsorbate species: O2-, Cl- and H+. Machine
learning (ML) with combined representation was then utilised to predict the
adsorption and vacancy energies as descriptors for surface activity. The
capability of the combined computational methods of MC, DFT and ML, as a
virtual electrochemical performance simulator for MPEAs was established and may
be useful in exploring other MPEAs.",2305.12059v1
2023-06-16,Epitaxial α-Ta (110) film on a-plane sapphire substrate for superconducting qubits on wafer scale,"Realization of practical superconducting quantum computing requires many
qubits of long coherence time. Compared to the commonly used Ta deposited on
c-plane sapphire, which occasionally form {\alpha}-Ta (111) grains and
\b{eta}-tantalum grains, high quality Ta (110) film can grow epitaxial on
a-plane sapphire because of the atomic relationships at the interface.
Well-ordered {\alpha}-Ta (110) film on wafer-scale a-plane sapphire has been
prepared. The film exhibits high residual resistance ratio. Transmon qubits
fabricated using these film shows relaxation times exceeding 150 {\mu}s. The
results suggest Ta film on a-plane sapphire is a promising choice for long
coherence time qubit on wafer scale.",2306.09568v2
2023-08-07,Modeling of electrochemical oxide film growth -- impact of band-to-band tunneling,"The Point Defect Model (PDM) describes the corrosion resistance properties of
oxide films based on interfacial reactions and defect transport, which are
affected by the electric field inside the oxide film. The PDM assumes a
constant electric field strength due to band-to-band tunneling (BTBT) of
electrons and the separation of electrons and holes by high electric fields. In
this manuscript we present a more complex expansion of the common models to
simulate steady state oxide films to test this assumption. The R-PDM was
extended by including the transport of electrons and holes and BTBT. It could
be shown that BTBT only occurs in very rare cases of narrow band gaps and high
electric fields and the impact of electrons and holes does indeed lead to a
buffering effect on the electric field, but does not lead to a constant
electric field strength. Modeling the transport of electrons and holes on the
oxide film allows to specifically estimate their potential impact on the film
growth. Especially during modeling of oxide films with narrow band gap and/or
electrochemical reactions at the film/solution interface the electrons and
holes needs to be included to the model.",2308.05113v1
2023-09-09,High-throughput screening of coherent topologically close-packed precipitates in hexagonal close-packed metallic systems,"The nanoscale, coherent topologically close-packed (TCP) precipitate plates
in magnesium alloys are found beneficial to the strength and creep resistance
of alloys. However, the conventional trial-and-error method is too
time-consuming and costly, which impedes the application of TCP precipitates to
hcp-based metallic alloys. Here, we systematically screen the potential
coherent TCP precipitate plates in the three most common hcp alloys, magnesium
(Mg), titanium (Ti), and zirconium (Zr) alloys, using an efficient
high-throughput screening methodology. Our findings indicate that the
hcp-to-TCP structural transformations readily occur in Mg alloys, leading to
abundant precipitation of TCP plates. However, hcp-Ti and Zr alloys exhibit a
preference for hcp-to-bcc structural transformations, rather than the in situ
precipitation of TCP plates. These screening results are largely consistent
with experimental observations. The insights gained contribute to a deeper
understanding of precipitation behavior in various hcp-based alloys at the
atomic level and provide insightful reference results for designing novel
alloys containing TCP phases.",2309.04822v2
2023-09-18,Superconductivity in the bcc-type High-entropy Alloy TiHfNbTaMo,"X-ray powder diffraction, electrical resistivity, magnetization, and
thermodynamic measurements were conducted to investigate the structure and
superconducting properties of TiHfNbTaMo, a novel high-entropy alloy possessing
a valence electron count (VEC) of 4.8. The TiHfNbTaMo HEA was discovered to
have a body-centered cubic structure and a microscopically homogeneous
distribution of the constituent elements. This material shows type-II
superconductivity with Tc = 3.42 K, lower critical field with 22.8 mT, and
upper critical field with 3.95 T. Low-temperature specific heat measurements
show that the alloy is a conventional s-wave type with a moderately coupled
superconductor. First-principles calculations show that the density of states
(DOS) of the TiHfNbTaMo alloy is dominated by hybrid d orbitals of these five
metal elements. Additionally, the TiHfNbTaMo HEA exhibits three van Hove
singularities. Furthermore, the VEC and the composition of the elements
(especially the Nb elemental content) affect the Tc of the bcc-type HEA.",2309.09494v1
2023-11-26,On the special oxidation mechanism of a Mg-Y-Al alloy contained LPSO phase at high temperatures,"This work investigated the oxidation of Mg-11Y-1Al alloy in Ar-20%O2 at
500{\deg}through multiscale characterization. The results show that the
network-like long-period stacking ordered(LPSO) phase decomposed into a
needle-like LPSO phase and a polygonal Mg24Y5 phase. The needle-like LPSO phase
resulted in the formation of a high-dense of needle-like oxide at the oxidation
front of the area initially occupied by the network-like LPSO phase. The
further inward oxygen would diffuse along the needle-like oxide-matrix
interfaces and react with Y in the surrounding Mg matrix, resulting in the
lateral growth of these needle-like oxides. Finally, the discrete needle-like
oxides were interconnected to form a thicker and continuous oxide scale which
could be more effective in hindering the elemental diffusion. Meanwhile, Al
could partially enter the Y2O3 oxide scale and formed a strengthened (Y,Al)O
oxide scale which could show a greater resistance to cracking and debonding.",2311.15182v1
2024-03-29,Metamagnetism in the high-pressure tetragonal phase of UTe$_2$,"A structural orthorhombic-to-tetragonal phase transition was recently
discovered in the heavy-fermion compound UTe$_2$ at a pressure
$p^*\simeq3-8$~GPa [Honda \textit{et al.}, J. Phys. Soc. Jpn. \textbf{92},
044702 (2023); Huston \textit{et al.}, Phys. Rev. Mat. \textbf{6}, 114801
(2022)]. In the high-pressure tetragonal phase, a phase transition at
$T_x=235$~K and a superconducting transition at $T_{sc}=2$~K have been
revealed. In this work, we present an electrical-resistivity study of UTe$_2$
in pulsed magnetic fields up to $\mu_0H=58$~T combined with pressures up to $p$
= 6 GPa. The field was applied in a direction tilted by 30~$^\circ$~from
\textbf{b} to \textbf{c} in the orthogonal structure, which is identified as
the direction \textbf{c} of the tetragonal structure. In the tetragonal phase,
the presence of superconductivity is confirmed and signatures of metamagnetic
transitions are observed at the fields $\mu_0H_{x1}=24$~T and
$\mu_0H_{x2}=34$~T and temperatures smaller than $T_x$. We discuss the effects
of uniaxial pressure and we propose that a magnetic ordering drives the
transition at $T_x$.",2403.20277v1
2024-04-17,Anisotropic Nonsaturating Magnetoresistance Observed in HoMn$_6$Ge$_6$: A Kagome Dirac Semimetal,"We report the magnetic and magnetotransport properties and electronic band
structure of the kagome Dirac semimetal HoMn$_6$Ge$_6$. Temperature-dependent
electrical resistivity demonstrates various magnetic-transition-driven
anomalies. Notably, a crossover from negative to positive magnetoresistance
(MR) is observed at around 150 K. While the linear nonsaturating positive MR in
the low-temperature region is mainly driven by the linear Dirac-like band
dispersions as predicted by the first-principles calculations, the negative MR
observed in the high-temperature region is due to the spin-flop type magnetic
transition. Consistent with anisotropic Fermi surface topology, we observe
anisotropic magnetoresistance at low temperatures. A significant anomalous Hall
effect has been noticed at high temperatures in addition to a switching of the
dominant charge carrier from electron to hole at around 215 K.",2404.11414v2
2009-01-15,Metal-insulator transition and electroresistance in lanthanum/calcium manganites La_<1-x>Ca_<x>MnO_<3> (x = 0-0.5) from voltage-current-temperature surfaces,"Of the perovskites, ABX_<3>, a subset of special interest is the family in
which the A site is occupied by a lanthanide ion, the B site by a rare earth
and X is oxygen, as such materials often exhibit a large change in electrical
resistance in a magnetic field, a phenomenon known as ""colossal""
magnetoresistance (MR). Two additional phenomena in this family have also drawn
attention: the metal-insulator transition (MIT) and electroresistance (ER). The
MIT is revealed by measuring resistance as a function of temperature, and
observing a change in the sign of the gradient. ER - the dependence of the
resistance on applied current - is revealed by measuring resistance as a
function of applied current. Up until now, the phenomena of MIT and ER have
been treated separately. Here we report simultaneous observation of the MIT and
ER in the lanthanum/calcium manganites. We accomplish this by measuring
voltage-current curves over a wide temperature range (10-300 K) allowing us to
build up an experimental voltage surface over current-temperature axes. These
data directly lead to resistance surfaces. This approach provides additional
insight into the phenomena of electrical transport in the lanthanum/calcium
manganites, in particular the close connection of the maximum ER to the
occurrence of the MIT in those cases of a paramagnetic insulator (PMI) to
ferromagnetic metal (FMM) transition.",0901.2243v1
2009-10-24,Monte Carlo Study of the Spin Transport in Magnetic Materials,"The resistivity in magnetic materials has been theoretically shown to depend
on the spin-spin correlation function which in turn depends on the
magnetic-field, the density of conduction electron, the magnetic ordering
stability, etc. However, these theories involved a lot of approximations, so
their validity remained to be confirmed. The purpose of this work is to show by
extensive Monte Carlo (MC) simulation the resistivity of the spin current from
low-$T$ ordered phase to high-$T$ paramagnetic phase in a ferromagnetic film.
We take into account the interaction between the itinerant spins and the
localized lattice spins as well as the interaction between itinerant spins
themselves. We show that the resistivity undergoes an anomalous behavior at the
magnetic phase transition in agreement with previous theories in spite of their
numerous approximations. The origin of the resistivity peak near the phase
transition in ferromagnets is interpreted here as stemming from the existence
of magnetic domains in the critical region. This interpretation is shown to be
in consistence with previous theoretical pictures. Resistivity in a simple
cubic antiferromagnet is also shown. The absence of a peak in this case is
explained.",0910.4619v3
2021-01-04,Thermal Resistance at a Twist Boundary and Semicoherent Heterointerface,"Traditional models of interfacial phonon scattering, including the acoustic
mismatch model (AMM) and diffuse mismatch model (DMM), take into account the
bulk properties of the material surrounding the interface, but not the atomic
structure and properties of the interface itself. Here, we derive a theoretical
formalism for the phonon scattering at a dislocation grid, or two
interpenetrating orthogonal arrays of dislocations, as this is the most stable
structure of both the symmetric twist boundary and semicoherent
heterointerface. With this approach, we are able to separately examine the
contribution to thermal resistance due to the step function change in acoustic
properties and due to interfacial dislocation strain fields, which induces
diffractive scattering. Both low-angle Si-Si twist boundaries and the Si-Ge
heterointerfaces are considered here and compared to previous experimental and
simulation results. This work indicates that scattering from misfit dislocation
strain fields doubles the thermal boundary resistance of Si-Ge heterointerfaces
compared to scattering due to acoustic mismatch alone. Scattering from grain
boundary dislocation strain fields is predicted to dominate the thermal
boundary resistance of Si-Si twist boundaries. This physical treatment can
guide the thermal design of devices by quantifying the relative importance of
interfacial strain fields, which can be engineered via fabrication and
processing methods, versus acoustic mismatch, which is fixed for a given
interface. Additionally, this approach captures experimental and simulation
trends such as the dependence of thermal boundary resistance on the grain
boundary angle and interfacial strain energy.",2101.01058v2
2015-07-15,Influence of Periodic Surface Nanopatterning Profiles on Series Resistance in Thin-Film Crystalline Silicon Heterojunction Solar Cells,"In the frame of the development of thin crystalline silicon solar cell
technologies, surface nanopatterning of silicon is gaining importance. Its
impact on the material quality is, however, not yet fully controlled.We
investigate here the influence of surface nanotexturing on the series
resistance of a contacting scheme relevant for thin-film crystalline silicon
heterojunction solar cells. Two dimensional periodic nanotextures are
fabricated using a combination of nanoimprint lithography and either dry or wet
etching, while random pyramid texturing is used for benchmarking. We compare
these texturing techniques in terms of their effect on the series resistance of
a solar cell through a study of the sheet resistance (Rsh ) and contact
resistance (Rc) of its front layers, i.e., a sputtered transparent conductive
oxide and evaporated metal contacts. We have found by four-point probe and the
transfer length methods that dry-etched nanopatterns render the highest Rsh and
Rc values. Wet-etched nanopatterns, on the other hand, have less impact on Rc
and render Rsh similar to that obtained from the nontextured case.",1507.07819v1
2023-01-12,On the switching mechanism and optimisation of ion irradiation enabled 2D $MoS_2$ memristors,"Memristors are prominent passive circuit elements with promising futures for
energy-efficient in-memory processing and revolutionary neuromorphic
computation. State-of-the-art memristors based on two-dimensional (2D)
materials exhibit enhanced tunability, scalability and electrical reliability.
However, the fundamental of the switching is yet to be clarified before they
can meet industrial standards in terms of endurance, variability, resistance
ratio, and scalability. This new physical simulator based on the kinetic Monte
Carlo (kMC) algorithm reproduces the defect migration process in 2D materials
and sheds light on the operation of 2D memristors. The present work employs the
simulator to study a two-dimensional $2H-MoS_2$ planar resistive switching (RS)
device with an asymmetric defect concentration introduced by ion irradiation.
The simulations unveil the non-filamentary RS process and propose practical
routes to optimize the device's performance. For instance, the resistance ratio
can be increased by 53% by controlling the concentration and distribution of
defects, while the variability can be reduced by 55% by increasing 5-fold the
device size from 10 to 50 nm. Our simulator also explains the trade-offs
between the resistance ratio and variability, resistance ratio and scalability,
and variability and scalability. Overall, the simulator may enable an
understanding and optimization of devices to expedite cutting-edge
applications.",2301.05260v2
2011-12-13,Online in-situ X-ray diffraction setup for structural modification studies during swift heavy ion irradiation,"The high energy density of electronic excitations due to the impact of swift
heavy ions can induce structural modifications in materials. We present a X-ray
diffractometer called ALIX, which has been set up at the low-energy IRRSUD
beamline of the GANIL facility, to allow the study of structural modification
kinetics as a function of the ion fluence. The X-ray setup has been modified
and optimized to enable irradiation by swift heavy ions simultaneously to X-ray
pattern recording. We present the capability of ALIX to perform simultaneous
irradiation - diffraction by using energy discrimination between X-rays from
diffraction and from ion-target interaction. To illustrate its potential,
results of sequential or simultaneous irradiation - diffraction are presented
in this article to show radiation effects on the structural properties of
ceramics. Phase transition kinetics have been studied during xenon ion
irradiation of polycrystalline MgO and SrTiO3. We have observed that MgO oxide
is radiation-resistant to high electronic excitations, contrary to the high
sensitivity of SrTiO3, which exhibits transition from the crystalline to the
amorphous state during irradiation. By interpreting the amorphization kinetics
of SrTiO3, defect overlapping models are discussed as well as latent track
characteristics. Together with a transmission electron microscopy study, we
conclude that a single impact model describes the phase transition mechanism.",1112.2832v2
2017-10-07,High pressure x-ray study of spin-Peierls physics in the quantum spin chain material TiOCl,"The application of pressure can induce transitions between unconventional
quantum phases in correlated materials. The inorganic compound TiOCl, composed
of chains of S=1/2 Ti ions, is an ideal realization of a spin-Peierls system
with a relatively simple unit cell. At ambient pressure, it is an insulator due
to strong electronic interactions (a Mott insulator). Its resistivity shows a
sudden decrease with increasing pressure, indicating a transition to a more
metallic state which may coincide with the emergence of charge density wave
order. Therefore, high pressure studies of the structure with x-rays are
crucial in determining the ground-state physics in this quantum magnet. In
ambient pressure, TiOCl exhibits a transition to an incommensurate nearly
dimerized state at $T_{c2}=92$ K and to a commensurate dimerized state at
$T_{c1}=66$ K. Here, we discover a rich phase diagram as a function of
temperature and pressure using x-ray diffraction on a single crystal in a
diamond anvil cell down to $T=4$ K and pressures up to 14.5 GPa. Remarkably,
the magnetic interaction scale increases dramatically with increasing pressure,
as indicated by the high onset temperature of the spin-Peierls phase. At
$\sim$7 GPa, the extrapolated onset of the spin-Peierls phase occurs above
$T=300$ K, indicating a quantum singlet state exists at room temperature.
Further comparisons are made with the phase diagrams of related spin-Peierls
systems that display metallicity and superconductivity under pressure.",1710.02632v1
2019-02-28,Quenched nematic criticality separating two superconducting domes in an iron-based superconductor under pressure,"The nematic electronic state and its associated nematic critical fluctuations
have emerged as potential candidates for superconducting pairing in various
unconventional superconductors. However, in most materials their coexistence
with other magnetically-ordered phases poses significant challenges in
establishing their importance. Here, by combining chemical and hydrostatic
physical pressure in FeSe$_{0.89}$S$_{0.11}$, we provide a unique access to a
clean nematic quantum phase transition in the absence of a long-range magnetic
order. We find that in the proximity of the nematic phase transition, there is
an unusual non-Fermi liquid behavior in resistivity at high temperatures that
evolves into a Fermi liquid behaviour at the lowest temperatures. From quantum
oscillations in high magnetic fields, we trace the evolution of the Fermi
surface and electronic correlations as a function of applied pressure. We
detect experimentally a Lifshitz transition that separates two distinct
superconducting regions: one emerging from the nematic electronic phase with a
small Fermi surface and strong electronic correlations and the other one with a
large Fermi surface and weak correlations that promotes nesting and
stabilization of a magnetically-ordered phase at high pressures. The lack of
mass divergence suggests that the nematic critical fluctuations are quenched by
the strong coupling to the lattice. This establishes that superconductivity is
not enhanced at the nematic quantum phase transition in the absence of magnetic
order.",1902.11276v1
2020-09-03,Topological Nature of High Temperature Superconductivity,"The key to unraveling the nature of high-temperature superconductivity (HTS)
lies in resolving the enigma of the pseudogap state. The pseudogap state in the
underdoped region is a distinct thermodynamic phase characterized by
nematicity, temperature-quadratic resistive behavior, and magnetoelectric
effects. Till present, a general description of the observed universal features
of the pseudogap phase and their connection with HTS was lacking. The proposed
work constructs a unifying effective field theory capturing all universal
characteristics of HTS materials and explaining the observed phase diagram. The
pseudogap state is established to be a phase where a charged magnetic monopole
condensate confines Cooper pairs to form an oblique version of a
superinsulator. The HTS phase diagram is dominated by a tricritical point (TCP)
at which the first order transition between a fundamental Cooper pair
condensate and a charged magnetic monopole condensate merges with the
continuous superconductor-normal metal and superconductor-pseudogap state phase
transitions. The universality of the HTS phase diagram reflects a unique
topological mechanism of competition between the magnetic monopole condensate,
inherent to antiferromagnetic-order-induced Mott insulators and the Cooper pair
condensate. The obtained results establish the topological nature of the HTS
and provide a platform for devising materials with the enhanced superconducting
transition temperature.",2009.01763v2
2020-09-16,Tailoring c-axis orientation in epitaxial Ruddlesden-Popper Pr$_{0.5}$Ca$_{1.5}$MnO$_{4}$ films,"Interest for layered Ruddlesden-Popper strongly correlated manganites of
Pr$_{0.5}$Ca$_{1.5}$MnO$_4$ as well as to their thin film polymorphs is
motivated by the high temperature of charge orbital ordering above room
temperature. We report on the tailoring of the c-axis orientation in epitaxial
RP-PCMO films grown on SrTiO$_3$ (STO) substrates with different orientations
as well as the use of CaMnO$_3$ (CMO) buffer layers. Films on STO(110) reveal
in-plane alignment of the c-axis lying along to the [100] direction. On
STO(100), two possible directions of the in-plane c-axis lead to a mosaic like,
quasi two-dimensional nanostructure, consisting of RP, rock-salt and perovskite
building blocks. With the use of a CMO buffer layer, RP-PCMO epitaxial films
with c-axis out-of-plane were realized. Different physical vapor deposition
techniques, i.e. ion beam sputtering (IBS), pulsed laser deposition (PLD) as
well as metalorganic aerosol deposition (MAD) are applied in order to
distinguish between the effect of growth conditions and intrinsic epitaxial
properties. For all deposition techniques, despite their very different growth
conditions, the surface morphology, crystal structure and orientation of the
thin films reveal a high level of similarity as verified by X-ray diffraction,
scanning and high resolution transmission electron microscopy. We found that
for different epitaxial relations the stress in the films can be relaxed by
means of a modified interface chemistry. The charge ordering in the films
estimated by resistivity measurements occurs at a temperature close to that
expected in bulk material.",2009.07523v1
2020-09-28,Pressure-induced reconstructive phase transition in Cd$_3$As$_2$,"Cadmium arsenide Cd$_3$As$_2$ hosts massless Dirac electrons in its
ambient-conditions tetragonal phase. We report X-ray diffraction and electrical
resistivity measurements of Cd$_3$As$_2$ upon cycling pressure beyond the
critical pressure of the tetragonal phase and back to ambient conditions. We
find that at room temperature the transition between the low- and high-pressure
phases results in large microstrain and reduced crystallite size both on rising
and falling pressure. This leads to non-reversible electronic properties
including self-doping associated with defects and a reduction of the electron
mobility by an order of magnitude due to increased scattering. Our study
indicates that the structural transformation is sluggish and shows a sizable
hysteresis of over 1~GPa. Therefore, we conclude that the transition is
first-order reconstructive, with chemical bonds being broken and rearranged in
the high-pressure phase. Using the diffraction measurements we demonstrate that
annealing at ~200$^\circ$C greatly improves the crystallinity of the
high-pressure phase. We show that its Bragg peaks can be indexed as a primitive
orthorhombic lattice with a_HP~8.68 A b_HP~17.15 A and c_HP~18.58 A. The
diffraction study indicates that during the structural transformation a new
phase with another primitive orthorhombic structure may be also stabilized by
deviatoric stress, providing an additional venue for tuning the unconventional
electronic states in Cd3As2.",2009.13228v2
2016-03-01,Superconductivity in HfTe5 Induced via Pressures,"Recently, ZrTe5 and HfTe5 are theoretically studied to be the most promising
layered topological insulators since they are both interlayer weakly bonded
materials and also with a large bulk gap in the single layer. It paves a new
way for the study of novel topological quantum phenomenon tuned via external
parameters. Here, we report the discovery of superconductivity and properties
evolution in HfTe5 single crystal induced via pressures. Our experiments
indicated that anomaly resistance peak moves to low temperature first before
reverses to high temperature followed by disappearance which is opposite to the
low pressure effect on ZrTe5. HfTe5 became superconductive above ~5.5 GPa up to
at least 35 GPa in the measured range. The highest superconducting transition
temperature (Tc) around 5 K was achieved at 20 GPa. High pressure Raman
revealed that new modes appeared around pressure where superconductivity
occurs. Crystal structure studies shown that the superconductivity is related
to the phase transition from Cmcm structure to monoclinic C2/m structure. The
second phase transition from C2/m to P-1 structure occurs at 12 GPa. The
combination of transport, structure measurement and theoretical calculations
enable a completely phase diagram of HfTe5 at high pressures.",1603.00514v1
2021-01-29,Tunable Doping of Rhenium and Vanadium into Transition Metal Dichalcogenides for Two-Dimensional Electronics,"Two-dimensional (2D) transition metal dichalcogenides (TMDCs) with unique
electrical properties are fascinating materials used for future electronics.
However, the strong Fermi level pinning effect at the interface of TMDCs and
metal electrodes always leads to high contact resistance, which seriously
hinders their application in 2D electronics. One effective way to overcome this
is to use metallic TMDCs or transferred metal electrodes as van der Waals (vdW)
contacts. Alternatively, using highly conductive doped TMDCs will have a
profound impact on the contact engineering of 2D electronics. Here, a novel
chemical vapor deposition using mixed molten salts is established for
vapor-liquid-solid growth of high-quality rhenium (Re) and vanadium (V)-doped
TMDC monolayers with high controllability and reproducibility. A tunable
semiconductor to metal transition is observed in the Re and V-doped TMDCs.
Electrical conductivity increases up to a factor of 108 in the degenerate
V-doped WS2 and WSe2. Using V-doped WSe2 as vdW contact, the on-state current
and on/off ratio of WSe2-based field-effect transistors have been substantially
improved (from ~10-8 to 10-5 A; ~104 to 108), compared to metal contacts.
Future studies on lateral contacts and interconnects using doped TMDCs will
pave the way for 2D integrated circuits and flexible electronics.",2101.12423v1
2020-11-05,Temperature-dependent elastic properties of binary and multicomponent high-entropy refractory carbides,"Available information concerning the elastic moduli of refractory carbides at
temperatures (T) of relevance for practical applications is sparse and/or
inconsistent. We carry out ab initio molecular dynamics (AIMD) simulations at T
= 300, 600, 900, and 1200 K to determine the temperature-dependences of the
elastic constants of rocksalt-structure (B1) TiC, ZrC, HfC, VC, and TaC
compounds as well as multicomponent high-entropy carbides (Ti,Zr,Hf,Ta,W)C and
(V,Nb,Ta,Mo,W)C. The second order elastic constants are calculated by
least-square fitting of the analytical expressions of stress vs. strain
relationships to simulation results obtained from three tensile and three shear
deformation modes. Moreover, we employ sound velocity measurements to evaluate
the bulk, shear, elastic moduli and Poisson's ratios of single-phase B1
(Ti,Zr,Hf,Ta,W)C and (V,Nb,Ta,Mo,W)C at ambient conditions. Our experimental
results are in excellent agreement with the values obtained by AIMD
simulations. In comparison with the predictions of previous ab initio
calculations - where the extrapolation of finite-temperature elastic properties
accounted for thermal expansion while neglecting intrinsic vibrational effects
- AIMD simulations produce a softening of elastic moduli with T in closer
agreement with experiments. Results of our simulations show that TaC is the
system which exhibits the highest elastic resistances to both tensile and shear
deformation up to 1200 K, and identify the high-entropy (V,Nb,Ta,Mo,W)C system
as candidate for applications that require good ductility and toughness at room
as well as elevated temperatures.",2011.02742v1
2021-03-09,Crack-free caustic magnesia-bonded refractory castables,"A growing interest in designing high-alumina MgO-bonded refractory castables
has been identified in recent years due to the magnesia ability to react: (i)
with water at the initial processing stages of these materials (inducing the
precipitation of brucite phase) or (ii) with alumina, giving rise to in situ
MgAl2O4 generation at high temperatures. Nevertheless, despite the great
potential of caustic magnesia to be used as a binder in such systems due to its
high reactivity, it is still a challenge to control the hydration reaction rate
of this oxide and the negative effects derived from the expansive feature of
Mg(OH)2 formation. Thus, this work evaluated the incorporation of different
contents of aluminum hydroxyl lactate (AHL) into caustic magnesia-bonded
castables, aiming to control the brucite precipitation during the curing and
drying steps of the prepared samples, resulting in crack-free refractories. The
designed compositions were characterized via flowability, setting behavior,
X-ray diffraction, cold flexural strength, porosity, permeability and
thermogravimetric measurements. According to the results, instead of Mg(OH)2,
hydrotalcite-like phases [Mg6Al2(OH)16(OH)2.4.5H2O and Mg6Al2(OH)16(CO3).4H2O]
were the main hydrated phases identified in the AHL-containing compositions.
The addition of 1.0 wt.% of aluminum hydroxyl lactate to the designed castable
proved to be, so far, the best option for this magnesia source, resulting in
the development of a crack-free refractory with enhanced properties and greater
spalling resistance under heating.",2103.05361v1
2021-03-20,Towards Superior High Temperature Properties in Low Density AlCrFeNiTi Compositionally Complex Alloys,"Three novel precipitation strengthened bcc alloys which exhibit a smooth
microstructural gradient with composition have been fabricated in bulk form by
induction casting. All three alloys are comprised of a mixture of disordered
A2-(Fe, Cr) and L2$_1$-ordered (Ni, Fe)$_{2}$AlTi type phases both as-cast and
after long-term annealing at 900 $^{\circ}$C. The ratio of disordered to
ordered phase, primary dendrite fraction, and overall microstructural
coarseness all decrease as Cr is replaced by Al and Ti. Differences in phase
composition are quantified through domain averaged principal component analysis
of energy dispersive spectroscopy data obtained during scanning transmission
electron microscopy. Bulk tensile testing reveals retained strengths of nearly
250 MPa up to 900 $^{\circ}$C for the alloys which contain a nanoscale
maze-like arrangement of ordered and disordered phases. One alloy, containing a
duplex microstructure with ductile dendritic regions and highly creep resistant
interdendritic regions, shows a promising balance between high temperature
ductility and strength. For this alloy, tension creep testing was carried out
at 700, 750, and 800 $^{\circ}$C for a broad range of loading conditions and
revealed upper bound creep rates which surpass similar ferritic superalloys and
rival those of several conventionally employed high temperature structural
alloys, including Inconel 617 and 718, at much lower density and raw material
cost.",2103.11173v1
2021-06-02,Dopant redistribution and activation in Ga ion-implanted high Ge content SiGe by explosive crystallization during UV nanosecond pulsed laser annealing,"Explosive crystallization (EC) is often observed when using nanosecond-pulsed
melt laser annealing (MLA) in amorphous silicon (Si) and germanium (Ge). The
solidification velocity in EC is so fast that a diffusion-less crystallization
can be expected. In the contacts of advanced transistors, the active level at
the metal/semiconductor Schottky interface must be very high to achieve a
sub-10^{-9} ohm.cm2 contact resistivity, which has been already demonstrated by
using the dopant surface segregation induced by MLA. However, the beneficial
layer of a few nanometers at the surface may be easily consumed during
subsequent contact cleaning and metallization. EC helps to address such kind of
process integration issues, enabling the optimal positioning of the peak of the
dopant chemical profile. However, there is a lack of experimental studies of EC
in heavily-doped semiconductor materials. Furthermore, to the best of our
knowledge, dopant activation by EC has never been experimentally reported. In
this paper, we present dopant redistribution and activation by an EC process
induced by UV nanosecond-pulsed MLA in heavily gallium (Ga) ion-implanted high
Ge content SiGe. Based on the obtained results, we also highlight potential
issues of integrating EC into real device fabrication processes and discuss how
to manage them.",2106.00946v1
2022-06-29,Designing wake-up free ferroelectric capacitors based on the $\mathrm{HfO_2/ZrO_2}$ superlattice structure,"The wake-up phenomenon widely exists in hafnia-based ferroelectric
capacitors, which causes device parameter variation over time. Crystallization
at higher temperatures have been reported to be effective in eliminating
wake-up, but high temperature may yield the monoclinic phase or generate high
concentration oxygen vacancies. In this work, a unidirectional annealing method
is proposed for the crystallization of $\mathrm{Hf_{0.5}Zr_{0.5}O_2}$ (HZO)
superlattice ferroelectrics, which involves heating from the
$\mathrm{Pt/ZrO_2}$ interface side. Nanoscale $\mathrm{ZrO_2}$ is selected to
resist the formation of monoclinic phase, and the chemically inert Pt electrode
can avoid the continuous generation of oxygen vacancies during annealing. It is
demonstrated that $\mathrm{600^oC}$ annealing only leads to a moderate content
of monoclinic phase in HZO, and the TiN/HZO/Pt capacitor exhibits wake-up free
nature and a $2P_\mathrm{r}$ value of 27.4 $\mu\mathrm{C/cm^2}$. On the other
hand, heating from the $\mathrm{TiN/HfO_2}$ side, or using $\mathrm{500^oC}$
annealing temperature, both yield ferroelectric devices that require a wake-up
process. The special configuration of $\mathrm{Pt/ZrO_2}$ is verified by
comparative studies with several other superlattice structures and HZO
solid-state solutions. It is discovered that heating from the
$\mathrm{Pt/HfO_2}$ side at $\mathrm{600^oC}$ leads to high leakage current and
a memristor behavior. The mechanisms of ferroelectric phase stabilization and
memristor formation have been discussed. The unidirectional heating method can
also be useful for other hafnia-based ferroelectric devices.",2206.14393v1
2022-09-06,Silicide-based Josephson field effect transistors for superconducting qubits,"Scalability in the fabrication and operation of quantum computers is key to
move beyond the NISQ era. So far, superconducting transmon qubits based on
aluminum Josephson tunnel junctions have demonstrated the most advanced
results, though this technology is difficult to implement with large-scale
facilities. An alternative ""gatemon"" qubit has recently appeared, which uses
hybrid superconducting/semiconducting (S/Sm) devices as gate-tuned Josephson
junctions. Current implementations of these use nanowires however, of which the
large-scale fabrication has not yet matured either. A scalable gatemon design
could be made with CMOS Josephson Field-Effect Transistors as tunable weak
link, where an ideal device has leads with a large superconducting gap that
contact a short channel through high-transparency interfaces. High
transparency, or low contact resistance, is achieved in the microelectronics
industry with silicides, of which some turn out to be superconducting. The
first part of the experimental work in this thesis covers material studies on
two such materials: $\text{V}_3\text{Si}$ and PtSi, which are interesting for
their high $T_\text{c}$, and mature integration, respectively. The second part
covers experimental results on 50 nm gate length PtSi transistors, where the
transparency of the S/Sm interfaces is modulated by the gate voltage. At low
voltages, the transport shows no conductance at low energy, and well-defined
features at the superconducting gap. The barrier height at the S/Sm interface
is reduced by increasing the gate voltage, until a zero-bias peak appears
around zero drain voltage, which reveals the appearance of an Andreev current.
The successful gate modulation of Andreev current in a silicon-based transistor
represents a step towards fully CMOS-integrated superconducting quantum
computers.",2209.02721v1
2023-03-21,Thermal decoupling in high-$T_c$ cuprate superconductors,"Although many years have passed since the discovery of
high-critical-temperature (high-$T_c$) superconducting materials, the
underlying mechanism is still unknown. The B1g phonon anomaly in high-Tc
cuprate superconductors has long been studied; however, the correlation between
the B1g phonon anomaly and superconductivity has yet to be clarified. In the
present study, we successfully reproduced the B1g phonon anomaly in
YBa$_2$Cu$_3$O$_7$ (YBCO) using an ab initio molecular dynamics (AIMD)
simulation and temperature-dependent effective potential (TDEP) method. The Ag
phonon by Ba atoms shows a more severe anomaly than the B1g phonon at low
temperatures. Our analysis of the phonon anomaly and the temperature-dependent
phonon dispersion indicated that decoupling between thermal phenomena and
electron transport at low temperatures leads to layer-by-layer thermal
decoupling in YBCO. Electronically and thermally isolated Ba atoms in YBCO are
responsible for the thermal decoupling. The analytic study of the thermal
dcoupling revealed that Planckian dissipation expressing linear-T resistivity
is another expression of the Fermi liquid of the CuO$_2$ plane. The Uemura plot
of the relationship between Tc and the Fermi temperature, as well as the
superconducting dome in YBCO, is explained rigorously and quantitatively. Our
findings not only present a new paradigm for understanding high-Tc
superconductivity but also imply that the spontaneous formation of
low-temperature layers in materials can lead to revolutionary changes in the
thermal issues of industrial fields.",2303.11600v1
2023-03-24,A review on the advancements in the characterization of the high-pressure properties of iodates,"The goal of this work is to report a systematic and balanced review of the
progress made in recent years on the high-pressure behavior of iodates, a group
of materials with multiple technological applications and peculiar behaviors
under external compression. This review article presents results obtained from
multiple characterization techniques which include: X-ray diffraction, Raman
and infrared spectroscopy, optical-absorption, resistivity, and second-harmonic
generation measurements. The discussion of the results from experiments will be
combined with density-functional theory calculations which have been shown to
be a very useful tool for the interpretation of experimental data. Throughout
the manuscript many of the phenomena observed will be connected to the presence
of a lone electron pairs of the iodine atoms in the studied iodates. The
presence of the lone electron pairs plays a crucial role in the high-pressure
behavior of iodates and it is associated with many of the phenomena discussed
here, in particular with the pressure-induced changes in the character of
iodine-oxygen bonds, which causes many physical properties to behave
nonlinearly. Towards the end of this review, a discussion of current problems
that remain unsolved is presented as well as proposals for possible avenues for
future studies.",2303.14215v1
2023-11-22,"Durable, ultrathin, and antifouling polymer brush coating for efficient condensation heat transfer","Heat exchangers are made of metals because of their high heat conductivity
and mechanical stability. Metal surfaces are inherently hydrophilic, leading to
inefficient filmwise condensation. It is still a challenge to coat these metal
surfaces with a durable, robust and thin hydrophobic layer, which is required
for efficient dropwise condensation. Here, we report the non-structured and
ultrathin (~6 nm) polydimethylsiloxane (PDMS) brushes on copper that sustain
high-performing dropwise condensation in high supersaturation. Due to the
flexible hydrophobic siloxane polymer chains, the coating has low resistance to
drop sliding and excellent chemical stability. The PDMS brushes can sustain
dropwise condensation for up to ~8 h during exposure to 111 {\deg}C saturated
steam flowing at 3 m/s, with a 5-7 times higher heat transfer coefficient
compared to filmwise condensation. The surface is self-cleaning and can reduce
bacterial attachment by 99%. This low-cost, facile, fluorine-free, and scalable
method is suitable for a great variety of condensation heat transfer
applications.",2311.13353v1
2023-12-01,"Insulator to Metal Transition, Spin-Phonon Coupling, and Potential Magnetic Transition Observed in Quantum Spin Liquid Candidate LiYbSe$_2$ under High Pressure","Metallization of quantum spin liquid (QSL) materials has long been considered
as a potential route to achieve unconventional superconductivity. Here we
report our endeavor in this direction by pressurizing a three-dimensional QSL
candidate, LiYbSe$_2$, with a previously unreported pyrochlore structure.
High-pressure X-ray diffraction and Raman studies up to 50 GPa reveal no
appreciable changes of structural symmetry or distortion in this pressure
range. This compound is so insulating that its resistance decreases below
10$^5$ ${\Omega}$ only at pressures above 25 GPa in the corresponding
temperature range accompanying the gradual reduction of band gap upon
compression. Interestingly, an insulator-to-metal transition takes place in
LiYbSe$_2$ at about 68 GPa and the metallic behavior remains up to 123.5 GPa,
the highest pressure reached in the present study. A possible sign of magnetic
or other phase transition was observed in LiYbSe$_2$. The insulator-to-metal
transition in LiYbSe$_2$ under high pressure makes it an ideal system to study
the pressure effects on QSL candidates of spin-1/2 Yb$^{3+}$ system in
different lattice patterns.",2312.00270v2
2024-01-06,Endless Dirac nodal lines and high mobility in kagome semimetal Ni3In2Se2 single crystal,"Kagome-lattice crystal is crucial in quantum materials research, exhibiting
unique transport properties due to its rich band structure and the presence of
nodal lines and rings. Here, we investigate the electronic transport properties
and perform first-principles calculations for Ni$_{3}$In$_{2}$Se$_{2}$ kagome
topological semimetal. First-principle calculations indicate six endless Dirac
nodal lines and two nodal rings with a $\pi$-Berry phase in the
Ni$_{3}$In$_{2}$Se$_{2}$ compound. The temperature-dependent resistivity is
dominated by two scattering mechanisms: $s$-$d$ interband scattering occurs
below 50 K, while electron-phonon ($e$-$p$) scattering is observed above 50 K.
The magnetoresistance (MR) curve aligns with the theory of extended Kohler's
rule, suggesting multiple scattering origins and temperature-dependent carrier
densities. A maximum MR of 120\% at 2 K and 9 T, with a maximum estimated
mobility of approximately 3000 cm$^{2}$V$^{-1}$s$^{-1}$ are observed. The Ni
atom's hole-like d$_{x^{2}-y^{2} }$ and electron-like d$_{z^{2}}$ orbitals
exhibit peaks and valleys, forming a local indirect-type band gap near the
Fermi level (E$_{F}$). This configuration enhances the motion of electrons and
holes, resulting in high mobility and relatively high magnetoresistance.",2401.03130v1
2024-04-18,Omnidirectional 3D printing of PEDOT:PSS aerogels with tunable electromechanical performance for unconventional stretchable interconnects and thermoelectrics,"The next generation of soft electronics will expand to the third dimension.
This will require the integration of mechanically-compliant three-dimensional
functional structures with stretchable materials. This study demonstrates
omnidirectional direct ink writing (DIW) of Poly(3,4-ethylenedioxythiophene)
polystyrene sulfonate (PEDOT:PSS) aerogels with tunable electrical and
mechanical performance, which can be integrated with soft substrates. Several
PEDOT:PSS hydrogels were formulated for DIW and freeze-dried directly on
stretchable substrates to form integrated aerogels displaying high shape
fidelity and minimal shrinkage. The effect of additives and processing in the
PEDOT:PSS hydro and aerogels morphology, and the link with their
electromechanical properties was elucidated. This technology demonstrated
3D-structured stretchable interconnects and planar thermoelectric generators
(TEGs) for skin electronics, as well as vertically-printed high aspect ratio
thermoelectric pillars with a high ZT value of 3.2 10^-3 and ultra-low thermal
conductivity of 0.065 W/(m K). Despite their comparatively low ZT, the aerogel
pillars outpowered their dense counterparts in realistic energy harvesting
scenarios where contact resistances cannot be ignored, and produced up to 26
nW/cm2 (corresponding to a gravimetric power density of 0.76 mW/kg) for a
difference of temperature of 15 K. This work suggests promising advancements in
soft and energy-efficiency electronic systems relevant to soft robotics and
wearable.",2404.12254v1
2024-05-21,Pick-and-place transfer of arbitrary-metal electrodes for van der Waals device fabrication,"Van der Waals electrode integration is a promising strategy to create
near-perfect interfaces between metals and two-dimensional materials, with
advantages such as eliminating Fermi-level pinning and reducing contact
resistance. However, the lack of a simple, generalizable pick-and-place
transfer technology has greatly hampered the wide use of this technique. We
demonstrate the pick-and-place transfer of pre-fabricated electrodes from
reusable polished hydrogenated diamond substrates without the use of any
surface treatments or sacrificial layers. The technique enables transfer of
large-scale arbitrary metal electrodes, as demonstrated by successful transfer
of eight different elemental metals with work functions ranging from 4.22 to
5.65 eV. The mechanical transfer of metal electrodes from diamond onto van der
Waals materials creates atomically smooth interfaces with no interstitial
impurities or disorder, as observed with cross-sectional high-resolution
transmission electron microscopy and energy-dispersive X-ray spectroscopy. As a
demonstration of its device application, we use the diamond-transfer technique
to create metal contacts to monolayer transition metal dichalcogenide
semiconductors with high-work-function Pd, low-work-function Ti, and semi metal
Bi to create n- and p-type field-effect transistors with low Schottky barrier
heights. We also extend this technology to other applications such as ambipolar
transistor and optoelectronics, paving the way for new device architectures and
high-performance devices.",2405.12830v1
2013-08-15,Spin heat accumulation induced by tunneling from a ferromagnet,"An electric current from a ferromagnet into a non-magnetic material can
induce a spin-dependent electron temperature. Here it is shown that this spin
heat accumulation, when created by tunneling from a ferromagnet, produces a
non-negligible voltage signal that is comparable to that due to the coexisting
electrical spin accumulation and can give a different Hanle spin precession
signature. The effect is governed by the spin polarization of the Peltier
coefficient of the tunnel contact, its Seebeck coefficient, and the spin heat
resistance of the non-magnetic material, which is related to the electrical
spin resistance by a spin-Wiedemann-Franz law. Moreover, spin heat injection is
subject to a heat conductivity mismatch that is overcome if the tunnel
interface has a sufficiently large resistance.",1308.3365v2
2015-08-21,In-Plane fracture of laminated fiber reinforced composites with varying fracture resistance: experimental observations and numerical crack propagation simulations,"A series of experimental results on the in-plane fracture of a fiber
reinforced laminated composite panel is analyzed using the variational
multi-scale cohesive method (VMCM). The VMCM results demonstrate the influence
of specimen geometry and load distribution on the propagation of large scale
bridging cracks in the fiber reinforced panel. Experimentally observed
variation in fracture resistance is substantiated numerically by comparing the
experimental and VMCM load-displacement responses of geometrically scaled
single edge-notch three point bend (SETB) specimens. The results elucidate the
size dependence of the traction-separation relationship for this class of
materials even in moderately large specimens, contrary to the conventional
understanding of it being a material property. The existence of a ""free
bridging zone"" (different from the conventional ""full bridging zone"") is
recognized, and its influence on the evolving fracture resistance is discussed.
The numerical simulations and ensuing bridging zone evolution analysis
demonstrates the versatility of VMCM in objectively simulating progressive
crack propagation, compared against conventional numerical schemes like
traditional cohesive zone modeling, which require a priori knowledge of the
crack path.",1508.06220v1
2016-06-17,Atomically-thin Ohmic Edge Contacts Between Two-dimensional Materials,"With the decrease of the dimensions of electronic devices, the role played by
electrical contacts is ever increasing, eventually coming to dominate the
overall device volume and total resistance. This is especially problematic for
monolayers of semiconducting transition metal dichalcogenides (TMDs), which are
promising candidates for atomically thin electronics. Ideal electrical contacts
to them would require the use of similarly thin electrode materials while
maintaining low contact resistances. Here we report a scalable method to
fabricate ohmic graphene edge contacts to two representative monolayer TMDs -
MoS2 and WS2. The graphene and TMD layer are laterally connected with
wafer-scale homogeneity, no observable overlap or gap, and a low average
contact resistance of 30 k$\Omega$ $\mu$m. The resulting graphene edge contacts
show linear current-voltage (IV) characteristics at room temperature, with
ohmic behavior maintained down to liquid helium temperatures.",1606.05393v1
2017-10-04,A phononic switch based on ferroelectric domain walls,"The ease with which domain walls (DWs) in ferroelectric materials can be
written and erased provides a versatile way to dynamically modulate heat
fluxes. In this work we evaluate the thermal boundary resistance (TBR) of
180$^{\circ}$ DWs in prototype ferroelectric perovskite PbTiO$_3$ within the
numerical formalisms of nonequilibrium molecular dynamics and nonequilibrium
Green's functions. An excellent agreement is obtained for the TBR of an
isolated DW derived from both approaches, which reveals the harmonic character
of the phonon-DW scattering mechanism. The thermal resistance of the
ferroelectric material is shown to increase up to around 20%, in the system
sizes here considered, due to the presence of a single DW, and larger
resistances can be attained by incorporation of more DWs along the path of
thermal flux. These results, obtained at device operation temperatures, prove
the viability of an electrically actuated phononic switch based on
ferroelectric DWs.",1710.01574v1
2019-09-13,Theory of anisotropic elastoresistivity of two-dimensional extremely strongly correlated metals,"There is considerable recent interest in the phenomenon of anisotropic
electroresistivity of correlated metals. While some interesting work has been
done on the iron-based superconducting systems, not much is known for the
cuprate materials. Here we study the anisotropy of elastoresistivity for
cuprates in the normal state. We present theoretical results for the effect of
strain on resistivity, and additionally on the optical weight and local density
of states. We use the recently developed extremely strongly correlated Fermi
liquid theory in two dimensions, which accounts quantitatively for the
unstrained resistivities for three families of single-layer cuprates. The
strained hoppings of a tight-binding model are roughly modeled analogously to
strained transition metals. The strained resistivity for a two-dimensional
$t$-$t'$-$J$ model are then obtained, using the equations developed in recent
work. Our quantitative predictions for these quantities have the prospect of
experimental tests in the near future, for strongly correlated materials such
as the hole-doped and electron-doped high-$T_c$ materials.",1909.06471v4
2020-09-04,Relation between resistance drift and optical gap in phase change materials,"The optical contrast in a phase change material is concomitant with its
structural transition. We connect these two by first recognizing that Friedel
oscillations couple electrons propagating in opposite directions and supply an
additional Coulomb energy. As the crystal switches phase, this energy acquires
time dependence and the Landau-Zener mechanism operates, steering population
transfer from the valence to the conduction band and vice versa. Spectroscopy
suggests that the oscillator energy dominates the optical properties and a
calculation involving the crystalline field and spin-orbit interaction yields
good estimates for of both structural phases. Further analysis relates the
optical gap with the crystalline-field energy as well as activation energy for
electrical conduction. This last property characterizes the amorphous phase,
thereby furnishing a link between the crystalline field and the activation
energy and ultimately with the resistance drift exponent. Providing optical
means to quantify resistance drift in PCMs could circumvent the need for
fabricating expensive devices and performing time consuming measurements.",2009.02048v1
2017-05-23,Reducing Graphene Device Variability with Yttrium Sacrificial Layers,"Graphene technology has made great strides since the material was isolated
more than a decade ago. However, despite improvements in growth quality and
numerous 'hero' devices, challenges of uniformity remain, restricting
large-scale development of graphene-based technologies. Here we investigate and
reduce the variability of graphene transistors by studying the effects of
contact metals (with and without Ti layer), resist, and yttrium (Y) sacrificial
layers during the fabrication of hundreds of devices. We find that with optical
photolithography, residual resist and process contamination is unavoidable,
ultimately limiting device performance and yield. However, using Y sacrificial
layers to isolate the graphene from processing conditions improves the yield
(from 73% to 97%), average device performance (three-fold increase of mobility,
58% lower contact resistance), and the device-to-device variability (standard
deviation of Dirac voltage reduced by 20%). In contrast to other sacrificial
layer techniques, removal of the Y sacrificial layer with HCl does not harm
surrounding materials, simplifying large-scale graphene fabrication.",1705.09388v1
2019-10-24,Magneto-memristive switching in a two-dimensional layer antiferromagnet,"Memristive devices whose resistance can be hysteretically switched by
electric field or current are intensely pursued both for fundamental interest
as well as potential applications in neuromorphic computing and phase-change
memory. When the underlying material exhibits additional charge or spin order,
the resistive states can be directly coupled, further allowing for electrical
control of the collective phases. Here, we report the observation of abrupt,
memristive switching of tunneling current in nanoscale junctions of ultrathin
CrI$_3$, a natural layer antiferromagnet. The coupling to spin order enables
both tuning of the resistance hysteresis by magnetic field, and electric-field
switching of magnetization even in multilayer samples.",1910.11383v1
2019-11-14,Nonvolatile Resistive Switching in Nanocrystalline Molybdenum Disulfide with Ion-Based Plasticity,"Non-volatile resistive switching is demonstrated in memristors with
nanocrystalline molybdenum disulfide (MoS$_2$) as the active material. The
vertical heterostructures consist of silicon, vertically aligned MoS$_2$ and
chrome / gold metal electrodes. Electrical characterizations reveal a bipolar
and forming free switching process with stable retention for at least 2500
seconds. Controlled experiments carried out in ambient and vacuum conditions
suggest that the observed resistive switching is based on hydroxyl ions
(OH$^-$). These originate from catalytic splitting of adsorbed water molecules
by MoS$_2$. Experimental results in combination with analytical simulations
further suggest that electric field driven movement of the mobile OH$^-$ ions
along the vertical MoS$_2$ layers influences the energy barrier at the
Si/MoS$_2$ interface. The scalable and semiconductor production compatible
device fabrication process used in this work offers the opportunity to
integrate such memristors into existing silicon technology for future
neuromorphic applications. The observed ion-based plasticity may be exploited
in ionicelectronic devices based on TMDs and other 2D materials for memristive
applications.",1911.06032v1
2023-02-20,Extraordinary Bulk Insulating Behavior in the Strongly Correlated Materials FeSi and FeSb$_2$,"4$f$ electron-based topological Kondo insulators have long been researched
for their potential to conduct electric current via protected surface states,
while simultaneously exhibiting unusually robust insulating behavior in their
interiors. To this end, we have investigated the electrical transport of the
3$d$-based correlated insulators FeSi and FeSb$_2$, which have exhibited enough
similarities to their $f$ electron cousins to warrant investigation. By using a
double-sided Corbino disk transport geometry, we show unambiguous evidence of
surface conductance in both of these Fe-based materials. In addition, by using
a 4-terminal Corbino inverted resistance technique, we extract the bulk
resistivity as a function of temperature. Similar to topological Kondo
insulator SmB$_6$, the bulk resistivity of FeSi and FeSb$_2$ are confirmed to
exponentially increase by up to 9 orders of magnitude from room temperature to
the lowest accessible temperature. This demonstrates that these materials are
excellent bulk insulators, providing an ideal platform for studying correlated
2D physics.",2302.09996v1
2023-06-27,Phase transitions associated with magnetic-field induced topological orbital momenta in a non-collinear antiferromagnet,"Resistivity measurements are widely exploited to uncover electronic
excitations and phase transitions in metallic solids. While single crystals are
preferably studied to explore crystalline anisotropies, these usually cancel
out in polycrystalline materials. Here we show that in polycrystalline
Mn3Zn0.5Ge0.5N with non-collinear antiferromagnetic order, changes in the
diagonal and, rather unexpected, off-diagonal components of the resistivity
tensor occur at low temperatures indicating subtle transitions between magnetic
phases of different symmetry. This is supported by neutron scattering and
explained within a phenomenological model which suggests that the phase
transitions in magnetic field are associated with field induced topological
orbital momenta. The fact that we observe transitions between spin phases in a
polycrystal, where effects of crystalline anisotropy are cancelled suggests
that they are only controlled by exchange interactions. The observation of an
off-diagonal resistivity extends the possibilities for realising
antiferromagnetic spintronics with polycrystalline materials.",2306.15332v1
2023-10-20,3D Printed Architectured Silicones with Autonomic Self-healing and Creep-resistant Behavior,"Self-healing silicones that are able to restore the functionalities and
extend the lifetime of soft devices hold great potential in many applications.
However, currently available silicones need to be triggered to self-heal or
suffer from creep-induced irreversible deformation during use. Here, we design
and print silicone objects that are programmed at the molecular and
architecture levels to achieve self-healing at room temperature while
simultaneously resisting creep. At the molecular scale, dioxaborolanes moieties
are incorporated into silicones to synthesize self-healing vitrimers, whereas
conventional covalent bonds are exploited to make creep-resistant elastomers.
When combined into architectured printed parts at a coarser length scale,
layered materials exhibit fast healing at room temperature without compromising
the elastic recovery obtained from covalent polymer networks. A
patient-specific vascular phantom is printed to demonstrate the potential of
architectured silicones in creating damage-resilient functional devices using
molecularly designed elastomer materials.",2311.05633v1
2024-04-30,Evaluation of Thermal Performance of a Wick-free Vapor Chamber in Power Electronics Cooling,"Efficient thermal management in high-power electronics cooling can be
achieved using phase-change heat transfer devices, such as vapor chambers.
Traditional vapor chambers use wicks to transport condensate for efficient
thermal exchange and to prevent ""dry-out"" of the evaporator. However, wicks in
vapor chambers present significant design challenges arising out of large
pressure drops across the wicking material, which slows down condensate
transport rates and increases the chances for dry-out. Thicker wicks add to
overall thermal resistance, while deterring the development of thinner devices
by limiting the total thickness of the vapor chamber. Wickless vapor chambers
eliminate the use of metal wicks entirely, by incorporating complementary
wettability-patterned flat plates on both the evaporator and the condenser
side. Such surface modifications enhance fluid transport on the evaporator
side, while allowing the chambers to be virtually as thin as imaginable,
thereby permitting design of thermally efficient thin electronic cooling
devices. While wick-free vapor chambers have been studied and efficient design
strategies have been suggested, we delve into real-life applications of
wick-free vapor chambers in forced air cooling of high-power electronics. An
experimental setup is developed wherein two Si-based MOSFETs of TO-247-3
packaging having high conduction resistance, are connected in parallel and
switched at 100 kHz, to emulate high frequency power electronics operations. A
rectangular copper wick-free vapor chamber spreads heat laterally over a
surface 13 times larger than the heating area. This chamber is cooled
externally by a fan that circulates air at room temperature. The present
experimental setup extends our previous work on wick-free vapor chambers, while
demonstrating the effectiveness of low-cost air cooling in vapor-chamber
enhanced high-power electronics applications.",2404.19195v1
2017-07-26,Particle acceleration with anomalous pitch angle scattering in 2D MHD reconnection simulations,"The conversion of magnetic energy into other forms during solar flares is one
of the outstanding open problems in solar physics. It is generally accepted
that magnetic reconnection plays a crucial role in these conversion processes.
To achieve the rapid energy release required in solar flares, an anomalous
resistivity, orders of magnitude higher than the Spitzer resistivity, is often
used in MHD simulations of reconnection. Spitzer resistivity is based on
Coulomb scattering, which becomes negligible at the high energies achieved by
accelerated particles. As a result, simulations of particle acceleration in
reconnection events are often performed in the absence of any interaction
between accelerated particles and any background plasma. This need not be the
case for scattering associated with anomalous resistivity caused by turbulence
within solar flares, as the higher resistivity implies an elevated scattering
rate. We present results of test particle calculations, with and without pitch
angle scattering, subject to fields derived from MHD simulations of
two-dimensional (2D) X-point reconnection. Scattering rates proportional to the
ratio of the anomalous resistivity to the local Spitzer resistivity, as well as
at fixed values, are considered. Pitch angle scattering, which is independent
of the anomalous resistivity, causes higher maximum energies in comparison to
those obtained without scattering. Scattering rates which are dependent on the
local anomalous resistivity tend to produce fewer highly energised particles
due to weaker scattering in the separatrices, even though scattering in the
current sheet may be stronger when compared to resistivity-independent
scattering. Strong scattering also causes an increase in the number of
particles exiting the computational box in the reconnection outflow region, as
opposed to along the separatrices as is the case in the absence of scattering.",1709.00305v1
2023-02-04,"Smooth, homogeneous, high-purity Nb3Sn superconducting RF resonant cavity by seed-free electrochemical synthesis","Workbench-size particle accelerators, enabled by Nb3Sn-based superconducting
radio-frequency (SRF) cavities, hold the potential of driving scientific
discovery by offering a widely accessible and affordable source of high-energy
electrons and X-rays. Thin-film Nb3Sn RF superconductors with high quality
factors, high operation temperatures, and high-field potentials are critical
for these devices. However, surface roughness, non-stoichiometry, and
impurities in Nb3Sn deposited by conventional Sn-vapor diffusion prevent them
from reaching their theoretical capabilities. Here we demonstrate a seed-free
electrochemical synthesis that pushes the limit of chemical and physical
properties in Nb3Sn. Utilization of electrochemical Sn pre-deposits reduces the
roughness of converted Nb3Sn by five times compared to typical vapor-diffused
Nb3Sn. Quantitative mappings using chemical and atomic probes confirm improved
stoichiometry and minimized impurity concentrations in electrochemically
synthesized Nb3Sn. We have successfully applied this Nb3Sn to the large-scale
1.3 GHz SRF cavity and demonstrated ultra-low BCS surface resistances at
multiple operation temperatures, notably lower than vapor-diffused cavities.
Our smooth, homogeneous, high-purity Nb3Sn provides the route toward high
efficiency and high fields for SRF applications under helium-free cryogenic
operations.",2302.02054v2
2018-03-08,Design of a nickel-base superalloy using a neural network,"A new computational tool has been developed to model, discover, and optimize
new alloys that simultaneously satisfy up to eleven physical criteria. An
artificial neural network is trained from pre-existing materials data that
enables the prediction of individual material properties both as a function of
composition and heat treatment routine, which allows it to optimize the
material properties to search for the material with properties most likely to
exceed a target criteria. We design a new polycrystalline nickel-base
superalloy with the optimal combination of cost, density, gamma' phase content
and solvus, phase stability, fatigue life, yield stress, ultimate tensile
strength, stress rupture, oxidation resistance, and tensile elongation.
Experimental data demonstrates that the proposed alloy fulfills the
computational predictions, possessing multiple physical properties,
particularly oxidation resistance and yield stress, that exceed existing
commercially available alloys.",1803.03039v1
2023-04-22,Studies of two-dimensional material resistive random-access memory by kinetic Monte Carlo simulations,"Resistive memory based on 2D WS2, MoS2, and h-BN materials has been studied,
including experiments and simulations. The influences with different active
layer thicknesses have been discussed, including experiments and simulations.
The thickness with the best On/Off ratio is also found for the 2D RRAM. This
work reveals fundamental differences between a 2D RRAM and a conventional oxide
RRAM. Furthermore, from the physical parameters extracted with the KMC model,
the 2D materials have a lower diffusion activation energy from the vertical
direction, where a smaller bias voltage and a shorter switching time can be
achieved. It was also found the diffusion activation energy from the CVD-grown
sample is much lower than the mechanical exfoliated sample. The result shows
MoS2 has the fastest switching speed among three 2D materials.",2304.11345v2
2018-11-25,Atomic mechanisms of fast diffusion of large atoms in Germanium,"The performance of strained silicon as the channel material for transistors
has plateaued. Motivated by increasing charge-carrier mobility within the
device channel to improve transistor performance, germanium (Ge) is considered
as an attractive option as a silicon replacement due to its highest p-type
mobility in all of the known semiconductor materials and being compatible with
today's conventional CMOS manufacturing process. However, the intrinsically
high carrier mobility of Ge becomes significantly degraded because Ge's native
oxide is unstable and readily decomposes into several GexOy suboxides with a
high density of dangling bonds at the surface. In addition, these interface
trap states will also degrade the off-state leakage current and subthreshold
turn-off of a Ge-based device, significantly affecting its stability.
Furthermore, obtaining low-resistance Ohmic contacts to n-type Ge is another
key challenge in developing Ge CMOS. To solve these challenges, extensive
efforts have been made about the incorporation of new materials, such as Al2O3,
SiN3, TiO2, ZnO, Ge3N4, MgO, HfO2, SrTiO3, and Y2O3, into Ge transistors.
Controlling the diffusion of foreign atoms into Ge is therefore a critical
issue in developing Ge transistors regarding that foreign impurities may be
detrimental to devices. In this work, we study the diffusion properties of all
common elements in Ge by performing the first-principle calculations with a
nudged elastic band method. We find some large atoms, such as Cu, Au, Pd, etc.,
have a very small diffusion barrier. We reveal the underlying mechanism in a
combination of local distortion induced by size effect and bonding effect that
controls the diffusion behaviors of different atoms in Ge. This comprehensive
study and relatively in-depth understanding of diffusion in Ge provides us with
a practical guide for utilizing it more efficiently in semiconductor devices.",1811.10046v1
2022-07-29,Reactive Two-Step Additive Manufacturing of Ultra-high Temperature Carbide Ceramics,"Ultra-high-temperature ceramics (UHTCs) are candidate structural materials
for applications that require resiliency to extreme temperature (>2000{\deg}C),
high mechanical loads, or aggressive oxidizing environments. Processing UHTC
transition metal carbides as standalone materials using additive manufacturing
(AM) methods has not been fully realized due to their extremely slow atomic
diffusivities that impede sintering and large volume changes during indirect AM
that can induce defect structures. In this work, a two-step, reactive AM
approach was studied for the formation of the ultra-high temperature ceramic
TiCx. Readily available equipment including a polymer powder bed fusion AM
machine and a traditional tube furnace were used to produce UHTC cubes and
lattice structures with sub-millimeter resolution. This processing scheme
incorporated, (1) selective laser sintering of a Ti precursor mixed with a
phenolic binder for green body shaping, and (2) ex-situ, isothermal gas-solid
conversion of the green body in CH4 to form TiCx structures. Reactive
post-processing in CH4 resulted in up to 98.2 wt% TiC0.90 product yield and a
reduction in net-shrinkage during consolidation due to the volume expansion
associated with the conversion of Ti to TiC. Results indicated that reaction
bonding associated with the Gibbs free energy release associated with TiC
formation produced interparticle adhesion at low furnace processing
temperatures. The ability to bond highly refractory materials through this type
of process resulted in structures that were crack-free and resisted fracture
during thermal shock testing. Broadly, the additive manufacturing approach
presented could be useful for the production of many UHTC carbides that might
otherwise be incompatible with prevailing AM techniques that do not include
reaction synthesis.",2208.00052v3
2003-05-29,Structural and electrical properties of tantalum nitride thin films fabricated by using reactive radio-frequency magnetron sputtering,"TaN thin film is an attractive interlayer as well as a diffusion barrier
layer in [FeN/TaN](n) multilayers for the application as potential write-head
materials in high-density magnetic recording. We synthesized two series of TaN
films on glass and Si substrates by using reactive radio-frequency sputtering
under 5-mtorr Ar/N-2 processing pressure with varied N-2 partial pressure, and
carried out systematic characterization analyses of the films. We observed
clear changes of phases in the films from metallic bcc Ta to a mixture of bcc
Ta(N) and hexagonal Ta2N, then sequentially to fcc TaN and a mixture of TaN
with N-rich phases when the N2 partial pressure increased from 0.0% to 30%. The
changes were associated with changes in the grain shapes as well as in the
preferred crystalline orientation of the films from bcc Ta [100] to [110], then
to random and finally to fcc TaN [111], correspondingly. They were also
associated with a change in film resistivity from metallic to
semiconductor-like behavior in the range of 77-295 K. The films showed a
typical polycrystalline textured structure with small, crystallized domains and
irregular grain shapes. Clear preferred (111) stacks parallel to the substrate
surface with embedded amorphous regions were observed in the film. TaN film
with [ 111]-preferred orientation and a resistivity of 6.0 m Omega cm was
obtained at 25% N-2 partial pressure, which may be suitable for the interlayer
in [FeN/TaN](n) multilayers.",0305683v2
2011-12-08,"Structural, Thermal, Magnetic and Electronic Transport Properties of the LaNi2(Ge{1-x}P{x})2 System","Polycrystalline samples of LaNi2(Ge{1-x}P{x})2 (x = 0, 0.25, 0.50, 0.75, 1)
were synthesized and their properties investigated by x-ray diffraction (XRD),
heat capacity Cp, magnetic susceptibility chi, and electrical resistivity rho
measurements versus temperature T. These compounds all crystallize in the
body-centered-tetragonal ThCr2Si2-type structure. The rho(T) measurements
indicate that all compositions in this system are metallic. The low-T Cp
measurements yield a rather large Sommerfeld coefficient gamma = 12.4(2) mJ/mol
K^2 for x = 0 reflecting a large density of states at the Fermi energy that is
comparable with the largest values found for the AFe2As2 class of materials
with the same crystal structure. The gamma decreases approximately linearly
with x to 7.4(1) mJ/mol K^2 for x = 1. The chi measurements show nearly
temperature-independent paramagnetic behavior across the entire range of
compositions except for LaNi2Ge2, where a broad peak is observed at 300 K from
chi(T) measurements up to 1000 K that may arise from short-range
antiferromagnetic correlations in a quasi-two-dimensional magnetic system.
High-accuracy Pade approximants representing the Debye lattice heat capacity
and Bloch-Gruneisen electron-phonon resistivity functions versus T are
presented and are used to analyze our experimental Cp(T) and rho(T) data,
respectively. The T-dependences of rho for all samples are well-described by
the Bloch-Gruneisen model, although the observed rho(300 K) values are larger
than calculated from this model. A significant T-dependence of the Debye
temperature determined from the Cp(T) data was observed for each composition.
No clear evidence for bulk superconductivity or any other long-range phase
transition was found for any of the compositions studied.",1112.1864v2
2013-08-14,Stable pseudoanalytical computation of electromagnetic fields from arbitrarily-oriented dipoles in cylindrically stratified media,"Computation of electromagnetic fields due to point sources (Hertzian dipoles)
in cylindrically stratified media is a classical problem for which analytical
expressions of the associated tensor Green's function have been long known.
However, under finite-precision arithmetic, direct numerical computations based
on the application of such analytical (canonical) expressions invariably lead
to underflow and overflow problems related to the poor scaling of the
eigenfunctions (cylindrical Bessel and Hankel functions) for extreme arguments
and/or high-order, as well as convergence problems related to the numerical
integration over the spectral wavenumber and to the truncation of the infinite
series over the azimuth mode number. These problems are exacerbated when a
disparate range of values is to be considered for the layers' thicknesses and
material properties (resistivities, permittivities, and permeabilities), the
transverse and longitudinal distances between source and observation points, as
well as the source frequency. To overcome these challenges in a systematic
fashion, we introduce herein different sets of range-conditioned, modified
cylindrical functions (in lieu of standard cylindrical eigenfunctions), each
associated with non-overlapped subdomains of (numerical) evaluation to allow
for stable computations under any range of physical parameters. In addition
adaptively-chosen integration contours are employed in the complex spectral
wavenumber plane to ensure convergent numerical integration in all cases. We
illustrate the application of the algorithm to problems of geophysical interest
involving layer resistivities ranging from 1000 $\Omega \cdot$m to 10$^{-8}
\Omega \cdot$m, frequencies of operation ranging from 10 MHz down to the low
magnetotelluric range of 0.01 Hz, and for various combinations of layer
thicknesses.",1308.3179v2
2019-03-01,Coexistence of metallic and nonmetallic properties in the pyrochlore Lu$_2$Rh$_2$O$_7$,"Transition metal oxides of the $4d$ and $5d$ block have recently become the
targets of materials discovery, largely due to their strong spin-orbit coupling
that can generate exotic magnetic and electronic states. Here we report the
high pressure synthesis of Lu$_2$Rh$_2$O$_7$, a new cubic pyrochlore oxide
based on $4d^5$ Rh$^{4+}$ and characterizations via thermodynamic, electrical
transport, and muon spin relaxation measurements. Magnetic susceptibility
measurements reveal a large temperature-independent Pauli paramagnetic
contribution, while heat capacity shows an enhanced Sommerfeld coefficient,
$\gamma$ = 21.8(1) mJ/mol-Rh K$^2$. Muon spin relaxation measurements confirm
that Lu$_2$Rh$_2$O$_7$ remains paramagnetic down to 2 K. Taken in combination,
these three measurements suggest that Lu$_2$Rh$_2$O$_7$ is a correlated
paramagnetic metal with a Wilson ratio of $R_W = 2.5$. However, electric
transport measurements present a striking contradiction as the resistivity of
Lu$_2$Rh$_2$O$_7$ is observed to monotonically increase with decreasing
temperature, indicative of a nonmetallic state. Furthermore, although the
magnitude of the resistivity is that of a semiconductor, the temperature
dependence does not obey any conventional form. Thus, we propose that
Lu$_2$Rh$_2$O$_7$ may belong to the same novel class of non-Fermi liquids as
the nonmetallic metal FeCrAs.",1903.00399v1
2022-01-10,"Alloyed B-(AlxGa1-x)2O3 bulk Czochralski single B-(Al0.1Ga0.9)2O3 and polycrystals B-(Al0.33Ga0.66)2O3, B-(Al0.5Ga0.5)2O3), and property trends","In this work, bulk Czochralski-grown single crystals of 10 mol. % Al2O3
alloyed B-Ga2O3 - monoclinic 10% AGO or B-(Al0.1Ga0.9)2O3 - are obtained, which
show +0.20 eV increase in the bandgap compared with unintentionally doped
B-Ga2O3. Further, growths of 33% AGO - B-(Al0.33Ga0.67)2O3 - and 50% AGO -
B-(Al0.5Ga0.5)2O3 or B-AlGaO3 - produce polycrystalline single-phase monoclinic
material (B-AGO). All three compositions are investigated by x-ray diffraction,
Raman spectroscopy, optical absorption, and 27Al nuclear magnetic resonance
(NMR). By investigating single phase B-AGO over a large range of Al2O3
concentrations (10 - 50 mol. %), broad trends in the lattice parameter,
vibrational modes, optical bandgap, and crystallographic site preference are
determined. All lattice parameters show a linear trend with Al incorporation.
According to NMR, aluminum incorporates on both crystallographic sites of
B-Ga2O3, with a slight preference for the octahedral (GaII) site, which becomes
more disordered with increasing Al. Single crystals of 10% AGO were also
characterized by x-ray rocking curve, transmission electron microscopy, purity
(glow discharge mass spectroscopy and x-ray fluorescence), optical transmission
(200 nm - 20 um wavelengths), and resistivity. These measurements suggest that
electrical compensation by impurity acceptor doping is not the likely
explanation for high resistivity, but rather the shift of a hydrogen level from
a shallow donor to a deep acceptor due to Al alloying. .. Cont.
  This article may be downloaded for personal use only. Any other use requires
prior permission of the author and AIP Publishing. This article appeared in
Journal of Applied Physics 131 155702.",2201.03673v2
2023-02-09,Spark Discharge Generator as a Stable and Reliable Nanoparticle Synthesis Device: Analysis of the Impact of Process and Circuit Variables on the Characteristics of Synthesized Nanoparticles,"Nanotechnology offers the promise of harnessing quantum properties not
available in the bulk phase. These desirable properties are highly dependent on
size and composition. Generators that control these variables are therefore
essential for progress in the field. The spark discharge generator (SDG) is an
outstanding aerosol route for nanoparticle synthesis, which stands out due to
its fast kinetics, scalability, high purity, accuracy and reproducibility with
the added advantage of allowing the synthesis of nanoparticles of any
conducting material. These advantages are a consequence of its vast heating and
cooling rates, its intrinsic and easily controllable electronic variables at
the reach of a click. However, the mechanistic impact of these variables on the
actual aerosol generated is still not fully understood. In this work, we
constructed an SDG and systematically studied its behavior with particular
interest in the effect that resistance, capacitance, inductance, flow rate, gap
separation and current have on the electrical behavior of the spark. Our model
system produced primarily Fe and Cu nanoparticles with measured concentrations.
We discuss how the spark influences particle size and number concentration and
provide useful correlations that link dependent with independent variables.
Remarkably, a finite resistance produces a maximum in the output of the
generated aerosols. This suggests a direct link between RLC properties of the
circuit and cabling into the frequency of the spark, and nanoparticle number
concentration, indicating potential for exploiting such behavior towards
maximizing nanoparticle generation. Furthermore, we discuss a link between
spark oscillations and energy release with its consequent aerosol generation.",2302.04760v1
2013-08-08,"Ultra-low Energy, High-Performance Dynamic Resistive Threshold Logic","We propose dynamic resistive threshold-logic (DRTL) design based on
non-volatile resistive memory. A threshold logic gate (TLG) performs summation
of multiple inputs multiplied by a fixed set of weights and compares the sum
with a threshold. DRTL employs resistive memory elements to implement the
weights and the thresholds, while a compact dynamic CMOS latch is used for the
comparison operation. The resulting DRTL gate acts as a low-power, configurable
dynamic logic unit and can be used to build fully pipelined, high-performance
programmable computing blocks. Multiple stages in such a DRTL design can be
connected using energy-efficient low swing programmable interconnect networks
based on resistive switches. Owing to memory-based compact logic and
interconnect design and highspeed dynamic-pipelined operation, DRTL can achieve
more than two orders of magnitude improvement in energy-delay product as
compared to look-up table based CMOS FPGA.",1308.4672v1
2013-10-11,Curvature dependence of the interfacial heat and mass transfer coefficients,"Nucleation is often accompanied by heat transfer between the surroundings and
a nucleus of a new phase. The interface between two phases gives an additional
resistance to this transfer. For small nuclei the interfacial curvature is
high, which affects not only equilibrium quantities such as surface tension,
but also the transport properties. In particular, high curvature affects the
interfacial resistance to heat and mass transfer. We develop a framework for
determining the curvature dependence of the interfacial heat and mass transfer
resistances. We determine the interfacial resistances as a function of a
curvature. The analysis is performed for a bubble of a one-component fluid and
may be extended to various nuclei of multicomponent systems. The curvature
dependence of the interfacial resistances is important in modeling transport
processes in multiphase systems.",1310.3025v1
2014-08-30,Anisotropic resistivity of the monolayer graphene in the trigonal warping and connected Fermi curve regimes,"In the present study, the anisotropic resistivity of the monolayer graphene
has been obtained in semiclassical regime beyond the Dirac point approximation.
In particular, detailed investigations were made on the dependence of
conductivity on the Fermi energy. At low energies, in the vicinity of the Dirac
points, band energy of the monolayer graphene is isotropic at the Fermi level.
Meanwhile, at the intermediate Fermi energies anisotropic effects such as
trigonal warping is expected to be the origin of the anisotropic resistivity.
However, besides the band anisotropy there also exists an other source of
anisotropic resistivity which was introduced by scattering matrix. At high
energies it was shown that the band anisotropy is less effective than the
anisotropy generated by the scattering matrix. It was also shown that there
exist two distinct regimes of anisotropic resistivity corresponding the
trigonal warping and connected Fermi curve at intermediate and high energies
respectively.",1409.0130v1
2018-08-19,Temperature Dependence of In-plane Resistivity and Inverse Hall Angle in NLED Holographic Model,"In the strange metal phase of the high-$T_{c}$ cuprates, it is challenging to
explain the linear temperature dependence of the in-plane resistivity and the
quadratic temperature dependence of the inverse Hall angle. In this paper, we
investigate the temperature dependence of the in-plane resistivity and inverse
Hall angle in the nonlinear electrodynamics holographic model developed in our
recent work. Maxwell electrodynamics and Born-Infeld electrodynamics are
considered. Both cases support a wide spectrum of temperature scalings in
parameter space. For Maxwell electrodynamics, the T-linear in-plane resistivity
generally dominates at low temperatures and survives into higher temperatures
in a narrow strip-like manner. Meanwhile, the T-quadratic inverse Hall angle
dominates at high temperatures and extends down to lower temperatures. The
overlap between the T-linear in-plane resistivity and the T-quadratic inverse
Hall angle, if occurs, would generally present in the intermediate temperate
regime. The Born-Infeld case with $a>0$ is quite similar to the Maxwell case.
For the Born-Infeld case with $a<0$, there can be a constraint on the charge
density and magnetic field. Moreover, the overlap can occur for strong charge
density.",1808.06158v1
2019-04-18,Non-Stationary Polar Codes for Resistive Memories,"Resistive memories are considered a promising memory technology enabling high
storage densities with in-memory computing capabilities. However, the readout
reliability of resistive memories is impaired due to the inevitable existence
of wire resistance, resulting in the sneak path problem. Motivated by this
problem, we study polar coding over channels with different reliability levels,
termed non-stationary polar codes, and we propose a technique improving its bit
error rate (BER) performance. We then apply the framework of non-stationary
polar codes to the crossbar array and evaluate its BER performance under two
modeling approaches, namely binary symmetric channels (BSCs) and binary
asymmetric channels (BSCs). Finally, we propose a technique for biasing the
proportion of high-resistance states in the crossbar array and show its
advantage in reducing further the BER. Several simulations are carried out
using a SPICE-like simulator, exhibiting significant reduction in BER.",1904.08966v1
2019-12-06,Write and Read Channel Models for 1S1R Crossbar Resistive Memory with High Line Resistance,"Crossbar resistive memory with 1 Selector 1 Resistor (1S1R) structure is
attractive for low-cost and high-density nonvolatile memory applications. As
technology scales down to the single-nm regime, the increasing resistivity of
wordline/bitline becomes a limiting factor to device reliability. This paper
presents write/read communication channels while considering the line
resistance and device variabilities by statistically relating the degraded
write/read margins and the channel parameters. Binary asymmetric channel (BAC)
models are proposed for the write/read operations. Simulations based on these
models suggest that the bit-error rate of devices are highly non-uniform across
the memory array. These models provide quantitative tools for evaluating the
trade-offs between memory reliability and design parameters, such as array
size, technology nodes, and aspect ratio, and also for designing
coding-theoretic solutions that would be most effective for crossbar memory.",1912.02963v3
2020-05-15,Anomalous Electrical Conduction and Negative Temperature Coefficient of Resistance in Nanostructured Gold Resistive Switching Films,"We report on the observation of non-metallic electrical conduction, resistive
switching, and a negative temperature coefficient of resistance in
cluster-assembled nanostructured gold films above the electrical percolation
and in strong-coupling regime, from room to cryogenic temperatures (24K). The
structure of the films is characterized by an extremely high density of
randomly oriented crystalline nanodomains, separated by grain boundaries. The
observed behavior can be explained by considering space charge limited
conduction and Coulomb blockade phenomena highlighting the influence of the
high density of defects and grain boundaries on the localization of conduction
electrons. Our findings have implications for a broad class of resistive
switching systems based on random assemblies of nanoobjects.",2005.07401v1
2021-05-22,Dynamic-quenching of a single-photon avalanche photodetector using an adaptive resistive switch,"One of the most common approaches for quenching single-photon avalanche
diodes is to use a passive resistor in series with it. A drawback of this
approach has been the limited recovery speed of the single-photon avalanche
diodes. High resistance is needed to quench the avalanche, leading to slower
recharging of the single-photon avalanche diodes depletion capacitor. We
address this issue by replacing a fixed quenching resistor with a
bias-dependent adaptive resistive switch. Reversible generation of metallic
conduction enables switching between low and high resistance states under
unipolar bias. As an example, using a Pt/Al2O3/Ag resistor with a commercial
silicon single-photon avalanche diodes, we demonstrate avalanche pulse widths
as small as ~30 ns, 10x smaller than a passively quenched approach, thus
significantly improving the single-photon avalanche diodes frequency response.
The experimental results are consistent with a model where the adaptive
resistor dynamically changes its resistance during discharging and recharging
the single-photon avalanche diodes.",2105.11454v2
2022-09-14,Picosecond Time-Scale Resistive Switching Monitored in Real-Time,"The resistance state of filamentary memristors can be tuned by relocating
only a few atoms at interatomic distances in the active region of a conducting
filament. Thereby the technology holds promise not only in its ultimate
downscaling potential and energy efficiency but also in unprecedented speed.
Yet, the breakthrough in high-frequency applications still requires the
clarification of the dominant mechanisms and inherent limitations of ultra-fast
resistive switching. Here we investigate bipolar, multilevel resistive
switchings in tantalum pentoxide based memristors with picosecond time
resolution. We experimentally demonstrate cyclic resistive switching operation
due to 20 ps long voltage pulses of alternating polarity. Through the analysis
of the real-time response of the memristor we find that the set switching can
take place at the picosecond time-scale where it is only compromised by the
bandwidth limitations of the experimental setup. In contrast, the completion of
the reset transitions significantly exceeds the duration of the ultra-short
voltage bias, demonstrating the dominant role of thermal diffusion and
underlining the importance of dedicated thermal engineering for future
high-frequency memristor circuit applications.",2209.06732v1
2022-12-02,Nondestructive KPFM-assisted Quality Control in Fabrication of GaAs High-Speed Electronics,"In this paper, we report on the method of nondestructive quality control that
can be used in fabrication of GaAs high-speed electronics. The method relies on
the surface potential mapping and enables rigid in vivo analysis of transport
properties of an active electronic device incorporated into a complex
integrated circuit. The study is inspired by our ongoing development of a
millimeter wave intelligent reflective surface for 6G communications. To
provide desired beamforming capabilities, such a surface should utilize
hundreds of identical microscale GaAs diode switches with series resistance of
a few ohms. Thus, we develop a ladder-like layered ohmic contact to heavily
Si-doped GaAs and cross-study it via transmission line method and Kelvin probe
force microscopy. The contact resistivity as low as 0.15~$\mu \Omega \,$cm$^2$
is measured resulting in only a 0.6~$\Omega$ of resistance for the contact area
of 3$\times$3~$\mu$m$^2$. Moreover, the tendencies observed suggest that one
can rigidly analyze the evolution of contact resistance and the profile of
resistivity under contact in response to rapid thermal annealing, once the
surface potential map across the ``ladder'' is known.",2212.01474v1
2023-09-22,Terahertz scale microbunching instability driven by nonevaporable getter coating resistive-wall impedance,"Non-evaporable getter (NEG) coating is widely required in the next generation
of light sources and circular $e^+e^-$ colliders for small vacuum pipes to
improve the vacuum level, which, however, also enhances the high-frequency
resistive-wall impedance and often generates a resonator-like peak in the
terahertz frequency region. In this paper, we will use the parameters of the
planned Hefei Advanced Light Facility (HALF) storage ring to study the impact
of NEG coating resistive-wall impedance on the longitudinal microwave
instability via particle tracking simulation. Using different NEG coating
parameters (resistivity and thickness) as examples, we find that the impedance
with a narrow and strong peak in the high frequency region can cause
micro-bunching instability, which has a low instability threshold current and
contributes to a large energy spread widening above the threshold. In order to
obtain a convergent simulation of the beam dynamics, one must properly resolve
such a peak. The coating with a lower resistivity has a much less sharp peak in
its impedance spectrum, which is helpful to suppress the micro-bunching
instability and in return contributes to a weaker microwave instability.",2309.12779v1
2024-04-29,Evolution of secondary electron spectrum during cosmic-ray discharge in the universe,"We recently found that streaming cosmic rays (CRs) induce a resistive
electric field that can accelerate secondary electrons produced by CR
ionization. In this work, we study the evolution of the energy spectrum of
secondary electrons by numerically solving the one-dimensional Boltzmann
equation and Ohm's law. We show that the accelerated secondary electrons
further ionize a gas, that is, the electron avalanche occurs, resulting in
increased ionization and excitation of the gas. Although the resistive electric
field becomes weaker than one before the CR discharge, the weak resistive
electric field weakly accelerates the secondary electrons. The quasi-steady
state is almost independent of the initial resistive electric field, but
depends on the electron fraction in the gas. The resistive electric field in
the quasi-steady state is larger for the higher electron fraction, which makes
the number of secondary electrons that can ionize the gas larger, resulting in
a higher ionization rate. The CR discharge could explain the high ionization
rate that are observed in some molecular clouds.",2404.18513v1
2007-03-26,An alternative normal state c-axis resistivity model for high-Tc superconductors,"An alternative model for c-axis resistivity in layered high-Tc crystalline
superconductors is proposed and has been characterized as an essentially
two-dimensional Fermi liquid. Average ionization energy is included as
additional parameter that determines the concentration of tunnelling electrons
between Cu-O2 layers. This model agrees well quantitatively with the Bi2212 and
Y123 single crystals, and qualitatively with the pure 1212 phase polycrystals.",0703658v1
2005-02-02,Phase transitions in Lu$_2$Ir$_3$Si$_5$,"We report the results of our investigations on a polycrystalline sample of
Lu$_2$Ir$_3$Si$_5$ which crystallizes in the U$_2$Co$_3$Si$_5$ type structure
(Ibam). These investigations comprise powder X-ray diffraction, magnetic
susceptibility, electrical resistivity and high temperature (120-300 K) heat
capacity studies. Our results reveal that the sample undergoes a
superconducting transition below 3.5 K. It also undergoes a first order phase
transition between 150-250 K as revealed by an upturn in the resistivity, a
diasmagnetic drop in the magnetic susceptibility and a large anomaly (20-30
J/mol K) in the specific heat data. We observe a huge thermal hysteresis of
almost 45 K between the cooling and warming data across this high temperature
transition in all our measurements. Low temperature X-ray diffraction
measurements at 87 K reveals that the compound undergoes a structural change at
the high temperature transition. Resistivity data taken in repeated cooling and
warming cycles indicate that at the high temperature transition, the system
goes into a highly metastable state and successive heating/cooling curves are
found to lie above the previous one and the resistance keeps increasing with
every thermal cycle. The room temperature resistance of a thermaly cycled piece
of the sample decays exponentialy with time with a decay time constant
estimated to be about 10$^4$ secs. The anomaly (upturn) in the resistivity and
the large drop (almost 45%) in the susceptibility across the high temperature
transition suggest that the observed structural change is accompanied or
induced by an electronic transition.",0502041v2
2014-06-23,Resistance of helical edges formed in a semiconductor heterostructure,"Time-reversal symmetry prohibits elastic backscattering of electrons
propagating within a helical edge of a two-dimensional topological insulator.
However, small band gaps in these systems make them sensitive to doping
disorder, which may lead to the formation of electron and hole puddles. Such a
puddle -- a quantum dot -- tunnel-coupled to the edge may significantly enhance
the inelastic backscattering rate, due to the long dwelling time of an electron
in the dot. The added resistance is especially strong for dots carrying an odd
number of electrons, due to the Kondo effect. For the same reason, the
temperature dependence of the added resistance becomes rather weak. We present
a detailed theory of the quantum dot effect on the helical edge resistance. It
allows us to make specific predictions for possible future experiments with
artificially prepared dots in topological insulators. It also provides a
qualitative explanation of the resistance fluctuations observed in short HgTe
quantum wells. In addition to the single-dot theory, we develop a statistical
description of the helical edge resistivity introduced by random charge puddles
in a long heterostructure carrying helical edge states. The presence of charge
puddles in long samples may explain the observed coexistence of a high sample
resistance with the propagation of electrons along the sample edges.",1406.6052v2
2016-08-03,Non-Fermi liquid behavior of electrical resistivity close to the nematic critical point in Fe$_{1-x}$Co$_x$Se and FeSe$_{1-y}$S$_y$,"Temperature dependence of resistivity of single crystals of
Fe$_{1-x}$Co$_x$Se and FeSe$_{1-y}$S$_y$ is studied in detail under zero and
high magnetic field (magnetoresistance), the latter of which enables to monitor
the temperature ($T$) evolution of resistivity below the onset of
superconducting transition temperature ($T_{\rm c}$). In FeSe$_{1-y}$S$_y$,
$T$-linear dependence of resistivity is prominent in $y$ = 0.160 below 40 K,
whereas it changes to a Fermi-liquid(FL)-like $T^2$ one below 10 K in $y$ =
0.212. These suggest that the quantum critical point (QCP) originating from the
electronic nematicity resides around $y$ = 0.160 and the fluctuation in QCP
gives rise anomalous $T$-linear dependence in resistivity in a wide $T$ range.
In Fe$_{1-x}$Co$_x$Se, resistivity gradually changes from linear- to quadratic-
$T$-dependent one at low temperatures in the range between $x$ = 0.036 and
0.075. These could be interpreted by scenarios of both the nematic QCP and the
crossover in the ground states between the orthorhombic nematic phase and the
tetragonal phase. The anomalies found as $T$-linear resistivity are discussed
in terms of orbital and spin fluctuation arising from the nematic QCP.",1608.01044v1
2017-08-01,Heterogeneous Memristive Devices Enabled by Magnetic Tunnel Junction Nanopillars Surrounded by Resistive Silicon Switches,"Emerging non-volatile memories (NVMs) have currently attracted great interest
for their potential applications in advanced low-power information storage and
processing technologies. Conventional NVMs, such as magnetic random access
memory (MRAM) and resistive random access memory (RRAM) suffer from limitations
of low tunnel magnetoresistance (TMR), low access speed or finite endurance.
NVMs with synergetic advantages are still highly desired for future computer
architectures. Here, we report a heterogeneous memristive device composed of a
magnetic tunnel junction (MTJ) nanopillar surrounded by resistive silicon
switches, named resistively enhanced MTJ (Re-MTJ), that may be utilized for
novel memristive memories, enabling new functionalities that are inaccessible
for conventional NVMs. The Re-MTJ device features a high ON/OFF ratio of >1000%
and multilevel resistance behaviour by combining magnetic switching together
with resistive switching mechanisms. The magnetic switching originates from the
MTJ, while the resistive switching is induced by a point-switching filament
process that is related to the mobile oxygen ions. Microscopic evidence of
silicon aggregated as nanocrystals along the edges of the nanopillars verifies
the synergetic mechanism of the heterogeneous memristive device. This device
may provide new possibilities for advanced memristive memory and computing
architectures, e.g., in-memory computing and neuromorphics.",1708.00372v2
2021-11-11,Imaging Hydrodynamic Electrons Flowing Without Landauer-Sharvin Resistance,"Electrical resistance usually originates from lattice imperfections. However,
even a perfect lattice has a fundamental resistance limit, given by the
Landauer conductance caused by a finite number of propagating electron modes.
This resistance, shown by Sharvin to appear at the contacts of electronic
devices, sets the ultimate conductance limit of non-interacting electrons.
Recent years have seen growing evidence of hydrodynamic electronic phenomena,
prompting recent theories to ask whether an electronic fluid can radically
break the fundamental Landauer-Sharvin limit. Here, we use single-electron
transistor imaging of electronic flow in high-mobility graphene Corbino disk
devices to answer this question. First, by imaging ballistic flows at
liquid-helium temperatures, we observe a Landauer-Sharvin resistance that does
not appear at the contacts but is instead distributed throughout the bulk. This
underpins the phase-space origin of this resistance - as emerging from spatial
gradients in the number of conduction modes. At elevated temperatures, by
identifying and accounting for electron-phonon scattering, we reveal the
details of the purely hydrodynamic flow. Strikingly, we find that electron
hydrodynamics eliminates the bulk Landuer-Sharvin resistance. Finally, by
imaging spiraling magneto-hydrodynamic Corbino flows, we reveal the key
emergent length scale predicted by hydrodynamic theories - the Gurzhi length.
These observations demonstrate that electronic fluids can dramatically
transcend the fundamental limitations of ballistic electrons, with important
implications for fundamental science and future technologies",2111.06412v1
2022-07-30,Superconductor relaxation -- A must to be integrated into stability calculations,"A superconductor is stable if it does not quench. Quench is a short-time
physics problem. For its deeper understanding of, and how to avoid quench, the
physics behind stability has to be analysed. A previously suggested dynamic
relaxation model is re-considered and applied to YBaCuO 123 and BSCCO 2223
high-temperature, thin film superconductors. Parallel to this investigation, an
unconventional approach using an electrical resistance network (a cell model)
is applied to introduce a method how to estimate the extent by which, in
resistance measurements, exact determination of critical temperature of
superconductors is possible. This resistive cell model, when considering its
numerical convergence behaviour, in a side result may provide an alternative
explanation of (at least a contribution to) bending of resistivity vs.
temperature curves, and perhaps also an alternative to standard explanations of
the thermal fluctuations impact on these curves.
  The dynamic relaxation and the resistance models provide a parenthesis that
correlates, in terms of the Ginzburg-Landau order parameter, (i) solution of
superconductor stability problem (the main objective of this paper), with
tentative explanation of (ii) bending of the resistivity curves near critical
temperature and (iii) with predictions from thermal fluctuations.",2208.00190v4
2023-09-25,Non-Volatile Resistive Switching of Polymer Residues in 2D Material Memristors,"Two-dimensional (2D) materials are popular candidates for emerging nanoscale
devices, including memristors. Resistive switching (RS) in such 2D material
memristors has been attributed to the formation and dissolution of conductive
filaments created by the diffusion of metal ions between the electrodes.
However, the area-scalable fabrication of patterned devices involves polymers
that are difficult to remove from the 2D material interfaces without damage.
Remaining polymer residues are often overlooked when interpreting the RS
characteristics of 2D material memristors. Here, we demonstrate that the
parasitic residues themselves can be the origin of RS. We emphasize the
necessity to fabricate appropriate reference structures and employ atomic-scale
material characterization techniques to properly evaluate the potential of 2D
materials as the switching layer in vertical memristors. Our
polymer-residue-based memristors exhibit RS typical for a filamentary mechanism
with metal ion migration, and their performance parameters are strikingly
similar to commonly reported 2D material memristors. This reveals that the
exclusive consideration of electrical data without a thorough verification of
material interfaces can easily lead to misinterpretations about the potential
of 2D materials for memristor applications.",2309.13900v1
2023-11-14,Observation of high-temperature superconductivity in the high-pressure tetragonal phase of La2PrNi2O7-δ,"The recent discovery of high-temperature superconductivity in the
Ruddlesden-Popper phase La3Ni2O7 under high pressure marks a significant
breakthrough in the field of 3d transition-metal oxide superconductors. For an
emerging novel class of high-Tc superconductors, it is crucial to find more
analogous superconducting materials with a dedicated effort toward broadening
the scope of nickelate superconductors. Here, we report on the observation of
high-Tc superconductivity in the high-pressure tetragonal I4/mmm phase of
La2PrNi2O7 above ~10 GPa, which is distinct from the reported orthorhombic Fmmm
phase of La3Ni2O7 above 14 GPa. For La2PrNi2O7, the onset and the
zero-resistance temperatures of superconductivity reach Tconset = 78.2 K and
Tczero = 40 K at 15 GPa. This superconducting phase shares the samilar
structural symmetry as many cuprate superconductors, providing a fresh platform
to investigate underlying mechanisms of nickelate superconductors.",2311.08212v2
1999-01-11,SQUID based resistance bridge for shot noise measurement on low impedance samples,"We present a resistance bridge which uses a SQUID to measure the shot noise
in low impedance samples. The experimental requirements are high DC bias
currents (typically 10mA) together with high AC sensitivity (pA/VHz). This
system is used to investigate the shot noise in
Superconductor/Normal/Superconductor junctions where Andreev reflection
enhanced shot noise is expected. Because our setup has an intrinsic noise much
smaller than the thermal noise of the resistance bridge at 4.2K, reliable
results can be obtained on impedances out of the range of classical measurement
schemes.",9901090v2
1999-05-12,Nonmonotonic Temperature-dependent Resistance in Low Density 2D Hole Gases,"The low temperature longitudinal resistance-per-square Rxx(T) in ungated
GaAs/AlGaAs quantum wells of high peak hole mobility 1.7x10^6 cm^2/Vs is
metallic for 2D hole density p as low as 3.8x10^9 cm-2. The electronic
contribution to the resistance, R_{el}(T), is a nonmonotonic function of T,
exhibiting thermal activation, R_{el}(T) ~ exp{-E_a/kT}, for kT<<E_F and a
heretofore unnoted decay R_{el}(T) ~ 1/T for k_T>EF. The form of R_{el}(T) is
independent of density, indicating a fundamental relationship between the low
and high T scattering mechanisms in the metallic state.",9905176v1
2005-07-28,Phononless thermally activated transport through a disordered array of quantum wires,"Phononless plasmon assisted transport through a long disordered array of
finite length quantum wires is investigated analytically. Two temperature
regimes, the low- and the high-temperature ones, with qualitatively different
temperature dependencies of thermally activated resistance are identified. The
characteristics of plasmon assisted and phonon assisted transport mechanisms
are compared. Generically strong electron-electron interaction in quantum wires
results in a qualitative change of the temperature dependence of thermally
activated resistance in comparison to phonon assisted transport. At high
temperatures, the thermally activated resistance is determined by the Luttinger
liquid interaction parameter of the wires.",0507687v1
2007-02-22,High-field Hall resistivity and magnetoresistance in electron-doped Pr_2-xCe_xCuO_{4-δ},"We report resistivity and Hall effect measurements in electron-doped
Pr$_{2-x}$Ce$_{x}$CuO$_{4-\delta}$ films in magnetic field up to 58 T. In
contrast to hole-doped cuprates, we find a surprising non-linear magnetic field
dependence of Hall resistivity at high field in the optimally doped and
overdoped films. We also observe a crossover from quadratic to linear field
dependence of the positive magnetoresistance in the overdoped films. A spin
density wave induced Fermi surface reconstruction model can be used to
qualitatively explain both the Hall effect and magnetoresistance.",0702534v2
2007-01-13,First Tests of Thick GEMs with Electrodes Made of a Resistive Kapton,"We have developed a new design of a GEM-like detector with single-layer
electrodes made of a resistive kapton. This detector can operate at gains close
to 10E5 even in pure Ar and Ne and if transited to discharges at higher gains
they, due to the high resistivity of electrodes, do not damage either the
detector or the front-end electronics. Gains ~ 106 can be achieved in a
cascaded mode of the operation. The detector can operate without gain
degradation at counting rates up to 10E4Hz/cm2 and thus it could be very useful
in many applications which require safe high gain operation, for example in
RICH, TPCs, calorimetric.",0701154v1
1995-07-03,Percolation transition of the vortex lattice and c-axis resistivity in high-temperature superconductors,"We use the three-dimensional Josephson junction array system as a model for
studying the temperature dependence of the c-axis resistivity of high
temperature superconductors, in the presence of an external magnetic field H
applied in the c-direction. We show that the temperature at which the
dissipation becomes different from zero corresponds to a percolation transition
of the vortex lattice. In addition, the qualitative features of the resistivity
vs. temperature curves close to the transition are obtained starting from the
geometrical configurations of the vortices. The results apply to the cases H
greater than 0 and H=0.",9507001v1
2007-06-21,"Addendum: ""On the nature of the phase transition in the itinerant helimagnet MnSi"", arXiv:cond-mat/0702460v1 [cond-mat.str-el]","New high resolution data for heat capacity, heat capacity under applied
magnetic fields and resistivity of high quality single crystal of MnSi are
reported. Striking mirror symmetry between temperature derivative of
resistivity and thermal expansion coefficient of MnSi is displayed. Close
similarity between variation of the heat capacity and the temperature
derivative of resistivity through the phase transition is observed. It is shown
that the heat capacity and thermal expansion coefficient of the helical phase
are not influenced by moderate magnetic field.",0706.3093v1
2009-02-24,Phonon-induced Resistance Oscillations in Very-high Mobility 2D Electron Systems,"We report on temperature dependence of acoustic phonon-induced resistance
oscillations in very high mobility two-dimensional electron systems. We observe
that the temperature dependence is non-monotonic and that higher order
oscillations are best developed at progressively lower temperatures. Our
analysis shows that, in contrast to Shubnikov-de Haas effect, phonon-induced
resistance oscillations are sensitive to electron-electron interactions
modifying the single particle lifetime.",0902.4208v1
2009-09-11,Resistive g-modes in a reversed field pinch plasma,"First direct experimental evidence of high frequency, high toroidal mode
number (n>20), magnetic fluctuations due to unstable resistive interchange
modes (g-modes) resonant in the edge region of a reversed field pinch (RFP)
plasma is presented. Experimental characterization of time and space
periodicities of the modes is provided by means of highly resolved in-vessel
edge and insertable magnetic diagnostics. It is found that the spectral mode
properties are in good agreement with the predictions of the theoretical linear
resistive magnetohydrodynamic stability analysis. A simple model is proposed
for the observed saturation levels of the modes.",0909.2153v1
2010-07-16,Zero differential resistance in two-dimensional electron systems at large filling factors,"We report on a state characterized by a zero differential resistance observed
in very high Landau levels of a high-mobility two-dimensional electron system.
Emerging from a minimum of Hall field-induced resistance oscillations at low
temperatures, this state exists over a continuous range of magnetic fields
extending well below the onset of the Shubnikov-de Haas effect. The minimum
current required to support this state is largely independent on the magnetic
field, while the maximum current increases with the magnetic field tracing the
onset of inter-Landau level scattering.",1007.2832v1
2013-10-09,Effect of Temperature and Charged Particle Fluence on the Resistivity of Polycrystalline CVD Diamond Sensors,"The resistivity of polycrystalline chemical vapor deposition diamond sensors
is studied in samples exposed to fluences relevant to the environment of the
High Luminosity Large Hadron Collider. We measure the leakage current for a
range of bias voltages on samples irradiated with 800 MeV protons up to
1.6\times 10^{16} p/cm^2. The proton beam at LANSCE, Los Alamos National
Laboratory, was applied to irradiate the samples. The devices' resistivity is
extracted for temperatures in the -10^\circC to +20^\circC range.",1310.2620v1
2016-07-04,Vortex motion and flux-flow resistivity in dirty multiband superconductors,"The conductivity of vortex lattices in multiband superconductors with high
concentration of impurities is calculated based on microscopic kinetic theory.
Both the limits of high and low fields are considered, when the magnetic
induction is close to or much smaller than the critical field strength
$H_{c2}$, respectively. It is shown that in contrast to single-band
superconductors the resistive properties are not universal but depend on the
pairing constants and ratios of diffusivities in different bands. The low-field
magneto-resistance can strongly exceed Bardeen-Stephen estimation in a
quantitative agreement with experimental data for two-band superconductor
MgB$_2$.",1607.00708v2
2023-02-27,Ferromagnetism and Metal-Insulator transition in F-doped LaMnO3,"We present our studies on polycrystalline samples of fluorine doped LaMnO3
(LaMnO3-yFy). LaMnO2.5F0.5 exhibits remarkable magnetic and electrical
properties. It shows ferromagnetic and metallic behavior with a high Curie
temperature of ~ 239 K and a high magnetoresistance of -64. This drastic change
in magnetic properties in comparison to pure LaMnO3 is ascribed to the presence
of mixed-valence Mn ions driven by the F-doping at the O-sites, which enables
double exchange (DE) in LMOF. Furthermore, the resistivity data exhibits two
resistivity peaks at 239 K and 213 K, respectively. Our results point towards
the possibility of multiple double exchange hopping paths of two distinct
resistances existing simultaneously in the sample below 213 K.",2302.13845v1
2009-07-25,Superconductivity in Undoped Single Crystals of BaFe2As2: Field and Current Dependence,"In previous work in undoped MFe2As2, partial drops in the resistivity
indicative of traces of superconductivity have been observed in some samples of
M=Ba (Tc ~ 20 K, up to 25% drop in resistivity) and M=Ca (Tc ~ 10 K, up to 45 %
drop in resistivity.) A complete drop in the resistivity to 0, along with a
finite fraction of Meissner flux expulsion, has been observed in M=Sr, Tc = 22
K. Using In-flux grown single crystal samples of undoped BaFe2As2, we find a
complete drop in the resistivity to 0 in most samples beginning at Tc(onset) =
22.5 K. However, in contrast to the SrFe2As2 results, there is no measurable
Meissner effect and no suppression of the resistive superconducting transition
with annealing. The current sensitivity of the superconducting resistive
transition in our samples of BaFe2As2 is quite strong, with an increase in the
current density of a factor of 15 to ~ 1.5 A/cm2 not changing Tc(onset) but
broadening the transition significantly and causing the resistivity to remain
finite as T approaches 0. To investigate if this unusually low critical current
is indicative of filamentary conduction lacking the apparent anisotropy seen in
the critical magnetic field, Hc2, measurements of, e. g., the bulk
superconductor Co-doped BaFe2As2, Hc2 was measured in both crystalline
directions. These BaFe2As2 samples show Hc2(T) values in the ab-plane and along
the c-axis comparable to those seen in BaFe2-xCoxAs2, which has a similar Tc.
Since the lack of Tc suppression after annealing argues against strain-induced
superconductivity as proposed for the other undoped MFe2As2 materials, another
possible cause for the superconductivity in BaFe2As2 is discussed.",0907.4429v1
2019-03-12,Signatures of Anelastic Domain Relaxation in Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ Investigated by Mechanical Modulation of Resistivity,"The resistive response of Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ to AC
mechanical deformation is considered in the multi-domain state. This resistance
change depends both upon the anelastic relaxation of domain walls and upon the
relation between resistance and the domain wall configuration. Samples are
adhered to the surface of a piezoelectric stack, which is driven by an AC
voltage while the AC modulation of the sample resistance is measured. As the
response time of electrons is faster than that of the lattice, the phase
difference $\phi$ between the AC resistance modulation and the AC deformation
of the piezoelectric is entirely due to anelastic relaxation effects in the
sample. An expression is derived for relating $\phi$ to a sample's complex
compliance, $J(\omega)$, in this experimental configuration. Measurements of
Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ for x= (0.025, 0.052) reveal a peak in the
out-of-phase resistivity modulation in the orthorhombic antiferromagnetic state
well below the Ne\'el temperature $T_N$ and structural transition $T_S$.
Meanwhile, for a composition that is tetragonal at all temperatures, x=0.07,
the resistance modulation remains entirely in phase over the same temperatures,
establishing domain motion as a probable cause of the observed effects in the
samples that do undergo the tetragonal-to-orthorhombic transition. Fits are
provided of $\tan\phi$ for a sample with x=0.025 for various amplitude
excitations on the piezoelectric stack, from which the apparent activation
energy $E_a$ for domain wall motion is found to decreases with increasing
amplitude of the deformation along the $[110]_T$ axis. We find
$\frac{dE_a}{d\varepsilon^0_{[110,110]_T}} = -1115\pm 196$ eV with $E_a = 9.09
\pm 0.74 \times 10^{-3}$ eV in the zero strain limit if we assume linearity
over the entire range of strain amplitudes.",1903.04732v1
2005-02-09,"Structure, magnetic and transport properties of Ti-substituted La0.7Sr0.3MnO3","Ti-substituted perovskites, La0.7Sr0.3Mn1-xTixO3, with x between 0 to 0.20,
were investigated by neutron diffraction, magnetization, electric resistivity,
and magnetoresistance (MR) measurements. All samples show a rhombohedral
structure (space group R3c) from 10 K to room temperature. At room temperature,
the cell parameters a, c and the unit cell volume increase with increasing Ti
content. However, at 10 K, the cell parameter a has a maximum value for x =
0.10, and decreases for x greater than 0.10, while the unit cell volume remains
nearly constant for x greater than 0.10. The average (Mn,Ti)-O bond length
increases up to x=0.15, and the (Mn,Ti)-O-(Mn,Ti) bond angle decreases with
increasing Ti content to its minimum value at x=0.15 at room temperature. Below
the Curie temperature T_C, the resistance exhibits metallic behavior for the x
_ 0.05 samples. A metal (semiconductor) to insulator transition is observed for
the x_ 0.10 samples. A peak in resistivity appears below T_C for all samples,
and shifts to a lower temperature as x increases. The substitution of Mn by Ti
decreases the 2p-3d hybridization between O and Mn ions, reduces the bandwidth
W, and increases the electron-phonon coupling. Therefore, the TC shifts to a
lower temperature and the resistivity increases with increasing Ti content. A
field-induced shift of the resistivity maximum occurs at x less than or equal
to 0.10. The maximum MR effect is about 70% for La0.7Sr0.3Mn0.8Ti0.2O3. The
separation of TC and the resistivity maximum temperature Tmax enhances the MR
effect in these compounds due to the weak coupling between the magnetic
ordering and the resistivity as compared with La0.7Sr0.3MnO3.",0502235v1
2020-12-08,Quantitative measurement of the thermal contact resistance between a glass microsphere and a plate,"Accurate measurements of the thermal resistance between micro-objects made of
insulating materials are complex because of their small size, low conductivity,
and the presence of various ill-defined gaps. We address this issue using a
modified scanning thermal microscope operating in vacuum and in air. The
sphere-plate geometry is considered. Under controlled heating power, we measure
the temperature on top of a glass microsphere glued to the probe as it
approaches a glass plate at room temperature with nanometer accuracy. In
vacuum, a jump is observed at contact. From this jump in temperature and the
modeling of the thermal resistance of a sphere, the sphere-plate contact
resistance $ R_K=(1.4 \pm 0.18)\times10^7 \ \mathrm{K.W^{-1}}$ and effective
radius $r=(36 \pm 4)$ nm are obtained. In air, the temperature on top of the
sphere shows a decrease starting from a sphere-plate distance of 200
$\mathrm{\mu m}$. A jump is also observed at contact, with a reduced amplitude.
The sphere-plate coupling out of contact can be described by the resistance
shape factor of a sphere in front of a plate in air, placed in a circuit
involving a series and a parallel resistance that are determined by fitting the
approach curve. The contact resistance in air $R^*_K=(1.2 \pm 0.46)\times 10^7
\ \mathrm{K.W^{-1}}$ is then estimated from the temperature jump. The method is
quantitative without requiring any tedious multiple-scale numerical simulation,
and is versatile to describe the coupling between micro-objects from large
distances to contact in various environments.",2012.04291v1
2002-01-19,Antiferromagnetic Order Induced by an Applied Magnetic Field in a High-Temperature Superconductor,"One view of the cuprate high-transition temperature (high-Tc) superconductors
is that they are conventional superconductors where the pairing occurs between
weakly interacting quasiparticles, which stand in one-to-one correspondence
with the electrons in ordinary metals - although the theory has to be pushed to
its limit. An alternative view is that the electrons organize into collective
textures (e.g. charge and spin stripes) which cannot be mapped onto the
electrons in ordinary metals. The phase diagram, a complex function of various
parameters (temperature, doping and magnetic field), should then be approached
using quantum field theories of objects such as textures and strings, rather
than point-like electrons. In an external magnetic field, magnetic flux
penetrates type-II superconductors via vortices, each carrying one flux
quantum. The vortices form lattices of resistive material embedded in the
non-resistive superconductor and can reveal the nature of the ground state -
e.g. a conventional metal or an ordered, striped phase - which would have
appeared had superconductivity not intervened. Knowledge of this ground state
clearly provides the most appropriate starting point for a pairing theory. Here
we report that for one high-Tc superconductor, the applied field which imposes
the vortex lattice, also induces antiferromagnetic order. Ordinary
quasiparticle pictures cannot account for the nearly field-independent
antiferromagnetic transition temperature revealed by our measurements.",0201349v1
2013-01-22,Exceptional ballistic transport in epitaxial graphene nanoribbons,"Graphene electronics has motivated much of graphene science for the past
decade. A primary goal was to develop high mobility semiconducting graphene
with a band gap that is large enough for high performance applications.
Graphene ribbons were thought to be semiconductors with these properties,
however efforts to produce ribbons with useful bandgaps and high mobility has
had limited success. We show here that high quality epitaxial graphene
nanoribbons 40 nm in width, with annealed edges, grown on sidewall SiC are not
semiconductors, but single channel room temperature ballistic conductors for
lengths up to at least 16 micrometers. Mobilities exceeding one million
corresponding to a sheet resistance below 1 Ohm have been observed, thereby
surpassing two dimensional graphene by 3 orders of magnitude and theoretical
predictions for perfect graphene by more than a factor of 10. The graphene
ribbons behave as electronic waveguides or quantum dots. We show that transport
in these ribbons is dominated by two components of the ground state transverse
waveguide mode, one that is ballistic and temperature independent, and a second
thermally activated component that appears to be ballistic at room temperature
and insulating at cryogenic temperatures. At room temperature the resistance of
both components abruptly increases with increasing length, one at a length of
160 nm and the other at 16 micrometers. These properties appear to be related
to the lowest energy quantum states in the charge neutral ribbons. Since
epitaxial graphene nanoribbons are readily produced by the thousands, their
room temperature ballistic transport properties can be used in advanced
nanoelectronics as well.",1301.5354v2
2022-01-25,KCo$_2$As$_2$: A New Portal for the Physics of High-Purity Metals,"High-quality single crystals of KCo$_2$As$_2$ with the body-centered
tetragonal ThCr$_2$Si$_2$ structure were grown using KAs self flux. Structural,
magnetic, thermal, and electrical transport were investigated. No clear
evidence for any phase transitions was found in the temperature range 2 to 300
K. The in-plane electrical resistivity $\rho$ versus temperature $T$ is highly
unusual, showing a $T^4$ behavior below 30 K and an anomalous positive
curvature up to 300 K which is different from the linear behavior expected from
the Bloch-Gr\""uneisen theory for electron scattering by acoustic phonons. This
positive curvature has been previously observed in the in-plane resistivity of
high-conductivity layered delafossites such as PdCoO$_2$ and PtCoO$_2$. The
in-plane $\rho(T\to0) = 0.36~\mu\Omega$ cm of KCo$_2$As$_2$ is exceptionally
small for this class of compounds. The material also exhibits a nearly linear
magnetoresistance at low $T$ which attains a value of about 40% at $T=2$K and
magnetic field $H= 80$ kOe. The magnetic susceptibility $\chi$ of KCo$_2$As$_2$
is isotropic and about an order of magnitude smaller than the values for the
related compounds SrCo$_2$As$_2$ and BaCo$_2$As$_2$. The $\chi$ increases above
100 K which is found from our first-principles calculations to arise from a
sharp peak in the electronic density of states just above the Fermi energy
$E_{\rm F}$. Heat capacity $C_{\rm p}(T)$ data at low $T$ yield an electronic
density of states $N(E_{\rm F})$ that is about 36% larger than predicted by the
first-principles theory. The $C_{\rm p}(T)$ data near room temperature suggest
the presence of excited optic vibration modes which may also be the source of
the positive curvature in $\rho(T)$. Our results show that KCo$_2$As$_2$
provides a new avenue for investigating the physics of high-purity metals.",2201.10325v1
2023-01-25,Investigation of Planckian behavior in a high-conductivity oxide: PdCrO$_2$,"The layered delafossite metal PdCrO$_2$ is a natural heterostructure of
highly conductive Pd layers Kondo coupled to localized spins in the adjacent
Mott insulating CrO$_2$ layers. At high temperatures $T$ it has a $T$-linear
resistivity which is not seen in the isostructural but non-magnetic PdCoO$_2$.
The strength of the Kondo coupling is known, as-grown crystals are extremely
high purity and the Fermi surface is both very simple and experimentally known.
It is therefore an ideal material platform in which to investigate 'Planckian
metal' physics. We do this by means of controlled introduction of point
disorder, measurement of the thermal conductivity and Lorenz ratio and studying
the sources of its high temperature entropy. The $T$-linear resistivity is seen
to be due mainly to elastic scattering and to arise from a sum of several
scattering mechanisms. Remarkably, this sum leads to a scattering rate within
10$\%$ of the Planckian value of $k_BT/$$\hbar$.",2301.10631v1
1995-06-01,Role of phason-defects on the conductance of a 1-d quasicrystal,"We have studied the influence of a particular kind of phason-defect on the
Landauer resistance of a Fibonacci chain. Depending on parameters, we sometimes
find the resistance to decrease upon introduction of defect or temperature, a
behavior that also appears in real quasicrystalline materials. We demonstrate
essential differences between a standard tight-binding model and a full
continuous model. In the continuous case, we study the conductance in relation
to the underlying chaotic map and its invariant. Close to conducting points,
where the invariant vanishes, and in the majority of cases studied, the
resistance is found to decrease upon introduction of a defect. Subtle
interference effects between a sudden phason-change in the structure and the
phase of the wavefunction are also found, and these give rise to resistive
behaviors that produce exceedingly simple and regular patterns.",9506004v2
1997-12-12,Surface Resistance Imaging with a Scanning Near-Field Microwave Microscope,"We describe near-field imaging of sample sheet resistance via frequency
shifts in a resonant coaxial scanning microwave microscope. The frequency
shifts are related to local sample properties, such as surface resistance and
dielectric constant. We use a feedback circuit to track a given resonant
frequency, allowing measurements with a sensitivity to frequency shifts as
small as one parts in 50000 for a 30 ms sampling time. The frequency shifts can
be converted to sheet resistance based on a simple model of the system.",9712142v1
1997-12-15,Quantitative Imaging of Sheet Resistance with a Scanning Near-Field Microwave Microscope,"We describe quantitative imaging of the sheet resistance of metallic thin
films by monitoring frequency shift and quality factor in a resonant scanning
near-field microwave microscope. This technique allows fast acquisition of
images at approximately 10 ms per pixel over a frequency range from 0.1 to 50
GHz. In its current configuration, the system can resolve changes in sheet
resistance as small as 0.6 Ohms/sq for 100 Ohms/sq films. We demonstrate its
use at 7.5 GHz by generating a quantitative sheet resistance image of a
YBa2Cu3O7 (YBCO) thin film on a 5 cm-diameter sapphire wafer.",9712171v1
1999-07-13,Na-site substitution effects of the thermoelectric properties of NaCo_2O_4,"The resistivity and thermopower of Na$_{1+x}$Co$_2$O$_4$ and
Na$_{1.1-x}$Ca$_x$Co$_2$O$_4$ are measured and analyzed. In
Na$_{1+x}$Co$_2$O$_4$, whereas the resistivity increases with $x$, the
thermopower is nearly independent of $x$. This suggests that the excess Na is
unlikely to supply carriers, and decreases effective conduction paths in the
sample. In Na$_{1.1-x}$Ca$_x$Co$_2$O$_4$, the resistivity and the thermopower
increase with $x$, and the Ca$^{2+}$ substitution for Na$^+$ reduces the
majority carriers in NaCo$_2$O$_4$. This means that they are holes, which is
consistent with the positive sign of the thermopower. Strong correlation in
this compound is evidenced by the peculiar temperature dependence of the
resistivity.",9907179v1
1999-11-06,Electrical Resistivity of a Thin Metallic Film,"The electrical resistivity of a pure sample of a thin metallic film is found
to depend on the boundary conditions. This conclusion is supported by a
free-electron model calculation and confirmed by an ab initio relativistic
Korringa-Kohn-Rostoker computation. The low-temperature resistivity is found to
be zero for a free-standing film (reflecting boundary conditions) but nonzero
when the film is sandwiched between two semi-infinite samples of the same
material (outgoing boundary conditions). In the latter case, this resistivity
scales inversely with the number of monolayers and is due to the background
diffusive scattering by a finite lattice.",9911093v1
2000-03-09,On the Mooij Rule,"Weak localization leads to the same correction to both the conductivity and
the electron-phonon coupling constant $\lambda$ (and $\lambda_{tr}$).
Consequently the temperature dependence of the (thermal) electrical resistivity
is decreasing as the conductivity is decreasing due to weak localization, which
results in the decrease of the temperature coefficient of resistivity (TCR)
with increasing the residual resistivity. When $\lambda$ is approaching zero,
only residual resistivity part remains and gives rise to the negative TCR.
Accordingly, the Mooij rule is a manifestation of weak localization correction
to the conductivity and the electron-phonon interaction. This study may provide
a new means of probing the phonon-mechanism in exotic superconductors.",0003144v1
2001-05-04,Weak localization and the Mooij rule in disordered metals,"Weak localization leads to the same correction to both the conductivity and
the McMillan's electron-phonon coupling constant $\lambda$ (and
$\lambda_{tr}$). Consequently the temperature dependence of the thermal
electrical resistivity is decreasing as the conductivity is decreasing due to
weak localization, which results in the decrease of the temperature coefficient
of resistivity (TCR) with increasing the residual resistivity. When $\lambda$
and $\lambda_{tr}$ are approaching zero, only residual resistivity part remains
and gives rise to the negative TCR. Accordingly, the Mooij rule is a
manifestation of weak localization correction to the conductivity and the
electron-phonon interaction. This study may provide a new means of probing the
phonon-mechanism in exotic superconductors.",0105090v1
2001-10-31,Stationary Regime of Random Resistor Networks Under Biased Percolation,"The state of a 2-D random resistor network, resulting from the simultaneous
evolutions of two competing biased percolations, is studied in a wide range of
bias values. Monte Carlo simulations show that when the external current $I$ is
below the threshold value for electrical breakdown, the network reaches a
steady state with a nonlinear current-voltage characteristic. The properties of
this nonlinear regime are investigated as a function of different model
parameters. A scaling relation is found between $<R>/<R>_0$ and $I/I_0$, where
$<R>$ is the average resistance, $<R>_0$ the linear regime resistance and $I_0$
the threshold value for the onset of nonlinearity. The scaling exponent is
found to be independent of the model parameters. A similar scaling behavior is
also found for the relative variance of resistance fluctuations. These results
compare well with resistance measurements in composite materials performed in
the Joule regime up to breakdown.",0110646v1
2002-05-27,Resistivity and thermoelectric power measurements on CeFe$_2$ and its pseudobinaries,"Resistivity and thermoelectric power (TEP) measurements on CeFe$_2$ and two
of its pseudo-binaries Ce(Fe, 5% Ir)$_2$ and Ce(Fe, 7% Ru)$_2$ between 78K and
275K are reported. The resistivity data are analysed in terms of contributions
from scattering due to phonon, magnon, spin fluctuation and lattice defects,
and also from interband scattering. Attempts are made to analyze the TEP data
in terms of these resistivity components. Thermal hysteresis is observed in the
temperature dependence of TEP in the Ir and Ru doped CeFe$_2$ samples around
the ferromagnetic to antiferromagnetic transition, indicating the first order
nature of this transition.",0205539v1
2003-02-12,Temperature Dependence of the Dielectric Constant and Resistivity of Diluted Magnetic Semiconductors,"We study the effect that the ferromagnetic order has on the electrical
properties of Diluted Magnetic Semiconductors. We analyze the temperature
dependence of the dielectric constant and of the resistivity of
Ga$_{1-x}$Mn$_x$As. In our treatment the electronic structure of the
semiconductor is described by a six band Kohn-Luttinger Hamiltonian, the
thermal fluctuations of the Mn magnetic moments are treated in the mean field
approximation, the carrier-carrier interaction within the random phase
approximation, and the transport properties using the relaxation time
approximation. We find that the Thomas-Fermi length changes near 8% when going
from the ferromagnetic to the paramagnetic phase. We also find, in good
agreement with the experiments, that the resistivity changes near 20% when
going from zero to the Curie temperature. We explain this change in the
resistivity in terms of the variation of the Fermi surface and the transport
scattering time when going from the ferromagnetic phase to the paramagnetic
phase.",0302237v1
2003-02-19,Small-polaron hopping conductivity in bilayer manganite La$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$,"We report anisotropic resistivity measurements on a
La$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ single crystal over a temperature $T$ range
from 2 to 400 K and in magnetic fields $H$ up to 14 T. For $T\geq 218$ K, the
temperature dependence of the zero-field in-plane $\rho_{ab}(T)$ resistivity
obeys the adiabatic small polaron hopping mechanism, while the out-of-plane
$\rho_{c}(T)$ resistivity can be ascribed by an Arrhenius law with the same
activation energy. Considering the magnetic character of the polarons and the
close correlation between the resistivity and magnetization, we developed a
model which allows the determination of $\rho_{ab,c}(H,T)$. The excellent
agreement of the calculations with the measurements indicates that small
polarons play an essential role in the electrical transport properties in the
paramagnetic phase of bilayer manganites.",0302392v1
2003-07-21,Detecting percolative metal-insulator transition in manganites by resistive relaxation,"We report an experimental study of the time dependence of resistivity of a
La$_{0.9}$Sr$_{0.1}$MnO$_{3}$ ultrathin film in order to elucidate the
underlying mechanism for metal-insulator transition and colossal
magnetoresistance CMR effect. There is a clear change of sign in the resistive
relaxation rate across the metal-insulator transition driven by temperature or
magnetic field. When measuring in increasing temperature or decreasing magnetic
field, the resistivity increases with time in the metallic state but decreases
with time in the insulating state. These relaxation processes indicate that the
metal-insulator transition and the associated CMR are a direct result of phase
separation and of percolation of the metallic phase.",0307501v1
2004-11-24,Electrical Spin Injection in Multi-Wall carbon NanoTubes with transparent ferromagnetic contacts,"We report on electrical spin injection measurements on MWNTs . We use a
ferromagnetic alloy Pd$_{1-x}$Ni$_{x}$ with x $\approx$ 0.7 which allows to
obtain devices with resistances as low as 5.6 $k\Omega$ at 300 $K$. The yield
of device resistances below 100 $k\Omega$, at 300 $K$, is around 50%. We
measure at 2 $K$ a hysteretic magneto-resistance due to the magnetization
reversal of the ferromagnetic leads. The relative difference between the
resistance in the antiparallel (AP) orientation and the parallel (P)
orientation is about 2%.",0411623v2
2005-04-22,Possible Localization Behavior of the Inherent Conducting Polymer (CH$_3$)$_{0.9}$ReO$_3$,"Polymeric methyltrioxorhenium (poly-MTO) represents the first example of an
inherent conducting organometallic oxide. It adopts the structural motives and
transport properties of some classical perovskites in two dimensions. In this
study we present resistivity data down to 30 mK which exhibit a crossover from
a metallic (d$\rho$/d$T >$ 0) to an insulating (d$\rho$/d$T <$ 0) behavior at
about 30 K. Below 30 K an unusual resistivity behavior, similar to that of some
doped cuprate systems, is observed: initially the resistivity increases
approximately as $\rho \sim$ log$(1/T$) before it starts to saturate below 2 K.
Furthermore, a linear positive magnetoresistance is found (up to 7 T).
Temperature dependent magnetization and specific heat measurements in various
magnetic fields indicate that the unusual resistivity behavior may be driven by
spatial localization of the d$^1$ moments at the Re atoms.",0504585v1
2005-04-27,Colossal resistivity change besides magnetoresistance: an extended theoretical framework for electronic transport of manganites,"Current theoretical approaches to manganites mainly stem from magnetic
framework, in which the electronic transport is thought to be spin-dependent
and the double exchange mechanism plays a core role. However, quite a number of
experimental observations can yet not be reasonably explained. For example,
multiplicate insulator-metal transitions and resistivity reduction induced by
perturbations other than magnetic field, such as electric current, are not well
understood. A comprehensive analysis on earlier extensive studies is performed
and two types of origins for resistivity change are highlighted. Besides the
insulated-to-metallic transition induced by external field such as magnetic
field, the insulated-to-insulated transition induced extrinsically is even a
more important source for the colossal resistivity change. We propose an
extended framework for the electronic transport of manganites, in which the
contribution of charge degree of freedom is given a special priority.",0504706v2
2006-01-31,Phase coexistence and resistivity near the ferromagnetic transition of manganites,"Pairing of oxygen holes into heavy bipolarons in the paramagnetic phase and
their magnetic pair-breaking in the ferromagnetic phase [the so-called
current-carrier density collapse (CCDC)] has accounted for the first-order
ferromagnetic phase transition, colossal magnetoresistance (CMR), isotope
effect, and pseudogap in doped manganites. Here we propose an explanation of
the phase coexistence and describe the magnetization and resistivity of
manganites near the ferromagnetic transition in the framework of CCDC. The
present quantitative description of resistivity is obtained without any fitting
parameters by using the experimental resistivities far away from the transition
and the experimental magnetization, and essentially model independent.",0601712v2
2006-02-03,Boundary resistance in magnetic multilayers,"Quasiclassical boundary conditions for electrochemical potentials at the
interface between diffusive ferromagnetic and non-magnetic metals are derived
for the first time. An expression for the boundary resistance accurately
accounts for the momentum conservation law as well as essential gradients of
the chemical potentials. Conditions are established at which spin-asymmetry of
the boundary resistance has positive or negative sign. Dependence of the spin
asymmetry and the absolute value of the boundary resistance on the exchange
splitting of the conduction band opens up new possibility to estimate spin
polarization of the conduction band of ferromagnetic metals. Consistency of the
theory is checked on existing experimental data.",0602070v1
2006-06-23,Angular dependence of domain wall resistivity in artificial magnetic domain structures,"We exploit the ability to precisely control the magnetic domain structure of
perpendicularly magnetized Pt/Co/Pt trilayers to fabricate artificial domain
wall arrays and study their transport properties. The scaling behaviour of this
model system confirms the intrinsic domain wall origin of the
magnetoresistance, and systematic studies using domains patterned at various
angles to the current flow are excellently described by an angular-dependent
resistivity tensor containing perpendicular and parallel domain wall
resistivities. We find that the latter are fully consistent with Levy-Zhang
theory, which allows us to estimate the ratio of minority to majority spin
carrier resistivities, rho-down/rho-up~5.5, in good agreement with thin film
band structure calculations.",0606614v1
2006-07-26,"Angle-dependent magnetotransport in cubic and tetragonal ferromagnets: Application to (001)- and (113)A-oriented (Ga,Mn)As","General expressions for the longitudinal and transverse resistivities of
single-crystalline cubic and tetragonal ferromagnets are derived from a series
expansion of the resistivity tensor with respect to the magnetization
orientation. They are applied to strained (Ga,Mn)As films, grown on (001)- and
(113)A-oriented GaAs substrates, where the resistivities are theoretically and
experimentally studied for magnetic fields rotated within various planes
parallel and perpendicular to the sample surface. We are able to model the
measured angular dependences of the resistivities within the framework of a
single ferromagnetic domain, calculating the field-dependent orientation of the
magnetization by numerically minimizing the free-enthalpy density.
Angle-dependent magnetotransport measurements are shown to be a powerful tool
for probing both anisotropic magnetoresistance and magnetic anisotropy. The
anisotropy parameters of the (Ga,Mn)As films inferred from the magnetotransport
measurements agree with those obtained by ferromagnetic resonance measurements
within a factor of two.",0607679v1
2006-11-14,Calculations of spin-disorder resistivity from first principles,"Spin-disorder resistivity of Fe and Ni is studied using the noncollinear
density functional theory. The Landauer conductance is averaged over random
disorder configurations and fitted to Ohm's law. The distribution function is
approximated by the mean-field theory. The dependence of spin-disorder
resistivity on magnetization in Fe is found to be in excellent agreement with
the results for the isotropic s-d model. In the fully disordered state,
spin-disorder resistivity for Fe is close to experiment, while for fcc Ni it
exceeds the experimental value by a factor of 2.3. This result indicates strong
magnetic short-range order in Ni at the Curie temperature.",0611377v2
2007-04-04,Vortex Dynamics at the Initial Stage of Resistive Transition in Superconductors with Fractal Cluster Structure,"The effect of fractal normal-phase clusters on vortex dynamics in a
percolative superconductor is considered. The superconductor contains
percolative superconducting cluster carrying a transport current and clusters
of a normal phase, acting as pinning centers. A prototype of such a structure
is YBCO film, containing clusters of columnar defects, as well as the BSCCO/Ag
sheathed tape, which is of practical interest for wire fabrication. Transition
of the superconductor into a resistive state corresponds to the percolation
transition from a pinned vortex state to a resistive state when the vortices
are free to move. The dependencies of the free vortex density on the fractal
dimension of the cluster boundary as well as the resistance on the transport
current are obtained. It is revealed that a mixed state of the vortex glass
type is realized in the superconducting system involved. The current-voltage
characteristics of superconductors containing fractal clusters are obtained and
their features are studied.",0704.0494v1
2008-02-19,Temperature memory and resistive glassy behaviors of a perovskite manganite,"This paper reports the observations of long-time relaxation, aging, and
temperature memory behaviors of resistance and magnetization in the
ferromagnetic state of a polycrystalline La0.7Ca0.3Mn0.925Ti0.075O3 compound.
The observed glassy dynamics of the electrical transport appears to be
magnetically originated and has a very close association with the magnetic
glassiness of the sample. Phase separation and strong correlation between
magnetic interactions and electronic conduction play the essential roles in
producing such a resistive glassiness. We explain the observed effects in terms
of a coexistence of two competing thermomagnetic processes, domain growth and
magnetic freezing, and propose that hole-doped perovskite manganites can be
considered as ""resistive glasses"".",0802.2729v1
2008-02-26,Effects of heat dissipation on unipolar resistance switching in Pt/NiO/Pt capacitors,"We fabricated Pt/NiO/Pt capacitor structures with various bottom electrode
thicknesses, $t_{BE}$, and investigated their resistance switching behaviors.
The capacitors with $t_{BE} \geq 50$ nm exhibited typical unipolar resistance
memory switching, while those with $t_{BE} \leq 30$ nm showed threshold
switching. This interesting phenomenon can be explained in terms of the
temperature-dependent stability of conducting filaments. In particular, the
thinner $t_{BE}$ makes dissipation of Joule heat less efficient, so the
filaments will be at a higher temperature and become less stable. This study
demonstrates the importance of heat dissipation in resistance random access
memory.",0802.3739v1
2008-08-25,Stability and normal zone propagation speed in YBCO coated conductors with increased interfacial resistance,"We will discuss how stability and speed of normal zone propagation in
YBCO-coated conductors is affected by interfacial resistance between the
superconducting film and the stabilizer. Our numerical simulation has shown
that the increased interfacial resistance substantially increases speed of
normal zone propagation and decreases the stability margins. Optimization of
the value of the resistance may lead to a better compromise between stability
and quench protection requirements than what is found in currently manufactured
coated conductors.",0808.3409v3
2008-12-12,Magnetic tunnel junctions with ferroelectric barriers: Prediction of four resistance states from first-principles,"Magnetic tunnel junctions (MTJs), composed of two ferromagnetic electrodes
separated by a thin insulating barrier layer, are currently used in spintronic
devices, such as magnetic sensors and magnetic random access memories.
Recently, driven by demonstrations of ferroelectricity at the nanoscale,
thin-film ferroelectric barriers were proposed to extend the functionality of
MTJs. Due to the sensitivity of conductance to the magnetization alignment of
the electrodes (tunnelling magnetoresistance) and the polarization orientation
in the ferroelectric barrier (tunnelling electroresistance), these multiferroic
tunnel junctions (MFTJs) may serve as four-state resistance devices. Based on
first-principles calculations we demonstrate four resistance states in
SrRuO3/BaTiO3/SrRuO3 MFTJs with asymmetric interfaces. We find that the
resistance of such a MFTJ is significantly changed when the electric
polarization of the barrier is reversed and/or when the magnetizations of the
electrodes are switched from parallel to antiparallel. These results reveal the
exciting prospects of MFTJs for application as multifunctional spintronic
devices.",0812.2393v1
2008-12-23,Specific Resistance of Pd/Ir Interfaces,"From measurements of the current-perpendicular-to-plane (CPP) total specific
resistance (AR = area times resistance) of sputtered Pd/Ir multilayers, we
derive the interface specific resistance, 2AR(Pd/Ir) = 1.02 +/- 0.06 fOhmm^2,
for this metal pair with closely similar lattice parameters. Assuming a single
fcc crystal structure with the average lattice parameter, no-free-parameter
calculations, including only spd orbitals, give for perfect interfaces,
2AR(Pd/Ir)(Perf) = 1.21 +/-0.1 fOhmm^2, and for interfaces composed of two
monolayers of a random 50%-50% alloy, 2AR(Pd/Ir)(50/50) = 1.22 +/- 0.1 fOhmm^2.
Within mutual uncertainties, these values fall just outside the range of the
experimental value. Updating to add f-orbitals gives 2AR(Pd/Ir)(Perf) = 1.10
+/- 0.1 fOhmm^2 and 2AR(Pd/Ir)(50-50) = 1.13 +/- 0.1 fOhmm^2, values now
compatible with the experimental one. We also update, with f-orbitals,
calculations for other pairs",0812.4421v1
2010-01-11,Anomalous Hall Effect in Fe/Gd Bilayers,"Non-monotonic dependence of anomalous Hall resistivity on temperature and
magnetization, including a sign change, was observed in Fe/Gd bilayers. To
understand the intriguing observations, we fabricated the Fe/Gd bilayers and
single layers of Fe and Gd simultaneously. The temperature and field
dependences of longitudinal resistivity, Hall resistivity and magnetization in
these films have also been carefully measured. The analysis of these data
reveals that these intriguing features are due to the opposite signs of Hall
resistivity/or spin polarization and different Curie temperatures of Fe and Gd
single-layer films.",1001.1586v2
2010-10-26,Evanescent incompressible strips as origin of the observed Hall resistance overshoot,"In this work we provide a systematic explanation to the unusual non-monotonic
behavior of the Hall resistance observed at two-dimensional electron systems.
We use a semi-analytical model based on the interaction theory of the integer
quantized Hall effect to investigate the existence of the anomalous, \emph{i.e}
overshoot, Hall resistance $R_{H}$. The observation of the overshoot resistance
at low magnetic field edge of the plateaus is elucidated by means of
overlapping evanescent incompressible strips, formed due to strong magnetic
fields and interactions. Utilizing a self-consistent numerical scheme we also
show that, if the magnetic field is decreased the $R_{H}$ decreases to its
expected value. The effects of the sample width, temperature, disorder strength
and magnetic field on the overshoot peaks are investigated in detail. Based on
our findings, we predict a controllable procedure to manipulate the maxima of
the peaks, which can be tested experimentally. Our model does not depend on
specific and intrinsic properties of the material, provided that a single
particle gap exists.",1010.5432v1
2010-12-13,Distinct electronic nematicities between electron and hole underdoped iron pnictides,"We systematically investigated the in-plane resistivity anisotropy of
electron-underdoped $EuFe_{2-x}Co_xAs_2$ and $BaFe_{2-x}Co_xAs_2$, and
hole-underdoped $Ba_{1-x}K_xFe_2As_2$. Large in-plane resistivity anisotropy
was found in the former samples, while {\it tiny} in-plane resistivity
anisotropy was detected in the latter ones. When it is detected, the anisotropy
starts above the structural transition temperature and increases smoothly
through it. As the temperature is lowered further, the anisotropy takes a
dramatic enhancement through the magnetic transition temperature. We found that
the anisotropy is universally tied to the presence of non-Fermi liquid T-linear
behavior of resistivity. Our results demonstrate that the nematic state is
caused by electronic degrees of freedom, and the microscopic orbital
involvement in magnetically ordered state must be fundamentally different
between the hole and electron doped materials.",1012.2731v1
2011-01-31,Phase Mixing of Nonlinear Visco-resistive Alfvén Waves,"We investigate the behaviour of nonlinear, nonideal Alfv\'en wave propagation
within an inhomogeneous magnetic environment. The governing MHD equations are
solved in 1D and 2D using both analytical techniques and numerical simulations.
We find clear evidence for the ponderomotive effect and visco-resistive
heating. The ponderomotive effect generates a longitudinal component to the
transverse Alfv\'en wave, with a frequency twice that of the driving frequency.
Analytical work shows the addition of resistive heating. This leads to a
substantial increase in the local temperature and thus gas pressure of the
plasma, resulting in material being pushed along the magnetic field. In 2D, our
system exhibits phase mixing and we observe an evolution in the location of the
maximum heating, i.e. we find a drifting of the heating layer. Considering
Alfv\'en wave propagation in 2D with an inhomogeneous density gradient, we find
that the equilibrium density profile is significantly modified by both the flow
of density due to visco-resistive heating and the nonlinear response to the
localised heating through phase mixing.",1101.5945v1
2011-03-04,Voltage bias induced modification of all oxide Pr0.5Ca0.5MnO3/SrTi0.95Nb.05O3 junctions,"In this paper we report what happens to a pristine oxide junction
Pr0.5Ca0.5MnO3/SrTi0.95Nb.05O3 (PCMO/Nb:STO), when it is subjected to cycling
of voltage bias of moderate value ({\pm}4V). It is found that the initial
cycling leads to formation of a permanent state of lower resistance where the
lower resistance arises predominantly due to development of a shunt across the
device film (PCMO). On successive voltage cycling with increasing magnitude,
this state transforms into states of successive lower resistance that can be
transformed back to the initial stable state on cycling to below a certain
bias. A simple model based on p-n junction with shunt has been used to obtain
information on the change of the junction on voltage cycling. It has been shown
that the observation can be explained if the voltage cycling leads to lowering
of barrier at the interface and also reduction in series resistance. It is
suggested that this lowering can be related to the migration of oxygen ions and
vacancies at the junction region. Cross-sectional imaging of the junction shows
formation of permanent filamentary bridges across the thickness of the PCMO
after the pristine p-n junction is first taken through a voltage cycle, which
would explain appearance of a finite shunt across the p-n junction.",1103.0884v1
2011-07-11,Magnetotransport properties of iron microwires fabricated by focused electron beam induced autocatalytic growth,"We have prepared iron microwires in a combination of focused electron beam
induced deposition (FEBID) and autocatalytic growth from the iron
pentacarbonyl, Fe(CO)5, precursor gas under UHV conditions. The electrical
transport properties of the microwires were investigated and it was found that
the temperature dependence of the longitudinal resistivity (rhoxx) shows a
typical metallic behaviour with a room temperature value of about 88
micro{\Omega} cm. In order to investigate the magnetotransport properties we
have measured the isothermal Hall-resistivities in the range between 4.2 K and
260 K. From these measurements positive values for the ordinary and the
anomalous Hall coefficients were derived. The relation between anomalous Hall
resistivity (rhoAN) and longitudinal resistivity is quadratic, rhoAN rho^2 xx,
revealing an intrinsic origin of the anomalous Hall effect. Finally, at low
temperature in the transversal geometry a negative magnetoresistance of about
0.2 % was measured.",1107.2014v1
2011-08-11,Effect of Electron-electron Interaction on Surface Transport in Three-Dimensional Topological Insulators,"We study the effect of electron-electron interaction on the surface
resistivity of three-dimensional (3D) topological insulators. In the absence of
umklapp scattering, the existence of the Fermi-liquid ($T^2$) term in
resistivity of a two-dimensional (2D) metal depends on the Fermi surface
geometry, in particular, on whether it is convex or concave. On doping, the
Fermi surface of 2D metallic surface states in 3D topological insulators of the
Bi$_2$Te$_3$ family changes its shape from convex to concave due to hexagonal
warping, while still being too small to allow for umklapp scattering. We show
that the $T^2$ term in the resistivity is present only in the concave regime
and demonstrate that the resistivity obeys a universal scaling form valid for
an arbitrary 2D Fermi surface near a convex/concave transition.",1108.2435v1
2011-10-31,Spin Transfer from a Ferromagnet into a Semiconductor through an Oxide barrier,"We present results on the magnetoresistance of the system Ni/Al203/n-doped
Si/Al2O3/Ni in fabricated nanostructures. The results at temperature of 14K
reveal a 75% magnetoresistance that decreases in value up to approximately 30K
where the effect disappears. We observe minimum resistance in the antiparallel
configurations of the source and drain of Ni. As a possibility, it seems to
indicate the existence of a magnetic state at the Si/oxide interface. The
average spin diffusion length obtained is of 650 nm approximately. Results are
compared to the window of resistances that seems to exist between the tunnel
barrier resistance and two threshold resistances but the spin transfer seems to
work in the range and outside the two thresholds.",1110.6810v1
2012-08-22,Why is the bulk resistivity of topological insulators so small?,"As-grown topological insulators (TIs) are typically heavily-doped $n$-type
crystals. Compensation by acceptors is used to move the Fermi level to the
middle of the band gap, but even then TIs have a frustratingly small bulk
resistivity. We show that this small resistivity is the result of band bending
by poorly screened fluctuations in the random Coulomb potential. Using
numerical simulations of a completely compensated TI, we find that the bulk
resistivity has an activation energy of just 0.15 times the band gap, in good
agreement with experimental data. At lower temperatures activated transport
crosses over to variable range hopping with a relatively large localization
length.",1208.4601v2
2012-09-26,Substrate effect on the resistive switching in BiFeO3 thin films,"BiFeO3 thin films have been deposited on Pt/sapphire and Pt/Ti/SiO2/Si
substrates with pulsed laser deposition using the same growth conditions,
respectively. Au was sputtered as the top electrode. The microscopic structure
of the thin film varies by changing the underlying substrate. Thin films on
Pt/sapphire are not resistively switchable due to the formation of Schottky
contacts at both the top and the bottom interface. However, thin films on
Pt/Ti/SiO2/Si exhibit an obvious resistive switching behavior under forward
bias. The conduction mechanisms in BiFeO3 thin films on Pt/sapphire and
Pt/Ti/SiO2/Si substrates are discussed to understand the different resistive
switching behaviors.",1209.5868v1
2012-10-22,"Thickness-dependent structural, magnetic and transport properties of epitaxial Co2FeAl Heusler alloy thin films","We report on a systematic study of the structural, magnetic properties and
the anomalous Hall effect, in the Heusler alloy Co2FeAl (CFA) epitaxial films
on MgO(001), as a function of film thickness. It was found that the epitaxial
CFA films show a highly ordered B2 structure with an in-plane uniaxial magnetic
anisotropy. An analysis of the electrical transport properties reveals that the
lattice and magnon scattering contributions to the longitudinal resistivity.
Independent on the thickness of films, the anomalous Hall resistivity of CFA
films is found to be dominated by skew scattering only. Moreover, the anomalous
Hall resistivity shows weakly temperature dependent behavior, and its absolute
value increases as the thickness decreases. We attribute this temperature
insensitivity in the anomalous Hall resistivity to the weak temperature
dependent of tunneling spin-polarization in the CFA films, while the thickness
dependence behavior is likely due to the increasing significance of interface
or free surface electronic states.",1210.5807v1
2012-12-06,Barkhausen-type noise in the resistance of antiferromagnetic Cr thin films,"We present an experimental study of the changes generated on the electrical
resistance $R(T)$ of epitaxial Cr thin films by the transformation of quantized
spin density wave domains as the temperature is changed. A characteristic
resistance noise appears only within the same temperature region where a
cooling-warming cycle in $R(T)$ displays hysteretic behavior. We propose an
analysis based on an analogy with the Barkhausen noise seen in ferromagnets.
There fluctuations in the magnetization $M(H)$ occur when the magnetic field
$H$ is swept. By mapping $M \rightarrow \Psi_0$ and $H \rightarrow T$, where
$\Psi_0$ corresponds to the order parameter of the spin density wave, we
generalize the Preisach model in terms of a random distribution of {\it
resistive hysterons} to explain our results. These hysterons are related to
distributions of quantized spin density wave domains with different sizes,
local energies and number of nodes.",1212.1411v1
2012-12-10,YCr6Ge6 as a Candidate Compound for a Kagome Metal,"We show that YCr6Ge6, comprising a kagome lattice made up of Cr atoms, is a
plausible candidate compound for a kagome metal that is expected to exhibit
anomalous phenomena such as flat-band ferromagnetism. Resistivity,
magnetization, and heat capacity are measured on single crystals of YCr6Ge6,
and band structure calculations are performed to investigate the electronic
structure. Curie-Weiss-like behavior in magnetic susceptibility, T2 dependence
in resistivity, and a Sommerfeld coefficient doubly enhanced from a calculated
value indicate a moderately strong electron correlation. Interestingly, the
in-plane resistivity is twice as large as the interplane resistivity, which is
contrary to the simple expectation from the layered structure. Band structure
calculations demonstrate that there are partially flat bands slightly below the
Fermi level near the {\Gamma} point, which is ascribed to Cr 3d3z2-r2 bands and
may govern the properties of this compound.",1212.1976v1
2013-03-26,Quantum corrections to conductivity in Si doped ZnO thin films,"Si doped ZnO thin films with Si concentrations ranging from 0.4 to 10 % have
been grown by sequential pulsed laser deposition on sapphire substrates. The
resistivity of the films first decreased from ~ 6.6x10-3 to 4.7x10-4 ohm-cm as
the Si concentration was increased from ~ 0.4 to 2% and then it increased with
further increase in Si concentration. The electron concentrations in the films
were in the range from 3x1019 to 4x1020 cm-3 showing their degenerate nature.
However, temperature dependent resistivity measurements in the range from 300
to 4.2 K revealed negative temperature coefficient of resistivity (TCR) for the
0.4, 6 and 10% Si doped ZnO films in the entire measurement temperature range.
The 0.6, 0.9 and 2% Si doped films showed a transition from negative to
positive TCR with increasing temperature. The negative magnetoresistance found
in the films at low temperatures and 0.5 T magnetic field pointed to weak
localization as the dominant contributor towards negative TCR. A quantitative
fit of the temperature dependent resistivity data for all the films could be
obtained by considering the quantum correction to conductivity arising due to
disorder induced weak localization effect.",1303.6443v2
2013-08-29,Percolation model for a selective response of the resistance of composite semiconducting np-systems towards reducing gases,"It is shown that a two-component percolation model can explain an
experimentally observed behavior, namely that a network built up by a mixture
of sintered nanocrystalline semiconducting n- and p-grains can exhibit
selective behavior, i.e. respond with a resistance increase when exposed to a
reducing gas A and with a resistance decrease in response to another reducing
gas B. To this end, a simple model is developed based on realistic assumptions
about the reactions on the grain surfaces. The resistance is calculated by
random walk simulations with nn-, pp- and np-bonds between the grains and the
results are found in very good agreement with the experiments. Contrary to
former assumptions, the np-bonds are crucial to obtain this accordance.",1308.6442v2
2013-11-08,Low-Contact-Resistance Graphene Devices with Nickel-Etched-Graphene Contacts,"The performance of graphene-based transistors is often limited by the large
electrical resistance across the metal-graphene contact. We report an approach
to achieve ultra-low resistance metal contacts to graphene transistors. Through
a process of metal-catalyzed etching in hydrogen, multiple nano-sized pits with
zigzag edges are created in the graphene that form strong chemical bonds with
deposited nickel metallization for source-drain contacts without the need for
further annealing. This facile contact treatment prior to electrode
metallization results in contact resistance as low as 100 ohm-um in
single-layer graphene field-effect transistors, and 11 ohm-um in bilayer
graphene transistors. The treatment is compatible with complementary
metal-oxide-semiconductor fabrication processes, and holds great promise to
meet the contact performance required for the integration of graphene in future
integrated circuits.",1311.1944v2
2014-06-14,Negative magnetoresistance dynamics in expanded graphite under hydrostatic pressure up to 1.8 GPa,"Basal plane resistivity of expanded graphite was studied under simultaneous
influence of hydrostatic pressure up to 1.8 GPa and magnetic field 0.8 T in the
77-300 K temperature region. Magnetic field induces negative magnetoresistance
in the sample within all temperature and pressure range studied. A change in
resistivity of the sample under maximum pressure reaches 80%. Significant
change in resistivity dependence on temperature under the pressure of 0.6 GPa
suggests for ordering transition in the sample studied. Negative
magnetoresistance in the graphite reaches about 15% at 0.6 GPa. Magnetic field
acts in the same way as pressure and potentiates the transition formation and
further magnetoresistance dynamics. The effects observed are mostly of elastic
character according to resistivity of the unloaded sample.",1406.3770v1
2014-06-23,Control of Thermoelectric Properties of ZnO using Electric Double Layer,"We have successfully controlled thermoelectric properties of ZnO by changing
carrier concentration using an electric double layer transistor (EDLT) which is
a feld effect transistor gated by electrolyte solution. The resistivity and the
thermopower decreased abruptly by applying gate voltage larger than a threshold
voltage ( 2V), indicating the increase of carrier concentration on the ZnO
surface. The temperature dependence of resistivity became metallic, which is
characterized by weak temperature dependence of the resistivity, when gate
voltage exceeded 2V. Corresponding to the resistivity, the temperature
dependence of thermopower changed remarkably. The thickness of the induced
metallic layer was estimated to be about 10nm from the critical carrier
concentration of metal-insulator transition, and the power factor was
calculated to ~8*10-5Wm-1K2. Although the power factor is not as large as bulk
ZnO ceramics of optimum doping condition, EDLT is considered to be a useful way
to optimize thermoelectric properties by tuning carrier concentration.",1406.5850v1
2014-09-28,Universal Ratio of Intrinsic Resistivities of Spin Helix in B20 (Fe-Co)Si Magnets,"The B20 magnets with the Dzyaloshinskii-Moriya (D-M) interaction exhibit spin
helix and Skyrmion spin textures unattainable in traditional Heisenberg
ferromagnets. We have determined the intrinsic resistivity of the spin helix,
which is a macroscopic Bloch domain wall, in B20 (Fe-Co)Si magnets. We found a
universal resistance ratio of gamma = 1.35 with current parallel and
perpendicular to the helix, independent of composition and temperature. This
gamma value is much smaller than 3, the well-known minimum value for domain
wall resistivity in traditional ferromagnets, due to the significant spin-orbit
coupling in the B20 magnets.",1409.7869v1
2014-11-13,Graphene-Passivated Nickel as an Oxidation-Resistant Electrode for Spintronics,"We report on graphene-passivated ferromagnetic electrodes (GPFE) for spin
devices. GPFE are shown to act as spin-polarized oxidation-resistant
electrodes. The direct coating of nickel with few layer graphene through a
readily scalable chemical vapour deposition (CVD) process allows the
preservation of an unoxidized nickel surface upon air exposure. Fabrication and
measurement of complete reference tunneling spin valve structures demonstrates
that the GPFE is maintained as a spin polarizer and also that the presence of
the graphene coating leads to a specific sign reversal of the
magneto-resistance. Hence, this work highlights a novel oxidation-resistant
spin source which further unlocks low cost wet chemistry processes for
spintronics devices.",1411.3476v1
2014-11-22,"Crystal growth, resistivity and Hall effect of the delafossite metal PtCoO$_2$","We report single crystal growth of the delafossite oxide PtCoO$_2$, and basic
transport measurements on single crystals etched to well-defined geometries
using focused ion beam techniques. The room temperature resistivity is 2.1
$\mu\Omega$ cm, and the Hall coefficient is consistent with the existence of
one free electron per Pt. Although the residual resistivity ratio is greater
than fifty, a slight upturn of resistivity is seen below 15 K. The angle
dependence of the in-plane magnetoresistance is also reported.",1411.6162v2
2015-03-02,High-Q operation of SRF cavities: The potential impact of thermocurrents on the RF surface resistance,"For many new accelerator applications, superconducting radio frequency (SRF)
systems are the enabling technology. In particular for CW applications, much
effort is being expended to minimize the power dissipation (surface resistance)
of niobium cavities. Starting in 2009, we suggested a means of reducing the
residual resistance by performing a thermal cycle [1], a procedure of warming
up a cavity after initial cooldown to about 20K and cooling it down again. In
subsequent studies [2], this technique was used to manipulate the residual
resistance by more than a factor of 2. It was postulated that thermocurrents
during cooldown generate additional trapped magnetic flux that impacts the
cavity quality factor. Here, we present a more extensive study that includes
measurements of two additional passband modes and that confirms the effect. In
this paper, we also discuss simulations that support the claim. While the
layout of the cavity LHe tank system is cylindrically symmetric, we show that
the temperature dependence of the material parameters results in a
non-symmetric current distribution. Hence a significant amount of magnetic flux
can be generated at the RF surface.",1503.00601v2
2015-05-28,Effect of the interface resistance in non-local Hanle measurements,"We use lateral spin valves with varying interface resistance to measure
non-local Hanle effect in order to extract the spin-diffusion length of the
non-magnetic channel. A general expression that describes spin injection and
transport, taking into account the influence of the interface resistance, is
used to fit our results. Whereas the fitted spin-diffusion length value is in
agreement with the one obtained from standard non-local measurements in the
case of a finite interface resistance, in the case of transparent contacts a
clear disagreement is observed. The use of a corrected expression, recently
proposed to account for the anisotropy of the spin absorption at the
ferromagnetic electrodes, still yields a deviation of the fitted spin-diffusion
length which increases for shorter channel distances. This deviation shows how
sensitive the non-local Hanle fittings are, evidencing the complexity of
obtaining spin transport information from such type of measurements.",1505.07592v1
2016-01-25,Lower limits of line resistance in nanocrystalline Back End of Line Cu interconnects,"The strong non-linear increase in Cu interconnect line resistance with a
decrease in linewidth presents a significant obstacle to their continued
downscaling. In this letter we use first principles density functional theory
based electronic structure of Cu interconnects to find the lower limits of
their line resistance for metal linewidths corresponding to future technology
nodes. We find that even in the absence of scattering due to grain boundaries,
edge roughness or interfaces, quantum confinement causes a severe reduction in
current carrying capacity of Cu. We discuss the causes of transport orientation
dependent anisotropy of quantum confinement in Cu. We also find that when the
simplest scattering mechanism in the grain boundary scattering dominated limit
is added to otherwise coherent electronic transmission in monocrystalline
nanowires, the lower limits of line resistance are significantly higher than
projected roadmap requirements in the International Technology Roadmap for
Semiconductors.",1601.06675v2
2016-05-12,NdCeCuO - NdCeO boundary and resistive switchings in mesoscopic structures on base of epitaxial NdCeCuO films,"Reverse and stable bipolar resistive switching effect was observed in planar
NdCeCuO - NdCeO - Ag heterostructures. It was shown that the current voltage
charactereriscs of the BRSE observed has a diode character. Simulations were
used to consider the influence of the nonuniform distribution of an electric
field at the interface of a heterojunction on the effect of bipolar resistive
switching in investigated structures. The inhomogeneous distribution of the
electric field near the contact edge creates regions of higher electric field
strength which, in turn, stimulates motion and redistribution of defects,
changes of the resistive properties of the whole structure and formation of a
percolation channel.",1605.03913v1
2016-08-25,Resistive Switching in Aqueous Nanopores by Shock Electrodeposition,"Solid-state programmable metallization cells have attracted considerable
attention as memristive elements for Redox-based Resistive Random Access Memory
(ReRAM) for low-power and low-voltage applications. In principle, liquid-state
metallization cells could offer the same advantages for aqueous systems, such
as biomedical lab-on-a-chip devices, but robust resistive switching has not yet
been achieved in liquid electrolytes, where electrodeposition is notoriously
unstable to the formation of fractal dendrites. Here, the recently discovered
physics of shock electrodeposition are harnessed to stabilize aqueous copper
growth in polycarbonate nanopores, whose surfaces are modified with charged
polymers. Stable bipolar resistive switching is demonstrated for 500 cycles
with <10s retention times, prior to any optimization of the geometry or
materials.",1608.07007v1
2017-02-17,An alternative to the spin-coupled interface resistance for describing heat generation,"Using a macroscopic approach, we studied theoretically the heat generation in
a typical spin valve with nonmagnetic spacer layer of finite thickness. Our
analysis shows that the spin-dependent heat generation cannot be interpreted as
the Joule heating of the spin-coupled interface resistance except for some
special segments. Moreover, the spin-coupled interface resistance can be
negative in certain situation, and thus its ""Joule heating"" should be
understood instead as the work done by the extra field in the ferromagnetic
layers and at the spin-selective interfaces. Effective resistances are proposed
as alternatives so that the spin-dependent heat generation can still be
expressed in a form resembling Joule's law.",1702.05283v1
2017-09-27,Kapitza thermal resistance across individual grain boundaries in graphene,"We study heat transport across individual grain boundaries in suspended
monolayer graphene using extensive classical molecular dynamics (MD)
simulations. We construct bicrystalline graphene samples containing grain
boundaries with symmetric tilt angles using the two-dimensional phase field
crystal method and then relax the samples with MD. The corresponding Kapitza
resistances are then computed using nonequilibrium MD simulations. We find that
the Kapitza resistance depends strongly on the tilt angle and shows a clear
correlation with the average density of defects in a given grain boundary, but
is not strongly correlated with the grain boundary line tension. We also show
that quantum effects are significant in quantitative determination of the
Kapitza resistance by applying the mode-by-mode quantum correction to the
classical MD data. The corrected data are in good agreement with quantum
mechanical Landauer-B\""utticker calculations.",1709.09529v1
2017-12-08,A Novel Effect of Electron Spin Resonance on Electrical Resistivity,"We extend the well known phenomenon of magnetoresistance (extra resistivity
of materials in transverse magnetic field) to a new and unexplored regime where
in addition to a transverse magnetic field, a transverse AC field of resonant
frequency is also applied. In a magnetic field, electron spin levels are Zeeman
split. In a resonant AC field, we uncover a new channel of momentum relaxation
in which electrons in upper Zeeman level can deexcite to lower Zeeman level by
generating spin fluctuation excitation in the lattice (similar to what happens
in Electron Spin Resonance (ESR) spectroscopy). An additional resistivity due
to this novel mechanism is predicted in which momentum randomization of Zeeman
split electrons happen via bosonic excitations (spin fluctuations). An order of
magnitude of this additional resistivity is calculated. The whole work is based
upon an extension of Einstein's derivation of equilibrium Planckian formula to
near equilibrium systems.",1712.03062v1
2017-12-11,Finite Size Effects in Highly Scaled Ruthenium Interconnects,"Ru has been considered a candidate to replace Cu-based interconnects in VLSI
circuits. Here, a methodology is proposed to predict the resistivity of (Ru)
interconnects. First, the dependence of the Ru thin film resistivity on the
film thickness is modeled by the semiclassical Mayadas-Shatzkes (MS) approach.
The fitting parameters thus obtained are then used as input in a modified MS
model for nanowires to calculate wire resistivities. Predicted experimental
resistivities agreed within about 10%. The results further indicate that grain
boundary scattering was the dominant scattering mechanism in scaled Ru
interconnects.",1712.03859v2
2017-12-23,A micromechanics-based analytical solution for the effective thermal conductivity of composites with orthotropic matrices and interfacial thermal resistance,"We obtained an analytical solution for the effective thermal conductivity of
composites composed of orthotropic matrices and spherical inhomogeneities with
interfacial thermal resistance using a micromechanics-based homogenization. We
derived the closed form of a modified Eshelby tensor as a function of the
interfacial thermal resistance. We then predicted the heat flux of a single
inhomogeneity in the infinite media based on the modified Eshelby tensor, which
was validated against the numerical results obtained from the finite element
analysis. Based on the modified Eshelby tensor and the localization tensor
accounting for the interfacial resistance, we derived an analytical expression
for the effective thermal conductivity tensor for the composites by a
mean-field approach called the Mori-Tanaka method. Our analytical prediction
matched very well with the effective thermal conductivity obtained from finite
element analysis with up to 10% inhomogeneity volume fraction.",1712.08715v2
2019-09-06,Strong suppression of the resistivity near the transition to superconductivity in narrow micro-bridges in external magnetic fields,"We have investigated a series of superconducting bridges based on homogeneous
amorphous WSi and MoSi films, with bridge widths w ranging from 2 um to 1000 um
and film thicknesses d ~ 4-6 nm and 100 nm. Upon decreasing the bridge widths
below the respective Pearl lengths, we observe in all cases distinct changes in
the characteristics of the resistive transitions to superconductivity. For each
of the films, the resistivity curves R(B,T) separate at a well-defined and
field-dependent temperature T*(B) with decreasing the temperature, resulting in
a dramatic suppression of the resistivity and a sharpening of the transitions
with decreasing bridge width w. The associated excess conductivity in all the
bridges scales as 1/w, which may suggest the presence of a highly conducting
region that is dominating the electric transport in narrow bridges. We argue
that this effect can only be observed in materials with sufficiently weak
vortex pinning.",1909.02915v2
2019-09-13,Tunable resistivity exponents in the metallic phase of epitaxial nickelates,"We report a detailed analysis of the electrical resistivity exponent of thin
films of NdNiO3 as a function of epitaxial strain. Strain-free thin-films show
a linear dependence of the resistivity vs temperature, consistent with a
classical Fermi gas ruled by electron-phonon interactions. In addition, the
apparent temperature exponent, n, can be tuned with the epitaxial strain
between n= 1 and n= 3. We discuss the critical role played by quenched random
disorder in the value of n. Our work shows that the assignment of
Fermi/Non-Fermi liquid behaviour based on experimentally obtained resistivity
exponents requires an in-depth analysis of the degree of disorder in the
material.",1909.06256v1
2014-08-08,Effects of Lifshitz Transition on Charge Transport in Magnetic Phases of Fe-Based Superconductors,"The unusual temperature dependence of the resistivity and its in-plane
anisotropy observed in the Fe-based superconducting materials, particularly
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, has been a longstanding puzzle. Here we
consider the effect of impurity scattering on the temperature dependence of the
average resistivity within a simple two-band model of a dirty spin density wave
metal. The sharp drop in resistivity below the N\'eel temperature $T_N$ in the
parent compound can only be understood in terms of a Lifshitz transition
following Fermi surface reconstruction upon magnetic ordering. We show that the
observed resistivity anisotropy in this phase, arising from nematic defect
structures, is affected by the Lifshitz transition as well.",1408.1933v3
2019-07-01,A perspective on effective medium models of thermal conductivity in (ultra)nanocrystalline diamond films,"Thermal conductivity of nanocrystalline and ultra-nanocrystalline films is
analyzed with effective medium theory (EMT) models. The existing EMT models use
the spherical inclusion approximation. Although this approximation works quite
well it is inconsistent, mostly with respect to the maximal packing of 74{\%},
which may be unrealistic for polycrystalline films. To check the consistency of
these models we devise an EMT model with arbitrarily shaped inclusions. We pick
the EMT model with cubic inclusions and we compare its results with the results
of the EMT model with spherical inclusions. It is found a very good agreement
between both calculations. This agreement is explained by general geometrical
arguments. We further employ these models to analyze thermal conductivity of
nanocrystalline and ultra-nanocrystalline diamond films. It is noticed that the
effective conductivity is strongly affected not only by the boundary Kapitza
resistance but also by intra-grain scattering for grain sizes below 100 nm.
Generally, both intra-grain conductivity and Kapitza resistance increase with
grain size. However, the effect of Kapitza resistance increase is negligible
due to the geometrical factor accompanying Kapitza resistance contribution to
the effective conductivity.",1907.00753v1
2016-03-02,Giant Frictional Drag in Double Bilayer Graphene Heterostructures,"We study the frictional drag between carriers in two bilayer graphene flakes
separated by a 2 $-$ 5 nm thick hexagonal boron nitride dielectric. At
temperatures ($T$) lower than $\sim$ 10 K, we observe a large anomalous
negative drag emerging predominantly near the drag layer charge neutrality. The
anomalous drag resistivity increases dramatically with reducing {\it T}, and
becomes comparable to the layer resistivity at the lowest {\it T} = 1.5 K. At
low $T$ the drag resistivity exhibits a breakdown of layer reciprocity. A
comparison of the drag resistivity and the drag layer Peltier coefficient
suggests a thermoelectric origin of this anomalous drag.",1603.00757v1
2017-04-05,Stateful characterization of resistive switching TiO2 with electron beam induced currents,"Metal oxide resistive switches are increasingly important as possible
artificial synapses in next generation neuromorphic networks. Nevertheless,
there is still no codified set of tools for studying properties of the devices.
To this end, we demonstrate electron beam induced current measurements as a
powerful method to monitor the development of local resistive switching in TiO2
based devices. By comparing beam-energy dependent electron beam induced
currents with Monte Carlo simulations of the energy absorption in different
device layers, it is possible to deconstruct the origins of filament image
formation and relate this to both morphological changes and the state of the
switch. By clarifying the contrast mechanisms in electron beam induced current
microscopy it is possible to gain new insights into the scaling of the
resistive switching phenomenon and observe the formation of a current leakage
region around the switching filament. Additionally, analysis of symmetric
device structures reveals propagating polarization domains.",1704.01475v2
2017-08-31,Antiferromagnetic anisotropy determination by spin Hall magnetoresistance,"An electric method for measuring magnetic anisotropy in antiferromagnetic
insulators (AFIs) is proposed. When a metallic film with strong spin-orbit
interactions, e.g., platinum (Pt), is deposited on an AFI, its resistance
should be affected by the direction of the AFI N eel vector due to the spin
Hall magnetoresistance (SMR). Accordingly, the direction of the AFI N eel
vector, which is affected by both the external magnetic field and the magnetic
anisotropy, is reflected in resistance of Pt. The magnetic field angle
dependence of the resistance of Pt on AFI is calculated by consider- ing the
SMR, which indicates that the antiferromagnetic anisotropy can be obtained
experimentally by monitoring the Pt resistance in strong magnetic fields.
Calculations are performed for realistic systems such as Pt/Cr2O3, Pt/NiO, and
Pt/CoO.",1708.09564v1
2019-08-12,Graphene-based spinmechatronic valve,"Interlayer twist between van der Waals graphene crystals led to the discovery
of superconducting and insulating states near the magic angle. In this work, we
exploit this mechanical degree of freedom by twisting the graphene middle layer
in a trilayer graphene spacer between two metallic lead (Magnetic and
nonmagnetic). A large difference in conductance is found depending on the angle
of twist between the middle layer graphene and the ones at the interface this
difference, called twisting resistance, reach more than 1000% in the
non-magnetic Cu case. For the magnetic Ni case, the magneto-resistance
decreases and the difference in conductance between twisted and not twisted
depends strongly on the relative magnetization configuration. For the parallel
configuration, the twisting resistance is about -40%, while for the
anti-parallel configuration it can reach up to 130%. Furthermore, we show that
the twisting resistance can be enhanced by inserting a thin Cu layer at the
interface of Ni/graphene where it reaches a value of 200% and 1600% for
parallel and antiparallel configurations, respectively. These finding could
pave the way toward the integration of 2D materials on novel spinmechatronics
based devices.",1908.04076v1
2019-08-15,Observation of Highly Nonlinear Resistive Switching of Al2O3/TiO2-x Memristors at Cryogenic Temperature (1.5 K),"In this work, we investigate the behavior of Al2O3/TiO2-x cross-point
memristors in cryogenic environment. We report successful resistive switching
of memristor devices from 300 K down to 1.5 K. The I-V curves exhibit negative
differential resistance effects between 130 and 1.5 K, attributed to a
metal-insulator transition (MIT) of the Ti4O7 conductive filament. The
resulting highly nonlinear behavior is associated to a maximum ION/IOFF ratio
of 84 at 1.5 K, paving the way to selector-free cryogenic passive crossbars.
Finally, temperature-dependant thermal activation energies related to the
conductance at low bias (20 mV) are extracted for memristors in low resistance
state, suggesting hopping-type conduction mechanisms.",1908.05545v4
2018-07-28,Anomalous Hall Effect and Spin Fluctuations in Ionic Liquid Gated SrCoO$_3$ Thin Films,"The recent realization of epitaxial SrCoO$_3$ thin films has triggered a
renewed interest in their electronic, magnetic, and ionic properties. Here we
uncover several unusual magneto-transport properties of this compound,
suggesting that it hosts persistent spin fluctuation down to low temperatures.
We achieve the metallic SrCoO$_3$ with record-low resistivity from insulating
SrCoO$_{2.5}$ by the ionic liquid gating. We find a linear relationship between
the anomalous Hall resistivity and the longitudinal resistivity, which cannot
be accounted for by the conventional mechanisms. We theoretically propose that
the impurity induced chiral spin fluctuation gives rise to such a dependence.
The existence of spin fluctuation manifests itself as negatively enhanced
magneto-resistance of SrCoO$_3$ when the temperature approaches zero. Our study
brings further insight into the unique spin state of SrCoO$_3$ and unveils a
novel skew scattering mechanism for the anomalous Hall effect.",1807.10877v1
2019-01-14,Phonon and electronic structures and resistance of layered electride Ca2N: DFT calculations,"The phonon and electronic properties, the Eliashberg function and the
temperature dependence of resistance of electride Ca2N are investigated by the
DFT-LDA plane-wave method. The phonon dispersion, the partial phonon density of
states and the atomic eigenvectors of zero-center phonons are studied. The
electronic band dispersion and partial density of states conclude that Ca2N is
a metal and the Ca 3p, 4s and N 2p orbitals are hybridized. For the analysis of
an electron - phonon interaction (EPI) and its contribution to resistance the
Eliashberg function was calculated and a temperature dependence of resistance
caused EPI was found. The present results are in good agreement with experiment
data.",1901.04594v1
2020-05-22,VoteAgain: A scalable coercion-resistant voting system,"The strongest threat model for voting systems considers coercion resistance:
protection against coercers that force voters to modify their votes, or to
abstain. Existing remote voting systems either do not provide this property;
require an expensive tallying phase; or burden users with the need to store
cryptographic key material and with the responsibility to deceive their
coercers. We propose VoteAgain, a scalable voting scheme that relies on the
revoting paradigm to provide coercion resistance. VoteAgain uses a novel
deterministic ballot padding mechanism to ensure that coercers cannot see
whether a vote has been replaced. This mechanism ensures tallies take
quasilinear time, making VoteAgain the first revoting scheme that can handle
elections with millions of voters. We prove that VoteAgain provides ballot
privacy, coercion resistance, and verifiability; and we demonstrate its
scalability using a prototype implementation of all cryptographic primitives.",2005.11189v3
2020-06-06,Radiative Resistance at The Nano-scale: Thermal Barrier,"In present article the radiative thermal current and radiative resistance are
introduced and investigated in a system of parallel slabs. The system is placed
in an environment with a constant temperature and subjected to a constant
temperature gradient, which causes a radiative energy flux through the system.
We have calculated the steady-state temperatures profile of the system,
assuming that the material and thickness of the middle slab could be different
from the other slabs. We propose the exact formulation for calculating the
thermal current and thermal resistances in both linear and nonlinear regimes.
According to our results, the middle slab acts as a thermal barrier and
depending on the width of this barrier, an extreme thermal isolation is
achievable. Simulation results indicate that the thermal resistance of the
barrier is an increasing function of the thickness for near-field separation
distances but it is virtually insensitive to the barrier width in far field
regime. The long range character of the radiative heat transfer, which occurs
in system with identical slabs is also discussed.",2006.03842v4
2020-08-16,Strange metal behavior of the Hall angle in twisted bilayer graphene,"Twisted bilayer graphene (TBG) with interlayer twist angles near the magic
angle $\approx 1.08^{\circ}$ hosts flat bands and exhibits correlated states
including Mott-like insulators, superconductivity and magnetism. Here we report
combined temperature-dependent transport measurements of the longitudinal and
Hall resistivities in close to magic-angle TBG. While the observed longitudinal
resistivity follows linear temperature $T$ dependence consistent with previous
reports, the Hall resistance shows an anomalous $T$ dependence with the
cotangent of the Hall angle cot $\Theta{_H} \propto T^2$. Boltzmann theory for
quasiparticle transport predicts that both the resistivity and cot $\Theta{_H}$
should have the same $T$ dependence, contradicting the observed behavior. This
failure of quasiparticle-based theories is reminiscent of other correlated
strange metals such as cuprates.",2008.06907v1
2020-08-23,Negative resistance state in superconducting NbSe$_2$ induced by surface acoustic waves,"We report a negative resistance, namely, a voltage drop along the opposite
direction of a current flow, in the superconducting gap of NbSe$_2$ thin films
under the irradiation of surface acoustic waves (SAWs). The amplitude of the
negative resistance becomes larger by increasing the SAW power and decreasing
temperature. As one possible scenario, we propose that soliton-antisoliton
pairs in the charge density wave of NbSe$_2$ modulated by the SAW serve as a
time-dependent capacitance in the superconducting state, leading to the dc
negative resistance. The present experimental result would provide a previously
unexplored way to examine nonequilibrium manipulation of the superconductivity.",2008.09948v1
2020-11-17,Effect of Substrate Roughness on Oxidation Resistance of an Aluminized Ni-Base Superalloy,"In the present work, it is shown that the surface preparation method used on
two Ni-based superalloys prior to aluminizing chemical vapor deposition (CVD)
is one of the most important factors determining the oxidation resistance of
aluminized Ni-based superalloys. It was found that grit blasting the substrate
surface negatively affects the oxidation resistance of the aluminized coatings.
For grit blasted and aluminized IN 625, a thicker outer NiAl coating was formed
compared to that of IN 738. In contrast, no effect on NiAl coating thickness
was found for grit blasted and aluminized IN 738. However, a thicker
interdiffusion zone (IDZ) was observed. It was shown that the systems with
grit-blasted surfaces reveal worse oxidation resistance during thermal shock
tests, namely, a higher mass loss was observed for both grit blasted and
aluminized alloys, as compared to ground and aluminized alloys. A possible
reason for this effect of remaining alumina particles originating from surface
grit blasting on the diffusion processes and stress distribution at the
coating/substrate is proposed.",2011.08921v1
2021-04-23,Microstructure and wear resistance of Fe-Cr-C-Mo-V-Ti-N hardfacing layers,"In this paper, to improve wear resistance of components such as screws under
severe friction-wear, Fe-Cr-C-Mo-V-Ti-N hardfacing coatings were further
developed. The hardfacing coatings were acquired by shielded manual arc welding
(SMAW) method. The ferroalloys added into the coating flux of the hardfaced
electrode were jointly nitrided. The microstructure of the coatings was carried
out using X-ray diffraction(XRD), optical microscope(OM), field emission
scanning electron microscope (FESEM) and energy dispersive Xray spectrometry
(EDS). In addition, FactSage 7.0 software was employed to calculate the
equilibrium phase diagram of the hardfacings. The wear resistance was performed
on a pin-on-disc machine. The Fe-Cr-C- Mo-V-Ti-N hardfacings exhibited higher
wear resistance than cladding layer without nitrides.",2104.11402v1
2021-05-27,Systematic manipulation of the surface conductivity of SmB$_6$,"We show that the resistivity plateau of SmB$_6$ at low temperature, typically
taken as a hallmark of its conducting surface state, can systematically be
influenced by different surface treatments. We investigate the effect of
inflicting an increasing number of hand-made scratches and microscopically
defined focused ion beam-cut trenches on the surfaces of flux-grown
Sm$_{1-x}$Gd$_x$B$_6$ with $x =$ 0, 0.0002. Both treatments increase the
resistance of the low-temperature plateau, whereas the bulk resistance at
higher temperature largely remains unaffected. Notably, the temperature at
which the resistance deviates from the thermally activated behavior decreases
with cumulative surface damage. These features are more pronounced for the
focused ion beam treated samples, with the difference likely being related to
the absence of microscopic defects like subsurface cracks. Therefore, our
method presents a systematic way of controlling the surface conductance.",2105.13057v1
2021-06-23,A new symmetry-based extraction method of Schottky diode parameters from resistance-compensated I-V characteristics,"We present a novel resistance-compensated I-V method to extract the series
resistance, ideality factor, barrier height and built-in potential of a
metal-semiconductor diode. We show that a reduced equation arises from a unique
but hitherto unreported symmetry in the Schottky equation when it is written as
an ordinary differential equation. In spite of the intense mathematical
justification, we show how this new equation is directly applicable to an
empirical data set through a simple algorithm. We test the method on a new
Al/p-Si/Bi$_2$Se$_3$/Al Schottky diode and compare it with the Cheung-Cheung
method on the same data. The series resistance was found to change
exponentially with applied bias with a rate constant that depends on the
incident illumination. The barrier height decreased with bias but was
independent of the incident illumination. The trends in the results of the
method agree strongly with the literature and may yield more accurate diode
parameters compared to other electrical methods.",2106.12324v1
2021-08-19,Influence of charged walls and defects on DC resistivity and dielectric relaxation in Cu-Cl boracite,"Charged domain walls form spontaneously in Cu-Cl boracite on cooling through
the phase transition. These walls exhibit changed conductivity compared to the
bulk and motion consistent with the existence of negative capacitance. Here, we
present the dielectric permittivity and DC resistivity of bulk Cu-Cl boracite
as a function of temperature (-140 {\deg}C to 150 {\deg}C) and frequency (1 mHz
to 10 MHz). The thermal behaviour of the two observed dielectric relaxations
and the DC resistivity is discussed. We propose that the relaxations can be
explained by the existence of point defects, most likely local complexes
created by a change of valence of Cu and accompanying oxygen vacancies. In
addition, the sudden change in resistivity seen at the phase transition
suggests that conductive domain walls contribute significantly to the
conductivity in the ferroelectric phase.",2108.08582v2
2022-01-10,Designs for programmable quantum resistance standards based on epitaxial graphene p-n junctions,"We report the fabrication and measurement of top gated epitaxial graphene p-n
junctions where exfoliated hexagonal boron nitride (h-BN) is used as the gate
dielectric. The four-terminal longitudinal resistance across a single junction
is well quantized at the von Klitzing constant R_K with a relative uncertainty
of 10-7. After the exploration of numerous parameter spaces, we summarize the
conditions upon which these devices could function as potential resistance
standards. Furthermore, we offer designs of programmable electrical resistance
standards over six orders of magnitude by using external gating.",2201.03621v1
2022-04-26,"Nonreciprocal electrical transport in multiferroic semiconductor (Ge,Mn)Te","We have investigated the nonreciprocal electrical transport, that is a
nonlinear resistance effect depending on the current direction, in multiferroic
Rashba semiconductor (Ge,Mn)Te. Due to coexistence of ferromagnetic and
ferroelectric orders, (Ge,Mn)Te provides a unique platform for exploring the
nonreciprocal electrical transport in a bulk form. (Ge,Mn)Te thin films shows a
large nonreciprocal resistance compared to GeTe, the nonmagnetic counterpart
with the same crystal structure. The magnetic-field-angle dependence of the
nonreciprocal resistance is maximized when magnetic field is orthogonal to both
current and electric polarization, in accord with the symmetry argument. From
the analysis of temperature and magnetic field dependence, we deduce that
inelastic scatterings of electrons mediated by magnons dominantly contribute to
the observed nonreciprocal response. Furthermore, the nonreciprocal resistance
is significantly enhanced by lowering hole density. The Fermi level dependence
is attributed to the deformation of the Rashba band in which the spin-momentum
locked single Fermi surface appears by exchange field from the in-plane
magnetization. The present study provides a key insight to the mechanisms of
novel transport phenomena caused by the interplay of ferroelectric and
ferromagnetic orders in a semiconductor.",2204.12427v1
2022-08-17,Transport properties of dipole skyrmions in amorphous FeGd multilayers,"The transport response of dipole skyrmions in amorphous centrosymmetric Fe/Gd
multilayer is investigated by temperature and field-dependent resistivity
measurements collected in three current and magnetic field configurations. It
is shown that a dipole skyrmion lattice phase may form at certain temperatures
leading to a unique signature of the polar longitudinal resistivity. This
signature differs from the conventional field-varying parabolic response
associated with stripe phases, which transition to a disordered skyrmion phase
under applied fields. Transport measurements under different field history
protocols reveal that the anomaly in the polar longitudinal resistivity appears
under specific field history reversal processes. Our experimental results are
reproduced using micromagnetic simulations that show the anomaly in the polar
longitudinal resistivity is related to a domain wall reconfiguration that
occurs as the domain morphology transitions from disordered stripes to a
skyrmion lattice under applied perpendicular fields.",2208.08487v1
2023-01-18,Synthesizing $2h/e^2$ resistance plateau at the first Landau level confined in a quantum point contact,"A comprehensive understanding of quantum Hall edge transmission, especially
the hole-conjugate of a Laughlin state such as a $2/3$ state, is critical for
advancing fundamental quantum Hall physics and enhancing the design of quantum
Hall edge interferometry. In this study, we report a robust intermediate
$2h/e^2$ resistance quantization in a quantum point contact (QPC) when the bulk
is set at the fractional filling $2/3$ quantum Hall state. Our results suggest
the occurrence of two equilibration processes. First, the co-propagating $1/3$
edges moving along a soft QPC arm confining potential fully equilibrate and act
as a single $2/3$ edge mode. Second, the $2/3$ edge mode is further
equilibrated with an integer $1$ edge mode formed in the QPC. The complete
mixing between them results in a diagonal resistance value quantized at
$2h/e^2$. Similar processes occur for a bulk filling $5/3$, leading to an
intermediate $(2/3)h/e^2$ resistance quantization.",2301.07488v2
2024-02-28,Impact of etches on thin-film single-crystal niobium resonators,"A single crystal niobium thin film was grown using molecular beam epitaxy on
a c-plane sapphire wafer. Several samples were fabricated into dc resistivity
test devices and coplanar waveguide resonator chips using the same
microfabrication procedures and solvent cleans. The samples were then subject
to different acid cleaning treatments using different combinations of piranha,
hydrofluoric acid, and buffered oxide etch solutions. The different samples
expressed changes in dc resistivity in the normal and superconducting states
such that the low temperature resistivities changed by more than 100\%, and the
residual resistivity ratio dropped by a factor of 2. The internal quality
factor of coplanar waveguide resonators measured near 5~GHz also showed
significant variation at single photon powers ranging from 1.4$\times 10^6$ to
less than 60$\times 10^3$. These changes correlate with the formation of
surface crystallites that appear to be hydrocarbons. All observations are
consistent with hydrogen diffusing into the niobium film at levels below the
saturation threshold that is needed to observe niobium hydrides.",2402.18051v1
2024-05-02,Optimization of reactively sputtered Mn3GaN films based on resistivity measurements,"Mn-based nitrides with antiperovskite structures have several properties that
can be utilised for antiferromagnetic spintronics. Their magnetic properties
depend on the structural quality, composition and doping of the cubic
antiperovskite structure. Such nitride thin films are usually produced by
reactive physical vapour deposition, where the deposition rate of N can only be
controlled by the N2 gas flow. We show that the tuning of the N content can be
optimised using low temperature resistivity measurements, which serve as an
indicator of the degree of structural disorder. Several Mn3GaNx films were
prepared by reactive magnetron sputtering under different N2 gas flows. Under
optimised conditions, we obtain films that exhibit a metal-like temperature
dependence, a vanishing logarithmic increase in resistivity towards zero, the
highest resistivity ratio and a lattice contraction of 0.4 % along the growth
direction when heated above that of the N\'eel temperature in agreement with
the bulk samples.",2405.01203v1
2004-02-04,A simple estimate of the electron hopping energy in the Bechgaard salts,"Starting from a previously derived theoretical expression for the electrical
conductivity of the Bechgaard salts,and experimental data on the resistivity of
these materials,it is shown how a valueof the electron hopping energy can be
determined.Values obtained in this way are in agreement with estimates made by
more complicated methods.",0402127v1
2019-09-12,Gallium Nitride FET Model,"We have presented an analytical physics-based compact model of GaN power FET,
which can accurately describe the I-V characteristics in all operation modes.
The model considers the source-drain resistance, different interface trap
densities and self-heating effects.",1909.05702v1
2019-09-18,A current-voltage characteristic of photoresistance. A plane case,"The formation of photo-electron current in the volume of semi-conductor
material is investigated in this article. A plane case when a material is
uniformly illuminated by light is considered. The current-voltage
characteristic of a photo resistance is obtained in analytical form.",1909.09135v1
2019-10-04,The Test of Topological Property of YbB6,"Topological insulator is a recently discovered class of material with
topologically protected surface state. YbB6 is predicted to be moderately
correlated Z2 topological insulator similar to SmB6. Here, I experimentally
test the resistance property of bulk YbB6 to verify its topological property.
By changing the thickness of YbB6, I found out that although the data curves
did not completely conform to the theory of topology, the experimental
observation to the overall trend showed a similar topological phenomenon.",1910.02056v1
2020-01-25,Exfoliation of Two-Dimensional Nanosheets of Metal Diborides,"The metal diborides are a class of ceramic materials with crystal structures
consisting of hexagonal sheets of boron atoms alternating with planes of metal
atoms held together with mixed character ionic/covalent bonds. Many of the
metal diborides are ultrahigh temperature ceramics like HfB$_2$, TaB$_2$, and
ZrB$_2$, which have melting points above 3000$^\circ$C, high mechanical
hardness and strength at high temperatures, and high chemical resistance, while
MgB$_2$ is a superconductor with a transition temperature of 39 K. Here we
demonstrate that this diverse family of non-van der Waals materials can be
processed into stable dispersions of two-dimensional (2D) nanosheets using
ultrasonication-assisted exfoliation. We generate 2D nanosheets of the metal
diborides AlB$_2$, CrB$_2$, HfB$_2$, MgB$_2$, NbB$_2$, TaB$_2$, TiB$_2$, and
ZrB$_2$, and use electron and scanning probe microscopies to characterize their
structures, morphologies, and compositions. The exfoliated layers span up to
micrometers in lateral dimension and reach thicknesses down to 2-3 nm, while
retaining their hexagonal atomic structure and chemical composition. We exploit
the convenient solution-phase dispersions of exfoliated CrB$_2$ nanosheets to
incorporate them directly into polymer composites. In contrast to the hard and
brittle bulk CrB$_2$, we find that CrB$_2$ nanocomposites remain very flexible
and simultaneously provide increases in the elastic modulus and the ultimate
tensile strength of the polymer. The successful liquid-phase production of 2D
metal diborides enables their processing using scalable low-temperature
solution-phase methods, extending their use to previously unexplored
applications, and reveals a new family of non-van der Waals materials that can
be efficiently exfoliated into 2D forms.",2001.09237v1
2005-10-07,"Collective Spin and Charge Excitations in (Sr,La)_{14-x}Ca_xCu_{24}O_{41} Quantum Spin Ladders","We study magnetic and electronic properties of two-leg ladder materials. We
observed a two-magnon (2M) resonance which we analyze in terms of symmetry,
relaxation and resonance properties. Our findings were contrasted to 2M Raman
measurements in other magnetic crystals. This comparison made us suggest that
the spin-spin correlations in a self-doped two leg ladder may have a modulated
component besides the exponential decay characteristic of a spin liquid ground
state. We found that the 2M intensity resonates at the Mott gap energy.
Interplane Sr substitution for Ca introduces strong disorder leading to
inhomogeneous broadening of the 2M resonance. The doped holes in the spin
liquid ground state further dilute the magnetic correlations, suppressing the
spectral weight of this excitation. At high Ca concentrations are
superconducting under pressure and hole pairing was proposed to be a robust
feature of doped ladders. The measured dielectric response in the microwave
region, the low energy Raman data, the non-linear transport properties along
with soft x-ray scattering allowed us to conclude that the ground state for a
wide range of Ca concentrations (x < 12) is characterized by charge density
wave correlations. This state seems to be driven not by phonons but by Coulomb
forces and many-body effects. We highlighted the similarity in the finite
frequency Raman response as opposed to the very different behavior of the DC
resistivity between undoped and doped ladders. We found that at high Ca
concentrations the carrier relaxation is characterized by the same large
activation energy (~2000 K) as in the self-doped compound. This observation
prompted us to suggest an unconventional metallic transport driven by
collective electronic response.",0510193v1
2009-02-13,Nanoscale Electronic Inhomogeneity in In2Se3 Nanoribbons Revealed by Microwave Impedance Microscopy,"Driven by interactions due to the charge, spin, orbital, and lattice degrees
of freedom, nanoscale inhomogeneity has emerged as a new theme for materials
with novel properties near multiphase boundaries. As vividly demonstrated in
complex metal oxides and chalcogenides, these microscopic phases are of great
scientific and technological importance for research in high-temperature
superconductors, colossal magnetoresistance effect, phase-change memories, and
domain switching operations. Direct imaging on dielectric properties of these
local phases, however, presents a big challenge for existing scanning probe
techniques. Here, we report the observation of electronic inhomogeneity in
indium selenide (In2Se3) nanoribbons by near-field scanning microwave impedance
microscopy. Multiple phases with local resistivity spanning six orders of
magnitude are identified as the coexistence of superlattice, simple hexagonal
lattice and amorphous structures with 100nm inhomogeneous length scale,
consistent with high-resolution transmission electron microscope studies. The
atomic-force-microscope-compatible microwave probe is able to perform
quantitative sub-surface electronic study in a noninvasive manner. Finally, the
phase change memory function in In2Se3 nanoribbon devices can be locally
recorded with big signal of opposite signs.",0902.2255v1
2009-10-01,Template engineering of Co-doped BaFe2As2 single-crystal thin films,"Understanding new superconductors requires high-quality epitaxial thin films
to explore intrinsic electromagnetic properties, control grain boundaries and
strain effects, and evaluate device applications. So far superconducting
properties of ferropnictide thin films appear compromised by imperfect
epitaxial growth and poor connectivity of the superconducting phase. Here we
report novel template engineering using single-crystal intermediate layers of
(001) SrTiO3 and BaTiO3 grown on various perovskite substrates that enables
genuine epitaxial films of Co-doped BaFe2As2 with high transition temperature
(zero resistivity Tc of 21.5K), small transition widths (delta Tc = 1.3K),
superior Jc of 4.5 MA/cm2 (4.2K, self field) and strong c-axis flux pinning.
Implementing SrTiO3 or BaTiO3 templates to match the alkaline earth layer in
the Ba-122 with the alkaline earth-oxygen layer in the templates opens new
avenues for epitaxial growth of ferropnictides on multi-functional single
crystal substrates. Beyond superconductors, it provides a framework for growing
heteroepitaxial intermetallic compounds on various substrates by matching
interfacial layers between templates and thin film overlayers.",0910.0268v1
2009-11-19,Large transport critical currents of powder-in-tube Sr0.6K0.4Fe2As2/Ag superconducting wires and tapes,"We report significant transport critical currents firstly achieved in
Sr0.6K0.4Fe2As2 wires and tapes with a Tc = 34 K, which were fabricated through
an in-situ powder-in-tube process. Silver was used as a chemical addition as
well as a sheath material. Transport measurements were performed by a standard
four-probe resistive method. All the wire and tape samples have shown transport
properties. Critical current density Jc was enhanced upon silver addition, and
at 4.2 K, a best Jc of ~1200 A/cm^2 (Ic = 9 A) was achieved for 20 % silver
added tapes, which is the highest in iron-based wires and tapes so far. The Jc
is almost field independent between 1 T and 10 T, exhibiting a strong vortex
pinning. Such a high transport critical current density is attributed to the
absence of reaction layer between the silver sheath and superconducting core,
as well as an improved connectivity between grains. We also identify a
weak-link behavior from the creep drop of Jc at low fields and a hysteretic
phenomenon. Finally, we found that compared to Fe, Ta and Nb tubes, Ag was the
best sheath material for the fabrication of high-performance 122 type pnictide
wires and tapes.",0911.3701v1
2010-10-05,Hierarchical formation of bulgeless galaxies: Why outflows have low angular momentum,"Using high resolution, fully cosmological smoothed particle hydro-dynamical
simulations of dwarf galaxies in a Lambda cold dark matter Universe, we show
how baryons attain a final angular momentum distribution which allows pure disc
galaxies to form. Blowing out substantial amounts of gas through supernovae and
stellar winds, which is well supported observationally, is a key ingredient in
forming bulgeless discs. We outline why galactic outflows preferentially remove
low angular momentum material, and show that this is a natural result when
structure forms in a cold dark matter cosmology. The driving factors are a) the
mean angular momentum of accreted material increases with time, b) lower
potentials at early times, c) the existence of an extended reservoir of high
angular momentum gas which is not within star forming regions, meaning that
only gas from the inner region (low angular momentum gas) is expelled and d)
the tendency for outflows to follow the path of least resistance which is
perpendicular to the disc. We also show that outflows are enhanced during
mergers, thus expelling much of the gas which has lost its angular momentum
during these events, and preventing the formation of ""classical"", merger driven
bulges in low mass systems. Stars formed prior to such mergers form a diffuse,
extended stellar halo component.",1010.1004v3
2014-02-13,On the spheroidized carbide dissolution and elemental partitioning in a high carbon bearing steel 100Cr6,"We report on the characterization of high carbon bearing steel 100Cr6 using
electron microscopy and atom probe tomography in combination with
multi-component diffusion simulations (DICTRA). Scanning electron micrographs
show that around 14 vol.% spheroidized carbides are formed during soft
annealing and only 3 vol.% remain after dissolution into the austenitic matrix
by austenitization at 1123 K (850 {\deg}C) for 300 s. The spheroidized
particles are identified as (Fe, Cr)3C by transmission electron microscopy.
Atom probe analyses reveal the redistribution and partitioning behaviors of
elements, i.e. C, Si, Mn, Cr, Fe in both, the spheroidized carbides and the
bainitic matrix in the sample isothermally heat-treated at 773 K (500 {\deg}C)
after austenitization. A homogeneous distribution of C and gradual gradient of
Cr was detected within the spheroidized carbides. Due to its limited
diffusivity in (Fe, Cr)3C, Cr exhibits a maximum concentration at the surface
of spheroidized carbides (16 at.%) and decreases gradually from surface towards
the core down to a level of about 2 at.%. The atom probe results also indicate
that the partially dissolved spheroidized carbides during austenitization may
serve as nucleation sites for intermediate temperature cementite within
bainite, which results in a relatively softer surface and harder core in
spheroidized particles. This microstructure may contribute to the good wear
resistance and fatigue properties",1402.3315v1
2014-05-23,Proof-of-principle of a new geometry for sampling calorimetry using inorganic scintillator plates,"A novel geometry for a sampling calorimeter employing inorganic scintillators
as an active medium is presented. To overcome the mechanical challenges of
construction, an innovative light collection geometry has been pioneered, that
minimises the complexity of construction. First test results are presented,
demonstrating a successful signal extraction. The geometry consists of a
sampling calorimeter with passive absorber layers interleaved with layers of an
active medium made of inorganic scintillating crystals. Wavelength-shifting
(WLS) fibres run along the four long, chamfered edges of the stack,
transporting the light to photodetectors at the rear. To maximise the amount of
scintillation light reaching the WLS fibres, the scintillator chamfers are
depolished. It is shown herein that this concept is working for cerium fluoride
(CeF$_3$) as a scintillator. Coupled to it, several different types of
materials have been tested as WLS medium. In particular, materials that might
be sufficiently resistant to the High-Luminosity Large Hadron Collider
radiation environment, such as cerium-doped Lutetium-Yttrium Orthosilicate
(LYSO) and cerium-doped quartz, are compared to conventional plastic WLS
fibres. Finally, an outlook is presented on the possible optimisation of the
different components, and the construction and commissioning of a full
calorimeter cell prototype is presented.",1405.6202v1
2015-02-10,Emergence of the minority hole with high mobility on the electrical transport in the Fe-pnictides Ba(Fe$_{1-x}$Mn$_x$As)$_2$,"In Fe pnictide (Pn) superconducting materials, neither Mn- nor Cr- doping to
the Fe site induces superconductivity, even though hole carriers are generated.
This is in strong contrast with the superconductivity appearing when holes are
introduced by alkali metal substitution on the insulating blocking layers. We
investigate in detail the effects of Mn doping on magneto-transport properties
in Ba(Fe$_{1-x}$Mn$_x$As)$_2$ for elucidating the intrinsic reason. The
negative Hall coefficient for $x$ = 0 estimated in the low magnetic field ($B$)
regime gradually increases as $x$ increases, and its sign changes to a positive
one at $x$ = 0.020. Hall resistivities as well as simultaneous interpretation
using the magnetoconductivity tensor including both longitudinal and transverse
transport components clarify that minority holes with high mobility are
generated by the Mn doping via spin density wave (SDW) transition at low
temperatures, while original majority electrons and holes residing in the
parabolic-like Fermi surfaces (FSs) of the semimetallic Ba(FeAs)$_2$ are
negligibly affected. Present results indicate that the mechanism of hole doping
in Ba(Fe$_{1-x}$Mn$_x$As)$_2$ is greatly different from that of the other
superconducting FePns family.",1502.02845v3
2015-08-16,Surface States Engineering of Metal/MoS2 Contacts Using Sulfur Treatment for Reduced Contact Resistance and Variability,"Variability and lack of control in the nature of contacts between metal/MoS2
interface is a major bottleneck in the realisation of high-performance devices
based on layered materials for several applications. In this letter, we report
on the reduction in Schottky barrier height at metal/MoS2 interface by
engineering the surface states through sulphur treatment. Electrical
characteristics for back-gated MoS2 field effect transistor structures were
investigated for two high work-function metal contacts Ni and Pd. Contacts on
MoS2 treated with sulphur exhibited significant improvements in Ohmic nature
with concomitant reduction in variability compared to those on untreated MoS2
films leading to a 2x increase in extracted mobility. X-ray Photoelectron
Spectroscopy (XPS) measurements, Raman Spectroscopy and comparison of threshold
voltages indicated absence of additional doping or structural changes due to
sulphur treatment. The Schottky barrier heights were extracted from
temperature-dependent transfer characteristics based on the thermionic current
model. A reduction in barrier height of 80 and 135 meV extracted for Ni/MoS2
and Pd/MoS2 contacts respectively is hence attributed to the increase in
surface states (or stronger Fermi level pinning) due to sulphur treatment. The
corresponding charge neutrality levels at metal/MoS2 interface, were extracted
to be 0.16 eV (0.17 eV) below the conduction band before (after) Sulphur
treatment. This first report of surface states engineering in MoS2 leading to
superior contacts is expected to significantly benefit the entire class of
devices based on layered 2D materials.",1508.03795v2
2016-06-28,Method for Transferring High-Mobility CVD-Grown Graphene with Perfluoropolymers,"The transfer of graphene grown by chemical vapor deposition (CVD) using
amorphous polymers represents a widely implemented method for graphene-based
electronic device fabrication. However, the most commonly used polymer,
poly(methyl methacrylate) (PMMA), leaves a residue on the graphene that limits
the mobility. Here we report a method for graphene transfer and patterning that
employs a perfluoropolymer---Hyflon---as a transfer handle and to protect
graphene against contamination from photoresists or other polymers. CVD-grown
graphene transferred this way onto LaAlO$_3$/SrTiO$_3$ heterostructures is
atomically clean, with high mobility (~30,000 cm$^2$V$^{-1}$s$^{-1}$) near the
Dirac point at 2 K and clear, quantized Hall and magneto-resistance. Local
control of the LaAlO$_3$/SrTiO$_3$ interfacial metal-insulator
transition---through the graphene---is preserved with this transfer method. The
use of perfluoropolymers such as Hyflon with CVD-grown graphene and other 2D
materials can readily be implemented with other polymers or photoresists.",1606.08802v1
2016-10-31,High Electric Field Carrier Transport and Power Dissipation in Multilayer Black Phosphorus Field Effect Transistor with Dielectric Engineering,"This study addresses high electric field transport in multilayer black
phosphorus (BP) field effect transistors (FETs) with self-heating and thermal
spreading by dielectric engineering. Interestingly, we found that multilayer BP
device on a SiO2 substrate exhibited a maximum current density of 3.3 x 10E10
A/m2 at an electric field of 5.58 MV/m, several times higher than multilayer
MoS2. Our breakdown thermometry analysis revealed that self-heating was impeded
along BP-dielectric interface, resulting in a thermal plateau inside the
channel and eventual Joule breakdown. Using a size-dependent electro-thermal
transport model, we extracted an interfacial thermal conductance of 1-10 MW/m2
K for the BP-dielectric interfaces. By using hBN as a dielectric material for
BP instead of thermally resistive SiO2 (about 1.4 W/m K), we observed a 3 fold
increase in breakdown power density and a relatively higher electric field
endurance together with efficient and homogenous thermal spreading because hBN
had superior structural and thermal compatibility with BP. We further confirmed
our results based on micro-Raman spectroscopy and atomic force microscopy, and
observed that BP devices on hBN exhibited centrally localized hotspots with a
breakdown temperature of 600K, while the BP device on SiO2 exhibited a hotspot
in the vicinity of the electrode at 520K.",1610.09951v1
2017-02-02,High-Pressure Synthesis and Characterization of $β$-GeSe - A Semiconductor with Six-Rings in an Uncommon Boat Conformation,"Two-dimensional materials have significant potential for the development of
new devices. Here we report the electronic and structural properties of
$\beta$-GeSe, a previously unreported polymorph of GeSe, with a unique crystal
structure that displays strong two-dimensional structural features.
$\beta$-GeSe is made at high pressure and temperature and is stable under
ambient conditions. We compare it to its structural and electronic relatives
$\alpha$-GeSe and black phosphorus. The $\beta$ form of GeSe displays a boat
conformation for its Ge-Se six-ring, while the previously known $\alpha$ form,
and black phosphorus, display the more common chair conformation for their
six-rings. Electronic structure calculations indicate that $\beta$-GeSe is a
semiconductor, with an approximate bulk band gap of $\Delta~\approx$ 0.5 eV,
and, in its monolayer form, $\Delta~\approx$ 0.9 eV. These values fall between
those of $\alpha$-GeSe and black phosphorus, making $\beta$-GeSe a promising
candidate for future applications. The resistivity of our $\beta$-GeSe crystals
measured in-plane is on the order of $\rho \approx$ 1 $\Omega$cm, while being
essentially temperature independent.",1702.00715v1
2017-09-21,Effect of nanostructure on thermoelectric properties of La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ in 300-600 K range,"In oxide materials, nanostructuring effect has been found very promising
approach for the enhancement of \textit{figure-of-merit}, \textit{ZT}. In the
present work, we have synthesized La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) compound
using sol-gel method and samples of crystallite size of 34, 41, and 49 nm were
obtained by giving different heat treatment. Seebeck coefficient ($\alpha$),
electrical resistivity ($\rho$), and thermal conductivity ($\kappa$)
measurements were carried out in 300-600 K temperature range. The systematic
change in the values of $\alpha$ from $\sim$ -19 $\mu$V/K to $\sim$ -24
$\mu$V/K and drastic reduction in the values of $\kappa$ from $\sim$0.88 W/mK
to $\sim$0.23 W/mK are observed as crystallite size is reduced from 49 nm to 34
nm at $\sim$600 K. Also, fall in the values of $\rho$ in the paramagnetic (PM)
insulator phase (400-600 K) are effectively responsible for the increasing
trend in the values of \textit{ZT} at high temperature. For the crystallite
size of 41 nm, value of \textit{ZT} at 600 K was found to be $\sim$0.017, which
can be further increased up to $\sim$0.045 around 650 K temperature. The
predicted value of \textit{ZT} suggests that LSMO can be suitable oxide
material for thermoelectric applications at high temperature.",1709.07205v2
2017-12-17,Short range order in the quantum XXZ honeycomb lattice material BaCo$_2$(PO$_4$)$_2$,"We present observations of highly frustrated quasi two-dimensional (2D)
magnetic correlations in the honeycomb lattice layers of the S$_{eff}$ = 1/2
compound $\gamma$-BaCo$_2$(PO$_4$)$_2$ ($\gamma$-BCPO). Specific heat shows a
broad peak comprised of two weak kink features at $T_{N1} \sim$ 6 K and $T_{N2}
\sim$ 3.5 K, the relative weights of which can be modified by sample annealing.
Neutron powder diffraction measurements reveal short range quasi-2D order that
is established below $T_{N1}$ and $T_{N2}$, at which two separate,
incompatible, short range magnetic orders onset: commensurate antiferromagnetic
correlations with correlation length $\xi_c = 60\pm2$ \AA \ ($T_{N1}$) and in
quasi-2D helical domains with $\xi_h = 350 \pm 11$ \AA \ ($T_{N2}$). The ac
magnetic susceptibility response lacks frequency dependence, ruling out spin
freezing. Inelastic neutron scattering data on $\gamma$-BCPO is compared with
linear spin wave theory, and two separate parameter regions of the XXZ
$J_1$-$J_2$-$J_3$ model with ferromagnetic nearest-neighbor exchange $J_1$ are
favored, both near regions of high classical degeneracy. High energy coherent
excitations ($\sim 10$ meV) persist up to at least 40 K, suggesting strong
in-plane correlations persist above $T_N$. These data show that $\gamma$-BCPO
is a rare highly frustrated, quasi-2D S$_{eff}$ = 1/2 honeycomb lattice
material which resists long range magnetic order and spin freezing.",1712.06208v2
2018-02-22,Touch Sensors with Overlapping Signals: Concept Investigation on Planar Sensors with Resistive or Optical Transduction,"Traditional methods for achieving high localization accuracy on tactile
sensors usually involve a matrix of miniaturized individual sensors distributed
on the area of interest. This approach usually comes at a price of increased
complexity in fabrication and circuitry, and can be hard to adapt to non-planar
geometries. We propose a method where sensing terminals are embedded in a
volume of soft material. Mechanical strain in this material results in a
measurable signal between any two given terminals. By having multiple terminals
and pairing them against each other in all possible combinations, we obtain a
rich signal set using few wires. We mine this data to learn the mapping between
the signals we extract and the contact parameters of interest. Our approach is
general enough that it can be applied with different transduction methods, and
achieves high accuracy in identifying indentation location and depth. Moreover,
this method lends itself to simple fabrication techniques and makes no
assumption about the underlying geometry, potentially simplifying future
integration in robot hands.",1802.08209v2
2018-11-27,Unifying Description of Competing Orders in Two Dimensional Quantum Magnets,"Quantum magnets provide the simplest example of strongly interacting quantum
matter, yet they continue to resist a comprehensive understanding above one
spatial dimension (1D). In 1D, a key ingredient to progress is Luttinger liquid
theory which provides a unified description. Here we explore a promising
analogous framework in two dimensions, the Dirac spin liquid (DSL), which can
be constructed on several different lattices. The DSL is a version of Quantum
Electrodynamics ( QED$_3$) with four flavors of Dirac fermions coupled to
photons. Importantly, its excitations also include magnetic monopoles that
drive confinement. By calculating the complete action of symmetries on
monopoles on the square, honeycomb, triangular and kagom\`e lattices, we answer
previously open key questions. We find that the stability of the DSL is
enhanced on the triangular and kagom\`e lattices as compared to the bipartite
(square and honeycomb) lattices. We obtain the universal signatures of the DSL
on the triangular and kagom\`e lattices, including those that result from
monopole excitations, which serve as a guide to numerics and to experiments on
existing materials. Interestingly, the familiar 120 degree magnetic orders on
these lattices can be obtained from monopole proliferation. Even when unstable,
the Dirac spin liquid unifies multiple ordered states which could help organize
the plethora of phases observed in strongly correlated two-dimensional
materials.",1811.11186v2
2017-03-18,The Effect of Temperature on Cu-K-In-Se Thin Films,"Films of Cu-K-In-Se were co-evaporated at varied K/(K+Cu) compositions and
substrate temperatures (with constant (K+Cu)/In ~ 0.85). Increased Na
composition on the substrate's surface and decreased growth temperature were
both found to favor Cu1-xKxInSe2 (CKIS) alloy formation, relative to
mixed-phase CuInSe2 + KInSe2 formation. Structures from X-ray diffraction
(XRD), band gaps, resistivities, minority carrier lifetimes and carrier
concentrations from time-resolved photoluminescence were in agreement with
previous reports, where low K/(K+Cu) composition films exhibited properties
promising for photovoltaic (PV) absorbers. Films grown at 400-500 C were then
annealed to 600 C under Se, which caused K loss by evaporation in proportion to
initial K/(K+Cu) composition. Similar to growth temperature, annealing drove
CKIS alloy consumption and CuInSe2 + KInSe2 production, as evidenced by high
temperature XRD. Annealing also decomposed KInSe2 and formed K2In12Se19. At
high temperature the KInSe2 crystal lattice gradually contracted as temperature
and time increased, as well as just time. Evaporative loss of K during
annealing could accompany the generation of vacancies on K lattice sites, and
may explain the KInSe2 lattice contraction. This knowledge of Cu-K-In-Se
material chemistry may be used to predict and control minor phase impurities in
Cu(In,Ga)(Se,S)2 PV absorbers-where impurities below typical detection limits
may have played a role in recent world record PV efficiencies that utilized KF
post-deposition treatments.",1703.06366v1
2019-02-26,Bonding and oxidation protection of Ti${_2}$AlC and Cr${_2}$AlC for a Ni-based Superalloy,"Alumina forming, oxidation and thermal shock resistant MAX phases are of a
high interest for high temperature applications. Herein we report, on bonding
and resulting interactions between a Ni-based superalloy, NSA, and two alumina
forming MAX phases. The diffusion couples Cr${_2}$AlC/Inconel-718/Ti${_2}$AlC
were assembled and heated to 1000 or 1100{\deg}C in a vacuum hot press under
loads corresponding to stresses of either 2 MPa or 20 MPa. The resulting
interfaces were examined using X-ray diffraction, scanning electron microscopy
and energy-dispersive X-ray spectroscopy. Good bonding between Cr${_2}$AlC and
NSA was achieved after hot pressing at 1000{\deg}C and a contact pressure of
only 2 MPa; in the case of Ti${_2}$AlC a higher temperature (1100{\deg}C) and
pressure (20 MPa) were needed. In both cases, a diffusion bond was realized
with no evidence of interfacial damage or cracking after cooling to room
temperature. Twenty thermal cycles from room temperature to 1000{\deg}C showed
that Ti${_2}$AlC is a poor oxidation barrier for Inconel-718. However, in the
case of Cr${_2}$AlC no cracks, delamination nor surface degradation were
observed, suggesting that this material could be used to protect Inconel-718
from oxidation.",1902.10001v2
2020-04-22,Deformation of micrometer and mm-sized Fe2.4wt.%Si single- and bi-crystals with a high angle grain boundary at room temperature,"Plasticity in body-centred cubic (BCC) metals, including dislocation
interactions at grain boundaries, is much less understood than in face-centred
cubic (FCC) metals. At low temperatures additional resistance to dislocation
motion due to the Peierls barrier becomes important, which increases the
complexity of plasticity. Iron-silicon steel is an interesting, model BCC
material since the evolution of the dislocation structure in
specifically-oriented grains and at particular grain boundaries have
far-reaching effects not only on the deformation behaviour but also on the
magnetic properties, which are important in its final application as electrical
steel. In this study, two different orientations of micropillars (1, 2, 4
microns in diameter) and macropillars (2500 microns) and their corresponding bi
crystals are analysed after compression experiments with respect to the effect
of size on strength and dislocation structures. Using different experimental
methods, such as slip trace analysis, plane tilt analysis and cross-sectional
EBSD, we show that direct slip transmission occurs, and different slip systems
are active in the bi-crystals compared to their single-crystal counterparts.
However, in spite of direct transmission and a very high transmission factor,
dislocation pile-up at the grain boundary is also observed at early stages of
deformation. Moreover, an effect of size scaling with the pillar size in single
crystals and the grain size in bi-crystals is found, which is consistent with
investigations elsewhere in FCC metals.",2004.10598v2
2022-02-01,Strong Edge Stress in Molecularly Thin Organic$-$Inorganic Hybrid Ruddlesden$-$Popper Perovskites and Modulations of Their Edge Electronic Properties,"Organic$-$inorganic hybrid Ruddlesden$-$Popper perovskites (HRPPs) have
gained much attention for optoelectronic applications due to their high
moisture resistance, good processibility under ambient conditions, and long
functional lifetimes. Recent success in isolating molecularly thin hybrid
perovskite nanosheets and their intriguing edge phenomena have raised the need
for understanding the role of edges and the properties that dictate their
fundamental behaviours. In this work, we perform a prototypical study on the
edge effects in ultrathin hybrid perovskites by considering monolayer
(BA)$_2$PbI$_4$ as a representative system. Based on first-principles
simulations of nanoribbon models, we show that in addition to significant
distortions of the octahedra network at the edges, strong edge stresses are
also present in the material. Structural instabilities that arise from the edge
stress could drive the relaxation process and dominate the morphological
response of edges in practice. A clear downward shift of the bands at the
narrower ribbons, as indicative of the edge effect, facilitates the separation
of photo-excited carriers (electrons move towards the edge and holes move
towards the interior part of the nanosheet). Moreover, the desorption energy of
the organic molecule can also be much lower at the free edges, making it easier
for functionalization and/or substitution events to take place. The findings
reported in this work elucidate the underlying mechanisms responsible for edge
states in HRPPs and will be important in guiding the rational design and
development of high-performance layer$-$edge devices.",2202.00296v1
2016-03-11,Quantum Critical Behavior in a Concentrated Ternary Solid Solution,"Quantum critical behavior has been associated with some of the most exotic
emergent states of matter including high-temperature superconductivity. Much of
the research into quantum critical point (QCP) physics has been hampered by the
lack of model systems simple enough to be analyzed by theory. Here, we show
that the concentrated solid solution fcc alloys, including the so-called
high-entropy alloys, are ideal model systems to study the effects of chemical
disorder on emergent properties near a quantum critical region. The face
centered cubic (fcc) alloy NiCoCrx with x near 1 is found to be close to the Cr
concentration where the ferromagnetic transition temperature, Tc, goes to 0.
Near this composition these alloys exhibit a resistivity linear in temperature
to 2 K, a linear magnetoresistance, an excess -TlnT contribution to the low
temperature heat capacity and excess low temperature entropy. All of the low
temperature electrical, magnetic and thermodynamic properties of the alloys
with compositions near x near 1 are not typical of a Fermi liquid and suggest
strong magnetic fluctuations associated with a quantum critical region. The
limit of extreme chemical disorder in these simple fcc materials thus provides
a novel and unique platform to study quantum critical behavior in a highly
tunable system.",1603.03781v1
2019-03-09,Dry transfer method for suspended graphene on lift-off-resist: simple ballistic devices with Fabry-Pérot interference,"We demonstrate a fabrication scheme for clean suspended structures using
chemical-vapor-deposition-grown graphene and a dry transfer method on
lift-off-resist-coated substrates to facilitate suspended graphene
nanoelectronic devices for technology applications. It encompasses the demands
for scalable fabrication as well as for ultra-fast response due to weak
coupling to environment. The fabricated devices exhibited initially a weak
field-effect response with substantial positive ($p$) doping which transformed
into weak negative ($n$) doping upon current annealing at the temperature of 4
Kelvin. With increased annealing current, $n$-doping gradually decreased while
the Dirac peak position approached zero in gate voltage. An ultra-low residual
charge density of $9\times10^8 \mathrm{ \ cm^{-2}}$ and a mobility of $1.9
\times 10^5 \mathrm{\ cm^2/Vs}$ were observed. Our samples display clear
Fabry-P\'{e}rot (FP) conductance oscillation which indicates ballistic electron
transport. The spacing of the FP oscillations are found to depend on the charge
density in a manner that agrees with theoretical modeling based on Klein
tunneling of Dirac particles. The ultra-low residual charge, the FP
oscillations with density dependent period, and the high mobility prove
excellent quality of our suspended graphene devices. Owing to its simplicity,
scalability and robustness, this fabrication scheme enhances possibilities for
production of suspended, high-quality, two-dimensional-material structures for
novel electronic applications.",1903.03780v1
2019-12-11,Quantum oscillations and electronic structures in large Chern number semimetal RhSn,"We report the magnetoresistance, Hall effect, de Haas-van Alphen (dHvA)
oscillations and the electronic structures of single crystal RhSn, which is a
typical material of CoSi family holding a large Chern number. The large
unsaturated magnetoresistance is observed with B//[001]. The Hall resistivity
curve indicates that RhSn is a multi-band system with high mobility. Evident
quantum oscillations have been observed, from which the light effective masses
are extracted. Ten fundamental frequencies are extracted after the fast Fourier
transform analysis of the dHvA oscillations with B//[001] configuration. The
two low frequencies F$_1$ and F$_2$ do not change obviously and the two high
frequencies F$_9$ and F$_{10}$ evolve into four when B rotates from B//[001] to
B//[110], which is consistent with the band structure in the first-principles
calculations with spin-orbit coupling (SOC). The extracted Berry phases of the
relative pockets show a good agreement with the Chern number $\pm4$ (with SOC)
in the first-principles calculations. Above all, our studies indicate that RhSn
is an ideal platform to study the unconventional chiral fermions and the
surface states.",1912.05148v1
2019-12-11,Bulk and Two-dimensional Silver and Copper Monohalides: A Unique Class of Materials with Modest Ionicity/Covalency and Ferroelasticity/Multiferroicity,"Silver and copper monohalides can be viewed as a class of compounds in the
neutral zone between predominantly covalent and ionic compounds, thereby
exhibiting neither strong ionicity nor strong covalency. We show ab initio
calculation evidence that silver and copper monohalides entail relatively low
transition barriers between the non-polar rock-salt phase and the polar
zinc-blende phase, due largely to their unique chemical nature of modest
iconicity or covalency. Notably, the low transition barriers endow both
monohalides with novel mechanical and electronic properties, i.e., coupled
ferroelasticity and ferroelectricity with large polarizations and relatively
low switching barriers at ambient conditions. Several halides even possess very
similar lattice constants and structures as the prevailing semiconductors such
as silicon, thereby enabling epitaxial growth on silicon. Moreover, based on
extensive structural search, we find that the most stable two-dimensional (2D)
polymorphs of the monolayer halides are close or even greater in energy than
their bulk counterparts, a feature not usually seen in the family of rock-salt
or zinc-blende semiconductors. The low transition barrier between zinc-blende
phase and 2D phase is predicted. Moreover, several 2D monolayer halides also
exhibit multiferroicity with coupled ferroelasticity or ferroelectricity,
thereby rendering their potential applications as high-density integrated
memories for efficient data reading and writing. Their surfaces, covered by
halides, also provide oxidation resistance and give low cleave energy from
layered structure, suggesting high likelihood of experimental synthesis of
these 2D polymorphs.",1912.05172v1
2015-04-14,Carrier Transport at the Metal-MoS2 Interface,"This study illustrates the nature of electronic transport and its transition
from one mechanism to another between a metal electrode and MoS2 channel
interface in a field effect transistor (FET) device. Interestingly,
measurements of the contact resistance (Rc) as a function of temperature
indicate a transition in the carrier transport across the energy barrier from a
thermionic emission at a high temperature to tunneling at a low temperature.
Furthermore, at a low temperature, the nature of the tunneling behavior is
ascertained by the current-voltage dependency that helps us feature direct
tunneling at a low bias and Fowler-Nordheim tunneling at a high bias for a
Pd-MoS2 contact due to the effective barrier shape modulation by biasing. In
contrast, only direct tunneling is observed for a Cr-MoS2 contact over the
entire applied bias range. In addition, simple analytical calculations were
carried out to extract Rc at the gating range, and the results are consistent
with the experimental data. Our results describe the transition in carrier
transport mechanisms across a metal-MoS2 interface, and this information
provides guidance for the design of future flexible, transparent electronic
devices based on 2-dimensional materials.",1504.03466v1
2018-12-28,Nanoscale Self-Healing Mechanisms in Shape Memory Ceramics,"Shape memory (SM) ceramics, such as yttria-stabilized tetragonal zirconia
(YSTZ), are a unique family of SM materials that offer unique properties
including ultra-high operating temperature, and high resistance to chemical
corrosion and oxidation. However, formation of defects is usually observed in
SM ceramics during manufacturing and/or by mechanical deformation. To fully
take advantage of the SM properties of these ceramics, it is necessary to fully
understand the nano-structural evolution of defects under external stimuli. In
this study, defect closure behaviors in YSTZ nanopillars are investigated by
atomistic simulations. Two characteristic orientations of [011-] and [001] are
selected to represent the dominant deformation mechanisms of phase
transformation and dislocation migration, respectively. With the presence of
crack and void, the strength and yield strain of nanopillars are noted to
decrease significantly, especially for [011-]-oriented YSTZ nanopillars. Volume
expansion associated with the tetragonal to monoclinic phase transformation is
observed to promote healing of crack and void. Atom stress analyses reveal
stress concentrations along the newly formed monoclinic phase bands. A critical
crack width is identified, less than which the crack can be fully closed in
compression. Size effect study reveals that an increase in nanopillar size has
a positive effect on crack self-healing behavior. For [001]-oriented YSTZ
nanopillars, dislocation migration leads to formations of an amorphous phase,
which also assist the crack and void closure process. The revealed crack/void
healing mechanisms may provide a path for mitigating internal defects that
influences the mechanical properties and deformation mechanisms of SM ceramics.",1812.11136v1
2019-06-24,Melting of vortex lattice in magnetic superconductor $\mathrm{Rb}\mathrm{Eu}\mathrm{Fe}_{4}\mathrm{As}_{4}$,"The iron-based superconductors are characterized by strong fluctuations due
to high transition temperatures and small coherence lengths. We investigate
fluctuation behavior in the magnetic iron-pnictide superconductor
$\mathrm{Rb}\mathrm{Eu}\mathrm{Fe}_{4}\mathrm{As}_{4}$ by calorimetry and
transport. We find that the broadening of the specific-heat transition in
magnetic fields is very well described by the lowest-Landau-level scaling. We
report calorimetric and transport observations for vortex-lattice melting,
which is seen as a sharp drop of the resistivity and a step of the specific
heat at the magnetic-field-dependent temperature. The melting line in the
temperature/magnetic-field plane lies noticeably below the upper-critical-field
line and its location is in quantitative agreement with theoretical predictions
without fitting parameters. Finally, we compare the melting behavior of
$\mathrm{Rb}\mathrm{Eu}\mathrm{Fe}_{4}\mathrm{As}_{4}$ with other
superconducting materials showing that thermal fluctuations of vortices are not
as prevalent as in the high-temperature superconducting cuprates, yet they
still noticeably influence the properties of the vortex matter.",1906.10236v2
2020-01-23,Magnetic-field-induced robust zero Hall plateau state in MnBi$_2$Te$_4$ Chern insulator,"The intrinsic antiferromagnetic topological insulator MnBi2Te4 provides an
ideal platform for exploring exotic topological quantum phenomena. Recently,
the Chern insulator and axion insulator phases have been realized in few-layer
MnBi2Te4 devices at low magnetic field regime. However, the fate of MnBi2Te4 in
high magnetic field has never been explored in experiment. In this work, we
report transport studies of exfoliated MnBi2Te4 flakes in pulsed magnetic
fields up to 61.5 T. In the high-field limit, the Chern insulator phase with
Chern number C = -1 evolves into a robust zero Hall resistance plateau state.
Nonlocal transport measurements and theoretical calculations demonstrate that
the charge transport in the zero Hall plateau state is conducted by two
counter-propagating edge states that arise from the combined effects of Landau
levels and large Zeeman effect in strong magnetic fields. Our result
demonstrates the intricate interplay among intrinsic magnetic order, external
magnetic field, and nontrivial band topology in MnBi2Te4.",2001.08401v2
2020-04-14,Highly Conducting Spaced TiO$_2$ Nanotubes Enable Defined Conformal Coating with Nanocrystalline Nb$_2$O$_5$ and High Performance Supercapacitor Applications,"In this work, we report on the electrochemical behavior of nitrided spaced
TiO$_2$ nanotubes conformally coated with a nanocrystalline Nb$_2$O$_5$ layer
and find for these hierarchical structures an excellent supercapacitor
performance. Highly aligned conductive 1D electrodes were obtained by a three
step process: i) growth of self-organized nanotubes with defined and adjustable
intertube spacing, ii) conformal Nb$_2$O$_5$ decoration in the tube interspace
(while providing full electrolyte access to the entire active area), and iii)
high temperature nitridation. Key is the growth of a nanotube array with
regular tube-to-tube interspacing that enables an optimized decoration with
secondary materials such as Nb$_2$O$_5$. We observe an increase in electrode
capacitance from 158 $\mu$F cm-2 for bare TiO$_2$ NTs, to 1536 $\mu$F cm-2 for
TiO$_2$/Nb$_2$O$_5$ NTs, to finally 37 mF cm-2 for Nb$_2$O$_5$ decorated and
then nitrided nanotubes. This drastic increase can be ascribed firstly to the
defined spacing established between the tube arrays that then allows for a
conformal coating with a secondary active coating. Secondly, nitridation causes
a drastic increase of the electron conductivity of the entire scaffold and thus
reduces resistive losses.",2005.01603v1
2020-10-13,"High-pressure synthesis of Ba$_2$RhO$_4$, a rhodate analogue of the layered perovskite Sr-ruthenate","A new layered perovskite-type oxide Ba$_2$RhO$_4$ was synthesized by a
high-pressure technique with the support of convex-hull calculations. The
crystal and electronic structure were studied by both experimental and
computational tools. Structural refinements for powder x-ray diffraction data
showed that Ba$_2$RhO$_4$ crystallizes in a K$_2$NiF$_4$-type structure,
isostructural to Sr$_2$RuO$_4$ and Ba$_2$IrO$_4$. Magnetic, resistivity, and
specific heat measurements for polycrystalline samples of Ba$_2$RhO$_4$
indicate that the system can be characterized as a correlated metal. Despite
the close similarity to its Sr$_2$RuO$_4$ counterpart in the electronic
specific heat coefficient and the Wilson ratio, Ba$_2$RhO$_4$ shows no
signature of superconductivity down to 0.16 K. Whereas the Fermi surface
topology has reminiscent pieces of Sr$_2$RuO$_4$, an electron-like
e$_g$-($d_{x^2-y^2}$) band descends below the Fermi level, making of this
compound unique also as a metallic counterpart of the spin-orbit-coupled Mott
insulator Ba$_2$IrO$_4$.",2010.06556v1
2021-02-15,Magic thickness of 25 Å makes periodic metal-insulator transitions,"Novel quantum phenomena, including high-temperature superconductivity,
topological properties, and charge/spin density waves, appear in
low-dimensional conductive materials. It is possible to artificially create
low-dimensional systems by fabricating ultrathin films, quantum wires, or
quantum dots with flat interfaces. Some experiments have been performed on
ultrathin compounds of strongly correlated electron systems. However, since it
is technically difficult to control multiple elements precisely, most of the
properties of artificially fabricated low-dimensional compounds fall into
uncharted territory. Here we show that extraordinary metal-insulator
transitions that oscillate depending on the scale occur in CaRuO_3 films with a
thickness of around several unit cells. We grow high-crystalline CaRuO_3
ultrathin films, whose surface roughness is controlled at 199 pm, by molecular
beam epitaxy. We observe that resistivity oscillates with a magic thickness of
25 {\AA}, which changes by 3 and 9 orders of magnitude at room temperature and
at low temperature, respectively. These changes are much larger than quantum
size effects. We also confirm the same periodicity with photoelectron
spectroscopy by etching the ultrathin film. Considering the large energy,
periodicity and anisotropy, we conclude that the oscillating transitions
originate from the commensurability of Mott insulation triggered by Peierls
instability arising from a dual restriction on the dimensions in wavenumber
space and real space. We have shown the possibility of producing new functional
materials by controlling film thickness on electron correlated compounds at the
picometer level.",2102.07323v1
2021-06-17,Synthesis of Murunskite Single Crystals: A Bridge Between Cuprates and Pnictides,"Numerous contemporary investigations in condensed matter physics are devoted
to high temperature (high-$T_c$ ) cuprate superconductors. Despite its unique
effulgence among research subjects, the enigma of the high-$T_c$ mechanism
still persists. One way to advance its understanding is to discover and study
new analogous systems. Here we begin a novel exploration of the natural mineral
murunskite, K$_2$FeCu$_3$S$_4$, as an interpolation compound between cuprates
and ferropnictides, the only known high-$T_c$ superconductors at ambient
pressure. Because in-depth studies can be carried out only on single crystals,
we have mastered the synthesis and growth of high quality specimens. Similar to
the cuprate parent compounds, these show semiconducting behavior in resistivity
and optical transmittance, and an antiferromagnetic ordering at 100 K.
Spectroscopy (XPS) and calculations (DFT) concur that the sulfur 3$p$ orbitals
are partially open, making them accessible for charge manipulation, which is a
prerequisite for superconductivity in analogous layered structures. DFT
indicates that the valence band is more cuprate-like, while the conduction band
is more pnictide-like. With appropriate doping strategies, this parent compound
promises exciting future developments.",2106.09555v1
2021-09-14,Creep properties and deformation mechanisms of single-crystalline $γ^\prime$-strengthened superalloys in dependence of the Co/Ni ratio,"Co-base superalloys are considered as promising high temperature materials
besides the well-established Ni-base superalloys. However, Ni appears to be an
indispensable alloying element also in Co-base superalloys. To address the
influence of the base elements on the deformation behavior, high-temperature
compressive creep experiments were performed on a single crystal alloy series
that was designed to exhibit a varying Co/Ni ratio and a constant Al, W and Cr
content. Creep tests were performed at 900 {\deg}C and 250 MPa and the
resulting microstructures and defect configurations were characterized via
electron microscopy. The minimum creep rates differ by more than one order of
magnitude with changing Co/Ni ratio. An intermediate CoNi-base alloy exhibits
the overall highest creep strength. Several strengthening contributions like
solid solution strengthening of the $\gamma$ phase, effective diffusion
coefficients or stacking fault energies were quantified. Precipitate shearing
mechanisms differ significantly when the base element content is varied. While
the Ni-rich superalloys exhibit SISF and SESF shearing, the Co-rich alloys
develop extended APBs when the $\gamma^\prime$ phase is cut. This is mainly
attributed to a difference in planar fault energies, caused by a changing
segregation behavior. As result, it is assumed that the shearing resistivity
and the occurring deformation mechanisms in the $\gamma^\prime$ phase are
crucial for the creep properties of the investigated alloy series.",2109.06767v1
2022-06-29,Tailoring of rhenium oxidation state in ReOx thin films during reactive HiPIMS deposition process and following annealing,"Bulk rhenium trioxide (ReO3) has an unusually high electrical conductivity
and, being nanosized, has promising catalytic properties. However, the
production of pure ReO3 thin films is challenging due to the difficulty to
stabilize rhenium in a 6+ oxidation state. Here we present a novel approach for
the deposition of ReOx (x = 1.6-2.9) thin films using reactive high power
impulse magnetron sputtering (r-HiPIMS) from a metallic rhenium target in a
mixed Ar/O2 atmosphere. The thin films were deposited in the gas-sustained
self-sputtering regime, observed during r-HiPIMS process according to current
waveforms. The influence of the substrate temperature, the oxygen-to-argon flow
ratio and post-annealing at 250 {\deg}C in the air for 3 h on the properties of
the films were studied. The as-deposited films have an X-ray amorphous
structure (a-ReOx) when deposited at room temperature while a nano-crystalline
\b{eta}-ReO2 phase when deposited at elevated temperatures (150 or 250
{\deg}C). The amorphous a-ReOx can be converted into the crystalline ReO3 with
a lattice parameter of 3.75 {\AA} upon annealing in the air. The surface
morphology of the films is dense without detectable voids when elevated
substrate temperatures are used. Various Re oxidation states are observed on
the surface of the films in different ratios depending on the deposition
parameters. All samples exhibit electrical resistivity on the order of 10-3
Ohmxcm and optical properties typical for thin metallic films.",2206.14665v1
2022-06-02,A mechanically strong and ductile soft magnet with extremely low coercivity,"Soft magnetic materials (SMMs) serve in electrical applications and
sustainable energy supply, allowing magnetic flux variation in response to
changes in applied magnetic field, at low energy loss1. The electrification of
transport, households and manufacturing leads to an increase in energy
consumption due to hysteresis losses2. Therefore, minimizing coercivity, which
scales these losses, is crucial3. Yet, meeting this target alone is not enough:
SMMs in electrical engines must withstand severe mechanical loads, i.e., the
alloys need high strength and ductility4. This is a fundamental design
challenge, as most methods that enhance strength introduce stress fields that
can pin magnetic domains, thus increasing coercivity and hysteretic losses5.
Here, we introduce an approach to overcome this dilemma. We have designed a
Fe-Co-Ni-Ta-Al multicomponent alloy with ferromagnetic matrix and paramagnetic
coherent nanoparticles (~91 nm size, ~55% volume fraction). They impede
dislocation motion, enhancing strength and ductility. Their small size, low
coherency and small magnetostatic energy create an interaction volume below the
magnetic domain wall width, leading to minimal domain wall pinning, thus
maintaining the soft magnetic properties. The alloy has a tensile strength of
1336 MPa at 54% tensile elongation, extremely low coercivity of 78 A/m (<1 Oe),
moderate saturation magnetization of 100 Am2/kg, and high electrical
resistivity of 103 {\mu}{\Omega} u Ohm cm.",2207.05686v1
2022-07-26,"Cr$_3$X$_4$ (X=Se, Te) monolayers as new platform to realize robust spin filter, spin diode and spin valve","Two-dimensional ferromagnetic (FM) half-metals are promising candidates for
advanced spintronic devices with small-size and high-capacity. Motivated by
recent report on controlling synthesis of FM Cr$_3$Te$_4$ nanosheet, herein, to
explore the potential application in spintronics, we designed spintronic
devices based on Cr$_3$X$_4$ (X=Se, Te) monolayers and investigated their spin
transport properties. We found that Cr$_3$Te$_4$ monolayer based device shows
spin filtering and dual spin diode effect when applying bias voltage, while
Cr$_3$S$_4$ monolayer is an excellent platform to realize a spin valve. The
different transport properties are primarily ascribed to the semiconducting
spin channel, which is close to and away from the Fermi level in Cr$_3$Te$_4$
and Cr$_3$Se$_4$ monolayers, respectively. Interestingly, the current in
monolayer Cr$_3$Se$_4$ based device also displays a negative differential
resistance effect (NDRE) and a high magnetoresistance ratio (up to 2*10$^3$).
Moreover, we found thermally induced spin filtering effect and NDRE in
Cr$_3$Se$_4$ junction when applying temperature gradient instead of bias
voltage. These theoretical findings highlight the potential of Cr$_3$X$_4$
(X=Se, Te) monolayers in spintronic applications and put forward realistic
materials to realize nanosale spintronic device.",2207.12679v1
2022-10-26,Ion-beam Assisted Sputtering of Titanium Nitride Thin Films,"Titanium nitride is a material of interest for many superconducting devices
such as nanowire microwave resonators and photon detectors. Thus, controlling
the growth of TiN thin films with desirable properties is of high importance.
In previous work on niobium nitride, ion beam-assisted sputtering (IBAS)
reduced nitrogen sensitivity during deposition in tandem with an increase in
nominal critical temperature. We have deposited thin films of titanium nitride
by both, the conventional method of DC reactive magnetron sputtering and the
IBAS method and compare their superconducting critical temperatures Tc as
functions of thickness, sheet resistance, and nitrogen flow rate. We perform
electrical and structural characterizations by electric transport and X-ray
diffraction measurements. Compared to the conventional method of reactive
sputtering, the IBAS technique has demonstrated a 10% increase in nominal
critical temperature and 33% reduced sensitivity to nitrogen flow, without
noticeable variation in the lattice structure. Additionally, we explore the
behavior of superconducting Tc in ultra-thin films. Trends in films grown at
high nitrogen concentrations follow predictions of mean-field theory in
disordered films and show suppression of superconducting Tc due to geometric
effects, while nitride films grown at low nitrogen concentrations strongly
deviate from the theoretical models.",2210.15065v3
2023-02-14,MgF$_2$ as an effective additive for improving ionic conductivity of ceramic solid electrolytes,"As typical solid-state electrolytes (SSEs),
{Na}$_{1+x}${Zr}$_2${Si}$_{x}${P}$_{3-x}${O}$_{12}$ NASICONs provide an ideal
platform for solid-state batteries (SSBs) that display higher safety and
accommodate higher energy densities. The critical points for achieving SSBs
with higher efficiencies are to improve essentially the ionic conductivity and
to reduce largely the interfacial resistance between SSEs and cathode
materials, which would necessitate extremely high level of craftsmanship and
high-pressure equipment. An alternative to higher-performance and lower-cost
SSBs is additive manufacturing. Here, we report on an effective additive,
MgF$_2$, which was used in synthesizing NASICONs, resulting in SSEs with fewer
defects and higher performance. With an addition of mere 1 wt$\%$ MgF$_2$
additive, the total room-temperature ionic conductivity of the NASICON
electrolyte reaches up to 2.03 mS cm$^{-1}$, improved up to $\sim$ 181.3$\%$,
with an activation energy of 0.277 eV. Meanwhile, the stability of the Na
plating/stripping behavior in symmetric cells increases from 236 to 654 h. We
tried to reveal the microscopic origins of the higher ionic conductivity of
MgF$_2$-doped NASICONs by comprehensive in-house characterizations. Our study
discovers a novel MgF$_2$ additive and provides an efficient way to prepare
higher-performance SSEs, making it possible to fabricate lower-cost SSBs in
industries.",2302.07264v1
2023-07-03,Low temperature dynamic polaron liquid in a manganite exhibiting colossal magnetoresistance,"Polarons - fermionic charge carriers bearing a strong companion lattice
deformation - exhibit a natural tendency for self-localization due to the
recursive interaction between electrons and the lattice. While polarons are
ubiquitous in insulators, how they evolve in transitions to metallic and
superconducting states in quantum materials remains an open question. Here, we
use resonant inelastic x-ray scattering (RIXS) to track the electron-lattice
coupling in the colossal magneto-resistive bi-layer manganite
La$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$ across its metal-to-insulator transition. The
response in the insulating high-temperature state features harmonic emissions
of a dispersionless oxygen phonon at small energy transfer. Upon cooling into
the metallic state, we observe a drastic redistribution of spectral weight from
the region of these harmonic emissions to a broad high energy continuum. In
concert with theoretical calculations, we show that this evolution implies a
shift in electron-lattice coupling from static to dynamic lattice distortions
that leads to a distinct polaronic ground state in the low temperature metallic
phase - a dynamic polaron liquid.",2307.00718v3
2023-09-24,FeCo Nanowire-Strontium Ferrite Powder Composites for Permanent Magnets with High-Energy Products,"Due to the issues associated with rare-earth elements, there arises a strong
need for magnets with properties between those of ferrites and rare-earth
magnets that could substitute the latter in selected applications. Here, we
produce a high remanent magnetization composite bonded magnet by mixing FeCo
nanowire powders with hexaferrite particles. In the first step, metallic
nanowires with diameters between 30 and 100 nm and length of at least 2 {\mu}m
are fabricated by electrodeposition. The oriented as-synthesized nanowires show
remanence ratios above 0.76 and coercivities above 199 kA/m and resist core
oxidation up to 300 {\deg}C due to the existence of a > 8 nm thin oxide
passivating shell. In the second step, a composite powder is fabricated by
mixing the nanowires with hexaferrite particles. After the optimal nanowire
diameter and composite composition are selected, a bonded magnet is produced.
The resulting magnet presents a 20% increase in remanence and an enhancement of
the energy product of 48% with respect to a pure hexaferrite (strontium
ferrite) magnet. These results put nanowire-ferrite composites at the forefront
as candidate materials for alternative magnets for substitution of rare earths
in applications that operate with moderate magnet performance.",2309.13724v1
2023-11-01,Transport and electrical properties of cryogenic thermoelectric FeSb2: the effect of isoelectronic and hole doping,"Thermoelectric materials operating at cryogenic temperatures are in high
demand for efficient cooling and power generation in applications ranging from
superconductors to quantum computing. The narrow band-gap semiconductor FeSb2,
known for its colossal Seebeck coefficient, holds promise for such
applications, provided its thermal conductivity value can be reduced. This
study investigates the impact of isoelectronic substitution (Bi) and hole
doping (Pb) at the Sb site on the transport properties of FeSb2, with a
particular focus on thermal conductivity (\k{appa}). Polycrystalline FeSb2
powder, along with Bi- and Pb-doped samples, were synthesized using a simple
co-precipitation approach, followed by thermal treatment in an H2 atmosphere.
XRD and SEM analysis confirms the formation of the desired phase pre- and
post-consolidation using spark plasma sintering (SPS). The consolidation
process resulted in a high compaction density and the formation of
submicrometer-sized grains, as substantiated by electron backscattered
diffraction (EBSD) analysis. Substituting 1% of Bi and Pb at the Sb site
successfully suppressed the thermal conductivity (\k{appa}) from ~15 W/m-K in
pure FeSb2 to ~10 and ~8.7 W/m-K, respectively. Importantly, resistivity
measurements revealed a metal-to-insulator transition at around 6.5 K in
undoped FeSb2 and isoelectronically Bi-substituted FeSb2, suggesting the
existence of metallic surface states and provides valuable evidence for the
perplexing topological behavior exhibited by FeSb2.",2311.00326v1
2023-12-13,Computational design of NDR tunnel diodes with high peak-to-valley current ratio based on two-dimensional cold metals: The case of NbSi$_2$N$_4$/HfSi$_2$N$_4$/NbSi$_2$N$_4$ lateral heterojunction diode,"Cold metals have recently gained attention as a promising platform for
innovative devices, such as tunnel diodes with negative differential resistance
(NDR) and field-effect transistors with subthreshold swings below the
thermionic limit. Recently discovered two-dimensional (2D) MA$_2$Z$_4$ (M = Ti,
Zr, Hf, Nb, Ta; A = Si, Ge; Z = N, P) compounds exhibit both cold metallic and
semiconducting behavior. In this work, we present a computational study of
lateral heterojunction tunnel diodes based on 2D NbSi$_2$N$_4$ and
HfSi$_2$N$_4$ compounds. Employing density functional theory combined with a
nonequilibrium Green function method, we investigate the current-voltage
($I$-$V$) characteristics of lateral tunnel diodes with varying barrier
thicknesses in both zigzag and armchair orientations. We find that tunnel
diodes in the zigzag orientation exhibit significantly higher peak current
densities, while those in the armchair orientation display larger
peak-to-valley current ratios (PVCRs) compared to the zigzag orientation. Our
findings suggest that MA$_2$Z$_4$ materials are promising candidates for
realizing NDR tunnel diodes with high PVCR values, which could have potential
applications in memory, logic circuits, and other electronic devices.",2312.08473v2
2024-01-29,Increasing the Collection Efficiency in Selenium Thin-Film Solar Cells Using a Closed-Space Annealing Strategy,"Elemental selenium is a promising wide-bandgap ($E_\mathrm{G}\approx$ 1.95
eV) photovoltaic material for the next generation of thin-film solar cells. To
realize high-efficiency selenium solar cells, it is crucial to optimize the
crystallization process of the selenium thin-film photoabsorber. However, the
high vapor pressure of selenium restricts the processing conditions to a
compromise between the growth of large crystal grains and the formation of
pinholes. In this study, we introduce a closed-space annealing (CSA) strategy
designed to suppress the sublimation of selenium, enabling thermal annealing
processes at higher temperatures and for longer periods of time. As a result,
we consistently improve carrier collection and the overall photovoltaic device
performance in our selenium solar cells. By characterizing the carrier dynamics
in our devices, we conclude that the observed improvements result from a
reduction in charge transfer resistance rather than an increase in carrier
diffusion length. The CSA strategy is a promising method for controlling
surface morphology and roughness without reducing crystal grain sizes, which
paves the way for further advancements in the efficiency and reproducibility of
selenium thin-film solar cells.",2401.15936v1
2024-02-10,Cylindrical compression of thin wires by irradiation with a Joule-class short pulse laser,"Equation of state measurements at Jovian or stellar conditions are currently
conducted by dynamic shock compression driven by multi-kilojoule multi-beam
nanosecond-duration lasers. These experiments require precise design of the
target and specific tailoring of the spatial and temporal laser profiles to
reach the highest pressures. At the same time, the studies are limited by the
low repetition rate of the lasers. Here, we show that by the irradiation of a
thin wire with single beam Joule-class short-pulse laser, a converging
cylindrical shock is generated compressing the wire material to conditions
relevant for the above applications. The shockwave was observed using Phase
Contrast Imaging employing a hard X-ray Free Electron Laser with unprecedented
temporal and spatial sensitivity. The data collected for Cu wires is in
agreement with hydrodynamic simulations of an ablative shock launched by a
highly-impulsive and transient resistive heating of the wire surface. The
subsequent cylindrical shockwave travels towards the wire axis and is predicted
to reach a compression factor of 9 and pressures above 800 Mbar. Simulations
for astrophysical relevant materials underline the potential of this
compression technique as a new tool for high energy density studies at high
repetition rates.",2402.06983v1
2024-03-04,Quantum Hall Transport Measurements of Lateral p-n Junctions Formed via Precise Spatial Photodoping of Graphene/hBN Heterostructures,"Heterostructures composed of 2-dimensional (2D) materials are spatially dope
in-operando to modify devices for custom functionalities, such as lateral p-n-p
junctions. After optically photodoping an hBN/Graphene/hBN heterostructure,
detailed magnetotransport measurements including quantum Hall transport show
several clear electronic regimes. In the p+-p-p+ and n-n+-n configurations, we
see clear quantization of the longitudinal resistance. Using the
Landauer-Buttiker model we elucidate the nature of the electrostatic profile at
the interface between the doped regions. In the p-n-p configuration, due to the
heavily graded junction profile that completely separates the p- and n-Landau
level edge states from interacting, an ""insulating"" state is observed that is
not common and has not been measured in previous quantum Hall transport
measurements of graphene pnJ devices in high magnetic fields. This insulating
state is promising as the basis for a high-performance graphene switching
device with a good ON/OFF ratio. In principle, these doping and measurement
techniques can be applied to any other 2D heterostructure encapsulated within
an hBN sandwich to understand the quality of the electrostatic interface
between doped regions.",2403.01998v1
2020-12-05,"A15 Nb$_3$Si -- A ""high"" Tc superconductor synthesized at a pressure of one megabar and metastable at ambient conditions","A15 Nb$_3$Si is, until now, the only high temperature superconductor produced
at high pressure (~110 GPa) that has been successfully brought back to room
pressure conditions in a metastable condition. Based on the current great
interest in trying to create metastable-at-room-pressure high temperature
superconductors produced at high pressure, we have restudied explosively
compressed A15 Nb$_3$Si and its production from tetragonal Nb$_3$Si. First,
diamond anvil cell pressure measurements up to 88 GPa were performed on
explosively compressed A15 Nb$_3$Si material to trace Tc as a function of
pressure. Tc is suppressed to ~ 5.2 K at 88 GPa. Then, using these Tc (P) data
for A15 Nb$_3$Si, pressures up to 92 GPa were applied at room temperature
(which increased to 120 GPa at 5 K) on tetragonal Nb$_3$Si. Measurements of the
resistivity gave no indication of any A15 structure production, i.e., no
indications of the superconductivity characteristic of A15 Nb$_3$Si. This is in
contrast to the explosive compression (up to P~110 GPa) of tetragonal Nb$_3$Si,
which produced 50-70% A15 material, Tc = 18 K at ambient pressure, in a 1981
Los Alamos National Laboratory experiment. Our theoretical calculations show
that A15 Nb$_3$Si has an enthalpy vs the tetragonal structure that is 0.07
eV/atom smaller at 100 GPa, implying that the accompanying high temperature
(1000 deg C) caused by explosive compression is necessary to successfully drive
the reaction kinetics of the tetragonal -> A15 Nb$_3$Si structural
transformation. Annealing experiments on the A15 explosively compressed
material reaching time scales of 39 years are consistent with this viewpoint.",2012.02905v2
2006-03-17,Second Core Formation and High Speed Jets: Resistive MHD Nested Grid Simulations,"The stellar core formation and high speed jets driven by the formed core are
studied by using three-dimensional resistive MHD nested grid simulations.
Starting with a Bonnor-Ebert isothermal cloud rotating in a uniform magnetic
field, we calculate the cloud evolution from the molecular cloud core (n = 10^6
cm^-3, r_c = 4.6 times 10^4 AU) to the stellar core (n \simeq 10^23 cm^-3, r_c
\simeq 1 solar radius). We resolve cloud structure over 7 orders of magnitude
in spatial extent and over 17 orders of magnitude in density contrast. For
comparison, we calculate two models: resistive and ideal MHD models. Both
models have the same initial condition, but the former includes dissipation
process of magnetic field while the latter does not. The magnetic fluxes in
resistive MHD model are extracted from the first core during 10^12 cm^-3 < n <
10^16 cm^-3 by Ohmic dissipation. Magnetic flux density of the formed stellar
core (n \simeq 10^20 cm^-3) in resistive MHD model is two orders of magnitude
smaller than that in ideal MHD model. Since magnetic braking is less effective
in resistive MHD model, rapidly rotating stellar core (the second core) is
formed. After stellar core formation, the magnetic field of the core is largely
amplified both by magneto-rotational instability and the shearing motion
between the stellar core and ambient medium. As a consequence, high speed
(simeq 45 km,s^-1) jets are driven by the second core, which results in strong
mass ejection. A cocoon-like structure around the second core also forms with
clear bow shocks.",0603456v1
2018-05-07,Appearance of ferromagnetism property for Si nano-polycrystalline body and vanishing of electrical resistances at local high frequencies,"Reduction in the skin effect for the sintered Si nanopolycrystalline body as
an electricity conductor at a high frequency due to its nano-structure was
studied. Singular vanishing of electrical resistances near a local high
magnetic harmonic frequency of a few MHz was observed. This phenomenon has not
been observed for conventional ferromagnetic metals. The measured electrical
resistances changed to almost 0 m{\Omega} at room temperature. At the same
time, negative resistance of the sintered Si nano-polycrystalline body was
observed. It will be applicable to electronic transmittance lines or
semiconductors. Numerical calculation was also performed on the electrical
resistance with frequency dependency while considering the electric field and
magnetic field in the sintered Si nanopolycrystalline body. The calculation
could explain the variation of the relative permittivity of the Si
nanopolycrystalline and the phenomenon for vanishing the resistivity at
frequency of MHz theoretically. Reduced Si nanoparticles from SiO2 powder were
synthesized by laser ablation in liquid. A Si nano-polycrystalline body made of
the reduced Si nanoparticles was fabricated. It was found by measuring the
magnetization property of the body that the sintered Si nano-polycrystalline
body has ferromagnetism. High-density dangling bonds cause the sintered Si
nanopolycrystalline to have ferromagnetism. In this study, the density of the
unpaired electrons in the sintered Si nanopolycrystalline was observed using
ESR. It has been clarified that the Si nanopowder and the sintered Si
nanopolycrystalline have numerous dangling bonds. Both densities of the
dangling bonds were evaluated.",1805.02312v1
2019-03-26,The micro-RWELL layouts for high particle rate,"The $\mu$-RWELL is a single-amplification stage resistive Micro-Pattern
Gaseous Detector (MPGD). The detector amplification element is realized with a
single copper-clad polyimide foil micro-patterned with a blind hole (well)
matrix and embedded in the readout PCB through a thin Diamond-Like-Carbon (DLC)
sputtered resistive film. The introduction of the resistive layer, suppressing
the transition from streamer to spark, allows to achieve large gains
($\geq$10$^4$) with a single amplification stage, while partially reducing the
capability to stand high particle fluxes. The simplest resistive layout,
designed for low-rate applications, is based on a single-resistive layer with
edge grounding. At high particle fluxes this layout suffers of a non-uniform
response. In order to get rid of such a limitation different current evacuation
geometries have been designed. In this work we report the study of the
performance of several high rate resistive layouts tested at the CERN H8-SpS
and PSI $\pi$M1 beam test facilities. These layouts fulfill the requirements
for the detectors at the HL-LHC and for the experiments at the next generation
colliders FCC-ee/hh and CepC.",1903.11017v2
2018-04-15,$\mathrm{Co_2Fe_{1-x}Cr_xSi}$ Heusler Alloys : A promising material for spintronics application,"In this article, we investigated the effect of Cr substitution in place of Fe
on the structural, magnetic and transport properties of $\mathrm{Co_2FeSi}$
alloy. A comprehensive structural analysis is done using X-ray diffraction
(XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy.
Quaternary Heusler compounds $\mathrm{Co_2Fe_{1-x}Cr_xSi}$ with Cr content (x =
0.1, 0.3, 0.5) were found to crystallize in cubic structure. The synchrotron
based EXAFS studies reveal that the anti-site disorder increases with the
increase in Cr concentration. The saturation magnetization values in all the
alloys are found to be less than those expected from the Slater-Pauling rule,
which may be due to the some inherent disorder. A detailed resistivity analysis
in the temperature range of 5-300 K is done, taking into account different
scattering mechanisms. The residual resistivity ratio is found to decrease with
increasing Cr concentration. A disorder induced resistivity minimum due to weak
localization effect is seen for x = 0.5. The resistivity measurements also
indicate that the half-metallic character survives upto 100 K for x = 0.1,
whereas the alloys with x= 0.3 and 0.5 show signature of half- metallic nature
even at higher temperatures. First principles calculation done with a more
robust exchange correlation functional (namely HSE-06) confirms the half
metallicity in the entire concentration range. Theoretically simulated band gap
and magnetic moments compliment the experimental findings and are compared
wherever possible. All these properties make $\mathrm{Co_2Fe_{1-x}Cr_xSi}$ a
promising material for spintronics application.",1804.05321v1
2021-10-16,Giant magnetoresistance and topological Hall effect in the EuGa4 antiferromagnet,"We report on systematic temperature- and magnetic field-dependent studies of
the EuGa$_4$ binary compound, which crystallizes in a centrosymmetric
tetragonal BaAl$_4$-type structure with space group $I4/mmm$. The electronic
properties of EuGa$_4$ single crystals, with an antiferromagnetic (AFM)
transition at $T_\mathrm{N} \sim 16.4$ K, were characterized via electrical
resistivity and magnetization measurements. A giant nonsaturating
magnetoresistance was observed at low temperatures, reaching $\sim 7 \times
10^4$ % at 2 K in a magnetic field of 9 T. In the AFM state, EuGa$_4$ undergoes
a series of metamagnetic transitions in an applied magnetic field, clearly
manifested in its field-dependent electrical resistivity. Below $T_\mathrm{N}$,
in the $\sim$4-7 T field range, we observe also a clear hump-like anomaly in
the Hall resistivity which is part of the anomalous Hall resistivity. We
attribute such a hump-like feature to the topological Hall effect, usually
occurring in noncentrosymmetric materials known to host topological spin
textures (as e.g., magnetic skyrmions). Therefore, the family of materials with
a tetragonal BaAl$_4$-type structure, to which EuGa$_4$ and EuAl$_4$ belong,
seems to comprise suitable candidates on which one can study the interplay
among correlated-electron phenomena (such as charge-density wave or exotic
magnetism) with topological spin textures and topologically nontrivial bands.",2110.08522v1
2016-01-09,Field-induced resistivity plateau and unsaturated negative magnetoresistance in topological semimetal TaSb2,"Several prominent transport properties have been identified as key signatures
of topologicalmaterials. One is the resistivity plateau at low temperatures as
observed in several topological insulators (TIs), another is the negative
magnetoresistance (MR) when the applied magnetic field is parallel to the
current direction as observed in several topological semimetals (TSMs)
including Dirac semimetals (DSMs) and Weyl semimetals (WSMs). Usually, these
two exotic phenomena emerge in distinct materials with or without time reversal
symmetry (TRS), respectively. Here we report the discovery of a new member in
TSMs, TaSb2, which clearly exhibits both of these phenomena in a single
material. This compound crystallizes in a base-centered monoclinic,
centrosymmetric structure, and is metallic with a low carrier density in the
zero field. While applying magnetic field it exhibits insulating behavior
before appearance of a resistivity plateau below Tc =13 K. In the plateau
regime, the ultrahigh carrier mobility and extreme magnetoresistance (XMR) for
the field perpendicular to the current are observed as in DSMs and WSMs, in
addition to a quantum oscillation behavior with non-trivial Berry phases. In
contrast to the most known DSMs and WSMs, the negative MR in TaSb2 does not
saturate up to 9 T, which, together with the almost linear Hall resistivity,
manifests itself an electron-hole non-compensated TMS. These findings indicate
that the resistivity plateau could be a generic feature of topology-protected
metallic states even in the absence of TRS and compatible with the negative MR
depending on the field direction. Our experiment extends a materials basis
represented by TaSb2 as a new platform for future theoretical investigations
and device applications of topological materials.",1601.02062v1
2011-01-31,Encapsulation and Electronic Control of Epitaxial Graphene by Photosensitive Polymers and UV light,"Electronic devices using epitaxial graphene on Silicon Carbide require
encapsulation to avoid uncontrolled doping by impurities deposited in ambient
conditions. Additionally, interaction of the graphene monolayer with the
substrate causes relatively high level of electron doping in this material,
which is rather difficult to change by electrostatic gating alone.
  Here we describe one solution to these problems, allowing both encapsulation
and control of the carrier concentration in a wide range. We describe a novel
heterostructure based on epitaxial graphene grown on silicon carbide combined
with two polymers: a neutral spacer and a photoactive layer that provides
potent electron acceptors under UV light exposure. Unexposed, the same double
layer of polymers works well as capping material, improving the temporal
stability and uniformity of the doping level of the sample. By UV exposure of
this heterostructure we controlled electrical parameters of graphene in a
non-invasive, non-volatile, and reversible way, changing the carrier
concentration by a factor of 50. The electronic properties of the exposed SiC/
graphene/polymer heterostructures remained stable over many days at room
temperature, but heating the polymers above the glass transition reversed the
effect of light.
  The newly developed photochemical gating has already helped us to improve the
robustness (large range of quantizing magnetic field, substantially higher
opera- tion temperature and significantly enhanced signal-to-noise ratio due to
significantly increased breakdown current) of a graphene resistance standard to
such a level that it starts to compete favorably with mature semiconductor
heterostructure standards. [2,3]",1101.6014v1
2020-11-20,Phase Transitions in Germanium Telluride Nanoparticle Phase-Change Materials Studied by Time-Resolved X-Ray Diffraction,"Germanium telluride (GeTe), a phase-change material, is known to exhibit four
different structural phases: three at room temperature (one amorphous and two
crystalline, $\alpha$ and $\gamma$) and one at high temperature (crystalline
$\beta$). Because transitions between the amorphous and crystalline phases lead
to significant changes in material properties (e.g., refractive index and
resistivity), GeTe has been investigated as a phase-change material for
photonics, thermoelectrics, ferroelectrics, and spintronics. Consequently, the
temperature-dependent phase transitions in GeTe have been studied for bulk and
thin-film GeTe, both fabricated by sputtering. Colloidal synthesis of
nanoparticles offers a more flexible fabrication approach for amorphous and
crystalline GeTe. These nanoparticles are known to exhibit size-dependent
properties, such as an increased crystallization temperature for the
amorphous-to-$\alpha$ transition in sub-10\,nm GeTe particles. The
$\alpha$-to-$\beta$ phase transition is also expected to vary with size, but
this effect has not yet been investigated for GeTe. Here, we report
time-resolved X-ray diffraction of GeTe nanoparticles with different diameters
and from different synthetic protocols. We observe a non-volatile
amorphous-to-$\alpha$ transition between 210$^{\circ}$C and 240$^{\circ}$C and
a volatile $\alpha$-to-$\beta$ transition between 370$^{\circ}$C and
420$^{\circ}$C. The latter transition was reversible and repeatable. While the
transition temperatures are shifted relative to the values known for bulk GeTe,
the nanoparticle-based samples still exhibit the same structural phases
reported for sputtered GeTe. Thus, colloidal GeTe maintains the same general
phase behavior as bulk GeTe while allowing for more flexible and accessible
fabrication. Therefore, nanoparticle-based GeTe films show great potential for
applications, such as in active photonics.",2011.10633v1
2022-08-23,Electrochemical investigation of MoSeTe as an anode for sodium-ion batteries,"Sodium ion batteries (SIBs) are considered as an efficient alternative for
lithium-ion batteries (LIBs) owing to the natural abundance and low cost of
sodium than lithium. In this context, the anode materials play a vital role in
rechargeable batteries to acquire high energy and power density. In order to
demonstrate transition metal dichalcogenide (TMD) as potential anode materials,
we have synthesized MoSeTe sample by conventional flux method, and the
structure and morphology are characterized using x-ray diffraction (XRD),
field-emission scanning electron microscopy (FESEM), transmission electron
microscopy (TEM), and Raman spectroscopy. These characterisations confirm the
hexagonal crystal symmetry with p63/mmc space group and layered morphology of
MoSeTe. We investigate the electrochemical performance of a MoSeTe as a
negative electrode (anode) for SIBs in the working potential range of 0.01 to
3.0~V. In a half-cell configuration, the MoSeTe as an anode and Na metal as
counter/reference electrode exhibits significant initial specific discharge
capacities of around 475 and 355 mAhg$^{-1}$ at current densities of 50 and 100
mAg$^{-1}$, respectively. However, the capacity degraded significantly like
$\approx$200~mAhg$^{-1}$ in 2nd cycle, but having $\approx$100\% Coulombic
efficiency, which suggest for further modification in this material to improve
its stability. The cyclic voltammetry (CV) study reveals the reversibility of
the material after 1st cycle, resulting no change in the initial peak
positions. The electrochemical impedance spectroscopy (EIS) measurements
affirms the smaller charge transfer resistance of fresh cells than the cells
after 10th cycle. Moreover, the extracted diffusion coefficient is found to be
of the order of 10$^{-14}$ cm$^2$s$^{-1}$.",2208.10911v1
2024-05-13,"Reducing the oxygen contamination in conductive (Ti,Zr)N coatings via RF-bias assisted reactive sputtering","Ternary transition metal nitride coatings are promising for many applications
as they can offer improved hardness and oxidation resistance compared to binary
counterparts. A common challenge in the deposition of functional nitride thin
films is oxygen contamination. Even low amounts of oxygen contamination can
adversely affect the functional properties of the thin films. Here, we present
a practical approach for the growth of virtually oxygen-free (Ti, Zr)N thin
films. To cover the complete compositional range of (Ti,Zr)N coatings we employ
combinatorial reactive co-sputtering. The depositions are carried out with or
without applying a low-power radio-frequency (RF) bias voltage to the substrate
holder to study the possibility of decelerating energetic oxygen ions and
effectively reducing oxygen contamination in the growing film. High-throughput
structural analysis and functional property mapping are used to elucidate the
synthesis-property relationships. The structural analysis indicates solid
solution formation over the entire compositional range, as evidenced by
Vegardian lattice scaling, regardless of the applied RF substrate bias.
Irrespective of the composition of the films, the application of RF substrate
bias leads to a dramatic reduction of oxygen contamination, as demonstrated by
X-ray photoelectron spectroscopy (XPS) depth-profile mapping. This is reflected
in a significant improvement in the films' conductivity and hardness. We
demonstrate that the reduction in oxygen contamination is intrinsic to the
process and not due to changes in the microstructure. The approach presented
here is applicable to both conductive and insulating substrates and provides a
practical route to synthesize nitride thin films with improved purity that can
be applied in standard sputter chambers and on many different material systems.",2405.07789v1
2018-11-03,"Pressure-induced Insulator to Metal Transition of Mixed Valence Compound Ce(O,F)SbS$_{2}$","Transport properties of Ce$_{0.85}$F0.15SbS$_{2}$ and undoped CeOSbS$_{2}$
under high pressure were investigated experimentally and theoretically.
Electrical resistivity measurements of the Ce$_{0.85}$F0.15SbS$_{2}$ single
crystals were performed under various high pressures using a diamond anvil cell
with boron-doped diamond electrodes. The samples showed the insulator to metal
transition by applying high pressure up to 30-40 GPa. On the other hand, the
undoped CeOSbS$_{2}$ showed almost same transport property with the F-doped
sample under high pressure. The valence state analysis using X-ray
photoelectron spectroscopy revealed a simple valence state of Ce3+ in
Ce$_{0.85}$F0.15SbS$_{2}$ and mixed valence state between Ce3+ and Ce4+ in
undoped CeOSbS$_{2}$. The valence fluctuation in Ce carried out the comparable
transport nature in the both samples. A band calculation suggests that the
undoped CeOSbS$_{2}$ could be metallic under high pressure of 30 GPa in
accordance with the experimental results. A superior thermoelectric property of
power factor in CeOSbS$_{2}$ was estimated under high pressure around 20 GPa in
comparison with that of ambient pressure.",1811.01151v1
2020-10-22,A photogrammetric method for target monitoring inside the MEG II detector,"An automatic target monitoring method based on photographs taken by a CMOS
photo-camera has been developed for the MEG II detector. The technique could be
adapted for other fixed-target experiments requiring good knowledge of their
target position to avoid biases and systematic errors in measuring the
trajectories of the outcoming particles. A CMOS-based, high resolution, high
radiation tolerant and high magnetic field resistant photo-camera was mounted
inside the MEG II detector at the Paul Scherrer Institute (Switzerland). MEG II
is used to search for lepton flavour violation in muon decays. The
photogrammetric method's challenges, affecting measurements of low momentum
particles' tracks, are high magnetic field of the spectrometer, high radiation
levels, tight space constraints, and the need to limit the material budget in
the tracking volume. The camera is focused on dot pattern drawn on the thin MEG
II target, about 1 m away from the detector endcaps where the photo-camera is
placed. Target movements and deformations are monitored by comparing images of
the dots taken at various times during the measurement. The images are acquired
with a Raspberry board and analyzed using a custom software. Global alignment
to the spectrometer is guaranteed by corner cubes placed on the target support.
As a result, the target monitoring fulfils the needs of the experiment.",2010.11576v2
2021-02-04,Disorder-robust high-field superconducting phase of FeSe single crystals,"When exposed to high magnetic fields, certain materials manifest an exotic
superconducting (SC) phase that has attracted considerable attention. A
proposed explanation for the origin of the high-field SC phase is the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. This state is characterized by
inhomogeneous superconductivity, where the Cooper pairs have finite
center-of-mass momenta. Recently, the high-field SC phase was observed in FeSe,
and it was deemed to originate from the FFLO state. Here, we synthesize FeSe
single crystals with different levels of disorder. The level of disorder is
expressed by the ratio of the mean free path to the coherence length and ranges
between 35 and 1.2. The upper critical field \textit{B}$_{\rm{c}2}$ was
obtained by both resistivity and magnetic torque measurements over a wide range
of temperatures, which went as low as $\sim$0.5 K, and magnetic fields, which
went up to $\sim$38 T along the \textit{c} axis and in the \textit{ab} plane.
In the high-field region parallel to the \textit{ab} plane, an unusual SC phase
was confirmed in all the crystals, and the phase was found to be robust against
disorder. This result suggests that the high-field SC phase in FeSe is not a
conventional FFLO state.",2102.02353v2
2021-03-03,On the early stages of precipitation during direct ageing of Alloy 718,"The Ni-based superalloy Alloy 718 is used in aircraft engines as
high-pressure turbine discs and must endure challenging demands on
high-temperature yield strength, creep-, and oxidation-resistance. Nanoscale
$\gamma^{\prime}$- and $\gamma^{\prime \prime}$-precipitates commonly found in
duplet and triplet co-precipitate morphologies provide high-temperature
strength under these harsh operating conditions. Direct ageing of Alloy 718 is
an attractive alternative manufacturing route known to increase the yield
strength at 650 $^{\deg}$C by at least +10 $\%$, by both retaining high
dislocation densities and changing the nanoscale co-precipitate morphology.
However, the detailed nucleation and growth mechanisms of the duplet and
triplet co-precipitate morphologies of $\gamma^{\prime}$ and $\gamma^{\prime
\prime}$ during the direct ageing process remain unknown. We provide a
correlative high-resolution microscopy approach using transmission electron
microscopy, high-angle annular dark-field imaging, and atom probe microscopy to
reveal the early stages of precipitation during direct ageing of Alloy 718.
Quantitative stereological analyses of the $\gamma^{\prime}$- and
$\gamma^{\prime \prime}$-precipitate dispersions as well as their chemical
compositions have allowed us to propose a qualitative model of the
microstructural evolution. It is shown that fine $\gamma^{\prime}$- and
$\gamma^{\prime \prime}$-precipitates nucleate homogeneously and grow
coherently. However, $\gamma^{\prime \prime}$-precipitates also nucleate
heterogeneously on dislocations and experience accelerated growth due to Nb
pipe diffusion. Moreover, the co-precipitation reactions are largely influenced
by solute availability and the potential for enrichment of Nb and rejection of
Al+Ti.",2103.02763v1
2022-06-25,High-Mobility Tri-Gate $β$-Ga$_2$O$_3$ MESFETs with a Power Figure of Merit over 0.9 GW/cm$^2$,"In this letter, fin-shape tri-gate $\beta$-Ga$_{2}$O$_{3}$ lateral MESFETs
are demonstrated with a high power figure of merit of 0.95 GW/cm$^{2}$ - a
record high for any $\beta$-Ga$_{2}$O$_{3}$ transistor to date. A
low-temperature undoped buffer-channel stack design is developed which
demonstrates record high Hall and drift electron mobilities in doped
$\beta$-Ga$_{2}$O$_{3}$ channels allowing for low ON resistances R$_{ON}$ in
$\beta$-Ga$_{2}$O$_{3}$ MESFETs. Fin-widths (W$_{fin}$) were 1.2-1.5 $\mu$m and
there were 25 fins (N$_{fin}$) per device with a trench depth of $\sim$1$\mu$m.
A $\beta$-Ga$_2$O$_3$ MESFET with a source-drain length of 6.4 $\mu$m exhibits
a high ON current (187 mA/mm), low R$_{ON}$ (20.5 $\Omega$.mm) and a high
average breakdown field (4.2 MV/cm). All devices show very low reverse leakage
until catastrophic breakdown for breakdown voltages scaled from 1.1kV to
$\sim$3kV. This work demonstrates the potential of channel engineering in
improving $\beta$-Ga$_{2}$O$_{3}$ device performance toward lower conduction
losses for low-to-medium voltage applications.",2206.12539v2
2023-10-22,Pressure-induced volumetric negative thermal expansion in CoZr2 superconductor,"We investigate the thermal expansion and superconducting properties of a
CuAl2-type (tetragonal) superconductor CoZr2 under high pressures. We perform
high-pressure synchrotron X-ray diffraction in a pressure range of 2.9 GPa < P
< 10.4 GPa and discover that CoZr2 exhibits volumetric negative thermal
expansion under high pressures. Although the uniaxial positive thermal
expansion (PTE) along the a-axis is observed under ambient pressure, that is
suppressed by pressure, while the large uniaxial negative thermal expansion
(NTE) along the c-axis is maintained under the pressure regime. As a result of
a combination of the suppressed uniaxial PTE along the a-axis and uniaxial NTE
along the c-axis, volumetric negative thermal expansion is achieved under high
pressure in CoZr2. The mechanisms of volumetric NTE would be based on the
flexible crystal structure caused by the soft Co-Co bond as seen in the
iso-structural compound FeZr2, which exhibits uniaxial NTE along the c-axis. We
also perform high-pressure electrical resistance measurements of CoZr2 to
confirm the presence of superconductivity under the examined pressure regime in
the range of 0.03 GPa < P < 41.9 GPa. We confirm the presence of
superconductivity under all pressures and observe dome-like shape pressure
dependence of superconducting transition temperature. Because of the
coexistence of two phenomena, which are volumetric NTE and superconductivity,
in CoZr2 under high pressure, the coexistence would be achievable under ambient
pressure by tuning chemical compositions after our present observation.",2310.14254v2
2023-10-22,Superconductivity in the high-entropy ceramics Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx with possible nontrivial band topology,"Topological superconductors have drawn significant interest from the
scientific community due to the accompanying Majorana fermions. Here, we report
the discovery of electronic structure and superconductivity in high-entropy
ceramics Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx (x = 1 and 0.8) combined with experiments
and first-principles calculations. The Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2Cx high-entropy
ceramics show bulk type-II superconductivity with Tc about 4.00 K (x = 1) and
2.65 K (x = 0.8), respectively. The specific heat jump is equal to 1.45 (x = 1)
and 1.52 (x = 0.8), close to the expected value of 1.43 for the BCS
superconductor in the weak coupling limit. The high-pressure resistance
measurements show that a robust superconductivity against high physical
pressure in Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2C, with a slight Tc variation of 0.3 K
within 82.5 GPa. Furthermore, the first-principles calculations indicate that
the Dirac-like point exists in the electronic band structures of
Ti0.2Zr0.2Nb0.2Mo0.2Ta0.2C, which is potentially a topological superconductor.
The Dirac-like point is mainly contributed by the d orbitals of transition
metals M and the p orbitals of C. The high-entropy ceramics provide an
excellent platform for the fabrication of novel quantum devices, and our study
may spark significant future physics investigations in this intriguing
material.",2310.14271v1
2024-03-25,In situ growth of hydrophilic nickel-cobalt layered double hydroxides nanosheets on biomass waste-derived porous carbon for high-performance hybrid supercapacitors,"Rational design and cost-effective fabrication of layered double hydroxides
(LDHs) nanosheets with extraordinary electrochemical performance is a key
challenge for hybrid supercapacitors (HSCs). Herein, we report a facile in situ
growth methodology to eco-friendly synthesize hydrophilic NiCo-LDHs nanosheets
on biomass waste-derived porous carbon (BC) for robust high-performance HSC
cathode. The in situ growth process under ultrasonication realizes the rational
arrangement of NiCo-LDHs nanosheets on the surface of BC, which effectively
increases the specific surface area, promotes the electronic conductivity and
enhances the wettability of NiCo-LDHs nanosheets without affecting their
thickness values. With the beneficial effects of ultrathin thickness of LDHs
nanosheets (6.20 nm), large specific surface area (2324.1 m2 g-1), low charge
transfer resistance (1.65 ohm), and high wettability with electrolyte (34-35
degree), the obtained Ni2Co1-LDHs/BC50 electrode possesses an ultra-high
specific capacitance of 2390 F g-1 (956 C g-1) at 1 A g-1, which is superior to
most reported values. Furthermore, an assembled Ni2Co1-LDHs/BC50//YP-80F HSC
delivers a maximum specific energy of 52.47 Wh kg-1 at 375 W kg-1, and
maintains a high capacitance retention of 75.9% even after 4000 cycles. This
work provides a facile approach to fabricate LDHs nanosheets based cathode
materials for high-performance HSCs.",2403.16506v1
1997-01-08,Coupling between phonons and intrinsic Josephson oscillations in cuprate superconductors,"The recently reported subgap structures observed in the current-voltage
characteristic of intrinsic Josephson junctions in the high-T_c superconductors
Tl_2Ba_2Ca_2Cu_3O_{10+\delta} and Bi_2Sr_2CaCu_2O_{8+\delta} are explained by
the coupling between c-axis phonons and Josephson oscillations. A model is
developed where c-axis lattice vibrations between adjacent superconducting
multilayers are excited by the Josephson oscillations in a resistive junction.
The voltages of the lowest structures correspond well to the frequencies of
longitudinal c-axis phonons with large oscillator strength in the two
materials, providing a new measurement technique for this quantity.",9701049v2
1997-07-17,Anomalous magnetotransport in wide quantum wells,"We present magneto transport experiments of quasi 3D PbTe wide quantum wells.
A plateau-like structure in the Hall resistance is observed, which corresponds
to the Shubnikov de Haas oscillations in the same manner as known from the
quantum Hall effect. The onsets of plateaux in Rxy do not correspond to 2D
filling factors but coincide with the occupation of 3D (bulk-) Landau levels.
At the same time a non-local signal is observed which corresponds to the
structure in Rxx and Rxy and fulfils exactly the Onsager-Casimir relation
(Rij,kl(B) = Rkl,ij(-B)). We explain the behaviour in terms of edge channel
transport which is controlled by a permanent backscattering across a system of
""percolative EC - loops"" in the bulk region. Long range potential fluctuations
with an amplitude of the order of the subband splitting are explained to play
an essential role in this electron system.",9707173v1
1997-07-18,Edge Channel Dominated Magnetotransport in PbTe Wide Parabolic Quantum Wells,"In PbTe wide parabolic quantum wells (WPQW) a plateau-like structure is
observed in the Hall resistance, which corresponds to the Shubnikov-de Haas
oscillations in the same manner as known from the quantum Hall effect. At the
same time a non-local signal is observed which corresponds to the structure in
Rxx and Rxy. We find a striking correspondence between a standard quantum Hall
system and this quasi 3D WPQW system.",9707188v1
1997-10-28,Investigation of acceptor levels and hole scattering mechanisms in p-gallium selenide by means of transport measurements under pressure,"The effect of pressure on acceptor levels and hole scattering mechanisms in
p-GaSe is investigated through Hall effect and resistivity measurements under
quasi-hydrostatic conditions up to 4 GPa. The pressure dependence of the hole
concentration is interpreted through a carrier statistics equation with a
single (nitrogen) or double (tin) acceptor whose ionization energies decrease
under pressure due to the dielectric constant increase. The pressure effect on
the hole mobility is also accounted for by considering the pressure
dependencies of both the phonon frequencies and the hole-phonon coupling
constants involved in the scattering rates.",9710296v1
1998-12-24,Electron Correlations in Molecular Systems,"A short review of correlated electrons in molecular systems has been
performed. Main attention has been focussed on ET salts, which are the d=2
systems. They show the Mott transition in high temperatures and the transition
from the antiferromagnetic to the superconducting phase in low temperatures,
under a (chemical) pressure. Physical properties (the electrical resistivity,
the specific heat, the magnetic susceptibility, the photoemission spectra, the
optical conductivity) of ET salts have been compared with those ones in other
strongly correlated systems. The optical conductivity is described in the
framework of the Hubbard model, with a low frequency peak as an evidence for
the Abrikosov-Suhl resonance.",9812392v1
1998-12-30,Giant transverse magnetoresistance in an asymmetric system of three GaAs/AlGaAs quantum wells in a strong magnetic field at room temperature,"The giant transverse magnetoresistance is observed in the case of
photoinduced nonequilibrium carriers in an asymmetric undoped system of three
GaAs/AlGaAs quantum wells at room temperature. In a magnetic field of 75 kOe,
the resistance of nanostructure being studied increases by a factor of 1.85.
The magnetoresistance depends quadratically on the magnetic field in low fields
and tends to saturation in high fields. This phenomenon is attributed to the
rearrangement of the electron wave function in magnetic field. Using the fact
that the incoherent part of the scattering probability for electron scattering
on impurities and bulk defects is proportional to the integral of the forth
power of the envelope wave function, the calculated field dependence of the
magnetoresistance is shown to be similar to that observed experimentally.",9812426v1
1999-03-03,Non linear flux flow in TiN superconducting thin film,"We have studied the superconducting behavior of 100 nm Titanium Nitride (TiN)
thin film in a perpendicular magnetic field. We found a zero field transition
temperature of 4.6 K and a slope in the H-T plane of -0.745 T/K. At 4.2 K, we
have performed careful transport measurements by measuring both the
differential resistivity and voltage as a function of a DC current. Our results
are analyzed in the framework of linear and non linear flux flow behavior. In
particular, we have observed an electronic instability at high vortex
velocities and from its dependence with respect to the applied magnetic field,
we can exctract the inelastic scattering time and diffusion length of the
quasiparticles.",9903060v2
1999-08-26,Destruction of the Mott Insulating Ground State of Ca_2RuO_4 by a Structural Transition,"We report a first-order phase transition at T_M=357 K in single crystal
Ca_2RuO_4, an isomorph to the superconductor Sr_2RuO_4. The discontinuous
decrease in electrical resistivity signals the near destruction of the Mott
insulating phase and is triggered by a structural transition from the low
temperature orthorhombic to a high temperature tetragonal phase. The magnetic
susceptibility, which is temperature dependent but not Curie-like decreases
abruptly at TM and becomes less temperature dependent. Unlike most insulator to
metal transitions, the system is not magnetically ordered in either phase,
though the Mott insulator phase is antiferromagnetic below T_N=110 K.",9908390v1
1999-08-29,Anomalous microwave response of high-temperature superconducting thin-film microstrip resonator in weak dc magnetic fields,"We have studied an anomalous microwave (mw) response of superconducting
YBa_{2}Cu_{3}O_{7-delta} (YBCO) microstrip resonators in the presence of a weak
dc magnetic field, H_{dc}. The surface resistance (R_{s}) and reactance (X_{s})
show a correlated non-monotonic behaviour as a function of H_{dc}. R_{s} and
X_{s} were found to initially decrease with elevated H_{dc} and then increase
after H_{dc} reaches a crossover field, H_{c}, which is independent of the
amplitude and frequency of the input mw signal within the measurements. The
frequency dependence of R_{s} is almost linear at fixed H_{dc} with different
magnitudes (<H_{c}, =H_{c} and >H_{c}). The impedance plane analysis
demonstrates that r_{H}, which is defined as the ratio of the change in
R_{s}(H_{dc}) and that in X_{s}(H_{dc}), is about 0.6 at H_{dc}<H_{c} and 0.1
at H_{dc}>H_{c}. The H_{dc} dependence of the surface impedance is
qualitatively independent of the orientation of H_{dc}.",9908429v1
2000-05-11,Magnetic Field resulting from non-linear electrical transport in single crystals of charge-ordered Pr$_{0.63}$ Ca$_{0.37}$ MnO$_{3}$},"In this letter we report that the current induced destabilization of the
charge ordered (CO) state in a rare-earth manganite gives rise to regions with
ferromagnetic correlation. We did this experiment by measurement of the I-V
curves in single crystal of the CO system
  Pr$_{0.63}$Ca$_{0.37}$MnO$_{3}$ and simultanously measuring the magnetization
of the current carrying conductor using a high T$_c$ SQUID working at T = 77K.
We have found that the current induced destabilization of the CO state leads to
a regime of negative differential resistance which leads to a small enhancement
of the magnetization of the sample, indicating ferromagnetically aligned
moments.",0005194v1
2000-06-22,High field magnetotransport in composite conductors: the effective medium approximation revisited,"The self consistent effective medium approximation (SEMA) is used to study
three-dimensional random conducting composites under the influence of a strong
magnetic field {\bf B}, in the case where all constituents exhibit isotropic
response. Asymptotic analysis is used to obtain almost closed form results for
the strong field magnetoresistance and Hall resistance in various types of two-
and three-constituent isotropic mixtures for the entire range of compositions.
Numerical solutions of the SEMA equations are also obtained, in some cases, and
compared with those results. In two-constituent
free-electron-metal/perfect-insulator mixtures, the magnetoresistance is
asymptotically proportional to $|{\bf B}|$ at {\em all concentrations above the
percolation threshold}. In three-constituent metal/insulator/superconductor
mixtures a line of critical points is found, where the strong field
magnetoresistance switches abruptly from saturating to non-saturating
dependence on $|{\bf B}|$, at a certain value of the
insulator-to-superconductor concentration ratio. This transition appears to be
related to the phenomenon of anisotropic percolation.",0006351v1
2000-08-02,The Zeno effect and an inter-layer pairing mechanism for high-temperature superconductivity in layered materials,"Quantum Zeno Effect (QZE) is the suppression of the inter-subspace transition
by a relatively fast intra-subspace decoherence. Earlier, we had proposed a
QZE-based mechanism for the temperature-dependent normal-state c-axis
resistivity of the layered high-T$_c$ cuprate superconductors in which the
single-particle inter-layer tunneling is blocked by the strong intra-layer
decoherence (entanglement). We now argue that while the single-particle
inter-layer tunneling is thus blocked, the tunneling of the bosonic BCS-like
pairs must remain unblocked inasmuch as a BCS pairing condensate is an
eigenstate of the pair annihilation operator. This pair tunneling stabilizes",0008023v1
2000-12-14,Electronic Transmission Through Metallic Nanowires: Generalized Scattering Matrix Approach,"An easy to implement and powerful method for the solution of 3D scattering
problems that can be well described by Helmholtz equation is presented. The
matrix algebra used provides excellent stability versus the number of junctions
as well as great computational speed. The matrix truncation method yields an
easy single-parameter convergence procedure. Subsequently, some aspects of the
electronic transport through metal nanowires are studied by the use of
Landauer's scattering approach to the conductance. We predict the existence of
current vortex-rings patterns due to sharp enough narrow-wide connections in
atomic size point contacts. Longitudinal resonances between scattering centers
provide a simple physical picture for the understanding of negative
differential resistance in ideal monoatomic contacts. Relatively long nanowires
with high geometrical perfection -like those recently observed by Transmission
Electron Microscopy- are modelled exhibiting resonant tunnelling and total
reflection at given incident energy intervals.",0012250v1
2001-03-16,Giant Magnetoresistance by Exchange Springs in DyFe$_2$/YFe$_2$ Superlattices,"Magnetization and magnetoresistance measurements are reported for
antiferromagnetically coupled DyFe$_2$/YFe$_2$ multilayers in fields up to 23
T. We demonstrate that the formation of short exchange springs (~ 2 nm) in the
magnetically soft YFe$_2$ layers results in a giant magneto-resistance as high
as 32% in the spring region. It is shown that both the magnitude of the effect,
and its dependence on magnetic field, are in good agreement with the theory of
Levy and Zhang for giant magnetoresistance due to domain wall like structures.",0103354v1
2001-04-05,Fractal Nature and Scaling Exponent of Non-Drude Currents in Non-Fermi Liquids,"In many oxides of the perovskite and pseudoperovskite families there are
phase transitions between insulating and normal metallic (Fermi liquid) phases
that are separated by an intermediate phase that is often called a non-Fermi
liquid (NFL). The dc resistivity of the intermediate or NFL phase often
exhibits a T temperature dependence, in contrast to the T2 dependence expected
from a bad normal metal. The same alloys exhibit a non-Drude (ND) w2alpha
frequency dependence, with alpha ~ 0.5, in contrast to the Drude dependence w2
characteristic of samples with the T2 behavior. Various attempts have been made
to modify the algebra of continuum Fermi liquid theory (FLT) to derive the ND
exponent alpha, but these have been based on artifices designed to explain only
this one parameter. The discrete filamentary model has been used to calculate
many properties of high temperature superconductors, and to explain the
asymmetric nature of the intermediate phase. Here it is used to derive a by the
same rules previously used for several other discrete relaxation calculations
that are in excellent agreement with other quite different experiments. The
results are: (cubic) perovskites, alpha = 0.45, and planar conductivity of
bilayered pseudoperovskites, alpha = 0.70. The corresponding experimental
values are (0.4, 0.5) and 0.7.",0104095v1
2001-04-06,Evidence for high inter-granular current flow in single-phase polycrystalline MgB2 superconductor,"The distribution of magnetic field in single-phase polycrystalline bulk MgB2
has been measured using a Magneto-Optical (MO) technique for an external
magnetic field applied perpendicular to the sample surface. The MO studies
indicate that an inter-granular current network is readily established in this
material and the current is not limited by weak-linked grain boundaries. The
grain boundaries are observed to resist preferential magnetic field
penetration, with the inter-grain mechanism dominating the current flow in the
sample at temperatures up to 30K. The results provide clear evidence that the
intra-granular current flow is isotropic. A critical current density of ~10^4
Acm-2 was estimated at 30K in a field of 150mT from the MO measurements. These
results provide further evidence of the considerable potential for MgB2 for
engineering applications.",0104114v1
2002-04-17,Epitaxial Growth of La$_{1/3}$Sr$_{2/3}$FeO$_3$ thin films by laser ablation,"We report on the synthesis of high quality La$_{1/3}$Sr$_{2/3}$FeO$_3$ (LSFO)
thin films using the pulsed laser deposition technique on both SrTiO$_3$ (STO)
and LaAlO$_3$ (LAO) substrates (100)-oriented. From X-Ray diffraction (XRD)
studies, we find that the films have an out-of-plane lattice parameter around
0.3865nm, almost independent of the substrate (i.e. the nature of the strains).
The transport properties reveal that, while LSFO films deposited on STO exhibit
an anomaly in the resistivity vs temperature at 180K (corresponding to the
charge-ordered transition and associated with a transition from a paramagnetic
to an antiferromagnetic state), the films grown on LAO display a very small
magnetoresistance behavior and present an hysteresis around 270K under the
application of a 4T magnetic field. The changes in transport properties between
both substrates are discussed and compared with the corresponding single
crystals.",0204370v1
2002-05-24,The Hall effect and hole densities in high Tc GaMnAs thin films,"By studying the Hall effect in a series of low resistivity Ga1-xMnxAs
samples, accurate values for the hole density p, Mn concentration x, and Curie
temperature Tc are obtained over the range 0.015=<x=<0.08. The hole density
corresponds to 90% of the Mn concentration at low x, and has a maximum value of
1.0x10-27 m-3 when Tc=125K for x=0.06. This data allows the first meaningful
comparison of mean field predicted Curie temperatures with experiment over a
wide range of x. The theory is in qualitative agreement with experiment, but
overestimates Tc at large x and underestimates TC at low x.",0205517v3
2002-06-19,Transport and magnetic properties of LT annealed Ga1-xMnxAs,"We present the results of low temperature (LT) annealing studies of
Ga1-xMnxAs epilayers grown by low temperature molecular beam epitaxy in a wide
range of Mn concentrations (0.01<x<0.084). Transport measurements in low and
high magnetic fields as well as SQUID measurements were performed on a wide
range of samples, serving to establish optimal conditions of annealing. Optimal
annealing procedure succeeded in the Curie temperatures higher than 110K. The
highest value of Curie temperature estimated from the maximum in the
temperature dependence of zero-field resistivity (Tr) was 127K. It is generally
observed that annealing leads to large changes in the magnetic and transport
properties of GaMnAs in the very narrow range of annealing temperature close to
the growth temperature.",0206371v1
2002-07-08,Magnetic behavior of single crystalline Ho$_2$PdSi$_3$,"The magnetic behavior of single-crystal Ho$_2$PdSi$_3$, crystallizing in an
AlB$_2$-derived hexagonal structure, is investigated by magnetic susceptibility
($\chi$) and electrical resistivity ($\rho$) measurements along two directions.
There is no dramatic anisotropy in the high temperature Curie-Weiss parameter
or in the $\rho$ and isothermal magnetization data, though there is a
noticeable anisotropy in the magnitude of $\rho$ between two perpendicular
orientations. The degree of anisotropy is overall less prominent than in the Gd
(which is an S-state ion!) and Tb analogues. A point of emphasis is that this
compound undergoes long range magnetic ordering below 8 K as in the case of
analogous Gd and Dy compounds. Considering this fact for these compounds with
well-localised f-orbital, the spin glass freezing noted for isomorphous U
compounds in the recent literature could be attributed to the role of the
f-ligand hybridization, rather than just Pd-Si disorder.",0207199v1
2002-10-22,Unipolar transport and shot noise in metal-semiconductor-metal structures,"We carry out a self-consistent analytical theory of unipolar current and
noise properties of metal-semiconductor-metal structures made of highly
resistive semiconductors in the presence of an applied bias of arbitrary
strength. By including the effects of the diffusion current we succeed to study
the whole range of carrier injection conditions going from low level injection,
where the structure behaves as a linear resistor, to high level injection,
where the structure behaves as a space charge limited diode. We show that these
structures display shot noise at the highest voltages. Remarkably the crossover
from Nyquist noise to shot noise exhibits a complicate behavior with increasing
current where an initial square root dependence (double thermal noise) is
followed by a cubic power law.",0210484v1
2002-11-14,Synthesis and Properties of YbB2,"We report temperature and field dependent measurements of the magnetic
susceptibility, specific heat and resistivity of sintered YbB2 pellets,
prepared via two distinct reaction routes, utilizing different temperatures,
pressures and sintering times. Sample behavior is affected by the preparation
procedure, as a consequence of different secondary phases, most of which were
identified via x-ray diffraction. These experiments show that YbB2 is a metal
with the Yb atoms in or very close to their 3+ state. YbB2 appears to order
anti-ferromagnetically at TN ~ 5.6 K, which can be considered a relatively high
ordering temperature for an ytterbium-based intermetallic compound.",0211288v1
2003-07-07,"Mn Interstitial Diffusion in (Ga,Mn)As","We present a combined theoretical and experimental study of the ferromagnetic
semiconductor (Ga,Mn)As which explains the remarkably large changes observed on
low temperature annealing. Careful control of the annealing conditions allows
us to obtain samples with ferromagnetic transition temperatures up to 159 K. Ab
initio calculations, and resistivity measurements during annealing, show that
the observed changes are due to out-diffusion of Mn interstitials towards the
surface, governed by an energy barrier of about 0.7-0.8 eV. The Mn interstitial
is a double donor resulting in compensation of charge carriers and suppression
of ferromagnetism. Electric fields induced by high concentrations of
substitutional Mn acceptors have a significant effect on the diffusion.",0307140v1
2003-07-09,Direct Observation of Long-Term Durability of Superconductivity in YBa$_2$Cu$_3$O$_7$-Ag$_2$O Composites,"We report direct observation of long-term durability of superconductivity of
several YBa$_2$Cu$_3$O$_7$-Ag$_2$O composites that were first prepared and
studied almost 14 years ago [J. J. Lin {\it et al}., Jpn. J. Appl. Phys. {\bf
29}, 497 (1990)]. Remeasurements performed recently on both resistances and
magnetizations indicate a sharp critical transition temperature at 91 K. We
also find that such long-term environmental stability of high-temperature
superconductivity can only be achieved in YBa$_2$Cu$_3$O$_7$ with Ag$_2$O
addition, but not with pure Ag addition.",0307187v1
2003-07-18,Probing quasiparticle dynamics in Bi2Sr2CaCu2O(8+delta) with a driven Josephson vortex lattice,"We show that the flux-flow transport of the Josephson vortex lattice (JVL) in
layered high-temperature superconductors provides a convenient probe for both
components of quasiparticle conductivity, $\sigma_{c}$ and $\sigma_{ab}$. We
found that the JVL flux-flow resistivity, $\rho_{ff}$, in a wide range of
magnetic fields is mainly determined by the in-plane dissipation. In the dense
lattice regime ($B>1$ T) $\rho_{ff}(B)$ dependence is well fitted by the
theoretical formula for that limit. That allows us to independently extract
from the experimental data the values of $\sigma_{c}$ and of the ratio $\sigma
_{ab}/(\sigma_{c}\gamma ^{4})$. The extracted temperature dependence $\sigma
_{ab}(T)$ is consistent with microwave data. The shape of the current-voltage
characteristics is also sensitive to the frequency dependence of $\sigma_{ab}$
and that allows us to estimate the quasiparticle relaxation time and relate it
to the impurity bandwidth using data obtained for the same crystal.",0307450v1
2003-09-02,The enhancement of phase separation aspect in electron doped manganite Ca0.8Sm0.16Nd0.04MnO3,"The complex lanthanide doping of electron manganites results in enhancement
of various phase separation effects in physical properties of these compounds.
Selecting Ca0.8Sm0.16Nd0.04MnO3 as a model case we show that the first order
structural phase transition from paramagnetic semi-metallic phase into
anti-ferromagnetic semi-metallic phase at TS ~ 158 +- 4 K is marked by an
abrupt decrease in magnetization, a step like anomaly DL/L = 10-4 in thermal
expansion and large latent heat DQ = 610 J/mol. In a certain temperature range
below TS, the high field magnetization exhibits hysteretic metamagnetic
behavior due to field-induced first order transformation. ac-susceptibility,
magnetization and resistivity data suggest rather a non-uniform state in
Ca0.8Sm0.16Nd0.04MnO3 at low temperatures. The metal - insulator transition
occurs at TMI ~112 +- 3 K, accompanied by a step-like increase in
magnetization. These features could be ascribed to ""sponging"" of electrons from
neighboring anti-ferromagnetic matrix by clusters undergoing the ferromagnetic
ordering.",0309065v1
2003-12-28,Optical properties of pyrochlore oxide $Pb_{2}Ru_{2}O_{7-δ}$,"We present optical conductivity spectra for $Pb_{2}Ru_{2}O_{7-{\delta}}$
single crystal at different temperatures. Among reported pyrochlore ruthenates,
this compound exhibits metallic behavior in a wide temperature range and has
the least resistivity. At low frequencies, the optical spectra show typical
Drude responses, but with a knee feature around 1000 \cm. Above 20000 \cm, a
broad absorption feature is observed. Our analysis suggests that the low
frequency responses can be understood from two Drude components arising from
the partially filled Ru $t_{2g}$ bands with different plasma frequencies and
scattering rates. The high frequency broad absorption may be contributed by two
interband transitions: from occupied Ru $t_{2g}$ states to empty $e_{g}$ bands
and from the fully filled O 2p bands to unoccupied Ru $t_{2g}$ states.",0312662v1
2004-01-31,Unprecedented Superconductivity in the beta-Pyrochlore Osmate KOs2O6,"Superconductivity in the potassium osmium oxide KOs2O6 crystallizing in the
beta-pyrochlore structure is studied by means of electrical resistivity,
magnetic susceptibility and specific heat. It is the second superconductor in
the family of pyrochlore oxides, following the alfa-type pyrochlore oxide
Cd2Re2O7 which is believed to be a conventional s-wave superconductor. The
superconducting transition temperature Tc of KOs2O6 is 9.6 K, almost one order
higher than the Tc = 1.0 K of Cd2Re2O7. Moreover, the superconductivity of
KOs2O6 is remarkably robust under high magnetic fields, with a large upper
critical magnetic field Hc2 of about 38 T, which seems to exceed Pauli's limit
expected for conventional superconductivity. This is also in contrast to the
case of Cd2Re2O7, in which the Hc2 is 0.29 T, much smaller than the
corresponding Pauli's limit. These distinct contrasts strongly suggest that the
mechanism of superconductivity is essentially different between the two
pyrochlore oxides.",0402006v3
2004-03-31,Spin-Transfer Effects in Nanoscale Magnetic Tunnel Junctions,"We report measurements of magnetic switching and steady-state magnetic
precession driven by spin-polarized currents in nanoscale magnetic tunnel
junctions with low-resistance, < 5 Ohm-micron-squared, barriers. The current
densities required for magnetic switching are similar to values for
all-metallic spin-valve devices. In the tunnel junctions, spin-transfer-driven
switching can occur at voltages that are high enough to quench the tunnel
magnetoresistance, demonstrating that the current remains spin-polarized at
these voltages.",0404002v2
2004-08-16,"Structural, transport, magnetic properties and Raman spectroscopy of orthorhombic Y$1-x$CaxMnO3(0 <= x <= 0.5)","Orthorhombic Y$_{1-x}$Ca$_x$MnO$_3$ ($0 \leq x \leq 0.5$) was prepared under
high pressure and the variations with $x$ of its structural, magnetic,
electrical properties and the polarized Raman spectra were investigated. The
lattice parameters change systematically with $x$. Although there are strong
indications for increasing disorder above $x = 0.20$, the average structure
remains orthorhombic in the whole substitutional range. Ca doping increases
conductivity, but temperature dependence of resistivity $\rho$(T) remains
semiconducting for all $x$. The average magnetic exchange interaction changes
from antiferromagnetic for $x < 0.08$ to ferromagnetic for $x > 0.08$. The
evolution with $x$ of the Raman spectra provides evidence for increasingly
disordered oxygen sublattice at $x \geq 0.10$, presumably due to quasistatic
and/or dynamical Jahn-Teller distortions.",0408360v1
2004-09-08,Evidence for charge Kondo effect in superconducting Tl-doped PbTe,"We report results of low-temperature thermodynamic and transport measurements
of Pb_{1-x}Tl_{x}Te single crystals for Tl concentrations up to the solubility
limit of approximately x = 1.5%. For all doped samples, we observe a
low-temperature resistivity upturn that scales in magnitude with the Tl
concentration. The temperature and field dependence of this upturn are
consistent with a charge Kondo effect involving degenerate Tl valence states
differing by two electrons, with a characteristic Kondo temperature T_K ~ 6 K.
The observation of such an effect supports an electronic pairing mechanism for
superconductivity in this material and may account for the anomalously high T_c
values.",0409174v2
2004-09-08,Tailoring of ferromagnetic Pr0.85Ca0.15MnO3/ferroelectric Ba0.6Sr0.4TiO3 superlattices for multiferroic properties,"Superlattices composed of ferromagnetic Pr0.85Ca0.15MnO3 and ferroelectric
Ba0.6Sr0.4TiO3 layers were fabricated on (100) SrTiO3 substrates by a
pulsed-laser deposition method. The capacitance and resistive parts of the
samples were analyzed from the complex impedance measurements, performed on the
samples using a special experimental set-up. The superlattice with larger
ferroelectric thickness shows unique characteristics which are not present in
the parent ferromagnetic thin film. The superlattice show both ferromagnetic
and ferroelectric transitions which is an evidence for the coexistence of both
the properties. The high magnetoresistance (40 % at 80K) shown by the
superlattice can be attributed to the coupling between ferromagnetic and
ferroelectric layers, i.e, to the magnetoelectric effect.",0409182v1
2004-09-20,Effect of Joule heating in current-driven domain wall motion,"It was found that high current density needed for the current-driven domain
wall motion results in the Joule heating of the sample. The sample temperature,
when the current-driven domain wall motion occurred, was estimated by measuring
the sample resistance during the application of a pulsed-current. The sample
temperature was 750 K for the threshold current density of 6.7 x 10^11 A/m2 in
a 10 nm-thick Ni81Fe19 wire with a width of 240 nm. The temperature was raised
to 830 K for the current density of 7.5 x 10^11 A/m2, which is very close to
the Curie temperature of bulk Ni81Fe19. When the current density exceeded 7.5 x
10^11 A/m2, an appearance of a multi-domain structure in the wire was observed
by magnetic force microscopy, suggesting that the sample temperature exceeded
the Curie temperature.",0409494v1
2004-11-12,Observation of abrupt first-order metal-insulator transition in GaAs-based two-terminal device,"An abrupt first-order metal-insulator transition (MIT) as a jump of the
density of states is observed for Be doped GaAs, which is known as a
semiconductor, by inducing very low holes of approximately n_p=5x10^{14}
cm^{-3} into the valence band by the electric field; this is anomalous. In a
higher hole doping concentration of n_p=6x10^{16} cm^{-3}, the abrupt MIT is
not observed at room temperature, but measured at low temperature. A large
discontinuous decrease of photoluminescence intensity at 1.43 eV energy gap and
a negative differential resistance are also observed as further evidence of the
MIT. The abrupt MIT does not undergo a structural phase transition and is
accompanied with inhomogeneity. The upper limit of the temperature allowing the
MIT is deduced to be approximately 440K from experimental data. The abrupt MIT
rather than the continuous MIT is intrinsic and can explain the ""breakdown""
phenomenon (unsolved problem) incurred by a high electric field in
semiconductor devices.",0411328v2
2004-11-13,Large magnetoresistance anomalies in Dy7Rh3,"The compound Dy7Rh3 ordering antiferromagnetically below (TN=) 59 K has been
known to exhibit a temperature (T) dependent electrical resistivity (rho)
behavior in the paramagnetic state unusual for intermetallic compounds in the
sense that there is a broad peak in rho(T) in the paramagnetic state (around
130 K) as though there is a semi-conductor to metal transition. In addition,
there is an upturn below T_N due to magnetic super-zone gap effects. Here we
report the influence of external magnetic field (H) on the rho(T) behavior of
this compound below 300 K. The rise of rho(T) found below TN could be
suppressed at very high fields (>> 60 kOe), thus resulting in a very large
magnetoresistance (MR) in the magnetically ordered state. The most notable
finding is that the magnitude of MR is large for moderate applications of H
(say 80 kOe) in a temperature range far above T_N as well, which is untypical
of intermetallic compounds. Thus, this compound is characterized by large MR
anomalies in the entire T range of investigation.",0411360v1
2004-11-24,"Large magnetoresistance in the magnetically ordered state as well as in the paramagnetic state near 300 K in an intermetallic compound,Gd7Rh3","We report the response of electrical resistivity $\rho$ to the application of
magnetic fields (H) up to 140 kOe in the temperature interval 1.8-300 K for the
compound, Gd7Rh3, ordering antiferromagnetically below 150 K. We find that
there is an unusually large decrease of $\rho$ for moderate values of H in the
close vicinity of room temperature uncharacteristic of paramagnets, with the
magnitude of the magnetoresistance increasing with decreasing temperature as
though the spin-order contribution to $\rho$ is temperature dependent. In
addition, this compound exhibits giant magnetoresistance behaviour at rather
high temperatures (above 77 K) in the magnetically ordered state due to a
metamagnetic transition.",0411608v1
2005-04-05,Coherent transport in homojunction between excitonic insulator and semimetal,"From the solution of a two-band model, we predict that the thermal and
electrical transport across the junction of a semimetal and an excitonic
insulator will exhibit high resistance behavior and low entropy production at
low temperatures, distinct from a junction of a semimetal and a normal
semiconductor. This phenomenon, ascribed to the dissipationless exciton flow
which dominates over the charge transport, is based on the much longer length
scale of the change of the effective interface potential for electron
scattering due to the coherence of the condensate than in the normal state.",0504121v1
2005-04-25,Impurity scattering and quantum confinement in giant magnetoresistance systems,"Ab initio calculations for the giant magnetoresistance (GMR) in Co/Cu, Fe/Cr,
and Fe/Au multilayers are presented. The electronic structure of the
multilayers and the scattering potentials of point defects therein are
calculated self-consistently. Residual resistivities are obtained by solving
the quasi-classical Boltzmann equation including the electronic structure of
the layered system, the anisotropic scattering cross sections derived by a
Green's function method and the vertex corrections. Furthermore, the influence
of scattering centers at the interfaces and within the metallic layers is
incorporated by averaging the scattering cross sections of different impurities
at various sites. An excellent agreement of experimental and theoretical
results concerning the general trend of GMR in Co/Cu systems depending on the
type and the position of impurities is obtained. Due to the quantum confinement
in magnetic multilayers GMR can be tailored as a function of the impurity
position. In Co/Cu and Fe/Au systems impurities in the magnetic layer lead to
high GMR values, whereas in Fe/Cr systems defects at the interfaces are most
efficient to increase GMR.",0504634v1
2005-05-16,Novel procedure to prepare cadmium stannate films using spray pyrolysis technique for solar cell applications,"Thin films of cadmium stannate was prepared using low cost cadmium acetate
and tin (II) chloride precursors by spray pyrolysis technique at three
different substrate temperatures of 400, 450 and 5000 C. A novel procedure of
simultaneously forming additional layer, introduced for the first time in this
work, on the already coated cadmium stannate film reduced the sheet resistance
from 160 ohms/sq to 15 ohms/sq. Further, it is identified that the formation of
additional layer does not affect the structural and optical properties of the
cadmium stannate films, but improves the electrical property; thus the
formation of additional layer seems to be an effective alternate for annealing
the films at high temperature in the presence of Ar, CdS, Ar/CdS mixture,
hydrogen or nitrogen to improve the structural, electrical and optical
properties of the cadmium stannate films as has been reported in the
literature. The maximum optical transmittance value of the prepared cadmium
stannate film is about 99.8 % and the optical band gap energy value is about
2.9 eV.",0505383v1
2005-05-30,Mechanisms limiting the coherence time of spontaneous magnetic oscillations driven by DC spin-polarized currents,"The spin-transfer torque from a DC spin-polarized current can generate
highly-coherent magnetic precession in nanoscale magnetic-multilayer devices.
By measuring linewidths of spectra from the resulting resistance oscillations,
we argue that the coherence time can be limited at low temperature by thermal
deflections about the equilibrium magnetic trajectory, and at high temperature
by thermally-activated transitions between dynamical modes. Surprisingly, the
coherence time can be longer than predicted by simple macrospin simulations.",0505733v2
2005-06-05,On the unusual behavior of nitride compounds,"This report presents consistent insight into the mechanism behind the unusual
behavior of nitride compounds from the perspective of tetrahedron bond
formation and its consequence on valence density of states. An extension of the
recent bond-band-barrier (BBB) correlation mechanism for oxidation [Sun CQ,
Prog Mater Sci 2003;48:521-685] to the electronic process of nitridation has
led to the essentiality of sp-orbital hybridization for a nitrogen atom upon
interacting with atoms in solid phase of arbitrary less-electronegative
element. In the process of nitridation, a nitrogen atom forms a
quasi-tetrahedron with surrounding host atoms through bonding and nonbonding
interaction associated with production of electronic holes and antibonding
dipoles, which add corresponding density of states to the valence band of the
host. It is suggested that the valance alteration of the system takes the
responsibility for the blue shift in photoluminescence, lowered work function
for cold cathode field emission, corrosion and wear resistant, high elasticity,
and magnetic modulation as well.",0506109v1
2005-06-10,"Anisotropic Magnetoresistance and Magnetic Anisotropy in High-quality (Ga,Mn)As Films","We have performed a systematic investigation of magnetotransport of a series
of as-grown and annealed Ga1-xMnxAs samples with 0.011 <= x <= 0.09. We find
that the anisotropic magnetoresistance (AMR) generally decreases with
increasing magnetic anisotropy, with increasing Mn concentration and on low
temperature annealing. We show that the uniaxial magnetic anisotropy can be
clearly observed from AMR for the samples with x >= 0.02. This becomes the
dominant anisotropy at elevated temperatures, and is shown to rotate by 90o on
annealing. We find that the in-plane longitudinal resistivity depends not only
on the relative angle between magnetization and current direction, but also on
the relative angle between magnetization and the main crystalline axes. The
latter term becomes much smaller after low temperature annealing. The planar
Hall effect is in good agreement with the measured AMR indicating the sample is
approximately in a single domain state throughout most of the magnetisation
reversal, with a two-step magnetisation jump ascribed to domain wall nucleation
and propagation.",0506250v1
2005-06-14,The O-M-O triatomic molecule: Basic unit of cuprates & manganates,"The O(oxygen)-M(metal)-O(oxygen) molecule is a basic unit of high-temperature
superconducting cuprates and colossal magnetoresistance exhibiting manganates.
This molecule can be regarded either as an element of a linear chain or as an
ingredient of the corresponding cuprate or manganate lattice. The symmetry of
the unit being different in the two approaches, group theory imposes different
limitations on conceivable vibrational modes and atomic otbitals that control
its transport and optical properties. We now calculate the electron hopping
energies along Cu(P0-O(A) bonds, sites for nonlocal electron-vibrational mode
coupling. We find the electric transport along the O(A)-Cu(P)-O(A) molecule
dominated by scattering from bond polarons which is reflected in the two-branch
character of the temperature dependence of its electric resistance.",0506308v1
2005-09-27,Critical currents and vortex dynamics in percolative superconductors containing fractal clusters of a normal phase,"The effect of fractal clusters on magnetic and transport properties of
percolative superconductors is considered. The superconductor contains
percolative superconducting cluster, carrying a transport current, as well as
clusters of a normal phase, which act as pinning centers. A prototype of such a
structure is a high-temperature superconducting wire. It is found that
normal-phase clusters can have fractal features that affect the vortex
dynamics. The fractal dimension of the normal-phase cluster boundary in YBCO
films is estimated. Depinning and transport of vortices in fractal
superconducting structures are investigated. The current-voltage
characteristics of superconductors containing fractal clusters are obtained.
Dependencies of free vortex density on the fractal dimension as well as the
resistance on the transport current are studied. It is found that the
fractality of the cluster boundary intensifies pinning. This feature enables
the current-carrying capability of a superconductor to be enhanced without
changing of its chemical composition.",0509701v1
2005-10-18,Surface Roughness and Hydrodynamic Boundary Conditions,"We report results of investigations of a high-speed drainage of thin aqueous
films squeezed between randomly nanorough surfaces. A significant decrease in
hydrodynamic resistance force as compared with predicted by Taylor's equation
is observed. However, this reduction in force does not represents the slippage.
The measured force is exactly the same as that between equivalent smooth
surfaces obeying no-slip boundary conditions, but located at the intermediate
position between peaks and valleys of asperities. The shift in hydrodynamic
thickness is shown to be independent on the separation and/or shear rate. Our
results disagree with previous literature data reporting very large and
shear-dependent boundary slip for similar systems.",0510462v2
2005-10-20,Current-driven magnetization switching in CoFeB/MgO/CoFeB magnetic tunnel junctions,"Current-driven magnetization switching in low-resistance
Co40Fe40B20/MgO/Co40Fe40B20 magnetic tunnel junctions (MTJs) is reported. The
critical-current densities Jc required for current-driven switching in samples
annealed at 270C and 300C are found to be as low as 7.8 x 10^5 A/cm^2 and 8.8 x
10^5 A/cm^2 with accompanying tunnel magnetoresistance (TMR) ratios of 49% and
73 %, respectively. Further annealing of the samples at 350C increases TMR
ratio to 160 %, while accompanying Jc increases to 2.5 x 10^6 A/cm^2. We
attribute the low Jc to the high spin-polarization of tunnel current and small
MsV product of the CoFeB single free layer, where Ms is the saturation
magnetization and V the volume of the free layer.",0510538v1
2006-02-13,Doping of Ce in T-La2CuO4: Rigorous test for electron-hole symmetry for high-Tc superconductivity,"We report that Ce doping was achieved in La2CuO4 with the K2NiF4 (T)
structure for the first time by molecular beam epitaxy. A synthesis temperature
of as low as ~ 630C and an appropriate substrate choice, i.e., (001)LaSrGaO4 (a
\~ 3.843 A), enebled us to incorporate Ce into K2NiF4 lattice and to obtain
Ce-doped T-La2-xCexCuO4 up to x ~ 0.06. The doping of Ce makes T-La2CuO4 more
insulating, which is in sharp contrast to Sr (or Ba) doping in T-La2CuO4, which
make the compound metallic and superconducting. The observed smooth increase in
resistivity from the hole-doped side (T-La2-xSrxCuO4) to the electron-doped
side (T-La2-xCexCuO4) indicates that the electron-hole symmetry is broken in
the T-phase materials.",0602303v1
2006-03-02,Coupled dynamics of electrons and phonons in metallic nanotubes: current saturation from hot phonons generation,"We show that the self-consistent dynamics of both phonons and electrons is
the necessary ingredient for the reliable description of the hot phonons
generation during electron transport in metallic single-wall carbon nanotubes
(SWNTs). We solve the coupled Boltzmann transport equations to determine in a
consistent way the current vs. voltage (IV) curve and the phonon occupation in
metallic SWNTs which are lying on a substrate. We find a good agreement with
measured IV curves and we determine an optical phonon occupation which
corresponds to an effective temperature of several thousands K (hot phonons),
for the voltages typically used in experiments. We show that the high-bias
resistivity strongly depends on the optical phonon thermalization time. This
implies that a drastic improvement of metallic nanotubes performances can be
achieved by increasing the coupling of the optical phonons with a
thermalization source.",0603046v1
2006-03-05,Electro-Thermal Transport in Metallic Single-Wall Carbon Nanotubes for Interconnect Applications,"This work represents the first electro-thermal study of metallic single-wall
carbon nanotubes (SWNTs) for interconnect applications. Experimental data and
careful modeling reveal that self-heating is of significance in short (1 < L <
10 um) nanotubes under high-bias. The low-bias resistance of micron scale SWNTs
is also found to be affected by optical phonon absorption (a scattering
mechanism previously neglected) above 250 K. We also explore length-dependent
electrical breakdown of SWNTs in ambient air. Significant self-heating in SWNT
interconnects can be avoided if power densities per unit length are limited to
less than 5 uW/um.",0603110v1
2006-03-24,Single-crystalline nanopillars for spin-transfer measurements,"We report on current-induced magnetization switching (CIMS) in single-
crystalline nanopillars. Fe(14 nm)/Cr(0.9 nm)/Fe(10 nm)/Ag(6 nm)/Fe(2 nm)
multilayers are deposited by molecular-beam epitaxy. The central Fe layer is
coupled to the thick one by interlayer exchange coupling over Cr. The topmost
Fe layer is decoupled (free layer). Nanopillars with 150 nm diameter are
prepared by optical and e-beam lithography. The opposite spin scattering
asymmetries of Fe/Cr and Fe/Ag interfaces enable us to observe CIMS at small
magnetic fields and opposite current polarity in a single device. At high
magnetic fields, step-like resistance changes are measured at positive currents
and are attributed to current-driven magnetic excitations.",0603662v1
2006-07-03,Knight shift detection using gate-induced decoupling of the hyperfine interaction in quantum Hall edge channels,"A method for the observation of the Knight shift in nanometer-scale region in
semiconductors is developed using resistively detected nuclear magnetic
resonance (RDNMR) technique in quantum Hall edge channels. Using a gate-induced
decoupling of the hyperfine interaction between electron and nuclear spins, we
obtain the RDNMR spectra with or without the electron-nuclear spin coupling. By
a comparison of these two spectra, the values of the Knight shift can be given
for the nuclear spins polarized dynamically in the region between the relevant
edge channels in a single two-dimensional electron system, indicating that this
method has a very high sensitivity compared to a conventional NMR technique.",0607028v1
2006-12-01,New Type Phase Transition of Li2RuO3 with Honeycomb Structure,"A new-type structural transition has been found in Li2RuO3 with honeycomb
lattice of edge-sharing RuO6-octahedra. With decreasing temperature T, the
electrical resistivity exhibits an anomalous increase at T=Tc~540 K, suggesting
the (metal to insulator)-like transition and the magnetic susceptibility also
shows a sharp decrease. Detailed structure analyses have revealed that the high
temperature space group C2/m changes to P21/m at Tc. The most striking fact is
that a significant reduction of the bond lengths is found between two of six
Ru-Ru pairs of the hexagon in the low temperature phase, indicating a new type
phase transition by the mechanism of the formation of molecular orbits of these
Ru-Ru pairs.",0612026v1
2006-12-26,Transport properties of n-type ultrananocrystalline diamond films,"We investigate transport properties of ultrananocrystalline diamond films for
a broad range of temperatures. Addition of nitrogen during plasma-assisted
growth increases the conductivity of ultrananocrystalline diamond films by
several orders of magnitude. We show that films produced at low concentration
of nitrogen in the plasma are very resistive and electron transport occurs via
a variable range hopping mechanism while in films produced at high nitrogen
concentration the electron states become delocalized and the transport
properties of ultrananocrystalline diamond films can be described using the
Boltzmann formalism. We discuss the critical concentration of carriers at which
the metal to insulator transition in ultrananocrystalline diamond films occurs
and compare our results with available experimental data.",0612633v1
2007-01-29,Parameters of the Dzyaloshinsky-Moriya type weak ferromagnetism for some perovskite compounds,"Compounds with distorted perovskite structure of the 4-f and 3-d transition
metals with the common formula LnTO3 (where Ln is rare-earth element, T is an
element from the Fe group) are the most multifold binary oxides of these two
groups elements. Wide range of stability for this structure allows the
realization of combinations of the Lanthanides with all the transition metals
except the Nickel. Quite interesting physical phenomena take place in these
oxides like charge and orbital ordering; relatively independent magnetic
lattices of the both metals; particular magnetic structures; high optical
indicators; giant magneto-resistance; peculiar dielectric and ferroelectric
properties etc. We have investigated the magnetic properties of pure ferrites
and chromium-based materials as well as of some mixed type oxides like
HoxTb1-xO3, HoMnxFe1-xO3, HoMnxCr1-xO3 and DyFexCr1-xO3.",0701708v1
2007-02-20,Organic small molecule field-effect transistors with Cytop(TM) gate dielectric: eliminating gate bias stress effects,"We report on organic field-effect transistors with unprecedented resistance
against gate bias stress. The single crystal and thin-film transistors employ
the organic gate dielectric Cytop(TM). This fluoropolymer is highly water
repellent and shows a remarkable electrical breakdown strength. The single
crystal transistors are consistently of very high electrical quality: near zero
onset, very steep subthreshold swing (average: 1.3 nF V/(dec cm2)) and
negligible current hysteresis. Furthermore, extended gate bias stress only
leads to marginal changes in the transfer characteristics. It appears that
there is no conceptual limitation for the stability of organic semiconductors
in contrast to hydrogenated amorphous silicon.",0702472v1
2007-02-25,Broadband dielectric microwave microscopy on $μ$m length scales,"We demonstrate that a near-field microwave microscope based on a transmission
line resonator allows imaging in a substantially wide range of frequencies, so
that the microscope properties approach those of a spatially-resolved impedance
analyzer. In the case of an electric probe, the broadband imaging can be used
in a direct fashion to separate contributions from capacitive and resistive
properties of a sample at length scales on the order of one micron. Using a
microwave near-field microscope based on a transmission line resonator we
imaged the local dielectric properties of a Focused Ion Beam (FIB) milled
structure on a high-dielectric-constant Ba_{0.6}Sr_{0.4}TiO_3 (BSTO) thin film
in the frequency range from 1.3 GHz to 17.4 GHz. The electrostatic
approximation breaks down already at frequencies above ~10 GHz for the probe
geometry used, and a full-wave analysis is necessary to obtain qualitative
information from the images.",0702573v1
2007-06-05,Structure-Property Relationship in the Ordered-Perovskite- Related Oxide Sr3.12Er0.88Co4O10.5,"Synchrotron X-ray diffraction patterns were measured and analyzed for a
polycrystalline sample of the room-temperature ferromagnet Sr3.12Er0.88Co4O10.5
from 300 to 650 K, from which two structural phase transitions were found to
occur successively. The higher-temperature transition at 509 K is driven by
ordering of the oxygen vacancies, which is closely related to the metallic
state at high temperatures. The lower-temperature transition at 360 K is of
first order, at which the ferromagnetic state suddenly appears with exhibiting
a jump in magnetization and resistivity. Based on the refined structure,
possible spin and orbital models for the magnetic order are proposed.",0706.0605v2
2007-08-14,Origin of the Non-Linear Pressure Effects in Perovskite Manganites: Buckling of Mn-O-Mn Bonds and Jahn-Teller Distortion of the MnO6 Octahedra Induced by Pressure,"High-pressure resistivity and x-ray diffraction have been measured on
La0.85MnO3-d. At low pressures the metal-insulator transition temperature (TMI)
increases linearly with pressure up to a critical pressure, P* ~ 3.4 GPa, which
is followed by reduction of TMI with increasing pressure. Analysis of the bond
distances and bond angles reveal that a bandwidth increase drives the in-crease
of TMI for pressure below P*. The reduction of TMI at higher pressures is found
to result from Jahn-Teller distortions of the MnO6 octahedra. The role of
anharmonic interatomic potential is discussed.",0708.1963v2
2007-08-15,Insulator to semiconductor transition and magnetic properties of the one-dimensional S = 1/2 system In_2VO_5,"We report structural, magnetization, electrical resistivity and nuclear- and
electron spin resonance data of the complex transition metal oxide In_2VO_5 in
which structurally well-defined V-O chains are realized. An itinerant character
of the vanadium d-electrons and ferromagnetic correlations, revealed at high
temperatures, are contrasted with the insulating behavior and predominantly
antiferromagnetic exchange between the localized V^{4+} S = 1/2-magnetic
moments which develop below a certain characteristic temperature T* ~ 120 K.
Eventually the compound exhibits short-range magnetic order at $T_SRO ~ 20 K.
We attribute this crossover occurring around T* to the unusual anisotropic
thermal contraction of the lattice which changes significantly the overlap
integrals and the character of magnetic intra- and interchain interactions.",0708.2088v1
2007-11-15,Recrystallization of glass: homogeneous vs. heterogeneous nucleation in La(0.5)Ca(0.5)MnO3,"We probe through magnetization and resistivity measurements a kinetically
arrested glass-like but long-range ordered magnetic state. The transformation
kinetics of the magnetic field-temperature induced broad first-order transition
from ferromagnetic-metallic (FMM) to antiferromagnetic-insulating (AFI) state
gets hindered at low temperature in a La(0.5)Ca(0.5)MnO3 sample. A fraction of
high-temperature FMM phase persists to the lowest temperature, albeit as a
non-ergodic state. We present a phenomenology for this glass-like but
long-range order FMM phase which devitrifies on heating and converts to
equilibrium AFI phase. The residual kinetically arrested FMM phase can be
`recrystallized' to AFI state by annealing and more efficiently by successive
annealing, presumably by heterogeneous nucleation. This glass-like state shows
a stimulating feature that when the fraction of glass is larger the
`recrystallization' is easier.",0711.2347v1
2007-11-28,Radiation Damage in Polarized Ammonia Solids,"Solid NH3 and ND3 provide a highly polarizable, radiation resistant source of
polarized protons and deuterons and have been used extensively in high
luminosity experiments investigating the spin structure of the nucleon. Over
the past twenty years, the UVA polarized target group has been instrumental in
producing and polarizing much of the material used in these studies, and many
practical considerations have been learned in this time. In this discussion, we
analyze the polarization performance of the solid ammonia targets used during
the recent JLab Eg4 run. Topics include the rate of polarization decay with
accumulated charge, the annealing procedure for radiation damaged targets to
recover polarization, and the radiation induced change in optimum microwave
frequency used to polarize the sample. We also discuss the success we have had
in implementing frequency modulation of the polarizing microwave frequency.",0711.4413v1
2008-03-06,Field emission from single multi-wall carbon nanotubes,"Electron field emission characteristics of individual multiwalled carbon
nanotubes have been investigated by a piezoelectric nanomanipulation system
operating inside a scanning electron microscopy chamber. The experimental setup
ensures a high control capability on the geometric parameters of the field
emission system (CNT length, diameter and anode-cathode distance). For several
multiwalled carbon nanotubes, reproducible and quite stable emission current
behaviour has been obtained with a dependence on the applied voltage well
described by a series resistance modified Fowler-Nordheim model. A turn-on
field of about 30 V/um and a field enhancement factor of around 100 at a
cathode-anode distance of the order of 1 um have been evaluated. Finally, the
effect of selective electron beam irradiation on the nanotube field emission
capabilities has been extensively investigated.",0803.0810v1
2008-04-10,Electronic properties and phase transitions in low-dimensional semiconductors,"We present the first review of the current state of the literature on
electronic properties and phase transitions in TlX and TlMX2 (M = Ga, In; X =
Se, S, Te) compounds. These chalcogenides belong to a family of the
low-dimensional semiconductors possessing chain or layered structure. They are
of significant interest because of their highly anisotropic properties, semi-
and photoconductivity, non-linear effects in their I-V characteristics
(including a region of negative differential resistance), switching and memory
effects, second harmonic optical generation, relaxor behavior and potential
applications for optoelectronic devices. We review the crystal structure of TlX
and TlMX2 compounds, their transport properties under ambient conditions,
experimental and theoretical studies of the electronic structure, transport
properties and semiconductor-metal phase transitions under high pressure, and
sequences of temperature-induced structural phase transitions with intermediate
incommensurate states. Electronic nature of the ferroelectric phase transitions
in the above-mentioned compounds, as well as relaxor behavior, nanodomains and
possible occurrence of quantum dots in doped and irradiated crystals is
discussed.",0804.1639v2
2008-04-23,Superconductivity at 53.5 K in GdFeAsO1-delta,"Here we report the fabrication and superconductivity of the iron-based
arsenic-oxide GdFeAsO1-delta compound with oxygen-deficiency, which has an
onset resistivity transition temperature at 53.5 K. This material has a same
crystal structure as the newly discovered high-Tc ReFeAsO1-delta family (Re =
rare earth metal) and a further reduced crystal lattice, while the Tc starts to
decrease compared with the SmFeAsO1-delta system.",0804.3727v3
2008-05-28,Effect of pressure on the superconducting critical temperature of La[O_{0.89}F_{0.11}]FeAs and Ce[O_{0.88}F_{0.12}]FeAs,"We have performed several high-pressure resistivity experiments on the
recently discovered superconductors La[O_{0.89}F_{0.11}]FeAs and
Ce[O_{0.88}F_{0.12}]FeAs. At ambient pressure, these materials have
superconducting onset temperatures T_c of 28 K and 44 K, respectively. While
the T_c of La[O_{0.89}F_{0.11}]FeAs goes through a maximum between 10-68 kbar,
in qualitative agreement with a recent report by Takahashi et al., the T_c of
Ce[O_{0.88}F_{0.12}]FeAs decreases monotonically over the measured pressure
range. At 265 kbar, the T_c of the cerium-based compound has been suppressed
below 1.1 K.",0805.4372v3
2008-06-18,UV-photon and electrically driven resistance switching in ZnO nanotube arrays,"Vertically aligned ZnO nanotube arrays fabricated on an ITO substrate are
found to exhibit strong persistent photoconductivity (PPC) effect and
electrically driven conductance switching behavior, though the latter shows a
gradual decay from high conductance state to a low conductance state. Unlike
the electrical switching, the PPC cannot be reset or reversed by an electrical
pulse. Excitation wavelength dependent conductance measurement indicates the
presence of the defect localized states (DLS) ~ 240meV above the valence band
edge, in support of the hypothesis that the doubly ionization of these DLS are
responsible for the PPC effect.",0806.2907v2
2008-06-20,Ferromagnetic spin fluctuation in LaFeAsO1-xFx,"The F doped LaFeAsO, a recently discovered superconductor with the high Tc of
26 K, has been studied by the resistivity, magnetic susceptibility, and heat
capacity measurements in the F doping range from 0 to 0.14 (x in LaFeAsO1-xFx).
In the low temperature region, a T3lnT term in the heat capacity and a T2 term
in the magnetic susceptibility, which are derived from the spin fluctuation,
are observed. The nearly ferromagnetic nature evidenced by a large Wilson ratio
(6.5 for x = 0, and 11.2 for x = 0.025) suggests that the superconductivity in
the LaFeAsO system is mediated by ferromagnetic spin fluctuation.",0806.3304v1
2008-06-27,Magnetoresistance oscillations and relaxation effects at the SrTiO3-LaAlO3 interface,"We present low-temperature and high-field magnetotransport data on
SrTiO3-LaAlO3 interfaces. The resistance shows hysteresis in magnetic field and
a logarithmic relaxation as a function of time. Oscillations in the
magnetoresistance are observed, showing a square root periodicity in the
applied magnetic field, both in large-area unstructured samples as well as in a
structured sample. An explanation in terms of a commensurability condition of
edge states in a highly mobile two-dimensional electron gas between substrate
step edges is suggested.",0806.4450v1
2008-07-24,Fishtail effect and the vortex phase diagram of single crystal Ba0.6K0.4Fe2As2,"By measuring the magnetization hysteresis loops of superconducting
Ba0.6K0.4Fe2As2 single crystals, we obtained the high upper critical field and
large current carrying ability, which point to optimistic applications. The
fishtail (or second peak) effect is also found in the material, and the
position of the vortex pinning force shows a maximum at 1/3 of the reduced
field, being consistent with the picture of vortex pinning by small size normal
cores in the sample. Together with the resistive measurements, for the first
time the vortex phase diagram is obtained for superconductor Ba0.6K0.4Fe2As2.",0807.3786v3
2008-07-25,Adaptation of the Bridgman anvil cell to liquid pressure mediums,"The advantage of Bridgman anvil pressure cells is their wide pressure range
and the large number of wires which can be introduced into the pressure
chamber. In these pressure cells soft solid pressure mediums like steatite are
used. We have succeeded in adapting the Bridgman cell to liquid pressure
mediums. With this breakthrough it is now possible to measure in very good
hydrostatic pressure conditions up to 7 GPa, which is about twice the pressure
attainable in piston-cylinder cells. The pressure gradient in the cell,
estimated from the superconducting transition width of lead, is reduced by a
factor of five in the liquid medium with respect to steatite. By the use of
non-magnetic materials for the anvils and the clamp and due to the small
dimensions of the latter, our device is specially suitable for
magneto-transport measurements in dilution fridges. This pressure cell has been
developed to measure very fragile and brittle samples like organic conductors.
Resistivity measurements of (TMTTF)2BF4 performed in a solid and liquid
pressure medium demonstrate the necessity of hydrostatic pressure conditions
for the study of organic conductors at high pressures.",0807.4137v1
2008-08-15,"Localization and the Anomalous Hall Effect in a ""Dirty"" Metallic Ferromagnet","We report magnetoresistance measurements over an extensive temperature range
(0.1 K $\leq T \leq$ 100 K) in a disordered ferromagnetic semiconductor (\gma).
The study focuses on a series of metallic \gma~ epilayers that lie in the
vicinity of the metal-insulator transition ($k_F l_e\sim 1$). At low
temperatures ($T < 4$ K), we first confirm the results of earlier studies that
the longitudinal conductivity shows a $T^{1/3}$ dependence, consistent with
quantum corrections from carrier localization in a ``dirty'' metal. In
addition, we find that the anomalous Hall conductivity exhibits universal
behavior in this temperature range, with no pronounced quantum corrections. We
argue that observed scaling relationship between the low temperature
longitudinal and transverse resistivity, taken in conjunction with the absence
of quantum corrections to the anomalous Hall conductivity, is consistent with
the side-jump mechanism for the anomalous Hall effect. In contrast, at high
temperatures ($T \gtrsim 4$ K), neither the longitudinal nor the anomalous Hall
conductivity exhibit universal behavior, indicating the dominance of inelastic
scattering contributions down to liquid helium temperatures.",0808.2079v2
2008-08-22,Phase Coherence Effects in the Vortex Transport Entropy,"Nernst and electrical resistivity measurements in superconducting YBCO and
BSCCO with and without columnar defects show a distinctive thermodynamics of
the respective liquid vortex matter. At a field dependent high temperature
region in the phase diagram the Nernst signal is independent of structural
defects in both materials. At lower temperatures, in YBCO, defects contribute
only to the vortex mobility and the transport entropy is that of a system of
vortex lines. The transition to lower temperatures in BSCCO has a different
origin, the maximum in the Nernst signal when decreasing temperature is not
associated with transport properties but with the entropy behavior of pancake
vortices in the presence of structural defects.",0808.3015v1
2009-02-05,Itinerant antiferromagnetism in BaCr$_2$As$_2$,"We report single crystal synthesis, specific heat and resistivity
measurements and electronic structure calculations for BaCr$_2$As$_2$. This
material is a metal with itinerant antiferromagnetism, similar to the parent
phases of Fe-based high temperature superconductors, but differs in magnetic
order. Comparison of bare band structure density of states and the low
temperature specific heat implies a mass renormalization of $\sim$ 2.
BaCr$_2$As$_2$ shows stronger transition metal - pnictogen covalency than the
Fe compounds, and in this respect is more similar to BaMn$_2$As$_2$. This
provides an explanation for the observation that Ni and Co doping is effective
in the Fe-based superconductors, but Cr or Mn doping is not.",0902.0945v2
2009-04-05,Superconductivity in Ir-doped LaFe1-xIrxAsO,"We report the realization of superconductivity by 5d element Ir doping in
LaFeAsO, a prototype parent compound of high-temperature iron based
superconductors. X-ray diffraction patterns indicate that the material has
formed the ZrCuSiAs-type structure with a space group P4/nmm. The systematic
evolution of the lattice constants demonstrated that the Fe ions were
successfully replaced by the Ir. Both electrical resistance and magnetization
measurements show superconductivity up to 11 K in LaFe1-xIrxAsO. The
superconducting transitions at different magnetic fields were also measured
yielding a slope of -dHc2/dT = 6.7 T / K near Tc, and the upper critical field
at zero K is found to be about 55 T. This is the first example of bulk
superconductivity induced by replacing the Fe sites with higher d-orbital
electrons in FeAs-1111 family, which should add more ingredients to the
underlying physics of the iron-based superconductors.",0904.0772v4
2009-04-06,Gap opening in the zeroth Landau level of graphene,"We have measured a strong increase of the low-temperature resistivity
$\rho_{xx}$ and a zero-value plateau in the Hall conductivity $\sigma_{xy}$ at
the charge neutrality point in graphene subjected to high magnetic fields up to
30 T. We explain our results by a simple model involving a field dependent
splitting of the lowest Landau level of the order of a few Kelvin, as extracted
from activated transport measurements. The model reproduces both the increase
in $\rho_{xx}$ and the anomalous $\nu=0$ plateau in $\sigma_{xy}$ in terms of
coexisting electrons and holes in the same spin-split zero-energy Landau level.",0904.0948v1
2009-07-09,Agglomeration and filtration of colloidal suspensions with DVLO interactions in simulation and experiment,"Cake filtration is a widely used solid-liquid separation process. However,
the high flow resistance of the nanoporous filter cake lowers the efficiency of
the process significantly. The structure and thus the permeability of the
filter cakes depend on the compressive load acting on the particles, the
particles size, and the agglomeration of the particles. The latter is
determined by the particle charge and the ionic strength of the suspension, as
described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. In this paper,
we propose a combined stochastic rotation dynamics (SRD) and molecular dynamics
(MD) methodology to simulate the cake formation. The simulations give further
insight into the dependency of the filter cakes' structure on the agglomeration
of the particles, which cannot be accessed experimentally. The permeability, as
investigated with lattice Boltzmann (LB) simulations of flow through the
discretized cake, depends on the particle size and porosity, and thus on the
agglomeration of the particles. Our results agree qualitatively with
experimental data obtained from colloidal boehmite suspensions.",0907.1551v2
2009-07-12,Vortex-like state observed in ferromagnetic contacts,"Point-contacts (PC) offer a simple way to create high current densities, 10^9
A/cm^2 and beyond, without substantial Joule heating. We have shown recently
(Nano Letters, 7 (2007) 927) that conductivity of nanosized PCs between a
normal and ferromagnetic metals exhibits bi-stable hysteretic states versus
both bias current and external magnetic field - the effect typical for
spin-valve structures. Here we report that apart from the bi-stable state a
third intermediate-resistance state is occasionally observed. We interpret this
state as due to a spin-vortex in the PC, nucleated either by Oersted field of
the bias current and/or by the circular geometry of PC. The observed
three-level-states in the PC conductivity testify that the interface spins are
both weakly coupled to the spins in the bulk and have depressed exchange
interaction within the surface layer.",0907.2027v2
2009-07-16,Dynamical correlations in electronic transport through a system of coupled quantum dots,"Current auto- and cross-correlations are studied in a system of two
capacitively coupled quantum dots. We are interested in a role of Coulomb
interaction in dynamical correlations, which occur outside the Coulomb blockade
region (for high bias). After decomposition of the current correlation
functions into contributions between individual tunneling events, we can show
which of them are relevant and lead to sub-/supper-Poissonian shot noise and
negative/positive cross-correlations. The results are differentiated for a weak
and strong inter-dot coupling. Interesting results are for the strong coupling
case when electron transfer in one of the channel is strongly correlated with
charge drag in the second channel. We show that cross-correlations are
non-monotonic functions of bias voltage and they are in general negative
(except some cases with asymmetric tunnel resistances). This is effect of local
potential fluctuations correlated by Coulomb interaction, which mimics the
Pauli exclusion principle.",0907.2879v1
2009-07-30,Solvothermal Reduction of Chemically Exfoliated Graphene Sheets,"Graphene has attracted much attention due to its interesting properties and
potential applications. Chemical exfoliation methods have been developed to
make graphene recently, aimed at large-scale assembly and applications such as
composites and Li ion batteries. Although efficient, the chemical exfoliation
methods involve oxidation of graphene and introduce defects in the as-made
sheets. Hydrazine reduction at 100 has shown to partially restore the structure
and conductance of graphite oxide. However, the reduced GO still shows strong
defect peaks in Raman spectra with higher resistivity than pristine graphene by
2 to 3 orders of magnitude. It is important to produce much less defective
graphene sheets than GO, and develop more effective graphene reduction.
Recently, we reported a mild exfoliation-reintercalation-expansion method to
form high-quality GS with higher conductivity and lower oxidation degree than
GO.5 Here, we present a 180 solvothermal reduction method for our GS and GO.
The solvothermal reduction is more effective than the earlier reduction methods
in lowering the oxygen and defect levels in GS, increasing the graphene
domains, and bringing the conductivity of GS close to pristine graphene. The
reduced GS possess the highest degree of pristinity among chemically derived
graphene.",0907.5417v1
2009-09-23,Intermediate-valence behavior of the transition-metal oxide CaCu$_3$Ru$_4$O$_{12}$,"The transition--metal oxide CaCu$_3$Ru$_4$O$_{12}$ with perovskite--type
structure shows characteristic properties of an intermediate--valence system.
The temperature--dependent susceptibility exhibits a broad maximum around $150
- 160$ K. At this temperature, neutron powder diffraction reveals a small but
significant volume change whereby the crystal structure is preserved. Moreover,
the temperature--dependent resistivity changes its slope. NMR Knight shift
measurements of Ru reveal a cross--over from high temperature paramagnetic
behavior of localized moments to itinerant band states at low temperatures.
Additional density--functional theory calculations can relate the structural
anomaly with the $d$--electron number. The different experimental and
calculational methods result in a mutually consistent description of
CaCu$_3$Ru$_4$O$_{12}$ as an intermediate--valent system in the classical sense
of having low--energy charge fluctuations.",0909.4208v1
2009-10-09,Observation of a d-wave nodal liquid in highly underdoped Bi_2Sr_2CaCu_2O_{8+δ},"We use angle resolved photoemission spectroscopy to probe the electronic
excitations of the non-superconducting state that exists between the
antiferromagnetic Mott insulator at zero doping and the superconducting state
at larger dopings in Bi_2Sr_2CaCu_2O_{8+\delta}. We find that this state is a
nodal liquid whose excitation gap becomes zero only at points in momentum
space. Despite exhibiting a resistivity characteristic of an insulator and the
absence of coherent quasiparticle peaks, this material has the same gap
structure as the d-wave superconductor. We observe a smooth evolution of the
spectrum across the insulator-to-superconductor transition, which suggests that
high temperature superconductivity emerges when quantum phase coherence is
established in a non-superconducting nodal liquid.",0910.1648v1
2009-10-26,Wafer-scale synthesis and transfer of graphene films,"We developed means to produce wafer scale, high-quality graphene films as
large as 3 inch wafer size on Ni and Cu films under ambient-pressure and
transfer them onto arbitrary substrates through instantaneous etching of metal
layers. We also demonstrated the applications of the large-area graphene films
for the batch fabrication of field-effect transistor (FET) arrays and
stretchable strain gauges showing extraordinary performances. Transistors
showed the hole and electron mobilities of the device of 1,100 cm2/Vs and 550
cm2/Vs at drain bias of -0.75V, respectively. The piezo-resistance gauge factor
of strain sensor was ~6.1. These methods represent a significant step toward
the realization of graphene devices in wafer scale as well as application in
optoelectronics, flexible and stretchable electronics.",0910.4783v1
2009-11-25,RETGEM with polyvinylchloride (PVC) electrodes,"This paper presents a new design of the RETGEM (Resistive Electrode Thick
GEM) based on electrodes made of a polyvinylchloride material (PVC). Our device
can operate with gains of 10E5 as a conventional TGEM at low counting rates and
as RPC in the case of high counting rates without of the transit to the violent
sparks. The distinct feature of present RETGEM is the absent of the metal
coating and lithographic technology for manufacturing of the protective
dielectric rms. The electrodes from PVC permit to do the holes by a simple
drilling machine. Detectors on a RETGEM basis could be useful in many fields of
an application requiring a more cheap manufacturing and safe operation, for
example, in a large neutrino experiments, in TPC, RICH systems.",0911.4807v1
2009-12-03,Atomic-scale patterning of hydrogen terminated Ge(001) by scanning tunneling microscopy,"In this paper we demonstrate atomic-scale lithography on hydrogen terminated
Ge(001. The lithographic patterns were obtained by selectively desorbing
hydrogen atoms from a H resist layer adsorbed on a clean, atomically flat
Ge(001) surface with a scanning tunneling microscope tip operating in
ultra-high vacuum. The influence of the tip-to-sample bias on the lithographic
process have been investigated. Lithographic patterns with feature-sizes from
200 nm to 1.8 nm have been achieved by varying the tip-to-sample bias. These
results open up the possibility of a scanning-probe lithography approach to the
fabrication of future atomic-scale devices in germanium.",0912.0754v1
2009-12-10,Highly Uniform 300 mm Wafer-Scale Deposition of Single and Multilayered Chemically Derived Graphene Thin Films,"The deposition of atomically thin highly uniform chemically derived graphene
(CDG) films on 300 mm SiO2/Si wafers is reported. We demonstrate that the very
thin films can be lifted off to form uniform membranes than can be
free-standing or transferred onto any substrate. Detailed maps of thickness
using Raman spectroscopy and atomic force microscopy (AFM) height profiles
reveal that the film thickness is very uniform and highly controllable, ranging
from 1-2 layers up to 30 layers. After reduction using a variety of methods,
the CDG films are transparent and electrically active with FET devices yielding
exceptionally high mobilities of ~ 15 cm2/Vs and sheet resistance of ~ 1 k
Ohm/sq at ~ 70 % transparency.",0912.2087v1
2009-12-21,Microstructure and superconductivity of Ir-doped BaFe2As2 superconductor,"Polycrystalline samples with nominal composition of Ba(Fe1-xIrx)2As2 (x=0.10,
0.15, and 0.20) were investigated by means of X-ray diffraction (XRD), scanning
electron microscopy (SEM), electrical resistivity, and magnetization
measurements. XRD and SEM results showed that almost single phase samples were
obtained. Bulk superconductivity with TC~28 K was observed in the x=0.10
sample. TC~28 K is the highest superconducting critical temperature among the
reported data for electron-doped AFe2As2-type (A=Ca, Sr, and Ba)
superconductors. The upper critical field Hc2(0) reaches as high as 65 T for
the x=0.10 sample. The underlying physics is discussed in connection with
Co-doping case.",0912.4113v1
2010-01-21,Photon assisted tunneling as an origin of the Dynes density of states,"We show that the effect of a high-temperature environment in current
transport through a normal metal-insulator-superconductor tunnel junction can
be described by an effective density of states (DOS) in the superconductor. In
the limit of a resistive low-ohmic environment, this DOS reduces into the
well-known Dynes form. Our theoretical result is supported by experiments in
engineered environments. We apply our findings to improve the performance of a
single-electron turnstile, a potential candidate for a metrological current
source.",1001.3853v3
2010-02-07,Time-Dependent Transport Through Molecular Junctions,"We investigate transport properties of molecular junctions under two types of
bias--a short time pulse or an AC bias--by combining a solution for the Green
functions in the time domain with electronic structure information coming from
ab initio density functional calculations. We find that the short time response
depends on lead structure, bias voltage, and barrier heights both at the
molecule-lead contacts and within molecules. Under a low frequency AC bias, the
electron flow either tracks or leads the bias signal (capacitive or resistive
response) depending on whether the junction is perfectly conducting or not. For
high frequency, the current lags the bias signal due to the kinetic inductance.
The transition frequency is an intrinsic property of the junctions.",1002.1441v1
2010-03-16,All Magnesium diboride Josephson Junctions with MgO and native oxide barriers,"We present results on all-MgB2 tunnel junctions, where the tunnel barrier is
deposited MgO or native-oxide of base electrode. For the junctions with MgO,
the hysteretic I-V curve resembles a conventional underdamped Josephson
junction characteristic with critical current-resistance product nearly
independent of the junction area. The dependence of the critical current with
temperature up to 20 K agrees with the [Ambegaokar and Baratoff, Phys. Rev.
Lett. 10, 486 (1963)] expression. For the junctions with native-oxide,
conductance at low bias exhibits subgap features while at high bias reveals
thick barriers. As a result no supercurrent was observed in the latter, despite
the presence of superconducting-gaps to over 30 K.",1003.3158v1
2010-03-31,Magneto-transport Effects in Topological Insulator Bi$_2$Se$_3$ Nanoribbons,"Magneto-resistance (MR) of Bi$_2$Se$_3$ nanoribbons is studied over a broad
range of temperature ($T$=300K-2K) and under various magnetic field ($B$)
orientations. The MR is strongly anisotropic with the perpendicular MR much
larger than the longitudinal and transverse MRs. The perpendicular MR exhibits
quadratic $B$-dependence in low fields and becomes linear at high $B$. However,
when $T$ increases, the perpendicular MR becomes linear over the whole magnetic
field range (0-9T) up to room temperature. This unusual linear MR is discussed
in the context of the linear quantum MR of the topological surface-states. We
also observe the boundary-scattering effect in MR at low temperatures, which
indicates that the out-of-plane Fermi momentum is much smaller the in-plane
Fermi momentum, excluding the simple three-dimensional Fermi surface picture.",1003.6099v4
2010-04-05,Hysteresis in the magneto-transport of Manganese-doped Germanium: evidence for carrier-mediated ferromagnetism,"We report the fabrication of Ge:Mn ferromagnetic semiconductors by Mn-ion
implantation into Ge followed by pulsed laser annealing. Benefiting from the
short time annealing, the hole concentration in Mn-implanted Ge has been
increased by two orders of magnitude from 10$^{18}$ to over 10$^{20}$
cm$^{-3}$. Likely due to the high hole concentration, we observe that the
longitudinal and Hall resistances exhibit the same hysteresis as the
magnetization, which is usually considered as a sign of carrier-mediated
ferromagnetism.",1004.0568v1
2010-04-21,"Effect of pressure on the magnetic, transport, and thermal-transport properties of the electron-doped manganite CaMn$_{1-x}$Sb$_{x}$O$_{3}$","We have demonstrated the effect of hydrostatic pressure on magnetic and
transport properties, and thermal transport properties in electron-doped
manganites CaMn$_{1-x}$Sb$_{x}$O$_{3}$. The substitution of Sb$^{5+}$ ion for
Mn $^{4+}$site of the parent matrix causes one-electron doping with the
chemical formula CaMn$^{4+}_{1-2x}$Mn$^{3+}_{x}$Sb$^{5+}_{x}$O$_{3}$
accompanied by a monotonous increase in unit cell volume as a function of $x$.
Upon increasing the doping level of Sb, the magnitudes of both electrical
resistivity and negative Seebeck coefficient are suppressed at high
temperatures, indicating the electron doping. Anomalous diamagnetic behaviors
at $x=0.05$ and 0.08 are clearly observed in field cooled dc magnetization. The
effect of hydrostatic pressure on dc magnetization is in contrast to the
chemical pressure effect due to Sb doping. The dynamical effect of ac magnetic
susceptibility measurement points to the formation of the magnetically
frustrated clusters such as FM clusters embedded in canted AFM matrix.",1004.3669v3
2010-05-06,Theoretical and Experimental Studies of Schottky Diodes That Use Aligned Arrays of Single Walled Carbon Nanotubes,"We present theoretical and experimental studies of Schottky diodes that use
aligned arrays of single walled carbon nanotubes. A simple physical model,
taking into account the basic physics of current rectification, can adequately
describe the single-tube and array devices. We show that for as grown array
diodes, the rectification ratio, defined by the
maximum-to-minimum-current-ratio, is low due to the presence of m-SWNT shunts.
These tubes can be eliminated in a single voltage sweep resulting in a high
rectification array device. Further analysis also shows that the channel
resistance, and not the intrinsic nanotube diode properties, limits the
rectification in devices with channel length up to ten micrometer.",1005.0870v1
2010-06-16,Perfect Domain-Lattice Matching Between MgB2 and Al2O3: Single-Crystal MgB2 Thin Films Grown on Sapphire,"We have found that single-crystal films can be grown on (0001) Al2O3
substrates through the golden relation of a perfect lattice-matching ratio
between the a-axis lattice constants of MgB2 and Al2O3. Selected area electron
diffraction patterns evidently indicate hexagonal MgB2 film with a 30 degrees
in-plane rotation with respect to the Al2O3 substrate. The films grown on Al2O3
show a zero-resistance transition temperature of 39.6 K with a transition width
of 0.1 K. The critical current density at zero field is comparable to the
depairing critical current density and rapidly decreases with increasing
applied field due to the lack of pinning sites, as observed for high-quality
MgB2 single crystals.",1006.3169v1
2010-07-01,Chip-scale nanofabrication of single spins and spin arrays in diamond,"We demonstrate a technique to nanofabricate nitrogen vacancy (NV) centers in
diamond based on broad-beam nitrogen implantation through apertures in electron
beam lithography resist. This method enables high-throughput nanofabrication of
single NV centers on sub-100 nm length scales. Secondary ion mass spectroscopy
(SIMS) measurements facilitate depth profiling of the implanted nitrogen to
provide three-dimensional characterization of the NV center spatial
distribution. Measurements of NV center coherence with on-chip coplanar
waveguides suggest a pathway for incorporating this scalable nanofabrication
technique in future quantum applications.",1007.0240v2
2010-08-04,Transport in gapped bilayer graphene: the role of potential fluctuations,"We employ a dual-gated geometry to control the band gap \Delta in bilayer
graphene and study the temperature dependence of the resistance at the charge
neutrality point, RNP(T), from 220 to 1.5 K. Above 5 K, RNP(T) is dominated by
two thermally activated processes in different temperature regimes and exhibits
exp(T3/T)^{1/3} below 5 K. We develop a simple model to account for the
experimental observations, which highlights the crucial role of localized
states produced by potential fluctuations. The high temperature conduction is
attributed to thermal activation to the mobility edge. The activation energy
approaches \Delta /2 at large band gap. At intermediate and low temperatures,
the dominant conduction mechanisms are nearest neighbor hopping and
variable-range hopping through localized states. Our systematic study provides
a coherent understanding of transport in gapped bilayer graphene.",1008.0783v1
2010-09-13,Cooper Pair Writing at the LaAlO3/SrTiO3 Interface,"The LaAlO3/SrTiO3 interface provides a unique platform for controlling the
electronic properties of the superconducting semiconductor SrTiO3. Prior
investigations have shown that two-dimensional superconductivity can be
produced at the LaAlO3/SrTiO3 interface and tuned electrostatically. The
recently demonstrated reversible control of the metal-insulator transition at
the same interface using conductive atomic force microscopy (c-AFM) raises the
question of whether this room-temperature technique can produce structures that
exhibit superconducting, normal metallic and insulating phases at sub-Kelvin
temperatures. Here we report low-temperature magnetotransport experiments on
conducting structures defined at an otherwise insulating LaAlO3/SrTiO3
interface. A quantum phase transition associated with the formation of Cooper
pairs is observed in these predefined structures at sub-Kelvin temperatures.
However, a finite resistance remains even at the lowest temperature. At higher
magnetic fields, interfaces with high mobility also exhibit strong Shubnikov-de
Haas oscillations as well as a larger Ginsburg-Landau coherence length. Cooper
pair localization, spin-orbit coupling, and finite-size effects may factor into
an explanation for some of the unusual properties observed.",1009.2424v2
2010-09-16,Overlapping-gate architecture for silicon Hall bar MOSFET devices in the low electron density regime,"We report the fabrication and study of Hall bar MOSFET devices in which an
overlapping-gate architecture allows four-terminal measurements of low-density
2D electron systems, while maintaining a high density at the ohmic contacts.
Comparison with devices made using a standard single gate show that
measurements can be performed at much lower densities and higher channel
resistances, despite a reduced peak mobility. We also observe a voltage
threshold shift which we attribute to negative oxide charge, injected during
electron-beam lithography processing.",1009.3109v1
2010-10-01,Contactless measurement of electrical conductance of a thin film of amorphous germanium,"We present a contactless method for measuring charge in a thin film of
amorphous germanium (a-Ge) with a nanoscale silicon MOSFET charge sensor. This
method enables the measurement of conductance of the a-Ge film even in the
presence of blocking contacts. At high bias voltage, the resistance of the
contacts becomes negligible and a direct measurement of current gives a
conductance that agrees with that from the measurement of charge. This
charge-sensing technique is used to measure the temperature- and
field-dependence of the conductance, and they both agree with a model of Mott
variable-range hopping. From the model, we obtain a density of states at the
Fermi energy of 1.6 x 10^18 eV^-1 cm^-3 and a localization length of 1.06 nm.
This technique enables the measurement of conductance as low as 10^-19 S.",1010.0045v1
2010-10-05,Optical property modification of ZnO: Effect of 1.2 MeV Ar irradiation,"We report a systematic study on 1.2 MeV Ar^8+ irradiated ZnO by x-ray
diffraction (XRD), room temperature photoluminescence (PL) and
ultraviolet-visible (UV-Vis) absorption measurements. ZnO retains its wurtzite
crystal structure up to maximum fluence of 5 x 10^16 ions/cm^2. Even, the width
of the XRD peaks changes little with irradiation. The UV-Vis absorption spectra
of the samples, unirradiated and irradiated with lowest fluence (1 x 10^15
ions/cm^2), are nearly same. However, the PL emission is largely quenched for
this irradiated sample. Red shift of the absorption edge has been noticed for
higher fluence. It has been found that red shift is due to at least two defect
centers. The PL emission is recovered for 5 x 10^15 ions/cm^2 fluence. The
sample colour is changed to orange and then to dark brown with increasing
irradiation fluence. Huge resistivity decrease is observed for the sample
irradiated with 5 x 10^15 ions/cm^2 fluence. Results altogether indicate the
evolution of stable oxygen vacancies and zinc interstitials as dominant defects
for high fluence irradiation.",1010.0753v1
2010-11-23,Transport in Graphene Tunnel Junctions,"We present a technique to fabricate tunnel junctions between graphene and Al
and Cu, with a Si back gate, as well as a simple theory of tunneling between a
metal and graphene. We map the differential conductance of our junctions versus
probe and back gate voltage, and observe fluctuations in the conductance that
are directly related to the graphene density of states. The conventional
strong-suppression of the conductance at the graphene Dirac point can not be
clearly demonstrated, but a more robust signature of the Dirac point is found:
the inflection in the conductance map caused by the electrostatic gating of
graphene by the tunnel probe. We present numerical simulations of our
conductance maps, confirming the measurement results. In addition, Al causes
strong n-doping of graphene, Cu causes a moderate p-doping, and in high
resistance junctions, phonon resonances are observed, as in STM studies.",1011.5067v1
2010-12-14,Reentrant spin-glass behavior in $TlFe_{2-x}Se_2$ with the $ThCr_2Si_2$-type structure,"We investigated the physical properties of $TlFe_{2-x}Se_2$ single crystals.
The resistivity of $TlFe_{2-x}Se_2$ shows typical semiconductor behavior with
an activation energy of 25 meV. DC susceptibility indicates an
antiferromagnetic transition at about 450 K. Reentrant spin-glass (RSG)
behavior was found at about 130 K through DC and AC magnetic measurements. The
RSG behavior suggests the existence of a strong competition between
ferromagnetic (FM) and antiferromagnetic (AFM) interactions due to Fe
deficiencies. Strong electron-electron correlation may exist in this material
and it is possibly a candidate of parent compound for high $T_c$
superconductors.",1012.2929v1
2010-12-23,Effect of chromium disorder on the thermoelectric properties of Layered-antiferromagnet CuCrS2,"Layered-antiferromagnetic compound CuCrS2 has been prepared by different
methods. The analysis of X-ray diffraction patterns of different samples gave
significant amount of vacancy-disorder of Cr-atoms within the layers. Extended
period of sintering above 9000C increases the transfer of Cr-atoms to the
interstitial sites between the layers. This disorder has marginal effect on the
Antiferromagnetic properties. The electrical conductivity is increased and the
thermoelectric power remains positive and quite high between 150-400\muV/K in
the paramagnetic state around room temperature with increase in disorder in
different samples. We interpret the temperature dependence of electrical
resistivity and thermoelectric power due to the localization of carriers by
interstitial defects and the formation of magnetic polarons in the paramagnetic
phase of CuCrS2.",1012.5147v1
2011-03-04,Giant enhancement of spin accumulation and long-distance spin precession in metallic lateral spin valves,"The nonlocal spin injection in lateral spin valves is highly expected to be
an effective method to generate a pure spin current for potential spintronic
application. However, the spin valve voltage, which decides the magnitude of
the spin current flowing into an additional ferromagnetic wire, is typically of
the order of 1 {\mu}V. Here we show that lateral spin valves with low resistive
NiFe/MgO/Ag junctions enable the efficient spin injection with high applied
current density, which leads to the spin valve voltage increased hundredfold.
Hanle effect measurements demonstrate a long-distance collective 2-pi spin
precession along a 6 {\mu}m long Ag wire. These results suggest a route to
faster and manipulable spin transport for the development of pure spin current
based memory, logic and sensing devices.",1103.0852v2
2011-03-23,Local Electrical Stress-Induced Doping and Formation of 2D Monolayer Graphene P-N Junction,"We demonstrated doping in 2D monolayer graphene via local electrical
stressing. The doping, confirmed by the resistance-voltage transfer
characteristics of the graphene system, is observed to continuously tunable
from N-type to P-type as the electrical stressing level (voltage) increases.
Two major physical mechanisms are proposed to interpret the observed phenomena:
modifications of surface chemistry for N-type doping (at low-level stressing)
and thermally-activated charge transfer from graphene to SiO2 substrate for
P-type doping (at high-level stressing). The formation of P-N junction on 2D
graphene monolayer is demonstrated with complementary doping based on locally
applied electrical stressing.",1103.4568v3
2011-03-25,Giant Positive Magnetoresistance in Co@CoO Nanoparticle Arrays,"We report the magnetotransport properties of self-assembled Co@CoO
nanoparticle arrays at temperatures below 100 K. Resistance shows thermally
activated behavior that can be fitted by the general expression of R
exp{(T/T0)^v}. Efros-Shklovskii variable range hopping (v=1/2) and simple
activation (hard gap, v=1) dominate the high and low temperature region,
respectively, with a strongly temperature-dependent transition regime in
between. A giant positive magnetoresistance of >1,400% is observed at 10K,
which decreases with increasing temperature. The positive MR and most of its
features can be explained by the Zeeman splitting of the localized states that
suppresses the spin dependent hopping paths in the presence of on-site Coulomb
repulsion.",1103.5029v1
2011-05-06,Optical excitation of Electron-Glasses,"Electron-glasses can be readily driven far from equilibrium by a variety of
means. Several mechanisms to excite the system and their relative merits are
reviewed. In this study we focus on the process of exciting electron-glasses by
interaction with near infrared radiation. The efficiency of this protocol
varies considerably among different electron-glasses, but it only weakly
depends on their resistance at liquid helium temperatures. A dramatic
enhancement of the excitation efficiency is observed upon doping crystalline
indium-oxide with Au. Some enhancement is observed also in samples doped with
Pb but this enhancement fades away with time unlike the situation in the
Au-doped samples. Several structural and analytical tools are used to
characterize the changes in the materials that may be responsible for these
effects. Possible routes by which high-frequency electromagnetic fields take
the system far from equilibrium are discussed.",1105.1350v1
2011-05-22,Evidence for a capacitor network near the metal insulator transition in VO2 thin films probed by in-plane impedance spectroscopy,"Impedance spectroscopy measurements were performed in high quality Vanadium
dioxide (VO2) thin films. This technique allows us investigate the resistive
and capacitive contribution to the dielectric response near the metal-insulator
transition (MIT). A non ideal RC behavior was found in our films from room
temperature up to 334 K. A decrease of the total capacitance was found in this
region, possibly due to interface effects. Above the MIT, the system behaves
like a metal as expected, and a modified equivalent circuit is necessary to
describe the impedance data adequately. Around the MIT, an increase of the
total capacitance is observed.",1105.4308v1
2011-05-24,Rectification at Graphene-Semiconductor Interfaces: Zero-Gap Semiconductor Based Diodes,"Using current-voltage (I-V) and capacitance-voltage (C-V) measurements, we
report on the unusual physics and promising technical applications associated
with the formation of Schottky barriers at the interface of a one-atom-thick
zero-gap semiconductor (graphene) and conventional semiconductors. When
chemical vapor deposited graphene is transferred onto n-type Si, GaAs, 4H-SiC
and GaN semiconductor substrates, there is a strong van der Waals attraction
that is accompanied by charge transfer across the interface and the formation
of a rectifying (Schottky) barrier. Thermionic emission theory in conjunction
with the Schottky-Mott model within the context of bond-polarization theory
provides a surprisingly good description of the electrical properties.
Applications, such as to sensors where in forward bias there is exponential
sensitivity to changes in the Schottky barrier height due to the presence of
absorbates on the graphene or to analogue devices for which Schottky barriers
are integral components are promising because of graphene's mechanical
stability, its resistance to diffusion, its robustness at high temperatures and
its demonstrated capability to embrace multiple functionalities.",1105.4811v2
2011-05-27,"Magnonic spin-transfer torque MRAM with low power, high speed, and error-free switching","A new class of spin-transfer torque magnetic random access memory (STT-MRAM)
is discussed, in which writing is achieved using thermally initiated magnonic
current pulses as an alternative to conventional electric current pulses. The
magnonic pulses are used to destabilize the magnetic free layer from its
initial direction, and are followed immediately by a bipolar electric current
exerting conventional spin-transfer torque on the free layer. The combination
of thermal and electric currents greatly reduces switching errors, and
simultaneously reduces the electric switching current density by more than an
order of magnitude as compared to conventional STT-MRAM. The energy efficiency
of several possible electro-thermal circuit designs have been analyzed
numerically. As compared to STT-MRAM with perpendicular magnetic anisotropy,
magnonic STT-MRAM reduces the overall switching energy by almost 80%.
Furthermore, the lower electric current density allows the use of thicker
tunnel barriers, which should result in higher tunneling magneto-resistance and
improved tunnel barrier reliability. The combination of lower power, improved
reliability, higher integration density, and larger read margin make magnonic
STT-MRAM a promising choice for future non-volatile storage.",1105.5473v1
2011-05-27,Temperature Dependence of the Intrinsic Anomalous Hall Effect in Nickel,"We investigate the unusual temperature dependence of the anomalous Hall
effect in Ni. By varying the thickness of the MBE-grown Ni films, the
longitudinal resistivity is uniquely tuned without resorting to doping
impurities; consequently, the intrinsic and extrinsic contributions are cleanly
separated out. In stark contrast to other ferromagnets such as Fe, the
intrinsic contribution in Ni is found to be strongly temperature dependent with
a value of 1100 (ohm*cm)^(-1) at low temperatures and 500 (ohm*cm)^(-1) at high
temperatures. This pronounced temperature dependence, a cause of long-standing
confusion concerning the physical origin of the AHE, is likely due to the small
energy level splitting caused by the spin orbit coupling close to the Fermi
surface. Our result helps pave the way for the general claim of the Berry-phase
interpretation for the AHE.",1105.5664v1
2011-05-31,Interplay between topological insulators and superconductors,"Topological insulators are insulating in the bulk but possess metallic
surface states protected by time-reversal symmetry. Here, we report a detailed
electronic transport study in high quality Bi2Se3 topological insulator thin
films contacted by superconducting (In, Al and W) electrodes. The resistance of
the film shows an abrupt and significant upturn when the electrodes become
superconducting. In turn, the Bi2Se3 film strongly weakens the
superconductivity of the electrodes, significantly reducing both their
transition temperatures and critical fields. A possible interpretation of these
results is that the superconducting electrodes are accessing the surface states
and the experimental results are the consequence of the interplay between the
Cooper pairs of the electrodes and the spin polarized current of the surface
states in Bi2Se3.",1105.6174v3
2011-06-04,Facile fabrication of lateral nanowire wrap-gate devices with improved performance,"We present a simple fabrication technique for lateral nanowire wrap-gate
devices with high capacitive coupling and field-effect mobility. Our process
uses e-beam lithography with a single resist-spinning step, and does not
require chemical etching. We measure, in the temperature range 1.5-250 K, a
subthreshold slope of 5-54 mV/decade and mobility of 2800-2500 $cm^2/Vs$ --
significantly larger than previously reported lateral wrap-gate devices. At
depletion, the barrier height due to the gated region is proportional to
applied wrap-gate voltage.",1106.0796v1
2011-06-04,Mechanochemical reaction in graphane under uniaxial tension,"The quantum-mechanochemical-reaction-coordinate simulations have been
performed to investigate the mechanical properties of hydrogen functionalized
graphene. The simulations disclosed atomically matched peculiarities that
accompany the deformation-failure-rupture process occurred in the body. A
comparative study of the deformation peculiarities related to equi-carbon-core
(5,5) nanographene and nanographane sheets exhibited a high stiffness of both
bodies that is provided by the related hexagon units, namely benzenoid and
cyclohexanoid, respectively. The two units are characterized by anisotropy in
the microscopic behavior under elongation along mechanochemical internal
coordinates when the later are oriented either along (zg) or normally (ach) to
the C-C bonds chain. The unit feature in combination with different
configuration of their packing with respect to the body C-C bond chains forms
the ground for the structure-sensitive mechanical behavior that is different
for zg and ach deformation modes. Hydrogenation of graphene drastically
influences behavior and numerical characteristics of the body making
tricotage-like pattern of the graphene failure less pronounced and inverting it
from the zg to ach mode as well as providing less mechanical resistance of
graphane it total.",1106.0837v2
2011-07-09,Huge Volume Expansion and Structural Transformation of Carbon Nanotube Aligned Arrays during Electrical Breakdown in Vacuum,"We observed a huge volume expansion of aligned single walled carbon nanotube
(SWNT) arrays accompanied by structural transformation during electrical
breakdown in vacuum. The SWNT arrays were assembled between prefabricated Pd
source and drain electrodes of 2 \mu m separation on Si/SiO_2 substrate via
dielectrophoresis. At high electrical field, the SWNT arrays erupt into large
mushroom-like structure. Systematic studies with controlled electrical bias
show that above a certain field SWNTs swell and transform to nanoparticles and
flower-like structures with small volume increase. Further increase in
electrical bias and repeated sweeping results into amorphous carbon as
determined from scanning and transmission electron microscopy (TEM). Cross
sectional studies using focused ion beam and TEM show the height of 2-3 nm SWNT
array increased to about 1 \mu m with a volume gain of ~ 400 times. The
electron energy loss spectroscopy reveals that graphitic sp^2 networks of SWNTs
are transformed predominantly to sp^3. The current-voltage measurements also
show an increase in the resistance of the transformed structure.",1107.1758v1
2011-07-20,Macroscopic Superconducting Current through a Silicon Surface Reconstruction with Indium Adatoms: Si(111)-(R7$\times$R3)-In,"Macroscopic and robust supercurrents are observed by direct electron
transport measurements on a silicon surface reconstruction with In adatoms
(Si(111)-(R7xR3)-In). The superconducting transition manifests itself as an
emergence of the zero resistance state below 2.8 K. $I-V$ characteristics
exhibit sharp and hysteretic switching between superconducting and normal
states with well-defined critical and retrapping currents. The two-dimensional
(2D) critical current density $J_\mathrm{2D,c}$ is estimated to be as high as
$1.8 \ \mathrm{A/m}$ at 1.8 K. The temperature dependence of $J_\mathrm{2D,c}$
indicates that the surface atomic steps play the role of strongly coupled
Josephson junctions.",1107.3902v2
2011-07-30,Indications of an Electronic Phase Transition in 2D YBa2Cu3O7-x Induced by Electrostatic Doping,"We successfully tuned an underdoped ultrathin YBa2Cu3O7-x film into the
overdoped regime by means of electrostatic doping using an ionic liquid as a
dielectric material. This process proved to be reversible. Transport
measurements showed a series of anomalous features compared to chemically doped
bulk samples and a different two-step doping mechanism for electrostatic doping
was revealed. The normal resistance increased with carrier concentration on the
overdoped side and the high temperature (180 K) Hall number peaked at a doping
level of p$\sim$0.15. These anomalous behaviors suggest that there is an
electronic phase transition in the Fermi surface around the optimal doping
level.",1108.0083v1
2011-08-01,Evolution of Structural and Physical Properties of Sr3(Ru1-xMnx)2O7 with Mn Concentration,"Layered ruthenates are prototype materials with strong structure-property
correlations. We report the structural and physical properties of
double-layered perovskite Sr3(Ru1-xMnx)2O7 single crystals with 0<=x<=0.7.
Single crystal x-ray diffraction refinements reveal that Mn doping on the Ru
site leads to the shrinkage of unit-cell volume and disappearance of (Ru/Mn)O6
octahedron rotation when x>0.16, while the crystal structure remains
tetragonal. Correspondingly, the electric and magnetic properties change with
x. The electrical resistivity reveals metallic character (d rho/d T>0) at high
temperatures but insulating behavior (d rho/d T<0) below a characteristic
temperature T_MIT. Interestingly, T_MIT is different from T_M, at which
magnetic susceptibility reaches maximum. T_MIT monotonically increases with
increasing x while T_M shows non-monotonic dependence with x. The difference
between T_MIT and T_M (T_MIT>T_M) becomes larger when x>0.16. The constructed
phase diagram consists of five distinct regions, demonstrating that the
physical properties of such a system can easily be tuned by chemical doping.",1108.0392v1
2011-08-15,Large conductance modulation of gold thin films by huge charge injection via electrochemical gating,"By using an electrochemical gating technique with a new combination of
polymer and electrolyte, we were able to inject surface charge densities n_2D
as high as 3.5 \times 10^15 e/cm^2 in gold films and to observe large relative
variations in the film resistance, DeltaR/R', up to 10% at low temperature.
DeltaR/R' is a linear function of n_2D - as expected within a free-electron
model - if the film is thick enough (> 25 nm), otherwise a tendency to
saturation due to size effects is observed. The application of this technique
to 2D materials will allow extending the field-effect experiments to a range of
charge doping where giant conductance modulations and, in some cases, even the
occurrence of superconductivity are expected.",1108.3099v1
2011-09-19,Fe-doping induced superconductivity in charge-density-wave system 1T-TaS2,"We report the interplay between charge-density-wave (CDW) and
superconductivity of 1$T$-Fe$_{x}$Ta$_{1-x}$S$_{2}$ ($0\leq x \leq 0.05$)
single crystals. The CDW order is gradually suppressed by Fe-doping,
accompanied by the disappearance of pseudogap/Mott-gap as shown by the density
functional theory (DFT) calculations. The superconducting state develops at low
temperatures within the CDW state for the samples with the moderate doping
levels. The superconductivity strongly depends on $x$ within a narrow range,
and the maximum superconducting transition temperature is 2.8 K as $x=0.02$. We
propose that the induced superconductivity and CDW phases are separated in real
space. For high doping level ($x>0.04$), the Anderson localization (AL) state
appears, resulting in a large increase of resistivity. We present a complete
electronic phase diagram of 1$T$-Fe$_{x}$Ta$_{1-x}$S$_{2}$ system that shows a
dome-like $T_{c}(x)$.",1109.3962v3
2011-09-28,A combination of capillary assembly and dielectrophoresis for wafer scale integration of carbon nanotubes-based electrical and mechanical devices,"The wafer scale integration of carbon nanotubes (CNT) remains a challenge for
electronic and electromechanical applications. We propose a novel CNT
integration process relying on the combination of controlled capillary assembly
and buried electrode dielectrophoresis (DEP). This process enables to monitor
the precise spatial localization of a high density of CNTs and their alignment
in a pre-defined direction. Large arrays of independent and low resistivity
(4.4 x 10^-5 {\Omega}.m) interconnections were achieved using this hybrid
assembly with double-walled carbon nanotubes (DWNT). Finally, arrays of
suspended individual CNT carpets have been realized and we demonstrate their
potential use as functional nano-electromechanical systems (NEMS) by monitoring
their resonance frequencies (ranging between 1.7 MHz to 10.5MHz) using a
Fabry-Perot interferometer.",1109.6268v1
2011-11-14,Thermoelectric properties of Ba-Cu-Si clathrates,"Thermoelectric properties of the type-I clathrates Ba$_8$Cu$_x$Si$_{46-x}$
($3.6 \leq x \leq 7$, $x$ = nominal Cu content) are investigated both
experimentally and theoretically. The polycrystalline samples are prepared
either by melting, ball milling and hot pressing or by melt spinning, hand
milling and hot pressing techniques. Temperature-dependent electrical
resistivity, $\rho(T)$, and the Seebeck coefficient, $S(T)$, measurements
reveal metal-like behavior for all samples. For $x = 5$ and 6, density
functional theory calculations are performed for deriving the enthalpy of
formation and the electronic structure which is exploited for the calculation
of Seebeck coefficients and conductivity within Boltzmann's transport theory.
For simulating the properties of doped clathrates the rigid band model is
applied. On the basis of the density functional theory results the
experimentally observed compositional dependence of $\rho(T)$ and $S(T)$ of the
whole sample series is analyzed. The highest dimensionless thermoelectric
figure of merit $ZT$ of 0.28 is reached for a melt-spun sample at
$600^{\circ}$C. The relatively low $ZT$ values in this system are attributed to
the too high charge carrier concentrations.",1111.3278v1
2011-12-13,The Disordered Induced Interaction and the Phase Diagram of Cuprates,"There are processes in nature that resemble a true force but arise due to the
minimization of the local energy. The most well-known case is the exchange
interaction that leads to magnetic order in some materials. We discovered a new
similar process occurring in connection with an electronic phase separation
transition that leads to charge inhomogeneity in cuprate superconductors. The
minimization of the local free energy, described here by the Cahn-Hilliard
diffusion equation, drives the charges into regions of low and high densities.
This motion leads to an effective potential with two-fold effect: creation of
tiny isolated regions or micrograins, and two-body attraction, which promotes
local or intra-grain superconducting pairing. Consequently, as in granular
superconductors, the superconducting transition appears in two steps. First,
with local intra-grain superconducting amplitudes and, at lower temperature,
the superconducting phase or resistivity transition is attained by intergrain
Josephson coupling. We show here that this approach reproduces the main
features of the cuprates phase diagram, gives a clear interpretation to the
pseudogap phase and yields the position dependent local density of states gap
$\Delta(\vec r)$ measured by tunnelling experiments.",1112.2880v1
2012-05-08,Normal and intrinsic anomalous Hall effect in Nb1-yFe2+y,"The Hall effect on selected samples of the dilution series Nb1-yFe2+y is
studied. Normal and anomalous contributions are observed, with positive normal
Hall effect dominating at high temperatures. Consistent analysis of the
anomalous contribution is only possible for Fe-rich Nb0.985Fe2.015 featuring a
ferromagnetic ground state. Here, a positive normal Hall coefficient is found
at all temperatures with a moderate maximum at the spin-density-wave
transition. The anomalous Hall effect is consistent with an intrinsic
(Berry-phase) contribution which is constant below the ordering temperature TC
and continuously vanishes above TC. For stoichiometric NbFe2 and Nb-rich
Nb1.01Fe1.99 - both having a spin-density-wave ground state - an additional
contribution to the Hall resistivity impedes a complete analysis and indicates
the need for more sophisticated models of the anomalous Hall effect in
itinerant antiferromagnets.",1205.1651v1
2012-05-10,Physical properties and crystal chemistry of Ce2Ga12Pt,"Single crystals of the new ternary compound Ce2Ga12Pt were prepared by the
self-flux technique. The crystal structure with the space group P4/nbm was
established from single-crystal X-ray diffraction data and presents a
derivative of the LaGa6Ni0.6 prototype. Magnetic susceptibility measurements
show Curie-Weiss behaviour due to local Ce^3+ moments. At high temperatures,
the magnetic anisotropy is dominated by the crystal-electric-field (CEF) effect
with the easy axis along the crystallographic c direction. Ce2Ga12Pt undergoes
two antiferromagnetic phase transitions at T_N,1 = 7.3K and T_N,2 = 5.5K and
presents several metamagnetic transitions for the magnetic field along c.
Specific-heat measurements prove the bulk nature of these magnetic transitions
and reveal a doublet CEF ground state. The 4f contribution to the resistivity
shows a broad maximum at T_max ~ 85K due to Kondo scattering off the CEF ground
state and excited levels.",1205.2301v1
2012-05-13,Voltage-Induced Ferromagnetic Resonance in Magnetic Tunnel Junctions,"We demonstrate excitation of ferromagnetic resonance in CoFeB/MgO/CoFeB
magnetic tunnel junctions (MTJs) by the combined action of voltage-controlled
magnetic anisotropy (VCMA) and spin transfer torque (ST). Our measurements
reveal that GHz-frequency VCMA torque and ST in low-resistance MTJs have
similar magnitudes, and thus that both torques are equally important for
understanding high-frequency voltage-driven magnetization dynamics in MTJs. As
an example, we show that VCMA can increase the sensitivity of an MTJ-based
microwave signal detector to the sensitivity level of semiconductor Schottky
diodes.",1205.2835v2
2012-05-15,Field-induced high coercive ferromagnetic state and magnetoresistance in the antiferromagnetically ordered compound Fe0.5TiS2,"The measurements of the magnetic susceptibility, magnetization, electrical
resistivity and magnetoresistance have been performed for the Fe intercalated
compound Fe0.5TiS2. According to X-ray diffraction measurements the Fe0.5TiS2
compound synthesized in the present work has a monoclinic crystal structure
(space group I12/m1) which results from the ordering of Fe ions and vacancies
between S-Ti-S tri-layres. The changes in the heat-treatment conditions at
temperatures below 1100 Celsius degrees do not lead to an order-disorder
transition within the subsystem of intercalated Fe ions. It has been shown that
this compound exhibits an antiferromagnetic (AF) ground state below the Neel
temperature TN = 140 K. Application of the magnetic field at T < TN induces a
metamagnetic phase transition to the ferromagnetic (F) state, which is
accompanied by the large magnetoresistance effect (up to 27 %). The
field-induced AF-F transition is found to be irreversible below ~ 100 K. The
magnetization reversal in the metastable F state at low temperatures is
accompanied by substantial hysteresis (~ 100 kOe) which is associated with the
Ising character of Fe ions.",1205.3242v1
2012-05-16,A new approach for improving global critical current density in Fe(Se0.5Te0.5) polycrystalline materials,"A novel method to prepare bulk Fe(Se0.5Te0.5) samples is presented, based on
a melting process and a subsequent annealing treatment. With respect to the
standard sintering technique, it produces much more homogeneous and denser
samples, characterized by large and well interconnected grains. The resulting
samples exhibit optimal critical temperature values, sharp resistive and
magnetic transitions, large magnetic hysteresis loops and high upper critical
fields are observed. Interestingly, the global critical current density is much
enhanced as compared to the values reported in literature for bulk samples of
the same 11 family, reaching about 103 A/cm2 at zero field at 4.2 K as assessed
by magnetic, transport and magneto-optical techniques. Even more importantly,
its field dependence turns out to be very weak, such that at \mu_{0}H = 7 T it
is suppressed only by a factor \sim2.",1205.3618v2
2012-05-29,Transformation Electronics: Tailoring Electron's Effective Mass,"The speed of integrated circuits is ultimately limited by the mobility of
electrons or holes, which depend on the effective mass in a semiconductor.
Here, building on an analogy with electromagnetic metamaterials and
transformation optics, we describe a new transport regime in a semiconductor
superlattice characterized by extreme anisotropy of the effective mass and a
low intrinsic resistance to movement - with zero effective mass - along some
preferred direction of electron motion. We theoretically demonstrate that such
regime may permit an ultra fast, extremely strong electron response, and
significantly high conductivity, which, notably may be weakly dependent on the
temperature at low temperatures. These ideas may pave the way for faster
electronic devices and detectors and new functional materials with a strong
electrical response in the infrared regime.",1205.6325v2
2012-07-13,Association of indigo with zeolites for improved colour stabilization,"The durability of an organic colour and its resistance against external
chemical agents and exposure to light can be significantly enhanced by
hybridizing the natural dye with a mineral. In search for stable natural
pigments, the present work focuses on the association of indigo blue with
several zeolitic matrices (LTA zeolite, mordenite, MFI zeolite). The
manufacturing of the hybrid pigment is tested under varying oxidising
conditions, using Raman and UV-visible spectrometric techniques. Blending
indigo with MFI is shown to yield the most stable composite in all of our
artificial indigo pigments. In absence of defects and substituted cations such
as aluminum in the framework of the MFI zeolite matrix, we show that matching
the pore size with the dimensions of the guest indigo molecule is the key
factor. The evidence for the high colour stability of indigo@MFI opens a new
path for modeling the stability of indigo in various alumino-silicate
substrates such as in the historical Maya Blue pigment.",1207.3236v1
2012-08-09,The role of charge traps in inducing hysteresis: capacitance - voltage measurements on top gated bilayer graphene,"Understanding the origin of hysteresis in the channel resistance from top
gated graphene transistors is important for transistor applications.
Capacitance - voltage measurements across the gate oxide on top gated bilayer
graphene show hysteresis with a charging and discharging time constant of ~100
{\mu}s. However, the measured capacitance across the graphene channel does not
show any hysteresis, but shows an abrupt jump at a high channel voltage due to
the emergence of an order, indicating that the origin of hysteresis between
gate and source is due to charge traps present in the gate oxide and graphene
interface.",1208.1831v1
2012-08-15,A GEANT4 Simulation Studyof BESIII endcap TOF Upgrade,"A GEANT4-based Monte-Carlo model is developed to study the performance of
Endcap Time-Of-Flight (ETOF) at BESIII. It's found that the multiple scattering
effects, mainly from the materials at the MDC endcap, can cause multi-hit on
the ETOF's readout cell and significantly influence the timing property of
ETOF. Multi-gap Resistive Plate Chamber (MRPC) with a smaller readout cell
structure is more suitable for ETOF detector due to significantly reduced
multi-hit rate, from 71.5% for currently-used scintillator-based ETOF to 21.8%
or 16.7% for MRPC-based ETOF, depending on the readout pad size used. The
timing performance of a MRPC ETOF is also improved. These simulation results
suggest and guide an ETOF upgrade effort at BESIII.",1208.3049v1
2012-09-03,High Efficiency Graphene Solar Cells by Chemical Doping,"We demonstrate single layer graphene/n-Si Schottky junction solar cells that
under AM1.5 illumination exhibit a power conversion efficiency (PCE) of 8.6%.
This performance, achieved by doping the graphene with
bis(trifluoromethanesulfonyl)amide, exceeds the native(undoped) device
performance by a factor of 4.5 and the best previously reported PCE in similar
devices by a factor of nearly 6. Current-voltage, capacitance-voltage and
external quantum efficiency measurements show the enhancement to be due to the
doping induced shift in the graphene chemical potential which increases the
graphene carrier density (decreasing the cell series resistance) and increases
the built-in potential.",1209.0432v1
2012-09-12,Channel Length Scaling of MoS2 MOSFETs,"In this article, we investigate electrical transport properties in ultrathin
body (UTB) MoS2 two-dimensional (2D) crystals with channel lengths ranging from
2 {\mu}m down to 50 nm. We compare the short channel behavior of sets of
MOSFETs with various channel thickness, and reveal the superior immunity to
short channel effects of MoS2 transistors. We observe no obvious short channel
effects on the device with 100 nm channel length (Lch) fabricated on a 5 nm
thick MoS2 2D crystal even when using 300 nm thick SiO2 as gate dielectric, and
has a current on/off ratio up to ~109. We also observe the on-current
saturation at short channel devices with continuous scaling due to the carrier
velocity saturation. Also, we reveal the performance limit of short channel
MoS2 transistors is dominated by the large contact resistance from the Schottky
barrier between Ni and MoS2 interface, where a fully transparent contact is
needed to achieve a high-performance short channel device.",1209.2525v1
2012-09-24,Ba1-xNaxTi2Sb2O (0.0 <= x <= 0.33): A Layered Titanium-based Pnictide Oxide Superconductor,"A new layered Ti-based pnictide oxide superconductor, Ba1-xNaxTi2Sb2O (0.0 <=
x <= 0.33), is reported. X-ray studies reveal it crystallizes in the tetragonal
CeCr2Si2C structure. The undoped parent compound, BaTi2Sb2O (P4/mmm;
a=4.1196(1){\AA}; c=8.0951(2){\AA}), exhibits a CDW/SDW transition at 54K. Upon
chemical doping with Na, the CDW/SDW transition is systematically suppressed
and super-conductivity arises with the critical temperatures, Tc, increasing to
5.5 K. Bulk superconductivity is confirmed by resistivity, magnetic and heat
capacity measurements. Like the high-Tc cuprates and the iron pnictides,
superconductivity in BaTi2Sb2O arises from an ordered state. Similarities and
differences to the cuprate and iron pnictide supercon-ductors are discussed.",1209.5447v2
2012-09-27,Fabrication and characterization of semiconducting half Heusler YPtSb thin films,"The semiconducting half Heusler compound YPtSb was predicted theoretically to
be capable of changing into topological insulator under proper strain. In this
work, p type semiconducting half-Heusler YPtSb thin films were prepared by
magnetron co-sputtering method from a specially designed target for the first
time. Textured structure with (111) plane paralleling with (001) of MgO
substrate was observed when YPtSb thin films were grown on MgO (100) substrate
at 600{\deg}C.Electrical measurements show that the resistivity of YPtSb films
decreases with increasing temperature, indicating a semiconductor-like
behavior. The carrier density is as high as 1.15 X 10^21 cm-3 at 300 K. The
band gap of YPtSb thin films obtained by infrared spectroscopy is around 0.1 -
0.15 eV, which is well in agreement with the theoretical prediction and the
value measured in bulk YPtSb.",1209.6288v2
2012-10-08,Phonon thermal transport outside of local equilibrium in nanowires via molecular dynamics,"We study thermal transport through Pt nanowires that bridge planar contacts
as a function of wire length and vibrational frequency of the contacts. When
phonons in the contacts have lower average frequencies than those in the wires
thermal transport occurs under conditions away from local equilibrium with
low-frequency phonons experiencing a higher thermal gradient than
high-frequency ones. This results in a size-dependent increase in the effective
thermal conductivity of the wire with decreasing vibrational frequencies of the
contacts. The interfacial resistivity when heat flows from the wire to the
contact is also size-dependent and has the same physical origin in the lack of
full equilibration in short nanowires. We develop a model based on a 1D atomic
chain that captures the salient physics of the MD results.",1210.2321v1
2012-10-19,Self-aligned graphene field-effect transistors with polyethyleneimine doped source/drain access regions,"We report a method of fabricating self-aligned, top-gated graphene
field-effect transistors (GFETs) employing polyethyleneimine spin-on-doped
source/drain access regions, resulting in a 2X reduction of access resistance
and a 2.5X improvement in device electrical characteristics, over undoped
devices. The GFETs on Si/SiO$_2$ substrates have high carrier mobilities of up
to 6,300 cm$^2$/Vs. Self-aligned spin-on-doping is applicable to GFETs on
arbitrary substrates, as demonstrated by a 3X enhancement in performance for
GFETs on insulating quartz substrates, which are better suited for radio
frequency applications.",1210.5535v2
2012-10-22,Fabrication and characterization of the gapless half-Heusler YPtSb thin films,"Half-Heusler YPtSb thin films were fabricated by magnetron co-sputtering
method on MgO-buffered SiO2/Si(001) substrates. X-ray diffraction pattern and
Energy dispersive X-ray spectroscopy confirmed the high-quality growth and
stoichiometry. The temperature dependence of the resistivity shows a
semiconducting-type behavior down to low temperature. The Hall mobility was
determined to be 450 cm2/Vs at 300K, which is much higher than the bulk value
(300 cm2/Vs). In-plane magnetoresistance (MR) measurements with fields applied
along and perpendicular to the current direction show opposite MR signs, which
suggests the possible existence of the topological surface states.",1210.5808v1
2012-10-29,Impact of graphene quantum capacitance on transport spectroscopy,"We demonstrate experimentally that graphene quantum capacitance
$C_{\mathrm{q}}$ can have a strong impact on transport spectroscopy through the
interplay with nearby charge reservoirs. The effect is elucidated in a
field-effect-gated epitaxial graphene device, in which interface states serve
as charge reservoirs. The Fermi-level dependence of $C_{\mathrm{q}}$ is
manifested as an unusual parabolic gate voltage ($V_{\mathrm{g}}$) dependence
of the carrier density, centered on the Dirac point. Consequently, in high
magnetic fields $B$, the spectroscopy of longitudinal resistance ($R_{xx}$) vs.
$V_{\mathrm{g}}$ represents the structure of the unequally spaced relativistic
graphene Landau levels (LLs). $R_{xx}$ mapping vs. $V_{\mathrm{g}}$ and $B$
thus reveals the vital role of the zero-energy LL on the development of the
anomalously wide $\nu=2$ quantum Hall state.",1210.7601v1
2012-11-02,Interface characterization of Co2MnGe/Rh2CuSn Heusler multilayers,"All-Heusler multilayer structures have been investigated by means of high
kinetic x-ray photoelectron spectroscopy and x-ray magnetic circular dichroism,
aiming to address the amount of disorder and interface diffusion induced by
annealing of the multilayer structure. The studied multilayers consist of
ferromagnetic Co$_2$MnGe and non-magnetic Rh$_2$CuSn layers with varying
thicknesses. We find that diffusion begins already at comparably low
temperatures between 200 $^{\circ}$C and 250 $^{\circ}$C, where Mn appears to
be most prone to diffusion. We also find evidence for a 4 {\AA} thick
magnetically dead layer that, together with the identified interlayer
diffusion, are likely reasons for the small magnetoresistance found for
current-perpendicular-to-plane giant magneto-resistance devices based on this
all-Heusler system.",1211.0489v2
2012-11-13,The giant plasticity of a quantum crystal,"When submitted to large stresses at high temperature, usual crystals may
irreversibly deform. This phenomenon is known as plasticity and it is due to
the motion of crystal defects such as dislocations. We have discovered that, in
the absence of impurities and in the zero temperature limit, helium 4 crystals
present a giant plasticity that is anisotropic and reversible. Direct
measurements on oriented single crystals show that their resistance to shear
nearly vanishes in one particular direction because dislocations glide freely
parallel to the basal planes of the hexagonal structure. This plasticity
disappears as soon as traces of helium 3 impurities bind to the dislocations or
if their motion is damped by collisions with thermal phonons.",1211.2976v2
2012-11-14,High-temperature structural phase transition in multiferroic LiCu_2O_2,"LiCu_2O_2 single crystals were studied in the temperature range 300-1100 K by
means of heating-cooling curves of differential thermal analysis (DTA),
thermogravimetry (TG), X-ray powder diffraction and electrical measurements. A
reversible first-order phase transition between orthorhombic and tetragonal
phases was found to take place at 993 K. At the transition, a peak is observed
in the DTA curves, as well as jumps of the unit cell parameters and electrical
resistivity. Considering the crystal structure of LiCu_2O_2 and the entropy
change associated with the phase transition, it is concluded that the phase
transition is related to processes of order-disorder of the Cu2+ and Li+
cations onto their crystallographic positions.",1211.3275v1
2012-11-14,Anisotropy and directional pinning in YBaCuO with BaZrO3 nanorods,"Measurements of anisotropic transport properties (dc and high-frequency
regime) of driven vortex matter in YBa$_2$Cu$_3$O$_{7-x}$ with elongated
strong-pinning sites (c-axis aligned, self-assembled BaZrO$_3$ nanorods) are
used to demonstrate that the effective-mass angular scaling takes place only in
intrinsic physical quantities (flux-flow resistivity), and not in
pinning-related Labusch parameter and critical currents. Comparison of the
dynamics at different time scales shows evidence for a transition of the vortex
matter toward a Mott phase, driven by the presence of nanorods. The strong
pinning in dc arises partially from a dynamic effect.",1211.3311v2
2012-11-23,1D to 3D Dimensional Crossover in the Superconducting Transition of the Quasi-One-Dimensional Carbide Superconductor Sc3CoC4,"The transition metal carbide superconductor Sc3CoC4 may represent a new
benchmark system of quasi-1D superconducting behavior. We investigate the
superconducting transition of a high-quality single crystalline sample by
electrical transport experiments. Our data show that the superconductor goes
through a complex dimensional crossover below the onset Tc of 4.5 K. First, a
quasi-1D fluctuating superconducting state with finite resistance forms in the
CoC4 ribbons which are embedded in a Sc matrix in this material. At lower
temperature, the transversal Josephson or proximity coupling of neighboring
ribbons establishes a 3D bulk superconducting state. This dimensional crossover
is very similar to Tl2Mo6Se6, which for a long time has been regarded as the
most appropriate model system of a quasi-1D superconductor. Sc3CoC4 appears to
be even more in the 1D limit than Tl2Mo6Se6.",1211.5430v4
2012-11-26,Local transport measurements at mesoscopic length scales using scanning tunneling potentiometry,"Under mesoscopic conditions, the transport potential on a thin film with
current is theoretically expected to bear spatial variation due to quantum
interference. Scanning tunneling potentiometry is the ideal tool to investigate
such variation, by virtue of its high spatial resolution. We report in this
{\it Letter} the first detailed measurement of transport potential under
mesoscopic conditions. Epitaxial graphene at a temperature of 17K was chosen as
the initial system for study because the characteristic transport length scales
in this material are relatively large. Tip jumping artifacts are a major
possible contribution to systematic errors; and we mitigate such problems by
using custom-made slender and sharp tips manufactured by focussed ion beam. In
our data, we observe residual resistivity dipoles associated with
topoographical defects, and local peaks and dips in the potential that are not
associated with topographical defects.",1211.6088v2
2012-12-06,Effects of spin density wave quantization on the electrical transport in epitaxial Cr thin films,"We present measurements of the electrical resistivity, $\rho$, in epitaxial
Cr films of different thicknesses grown on MgO (100) substrates, as a function
of temperature, $T$. The $\rho(T)$ curves display hysteretic behavior in
certain temperature range, which is film thickness dependent. The hysteresis
are related to the confinement of quantized incommensurate spin density waves
(ISDW) in the film thickness. Our important finding is to experimentally show
that the temperature $T_{mid}$ where the ISDW changes from $N$ to $N$\,+\,1
nodes {\it decreases} as the film thickness {\it increases}. Identifying
$T_{mid}$ with a first order transition between ISDW states with $N$ and
$N$\,+\,1 nodes, and using a Landau approach to the free energy of the ISDW
together with Monte Carlo simulations, we show that the system at high
temperatures explores all available modes for the ISDW, freezing out in one
particular mode at a transition temperature that indeed decreases with film
thickness, $L$. The detailed dependence of $T_{mid}(L)$ seems to depend rather
strongly on the boundary conditions at the Cr film interfaces.",1212.1408v1
2013-01-09,Hall effect measurements on epitaxial SmNiO3 thin films and implications for antiferromagnetism,"The rare-earth nickelates (RNiO3) exhibit interesting phenomena such as
unusual antiferromagnetic order at wavevector q = (1/2, 0, 1/2) and a tunable
insulator-metal transition that are subjects of active research. Here we
present temperature-dependent transport measurements of the resistivity,
magnetoresistance, Seebeck coefficient, and Hall coefficient (RH) of epitaxial
SmNiO3 thin films with varying oxygen stoichiometry. We find that from room
temperature through the high temperature insulator-metal transition, the Hall
coefficient is hole-like and the Seebeck coefficient is electron-like. At low
temperature the N\'eel transition induces a crossover in the sign of RH to
electron-like, similar to the effects of spin density wave formation in
metallic systems but here arising in an insulating phase ~200 K below the
insulator-metal transition. We propose that antiferromagnetism can be
stabilized by bandstructure even in insulating phases of correlated oxides,
such as RNiO3, that fall between the limits of strong and weak electron
correlation.",1301.1968v3
2013-01-11,Batch-fabricated cantilever probes with electrical shielding for nanoscale dielectric and conductivity imaging,"This paper presents the design and fabrication of batch-processed cantilever
probes with electrical shielding for scanning microwave impedance microscopy.
The diameter of the tip apex, which defines the electrical resolution, is less
than 50 nm. The width of the stripline and the thicknesses of the insulation
dielectrics are optimized for a small series resistance (< 5 W) and a small
background capacitance (~ 1 pF), both critical for high sensitivity imaging on
various samples. The coaxial shielding ensures that only the probe tip
interacts with the sample. The structure of the cantilever is designed to be
symmetric to balance the stresses and thermal expansions of different layers so
that the cantilever remains straight under variable temperatures. Such shielded
cantilever probes produced in the wafer scale will facilitate enormous
applications on nanoscale dielectric and conductivity imaging.",1301.2402v1
2013-01-14,Pressure-Induced Superconductivity and Its Scaling with Doping-Induced Superconductivity in the Iron Pnictide with Skutterudite Intermediary Layers,"The Ca10(PtnAs8)(Fe2As2)5 (n=3,4) compounds are a new type of iron pnictide
superconductors whose structures consist of stacking Ca-PtnAs8-Ca-Fe2As2 layers
in a unit cell. When n=3 (the 10-3-8 phase), the undoped compound is an
antiferromagnetic (AFM) semiconductor, while, when n=4 (the 10-4-8 phase), the
undoped compound is a superconductor with the transition temperature of 26K.
Here we report the results of high-pressure studies on the 10-3-8 compound
obtained through a combination of in-situ resistance, magnetic susceptibility,
and Hall coefficient measurements. We find that its AFM order can be suppressed
completely at 3.5 GPa and then superconducting state appears in the pressure
range of 3.5-7 GPa. The pressure dependence of superconducting transition
temperature displays a dome-like shape.",1301.2863v2
2013-02-08,Electrical transport across Au/Nb:SrTiO3 Schottky interface with different Nb doping,"We have investigated electron transport in Nb doped SrTiO$_3$ single crystals
for two doping densities. We find that the resistivity and mobility are
temperature dependent in both whereas the carrier concentration is almost
temperature invariant. We rationalize this using the hydrogenic theory for
shallow donors. Further, we probe electrical transport across Schottky
interfaces of Au on TiO$_2$ terminated n-type SrTiO$_3$. Quantitative analysis
of macroscopic I-V measurements reveal thermionic emission dominated transport
for the low doped substrate whereas it deviates from such behavior for the high
doped substrate. This work is relevant for designing devices to study
electronic transport using oxide-semiconductors.",1302.2096v1
2013-02-14,Transport studies of dual-gated ABC and ABA trilayer graphene: band gap opening and band structure tuning in very large perpendicular electric field,"We report on the transport properties of ABC and ABA stacked trilayer
graphene using dual, locally gated field effect devices. The high efficiency
and large breakdown voltage of the HfO2 top and bottom gates enables
independent tuning of the perpendicular electric field and the Fermi level over
an unprecedentedly large range. We observe a resistance change of six orders of
magnitude in the ABC trilayer, which demonstrates the opening of a band gap.
Our data suggest that the gap saturates at a large displacement field of D ~ 3
V/nm, in agreement with self-consistent Hartree calculations. In contrast, the
ABA trilayer remains metallic even under a large perpendicular electric field.
Despite the absence of a band gap, the band structure of the ABA trilayer
continues to evolve with increasing D. We observe signatures of two-band
conduction at large D fields. Our self-consistent Hartree calculation
reproduces many aspects of the experimental data, but also points to the need
for more sophisticated theory.",1302.3432v1
2013-02-21,Superconductivity induced by U-doping in the SmFeAsO system,"Through partial substitution of Sm by U in SmFeAsO, a different member of the
family of iron-based superconductors was successfully synthesized. X-ray
diffraction measurements show that the lattice constants along the a and c axes
are both squeezed through U doping, indicating a successful substitution of U
at the Sm site. The parent compound shows a strong resistivity anomaly near 150
K, associated with spin-density-wave instability.U doping suppresses this
instability and leads to a transition to the superconducting state at
temperatures up to 49 K. Magnetic measurements confirm the bulk
superconductivity in this system. For the sample with a doping level of x =
0.2, the external magnetic field suppresses the onset temperature very slowly,
indicating a rather high upper critical field. In addition, the Hall effect
measurements show that U clearly dopes electrons into the material.",1302.5155v1
2013-04-10,Pinning in a Porous Bi2223,"The current-voltage characteristics of a porous superconductor Bi2Sr2Ca2Cu3Ox
(Bi2223) have been measured at temperature range from 10 to 90 K. The
experimental dependences have been analyzed within the model allowing for
pinning by clusters of a normal phase with fractal boundaries, as well as the
model taking into account phase transformations of vortex matter. It has been
found that the electrical resistance of the superconductor material
significantly increases at temperatures of 60-70 K over the entire range of
magnetic fields under consideration without changing in the sign of the
curvature of the R(I) dependence. The melting of the vortex structure occurs at
these temperatures. It has been assumed that this behavior is associated with
the specific feature of the pinning in a highly porous high-temperature
superconductor, which lies in the fractal distribution of pinning centers in a
wide range of self-similarity scales.",1304.2844v1
2013-04-10,Multi-band superconductivity and nanoscale inhomogeneity at oxide interfaces,"The two-dimensional electron gas at the LaTiO3/SrTiO3 or LaAlO3/SrTiO3 oxide
interfaces becomes superconducting when the carrier density is tuned by gating.
The measured resistance and superfluid density reveal an inhomogeneous
superconductivity resulting from percolation of filamentary structures of
superconducting ""puddles"" with randomly distributed critical temperatures,
embedded in a non-superconducting matrix. Following the evidence that
superconductivity is related to the appearance of high-mobility carriers, we
model intra-puddle superconductivity by a multi-band system within a weak
coupling BCS scheme. The microscopic parameters, extracted by fitting the
transport data with a percolative model, yield a consistent description of the
dependence of the average intra-puddle critical temperature and superfluid
density on the carrier density.",1304.2970v1
2013-04-22,Electrical transport in C-doped GaAs nanowires: surface effects,"The resistivity and the mobility of Carbon doped GaAs nanowires have been
studied for different doping concentrations. Surface effects have been
evaluated by comparing upassivated with passivated nanowires. We directly see
the influence of the surface: the pinning of the Fermi level and the consequent
existence of a depletion region lead to an increase of the mobility up to 30
cm^2/(V*s) for doping concentrations lower than 3*10^18 cm^-3. Electron beam
induced current measurements show that the minority carrier diffusion path can
be as high as 190 nm for passivated nanowires.",1304.5891v1
2013-05-23,Electronic origin of the orthorhombic Cmca structure in compressed elements and binary alloys,"Formation of the complex structure with 16 atoms in the orthorhombic cell,
space group Cmca (Pearson symbol oC16) was experimentally found under high
pressure in the alkali elements (K, Rb, Cs) and polyvalent elements of groups
IV (Si, Ge) and V (Bi). Intermetallic phases with this structure form under
pressure in binary Bi-based alloys (Bi-Sn, Bi-In, Bi-Pb). Stability of the Cmca
- oC16 structure is analyzed within the nearly free-electron model in the frame
of Fermi sphere - Brillouin zone interaction. A Brillouin-Jones zone formed by
a group of strong diffraction reflections close to the Fermi sphere is the
reason for reduction of crystal energy and stabilization of the structure. This
zone corresponds well to the 4 valence electrons in Si and Ge and leads to
assume a spd-hybridization for Bi. To explain the stabilization of this
structure within the same model in alkali metals, that are monovalent at
ambient conditions, a possibility of an overlap of the core and valence band
electrons at strong compression is considered. The assumption of the increase
in the number of valence electrons helps to understand sequences of complex
structures in compressed alkali elements and unusual changes in their physical
properties such as electrical resistance and superconductivity.",1305.5341v1
2013-05-29,Intrinsic and extrinsic origins of low-frequency noise in GaAs/AlGaAs Schottky-gated nanostructures,"We study low-frequency noise in current passing through quantum point
contacts fabricated from several GaAs/AlGaAs heterostructures with different
layer structures and fabrication processes. In contrast to previous reports,
there is no gate-dependent random telegraph noise (RTN) originating from
tunneling through a Schottky barrier in devices fabricated using the standard
low-damage process. Gate-dependent RTN appears only in devices fabricated with
a high-damage process that induces charge trap sites. We show that the
insertion of AlAs/GaAs superlattices in the AlGaAs barrier helps to suppress
trap formation. Our results enable the fabrication of damage-resistant and thus
low-noise devices.",1305.6701v1
2013-06-29,Coexistence of Half-Metallic Itinerant Ferromagnetism with Local-Moment Antiferromagnetism in Ba{0.60}K{0.40}Mn2As2,"Magnetization, nuclear magnetic resonance, high-resolution x-ray diffraction
and magnetic field-dependent neutron diffraction measurements reveal a novel
magnetic ground state of Ba{0.60}K{0.40}Mn2As2 in which itinerant
ferromagnetism (FM) below a Curie temperature TC = 100 K arising from the doped
conduction holes coexists with collinear antiferromagnetism (AFM) of the Mn
local moments that order below a Neel temperature TN = 480 K. The FM ordered
moments are aligned in the tetragonal ab-plane and are orthogonal to the
AFM-ordered Mn moments that are aligned along the c-axis. The magnitude and
nature of the low-T FM ordered moment correspond to complete polarization of
the doped-hole spins (half-metallic itinerant FM) as deduced from magnetization
and ab-plane electrical resistivity measurements.",1307.0091v2
2013-07-22,Dimensional-Crossover-Driven Mott Insulators in SrVO3 Ultrathin Films,"High-quality epitaxial SrVO3 (SVO) thin films of various thicknesses were
grown on (001)-oriented LSAT substrates by pulsed electron-beam deposition
technique. Thick SVO films (~25 nm) exhibited metallic behavior with the
electrical resistivity following the T2 law corresponding to a Fermi liquid
system. We observed a temperature driven metal-insulator transition (MIT) in
SVO ultrathin films with thicknesses below 6.5 nm, the transition temperature
TMIT was found to be at 50 K for the 6.5 nm film, 120 K for the 5.7 nm film and
205 K for the 3 nm film. The emergence of the observed MIT can be attributed to
the dimensional crossover from a three-dimensional metal to a two-dimensional
Mott insulator, as the resulting reduction in the effective bandwidth W opens a
band gap at the Fermi level. The magneto-transport study of the SVO ultrathin
films also confirmed the observed MIT is due to the electron-electron
interactions other than localization.",1307.5819v2
2013-07-26,Electron-phonon coupling in cuprate and iron-based superconductors revealed by Raman scattering,"Electron-phonon coupling (EPC) is one of the most common and fundamental
interactions in solids. It not only dominates many basic dynamic processes like
resistivity, thermal conductivity etc, but also provides the pairing glue in
conventional superconductors. But in high-temperature superconductors (HTSC),
it is still controversial whether or not EPC is in favor of paring. Despite the
controversies, many experiments have provided clear evidence for EPC in HTSC.
In this paper, we briefly review EPC in cuprate and iron-based superconducting
systems revealed by Raman scattering. We introduce how to extract the coupling
information through phonon lineshape. Then we discuss the strength of EPC in
different HTSC systems and possible factors affecting the strength. The
comparative study between Raman phonon theories and experiments allows us to
gain insight into some crucial electronic properties, especially
superconductivity. Finally we summarize and compare EPC in the two existing
HTSC systems, and discuss what role it may play in HTSC.",1307.6972v1
2014-02-10,Evolution and defect analysis of vertical graphene nanosheets,"We report catalyst-free direct synthesis of vertical graphene nanosheets
(VGNs) on SiO2/Si and quartz substrates using microwave electron cyclotron
resonance - plasma enhanced chemical vapor deposition. The evolution of VGNs is
studied systematically at different growth stages. Raman analysis as a function
of growth time reveals that two different disorder-induced competing mechanisms
contributing to the defect band intensity. The VGNs grown on SiO2/Si substrates
predominantly consists of both vacancy-like and hopping defects. On the other
hand, the VGNs grown on quartz substrates contain mainly boundary-like defects.
XPS studies also corroborate Raman analysis in terms of defect density and
vacancy-like defects for the VGNs grown on SiO2/Si substrates. Moreover, the
grown VGNs exhibit a high optical transmittance from 95 to 78 % at 550 nm and
the sheet resistance varies from 30 to 2.17 kohms/square depending on growth
time.",1402.2074v3
2014-02-19,Phase Diagram of Micron-Size Bridges of SrTiO$_3/$LaAlO$_3$ Interface: Link Between Multiple Band Structure and Superconductivity,"The rich phase diagram of the two dimensional electron gas (2DEG) at the
\STO/\LAO interface is probed using Hall and longitudinal resistivity. Thanks
to a special bridge design we are able to tune through the superconducting
transition temperature T$_c$ and to mute superconductivity by either adding or
removing carriers in a gate bias range of a few volts. Hall signal measurements
pinpoint the onset of population of a second mobile band right at the carrier
concentration where maximum superconducting T$_c$ and critical field H$_c$
occur. These results emphasize the advantages of our design, which can be
applied to many other two dimensional systems assembled on top of a dielectric
substrate with high permittivity.",1402.4646v1
2014-03-04,Effect of modulations of doping and strain on the electron transport in monolayer MoS_2,"The doping and strain effects on the electron transport of monolayer MoS_2
are systematically investigated using the first-principles calculations with
Boltzmann transport theory. We estimate the mobility has a maximum 275
cm^2/(Vs) in the low doping level under the strain-free condition. The applying
a small strain (3%) can improve the maximum mobility to 1150 cm^2/(Vs) and the
strain effect is more significant in the high doping level. We demonstrate that
the electric resistance mainly due to the electron transition between K and Q
valleys scattered by the M momentum phonons. However, the strain can
effectively suppress this type of electron-phonon coupling by changing the
energy difference between the K and Q valleys. This sensitivity of mobility to
the external strain may direct the improving electron transport of MoS_2.",1403.0695v2
2014-03-29,Two components for one resistivity in LaVO3/SrTiO3 heterostructures,"A series of 100 nm LaVO3 thin films have been synthesized on (001)-oriented
SrTiO3 substrates using the pulsed laser deposition technique, and the effects
of growth temperature are analyzed. Transport properties reveal a large
electronic mobility and a non-linear Hall effect at low temperature. In
addition, a cross-over from a semiconducting state at high-temperature to a
metallic state at low-temperature is observed, with a clear enhancement of the
metallic character as the growth temperature increases. Optical absorption
measurements combined with the two-bands analysis of the Hall effect show that
the metallicity is induced by the diffusion of oxygen vacancies in the SrTiO3
substrate. These results allow to understand that the film/substrate
heterostructure behaves as an original semiconducting-metallic parallel
resistor, and electronic transport properties are consistently explained.",1403.7648v2
2014-04-07,Directional pinning and anisotropy in YBa2Cu3O7-x with BaZrO3 nanorods: intrinsic and nanorods-induced anisotropy,"We present a study of the anisotropic vortex parameters as obtained from
measurements of the microwave complex resistivity in the vortex state with a
tilted applied magnetic field in YBa2Cu3O7-x thin films with BaZrO3 nanorods.
We present the angular dependence of the vortex viscosity $\eta$, the pinning
constant k_p and the upper limit for the creep factor \chi_M. We show that the
directional effect of the nanorods is absent in \eta, which is dictated by the
mass anisotropy \gamma. By contrast, pinning-mediated properties are strongly
affected by the nanorods. It is significant that the pinning and creep affected
by the nanorods is detectable also at our very high operating frequency, which
implies very short-range displacements of the vortices from their equilibrium
position.",1404.1670v1
2014-05-07,Anisotropic giant magnetoresistance in NbSb2,"The extremely large transverse magnetoreistance (the magnetoresistant ratio
$\sim 1.3\times10^5\%$ in 2 K and 9 T field, and $4.3\times 10^6\%$ in 0.4 K
and 32 T field, without saturation), and the metal-semiconductor crossover
induced by magnetic field, are reported in NbSb$_2$ single crystal with
electric current parallel to the $b$-axis. The metal-semiconductor crossover is
preserved when the current is along the $ac$-plane but the magnetoresistant
ratio is significantly suppressed. The sign reversal of the Hall resistivity in
the field close to the crossover point, and the electronic structure
calculation reveals the coexistence of a small number of holes with very high
mobility and a large number of electrons with low mobility. These effects are
attributed to the change of the Fermi surface induced by the magnetic field.",1405.1719v2
2014-06-05,Current transport and thermoelectric properties of very high power factor Fe3O4 / SiO2 / p-type Si (001) devices,"The current transport and thermoelectric properties of Fe3O4 / SiO2 / p-type
Si(001) heterostructures with Fe3O4 thicknesses of 150, 200, and 350 nm have
been investigated between 100 and 300 K. We observe a sharp drop of the
in-plane resistivity at 200K due to the onset of conduction along the Si / SiO2
interface related to tunneling of electrons from the Fe3O4 into the
accumulation layer of holes at the Si / SiO2 interface, whose existence was
confirmed by capacitance-voltage measurements and a two band analysis of the
Hall effect. This is accompanied by a large increase of the Seebeck coefficient
reaching +1000 {\mu}V/K at 300K that is related to holes in the p-type Si(001)
and gives a power factor of 70 mW/K2m when the Fe3O4 layer thickness is reduced
down to 150 nm. We show that most of the current flows in the Fe3O4 layer at
300 K, while the Fe3O4 / SiO2 / p-type Si(001) heterostructures behave like
tunneling p-n junctions in the transverse direction.",1406.1282v1
2014-06-20,Anomalous Hall Effect in Ge(1-x-y)Pb(x)Mn(y)Te Composite System,"The purpose of this study was to investigate the magnetotransport properties
of the Ge(0.743)Pb(0.183)Mn(0.074)Te mixed crystal. The results of
magnetization measurements indicated that the compound is a spin-glass-like
diluted magnetic semiconductor with critical temperature TSG = 97.5 K.
Nanoclusters in the sample are observed. Both, matrix and clusters are
magnetically active. Resistivity as a function of temperature has a minimum at
30 K. Below the minimum a variable-range hopping is observed, while above the
minimum a metallic-like behavior occurs. The crystal has high hole
concentration, p = 6.6E20 cm-3, temperature-independent. Magnetoresistance
amplitude changes from -0.78 to 1.18% with increase of temperature. In the
magnetotransport measurements we observed the anomalous Hall effect (AHE) with
hysteresis loops. Calculated AHE coefficient, RS = 2.0E6 m3/C, is temperature
independent. The analysis indicates the extrinsic skew scattering mechanism to
be the main physical mechanism responsible for AHE in
Ge(0.743)Pb(0.183)Mn(0.074)Te alloy.",1406.5294v1
2014-07-22,Universal scaling of the critical temperature for thin films near the superconducting-to-insulating transition,"Thin superconducting films form a unique platform for geometrically-confined,
strongly-interacting electrons. They allow an inherent competition between
disorder and superconductivity, which in turn enables the intriguing
superconducting-to-insulator transition and believed to facilitate the
comprehension of high-Tc superconductivity. Furthermore, understanding thin
film superconductivity is technologically essential e.g. for photo-detectors,
and quantum-computers. Consequently, the absence of an established universal
relationships between critical temperature ($T_c$), film thickness ($d$) and
sheet resistance ($R_s$) hinders both our understanding of the onset of the
superconductivity and the development of miniaturised superconducting devices.
We report that in thin films, superconductivity scales as $d^.$$T_c(R_s)$. We
demonstrated this scaling by analysing the data published over the past 46
years for different materials (and facilitated this database for further
analysis). Moreover, we experimentally confirmed the discovered scaling for NbN
films, quantified it with a power law, explored its possible origin and
demonstrated its usefulness for superconducting film-based devices.",1407.5945v2
2014-09-18,Electrical and optical properties of ITO thin films prepared by DC magnetron sputtering for low-emitting coatings,"Optimized DC magnetron sputtering system for the deposition of transparent
conductive oxides (TCOs), such indium tin oxide (ITO) on glass substrate has
been applied in order to achieve low-emitting (low-e) transparent coatings. To
obtain the concerned electrical resistance and high infrared reflection, first
the effect of applied sputtering power then oxygen flow on the properties of
films have been investigated. The other depositions parameters are kept
constant. Film deposition at at temperature 400 degree of Celsius in oxygen
flow of 3 Standard Cubic Centimeters per Minute results in transparent and
infrared reflecting coatings. Under this condition the highest attained average
reflectance in the infrared is ({\lambda}=3-25 micron) 89.5% (lowest emittance
equals to less than 11%), whereas transparency in the visible is 85%
approximately. Plasma wavelength and carrier concentration was measured.",1409.5293v1
2014-09-25,Characterisation of Glass Electrodes and RPC Detectors for $INO-ICAL$ Experiment,"India-based Neutrino Observatory (INO) is a planned neutrino experiment to be
build up in southern part of India.The INO observatory will host a 51 kton Iron
Calorimeter (ICAL) detector to detect atmospheric neutrinos. Resistive Plate
Chamber (RPC) has been chosen as the active detector element for the ICAL
experiment. The ICAL experiment will consist of about 28,000 RPC's of dimension
$2~m\times 2~m$, divided into three modules. The experiment is planned to take
data at least for 20 years from its start date. Due to the large number of RPC
needed for ICAL experiment and the long lifetime of the experiment, it is
necessary to carry out detailed $R\&D$ to optimise each and every parameter of
the detector performance. We report on the performance studies carried out on
the RPC's made with these electrodes, and finally compare the detector
performance with that of the material properties to optimise the detector
parameters.",1409.7184v1
2014-11-24,Thermoelectric power of bulk black-phosphorus,"The potential of bulk black-phosphorus for thermoelectric applications has
been experimentally studied. The Seebeck Coefficient (S) has been measured in
the temperature range from 300 K to 385 K, finding a value of S = +335 +- 10
uV/K at room temperature (indicating a naturally occurring p-type
conductivity). S increases with temperature, as expected for p-type
semiconductors, which can be attributed to an increase of the charge carrier
density. The electrical resistance drops up to a 40 % while heating in the
studied temperature range. As a consequence, the power factor at 385 K is 2.7
times higher than that at room temperature. This work demonstrates the
feasibility of black-phosphorus in thermoelectric applications, such as thermal
energy scavenging, which typically require devices with high performance at
temperatures above room temperature.",1411.6468v2
2014-11-26,Towards high mobility InSb nanowire devices,"We study the low-temperature electron mobility of InSb nanowires. We extract
the mobility at 4.2 Kelvin by means of field effect transport measurements
using a model consisting of a nanowire-transistor with contact resistances.
This model enables an accurate extraction of device parameters, thereby
allowing for a systematic study of the nanowire mobility. We identify factors
affecting the mobility, and after optimization obtain a field effect mobility
of $\sim2.5\mathbin{\times}10^4$ cm$^2$/Vs. We further demonstrate the
reproducibility of these mobility values which are among the highest reported
for nanowires. Our investigations indicate that the mobility is currently
limited by adsorption of molecules to the nanowire surface and/or the
substrate.",1411.7285v2
2014-12-22,Large anisotropic thermal conductivity of intrinsically two-dimensional metallic oxide PdCoO$_2$,"The highly conductive layered metallic oxide \pdcoo{} is a near-perfect
analogue to an alkali metal in two dimensions. It is distinguished from other
two-dimensional electron systems where the Fermi surface does not reach the
Brillouin zone boundary by a high planar electron density exceeding $10^{15}$
cm$^{-2}$. The simple single-band quasi-2D electronic structure results in
strongly anisotropic transport properties and limits the effectiveness of
electron-phonon scattering. Measurements on single crystals in the temperature
range from 10-300K show that the thermal conductivity is much more weakly
anisotropic than the electrical resistivity, as a result of significant phonon
heat transport. The in-plane thermoelectric power is linear in temperature at
300\,K and displays a purity-dependent peak around 50K. Given the extreme
simplicity of the band-structure, it is possible to identify this peak with
phonon drag driven by normal electron-phonon scattering processes.",1412.6919v1
2015-02-06,Anomalous Pressure Dependence of magnetic Ordering Temperature in Tb to 141 GPa: Comparison with Gd and Dy,"In previous studies the pressure dependence of the magnetic ordering
temperature $T_{\text{o}}$ of Dy was found to exhibit a sharp increase above
its volume collapse pressure of 73 GPa, appearing to reach temperatures well
above ambient at 157 GPa. In a search for a second such lanthanide, electrical
resistivity measurements were carried out on neighboring Tb to 141 GPa over the
temperature range 3.8 - 295 K. Below Tb's volume collapse pressure of 53 GPa,
the pressure dependence $T_{\text{o}}(P)$ mirrors that of both Dy and Gd.
However, at higher pressures $T_{\text{o}}(P)$ for Tb becomes highly anomalous.
This result, together with the very strong suppression of superconductivity by
dilute Tb ions in Y, suggests that extreme pressure transports Tb into an
unconventional magnetic state with an anomalously high magnetic ordering
temperature.",1502.01785v1
2015-02-07,Interband Tunneling for Hole Injection in III-Nitride Ultra-violet Emitters,"Ultra-violet emitters have several applications in the areas of sensing,
water purification, and data storage. While the III-Nitride semiconductor
system has the band gap region necessary for ultraviolet emission, achieving
efficient ultraviolet solid state emitters remains a challenge due to the low
p-type conductivity and high contact resistance in wide band gap AlGaN-based
ultra-violet light emitters. In this work, we show that efficient interband
tunneling can be used for non-equilibrium injection of holes into ultraviolet
emitters. Polarization-engineered tunnel junctions were used to enhance
tunneling probability by several orders of magnitude over a PN homojunction,
leading to highly efficient tunnel injection of holes to ultraviolet light
emitters. This demonstration of efficient interband tunneling introduces a new
paradigm for design of ultra-violet light emitting diodes and diode lasers, and
enables higher efficiency and lower cost ultra-violet emitters.",1502.02080v1
2015-02-27,"Quantum oscillations, thermoelectric coefficients and the Fermi surface of semi-metallic WTe2","We present a study of angle-resolved quantum oscillations of electric and
thermoelectric transport coefficients in semi-metallic WTe$_{2}$, which has the
particularity of displaying a large B$^{2}$ magneto-resistance. The Fermi
surface consists of two pairs of electron-like and hole-like pockets of equal
volumes in a ""Russian doll"" structure. Carrier density, Fermi energy, mobility
and the mean-free-path of the system are quantified. An additional frequency is
observed above a threshold field and attributed to magnetic breakdown across
two orbits. In contrast to all other dilute metals, the Nernst signal remains
linear in magnetic field even in the high-field ($\omega_c\tau \gg 1$) regime.
Surprisingly, none of the pockets extend across the c-axis of the first
Brillouin zone, making the system a three-dimensional metal with moderate
anisotropy in Fermi velocity yet a large anisotropy in mean-free-path.",1502.07797v2
2015-05-19,Energy Exchange between Phononic and Electronic Subsystem Governing The Nonlinear Conduction in DCNQI$_2$Cu,"We present a dynamical study on the nonlinear conduction behaviour in the
commensurate charge-density-wave phase of the quasi-one-dimensional conductor
DCNQI$_2$Cu below 75 K. We can accurately simulate magnitude and
time-dependence of the measured conductivity in response to large voltage
pulses by accounting for the energy exchange between the phononic and
electronic subsystems by means of an electrothermal model. Our simulations
reveal a distinct non-equilibrium population of optical phonon states with an
average energy of E$_{ph}$ = 19 meV being half the activation energy of about
$\Delta$E$_a$ = 39 meV observed in DC resistivity measurements. By inelastic
scattering, this hot optical phonon bath generates additional charge-carrying
excitations thus providing a multiplication effect while energy transferred to
the acoustic phonons is dissipated out of the system via heat conduction.
Therefore, in high electric fields a preferred interaction of charge-carrying
excitations with optical phonons compared to acoustic phonon modes is
considered to be responsible for the nonlinear conduction effects observed in
DCNQI$_2$Cu.",1505.04907v2
2015-08-19,Argument on superconductivity pairing mechanism from cobalt impurity doping in FeSe: spin ($s_{\pm}$) or orbital ($s_{++}$) fluctuation,"In high-superconducting transition temperature ($T_{\rm c}$) iron-based
superconductors, interband sign reversal ($s_{\rm \pm}$) and sign preserving
($s_{\rm ++}$) $s$-wave superconducting states have been primarily discussed as
the plausible superconducting mechanism. We study Co impurity scattering
effects on the superconductivity in order to achieve an important clue on the
pairing mechanism using single crystal Fe$_{1-x}$Co$_x$Se and depict a phase
diagram of a FeSe system. Both superconductivity and structural transition /
orbital order are suppressed by the Co replacement on the Fe sites and
disappear above $x$ = 0.036. These correlated suppressions represent a common
background physics behind these physical phenomena in the multiband Fermi
surfaces of FeSe. By comparing experimental data and theories so far proposed,
the suppression of $T_{\rm c}$ against the residual resistivity is shown to be
much weaker than that predicted in the case of a general sign reversal and a
full gap $s_{\pm}$ models. The origin of the superconducting paring in FeSe is
discussed in terms of its multiband electronic structure.",1508.04605v2
2015-08-19,Electric field control of spin lifetimes in Nb-SrTiO$_3$ by spin-orbit fields,"We show electric field control of the spin accumulation at the interface of
the oxide semiconductor Nb-SrTiO$_{3}$ with Co/AlO$_{x}$ spin injection
contacts at room temperature. The in-plane spin lifetime $\tau_\parallel$ as
well as the ratio of the out-of-plane to in-plane spin lifetime
$\tau_\perp/\tau_\parallel$ is manipulated by the built-in electric field at
the semiconductor surface, without any additional gate contact. The origin of
this manipulation is attributed to Rashba Spin-Orbit Fields (SOFs) at the
Nb-SrTiO$_3$ surface and shown to be consistent with theoretical model
calculations based on SOF spin flip scattering. Additionally, the junction can
be set in a high or low resistance state, leading to a non-volatile control of
$\tau_\perp/\tau_\parallel$, consistent with the manipulation of the Rashba SOF
strength. Such room temperature electric field control over the spin state is
essential for developing energy-efficient spintronic devices and shows promise
for complex oxide based (spin)electronics",1508.04649v1
2015-09-13,Effects of Cr substitution on the magnetic and transport properties and electronic states of SrRuO3 epitaxial thin films,"The effect of Cr substitution in a SrRuO3 epitaxial thin film on SrTiO3
substrate was investigated by measuring the magnetic and transport properties
and the electronic states. The ferromagnetic transition temperature of the
SrRu0.9Cr0.1O3 film (166 K) was higher than that of the SrRuO3 film (147 K).
Resonant photoemission spectroscopy experimentally revealed that the Cr 3dt2g
orbital is hybridized with the Ru 4dt2g orbital in the SrRu0.9Cr0.1O3 film,
supporting the assumption that the enhancement of the ferromagnetic transition
temperature through Cr substitution stems from the widening of energy bands due
to the hybridization of Cr 3dt2g and Ru 4dt2g orbitals. Furthermore, we found
that the Hall resistivity of the SrRu0.9Cr0.1O3 film at low temperature is not
a linear function of magnetic field in the high-field region where the
out-of-plane magnetization was saturated; this result suggests that the
SrRu0.9Cr0.1O3 film undergoes a structural transition at low temperature
accompanied with the modulation of the Fermi surface.",1509.03804v1
2015-10-22,Anomalous transport and thermoelectric performances of CuAgSe compounds,"The copper silver selenide has two phases: the low-temperature semimetal
phase ({\alpha}-CuAgSe) and high-temperature phonon-glass superionic phase
(\b{eta}-CuAgSe). In this work, the electric transport and thermoelectric
properties of the two phases are investigated. It is revealed that the
\b{eta}-CuAgSe is a p-type semiconductor and exhibits low thermal conductivity
while the {\alpha}-CuAgSe shows metallic conduction with dominant n-type
carriers and low electrical resistivity. The thermoelectric figure of merit zT
of the polycrystalline \b{eta}-CuAgSe at 623 K is ~0.95, suggesting that
superionic CuAgSe can be a promising thermoelectric candidate in the
intermediate temperature range.",1510.06616v1
2015-11-12,Experimental and numerical analysis of tribological behavior of CrAl(Si)N films during Scratch,"Scratch sliding tests with a ZrO2 ball and CrAlSiN films with different Si
content were conducted due to CrAlSiN films having high hardness and good wear
resistance. After up to 6000 cycles the specimens were analyzed by Scanning
Electron Microscopy. The friction coefficient of CrAlSiN was lower than that of
CrAlN film.A corresponding three-dimensional finite element model was
constructed with the help of the ABAQUS to describe the mechanical response
during scratch. A comparison of experimental and computational results revealed
that the small elastic deformation took place in the films and substrates;the
deformation friction coefficient was negligible in comparison with the Coulomb
friction coefficient;and with increasing Young's modulus, the stress
concentration was more obvious in CrAlSiN than in CrAlN.",1511.04092v2
2015-12-27,Room-temperature paramagnetoelectric effect in magnetoelectric multiferroics Pb(Fe1/2Nb1/2)O3 and its solid solution with PbTiO3,"We have observed the magnetoelectric response at room temperature and above
in high-resistive ceramics made of multiferroic Pb(Fe1/2Nb1/2)O3 (PFN) and
PFN-based solid solution 0.91PFN-0.09PbTiO3 (PFN-PT). The value of the
paramagnetoelectric (PME) coefficient shows a pronounced maximum near the
ferroelectric-to-paraelectric phase transition temperature, T_C, and then
decreases sharply to zero for T>T_C. The maximal PME coefficient in PFN is
about 4x10(-18) s/A. The theoretical description of the PME effect, within the
framework of a Landau theory of phase transitions allowing for realistic
temperature dependences of spontaneous polarization, dielectric and magnetic
susceptibilities, qualitatively reproduces well the temperature dependence of
the PME coefficient. In particular, the Landau theory predicts the significant
increase of the PME effect at low temperatures and near the temperature of the
paraelectric-to-ferroelectric phase transition, since the PME coefficient is
equal to the product of the spontaneous polarization, dielectric permittivity,
square of magnetic susceptibility and the coefficient quantifying the strength
of the biquadratic magnetoelectric coupling",1512.08217v1
2015-12-31,Intrinsic Nanotwin Effect on Thermal Boundary Conductance in Bulk and Single-Nanowire Twinning Superlattices,"Coherent twin boundaries form periodic lamellar twinning in a wide variety of
semiconductor nanowires, and are often viewed as near-perfect interfaces with
reduced phonon and electron scattering behaviors. Such unique characteristics
are of practical interest for high-performance thermoelectrics and
optoelectronics; however, insufficient understanding of twin-size effects on
thermal boundary resistance poses significant limitations for potential
applications. Here, using atomistic simulations and ab-initio calculations, we
report direct computational observations showing a crossover from diffuse
interface scattering to superlattice-like behavior for thermal transport across
nanoscale twin boundaries present in prototypical bulk and nanowire Si
examples. Intrinsic interface scattering is identified for twin periods larger
than or equal to 22.6 nm, but also vanishes below this size to be replaced by
ultrahigh Kapitza thermal conductances. Detailed analysis of vibrational modes
shows that modeling twin boundaries as atomically-thin 6H-Si layers, rather
than phonon scattering interfaces, provides an accurate description of
effective cross-plane and in-plane thermal conductivities in twinning
superlattices, as a function of the twin period thickness.",1512.09357v2
2016-02-20,Investigation of the electron-phonon interaction in $N{{b}_{3}}Sn$ with the aid of microcontacts,"The method of microcontact spectroscopy in the superconducting state was used
to investigate weak nonlinearities of the current-voltage characteristics of
point contacts made of $N{{b}_{3}}Sn$ single crystals. The nature of the
spectrum of the electron-phonon interaction was found to vary considerably from
contact to contact, indicating considerable deviations of the composition of
the surface of $N{{b}_{3}}Sn$ from stoichiometry. A correlation was established
between the nature of the spectrum and the magnitude of the gap singularities
of the current-voltage characteristics. In the case of ""dirty"" high-resistance
contacts with strong gap singularities the microcontact spectra were reasonably
reproducible, which made it possible to relate them sufficiently closely to the
microcontact function of the electron-phonon interaction in the bulk material.
It was found that microcontact spectroscopy of this interaction was possible in
the superconducting state not only in dirty $S-c-S$ contacts, but also in dirty
$S-c-N$ contacts.",1602.06398v1
2016-04-11,"Single crystal growth of CeTAl$_3$ (T = Cu, Ag, Au, Pd and Pt)","We report single crystal growth of the series of CeTAl$_3$ compounds with T =
Cu, Ag, Au, Pd and Pt by means of optical float zoning. High crystalline
quality was confirmed in a thorough characterization process. With the
exception of CeAgAl$_3$, all compounds crystallize in the non-centrosymmetric
tetragonal BaNiSn$_{3}$ structure (space group: I4mm, No. 107), whereas
CeAgAl$_3$ adopts the related orthorhombic PbSbO$_2$Cl structure (Cmcm, No.
63). An attempt to grow CeNiAl$_3$ resulted in the composition CeNi$_2$Al$_5$.
Low temperature resistivity measurements down to $\sim$0.1K did not reveal
evidence suggestive of magnetic order in CePtAl$_3$ and CePdAl$_3$. In
contrast, CeAuAl$_3$, CeCuAl$_3$ and CeAgAl$_3$ display signatures of magnetic
transitions at 1.3K, 2.1K and 3.2K, respectively. This is consistent with
previous reports of antiferromagnetic order in CeAuAl$_3$, and CeCuAl$_3$ as
well as ferromagnetism in CeAgAl$_3$, respectively.",1604.03146v1
2016-04-14,Large magnetothermopower and Fermi surface reconstruction in Sb$_2$Te$_2$Se,"We report the magnetoresistance, magnetothermopower and quantum oscillation
study of Sb$_2$Te$_2$Se single crystal. The in-plane transverse
magnetoresistance exhibits a crossover at a critical field $B^*$ from
semiclassical weak-field $B^2$ dependence to the high-field unsaturated linear
magnetoresistance which persists up to the room temperature. The
low-temperature Seebeck coefficient is negative in zero field contrary to the
positive Hall resistivity, indicating the multiband effect. The magnetic field
induced the sign reversion of the Seebeck coefficient between 2 K and 150 K, .
The quantum oscillation of crystals reveals the quasi-two-dimensional
(quasi-2D) Fermi surface. These effects are possibly attributed to the large
Fermi surface which touches Brillouin zone boundary to becomes quasi-2D and the
variation in the chemical potential induced by the magnetic field.",1604.04281v1
2016-04-15,Electronic Structure Descriptor for Discovery of Narrow-Band Red-Emitting Phosphors,"Narrow-band red-emitting phosphors are a critical component in
phosphor-converted light-emitting diodes for highly efficient
illumination-grade lighting. In this work, we report the discovery of a
quantitative descriptor for narrow-band Eu2+-activated emission identified
through a comparison of the electronic structure of known narrow-band and
broad-band phosphors. We find that a narrow emission bandwidth is characterized
by a large splitting of more than 0.1 eV between the two highest Eu2+ 4f7
bands. By incorporating this descriptor in a high throughput first principles
screening of 2,259 nitride compounds, we identify five promising new nitride
hosts for Eu2+-activated red-emitting phosphors that are predicted to exhibit
good chemical stability, thermal quenching resistance and quantum efficiency,
as well as narrow-band emission. Our findings provide important insights into
the emission characteristics of rare-earth activators in phosphor hosts, and a
general strategy to the discovery of phosphors with a desired emission peak and
bandwidth.",1604.04581v1
2016-04-18,Superconductivity in undoped CaFe2As2 single crystals,"Single crystals of undoped CaFe2As2 were grown by a FeAs self-flux method,
and the crystals were quenched in ice-water rapidly after high temperature
growth. The quenched crystal undergoes a collapsed tetragonal structural phase
transition around 80 K revealed by the temperature dependent X-ray diffraction
measurements. Superconductivity below 25 K was observed in the collapsed phase
by resistivity and magnetization measurements. The isothermal magnetization
curve measured at 2 K indicates that this is a typical type-II superconductor.
For comparison, we systematically characterized the properties of the furnace
cooled, quenched, and post-annealed single crystals, and found strong internal
crystallographic strain existing in the quenched samples, which is the key for
the occurrence of superconductivity in the undoped CaFe2As2 single crystals.",1604.04964v1
2016-04-22,Multiband behavior and non-metallic low-temperature state of K$_{0.50}$Na$_{0.24}$Fe$_{1.52}$Se$_{2}$,"We report evidence for multiband transport and an insulating low-temperature
normal state in superconducting K$_{0.50}$Na$_{0.24}$Fe$_{1.52}$Se$_{2}$ with
$T_{c}\approx 20$ K. The temperature-dependent upper critical field, $H_{c2}$,
is well described by a two-band BCS model. The normal-state resistance,
accessible at low temperatures only in pulsed magnetic fields, shows an
insulating logarithmic temperature dependence as $T \rightarrow 0$ after
superconductivity is suppressed. This is similar as for high-$T_{c}$ copper
oxides and granular type-I superconductors, suggesting that the
superconductor-insulator transition observed in high magnetic fields is related
to intrinsic nanoscale phase separation.",1604.06793v1
2016-05-30,High-field electron transport in bulk ZnO,"Current-voltage dependence is measured in (Ga,Sb)-doped ZnO up to 150 kV/cm
electric fields. A channel temperature is controlled by applying relatively
short (few ns) voltage pulses to two-terminal samples. The dependence of
electron drift velocity on electron density ranging from 1.42$\times$10$^{17}$
cm$^{-3}$ to 1.3$\times$10$^{20}$ cm$^{-3}$ at a given electric field is
deduced after estimation of the sample contact resistance and the Hall electron
mobility. Manifestation of the highest electron drift velocity up to
$\sim$1.5$\times$10$^{7}$ cm/s is estimated for electron density of
1.42$\times$10$^{17}$ cm$^{-3}$ and is in agreement with Monte Carlo simulation
when hot-phonon lifetime is below 1 ps. A local drift velocity maximum is
observed at $\sim$1.1$\times$10$^{19}$ cm$^{-3}$ and is in agreement with
ultra-fast hot phonon decay.",1605.09117v1
2016-06-27,Hafnium carbide formation in oxygen deficient hafnium oxide thin films,"On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO$_{2-x}$)
contaminated with adsorbates of carbon oxides, the formation of hafnium carbide
(HfC$_x$) at the surface during vacuum annealing at temperatures as low as 600
{\deg}C is reported. Using X-ray photoelectron spectroscopy the evolution of
the HfC$_x$ surface layer related to a transformation from insulating into
metallic state is monitored in situ. In contrast, for fully stoichiometric
HfO$_2$ thin films prepared and measured under identical conditions, the
formation of HfC$_x$ was not detectable suggesting that the enhanced adsorption
of carbon oxides on oxygen deficient films provides a carbon source for the
carbide formation. This shows that a high concentration of oxygen vacancies in
carbon contaminated hafnia lowers considerably the formation energy of hafnium
carbide. Thus, the presence of a sufficient amount of residual carbon in
resistive random access memory devices might lead to a similar carbide
formation within the conducting filaments due to Joule heating.",1606.08227v1
2016-06-29,Improved model for the thermal conductivity of binary metallic systems,"We extended and corrected Mott's two-band model for the
composition-dependence of thermal and electrical conductivity in binary metal
alloys based on high-throughput time-domain thermoreflectance (TDTR)
measurements on diffusion multiples and scatterer-density calculations from
first principles. Examining PdAg, PtRh, AuAg, AuCu, PdCu, PdPt, and NiRh binary
alloys, we found that the nature of the two dominant scatterer-bands considered
in the Mott model changes with the alloys, and should be interpreted as a
combination of the dominant element-specific s- and/or d-orbitals. Using
calculated orbital and element-resolved density-of-states values calculated
with density functional theory as input, we determined the correct orbital mix
that dominates electron scattering for all examined alloys and find excellent
agreement between fitted models and experiments. The proposed description of
the composition dependence of the resistivity can be readily implemented into
the CALPHAD framework.",1606.09287v2
2016-06-30,Superconductivity at 5.5 K in Nb2PdSe5 compound,"We report superconductivity in as synthesized Nb2PdSe5, which is similar to
recently discovered Nb2PdS5 compound having very high upper critical field,
clearly above the Pauli paramagnetic limit [Sci. Rep. 3, 1446 (2013)]. A bulk
polycrystalline Nb2PdSe5 sample is synthesized by solid state reaction route in
phase pure structure. The structural characterization has been done by X ray
diffraction, followed by Rietveld refinements, which revealed that Nb2PdSe5
sample is crystallized in monoclinic structure with in space group C2/m.
Structural analysis revealed the formation of sharing of one dimensional PdSe2
chains. Electrical and magnetic measurements confirmed superconductivity in
Nb2PdSe5 compound at 5.5K. Detailed magneto-resistance results, exhibited the
value of upper critical field to be around 8.2Tesla. The estimated Hc2(0) is
within Pauli Paramagnetic limit, which is unlike the Nb2PdS5.",1606.09369v2
2016-08-01,Phase Transition in IrTe$_2$ induced by spin-orbit coupling,"IrTe$_2$ has been renewed as an interesting system showing competing
phenomenon between a questionable density-wave transition near 270 K followed
by superconductivity with doping of high atomic number materials. Higher atomic
numbers of Te and Ir supports strong spin-orbital coupling in this system.
Using dynamical mean field theory with LDA band structure I have introduced
Rashba spin orbit coupling in this system to get the interpretation for
anomalous resistivity and related transition in this system. While no
considerable changes are observed in DMFT results of Ir-5d band other than
orbital selective pseudogap pinned to Fermi level, Te-p band shows a van Hove
singularity at the Fermi level except low temperature. Finally I discuss the
implications of these results in theoretical understanding of ordering in
IrTe$_2$.",1608.00467v1
2016-08-03,Edge-induced Schottky barrier modulation at metal contacts to exfoliated molybdenum disulfide flakes,"Ultrathin two-dimensional semiconductors obtained from layered
transition-metal dichalcogenides such as molybdenum disulfide (MoS2) are
promising for ultimately scaled transistors beyond Si. Although the shortening
of the semiconductor channel is widely studied, the narrowing of the channel,
which should also be important for scaling down the transistor, has been
examined to a lesser degree thus far. In this study, the impact of narrowing on
mechanically exfoliated MoS2 flakes was investigated according to the
channel-width-dependent Schottky barrier heights at Cr/Au contacts. Narrower
channels were found to possess a higher Schottky barrier height, which is
ascribed to the edge-induced band bending in MoS2. The higher barrier heights
degrade the transistor performance as a higher electrode-contact resistance.
Theoretical analyses based on Poisson's equation showed that the edge-induced
effect can be alleviated by a high dopant impurity concentration, but this
strategy should be limited to channel widths of roughly 0.7 micrometers because
of the impurity-induced charge-carrier mobility degradation. Therefore, proper
termination of the dangling bonds at the edges should be necessary for
aggressive scaling with layered semiconductors.",1608.01061v1
2016-08-23,Chiral anomaly and longitudinal magnetotransport in type-II Weyl semimetals,"In the presence of parallel electric and magnetic fields, the violation of
separate number conservation laws for the three dimensional left and right
handed Weyl fermions is known as the chiral anomaly. The recent discovery of
Weyl and Dirac semimetals has paved the way for experimentally testing the
effects of chiral anomaly via longitudinal magneto-transport measurements. More
recently, a type-II Weyl semimetal (WSM) phase has been proposed, where the
nodal points possess a finite density of states due to the touching between
electron- and hole- pockets. It has been suggested that the main difference
between the two types of WSMs (type-I and type-II) is that in the latter,
chiral anomaly and the associated longitudinal magneto-resistance are strongly
anisotropic, vanishing when the applied magnetic field is perpendicular to the
direction of tilt of Weyl fermion cones in a type-II WSM. We analyze chiral
anomaly in a type-II WSM in quasiclassical Boltzmann framework, and find that
the chiral anomaly induced positive longitudinal magneto-conductivity is
present along any arbitrary direction.",1608.06625v2
2016-10-19,Anomalous Thermal Diffusivity in Underdoped YBa$_2$Cu$_3$O$_{6+x}$,"We present local optical measurements of thermal diffusivity in the $ab$
plane of underdoped YBCO crystals. We find that the diffusivity anisotropy is
comparable to reported values of the electrical resistivity anisotropy,
suggesting that the anisotropies have the same origin. The anisotropy drops
sharply below the charge order transition. We interpret our results through a
strong electron-phonon scattering picture and find that both electronic and
phononic contributions to the diffusivity saturate a proposed bound. Our
results suggest that neither well-defined electron nor phonon quasiparticles
are present in this material.",1610.05845v2
2016-10-22,High performance THz emitters based on ferromagnetic/nonmagnetic heterostructures,"We report a THz emitter with excellent performances based on nonmagnetic (NM)
and ferromagnetic (FM) heterostructures. The spin currents are first excited by
the femtosecond laser beam in the NM/FM bilayer, and then transient charge
currents are generated by inverse spin Hall effect, leading to THz emission out
of the structure. The broadband THz waves emitted from our film stacks have a
peak intensity exceeding 500 um thick ZnTe crystals (standard THz emitters).
Our device is insensitive to the polarization of an incident laser beam which
indicates the noise resistive feature. In contrast, the polarization of THz
waves is fully controllable by an external magnetic field. We have also
fabricated the devices on flexible substrates with a great performance, and
demonstrated that the devices can be driven by low power lasers. Together with
the low cost and mass productive sputtering growth method for the film stacks,
the proposed THz emitters can be readily applied to a wide range of THz
equipment. Our study also points towards an alternative approach to
characterize spintronic devices with NM/FM bilayers.",1610.07020v1
2016-10-26,S2DS: Physics-Based Compact Model for Circuit Simulation of Two-Dimensional Semiconductor Devices Including Non-Idealities,"We present a physics-based compact model for two-dimensional (2D)
field-effect transistors (FETs) based on monolayer semiconductors such as MoS2.
A semi-classical transport approach is appropriate for the 2D channel, enabling
simplified analytical expressions for the drain current. In addition to
intrinsic FET behavior, the model includes contact resistance, traps and
impurities, quantum capacitance, fringing fields, high-field velocity
saturation and self-heating, the latter being found to play a strong role. The
model is calibrated with state-of-the-art experimental data for n- and p-type
2D-FETs, and it can be used to analyze device properties for sub-100 nm gate
lengths. Using the experimental fit, we demonstrate feasibility of circuit
simulations using properly scaled devices. The complete model is implemented in
SPICE-compatible Verilog-A, and a downloadable version is freely available on
the nanoHUB.org.",1610.08489v2
2016-11-14,Nonlinear Transport of Graphene in the Quantum Hall Regime,"We have studied the breakdown of the integer quantum Hall (QH) effect with
fully broken symmetry, in an ultra-high mobility graphene device sandwiched
between two single crystal hexagonal boron nitride substrates. The evolution
and stabilities of the QH states are studied quantitatively through the
nonlinear transport with dc Hall voltage bias. The mechanism of the QH
breakdown in graphene and the movement of the Fermi energy with the electrical
Hall field are discussed. This is the first study in which the stabilities of
fully symmetry broken QH states are probed all together. Our results raise the
possibility that the v=6 states might be a better target for the quantum
resistance standard.",1611.04221v1
2016-11-15,Encapsulated Nanowires: Boosting Electronic Transport in Carbon Nanotubes,"The electrical conductivity of metallic carbon nanotubes (CNTs) quickly
saturates with respect to bias voltage due to scattering from a large
population of optical phonons. Decay of these dominant scatterers in pristine
CNTs is too slow to offset an increased generation rate at high voltage bias.
We demonstrate from first principles that encapsulation of 1D atomic chains
within a single-walled CNT can enhance decay of ""hot"" phonons by providing
additional channels for thermalisation. Pacification of the phonon population
growth reduces electrical resistivity of metallic CNTs by 51% for an example
system with encapsulated beryllium.",1611.04867v2
2016-12-06,Enhanced Structural Stability and Photo Responsiveness of CH3NH3SnI3 Perovskite via Pressure-Induced Amorphization and Recrystallization,"An organic-inorganic halide perovskite of CH3NH3SnI3 with significantly
improved structural stability is obtained via pressure-induced amorphization
and recrystallization. In situ high-pressure resistance measurements reveal an
increased electrical conductivity by 300% in the pressure-treated perovskite.
Photocurrent measurements also reveal a substantial enhancement in
visible-light responsiveness. The mechanism underlying the enhanced properties
is demonstrated to be associated with the improved structural stability.",1612.01649v1
2016-12-20,Enhanced Superconductivity in TiO Epitaxial Thin Films,"Titanium oxides have many fascinating optical and electrical properties, such
as the superconductivity at 2.0 K in cubic titanium monoxide TiO
polycrystalline bulk. However, the lack of TiO single crystals or epitaxial
films has prevented systematic investigations on its superconductivity. Here,
we report the basic superconductivity characterizations of cubic TiO films
epitaxially grown on (0001)-oriented Al2O3 substrates. The magnetic and
electronic transport measurements confirmed that TiO is a type-II
superconductor and the record high Tc is about 7.4 K. The lower critical field
(Hc1) at 1.9 K, the extrapolated upper critical field Hc2(0) and coherence
length are about 18 Oe, 13.7 T and 4.9 nm, respectively. With increasing
pressure, the value of Tc shifts to lower temperature while the normal state
resistivity increases. Our results on the superconducting TiO films confirm the
strategy to achieve higher Tc in epitaxial films, which may be helpful for
finding more superconducting materials in various related systems.",1612.06506v1
2017-02-02,Two-temperature equations of state for d-band metals irradiated by femtosecond laser pulses,"The cold curves for energy and pressure of Copper, Iron, and Tantalum were
obtained using methods of the density functional theory. We consider
hydrostatic and uniaxial deformations in the range from double compression of
the initial volume per atom to double stretching. The presence of allotropic
transformation from $\alpha$ - phase of Iron to the hexaferrum with the growth
of pressure is observed. In the case of hydrostatic deformations we also have
obtained analogous cold curves, but with non-zero electronic temperatures in
the range up to 5 eV. The similar volume and electronic temperature ranges have
been considered recently. The behavior of electronic internal energy, pressure,
and density of states was investigated in the volume and temperature ranges
called above. The maximum hydrostatic strains and the types of lattice
instabilities were theoretically predicted for the considered metals. The
influence of high electronic temperature on the electronic heat conductivity
and electric resistivity has been provided for d-band metals by the approach
based on the solution of Boltzmann kinetic equation in $\tau$-approximation.
This data is compared with the results of quantum molecular dynamics for Gold.",1702.00825v3
2017-02-15,"New bulk p-type skutterudites DD0.7Fe2.7Co1.3Sb12-xXx (X = Ge, Sn) reaching ZT>1.3","The best p-type skutterudites so far are didymium filled, Fe/Co substituted,
Sb-based skutterudites. Substitution at the Sb-sites influences the electronic
structure, deforms the Sb4-rings, enhances the scattering of phonons on
electrons and impurities and this way reduces the lattice thermal conductivity.
In this paper we study structural and transport properties of p-type
skutterudites with the nominal composition DD0.7Fe2.7Co1.3Sb11.7{Ge/Sn}0.3,
which were prepared by a rather fast reaction-annealing-melting technique. The
Ge-doped sample showed impurities, which did not anneal out completely and even
with ZT > 1 the result was not satisfying. However, the single-phase Sn-doped
sample, DD0.7Fe2.7Co1.3Sb11.8Sn0.2, showed a lower thermal and lattice thermal
conductivity than the undoped skutterudite leading to a higher ZT=1.3, hitherto
the highest ZT for a p-type skutterudite. Annealing at 570 K for 3 days proved
the stability of the microstructure. After severe plastic deformation (SPD),
due to additionally introduced defects, an enhancement of the electrical
resistivity was compensated by a significantly lower thermal conductivity and
the net effect led to a record high figure of merit: ZT = 1.45 at 850 K for
DD0.7Fe2.7Co1.3Sb11.8Sn0.2.",1702.04498v1
2017-02-24,Out-of-plane easy-axis in thin films of diluted magnetic semiconductor Ba1-xKx(Zn1-yMny)2As2,"Single-phased, single-oriented thin films of Mn-doped ZnAs-based diluted
magnetic semiconductor (DMS) Ba1-xKx(Zn1-yMny)2As2 (x = 0.03, 0.08; y = 0.15)
have been deposited on Si, SrTiO3, LaAlO3, (La,Sr)(Al,Ta)O3, and MgAl2O4
substrates, respectively. Utilizing a combined synthesis and characterization
system excluding the air and further optimizing the deposition parameters,
high-quality thin films could be obtained and be measured showing that they can
keep inactive-in-air up to more than 90 hours characterized by electrical
transport measurements. In comparison with films of x = 0.03 which possess
relatively higher resistivity, weaker magnetic performances, and larger energy
gap, thin films of x = 0.08 show better electrical and magnetic performances.
Strong magnetic anisotropy was found in films of x = 0.08 grown on
(La,Sr)(Al,Ta)O3 substrate with their magnetic polarization aligned almost
solely on the film growth direction.",1702.07506v1
2017-06-16,An argon ion beam milling process for native $\text{AlO}_\text{x}$ layers enabling coherent superconducting contacts,"We present an argon ion beam milling process to remove the native oxide layer
forming on aluminum thin films due to their exposure to atmosphere in between
lithographic steps. Our cleaning process is readily integrable with
conventional fabrication of Josephson junction quantum circuits. From
measurements of the internal quality factors of superconducting microwave
resonators with and without contacts, we place an upper bound on the residual
resistance of an ion beam milled contact of 50$\,\mathrm{m}\Omega \cdot \mu
\mathrm{m}^2$ at a frequency of 4.5 GHz. Resonators for which only $6\%$ of the
total foot-print was exposed to the ion beam milling, in areas of low electric
and high magnetic field, showed quality factors above $10^6$ in the single
photon regime, and no degradation compared to single layer samples. We believe
these results will enable the development of increasingly complex
superconducting circuits for quantum information processing.",1706.06424v1
2017-06-29,Magnetotransport properties of MoP$_2$,"We report magnetotransport and de Haas-van Alphen (dHvA) effect studies on
MoP$_2$ single crystals, predicted to be type-2 Weyl semimetal with four pairs
of robust Weyl points located below the Fermi level and long Fermi arcs. The
temperature dependence of resistivity shows a peak before saturation, which
does not move with magnetic field. Large nonsaturating magnetoresistance (MR)
was observed, and the field dependence of MR exhibits a crossover from
semicalssical weak-field $B^2$ dependence to the high-field linear-field
dependence, indicating the presence of Dirac linear energy dispersion. In
addition, systematic violation of Kohler's rule was observed, consistent with
multiband electronic transport. Strong spin-orbit coupling (SOC) splitting has
an effect on dHvA measurements whereas the angular-dependent dHvA orbit
frequencies agree well with the calculated Fermi surface. The cyclotron
effective mass $\sim$ 1.6$m_e$ indicates the bands might be trivial, possibly
since the Weyl points are located below the Fermi level. Interestingly,
quasi-two dimensional(2D) band structure is observed even though the crystal
structure of MoP$_2$ is not layered.",1706.09830v1
2017-09-11,Massive fermions with low mobility in antiferromagnet orthorhombic CuMnAs single crystals,"We report the physical properties of orthorhombic o-CuMnAs single crystal,
which is predicted to be a topological Dirac semimetal with magnetic ground
state and inversion symmetry broken. o-CuMnAs exhibits an antiferromagnetic
transition with TN ~ 312 K. Further characterizations of magnetic properties
suggest that the AFM order may be canted with the spin orientation in the bc
plane. Small isotropic MR and linearly field-dependent Hall resistivity with
positive slope indicate that single hole-type carries with high density and low
mobility dominate the transport properties of o-CuMnAs. Furthermore, the result
of low-temperature heat capacity shows that the effective mass of carriers is
much larger than those in typical topological semimetals. These results imply
that the carriers in o-CuMnAs exhibit remarkably different features from those
of Dirac fermions predicted in theory.",1709.03394v2
2017-09-13,Ultra-broadband photodetectors based on epitaxial graphene quantum dots,"Graphene is an ideal material for hot-electron bolometers, due to its low
heat capacity and weak electron-phonon coupling. Nanostructuring graphene with
quantum dot constrictions yields detectors with extraordinarily high intrinsic
responsivity, higher than 1x10^9 V/W at 3K. The sensing mechanism is bolometric
in nature: the quantum confinement gap causes a strong dependence of the
electrical resistance on the electron temperature. Here we show that this
quantum confinement gap does not impose a limitation on the photon energy for
light detection and these quantum dot bolometers work in a very broad spectral
range, from terahertz, through telecom to ultraviolet radiation, with
responsivity independent of wavelength. We also measure the power dependence of
the response. Although the responsivity decreases with increasing power, it
stays higher than 1x10^8 V/W in a wide range of absorbed power, from 1 pW to
0.4 nW.",1709.04498v1
2017-09-27,"Pressure-induced Lifshitz transition in NbP: Raman, x-ray diffraction, electrical transport and density functional theory","We report high pressure Raman, synchrotron x-ray diffraction and electrical
transport studies on Weyl semimetals NbP and TaP along with first-principles
density functional theoretical (DFT) analysis. The frequencies of first-order
Raman modes of NbP harden with increasing pressure and exhibit a slope change
at P$_c$ $\sim$ 9 GPa, and its resistivity exhibits a minimum at P$_c$. The
pressure-dependent volume of NbP exhibits a change in its bulk modulus from 207
GPa to 243 GPa at P$_c$. Using DFT calculations, we show that these anomalies
are associated with pressure induced Lifshitz transition which involves
appearance of electron and hole pockets in its electronic structure. In
contrast, results of Raman and synchrotron x-ray diffraction experiments on TaP
and DFT calculations show that TaP is quite robust under pressure and does not
undergo any phase transition.",1709.09368v1
2017-10-27,Unusual behavior of cuprates explained by heterogeneous charge localization,"The cuprate high-temperature superconductors are among the most intensively
studied materials, yet essential questions regarding their principal phases and
the transitions between them remain unanswered. Generally thought of as doped
charge-transfer insulators, these complex lamellar oxides exhibit pseudogap,
strange-metal, superconducting and Fermi-liquid behaviour with increasing
hole-dopant concentration. Here we propose a simple inhomogeneous Mott-like
(de)localization model wherein exactly one hole per copper-oxygen unit is
gradually delocalized with increasing doping and temperature. The model is
percolative in nature, with parameters that are experimentally constrained. It
comprehensively captures pivotal unconventional experimental results, including
the temperature and doping dependence of the pseudogap phenomenon, the
strange-metal linear temperature dependence of the planar resistivity, and the
doping dependence of the superfluid density. The success and simplicity of our
model greatly demystify the cuprate phase diagram and point to a local
superconducting pairing mechanism involving the (de)localized hole.",1710.10221v1
2017-11-05,Investigations of a Robotic Testbed with Viscoelastic Liquid Cooled Actuators,"We design, build, and thoroughly test a new type of actuator dubbed
viscoelastic liquid cooled actuator (VLCA) for robotic applications. VLCAs
excel in the following five critical axes of performance: energy efficiency,
torque density, impact resistence, joint position and force controllability. We
first study the design objectives and choices of the VLCA to enhance the
performance on the needed criteria. We follow by an investigation on
viscoelastic materials in terms of their damping, viscous and hysteresis
properties as well as parameters related to the long- term performance. As part
of the actuator design, we configure a disturbance observer to provide
high-fidelity force control to enable a wide range of impedance control
capabilities. We proceed to design a robotic system capable to lift payloads of
32.5 kg, which is three times larger than its own weight. In addition, we
experiment with Cartesian trajectory control up to 2 Hz with a vertical range
of motion of 32 cm while carrying a payload of 10 kg. Finally, we perform
experiments on impedance control and mechanical robustness by studying the
response of the robotics testbed to hammering impacts and external force
interactions.",1711.01649v2
2017-11-07,Epitaxial stabilization of pulsed laser deposited Sr$_{n+1}$Ir$_n$O$_{3n+1}$ thin films: entangled effect of growth dynamics and strain,"The subtle balance of electronic correlations, crystal field splitting and
spin--orbit coupling in layered Ir$^{4+}$ oxides can give rise to novel
electronic and magnetic phases. Experimental progress in this field relies on
the synthesis of epitaxial films of these oxides. However, the growth of
layered iridates with excellent structural quality is a great experimental
challenge. Here we selectively grow high quality single--phase films of
Sr$_2$IrO$_4$, Sr$_3$Ir$_2$O$_7$, and SrIrO$_3$ on various substrates from a
single Sr$_3$Ir$_2$O$_7$ target by tuning background oxygen pressure and
epitaxial strain. We demonstrate a complex interplay between growth dynamics
and strain during thin film deposition. Such interplay leads to the
stabilization of different phases in films grown on different substrates under
identical growth conditions, which cannot be explained by a simple kinetic
model. We further investigate the thermoelectric properties of the three phases
and propose that weak localization is responsible for the low temperature
activated resistivity observed in SrIrO$_3$ under compressive strain.",1711.02767v3
2017-11-09,Magnetic phase separation and strong AFM nature of hexagonal Gd$_5$Sb$_3$,"We report on the combined results of structural, magnetic, transport and
calorimetric properties of Mn$_5$Si$_3$-type hexagonal Gd$_5$Sb$_3$. With
decreasing temperature, it exhibits a ferromagnetic-like transition at 265 K,
N\'{e}el transition at 95.5 K and a spin-orientation transition at 62 K. The
system is found to be in AFM state down to 2 K in a field of 70 kOe. Magnetic
phase coexistence is not noticeable despite large positive Curie-Weiss
temperature. Instead low-temperature AFM and high-temperature FM-like phases
are separated in large temperature. Temperature-magnetic field ($H$-$T$) phase
diagram reveals field-driven complex magnetic phases. Within the AFM phase, the
system is observed to undergo field-driven spin-orientation transitions.
Field-induced tricritical and quantum critical points appear to be absent due
to strong AFM nature and by the intervention of FM-like state between PM and
AFM states. Electrical resistivity along with large Sommerfeld parameter
suggests metallic nature.",1711.03263v1
2017-11-29,Pressure-induced ferromagnetism due to an anisotropic electronic topological transition in Fe1.08Te,"A rapid and anisotropic modification of the Fermi-surface shape can be
associated with abrupt changes in crystalline lattice geometry or in the
magnetic state of a material. In this study we show that such an electronic
topological transition is at the basis of the formation of an unusual
pressure-induced tetragonal ferromagnetic phase in Fe$_{1.08}$Te. Around 2 GPa,
the orthorhombic and incommensurate antiferromagnetic ground-state of
Fe$_{1.08}$Te is transformed upon increasing pressure into a tetragonal
ferromagnetic state via a conventional first-order transition. On the other
hand, an isostructural transition takes place from the paramagnetic
high-temperature state into the ferromagnetic phase as a rare case of a `type
0' transformation with anisotropic properties. Electronic-structure
calculations in combination with electrical resistivity, magnetization, and
x-ray diffraction experiments show that the electronic system of Fe$_{1.08}$Te
is instable with respect to profound topological transitions that can drive
fundamental changes of the lattice anisotropy and the associated magnetic
order.",1711.10745v1
2018-01-15,Improving Graphene-metal Contacts: Thermal Induced Polishing,"Graphene is a very promising material for nanoelectronics applications due to
its unique and remarkable electronic and thermal properties. However, when
deposited on metallic electrodes the overall thermal conductivity is
significantly decreased. This phenomenon has been attributed to the mismatch
between the interfaces and contact thermal resistance. Experimentally, one way
to improve the graphene/metal contact is thorough high-temperature annealing,
but the detailed mechanisms behind these processes remain unclear. In order to
address these questions, we carried out fully atomistic reactive molecular
dynamics simulations using the ReaxFF force field to investigate the
interactions between multi-layer graphene and metallic electrodes (nickel)
under (thermal) annealing. Our results show that the annealing induces an
upward-downward movement of the graphene layers, causing a pile-driver-like
effect over the metallic surface. This graphene induced movements cause a
planarization (thermal polishing-like effect) of the metallic surface, which
results in the increase of the effective graphene/metal contact area. This can
also explain the experimentally observed improvements of the thermal and
electric conductivities.",1801.04785v1
2018-01-31,Commensurability Oscillations in One-Dimensional Graphene Superlattices,"We report the experimental observation of commensurability oscillations (COs)
in 1D graphene superlattices. The widely tunable periodic potential modulation
in hBN encapsulated graphene is generated via the interplay of nanopatterned
few layer graphene acting as a local bottom gate and a global Si back gate. The
longitudinal magneto-resistance shows pronounced COs, when the sample is tuned
into the unipolar transport regime. We observe up to six CO minima, providing
evidence for a long mean free path despite the potential modulation. Comparison
to existing theories shows that small angle scattering is dominant in
hBN/graphene/hBN heterostructures. We observe robust COs persisting to
temperature exceeding $T=150$ K. At high temperatures, we find deviations from
the predicted $T$-dependence, which we ascribe to electron-electron scattering.",1802.00016v2
2018-03-22,High density carriers at a strongly coupled graphene-topological insulator interface,"We report on a strongly coupled bilayer graphene (BLG) - \bise\ device with a
junction resistance of less than 1.5 k$\Omega\mu$m$^2$. This device exhibits
unique behavior at the interface, which cannot be attributed to either material
in absence of the other. We observe quantum oscillations in the
magnetoresistance of the junction, indicating the presence of well-resolved
Landau levels due to hole carriers of unknown origin with a very large Fermi
surface. These carriers, found only at the interface, could conceivably arise
due to significant hole doping of the bilayer graphene with charge transfer on
the order of 2$\times$10$^{13}$ cm$^{-2}$, or due to twist angle dependent
mini-band transport.",1803.08260v1
2018-03-27,Large-Scale Fabrication of RF MOSFETs on Liquid-Exfoliated MoS2,"For the first time, thousands of RF MOSFETs were batch-fabricated on
liquid-exfoliated MoS2 below 300 {\deg}C with nearly 100% yield. The
large-scale fabrication with high yield allowed the average performance instead
of the best performance to be reported. The DC performance of these devices
were typical, but the RF performance, enabled by buried gates and on the order
of 100 MHz, was reported for the first time for liquid-exfoliated MoS2. To
resolve the dilemma of thin vs. thick films, gate recess was used on 20-nm
thick films to improve the gate control while keeping the contact resistance
lower than that on 10-nm films. These innovations may enable thin-film
transistors to operate in the microwave range.",1803.09906v1
2018-05-20,Autonomous actuation of zero modes in mechanical networks far from equilibrium,"A zero mode, or floppy mode, is a non-trivial coupling of mechanical
components yielding a degree of freedom with no resistance to deformation.
Engineered zero modes have the potential to act as microscopic motors or memory
devices, but this requires an internal actuation mechanism that can overcome
unwanted fluctuations in other modes and the dissipation inherent in real
systems. In this work, we show theoretically and experimentally that complex
zero modes in mechanical networks can be selectively mobilized by
non-equilibrium activity. We find that a correlated active bath actuates an
infinitesimal zero mode while simultaneously suppressing fluctuations in higher
modes compared to thermal fluctuations, which we experimentally mimic by high
frequency shaking of a physical network. Furthermore, self-propulsive dynamics
spontaneously mobilise finite mechanisms as exemplified by a self-propelled
topological soliton. Non-equilibrium activity thus enables autonomous actuation
of coordinated mechanisms engineered through network topology.",1805.07728v2
2018-06-06,Pressure Evolution of Magnetism in URhGa,"In this paper, we report the results of an ambient and high pressure study of
a 5f-electron ferromagnet URhGa. The work is focused on measurements of
magnetic and thermodynamic properties of a single crystal sample and on the
construction of the p-T phase diagram. Diamond anvil cells were employed to
measure the magnetization and electrical resistivity pressures up to ~ 9 GPa.
At ambient pressure, URhGa exhibits collinear ferromagnetic ordering of uranium
magnetic moments {\mu}U ~ 1.1 {\mu}B (at 2 K) aligned along the c-axis of the
hexagonal crystal structure below the Curie temperature TC = 41K. With the
application of pressure up to 5GPa the ordering temperature TC initially
increases whereas the saturated moment slightly decreases. The rather
unexpected evolution is put in the context of the UTX family of compounds.",1806.02686v1
2018-06-25,Ferromagnetism above 1000 K in highly cation-ordered double-perovskite insulator Sr3OsO6,"Magnetic insulators have been intensively studied for over 100 years, and
they, in particular ferrites, are considered to be the cradle of magnetic
exchange interactions in solids. Their wide range of applications include
microwave devices and permanent magnets . They are also suitable for spintronic
devices owing to their high resistivity, low magnetic damping, and
spin-dependent tunneling probabilities. The Curie temperature is the crucial
factor determining the temperature range in which any ferri/ferromagnetic
system remains stable. However, the record Curie temperature has stood for over
eight decades in insulators and oxides (943 K for spinel ferrite LiFe5O8). Here
we show that a highly B-site ordered double-perovskite, Sr2(SrOs)O6 (Sr3OsO6),
surpasses this long standing Curie temperature record by more than 100 K. We
revealed this B-site ordering by atomic-resolution scanning transmission
electron microscopy. The density functional theory (DFT) calculations suggest
that the large spin-orbit coupling (SOC) of Os6+ 5d2 orbitals drives the system
toward a Jeff = 3/2 ferromagnetic (FM) insulating state. Moreover, the Sr3OsO6
is the first epitaxially grown osmate, which means it is highly compatible with
device fabrication processes and thus promising for spintronic applications.",1806.09308v1
2018-06-26,Ultrahigh Magnetic Fields Produced by Shearing Carbon Nanotubes,"In laboratories, ultrahigh magnetic fields are usually produced with very
large currents through superconducting, resistive or hybrid magnets, which
require extreme conditions, such as low temperature, huge cooling water or tens
of megawatts of power. In this work we report that when single walled carbon
nanotubes (SWNTs) are cut, there are magnetic moments at the shearing end of
SWNTs. The average magnetic moment is found to be 41.5+-9.8uB per carbon atom
in the end states with a width of 1 nm at temperature of 300.0K, suggesting
ultrahigh magnetic fields can be produced. The dangling sigma and pi bonds of
the carbon atoms at the shearing ends play important roles for this
unexpectedly high magnetic moments because the oxidation temperature of cut
SWNTs is found to be as low as 312 in dry air. Producing ultrahigh magnetic
field with SWNTs has the advantage of working at higher working temperature and
with low energy consumption, suggesting great potentials of applications.",1806.09891v1
2018-06-27,Slip Detection: Analysis and Calibration of Univariate Tactile Signals,"The existence of tactile afferents sensitive to slip-related mechanical
transients in the human hand augments the robustness of grasping through
secondary force modulation protocols. Despite this knowledge and the fact that
tactile-based slip detection has been researched for decades, robust slip
detection is still not an out-of-the-box capability for any commercially
available tactile sensor. This research seeks to bridge this gap with a
comprehensive study addressing several aspects of slip detection. Key
developments include a systematic data collection process yielding millions of
sensory data points, the generalized conversion of multivariate-to-univariate
sensor output, an insightful spectral analysis of the univariate sensor
outputs, and the application of Long Short-Term Memory (LSTM) neural networks
on the univariate signals to produce robust slip detectors from three
commercially available sensors capable of tactile sensing. The sensing elements
underlying these sensors vary in quantity, spatial arrangement, and mechanics,
leveraging principles in electro-mechanical resistance, optics, and
hydro-acoustics. Critically, slip detection performance of the tactile
technologies is quantified through a measurement methodology that unveils the
effects of data window size, sampling rate, material type, slip speed, and
sensor manufacturing variability. Results indicate that the investigated
commercial tactile sensors are inherently capable of high-quality slip
detection.",1806.10451v1
2018-06-27,Electron-hole tunneling revealed by quantum oscillations in the nodal-line semimetal HfSiS,"We report a study of quantum oscillations in the high-field
magneto-resistance of the nodal-line semimetal HfSiS. In the presence of a
magnetic field up to 31 T parallel to the c-axis, we observe quantum
oscillations originating both from orbits of individual electron and hole
pockets, and from magnetic breakdown between these pockets. In particular, we
find an oscillation associated with a breakdown orbit enclosing one electron
and one hole pocket in the form of a `figure of eight'. This observation
represents an experimental confirmation of the momentum space analog of Klein
tunneling. When the c-axis and the magnetic field are misaligned with respect
to one another, this oscillation rapidly decreases in intensity. Finally, we
extract the cyclotron masses from the temperature dependence of the
oscillations, and find that the mass of the 'figure of eight' orbit corresponds
to the sum of the individual pockets, consistent with theoretical predictions
for Klein tunneling in topological semimetals.",1806.10592v1
2018-06-28,Bloch surface waves at the telecommunication wavelength with Lithium Niobate as top layer for integrated optics,"Lithium niobate (LN) based devices are widely used in integrated and
nonlinear optics. This material is robust and resistive to high temperatures,
which makes the LN-based devices table, but challenging to fabricate. In this
work we report on the design, manufacturing and characterization of engineered
dielectric media with thin film lithium niobate (TFLN) on top for the coupling
and propagation of electromagnetic surface waves at the telecommunication
wavelengths. The designed one-dimentional photonic crystal (1DPhC) sustains
Bloch surface waves at the multilayer/air interface at 1550 nm wavelength with
a propagation detected over a distance of 3 mm. The working wavelength and
improved BSW propagation parameters open the way for exploration of nonlinear
properties of BSW based devices. It is also expected that these novel devices
will modify BSW propagation and coupling by external thermal/electrical stimuli
due to the improved quality of the TFLN top layer of 1DPhC.",1806.11142v1
2018-11-06,Low-dispersion low-loss dielectric gratings for efficient ultrafast laser pulse compression at high average powers,"We have developed low-dispersion (1480 l/mm), resonance-free, diffraction
gratings made of dielectric materials resistant to femtosecond laser damage
$(SiO_{2}/HfO_{2})$. A 14 cm diameter sample was fabricated resulting in a mean
diffraction efficiency of 99.1% at {\lambda} = 810 nm with 0.4% uniformity
using equipment which can fabricate gratings up to 1m diagonal. The
implementation of these gratings in the compression of 30 fs pulses in an
out-of-plane geometry can result in compressor efficiencies of ~95%. The
measured laser absorption is 500x lower than current ultrafast petawatt-class
compressor gratings which will enable a substantial increase in average power
handling capabilities of these laser systems.",1811.03091v1
2018-11-13,Fermi- to non-Fermi-liquid crossover and Kondo transition in two-dimensional Cu$_{2/3}$V$_{1/3}$V$_2$S$_4$,"By means of a specific heat ($C$) and electrical resistivity ($\varrho$)
study, we give evidence of a pronounced Fermi liquid (FL) behavior with sizable
mass renormalization, $m^{\ast}/m = 30$, up to unusually high temperatures
$\sim$70 K in the layered system Cu$_{2/3}$V$_{1/3}$V$_2$S$_4$. At low
temperature, a marked upturn of both $C$ and $\varrho$ is suppressed by
magnetic field, which suggests a picture of Kondo coupling between conduction
electrons in the VS$_2$ layers and impurity spins of the V$^{3+}$ ions located
between layers. This picture opens the possibility of controlling electronic
correlations and the FL to non-FL crossover in simple layered materials. For
instance, we envisage that the coupling between layers provided by the impurity
spins may realize a two-channel Kondo state.",1811.05431v1
2019-05-09,A lower bound to the thermal diffusivity of insulators,"It has been known for decades that thermal conductivity of insulating
crystals becomes proportional to the inverse of temperature when the latter is
comparable to or higher than the Debye temperature. This behavior has been
understood as resulting from Umklapp scattering among phonons. We put under
scrutiny the magnitude of the thermal diffusion constant in this regime and
find that it does not fall below a threshold set by the square of sound
velocity times the Planckian time ($\tau_p=\hbar/k_BT$). The conclusion, based
on scrutinizing the ratio in cubic crystals with high thermal resistivity,
appears to hold even in glasses where Umklapp events are not conceivable.
Explaining this boundary, reminiscent of a recently-noticed limit for charge
transport in metals, is a challenge to theory.",1905.03551v3
2019-05-19,Unraveling the Effect of Electron-Electron Interaction on Electronic Transport in High-Mobility Stannate Films,"Contrary to the common belief that electron-electron interaction (EEI) should
be negligible in s-orbital-based conductors, we demonstrated that the EEI
effect could play a significant role on electronic transport leading to the
misinterpretation of the Hall data. We show that the EEI effect is primarily
responsible for an increase in the Hall coefficient in the La-doped SrSnO3
films below 50 K accompanied by an increase in the sheet resistance. The
quantitative analysis of the magnetoresistance (MR) data yielded a large phase
coherence length of electrons exceeding 450 nm at 1.8 K and revealed the
electron-electron interaction being accountable for breaking of electron phase
coherency in La-doped SrSnO3 films. These results while providing critical
insights into the fundamental transport behavior in doped stannates also
indicate the potential applications of stannates in quantum coherent electronic
devices owing to their large phase coherence length.",1905.07810v1
2019-05-30,Molecular Beam Epitaxy Growth of Antiferromagnetic Kagome Metal FeSn,"FeSn is a room-temperature antiferromagnet expected to host Dirac fermions in
its electronic structure. The interplay of magnetic degree of freedom and the
Dirac fermions makes FeSn an attractive platform for spintronics and electronic
devices. While stabilization of thin film FeSn is needed for the development of
such devices, there exist no previous report of epitaxial growth of single
crystalline FeSn. Here we report the realization of epitaxial thin films of
FeSn (001) grown by molecular beam epitaxy on single crystal SrTiO$_{3}$ (111)
substrates. By combining X-ray diffraction, electrical transport, and torque
magnetometry measurements, we demonstrate the high quality of these films with
the residual resistivity ratio $\rho_{xx}(300 \hspace{0.2em}{\rm
K})/\rho_{xx}(2 \hspace{0.2em}{\rm K}) = 24$ and antiferromagnetic ordering at
$T_{\rm N}$ = 353 K. These developments open a pathway to manipulate the Dirac
fermions in FeSn by both magnetic interactions and the electronic field effect
for use in antiferromagnetic spintronics devices.",1905.13073v1
2019-09-20,Pressure-tunable large anomalous Hall effect of the ferromagnetic kagome-lattice Weyl semimetal Co3Sn2S2,"We investigate the pressure evolution of the anomalous Hall effect in
magnetic topological semimetal Co3Sn2S2 in diamond anvil cells with pressures
up to 44.9-50.9 GPa. No evident trace of structural phase transition is
detected through synchrotron x-ray diffraction over the measured pressure range
of 0.2-50.9 GPa. We find that the anomalous Hall resistivity and the
ferromagnetism are monotonically suppressed as increasing pressure and almost
vanish around 22 GPa. The anomalous Hall conductivity varies non-monotonically
against pressure at low temperatures, involving competition between original
and emergent Weyl nodes. Combined with first-principle calculations, we reveal
that the intrinsic mechanism due to the Berry curvature dominates the anomalous
Hall effect under high pressure.",1909.09382v1
2019-09-22,Robust pseudogap across the magnetic field driven superconductor to insulator-like transition in strongly disordered NbN films,"We investigate the magnetic field evolution of the superconducting state in a
strongly disordered NbN thin film which exhibits a magnetic field tuned
superconductor to insulator-like transition, employing low temperature scanning
tunneling spectroscopy (STS). Transport measurements of the sample reveals a
characteristic magnetic field, which separates the low field state where
resistance decreases with decreasing temperature, i.e. dR/dT > 0 and a
high-field state where dR/dT < 0. However, STS imaging of the superconducting
state reveals a smooth evolution across this field and the presence of a robust
pseudogap on both sides of this characteristic field. Our results suggest that
the superconductor-insulator transition might be a percolative transition
driven by the shrinking of superconducting fraction with magnetic field.",1909.10071v1
2020-03-04,High-Performance Atomically-Thin Room-Temperature NO2 Sensor,"The development of room-temperature sensing devices for detecting small
concentrations of molecular species is imperative for a wide range of low-power
sensor applications. We demonstrate a room-temperature, highly sensitive,
selective, and reversible chemical sensor based on a monolayer of the
transition metal dichalcogenide Re0.5Nb0.5S2. The sensing device exhibits
thickness dependent carrier type, and upon exposure to NO2 molecules, its
electrical resistance considerably increases or decreases depending on the
layer number. The sensor is selective to NO2 with only minimal response to
other gases such as NH3, CH2O, and CO2. In the presence of humidity, not only
are the sensing properties not deteriorated, but also the monolayer sensor
shows complete reversibility with fast recovery at room temperature. We present
a theoretical analysis of the sensing platform and identify the
atomically-sensitive transduction mechanism.",2003.01909v2
2020-03-17,Measurement of the heat flux normalised spin Seebeck coefficient of thin films as a function of temperature,"The spin Seebeck effect (SSE) has generated interest in the thermoelectric
and magnetic communities for potential high efficiency energy harvesting
applications, and spintronic communities as a source of pure spin current. To
understand the underlying mechanisms requires characterisation of potential
materials across a range of temperatures, however, for thin films the default
measurement of an applied temperature gradient (across the sample) has been
shown to be compromised by the presence of thermal resistances. Here, we
demonstrate a method to perform low temperature SSE measurements where instead
of monitoring the temperature gradient, the heat flux passing through the
sample is measured using two calibrated heat flux sensors. This has the
advantage of measuring the heat loss through the sample as well as providing a
reliable method to normalise the SSE response of thin film samples. We
demonstrate this method with an $\text{SiO}_{2}/\text{Fe}_{3}O_{4}/\text{Pt}$
sample, where a semiconducting-insulating transition occurs at the Verwey
transition, $T_{\text{V}}$, of $\text{Fe}_{3}\text{O}_{4}$ and quantify the
thermomagnetic response above and below $T_{\text{V}}$.",2003.07925v1
2020-03-25,Dualism of the 4f electrons and high-temperature antiferromagnetism of the heavy-fermion compound YbCoC$_{2}$,"We report on the first study of the noncentrosymmetric ternary carbide
YbCoC$_{2}$. Our magnetization, specific heat, resistivity and neutron
diffraction measurements consistently show that the system behaves as a
heavy-fermion compound, displaying an amplitude-modulated magnetic structure
below the N\'eel temperature reaching $T_{N}$ = 33 K under pressure. Such a
large value, being the highest among the Yb-based systems, is explained in the
light of our ab initio calculations, which show that the 4f electronic states
of Yb have a dual nature -- i.e., due to their strong hybridization with the 3d
states of Co, 4f states expose both localized and itinerant properties.",2003.11601v1
2014-08-13,Crossover from charge order to strain glass in phase separated manganite thin films: Impact of thermal cycling and substrate induced strain,"The magnetic and magnetotransport properties of single crystalline
La1-x-yPryCaxMnO3 (x=0.42, y=0.40) thin films (~140 nm) deposited on (110)
oriented LaAlO3 and SrTiO3 substrates exhibit a crossover from the high
temperature antiferromagnetic-charge ordered insulator (AFM-COI) phase (T>TN)
to strain glass (T<Tg). At intermediate temperatures (Tg<T<TN) dynamical liquid
having prominent thermal-magneto-resistive hysteresis dominates in the cooling
cycle, while in the warming cycle it is preceded by ferromagnetic metal (FMM)
phase. Magnetic field required to drive AFM-COI to FMM phase transition are
higher than that for the strain glass. The magneto-electric nature and
temperature span of the distinct magnetic regimes are sensitive to the thermal
cycling and substrate induced strain.",1408.2966v1
2014-08-14,Anomalous diffusion and Griffiths effects near the many-body localization transition,"We explore the high-temperature dynamics of the disordered, one-dimensional
XXZ model near the many-body localization (MBL) transition, focusing on the
delocalized (i.e., ""metallic"") phase. In the vicinity of the transition, we
find that this phase has the following properties: (i) Local magnetization
fluctuations relax subdiffusively; (ii) the a.c. conductivity vanishes near
zero frequency as a power law; (iii) the distribution of resistances becomes
increasingly broad at low frequencies, approaching a power law in the
zero-frequency limit. We argue that these effects can be understood in a
unified way if the metallic phase near the MBL transition is a Griffiths phase.
We establish scaling relations between the associated exponents, using exact
linear-response arguments as well as a phenomenological resistor-capacitor
model.",1408.3413v2
2014-08-19,Bipolar switching in an orthogonal spin transfer spin valve device,"We demonstrate current-induced bipolar switching in in-plane magnetized
spin-valve devices that incorporate a perpendicularly magnetized spin
polarizing layer. Further, hysteretic transitions into a state with
intermediate resistance occur at high currents, again for both current
polarities. These transitions are shown to be consistent with a macrospin model
that considers a spin-polarized current that is tilted with respect to the free
layer plane, due to the presence of spin-transfer torque from the polarizing
layer. These unique switching characteristics, which have their origin in the
noncollinear layer magnetizations, are of interest for magnetic random access
memory and spin-torque oscillator devices.",1408.4494v1
2017-01-19,Comparative study of LaNiO$_3$/LaAlO$_3$ heterostructures grown by pulsed laser deposition and oxide molecular beam epitaxy,"Variations in growth conditions associated with different deposition
techniques can greatly affect the phase stability and defect structure of
complex oxide heterostructures. We synthesized superlattices of the
paramagnetic metal LaNiO3 and the large band gap insulator LaAlO3 by atomic
layer-by-layer molecular beam epitaxy (MBE) and pulsed laser deposition (PLD)
and compared their crystallinity, microstructure as revealed by high-resolution
transmission electron microscopy images and resistivity. The MBE samples show a
higher density of stacking faults, but smoother interfaces and generally higher
electrical conductivity. Our study identifies the opportunities and challenges
of MBE and PLD growth and serves as a general guide for the choice of
deposition technique for perovskite oxides.",1701.05366v1
2017-01-23,Sonication-assisted synthesis of semiconducting atomic crystals of germanium monoselenide: An isostructural and isoelectronic analog of black phosphorous,"Monochalcogenides of germanium (or tin) are considered as stable
isoelectronic and isostructural analogue of black phosphorous. Their
two-dimensional (2D) forms have been just predicted to shown strong
thickness-dependent physical properties, and even indirect to direct band gap
crossover at the monolayer limit. Here, we demonstrate the synthesis of
atomically thin GeSe by direct sonication-assisted exfoliation of bulk
microcrystalline powders in solvents. The exfoliated few-layer GeSe sheets
characterize high crystallinity with lateral sizes over 100 nm and,
importantly, strong resistance against oxidation and degradation in ambient
conditions. Density functional theory calculation combined with optical
characterizations confirm the layer-number dependent optical bandgap, which,
for few-layer sheets, is optimal for solar light harvesting, and promising for
relevant applications, such as optoelectronics and photonics.",1701.06285v2
2017-03-18,Analytical expressions for thermophysical properties of solid and liquid tungsten relevant for fusion applications,"The status of the literature is reviewed for several thermophysical
properties of pure solid and liquid tungsten which constitute input for the
modelling of intense plasma-surface interaction phenomena that are important
for fusion applications. Reliable experimental data are analyzed for the latent
heat of fusion, the electrical resistivity, the specific isobaric heat
capacity, the thermal conductivity and the mass density from the room
temperature up to the boiling point of tungsten as well as for the surface
tension and the dynamic viscosity across the liquid state. Analytical
expressions of high accuracy are recommended for these thermophysical
properties that involved a minimum degree of extrapolations. In particular,
extrapolations were only required for the surface tension and viscosity.",1703.06302v4
2017-03-28,Thermoelectric La-doped SrTiO3 epitaxial layers with single-crystal quality: from nanometer to micrometer and mosaicity effects,"High-quality thermoelectric LaxSr1-xTiO3 (LSTO) layers (here with x = 0.2),
with thicknesses ranging from 20 nm to 700 nm, have been epitaxially grown on
SrTiO3(001) substrates by enhanced solid-source oxide molecular-beam epitaxy.
All films are atomically flat (with rms roughness < 0.2 nm), with low mosaicity
(<0.1{\deg}), and present very low electrical resistivity (<5 x 10-4 ohm.cm at
room temperature), one order of magnitude lower than commercial Nb-doped SrTiO3
single-crystalline substrate. The conservation of transport properties within
this thickness range has been confirmed by thermoelectric measurements where
Seebeck coefficients of around -60 microV/K have been found for all films,
accordingly. Finally, a correlation is given between the mosaicity and the
(thermo)electric properties. These functional LSTO films can be integrated on
Si in opto-microelectronic devices as transparent conductor, thermoelectric
elements or in non-volatile memory structures.",1703.09451v1
2018-10-01,Evolution of magnetic properties in the vicinity of the Verwey transition in Fe3O4 thin films,"We have systematically studied the evolution of magnetic properties,
especially the coercivity and the remanence ratio in the vicinity of the Verwey
transition temperature (TV ), of high-quality epitaxial Fe3O4 thin films grown
on MgO (001), MgAl2O4 (MAO) (001), and SrTiO3 (STO) (001) substrates. We
observed rapid change of magnetization, coercivity, and remanence ratio at TV ,
which are consistent with the behaviors of resistivity versus temperature
[\r{ho}(T )] curves for the different thin films. In particular, we found quite
different magnetic behaviors for the thin films onMgOfrom those onMAOand STO,
inwhich the domain size and the strain state play very important roles. The
coercivity is mainly determined by the domain size but the demagnetization
process is mainly dependent on the strain state. Furthermore, we observed a
reversal of remanence ratio at TV with thickness for the thin films grown on
MgO: from a rapid enhancement for 40-nm- to a sharp drop for 200-nm-thick film,
and the critical thickness is about 80 nm. Finally, we found an obvious
hysteretic loop of coercivity (or remanence ratio) with temperature around TV ,
corresponding to the hysteretic loop of the \r{ho}(T ) curve, in Fe3O4 thin
film grown on MgO.",1810.00538v1
2018-10-16,Effect of Graded Bias Voltage on the Microstructure of arc-PVD CrN Films and its Response in Electrochemical & Mechanical Behavior,"The effect of graded or constant bias voltages (-40 V, -80 V and -40/60/80 V)
on size grain and surface defects of arc PVD deposited CrN films was
investigated. Corrosion resistance evaluated using electrochemical impedance
spectroscopy (EIS) and potentiodynamic curves (Tafel) and the mechanical
behavior evaluated by means of instrumented nanoindentation and scratch testing
was correlated with the microstructural changes. It was found that the bias
voltage variation affects corrosion behavior due to the presence of defects
(i.e. open voids, droplets) which also affects the failure mechanisms and
increasing spallation. High bias voltage (-80 V) increases nano-hardness and
the elastic modulus due to the dense microstructure of the CrN coating.",1810.07293v1
2018-10-30,Theory of the Strange Metal Sr$_3$Ru$_2$O$_7$,"The bilayer perovskite Sr$_3$Ru$_2$O$_7$ has been widely studied as a
canonical strange metal. It exhibits $T$-linear resistivity and a $T\log(1/T)$
electronic specific heat in a field-tuned quantum critical fan. Criticality is
known to occur in `hot' Fermi pockets with a high density of states close to
the Fermi energy. We show that while these hot pockets occupy a small fraction
of the Brillouin zone, they are responsible for the anomalous transport and
thermodynamics of the material. Specifically, a scattering process in which two
electrons from the large, `cold' Fermi surfaces scatter into one hot and one
cold electron renders the ostensibly non-critical cold fermions a marginal
Fermi liquid. From this fact the transport and thermodynamic phase diagram is
reproduced in detail. Finally, we show that the same scattering mechanism into
hot electrons that are instead localized near a two-dimensional van Hove
singularity explains the anomalous transport observed in strained
Sr$_2$RuO$_4$.",1810.12945v2
2019-02-08,Magnetic tunnel junctions based on ferroelectric Hf0.5Zr0.5O2 tunnel barriers,"A ferroelectric tunnel barrier in between two ferromagnetic electrodes
(multiferroic tunnel junction, MFTJ), is one of the most promising concepts for
future microelectronic devices. In parallel, Hafnia based ferroelectrics are
showing great potential for device miniaturization down to the nanoscale. Here
we utilize ferroelectric Hf0.5Zr0.5O2 (HZO) with thickness of only 2 nm,
epitaxially grown on La0.7Sr0.3MnO3 (LSMO) ferromagnetic electrodes, as a large
band-gap insulating barrier integrated in MFTJs with cobalt top electrodes. As
previously reported for other MFTJs with similar electrodes, the tunneling
magnetoresistance (TMR) can be tuned and its sign can even be reversed by the
bias voltage across the junction. We demonstrate four non-volatile resistance
states generated by magnetic and electric field switching with high
reproducibility in this system.",1902.08021v1
2019-02-27,"Tunable light-emission through the range 1.8-3.2 eV and p-type conductivity at room temperature for nitride semiconductors, Ca(Mg1-xZnx)2N2 (x=0-1)","The ternary nitride CaZn2N2, composed only of earth-abundant elements, is a
novel semiconductor with a band gap of 1.8 eV. First-principles calculations
predict that continuous Mg substitution at the Zn site will change the optical
band gap in a wide range from ~3.3 eV to ~1.9 eV for Ca(Mg1-xZnx)2N2 (x = 0-1).
In this study, we demonstrate that a solid-state reaction at ambient pressure
and a high-pressure synthesis at 5 GPa produce x = 0 and 0.12, and x = 0.12-1
polycrystalline samples, respectively. It is experimentally confirmed that the
optical band gap can be continuously tuned from ~3.2 eV to ~1.8 eV, a range
very close to that predicted by theory. Band-to-band photoluminescence is
observed at room temperature in the ultravioletfired region depending on x. A
2% Na doping at the Ca site of CaZn2N2 converts its highly resistive state to a
p-type conducting state. Particularly, the x = 0.50 sample exhibits intense
green emission with a peak at 2.45 eV (506 nm) without any other emission from
deep-level defects. These features meet the demands of the III-V group nitride
and arsenide/phosphide light-emitting semiconductors.",1902.10495v1
2019-07-09,Modulation of crystal and electronic structures in topological insulators by rare-earth doping,"We study magnetotransport in a rare earth doped topological insulator,
Sm0.1Sb1.9Te3 single crystals, under magnetic fields up to 14 T. It is found
that that the crystals exhibit Shubnikov de Haas oscillations in their
magneto-transport behaviour at low temperatures and high magnetic fields. The
SdH oscillations result from the mixed contributions of bulk and surface
states. We also investigate the SdH oscillations in different orientations of
the magnetic field, which reveals a three dimensional Fermi surface topology.
By fitting the oscillatory resistance with the Lifshitz Kosevich theory, we
draw a Landau-level fan diagram that displays the expected nontrivial phase. In
addition, the density functional theory calculations shows that Sm doping
changes the crystal structure and electronic structure compared with pure
Sb2Te3. This work demonstrates that rare earth doping is an effective way to
manipulate the Fermi surface of topological insulators. Our results hold
potential for the realization of exotic topological effects in magnetic
topological insulators.",1907.03930v2
2019-07-22,Development and characterization of six-gap glass MRPCs and feasibility study of a PET device,"The Multigap Resistive Plate Chambers (MRPCs) provide excellent timing as
well as position resolutions at relatively low cost. Therefore, they can be
used in medical imaging applications such as PET where precise timing is a
crucial parameter of measurement. We have designed and fabricated several
six-gap glass MRPCs and extensively studied their performance. In this paper,
we describe the fabrication and characterization of the detector, the
electronics and the data acquisition system of the setup. We present here the
result of our Time Of Flight (TOF) experiment using a radioactive source Na-22
hence to demonstrate their potential applications in medical imaging. We also
present the Geant4 based simulation results on the efficiency of our detector
as a function of the number of gaps and thickness of the converter material.",1907.09379v1
2020-02-24,Miniature capacitive Faraday force magnetometer for magnetization measurements at low temperatures and high magnetic fields,"A Faraday force magnetometer is presented for measurements of magnetization
at temperatures down to 100~mK and in magnetic fields up to 14~T. The specimen
is mounted on a flexible cantilever forming a force-sensing capacitor in
combination with a fixed back plate. Two different cantilever designs are
presented. A torsion resistant cantilever allows to measure magnetization of
highly anisotropic single crystal samples. Measurements of the metal organic
quantum magnets (C$_5$H$_{12}$N)$_2$CuBr$_4$ (BPCB) and NiCl$_2$$\cdot$4
SC(NH$_2$)$_2$ (DTN) demonstrate the device's capabilities. Routinely, a
specimen's magnetic moment is measured with a resolution better than $10^{-7}$
A$\,$m$^2$ ($10^{-4}$ emu). The device in miniaturized to fit is almost any
cryostat.",2002.10168v1
2020-02-24,Silicon Vertex & Tracking Detectors for the Compact Linear Collider,"CLIC is a proposed linear $e^+e^-$ collider with center-of-mass energies of
up to 3 TeV. Its main objectives are precise top quark, Higgs boson and Beyond
Standard Model physics. In addition to spatial resolutions of a few micrometers
and a very low material budget, the vertex and tracking detectors also require
timing capabilities with a precision of a few nanoseconds to allow suppression
of beam-induced background particles. Different technologies using hybrid
silicon detectors are explored for the vertex detectors, such as dedicated 65
nm readout ASICs, small-pitch sensors as well as bonding using anisotropic
conductive films. Monolithic sensors are the current choice for the tracking
detector, and a prototype using a 180 nm high-resistivity CMOS process has been
designed and produced, and is currently under evaluation. Different designs
using a silicon-on-insulator process are under investigation for both vertex
and tracking detector. All prototypes are tested in laboratory and beam tests,
and newly developed simulation tools combining Geant4 and TCAD are used to
assess and optimize their performance. This contribution gives an overview of
the R&D program for the CLIC vertex and tracking detectors, highlighting new
results from the prototypes.",2002.10169v1
2020-02-27,Non-trivial quantum magnetotransport oscillations in pure and robust topological $α$-Sn films,"We report experimental evidence of topological Dirac fermion charge carriers
in pure and robust $\alpha$-Sn films grown on InSb substrates. This evidence
was acquired using standard macroscopic four-point contact resistance
measurements, conducted on uncapped films with a significantly reduced bulk
mobility. We analyzed and compared electrical characteristics of the
constituting components of the $\alpha$-Sn/InSb sample, and propose a
three-band drift velocity model accordingly. A surface band, with low carrier
density and high mobility, is identified as the origin of the observed
Shubnikov -- de Haas oscillations. The analysis of these quantum oscillations
results in a non-trivial value of the phase shift $\gamma =0$, characteristic
for topologically protected Dirac fermions. For the same uncapped samples we
estimate the momentum relaxation time $\tau\approx 300\ \mathrm{fs}$, which is
significantly larger in comparison with the previous reports on grown
$\alpha$-Sn films.",2002.12248v2
2020-04-20,Structural and transport properties of La$_{1-x}$Sr$_x$Co$_{1-y}$Nb$_y$O$_3$ thin films,"We present the structural and transport properties of
La$_{1-x}$Sr$_x$Co$_{1-y}$Nb$_y$O$_3$ ($y=$ 0.1 and $x=$ 0; $y=$ 0.15 and $x=$
0.3) thin films grown on (001) orientated single crystalline ceramic substrates
to investigate the effect of lattice induced compressive and tensile strain.
The high resolution x-ray diffraction measurements, including
$\theta$-2$\theta$ scan, $\Phi$-scan, and reciprocal space mapping, affirm
single phase; four-fold symmetry; good quality of deposited thin films. The
atomic force micrographs confirm that these films have small root mean square
roughness in the range of $\sim$0.5--7~nm. We observed additional Raman active
modes in the films owing to the lowered crystal symmetry as compared to the
bulk. More interestingly, the temperature dependent dc-resistivity measurements
reveal that films become insulating due to induced lattice strain in comparison
to bulk, however for the larger compressive strained films conductivity
increase significantly owing to the higher degree of $p-d$ hybridization and
reduction in bandwidth near the Fermi level.",2004.09162v1
2020-04-29,"Raman spectroscopy of ion irradiated SiC: chemical defects, strain, annealing, and oxidation","Raman spectroscopy has been used to identify defective bonding in neon and
silicon ion irradiated single crystals of 6H-SiC. Observable differences exist
in the C-C bonding region corresponding to different defect structures for neon
and silicon ion implantations. Raman spectra of ion irradiated SiC show less
tensile strain than neutron irradiations, explained by a residual compressive
stress caused by the swelling constrained by the undamaged substrate. Evidence
of oxidation during high temperature ion implantation is observed as C-O and
Si-O Raman signals. Annealing irradiated SiC while acquiring Raman spectra
shows rapid recovery of Si-C bonding, but not a complete recovery of the
unirradiated structure. Annealing irradiated SiC causes surface oxidation where
unirradiated SiC does not oxidise. Comparisons are made to the apparent
radiation resistance of diamond and silicon which have similar crystal
structures, but are monatomic, leading to the suggestion that chemical defects
are responsible for increased radiation damage in SiC.",2004.14335v3
2020-09-01,Molecular beam epitaxy of the half-Heusler antiferromagnet CuMnSb,"We report growth of CuMnSb thin films by molecular beam epitaxy on InAs(001)
substrates. The CuMnSb layers are compressively strained ($0.6~\text{%}$) due
to lattice mismatch. The thin films have a $\omega$ full width half max of
$7.7^{''}$ according to high resolution X-ray diffraction, and a root mean
square roughness of $0.14~\text{nm}$ as determined by atomic force microscopy.
Magnetic and electrical properties are found to be consistent with reported
values from bulk samples. We find a N\'eel temperature of $62~\text{K}$, a
Curie-Weiss temperature of $-65~\text{K}$ and an effective moment of
$5.9~\mu_{\text{B}}/\text{f.u.}$. Transport measurements confirm the
antiferromagetic transition and show a residual resistivity at $4~\text{K}$ of
$35~\mu\Omega\cdot \text{cm}$.",2009.00342v1
2020-09-24,Magneto-transport properties of tellurium under extreme conditions,"This study investigates the transport properties of a chiral elemental
semiconductor tellurium (Te) under magnetic fields and pressure. Application of
hydrostatic pressure reduces the resistivity of Te, while its temperature
dependence remains semiconducting up to 4 GPa, contrary to recent theoretical
and experimental studies. Application of higher pressure causes structural as
well as semiconductor--metal transitions. The resulting metallic phase above 4
GPa exhibits superconductivity at 2 K along with a noticeable linear
magnetoresistance effect. On the other hand, at ambient pressure, we identified
metallic surface states on the as-cleaved (10$\bar{1}$0) surfaces of Te. The
nature of these metallic surface states has been systematically studied by
analyzing quantum oscillations observed in high magnetic fields. We clarify
that a well-defined metallic surface state exists not only on chemically etched
samples that were previously reported, but also on as-cleaved ones.",2009.11511v1
2022-02-01,Prominent electron-hole asymmetry in thermoelectric transport of LaCoO$_3$,"We have measured the electrical resistivity and the thermopower of the
electron-doped perovskite cobaltites LaCo$_{1-y}$Te$_y$O$_3$. In contrast to
the hole-doped systems such as metallic ferromagnets La$_{1-x}M_x$CoO$_3$ ($M$
= Ca, Sr, Ba), the electron-doped samples show an insulating behavior even in a
heavily doped range due to a spin-state blockade mechanism that an electron
hopping from high-spin Co$^{2+}$ to low-spin Co$^{3+}$ site is energetically
suppressed. We find that, despite the electron doping, the thermopower shows
relatively large positive values above $y=0.05$, strikingly distinct from the
hole-doped case where it comes close to zero with doping. This prominent
electron-hole asymmetry seen in the thermopower originates from a bipolar
conduction which consists of a slight amount of mobile holes and the main
immobile electrons, demonstrating an impact of spin-state blockade on
thermoelectric transport.",2202.00166v1
2022-02-11,Temperature control of diffusive memristor hysteresis and artificial neuron spiking,"Memristive devices are promising elements for energy-efficient neuromorphic
computing and future artificial intelligence systems. For diffusive memristors,
the device state switching occurs because of the sequential formation and
disappearance of conduction pillars between device terminals due to the drift
and diffusion of Ag nanoparticles in the dielectric matrix. This process is
governed by the application of the voltage to the device contacts. Here, both
in experiment and in theory we demonstrate that varying temperature offers an
efficient control of memristor states and charges transport in the device. We
found out that by raising and lowering the device temperature, one can reset
the memristor state as well as change the residual time the memristor stays in
high and low resistive states when the current spiking is generated in the
memristive circuit at a constant applied voltage. Our theoretical model
demonstrates a good qualitative agreement with the experiments and helps to
explain the effects reported.",2202.05571v1
2007-10-07,Mapping the Spatial Distribution of Charge Carriers in LaAlO3/SrTiO3 Heterostructures,"At the interface between complex insulating oxides, novel phases with
interesting properties may occur, such as the metallic state reported in the
LaAlO3/SrTiO3 system. While this state has been predicted and reported to be
confined at the interface, some works indicate a much broader spatial
extension, thereby questioning its origin. Here we provide for the first time a
direct determination of the carrier density profile of this system through
resistance profile mappings collected in cross-section LaAlO3/SrTiO3 samples
with a conducting-tip atomic force microscope (CT-AFM). We find that, depending
upon specific growth protocols, the spatial extension of the high-mobility
electron gas can be varied from hundreds of microns into SrTiO3 to a few
nanometers next to the LaAlO3/SrTiO3 interface. Our results emphasize the
potential of CT-AFM as a novel tool to characterize complex oxide interfaces
and provide us with a definitive and conclusive way to reconcile the body of
experimental data in this system.",0710.1395v2
2014-01-05,Electron-hole pairing in graphene-GaAs heterostructures,"Vertical heterostructures combining different layered materials offer novel
opportunities for applications and fundamental studies of collective behavior
driven by inter-layer Coulomb coupling. Here we report heterostructures
comprising a single-layer (or bilayer) graphene carrying a fluid of massless
(massive) chiral carriers, and a quantum well created in GaAs 31.5 nm below the
surface, supporting a high-mobility two-dimensional electron gas. These are a
new class of double-layer devices composed of spatially-separated electron and
hole fluids. We find that the Coulomb drag resistivity significantly increases
for temperatures below 5-10 K, following a logarithmic law. This anomalous
behavior is a signature of the onset of strong inter-layer correlations,
compatible with the formation of a condensate of permanent excitons. The
ability to induce strongly-correlated electron-hole states paves the way for
the realization of coherent circuits with minimal dissipation and nanodevices
including analog-to-digital converters and topologically protected quantum
bits.",1401.0902v1
2017-04-17,"Mesoscopic quantum effects in a bad metal, hydrogen-doped vanadium dioxide","The standard treatment of quantum corrections to semiclassical electronic
conduction assumes that charge carriers propagate many wavelengths between
scattering events, and succeeds in explaining multiple phenomena (weak
localization magnetoresistance (WLMR), universal conductance fluctuations,
Aharonov-Bohm oscillations) observed in polycrystalline metals and doped
semiconductors in various dimensionalities. We report apparent WLMR and
conductance fluctuations in H$_{x}$VO$_{2}$, a poor metal (in violation of the
Mott-Ioffe-Regel limit) stabilized by the suppression of the VO$_{2}$
metal-insulator transition through atomic hydrogen doping. Epitaxial thin
films, single-crystal nanobeams, and nanosheets show similar phenomenology,
though the details of the apparent WLMR seem to depend on the combined effects
of the strain environment and presumed doping level. Self-consistent
quantitative analysis of the WLMR is challenging given this and the high
resistivity of the material, since the quantitative expressions for WLMR are
derived assuming good metallicity. These observations raise the issue of how to
assess and analyze mesoscopic quantum effects in poor metals.",1704.05080v1
2017-04-19,"Epitaxy and Structural Properties of (V,Bi,Sb)$_2$Te$_3$ Layers Exhibiting the Quantum Anomalous Hall Effect","The influence of Sb content, substrate type and cap layers on the quantum
anomalous Hall effect observed in V-doped (Bi,Sb)$_2$Te$_3$ magnetic
topological insulators is investigated. Thin layers showing excellent
quantization are reproducibly deposited by molecular beam epitaxy at growth
conditions effecting a compromise between controlled layer properties and high
crystalline quality. The Sb content can be reliably determined from the
in-plane lattice constant measured by X-ray diffraction, even in thin layers.
This is the main layer parameter to be optimized in order to approach charge
neutrality. Within a narrow range at about 80% Sb content, the Hall resistivity
shows a maximum of about 10 k$\Omega$ at 4 K and quantizes at mK temperatures.
Under these conditions, thin layers grown on Si(111) or InP(111) and with or
without a Te cap exhibit quantization. The quantization persists independently
of the interfaces between cap, layer and substrate, the limited crystalline
quality, and the degradation of the layer proving the robustness of the quantum
anomalous Hall effect.",1704.05677v2
2017-04-24,Electronic properties and the nature of metal-insulator transition in NdNiO3 prepared at ambient oxygen pressure,"We report the electronic properties of the NdNiO3, prepared at the ambient
oxygen pressure condition. The metal-insulator transition temperature is
observed at 192 K, but the low temperature state is found to be less insulating
compared to the NdNiO3 prepared at high oxygen pressure. The electric
resistivity, Seebeck coefficient and thermal conductivity of the compound show
large hysteresis below the metal-insulator transition. The large value of the
effective mass (m* ~ 8me) in the metallic state indicate the narrow character
of the 3d band. The electric conduction at low temperatures (T = 2 - 20 K) is
governed by the variable range hopping of the charge carriers.",1704.07143v1
2017-05-15,The role of the coherence length for the establishment of global phase coherence in three-dimensional arrays of ultra-thin quasi-one-dimensional superconducting Pb and NbN nanowires,"We have fabricated 5 nm ultra-thin NbN nanowires that form a dense and
regular array in the linear channels of mesoporous SBA-15 silica substrates.
Bulk NbN is a well-known classical superconductor with Tc of 16 K. We show
that, by being incorporated into this nanostructure, the composite material
exhibits typical quasi-one-dimensional characteristics. We compare the
superconducting properties with those of superconducting Pb nanowires of same
dimensionality in identical configuration within the linear SBA-15 pores. While
Pb nanowire arrays show a pronounced crossover from 1D superconductivity at
high temperatures to a 3D bulk superconducting state in the low temperature
regime with true zero resistance triggered by transversal Josephson
interaction, this transition appears to be completely absent in the NbN
nanowire array. The small coherence length in NbN, which strongly suppresses
the Josephson coupling is discussed as the origin of this difference.",1705.05097v1
2017-05-30,"High-pressure structural, elastic, and thermodynamic properties of zircon-type HoPO4 and TmPO4","Zircon-type HoPO4 and TmPO4 have been studied by single-crystal x-ray
diffraction and ab initio calculations. We report information on the influence
of pressure on the crystal structure, and on the elastic and thermodynamic
properties. The equation of state for both compounds is accurately determined.
We have also obtained information on the polyhedral compressibility which is
used to explain the anisotropic axial compressibility and the bulk
compressibility. Both compounds are ductile and more resistive to volume
compression than to shear deformation at all pressures. Furthermore, the
elastic anisotropy is enhanced upon compression. Finally, the calculations
indicate that the possible causes that make unstable the zircon structure are
mechanical instabilities and the softening of a silent B1u mode.",1705.10721v1
2017-07-06,RF-quantum capacitance of the topological insulator Bi2Se3 in the bulk depleted regime for field-effect transistors,"A Metal-dielectric-topological insulator capacitor device based on
hBN-encapsulated CVD grown Bi2Se3 is realized and investigated in the radio
frequency regime. The RF quantum capacitance and device resistance are
extracted for frequencies as a high as 10 GHz, and studied as a function of the
applied gate voltage. The combination of the superior quality hBN dielectric
gate with the optimized transport characteristics of CVD grown Bi2Se3
(n~10^18cm-3 in 8 nm) allow us to attain a bulk depleted regime by dielectric
gating. A quantum capacitance minimum is observed revealing a purely Dirac
regime, where the Dirac surface state in proximity to the gate reaches charge
neutrality, but the bottom surface Dirac cone remains charged, and couples
capacitively to the top surface via the insulating bulk. Our work paves the way
towards implementation of topological materials in RF devices.",1707.01657v2
2017-07-29,Experimental study of extrinsic spin Hall effect in CuPt alloy,"We have experimentally studied the effects on the spin Hall angle due to
systematic addition of Pt into the light metal Cu. We perform spin torque
ferromagnetic resonance measurements on Py/CuPt bilayer and find that as the Pt
concentration increases, the spin Hall angle of CuPt alloy increases. Moreover,
only 28% Pt in CuPt alloy can give rise to a spin Hall angle close to that of
Pt. We further extract the spin Hall resistivity of CuPt alloy for different Pt
concentrations and find that the contribution of skew scattering is larger for
lower Pt concentrations, while the side-jump contribution is larger for higher
Pt concentrations. From technological perspective, since the CuPt alloy can
sustain high processing temperatures and Cu is the most common metallization
element in the Si platform, it would be easier to integrate the CuPt alloy
based spintronic devices into existing Si fabrication technology.",1707.09525v1
2017-08-17,Enhanced superconductivity and anisotropy of FeTe0.6Se0.4 single crystals with Li-NH3 intercalation,"We report a systematic study of anisotropy resistivity, magnetoresistance and
Hall effect of Li0.32(NH3)yFe2Te1.2Se0.8 single crystals. When compared to the
parent compound FeTe0.6Se0.4, the Li-NH3 intercalation not only increases the
superconducting transition temperature, but also enhances the electronic
anisotropy in both normal and superconducting states. Moreover, in contrast to
the parent compound, the Hall coefficient RH becomes negative at low
temperature, indicating electron-type carriers are dominant due to Li doping.
On the other hand, the sign reverse of RH at high temperature and the failure
of scaling behavior of magnetoresistance imply that hole pockets may be still
crossing or just below the Fermi energy level, leading to the multiband
behavior in Li0.32(NH3)yFe2Te1.2Se0.8.",1708.05310v2
2017-08-30,Large enhancement of the spin Hall effect in Au by scattering with side-jump on Ta impurities,"We present measurements of the Spin Hall Effect (SHE) in AuW and AuTa alloys
for a large range of W or Ta concentrations by combining experiments on lateral
spin valves and Ferromagnetic-Resonance/spin pumping technique. The main result
is the identification of a large enhancement of the Spin Hall Angle (SHA) by
the side-jump mechanism on Ta impurities, with a SHA as high as + 0.5 (i.e
$50\%$) for about 10\% of Ta. In contrast the SHA in AuW does not exceed + 0.15
and can be explained by intrinsic SHE of the alloy without significant
extrinsic contribution from skew or side-jump scattering by W impurities. The
AuTa alloys, as they combine a very large SHA with a moderate resistivity
(smaller than $85\,\mu\Omega.cm$), are promising for spintronic devices
exploiting the SHE.",1708.09214v1
2018-08-17,Magnetic and structural properties of Co$_2$MnSi based Heusler compound,"The influence of antisite disorder occupancies on the magnetic properties of
the half-metallic Co$_2$MnSi compound was studied by experimental techniques
and first-principles calculations. The neutron diffraction studies show almost
identical amount of Mn and Co disorders of 6.5\% and 7.6\%, which was found to
be in good agreement with density functional theory (DFT) calculations of the
stable Co$_2$MnSi system with the corresponding disorders. DFT studies reveal
that antiferromagnetic interactions introduced by Mn disorder lead to a
reduction of the net magnetic moment. The results are discussed in conjunction
with neutron diffraction and magnetization measurements. Transport property
measurement under magnetic field up to 9 Tesla revealed a positive
magnetoresistance for bulk Co$_2$MnSi that persists up to room temperature. A
Curie temperature of $\sim$1014 K was determined for the compound by high
temperature electrical resistivity and dilatometry measurements.",1808.05743v3
2018-08-21,Superconductivity at 215 K in lanthanum hydride at high pressures,"We synthesized lanthanum hydride (LaHx) by laser heating of lanthanum in
hydrogen atmosphere at pressure P = 170 GPa. The sample shows a superconducting
step at 209 K and 170 GPa and temperature dependence of resistance. By
releasing the pressure to 150 GPa, the superconducting transition temperature
Tc increases to 215 K - the record Tc. This finding supports a way of achieving
Tc higher than the one in H3S (203 K) in hydrides with sodalite-like
structures, first proposed for CaH6 (Tc=245 K) and later for yttrium and
lanthanum hydrides where higher, room temperature superconductivity is
expected.",1808.07039v1
2019-03-25,"Simulations of CMOS pixel sensors with a small collection electrode, improved for a faster charge collection and increased radiation tolerance","CMOS pixel sensors with a small collection electrode combine the advantages
of a small sensor capacitance with the advantages of a fully monolithic design.
The small sensor capacitance results in a large ratio of signal-to-noise and a
low analogue power consumption, while the monolithic design reduces the
material budget, cost and production effort. However, the low electric field in
the pixel corners of such sensors results in an increased charge collection
time, that makes a fully efficient operation after irradiation and a timing
resolution in the order of nanoseconds challenging for pixel sizes larger than
approximately forty micrometers. This paper presents the development of
concepts of CMOS sensors with a small collection electrode to overcome these
limitations, using three-dimensional Technology Computer Aided Design
simulations. The studied design uses a 0.18 micrometer process implemented on a
high-resistivity epitaxial layer.",1903.10190v2
2019-03-28,PtSe2 grown directly on polymer foil for use as a robust piezoresistive sensor,"Robust strain gauges are fabricated by growing PtSe2 layers directly on top
of flexible polyimide foils. These PtSe2 layers are grown by low-temperature,
thermally-assisted conversion of predeposited Pt layers. Under applied flexure
the PtSe2 layers show a decrease in electrical resistance signifying a negative
gauge factor. The influence of the growth temperature and film thickness on the
electromechanical properties of the PtSe2 layers is investigated. The
best-performing strain gauges fabricated have a superior gauge factor to that
of commercial metal-based strain gauges. Notably, the strain gauges offer good
cyclability and are very robust, surviving repeated peel tests and immersion in
water. Furthermore, preliminary results indicate that the stain gauges also
show potential for high-frequency operation. This host of advantageous
properties, combined with the possibility of further optimization and channel
patterning, indicate that PtSe2 grown directly on polyimide holds great promise
for future applications.",1903.11894v1
2019-08-09,Doping-dependent competition between superconductivity and polycrystalline charge density waves,"From systematic analysis of the high pulsed magnetic field resistance data of
La$_{2-x}$Sr$_x$CuO$_{4}$ thin films, we extract an experimental phase diagram
for several doping values ranging from the very underdoped to the very
overdoped regimes. Our analysis highlights a competition between charge density
waves and superconductivity which is ubiquitous between $x=0.08$ and $x=0.19$
and produces the previously observed double step transition. When suppressed by
a strong magnetic field, superconductivity is resilient for two specific doping
ranges centered around respectively $x\approx 0.09$ and $x\approx 0.19$ and the
characteristic temperature for the onset of the competing charge density wave
phase is found to vanish above $x = 0.19$. At $x=1/8$ the two phases are found
to coexist exactly at zero magnetic field.",1908.03408v3
2019-08-12,Exchange Bias and Quantum Anomalous Hall Effect in the MnBi2Te4-CrI3 Heterostructure,"The layered antiferromagnetic MnBi2Te4 films have been proposed to be an
intrinsic quantum anomalous Hall (QAH) insulator with a large gap. To realize
this proposal, it is crucial to open a magnetic gap of surface states. However,
recent experiments have observed gapless surface states, indicating the absence
of out-of-plane surface magnetism, and thus the quantized Hall resistance can
only be achieved at the magnetic field above 6 T. In this work, we propose to
induce out-of-plane surface magnetism of MnBi2Te4 films via the magnetic
proximity with magnetic insulator CrI3. Our calculations have revealed a strong
exchange bias ~ 40 meV, originating from the long Cr-eg orbital tails that
hybridize strongly with Te p-orbitals. By stabilizing surface magnetism, the
QAH effect can be realized in the MnBi2Te4/CrI3 heterostructure. Our
calculations also demonstrate the high Chern number QAH state can be achieved
by controlling external electric gates. Thus, the MnBi2Te4/CrI3 heterostructure
provides a promising platform to realize the electrically tunable zero-field
QAH effect.",1908.04322v2
2019-08-13,Evolution of structure and magnetism across the metal-insulator transition in the pyrochlore iridate $($Nd$_{1-x}$Ca$_x)_2$Ir$_2$O$_7$,"We report on the evolution of the thermal metal-insulator transition in
polycrystalline samples of Nd$_2$Ir$_2$O$_7$ upon hole-doping via substitution
of Ca$^{2+}$ for Nd$^{3+}$. Ca substitution mediates a filling-controlled
Mott-like transition with minimal resolvable structural changes and without
altering site symmetry. Local structure confirms that Ca substitution does not
result in local chemical phase separation, and absorption spectroscopy
establishes that Ir cations maintain a spin-orbit entangled electronic
configuration. The metal-insulator transition coincides with antiferromagnetic
ordering on the Ir sublattice for all measured samples, and both decrease in
onset temperature with Ca content. Weak low-temperature upturns in
susceptibility and resistivity for samples with high Ca content suggest that Nd
sublattice antiferromagnetism continues to couple to carriers in the metallic
regime.",1908.04874v1
2019-12-11,Non-quadratic transverse magnetoresistance of the nodal line Dirac semimetal InBi,"The transverse magnetoresistance of a nodal line Dirac semi-metal InBi has
been studied. It is found that the magnetoresistance is not quadratic. In the
region of small magnetic fields $ B\lesssim 0.1$~T, it is characterized by high
curvature, in the region of medium magnetic fields it is described by the sum
of linear and quadratic contributions, and in the region of large magnetic
fields $ B\gtrsim 1$~T, it approaches a quadratic law with a curvature several
times smaller its zero field value. A phenomenological equation is proposed
that allows to describe the entire dependence of the resistance on the magnetic
field with an error not exceeding the measurement error of several percent.",1912.05321v1
2021-01-14,Superconducting critical temperature in the extended diffusive SYK model,"Models for strongly interacting fermions in disordered clusters forming an
array, with electron hopping between sites, reproduce the linear dependence on
temperature of the resistivity, typical of the strange metal phase of High
Temperature Superconducting materials (Extended Sachdev-Ye-Kitaev (SYK)
models). Our hydrodynamical approach to the marginal Fermi liquid emerging out
of the interaction, identifies the low energy collective excitations of the
system in its coherent phase. These neutral excitations diffuse in the lattice,
but the diffusion is heavily hindered by coupling to the pseudo Goldstone modes
of the conformal broken symmetry SYK phase, which are local in space. A
critical temperature for superconductivity arises in the electron liquid,in
case these excitations are assumed to mediate an attractive Cooper-pairing, in
the electron liquid, which is not BCS-like.",2101.05627v4
2021-01-22,A Robust Coherent Single-Photon Interface for Moderate- NA Optics Based on SiV Center in Nanodiamonds and a Plasmonic Bullseye Antenna,"Coherent exchange of single photons is at the heart of applied Quantum
Optics. The negatively-charged silicon vacancy center in diamond is among most
promising sources for coherent single photons. Its large Debye-Waller factor,
short lifetime and extraordinary spectral stability is unique in the field of
solid-state single photon sources. However, the excitation and detection of
individual centers requires high numerical aperture optics which, combined with
the need for cryogenic temperatures, puts technical overhead on experimental
realizations. Here, we investigate a hybrid quantum photonics platform based on
silicon-vacancy center in nanodiamonds and metallic bullseye antenna to realize
a coherent single-photon interface that operates efficiently down to low
numerical aperture optics with an inherent resistance to misalignment.",2101.09223v2
2011-04-06,Improved tunneling magnetoresistance at low temperature in manganite junctions grown by molecular beam epitaxy,"We report resistance versus magnetic field measurements for a
La0.65Sr0.35MnO3/SrTiO3/La0.65Sr0.35MnO3 tunnel junction grown by
molecular-beam epitaxy, that show a large field window of extremely high
tunneling magnetoresistance (TMR) at low temperature. Scanning the in-plane
applied field orientation through 360^/circ, the TMR shows 4-fold symmetry,
i.e. biaxial anisotropy, aligned with the crystalline axes but not the junction
geometrical long axis. The TMR reaches ~ 1900% at 4K, corresponding to an
interfacial spin polarization of > 95% assuming identical interfaces. These
results show that uniaxial anisotropy is not necessary for large TMR, and lay
the groundwork for future improvements in TMR in manganite junctions.",1104.1072v1
2011-04-07,Electrostatic Control of the Evolution from Superconductor to Insulator in Ultrathin Films of Yttrium Barium Copper Oxide,"The electrical transport properties of ultrathin YBCO films have been
modified using an electric double layer transistor configuration employing an
ionic liquid. The films were grown on SrTiO3 substrates using high pressure
oxygen sputtering. A clear evolution from superconductor to insulator was
observed in nominally 7 unit cell thick films. Using a finite size scaling
analysis, curves of resistance versus temperature, R(T), over the temperature
range from 6K to 22K were found to collapse onto a single scaling function,
which suggests the the presence of a quantum critical point. However the
scaling failed at the lowest temperatures suggesting the presence of an
additional phase between the superconducting and insulating regimes.",1104.1357v1
2011-04-07,Interference effects in phtalocyanine controlled by H-H tautomerization: a potential two-terminal unimolecular electronic switch,"We investigate the electrical transport properties of two hydrogen tautomer
configurations of phthalocyanine (H2Pc) connected to cumulene and gold leads.
Hydrogen tautomerization affects the electronic state of H2Pc by switching the
character of molecular orbitals with the same symmetry close to the Fermi
level. The near degeneracy between the HOMO and HOMO-1 leads to pronounced
interference effects, causing a large change in current for the two tautomer
configuratons, especially in the low-bias regime. Two types of planar junctions
are considered: cumulene-H2Pc-cumulene and gold-H2Pc-gold. Both demonstrate
prominent difference in molecular conductance between ON and OFF states. In
addition, junctions with gold leads show pronounced negative differential
resistance (NDR) at high bias voltage, as well as weak NDR at intermediate
bias.",1104.1441v2
2012-03-07,Hall helps Ohm: some corrections to negative-U centers approach to transport properties of YBa$_2$Cu$_3$O$_x$ and La$_{2-x}$Sr$_x$CuO$_4$,"For broad oxygen and strontium doping ranges, temperature dependences
(T-dependences) of the normal state resistivity \rho(T) of YBa_2Cu_3O_x (YBCO)
and La_(2-x)Sr_xCuO_4 (LSCO) are calculated and compared to experiments. Holes
transport was taken in the \tau-approximation, where \tau(T,\epsilon) is due to
acoustic phonons. Besides, T-dependence of the chemical potential \mu(T) and
effective carrier mass m* ~10-100 free electron masses, obtained by negative-U
centers modelling the T-dependence of the Hall coefficient, were used to
calculate \rho(T). In addition, it is demonstrated that anisotropy of the
cuprates does not affect the calculated T-variation of neither Hall coefficient
nor \rho, but only rescale their magnitudes by factors depending on
combinations of m_ab and m_c.",1203.1579v1
2012-03-29,Fermi level tuning and a large activation gap achieved in the topological insulator Bi_{2}Te_{2}Se by Sn doping,"We report the effect of Sn doping on the transport properties of the
topological insulator Bi_{2}Te_{2}Se studied in a series of
Bi_{2-x}Sn_{x}Te_{2}Se crystals with 0 \leq x \leq 0.02. The undoped
stoichiometric compound (x = 0) shows an n-type metallic behavior with its
Fermi level pinned to the conduction band. In the doped compound, it is found
that Sn acts as an acceptor and leads to a downshift of the Fermi level. For x
\geq 0.004, the Fermi level is lowered into the bulk forbidden gap and the
crystals present a resistivity considerably larger than 1 Ohmcm at low
temperatures. In those crystals, the high-temperature transport properties are
essentially governed by thermally-activated carriers whose activation energy is
95-125 meV, which probably signifies the formation of a Sn-related impurity
band. In addition, the surface conductance directly obtained from the
Shubnikov-de Haas oscillations indicates that a surface-dominated transport can
be achieved in samples with several um thickness.",1203.6411v1
2015-04-14,Pressure Induced Enhancement of Superconductivity in LaRu2P2,"To explore new superconductors beyond the copper-based and iron-based systems
is very important. The Ru element locates just below the Fe in the periodic
table and behaves like the Fe in many ways. One of the common thread to induce
high temperature superconductivity is to introduce moderate correlation into
the system. In this paper, we report the significant enhancement of
superconducting transition temperature from 3.84K to 5.77K by using a pressure
only of 1.74 GPa in LaRu2P2 which has an iso-structure of the iron-based 122
superconductors. The ab-initio calculation shows that the superconductivity in
LaRu2P2 at ambient pressure can be explained by the McMillan's theory with
strong electron-phonon coupling. However, it is difficult to interpret the
significant enhancement of Tc versus pressure within this picture. Detailed
analysis of the pressure induced evolution of resistivity and upper critical
field Hc2(T) reveals that the increases of Tc with pressure may be accompanied
by the involvement of extra electronic correlation effect. This suggests that
the Ru-based system has some commonality as the Fe-based superconductors.",1504.03652v1
2015-04-16,Electron mobility in InxGa1-xN channel HEMTs,"In this letter, we report on the theoretical investigations of electron
mobility in practically viable designs of InxGa1-xN channel high electron
mobility transistors (HEMT). Carriers in such devices are expected to exhibit a
higher velocity and hence higher cut-off frequencies (fT) for highly scaled
architectures. We estimate that the mobility of two dimensional electron gas
(2DEG) is limited by alloy scattering rather than phonon scattering unlike in
conventional GaN-channel HEMTs. For indium composition of 0.30, the mobility
and sheet resistance are found to be 500 cm2/Vs and 700 ohm per sq.
respectively, which can severely affect the parasitic voltage drop in access
regions. The results presented here are believed to significantly guide the
practical exploration of InxGa1-xN channel HEMTs towards next-generation
electronics by enabling careful design of device layouts in highly scaled
transistors to minimize parasitic access region voltage drop which results due
to significant degradation of 2DEG mobility.",1504.04336v1
2015-06-01,Topological stability versus thermal agitation in a metastable magnetic skyrmion lattice,"Topologically stable matters can have a long lifetime, even if
thermodynamically costly, when the thermal agitation is sufficiently low. A
magnetic skyrmion lattice (SkL) represents a unique form of long-range magnetic
order that is topologically stable, and therefore, a long-lived, metastable SkL
can form. Experimental observations of the SkL in bulk crystals, however, have
mostly been limited to a finite and narrow temperature region in which the SkL
is thermodynamically stable; thus, the benefits of the topological stability
remain unclear. Here, we report a metastable SkL created by quenching a
thermodynamically stable SkL. Hall-resistivity measurements of MnSi reveal
that, although the metastable SkL is short-lived at high temperatures, the
lifetime becomes prolonged (>> 1 week) at low temperatures. The manipulation of
a delicate balance between thermal agitation and the topological stability
enables a deterministic creation/annihilation of the metastable SkL by
exploiting electric heating and subsequent rapid cooling, thus establishing a
facile method to control the formation of a SkL.",1506.00363v2
2015-07-02,Wavelength tuning and stabilization of microring-based filters using silicon in-resonator photoconductive heaters,"We demonstrate that n-doped resistive heaters in silicon waveguides show
photoconductive effects with high responsivities. These photoconductive
heaters, integrated into microring resonator (MRR)-based filters, were used to
automatically tune and stabilize the filter's resonance wavelength to the input
laser's wavelength. This is achieved without requiring dedicated defect
implantations, additional material depositions, dedicated photodetectors, or
optical power tap-outs. Automatic wavelength stabilization of first-order MRR
and second-order series-coupled MRR filters is experimentally demonstrated.
Open eye diagrams were obtained for data transmission at 12.5 Gb/s while the
temperature was varied by 5 C at a rate of 0.28 C/s. We theoretically show that
series-coupled MRR-based filters of any order can be automatically tuned by
using photoconductive heaters to monitor the light intensity in each MRR, and
sequentially aligning the resonance of each MRR to the laser's wavelength.",1507.00686v2
2015-07-18,Addressing the Challenges of Using Ferromagnetic Electrodes in the Molecular Spintronics Devices,"Ferromagnetic electrodes chemically bonded with thiol functionalized
molecules can produce novel molecular spintronics devices. However, major
challenges lie in developing Ferromagnetic electrodes based commercially viable
device fabrication scheme that consider the susceptibility of ferromagnetic
electrodes to oxidation, chemical etching, and stress induced deformations
during fabrication and usage. This paper studies NiFe, an alloy used in the
present day memory devices and high-temperature engineering applications, as a
candidate FM electrode for the fabrication of MSDs. Our spectroscopic
reflectance studies show that NiFe start oxidizing aggressively beyond 90 C.
The NiFe surfaces, aged for several months or heated for several minutes below
90 C, exhibited remarkable electrochemical activity and were suitable for
chemical bonding with the thiol functionalized molecular device elements. NiFe
also demonstrated excellent etching resistance and minimized the mechanical
stress induced deformities. This paper demonstrates the successful utilization
of NiFe electrodes in the tunnel junction based molecular device fabrication
approach. This paper is expected to fill the knowledge gap impeding the
experimental development of ferromagnetic electrode based molecular spintronics
devices for realizing novel logic and memory devices and observing a numerous
theoretically predicted phenomenon.",1507.05146v1
2015-07-26,Topological Phase Transition in Single Crystals of $(Cd_{1-x} Zn_x)_3 As_2$,"Single crystals of $(Cd_{1-x} Zn_x)_3 As_2$ were synthesized from
high-temperature solutions and characterized in terms of their structural and
electrical properties. Based on the measurements of resistivity and Hall
signals, we revealed a chemical-doping-controlled transition from a three
dimensional Dirac semimetal to a semiconductor with a critical point $x_c/sim
0.38$. We observed structural transitions from a body-center tetragonal phase
to a primary tetragonal phase then back to a body-center tetragonal phase in
the solid solutions as well, which are irrelevant to the topological phase
transition. This continuously tunable system controlled by chemical doping
provides a platform for investigating the topological quantum phase transition
of 3D Dirac electrons.",1507.07169v1
2016-09-08,Collective Dynamics and Strong Pinning near the Onset of Charge Order in La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_{4}$,"The dynamics of charge-ordered states is one of the key issues in underdoped
cuprate high-temperature superconductors, but static short-range charge-order
(CO) domains have been detected in almost all cuprates. We probe the dynamics
across the CO (and structural) transition in
La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_{4}$ by measuring nonequilibrium charge
transport, or resistance $R$ as the system responds to a change in temperature
and to an applied magnetic field. We find evidence for metastable states,
collective behavior, and criticality. The collective dynamics in the critical
regime indicates strong pinning by disorder. Surprisingly, nonequilibrium
effects, such as avalanches in $R$, are revealed only when the critical region
is approached from the charge-ordered phase. Our results on
La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_{4}$ provide the long-sought evidence for
the fluctuating order across the CO transition, and also set important
constraints on theories of dynamic stripes.",1609.02591v3
2016-09-21,Change-over of carrier type and magneto-transport property in Cu doped Bi2Te3 Topological Insulators,"Structural, resistivity, thermoelectric power and magneto-transport
properties of Cu doped Bi2Te3 topological insulators have been investigated.
The occurrence of the tuning of charge carriers from n type to p type by Cu
doping at Te sites of Bi2Te3 is observed both from Hall effect and
thermoelectric power measurements. Carrier mobility decreases with the doping
of Cu which provides evidence of the movement of Fermi level from bulk
conduction band to the bulk valence band. Thermoelectric power also
increaseswith doping of Cu.Moreover linear magnetoresistance (LMR) has been
observed at high magnetic field in pure Bi2Te3 which is associated to the
gapless topological surface states protected by time reversal symmetry (TRS),
whereas doping of Cu breaks TRS and an opening of band gap occurs which
quenches the LMR.",1609.06542v1
2016-09-26,Anisotropic heat conduction in silicon nanowire network revealed by Raman scattering,"Anisotropic nanomaterials possess interesting thermal transport properties
because they allow orientation of heat fluxes along preferential directions due
to a high ratio (up to three orders of magnitude) between their in-plane and
cross-plane thermal conductivities. Among different techniques allowing thermal
conductivity evaluation, micro-Raman scattering is known to be one of the most
efficient contactless measurement approaches. In this letter, a new
experimental approach based on Raman scattering measurements with variable
laser spot sizes is reported. Correlation between experimental and calculated
thermal resistances of one-dimensional nanocrystalline solids allows
simultaneous estimation of their in-plane and cross-plane thermal
conductivities. In particular, our measurement approach is illustrated to be
successfully applied for anisotropic thermal conductivity evaluation of silicon
nanowire arrays.",1609.08133v3
2016-09-27,Lifshitz Transitions in the Ferromagnetic Superconductor UCoGe,"We present high field magnetoresistance, Hall effect and thermopower
measurements in the Ising-type ferromagnetic superconductor UCoGe. Magnetic
field is applied along the easy magnetization $c$ axis of the orthorhombic
crystal. In the different experimental probes we observed five successive
anomalies at $H \approx 4$, 9, 12, 16, and 21~T. Magnetic quantum oscillations
were detected both in resistivity and thermoelectric power. At most of the
anomalies, significant changes of the oscillation frequencies and the effective
masses have been observed indicating successive Fermi surface instabilities
induced by the strong magnetic polarization under magnetic field.",1609.08466v1
2018-07-07,Oxygen Potential Transition in Mixed Conducting Oxide Electrolyte,"It is generally assumed that oxygen potential in a thin oxide electrolyte
follows a linear distribution between electrodes. Jacobsen and Mogensen have
shown, however, that this is not the case for thin zirconia membranes in solid
oxide electrochemical cells. Here we demonstrate that there is a ubiquitous
oxygen potential transition rooted in the p-type/n-type transition of
electronic conductivity inside mixed conducting oxides, and that the transition
is extremely sensitive to electrode potential and current density. It is also
remarkably sensitive to the conductivity ratio of electrons and holes, as well
as their association with lattice oxygens and vacancies, which tends to
increase the oxygen flow. Direct evidence of a sharp oxygen potential
transition has been found in an equally sharp grain size transition in
electrically loaded zirconia. More broadly speaking, the oxygen potential
transition is akin to a first-order phase transition. Therefore, it will suffer
interface instability, especially in high-current-density devices. These
findings provide new opportunities to understand several disparate observations
in the literature, from microstructural degradation and stress distribution in
solid oxide fuel/electrolyzer cells, to field-assisted sintering, to conducting
filaments in resistance memory, to dendrite formation in electrochemical cells.",1807.02704v1
2018-07-31,Visible absorbing TiO2 thin films by physical deposition methods,"Titanium dioxide is one of the most widely used wide bandgap materials.
However, the TiO2 deposited on a substrate is not always transparent leading to
a loss in efficiency of the device, especially, the photo response. Herein, we
show that atomic layer deposition (ALD) and sputtered TiO2 thin films can be
highly absorbing in the visible region. While in ALD, the mechanism is
purported to be due to oxygen deficiency, intriguingly, in sputtered films it
has been observed that in fact oxygen rich atmosphere leads to visible
absorption. We show that the oxygen content during deposition, the resistivity
of the film could be controlled and also the photocatalysis response has been
evaluated for both the ALD and sputtered films. High resolution TEM and STEM
studies show that the origin of visible absorption could be due to the presence
of nanoparticles with surface defects inside the amorphous film.",1807.11748v1
2018-12-03,Anomalous scalings of the cuprate strange metals from nonlinear electrodynamics,"We examine transport in a holographic model which describes, through a
nonlinear gauge field sector, generic nonlinear interactions between the charge
carriers. Scaling exponents are introduced by using geometries which are
nonrelativistic and hyperscaling-violating in the infrared. In the dilute
charge limit in which the gauge field sector does not backreact on the
geometry, a particularly simple nonlinear theory reproduces the anomalous
temperature dependence of the resistivity and Hall angle of the cuprate strange
metals, $R \sim T$ and $\cot\Theta_H \sim T^2$ while also allowing for a linear
entropy $S \sim T$, and predicts that the magnetoresistance for small values of
the magnetic field $h$ should scale as $\sim h^2 T^{-4}$. Our study lends
evidence to the idea that the strange metal behavior of the cuprates relies
crucially on the linear temperature dependence of the entropy.",1812.01040v2
2018-12-17,PNADIS: An automated Peierls-Nabarro Analyzer for DISlocation core structure and slip resistance,"Dislocation is one of the most critical and fundamental crystal defects that
dominate the mechanical behavior of crystalline solids, however, a quantitative
determination of its character and property in experiments is quite challenging
and limited so far. In this paper, a fully automated Peierls-Nabarro (P-N)
analyzer named PNADIS is presented; a complete set of the character and
property of dislocation can be automatically derived, including the dislocation
core structure, Peierls energy and stress, pressure field around dislocation
core, solute/dislocation interaction energy, as well as the energy barrier and
yield stress at 0K for solid solution strengthening. Furthermore, both
one-dimensional (1D) and two-dimensional (2D) P-N models are implemented to
meet the demand to analyze the character and property of dislocation for not
only simple FCC and HCP structures but also complex crystals. The
implementation of this code has been critically validated by a lot of
evaluations and tests including 1D P-N model for complex crystals, 2D P-N model
for FCC and HCP metals, pressure field around dislocation core, and solid
solution strengthening for alloys. We expect that the automated feature of this
code would provide a high-efficiency solution for determining the character and
property of dislocation.",1812.06630v1
2019-01-23,Stacking of nanocrystalline graphene for Nano-Electro-Mechanical (NEM) actuator applications,"Graphene nano-electro-mechanical switches are promising components due to
their excellent switching performance such as low pull-in voltage and low
contact resistance. Mass fabrication with an appropriate counter electrode
remains challenging. In this work, we report the stacking of nanocrystalline
graphene (NCG) with a 70-nm dielectric separation layer. The buried NCG layer
is contacted through the formation of vias and acts as actuation electrode.
After metallization, the top 7.5-nm thin NCG layer is patterned to form
double-clamped beams, and the structure is released by hydrofluoric acid
etching. By applying a voltage between the top and buried NCG layer, a
step-like current increase is observed below 1.5 V, caused by the contact of
the movable beam with the buried NCG. No pull-out is observed due to the thin
sacrificial layer and high beam length, resulting in low mechanical restoring
force. We discuss the possible applications of the NCG stacking approach to
realize Nano-Electro-Mechanical (NEM) contact switches and advanced logical
components such as a AND logic.",1901.07754v1
2019-06-10,Successive Symmetry Breaking in a Jeff = 3/2 Quartet in the Spin-Orbit Coupled Insulator Ba2MgReO6,"We report on the cubic double perovskite Ba2MgReO6 containing Re6+ ions with
the 5d1 electron configuration. Resistivity, magnetization, and heat capacity
measurements using single crystals show that the compound is a Mott insulator
with a magnetic transition at Tm = 18 K, which is accompanied by a weak
ferromagnetic moment with [110] anisotropy. Another transition is observed at
Tq = 33 K in heat capacity, where the inverse of magnetic susceptibility
changes its slope, indicating a substantial change in the electronic state. The
significance of spin-orbit coupling is revealed by the reduced effective
magnetic moment of ~0.68{\mu}B at high temperature above Tq and the total
electronic entropy close to Rln4. These features indicate that Ba2MgReO6 is a
spin-orbit coupled Mott insulator possessing a Jeff = 3/2 quartet state, which
exhibits quadrupolar and dipolar orders at Tq and Tm, respectively.",1906.03802v1
2019-10-07,Ultrasound homogenises suspensions of hydrophobic particles,"Hydrophobic particles inherently resist being suspended. Hydrophobic
particles might be regarded as tiny solid particles surrounded by a thin
gaseous shell. It has been hypothesised that hydrophobic particles act as
cavitation nuclei. This cavitation behaviour would explain the translation
speeds observed when hydrophobic polystyrene microspheres were driven through a
liquid medium by means of ultrasound. These translation speeds corresponded to
those observed with gas microbubbles of similar sizes. If hydrophobic particles
do have a thin gaseous layer surrounding the solid cores, a sound field of
sufficient pressure amplitude might force the gas layer to form and inertial
cavity and subsequently fragment during the collapse phase. In this study, we
investigated whether hydrophobic particles can be forced to suspend by using
ultrasound. Hydrophobic particles of the materials C65 and ZnO can be forced to
be suspended in water using ultrasound. The high-speed observations confirm
that hydrophobic particles can act as cavitation nuclei. The lack of cavitation
after the first pulse indicates that the gas layer surrounding the hydrophobic
particle dissolves after inertial cavitation.",1910.02714v2
2019-10-19,Wafer-size VO2 film prepared by water-vapor oxidant,"The growth of wafer-scale and uniform monoclinic VO2 film was a challenge if
considering the multivalent vanadium atom and the various phase structures of
VO2 compound. Directly oxidizing metallic vanadium film in oxygen gas seemed to
be an easy way, while the oxidation parameters were extremely sensitive due to
the critical preparation window. Here we proposed a facile thermal oxidation by
water-vapor to produce wafer-scale VO2 films with high quality. Results
indicated that by using the water-vapor oxidant, the temperature window for VO2
growth was greatly broadened. In addition, the obtained wafer-size VO2 film
showed very uniform surface and sharp resistance change. The chemical reaction
routes with water-vapor were calculated, which favored the VO2 film growth. Our
results not only demonstrated that the water-vapor could be used as a modest
oxidizing agent, but also showed the unique advantage for large size VO2 film
preparation.",1910.08776v3
2019-10-28,Hikami-Larkin-Nagaoka (HLN) Fitting of Magneto Transport of Bi2Se3 Single Crystal in Different Magnetic Field Ranges,"We report the detailed study of structural micro-structuraland high magnetic
field magneto transport propertiesof Bi2Se3single crystal. Bi2Se3 single
crystal is grown through conventional solid-state reaction route via the
self-flux method. Rietveld analysis on Powder X-ray Diffraction showed that the
studied Bi2Se3 crystal is crystallized in single-phase without any impurity.
The surface morphology analyzed through Scanning Electron Microscopy study
which shows that as-grown single crystal exhibit layered type structure and the
quantitative weight of the atomic constituents (Bi and Se) are found to be
closeto the stoichiometric amount in energy-dispersive X-ray spectroscopy
analysis. Low temperature (2.5K) magneto-resistance (MR) exhibited a v-type
cusp around origin at lower magnetic field, which is the sign of weak
anti-localization effect. Further, Bi2Se3 single crystal magneto conductivity
data is fitted by well-known HLN equation in different magnetic field range of
2Tesla, 4Tesla and 6Tesla and the resultant found that the conduction mechanism
of Bi2Se3 is dominated by WAL state.",1910.12438v1
2019-11-06,Microscopic charging and in-gap states in superconducting granular aluminum,"Following the emergence of superconducting granular aluminum (grAl) as a
material for high-impedance quantum circuits, future development hinges on a
microscopic understanding of its phase diagram, and whether the
superconductor-to-insulator transition (SIT) is driven by disorder or charging
effects. Beyond fundamental relevance, these mechanisms govern noise and
dissipation in microwave circuits. Although the enhancement of the critical
temperature, and the SIT in granular superconductors have been studied for more
than fifty years, experimental studies have so far provided incomplete
information on the microscopic phenomena. Here we present scanning tunneling
microscope measurements of the local electronic structure of superconducting
grAl. We confirm an increased superconducting gap in individual grains both
near and above the Mott resistivity $\rho_\mathrm{M} \approx 400\ \mu \Omega
cm$. Above $\rho_\mathrm{M}$ we find Coulomb charging effects, a first
indication for decoupling, and in-gap states on individual grains, which could
contribute to flux noise and dielectric loss in quantum devices. We also
observe multiple low-energy states outside the gap, which may indicate bosonic
excitations of the superconducting order parameter.",1911.02312v2
2019-11-14,GFET Asymmetric Transfer Response Analysis through Access Region Resistances,"Graphene-based devices are planned to augment the functionality of Si and
III-V based technology in radio-frequency (RF) electronics. The expectations in
designing graphene {field-effect} transistors (GFETs) with enhanced RF
performance have attracted significant experimental efforts, mainly
concentrated on achieving high mobility samples. However, little attention has
been paid, so far, to the role of the access regions in these devices.
\mbox{Here, we analyse} in detail, via numerical simulations, how the GFET
transfer response is severely impacted by these regions, showing that they play
a significant role in the asymmetric saturated behaviour commonly observed in
GFETs. We also investigate how the modulation of the access region conductivity
(i.e., by the influence of a back gate) and the presence of imperfections in
the graphene layer (e.g., charge puddles) affects the transfer response. The
analysis is extended to assess the application of GFETs for RF applications,
by~evaluating their cut-off frequency.",1911.06360v1
2020-01-30,Extreme Fermi surface smearing in a maximally disordered concentrated solid solution,"We show that the Fermi surface can survive the presence of extreme
compositional disorder in the equiatomic alloy
Ni$_{0.25}$Fe$_{0.25}$Co$_{0.25}$Cr$_{0.25}$. Our high-resolution Compton
scattering experiments reveal a Fermi surface which is smeared across a
significant fraction of the Brillouin zone (up to 40\% of $\frac{2\pi}{a}$).
The extent of this smearing and its variation on and between different sheets
of the Fermi surface has been determined, and estimates of the electron
mean-free-path and residual resistivity have been made by connecting this
smearing with the coherence length of the quasiparticle states.",2001.11416v1
2020-05-12,Superconductivity in Hydrogenated Graphites,"We report transport and magnetization measurements on graphitic materials
that have been hydrogenated after being treated with octane. The
temperature-dependent electrical resistivity shows anomalies manifested as
re-entrant insulator-metal transitions. Below 50 K, the magnetoresistance data
shows both antiferromagnetic and ferromagnetic behavior as the magnetic field
is decrease or increased, respectively. The system is possibly an
unconventional magnetic superconductor. The irreversible behavior observed in
the field-cooled vs. the zero-field cooled data for a sufficiently high
magnetic field suggests that the system might enter a superconducting state
below 50 K. Energy gap data is obtained from nonlocal electric differential
conductance measurements. An exciton-based mechanism is likely driving the
system to the superconducting state below 50 K, where the gap is divergent. We
find that the hydrogenated carbon fiber is a multiple gap system with critical
temperatures estimates above room temperature. The temperature dependence of
the superconducting gap follows the flat-band energy relationship, with the
flat band gap parameter linearly increasing with the temperature above 50 K.
Thus, we find that either a magnetic or an electric field can drive this
hydrogenated graphitic system to superconducting state below 50 K. In addition,
AF spin fluctuations creates pseudo-gap states above 50 K.",2005.05876v1
2020-07-02,Drone swarms in fire suppression activities,"Recent huge technological development of Unmanned Aerial Vehicles (UAVs) can
provide breakthrough means of fighting wildland fires. We propose an innovative
forest firefighting system based on the use of a swarm of hundreds of UAVs able
to generate a continuous flow of extinguishing liquid on the fire front,
simulating rain effect. Automatic battery replacement and refilling of the
extinguishing liquid ensure the continuity of the action, and fire-resistant
materials protect drones exposed to possible high temperatures. We demonstrate
the validity of the approach in Mediterranean scrub first computing the
critical water flow rate according to the main factors involved in the
evolution of a fire, then estimating the number of linear meters of active fire
front that can be extinguished depending on the number of drones available and
the amount of extinguishing fluid carried. A fire propagation cellular automata
model is also employed to study the evolution of the fire. Simulation results
suggest that the proposed system can successfully integrate, or in case of
low-intensity and limited extent fires completely replace, current forest
firefighting techniques.",2007.00883v2
2020-07-29,Energy Transfer to a Stable Donor Suppresses Degradation in Organic Solar Cells,"Despite many advances towards improving the stability of organic photovoltaic
devices, environmental degradation under ambient conditions remains a
challenging obstacle for future application. Particularly conventional systems
employing fullerene derivatives are prone to oxidise under illumination,
limiting their applicability. Herein, we report on the environmental stability
of the small molecule donor DRCN5T together with the fullerene acceptor PC70BM.
We find that this system exhibits exceptional device stability, mainly due to
almost constant short-circuit current. By employing ultrafast femtosecond
transient absorption spectroscopy we attribute this remarkable stability to two
separate mechanisms: 1) DRCN5T exhibits high intrinsic resistance towards
external factors, showing no signs of deterioration. 2) The highly sensitive
PC70BM is stabilised against degradation by the presence of DRCN5T through
ultrafast long-range energy transfer to the donor, rapidly quenching the
fullerene excited states which are otherwise precursors for chemical oxidation.
We propose that this photoprotective mechanism be utilised to improve the
device stability of other systems, including non-fullerene acceptors and
ternary blends.",2007.14651v1
2020-10-13,Strong anisotropy of electron-phonon interaction in NbP probed by magnetoacoustic quantum oscillations,"In this study, we report on the observation of de Haas-van Alphen-type
quantum oscillations (QO) in the ultrasound velocity of NbP as well as `giant
QO' in the ultrasound attenuation in pulsed magnetic fields. The difference of
the QO amplitude for different acoustic modes reveals a strong anisotropy of
the effective deformation potential, which we estimate to be as high as
$9\,\mathrm{eV}$ for certain parts of the Fermi surface. Furthermore, the
natural filtering of QO frequencies and the tracing of the individual Landau
levels to the quantum limit allows for a more detailed investigation of the
Fermi surface of NbP as was previously achieved by means of analyzing QO
observed in magnetization or electrical resistivity.",2010.06530v2
2020-10-13,Stacking-engineered ferroelectricity in bilayer boron nitride,"2D ferroelectrics with robust polarization down to atomic thicknesses provide
novel building blocks for functional heterostructures. Experimental reports,
however, remain scarce because of the requirement of a layered polar crystal.
Here, we demonstrate a rational design approach to engineering 2D
ferroelectrics from a non-ferroelectric parent compound via employing van der
Waals assembly. Parallel-stacked bilayer boron nitride is shown to exhibit
out-of-plane electric polarization that reverses depending on the stacking
order. The polarization switching is probed via the resistance of an
adjacently-stacked graphene sheet. Furthermore, twisting the boron nitride
sheets by a small-angle changes the dynamics of switching due to the formation
of moir\'e ferroelectricity with staggered polarization. The ferroelectricity
persists to room temperature while keeping the high mobility of graphene,
paving the way for potential ultrathin nonvolatile memory applications.",2010.06600v2
2020-10-16,Visualizing half-metallic bulk band structure with multiple Weyl cones of the Heusler ferromagnet,"Using a well-focused soft X-ray synchrotron radiation beam, angle-resolved
photoelectron spectroscopy was applied to a full-Heusler-type Co$_2$MnGe alloy
to elucidate its bulk band structure. A large parabolic band at the Brillouin
zone center and several bands that cross the Fermi level near the Brillouin
zone boundary were identified in line with the results from first-principles
calculations. These Fermi level crossings are ascribed to majority spin bands
that are responsible for electron transport with extremely high spin
polarization especially along the direction being perpendicular to the
interface of magneto-resistive devices. The spectroscopy confirms there is no
contribution of the minority spin bands to the Fermi surface, signifying
half-metallicity for the alloy. Furthermore, two topological Weyl cones with
band crossing points were identified around the $X$ point, yielding the
conclusion that Co$_2$MnGe could exhibit topologically meaningful behavior such
as large anomalous Hall and Nernst effects driven by the Berry flux in its
half-metallic band structure.",2010.08415v1
2020-10-27,Superconductivity and Fermi Surface Nesting in the Candidate Dirac Semimetal NbC,"We report the synthesis of single-crystal NbC, a transition metal carbide
with various unusual properties. Transport, magnetic susceptibility, and
specific heat measurements demonstrate that NbC is a conventional
superconductor with a superconducting transition temperature ($T_c$) of 11.5 K.
Our theoretical calculations show that NbC is a type-II Dirac semimetal with
strong Fermi surface nesting, which is supported by our ARPES measurement
results. We also observed the superconducting gaps of NbC using angle-resolved
photoemission spectroscopy (ARPES) and found some unconventional behaviors.
These intriguing superconducting and topological properties, combined with the
high corrosion resistance, make NbC an ideal platform for both fundamental
research and device applications.",2010.14259v2
2020-11-02,Phase field predictions of microscopic fracture and R-curve behaviour of fibre-reinforced composites,"We present a computational framework to explore the effect of microstructure
and constituent properties upon the fracture toughness of fibre-reinforced
polymer composites. To capture microscopic matrix cracking and fibre-matrix
debonding, the framework couples the phase field fracture method and a cohesive
zone model in the context of the finite element method. Virtual single-notched
three point bending tests are conducted. The actual microstructure of the
composite is simulated by an embedded cell in the fracture process zone, while
the remaining area is homogenised to be an anisotropic elastic solid. A
detailed comparison of the predicted results with experimental observations
reveals that it is possible to accurately capture the crack path, interface
debonding and load versus displacement response. The sensitivity of the crack
growth resistance curve (R-curve) to the matrix fracture toughness and the
fibre-matrix interface properties is determined. The influence of porosity upon
the R-curve of fibre-reinforced composites is also explored, revealing a
stabler response with increasing void volume fraction. These results shed light
into microscopic fracture mechanisms and set the basis for efficient design of
high fracture toughness composites.",2011.00779v1
2020-11-10,Rebound suppression of a droplet impact on a supersolvophobic surface by a small amount of polymer additives,"A small amount of polymer dissolved in a droplet suppresses droplet rebound
when it impinges on a supersolvophobic surface. This work investigates
impacting dynamics of a droplet of dilute polymer solution depending on the
molecular weight and the concentration of the polymer by using multi-body
dissipative particle dynamics simulations. Either the longer polymer or the
high polymer concentration suppresses rebound of a droplet although its shear
viscosity and the liquid-vapor surface tension are not different from those of
a pure solvent droplet. We found a new mechanism of the anti-rebound in which
the resistance is applied against the hopping motion, while behavior of the
non-rebounding droplet at the earlier spreading and retraction stages is same
as for the rebounding droplets. Two polymer contributions to reducing the
rebound tendency are quantitatively analyzed: the alteration of the substrate
wettability by the polymer adsorption and the polymer elongation force.",2011.05086v1
2020-12-03,Optical and Hidden Transport Properties of BaFe$_{1.91}$Ni$_{0.09}$As$_{2}$ Film,"Optical spectroscopy was used to study the electrodynamics and hidden
transport properties of a BaFe$_{1.91}$Ni$_{0.09}$As$_{2}$ thin superconducting
film. We analyzed the normal state data using a Drude-Lorentz model with two
Drude components: one narrow ($D_1$) and another broad one ($D_2$). In the
superconducting state, two gaps with $2\Delta _{0}^{(2)}/k_BT_c=1.9$--2.0 and
$2\Delta _{0}^{(1)}/k_BT_c=4.0$--4.3 are formed from the narrow component $D_1$
while the broad component $D_2$ remains ungapped. The calculated total DC
resistivity of the film and the low-temperature scattering rate for the narrow
Drude component show a hidden Fermi-liquid behavior. The change of total
electron-boson coupling ($\lambda_{tot}$) and representative energy
($\Omega_{0}$) in the normal state with respect to the superconducting state is
typical of other iron-based materials as well as high-temperature
superconducting (HTSC) cuprates.",2012.01962v1
2020-12-08,Phonon modes contribution in thermal rectification in graphene-C3B junction: A molecular dynamics study,"In this work using non-equilibrium molecular dynamics simulation we implement
a series of simulation under positive and negative temperature gradient in
order to investigate the thermal rectification in the graphene C3B junction
GCB. The dependence of thermal rectification on temperature difference between
the hot and the cold baths is obtained. The important quantity that we present
here is the inplanes and out of plane phonon modes contribution in the thermal
rectification. We see that the Y mode has high and positive thermal
rectification while that the X and Z modes have small and negative thermal
rectifications. Thermal rectification for Y mode increases sharply beyond T 30
K to 150 but for X and Z modes decrease slowly by increasing T Our results show
that Y mode has major role in the thermal rectification Moreover the underlying
mechanisms that leads to the thermal rectification and also Kapitza resistance
at the interface are studied via the phonon density of states DOS",2012.04363v1
2021-04-14,Lack of Fusion in Additive Manufacturing: Defect or Asset?,"Rapid cooling rates and stochastic interactions between the heat source and
feedstock in additive manufacturing (AM) result in strong anisotropy and
process-induced defects deteriorating the tensile ductility and fatigue
resistance of printed parts. We show that by deliberately introducing a high
density of lack of fusion (LoF) defects, a processing regime that has been
avoided so far, followed by pressure assisted heat treatment, we can print
Ti-6Al-4V with reduced texture and exceptional properties surpassing that of
wrought, cast, forged, annealed, and solution-treated and aged counterparts.
Such improvement is achieved through the formation of low aspect ratio
{\alpha}-grains around LoF defects upon healing, surrounded by {\alpha}-laths.
This occurrence is attributed to surface energy reduction and recrystallization
events taking place during healing of LoF defects. Our approach to design
duplex microstructures is applicable to a wide range of AM processes and alloys
and can be used in the design of damage tolerant microstructures.",2104.07014v1
2021-04-21,Electrically detected paramagnetic resonance in Ag-paint coated DPPH,"We describe a simple experimental method to detect electron paramagnetic
resonance (EPR) in polycrystalline 2,2-diphenyl-1-picrylhydrazyl (DPPH) sample,
the standard g-marker for EPR spectroscopy, without using a cavity resonator or
a prefabricated waveguide. It is shown that microwave(MW) current injected into
a layer of silver paint coated on an insulating DPPH sample is able to excite
the paramagnetic resonance in DPPH. As the applied dc magnetic field H is
swept, the high-frequency resistance of the Ag-paint layer, measured at room
temperature with a single port impedance analyzer in the MW frequency range 1
to 2.5 GHz, exhibits a sharp peak at a critical value of the dc field (H =
Hres) while the reactance exhibits a dispersion-like behavior around the same
field value for a given frequency. Hres increases linearly with the frequency
of MW current. We interpret the observed features in the impedance to EPR in
DPPH driven by the Oersted magnetic field arising from the MW current in the
Ag-paint layer. We also confirm the occurrence of EPR in DPPH independently
using a coplanar waveguide-based broadband technique. This technique has the
potential to investigate other EPR active inorganic and organic compounds.",2104.10794v1
2021-05-26,Theoretical study for 3D quantum Hall effect in a periodic electron system,"The exsitance of three-dimensional Hall effect (3DQHE) due to spontaneous
Fermi surface instabilities in strong magnetic field was proposed decades ago,
and has stimulated recent progress in experiments. The reports in recent
experiments show that the Hall plateaus and vanishing transverse
magneto-resistivities (TMRs) (which are two main signatures of 3DQHE) are not
easy to be observed in natural materials. And two main different explanations
of the slow varying slope like Hall plateaus and non-vanishing
  TMRs (which can be called as quasi-quantized Hall effect (QQHE)) have been
proposed. By studying the magneto-transport with a simple effective periodic 3D
system, we show how 3DQHE can be achieved in certain parameter regimes at
first. We find two new mechanisms that may give rise to QQHE. One mechanism is
the ""low"" Fermi energy effect, and the other is the ""strong"" impurity effect.
Our studies also proved that the artificial superlattice is an ideal platform
for realizing 3DQHE with high layer barrier periodic potential.",2105.12461v2
2021-06-09,"The extended diffusive Sachdev-Ye-Kitaev model as a sort of ""strange metal""","The 0+1-d Sachdev-Ye-Kitaev (SYK) fermionic model attracts nowadays a wide
spread interest of the Condensed Matter community, as a benchmark toy model for
strong electron correlation and non Fermi Liquid behavior. It is exactly
solvable in the infrared limit and reproduces the linear dependence of the
resistivity on temperature T, in linear response, typical of the strange metal
phase of High Temperature Superconducting (HTS) materials. The breaking of its
conformal symmetry requires ultraviolet corrections for a faithful description
of its pseudo Goldstone Modes. Extension of the model to higher space dimension
includes a local U(1) phase generating collective bosonic excitations driven by
the additional ultraviolet contribution to the action. These excitations are
studied here, in a temperature window of incoherent dynamics in which the
expected chaotic regime has not yet taken over. We identify them as neutral
diffusive energy excitations with temperature dependent lifetime h / k_B T.
They provide thermalization of the system and contribute to the T dependence of
the transport coefficients. The linear unbound T increase of particle current
is confirmed by our hydrodynamic modelization. A quantum liquid in interaction
with this system would become a Marginal Fermi Liquid.",2106.05383v2
2021-06-15,Charge Carrier Transport in Iron Pyrite Thin Films: Disorder Induced Variable Range Hopping,"The origin of p-type conductivity and the mechanism responsible for low
carrier mobility was investigated in pyrite (FeS2) thin films. Temperature
dependent resistivity measurements were performed on polycrystalline and
nanostructured thin films prepared by three different methods. Films have a
high hole density and low mobility regardless of the method used for their
preparation. The charge transport mechanism is determined to be nearest
neighbour hopping (NNH) at near room temperature with Mott-type variable range
hopping (VRH) of holes via localized states occurring at lower temperatures.
Density functional theory (DFT) predicts that sulfur vacancy induced localized
defect states will be situated within the band gap with the charge remaining
localized around the defect. The data indicate that the electronic properties
including hopping transport in pyrite thin films can be correlated to sulfur
vacancy related defect. The results provide insights on electronic properties
of pyrite thin films and its implications for charge transport",2106.08401v2
2021-06-24,Epitaxial growth of Ruddlesden-Popper neodymium nickelates Nd$_{n+1}$Ni$_{n}$O$_{3n+1}$ (${n}$ = 1-5),"A series of Ruddlesden-Popper nickelates, Nd$_{n+1}$Ni$_{n}$O$_{3n+1}$ (${n}$
= 1-5), have been stabilized in thin film form using reactive molecular-beam
epitaxy. High crystalline quality has been verified by X-ray diffraction and
scanning transmission electron microscopy. X-ray photoelectron spectroscopy
indicates the ${n}$-dependent valence states of nickel in these compounds.
Metal-insulator transitions show clear ${n}$ dependence for intermediate
members (${n}$ = 3-5), and the low-temperature resistivities of which show
logarithmic dependence, resembling the Kondo-scattering as observed in the
parent compounds of superconducting infinite-layer nickelates.",2106.12941v1
2021-07-28,Narrow-gap semiconducting behavior in antiferromagnetic Eu$_{11}$InSb$_9$,"Here we investigate the thermodynamic and electronic properties of
Eu$_{11}$InSb$_9$ single crystals. Electrical transport data show that
Eu$_{11}$InSb$_9$ has a semiconducting ground state with a relatively narrow
band gap of $320$~meV. Magnetic susceptibility data reveal antiferromagnetic
order at low temperatures, whereas ferromagnetic interactions dominate at high
temperature. Specific heat, magnetic susceptibility, and electrical resistivity
measurements reveal three phase transitions at $T_{N1}=9.3$~K, $T_{N2} =8.3$~K,
and $T_{N3} =4.3$~K. Unlike Eu$_{5}$In$_{2}$Sb$_6$, a related
europium-containing Zintl compound, no colossal magnetoresistance (CMR) is
observed in Eu$_{11}$InSb$_9$. We attribute the absence of CMR to the smaller
carrier density and the larger distance between Eu ions and In-Sb polyhedra in
Eu$_{11}$InSb$_9$. Our results indicate that Eu$_{11}$InSb$_9$ has potential
applications as a thermoelectric material through doping or as a
long-wavelength detector due to its narrow gap.",2107.13145v1
2021-08-04,Theory of Huge Thermoelectric Effect Based on Magnon Drag Mechanism: Application to Thin-Film Heusler Alloy,"To understand the unexpectedly high thermoelectric performance observed in
the thin-film Heusler alloy Fe$_2$V$_{0.8}$W$_{0.2}$Al, we study the magnon
drag effect, generated by the tungsten based impurity band, as a possible
source of this enhancement, in analogy to the phonon drag observed in FeSb$_2$.
Assuming that the thin-film Heusler alloy has a conduction band integrating
with the impurity band, originated by the tungsten substitution, we derive the
electrical conductivity $L_{11}$ based on the self-consistent t-matrix
approximation and the thermoelectric conductivity $L_{12}$ due to magnon drag,
based on the linear response theory, and estimate the temperature dependent
electrical resistivity, Seebeck coefficient and power factor. Finally, we
compare the theoretical results with the experimental results of the thin-film
Heusler alloy to show that the origin of the exceptional thermoelectric
properties is likely to be due to the magnon drag related with the
tungsten-based impurity band.",2108.01880v1
2021-08-10,Nature of electrons from oxygen vacancies and polar catastrophe at LaAlO3/SrTiO3 interfaces,"The relative significance of quantum conductivity correction and magnetic
nature of electrons in understanding the intriguing low-temperature resistivity
minimum and negative magnetoresistance of the two-dimensional electron gas at
LaAlO3/SrTiO3 interfaces has been a long outstanding issue since its discovery.
Here we report a comparative magnetotransport study on amorphous and
oxygen-annealed crystalline LaAlO3/SrTiO3 heterostructures at a relatively
high-temperature range, where the orbital scattering is largely suppressed by
thermal fluctuations. Despite of a predominantly negative out-of-plane
magnetoresistance effect for both, the magnetotransport is isotropic for
amorphous LaAlO3/SrTiO3 while strongly anisotropic and well falls into a
two-dimensional quantum correction frame for annealed crystalline
LaAlO3/SrTiO3. These results clearly indicate that a large portion of electrons
from oxygen vacancies are localized at low temperatures, serving as magnetic
centers, while the electrons from the polar field are only weakly localized due
to constructive interference between time-reversed electron paths in the clean
limit and no signature of magnetic nature is visible.",2108.04532v1
2021-08-19,"Chemomechanics: friend or foe of the ""AND problem"" of solid-state batteries?","Solid electrolytes are widely considered as the enabler of lithium metal
anodes for safe, durable, and high energy density rechargeable lithium-ion
batteries. Despite the promise, failure mechanisms associated with solid-state
batteries are not well-established, largely due to limited understanding of the
chemomechanical factors governing them. We focus on the recent developments in
understanding solid-state aspects including the effects of mechanical stresses,
constitutive relations, fracture, and void formation, and outline the gaps in
the literature. We also provide an overview of the manufacturing and processing
of solid-state batteries in relation to chemomechanics. The gaps identified
provide concrete directions towards the rational design and development of
failure-resistant solid-state batteries.",2108.10150v2
2021-09-01,Electrical switching of antiferromagnetic CoO | Pt across the Néel temperature,"One of the most important challenges in antiferromagnetic spintronics is the
read-out of the N\'eel vector state. High current densities up to 10$^8$
Acm$^{-2}$ used in the electrical switching experiments cause notorious
difficulty in distinguishing between magnetic and thermal origins of the
electrical signals. To overcome this problem, we present a temperature
dependence study of the transverse resistance changes in the switching
experiment with CoO|Pt devices. We demonstrate the possibility to extract a
pattern of spin Hall magnetoresistance for current pulses density of $5 \times
10^7$ Acm$^{-2}$ that is present only below the N\'eel temperature and does not
follow a trend expected for thermal effects. This is the compelling evidence
for the magnetic origin of the signal, which is observed using purely
electrical techniques. We confirm these findings by complementary experiments
in an external magnetic field. Such an approach can allow determining the
optimal conditions for switching antiferromagnets and be very valuable when no
imaging techniques can be applied to verify the origin of the electrical
signal.",2109.00293v2
2021-09-22,Dynamic Behaviors and Training Effects in TiN/Ti/HfO$_x$/TiN Nanolayered Memristors with Controllable Quantized Conductance States: Implications for Quantum and Neuromorphic Computing Devices,"Controllable quantized conductance states of TiN/Ti/HfO$_x$/TiN memristors
are realized with great precision through a pulse-mode reset procedure,
assisted with analytical differentiation of the condition of the set procedure,
which involves critical monitoring of the measured bias voltage. An intriguing
training effect that leads to faster switching of the states is also observed
during the operation. Detailed analyses on the low- and high-resistance states
under different compliance currents reveal a complete picture of the structural
evolution and dynamic behaviors of the conductive filament in the HfO$_x$
layer. This study provides a closer inspection on the quantum-level
manipulation of nanoscale atomic configurations in the memristors, which helps
to develop essential knowledge about the design and fabrication of the future
memristor-based quantum devices and neuromorphic computing devices.",2109.10783v1
2021-09-27,Strongly electron-correlated semimetal RuI$_3$ with a layered honeycomb structure,"A polymorph of RuI$_3$ synthesized under high pressure was found to have a
two-layered honeycomb structure. The resistivity of RuI$_3$ exhibits a
semimetallic behavior, in contrast to insulating properties in
$\alpha$-RuCl$_3$. In addition, Pauli paramagnetic behavior was observed in the
temperature dependence of a magnetic susceptibility and a nuclear spin-lattice
relaxation rate 1/$T_1$. The band structure calculations indicate that
contribution of the I 5$p$ components to the low-energy $t_\mathrm{2g}$ bands
effectively decreases Coulomb repulsion, leading to semimetallic properties.
The physical properties also suggest strong electron correlations in RuI$_3$.",2109.12864v2
2021-10-12,Single-component superconducting state in UTe2 at 2 K,"UTe2 is a newly-discovered unconventional superconductor wherein
multicomponent topological superconductivity is anticipated based on the
presence of two superconducting transitions and time-reversal symmetry breaking
in the superconducting state. The observation of two superconducting
transitions, however, remains controversial. Here we demonstrate that UTe2
single crystals displaying an optimal superconducting transition temperature at
2 K exhibit a single transition and remarkably high quality supported by their
small residual heat capacity in the superconducting state and large residual
resistance ratio. Our results shed light on the intrinsic superconducting
properties of UTe2 and bring into question whether UTe2 is a multicomponent
superconductor at ambient pressure.",2110.06200v1
2021-10-13,Large-Gap Quantum Spin Hall State and Temperature-Induced Lifshitz Transition in Bi4Br4,"Searching for new quantum spin Hall insulators with large fully opened energy
gap to overcome the thermal disturbance at room temperature has attracted
tremendous attention due to the one-dimensional (1D) spin-momentum locked
topological edge states serving as dissipationless channels for the practical
applications in low consumption electronics and high performance spintronics.
Here, we report the investigation of topological nature of monolayer Bi4Br4 by
the techniques of scanning tunneling microscopy and angle-resolved
photoemission spectroscopy (ARPES). The topological non-triviality of 1D edge
state integrals within the large bulk energy gap (~ 0.2 eV) is revealed by the
first-principle calculations. The ARPES measurements at different temperature
show a temperature-induced Lifshitz transition, corresponding to the
resistivity anomaly caused by the shift of chemical potential. The connection
between the emergency of superconductivity and the Lifshitz transition is
discussed.",2110.06658v1
2021-11-09,Weak antilocalization and Shubnikov-de Haas oscillations in CaCuSb single crystal,"Quantum oscillations in both linear and Hall resistivities and weak
antilocalization (WAL) are barely observed in bulk single crystals. Here we
report the transport properties of a CaCuSb single crystal that crystallizes in
the hexagonal crystal structure. The magnetotransport studies reveal WAL and
Shubnikov-de Haas (SdH) quantum oscillations with a unique frequency at 314 T.
A cusp-like behavior in the low field regime of magnetotransport for J //
(ab)-plane and B // [0001] confirms the WAL in CaCuSb. Angular-dependent
normalized magnetoconductance and SdH oscillations studies reveal that the
observed phenomena originate from the 2D transport channels. The high magnetic
field (up to 45 T) experiments demonstrate plateau-like features in the Hall
measurements. The first-principles calculations unfold that CaCuSb is a
non-topological semimetal with dominant hole carries at the Fermi level. Our
study reveals that CaCuSb is a promising candidate to explore the quasi-2D
quantum transport phenomenon in the transition metal pnictide materials.",2111.04996v1
2021-11-29,High-Speed Light Focusing through Scattering Medium by Cooperatively Accelerated Genetic Algorithm,"We develop an accelerated Genetic Algorithm (GA) system constructed by the
cooperation of field-programmable gate array (FPGA) and optimized parameters of
the GA. We found the enhanced decay of mutation rate makes convergence of the
GA much faster, enabling the parameter-induced acceleration of the GA.
Furthermore, the accelerated configuration of the GA is programmed in FPGA to
boost processing speed at the hardware level without external computation
devices. This system has ability to focus light through scattering medium
within 4 seconds with robust noise resistance and stable repetition
performance, which could be further reduced to millisecond level with advanced
board configuration. This study solves the long-term limitation of the GA, it
promotes the applications of the GA in dynamic scattering mediums, with the
capability to tackle wavefront shaping in biological material.",2111.14916v1
2021-12-01,Atomistic simulations of twin boundary effect on the crack growth behaviour in BCC Fe,"In this paper, the effect of twin boundaries on the crack growth behaviour of
single crystal BCC Fe has been investigated using molecular dynamics
simulations. The growth of an atomically sharp crack with an orientation of
(111)$<$110$>$ (crack plane/crack front) has been studied under mode-I loading
at constant strain rate. In order to study the influence of twin boundaries on
the crack growth behaviour, single and multiple twin boundaries were introduced
perpendicular to crack growth direction. The results indicate that the
(111)$<$110$>$ crack in single crystal BCC Fe grows in brittle manner. However,
following the introduction of twin boundaries, a noticeable plastic deformation
has been observed at the crack tip. Further, increasing the number of twin
boundaries increased the amount of plastic deformation leading to better crack
resistance and high failure strains. Finally, an interesting relationship has
been observed between the crack growth rate and flow stress.",2112.00354v1
2022-01-10,Phase Boundary Segregation in Multicomponent Alloys: A Diffuse-Interface Thermodynamic Model,"Microalloying elements tend to segregate to the matrix-precipitate phase
boundaries to reduce the interfacial energy. The segregation mechanism is
emerging as a novel design strategy for developing precipitation-hardened
alloys with significantly improved coarsening resistance for high temperature
applications. In this paper, we report a nanoscopic diffuse-interface
thermodynamic model that describes multicomponent segregation behavior in
two-phase substitutional alloys. Following classical approaches for grain
boundaries, we employ the regular solution thermodynamics to establish
segregation isotherms. We show that the model recovers the Guttmann
multicomponent isotherm describing local interfacial concentrations, and the
generalized Gibbs adsorption isotherm that governs the total solute excess and
interfacial energy. A variety of multicomponent segregation behaviors are
demonstrated for a model two-phase quaternary alloy. The nature of interfacial
parameters and the resulting analytic solutions make the model amenable for
parameterization and comparison with atomistic calculations and experimental
characterizations.",2201.03117v1
2022-03-09,Magnetotransport due to conductivity fluctuations in non-magnetic ZrTe2 nanoplates,"Transition metal dichalcogenides with nontrivial band structures exhibit
various fascinating physical properties and have sparked intensively research
interest. Here, we performed systematic magnetotransport measurements on
mechanical exfoliation prepared ZrTe2 nanoplates. We revealed that the negative
longitudinal magnetoresistivity observed at high field region in the presence
of parallel electric and magnetic fields could stem from the conductivity
fluctuations due to the excess Zr in the nanoplates. In addition, the
parametric plot, the planar Hall resistivity as function of the in-plane
anisotropic magnetoresistivity, has an ellipse-shaped pattern with shifted
orbital center, which further strengthen the evidence for the conductivity
fluctuations. Our work provides some useful insights into transport phenomena
in topological materials.",2203.04486v1
2022-03-11,Ultrafast intrinsic optical-to-electrical conversion dynamics in graphene photodetector,"Optical-to-electrical (O-E) conversion in graphene is a central phenomenon
for realizing anticipated ultrafast and low-power-consumption information
technologies. However, revealing its mechanism and intrinsic time scale require
uncharted terahertz (THz) electronics and device architectures. Here, we
succeeded in resolving O-E conversion processes in high-quality graphene by
on-chip electrical readout of ultrafast photothermoelectric current. By
suppressing the RC time constant using a resistive zinc oxide top gate, we
constructed a gate-tunable graphene photodetector with a bandwidth of up to 220
GHz. By measuring nonlocal photocurrent dynamics, we found that the
photocurrent extraction from the electrode is instantaneous without a
measurable carrier transit time across several-micrometer-long graphene,
following the Shockley-Ramo theorem. The time for photocurrent generation is
exceptionally tunable from immediate to > 4 ps, and its origin is identified as
Fermi-level-dependent intraband carrier-carrier scattering. Our results bridge
the gap between ultrafast optical science and device engineering, accelerating
ultrafast graphene optoelectronic applications.",2203.05752v1
2022-03-14,Little-Parks like oscillations in lightly doped cuprate superconductors,"Understanding the rich and competing electronic orders in cuprate
superconductors may provide important insight into the mechanism of
high-temperature superconductivity. Here, by measuring Bi2Sr2CaCu2O8+x in the
extremely underdoped regime, we obtain evidence for a distinct type of
ordering, which manifests itself as resistance oscillations at low magnetic
fields (<10 T) and at temperatures around the superconducting transition. By
tuning the doping level p continuously, we reveal that these low-field
oscillations occur only when p<0.1. The oscillation amplitude increases with
decreasing p but the oscillation period stays almost constant. We show that
these low-field oscillations can be well described by assuming a periodic
superconducting structure with a mesh size of about 50 nm. Such a charge order,
which is distinctly different from the well-established charge density wave and
pair density wave, seems to be an unexpected piece of the puzzle on the
correlated physics in cuprates.",2203.06971v1
2022-03-25,Hydrodynamic Interactions Between Charged and Uncharged Brownian Colloids at a Fluid-Fluid Interface,"Hypothesis: The collective dynamics and self-assembly of colloids floating at
a fluid/fluid interface is a balance between deterministic lateral interaction
forces, viscous resistance to colloid motion along the surface and thermal
(Brownian) fluctuations. As the colloid size decreases, thermal forces become
important and can affect the self assembly into ordered patterns and crystal
structures that are the starting point for various materials applications.
Numerics: Langevin dynamic simulations involving two particles straddling a
liquid/liquid interface with a high viscosity contrast are presented to
describe the lateral interfacial assembly of particles in Brownian and
non-Brownian dominated regimes. These simulations incorporate capillary
attraction, electrostatic repulsion, thermal fluctuations and HI between
particles (including the effect of the particle immersion depth). Simulation
results are presented for neutrally wetted particles which form a contact angle
of 90 degrees at the interface. Findings: Clustering, fractal growth and
particle ordering are observed at critically large values of the Pe numbers,
while smaller Pe numbers exhibit higher probabilities of yielding states in
which particles remain uncorrelated in space and more widely separated.",2203.13925v2
2022-04-02,Upscaling of a reaction-diffusion-convection problem with exploding non-linear drift,"We study a reaction-diffusion-convection problem with nonlinear drift posed
in a domain with periodically arranged obstacles. The non-linearity in the
drift is linked to the hydrodynamic limit of a totally asymmetric simple
exclusion process (TASEP) governing a population of interacting particles
crossing a domain with obstacle. Because of the imposed large drift scaling,
this nonlinearity is expected to explode in the limit of a vanishing scaling
parameter. As main working techniques, we employ two-scale formal
homogenization asymptotics with drift to derive the corresponding upscaled
model equations as well as the structure of the effective transport tensors.
Finally, we use Schauder's fixed point theorem as well as monotonicity
arguments to study the weak solvability of the upscaled model posed in an
unbounded domain. This study wants to contribute with theoretical understanding
needed when designing thin composite materials that are resistant to high
velocity impacts.",2204.00931v1
2022-06-01,Charge density wave and superconductivity in 6R-TaS2,"The layered transition metal dichalcogenide compounds 1T-TaS2 and 4H-TaS2 are
well known for their exotic properties, which include charge density wave,
superconductivity, Mott transition, etc., and lately quantum spin liquid. Here,
we report the magnetic, transport and transmission electron microscopy study of
the charge density wave and superconductivity in 6R-TaS2 which is a relatively
less studied polymorph of this dichalcogenide TaS2. Our high temperature
electron microscopy reveals multiple charge density wave transitions between
room temperature and 650K. Magnetization, and the electrical resistivity
measurements in the temperature range of 2-400 K reveal that 6R-TaS2 undergoes
a charge density wave transition around 305 K and is followed by a transition
to a superconducting state around 3.5 K. The low temperature specific heat
measurement exhibits anomaly associated with the superconducting transition
around 2.4 K. The estimated Ginzburg Landau parameter suggests that this
compound lies at the extreme limit of type-II superconductivity.",2206.00281v3
2022-06-03,Effects of charge dopants in quantum spin Hall materials,"Semiconductors' sensitivity to electrostatic gating and doping accounts for
their widespread use in information communication and new energy technologies.
It is demonstrated quantitatively and with no adjustable parameters that the
presence of paramagnetic acceptor dopants elucidates a variety of hitherto
puzzling properties of two-dimensional topological semiconductors at the
topological phase transition and in the regime of the quantum spin Hall effect.
The concepts of charge correlation, Coulomb gap, exchange interaction between
conducting electrons and holes localized on acceptors, strong coupling limit of
the Kondo effect, and bound magnetic polaron explain a short topological
protection length, high hole mobilities compared with electron mobilities, and
different temperature dependence of the spin Hall resistance in HgTe and
(Hg,Mn)Te quantum wells.",2206.01613v3
2022-06-02,Modeling Defect-Level Switching for Highly-Nonlinear and Hysteretic Electronic Devices,"Many semiconductors feature defects with charge state transition levels that
can switch due to structure changes following defect ionization: we call this
defect-level switching (DLS). For example, DX centers in III-V compounds, and
oxygen vacancies in ZnO, can switch between deep and shallow donor
configurations, and these bistable dynamics are responsible for persistent
photoconductivity. We recently demonstrated highly-nonlinear, hysteretic,
two-terminal electronic devices using DLS in CdS [H. Yin, A. Kumar, J.M.
LeBeau, and R. Jaramillo, Phys. Rev. Applied 15, 014014 (2021).] The resulting
devices operate without mass transport, and in the opposite sense to most
resistive switches: they are in a high-conductivity state at equilibrium, and
switch to a low-conductivity state at forward bias. Although DLS uses the same
defect transitions that are responsible for persistent photoconductivity, DLS
devices operate without light and can be orders-of-magnitude faster due to
exponential tuning of transition rates with voltage. In this work we use theory
and numerical simulation to explore the design space of DLS devices,
emphasizing the tradeoff between speed and on/off ratio. Our results will be
useful to guide future applications of these unusual devices.",2206.04108v1
2022-10-14,The Electrical Property of Large Few Layer Graphene Flakes Obtained by Microwaves Assisted Exfoliation of Expanded Graphite,"Few layer graphene (FLG) was synthesized by $\mu$-wave assisted exfoliation
of expanded graphite in toluene with an overall yield from c.a. 7% to 20%. A
significant difference in the absorption of $\mu$-waves by the expanded
graphite and toluene allowed a rapid heating of the medium. The number of FLG
sheets varies from 3 to 12, while the lateral size of the sheets exceeds few
$\mu$ms. The obtained FLG exhibits very low resistance with average value of
1.6 k$\Omega$ (500 $\Omega$ minimum) which is comparable to that of high
quality graphenes synthesized by CVD methods, and lower than numbers of
exfoliated graphenes.",2210.07627v1
2022-10-26,Superior damage tolerance of fish skins,"Skin is the largest organ of many animals. Its protective function against
hostile environments and predatorial attack makes high mechanical strength a
vital characteristic. Here, we measured the mechanical properties of bass fish
skins and found that fish skins are highly ductile with a rupture strain of up
to 30-40% and a rupture strength of 10-15 MPa. The fish skins exhibit a
strain-stiffening behavior. Stretching can effectively eliminate the stress
concentrations near the pre-existing holes and edge notches, suggesting that
the skins are highly damage tolerant. Our measurement determined a
flaw-insensitivity length of several millimeters, which exceeds that of most
engineering materials. The strain-stiffening and damage tolerance of fish skins
are explained by an agent-based model of collagen network in which the
load-bearing collagen microfibers assembled from nanofibrils undergo
straightening and reorientation upon stretching. Our study inspires development
of artificial skins that are thin, flexible, but highly fracture-resistant and
widely applicable in soft robots.",2210.14651v1
2022-10-29,Magnetotransport Properties and Fermi Surface Topology of Nodal line Semimetal InBi,"In the present study, we have discussed the up-turn behavior in the
resistivity pattern of the topological nodal line semimetal InBi. We argued
that such nature could be generalized with a mathematical model, that can be
applied to any compounds exhibiting similar behavior. The extremely high
magnetoresistance (XMR) has also been explained by the carrier compensation in
the compound, estimated from the Hall conductivity. Moreover, from the study of
Subhnikov-de Haas (SdH) oscillation and density functional theory (DFT), we
obtained the complete three-dimensional (3D) Fermi surface topology of the
compound InBi. A detailed understanding of carriers' behavior has been
discussed using those studies. We have also unfurled the topology of each
electron and hole pocket and its possible modulation with electron and hole
doping.",2210.16527v1
2022-11-30,"Mixed Valence Pseudobrookite Al$_{1.75}$Ti$_{1.25}$O$_5$: High Temperature Phase Transitions, Magnetism and Resistivity","Dark blue single crystals of Al$_{1.75}^{3+}$ Ti$_{1.0}^{4+}$
Ti$_{0.25}^{3+}$O$_5$ were grown with a novel synthesis method based on the
reaction of a Ti3+/Ti4+ containing langbeinite melt and Al$_2$O$_3$. The
obtained needles crystallize in the pseudobrookite structure and undergo two
reversible phase transitions from orthorhombic Cmcm to C2/m first and
subsequently to C2 symmetry. Like the known aluminum titanate pseudobrookites,
anistropic thermal expansion is observed. The temperature evolution of the
crystal structure reveals some insights into the mechanism leading to the
decomposition of the Al$_{1.75}$Ti$_{1.25}$O$_5$ above 725$^\circ$C. The
magnetic and electrical properties are discussed and compared to other reported
aluminum titanate pseudobrookites.",2211.17252v2
2022-12-14,Study of the V$_2^0$ state in neutron-irradiated silicon using photon-absorption measurements,"Pieces of $n$-type silicon with 3.5 k$\Omega \cdot $cm resistivity have been
irradiated by reactor neutrons to fluences of (1, 5 and 10) $\times 10^{16}$
cm$^{-2}$. Using light-transmission measurements, the absorption coefficients
have been determined for photon energies, $E_\gamma $, between 0.62 and 1.30 eV
for the samples as irradiated and after 15 min isochronal annealing with
temperatures between 80{\deg}C and 330{\deg}C. The radiation-induced absorption
coefficient, $\alpha_\mathit{irr}$, has been obtained by subtracting the
absorption coefficient for non-irradiated silicon. The $E_\gamma $-dependence
of $\alpha_\mathit{irr}$ shows a resonance peak, which is ascribed to the
neutral divacancy, V$_2^0$, sitting on a background, and $\alpha_\mathit{irr}
(E_\gamma )$ is fitted by a Breit-Wigner line shape on a parameterized
background. It is found that at an annealing temperature of 210{\deg}C the
V$_2^0$ intensity is reduced by a factor 2, and that at the meV level, the
position and the width of the fitted Breit-Wigner do not change with
irradiation dose and annealing.",2212.07320v2
2023-01-18,Schramm-Loewner evolution in 2d rigidity percolation,"Amorphous solids may resist external deformation such as shear or compression
while they do not present any long-range translational order or symmetry at the
microscopic scale. Yet, it was recently discovered that, when they become
rigid, such materials acquire a high degree of symmetry hidden in the disorder
fluctuations: their microstructure becomes statistically conformally invariant.
In this Letter we exploit this finding to characterise the universality class
of central-force rigidity percolation (RP), using Schramm-Loewner Evolution
(SLE) theory. We provide numerical evidences that the interfaces of the
mechanically stable structures (rigid clusters), at the rigidification
transition, are consistently described by SLE$_\kappa$, showing that this
powerful framework can be applied to a mechanical percolation transition. Using
well-known relations between different SLE observables and the universal
diffusion constant $\kappa$, we obtain the estimation $\kappa\sim2.9$ for
central-force RP. This value is consistent, through relations coming from
conformal field theory, with previously measured values for the clusters'
fractal dimension $D_f$ and correlation length exponent $\nu$, providing new,
non-trivial relations between critical exponents for RP. These findings open
the way to a fine understanding of the microstructure in other important
classes of rigidity and jamming transitions.",2301.07614v2
2023-01-26,3D-imaging of Printed Nanostructured Networks using High-resolution FIB-SEM Nanotomography,"Networks of solution-processed nanomaterials are important for multiple
applications in electronics, sensing and energy storage/generation. While it is
known that network morphology plays a dominant role in determining the physical
properties of printed networks, it remains difficult to quantify network
structure. Here, we utilise FIB-SEM nanotomography to characterise the
morphology of nanostructured networks. Nanometer-resolution 3D-images were
obtained from printed networks of graphene nanosheets of various sizes, as well
as networks of WS2 nanosheets, silver nanosheets and silver nanowires.
Important morphological characteristics, including network porosity,
tortuosity, pore dimensions and nanosheet orientation were extracted and linked
to network resistivity. By extending this technique to interrogate the
structure and interfaces within vertical printed heterostacks, we demonstrate
the potential of this technique for device characterisation and optimisation.",2301.11046v1
2023-03-08,Optical rogue waves in spheroids of tumor cells,"Rogue waves are intense and unexpected wavepackets ubiquitous in complex
systems. In optics, they are promising as robust and noise-resistant beams for
probing and manipulating the underlying material. Localizing large optical
power is crucial especially in biomedical systems, where, however, extremely
intense beams have not yet been observed. We here discover that tumor-cell
spheroids manifest optical rogue waves when illuminated by randomly modulated
laser beams. The intensity of light transmitted through bio-printed
three-dimensional tumor models follows a signature Weibull statistical
distribution, where extreme events correspond to spatially-localized optical
modes propagating within the cell network. Experiments varying the input beam
power and size indicate the rogue waves have a nonlinear origin. We show these
optical filaments form high-transmission channels with enhanced transmission.
They deliver large optical power through the tumor spheroid, which can be
exploited to achieve a local temperature increase controlled by the input wave
shape. Our findings shed new light on optical propagation in biological
aggregates and demonstrate how extreme event formation allows light
concentration in deep tissues, paving the way to using rogue waves in
biomedical applications such as light-activated therapies.",2303.04553v1
2023-04-28,Experimental observation of metallic states with different dimensionality in a quasi-1D charge density wave compound,"TaTe$_4$ is a quasi-1D tetrachalcogenide that exhibits a CDW instability
caused by a periodic lattice distortion. Recently, pressure-induced
superconductivity has been achieved in this compound, revealing a competition
between these different ground states and making TaTe$_4$ very interesting for
fundamental studies. Although TaTe$_4$ exhibits CDW ordering below 475 K,
transport experiments have reported metallic behavior with a resistivity
plateau at temperatures lower than 10 K. In this paper, we study the electronic
structure of TaTe$_4$ using a combination of high-resolution angle-resolved
photoemission spectroscopy and density functional calculations. Our results
reveal the existence of the long-sought metallic states. These states exhibit
mixed dimensionality, while some of them might have potential topological
properties.",2305.00053v1
2023-05-15,Magnetic order and electronic transport properties in the Mn$_3$Al compound: the role of the structural state,"Electronic transport and magnetic properties of bulk and rapid melt quenched
samples of the Mn$_3$Al Heusler alloy were studied. A correlation between the
magnetic and structural states was established. For a cast sample, there is no
ferromagnetic moment, and the behavior of the magnetic susceptibility (break at
low temperatures and the Curie-Weiss law with high values of the paramagnetic
Curie temperature) indicates a frustrated antiferromagnetic state. At the same
time, for a rapid melt quenched sample, a ferrimagnetic state is observed with
a moment close to compensation. The results of measurements of the electrical
resistivity and the Hall effect evidence as well in favor of the implementation
of these magnetic states.",2305.08646v1
2023-06-01,Native defect association in beta-Ga2O3 enables room-temperature p-type conductivity,"The room temperature hole conductivity of the ultra wide bandgap
semiconductor beta Ga2O3 is a pre-requisite for developing the next-generation
electronic and optoelectronic devices based on this oxide. In this work,
high-quality p-type beta-Ga2O3 thin films grown on r-plane sapphire substrate
by metalorganic chemical vapor deposition (MOCVD) exhibit Rho = 50000Ohm.cm
resistivity at room temperature. A low activation energy of conductivity as
Ea2=170 meV was determined, associated to the oxygen - gallium native acceptor
defect complex. Further, taking advantage of cation (Zn) doping, the
conductivity of Ga2O3:Zn film was remarkably increased by three orders of
magnitude, showing a long-time stable room-temperature hole conductivity with
the conductivity activation energy of around 86 meV.",2306.01115v1
2023-06-07,Phase formation in hole- and electron-doped rare-earth nickelate single crystals,"The recent discovery of superconductivity in hole-doped infinite-layer
nickelates has triggered a great interest in the synthesis of novel nickelate
phases, which have primarily been examined in thin film samples. Here, we
report the high-pressure optical floating zone (OFZ) growth of various
perovskite and perovskite-derived rare-earth nickelate single-crystals, and
investigate the effects of hole-, electron-, and self-doping. For hole-doping
with Ca and Sr, we observe phase separations during the growth process when a
substitution level of 8% is exceeded. A similar trend emerges for
electron-doping with Ce and Zr. Employing lower doping levels allows us to grow
sizeable crystals in the perovskite phase, which exhibit significantly
different electronic and magnetic properties than the undoped parent compounds,
such as a decreased resistivity and a suppressed magnetic response. Our
insights into the doping-dependent phase formation and the resulting properties
of the synthesized crystals reveal limitations and opportunities for the
exploration and manipulation of electronic states in rare-earth nickelates.",2306.04157v1
2023-07-21,Superexchange Interaction in Insulating EuZn$_{2}$P$_{2}$,"We report magnetic and transport properties of single-crystalline
EuZn$_{2}$P$_{2}$, which has trigonal CaAl$_2$Si$_2$-type crystal structure and
orders antiferromagnetically at $\approx$23~K. Easy $ab$-plane
magneto-crystalline anisotropy was confirmed from the magnetization isotherms,
measured with a magnetic field applied along different crystallographic
directions ($ab$-plane and $c$-axis). Positive Curie-Weiss temperature
indicates dominating ferromagnetic correlations. Electrical resistivity
displays insulating behavior with a band-gap of $\approx\,$0.177~eV, which
decreases to $\approx\,$0.13~eV upon application of a high magnetic field. We
explained the intriguing presence of magnetic interactions in an intermetallic
insulator by the mechanism of extended superexchange, with phosphorus as an
anion mediator, which is further supported by our analysis of the charge and
spin density distributions. We constructed the effective Heisenberg model, with
exchange parameters derived from the \textit{ab initio} DFT calculations, and
employed it in Monte-Carlo simulations, which correctly reproduced the
experimental value of N\'eel temperature.",2307.11924v1
2023-08-04,Learning to Shape by Grinding: Cutting-surface-aware Model-based Reinforcement Learning,"Object shaping by grinding is a crucial industrial process in which a
rotating grinding belt removes material. Object-shape transition models are
essential to achieving automation by robots; however, learning such a complex
model that depends on process conditions is challenging because it requires a
significant amount of data, and the irreversible nature of the removal process
makes data collection expensive. This paper proposes a cutting-surface-aware
Model-Based Reinforcement Learning (MBRL) method for robotic grinding. Our
method employs a cutting-surface-aware model as the object's shape transition
model, which in turn is composed of a geometric cutting model and a
cutting-surface-deviation model, based on the assumption that the robot action
can specify the cutting surface made by the tool. Furthermore, according to the
grinding resistance theory, the cutting-surface-deviation model does not
require raw shape information, making the model's dimensions smaller and easier
to learn than a naive shape transition model directly mapping the shapes.
Through evaluation and comparison by simulation and real robot experiments, we
confirm that our MBRL method can achieve high data efficiency for learning
object shaping by grinding and also provide generalization capability for
initial and target shapes that differ from the training data.",2308.02150v1
2023-08-16,Growth of millimeter-sized high-quality CuFeSe$_2$ single crystals by the molten salt method and study of their semiconducting behavior,"An eutectic AlCl$_3$/KCl molten salt method in a horizontal configuration was
employed to grow millimeter-sized and composition homogeneous CuFeSe$_2$ single
crystals due to the continuous growth process in a temperature gradient induced
solution convection. The typical as-grown CuFeSe$_2$ single crystals in cubic
forms are nearly 1.6$\times$1.2$\times$1.0 mm3 in size. The chemical
composition and homogeneity of the crystals was examined by both inductively
coupled plasma atomic emission spectroscopy and energy dispersive spectrometer
with Cu:Fe:Se = 0.96:1.00:1.99 consistent with the stoichiometric composition
of CuFeSe$_2$. The magnetic measurements suggest a ferrimagnetic or weak
ferromagnetic transition below T$_C$ = 146 K and the resistivity reveals a
semiconducting behavior and an abrupt increase below T$_C$.",2308.08223v1
2023-08-25,WSTac: Interactive Surface Perception based on Whisker-Inspired and Self-Illuminated Vision-Based Tactile Sensor,"Modern Visual-Based Tactile Sensors (VBTSs) use cost-effective cameras to
track elastomer deformation, but struggle with ambient light interference.
Solutions typically involve using internal LEDs and blocking external light,
thus adding complexity. Creating a VBTS resistant to ambient light with just a
camera and an elastomer remains a challenge. In this work, we introduce WStac,
a self-illuminating VBTS comprising a mechanoluminescence (ML) whisker
elastomer, camera, and 3D printed parts. The ML whisker elastomer, inspired by
the touch sensitivity of vibrissae, offers both light isolation and high ML
intensity under stress, thereby removing the necessity for additional LED
modules. With the incorporation of machine learning, the sensor effectively
utilizes the dynamic contact variations of 25 whiskers to successfully perform
tasks like speed regression, directional identification, and texture
classification. Videos are available at: https://sites.google.com/view/wstac/.",2308.13241v1
2023-09-03,Validation of the Wiedemann-Franz Law in solid and molten tungsten above 2000 K through thermal conductivity measurements via steady state temperature differential radiometry,"We measure the thermal conductivity of solid and molten tungsten using Steady
State Temperature Differential Radiometry. We demonstrate that the thermal
conductivity can be well described by application of Wiedemann-Franz Law to
electrical resistivity data, thus suggesting the validity of Wiedemann-Franz
Law to capture the electronic thermal conductivity of metals in their molten
phase. We further support this conclusion using ab initio molecular dynamics
simulations with a machine-learned potential. Our results show that at these
high temperatures, the vibrational contribution to thermal conductivity is
negligible compared to the electronic component.",2309.01062v1
2023-10-05,Demonstration of a monocrystalline GaAs-$β$-Ga$_2$O$_3$ p-n heterojunction,"In this work, we report the fabrication and characterizations of a
monocrystalline GaAs/$\beta$-Ga$_2$O$_3$ p-n heterojunction by employing
semiconductor grafting technology. The heterojunction was created by lifting
off and transfer printing a p-type GaAs single crystal nanomembrane to an
Al$_2$O$_3$-coated n-type$\beta$-Ga$_2$O$_3$ epitaxial substrate. The resultant
heterojunction diodes exhibit remarkable performance metrics, including an
ideality factor of 1.23, a high rectification ratio of 8.04E9 at +/- 4V, and a
turn on voltage of 2.35 V. Furthermore, at +5 V, the diode displays a large
current density of 2500 A/cm$^2$ along with a low ON resistance of 2
m$\Omega\cdot$cm$^2$.",2310.03886v1
2023-11-03,Effects of Cr content on ion-irradiation hardening of FeCrAl ODS ferritic steels with 9 wt\% Al,"FeCrAl ODS steels for accident tolerant fuel claddings are designed to bear
high-Cr and Al for enhancing oxidation resistance. In this study, we
investigated the effects of Cr content on ion-irradiation hardening of three
ODS ferritic steels with different Cr contents added with 9 wt\% Al, Fe12Cr9Al
(SP12), Fe15Cr9Al (SP13), and Fe18Cr9Al (SP14). The specimens were irradiated
with 6.4MeV Fe\textsuperscript{3+} at 300 \textdegree C to nominal 3 dpa. The
irradiation hardening was measured by nanoindentation method, and the Nix-Gao
plots were used to evaluate the bulk-equivalent hardness. The results showed
that the irradiation hardening decreased with increasing Cr content. The reason
is due to the growth of dislocation loops hindered by solute Cr atoms. TEM
observations showed both $\langle 100\rangle$ and $1/2\langle 111\rangle$
dislocation loops existed in the irradiated area. The irradiation hardening was
estimated by dispersed barrier hardening (DBH) model with dislocation loops.",2311.01879v1
2023-11-11,Evidence of Ordering in Cu-Ni Alloys from Experimental Electronic Entropy Measurements,"Phase diagrams exhibiting extended solid-solution and lens-like melting are
often reproduced using ideal solutions, where ideal mixing considers a fully
random configurational entropy of mixing. In the field of irreversible
thermodynamics, experimental measurements of the composition variation of
high-temperature electronic transport and molten-state properties suggest
however a strong role for short-range atomic ordering in these systems. Herein,
measurements of the thermopower and resistivity are reported for Cu-Ni
solid-solutions as a function of temperature and composition. The electronic
transport properties were interpreted with an irreversible thermodynamic
framework, revealing a large electronic contribution to the entropy of mixing.
Through appeal to a cluster model for the configurational entropy that uses the
electronic contribution to inform the existence of ordered associates, we
rationalize such contribution of the electronic entropy with the notion of an
ideal entropy of mixing commonly used to model such systems. These results
suggest that the short range order (S.R.O.) of the atoms plays a significant
role in both the solid and molten states, even when there are no dominant
intermetallic compounds in these alloys.",2311.06603v2
2023-11-12,First-principles pressure dependent investigation of the physical properties of KB2H8: a prospective high-TC superconductor,"Using the density functional theory (DFT) based first-principles
investigation, the structural, mechanical, hardness, elastic anisotropy,
optoelectronic, and thermal properties of cubic KB2H8 have been studied within
the uniform pressure range of 0 - 24 GPa. The calculated structural parameters
are in good agreement with the previous theoretical work. The compound KB2H8 is
found to be structurally and thermodynamically stable in the pressure range
from 8 GPa to 24 GPa. Single crystal elastic constants Cij and bulk elastic
moduli (B, G and Y) increase systematically with pressure from 8 GPa to 24 GPa.
In the stable phase, KB2H8 is moderately elastically anisotropic and ductile in
nature. The compound is highly machinable and fracture resistant. The Debye
temperature, melting temperature and thermal conductivity increases with
pressure. The results of electronic band structure calculations and optical
parameters at different pressures are consistent with each other. The compound
is optically isotropic. The compound KB2H8 has potential to be used as a very
efficient solar energy reflector. The electronic energy density of states at
the Fermi level decreases systematically with increasing pressure. The same
trend is found for the repulsive Coulomb pseudopotential. Possible relevance of
the studied properties to superconductivity has also been discussed in this
paper.",2311.06709v1
2023-12-08,Gate-controlled neuromorphic functional transition in an electrochemical graphene transistor,"Neuromorphic devices have gained significant attention as potential building
blocks for the next generation of computing technologies owing to their ability
to emulate the functionalities of biological nervous systems. The essential
components in artificial neural network such as synapses and neurons are
predominantly implemented by dedicated devices with specific functionalities.
In this work, we present a gate-controlled transition of neuromorphic functions
between artificial neurons and synapses in monolayer graphene transistors that
can be employed as memtransistors or synaptic transistors as required. By
harnessing the reliability of reversible electrochemical reactions between C
atoms and hydrogen ions, the electric conductivity of graphene transistors can
be effectively manipulated, resulting in high on/off resistance ratio,
well-defined set/reset voltage, and prolonged retention time. Overall, the
on-demand switching of neuromorphic functions in a single graphene transistor
provides a promising opportunity to develop adaptive neural networks for the
upcoming era of artificial intelligence and machine learning.",2312.04934v2
2023-12-20,Collective dynamics and long-range order in thermal neuristor networks,"In the pursuit of scalable and energy-efficient neuromorphic devices, recent
research has unveiled a novel category of spiking oscillators, termed ""thermal
neuristors"". These devices function via thermal interactions among neighboring
vanadium dioxide resistive memories, emulating biological neuronal behavior.
Here, we show that the collective dynamical behavior of networks of these
neurons showcases a rich phase structure, tunable by adjusting the thermal
coupling and input voltage. Notably, we identify phases exhibiting long-range
order that, however, does not arise from criticality, but rather from the time
non-local response of the system. In addition, we show that these thermal
neuristor arrays achieve high accuracy in image recognition and time series
prediction through reservoir computing, without leveraging long-range order.
Our findings highlight a crucial aspect of neuromorphic computing with possible
implications on the functioning of the brain: criticality may not be necessary
for the efficient performance of neuromorphic systems in certain computational
tasks.",2312.12899v2
2024-01-30,Momentum Matching for 2D-3D Heterogeneous Ohmic van der Waals Contact,"Construction of ohmic contact is a long-standing challenge encountered by
two-dimensional (2D) device fabrication and integration. van der Waals
contacts, as a new solution for 2D contact construction, can effectively
eliminate issues, such as Fermi-level pining and formation of Schottky barrier.
Nevertheless, current research primarily considers energy band alignment, while
ignoring the transverse momentum conservation of charge carriers during the
quantum tunneling across the van der Waals contacts. In this study, by
comparing the IV characteristics and tunneling spectra of graphene-silicon
tunneling junctions with various interfacial transverse momentum distribution,
we demonstrate the importance of charge carrier momentum in constructing
high-performance 2D contact. Further, by conditioning the van der Waals
contacts and minimizing the momentum mismatch, we successfully enhanced the
quantum tunneling current with more than three orders of magnitude and obtain
ohmic-like contact. Our study provide and effective method for the construction
of direction 2D-3D contact with low resistance and can potentially benefit the
heterogeneous of integration of 2D materials in post-CMOS architectures.",2401.17114v1
2024-02-11,Langmuir-like model of dilute impurities in concentrated solid solutions,"High-entropy alloys have drawn recent interest for their promising mechanical
properties and irradiation resistance. Various properties, namely transport
properties, are controlled by point defect concentration, which must be known
before performing atomistic simulations to compute transport coefficients. In
this work, we present a general Langmuir-like model for impurity concentration
in an arbitrarily complex solid solution and apply this model to generate
expressions for concentrations of vacancies and small interstitial atoms. We
then calculate the vacancy concentration as a function of temperature in the
equiatomic CoNiCrFeMn and FeAl alloys with modified embedded-atom-method
potentials for various chemical orderings, showing there is no clear
correlation between vacancy thermodynamics and chemical ordering in the
CoNiCrFeMn alloy but clear systematic patterns for FeAl.",2402.07324v1
2024-02-28,Strange metal in the doped Hubbard model via percolation,"Many strongly correlated systems, including high-temperature superconductors
such as the cuprates, exhibit strange metallic behavior in certain parameter
regimes characterized by anomalous transport properties that are irreconcilable
with a Fermi-liquid-like description in terms of quasiparticles. The Hubbard
model is a standard theoretical starting point to examine the properties of
such systems and also exhibits non-Fermi-liquid behavior in simulations. Here
we analytically study the two-dimensional hole-doped Hubbard model, first
identifying a percolation transition that occurs in the low-energy sector at
critical hole doping $p_c\sim 0.19$. We then use the critical properties near
this transition to rewrite the Hubbard Hamiltonian in a way that motivates a
large-$N$ model with strange metallic properties. In particular, we show that
this model has the linear-in-$T$ resistivity and power-law optical conductivity
$\sim |\omega|^{-2/3}$ observed in the strange metal regime of cuprates,
suggesting potential relevance for describing this important class of
materials.",2402.18626v2
2024-03-25,Facile synthesis of micro-flower NiCo2O4 assembled by nanosheets efficient for electrocatalysis of water,"Effective regulation of the morphology of transition metal spinel structures
is crucial for creating efficient and stable bifunctional catalysts for
electrocatalysis of water. In this work, micro-flower NiCo2O4 (F-NCO) assembled
by nanosheets via a chemical template method for the simultaneous promotion of
hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).
Electronic microscope analysis revealed that the thickness of the F-NCO
catalyst was only 2.7% of that of the NiCo2O4 bulk (B-NCO), and this ultrathin
lamellar structure was conducive to further exposure of the active site and
improved reaction kinetics. The F-NCO catalyst exhibited superior HER and OER
performance (10 = 236 and 310 mV) and robust long-term stability over the B-NCO
catalyst in 1.0 M KOH, with a 2.68-fold and 4.16-fold increase in active
surface area and a 0.42-fold and 0.61-fold decrease in charge transfer
resistance values, respectively. This micro-flower-structured electrode has
remarkable electrocatalytic property and long-term durability, providing a
novel insight for characterizing cost-effective and high-performance
bifunctional electrocatalysts.",2403.17744v1
2024-04-30,Aluminum nuclear demagnetization refrigerator for powerful continuous cooling,"Many laboratories routinely cool samples to 10 mK, but relatively few can
cool condensed matter below 1 mK. Easy access to the microkelvin range would
propel fields such as quantum sensors and quantum materials. Such temperatures
are achieved with adiabatic nuclear demagnetization. Existing nuclear
demagnetization refrigerators (NDR) are ""single-shot"", and the recycling time
is incompatible with proposed sub-mK experiments. Furthermore, a high cooling
power is required to overcome the excess heat load of order nW on NDR
pre-cooled by cryogen-free dilution refrigerators. We report the performance of
an aluminum NDR designed for powerful cooling when part of a dual stage
continuous NDR (CNDR). Its thermal resistance is minimized to maximize the
cycling rate of the CNDR and consequently its cooling power. At the same time,
its susceptibility to eddy current heating is minimized. A CNDR based on two of
the aluminum NDR presented here would have a cooling power of approximately 40
nW at 560 $\mu$K.",2404.19352v1
2024-05-10,Effects of vortex and anti-vortex excitations in underdoped Bi-2223 bulk single crystals,"To gain insights into mechanisms underlying superconducting transition in
copper oxide high-transition temperature ($T_c$) superconductors, we studied
transport properties of underdoped Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$
(Bi-2223) bulk single crystals. The power exponent $\alpha$ ($V \propto
I^{\alpha}$) reached 3 just below $T_c$, and the temperature dependence of
in-plane resistivity ($\rho_{ab}$) exhibited typical tailing behavior,
consistent with Kosterlitz--Thouless transition characteristics. Thus, with
increasing temperature, copper oxide high-$T_c$ superconductors undergo
transition to the normal state because of destruction of its phase
correlations, although a finite Cooper pair density exists at $T_c$.",2405.06272v1
2024-05-15,Unraveling impacts of polycrystalline microstructures on ionic conductivity of ceramic electrolytes by computational homogenization and machine learning,"The ionic conductivity at the grain boundaries (GBs) in oxide ceramics is
typically several orders of magnitude lower than that within the grain
interior. This detrimental GB effect is the main bottleneck for designing
high-performance ceramic electrolytes intended for use in solid-state
Lithium-ion batteries, fuel cells, and electrolyzer cells. The macroscopic
ionic conductivity in oxide ceramics is essentially governed by the underlying
polycrystalline microstructures where GBs and grain morphology go hand in hand.
This provides the possibility to enhance the ion conductivity by microstructure
engineering. To this end, a thorough understanding of microstructure-property
correlation is highly desirable. In this work, we investigate numerous
polycrystalline microstructure samples with varying grain and grain boundary
features. Their macroscopic ionic conductivities are numerically evaluated by
the finite element homogenization method, whereby the GB resistance is
explicitly regarded. The influence of different microstructural features on the
effective ionic conductivity is systematically studied. The
microstructure-property relationships are revealed. Additionally, a graph
neural network-based machine learning model is constructed and trained. It can
accurately predict the effective ionic conductivity for a given polycrystalline
microstructure. This work provides crucial quantitative guidelines for
optimizing the ionic conducting performance of oxide ceramics by tailoring
microstructures.",2405.09227v1
2024-05-20,High-Mobility Carriers in Epitaxial IrO2 Films Grown using Hybrid Molecular Beam Epitaxy,"Binary rutile oxides of 5d metals such as IrO2, stand out as a paradox due to
limited experimental studies despite the rich predicted quantum phenomena.
Here, we investigate the electrical transport properties of IrO2 by engineering
epitaxial thin films grown via hybrid molecular beam epitaxy. Our findings
reveal phonon-limited carrier transport and thickness-dependent anisotropic
in-plane resistance in IrO2 (110) films, the latter suggesting a complex
relationship between strain relaxation and orbital hybridization.
Magneto-transport measurements reveal a previously unobserved non-linear Hall
effect. A two-carrier analysis of this effect shows the presence of minority
carriers with mobility exceeding 3000 cm2/Vs at 1.8 K. These results point
towards emergent properties in 5d metal oxides that can be controlled using
dimensionality and epitaxial strain.",2405.11716v1
2024-05-21,A single crystal study of Kagome metals U$_2$Mn$_3$Ge and U$_2$Fe$_3$Ge,"Single crystals of U$_2$Mn$_3$Ge and and U$_2$Fe$_3$Ge with a Kagome lattice
structure were synthesized using a high-temperature self-flux crystal growth
method. The physical properties of these crystals were characterized through
measurements of resistivity, magnetism, and specific heat. U$_2$Fe$_3$Ge
exhibits ferromagnetic ground state and Anomalous Hall Effect, and
U$_2$Mn$_3$Ge demonstrates a complex magnetic structure. Both compounds exhibit
large Sommerfeld coefficient, indicating coexistence of heavy Fermion behavior
with magnetism. Our results suggest that this U$_2$TM$_3$Ge (TM = Mn, Fe, Co)
family is a promising platform to investigate the interplay of magnetism, Kondo
physics and the Kagome lattice.",2405.12905v1
2007-07-30,Control of the Casimir force by the modification of dielectric properties with light,"The experimental demonstration of the modification of the Casimir force
between a gold coated sphere and a single-crystal Si membrane by light pulses
is performed. The specially designed and fabricated Si membrane was irradiated
with 514 nm laser pulses of 5 ms width in high vacuum leading to a change of
the charge-carrier density. The difference in the Casimir force in the presence
and in the absence of laser radiation was measured by means of an atomic force
microscope as a function of separation at different powers of the absorbed
light. The total experimental error of the measured force differences at a
separation of 100 nm varies from 10 to 20% in different measurements. The
experimental results are compared with theoretical computations using the
Lifshitz theory at both zero and laboratory temperatures. The total theoretical
error determined mostly by the uncertainty in the concentration of charge
carriers when the light is incident is found to be about 14% at separations
less than 140 nm. The experimental data are consistent with the Lifshitz theory
at laboratory temperature, if the static dielectric permittivity of
high-resistivity Si in the absence of light is assumed to be finite. If the dc
conductivity of high-resistivity Si in the absence of light is included into
the model of dielectric response, the Lifshitz theory at nonzero temperature is
shown to be experimentally inconsistent at 95% confidence. The demonstrated
phenomenon of the modification of the Casimir force through a change of the
charge-carrier density is topical for applications of the Lifshitz theory to
real materials in fields ranging from nanotechnology and condensed matter
physics to the theory of fundamental interactions.",0707.4390v1
2014-09-03,The influence of the Al stabilizer layer thickness on the normal zone propagation velocity in high current superconductors,"The stability of high-current superconductors is challenging in the design of
superconducting magnets. When the stability requirements are fulfilled, the
protection against a quench must still be considered. A main factor in the
design of quench protection systems is the resistance growth rate in the magnet
following a quench. The usual method for determining the resistance growth in
impregnated coils is to calculate the longitudinal velocity with which the
normal zone propagates in the conductor along the coil windings.
  Here, we present a 2D numerical model for predicting the normal zone
propagation velocity in Al stabilized Rutherford NbTi cables with large cross
section. By solving two coupled differential equations under adiabatic
conditions, the model takes into account the thermal diffusion and the current
redistribution process following a quench. Both the temperature and magnetic
field dependencies of the superconductor and the metal cladding materials
properties are included. Unlike common normal zone propagation analyses, we
study the influence of the thickness of the cladding on the propagation
velocity for varying operating current and magnetic field.
  To assist in the comprehension of the numerical results, we also introduce an
analytical formula for the longitudinal normal zone propagation. The analysis
distinguishes between low-current and high-current regimes of normal zone
propagation, depending on the ratio between the characteristic times of thermal
and magnetic diffusion. We show that above a certain thickness, the cladding
acts as a heat sink with a limited contribution to the acceleration of the
propagation velocity with respect to the cladding geometry. Both numerical and
analytical results show good agreement with experimental data.",1409.1186v1
2020-01-10,A barrier/seed system for electroless metallization on complex surfaces using (aminomethylaminoethyl)phenethyltrimethoxysilane self-assembled films,"High frequency signals propagate along the edges of conductors. If the
conductors are electroplated, then the seed layer forms at least one edge, so
care must be taken to insure the electrical quality of these layers. In this
work, we study the initial quality of SAM-based seed layers that are compatible
with complex surfaces including through-silicon vias (TSVs), as are used in
via-last three-dimensional semiconductor device packaging. The conformal and
electrical quality of the seed metal is very important. Also important for a
multifunction seed layer is its ability as a barrier layer, which protects the
substrate from high temperature diffusion of the deposited metal. Thus, the
barrier layer must be robust enough to withstand diffusion, yet thin enough to
provide a conformal surface that allows metal seed layer deposition. Standard
barrier layer deposition methods such as evaporation or sputtering require
either a line of sight from the source or aspect ratios large enough to provide
scattering from the background gas within the structure to coat all surfaces.
Electrochemical and chemical vapor deposition provide alternatives, but
concerns arise about contamination and compatibility with radio frequency or
high-speed digital signals. We propose a barrier layer based on an aromatic
self-assembled monolayer (SAM) for use in electroless copper seed layer
deposition. The viability of the SAM barrier layer is determined by the quality
of the deposited copper seed film, judged quantitatively by thin film
resistivity and qualitatively by surface adhesion and morphological properties
such as cracks and bubbles. Insights to the origins of problems and an optimal
scheme are described. Extensions for use as a photolithographic resist layer
are suggested. Our SAM approach for TSV applications yields a 'smart' seed
layer that can be used with a 'simple,' scalloped, easy to fabricate, via hole.",2001.03295v1
2022-04-04,Exceptional fracture toughness of CrCoNi-based medium- and high-entropy alloys close to liquid helium temperatures,"Medium- and high-entropy alloys based on the CrCoNi-system have been shown to
display outstanding strength, tensile ductility and fracture toughness
(damage-tolerance properties), especially at cryogenic temperatures. Here we
examine the JIc and (back-calculated) KJIc fracture toughness values of the
face-centered cubic, equiatomic CrCoNi and CrMnFeCoNi alloys at 20 K. At flow
stress values of ~1.5 GPa, crack-initiation KJIc toughnesses were found to be
exceptionally high, respectively 235 and 415 MPa(square-root)m for CrMnFeCoNi
and CrCoNi, with the latter displaying a crack-growth toughness Kss exceeding
540 MPa(square-root)m after 2.25 mm of stable cracking, which to our knowledge
is the highest such value ever reported. Characterization of the crack-tip
regions in CrCoNi by scanning electron and transmission electron microscopy
reveal deformation structures at 20 K that are quite distinct from those at
higher temperatures and involve heterogeneous nucleation, but restricted
growth, of stacking faults and fine nano-twins, together with transformation to
the hexagonal closed-packed phase. The coherent interfaces of these features
can promote both the arrest and transmission of dislocations to generate
respectively strength and ductility which strongly contributes to sustained
strain hardening. Indeed, we believe that these nominally single-phase,
concentrated solid-solution alloys develop their fracture resistance through a
progressive synergy of deformation mechanisms, including dislocation glide,
stacking-fault formation, nano-twinning and eventually in situ phase
transformation, all of which serve to extend continuous strain hardening which
simultaneously elevates strength and ductility (by delaying plastic
instability), leading to truly exceptional resistance to fracture.",2204.01635v1
2023-10-16,Electronic Transport and Fermi Surface Topology of Zintl phase Dirac Semimetal SrZn2Ge2,"We report a comprehensive study on the electronic transport properties of
SrZn$_2$Ge$_2$ single crystals. The in-plane electrical resistivity of the
compound exhibits linear temperature dependence for 80 K < T < 300 K, and T^2
dependence below 40 K, consistent with the Fermi liquid behavior. Both the
transverse and longitudinal magnetoresistance exhibit a crossover at critical
field B* from weak-field quadratic-like to high-field unsaturated linear field
dependence at low temperatures (T \leq 50 K). Possible sources of linear
magnetoresistance are discussed based on the Fermi surface topology, classical
and quantum transport models. The Hall resistivity data establish
SrZn$_2$Ge$_2$ as a multiband system with contributions from both the electrons
and holes. The Hall coefficient is observed to decrease with increasing
temperature and magnetic field, changing its sign from positive to negative.
The negative Hall coefficient observed at low temperatures in high fields and
at high temperatures over the entire field range suggests that the highly
mobile electron charge carriers dominate the electronic transport. Our
first-principles calculations show that nontrivial topological surface states
exist in SrZn$_2$Ge$_2$ within the bulk gap along the {\Gamma}-M path. Notably,
these surface states extend from the valence to conduction band with their
number varying based on the Sr and Ge termination plane. The Fermi surface of
the compound exhibits a distinct tetragonal petal-like structure, with one open
and several closed surfaces. Overall, these findings offer crucial insights
into the mechanisms underlying the electronic transport of the compound.",2310.10621v2
2023-06-24,High Strength Refractory AlHfNbTiV B2 High Entropy Alloys with High Fracture Strains,"We demonstrate the development of a series of refractory high-entropy alloys
containing aluminum AlRHEAs in the ordered BCC-B2 phase by varying the aluminum
content within 10 to 25 atomic percent, with the goal of high strength and good
ductility synergy. The AlRHEAs obtained are found to show promising potential
for high-temperature applications. The incorporation of Al lowers the density
and promotes the long-range atomic ordering, which in turn stabilizes the B2
formation, and strengthens the material but usually deteriorates ductility.
Several B2 AlRHEAs that contain a combination of Ti, Hf, Nb, and V with
moderate to high Poisson ratios are investigated for high strength and
ductility. Furthermore, through statistical analysis, we identify a valley
around the valence electron concentration VEC of 6 where low ductility is
prominently observed. Machine-learning models are employed to screen the vast
compositional space of AlRHEA alloys to predict B2 formation and toughness
indicated by the yield strength and fracture strain. High prediction accuracies
are achieved. As the Al content decreases, the B2 atomic ordering decreases,
compression yield strengths decrease from 1500 MPa to 1200 MPa, and compression
fracture strains increase from 0.06 to over 0.5. Notably, Al10Hf20Nb22Ti33V15
retains a compression yield strength exceeding 800 MPa up to 700 C, tensile
yield strength of 1100 MPa, and fracture strain of 0.083. Our findings on
enhancing ductility in pure B2 alloys pave the way for further research on
Al-RHEA superalloys, striving to achieve high strength and ductility, reduced
density, and improved oxidation resistance.",2306.14057v2
1998-04-04,Ohmic Decay of Magnetic Fields due to non-spherical accretion in the Crusts of Neutron Stars,"We consider magnetic field evolution of neutron stars during polar-cap
accretion. The size of the polar cap increases as the field decays, and is set
by the last open field line before the accretion disk. Below the polar cap we
find the temperature to be so high that electron-phonon scattering dominates
the resistivity. Outside the polar cap region, the temperature is such the
resistivity is dominated by temperature independent impurity scattering which
can be a few orders of magnitude larger than the electron- phonon resistivity.
The time-scale for field decay is therefore initially given by impurity
scattering dominated resistivity. When the field strength has been reduced to
$\sim 10^8 gauss$ the accretion is spherical and the time scale for field decay
is given by the smaller electron-phonon scattering resistivity. The field
strength is now reduced rapidly compared to before and this could be a reason
for there being no pulsars known with field strengths below $10^8 gauss$. We
also investigate the evolution of multipoles at the neutron star surface. We
find that contribution from higher-order multipoles are at most 30% to that of
the dipole mode.",9804047v1
2000-01-10,The Effect of Resistivity on the Nonlinear Stage of the Magnetorotational Instability in Accretion Disks,"We present three-dimensional magnetohydrodynamic simulations of the nonlinear
evolution of the magnetorotational instability (MRI) with a non-zero Ohmic
resistivity. The properties of the saturated state depend on the initial
magnetic field configuration. In simulations with an initial uniform vertical
field, the MRI is able to support angular momentum transport even for large
resistivities through the quasi-periodic generation of axisymmetric radial
channel solutions rather than through the maintenance of anisotropic
turbulence. Simulations with zero net flux show that the angular momentum
transport and the amplitude of magnetic energy after saturation are
significantly reduced by finite resistivity, even at levels where the linear
modes are only slightly affected. This occurs at magnetic Reynolds numbers
expected in low, cool states of dwarf novae, these results suggest that finite
resistivity may account for the low and high angular momentum transport rates
inferred for these systems.",0001164v1
1998-10-15,The Quantized Hall Insulator: A New Insulator in Two-Dimensions,"Quite generally, an insulator is theoretically defined by a vanishing
conductivity tensor at the absolute zero of temperature. In classical
insulators, such as band insulators, vanishing conductivities lead to diverging
resistivities. In other insulators, in particular when a high magnetic field
(B) is added, it is possible that while the magneto-resistance diverges, the
Hall resistance remains finite, which is known as a Hall insulator. In this
letter we demonstrate experimentally the existence of another, more exotic,
insulator. This insulator, which terminates the quantum Hall effect series in a
two-dimensional electron system, is characterized by a Hall resistance which is
approximately quantized in the quantum unit of resistance h/e^2. This insulator
is termed a quantized Hall insulator. In addition we show that for the same
sample, the insulating state preceding the QHE series, at low-B, is of the HI
kind.",9810172v1
1999-03-05,Comment on ``Evidence for Anisotropic State of Two-Dimensional Electrons in High Landau Levels'',"In a recent letter M. Lilly et al [PRL 82, 394 (1999)] have shown that a
highly anisotropic state can arise in certain two dimensional electron systems.
In the large square samples studied, resistances measured in the two
perpendicular directions are found to have a ratio that may be 60 or larger at
low temperature and at certain magnetic fields. In Hall bar measurements, the
anisotropy ratio is found to be much smaller (roughly 5). In this comment we
resolve this discrepancy by noting that the anisotropy of the underlying sheet
resistivities is correctly represented by Hall bar resistance measurements but
shows up exponentially enhanced in resistance measurements on square samples
due to simple geometric effects. We note, however, that the origin of this
underlying resistivity anisotropy remains unknown, and is not addressed here.",9903086v3
1999-12-01,Fractional-flux Little-Parks resistance oscillations in disordered superconducting Au$_{0.7}$In$_{0.3}$ cylinders,"Resistance of disordered superconducting Au$_{0.7}$In$_{0.3}$ cylindrical
films was measured as a function of applied magnetic field. In the
high-temperature part of the superconducting transition regime, the resistance
oscillated with a period of $h/2e$ in the unit of the enclosed magnetic flux.
However, at lower temperatures, the resistance peaks split. We argue that this
splitting is due to the emergence of an oscillation with a period of $h/4e$,
half of the flux quantum for paired electrons. The possible physical origin of
the $h/4e$ resistance oscillation is discussed in the context of new minima in
the free energy of a disordered superconducting cylinder.",9912003v3
2000-04-05,Linear response conductance and magneto-resistance of ferromagnetic single-electron transistors,"The current through ferromagnetic single-electron transistors (SET's) is
considered. Using path integrals the linear response conductance is formulated
as a function of the tunnel conductance vs. quantum conductance and the
temperature vs. Coulomb charging energy. The magneto-resistance of
ferromagnet-normal metal-ferromagnet (F-N-F) SET's is almost independent of the
Coulomb charging energy and is only reduced when the transport dwell time is
longer than the spin-flip relaxation time. In all-ferromagnetic (F-F-F) SET's
with negligible spin-flip relaxation time the magneto-resistance is calculated
analytically at high temperatures and numerically at low temperatures. The
F-F-F magneto-resistance is enhanced by higher order tunneling processes at low
temperatures in the 'off' state when the induced charges vanishes. In contrast,
in the 'on' state near resonance the magneto-resistance ratio is a
non-monotonic function of the inverse temperature.",0004082v3
2001-09-10,Transport properties of MgB2,"In this paper we present the resistivity, the Seebeck effect, and the thermal
conductivity measurements on a MgB2 sintered sample. Such transport properties
highlight the role of the junctions between the grains to a different extent.
In particular, the temperature dependence of resistivity may be explained with
the assumption that grain boundaries have a resistance, independent of
temperature, in series with the resistance of grains. Also the behaviour of the
Seebeck effect, as long as the scattering at the grain boundaries is elastic,
is not affected at all by granularity. Thus, the thermopower can be a useful
tool to provide information on the electronic structure. On the other hand, the
grain boundary resistance affects the thermal conductivity strongly, masking
the superconducting transition completely.",0109174v2
2003-10-22,Unconventional superconductivity and normal state properties of epsilon-iron at high pressure,"Following the discovery of superconductivity in epsilon-iron, subsequent
experiments hinted at non-Fermi liquid behaviour of the normal phase and
sensitive dependence of the superconducting state on disorder, both signatures
of unconventional pairing. We report further resistive measurements under
pressure of samples of iron from multiple sources. The normal state resistivity
of epsilon-iron varied as rho_0+AT^{5/3} at low temperature over the entire
superconducting pressure domain. The superconductivity could be destroyed by
mechanical work, and was restored by annealing, demonstrating sensitivity to
the residual resistivity rho_0. There is a strong correlation between the rho_0
and A coefficients and the superconducting critical temperature T_c. Within the
partial resistive transition there was a significant current dependence, with
V(I)=a(I-I_0)+bI^2, with a >> b, possibly indicating flux-flow resistivity,
even in the absence of an externally applied magnetic field.",0310519v1
2003-12-10,Phase slips in superconducting films with constrictions,"A system of two coplanar superconducting films seamlessly connected by a
bridge is studied. We observe two distinct resistive transitions as the
temperature is reduced. The first one, occurring in the films, shows some
properties of the Berezinskii-Kosterlitz-Thouless (BKT) transition. The second
apparent transition (which is in fact a crossover) is related to freezing out
of thermally activated phase slips (TAPS) localized on the bridge. We also
propose a powerful indirect experimental method allowing an extraction of the
sample's zero-bias resistance from high-current-bias measurements. Using direct
and indirect measurements, we determined the resistance $R(T)$ of the bridges
within a range of {\em eleven orders of magnitude}. Over such broad range, the
resistance follows a simple relation $R(T)=R_N \text{exp} [-(c/t)(1-t)^{3/2}]$,
where $c=\Delta F(0) / kT_c$ is the normalized free energy of a phase slip at
zero temperature, $t=T/T_c$ is normalized temperature, and $R_N$ is the normal
resistance of the bridge.",0312268v2
2004-10-04,"The ""normal"" state of superconducting cuprates might really be normal after all","High magnetic field studies of cuprate superconductors revealed a non-BCS
temperature dependence of the upper critical field $H_{c2}(T)$ determined
resistively by several groups.
  These determinations caused some doubts on the grounds of both the
contrasting effect of the magnetic field on the in-plane and out-of-plane
resistances reported for large Bi2212 sample and the large Nernst signal
\emph{well above} $T_{c}$.
  Here we present both $\rho_{ab}(B)$ and $\rho_{c}(B)$ of tiny Bi2212 crystals
in magnetic fields up to 50 Tesla.
  None of our measurements revealed a situation when on the field increase
$\rho_c$ reaches its maximum while $\rho_{ab}$ remains very small if not zero.
  The resistive %upper critical fields estimated from the in-plane and
out-of-plane $H_{c2}(T)$ estimated from $\rho_{ab}(B)$ and $\rho_{c}(B)$ are
approximately the same. Our results support any theory of cuprates that
describes the state above the resistive phase transition as perfectly normal
with a zero off-diagonal order parameter. In particular, the anomalous Nernst
effect above the resistive phase transition in high-$T_{c}$ cuprates can be
described quantitatively as a normal state phenomenon in a model with itinerant
and localised fermions and/or charged bosons.",0410075v1
2008-04-03,Pressure-temperature Phase Diagram of Polycrystalline UCoGe Studied by Resistivity Measurement,"Recently, coexistence of ferromagnetism (T_Curie = 2.8K) and
superconductivity (T_sc = 0.8K) has been reported in UCoGe, a compound close to
a ferromagnetic instability at ambient pressure P. Here we present resistivity
measurements under pressure on a UCoGe polycrystal. The phase diagram obtained
from resistivity measurements on a polycrystalline sample is found to be
qualitatively different to those of all other ferromagnetic superconductors. By
applying high pressure, ferromagnetism is suppressed at a rate of 1.4 K/GPa. No
indication of ferromagnetic order has been observed above P ~ 1GPa. The
resistive superconducting transition is, however, quite stable in temperature
and persists up to the highest measured pressure of about 2.4GPa.
Superconductivity would therefore appear also in the paramagnetic phase.
However, the appearance of superconductivity seems to change at a
characteristic pressure P* ~ 0.8GPa. Close to a ferromagnetic instability, the
homogeneity of the sample can influence strongly the electronic and magnetic
properties and therefore bulk phase transitions may differ from the
determination by resistivity measurements.",0804.0500v1
2008-08-18,"Upper critical field, anisotropy, and superconducting properties of Ba$_{1-x}$K$_x$Fe$_2$As$_2$ single crystals","The temperature dependent resistivity of Ba$_{1-x}$K$_x$Fe$_2$As$_2$ (x =
0.23, 0.25, 0.28 and 0.4) single crystals and the angle dependent resistivity
of superconducting Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ single crystals were
measured in magnetic fields up to 9 T. The measurements of temperature
dependent resistivity for samples with different doping levels revealed very
high upper critical fields which increase with the transition temperature
monotonously, and a very low superconducting anisotropy ratio
$\Gamma=H_{c2}^{ab}/H_{c2}^c \approx$ 2. By scaling the resistivity in the
frame of the anisotropic Ginzburg-Landau theory, the angle dependent
resistivity of the Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ single crystal measured with
different magnetic fields at a certain temperature collapsed onto one curve. As
the only scaling parameter, the anisotropy $\Gamma$ was determined
alternatively for each temperature and was found to be between two and three.",0808.2392v3
2009-04-28,Complete pressure dependent phase diagrams for SrFe2As2 and BaFe2As2,"The temperature dependent electrical resistivity of single crystalline
SrFe2As2 and BaFe2As2 has been measured in a liquid medium, modified Bridgman
anvil cell for pressures in excess of 75 kbar. These data allow for the
determination of the pressure dependence of the higher temperature, structural
/ antiferromagnetic phase transitions as well as the lower temperature
superconducting phase transition. For both compounds the ambient pressure,
higher temperature structural / antiferromagnetic phase transition can be fully
suppressed with a dome-like region of zero resistivity found to be centered
about its critical pressure. Indeed, qualitatively, the temperature dependence
of the resistivity curves closest to the critical pressures are the closest to
linear, consistent with possible quantum criticality. For pressures
significantly higher than the critical pressure the zero resistivity state is
suppressed and the low temperature resistivity curves asymptotically approach a
universal, low temperature manifold. These results are consistent with the
hypothesis that correlations / fluctuations associated with the
ambient-pressure, high-temperature, tetragonal phase have to be brought to low
enough temperature to allow superconductivity, but if too fully suppressed can
lead to the loss of the superconducting state.",0904.4488v1
2011-01-17,The magnetoresistance and Hall effect in CeFeAsO: a high magnetic field study,"The longitudinal electrical resistivity and the transverse Hall resistivity
of CeFeAsO are simultaneously measured up to a magnetic field of 45T using the
facilities of pulsed magnetic field at Los Alamos. Distinct behaviour is
observed in both the magnetoresistance Rxx({\mu}0H) and the Hall resistance
Rxy({\mu}0H) while crossing the structural phase transition at Ts \approx 150K.
At temperatures above Ts, little magnetoresistance is observed and the Hall
resistivity follows linear field dependence. Upon cooling down the system below
Ts, large magnetoresistance develops and the Hall resistivity deviates from the
linear field dependence. Furthermore, we found that the transition at Ts is
extremely robust against the external magnetic field. We argue that the
magnetic state in CeFeAsO is unlikely a conventional type of spin-density-wave
(SDW).",1101.3170v1
2013-07-23,"Nonlocal resistance and its fluctuations in microstructures of band-inverted HgTe/(Hg,Cd)Te quantum wells","We investigate experimentally transport in gated microsctructures containing
a band-inverted HgTe/Hg_{0.3}Cd_{0.7}Te quantum well. Measurements of nonlocal
resistances using many contacts prove that in the depletion regime the current
is carried by the edge channels, as expected for a two-dimensional topological
insulator. However, high and non-quantized values of channel resistances show
that the topological protection length (i.e. the distance on which the carriers
in helical edge channels propagate without backscattering) is much shorter than
the channel length, which is ~100 micrometers. The weak temperature dependence
of the resistance and the presence of temperature dependent reproducible
quasi-periodic resistance fluctuations can be qualitatively explained by the
presence of charge puddles in the well, to which the electrons from the edge
channels are tunnel-coupled.",1307.6115v3
2013-08-01,Resistive Threshold Logic,"We report a resistance based threshold logic family useful for mimicking
brain like large variable logic functions in VLSI. A universal Boolean logic
cell based on an analog resistive divider and threshold logic circuit is
presented. The resistive divider is implemented using memristors and provides
output voltage as a summation of weighted product of input voltages. The output
of resistive divider is converted into a binary value by a threshold operation
implemented by CMOS inverter and/or Opamp. An universal cell structure is
presented to decrease the overall implementation complexity and number of
components. When the number of input variables become very high, the proposed
cell offers advantages of smaller area and design simplicity in comparison with
CMOS based logic circuits.",1308.0090v1
2014-02-03,"The Effect of Magnetic Fields, Temperature and Current on the Resistivity of Bi-2223 High Temperature Superconductors","The electrical resistivity of polycrystalline Bi2Sr2Ca2Cu3O10-x (Bi-2223) was
measured vs. applied magnetic fields up to 0.45 T, applied currents up to 1 A,
and temperature from liquid nitrogen temperature (LN2) to room temperature. In
the lowest temperature region, the only truly zero resistivity was observed
when the magnetic field was zero; otherwise, a quadratic dependence on the
magnetic field occurred. Hysteresis was noted at the higher currents. Current
vs. voltage curves in this region revealed a non-ohmic resistivity. In the
transition region to the mixed state, indications of negative resistivity and
suggestions of a phase change were observed. Arrhenius plots yielded activation
energies of around 0.05 eV/molecule. In the mixed state region up to the
transition temperature of ~110K, analysis implied that 4 superconducting
quantum states exist and that they are cooperatively filled by the
superconducting charge carriers. The occupation of the superconducting quantum
states is negatively affected by the applied magnetic field and by the applied
current. No effect on the polarity or direction of the magnetic field with
respect to the direction of the current was observed.",1402.0436v1
2014-10-06,Low Resistance Metal Contacts to MoS2 Devices with Nickel-Etched-Graphene Electrodes,"We report an approach to achieve low-resistance contacts to MoS2 transistors
with the intrinsic performance of the MoS2 channel preserved. Through a dry
transfer technique and a metal-catalyzed graphene treatment process,
nickel-etched-graphene electrodes were fabricated on MoS2 that yield contact
resistance as low as 200 ohm-um. The substantial contact enhancement (~2 orders
of magnitude) as compared to pure nickel electrodes, is attributed to the much
smaller work function of nickel-graphene electrodes, together with the fact
that presence of zigzag edges in the treated graphene surface enhances
tunneling between nickel and graphene. To this end, the successful fabrication
of a clean graphene-MoS2 interface and a low resistance nickel-graphene
interface is critical for the experimentally measured low contact resistance.
The potential of using graphene as an electrode interlayer demonstrated in this
work paves the way towards achieving high performance next-generation
transistors.",1410.1328v2
2017-06-14,Kinetic theory of transport for inhomogeneous electron fluids,"The interplay between electronic interactions and disorder is neglected in
the conventional Boltzmann theory of transport, yet can play an essential role
in determining the resistivity of unconventional metals. When quasiparticles
are long-lived, one can account for these intertwined effects by solving
spatially inhomogeneous Boltzmann equations. Assuming smooth disorder and
neglecting umklapp scattering, we solve these inhomogeneous kinetic equations
and compute the electrical resistivity across the ballistic-to-hydrodynamic
transition. An important consequence of electron-electron interactions is the
modification of the momentum relaxation time; this effect is ignored in the
conventional theory. We characterize precisely when interactions enhance the
momentum scattering rate, and when they decrease it. Our approach unifies
existing semiclassical theories of transport and reveals novel transport
mechanisms. In particular, we explain how the resistivity can be proportional
to the rate of momentum-conserving collisions. We compare this result with
existing transport mysteries, including the disorder-independent $T^2$
resistivity of many Fermi liquids, and the linear-in-$T$ ""Planckian-limited""
resistivity of many strange metals.",1706.04621v3
2017-10-11,Zero-field quantum anomalous Hall metrology as a step towards a universal quantum standard unit system,"In the quantum anomalous Hall effect, the edge states of a ferromagnetically
doped topological insulator exhibit quantized Hall resistance and
dissipationless transport at zero magnetic field. Up to now, however, the
resistance was experimentally assessed with standard transport measurement
techniques which are difficult to trace to the von-Klitzing constant R$_K$ with
high precision. Here, we present a metrologically comprehensive measurement,
including a full uncertainty budget, of the resistance quantization of V-doped
(Bi,Sb)$_2$Te$_3$ devices without external magnetic field. We established as a
new upper limit for a potential deviation of the quantized anomalous Hall
resistance from RK a value of 0.26 +- 0.22 ppm, the smallest and most precise
value reported to date. This provides another major step towards realization of
the zero-field quantum resistance standard which in combination with Josephson
effect will provide the universal quantum units standard in the future.",1710.04090v1
2019-09-20,Phenomenology of anomalous transport in disordered one-dimensional systems,"We study anomalous transport arising in disordered one-dimensional spin
chains, specifically focusing on the subdiffusive transport typically found in
a phase preceding the many-body localization transition. Different types of
transport can be distinguished by the scaling of the average resistance with
the system's length. We address the following question: what is the
distribution of resistance over different disorder realizations, and how does
it differ between transport types? In particular, an often evoked so-called
Griffiths picture, that aims to explain slow transport as being due to rare
regions of high disorder, would predict that the diverging resistivity is due
to fat power-law tails in the resistance distribution. Studying many-particle
systems with and without interactions we do not find any clear signs of fat
tails. The data is compatible with distributions that decay faster than any
power law required by the fat tails scenario. Among the distributions
compatible with the data, a simple additivity argument suggests a Gaussian
distribution for a fractional power of the resistance.",1909.09507v2
2019-06-29,Ultra-Low Surface Resistance via Vacuum Heat Treatment of Superconducting Radiofrequency Cavities,"We report on an effort to improve the performance of superconducting
radiofrequency cavities by the use of heat treatment in a temperature range
sufficient to dissociate the natural surface oxide. We find that the residual
resistance is significantly decreased, and we find an unexpected reduction in
the BCS resistance. Together these result in extremely high quality factor
values at relatively large accelerating fields Eacc ~20 MV/m: Q0 of 3-4x10^11
at <1.5 K and Q0 ~5x10^10 at 2.0 K. In one cavity, measurements of surface
resistance versus temperature showed an extremely small residual resistance of
just 0.63+/-0.06 nOhms at 16 MV/m. SIMS measurements confirm that the oxide was
significantly dissociated, but they also show the presence of nitrogen after
heat treatment. We also present studies of surface oxidation via exposure to
air and to water, as well as the effects of very light surface removal via HF
rinse. The possibilities for applications and the planned future development
are discussed.",1907.00147v1
2012-03-21,Magnetoplasmon resonance in 2D electron system driven into a zero-resistance state,"We report on a remarkably strong, and a rather sharp, photoresistance peak
originating from a dimensional magnetoplasmon resonance (MPR) in a high
mobility GaAs/AlGaAs quantum well driven by microwave radiation into a
zero-resistance state (ZRS). The analysis of the MPR signalreveals a negative
background providing experimental evidence for the concept of absolute negative
resistance associated with the ZRS. When a system is further subject to a dc
field, the maxima of microwave-induced resistance oscillations decay away and a
system reveals a state with close-to-zero differential resistance. The MPR
peak, on the other hand, remains essentially unchanged, indicating surprisingly
robust Ohmic behavior under the MPR conditions.",1203.4781v1
2015-04-21,Radiation-induced resistance oscillations in a 2D hole gas: a demonstration of a universal effect,"We report on a theoretical insight about the microwave-induced resistance
oscillations and zero resistance states when dealing with p-type semiconductors
and holes instead of electrons. We consider a high-mobility two-dimensional
hole gas hosted in a pure Ge/SiGe quantum well. Similarly to electrons we
obtain radiation-induce resistance oscillations and zero resistance states. We
analytically deduce a universal expression for the irradiated
magnetoresistance, explaining the origin of the minima positions and their
$1/4$ cycle phase shift. The outcome is that these phenomena are universal and
only depend on radiation and cyclotron frequencies. We also study the
possibility of having simultaneously two different carriers driven by
radiation: light and heavy holes. As a result the calculated magnetoresistance
reveals an interference profile due to the different effective masses of the
two types of carriers.",1504.05564v2
2019-10-03,Modeling of Electrical Resistivity of Soil Based on Geotechnical Properties,"Determining the relationship between the electrical resistivity of soil and
its geotechnical properties is an important engineering problem. This study
aims to develop methodology for finding the best model that can be used to
predict the electrical resistivity of soil, based on knowing its geotechnical
properties. The research develops several linear models, three non-linear
models, and three artificial neural network models (ANN). These models are
applied to the experimental data set comprises 864 observations and five
variables. The results show that there are significant exponential negative
relationships between the electrical resistivity of soil and its geotechnical
properties. The most accurate prediction values are obtained using the ANN
model. The cross-validation analysis confirms the high precision of the
selected predictive model. This research is the first rigorous systematic
analysis and comparison of difference methodologies in ground electrical
resistivity studies. It provides practical guidelines and examples of design,
development and testing non-linear relationships in engineering intelligent
systems and applications.",1910.01325v1
2019-10-16,$T$-linear resistivity in models with local self-energy,"A theoretical understanding of the enigmatic linear-in-temperature ($T$)
resistivity, ubiquitous in strongly correlated metallic systems, has been a
long sought-after goal. Furthermore, the slope of this robust $T$-linear
resistivity is also observed to stay constant through crossovers between
different temperature regimes: a phenomenon we dub ""slope invariance"".
Recently, several solvable models with $T$-linear resistivity have been
proposed, putting us in an opportune moment to compare their inner workings in
various explicit calculations. We consider two strongly correlated models with
local self-energies that demonstrate $T$-linearity: a lattice of coupled
Sachdev-Ye-Kitaev (SYK) models and the Hubbard model in single-site dynamical
mean-field theory (DMFT). We find that the two models achieve $T$-linearity
through distinct mechanisms at intermediate temperatures. However, we also find
that these mechanisms converge to an identical form at high temperatures.
Surprisingly, both models exhibit ""slope invariance"" across the two temperature
regimes. We thus not only reveal some of the diversity in the theoretical inner
workings that can lead to $T$-linear resistivity, but we also establish that
different mechanisms can result in ""slope invarance"".",1910.07530v2
2020-05-28,Contact resistance extraction of graphene FET technologies based on individual device characterization,"Straightforward contact resistance extraction methods based on electrical
device characteristics are described and applied here to graphene field-effect
transistors from different technologies. The methods are an educated adaptation
of extraction procedures originally developed for conventional transistors by
exploiting the drift-diffusion-like transport in graphene devices under certain
bias conditions. In contrast to other available approaches for contact
resistance extraction of graphene transistors, the practical methods used here
do not require either the fabrication of dedicated test structures or internal
device phenomena characterization. The methodologies are evaluated with
simulation-based data and applied to fabricated devices. The extracted values
are close to the ones obtained with other more intricate methodologies.
Bias-dependent contact and channel resistances studies, bias-dependent
high-frequency performance studies and contact engineering studies are enhanced
and evaluated by the extracted contact resistance values.",2005.13926v1
2021-10-29,Influence of Device Geometry on Transport Properties of Topological Insulator Microflakes,"In the transport studies of topological insulators, microflakes exfoliated
from bulk single crystals are often used because of the convenience in sample
preparation and the accessibility to high carrier mobilities. Here, based on
finite element analysis, we show that for the non-Hall-bar shaped topological
insulator samples, the measured four-point resistances can be substantially
modified by the sample geometry, bulk and surface resistivities, and magnetic
field. Geometry correction factors must be introduced for accurately converting
the four-point resistances to the longitudinal resistivity and Hall
resistivity. The magnetic field dependence of inhomogeneous current density
distribution can lead to pronounced positive magnetoresistance and nonlinear
Hall effect that would not exist in the samples of ideal Hall bar geometry.",2110.15589v1
2022-04-14,DC-coupled resistive silicon detectors for 4-D tracking,"In this work, we introduce a new design concept: the DC-Coupled Resistive
Silicon Detectors, based on the LGAD technology. This new approach intends to
address a few known features of the first generation of AC-Coupled Resistive
Silicon Detectors (RSD). Our simulation exploits a fast hybrid approach based
on a combination of two packages, Weightfield2 and LTSpice. It demonstrates
that the key features of the RSD design are maintained, yielding excellent
timing and spatial resolutions: a few tens of ps and a few microns. In the
presentation, we will outline the optimization methodology and the results of
the simulation. We will present detailed studies on the effect of changing the
ratio between the n+ layer resistivity and the low-resistivity ring and on the
achievable temporal and spatial resolution.",2204.07226v1
2022-10-19,"Vector graphics extraction and analysis of electrical resistance data in Nature volume 586, pages 373-377 (2020)","In this paper, I present an analysis of the electrical resistance graphs in
Nature volume 586, pages 373-377 (2020), which reported the discovery of room
temperature superconductivity in a carbonaceous sulfur hydride and was
subsequently retracted on September 26th, 2022. I show that, over a single
temperature interval, the electrical resistance data can be decomposed into at
least two signals of differing digital precision, thus raising questions
concerning the methods used to obtain the published data. Since the raw
data-files for the electrical resistance measurements have not been made
available, in order to perform this analysis, I have developed a set of python
scripts to extract the data-points with high precision from the internal
structure of the vector graphics image files. I describe the data extraction
method. Example code and the resulting electrical resistance vs temperature
data-files are made available in public repositories.",2210.10766v1
2023-06-26,Towards Optimal Effective Resistance Estimation,"We provide new algorithms and conditional hardness for the problem of
estimating effective resistances in $n$-node $m$-edge undirected, expander
graphs. We provide an $\widetilde{O}(m\epsilon^{-1})$-time algorithm that
produces with high probability, an $\widetilde{O}(n\epsilon^{-1})$-bit sketch
from which the effective resistance between any pair of nodes can be estimated,
to $(1 \pm \epsilon)$-multiplicative accuracy, in $\widetilde{O}(1)$-time.
Consequently, we obtain an $\widetilde{O}(m\epsilon^{-1})$-time algorithm for
estimating the effective resistance of all edges in such graphs, improving (for
sparse graphs) on the previous fastest runtimes of
$\widetilde{O}(m\epsilon^{-3/2})$ [Chu et. al. 2018] and
$\widetilde{O}(n^2\epsilon^{-1})$ [Jambulapati, Sidford, 2018] for general
graphs and $\widetilde{O}(m + n\epsilon^{-2})$ for expanders [Li, Sachdeva
2022]. We complement this result by showing a conditional lower bound that a
broad set of algorithms for computing such estimates of the effective
resistances between all pairs of nodes require $\widetilde{\Omega}(n^2
\epsilon^{-1/2})$-time, improving upon the previous best such lower bound of
$\widetilde{\Omega}(n^2 \epsilon^{-1/13})$ [Musco et. al. 2017]. Further, we
leverage the tools underlying these results to obtain improved algorithms and
conditional hardness for more general problems of sketching the pseudoinverse
of positive semidefinite matrices and estimating functions of their
eigenvalues.",2306.14820v1
2023-08-22,Non-Hermitian topological ohmmeter,"Measuring large electrical resistances forms an essential part of common
applications such as insulation testing, but suffers from a fundamental
problem: the larger the resistance, the less sensitive a canonical ohmmeter is.
Here we develop a conceptually different electronic sensor by exploiting the
topological properties of non-Hermitian matrices, whose eigenvalues can show an
exponential sensitivity to perturbations. The ohmmeter is realized in an
multi-terminal, linear electric circuit with a non-Hermitian conductance
matrix, where the target resistance plays the role of the perturbation. We
inject multiple currents and measure a single voltage in order to directly
obtain the value of the resistance. The relative accuracy of the device
increases exponentially with the number of terminals, and for large resistances
outperforms a standard measurement by over an order of magnitude. Our work
paves the way towards leveraging non-Hermitian conductance matrices in
high-precision sensing.",2308.11367v1
2019-09-12,Analysis of RF losses and material characterization of samples removed from a Nb3Sn-coated superconducting RF cavity,"Nb3Sn (Tc ~ 18 K and Hsh ~ 400 mT) is a prospective material to replace Nb
(Tc ~ 9 K and Hsh ~ 200 mT) in SRF accelerator cavities for significant cost
reduction and performance enhancement. Because of its material properties,
Nb3Sn is best employed as a thin film (coating) inside an already built RF
cavity structure. A particular test cavity noted as C3C4 was a 1.5 GHz
single-cell Nb cavity, coated with Nb3Sn using Sn vapor diffusion process at
Jefferson Lab. Cold measurements of the coated cavity indicated the
superconducting transition temperature of about 18 K. Subsequent RF
measurements indicated field-dependent surface resistance both at 4.3 K and 2.0
K. After initial cold measurements, the cavity RF loss distribution was studied
with a thermometry mapping system. Loss regions were identified with
thermometry and were cut out for material analysis. The presence of
significantly thin patchy regions and other carbon-rich defects is associated
with strong local field-dependent surface resistance. This paper summarizes RF
and thermometry results correlated with material science findings.",1909.05695v1
2020-02-27,A simple approach to bulk bioinspired tough ceramics,"The development of damage-resistant structural materials that can withstand
harsh environments is a major issue in materials science and engineering.
Bioinspired brick-and-mortar designs have recently demonstrated a range of
interesting mechanical properties in proof-of-concept studies. However,
reproducibility and scalability issues associated with the actual processing
routes have impeded further developments and industrialization of such
materials. Here we demonstrate a simple approach based on uniaxial pressing and
field assisted sintering of commercially available raw materials to process
bioinspired ceramic/ceramic composites of larger thickness than previous
approaches, with a sample thickness up to 1 cm. The ceramic composite retains
the strength typical of dense alumina ($430~\pm 30MPa$) while keeping the
excellent damage resistance demonstrated previously at the millimeter scale
with a crack initiation toughness of $6.6MPa.m^{1/2}$ and fracture toughness up
to $17.6 MPa.m^{1/2}$. These results validate the potential of these
all-ceramic composites, previously demonstrated at lab scale only, and could
enable their optimization, scale-up, and industrialization.",2003.11898v1
2021-10-09,Fracture Diodes: Directional asymmetry of fracture toughness,"Toughness describes the ability of a material to resist fracture or crack
propagation. It is demonstrated here that fracture toughness of a material can
be asymmetric, i.e., the resistance of a medium to a crack propagating from
right to left can be significantly different from that to a crack propagating
from left to right. Such asymmetry is unknown in natural materials, but we show
that it can be built into artificial materials through the proper control of
microstructure. This paves the way for control of crack paths and direction,
where fracture -- when unavoidable -- can be guided through pre-designed paths
to minimize loss of critical components.",2110.04613v1
2022-07-20,Do thermoelectric generator modules degrade due to nickel diffusion,"The paper shows by calculation that the diffusion of nickel even for 50 years
does not lead to degradation of thermoelectric generator modules. In the
process, we used the theory of composites to calculate the electrical contact
resistance, our own diffusion theory of electrical contact resistance, as well
as the method for approximating the temperature dependences of thermoelectric
material characteristics from the experimental data. When using the above
method, it was assumed that the main mechanism of scattering of free charge
carriers in a thermoelectric material is their scattering on the deformation
potential of acoustic phonons with a free path length independent of energy but
inversely proportional to temperature, and the main mechanism of phonon
scattering is phonon-phonon scattering with Umklapp, which is not affected by
the nickel impurity in the thermoelectric material. Thus, it was believed that
the role of nickel is reduced only to a change in the concentration of free
charge carriers in the material.",2207.12122v1
2023-03-10,Engineering heat transport across epitaxial lattice-mismatched van der Waals heterointerfaces,"Artificially engineered 2D materials offer unique physical properties for
thermal management, surpassing naturally occurring materials. Here, using van
der Waals epitaxy, we demonstrate the ability to engineer extremely insulating
ultra-thin thermal metamaterials based on crystalline lattice-mismatched
Bi2Se3/MoSe2 superlattices and graphene/PdSe2 heterostructures with exceptional
thermal resistances (70-202 m^2K/GW) and ultralow cross-plane thermal
conductivities (0.01-0.07 Wm^-1K^-1) at room temperature, comparable to those
of amorphous materials. Experimental data obtained using frequency-domain
thermoreflectance and low-frequency Raman spectroscopy, supported by
tight-binding phonon calculations, reveal the impact of lattice mismatch,
phonon-interface scattering, size effects, temperature and interface thermal
resistance on cross-plane heat dissipation, uncovering different thermal
transport regimes and the dominant role of long-wavelength phonons. Our
findings provide essential insights into emerging synthesis and thermal
characterization methods and valuable guidance for the development of
large-area heteroepitaxial van der Waals films of dissimilar materials with
tailored thermal transport characteristics.",2303.05808v1
2023-09-25,Integrated bolometric photodetectors based on transparent conductive oxides from near- to mid-infrared wavelengths,"On-chip photodetectors are essential components in optical communications as
they convert light into an electrical signal. Photobolometers are type of
photodetector that functions through a resistance change caused by electronic
temperature fluctuations upon light absorption. They are widely used in the
broad wavelength range from UV to MIR and can operate on a wide material
platform. In this work, I introduce a novel waveguide-integrated bolometer that
operates in a wide wavelength range from NIR to MIR on the standard material
platform with the transparent conductive oxides (TCOs) as the active material.
This material platform enables the construction of both modulators and
photodetectors using the same material, which is fully CMOS compatible and
easily integrated with passive on-chip components. The photobolometers proposed
here consist of a thin TCO layer placed inside the rib photonic waveguide to
enhance light absorption and then heat the electrons in the TCO to temperatures
above 1000 K. This rise in electron temperature leads to decreasing electron
mobility and consequential electrical resistance change. In consequence, a
responsivity exceeding 10 A/W can be attained with a mere few microwatts of
optical input power. Calculations suggest that further improvements can be
expected with lower doping of the TCO, thus opening new doors in on-chip
photodetectors.",2309.14454v1
2023-10-04,Current-driven magnetic resistance in van der Waals spin-filter antiferromagnetic tunnel junctions with MnBi$_2$Te$_4$,"The field of 2D magnetic materials has paved the way for the development of
spintronics and nanodevices with new functionalities. Utilizing
antiferromagnetic materials, in addition to layered van der Waals (vdW)
ferromagnetic materials, has garnered significant interest. In this work, we
present a theoretical investigation of the behavior of MnBi$_2$Te$_4$ devices
based on the non-equilibrium Green's function method. Our results show that the
current-voltage (I-V) characteristics can be influenced significantly by
controlling the length of the device and bias voltage and thus allow us to
manipulate the tunneling magneto-resistance (TMR) with an external bias
voltage. This can be further influenced by the presence of the boron nitride
layer which shows significantly enhanced TMR by selectively suppressing
specific spin channels for different magnetic configurations. By exploiting
this mechanism, the observed TMR value reaches up to 3690\%, which can be
attributed to the spin-polarized transmission channel and the projected local
density of states. Our findings on the influence of structural and magnetic
configurations on the spin-polarized transport properties and TMR ratios give
the potential implementation of antiferromagnetic vdW layered materials in
ultrathin spintronics.",2310.02830v1
2019-05-04,"Pressure enhanced interplay among lattice, spin and charge in La2FeMnO6 mixed perovskite","Spin crossover plays a central role in the structural instability, net
magnetic moment modification, metallization, and even in superconductivity in
corresponding materials. Most reports on the pressure-induced spin crossover
with a large volume collapse so far focused on compounds with single transition
metal. Here we report a comprehensive high-pressure investigation of a mixed
Fe-Mn perovskite La2FeMnO6. Under pressure, the strong coupling between Fe and
Mn leads to a combined valence/spin transition: Fe3+(S = 5/2) to Fe2+(S = 0)
and Mn3+(S = 2) to Mn4+(S = 3/2), with an isostructural phase transition. The
spin transitions of both Fe and Mn are offset by ~ 20 GPa of the onset
pressure, and the lattice collapse occurs in between. Interestingly, Fe3+ ion
shows an abnormal behavior when it reaches a lower valence state (Fe2+)
accompanied by a + 0.5 eV energy shift in Fe K-absorption edge at 15 GPa. This
process is associated with the charge-spin-orbital state transition from high
spin Fe3+ to low spin Fe2+, caused by the significantly enhanced t2g-eg crystal
field splitting in the compressed lattice under high pressure. Density
Functional Theory calculations confirm the energy preference of the
high-pressure state with charge redistribution accompanied by spin state
transition of Fe ions. Moreover, La2FeMnO6 maintains semiconductor behaviors
even when the pressure reached 144.5 GPa as evidenced by the electrical
transport measurements, despite the huge resistivity decreasing 7 orders of
magnitude compared with that at ambient pressure. The investigation carried out
here demonstrates high flexibility of double perovskites and their good
potentials for optimizing the functionality of these materials.",1905.01521v1
2012-03-16,Development and preliminary tests of resistive microdot and microstrip detectors,"In the last few years our group have focused on developing various designs of
spark-protected micropattern gaseous detectors featuring resistive electrodes
instead of the traditional metallic ones: resistive microstrip counters,
resistive GEM, resistive MICROMEGAS. These detectors combine in one design the
best features of RPCs (spark-protection) and micropattern detectors (a high
position resolution). In this paper we report the progress so far made in
developing other types of resistive micropattern detectors: a
microdot-microhole detector and a microgap-microstrip detector. The former
detector is an optimal electron amplifier for some special designs of dual
phase noble liquid TPCs, for example with a CsI photocathode immersed inside
the noble liquid. Preliminary tests of such a detector, for the first time
built and investigated, are reported in this paper. The latter detector is
mainly orientated towards medical imaging applications such as X-ray scanners.
However, we believe that after a proper gas optimization, these detectors could
also achieve a high time resolution and could thus be used in applications as
TOF-PET, detection of charged particles with simultaneous high time and
position resolution etc.",1203.3658v2
2022-10-25,Stopping Resistance Drift in Phase Change Memory Cells and Analysis of Charge Transport in Stable Amorphous Ge2Sb2Te5,"We stabilize resistance of melt-quenched amorphous Ge2Sb2Te5 (a-GST) phase
change memory (PCM) line cells by substantially accelerating resistance drift
and bringing it to a stop within a few minutes with application of high
electric field stresses. The acceleration of drift is clearly observable at
electric fields > 26 MV/m at all temperatures (85 K - 300 K) and is independent
of the current forced through the device, which is a strong function of
temperature. The low-field (< 21 MV/m) I-V characteristics of the stabilized
cells measured in 85 K - 300 K range fit well to a 2D thermally-activated
hopping transport model, yielding hopping distances in the direction of the
field and activation energies ranging from 2 nm and 0.2 eV at 85 K to 6 nm and
0.4 eV at 300 K. Hopping transport appears to be better aligned with the field
direction at higher temperatures. The high-field current response to voltage is
significantly stronger and displays a distinctly different characteristic: the
differential resistances at different temperatures extrapolate to a single
point (8.9x10-8 ohm.cm), comparable to the resistivity of copper at 60 K, at
65.6 +/- 0.4 MV/m. The physical mechanisms that give rise to the substantial
increase in current in the high-field regime also accelerate resistance drift.
We constructed field and temperature dependent conduction models based on the
experimental results and integrated it with our electro-thermal finite element
device simulation framework to analyze reset, set and read operations of PCM
devices.",2210.14035v1
2013-07-08,5d transition metal oxide IrO2 as a material for spin current detection,"Devices based on a pure spin current (a flow of spin angular momentum) have
been attracting increasing attention as key ingredients for low-dissipation
electronics. To integrate such spintronics devices into charge-based
technologies, an electric detection of spin current is essential. Inverse spin
Hall effect converts a spin current into an electric voltage through spin-orbit
coupling. Noble metals such as Pt and Pd, and also Cu-based alloys, owing to
the large direct spin Hall effect, have been regarded as potential materials
for a spin-current injector. Those materials, however, are not promising as a
spin-current detector based on inverse spin Hall effect. Their spin Hall
resistivity rho_SH, representing the performance as a detector, is not large
enough mainly due to their low charge resistivity. Here we demonstrate that
heavy transition metal oxides can overcome such limitations inherent to
metal-based spintronics materials. A binary 5d transition metal oxide IrO2,
owing to its large resistivity as well as a large spin-orbit coupling
associated with 5d character of conduction electrons, was found to show a
gigantic rho_SH ~ 38 microohm cm at room temperature, one order of magnitude
larger than those of noble metals and Cu-based alloys and even comparable to
those of atomic layer thin film of W and Ta.",1307.2121v1
2018-10-31,Challenges in materials and devices for Resistive-Switching-based Neuromorphic Computing,"This tutorial describes challenges and possible avenues for the
implementation of the components of a solid-state system, which emulates a
biological brain. The tutorial is devoted mostly to a charge-based (i.e.
electric controlled) implementation using transition metal oxides materials,
which exhibit unique properties that emulate key functionalities needed for
this application. In the Introduction, we compare the main differences between
a conventional computational machine, based on the Turing-von Neumann paradigm,
to a Neuromorphic machine, which tries to emulate important functionalities of
a biological brain. We also describe the main electrical properties of
biological systems, which would be useful to implement in a charge-based
system. In Chapter II, we describe the main components of a possible
solid-state implementation. In Chapter III, we describe a variety of Resistive
Switching phenomena, which may serve as the functional basis for the
implementation of key devices for Neuromorphic computing. In Chapter IV we
describe why transition metal oxides, are promising materials for future
Neuromorphic machines. Theoretical models describing different resistive
switching mechanisms are discussed in Chapter V while existing implementations
are described in Chapter VI. Chapter VII presents applications to practical
problems. We list in Chapter VIII important basic research challenges and open
issues. We discuss issues related to specific implementations, novel materials,
devices and phenomena. The development of reliable, fault tolerant, energy
efficient devices, their scaling and integration into a Neuromorphic computer
may bring us closer to the development of a machine that rivals the brain.",1812.01120v1
2023-01-25,$T-$linear resistivity from magneto-elastic scattering: application to PdCrO$_2$,"An electronic solid with itinerant carriers and localized magnetic moments
represents a paradigmatic strongly correlated system. The electrical transport
properties associated with the itinerant carriers, as they scatter off these
local moments, has been scrutinized across a number of materials. Here we
analyze the transport characteristics associated with ultra-clean PdCrO$_2$ --
a quasi two-dimensional material consisting of alternating layers of itinerant
Pd-electrons and Mott-insulating CrO$_2$ layers -- which shows a pronounced
regime of $T-$linear resistivity over a wide-range of intermediate
temperatures. By contrasting these observations to the transport properties in
a closely related material PdCoO$_2$, where the CoO$_2$ layers are
band-insulators, we can rule out the traditional electron-phonon interactions
as being responsible for this interesting regime. We propose a previously
ignored electron-magnetoelastic interaction between the Pd-electrons, the Cr
local-moments and an out-of-plane phonon as the main scattering mechanism that
leads to the significant enhancement of resistivity and a $T-$linear regime in
PdCrO$_2$ at temperatures far in excess of the magnetic ordering temperature.
We suggest a number of future experiments to confirm this picture in PdCrO$_2$,
as well as other layered metallic/Mott-insulating materials.",2301.10776v2
2011-11-14,Nanostructuring of Ba8Ga16Ge30 clathrates,"First thermoelectric properties measurements on bulk nanostructured
Ba8Ga16Ge30 clathrate-I are presented. A sol-gel-calcination route was
developed for preparing amorphous nanosized precursor oxides. The further
reduction of the oxides led to quantitative yield of crystalline nanosized
Ba8Ga16Ge30 clathrate-I. TEM investigations show the clathrate nanoparticles
retain the size and morphology of the precursor oxides. The clathrate
nanoparticles contain mainly thin plates (approx. 300 nm x 300 nm x 50 nm) and
a small amount of nanospheres (diameter ~ 10 nm). SAED patterns confirm the
clathrate-I structure type for both morphologies. The powders were compacted
via Spark Plasma Sintering (SPS) to obtain a bulk nano-structured material. The
Seebeck coefficient S, measured on low-density samples (53% of {\delta}x-ray),
reaches -145 {\mu}V/k at 375 {\deg}C. The ZT values are quite low (0.02) due to
the high resistivity of the sample (two orders of magnitude larger than bulk
materials) and the low sample density. The trend of the temperature dependence
of S is in agreement with the values obtained from electronic structure
calculations and semi-classical Boltzmann transport theory within the constant
scattering approximation. The total thermal conductivity (1.61 W/mK), measured
on high density samples (93% of {\delta}x-ray), shows a reduction of 20-25% in
relation to the bulk materials (2.1 W/mK). A further shaping of the sample for
the Seebeck coefficient and electrical conductivity measurements was not
possible due to the presence of cracks. An improvement on the design of the
pressing tools, loading of the sample and profile of the applied pressure will
enhance the mechanical stability of the samples. These investigations are now
in progress.",1111.3233v1
2013-02-10,"Synthesis and properties of charge-ordered thallium halide perovskites, CsTl1+0.5Tl3+0.5X3 (X = F, Cl)- theoretical precursors for superconductivity?","Recently CsTlCl3 and CsTlF3 perovskites were theoretically predicted to be
potential superconductors if they are optimally doped. The synthesis of these
two compounds, together with a complete characterization of the samples are
reported. CsTlCl3 is obtained as orange crystals in two different polymorphs: a
tetragonal (I4/m) and a cubic (Fm-3m) phase. CsTlF3 is formed as a light brown
powder, also as a double cubic perovskite (Fm-3m). In all three CsTlX3 phases
Tl1+ and Tl3+ were located in two different crystallographic positions that
accommodate their different bond lengths. In CsTlCl3 some Tl vacancies are
found in the Tl1+ position. The charge ordering between Tl1+ and Tl3+ was
confirmed by x-ray absorption and Raman spectroscopy. The Raman spectroscopy of
CsTlCl3 under high pressure (58 GPa) did not indicate any phase transition to a
possible single Tl2+ state. However, the highly insulating material becomes
less resistive with increasing high pressure, while undergoing a change in the
optical properties, from transparent to deeply opaque red, indicative of a
decrease of the band gap. The theoretical design and experimental validation of
the existence of CsTlF3 and CsTlCl3 cubic perovskites is the necessary first
step in confirming the theoretical prediction of superconductivity in these
materials.",1302.2353v3
2021-03-28,Radiation-tolerant high-entropy alloys via interstitial-solute-induced chemical heterogeneities,"High-entropy alloys (HEAs) composed of multiple principal elements have been
shown to offer improved radiation resistance over their elemental or
dilute-solution counterparts. Using NiCoFeCrMn HEA as a model, here we
introduce carbon and nitrogen interstitial alloying elements to impart chemical
heterogeneities in the form of the local chemical order (LCO) and associated
compositional variations. Density functional theory simulations predict
chemical short-range order (CSRO) (nearest neighbors and the next couple of
atomic shells) surrounding C and N, due to the chemical affinity of C with (Co,
Fe) and N with (Cr, Mn). Atomic-resolution chemical mapping of the elemental
distribution confirms marked compositional variations well beyond statistical
fluctuations. Ni+ irradiation experiments at elevated temperatures demonstrate
a remarkable reduction in void swelling by at least one order of magnitude
compared to the base HEA without C and N alloying. The underlying mechanism is
that the interstitial-solute-induced chemical heterogeneities roughen the
lattice as well as the energy landscape, impeding the movements of, and
constraining the path lanes for, the normally fast-moving self-interstitials
and their clusters. The irradiation-produced interstitials and vacancies
therefore recombine more readily, delaying void formation. Our findings thus
open a promising avenue towards highly radiation-tolerant alloys.",2103.15134v1
2024-01-21,Hydrostatic pressure effect on structural and transport properties of co-existing layered and disordered rock-salt phase of LixCoO2,"It is widely believed that the origin of a significant cause for the voltage
and capacity fading observed in lithium (Li)-ion batteries is related to
structural modifications occurring in the cathode material during the Li-ion
insertion/de-insertion process. The Li-ion insertion/de-insertion mechanism and
the resulting structural changes are known to exert a severe strain on the
lattice, and consequently leading to performance degradation. Here, with a view
to shed more light on the effect of such strain on the structural properties of
the cathode material, we have systematically investigated the pressure
dependence of structural and transport properties of an LixCoO2 single crystal,
grown using 5% excess Li in the precursors. Ambient pressure synchrotron
diffraction on these crystals reveals that, the excess Li during the growth,
has facilitated the stabilization of a layered rhombohedral phase (space group
R3m) as well as a disordered rock-salt phase (space group Fm3m). The volume
fraction of the rhombohedral and cubic phase is 60:40, respectively, which
remains unchanged up to 10.6 GPa. No structural phase transition has been
observed up to 10.6 GPa. An increase in resistance with a decrease in
temperature has revealed the semi-metallic nature of the sample. Further, the
application of hydrostatic pressure up to 2.8 GPa shows the enhancement of
semi-metallic nature. The obtained experimental results can be qualitatively
explained via density functional theory (DFT) and thermodynamics modelling. The
calculated density of states was reduced, and the activation energy was
increased by applied pressure. Our investigations indicate a significant phase
stability of the mixed phase crystals under externally applied high pressure
and thus suggest the possible use of such mixed phase materials as a cathode in
lithium-ion batteries.",2401.11446v1
2017-01-18,Intermittent Preventive Treatment (IPT): Its role in averting disease-induced mortalities in children and in promoting the spread of antimalarial drug resistance,"We develop a variable population age-structured ODE model to investigate the
role of Intermittent Preventive Treatment (IPT) in averting malaria-induced
mortalities in children, as well as its related cost in promoting the spread of
anti-malarial drug resistance. IPT, a malaria control strategy in which a full
curative dose of an antimalarial medication is administered to vulnerable
asymptomatic individuals at specified intervals, has been shown to have a
positive impact on reducing malaria transmission and deaths in children and
pregnant women. However, it can also promote drug resistance spread. Our
mathematical model is used to explore IPT effects on drug resistance in
holoendemic malaria regions while quantifying the benefits in deaths averted.
Our model includes both drug-sensitive and drug-resistant strains of the
parasite as well as interactions between human hosts and mosquitoes. The basic
reproduction numbers for both strains as well as the invasion reproduction
numbers are derived and used to examine the role of IPT on drug resistance.
Numerical simulations show the individual and combined effects of IPT and
treatment of symptomatic infections on the prevalence levels of both parasite
strains and on the number of lives saved. The results suggest that while IPT
can indeed save lives, particularly in the high transmission region, certain
combinations of drugs used for IPT and drugs used to treat symptomatic
infection may result in more deaths when resistant parasite strains are
circulating. Moreover, the half-lives of the treatment and IPT drugs used play
an important role in the extent to which IPT may influence the rate of spread
of the resistant strain. A sensitivity analysis indicates the model outcomes
are most sensitive to the reduction factor of transmission for the resistant
strain, rate of immunity loss, and the clearance rate of sensitive infections.",1701.05210v1
2019-12-22,Bulk Polycrystalline Ceria Doped Al$_2$O$_3$ and YAG Ceramics for High-Power Density Laser-Driven Solid-State White Lighting: Effects of Crystallinity and Extreme Temperatures,"Here we develop and characterize high thermal conductivity/high thermal shock
resistant bulk Ce doped Al2O3 and propose it as a new phosphor converting
capping layer for high-powered/high-brightness solid-state white lighting
(SSWL). The bulk, dense Ce:Al2O3 ceramics have a 0.5 at.% Ce:Al concentration
(significantly higher than the equilibrium solubility limit), and were produced
using a simultaneous solid-state reactive Current Activated Pressure-Assisted
Densification (CAPAD) approach. Ce:Al2O3 exhibits a broadband emission from
400-600nm, which encompasses the entire blue and green portions of the visible
spectrum when pumped with ultra-violet (UV) light that is now commercially
available in UV light emitting devices (LED) and laser diodes (LD). These
broadband phosphors can be used in the commonly employed scheme of mixing with
other UV converting capping layers that emit red light to produce white light.
Alternatively, they can be used in a novel composite down converter approach
that ensures improved thermal-mechanical properties of the converting phosphor
capping layer. In this configuration Ce:Al2O3 is used with proven phosphor
conversion materials such as Ce:YAG as an active encapsulant or as a capping
layer to produce SSWL with an improved bandwidth in the blue portion of the
visible spectrum. In order to study the effect of crystallinity on the Ce PL
emission, we synthesize Ce:YAG ceramics using high-pressure CAPAD at moderate
temperatures to obtain varying crystallinity (amorphous through fully
-crystalline). We investigate the PL characteristics of Ce:Al2O3 and Ce:YAG
from 295K to 4K, revealing unique crystal field effects from the matrix on the
Ce-dopants. The unique PL properties in conjunction with the superior
thermal-mechanical properties of Ce:Al2O3 can be used in
high-powered/high-brightness integrated devices based on high-efficiency UV-LD
that do not suffer",1912.10393v1
1992-08-05,Transport Properties of the Infinite Dimensional Hubbard Model,"Results for the optical conductivity and resistivity of the Hubbard model in
infinite spatial dimensions are presented. At half filling we observe a gradual
crossover from a normal Fermi-liquid with a Drude peak at $\omega=0$ in the
optical conductivity to an insulator as a function of $U$ for temperatures
above the antiferromagnetic phase transition. When doped, the ``insulator''
becomes a Fermi-liquid with a corresponding temperature dependence of the
optical conductivity and resistivity. We find a $T^2$-coefficient in the low
temperature resistivity which suggests that the carriers in the system acquire
a considerable mass-enhancement due to the strong local correlations. At high
temperatures, a crossover into a semi-metallic regime takes place.",9208002v1
1997-12-05,Spin flip scattering in magnetic junctions,"Processes which flip the spin of an electron tunneling in a junction made up
of magnetic electrodes are studied. It is found that: i) Magnetic impurities
give a contribution which increases the resistance and lowers the
magnetoresistance, which saturates at low temperatures. The conductance
increases at high fields. ii) Magnon assisted tunneling reduces the
magnetoresistance as $T^{3/2}$, and leads to a non ohmic contribution to the
resistance which goes as $V^{3/2}$, iii) Surface antiferromagnetic magnons,
which may appear if the interface has different magnetic properties from the
bulk, gives rise to $T^2$ and $V^2$ contributions to the magnetoresistance and
resistance, respectively, and, iv) Coulomb blockade effects may enhance the
magnetoresistance, when transport is dominated by cotunneling processes.",9712075v1
1998-12-14,Charged impurity scattering limited low temperature resistivity of low density silicon inversion layers,"We calculate within the Boltzmann equation approach the charged impurity
scattering limited low temperature electronic resistivity of low density
$n$-type inversion layers in Si MOSFET structures. We find a rather sharp
quantum to classical crossover in the transport behavior in the $0 - 5$K
temperature range, with the low density, low temperature mobility showing a
strikingly strong non-monotonic temperature dependence, which may qualitatively
explain the recently observed anomalously strong temperature dependent
resistivity in low-density, high-mobility MOSFETs.",9812216v3
2000-02-17,"Strong, Ultra-narrow Peaks of Longitudinal and Hall Resistances in the Regime of Breakdown of the Quantum Hall Effect","With unusually slow and high-resolution sweeps of magnetic field, strong,
ultra-narrow (width down to $100 {\rm \mu T}$) resistance peaks are observed in
the regime of breakdown of the quantum Hall effect. The peaks are dependent on
the directions and even the history of magnetic field sweeps, indicating the
involvement of a very slow physical process. Such a process and the sharp peaks
are, however, not predicted by existing theories. We also find a clear
connection between the resistance peaks and nuclear spin polarization.",0002267v1
2001-03-28,Microwave Surface Resistance in MgB2,"Measurements of the temperature dependence of the surface resistance at 3 GHz
of 100 micron size grains of MgB_2 separated powder are presented and
discussed. The microwave surface resistance data is compared to experimental
results of Nb, Bi_2Sr_2CaCu_2O_{8+\delta} (BSCCO) and theoretical predictions
of s-wave weak coupling electron-phonon theory (BCS).",0103587v2
2002-10-17,Origin of superconductivity transition broadening in MgB2,"We report resistivity and magnetization of single crystal MgB2, focusing on
the broadening of superconducting (SC) transition in magnetic fields. In-plane
and out-of-plane resistivity indicate that the broadening of superconducting
transition is independent of Lorentz force and that it is merely dependent on
the magnetic field direction. In magnetization, diamagnetic signal begins to
appear at almost the same temperature as the onset temperature of resistivity
transition. These results suggest that the broadening is attributed not to the
surface superconductivity but to the superconducting fluctuation or the
vortex-liquid picture, owing to the short coherence length and the high
transition temperature of MgB2.",0210358v1
2003-03-07,Drift plasma instability near the edge as the origin of the microwave-induced zero-resistance states,"We discuss a possible origin of the recently discovered microwave-induced
zero-resistance states in very-high-electron-mobility two-dimensional electron
systems. We suggest a scenario, in which two mechanisms, bulk and edge,
contribute to the measured photosignal. Zero-resistance states are assumed to
be due to a drift plasma instability, developing {\em near the edge} of the
system under the microwave radiation. The proposed scheme qualitatively agrees
with the microwave power, temperature, frequency, magnetic field, and mobility
dependencies of the measured photosignal.",0303130v1
2003-04-22,Upper critical fields of MgB2 thin films,"Critical fields of four MgB2 thin films with a normal state resistivity
ranging from 5 to 50 mWcm and Tc from 29.5 to 38.8 K were measured up to 28 T.
Hc2(T) curves present a linear behavior towards low temperatures. Very high
critical field values have been found, up to 24 T along the c-axis and 57 T in
the basal plane not depending on the normal state resistivity values. In this
paper, critical fields will be analyzed taking into account the multiband
nature of MgB2; we will show that resistivity and upper critical fields can be
ascribed to different scattering mechanisms.",0304478v1
2004-07-14,Zero-Resistance States Induced by Electromagnetic-Wave Excitation in GaAs/AlGaAs Heterostructures,"We report the detection of novel zero-resistance states induced by
electromagnetic wave excitation in ultra high mobility GaAs/AlGaAs
heterostructure devices, at low magnetic fields, $B$, in the large filling
factor limit. Vanishing resistance is observed in the vicinity of $B =
[4/(4j+1)] B_{f}$, where $B_{f} = 2\pi\textit{f}m^{*}/e$, where m$^{*}$ is the
effective mass, e is the charge, and \textit{f} is the microwave frequency. The
dependence of the effect is reported as a function of \textit{f}, the
temperature, and the power.",0407367v1
2006-04-03,Pulsed versus DC I-V characteristics of resistive manganites,"We report on pulsed and DC I-V characteristics of polycrystalline samples of
three charge-ordered manganites, Pr_{2/3}Ca_{1/3}MnO_3, Pr_{1/2}Ca_{1/2}MnO_3,
Bi_{1/2}Sr_{1/2}MnO_3 and of a double-perovskite Sr_2MnReO_6, in a temperature
range where their ohmic resistivity obeys the Efros-Shklovskii variable range
hopping relation. For all samples, the DC I(V) exhibits at high currents
negative differential resistance and hysteresis, which mask a perfectly ohmic
or a moderately nonohmic conductivity obtained by pulsed measurements. This
demonstrates that the widely used DC I-V measurements are usually misleading.",0604049v1
2006-06-13,Peculiar behavior of the electrical resistivity of MnSi at the ferromagnetic phase transition,"The electrical resistivity of a single crystal of MnSi was measured across
its ferromagnetic phase transition line at ambient and high pressures. Sharp
peaks of the temperature coefficient of resistivity characterize the transition
line. Analysis of these data shows that at pressures to ~0.35 GPa these peaks
have fine structure, revealing a shoulder at ~ 0.5 K above the peak. It is
symptomatic that this structure disappears at pressures higher than ~0.35 GPa,
which was identified earlier as a tricritical point",0606324v1
2006-10-23,Microwave induced negative resistance states in 2D electron gas with periodic modulation,"We study the microwave-induced photoconductivity of a two-dimensional
electron system (2DES) in the presence of a magnetic field and a
two-dimensional modulation. The microwave and Landau contributions are exactly
taken into account, while the periodic potential is treated perturbatively. The
longitudinal resistivity exhibits oscillations, periodic in $\omega /
\omega_c$. Negative resistance states (NRS) develop for sufficiently high
electron mobility and microwave power. This phenomenon appears in a narrow
window region of values of the lattice parameter ($a$), around $a \sim l_B$,
where $l_B$ is the magnetic length. It is proposed that these phenomena may be
observed in artificially fabricated arrays of periodic scatterers at the
interface of ultraclean heterostructures. {73.20.At,05.60.-k, 72.15.Rn}",0610643v1
2002-09-10,"Evolution of Electrical Resistivity, Thermal Conductivity, and Temperature of a solid under the action of Intense Ultrashort Laser pulse","The dynamical properties of Cu in a regime relevant to femtosecond micro
machining are obtained on picosecond time scales using pump-probe reflectivity
study for 100fs, 1015 W cm-2 laser pulses. The electrical resistivity is
obtained by solving Helmoltz equations. The dissipation mechanisms and scaling
laws are obtained in high and low temperature limits. The 'resistivity
saturation' effect in an unexplored regime intermediate to hot plasma and cold
solid is studied in detail. The temperature evolution and thermal conductivity
is obtained in the temporal range 0 to 30ps after the interaction of laser
pulse with solid Cu.",0209037v1
1996-07-12,Flux flow resistivity and vortex viscosity of high-Tc films,"The flux flow regime of high-T$_{\rm c}$ samples of different normal state
resistivities is studied in the temperature range where the sign of the Hall
effect is reversed. The scaling of the vortex viscosity with normal state
resistivity is consistent with the Bardeen-Stephen theory. Estimates of the
influence of possible mechanisms suggested for the sign reversal of the Hall
effect are also given.",9607003v1
2007-05-15,Excitation of MHD waves in magnetized anisotropic cosmologies,"The excitation of cosmological perturbations in an anisotropic cosmological
model and in the presence of a homogeneous magnetic field was studied, using
the resistive magnetohydrodynamic (MHD) equations. We have shown that
fast-magnetosonic modes, propagating normal to the magnetic field grow
exponentially and saturated at high values, due to the resistivity. We also
demonstrate that the jeans-like instabilities are enhanced inside a resistive
and the formation of condensations formed within an anisotropic fluid influence
the growing magnetosonic waves.",0705.2194v1
2007-12-10,Non-local electron transport and cross-resistance peak in NSN heterostructures,"We develop a microscopic theory describing the peak in the temperature
dependence of the non-local resistance of three-terminal NSN devices. This peak
emerges at sufficiently high temperatures as a result of a competition between
quasiparticle/charge imbalance and subgap (Andreev) contributions to the
conductance matrix. Both the height and the shape of this peak demonstrate the
power law dependence on the superconductor thickness $L$ in contrast to the
zero-temperature non-local resistance which decays (roughly) exponentially with
increasing $L$. A similar behavior was observed in recent experiments.",0712.1408v1
2008-10-08,Pressure-induced superconductivity in Iron pnictide compound SrFe2As2,"Electrical resistivity under high pressure have been measured on nominally
pure SrFe2As2 up to 14 GPa. The resistivity drop appeared with increasing
pressure, and we clearly observed zero resistivity. The maximum of
superconducting transition temperature (Tc) is 38 K. The value is corresponding
to the one of optimally doping AFe2As2 (A=Sr, Ba) system with K+ ions at the
A2+ site.",0810.1377v1
2010-12-13,Role of domain wall fluctuations in non-Fermi liquid behavior of metamagnets,"We study resistivity temperature dependence of a three dimensional metamagnet
near the metamagnet phase transition point in the case when magnetic structure
tends to split into regions with high and low magnetization. We show that in
the case of weak pinning the spin relaxation time of domain wall is much larger
than that of the volume spin fluctuations. This opens a temperature range where
resistivity temperature dependence is determined by scattering of conducting
electrons by the domain wall fluctuations. We show that it leads to
quasi-linear low temperature dependence of resistivity.",1012.2617v2
2011-09-04,Phase diffusion in graphene-based Josephson junctions,"We report on graphene-based Josephson junctions with contacts made from lead.
The high transition temperature of this superconductor allows us to observe the
supercurrent branch at temperatures up to $\sim 2$ K, at which point we can
detect a small, but non-zero, resistance. We attribute this resistance to the
phase diffusion mechanism, which has not been yet identified in graphene. By
measuring the resistance as a function of temperature and gate voltage, we can
further characterize the nature of electromagnetic environment and dissipation
in our samples.",1109.0769v1
2012-12-01,Modeling magnetized neutron stars using resistive MHD,"This work presents an implementation of the resistive MHD equations for a
generic algebraic Ohm's law which includes the effects of finite resistivity
within full General Relativity. The implementation naturally accounts for
magnetic-field-induced anisotropies and, by adopting a phenomenological
current, is able to accurately describe electromagnetic fields in the star and
in its magnetosphere. We illustrate the application of this approach in
interesting systems with astrophysical implications; the aligned rotator
solution and the collapse of a magnetized rotating neutron star to a black
hole.",1212.0130v1
2013-06-29,On the beneficial role of noise in resistive switching,"We study the effect of external noise on resistive switching. Experimental
results on a manganite sample are presented showing that there is an optimal
noise amplitude that maximizes the contrast between high and low resistive
states. By means of numerical simulations, we study the causes underlying the
observed behavior. We find that experimental results can be related to general
characteristics of the equations governing the system dynamics.",1307.0143v1
2015-01-22,Tests of a Novel Design of Resistive Plate Chambers,"A novel design of Resistive Plate Chambers (RPCs), using only a single
resistive plate, is being proposed. Based on this design, two large size
prototype chambers were constructed and were tested with cosmic rays and in
particle beams. The tests confirmed the viability of this new approach. In
addition to showing an improved single-particle response compared to the
traditional 2-plate design, the novel chambers also prove to be suitable for
calorimetric applications.",1501.05907v2
2015-10-12,Radiation-assisted magnetotransport in two-dimensional electron gas systems: appearance of zero resistance states,"Zero-Resistance States (ZRS) are normally associated with superconducting and
quantum Hall phases. Experimental detection of ZRS in two-dimensional electron
gas (2DEG) systems irridiated by microwave(MW) radiation in a magnetic field
has been quite a surprise. We develop a semiclassical transport formalism to
explain the phenomena. We find a sequence of Zero-Resistance States (ZRS)
inherited from the suppression of Shubnikov-de Haas (SdH) oscillations under
the influence of high-frequency and large amplitude microwave radiation.
Furthermore, the ZRS are well pronounced and persist up to broad intervals of
magnetic field as observed in experiments on microwave illuminated 2DEG
systems.",1510.03187v1
2016-06-27,"Characterization of Methicillin-resistant Staphylococcus aureus Isolates from Fitness Centers in Memphis Metropolitan Area, USA","Indoor skin-contact surfaces of public fitness centers may serve as
reservoirs of potential human transmission of methicillin-resistant
Staphylococcus aureus (MRSA). We found a high prevalence of multi-drug
resistant (MDR)-MRSA of CC59 lineage harboring a variety of extracellular toxin
genes from surface swab samples collected from inanimate surfaces of fitness
centers in Memphis metropolitan area, USA. Our findings underscore the role of
inanimate surfaces as potential sources of transmission of MDR-MRSA strains
with considerable genetic diversity.",1606.08377v1
2017-08-18,Map-based cloning of the gene Pm21 that confers broad spectrum resistance to wheat powdery mildew,"Common wheat (Triticum aestivum L.) is one of the most important cereal
crops. Wheat powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is
a continuing threat to wheat production. The Pm21 gene, originating from
Dasypyrum villosum, confers high resistance to all known Bgt races and has been
widely applied in wheat breeding in China. In this research, we identify Pm21
as a typical coiled-coil, nucleotide-binding site, leucine-rich repeat gene by
an integrated strategy of resistance gene analog (RGA)-based cloning via
comparative genomics, physical and genetic mapping, BSMV-induced gene silencing
(BSMV-VIGS), large-scale mutagenesis and genetic transformation.",1708.05475v1
2021-04-27,Unified description of resistivity and thermopower of Pr$_2$Ir$_2$O$_7$: possible influence of crystal field excitation in a Kondo lattice,"We present experimental evidence of incoherent Kondo scattering as the source
of resistivity minima in bulk polycrystalline and nanocrystalline
Pr$_2$Ir$_2$O$_7$. The temperature dependence of thermopower shows a positive
maximum at high temperature followed by a negative minimum at low temperature,
with the sign inversion occurring at a much higher temperature than $T_K$.
Moreover, we observe little correlation between TK and intersite coupling
strength given by $\theta_{CW}$. We describe the temperature dependence of
thermopower and resistivity within the framework of crystal field excitation in
a Kondo lattice.",2105.05149v1
2022-05-03,On the problem of projectile motion in a medium with quadratic resistance,"A classic problem of the motion of a projectile thrown at an angle to the
horizon in a medium with a quadratic resistance law is studied. An approximate
analytical solution of the equations of projectile motion is presented, which
has a high accuracy. The proposed formulas are universal, that is, they can be
used for any initial conditions of throwing over a wide range of the change of
medium resistance coefficient. The motion of a shuttlecock of badminton,
bullet, table tennis ball and volleyball are presented as examples.",2205.01564v1
2013-08-15,Structural and optical investigations of the iron-chalcogenide superconductor Fe$_{1.03}$Se$_{0.5}$Te$_{0.5}$ under high pressure,"Iron-chalcogenide superconductor Fe$_{1.03}$Se$_{0.5}$Te$_{0.5}$ has been
investigated under high pressure using synchrotron based x-ray diffraction and
mid-infrared reflectance measurements at room temperature. Pressure dependence
of the superconducting transition temperature (T$_c$) of the same sample has
been determined by temperature-dependent resistance measurements up to 10 GPa.
Although the high pressure orthorhombic phase ($\textit{Pbnm}$) starts emerging
at 4 GPa, structural transition becomes clearly observable above 10 GPa. A
strong correlation is observed between the Fe(Se,Te)$_{4}$ tetrahedral
deformation in the tetragonal phase ($\textit{P4/nmm}$) and the sharp rise of
T$_c$ up to $\sim$4 GPa, above which T$_c$ is found to be almost pressure
independent at least up to 10 GPa. A subtle structural modification of the
tetragonal phase is noticed above 10 GPa, suggesting a structural transition
with possible Fe$^{2+}$ spin-state transition. The evolution with pressure of
the optical conductivity shows that the Drude term increases systematically
with pressure up to 5.4 GPa, indicating the evolution of the tetragonal phase
towards a conventional metallic state. At further higher pressures the Drude
term reduces drastically implying a poor metallic character of the high
pressure orthorhombic phase. Our results suggest that occurrence of large onset
T$_c$ above 4 GPa is due to a systematic increase of high pressure orthorhombic
phase fraction.",1308.3367v1
2016-07-11,High pressure studies on properties of FeGa3: role of on-site coulomb correlation,"High pressure X-ray diffraction measurements have been carried out on the
intermetallic semiconductor FeGa$_3$ and the equation of state for FeGa$_3$ has
been determined. First principles based DFT calculations within the GGA
approximation indicate that although the unit cell volume matches well with the
experimentally obtained value at ambient pressure, it is significantly
underestimated at high pressures and the difference between them increases as
pressure increases. GGA + U calculations with increasing values of U$_{Fe(3d)}$
(on-site Coulomb repulsion between the Fe 3d electrons) at high pressures,
correct this discrepancy. Further, the GGA+U calculations also show that along
with U$_{Fe(3d)}$, the Fe 3d band width also increases with pressure and around
a pressure of 4 GPa, a small density of states appear at the Fermi level. High
pressure resistance measurements carried out on FeGa$_3$ also clearly show a
signature of an electronic transition. Beyond the pressure of 19.7 GPa, the
diffraction peaks reduce in intensity and are not observable beyond $\sim$ 26
GPa, leading to an amorphous state.",1607.02905v2
2016-10-24,Deep Reactive Ion Etched Anti-Reflection Coatings for Sub-millimeter Silicon Optics,"Refractive optical elements are widely used in millimeter and sub-millimeter
astronomical telescopes. High resistivity silicon is an excellent material for
dielectric lenses given its low loss-tangent, high thermal conductivity and
high index of refraction. The high index of refraction of silicon causes a
large Fresnel reflectance at the vacuum-silicon interface (up to 30%), which
can be reduced with an anti-reflection (AR) coating. In this work we report
techniques for efficiently AR coating silicon at sub-millimeter wavelengths
using Deep Reactive Ion Etching (DRIE) and bonding the coated silicon to
another silicon optic. Silicon wafers of 100 mm diameter (1 mm thick) were
coated and bonded using the Silicon Direct Bonding technique at high
temperature (1100 C). No glue is used in this process. Optical tests using a
Fourier Transform Spectrometer (FTS) show sub-percent reflections for a
single-layer DRIE AR coating designed for use at 320 microns on a single wafer.
Cryogenic (10 K) measurements of a bonded pair of AR-coated wafers also reached
sub-percent reflections. A prototype two-layer DRIE AR coating to reduce
reflections and increase bandwidth is presented and plans for extending this
approach are discussed.",1610.07655v1
2020-03-09,CACTUS: A depleted monolithic active timing sensor using a CMOS radiation hard technology,"The planned luminosity increase at the Large Hadron Collider in the coming
years has triggered interest in the use of the particles' time of arrival as
additional information in specialized detectors to mitigate the impact of
pile-up. The required time resolution is of the order of tens of picoseconds,
with a spatial granularity of the order of 1 mm. A time measurement at this
precision level will also be of interest beyond the LHC and beyond high energy
particle physics. We present in this paper the first developments towards a
radiation hard Depleted Monolithic Active Pixel Sensor (DMAPS), with
high-resolution time measurement capability. The technology chosen is a
standard high voltage CMOS process, in conjunction with a high resistivity
detector material, which has already proven to efficiently detect particles in
tracking applications after several hundred of Mrad of irradiation.",2003.04102v4
2019-02-23,Pixel detector R&D for the Compact Linear Collider,"The physics aims at the proposed future CLIC high-energy linear $e^+ e^-$
collider pose challenging demands on the performance of the detector system. In
particular the vertex and tracking detectors have to combine precision
measurements with robustness against the expected high rates of beam-induced
backgrounds. A spatial resolution of a few microns and a material budget down
to 0.2\% of a radiation length per vertex-detector layer have to be achieved
together with a few nanoseconds time stamping accuracy. These requirements are
addressed with innovative technologies in an ambitious detector R\&D programme,
comprising hardware developments as well as detailed device and Monte Carlo
simulations based on TCAD, Geant4 and Allpix-Squared. Various fine pitch hybrid
silicon pixel detector technologies are under investigation for the CLIC vertex
detector. The CLICpix and CLICpix2 readout ASICs with \SI{25}{\micro\meter}
pixel pitch have been produced in a \SI{65}{\nano\meter} commercial CMOS
process and bump-bonded to planar active edge sensors as well as capacitively
coupled to High-Voltage (HV) CMOS sensors. Monolithic silicon tracking
detectors are foreseen for the large surface ($\approx$
\SI{140}{\meter\squared}) CLIC tracker. Fully monolithic prototypes are
currently under development in High-Resistivity (HR) CMOS, HV-CMOS and Silicon
on Insulator (SOI) technologies. The laboratory and beam tests of all recent
prototypes profit from the development of the CaRIBou universal readout system.
This talk presents an overview of the CLIC pixel-detector R\&D programme,
focusing on recent test-beam and simulation results.",1902.08752v4
2017-05-30,Structural evolution of CO2 filled pure silica LTA zeolite under high-pressure high-temperature conditions,"The crystal structure of CO2 filled pure SiO2 LTA zeolite has been studied at
high pressures and temperatures using synchrotron based x ray powder
diffraction. Its structure consists of 13 CO2 guest molecules, 12 of them
accommodated in the large alpha cages and 1 in the beta cages, giving a
SiO2:CO2 stoichiometric ratio smaller than 2. The structure remains stable
under pressure up to 20 GPa with a slight pressure dependent rhombohedral
distortion, indicating that pressure induced amorphization is prevented by the
insertion of guest species in this open framework. The ambient-temperature
lattice compressibility has been determined. In situ high pressure resistive
heating experiments up to 750 K allow us to estimate the thermal expansivity at
5 GPa. Our data confirm that the insertion of CO2 reverses the negative thermal
expansion of the empty zeolite structure. No evidence of any chemical reaction
was observed. The possibility of synthesizing a silicon carbonate at high
temperatures and higher pressures is discussed in terms of the evolution of C-O
and Si-O distances between molecular and framework atoms.",1705.10507v1
2018-08-22,Record-High Superconductivity in Niobium-Titanium Alloy,"Here we report the observation of extraordinary superconductivity in a
pressurized commercial niobium-titanium alloy. We find that its zero-resistance
superconductivity persists from ambient pressure to the pressure as high as
261.7 GPa, a record high pressure up to which a known superconducting state can
continuously survives. Remarkably, at such an ultra-high pressure, although the
ambient pressure volume is shrunk by 45% without structural phase transition,
the superconducting transition temperature (TC) increases to ~19.1 K from ~9.6
K, and the critical magnetic field (HC2) at 1.8 K has been enhanced to 19 T
from 15.4 T. These results set new records for both of the TC and the HC2 among
all the known alloy superconductors composed of only transition metal elements.
The remarkable high pressure superconducting properties observed in the NbTi
alloy not only expand our knowledge on this important commercial superconductor
but also are helpful for a better understanding on the superconducting
mechanism.",1808.07215v3
2022-09-02,Ultra-Low Temperature Li/CFx Batteries Enabled by Fast-transport and Anion-pairing Liquefied Gas Electrolytes,"Lithium fluorinated carbon is one of the most promising chemistries for
high-energy-density primary energy storage systems in applications where
rechargeability is not required. Though Li/CFx demonstrates high energy density
under ambient conditions, achieving such a high energy density when exposed to
subzero temperatures remains a challenge, particularly under high current
density. Here, we report a liquefied gas electrolyte with an anion-pair
solvation structure based on dimethyl ether with a low melting point and low
viscosity, leading to high ionic conductivity between a wide temperature range.
Besides that, through systematic X-ray photoelectron spectroscopy integrated
with transmission electron microscopy characterizations, we evaluate the
interface of CFx for low-temperature performance. We conclude that the fast
transport and anion-pairing solvation structure of the electrolyte bring about
reduced charge transfer resistance at low temperatures, which resulted in
significantly enhanced performance of Li/CFx cells. Utilizing 50 mg/cm2 loading
electrodes, the Li/CFx still displayed 1530 Wh/kg at reduced temperature. This
work provides insights into the electrolyte design that may overcome the
operational limits of batteries in extreme environments.",2209.02409v1
2023-03-09,Superconductivity above 70 K observed in lutetium polyhydrides,"The binary polyhydrides of heavy rare earth lutetium that shares a similar
valence electron configuration to lanthanum have been experimentally discovered
to be superconductive. The lutetium polyhydrides were successfully synthesized
at high pressure and high temperature conditions using a diamond anvil cell in
combinations with the in-situ high pressure laser heating technique. The
resistance measurements as a function of temperature were performed at the same
pressure of synthesis in order to study the transitions of superconductivity
(SC). The superconducting transition with a maximum onset temperature (Tc) 71 K
was observed at pressure of 218 GPa in the experiments. The Tc decreased to 65
K when pressure was at 181 GPa. From the evolution of SC at applied magnetic
fields, the upper critical field at zero temperature {\mu}0Hc2(0) was obtained
to be ~36 Tesla. The in-situ high pressure X-ray diffraction experiments imply
that the high Tc SC should arise from the Lu4H23 phase with Pm-3n symmetry that
forms a new type of hydrogen cage framework different from those reported for
previous light rare earth polyhydride superconductors.",2303.05117v3
2023-04-04,Ultrathin Stable Ohmic Contacts for High-Temperature Operation of $β$-Ga$_2$O$_3$ Devices,"Beta gallium oxide ($\beta$-Ga$_2$O$_3$) shows significant promise in the
high-temperature, high-power, and sensing electronics applications. However,
long-term stable metallization layers for Ohmic contacts at high temperature
present unique thermodynamic challenges. The current most common Ohmic contact
design based on 20 nm of Ti has been repeatedly demonstrated to fail at even
moderately elevated temperatures (300-400$^{\circ}$C) due to a combination of
non-stoichiometric Ti/Ga$_2$O$_3$ interfacial reactions and kinetically favored
Ti diffusion processes. Here we demonstrate stable Ohmic contacts for
Ga$_2$O$_3$ devices operating up to 500-600$^{\circ}$C using ultrathin Ti
layers with a self-limiting interfacial reaction. The ultrathin Ti layer in the
5nm Ti / 100nm Au contact stack is designed to fully oxidize while forming an
Ohmic contact, thereby limiting both thermodynamic and kinetic instability.
This novel contact design strategy results in an epitaxial conductive anatase
titanium oxide interface layer that enables low-resistance Ohmic contacts that
are stable both under long-term continuous operation (>500 hours) at
600$^{\circ}$C in vacuum ($\leq$ 10$^{-4}$ Torr), as well as after repeated
thermal cycling (15 times) between room temperature and 550$^{\circ}$C in
flowing N$_2$. This stable Ohmic contact design will accelerate the development
of high-temperature devices by enabling research focus to shift towards
rectifying contacts and other interfacial layers.",2304.02161v1
2023-07-31,Coexistence of Superconductivity and ferromagnetism in high entropy carbide ceramics,"Generally, the superconductivity was expected to be absent in magnetic
systems, but this reception was disturbed by unconventional superconductors,
such as cuprates, iron-based superconductors and recently discovered nickelate,
since their superconductivity is proposed to be related to the
electron-electron interaction mediated by the spin fluctuation. However, the
coexistence of superconductivity and magnetism is still rare in conventional
superconductors. In this work, we reported the coexistence of these two quantum
orderings in high entropy carbide ceramics (Mo0.2Nb0.2Ta0.2V0.2W0.2)C0.9,
(Ta0.25Ti0.25Nb0.25Zr0.25)C, and they are expected to be conventional
superconductors. Clear magnetic hysteresis loop was observed in these high
entropy carbides, indicating a ferromagnetic ground state. A sharp
superconducting transition is observed in (Mo0.2Nb0.2Ta0.2V0.2W0.2)C0.9 with a
Tc of 3.4 K and upper critical field of ~3.35 T. Meanwhile, superconductivity
is suppressed to some extent and zero-resistance state disappears in
(Ta0.25Ti0.25Nb0.25Zr0.25)C, in which stronger magnetism is presented. The
upper critical field of (Ta0.25Ti0.25Nb0.25Zr0.25)C is only ~1.5 T, though they
show higher transition temperature near 5.7 K. The ferromagnetism stems from
the carbon vacancies which occurs often during the high temperature synthesis
process. This work not just demonstrate the observation of superconductivity in
high entropy carbide ceramics, but also provide alternative exotic platform to
study the correlation between superconductivity and magnetism, and is of great
benefit for the design of multifunctional electronic devices.",2307.16438v1
2023-09-09,High-speed metasurface modulator using critically coupled bimodal plasmonic resonance,"Free-space electro-optic (EO) modulators operating at gigahertz and beyond
are attractive for a wide range of emerging applications, including high-speed
imaging, free-space optical communication, microwave photonics, and diffractive
computing. Here we experimentally demonstrate a high-speed plasmonic
metasurface EO modulator operating at a near-infrared wavelength range with a
gigahertz modulation bandwidth. To achieve efficient intensity modulation of
reflected light from an ultrathin metasurface layer, we utilize the bimodal
plasmonic resonance inside a subwavelength metal-insulator-metal grating, which
is precisely tuned to satisfy the critical coupling condition. As a result,
perfect absorption of -27 dB (99.8%) and a high quality (Q) factor of 113 are
obtained at a resonant wavelength of 1650 nm. By incorporating an EO polymer
inside the grating, we achieve a modulation depth of up to 9.5 dB under an
applied voltage of $\pm$30 V. The 3-dB modulation bandwidth is confirmed to be
1.25 GHz, which is primarily limited by the undesired contact resistance. Owing
to the high electrical conductivity of metallic gratings and a compact device
structure with a minimal parasitic capacitance, the demonstrated device can
potentially operate at several tens of gigahertz, which opens up exciting
opportunities for ultrahigh-speed active metasurface devices in various
applications.",2309.04835v1
2000-07-10,"Comment on ""Microwave vortex dissipation of superconducting Nd-Ce-Cu-O epitaxial films in high magnetic fields""","While the electrodynamic treatment of a superconducting thin film by Yeh et
al. [Phys. Rev. B 48, 9861 (1993)] ostensibly has application for the
""thin-film limit,"" their work is shown to employ bulk-like instead of thin-film
electrodynamics, and as such obtains an ostensible violation of the first law
of thermodynamics and a surface resistance independent of the resistivity.
Other theoretical and experimental difficulties are briefly noted.",0007167v1
2000-10-27,Negative differential resistance in nanotube devices,"Carbon nanotube junctions are predicted to exhibit negative differential
resistance, with very high peak-to-valley current ratios even at room
temperature. We treat both nanotube p-n junctions and undoped
metal-nanotube-metal junctions, calculating quantum transport through the
self-consistent potential within a tight-binding approximation. The undoped
junctions in particular may be suitable for device integration.",0010456v1
2002-05-20,Resistive Transition Equation of Mixed State,"We present a microscopic derivation of the resistive transition equation for
mixed state of superconductors. This form fits the experimental data of MgB2
with parameters in agreement with the prediction of BCS superconductivity. It
also fits the experimental data of high quality untwined YBCO single crystal
but with parameters somewhat different from the BCS prediction. A discussion in
connection with the problem of cuprate superconductivity is given.",0205407v1
2005-04-08,Photo-excited zero-resistance states in the GaAs/AlGaAs system,"The microwave-excited high mobility two-dimensional electron system exhibits,
at liquid helium temperatures, vanishing resistance in the vicinity of $B =
[4/(4j+1)] B_{f}$, where $B_{f} = 2\pi\textit{f}m^{*}/e$, m$^{*}$ is an
effective mass, e is the charge, and \textit{f} is the microwave frequency.
Here, we summarize some experimental results.",0504206v1
2009-12-09,2-D MHD Configurations for Accretion Disks Around Magnetized Stars,"We discuss basic features of steady accretion disk morphology around
magnetized compact astrophysical objects. A comparison between the standard
model of accretion based on visco-resistive MHD and the plasma instabilities,
like ballooning modes, triggered by very low value of resistivity, is proposed.",0912.1721v1
2021-06-18,The effect of viscosity and resistivity on Rayleigh-Taylor instability induced mixing in magnetized high energy density plasmas,"This work numerically investigates the role of viscosity and resistivity on
Rayleigh-Taylor instabilities in magnetized high-energy-density (HED) plasmas
for a high Atwood number and high plasma beta regimes surveying across plasma
beta and magnetic Prandtl numbers. The numerical simulations are performed
using the visco-resistive magnetohydrodynamic (MHD) equations. Results
presented here show that the inclusion of self-consistent viscosity and
resistivity in the system drastically changes the growth of the Rayleigh-Taylor
instability (RTI) as well as modifies its internal structure at smaller scales.
It is seen here that the viscosity has a stabilizing effect on the RTI.
Moreover, the viscosity inhibits the development of small scale structures and
also modifies the morphology of the tip of the RTI spikes. On the other hand,
the resistivity reduces the magnetic field stabilization supporting the
development of small scale structures. The morphology of the RTI spikes is seen
to be unaffected by the presence of resistivity in the system. An additional
novelty of this work is in the disparate viscosity and resistivity profiles
that may exist in HED plasmas and their impact on RTI growth, morphology, and
the resulting turbulence spectra. Furthermore, this work shows that the
dynamics of the magnetic field is independent of viscosity and likewise the
resistivity does not affect the dissipation of enstrophy and kinetic energy. In
addition, power-law scalings of enstrophy, kinetic energy, and magnetic field
energy are provided in both injection range and inertial sub-range which could
be useful for understanding RTI induced turbulent mixing in HED laboratory and
astrophysical plasmas and could aid in the interpretation of observations of
RTI-induced turbulence spectra.",2106.10391v2
2003-03-20,Current-induced phase control in charged-ordered Nd0.5Ca0.5MnO3 and Pr0.6Ca0.4MnO3 crystals,"Single crystals of Nd0.5Ca0.5MnO3 and Pr0.6Ca0.4MnO3 show current-induced
insulator-metal transitions at low temperatures. In addition, the
charge-ordering transition temperature decreases with increasing current. The
electroresistive ratio, defined as r0.5/rI where r0.5 is the resistivity at a
current of 0.5 mA and rI the resistivity at a given applied current, I, varies
markedly with temperature and the value of I. Thermal hysteresis observed in
Nd0.5Ca0.5MnO3 and Pr0.6Ca0.4MnO3 at the insulator-metal transition indicates
that the transition is first-order. The current-induced changes are comparable
to those induced by magnetic fields, and the insulator-metal transition in
Pr0.6Ca0.4MnO3 is accordingly associated with a larger drop in resistivity.",0303407v1
2003-07-22,Temperature Dependence of Resistivity of $Sr_2CoMoO_{6-δ}$ Films,"We investigate the temperature dependence of the resistivity and
magnetoresistance of a polycrystalline $Sr_2CoMoO_{6-\delta}$ film deposited on
(100)-$SrTiO_3$ substrate prepared by the pulsed laser deposition method. X-ray
diffraction, Raman and magnetoresistance results demonstrate clearly the
coexistence of a ferromagnetic metallic and an antiferromagnetic (or
paramagnetic) insulating domain. Percolative transition between these two
phases as the temperature varies, which is believed to induce a metal-insulator
transition at around $T_C$, has been directly observed in our measurements of
the temperature dependence of the sample resistivity. Thus we have provided new
direct evidence that a phase separation scenario also exists in the ordered
double-perovskite structure materials.",0307527v2
2005-02-13,Transport properties in correlated systems: An analytical model,"Several studies have so far investigated transport properties of strongly
correlated systems. Interesting features of these materials are the lack of
resistivity saturation well beyond the Mott-Ioffe-Regel limit and the scaling
of the resistivity with the hole density in underdoped cuprates. Due to the
strongly correlated nature of these materials, mainly numerical techniques have
been employed. A key role in this regards is thought to be played by the
continuous transfer of spectral weight from coherent to incoherent states. In
this paper we employ a simple analytical expression for the electronic Green's
function to evaluate both quasi-particle and transport properties in correlated
systems. Our analytical approach permits to enlighten the specific role of the
spectral transfer due to the correlation on different features. In particular
we investigate the dependence of both quasi-particle and transport scattering
rate on the correlation degree and the criterion for resistivity saturation.
systems.",0502297v3
2005-08-05,Is ZrB12 two gap superconductor?,"We report the measurements of the temperature dependence of the resistivity,
\rho(T), magnetic penetration depth,\lambda(T) the lower, Hc1(T), and upper,
Hc2(T), critical magnetic fields, for single crystals of dodecaboride ZrB12,
diboride ZrB2 and thin films of diboride MgB2. We observe a number of
deviations from conventional behavior in these materials. Although ZrB12
behaves like a simple metal in the normal state, the resistive Debye
temperature, 300 K, is three times smaller relative to that (800-1200 K)
calculated from the specific heat, C(T), data. We observe predominantly
quadratic temperature behavior of resistivity in ZrB12 below 25 K, and in ZrB2
below 100 K, indicating the possible importance of the electron-electron
interaction in these borides. Superfluid density of ZrB12 displays
unconventional temperature dependence with pronounced shoulder at T/Tc equal to
0.65. Contrary to conventional theories we found a linear temperature
dependence of Hc2(T) for ZrB12 from Tc down to 0.35 K. We suggest that both
\lambda(T) and Hc2(T) dependencies in ZrB12 can be explained by two band BCS
model with different superconducting gap and Tc.",0508151v2
2005-10-05,Equipartition of Current in Parallel Conductors on Cooling Through the Superconducting Transition,"Our experiments show that for two or more pieces of a wire, of different
lengths in general, combined in parallel and connected to a dc source, the
current ratio evolves towards unity as the combination is cooled to the
superconducting transition temperature Tc, and remains pinned at that value
below it. This re-distribution of the total current towards equipartition
without external fine tuning is a surprise. It can be physically understood in
terms of a mechanism that involves the flux-flow resistance associated with the
transport current in a wire of type-II superconducting material. It is the fact
that the flux-flow resistance increases with current that drives the current
division towards equipartition.",0510099v3
2006-04-06,Giant magneto-impedance in Ag-doped La0.7Sr0.3MnO3,"The resistive and reactive parts of the magneto-impedance of sintered
ferromagnetic samples of La0.7Sr0.3-xAgxMnO3 (x = 0.05, 0.25) have been
measured at room temperature (<Tc) over frequency interval 1KHz to 15MHz and in
presence of magnetic field up to 4KOe. The field dependence of relative change
in resistance is small in KHz region but increases strongly for higher
frequency of excitation. The maximum value of relative change in resistance at
H =4KOe was found to be around 70% at 15MHz frequency.On the contrary the
corresponding change in reactance has less frequency sensitivity and the
maximum occurs at 1MHz frequency. The magneto-impedance is negative for all
frequencies. The 'normalized magneto-impedance' as defined by
[Z(H)-Z(0)]/[Z(0)-Z(4K)] when plotted against scaled field H/H1/2 is found to
be frequency independent ; H1/2 is the field where 'normalized
magneto-impedance' is reduced to half its maximum. A phenomenological formula
for magneto-impedance Z (H) in ferromagnetic material is proposed based on Pade
approximant. The formula for Z (H) predicts the scaled behavior of 'normalized
magneto-impedance'.",0604181v3
2007-09-12,Thermal Design of Power Semiconductor Modules for Mobile Communication Systems,"We will describe the thermal performance of power semiconductor module, which
consists of hetero-junction bipolar transistors (HBTs), for mobile
communication systems. We calculate the thermal resistance between the HBT
fingers and the bottom surface of a multi-layer printed circuit board (PCB)
using a finite element method (FEM). We applied a steady state analysis to
evaluate the influence of design parameters on thermal resistance of the
module. We found that the thickness of GaAs substrate, the thickness of
multi-layer circuit board, the thermal conductivity of bonding material under
GaAs substrate, and misalignment of thermal vias between each layer of PCB are
the dominant parameter in thermal resistance of the module.",0709.1879v1
2007-09-26,Influence of Zeeman splitting and thermally excited polaron states on magneto-electrical and magneto-thermal properties of magnetoresistive polycrystalline manganite La_{0.8}Sr_{0.2}MnO_3,"Some possible connection between spin and charge degrees of freedom in
magneto-resistive manganites is investigated through a thorough experimental
study of the magnetic (AC susceptibility and DC magnetization) and transport
(resistivity and thermal conductivity) properties. Measurements are reported in
the case of well characterized polycrystalline La_{0.8}Sr_{0.2}MnO_3 samples.
The experimental results suggest rather strong field-induced polarization
effects in our material, clearly indicating the presence of ordered FM regions
inside the semiconducting phase. Using an analytical expression which fits the
spontaneous DC magnetization, the temperature and magnetic field dependences of
both electrical resistivity and thermal conductivity data are found to be well
reproduced through a universal scenario based on two mechanisms: (i) a
magnetization dependent spin polaron hopping influenced by a Zeeman splitting
effect, and (ii) properly defined thermally excited polaron states which have
to be taken into account in order to correctly describe the behavior of the
less conducting region. Using the experimentally found values of the magnetic
and electron localization temperatures, we obtain L=0.5nm and m_p=3.2m_e for
estimates of the localization length (size of the spin polaron) and effective
polaron mass, respectively.",0709.4210v1
2008-11-12,Slow Dynamics in Hard Condensed Matter: A Case Study of the Phase Separating System NdNiO$_3$,"We report the time dependent response of electrical resistivity in the
non-magnetic perovskite oxide NdNiO$_3$ in its phase separated state and
provide a physical explanation of the observations. We also model the system
and do an accurate Monte Carlo simulation of the observed behavior. While
cooling a phase separation takes place in this system below its metal-insulator
transition temperature and in this state the material exhibits various
dynamical phenomena such as relaxation of resistivity, dependence of
resistivity on cooling rate and rejuvenation of the material after ageing.
These phenomena signal that the phase separated state of NdNiO$_3$ is not in
thermodynamic equilibrium and we conjecture that it consists of supercooled
paramagnetic metallic and antiferromagnetic insulating phases. The supercooled
phases are metastable and they switch over to the insulating equilibrium state
stochastically and this can account for the slow dynamics observed in our
system. We also verify the predictive power of our model by simulating the
result of a new experiment and confirming it by actual measurements.",0811.1836v1
2009-04-06,Superconductivity in Ti-doped Iron-Arsenide Compound Sr4Cr0.8Ti1.2O6Fe2As2,"Superconductivity was achieved in Ti-doped iron-arsenide compound
Sr4Cr0.8Ti1.2O6Fe2As2 (abbreviated as Cr-FeAs-42622). The x-ray diffraction
measurement shows that this material has a layered structure with the space
group of \emph{P4/nmm}, and with the lattice constants a = b = 3.9003 A and c =
15.8376 A. Clear diamagnetic signals in ac susceptibility data and
zero-resistance in resistivity data were detected at about 6 K, confirming the
occurrence of bulk superconductivity. Meanwhile we observed a superconducting
transition in the resistive data with the onset transition temperature at 29.2
K, which may be induced by the nonuniform distribution of the Cr/Ti content in
the FeAs-42622 phase, or due to some other minority phase.",0904.0972v3
2010-01-15,"Domain Wall Resistance in Perpendicular (Ga,Mn)As: dependence on pinning","We have investigated the domain wall resistance for two types of domain walls
in a (Ga,Mn)As Hall bar with perpendicular magnetization. A sizeable positive
intrinsic DWR is inferred for domain walls that are pinned at an etching step,
which is quite consistent with earlier observations. However, much lower
intrinsic domain wall resistance is obtained when domain walls are formed by
pinning lines in unetched material. This indicates that the spin transport
across a domain wall is strongly influenced by the nature of the pinning.",1001.2631v2
2010-11-03,A semiquantitative approach to the impurity-band-related transport properties of GaMnAs nanolayers,"We investigate the spin-polarized transport of GaMnAs nanolayers in which a
ferromagnetic order exists below a certain transition temperature. Our
calculation for the self-averaged resistivity takes into account the existence
of an impurity band determining the extended (""metallic"" transport) or
localized (hopping by thermal excitation) nature of the states at and near the
Fermi level. Magnetic order and resistivity are inter-related due to the
influence of the spin polarization of the impurity band and the effect of the
Zeeman splitting on the mobility edge. We obtain, for a given range of Mn
concentration and carrier density, a ""metallic"" behavior in which the transport
by extended carriers dominates at low temperature, and is dominated by the
thermally excited localized carriers near and above the transition temperature.
This gives rise to a conspicuous hump of the resistivity which has been
experimentally observed and brings light onto the relationship between
transport and magnetic properties of this material.",1011.1006v1
2011-06-30,The effect of changing electrode metal on solution-processed flexible titanium dioxide memristors,"Flexible solution processed memristors show different behaviour dependent on
the choice of electrode material. Use of gold for both electrodes leads to
switchable WORM (Write Once Read Many times) resistive devices. Use of
aluminium for both electrodes increases the richness of behaviour allowing both
curved and triangular memristive switching resistance memories. A comparison
device with an aluminium bottom electrode and gold top electrode only exhibited
significant memristive resistance switching when the aluminium electrode was
the cathode, suggesting that the electrode is acting as a source/sink of oxygen
anions. When the gold electrode was the cathode this electrode was deformed by
oxygen evolution. These results demonstrate that aluminium is helpful for
stabilising and promoting memristive behaviour in sol-gel TiO$_2$ devices and
that changing electrodes from aluminium to gold creates fundamentally different
device characteristics.",1106.6293v2
2011-12-12,Realization of the Switching Mechanism in Resistance Random Access Memory (RRAMTM) Devices: Structural and Electronic Properties Affecting Electron Conductivity in Halfnium Oxide-Electrode System through First Principles Calculations,"Resistance Random Access Memory (RRAMTM) device, with its electrically
induced nanoscale resistive switching capacity, has been gaining considerable
attention as future non-volatile memory device. Here, we propose a mechanism of
switching based on oxygen vacancy migration-driven change in electronic
properties of the transition metal oxide (TMO) film stimulated by set pulse
voltages. We used density functional theory (DFT)-based calculations to account
for the effect of oxygen vacancy and its migration on the electronic properties
of HfO2 and Ta/HfO2 systems, and thereby create the entire story on RRAMTM's
switching mechanism. Computational results on the activation energy barrier for
oxygen vacancy migration were found to be consistent with the results of set
and reset pulse voltage obtained from experiment. Understanding of this
mechanism would be beneficial to effectively realize materials design in these
devices.",1112.2500v1
2012-11-21,Low Resistance GaN/InGaN/GaN Tunnel Junctions,"Enhanced interband tunnel injection of holes into a PN junction is
demonstrated using P-GaN/InGaN/N-GaN tunnel junctions with a specific
resistivity of 1.2 X 10-4 {\Omega} cm2. The design methodology and
low-temperature characteristic of these tunnel junctions is discussed, and
insertion into a PN junction device is described. Applications of tunnel
junctions in III-nitride optoelectronics devices are explained using energy
band diagrams. The lower band gap and polarization fields reduce tunneling
barrier, eliminating the need for ohmic contacts to p-type GaN. This
demonstration of efficient tunnel injection of carriers in III-Nitrides can
lead to a replacement of existing resistive p-type contact material in light
emitters with tunneling contact layers, requiring very little metal footprint
on the surface, resulting in enhanced light extraction from top emitting
emitters.",1211.4905v2
2013-06-04,Bipolar electrical switching in metal-metal contacts,"Electrical switching has been observed in carefully designed
metal-insulator-metal devices built at small geometries. These devices are also
commonly known as memristors and consist of specific materials such as
transition metal oxides, chalcogenides, perovskites, oxides with valence
defects, or a combination of an inert and an electrochemically active
electrode. No simple physical device has been reported to exhibit electrical
switching. We have discovered that a simple point-contact or a granular
arrangement formed of metal pieces exhibits bipolar switching. These devices,
referred to as coherers, were considered as one-way electrical fuses. We have
identified the state variable governing the resistance state and can program
the device to switch between multiple stable resistance states. Our
observations render previously postulated thermal mechanisms for their
resistance-change as inadequate. These devices constitute the missing canonical
physical implementations for memristor, often referred as the fourth passive
element. Apart from the theoretical advance in understanding metallic contacts,
the current discovery provides a simple memristor to physicists and engineers
for widespread experimentation, hitherto impossible.",1306.0942v2
2013-10-08,Mechanism for Radiation Damage Resistance in Yttrium Oxide Dispersion Strengthened Steels,"ODS steels based on yttrium oxide have been suggested as potential fusion
reactor wall materials due to their observed radiation resistance properties.
Presumably this radiation resistance can be related to the interaction of the
particle with vacancies,self-interstitial atoms (SIAs) and other radiation
damage debris. Density functional theory has been used to investigate this at
the atomic scale. Four distinct interfaces, some based on HRTEM observations,
between iron and yttrium oxide were investigated. It is been shown that the
Y$_2$O$_3$-Fe interface acts as a strong trap with long-range attraction for
both interstitial and vacancy defects, allowing recombination without altering
the interface structure. The catalytic elimination of defects without change to
the microstructure explains the improved behaviour of ODS steels with respect
to radiation creep and swelling.",1310.2061v1
2014-02-21,Simultaneous Extraction of Charge Density Dependent Mobility and Variable Contact Resistance from Thin Film Transistors,"A model for the extraction of the charge density dependent mobility and
variable contact resistance in thin film transistors is proposed by performing
a full derivation of the current-voltage characteristics both in the linear and
saturation regime of operation. The calculated values are validated against the
ones obtained from direct experimental methods. This approach allows
unambiguous determination of both contact and channel resistance from the
analysis of the current voltage characteristics of a single device, with no
a-priori assumption on the two parameters. It solves the inconsistencies in the
commonly accepted mobility extraction methods and provides new possibilities
for the analysis of the injection and transport processes in semiconducting
materials.",1402.5241v1
2014-02-22,Influence of gas ambient on charge writing at the LaAlO3/SrTiO3 heterointerface,"We investigated the influences charge writing on the surface work function
and resistance of the LaAlO3/SrTiO3 (LAO/STO) heterointerface in several gas
environments (air, O2, N2, and H2/N2). Charge writing decreased the surface
work function and resistance of the LAO/STO sample quite a lot in air but
slightly in O2.The interface carrier density was extracted from the measured
sheet resistance and compared with that obtained from the proposed
charge-writing mechanisms, such as carrier transfer via surface adsorbates and
surface redox. Such quantitative analyses suggested that additional processes
(e.g., electronic state modification and electrochemical surface reaction) were
required to explain charge writing on the LAO/STO interface.",1402.5479v1
2014-07-07,Influence of surfactants on the electrical resistivity and thermopower of Ni nanoparticles,"Compacted pellets of nanocrystalline nickel (NC-Ni) of average particle size
ranging from 18 to 33 nm were prepared using a variety of surfactants. They
were characterized well and were studied on the influence of the surfactants on
the electrical resistivity and thermopower in the temperature range 5 to 300 K.
It was found that the type of the surfactant used dominates over the average
particle size in their electrical transport and the detail transport behaviors
have been discussed. Moreover, the observed thermopower and resistivity
features were contrasting compared to what are normally seen in the well-known
materials. They are interpreted as indicative of attractive features these
surfactants for the design of nanostructured thermoelectric materials with
enhanced thermoelectric figure of merits.",1407.1705v2
2014-12-15,Antagonistic in-plane resistivity anisotropies from competing fluctuations in underdoped cuprates,"One of the prime manifestations of an anisotropic electronic state in
underdoped cuprates is the in-plane resistivity anisotropy
$\Delta\rho\equiv(\rho_{a}-\rho_{b})/\rho_{b}$. Here we use a
Boltzmann-equation approach to compute the contribution to $\Delta\rho$ arising
from scattering by anisotropic charge and spin fluctuations, which have been
recently observed experimentally. While the anisotropy in the charge
fluctuations is manifested in the correlation length, the anisotropy in the
spin fluctuations emerges only in the structure factor. As a result, we find
that spin fluctuations favor $\Delta\rho>0$, whereas charge fluctuations
promote $\Delta\rho<0$, which are both consistent with the doping dependence of
$\Delta\rho$ observed in YBa$_{2}$Cu$_{3}$O$_{7}$. We also discuss the role
played by CuO chains in these materials, and propose transport experiments in
strained HgBa$_{2}$CuO$_{4}$ and Nd$_{2}$CuO$_{4}$ to probe directly the
different resistivity anisotropy regimes.",1412.4745v2
2015-01-26,Granularity Controlled Non-Saturating Linear Magneto-resistance in Topological Insulator Bi2Te3 Films,"We report on the magneto-transport properties of chemical vapor deposition
grown films of interconnected Bi2Te3 nanoplates. Similar to many other
topological insulator (TI) materials, these granular Bi2Te3 films exhibit a
linear magneto-resistance (LMR) effect which has received much recent
attention. Studying samples with different degree of granularity, we find a
universal correlation between the magnitude of the LMR and the average mobility
(<\mu>) of the films over nearly two orders of magnitude change of <\mu>. The
granularity controlled LMR effect here is attributed to the mobility
fluctuation induced classical LMR according to the Parish-Littlewood theory.
These findings have implications to both the fundamental understanding and
magneto-resistive device applications of TI and small bandgap semiconductor
materials.",1501.06497v2
2015-08-20,Atomic Diffusion in the Surface State of Mott Insulator NiS2,"We present resistivity measurements of Mott insulator NiS2 single crystals
after heat treatment. We find a strong increase of the low temperature
resistivity that relaxes back towards the pristine behaviour over several days
with a time constant of 45 h at room temperature. The low temperature
resistivity has previously been shown to be dominated by surface conduction (T.
Thio and J. Bennett, PRB 50 10574 1994). Consequently, the changes induced by
heat treatment are attributed to changes to surface states. Our results suggest
the creation of vacancies in the surface that re refilled from the bulk via
atomic diffusion. We estimate a diffusion constant of $D \approx 10^{-10}$
m$^2$/s at room temperature. We identify sulphur vacancies as the most likely
to form via oxidisation of sulphur forming volatile SO2 during heat treatment.
Our results point towards these sulphur vacancies to be the source of surface
state localisation in NiS2.",1508.05020v1
2016-11-12,Thermal boundary resistance from transient nanocalorimetry: a multiscale modeling approach,"The Thermal Boundary Resistance at the interface between a nanosized Al film
and an Al_{2}O_{3} substrate is investigated at an atomistic level. A room
temperature value of 1.4 m^{2}K/GW is found. The thermal dynamics occurring in
time-resolved thermo-reflectance experiments is then modelled via macro-physics
equations upon insertion of the materials parameters obtained from atomistic
simulations. Electrons and phonons non-equilibrium and spatio-temporal
temperatures inhomo- geneities are found to persist up to the nanosecond time
scale. These results question the validity of the commonly adopted lumped
thermal capacitance model in interpreting transient nanocalorimetry
experiments. The strategy adopted in the literature to extract the Thermal
Boundary Resistance from transient reflectivity traces is revised at the light
of the present findings. The results are of relevance beyond the specific
system, the physical picture being general and readily extendable to other
heterojunctions.",1611.04042v1
2018-01-11,Forbidden Backscattering and Resistance Dip in the Quantum Limit as a Signature for Topological Insulators,"Identifying topological insulators and semimetals often focuses on their
surface states, using spectroscopic methods such as angle-resolved
photoemission spectroscopy or scanning tunneling microscopy. In contrast,
studying the topological properties of topological insulators from their
bulk-state transport is more accessible in most labs but seldom addressed. We
show that, in the quantum limit of a topological insulator, the backscattering
between the only two states on the Fermi surface of the lowest Landau band can
be forbidden, at a critical magnetic field. The conductivity is determined
solely by the backscattering between the two states, leading to a resistance
dip that may serve as a signature for topological insulator phases. More
importantly, this forbidden backscattering mechanism for the resistance dip is
irrelevant to details of disorder scattering. Our theory can be applied to
revisit the experiments on Pb$_{1-x}$Sn$_x$Se, ZrTe$_5$, and Ag$_2$Te families,
and will be particularly useful for controversial small-gap materials at the
boundary between topological and normal insulators.",1801.03617v3
2018-02-28,Integration of external electric fields in molecular dynamics simulation models for resistive switching devices,"Resistive switching devices emerged a huge amount of interest as promising
candidates for non-volatile memories as well as artificial synapses due to
their memristive behavior. The main physical and chemical phenomena which
define their functionality are driven by externally applied voltages, and the
resulting electric fields. Although molecular dynamics simulations are widely
used in order to describe the dynamics on the corresponding atomic length and
time scales, there is a lack of models which allow for the actual driving force
of the dynamics, i.e. externally applied electric fields. This is due to the
restriction of currently applied models to either solely conductive,
non-reactive or insulating materials, with thicknesses in the order of the
potential cutoff radius, i.e., 10 \r{A}. In this work, we propose a generic
model, which can be applied in particular to describe the resistive switching
phenomena of metal-insulator-metal systems. It has been shown that the
calculated electric field and force distribution in case of the chosen example
system Cu/a-SiO$_2$/Cu are in agreement with fundamental field theoretical
expectations.",1802.10590v4
2018-03-07,Modelling the longitudinal intensity pattern of diffraction resistant beams in stratified media,"In this paper, we study the propagation of the Frozen Wave type beams through
non-absorbing stratified media and develop a theoretical method capable to
provide the desired spatially shaped diffraction resistant beam in the last
material medium. In this context, we also develop a matrix method to deal with
stratified media with large number of layers. Additionally, we undertake some
discussion about minimizing reflection of the incident FW beam on the first
material interface by using thin films. Our results show that it is indeed
possible to obtain the control, on demand, of the longitudinal intensity
pattern of a diffraction resistant beam even after it undergoes multiple
reflections and transmissions at the layer interfaces. Remote sensing, medical
and military applications, noninvasive optical measurements, etc., are some
fields that can be benefited by the method here proposed.",1803.03529v1
2019-08-22,Non-Thermal Resistive Switching in Mott Insulators,"Resistive switching can be achieved in a Mott insulator by applying
current/voltage, which triggers an insulator-metal transition (IMT). This
phenomenon is key for understanding IMT physics and developing novel memory
elements and brain-inspired technology. Despite this, the roles of electric
field and Joule heating in the switching process remain controversial. We
resolve this issue by studying nanowires of two archetypical Mott insulators -
VO2 and V2O3. Our findings show a crossover between two qualitatively different
regimes. In one, the IMT is driven by Joule heating to the transition
temperature, while in the other, field-assisted carrier generation gives rise
to a doping driven IMT which is purely non-thermal. By identifying the key
material properties governing these phenomena, we propose a universal mechanism
for resistive switching in Mott insulators. This understanding enabled us to
control the switching mechanism using focused ion-beam irradiation, thereby
facilitating an electrically driven non-thermal IMT. The energy consumption
associated with the non-thermal IMT is extremely low, rivaling that of state of
the art electronics and biological neurons. These findings pave the way towards
highly energy-efficient applications of Mott insulators.",1908.08555v1
2019-06-06,Training large-scale ANNs on simulated resistive crossbar arrays,"Accelerating training of artificial neural networks (ANN) with analog
resistive crossbar arrays is a promising idea. While the concept has been
verified on very small ANNs and toy data sets (such as MNIST), more
realistically sized ANNs and datasets have not yet been tackled. However, it is
to be expected that device materials and hardware design constraints, such as
noisy computations, finite number of resistive states of the device materials,
saturating weight and activation ranges, and limited precision of
analog-to-digital converters, will cause significant challenges to the
successful training of state-of-the-art ANNs. By using analog hardware aware
ANN training simulations, we here explore a number of simple algorithmic
compensatory measures to cope with analog noise and limited weight and output
ranges and resolutions, that dramatically improve the simulated training
performances on RPU arrays on intermediately to large-scale ANNs.",1906.02698v1
2020-11-03,Thermodynamically Induced Transport Anomaly in Dilute Metals ZrTe$_5$ and HfTe$_5$,"A 40-year-old puzzle in transition metal pentatellurides ZrTe$_5$ and
HfTe$_5$ is the anomalous peak in the temperature dependence of the
longitudinal resistivity, which is accompanied by sign reverses of the Hall and
Seebeck coefficients. We give a plausible explanation for these phenomena
without assuming any phase transition or strong interaction effect. We show
that due to intrinsic thermodynamics and diluteness of the conducting electrons
in these materials, the chemical potential displays a strong dependence on the
temperature and magnetic field. With that, we compute resistivity, Hall and
Seebeck coefficients in zero field, and magnetoresistivity and Hall resistivity
in finite magnetic fields, in all of which we reproduce the main features that
are observed in experiments.",2011.01952v2
2020-11-13,Ab initio screening of metallic MAX ceramics for advanced interconnect applications,"The potential of a wide range of layered ternary carbide and nitride MAX
phases as conductors in interconnect metal lines in advanced CMOS technology
nodes has been evaluated using automated first principles simulations based on
density functional theory. The resistivity scaling potential of these
compounds, i.e. the sensitivity of their resistivity to reduced line
dimensions, has been benchmarked against Cu and Ru by evaluating their
transport properties within a semiclassical transport formalism. In addition,
their cohesive energy has been assessed as a proxy for the resistance against
electromigration and the need for diffusion barriers. The results indicate that
numerous MAX phases show promise as conductors in interconnects of advanced
CMOS technology nodes.",2011.06902v2
2020-12-02,Interfacial studies in CNT fibre/TiO$_{2}$ photoelectrodes for efficient H$_{2}$ production,"An attractive class of materials for photo(electro)chemical reactions are
hybrids based on semiconducting metal oxides and nanocarbons (e.g. carbon
nanotubes (CNT), graphene), where the nanocarbon acts as a highly-stable
conductive scaffold onto which the nanostructured inorganic phase can be
immobilised; an architecture that maximises surface area and minimises charge
transport/transfer resistance. TiO$_{2}$/CNT photoanodes produced by atomic
layer deposition on CNT fabrics are shown to be efficient for H$_{2}$
production ($0.07 \mu mol/min$ $H_{2}$ at $0.2V$ $vs Ag/AgCl$), nearly doubling
the performance of TiO$_{2}$ deposited on planar substrates, with $100 \%$
Faradaic efficiency. The results are rationalised based on electrochemical
impedance spectroscopy measurements showing a large reduction in photoelectron
transport resistance compared to control samples and a higher surface area. The
low TiO$_{2}$/CNT interfacial charge transfer resistance ($10 \Omega$) is
consistent with the presence of an interfacial Ti-O-C bond and corresponding
electronic hybridisation determined by spatially-resolved Scanning
Photoelectron Microscopy (SPEM) using synchrotron radiation.",2012.01109v1
2021-04-26,Role of electron and ion irradiation in a reliable lift-off process with e-beam evaporation and a bilayer PMMA resist system,"This paper addresses issues related to cracking and blisters in deposited
films encountered in a lift-off process with electron beam evaporation and a
bilayer PMMA resist system. The impact of charged particles, i.e. electrons and
ions, is investigated using an electron beam evaporation chamber equipped with
ring-magnets and a plate electrode placed in front of the sample. By replacing
the plate electrode with a hollow cylinder, the modified evaporation setup
utilizing passive components allows a complete elimination of resist shrinkage
and blistering yielding near perfect deposition results for a large variety of
different materials.",2104.12452v1
2021-05-24,Spatio-temporal dynamics of voltage-induced resistance transition in the double-exchange model,"We present multi-scale dynamical simulations of voltage-induced
insulator-to-metal transition in the double exchange model, a canonical example
of itinerant magnet and correlated electron systems. By combining
nonequilibrium Green's function method with large-scale Landau-Lifshitz-Gilbert
dynamics, we show that the transition from an antiferromagnetic insulator to
the low-resistance state is initiated by the nucleation of a thin ferromagnetic
conducting layer at the anode. The metal-insulator interface separating the two
phases is then driven toward the opposite electrode by the voltage stress,
giving rise to a growing metallic region. We further show that the initial
transformation kinetics is well described by the Kolmogorov-Avrami-Ishibashi
model with an effective spatial-dimension that depends on the applied voltage.
Implications of our findings for the resistive switching in colossal
magnetoresistant materials are also discussed.",2105.11076v2
2021-10-14,Filamentary superconductivity of resistively-switched strontium titanate,"SrTiO$_3$, although a wide gap insulator, has long been known to become
metallic and superconducting at extremely low doping levels. This has given
rise to questions concerning the coexistence or interdependence of metallicity,
superconductivity, and the material's polar properties. This issue becomes
especially intriguing in conjunction with the observation that filamentary
metallicity can be induced by means of resistive switching at conditions well
below relevant doping levels for homogeneous metallicity. In this study, we
demonstrate that resistive switching can also be employed to generate
superconductivity at the superconducting transition temperature of $T_c$
$\approx$ 0.2 K in SrTiO$_3$. By combining local characterization of the
conductivity with theoretical analysis, we propose that the superconducting
properties are associated with the electro-formation of columnar-like bundles
with a diameter of 40-50 nm, consisting of metallic filaments surrounded by
polar regions. We provide a theoretical model identifying the coexistence of
metallic and polar regions as a prerequisite for the filamentary-like
superconductivity observed.",2110.07230v1
2022-01-20,Algorithm for constructing customized quantized resistances in graphene $p-n$ junctions,"An algorithm is introduced for predicting quantized resistances in graphene
p-n junction devices that utilize more than a single entry and exit point for
electron flow. Depending on the configuration of an arbitrary number of
terminals, electrical measurements yield fractional multiples of the typical
quantized Hall resistance at the $\nu=2$ plateau $R_H \approx 12906 {\Omega}$
and take the form: $\frac{a}{b}R_H$. This theoretical formulation is
independent of material, and applications to other material systems that
exhibit quantum Hall behaviors are to be expected. Furthermore, this
formulation is supported with experimental data from graphene-based devices
with multiple source and drain terminals.",2201.08290v1
2022-12-08,Terahertz photoconductivity in bilayer graphene transistors: evidence for tunneling at gate-induced junctions,"Photoconductivity of novel materials is the key property of interest for
design of photodetectors, optical modulators, and switches. Despite the
photoconductivity of most novel 2d materials has been studied both
theoretically and experimentally, the same is not true for 2d p-n junctions
that are necessary blocks of most electronic devices. Here, we study the
sub-terahertz photocoductivity of gapped bilayer graphene with
electrically-induced p-n junctions. We find a strong positive contribution from
junctions to resistance, temperature resistance coefficient and
photo-resistivity at cryogenic temperatures T ~ 20 K. The contribution to these
quantities from junctions exceeds strongly the bulk values at uniform channel
doping even at small band gaps ~ 10 meV. We further show that positive junction
photoresistance is a hallmark of interband tunneling, and not of intra-band
thermionic conduction. Our results point to the possibility of creating various
interband tunneling devices based on bilayer graphene, including
steep-switching transistors and selective sensors.",2212.04378v1
2024-03-17,Resistive and ballistic phonon transport in $β$-Ga$_2$O$_3$,"The anisotropic thermal conductivity and the phonon mean free path (mfp) in
monoclinic $\beta$-Ga$_2$O$_3$ single crystals and homoepitaxial films of
several $\mu$m were determined using the 3$\omega$-method in the temperature
range from 10K-300 K. The measured effective thermal conductivity of both,
single crystal and homoepitaxial films are in the order of 20 W/(mK) at room
temperature, below 30 K it increases with a maximum of 1000 to 2000 W/(mK) and
decreases with T$^3$ below 25 K. Analysis of the phonon mfp shows a dominance
of phonon-phonon-Umklapp scattering above 80 K, below which the influence of
point-defect scattering is observed. Below 30 K the phonon mfp increases until
it is limited by the total $\beta$-Ga$_2$O$_3$ sample size. A crossover from
resistive to ballistic phonon transport is observed below 20 K and boundary
effects of the total sample size become dominant. This reveals that the
homoepitaxial film-substrate interface is highly phonon-transparent. The
resistive and ballistic phonon transport regimes in $\beta$-Ga$_2$O$_3$ are
discussed corresponding to the models of Callaway and Majumdar, respectively.",2403.11341v1
2004-05-05,Low temperature field-effect in crystalline organic material,"Molecular organic materials offer the promise of novel electronic devices but
also present challenges for understanding charge transport in narrow band
systems. Low temperature studies elucidate fundamental transport processes. We
report the lowest temperature field effect transport results on a crystalline
oligomeric organic material, rubrene. We find field effect switching with
on-off ratio up to 10^7 at temperatures down to 10 K. Gated transport shows a
factor of ~10 suppression of the thermal activation energy in 10-50 K range and
nearly temperature independent resistivity below 10 K.",0405077v1
2022-07-22,Fabrication of highly resistive NiO thin films for nanoelectronic applications,"Thin films of the prototypical charge transfer insulator NiO appear to be a
promising material for novel nanoelectronic devices. The fabrication of the
material is challenging however, and mostly a p-type semiconducting phase is
reported. Here, the results of a factorial experiment are presented that allow
optimization of the film properties of thin films deposited using sputtering. A
cluster analysis is performed, and four main types of films are found. Among
them, the desired insulating phase is identified. From this material, nanoscale
devices are fabricated, which demonstrate that the results carry over to
relevant length scales. Initial switching results are reported.",2207.10837v1
2022-11-15,Nucleation and development of multiple cracks in thin composite fibers,"We study the nucleation and development of crack patterns in thin composite
fibers under tension in this work. A fiber comprises an elastic core and an
outer layer of a weaker brittle material. In recent tensile experiments on such
composites, multiple cracks were observed to develop simultaneously on the
outer layer. We propose here a simple one-dimensional model to predict such
phenomenon. We idealize the problem as two axially loaded rods coupled by a
linear interfacial condition. The latter can be regarded as an adhesive that
resists slip between the two materials. One rod is modeled as a brittle
material, and the other a linearly elastic material, both undergoing finite
deformations.",2212.02232v1
2024-05-19,"Modes, Bounds, and Synthesis of Optimal Electromagnetic Scatterers","This paper presents an optimal synthesis of material distributions in
obstacles for maximal extinction, scattering, or absorption. The material
synthesis is based on an explicit construction utilizing the current
distribution derived from physical bounds excited from the far-field. The
bounds are expressed in radiation modes for materials restricted by their
resistivity and characteristic modes for materials restricted by the contrast.
The results are valid for arbitrary shapes, and analytical expressions are
provided for spherical shapes.",2405.11499v1
2002-10-29,Electrical anisotropy in high-Tc granular superconductors in a magnetic field,"We propose an analytical model devoted to explain the anisotropy of the
electrical resistance observed below the critical temperature in granular
high-Tc superconductors submitted to a magnetic field H. Reported experimental
results obtained on a YBCO sample show that the superconducting transition
occurs in two stages, with a steep drop of the resistance at Tc and a
subsequent, smoother decrease. In this second stage, the resistance vs.
temperature curve is strongly dependent not only on the field intensity, but
also on the angle between H and the macroscopic current density j.
  We start from the assumption that the resistance below Tc is mainly due to
the weak links between grains. In the model, weak links are thought of as flat
surface elements separating adjacent grains. We calculate the probability for a
weak link to undergo the transition to the resistive state, as a function of
the angles it makes with the external magnetic field H and the macroscopic
current density j. In doing this, an important role is given to the strong
non-uniformity of the local magnetic field within the specimen, due to the
effect of the screening supercurrents flowing on the surface of the grains.
Finally, we calculate the electrical resistance of the sample in the two cases
where H is parallel and perpendicular to j, respectively. The predictions of
this simple model turn out to be in reasonable agreement with reported
experimental results obtained on a YBCO granular specimen.",0210648v1
2008-02-20,In-plane current-voltage characteristics and oscillatory Josephson-vortex flow resistance in La-free Bi$_{2+x}$Sr$_{2-x}$CuO$_{6+δ}$ single crystals in high magnetic fields,"We have investigated the in-plane $I(V)$ characteristics and the Josephson
vortex flow resistance in high-quality La-free
Bi$_{2+x}$Sr$_{2-x}$CuO$_{6+\delta}$ (Bi2201) single crystals in parallel and
tilted magnetic fields at temperatures down to 40 mK. For parallel magnetic
fields below the resistive upper critical field $H^{*}_{c2}$, the $I(V)$
characteristic obey a power-law with a smooth change with increasing
magnetic-field of the exponent from above 5 down to 1. In contrast to the
double-layer cuprate Bi2212, the observed smooth change suggests that there is
no change in the mechanism of dissipation (no Kosterlitz-Thouless transition)
over the range of temperatures investigated. At small angles between the
applied field and the $ab$-plane, prominent current steps in the $I(V)$
characteristics and periodic oscillations of Josephson-vortex flow resistance
are observed. While the current steps are periodic in the voltage at constant
fields, the voltage position of the steps, together with the flux-flow voltage,
increases nonlinearly with magnetic field. The $ab$-flow resistance oscillates
as a function of field with a constant period over a wide range of magnetic
fields and temperatures. The current steps in the $I(V)$ characteristics and
the flow resistance oscillations can be linked to the motion of Josephson
vortices across layers.",0802.2791v1
2009-06-01,Phase study of oscillatory resistances in microwave-irradiated- and dark- GaAs/AlGaAs devices: Indications of a new class of integral quantum Hall effect,"We report the experimental results from a dark study and a photo-excited
study of the high mobility GaAs/AlGaAs system at large filling factors, $\nu$.
At large-$\nu$, the dark study indicates several distinct phase relations
(""Type-1"", ""Type-2"", and ""Type-3"") between the oscillatory diagonal- and Hall-
resistances, as the canonical Integral Quantum Hall Effect (IQHE) is manifested
in the ""Type-1"" case of approximately orthogonal diagonal- and Hall resistance-
oscillations. Surprisingly, the investigation indicates quantum Hall plateaus
also in the ""Type-3"" case characterized by approximately ""anti-phase"" Hall- and
diagonal- resistance oscillations, suggesting a new class of IQHE.
  Transport studies under microwave photo-excitation exhibit radiation-induced
magneto-resistance oscillations in both the diagonal, $R_{xx}$, and
off-diagonal, $R_{xy}$, resistances. Further, when the radiation-induced
magneto-resistance oscillations extend into the quantum Hall regime, there
occurs a radiation-induced non-monotonic variation in the amplitude of
Shubnikov-de Haas (SdH) oscillations in $R_{xx}$ \textit{vs}. B, and a
non-monotonic variation in the width of the quantum Hall plateaus in $R_{xy}$.
The latter effect leads into the vanishing of IQHE at the minima of the
radiation-induced $R_{xx}$ oscillations with increased photo-excitation. We
reason that the mechanism which is responsible for producing the non-monotonic
variation in the amplitude of SdH oscillations in $R_{xx}$ under
photo-excitation is also responsible for eliminating, under photo-excitation,
the novel ""Type-3"" IQHE in the high mobility specimen.",0906.0032v1
2016-10-19,Pressure induced superconductivity in Bi single crystals,"Measurements on resistivity and magnetic susceptibility have been carried out
for Bi single crystals under pressures up to 10.5GPa. The temperature dependent
resistivity shows a semimetallic behavior at ambient and low pressures (below
about 1.6GPa). This is followed by an upturn of resistivity in low temperature
region when the pressure is increased, which is explained as a semiconductor
behavior. This feature gradually gets enhanced up to a pressure of about
2.52GPa. Then a non-monotonic temperature dependent resistivity appears upon
further increasing pressure, which is accompanied by a strong suppression to
the low temperature resistivity upturn. Simultaneously, a superconducting
transition occurs at about 3.92K under a pressure of about 2.63GPa. With
further increasing pressure, a second superconducting transition emerges at
about 7K under about 2.8GPa. For these two superconducting states, the
superconductivity induced magnetic screening volumes are quite large. As the
pressure further increased to 8.1GPa, we observe the third superconducting
transition at about 8.2K. The resistivity measurements under magnetic field
allow us to determine the upper critical fields $\mu_0 H_{c2}$ of the
superconducting phases. The upper critical field for the phase with $T_c=3.92$K
is extremely low. Based on the Werthamer-Helfand-Hohenberg (WHH) theory, the
estimated value of $\mu_0 H_{c2}$ for this phase is about 0.103T. While the
upper critical field for the phase with $T_c$=7K is very high with a value of
about 4.56T. Finally, we present a pressure dependent phase diagram of Bi
single crystals. Our results reveal the interesting and rich physics in bismuth
single crystals under high pressure.",1610.06062v1
2021-01-14,Effects of resistivity on standing shocks in low angular momentum flows around black holes,"We study two dimensional low angular momentum flow around the black hole
using the resistive magnetohydrodynamic module of PLUTO code. Simulations have
been performed for the flows with parameters of specific angular momentum,
specific energy, and magnetic field which may be expected for the flow around
Sgr A*. For flows with lower resistivity $\eta=10^{-6}$ and $0.01$, the
luminosity and the shock location on the equator vary quasi-periodically. The
power density spectra of luminosity variation show the peak frequencies which
correspond to the periods of $5 \times 10^5$, $1.4 \times 10^5$, and $5 \times
10^4$ seconds, respectively. These quasi-periodic oscillations (QPOs) occur due
to the interaction between the outer oscillating standing shock and the inner
weak shocks occurring at the innermost hot blob. While for cases with higher
resistivity $\eta=0.1$ and 1.0, the high resistivity considerably suppresses
the magnetic activity such as the MHD turbulence and the flows tend to be
steady and symmetric to the equator. The steady standing shock is formed more
outward compared with the hydrodynamical flow. The low angular momentum flow
model with the above flow parameters and with low resistivity has a possibility
for the explanation of the long-term flares with $\sim$ one per day and $\sim 5
- 10$ days of Sgr A* in the latest observations by Chandra, Swift, and
XMM-Newton monitoring of Sgr A*.",2101.05474v2
2014-06-19,AC loss and coupling currents in YBCO coated conductors with varying number of filaments,"Striation of HTS coated conductors (CCs) as a way to reduce their
magnetization AC losses has been the subject of intense research in the past
years by several groups. While the principle of this approach is well
understood, its practical application on commercial material to be used in
power application is still far to be implemented due to manufacturing and
technological constraints. Recent advances in tape quality and striation
technology are now enabling systematic investigations of the influence of the
number of filaments on AC loss reduction with a consistency that was not
available in the past. In this work we demonstrate the technological
feasibility of reducing the magnetization losses of commercially available CC
by striating them into a high number of filaments (up to 120). The loss
reduction exceeds one order of magnitude and does not come at the expense of
current-carrying capability: samples with 10 and 20 filaments are unaffected by
the striation process, while samples with 80 and 120 filaments still retain 80
and 70% of the current-carrying potential, respectively. We also investigate
the transverse resistivity in order to understand the paths followed by the
coupling currents: we found that the coupling current prevalently flows in the
metallic substrate, rather than in and out of the filaments. Finally, we use
oxidation as a method to reduce the coupling currents and losses. The
contribution of this work is three-fold: 1) It describes the know-how to
produce a large number of high quality striations in commercially available
CCs, greatly reducing their losses without extensively degrading their
transport properties; 2) It provides a comprehensive characterization of said
samples (e.g. measurements in a wide frequency range, transverse resistance
profiles, influence of oxidation on DC and AC behavior); 3) It provides new
insight on the patterns of the coupling currents.",1406.4990v2
2017-09-21,Electrical properties of single crystal Yttrium Iron Garnet ultra-thin films at high temperatures,"We report a study on the electrical properties of 19 nm thick Yttrium Iron
Garnet (YIG) films grown by liquid phase epitaxy. The electrical conductivity
and Hall coefficient are measured in the high temperature range [300,400]~K
using a Van der Pauw four-point probe technique. We find that the electrical
resistivity decreases exponentially with increasing temperature following an
activated behavior corresponding to a band-gap of $E_g\approx 2$ eV, indicating
that epitaxial YIG ultra-thin films behave as large gap semiconductor, and not
as electrical insulator. The resistivity drops to about $5\times 10^3$~$\Omega
\cdot \text{cm}$ at $T=400$ K. We also infer the Hall mobility, which is found
to be positive ($p$-type) at 5 cm$^2$/(V$\cdot$sec) and about independent of
temperature. We discuss the consequence for non-local transport experiments
performed on YIG at room temperature. These electrical properties are
responsible for an offset voltage (independent of the in-plane field direction)
whose amplitude, odd in current, grows exponentially with current due to Joule
heating. These electrical properties also induce a sensitivity to the
perpendicular component of the magnetic field through the Hall effect. In our
lateral device, a thermoelectric offset voltage is produced by a temperature
gradient along the wire direction proportional to the perpendicular component
of the magnetic field (Righi-Leduc effects).",1709.07207v1
2020-04-01,Perovskite-type cobalt oxide at the multiferroic Co/Pb Zr$_{0.2}$Ti$_{0.8}$O$_{3}$ interface,"Magnetic Tunnel Junctions whose basic element consists of two ferromagnetic
electrodes separated by an insulating non-magnetic barrier have become
intensely studied and used in non-volatile spintronic devices. Since ballistic
tunnel of spin-polarized electrons sensitively depends on the chemical
composition and the atomic geometry of the lead/barrier interfaces their proper
design is a key issue for achieving the required functionality of the devices
such as e.g. a high tunnel magneto resistance. An important leap in the
development of novel spintronic devices is to replace the insulating barrier by
a ferroelectric which adds new additional functionality induced by the
polarization direction in the barrier giving rise to the tunnel electro
resistance (TER). The multiferroic tunnel junction
Co/PbZr$_{0.2}$Ti$_{0.8}$O$_{3}$/La$_{2/3}$Sr$_{1/3}$MnO$_3$ (Co/PZT/LSMO)
represents an archetype system for which - despite intense studies - no
consensus exists for the interface geometry and their effect on transport
properties. Here we provide the first analysis of the Co/PZT interface at the
atomic scale using complementary techniques, namely x-ray diffraction and
extended x-ray absorption fine structure in combination with x-ray magnetic
circular dichroism and ab-initio calculations. The Co/PZT interface consists of
one perovskite-type cobalt oxide unit cell [CoO$_{2}$/CoO/Ti(Zr)O$_{2}$] on
which a locally ordered cobalt film grows. Magnetic moments (m) of cobalt lie
in the range between m=2.3 and m=2.7$\mu_{B}$, while for the interfacial
titanium atoms they are small (m=+0.005 $\mu_{B}$) and parallel to cobalt which
is attributed to the presence of the cobalt-oxide interface layers. These
insights into the atomistic relation between interface and magnetic properties
is expected to pave the way for future high TER devices.",2004.00489v1
2020-05-26,"Influence of Different Surface Morphologies on the Performance of High Voltage, Low Resistance Diamond Schottky Diodes","Vertical diamond Schottky diodes with blocking voltages $V_{\text{BD}} > 2.4
\text{ kV}$ and on-resistances $R_{\text{On}} < 400 \text{ m}\Omega
\text{cm}^{2}$ were fabricated on homoepitaxially grown diamond layers with
different surface morphologies. The morphology (smooth as-grown, hillock-rich,
polished) influences the Schottky barrier, the carrier transport properties,
and consequently the device performance. The smooth as-grown sample exhibited a
low reverse current density $J_{\text{Rev}} < 10^{-4} \text{ A}/\text{cm}^{2}$
for reverse voltages up to $2.2 \text{ kV}$. The hillock-rich sample blocked
similar voltages with a slight increase in the reverse current density
($J_{\text{Rev}} < 10^{-3} \text{ A}/\text{cm}^{2}$). The calculated
1D-breakdown field, however, was reduced by $30 \text{ } \%$, indicating a
field enhancement induced by the inhomogeneous surface. The polished sample
demonstrated a similar breakdown voltage and reverse current density as the
smooth as-grown sample, suggesting that a polished surface can be suitable for
device fabrication. However, a statistical analysis of several diodes of each
sample showed the importance of the substrate quality: A high density of
defects both reduces the feasible device area and increases the reverse current
density. In forward direction, the hillock-rich sample exhibited a secondary
Schottky barrier, which could be fitted with a modified thermionic emission
model employing the Lambert W-function. Both polished and smooth sample showed
nearly ideal thermionic emission with ideality factors $1.08$ and $1.03$,
respectively. Compared with literature, all three diodes exhibit an improved
Baliga Figure of Merit for diamond Schottky diodes with $V_{\text{BD}} > 2
\text{ kV}$.",2005.12591v1
2023-11-21,Evidence of filamentary superconductivity in pressurized La3Ni2O7,"Recently, the signatures of superconductivity near 80 K have been discovered
in the single crystal of La3Ni2O7 under pressure, which makes it a new
candidate of the high-temperature superconductors dominated by 3d transition
elements after the cuprate and iron-pnictide superconductors, and thus has
attracted significant attention. However, the superconductivity, characterized
by the zero resistance and the Meissner effect, is anomalously irreproducible
in the compressed La3Ni2O7. In this study, we report the experimental results
obtained through highly sensitive modulated ac susceptibility measurements,
which reveal that the maximum superconducting volume fraction in the La3Ni2O7
sample is only approximately 1% (employing superconducting element vanadium as
a reference). In tandem with our observation of the zero-resistance state only
in some of the samples, we suggest that the superconductivity in this nickelate
is filamentary-like. In combination of our scanning transmission electron
microscopy (STEM) investigations, we propose that the filamentary
superconductivity most likely emerges at the interface between the La3Ni2O7 and
La4Ni3O10 phases. Further, the connection of the oxygen vacancy in La3Ni2O7
with the presence of superconductivity and superconducting transition
temperature (Tc) has been established, through which the upper and lower bounds
of the oxygen content for the presence of superconductivity were determined to
be 6.89 and 7.35, respectively. Our results not only provide new insights into
understanding the puzzling issues in this material, but also highlight a new
route for exploring new high-Tc nickelate superconductors with a higher
superconducting volume fraction, as well as pose a new challenge in
comprehending the complex nature of this filamentary superconductivity.",2311.12361v2
2024-03-01,Electrochemical Evaluation of Mg and a Mg-Al 5%Zn Metal Rich Primers for Protection of Al-Zn-Mg-Cu Alloy in NaCl,"High purity magnesium and a Mg-Al 5wt% Zn metal rich primer (MRP) were
compared for their ability to suppress intergranular corrosion (IGC) and
intergranular stress corrosion cracking (IG-SCC) in peak aged AA 7075-T651 by
sacrificial anode-based cathodic prevention. Tests were conducted in 0.6 M NaCl
solution under full immersion. These evaluations considered the ability of the
primer to attain an intermediate negative open circuit potential (OCP) such
that the galvanic couple potential with bare aluminum alloy (AA) 7075-T651
resided below a range of potentials where IGC is prevalent. The ability of the
primer to achieve an OCP negative enough that the AA 7075-T651 could be
protected by sacrificial anode-based cathodic prevention and the ability to
sustain this function over time were evaluated as a first step by utilizing a
NaCl solution. The primers consisted of epoxy resins embedded with either (1)
Mg flake pigments (MgRP) or (2) Mg flake pigments and spherical Al-5 wt.% Zn
together as a composite (MgAlRP). MgRP was an effective coating for cathodic
protection but dispensed less anodic charge than the composite MgAlRP.
Cross-sectional analysis demonstrated that some Mg flakes dissolved while
uniform surface oxidation occurred on the remaining Mg flakes which led to
impaired activation. The composite MgAlRP maintained a suitably negative OCP
over time, remained activated, dispensed high anodic charge, and remained an
anode in zero resistance ammeter testing. Chemical stability modeling and zero
resistance ammeter testing suggest that Mg corrosion elevates the pH which
dissolved aluminum oxides and hydroxide thereby activates the Al-5wt.% Zn
pigments, thereby providing a primary (i.e. Mg corrosion) and secondary process
to enable superior (activation of Al-5wt%Zn) sacrificial anode-based cathodic
protection.",2403.00610v1
2007-09-14,High pressure study on the strong-coupling superconductivity in non-centrosymmetric compound CeIrSi_3,"We have carried out high pressure experiment on the pressure-induced
superconductor CeIrSi$_3$ without inversion center. The electrical resistivity
and ac heat capacity were measured in the same run for the same sample. The
critical pressure of the antiferromagnetic state was determined to be $P_{\rm
c}$ = 2.25 GPa. The heat capacity $C_{\rm ac}$ shows both antiferromagnetic and
superconducting transitions at pressures close to $P_{\rm c}$. The
superconducting transition temperature $T_{\rm sc}$ shows a maximum value of
1.6 K around $2.5-2.7$ GPa. At 2.58 GPa, a large heat capacity anomaly was
observed at $T_{\rm sc}$ = 1.59 K. The jump of the heat capacity in the form of
${\Delta}{C_{\rm ac}}/C_{\rm ac}(T_{\rm sc})$ is 5.7 $\pm$ 0.1. This is the
largest value observed among all superconductors studied previously, suggesting
the strong-coupling superconductivity in CeIrSi$_3$. The large magnitude and
anisotropy of the upper critical field $B_{\rm c2}$ at 2.65 GPa is discussed
from view points of the strong-coupling superconductivity and the reduced
paramagnetic effect in the non-centrosymmetric superconductor. Above $P_{\rm
c}$, the electrical resistivity shows the anomalous $T$-linear dependence in
the wide temperature region from $T_{\rm sc}$ to 30 K, which is different from
the Fermi liquid theory. Meanwhile, the heat capacity $C_{\rm ac}/T$ shows a
simple temperature dependence in the normal state above $T_{\rm sc}$. These
features do not seem to be explained simply by the spin fluctuation theory. The
electronic specific heat coefficient at $T_{\rm sc}$ is approximately unchanged
as a function of pressure, even at $P_{\rm c}$.",0709.2199v1
2016-06-09,Ternary borides Nb$_7$Fe$_3$B$_8$ and Ta$_7$Fe$_3$B$_8$ with Kagome-type iron framework,"Two new ternary borides $TM$$_7$Fe$_3$B$_8$ ($TM$ = Nb, Ta) were synthesized
by high-temperature thermal treatment of samples obtained by arc-melting. This
new type of structure with space group $P$6/$mmm$, comprises $TM$ slabs
containing isolated planar hexagonal [B$_6$] rings and iron centered $TM$
columns in a Kagome type of arrangement. Chemical bonding analysis in
Nb$_7$Fe$_3$B$_8$ by means of the electron localizability approach reveals
two-center interactions forming the Kagome net of Fe and embedded B, while
weaker multicenter bonding present between this net and Nb atoms. Magnetic
susceptibility measurements reveal antiferromagnetic order below $T_N$ = 240 K
for Nb$_7$Fe$_3$B$_8$ and $T_N$ =265 K for Ta$_7$Fe$_3$B$_8$. Small remnant
magnetization below 0.01 $\mu_B$/f.u. is observed in the antiferromagnetic
state. The bulk nature of the magnetic transitions was confirmed by the
hyperfine splitting of the M\""o{\ss}bauer spectra, the sizable anomalies in the
specific heat capacity, and the kinks in the resistivity curves. The high-field
paramagnetic susceptibilities fitted by the Curie-Weiss law show effective
paramagnetic moments $\mu_{eff}$ about 3.1 $\mu_B$/Fe in both compounds. The
temperature dependence of the electrical resistivity also reveals metallic
character of both compounds. Density functional calculations corroborate the
metallic behaviour of both compounds and demonstrate the formation of a sizable
local magnetic moment on the Fe-sites. They indicate the presence of both
antiferro- and ferromagnetic interactions.",1606.03123v1
2020-01-24,Quantum transport in topological surface states of Bi$_2$Te$_3$ nanoribbons,"Quasi-1D nanowires of topological insulators are emerging candidate
structures in superconductor hybrid architectures for the realization of
Majorana fermion based quantum computation schemes. It is however technically
difficult to both fabricate as well as identify the 1D limit of topological
insulator nanowires. Here, we investigated selectively-grown Bi$_2$Te$_3$
topological insulator nanoribbons and nano Hall bars at cryogenic temperatures
for their topological properties. The Hall bars are defined in deep-etched
Si$_3$N$_4$/SiO$_2$ nano-trenches on a silicon (111) substrate followed by a
selective area growth process via molecular beam epitaxy. The selective area
growth is beneficial to the device quality, as no subsequent fabrication needs
to be performed to shape the nanoribbons. Transmission line measurements are
performed to evaluate contact resistances of Ti/Au contacts applied as well as
the specific resistance of the Bi$_2$Te$_3$ binary topological insulator. In
the diffusive transport regime of these unintentionally $n$-doped Bi$_2$Te$_3$
topological insulator nano Hall bars, we identify distinguishable electron
trajectories by analyzing angle-dependent universal conductance fluctuation
spectra. When the sample is tilted from a perpendicular to a parallel magnetic
field orientation, these high frequent universal conductance fluctuations merge
with low frequent Aharonov-Bohm type oscillations originating from the
topologically protected surface states encircling the nanoribbon cross section.
For 500 nm wide Hall bars we also identify low frequent Shubnikov-de Haas
oscillations in the perpendicular field orientation, that reveal a topological
high-mobility 2D transport channel, partially decoupled from the bulk of the
material.",2001.09028v1
2020-06-01,"PrVO$_4$ under High Pressure: Effects on Structural, Optical and Electrical Properties","In pursue of a systematic characterization of rare-earth vanadates under
compression, in this work we present a multifaceted study of the phase behavior
of zircon-type orthovanadate PrVO$_4$ under high pressure conditions, up until
24 GPa. We have found that PrVO$_4$ undergoes a zircon to monazite transition
at around 6 GPa, confirming previous results found by Raman experiments. A
second transition takes place above 14 GPa, to a BaWO$_4$-I--type structure.
The zircon to monazite structural sequence is an irreversible first-order
transition, accompanied by a volume collapse of about 9.6%. Monazite phase is
thus a metastable polymorph of PrVO$_4$. The monazite-BaWO$_4$-II transition is
found to be reversible instead and occurs with a similar volume change. Here we
report and discuss the axial and bulk compressibility of all phases. We also
compare our results with those for other rare-earth orthovanadates. Finally, by
means of optical-absorption experiments and resistivity measurements we
determined the effect of pressure on the electronic properties of PrVO$_4$. We
found that the zircon-monazite transition produces a collapse of the band gap
and an abrupt decrease of the resistivity. The physical reasons for this
behavior are discussed. Density-functional-theory simulations support our
conclusions.",2006.01299v2
2024-04-04,"Electronic transport, metal-insulator transition, and Wigner crystallization in transition metal dichalcogenide monolayers","Two recent electronic transport experiments from Columbia University and
Harvard University have reported record high mobility and low channel densities
in transition metal dichalcogenide (TMD) WSe$_2$ monolayers [J. Pack, et al.,
arXiv:2310.19782; A. Y. Joe, et al., Phys. Rev. Lett. 132, 056303 (2024)]. A
two-dimensional (2D) metal-insulator transition (MIT) is demonstrated in the
Columbia sample at low densities, a regime where the formation of a Wigner
crystal (WC) is theoretically anticipated in the absence of disorder. We employ
the finite-temperature Boltzmann theory to understand the low-temperature
transport properties of monolayer TMDs, taking into account realistic disorder
scattering. We analyze the experimental results, focusing on the 2D MIT
behavior and the influence of temperature and density on mobility and
resistivity in the metallic phase. We provide a discussion of the nontrivial
carrier density dependence of our transport results. Our analysis elucidates
the linear-in-$T$ resistivity in the metallic phase, attributing it to Friedel
oscillations associated with screened charged impurities. Furthermore, we
explore whether Coulomb disorder could lead to the MIT through either a quantum
Anderson localization transition or a classical percolation transition. Our
theoretical estimates of the disorder-induced MIT critical densities, although
smaller, are within a factor of ~2 of the experimental critical density. We
examine the exceptionally high melting temperature ~10 K of WCs observed
experimentally in the MoSe$_2$ systems at low density, an order of magnitude
larger than the pristine melting temperature. This suggests that the observed
2D low-density MIT behavior is likely a result of the complex interplay between
disorder effects and interaction-driven WC physics, offering a comprehensive
understanding of the low-temperature transport phenomena in TMD monolayers.",2404.03488v1
2005-06-08,X-ray Diagnostics of Grain Depletion in Matter Accreting onto T Tauri Stars,"Recent analysis of high resolution Chandra X-ray spectra has shown that the
Ne/O abundance ratio is remarkably constant in stellar coronae. Based on this
result, we point out the utility of the Ne/O ratio as a discriminant for
accretion-related X-rays from T Tauri stars, and for probing the measure of
grain-depletion of the accreting material in the inner disk. We apply the Ne/O
diagnostic to the classical T Tauri stars BP Tau and TW Hya--the two stars
found to date whose X-ray emission appears to originate, at least in part, from
accretion activity. We show that TW Hya appears to be accreting material which
is significantly depleted in O relative to Ne. In constrast, BP Tau has an Ne/O
abundance ratio consistent with that observed for post-T Tauri stars. We
interpret this result in terms of the different ages and evolutionary states of
the circumstellar disks of these stars. In the young BP Tau disk (age 0.6 Myr)
dust is still present near the disk corotation radius and can be ionized and
accreted, re-releasing elements depleted onto grains. In the more evolved TW
Hya disk (age 10 Myr), evidence points to ongoing coagulation of grains into
much larger bodies, and possibly planets, that can resist the drag of
inward-migrating gas, and accreting gas is consequently depleted of
grain-forming elements.",0506185v1
2003-02-13,"Electronic phase separation in the rare earth manganates, (La1-xLnx)0.7Ca0.3MnO3 (Ln = Nd, Gd and Y)","All the three series of manganates showsaturation magnetization
characteristic of ferromagnetism, with the ferromagnetic Tc decreasing with
increasing in x up to a critical value of x, xc (xc = 0.6, 0.3, 0.2
respectively for Nd, Gd, Y). For x > xc, the magnetic moments are considerably
smaller showing a small increase around TM, the value of TM decreasing slightly
with increase in x or decrease in < rA >. The ferromagnetic compositions (x xc)
show insulator-metal (IM) transitions, while the compositions with x > xc are
insulating. The magnetic and electrical resistivity behavior of these
manganates is consistent with the occurrence of phase separation in the
compositions around xc, corresponding to a critical average radius of the
A-site cation, < rAc >, of 1.18 A. Both Tc and TIM increase linearly when < rA
> > < rAc > or x xc as expected of a homogenous ferromagnetic phase. Both Tc
and TM decrease linearly with the A-site cation size disorder at the A-site as
measured by the variance s2. Thus, an increase in s2 favors the insulating AFM
state. Percolative conduction is observed in the compositions with < rA > > <
rAc >. Electron transport properties in the insulating regime for x > xc
conforms to the variable range hopping mechanism. More interestingly, when x >
xc, the real part of dielectric constant (e') reaches a high value (104-106) at
ordinary temperatures dropping to a very small (~500) value below a certain
temperature, the value of which decreases with decreasing frequency.",0302268v1
2003-03-21,"Independent Electronic and Magnetic Doping in (Ga,Mn)As Based Digital Ferromagnetic Heterostructures","Ferromagnetic semiconductors promise the extension of metal-based spintronics
into a material system that combines widely tunable electronic, optical, and
magnetic properties. Here, we take steps towards realizing that promise by
achieving independent control of electronic doping in the ferromagnetic
semiconductor (Ga,Mn)As. Samples are comprised of superlattices of 0.5
monolayer (ML) MnAs alternating with 20 ML GaAs and are grown by low
temperature (230 C) atomic layer epitaxy (ALE). This allows for the reduction
of excess As incorporation and hence the number of charge-compensating
As-related defects. We grow a series of samples with either Be or Si doping in
the GaAs spacers (p- and n-type dopants, respectively), and verify their
structural quality by in situ reflection high-energy electron diffraction
(RHEED) and ex situ x-ray diffraction. Magnetization measurements reveal
ferromagnetic behavior over the entire doping range, and show no sign of MnAs
precipitates. Finally, magneto-transport shows the giant planar Hall effect and
strong (20%) resistance fluctuations that may be related to domain wall motion.",0303461v1
2006-02-26,Physical properties and magnetic structure of TbRhIn5 intermetallic compound,"In this work we report the physical properties of the new intermetallic
compound TbRhIn5 investigated by means of temperature dependent magnetic
susceptibility, electrical resistivity, heat-capacity and resonant x-ray
magnetic diffraction experiments. TbRhIn5 is an intermetallic compound that
orders antiferromagnetically at TN = 45.5 K, the highest ordering temperature
among the existing RRhIn5 (1-1-5, R = rare earth) materials. This result is in
contrast to what is expected from a de Gennes scaling along the RRhIn5 series.
The X-ray resonant diffraction data below TN reveal a commensurate
antiferromagnetic (AFM) structure with a propagation vector (1/2 0 1/2) and the
Tb moments oriented along the c-axis. Strong (over two order of magnitude)
dipolar enhancements of the magnetic Bragg peaks were observed at both Tb
absorption edges LII and LIII, indicating a fairly high polarization of the Tb
5d levels. Using a mean field model including an isotropic first-neighbors
exchange interaction J(R-R) and the tetragonal crystalline electrical field
(CEF), we were able to fit our experimental data and to explain the direction
of the ordered Tb-moments and the enhanced TN of this compound. The evolution
of the magnetic properties along the RRhIn5 series and its relation to CEF
effects for a given rare-earth is discussed.",0602612v1
2006-06-28,Dielectric anomaly at the orbital order-disorder transition in LaMnO_(3+delta),"We report a novel dielectric anomaly around the Jahn-Teller orbital
order-disorder transition temperature T_JT in LaMnO_(3+delta). The transition
has been characterized by resistivity (rho)versus temperature (T), calorimetry,
and temperature-dependent X-ray diffraction studies. Measurements of complex
dielectric permittivity epsilon* (= epsilon'-i.epsilon'') over a low-frequency
range (1 Hz - 10 MHz)across T_JT reveal a distinct anomaly. This observation,
and the reported relatively high static dielectric constant at T = 0 (epsilon0
\~18-20), possibly indicate that the orbital order gives rise to intrinsic
polarization that undergoes transition at T_JT. The frequency dispersion of the
dielectric response at any given temperature, however, reveals that the
dielectric response consists of Maxwell-Wagner component, due to interfaces,
within such a low frequency range. The T_JT and the nature of the anomaly in
epsilon'(omega,T), epsilon''(omega,T) at T_JT, of course, vary - from a sharp
upward feature to a smeared plateau and then a downward trend - depending on
the Mn^4+ concentration of the sample. The observation of an intrinsic
dielectric response due to long-range orbital order in LaMnO_3 - where no
ferroelectric order is possible due to the absence of off-centre distortion in
MnO_6 octahedra - may throw a new light onto these classes of materials
vis-a-vis multiferroic materials.",0606731v1
2003-10-07,Role of Oxygen and Carbon Impurities in the Radiation Resistance of Silicon Detectors,"The influence of oxygen and carbon impurities on the concentrations of
defects in silicon for detector uses, in complex fields of radiation (proton
cosmic field at low orbits around the Earth, at Large Hadron Collider and at
the next generation of accelerators as Super-LHC) is investigated in the frame
of the quantitative model developed previously by the authors. The generation
rate of primary defects is calculated starting from the projectile - silicon
interaction and from recoil energy redistribution in the lattice. The
mechanisms of formation of complex defects are explicitly analysed.
Vacancy-interstitial annihilation, interstitial and vacancy migration to sinks,
divacancy, vacancy and interstitial impurity complex formation and
decomposition are considered. Oxygen and carbon impurities present in silicon
could monitor the concentration of all stable defects, due to their interaction
with vacancies and interstitials. Their role in the mechanisms of formation and
decomposition of the following stable defects: VP, VO, V_2, V_2O, C_i, C_iO_i
and C_iC_s is studied. The model predictions could be a useful clue in
obtaining harder materials for detectors at the new generation of accelerators,
for space missions or for industrial applications.",0310032v1
2009-01-22,Signal height in silicon pixel detectors irradiated with pions and protons,"Pixel detectors are used in the innermost part of multi purpose experiments
at the Large Hadron Collider (LHC) and are therefore exposed to the highest
fluences of ionising radiation, which in this part of the detectors consists
mainly of charged pions. The radiation hardness of the detectors has thoroughly
been tested up to the fluences expected at the LHC. In case of an LHC upgrade
the fluence will be much higher and it is not yet clear up to which radii the
present pixel technology can be used. In order to establish such a limit, pixel
sensors of the size of one CMS pixel readout chip (PSI46V2.1) have been bump
bonded and irradiated with positive pions up to 6E14 Neq/cm^2 at PSI and with
protons up to 5E15 Neq/cm^2. The sensors were taken from production wafers of
the CMS barrel pixel detector. They use n-type DOFZ material with a resistance
of about 3.7kOhm cm and an n-side read out. As the performance of silicon
sensors is limited by trapping, the response to a Sr-90 source was
investigated. The highly energetic beta-particles represent a good
approximation to minimum ionising particles. The bias dependence of the signal
for a wide range of fluences will be presented.",0901.3422v1
2012-04-17,Beta-Ag2Te: A topological insulator with strong anisotropy,"We present evidence of topological surface states in beta-Ag2Te through
first-principles calculations and periodic quantum interference effect in
single crystalline nanoribbon. Our first-principles calculations show that
beta-Ag2Te is a topological insulator with a gapless Dirac cone with strong
anisotropy. To experimentally probe the topological surface state, we
synthesized high quality beta-Ag2Te nanoribbons and performed electron
transport measurements. The coexistence of pronounced Aharonov-Bohm
oscillations and weak Altshuler-Aronov-Spivak oscillations clearly demonstrates
coherent electron transport around the perimeter of beta-Ag2Te nanoribbon and
therefore the existence of metallic surface states, which is further supported
by the temperature dependence of resistivity for beta-Ag2Te nanoribbons with
different cross section areas. Highly anisotropic topological surface state of
beta-Ag2Te suggests that the material is a promising material for fundamental
study and future spintronic devices.",1204.3816v6
2012-09-16,Glass-like recovery of antiferromagnetic spin ordering and dimensional crossover in a photo-excited manganite Pr$_{0.7}$Ca$_{0.3}$MnO$_3$,"Electronic orderings of charges, orbitals and spins are observed in many
strongly correlated electron materials, and revealing their dynamics is a
critical step toward understanding the underlying physics of important emergent
phenomena. Here we use time-resolved resonant soft x-ray scattering
spectroscopy to probe the dynamics of antiferromagnetic spin ordering in the
manganite Pr$_{0.7}$Ca$_{0.3}$MnO$_3$ following ultrafast photo-exitation. Our
studies reveal a glass-like recovery of the spin ordering and a crossover in
the dimensionality of the restoring interaction from quasi-1D at low pump
fluence to 3D at high pump fluence. This behavior arises from the metastable
state created by photo-excitation, a state characterized by spin disordered
metallic droplets within the larger charge- and spin-ordered insulating
domains. Comparison with time-resolved resistivity measurements suggests that
the collapse of spin ordering is correlated with the insulator-to-metal
transition, but the recovery of the insulating phase does not depend on the
re-establishment of the spin ordering.",1209.3452v2
2013-05-30,Kelvin Probe Microscopy and Electronic Transport Measurements in Reduced Graphene Oxide Chemical Sensors,"Reduced Graphene Oxide (RGO) is an electronically hybrid material that
displays remarkable chemical sensing properties. Here, we present a
quantitative analysis of the chemical gating effects in RGO-based chemical
sensors. The gas sensing devices are patterned in a field-effect transistor
geometry, by dielectrophoretic assembly of RGO platelets between gold
electrodes deposited on SiO2/Si substrates. We show that these sensors display
highly selective and reversible responses to the measured analytes, as well as
fast response and recovery times (tens of seconds). We use combined electronic
transport/Kelvin Probe Microscopy measurements to quantify the amount of charge
transferred to RGO due to chemical doping when the device is exposed to
electron-acceptor (acetone) and electron-donor (ammonia) analytes. We
demonstrate that this method allows us to obtain high-resolution maps of the
surface potential and local charge distribution both before and after chemical
doping, to identify local gate-susceptible areas on the RGO surface, and to
directly extract the contact resistance between the RGO and the metallic
electrodes. The method presented is general, suggesting that these results have
important implications for building graphene and other nanomaterial-based
chemical sensors.",1305.7222v1
2014-04-02,Direct observation of the leakage current in epitaxial diamond Schottky barrier devices by conductive-probe atomic force microscopy and Raman imaging,"The origin of the high leakage current measured in several vertical-type
diamond Schottky devices is conjointly investigated by conducting probe atomic
force microscopy (CP-AFM) and confocal micro-Raman/Photoluminescence (PL)
imaging analysis. Local areas characterized by a strong decrease of the local
resistance (5-6 orders of magnitude drop) with respect to their close
surrounding have been identified in several different regions of the sample
surface. The same local areas, also referenced as electrical hot-spots, reveal
a slightly constrained diamond lattice and three dominant Raman bands in the
low-wavenumber region (590, 914 and 1040 cm-1). These latter bands are usually
assigned to the vibrational modes involving boron impurities and its possible
complexes that can electrically act as traps for charge carriers. Local
current-voltage measurements performed at the hot-spots point out a
trap-filled-limited (TFL) current as the main conduction mechanism favoring the
leakage current in the Schottky devices.",1404.0472v2
2014-09-20,Crystallization characteristics and chemical bonding properties of nickel carbide thin film nanocomposites,"The crystal structure and chemical bonding of magnetron-sputtering deposited
nickel carbide Ni$_{1-x}$C$_{x}$ (0.05$\leq$x$\leq$0.62) thin films have been
investigated by high-resolution X-ray diffraction, transmission electron
microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and soft
X-ray absorption spectroscopy. By using X-ray as well as electron diffraction,
we found carbon-containing hcp-Ni (hcp-NiC$_{y}$ phase), instead of the
expected rhombohedral-Ni$_{3}$C. At low carbon content (4.9 at\%) the thin film
consists of hcp-NiC$_{y}$ nanocrystallites mixed with a smaller amount of
fcc-NiC$_{x}$. The average grain size is about 10-20 nm. With the increase of
carbon content to 16.3 at\%, the film contains single-phase hcp-NiC$_{y}$
nanocrystallites with expanded lattice parameters. With further increase of
carbon content to 38 at\%, and 62 at\%, the films transform to X-ray amorphous
materials with hcp-NiC$_{y}$ and fcc-NiC$_{x }$ nanodomain structures in an
amorphous carbon-rich matrix. Raman spectra of carbon indicate dominant
$sp^{2}$ hybridization, consistent with photoelectron spectra that show a
decreasing amount of C-Ni phase with increasing carbon content. The Ni $3d$ - C
$2p$ hybridization in the hexagonal structure gives rise to the salient
double-peak structure in Ni $2p$ soft X-ray absorption spectra at 16.3 at\%
that changes with carbon content. We also show that the resistivity is not only
governed by the amount of carbon, but increases by more than a factor of two
when the samples transform from crystalline to amorphous.",1409.5912v1
2015-03-04,Signature of strong spin-orbital coupling in the large non-saturating magnetoresistance material WTe2,"We report the detailed electronic structure of WTe$_2$ by high resolution
angle-resolved photoemission spectroscopy. Unlike the simple one electron plus
one hole pocket type of Fermi surface topology reported before, we resolved a
rather complicated Fermi surface of WTe$_2$. Specifically, there are totally
nine Fermi pockets, including one hole pocket at the Brillouin zone center
$\Gamma$, and two hole pockets and two electron pockets on each side of
$\Gamma$ along the $\Gamma$-$X$ direction. Remarkably, we have observed
circular dichroism in our photoemission spectra, which suggests that the
orbital angular momentum exhibits a rich texture at various sections of the
Fermi surface. As reported previously for topological insulators and Rashiba
systems, such a circular dichroism is a signature for spin-orbital coupling
(SOC). This is further confirmed by our density functional theory calculations,
where the spin texture is qualitatively reproduced as the conjugate consequence
of SOC. Since the backscattering processes are directly involved with the
resistivity, our data suggest that the SOC and the related spin and orbital
angular momentum textures may be considered in the understanding of the
anomalous magnetoresistance of WTe$_2$.",1503.01422v1
2015-11-03,Two-dimensional epitaxial superconductor-semiconductor heterostructures: A platform for topological superconducting networks,"Progress in the emergent field of topological superconductivity relies on
synthesis of new material combinations, combining superconductivity, low
density, and spin-orbit coupling (SOC). For example, theory [1-4] indicates
that the interface between a one-dimensional (1D) semiconductor (Sm) with
strong SOC and a superconductor (S) hosts Majorana modes with nontrivial
topological properties [5-8]. Recently, epitaxial growth of Al on InAs
nanowires was shown to yield a high quality S-Sm system with uniformly
transparent interfaces [9] and a hard induced gap, indicted by strongly
suppressed sub gap tunneling conductance [10]. Here we report the realization
of a two-dimensional (2D) InAs/InGaAs heterostructure with epitaxial Al,
yielding a planar S-Sm system with structural and transport characteristics as
good as the epitaxial wires. The realization of 2D epitaxial S-Sm systems
represent a significant advance over wires, allowing extended networks via
top-down processing. Among numerous potential applications, this new material
system can serve as a platform for complex networks of topological
superconductors with gate-controlled Majorana zero modes [1-4]. We demonstrate
gateable Josephson junctions and a highly transparent 2D S-Sm interface based
on the product of excess current and normal state resistance.",1511.01127v2
2015-11-08,Real-time Stress Measurements in Germanium Thin Film Electrodes during Electrochemical Lithiation/delithiation Cycling,"An in situ study of stress evolution and mechanical behavior of germanium as
a lithium-ion battery electrode material is presented. Thin films of germanium
are cycled in a half-cell configuration with lithium metal foil as
counter/reference electrode, with 1M LiPF6 in ethylene carbonate, diethyl
carbonate, dimethyl carbonate solution (1:1:1, wt. %) as electrolyte. Real-time
stress evolution in the germanium thin-film electrodes during electrochemical
lithiation/delithiation is measured by monitoring the substrate curvature using
the multi-beam optical sensing method. Upon lithiation a-Ge undergoes extensive
plastic deformation, with a peak compressive stress reaching as high as -0.76
+/- 0.05 GPa (mean +/- standard deviation). The compressive stress decreases
with lithium concentration reaching a value of approximately -0.3 GPa at the
end of lithiation. Upon delithiation the stress quickly became tensile and
follows a trend that mirrors the behavior on compressive side; the average peak
tensile stress of the lithiated Ge samples was approximately 0.83 GPa. The peak
tensile stress data along with the SEM analysis was used to estimate a lower
bound fracture resistance of lithiated Ge, which is approximately 5.3 J/m^2. It
was also observed that the lithiated Ge is rate sensitive, i.e., stress depends
on how fast or slow the charging is carried out.",1511.02442v1
2016-02-03,Full range of proximity effect probed with Superconductor/Graphene/Superconductor junctions,"The high tunability of the density of states of graphene makes it an ideal
probe of quantum transport in different regimes. In particular, the
supercurrent that can flow through a non-superconducting (N) material connected
to two superconducting electrodes, crucially depends on the lenghth of the N
relative to the superconducting coherence length. Using graphene as the N
material we have investigated the full range of the superconducting proximity
effect, from short to long diffusive junctions. By combining several
S/graphene/S samples with different contacts and lengths, and measuring their
gate-dependent critical currents ($ I_c $) and normal state resistance $ R_N $,
we compare the product $eR_NI_c$ to the relevant energies, the Thouless energy
in long junctions and the superconducting gap of the contacts in short
junctions, over three orders of magnitude of Thouless energy. The experimental
variations strikingly follow a universal law, close to the predictions of the
proximity effect both in the long and short junction regime, as well as in the
crossover region, thereby revealing the interplay of the different energy
scales. Differences in the numerical coefficients reveal the crucial role
played by the interfacial barrier between graphene and the superconducting
electrodes, which reduces the supercurrent in both short and long junctions.
Surprisingly the reduction of supercurrent is independent of the gate voltage
and of the nature of the electrodes. A reduced induced gap and Thouless energy
are extracted, revealing the role played by the dwell time in the barrier in
the short junction, and an effective increased diffusion time in the long
junction. We compare our results to the theoretical predictions of Usadel
equations and numerical simulations which better reproduce experiments with
imperfect NS interfaces.",1602.01489v1
2016-02-16,An Integrated Tantalum Sulfide - Boron Nitride - Graphene Oscillator: A Charge-Density-Wave Device Operating at Room Temperature,"The charge-density-wave (CDW) phase is a macroscopic quantum state consisting
of a periodic modulation of the electronic charge density accompanied by a
periodic distortion of the atomic lattice in quasi-1D or layered 2D metallic
crystals. Several layered transition metal dichalcogenides, such as 1T-TaSe2,
1T-TaS2 and 1T-TiSe2, exhibit unusually high transition temperatures to
different CDW symmetry-reducing phases. These transitions can be affected by
environmental conditions, film thickness and applied electric bias. However,
device applications of these intriguing systems at room temperature or their
integration with other 2D materials have not been explored. Here we show that
in 2D CDW 1T-TaS2, the abrupt change in the electrical conductivity and
hysteresis at the transition point between nearly-commensurate and
incommensurate charge-density-wave phases can be used for constructing an
oscillator that operates at room temperature. The hexagonal boron nitride was
capped on 1T-TaS2 thin film to provide protection from oxidation, and an
integrated graphene transistor provides a voltage tunable, matched,
low-resistance load enabling precise voltage control of the oscillator
frequency. The integration of these three disparate two-dimensional materials,
in a way that exploits the unique properties of each, yields a simple,
miniaturized, voltage-controlled oscillator device. Theoretical considerations
suggest that the upper limit of oscillation frequency to be in the THz regime.",1602.05147v1
2016-05-05,"Structural, optical and complex impedance spectroscopy study of multiferroic Bi2Fe4O9 ceramic","Multiferroic bismuth ferrite Bi_2Fe_4O_9 (BFO) ceramic was synthesized by
conventional solid state reaction route. X-ray diffraction and Rietveld
refinement show formation of single phase ceramic with orthorhombic crystal
structure (space group Pbam). The morphological study depicted a well-defined
grain of size $\simeq$2{\mu}m. The optical studies were carried out by using
UV-Vis spectrophotometer which shows a band gap of 1.53 eV and a green emission
spectrum at 537 is observed in the Photoluminescence study. The frequency
dependent dielectric study at various temperature revealed that the dielectric
constant decreases with increase in frequency. A noticeable peak shift towards
higher frequency with increasing temperature is observed in the frequency
dependent dielectric loss plot. The impedance spectroscopy shows a substantial
shift in imaginary impedance (Z"") peaks toward the high frequency side
described that the conduction in material favoring the long range motion of
mobile charge carriers. The presence of non-Debye type multiple relaxations has
been confirmed by complex modulus analysis. The frequency dependent ac
conductivity at different temperatures indicates that the conduction process is
thermally activated. The variation of dc conductivity exhibited a negative
temperature coefficient of resistance behavior. The activation energy
calculated from impedance, modulus and conductivity data confirmed that the
oxygen vacancies play a vital role in the conduction mechanism.",1605.01574v1
2016-08-24,Engineering quantum spin Hall insulators by strained-layer heterostructures,"Quantum spin Hall insulators (QSHIs), also known as two-dimensional
topological insulators, have emerged as an unconventional class of quantum
states with insulating bulk and conducting edges originating from nontrivial
inverted band structures, and have been proposed as a platform for exploring
spintronics applications and exotic quasiparticles related to the spin-helical
edge modes. Despite theoretical proposals for various materials, however,
experimental demonstrations of QSHIs have so far been limited to two
systems--HgTe/CdTe and InAs/GaSb--both of which are lattice-matched
semiconductor heterostructures. Here we report transport measurements in yet
another realization of a band-inverted heterostructure as a QSHI
candidate--InAs/In$_{x}$Ga$_{1-x}$Sb with lattice mismatch. We show that the
compressive strain in the In$_{x}$Ga$_{1-x}$Sb layer enhances the band overlap
and energy gap. Consequently, high bulk resistivity, two orders of magnitude
higher than for InAs/GaSb, is obtained deep in the band-inverted regime. The
strain also enhances bulk Rashba spin-orbit splitting, leading to an unusual
situation where the Fermi level crosses only one spin branch for electronlike
and holelike bands over a wide density range. These properties make this system
a promising platform for robust QSHIs with unique spin properties and
demonstrate strain to be an important ingredient for tuning spin-orbit
interaction.",1608.06751v2
2016-11-29,Magnetoelectric effect in antiferromagnetic multiferroic Pb(Fe1/2Nb1/2)O3 and its solid solutions with PbTiO3,"Antiferromagnets (AFMs) are presently considered as promising materials for
applications in spintronics and random access memories due to the robustness of
information stored in AFM state against perturbing magnetic fields (P. Wadley
et al., Science 351, 587 (2016)). In this respect, AFM multiferroics maybe
attractive alternatives for conventional AFMs as the coupling of magnetism with
ferroelectricity (magnetoelectric effect) offers an elegant possibility of
electric field control and switching of AFM domains. Here we report the results
of comprehensive experimental and theoretical investigations of the quadratic
magnetoelectric (ME) effect in single crystals and high-resistive ceramics of
Pb(Fe1/2Nb1/2)O3 (PFN) and (1- x)Pb(Fe1/2Nb1/2)O3xPbTiO3 (PFNxPT). We are
interested primarily in the temperature range of multiferroic phase, T < 150 K,
where the ME coupling coefficient is extremely large (as compared to well-known
multiferroic BiFeO3) and shows sign reversal at
paramagnetic-to-antiferromagnetic phase transition. Moreover, we observe strong
ME response nonlinearity in the AFM phase in the magnetic fields of only few
kOe. To describe the temperature and magnetic field dependencies of the above
unusual features of ME effect in PFN and PFN-xPT, we use simple
phenomenological Landau approach which explains experimental data surprisingly
well. Our ME measurements demonstrate that the electric field of only 20-25
kV/cm is able to switch the AFM domains and align them with ferroelectric ones
even in PFN ceramic samples.",1611.09899v1
2017-11-21,Nanofeatures Induced by Severe Shot Peening (SSP) on Magnesium Alloy AZ31,"Considering the sensitivity of both fatigue strength and corrosion rate to
the surface characteristics, apposite surface treatments could address the
related challenges for biodegradable magnesium-based materials. Herein, we
treated the surface of a biocompatible magnesium alloy by a low cost and
versatile severe plastic deformation technique, severe shot peening, to
evaluate the potential of surface grain refinement to enhance functionality in
biological environment. The evolution of surface grain structure and surface
morphology were investigated using optical as well as scanning and transmission
electron microscopy. Surface roughness, wettability and chemical composition,
as well as in depth-microhardness and residual stress distribution, and
corrosion resistance were investigated. Successive light surface grinding was
used after severe shot peening to eliminate the effect of surface roughness and
separately investigate the influence of grain refinement alone.
Cytocompatibility tests with osteoblasts (or bone forming cells) were performed
using sample extracts. Results revealed for the first time that severe shot
peening can significantly enhance mechanical properties without causing adverse
effects to the growth of surrounding osteoblasts. The corrosion behavior, on
the other hand, was not improved by severe shot peening; nevertheless, slight
grinding of the rough surface layer with a high density of crystallographic
lattice defects, without removing the entire nanocrystallized layer, provided a
good potential for improving corrosion characteristics after severe shot
peening and thus, this method should be studied for a wide range of orthopedic
applications in which biodegradable magnesium is used.",1712.02834v1
2017-12-13,Quantum effects on dislocation motion from Ring-Polymer Molecular Dynamics,"Quantum motion of atoms known as zero-point vibrations is recognized to be
important at low temperatures in condensed matter systems comprised of light
atoms or ions, affecting such properties and behaviors as proton-transfer
reactions, vibrational spectra of water and ice, and mechanical properties of
low temperature helium. Recently, quantum motion of atoms was proposed to
explain a long-standing discrepancy between theoretically computed and
experimentally measured low-temperature resistance (Peierls stress) to
dislocation motion in iron and possibly other metals with high atomic masses.
Here we report the first direct simulations of quantum motion of screw
dislocations in iron within the exact formalism of Ring-Polymer Molecular
Dynamics (RPMD) that rigorously accounts for quantum effects on the statistics
of condensed-phase systems. Our quantum RPMD simulations predict only a modest
($\approx\!13\%$) reduction in the Peierls stress in iron compared to its fully
classical prediction. Our simulations confirm that reduction in the Peierls
stress solely due to the zero-point energy is close to $50\%$ predicted
earlier, but its effect is substantially offset by an increase in the effective
atom size with decreasing temperature, an effect known as quantum dispersion.
Thus, quantum motion of atoms does not resolve the notorious discrepancy
between theoretical and experimental values of the Peierls stress in iron.",1712.04629v2
2018-02-06,Quasiparticle dynamics in granular aluminum close to the superconductor to insulator transition,"Superconducting high kinetic inductance elements constitute a valuable
resource for quantum circuit design and millimeter-wave detection. Granular
aluminum (GrAl) in the superconducting regime is a particularly interesting
material since it has already shown a kinetic inductance in the range of
nH$/\Box$ and its deposition is compatible with conventional Al/AlOx/Al
Josephson junction fabrication. We characterize microwave resonators fabricated
from GrAl with a room temperature resistivity of $4 \times
10^3\,\mu\Omega\cdot$cm, which is a factor of 3 below the superconductor to
insulator transition, showing a kinetic inductance fraction close to unity. The
measured internal quality factors are on the order of $Q_{\mathrm{i}} = 10^5$
in the single photon regime, and we demonstrate that non-equilibrium
quasiparticles (QP) constitute the dominant loss mechanism. We extract QP
relaxation times in the range of 1 s and we observe QP bursts every $\sim 20$
s. The current level of coherence of GrAl resonators makes them attractive for
integration in quantum devices, while it also evidences the need to reduce the
density of non-equilibrium QPs.",1802.01858v2
2018-01-06,Apically Dominant Mechanism for Improving Catalytic Activities of N-Doped Carbon Nanotube Arrays in Rechargeable Zinc-Air Battery,"The oxygen reduction (ORR) and oxygen evolution reactions (OER) in Zn-air
batteries (ZABs) require highly efficient, cost-effective and stable
electrocatalysts as replacements to traditionally high cost, inconsistently
stable and low poison resistant Platinum group metals (PGM) catalysts.
Although, nitrogen-doped carbon nanotube (NCNT) arrays have been developed over
recent decades through various advanced technologies are now capable of
catalyzing ORR efficiently, their underdeveloped bifunctional property,
hydrophobic surface, and detrimental preparation strategy are found to limit
practical large-scale commercialization for effective rechargeable ZABs. Here,
we have demonstrated fabrication of a three-dimensional (3D) nickel foam
supported NCNT arrays with CoNi nanoparticles (NPs) encapsulated within the
apical domain (denoted as CoNi@NCNT/NF) that exhibits excellent bifunctional
catalytic performance toward both ORR (onset potential of 0.97 V vs. RHE) and
OER (overpotential of 1.54 V vs. RHE at 10 mA cm$^{-2}$). We further examined
the practicability of this CoNi@NCNT/NF material being used as an air electrode
for rechargeable ZAB coin cell and pouch cell systems. The ZAB coin cell showed
a peak power density of 108 mW cm$^{-2}$ with an energy density of 845 Wh
kg$_{Zn}^{-1}$ and robust rechargeability over 28h under ambient conditions,
which exceeds the performance of PGM catalysts and leading non-PGM
electrocatalysts. In addition, density functional theory (DFT) calculations
revealed that the ORR and OER catalytic performance of the CoNi@NCNT/NF
electrode are mainly derived from the d-orbitals from the CoNi NPs encapsulated
within the apical dominant end of the NCNTs.",1802.02063v1
2018-03-06,Magic-angle graphene superlattices: a new platform for unconventional superconductivity,"The understanding of strongly-correlated materials, and in particular
unconventional superconductors, has puzzled physicists for decades. Such
difficulties have stimulated new research paradigms, such as ultra-cold atom
lattices for simulating quantum materials. Here we report on the realization of
intrinsic unconventional superconductivity in a 2D superlattice created by
stacking two graphene sheets with a small twist angle. For angles near
$1.1^\circ$, the first `magic' angle, twisted bilayer graphene (TBG) exhibits
ultra-flat bands near charge neutrality, which lead to correlated insulating
states at half-filling. Upon electrostatic doping away from these correlated
insulating states, we observe tunable zero-resistance states with a critical
temperature $T_c$ up to 1.7 K. The temperature-density phase diagram shows
similarities with that of the cuprates, including superconducting domes.
Moreover, quantum oscillations indicate small Fermi surfaces near the
correlated insulating phase, in analogy with under-doped cuprates. The relative
high $T_c$, given such small Fermi surface (corresponding to a record-low 2D
carrier density of $10^{11} \textrm{cm}^{-2}$ , renders TBG among the strongest
coupling superconductors, in a regime close to the BCS-BEC crossover. These
novel results establish TBG as the first purely carbon-based 2D superconductor
and as a highly tunable platform to investigate strongly-correlated phenomena,
which could lead to insights into the physics of high-$T_c$ superconductors and
quantum spin liquids.",1803.02342v2
2018-03-31,The Role of Crystal Orientation in the Dissolution of UO$_2$ Thin Films,"Epitaxial thin films have been utilised to investigate the radiolytic
dissolution of uranium dioxide interfaces. Thin films of UO$_2$ deposited on
single crystal yttria stabilised zirconia substrates have been exposed to water
in the presence of a high flux, monochromatic, synchrotron x-ray source. In
particular, this technique was applied to induce dissolution of three UO$_2$
thin films, grown along the principle UO$_2$ crystallographic orientations:
(001), (110) and (111). Dissolution of each film was induced for 9 accumulative
corrosion periods, totalling 270s, after which XRR spectra were recorded to
observe the change in morphology of the films as a function of exposure time.
While the (001) and (110) oriented films were found to corrode almost linearly
and at comparable rates, the (111) film was found to be significantly more
corrosion resistant, with no loss of UO$_2$ material being observed after the
initial 90s corrosion period. These results distinctly show the effect of
crystallographic orientation on the rate of x-ray induced UO$_2$ dissolution.
This result may have important consequences for theoretical dissolution models,
as it is evident that orientation dependence must be taken into consideration
to obtain accurate predictions of the dissolution behaviour of UO$_2$.",1804.00201v1
2018-05-24,Impact of thermal fluctuations on transport in antiferromagnetic semimetals,"Recent demonstrations on manipulating antiferromagnetic (AF) order have
triggered a growing interest in antiferromagnetic metal (AFM), and potential
high-density spintronic applications demand further improvements in the
anisotropic magnetoresistance (AMR). The antiferromagnetic semimetals (AFS) are
newly discovered materials that possess massless Dirac fermions that are
protected by the crystalline symmetries. In this material, a reorientation of
the AF order may break the underlying symmetries and induce a finite energy
gap. As such, the possible phase transition from the semimetallic to insulating
phase gives us a choice for a wide range of resistance ensuring a large AMR. To
further understand the robustness of the phase transition, we study thermal
fluctuations of the AF order in AFS at a finite temperature. For macroscopic
samples, we find that the thermal fluctuations effectively decrease the
magnitude of the AF order by renormalizing the effective Hamiltonian. Our
finding suggests that the insulating phase exhibits a gap narrowing at elevated
temperatures, which leads to a substantial decrease in AMR. We also examine
spatially correlated thermal fluctuations for microscopic samples by solving
the microscopic Landau-Lifshitz-Gilbert equation finding a qualitative
difference of the gap narrowing in the insulating phase. For both cases, the
semimetallic phase shows a minimal change in its transmission spectrum
illustrating the robustness of the symmetry protected states in AFS. Our
finding may serve as a guideline for estimating and maximizing AMR of the AFS
samples at elevated temperatures.",1805.09826v1
2018-09-03,Imparting icephobicity with substrate flexibility,"Ice accumulation hinders the performance of, and poses safety threats for
infrastructure both on the ground and in the air. Previously, rationally
designed superhydrophobic surfaces have demonstrated some potential as a
passive means to mitigate ice accretion; however, further studies on material
solutions that reduce impalement and contact time for impacting supercooled
droplets and can also repel droplets that freeze during surface contact are
urgently needed. Here we demonstrate the collaborative effect of substrate
flexibility and surface nanotexture on enhancing both icephobicity and the
repellency of viscous droplets. We first investigate the influence of increased
viscosity on impalement resistance and droplet-substrate contact time after
impact. Then we examine the effect of droplet partial solidification on recoil
and simulate more challenging icing conditions by impacting supercooled water
droplets onto flexible and rigid surfaces containing ice nucleation promoters.
We demonstrate a passive mechanism for shedding partially solidified droplets
under conditions where partial solidification occurs much faster than the
natural droplet oscillation which does not rely on converting droplet surface
energy into kinetic energy. Using an energy-based model, we identify a
previously unexplored mechanism whereby the substrate oscillation and velocity
govern the rebound process, with low-areal density and moderately stiff
substrates acting to efficiently absorb the incoming droplet kinetic energy and
rectify it back, allowing droplets to overcome adhesion and gravitational
forces, and recoil. This mechanism applies for a range of droplet viscosities,
spanning from low to high viscosity fluids and even ice slurries, which do not
rebound from rigid superhydrophobic substrates.",1809.00490v1
2018-11-12,Antiferromagnet-based spintronic functionality by controlling isospin domains in a layered perovskite iridate,"The novel electronic state of the canted antiferromagnetic (AFM) insulator,
strontium iridate (Sr2IrO4) has been well described by the spin-orbit-entangled
isospin Jeff = 1/2, but the role of isospin in transport phenomena remains
poorly understood. In this study, antiferromagnet-based spintronic
functionality is demonstrated by combining unique characteristics of the
isospin state in Sr2IrO4. Based on magnetic and transport measurements, large
and highly anisotropic magnetoresistance (AMR) is obtained by manipulating the
antiferromagnetic isospin domains. First-principles calculations suggest that
electrons whose isospin directions are strongly coupled to in-plane net
magnetic moment encounter the isospin mismatch when moving across
antiferromagnetic domain boundaries, which generates a high resistance state.
By rotating a magnetic field that aligns in-plane net moments and removes
domain boundaries, the macroscopically-ordered isospins govern dynamic
transport through the system, which leads to the extremely angle-sensitive AMR.
As with this work that establishes a link between isospins and magnetotransport
in strongly spin-orbit-coupled AFM Sr2IrO4, the peculiar AMR effect provides a
beneficial foundation for fundamental and applied research on AFM spintronics.",1811.04562v1
2018-11-30,Spin Gapless Semiconducting Nature in Co-rich Co1+xFe1-xCrGa: Insight and Advancements,"In this report, we present structural, electronic, magnetic and transport
properties of Co-rich spin gapless semiconductor CoFeCrGa using both
theoretical and experimental techniques. The key advantage of Co-rich samples
$\mathrm{Co_{1+x}Fe_{1-x}CrGa}$ is the high Curie temperature (T$\mathrm{_C}$)
and magnetization, without compromising the SGS nature (up to x = 0.4), and
hence our choice. The quaternary Heusler alloys $\mathrm{Co_{1+x}Fe_{1-x}CrGa}$
(x = 0.1 to 0.5) are found to crystallize in LiMgPdSn-type structure having
space group $F\bar{4}3m$ (\# 216). The measured Curie temperature increases
from 690 K (x = 0) to 870 K (x = 0.5). Observed magnetization values follow the
Slater-Pauling rule. Measured electrical resistivity, in the temperature range
of 5-350 K, suggests that the alloys retain the SGS behavior up to x = 0.4,
beyond which it reflects metallic character. Unlike conventional
semiconductors, the conductivity value ($\mathrm{\sigma_{xx}}$) at 300 K lies
in the range of 2289 S $\mathrm{cm^{-1}}$ to 3294 S $\mathrm{cm^{-1}}$, which
is close to that of other reported SGS materials. The anomalous Hall effect is
comparatively low. The intrinsic contribution to the anomalous Hall
conductivity increase with x, which can be correlated with the enhancement in
chemical order. The anomalous Hall coefficient is found to increase from 38
S/cm for x = 0.1 to 43 S/cm for 0.3. Seebeck coefficients turn out to be
vanishingly small below 300 K, another signature for being SGS. All the alloys
(for different x) are found to be both chemically and thermally stable.
Simulated magnetization agrees fairly with the experiment. As such Co-rich
CoFeCrGa is a promising candidate for room temperature spintronic applications,
with enhanced T$\mathrm{_C}$, magnetic properties and SGS nature.",1811.12684v1
2019-09-24,Spin-transfer dynamics in MgO-based magnetic tunnel junctions with an out-of-plane magnetized free layer and an in-plane polarizer,"Here, we present an analytical and numerical model describing the
magnetization dynamics in MgO-based spin-torque nano-oscillators with an
in-plane magnetized polarizer and an out-of-plane free layer. We introduce the
spin-transfer torque asymmetry by considering the cosine angular dependence of
the resistance between the two magnetic layers in the stack. For the analytical
solution, dynamics are determined by assuming a circular precession trajectory
around the direction perpendicular to the plane, as set by the effective field,
and calculating the energy integral over a single precession period. In a more
realistic approach, we include the bias dependence of the tunnel
magnetoresistance, which is assumed empirically to be a piecewise linear
function of the applied voltage. The dynamical states are found by solving the
stability condition for the Jacobian matrix for out-of-plane static states. We
find that the bias dependence of the tunnel magnetoresistance, which is an
inseparable effect in every tunnel junction, exhibits drastic impact on the
spin-torque nano-oscillator phase diagram, mainly by increasing the critical
current for dynamics and quenching the oscillations at high currents. The
results are in good agreement with our experimental data published elsewhere.",1909.10983v1
2020-03-16,Unconventional Hall response in the quantum limit of HfTe5,"Interacting electrons confined to their lowest Landau level in a high
magnetic field can form a variety of correlated states, some of which manifest
themselves in a Hall effect. Although such states have been predicted to occur
in three dimensional semimetals, a corresponding Hall response has not yet been
experimentally observed. Here, we report the observation of an unconventional
Hall response in the quantum limit of the bulk semimetal HfTe5, adjacent to the
three-dimensional quantum Hall effect of a single electron band at low magnetic
fields. The additional plateau-like feature in the Hall conductivity of the
lowest Landau level is accompanied by a Shubnikov-de Haas minimum in the
longitudinal electrical resistivity and its magnitude relates as 3/5 to the
height of the last plateau of the three-dimensional quantum Hall effect. Our
findings are consistent with strong electron-electron interactions, stabilizing
an unconventional variant of the Hall effect in a three-dimensional material in
the quantum limit.",2003.07213v3
2017-03-07,Fast multicolor photodetectors based on graphene-contacted p-GaSe/n-InSe van der Waals heterostructures,"The integration of different two-dimensional materials within a multilayer
van der Waals (vdW) heterostructure offers a promising technology for realizing
high performance opto-electronic devices such as photodetectors and light
sources1-3. Transition metal dichalcogenides, e.g. MoS2 and WSe2, have been
employed as the optically-active layer in recently developed heterojunctions.
However, MoS2 and WSe2 become direct band gap semiconductors only in mono- or
bilayer form4,5. In contrast, the metal monochalcogenides InSe and GaSe retain
a direct bandgap over a wide range of layer thicknesses from bulk crystals down
to exfoliated flakes only a few atomic monolayers thick6,7. Here we report on
vdW heterojunction diodes based on InSe and GaSe: the type II band alignment
between the two materials and their distinctive spectral response, combined
with the low electrical resistance of transparent graphene electrodes, enable
effective separation and extraction of photoexcited carriers from the
heterostructure even when no external voltage is applied. Our devices are fast
(< 10 {\mu}s), self-driven photodetectors with multicolor photoresponse ranging
from the ultraviolet to the near-infrared and have the potential to accelerate
the exploitation of two-dimensional vdW crystals by creating new routes to
miniaturized optoelectronics beyond present technologies.",1703.02534v1
2017-03-28,Co-appearance of superconductivity and ferromagnetism in a Ca$_2$RuO$_4$ nanofilm crystal,"By tuning the physical and chemical pressures of layered perovskite materials
we can realize the quantum states of both superconductors and insulators. By
reducing the thickness of a layered crystal to a nanometer level, a nanofilm
crystal can provide novel quantum states that have not previously been found in
bulk crystals. Here we report the realization of high-temperature
superconductivity in Ca$_2$RuO$_4$ nanofilm single crystals. Ca$_2$RuO$_4$ thin
film with the highest transition temperature $T_c$ (midpoint) of 64~K exhibits
zero resistance in electric transport measurements. The superconducting
critical current exhibited a logarithmic dependence on temperature and was
enhanced by an external magnetic field. Magnetic measurements revealed a
ferromagnetic transition at 180~K and diamagnetic magnetization due to
superconductivity. Our results suggest the co-appearance of superconductivity
and ferromagnetism in Ca$_2$RuO$_4$ nanofilm crystals. We also found that the
induced bias current and the tuned film thickness caused a
superconductor-insulator transition. The fabrication of micro-nanocrystals made
of layered material enables us to discuss rich superconducting phenomena in
ruthenates.",1703.09459v2
2018-10-16,The superconductor-superinsulator transition: S-duality and QCD on the desktop,"We show that the nature of quantum phases around the superconductor-insulator
transition (SIT) is controlled by charge-vortex topological interactions and
does not depend on the details of material parameters and disorder. We find
three distinct phases, superconductor, superinsulator and bosonic topological
insulator. The superinsulator is a state of matter with infinite resistance in
a finite temperature range, which is the S-dual of the superconductor and in
which charge transport is prevented by electric strings binding charges of
opposite sign. The electric strings ensuring linear confinement of charges are
generated by instantons and are dual to superconducting Abrikosov vortices.
Material parameters and disorder enter the London penetration depth of the
superconductor, the string tension of the superinsulator and the quantum
fluctuation parameter driving the transition between them. They are entirely
encoded in four phenomenological parameters of a topological gauge theory of
the SIT. Finally, we point out that, in the context of strong coupling gauge
theories, the many-body localization phenomenon that is often referred to as an
underlying mechanism for superinsulation is a mere transcription of the
well-known phenomenon of confinement into solid state physics language and is
entirely driven by endogenous disorder embodied by instantons with no need of
exogenous disorder.",1810.06862v1
2020-04-14,Intrinsically Activated SrTiO3: Photocatalytic H2 Evolution from Neutral Aqueous Methanol Solution in the Absence of Any Noble Metal Cocatalyst,"Noble metal cocatalysts are conventionally a crucial factor in
oxide-semiconductor-based photocatalytic hydrogen generation. In the present
work, we show that optimized high-temperature hydrogenation of commercially
available strontium titanate (SrTiO3) powder can be used to engineer an
intrinsic cocatalytic shell around nanoparticles that can create a
photocatalyst that is highly effective without the use of any additional
cocatalyst for hydrogen generation from neutral aqueous methanol solutions.
This intrinsic activation effect can also be observed for SrTiO3[100] single
crystal as well as Nb-doped SrTiO3 (100) single crystal. For all types of
SrTiO3 samples (nanopowders and either of the single crystals), hydrogenation
under optimum conditions leads to a surface-hydroxylated layer together with
lattice defects visible by transmission electron microscopy, electron
paramagnetic resonance (EPR), and photoluminescence (PL). Active samples
provide states in a defective matrix -- this is in contrast to the inactive
defects formed in other reductive atmospheres. In aqueous media, active SrTiO3
samples show a significant negative shift of the flatband potential (in
photoelectrochemical as well as in capacitance data) and a lower
charge-transfer resistance for photoexcited electrons. We therefore ascribe the
remarkable cocatalyst-free activation of the material to a synergy between
thermodynamics (altered interface energetics induced by hydroxylation) and
kinetics (charge transfer mediation by suitable Ti3+ states).",2004.06573v1
2022-02-10,Dynamics of Multi-Domains in Ferroelectric Tunnel Junction,"The Discovery of giant tunnel electroresistance (TER) in Ferroelectric Tunnel
Junction (FTJ) paves a futuristic possibility of utilizing the FTJ as a
bistable resistive device with an enormously high ON/OFF ratio. In the last 20
years, numerous studies have reported that the formation of multidomain in
ferroelectric material is an inevitable process to minimize the total system
energy. Recent studies based on phase-field simulations have demonstrated that
domain nucleation/motion substantially alters the electrostatics of a
ferroelectric material. However, the impact of domain dynamics on quantum
transport in FTJ remains elusive. This paper presents a comprehensive study of
multidomain dynamics in a ferroelectric tunnel junction. Analysis of this
article is twofold; firstly, we study the impact of domain dynamics on
electrostatics in an FTJ. Subsequently, the obtained electrostatics is used to
study the variations in tunneling current, and TER originated from multidomain
dynamics. We show that ON/OFF current density and TER vary locally in the
ferroelectric region. Furthermore, the device's electrostatics and quantum
transport exhibit an oscillatory nature due to periodic domain texture. ON/OFF
current density shows a sine/cosine distribution in ferroelectric, and
approximately one-decade local variation in current density is observed. These
local fluctuations in current density cause oscillations in the device's ON/OFF
ratio. Optimization techniques to achieve a uniform and maximum TER are also
discussed. A 2D analytical and explicit model is derived by solving coupled 2D
Poisson's equation and Landau-Ginzburg equation. The model incorporates the
switching and nucleation of domains by minimizing net ferroelectric energy
(depolarization+free+gradient energy density). Furthermore, the impact of the
bottom insulator layer on ferroelectric's gradient energy is also studied.",2202.04926v1
2022-02-15,A Ta-TaS2 monolithic catalyst with robust and metallic interface for superior hydrogen evolution,"The use of highly active and robust catalysts is crucial for producing green
hydrogen by water electrolysis as we strive to achieve global carbon
neutrality. Noble metals like platinum are currently used in industry for the
hydrogen evolution reaction (HER), but suffer from scarcity, high price and
unsatisfied performance and stability at large current density, restricting
their large scale implementations. Here we report the synthesis of a new type
of monolithic catalyst (MC) consisting of a metal disulfide (e.g., TaS2)
catalyst vertically bonded to a conductive substrate of the same metal by
strong covalent bonds. These features give the MC a mechanically robust and
electrically near zero resistance interface, leading to an outstanding HER
performance including rapid charge transfer and excellent durability, together
with a low overpotential of 398 mV to achieve a current density of 2,000 mA
cm-2 as required by industry. The Ta TaS2 MC has a negligible performance decay
after 200 h operation at large current densities. In light of its unique
interface and the various choice of metal elements giving the same structure,
such monolithic materials may have broad uses besides catalysis.",2202.07339v1
2017-04-19,Potential Fluctuations at Low Temperatures in Mesoscopic-Scale SmTiO$_{3}$/SrTiO$_{3}$/SmTiO$_{3}$ Quantum Well Structures,"Heterointerfaces of SrTiO$_{3}$ with other transition metal oxides make up an
intriguing family of systems with a bounty of coexisting and competing physical
orders. Some examples, such as LaAlO$_{3}$/SrTiO$_{3}$, support a high carrier
density electron gas at the interface whose electronic properties are
determined by a combination of lattice distortions, spin-orbit coupling,
defects, and various regimes of magnetic and charge ordering. Here, we study
electronic transport in mesoscale devices made with heterostructures of
SrTiO$_{3}$ sandwiched between layers of SmTiO$_{3}$, in which the transport
properties can be tuned from a regime of Fermi-liquid like resistivity ($\rho
\sim T^{2}$) to a non-Fermi liquid ($\rho \sim T^{5/3}$) by controlling the
SrTiO$_{3}$ thickness. In mesoscale devices at low temperatures, we find
unexpected voltage fluctuations that grow in magnitude as $T$ is decreased
below 20 K, are suppressed with increasing contact electrode size, and are
independent of the drive current and contact spacing distance.
Magnetoresistance fluctuations are also observed, which are reminiscent of
universal conductance fluctuations but not entirely consistent with their
conventional properties. Candidate explanations are considered, and a mechanism
is suggested based on mesoscopic temporal fluctuations of the Seebeck
coefficient. An improved understanding of charge transport in these model
systems, especially their quantum coherent properties, may lead to insights
into the nature of transport in strongly correlated materials that deviate from
Fermi liquid theory.",1704.05744v1
2017-08-06,Electrical transport and optical band gap of NiFe$_\textrm{2}$O$_\textrm{x}$ thin films,"We fabricated NiFe$_\textrm{2}$O$_\textrm{x}$ thin films on
MgAl$_2$O$_4$(001) substrates by reactive dc magnetron co-sputtering varying
the oxygen partial pressure during deposition. The fabrication of a variable
material with oxygen deficiency leads to controllable electrical and optical
properties which would be beneficial for the investigations of the transport
phenomena and would, therefore, promote the use of such materials in spintronic
and spin caloritronic applications. We used several characterization techniques
in order to investigate the film properties, focusing on their structural,
magnetic, electrical, and optical properties. From the electrical resistivity
measurements we obtained the conduction mechanisms that govern the systems in
high and low temperature regimes, extracting low thermal activation energies
which unveil extrinsic transport mechanisms. The thermal activation energy
decreases in the less oxidized samples revealing the pronounced contribution of
a large amount of electronic states localized in the band gap to the electrical
conductivity. Hall effect measurements showed the mixed-type semiconducting
character of our films. The optical band gaps were determined via
ultraviolet-visible spectroscopy. They follow a similar trend as the thermal
activation energy, with lower band gap values in the less oxidized samples.",1708.01937v1
2019-03-05,All-optical cryogenic thermometry based on NV centers in nanodiamonds,"The nitrogen-vacancy (NV) center in diamond has been recognized as a
high-sensitivity nanometer-scale metrology platform. Thermometry has been a
recent focus, with attention largely confined to room temperature applications.
Thermometry has been a recent focus, with attention largely confined to room
temperature applications. Temperature sensing at low temperatures, however,
remains challenging as the sensitivity decreases for many commonly used
techniques which rely on a temperature dependent frequency shift of the NV
centers spin resonance and its control with microwaves. Here we use an
alternative approach that does not require microwaves, ratiometric all-optical
thermometry, and demonstrate that it may be utilized to liquid nitrogen
temperatures without deterioration of the sensitivity. The use of an array of
nanodiamonds embedded within a portably polydimethylsiloxane (PDMS) sheet
provides a versatile temperature sensing platform that can probe a wide variety
of systems without the configurational restrictions needed for applying
microwaves. With this device, we observe a temperature gradient over tens of
microns in a ferromagnetic-insulator substrate (YIG) under local heating by a
resistive heater. This thermometry technique provides a cryogenically
compatible, microwave-free, minimally invasive approach capable of probing
local temperatures with few restrictions on the substrate materials.",1903.01605v1
2021-01-03,3D Fluorescent Mapping of Invisible Molecular Damage after Cavi-tation in Hydrogen Exposed Elastomers,"Elastomers saturated with gas at high pressure suffer from cavity nucleation,
inflation, and deflation upon rapid or explosive de-compression. Although this
process often results in undetectable changes in appearance, it causes internal
damage, hampers func-tionality (e.g., permeability), and shortens lifetime.
Here, we tag a model poly(ethyl acrylate) elastomer with {\pi}-extended
anthracene-maleimide adducts that fluoresce upon polymer chain scission, and
map in 3D the internal damage present after a cycle of gas satu-ration and
rapid decompression. Interestingly, we observe that each cavity observable
during the decompression results in a dam-aged region, the shape of which
reveals a fracture locus of randomly oriented penny-shape cracks (i.e., with a
flower-like morpholo-gy) that contain crack arrest lines. Thus, cavity growth
likely proceeds discontinuously (i.e., non-steadily) through the stable and
unstable fracture of numerous 2D crack planes. This non-destructive methodology
to visualize in 3D molecular damage in polymer networks is novel and serves to
understand how fracture occurs under complex 3D loads, predict mechanical aging
of pristine look-ing elastomers, and holds potential to optimize
cavitation-resistant materials.",2101.00709v2
2021-01-28,Macroscopic yarns of FeCl$_{3}$-intercalated collapsed carbon nano-tubes with high doping and stability,"Macroscopic arrays of highly crystalline nanocarbons offer the possibility of
modifying the electronic structure of their low dimensional constituents, for
example through doping, and studying the resulting collective bulk behaviour.
Insertion of electron donors or acceptors between graphitic layers is an
attractive method to reversibly increase charge carrier concentra-tion without
disruption of the sp$2$-conjugated system. This work demonstrates FeCl$_{3}$
intercalation into fibres made up of collapsed (flattened) carbon nanotubes.
The bundles of collapsed CNTs, similar to crystallites of graphitic
nanoribbons, host elongated layered FeCl$_{3}$ crystals of hundreds of $nm$
long, much longer than previous reports on graphitic materials and directly
observable by transmission electron microscopy and X-ray diffraction.
Intercalated CNT fibres remain stable after months of exposure to ambient
conditions, partly due to the spontaneous formation of passivating monolayers
of FeClO at the crystal edge, preventing both desorption of intercalant and
further hydrolysis. Raman spectroscopy shows substantial electron transfer from
the CNTs to FeCl$_{3}$, a well-known acceptor, as observed by G band upshifts
as large as $25 cm^{-1}$. After resolving Raman features for the inner and
outer layers of the collapsed CNTs, strain and dynamic effect contributions of
charge transfer to the Raman upshift could be decoupled, giving a Fermi level
downshift of $- 0.72 eV$ and a large average free carrier concentration of
$5.3X10^{13}$ $cm^{-2}$ ($0.014$ electrons per carbon atom) in the intercalated
system. Four-probe resistivity measurements show an increase in conductivity by
a factor of six upon intercalation",2101.12077v1
2021-01-29,Doping isolated one-dimensional antiferro-magnetic semiconductor Vanadium tetrasulfide ($VS_4$) nanowires with carriers induces half-metallicity,"Quasi one-dimensional (1D) vanadium tetrasulfide ($VS_4$) nanowires (NWs) are
synthetic semiconductors which combine with each other through Van der Waals
interactions to form bulk phases. However, the properties of these individual
nanowires remain unknown. Nevertheless, our calculations of their stability
indicate that $VS_4$) NWs can be separated from their bulk structures.
Accordingly, we theoretically investigated the geometrical, electronic, and
magnetic properties of bulk phase and isolated $VS_4$ NWs. Our results indicate
that both bulk phase and isolated $VS_4$ NWs are semiconductors with band gaps
of 2.24 and 2.64 eV, respectively, and that they prefer the antiferromagnetic
(AFM) ground state based on DFT calculations. These calculations also suggested
that isolated $VS_4$ NWs show half-metallic antiferromagnetism upon electron
and hole doping because carrier doping splits the spin degeneracy to induce
local spin polarisation. As a result, spin polarisation currents in isolated
$VS_4$ NWs can be manipulated with locally applied gate voltage. Therefore,
these 1D AFM materials have a high potential for advancing both fundamental
research and spintronic applications because they are more resistant to
magnetic perturbation than their 1D ferromagnetic counterparts.",2101.12658v1
2016-09-29,Quantum imaging of current flow in graphene,"Since its first isolation in 2004, graphene has been found to host a plethora
of unusual electronic transport phenomena, making it a fascinating system for
fundamental studies in condensed-matter physics as well as offering tremendous
opportunities for future electronic and sensing devices. However, to fully
realise these goals a major challenge is the ability to non-invasively image
charge currents in monolayer graphene structures and devices. Typically,
electronic transport in graphene has been investigated via resistivity
measurements, however, such measurements are generally blind to spatial
information critical to observing and studying landmark transport phenomena
such as electron guiding and focusing, topological currents and viscous
electron backflow in real space, and in realistic imperfect devices. Here we
bring quantum imaging to bear on the problem and demonstrate high-resolution
imaging of current flow in graphene structures. Our method utilises an
engineered array of near-surface, atomic-sized quantum sensors in diamond, to
map the vector magnetic field and reconstruct the vector current density over
graphene geometries of varying complexity, from mono-ribbons to junctions, with
spatial resolution at the diffraction limit and a projected sensitivity to
currents as small as 1 {\mu}A. The measured current maps reveal strong spatial
variations corresponding to physical defects at the sub-{\mu}m scale. The
demonstrated method opens up an important new avenue to investigate fundamental
electronic and spin transport in graphene structures and devices, and more
generally in emerging two-dimensional materials and thin film systems.",1609.09208v1
2019-01-08,Quadratic to linear magnetoresistance tuning in TmB4,"The change of a material's electrical resistance (R) in response to an
external magnetic field (B) provides subtle information for the
characterization of its electronic properties and has found applications in
sensor and storage related technologies. In good metals, Boltzmann's theory
predicts a quadratic growth in magnetoresistance (MR) at low B, and saturation
at high fields. On the other hand, a number of nonmagnetic materials with weak
electronic correlation and low carrier concentration for metallicity, such as
inhomogeneous conductors, semimetals, narrow gap semiconductors and topological
insulators, two-dimensional electron gas (2DEG) show positive, non-saturating
linear magnetoresistance (LMR). However, observation of LMR in single crystals
of a good metal is rare. Here we present low-temperature, angle dependent
magnetotransport in single crystals of the antiferromagnetic metal, TmB4. We
observe large, positive and anisotropic MR(B), which can be tuned from
quadratic to linear by changing the direction of the applied field. In view of
the fact that isotropic, single crystalline metals with large Fermi surface
(FS) are not expected to exhibit LMR, we attribute our observations to the
anisotropic FS topology of TmB4. Furthermore, the linear MR is found to be
temperature-independent, suggestive of quantum mechanical origin.",1901.02165v1
2019-01-30,Cathodoluminescence of CdZnSSe crystals synthesized in 19th century bead glass,"The article presents an experimental investigation of band-edge
cathodoluminescence of CdZnSSe crystals that nucleated and grew in silicate
glass melt during its production. We have studied Zn-rich red glass made for
manufacture of seed beads in the 19th century and found it to contain CdZnSSe
crystals. Due to colloidal staining using the CdZnSSe crystallites embedded in
glass, glass makers were enabled to produce lustrous red glass that, as we
presently know, manifests bright luminescence. The CdZnSSe crystallites exhibit
intense band-edge cathodoluminescence both at room temperature and at liquid
nitrogen temperature. We have found the band-edge cathodoluminescence of these
crystals to peak in the range from 2.00 to 2.03 eV at 300 K and from 2.02 to
2.06 eV at 80 K. We have also estimated the value of the band gap derivative
d$E_g$/d$T$ in the interval from 80 to 300 K and found it to lie in the range
from $-2.5 \times 10^{-4}$ to 0 eV/K. CdZnSSe crystals in glass demonstrate
high temperature and temporal stability. The glass-crystal composite on their
basis is resistant to the electron-beam irradiation and long-term weathering.
Possible applications of this composite in modern technologies, and processes
and components that might be used for making glass stained with CdZnSSe in the
past are also discussed.",1901.10764v3
2019-10-21,Revisiting Effects of Nitrogen Incorporation and Graphitization on Conductivity of Ultra-nano-crystalline Diamond Films,"Detailed structural and electrical properties of ultra-nano-crystalline
diamond (UNCD) films grown in H$_\text{2}$/CH$_\text{4}$/N$_\text{2}$ plasma
were systematically studied as a function of deposition temperature ($T_d$) and
nitrogen content ($\%$ N$_2$) to thoroughly evaluate their effects on
conductivity. $T_d$ was scanned from 1000 to 1300 K for N$_2$ fixed at 0, 5, 10
and 20 $\%$. It was found that even the films grown in the synthetic gas
mixture with no nitrogen could be made as conductive as 1$-$10$^{-2}$ $\Omega$
cm with overall resistivity of all the films tuned over 4 orders of magnitude
through varying growth parameters. On a set of 27 samples, Raman spectroscopy
and scanning electron microscopy show a progressive and highly reproducible
film material phase transformation, from ultra-nano-crystalline diamond to
nano-crystalline graphite as deposition temperature increases. The rate of this
transformation is heavily dependent on N$_2$ content. Addition of nitrogen
greatly increases the amount of $sp^2$ bonded carbon in the films thus
enhancing the physical connectivity in the GB network that have high electronic
density of states. However, addition of nitrogen greatly slows down
crystallization of $sp^2$ phase in the GBs. Therefore, proper balance between
GB connectivity and crystallinity is the key in conductivity engineering of
(N)UNCD.",1910.09595v1
2020-05-28,Powering Electronic Devices from Salt Gradients in AA Battery-Sized Stacks of Hydrogel-Infused Paper,"Strongly electric fish use gradients of ions within their bodies to generate
stunning external electrical discharges; the most powerful of these organisms,
the Atlantic torpedo ray, can produce pulses of over 1 kW from its electric
organs. Despite extensive study of this phenomenon in nature, the development
of artificial power generation schemes based on ion gradients for portable,
wearable, or implantable human use has remained out of reach. Previously,
inspired by the electric eel, we developed an artificial electric organ that
generated electricity from ion gradients within stacked hydrogels and, like the
eel, was optimized to deliver large voltages that exceeded 100 V. Due to its
high internal resistance, the current of this power source was, however, too
low to power standard electronics. Here we introduce an artificial electric
organ that takes inspiration from the unique morphologies of torpedo rays for
maximal current output. This power source uses a hybrid material of
hydrogel-infused paper to create, organize, and reconfigure stacks of thin,
arbitrarily large gel films both in series and in parallel. The resulting
increase in electrical power by almost two orders of magnitude compared to the
original eel-inspired design makes it possible to power electronic devices and
establishes that biology's mechanism of generating significant electrical power
can now be realized from benign and soft materials in a portable size.",2005.13775v1
2020-06-27,Controlling local resistance via electric-field induced dislocations,"Dislocations are one-dimensional (1D) topological line defects where the
lattice deviates from the perfect crystal structure. The presence of
dislocations transcends condensed matter research and gives rise to a diverse
range of emergent phenomena [1-6], ranging from geological effects [7] to light
emission from diodes [8]. Despite their ubiquity, to date, the controlled
formation of dislocations is usually achieved via strain fields, applied either
during growth [9,10] or retrospectively via deformation, e.g., (nano
[11-14])-indentation [15]. Here we show how partial dislocations can be induced
using local electric fields, altering the structure and electronic response of
the material where the field is applied. By combining high-resolution imaging
techniques and density functional theory calculations, we directly image these
dislocations in the ferroelectric hexagonal manganite Er(Ti,Mn)O3 and study
their impact on the local electric transport behaviour. The use of an electric
field to induce partial dislocations is a conceptually new approach to the
burgeoning field of emergent defect-driven phenomena and enables local property
control without the need of external macroscopic strain fields. This control is
an important step towards integrating and functionalising dislocations in
practical devices for future oxide electronics.",2006.15252v1
2020-07-13,Approaching the Practical Conductivity Limits of Aerosol Jet Printed Silver,"Previous efforts to directly write conductive metals have been narrowly
focused on nanoparticle ink suspensions that require aggressive sintering (>200
{\deg}C) and result in low-density, small-grained agglomerates with electrical
conductivities <25% of bulk metal. Here, we demonstrate aerosol jet printing of
a reactive ink solution and characterize high-density (93%) printed silver
traces having near-bulk conductivity and grain sizes greater than the electron
mean free path, while only requiring a low-temperature (80 {\deg}C) treatment.
We have developed a predictive electronic transport model which correlates the
microstructure to the measured conductivity and identifies a strategy to
approach the practical conductivity limit for printed metals. Our analysis of
how grain boundaries and tortuosity contribute to electrical resistivity
provides insight into the basic materials science that governs how an ink
formulator or process developer might approach improving the conductivity.
Transmission line measurements validate that electrical properties are
preserved up to 20 GHz, which demonstrates the utility of this technique for
printed RF components. This work reveals a new method of producing robust
printed electronics that retain the advantages of rapid prototyping and
three-dimensional fabrication while achieving the performance necessary for
success within the aerospace and communications industries.",2007.06645v1
2020-07-14,A phase field model for elastic-gradient-plastic solids undergoing hydrogen embrittlement,"We present a gradient-based theoretical framework for predicting hydrogen
assisted fracture in elastic-plastic solids. The novelty of the model lies in
the combination of: (i) stress-assisted diffusion of solute species, (ii)
strain gradient plasticity, and (iii) a hydrogen-sensitive phase field fracture
formulation, inspired by first principles calculations. The theoretical model
is numerically implemented using a mixed finite element formulation and several
boundary value problems are addressed to gain physical insight and showcase
model predictions. The results reveal the critical role of plastic strain
gradients in rationalising decohesion-based arguments and capturing the
transition to brittle fracture observed in hydrogen-rich environments. Large
crack tip stresses are predicted, which in turn raise the hydrogen
concentration and reduce the fracture energy. The computation of the steady
state fracture toughness as a function of the cohesive strength shows that
cleavage fracture can be predicted in otherwise ductile metals using sensible
values for the material parameters and the hydrogen concentration. In addition,
we compute crack growth resistance curves in a wide variety of scenarios and
demonstrate that the model can appropriately capture the sensitivity to: the
plastic length scales, the fracture length scale, the loading rate and the
hydrogen concentration. Model predictions are also compared with fracture
experiments on a modern ultra-high strength steel, AerMet100. A promising
agreement is observed with experimental measurements of threshold stress
intensity factor $K_{th}$ over a wide range of applied potentials.",2007.07093v1
2020-07-16,Magnetotransport properties of the topological nodal-line semimetal CaCdSn,"Topological nodal-line semimetals support protected band crossings which form
nodal lines or nodal loops between the valence and conduction bands and exhibit
novel transport phenomena. Here we address the topological state of the
nodal-line semimetal candidate material, CaCdSn, and report magnetotransport
properties of its single crystals grown by the self-flux method. Our
first-principles calculations show that the electronic structure of CaCdSn
harbors a single nodal loop around the $\Gamma$ point in the absence of
spin-orbit coupling (SOC) effects. The nodal crossings in CaCdSn are found to
lie above the Fermi level and yield a Fermi surface that consists of both
electron and hole pockets. CaCdSn exhibits high mobility ($\mu \approx
3.44\times 10^4$ cm$^2$V$^{-1}$s$^{-1}$) and displays a field-induced
metal-semiconductor like crossover with a plateau in resistivity at low
temperature. We observe an extremely large and quasilinear non-saturating
transverse as well as longitudinal magnetoresistance (MR) at low temperatures
($\approx 7.44\times 10^3 \%$ and $\approx 1.71\times 10^3\%$, respectively, at
4K). We also briefly discuss possible reasons behind such a large quasilinear
magnetoresistance and its connection with the nontrivial band structure of
CaCdSn.",2007.08156v1
2020-07-27,Thermodynamic and corrosion study of Sm$_{1-x}$Mg$_x$Ni$_y$ (y = 3.5 or 3.8) compounds forming reversible hydrides,"AB5 compounds (A = rare earth, B = transition metal) have been widely studied
as anodes for Ni-MH applications. However, they have reached their technical
limitations and the search for new promising materials with high capacity is
foreseen. ABy compounds (2 < y < 5) are good candidates. They are made by
stacking [AB5] and [A2B4] units along the c crystallographic axis. The latter
unit allows a large increase in capacity, while the [AB5] unit provides good
cycling stability. Consequently, the AB3.8 composition (i.e. A5B19 with three
[AB5] for one [A2B4]) is expected to exhibit better cycling stability than the
AB3.5 (i.e. A2B7 with two [AB5] for one [A2B4]). Furthermore, substitution of
rare earth by light magnesium improves both the capacity and cycling stability.
In this paper, we compare the hydrogenation and corrosion properties of two
binary compounds SmNi$_{3.5}$ and SmNi$_{3.8}$ and two pseudo-binary ones
(Sm,Mg)Ni$_{3.5}$ and (Sm,Mg)Ni$_{3.8}$. A better solid-gas cycling stability
is highlighted for the binary SmNi$_{3.8}$. The pseudo-binary compounds also
exhibit higher cycling stability than the binary ones. Furthermore, their
resistance to corrosion was investigated.",2007.13456v1
2020-08-12,"Investigation of the lead-free double perovskites Cs2AgSbX6 (X= Cl, Br, I) for optoelectronic and thermoelectric applications","Perovskite compounds have the potential to harvest solar energy as well as
exploit the thermoelectric potential of a number of available materials. Here,
we present the electronic, structural, thermoelectric, and optical properties
of Cs2AgSbX6 (X = Cl, Br, I) perovskite with the help of the density functional
theory (DFT). The WC-GGA approximation was used to calculate the structural
parameters. All these compounds crystalize in a cubic unit cell with lattice
constant increasing from 10.65 {\AA} (Cl) to 11.14 {\AA} (Br) to 11.86 {\AA}
(I). The mBJ-functional shows a semiconducting nature for these compounds with
an indirect band gap lying at the L-X symmetry points. The optical conductivity
and absorption coefficient show their peaks in the ultraviolet region, moving
towards a lower energy range by inserting large size anion. The band gap of
these compounds (2.08, 1.37, 0.64 eV) indicates their potential in single and
multijunction solar cells. The value of refractive index at zero energy was
evaluated to be 3.1, 2.2, and 1.97 for Cs2AgSbCl6, Cs2AgSbBr6 and Cs2AgSbI6.
Effective mass of electrons is smaller than those of holes resulting in higher
carrier mobility for electrons. The Seebeck coefficient, power factor, and the
figure of merit were computed using the BoltzTrap code. The negative
temperature coefficient of resistivity also supports the semiconductor nature
of these compounds. The high electrical, small thermal conductivity, positive
Seebeck coefficient, and the optimum figure of merit make these compounds
suitable for thermoelectric applications.",2008.06384v3
2020-08-27,Direct Imaging and Electronic Structure Modulation of Moiré Superlattices at the 2D/3D Interface,"The atomic structure at the interface between two-dimensional (2D) and
three-dimensional (3D) materials influences properties such as contact
resistance, photo-response, and high-frequency electrical performance. Moir\'e
engineering is yet to be utilized for tailoring this 2D/3D interface, despite
its success in enabling correlated physics at 2D/2D interfaces. Using
epitaxially aligned MoS2/Au{111} as a model system, we demonstrate the use of
advanced scanning transmission electron microscopy (STEM) combined with a
geometric convolution technique in imaging the crystallographic 32 A moir\'e
pattern at the 2D/3D interface. This moir\'e period is often hidden in
conventional electron microscopy, where the Au structure is seen in projection.
We show, via ab initio electronic structure calculations, that charge density
is modulated according to the moir\'e period, illustrating the potential for
(opto-)electronic moir\'e engineering at the 2D/3D interface. Our work presents
a general pathway to directly image periodic modulation at interfaces using
this combination of emerging microscopy techniques.",2008.12215v2
2020-10-08,"Microstructure, mechanical properties, corrosion resistance and cytocompatibility of WE43 Mg alloy scaffolds fabricated by laser powder bed fusion for biomedical applications","Open-porous scaffolds of WE43 Mg alloy with a body-center cubic cell pattern
were manufactured by laser powder bed fusion with different strut diameters.
The geometry of the unit cells was adequately reproduced during additive
manufacturing and the porosity within the struts was minimized. The
microstructure of the scaffolds was modified by means of thermal solution and
ageing heat treatments and was analysed in detail by means of X-ray
microtomography, optical, scanning and transmission electron microscopy.
Moreover, the corrosion rates and the mechanical properties of the scaffolds
were measured as a function of the strut diameter and metallurgical condition.
The microstructure of the as-printed scaffolds contained a mixture of Y-rich
oxide particles and Rare Earth-rich intermetallic precipitates. The latter
could be modified by heat treatments. The lowest corrosion rates of 2-3 mm/year
were found in the as-printed and solution treated scaffolds and they could be
reduced to ~0.1 mm/year by surface treatments using plasma electrolytic
oxidation. The mechanical properties of the scaffolds improved with the strut
diameter: the yield strength increased from 8 to 40 MPa and the elastic modulus
improved from 0.2 to 0.8 GPa when the strut diameter increased from 275 \mu m
to 800 \mu m. Nevertheless, the strength of the scaffolds without plasma
electrolytic oxidation treatment decreased rapidly when immersed in simulated
body fluid. In vitro biocompatibility tests showed surface treatments by plasma
electrolytic oxidation were necessary to ensure cell proliferation in scaffolds
with high surface-to-volume ratio.",2010.03812v1
2020-10-11,Capping layer influence and isotropic in-plane upper critical field of the superconductivity at the FeSe/SrTiO3 interface,"Understanding the superconductivity at the interface of FeSe/SrTiO3 is a
problem of great contemporary interest due to the significant increase in
critical temperature (Tc) compared to that of bulk FeSe, as well as the
possibility of an unconventional pairing mechanism and topological
superconductivity. We report a study of the influence of a capping layer on
superconductivity in thin films of FeSe grown on SrTiO3 using molecular beam
epitaxy. We used in vacuo four-probe electrical resistance measurements and ex
situ magneto-transport measurements to examine the effect of three capping
layers that provide distinctly different charge transfer into FeSe: compound
FeTe, non-metallic Te, and metallic Zr. Our results show that FeTe provides an
optimal cap that barely influences the inherent Tc found in pristine
FeSe/SrTiO3, while the transfer of holes from a non-metallic Te cap completely
suppresses superconductivity and leads to insulating behavior. Finally, we used
ex situ magnetoresistance measurements in FeTe-capped FeSe films to extract the
angular dependence of the in-plane upper critical magnetic field. Our
observations reveal an almost isotropic in-plane upper critical field,
providing insight into the symmetry and pairing mechanism of high temperature
superconductivity in FeSe.",2010.05308v1
2020-10-16,Synthesis of narrow SnTe nanowires using alloy nanoparticles,"Topological crystalline insulator tin telluride (SnTe) provides a rich
playground to examine interactions of correlated electronic states, such as
ferroelectricity, topological surface states, and superconductivity. Making
SnTe into nanowires further induces novel electronic states due to
one-dimensional (1D) confinement effects. Thus, for transport measurements,
SnTe nanowires must be made narrow in their diameters to ensure the 1D
confinement and phase coherence of the topological surface electrons. This
study reports a facile growth method to produce narrow SnTe nanowires with a
high yield using alloy nanoparticles as growth catalysts. The average diameter
of the SnTe nanowires grown using the alloy nanoparticles is 85 nm, nearly a
factor of three reduction from the previous average diameter of 240 nm using
gold nanoparticles as growth catalysts. Transport measurements reveal the
effect of the nanowire diameter on the residual resistance ratio and
magnetoresistance. Particularly, the ferroelectric transition temperature for
SnTe is observed to change systematically with the nanowire diameter. In situ
cryogenic cooling of narrow SnTe nanowires in a transmission electron
microscope directly reveals the cubic to rhombohedral structural transition,
which is associated with the ferroelectric transition. Thus, these narrow SnTe
nanowires represent a model system to study electronic states arising from the
1D confinement, such as 1D topological superconductivity as well as a potential
multi-band superconductivity.",2010.08078v1
2021-02-12,Universal size-dependent nonlinear charge transport in single crystals of the Mott insulator Ca$_2$RuO$_4$,"The surprisingly low current density required for inducing the insulator to
metal transition has made Ca$_2$RuO$_4$ an attractive candidate material for
developing Mott-based electronics devices. The mechanism driving the resistive
switching, however, remains a controversial topic in the field of strongly
correlated electron systems. Here we probe an uncovered region of phase space
by studying high-purity Ca$_2$RuO$_4$ single crystals, using the sample size as
principal tuning parameter. Upon reducing the crystal size, we find a four
orders of magnitude increase in the current density required for driving
Ca$_2$RuO$_4$ out of the insulating state into a non-equilibrium (also called
metastable) phase which is the precursor to the fully metallic phase. By
integrating a microscopic platinum thermometer and performing thermal
simulations, we gain insight into the local temperature during simultaneous
application of current and establish that the size dependence is not a result
of Joule heating. The findings suggest an inhomogeneous current distribution in
the nominally homogeneous crystal. Our study calls for a reexamination of the
interplay between sample size, charge current, and temperature in driving
Ca$_2$RuO$_4$ towards the Mott insulator to metal transition.",2102.06556v3
2021-02-23,Huge permittivity and premature metallicity in Bi$_2$O$_2$Se single crystals,"Bi$_2$O$_2$Se is a promising material for next-generation semiconducting
electronics. It exhibits premature metallicity on the introduction of a tiny
amount of electrons, the physics behind which remains elusive. Here we report
on transport and dielectric measurements in Bi$_2$O$_2$Se single crystals at
various carrier densities. The temperature-dependent resistivity ($\rho$)
indicates a smooth evolution from the semiconducting to the metallic state. The
critical concentration for the metal-insulator transition (MIT) to occur is
extraordinarily low ($n_\textrm{c}\sim10^{16}$ cm$^{-3}$). The relative
permittivity of the insulating sample is huge
($\epsilon_\textrm{r}\approx155(10)$) and varies slowly with temperature.
Combined with the light effective mass, a long effective Bohr radius
($a_\textrm{B}^*\approx36(2)$ $\textrm{nm}$) is derived, which provides a
reasonable interpretation of the metallic prematurity according to Mott's
criterion for MITs. The high electron mobility ($\mu$) at low temperatures may
result from the screening of ionized scattering centers due to the huge
$\epsilon_\textrm{r}$. Our findings shed light on the electron dynamics in two
dimensional (2D) Bi$_2$O$_2$Se devices.",2102.11451v1
2021-04-30,Local inhomogeneities resolved by scanning probe techniques and their impact on local 2DEG formation in oxide heterostructures,"Lateral inhomogeneities in the formation of 2-dimensional electron gases
(2DEG) directly influence their electronic properties. Understanding their
origin is an important factor for fundamental interpretations, as well as high
quality devices. Here, we studied the local formation of the buried 2DEG at
LaAlO3/SrTiO3 (LAO/STO) interfaces grown on STO (100) single crystals with
partial TiO2 termination, utilizing in-situ local conductivity atomic force
microscopy (LC-AFM) and scattering-type scanning near-field optical microscopy
(s-SNOM). Using substrates with different degrees of chemical surface
termination, we can link the resulting interface chemistry to an inhomogeneous
2DEG formation. In conductivity maps recorded by LC-AFM, a significant lack of
conductivity is observed at topographic features, indicative of a local
SrO/AlO2 interface stacking order, while significant local conductivity can be
probed in regions showing TiO2/LaO interface stacking order. These results
could be corroborated by s SNOM, showing a similar contrast distribution in the
optical signal which can be linked to the local electronic properties of the
material. The results are further complimented by low-temperature conductivity
measurements, which show an increasing residual resistance at 5 K with
increasing portion of insulating SrO terminated areas. Therefore, we can
correlate the macroscopic electrical behavior of our samples to its nanoscopic
structure. Using proper parameters, 2DEG mapping can be carried out without any
visible alteration of sample properties, proving LC AFM and s SNOM to be viable
and destruction-free techniques for the identification of local 2DEG formation.
Furthermore, applying LC AFM and s SNOM in this manner opens the exciting
prospect to link macroscopic low temperature transport to its nanoscopic
origin.",2104.14838v1
2021-05-04,Thermal transport in two-dimensional C3N/C2N superlattices: A molecular dynamics approach,"Nanostructured superlattices have been the focus of many researchers due to
their physical and manipulatable properties. They aim to find promising
materials for new electronic and thermoelectric devices. In the present study,
we investigate the thermal conductivity of two-dimensional (2D) C3N/ C2N
superlattices using non-equilibrium molecular dynamics. We analyze the
dependence of thermal conductivity on the total length, temperature, and the
temperature difference between thermal baths for the superlattices. The minimum
thermal conductivity and the phonon mean free path at a superlattice period of
5.2 nm are 23.2W/m.K and 24.7 nm, respectively. Our results show that at a
specific total length, as the period increases, the number of interfaces
decreases, thus the total thermal resistance decreases, and the effective
thermal conductivity of the system increases. We found that at long lengths
(L_x >80 nm), the high-frequency and low-wavelength phonons are scattered
throughout the interfaces, while at short lengths, there is a wave interference
that reduces the thermal conductivity. The combination of these two effects,
i.e., the wave interference and the interface scattering, is the reason for the
existence of a minimum thermal conductivity in superlattices.",2105.01378v2
2021-07-09,Lithium-Metal Batteries Using Sustainable Electrolyte Media and Various Cathode Chemistries,"Lithium-metal batteries employing concentrated glyme-based electrolytes and
different cathode chemistries are herein evaluated in view of a safe use of the
highly energetic alkali-metal anode. Indeed, diethylene-glycol dimethyl-ether
(DEGDME) and triethylene-glycol dimethyl-ether (TREGDME) dissolving lithium
bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium nitrate (LiNO3) in
concentration approaching the solvents saturation limit are used in lithium
batteries employing either a conversion sulfur-tin composite (S:Sn 80:20 w/w)
or a Li+ (de-)insertion LiFePO4 cathode. Cyclic voltammetry (CV) and
electrochemical impedance spectroscopy (EIS) clearly show the suitability of
the concentrated electrolytes in terms of process reversibility and low
interphase resistance, particularly upon a favorable activation. Galvanostatic
measurements performed in the lithium-sulfur (Li/S) batteries reveal promising
capacities at room temperature (25 {\deg}C) and a value as high as 1300 mAh
gS-1 for DEGDME-based electrolyte at 35 {\deg}C. On the other hand, the
lithium-LiFePO4 (Li/LFP) cells exhibit satisfactory cycling behavior, in
particular when employing an additional reduction step at low voltage cutoff
(i.e., 1.2 V) during the first discharge to consolidate the solid electrolyte
interphase (SEI). This procedure allows a coulombic efficiency near 100 %, a
capacity approaching 160 mAh g-1 and relevant retention particularly for the
cell using TREGDME-based electrolyte. Therefore, this work suggests the use of
concentrated glyme-based electrolytes, the fine tuning of the operative
conditions, and the careful selection of active materials chemistry as
significant steps to achieve practical and safe lithium-metal batteries.",2107.04446v1
2021-08-30,Realization of A Non-Markov Chain in A Single 2D Crystal RRAM,"The non-Markov processes widely exist in thermodymanic processes, while it
usually requires packing of many transistors and memories with great system
complexity in traditional device architecture to minic such functions.
Two-dimensional (2D) material-based resistive random access memory (RRAM)
devices show potential for next-generation computing systems with much-reduced
complexity. Here, we achieve the non-Markov chain in an individual RRAM device
based on 2D mica with a vertical metal/mica/metal structure. We find that the
internal potassium ions (K+) in 2D mica gradually move along the direction of
the applied electric field, making the initially insulating mica conductive.
The accumulation of K+ is tuned by electrical field, and the 2D-mica RRAM
possesses both unipolar and bipolar memory windows, high on/off ratio, decent
stability and repeatability.Importantly, the non-Markov chain algorithm is
established for the first time in a single RRAM, in which the movement of K+ is
dependent on the stimulated voltage as well as their past states. This work not
only uncovers the inner ionic conductivity of 2D mica, but also opens the door
for such novel RRAM devices with numerous functions and applications.",2108.13244v1
2021-09-23,Creating superconductivity in WB2 through pressure-induced metastable planar defects,"High-pressure electrical resistivity measurements reveal that the mechanical
deformation of ultra-hard WB2 during compression induces superconductivity
above 50 GPa with a maximum superconducting critical temperature, Tc of 17 K at
90 GPa. Upon further compression up to 190 GPa, the Tc gradually decreases.
Theoretical calculations show that electron-phonon mediated superconductivity
originates from the formation of metastable stacking faults and twin boundaries
that exhibit a local structure resembling MgB2} (hP3, space group 191,
prototype AlB2). Synchrotron x-ray diffraction measurements up to 145 GPa} show
that the ambient pressure hP12 structure (space group 194, prototype WB2)
continues to persist to this pressure, consistent with the formation of the
planar defects above 50 GPa. The abrupt appearance of superconductivity under
pressure does not coincide with a structural transition but instead with the
formation and percolation of mechanically-induced stacking faults and twin
boundaries. The results identify an alternate route for designing
superconducting materials.",2109.11521v2
2021-12-08,Precise Damage Shaping in Self-Sensing Composites Using Electrical Impedance Tomography and Genetic Algorithms,"Fiber-reinforced composites with nanofiller-modified polymer matrices have
immense potential to improve the safety of high-risk engineering structures.
These materials are intrinsically self-sensing because their electrical
conductivity is affected by deformations and damage. This property, known as
piezoresistivity, has been extensively leveraged for conductivity-based damage
detection via electrical resistance change methods and tomographic imaging
techniques such as electrical impedance tomography (EIT). Although these
techniques are very effective at detecting the presence of damage, they suffer
from an inability to provide precise information about damage shape, size, or
mechanism. This is particularly detrimental for laminated composites which can
suffer from complex failure modes, such as delaminations, that are difficult to
detect. To that end, we herein propose a new technique for precisely
determining damage shape and size in self-sensing composites. Our technique
makes use of a genetic algorithm (GA) integrated with realistic physics-based
damage models to recover precise damage shape from conductivity changes imaged
via EIT. We experimentally validate this technique on carbon nanofiber
(CNF)-modified glass fiber-reinforced polymer (GFRP) laminates by considering
two specific damage mechanisms: through-holes and delaminations. Our results
show that this novel technique can accurately reconstruct multiple
through-holes with radii as small as 1.19 mm and delaminations caused by low
velocity impacts. These findings illustrate that coupling piezoresistivity with
conductivity-based spatial imaging techniques and physics-based inversion
strategies can enable damage shaping capabilities in self-sensing composite
structures.",2112.04419v2
2022-01-10,$B^2$ to $B$-linear magnetoresistance due to impeded orbital motion,"Strange metals exhibit a variety of anomalous magnetotransport properties,
the most striking of which is a resistivity that increases linearly with
magnetic field $B$ over a broad temperature and field range. The ubiquity of
this behavior across a spectrum of correlated metals - both single- and
multi-band, with either dominant spin and/or charge fluctuations, of varying
levels of disorder or inhomogeneity and in proximity to a quantum critical
point or phase - obligates the search for a fundamental underlying principle
that is independent of the specifics of any material. Strongly anisotropic
(momentum-dependent) scattering can generate $B$-linear magnetoresistance but
only at intermediate field strengths. At high enough fields, the
magnetoresistance must eventually saturate. Here, we consider the ultimate
limit of such anisotropy, a region or regions on the Fermi surface that impede
all orbital (cyclotron) motion through them, but whose imposition can be
modelled nonetheless through a modified Boltzmann theoretical treatment.
Application of the proposed theorem suggests that the realization of
quadratic-to-linear magnetoresistance requires the presence of a bounded sector
on the Fermi surface possibly separating two distinct types of carriers. While
this bounded sector may have different origins or manifestations, we expect its
existence to account for the anomalous magnetotransport found in a wide range
of correlated materials.",2201.03292v1
2022-01-12,Controlled chemical functionalization toward 3D-2D carbon nanohorn-MoS2 heterostructures with enhanced electrocatalytic activity for protons reduction,"The realization of novel heterostructures arising from the combination of
nanomaterials is an effective way to modify their physicochemical and
electrocatalytic properties, giving them enhanced characteristics stemming from
their individual constituents. Interfacing carbon nanohorns (CNHs) possessing
high porosity, large specific surface area and good electrical conductivity,
with MoS2 owning multiple electrocatalytic active sites but lacking significant
conductivity, robust interactions and effective structure, can be a strategy to
boost the electrocatalytic reduction of protons to molecular hydrogen. Herein,
we covalently introduce, in a stepwise approach, complementary functional
groups at the conical tips and sidewalls of CNHs, along with the basal plane of
MoS2, en route the construction of 3D-2D CNH-MoS2 heterostructures. The
increased MoS2 loading onto CNHs, improving and facilitating charge
delocalization and transfer in neighboring CNHs, along with the plethora of
active sites, results in excellent electrocatalytic activity for protons
reduction same to that of commercial Pt/C. We have registered minute
overpotential, low Tafel slope and small charge-transfer resistance for
electrocatalyzing the evolution of hydrogen from the newly prepared
heterostructure of 0.029 V, 71 mV/dec and 34.5 {\Omega}, respectively.
Furthermore, the stability of the 3D-2D CNH-MoS2 heterostructure was validated
after performing 10,000 ongoing electrocatalytic cycles.",2201.05450v1
2022-01-26,AI-Aided Mapping of the Structure-Composition-Conductivity Relationships of Glass-Ceramic Lithium Thiophosphate Electrolytes,"Lithium thiophosphates (LPS) with the composition
(Li$_2$S)$_x$(P$_2$S$_5$)$_{1-x}$ are among the most promising prospective
electrolyte materials for solid-state batteries (SSBs), owing to their
superionic conductivity at room temperature ($>10^{-3}$ S cm$^{-1}$), soft
mechanical properties, and low grain boundary resistance. Several glass-ceramic
(gc) LPS with different compositions and good Li conductivity have been
previously reported, but the relationship between composition, atomic
structure, stability, and Li conductivity remains unclear due to the challenges
in characterizing non-crystalline phases in experiments or simulations. Here,
we mapped the LPS phase diagram by combining first principles and artificial
intelligence (AI) methods, integrating density functional theory, artificial
neural network potentials, genetic-algorithm sampling, and ab initio molecular
dynamics simulations. By means of an unsupervised structure-similarity
analysis, the glassy/ceramic phases were correlated with the local structural
motifs in the known LPS crystal structures, showing that the energetically most
favorable Li environment varies with the composition. Based on the discovered
trends in the LPS phase diagram, we propose a candidate solid-state electrolyte
composition, (Li$_{2}$S)$_{x}$(P$_{2}$S$_{5}$)$_{1-x}$ ($x\sim{}0.725$), that
exhibits high ionic conductivity ($>10^{-2}$ S cm$^{-1}$) in our simulations,
thereby demonstrating a general design strategy for amorphous or glassy/ceramic
solid electrolytes with enhanced conductivity and stability.",2201.11203v1
2022-03-02,Emergence of insulating ferrimagnetism and perpendicular magnetic anisotropy in 3d-5d perovskite oxide composite films for insulator spintronic,"Magnetic insulators with strong perpendicular magnetic anisotropy (PMA) play
a key role in exploring pure spin current phenomena and developing
ultralow-dissipation spintronic devices, thereby it is highly desirable to
develop new material platforms. Here we report epitaxial growth of
La2/3Sr1/3MnO3 (LSMO)-SrIrO3 (SIO) composite oxide films (LSMIO) with different
crystalline orientations fabricated by sequential two-target ablation process
using pulsed laser deposition. The LSMIO films exhibit high crystalline quality
with homogeneous mixture of LSMO and SIO at atomic level. Ferrimagnetic and
insulating transport characteristics are observed, with the
temperature-dependent electric resistivity well fitted by Mott
variable-range-hopping model. Moreover, the LSMIO films show strong PMA.
Through further constructing all perovskite oxide heterostructures of the
ferrimagnetic insulator LSMIO and a strong spin-orbital coupled SIO layer,
pronounced spin Hall magnetoresistance (SMR) and spin Hall-like anomalous Hall
effect (SH-AHE) were observed. These results illustrate the potential
application of the ferrimagnetic insulator LSMIO in developing all-oxide
ultralow-dissipation spintronic devices.",2203.00818v1
2022-04-07,Spin sensitive transport in a spin liquid material: revealing a robustness of spin anisotropy,"Alpha-phase (a-) RuCl_3 has emerged as a prime candidate for a quantum spin
liquid (QSL) that promises exotic quasiparticles relevant for fault-tolerant
quantum computation. Here, we report spin sensitive transport measurements to
probe spin correlation in a-RuCl_3 using a proximal spin Hall metal platinum
(Pt). Both transverse and longitudinal resistivities exhibit oscillations as
function of the angle between an in-plane magnetic field and the current, akin
to previously measured spin Hall magnetoresistance (SMR) in antiferromagnet/Pt
heterostructures. The oscillations are observed from 1.5 T to 18 T, both within
and beyond the magnetic field range where the antiferromagnetic order and QSL
state are reported in a-RuCl_3. The SMR oscillations show that spins in a-RuCl3
are largely locked to an in-plane quantization axis transverse to the magnetic
field, constituting a continuous-symmetry-broken state that does not
necessarily represent a long-range order. This robust anisotropy of spin axis
uncovers critical energy scales connected with reported QSL signatures in
a-RuCl_3. Simulations suggest a predominantly antiferromagnetic correlation to
moderately high magnetic-fields, that may support the SMR oscillations. The
coupling of the spin states within a-RuCl_3 and Pt demonstrated in our
experiment opens a transport route to exploring exotic spin phases and device
functionalities of QSL materials.",2204.03158v1
2022-06-14,Probing of large interfacial contribution to spin orbit coupling in CoFeB/Ta heterostructure by ultrafast THz emission spectroscopy,"Ultrafast THz radiation generation from ferromagnetic/nonmagnetic bilayer
heterostructure-based spintronic emitters generally exploits the conversion
from spin- to charge-current within the nonmagnetic layer and its interface
with the ferromagnetic layer. Various possible sub-contributions to the
underlying mechanism of inverse spin Hall effect for the THz emission from such
structures, need to be exploited for not only investigating the intricacies at
the fundamental level in the material properties themselves but also for
improving their performance for broadband and high-power THz emission. Here, we
report ultrafast THz emission from CoFeB/Ta bilayer at varying sample
temperatures in a large range to unravel the role of intrinsic and extrinsic
spin to charge conversion processes. In addition to an enhancement in the THz
emission, its temperature dependence shows a THz signal polarity reversal if
the CoFeB/Ta sample is annealed at an elevated temperature. We extract the
behaviour of the spin Hall resistivity, determine the intrinsic spin Hall
conductivity contribution in it and compare those with the standard Fe/Pt
system. Our results clearly demonstrate a giant interfacial contribution to the
overall spin Hall angle arising from the modified interface in the annealed
CoFeB/Ta, where a sign reversal in the corresponding spin Hall angle is
manifested from the THz amplitude variation with the temperature.",2206.06718v2
2022-08-04,Studies on tuning surface electronic properties of hydrogenated diamond by oxygen functionalization,"Ultra-wide bandgap and the absence of shallow dopants are the major
challenges in realizing diamond based electronics. However, the surface
functionalization offers an excellent alternative to tune electronic structure
of diamonds. Herein, we report on tuning the surface electronic properties of
hydrogenated polycrystalline diamond films through oxygen functionalization.
The hydrogenated diamond (HD) surface transforms from hydrophobic to
hydrophilic nature and the sheet resistance increases from ~ 8 kohms/sq. to
over 10 Gohms/sq. with progressive ozonation. The conductive atomic force
microscopic (c-AFM) studies reveal preferential higher current conduction on
selective grain interiors (GIs) than that of grain boundaries confirming the
surface charge transfer doping on these HDs. In addition, the local current
conduction is also found to be much higher on (111) planes as compared to (100)
planes on pristine and marginally O-terminated HD. However, there is no current
flow on the fully O-terminated diamond (OD) surface. Further, X-ray
photoelectron spectroscopic (XPS) studies reveal a redshift in binding energy
(BE) of C1s on pristine and marginally O-terminated HD surfaces indicating
surface band bending whilst the BE shifts to higher energy for OD. Moreover,
XPS analysis also corroborate c-AFM study for the possible charge transfer
doping mechanism on the diamond films which results in high current conduction
on GIs of pristine and partially O-terminated HDs.",2208.02465v1
2022-09-01,Four-point bending piezoelectric energy harvester with uniform surface strain toward better energy conversion performance and material usage,"Improving the energy conversion efficiency of piezoelectric energy harvesters
is of great importance, and one approach is to make more uniform use of the
working material by ensuring a uniform strain state. To achieve better
performance, this paper presents a four-point bending piezoelectric energy
harvester with extensive investigation and modeling to identify the influential
parameters. An electromechanical analytical model is presented and verified by
experimental data. The frequency-domain method extracts the solutions for a
general time-variable force and impact. Four-point bending is compared with the
standard cantilever harvesters regarding voltage generation, mechanical strain,
and figure of merit. Strain contours are analyzed and interpreted for this
innovative approach, and the power generation by the optimal resistance load is
studied. Dimensionless parameters are introduced and investigated to find the
optimal operating conditions for the four-point bending harvester. Finally, the
four-point bending performance and the best figure of merit are discussed with
a view to the long-term fatigue life of the harvester. The results show that in
the best four-point bending energy conversion conditions; the energy conversion
coefficient is more than three times higher than that of typical cantilever
energy harvesters. The results also illustrate that the axial strain
experienced in a standard cantilever harvester is more than three times higher
than that of the four-point bending harvester, suggesting the latter device may
have favorable fatigue performance. Overall, the presented piezoelectric
harvester has improved energy conversion efficiency and experiences a reduced
and uniform surface strain, making it appropriate for high-efficiency energy
harvesting systems.",2209.00252v1
2022-09-08,Observation of strange metal in hole-doped valley-spin insulator,"Temperature-linear resistance at low temperatures in strange metals is an
exotic characteristic of strong correlation systems, as observed in high-TC
superconducting cuprates, heavy fermions, Fe-based superconductors, ruthenates,
and twisted bilayer graphene. Here, we introduce a hole-doped valley-spin
insulator, V-doped WSe2, with hole pockets in the valence band. The strange
metal characteristic was observed in VxW1-xSe2 at a critical carrier
concentration of 9.5 x 10^20 cm-3 from 150 K to 1.8 K. The unsaturated
magnetoresistance is almost linearly proportional to the magnetic field. Using
the ansatz R(H,T) - R(0,0) ~ [(alpha.k.T)^2+(gamma.mu.B)^2]^1/2, the
gamma/alpha ratio is estimated approximately to 4, distinct from that for the
quasiparticles of LSCO, BaFe2(As1-xPx)2 (gamma/alpha=1) and bosons of YBCO
(gamma/alpha=2). Our observation opens up the possible routes that induce
strong correlation and superconductivity in two-dimensional materials with
strong spin-orbit coupling.",2209.03672v1
2022-09-26,Study of pnictides for photovoltaic applications,"For the transition into a sustainable mode of energy usage, it is important
to develop photovoltaic materials that exhibit better solar-to-electricity
conversion efficiencies, a direct optimal band gap, and made of non-toxic,
earth abundant elements compared to the state-of-the-art silicon photovoltaics.
Here, we explore the non-redox-active pnictide chemical space, including binary
A$_3$B$_2$, ternary AA'$_2$B$_2$, and quaternary AA'A""B$_2$ compounds (A, A',
A"" = Ca, Sr, or Zn; B = N or P), as candidate beyond-Si photovoltaics using
density functional theory calculations. Specifically, we evaluate the ground
state configurations, band gaps, and 0 K thermodynamic stability for all 20
pnictide compositions considered, besides computing the formation energy of
cation vacancies, anion vacancies, and cation anti-sites in a subset of
candidate compounds. Importantly, we identify SrZn$_2$N$_2$, SrZn$_2$P$_2$, and
CaZn$_2$P$_2$ to be promising candidates, exhibiting optimal (1.1-1.5 eV)
hybrid-functional-calculated band gaps, stability at 0 K, and high resistance
to point defects (formation energies $>$1 eV), while other possible candidates
include ZnCa$_2$N$_2$ and ZnSr$_2$N$_2$, which may be susceptible to N-vacancy
formation. We hope that our study will contribute to the practical development
of pnictide semiconductors as beyond-silicon light absorbers.",2209.12458v1
2022-09-28,Dissolution and Recrystallization Behavior of Li3PS4 in Different Organic Solvents,"Solid state batteries can be built based on thiophosphate electrolytes such
as beta-Li3PS4. For the preparation of these electrolytes, various
solvent-based routes have been reported. For recycling of end-of-life solid
state batteries based on such thiophosphates, we consider the development of
dissolution and recrystallization strategies for the recovery of the model
compound beta-Li3PS4. We show that recrystallization can only be performed in
polar, slightly protic solvents such as N-methylformamide (NMF). The
recrystallization is comprehensively studied, showing that it proceeds via an
intermediate phase with composition Li3PS4*2NMF, which is structurally
characterized. This phase has a high resistivity for the transport of lithium
ions and must be removed in order to obtain a recrystallized product with a
conductivity similar to the pristine material. Moreover, the recrystallization
from solution results in an increase of the amorphous phase fraction next to
crystalline beta-Li3PS4, which results in a decrease of the activation energy
to 0.2 eV compared to 0.38 eV for the pristine phase.",2209.13955v1
2022-11-02,One-Step Formation of Plasmonic Cu Nanodomains in p-Type Cu$_2$O Matrix Films for Enhanced Photoconversion of n-ZnO/p-Cu$_2$O Heterojunctions,"Plasmonic Cu nanoparticles were in-situ grown into a Cu$_2$O semiconductor
matrix by using reactive magnetron sputtering and adjusting the amount of
oxygen available during the synthesis in order to prevent the oxidation of part
of copper atoms landed on the film surface. Varying only the oxygen flowrate
(OFR) and using a single Cu target it was possible to observe the evolution in
the simultaneous formation of metallic Cu and Cu$_2$O phases for oxygen-poor
conditions. Suchformation is accompanied by the development of the surface
plasmon band (SPB) corresponding to Cu, as evidenced by UV-Vis
spectrophotometry and spectroscopic ellipsometry. The bandgap values of the
elaborated composites containing embedded Cu plasmonic nanodomains were lower
than the bandgap of single-phased Cu$_2$O films, likely due to the higher
defect density associated to the nanocrystalline nature of films, promoted by
the presence of metallic Cu. The resistivity of the thin films increased with
more oxidative deposition conditions and was associated to an increase in
Cu$_2$O/Cu ratio and smaller and more isolated Cu particles, as evidenced by
high resolution transmission electron microscopy and X-ray diffraction.
Photoconversion devices based on the studied nanocomposites were characterized
by I-V and spectral photocurrent measurements, showing an increase in the
photocurrent density under light illumination as consequence of the plasmonic
particles excitation leading to hot carrier's injection in the nearby ZnO and
Cu$_2$O semiconductors.",2211.01010v1
2023-02-25,Strain-adjustable reflectivity of polyurethane nanofiber membrane for thermal management applications,"Passive radiative cooling technologies are highly attractive in pursuing
sustainable development. However, current cooling materials are often static,
which makes it difficult to cope with the varying needs of all-weather thermal
comfort management. Herein, a strategy is designed to obtain flexible
thermoplastic polyurethane nanofiber (Es-TPU) membranes via electrospinning,
realizing reversible in-situ solvent-free switching between radiative cooling
and solar heating through changes in its optical reflectivity by stretching. In
its radiative cooling state (0% strain), the Es-TPU membrane shows a high and
angular-independent reflectance of 95.6% in the 0.25-2.5 {\mu}m wavelength
range and an infrared emissivity of 93.3% in the atmospheric transparency
window (8-13 {\mu}m), reaching a temperature drop of 10 {\deg}C at midday, with
a corresponding cooling power of 118.25 W/m2. The excellent mechanical
properties of the Es-TPU membrane allows the continuous adjustment of
reflectivity by reversibly stretching it, reaching a reflectivity of 61.1%
({\Delta}R=34.5%) under an elongation strain of 80%, leading to a net
temperature increase of 9.5 {\deg}C above ambient of an absorbing substrate and
an equivalent power of 220.34 W/m2 in this solar heating mode. The strong haze,
hydrophobicity and outstanding aging resistance exhibited by this scalable
membrane hold promise for achieving uniform illumination with tunable strength
and efficient thermal management in practical applications.",2302.13043v2
2023-03-26,Molecular lighting goes less powering,"The present era has seen tremendous demands for low-cost electrochromic
materials for visible-region multicolor display technology, paper-based,
flexible, and wearable electronic devices, smart windows, and optoelectronic
applications. Towards this goal, we report large-scale polyelectrochromic
devices fabricated on rigid to flexible ITO substrates comprising novel
anthracene containing viologen,
(1,1'-bis(anthracen-9-ylmethyl)-[4,4'-bipyridine]-1,1'-diium bromide,
abbreviated as AnV2+), and polythiophene (P3HT). Inter-estingly, the devices
show three states of reversible visible color in response to the applied bias,
sub-second to second switching time (0.7 s/1.6 s), and high coloration
efficiency (484 cm2/C), longer cycling stability up to 3000 s (103 switching
cycles). Thanks to the anthracenes moieties introduced to viologen that inhibit
formation of undesired dimer of cation radicals formed in response to the
applied bias, other-wise it would hamper the devices reconfiguration. The
devices are fully characterized, and electrochromic performances are ensured by
bias-dependent UV-Vis, and Raman spectroscopy. The fabricated electro-chromic
devices are tested with the commercially available low-cost cells to perform,
which is highly de-sired for practical applications. The computational study
facilitates the understanding of experimental re-sults. The alternating current
(AC)-based electrical impedance spectroscopy reveals that P3HT facilitates
reducing charge transfer resistance of the devices. Our work shows CMOS
compatibility and one of the best-performing devices that could pave the way
for developing cost-effective flexible, and wearable electrochromic devices.",2303.14648v2
2023-04-12,Potential Major Improvement in Superconductors for High-Field Magnets,"Fusion reactors are limited by the magnetic field available to confine their
plasma. The commercial fusion industry uses the larger magnetic field and
higher operating temperature of the cuprate superconductor
$\mathbf{YBa_{2}Cu_{3}O_{7-\delta}}$ (YBCO) in order to confine their plasma
into a dense volume. A superconductor is a macroscopic quantum state that is
protected from the metallic (resistive) state by an energy gap. Unfortunately,
YBCO has an anisotropic gap, known as D-wave because it has the shape of a
$\mathbf{d_{x^2-y^2}}$ chemical orbital. This D-wave gap means that
poly-crystalline wire cannot be made because a few degree misalignment between
grains in the wire leads to a drastic loss in its supercurrent carrying
ability, and thereby its magnetic field limit. The superconductor industry has
responded by growing nearly-single-crystal superconducting YBCO films on
carefully prepared substrate tapes kilometers in length. Heroic development
programs have made such tapes commercially available, but they are very
expensive and delicate. MRI magnet superconductors, such as $\mathbf{NbTi}$ and
$\mathbf{Nb_{3}Sn}$, are formed into poly-crystalline wires because they have
an isotropic gap in the shape of an s chemical orbital (called S-wave) that
makes them insensitive to grain misalignment. However, these materials are
limited to lower magnetic fields and liquid-He temperatures. Here, we modified
YBCO by doping the Y site with Ca and Ce atoms to form
$\mathbf{(Y_{1-x-y}Ca_{x}Ce_{y})Ba_{2}Cu_{3}O_{7-\delta}}$, and show evidence
that it changes to an S-wave gap. Its superconducting transition temperature,
$\mathbf{T_c}$, of $\mathbf{\sim 70K}$, while lower than that of D-wave YBCO at
$\mathbf{\sim 90K}$, is easily maintained using common, economic cryogenic
equipment.",2304.06171v1
2023-05-11,Highly tunable lateral homojunction formed in 2D layered CuInP2S6 via in-plane ionic migration,"As basic building blocks for next-generation information technologies
devices, high-quality p-n junctions based on van der Waals (vdW) materials have
attracted widespread interest.Compared to traditional two dimensional (2D)
heterojunction diodes, the emerging homojunctions are more attractive owing to
their intrinsic advantages, such as continuous band alignments and smaller
carrier trapping. Here, utilizing the long-range migration of Cu + ions under
in-plane electric field, a novel lateral p-n homojunction was constructed in
the 2D layered copper indium thiophosphate (CIPS). The symmetric Au/CIPS/Au
devices demonstrate an electric-field-driven resistance switching (RS)
accompanying by a rectification behavior without any gate control. Moreover,
such rectification behavior can be continuously modulated by poling voltage. We
deduce that the reversable rectifying RS behavior is governed by the effective
lateral build-in potential and the change of the interfacial barrier during the
poling process. Furthermore, the CIPS p-n homojuction is evidenced by the
photovoltaic effect, with the spectral response extending up to visible region
due to the better photogenerated carrier separation efficiency. Our study
provides a facile route to fabricate homojuctions through electric-field-driven
ionic migration and paves the way towards the use of this method in other vdW
materials.",2305.06607v1
2023-06-26,"Spin-flop quasi metamagnetic, anisotropic magnetic, and electrical transport behavior of Ho substituted kagome magnet ErMn$_6$Sn$_6$","We report on the magnetic and electrical properties of a (Mn$_3$Sn)$_2$
triangular network kagome structured high quality Ho substituted ErMn$_6$Sn$_6$
single-crystal sample by magneto-transport measurements.
Er$_{0.5}$Ho$_{0.5}$Mn$_6$Sn$_6$ orders antiferromagnetically at N\'{e}el
temperature $T_\mathrm{N} \sim$ 350 K followed by a ferrimagnetic (FiM)
transition at $T_\mathrm{C} \sim$ 114 K and spin-orientation transition at
$T_\mathrm{t} \sim$ 20 K. The field-manifestations of these magnetic phases in
the \textit{ab}-basal plane and along the \textit{c}-axis are illustrated
through temperature-field \textit{T-H} phase diagrams. In
\textit{H}$\parallel$\textit{c}, narrow hysteresis between spin reorientation
and field-induced FiM phases below $T_\mathrm{t}$, enhanced/strengthened FiM
phase below $T_\mathrm{C}$ and stemming of FiM phase out of strongly coexisting
AFM and FiM phases below $T_\mathrm{N}$ through a non-meta-magnetic transition
are confirmed to arise from strong R-Mn sublattices interaction. In contrast,
\textit{H}$\parallel$\textit{ab}-plane, between $T_\mathrm{N}$ and
$T_\mathrm{C}$, individually contributing R-Mn sublattices with weak
antiferromagnetic interactions undergo a field-induced spin-flop
quasi-metamagnetic transition to FiM state. The temperature dependent
electrical resistivity suggests metallic nature with Fermi liquid behavior at
low temperatures. Essentially, the current study stimulates interest to
investigate the magnetic and electrical properties of mixed rare-earth layered
kagome magnetic metals for possible novel and exotic behavior.",2306.14417v1
2023-07-28,Pressure-induced Superconductivity in Zintl Topological Insulator SrIn2As2,"The Zintl compound AIn2X2 (A = Ca, Sr, and X = P, As), as a theoretically
predicted new non-magnetic topological insulator, requires experiments to
understand their electronic structure and topological characteristics. In this
paper, we systematically investigate the crystal structures and electronic
properties of the Zintl compound SrIn2As2 under both ambient and high-pressure
conditions. Based on systematic angle-resolved photoemission spectroscopy
(ARPES) measurements, we observed the topological surface states on its (001)
surface as predicted by calculations, indicating that SrIn2As2 is a strong
topological insulator. Interestingly, application of pressure effectively tuned
the crystal structure and electronic properties of SrIn2As2. Superconductivity
is observed in SrIn2As2 for pressure where the temperature dependence of the
resistivity changes from a semiconducting-like behavior to that of a metal. The
observation of nontrivial topological states and pressure-induced
superconductivity in SrIn2As2 provides crucial insights into the relationship
between topology and superconductivity, as well as stimulates further studies
of superconductivity in topological materials.",2307.15629v1
2023-07-31,Ferroelectricity in tetragonal ZrO$_2$ thin films,"We report on the crystal structure and ferroelectric properties of epitaxial
ZrO$_2$ films ranging from 7 to 42 nm thickness grown on
La$_{0.67}$Sr$_{0.33}$MnO$_3$-buffered (110)-oriented SrTiO$_3$ substrate. By
employing X-ray diffraction, we confirm a tetragonal phase at all investigated
thicknesses, with slight in-plane strain due to the substrate in the thinnest
films. Further confirmation of the tetragonal phase was obtained through
Infrared absorption spectroscopy with synchrotron light, performed on ZrO$_2$
membrane transferred onto a high resistive Silicon substrate. Up to a thickness
of 31 nm, the ZrO$_2$ epitaxial films exhibit ferroelectric behavior, at
variance with the antiferroelectric behavior reported previously for the
tetragonal phase in polycrystalline films. However, the ferroelectricity is
found here to diminish with increasing film thickness, with a polarization of
about 13 $\mu$C.cm$^{-2}$ and down to 1 $\mu$C.cm$^{-2}$ for 7 nm and 31
nm-thick ZrO$_2$ films, respectively. This highlights the role of thickness
reduction, substrate strain, and surface effects in promoting polarization in
the tetragonal ZrO$_2$ thin films. These findings provide new insights into the
ferroelectric properties and structure of ZrO$_2$ thin films, and open up new
directions to investigate the origin of ferroelectricity in ZrO$_2$ and to
optimize this material for future applications.",2307.16492v1
2023-08-16,Automated Semiconductor Defect Inspection in Scanning Electron Microscope Images: a Systematic Review,"A growing need exists for efficient and accurate methods for detecting
defects in semiconductor materials and devices. These defects can have a
detrimental impact on the efficiency of the manufacturing process, because they
cause critical failures and wafer-yield limitations. As nodes and patterns get
smaller, even high-resolution imaging techniques such as Scanning Electron
Microscopy (SEM) produce noisy images due to operating close to sensitivity
levels and due to varying physical properties of different underlayers or
resist materials. This inherent noise is one of the main challenges for defect
inspection. One promising approach is the use of machine learning algorithms,
which can be trained to accurately classify and locate defects in semiconductor
samples. Recently, convolutional neural networks have proved to be particularly
useful in this regard. This systematic review provides a comprehensive overview
of the state of automated semiconductor defect inspection on SEM images,
including the most recent innovations and developments. 38 publications were
selected on this topic, indexed in IEEE Xplore and SPIE databases. For each of
these, the application, methodology, dataset, results, limitations and future
work were summarized. A comprehensive overview and analysis of their methods is
provided. Finally, promising avenues for future work in the field of SEM-based
defect inspection are suggested.",2308.08376v2
2023-10-05,Spin-orbit torques and spin Hall magnetoresistance generated by twin-free and amorphous Bi0.9Sb0.1 topological insulator films,"Topological insulators have attracted great interest as generators of
spin-orbit torques (SOTs) in spintronic devices.
Bi\textsubscript{1-x}Sb\textsubscript{x} is a prominent topological insulator
that has a high charge-to-spin conversion efficiency. However, the origin and
magnitude of the SOTs induced by current-injection in
Bi\textsubscript{1-x}Sb\textsubscript{x} remain controversial. Here we report
the investigation of the SOTs and spin Hall magnetoresistance resulting from
charge-to-spin conversion in twin-free epitaxial layers of
Bi\textsubscript{0.9}Sb\textsubscript{0.1}(0001) coupled to FeCo, and compare
it with that of amorphous Bi\textsubscript{0.9}Sb\textsubscript{0.1}. We find a
large charge-to-spin conversion efficiency of 1 in the first case and less than
0.1 in the second, confirming crystalline
Bi\textsubscript{0.9}Sb\textsubscript{0.1} as a strong spin injector material.
The SOTs and spin Hall magnetoresistance are independent of the direction of
the electric current, indicating that charge-to-spin conversion in
single-crystal Bi\textsubscript{0.9}Sb\textsubscript{0.1}(0001) is isotropic
despite the strong anisotropy of the topological surface states. Further, we
find that the damping-like SOT has a non-monotonic temperature dependence with
a minimum at 20~K. By correlating the SOT with resistivity and weak
antilocalization measurements, we conclude that charge-spin conversion occurs
via thermally-excited holes from the bulk states above 20~K, and conduction
through the isotropic surface states with increasing spin polarization due to
decreasing electron-electron scattering below 20~K.",2310.03487v1
2023-12-09,Extended Kohler's Rule of Magnetoresistance in TaCo$_2$Te$_2$,"TaCo$_2$Te$_2$ is recently reported to be an air-stable, high mobility Van
der Waals material with probable magnetic order. Here we investigate the
scaling behavior of its magnetoresistance. We measured both the longitudinal
($\rho_{xx}$) and Hall ($\rho_{xy}$) magnetoresistivities of TaCo$_2$Te$_2$
crystals in magnetic fields parallel to the c-axis and found that the
magnetoresistance violates the Kohler's rule $MR \sim f[H/\rho_0]$ while
obeying the extended Kohler's rule $MR \sim f[H/(n_T\rho_0)]$, where $MR \sim
[\rho_{xx}(H)-\rho_0]/\rho_0$, $H$ is the magnetic field, $n_T$ is a thermal
factor, $\rho_{xx}(H)$ and $\rho_0$ are the resistivities at $H$ and zero
field, respectively. While deviating from those of the densities of electrons
($n_e$) and holes ($n_h$) obtained from the two-band model analysis of the
magnetoconductivities, the temperature dependence of $n_T$ is close to that of
the Hall carrier densities $n_H$ calculated from the slopes of $\rho_{xy}(H)$
curves at low magnetic fields, providing a new way to obtain the thermal factor
in the extended Kohler's rule.",2312.05624v1
2023-12-16,"Electronic phase transition, vibrational properties and structural stability of single and two polyyne chains under external electric field","Search for one dimensional (1D) van der Waals materials has become an urgent
need to meet the demand as building blocks for high performance, miniaturized,
lightweight device applications. Polyyne, a 1D atomic chain of carbon is the
thinnest and strongest allotrope of carbon, showing promising applications in
new generation low dimensional devices due to the presence of a band gap. A
system of two carbon chains held together by van der Waals interaction has been
theoretically postulated and shows band gap tunability under structural changes
which finds applications in the realms of resistive switching and spintronics.
In this study, we use first principles Density Functional Theory (DFT) to show
a sharp semiconductor to metal transition along with the emergence of an
asymmetry in the spin polarized density of states for single and two polyyne
chains under a transverse electric field. The thermodynamic stability of the
system has been substantiated through the utilization of Ab Initio Molecular
Dynamics (AIMD) simulations, phonon dispersion curve analyses, and formation
energy calculations. Furthermore, in addition to its dynamic stability
assessment, phonon calculations have served to identify Raman active
vibrational modes which offers an invaluable non-destructive experimental
avenue for discerning electronic phase transitions in response to an applied
electric field. Our study presents a predictive framework for the prospective
utilization of one and two polyyne chains in forthcoming flexible
nano-electronic and spintronic devices. The future prospects of the system are
contingent upon advancements in nano-electronics fabrication techniques and the
precise construction of circuitry for harnessing spin-related applications.",2312.10335v1
2024-02-06,Observation of the double quantum spin Hall phase in moiré WSe2,"Quantum spin Hall (QSH) insulators are a topologically protected phase of
matter in two dimensions that can support non-dissipative spin transport. A
hallmark of the phase is a pair of helical edge states surrounding an
insulating bulk. A higher (even) number of helical edge state pairs is usually
not possible in real materials because spin mixing would gap out the edge
states. Multiple pairs of helical edge states have been proposed in materials
with spin conservation symmetry and high spin Chern bands, but remained
experimentally elusive. Here, we demonstrate a QSH phase with one and two pairs
of helical edge states in twisted bilayer WSe2 at moir\'e hole filling factor
{\nu}= 2 and 4, respectively. We observe nearly quantized conductance or
resistance plateaus of h/({\nu}e^2 ) at {\nu} = 2 and 4 while the bulk is
insulating. The conductance is nearly independent of out-of-plane magnetic
field and decreases under an in-plane magnetic field. We also observe nonlocal
transport, which is sensitive only to the in-plane magnetic field. The results
agree with quantum transport of helical edge states protected by Ising spin
conservation symmetry and open a promising platform for low-power spintronics.",2402.04196v1
2024-02-13,Coarse-Graining in Space versus Time,"Understanding the structure and dynamics of liquids is pivotal for the study
of larger spatiotemporal processes, particularly for glass-forming materials at
low temperatures. The so-called thermodynamic scaling relation, validated for
many molecular systems through experiments, offers an efficient means to
explore a vast range of time scales along a one-dimensional phase diagram.
Isomorph theory provides a theoretical framework for thermodynamic scaling
based on strong virial-potential energy correlations, but this approach is most
successful for simple point particles. In particular, isomorph theory has
resisted extension to complex molecular liquids due to the existence of
high-frequency intramolecular interactions. To elucidate the microscopic origin
of density scaling for molecular systems, we employ two distinct approaches for
coarse-graining in space or in time. The former eliminates fast degrees of
freedom by reducing a molecule to a center-of-mass-level description, while the
latter involves temporally averaged fluctuations or correlation functions over
the characteristic time scale. We show that both approaches yield a consistent
density scaling coefficient for ortho-terphenyl, which is moreover in agreement
with the experimental value. Building upon these findings, we derive the
density scaling relationship exhibiting a single-parameter phase diagram from
fully atomistic simulations. Our results unravel the microscopic nature
underlying thermodynamic scaling and shed light on the role of coarse-graining
for assessing the slow fluctuations in molecular systems, ultimately enabling
the extension of systematic bottom-up approaches to larger and more complex
molecular liquids that are experimentally challenging to probe.",2402.08675v1
2024-02-27,Design principles of nonlinear optical materials for Terahertz lasers,"We have investigated both inter-band and intra-band second order nonlinear
optical conductivity based on the velocity correlation formalism and the
spectral expansion technique. We propose a scenario in which the second order
intra-band process is nonzero while the inter-band process is zero. This occurs
for a band structure with momentum asymmetry in the Brillouin zone. Very
low-energy photons are blocked by the Pauli exclusion principle from
participating in the inter-band process; however, they are permitted to
participate in the intra-band process, with the band smeared by some impurity
scattering. We establish a connection between the inter-band nonlinear optical
conductivity in the velocity gauge and the shift vector in the length gauge for
a two-band model. Using a quasiclassical kinetic approach, we demonstrate the
importance of intra-band transitions in high harmonic generations for the
single tilted Dirac cone model and hexagonal warping model. We confirm that the
Kramers-Kronig relations break down for the limit case of ($\omega$, $-\omega$)
in the nonlinear optical conductivity. Finally, we calculate the
superconducting transition temperature of NbN and the dielectric function of
AlN, and the resistance of the NbN/AlN junction. The natural non-linearity of
the Josephson junction brings a Josephson plasma with frequency in the
Terahertz region.",2402.17126v1
2024-03-25,Multi-Objective Quality-Diversity for Crystal Structure Prediction,"Crystal structures are indispensable across various domains, from batteries
to solar cells, and extensive research has been dedicated to predicting their
properties based on their atomic configurations. However, prevailing Crystal
Structure Prediction methods focus on identifying the most stable solutions
that lie at the global minimum of the energy function. This approach overlooks
other potentially interesting materials that lie in neighbouring local minima
and have different material properties such as conductivity or resistance to
deformation. By contrast, Quality-Diversity algorithms provide a promising
avenue for Crystal Structure Prediction as they aim to find a collection of
high-performing solutions that have diverse characteristics. However, it may
also be valuable to optimise for the stability of crystal structures alongside
other objectives such as magnetism or thermoelectric efficiency. Therefore, in
this work, we harness the power of Multi-Objective Quality-Diversity algorithms
in order to find crystal structures which have diverse features and achieve
different trade-offs of objectives. We analyse our approach on 5 crystal
systems and demonstrate that it is not only able to re-discover known real-life
structures, but also find promising new ones. Moreover, we propose a method for
illuminating the objective space to gain an understanding of what trade-offs
can be achieved.",2403.17164v1
2002-08-26,Magnetized Accretion-Ejection Structures: 2.5D MHD simulations of continuous Ideal Jet launching from resistive accretion disks,"We present numerical magnetohydrodynamic (MHD) simulations of a magnetized
accretion disk launching trans-Alfvenic jets. These simulations, performed in a
2.5 dimensional time-dependent polytropic resistive MHD framework, model a
resistive accretion disk threaded by an initial vertical magnetic field. The
resistivity is only important inside the disk, and is prescribed as eta =
alpha_m V_AH exp(-2Z^2/H^2), where V_A stands for Alfven speed, H is the disk
scale height and the coefficient alpha_m is smaller than unity. By performing
the simulations over several tens of dynamical disk timescales, we show that
the launching of a collimated outflow occurs self-consistently and the ejection
of matter is continuous and quasi-stationary. These are the first ever
simulations of resistive accretion disks launching non-transient ideal MHD
jets. Roughly 15% of accreted mass is persistently ejected. This outflow is
safely characterized as a jet since the flow becomes super-fastmagnetosonic,
well-collimated and reaches a quasi-stationary state. We present a complete
illustration and explanation of the `accretion-ejection' mechanism that leads
to jet formation from a magnetized accretion disk. In particular, the magnetic
torque inside the disk brakes the matter azimuthally and allows for accretion,
while it is responsible for an effective magneto-centrifugal acceleration in
the jet. As such, the magnetic field channels the disk angular momentum and
powers the jet acceleration and collimation. The jet originates from the inner
disk region where equipartition between thermal and magnetic forces is
achieved. A hollow, super-fastmagnetosonic shell of dense material is the
natural outcome of the inwards advection of a primordial field.",0208459v1
2006-02-17,Coupling losses and transverse resistivity of multifilament YBCO coated superconductors,"We studied the magnetization losses of four different types of filamentary
YBCO coated conductors. A 10 mm wide YBCO coated conductor was subdivided into
20 filaments by laser cutting. The separation of coupling loss from the total
is possible because the energy loss per cycle in samples with electrically
insulated filaments has a very small frequency dependence. We measured the
frequency dependence of the total losses in the frequency range between 0.1 Hz
and 500 Hz. The coupling loss was obtained from the total by subtracting the
hysteresis loss. The latter was measured at low frequencies since only
hysteresis loss is non-negligible at frequencies below 1 Hz. The transverse
resistivity was determined from the coupling losses; it was assumed that the
sample length is equal to half of the twist pitch. The values of transverse
resistivity deduced from the loss data were compared with those obtained by the
four-point measurements with current flowing perpendicular to the filaments.
Preliminary results indicate that the current method of laser ablation creates
electrical contacts between the superconducting filaments and the substrate.
This was also confirmed by the Hall probe mapping of the magnetic field in the
vicinity of the tape. The measured transverse resistivity was close to the
resistivity of the substrate (Hastelloy).",0602422v1
2007-02-21,Electrical current-driven pinhole formation and insulator-metal transition in tunnel junctions,"Current Induced Resistance Switching (CIS) was recently observed in thin
tunnel junctions (TJs) with ferromagnetic (FM) electrodes and attributed to
electromigration of metallic atoms in nanoconstrictions in the insulating
barrier. The CIS effect is here studied in TJs with two thin (20 \AA)
non-magnetic (NM) Ta electrodes inserted above and below the insulating
barrier. We observe resistance (R) switching for positive applied electrical
current (flowing from the bottom to the top lead), characterized by a
continuous resistance decrease and associated with current-driven displacement
of metallic ions from the bottom electrode into the barrier (thin barrier
state). For negative currents, displaced ions return into their initial
positions in the electrode and the electrical resistance gradually increases
(thick barrier state). We measured the temperature (T) dependence of the
electrical resistance of both thin- and thick-barrier states ($R_b$ and R$_B$
respectively). Experiments showed a weaker R(T) variation when the tunnel
junction is in the $R_b$ state, associated with a smaller tunnel contribution.
By applying large enough electrical currents we induced large irreversible
R-decreases in the studied TJs, associated with barrier degradation. We then
monitored the evolution of the R(T) dependence for different stages of barrier
degradation. In particular, we observed a smooth transition from tunnel- to
metallic-dominated transport. The initial degradation-stages are related to
irreversible barrier thickness decreases (without the formation of pinholes).
Only for later barrier degradation stages do we have the appearance of metallic
paths between the two electrodes that, however, do not lead to metallic
dominated transport for small enough pinhole radius.",0702501v2
2008-12-15,Nanomechanical detection of antibiotic-mucopeptide binding in a model for superbug drug resistance,"The alarming growth of the antibiotic-resistant superbugs
methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant
Enterococcus (VRE) is driving the development of new technologies to
investigate antibiotics and their modes of action. We report the label-free
detection of vancomycin binding to bacterial cell wall precursor analogues
(mucopeptides) on cantilever arrays, with 10 nM sensitivity and at clinically
relevant concentrations in blood serum. Differential measurements quantified
binding constants for vancomycin-sensitive and vancomycin-resistant mucopeptide
analogues. Moreover, by systematically modifying the mucopeptide density we
gain new insights into the origin of surface stress. We propose that stress is
a product of a local chemical binding factor and a geometrical factor
describing the mechanical connectivity of regions affected by local binding in
terms of a percolation process. Our findings place BioMEMS devices in a new
class of percolative systems. The percolation concept will underpin the design
of devices and coatings to significantly lower the drug detection limit and may
also impact on our understanding of antibiotic drug action in bacteria.",0812.2728v1
2010-05-19,Resistance in Superconductors,"In this pedagogical review, we discuss how electrical resistance can arise in
superconductors. Starting with the idea of the superconducting order parameter
as a condensate wave function, we introduce vortices as topological excitations
with quantized phase winding, and we show how phase slips occur when vortices
cross the sample. Superconductors exhibit non-zero electrical resistance under
circumstances where phase slips occur at a finite rate. For one-dimensional
superconductors or Josephson junctions, phase slips can occur at isolated
points in space-time. Phase slip rates may be controlled by thermal activation
over a free-energy barrier, or in some circumstances, at low temperatures, by
quantum tunneling through a barrier. We present an overview of several
phenomena involving vortices that have direct implications for the electrical
resistance of superconductors, including the Berezinskii-Kosterlitz-Thouless
transition for vortex-proliferation in thin films, and the effects of vortex
pinning in bulk type II superconductors on the non-linear resistivity of these
materials in an applied magnetic field. We discuss how quantum fluctuations can
cause phase slips and review the non-trivial role of dissipation on such
fluctuations. We present a basic picture of the superconductor-to-insulator
quantum phase transitions in films, wires, and Josephson junctions. We point
out related problems in superfluid helium films and systems of ultra-cold
trapped atoms. While our emphasis is on theoretical concepts, we also briefly
describe experimental results, and we underline some of the open questions.",1005.3347v1
2013-06-28,Impact of sintering temperature on room temperature magneto-resistive and magneto-caloric properties of Pr2/3Sr1/3MnO3,"Magneto-resistive and magneto-caloric properties of polycrystalline
Pr2/3Sr1/3MnO3 have been studied as a function of sintering temperature (Ts)
between 1260-1450{\deg}C. Reitveld refinement of their X-ray diffraction (XRD)
patterns confirms their single phase crystalline structure with orthorhombic
Pbnm space group. The point of maximum value of temperature coefficient of
resistance (TCRmax) and Curie temperature (Tc) decreased slightly with Ts.
Magneto-resistance (MR) and magnetic entropy ({\Delta}SM) increased markedly
with sintering temperature. This could be attributed to the observed sharpness
of both the magnetic and resistive transitions due to better grain
connectivity. Optimum results are obtained for the sample with Ts =
1400{\deg}C. MR at Tc of the same is found to be as large as 32% at 1T and 58%
at 5T magnetic fields. The maximum entropy change ({\Delta}SMmax) near its Tc
is 2.3Jkg-1K-1 and 7.8 Jkg-1K-1 upon 1T and 5T fields change respectively.
These characteristics [MR (32% 1T, 58% 5T) and reasonable change in magnetic
entropy (7.8Jkg-1K-1, 5T)] generate possibility that the optimized compound can
be used as a potential magnetic refrigerant close to room temperature.",1306.6792v2
2014-11-15,Shock-waves and commutation speed of memristors,"Progress of silicon based technology is nearing its physical limit, as
minimum feature size of components is reaching a mere 10 nm. The resistive
switching behaviour of transition metal oxides and the associated memristor
device is emerging as a competitive technology for next generation electronics.
Significant progress has already been made in the past decade and devices are
beginning to hit the market; however, it has been mainly the result of
empirical trial and error. Hence, gaining theoretical insight is of essence. In
the present work we report the striking result of a connection between the
resistive switching and {\em shock wave} formation, a classic topic of
non-linear dynamics. We argue that the profile of oxygen vacancies that migrate
during the commutation forms a shock wave that propagates through a highly
resistive region of the device. We validate the scenario by means of model
simulations and experiments in a manganese-oxide based memristor device. The
shock wave scenario brings unprecedented physical insight and enables to
rationalize the process of oxygen-vacancy-driven resistive change with direct
implications for a key technological aspect -- the commutation speed.",1411.4198v3
2015-09-29,Extraordinary Hall resistance and unconventional magnetoresistance in Pt/LaCoO3 hybrids,"We report an investigation of transverse Hall resistance and longitudinal
resistance on Pt thin films sputtered on epitaxial LaCoO$_3$ (LCO)
ferromagnetic insulator films. The LaCoO$_3$ films were deposited on several
single crystalline substrates [LaAlO$_3$ (LAO), (La,Sr)(Al,Ta)O$_3$ (LSAT), and
SrTiO$_3$ (STO)] with (001) orientation. The physical properties of LaCoO$_3$
films were characterized by the measurements of magnetic and transport
properties. The LaCoO$_3$ films undergo a paramagnetic to ferromagnetic (FM)
transition at Curie temperatures ranging from 40 K to 85 K, below which the
Pt/LCO hybrids exhibit significant extraordinary Hall resistance (EHR) up to 50
m$\Omega$ and unconventional magnetoresistance (UCMR) ratio
$\Delta$$\rho$/$\rho_0$ about $1.2 \times 10^{-4}$, accompanied by the
conventional magnetoresistance (CMR). The observed spin transport properties
share some common features as well as some unique characteristics when compared
with well-studied Y$_3$Fe$_5$O$_{12}$-based Pt thin films. Our findings call
for new theories since the extraordinary Hall resistance and magnetoresistance
cannot be consistently explained by the existing theories.",1509.08691v1
2016-02-24,Contact resistances in trigate and FinFET devices in a Non-Equilibrium Green's Functions approach,"We compute the contact resistances $R_{\rm c}$ in trigate and FinFET devices
with widths and heights in the 4 to 24 nm range using a Non-Equilibrium Green's
Functions approach. Electron-phonon, surface roughness and Coulomb scattering
are taken into account. We show that $R_{\rm c}$ represents a significant part
of the total resistance of devices with sub-30 nm gate lengths. The analysis of
the quasi-Fermi level profile reveals that the spacers between the heavily
doped source/drain and the gate are major contributors to the contact
resistance. The conductance is indeed limited by the poor electrostatic control
over the carrier density under the spacers. We then disentangle the ballistic
and diffusive components of $R_{\rm c}$, and analyze the impact of different
design parameters (cross section and doping profile in the contacts) on the
electrical performances of the devices. The contact resistance and variability
rapidly increase when the cross sectional area of the channel goes below
$\simeq 50$ nm$^2$. We also highlight the role of the charges trapped at the
interface between silicon and the spacer material.",1602.07545v1
2017-10-26,Effect of air confinement on thermal contact resistance in nanoscale heat transfer,"We report herein the pressure dependent thermal contact resistance (Rc)
between Wollaston wire thermal probe and samples which is evaluated within the
framework of an analytical model. This work presents heat transfer between the
Wollaston wire thermal probe and samples at nanoscale for different air
pressure ranging from 1 Pa to 10e5 Pa. We make use of a scanning thermal
microscopy (SThM) for the thermal analysis of two samples, fused silica (SiO2)
and Titanium (Ti), with different thermal conductivities. The thermal probe's
output voltage difference (deltaV) between out-off contact output voltage (Voc)
and in-contact output voltage (Vic) was recorded. The result shows that the
heat transfer increases with the increasing air pressure and it is found higher
for higher thermal conductive material. We also propose an analytical model
based on the normalized output voltage difference to extract the probe-sample
thermal contact resistance. The obtained Rc values in the range of ~1.8e7 K/W
to ~14.3e7 K/W validate the presented analytical model. Further analysis
reveals that the thermal contact resistance between the probe and sample
decreases with increasing air pressure. Such behavior is interpreted by the
contribution of heat transfer through confined air on thermal contact
resistance. In addition, the signature of Rc is also evidenced in the context
of thermal mismatch behavior which is studied by using acoustic mismatch model
(AMM) and diffuse mismatch model (DMM).",1710.09501v1
2017-11-08,Surface impedance and optimum surface resistance of a superconductor with imperfect surface,"We calculate a low-frequency surface impedance of a dirty, s-wave
superconductor with an imperfect surface incorporating either a thin layer with
a reduced pairing constant or a thin, proximity-coupled normal layer. Such
structures model realistic surfaces of superconducting materials which can
contain oxide layers, absorbed impurities or nonstoichiometric composition. We
solved the Usadel equations self-consistently and obtained spatial
distributions of the order parameter and the quasiparticle density of states
which then were used to calculate a low-frequency surface resistance $R_s(T)$
and the magnetic penetration depth $\lambda(T)$ as functions of temperature in
the limit of local London electrodynamics. It is shown that the imperfect
surface in a single-band s-wave superconductor results in a non-exponential
temperature dependence of $Z(T)$ at $T\ll T_c$ which can mimic the behavior of
multiband or d-wave superconductors. The imperfect surface and the broadening
of the gap peaks in the quasiparticle density of states $N(\epsilon)$ in the
bulk give rise to a weakly temperature-dependent residual surface resistance.
We show that the surface resistance can be optimized and even reduced below its
value for an ideal surface by engineering $N(\epsilon)$ at the surface using
pairbreaking mechanisms, particularly, by incorporating a small density of
magnetic impurities or by tuning the thickness and conductivity of the normal
layer and its contact resistance. The results of this work address the limit of
$R_s$ in superconductors at $T\ll T_c$, and the ways of engineering the optimal
density of states by surface nano-structuring and impurities to reduce losses
in superconducting micro-resonators, thin film strip lines, and radio frequency
cavities for particle accelerators.",1711.03077v1
2018-02-15,Parallel magnetic field suppresses dissipation in superconducting nanostrips,"The motion of Abrikosov vortices in type-II superconductors results in a
finite resistance in the presence of an applied electric current. Elimination
or reduction of the resistance via immobilization of vortices is the ""holy
grail"" of superconductivity research. Common wisdom dictates that an increase
in the magnetic field escalates the loss of energy since the number of vortices
increases. Here we show that this is no longer true if the magnetic field and
the current are applied parallel to each other.Our experimental studies on the
resistive behavior of a superconducting Mo$_{0.79}$Ge$_{0.21}$ nanostrip reveal
the emergence of a dissipative state with increasing magnetic field, followed
by a pronounced resistance drop, signifying a reentrance to the superconducting
state. Large-scale simulations of the 3D time-dependent Ginzburg-Landau model
indicate that the intermediate resistive state is due to an unwinding of
twisted vortices. When the magnetic field increases, this instability is
suppressed due to a better accommodation of the vortex lattice to the pinning
configuration. Our findings show that magnetic field and geometrical
confinement can suppress the dissipation induced by vortex motion and thus
radically improve the performance of superconducting materials.",1802.05673v1
2018-05-22,Structural properties and anisotropic electronic transport in SrIrO3 films,"Perovskite SrIrO3 (SIO) films epitaxially deposited with a thickness of about
60 nm on various substrate materials display nearly strain-relieved state.
Films grown on orthorhombic (110) DyScO3 (DSO) are found to display untwinned
bulk-like orthorhombic structure. However, film deposition on cubic (001)
SrTiO3 induces a twinned growth of SIO. Resistance measurements on the SIO
films reveal only weak temperature dependence, where the resistance R increases
with decreasing temperature T. Hall measurements show dominant electron-like
transport throughout the temperature range from 2 K to 300 K. At 2 K, the
electron concentration and resistivity for SIO on STO amount to ne = 1.4*10^20
cm-3 and 1 mohmcm. Interestingly, the film resistance of untwinned SIO on DSO
along the [1-10] and the [001] direction differs by up to 25% indicating
pronounced anisotropic electronic transport. The anisotropy of the resistance
increases with decreasing T and displays a distinct maximum around 86 K. The
specific T-dependence is similar to that of the structural anisotropy
sqrt(a2+b2)/c of bulk SIO. Therefore, anisotropic electronic transport in SIO
is very likely induced by the orthorhombic distortion. Consequently, for
twinned SIO films on STO anisotropy vanishes nearly completely. The
experimental results show that structural changes are very likely responsible
for the observed anisotropic electronic transport. The strong sensitivity of
the electronic transport in SIO films may be explained in terms of the narrow
electron-like bands in SIO caused by spin-orbit-coupling and orthorhombic
distortion.",1805.08473v2
2022-02-24,Thermal spreading resistance of GaN HEMTs with heat source heating studied by hybrid Monte Carlo-diffusion simulations,"Exact assessment of thermal spreading resistance is of great importance to
the thermal management of electronic devices, especially when completely
considering the heat conduction process from the nanoscale heat source to the
macroscopic scale heat sink. The existing simulation methods are either based
on convectional Fourier's law or limited to small system sizes, making it
difficult to accurately and efficiently study the cross-scale heat transfer. In
this paper, a hybrid phonon Monte Carlo-diffusion method that couples phonon
Monte Carlo (MC) method with Fourier's law by dividing the computational domain
is adopted to analyze thermal spreading resistance in ballistic-diffusive
regime. Compared with phonon MC simulation, the junction temperature of the
hybrid method has the same precision, while the time costs could be reduced up
to 2 orders of magnitude at most. Furthermore, the simulation results indicate
that the heating scheme has a remarkable impact on phonon transport. The
thermal resistance of the heat source (HS) scheme can be larger than that of
the heat flux (HF) scheme, which is opposite from the prediction of Fourier's
law. In the HS scheme, the enhanced phonon-boundary scattering counteracts the
broadening of the heat source, leading to a stronger ballistic effect as the
heat source thickness decreases. The conclusion is verified by a
one-dimensional thermal resistance model. This work has opened up an
opportunity for the fast and extensive thermal modeling of cross-scale heat
transfer in electronic devices and highlighted the influence of heating
schemes.",2202.13770v1
2007-10-10,Strong Reduction of the Field-Dependent Microwave Surface Resistance in YBCO with BaZrO_3 Inclusions,"We present measurements of the magnetic field dependent microwave surface
resistance in laser-ablated YBa$_2$Cu$_3$O$_{7-\delta}$ films on SrTiO$_3$
substrates. BaZrO$_3$ crystallites were included in the films using composite
targets containing BaZrO$_3$ inclusions with mean grain size smaller than 1
$\mu$m. X-ray diffraction showed single epitaxial relationship between
BaZrO$_3$ and YBa$_2$Cu$_3$O$_{7-\delta}$. The effective surface resistance was
measured at 47.7 GHz for 60$< T <$90 K and 0$< \mu_0H <$0.8 T. The magnetic
field had a very different effect on pristine YBa$_2$Cu$_3$O$_{7-\delta}$ and
YBa$_2$Cu$_3$O$_{7-\delta}$/BaZrO$_3$, while for $\mu_0H=$0 only a reduction of
$T_c$ in the YBa$_2$Cu$_3$O$_{7-\delta}$/BaZrO$_3$ film was observed,
consistent with dc measurements. At low enough $T$, in moderate fields
YBa$_2$Cu$_3$O$_{7-\delta}$/BaZrO$_3$ exhibited an intrinsic thin film
resistance lower than the pure film. The results clearly indicate that
BaZrO$_3$ inclusions determine a strong reduction of the field-dependent
surface resistance. From the analysis of the data in the framework of simple
models for the microwave surface impedance in the mixed state we argue that
BaZrO$_3$ inclusions determine very steep pinning potentials.",0710.1953v1
2018-07-19,Theoretical study of scattering in graphene ribbons in the presence of structural and atomistic edge roughness,"We investigate the diffusive electron-transport properties of charge-doped
graphene ribbons and nanoribbons with imperfect edges. We consider different
regimes of edge scattering, ranging from wide graphene ribbons with (partially)
diffusive edge scattering to ribbons with large width variations and
nanoribbons with atomistic edge roughness. For the latter, we introduce an
approach based on pseudopotentials, allowing for an atomistic treatment of the
band structure and the scattering potential, on the self-consistent solution of
the Boltzmann transport equation within the relaxation-time approximation and
taking into account the edge-roughness properties and statistics. The resulting
resistivity depends strongly on the ribbon orientation, with zigzag (armchair)
ribbons showing the smallest (largest) resistivity and intermediate ribbon
orientations exhibiting intermediate resistivity values. The results also show
clear resistivity peaks, corresponding to peaks in the density of states due to
the confinement-induced subband quantization, except for armchair-edge ribbons
that show a very strong width dependence because of their claromatic behavior.
Furthermore, we identify a strong interplay between the relative position of
the two valleys of graphene along the transport direction, the correlation
profile of the atomistic edge roughness, and the chiral valley modes, leading
to a peculiar strongly suppressed resistivity regime, most pronounced for the
zigzag orientation.",1807.07263v2
2020-10-07,Correlation of uniaxial magnetic anisotropy axes and principal resistivities in polycrystalline ferromagnetic films,"In the present study, we demonstrate the measurement of resistivity tensor
($\rho$) along the magnetic axes of a polycrystalline film of ferromagnetic
permalloy (Py). To this end, conventional Hall-bar and a more recent extended
van der Pauw methods were utilized for determining 2D $\rho$ in the film plane.
The samples were prepared by normal incidence sputter deposition within an
in-situ magnetic field to induce in-plane uniaxial magnetic anisotropy in the
film. Since $\rho$ might be affected by the internal magnetization of the film,
we performed measurements by rotation of a saturating magnetic field in the
film plane. Both methods indicate that the average resistivity is lower along
the easy axis of the film compared to the hard axis. Since X-ray diffraction
results indicated no dominating texture in the film, we concluded that there is
a correlation between uniaxial magnetic axes and principal resistivity axes.
This is an important finding that allows determining the direction of magnetic
anisotropy axes without magnetometry. The results also verify atomic or pair
ordering to be the origin of uniaxial magnetic anisotropy in the Py since
resistivity is sensitive to the level of order in solids. The extended van der
Pauw utilized here can be easily performed on the as-received samples which is
of practical interest.",2010.03554v3
2020-12-31,DC Resistance Degradation of SrTiO$_3$: The Role of Virtual-Cathode Needles and Oxygen Bubbles,"This study of highly accelerated lifetime tests of SrTiO$_3$, a model
semiconducting oxide, is motivated by the interest in reliable multilayer
ceramic capacitors and resistance-switching thin-film devices. Our analytical
solution to oxygen-vacancy migration under a DC voltage -- the cause of
resistance degradation in SrTiO$_3$ -- agrees with previous numerical
solutions. However, all solutions fail to explain why degradation kinetics
feature a very strong voltage dependence, which we attribute to the nucleation
and growth of cathode-initiated fast-conducting needles. While they have no
color contrast in SrTiO$_3$ single crystals and are nominally invisible,
needles presence in DC-degraded samples -- in silicone oil and in air -- was
unambiguously revealed by in-situ hot-stage photography. Observations in
silicone oil and thermodynamic considerations of voltage boundary conditions
further revealed a cooccurrence of copious oxygen bubbling and the onset of
final accelerating degradation, suggesting sudden oxygen loss is a precursor of
final failure. Remarkably, both undoped and Fe-doped SrTiO$_3$ can emit
electroluminescence at higher current densities, thus providing a vivid
indicator of resistance degradation and a metal-to-insulator resistance
transition during cooling. The implications of these findings to thin ceramic
and thin film SrTiO$_3$ devices are discussed, along with connections to
similar findings in likewise degraded fast-ion yttria-stabilized zirconia.",2012.15777v1
2021-04-12,Temperature-linear Resistivity in Twisted Double Bilayer Graphene,"We report an experimental study of carrier density (n), displacement field
(D) and twist angle ({\theta}) dependence of temperature (T)-linear resistivity
in twisted double bilayer graphene (TDBG). For a large twist angle
({\theta}>1.5{\deg}) where correlated insulating states are absent, we observe
a T-linear resistivity (with the slope of the order ~10{\Omega}/K) over a wide
range of carrier density and its slope decreases with increasing of n, in
agreement with acoustic phonon scattering model semi-quantitatively. The slope
of T-linear resistivity is non-monotonically dependent on the displacement
field with a single peak structure. For device with {\theta}~1.23{\deg} at
which correlated states emerge, the slope of T-linear resistivity is found
maximum (~100{\Omega}/K) at the boundary of the halo structure where phase
transition occurs, with signatures of continuous phase transition, Planckian
dissipation, and the diverging effective mass; these observations are in line
with quantum critical behaviors, which might be due to the symmetry-breaking
instability at the critical points. Our results shed new light on correlated
physics in TDBG and other twisted moir\'e systems.",2104.05406v3
2022-01-06,Coulomb drag in metal monochalcogenides double-layer structures with Mexican-hat band dispersions,"We theoretically study the Coulomb drag resistivity and plasmon modes
behavior for a system composed of two parallel p-type doped GaS monolayers with
Mexican-hat valence energy band using the Boltzmann transport theory formalism.
We investigate the effect of temperature,$\ T$, carrier density,$\ p$, and
layer separation,$\ d$, on the plasmon modes and drag resistivity within the
energy-independent scattering time approximation. Our results show that the
density dependence of plasmon modes can be approximated by$\ p^{0.5}$. Also,
the calculations suggest a$\ d^{0.2}$ and a$\ d^{0.1}$ dependencies for the
acoustic and optical plasmon energies, respectively. Interestingly, we obtain
that the behavior of drag resistivity in the double-layer metal
monochalcogenides swings between the behavior of a double-quantum well system
with parabolic dispersion and that of a double-quantum wire structure with a
large carrier density of states. In particular, the transresistivity value
reduces exponentially with increasing the distance between layers. Furthermore,
the drag resistivity changes as$\ T^{2}/p^{4}$ ($\ T^{2.8}/p^{4.5}$) at low
(intermediate) temperatures. Finally, we compare the drag resistivity as a
function of temperature for GaS with other Mexican-hat materials including GaSe
and InSe and find that it adopts higher values when the metal monochalcogenide
has smaller Mexican-hat height.",2201.02077v1
2023-02-14,Acoustic phonon contribution to the resistivity of twisted bilayer graphene,"We calculate the contribution to the doping ($n$) and temperature ($T$)
dependence of the electrical resistivity of twisted bilayer graphene (TBLG) due
to scattering by acoustic phonons. Our calculation retains the full
Bistritzer-MacDonald (BM) band structure, with a focus on understanding the
role of the complicated geometric features present in the BM band structure on
electronic transport theory. We find that the band geometry plays an important
role in determining the resistivity, giving an intricate dependence on both $n$
and $T$ that mirrors features in the band structure and complicates the
Bloch-Gr\""{u}neisen (BG) crossover. Our calculations predict pronounced
departures from the standard simplistic expectation of a linear $T$-dependence
above the BG crossover. In particular, we are able to explain the presence of
the resistance peaks that have been observed in experiment, as well as
quantitatively predict the temperatures at which they occur. Our calculated
theoretical results are germane to an ongoing debate over the existence of a
strange metal state in TBLG by providing a quantitatively accurate theory for
the TBLG resistivity at finite temperatures.",2302.07275v3
2023-04-21,Star-Mesh Quantized Hall Array Resistance Devices,"Advances in the development of graphene-based technology have enabled
improvements in DC resistance metrology. Devices made from epitaxially grown
graphene have replaced the GaAs-based counterparts, leading to an easier and
more accessible realization of the ohm. By optimizing the scale of the growth,
it has become possible to fabricate quantized Hall array resistance standards
(QHARS) with nominal values between 1 k{\Omega} and 1.29 M{\Omega}. One of
these QHARS device designs accommodates a value of about 1.01 M{\Omega}, which
made it an ideal candidate to pursue a proof-of-concept that graphene-based
QHARS devices are suitable for forming wye-delta resistance networks. In this
work, the 1.01 M{\Omega} array output nearly 20.6 M{\Omega} due to the
wye-delta transformation, which itself is a special case of star-mesh
transformations. These mathematical equivalence principles allow one to extend
the QHR to the 100 M{\Omega} and 10 G{\Omega} resistance levels with fewer
array elements than would be necessary for a single array with many more
elements in series. The 1.01 M{\Omega} device shows promise that the wye-delta
transformation can shorten the calibration chain, and, more importantly,
provide a chain with a more direct line to the quantum SI.",2304.11243v1
2023-06-12,"Symmetric, off-diagonal, resistance from rotational symmetry breaking in graphene-WSe$_2$ heterostructure: prediction for a large magic angle in a Moire system","We show that any two-dimensional system with a non-zero \textit{symmetric}
off-diagonal component of the resistance matrix, $R_{xy}=R_{yx} \neq 0$, must
have the in-plane rotational symmetry broken down to $C_2$. Such a resistance
response is Ohmic, and is different from the Hall response which is the
\textit{anti-symmetric} part of the resistance tensor, $R_{xy}=-R_{yx}$, is
rotationally symmetric in the 2D plane, and requires broken time-reversal
symmetry. We show how a minute amount of strain due to lattice mismatch - less
than $1 \%$ - can produce a vastly exaggerated symmetric off-diagonal response
- $\frac{R_{xy}}{R_{xx}} \sim 20\%$ - because of the momentum matching
constraints in a Moire system. Our results help explain an important new
transport experiment on graphene-WSe$_2$ heterostructures, as well as are
relevant for other experimental systems with rotational symmetry breaking, such
as nematic systems and Kagome charge density waves. Additionally, our work
predicts an example of a `magic' angle, $\theta\sim 27^0$, in a Moire system
which is a significant fraction of $\pi$. Our prediction that the anomalous
resistance anisotropy occurs at a large value of magic angle, in contrast to
known examples of magic angle transport anomalies that are small fractions of
$\pi$, can be experimentally tested in graphene-WSe$_2$ heterostructures.",2306.06840v2
2024-03-04,"Electric field induced resistive switching in M$^{3+}_x$V$_{1-x}$O$_2$ (M$^{3+}$= Ga$^{3+}$, Al$^{3+}$) single crystals at temperatures below the T $\to$ M2 phase transition","The phase diagram of VO$_2$ strained or doped with several trivalent ions
consists of four phases; in order of increasing temperatures, three (M1, T and
M2) are insulating while the fourth (R), above ~340 K, is metallic. These
phases and the three phase transitions have been thoroughly investigated for
about half a century by a wide variety of techniques, including electronic
transport. While an upwards jump of the resistance of up to a factor of 2 was
observed at the T-M2 transition and a drop of several orders of magnitude was
observed at the M2$\to$R one, resistive switching at the M1$\to$T transition
remained elusive over all these years. Here we report on the investigation of
Ga- and Al-doped VO$_2$ single crystals, following the rather surprising
appearance of a small and steep drop of a factor of ~ 0.12 in the resistance of
Ga-doped VO$_2$ single crystals detected by pulsed and DC I-V measurements
carried out at room temperature, below the T$\to$M2 phase transition. Similar
results were obtained also from measurements on Al-doped VO2 single crystals.
Raman spectra of Ga-, and Al-doped crystals resolved their structures as
function of temperature. The accumulated results of the measurements on Ga-,
and Al-doped single crystals provide evidence for identifying the resistive
switching at T$_{\rm RS}$<T$_{\rm T\to M2}$ with the M1$\to$T transition.",2403.01808v2
2017-07-27,Experimental study of electron and phonon dynamics in nanoscale materials by ultrafast laser time-domain spectroscopy,"With the rapid advances in the development of nanotechnology, nowadays, the
sizes of elementary unit, i.e. transistor, of micro- and nanoelectronic devices
are well deep into nanoscale. For the pursuit of cheaper and faster nanoscale
electronic devices, the size of transistors keeps scaling down. As the
miniaturization of the nanoelectronic devices, the electrical resistivity
increases dramatically, resulting rapid growth in the heat generation. The heat
generation and limited thermal dissipation in nanoscale materials have become a
critical problem in the development of the next generation nanoelectronic
devices. Copper (Cu) is widely used conducting material in nanoelectronic
devices, and the electron-phonon scattering is the dominant contributor to the
resistivity in Cu nanowires at room temperature. Meanwhile, phonons are the
main carriers of heat in insulators, intrinsic and lightly doped
semiconductors. The thermal transport is an ensemble of phonon transport, which
strongly depends on the phonon frequency. In addition, the phonon transport in
nanoscale materials can behave fundamentally different than in bulk materials,
because of the spatial confinement. However, the size effect on electron-phonon
scattering and frequency dependent phonon transport in nanoscale materials
remain largely unexplored, due to the lack of suitable experimental techniques.
This thesis is mainly focusing on the study of carrier dynamics and acoustic
phonon transport in nanoscale materials.",1707.08698v2
2002-10-17,New heat treatment to prepare high quality polycrystalline and single crystal MgB2 in single process,"We report here on a new heat treatment to prepare both dense polycrystalline
and single crystal MgB2 high quality samples in one single process. Resistivity
measurements for polycrystalline part of the sample gives a residual
resistivity ratio RRR=16.6 and a very low normal state resistivity rho(40K)=
0.28 microOhmcm. Both SEM and SQUID study on polycrystals reveal the high
quality, dense character and well coupling of grain boundaries. On the other
hand, the high quality single crystals have a unique shape that resembles the
hexagonal crystal structure. SQUID measurements reveals very weak flux pinning
character implying our single crystals to be very clean. In this study, we
conclude that heat treatment is playing a major rule on the characteristics of
both polycrystalline and single crystal MgB2. Samples are thoroughly
characterized by x-ray, resistivity, dc SQUID and SEM.",0210384v1
2010-05-03,Overview of the DHCAL Project,"We review the status and plans of the Digital Hadron Calorimeter with
Resistive Plate Chambers project.",1005.0412v1
2010-08-26,Simulation of Edge Localised Modes using BOUT++,"The BOUT++ code is used to simulate ELMs in a shifted circle equilibrium.
Reduced ideal MHD simulations are first benchmarked against the linear ideal
MHD code ELITE, showing good agreement. Diamagnetic drift effects are included
finding the expected suppression of high toroidal mode number modes. Nonlinear
simulations are performed, making the assumption that the anomalous kinematic
electron viscosity is comparable to the anomalous electron thermal diffusivity.
This allows simulations with realistically high Lundquist numbers S = 1e8,
finding ELM sizes of 5-10% of the pedestal stored thermal energy. Scans show a
strong dependence of the ELM size resistivity at low Lundquist numbers, with
higher resistivity leading to more violent eruptions. At high Lundquist numbers
relevant to high-performance discharges, ELM size is independent of resistivity
as hyper-resistivity becomes the dominant dissipative effect.",1008.4554v1
2021-05-24,Ageing studies of Multi-Strip Multi-Gap Resistive Plate Counters based on low resistivity glass electrodes in high irradiation dose,"Detailed tests and analysis of ageing effects of high irradiation dose on
Multi-Strip Multi-Gap Resistive Plate Counters based on low resistivity glass
electrodes were performed. MSMGRPC efficiency and cluster size before
irradiation are measured and compared with their values after irradiation in a
high irradiation dose accessed at a multi-purpose irradiation facility of
IFIN-HH based on $^{60}$Co source. The composition and properties of the
deposited layers on the glass electrodes, studied based on a multitude of
analysis methods, i.e. SEM, XPS, foil-ERDA, RBS, AFM and THz-TDS, are
presented.",2105.12214v2
2021-11-23,Superconducting aluminum heat switch with 3 n$Ω$ equivalent resistance,"Superconducting heat switches with extremely low normal state resistances are
needed for constructing continuous nuclear demagnetization refrigerators with
high cooling power. Aluminum is a suitable superconductor for the heat switch
because of its high Debye temperature and its commercial availability in high
purity. We have constructed a high quality Al heat switch whose design is
significantly different than that of previous heat switches. In order to join
the Al to Cu with low contact resistance, we plasma etched the Al to remove its
oxide layer then immediately deposited Au without breaking the vacuum of the
e-beam evaporator. In the normal state of the heat switch, we measured a
thermal conductance of $8 T$ W/K$^2$ which is equivalent to an electrical
resistance of 3 n$\Omega$ according to the Wiedemann-Franz law. In the
superconducting state we measured a thermal conductance that is $2\times10^6$
times lower than that of the normal state at 50 mK.",2111.11896v2
2023-02-18,Search for universal minimum drag resistance underwater vehicle hull using CFD,"In Autonomous Underwater Vehicles (AUVs) design, hull resistance is an
important factor in determining the power requirements and range of vehicle and
consequently affect battery size, weight, and volume requirement of the design.
In this paper, we leverage on AI-based optimization algorithm along with
Computational Fluid Dynamics (CFD) simulation to study the optimal hull design
that minimizing the resistance. By running the CFD-based optimization at
different operating velocities and turbulence intensity, we want to
study/search the possibility of a universal design that will provide least
resistance/near-optimal design across all operating conditions (operating
velocity) and environmental conditions (turbulence intensity). Early result
demonstrated that the optimal design found at low velocity and low turbulence
condition performs very poor at high velocity and high turbulence conditions.
However, a design that is optimal at high velocity and high turbulence
conditions performs near-optimal across many considered velocity and turbulence
conditions.",2302.09441v2
2019-11-22,Radiation Damage Studies on Titanium Alloys as High Intensity Proton Accelerator Beam Window Materials,"A high-strength dual alpha+beta phase titanium alloy Ti-6Al-4V is utilized as
a material for beam windows in several accelerator target facilities. However,
relatively little is known about how material properties of this alloy are
affected by high-intensity proton beam irradiation. With plans to upgrade
neutrino facilities at J-PARC and Fermilab to over 1 MW beam power, the
radiation damage in the window material will reach a few displacements per atom
(dpa) per year, significantly above the ~0.3 dpa level of existing data. The
RaDIATE collaboration has conducted a high intensity proton beam irradiation of
various target and window material specimens at BLIP facility, including a
variety of titanium alloys. Post-Irradiation Examination of the specimens in
the 1st capsule, irradiated at up to 0.25 dpa, is in progress. Tensile tests in
a hot cell at PNNL exhibited a clear signature of radiation hardening and loss
of ductility for Ti-6Al-4V, while Ti-3Al-2.5V, with less beta phase, exhibited
less severe hardening. Microstructural investigations will follow to study the
cause of the difference in tensile behavior between these alloys. High-cycle
fatigue (HCF) performance is critical to the lifetime estimation of beam
windows exposed to a periodic thermal stress from a pulsed proton beam. The 1st
HCF data on irradiated titanium alloys are to be obtained by a conventional
bend fatigue test at Fermilab and by an ultrasonic mesoscale fatigue test at
Culham Laboratory. Specimens in the 2nd capsule, irradiated at up to ~1 dpa,
cover typical titanium alloy grades, including possible radiation-resistant
candidates. These systematic studies on the effects of radiation damage of
titanium alloys are intended to enable us to predict realistic lifetimes of
current beam windows made of Ti-6Al-4V and to extend the lifetime by choosing a
more radiation and thermal shock tolerant alloy.",1911.10198v1
2023-09-26,"The $p_0$-Laplace ""Signature"" for Quasilinear Inverse Problems","This paper refers to an imaging problem in the presence of nonlinear
materials. Specifically, the problem we address falls within the framework of
Electrical Resistance Tomography and involves two different materials, one or
both of which are nonlinear. Tomography with nonlinear materials in the early
stages of developments, although breakthroughs are expected in the
not-too-distant future. The original contribution this work makes is that the
nonlinear problem can be approximated by a weighted $p_0$-Laplace problem. From
the perspective of tomography, this is a significant result because it
highlights the central role played by the $p_0$-Laplacian in inverse problems
with nonlinear materials. Moreover, when $p_0=2$, this result allows all the
imaging methods and algorithms developed for linear materials to be brought
into the arena of problems with nonlinear materials. The main result of this
work is that for ""small"" Dirichlet data, (i) one material can be replaced by a
perfect electric conductor and (ii) the other material can be replaced by a
material giving rise to a weighted $p_0$-Laplace problem.",2309.15865v2
1996-11-30,Exchange coupling and current-perpendicular-to-plane giant magneto-resistance of magnetic trilayers. Rigorous results within a tight-binding single-band model,"It is shown that the current-perpendicular-to-plane giant magneto-resistance
(CPP-GMR) oscillations, in the ballistic regime, are strongly correlated with
those of the exchange coupling (J). Both the GMR and J are treated on equal
footing within a rigorously solvable tight-binding single-band model. The
strong correlation consists in sharing asymptotically the same period,
determined by the spacer Fermi surface, and oscillating with varying spacer
thickness predominantly in opposite phases.",9612008v1
1998-09-30,Thickness dependent magnetotransport in ultra-thin manganite films,"To understand the near-interface magnetism in manganites, uniform, ultra-thin
films of La_{0.67}Sr_{0.33}MnO_3 were grown epitaxially on single crystal (001)
LaAlO_3 and (110) NdGaO_3 substrates. The temperature and magnetic field
dependent film resistance is used to probe the film's structural and magnetic
properties. A surface and/or interface related dead-layer is inferred from the
thickness dependent resistance and magnetoresistance. The total thickness of
the dead layer is estimated to be $\sim 30 \AA$ for films on NdGaO_3 and $\sim
50 \AA$ for films on LaAlO_3.",9809414v1
1999-10-14,Giant 1/f noise in perovskite manganites: evidence of the percolation threshold,"We discovered an unprecedented magnitude of the 1/f noise near the Curie
temperature Tc in low-Tc manganites. The scaling behavior of the 1/f noise and
the resistance provides strong evidence of the percolation nature of the
ferromagnetic transition in the polycrystalline samples. The step-like changes
of the resistance with temperature, observed for single crystals, suggest that
the size of the ferromagnetic domains depends on the size of crystallites.",9910220v1
2000-01-12,Anomalous Hopping Exponents of Ultrathin Films of Metals,"The temperature dependence of the resistance R(T) of ultrathin
quench-condensed films of Ag, Bi, Pb and Pd has been investigated. In the most
resistive films, R(T)=Roexp(To/T)^x, where x=0.75. Surprisingly, the exponent x
was found to be constant for a wide range of Ro and To in all four materials,
possibly implying a consistent underlying conduction mechanism. The results are
discussed in terms of several different models of hopping conduction.",0001162v1
2000-07-03,The mean free path for electron conduction in metallic fullerenes,"We calculate the electrical resistivity due to electron-phonon scattering for
a model of A3C60 (A= K, Rb), using an essentially exact quantum Monte-Carlo
calculation. In agreement with experiment, we obtain exceptionally large
metallic resistivities at large temperatures T. This illustrates that the
apparent mean free path can be much shorter than the separation of the
molecules. An interpretation of this result is given. The calculation also
explains the linear behavior in T at small T.",0007024v1
2000-09-04,Observation of anomalous single-magnon scattering in half-metallic ferromagnets by chemical pressure control,"Temperature variation of resistivity and specific heat have been measured for
prototypical half-metallic ferromagnets,
  R_0.6Sr_0.4MnO_3, with controlling the one-electron bandwidth W. We have
found variation of the temperature scalings in the resistivity from
  T^2 (R = La, and Nd) to T^3 (R = Sm), and have interpreted the $T^3-law in
terms of the anomalous single-magnon scattering (AMS) process in the
half-metallic system.",0009035v1
2000-10-25,Ca0.85Sm0.15MnO3: A mixed antiferromagnet with unusual properties,"We investigated electrical and magnetic properties of the electron-doped
manganites Ca1-xSmxMnO3 (0<x<0.2). Our results indicate the possibility of
phase separation in electron doped manganites. The compounds with x = 0.13-0.15
show unusual difference between zero-field cooled and field-cooled
resistivities which are not observed in lower compositions. Our results suggest
that electronic phase separation alone is insufficient to understand the origin
of the resistivity irreversibilities.",0010384v1
2001-08-21,Metals with Small Electron Mean-Free Path: Saturation versus Escalation of Resistivity,"Resistivity of metals is commonly observed either to 'escalate' beyond the
Ioffe-Regel limit (mean free path l equal to lattice constant a) or to
'saturate' at this point. It is argued that neither behavior is
well-understood, and that 'escalation' is not necessarily more mysterious than
'saturation.'",0108343v2
2002-02-18,Conductivity Oscillations in Current-Induced Metastable States in Low-Doped Manganite Single Crystals,"Deterministic oscillations of current-induced metastable resistivity in
changing voltage have been detected in La$_{0.82}$Ca$_{0.18}$MnO$_3$ single
crystals. At low temperatures, below the Curie point, application of specific
bias procedures switches the crystal into metastable resistivity state
characterized by appearance of pronounced reproducible and random structures in
the voltage dependence of the differential conductivity. In certain bias range
equally spaced broad conductivity peaks have been observed. The oscillating
conductivity has been tentatively ascribed to resonances in a quantum well
within the double tunnel barrier of intrinsic weak-links associated with
twin-like defect boundaries.",0202284v1
2002-02-20,Universal transport in 2D granular superconductors,"The transport properties of quench condensed granular superconductors are
presented and analyzed. These systems exhibit transitions from insulating to
superconducting behavior as a function of inter-grain spacing.
Superconductivity is characterized by broad transitions in which the resistance
drops exponentially with reducing temperature. The slope of the log R versus T
curves turns out to be universaly dependent on the normal state film resistance
for all measured granular systems. It does not depend on the material, critical
temperature, geometry, or experimental set-up. We discuss possible physical
scenarios to explain these findings.",0202342v1
2002-05-22,Universal angular magnetoresistance and spin torque in ferromagnetic/normal metal hybrids,"The electrical resistance of ferromagnetic/normal-metal (F/N)
heterostructures depends on the nature of the junctions which may be tunnel
barriers, point contacts, or intermetallic interfaces. For all junction types,
the resistance of disordered F/N/F perpendicular spin valves as a function of
the angle between magnetization vectors is shown to obey a simple universal
law. The spin-current induced magnetization torque can be measured by the
angular magnetoresistance of these spin valves. The results are generalized to
arbitrary magnetoelectronic circuits.",0205453v1
2002-08-22,A scheme for electrical detection of spin resonance signal from a single electron trap,"We study a scheme for electrical detection of the spin resonance (ESR) of a
single electron trapped near a Field Effect Transistor (FET) conduction
channel. In this scheme, the resonant Rabi oscillations of the trapped electron
spin cause a modification of the average occupancy of a shallow trap, which can
be detected through the change in the FET channel resistivity. We show that the
dependence of the channel resistivity on the frequency of the rf field can have
either peak or dip at the Larmor frequency of the electron spin in the trap.",0208438v1
2003-02-20,Electron scattering near an itinerant to localized electronic transition,"We report an unconventional temperature dependence of the resistivity in
several strongly correlated systems approaching a localized to itinerant
electronic transition from the itinerant electron side. The observed
resistivity, proportioanl to T^(3/2)over the entire range of materials
discussed, cannot be explained within the framework of existing theories. We
propose a model in which the scattering of the conduction electrons by locally
cooperative bond-length fluctuations in a matrix of vibronic and Fermi-liquid
electrons can account for the experimental data.",0302426v1
2003-03-10,New collective zero-resistance states in GaAs/AlGaAs heterostructures,"Exponentially small resistance in crossed static magnetic and microwave
fields occurs in ultrapure two dimensional electron gases (2DEG), while in less
pure systems the magnetoresistance oscillates but is always positive. A
non-perturbative theory of self-organization explains the new collective states
in terms of open orbits. There are analogies to many other anomalous physical
phenomena, as well as to scaling and evolutionary principles of biophysics.",0303181v1
2003-04-04,Co-ordination between Rashba spin-orbital interaction and space charge effect and enhanced spin injection into semiconductors,"We consider the effect of the Rashba spin-orbital interaction and space
charge in a ferromagnet-insulator/semiconductor/insulator-ferromagnet junction
where the spin current is severely affected by the doping, band structure and
charge screening in the semiconductor. In diffusion region, if the the
resistance of the tunneling barriers is comparable to the semiconductor
resistance, the magnetoresistance of this junction can be greatly enhanced
under appropriate doping by the co-ordination between the Rashba effect and
screened Coulomb interaction in the nonequilibrium transport processes within
Hartree approximation.",0304117v1
2003-07-17,Electron interaction with domain walls in antiferromagnetically coupled multilayers,"For antiferromagnetically coupled Fe/Cr multilayers the low field
contribution to the resistivity, which is caused by the domain walls, is
strongly enhanced at low temperatures. The low temperature resistivity varies
according to a power law with the exponent about 0.7 to 1. This behavior can
not be explained assuming ballistic electron transport through the domain
walls. It is necessary to invoke the suppression of anti-localization effects
(positive quantum correction to conductivity) by the nonuniform gauge fields
caused by the domain walls.",0307414v1
2004-01-16,Break-Junction Tunneling Spectroscopy for Doped Semiconductors in the Hopping Regime,"We present a theory for tunneling spectroscopy in a break-junction
semiconductor device for materials in which the electronic conduction mechanism
is hopping transport. Starting from the conventional expression for the hopping
current we develop an expression for the break-junction tunnel current for the
case in which the tunnel resistance is much larger than the effective
single-hop resistances. We argue that percolation like methods are inadequate
for this case and discuss in detail the interplay of the relevant scales that
control the possibility to extract spectroscopic information from the
characteristic of the device.",0401282v1
2004-02-05,Resistivity model for both paramagnetic and ferromagnetic phases,"The resistivity, $\rho$ as a function of temperature and ionization energy
(doping) and magnetization respectively is derived with further confinements
from spin-disorder scattering. The computed $T_{crossover}$ below $T_C$ and
carrier density in Ga$_{1-x}$Mn$_x$As system are 8-12 K and 10$^{19}$
cm$^{-3}$, remarkably identical with the experimental values of 10-12 K and
10$^{18}-10^{20}$ cm$^{-3}$ respectively.",0402153v5
2004-05-26,The steady state in noncollinear magnetic multilayers,"There are at least two different putative steady state solutions for current
across noncollinear magnetic multilayers; one has a discontinuity in the spin
current at the interface the other is continuous. We compare the resistance of
the two and find the solution with the continuous spin currents is lower. By
using the entropic principle we can state that this solution is a better
estimate of the resistance for a noncollinear magnetic",0405624v1
2004-06-09,"Negative Magnetoresistance in (In,Mn)As","The magnetotransport properties of an In0.95Mn0.05As thin film grown by
metal-organic vapor phase epitaxy were measured. Resistivity was measured over
the temperature range of 5 to 300 K. The resistivity decreased with increasing
temperature from 90 ohm-cm to 0.05 ohm-cm. The field dependence of the low
temperature magnetoresistance was measured. A negative magnetoresistance was
observed below 17 K with a hysteresis in the magnetoresistance observed at 5 K.
The magnetoresistance as a function of applied field was described by the
Khosla-Fischer model for spin scattering of carriers in an impurity band.",0406230v1
2004-06-21,Large negative magnetoresistance in thiospinel CuCrZrS4,"We report on large negative magnetoresistance observed in ferromagnetic
thiospinel compound CuCrZrS$_{4}$. Electrical resistivity increased with
decreasing temperature according to the form proportional to
$\textrm{exp}(T_{0}/T)^{1/2} $, derived from variable range hopping with strong
electron-electron interaction. Resistivity under magnetic fields was expressed
by the same form with the characteristic temperature T0 decreasing with
increasing magnetic field. Magnetoresistance ratio $\rho (T,0)/\rho(T,H)$ is
1.5 at 100 K for H=90 kOe and increases divergently with decreasing temperature
reaching 80 at 16 K. Results of magnetization measurements are also presented.
Possible mechanism of the large magnetoresistance is discussed.",0406459v1
2004-08-27,Disorder-Induced Resistive Anomaly Near Ferromagnetic Phase Transitions,"We show that the resistivity rho(T) of disordered ferromagnets near, and
above, the Curie temperature T_c generically exhibits a stronger anomaly than
the scaling-based Fisher-Langer prediction. Treating transport beyond the
Boltzmann description, we find that within mean-field theory, d\rho/dT exhibits
a |T-T_c|^{-1/2} singularity near T_c. Our results, being solely due to
impurities, are relevant to ferromagnets with low T_c, such as SrRuO3 or
diluted magnetic semiconductors, whose mobility near T_c is limited by
disorder.",0408602v2
2004-10-07,Negative differential thermal resistance and thermal transistor,"We report on the first model of a thermal transistor to control heat flow.
Like its electronic counterpart, our thermal transistor is a three-terminal
device with the important feature that the current through the two terminals
can be controlled by small changes in the temperature or in the current through
the third terminal. This control feature allows us to switch the device between
""off"" (insulating) and ""on"" (conducting) states or to amplify a small current.
The thermal transistor model is possible because of the negative differential
thermal resistance.",0410172v2
2004-11-23,Current perpendicular to plane Giant Magnetoresistance (GMR) in laminated nanostructures,"We theoretically studied spin dependent electron transport
perpendicular-to-plain (CPP) in magnetic laminated multilayered structures by
using Kubo formalism. We took into account not only bulk scattering, but the
interface resistance due to both specular and diffuse reflection and also spin
conserving and spin-flip processes. It was shown that spin-flip scattering at
interfaces substantially reduces the value of GMR. This can explain the
experimental observations that the CPP GMR ratio for laminated structures only
slightly increases as compared to non-laminated ones despite lamination induces
a significant increase in CPP resistance.",0411571v1
2004-12-08,Ageing effects around the glass and melting transitions in poly(dimethylsiloxane) visualized by resistance measurements,"The process of ageing in rubbers requires monitoring over long periods (days
to years). To do so in non-conducting rubbers, small amounts of carbon-black
particles were dispersed in a fractal network through the rubber matrix, to
make the rubber conducting without modifying its properties. Continuous
monitoring of the resistance reveals the structural changes around the glass
and melting transitions and especially details about the hysteresis and ageing
processes. We illustrate the method for the semicrystalline polymer
poly(dimethylsiloxane) (PDMS).",0412187v1
2005-04-19,Enhancement of low field magnetoresistance at room temperature in La$_{0.67}$Sr$_{0.33}$MnO$_{3}$/Al$_{2}$O$_{3}$ nanocomposite,"Magnetotransport properties in a nanocrystalline
La$_{0.67}$Sr$_{0.33}$MnO$_{3}$/micron sized Al$_{2}$O$_{3}$ granular composite
with different concentrations of Al$_{2}$O$_{3}$ have been studied. The
resistivity curves in absence of magnetic field and the various transport
mechanisms which might account for the upturn in resistivity at low
temperature, has been discussed. Enhancement of low field magnetoresistance at
room temperature with the introduction of Al$_{2}$O$_{3}$ has been observed.",0504469v1
2005-09-09,Negative differential resistance in single crystal La_{2}CuO_{4} at low temperature,"A current-controlled negative differential resistance has been revealed in
the I-V characteristics of single crystal La$_{2}$CuO$_{4+\delta}$ in the low
temperature region. The non-linear behavior of conductivity is accompanied by a
transition from positive to negative magnetoresistance when the current is
growing. Possible reasons for the effect observed are discussed.",0509247v1
2005-11-02,Current-induced vortex displacement and annihilation in a single Permalloy disk,"The induced motion of a magnetic vortex in a micron-sized ferromagnetic disk
due to the DC current injection is studied by measuring planar Hall effect. The
DC current injection is found to induce the spin torque that sweeps the vortex
out of the disk at the critical current while bias magnetic field are applied.
The current-induced vortex core displacement deduced from the change in planar
Hall resistance is quantitatively consistent with theoretical prediction. Peak
structures similar to those originated from spin wave excitations are observed
in the differential planar Hall resistance curve.",0511040v1
2006-01-20,"Domain-wall resistance in ferromagnetic (Ga,Mn)As","A series of microstructures designed to pin domain-walls (DWs) in (Ga,Mn)As
with perpendicular magnetic anisotropy has been employed to determine extrinsic
and intrinsic contributions to DW resistance. The former is explained
quantitatively as resulting from a polarity change in the Hall electric field
at DW. The latter is one order of magnitude greater than a term brought about
by anisotropic magnetoresistance and is shown to be consistent with
disorder-induced misstracing of the carrier spins subject to spatially varying
magnetization.",0601464v1
2006-01-25,"Single-ion Kondo behavior of a novel Kondo lattice, CeNi9Si4","The compound, CeNi9Si4 has been recently reported to be an unusual Kondo
lattice with a large Ce-Ce separation, with a breakdown of Kadowaki-Woods
relationship governing low temperature electrical resistivity and
heat-capacity. Here we report the results of magnetic susceptibility,
heat-capacity and electrical resistivity of the solid solution,
Ce(1-x)La(x)Ni9Si4 to understand the Kondo behavior of this compound. The
results establish that the observed properties of Ce in this compound are
single-ionic in character.",0601577v1
2006-05-12,Large domain wall resistance in self-organised manganite film,"The electrical resistance of magnetic domain walls in ferromagnetic metallic
manganites can be enhanced to 10-12 Ohm.m2 by patterning nanoconstrictions [J.
Appl. Phys. 89, 6955 (2001)]. We show equally large enhancements in a phase
separated La0.60Ca0.40MnO3 manganite film without recourse to nanopatterning.
The domain walls were measured in the current-perpendicular-to-the-plane (CPP)
geometry between ferromagnetic metallic La0.70Ca0.30MnO3 electrodes patterned
like magnetic tunnel junctions.",0605341v2
2006-06-18,Cotunneling and one-dimensional localization in individual single-wall carbon nanotubes,"We report on the temperature dependence of the intrinsic resistance of long
individual disordered single-wall carbon nanotubes. The resistance grows
dramatically as the temperature is reduced, and the functional form is
consistent with an activated behavior. These results are described by Coulomb
blockade along a series of quantum dots. We occasionally observe a kink in the
activated behavior that reflects the change of the activation energy as the
temperature range is changed. This is attributed to charge hopping events
between non-adjacent quantum dots, which is possible through cotunneling
processes.",0606473v1
2006-10-10,Nanofabrication of spin-transfer torque devices by a PMMA mask one step process: GMR versus single layer devices,"We present a method to prepare magnetic spin torque devices of low specific
resistance in a one step lithography process. The quality of the pillar devices
is demonstrated for a standard magnetic double layer device. For single layer
devices, we found hysteretic switching and a more complex dynamical excitation
pattern in higher fields. A simple model to explain the resistance spikes is
presented.",0610277v1
2006-11-27,Complete stabilization and improvement of the characteristics of tunnel junctions by thermal annealing,"We have observed that submicron sized Al--AlO{$_x$}--Al tunnel junctions can
be stabilized completely by annealing them in vacuum at temperatures between
$350^{\circ}$C and $450^{\circ}$C. In addition, low temperature
characterization of the samples after the annealing treatment showed a marked
improvement of the tunneling characteristics due to disappearance of unwanted
resonances in the current. Charging energy, tunneling resistance, barrier
thickness and height all increase after the treatment. The superconducting gap
is not affected, but supercurrent is reduced in accordance with the increase of
tunneling resistance.",0611664v1
2007-01-17,"Theory of Spin Transport Across Domain-Walls in (Ga,Mn)As","We present results of numerical calculations of domain-wall resistance in the
ferromagnetic semiconductor (Ga,Mn)As. We employ Landauer-Buttiker formalism
and the tight binding method. Taking into account the full valence band
structure we predict the magnitude of the domain-wall resistance without
disorder and compare it to experimental values. Next we add disorder to the
model and study numerically both small and large disorder regime.",0701398v1
2007-06-01,Treatment of electron viscosity in quantum conductance,"In a recent paper Sai {\it et al.} [1] identified a correction $R^{dyn}$ to
the DC conductance of nanoscale junctions arising from dynamical
exchange-correlation ($XC$) effects within time-dependent density functional
theory. This quantity contributes to the total resistance through
$R=R_{s}+R^{dyn}$ where $R_{s}$ is the resistance evaluated in the absence of
dynamical $XC$ effects. In this Comment we show that the numerical estimation
of $R^{dyn}$ in example systems of the type they considered should be
considerably reduced, once a more appropriate form for the shear electron
viscosity $\eta$ is used.",0706.0140v1
2007-07-05,Observation of a uniform temperature dependence in the electrical resistance across the structural phase transition in thin film vanadium oxide ($VO_{2}$),"An electrical study of thin $VO_{2}$ films in the vicinity of the structural
phase transition at $68^{0}C$ shows (a) that the electrical resistance $R$
follows $log (R)$ $\propto$ $-T$ over the $T$-range, $20 < T < 80 ^{0}C$
covering both sides of the structural transition, and (b) a history dependent
hysteresis loop in $R$ upon thermal cycling. These features are attributed here
to transport through a granular network.",0707.0885v1
2007-08-07,Nonlinear screening and ballistic transport in a graphene p-n junction,"We study the charge density distribution, the electric field profile, and the
resistance of an electrostatically created lateral p-n junction in graphene. We
show that the electric field at the interface of the electron and hole regions
is strongly enhanced due to limited screening capacity of Dirac quasiparticles.
Accordingly, the junction resistance is lower than estimated in previous
literature.",0708.0892v2
2007-08-22,Voltage and temperature dependencies of conductivity in gated graphene,"The resistivity of gated graphene is studied taking into account electron and
hole scattering by short- and long-range structural imperfections the
characteristics of disorder were taken from the scanning tunneling microscopy
data and by acoustic phonons. The calculations are based on the quasiclassical
kinetic equation with the normalization condition fixed by surface charge. The
gate-voltage and temperature effects on the resistance peak, which is centered
at the point of intrinsic conductivity, are found to be in agreement with the
transport measurements.",0708.2976v2
2007-09-12,Design issues of a variable thermal resistance,"Some years ago we have proposed a thermal mount with electronically variable
thermal resistance [1]. In this earlier work the feasibility of such a
structure has been demonstrated. Now we intend to realize this mount in a
maturated form, suitable to the everyday use in the practice of package thermal
qualification and modeling. The design of such a device raises a number of new
questions and problems. The present paper is dealing with these problems and
the possible solutions.",0709.1836v1
2007-11-29,Quantum size effects in solitary wires of bismuth,"We have performed four-probe electrical transport measurements on solitary
highly crystalline wires of semimetallic bismuth with aspect ratios up to 60 at
room and at cryogenic temperatures. By proper choice of the substrate material
and the film deposition parameters, lithographic wires with lateral dimensions
of down to one single grain, $\sim 250$ nm, were fabricated. The electrical
resistance of each wire was measured against its thickness through successive
reactive ion etching of the self-same wire. Quantum size effects revealed
themselves as regular oscillations in the electrical resistance. Some evidence
for the semimetal-to-semiconductor phase transition has been detected. The
measured data are discussed within the framework of the existing theoretical
models.",0711.4816v1
2008-02-15,Non-intrinsic superconductivity in InN epilayers: role of Indium Oxide,"In recent years there have been reports of anomalous electrical resistivity
and the presence of superconductivity in semiconducting InN layers. By a
careful correlation of the temperature dependence of resistivity and magnetic
susceptibility with structural information from highresolution x-ray
diffraction measurements we show that superconductivity is not intrinsic to InN
and is seen only in samples that show traces of oxygen impurity. We hence
believe that InN is not intrinsically a superconducting semiconductor.",0802.2126v1
2008-03-26,Quasi-Two-Dimensional Extraordinary Hall Effect,"Quasi-two-dimensional transport is investigated in a system consisting of one
ferromagnetic layer placed between two insulating layers. Using the mechanism
of skew-scattering to describe the Extraordinary Hall Effect (EHE) and
calculating the conductivity tensor, we compare the quasi- two-dimensional Hall
resistance with the resistance of a massive sample. In this study a new
mechanism of EHE (geometric mechanism of EHE) due to non-ideal interfaces and
volume defects is also proposed.",0803.3649v2
2008-04-17,Conductivity behavior of La$_{0.75}$Ca$_{0.25}$MnO$_{3}$ in vicinity of ferromagnetic-paramagnetic transition studied with single current pulses,"Temperature and current dependences of resistivity of bulk
La$_{0.75}$Ca$_{0.25}$MnO$_{3}$ sample grown by the floating-zone method were
studied using single ramp pulses of current. It is found that near the Curie
temperature $T_C$ the sample resistance depends substantially on current
magnitude. The observed features can be determined by inhomogeneous Joule
overheating due to mixed phase state of manganites near the
ferromagnetic-paramagnetic transition and percolation character of this
transition.",0804.2806v1
2008-05-13,Temperature dependent transport in suspended graphene,"The resistivity of ultra-clean suspended graphene is strongly temperature
dependent for 5K<T<240K. At T~5K transport is near-ballistic in a device of
~2um dimension and a mobility ~170,000 cm^2/Vs. At large carrier density,
n>0.5*10^11 cm^-2, the resistivity increases with increasing T and is linear
above 50K, suggesting carrier scattering from acoustic phonons. At T=240K the
mobility is ~120,000 cm^2/Vs, higher than in any known semiconductor. At the
charge neutral point we observe a non-universal conductivity that decreases
with decreasing T, consistent with a density inhomogeneity <10^8 cm^-2.",0805.1830v1
2008-06-20,Effective Resistance Mismatch and Magnetoresistance of a CPP-GMR system with Current-Confined-Paths,"We theoretically study the magnetoresistance of a CPP-GMR system with current
confined paths (CCP) in the framework of Valet-Fert theory. The continuity
equations for charge and spin currents are numerically solved with the
three-dimensional CCP geometry by use of finite element method. It is confirmed
that the MR ratio is enhanced by the CCP structure, which is consistent with
the experimental results. Moreover, we find that there exists a certain contact
width which maximize the MR ratio. We show that the contact width which
maximize the MR ratio is well described by the effective resistance matching.",0806.3314v1
2008-06-26,Negative differential resistance in molecular junctions: The effect of the electrodes electronic structure,"We have carried out calculations of electron transport through a
metal-molecule-metal junction with metal nanoclusters taking the part of
electrodes. We show that negative differential resistance peaks could appear in
the current-voltage curves. The peaks arise due to narrow features in the
electron density of states of the metal clusters. The proposed analysis is
based on the ab initio computations of the relevant wave functions and energies
within the framework of the density functional theory using NRLMOL software
package.",0806.4397v2
2008-10-07,Huge anisotropic magneto-resistance in iridium atomic chains,"We analyze in this article the magneto-resistance ratio of finite and
infinite iridium and platinum chains. Our calculations, that are based on a
combination of non equilibrium Green function techniques and density functional
theory, include a fully self-consistent treatment of non-collinear magnetism
and of the spin-orbit interaction. They indicate that, in addition to having an
extremely large magnetic anisotropy that may overcome the super-paramagnetic
limit, infinite and also realistic finite-length iridium chains show sizeable
anisotropic magnetoresistance ratios. We therefore propose iridium
nanostructures as promising candidates for nanospintronics logic devices.",0810.1170v1
2008-10-22,Itinerant Ferromagnetism in the electronic localization limit,"We present Hall effect, $R_{xy}(H)$, and magnetoresistance, $R_{xx}(H)$,
measurements of ultrathin films of Ni, Co and Fe with thicknesses varying
between 0.2-8 nm and resistances between 1 M$\Omega$ - 100 $\Omega.$ Both
measurements show that films having resistance above a critical value, $R_{C}$,
(thickness below a critical value, $d_{C}$) show no signs for ferromagnetism.
Ferromagnetism appears only for films with $R<R_{C}$, where $R_{C}$ is material
dependent. We raise the possibility that the reason for the absence of
spontaneous magnetization is suppression of itinerant ferromagnetism by
electronic disorder in the strong localization regime.",0810.4081v2
2008-11-06,Connectivity and Critical Currents in Polycrystalline MgB2,"Current transport in polycrystalline magnesium diboride is highly non-uniform
(percolative) due to the presence of secondary phases and also due to the
intrinsic anisotropy of the material. The influence of secondary phases on the
transport properties of MgB2 was investigated. Bulk samples were prepared from
a mixture of MgB2 and MgO powders by the ex-situ technique in order to vary the
MgO content systematically. The samples were characterized by resistive and
magnetization measurements. The reduced MgB2 fraction is modeled by a reduced
effective cross section (connectivity), which was assessed directly by the
experiments. The presence of MgO also increases the percolation threshold,
which reduces the zero resistivity (or irreversibility) field.",0811.0986v1
2008-12-02,Independent magnetization behavior of a ferromagnetic metal/semiconductor hybrid system,"We report the discovery of an effect where two ferromagnetic materials, one
semiconductor ((Ga,Mn)As) and one metal (permalloy), can be directly deposited
on each other and still switch their magnetization independently. We use this
independent magnetization behavior to create various resistance states
dependent on the magnetization direction of the individual layers. At zero
magnetic field a two layer device can reach up to four non-volatile resistance
states.",0812.0455v1
2009-03-31,Proper Scaling of the Anomalous Hall Effect,"Working with epitaxial films of Fe, we succeeded in independent control of
different scattering processes in the anomalous Hall effect. The result
appropriately accounted for the role of phonons, thereby clearly exposing the
fundamental flaws of the standard plot of the anomalous Hall resistivity versus
longitudinal resistivity. A new scaling has been thus established that allows
an unambiguous identification of the intrinsic Berry curvature mechanism as
well as the extrinsic skew scattering and side-jump mechanisms of the anomalous
Hall effect.",0903.5360v1
2009-04-08,Negative differential resistance in nanoscale transport in the Coulomb blockade,"Motivated by recent experiments, we have studied transport behavior of
coupled quantum dot systems in the Coulomb blockade regime using the master
(rate) equation approach. We explore how electron-electron interactions in a
donor-acceptor system, resembling weakly coupled quantum dots with varying
charging energy, can modify the systems response to an external bias, taking it
from normal Coulomb blockade behavior to negative differential resistance (NDR)
in the curent-voltage characteristics.",0904.1335v1
2009-05-18,On the origin of the electric carrier concentration in graphite,"We investigate the dependence of the electrical resistivity of $\sim 60 $nm
thick single crystalline graphite samples on the defect concentration produced
by proton irradiation at very low fluences. We show that the resistivity
decreases few percent at room temperature after inducing defects at
concentrations as low as $\sim 0.1 $ppm due to the increase in the carrier
density, in agreement with theoretical estimates. The overall results indicate
that the carrier densities measured in graphite are not intrinsic but related
to defects and impurities.",0905.2945v2
2009-06-18,Temperature-dependent resistivity of ferromagnetic GaMnAs: Interplay between impurity scattering and many-body effects,"The static conductivity of the dilute magnetic semiconductor GaMnAs is
calculated using the memory function formalism and time-dependent
density-functional theory to account for impurity scattering and to treat
Hartree and exchange interactions within the hole gas. We find that the Coulomb
scattering off the charged impurities alone is not sufficient to explain the
experimentally observed drop in resistivity below the ferromagnetic transition
temperature: the often overlooked scattering off the fluctuations of localized
spins is shown to play a significant role.",0906.3526v1
2009-09-11,Kinetic Friction by a Small Number of Intervening Inelastic Particles between Rough Surfaces,"We investigate a mechanism of the appearance of kinetic friction in granular
materials. We consider a small number of intervening inelastic particles
between two rough surfaces as one of the simplest dynamical models to study
granular friction. The resistance force applied to the upper surface is
numerically calculated. We find that the resistance force F(t) is scaled as
F'(vt) for a small pulling velocity v. The time average F_0=<F(t)> in the limit
v->0 is not zero owing to the mutual collisions between the intervening
particles. The nonzero F_0 implies the appearance of kinetic friction in this
simple dynamical system.",0909.2132v1
2009-10-13,Superconductivity of FeSe0.5Te0.5 Thin Films Grown by Pulsed Laser Deposition,"FeSe0.5Te0.5 thin films with PbO-type structure are successfully grown on
MgO(100) and LaSrAlO4(001) substrates from FeSe0.5Te0.5 or FeSe0.5Te0.75
polycrystalline targets by pulsed-laser deposition. The film deposited on the
MgO substrate (film thickness ~ 55 nm) shows superconductivity at 10.6 K
(onset) and 9.2 K (zero resistivity). On the other hand, the film deposited on
the LaSrAlO4 substrate (film thickness ~ 250 nm) exhibits superconductivity at
5.4 K (onset) and 2.7 K (zero resistivity). This suggests the strong influence
of substrate materials and/or the c-axis length to superconducting properties
of FeSe0.5Te0.5 thin films.",0910.2301v1
2010-01-25,Evidence for effective thermal boundary resistance from magnon/phonon disequilibrium,"We use the time-resolved magneto-optical Kerr effect (TRMOKE) to measure the
local temperature and heat flow dynamics in ferromagnetic SrRuO3 thin films.
After heating by a pump pulse, the film temperature decays exponentially,
indicating that the heat flow out of the film is limited by the film/substrate
interface. We show that this behavior is consistent with an effective boundary
resistance resulting from disequilibrium between the spin and phonon
temperatures in the film.",1001.4557v1
2010-03-12,Electronic phase diagram of NdFe1-xRhxAsO,"We report on the electrical resistivity, thermoelectric power and electronic
phase diagram of rhodium-doped NdFeAsO. Rhodium doping suppresses the
structural phase transition and spin density wave observed in the undoped
material, and superconductivity emerges at x close to 0.05, despite the
distortion of FeAs4 tetrahedra induced by the large size difference between Rh
and Fe elements. The Tc(x) curve is dome-like, and the highest Tc is reached at
x = 0.1, with Tconset = 18K. An upturn of the electrical resistivity above Tc
has been observed, with a Kondo like behaviour above Tc and a Fermi-liquid
behaviour close to room temperature.",1003.2528v1
2010-06-02,Emergence of current branches in a series array of negative differential resistance circuit elements,"We study a series array of nonlinear electrical circuit elements that possess
negative differential resistance and find that \emph{heterogeneity} in the
element properties leads to the presence of multiple branches in
current-voltage curves and a non-uniform distribution of voltages across the
elements. An inhomogeneity parameter $r_{max}$ is introduced to characterize
the extent to which the individual element voltages deviate from one another,
and it is found to be strongly dependent on the rate of change of applied
voltage. Analytical expressions are derived for the dependence of $r_{max}$ on
voltage ramping rate in the limit of fast ramping and are confirmed by direct
numerical simulation.",1006.0434v1
2010-10-08,On giant piezoresistance effects in silicon nanowires and microwires,"The giant piezoresistance (PZR) previously reported in silicon nanowires is
experimentally investigated in a large number of surface depleted silicon nano-
and micro-structures. The resistance is shown to vary strongly with time due to
electron and hole trapping at the sample surfaces. Importantly, this time
varying resistance manifests itself as an apparent giant PZR identical to that
reported elsewhere. By modulating the applied stress in time, the true PZR of
the structures is found to be comparable with that of bulk silicon.",1010.1633v1
2011-03-08,Electric--field effect on electron-doped infinite-layer Sr$_{0.88}$La$_{0.12}$CuO$_{2+x}$ thin films,"We have used the electric--field effect to modulate the resistivity of the
surface of underdoped Sr$_{0.88}$La$_{0.12}$CuO$_{2+x}$ thin films, allowing
opposite modifications of the electron and hole density in the CuO$_2$ planes,
an original situation with respect to conventional chemical doping in
electron-doped materials. When the Hall effect indicates a large contribution
of a hole band, the electric--field effect on the normal state resistivity is
however dominated by the electrons, and the superconducting transition
temperature increases when carriers are transfered from holes to electrons.",1103.1548v2
2011-03-17,Structure-related transport properties of A-site ordered perovskite Sr3ErMn4-xGaxO10.5-d,"We report x-ray diffraction, resistivity, thermopower, and magnetization of
Sr3ErMn4-xGaxO10.5-d, in which A-site ordered tetragonal phase appears above
x=1, and reveal that the system exhibits typical properties seen in the
antiferromagnetic insulator with Mn3+. We succeed in preparing both A-site
ordered and disordered phases for x=1 in different preparation conditions, and
observe a significant decrease of the resistivity in the disordered phase. We
discuss possible origins of the decrease focusing on the dimensionality and the
disordered effect.",1103.3342v1
2011-08-19,"Hydrostatic pressure study of paramagnetic-ferromagnetic phase transition in (Ga,Mn)As","The effect of hydrostatic pressure on the paramagnetic - ferromagnetic phase
transition has been studied in (Ga,Mn)As. The variation of the Curie
temperature (TC) with pressure was monitored by two transport methods: (1) -
measurement of zero field resistivity versus temperature {\rho}(T), (2) -
dependence on temperature of the Hall voltage hysteresis loop. Two specimens of
different resistivity characteristics were examined. The measured
pressure-induced changes of TC were relatively small (of the order of 1K/GPa)
for both samples, however they were opposite for the two.",1108.3960v1
2011-09-26,Anomalous Hall effect in the Co-based Heusler compounds Co$_{2}$FeSi and Co$_{2}$FeAl,"The anomalous Hall effect (AHE) in the Heusler compounds Co$_{2}$FeSi and
Co$_{2}$FeAl is studied in dependence of the annealing temperature to achieve a
general comprehension of its origin. We have demonstrated that the crystal
quality affected by annealing processes is a significant control parameter to
tune the electrical resistivity $\rho_{xx}$ as well as the anomalous Hall
resistivity $\rho_{ahe}$. Analyzing the scaling behavior of $\rho_{ahe}$ in
terms of $\rho_{xx}$ points to a temperature-dependent skew scattering as the
dominant mechanism in both Heusler compounds.",1109.5498v1
2011-10-22,Anomalous negative differential thermal resistance in a momentum-conserving lattice,"A two-segment Fermi-Pasta-Ulam lattices has been investigated by using
nonequilibrium molecular dynamics. Here we present an anomalous negative
differential thermal resistance (NDTR) that have not been reported in
Frenkel-Kontorova and \phi_4 lattices up to the present. The NDTR disappears at
low temperature region. The region of NDTR shifts from the large to the small
temperature difference region as the system size increases. Anomalous
dependence of NDTR on the temperature can be explained as the negative effect
induced by the nonlinear coupling. The explanation can also cover the
phenomenon of NDTR in momentum-nonconserved lattices.",1110.4942v1
2011-12-09,Temperature Coefficient of Resistivity in Amorphous Semiconductors,"By invoking the microscopic response method in conjunction with a reasonable
set of approximations, we obtain new explicit expressions for the electrical
conductivity and temperature coefficient of resistivity (TCR) in amorphous
semiconductors, especially a-Si:H and a-Ge:H. The predicted TCR for n-doped
a-Si:H and a-Ge:H is in agreement with experiments. The conductivity from the
transitions from a localized state to an extended state (LE) is comparable to
that from the transitions between two localized states (LL). This resolves a
long-standing anomaly, a ""kink"" in the experimental $\log_{10}\sigma $ vs.
T$^{-1}$ curve.",1112.2169v2
2012-08-19,Interplay between sheet resistance increase and magnetotransport properties in ${\rm LaAlO_3}/{\rm SrTiO_3}$,"We find that the sheet resistance ($R_s$) of patterned samples of ${\rm
LaAlO_3}/{\rm SrTiO_3}$ with a length scale of several microns may increase
significantly at low temperatures in connection with driving electrical
currents and applying in-plane magnetic fields. As the samples are warmed up,
$R_s$ recovers to its original value with accelerated recovery near ${\rm 70 \
K}$ and ${\rm 160 \ K}$. Concomitantly with the increase in $R_s$, the carrier
density and the mobility decrease and magnetotransport properties which may be
linked to magnetism are suppressed.",1208.3837v1
2012-09-24,Observation of linear-polarization-sensitivity in the microwave-radiation-induced magnetoresistance oscillations,"In the quasi two-dimensional GaAs/AlGaAs system, we investigate the effect of
rotating \textit{in-situ} the electric field of linearly polarized microwaves
relative to the current, on the microwave-radiation-induced magneto-resistance
oscillations. We find that the frequency and the phase of the photo-excited
magneto-resistance oscillations are insensitive to the polarization. On the
other hand, the amplitudes of the magnetoresistance oscillations are remarkably
responsive to the relative orientation between the microwave antenna and the
current-axis in the specimen. The results suggest a striking
linear-polarization-sensitivity in the radiation-induced magnetoresistance
oscillations.",1209.5135v1
2012-10-09,Thermopower as sensitive probe of electronic nematicity in iron pnictides,"We study the in-plane anisotropy of the thermoelectric power and electrical
resistivity on detwinned single crystals of isovalent substituted
EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_2$. Compared to the resistivity anisotropy the
thermopower anisotropy is more pronounced and clearly visible already at
temperatures much above the structural and magnetic phase transitions. Most
remarkably, the thermopower anisotropy changes sign below the structural
transition. This is associated with the interplay of two contributions due to
anisotropic scattering and orbital polarization, which dominate at high- and
low-temperatures, respectively.",1210.2634v2
2012-10-29,Anomalous Energy Transport across Topological Insulator Superconductor Junctions,"We study the nonequilibrium energy transport across a topological
insulator/superconductor junction, by deriving an interfacial heat current
formula through scattering wave approach. Several anomalous thermal properties
are uncovered, such as thermal energy's Klein tunneling, asymmetric Kapitza
resistance and negative differential thermal resistance. We expect these
findings could have potential applications for the energy control in various
hybridized mesoscopic systems.",1210.7551v2
2012-10-29,Resistance Switching Induced by Electric Field and Light Illumination in Device of FTO/CeO2/Electrolyte/FTO,"A heterojunction-like device consisting of FTO/CeO2/electrolyte/FTO is
established with distinct transport performance, where FTO denotes F-doped
transparent conducting glass, and the electrolyte is LiI and I2 in
acetonitrile. The resistive switching behavior is observed, being induced
through applying sufficient negative pulse as well as light illumination. The
endurance measurements confirm that the write/erase periodic operation is
reproducible and stable in the present device. Furthermore, the retention
measurements demonstrate that the information can be stored temporarily for
about 100 seconds. A possible mechanism regarding the formation of diiodide
radical is proposed to give a reasonable explanation for the observed switching
behavior.",1210.7558v2
2012-11-06,Angular dependence of the Hall effect of lsmo films,"We find that the Hall effect resistivity ($\rho_{xy}$) of thin films of
\lsmo\ varies as a function of the angle $\theta$ between the applied magnetic
field and the film normal as $\rho_{xy}=a\cos \theta + b\cos 3\theta$, where
$|b|$ increases with increasing temperature and decreases with increasing
magnetic field. We find that the angular dependence of the longitudinal
resistivity and the magnetization cannot fully explain the surprising term $b$,
suggesting it is a manifestation of an intrinsic transport property.",1211.1160v1
2013-09-25,Magnetic and transport properties of Mn2CoAl oriented thin films,"The structure, magnetic and transport properties of thin films of the Heusler
ferrimagnet Mn_{2}CoAl have been investigated for properties related to spin
gapless semiconductors. Oriented films were grown by molecular beam epitaxy on
GaAs substrates and the structure was found to transform from tetragonal to
cubic for increasing annealing temperature. The anomalous Hall resistivity is
found to be proportional to the square of the longitudinal resistivity and
magnetization expected for a topological Berry curvature origin. A delicate
balance of the spin-polarized carrier type when coupled with voltage
gate-tuning could significantly impact advanced electronic devices.",1309.6660v1
2014-02-15,Ferromagnetism and transport properties of the Kondo system Ce4Sb1.5Ge1.5,"Ferromagnetic ordering with a small magnetic moment is found below 14 K from
SQUID measurements for the compound Ce4Sb1.5Ge1.5. The transport
characteristics of a number of Ce4Sb3-xTx (T = Ge, Si, Sn, Pb, Al) systems were
measured at room temperature, Ce4Sb1.5Ge1.5 demonstrating the highest Seebeck
coefficient. Its transport properties (resistivity, thermal conductivity,
thermoelectric power) are experimentally investigated in detail up to low
temperatures. The Kondo-lattice behavior of resistivity and its anomaly at the
ordering point are found. A comparison with the Wiedemann-Franz law is
performed.",1402.3667v2
2014-02-20,Transverse ultrasonic anomaly in La1/3Sr2/3MnO3,"The charge ordering (CO) transition in polycrystalline La1/3Sr2/3MnO3 has
been studied by measuring the resistivity, magnetization and transverse
ultrasonic velocity. At about 235K, a conspicuous increase in resistivity was
observed, while the magnetization shows a cusp structure, corresponding to an
antiferromagnetic charge ordering transition. Around this transition
temperature, dramatic anomaly in transverse sound velocity was observed. The
simultaneous occurrence of electron, magnon and phonon anomalous features
implies strong spin-phonon coupling and electron-phonon in La1/3Sr2/3MnO3. The
analysis suggests that the spin-phonon interaction is due to single-ion
magnetostriction, and electron-phonon coupling originates from the Jahn-Teller
effect of Mn3+.",1402.4857v2
2014-03-01,Anomalies of transport properties in antiferromagnetic YbMn2Sb2 compound,"The low-temperature transport properties (resistivity, thermal conductivity,
thermoelectric power) are experimentally investigated for the compound
YbMn2Sb2. Large Seebeck coefficient and nearly linear temperature dependence of
resistivity are obtained. The thermal conductivity is large and has mainly
phonon origin. Appreciable anomalies of transport characteristics near the
antiferromagnetic transition point are found. Possible influence of
pseudo-Kondo scattering is discussed.",1403.0077v2
2014-05-23,Photovoltaic performance of n-type SnS active layer in ITO/PEDOT:PSS/SnS/Al structure,"The present paper discusses the influence of Tin Sulphide's grain size on the
performance of ITO/PEDOT:PSS/SnS/Al structured solar cells fabricated by
thermal evaporation. The grain sizes were maintained in the range of 11-18~nm
by controlling the thickness of SnS films. While the open circuit voltage (Voc)
was found to be a constant for this structure, Parameters such as short circuit
current density (Jsc), series resistance (Rs), parallel resistance (Rp),
ideality factor and the overall efficiency were found to be dependent on the
SnS grain size and incident light intensity. The experimental work directly
reconfirms the theoretical results and ideas raised in literature by early
researchers.",1405.6013v1
2014-07-29,Proximity coupling of granular film with ferroelectric substrate and giant electro-resistance effect,"We study electron transport in granular film placed above the ferroelectric
substrate. We show that the conductivity of granular film strongly depends on
the ferroelectric state due to screening effects which modify the Coulomb
blockade in granular film. In particular, the electric current in granular film
is controlled by the direction of ferroelectric polarization. We show that the
ferroelectric/granular film system has a large electro-resistance effect. This
effect can be utilized in memory and electric field sensor applications.",1407.7719v2
2014-10-28,Tunable Solid State and Flexible Graphene Electronics,"We demonstrate tunable solid state and flexible graphene field effect devices
(FEDs) fabricated using a poly(methylmethacrylate) (PMMA) and lithium fluoride
(LiF) composite dielectric. Increasing the concentration of LiF in the
composite dielectric reduces the operating gate voltages significantly from 10
V to 1 V required leading to a decrease in resistance. Electron and hole
mobility of 350 and 310 cm2/Vs at VD = -5 V are obtained for graphene FEDs with
10 % LiF concentration in the composite. Using composite dielectric also
enabled excellent performance on flexible substrates without any significant
change in mobility and resistance. Flexible FEDs with only 5 % and 12 %
variation in mobility for 300 and 750 bending are obtained.",1410.7563v1
2015-12-29,Scaling like behaviour of resistivity observed in LaNiO_3 thin films grown on SrTiO_3 substrate by pulsed laser deposition,"We discuss the origin of the temperature dependence of resistivity observed
in highly oriented LaNiO_3 thin films (of thickness d) grown on SrTiO_3
substrate by a pulsed laser deposition technique. All the experimental data are
found to collapse into a single universal curve [T/T_{sf}(d)]^{3/2} for the
entire temperature interval (20K<T<300K) with T_{sf}(d) being the onset
temperature for triggering a resonant scattering of conduction electrons by
spin fluctuations in LaNiO_3/SrTiO_3 heterostructure.",1512.08812v1
2016-02-22,Exchange magnon induced resistance asymmetry in permalloy spin-Hall oscillators,"We investigate magnetization dynamics in a spin-Hall oscillator using a
direct current measurement as well as conventional microwave spectrum analysis.
When the current applies an anti-damping spin-transfer torque, we observe a
change in resistance which we ascribe to the excitation of incoherent exchange
magnons. A simple model is developed based on the reduction of the effective
saturation magnetization, quantitatively explaining the data. The observed
phenomena highlight the importance of exchange magnons on the operation of
spin-Hall oscillators.",1602.06710v1
2016-06-16,"Determining Curie temperature of (Ga,Mn)As samples based on electrical transport measurements: low Curie temperature case","In this paper we show that the widely accepted method of the determination of
Curie temperature (TC) in (Ga,Mn)As samples, based on the position of the peak
in the temperature derivative of the resistivity,completely fails in the case
of non-metallic and low-TC unannealed samples. In this case we propose an
alternative method, also based on electric transport measurements, which
exploits temperature dependence of the second derivative of the resistivity
upon magnetic field.",1606.05132v1
2016-10-04,Hidden Fermi-liquid charge transport in the antiferromagnetic phase of the electron-doped cuprates,"Systematic analysis of the planar resistivity, Hall effect and cotangent of
the Hall angle for the electron-doped cuprates reveals underlying Fermi-liquid
behavior even deep in the antiferromagnetic part of the phase diagram. The
transport scattering rate exhibits a quadratic temperature dependence, and is
nearly independent of doping, compound and carrier type (electrons vs. holes),
and hence universal. Our analysis moreover indicates that the material-specific
resistivity upturn at low temperatures and low doping has the same origin in
both electron- and hole-doped cuprates.",1610.01181v1
2018-02-06,Exploring the energy landscape of resistive switching in antiferromagnetic Sr(3)Ir(2)O(7),"We study the resistive switching triggered by an applied electrical bias in
antiferromagnetic Mott insulator Sr(3)Ir(2)O(7). The switching was previously
associated with an electric-field driven structural transition. Here we use
time-resolved measurements of the switching to probe the energy barrier
associated with the transition. We quantify the changes in the energy barrier
height with respect to the applied bias and find a linear decrease of the
barrier with increasing bias. Our observations support the potential of
antiferromagnetic transition metal oxides for spintronic applications.",1802.01923v1
2018-01-13,Electrochemical and mechanical behaviors of dissimilar friction stir welding between 5086 and 6061 aluminum alloy,"The electrochemical behavior and mechanical properties of friction stir
welded AA5086 and AA6061 Al alloys were investigated. Micro-hardness
measurements and tensile tests showed that the heat-affected zone (HAZ) in
AA6061 had minimum hardness value (i.e., 88 HV) and served as failure site in
the dissimilar weld. Corrosion testing revealed that the minimum value of Icorr
appeared in the HAZ 5086 (0.54 uA/cm2) and HAZ 5086 was most resistant to
corrosion. The AA 5086 side of the weld showed better corrosion resistance than
the AA 6061 side.",1802.03460v1
2018-02-21,Gate-tunable memristors from monolayer MoS2,"We report here gate-tunable memristors based on monolayer MoS2 grown by
chemical vapor deposition (CVD). These memristors are fabricated in a
field-effect geometry with the channel consisting of polycrystalline MoS2 films
with grain sizes of 3-5 um. The device characteristics show switching ratios up
to 500, with the resistance in individual states being continuously
gate-tunable by over three orders of magnitude. The resistive switching results
from dynamically varying threshold voltage and Schottky barrier heights, whose
underlying physical mechanism appears to be vacancy migration and/or charge
trapping. Top-gated devices achieve reversible tuning of the threshold voltage,
with potential utility in non-volatile memory or neuromorphic architectures.",1802.07785v1
2018-06-11,Low-temperature resistance in metals without inversion Center,"The well known quadratic low-temperature dependence of resistance in ordinary
metals habitually serves as the criterium of applicability of the Landau Fermi
liquid theory to the description of electron liquid in concrete material. Such
a type of behavior is determined by momentum relaxation due to the
electron-electron scattering.Here I consider this problem in the metals without
inversion center. It is shown that the corresponding scattering time at
temperatures much smaller than the spin-orbit coupling is practically
temperature independent.",1806.03952v3
2019-02-24,Half-Metallic Ferromagnets and Spin Gapless Semiconductors,"A brief review of experimental and theoretical studies of half-metallic
ferromagnets (HMF) and spin gapless semiconductors (SGS) is given. The data on
resistivity and magnetoresistivity are presented. An important role of
non-quasiparticle states owing to electron-magnon scattering in transport
properties is discussed. The problem of low-temperature resistivity in HMF is
treated in terms of one-magnon and two-magnon scattering processes.",1902.08972v1
2007-10-09,The approach to a superconductor-to-Bose-insulator transition in disordered films,"Through a detailed study of scaling near the magnetic field-tuned
superconductor-to-insulator transition in strongly disordered films, we find
that results for a variety of materials can be collapsed onto a single phase
diagram. The data display two clear branches, one with weak disorder and an
intervening metallic phase, the other with strong disorder. Along the strongly
disordered branch, the resistance at the critical point approaches $R_Q =
h/4e^2$ and the scaling of the resistance is consistent with quantum
percolation, and therefore with the predictions of the dirty boson model.",0710.1822v1
2019-04-26,Semiconductor to metal transition for Ni doped CdO thin films,"In the present investigation resistivity Vs temperature measurements have
been performed for solgel prepared pure and Ni doped CdO (NDO) thin films. The
semiconducting behavior i.e. negative temperature coefficient of resistivity
(TCR) of pure CdO thin film through-out the whole temperature range can be
attributed mainly due to concentration dependent thermally activation mechanism
of the carriers. The semiconductor to metal transition (SMT) for NDO thin films
has been elucidated via combined effect of involved grain boundaries, ionic
impurities, phonon scattering and carrier activation.",1904.11683v1
2012-03-02,Oxygen-vacancy-mediated Negative Differential Resistance in La and Mg co-substituted BiFeO3 Thin Film,"The conductive characteristics of Bi0.9La0.1Fe0.96Mg0.04O3(BLFM) thin film
are investigated at various temperatures and a negative differential resistance
(NDR) is observed in the thin film, where a leakage current peak occurs upon
application of a downward electric field above 80 oC. The origin of the NDR
behavior is shown to be related to the ionic defect of oxygen vacancies (VO..)
present in the film. On the basis of analyzing the leakage mechanism and
surface potential behavior, the NDR behavior can be understood by considering
the competition between the polarized distribution and neutralization of VO...",1203.0458v1
2015-06-01,Soft-mask fabrication of gallium arsenide nanomembranes for integrated quantum photonics,"We report on the fabrication of quantum photonic integrated circuits based on
suspended GaAs membranes. The fabrication process consists of a single
lithographic step followed by inductively-coupled-plasma dry etching through an
electron-beam-resist mask and wet etching of a sacrificial layer. This method
does not require depositing, etching, and stripping a hard mask, greatly
reducing fabrication time and costs, while at the same time yielding devices of
excellent structural quality. We discuss in detail the procedures for cleaning
the resist residues caused by the plasma etching and present a statistical
analysis of the etched feature size after each fabrication step.",1506.00376v1
2015-06-11,Three-dimensional continuum dislocation theory,"A three-dimensional continuum dislocation theory for single crystals
containing curved dislocations is proposed. A set of governing equations and
boundary conditions is derived for the true placement, plastic slips, and loop
functions in equilibrium that minimize the free energy of crystal among all
admissible functions, provided the resistance to the dislocation motion is
negligible. For the non-vanishing resistance to dislocation motion the
governing equations are derived from the variational equation that includes the
dissipation function. A simplified theory for small strains is also provided.
An asymptotic solution is found for the two-dimensional problem of a single
crystal beam deforming in single slip and simple shear.",1506.03570v1
2015-07-16,Operation of graphene quantum Hall resistance standard in a cryogen-free table-top system,"We demonstrate quantum Hall resistance measurements with metrological
accuracy in a small cryogen-free system operating at a temperature of around
3.8K and magnetic fields below 5T. Operating this system requires little
experimental knowledge or laboratory infrastructure, thereby greatly advancing
the proliferation of primary quantum standards for precision electrical
metrology. This significant advance in technology has come about as a result of
the unique properties of epitaxial graphene on SiC.",1507.04601v1
2019-01-15,Effect of thermal history on magnetism in UCoGa,"Single crystals of UCoGa have been grown in different conditions and
subsequently annealed in order to provide a collection of samples representing
various quality as to concentration of lattice defects. The different sample
quality ""grades"" have been characterized by values of residual electrical
resistivity. Correlations of magnetic parameters (coercive field, Curie
temperature) with residual resistivity have been determined and domain-wall
pinning by crystal defects has been confirmed as the underlying mechanism of
coercive field in strongly anisotropic ferromagnets.",1901.04806v2
2019-11-12,Effect of Interfacial Thermal Resistance in Thermal Cloak,"When heat transfers through interface between two different materials, it
will encounter an interfacial thermal resistance (ITR) that makes the
temperature discontinuous. This effect has been totally neglected so far in the
research of thermal cloak, in particular when the thermal cloak is built with
multilayer structures. In this paper, we investigate the effect of ITR on the
performance of the thermal cloak by using both analytical and numerical method.
Our results show that the existence of ITR will distort the external field,
thus destroy the cloak. Moreover, we found that the effect of ITR can be
quantified by a parameter called characteristic length.",1911.05098v2
2020-07-02,Current distribution in metallic multilayers from resistance measurements,"The in-plane current profile within multilayers of generic structure
Ta/Pt/(CoNi)/Pt/Ta is investigated. A large set of samples where the thickness
of each layer is systematically varied was grown, followed by the measurement
of the sheet resistance of each sample. The data are analyzed by a series of
increasingly elaborate models, from a macroscopic engineering approach to
mesoscopic transport theory. Non-negligible variations of the estimated
repartition of current between the layers are found. The importance of having
additional structural data is highlighted.",2007.00990v1
2021-07-09,Transport and relaxation of current-generated nonequilibrium phonons from nonlocal electronic measurements,"We study phonons generated by current in a Pt nanowire, by measuring
resistance of another nanowire separated from the first one by an insulating
spacer. For thin spacers, the resistance varies almost linearly with current at
cryogenic temperatures, while an additional quadratic contribution emerges for
thicker spacers. These observations suggest a non-thermal distribution of
current-generated phonons that relax via strongly nonlinear dynamical processes
rather than few-phonon scattering. Our results provide insight into the
nonequilibrium phonon dynamics at nanoscale, which may facilitate efficient
heat management in electronic nanodevices.",2107.04634v1
2022-05-27,Adhesive Transfer operates during Galling,"In order to reduce cobalt within the primary circuit of pressurised water
reactors (PWRs), wear-resistant steels are being researched and developed. In
particular interest is the understanding of galling mechanisms, an adhesive
wear mechanism which is particularly prevalent in PWR valves. Here we show that
large shear stresses and adhesive transfer occur during galling by exploiting
the 2 wt per cent manganese difference between 304L and 316L stainless steels,
even at relatively low compressive stresses of 50 MPa. Through these findings,
the galling mechanisms of stainless steels can be better understood, which may
help with the development of galling resistant stainless steels.",2205.14231v2
2022-07-12,Multiscale Modeling of Semimetal Contact to Two-Dimensional Transition Metal Dichalcogenide Semiconductor,"A multiscale simulation approach is developed to simulate the contact
transport properties between semimetal to a monolayer two-dimensional (2D)
transition metal dichalcogenide (TMDC) semiconductor. The results elucidate the
mechanisms for low contact resistance between semimetal and TMDC semiconductor
contacts from a quantum transport perspective. The simulation results compare
favorably with recent experiments. Furthermore, the results show that the
contact resistance of a Bismuth-MoS2 contact can be further reduced by
engineering the dielectric environment and doping the TMDC material to <100
${\Omega}$.${\mu}$m. The quantum transport simulation indicates the possibility
to achieve an ultrashort contact transfer length of ~1 nm, which can allow
aggressive scaling of the contact size.",2207.05781v1
2023-05-09,Thermo-electric history effects and resistive switching in epitaxial thin film of Mott insulator V2O3,"We report interesting thermo-electric history effects associated with an
electric field-induced first order phase transition from Mott-insulator to the
metallic state in the epitaxial thin film of V2O3. This phase transition
results in tuneable resistive switching in V2O3. These findings are promising
for novel technologies like optoelectronics and neuromorphic computing and may
lead to highly energy-efficient switching applications of Mott insulators.",2305.05190v1
2023-11-20,First principles residual resistivity using locally self-consistent multiple scattering method,"The locally self-consistent multiple scattering (LSMS) method can perform
efficient first-principles calculations of systems with large number of atoms.
In this work, we combine the Kubo-Greenwood equation with LSMS, enabling us to
calculate first-principles residual resistivity of large systems. This has been
implemented in the open-source code lsms. We apply this method to selected pure
elements and binary random alloys. The results compare well with experiment,
and with values obtained from a first-principles effective medium technique
(KKR-CPA). We discuss future applications of this method to complex systems
where other methods are not applicable.",2311.12134v1
2024-02-29,Current-induced sliding motion in a helimagnet MnAu$_2$,"We have found a signature of current-induced sliding motion in a helimagnet
MnAu$_2$ thin film. In the helimagnetic state with a uniform chirality,
differential resistivity shows an abrupt change at a threshold bias current.
Judging from the similarity to the canonical charge/spin density wave systems,
we have ascribed the abrupt change to the sliding motion of the helimagnetic
structure. When the two chiral domains are equally mixed, the anomaly in the
differential resistivity disappears, indicating the strong pinning effect of
chiral domain wall.",2403.00167v1
2005-09-21,Effect of iron-doping on spin-state transition and ferromagnetism in Pr$_{0.5}$Ca$_{0.5}$CoO$_{3-δ}$ cobalt oxides,"Resistivity and dc magnetization measurements were performed for the
polycrystalline Pr$_{0.5}$Ca$_{0.5}$Co$_{1-x}$Fe$_{x}$O$_{3-\delta}$ ($x$ = 0,
0.05, 0.10 and 0.15) samples. The as-fabricated samples exhibit ferromagnetic
(FM) transition and the transition temperature increases with increasing the
iron doping level. Annealing under high oxygen pressure induces a spin-state
transition of Co ions in the \emph{iron-free} sample and such transition is
reinforced with increasing the annealing oxygen pressure, while the annealing
under high oxygen pressure suppresses the ferromagnetic ordering. Contrary to
the case of the \emph{iron-free} sample, no spin-state transition is induced by
the annealing under high oxygen pressure for the \emph{iron-doped} samples, and
the ferromagnetic transition temperature is nearly independent of the annealing
procedures. The enhancement of the spin-state transition in the
\emph{iron-free} sample after annealing under high oxygen pressure should be
attributed to the reduction of the cell volume. The suppression of the
spin-state transition by the Fe doping is related to the enlargement of the
cell volume and the stronger Fe-O bonds than Co-O bonds. The enhancement of the
ferromagnetism by the iron-doping might arise from the ferromagnetic exchange
interaction between Fe$^{3+}$ and Co$^{4+}$ through oxygen
(Fe$^{3+}$-O-Co$^{4+}$).",0509533v1
2008-01-08,Quantum oscillations and the Fermi surface in an underdoped high-Tc superconductor,"Despite twenty years of research, the phase diagram of high transition-
temperature superconductors remains enigmatic. A central issue is the origin of
the differences in the physical properties of these copper oxides doped to
opposite sides of the superconducting region. In the overdoped regime, the
material behaves as a reasonably conventional metal, with a large Fermi
surface. The underdoped regime, however, is highly anomalous and appears to
have no coherent Fermi surface, but only disconnected ""Fermi arcs"". The
fundamental question, then, is whether underdoped copper oxides have a Fermi
surface, and if so, whether it is topologically different from that seen in the
overdoped regime. Here we report the observation of quantum oscillations in the
electrical resistance of the oxygen-ordered copper oxide YBa2Cu3O6.5,
establishing the existence of a well-defined Fermi surface in the ground state
of underdoped copper oxides, once superconductivity is suppressed by a magnetic
field. The low oscillation frequency reveals a Fermi surface made of small
pockets, in contrast to the large cylinder characteristic of the overdoped
regime. Two possible interpretations are discussed: either a small pocket is
part of the band structure specific to YBa2Cu3O6.5 or small pockets arise from
a topological change at a critical point in the phase diagram. Our
understanding of high-transition temperature (high-Tc) superconductors will
depend critically on which of these two interpretations proves to be correct.",0801.1281v1
2015-11-16,Accurate Measurements of Cross-plane Thermal Conductivity of Thin Films by Dual-Frequency Time-Domain Thermoreflectance (TDTR),"Accurate measurements of the cross-plane thermal conductivity {\Lambda}_cross
of a high-thermal-conductivity thin film on a low-thermal-conductivity
({\Lambda}_s) substrate (e.g., {\Lambda}_cross/{\Lambda}_s>20) are challenging,
due to the low thermal resistance of the thin film compared to that of the
substrate. In principle, {\Lambda}_cross could be measured by time-domain
thermoreflectance (TDTR), using a high modulation frequency f_h and a large
laser spot size. However, with one TDTR measurement at f_h, the uncertainty of
the TDTR measurement is usually high due to low sensitivity of TDTR signals to
{\Lambda}_cross and high sensitivity to the thickness h_Al of Al transducer
deposited on the sample for TDTR measurements. We observe that in most TDTR
measurements, the sensitivity to h_Al only depends weakly on the modulation
frequency f. Thus, we performed an additional TDTR measurement at a low
modulation frequency f_0, such that the sensitivity to h_Al is comparable but
the sensitivity to {\Lambda}cross is near zero. We then analyze the ratio of
the TDTR signals at f_h to that at f_0, and thus significantly improve the
accuracy of our {\Lambda}cross measurements. As a demonstration of the
dual-frequency approach, we measured the cross-plane thermal conductivity of a
400-nm-thick nickel-iron alloy film and a 3-{\mu}m-thick Cu film, both with an
accuracy of ~10%. The dual-frequency TDTR approach is useful for future studies
of thin films.",1511.04852v2
2015-12-04,2D layered transport properties from topological insulator Bi$_2$Se$_3$ single crystals and micro flakes,"Low-field magnetotransport measurements of topological insulators such as
Bi$_2$Se$_3$ are important for revealing the nature of topological surface
states by quantum corrections to the conductivity, such as
weak-antilocalization. Recently, a rich variety of high-field magnetotransport
properties in the regime of high electron densities ($\sim10^{19}$ cm$^{-3}$)
were reported, which can be related to additional two-dimensional layered
conductivity, hampering the identification of the topological surface states.
Here, we report that quantum corrections to the electronic conduction are
dominated by the surface states for a semiconducting case, which can be
analyzed by the Hikami-Larkin-Nagaoka model for two coupled surfaces in the
case of strong spin-orbit interaction. However, in the metallic-like case this
analysis fails and additional two-dimensional contributions need to be
accounted for. Shubnikov-de Haas oscillations and quantized Hall resistance
prove as strong indications for the two-dimensional layered metallic behavior.
Temperature-dependent magnetotransport properties of high-quality Bi$_2$Se$_3$
single crystalline exfoliated macro and micro flakes are combined with high
resolution transmission electron microscopy and energy-dispersive x-ray
spectroscopy, confirming the structure and stoichiometry. Angle-resolved
photoemission spectroscopy proves a single-Dirac-cone surface state and a
well-defined bulk band gap in topological insulating state. Spatially resolved
core-level photoelectron microscopy demonstrates the surface stability.",1512.01442v2
2015-12-22,Dome-shaped magnetic order competing with high-temperature superconductivity at high pressures in FeSe,"The coexistence and competition between superconductivity and electronic
orders, such as spin or charge density waves, have been a central issue in high
transition-temperature (${T_{\rm c}}$) superconductors. Unlike other iron-based
superconductors, FeSe exhibits nematic ordering without magnetism whose
relationship with its superconductivity remains unclear. More importantly, a
pressure-induced fourfold increase of ${T_{\rm c}}$ has been reported, which
poses a profound mystery. Here we report high-pressure magnetotransport
measurements in FeSe up to $\sim9$ GPa, which uncover a hidden magnetic dome
superseding the nematic order. Above ${\sim6}$ GPa the sudden enhancement of
superconductivity (${T_{\rm c}\le38.3}$ K) accompanies a suppression of
magnetic order, demonstrating their competing nature with very similar energy
scales. Above the magnetic dome we find anomalous transport properties
suggesting a possible pseudogap formation, whereas linear-in-temperature
resistivity is observed above the high-${T_{\rm c}}$ phase. The obtained phase
diagram highlights unique features among iron-based superconductors, but bears
some resemblance to that of high-${T_{\rm c}}$ cuprates.",1512.06951v1
2016-06-06,Comeback of epitaxial graphene for electronics: large-area growth of bilayer-free graphene on SiC,"We present a new fabrication method for epitaxial graphene on SiC which
enables the growth of ultra-smooth defect- and bilayer-free graphene sheets
with an unprecedented reproducibility, a necessary prerequisite for wafer-scale
fabrication of high quality graphene-based electronic devices. The inherent but
unfavorable formation of high SiC surface terrace steps during high temperature
sublimation growth is suppressed by rapid formation of the graphene buffer
layer which stabilizes the SiC surface. The enhanced nucleation is enforced by
decomposition of polymer adsorbates which act as a carbon source. With most of
the steps well below 0.75 nm pure monolayer graphene without bilayer inclusions
is formed with lateral dimensions only limited by the size of the substrate.
This makes the polymer assisted sublimation growth technique the most promising
method for commercial wafer scale epitaxial graphene fabrication. The
extraordinary electronic quality is evidenced by quantum resistance metrology
at 4.2 K with until now unreached precision and high electron mobilities on mm
scale devices.",1606.01709v1
2018-06-01,Amplifier for scanning tunneling microscopy at MHz frequencies,"Conventional scanning tunneling microscopy (STM) is limited to a bandwidth of
circa 1kHz around DC. Here, we develop, build and test a novel amplifier
circuit capable of measuring the tunneling current in the MHz regime while
simultaneously performing conventional STM measurements. This is achieved with
an amplifier circuit including a LC tank with a quality factor exceeding 600
and a home-built, low-noise high electron mobility transistor (HEMT). The
amplifier circuit functions while simultaneously scanning with atomic
resolution in the tunneling regime, i.e. at junction resistances in the range
of giga-ohms, and down towards point contact spectroscopy. To enable high
signal-to-noise and meet all technical requirements for the inclusion in a
commercial low temperature, ultra-high vacuum STM, we use superconducting
cross-wound inductors and choose materials and circuit elements with low heat
load. We demonstrate the high performance of the amplifier by spatially mapping
the Poissonian noise of tunneling electrons on an atomically clean Au(111)
surface. We also show differential conductance spectroscopy measurements at
3MHz, demonstrating superior performance over conventional spectroscopy
techniques. Further, our technology could be used to perform impedance matched
spin resonance and distinguish Majorana modes from more conventional edge
states.",1806.00374v1
2019-09-27,Distinctive Thermoelectric Properties of Supersaturated Si-Ge-P Compounds: Achieving Figure of Merit ZT > 3.6,"The efficiency of energy conversion in thermoelectric generators (TEGs) is
directly proportional to electrical conductivity and Seebeck coefficient while
inversely to thermal conductivity. The challenge is to optimize these
interdependent parameters simultaneously. In this work, the problem is
addressed with a novel approach of nanostructuring and constructive electronic
structure modification to achieve a very high value of dimensionless figure of
merit ZT greater than 3.6 at 1000 K with negative Seebeck coefficient.
Supersaturated solid-solutions of Si-Ge containing 1 atomic percent Fe and 10
atomic percent P are prepared by high-energy ball milling. The bulk samples
consisting of ultra-fine nano-crystallites 9.7 nm are obtained by the
sophisticated low-temperature & high-pressure sintering process. Despite that
the electrical resistivity is slightly high due to the localization of
electrons is associated with the highly disordered structure and low electrical
density of states near the chemical potential, a very low thermal conductivity
\k{appa} less than 1 W m-1K-1 and very large magnitude of Seebeck coefficient
exceeding 470 uV K-1 are achieved in association with the nanostructuring and
the Fe 3d impurity states, respectively, to realize a very large magnitude of
ZT.",1909.12476v1
2019-02-27,Learning nonlinear level sets for dimensionality reduction in function approximation,"We developed a Nonlinear Level-set Learning (NLL) method for dimensionality
reduction in high-dimensional function approximation with small data. This work
is motivated by a variety of design tasks in real-world engineering
applications, where practitioners would replace their computationally intensive
physical models (e.g., high-resolution fluid simulators) with fast-to-evaluate
predictive machine learning models, so as to accelerate the engineering design
processes. There are two major challenges in constructing such predictive
models: (a) high-dimensional inputs (e.g., many independent design parameters)
and (b) small training data, generated by running extremely time-consuming
simulations. Thus, reducing the input dimension is critical to alleviate the
over-fitting issue caused by data insufficiency. Existing methods, including
sliced inverse regression and active subspace approaches, reduce the input
dimension by learning a linear coordinate transformation; our main contribution
is to extend the transformation approach to a nonlinear regime. Specifically,
we exploit reversible networks (RevNets) to learn nonlinear level sets of a
high-dimensional function and parameterize its level sets in low-dimensional
spaces. A new loss function was designed to utilize samples of the target
functions' gradient to encourage the transformed function to be sensitive to
only a few transformed coordinates. The NLL approach is demonstrated by
applying it to three 2D functions and two 20D functions for showing the
improved approximation accuracy with the use of nonlinear transformation, as
well as to an 8D composite material design problem for optimizing the
buckling-resistance performance of composite shells of rocket inter-stages.",1902.10652v3
2015-06-29,Bilayer Insulator Tunnel Barriers for Graphene-Based Vertical Hot-electron Transistors,"Vertical graphene-based device concepts that rely on quantum mechanical
tunneling are intensely being discussed in literature for applications in
electronics and optoelectronics. In this work, the carrier transport mechanisms
in semiconductor-insulator-graphene (SIG) capacitors are investigated with
respect to their suitability as the electron emitter in vertical graphene base
transistors (GBTs). Several dielectric materials as tunnel barriers are
compared, including dielectric double layers. Using bilayer dielectrics, we
experimentally demonstrate significant improvements in the electron injection
current by promoting Fowler-Nordheim tunneling (FNT) and step tunneling (ST)
while suppressing defect mediated carrier transports. High injected tunneling
current densities approaching 10$^3$ A/cm$^2$ (limited by series resistance),
and excellent current-voltage nonlinearity and asymmetry are achieved using a 1
nm-thick high quality dielectric, thulium silicate (TmSiO), as the first
insulator layer, and titanium dioxide (TiO$_2$) as a high electron affinity
second layer insulator. We also confirm the feasibility and effectiveness of
our approach in a full GBT structure which shows dramatic improvement in the
collector on-state current density with respect to the previously reported
GBTs. The device design and the fabrication scheme have been selected with
future CMOS process compatibility in mind. This work proposes a bilayer tunnel
barrier approach as a promising candidate to be used in high performance
vertical graphene-based tunneling devices.",1506.08721v2
2019-01-05,"Transmission lines and resonators based on quantum Hall plasmonics: electromagnetic field, attenuation and coupling to qubits","Quantum Hall edge states have some characteristic features that can prove
useful to measure and control solid state qubits. For example, their high
voltage to current ratio and their dissipationless nature can be exploited to
manufacture low-loss microwave transmission lines and resonators with a
characteristic impedance of the order of the quantum of resistance $h/e^2\sim
25\mathrm{k\Omega}$. The high value of the impedance guarantees that the
voltage per photon is high and for this reason high impedance resonators can be
exploited to obtain larger values of coupling to systems with a small charge
dipole, e.g. spin qubits. In this paper, we provide a microscopic analysis of
the physics of quantum Hall effect devices capacitively coupled to external
electrodes. The electrical current in these devices is carried by edge
magnetoplasmonic excitations and by using a semiclassical model, valid for a
wide range of quantum Hall materials, we discuss the spatial profile of the
electromagnetic field in a variety of situations of interest. Also, we perform
a numerical analysis to estimate the lifetime of these excitations and, from
the numerics, we extrapolate a simple fitting formula which quantifies the $Q$
factor in quantum Hall resonators. We then explore the possibility of reaching
the strong photon-qubit coupling regime, where the strength of the interaction
is higher than the losses in the system. We compute the Coulomb coupling
strength between the edge magnetoplasmons and singlet-triplet qubits, and we
obtain values of the coupling parameter of the order $100\mathrm{MHz}$;
comparing these values to the estimated attenuation in the resonator, we find
that for realistic qubit designs the coupling can indeed be strong.",1901.01455v1
2020-01-16,Anisotropic character of the metal-to-metal transition in Pr4Ni$_3$O$_{10}$,"As a member of the Ruddlesden-Popper Ln$_{n+1}$Ni$_n$O$_{3n+1}$ series
rare-earth-nickelates, the Pr4Ni$_3$O$_{10}$ consists of infinite
quasi-two-dimensional perovskite-like Ni-O based layers. Although a
metal-to-metal phase transition at Tpt = 157 K has been revealed by previous
studies, a comprehensive study of physical properties associated with this
transition has not yet been performed. We have grown single crystals of
Pr4Ni3O10 at high oxygen pressure, and report on the physical properties around
that phase transition, such as heat-capacity, electric-transport and
magnetization. We observe a distinctly anisotropic behavior between in-plane
and out-of-plane properties: a metal-to-metal transition at Tpt within the a-b
plane, and a metal-to-insulator-like transition along the c-axis with
decreasing temperature. Moreover, an anisotropic and anomalous negative
magneto-resistance is observed at Tpt that we attribute to a slight suppression
of the first-order transition with magnetic field. The magnetic-susceptibility
can be well described by a Curie-Weiss law, with different Curie-constants and
Pauli-spin susceptibilities between the high-temperature and the
low-temperature phases. The single crystal X-ray diffraction measurements show
a shape variation of the different NiO6 octahedra from the high-temperature
phase to the low-temperature phase. This subtle change of the environment of
the Ni sites is likely responsible for the different physical properties at
high and low temperatures.",2001.05916v2
2020-06-08,200 mm Sensor Development Using Bonded Wafers,"Sensors fabricated from high resistivity, float zone, silicon material have
been the basis of vertex detectors and trackers for the last 30 years. The
areas of these devices have increased from a few square cm to $\> 200\ m^2$ for
the existing CMS tracker. High Luminosity Large Hadron Collider (HL-LHC), CMS
and ATLAS tracker upgrades will each require more than $200\ m^2$ of silicon
and the CMS High Granularity Calorimeter (HGCAL) will require more than $600\
m^2$. The cost and complexity of assembly of these devices is related to the
area of each module, which in turn is set by the size of the silicon sensors.
In addition to large area, the devices must be radiation hard, which requires
the use of sensors thinned to 200 microns or less. The combination of wafer
thinning and large wafer diameter is a significant technical challenge, and is
the subject of this work. We describe work on development of thin sensors on
$200 mm$ wafers using wafer bonding technology. Results of development runs
with float zone, Silicon-on-Insulator and Silicon-Silicon bonded wafer
technologies are reported.",2006.04888v2
2021-02-11,High-Mobility p-Channel Wide Bandgap Transistors Based on h-BN/Diamond Heterostructures,"Field-effect transistors made of wide-bandgap semiconductors can operate at
high voltages, temperatures and frequencies with low energy losses, and have
been of increasing importance in power and high-frequency electronics. However,
the poor performance of p-channel transistors compared with that of n-channel
transistors has constrained the production of energy-efficient complimentary
circuits with integrated n- and p-channel transistors. The p-type surface
conductivity of hydrogen-terminated diamond offers great potential for solving
this problem, but surface transfer doping, which is commonly believed to be
essential for generating the conductivity, limits the performance of
transistors made of hydrogen-terminated diamond because it requires the
presence of ionized surface acceptors, which cause hole scattering. Here, we
report on fabrication of a p-channel wide-bandgap heterojunction field-effect
transistor consisting of a hydrogen-terminated diamond channel and hexagonal
boron nitride ($h$-BN) gate insulator, without relying on surface transfer
doping. Despite its reduced density of surface acceptors, the transistor has
the lowest sheet resistance ($1.4$ k$\Omega$) and largest on-current ($1600$
$\mu$m mA mm$^{-1}$) among p-channel wide-bandgap transistors, owing to the
highest hole mobility (room-temperature Hall mobility: $680$
cm$^2$V$^{-1}$s$^{-1}$). Importantly, the transistor also shows normally-off
behavior, with a high on/off ratio exceeding $10^8$. These characteristics are
suited for low-loss switching and can be explained on the basis of standard
transport and transistor models. This new approach to making diamond
transistors paves the way to future wide-bandgap semiconductor electronics.",2102.05982v2
2021-03-30,High-Tc superconductivity in clathrate calcium hydride CaH6,"Recent discovery of superconductive rare earth/actinide superhydrides has
ushered in a new era of superconductivity research at high pressures. This
distinct type of clathrate metal hydrides was first proposed for
alkaline-earth-metal hydride CaH6 that, however, has long eluded experimental
synthesis, impeding an understanding of pertinent physics. Here, we report
successful synthesis of CaH6 and its measured superconducting critical
temperature Tc of 215 K at 172 GPa, which is evidenced by a sharp drop of
resistivity to zero and a characteristic decrease of Tc under a magnetic field
up to 9 T.An estimate based on the Werthamer-Helfand-Hohenberg model gives a
giant zero-temperature upper critical magnetic field of 203 T. These remarkable
benchmark superconducting properties place CaH6 among the most outstanding
high-Tc superhydrides, marking it as the hitherto only clathrate metal hydride
outside the family of rare earth/actinide hydrides. This exceptional case
raises great prospects of expanding the extraordinary class of high-Tc
superhydrides to a broader variety of compounds that possess more diverse
material features and physics characteristics.",2103.16282v3
2022-12-28,Superconductivity Observed in Tantalum Polyhydride at High Pressure,"We report experimental discovery of tantalum polyhydride superconductor. It
was synthesized at high pressure and high temperature conditions using diamond
anvil cell combined with in-situ high pressure laser heating techniques. The
superconductivity was investigated via resistance measurements at pressures.
The highest superconducting transition temperature Tc was found to be ~30 K at
197 GPa in the sample that was synthesized at the same pressure with ~2000 K
heating. The transitions are shifted to low temperature upon applying magnetic
fields that supports the superconductivity nature. The upper critical field at
zero temperature {\mu}0Hc2(0) of the superconducting phase is estimated to be
~20 T that corresponds to GL coherent length ~40 angstroms. Our results suggest
that the superconductivity may arise from I-43d phase of TaH3. It is, for the
first time to our best knowledge, experimental realization of superconducting
hydrides for the VB group of transitional metals.",2212.13739v3
2024-02-19,Cross talk of a large-scale depleted monolithic active pixel sensor (DMAPS) in 180 nm CMOS technology,"Monolithic pixel detectors combine readout electronics and sensor in a single
entity of silicon, which simplifies the production procedure and lowers the
material budget compared to conventional hybrid pixel detector concepts.
Benefiting from the advances in commercial CMOS processes towards large biasing
voltage capabilities and the increasing availability of high-resistivity
substrates, depleted monolithic active pixel sensors (DMAPS) are able to cope
with the high-rate and high-radiation environments faced in modern high-energy
physics experiments. TJ-Monopix2 is the latest iteration of a DMAPS development
line designed in 180 nm TowerSemicondutor technology, which features a large
scale (2 x 2) cm$^2$ chip divided into (512 x 512) pixels with a pitch of (33 x
33) um$^2$. All in-pixel electronics are separated from its small collection
electrode and process modifications are implemented to improve charge
collection efficiency especially after irradiation. The latest laboratory
measurements and investigations of a threshold variation observed for
TJ-Monopix2 in typical operating conditions are presented.",2402.12153v1
2019-02-08,Investigating Short-term and Long-term Binder Performance of High-RAP Mixtures Containing Waste Cooking Oil,"The environmental and economic benefits of recycling asphalt pavements have
received much attention in recent years. Because of the increase in the cost of
raw materials and energy carriers, the reuse of large portions of reclaimed
asphalt pavement (RAP) is critical in reducing both the cost and environmental
footprint of asphalt pavements. High-RAP mixtures are more prone to low
temperature cracking and poor mixture workability because of the higher
stiffness of RAP binder. Recycling agents are one of the additives which are
used to improve these deficiencies. However, there is some ambiguity about the
optimum content of recycling agent to assure proper performance of recycled
asphalt pavement during its service life. The current study used 60% and 100%
fractionated RAP with waste cooking oil as a recycling agent and crumb rubber
to alleviate the aforementioned problems. Laboratory evaluation showed that
increasing the amount of recycling agent in the high-RAP mixtures improved
their workability and low temperature performance while decreasing moisture
damage and rutting resistance. The long-term susceptibility to aging of
recycled binder with the organically-based recycling agent was also
investigated. A procedure to obtain the optimum percentage of recycling agent
was devised to strike a balance between the performance characteristics of
mixtures with a high-RAP content.",1905.13701v1
2016-03-12,Complex structures of dense lithium: electronic origin,"Lithium - the lightest alkali metal - exhibits unexpected structures and
electronic behaviour at high pressures. As the heavier alkalis, Li is bcc at
ambient pressure and transforms first to fcc (at 7.5 GPa). The post-fcc
high-pressure form Li-cI16 (at 40-60 GPa) is similar to Na-cI16 and related to
more complex structures of heavy alkalis Rb-oC52 and Cs-oC84. The other high
pressure phases for Li (oC88, oC40, oC24) found at pressures up to 130 GPa are
specific the only to Li. The different route of Li high-pressure structures
correlates with its special electronic configuration containing the only 3
electrons (at 1s and 2s levels). Crystal structures for Li are analyzed within
the model of Fermi sphere - Brillouin zone interactions. Stability of post-fcc
structures for Li can be supported by Hume-Rothery arguments when new Brillouin
zone plains appear close to the Fermi level producing pseudogaps near the Fermi
level and decreasing the crystal energy. The filling of Brillouin-Jones zones
by electron states for a given structure defines the physical properties as
optical reflectivity, electrical resistivity and superconductivity. To
understand complexity of structural and physical properties of Li above 60 GPa
is necessary to assume the valence electrons band overlap with the upper core
electrons and increase the valence electron count under compression.",1603.03926v1
2019-03-28,High spin-polarization in the low Curie temperature complex itinerant ferromagnet EuTi$_{1-x}$Nb$_x$O$_3$,"The physical systems with ferromagnetism and ""bad"" metallicity hosting
unusual transport properties are playgrounds of novel quantum phenomena.
Recently EuTi$_{1-x}$Nb$_x$O$_3$ emerged as a ferromagnetic system where
non-trivial temperature dependent transport properties are observed due to
coexistence and competition of various magnetic and non-magnetic scattering
processes. In the ferromagnetic state, the resistivity shows a $T^2$
temperature dependence possibly due to electron-magnon scattering and above the
Curie temperature $T_c$, the dependence changes to $T^{3/2}$ behaviour
indicating a correlation between transport and magnetic properties. In this
paper, we show that the transport spin-polarization in EuTi$_{1-x}$Nb$_x$O$_3$,
a low Curie temperature ferromagnet, is as high ($\sim 40\%$) as that in some
of the metallic ferromagnets with high Curie temperatures. In addition, owing
to the low Curie temperature of EuTi$_{1-x}$Nb$_x$O$_3$, the temperature ($T$)
dependence of $P_t$ could be measured systematically up to $T_c$ which revealed
a proportionate relationship with magnetization $M_s$ vs. $T$. This indicates
that such proportionality is far more universally valid than the ferromagnets
with ideal parabolic bands. Furthermore, our band structure calculations not
only helped understand the origin of such high spin polarization in
EuTi$_{1-x}$Nb$_x$O$_3$ but also provided a route to estimate the Hubbard $U$
parameter in complex metallic ferromagnets in general using experimental
inputs.",1903.12022v1
2011-04-22,Can nothing be a superconductor and a superfluid?,"A superconductor is a material that conducts electric current with no
resistance. Superconductivity and magnetism are known to be antagonistic
phenomena: superconductors expel weak external magnetic field (the Meissner
effect) while a sufficiently strong magnetic field, in general, destroys
superconductivity. In a seemingly contradictory statement, we show that a very
strong magnetic field can turn an empty space into a superconductor. The
external magnetic field required for this effect should be about 10^{16} Tesla
(eB ~ 1 GeV^2). The physical mechanism of the exotic vacuum superconductivity
is as follows: in strong magnetic field the dynamics of virtual quarks and
antiquarks is effectively one-dimensional because these electrically charged
particles tend to move along the lines of the magnetic field. In one spatial
dimension a gluon-mediated attraction between a quark and an antiquark of
different flavors inevitably leads to formation of a colorless spin-triplet
bound state (a vector analogue of the Cooper pair) with quantum numbers of an
electrically charged rho meson. Such quark-antiquark pairs condense to form an
anisotropic inhomogeneous superconducting state similar to the Abrikosov vortex
lattice in a type-II superconductor. The onset of the superconductivity of the
charged rho mesons should also induce an inhomogeneous superfluidity of the
neutral rho mesons. The vacuum superconductivity should survive at very high
temperatures of typical Quantum Chromodynamics (QCD) scale of 10^{12} K (T ~
100 MeV). We propose the phase diagram of QCD in the plane ""magnetic field -
temperature"".",1104.4404v1
2019-06-14,Tunneling Magnetoresistance and Spin-Dependent Diode Performance in Fully Epitaxial Magnetic Tunnel Junctions with Rock-salt Type ZnO/MgO,"We fabricate fully epitaxial Fe/ZnO/MgO/Fe magnetic tunnel junctions (MTJs)
with a bilayer tunnel barrier, in which ZnO has a metastable rock-salt crystal
structure. We observe a high magnetoresistance ratio up to 96% at room
temperature (RT) and find that these MTJs have asymmetric current-voltage
characteristics, and their rectifying performances are largely dependent on the
magnetization alignments of the Fe electrodes. Diode responsibilities at a
zero-bias voltage ($\beta_{0}$), which is an important performance index for
harvesting applications, are observed up to 1.3 A/W at RT in the antiparallel
alignment of the magnetizations while maintaining rather low resistance-area
(RA) products (a few tens of k${\Omega\mu}$m$^2$). Even with the same top and
bottom electrodes (Fe), the obtained $\beta_{0}$ values are comparable to those
of reported high-performance tunnel diodes consisting of amorphous bilayer
tunnel barriers with polycrystalline dissimilar electrodes. This strongly
suggests that the epitaxial ZnO/MgO bilayer tunnel barrier is effective for
enhancing the $\beta_{0}$ without significant increase in the RA. In addition,
we demonstrate that a zero-bias anomaly in thetunnel conductance, which
originates from the magnon excitations at the Fe/barrier interfaces, plays a
crucial role in observed spin-dependent diode performance. The results indicate
that a fully epitaxial MTJ with a bilayer tunnel barrier is a promising
candidate to establish a high-performance high-frequency rectifying system.",1906.05981v1
2020-11-24,Inkjet printed circuits with two-dimensional semiconductor inks for high-performance electronics,"Air-stable semiconducting inks suitable for complementary logic are key to
create low-power printed integrated circuits (ICs). High-performance printable
electronic inks with two-dimensional materials have the potential to enable the
next generation of high performance, low-cost printed digital electronics. Here
we demonstrate air-stable, low voltage (< 5 V) operation of inkjet-printed
n-type molybdenum disulfide (MoS2) and p-type
indacenodithiophene-co-benzothiadiazole (IDT-BT) field-effect transistors
(FETs), estimating a switching time of {\tau} ~ 3.3 {\mu}s for the MoS2 FETs.
We achieve this by engineering high-quality MoS2 and air-stable IDT-BT inks
suitable for inkjet-printing complementary pairs of n-type MoS2 and p-type
IDT-BT FETs. We then integrate MoS2 and IDT-BT FETs to realise inkjet-printed
complementary logic inverters with a voltage gain |Av| ~ 4 when in resistive
load configuration and |Av| ~ 1.36 in complementary configuration. These
results represent a key enabling step towards ubiquitous long-term stable,
low-cost printed digital ICs.",2011.12359v1
2020-11-26,A two-dimensional electron gas based on a 5s oxide with high room-temperature mobility and strain sensitivity,"The coupling of optical and electronic degrees of freedom together with
quantum confinement in low-dimensional electron systems is particularly
interesting for achieving exotic functionalities in strongly correlated oxide
electronics. Recently, high room-temperature mobility has been achieved for a
large bandgap transparent oxide - BaSnO$_3$ upon extrinsic La or Sb doping,
which has excited significant research attention. In this work, we report the
observation of room-temperature ferromagnetism in BaSnO$_3$ thin films and the
realization of a two-dimensional electron gas (2DEG) on the surface of
transparent BaSnO$_3$ via oxygen vacancy creation, which exhibits a high
carrier density of $\sim 7.72*10^{14} /{\rm cm}^2$ and a high room-temperature
mobility of ~18 cm$^2$/V/s. Such a 2DEG is rather sensitive to strain and a
less than 0.1% in-plane biaxial compressive strain leads to a giant resistance
enhancement of 350% (more than 540 kOhm/Square) at room temperature. Thus, this
work creates a new path to exploring the physics of low-dimensional oxide
electronics and devices applicable at room temperature.",2011.13106v2
2021-06-17,Quasi-solid-state sodium-ion hybrid capacitors enabled by UiO-66@PVDF-HFP multifunctional separators: selective charge transfer and high safety,"The practical application of sodium-ion hybrid capacitors is limited by their
low energy densities resulted from the kinetics mismatch between cathodes and
anodes, and the fire safety related to the flammable electrolyte-separator
system. Hence, we report a rational design of metal-organic frameworks (MOFs,
UiO-66) modified PVDF-HFP separator. High tensile strength and dimensional
thermal stability of the separator reduce the risk of electrode short circuit
caused by the separator deformation. MCC test demonstrates a reduction of 75%
in peak heat release rate (pHRR), indicating an enhanced fire-resistant
property of the separator. This is due to the transformation of UiO-66 into
ZrO2 accompanied by the consumption of oxygen and the formation of the barrier
char that suppresses further heat release. Quasi-solid-state electrolyte
prepared based on this separator presents an enhanced ionic conductivity of
2.44 mS*cm-1 and Na-ion transference number of 0.55, which are related to the
high porosity ( >70%) and electrolyte uptake (~ 320%) of the separator.
Moreover, the open metal sites of UiO-66 can capture PF6- and consequently
liberate the Na+ for faster migration, thus reducing the kinetics mismatch
between cathodes and anodes. Such multifunctional separator enables the
quasi-solid-state Na-ion hybrid capacitor to achieve high energy density (182
Wh*kg-1 @31 W*kg-1) and power density (5280 W*kg-1 @22 Wh*kg-1), as well as
excellent cyclic stability (10000 cycles @1000 mA*g-1).
  Keywords: Quasi-solid-state; PVDF-HFP; Metal-organic frameworks; Dimensional
thermal stability; Fire safety; Selective charge transfer",2106.09654v1
2021-12-13,Robustness of superconductivity to external pressure in high-entropy-alloy-type metal telluride AgInSnPbBiTe5,"High-entropy-alloy (HEA) superconductors are a new class of disordered
superconductors. In this study, we investigate the robustness of
superconducting states in HEA-type metal telluride (MTe; M = Ag, In, Sn, Pb,
Bi) under high pressure. PbTe exhibits a structural transition from a NaCl-type
to an orthorhombic Pnma structure at low pressures, and further transitions to
a CsCl-type structure at high pressures. When the superconductivity of the
CsCl-type PbTe is observed, it is found that its superconducting transition
temperature (Tc) decreases with pressure. However, in the HEA-type
AgInSnPbBiTe5, Tc is almost independent of pressure, for pressures ranging from
13.0 to 35.1 GPa. This trend is quite similar to that observed in an HEA
superconductor (TaNb)0.67(HfZrTi)0.33, which shows that the robustness of
superconductivity to external pressure is a universal feature in HEA-type
superconductors. To clarify the effects of the modification of the
configurational entropy of mixing on the crystal structure, superconducting
states, and electronic structure of MTe, electrical resistance measurements,
synchrotron X-ray diffraction, and synchrotron X-ray absorption spectroscopy
with partial fluorescence mode (PFY-XAS) for three MTe polycrystalline samples
of PbTe, AgPbBiTe3, and AgInSnPbBiTe5 with different configurational entropies
of mixing at the M site were performed.",2112.06461v1
2022-12-12,Robust superconductivity and fragile magnetism induced by the strong Cu impurity scattering in the high-pressure phase of FeSe,"Superconductivity in FeSe is strongly enhanced under applied pressure and it
is proposed to emerge from anomalously coupled structural and magnetic phases.
Small impurities inside the Fe plane can strongly disrupt the pair formation in
FeSe at ambient pressure and can also reveal the interplay between normal and
superconducting phases. Here, we investigate how an impurity inside the Fe
plane induced by the Cu substitution can alter the balance between competing
electronic phases of FeSe at high pressures. In the absence of an applied
magnetic field, at low pressures the nematic and superconducting phases are
suppressed by a similar factor. On the other hand, at high pressures, above 10
kbar, the superconductivity remains unaltered despite the lack of any signature
in transport associated to a magnetic phase in zero-magnetic field. However, by
applying a magnetic field, the resistivity displays an anomaly preceding the
activated behaviour in temperature, assigned to a magnetic anomaly. We find
that the high-pressure superconducting phase of FeSe is robust and remains
enhanced in the presence of Cu impurity, whereas the magnetic phase is not.
This could suggest that high-$T_{\rm c}$ superconductivity has a
sign-preserving order parameter in a presence of a rather glassy magnetic
phase.",2212.06128v1
2023-01-30,Semimetal-Monolayer Transition Metal Dichalcogenides Photodetectors for Wafer-Scale Ultraviolet Photonics,"Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs),
such as MoS$_2$, are promising candidates for nanoscale photonics because of
strong-light matter interactions. However, Fermi level pinning due to
metal-induced gap (MIGS) states at the metals-monolayer MoS$_2$ interface
limits the application of optoelectronic devices based on conventional metals
because of the high contact resistance of the Schottky contacts. On the other
hand, a semimetal-TMD-semimetal device can overcome this limitation, where the
MIGS are sufficiently suppressed and can result in ohmic contacts. Here we
demonstrate the optoelectronic performance of a bismuth-monolayer (1L)
MoS$_2$-bismuth device with ohmic electrical contacts and extraordinary
optoelectronic properties. To address the wafer-scale production, we grew full
coverage 1L MoS$_2$ by using chemical vapor deposition method. We measured high
photoresponsivity of 300 A/W in the UV regime at 77 K, which translates into an
external quantum efficiency (EQE) ~ 1000 or $10^5$%. We found that the 90% rise
time of our devices at 77 K is 0.1 ms, which suggests that the current devices
can operate at the speed of ~ 10 kHz. The combination of large-array device
fabrication, high sensitivity, and high-speed response offers great potential
for applications in photonics that includes integrated optoelectronic circuits.",2301.12635v1
2023-04-13,Self-doping effect in confined copper selenide semiconducting quantum dots for efficient photoelectrocatalytic oxygen evolution,"Self-doping can not only suppress the photogenerated charge recombination of
semiconducting quantum dots by self-introducing trapping states within the
bandgap, but also provide high-density catalytic active sites as the
consequence of abundant non-saturated bonds associated with the defects. Here,
we successfully prepared semiconducting copper selenide (CuSe) confined quantum
dots with abundant vacancies and systematically investigated their
photoelectrochemical characteristics. Photoluminescence characterizations
reveal that the presence of vacancies reduces the emission intensity
dramatically, indicating a low recombination rate of photogenerated charge
carriers due to the self-introduced trapping states within the bandgap. In
addition, the ultra-low charge transfer resistance measured by electrochemical
impedance spectroscopy implies the efficient charge transfer of CuSe
semiconducting quantum dots-based photoelectrocatalysts, which is guaranteed by
the high conductivity of their confined structure as revealed by
room-temperature electrical transport measurements. Such high conductivity and
low photogenerated charge carriers recombination rate, combined with
high-density active sites and confined structure, guaranteeing the remarkable
photoelectrocatalytic performance and stability as manifested by
photoelectrocatalysis characterizations. This work promotes the development of
semiconducting quantum dots-based photoelectrocatalysis and demonstrates CuSe
semiconducting quantum confined catalysts as an advanced photoelectrocatalysts
for oxygen evolution reaction.",2304.06422v1
2009-12-15,Kondo effect and absence of quantum interference effects in the charge transport of cobalt doped iron pyrite,"The Hall effect and resistivity of the carrier doped magnetic semiconductor
Fe$_{1-x}$Co$_x$S$_2$ were measured for $0\le x \le 0.16$, temperatures between
0.05 and 300 K, and fields of up to 9 T. Our Hall data indicate electron charge
carriers with a density of only 10 to 30% of the Co density of our crystals.
Despite the previous identification of magnetic Griffiths phase formation in
the magnetic and thermodynamic properties of this system for the same range of
$x$, we measure a temperature independent resistivity below 0.5 K indicating
Fermi liquid-like transport. We also observe no indication of quantum
corrections to the conductivity despite the small values of the product of the
Fermi wave vector and the mean-free-path, $1.5 \le k_F\ell \le 15$, over the
range of $x$ investigated. This implies a large inelastic scattering rate such
that the necessary condition for the observation of quantum contributions to
the carrier transport, quantum coherence over times much longer than the
elastic scattering time, is not met in our samples. Above 0.5 K we observe a
temperature and magnetic field dependent resistivity that closely resembles a
Kondo anomaly for $x$ less than that required to form a long range magnetic
state, $x_c$. For $x>x_c$, the resistivity and magnetoresistance resemble that
of a spin glass with a reduction of the resistivity by as much as 35% in 5 T
fields. We also observe an enhancement of the residual resistivity ratio by
almost a factor of 2 for samples with $x\sim x_c$ indicating temperature
dependent scattering mechanisms beyond simple carrier-phonon scattering. We
speculate that this enhancement is due to charge carrier scattering from
magnetic fluctuations which contribute to the resistivity over a wide
temperature range.",0912.2980v1
2022-01-04,Superior effect of edge relative to basal plane functionalization of graphene in enhancing polymer-graphene nanocomposite thermal conductivity-A combined molecular dynamics and Greens functions study,"To achieve high thermal conductivity (k) of polymer graphene nanocomposites,
it is critically important to achieve efficient thermal coupling between
graphene and its surrounding polymers through effective functionalization
schemes. In this work, we demonstrate that edge-functionalization of graphene
nanoplatelets (GnPs) can enable a larger enhancement of effective thermal
conductivity in polymer-graphene nanocomposites, relative to basal plane
functionalization. Effective thermal conductivity for edge case is predicted,
through molecular dynamics simulations, to be up to 48% higher relative to
basal plane bonding for 35 wt.% graphene loading with 10 layers thick
nanoplatelets. This unique result opens up promising new avenues for achieving
high thermal-conductivity polymer materials, which is of key importance for a
wide range of thermal management technologies. The anisotropy of thermal
transport in single layer graphene leads to very high in-plane thermal
conductivity (~2000 W/mK) compared to the low out-of-plane thermal conductivity
(~10 W/mK). Likewise, in multilayer graphene nanoplatelet (GnP), the thermal
conductivity across the layers is even lower due to the weak van der Waals
bonding between each pair of layers. Edge functionalization couples the polymer
chains to the high in-plane thermal conduction pathway of graphene, thus
leading to high overall high composite thermal conductivity. Basal-plane
functionalization, however, lowers the thermal resistance between the polymer
and the surface graphene sheets of the nanoplatelet only, causing the heat
conduction through inner layers to be less efficient, thus resulting in basal
plane scheme to be outperformed by edge scheme. The present study fundamentally
enables novel pathways for achieving high thermal-conductivity polymer
composites.",2201.01011v1
2008-11-14,Electronic transport in ferromagnetic alloys and the Slater-Pauling Curve,"Experimental measurements of the residual resistivity $\rho(x)$ of the binary
alloy system Fe$_{1-x}$Cr$_x$ have shown an anomalous concentration dependence
which deviates significantly from Nordheim's rule. In the low ($x < 10%$) Cr
concentration regime the resistivity has been found to increase linearly with
$x$ until $\approx$ 10% Cr where the resistivity reaches a plateau persisting
to $\approx$ 20% Cr. In this paper we present $ab$-$initio$ calculations of
$\rho(x)$ which explain this anomalous behavior and which are based on the
Korringa-Kohn-Rostoker (KKR) method in conjunction with the Kubo-Greenwood
formalism. Furthermore we are able to show that the effects of short-range
ordering or clustering have little effect via our use of the nonlocal
coherent-potential approximation (NL-CPA). For the interpretation of the
results we study the alloys' electronic structure by calculating the Bloch
spectral function particularly in the vicinity of the Fermi energy. From the
analysis of our results we infer that a similar behavior of the resistivity
should also be obtained for iron-rich Fe$_{1-x}$V$_x$ alloys - an inference
confirmed by further explicit resistivity calculations. Both of these alloy
systems belong to the same branch of the famous Slater-Pauling plot and we
postulate that other alloy systems from this branch should show a similar
behavior. Our calculations show that the appearance of the plateau in the
resistivity can be attributed to the dominant contribution of minority spin
electrons to the conductivity which is nearly unaffected by increase in Cr/V
concentration $x$ and we remark that this minority spin electron feature is
also responsible for the simple linear variation of the average moment in the
Slater-Pauling plot for these materials.",0811.2303v1
2020-12-11,Improving fretting corrosion resistance of CoCrMo alloy with TiSiN and ZrN coatings for orthopedic applications,"Total hip replacement is the most effective treatment for late stage
osteoarthritis. However, adverse local tissue reactions (ALTRs) associated with
fretting corrosion have been observed in patients with modular total hip
implants. The purpose of this study is to increase the fretting corrosion
resistance of the CoCrMo alloy and the associated metal ion release by applying
hard coatings to the surface. Cathodic arc evaporation technique (arc-PVD) was
used to deposit TiSiN and ZrN hard coatings on to CoCrMo substrates. The
morphology, chemical composition, crystal structures and residual stress of the
coatings were characterized by scanning electron microscopy, energy dispersive
x-ray spectroscopy, and X-ray diffractometry. Hardness, elastic modulus, and
adhesion of the coatings were measured by nano-indentation, nano-scratch test,
and the Rockwell C test. Fretting corrosion resistance tests of coated and
uncoated CoCrMo discs against Ti6Al4V spheres were conducted on a four-station
fretting testing machine in simulated body fluid at 1Hz for 1 million cycles.
Post-fretting samples were analyzed for morphological changes, volume loss and
metal ion release. Our analyses showed better surface finish and lower residual
stress for ZrN coating, but higher hardness and better scratch resistance for
TiSiN coating. Fretting results demonstrated substantial improvement in
fretting corrosion resistance of CoCrMo with both coatings. ZrN and TiSiN
decreased fretting volume loss by more than 10 times and 1000 times,
respectively. Both coatings showed close to 90% decrease of Co ion release
during fretting corrosion tests. Our results suggest that hard coating
deposition on CoCrMo alloy can significantly improve its fretting corrosion
resistance and could thus potentially alleviate ALTRs in metal hip implants.",2012.06614v1
2018-03-06,Approach combining the Rietveld method and pairs distribution function analysis to study crystalline materials under high-pressure and/or temperature: Application to rhombohedral Bi2Te3 phase,"An approach combining the Rietveld method and pairs distribution function
analysis to study crystalline materials under high pressure or temperature was
early proposed by us, and in this study, it was applied to investigate de
effect of high pressure on the rhombohedral Bi2Te3 phase. The refined
structural parameters obtained from the Rietveld refinement of the XRD patterns
measured for pressures up to 9.1 GPa were used as input data to simulate the
partial and total structure factors SBiBi, SBiTe, STeTe, and SBi2Te3. Fourier
transformation of the Sij factors permitted to obtain the partial and total
pairs distribution functions GBiBi, GBiTe, GTeTe, and GBi2Te3. The first
coordination shells of these Gij functions are formed by subshells and, with
increasing pressure in the 1.1 to 6.3 GPa range, occur a partial separation of
subshells. Also, the increase of pressure in this range promotes a drastic
reduction in the values of the intralayer angles TeBiTe, and consequently, in
the intralayer distance TeTe. A drastic reduction in the interlayers distance
Te-Te was also observed. Several studies are reported in the literature,
including one carried out by us, show the presence of an ETT in this pressure
range. The obtained results suggest that the ETT is related with the decrease
of the intralayer angles TeBiTe, and intra- and interlayer distance TeTe.
Experimental results describing the pressure dependence the thermoelectric
power, electrical resistivity, and power fator for rhombohedral Bi2Te3 are
reported, and an enhancement of the power factor in the 1.1 to 6.3 GPa range is
observed. The results obtained in this study give evidence that this
enhancement in the power factor is related with the decrease of the intralayer
angles TeBiTe, and with the decrease of intralayer- and interlayers homopolar
TeTe bonds.",1803.02479v1
2021-01-30,Fast drying of high-alumina MgO-bonded refractory castables,"Refractory producers face many challenges in terms of producing
MgO-containing castables due to the high likelihood of magnesia to hydrate in
contact with water, resulting in Mg(OH)2 generation. The expansive feature of
this transformation affects the performance of such refractories, as (i) if
this hydrated phase is not accommodated in the formed microstructure, ceramic
linings with cracks and low green mechanical strength will be obtained; and
(ii) if crack-free pieces are prepared, they should present low porosity and
reduced permeability, which require special attention when heating these
materials. This work investigated the ability of various additives in the
optimization of the drying behavior of Al2O3-MgO castables. Vibratable
compositions were tested after incorporating polymeric fibers (PF), an organic
salt (OAS), SiO2-based additive (SM) or permeability enhancing active compound
(MP) into the dry-mixtures. Various experimental measurements were performed to
infer the role of the drying agents to prevent the samples explosion and
whether they would also influence other properties of the castables. As
observed, OAS and MP helped to inhibit the MgO-bonded samples explosion even
under severe heating conditions (2-20C/min) and increased their green
mechanical strength and slag infiltration resistance when compared to the
additive-free composition. On the other hand, the addition of polymeric fibers
(PF) or silica-based compound (SM) to the formulations was not able to prevent
the castables explosion when using a high heating rate and other side effects
could also be observed when testing these materials. Thus, the selection of
suitable drying agents is a key issue, as they may allow the development of
MgO-bonded castables with enhanced properties and lower spalling risk during
their first thermal treatment.",2102.00217v1
2022-03-14,Revisiting stress-corrosion cracking and hydrogen embrittlement in 7xxx-Al alloys at the near-atomic-scale,"Hydrogen embrittlement (HE) affects all major high-strength structural
materials and as such is a major impediment to lightweighting e.g. vehicles and
help reduce carbon-emissions and reach net-zero. The high-strength 7xxx series
aluminium alloys can fulfil the need for light, high strength materials, and
are already extensively used in aerospace for weight reduction purposes.
However, depending on the thermomechanical and loading state, these alloys can
be sensitive to stress-corrosion cracking (SCC) through anodic dissolution and
hydrogen embrittlement. Here, we study at the near-atomic-scale the intra- and
inter-granular microstructure ahead and in the wake of a propagating SCC crack.
Moving away from model cases not strictly relevant to application, we performed
an industry-standard test on an engineering Al-7XXX alloy. H is found
segregated to planar arrays of dislocations and to grain boundaries that we can
associate to the combined effects of hydrogen-enhanced localized plasticity
(HELP) and hydrogen-enhanced decohesion (HEDE) mechanisms. We report on a
Mg-rich H-rich amorphous oxide on the corroded crack surface and evidence of
Mg-related diffusional processes leading to dissolution of the strengthening
eta-phase precipitates ahead of the crack. We show ingress of up to 1 at% O,
i.e. well above the solubility limit of O in Al, near the oxide-metal
interface, while no increased level of H is found in the matrix. We provide an
array of discussion points relative to the interplay of structural defects,
transport of solutes, thereby changing the resistance against crack
propagation, which have been overlooked across the SCC literature and prevent
accurate service life predictions.",2203.07058v1
2022-04-06,First principles investigation of anionic redox in bisulfate lithium battery cathodes,"The search for an alternative high-voltage polyanionic cathode material for
Li-ion batteries is vital to improve the energy densities beyond the
state-of-the-art, where sulfate frameworks form an important class of
high-voltage cathode materials due to the strong inductive effect of the
S$^{6+}$ ion. Here, we have investigated the mechanism of cationic and/or
anionic redox in Li$_x$M(SO$_4$)$_2$ frameworks (M = Mn, Fe, Co, and Ni and 0
$\leq$ x $\leq$ 2) using density functional calculations. Specifically, we have
used a combination of Hubbard $U$ corrected strongly constrained and
appropriately normed (SCAN+$U$) and generalized gradient approximation
(GGA+$U$) functionals to explore the thermodynamic (polymorph stability),
electrochemical (intercalation voltage), geometric (bond lengths), and
electronic (band gaps, magnetic moments, charge populations, etc.) properties
of the bisulfate frameworks considered. Importantly, we find that the anionic
(cationic) redox process is dominant throughout delithiation in the Ni (Mn)
bisulfate, as verified using our calculated projected density of states, bond
lengths, and on-site magnetic moments. On the other hand, in Fe and Co
bisulfates, cationic redox dominates the initial delithiation (1 $\leq$ x
$\leq$ 2), while anionic redox dominates subsequent delithiation (0 $\leq$ x
$\leq$ 2). In addition, evaluation of the crystal overlap Hamilton population
reveals insignificant bonding between oxidizing O atoms throughout the
delithiation process in the Ni bisulfate, indicating robust battery performance
that is resistant to irreversible oxygen evolution. Finally, we observe both
GGA+$U$ and SCAN+$U$ predictions are in qualitative agreement for the various
properties predicted. Our work should open new avenues for exploring lattice
oxygen redox in novel high voltage polyanionic cathodes, especially using the
SCAN+$U$ functional.",2204.02673v1
2012-09-07,Phase relations in K_xFe_{2-y}Se_2 and the structure of superconducting K_xFe_2Se_2 via high-resolution synchrotron diffraction,"Superconductivity in iron selenides has experienced a rapid growth, but not
without major inconsistencies in the reported properties. For
alkali-intercalated iron selenides, even the structure of the superconducting
phase is a subject of debate, in part because the onset of superconductivity is
affected much more delicately by stoichiometry and preparation than in cuprate
or pnictide superconductors. If high-quality, pure, superconducting
intercalated iron selenides are ever to be made, the intertwined physics and
chemistry must be explained by systematic studies of how these materials form
and by and identifying the many coexisting phases. To that end, we prepared
pure K_2Fe_4Se_5 powder and superconductors in the K_xFe_{2-y}Se_2 system, and
examined differences in their structures by high-resolution synchrotron and
single-crystal x-ray diffraction. We found four distinct phases: semiconducting
K_2Fe_4Se_5, a metallic superconducting phase K_xFe_2Se_2 with x ranging from
0.38 to 0.58, an insulator KFe_{1.6}Se_2 with no vacancy ordering, and an
oxidized phase K_{0.51(5)}Fe_{0.70(2)}Se that forms the PbClF structure upon
exposure to moisture. We find that the vacancy-ordered phase K_2Fe_4Se_5 does
not become superconducting by doping, but the distinct iron-rich minority phase
K_xFe_2Se_2 precipitates from single crystals upon cooling from above the
vacancy ordering temperature. This coexistence of metallic and semiconducting
phases explains a broad maximum in resistivity around 100 K. Further studies to
understand the solubility of excess Fe in the K_xFe_{2-y}Se_2 structure will
shed light on the maximum fraction of superconducting K_xFe_2Se_2 that can be
obtained by solid state synthesis.",1209.1650v1
2015-04-10,Esaki diodes in van der Waals heterojunctions with broken-gap energy band alignment,"Van der Waals (vdW) heterojunctions composed of 2-dimensional (2D) layered
materials are emerging as a solid-state materials family that exhibit novel
physics phenomena that can power high performance electronic and photonic
applications. Here, we present the first demonstration of an important building
block in vdW solids: room temperature (RT) Esaki tunnel diodes. The Esaki
diodes were realized in vdW heterostructures made of black phosphorus (BP) and
tin diselenide (SnSe2), two layered semiconductors that possess a broken-gap
energy band offset. The presence of a thin insulating barrier between BP and
SnSe2 enabled the observation of a prominent negative differential resistance
(NDR) region in the forward-bias current-voltage characteristics, with a peak
to valley ratio of 1.8 at 300 K and 2.8 at 80 K. A weak temperature dependence
of the NDR indicates electron tunneling being the dominant transport mechanism,
and a theoretical model shows excellent agreement with the experimental
results. Furthermore, the broken-gap band alignment is confirmed by the
junction photoresponse and the phosphorus double planes in a single layer of BP
are resolved in transmission electron microscopy (TEM) for the first time. Our
results represent a significant advance in the fundamental understanding of vdW
heterojunctions, and widen the potential applications base of 2D layered
materials.",1504.02810v5
2018-12-01,Extrinsic n-type semiconductor transition in ZrSe2 with the metallic character through hafnium substitution,"Two dimensional layered materials exhibit versatile electronic properties in
their different phases. The intrinsic electronic properties of these materials
can be modulated through doping or intercalation. In this study, we
investigated the electronic properties of Hf doped ZrSe2 single crystals using
angle-resolved photoemission spectroscopy (ARPES) combined with first
principles density functional theory (DFT) calculations. It is observed that
the valence band maxima of ZrSe2, located below the Fermi level, undergo a
significant change with the introduction of Hf substitution. Hf can introduce
extra charges into the conduction band, rather than making a mixed structure of
HfSe2 and ZrSe2 band structure, which can cross the Fermi level. Compared to
the semiconducting band structure of ZrSe2, we observed that the conduction
band crosses the Fermi level at the high symmetry M point in Hf-doped ZrSe2.
This suggests an increase of electron type carriers around the Fermi level,
resulting in an extrinsic charge carrier density in the conduction band, which
can form a metallic behaviour. It can be noticed that the Hf cations can create
disorder in the form of excess atoms of Zr, which yields more carriers in the
conduction band in the shape of smeared bands. The tails of the smeared band
occupied the d-orbitals extended into the Fermi level and left the d band
below. Similarly, the electrical resistance measurements further confirm the
metallic-like character of Hf doped ZrSe2 compared to the semiconductor ZrSe2,
indicating increased carriers. This metallic like behavior is suggested to be
predisposed by the extrinsic electrons induced by the substitutional disorder.
This study further demonstrates the possibility of band gap engineering through
heavy metal doping in 2D materials.",1812.00157v2
2021-05-19,Synthesis and properties of free-standing monolayer amorphous carbon,"Bulk amorphous materials have been studied extensively and are widely used,
yet their atomic arrangement remains an open issue. Although they are generally
believed to be Zachariasen continuous random networks, recent experimental
evidence favours the competing crystallite model in the case of amorphous
silicon. In two-dimensional materials, however, the corresponding questions
remain unanswered. Here we report the synthesis, by laser-assisted chemical
vapour deposition, of centimetre-scale, free-standing, continuous and stable
monolayer amorphous carbon, topologically distinct from disordered graphene.
Unlike in bulk materials, the structure of monolayer amorphous carbon can be
determined by atomic-resolution imaging. Extensive characterization by Raman
and X-ray spectroscopy and transmission electron microscopy reveals the
complete absence of long-range periodicity and a threefold-coordinated
structure with a wide distribution of bond lengths, bond angles, and five-,
six-, seven- and eight-member rings. The ring distribution is not a Zachariasen
continuous random network, but resembles the competing (nano)crystallite model.
We construct a corresponding model that enables density-functional-theory
calculations of the properties of monolayer amorphous carbon, in accordance
with observations. Direct measurements confirm that it is insulating, with
resistivity values similar to those of boron nitride grown by chemical vapour
deposition. Free-standing monolayer amorphous carbon is surprisingly stable and
deforms to a high breaking strength, without crack propagation from the point
of fracture. The excellent physical properties of this stable, free-standing
monolayer amorphous carbon could prove useful for permeation and diffusion
barriers in applications such as magnetic recording devices and flexible
electronics.",2105.08926v1
2021-07-08,Synergistic effect of workfunction and acoustic impedance mismatch for improved thermoelectric performance in GeTe/WC composite,"The preparation of composite materials is promising for concurrent
optimization of electrical and thermal transport properties to realize an
improved thermoelectric (TE) performance. We report the effect of work function
and acoustic impedance mismatch (AIM) on the TE properties of
(1-z)Ge0.87Mn0.05Sb0.08Te/(z)WC composite. In particular, a composite
consisting of Mn and Sb co-doped GeTe as a matrix and WC as a dispersed phase
is prepared, and its structural and TE properties are investigated. The
simultaneous increase in electrical conductivity ({\sigma}) and Seebeck
coefficient ({\alpha}) with WC volume fraction (z) results in an enhanced power
factor ({\alpha}^2{\sigma}) in the composite. The rise in {\sigma} is
attributed to increased carrier mobility in the composite. This is further
established from the work function measurement using the Kelvin probe force
microscopy (KPFM) technique and is also supported by the density functional
theory (DFT) calculations. The difference in elastic properties (sound
velocity) between Ge0.87Mn0.05Sb0.08Te and WC results in a high AIM that leads
to a large interface thermal resistance (Rint) between the phases. The
correlation between Rint and the Kapitza radius results in reduced phonon
thermal conductivity (\kappa_ph) of the composite and is discussed using the
Bruggeman asymmetrical model. The decrease in \kappa_{ph} is further
established using phonon dispersion calculations that indicates the decrease in
phonon group velocity in the composite. The simultaneous effect of enhanced
{\alpha}^2{\sigma} and reduced \kappa_ph results in a maximum figure of merit
(zT) of 1.93 at 773K for (1-z)Ge0.87Mn0.05Sb0.08Te/(z)WC composite having
z=0.010. This study shows promise to achieve higher zTav across a wide range of
composite materials having similar electronic structure and different elastic
properties.",2107.03803v2
2022-09-09,Asymmetrical contact scaling and measurements in MoS2 FETs,"Two-dimensional (2D) materials have great potential for use in future
electronics due to their atomically thin nature which withstands short channel
effects and thus enables better scalability. Device scaling is the process of
reducing all device dimensions to achieve higher device density in a certain
chip area. For 2D materials-based transistors, both the channel and contact
scalability must be investigated. The channel scalability of 2D materials has
been thoroughly investigated, confirming their resilience to short-channel
effects. However, systematic studies on contact scalability remain rare and the
current understanding of contact scaling in 2D FET is inconsistent and
oversimplified. Here we combine physically scaled contacts and asymmetrical
contact measurements to investigate the contact scaling behavior in 2D
field-effect transistors (FETs). The asymmetrical contact measurements directly
compare electron injection with different contact lengths while using the exact
same channel, eliminating channel-to-channel variations. Compared to devices
with long contact lengths, devices with short contact lengths (scaled contacts)
exhibit larger variation, smaller drain currents at high drain-source voltages,
and a higher chance of showing early saturation and negative differential
resistance. Quantum transport simulations show that the transfer length of
Ni-MoS2 contacts can be as short as 5 nm. Our results suggest that charge
injection at the source contact is different from injection at the drain side:
scaled source contacts can limit the drain current, whereas scaled drain
contacts cannot. Furthermore, we clearly identified that the transfer length
depends on the quality of the metal-2D interface. The asymmetrical contact
measurements proposed here will enable further understanding of contact scaling
behavior at various interfaces.",2209.04144v2
2023-05-12,Disorder and cavity evolution in single-crystalline Ge during implantation of Sb ions monitored in-situ by spectroscopic ellipsometry,"Ion implantation has been a key technology for the controlled surface
modification of materials in microelectronics and generally, for tribology,
biocompatibility, corrosion resistance and many more. To form shallow junctions
in Ge is a challenging task. In this work the formation and accumulation of
shallow damage profiles was studied by in-situ spectroscopic ellipsometry (SE)
for the accurate tracking and evaluation of void and damage fractions in
crystalline Ge during implantation of 200-keV Sb ions with a total fluence up
to 1E16 cm-2 and an ion flux of 2.1E12 cm-2 s-1. The consecutive stages of
damage accumulation were identified using optical multi-layer models with
quantitative parameters of the thickness of modified layers as well as the
volume fractions of amorphized material and voids. The effective size of
damaged zones formed from ion tracks initiated by individual bombarding ions
can be estimated by numerical simulation compared with the dynamics of damage
profiles measured by ion beam analysis and ellipsometry. According to our
observations, the formation of initial partial disorder was followed by
complete amorphization and void formation occurring at the fluence of about
1E15 cm-2, leading to a high volume fraction of voids and a modified layer
thickness of approx. 200 nm by the end of the irradiation process. This agrees
with the results of numerical simulations and complementary scanning electron
microscopy (SEM) measurements. In addition, we found a quasi-periodic time
dependent behavior of amorphization and void formation represented by
alternating accelerations and decelerations of different reorganization
processes, respectively.",2305.07635v1
2006-03-08,Colossal Magnetoresistance Observed in Monte Carlo Simulations of the One- and Two-Orbital Models for Manganites,"The one- and two-orbital double-exchange models for manganites are studied
using Monte Carlo computational techniques in the presence of a robust
electron-phonon coupling (but neglecting the antiferromagnetic exchange $J_{\rm
AF}$ between the localized spins). The focus in this effort is on the analysis
of charge transport. Our results for the one-orbital case confirm and extend
previous recent investigations that showed the presence of robust peaks in the
resistivity vs. temperature curves for this model. Quenched disorder
substantially enhances the magnitude of the effect, while magnetic fields
drastically reduce the resistivity. A simple picture for the origin of these
results is presented. It is also shown that even for the case of just one
electron, the resistance curves present metallic and insulating regions by
varying the temperature, as it occurs at finite electronic density. Moreover,
in the present study these investigations are extended to the more realistic
two-orbital model for manganites. The transport results for this model show
large peaks in the resistivity vs. temperature curves, located at approximately
the Curie temperature, and with associated large magnetoresistance factors.
Overall, the magnitude and shape of the effects discussed here closely resemble
experiments for materials such as $\rm La_{0.70} Ca_{0.30} Mn O_{3}$, and they
are in qualitative agreement with the current predominant theoretical view that
competition between a metal and an insulator, enhanced by quenched disorder, is
crucial to understand the colossal magnetoresistance (CMR) phenomenon.",0603221v1
2017-11-02,Non-equilibrium character of resistive switching and negative differential resistance in Ga-doped Cr2O3 system,"We have synthesized Ga-doped Cr2O3 system with compositions Cr1.45Ga0.55O3
and Cr1.17Ga0.83O3 by chemical co-precipitation route and post annealing at
800^C. The samples have been stabilized in rhombohedral crystal structure with
space group R3C. The present work focuses on the study of non-linear
current-voltage (I-V) characteristics of the samples, which exhibited many
interesting electronic properties, e.g., I-V loop, resistive switching,
bi-stable electronic states, and negative differential resistance. The
non-equilibrium character of the I-V characteristics has been studied by
measurement of bias voltage cycling up to 20 times and current relaxation with
time at set bias voltage. The charge conduction process in the samples has been
understood by analysing I-V curves using different phenomenological models
based on electrode-limited and bulk-limited charge conduction mechanisms
proposed for metal electrode-metal oxide-metal electrode (M-MO-M) junctions. It
is understood that competitions between injection of charge carriers from metal
electrode to metal oxide, charge flow through the material
(trapping/de-trapping and recombination of charge carriers at the defect
sites), space charge formation at the junctions of electrodes and metal oxides,
and ejection of electrons from metal oxide to metal electrode control the
non-equilibrium I-V characteristics in the present samples.",1711.00687v1
2020-04-24,Graphene-Polyurethane Coatings for Deformable Conductors and Electromagnetic Interference Shielding,"Electrically conductive, polymeric materials that maintain their conductivity
even when under significant mechanical deformation are needed for actuator
electrodes, conformable electromagnetic shielding, stretchable tactile sensors
and flexible energy storage. The challenge for these materials is that the
percolated, electrically conductive networks tend to separate even at low
strains, leading to significant piezoresistance. Herein, deformable conductors
were fabricated by spray-coating a nitrile substrate with a graphene-elastomer
solution. The coatings showed only slight increase in electrical resistance
after thousands of bending cycles and repeated folding-unfolding events. The
deformable conductors doubled their electrical resistance at 12% strain and
were washable without changing their electrical properties. The
conductivity-strain behaviour was modelled by considering the nanofiller
separation upon deformation. To boost the conductivity at higher strains, the
production process was adapted by stretching the nitrile substrate before
spraying, after which it was released. This adaption meant that the electrical
resistance doubled at 25 % strain. The electrical resistance was found
sufficiently low to give a 1.9 dB/{\mu}m shielding in the 8-12 GHz
electromagnetic band. The physical and electrical properties, including the EM
screening, of the flexible conductors, were found to deteriorate upon cycling
but could be recovered through reheating the coating.",2004.11613v1
2016-03-20,Three-dimensional resistivity switching between correlated electronic states in 1T-TaS2,"Recent demonstrations of controlled switching between different ordered
macroscopic states by impulsive electromagnetic perturbations in complex
materials have opened some fundamental questions on the mechanisms responsible
for such remarkable behavior. Here we experimentally address the question of
whether two-dimensional (2D) Mott physics can be responsible for unusual
switching between states of different electronic order in the layered
dichalcogenide 1T-TaS2, or it is a result of subtle inter-layer orbitronic
re-ordering of its helical stacking structure. We report on the switching
properties both in-plane and perpendicular to the layers by current-pulse
injection, the anisotropy of electronic transport in the commensurate ground
state, and relaxation properties of the switched metastable state. Contrary to
recent theoretical calculations, which predict a uni-directional metal
perpendicular to the layers, we observe a large resistivity in this direction,
with a temperature-dependent anisotropy. Remarkably, large resistance ratios
are observed in the memristive switching both in-plane (IP) and out-of-plane
(OP). The relaxation dynamics of the metastable state for both IP and OP
electron transport are seemingly governed by the same mesoscopic quantum
re-ordering process. We conclude that 1T-TaS2 shows resistance switching
arising from an interplay of both IP and OP correlations.",1603.06214v1
2019-12-17,Antiferromagnetic CuMnAs: Ab initio description of finite temperature magnetism and resistivity,"Noncollinear magnetic moments in antiferromagnets (AFM) lead to a complex
behavior of electrical transport, even to a decreasing resistivity due to an
increasing temperature. Proper treatment of such phenomena is required for
understanding AFM systems at finite temperatures; however first-principles
description of these effects is complicated. With ab initio techniques, we
investigate three models of spin fluctuations (magnons) influencing the
transport in AFM CuMnAs; the models are numerically feasible and easily
implementable to other studies. We numerically justified a fully relativistic
collinear disordered local moment approach and we present its uncompensated
generalization. A saturation or a decrease of resistivity caused by magnons,
phonons, and their combination (above approx. 400 K) was observed and explained
by changes in electronic structure. Within the coherent potential
approximation, our finite-temperature approaches may be applied also to systems
with impurities, which are found to have a large impact not only on residual
resistivity, but also on canting of magnetic moments from the AFM to the
ferromagnetic (FM) state.",1912.08025v4
2020-12-30,Non-thermal light-assisted resistance collapse in a V$_2$O$_3$-based Mott-insulator device,"The insulator-to-metal transition in Mott insulators is the key mechanism for
a novel class of electronic devices, belonging to the Mottronics family.
Intense research efforts are currently devoted to the development of specific
control protocols, usually based on the application of voltage, strain,
pressure and light excitation. The ultimate goal is to achieve the complete
control of the electronic phase transformation, with dramatic impact on the
performance, for example, of resistive switching devices. Here, we investigate
the simultaneous effect of external voltage and excitation by ultrashort light
pulses on a single Mottronic device based on a V$_2$O$_3$ epitaxial thin film.
The experimental results, supported by finite-element simulations of the
thermal problem, demonstrate that the combination of light excitation and
external electrical bias drives a volatile resistivity drop which goes beyond
the combined effect of laser and Joule heating. Our results impact on the
development of protocols for the non-thermal control of the resistive switching
transition in correlated materials.",2012.15255v2
2023-06-07,Slip Resistance Test Apparatus of Synthetic Rubber Trackpad on Photovoltaic Surface,"The increasing development of the solar energy industry in many countries has
led to a rising frequency of human and robot presence in this area. To ensure
occupational safety, various protective equipment, including rubber material,
is commonly used for slip resistance while moving on the surface of solar PV
panels. Therefore, the slip resistance test apparatus is built for testing the
slip resistance between the synthetic rubber trackpad and the photovoltaic
panel (PV) surface. Synthetic rubber is a man-made material, so it is difficult
to control the parameters of its mechanical and chemical properties absolutely.
Variations in wet/dry working conditions or Shore hardness are factors that
make slip computation more challenging. Therefore, an apparatus with the
principle of converting the reciprocating motion of the screw and the casters
into the rotation of the hinge is introduced to adjust the tilt angle of the
upper surface, detect and evaluate the slippage of the rubber trackpad by
sensors. Some parameters related to accuracy such as vibration and
theoretical-empirical assessment, are also mentioned. In addition to designing
a reliable apparatus, the article also succeeded in providing a safety standard
for synthetic rubber with Shore A30-A40 when moving on PV surfaces.",2306.10032v1
2023-08-14,Temperature-dependent $f$-electron evolution in CeCoIn$_5$ via a comparative infrared study with LaCoIn$_5$,"We investigated CeCoIn$_5$ and LaCoIn$_5$ single crystals, which have the
same HoCoGa$_5$-type tetragonal crystal structure, using infrared spectroscopy.
However, while CeCoIn$_5$ has 4$f$ electrons, LaCoIn$_5$ does not. By comparing
these two material systems, we extracted the temperature-dependent electronic
evolution of the $f$ electrons of CeCoIn$_5$. We observed that the differences
caused by the $f$ electrons are more obvious in low-energy optical spectra at
low temperatures. We introduced a complex optical resistivity and obtained a
magnetic optical resistivity from the difference in the optical resistivity
spectra of the two material systems. From the temperature-dependent average
magnetic resistivity, we found that the onset temperature of the Kondo effect
is much higher than the known onset temperature of Kondo scattering ($\simeq$
200 K) of CeCoIn$_5$. Based on momentum-dependent hybridization, the periodic
Anderson model, and a maximum entropy approach, we obtained the hybridization
gap distribution function of CeCoIn$_5$ and found that the resulting gap
distribution function of CeCoIn$_5$ was mainly composed of two (small and
large) components (or gaps). We assigned the small and large gaps to the
in-plane and out-of-plane hybridization gaps, respectively. We expect that our
results will provide useful information for understanding the
temperature-dependent electronic evolution of $f$-electron systems near Fermi
level.",2308.06881v1
2024-02-01,Mott resistive switching initiated by topological defects,"Resistive switching is the fundamental process that triggers the sudden
change of the electrical properties in solid-state devices under the action of
intense electric fields. Despite its relevance for information processing,
ultrafast electronics, neuromorphic devices, resistive memories and
brain-inspired computation, the nature of the local stochastic fluctuations
that drive the formation of metallic nuclei out of the insulating state has
remained hidden. Here, using operando X-ray nano-imaging, we have captured the
early-stages of resistive switching in a V2O3-based device under working
conditions. V2O3 is a paradigmatic Mott material, which undergoes a first-order
metal-to-insulator transition coupled to a lattice transformation that breaks
the threefold rotational symmetry of the rhombohedral metal phase. We reveal a
new class of volatile electronic switching triggered by nanoscale topological
defects of the lattice order parameter of the insulating phase. Our results
pave the way to the use of strain engineering approaches to manipulate
topological defects and achieve the full control of the electronic Mott
switching. The concept of topology-driven reversible electronic transition is
of interest for a broad class of quantum materials, comprising transition metal
oxides, chalcogenides and kagome metals, that exhibit first-order electronic
transitions coupled to a symmetry-breaking order.",2402.00747v1
2024-05-14,"A new ferromagnetic semiconductor system of Eu$_{1-x}$Sr$_x$AgP $(x = 0.0-0.6)$ compounds: Crystallographic, magnetic, and magneto-resistive properties","Adjusting chemical pressure through doping is a highly effective method for
customizing the chemical and physical properties of materials, along with their
respective phase diagrams, thereby uncovering novel quantum phenomena. Here, we
successfully synthesized Sr-doped Eu$_{1-x}$Sr$_x$AgP $(x = 0.0-0.6)$ and
conducted a comprehensive investigation involving crystallography,
magnetization, heat capacity, and magnetoresistance. Utilizing X-ray
diffraction and PPMS DynaCool measurements, we studied Eu$_{1-x}$Sr$_x$AgP in
detail. The hexagonal structure of parent EuAgP at room temperature, with the
$P6_3/mmc$ space group, remains unaltered, while the lattice constants expand.
The magnetic phase transition from paramagnetism to ferromagnetism, as
temperature decreases, is suppressed through the gradual introduction of
strontium doping. Heat capacity measurements reveal a shift from
magnon-dominated to predominantly phonon and electron contributions near the
ferromagnetic phase with increasing doping levels. The resistivity-temperature
relationship displays distinct characteristics, emphasizing the impact of Sr
doping on modifying charge transport. Magnetoresistance measurements uncover
novel phenomena, illustrating the adjustability of magnetoresistance through Sr
doping. Notably, Sr doping results in both positive magnetoresistance (up to
20\%) and negative magnetoresistance (approximately -60\%). The resistivity and
magnetic phase diagram were established for the first time, revealing the
pronounced feasibility of Sr doping in modulating EuAgP's resistivity. This
study has provided valuable insights into the intricate interplay between
structural modifications and diverse physical properties. The potential for
technological advancements and the exploration of novel quantum states make
Sr-doped Eu$_{1-x}$Sr$_x$AgP a compelling subject for continued research in the
field of applied physics.",2405.08357v1
1999-04-01,Radio-frequency impedance measurements using a tunnel-diode oscillator (TDO) technique,"A resonant method based on a tunnel-diode oscillator (TDO) for precision
measurements of relative impedance changes in materials, is described. The
system consists of an effective self-resonant LC-tank circuit driven by a
forward-biased tunnel diode operating in its negative resistance region.
Samples under investigation are placed in the core of an inductive coil and
impedance changes are determined directly from the measured shift in resonance
frequency. A customized low temperature insert is used to integrate this
experiment with a commercial Model 6000 Physical Property Measurement System
(Quantum Design). Test measurements on a manganese-based perovskite sample
exhibiting colossal magneto-resistance (CMR) indicate that this method is well
suited to study the magneto-impedance in these materials.",9904026v1
2000-01-19,Pseudogap effects on the c-axis charge dynamics in copper oxide materials,"The c-axis charge dynamics of copper oxide materials in the underdoped and
optimally doped regimes has been studied by considering the incoherent
interlayer hopping. It is shown that the c-axis charge dynamics for the chain
copper oxide materials is mainly governed by the scattering from the in-plane
fluctuation, and the c-axis charge dynamics for the no-chain copper oxide
materials is dominated by the scattering from the in-plane fluctuation
incorporating with the interlayer disorder, which would be suppressed when the
holon pseudogap opens at low temperatures and lower doping levels, leading to
the crossovers to the semiconducting-like range in the c-axis resistivity and
the temperature linear to the nonlinear range in the in-plane resistivity.",0001260v1
2002-02-27,Anisotropic Magnetoresistance in Ga$_{1-x}$Mn$_x$As,"We have measured the magnetoresistance in a series of Ga$_{1-x}$Mn$_x$As
samples with 0.033$\le x \le$ 0.053 for three mutually orthogonal orientations
of the applied magnetic field. The spontaneous resistivity anisotropy (SRA) in
these materials is negative (i.e. the sample resistance is higher when its
magnetization is perpendicular to the measuring current than when the two are
parallel) and has a magnitude on the order of 5% at temperatures near 10K and
below. This stands in contrast to the results for most conventional magnetic
materials where the SRA is considerably smaller in magnitude for those few
cases in which a negative sign is observed. The magnitude of the SRA drops from
its maximum at low temperatures to zero at T$_C$ in a manner that is consistent
with mean field theory. These results should provide a significant test for
emerging theories of transport in this new class of materials.",0202508v1
2008-05-28,Unified explanation of the Kadowaki-Woods ratio in strongly correlated materials,"Discoveries of ratios whose values are constant within broad classes of
materials have led to many deep physical insights. The Kadowaki-Woods ratio
(KWR) compares the temperature dependence of a metal's resistivity to that of
its heat capacity; thereby probing the relationship between the
electron-electron scattering rate and the renormalisation of the electron mass.
However, the KWR takes very different values in different materials. Here we
introduce a ratio, closely related to the KWR, that includes the effects of
carrier density and spatial dimensionality and takes the same (predicted) value
in organic charge transfer salts, transition metal oxides, heavy fermions and
transition metals - despite the numerator and denominator varying by ten orders
of magnitude. Hence, in these materials, the same emergent physics is
responsible for the mass enhancement and the quadratic temperature dependence
of the resistivity and no exotic explanations of their KWRs are required.",0805.4275v4
2016-06-15,Suppression of lattice thermal conductivity by mass-conserving cation mutation in multi-component semiconductors,"In semiconductors almost all heat is conducted by phonons (lattice
vibrations), which is limited by their quasi-particle lifetimes. Phonon-phonon
interactions represent scattering mechanisms that produce thermal resistance.
In thermoelectric materials, this resistance due to anharmonicity should be
maximised for optimal performance. We use a first-principles lattice-dynamics
approach to explore the changes in lattice dynamics across an isostructural
series where the average atomic mass is conserved: ZnS to CuGaS$_2$ to
Cu$_2$ZnGeS$_4$. Our results demonstrate an enhancement of phonon interactions
in the multernary materials, and confirm that lattice thermal conductivity can
be controlled independently of the average mass and local coordination
environments.",1606.04914v1
2018-06-12,Determination of the BCS material parameters of the HIE-ISOLDE superconducting resonator,"Superconducting material parameters of the Nb film coating on the
Quarter-Wave Resonator (QWR) for the HIE-ISOLDE project were studied by fitting
experimental results with the Mattis-Bardeen theory. We pointed out a strong
correlation among fitted estimators of material parameters in the BCS theory,
and proposed a procedure to remove the correlation by simultaneously fitting
the surface resistance and effective penetration depth. Unlike previous
studies, no literature values were assumed in the fitting. As surface
resistance and penetration depth had a similar dependence on coherence length
and mean free path, the correlation between these two parameters could not be
eliminated by this fitting. The upper critical field measured by SQUID
magnetometry showed complementary constraint to the RF result, and this allowed
all the material parameters to be determined.",1806.04443v1
2018-09-19,Electrical Parameters for Planar Transport in Graphene and 2-D Materials,"Classical electrodynamics has been revisited with a view to recast the
electrical parameters for planar transport in 2-dimensional (2-D) materials
like graphene. In this attempt a new line integral, named transverse line
integral, with extensive applications in 2-D, is defined. Since the existing
divergence theorem in not applicable in 2-D, we introduced a new divergence
theorem. A new definition for the in-plane flux of any 2-D vector is
introduced. A new vector named electric vector potential is defined and Gauss
law is modified in terms of the 2-D flux of the new vector. The new Gauss law
in presence of dielectric is obtained and a new electric displacement vector is
defined for the 2-D materials. The conduction and displacement current
densities in 2-D are defined. Resistance and resistivity in 2-D materials are
discussed. The continuity equation for planar transport is derived.",1809.07319v1
2020-09-04,Fracture mechanics of micro samples: Fundamental considerations,"In this review article we consider the crack growth resistance ofmicrometer
and submicrometer sized samples from the fracture mechanics point of view.
Standard fracture mechanics test procedures were developed for macroscale
samples, and reduction of the specimen dimensions by three to five orders of
magnitude has severe consequences. This concerns the interpretation of results
obtained by micro and nanomechanics, as well as the life time and failure
prediction of micro and nano devices. We discuss the relevant fracture
mechanics length scales and their relation to the material specific structural
lengths in order to conduct rigorous fracture mechanics experiments. To ensure
general validity and applicability of evaluation concepts, these scaling
considerations are detailed for ideally brittle, semi brittle and micro ductile
crack propagation, subject to both monotonic and cyclic loading. Special
attention is devoted to the requirements for determining specimen size for
various loading types to measure material characteristic crack propagation
resistance at small scales. Finally, we discuss novel possibilities of micron
and submicron fracture mechanics tests to improve the basic understanding of
specific crack propagation processes.",2009.05386v1
2015-07-23,Ba{0.4}Rb{0.6}Mn2As2: A Prototype Half-Metallic Ferromagnet,"Half-metallic ferromagnetism (FM) in single-crystal
Ba{0.39(1)}Rb{0.61(1)}Mn2As2 below its Curie temperature TC = 103(2) K is
reported. The magnetization M versus applied magnetic field H isotherm data at
1.8 K show complete polarization of the itinerant doped-hole magnetic moments
that are introduced by substituting Rb for Ba. The material exhibits extremely
soft FM, with unobservably small remanent magnetization and coercive field.
Surprisingly, and contrary to typical itinerant FMs, the M(H) data follow the
Arrott-plot paradigm that is based on a mean-field theory of local-moment FMs.
The in-plane electrical resistivity data are fitted well by an activated-T^2
expression for T < TC, whereas the data sharply deviate from this model for T >
TC. Hence the activated-T^2 resistivity model is an excellent diagnostic for
determining the onset of half-metallic FM in this compound, which in turn
demonstrates the presence of a strong correlation between the electronic
transport and magnetic properties of the material. Together with previous data
on 40% hole-doped Ba{0.6}K{0.4}Mn2As2, these measurements establish 61%-doped
Ba{0.39}Rb{0.61}Mn2As2 as a prototype for a new class of half-metallic
ferromagnets in which all the itinerant carriers in the material are
ferromagnetic.",1507.06679v1
2018-12-18,Atomistic study of an ideal metal/thermoelectric contact: the full-Heusler/half-Heusler interface,"Half-Heusler alloys such as the (Zr,Hf)NiSn intermetallic compounds are
important thermoelectric materials for converting waste heat into electricity.
Reduced electrical resistivity at the hot interface between the half-Heusler
material and a metal contact is critical for device performance, however this
has yet to be achieved in practice. Recent experimental work suggests that a
coherent interface between half-Heusler and full-Heusler compounds can form due
to diffusion of transition metal atoms into the vacant sublattice of the
half-Heusler lattice. We study theoretically the structural and electronic
properties of such an interface using a first-principles based approach that
combines {\it ab initio} calculations with macroscopic modeling. We find that
the prototypical interface HfNi$_2$Sn/HfNiSn provides very low contact
resistivity and almost ohmic behavior over a wide range of temperatures and
doping levels. Given the potential of these interfaces to remain stable over a
wide range of temperatures, our study suggests that full-Heuslers might provide
nearly ideal electrical contacts to half-Heuslers that can be harnessed for
efficient thermoelectric generator devices.",1812.07189v1
2020-11-21,All-Materials-Inclusive Flash Spark Plasma Sintering,"A new flash (ultra-rapid) spark plasma sintering method applicable to various
materials systems, regardless of their electrical resistivity, is developed. A
number of powders ranging from metals to electrically insulative ceramics have
been successfully densified resulting in homogeneous microstructures within
sintering times of 8-35 s. A finite element simulation reveals that the
developed method, providing an extraordinary fast and homogeneous heating
concentrated in the sample's volume and punches, is applicable to all the
different samples tested. The utilized uniquely controllable flash phenomenon
is enabled by the combination of the electric current concentration around the
sample and the confinement of the heat generated in this area by the lateral
thermal contact resistance. The presented new method allows: extending flash
sintering to nearly all materials, controlling sample shape by an added
graphite die, and an energy efficient mass production of small and intermediate
size objects. This approach represents also a potential venue for future
investigations of flash sintering of complex shapes.",2011.14012v1
2021-03-26,A micropolar continuum model of diffusion creep,"Solid polycrystalline materials undergoing diffusion creep are usually
described by Cauchy continuum models with a Newtonian viscous rheology
dependent on the grain size. Such a continuum lacks the rotational degrees of
freedom needed to describe grain rotation. Here we provide a more general
continuum description of diffusion creep that includes grain rotation, and
identifies the deformation of the material with that of a micropolar (Cosserat)
fluid. We derive expressions for the micropolar constitutive tensors by a
homogenisation of the physics describing a discrete collection of rigid grains,
demanding an equivalent dissipation between the discrete and continuum
descriptions. General constitutive laws are derived for both Coble
(grain-boundary diffusion) and Nabarro-Herring (volume diffusion) creep.
Detailed calculations are performed for a two-dimensional tiling of irregular
hexagonal grains, which illustrates a potential coupling between the rotational
and translational degrees of freedom. If only the plating out or removal of
material at grain boundaries is considered, the constitutive laws are
degenerate: modes of deformation that involve pure tangential motion at the
grain boundaries are not resisted. This degeneracy can be removed by including
the resistance to grain-boundary sliding, or by imposing additional constraints
on the deformation.",2103.14458v3
2021-04-30,Material surface -- analyte interactions with similar energy rates vary as univariate quadratic function of topological polar surface area of analytes,"Material surface - analyte interactions play important roles in numerous
processes including gas sensing. However, the effects of topological polar
surface area (TPSA) of analytes on surface interactions during gas sensing have
been so far largely disregarded. In this work, based on experimental
observations on changes in electrical resistance of cadmium sulphide (CdS) due
to surface interactions during gas sensing, we found that unexpected univariate
quadratic correlation exists between changes in resistance of CdS and TPSA of
analytes. Further experiments on four other material systems showed the same
trend, revealing a generalized picture of TPSA dependence of surface
interactions.",2104.14867v1
2022-06-08,Scalable fabrication of edge contacts to 2D materials,"We present a fabrication method for reliably and reproducibly forming
electrical contacts to 2D materials, based on the tri-layer resist system. We
demonstrate the applicability of this method for epitaxial graphene on silicon
carbide (epigraphene) and the transition metal dichalcogenides (TMDCs)
molybdenum disulfide ($MoS_2$). For epigraphene, the specific contact
resistances are of the order of $\rho_c$ ~ $50$ $\Omega\mu m$, and follow the
Landauer quantum limit, $\rho_c \propto n^{-1/2}$, with $n$ being the carrier
density of graphene. For $MoS_2$ flakes, our edge contacts enable field effect
transistors (FET) with ON/OFF ratio of $> 10^6$ at room temperature ( $> 10^9$
at cryogenic temperatures). The fabrication route here demonstrated allows for
contact metallization using thermal evaporation and also by sputtering, giving
an additional flexibility when designing electrical interfaces, which is key in
practical devices and when exploring the electrical properties of emerging
materials.",2206.03839v2
2022-07-04,An Important Structural Requirement for the Superconductor Material: A Hypothesis,"On a microscopic scale, resistivity during electric conduction is caused by
collisions of the free conduction electrons with the obstructing atoms or
molecules of the conductor material, resulting in heat production. Based on
this fundamental understanding, a hypothesis concerning a physical requirement
of the superconductor material is proposed, which suggests that for
superconductivity (i.e., with zero resistivity) to occur, the conductor
material must have nano-sized, continuous and straight vacuum tunnels inside
with effective radius size large enough to allow collision-free conduction of
free electrons. Besides, some of the composite atoms of the conductor should be
able to readily release electrons to form the conduction band; in fact, this
basic requirement is for all forms of electrical conductors, not just for
superconductors. The proposed hypothesis is supported by experimental
observations in the literature, and also offers a plausible explanation for
some of the poorly-understood experimental phenomena observed in the past. In
addition, the hypothesis offers practical strategies for the rational design of
electrical conductors with (quasi-)superconductivity. Lastly, the proposed new
hypothesis also suggests a novel mechanism for neural microtubule-mediated
electrical quasi-superconductance in the nervous system.",2207.01226v2
1994-06-03,"Localization Effects in Bi2Sr2Ca(Cu,Co)2O8+y High Temperature Superconductors","Doping Bi2Sr2Ca1Cu2O8+y with Co causes a superconductor-insulator transition.
We study correlations between changes in the electrical resistivity RHOab(T)
and the electronic bandstructure using identical single crystalline samples.
For undoped samples the resistivity is linear in temperature and has a
vanishing residual resistivity. In angle resolved photoemission these samples
show dispersing band-like states. Co-doping decreases TC and causes and
increase in the residual resistivity. Above a threshold Co-concentration the
resistivity is metallic (drab/dT >0) at room temperature, turns insulating
below a characteristic temperature Tmin and becomes super- conducting at even
lower temperature. These changes in the resistivity correlate with the
disappearance of the dispersing band-like states in angle resolved
photoemission. We show that Anderson localization caused by the impurity
potential of the doped Co-atoms provides a consistent explanation of all
experimental features. Therefore the TC reduction in 3d-metal doped high-
temperature superconductors is not caused by Abrikosov Gor'kov pair- breaking
but by spatial localization of the carriers. The observed suppression of TC
indicates that the system is in the homogenous limit of the
superconductor-insulator transition. The coexistance of insulating (dRHOab/dT
<0) normal state behavior and super- conductivity indicates that the
superconducting ground state is formed out of spatially almost localized
carriers.",9406021v1
2011-11-17,Stability of a self-gravitating homogeneous resistive plasma,"In this paper, we analyze the stability of a homogeneous self-gravitating
plasma, having a non-zero resistivity. This study provides a generalization of
the Jeans paradigm for determining the critical scale above which gravitational
collapse is allowed. We start by discussing the stability of an ideal
self-gravitating plasma embedded in a constant magnetic field. We outline the
existence of an anisotropic feature of the gravitational collapse. In fact,
while in the plane orthogonal to the magnetic field the Jeans length is
enhanced by the contribution of the magnetic pressure, outside this plane
perturbations are governed by the usual Jeans criterium. The anisotropic
collapse of a density contrast is sketched in details, suggesting that the
linear evolution provides anisotropic initial conditions for the non-linear
stage, where this effect could be strongly enforced. The same problem is then
faced in the presence of non-zero resistivity and the conditions for the
gravitational collapse are correspondingly extended. The relevant feature
emerging in this resistive scenario is the cancellation of the collapse
anisotropy in weakly conducting plasmas. In this case, the instability of a
self-gravitating resistive plasma is characterized by the standard isotropic
Jeans length in any directions. The limit of very small resistivity coefficient
is finally addressed, elucidating how reminiscence of the collapse anisotropy
can be found in the different value of the perturbation frequency inside and
outside the plane orthogonal to the magnetic field.",1111.4051v1
2013-02-26,Inter-plane resistivity of isovalent doped BaFe$_2$(As$_{1-x}$P$_x$)$_2$,"Temperature-dependent inter-plane resistivity, $\rho_c(T)$, was measured for
the iron-based superconductor BaFe$_2$(As$_{1-x}$P$_x$)$_2$ over a broad
isoelectron phosphorus substitution range from $x$=0 to $x$=0.60, from
non-superconducting parent compound to heavily overdoped superconducting
composition with $T_c\approx 10 K$. The features due to structural and magnetic
transitions are clearly resolved in $\rho_c(T)$ of the underdoped crystals. A
characteristic maximum in $\rho_c(T)$, found in the parent BaFe$_2$As$_2$ at
around 200 K, moves rapidly with phosphorus substitution to high temperatures.
At the optimal doping, the inter-plane resistivity shows $T$-linear temperature
dependence without any cross-over anomalies, similar to the previously reported
in-plane resistivity. This observation is in stark contrast with dissimilar
temperature dependences found at optimal doping in electron-doped
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$. Our finding suggests that despite similar
values of the resistivity and its anisotropy, the temperature dependent
transport in the normal state is very different in electron and isoelectron
doped compounds. Similar temperature dependence of both in-plane and
inter-plane resistivities, in which the dominant contributions are coming from
different parts of the Fermi surface, suggests that scattering is the same on
the whole Fermi surface. Since magnetic fluctuations are expected to be much
stronger on the quasi-nested sheets, this observation may point to the
importance of the inter-orbital scattering between different sheets.",1302.6440v1
2013-05-16,Effect of doping on the magnetostructural ordered phase of iron arsenides: A comparative study of the resistivity anisotropy in the doped BaFe$_2$As$_2$ with doping into three different sites,"In order to unravel a role of doping in the iron-based superconductors, we
investigated the in-plane resistivity for BaFe$_2$As$_2$ doped at either of the
three different lattice sites, Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$,
BaFe$_2$(As$_{1-x}$P$_x$)$_2$, and Ba$_{1-x}$K$_x$Fe$_2$As$_2$, focusing on the
doping effect in the low-temperature antiferromagnetic/orthorhombic (AFO)
phase. A major role of doping in the high-temperature paramagnetic/tetragonal
(PT) phase is known to change the Fermi surface by supplying charge carriers or
by exerting chemical pressure. In the AFO phase, we found a clear correlation
between the magnitude of residual resistivity and resistivity anisotropy. This
indicates that the resistivity anisotropy originates from the anisotropic
impurity scattering from dopant atoms. The magnitude of residual resistivity is
also found to be a parameter controlling the suppression rate of AFO ordering
temperature $T_s$. Therefore, the dominant role of doping in the AFO phase is
to introduce disorder to the system, distinct from that in the PT phase.",1305.3744v1
2016-01-13,Limiting the Development of Anti-Cancer Drug Resistance in a Spatial Model of Micrometastases,"While chemoresistance in primary tumors is well-studied, much less is known
about the influence of systemic chemotherapy on the development of drug
resistance at metastatic sites. In this work, we use a hybrid spatial model of
tumor response to a DNA damaging drug to study how the development of
chemoresistance in micrometastases depends on the drug dosing schedule. We
separately consider cell populations that harbor pre-existing resistance to the
drug, and those that acquire resistance during the course of treatment. For
each of these independent scenarios, we consider one hypothetical cell line
that is responsive to metronomic chemotherapy, and another that with high
probability cannot be eradicated by a metronomic protocol. Motivated by
experimental work on ovarian cancer xenografts, we consider all possible
combinations of a one week treatment protocol, repeated for three weeks, and
constrained by the total weekly drug dose. Simulations reveal a small number of
fractionated-dose protocols that are at least as effective as metronomic
therapy in eradicating micrometastases with acquired resistance (weak or
strong), while also being at least as effective on those that harbor weakly
pre-existing resistant cells. Given the responsiveness of very different
theoretical cell lines to these few fractionated-dose protocols, these may
represent more effective ways to schedule chemotherapy with the goal of
limiting metastatic tumor progression.",1601.03412v2
2014-01-08,Angular and Polarization Response of Multimode Sensors with Resistive-Grid Absorbers,"High sensitivity receiver systems with near ideal polarization sensitivity
are highly desirable for development of millimeter and sub-millimeter radio
astronomy. Multimoded bolometers provide a unique solution to achieve such
sensitivity, for which hundreds of single-mode sensors would otherwise be
required. The primary concern in employing such multimoded sensors for
polarimetery is the control of the polarization systematics. In this paper, we
examine the angular- and polarization- dependent absorption pattern of a thin
resistive grid or membrane, which models an absorber used for a multimoded
bolometer. The result shows that a freestanding thin resistive absorber with a
surface resistivity of \eta/2, where \eta\ is the impedance of free space,
attains a beam pattern with equal E- and H-plane responses, leading to zero
cross polarization. For a resistive-grid absorber, the condition is met when a
pair of grids is positioned orthogonal to each other and both have a
resistivity of \eta/2. When a reflective backshort termination is employed to
improve absorption efficiency, the cross-polar level can be suppressed below
-30 dB if acceptance angle of the sensor is limited to <60degrees. The small
cross-polar systematics have even-parity patterns and do not contaminate the
measurements of odd-parity polarization patterns, for which many of recent
instruments for cosmic microwave background are designed. Underlying symmetry
that suppresses these cross-polar systematics is discussed in detail. The
estimates and formalism provided in this paper offer key tools in the design
consideration of the instruments using the multimoded polarimeters.",1401.1859v1
2021-08-30,Clonal Diversity at Cancer Recurrence,"Despite initial success, cancer therapies often fail due to the emergence of
drug-resistant cells. In this study, we use a mathematical model to investigate
how cancer evolves over time, specifically focusing on the state of the tumor
when it recurs after treatment. We use a two-type branching process to capture
the dynamics of both drug-sensitive and drug-resistant cells. We analyze the
clonal diversity of drug-resistant cells at the time of cancer recurrence,
which is defined as the first time the population size of drug-resistant cells
exceeds a specified proportion of the initial population size of drug-sensitive
cells. We examine two clonal diversity indices: the number of clones and the
Simpson's Index. We calculate the expected values of these indices and utilize
them to develop statistical methods for estimating model parameters.
Additionally, we examine these two indices conditioned on early recurrence in
the special case of a deterministically decaying sensitive population, with the
aim of addressing the question of whether early recurrence is driven by a
single mutation that generates an unusually large family of drug-resistant
cells (corresponding to a low clonal diversity), or if it is due to the
presence of an unusually large number of mutations causing drug resistance
(corresponding to a high clonal diversity). Our findings, based on both
indices, support the latter possibility. Furthermore, we demonstrate that the
time of cancer recurrence can serve as a valuable indicator of clonal
diversity, offering new insights for the treatment of recurrent cancers.",2108.13472v3
2022-03-23,A Fast Diagnostic to Inform Screening of Discarded or Retired Batteries,"With the increased pervasiveness of Lithium-ion batteries, there is growing
concern for the amount of retired batteries that will be entering the waste
stream. Although these batteries no longer meet the demands of their first
application, many still have a significant portion of their initial capacity
remaining for use in secondary applications. Yet, direct repurposing is
generally not possible and each cell in a battery must be evaluated, increasing
the cost of the repurposed packs due to the time intensive screening process.
In this paper, a rapid assessment of the internal resistance of a cell is
proposed. First, this method of measuring the resistance is completed on cells
from twelve retired battery packs and one fresh pack using a hybrid pulse power
characterization (HPPC) test as a benchmark for the analysis. Results from
these tests show relatively constant resistance measurements across mid to high
terminal voltages, allowing this metric to be independent of state of charge
(SOC). Then, the relation between internal resistance and capacity across the
various packs is discussed. Initial experimental results from this study show a
correlation between internal resistance and capacity which can be approximated
with a linear fit, suggesting internal resistance measurements taken above a
threshold cell terminal voltage may be a suitable initial screening metric for
the capacity of retired cells without knowledge of the SOC.",2203.12376v1
2023-01-15,Effects of quantum recoil forces in resistive switching in memristors,"Memristive devices, whose resistance can be controlled by applying a voltage
and further retained, are attractive as possible circuit elements for
neuromorphic computing. This new type of devices poses a number of both
technological and theoretical challenges. Even the physics of the key process
of resistive switching, usually associated with formation or breakage of
conductive filaments in the memristor, is not completely understood yet. This
work proposes a new resistive switching mechanism, which should be important in
the thin-filament regime and take place due to the back reaction, or recoil, of
quantum charge carriers -- independently of the conventional
electrostatically-driven ion migration. Since thinnest conductive filaments are
in question, which are only several atoms thick and allow for a
quasi-ballistic, quantized conductance, we use a mean-field theory and the
framework of nonequilibrium Green's functions to discuss the electron recoil
effect for a quantum current through a nanofilament on its geometry and compare
it with the transmission probability of charge carriers. Namely, we first study
an analytically tractable toy model of a 1D atomic chain, to qualitatively
demonstrate the importance of the charge-carrier recoil, and further proceed
with a realistic molecular-dynamics simulation of the recoil-driven ion
migration along a copper filament and the resulting resistive switching. The
results obtained are expected to add to the understanding of resistive
switching mechanisms at the nanoscale and to help downscale high-retention
memristive devices.",2301.06066v2
2024-01-16,Resistively controlled primordial magnetic turbulence decay,"Magnetic fields generated in the early Universe undergo turbulent decay
during the radiation-dominated era. The decay is governed by a decay exponent
and a decay time. It has been argued that the latter is prolonged by magnetic
reconnection, which depends on the microphysical resistivity and viscosity.
Turbulence, on the other hand, is not usually expected to be sensitive to
microphysical dissipation, which affects only very small scales. We want to
test and quantify the reconnection hypothesis in decaying hydromagnetic
turbulence. We performed high-resolution numerical simulations with zero net
magnetic helicity using the Pencil Code with up to $2048^3$ mesh points and
relate the decay time to the Alfv\'en time for different resistivities and
viscosities. The decay time is found to be longer than the Alfv\'en time by a
factor that increases with increasing Lundquist number to the 1/4 power. The
decay exponent is as expected from the conservation of the Hosking integral,
but a timescale dependence on resistivity is unusual for developed turbulence
and not found for hydrodynamic turbulence. In two dimensions, the Lundquist
number dependence is shown to be leveling off above values of $\approx25,000$,
independently of the value of the viscosity. Our numerical results suggest that
resistivity effects have been overestimated in earlier work. Instead of
reconnection, it may be the magnetic helicity density in smaller patches that
is responsible for the resistively slow decay. The leveling off at large
Lundquist number cannot currently be confirmed in three dimensions.",2401.08569v3
2015-09-11,Model of Flux Trapping in Cooling Down Process,"The flux trapping that occurs in the process of cooling down of the
superconducting cavity is studied. The critical fields $B_{c2}$ and $B_{c1}$
depend on a position when a material temperature is not uniform. In a region
with $T\simeq T_c$, $B_{c2}$ and $B_{c1}$ are strongly suppressed and can be
smaller than the ambient magnetic field, $B_a$. A region with $B_{c2}\le B_a$
is normal conducting, that with $B_{c1}\le B_a < B_{c2}$ is in the vortex
state, and that with $B_{c1}> B_a$ is in the Meissner state. As a material is
cooled down, these three domains including the vortex state domain sweep and
pass through the material. In this process, vortices contained in the vortex
state domain are trapped by pinning centers distributing in the material. A
number of trapped fluxes can be evaluated by using the analogy with the
beam-target collision event, where beams and a target correspond to pinning
centers and the vortex state domain, respectively. We find a number of trapped
fluxes and thus the residual resistance are proportional to the ambient
magnetic field and the inverse of the temperature gradient. The obtained
formula for the residual resistance is consistent with experimental results.
The present model focuses on what happens at the phase transition fronts during
a cooling down, reveals why and how the residual resistance depends on the
temperature gradient, and naturally explains how the fast cooling works.",1509.03369v1
2020-06-21,A Novel Magnetic Material by Design: Observation of Yb3+ with Spin-1/2 and Possible Superconducting Trace in YbxPt5P,"The localized f-electrons enrich the magnetic properties in rare-earth-based
intermetallics. Among those, compounds with heavier 4d and 5d transition metals
are even more fascinating because anomalous electronic properties may be
induced by the hybridization of 4f and itinerant conduction electrons primarily
from the d orbitals. Here, we describe the observation of trivalent Yb3+ with S
= 1/2 at low temperatures in YbxPt5P, the first of a new family of materials.
YbxPt5P (0.20< x <1) phases were synthesized and structurally characterized.
They exhibit a large homogeneity width with the Yb ratio exclusively occupying
the 1a site in the anti-CeCoIn5 structure. Moreover, the resistivity
measurement of a sample analyzed as Yb0.25Pt5P shows it to exist a complete
zero-resistance transition with a critical transition temperature of ~0.6 K,
possible superconductivity. However, the zero-resistivity transition was not
observed in YbPt5P with antiferromagnetic ordering existing solely.
First-principles electronic structure calculations substantiate the
antiferromagnetic ground state and indicate that 2D nesting around the Fermi
level may give rise to exotic physical properties, such as superconductivity.
YbxPt5P appears to be a unique case among materials.",2006.11891v1
2024-03-19,Giant electrode effect on tunneling magnetoresistance and electroresistance in van der Waals intrinsic multiferroic tunnel junctions using VS2,"Van der Waals multiferroic tunnel junctions (vdW-MFTJs) with multiple
nonvolatile resistive states are highly suitable for new physics and
next-generation storage electronics. However, currently reported vdW-MFTJs are
based on two types of materials, i.e., vdW ferromagnetic and ferroelectric
materials, forming a multiferroic system. This undoubtedly introduces
additional interfaces, increasing the complexity of experimental preparation.
Herein, we engineer vdW intrinsic MFTJs utilizing bilayer VS$_2$. By employing
the nonequilibrium Green's function combined with density functional theory, we
systematically investigate the influence of three types of electrodes
(including non-vdW pure metal Ag/Au, vdW metallic 1T-MoS$_2$/2H-PtTe$_2$, and
vdW ferromagnetic metallic Fe$_3$GaTe$_2$/Fe$_3$GeTe$_2$) on the electronic
transport properties of VS$_2$-based intrinsic MFTJs. We demonstrate that these
MFTJs manifest a giant electrode-dependent electronic transport characteristic
effect. Comprehensively comparing these electrode pairs, the
Fe$_3$GaTe$_2$/Fe$_3$GeTe$_2$ electrode combination exhibits optimal transport
properties, the maximum TMR (TER) can reach 10949\% (69\%) and the minimum
resistance-area product (RA) is 0.45 $\Omega$$\mu$m$^{2}$, as well as the
perfect spin filtering and negative differential resistance effects. More
intriguingly, TMR (TER) can be further enhanced to 34000\% (380\%) by applying
an external bias voltage (0.1 V), while RA can be reduced to 0.16
$\Omega$$\mu$m$^{2}$ under the influence of biaxial stress (-3\%). Our proposed
concept of designing vdW-MFTJs using intrinsic multiferroic materials points
towards new avenues in experimental exploration.",2403.12845v2
2001-05-15,Current-Driven Magnetic Memory with Tunable Magnetization Switching,"Co(x nm, x=10nm or 40nm)/Cu(5nm)/Co(2.5nm) layers were deposited between
copper electrodes in SiO2 vias. Magnetic states, and the corresponding
resistance states, of these devices were switched by electric currents
perpendicular to the layers. The I-V loops show asymmetric behavior with
hysteresis. When electrons flow in the direction from thick to thin Co layer
(positive current), multiple switches were observed on increasing current up to
a chosen maximum positive I(write). On decreasing current from I(write), the
I-V curve was smooth and characterized by considerably lower resistance. Under
reverse current, an abrupt switch to the high resistance state occurred at the
current value I(erase)~ -0.9*I(write). Resistance had a maximum at zero current
in both states, where the ratio R(high)/R(low) could be as high as factor of
four.",0105290v1
2005-12-19,Multiphoton processes in microwave photoresistance of 2D electron system,"We extend our studies of microwave photoresistance of ultra-high mobility
two-dimensional electron system (2DES) into the high-intensity, non-linear
regime employing both monochromatic and bichromatic radiation. Under
high-intensity monochromatic radiation $\omega$ we observe new zero-resistance
states (ZRS) which correspond to rational values of $\epsilon=\omega/\omega_C$
($\omega_C$ is the cyclotron frequency) and can be associated with multiphoton
processes. %Formation of these rational ZRS is accompanied by a dramatic
reconstruction of the photoresistance spectrum which reveals diminishing,
narrowing, and phase reduction of the resistance peaks, as well as overall
suppression of resistance at $\epsilon<1/2$. Under bichromatic radiation
$\omega_1,\omega_2$ we discover new resistance minimum, possibly a precursor of
bichromatic ZRS, which seems to originate from a frequency mixing process,
$\omega_1+\omega_2$. These findings indicate that multiphoton processes play
important roles in the physics of non-equilibrium transport of microwave-driven
2DES, and suggest new directions for theoretical and experimental studies.",0512479v1
2007-08-17,Developments and the preliminary tests of Resistive GEMs manufactured by a screen printing technology,"We report promising initial results obtained with new resistive-electrode GEM
(RETGEM) detectors manufactured, for the first time, using screen printing
technology. These new detectors allow one to reach gas gains nearly as high as
with ordinary GEM-like detectors with metallic electrodes; however, due to the
high resistivity of its electrodes the RETGEM, in contrast to ordinary
hole-type detectors, has the advantage of being fully spark protected. We
discovered that RETGEMs can operate stably and at high gains in noble gases and
in other badly quenched gases, such as mixtures of noble gases with air and in
pure air; therefore, a wide range of practical applications, including
dosimetry and detection of dangerous gases, is foreseeable. To promote a better
understanding of RETGEM technology some comparative studies were completed with
metallic-electrode thick GEMs. A primary benefit of these new RETGEMs is that
the screen printing technology is easily accessible to many research
laboratories. This accessibility encourages the possibility to manufacture
these GEM-like detectors with the electrode resistivity easily optimized for
particular experimental or practical applications.",0708.2344v1
2016-03-15,Thermo Activated Hysteresis on High Quality Graphene/h-BN Devices,"We report on gate hysteresis in resistance on high quality graphene/h-BN
devices. We observe a thermal activated hysteretic behavior in resistance as a
function of the applied gate voltage at temperatures above 375K. In order to
investigate the origin of the hysteretic phenomenon, we design heterostructures
involving graphene/h-BN devices with different underlying substrates such as:
SiO2/Si and graphite; where heavily doped silicon and graphite are used as a
back gate electrodes, respectively. The gate hysteretic behavior of the
resistance shows to be present only in devices with an h-BN/SiO2 interface and
is dependent on the orientation of the applied gate electric field and sweep
rate. Finally, we suggest a phenomenological model, which captures all of our
findings based on charges trapped at the h-BN/SiO2. Certainly, such hysteretic
behavior in graphene resistance represents a technological problem for the
application of graphene devices at high temperatures, but conversely, it can
open new routes for applications on digital electronics and graphene memory
devices.",1603.04872v1
2021-09-29,Magnetotransport patterns of collective localization near $ν=1$ in a high-mobility two-dimensional electron gas,"We report complex magnetotransport patterns of the $\nu=1$ integer quantum
Hall state in a GaAs/AlGaAs sample from the newest generation with a record
high electron mobility. The reentrant integer quantum Hall effect in the flanks
of the $\nu=1$ plateau indicates the formation of the integer quantum Hall
Wigner solid, a collective insulator. Moreover, at a fixed filling factor, the
longitudinal resistance versus temperature in the region of the integer quantum
Hall Wigner solid exhibits a sharp peak. Such sharp peaks in the longitudinal
resistance versus temperature so far were only detected for bubble phases
forming in high Landau levels but were absent in the region of the Anderson
insulator. We suggest that in samples of sufficiently low disorder sharp peaks
in the longitudinal resistance versus temperature traces are universal
transport signatures of all isotropic electron solids that form in the flanks
of integer quantum Hall plateaus. We discuss possible origins of these sharp
resistance peaks and we draw a stability diagram for the insulating phases in
the $\nu$-$T$ phase space.",2109.14649v1
2024-04-29,Mobility and Threshold Voltage Extraction in Transistors with Gate-Voltage-Dependent Contact Resistance,"The mobility of emerging (e.g., two-dimensional, oxide, organic)
semiconductors is commonly estimated from transistor current-voltage
measurements. However, such devices often experience contact gating, i.e.,
electric fields from the gate modulate the contact resistance during
measurements, which can lead conventional extraction techniques to estimate
mobility incorrectly even by a factor >2. This error can be minimized by
measuring transistors at high gate-source bias, |$V_\mathrm{gs}$|, but this
regime is often inaccessible in emerging devices that suffer from high contact
resistance or early gate dielectric breakdown. Here, we propose a method of
extracting mobility in transistors with gate-dependent contact resistance that
does not require operation at high |$V_\mathrm{gs}$|, enabling accurate
mobility extraction even in emerging transistors with strong contact gating.
Our approach relies on updating the transfer length method (TLM) and can
achieve <10% error even in regimes where conventional techniques overestimate
mobility by >2$\times$.",2404.19022v1
2004-09-11,"Magnetic and electron transport properties of the rare-earth cobaltates, La0.7-xLnxCa0.3CoO3 (Ln = Pr, Nd, Gd and Dy) : A case of phase separation","Magnetic and electrical properties of four series of rare earth cobaltates of
the formula La0.7-xLnxCa0.3CoO3 with Ln = Pr, Nd, Gd and Dy have been
investigated. Compositions close to x = 0.0 contain large ferromagnetic
clusters or domains, and show Brillouin-like behaviour of the field-cooled DC
magnetization data with fairly high ferromagnetic Tc values, besides low
electrical resistivities with near-zero temperature coefficients. The
zero-field-cooled data generally show a non-monotonic behaviour with a peak at
a temperatures slightly lower than Tc. The near x = 0.0 compositions show a
prominent peak corresponding to the Tc in the AC-susceptibility data. The
ferromagnetic Tc varies linearly with x or the average radius of the A-site
cations, (rA). With increase in x or decrease in (rA), the magnetization value
at any given temperature decreases markedly and the AC-susceptibility
measurements show a prominent transition arising from small magnetic clusters
with some characteristics of a spin-glass. Electrical resistivity increases
with increase in x, showed a significant increase around a critical value of x
or (rA), at which composition the small clusters also begin to dominate. These
properties can be understood in terms of a phase separation scenario wherein
large magnetic clusters give way to smaller ones with increase in x, with both
types of clusters being present in certain compositions. The changes in
magnetic and electrical properties occur parallely since the large
ferromagnetic clusters are hole-rich and the small clusters are hole-poor.
Variable-range hopping seems to occur at low temperatures in these cobaltates.",0409288v2
2004-11-17,Al substitution in MgB2 crystals: influence on superconducting and structural properties,"Single crystals of Mg1-xAlxB2 have been grown at a pressure of 30 kbar using
the cubic anvil technique. Precipitation free crystals with x < 0.1 were
obtained as a result of optimization of already developed MgB2 crystal growth
procedure. Systematic decrease of the c-axis lattice constant with increasing
Al content, when the a-axis lattice constant is practically unchanged, was
observed. Variation of the critical temperature on Al content in Mg1-xAlxB2
crystals was found to be slightly different than that one observed for
polycrystalline samples since, even a very small substitution of 1-2% of Al
leads to the decrease of Tc by about 2-3 K. X-ray and high resolution
transmission electron microscopy investigations indicate on the appearance of
second precipitation phase in the crystals with x > 0.1. This is in a form of
non-superconducting MgAlB4 domains in the structure of superconducting
Mg1-xAlxB2 matrix. Resistivity and magnetic investigations show the slight
increase of the upper critical field, Hc2, for H//c for the samples with small
x, significant reduction of the Hc2 anisotropy at lower temperatures, and
decrease of the residual resistance ratio value for Al substituted samples as
compared to those of unsubstituted crystals. Superconducting gaps variation as
a function of Al content, investigated with point contact spectroscopy for the
series of the crystals with Tc in the range from 20 to 37 K, does not indicate
on the merging of the gaps with decreasing Tc down to 20 K. It may be related
to an appearance of the precipitation phase in the Mg1-xAlxB2 structure.",0411449v2
2007-08-01,Structural and transport properties of GaAs/delta<Mn>/GaAs/InxGa1-xAs/GaAs quantum wells,"We report results of investigations of structural and transport properties of
GaAs/Ga(1-x)In(x)As/GaAs quantum wells (QWs) having a 0.5-1.8 ML thick Mn
layer, separated from the QW by a 3 nm thick spacer. The structure has hole
mobility of about 2000 cm2/(V*s) being by several orders of magnitude higher
than in known ferromagnetic two-dimensional structures. The analysis of the
electro-physical properties of these systems is based on detailed study of
their structure by means of high-resolution X-ray diffractometry and
glancing-incidence reflection, which allow us to restore the depth profiles of
structural characteristics of the QWs and thin Mn containing layers. These
investigations show absence of Mn atoms inside the QWs. The quality of the
structures was also characterized by photoluminescence spectra from the QWs.
Transport properties reveal features inherent to ferromagnetic systems: a
specific maximum in the temperature dependence of the resistance and the
anomalous Hall effect (AHE) observed in samples with both ""metallic"" and
activated types of conductivity up to ~100 K. AHE is most pronounced in the
temperature range where the resistance maximum is observed, and decreases with
decreasing temperature. The results are discussed in terms of interaction of
2D-holes and magnetic Mn ions in presence of large-scale potential fluctuations
related to random distribution of Mn atoms. The AHE values are compared with
calculations taking into account its ""intrinsic"" mechanism in ferromagnetic
systems.",0708.0056v1
2009-08-03,Fabrication of Diamond Nanowires for Quantum Information Processing Applications,"We present a design and a top-down fabrication method for realizing diamond
nanowires in both bulk single crystal and polycrystalline diamond. Numerical
modeling was used to study coupling between a Nitrogen Vacancy (NV) color
center and optical modes of a nanowire, and to find an optimal range of
nanowire diameters that allows for large collection efficiency of emitted
photons. Inductively coupled plasma (ICP) reactive ion etching (RIE) with
oxygen is used to fabricate the nanowires. Drop-casted nanoparticles (including
$\mathrm{Au}$, $\mathrm{SiO_{2}}$ and $\mathrm{Al_2O_3}$) as well as electron
beam lithography defined spin-on glass and evaporated $\mathrm{Au}$ have been
used as an etch mask. We found $\mathrm{Al_2O_3}$ nanoparticles to be the most
etch resistant. At the same time FOx e-beam resist (spin-on glass) proved to be
a suitable etch mask for fabrication of ordered arrays of diamond nanowires. We
were able to obtain nanowires with near vertical sidewalls in both
polycrystalline and single crystal diamond. The heights and diameters of the
polycrystalline nanowires presented in this paper are $\unit[\approx1]{\mu m}$
and $\unit[120-340]{nm}$, respectively, having a $\unit[200]{nm/min}$ etch
rate. In the case of single crystal diamond (types Ib and IIa) nanowires the
height and diameter for different diamonds and masks shown in this paper were
$\unit[1-2.4]{\mu m}$ and $\unit[120-490]{nm}$ with etch rates between
$\unit[190-240]{nm/min}$.",0908.0352v2
2015-08-25,Central Acceptance Testing for Camera Technologies for CTA,"The Cherenkov Telescope Array (CTA) is an international initiative to build
the next generation ground based very-high energy gamma-ray observatory. It
will consist of telescopes of three different sizes, employing several
different technologies for the cameras that detect the Cherenkov light from the
observed air showers. In order to ensure the compliance of each camera
technology with CTA requirements, CTA will perform central acceptance testing
of each camera technology. To assist with this, the Camera Test Facilities
(CTF) work package is developing a detailed test program covering the most
important performance, stability, and durability requirements, including
setting up the necessary equipment. Performance testing will include a wide
range of tests like signal amplitude, time resolution, dead-time determination,
trigger efficiency, performance testing under temperature and humidity
variations and several others. These tests can be performed on fully-integrated
cameras using a portable setup at the camera construction sites. In addition,
two different setups for performance tests on camera sub-units are being built,
which can provide early feedback for camera development. Stability and
durability tests will include the long-term functionality of movable parts,
water tightness of the camera housing, temperature and humidity cycling,
resistance to vibrations during transport or due to possible earthquakes,
UV-resistance of materials and several others. Some durability tests will need
to be contracted out because they will need dedicated equipment not currently
available within CTA. The planned test procedures and the current status of the
test facilities will be presented.",1508.06074v1
2016-08-28,Magnetic order and spin-orbit coupled Mott state in double perovskite (La$_{1-x}$Sr$_x$)$_2$CuIrO$_6$,"Double-perovskite oxides that contain both 3d and 5d transition metal
elements have attracted growing interest as they provide a model system to
study the interplay of strong electron interaction and large spin-orbit
coupling (SOC). Here, we report on experimental and theoretical studies of the
magnetic and electronic properties of double-perovskites
(La$_{1-x}$Sr$_x$)$_2$CuIrO$_6$ ($x$ = 0.0, 0.1, 0.2, and 0.3). The undoped
La$_2$CuIrO$_6$ undergoes a magnetic phase transition from paramagnetism to
antiferromagnetism at T$_N$ $\sim$ 74 K and exhibits a weak ferromagnetic
behavior below $T_C$ $\sim$ 52 K. Two-dimensional magnetism that was observed
in many other Cu-based double-perovskites is absent in our samples, which may
be due to the existence of weak Cu-Ir exchange interaction. First-principle
density-functional theory (DFT) calculations show canted antiferromagnetic
(AFM) order in both Cu$^{2+}$ and Ir$^{4+}$ sublattices, which gives rise to
weak ferromagnetism. Electronic structure calculations suggest that
La$_2$CuIrO$_6$ is an SOC-driven Mott insulator with an energy gap of $\sim$
0.3 eV. Sr-doping decreases the magnetic ordering temperatures ($T_N$ and
$T_C$) and suppresses the electrical resistivity. The high temperatures
resistivity can be fitted using a variable-range-hopping model, consistent with
the existence of disorders in these double-pervoskite compounds.",1608.07763v2
2017-10-11,Fermi surface with Dirac fermions in CaFeAsF determined via quantum oscillation measurements,"Despite the fact that 1111-type iron arsenides hold the record transition
temperature of iron-based superconductors, their electronic structures have not
been studied much because of the lack of high-quality single crystals. In this
study, we completely determine the Fermi surface in the antiferromagnetic state
of CaFeAsF, a 1111 iron-arsenide parent compound, by performing quantum
oscillation measurements and band-structure calculations. The determined Fermi
surface consists of a symmetry-related pair of Dirac electron cylinders and a
normal hole cylinder. From analyses of quantum-oscillation phases, we
demonstrate that the electron cylinders carry a nontrivial Berry phase $\pi$.
The carrier density is of the order of 10$^{-3}$ per Fe. This unusual metallic
state with the extremely small carrier density is a consequence of the
previously discussed topological feature of the band structure which prevents
the antiferromagnetic gap from being a full gap. We also report a nearly
linear-in-$B$ magnetoresistance and an anomalous resistivity increase above
about 30 T for $B \parallel c$, the latter of which is likely related to the
quantum limit of the electron orbit. Intriguingly, the electrical resistivity
exhibits a nonmetallic temperature dependence in the paramagnetic tetragonal
phase ($T >$ 118 K), which may suggest an incoherent state. Our study provides
a detailed knowledge of the Fermi surface in the antiferromagnetic state of
1111 parent compounds and moreover opens up a new possibility to explore
Dirac-fermion physics in those compounds.",1710.03938v3
2020-04-23,Ultralow Schottky Barriers in hBN-Encapsulated Monolayer WSe$_2$ Tunnel Field-Effect Transistors,"To explore the potential of field-effect transistors (FETs) based on
monolayers of the two-dimensional semiconducting channel(SC) for spintronics,
the two most important issues are to ensure the formation of variable low
resistive tunnel ferromagnetic contacts(FC), and to preserve intrinsic
properties of the SC during fabrication. Large Schottky barriers lead to the
formation of high resistive contacts and methods adopted to control the
barriers often alter the intrinsic properties of the SC. This work aims at
addressing both issues in fully encapsulated monolayer WSe$_2$ FETs by using
bi-layer h-BN as a tunnel barrier at the FC/SC interface. We investigate the
electrical transport in monolayer WSe$_2$ FETs with current-in-plane geometry
that yields hole mobilities $\sim$ 38.3 $cm^{2}V^{-1}s^{-1}$ at 240 K and
On/Off ratios of the order of 10$^7$, limited by the contact regions. We have
achieved ultralow effective Schottky barrier ($\sim$ 5.34 meV) with
encapsulated tunneling device as opposed to a non-encapsulated device in which
the barrier heights are considerably higher. These observations provide an
insight into the electrical behavior of the FC/h-BN/SC/h-BN heterostructures
and such control over the barrier heights opens up the possibilities for
WSe$_2$-based spintronic devices.",2004.10962v1
2015-04-23,Fowler-Nordheim Plot Analysis: a Progress Report,"The commonest method of characterizing a cold field electron emitter is to
measure its current-voltage characteristics, and the commonest method of
analysing these characteristics is by means of a Fowler-Nordheim (FN) plot.
This tutorial/review-type paper outlines a more systematic method of setting
out the Fowler-Nordheim-type theory of cold field electron emission, and brings
together and summarises the current state of work by the authors on developing
the theory and methodology of FN plot analysis. This has turned out to be far
more complicated than originally expected. Emphasis is placed in this paper on:
(a) the interpretation of FN-plot slopes, which is currently both easier and of
more experimental interest than the analysis of FN-plot intercepts; and (b)
preliminary explorations into developing methodology for interpreting
current-voltage characteristics when there is series resistance in the
conduction path from the high-voltage generator to the emitter's emitting
regions. This work reinforces our view that FN-plot analysis is best carried
out on the raw measured current-voltage data, without pre-conversion into
another data format, particularly if series resistance is present in the
measuring circuit. Relevant formulae are given for extracting
field-enhancement-factor values from such an analysis.",1504.06134v7
2018-07-07,Three-dimensional quantum Hall effect and metal-insulator transition in ZrTe5,"Symmetry, dimensionality, and interaction are crucial ingredients for phase
transitions and quantum states of matter. As a prominent example, the integer
quantum Hall effect (QHE) represents a topological phase generally regarded as
characteristic for two-dimensional (2D) electronic systems, and its many
aspects can be understood without invoking electron-electron interaction. The
intriguing possibility of generalizing QHE to three-dimensional (3D) systems
was proposed decades ago, yet it remains elusive experimentally. Here, we
report clear experimental evidence for the 3D QHE observed in bulk ZrTe5
crystals. Owing to the extremely high sample quality, the extreme quantum limit
with only the lowest Landau level occupied can be achieved by an applied
magnetic field as low as 1.5 T. Remarkably, in this regime, we observe a
dissipationless longitudinal resistivity rho_xx=0 accompanied with a
well-developed Hall resistivity plateau rho_xy=(1\pm0.1) h/e^2
(\lambda_(F,z)/2), where \lambda_(F,z) is the Fermi wavelength along the field
direction (z axis). This striking result strongly suggests a Fermi surface
instability driven by the enhanced interaction effects in the extreme quantum
limit. In addition, with further increasing magnetic field, both rho_xx and
rho_xy increase dramatically and display an interesting metal-insulator
transition, representing another magnetic field driven quantum phase
transition. Our findings not only unambiguously reveal a novel quantum state of
matter resulting from an intricate interplay among dimensionality, interaction,
and symmetry breaking, but also provide a promising platform for further
exploration of more exotic quantum phases and transitions in 3D systems.",1807.02678v2
2019-01-14,Detailed physical property characterization of FeTe1-xSex x = 0.0 to 0.50 single crystals,"Here, we report self flux single crystal growth of FeTe1-xSex for x = 0 to
0.50 series via solid state reaction route,the resulted crystals as seen are
shiny. X Ray diffraction performed on the surface of crystals elucidated the
growth in 00l plane, i.e. orientation in c direction only. Scanning electron
microscopy (SEM) images showed slab like morphology and EDX (Energy dispersive
X ray analyzer) confirmed that the crystals are closed to their designed
compositions. Rietveld analysis of the XRD patterns of crushed crystal powders
showed that the cell parameters decrease with Se content increase. Coupled
magnetic and structural phase transition temperature, seen as a step in
resistivity for the lower Se concentration and it is not detected for higher x
values. Superconductivity is observed by resistivity measurement for higher Se
concentration with a maximum temperature of 14K at x = 0.50. Thermally
Activated Flux Flow (TAFF) analysis based on high field transport measurements
in superconducting region done for x = 0.20 crystal. Raman spectroscopy at room
temperature of synthesized samples exhibits all the allowed phonon modes with
slight shift to higher frequency with Se content. Mossbauer spectra of
FeTe1-xSex crystals series were recorded at 300 and 5K. At 5K, the average
hyperfine field decreases systematically with Se content increase from 10.6 to
6.1Tesla for x = 0.0 to x = 0.20 samples. This indicates a possibility of
co-existing magnetism and superconductivity in x = 0.07 to 0.20 crystals. For x
= 0.50 sample, no hyperfine field related to magnetic ordering is seen. Based
on above results, detailed phase diagram of the FeTe1-xSex compounds is defined
in the present study.",1901.04224v1
2019-01-24,Fascinating interplay between Charge Density Wave Order and magnetic field in Non-magnetic Rare-Earth Tritelluride LaTe$_{3}$,"Charge density wave (CDW) states in solids bear an intimate connection to
underlying fermiology. Modification of the latter by a suitable perturbation
provides an attractive handle to unearth novel CDW states. Here, we combine
extensive magnetotransport experiments and first-principles electronic
structure calculations on a non-magnetic tritelluride LaTe$_{3}$ single crystal
to uncover phenomena rare in CDW systems: $(i)$ hump-like feature in the
temperature dependence of resistivity at low temperature under application of
magnetic field, which moves to higher temperature with increasing field
strength, $(ii)$ highly anisotropic large transverse magnetoresistance (MR)
upon rotation of magnetic field about current parallel to crystallographic
c-axis, (iii) anomalously large positive MR with spike-like peaks at
characteristic angles when the angle between current and field is varied in the
bc-plane, (iv) extreme sensitivity of the angular variation of MR on field and
temperature. Moreover, our Hall measurement reveals remarkably high carrier
mobility $\sim$ 33000 cm$^{2}$/Vs, which is comparable to that observed in some
topological semimetals. These novel observations find a comprehensive
explication in our density functional theory (DFT) and dynamical mean field
theory (DMFT) calculations that capture field-induced electronic structure
modification in LaTe$_{3}$. The band structure theory together with transport
calculations suggest the possibility of a second field-induced CDW transition
from the field-reconstructed Fermi surface, which qualitatively explains the
hump in temperature dependence of resistivity at low temperature. Thus, our
study exposes the novel manifestations of the interplay between CDW order and
field-induced electronic structure modifications in LaTe$_{3}$, and establishes
a new route to tune CDW states by perturbations like magnetic field.",1901.08267v2
2019-06-09,Spin dynamics and unconventional magnetism in insulating La$_{(1-2x)}$Sr$_{2x}$Co$_{(1-x)}$Nb$_{x}$O$_3$,"We study the structural, magnetic, transport and electronic properties of
LaCoO$_3$ with Sr/Nb co-substitution, i.e.,
La$_{(1-2x)}$Sr$_{2x}$Co$_{(1-x)}$Nb$_{x}$O$_3$ using x-ray and neutron
diffraction, dc and ac-magnetization, neutron depolarization, dc-resistivity
and photoemission measurements. The powder x-ray and neutron diffraction data
were fitted well with the rhombohedral crystal symmetry (space group
\textit{R$\bar{3}$c}) in Rietveld refinement analysis. The calculated effective
magnetic moment ($\approx$3.85~$\mu_B$) and average spin ($\approx$1.5) of Co
ions from the analysis of magnetic susceptibility data are consistent with 3+
state of Co ions in intermediate-spin (IS) and high-spin (HS) states in the
ratio of $\approx$50:50, i.e., spin-state of Co$^{3+}$ is preserved at least up
to $x=$ 0.1 sample. Interestingly, the magnetization values were significantly
increased with respect to the $x=$ 0 sample, and the M-H curves show
non-saturated behavior up to an applied maximum magnetic field of $\pm$70 kOe.
The ac-susceptibility data show a shift in the freezing temperature with
excitation frequency and the detailed analysis confirm the slower dynamics and
a non-zero value of the Vogel-Fulcher temperature T$_0$, which suggests for the
cluster spin glass. The unusual magnetic behavior indicates the presence of
complex magnetic interactions at low temperatures. The dc-resistivity
measurements show the insulating nature in all the samples. However, relatively
large density of states $\approx$10$^{22}$ eV$^{-1}$cm$^{-3}$ and low
activation energy $\approx$130~meV are found in $x=$ 0.05 sample. Using x-ray
photoemission spectroscopy, we study the core-level spectra of La 3$d$, Co
2$p$, Sr 3$d$, and Nb 3$d$ to confirm the valence state.",1906.03659v1
2019-10-14,First predictive simulations for deuterium shattered pellet injection in ASDEX Upgrade,"First simulations of deuterium shattered pellet injection (SPI) into an ASDEX
Upgrade H-Mode plasma with the JOREK MHD code are presented. Resistivity is
increased by one order of magnitude in most simulations to reduce computational
costs and allow for extensive parameter scans. The effect of various physical
parameters onto MHD activity and thermal quench (TQ) dynamics is studied and
the influence of MHD onto ablation is shown. TQs are obtained quickly after
injection in most simulations with a typical duration of 100 microseconds,
which slows down at lower resistivity. Although the n=1 magnetic perturbation
dominates in the simulations, toroidal harmonics up to n=10 contribute to
stochastization and stochastic transport in the plasma core. The post-TQ
density profile remains hollow for a few hundred microseconds. However, when
flux surfaces re-form around the magnetic axis, the density has become
monotonic again suggesting a beneficial behaviour for runaway electron
avoidance/mitigation. With $10^{21}$ atoms injected, the TQ is typically
incomplete and triggered when the shards reach the q=2 rational surface. At a
larger number of injected atoms, the TQ can set in even before the shards reach
this surface. For low field side injection considered here, repeated formation
of outward convection cells is observed in the ablation region reducing
material assimilation. Responsible is a sudden rise of pressure in the high
density cloud when the stochastic region expands further releasing heat from
the hot core. After the TQ, strong sheared poloidal rotation is created by
Maxwell stress, which contributes to re-formation of flux surfaces.",1910.06095v4
2020-08-25,Isospin Pomeranchuk effect and the entropy of collective excitations in twisted bilayer graphene,"In condensed matter systems, higher temperatures typically disfavors ordered
phases leading to an upper critical temperature for magnetism,
superconductivity, and other phenomena. A notable exception is the Pomeranchuk
effect in 3He, in which the liquid ground state freezes upon increasing the
temperature due to the large entropy of the paramagnetic solid phase. Here we
show that a similar mechanism describes the finite temperature dynamics of spin
and valley-isospins in magic-angle twisted bilayer graphene. Most strikingly a
resistivity peak appears at high temperatures near superlattice filling factor
nu = -1, despite no signs of a commensurate correlated phase appearing in the
low-temperature limit. Tilted field magnetotransport and thermodynamic
measurements of the inplane magnetic moment show that the resistivity peak is
adiabatically connected to a finite-field magnetic phase transition at which
the system develops finite isospin polarization. These data are suggestive of a
Pomeranchuk-type mechanism, in which the entropy of disordered isospin moments
in the ferromagnetic phase stabilizes it relative to an isospin unpolarized
Fermi liquid phase at elevated temperatures. Measurements of the entropy, S/kB
indeed find it to be of order unity per unit cell area, with a measurable
fraction that is suppressed by an in-plane magnetic field consistent with a
contribution from disordered physical spins. In contrast to 3He, however, no
discontinuities are observed in the thermodynamic quantities across this
transition. Our findings imply a small isospin stiffness, with implications for
the nature of finite temperature transport as well as the mechanisms underlying
isospin ordering and superconductivity in twisted bilayer graphene and related
systems.",2008.10830v4
2021-05-18,One-reactor vacuum and plasma synthesis of transparent conducting oxide nanotubes and nanotrees: from single wire conductivity to ultra-broadband perfect absorbers in the NIR,"The eventual exploitation of one-dimensional nanomaterials yet needs the
development of scalable, high yield, homogeneous, and environmentally friendly
methods able to meet the requirements for the fabrication of under design
functional nanomaterials. In this article, we demonstrate a vacuum and plasma
one-reactor approach for the synthesis of the fundamental common element in
solar energy and optoelectronics, i.e. the transparent conducting electrode but
in the form of nanotubes and nanotrees architectures. Although the process is
generic and can be used for a variety of TCOs and wide-bandgap semiconductors,
we focus herein on Indium Doped Tin Oxide (ITO) as the most extended in the
previous applications. This protocol combines widely applied deposition
techniques such as thermal evaporation for the formation of organic nanowires
serving as 1D and 3D soft templates, deposition of polycrystalline layers by
magnetron sputtering, and removal of the template by simply annealing under
mild vacuum conditions. The process variables are tuned to control the
stoichiometry, morphology, and alignment of the ITO nanotubes and nanotrees.
Four-probe characterization reveals the improved lateral connectivity of the
ITO nanotrees and applied on individual nanotubes shows resistivities as low as
3.5 +/- 0.9 x 10-4 {\Omega}.cm, a value comparable to single-crystalline
counterparts. The assessment of diffuse reflectance and transmittance in the
UV-VIS range confirms the viability of the supported ITO nanotubes as a random
optical media working as strong scattering layers. Further ability to form ITO
nanotrees opens the path for practical applications as ultra-broadband
absorbers in the NIR. The demonstrated low resistivity and optical properties
of these ITO nanostructures open the way for their use in LEDs, IR shield,
energy harvesting, nanosensors, and photoelectrochemical applications",2105.08751v1
2021-09-01,Interaction driven giant thermopower in magic-angle twisted bilayer graphene,"Magic-angle twisted bilayer graphene (MtBLG) has proven to be an extremely
promising new platform to realize and study a host of emergent quantum phases
arising from the strong correlations in its narrow bandwidth flat band. In this
regard, thermal transport phenomena like thermopower, in addition to being
coveted technologically, is also sensitive to the particle-hole (PH) asymmetry,
making it a crucial tool to probe the underlying electronic structure of this
material. We have carried out thermopower measurements of MtBLG as a function
of carrier density, temperature and magnetic field, and report the observation
of an unusually large thermopower reaching up to a value as high as $\sim
\bf{100\mu V/K}$ at a low temperature of 1K. Surprisingly, our observed
thermopower exhibiting peak-like features in close correspondence to the
resistance peaks around the integer Moire fillings, including the Dirac Point,
violating the Mott formula. %Surprisingly, our observed thermopower exhibits
peak-like features in close correspondence to the resistance peaks around the
integer Moire fillings, including the Dirac Point, which completely violates
the Mott formula. We show that the large thermopower peaks and their
%non-monotonic dependence with temperature and magnetic field associated
behaviour arise from the emergent highly PH asymmetric electronic structure due
to the cascade of Dirac revivals. Furthermore, the thermopower shows an
anomalous peak around the superconducting transition on the hole side and
points towards the possible role of enhanced superconducting fluctuations in
MtBLG.",2109.00361v2
2022-06-13,Long-range magnetic order in the anisotropic triangular lattice system CeCd3As3,"We report the physical properties of $R$Cd$_{3}$As$_{3}$ ($R$ = La and Ce)
compounds, crystallized into a hexagonal ScAl$_{3}$C$_{3}$-type structure
($P$6$_{3}$/mmc) such that the $R$ sublattice forms a spin-orbit coupled
triangular lattice. Magnetic susceptibility measurements indicate the 4$f$
electrons of Ce$^{3+}$ ions are well localized and reveal a large magnetic
anisotropy. The electrical resistivity and specific heat measurement for
$R$Cd$_{3}$As$_{3}$ exhibit an anomaly at high temperatures ($T_{0}$ $\sim$ 63
K for $R$ = La and $T_{0}$ $\sim$ 136 K for $R$ = Ce), most likely due to a
structural transition. Specific heat measurements for CeCd$_{3}$As$_{3}$
clearly indicate a long range magnetic order below $T_{N}$ = 0.42 K. Although
the magnetic contribution to the specific heat $C_{m}/T$ increases
significantly below $\sim$ 10 K, the electrical resistivity for
CeCd$_{3}$As$_{3}$ follows typical, metallic behavior inconsistent with Kondo
lattice systems. In CeCd$_3$As$_3$ only $\sim$ 40 $\%$ of the $R \ln(2)$
magnetic entropy is recovered by $T_N$ and the $R$ln(2) entropy is fully
achieved at about the Curie-Weiss temperature $|\theta_{p}|$. Unusually, based
on our current investigations, the magnetic specific heat below $|\theta_{p}|$
is not attributed to a Kondo contribution, but rather associated with the
magnetic ordering and frustration on the triangular lattice. Specific heat
measurements in applied magnetic field show a negligible variation of $T_{N}$
for $H \parallel c$, whereas a suppression of $T_{N}$ is observed above 40 kOe
for $H \parallel ab$. Such behavior is consistent with the application a
magnetic field within the $ab$-plane breaking the triangular symmetry and
partially relieving the magnetic frustration in this system.",2206.06403v1
2022-11-05,"Effect of various electron and hole transport layers on the performance of CsPbI3-based perovskite solar cells: A numerical investigation in DFT, SCAPS-1D, and wxAMPS frameworks","CsPbI3 has recently received tremendous attention as a possible absorber of
perovskite solar cells (PSCs). However, CsPbI3-based PSCs have yet to achieve
the high performance of the hybrid PSCs. In this work, we performed a density
functional theory (DFT) study using the Cambridge Serial Total Energy Package
(CASTEP) code for the cubic CsPbI3 absorber to compare and evaluate its
structural, electronic, and optical properties. The calculated electronic band
gap (Eg) using the GGA-PBE approach of CASTEP was 1.483 eV for this CsPbI3
absorber. Moreover, the computed density of states (DOS) exhibited the dominant
contribution from the Pb-5d orbital, and most charge also accumulated for the
Pb atom as seen from the electronic charge density map. Fermi surface
calculation showed multiband character, and optical properties were computed to
investigate the optical response of CsPbI3. Furthermore, we used IGZO, SnO2,
WS2, CeO2, PCBM, TiO2, ZnO, and C60 as the electron transport layers (ETLs),
and Cu2O, CuSCN, CuSbS2, Spiro-MeOTAD, V2O5, CBTS, CFTS, P3HT, PEDOT: PSS, NiO,
CuO, and CuI as the hole transport layers (HTLs) to identify the best
HTL/CsPbI3/ETL combinations using the SCAPS-1D solar cell simulation software.
Among 96 device structures, the best-optimized device structure,
ITO/TiO2/CsPbI3/CBTS/Au was identified, which exhibited an efficiency of 17.9%.
The effect of absorber and ETL thickness, series resistance, shunt resistance,
and operating temperature was also evaluated for the six best devices along
with their corresponding generation rate, recombination rate,
capacitance-voltage, current density-voltage, and quantum efficiency
characteristics. The obtained results from SCAPS-1D were also compared with
wxAMPS simulation software.",2211.02968v1
2023-01-30,Infrared ellipsometry study of the charge dynamics in K3p-terphenyl,"We report an infrared ellipsometry study of the charge carrier dynamics in
polycrystalline Kxp-terphenyl samples with nominal $x=3$, for which signatures
of high-temperature superconductivity were previously reported. The infrared
spectra are dominated by two Lorentzian bands with maxima around 4 000
cm$^{-1}$ and 12 000 cm$^{-1}$ which, from a comparison with calculations based
on a H\""uckel model are assigned to intra-molecular excitations of $\pi$
electrons of the anionic p-terphenyl molecules. The inter-molecular electronic
excitations are much weaker and give rise to a Drude peak and a similarly weak
Lorentzian band around 220 cm$^{-1}$. A dc resistivity of about 0.3 $\Omega$ cm
at 300 K is deduced from the IR data, comparable to values measured by
electrical resistivity on a twin sample. The analysis of the temperature
dependence of the low-frequency response reveals a gradual decrease of the
plasma frequency and the scattering rate of the Drude peak below 300 K that
gets anomalously enhanced below 90 K. The corresponding missing spectral weight
of the Drude peak appears blue-shifted towards the Lorentz-band at 220
cm$^{-1}$. This characteristic blue-shift signifies an enhanced localization of
the charge carriers at low temperatures and contrasts the behavior expected for
a bulk superconducting state for which the missing spectral weight would be
redshifted to a delta-function at zero frequency that accounts for the
loss-free response of the superconducting condensate. Our data might still be
compatible with a filamentary superconducting state with a volume fraction well
below the percolation limit for which the spatial confinement of the condensate
can result in a plasmonic resonance at finite frequency.",2302.10097v2
2023-08-04,Observation of Fractionally Quantized Anomalous Hall Effect,"The integer quantum anomalous Hall (QAH) effect is a lattice analog of the
quantum Hall effect at zero magnetic field. This striking transport phenomenon
occurs in electronic systems with topologically nontrivial bands and
spontaneous time-reversal symmetry breaking. Discovery of its putative
fractional counterpart in the presence of strong electron correlations, i.e.,
the fractional quantum anomalous Hall (FQAH) effect, would open a new chapter
in condensed matter physics. Here, we report the direct observation of both
integer and fractional QAH effects in electrical measurements on twisted
bilayer MoTe$_2$. At zero magnetic field, near filling factor $\nu = -1$ (one
hole per moir\'e unit cell) we see an extended integer QAH plateau in the Hall
resistance $R_\text{xy}$ that is quantized to $h/e^2 \pm 0.1 \%$ while the
longitudinal resistance $R_\text{xx}$ vanishes. Remarkably, at $\nu=-2/3$ and
$-3/5$ we see plateau features in $R_\text{xy}$ at $3h/2e^2 \pm 1\%$ and
$5h/3e^2 \pm 3\%$, respectively, while $R_\text{xx}$ remains small. All these
features shift linearly in an applied magnetic field with slopes matching the
corresponding Chern numbers $-1$, $-2/3$, and $-3/5$, precisely as expected for
integer and fractional QAH states. In addition, at zero magnetic field,
$R_\text{xy}$ is approximately $2h/e^2$ near half filling ($\nu = -1/2$) and
varies linearly as $\nu$ is tuned. This behavior resembles that of the
composite Fermi liquid in the half-filled lowest Landau level of a
two-dimensional electron gas at high magnetic field. Direct observation of the
FQAH and associated effects paves the way for researching charge
fractionalization and anyonic statistics at zero magnetic field.",2308.02657v1
2023-09-29,Fractional Quantum Anomalous Hall Effect in a Graphene Moire Superlattice,"The fractional quantum anomalous Hall effect (FQAHE), the analog of the
fractional quantum Hall effect1 at zero magnetic field, is predicted to exist
in topological flat bands under spontaneous time-reversal-symmetry breaking.
The demonstration of FQAHE could lead to non-Abelian anyons which form the
basis of topological quantum computation. So far, FQAHE has been observed only
in twisted MoTe2 (t-MoTe2) at moire filling factor v > 1/2. Graphene-based
moire superlattices are believed to host FQAHE with the potential advantage of
superior material quality and higher electron mobility. Here we report the
observation of integer and fractional QAH effects in a rhombohedral pentalayer
graphene/hBN moire superlattice. At zero magnetic field, we observed plateaus
of quantized Hall resistance Rxy = h/(ve^2) at filling factors v = 1, 2/3, 3/5,
4/7, 4/9, 3/7 and 2/5 of the moire superlattice respectively. These features
are accompanied by clear dips in the longitudinal resistance Rxx. In addition,
at zero magnetic field, Rxy equals 2h/e^2 at v = 1/2 and varies linearly with
the filling factor-similar to the composite Fermi liquid (CFL) in the
half-filled lowest Landau level at high magnetic fields. By tuning the gate
displacement field D and v, we observed phase transitions from CFL and FQAH
states to other correlated electron states. Our graphene system provides an
ideal platform for exploring charge fractionalization and (non-Abelian) anyonic
braiding at zero magnetic field, especially considering a lateral junction
between FQAHE and superconducting regions in the same device.",2309.17436v4
2024-03-20,Effect of annealing on the hot salt corrosion resistance of the fine-grained titanium alpha-alloy Ti-2.5Al-2.6Zr obtained via cold Rotary Swaging,"A hot salt corrosion (HSC) test was performed on the fine-grained titanium
alpha-alloy Ti-2.5Al-2.6Zr (Russian industrial alloy PT-7M). The
ultrafine-grained (UFG) microstructure in the titanium alpha-alloy was formed
via cold Rotary Swaging. The grain size and volume fraction of the
recrystallized microstructure in the alloy were varied by choosing appropriate
annealing temperatures and times. The microstructure and corrosion resistance
of UFG alloys were studied after 30 min of annealing at 500-700C and after 1000
h of annealing at 250C. Metallographic studies were carried out to investigate
the effects of annealing on the nature and extent of corrosive damage in the
titanium alpha-alloy Ti-2.5Al-2.6Zr. After HSC tests, surface analyses of the
titanium alpha-alloy samples were conducted using X-ray diffraction and
electron microscopy. During the HSC testing of the titanium alpha-alloy
Ti-2.5Al-2.6Zr, a competitive interaction between intergranular corrosion (IGC)
and pitting corrosion was observed. To the best of our knowledge, it was shown
for the first time that annealing affects the relationship among the IGC,
pitting corrosion and uniform corrosion rates of the titanium alloy. Prolonged
low-temperature annealing at 250C resulted in a more pronounced increase in the
uniform corrosion rate than short-term high-temperature annealing for 30 min at
500-700C. An in-depth analysis of the effect of the structure and phase
composition of the grain boundaries on the susceptibility of the alpha-alloy
Ti-2.5Al-2.6Zr to HSC was conducted.",2403.13587v1
2024-04-23,Magnetic anisotropy in single-crystalline antiferromagnetic Mn$_2$Au,"Multiple recent studies have identified the metallic antiferromagnet Mn$_2$Au
to be a candidate for spintronic applications due to apparent in-plane
anisotropy, preserved magnetic properties above room temperature, and
current-induced N\'eel vector switching. Crystal growth is complicated by the
fact that Mn$_2$Au melts incongruently. We present a bismuth flux method to
grow millimeter-scale bulk single crystals of Mn$_2$Au in order to examine the
intrinsic anisotropic electrical and magnetic properties. Flux quenching
experiments reveal that the Mn$_2$Au crystals precipitate below 550{\deg}C,
about 100{\deg}C below the decomposition temperature of Mn$_2$Au. Bulk Mn$_2$Au
crystals have a room-temperature resistivity of 16-19 $\mu\Omega$-cm and a
residual resistivity ratio of 41. Mn$_2$Au crystals have a dimensionless
susceptibility on the order of 10$^{-4}$, comparable to calculated and
experimental reports on powder samples. Single-crystal neutron diffraction
confirms the in-plane magnetic structure. The tetragonal symmetry of Mn$_2$Au
constrains the $ab$-plane magnetic susceptibility to be constant, meaning that
$\chi_{100}=\chi_{110}$ in the low-field limit, below any spin-flop transition.
We find that three measured magnetic susceptibilities $\chi_{100}$,
$\chi_{110}$, and $\chi_{001}$ are the same order of magnitude and agree with
the calculated prediction, meaning the low-field susceptibility of Mn$_2$Au is
quite isotropic, despite clear differences in $ab$-plane and $ac$-plane
magnetocrystalline anisotropy. Mn$_2$Au is calculated to have an extremely high
in-plane spin-flop field above 30 T, which is much larger than that of another
in-plane antiferromagnet Fe$_2$As (less than 1 T). The subtle anisotropy of
intrinsic susceptibilities may lead to dominating effects from shape,
crystalline texture, strain, and defects in devices that attempt spin readout
in Mn$_2$Au.",2404.15525v1
2006-05-06,Three-dimensionality of field-induced magnetism in a high-temperature superconductor,"Many physical properties of high-temperature (high-Tc) superconductors are
two-dimensional phenomena derived from their square planar CuO2 building
blocks. This is especially true of the magnetism from the copper ions. As
mobile charge carriers enter the CuO2 layers, the antiferromagnetism of the
parent insulators, where each copper spin is antiparallel to its nearest
neighbours1, evolves into a fluctuating state where the spins show tendencies
towards magnetic order of a longer periodicity. For certain charge carrier
densities, quantum fluctuations are sufficiently suppressed to yield static
long-period order2,3,4,5,6, and external magnetic fields also induce such
order7,8,9,10,11,12. Here we show that in contrast to the chemically-controlled
order in superconducting samples, the field-induced order in these same samples
is actually three-dimensional, implying significant magnetic linkage between
the CuO2 planes. The results are important because they show that there are
three-dimensional magnetic couplings which survive into the superconducting
state, and coexist with the crucial inter-layer couplings responsible for
three-dimensional superconductivity. Both types of coupling will straighten the
vortex lines, implying that we have finally established a direct link between
technical superconductivity, which requires zero electrical resistance in an
applied magnetic field and depends on vortex dynamics, and the underlying
antiferromagnetism of the cuprates.",0605164v1
2008-06-24,Crystal structure and phase transitions across the metal-superconductor boundary in the SmFeAsO1-xFx (0 < x < 0.20) family,"The fluorine-doped rare-earth iron oxyarsenides, REFeAsO1-xFx (RE =rare
earth) have recently emerged as a new family of high-temperature
superconductors with transition temperatures (Tc) as high as 55 K (refs 1-4).
Early work has provided compelling evidence that the undoped parent materials
exhibit spin-density-wave (SDW) antiferromagnetic order and undergo a
structural phase transition from tetragonal to orthorhombic crystal symmetry
upon cooling.5 Both the magnetic and structural instabilities are suppressed
upon doping with fluoride ions before the appearance of superconductivity.6,7
Here we use high-resolution synchrotron X-ray diffraction to study the
structural properties of SmFeAsO1-xFx (0 < x < 0.20) in which superconductivity
emerges near x ~ 0.07 and Tc increases monotonically with doping up to x ~
0.20.8 We find that orthorhombic symmetry survives through the
metal-superconductor boundary well into the superconducting regime 2 and the
structural distortion is only suppressed at doping levels, x > 0.15 when the
superconducting phase becomes metrically tetragonal. Remarkably this crystal
symmetry crossover coincides with reported drastic anomalies in the resistivity
and the Hall coefficient8 and a switch of the pressure coefficient of Tc from
positive to negative,9 thereby implying that the low-temperature structure
plays a key role in defining the electronic properties of these
superconductors.",0806.3962v1
2012-04-23,Integrating Functional Oxides with Graphene,"Graphene-oxide hybrid structures offer the opportunity to combine the
versatile functionalities of oxides with the excellent electronic transport in
graphene. Understanding and controlling how the dielectric environment affects
the intrinsic properties of graphene is also critical to fundamental studies
and technological development of graphene. Here we review our recent effort on
understanding the transport properties of graphene interfaced with
ferroelectric Pb(Zr,Ti)O_3 (PZT) and high-k HfO_2. Graphene field effect
devices prepared on high-quality single crystal PZT substrates exhibit up to
tenfold increases in mobility compared to SiO_2-gated devices. An unusual and
robust resistance hysteresis is observed in these samples, which is attributed
to the complex surface chemistry of the ferroelectric. Surface polar optical
phonons of oxides in graphene transistors play an important role in the device
performance. We review their effects on mobility and the high source-drain bias
saturation current of graphene, which are crucial for developing graphene-based
room temperature high-speed amplifiers. Oxides also introduce scattering
sources that limit the low temperature electron mobility in graphene. We
present a comprehensive study of the transport and quantum scattering times to
differentiate various scattering scenarios and quantitatively evaluate the
density and distribution of charged impurities and the effect of dielectric
screening. Our results can facilitate the design of multifunctional
nano-devices utilizing graphene-oxide hybrid structures.",1204.5161v1
2012-08-30,"High-pressure flux growth, structural, and superconducting properties of LnFeAsO (Ln = Pr, Nd, Sm) single crystals","Single crystals of the LnFeAsO (Ln1111, Ln = Pr, Nd, and Sm) family with
lateral dimensions up to 1 mm were grown from NaAs and KAs flux at high
pressure. The crystals are of good structural quality and become
superconducting when O is partially substituted by F (PrFeAsO1-xFx and
NdFeAsO1-xFx) or when Fe is substituted by Co (SmFe1-xCoxAsO). From
magnetization measurements, we estimate the temperature dependence and
anisotropy of the upper critical field and the critical current density of
underdoped PrFeAsO0.7F0.3 crystal with Tc = 25 K. Single crystals of
SmFe1-xCoxAsO with maximal Tc up to 16.3 K for x = 0.08 were grown for the
first time. From transport and magnetic measurements we estimate the critical
fields and their anisotropy, and find these superconducting properties to be
quite comparable to the ones in SmFeAsO1-xFx with a much higher Tc of = 50 K.
The magnetically measured critical current densities are as high as 109 A/m2 at
2 K up to 7 T, with indication of the usual fishtail effect. The upper critical
field estimated from resistivity measurements is anisotropic with slopes of
-8.7 T/K (H // ab-plane) and -1.7 T/K (H // c-axis). This anisotropy (= 5) is
similar to that in other Ln1111 crystals with various higher Tc s.",1208.6207v2
2013-09-06,MgB2 nonlinear properties investigated under localized high rf magnetic field excitation-report 2,"The high transition temperature and low surface resistance of MgB2 attracts
interest in its potential application in superconducting radio frequency
accelerating cavities. However, compared to traditional Nb cavities, the
viability of MgB2 at high rf fields is still open to question. Our approach is
to study the nonlinear electrodynamics of the material under localized rf
magnetic fields. Because of the presence of the small superconducting gap in
the $\pi$ band, the nonlinear response of MgB2 at low temperature is
potentially complicated compared to a single-gap s-wave superconductor such as
Nb. Understanding the mechanisms of nonlinearity coming from the two-band
structure of MgB2, as well as extrinsic sources of nonlinearity, is an urgent
requirement. A localized and strong rf magnetic field, created by a magnetic
write head, is integrated into our nonlinear-Meissner-effect scanning microwave
microscope [Tamin Tai, X. X. Xi, C. G. Zhuang, D. I. Mircea, and S. M. Anlage,
IEEE Trans. Appl. Supercond. 21, 2615 (2011)]. MgB2 films with thickness 50 nm,
fabricated by a hybrid physical-chemical vapor deposition technique on
dielectric substrates, are measured at a fixed location and show a strongly
temperature-dependent third harmonic response. We propose that several possible
mechanisms are responsible for this nonlinear response.",1309.1706v1
2013-12-26,A Novel High-Pressure Monoclinic Metallic Phase of V2O3,"Vanadium sesquioxide, V2O3, is a prototypical metal-to-insulator system
where, in temperature-dependent studies, the transition always coincides with a
corundum-to-monoclinic structural transition. As a function of pressure, V2O3
follows the expected behavior of increased metallicity due to a larger
bandwidth for pressures up to 12.5 GPa. Surprisingly, for higher pressures when
the structure becomes unstable, the resistance starts to increase. Around 32.5
GPa at 300 K, we observe a novel pressure-induced corundum-to-monoclinic
transition between two metallic phases, showing that the structural phase
transition can be decoupled from the metal-insulator transition. Using X-ray
Raman scattering, we find that screening effects, which are strong in the
corundum phase, become weakened at high pressures. Theoretical calculations
indicate that this can be related to a decrease in coherent quasiparticle
strength, suggesting that the high-pressure phase is likely a critical
correlated metal, on the verge of Mott-insulating behavior.",1312.7063v1
2014-06-19,Synthesis of SnTe Nanoplates with {100} and {111} Surfaces,"SnTe is a topological crystalline insulator that possesses spin-polarized,
Dirac-dispersive surface states protected by crystal symmetry. Multiple surface
states exist on the {100}, {110}, and {111} surfaces of SnTe, with the band
structure of surface states depending on the mirror symmetry of a particular
surface. Thus, to access surface states selectively, it is critical to control
the morphology of SnTe such that only desired crystallographic surfaces are
present. Here, we grow SnTe nanostructures using vapor-liquid-solid and
vapor-solid growth mechanisms. Previously, SnTe nanowires and nanocrystals have
been grown.1-4 In this report, we demonstrate synthesis of SnTe nanoplates with
lateral dimensions spanning tens of microns and thicknesses of a hundred
nanometers. The top and bottom surfaces are either (100) or (111), maximizing
topological surface states on these surfaces. Magnetotransport on these SnTe
nanoplates shows high bulk carrier density, consistent with bulk SnTe crystals
arising due to defects such as Sn vacancies. In addition, we observe a
structural phase transition in these nanoplates from the high temperature rock
salt to low temperature rhombohedral structure. For nanoplates with very high
carrier density, we observe a slight upturn in resistance at low temperatures,
indicating electron-electron interactions.",1406.5227v1
2017-12-13,High Field (up to 140kOe) Angle Dependent Magneto Transport of Bi2Te3 Single Crystals,"We report the angle dependent high field (up to 140kOe) magneto transport of
Bi2Te3 single crystals, a well-known topological insulator. The crystals were
grown from melt of constituent elements via solid state reaction route by
self-flux method. Details of crystal growth along with their brief
characterization up to 5 Tesla applied field was reported by some of us
recently [J. Magn. Mag. Mater. 428, 213 (2017)]. The angle dependence of the
magneto-resistance (MR) of Bi2Te3 follows the cos Theta function i.e., MR is
responsive, when the applied field is perpendicular (tilt angle Theta = o
and/or 180) to the transport current. The low field (10 kOe) MR showed the
signatures of weak anti localization (WAL) character with typical cusp near
origin at 5 K. Further, the MR is linear right up to highest applied field of
140 kOe. The large positive MR are observed up to high temperatures and are
above 250 and 150 percent at 140 kOe in perpendicular fields at 50 K and 100 K
respectively. Heat capacity CP(T) measurements revealed the value of Debye
temperature to be 135 K. ARPES (angle resolved photoemission spectroscopy) data
clearly showed that the bulk Bi2Te3 single crystal consists of a single Dirac
cone.",1712.04632v1
2018-05-14,Structural Dependence of Chemical Durability in Modified Aluminoborate Glasses,"Alkali and alkaline earth aluminoborate glasses feature high resistance to
cracking under sharp contact loading compared to other oxide glasses. However,
due to the high content of hygroscopic B2O3, it is expected that applications
of these glasses could be hindered by poor chemical durability in aqueous
solutions. Indeed, the compositional and structural dependence of their
dissolution kinetics remains unexplored. In this work, we correlate the
dissolution rates of aluminoborate glasses in acidic, neutral, and basic
solutions with the structural changes induced by varying the aluminum-to-boron
ratio. In detail, we investigate a total of seventeen magnesium, lithium, and
sodium aluminoborate glasses with fixed modifier content of 25 mol%. We show
that the structural changes induced by alumina depend on the network modifier.
We also demonstrate a correlation between the chemical durability at various pH
values and the structural changes in Mg-, Li- and Na- aluminoborate glasses.
The substitution of alumina by boron oxide leads to a general decrease of
chemical corrosion in neutral and acidic solutions. The lowest dissolution rate
value is observed in Mg-aluminoborate glasses, as a consequence of the
intermediate character of magnesium which can increase the network
cross-linking. For basic solutions, the chemical durability is almost constant
for the different amount of alumina in the three series, likely because B2O3 is
susceptible to nucleophilic attack, which is favored in high-OH- solutions.",1805.05191v1
2018-06-12,Characterization of a depleted monolithic pixel sensors in 150 nm CMOS technology for the ATLAS Inner Tracker upgrade,"This work presents a depleted monolithic active pixel sensor (DMAPS)
prototype manufactured in the LFoundry 150\,nm CMOS process. DMAPS exploit high
voltage and/or high resistivity inclusion of modern CMOS technologies to
achieve substantial depletion in the sensing volume. The described device,
named LF-Monopix, was designed as a proof of concept of a fully monolithic
sensor capable of operating in the environment of outer layers of the ATLAS
Inner Tracker upgrade in 2025 for the High Luminosity Large Hadron Collider
(HL-LHC). This type of devices has a lower production cost and lower material
budget compared to presently used hybrid designs. In this work, the chip
architecture will be described followed by the characterization of the
different pre-amplifier and discriminator flavors with an external injection
signal and an iron source (5.9\,keV x-rays).",1806.04400v1
2018-06-14,Demonstration of nonpolar m-plane vertical GaN-on-GaN p-n power diodes grown on free-standing GaN substrates,"This work demonstrates the first nonpolar vertical GaN on GaN pn power diodes
grown on m-plane free standing substrates by MOCVD. The SEM and HRXRD results
showed the good crystal quality of the homoepitaxial nonpolar structure with
low defect densities. The CL result confirmed the nonpolar p GaN was of high
quality with considerably reduced deep level states. At forward bias, the
device showed good rectifying behaviors with a turn-on voltage of 4.0 V, an
on-resistance of 2.3 mohmcm2, and a high on off ratio of 1e10. At reverse bias,
the current leakage and breakdown were described by the trap assisted space
charge limited current conduction mechanism, where I was proportional to V
power 4.5. The critical electrical field was calculated to be 2.0 MV per cm
without field plates or edge termination, which is the highest value reported
on nonpolar power devices. The high performance m-plane p-n diodes can serve as
key building blocks to further develop nonpolar GaN power electronics and
polarization-engineering-related advanced power device structures for power
conversion applications.",1806.05308v1
2019-09-23,Superconductivity up to 243 K in yttrium hydrides under high pressure,"The discovery of high-temperature conventional superconductivity in H3S with
a critical temperature of Tc=203 K was followed by the recent record of Tc ~250
K in the face-centered cubic (fcc) lanthanum hydride LaH10 compound. It was
realized in a new class of hydrogen-dominated compounds having a clathrate-like
crystal structure in which hydrogen atoms form a 3D framework and surround a
host atom of rare earth elements. Yttrium hydrides are predicted to have even
higher Tc exceeding room temperature. In this paper, we synthesized and refined
the crystal structure of new hydrides: YH4, YH6, and YH9 at pressures up to 237
GPa finding that YH4 crystalizes in the I4/mmm lattice, YH6 in Im-3m lattice
and YH9 in P63/mmc lattice in excellent agreement with the calculations. The
observed very high-temperature superconductivity is comparable to that found in
fcc-LaH10: the pressure dependence of Tc for YH9 also displays a ""dome like
shape"" with the highest Tc of 243 K at 201 GPa. We also observed a Tc of 227 K
at 237 GPa for the YH6 phase. However, the measured Tcs are notably lower by
~30 K than predicted. Evidence for superconductivity includes the observation
of zero electrical resistance, a decrease of Tc under an external magnetic
field and an isotope effect. The theoretically predicted fcc YH10 with the
promising highest Tc>300 K was not stabilized in our experiments under
pressures up to 237 GPa.",1909.10482v1
2019-02-26,Modelling a Transition-Edge Sensor X-ray Microcalorimeter Linear Array for Compton Profile Measurements and Energy Dispersive Diffraction,"Transition-edge sensors are a type of superconducting detector that offers
high energy resolution based on their sharp resistance-temperature feature in
the superconducting-to-normal transition. TES X-ray microcalorimeters have
typically been designed and used for spectroscopic applications. In this work,
we present a design optimization for a TES X-ray microcalorimeter array for
high-energy scattering and diffraction measurements. In particular, Compton
scattering provides information about the electron momentum distribution, while
energy dispersive diffraction provides structural information about dense
engineering materials. Compton scattering and energy dispersive diffraction
experiments must be conducted in the very hard X-ray regime (~ 100 keV),
demanding a high X-ray stopping power in the detector; therefore, an absorber
with a large heat capacity is needed in conjunction with the TES. In addition,
both applications would benefit from an array composed of parallel strips. We
present a design for a TES X-ray microcalorimeter optimized for such
applications. In particular, we model the longitudinal position dependence due
to the finite thermal diffusion time in the absorber.",1902.10047v2
2019-07-14,Current-Induced magnetization switching by the high spin Hall conductivity $α$-W,"The spin Hall effect originating from 5d heavy transition metal thin films
such as Pt, Ta, and W is able to generate efficient spin-orbit torques that can
switch adjacent magnetic layers. This mechanism can serve as an alternative to
conventional spin-transfer torque for controlling next-generation magnetic
memories. Among all 5d transition metals, W in its resistive amorphous phase
typically shows the largest spin-orbit torque efficiency ~ 0.20-0.50. In
contrast, its conductive and crystalline $\alpha$ phase possesses a
significantly smaller efficiency ~ 0.03 and no spin-orbit torque switching has
yet been realized using $\alpha$-W thin films as the spin Hall source. In this
work, through a comprehensive study of high quality W/CoFeB/MgO and the
reversed MgO/CoFeB/W magnetic heterostructures, we show that although
amorphous-W has a greater spin-orbit torque efficiency, the spin Hall
conductivity of $\alpha$-W
($|\sigma_{\operatorname{SH}}^{\alpha\operatorname{-W}}|=3.71\times10^{5}\operatorname{\Omega}^{-1}\operatorname{m}^{-1}$)
is ~3.5 times larger than that of amorphous-W
($|\sigma_{\operatorname{SH}}^{\operatorname{amorphous-W}}|=1.05\times10^{5}\operatorname{\Omega}^{-1}\operatorname{m}^{-1}$).
Moreover, we demonstrate spin-orbit torque driven magnetization switching using
a MgO/CoFeB/$\alpha$-W heterostructure. Our findings suggest that the
conductive and high spin Hall conductivity $\alpha$-W can be a potential
candidate for future low power consumption spin-orbit torque memory
applications.",1907.06192v1
2020-02-22,Electron irradiation on multilayer PdSe$_2$ field effect transistors,"Palladium diselenide (PdSe2) is a recently isolated layered material that has
attracted a lot of interest for the pentagonal structure, the air stability and
the electrical properties largely tunable by the number of layers. In this
work, PdSe2 is used in the form of multilayer as the channel of back-gate
field-effect transistors, which are studied under repeated electron
irradiations. Source-drain Pd leads enable contacts with resistance below 350
kOhm um. The transistors exhibit a prevailing n-type conduction in high vacuum,
which reversibly turns into ambipolar electric transport at atmospheric
pressure. Irradiation by 10 keV electrons suppresses the channel conductance
and promptly transforms the device from n-type to p-type. An electron fluence
as low as 160 e-/nm2 dramatically change the transistor behavior demonstrating
a high sensitivity of PdSe2 to electron irradiation. The sensitivity is lost
after few exposures, that is a saturation condition is reached for fluence
higher than 4000 e-/nm2. The damage induced by high electron fluence is
irreversible as the device persist in the radiation-modified state for several
hours, if kept in vacuum and at room temperature. With the support of numerical
simulation, we explain such a behavior by electron-induced Se atom vacancy
formation and charge trapping in slow trap states at the Si/SiO_2 interface.",2002.09785v1
2020-04-27,Recent advancements of the NEWS-G experiment,"NEWS-G (New Experiments With Spheres-Gas) is an experiment aiming to shine a
light on the dark matter conundrum with a novel gaseous detector, the spherical
proportional counter. It uses light gases, such as hydrogen, helium, and neon,
as targets to expand dark matter searches to the sub-GeV/c$^{2}$ mass region.
NEWS-G produced its first results with a 60 cm in diameter detector installed
at LSM (France), excluding at 90% C.L. cross-sections above $4.4\cdot{10}^{37}$
cm$^{2}$ for dark matter candidates of 0.5 GeV/c$^{2}$ mass. Currently, a 140
cm in diameter detector is being built at LSM and a commissioning run is
underway, prior to its installation at SNOLAB (Canada) at the end of the year.
Presented here are developments incorporated in this new detector: a) sensor
technologies using resistive materials and multi-anode read-out that allow high
gain and high pressure operation; b) gas purification techniques to remove
contaminants (H$_{2}$O, O$_{2}$); c) reduction of ${}^{210}$Pb induced
background through copper electroforming methods; d) utilisation of UV-lasers
for detector calibration, detector response monitoring and estimation of gas
related fundamental properties. This next phase of NEWS-G will allow searches
for low mass dark matter with unprecedented sensitivity.",2004.12795v1
2016-03-02,Conformal Titanium Nitride in a Porous Silicon Matrix: a Nanomaterial for In-Chip Supercapacitors,"Today's supercapacitor energy storages are typically discrete devices aimed
for printed boards and power applications. The development of autonomous sensor
networks and wearable electronics and the miniaturisation of mobile devices
would benefit substantially from solutions in which the energy storage is
integrated with the active device. Nanostructures based on porous silicon (PS)
provide a route towards integration due to the very high inherent surface area
to volume ratio and compatibility with microelectronics fabrication processes.
Unfortunately, pristine PS has limited wettability and poor chemical stability
in electrolytes and the high resistance of the PS matrix severely limits the
power efficiency. In this work, we demonstrate that excellent wettability and
electro-chemical properties in aqueous and organic electrolytes can be obtained
by coating the PS matrix with an ultra-thin layer of titanium nitride by atomic
layer deposition. Our approach leads to very high specific capacitance (15
F/cm$^3$), energy density (1.3 mWh/cm$^3$), power density (up to 214 W/cm$^3$)
and excellent stability (more than 13,000 cycles). Furthermore, we show that
the PS-TiN nanomaterial can be integrated inside a silicon chip monolithically
by combining MEMS and nanofabrication techniques. This leads to realisation of
in-chip supercapacitor, i.e., it opens a new way to exploit the otherwise
inactive volume of a silicon chip to store energy.",1603.00798v1
2019-02-28,Effect of atomic ordering on the magnetic anisotropy of single crystal Ni80Fe20,"We investigate the effect of atomic ordering on the magnetic anisotropy of
Ni80Fe20 at.% (Py). To this end, Py films were grown epitaxially on MgO (001)
using dc magnetron sputtering (dcMS) and high power impulse magnetron
sputtering (HiPIMS). Aside from twin boundaries observed in the latter case,
both methods present high quality single crystals with cube-on-cube epitaxial
relationship as verified by the polar mapping of important crystal planes.
However, X-ray diffraction results indicate higher order for the dcMS deposited
film towards L12 Ni3Fe superlattice. This difference can be understood by the
very high deposition rate of HiPIMS during each pulse which suppresses adatom
mobility and ordering. We show that the dcMS deposited film presents biaxial
anisotropy while HiPIMS deposition gives well defined uniaxial anisotropy.
Thus, higher order achieved in the dcMS deposition behaves as predicted by
magnetocrystalline anisotropy i.e. easy axis along the [111] direction that
forced in the plane along the [110] direction due to shape anisotropy. The
uniaxial behaviour in HiPIMS deposited film then can be explained by pair
ordering or more recent localized composition non-uniformity theories. Further,
we studied magnetoresistance of the films along the [100] directions using an
extended van der Pauw method. We find that the electrical resistivities of the
dcMS deposited film are lower than in their HiPIMS counterparts verifying the
higher order in the dcMS case.",1903.00105v1
2019-03-29,Multi-contact Phase Change Toggle Logic Device Utilizing Thermal Crosstalk,"Phase change memory (PCM) is an emerging high speed, high density, high
endurance, and scalable non-volatile memory technology which utilizes the large
resistivity contrast between the amorphous and crystalline phases of
chalcogenide materials such as Ge2Sb2Te5 (GST). In addition to being used as a
standalone memory, there has been a growing interest in integration of PCM
devices on top of the CMOS layer for computation in memory and neuromorphic
computing. The large CMOS overhead for memory controllers is a limiting factor
for this purpose. Transferring functionality like routing, multiplexing, and
logic to the memory layer can substantially reduce the CMOS overhead, making it
possible to integrate 100s of GB of PCM storage on top of a conventional CPU.
In this work, we present computational analysis of a phase change device
concept that can perform toggle operations. The toggle functionality is
achieved using two physical mechanisms: (i) isolation of different read
contacts due to amorphization between different write contact pairs, and (ii)
thermal cross-talk between a molten region and a previously amorphized region.
Phase-change devices with six contacts can be implemented as toggle flip-flops,
multiplexer, or demultiplexer when interfaced with CMOS transistors. Here, we
demonstrate the operation of the device as a toggle flip-flop with 5
transistors, requiring ~50% of the footprint compared to conventional CMOS
alternatives, with the added advantage of non-volatility.",1904.00836v1
2021-01-05,High-Temperature Superconductivity in Cerium Superhydrides,"The discoveries of high-temperature superconductivity in H3S and LaH10 have
excited the search for superconductivity in compressed hydrides. In contrast to
rapidly expanding theoretical studies, high-pressure experiments on hydride
superconductors are expensive and technically challenging. Here we
experimentally discover superconductivity in two new phases,Fm-3m-CeH10 (SC-I
phase) and P63/mmc-CeH9 (SC-II phase) at pressures that are much lower (<100
GPa) than those needed to stabilize other polyhydride superconductors.
Superconductivity was evidenced by a sharp drop of the electrical resistance to
zero, and by the decrease of the critical temperature in deuterated samples and
in an external magnetic field. SC-I has Tc=115 K at 95 GPa, showing expected
decrease on further compression due to decrease of the electron-phonon coupling
(EPC) coefficient {\lambda} (from 2.0 at 100 GPa to 0.8 at 200 GPa). SC-II has
Tc = 57 K at 88 GPa, rapidly increasing to a maximum Tc ~100 K at 130 GPa, and
then decreasing on further compression. This maximum of Tc is due to a maximum
of {\lambda} at the phase transition from P63/mmc-CeH9 into a symmetry-broken
modification C2/c-CeH9. The pressure-temperature conditions of synthesis affect
the actual hydrogen content, and the actual value of Tc. Anomalously low
pressures of stability of cerium superhydrides make them appealing for studies
of superhydrides and for designing new superhydrides with even lower pressures
of stability.",2101.01315v2
2015-07-30,Likelihood-free inference in high-dimensional models,"Methods that bypass analytical evaluations of the likelihood function have
become an indispensable tool for statistical inference in many fields of
science. These so-called likelihood-free methods rely on accepting and
rejecting simulations based on summary statistics, which limits them to low
dimensional models for which the absolute likelihood is large enough to result
in manageable acceptance rates. To get around these issues, we introduce a
novel, likelihood-free Markov-Chain Monte Carlo (MCMC) method combining two key
innovations: updating only one parameter per iteration and accepting or
rejecting this update based on subsets of statistics sufficient for this
parameter. This increases acceptance rates dramatically, rendering this
approach suitable even for models of very high dimensionality. We further
derive that for linear models, a one dimensional combination of statistics per
parameter is sufficient and can be found empirically with simulations. Finally,
we demonstrate that our method readily scales to models of very high
dimensionality using both toy models as well as by jointly inferring the
effective population size, the distribution of fitness effects of new mutations
(DFE) and selection coefficients for each locus from data of a recent
experiment on the evolution of drug-resistance in Influenza.",1507.08612v2
2019-06-19,"Scalable, green fabrication of single-crystal noble metal films and nanostructures for low-loss nanotechnology applications","High quality metal thin films and nanostructures are critical building blocks
for next generation nanotechnologies. They comprise low-loss circuit elements
in nanodevices, provide new catalytic pathways for water splitting and $CO_2$
reduction technologies, and enable the confinement of spatially extended
electromagnetic waves to be harnessed for application in information
processing, energy harvesting, engineered metamaterials, and new technologies
that will operate in the quantum plasmonics limit. However, the controlled
fabrication of high-definition single-crystal subwavelength metal
nanostructures remains a significant hurdle, due to the tendency for
polycrystalline metal growth using conventional physical vapor deposition
methods, and the challenges associated with placing solution-grown nanocrystals
in desired orientations and locations on a surface to fabricate functional
devices. Here, we introduce a new scalable, green, wet chemical approach to
monocrystalline noble metals that enables the fabrication of ultrasmooth,
epitaxial, single-crystal films of controllable thickness. They are ideal for
the subtractive manufacture of nanostructure through ion beam milling, and
additive crystalline nanostructure via lithographic patterning to enable large
area, single-crystal metamaterials and high aspect ratio nanowires. Our
single-crystal nanostructures demonstrate improved feature quality and pattern
transfer yield, reduced optical and resistive losses, tailored local fields,
and greatly improved stability compared to polycrystalline structures,
supporting greater local field enhancements and enabling new practical advances
at the nanoscale.",1906.07879v1
2019-10-23,Implications for Dark Matter Direct Detection in the Presence of LIGO-Motivated Primordial Black Holes,"We discuss formation of dark matter (DM) mini-halos around primordial black
holes (PBHs) and its implication on DM direct detection experiments, including
axion searches. Motivated by LIGO observations, we consider $f_{\textrm{DM}}
\simeq 0.01$ as the fraction of DM in PBHs with masses $10 M_{\odot} - 70
M_{\odot}$. In this case, we expect the presence of dressed PBHs after Milky
Way halo formation with mini-halo masses peaked around $M_{\textrm{halo}} \sim
(50-55) M_{\textrm{PBH}}$. We analyze the effect of tidal forces acting on
dressed PBHs within the Milky Way galaxy. In the solar neighborhood, the
mini-halos are resistant against tidal disruption from the mean-field potential
of the galaxy and encounters with stars, but they undergo a small level of
disruption caused by disk shocking. The presence of mini-halos around
LIGO-motivated PBHs today could reduce by half the local dark matter
background. High-resolution simulations are encouraged. If the proposed
scenario is realized, chances of direct detection of DM would decrease.",1910.10575v3
2020-06-24,Predicting the propensity for thermally activated $β$ events in metallic glasses via interpretable machine learning,"The elementary excitations in metallic glasses (MGs), i.e., $\beta$ processes
that involve hopping between nearby sub-basins, underlie many unusual
properties of the amorphous alloys. A high-efficacy prediction of the
propensity for those activated processes from solely the atomic positions,
however, has remained a daunting challenge. Recently, employing well-designed
site environment descriptors and machine learning (ML), notable progress has
been made in predicting the propensity for stress-activated $\beta$ processes
(i.e., shear transformations) from the static structure. However, the complex
tensorial stress field and direction-dependent activation would induce
non-trivial noises in the data, limiting the accuracy of the structure-property
mapping learned. Here, we focus on the thermally activated elementary
excitations and generate high-quality data in several Cu-Zr MGs, allowing
quantitative mapping of the potential energy landscape. After fingerprinting
the atomic environment with short- and medium-range interstice distribution, ML
can identify the atoms with strong resistance or high compliance to thermal
activation, at an unprecedented accuracy over ML models for stress-driven
activation events. Interestingly, a quantitative ""between-task"" transferring
test reveals that our learnt model can also generalize to predict the
propensity of shear transformation. Our dataset is potentially useful for
benchmarking future ML models on structure-property relationships in MGs.",2006.13552v1
2020-10-07,Physical properties and electronic structure of single-crystal KCo$_2$As$_2$,"We present a method for producing high quality KCo2As2 crystals, stable in
air and suitable for a variety of measurements. X-ray diffraction, magnetic
susceptibility, electrical transport and heat capacity measurements confirm the
high quality and an absence of long range magnetic order down to at least 2 K.
Residual resistivity values approaching 0.25 $\mu\Omega$~cm are representative
of the high quality and low impurity content, and a Sommerfeld coefficient
$\gamma$ = 7.3 mJ/mol K$^2$ signifies weaker correlations than the Fe-based
counterparts. Together with Hall effect measurements, angle-resolved
photoemission experiments reveal a Fermi surface consisting of electron pockets
at the center and corner of the Brillouin zone, in line with theoretical
predictions and in contrast to the mixed carrier types of other pnictides with
the ThCr2Si2 structure. A large, linear magnetoresistance of 200\% at 14~T,
together with an observed linear and hyperbolic, rather than parabolic, band
dispersions are unusual characteristics of this metallic compound and may
indicate more complex underlying behavior.",2010.03447v2
2020-10-16,Investigation of n-type dilute magnetic semiconductor property observed in amorphous AlNO alloy thin film incorporated with dilute nitrogen at 300K,"In the present work, a thin film was deposited on quartz substrate by
reactive RF magnetron sputtering of high purity (99.999%) aluminium target
using ultra-high pure (Ar + N2) gas mixture. The percentage ratio of Ar and N2
in the gas mixture was 95% and 5%, respectively. Chemical characterization
using x-ray photoelectron spectroscopy (XPS) and energy-dispersive xray (EDX)
spectroscopy reveals that in the presence of dilute nitrogen, Al prefers to
react with residual oxygen to form Al2O3 while the nitrogen is incorporated in
it. The stoichiometry of bulk film is Al2N0.38O3.1. Magnetic and electrical
properties measurement shows that the film exhibits ntype dilute magnetic
semiconductor (DMS) property at 300K. The film has low electrical resistivity
of 6.3 {\Omega}-cm and high carrier mobility of 5.7*106 cm2V-1s-1 at 300K. A
density functional theory (DFT) calculation was performed to investigate the
origin of observed magnetism in the film. From first-principles calculation
based on DFT, it is found that for thermodynamic stability dilute nitrogen
incorporated in Al2O3 preferred to sit at the interstitial site, which is
responsible for observed magnetic property. Present study reported here
provides a new insight to prepare rarely observed n-type DMS at room
temperature by incorporating nitrogen interstitials in Al2O3, which is
desirable for potential application in the field of spintronics.",2010.08361v1
2020-11-03,In situ mechanical testing of an Al matrix composite to investigate compressive plasticity and failure on multiple length scales,"SiC particle-reinforced Al matrix composites exhibit high strength, high wear
resistance, and excellent high-temperature performance, but can also have low
plasticity and fracture toughness, which limits their use in structural
applications. This study investigates the plasticity and failure of such a
composite on multiple length scales, from strain localization through a complex
microstructure to the debonding of individual microparticles from the matrix.
Three microscale pillars containing microstructures with different complexities
and sizes/volume fraction of SiC particles were used to study the effect of
these features on deformation. For the matrix, nanoscale intermetallic
precipitates within the Al grains contribute most to the strengthening effect,
and the Al grain boundaries are shown to be effective obstacles for preventing
strain localization by dominant shear bands and, therefore, catastrophic
failure. When shear localization occurs, SiC particles can then debond from the
matrix if the shear band and interface are aligned. To investigate whether the
interface is a weak point during catastrophic failure, a number of SiC
particles were separated from the matrix with direct debonding tests, which
yield an interface strength that is much higher than the critical resolved
shear stress for a pillar exhibiting both shear localization and interface
debonding. Therefore, the matrix-particle interface is ruled out as a possible
weak point, and instead shear localization is identified as the mechanism that
can drive subsequent interface debonding.",2011.01390v3
2020-12-04,"Revealing the Nanostructure of Mesoporous Fuel Cell Catalyst Supports for Durable, High-Power Performance","Achieving high power performance and durability with low Pt loadings are
critical challenges for proton exchange membrane fuel cells. PtCo catalysts
developed on new carbon black supports show promise by simultaneously providing
good oxygen reduction kinetics and local oxygen transport. We investigate the
role of nanoscale morphology in the performance of these catalysts supported on
accessible (HSC-e and HSC-f) and conventional (Ketjen Black) porous carbons
using 3D electron tomography, nitrogen sorption, and electrochemical
performance measurements. We find that the accessible porous carbons have
hollow interiors with mesopores that are larger and more numerous than
conventional porous carbons. However, mesopore-sized openings (>2nm width) are
too rare to account for significant oxygen transport. Instead we propose the
primary oxygen transport pathway into the interior is through 1-2nm microporous
channels permeating the carbon. The increased mesoporosity in the accessible
porous carbons results in a shorter diffusion pathlength through constrictive,
tortuous micropores in the support shell leading to lower local oxygen
transport resistance. In durability testing, the accessible porous carbons show
faster rates of electrochemical surface area loss, likely from fewer
constrictive pores that would mitigate coarsening, but maintain superior high
current density performance at end of life from the improved local oxygen
transport.",2012.02879v1
2020-12-08,Complex impedance and Raman spectroscopy of Na$_{0.5}$(Bi$_{1-x}$Dy$_x$)$_{0.5}$TiO$_3$ ceramics,"In this work structural refinement, complex impedance spectroscopy, and Raman
spectroscopy have been investigated on
Na$_{0.5}$(Bi$_{1-x}$Dy$_x$)$_{0.5}$TiO$_3$ (xDyNBT) ceramic systems. The pure
NBT, 2DyNBT and 5DyNBT compounds crystallize in a rhombohedral structure while
the 15DyNBT composition crystallizes in an orthorhombic Pnma structure. We
reported that dysprosium addition affects the phase transition temperatures as
well as the dielectric losses. The electrical transport at high temperatures
was investigated using the CIS over a wide frequency range. The studied samples
showed a non-Debye type process, with a short-range relaxation for the pure NBT
and a coexistence of both localized and long-range relaxations of charge
carriers for the 2DyNBT and 5DyNBT compounds. For the high concentration,
15DyNBT, a short-range relaxation is observed. Moreover, using a brick-layer
model we discuss the resistance and capacitance of the different contributors
(grain and grain boundaries) in our samples. High temperature Raman
spectroscopy investigation was performed in order to follow the temperature
evolution of the structural transformations on ferroelectric compounds.
Anomalies in the temperature evolution of the vibrational modes are seen to
correlate well with the temperature transitions observed from dielectric
measurements.",2012.04325v1
2021-02-18,Characterization of high aspect ratio TiAu TES X-ray microcalorimeters array using the X-IFU Frequency Domain Multiplexing readout,"We are developing X-ray microcalorimeters as a backup option for the baseline
detectors in the X-IFU instrument on board the ATHENA space mission led by ESA
and to be launched in the early 2030s.5$\times$5 mixed arrays with TiAu
transition-edge sensor (TES), which have different high aspect ratios and thus
high resistances, have been designed and fabricated to meet the energy
resolution requirement of the X-IFU instrument. Such arrays can also be used to
optimise the performance of the Frequency Domain Multiplexing (FDM) readout and
lead to the final steps for the fabrication of a large detector array. In this
work we present the experimental results from tens of the devices with an
aspect ratio (length-to-width) ranging from 1-to-1 up to 6-to-1, measured in a
single-pixel mode with a FDM readout system developed at SRON/VTT. We observed
a nominal energy resolution of about 2.5 eV at 5.9 keV at bias frequencies
ranging from 1 to 5 MHz. These detectors are proving to be the best TES
microcalorimeters ever reported in Europe, being able to meet not only the
requirements of the X-IFU instrument, but also those of other future
challenging X-ray space missions, fundamental physics experiments, plasma
characterization and material analysis.",2102.09378v1
2021-07-19,Miniaturization of Josephson junction for digital superconducting circuits,"In this work, we briefly overview various options for Josephson junctions
which should be scalable down to nanometer range for utilization in nanoscale
digital superconducting technology. Such junctions should possess high values
of critical current, $I_c$, and normal state resistance, $R_n$. Another
requirement is the high reproducibility of the junction parameters across a
wafer in a fabrication process. We argue that Superconductor - Normal metal -
Superconductor (SN-N-NS) Josephson junction of ""variable thickness bridge""
geometry is a promising choice to meet these requirements. Theoretical analysis
of SN-N-NS junction is performed in the case where the distance between the
S-electrodes is comparable to the coherence length of the N-material. The
restriction on the junction geometrical parameters providing the existence of
superconductivity in the S-electrodes is derived for the current flowing
through the junction of an order of $I_c$. The junction heating, as well as
available mechanisms for the heat removal, is analyzed. The obtained results
show that an SN-N-NS junction with a high (sub-millivolt) value of $I_cR_n$
product can be fabricated from a broadly utilized combination of materials like
Nb/Cu using well-established technological processes. The junction area can be
scaled down to that of semiconductor transistors fabricated in the frame of a
40-nm process.",2107.08711v1
2021-11-18,Searching for Superconductivity in High Entropy Oxide Ruddlesden-Popper Cuprate Films,"In this work, the high entropy oxide A2CuO4 Ruddlesden-Popper
(La0.2Pr0.2Nd0.2Sm0.2Eu0.2)2CuO4 is explored by charge doping with Ce+4 and
Sr+2 at concentrations known to induce superconductivity in the simple parent
compounds, Nd2CuO4 and La2CuO4. Electron doped
(La0.185Pr0.185Nd0.185Sm0.185Eu0.185Ce0.075)2CuO4 and hole doped
(La0.18Pr0.18Nd0.18Sm0.18Eu0.18Sr0.1)2CuO4 are synthesized and shown to be
single crystal, epitaxially strained, and highly uniform. Transport
measurements demonstrate that all as-grown films are insulating regardless of
doping. Annealing studies show that resistivity can be tuned by modifying
oxygen stoichiometry and inducing metallicity but without superconductivity.
These results in turn are connected to extended x-ray absorption fine structure
(EXAFS) results indicating that the lack of superconductivity in the high
entropy cuprates likely originates from a large distortion within the Cu-O
plane ({\sigma}2>0.015 {\AA}2) due to A-site cation size variance, which drives
localization of charge carriers. These findings describe new opportunities for
controlling charge- and orbital-mediated functional responses in
Ruddlesden-Popper crystal structures, driven by balancing of cation size and
charge variances that may be exploited for functionally important behaviors
such as superconductivity, antiferromagnetism, and metal-insulator transitions,
while opening less understood phase spaces hosting doped Mott insulators,
strange metals, quantum criticality, pseudogaps, and ordered charge density
waves.",2111.09767v1
2022-01-03,Phase Diagram of Infinite-layer Nickelate Compounds from First- and Second-principles Calculations,"The fundamental properties of infinite-layer rare-earth nickelates (RNiO2)
are carefully revisited and compared with those of CaCuO2 and RNiO3
perovskites. Combining first-principles and finite-temperature
second-principles calculations, we highlight that bulk NdNiO2 compound are far
from equivalent to CaCuO2, together at the structural, electronic, and magnetic
levels. Structurally, it is shown to be prone to spin-phonon coupling induced
oxygen square rotation motion, which might be responsible for the intriguing
upturn of the resistivity. At the electronic and magnetic levels, we point out
orbital-selective Mott localization with strong out-of-plane band dispersion,
which should result in the isotropic upper critical fields and weakly
three-dimensional magnetic interactions with in-plane local moment and
out-of-plane itinerant moment. We further demonstrate that as in RNiO3
perovskites, oxygen rotation motion and rare-earth ion controlled electronic
and magnetic properties can give rise in RNiO2 compounds to a rich phase
diagram and high tunability of various appealing properties. In line with that,
we reveal that key ingredients of high-Tc superconductor such as orbital
polarization, Fermi surface, and antiferromagnetic interactions can be
deliberately controlled in NdNiO2 through epitaxial strain. Exploiting
strain-orbital engineering, a crossover from three- to two-dimensional magnetic
transition can be established, making then NdNiO2 thin film a true analog of
high-Tc cuprates.",2201.00709v1
2022-03-20,Deposition temperature dependence of thermo-spin and magneto-thermoelectric conversion in Co$_2$MnGa films on Y$_3$Fe$_5$O$_{12}$ and Gd$_3$Ga$_5$O$_{12}$,"We have characterized Co$_2$MnGa (CMG) Heusler alloy films grown on
Y$_3$Fe$_5$O$_{12}$ (YIG) and Gd$_3$Ga$_5$O$_{12}$ (GGG) substrates at
different deposition temperatures and investigated thermo-spin and
magneto-thermoelectric conversion properties by means of a lock-in thermography
technique. X-ray diffraction, magnetization, and electrical transport
measurements show that the deposition at high substrate temperatures induces
the crystallized structures of CMG while the resistivity of the CMG films on
YIG (GGG) prepared at and above 500 {\deg}C (550 {\deg}C) becomes too high to
measure the thermo-spin and magneto-thermoelectric effects due to large
roughness, highlighting the difficulty of fabricating highly ordered continuous
CMG films on garnet structures. Our lock-in thermography measurements show that
the deposition at high substrate temperatures results in an increase in the
current-induced temperature change for CMG/GGG and a decrease in that for
CMG/YIG. The former indicates the enhancement of the anomalous Ettingshausen
effect in CMG through crystallization. The latter can be explained by the
superposition of the anomalous Ettingshausen effect and the spin Peltier effect
induced by the positive (negative) charge-to-spin conversion for the amorphous
(crystallized) CMG films. These results provide a hint to construct
spin-caloritronic devices based on Heusler alloys.",2203.10566v2
2022-04-10,Efficient route to achieve superconductivity improvement via substitutional La-Ce alloy superhydride at high pressure,"The discovery of clathrate superhydrides has approached the long-standing
dream of room-temperature superconductivity and thus inspired their prosperous
research under high pressure. However, how to experimentally optimize these
compelling superhydrides is still a formidable challenge. Here, we find that
half of the Ce atoms in the recently discovered hexagonal close packed (hcp)
CeH9 structure can be randomly replaced by adjacent La, resulting in the
formation of LaH9 unit that is impossible in a binary system. Our experiments
show that hcp (La, Ce)H9 can be synthesized at ~110 GPa and possesses a maximum
Tc of 178 K at higher pressure, which is evidenced by in-situ X-ray diffraction
and electronic transport measurement where a sharp drop of resistivity to zero
and a characteristic decrease of Tc under a magnetic field up to 9 T. More
importantly, the Tc of (La, Ce)H9 is significantly increased by ~50-80 K
compared to CeH9, showing the hitherto highest Tc at megabar pressure. Our
experimental results not only verify the feasibility of improving the
superconductivity of hydrides by introducing other suitable metals, but also
provide important inspiration for finding high-Tc superconductors in various
multinary superhydrides.",2204.04623v1
2022-06-16,A Lateral AlGaN/GaN Schottky Barrier Diode with 0.36 V Turn-on Voltage and 10 kV Breakdown Voltage by Using Double Barrier Anode Structure,"In this letter, we demonstrate a lateral AlGaN/GaN Schottky barrier diode
(SBD) on sapphire substrate with low turn-on voltage (Von) and high breakdown
voltage (VBK). By using a double barrier anode (DBA) structure formed by the
mixture of Platinum (Pt) and Tantalum (Ta), the Von of the SBD can be as low as
0.36 V with a leakage current of 2.5E-6 A/mm. Supported by the high-quality
carbon-doped GaN buffer on sapphire, the VBK can reach more than 10 kV with the
anode-to-cathode spacing of 85 {\mu}m. Combining the VBK and the specific
on-resistance (Ron,sp) of 25.1 m{\Omega}.cm^2, the power figure of merit of the
SBD can reach 4.0 GW/cm^2, demonstrating a great potential for the application
in ultra-high-voltage electronics.",2206.07881v1
2022-07-08,Synthesis and Superconductivity in yttrium superhydrides under high pressure,"The flourishing rare earth superhydrides are a class of recently discovered
materials that possess near-room-temperature superconductivity at high
pressures, opening a new era of superconductivity research at high pressures.
Among these superhydrides, yttrium superhydrides attracted great interest owing
to their abundance of stoichiometries and excellent superconductivities. Here,
we carried out a comprehensive study of yttrium superhydrides in a wide
pressure range of 145-300 GPa. We successfully synthesized a series of
superhydrides with the compositions of YH4, YH6, YH7, and YH9, and reported
their superconducting transition temperatures of 82 K at 167 GPa, 218 K at 165
GPa, 29 K at 162 GPa, and 230 K at 300 GPa, respectively, which were evidenced
by a sharp drop of resistivity. The structure and superconductivity of YH4,
which was taken as a representative example, were also examined by X-ray
diffraction measurements and the suppression of the superconductivity under
external magnetic fields, respectively. Clathrate YH10 as a candidate of
room-temperature superconductor was not synthesized within the studied pressure
and temperature ranges of up to 300 GPa and 2000 K, respectively. The current
work created a detailed platform for further searching room-temperature
superconductors in polynary yttrium-based superhydrides.",2207.03918v1
2022-08-31,Pouch cells with 15% silicon calendar-aged for 4 years,"Small amounts of high-capacity silicon-based materials are already used in
the anode of commercial Li-ion batteries, helping increase their energy
density. Despite their remarkable storage capability, silicon continuously
reacts with the electrolyte, accelerating time-dependent cell performance fade.
Nevertheless, very limited information is available on the specific
consequences of this reactivity for the calendar aging of Li-ion cells. Here,
we analyze aging effects on 450 mAh pouch cells containing 15 wt% of Si (and 73
wt% graphite) after storage at 21 oC for four years. We show that severe losses
of Si capacity occurred due to particle isolation when cells were stored at
high states of charge (SOC), but not when cells were fully discharged prior to
storage. Impedance rise was also significantly higher when cells were kept at
high SOCs and was mostly due to phenomena taking place at the cathode; the
continuous electrolyte reduction at the anode did not lead to a major increase
in bulk electrode resistance. A series of post-test characterization provided
additional information on the effects of time and SOC on the calendar aging of
Si-containing cells. Our study highlights the many challenges posed by Si
during calendar aging and can inform future studies in the field.",2209.00138v1
2022-10-13,Diffusion mechanism and electrochemical investigation of 1T phase Al-MoS$_{2}$@rGO nano-composite as a high-performance anode for sodium-ion batteries,"We report the electrochemical investigation of 5% Al doped MoS$_2$@rGO
composite as a high-performance anode for sodium (Na)-ion batteries. The x-ray
diffraction (XRD), Raman spectroscopy and high-resolution transmission electron
microscopy characterizations reveal that the Al doping increase the interlayer
spacing of (002) plane of MoS$_2$ nanosheets and form a stable 1T phase. The
galvanostatic charge-discharge measurements show the specific capacity stable
around 450, 400, 350, 300 and 200 mAhg$^{-1}$ at current densities of 0.05,
0.1, 0.3, 0.5 and 1~Ag$^{-1}$, respectively. Also, we observe the capacity
retentions of 86% and 66% at 0.1 and 0.3 Ag$^{-1}$, respectively, over 200
cycles with a consistent Coulombic efficiency of nearly 100%. The cyclic
voltammetry, galvanostatic intermittent titration technique, and
electrochemical impedance spectroscopy are used to find the kinetic behavior
and the obtained value of diffusion coefficient falls in the range of
10$^{-10}$ to 10$^{-12}$ cm$^2$s$^{-1}$. Intriguingly, the in-situ EIS also
explains the electrochemical kinetics of the electrode at different
charge-discharge states with the variation of charge transfer resistance.
Moreover, the post cycling investigation using ex-situ XRD and photoemission
spectroscopy indicate the coexistence of 1T/2H phase and field-emission
scanning electron microscopy confirm the stable morphology after 500 cycles.
Also, the Na-ion transport properties are calculated for 1T Al--MoS$_2$@rGO
interface and Al--MoS$_2$--MoS$_2$ interlayer host structure by theoretical
calculations using density functional theory.",2210.06735v1
2022-11-02,Discovery of a high-temperature antiferromagnetic state and transport signatures of exchange interactions in a Bi2Se3/EuSe heterostructure,"Spatial confinement of electronic topological surface states (TSS) in
topological insulators poses a formidable challenge because TSS are protected
by time-reversal symmetry. In previous works formation of a gap in the
electronic spectrum of TSS has been successfully demonstrated in topological
insulator/magnetic material heterostructures, where ferromagnetic exchange
interactions locally lifts the time-reversal symmetry. Here we report an
experimental evidence of exchange interaction between a topological insulator
Bi2Se3 and a magnetic insulator EuSe. Spin-polarized neutron reflectometry
reveals a reduction of the in-plane magnetic susceptibility within a 2 nm
interfacial layer of EuSe, and the combination of SQUID magnetometry and Hall
measurements points to the formation of an antiferromagnetic layer with at
least five-fold enhancement of N\'eel's temperature. Abrupt resistance changes
in high magnetic fields indicate interfacial exchange coupling that affects
transport in a TSS. High temperature local control of TSS with zero net
magnetization unlocks new opportunities for the design of electronic,
spintronic and quantum computation devices, ranging from quantization of Hall
conductance in zero fields to spatial localization of non-Abelian excitations
in superconducting topological qubits.",2211.01211v1
2022-11-09,Evolution of the strange-metal scattering in momentum space of electron-doped ${\rm La}_{2-x}{\rm Ce}_x{\rm CuO}_4$,"The linear-in-temperature resistivity is one of the important mysteries in
the strange metal state of high-temperature cuprate superconductors. To uncover
this anomalous property, the energy-momentum-dependent imaginary part of the
self-energy Im ${\rm \Sigma}(k, \omega)$ holds the key information. Here we
perform systematic doping, momentum, and temperature-dependent angle-resolved
photoemission spectroscopy measurements of electron-doped cuprate ${\rm
La}_{2-x}{\rm Ce}_x{\rm CuO}_4$ and extract the evolution of the strange metal
scattering in momentum space. At low doping levels and low temperatures, Im
${\rm\Sigma} \propto \omega$ dependence dominates the whole momentum space. For
high doping levels and high temperatures, Im ${\rm\Sigma} \propto \omega^2$
shows up, starting from the antinodal region. By comparing with the hole-doped
cuprates ${\rm La}_{2-x}{\rm Sr}_x{\rm CuO}_4$ and ${\rm Bi}_2{\rm Sr}_2{\rm
CaCu}_2{\rm O}_8$, we find a dichotomy of the scattering rate exists along the
nodal and antinodal direction, which is ubiquitous in the cuprate family. Our
work provides new insight into the strange metal state in cuprates.",2211.04833v1
2023-03-30,Physics-based bias-dependent compact modeling of 1/f noise in single- to few- layer 2D-FETs,"1/f noise is a critical figure of merit for the performance of transistors
and circuits. For two-dimensional devices (2D-FETs), and especially for
applications in the GHz range where short-channel FETs are required, velocity
saturation (VS) effect can result in the reduction of 1/f noise at high
longitudinal electric fields. A new physics-based compact model is for the
first time introduced for single- to few- layer 2D-FETs in this study,
precisely validating 1/f noise experiments for various types of devices. The
proposed model mainly accounts for the measured 1/f noise bias dependence as
the latter is defined by different physical mechanisms. Thus, analytical
expressions are derived, valid in all regions of operation in contrast to
conventional approaches available in literature so far, accounting for carrier
number fluctuation (DN), mobility fluctuation (Dmu}) and contact resistance
(DR) effects based on the underlying physics that rules these devices. DN
mechanism due to trapping/detrapping together with an intense Coulomb
scattering effect, dominates 1/f noise from medium to strong accumulation
region while Dmu, is also demonstrated to modestly contribute in subthreshold
region. DR can also be significant in very high carrier density. The VS induced
reduction of 1/f noise measurements at high electric fields, is also remarkably
captured by the model. The physical validity of the model can also assist in
extracting credible conclusions when conducting comparisons between
experimental data from devices with different materials or dielectrics.",2303.17162v1
2023-04-03,CVD Graphene Contacts for Lateral Heterostructure MoS${_2}$ Field Effect Transistors,"Intensive research is carried out on two-dimensional materials, in particular
molybdenum disulfide, towards high-performance transistors for integrated
circuits. Fabricating transistors with ohmic contacts is challenging due to the
high Schottky barrier that severely limits the transistors' performance.
Graphene-based heterostructures can be used in addition or as a substitute for
unsuitable metals. We present lateral heterostructure transistors made of
scalable chemical vapor-deposited molybdenum disulfide and chemical
vapor-deposited graphene with low contact resistances of about 9
k${\Omega}$${\mu}$m and high on/off current ratios of 10${^8}$. We also present
a theoretical model calibrated on our experiments showing further potential for
scaling transistors and contact areas into the few nanometers range and the
possibility of a strong performance enhancement by means of layer optimizations
that would make transistors promising for use in future logic circuits.",2304.01177v2
2023-09-21,Superconductivity in Compositionally-Complex Cuprates with the YBa$_2$Cu$_3$O$_{7-x}$ Structure,"High-temperature superconductivity is reported in a series of
compositionally-complex cuprates with varying degrees of size and spin
disorder. Three compositions of Y-site alloyed YBa$_2$Cu$_3$O$_{7-x}$, i.e.,
(5Y)BCO, were prepared using solid-state methods with different sets of rare
earth ions on the Y-site. Synchrotron X-ray diffraction and energy-dispersive
X-ray spectroscopy confirm these samples have high phase-purity and homogeneous
mixing of the Y-site elements. The superconducting phase transition was probed
using electrical resistivity and AC magnetometry measurements, which reveal the
transition temperature, T$_C$, is greater than 91 K for all series when near
optimal oxygen doping. Importantly, these T$_C$ values are only $\approx$1$\%$
suppressed relative to pure YBCO (T$_C$ = 93 K). This result highlights the
robustness of pairing in the YBCO structure to specific types of disorder. In
addition, the chemical flexibility of compositionally-complex cuprates allows
spin and lattice disorder to be decoupled to a degree not previously possible
in high-temperature superconductors. This feature makes compositionally-complex
cuprates a uniquely well-suited materials platform for studying proposed
pairing interactions in cuprates.",2309.12535v1
2023-12-11,Local laser-induced solid-phase recrystallization of phosphorus-implanted Si/SiGe heterostructures for contacts below 4.2 K,"Si/SiGe heterostructures are of high interest for high mobility transistor
and qubit applications, specifically for operations below 4.2 K. In order to
optimize parameters such as charge mobility, built-in strain, electrostatic
disorder, charge noise and valley splitting, these heterostructures require Ge
concentration profiles close to mono-layer precision. Ohmic contacts to undoped
heterostructures are usually facilitated by a global annealing step activating
implanted dopants, but compromising the carefully engineered layer stack due to
atom diffusion and strain relaxation in the active device region. We
demonstrate a local laser-based annealing process for recrystallization of
ion-implanted contacts in SiGe, greatly reducing the thermal load on the active
device area. To quickly adapt this process to the constantly evolving
heterostructures, we deploy a calibration procedure based exclusively on
optical inspection at room-temperature. We measure the electron mobility and
contact resistance of laser annealed Hall bars at temperatures below 4.2 K and
obtain values similar or superior than that of a globally annealed reference
samples. This highlights the usefulness of laser-based annealing to take full
advantage of high-performance Si/SiGe heterostructures.",2312.06267v1
2023-03-13,Unusual magnetotransport and anomalous Hall effect in quasi-two-dimensional van der Waals ferromagnet Fe$_4$GeTe$_2$,"Fe$_4$GeTe$_2$, an itinerant vdW ferromagnet (FM) having Curie temperature
(T$_C$) close to room temperature ($\sim 270$ K), exhibits another transition
(T$_{SR}$ $\sim$ 120 K) where the easy axis of magnetization changes from
in-plane to the out-of-plane direction in addition to T$_C$. Here, we have
studied the magnetotransport in a multilayer Hall bar device fabricated on 300
nm Si/SiO$_2$ substrate. Interestingly, the zero field resistivity shows a
negligible change in resistivity near T$_C$ unlike the typical metallic FM,
whereas, it exhibits a dramatic fall below T$_{SR}$. Also, the resistivity
shows a weak anomaly at T $ \sim $ 38 K (T$_Q$), below which the resistivity
shows a quadratic temperature dependence according to the Fermi liquid
behavior. Temperature-dependent Hall data exhibits important consequences. The
ordinary Hall coefficient changes sign near T$_{SR}$ indicating the change in
majority carriers. In a similar manner, the magnetoresistance (MR) data shows
significantly large negative MR near T$_{SR}$ and becomes positive below T$_Q$.
The observations of anomaly in the resistivity, sign-change of the ordinary
Hall coefficient and maximum negative MR near T$_{SR}$, together suggest a
possible Fermi surface reconstruction associated with the spin reorientation
transition. Furthermore, analysis of the Hall data reveals a significant
anomalous Hall conductivity (AHC) from $\sim 123 \Omega^{-1}$ cm$^{-1}$ (at T
$\approx$ 5 K) to the maximum value of $\sim 366 \Omega^{-1}$ cm$^{-1}$ near
T$_{SR}$. While the low-temperature part may originate due to the intrinsic KL
mechanism, our analysis indicates that the temperature-dependent AHC is
primarily appearing due to the side-jump mechanism as a result of the spin-flip
electron-magnon scattering. Our study demonstrates an interplay between
magnetism and band topology and its consequence on electron transport in
Fe$_4$GeTe$_2$.",2303.07440v1
2020-03-04,Adaptive phase field modelling of crack propagation in orthotropic functionally graded materials,"In this work, we extend the recently proposed adaptive phase field method to
model fracture in orthotropic functionally graded materials (FGMs). A recovery
type error indicator combined with quadtree decomposition is employed for
adaptive mesh refinement. The proposed approach is capable of capturing the
fracture process with a localized mesh refinement that provides notable gains
in computational efficiency. The implementation is validated against
experimental data and other numerical experiments on orthotropic materials with
different material orientations. The results reveal an increase in the
stiffness and the maximum force with increasing material orientation angle. The
study is then extended to the analysis of orthotropic FGMs. It is observed
that, if the gradation in fracture properties is neglected, the material
gradient plays a secondary role, with the fracture behaviour being dominated by
the orthotropy of the material. However, when the toughness increases along the
crack propagation path, a substantial gain in fracture resistance is observed.",2003.04689v1
2020-09-04,Impact of interfaces on the radiation response and underlying defect recovery mechanisms in nanostructured Cu-Fe-Ag,"Newest developments in nuclear fission and fusion technology as well as
planned long-distance space missions demand novel materials to withstand harsh,
irradiative environments. Radiation-induced hardening and embrittlement are a
concern that can lead to failure of materials deployed in these applications.
Here the underlying mechanisms are accommodation and clustering of lattice
defects created by the incident radiation particles. Interfaces, such as free
surfaces, phase and grain boundaries, are known for trapping and annihilating
defects and therefore preventing these radiation-induced defects from forming
clusters. In this work, differently structured nanocomposite materials based on
Cu-Fe-Ag were fabricated using a novel solid-state route, combining severe
plastic deformation with thermal and electrochemical treatments. The influence
of different interface types and spacings on radiation effects in these
materials was investigated using nanoindentation. Interface-rich bulk
nanocomposites showed a slight decrease in hardness after irradiation, whereas
the properties of a nanoporous material remain mostly unchanged. An explanation
for this different material behavior and its link to recovery mechanisms at
interfaces is attempted in this work, paving a concept towards radiation
resistant materials.",2009.02039v1
2021-03-05,Effect of spoke design and material nonlinearity on non-pneumatic tire stiffness and durability performance,"Non-pneumatic tire has been widely used due to their advantages of no
run-flat, no need of air maintenance, low rolling resistance, and improvement
of passengers comfort due to its better shock absorption. It has variety of
application in the military vehicle, earthmovers, lunar rover, stair climbing
vehicles etc. Recently UPTIS (Unique Puncture-Proof Tire System) non pneumatic
tire has been introduced for passenger vehicles. In this study three different
design configuration Tweel, Honeycomb and newly developed UPTIS have been
compared. Effect of Polyurethane (PU) material nonlinearity have also been
introduced by applying 5 different nonlinear PU material property in the
spokes. The combined analysis of the PU material nonlinearity and spoke design
configuration on the overall tire stiffness and spoke damage prediction is
analysed using 3-Dimensional FEM simulations performed in ANSYS 16.0. It has
been observed that Mooney Rivlin 5-parameter model is best to capture all 5
studied PU materials the nonlinearity. Effect of material nonlinearity on
various spoke designs have been studied. The best combination of spoke design
and the use of nonlinear material have been suggested in terms of riding
comfort, tire stiffness and durability performance.",2103.03637v1
2023-01-24,Seebeck-driven transverse thermoelectric generation in magnetic hybrid bulk materials,"The Seebeck-driven transverse thermoelectric generation in
magnetic/thermoelectric hybrid materials (STTG) has been investigated in
all-bulk hybrid materials. The transverse thermopower in a ferromagnetic
Co$_2$MnGa/thermoelectric $n$-type Si hybrid bulk material with the adjusted
dimensions reaches 16.0 $\mu$V/K at room temperature with the aid of the STTG
contribution, which is much larger than the anomalous Nernst coefficient of the
Co$_2$MnGa slab (6.8 $\mu$V/K). Although this transverse thermopower is smaller
than the value for previously reported thin-film-based hybrid materials, the
hybrid bulk materials exhibit much larger electrical power owing to their small
internal resistance. This demonstration confirms the validity of STTG in bulk
materials and clarifies its potential as a thermal energy harvester.",2301.09903v1
2023-01-24,Accelerate & Actualize: Can 2D Materials Bridge the Gap Between Neuromorphic Hardware and the Human Brain?,"Two-dimensional (2D) materials present an exciting opportunity for devices
and systems beyond the von Neumann computing architecture paradigm due to their
diversity of electronic structure, physical properties, and atomically-thin,
van der Waals structures that enable ease of integration with conventional
electronic materials and silicon-based hardware. All major classes of
non-volatile memory (NVM) devices have been demonstrated using 2D materials,
including their operation as synaptic devices for applications in neuromorphic
computing hardware. Their atomically-thin structure, superior physical
properties, i.e., mechanical strength, electrical and thermal conductivity, as
well as gate-tunable electronic properties provide performance advantages and
novel functionality in NVM devices and systems. However, device performance and
variability as compared to incumbent materials and technology remain major
concerns for real applications. Ultimately, the progress of 2D materials as a
novel class of electronic materials and specifically their application in the
area of neuromorphic electronics will depend on their scalable synthesis in
thin-film form with desired crystal quality, defect density, and phase purity.",2301.10277v1
2023-07-19,Emergence of high-temperature superconducting phase in the pressurized La3Ni2O7 crystals,"The recent report of pressure-induced structure transition and signature of
superconductivity with Tc = 80 K above 14 GPa in the La3Ni2O7 crystals has
garnered considerable attention. To further elaborate this discovery, we
carried out comprehensive resistance measurements on the La3Ni2O7 crystals
grown with the optical-image floating zone furnace under oxygen pressure (15
bar) by using the diamond anvil cell (DAC) and cubic anvil cell (CAC), which
employs the solid and liquid pressure transmitting medium, respectively. For
the sample #1 measured in DAC, it exhibits a semiconducting-like behavior with
large resistance at low pressures and becomes metallic gradually upon
compression. At the pressures P >= 13.7 GPa, we observed the appearance of
resistance drop as large as ~50% around 70 K, which evolves into a kink-like
anomaly at pressures above 40 GPa and shifts to lower temperatures gradually
with increasing magnetic field. These observations are consistent with the
recent report mentioned above. On the other hand, the sample #2 measured in CAC
retains the metallic behavior in the investigated pressure range up to 15 GPa.
The hump-like anomaly in resistance around ~130 K at ambient pressure
disappears at P >= 2 GPa. In the pressure range from 11 to 15 GPa, we observed
the gradual development of a shoulder-like anomaly in resistance at low
temperatures, which evolves into a pronounced drop of resistance by 98% below
62 K at 15 GPa, reaching a temperature-independent resistance of 20 uOhm below
20 K. Similarly, this resistance anomaly can be shifted to lower temperatures
progressively by applying external magnetic fields, resembling a typical
superconducting transition.",2307.09865v1
2023-07-27,High-temperature superconductivity with zero-resistance and strange metal behavior in La$_{3}$Ni$_{2}$O$_{7-δ}$,"Recently signatures of superconductivity were observed close to 80 K in \LN\
under pressure. This discovery positions \LN\ as the first bulk nickelate with
high-temperature superconductivity, but the lack of zero resistance presents a
significant drawback for validating the findings. Here we report pressure
measurements up to over 30 GPa using a liquid pressure medium and show that
single crystals of \LNO\ do exhibit zero resistance. We find that \LNO\ remains
metallic under applied pressures, suggesting the absence of a metal-insulator
transition proximate to the superconductivity. Analysis of the normal state
$T$-linear resistance suggests an intricate link between this strange metal
behaviour and superconductivity, whereby at high pressures both the linear
resistance coefficient and superconducting transition are slowly suppressed by
pressure, while at intermediate pressures both the superconductivity and
strange metal behaviour appear disrupted, possibly due to a nearby structural
instability. The association between strange metal behaviour and
high-temperature superconductivity is very much in line with diverse classes of
unconventional superconductors, including the cuprates and Fe-based
superconductors. Understanding the superconductivity of \LNO\ evidently
requires further revealing the interplay of strange metal behaviour,
superconductivity, as well as possible competing electronic or structural
phases.",2307.14819v2
2023-08-04,Stopping microfluidic flow,"We present a cross-comparison of three stop-flow configurations--such as
low-pressure (LSF), high-pressure open-circuit (OC-HSF), and high-pressure
short-circuit (SC-HSF) stop-flow--to rapidly bring a high flow velocity within
a microchannel to a standstill. The average velocities inside the microchannels
were reduced from > 1 m/s to < 10 um/s within 2s of initiating the stop-flow.
The performance of the three stop-flow configurations was assessed by measuring
the residual flow velocities within microchannels having three
orders-of-magnitude different flow resistances. The LSF configuration
outperformed the OC-HSF and SC-HSF configurations within the high flow
resistance microchannel, and resulted in a residual velocity of < 10 um/s. The
OC-HSF configuration resulted in a residual velocity of < 150 um/s within a low
flow resistance microchannel. The SC-HSF configuration resulted in a residual
velocity of < 200 um/s across the three orders-of-magnitude different flow
resistance microchannels, and < 100 um/s for the low flow resistance channel.
We hypothesized that the residual velocity resulted from the compliance in the
fluidic circuit, which was further investigated by varying the elasticity of
the microchannel walls and the connecting tubing. A numerical model was
developed to estimate the expanded volumes of the compliant microchannel and
connecting tubings under a pressure gradient and to calculate the distance
traveled by the sample fluid. A comparison of the numerically and
experimentally obtained traveling distances confirmed our hypothesis that the
residual velocities were an outcome of the compliance in the fluidic circuit.
Therefore, a configuration with minimal fluidic circuit compliance resulted in
the least residual velocity.",2308.02386v2
2009-06-02,The Evolution of Gas Clouds Falling in the Magnetized Galactic Halo: High Velocity Clouds (HVCs) Originated in the Galactic Fountain,"In the Galactic fountain scenario, supernovae and/or stellar winds propel
material into the Galactic halo. As the material cools, it condenses into
clouds. By using FLASH three-dimensional magnetohydrodynamic simulations, we
model and study the dynamical evolution of these gas clouds after they form and
begin to fall toward the Galactic plane. In our simulations, we assume that the
gas clouds form at a height of z=5 kpc above the Galactic midplane, then begin
to fall from rest. We investigate how the cloud's evolution, dynamics, and
interaction with the interstellar medium (ISM) are affected by the initial mass
of the cloud. We find that clouds with sufficiently large initial densities (>
0.1 hydrogen atoms per cc) accelerate sufficiently and maintain sufficiently
large column densities as to be observed and identified as high-velocity clouds
(HVCs) even if the ISM is weakly magnetized (1.3 micro Gauss). We also
investigate the effects of various possible magnetic field configurations. As
expected, the ISM's resistance is greatest when the magnetic field is strong
and perpendicular to the motion of the cloud. The trajectory of the cloud is
guided by the magnetic field lines in cases where the magnetic field is
oriented diagonal to the Galactic plane. The model cloud simulations show that
the interactions between the cloud and the ISM can be understood via analogy to
the shock tube problem which involves shock and rarefaction waves. We also
discuss accelerated ambient gas, streamers of material ablated from the clouds,
and the cloud's evolution from a sphere-shaped to a disk- or cigar-shaped
object.",0906.0613v1
2018-10-30,THz-TDS time-trace analysis for the extraction of material and metamaterial parameters,"We report on a method and an associated open source software, Fit@TDS,
working on an average personal computer. The method is based on the fitting of
a time-trace data of a terahertz time-domain-spectroscopy system enabling the
retrieval of the refractive index of a dielectric sample and the resonance
parameters of a metasurface (quality factor, absorption losses, etc.). The
software includes commonly used methods where the refractive index is extracted
from frequency domain data. However, these methods are limited, for instance in
case of a high noise level or when an absorption peak saturates the absorption
spectrum bringing the signal to the noise level. Our software allows to use a
new method where the refractive indices are directly fitted from the
time-trace. The idea is to model a material or a metamaterial through
parametric physical models (Drude-Lorentz model and time-domain coupled mode
theory) and to implement the subsequent refractive index in the propagation
model to simulate the time-trace. Then, an optimization algorithm is used to
retrieve the parameters of the model corresponding to the studied
material/metamaterial. In this paper, we explain the method and test it on
fictitious samples to probe the feasibility and reliability of the proposed
model. Finally, we used Fit@TDS on real samples of high resistivity silicon,
lactose and gold metasurface on quartz to show the capacity of our method",1810.12567v4
2020-05-28,Graphene-TiS$_3$ heterojunction for selective polar vapor sensing at room temperature,"In this work, the room temperature polar vapor sensing behavior of two
dimentional (2D) heterojunction Graphene-TiS3 materials and TiS3 nanoribbons is
investigated. TiS3 nanoribbons were synthesized via chemical vapor transport
(CVT) and their structure was investigated by scanning electron microscopy
(SEM), high resolution transmission electron microscopy (HRTEM), energy
dispersive X- ray spectroscopy (EDS), X-ray diffraction (XRD), Raman
spectroscopy and Fourier transform infrared spectroscopy (FT-IR) analysis. The
gas sensing performance of the TiS3 nanoribbons was assessed through the
observed changes in their electronic behavior. Sensing devices were fabricated
with gold contacts and with lithographically patterned graphene (Gr) electrodes
in a 2D heterojunction Gr-TiS3-Gr architecture.. It is observed that the gold
contacted TiS3 device has a rather linear I-V behavior while the Gr-TiS3-Gr
heterojunction forms a contact with a higher Schottky barrier (250 meV). I-V
responses of the sensors were recorded at room temperature with a relative
humidity of 55% and for different ethanol vapor concentrations (varying from 2
to 20 ppm). I-V plots indicated an increase in the resistance of Gr-TiS3-Gr by
the adsorption of water and ethanol molecules with relatively high sensing
response (~3353% at 2 ppm). Our results reveal that selective and stable
responses to a low concentration of ethanol vapor (2 ppm) can be achieved at
room temperature with transient response and recovery times of around 6 s and
40 s, respectively. Our proposed design demonstrate a new approach for
selective molecular recognition using polar interactions between analyte vapors
and heterojunctions of 2D-materials.",2005.14245v1
2022-01-06,A quantitative assessment of Imaging High-Z and Medium-Z materials using Muon Scattering Tomography,"Muon Scattering Tomography (MST) has been shown to be a powerful technique
for the non-invasive imaging of high-shielded objects. We present here the
application of the MST technique to investigate two types of nuclear waste
packages, a small-steel drum and a large nuclear waste cask, namely, a CASTOR
V/52. We have developed a quantitative method using the contrast-to-noise ratio
(CNR) to evaluate the performance of an MST detector system in differentiating
between high-, medium-, and low-Z materials inside nuclear waste packages with
different shielding types. This study reveals that our MST detector system is
able to differentiate between a (10 $\times$ 10 $\times$ 10 cm$^3$) uranium
cube, embedded within a concrete matrix inside the small-steel drum, and
regions of background signal in six hours of muon exposure time with a CNR
value of 3.1$\pm$0.2. During our investigation of the highly-shielded cask, the
reconstructed images of the cask contents indicated the ability of our system
to detect irregular baskets, such as empty baskets, with a CNR value of
5.0$\pm$0.3 after 30 days of muon exposure. These studies were done using a
Monte Carlo simulation tuned to the performance of resistive plate chambers
(RPCs) based muon tomography system built by the University of Bristol, which
had a reported position resolution of 350 micron.
  Here we also report the dependence of the performance on the position
resolution. We argue that using a combination of RPC and drift chambers (DC)
detectors with 700 micron and 4 mm position resolutions respectively is able to
generate tomographic images of well-shielded materials in a few hours of muon
exposure time. With these position resolutions, our system needs six hours of
muon exposure time to produce a good quality image of a cube of uranium with
side-length of 10 cm shielded by a concrete matrix with CNR value of
2.4$\pm$0.25.",2201.01877v3
2023-03-07,Stacking disorder and thermal transport properties of $α$-RuCl$_3$,"$\alpha$-RuCl$_3$, a well-known candidate material for Kitaev quantum spin
liquid, is prone to stacking disorder due to the weak van der Waals bonding
between the honeycomb layers. After a decade of intensive experimental and
theoretical studies, the detailed correlation between stacking degree of
freedom, structure transition, magnetic and thermal transport properties
remains unresolved. In this work, we reveal the effects of a small amount of
stacking disorder inherent even in high quality $\alpha$-RuCl$_3$ crystals.
This small amount of stacking disorder results in the variation of the magnetic
ordering temperature, suppresses the structure transition and thermal
conductivity. Crystals with minimal amount of stacking disorder have a
T$_N>$7.4\,K and exhibit a well-defined structure transition around 140\,K upon
cooling. For those with more stacking faults and a T$_N$ below 7\,K, the
structure transition occurs well below 140\,K upon cooling and is incomplete,
manifested by the diffuse streaks and the coexistence of both high temperature
and low temperature phases down to the lowest measurement temperature. Both
types of crystals exhibit oscillatory field dependent thermal conductivity and
a plateau-like feature in thermal Hall resistivity in the field-induced quantum
spin liquid state. However, $\alpha$-RuCl$_3$ crystals with minimal amount of
stacking disorder have a higher thermal conductivity that pushes the thermal
Hall conductivity to be closer to the half-integer quantized value. These
findings demonstrate a strong correlation between layer stacking, structure
transition, magnetic and thermal transport properties, underscoring the
importance of interlayer coupling in $\alpha$-RuCl$_3$ despite the weak van der
Waals bonding.",2303.03682v2
2023-12-27,"Combined effect of SiC and carbon on sintering kinetics, microstructure and mechanical properties of fine-grained binderless tungsten carbide","The study investigates the density, phase composition, microstructure and
mechanical properties (microhardness, fracture toughness) of binderless WC +
SiC and WC + SiC + C ceramics obtained by Spark Plasma Sintering (SPS).
Nanopowders of a-WC produced by DC arc plasma chemical synthesis were used as
raw materials. Powder compositions for sintering contained graphite (0.3, 0.5%
wt.) or b-SiC (1, 3, 5% wt.) with 0.3% wt. graphite. It was shown that WC + 1%
wt. SiC + 0.3% wt.C ceramics have a homogeneous fine-grained microstructure,
high relative density, increased microhardness and Palmquist fracture toughness
(Indentation Fracture Resistance). The kinetics of the initial sintering stage
of WC + C and WC + C + SiC powder compositions was also analyzed using
high-temperature dilatometry at the conventional pressureless sintering (CPS)
conditions. The CPS and SPS activation energies of WC + SiC powder at the
intensive shrinkage stage were determined using the Young-Cutler model. The CPS
activation energies of WC, WC + C and WC + C + SiC powder compositions are
close to the activation energy of diffusion of the carbon C along the a-WC
grain boundaries. The SPS activation energies of WC + C and WC+ C + SiC powder
compositions turn out to be lower than the activation energy of the C of a-WC
grain boundary.",2312.16579v1
2022-07-26,Hysteresis-Free High Mobility Graphene Encapsulated in Tungsten Disulfide,"High mobility is a crucial requirement for a large variety of electronic
device applications. The state-of-the-art for high quality graphene devices is
based on heterostructures made with graphene encapsulated in $>80\,$nm-thick
flakes of hexagonal boron nitride (hBN). Unfortunately, scaling up multilayer
hBN while precisely controlling the number of layers remains an elusive
challenge, resulting in a rough material unable to enhance the mobility of
graphene. This leads to the pursuit of alternative, scalable materials, which
can be simultaneously used as substrate and encapsulant for graphene. Tungsten
disulfide (WS$_2$) is a transition metal dichalcogenide, which was successfully
grown in large ($\sim$mm-size) multi-layers by chemical vapour deposition.
However, the resistance \textit{vs} gate voltage characteristics when gating
graphene through WS$_2$ exhibit largely hysteretic shifts of the charge
neutrality point (CNP) in the order of $\Delta n\sim$2.6$\cdot$10$^{11}$
cm$^{-2}$, hindering the use of WS$_2$ as a reliable encapsulant. The
hysteresis originates due to the charge traps from sulfur vacancies present in
WS$_2$. In this work, we report for the first time the use of WS$_2$ as a
substrate and the overcoming of hysteresis issues by chemically treating WS$_2$
with a super-acid, which passivates these vacancies and strips the surface from
contaminants. The hysteresis is significantly reduced below the noise level by
at least a factor five (to $\Delta n<$5$\cdot$10$^{10}$ cm$^{-2}$) and,
simultaneously, the room-temperature mobility of WS$_2$-encapsulated graphene
is as high as $\sim$6.2$\cdot$10$^{4}$ cm$^{-2}$V$^{-1}$s$^{-1}$ at a carrier
density $n$ $\sim$1$\cdot$ 10$^{12}$ cm$^{-2}$. Our results promote WS$_2$ to a
valid alternative to hBN as encapsulant for high-performance graphene devices.",2207.12836v1
2000-06-23,Temperature-Dependence of the Resistivity of a Dilute 2D Electron System in High Parallel Magnetic Field,"We report measurements of the resistance of silicon MOSFETs as a function of
temperature in high parallel magnetic fields where the 2D system of electrons
has been shown to be fully spin-polarized. A magnetic field suppresses the
metallic behavior observed in the absence of a magnetic field. In a field of
10.8 T, insulating behavior is found for densities up to n_s approximately 1.35
x 10^{11} cm^{-2} or 1.5 n_c; above this density the resistance is a very weak
function of temperature, varying less than 10% between 0.25 K and 1.90 K. At
low densities the resistance goes to infinity more rapidly as the temperature
is reduced than in zero field and the magnetoresistance diverges as T goes to
0.",0006379v4
2002-10-08,Resistivity of dilute 2D electrons in an undoped GaAs heterostructure,"We report resistivity measurements from 0.03 K to 10 K in a dilute high
mobility 2D electron system. Using an undoped GaAs/AlGaAs heterojunction in a
gated field-effect transistor geometry, a wide range of densities, $0.16 \times
10^{10} {cm}^{-2}$ to $7.5 \times 10^{10} {cm}^{-2}$, are explored. For high
densities, the results are quantitatively shown to be due to scattering by
acoustic phonons and impurities. In an intermediate range of densities, a peak
in the resistivity is observed for temperatures below 1 K. This non-monotonic
resistivity can be understood by considering the known scattering mechanisms of
phonons, bulk and interface ionized impurities. Still lower densities appear
insulating to the lowest temperature measured.",0210155v1
2003-09-11,Superconductivity on the localization threshold and magnetic-field-tuned superconductor-insulator transition in TiN films,"Temperature- and magnetic-field dependent measurements of the resistance of
ultrathin superconducting TiN films are presented. The analysis of the
temperature dependence of the zero field resistance indicates an underlying
insulating behavior, when the contribution of Aslamasov-Larkin fluctuations is
taken into account. This demonstrates the possibility of coexistence of the
superconducting and insulating phases and of a direct transition from the one
to the other. The scaling behavior of magnetic field data is in accordance with
a superconductor-insulator transition (SIT) driven by quantum phase
fluctuations in two-dimensional superconductor. The temperature dependence of
the isomagnetic resistance data on the high-field side of the SIT has been
analyzed and the presence of an insulating phase was confirmed. A transition
from the insulating to a metallic phase is found at high magnetic fields, where
the zero-temperature asymptotic value of the resistance being equal to h/e^2.",0309281v2
2003-10-02,Electrical resistivity of the Ti4O7 Magneli phase under high pressure,"We have measured resistivity as a function of temperature and pressure of
Ti4O7 twinned crystals using different contact configurations. Pressures over
4kbar depress the localization of bipolarons and allow the study of the
electrical conduction of the bipolaronic phase down to low temperatures. For
pressures P > 40 kbar the bipolaron formation transition is suppressed and a
nearly pressure independent behavior is obtained for the resistivity. We
observed an anisotropic conduction. When current is injected parallel to the
principal axis, a metallic conduction with interacting carrier effects is
predominant. A superconducting state was not obtained down to 1.2 K, although
evidences of the proximity of a quantum critical point were noticed. While when
current is injected non-parallel to the crystal's principal axis, we obtained a
logarithmic divergence of the resistivity at low temperatures. For this case,
our results for the high pressure regime can be interpreted in the framework of
interacting carriers (polarons or bipolarons) scattered by Two Level Systems.",0310048v1
2004-03-17,Interaction Correction to the Longitudinal Conductivity and Hall Resistivity in High Quality Two-Dimensional GaAs Electron and Hole Systems,"We present a systematic study of the corrections to both the longitudinal
conductivity and Hall resistivity due to electron-electron interactions in high
quality GaAs systems using the recent theory of Zala et al. [Phys. Rev. B 64,
214204 (2001)]. We demonstrate that the interaction corrections to the
longitudinal conductivity and Hall resistivity predicted by the theory are
consistent with each other. This suggests that the anomalous metallic drop in
resistivity at B=0 is due to interaction effects and supports the theory of
Zala et al.",0403411v1
2005-05-19,Universal scaling behavior of the c-axis resistivity of high-temperature superconductors,"We propose and show that the c-axis transport in high-temperature
superconductors is controlled by the pseudogap energy and the c-axis
resistivity satisfies a universal scaling law in the pseudogap phase. We
derived approximately a scaling function for the c-axis resistivity and found
that it fits well with the experimental data of
Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$,
and YBa$_2$Cu$_3$O$_{7-\delta}$. Our works reveals the physical origin of the
semiconductor-like behavior of the c-axis resistivity and suggests that the
c-axis hopping is predominantly coherent.",0505480v2
2006-07-27,Effect of DC electric field on longitudinal resistance of two dimensional electrons in a magnetic field,"The effect of a DC electric field on the longitudinal resistance of highly
mobile two dimensional electrons in heavily doped GaAs quantum wells is studied
at different magnetic fields and temperatures. Strong suppression of the
resistance by the electric field is observed in magnetic fields at which the
Landau quantization of electron motion occurs. The phenomenon survives at high
temperature where Shubnikov de Haas oscillations are absent. The scale of the
electric fields essential for the effect is found to be proportional to
temperature in the low temperature limit. We suggest that the strong reduction
of the longitudinal resistance is the result of a nontrivial change in the
distribution function of 2D electrons induced by the DC electric field.
Comparison of the data with recent theory yields the inelastic electron-electon
scattering time $\tau_{in}$ and the quantum scattering time $\tau_q$ of 2D
electrons at high temperatures, a regime where previous methods were not
successful.",0607741v1
2009-05-07,Correlation between linear resistivity and Tc in organic and pnictide superconductors,"A linear temperature dependence of the electrical resistivity as T -> 0 is
the hallmark of quantum criticality in heavy-fermion metals and the archetypal
normal-state property of high-Tc superconductors, yet in both cases it remains
unexplained. We report a linear resistivity on the border of spin-density-wave
order in the organic superconductor (TMTSF)2X (X = PF6, ClO4), whose strength
scales with the superconducting temperature Tc. This scaling, also present in
the pnictide superconductors, reveals an intimate connection between linear-T
scattering and pairing, shown by renormalization group theory to arise from
antiferromagnetic fluctuations, enhanced by the interference of superconducting
correlations. Our results suggest that linear resistivity in general may be a
consequence of such interference and pairing in overdoped high-Tc cuprates is
driven by antiferromagnetic fluctuations, as in organic and pnictide
superconductors.",0905.0964v1
2010-02-25,Signatures of pressure induced superconductivity in insulating Bi2212,"We have performed several high pressure electrical resistance experiments on
Bi1.98Sr2.06Y0.68Cu2O8, an insulating parent compound of the high-Tc Bi2212
family of copper oxide superconductors. We find a resistive anomaly, a downturn
at low temperature, that onsets with applied pressure in the 20-40 kbar range.
Through both resistance and magnetoresistance measurements, we identify this
anomaly as a signature of induced superconductivity. Resistance to higher
pressures decreases Tc, giving a maximum of 10 K. The higher pressure
measurements exhibit a strong sensitivity to the hydrostaticity of the pressure
environment. We make comparisons to the pressure induced superconductivity now
ubiquitous in the iron arsenides.",1002.4672v1
2010-05-10,Analysis and Design of Ultra Thin Electromagnetic Absorbers Comprising Resistively Loaded High Impedance Surfaces,"High-Impedance Surfaces (HIS) comprising lossy Frequency Selective Surfaces
(FSS) are employed to design thin electromagnetic absorbers. The structure,
despite its typical resonant behavior, is able to perform a very wideband
absorption in a reduced thickness. Losses in the frequency selective surface
are introduced by printing the periodic pattern through resistive inks and
hence avoiding the typical soldering of a large number of lumped resistors. The
effect of the surface resistance of the FSS and dielectric substrate
characteristics on the input impedance of the absorber is discussed by means of
a circuital model. It is shown that the optimum value of surface resistance is
affected both by substrate parameters (thickness and permittivity) and by FSS
element shape. The equivalent circuit model is then used to introduce the
working principles of the narrowband and the wideband absorbing structure and
to derive the best-suited element for wideband absorption. Finally, the
experimental validation of the presented structures is presented.",1005.1553v1
2011-07-05,Resistive Solutions for Pulsar Magnetospheres,"The current state of the art in the modeling of pulsar magnetospheres invokes
either the vacuum or force-free limits for the magnetospheric plasma. Neither
of these limits can simultaneously account for both the plasma currents and the
accelerating electric fields that are needed to explain the morphology and
spectra of high-energy emission from pulsars. To better understand the
structure of such magnetospheres, we combine accelerating fields and force-free
solutions by considering models of magnetospheres filled with resistive plasma.
We formulate Ohm's Law in the minimal velocity fluid frame and construct a
family of resistive solutions that smoothly bridges the gap between the vacuum
and the force-free magnetosphere solutions. The spin-down luminosity, open
field line potential drop, and the fraction of open field lines all transition
between the vacuum and force-free values as the plasma conductivity varies from
zero to infinity. For fixed inclination angle, we find that the spin-down
luminosity depends linearly on the open field line potential drop. We consider
the implications of our resistive solutions for the spin down of intermittent
pulsars and sub-pulse drift phenomena in radio pulsars.",1107.0979v2
2011-11-02,Development and Performance of spark-resistant Micromegas Detectors,"The Muon ATLAS MicroMegas Activity (MAMMA) focuses on the development and
testing of large-area muon detectors based on the bulk-Micromegas technology.
These detectors are candidates for the upgrade of the ATLAS Muon System in view
of the luminosity upgrade of Large Hadron Collider at CERN (sLHC). They will
combine trigger and precision measurement capability in a single device. A
novel protection scheme using resistive strips above the readout electrode has
been developed. The response and sparking properties of resistive Micromegas
detectors were successfully tested in a mixed (neutron and gamma) high
radiation field, in a X-ray test facility, in hadron beams, and in the ATLAS
cavern. Finally, we introduced a 2-dimensional readout structure in the
resistive Micromegas and studied the detector response with X-rays.",1111.0426v1
2011-11-09,Nonequilibrium phenomena in high Landau levels,"Developments in the physics of 2D electron systems during the last decade
have revealed a new class of nonequilibrium phenomena in the presence of a
moderately strong magnetic field. The hallmark of these phenomena is
magnetoresistance oscillations generated by the external forces that drive the
electron system out of equilibrium. The rich set of dramatic phenomena of this
kind, discovered in high mobility semiconductor nanostructures, includes, in
particular, microwave radiation-induced resistance oscillations and
zero-resistance states, as well as Hall field-induced resistance oscillations
and associated zero-differential resistance states. We review the experimental
manifestations of these phenomena and the unified theoretical framework for
describing them in terms of a quantum kinetic equation. The survey contains
also a thorough discussion of the magnetotransport properties of 2D electrons
in the linear response regime, as well as an outlook on future directions,
including related nonequilibrium phenomena in other 2D electron systems.",1111.2176v3
2011-12-12,Resistivity Calculations for Cuprate Superconductor Systems using an Electronic Phase Separation,"The resistivity as function of temperature of high temperature
superconductors is very unusual and despite its importance lacks an unified
theoretical explanation. It is linear with the temperature for overdoped
compounds but it falls more quickly as the doping level decreases, and for
weakly doped samples it has a minimum, increases like an insulator before it
drops to zero at low temperatures. We show that this overall behavior can be
explained by calculations using an electronic phase segregation into two main
component phases with low and high densities. The total resistivity is
calculated by the various contributions through several random picking
processes of the local resistivities and using the Random Resistor Network
approach.",1112.2631v1
2017-11-19,Global current circuit structure in a resistive pulsar magnetosphere model,"Pulsar magnetospheres have strong magnetic fields and large amounts of
plasma. The structures of these magnetospheres are studied using force-free
electrodynamics. To understand pulsar magnetospheres, discussions must include
their outer region. However, force-free electrodynamics is limited in it does
not handle dissipation. Therefore, a resistive pulsar magnetic field model is
needed. To break the ideal magnetohydrodynamic (MHD) condition $E \cdot B = 0$,
Ohm's law is used. In this work, I introduce resistivity depending upon the
distance from the star and obtain a self-consistent steady state by time
integration. Poloidal current circuits form in the magnetosphere while the
toroidal magnetic-field region expands beyond the light cylinder and the
Poynting flux radiation appears. High electric resistivity causes a large space
scale poloidal current circuit and the magnetosphere radiates a larger Poynting
flux than the linear increase outside of the light cylinder radius. The formed
poloidal current circuit has width, which grows with the electric conductivity.
This result contributes to a more concrete dissipative pulsar magnetosphere
model.",1711.07471v1
2018-10-10,Test particles in relativistic resistive magnetohydrodynamics,"The Black Hole Accretion Code (BHAC) has recently been extended with the
ability to evolve charged test particles according to the Lorentz force within
resistive relativistic magnetohydrodynamics simulations. We apply this method
to evolve particles in a reconnecting current sheet that forms due to the
coalescence of two magnetic flux tubes in 2D Minkowski spacetime. This is the
first analysis of charged test particle evolution in resistive relativistic
magnetohydrodynamics simulations. The energy distributions of an ensemble of
100.000 electrons are analyzed, as well as the acceleration of particles in the
plasmoids that form in the reconnection layer. The effect of the Lundquist
number, magnetization, and plasma-$\beta$ on the particle energy distribution
is explored for a range of astrophysically relevant parameters. We find that
electrons accelerate to non-thermal energies in the thin current sheets in all
cases. We find two separate acceleration regimes: An exponential increase of
the Lorentz factor during the island coalescence where the acceleration depends
linearly on the resistivity and a nonlinear phase with high variability. These
results are relevant for determining energy distributions and acceleration
sites obtaining radiation maps in large-scale magnetohydrodynamics simulations
of black hole accretion disks and jets.",1810.04323v2
2019-07-07,"First demonstration of 200, 100, and 50 um pitch Resistive AC-Coupled Silicon Detectors (RSD) with 100% fill-factor for 4D particle tracking","We designed, produced, and tested RSD (Resistive AC-Coupled Silicon
Detectors) devices, an evolution of the standard LGAD (Low-Gain Avalanche
Diode) technology where a resistive n-type implant and a coupling dielectric
layer have been implemented. The first feature works as a resistive sheet,
freezing the multiplied charges, while the second one acts as a capacitive
coupling for readout pads. We succeeded in the challenging goal of obtaining
very fine pitch (50, 100, and 200 um) while maintaining the signal waveforms
suitable for high timing and 4D-tracking performances, as in the standard
LGAD-based devices.",1907.03314v3
2020-09-01,On resistive spiking of fungi,"We study long-term electrical resistance dynamics in mycelium and fruit
bodies of oyster fungi P. ostreatus. A nearly homogeneous sheet of mycelium on
the surface of a growth substrate exhibits trains of resistance spikes. The
average width of spikes is c.~23~min and the average amplitude is c.~1~kOhm.
The distance between neighbouring spikes in a train of spikes is c.~30~min.
Typically there are 4-6 spikes in a train of spikes. Two types of resistance
spikes trains are found in fruit bodies: low frequency and high amplitude
(28~min spike width, 1.6~kOhm amplitude, 57~min distance between spikes) and
high frequency and low amplitude (10~min width, 0.6~kOhm amplitude, 44~min
distance between spikes). The findings could be applied in monitoring of
physiological states of fungi and future development of living electronic
devices and sensors.",2009.00292v1
2020-09-21,Contact resistance assessment and high-frequency performance projection of black phosphorus field-effect transistor technologies,"In this work, an evaluation of the contact quality of black phosphorus (BP)
field-effect transistors (FETs) from different technologies previously reported
is performed by means of an efficient and reliable contact resistance
extraction methodology based on individual device practical characteristics. A
good agreement is achieved between the extracted values with the Y-function
method used here and reference values obtained with other methods considering
internal values as well as with more expensive methods involving fabricated
test structures. The method enables a direct evaluation of different steps in
the same technology and it embraces the temperature dependence of the contact
characteristics. Channel phenomena have no impact on the extracted contact
resistance values. High-frequency performance projections are obtained for
fabricated devices based on the extracted contact resistance.",2009.09661v3
2012-06-25,Performances of silicone coated high resistive bakelite RPC,"Performances of several single gap (gas gap 2 mm) prototype Resistive Plate
Chambers (RPC) made of high resistive ({\rho} \sim 1010 - 1012 {\Omega} cm)
bakelite, commercially available in India have been studied in recent times. To
make the inner electrode surfaces smooth, a thin coating of silicone has been
applied. An efficiency > 90% and time resolution \sim 2 ns (FWHM) have been
obtained for both the streamer and the avalanche mode. The induced charge
distributions of those silicone coated RPC are studied and the results are
presented. A numerical study on the effect of surface roughness of the
resistive electrodes on the electric field of the device has been carried out
using Garfield-neBEM code. A few results for a simplified model representing
surface roughness, measured using a surface profilometer for the bakelite
surfaces, have also been presented.",1206.5627v1
2022-08-18,Observation of Fermi liquid phase with broken symmetry in a single crystalline nanorod of Pr$_2$Ir$_2$O$_7$,"We report experimental evidence of emergent broken symmetry Fermi liquid
state in an isolated single crystalline nanorod of $\rm Pr_2 Ir_2 O_7$. We find
clear signature of the onset of the Fermi liquid behavior at low temperature
marked by the sign inversion of magnetoresistance from negative at high
temperature, characteristic of incoherent Kondo scattering, to positive as well
as a $\rm T^2$ dependence of resistivity at low temperature. A resistive
anomaly is observed, which is accompanied by thermal hysteresis in the presence
of magnetic field, suggesting itinerant metamagnetism. The observed high field
negative magnetoresistance with quadratic field dependence at low temperature,
which is most likely due to suppression of itinerant spin fluctuation, and the
irreversibility of the magneto-resistive properties in the Fermi liquid regime
suggest existence of an unusual state with broken spin rotation and time
reversal symmetry, hallmark of `hastatic' order. The major features of such
temperature dependence of resistivity and magnetoresistance can be explained in
a phenomenological model incorporating two distinct hybridization channels,
which is physically consistent with the possibility of the formation of the
`hastatic' Fermi liquid phase.",2208.08811v1
2022-09-16,Prediction of Cross-Fitness for Adaptive Evolution to Different Environmental Conditions: Consequence of Phenotypic Dimensional Reduction,"How adaptive evolution to one environmental stress improves or suppresses
adaptation to another is an important problem in evolutionary biology. For
instance, in microbiology, the evolution of bacteria to be resistant to
different antibiotics is a critical issue that has been investigated as
cross-resistance. In fact, recent experiments on bacteria have suggested that
the cross-resistance of their evolution to various stressful environments can
be predicted by the changes to their transcriptome upon application of stress.
However, there are no studies so far that explain a possible theoretical
relationship between cross-resistance and changes in the transcriptome, which
causes high-dimensional changes to cell phenotype. Here, we show that a
correlation exists between fitness change in stress tolerance evolution and
response to the environment, using a cellular model with a high-dimensional
phenotype and establishing the relationship theoretically. The present results
allow for the prediction of evolution from transcriptome information in
response to different stresses before evolution. The relevance of this to
microbiological evolution experiments is discussed.",2209.07756v2
2023-09-29,Pressure-induced superconductivity in polycrystalline La3Ni2O7,"We synthesized polycrystalline La3Ni2O7 samples by using the sol-gel method
without post-annealing under high oxygen pressure, and then measured
temperature-dependent resistivity under various hydrostatic pressures up to
14.5 GPa in a cubic anvil cell apparatus. We find that the density-wave-like
anomaly in resistivity is progressively suppressed with increasing pressure and
the resistivity drop corresponding to the onset of superconductivity emerges at
pressure as low as 7 GPa. Zero resistivity is achieved at 9 GPa below 6.6 K,
which increases quickly with pressure to 35.6 K at 14.5 GPa. The observation of
zero-resistance state in the polycrystalline La3Ni2O7 samples under high
pressures not only corroborates the recent report of superconductivity in the
pressurized La3Ni2O7 crystals but also facilitates further studies on this
emerging family of nickelate high-Tc superconductors.",2309.17378v2
2005-10-12,Magnetodielectric effect without multiferroic coupling,"The existence of a magnetodielectric (magnetocapacitance) effect is often
used as a test for multiferroic behavior in new material systems. However,
strong magnetodielectric effects can also be achieved through a combination of
magnetoresistance and the Maxwell-Wagner effect, unrelated to multiferroic
coupling. The fact that this resistive magnetocapacitance does not require
multiferroic materials may be advantageous for some practical applications.
Conversely, it also implies that magnetocapacitance per se is not sufficient to
establish multiferroic coupling.",0510313v1
2007-09-24,External Control of a Metal-Insulator Transition in GaMnAs Wires,"Quantum transport in disordered ferromagnetic (III,Mn)V semiconductors is
studied theoretically. Mesoscopic wires exhibit an Anderson disorder-induced
metal-insulator transition that can be controlled by a weak external magnetic
field. This metal-insulator transition should also occur in other materials
with large anisotropic magneto resistance effects. The transition can be useful
for studies of zero-temperature quantum critical phase transitions and
fundamental material properties.",0709.3847v2
2008-01-28,Evidence for hyperconductivity and thermal superconductivity,"Physical explanation of hyperconductivity and thermal superconductivity
existence is done in given article on the basis of inherent atomic nuclei
oscillations in atoms of materials which are connected with electrons and
phonons and in accordance with the well known Bardeen-Cooper-Schrieffer
superconductivity theory.
  It is shown that hyperconductivity is the self-supporting, independent
physical phenomenon which is caused by oscillations of atomic nuclei in atoms
of materials and the minimal temperature of its existence does not reach
absolute zero temperature. Hyperconductivity represents the typical dynamic
condition of a material with zero electrical and zero thermal resistances.",0801.4212v1
2009-11-24,The possible superconductivity at 109 K in YBaCuO materials,"The new YBaCuO superconductors are synthesized by using the standard solid
state reaction method as Y5-6-11, Y7-9-16, Y5-8-13, Y7-11-18, Y156, Y3-8-11,
and Y13-20-23. We find that all material obtained are shown the Meissner effect
at 77 K. The resistivity measurements are used by the four-probe method .The
  Y 7-11-18 has the highest onset as 109 K . The XRD spectra are shown that
they have the same crystal structure as Y123 with some impurities peaks .",0911.4524v1
2012-12-20,Thermoelectricity in ternary rare-earth systems,"Crystallographic data, Seebeck coefficient, electrical resistance and thermal
conductivity are reported for a large number of rare-earth compounds,
manifestations of the Kondo effect being discussed. In more detail,
thermoelectric properties of Yb3Co4Ge13 and Yb3Co4Sn13 compounds and
Yb2CeCo4Ge13 and Yb2.3La0.7Co4Ge13 solid solutions are presented.",1212.4995v1
2015-05-07,Computer modelling of hafnium doping in lithium niobate,"Lithium niobate, LiNbO3, is an important technological material with good
electro-optic, acousto-optic, elasto-optic, piezoelectric and nonlinear
properties. Doping LiNbO3 with hafnium, Hf has been shown to improve the
resistance of the material to optical damage. Computer modelling provides a
useful means of determining the properties of doped and undoped LiNbO3,
including its defect chemistry, and the effect of doping on the structure. In
this paper, Hf doped LiNbO3 has been modelled, and the final defect
configurations are found to be consistent with experimental results.",1505.01661v2
2022-11-24,"Anisotropic magnetoresistance: materials, models and applications","Resistance of certain (conductive and otherwise isotropic) ferromagnets turns
out to exhibit anisotropy with respect to the direction of magnetisation:
R$_\parallel$ different from R$_\perp$ with reference to the electric current
direction. This century-old phenomenon is reviewed both from the perspective of
materials and physical mechanisms involved. More recently, this effect has also
been extended to antiferromagnets. This opens the possibility for industrial
applications reaching far beyond the current ones, e.g. hard drive read heads
or position sensors.",2212.03700v2
2024-05-15,The Detection of Unconventional Quantum Oscillations in Insulating 2D Materials,"In strongly correlated quantum materials, electrons behave in ways that often
extend beyond the confines of conventional Fermi-liquid theory. Interesting
results include the observation of low-temperature metallic behavior in systems
that are highly resistive. Here we provide an overview of experiments in which
insulators exhibit characteristics of a metal such as the Shubnikov de Haas
like quantum oscillations, focusing on recent findings in the correlated
insulating states of two-dimensional WTe2. We discuss the status of current
research, clarify the debates and challenges in interpreting the experiments,
rule out extrinsic explanations and discuss promising future directions.",2405.09666v2
1998-06-30,"Transport, optical and electronic properties of the half metal CrO2","The electronic structure of CrO_2 is critically discussed in terms of the
relation of existing experimental data and well converged LSDA and GGA
calculations of the electronic structure and transport properties of this half
metal magnet, with a particular emphasis on optical properties. We find only
moderate manifestations of many body effects. Renormalization of the density of
states is not large and is in the typical for transition metals range. We find
substantial deviations from Drude behavior in the far-infrared optical
conductivity. These appear because of the unusually low energy of interband
optical transitions. The calculated mass renormalization is found to be rather
sensitive to the exchange-correlation functional used and varies from 10%
(LSDA) to 90% (GGA), using the latest specific heat data. We also find that
dressing of the electrons by spin fluctuations, because of their high energy,
renormalizes the interband optical transition at as high as 4 eV by about 20%.
Although we find no clear indications of strong correlations of the Hubbard
type, strong electron-magnon scattering related to the half metallic band
structure is present and this leads to a nontrivial temperature dependence of
the resistivity and some renormalization of the electron spectra.",9806378v1
2002-08-14,Nonlinear microwave response of epitaxial YBaCuO films of varying oxygen content on MgO substrates,"We have investigated the nonlinear microwave properties of electron-beam
coevaporated YBaCuO films on MgO, using stripline resonators at 2.3 GHz and
temperatures 1.7-80 K. The oxygen content of the films ranged from strongly
underdoped to overdoped. Above 20 K, the nonlinear response of the resonators
was dominated by the superconductor. We could establish clear correlations
between the nonlinear surface resistance, two-tone intermodulation (IMD), and
oxygen content of the films, which indicate that the superconducting order
parameter is important for the nonlinearities. An exponential rather than a
power-law representation of the nonlinear current-voltage relation would be
required to explain our results phenomenologically. Below 20 K, the dielectric
loss tangent of MgO dominated the nonlinear response of the resonators. With
increasing power, the dissipation losses decreased markedly, accompanied by
enhanced IMD. The surface reactance passed through a shallow minimum at about 5
K, independent of power. We attribute these effects to resonant absorption by
impurity states in MgO.",0208285v1
2004-04-13,"Quantum Transparency of Anderson Insulator Junctions: Statistics of Transmission Eigenvalues, Shot Noise, and Proximity Conductance","We investigate quantum transport through strongly disordered barriers, made
of a material with exceptionally high resistivity that behaves as an Anderson
insulator or a ``bad metal'' in the bulk, by analyzing the distribution of
Landauer transmission eigenvalues for a junction where such barrier is attached
to two clean metallic leads. We find that scaling of the transmission
eigenvalue distribution with the junction thickness (starting from the single
interface limit) always predicts a non-zero probability to find high
transmission channels even in relatively thick barriers. Using this
distribution, we compute the zero frequency shot noise power (as well as its
sample-to-sample fluctuations) and demonstrate how it provides a single number
characterization of non-trivial transmission properties of different types of
disordered barriers. The appearance of open conducting channels, whose
transmission eigenvalue is close to one, and corresponding violent mesoscopic
fluctuations of transport quantities explain at least some of the peculiar
zero-bias anomalies in the Anderson-insulator/superconductor junctions observed
in recent experiments [Phys. Rev. B {\bf 61}, 13037 (2000)]. Our findings are
also relevant for the understanding of the role of defects that can undermine
quality of thin tunnel barriers made of conventional band-insulators.",0404271v2
2004-06-17,Phase formation of polycrystalline MgB2 at low temperature using nanometer Mg powder,"The MgB2 superconductor synthesized in a flowing argon atmosphere using
nanometer magnesium powder as the raw materials, denoted as Nano-MgB2, has been
studied by the technique of in-situ high temperature resistance measurement
(HT-RT measurement). The MgB2 phase is identified to form within the
temperature range of 430 to 490 C, which is much lower than that with the MgB2
sample fabricated in the same gas environment using the micron-sized magnesium
powder, denoted as Micro-MgB2, reported previously. The sample density of the
Nano-MgB2 reaches 1.7 g/cm3 with a crystal porosity structure less than a
micrometer, as determined by the scanning electron microscope (SEM) images,
while the Micro-MgB2 has a much more porous structure with corresponding
density of 1.0 g/cm3. This indicates that the Mg raw particle size, besides the
sintering temperature, is a crucial factor for the formation of high density
MgB2 sample, even at the temperature much lower than that of the Mg melting,
650 C. The X-ray diffraction (XRD) pattern shows a good MgB2 phase with small
amount of MgO and Mg and the transition temperature, TC, of the Nano-MgB2 was
determined as 39 K by the temperature dependent magnetization measurement
(M-T), indicating the existence of a good superconducting property.",0406398v1
2004-08-27,Spin reorientation and in-plane magnetoresistance of lightly doped La_{2-x}Sr_{x}CuO_{4} in magnetic fields up to 55 T,"The magnetoresistance (MR) in the in-plane resistivity is measured in
magnetic fields up to 55 T in lightly doped La_{2-x}Sr_{x}CuO_{4} in the N\'eel
state (x = 0.01) and in the spin-glass state (x = 0.03) using high-quality
untwinned single crystals. In both cases, a large negative MR is observed to
appear when the magnetic order is established. For x = 0.01, it is found that
the MR is indicative of a one-step transition into a high-field
weak-ferromagnetic state at around 20 T when the magnetic field is applied from
the spin easy axis (b axis), which means that there is no spin-flop transition
in the N\'eel state of this material; this is contrary to a previous report,
but is natural in light of the peculiar in-plane magnetic susceptibility
anisotropy recently found in this system. In the spin-glass state, we observe
that the large (up to \sim20%) negative MR saturates at around 40 T, and this
MR is found to be essentially isotropic when the magnetic field is rotated
within the ab plane. Our data show that the large negative MR is inherent to
LSCO in a magnetically ordered state, in which the weak-ferromagnetic (WF)
moment becomes well-defined; we discuss that the observed MR is essentially due
to the reorientation of the WF moments towards the magnetic field direction
both in the N\'eel state and in the spin-glass state.",0408604v1
2005-06-27,Strong-coupling theory of high-temperature superconductivity and colossal magnetoresistance,"We argue that the extension of the BCS theory to the strong-coupling regime
describes the high-temperature superconductivity of cuprates and the colossal
magnetoresistance (CMR) of ferromagnetic oxides if the phonon dressing of
carriers and strong attractive correlations are taken into account. The
long-range Froehlich electron-phonon interaction has been identified as the
most essential in cuprates providing ""superlight"" lattice polarons and
bipolarons. Here some kinetic, magnetic, and more recent thermomagnetic normal
state measurements are interpreted in the framework of the strong-coupling
theory, including the Nernst effect and normal state diamagnetism. Remarkably,
a similar strong-coupling approach offers a simple explanation of CMR in
ferromagnetic oxides. The pairing of oxygen holes into heavy bipolarons in the
paramagnetic phase and their magnetic pair-breaking in the ferromagnetic phase
account for the first-order ferromagnetic phase transition, CMR, isotope
effects, and pseudogaps in doped manganites. Here we propose an explanation of
the phase coexistence and describe the shape of resistivity of manganites near
the transition in the framework of the strong-coupling approach.",0506706v3
2006-06-05,Phenomenological theory of current driven exchange switching in ferromagnetic nanojunctions,"Phenomenological approach is developed in the theory of spin-valve type
ferromagnetic junctions to describe exchange switching by current flowing
perpendicular to interfaces. Forward and backward current switching effects are
described and they may be principally different in nature. Mobile electron
spins are considered as being free in all the contacting ferromagnetic layers.
Joint action of the following two current effects is investigated: the
nonequilibrium longitudinal spin-injection effective field and the transverse
spin-transfer surface torque. Dispersion relation for fluctuations is derived
and solved for a junction model having spatially localized spin transfer
torque: depth of the torque penetration into the free layer is assumed much
smaller than the total free layer thickness. Some critical value of the well
known Gilbert damping constant is established for the first time. Spin transfer
torque dominates in the instability threshold determination for small enough
damping constants, while the spin-injection effective field dominates for high
damping. Fine interplay between spin transfer torque and spin injection is
necessary to provide a hysteretic behavior of the resistance versus current
dependence. The state diagram building up shows the possibility of
non-stationary (time dependent) nonlinear states arising due to instability
development. Calculations lead to the instability rise time values of the order
of 0.1 ns. Spin wave resonance frequency spectrum softening occurs under the
current growing to the instability threshold. Magnetization fluctuations above
the threshold rise oscillating with time for low damping, but rise
aperiodically and much more rapid for high damping.",0606102v2
2007-02-28,A local field emission study of partially aligned carbon-nanotubes by AFM probe,"We report on the application of Atomic Force Microscopy (AFM) for studying
the Field Emission (FE) properties of a dense array of long and vertically
quasi-aligned multi-walled carbon nanotubes grown by catalytic Chemical Vapor
Deposition on a silicon substrate. The use of nanometric probes enables local
field emission measurements allowing investigation of effects non detectable
with a conventional parallel plate setup, where the emission current is
averaged on a large sample area. The micrometric inter-electrode distance let
achieve high electric fields with a modest voltage source. Those features
allowed us to characterize field emission for macroscopic electric fields up to
250 V/$\mu$m and attain current densities larger than 10$^5$ A/cm$^2$. FE
behaviour is analyzed in the framework of the Fowler-Nordheim theory. A field
enhancement factor $\gamma \approx$ 40-50 and a turn-on field $E_{turn-on}
\sim$15 V/$\mu$m at an inter-electrode distance of 1 $\mu$m are estimated.
Current saturation observed at high voltages in the I-V characteristics is
explained in terms of a series resistance of the order of M$\Omega$. Additional
effects as electrical conditioning, CNT degradation, response to laser
irradiation and time stability are investigated and discussed.",0702682v1
2007-11-09,Defect healing at room temperature in pentacene thin films and improved transistor performance,"We report on a healing of defects at room temperature in the organic
semiconductor pentacene. This peculiar effect is a direct consequence of the
weak intermolecular interaction which is characteristic of organic
semiconductors. Pentacene thin-film transistors were fabricated and
characterized by in situ gated four-terminal measurements. Under high vacuum
conditions (base pressure of order 10E-8 mbar), the device performance is found
to improve with time. The effective field-effect mobility increases by as much
as a factor of two and mobilities up to 0.45 cm2/Vs were achieved. In addition,
the contact resistance decreases by more than an order of magnitude and there
is a significant reduction in current hysteresis. Oxygen/nitrogen exposure and
annealing experiments show the improvement of the electronic parameters to be
driven by a thermally promoted process and not by chemical doping. In order to
extract the spectral density of trap states from the transistor
characteristics, we have implemented a powerful scheme which allows for a
calculation of the trap densities with high accuracy in a straightforward
fashion. We show the performance improvement to be due to a reduction in the
density of shallow traps <0.15 eV from the valence band edge, while the
energetically deeper traps are essentially unaffected. This work contributes to
an understanding of the shallow traps in organic semiconductors and identifies
structural point defects within the grains of the polycrystalline thin films as
a major cause.",0711.1457v1
2008-04-05,Strain rate effects in the mechanical response of polymer anchored carbon nanotube foams,"Super-compressible foam-like carbon nanotube films have been reported to
exhibit highly nonlinear viscoelastic behaviour in compression similar to soft
tissue. Their unique combination of light weight and exceptional electrical,
thermal and mechanical properties have helped identify them as viable building
blocks for more complex nanosystems and as stand-alone structures for a variety
of different applications. In the as-grown state, their mechanical performance
is limited by the weak adhesion between the tubes, controlled by the van der
Waals forces, and the substrate allowing the forests to split easily and to
have low resistance in shear. Under axial compression loading carbon nanotubes
have demonstrated bending, buckling8 and fracture9 (or a combination of the
above) depending on the loading conditions and on the number of loading cycles.
In this work, we partially anchor dense vertically aligned foam-like forests of
carbon nanotubes on a thin, flexible polymer layer to provide structural
stability, and report the mechanical response of such systems as a function of
the strain rate. We test the sample under quasi-static indentation loading and
under impact loading and report a variable nonlinear response and different
elastic recovery with varying strain rates. A Bauschinger-like effect is
observed at very low strain rates while buckling and the formation of permanent
defects in the tube structure is reported at very high strain rates. Using
high-resolution transmission microscopy",0804.0868v1
2008-04-10,Electrical transport and ferromagnetism in Ga1-xMnxAs synthesized by ion implantation and pulsed-laser melting,"We present a detailed investigation of the magnetic and magnetotransport
properties of thin films of ferromagnetic Ga1-xMnxAs synthesized using ion
implantation and pulsed-laser melting (II-PLM). The field and
temperature-dependent magnetization, magnetic anisotropy, temperature-dependent
resistivity, magnetoresistance, and Hall effect of II-PLM Ga1-xMnxAs films have
all of the characteristic signatures of the strong p-d interaction of holes and
Mn ions observed in the dilute hole-mediated ferromagnetic phase. The
ferromagnetic and electrical transport properties of II-PLM films correspond to
the peak substitutional Mn concentration meaning that the non-uniform Mn depth
distribution is unimportant in determining the film properties. Good
quantitative agreement is found with films grown by low temperature molecular
beam epitaxy (LT-MBE) and having the similar substitutional Mn_Ga composition.
Additionally, we demonstrate that II-PLM Ga1-xMnxAs films are free from
interstitial Mn_I because of the high temperature processing. At high Mn
implantation doses the kinetics of solute redistribution during solidification
alone determine the maximum resulting Mn_Ga concentration. Uniaxial anisotropy
between in-plane [-110]and [110] directions is present in II-PLM Ga1-xMnxAs
giving evidence for this being an intrinsic property of the carrier-mediated
ferromagnetic phase.",0804.1612v1
2010-01-26,Signature of checkerboard fluctuations in the phonon spectra of a possible polaronic metal La1.2Sr1.8Mn2O7,"Charge carriers in low-doped semiconductors may distort the atomic lattice
and trap themselves forming so-called small polarons. High carrier
concentrations can lead to short range ordered polarons (large polarons) and
even to long range charge and orbital order. Both systems should be insulating
with a large electrical resistivity, which decreases with increasing
temperature. However, photoemission measurements recently found a polaronic
pseudogap, in a metallic phase of La2-2xSr1+2xMn2O7. This layered manganite is
famous for colossal magnetoresistance (CMR) associated with a phase transition
from this low-temperature metallic phase to a high temperature insulating
phase. Broad charge order peaks due to large polarons observed by neutron and
x-ray scattering in the insulating phase disappear when La2-2xSr1+2xMn2O7
becomes metallic. We report results of inelastic neutron scattering
measurements showing that polarons remain inside the metallic phase as
fluctuations that strongly broaden and soften certain phonons near the wave
vectors where the charge order peaks appeared in the insulating phase. Our
findings imply that polaronic signatures in metals may generally come from a
competing insulating charge-ordered phase. It is highly relevant to cuprate
superconductors with both a pseudogap, and a similar phonon effect associated
with a competing stripe order.",1001.4636v1
2010-04-28,"Synthesis, Structure and Properties of Tetragonal Sr2M3As2O2 (M3 = Mn3, Mn2Cu and MnZn2) Compounds Containing Alternating CuO2-Type and FeAs-Type Layers","Polycrystalline samples of Sr2Mn2CuAs2O2, Sr2Mn3As2O2, and Sr2Zn2MnAs2O2 were
synthesized. Their temperature- and applied magnetic field-dependent
structural, transport, thermal, and magnetic properties were characterized by
means of x-ray and neutron diffraction, electrical resistivity rho, heat
capacity, magnetization and magnetic susceptibility measurements. These
compounds have a body-centered-tetragonal crystal structure (space group
I4/mmm) that consists of MO2 (M = Zn and/or Mn) oxide layers similar to the
CuO2 layers in high superconducting transition temperature Tc cuprate
superconductors, and intermetallic MAs (M = Cu and/or Mn) layers similar to the
FeAs layers in high-Tc pnictides. These two types of layers alternate along the
crystallographic c-axis and are separated by Sr atoms. The site occupancies of
Mn, Cu and Zn were studied using Rietveld refinements of x-ray and neutron
powder diffraction data. The temperature dependences of rho suggest metallic
character for Sr2Mn2CuAs2O2 and semiconducting character for Sr2Mn3As2O2 and
Sr2Zn2MnAs2O2. Sr2Mn2CuAs2O2 is inferred to be a ferrimagnet with a Curie
temperature TC = 95(1) K. Remarkably, we find that the magnetic ground state
structure changes from a G-type antiferromagnetic structure in Sr2Mn3As2O2 to
an A-type ferrimagnetic structure in Sr2Mn2CuAs2O2 in which the Mn ions in each
layer are ferromagnetically aligned, but are antiferromagnetically aligned
between layers.",1004.5038v1
2011-06-21,Transport properties and anisotropy in rare earth doped CaFe2As2 single crystals with Tc above 40 K,"In this paper we report the superconductivity above 40 K in the electron
doping single crystal Ca1-xRexFe2As2 (Re = La, Ce, Pr). The x-ray diffraction
patterns indicate high crystalline quality and c-axis orientation. the
resistivity anomaly in the parent compound CaFe2As2 is completely suppressed by
partial replacement of Ca by rare earth and a superconducting transition
reaches as high as 43 K, which is higher than the value in electron doping
FeAs-122 compounds by substituting Fe ions with transition metal, even
surpasses the highest values observed in hole doping systems with a transition
temperature up to 38 K. The upper critical field has been determined with the
magnetic field along ab-plane and c-axis, yielding the anisotropy of 2~3.
Hall-effect measurements indicate that the conduction in this material is
dominated by electron like charge carriers. Our results explicitly demonstrate
the feasibility of inducing superconductivity in Ca122 compounds via electron
doping using aliovalent rare earth substitution into the alkaline earth site,
which should add more ingredients to the underlying physics of the iron-based
superconductors.",1106.4208v1
2012-02-13,Graphene-on-Diamond Devices with Enhanced Current-Carrying Capacity: Carbon sp2-on-sp3 Technology,"Graphene demonstrated potential for practical applications owing to its
excellent electronic and thermal properties. Typical graphene field-effect
transistors and interconnects built on conventional SiO2/Si substrates reveal
the breakdown current density on the order of 1 uA/nm2 (i.e. 10^8 A/cm2) which
is ~100\times larger than the fundamental limit for the metals but still
smaller than the maximum achieved in carbon nanotubes. We show that by
replacing SiO2 with synthetic diamond one can substantially increase the
current-carrying capacity of graphene to as high as ~18 uA/nm2 even at ambient
conditions. Our results indicate that graphene's current-induced breakdown is
thermally activated. We also found that the current carrying capacity of
graphene can be improved not only on the single-crystal diamond substrates but
also on an inexpensive ultrananocrystalline diamond, which can be produced in a
process compatible with a conventional Si technology. The latter was attributed
to the decreased thermal resistance of the ultrananocrystalline diamond layer
at elevated temperatures. The obtained results are important for graphene's
applications in high-frequency transistors, interconnects, transparent
electrodes and can lead to the new planar sp2-on-sp3 carbon-on-carbon
technology.",1202.2886v1
2012-07-12,Structure and electronic transport in graphene wrinkles,"Wrinkling is a ubiquitous phenomenon in two-dimensional membranes. In
particular, in the large-scale growth of graphene on metallic substrates, high
densities of wrinkles are commonly observed. Despite their prevalence and
potential impact on large-scale graphene electronics, relatively little is
known about their structural morphology and electronic properties. Surveying
the graphene landscape using atomic force microscopy, we found that wrinkles
reach a certain maximum height before folding over. Calculations of the
energetics explain the morphological transition, and indicate that the tall
ripples are collapsed into narrow standing wrinkles by van der Waals forces,
analogous to large-diameter nanotubes. Quantum transport calculations show that
conductance through these collapsed wrinkle structures is limited mainly by a
density-of-states bottleneck and by interlayer tunneling across the collapsed
bilayer region. Also through systematic measurements across large numbers of
devices with wide folded wrinkles, we find a distinct anisotropy in their
electrical resistivity, consistent with our transport simulations. These
results highlight the coupling between morphology and electronic properties,
which has important practical implications for large-scale high-speed graphene
electronics.",1207.2994v1
2012-09-06,Terahertz time-domain spectroscopic ellipsometry: Instrumentation and calibration,"We present a new instrumentation and calibration procedure for terahertz
time-domain spectroscopic ellipsometry (THz-TDSE) that is a newly established
characterization technique. The experimental setup is capable of providing
arbitrary angle of incidence in the range of $15^\circ$--$85^\circ$ in the
reflection geometry, and with no need for realignment. The setup is also
configurable easily into transmission geometry. For this setup, we successfully
used hollow core photonic band gap fiber with no pre-chirping in order to
deliver a femtosecond laser into a THz photoconductive antenna detector, which
is the first demonstration of this kind. The proposed calibration scheme can
compensate for the non-ideality of the polarization response of the THz
photoconductive antenna detector as well as that of wire grid polarizers used
in the setup. In the calibration scheme, the ellipsometric parameters are
obtained through a regression algorithm which we have adapted from the
conventional regression calibration method developed for rotating element
optical ellipsometers, and used here for the first time for THz-TDSE. As a
proof-of-principle demonstration, results are presented for a high resistivity
silicon substrate as well as an opaque Si substrate with a high phosphorus
concentration. We also demonstrate the capacity to measure a few micron thick
grown thermal oxide on top of Si. Each sample was characterized by THz-TDSE in
reflection geometry with different angle of incidence.",1209.1294v2
2013-05-09,Fermilab experience of post-annealing losses in SRF niobium cavities due to furnace contamination and the ways to its mitigation: a pathway to processing simplification and quality factor improvement,"We investigate the effect of high temperature treatments followed by only
high-pressure water rinse (HPR) of superconducting radio frequency (SRF)
niobium cavities. The objective is to provide a cost effective alternative to
the typical cavity processing sequence, by eliminating the material removal
step post furnace treatment while preserving or improving the RF performance.
The studies have been conducted in the temperature range 800-1000C for
different conditions of the starting substrate: large grain and fine grain,
electro-polished (EP) and centrifugal barrel polished (CBP) to mirror finish.
An interesting effect of the grain size on the performances is found. Cavity
results and samples characterization show that furnace contaminants cause poor
cavity performance, and a practical solution is found to prevent surface
contamination. Extraordinary values of residual resistances ~ 1 nOhm and below
are then consistently achieved for the contamination-free cavities. These
results lead to a more cost-effective processing and improved RF performance,
and, in conjunction with CBP, open a potential pathway to acid-free processing.",1305.2182v2
2013-06-03,Electrical switching dynamics and broadband microwave characteristics of VO2 RF devices,"Vanadium dioxide is a correlated electron system that features a
metal-insulator phase transition (MIT) above room temperature and is of
interest in high speed switching devices. Here, we integrate VO2 into
two-terminal coplanar waveguides and demonstrate a large resistance modulation
of the same magnitude (>10^3) in both electrically (i.e. by bias voltage,
referred to as E-MIT) and thermally (T-MIT) driven transitions. We examine
transient switching characteristics of the E-MIT and observe two
distinguishable time scales for switching. We find an abrupt jump in
conductivity with a rise time of the order of 10 ns followed by an oscillatory
damping to steady state on the order of several {\mu}s. We characterize the RF
power response in the On state and find that high RF input power drives VO2
further into the metallic phase, indicating that electromagnetic
radiation-switching of the phase transition may be possible. We measure
S-parameter RF properties up to 13.5 GHz. Insertion loss is markedly flat at
2.95 dB across the frequency range in the On state and sufficient isolation of
over 25 dB is observed in the Off state. We are able to simulate the RF
response accurately using both lumped element and 3D electromagnetic models.
Extrapolation of our results suggests that optimizing device geometry can
reduce insertion loss further and maintain broadband flatness up to 40 GHz.",1306.0292v1
2013-07-16,ZnS/Diamond Composite Coatings for Infrared Transmission Applications Formed by the Aerosol Deposition Method,"The deposition of nano-crystalline ZnS/diamond composite protective coatings
on silicon, sapphire, and ZnS substrates, as a preliminary step to coating
infrared transparent ZnS substrates from powder mixtures by the aerosol
deposition method is presented. Advantages of the aerosol deposition method
include the ability to form dense, nanocrystalline films up to hundreds of
microns thick at room temperature and at a high deposition rate on a variety of
substrates. Deposition is achieved by creating a pressure gradient that
accelerates micrometer-scale particles in an aerosol to high velocity.
  Upon impact with the target substrate the particles fracture and embed.
Continued deposition forms the thick compacted film. Deposition from an
aerosolized mixture of ZnS and diamond powders onto all targets results in
linear trend from apparent sputter erosion of the substrate at 100% diamond to
formation of a film with increasing fractions of ZnS. The crossover from
abrasion to film formation on sapphire occurs above about 50% ZnS and a mixture
of 90% ZnS and 10% diamond forms a well-adhered film of about 0.7 \mu m
thickness at a rate of 0.14 \mu m/min. Resulting films are characterized by
scanning electron microscopy, profilometry, infrared transmission spectroscopy,
and x-ray photoemission spectroscopy. These initial films mark progress toward
the future goal of coating ZnS substrates for abrasion resistance.",1307.4319v1
2013-10-01,Unexpected Giant Superconducting Fluctuation and Anomalous Semiconducting Normal State in NdO1-xFxBi1-yS2 Single Crystals,"The BiS2-based superconductors were discovered recently. The
superconductivity has been proved by many other groups. Since the previous
experiments were all done on polycrystalline samples, therefore there remains a
concern whether the superconductivity is really derived from the materials
intrinsically or from some secondary phases. Experiments on single crystals are
highly desired. In this paper, we report the successful growth of the
NdO1-xFxBi1-yS2 single crystals. Resistive and magnetic measurements reveal
that the bulk superconducting transition occurs at about 5 K, while an
unexpected giant superconducting fluctuation appears at temperatures as high as
2-4 kBTC. Analysis based on the anisotropic Ginzbaug-Landau theory gives an
anisotropy of 30-45. Two gap features with magnitudes of about 3.5+-0.3 meV and
7.5+-1 meV were observed by scanning tunneling spectroscopy. The smaller gap is
associated with the bulk superconducting transition at about 5 K yielding a
huge ratio 2Delta_s/kBTc =16.8, the larger gap remains up to about 26 K. The
normal state recovered by applying a high magnetic field shows an anomalous
semiconducting behavior. All these suggest that the superconductivity in this
newly discovered superconductor cannot be formatted into the BCS theory.",1310.0377v1
2014-06-26,Electron localization and possible phase separation in the absence of a charge density wave in single-phase 1T-VS$_2$,"We report on a systematic study of the structural, magnetic and transport
properties of high-purity 1T-VS$_2$ powder samples prepared under high
pressure. The results differ notably from those previously obtained by
de-intercalating Li from LiVS$_2$. First, no Charge Density Wave (CDW) is found
by transmission electron microscopy down to 94 K. Though, \textit{ab initio}
phonon calculations unveil a latent CDW instability driven by an acoustic
phonon softening at the wave vector ${\bf q}_{CDW} \approx$ (0.21,0.21,0)
previously reported in de-intercalated samples. A further indication of latent
lattice instability is given by an anomalous expansion of the V-S bond distance
at low temperature. Second, infrared optical absorption and electrical
resistivity measurements give evidence of non metallic properties, consistent
with the observation of no CDW phase. On the other hand, magnetic
susceptibility and NMR data suggest the coexistence of localized moments with
metallic carriers, in agreement with \textit{ab initio} band structure
calculations. This discrepancy is reconciled by a picture of electron
localization induced by disorder or electronic correlations leading to a phase
separation of metallic and non-metallic domains in the nm scale. We conclude
that 1T-VS$_2$ is at the verge of a CDW transition and suggest that residual
electronic doping in Li de-intercalated samples stabilizes a uniform CDW phase
with metallic properties.",1406.6945v1
2014-11-07,Upgrade of the ALICE Inner Tracking System,"During the Long Shutdown 2 of the LHC in 2018/2019, the ALICE experiment
plans the installation of a novel Inner Tracking System. It will replace the
current six layer detector system with a seven layer detector using Monolithic
Active Pixel Sensors. The upgraded Inner Tracking System will have
significantly improved tracking and vertexing capabilities, as well as readout
rate to cope with the expected increased Pb-Pb luminosity of the LHC. The
choice of Monolithic Active Pixel Sensors has been driven by the specific
requirements of ALICE as a heavy ion experiment dealing with rare processes at
low transverse momenta. This leads to stringent requirements on the material
budget of 0.3$% X/X_{0}$ per layer for the three innermost layers. Furthermore,
the detector will see large hit densities of $\sim 19
\mathrm{cm}^{-2}/\mathrm{event}$ on average for minimum-bias events in the
inner most layer and has to stand moderate radiation loads of 700 kRad TID and
$1\times 10^{13}$ 1 MeV n$_\mathrm{eq}/\mathrm{cm}^{2}$ NIEL at maximum. The
Monolithic Active Pixel Sensor detectors are manufactured using the TowerJazz
0.18 $\mu$m CMOS Imaging Sensor process on wafers with a high-resistivity
epitaxial layer. This contribution summarises the recent R&D activities and
focuses on results on the large-scale pixel sensor prototypes.",1411.1802v2
2014-12-26,High Pressure Induced Binding Between Linear Carbon Chains and Nanotubes,"Recent studies of single-walled carbon nanotubes (CNTs) in aqueous media have
showed that water can significantly affect the tube mechanical properties. CNTs
under hydrostatic compression can preserve their elastic properties up to large
pressure values, while exhibiting exceptional resistance to mechanical
loadings. It was experimentally observed that CNTs with encapsulated linear
carbon chains (LCCs), when subjected to high hydrostatic pressure values,
present irreversible red shifts in some of their vibrational frequencies. In
order to address the cause of this phenomenon, we have carried out fully
atomistic reactive (ReaxFF) molecular dynamics (MD) simulations for model
structures mimicking the experimental conditions. We have considered the cases
of finite and infinite (cyclic boundary conditions) CNTs filled with LCCs (LCC
inside CNTs) of different lengths (from 9 up to 40 atoms). Our results show
that increasing the hydrostatic pressure causes the CNT to be deformed in an
inhomogeneous way due to the LCC presence. The LCC-CNT interface regions
exhibit convex curvatures, which results in more reactive sites, thus favoring
the formation of covalent chemical bonds between the chain and the nanotube.
This process is irreversible with the newly formed bonds continuing to exist
even after releasing the external pressure and causing an irreversibly red
shift in the chain vibrational modes from 1850 to 1500 cm$^{-1}$.",1412.7966v1
2015-01-29,Superconducting properties of sulfur-doped iron selenide,"The recent discovery of high-temperature superconductivity in single-layer
iron selenide has generated significant experimental interest for optimizing
the superconducting properties of iron-based superconductors through the
lattice modification. For simulating the similar effect by changing the
chemical composition due to S doping, we investigate the superconducting
properties of high-quality single crystals of FeSe$_{1-x}$S$_{x}$ ($x$=0, 0.04,
0.09, and 0.11) using magnetization, resistivity, the London penetration depth,
and low temperature specific heat measurements. We show that the introduction
of S to FeSe enhances the superconducting transition temperature $T_{c}$,
anisotropy, upper critical field $H_{c2}$, and critical current density
$J_{c}$. The upper critical field $H_{c2}(T)$ and its anisotropy are strongly
temperature dependent, indicating a multiband superconductivity in this system.
Through the measurements and analysis of the London penetration depth $\lambda
_{ab}(T)$ and specific heat, we show clear evidence for strong coupling two-gap
$s$-wave superconductivity. The temperature-dependence of $\lambda _{ab}(T)$
calculated from the lower critical field and electronic specific heat can be
well described by using a two-band model with $s$-wave-like gaps. We find that
a $d$-wave and single-gap BCS theory under the weak-coupling approach can not
describe our experiments. The change of specific heat induced by the magnetic
field can be understood only in terms of multiband superconductivity.",1501.07346v1
2015-09-28,"Thermoelectric properties of rare earth filled type-I like Clathrate, Dy8Al16Si30","Type-I clathrates with a cage structure are known to be of importance for
thermoelectric applications as the cage can be filled with a guest atom which
leads to reduced thermal conductivity. Among the type-I clathrates, Si-based
alloys are of relevance for high temperature application and most importantly
because they are made of earth abundant elements. Dysprosium, Dy has been
chosen as the guest atom because of its large mass and small size compared to
divalent alkali metal ion. The Dy8Al16Si30, DAS, alloy has been synthesized by
arc melting of pure elements followed by annealing at 780 K for 7 days.
Structural characterization performed using XRD and SEM indicates presence of
both binary and ternary silicides, DySi2, DyAl2Si2 together with Al solid
solution and Si. The phase mixture remains unchanged even after annealing. The
microstructure has a typical dendritic structure with interdendritic phases,
signifying a slow, liquid transformation after arc melting. The Seebeck
coefficient is found to be positive, a p-type and increases with increasing
temperature both before and after annealing. The resistivity is found to be low
in the whole temperature range, 2 to 10 micro Ohm m and increases with
increasing temperature. The power factor in the as-prepared state is found to
be higher at all temperatures in the range 300 K to 700 K compared to annealed
state. The thermal conductivity however has been found to decrease on annealing
from an unusually high value of 100 W/m K to 50 W/m K.",1509.08277v1
2016-01-06,Observation of quantum Hall plateau-plateau transition and scaling behavior of the zeroth Landau level in graphene p-n-p junctions,"We report distinctive magnetotransport properties of a graphene p-n-p
junction prepared by controlled diffusion of metallic contacts. In most cases,
materials deposited on a graphene surface introduce substantial carrier
scattering, which greatly reduces the high mobility of intrinsic graphene.
However, we show that an oxide layer only weakly perturbs the carrier
transport, which enables fabrication of a high-quality graphene p-n-p junction
through a one-step and resist-free method. The measured conductance-gate
voltage $(G-V_G)$ curves can be well described by a metal contact model, which
confirms the charge density depinning due to the oxide layer. The graphene
p-n-p junction samples exhibit pronounced quantum Hall effect, a well-defined
transition point of the zeroth Landau level (LL), and scaling behavior. The
scaling exponent obtained from the evolution of the zeroth LL width as a
function of temperature exhibits a relatively low value of
$\kappa=0.21\pm0.01$. Moreover, we calculate the energy level for the LLs based
on the distribution of plateau-plateau transition points, further validating
the assignment of the LL index of the QH plateau-plateau transition.",1601.01155v1
2017-02-07,Resonant spin transfer torque nano-oscillators,"Spin transfer torque nano-oscillators are potential candidates for replacing
the traditional inductor based voltage controlled oscillators in modern
communication devices. Typical oscillator designs are based on trilayer
magnetic tunnel junctions which are disadvantaged by low power outputs and poor
conversion efficiencies. In this letter, we theoretically propose to use
resonant spin filtering in pentalayer magnetic tunnel junctions as a possible
route to alleviate these issues and present device designs geared toward a high
microwave output power and an efficient conversion of the d.c. input power. We
attribute these robust qualities to the resulting non-trivial spin current
profiles and the ultra high tunnel magnetoresistance, both arising from
resonant spin filtering. The device designs are based on the nonequilibrium
Green's function spin transport formalism self-consistently coupled with the
stochastic Landau-Lifshitz-Gilbert-Slonczewski's equation and the Poisson's
equation. We demonstrate that the proposed structures facilitate oscillator
designs featuring a large enhancement in microwave power of around $775\%$ and
an efficiency enhancement of over $1300\%$ in comparison with typical trilayer
designs. We also rationalize the optimum operating regions via an analysis of
the dynamic and static device resistances. This work sets stage for pentalyer
spin transfer torque nano-oscillator device designs that extenuate most of the
issues faced by the typical trilayer designs.",1702.01869v1
2017-02-18,Ultralow 1/f Noise in a Heterostructure of Superconducting Epitaxial Cobalt-Disilicide Thin Film on Silicon,"High-precision resistance noise measurements indicate that the epitaxial
CoSi$_2$/Si hetero-structures at 150 K and 2 K (slightly above its
superconducting transition temperature $T_c$ of 1.54 K) exhibit an unusually
low 1/f noise level in the frequency range of 0.008-0.2 Hz. This corresponds to
an upper limit of Hooge constant $\gamma \leq 3 \times 10^{-6}$, about 100
times lower than that of single-crystalline aluminum films on SiO$_2$ capped Si
substrates. Supported by high-resolution cross-sectional transmission electron
microscopy studies, our analysis reveals that the 1/f noise is dominated by
excess interfacial Si atoms and their dimer reconstruction induced fluctuators.
Unbonded orbitals (i.e., dangling bonds) on excess Si atoms are intrinsically
rare at the epitaxial CoSi$_2$/Si(100) interface, giving limited
trapping-detrapping centers for localized charges. With its excellent
normal-state properties, CoSi$_2$ has been used in silicon-based integrated
circuits for decades. The intrinsically low noise properties discovered in this
work could be utilized for developing quiet qubits and scalable superconducting
circuits for future quantum computing.",1702.05566v1
2017-06-03,Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5,"Electronic nematics are exotic states of matter where electronic interactions
break a rotational symmetry of the underlying lattice, in analogy to the
directional alignment without translational order in nematic liquid crystals.
Intriguingly such phases appear in the copper- and iron-based superconductors,
and their role in establishing high-temperature superconductivity remains an
open question. Nematicity may take an active part, cooperating or competing
with superconductivity, or may appear accidentally in such systems. Here we
present experimental evidence for a phase of nematic character in the heavy
fermion superconductor CeRhIn5. We observe a field-induced breaking of the
electronic tetragonal symmetry of in the vicinity of an antiferromagnetic (AFM)
quantum phase transition at Hc~50T. This phase appears in out-of-plane fields
of H*~28T and is characterized by substantial in-plane resistivity anisotropy.
The anisotropy can be aligned by a small in-plane field component, with no
apparent connection to the underlying crystal structure. Furthermore no
anomalies are observed in the magnetic torque, suggesting the absence of
metamagnetic transitions in this field range. These observations are indicative
of an electronic nematic character of the high field state in CeRhIn5. The
appearance of nematic behavior in a phenotypical heavy fermion superconductor
highlights the interrelation of nematicity and unconventional
superconductivity, suggesting nematicity to be a commonality in such materials.",1706.00963v1
2017-09-03,Giant tunnel magnetoresistance with a single magnetic phase-transition electrode,"Magnetic phase transition tunnel magnetoresistance (MPT-TMR) effect with a
single magnetic electrode has been investigated by first-principles
calculations. The calculations show that the MPT-TMR of FeRh/MgO/Cu tunnel
junction can be as high as hundreds of percent when the magnetic structure of
FeRh changes from G-type antiferromagnetic (GAFM) to ferromagnetic order. This
new type of MPT-TMR may be superior to the tunnel anisotropic magnetoresistance
because of its huge magneto-resistance effect and similar structural
simplicity. The main mechanism for the giant MPT-TMR can be attributed to the
formation of interface resonant states at GAFM-FeRh/MgO interface. A direct
FeRh/MgO interface is found to be necessary for achieving high MPT-TMR
experimentally. Moreover, we find the FeRh/MgO interface with FeRh in
ferromagnetic phase has nearly full spin-polarization due to the negligible
majority transmission and significantly different Fermi surface of two spin
channels. Thus, it may act as a highly efficient and tunable spin-injector. In
addition, electric field driven MPT of FeRh-based hetero-magnetic
nanostructures can be utilized to design various energy efficient tunnel
junction structures and the corresponding lower power consumption devices. Our
results will stimulate further experimental investigations of MPT-TMR and other
fascinating phenomenon of FeRh-based tunnel junctions that may be promising in
antiferromagnetic spintronics.",1709.00687v2
2017-11-08,"X-ray photoelectron spectroscopy, Magnetotransport and Magnetization study of Nb2PdS5 superconductor","In the present report, we investigate various properties of the Nb2PdS5
superconductor. Scanning electron microscopy displayed slabs like laminar
growth of Nb2PdS5while X-ray photoelectron spectroscopy exhibited the
hybridization of Sulphur (2p) with both Palladium (3d)and Niobium (3d). High
field (140kOe) magneto-transport measurements revealed that superconductivity
(Tc onset =7K and Tc R = 0 = 6.2K) of the studied Nb2PdS5material is quite
robust against magnetic field with the upper critical field (Hc2) outside the
Pauli paramagnetic limit. Thermally activated flux flow (TAFF) of the compound
showed that resistivity curves follow Arrhenius behaviour. The activation
energy for Nb2PdS5 is found to decrease from 15.15meV at 10kOe to 2.35meV at
140kOe. Seemingly, the single vortex pinning is dominant in low field regions,
while collective pinning is dominant in high field region. The temperature
dependence of AC susceptibility confirmed the Tc at 6K, further varying
amplitude and frequency showed well coupled granular nature of
superconductivity. The lower critical field (Hc1) is extracted from DC
magnetisation measurements at various T below Tc. It is found that Hc1(T) of
Nb2PdS5 material seemingly follows the multiband nature of superconductivity.",1711.02830v1
2017-11-10,Thermodynamic Studies of \b{eta}-Ga2O3 Nanomembrane Field-Effect Transistors on a Sapphire Substrate,"The self-heating effect is a severe issue for high-power semiconductor
devices, which degrades the electron mobility and saturation velocity, and also
affects the device reliability. On applying an ultrafast and high-resolution
thermoreflectance imaging technique, the direct self-heating effect and surface
temperature increase phenomenon are observed on novel top-gate \b{eta}-Ga2O3 on
insulator field-effect transistors. Here, we demonstrate that by utilizing a
higher thermal conductivity sapphire substrate rather than a SiO2/Si substrate,
the temperature rise above room temperature of \b{eta}-Ga2O3 on the insulator
field-effect transistor can be reduced by a factor of 3 and thereby the
self-heating effect is significantly reduced. Both thermoreflectance
characterization and simulation verify that the thermal resistance on the
sapphire substrate is less than 1/3 of that on the SiO2/Si substrate.
Therefore, maximum drain current density of 535 mA/mm is achieved on the
sapphire substrate, which is 70% higher than that on the SiO2/Si substrate due
to reduced self-heating. Integration of \b{eta}-Ga2O3 channel on a higher
thermal conductivity substrate opens a new route to address the low thermal
conductivity issue of \b{eta}-Ga2O3 for power electronics applications.",1711.03672v1
2018-03-28,Study of nitrogen ion doping of titanium dioxide films,"This study reports on the properties of nitrogen doped titanium dioxide
$TiO_2$ thin films considering the application as transparent conducting oxide
(TCO). Sets of thin films were prepared by sputtering a titanium target under
oxygen atmosphere on a quartz substrate at 400 or 500{\deg}C. Films were then
doped at the same temperature by 150 eV nitrogen ions. The films were prepared
in Anatase phase which was maintained after doping. Up to 30at% nitrogen
concentration was obtained at the surface, as determined by in situ x-ray
photoelectron spectroscopy (XPS). Such high nitrogen concentration at the
surface lead to nitrogen diffusion into the bulk which reached about 25 nm.
Hall measurements indicate that average carrier density reached over $10^{19}
cm^{-3}$ with mobility in the range of $0.1$ to $1 cm^2V^{-1}s^{-1}$.
Resistivity about $3.10^{-1} \Omega cm$ could be obtained with 85% light
transmission at 550 nm. These results indicate that low energy implantation is
an effective technique for $TiO_2$ doping that allows an accurate control of
the doping process independently from the TiO2 preparation. Moreover, this
doping route seems promising to attain high doping levels without significantly
affecting the film structure. Such approach could be relevant for preparation
of $N:TiO_2$ transparent conduction electrodes (TCE).",1803.10828v1
2018-06-15,Quantum anomalous Hall multilayers grown by molecular beam epitaxy,"Quantum anomalous Hall (QAH) effect is a quantum Hall effect that occurs
without the need of external magnetic field. A system composed of multiple
parallel QAH layers is an effective high Chern number QAH insulator and the key
to the applications of the dissipationless chiral edge channels in low energy
consumption electronics. Such a QAH multilayer can also be engineered into
other exotic topological phases such as a magnetic Weyl semimetal with only one
pair of Weyl points. This work reports the first experimental realization of
QAH multilayers in the superlattices composed of magnetically doped
(Bi,Sb)$_2$Te$_3$ topological insulator and CdSe normal insulator layers grown
by molecular beam epitaxy. The obtained multilayer samples show quantized Hall
resistance $h/Ne$$^2$, where $h$ is the Planck's constant, $e$ is the
elementary charge and $N$ is the number of the magnetic topological insulator
layers, resembling a high Chern number QAH insulator.",1806.05923v1
2018-09-26,Rare earth permanent magnets prepared by hot deformation process,"Hot deformation process is one of the primary methods to produce anisotropic
rare earth permanent magnets. Firstly, rapidly quenched powder flakes with
nanocrystal structure are condensed into the full dense isotropic precursors by
hot pressing process. And then, the prepared isotropic precursors are hot
deformed to produce high-anisotropy uniaxial bulk rare earth permanent magnets,
in which the highly textured structure is obtained in the hot plastic
deformation process. The obtained hot-deformed magnets possess many advantages,
such as near net-shape, outstanding corrosion resistance and ultrafine-grain
structure. The noteworthy effects of preparation parameters employed in
hot-pressing and deformation processes on the magnetic properties and
microstructures characterizations are systemically summarized in this academic
monograph. As a near net-shape technique, hot deformation process has
noteworthy advantages in producing irregular shape magnets, especially for
radially oriented ring-shape magnets with high length-diameter ratio or thin
wall. The difficulties in producing crack-free, homogeneous and non-decentered
ring-shaped magnets are basically resolved through mold design, adjustment of
deformation parameters and application of theoretical simulation. Considering
the characteristics of hot-deformed magnets, such as the grain shapes and
sizes, anisotropic distribution of intergranular phases, etc., there is
practical significance to study and improve the mechanical, electric properties
and thermal stability to enlarge the applicable area of hot-deformed magnets or
ring-shaped magnets.",1809.09838v1
2018-11-05,SkyLogic - A proposal for a skyrmion logic device,"This work proposes a novel logic device (SkyLogic) based on skyrmions, which
are magnetic vortex-like structures that have low depinning current density and
are robust to defects. A charge current sent through a polarizer ferromagnet
(P-FM) nucleates a skyrmion at the input end of an intra-gate FM interconnect
with perpendicular magnetic anisotropy (PMA-FM). The output end of the PMA--FM
forms the free layer of an MTJ stack. A spin Hall metal (SHM) is placed beneath
the PMA-FM. The skyrmion is propagated to the output end of the PMA-FM by
passing a charge current through the SHM. The resistance of the MTJ stack is
low (high) when a skyrmion is present (absent) in the free layer, thereby
realizing an inverter. A framework is developed to analyze the performance of
the SkyLogic device. A circuit-level technique is developed that counters the
transverse displacement of skyrmion in the PMA-FM and allows use of high
current densities for fast propagation. The design space exploration of the
PMA-FM material parameters is performed to obtain an optimal design point. At
the optimal point, we obtain an inverter delay of 434 ps with a switching
energy of 7.1 fJ.",1811.02016v1
2019-09-06,Electronic correlation determining correlated plasmons in Sb-doped Bi$_2$Se$_3$,"Electronic correlation is believed to play an important role in exotic
phenomena such as insulator-metal transition, colossal magneto resistance and
high temperature superconductivity in correlated electron systems. Recently, it
has been shown that electronic correlation may also be responsible for the
formation of unconventional plasmons. Herewith, using a combination of
angle-dependent spectroscopic ellipsometry, angle resolved photoemission
spectroscopy and Hall measurements all as a function of temperature supported
by first-principles calculations, the existence of low-loss high-energy
correlated plasmons accompanied by spectral weight transfer, a fingerprint of
electronic correlation, in topological insulator
(Bi$_{0.8}$Sb$_{0.2}$)$_2$Se$_3$ is revealed. Upon cooling, the density of free
charge carriers in the surface states decreases whereas those in the bulk
states increase, and that the newly-discovered correlated plasmons are key to
explaining this phenomenon. Our result shows the importance of electronic
correlation in determining new correlated plasmons and opens a new path in
engineering plasmonic-based topologically-insulating devices.",1909.02703v1
2020-03-30,"Growth and transport properties of Mg3X2 (X = Sb, Bi) single crystals","The discovery of high thermoelectric performance in n-type polycrystalline
Mg3(Sb,Bi)2 based Zintl compounds has ignited intensive research interest.
However, some fundamental questions concerning the anisotropic transport
properties and the origin of intrinsically low thermal conductivity are still
elusive, requiring the investigation of single crystals. In this work,
high-quality p-type Mg3Sb2 and Mg3Bi2 single crystals have been grown by using
a self-flux method. The electrical resistivity \r{ho} of Mg3Bi2 single crystal
displays an anisotropy with \r{ho} in-plane twice larger than out-of-plane. The
low-temperature heat capacity and lattice thermal conductivity of Mg3Sb2 and
Mg3Bi2 single crystals have been investigated by using the Debye-Callaway
model, from which the existence of low-lying vibration mode could be concluded.
Large Gr\""uneisen parameters and strong anharmonicity are found responsible for
the intrinsically low thermal conductivity. Moreover, grain boundary scattering
does not contribute significantly to suppress the lattice thermal conductivity
of polycrystalline Mg3Sb2. Our results provide insights into the intrinsic
transport properties of Mg3X2 and could pave a way to realize enhanced
thermoelectric performance in single-crystalline Mg3X2-based Zintl compounds.",2003.13313v1
2017-03-13,Extremely high magnetoresistance and conductivity in the type-II Weyl semimetals WP2 and MoP2,"The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings
can lead to spectacular electronic properties such as large mobilities
accompanied by extremely high magnetoresistance. In particular, two closely
neighbouring Weyl points of the same chirality are protected from annihilation
by structural distortions or defects, thereby significantly reducing the
scattering probability between them. Here we present the electronic properties
of the transition metal diphosphides, WP2 and MoP2, that are type-II Weyl
semimetals with robust Weyl points. We present transport and angle resolved
photoemission spectroscopy measurements, and first principles calculations. Our
single crystals of WP2 display an extremely low residual low-temperature
resistivity of 3 nohm-cm accompanied by an enormous and highly anisotropic
magnetoresistance above 200 million % at 63 T and 2.5 K. These properties are
likely a consequence of the novel Weyl fermions expressed in this compound. We
observe a large suppression of charge carrier backscattering in WP2 from
transport measurements.",1703.04527v3
2017-03-20,Exceptional Anti-Icing Performance of Self-Impregnating Slippery Surfaces,"A heat exchange interface at subzero temperature in a water vapor
environment, exhibits high probability of frost formation due to freezing
condensation, a factor that markedly decreases the heat transfer efficacy due
to the considerable thermal resistance of ice. Here we report a novel strategy
to delay ice nucleation on these types of solid-water vapor interfaces. With a
process-driven mechanism, a self-generated liquid intervening layer immiscible
to water, is deposited on a textured superhydrophobic surface and acts as a
barrier between the water vapor and the solid substrate. This liquid layer
imparts remarkable slippery conditions resulting in high mobility of condensing
water droplets. A large increase of the ensuing ice coverage time is shown
compared to the cases of standard smooth hydrophilic or textured
superhydrophobic surfaces. During deicing of these self-impregnating surfaces
we show an impressive tendency of ice fragments to skate expediting defrosting.
Robustness of such surfaces is also demonstrated by operating them under
subcooling for at least 490hr without a marked degradation. This is attributed
to the presence of the liquid intervening layer, which protects the substrate
from hydrolyzation enhancing longevity and sustaining heat transfer efficiency.",1703.07349v1
2019-02-03,Non-monotonic pressure dependence of high-field nematicity and magnetism in CeRhIn$_5$,"CeRhIn$_5$ provides a textbook example of quantum criticality in a heavy
fermion system: Pressure suppresses local-moment antiferromagnetic (AFM) order
and induces superconductivity in a dome around the associated quantum critical
point (QCP) near $p_{c} \approx 23\,$kbar. Strong magnetic fields also suppress
the AFM order at a field-induced QCP at $B_{\rm c}\approx 50\,$T. In its
vicinity, a nematic phase at $B^*\approx 28\,$T characterized by a large
in-plane resistivity anisotropy emerges. Here, we directly investigate the
interrelation between these phenomena via magnetoresistivity measurements under
high pressure. As pressure increases, the nematic transition shifts to higher
fields, until it vanishes just below $p_{\rm c}$. While pressure suppresses
magnetic order in zero field as $p_{\rm c}$ is approached, we find magnetism to
strengthen under strong magnetic fields due to suppression of the Kondo effect.
We reveal a strongly non-mean-field-like phase diagram, much richer than the
common local-moment description of CeRhIn$_5$ would suggest.",1902.00970v3
2020-02-11,Observation of an antiferromagnetic quantum critical point in high-purity LaNiO$_3$,"Amongst the rare-earth perovskite nickelates, LaNiO$_3$ (LNO) is an
exception. While the former have insulating and antiferromagnetic ground
states, LNO remains metallic and non-magnetic down to the lowest temperatures.
It is believed that LNO is a strange metal, on the verge of an
antiferromagnetic instability. Our work suggests that LNO is a quantum critical
metal, close to an antiferromagnetic quantum critical point (QCP). The QCP
behavior in LNO is manifested in epitaxial thin films with unprecedented high
purities. We find that the temperature and magnetic field dependences of the
resistivity of LNO at low temperatures are consistent with scatterings of
charge carriers from weak disorder and quantum fluctuations of an
antiferromagnetic nature. Furthermore, we find that the introduction of a small
concentration of magnetic impurities qualitatively changes the magnetotransport
properties of LNO, resembling that found in some heavy-fermion Kondo lattice
systems in the vicinity of an antiferromagnetic QCP.",2002.04159v1
2020-09-18,Nanoscale structural and electrical properties of graphene grown on AlGaN by catalyst-free chemical vapor deposition,"The integration of graphene (Gr) with nitride semiconductors is highly
interesting for applications in high-power/high-frequency electronics and
optoelectronics. In this work, we demonstrated the direct growth of Gr on
Al0.5Ga0.5N/sapphire templates by propane (C3H8) chemical vapor deposition
(CVD) at temperature of 1350{\deg}C. After optimization of the C3H8 flow rate,
a uniform and conformal Gr coverage was achieved, which proved beneficial to
prevent degradation of AlGaN morphology. X-ray photoemission spectroscopy (XPS)
revealed Ga loss and partial oxidation of Al in the near-surface AlGaN region.
Such chemical modification of a 2 nm thick AlGaN surface region was confirmed
by cross-sectional scanning transmission electron microscopy (STEM) combined
with electron energy loss spectroscopy (EELS), which also showed the presence
of a bilayer of Gr with partial sp2/sp3 hybridization. Raman spectra indicated
that the deposited Gr is nanocrystalline (with domain size 7 nm) and
compressively strained. A Gr sheet resistance of 15.8 kOhm/sq was evaluated by
four-point-probe measurements, consistently with the nanocrystalline nature of
these films. Furthermore, nanoscale resolution current mapping by conductive
atomic force microscopy (C-AFM) indicated local variations of the Gr carrier
density at a mesoscopic scale, which can be ascribed to changes in the charge
transfer from the substrate due to local oxidation of AlGaN or to the presence
of Gr wrinkles.",2009.08673v1
2017-07-28,3D laser printing by ultra-short laser pulses for micro-optical applications: towards telecom wavelengths,"Three dimensional (3D) fast (< 0.5 hour) printing of micro-optical elements
down to sub-wavelength resolution over 100 micrometers footprint areas using
femtosecond (fs-)laser oscillator is presented. Using sub-1 nJ pulse energies,
optical vortex generators made of polymerised grating segments with an
azimuthally changing orientation have been fabricated in SZ2080 resist; width
of polymerised rods was ~150 nm and period 0.6-1 micrometers. Detailed phase
retardance analysis was carried out manually with Berek compensator (under a
white light illumination) and using an equivalent principle by an automated
Abrio implementation at 546 nm. Direct experimental measurements of retardance
was required since the period of the grating was comparable (or larger) than
the wavelength of visible light. By gold sputtering, transmission-type optical
vortex generators were turned into reflective ones with augmented retardance,
n.h defined by the form birefringence, n, and the height h = 2d where d is the
thickness of the polymerised structure. Retardance reached 315 nm as measured
with Berek compensator at visible wavelengths. Birefringent phase delays of 180
degrees (or half-wavelength) required for high purity vortex generators can be
made based on the proposed approach. Optical vortex generators for telecom
wavelengths with sub-wavelength patterns of azimuthally oriented gratings are
amenable by direct laser polymerisation.",1707.09365v1
2017-08-14,High-Kinetic Inductance Additive Manufactured Superconducting Microwave Cavity,"Investigations into the microwave surface impedance of superconducting
resonators have led to the development of single photon counters that rely on
kinetic inductance for their operation. While concurrent progress in additive
manufacturing, `3D printing', opens up a previously inaccessible design space
for waveguide resonators. In this manuscript, we present results from the first
synthesis of these two technologies in a titanium, aluminum, vanadium
(Ti-6Al-4V) superconducting radio frequency resonator which exploits a design
unattainable through conventional fabrication means. We find that Ti-6Al-4V has
two distinct superconducting transition temperatures observable in heat
capacity measurements. The higher transition temperature is in agreement with
DC resistance measurements. While the lower transition temperature, not
previously known in literature, is consistent with the observed temperature
dependence of the superconducting microwave surface impedance. From the surface
reactance, we extract a London penetration depth of $8\pm3{\mu}$m - roughly an
order of magnitude larger than other titanium alloys and several orders of
magnitude larger than other conventional elemental superconductors. This large
London penetration depth suggests that Ti-6Al-4V may be a suitable material for
high kinetic inductance applications such as single photon counting or
parametric amplification used in quantum computing.",1708.04273v1
2018-08-13,Ultra-compact graphene plasmonic photodetector with the bandwidth over 110GHz,"Graphene-based photodetectors, taking advantage of high carrier mobility and
broadband absorption in graphene, have recently experienced rapid development.
However, their performances with respect to the responsivity and bandwidth are
still limited by either weak light-graphene interaction or large
resistance-capacitance product. Here, we demonstrate a waveguide coupled
integrated graphene plasmonic photodetector on the silicon-on-insulator
platform. Benefiting from plasmonic enhanced graphene-light interactions and
subwavelength confinement of the optical energy, we present a small-footprint
graphene-plasmonic photodetector with bandwidth beyond 110GHz and intrinsic
responsivity of 360mA/W. Attributed to the unique electronic bandstructure of
graphene and its ultra-broadband absorption, the operational wavelength range
extending beyond mid-infrared, and possibly further, can be anticipated. Our
results show that the combination of graphene with plasmonic devices has great
potential to realize ultra-compact and high-speed optoelectronic devices for
graphene-based optical interconnects.",1808.04815v3
2019-03-22,Structure and mechanical behavior of ultrafine-grained aluminum-iron alloy stabilized by nanoscaled intermetallic particles,"Ultrafine-grained aluminum alloys offer interesting multifunctional
properties with a combination of high strength, low electrical resistivity, and
low density. However, due to thermally induced grain coarsening, they typically
suffer from an intrinsic poor thermal stability. To overcome this drawback, an
Al-2%Fe alloy has been selected because of the low solubility of Fe in Al and
their highly positive enthalpy of mixing leading to the formation of stable
intermetallic particles. The two-phase alloy has been processed by severe
plastic deformation to achieve simultaneously submicrometer Al grains and a
uniform distribution of nanoscaled intermetallic particles. The influence of
the level of deformation on the microstructure has been investigated thanks to
transmission electron microscopy and atom probe tomography and it is shown that
for the highest strain a partial dissolution of the metastable Al6Fe particle
occurred leading to the formation of a Fe super saturated solid solution. The
thermal stability, and especially the precipitation of particles from the
ultrafine-grained solid solution and the way they pin grain boundaries has been
investigated both from static annealing and in-situ transmission electron
microscopy experiments. The correlation between microstructural features and
microhardness has been established to identify the various strengthening
contributions. Finally, it is 2 shown that ultrafine grained high purity Al
with less than 0.01 at. % Fe in solid solution could preserve a grain size only
300nm after 1h at 250$^\circ$C.",1903.09391v1
2019-03-27,Homogeneous hierarchical NiMoO4@NiMoO4 nanostructure as a high-performance anode material for electrochemical energy storage,"Here we report the extraordinary electrochemical energy storage capability of
NiMoO4@NiMoO4 homogeneous hierarchical nanosheet-on-nanowire-arrays (SOWAs)
synthesized on nickel substrate by a two-stage hydrothermal process.
Comparatively speaking, the SOWAs electrode displays improved electrochemical
performances than the bare NiMoO4 nanowire arrays. Such improvements can be
ascribed to the characteristic homogeneous hierarchical structure which not
only effectively increases the active surface areas for fast charge transfer,
but also reduces the electrode resistance significantly by eliminating the
potential barrier at the nanowire/nanosheet junction, which is usually an issue
in other reported heterogeneous architectures. We further evaluate the
performances of the SOWAs by constructing an asymmetric hybrid supercapacitor
(ASC) with the SOWAs and activated carbon (AC). The optimized ASC shows
excellent electrochemical performances with 47.2 Wh/kg in energy density at
1.38 kW/kg at 0-1.2 V. Moreover, the specific capacity retention can be as high
as 91.4% after 4000 cycles, illustrating the remarkable cycling stability of
the NiMoO4@NiMoO4//AC ASC device. Our results show that this unique
NiMoO4@NiMoO4 SOWAs display great prospect for future energy storage
applications",1903.11513v1
2019-04-29,Type-II Ising superconductivity and anomalous metallic state in macro-size ambient-stable ultrathin crystalline films,"Recent emergence of two-dimensional (2D) crystalline superconductors has
provided a promising platform to investigate novel quantum physics and
potential applications. To reveal essential quantum phenomena therein, ultralow
temperature transport investigation on high quality ultrathin superconducting
films is critically required, although it has been quite challenging
experimentally. Here we report a systematic transport study on the ultrathin
crystalline PdTe2 films grown by molecular beam epitaxy (MBE). Interestingly, a
new type of Ising superconductivity in 2D centrosymmetric materials is revealed
by the detection of large in-plane critical field more than 7 times Pauli
limit. Remarkably, in perpendicular magnetic field, we provide solid evidence
of anomalous metallic state characterized by the resistance saturation at low
temperatures with high quality filters. The robust superconductivity with
intriguing quantum phenomena in the macro-size ambient-stable ultrathin PdTe2
films remains almost the same for 20 months, showing great potentials in
electronic and spintronic applications.",1904.12719v2
2016-09-08,Evidence of Ballistic Thermal Transport in Lithium Niobate at Room Temperature,"In ballistic transport, heat carriers such as phonons travel through the
solid without any scattering or interaction. Therefore, there is no temperature
gradient in the solid, which seems to transport the heat without getting heated
itself. Ballistic transport is typically seen in high purity crystals at either
temperatures below ~10 K, or physical size below ~100 nm, where the mean free
path of the carrier is larger than the solid itself. In this letter, we show
evidence of ballistic transport at room temperature in lithium niobate wafers
in the in-plane and cross-plane directions under both steady state and high
frequency heating that are monitored using both infrared and resistance
thermometry. We report phonon mean free path in lithium niobate around 425
microns, which is about 50 times higher than the largest phonon mean free path
in the literature at room temperature. Above this length-scale, temperature
gradient gradually emerges and the material shows completely diffusive, bulk
transport at about 4 mm length. Our observations will impact phonon-based
electronics such as thermal transistor, thermal logic gate and memory currently
impossible at room temperature. If 1 micron electron mean free path in graphene
gives the highest-mobility, the 425 microns mean free path of phonons in this
research may realize phononics without any need for nanoscale size or
ultra-cold temperatures.",1609.02585v1
2018-07-03,ssDNA sequencing by rectification,"Fast, reliable and inexpensive DNA sequencing is an important pursuit in
healthcare, especially in personalized medicine with possible deep societal
impacts. Despite significant progress of various nanopore-based sequencing
configurations, challenges remain in resolution (due to thermal fluctuations or
to sensitivity to molecular orientation) and speed, which are calling for new
approaches. Here we propose a sequencing protocol for DNA translocation through
a nanopore with side-embedded N-terminated carbon nanotube electrodes.
Employing DFT and Non-Equilibrium Green's Function formalism, we show that the
rectification ratio (response to square pulses of alternating bias) bears high
nucleobase specificity. The rectification arises due to bias-dependent
resistance asymmetry on the deoxyribonucleotide-electrode interfaces. The
asymmetry induces molecular charging and HOMO pinning to the electrochemical
potential of one of the electrodes, assisted by an in-gap electric field effect
caused by dipoles at the terminated electrode ends. This sequencing protocol is
sensitive, selective with orders of magnitude, has high resolution, and it is
robust to molecular orientation.",1807.01215v4
2018-12-16,Quantum dots formed in three-dimensional Dirac semimetal Cd$_3$As$_2$ nanowires,"We demonstrate quantum dot (QD) formation in three-dimensional Dirac
semimetal Cd$_{3}$As$_{2}$ nanowires using two electrostatically tuned p$-$n
junctions with a gate and magnetic fields. The linear conductance measured as a
function of gate voltage under high magnetic fields is strongly suppressed at
the Dirac point close to zero conductance, showing strong conductance
oscillations. Remarkably, in this regime, the Cd$_{3}$As$_{2}$ nanowire device
exhibits Coulomb diamond features, indicating that a clean single QD forms in
the Dirac semimetal nanowire. Our results show that a p$-$type QD can be formed
between two n$-$type leads underneath metal contacts in the nanowire by
applying gate voltages under strong magnetic fields. Analysis of the quantum
confinement in the gapless band structure confirms that p$-$n junctions formed
between the p$-$type QD and two neighboring n$-$type leads under high magnetic
fields behave as resistive tunnel barriers due to cyclotron motion, resulting
in the suppression of Klein tunneling. The p$-$type QD with magnetic
field-induced confinement shows a single hole filling. Our results will open up
a route to quantum devices such as QDs or quantum point contacts based on Dirac
and Weyl semimetals.",1812.06416v1
2019-01-17,Compositional dependence of epitaxial Tin+1SiCn MAX-phase thin films grown from a Ti3SiC2 compound target,"We investigate sputtering of a Ti3SiC2 compound target at temperatures
ranging from RT (no applied external heating) to 970 oC as well as the
influence of the sputtering power at 850 oC for the deposition of Ti3SiC2 films
on Al2O3(0001) substrates. Elemental composition obtained from time-of-flight
energy elastic recoil detection analysis shows an excess of carbon in all
films, which is explained by differences in angular distribution between C, Si
and Ti, where C scatters the least during sputtering. The oxygen content is 2.6
at.% in the film deposited at RT and decreases with increasing deposition
temperature, showing that higher temperatures favor high purity films. Chemical
bonding analysis by X-ray photoelectron spectroscopy shows C-Ti and Si-C
bonding in the Ti3SiC2 films and Si-Si bonding in the Ti3SiC2 compound target.
X-ray diffraction reveals that the phases Ti3SiC2, Ti4SiC3, and Ti7Si2C5 can be
deposited from a Ti3SiC2 compound target at substrate temperatures above 850 oC
and with growth of TiC and the Nowotny phase Ti5Si3Cx at lower temperatures.
High-resolution scanning transmission electron microscopy shows epitaxial
growth of Ti3SiC2, Ti4SiC3, and Ti7Si2C5 on TiC at 970 oC. Four-point probe
resistivity measurements give values in the range 120 to 450 micro-Ohm-cm and
with the lowest values obtained for films containing Ti3SiC2, Ti4SiC3, and
Ti7Si2C5.",1901.05904v1
2019-06-10,Anomalous electron transport in epitaxial NdNiO$_3$ films,"The origin of simultaneous electronic, structural and magnetic transitions in
bulk rare-earth nickelates ($RE$NiO$_3$) remains puzzling with multiple
conflicting reports on the nature of these entangled phase transitions.
Heterostructure engineering of these materials offers unique opportunity to
decouple metal-insulator transition (MIT) from the magnetic transition.
However, the evolution of underlying electronic properties across these
decoupled transitions remains largely unexplored. In order to address this, we
have measured Hall effect on a series of epitaxial NdNiO$_3$ films, spanning a
variety of electronic and magnetic phases. We find that the MIT results in only
partially gapped Fermi surface, whereas full insulating phase forms below the
magnetic transition. In addition, we also find a systematic reduction of the
Hall coefficient ($R_H$) in the metallic phase of these films with epitaxial
strain and also a surprising transition to negative value at large compressive
strain. Partially gapped weakly insulating, paramagnetic phase is reminiscence
of pseudogap behavior of high $T_c$ cuprates. The precursor metallic phase,
which undergoes transition to insulating phase is a non-Fermi liquid with the
temperature exponent ($n$) of resistivity of 1, whereas the exponent increases
to 4/3 in the non-insulating samples. Such nickelate phase diagram with
sign-reversal of $R_H$, pseudo-gap phase and non Fermi liquid behavior are
intriguingly similar to high $T_c$ cuprates, giving important guideline to
engineer unconventional superconductivity in oxide heterostructure.",1906.03809v1
2019-10-22,Magnetic topological insulator MnBi6Te10 with zero-field ferromagnetic state and gapped Dirac surface states,"Magnetic topological insulators (TIs) with nontrivial topological electronic
structure and broken time-reversal symmetry exhibit various exotic topological
quantum phenomena. The realization of such exotic phenomena at high temperature
is one of central topics in this area. We reveal that MnBi6Te10 is a magnetic
TI with an antiferromagnetic ground state below 10.8 K whose nontrivial
topology is manifested by Dirac-like surface states. The ferromagnetic axion
insulator state with Z4 = 2 emerges once spins polarized at field as low as 0.1
T, accompanied with saturated anomalous Hall resistivity up to 10 K. Such a
ferromagnetic state is preserved even external field down to zero at 2 K.
Theoretical calculations indicate that the few-layer ferromagnetic MnBi6Te10 is
also topologically nontrivial with a non-zero Chern number. Angle-resolved
photoemission spectroscopy experiments further reveal three types of Dirac
surface states arising from different terminations on the cleavage surfaces,
one of which has insulating behavior with an energy gap of ~ 28 meV at the
Dirac point. These outstanding features suggest that MnBi6Te10 is a promising
system to realize various topological quantum effects at zero field and high
temperature.",1910.10101v2
2020-01-03,Coulomb Blockade Effects in a Topological Insulator Grown on a High-Tc Cuprate Superconductor,"The evidence for proximity-induced superconductivity in heterostructures of
topological insulators and high-Tc cuprates has been intensely debated. We use
molecular beam epitaxy to grow thin films of topological insulator Bi2Te3 on a
cuprate Bi2Sr2CaCu2O8+x, and study the surface of Bi2Te3 using low-temperature
scanning tunneling microscopy and spectroscopy. In few unit-cell thick Bi2Te3
films, we find a V-shaped gap-like feature at the Fermi energy in dI/dV
spectra. By reducing the coverage of Bi2Te3 films to create nanoscale islands,
we discover that this spectral feature dramatically evolves into a much larger
hard gap, which can be understood as a Coulomb blockade gap. This conclusion is
supported by the evolution of dI/dV spectra with the lateral size of Bi2Te3
islands, as well as by topographic measurements that show an additional barrier
separating Bi2Te3 and Bi2Sr2CaCu2O8+x. We conclude that the prominent gap-like
feature in dI/dV spectra in Bi2Te3 films is not a proximity-induced
superconducting gap. Instead, it can be explained by Coulomb blockade effects,
which take into account additional resistive and capacitive coupling at the
interface. Our experiments provide a fresh insight into the tunneling
measurements of complex heterostructures with buried interfaces.",2001.00906v2
2020-07-14,Cyclic plasticity and fatigue damage of CrMnFeCoNi high entropy alloy fabricated by laser powder-bed fusion,"The CrMnFeCoNi high-entropy alloy is highly printable and holds great
potential for structural applications. However, no significant discussions on
cyclic plasticity and fatigue damage in previous studies. This study provides
significant insights into the link between print processes, solidification
microstructure, cyclic plasticity and fatigue damage evolution in the alloy
fabricated by laser powder bed fusion. Thermodynamics-based predictions
(validated by scanning transmission electron microscopy (STEM) energy
dispersive X-ray spectroscopy (EDX)) showed that Cr, Co and Fe partition to the
core of the solidification cells, whilst Mn and Ni to the cell boundaries in
all considered print parameters. Both dislocation slip and deformation twinning
were found to be responsible for plastic deformation under monotonic loading.
However, the former was found to be the single dominant mechanism for cyclic
plasticity. The surface finish helped to substantially delay the crack
initiation and cause lack-of-fusion porosity to be the main source of crack
initiation. Most significantly, the scan strategies significantly affect grain
arrangements and grain dimensions, leading to noticeable effects on fatigue
crack propagation; in particular, the highest resistance crack propagation was
seen in the meander scan strategy with 0{\deg} rotation thanks to the most
columnar grains and the smallest spacing of grain boundaries along the crack
propagation path.",2007.07043v1
2020-07-24,Integration of multi-layer black phosphorus into photoconductive antennas for THz emission,"We report the fabrication, characterization, and modeling of photoconductive
antennas using 40 nm thin-film flakes of black phosphorus (BP) as the
photoconductor and hexagonal boron nitride (hBN) as a capping layer to prevent
oxidation of BP. Dipole antennas were fabricated on oxidized high-resistivity
Si substrates, and BP and hBN flakes were picked up and transferred onto the
antenna inside a nitrogen glovebox. The transfer matrix technique was used to
optimize the thickness of BP and hBN for maximum absorption. BP flakes were
aligned with the armchair axis along the anode-cathode gap of the antenna, with
crystal orientation measured using reflection anisotropy. Photocurrent imaging
under illumination with 100 fs pulses at 780 and 1560 nm showed a
bias-dependent maximum photocurrent localized to the antenna gap with a peak
photoconductivity of 1 (2) S/cm in the linear regime of bias for excitation at
780 (1560) nm. Photocurrent saturation in bias (pump fluence) occurred at
approximately 1 V (0.25 mJ/cm$^2$). Device performance was modeled numerically
by solving Maxwell's equations and the drift-diffusion equation to obtain the
photocurrent density in response to pulsed laser excitation, which was largely
in qualitative agreement with the experimental observations. THz output
computed from surface current density suggests that BP THz PCA performance is
at least comparable to more traditional devices based on low-temperature-grown
GaAs. These devices represent a step toward high-performance THz
photoconductive antennas using BP.",2007.12775v1
2020-08-06,Constraining the ellipticity of millisecond pulsars with observed spin-down rates,"A spinning neutron star (NS) that is asymmetric with respect to its spin axis
can emit continuous gravitational wave (GW) signals. The spin frequencies and
their distribution of radio millisecond pulsars (MSPs) and accreting MSPs
provide some evidences of GW radiation, and MSPs are ideal probes detecting
high frequency GW signals. It is generally thought that MSPs originate from the
recycled process, in which the NS accretes the material and angular momentum
from the donor star. The accreted matter would be confined at the polar cap
zone by an equatorial belt of compressed magnetic field fixed in the deep crust
of the NS, and yields ""magnetic mountain"". Based on an assumption that the
spin-down rates of three transitional MSPs including PSR J1023+0038 are the
combinational contribution of the accretion torque, the propeller torque, and
the GW radiation torque, in this work we attempt to constrain the ellipticities
of MSPs with observed spin-down rates. Assuming some canonical parameters of
NSs, the ellipticities of three transitional MSPs and ten redbacks are
estimated to be $\epsilon=(0.9-23.4)\times 10^{-9}$. The electrical
resistivities of three transitional MSPs are also derived to be in the range
$\eta=(1.2-15.3)\times 10^{-31}~\rm s$, which display an ideal power law
relation with the accretion rate. The characteristic strains ($h_{\rm
c}=(0.6-2.5)\times10^{-27}$) of GW signals emitting by these sources are
obviously beyond the sensitivity scope of the aLIGO. We expect that the
third-generation GW detectors like the Einstein Telescope can seize the GW
signals from these sources in the future.",2008.02444v2
2020-08-22,Large Transport Gap Modulation in Graphene via Electric Field Controlled Reversible Hydrogenation,"Graphene is of interest in the development of next-generation electronics due
to its high electron mobility, flexibility and stability. However, graphene
transistors have poor on/off current ratios because of the absence of a
bandgap. One approach to introduce an energy gap is to use hydrogenation
reaction, which changes graphene into insulating graphane with sp3 bonding.
Here we show that an electric field can be used to control
conductor-to-insulator transitions in microscale graphene via a reversible
electrochemical hydrogenation in an organic liquid electrolyte containing
dissociative hydrogen ions. The fully hydrogenated graphene exhibits a lower
limit sheet resistance of 200 Gohm/sq, resulting in graphene field-effect
transistors with on/off current ratios of 10^8 at room temperature. The devices
also exhibit high endurance, with up to one million switching cycles. Similar
insulating behaviours are also observed in bilayer graphene, while trilayer
graphene remains highly conductive after the hydrogenation. Changes in the
graphene lattice, and the transformation from sp2 to sp3 hybridization, is
confirmed by in-situ Raman spectroscopy, supported by first-principles
calculations.",2008.09749v2
2020-10-04,Ballistic-hydrodynamic phase transition in flow of two-dimensional electrons,"Phase transitions are characterized by a sharp change in the type of dynamics
of microparticles, and their description usually requires quantum mechanics.
Recently, a peculiar type of conductors was discovered in which two-dimensional
(2D) electrons form a viscous fluid. In this work we reveal that such electron
fluid in high-quality samples can be formed from ballistic electrons via a
phase transition. For this purpose, we theoretically study the evolution of a
ballistic flow of 2D weakly interacting electrons with an increase of magnetic
field and trace an emergence of a fluid fraction at a certain critical field.
Such restructuring of the flow manifests itself in a kink in magnetic-field
dependencies of the longitudinal and the Hall resistances. It is remarkable
that the studied phase transition has a classical-mechanical origin and is
determined by both the ballistic size effects and the electron-electron
scattering. Our analysis shows that this effect was apparently observed in the
recent transport experiments on 2D electrons in graphene and high-mobility GaAs
quantum wells.",2010.01642v4
2020-10-22,Li-ion Battery Fault Detection in Large Packs Using Force and Gas Sensors,"Internal short circuits are a leading cause of battery thermal runaway, and
hence a major safety issue for electric vehicles. An internal short circuit
with low resistance is called a hard internal short, which causes a high
internal current flow that leads to an extremely fast temperature rise, gas
generation, cell swelling, and ultimately battery rupture and failure. Thus it
is crucial to detect these faults immediately after they get triggered. In
large battery packs with many cells in parallel, detecting an internal short
circuit event using voltage is difficult due to suppression of the voltage
signal from the faulty cell by the other healthy cells connected in parallel.
In contrast, analyzing the gas composition in the pack enclosure can provide a
robust single cell failure detection method. At elevated temperature,
decomposition of the battery materials results in gas generation and cell
swelling. The cell structure is designed to rupture at a critical gas pressure
and vent the accumulated $CO_2$ gas, in order to prevent explosive forces. In
this paper, we extend our previous work by combining the models of cell thermal
dynamics, swelling, and $CO_2$ gas generation. In particular, we developed a
fast and high confidence level detection method of hard internal short circuit
events for a battery pack by measuring cell expansion force and monitoring
$CO_2$ concentrations in a pack enclosure.",2010.13519v1
2020-11-01,Experimental demonstration of particle acceleration with normal conducting accelerating structure at cryogenic temperature,"Reducing the operating temperature of normal conducting particle accelerators
substantially increases their efficiency. Low-temperature operation increases
the yield strength of the accelerator material and reduces surface resistance,
hence a great reduction in cyclic fatigue could be achieved resulting in a
large reduction in breakdown rates compared to room-temperature operation.
Furthermore, temperature reduction increases the intrinsic quality factor of
the accelerating cavities, and consequently, the shunt impedance leading to
increased system efficiency and beam loading capabilities. In this paper, we
present an experimental demonstration of the high-gradient operation of an
X-band, 11.424 GHz, 20-cells linear accelerator (linac) operating at a liquid
nitrogen temperature of 77 K. The tested linac was previously processed and
tested at room temperature. We verified the enhanced accelerating parameters of
the tested accelerator at cryogenic temperature using different measurements
including electron beam acceleration up to a gradient of 150 MV/m,
corresponding to a peak surface electric field of 375 MV/m. We also measured
the breakdown rates in the tested structure showing a reduction of two orders
of magnitude, x100, compared to their values at room temperature for the same
accelerating gradient.",2011.00391v1
2020-12-13,Microfluidic device coupled with total internal reflection microscopy for in situ observation of precipitation,"In situ observation of precipitation or phase separation induced by solvent
addition is important in studying its dynamics. Combined with optical and
fluorescence microscopy, microfluidic devices have been leveraged in studying
the phase separation in various materials including biominerals, nanoparticles,
and inorganic crystals. However, strong scattering from the subphases in the
mixture is problematic for in situ study of phase separation with high temporal
and spatial resolution. In this work, we present a quasi-2D microfluidic device
combined with total internal reflection microscopy as an approach for in situ
observation of phase separation. The quasi-2D microfluidic device comprises of
a shallow main channel and a deep side channel. Mixing between a solution in
the main channel (solution A) and another solution (solution B) in the side
channel is predominantly driven by diffusion due to high fluid resistance from
the shallow height of the main channel, which is confirmed using fluorescence
microscopy. Moreover, relying on diffusive mixing, we can control the
composition of the mixture in the main channel by tuning the composition of
solution B. We demonstrate the application of our method for in situ
observation of asphaltene precipitation and beta-alanine crystallization.",2012.06962v1
2021-01-31,Monoclinic EuSn$_2$As$_2$: A Novel High-Pressure Network Structure,"The layered crystal of EuSn$_2$As$_2$ has a Bi$_2$Te$_3$-type structure in
rhombohedral ($R\bar{3}m$) symmetry and has been confirmed to be an intrinsic
magnetic topological insulator at ambient conditions. Combining {\it ab initio}
calculations and \emph{in-situ} x-ray diffraction measurements, we identify a
new monoclinic EuSn$_2$As$_2$ structure in $C2/m$ symmetry above $\sim$14 GPa.
It has a three-dimensional network made up of honeycomb-like Sn sheets and
zigzag As chains, transformed from the layered EuSn$_2$As$_2$ via a two-stage
reconstruction mechanism with the connecting of Sn-Sn and As-As atoms
successively between the buckled SnAs layers. Its dynamic structural stability
has been verified by phonon mode analysis. Electrical resistance measurements
reveal an insulator-metal-superconductor transition at low temperature around 5
and 15 GPa, respectively, according to the structural conversion, and the
superconductivity with a \textit{T}${\rm {_C}}$ value of $\sim 4$ K is observed
up to 30.8 GPa. These results establish a high-pressure EuSn$_2$As$_2$ phase
with intriguing structural and electronic properties and expand our
understandings about the layered magnetic topological insulators.",2102.00437v2
2021-02-18,Crystal orientation-dependent oxidation of epitaxial TiN films with tunable plasmonics,"Titanium nitride (TiN) is a paradigm of refractory transition metal nitrides
with great potential in vast applications. Generally, the plasmonic performance
of TiN can be tuned by oxidation, which was thought to be only temperature-,
oxygen partial pressure-, and time-dependent. Regarding the role of
crystallographic orientation in the oxidation and resultant optical properties
of TiN films, little is known thus far. Here we reveal that both the oxidation
resistance behavior and the plasmonic performance of epitaxial TiN films follow
the order of (001) < (110) < (111). The effects of crystallographic orientation
on the lattice constants, optical properties, and oxidation levels of epitaxial
TiN films have been systematically studied by combined high-resolution X-ray
diffraction, spectroscopic ellipsometry, X-ray absorption spectroscopy, and
X-ray photoemission spectroscopy. To further understand the role of
crystallographic orientation in the initial oxidation process of TiN films,
density-functional-theory calculations are carried out, indicating the energy
cost of oxidation is (001) < (110) < (111), consistent with the experiments.
The superior endurance of the (111) orientation against mild oxidation can
largely alleviate the previously stringent technical requirements for the
growth of TiN films with high plasmonic performance. The crystallographic
orientation can also offer an effective controlling parameter to design
TiN-based plasmonic devices with desired peculiarity, e.g., superior chemical
stability against mild oxidation or large optical tunability upon oxidation.",2102.09126v1
2021-03-15,Thermal Visualization of Buried Interfaces by Transient and Steady-State Responses of Time-Domain Thermoreflectance,"Thermal resistances from interfaces impede heat dissipation in
micro/nanoscale electronics, especially for high-power electronics. Despite the
growing importance of understanding interfacial thermal transport, advanced
thermal characterization techniques which can visualize thermal conductance
across buried interfaces, especially for nonmetal-nonmetal interfaces, are
still under development. This work reports a dual-modulation-frequency TDTR
mapping technique to visualize the thermal conduction across buried
semiconductor interfaces for beta-Ga2O3-SiC samples. Both the beta-Ga2O3
thermal conductivity and the buried beta-Ga2O3-SiC thermal boundary conductance
(TBC) are visualized for an area of 200 um x 200 um. Areas with low TBC values
( smaller than 20 MW/m2-K) are successfully identified on the TBC map, which
correspond to weakly bonded interfaces caused by high-temperature annealing.
The steady-state temperature rise (detector voltage), usually ignored in TDTR
measurements, is found to be able to probe TBC variations of the buried
interfaces without the limit of thermal penetration depth. This technique can
be applied to detect defects/voids in deeply buried heterogeneous interfaces
non-destructively, and also opens a door for the visualization of thermal
conductance in nanoscale nonhomogeneous structures.",2103.08084v1
2021-03-24,Quantum transport properties of beta-Bi4I4 near and well beyond the extreme quantum limit,"We have investigated the magneto-transport properties of beta-Bi4I4 bulk
crystal, which was recently theoretically proposed and experimentally
demonstrated to be a topological insulator. At low temperature T and magnetic
field B, a series of Shubnikov-De Haas(SdH) oscillations are observed on the
magnetoresistivity (MR). The detailed analysis reveals a light cyclotron mass
of 0.1 me, and the field angle dependence of MR reveals that the SdH
oscillations originate from a convex Fermi surface. In the extreme quantum
limit (EQL) region, there is a metal-insulator transition occurring soon after
the EQL. We perform the scaling analysis, and all the isotherms fall onto a
universal scaling with a fitted critical exponent of 6.5. The enormous value of
critical exponent implies this insulating quantum phase originated from strong
electron-electron interactions in high fields. However, in the far end of EQL,
both the longitudinal and Hall resistivity increase exponentially with B, and
the temperature dependence of the MR reveals an energy gap induced by the high
magnetic field, signifying a magnetic freeze-out effect. Our findings indicate
that bulk beta-Bi4I4 is an excellent candidate for a 3D topological system for
exploring EQL physics and relevant exotic quantum phases.",2103.13079v2
2021-04-15,"Negligible oxygen vacancies, low critical current density, electric-field modulation, in-plane anisotropic and high-field transport of a superconducting Nd0.8Sr0.2NiO2/SrTiO3 heterostructure","The emerging Ni-based superconducting oxide thin films are rather intriguing
to the entire condensed matter physics. Here we report some brief experimental
results on transport measurements for a 14-nm-thick superconducting
Nd0.8Sr0.2NiO2/SrTiO3 thin-film heterostructure with an onset transition
temperature of ~9.5 K. Photoluminescence measurements reveal that there is
negligible oxygen vacancy creation in the SrTiO3 substrate during thin-film
deposition and post chemical reduction for the Nd0.8Sr0.2NiO2/SrTiO3
heterostructure. It was found that the critical current density of the
Nd0.8Sr0.2NiO2/SrTiO3 thin-film heterostructure is relatively small, ~4x10^3
A/cm2. Although the surface steps of SrTiO3 substrates lead to an anisotropy
for in-plane resistivity, the superconducting transition temperatures are
almost the same. The out-of-plane magnetotransport measurements yield an upper
critical field of ~11.4 T and an estimated in-plane Ginzburg-Landau coherence
length of ~5.4 nm. High-field magnetotransport measurements up to 50 T reveal
anisotropic critical fields at 1.8 K for three different measurement geometries
and a complicated Hall effect. An electric field applied via the SrTiO3
substrate slightly varies the superconducting transition temperature. These
experimental results could be useful for this rapidly developing field.",2104.07316v2
2021-04-26,Impact of the nucleation of charge clusters on the retention of memristors: a self-consistent phase field computational study,"In recent years, resistive RAM often referred to as memristor is actively
pursued as a replacement for nonvolatile-flash memory due to its superior
characteristics such as high density, scalability, low power operation, high
endurance, and fast operating speed. However, one of the challenges that need
to be overcome is the loss of retention for both ON- and OFF-states; the
retention loss. While various models are proposed to explain the retention loss
in memristors consisting of a switching layer, in this paper, we propose that
the nucleation of clusters made of electrical charges, charge-clusters, in the
switching layer acts as a potential root cause for the retention loss. The
nucleation results from localized electric-field produced intermittently during
cyclic switching operations. We use the phase-field method to illustrate how
the nucleation of charge-clusters gives rise to the retention loss. Our results
suggest that the degree at which the retention loss arises is linked to the
number of cyclic switching operations since the probability at which nucleation
centers form increases with the number of cycle switching operations, which is
consistent with a range of experimental findings previously reported.",2104.12829v1
2021-06-02,Multiband effects on the upper critical field angular dependence of 122-family iron pnictide superconductors,"Detailed measurements of the in-plane resistivity were performed in a
high-quality Ba(Fe$_{1-x}$Co$_{x}$)$_2$As$_2$ ($x=0.065$) single crystal, in
magnetic fields up to 9 T and with different orientations $\theta$ relative to
the crystal $c$ axis. A significant $\rho(T)_{H,\theta}$ rounding is observed
just above the superconducting critical temperature $T_c$ due to Cooper pairs
created by superconducting fluctuations. These data are analyzed in terms of a
generalization of the Aslamazov-Larkin approach, that extends its applicability
to high reduced-temperatures and magnetic fields. This method allows us to
carry out a criterion-independent determination of the angular dependence of
the upper critical field, $H_{c2}(\theta)$. In spite of the relatively small
anisotropy of this compound, it is found that $H_{c2}(\theta)$ presents a
significant deviation from the single-band 3D anisotropic Ginzburg-Landau
(3D-aGL) approach, particularly for large $\theta$ (typically above
$\sim60^o$). These results are interpreted in terms of the multiband nature of
these materials, in contrast with other proposals for similar $H_{c2}(\theta)$
anomalies. Our results are also consistent with an effective anisotropy factor
almost temperature independent near $T_c$, a result that differs from the ones
obtained by using a single-band model.",2106.01307v1
2021-07-07,Magnetization-tuned topological quantum phase transition in MnBi2Te4 devices,"Recently, the intrinsic magnetic topological insulator MnBi2Te4 has attracted
enormous research interest due to the great success in realizing exotic
topological quantum states, such as the quantum anomalous Hall effect (QAHE),
axion insulator state, high-Chern-number and high-temperature Chern insulator
states. One key issue in this field is to effectively manipulate these states
and control topological phase transitions. Here, by systematic angle-dependent
transport measurements, we reveal a magnetization-tuned topological quantum
phase transition from Chern insulator to magnetic insulator with gapped Dirac
surface states in MnBi2Te4 devices. Specifically, as the magnetic field is
tilted away from the out-of-plane direction by around 40-60 degrees, the Hall
resistance deviates from the quantization value and a colossal, anisotropic
magnetoresistance is detected. The theoretical analyses based on modified
Landauer-Buttiker formalism show that the field-tilt-driven switching from
ferromagnetic state to canted antiferromagnetic state induces a topological
quantum phase transition from Chern insulator to magnetic insulator with gapped
Dirac surface states in MnBi2Te4 devices. Our work provides an efficient means
for modulating topological quantum states and topological quantum phase
transitions.",2107.03224v1
2021-07-22,Anomalous Transport in High-Mobility Superconducting SrTiO$_3$ Thin Films,"The study of subtle effects on transport in semiconductors requires
high-quality epitaxial structures with low defect density. Using hybrid
molecular beam epitaxy (MBE), SrTiO$_3$ films with low-temperature mobility
exceeding 42,000 cm$^2$V$^{-1}$s$^{-1}$ at low carrier density of 3 x 10$^{17}$
cm$^{-3}$ were achieved. A sudden and sharp decrease in residual resistivity
accompanied by an enhancement in the superconducting transition temperature
were observed across the second Lifshitz transition (LT) where the third band
becomes occupied, revealing dominant intra-band scattering. These films further
revealed an anomalous behavior in the Hall carrier density as a consequence of
the antiferrodistortive (AFD) transition and the temperature-dependence of the
Hall scattering factor. Using hybrid MBE growth, phenomenological modeling,
temperature-dependent transport measurements, and scanning superconducting
quantum interference device imaging, we provide critical insights into the
important role of inter- vs intra-band scattering and of AFD domain walls on
normal-state and superconducting properties of SrTiO$_3$.",2107.10904v1
2021-09-27,Pressure-induced monotonic enhancement of Tc to over 30 K in the superconducting Pr0.82Sr0.18NiO2 thin films,"The successful synthesis of superconducting infinite-layer nickelate thin
films with the highest Tc ~ 15 K has reignited great enthusiasms on this family
of potential analogue to high-Tc cuprates. Pursuing a higher Tc is always an
imperative task in studying a new superconducting material system. Here we
report high-quality Pr0.82Sr0.18NiO2 thin films with Tconset ~ 17 K synthesized
by carefully tuning the amount of CaH2 in the topological chemical reduction
and the effect of pressure on its superconducting properties by measuring
electrical resistivity under various pressures in a cubic anvil cell apparatus.
We find that the onset temperature of the superconductivity, Tconset, can be
enhanced monotonically from ~ 17 K at ambient pressure to ~ 31 K at 12.1 GPa
without showing signatures of saturation upon increasing pressure. This
encouraging result indicates that the Tc of infinite-layer nickelates
superconductors still has room to go higher and it can be further boosted by
applying higher pressures or strain engineering in the heterostructure films.",2109.12811v2
2021-10-26,Novel Lithium-Sulfur Polymer Battery Operating at Moderate Temperature,"A safe lithium-sulfur (Li-S) battery employs a composite polymer electrolyte
based on a poly(ethylene glycol) dimethyl ether (PEGDME) solid at room
temperature. The electrolyte membrane enables a stable and reversible Li-S
electrochemical process already at 50{\deg}C, with low resistance at the
electrode/electrolyte interphase and fast Li+ transport. The relatively low
molecular weight of the PEGDME and the optimal membrane composition in terms of
salts and ceramic allow a liquid-like Li-S conversion reaction by heating at
moderately high temperature, still holding the solid-like polymer state of the
cell. Therefore, the electrochemical reaction of the polymer Li-S cell is
characterized by the typical dissolution of lithium polysulfides into the
electrolyte medium during discharge and the subsequent deposition of sulfur at
the electrode/electrolyte interphase during charge. On the other hand, the
remarkable thermal stability of the composite polymer electrolyte (up to
300{\deg}C) suggests a lithium-metal battery with safety content significantly
higher than that using the common, flammable liquid solutions. Hence, the Li-S
polymer battery delivers at 50{\deg}C and 2 V a stable capacity approaching 700
mAhgS-1, with a steady-state coulombic efficiency of 98%. These results suggest
a novel, alternative approach to achieve safe, high energy batteries with solid
polymer configuration.",2110.13727v1
2021-11-30,Bosonic metal states in crystalline iron-based superconductors at the two-dimensional limit,"The nature of the anomalous metal, one of the quantum ground states of
two-dimensional (2D) bosonic systems, remains a major puzzle even after several
decades of study. Here, we report a systematic investigation on the transport
properties of ultrathin crystalline FeSe films grown on SrTiO3 (STO) as well as
the nanopatterned FeSe/STO, where the 2D high-temperature superconductivity is
confined at the interface. Remarkably, the bosonic anomalous metal state
emerges around 20 K, an exceptionally high temperature compared to all previous
observations. Furthermore, a linear-in-temperature (T-linear) resistance with
suppressed Hall coefficient below onset temperature for superconductivity is
observed, indicating a bosonic strange metal. We give quantitative analysis for
the bosonic anomalous metal state, based on the quantum dynamical property of
vortices influenced by ohmic dissipation. This microscopic model pins down the
origin of the intriguing anomalous state to the superconducting phase dynamics
in both spatial and temporal domain. Our findings shed new light on the bosonic
metal states in crystalline superconductors at the 2D limit.",2111.15488v2
2022-03-14,Large enhancement in thermal conductivity of solvent cast expanded-graphite/polyetherimide composites,"We demonstrate in this work, that expanded graphite (EG) can lead to a very
large enhancement in thermal conductivity of polyetherimide-graphene and
epoxy-graphene nanocomposites prepared via solvent casting technique. A k value
of 6.56 Wm-1K-1 is achieved for 10 weight % composition sample, representing an
enhancement of ~2770% over pristine polyetherimide (k ~ 0.23 Wm-1K-1). This
extraordinary enhancement in thermal conductivity is shown to be due to a
network of continuous graphene sheets over long length scales, resulting in low
thermal contact resistance at bends/turns due to the graphene sheets being
covalently bonded at such junctions. Solvent casting offers the advantage of
preserving the porous structure of expanded graphite in the composite,
resulting in the above highly thermally conductive interpenetrating network of
graphene and polymer. Solvent casting also does not break down the expanded
graphite particles, due to minimal forces involved, allowing for efficient heat
transfer over long length scales, further enhancing overall composite thermal
conductivity. Comparisons with a recently introduced effective medium model
shows a very high value of predicted particle-particle interfacial conductance,
providing evidence for efficient interfacial thermal transport in expanded
graphite composites. Field Emission Environmental Scanning Electron Microscopy
(FE-ESEM) is used to provide detailed understanding of interpenetrating
graphene-polymer structure in the expanded graphite composite. These results
open up novel avenues for achieving high thermal conductivity polymer
composites.",2203.06828v1
2022-03-18,Thermoelectric transport properties of gapless pinned charge density waves,"Quantum strongly correlated matter exhibits properties which are not easily
explainable in the conventional framework of Fermi liquids. Universal effective
field theory tools are applicable in these cases regardless of the microscopic
details of the quantum system, since they are based on symmetries. It is
necessary, however, to construct these effective tools in full generality,
avoiding restrictions coming from particular microscopic descriptions which may
inadequately constrain the coefficients that enter in the effective theory.
  In this work we demonstrate on explicit examples how the novel hydrodynamic
coefficients which have been recently reinstated in the effective theory of
pinned charge density waves (CDW) can affect the phenomenology of the
thermo-electric transport in strongly correlated quantum matter. Our examples,
based on two classes of holographic models with pinned CDW, have microscopics
which are conceptually different from Fermi liquids. Therefore, the above novel
transport coefficients are nonzero, contrary to the conventional approach. We
show how these coefficients allow to take into account the change of sign of
the Seebeck coefficient and the low resistivity of the CDW phase of the cuprate
high temperature superconductors, without referring to the effects of Fermi
surface reconstruction.",2203.10038v2
2022-05-11,An mCherry biolaser based on microbubble cavity with ultra-low threshold,"Biolasers show considerable potential in the biomedical field. Fluorescent
protein (FP) is a type of biomaterial with good luminescence efficiency that
can be used as the luminescent gain medium in biolasers. Due to the higher
cell/tissue permeability, lower cell phototoxicity, and relatively less
background fluorescence than other fluorescent proteins, the red fluorescent
protein is more suitable in biological applications. MCherry is the most
extensively used high-quality red fluorescent protein because of its short
maturation time and stable luminescence properties. In this study, using
mCherry and microbubble cavity, we realize a highly stable mCherry fluorescent
protein laser. The laser resonator achieves a quality factor of 10^8, which is
the highest Q factor among the currently available FP lasers. Moreover, this
laser exhibits low threshold of 286 fJ, which can effectively protect the
luminescent material from being damaged by pump light. Such a threshold is the
lowest in the FP lasers as per our knowledge. The prepared laser shows
excellent stability in a wide pH range with good photobleaching resistance and
can be stored at 4 degree for nearly a month. Also, the laser can serve as a
high-sensitivity molecular concentration detector with mCherry as biomarker,
owing to its lasing threshold behavior.",2205.05220v2
2022-07-01,Efficient and Scalable GaInAs Thermophotovoltaic Devices,"Thermophotovoltaics are promising solid-state energy converters for a variety
of applications such as grid-scale energy storage, concentrating solar-thermal
power, and waste heat recovery. Here, we report the design, fabrication, and
testing of large area (0.8 cm$^2$), scalable, single junction 0.74-eV GaInAs
thermophotovoltaic devices reaching an efficiency of 38.8$\pm$2.0% and an
electrical power density of 3.78 W/cm$^2$ at an emitter temperature of
1850{\deg}C. Reaching such a high emitter temperature and power density without
sacrificing efficiency is a direct result of combining good spectral management
with a highly optimized cell architecture, excellent material quality, and very
low series resistance. Importantly, fabrication of 12 high-performing devices
on a two-inch wafer is shown to be repeatable, and the cell design can be
readily transferred to commercial epitaxy on even larger wafers. Further
improvements in efficiency can be obtained by using a multijunction
architecture, and early results for a two-junction 0.84-eV GaInPAs / 0.74-eV
GaInAs device illustrate this promise.",2207.00565v1
2022-07-12,Non-destructive Depth-Resolved Characterization of Residual Strain Fields in High Electron Mobility Transistors using Differential Aperture X-ray Microscopy,"Localized residual stress and elastic strain concentrations in
microelectronic devices often affect the electronic performance, resistance to
thermomechanical damage, and, likely, radiation tolerance. A primary challenge
for characterization of these concentrations is that they exist over sub-$\mu$m
length-scales, precluding their characterization by more traditional residual
stress measurement techniques. Here we demonstrate the use of synchrotron X-ray
-based differential aperture X-ray microscopy (DAXM) as a viable,
non-destructive means to characterize these stress and strain concentrations in
a depth-resolved manner. DAXM is used to map two-dimensional strain fields
between source and drain in a gallium nitride (GaN) layer within high electron
mobility transistors (HEMTs) with sub-$\mu$m spatial resolution. Strain fields
at various positions in both pristine and irradiated HEMT specimens are
presented in addition to a preliminary stress analysis to estimate the
distribution of various stress components within the GaN layer.
$\gamma$-irradiation is found to significantly reduce the lattice plane spacing
in the GaN along the sample normal direction which is attributed to radiation
damage in transistor components bonded to the GaN during irradiation.",2207.05789v2
2022-08-10,Synthesis of Superconducting Phase of La$_{0.5}$Ce$_{0.5}$H$_{10}$ at High Pressures,"Clathrate hydride \emph{Fm}\={3}\emph{m}-LaH$_{10}$ has been proven as the
most extraordinary superconductor with the critical temperature $T_c$ above 250
K upon compression of hundreds of GPa in recent years. A general hope is to
reduce the stabilization pressure and maintain the high $T_c$ value of the
specific phase in LaH$_{10}$. However, strong structural instability distorts
\emph{Fm}\={3}\emph{m} structure and leads to a rapid decrease of $T_c$ at low
pressures. Here, we investigate the phase stability and superconducting
behaviors of \emph{Fm}\={3}\emph{m}-LaH$_{10}$ with enhanced chemical
pre-compression through partly replacing La by Ce atoms from both experiments
and calculations. For explicitly characterizing the synthesized hydride, we
choose lanthanum-cerium alloy with stoichiometry composition of 1:1. X-ray
diffraction and Raman scattering measurements reveal the stabilization of
\emph{Fm}\={3}\emph{m}-La$_{0.5}$Ce$_{0.5}$H$_{10}$ in the pressure range of
140-160 GPa. Superconductivity with $T_c$ of 175$\pm$2 K at 155 GPa is
confirmed with the observation of the zero-resistivity state and supported by
the theoretical calculations. These findings provide applicability in the
future explorations for a large variety of hydrogen-rich hydrides.",2208.05199v1
2022-09-12,Emergent magnetic states and tunable exchange bias at all 3d nitride heterointerfaces,"Interfacial magnetism stimulates the discovery of giant magnetoresistance and
spin-orbital coupling across the heterointerfaces, facilitating the intimate
correlation between spin transport and complex magnetic structures. Over
decades, functional heterointerfaces composed of nitrides are seldomly explored
due to the difficulty in synthesizing high-quality and correct composition
nitride films. Here we report the fabrication of single-crystalline
ferromagnetic Fe3N thin films with precisely controlled thickness. As film
thickness decreasing, the magnetization deteriorates dramatically, and
electronic state transits from metallic to insulating. Strikingly, the
high-temperature ferromagnetism maintains in a Fe3N layer with a thickness down
to 2 u. c. (~ 8 {\AA}). The magnetoresistance exhibits a strong in-plane
anisotropy and meanwhile the anomalous Hall resistance reserves its sign when
Fe3N layer thickness exceeds 5 u. c. Furthermore, we observe a sizable exchange
bias at the interfaces between a ferromagnetic Fe3N and an antiferromagnetic
CrN. The exchange bias field and saturation moment strongly depend on the
controllable bending curvature using cylinder diameter engineering (CDE)
technique, implying the tunable magnetic states under lattice deformation. This
work provides a guideline for exploring functional nitride films and applying
their interfacial phenomena for innovative perspectives towards the practical
applications.",2209.05209v1
2022-11-02,Tunable Rapid Electron Transport in Titanium Oxide Thin Films,"Rapid electron transport in the quantum well triggers many novel physical
phenomena and becomes a critical point for the high-speed electronics. Here, we
found electrical properties of the titanium oxide changed from semiconducting
to metallic as the degree of oxidation decreased and Schottky quantum well was
formed at the interface. We take the asymmetry interface electron scattering
effect into consideration when studying the electrical transport properties of
the multilayer thin films. A novel physical conductivity model for the
multilayer thin films was developed. We found electron would be transferred
from the low-mobility semiconducting and metallic conductive channels to the
high-mobility Schottky quantum well conductive channel with an in-plane applied
electric field. Electron concentration and mobility of the forming 2DEG in the
Schottky quantum well could be tuned thus the nano-devices exhibited non-linear
voltage-current curves. The differential resistivity of the nano-devices could
decrease by two orders with increasing electric field at room temperature. Weak
electron localization of electrons has been experimentally observed in our
nano-devices at low temperature, which further demonstrated the existence of
2DEG in the Schottky quantum well. Our work will provide us new physics about
the rapid electron transport in the multilayer thin films, and bring novel
functional devices for the modern microelectronic industry.",2211.01162v1
2023-03-06,A Miniaturised Camera-based Multi-Modal Tactile Sensor,"In conjunction with huge recent progress in camera and computer vision
technology, camera-based sensors have increasingly shown considerable promise
in relation to tactile sensing. In comparison to competing technologies (be
they resistive, capacitive or magnetic based), they offer
super-high-resolution, while suffering from fewer wiring problems. The human
tactile system is composed of various types of mechanoreceptors, each able to
perceive and process distinct information such as force, pressure, texture,
etc. Camera-based tactile sensors such as GelSight mainly focus on
high-resolution geometric sensing on a flat surface, and their force
measurement capabilities are limited by the hysteresis and non-linearity of the
silicone material. In this paper, we present a miniaturised dome-shaped
camera-based tactile sensor that allows accurate force and tactile sensing in a
single coherent system. The key novelty of the sensor design is as follows.
First, we demonstrate how to build a smooth silicone hemispheric sensing medium
with uniform markers on its curved surface. Second, we enhance the illumination
of the rounded silicone with diffused LEDs. Third, we construct a
force-sensitive mechanical structure in a compact form factor with usage of
springs to accurately perceive forces. Our multi-modal sensor is able to
acquire tactile information from multi-axis forces, local force distribution,
and contact geometry, all in real-time. We apply an end-to-end deep learning
method to process all the information.",2303.03093v1
2023-03-15,Rare observation of spin-gapless semiconducting characteristics and related band topology of quaternary Heusler alloy CoFeMnSn,"In this paper, we report the theoretical investigation and experimental
realization of a new spin-gapless semiconductor (SGSs) compound CoFeMnSn
belonging to the family of quaternary Heusler alloys. Through the use of
several ground-state energy calculations, the most stable structure has been
identified. Calculations of the spin-polarized band structure in optimized
structure's reveals the SGS nature of the compound. The compound form in an
ordered crystal structure and exhibit a high ferromagnetic transition
temperature (T$_{\rm C}$ = 560 K), making the material excellent for room
temperature applications. Adherence of saturation magnetization to the
Slater-Pauling rule, together with the nearly temperature-independent
resistivity, conductivity, and carrier concentration of the compound in the
temperature regime 5$-$300 K along with the low value of anomalous Hall
conductivity (AHC) further confirms the SGS nature. Theoretical calculations
also reveal the robustness of the SGS state due to lattice contraction and one
can obtain a high value of intrinsic AHC using hole doping. Combined SGS and
topological properties of the compound make CoFeMnSn suitable for spintronics
and magneto-electronics devices.",2303.08589v2
2023-04-11,"Effects of equivalent composition on superconducting properties of high-entropy REOBiS$_2$ (RE = La, Ce, Pr, Nd, Sm, Gd) single crystals","Superconductors are influenced by high-entropy alloys (HEAs); these have been
investigated in various functional materials. REOBiS$_2$ (RE = La, Ce, Pr, Nd,
Sm, and Gd in different combinations) single crystals with HEAs at the RE-site
were successfully grown using the flux method. The obtained crystals were
plate-shaped (1 mm$^2$) with a well-developed c-plane. Ce was present in both
trivalent (Ce$^{3+}$) and tetravalent (Ce$^{4+}$) electronic configurations;
the concentration of Ce$^{4+}$ at the RE-site was approximately 10 at% in all
single crystals. The single crystals showed superconducting transition
temperature with zero resistivity within 1.2-4.2 K. The superconducting
transition temperature, superconducting anisotropy, electronic specific heat
coefficient, and Debye temperature of the crystals were not correlated with the
mixed entropy at the RE-site. Except for the electronic specific heat
coefficient, the variation of these parameters as a function of mixed entropy
showed different trends for equivalent and non-equivalent RE element
compositions. Thus, the configuration of RE elements influences the
superconducting properties of REOBiS$_2$ single crystals, alluding to a method
of modulating transition temperatures.",2304.04993v1
2023-06-21,An Analytical Model to Quantify the Local Lattice Distortion of Refractory High Entropy Alloys,"Local lattice distortion (LLD) of high entropy alloys (HEAs) especially
refractory HEAs, which is different from one lattice site to another,
determines the mechanical properties of HEAs such as yield strength and
radiation resistance, and is crucial to modulating catalytic activity of HEAs
via the atomic strain. In particular, this site-to-site LLD is strongly coupled
with the short-range order (SRO) of HEAs. Therefore it is essential to reveal
the physical picture of LLD. However, the random distribution of
multi-principal constituents of HEAs prohibits the understanding of LLD,
including the determinants of LLD and their coupling rules. Herein, we build
the first analytical model to realize the site-to-site prediction of LLD in
refractory HEAs, by using the neighbor number ratio of central atoms, the
central-atom radii, the standard deviation of constituent radii and the
constituent number, which demonstrates that LLD surprisingly exhibits a similar
mechanism as the relaxation of metal surfaces. The involved parameters depend
only on the radii of constituents and are readily accessible. Moreover, our
scheme determines not only LLD but also the average lattice distortion, which
enables us to predict the phase stability and yield strength of HEAs. These
results build a novel physical picture of LLD, in particular the quantitative
relationship between LLD and SRO, which lay a solid foundation for the further
target-oriented design of HEAs.",2306.11959v1
2023-06-28,High-Q trenched aluminum coplanar resonators with an ultrasonic edge microcutting for superconducting quantum devices,"Dielectric losses are one of the key factors limiting the coherence of
superconducting qubits. The impact of materials and fabrication steps on
dielectric losses can be evaluated using coplanar waveguide (CPW) microwave
resonators. Here, we report on superconducting CPW microwave resonators with
internal quality factors systematically exceeding 5x106 at high powers and
2x106 (with the best value of 4.4x106) at low power. Such performance is
demonstrated for 100-nm-thick aluminum resonators with 7-10.5 um center trace
on high-resistivity silicon substrates commonly used in quantum Josephson
junction circuits. We investigate internal quality factors of the resonators
with both dry and wet aluminum etching, as well as deep and isotropic reactive
ion etching of silicon substrate. Josephson junction compatible CPW resonators
fabrication process with both airbridges and silicon substrate etching is
proposed. Finally, we demonstrate the effect of airbridges positions and extra
process steps on the overall dielectric losses. The best quality fa ctors are
obtained for the wet etched aluminum resonators and isotropically removed
substrate with the proposed ultrasonic metal edge microcutting.",2306.16301v1
2023-10-05,"Liquid Cooling System for a High Power, Medium Frequency, and Medium Voltage Isolated Power Converter","Power electronics systems, widely used in various applications such as
industrial automation, electric cars, and renewable energy, have the primary
function of converting and controlling electrical power to the desired type of
load. Despite their reliability and efficiency, power losses in these systems
generate significant heat that must be dissipated to maintain performance and
prevent damage. Cooling systems play a crucial role in ensuring safe operating
temperatures for system components. Air and liquid cooling are the leading
technologies used in the power electronics world. Air cooling is simple and
cost-effective but is limited by ambient temperature and component thermal
resistance. While more efficient, liquid cooling requires more maintenance and
has higher upfront costs. Water-cooling systems have become famous for
regulating thermal loads as they can effectively remove heat from localized
high-temperature areas, such as the challenging hotspots in power electronics
systems. In addition to designing a cooling system for a power electronic
system, this study investigated the impact of three major parameters; cold
plate material, channel shape/size, and coolant inlet velocity. The research
examined and analyzed these factors and their trade-off analysis to obtain
cooling system design and optimization insights. This study might improve power
electronics system performance, reliability, and durability by improving heat
dissipation and thermal management.",2310.03577v1
2023-10-19,Detailed and high-throughput measurement of composition dependence of magnetoresistance and spin-transfer torque using a composition-gradient film: application to Co$_{x}$Fe$_{1-x}$ (0 $\le$ $\textit{x}$ $\le$ 1) system,"We develop a high-throughput method for measuring the composition dependence
of magnetoresistance (MR) and spin-transfer-torque (STT) effects in
current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices and
report its application to the CoFe system. The method is based on the use of
composition-gradient films deposited by combinatorial sputtering. This
structure allows the fabrication of devices with different compositions on a
single substrate, drastically enhancing the throughput in investigating
composition dependence. We fabricated CPP-GMR devices on a single GMR film
consisting of a Co$_{x}$Fe$_{1-x}$ (0 $\le$ $\textit{x}$ $\le$ 1)
composition-gradient layer, a Cu spacer layer, and a NiFe layer. The MR ratio
obtained from resistance-field measurements exhibited the maximum in the broad
Co concentration range of 0.3 $\le$ $\textit{x}$ $\le$ 0.65. In addition, the
STT efficiency was estimated from the current to induce magnetization reversal
of the NiFe layer by spin injection from the Co$_{x}$Fe$_{1-x}$ layer. The STT
efficiency was also the highest around the same Co concentration range as for
the MR ratio, and this correlation was theoretically explained by the change in
the spin polarization of the Co$_{x}$Fe$_{1-x}$ layer. The results revealed the
Co$_{x}$Fe$_{1-x}$ composition range suitable for spintronic applications,
demonstrating the advantages of the developed method.",2310.12434v1
2023-11-25,Our Dark Matter Stopping in the Earth,"We have worked for some time on a model for dark matter, in which dark matter
consists of small bubbles of a new speculated type of vacuum, which are pumped
up by some ordinary matter such as diamond, so as to resist the pressure of the
domain wall separating the two vacua. Here we put forward thoughts on, how such
macroscopic pearls would have their surrounding dust cleaned off passing
through the atmosphere and the Earth, and what their distribution would be as a
function of the depth of their stopping point and the distribution of the
radiation emitted from them. In our model we assume that they radiate 3.5 keV
electrons and photons, after having been excited during their passage into the
Earth. The purpose of such an estimation of the radiation distribution is to
explain the truly mysterious fact that, among all the underground experiments
seeking dark matter colliding with the Earth material, only the DAMA-LIBRA
experiment has seen any evidence of dark matter. This is an experiment based on
solid NaI scintillators and is rather deep at 1400 m. It is our point that we
can arrange the main radiation to appear in the relatively deep DAMA- LIBRA
site, and explain that the dark matter pearls cannot stop in a fluid, such as
xenon in the xenon based experiments.",2311.14996v1
2023-11-27,Tailoring the Opto-Electronic Properties of Oxide-Metal-Oxide Transparent Electrode Using Cu Seed Layer,"The oxide-metal-oxide architecture is a promising approach for the
development of the high-performance indium-free transparent electrode (TE),
which is a key component of various optoelectronic applications such as solar
cells, organic LEDs, and touchscreen panels. Here in this work, we have shown
high-performance TE consisting of TiO2/Ag/TiO2 (TAT), with the incorporation of
a copper seed layer. The seed layer increases the wettability and improves the
adhesion of deposited Ag film on the bottom TiO2 layer. Before the experimental
realization, optical modeling is performed by using MATLAB code based on the
transfer matrix method. The optimum thickness obtained from the simulation is
30 nm for both undercoat and overcoat TiO2 with the average transmittance in
the visible region >85% with the Ag thickness of 9nm. With inputs from the
optical modeling, TEs were experimentally realized with and without the Cu seed
layer. It has been found that the TE with an additional sputtered Cu (1 nm)
seed layer is essential for the smooth growth of silver film and shows better
electro-optical performance (sheet resistance < 10 and average transmittance in
the visible spectral range > 80%) than TAT-TE without any seed layer. The
electro-optical and morphological properties of the TiO2/Cu/Ag/TiO2 structure
make it suitable for optoelectronic applications.",2311.15535v2
2023-11-30,Vanishing of the anomalous Hall effect and enhanced carrier mobility in the spin-gapless ferromagnetic Mn2CoGa1-xAlx alloys,"Spin gapless semiconductor (SGS) has attracted long attention since its
theoretical prediction, while concrete experimental hints are still lack in the
relevant Heusler alloys. Here in this work, by preparing the series alloys of
Mn2CoGa1-xAlx (x=0, 0.25, 0.5, 0.75 and 1), we identified the vanishing of
anomalous Hall effect in the ferromagnetic Mn2CoGa (or x=0.25) alloy in a wide
temperature interval, accompanying with growing contribution from the ordinary
Hall effect. As a result, comparatively low carrier density (1020 cm-3) and
high carrier mobility (150 cm2/Vs) are obtained in Mn2CoGa (or x=0.25) alloy in
the temperature range of 10-200K. These also lead to a large dip in the related
magnetoresistance at low fields. While in high Al content, despite the
magnetization behavior is not altered significantly, the Hall resistivity is
instead dominated by the anomalous one, just analogous to that widely reported
in Mn2CoAl. The distinct electrical transport behavior of x=0 and x=0.75 (or 1)
is presently understood by their possible different scattering mechanism of the
anomalous Hall effect due to the differences in atomic order and conductivity.
Our work can expand the existing understanding of the SGS properties and offer
a better SGS candidate with higher carrier mobility that can facilitate the
application in the spin-injected related devices.",2311.18335v1
2024-01-31,Electrical 180o switching of Néel vector in spin-splitting antiferromagnet,"Antiferromagnetic spintronics have attracted wide attention due to its great
potential in constructing ultra-dense and ultra-fast antiferromagnetic memory
that suits modern high-performance information technology. The electrical 180o
switching of N\'eel vector is a long-term goal for developing
electrical-controllable antiferromagnetic memory with opposite N\'eel vectors
as binary ""0"" and ""1"". However, the state-of-art antiferromagnetic switching
mechanisms have long been limited for 90o or 120o switching of N\'eel vector,
which unavoidably require multiple writing channels that contradicts
ultra-dense integration. Here, we propose a deterministic switching mechanism
based on spin-orbit torque with asymmetric energy barrier, and experimentally
achieve electrical 180o switching of spin-splitting antiferromagnet Mn5Si3.
Such a 180o switching is read out by the N\'eel vector-induced anomalous Hall
effect. Based on our writing and readout methods, we fabricate an
antiferromagnet device with electrical-controllable high and low resistance
states that accomplishes robust write and read cycles. Besides fundamental
advance, our work promotes practical spin-splitting antiferromagnetic devices
based on spin-splitting antiferromagnet.",2401.17608v1
2024-02-29,Controllable suppression of the unconventional superconductivity in bulk and thin-film Sr$_{2}$RuO$_{4}$ via high-energy electron irradiation,"In bulk Sr$_{2}$RuO$_{4}$, the strong sensitivity of the superconducting
transition temperature $T_{\text{c}}$ to nonmagnetic impurities provides robust
evidence for a superconducting order parameter that changes sign around the
Fermi surface. In superconducting epitaxial thin-film Sr$_{2}$RuO$_{4}$, the
relationship between $T_{\text{c}}$ and the residual resistivity $\rho_0$,
which in bulk samples is taken to be a proxy for the low-temperature elastic
scattering rate, is far less clear. Using high-energy electron irradiation to
controllably introduce point disorder into bulk single-crystal and thin-film
Sr$_{2}$RuO$_{4}$, we show that $T_{\text{c}}$ is suppressed in both systems at
nearly identical rates. This suggests that part of $\rho_0$ in films comes from
defects that do not contribute to superconducting pairbreaking, and establishes
a quantitative link between the superconductivity of bulk and thin-film
samples.",2402.19454v1
2017-07-09,Ultrafast Epitaxial Growth of Metre-Sized Single-Crystal Graphene on Industrial Cu Foil,"A foundation of the modern technology that uses single-crystal silicon has
been the growth of high-quality single-crystal Si ingots with diameters up to
12 inches or larger. For many applications of graphene, large-area high-quality
(ideally of single-crystal) material will be enabling. Since the first growth
on copper foil a decade ago, inch-sized single-crystal graphene has been
achieved. We present here the growth, in 20 minutes, of a graphene film of 5 x
50 cm2 dimension with > 99% ultra-highly oriented grains. This growth was
achieved by: (i) synthesis of sub-metre-sized single-crystal Cu(111) foil as
substrate; (ii) epitaxial growth of graphene islands on the Cu(111) surface;
(iii) seamless merging of such graphene islands into a graphene film with high
single crystallinity and (iv) the ultrafast growth of graphene film. These
achievements were realized by a temperature-driven annealing technique to
produce single-crystal Cu(111) from industrial polycrystalline Cu foil and the
marvellous effects of a continuous oxygen supply from an adjacent oxide. The
as-synthesized graphene film, with very few misoriented grains (if any), has a
mobility up to ~ 23,000 cm2V-1s-1 at 4 K and room temperature sheet resistance
of ~ 230 ohm/square. It is very likely that this approach can be scaled up to
achieve exceptionally large and high-quality graphene films with single
crystallinity, and thus realize various industrial-level applications at a low
cost.",1707.02512v1
2020-06-04,Thermal conductivity of amorphous and crystalline GeTe thin film at high temperature: Experimental and theoretical study,"Thermal transport properties bear a pivotal role in influencing the
performance of phase change memory (PCM) devices, in which the PCM operation
involves fast and reversible phase change between amorphous and crystalline
phases. In this paper, we present a systematic experimental and theoretical
study on the thermal conductivity of GeTe at high temperatures involving fast
change from amorphous to crystalline phase upon heating. Modulated photothermal
radiometry (MPTR) is used to experimentally determine thermal conductivity of
GeTe at high temperatures in both amorphous and crystalline phases. Thermal
boundary resistances are accurately taken into account for experimental
consideration. To develop a concrete understanding of the underlying physical
mechanism, rigorous and in-depth theoretical exercises are carried out. For
this, first-principles density functional methods and linearized Boltzmann
transport equations (LBTE) are employed using both direct and relaxation time
based approach (RTA) and compared with that of the phenomenological Slack
model. The amorphous phase experimental data has been described using the
minimal thermal conductivity model with sufficient precision. The theoretical
estimation involving direct solution and RTA method are found to retrieve well
the trend of the experimental thermal conductivity for crystalline GeTe at high
temperatures despite being slightly overestimated and underestimated,
respectively, compared to the experimental data. A rough estimate of vacancy
contribution has been found to modify the direct solution in such a way that it
agrees excellently with the experiment. Umklapp scattering has been determined
as the significant phonon-phonon scattering process. Umklapp scattering
parameter has been identified for GeTe for the whole temperature range which
can uniquely determine and compare Umklapp scattering processes for different
materials",2006.02625v1
2021-08-31,Toward 100% Spin-Orbit Torque Efficiency with High Spin-Orbital Hall Conductivity Pt-Cr Alloys,"5d transition metal Pt is the canonical spin Hall material for efficient
generation of spin-orbit torques (SOTs) in Pt/ferromagnetic layer (FM)
heterostructures. However, for a long while with tremendous engineering
endeavors, the damping-like SOT efficiencies (${\xi}_{DL}$) of Pt and Pt alloys
have still been limited to ${\xi}_{DL}$<0.5. Here we present that with proper
alloying elements, particularly 3d transition metals V and Cr, a high
spin-orbital Hall conductivity
(${\sigma}_{SH}{\sim}6.5{\times}10^{5}({\hbar}/2e){\Omega}^{-1}{\cdot} m^{-1}$)
can be developed. Especially for the Cr-doped case, an extremely high
${\xi}_{DL}{\sim}0.9$ in a Pt$_{0.69}$Cr$_{0.31}$/Co device can be achieved
with a moderate Pt$_{0.69}$Cr$_{0.31}$ resistivity of ${\rho}_{xx}{\sim}133
{\mu}{\Omega}{\cdot}cm$. A low critical SOT-driven switching current density of
$J_{c}{\sim}3.2{\times}10^{6} A{\cdot}cm^{-2}$ is also demonstrated. The
damping constant (${\alpha}$) of Pt$_{0.69}$Cr$_{0.31}$/FM structure is also
found to be reduced to 0.052 from the pure Pt/FM case of 0.078. The overall
high ${\sigma}_{SH}$, giant ${\xi}_{DL}$, moderate ${\rho}_{xx}$, and reduced
${\alpha}$ of such a Pt-Cr/FM heterostructure makes it promising for versatile
extremely low power consumption SOT memory applications.",2108.13857v3
2024-01-05,Signatures of room-temperature superconductivity emerging in two-dimensional domains within the new Bi/Pb-based ceramic cuprate superconductors at ambient pressure,"We predict the possibility of realizing room-temperature superconductivity in
different 2D domains within the ceramic high-Tc cuprates at ambient pressure
and experimentally confirm this prediction of 2D room-temperature
superconductivity in the newly derived Bi/Pb-based ceramic cuprates containing
many grain boundaries, interfaces and multiplate blocks. We argue that, in
these high-Tc materials, besides bulk superconductivity in 3D domains there is
also strongly enhanced 2D superconductivity emerging in the 3D-2D crossover
region well above the superconducting transition temperature Tc. We study the
possibility of the existence of distinct 3D and 2D superconducting phases in
high-Tc ceramic cuprates, in which the unconventional Cooper pairs behave like
bosons and condense below certain critical temperatures into 3D and 2D Bose
superfluids in 3D and 2D domains. We show that the superconducting transition
temperature in 2D domains is much higher than in 3D domains and can reach up to
room temperature. We report signatures of room-temperature superconductivity
occurring at different grain boundaries and 3D/2D interfaces and in multiplate
blocks within the ceramic superconductors, synthesized by using the new melt
technology in a large solar furnace. The samples of these materials synthesized
under the influence of concentrated solar energy have the bulk Tc values
ranging from 100 K to about 140 K and the more higher superconducting
transition temperatures, possibly even as high as room temperature in the 3D-2D
crossover region. The remnant 2D superconductivity in newly derived Bi/Pb-based
ceramic cuprate superconductors is observed at temperatures 200-300 K well
above the bulk Tc and the onset of room-temperature superconductivity is
evidenced by the observations of a sharp step-like drop in the resistance and a
well-detectable partial Meissner effect at around 300 K and ambient pressure.",2401.02642v1
2024-04-17,On-liquid-gallium surface synthesis of ultra-smooth conductive metal-organic framework thin films,"Conductive metal-organic frameworks (MOFs) are emerging electroactive
materials for (opto-)electronics. However, it remains a great challenge to
achieve reliable MOF-based devices via the existing synthesis methods that are
compatible with the complementary metal-oxide-semiconductor technology, as the
surface roughness of thus-far synthetic MOF films or pellets is rather high for
efficient electrode contact. Here, we develop an on-liquid-gallium surface
synthesis (OLGSS) strategy under chemical vapor deposition (CVD) conditions for
the controlled growth of two-dimensional conjugated MOF (2D c-MOF) thin films
with ten-fold improvement of surface flatness (surface roughness can reach as
low as ~2 {\AA}) compared with MOF films grown by the traditional methods.
Supported by theoretical modeling, we unveil a layer-by-layer CVD growth mode
for constructing flattening surfaces, that is triggered by the high adhesion
energy between gallium (Ga) and planar aromatic ligands. We further demonstrate
the generality of the as-proposed OLGSS strategy by reproducing such a flat
surface over nine different 2D c-MOF films with variable thicknesses (~2 to 208
nm) and large lateral sizes (over 1 cm2). The resultant ultra-smooth 2D c-MOF
films enable the formation of high-quality electrical contacts with gold (Au)
electrodes, leading to a reduction of contact resistance by over ten orders of
magnitude compared to the traditional uneven MOF films. Furthermore, due to the
efficient interfacial interaction benifited from the high-quality contacts, the
prepared van der Waals heterostructure (vdWH) of OLGSS c-MOF and MoS2 exhibits
intriguing photoluminescence (PL) enhancement, PL peak shift and large work
function modulation. The establishment of the reliable OLGSS method provides
the chances to push the development of MOF electronics and the construction of
multicomponent MOF-based heterostructure materials.",2404.15357v1
2009-01-08,Transport properties of Layer-Antiferromagnet CuCrS2: A possible thermoelectric material,"The electrical, thermal conductivity and Seebeck coefficient of the quenched,
annealed and slowly cooled phases of the layer compound CuCrS2 have been
reported between 15K to 300K. We also confirm the antiferromagnetic transition
at 40K in them by our magnetic measurements between 2K and 300K. The crystal
flakes show a minimum around 100K in their in-plane resistance behavior. For
the polycrystalline pellets the resistivity depends on their flaky texture and
it attains at most 10 to 20 times of the room temperature value at the lowest
temperature of measurement. The temperature dependence is complex and no
definite activation energy of electronic conduction can be discerned. We find
that the Seebeck coefficient is between 200-450 microV/K and is unusually large
for the observed resistivity values of between 5-100 mOhm-cm at room
temperature. The figure of merit ZT for the thermoelectric application is 2.3
for our quenched phases, which is much larger than 1 for useful materials. The
thermal conductivity K is mostly due to lattice conduction and is reduced by
the disorder in Cu- occupancy in our quenched phase. A dramatic reduction of
electrical and thermal conductivity is found as the antiferromagnetic
transition is approached from the paramagnetic region, and K subsequently rises
in the ordered phase. We discuss the transport properties as being similar to a
doped Kondo-insulator.",0901.0977v2
2009-06-29,A novel wear-resistant magnetic thin film material based on a $Ti_{1-x}Fe_xC_{1-y}$ nanocomposite alloy,"In this study we report on the film growth and characterization of thin
(approximately 50 nm thick) Ti-Fe-C films deposited on amorphous quartz. The
experimental studies have been complemented by first principles density
functional theory (DFT) calculations. Upon annealing of as-prepared films, the
composition of the metastable Ti-Fe-C film changes. An iron-rich phase is first
formed close to the film surface, but with increasing annealing time this phase
is gradually displaced toward the film-substrate interface where its position
stabilizes. Both the magnetic ordering temperature and the saturation
magnetization changes significantly upon annealing. The DFT calculations show
that the critical temperature and the magnetic moment both increase with
increasing Fe and C-vacancy concentration. The formation of the metastable
iron-rich Ti-Fe-C compound is reflected in the strong increase of the magnetic
ordering temperature. Eventually, after enough annealing time ($\geq 10$
minutes), nano-crystalline $\alpha$-Fe starts to precipitate and the amount and
size of these precipitates can be controlled by the annealing procedure; after
20 minutes of annealing, the experimental results indicate a nano-crystalline
iron-film embedded in a wear resistant TiC compound. This conclusion is further
supported by transmission electron microscopy studies on epitaxial Ti-Fe-C
films deposited on single crystalline MgO substrates where, upon annealing, an
iron film embedded in TiC is formed. Our results suggest that annealing of
metastable Ti-Fe-C films can be used as an efficient way of creating a
wear-resistant magnetic thin film material.",0906.5386v1
2010-11-25,Resistive transition in disordered superconductors with varying intergrain coupling,"The effect of disorder is investigated in granular superconductive materials
with strong and weak links. The transition is controlled by the interplay of
the \emph{tunneling} $g$ and \emph{intragrain} $g_{intr}$ conductances, which
depend on the strength of the intergrain coupling. For $g \ll g_{intr}$, the
transition involves first the grain boundary, while for $g \sim g_{intr}$ the
transition occurs into the whole grain. The different intergrain coupling is
considered by modelling the superconducting material as a disordered network of
Josephson junctions. Numerical simulations show that on increasing the
disorder, the resistive transition occurs for lower temperatures and the curve
broadens. These features are enhanced in disordered superconductors with strong
links. The different behaviour is further checked by estimating the average
network resistance for weak and strong links in the framework of the effective
medium approximation theory. These results may be relevant to shed light on
long standing puzzles as: (i) enhancement of the superconducting transition
temperature of many metals in the granular states; (ii) suppression of
superconductivity in homogeneously disordered films compared to standard
granular systems close to the metal-insulator transition; (iii) enhanced
degradation of superconductivity by doping and impurities in strongly linked
materials, such as magnesium diboride, compared to weakly-linked
superconductors, such as cuprates.",1011.5607v1
2015-10-23,Consequences of breaking time reversal symmetry in LaSb: a resistivity plateau and extreme magnetoresistance,"Time reversal symmetry (TRS) protects the metallic surface modes of
topological insulators (TIs). The transport signature of robust metallic
surface modes of TIs is a plateau that arrests the exponential divergence of
the insulating bulk with decreasing temperature. This universal behavior is
observed in all TI candidates ranging from Bi2Te2Se to SmB6. Recently, several
topological semimetals (TSMs) have been found that exhibit extreme
magnetoresistance (XMR) and TI universal resistivity behavior revealed only
when breaking TRS, a regime where TIs theoretically cease to exist. Among these
new materials, TaAs and NbP are nominated for Weyl semimetal due to their lack
of inversion symmetry, Cd3As2 is nominated for Dirac semimetal due to its
linear band crossing at the Fermi level, and WTe2 is nominated for resonant
compensated semimetal due to its perfect electron-hole symmetry. Here we
introduce LaSb, a simple rock-salt structure material without broken inversion
symmetry, without perfect linear band crossing, and without perfect
electron-hole symmetry. Yet LaSb portrays all the exotic field induced
behaviors of the aforementioned semimetals in an archetypal fashion. It shows
(a) the universal TI resistivity with a plateau at 15 K, revealed by a magnetic
field, (b) ultrahigh mobility of carriers in the plateau region, (c) quantum
oscillations with a non-trivial Berry phase, and (d) XMR of about one million
percent at 9 tesla rivaled only by WTe2 and NbP. Due to its dramatic
simplicity, LaSb is the ideal model system to formulate a theoretical
understanding of the exotic consequences of breaking TRS in TSMs.",1510.06931v1
2015-11-30,Electrical transport in nano-thick ZrTe$_5$ sheets: from three to two dimensions,"ZrTe$_5$ is a newly discovered topological material. Shortly after a single
layer ZrTe$_5$ had been predicted to be a two-dimensional topological
insulator, a handful of experiments have been carried out on bulk ZrTe$_5$
crystals, which however suggest that its bulk form may be a three-dimensional
topological Dirac semimetal. We report the first transport study on ultra thin
ZrTe$_5$ flakes down to 10 nm. A significant modulation of the characteristic
resistivity maximum in the temperature dependence by thickness has been
observed. Remarkably, the metallic behavior, occurring only below about 150 K
in bulk, persists to over 320 K for flakes less than 20 nm thick. Furthermore,
the resistivity maximum can be greatly tuned by ionic gating. Combined with the
Hall resistance, we identify contributions from a semiconducting and a
semimetallic bands. The enhancement of the metallic state in thin flakes are
consequence of shifting of the energy bands. Our results suggest that the band
structure sensitively depends on the film thickness, which may explain the
divergent experimental observations on bulk materials.",1511.09315v2
2016-06-08,Multi-orbital physics in lithium-molybdenum purple-bronze: going beyond paradigm,"We investigate the role of inter-orbital fluctuations in the low energy
physics of a quasi-1D material - lithium molybdenum purple bronze (LMO). It is
an exceptional material that may provide us a long sought realization of a
Tomonaga-Luttinger liquid (TLL) physics, but its behaviour at temperatures of
the order of $T^*\approx 30$K remains puzzling despite numerous efforts. Here
we make a conjecture that the physics around $T^*$ is dominated by
multi-orbital excitations. Their properties can be captured using an excitonic
picture. Using this relatively simple model we compute fermionic Green's
function in the presence of excitons. We find that the spectral function is
broadened with a Gaussian and its temperature dependence acquires an extra
$T^1$ factor. Both effects are in perfect agreement with experimental findings.
We also compute the resistivity for temperatures above and below critical
temperature $T_o$. We explain an upturn of the resistivity at 28K and interpret
the suppression of this extra component of resistivity when a magnetic field is
applied along the conducting axis. Furthermore, in the framework of our model,
we qualitatively discuss and consistently explain other experimentally detected
peculiarities of purple bronze: the breaking of Wiedmann-Franz law and the
magnetochromatic behaviour.",1606.02687v3
2016-10-08,Enhancement of Impedance by Chromium Substitution and Correlation with DC Resistivity in Cobalt Ferrite,"Chromium substituted cobalt ferrite with grain size less than the single
domain (approx. 70 nm) has been prepared by the sol-gel method. XRD analysis
reveals that the samples crystallize to cubic symmetry with spacegroup number
227. Two transition temperatures (TD (approx. 450 K) and TM (approx. 600 K)
have been observed from the impedance verses temperature measurement. TD
increases with the increase in frequency due to dipole response to the
frequency. TM is comparable with the para-ferrimagnetic transition temperature
of cobalt ferrite, which is independent of frequency. This result is well
supported by the temperature dependent DC conductivity measurement. The
modified Debye relaxation could be explained the impedance spectra of
CoFe2-xCrxO4. The grain and grain boundary effect on impedance spectroscopy has
been observed from Cole-Cole analysis. The ac conductivity follows Arrhenius
behavior at different frequencies. All the samples exhibit the negative
temperature coefficient of resistance behavior which reveals the semiconducting
behavior of the material. The Mott VRH model could explain the DC electrical
conductivity. Both ac impedance and DC resistivity are well co-related each
other to explain the electron transport properties in Cr substituted cobalt
ferrite. The electrical transport properties could be explained by the electron
hopping between different metal ions via oxygen in the material.",1610.02489v1
2018-08-08,The viscosities of partially molten materials undergoing diffusion creep,"Partially molten materials resist shearing and compaction. This resistance is
described by a fourth-rank effective viscosity tensor. When the tensor is
isotropic, two scalars determine the resistance: an effective shear and an
effective bulk viscosity. Here, calculations are presented of the effective
viscosity tensor during diffusion creep for a 2D tiling of hexagonal unit cells
and a 3D tessellation of tetrakaidecahedrons (truncated octahedrons). The
geometry of the melt is determined by assuming textural equilibrium. The
viscosity tensor for the 2D tiling is isotropic, but that for the 3D
tessellation is anisotropic. Two parameters control the effect of melt on the
viscosity tensor: the porosity and the dihedral angle. Calculations for both
Nabarro-Herring (volume diffusion) and Coble (surface diffusion) creep are
presented. For Nabarro-Herring creep the bulk viscosity becomes singular as the
porosity vanishes. This singularity is logarithmic, a weaker singularity than
typically assumed in geodynamic models. The presence of a small amount of melt
(0.1% porosity) causes the effective shear viscosity to approximately halve.
For Coble creep, previous modelling work has argued that a very small amount of
melt may lead to a substantial, factor of 5, drop in the shear viscosity. Here,
a much smaller, factor of 1.4, drop is obtained for tetrakaidecahedrons. Owing
to a Cauchy relation symmetry, the Coble creep bulk viscosity is a constant
multiple of the shear viscosity when melt is present.",1808.02734v2
2019-01-14,Gate tunable giant anisotropic resistance in ultra-thin GaTe,"In crystals, the duplication of atoms often follows different periodicity
along different directions. It thus gives rise to the so called anisotropy,
which is usually even more pronounced in two dimensional (2D) materials due to
the absence of $\textbf{z}$ dimension. Indeed, in the emerging 2D materials,
electrical anisotropy has been one of the focuses in recent experimental
efforts. However, key understandings of the in-plane anisotropic resistance in
low-symmetry 2D materials, as well as demonstrations of model devices taking
advantage of it, have proven difficult. Here, we show that, in few-layered
semiconducting GaTe, electrical conductivity along $\textbf{x}$ and
$\textbf{y}$ directions of the 2D crystal can be gate tuned from a ratio of
less than one order to as large as 10$^{3}$. This effect is further
demonstrated to yield an anisotropic memory resistor behaviour in ultra-thin
GaTe, when equipped with an architecture of van der Waals floating gate. Our
findings of gate tunable giant anisotropic resistance (GAR) effect pave the way
for potential applications in nano-electronics such as multifunctional
directional memories in the 2D limit.",1901.04262v1
2020-01-27,Graphene-based Nanoscale version of da Vinci's Reciprocal Structures,"A reciprocal structure (RS) is a mechanical resistant structure formed by a
set of self-supporting elements satisfying certain conditions of structural
reciprocity (SR) . The first condition is that each element of the structure
has to support and be supported by the others. The second condition is that
these functions cannot occur in the same part of the element. These two
properties make beams and two-dimensional materials very much appropriate to
build RSs. Commonly seen in floors or roofs, SR is also present in art,
religious symbols and decorative objects. Da Vinci has drawn several examples
of such RSs. Here, we propose a simple nano version of a da Vinci's RS based on
graphene nanoribbons. The stability and resistance against mechanical impacts
(ballistic projectile) were investigated through fully atomistic molecular
dynamics (MD) simulations. We considered structures with three and four joins
with and without RS topologies. Our MD results showed that structures with RS
topologies are more impact resistant than those without SR, despite the fact
that the used graphene nanoribbons are highly pliable. We discuss these results
in terms of the number of joins, energy absorption and stress on the
structures. We discuss possible applications in nanoengineering.",2001.10027v2
2021-05-21,Vanadium Dioxide Thin Films Synthesized Using Low Thermal Budget Atmospheric Oxidation,"Vanadium dioxide is a complex oxide material, which shows large resistivity
and optical reflectance change while transitioning from the insulator to metal
phase at ~68 {\deg}C. In this work, we use a modified atmospheric thermal
oxidation method to oxidize RF-sputtered Vanadium films. Structural,
surface-morphology and phase-transition properties of the oxidized films as a
function of oxidation duration are presented. Phase-pure VO2 films are obtained
by oxidizing ~130 nm Vanadium films in short oxidation duration of ~30 seconds.
Compared to previous reports on VO2 synthesis using atmospheric oxidation of
Vanadium films of similar thickness, we obtain a reduction in oxidation
duration by more than one order. Synthesized VO2 thin film shows resistance
switching of ~3 orders of magnitude. We demonstrate optical reflectance
switching in long-wave infrared wavelengths in VO2 films synthesized using
atmospheric oxidation of Vanadium. The extracted refractive index of VO2 in the
insulating and in the metallic phase is in good agreement with VO2 synthesized
using other methods. The considerable reduction in oxidation time of VO2
synthesis while retaining good resistance and optical switching properties will
help in integration of VO2 in limited thermal budget processes, enabling
further applications of this phase-transition material.",2105.10264v1
2023-08-18,Magnetoresistance anomaly during the electrical triggering of a metal-insulator transition,"Phase separation naturally occurs in a variety of magnetic materials and it
often has a major impact on both electric and magnetotransport properties. In
resistive switching systems, phase separation can be created on demand by
inducing local switching, which provides an opportunity to tune the electronic
and magnetic state of the device by applying voltage. Here we explore the
magnetotransport properties in the ferromagnetic oxide (La,Sr)MnO3 (LSMO)
during the electrical triggering of an intrinsic metal-insulator transition
(MIT) that produces volatile resistive switching. This switching occurs in a
characteristic spatial pattern, i.e., the formation of an insulating barrier
perpendicular to the current flow, enabling an electrically actuated
ferromagnetic-paramagnetic-ferromagnetic phase separation. At the threshold
voltage of the MIT triggering, both anisotropic and colossal magnetoresistances
exhibit anomalies including a large increase in magnitude and a sign flip.
Computational analysis revealed that these anomalies originate from the
coupling between the switching-induced phase separation state and the intrinsic
magnetoresistance of LSMO. This work demonstrates that driving the MIT material
into an out-of-equilibrium resistive switching state provides the means to
electrically control of the magnetotransport phenomena.",2308.09260v2
2024-01-30,Picosecond transfer from short-term to long-term memory in analog antiferromagnetic memory device,"Experiments in materials with a compensated ordering of magnetic moments have
demonstrated a potential for approaching the thermodynamic limit of the fastest
and least-dissipative operation of a digital memory bit. In addition, these
materials are very promising for a construction of energy-efficient analog
devices with neuromorphic functionalities, which are inspired by
computing-in-memory capabilities of the human brain. In this paper, we report
on experimental separation of switching-related and heat-related resistance
signal dynamics in memory devices microfabricated from CuMnAs antiferromagnetic
metal. We show that the memory variable multilevel resistance can be used as a
long-term memory (LTM), lasting up to minutes at room temperature. In addition,
ultrafast reflectivity change and heat dissipation from nanoscale-thickness
CuMnAs films, taking place on picosecond to hundreds of nanoseconds time
scales, can be used as a short-term memory (STM). Information about input
stimuli, represented by femtosecond laser pulses, can be transferred from STM
to LTM after rehearsals at picosecond to nanosecond times in these memory
devices, where information can be retrieved at times up to 10^15 longer than
the input pulse duration. Our results open a route towards ultra-fast low-power
implementations of spiking neuron and synapse functionalities using a resistive
analog antiferromagnetic memory.",2401.17370v1
2021-04-21,Machine-Learning Assisted Optimization Strategies for Phase Change Materials Embedded within Electronic Packages,"Leveraging the latent heat of phase change materials (PCMs) can reduce the
peak temperatures and transient variations in temperature in electronic
devices. But as the power levels increase, the thermal conduction pathway from
the heat source to the heat sink limits the effectiveness of these systems. In
this work, we evaluate embedding the PCM within the silicon device layer of an
electronic device to minimize the thermal resistance between the source and the
PCM to minimize this thermal resistance and enhance the thermal performance of
the device. The geometry and material properties of the embedded PCM regions
are optimized using a combination of parametric and machine learning
algorithms. For a fixed geometry, considering commercially available materials,
Solder 174 significantly outperforms other organic and metallic PCMs. Also with
a fixed geometry, the optimal melting points to minimize the peak temperature
is higher than the optimal melting point to minimize the amplitude of the
transient temperature oscillation, and both optima increase with increasing
heater power. Extending beyond conventional optimization strategies, genetic
algorithms and particle swarm optimization with and without neural network
surrogate models are used to enable optimization of many geometric and material
properties. For the test case evaluated, the optimized geometries and
properties are similar between all ML-assisted algorithms, but the
computational time depends on the technique. Ultimately, the optimized design
with embedded phase change materials reduces the maximum temperature rise by
19% and the fluctuations by up to 88% compared to devices without PCM.",2104.14433v1
2023-10-26,A Critical Assessment of Electronic Structure Descriptors for Predicting Perovskite Catalytic Properties,"The discovery and design of new materials which can efficiently catalyze the
oxygen reduction and evolution reactions at reduced temperatures is important
for facilitating the widespread adoption of fuel cell and electrolyzer
technologies. Numerous studies have produced correlations between catalytic
properties, such as oxygen surface exchange or electrode area specific
resistance (ASR), and properties of the catalyst material. However,
correlations have historically been limited in scope (e.g., using only a few
materials or at a single temperature) and it has been difficult to provide
detailed assessments of their robustness. Here, we assess the ability of the O
p-band center electronic structure descriptor, obtained from density functional
theory (DFT) calculations, to correlate with oxygen surface exchange rates,
diffusivities, and area specific resistances for a large database of perovskite
oxide catalytic properties. By data mining the literature, we obtain 747
catalytic property value data points spanning 299 unique perovskite
compositions from 313 studies. We assess linear correlations of each property
with the O p-band center and find generally modest correlations that are
qualitatively useful (prediction mean absolute errors of about 0.5 log units
are typical), where the correlations are improved at higher temperatures (e.g.,
800 {\deg}C vs. 500 {\deg}C) and significantly improve when considering fits to
the subset of materials which have multiple independent measurements. These
findings suggest that the spread of property data is significantly influenced
by experimental uncertainty, and subsequent measurements of additional
materials will likely improve the O p-band center correlations.",2310.17744v1
1998-11-11,Superconducting Material Diagnostics using a Scanning Near-Field Microwave Microscope,"We have developed scanning near-field microwave microscopes which can image
electrodynamic properties of superconducting materials on length scales down to
about 2 $\mu$m. The microscopes are capable of quantitative imaging of sheet
resistance of thin films, and surface topography. We demonstrate the utility of
the microscopes through images of the sheet resistance of a YBa2Cu3O7-d thin
film wafer, images of bulk Nb surfaces, and spatially resolved measurements of
Tc of a YBa2Cu3O7-d thin film. We also discuss some of the limitations of the
microscope and conclude with a summary of its present capabilities.",9811158v1
2001-08-21,Infrared and optical properties of pure and cobalt-doped LuNi_2B_2C,"We present optical conductivity data for Lu(Ni$_{1-x}$Co$_x$)$_2$B$_2$C over
a wide range of frequencies and temperatures for x=0 and x=0.09. Both materials
show evidence of being good Drude metals with the infrared data in reasonable
agreement with dc resistivity measurements at low frequencies. An absorption
threshold is seen at approximately 700 cm-1. In the cobalt-doped material we
see a superconducting gap in the conductivity spectrum with an absorption onset
at 24 +/- 2 cm-1 = 3.9$ +/- 0.4 k_BT_c suggestive of weak to moderately strong
coupling. The pure material is in the clean limit and no gap can be seen. We
discuss the data in terms of the electron-phonon interaction and find that it
can be fit below 600 cm-1 with a plasma frequency of 3.3 eV and an
electron-phonon coupling constant lambda_{tr}=0.33 using an alpha^{2}F(omega)
spectrum fit to the resistivity.",0108333v1
2005-04-22,Low field magneto-transport in La_0.7Ca_0.3MnO_3-PMMA composites synthesized by polymeric precursor route,"A detailed investigation of the effect of PMMA on the structure,
microstructure and magneto-transport properties of manganite La_0.7Ca_0.3MnO_3
(LCMO) is presented. LCMO-PMMA nanostructured composites have been synthesized
by a unique polymeric sol-gel route, which leads to improved solubility of PMMA
in the LCMO matrix. The LCMO phase is grown in the presence of varying PMMA
concentration at ~500 ^0 C. This route yields single phase material and the
grain size is observed to decrease slightly with increasing PMMA concentration.
On increasing the PMMA concentration, T_C undergoes a small decrease,
resistivity is observed to increase by two orders of magnitude, with a
concomitant large decrease in T_IM, e.g., from 218 K for virgin LCMO to 108 K
for 50 wt% PMMA admixed LCMO. Low field magneto-resistance measured in the
temperature range 77-300 K shows considerable enhancement as a function of the
PMMA concentration. These phenomena are explained by taking into account the
increased intergranular disorder as a consequence of PMMA admixture.",0504579v1
2007-03-01,Magnetic effects at the interface between nonmagnetic oxides,"The electronic reconstruction at the interface between two insulating oxides
can give rise to a highly-conductive interface. In analogy to this remarkable
interface-induced conductivity we show how, additionally, magnetism can be
induced at the interface between the otherwise nonmagnetic insulating
perovskites SrTiO3 and LaAlO3. A large negative magnetoresistance of the
interface is found, together with a logarithmic temperature dependence of the
sheet resistance. At low temperatures, the sheet resistance reveals magnetic
hysteresis. Magnetic ordering is a key issue in solid-state science and its
underlying mechanisms are still the subject of intense research. In particular,
the interplay between localized magnetic moments and the spin of itinerant
conduction electrons in a solid gives rise to intriguing many-body effects such
as Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions, the Kondo effect, and
carrier-induced ferromagnetism in diluted magnetic semiconductors. The
conducting oxide interface now provides a versatile system to induce and
manipulate magnetic moments in otherwise nonmagnetic materials.",0703028v2
2008-07-09,"Molecular Beam Epitaxy grown (Ga,Mn)(As,P) with perpendicular to plane magnetic easy axis","We present an experimental investigation of the magnetic, electrical and
structural properties of Ga0.94Mn0.06As1-yPy layers grown by molecular beam
epitaxy on GaAs substrates for y less than or equal to 0.3. X-ray diffraction
measurements reveal that the layers are under tensile strain which gives rise
to a magnetic easy axis perpendicular to the plane of the layers. The strength
of the magnetic anisotropy and the coercive field increase as the phosphorous
concentration is increased. The resistivity of all samples shows metallic
behaviour with the resistivity increasing as y increases. These materials will
be useful for studies of micromagnetic phenomena requiring metallic
ferromagnetic material with perpendicular magnetic anisotropy.",0807.1469v1
2009-09-10,"Electric Pulse Induced Resistive Switching, Electronic Phase Separation, and Possible Superconductivity in a Mott insulator","Metal-insulator transitions (MIT) belong to a class of fascinating physical
phenomena, which includes superconductivity, and colossal magnetoresistance
(CMR), that are associated with drastic modifications of electrical resistance.
In transition metal compounds, MIT are often related to the presence of strong
electronic correlations that drive the system into a Mott insulator state. In
these systems the MIT is usually tuned by electron doping or by applying an
external pressure. However, it was noted recently that a Mott insulator should
also be sensitive to other external perturbations such as an electric field. We
report here the first experimental evidence of a non-volatile
electric-pulse-induced insulator-to-metal transition and possible
superconductivity in the Mott insulator GaTa4Se8. Our Scanning Tunneling
Microscopy experiments show that this unconventional response of the system to
short electric pulses arises from a nanometer scale Electronic Phase Separation
(EPS) generated in the bulk material.",0909.1978v1
2010-03-13,Ferromagnetic Clusters in the Brownmillerite Bilayered Compounds Ca2.5-xLaxSr0.5GaMn2O8: An Approach to Achieve Layered Spintronics Materials,"We report the effect of La-substitution on the magnetic and magnetotransport
properties of Brownmillerite-like bilayered compounds Ca2.5-xLaxSr0.5GaMn2O8 (x
= 0, 0.05, 0.075, and 0.1) by using dc-magnetization, resistivity and
magnetoresistance techniques. The Rietveld analysis of the room temperature
x-ray diffraction patterns confirms no observable change of average crystal
structure with the La-substitution. Both magnetic and magnetotransport
properties are found to be very sensitive to the La-substitution.
Interestingly, the La-substituted compounds show ferromagnetic-like behavior
(due to the occurrence of a double exchange mechanism) whereas, the parent
compound is an antiferromagnet (TN 150 K). All compounds show an insulating
behavior, in the measured temperature range of 100 - 300 K, with an overall
decrease in the resistivity with the substitution. A higher value of
magnetoresistance has been successfully achieved by the La-substitution. We
have proposed an electronic phase separation model, considering the formation
of ferromagnetic clusters in the antiferromagnetic matrix, to interpret the
observed magnetization and magnetotransport results for the La-substituted
samples. The present study demonstrates an approach to achieve new functional
materials, based on naturally occurring layered system like
Ca2.5-xLaxSr0.5GaMn2O8, for possible spintronics applications.",1003.2685v1
2013-07-24,Large resistivity change and phase transition in LiMnAs,"Antiferromagnetic semiconductors are new alternative materials for spintronic
applications and spin valves. In this work, we report a detailed investigation
of two antiferromagnetic semiconductors AMnAs (A = Li, LaO), which are
isostructural to the well-known LiFeAs and LaOFeAs superconductors. Here we
present a comparison between the structural, magnetic, and electronic
properties of LiMnAs, LaOMnAs and related materials. Interestingly, both LiMnAs
and LaOMnAs show a variation in resistivity with more than five orders of
magnitude, making them particularly suitable for use in future electronic
devices. From neutron and X-ray diffraction measurements on LiMnAs we have
observed a magnetic phase transition corresponding to the Neel temperature of
373.8 K, and a structural transition from the tetragonal to the cubic phase at
768 K. These experimental results are supported by density functional theory
(DFT) calculations.",1307.6404v4
2014-03-31,Investigation of Complex Impedance and Modulus Properties of Nd Doped 0.5BiFeO3-0.5PbTiO3 Multiferroic Composites,"0.5BiNdxFe1-xO3-0.5PbTiO3 (x=0.05, 0.10, 0.15, 0.20) composites were
successfully synthesized by a solid state reaction technique. At room
temperature X-ray diffraction shows tetragonal structure for all concentrations
of Nd doped 0.5BiFeO3-0.5PbTiO3 composites. The nature of Nyquist plot confirms
the presence of bulk effects only for all compositions of Nd-doped
0.5BiFeO3-0.5PbTiO3 composites. The bulk resistance is found to decreases with
the increasing in temperature as well as Nd concentration and exhibits a
typical negative temperature coefficient of resistance (NTCR) behavior. Both
the complex impedance and modulus studies have suggested the presence of
non-Debye type of relaxation in the materials. Conductivity spectra reveal the
presence of hopping mechanism in the electrical transport process of the
materials. The activation energy of the composite increases with increasing Nd
concentration and were found to be 0.28, 0.27, 0.31 and 0.32eV for x=0.05,
0.10, 0.15, 0.20 respectively at 200-275 oC for conduction process.",1403.7981v1
2014-04-09,A new first-principles calculation of field-dependent RF surface impedance of BCS superconductor and application to SRF cavities,"There is a need to better understand the intrinsic limit of radiofrequency
(RF) surface impedance that determines the performance of superconducting RF
cavities in particle accelerators. Here we present a field-dependent derivation
of Mattis-Bardeen (M-B) theory of the RF surface impedance of BCS
superconductors based on the shifted Density of States (DoS) resulting from
coherently moving Cooper pairs [1].The surprising reduction in resistance with
increasing field is explained to be an intrinsic effect. Using this analysis
coded in MathematicaTM, survey calculations have been completed which examine
the sensitivities of this surface impedance to variation of the BCS material
parameters and temperature.Our theoretical prediction of the effective BCS RF
surface resistance (Rs) of niobium as a function of peak surface magnetic field
amplitude agrees well with recently reported record low loss resonant cavity
measurements from Jefferson Lab (JLab) and Fermi National Accelerator Lab
(FNAL) with carefully, yet differently, prepared niobium material. The results
present a refined description of the ""best theoretical"" performance available
to potential applications with corresponding materials. [1]Xiao, B.P., C.E.
Reece, and M.J. Kelley, Superconducting surface impedance under radiofrequency
field. Physica C: Superconductivity, 2013. 490(0): p. 26-31.",1404.2523v1
2014-11-25,Computing with spins and magnets,"The possible use of spin and magnets in place of charge and capacitors to
store and process information is well known. Magnetic tunnel junctions are
being widely investigated and developed for magnetic random access memories.
These are two terminal devices that change their resistance based on switchable
magnetization of magnetic materials. They utilize the interaction between
electron spin and magnets to read information from the magnets and write onto
them. Such advances in memory devices could also translate into a new class of
logic devices that offer the advantage of nonvolatile and reconfigurable
information processing over transistors. Logic devices having a transistor-like
gain and directionality could be used to build integrated circuits without the
need for transistor-based amplifiers and clocks at every stage. We review
device characteristics and basic logic gates that compute with spins and
magnets from the mesoscopic to the atomic scale, as well as materials,
integration, and fabrication challenges and methods.",1411.6960v1
2015-05-22,Direct Method for Calculating Temperature-Dependent Transport Properties,"We show how temperature-induced disorder can be combined in a direct way with
first-principles scattering theory to study diffusive transport in real
materials. Excellent (good) agreement with experiment is found for the
resistivity of Cu, Pd, Pt (and Fe) when lattice (and spin) disorder are
calculated from first principles. For Fe, the agreement with experiment is
limited by how well the magnetization (of itinerant ferromagnets) can be
calculated as a function of temperature. By introducing a simple Debye-like
model of spin disorder parameterized to reproduce the experimental
magnetization, the temperature dependence of the average resistivity, the
anisotropic magnetoresistance and the spin polarization of a Ni$_{80}$Fe$_{20}$
alloy are calculated and found to be in good agreement with existing data.
Extension of the method to complex, inhomogeneous materials as well as to the
calculation of other finite-temperature physical properties within the
adiabatic approximation is straightforward.",1505.06231v1
2015-11-04,Numerical Calculations of Wake Fields and Impedances of LHC Collimators' Real Structures,"The LHC collimators have very complicated mechanical designs including
movable jaws made of higly resistive materials, ferrite materials, tiny RF
contacts. Since the jaws are moved very close to the circulating beams their
contribution in the overall LHC coupling impedance is dominant, with respect to
other machine components. For these reasons accurate simulation of collimators'
impedance becomes very important and challenging. Besides, several dedicated
tests have been performed to verify correct simulations of lossy dispersive
material properties, such as resistive wall and ferrites, benchmarking code
results with analytical, semi-analytical and other numerical codes outcomes.
Here we describe all the performed numerical tests and discuss the results of
LHC collimators' impedances and wake fields calculations.",1511.01236v1
2016-04-19,Metallicity and conductivity crossover in white light illuminated CH$_3$NH$_3$PbI$_3$ perovskite,"The intrinsic d.c. electrical resistivity ($\rho$) - measurable on single
crystals only - is often the quantity first revealing the properties of a given
material. In the case of CH$_3$NH$_3$PbI$_3$ perovskite measuring $\rho$ under
white light illumination provides insight into the coexistence of extended and
shallow localized states (0.1 eV below the conduction band). The former ones
dominate the electrical conduction while the latter, coming from neutral
defects, serve as a long-lifetime charge carrier reservoir accessible for
charge transport by thermal excitation. Remarkably, in the best crystals the
electrical resistivity shows a metallic behaviour under illumination up to room
temperature, giving a new dimension to the material in basic physical studies.",1604.05637v1
2016-05-13,Quantifying structure-property relationships during resistance spot welding of an aluminum 6061-T6 joint,"Microstructure-property relationships of resistance spot welded 6061-T6
aluminum alloy lap joints were investigated via mechanical testing and
microscopy techniques. Quasi-static tensile and novel shear punch tests were
employed to measure the mechanical properties of the distinct weld regions.
Quasi-static tensile and shear punch tests revealed constantly decreasing
strength and ductility as the weld center was approached. For instance, the
ultimate tensile strength of the fusion zone decreased by ~52% from the parent
material (341 MPa to 162 MPa) while the yield strength decreased by ~62% (312
MPa to 120 MPa). The process-induced microstructures were analyzed with
scanning electron microscopy and optical microscopy to elucidate the underlying
cause of the reduced mechanical properties. Fractography reveals void growth
from particles being the dominant damage mechanism in the parent material as
compared to void nucleation in the fusion zone. Overall, significant changes in
the mechanical behavior across the weld are the result of a change in
microstructure congruent with a loss of T6 condition (precipitate coarsening).",1605.04251v1
2016-06-17,Electronic ground state of MnB$_{4}$,"Recent studies have dealt with the electronic and magnetic ground state
properties of the tetraboride material MnB$_4$. So far, however, the ground
state properties could not be established unambiguously. Therefore, here we
present an experimental study on single-crystalline MnB$_4$ by means of
resistivity and magnetization measurements. For this, we have developed a
sample holder that allows four-point ac resistivity measurements on these very
small ($\sim$\,100\,$\mu$m) samples. With our data we establish that the
electronic ground state of MnB$_4$ is intrinsically that of a pseudo-gap
system, in agreement with recent band structure calculations. Furthermore, we
demonstrate that the material does neither show magnetic order nor a behavior
arising from the vicinity to a magnetically ordered state, this way disproving
previous claims.",1606.05484v3
2016-12-15,Superconductivity above 500 K in conductors made by bringing n-alkane into contact with graphite,"In 1986, a cuprate superconductor (Ba-La-Cu-O system) having a critical
temperature which goes over the BCS limit (~30 K) was discovered and then a
cuprate superconductor (Y-Ba-Cu-O system) with a critical temperature higher
than 77 K was discovered. Furthermore, a Hg-based cuprate with a critical
temperature of 133 K was found. The 133 K is still the highest critical
temperature of conventional superconductors under atmospheric pressure.
  We have shown that materials obtained by bringing n-alkanes into contact with
graphite are capable of conducting electricity with almost no energy loss at
room temperature. We here report that the sudden jump in resistance showing a
phase transition is observed in the materials during heating by two-probe
resistance measurement. The measured critical temperatures of the materials
consisting of pitch-based graphite fibers and n-alkanes having 7-16 carbon
atoms range from 363.08 to 504.24 K and the transition widths range between
0.15 and 3.01 K. We also demonstrate that superconductors with critical
temperatures beyond 504 K are obtained by alkanes with 16 or more carbon atoms.",1612.05294v1
2017-02-20,Gate Tunable Magneto-resistance of Ultra-Thin WTe2 Devices,"In this work, the magneto-resistance (MR) of ultra-thin WTe2/BN
heterostructures far away from electron-hole equilibrium is measured. The
change of MR of such devices is found to be determined largely by a single
tunable parameter, i.e. the amount of imbalance between electrons and holes. We
also found that the magnetoresistive behavior of ultra-thin WTe2 devices is
well-captured by a two-fluid model. According to the model, the change of MR
could be as large as 400,000%, the largest potential change of MR among all
materials known, if the ultra-thin samples are tuned to neutrality when
preserving the mobility of 167,000 cm2V-1s-1 observed in bulk samples. Our
findings show the prospects of ultra-thin WTe2 as a variable magnetoresistance
material in future applications such as magnetic field sensors, information
storage and extraction devices, and galvanic isolators. The results also
provide important insight into the electronic structure and the origin of the
large MR in ultra-thin WTe2 samples.",1702.05876v1
2017-10-05,Multi-scale Modeling of Plasticity Nearby Precipitates in Nanostructured Materials,"Precipitation strengthening is one of the most effective methods to design
alloys with the desired combination of strength and ductility. The main
mechanism of strengthening is generally known to be the interaction between
dislocations and precipitates. When a dislocation encounters a precipitate, it
bends and therefore the level of applied stress to the precipitate increases.
Once the applied stress reaches the precipitate resistance, it passes the
precipitate. Dislocations can bypass precipitates either by forming the Orowan
loops or by cutting them. In this research, the focus is set on a small domain
nearby precipitates to investigate their effects on the effective plastic
strain. Both penetrable and impenetrable precipitates are considered. Two
scales are coupled to model this phenomenon, the nano-micro scale where
plasticity is determined by explicit three-dimensional discrete dislocation
dynamics analysis and the continuum scale where the finite element method is
applied. With this hybrid approach, complex problems in plastic deformation of
nanostructured materials can be addressed. Finally, the relation between the
precipitate resistance and the effective plastic strain is investigated.",1710.02075v3
2018-05-03,Enhanced Electron Transport in Thin Copper Films via Atomic-Layer Materials Capping,"Using first-principles calculations based on density functional theory and
non-equilibrium Green's functions, we characterized the effect of surface
termination on the electronic transport properties of nanoscale Cu slabs. With
ideal, clean (111) surfaces and oxidized ones as baselines we explore the
effect of capping the slabs with graphene, hexagonal boron nitrate, molybdenum
disulfide and stanene. Surface oxide suppresses balistic conductance by a
factor of 10 compared to the ideal surface. Capping the ideal copper surface
with graphene slightly increase conductance but MoS$_2$ and stanene have the
opposite effect due to stronger interactions at the interface. Interestingly,
we find that capping atomistically roughed copper surfaces with graphene or
MoS$_2$ decreases the resistance per unit length by 20 and 13%, respectively,
due to reduced scattering. The results presented in this work suggest that
two-dimensional materials can be used as an ultra-thin liner in metallic
interconnect technology without increasing the interconnect line resistivity
significantly.",1805.01517v1
2018-06-07,On the magnetic and electronic properties of NpPdSn,"We have studied NpPdSn by means of the heat capacity, electrical resistivity,
Seebeck and Hall effect, $^{237}$Np M\""{o}ssbauer spectroscopy, and neutron
diffraction measurements in the temperature range 2-300 K and under magnetic
fields up to 14 T. NpPdSn orders antiferromagnetically below the N\'eel
temperature $T_N$ = 19 K and shows localized magnetism of Np$^{3+}$ ion with a
a doubly degenerate ground state. In the magnetic state the electrical
resistivity and heat capacity are characterized by electron-magnon scattering
with spin-waves spectrum typical of anisotropic antiferromagnets. An enhanced
Sommerfeld coefficient and typical behavior of magnetorestistivity, Seebeck and
Hall coefficients are all characteristic of systems with strong electronic
correlations. The low temperature antiferromagnetic state of NpPdSn is verified
by neutron diffraction and $^{237}$Np M\""{o}ssbauer spectroscopy and possible
magnetic structures are discussed.",1806.02879v1
2019-09-06,Unveiling multiferroic proximity effect in graphene,"We demonstrate that electronic and magnetic properties of graphene can be
tuned via proximity of multiferroic substrate. Our first-principles
calculations performed both with and without spin-orbit coupling clearly show
that by contacting graphene with bismuth ferrite BiFeO$_3$ (BFO) film, the
spin-dependent electronic structure of graphene is strongly impacted both by
the magnetic order and by electric polarization in the underlying BFO. Based on
extracted Hamiltonian parameters obtained from the graphene band structure, we
propose a concept of six-resistance device based on exploring multiferroic
proximity effect giving rise to significant proximity electro- (PER), magneto-
(PMR), and multiferroic (PMER) resistance effects. This finding paves a way
towards multiferroic control of magnetic properties in two dimensional
materials.",1909.02844v1
2017-01-27,Strain-modulated Bandgap and Piezo-resistive Effect in Black Phosphorus Field-effect Transistors,"Energy bandgap largely determines the optical and electronic properties of a
semiconductor. Variable bandgap therefore makes versatile functionality
possible in a single material. In layered material black phosphorus, the
bandgap can be modulated by the number of layers; as a result, few-layer black
phosphorus has discrete bandgap values that are relevant for opto-electronic
applications in the spectral range from red, in monolayer, to mid-infrared in
the bulk limit. Here, we further demonstrate continuous bandgap modulation by
mechanical strain applied through flexible substrates. The strain-modulated
bandgap significantly alters the charge transport in black phosphorus at room
temperature; we for the first time observe a large piezo-resistive effect in
black phosphorus field-effect transistors (FETs). The effect opens up
opportunities for future development of electro-mechanical transducers based on
black phosphorus, and we demonstrate strain gauges constructed from black
phosphorus thin crystals.",1701.08041v1
2019-07-27,Microwave derived monoclinic Ba1-xSnxNb2O6 materials as an alternative of ITO,"Microwave synthesis was optimized for preparing novel monoclinic Tin-doped
Barium Niobate ceramics (Ba1-xSnxNb2O6; x= 0.0, 0.01, 0.05, 0.1, 0.2, 0.3) BSN.
The intensity of monoclinic phase formation was observed to decrease on
increasing tin as dopant indicating decreased crystallinity. Strained
crystalline phase was observed in undoped sample that became severe on doping
tin. Monoclinic metal alloy Sn2O3 formation was confirmed on increasing tin
doping beyond 5%. Electronic configuration of tin (II) oxide supports the local
site-wise monoclinic disorder in crystal structure due to sterically active
lone pair. Such a disorder arranges increased number of degenerate energy
states and reduce effective energy gap between conduction band minimum and
valence band maximum. All BSN compositions were investigated for monoclinic
phase stabilization, ultra-violet absorption, dielectric response, raman modes
and type of carrier concentration along with hall resistivity. All measurements
possessed inflexion corresponding to 5 atomic % tin doping indicating
successful site substitution and estimated Sn2O3 metal formation beyond this.
The values of reducing optical energy band gap, transparency to visible
spectrum and hall resistivity indicated utility of these materials as a
substitute transparent conducting oxide (TCO) for well-known indium tin oxide
(ITO).",1907.11946v1
2019-04-24,Progressive amorphization of GeSbTe phase-change material under electron beam irradiation,"Fast and reversible phase transitions in chalcogenide phase-change materials
(PCMs), in particular, Ge-Sb-Te compounds, are not only of fundamental
interests, but also make PCMs based random access memory (PRAM) a leading
candidate for non-volatile memory and neuromorphic computing devices. To RESET
the memory cell, crystalline Ge-Sb-Te has to undergo phase transitions firstly
to a liquid state and then to an amorphous state, corresponding to an abrupt
change in electrical resistance. In this work, we demonstrate a progressive
amorphization process in GeSb2Te4 thin films under electron beam irradiation on
transmission electron microscope (TEM). Melting is shown to be completely
absent by the in situ TEM experiments. The progressive amorphization process
resembles closely the cumulative crystallization process that accompanies a
continuous change in electrical resistance. Our work suggests that if
displacement forces can be implemented properly, it should be possible to
emulate symmetric neuronal dynamics by using PCMs.",1904.10601v2
2015-06-02,Nonmonotonic fracture behavior of polymer nanocomposites,"Polymer composite materials are widely used for their exceptional mechanical
properties, notably their ability to resist large deformations. Here we examine
the failure stress and strain of rubbers reinforced by varying amounts of
nano-sized silica particles. We find that small amounts of silica increase the
fracture stress and strain, but too much filler makes the material become
brittle and consequently fracture happens at small deformations. We thus find
that as a function of the amount of filler there is an optimum in the breaking
resistance at intermediate filler concentrations. We use a modified Griffith
theory to establish a direct relation between the material properties and the
fracture behavior that agrees with the experiment.",1506.00832v1
2015-07-23,Tuning bad metal and non-Fermi liquid behavior in a Mott material: rare earth nickelate thin films,"Resistances that exceed the Mott-Ioffe-Regel limit, known as bad metal
behavior, and non-Fermi liquid behavior are ubiquitous features of the normal
state of many strongly correlated materials. Here we establish the conditions
that lead to bad metal and non-Fermi liquid phases in NdNiO3, which exhibits a
prototype, bandwidth-controlled metal-insulator transition. We show that
resistance saturation is determined by the magnitude of the Ni eg orbital
splitting, which can be tuned by strain in epitaxial films, causing the
appearance of bad metal behavior under certain conditions. The results shed
light on the nature of a crossover to non-Fermi liquid metal phase and provide
a predictive criterion for strong localization. They elucidate a seemingly
complex phase behavior as a function of film strain and confinement and provide
guidelines for orbital engineering and novel devices.",1507.06619v1
2018-07-17,Current jetting distorted planar Hall effect in a Weyl semimetal with ultrahigh mobility,"A giant planar Hall effect (PHE) and anisotropic magnetoresistance (AMR) is
observed in TaP, a nonmagnetic Weyl semimetal with ultrahigh mobility. The
perpendicular resistivity (i.e., the planar magnetic field applied normal to
the current) far exceeds the zero-field resistivity, which thus rules out the
possible origin of negative longitudinal magnetoresistance. The giant PHE/AMR
is finally attributed to the large anisotropic orbital magnetoresistance that
stems from the ultrahigh mobility. Furthermore, the mobility-enhanced current
jetting effects are found to strongly deform the line shape of the curves, and
their evolution with the changing magnetic field and temperature is also
studied. Although the giant PHE/AMR suggests promising applications in
spintronics, the enhanced current jetting shows the other side of the coin,
which needs to be considered in the future device design.",1807.06229v3
2019-01-03,Realization of Kondo chain in CeCo$_2$Ga$_8$,"We revisited the anisotropy of the heavy-fermion material CeCo$_2$Ga$_8$ by
measuring the electrical resistivity and magnetic susceptibility along all the
principal $\mathbf{a}$-, $\mathbf{b}$- and $\mathbf{c}$-axes. Resistivity along
$\mathbf{c}$-axis ($\rho_c$) shows clear Kondo coherence below about 17 K,
while both $\rho_{a}$ and $\rho_{b}$ remain incoherent down to 2 K. The
magnetic anisotropy is well understood within the theoretical frame of
crystalline electric field effect in combination with magnetic exchange
interactions. We found the anisotropy ratio of these magnetic exchange
interactions, $|J_{ex}^c/J_{ex}^{a,b}|$, reaches a large value of 4-5. We,
therefore, firmly demonstrate that CeCo$_2$Ga$_8$ is a quasi-one-dimensional
heavy-fermion compound both electrically and magnetically, and thus provide a
realistic example of \textit{Kondo chain}.",1901.00558v2
2019-01-04,Experimental and Numerical Investigation of the Fracture Behavior of Particle Reinforced Alkali Activated Slag Mortars,"This paper presents fracture response of alkali-activated slag (AAS) mortars
with up to 30% (by volume) of slag being replaced by waste iron powder which
contains a significant fraction of elongated particles. The elongated iron
particles act as micro-reinforcement and improve the crack resistance of AAS
mortars by increasing the area of fracture process zone (FPZ). Increased area
of FPZ signifies increased energy-dissipation which is reflected in the form of
significant increase in the crack growth resistance as determined from
R-curves. Fracture response of notched AAS mortar beams under three-point
bending is simulated using extended finite element method (XFEM) to develop a
tool for direct determination of fracture characteristics such as crack
extension and fracture toughness in particulate-reinforced AAS mortars.
Fracture response simulated using the XFEM based framework correlates well with
experimental observations. The comprehensive fracture studies reported here
provide an economical and sustainable means towards improving the ductility of
AAS systems which are generally more brittle than their conventional ordinary
portland cement counterparts.",1901.01025v1
2019-10-17,The grain-size effect on thermal conductivity of uranium dioxide,"We have investigated the grain boundary scattering effect on the thermal
transport behavior of uranium dioxide (UO$_2$). The polycrystalline samples
having different grain-sizes (0.125, 1.8, and 7.2 $\mu$m) have been prepared by
spark plasma sintering technique and characterized by x-ray powder diffraction
(XRD), scanning electron microscope (SEM), and Raman spectroscopy. The thermal
transport properties (the thermal conductivity and thermoelectric power) have
been measured in the temperature range 2-300~K and the results were analyzed in
terms of various physical parameters contributing to the thermal conductivity
in these materials in relation to grain-size. We show that thermal conductivity
decreases systematically with lowering grain-size in the temperatures below 30
K, where the boundary scattering dominates the thermal transport. At higher
temperatures more scattering processes are involved in the heat transport in
these materials, making the analysis difficult. We determined the grain
boundary Kapitza resistance that would result in the observed increase in
thermal conductivity with grain size, and compared the value with Kapitza
resistances calculated for UO$_2$ using molecular dynamics from the literature.",1910.08014v1
2020-01-06,Transport characteristics of type II Weyl semimetal MoTe2 thin films grown by chemical vapor deposition,"Theoretical calculations and experimental observations show MoTe2 is a type
II Weyl semimetal, along with many members of transition metal dichalcogenides
family. We have grown highly crystalline large-area MoTe2 thin films on Si/SiO2
substrates by chemical vapor deposition. Very uniform, continuous, and smooth
films were obtained as confirmed by scanning electron microscopy and atomic
force microscopy analyses. Measurements of the temperature dependence of
longitudinal resistivity and current-voltage characteristics at different
temperature are discussed. Unsaturated, positive quadratic magnetoresistance of
the as-grown thin films has been observed from 10 K to 200 K. Hall resistivity
measurements confirm the majority charge carriers are hole.",2001.01703v1
2020-05-11,Skyrmion phase in MnSi on sapphire grown by a conventional sputtering,"Topologically protected chiral skyrmion is an intriguing spin texture, which
has attracted much attention because of fundamental research and future
spintronic applications. MnSi with the non-centrosymmetric structure is
well-known material hosting skyrmion phase. To date, preparation of MnSi
crystals has been investigated by using special instruments with ultrahigh
vacuum chamber. Here, we introduce a facile way to grow MnSi films on sapphire,
which is in relatively low vacuum environment of conventional magnetron
sputtering. Magnetotransport properties including Hall resistivity measurements
allow to confirm the existence of skyrmion phase in MnSi film. Because as-grown
MnSi films on sapphire has polycrystalline nature, the emergent features of
skyrmion phase are limited and complicated. However, we observed the stable
skyrmion phase in a broad range of temperatures and magnetic fields, which is
explained by phenomenological scaling analyses of Hall resistivities
contribution. Our findings provide not only a general way to prepare the
materials possessing skyrmion phase, but also insight into further research to
stimulate more degrees of freedom in our inquisitiveness.",2005.04841v1
2020-08-11,"Anomalous Hall effect in half-metallic Heusler compound Co$_{2}$Ti$X$ ($X$=Si, Ge)","Though Weyl fermions have recently been observed in several materials with
broken inversion symmetry, there are very few examples of such systems with
broken time reversal symmetry. Various Co$_{2}$-based half-metallic
ferromagnetic Heusler compounds are lately predicted to host Weyl type
excitations in their band structure. These magnetic Heusler compounds with
broken time reversal symmetry are expected to show a large momentum space Berry
curvature, which introduces several exotic magneto-transport properties. In
this report, we present systematic analysis of experimental results on
anomalous Hall effect (AHE) in Co$_2$Ti$X$ ($X$=Si and Ge). This study is an
attempt to understand the role of Berry curvature on AHE in Co$_2$Ti$X$ family
of materials. The anomalous Hall resistivity is observed to scale quadratically
with the longitudinal resistivity for both the compounds. The detailed analysis
indicates that in anomalous Hall conductivity, the intrinsic Karplus-Luttinger
Berry phase mechanism dominates over the extrinsic skew scattering and
side-jump mechanism.",2008.04837v1
2021-03-24,Manipulating Berry curvature of SrRuO3 thin films via epitaxial strain,"Berry curvature plays a crucial role in exotic electronic states of quantum
materials, such as intrinsic anomalous Hall effect. As Berry curvature is
highly sensitive to subtle changes of electronic band structures, it can be
finely tuned via external stimulus. Here, we demonstrate in SrRuO3 thin films
that both the magnitude and sign of anomalous Hall resistivity can be
effectively controlled with epitaxial strain. Our first-principles calculations
reveal that epitaxial strain induces an additional crystal field splitting and
changes the order of Ru d orbital energies, which alters the Berry curvature
and leads to the sign and magnitude change of anomalous Hall conductivity.
Furthermore, we show that the rotation of Ru magnetic moment in real space of
tensile strained sample can result in an exotic nonmonotonic change of
anomalous Hall resistivity with the sweeping of magnetic field, resembling the
topological Hall effect observed in non-coplanar spin systems. These findings
not only deepen our understanding of anomalous Hall effect in SrRuO3 systems,
but also provide an effective tuning knob to manipulate Berry curvature and
related physical properties in a wide range of quantum materials.",2103.12973v1
2022-06-06,Anomalous Transport Properties of Re$_3$Ge$_7$,"Single crystals of intermetallic Re$_3$Ge$_7$ were grown and characterized by
measuring magnetization, electrical resistivity, Hall coefficient, and specific
heat. Magnetization measurements show the material is weakly diamagnetic. A
phase transition is indicated by a kink in magnetic susceptibility at $T_{c} =
58.5$K and is confirmed by a $\lambda$-like anomaly in specific heat. In
zero-field, the temperature dependence of electrical resistivity $\rho(T)$
follows a typical metallic behavior above $T_c$ and sharply increases below
$T_c$, showing a metal-to-insulator-like transition. When a magnetic field is
applied, strong effects on the transport properties are observed. The
temperature dependence of magnetoresistivity $\Delta\rho$ = $\rho (T, H)$ -
$\rho (T, H=0)$ develops a maximum around 30 K, deviating from ordinary
metallic behavior. Analysis of the Hall coefficient measurements indicates that
the carrier density is 0.04 per formula unit at 300 K and drops by two orders
of magnitude below $T_c$. The effective mass of charge carriers is inferred
from the analysis of the Shubnikov-de Haas quantum oscillations to be close to
the bare electron mass.",2206.02943v1
2022-06-28,Colossal piezoresistance in narrow-gap Eu5In2Sb6,"Piezoresistance, the change of a material's electrical resistance ($R$) in
response to an applied mechanical stress ($\sigma$), is the driving principle
of electromechanical devices such as strain gauges, accelerometers, and
cantilever force sensors. Enhanced piezoresistance has been traditionally
observed in two classes of uncorrelated materials: nonmagnetic semiconductors
and composite structures. We report the discovery of a remarkably large
piezoresistance in Eu$_5$In$_2$Sb$_6$ single crystals, wherein anisotropic
metallic clusters naturally form within a semiconducting matrix due to
electronic interactions. Eu$_5$In$_2$Sb$_6$ shows a highly anisotropic
piezoresistance, and uniaxial pressure along [001] of only 0.4~GPa leads to a
resistivity drop of more than 99.95\% that results in a colossal
piezoresistance factor of $5000\times10^{-11}$Pa$^{-1}$. Our result not only
reveals the role of interactions and phase separation in the realization of
colossal piezoresistance, but it also highlights a novel route to
multi-functional devices with large responses to both pressure and magnetic
field.",2206.14073v1
2022-07-06,Sn2Pd: a possible superconducting material with topological surface states,"In this article, we report the detailed magneto transport measurements of the
topological semimetal (TSM) candidate, Sn2Pd. Single crystal of Sn2Pd is
synthesized through the self-flux method. Phase purity and crystalline
morphology are confirmed through powder X ray diffraction (PXRD) pattern and
field emission scanning electron microscopy (FESEM) image. Signatures of
superconducting transition are seen in both transport and magneto transport
measurements, which are further supported by the AC magnetization studies.
Sn2Pd is found to show superconductivity onset at below 2.8K, but not the zero
resistivity down to 2K. Although, isothermal magneto resistivity measurements
below superconducting onset (2.8K) clearly exhibited superconductor-like
behavior, but is not observed in heat capacity measurements, indicating the
same to be of weak nature. Magnetotransport measurements performed in a normal
state of Sn2Pd show the presence of a weak antilocalization (WAL) effect, which
is confirmed by modeling of low field magneto-conductivity (MC) through Hikami
Larkin Nagaoka (HLN) formalism. Here, it is worth mentioning that the present
article is the first report on magneto transport measurements of Sn2Pd, which
show the same to be a topological material with a weak superconducting phase
below around 2.8K.",2207.02579v1
2023-03-17,On the determination of the thermal shock parameter of MAX phases: A combined experimental-computational study,"Thermal shock resistance is one of the performance-defining properties for
applications where extreme temperature gradients are required. The thermal
shock resistance of a material can be described by means of the thermal shock
parameter RT. Here, the thermo-mechanical properties required for the
calculation of RT are quantum-mechanically predicted, experimentally
determined, and compared for Ti3AlC2 and Cr2AlC MAX phases. The coatings are
synthesized utilizing direct current magnetron sputtering without additional
heating, followed by vacuum annealing. It is shown that the RT of both Ti3AlC2
and Cr2AlC obtained via simulations are in good agreement with the
experimentally obtained ones. Comparing the MAX phase coatings, both
experiments and simulations indicate superior thermal shock behavior of Ti3AlC2
compared to Cr2AlC, attributed primarily to the larger linear coefficient of
thermal expansion of Cr2AlC. The results presented herein underline the
potential of ab initio calculations for predicting the thermal shock behavior
of ionically-covalently bonded materials.",2303.10266v2
2023-05-18,Observation and enhancement of room temperature bilinear magnetoelectric resistance in sputtered topological semimetal Pt3Sn,"Topological semimetal materials have become a research hotspot due to their
intrinsic strong spin-orbit coupling which leads to large charge-to-spin
conversion efficiency and novel transport behaviors. In this work, we have
observed a bilinear magnetoelectric resistance (BMER) of up to 0.1 nm2A-1Oe-1
in a singlelayer of sputtered semimetal Pt3Sn at room temperature. Different
from previous observations, the value of BMER in sputtered Pt3Sn does not
change out-of-plane due to the polycrystalline nature of Pt3Sn. The observation
of BMER provides strong evidence of the existence of spin-momentum locking in
the sputtered polycrystalline Pt3Sn. By adding an adjacent CoFeB magnetic
layer, the BMER value of this bilayer system is doubled compared to the single
Pt3Sn layer. This work broadens the material system in BMER study, which paves
the way for the characterization of topological states and applications for
spin memory and logic devices.",2305.10720v2
2023-09-12,In operando cryo-STEM of pulse-induced charge density wave switching in TaS$_2$,"The charge density wave (CDW) material 1T-TaS$_2$ exhibits a pulse-induced
insulator-to-metal transition, which shows promise for next-generation
electronics such as memristive memory and neuromorphic hardware. However, the
rational design of TaS$_2$ devices is hindered by a poor understanding of the
switching mechanism, the pulse-induced phase, and the influence of material
defects. Here, we operate a 2-terminal TaS$_2$ device within a scanning
transmission electron microscope (STEM) at cryogenic temperature, and directly
visualize the changing CDW structure with nanoscale spatial resolution and down
to 300 {\mu}s temporal resolution. We show that the pulse-induced transition is
driven by Joule heating, and that the pulse-induced state corresponds to nearly
commensurate and incommensurate CDW phases, depending on the applied voltage
amplitude. With our in operando cryo-STEM experiments, we directly correlate
the CDW structure with the device resistance, and show that dislocations
significantly impact device performance. This work resolves fundamental
questions of resistive switching in TaS$_2$ devices critical for engineering
reliable and scalable TaS$_2$ electronics.",2309.06406v1
2024-05-15,Laser Printing of Silver and Silver Oxide,"We show that direct laser writing (DLW) in aqueous silver nitrate with a 1030
nm femtosecond (fs) laser results in deposition of a mixture of silver oxide
and silver, in contrast to the pure silver deposition previously reported with
780 nm fs DLW. However, adding photoinitiator prevents silver oxide formation
in a concentration-dependent manner. As a result, the resistivity of the
material can also be controlled by photoinitiator concentration with
resistivity being reduced from approximately 9e-3 $\Omega m$ to 3e-7 $\Omega
m$. Silver oxide peaks dominate the X-ray diffraction spectra when no
photoinitiator is present, while the peaks disappear with photoinitiator
concentrations above 0.05wt%. While femtosecond pulses are needed to initiate
deposition, a continues-wave laser when well overlapped with the previously
written material and supplying enough average power can lead to further
printing, suggesting thermal deposition can also occur where the photoinitiator
molecule also acts as a general reducing agent that prevents oxide formation.
We also compare the surface quality of printed lines for different
photoinitiator concentrations and laser printing conditions. A THz polarizer
and metamaterial are printed as a demonstration of silver oxide printing.",2405.09340v1
2022-03-15,High Rate and High Precision Timing and Calorimeter Detectors,"High precision timing, high rate calorimeters, and radiation resistance are
becoming an important issue in particle physics especially in Energy and
Intensity Frontiers. We discuss doped Zinc Oxide (ZnO:Ga or GZO; ZnO:X where X
is Al, Cu or others) as a very fast scintillator and wavelength shifter (WLS),
Total internal reflection films, and PMT capable of counting at 300 MHz with 10
ps timing precision, with superior radiation resistance.",2203.09942v1
1998-01-20,"QHE, magnetoresistance and disordered transport on 2D mesoscopic plaquettes","The transport properties of a rectangular mesoscopic plaquette in the
presence of a perpendicular magnetic field are studied in a tight-binding model
with randomly distributed traps. The longitudinal and Hall resistances are
calculted in the four-probe Landauer-B\""{u}ttiker formalism which accounts
automatically both for the quantum coherence and the trapping-induced
localization. The localized character of eigenvectors and the specific aspect
of the density of states at a given magnetic flux are correlated with the
behaviour of the mentioned resistances as function of the Fermi energy. The
Hall insulator and quantum Hall regimes are evidentiated. The dependence on
magnetic field of the configurational averages of the longitudinal and Halll
resistance is studied in a purely quantum-mechanical approach. Both negative
and positive magnetoresistances are found.",9801192v1
1998-07-16,Low temperature resistivity in a nearly half-metallic ferromagnet,"We consider electron transport in a nearly half-metallic ferromagnet, in
which the minority spin electrons close to the band edge at the Fermi energy
are Anderson-localized due to disorder. For the case of spin-flip scattering of
the conduction electrons due to the absorption and emission of magnons, the
Boltzmann equation is exactly soluble to the linear order. From this solution
we calculate the temperature dependence of the resistivity due to single magnon
processes at sufficiently low temperature, namely $k_BT\ll D/L^2$, where $L$ is
the Anderson localization length and $D$ is the magnon stiffness. And depending
on the details of the minority spin density of states at the Fermi level, we
find a $T^{1.5}$ or $T^{2}$ scaling behavior for resistivity. Relevance to the
doped perovskite manganite systems is discussed.",9807244v1
1998-11-26,Kinetics of electric field induced oxygen ion migration in epitaxial metallic oxide films,"In this paper we report the observation of curent induced change of
resistance of thin metallic oxide films. The resistance changes at a very low
current (current density $J \geq 10^{3}$ A/cm$^{2}$). We find that the time
dependence associated with the processes (increase of resistance) show a
streched exponential type dependence at lower temperature, which crosses over
to a creep type behavior at $T \geq$ 350 K. The time scale associated shows a
drastic drop in the magnitude at $T \approx$ 350 K, where a long range
diffusion sets in increasing the conductivity noise. The phenomena is like a
""glass-transition"" in the random lattice of oxygen ions.",9811377v1
1999-09-14,Anomalous temperature behavior of resistivity in lightly doped manganites around a metal-insulator phase transition,"An unusual temperature and concentration behavior of resistivity in
$La_{0.7}Ca_{0.3}Mn_{1-x}Cu_xO_3$ has been observed at slight $Cu$ doping
($0\leq x \leq 0.05$). Namely, introduction of copper results in a splitting of
the resistivity maximum around a metal-insulator transition temperature
$T_0(x)$ into two differently evolving peaks. Unlike the original $Cu$-free
maximum which steadily increases with doping, the second (satellite) peak
remains virtually unchanged for $x<x_c$, increases for $x\ge x_c$ and finally
disappears at $x_m\simeq 2x_c$ with $x_c\simeq 0.03$. The observed phenomenon
is thought to arise from competition between substitution induced strengthening
of potential barriers (which hamper the charge hopping between neighboring $Mn$
sites) and weakening of carrier's kinetic energy. The data are well fitted
assuming a nonthermal tunneling conductivity theory with randomly distributed
hopping sites.",9909196v1
1999-11-25,Anomaly of AC resistance in magnetic nanoparticle alloys at spin-glass-like transition,"(withdrawn) A combined study of magnetic susceptibility and AC resistance was
performed on melt-spun Cu-Co granular magnetic ribbons. The AC resistance as a
function of temperature has a sharp maximum. We associate it with a diverging
correlation length at the temperature of collective freezing of magnetic
moments via increasing magnetic losses in the induced non-uniform field.
Application of this model to the experimental data allows a direct
determination of the critical exponent of correlation length on both sides of
the transition. Giant AC magnetoresistance is observed at the freezing
temperature.",9911414v2
1999-12-14,Giant AC magnetoresistance and anisotropic AC magnetoresistance in granular magnetic alloys,"(withdrawn)AC resistance of melt-spun granular magnetic Cu85Co15 ribbons was
measured as a function of temperature in the range 5-300 K, magnetic field Hdc
in the range -60 kOe to 60 kOe, and frequency in the range 1-1000 Hz. A sharp
peak of zero-field resistance, which scales with frequency, and an associated
isotropic giant AC magnetoresistance in small fields are observed around the
temperature of collective freezing of interacting magnetic moments. Anomalous
behavior of AC resistance in large fields (Hdc > 20 kOe) is observed in a much
broader temperature range. This effect is not only frequency- dependent, but
also highly sensitive to anisotropy. We call it anisotropic AC
magnetoresistance.",9912259v2
2000-07-31,Electrical transport properties of bulk Ni$_{c}$Fe$_{1-c}$ alloys and related spin-valve systems,"Within the Kubo-Greenwood formalism we use the fully relativistic,
spin-polarized, screened Korringa-Kohn-Rostoker method together with the
coherent-potential approximation for layered systems to calculate the
resistivity for the permalloy series Ni$_{c}$Fe$_{1-c}$. We are able to
reproduce the variation of the resistivity across the entire series; notably
the discontinuous behavior in the vicinity of the structural phase transition
from bcc to fcc. The absolute values for the resistivity are within a factor of
two of the experimental data. Also the giant magnetoresistance of a series of
permalloy-based spin-valve structures is estimated; we are able to reproduce
the trends and values observed on prototypical spin-valve structures.",0007507v1
2001-10-19,"Transport, magnetic, thermodynamic and optical properties in Ti-doped Sr_2RuO_4","We report on electrical resistivity, magnetic susceptibility and
magnetization, on heat capacity and optical experiments in single crystals of
Sr_2Ru_(1-x)Ti_xO_4. Samples with x=0.1 and 0.2 reveal purely semiconducting
resistivity behavior along c and the charge transport is close to localization
within the ab-plane. A strong anisotropy in the magnetic susceptibility appears
at temperatures below 100 K. Moreover magnetic ordering in c-direction with a
moment of order 0.01 mu_B/f.u. occurs at low temperatures. On doping the
low-temperature linear term of the heat capacity becomes reduced significantly
and probably is dominated by spin fluctuations. Finally, the optical
conductivity reveals the anisotropic character of the dc resistance, with the
in-plane conductance roughly following a Drude-type behavior and an insulating
response along c.",0110412v1
2002-01-10,Linear and nonlinear regime of a Random Resistor Network under biased percolation,"We investigate the steady state of a two-dimensional random resistor network
subjected to two competing biased percolations as a function of the bias
strength. The properties of the linear and nonlinear regimes are studied by
means of Monte Carlo simulations. In constant current conditions, a scaling
relation is found between $<R>/<R>_0$ and $I/I_0$, where $<R>$ is the average
network resistance, $<R>_0$ the Ohmic resistance and $I_0$ an appropriate
threshold value for the onset of nonlinearity. A similar scaling relation is
found also for the relative variance of resistance fluctuations. These results
are in good agreement with electrical breakdown measurements performed in
composite materials.",0201152v1
2002-04-11,In-plane Anisotropy on Resistivity and Thermopower in The Misfit Layered Oxide Bi2-xPbxSr2Co2Oy,"We investigated the in-plane anisotropy on the resistivity and thermopower of
Bi2-xPbxSr2Co2Oy single crystals, which have a misfit structure between the
hexagonal CoO2 layer and the rock salt Bi2Sr2O4 layer. The resistivity and
thermopower show significantly large anisotropy, which exceeds two at maximum.
This anisotropy would come from the anisotropic pseudogap formation enhanced by
the misfit structure. The thermopower changes with Pb doping to take a maximum
at x=0.4. The misfit structure improves the thermoelectric properties through
chemical pressure. The power factor is as large as 9 muW/cmK2 at 100 K for
x=0.6, which is the highest value for thermoelectric oxides at 100 K.",0204245v1
2002-05-23,Nonlinear AC resistivity in s-wave and d-wave disordered granular superconductors,"We model s-wave and d-wave disordered granular superconductors with a
three-dimensional lattice of randomly distributed Josephson junctions with
finite self-inductance. The nonlinear ac resistivity of these systems was
calculated using Langevin dynamical equations. The current amplitude dependence
of the nonlinear resistivity at the peak position is found to be a power law
characterized by exponent $\alpha$. The later is not universal but depends on
the self-inductance and current regimes. In the weak current regime $\alpha$ is
independent of the self-inductance and equal to 0.5 or both of s- and d-wave
materials. In the strong current regime this exponent depends on the screening.
We find $\alpha \approx 1$ for some interval of inductance which agrees with
the experimental finding for d-wave ceramic superconductors.",0205475v1
2002-12-06,Ab initio and finite-temperature molecular dynamics studies of lattice resistance in tantalum,"This manuscript explores the apparent discrepancy between experimental data
and theoretical calculations of the lattice resistance of bcc tantalum. We
present the first results for the temperature dependence of the Peierls stress
in this system and the first ab initio calculation of the zero-temperature
Peierls stress to employ periodic boundary conditions, which are those best
suited to the study of metallic systems at the electron-structure level. Our ab
initio value for the Peierls stress is over five times larger than current
extrapolations of experimental lattice resistance to zero-temperature. Although
we do find that the common techniques for such extrapolation indeed tend to
underestimate the zero-temperature limit, the amount of the underestimation
which we observe is only 10-20%, leaving open the possibility that mechanisms
other than the simple Peierls stress are important in controlling the process
of low temperature slip.",0212156v2
2003-02-21,Spin-Glass-like Transition and Hall Resistivity of Y2-xBixIr2O7,"Various physical properties of the pyrochlore oxide Y2-xBixIr2O7 have been
studied. The magnetizations M measured under the conditions of the
zero-field-cooling(ZFC) and the field-cooling(FC) have different values below
the temperature T=TG. The anomalous T-dependence of the electrical
resistivities r and the thermoelectric powers S observed at around TG indicates
that the behavior of the magnetization is due to the transition to the state
with the spin freezing. In this spin-frozen state, the Hall resistivities rH
measured with the ZFC and FC conditions are found to have different values,
too, in the low temperature phase (T<TG). Possible mechanisms which induce such
the hysteretic behavior are discussed.",0302437v1
2003-04-11,X-ray-induced electrical conduction in the insulating phase of thiospinel CuIr2S4,"Effects of x-ray irradiation on the crystal structure and the electrical
resistance were examined at low temperatures for the insulating phase of spinel
compound CuIr2S4. We found that the resistance decreases by more than five
decades by irradiation at 8.5 K. The structural change from triclinic to
tetragonal was observed at the same time. The x-ray-induced conductance is
deduced to result from the destruction of Ir4+ dimers formed in the insulating
phase. Slow relaxation of the resistance in the x-ray-induced state is also
reported.",0304256v1
2003-04-18,Magnetoresistance and percolation in the LaNi(1-x)Co(x)O3 solid solution,"A detailed study of the zero-field electrical resistivity and
magnetoresistance for the metallic members of the LaNi_{1-x}Co{x}O3 solid
solution with 0.3<=x<=0.6 is reported. The low temperature resistivity of the
compounds with 0.3<=x<=0.5 exhibits a logarithmic dependence that is
characteristic of systems with spin fluctuations. It is suggested that the
effect of the magnetic field dependence on the spin fluctuations plays a vital
role in determining the magnetoresistive behavior of these compounds. Concrete
experimental evidence that classify the chemically induced metal-to-insulator
transition (x_{c}=0.65) as a percolative phenomenon is provided. The
resistivity data for the x=0.6 metallic compound are analyzed in the framework
of cluster percolation threshold theory. The results of this analysis are
consistent with the suggestion that the growth of magnetic metallic clusters in
the presence of a magnetic field is mainly responsible for the observed giant
magnetoresistance effect at low temperatures for the compounds with x>=0.6.",0304423v2
2003-08-27,Room temperature domain wall pinning in bent ferromagnetic nanowires,"Mechanically bent nickel nanowires show clear features in their room
temperature magnetoresistance when a domain wall is pinned at the location of
the bend. By varying the direction of an applied magnetic field, the wire can
be prepared either in a single-domain state or a two-domain state. The presence
or absence of the domain wall acts to shift the switching fields of the
nanowire. In addition, a comparison of the magnetoresistance of the nanowire
with and without a domain wall shows a shift in the resistance correlated with
the presence of a wall. The resistance is decreased by 20-30 milli-Ohms when a
wall is present, compared to an overall resistance of 40-60 Ohms. A model of
the magnetization was developed that allowed calculation of the magnetostatic
energy of the nanowires, giving an estimate for the nucleation energy of a
domain wall.",0308579v1
2003-11-27,Fabrication and Electrical Properties of Pure VO2 Phase Films,"We have grown VO2 thin films by laser ablation for electronic device
applications. In obtaining the thin films of the pure VO2 phase, oxygen partial
pressure is a critical parameter because vanadium oxides have several phases
with the oxygen concentration. It is found that the pure VO2 films are
epitaxially grown on Al2O3 substrate in the narrow ranges of 55-60 mTorr in an
Ar+10% O2 ambient, and that the mixed phase films are synthesized when the
deposition pressure slightly deviates from the optimum pressure. The (100)
oriented VO2 films undergo an abrupt metal-insulator transition (MIT) with
resistance change of an order of 104 at 338K. In the films of mixed phases, the
small change of the resistance is observed at the same temperature. The
polycrystalline films grown on SiO2/Si substrate undergo a broaden MIT of the
resistance. Furthermore, the abrupt MIT and collective current motion appearing
in metal are observed when the electric field is applied to the film.",0311616v2
2004-01-20,Non-Gaussian Resistance Noise near Electrical Breakdown in Granular Materials,"The distribution of resistance fluctuations of conducting thin films with
granular structure near electrical breakdown is studied by numerical
simulations. The film is modeled as a resistor network in a steady state
determined by the competition between two biased processes, breaking and
recovery. Systems of different sizes and with different levels of internal
disorder are considered. Sharp deviations from a Gaussian distribution are
found near breakdown and the effect increases with the degree of internal
disorder. However, we show that in general this non-Gaussianity is related to
the finite size of the system and vanishes in the large size limit.
Nevertheless, near the critical point of the conductor-insulator transition,
deviations from Gaussianity persist when the size is increased and the
distribution of resistance fluctuations is well fitted by the universal
Bramwell-Holdsworth-Pinton distribution.",0401352v1
2004-07-23,Thermal and Electrical Properties of gamma-NaxCoO2 (0.70 < x < 0.78),"We have performed specific heat and electric resistivity measurements of
Na$_{x}$CoO$_{2}$ ($x=0.70$-0.78). Two anomalies have been observed in the
specific heat data for $x=0.78$, corresponding to magnetic transitions at
$T_{c}=22$ K and $T_{k}\simeq 9$ K reported previously. In the electrical
resistivity, a steep decrease at $T_{c}$ and a bending-like variation at
$T_{b}$(=120K for $x=0.78$) have been observed. Moreover, we have investigated
the $x$-dependence of these parameters in detail. The physical properties of
this system are very sensitive to $x$, and the inconsistent results of previous
reports can be explained by a small difference in $x$. Furthermore, for a
higher $x$ value, a phase separation into Na-rich and Na-poor domains occurs as
we previously proposed, while for a lower $x$ value, from characteristic
behaviors of the specific heat and the electrical resistivity at the
low-temperature region, the system is expected to be in the vicinity of the
magnetic instability which virtually exists below $x=0.70$.",0407614v1
2004-09-24,Hysteretic current-voltage characteristics and resistance switching at a rectifying Ti/Pr$_{0.7}$Ca$_{0.3}$MnO$_{3}$ interface,"We have characterized the vertical transport properties of epitaxial layered
structures composed of Pr$_{0.7}$Ca$_{0.3}$MnO$_{3}$ (PCMO) sandwiched between
SrRuO$_{3}$ (SRO) bottom electrode and several kinds of top electrodes such as
SRO, Pt, Au, Ag, and Ti. Among the layered structures, Ti/PCMO/SRO is distinct
due to a rectifying current-voltage ($I$--$V$) characteristic with a large
hysteresis. Corresponding to the hysteresis of the $I$--$V$ characteristics,
the contact resistance of the Ti/PCMO interface reversibly switches between two
stable states by applying pulsed voltage stress. We propose a model for the
resistance switching at the Ti/PCMO interface, in which the width and/or height
of a Schottky-like barrier are altered by trapped charge carriers in the
interface states.",0409657v1
2004-12-27,Depinning at the initial stage of the resistive transition in superconductors with a fractal cluster structure,"Depinning of vortices in percolative superconductor containing fractal
clusters of a normal phase is considered. Transition of the superconductor into
a resistive state corresponds to the percolation transition from a pinned
vortex state to a resistive state when the vortices are free to move. The
motion of the magnetic flux transferred by these vortices gives rise to the
region of initial dissipation on current-voltage characteristic. The influence
of normal phase clusters on distinctive features of current-voltage
characteristics of percolative type-II superconductors is considered. It is
found that an increase in the fractal dimension of the normal phase clusters
causes the initial dissipation region to broaden out. The reason of this effect
is an increase in the density of free vortices broken away from the pinning
centers by the Lorentz force. Dependencies of the free vortex density on the
fractal dimension of the normal phase cluster boundaries are obtained.",0412702v1
2005-04-20,Resistive relaxation in field-induced insulator-metal transition of a (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ bilayer manganite single crystal,"We have investigated the resistive relaxation of a
(La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ single crystal, in
order to examine the slow dynamics of the field-induced insulator to metal
transition of bilayered manganites. The temporal profiles observed in remanent
resistance follow a stretched exponential function accompanied by a slow
relaxation similar to that obtained in magnetization and magnetostriction data.
We demonstrate that the remanent relaxation in magnetotransport has a close
relationship with magnetic relaxation that can be understood in the framework
of an effective medium approximation by assuming that the first order parameter
is proportional to the second order one.",0504500v1
2005-05-19,Comparison of Measured and Calculated Specific Resistances of Pd/Pt Interfaces,"We compare specific resistances (AR equals area A times resistance R) of
sputtered Pd/Pt interfaces measured in two different ways with
no-free-parameter calculations. One way gives 2AR(Pd/Pt) of 0.29 (0.03)
fohm-m(2) and the other 0.17 (0.13) fohm-m(2). From these we derive a best
estimate of 2AR(Pd/Pt) of 0.28 (0.06) fohm-m(2), which overlaps with
no-free-parameter calculations: 2AR(predicted) of 0.30 (0.04) fohm-m(2) for
flat, perfect interfaces, or 0.33 (0.04) fohm-m(2) for interfaces composed of 2
monolayers of a 50percent-50percent PdPt alloy. These results support three
prior examples of agreement between calculations and measurements for pairs of
metals having the same crystal structure and the same lattice parameter to
within 1 percent. We also estimate the spin-flipping probability at Pd/Pt
interfaces as 0.13 (0.08).",0505488v2
2006-01-19,Spatially extended nature of resistive switching in perovskite oxide thin films,"We report the direct observation of the electric pulse induced
resistance-change (EPIR) effect at the nano scale on La1-xSrxMnO3 (LSMO) thin
films by the current measurement AFM technique. After a switching voltage of
one polarity is applied across the sample by the AFM tip, the conductivity in a
local nanometer region around the AFM tip is increased, and after a switching
voltage of the opposite polarity is applied, the local conductivity is reduced.
This reversible resistance switching effect is observed under both continuous
and short pulse voltage switching conditions. It is important for future
nanoscale non-volatile memory device applications.",0601451v1
2006-09-11,Imaging of Microscopic Sources of Resistive and Reactive Nonlinearities in Superconducting Microwave Devices,"The technique of low-temperature Laser Scanning Microscopy (LSM) has been
applied to the investigation of local microwave properties in operating
YBa2Cu3O7/LaAlO3 thin-film resonators patterned into a meandering strip
transmission line. By using a modified newly developed procedure of
spatially-resolved complex impedance partition, the influence of inhomogeneous
current flow on the formation of nonlinear (NL) microwave response in such
planar devices is analyzed in terms of the independent impact from resistive
and inductive components. The modified procedure developed here is dramatically
faster than our previous method. The LSM capability to probe the spatial
variations of two-tone, third-order intermodulation currents on micron length
scales is used to find the 2D distribution of the local sources of microwave
NL. The results show that the dominant sources of microwave NL are strongly
localized in the resistive domains.",0609244v1
2006-09-24,Swift-heavy-ion-irradiation-induced enhancement in electrical conductivity of chemical solution deposited La0.7Ba0.3MnO3 thin films,"Epitaxial thin films of La0.7Ba0.3MnO3 manganite, deposited using Chemical
Solution Deposition technique, were irradiated by 200 MeV Ag+15 ions with a
maximum ion dose up to 1x10^12 ions/cm2. Temperature- and magnetic
field-dependent resistivity measurements on all the films (before and after
irradiation) reveal a sustained decrease in resistivity with increasing ion
dose. A maximum dose of 1x10^12 ions/cm2 suppresses resistivity by factors of 3
and 10, at 330 K [insulator-metal (I-M) transition] and at 10 K, respectively.
On the other hand, with increasing ion dose, the magnetoresistance (MR)
enhances in the vicinity of I-M transition but decreases at low temperatures.
These results, corroborated by surface morphology of films, suggest that the
origin of such properties lies in the irradiation induced improved
crystallinity and epitaxial orientation, enhanced connectivity between grains,
and conglomeration of grains which result in better conductivity at grain
boundaries.",0609613v1
2006-10-06,Resistive hystersis effects in perovskite oxide-based heterostructure junctions,"In this paper, we report the electrical and structural properties of the
oxide-based metal/ferroelectric/metal (MFM) junctions. The heterostructures are
composed of ultrathin layers of La0.7Ca0.3MnO3 (LCMO) as a metallic layer and,
BaTiO3 (BTO) as a ferroelectric layer. Junction based devices, having the
dimensions of 400 x 200 micom2, have been fabricated upon LCMO/BTO/LCMO
heterostructures by photolithography and Ar-ion milling technique. The DC
current-voltage (I-V) characteristics of the MFM junctions were carried out. At
300 K, the devices showed the linear (I-V) characteristics, whereas at 77 K,
(I-V) curves exhibited some reproducible switching behaviours with well-defined
remnant currents. The resulting resistance modulation is very different from
what was already reported in ultrathin ferroelectric layers displaying
resistive switching. A model is presented to explain the datas",0610172v1
2007-02-26,Dielectrophoretically Assembled Polymer Nanowires for Gas Sensing,"We measured the electronic properties and gas sensing response of nanowires
containing segments of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)
(PEDOT/PSS) that were synthesized using anodic aluminum oxide (AAO) membranes.
The nanowires have a ""striped"" structure of gold-PEDOT/PSS-gold and are
typically 8 um long (1 um-6 um-1 um for each section, respectively) and 220 nm
in diameter. Dielectrophoretic assembly was used to position single nanowires
on pre-fabricated gold electrodes. A polymer conductivity of 11.5 +/- 0.7 S/cm
and a contact resistance of 27.6 +/- 4 kOhm were inferred from resistance
measurements of nanowires of varying length and diameter. When used as gas
sensors, the wires showed a resistance change of 10.5%, 9%, and 4% at the
saturation vapor pressure of acetone, methanol and ethanol, respectively.
Sensor response and recovery were rapid (seconds) with excellent
reproducibility in time and across devices. ""Striped"" template-grown nanowires
are thus intriguing candidates for use in electronic nose vapor sensing
systems.",0702619v1
2007-03-23,On the Kondo problem and thermodynamics of dilute magnetic alloys,"An argument is given showing that Coulomb attraction between conduction
electrons and impurity ions in a dilute magnetic alloy (DMA) can be
disregarded, provided the system's inverse temperature beta is replaced by an
effective inverse temperature t < beta. This replacement allows to remove the
singularity in Kondo's expression for DMA impurity resistivity and extend his
theory to 0 K. The extended Kondo formula agrees with experimental data on
resistivity of CuFe in the range of low temperatures and in the neighbourhood
of the resistivity minimum.
  Using an asymptotic solution of the thermodynamics of a dilute s-d system at
inverse temperature t, the impurity thermodynamic functions are derived and
shown to provide good agreement with experimental data on CuFe, CuCr and
(LaCe)Al_2 alloys in the low-temperature range. The magnitude of these
functions agrees with experiment and does not require rescaling as in previous
s-d theories. Nonlinear dependence of CuFe heat capacity on impurity
concentration has been accounted for the first time.",0703617v1
2007-05-14,Scaling analysis of the magnetoresistance in Ga_{1-x}Mn_xAs,"We compare experimental resistivity data on Ga_{1-x}Mn_xAs films with
theoretical calculations using a scaling theory for strongly disordered
ferromagnets. All characteristic features of the temperature dependence of the
resistivity can be quantitatively understood through this approach as
originating from the close vicinity of the metal-insulator transition. In
particular, we find that the magnetic field induced changes in resistance
cannot be explained within a mean-field treatment of the magnetic state, and
that accounting for thermal fluctuations is crucial for a quantitative
analysis. Similarly, while the non-interacting scaling theory is in reasonable
agreement with the data, we find clear evidence in favor of interaction effects
at low temperatures.",0705.2016v2
2007-06-07,Meta-nematic transitions in a bilayer system: Application to the bilayer ruthenate,"It was suggested that the two consecutive metamagnetic transitions and the
large residual resistivity discovered in Sr$_3$Ru$_2$O$_7$ can be understood
via the nematic order and its domains in a single layer system. However, a
recently reported anisotropy between two longitudinal resistivities induced by
tilting the magnetic field away from the c-axis cannot be explained within the
single layer nematic picture. To fill the gap in our understanding within the
nematic order scenario, we investigate the effects of bilayer coupling and
in-plane magnetic field on the electronic nematic phases in a bilayer system.
We propose that the in-plane magnetic field in the bilayer system modifies the
energetics of the domain formation, since it breaks the degeneracy of two
different nematic orientations. Thus the system reveals a pure nematic phase
with a resistivity anisotropy in the presence of an in-plane magnetic field. In
addition to the nematic phase, the bilayer coupling opens a novel route to a
hidden nematic phase that preserves the x-y symmetry of the Fermi surfaces.",0706.1069v3
2007-06-12,Graphene Spin Transistor,"Graphitic nanostructures, e.g. carbon nanotubes (CNT) and graphene, have been
proposed as ideal materials for spin conduction[1-7]; they have long electronic
mean free paths[8] and small spin-orbit coupling[9], hence are expected to have
very long spin-scattering times. In addition, spin injection and detection in
graphene opens new opportunities to study exotic electronic states such as the
quantum Hall[10,11] and quantum spin Hall[9] states, and spin-polarized edge
states[12] in graphene ribbons. Here we perform the first non-local four-probe
experiments[13] on graphene contacted by ferromagnetic Permalloy electrodes. We
observe sharp switching and often sign-reversal of the non-local resistance at
the coercive field of the electrodes, indicating definitively the presence of a
spin current between injector and detector. The non-local resistance changes
magnitude and sign quasi-periodically with back-gate voltage, and
Fabry-Perot-like oscillations[6,14,15] are observed, consistent with
quantum-coherent transport. The non-local resistance signal can be observed up
to at least T = 300 K.",0706.1597v1
2007-08-20,Negative magnetoresistance of ultra-narrow superconducting nanowires in the resistive state,"We present a phenomenological model qualitatively explaining negative
magnetoresistance in quasi-one-dimensional superconducting channels in the
resistive state. The model is based on the assumption that fluctuations of the
order parameter (phase slips) are responsible for the finite effective
resistance of a narrow superconducting wire sufficiently close to the critical
temperature. Each fluctuation is accompanied by an instant formation of a
quasi-normal region of the order of the non-equilibrium quasiparticle
relaxation length 'pinned' to the core of the phase slip. The effective
time-averaged voltage measured in experiment is a sum of two terms. First one
is the conventional contribution linked to the rate of the fluctuations via the
Josephson relation. Second term is the Ohmic contribution of this quasi-normal
region. Depending on material properties of the wire, there might be a range of
magnetic fields where the first term is not much affected, while the second
term is effectively suppressed contributing to the experimentally observed
negative magnetoresistance.",0708.2602v2
2007-11-23,Intrinsic and Extrinsic Performance Limits of Graphene Devices on SiO2,"The linear dispersion relation in graphene[1,2] gives rise to a surprising
prediction: the resistivity due to isotropic scatterers (e.g. white-noise
disorder[3] or phonons[4-8]) is independent of carrier density n. Here we show
that acoustic phonon scattering[4-6] is indeed independent of n, and places an
intrinsic limit on the resistivity in graphene of only 30 Ohm at room
temperature (RT). At a technologically-relevant carrier density of 10^12 cm^-2,
the mean free path for electron-acoustic phonon scattering is >2 microns, and
the intrinsic mobility limit is 2x10^5 cm^2/Vs, exceeding the highest known
inorganic semiconductor (InSb, ~7.7x10^4 cm^2/Vs[9]) and semiconducting carbon
nanotubes (~1x10^5 cm^2/Vs[10]). We also show that extrinsic scattering by
surface phonons of the SiO2 substrate[11,12] adds a strong temperature
dependent resistivity above ~200 K[8], limiting the RT mobility to ~4x10^4
cm^2/Vs, pointing out the importance of substrate choice for graphene
devices[13].",0711.3646v2
2008-02-11,Anomalous Hall effect in Fe/Cu bilayers,"The scaling of anomalous Hall resistivity on the longitudinal resistivity has
been intensively studied in the different magnetic systems, including
multilayers and granular films, to examine which mechanism, skew scattering or
side-jump, dominates. The basis of the scaling law is that both the
resistivities are due to the electron scattering at the imperfections in the
materials. By studying of anomalous Hall effect (AHE) in the simple Fe/Cu
bilayers, we demonstrate that the measured anomalous Hall effect should not
follow the scaling laws derived from skew scattering or side-jump mechanism due
to the short-circuit and shunting effects of the non-magnetic layers.",0802.1462v1
2008-04-09,Theory of a continuous Mott transition in two dimensions,"We study theoretically the zero temperature phase transition in two
dimensions from a Fermi liquid to a paramagnetic Mott insulator with a spinon
Fermi surface. We show that the approach to the bandwidth controlled Mott
transition from the metallic side is accompanied by a vanishing quasiparticle
residue and a diverging effective mass. The Landau parameters $F^0_s, F^0_a$
also diverge. Right at the quantum critical point there is a sharply defined
`critical Fermi surface' but no Landau quasiparticle. The critical point has a
$Tln\frac{1}{T}$ specific heat and a non-zero $T = 0$ resistivity. We predict
an interesting {\em universal resistivity jump} in the residual resistivity at
the critical point as the transition is approached from the metallic side. The
crossovers out of the critical region are also studied. Remarkably the initial
crossover out of criticality on the metallic side is to a Marginal Fermi Liquid
metal. At much lower temperatures there is a further crossover into the Landau
Fermi liquid. The ratio of the two crossover scales vanishes on approaching the
critical point. Similar phenomena are found in the insulating side. The filling
controlled Mott transition is also studied. Implications for experiments on the
layered triangular lattice organic material $\kappa-(ET)_2Cu_2(CN)_3$ are
discussed.",0804.1555v1
2008-04-28,Lattice Resistance to Dislocation Motion at the Nanoscale,"In this letter we propose a model that demonstrates the effect of free
surface on the lattice resistance experienced by a moving dislocation in
nanodimensional systems. This effect manifests in an enhanced velocity of
dislocation due to the proximity of the dislocation line to the surface. To
verify this finding, molecular dynamics simulations for an edge dislocation in
bcc molybdenum are performed and the results are found to be in agreement with
the numerical implementations of this model. The reduction in this effect at
higher stresses and temperatures, as revealed by the simulations, confirms the
role of lattice resistance behind the observed change in the dislocation
velocity.",0804.4360v2
2008-05-13,The Role of Electrical and Thermal Contact Resistance for Joule Breakdown of Single-Wall Carbon Nanotubes,"Several data sets of electrical breakdown in air of single-wall carbon
nanotubes (SWNTs) on insulating substrates are collected and analyzed. A
universal scaling of the Joule breakdown power with nanotube length is found,
which appears independent of the insulating substrates used or their thickness.
This suggests the thermal resistances at the interface between SWNT and
insulator, and between SWNT and electrodes, govern heat sinking from the
nanotube. Analytical models for the breakdown power scaling are presented,
providing an intuitive, physical understanding of the breakdown process. The
electrical and thermal resistance at the electrode contacts limit the breakdown
behavior for sub-micron SWNTs, the breakdown power scales linearly with length
for microns-long tubes, and a minimum breakdown power (~ 0.05 uW) is observed
for the intermediate (~ 0.5 um) length range.",0805.1937v1
2008-06-09,Transport properties and superconductivity in $Ba_{1-x}M_xFe_2As_2$ (M=La and K) with double FeAs layers,"We synthesized the samples $Ba_{1-x}M_xFe_2As_2$ (M=La and K) with
$ThCr_2Si_2$-type structure. These samples were systematically characterized by
resistivity, thermoelectic power (TEP) and Hall coefficient ($R_H$).
$BaFe_2As_2$ shows an anomaly in resistivity at about 140 K. Substitution of La
for Ba leads to a shift of the anomaly to low temperature, but no
superconducting transition is observed. Potassium doping leads to suppression
of the anomaly in resistivity and induces superconductivity at 38 K as reported
by Rotter et al.\cite{rotter}. The Hall coefficient and TEP measurements
indicate that the TEP is negative for $BaFe_2As_2$ and La-doped $BaFe_2As_2$,
indicating n-type carrier; while potassium doping leads to change of the sign
in $R_H$ and TEP. It definitely indicates p-type carrier in superconducting
$Ba_{1-x}K_xFe_2As_2$ with double FeAs layers, being in contrast to the case of
$LnO_{1-x}F_xFeAs$ with single FeAs layer. A similar superconductivity is also
observed in the sample with nominal composition $Ba_{1-x}K_xOFe_2As_2$.",0806.1459v1
2009-02-21,Negative nonlocal resistance in mesoscopic gold Hall bars: Absence of giant spin Hall effect,"We report the observation of negative nonlocal resistances in multiterminal
mesoscopic gold Hall bar structures whose characteristic dimensions are larger
than the electron mean-free path. Our results can only be partially explained
by a classical diffusive model of the nonlocal transport, and are not
consistent with a recently proposed model based on spin Hall effects. Instead,
our analysis suggests that a quasiballistic transport mechanism is responsible
for the observed negative nonlocal resistance. Based on the sensitivity of our
measurements and the spin Hall effect model, we find an upper limit for the
spin Hall angle in gold of 0.022 at 4.5 K.",0902.3686v1
2009-08-26,Piezoresistance in chemically synthesized polypyrrole thin films,"The resistance of chemically synthesized polypyrrole (PPy) thin films is
investigated as a function of the pressure of various gases as well as of the
film thickness. A physical, piezoresistive response is found to coexist with a
chemical response if the gas is chemically active, like, e.g., oxygen. The
piezoresistance is studied separately by exposing the films to the chemically
inert gases such as nitrogen and argon. We observe that the character of the
piezoresistive response is a function not only of the film thickness, but also
of the pressure. Films of a thickness below 70 nm show a decreasing resistance
as pressure is applied, while for thicker films, the piezoresistance is
positive. Moreover, in some films of thickness of about 70 nm, the
piezoresistive response changes from negative to positive as the gas pressure
is increased above 500 mbars. This behavior is interpreted in terms of a total
piezoresistance which is composed of a surface and a bulk component, each of
which contributes in a characteristic way. These results suggest that in
polypyrrole, chemical sensing and piezoresistivity can coexist, which needs to
be kept in mind when interpreting resistive responses of such sensors.",0908.3840v1
2009-09-28,The effects of superconductor-stabilizer interfacial resistance on quench of current-carrying coated conductor,"We present the results of numerical analysis of a model of normal zone
propagation in coated conductors. The main emphasis is on the effects of
increased contact resistance between the superconducting film and the
stabilizer on the speed of normal zone propagation, the maximum temperature
rise inside the normal zone, and the stability margins. We show that with
increasing contact resistance the speed of normal zone propagation increases,
the maximum temperature inside the normal zone decreases, and stability margins
shrink. This may have an overall beneficial effect on quench protection quality
of coated conductors. We also briefly discuss the propagation of solitons and
development of the temperature modulation along the wire.",0909.5209v1
2009-11-02,Giant anomalous Hall resistivity of the room temperature ferromagnet Fe3Sn2 - a frustrated metal with the kagome-bilayer structure,"We have investigated magnetic and transport properties of the {\it
kagom\'{e}-bilayer} ferromagnet Fe$_{3}$Sn$_{2}$. A soft ferromagnetism and a
large anomalous Hall effect are observed. The saturated Hall resistivity of
Fe$_{3}$Sn$_{2}$ is 3.2 $\mu\Omega$cm at 300 K, which is almost 20 times higher
than that of typical itinerant-ferromagnets such as Fe and Ni. The anomalous
Hall coefficient $R_{{\rm s}}$ is 6.7$\times10^{-9}$ $\Omega$cm/G at 300 K,
which is three orders of magnitude larger than that of pure Fe. $R_{{\rm s}}$
obeys an unconventional scaling to the longitudinal resistivity, $\rho_{xx}$,
of $R_{{\rm s}} \propto \rho_{xx}^{3.3}$. Such a relationship cannot be
explained by the skew and/or side-jump mechanisms and indicates that the origin
of the anomalous Hall effect in the frustrated magnet Fe$_{3}$Sn$_{2}$ is
indeed extraordinary.",0911.0289v1
2010-04-19,Towards a Quantitative Description of Solid Electrolyte Conductance Switches,"We present a quantitative analysis of the steady state electronic transport
in a resistive switching device. The device is composed of a thin film of
Ag$_{2}$S (solid electrolyte) contacted by a Pt nano-contact acting as
ion-blocking electrode, and a large area Ag reference electrode. When applying
a bias voltage both ionic and electronic transport occurs, and depending on the
polarity it causes an accumulation of ions around the nano-contact. At small
applied voltages (pre-switching) we observed this as a strongly nonlinear
current-voltage curve, which have been modeled using the Hebb-Wagner treatment
for polarization of a mixed conductor. This model correctly describes the
transport of the electrons within the polarized solid electrolyte in the steady
state up until the resistance switching, covering the entire range of
non-stoichiometries, and including the supersaturation range just before the
deposition of elemental silver. In this way, it is a step towards a
quantitative understanding of the processes that lead to resistance switching.",1004.3079v1
2010-05-18,A general figure of merit for thick and thin transparent conductive carbon nanotube coatings,"We suggest a wavelength-dependent figure of merit for transparent conducting
nanotube networks, composed of the sheet resistance and the optical density. We
argue that this would be more useful than other suggestions prevailing in the
literature, because it relies on more realistic assumptions regarding the
optical parameters of real nanotubes: it takes into account the fact that the
dc resistivity depends on the concentration of free carriers, while the visible
absorption is caused by bound carriers. Based on sheet resistance measurements
and wide-range transmission spectra, we compare several commercial nanotube
types and find correlation between metal enrichment and figure of merit. A
simple graphical approach is suggested to determine if the required optical and
transport properties can be achieved by varying the thickness of the nanotube
layer or a more aggressive treatment is needed. The procedure can be extended
to oxide coatings as well.",1005.3125v1
2010-05-30,On the Corrosion Resistance of Porous Electroplated Zinc Coatings in Different Corrosive Media,"The corrosion resistance of an electroplated (EP) Zn coating whose surface
was chemically etched to produce surface defects (pores) is investigated in
this work. Impedance and DC polarisation measururements were employed to study
the behaviour of such coating in various corrosive media (NaCl, NaOH and rain
water). Four different faradaic relaxation processes were clearly revealed in
different NaCl concentrations (from 0.1M to 1M). In the most concentrated
solutions at least three relaxation processes at low frequencies (LF) appeared
and were related to zinc deposition and dissolution. At lower concentrations
and depending on the pH, only one process was observed. The charge transfer
resistance (Rct) and the corrosion current (Icorr) were practically stable in
the pH range 5 to 10. In deaerated NaCl 0.1M, the EIS diagrams showed two
time-constants at very close frequencies. From the EIS diagrams the porous
nature of the coating was highlighted and showed that the dissolution
mechanisms occurred at the base of the pores.",1005.5554v1
2010-06-12,Ex-situ Tunnel Junction Process Technique Characterized by Coulomb Blockade Thermometry,"We investigate a wafer scale tunnel junction fabrication method, where a
plasma etched via through a dielectric layer covering bottom Al electrode
defines the tunnel junction area. The ex-situ tunnel barrier is formed by
oxidation of the bottom electrode in the junction area. Room temperature
resistance mapping over a 150 mm wafer give local deviation values of the
tunnel junction resistance that fall below 7.5 % with an average of 1.3 %. The
deviation is further investigated by sub-1 K measurements of a device, which
has one tunnel junction connected to four arrays consisting of N junctions (N =
41, junction diameter 700 nm). The differential conductance is measured in
single-junction and array Coulomb blockade thermometer operation modes. By
fitting the experimental data to the theoretical models we found an upper limit
for the local tunnel junction resistance deviation of ~5 % for the array of
2N+1 junctions. This value is of the same order as the minimum detectable
deviation defined by the accuracy of our experimental setup.",1006.2436v1
2010-08-24,"Magnetism of mixed quaternary Heusler alloys: (Ni,T)$_{2}$MnSn (T=Cu,Pd) as a case study","The electronic properties, exchange interactions, finite-temperature
magnetism, and transport properties of random quaternary Heusler Ni$_{2}$MnSn
alloys doped with Cu- and Pd-atoms are studied theoretically by means of {\it
ab initio} calculations over the entire range of dopant concentrations. While
the magnetic moments are only weakly dependent on the alloy composition, the
Curie temperatures exhibit strongly non-linear behavior with respect to
Cu-doping in contrast with an almost linear concentration dependence in the
case of Pd-doping. The present parameter-free theory agrees qualitatively and
also reasonably well quantitatively with the available experimental results. An
analysis of exchange interactions is provided for a deeper understanding of the
problem. The dopant atoms perturb electronic structure close to the Fermi
energy only weakly and the residual resistivity thus obeys a simple Nordheim
rule. The dominating contribution to the temperature-dependent resistivity is
due to thermodynamical fluctuations originating from the spin-disorder, which,
according to our calculations, can be described successfully via the disordered
local moments model. Results based on this model agree fairly well with the
measured values of spin-disorder induced resistivity.",1008.4060v1
2010-10-29,Nd induced Mn spin-reorientation transition in NdMnAsO,"A combination of synchrotron X-ray, neutron powder diffraction,
magnetization, heat capacity and electrical resistivity measurements reveals
that NdMnAsO is an antiferromagnetic semiconductor with large Neel temperature
(TN = 359(2) K). At room temperature the magnetic propagation vector k = 0 and
the Mn moments are directed along the crystallographic c-axis (mMn = 2.41(6)
BM). Upon cooling a spin reorientation (SR) transition of the Mn moments into
the ab-plane occurs (TSR = 23 K). This coincides with the long range ordering
of the Nd moments, which are restricted to the basal plane. The magnetic
propagation vector remains k = 0. At base temperature (1.6 K) the fitted
moments are mab,Mn = 3.72(1) BM and mab,Nd = 1.94(1) BM. The electrical
resistivity is characterized by a broad maximum at 250 K, below which it has a
metallic temperature dependence but semiconducting magnitude (rho250K = 50 Ohm
cm, residual resistivity ratio = 2), and a slight upturn at the SR transition.",1010.6145v1
2010-11-04,Electron interaction-driven insulating ground state in Bi2Se3 topological insulators in the two dimensional limit,"We report a transport study of ultrathin Bi2Se3 topological insulators with
thickness from one quintuple layer to six quintuple layers grown by molecular
beam epitaxy. At low temperatures, the film resistance increases
logarithmically with decreasing temperature, revealing an insulating ground
state. The sharp increase of resistance with magnetic field, however, indicates
the existence of weak antilocalization, which should reduce the resistance as
temperature decreases. We show that these apparently contradictory behaviors
can be understood by considering the electron interaction effect, which plays a
crucial role in determining the electronic ground state of topological
insulators in the two dimensional limit.",1011.1055v1
2011-02-03,Temperature dependent resistivity in bilayer graphene due to flexural phonons,"We have studied electron scattering by out-of-plane (flexural) phonons in
doped suspended bilayer graphene. We have found the bilayer membrane to follow
the qualitative behavior of the monolayer cousin. In the bilayer, different
electronic structure combine with different electron-phonon coupling to give
the same parametric dependence in resistivity, and in particular the same
temperature $T$ behavior. In parallel with the single layer, flexural phonons
dominate the phonon contribution to resistivity in the absence of strain, where
a density independent mobility is obtained. This contribution is strongly
suppressed by tension, and in-plane phonons become the dominant contribution in
strained samples. Among the quantitative differences an important one has been
identified: room $T$ mobility in bilayer graphene is substantially higher than
in monolayer. The origin of quantitative differences has been unveiled.",1102.0807v1
2011-05-19,Anisotropic in-plane resistivity in the nematic phase of the iron pnictides,"We show that the interference between scattering by impurities and by
critical spin fluctuations gives rise to anisotropic transport in the
Ising-nematic state of the iron pnictides. The effect is closely related to the
non-Fermi liquid behavior of the resistivity near an antiferromagnetic quantum
critical point. Our theory not only explains the observed sign of the
resistivity anisotropy $\Delta\rho$ in electron doped systems, but also
predicts a sign change of $\Delta\rho$ upon sufficient hole doping.
Furthermore, our model naturally addresses the changes in $\Delta\rho$ upon
sample annealing and alkaline-earth substitution.",1105.3906v2
2011-08-17,Control of rectifying and resistive switching behavior in BiFeO3 thin films,"BiFeO3 thin films have been grown on Pt/Ti/SiO2/Si substrates with pulsed
laser deposition using Au as the top electrode. The resistive switching
property of the Au/BiFeO3/Pt stack has been significantly improved by carefully
tuning the oxygen pressure during the growth, and a large switching ratio of
~4500 has been achieved. The deposition pressure modifies the concentration of
oxygen vacancies and the rectifying behavior of the Au/BiFeO3 junction, and
consequently influences the resistive switching behavior of the whole stack.
The switching takes place homogeneously over the entire electrode, and shows a
long-term retention.",1108.3454v1
2011-09-05,The direct relation between the coefficient of the low temperature resistivity T^2 term and the superconducting transition temperature Tc,"In several superconductors above the superconducting transition temperature
Tc, the electrical resistivity is of the form {\rho} =AT^2. We show that there
exists an empirical relation between Tc and A when both vary with an external
parameter, e.g. pressure. The more resistive the sample the higher the Tc.
Landau theory shows that it is a general feature of Fermi Liquids, as {\rho} is
governed by the scattering that bounds the pairs condensing at Tc. We develop a
method that allows the determination of the coupling constant {\lambda} that is
validated when used to the transport properties of superfluid 3He.",1109.0853v1
2011-10-17,In Situ Imaging of the Conducting Filament in a Silicon Oxide Resistive Switch,"The nature of the conducting filaments in many resistive switching systems
has been elusive. Through in situ transmission electron microscopy, we image
the real-time formation and evolution of the filament in a silicon oxide
resistive switch. The electroforming process is revealed to involve the local
enrichment of silicon from the silicon oxide matrix. Semi-metallic silicon
nanocrystals with structural variations from the conventional diamond cubic
form of silicon are observed, which likely accounts for the conduction in the
filament. The growth and shrinkage of the silicon nanocrystals in response to
different electrical stimuli show energetically viable transition processes in
the silicon forms, offering evidence to the switching mechanism. The study here
also provides insights into the electrical breakdown process in silicon oxide
layers, which are ubiquitous in a host of electronic devices.",1110.3755v1
2011-12-02,Wigner-Mott scaling of transport near the two-dimensional metal-insulator transition,"Electron-electron scattering usually dominates the transport in strongly
correlated materials. It typically leads to pronounced resistivity maxima in
the incoherent regime around the coherence temperature $T^{*}$, reflecting the
tendency of carriers to undergo Mott localization following the demise of the
Fermi liquid. This behavior is best pronounced in the vicinity of
interaction-driven (Mott-like) metal-insulator transitions, where the $T^{*}$
decreases, while the resistivity maximum $\rho_{max}$ increases. Here we show
that, in this regime, the entire family of resistivity curves displays a
characteristic scaling behavior $\rho(T)/\rho_{max}\approx F(T/T_{max}),$ while
the $\rho_{max}$ and $T_{max}\sim T^{*}$ assume a powerlaw dependence on the
quasi-particle effective mass $m^{*}$. Remarkably, precisely such trends are
found from an appropriate scaling analysis of experimental data obtained from
diluted two-dimensional electron gases in zero magnetic fields. Our analysis
provides strong evidence that inelastic electron-electron scattering -- and not
disorder effects -- dominates finite temperature transport in these systems,
validating the Wigner-Mott picture of the two-dimensional metal-insulator
transition.",1112.0440v2
2012-02-15,Non-linear resistivity and heat dissipation in monolayer graphene,"We have experimentally studied the nonlinear nature of electrical conduction
in monolayer graphene devices on silica substrates. This nonlinearity manifests
itself as a nonmonotonic dependence of the differential resistance on applied
DC voltage bias across the sample. At temperatures below ~70K, the differential
resistance exhibits a peak near zero bias that can be attributed to
self-heating of the charge carriers. We show that the shape of this peak arises
from a combination of different energy dissipation mechanisms of the carriers.
The energy dissipation at higher carrier temperatures depends critically on the
length of the sample. For samples longer than 10um the heat loss is shown to be
determined by optical phonons at the silica-graphene interface.",1202.3394v1
2012-04-19,Observation of Negative Contact Resistances in Graphene Field-Effect Transistors,"The gate-voltage (VG) dependence of the contact resistance (RC) in graphene
field-effect transistors is characterized by the transmission line model. The
RC-VG characteristics of Ag, Cu, and Au contacts display a dip around the
charge neutrality point, and become even negative with Ag contacts. The dip
structure is well reproduced by a model calculation that considers a
metal-contact-induced potential variation near the metal contact edges. The
apparently negative RC originates with the carrier doping from the metal
contacts to the graphene channel and appears when the doping effect is more
substantial than the actual contact resistance precisely at the contacts. The
negative RC can appear at the metal contacts to Dirac-cone systems such as
graphene.",1204.4315v2
2012-05-24,Intrinsic Electron-Phonon Resistivity in Bi2Se3 in the Topological Regime,"We measure the temperature-dependent carrier density and resistivity of the
topological surface state of thin exfoliated Bi2Se3 in the absence of bulk
conduction. When the gate-tuned chemical potential is near or below the Dirac
point the carrier density is strongly temperature dependent reflecting thermal
activation from the nearby bulk valence band, while above the Dirac point,
unipolar n-type surface conduction is observed with negligible thermal
activation of bulk carriers. In this regime linear resistivity vs. temperature
reflects intrinsic electron-acoustic phonon scattering. Quantitative comparison
with a theoretical transport calculation including both phonon and disorder
effects gives the ratio of deformation potential to Fermi velocity D/\hbarvF =
4.7 {\AA}-1. This strong phonon scattering in the Bi2Se3 surface state gives
intrinsic limits for the conductivity and charge carrier mobility at room
temperature of ~550 {\mu}S per surface and ~10,000 cm2/Vs.",1205.5554v2
2012-07-21,Simulation of magnetoresistance in disordered ultracold atomic Bose gases,"Anderson localization was first investigated in the context of electrons in
solids. One of the successes was in explaining the puzzle of negative
magneto-resistance - as early as the 1940s it had been observed that electron
diffusion rates in some materials can increase with the application of a
magnetic field. Anderson localization has now been demonstrated in ultra-cold
atomic gases. We present a theoretical study of the two-dimensional ultra-cold
Bose gas in the presence of disorder, to which we apply a synthetic magnetic
field. We demonstrate that, in the ballistic transport regime this leads to
positive magneto-resistance and that, in the diffusive and strong localization
regimes, can also lead to negative magneto-resistance. We propose experimental
scenarios to observe these effects.",1207.5095v1
2012-07-26,Spin-orbit-coupling induced domain-wall resistance in diffusive ferromagnets,"We investigate diffusive transport through a number of domain wall (DW)
profiles of the important magnetic alloy Permalloy taking into account
simultaneously noncollinearity, alloy disorder, and spin-orbit coupling fully
quantum mechanically, from first principles. In addition to observing the known
effects of magnetization mistracking and anisotropic magnetoresistance, we
discover a not-previously identified contribution to the resistance of a DW
that comes from spin-orbit-coupling-mediated spin-flip scattering in a textured
diffusive ferromagnet. This adiabatic DW resistance, which should exist in all
diffusive DWs, can be observed by varying the DW width in a systematic fashion
in suitably designed nanowires.",1207.6277v2
2012-08-01,Textured Superconductivity in the Presence of a Coexisting Order: Ce115s and Other Heavy-Fermion Compounds,"Superconductivity in strongly correlated electron systems frequently emerges
in proximity to another broken symmetry. In heavy-electron superconductors, the
nearby ordered state most commonly is magnetism, and the so-called Ce115
heavy-electron compounds have been particularly instructive for revealing new
relationships between magnetism and superconductivity. From measurements of the
resistive and bulk transitions to superconductivity in these materials, we find
that the resistive transition appears at a temperature considerably higher than
the bulk transition when superconductivity and magnetic order coexist, but this
temperature difference disappears in the absence of long-range magnetic order.
Further, in the pressure-temperature region of coexistence in CeRhIn5, a new
anisotropy in the resistive transition develops even though the tetragonal
crystal structure apparently remains unchanged, implying a form of textured
superconductivity. We suggest that this texture may be a generic response to
coexisting order in these and other heavy-fermion superconductors.",1208.0253v1
2012-09-20,Surface resistance measurements of HTS thin films using SLAO dielectric resonator,"Surface resistance of HTS films is typically measured using Sapphire
dielectric rod resonators enclosed in a copper cavity. In this paper we present
surface resistance measurements of YBa2Cu3O7-{\delta} films using Strontium
Lanthanum Aluminate (SLAO) at a resonant frequency of 18.2 GHz. We have
performed the error analysis of the cavity loaded with SLAO dielectric rod and
also verification measurements using two Sapphire (Al2O3) rod resonators
operating at resonant frequencies of 24.6 GHz and 10 GHz respectively. Good
agreement between the values of Rs of two sets of YBa2Cu3O7-{\delta} films
measured using the SLAO and the Sapphire dielectrics has been obtained after a
frequency scaling of Rs was applied. Using different dielectric rods of the
same size in the same cavity for measurements of Rs of HTS films, it is
feasible to do microwave characterization of the same films at differing
frequencies.",1209.4519v1
2012-12-04,UV/Ozone treatment to reduce metal-graphene contact resistance,"We report reduced contact resistance of single-layer graphene devices by
using ultraviolet ozone (UVO) treatment to modify the metal/graphene contact
interface. The devices were fabricated from mechanically transferred, chemical
vapor deposition (CVD) grown, single layer graphene. UVO treatment of graphene
in the contact regions as defined by photolithography and prior to metal
deposition was found to reduce interface contamination originating from
incomplete removal of poly(methyl methacrylate) (PMMA) and photoresist. Our
control experiment shows that exposure times up to 10 minutes did not introduce
significant disorder in the graphene as characterized by Raman spectroscopy. By
using the described approach, contact resistance of less than 200 {\Omega}
{\mu}m was achieved, while not significantly altering the electrical properties
of the graphene channel region of devices.",1212.0838v1
2013-03-25,Kinetics of excitations on the Fermi arcs in underdoped cuprates at low temperature,"The Fermi-liquid-like (FL) resistivity recently observed in clean HgBa2CuO4
below the pseudogap temperature was related to carriers at the nodal points on
the Fermi surface [4]. We show that this necessitates important implications
for the electronic spectrum of underdoped (UD) cuprates in whole. Photoemission
experiments picture the spectrum as of metallic arcs separated from each other
by regions with large energy gaps. We solved the kinetic equation in such model
rigorously. The Fermi arcs carriers contribute to FL resistivity, if scattering
between the opposite nodal points admits the Umklapp processes. The Hall
coefficient defines the effective number of carriers on arcs and has the
positive sign. For clean materials the expression is applicable only at weak
magnetic fields. We discuss the Fermi arcs concept further in light of recent
experimental findings and argue that the idea of reconstructed FS in UD
cuprates is not consistent with the FL-like resistivity.",1303.6252v2
2013-03-27,First-Principles Calculation of Thermal Transport in the Metal/Graphene System,"Thermal properties in the metal/graphene (Gr) systems are analyzed by using
an atomistic phonon transport model based on Landauer formalism and
first-principles calculations. The specific structures under investigation
include chemisorbed Ni(111)/Gr, physisorbed Cu(111)/Gr and Au(111)/Gr, as well
as Pd(111)/Gr with intermediate characteristics. Calculated results illustrate
a strong dependence of thermal transfer on the details of interfacial
microstructures. In particular, it is shown that the chemisorbed case provides
a generally smaller interfacial thermal resistance than the physisorbed due to
the stronger bonding. However, our calculation also indicates that the weakly
chemisorbed interface of Pd/Gr may be an exception, with the largest thermal
resistance among the considered. Further examination of the electrostatic
potential and interatomic force constants reveal that the mixed bonding force
between the Pd and C atoms results in incomplete hybridization of Pd and
graphene orbital states at the junction, leading effectively to two phonon
interfaces and a larger than expected thermal resistance. Comparison with
available experimental data shows good agreement. The result clearly suggests
the feasibility of phonon engineering for thermal property optimization at the
interface.",1303.6936v1
2013-05-22,Electron Transport Through Ag-Silicene-Ag Junctions,"For several years the electronic structure properties of the novel
two-dimensional system silicene have been studied extensively. Electron
transport across metal-silicence junctions, however, remains relatively
unexplored. To address this issue, we developed and implemented a theoretical
framework that utilizes the tight-binding Fisher-Lee relation to span
non-equilibrium Green's function (NEGF) techniques, the scattering method, and
semiclassical Boltzmann transport theory. Within this hybrid quantum-classical,
two-scale framework, we calculated transmission and reflection coefficients of
monolayer and bilayer Ag-silicene-Ag junctions using the NEGF method in
conjunction with density functional theory; derived and calculated the group
velocities; and computed resistance using the semi-classical Boltzmann
equation. We found that resistances of these junctions are $\sim${}$ 0.08 \fom$
for monolayer silicene junctions and $\sim${}$ 0.3 \fom$ for bilayer ones,
factors of $\sim$8 and $\sim$2, respectively, smaller than Sharvin resistances
estimated via the Landauer formalism.",1305.5285v1
2013-06-13,"Investigation of the quaternary Fe2-xCoxMnSi alloys by structural, magnetic, resistivity and spin polarization measurements","Effects of the Co substitution have been observed on the structural, magnetic
and magneto-transport properties of Fe2-xCoxMnSi alloy. Curie temperature (TC)
and saturation magnetization (MS) of these alloys increased linearly with the
Co substitution. Competitive magnetic interaction between ferromagnetic (FM)
and anti-ferromagnetic (AFM) phases exists in Fe2-xCoxMnSi for x less than 0.2,
AFM phase is completely disappears for x greater than or equal to 0.2. The
value of Rhodes-Wohlfarth ratio pc/ps is greater than one for these alloys
which is the characteristics of iterant magnetism present in the system.
M\""ossbauer spectroscopic measurements have been done to investigate the atomic
disorder and local magnetic moment for some x values. Resistivity measurements
also confirm the stability of ferromagnetism with the concentration of Co and
also show a sign of half metallicity. Resistivity shows semiconducting
behaviour for x = 0.4 which is interesting in view of spin gapless
semiconductors.",1306.3086v3
2013-06-21,Carrier density modulation in graphene underneath Ni electrode,"We investigate the transport properties of graphene underneath metal to
reveal whether the carrier density in graphene underneath source/drain
electrodes in graphene field-effect transistors is fixed. The resistance of the
graphene/Ni double-layered structure has shown a graphene-like back-gate bias
dependence. In other words, the electrical properties of graphene are not
significantly affected by its contact with Ni. This unexpected result may be
ascribed to resist residuals at the metal/graphene interface, which may reduce
the interaction between graphene and metals. In a back-gate device fabricated
using the conventional lithography technique with an organic resist, the
carrier density modulation in the graphene underneath the metal electrodes
should be considered when discussing the metal/graphene contact.",1306.5086v1
2013-07-29,Molecular Doping of Multilayer MoS2 Field-effect Transistors: Reduction in Sheet and Contact Resistances,"For the first time, polyethyleneimine (PEI) doping on multilayer MoS2
field-effect transistors are investigated. A 2.6 times reduction in sheet
resistance, and 1.2 times reduction in contact resistance have been achieved.
The enhanced electrical characteristics are also reflected in a 70% improvement
in ON current, and 50% improvement in extrinsic field-effect mobility. The
threshold voltage also confirms a negative shift upon the molecular doping. All
studies demonstrate the feasibility of PEI molecular doping in MoS2
transistors, and its potential applications in layer-structured semiconducting
2D crystals.",1307.7643v2
2013-09-15,Large lattice distortions associated with the magnetic transition in La0.7Sr0.3MnO3,"Colossal magnetoresistance (CMR) is associated with the phase transition from
a metallic ferromagnetic to insulating paramagnetic phase, which can be
controlled by an applied magnetic field. The insulating phase occurs due to
trapping of the charge carriers by polaronic lattice distortions, which raise
the resistivity. Theories based on local physics predict that the magnitude of
the resistivity jump at Tc is determined by how much, on average, the amplitude
of these distortions increases at the phase transition. Using neutron
scattering, we measured the average distortion amplitude in La0.7Sr0.3MnO3.
Surprisingly, its increase from below to above Tc is just as large as in other
manganites, which have a much larger resistivity jump. This result suggests
that the strength of CMR is determined not by the size of distortions, but by
their cooperative nature specific to each compound. Existing theories need to
be extended to include correlations between different unit cells to explain and
predict the strength of CMR.",1309.3747v1
2013-09-20,Surface-resistance measurements using superconducting stripline resonators,"We present a method to measure the absolute surface resistance of conductive
samples at a set of GHz frequencies with superconducting lead stripline
resonators at temperatures 1- 6K. The stripline structure can easily be applied
for bulk samples and allows direct calculation of the surface resistance
without the requirement of additional calibration measurements or sample
reference points. We further describe a correction method to reduce
experimental background on high-Q resonance modes by exploiting TEM-properties
of the external cabling. We then show applications of this method to the
reference materials gold, tantalum, and tin, which include the anomalous skin
effect and conventional superconductivity. Furthermore, we extract the complex
optical conductivity for an all-lead stripline resonator to find a coherence
peak and the superconducting gap of lead.",1309.5331v2
2013-10-17,The Influence of Ca and Y on the Microstructure and Corrosion Resistance of Vacuum Die Casting AZ91 Alloy,"The influence of Ca and Y on the microstructure and corrosion resistance of
vacuum die casting AZ91 alloy is investigated using optical microscope,
electron scanning microscope, weight-loss test and electrochemical corrosion
test. The results indicate that the microstructure of AZ91 alloy can be
refined, amount of Mg17Al12 phases is reduced, making Mg17Al12 phases transform
from banding to reticular, and stringer Al2Ca phases and block Al2Y phases are
formed through adding both Ca and Y. The corrosion resistance of AZ91 magnesium
alloy can be increased greatly by adding both Ca and Y. The corrosion rate of
AZ91-1.5Ca-1.0Y alloy is dropped to 16.2% of that of AZ91 alloy immersed in
3.5% NaCl aqueous solution for 24 hours. The corrosion current density of
AZ91-1.5Ca-1.0Y alloy is dropped by one order of magnitude.",1310.4671v1
2013-11-05,Effect of disorder on the resistivity anisotropy near the electronic nematic phase transition in pure and electron-doped BaFe$_2$As$_2$,"We show that the strain-induced resistivity anisotropy in the tetragonal
state of the representative underdoped Fe-arsenides BaFe$_2$As$_2$,
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ and Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$ is
independent of disorder over a wide range of defect and impurity
concentrations. This result demonstrates that the anisotropy in the in-plane
resistivity in the paramagnetic orthorhombic state of this material is not due
to elastic scattering from anisotropic defects, and is most easily understood
in terms of an intrinsic anisotropy in the electronic structure.",1311.0933v2
2013-11-14,Mechanically Modulated Tunneling Resistance in Monolayer MoS2,"We report on the modulation of tunneling resistance in MoS2 monolayers by
nano-indentation using an atomic force microscope (AFM). The resistance between
the conductive AFM tip and the bottom electrode separated by a monolayer MoS2
is reversibly reduced by up to 4 orders of magnitude, which is attributed to
enhanced quantum tunneling when the monolayer is compressed by the tip force.
Under the WKB approximation, the experimental data is quantitatively explained
by using the metal-insulator-metal tunneling diode model. As an ideal tunneling
medium, the defect-free, nanometer-thick MoS2 monolayer can serve as the active
layer for non-impacting nano-electro-mechanical switches.",1311.3608v1
2014-03-21,MoS2 Field-effect Transistors with Graphene/Metal Heterocontacts,"For the first time, n-type few-layer MoS2 field-effect transistors with
graphene/Ti as the hetero-contacts have been fabricated, showing more than 160
mA/mm drain current at 1 {\mu}m gate length with an on-off current ratio of
107. The enhanced electrical characteristic is confirmed in a nearly 2.1 times
improvement in on-resistance and a 3.3 times improvement in contact resistance
with hetero-contacts compared to the MoS2 FETs without graphene contact layer.
Temperature dependent study on MoS2/graphene hetero-contacts has been also
performed, still unveiling its Schottky contact nature. Transfer length method
and a devised I-V method have been introduced to study the contact resistance
and Schottky barrier height in MoS2/graphene /metal hetero-contacts structure.",1403.5485v2
2014-07-09,Thermal transport properties of metal/MoS2 interfaces from first principles,"Thermal transport properties at the metal/MoS2 interfaces are analyzed by
using an atomistic phonon transport model based on the Landauer formalism and
first-principles calculations. The considered structures include chemisorbed
Sc(0001)/MoS2 and Ru(0001)/MoS2, physisorbed Au(111)/MoS2, as well as
Pd(111)/MoS2 with intermediate characteristics. Calculated results illustrate a
distinctive dependence of thermal transfer on the details of interfacial
microstructures. More specifically, the chemisorbed case with a stronger
bonding exhibits a generally smaller interfacial thermal resistance than the
physisorbed. Comparison between metal/MoS2 and metal/graphene systems suggests
that metal/MoS2 is significantly more resistive. Further examination of lattice
dynamics identifies the presence of multiple distinct atomic planes and bonding
patterns at the interface as the key origin of the observed large thermal
resistance.",1407.2335v1
2014-10-30,Highly resistive epitaxial Mg-doped GdN thin films,"We report the growth by molecular beam epitaxy of highly resistive GdN, using
intentional doping with magnesium. Mg-doped GdN layers with resistivities of
1000 {\Omega}.cm and carrier concentrations of 10E16 cm-3 are obtained for
films with Mg concentrations up to 5 x 10E19 atoms/cm3. X-ray diffraction
rocking curves indicate that Mg-doped GdN films have crystalline quality very
similar to undoped GdN films, showing that the Mg doping did not affect the
structural properties of the films. A decrease of the Curie temperature with
decreasing the electron density is observed, supporting a recently suggested
magnetic polaron scenario [F. Natali et al., Phys. Rev. B 87, 035202 (2013)].",1410.8228v1
2014-11-12,Probing a spin-glass state in SrRuO3 thin films through higher-order statistics of resistance fluctuations,"The complex perovskite oxide SrRuO3 shows intriguing transport properties at
low temperatures due to the interplay of spin, charge, and orbital degrees of
freedom. One of the open questions in this system is regarding the origin and
nature of the low-temperature glassy state. In this paper we report on
measurements of higher-order statistics of resistance fluctuations performed in
epitaxial thin films of SrRuO3 to probe this issue. We observe large
low-frequency non-Gaussian resistance fluctuations over a certain temperature
range. Our observations are compatible with that of a spin-glass system with
properties described by hierarchical dynamics rather than with that of a simple
ferromagnet with a large coercivity.",1411.3101v1
2014-12-02,On the field dependent surface resistance of niobium on copper cavities,"The surface resistance Rs of superconducting cavities prepared by sputter
coating a thin niobium film on a copper substrate increases significantly
stronger with the applied RF field compared to cavities of bulk material. A
possible cause is that due to the thermal boundary resistance between the
copper substrate and the niobium film Rs is enhanced due to global heating of
the inner cavity wall. Introducing helium gas in the cavity and measuring its
pressure as a function of applied field allowed to conclude that the inner
surface of the cavity is heated up by only 60+/-60 mK when Rs increases with
Eacc by 100 nOhm. This is more than one order of magnitude less than what one
would expect from global heating. Additionally the effect of cooldown speed and
low temperature baking have been investigated in the framework of these
experiments. It is shown that for current state of the art niobium on copper
cavities there is only a detrimental effect of low temperature baking. A fast
cooldown results in a lowered Rs.",1412.0892v1
2015-01-20,Generation and detection of pure valley current by electrically induced Berry curvature in bilayer graphene,"Valley is a useful degree of freedom for non-dissipative electronics since
valley current that can flow even in an insulating material does not accompany
electronic current. We use dual-gated bilayer graphene in the Hall bar geometry
to electrically control broken inversion symmetry or Berry curvature as well as
the carrier density to generate and detect the pure valley current. We find a
large nonlocal resistance and a cubic scaling between the nonlocal resistance
and the local resistivity in the insulating regime at zero-magnetic field and
70 K as evidence of the pure valley current. The electrical control of the
valley current in the limit of zero conductivity allows non-dissipative
induction of valley current from electric field and thus provides a significant
contribution to the advancement of non-dissipative electronics.",1501.04776v1
2015-02-24,Unidirectional spin Hall magnetoresistance in ferromagnet/normal metal bilayers,"Magnetoresistive effects are usually invariant upon inversion of the
magnetization direction. In noncentrosymmetric conductors, however, nonlinear
resistive terms can give rise to a current dependence that is quadratic in the
applied voltage and linear in the magnetization. Here we demonstrate that such
conditions are realized in simple bilayer metal films where the spin-orbit
interaction and spin-dependent scattering couple the current-induced spin
accumulation to the electrical conductivity. We show that the longitudinal
resistance of Ta|Co and Pt|Co bilayers changes when reversing the polarity of
the current or the sign of the magnetization. This unidirectional
magnetoresistance scales linearly with current density and has opposite sign in
Ta and Pt, which we associate with the modification of the interface scattering
potential induced by the spin Hall effect in these materials. Our results
suggest a route to control the resistance and detect magnetization switching in
spintronic devices using a two-terminal geometry, which applies also to
heterostructures including topological insulators.",1502.06898v2
2015-08-17,"Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films: interplay between correlation, disorder, and spin-orbit coupling","We investigate the effects of compressive strain on the electrical
resistivity of 5d iridium based perovskite SrIrO3 by depositing epitaxial films
of thickness 35 nm on various substrates such as GdScO3 (110), DyScO3 (110),
and SrTiO3 (001). Surprisingly, we find anomalous transport behaviors in the
tempeature dependent resistivity, where the temperature exponent evolves
continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain.
Furthermore, magnetoresistance always remains positive irrespective of
resistivity upturns at low temperatures. These observations imply that the
delicate interplay between correlation and disorder in the presence of strong
spin-orbit coupling is responsible for the emergence of the non-Fermi liquid
behaviors in 5d perovskite SrIrO3 thin films. We offer a theoretical framework
for the interpretation of the experimental results.",1508.03944v1
2015-08-31,Scalable T^2 resistivity in a small single-component Fermi surface,"Scattering among electrons generates a distinct contribution to electrical
resistivity that follows a quadratic temperature dependence. In
strongly-correlated electron systems, the prefactor A of this T$^2$ resistivity
scales with the magnitude of the electronic specific heat. Here, we show that
one can change the magnitude of A by four orders of magnitude in metallic
SrTiO3 by tuning the concentration of the carriers and consequently, the Fermi
energy. The T$^2$ behavior persists in the single-band dilute limit despite the
absence of two known mechanisms for T$^2$ behavior, distinct electron
reservoirs and Umklapp processes. The results highlight the absence of a
microscopic theory for momentum decay through electron-electron scattering in
different Fermi liquids.",1508.07812v1
2015-08-31,In-Line-Test of Variability and Bit-Error-Rate of HfOx-Based Resistive Memory,"Spatial and temporal variability of HfOx-based resistive random access memory
(RRAM) are investigated for manufacturing and product designs. Manufacturing
variability is characterized at different levels including lots, wafers, and
chips. Bit-error-rate (BER) is proposed as a holistic parameter for the write
cycle resistance statistics. Using the electrical in-line-test cycle data, a
method is developed to derive BERs as functions of the design margin, to
provide guidance for technology evaluation and product design. The proposed BER
calculation can also be used in the off-line bench test and build-in-self-test
(BIST) for adaptive error correction and for the other types of random access
memories.",1509.00070v1
2015-11-30,Solidification and loss of hydrostaticity in liquid media used for pressure measurements,"We carried out a study of the pressure dependence of the solidification
temperature in nine pressure transmitting media that are liquid at ambient
temperature, under pressures up to 2.3 GPa. These fluids are: 1:1
isopentane/n-pentane, 4:6 light mineral oil/n-pentane, 1:1 isoamyl
alcohol/n-pentane, 4:1 methanol/ethanol, 1:1 FC72/FC84 (Fluorinert), Daphne
7373, isopentane, and Dow Corning PMX silicone oils 200 and 60,000 cst. We
relied on the sensitivity of the electrical resistivity of Ba(Fe1-xRux)2As2
single crystals to the freezing of the pressure media, and cross-checked with
corresponding anomalies observed in the resistance of the manganin coil that
served as the ambient temperature resistive manometer. In addition to
establishing the Temperature-Pressure line separating the liquid (hydrostatic)
and frozen (non-hydrostatic) phases, these data permit rough estimates of the
freezing pressure of these media at ambient temperature. This pressure
establishes the extreme limit for the medium to be considered hydrostatic. For
higher applied pressures the medium has to be treated as non-hydrostatic.",1512.00087v1
2015-12-18,The effect of quenching from different temperatures on Bi 0.88 Sb 0.12 alloy,"Structural, thermal, resistive and magnetic properties of melt quenched Bi
0.88 Sb 0.12 alloys are reported. The samples are heated at three different
temperatures, followed by rapid quenching in liquid nitrogen. Large temperature
difference between liquidus and solidus lines, led to microscopic
in-homogeneity in the alloy. The effect of quenching from different
temperatures in polycrystalline Bi 0.88 Sb 0.12 alloy has been studied. The
parameters such as strain, unit cell volume, and resistivity are found to
increase with temperature. Thermal variation of resistivity depicts non
monotonic temperature dependence. The total negative susceptibility increases
and band gap of semiconducting Bi 0.88 Sb 0.12 samples decreases with
increasing temperature.",1512.05883v1
2015-12-18,Exchange Bias and Bistable Magneto-Resistance States in Amorphous TbFeCo thin Films,"Amorphous TbFeCo thin films sputter deposited at room temperature on
thermally oxidized Si substrate are found to exhibit strong perpendicular
magnetic anisotropy (PMA). Atom probe tomography (APT), scanning transmission
electron microscopy (STEM), and energy dispersive spectroscopy (EDS) mapping
have revealed two nanoscale amorphous phases with different Tb atomic
percentages distributed within the amorphous film. Exchange bias accompanied by
bistable magneto-resistance states has been uncovered near room temperature by
magnetization and magneto-transport measurements. The exchange anisotropy
originates from the exchange interaction between the ferrimagnetic and
ferromagnetic components corresponding to the two amorphous phases. This study
provides a platform for exchange bias and magneto-resistance switching using
single-layer amorphous ferrimagnetic thin films that require no epitaxial
growth.",1512.06103v1
2015-12-23,Topological Critical Point and Resistivity Anomaly in HfTe5,"There is a long-standing confusion concerning the physical origin of the
anomalous resistivity peak in transition metal pentatelluride HfTe5. Several
mechanisms, like the formation of charge density wave or polaron, have been
proposed, but so far no conclusive evidence has been presented. In this work,
we investigate the unusual temperature dependence of magneto-transport
properties in HfTe5. We find that a three dimensional topological Dirac
semimetal state emerges only at around Tp (at which the resistivity shows a
pronounced peak), as manifested by a large negative magnetoresistance. This
accidental Dirac semimetal state mediates the topological quantum phase
transition between the two distinct weak and strong topological insulator
phases in HfTe5. Our work not only provides the first evidence of a
temperature-induced critical topological phase transition in HfTe5, but also
gives a reasonable explanation on the long-lasting question.",1512.07360v1
2016-01-03,Detection of DC currents and resistance measurements in longitudinal spin Seebeck effect experiments on Pt/YIG and Pt/NFO,"In this work we investigated thin films of the ferrimagnetic insulators YIG
and NFO capped with thin Pt layers in terms of the longitudinal spin Seebeck
effect (LSSE). The electric response detected in the Pt layer under an
out-of-plane temperature gradient can be interpreted as a pure spin current
converted into a charge current via the inverse spin Hall effect. Typically,
the transverse voltage is the quantity investigated in LSSE measurements (in
the range of \mu V). Here, we present the directly detected DC current (in the
range of nA) as an alternative quantity. Furthermore, we investigate the
resistance of the Pt layer in the LSSE configuration. We found an influence of
the test current on the resistance. The typical shape of the LSSE curve varies
for increasing test currents.",1601.00304v1
2016-04-25,Anisotropic transport and optical spectroscopy study on antiferromagentic triangular lattice EuCd_2As_2: an interplay between magnetism and charge transport properties,"We present anisotropic transport and optical spectroscopy studies on
EuCd_2As_2. The measurements reveal that EuCd_2As_2 is a low carrier density
semimetal with moderate anisotropic resistivity ratio. The charge carriers
experience very strong scattering from Eu magnetic moments, resulting in a
Kondo-like increase of resistivity at low temperature. Below the
antiferromagnetic transition temperature at $T_N$= 9.5 K, the resistivity drops
sharply due to the reduced scattering from the ordered Eu moments.
Nevertheless, the anisotropic ratio of $\rho_c/\rho_{ab}$ keeps increasing,
suggesting that the antiferromagnetic coupling is along the c-axis. The optical
spectroscopy measurement further reveals, besides an overdamped reflectance
plasma edge at low energy, a strong coupling between phonon and electronic
continuum. Our study suggests that EuCd_2As_2 is a promising candidate
displaying intriguing interplay among charge, magnetism and the underlying
crystal lattice.",1604.07114v2
2016-04-26,Multiband effects and the possible Dirac states in LaAgSb$_2$,"Here we report the possible signature of Dirac fermions in the
magnetoresistance, Hall resistivity and magnetothermopower of LaAgSb$_2$. The
opposite sign between Hall resistivity and Seebeck coefficient indicates the
multiband effect. Electronic structure calculation reveals the existence of the
linear bands and the parabolic bands crossing the Fermi level. The large linear
magnetoresistance was attributed to the quantum limit of the possible Dirac
fermions or the breakdown of weak-field magnetotransport at the charge density
wave phase transition. Analysis of Hall resistivity using two-band model
reveals that Dirac holes which dominate the electronic transport have much
higher mobility and larger density than conventional electrons. Magnetic field
suppresses the apparent Hall carrier density, and also induces the sign change
of the Seebeck coefficient from negative to positive. These effects are
possibly attributed to the magnetic field suppression of the density of states
at the Fermi level originating from the quantum limit of the possible Dirac
holes.",1604.07819v1
2016-04-27,Superconductivity at 7.8 K in the ternary LaRu2As2 compound,"Here we report the discovery of superconductivity in the ternary LaRu2As2
compound. The polycrystalline LaRu2As2 samples were synthesized by the
conventional solid state reaction method. Powder X-ray diffraction analysis
indicates that LaRu2As2 crystallizes in the ThCr2Si2-type crystal structure
with the space group I4/mmm (No. 139), and the refined lattice parameters are a
= 4.182(6) {\AA} and c = 10.590(3) {\AA}. The temperature dependent resistivity
measurement shows a clear superconducting transition with the onset Tc
(critical temperature) at 7.8 K, and zero resistivity happens at 6.8 K. The
upper critical field at zero temperature m0Hc2(0) was estimated to be 1.6 T
from the resistivity measurement. DC magnetic susceptibility measurement shows
a bulk superconducting Meissner transition at 7.0 K, and the isothermal
magnetization measurement indicates that LaRu2As2 is a type-II superconductor.",1604.07958v1
2016-06-02,First-principles calculation of the stabilities of lithium garnet compositions against hydration,"A series of density functional electronic structure calculations were carried
out to better understand the crystallographic factors governing the stability
of LinA3B2O12 lithium garnet phases against hydration. The reaction studied is
H2O + LinA3B2O12 = LiOH + HnA3B2O12. Most of the compositions are stable
against pure water; the main driving force for instability in the atmosphere is
the reaction of lithium hydroxide with CO2 to make lithium carbonate. The
calculated hydration resistance scales with the Pauling bond valence on the
oxygen atom contributed by the coordinating A and B ions. In the unexchanged
Li-garnets, this bond valence must be balanced by lithium, so there is also a
good overall correlation of hydration stability with lithium stoichiometry (n):
hydration resistance increases in the order Li8-garnet < Li7-garnet <
Li6-garnet < Li5-garnet < Li3-garnet. Only Li3A3B2O12 garnets have proton
exchange energies sufficiently positive to overcome the decomposition energy of
lithium hydroxide into lithium carbonate + water; the n=3 garnets are predicted
to be stable to hydration under atmospheric conditions, in agreement with
observations (Galven et al. Chem. Mater. 2012 24, 3335-3345). At a given
lithium ion stoichiometry, hydration resistance is greater for A, B ions having
smaller ionic radii.",1606.01807v1
2016-06-07,The temperature dependence of FeRh's transport properties,"The finite-temperature transport properties of FeRh compounds are
investigated by first-principles Density Functional Theory-based calculations.
The focus is on the behavior of the longitudinal resistivity with rising
temperature, which exhibits an abrupt decrease at the metamagnetic transition
point, $T = T_m$ between ferro- and antiferromagnetic phases. A detailed
electronic structure investigation for $T \geq 0$ K explains this feature and
demonstrates the important role of (i) the difference of the electronic
structure at the Fermi level between the two magnetically ordered states and
(ii) the different degree of thermally induced magnetic disorder in the
vicinity of $T_m$, giving different contributions to the resistivity. To
support these conclusions, we also describe the temperature dependence of the
spin-orbit induced anomalous Hall resistivity and Gilbert damping parameter.
For the various response quantities considered the impact of thermal lattice
vibrations and spin fluctuations on their temperature dependence is
investigated in detail. Comparison with corresponding experimental data finds
in general a very good agreement.",1606.02072v1
2016-06-21,Bad-Metal Relaxation Dynamics in a Fermi Lattice Gas,"We report the discovery of phenomena consistent with bad-metal relaxation
dynamics in the metallic regime of an optical-lattice Hubbard model. The
transport lifetime induced by inter-particle scattering for a mass current of
atoms excited by stimulated Raman transitions is measured, and the
corresponding analog of resistivity is inferred. By exploring a range of
temperature, we demonstrate incompatibility with weak-scattering theory and a
key characteristic of bad metals: anomalous resistivity scaling consistent with
$T$-linear behavior. We also observe the onset of two behaviors---incoherent
transport and the approach to the Mott-Ioffe-Regel limit---associated with bad
metals. The interaction and temperature scaling of resistivity are verified to
be consistent with dynamic mean-field theory (DMFT) predictions of a bad metal,
which is associated with the reduction of quasiparticle weight by strong
interactions.",1606.06669v5
2016-07-11,"The modification of the pore characteristics of activated carbon, for use in electrical double layer capacitors, through plasma processing","It was aimed to determine whether plasma processing could contribute to
enhanced capacitance and energy density of activated carbon electrode based
electrochemical capacitors, through the formation of additional surface
charges. While an increase of up to 35% of the gravimetric capacitance, along
with ~ 20% decrease in resistance, was obtained through optimal plasma
processing, increased plasma exposure yielded a drastic reduction (/increase)
in the capacitance (/resistance). It was also found that the capacitance and
resistance modulation was a sensitive function of sample processing as well as
electrochemical testing procedure. Considering the complexity of modeling
realistic porous matrices, a metric to parameterize the reach of an electrolyte
into the matrix has been posited.",1607.03201v1
2016-07-15,Chiral Phonons and Electrical Resistivity of Ferromagnetic Metals at Low Temperatures,"Ferromagnetism is an exciting phase of matter exhibiting strongly correlated
electron behavior and a standard example of spontaneously broken rotational
symmetry: below the Curie temperature, atomic magnets in an isotropic
single-domain ferromagnetic metal align along a spontaneously chosen direction.
The scattering of conduction electrons from thermal perturbations to this spin
order, together with electron-electron collisions, mark the material electrical
behavior at low temperatures, where the resistivity varies mostly quadratically
with the temperature. Around liquid-helium temperatures however, an interesting
phenomenon occurs, giving rise to an extra \emph{linear} contribution to the
variation of the electrical resistivity with temperature, whose theoretical
explanation has encountered problems for a long time. Here I introduce a
spin-flip scattering mechanism of conduction electrons in ferromagnetic metals
arising from their interaction with the internal magnetic induction and
mediated by chiral modes of the crystal lattice vibrations carrying spin 1.
This mechanism is able to explain the above anomaly and give a good account of
the spin-lattice relaxation times of iron, cobalt and nickel at room
temperatures.",1607.04585v2
2016-11-01,Boundary conditions and heat resistance at the moving solid--liquid interface,"Boundary conditions for the solid-liquid interface of the solidifying pure
melt have been derived. In the derivation the model of Gibbs interface is used.
The boundary conditions include both the state quantities of bulk phases are
taken at the interface and the quantities characterizing interfacial surface
such as the surface temperature and the surface heat flux. Introduction of the
surface temperature as an independent variable allows us to describe the
scattering energy at the interface. For the steady-state motion of the planar
interface the expression for the temperature discontinuity across the phase
boundary has been obtained. Effect of Kapitza resistance on the interface
velocity is considered. It is shown that heat resistance leads to non-linearity
in solidification kinetics, namely, in ""velocity-undercooling"" relationship.
The conditions of the steady--state motion of the planar interface has been
found.",1611.00160v1
2017-06-01,Edge transport in InAs and InAs/GaSb quantum wells,"We investigate low-temperature transport through single InAs quantum wells
and broken-gap InAs/GaSb double quantum wells. Non-local measurements in the
regime beyond bulk pinch-off confirm the presence of edge conduction in InAs
quantum wells. The edge resistivity of 1-2 $\mathrm{k\Omega/\mu m}$ is of the
same order of magnitude as edge resistivities measured in the InAs/GaSb double
quantum well system. Measurements in tilted magnetic field suggests an
anisotropy of the conducting regions at the edges with a larger extent in the
plane of the sample than normal to it. Finger gate samples on both material
systems shine light on the length dependence of the edge resistance with the
intent to unravel the nature of edge conduction in InAs/GaSb coupled quantum
wells.",1706.00320v1
2017-09-21,Zero-Field Quantum Critical Point in Ce$_{0.91}$Yb$_{0.09}$CoIn$_5$,"We present results of specific heat, electrical resistance, and
magnetoresistivity measurements on single crystals of the heavy-fermion
superconducting alloy Ce$_{0.91}$Yb$_{0.09}$CoIn$_5$. Non-Fermi liquid to Fermi
liquid crossovers are clearly observed in the temperature dependence of the
Sommerfeld coefficient $\gamma$ and resistivity data. Furthermore, we show that
the Yb-doped sample with $x=0.09$ exhibits universality due to an underlying
quantum phase transition without an applied magnetic field by utilizing the
scaling analysis of $\gamma$. Fitting of the heat capacity and resistivity data
based on existing theoretical models indicates that the zero-field quantum
critical point is of antiferromagnetic origin. Finally, we found that at zero
magnetic field the system undergoes a third-order phase transition at the
temperature $T_{c3}\approx 7$ K.",1709.07161v3
2017-12-01,Titanium Contacts to Graphene: Process-Induced Variability in Electronic and Thermal Transport,"Contact Resistance (RC) is a major limiting factor in the performance of
graphene devices. RC is sensitive to the quality of the interface and the
composition of the contact, which are affected by the graphene transfer process
and contact deposition conditions. In this work, a linear correlation is
observed between the composition of Ti contacts, characterized by X-ray
photoelectron spectroscopy, and the Ti/graphene (Gr) contact resistance
measured by the transfer length method. We find that contact composition is
tunable via deposition rate and base pressure. Reactor base pressure is found
to effect the resultant contact resistance. The effect of contact deposition
conditions on thermal transport measured by time-domain thermoreflectance is
also reported and interfaces with higher oxide composition appear to result in
a lower thermal boundary conductance. Possible origins of this thermal boundary
conductance change with oxide composition are discussed.",1712.00331v1
2017-12-04,Particle-hole symmetry reveals failed superconductivity in the metallic phase of two-dimensional superconducting films,"Electrons confined to two dimensions display an unexpected diversity of
behaviors as they are cooled to absolute zero. Noninteracting electrons are
predicted to eventually ""localize"" into an insulating ground state, and it has
long been supposed that electron correlations stabilize only one other phase:
superconductivity. However, many two-dimensional (2D) superconducting materials
have shown surprising evidence for metallic behavior, where the electrical
resistivity saturates in the zero-temperature limit, the nature of this
unexpected metallic state remains under intense scrutiny. We report electrical
transport properties for two disordered 2D superconductors, indium oxide and
tantalum nitride, and observe a magnetic field-tuned transition from a true
superconductor to a metallic phase with saturated resistivity. This metallic
phase is characterized by a vanishing Hall resistivity, suggesting that it
retains particle-hole symmetry from the disrupted superconducting state.",1712.00947v1
2018-01-15,A study of electron and thermal transport in layered Titanium disulphide single crystals,"We present a detailed study of thermal and electrical transport behavior of
single crystal Titanium disulphide flakes, which belongs to the two
dimensional, transition metal dichalcogenide class of materials. In-plane
Seebeck effect measurements revealed a typical metal-like linear temperature
dependence in the range of 85 - 285 K. Electrical transport measurements with
in-plane current geometry exhibited a nearly T^2 dependence of resistivity in
the range of 10 - 300 K. However, transport measurements along the out-of-plane
current geometry showed a transition in temperature dependence of resistivity
from T^2 to T^5 beyond 200 K. Interestingly, Au ion-irradiated TiS2 samples
showed a similar T 5 dependence of resistivity beyond 200 K, even in the
current-in-plane geometry. Micro- Raman measurements were performed to study
the phonon modes in both pristine and ion-irradiated TiS2 crystals.",1801.04677v1
2018-02-23,Possible charge-density-wave signatures in the anomalous resistivity of Li-intercalated multilayer MoS2,"We fabricate ion-gated field-effect transistors (iFET) on mechanically
exfoliated multilayer MoS$_2$. We encapsulate the flake by Al$_2$O$_3$, leaving
the device channel exposed at the edges only. A stable Li$^+$ intercalation in
the MoS$_2$ lattice is induced by gating the samples with a Li-based polymeric
electrolyte above $\sim$ 330 K and the doping state is fixed by quenching the
device to $\sim$ 300 K. This intercalation process induces the emergence of
anomalies in the temperature dependence of the sheet resistance and its first
derivative, which are typically associated with structural/electronic/magnetic
phase transitions. We suggest that these anomalies in the resistivity of
MoS$_2$ can be naturally interpreted as the signature of a transition to a
charge-density-wave phase induced by lithiation, in accordance with recent
theoretical calculations.",1802.08449v2
2018-03-13,Are thermal fluctuations the sole reason for finite longitudinal resistance in quantum anomalous Hall experiments?,"In some recent experiments [A. J. Bestwick, et. al., Phys. Rev. Lett. 114,
187201 (2015), Cui-Zu Chang, et. al., Nat. Materials. 14, 473-477 (2015)] it
has been shown that in observations of the quantum anomalous Hall (QAH) effect
the longitudinal resistance $R_L$ increases as temperature $T$ increases, while
Hall resistance $R_H$ loses its quantization with increase in $T$. This
behavior was explained due to increased thermal fluctuations as $T$ increases.
We show that similar effects arise in QAH samples with quasi-helical edge modes
as disorder increases in presence of inelastic scattering or otherwise even at
temperature $T=0$.",1803.04995v2
2018-03-21,Bad metallic transport in a modified Hubbard model,"Strongly correlated metals often display anomalous transport, including
$T$-linear resistivity above the Mott-Ioffe-Regel limit. We introduce a
tractable microscopic model for such bad metals, by supplementing the
well-known Hubbard model --- with hopping $t$ and on-site repulsion $U$ ---
with a `screened Coulomb' interaction between charge densities that decays
exponentially with spatial separation. This interaction entirely lifts the
extensive degeneracy in the spectrum of the $t=0$ Hubbard model, allowing us to
fully characterize the small $t$ electric, thermal and thermoelectric transport
in our strongly correlated model. Throughout the phase diagram we observe
$T$-linear resistivity above the Mott-Ioffe-Regel limit, together with strong
violation of the Weidemann-Franz law and a large thermopower that can undergo
sign change. At intermediate temperatures $t \ll k_B T \lesssim U$, the
approximate $T$-linear resistivity arises from a cancellation between the
nontrivial temperature dependence of both diffusivities and thermodynamic
susceptibilities, as observed in recent transport experiments on cold atomic
gases.",1803.08054v3
2018-04-06,Energy-Quality Scaling in Analog Mesh Computers,"The recent push for post-Moore computer architectures has introduced a wide
variety of application-specific accelerators. One particular accelerator, the
resistance network analogue, has been well received due to its ability to
efficiently solve partial differential equations by eliminating the iterative
stages required by today's numerical solvers. However, in the ago of
programmable integrated circuits, the static nature of the resistance network
analogue, and other analog mesh computers like it, has relegated it to an
academic curiosity. Recent developments in materials, such as the memristor,
have made the resistance network analogue viable for inclusion in future
heterogeneous computer architectures. However, selection of an appropriate
sized mesh to be incorporated into a computer system requires that
energy-quality trade-offs are made regarding the problem size and required
resolution of the solution. This paper provides an in-depth study of the
scaling of analog mesh computer hardware, from the perspective of energy per
bit and required resolution, introduces a metric to aid in quantifying analog
mesh computers with different parameters, and introduces a method of
virtualization which enables an analog mesh computer of a fixed size to
approximate the calculations of a larger-sized mesh.",1804.02389v2
2018-04-28,Nonequilibrium Mean-Field Theory of Resistive Phase Transitions,"We investigate the quantum mechanical origin of resistive phase transitions
in solids driven by a constant electric field in the vicinity of a
metal-insulator transition. We perform a nonequilibrium mean-field analysis of
a driven-dissipative anti-ferromagnet, which we solve analytically for the most
part. We find that the insulator-to-metal transition (IMT) and the
metal-to-insulator transition (MIT) proceed by two distinct electronic
mechanisms: Landau-Zener processes, and the destabilization of metallic state
by Joule heating, respectively. However, we show that both regimes can be
unified in a common effective thermal description, where the effective
temperature $T_{\rm eff}$ depends on the state of the system. This explains
recent experimental measurements in which the hot-electron temperature at the
IMT was found to match the equilibrium transition temperature. Our analytic
approach enables us to formulate testable predictions on the non-analytic
behavior of $I$-$V$ relation near the insulator-to-metal transition. Building
on these successes, we propose an effective Ginzburg-Landau theory which paves
the way to incorporating spatial fluctuations, and to bringing the theory
closer to a realistic description of the resistive switchings in correlated
materials.",1804.10733v1
2018-09-24,Fusion Between Frozen-Wave-Type Beams and Airy-Type Pulses: Diffraction-Dispersion-Attenuation Resistant Vortex Pulses in Absorbing Media,"In this paper we perform a fusion between two important theoretical
methodologies, one related to the Frozen Wave beams, which are non-diffracting
beams whose longitudinal intensity pattern can be chosen a priori in an medium
(absorbing or not), and the other related to the Airy-Type pulses, which are
pulses resistant to dispersion effects in dispersive materials. As a result, a
new method emerges, capable of providing vortex pulses resistant to three
concomitant effects, i.e.: diffraction, dispersion and attenuation; while
concurrently the spatial variation of the wave intensity along its axis of
propagation can be engineered at will. The new approach can be seen as a
generalization of the Localized Waves theory in the paraxial regime and the new
pulses can have potential applications in different fields such as optics
communications, nonlinear optics, micromanipulation, and so on.",1809.08740v1
2018-11-28,Investigation of effective thermoelectric properties of composite with interfacial resistance using micromechanics-based homogenisation,"We obtained the analytical expression for the effective thermoelectric
properties and dimensionless figure of merit of a composite with interfacial
electrical and thermal resistances using a micromechanics-based homogenisation.
For the first time, we derived the Eshelby tensor for a spherical inclusion as
a function of the interfacial resistances and obtained the solutions of the
effective Seebeck coefficient and the electrical and thermal conductivities of
a composite, which were validated against finite-element analysis (FEA). Our
analytical predictions well match the effective properties obtained from FEA
with an inclusion volume fraction up to 15%. Because the effective properties
were derived with the assumption of a small temperature difference, we discuss
a heuristic method for obtaining the effective properties in the case where a
thermoelectric composite is subjected to a large temperature difference.",1811.11340v2
2019-05-13,Quantum Oscillations of Electrical Resistivity in an Insulator,"In metals, orbital motions of conduction electrons on the Fermi surface are
quantized in magnetic fields, which is manifested by quantum oscillations in
electrical resistivity. This Landau quantization is generally absent in
insulators. Here we report a notable exception in an insulator, ytterbium
dodecaboride (YbB12). Despite much larger than that of metals, the resistivity
of YbB12 exhibits profound quantum oscillations. This unconventional
oscillation is shown to arise from the insulating bulk, yet the temperature
dependence of their amplitude follows the conventional Fermi liquid theory of
metals. The large effective masses indicate the presence of Fermi surface
consisting of strongly correlated electrons. Our result reveals a mysterious
bipartite ground state of YbB12: it is both a charge insulator and a strongly
correlated metal.",1905.05140v1
2019-09-27,Magnetoresistance effects in the metallic antiferromagnet Mn$_2$Au,"In antiferromagnetic spintronics, it is essential to separate the resistance
modifications of purely magnetic origin from other effects generated by current
pulses intended to switch the N\'eel vector. We investigate the
magnetoresistance effects resulting from magnetic field induced reorientations
of the staggered magnetization of epitaxial antiferromagnetic Mn2Au(001) thin
films. The samples were exposed to 60 T magnetic field pulses along different
crystallographic in-plane directions of Mn2Au(001), while their resistance was
measured. For the staggered magnetization aligned via a spin-flop transition
parallel to the easy [110]-direction, an ansiotropic magnetoresistance of -0.15
% was measured. In the case of a forced alignment of the staggered
magnetization parallel to the hard [100]-direction, evidence for a larger
anisotropic magnetoresistance effect was found. Furthermore, transient
resistance reductions of about 1 % were observed, which we associate with the
annihilation of antiferromagnetic domain walls by the magnetic field pulses.",1909.12606v3
2020-03-22,Monitoring of the formation of strontium molybdate intergrain tunneling barriers in strontium ferromolybdate,"This work is a contribution to the understanding of the electrical
resistivity in strontium ferromolybdate (SFMO) ceramics. It demonstrates that
an appropriate thermal treatment leads to the formation of dielectric SrMoO4
shells at the surface of SFMO nanograins. In samples without SrMoO4 shells, the
sign of the temperature coefficient of resistance changes with increasing
temperature from negative at very low temperature to positive at higher
temperatures. Samples exhibiting a negative temperature coefficient contain
SrMoO4 shells and demonstrate a behavior of the resistivity that can be
described in terms of the fluctuation-induced tunneling model, and near room
temperature the conductivity mechanism converts to a variable-range hopping
one. The results of this work serve as a starting point for the understanding
of the low-field magnetoresistance which is very promising for spintronic
device application.",2003.09997v1
2014-08-15,Correlation between electrical and magnetic properties of phase separated manganites studied with a General Effective Medium model,"We have performed electrical resistivity and DC magnetization measurements as
a function of temperature, on polycrystalline samples of phase separated
LaPrCaMnO. We have used the General Effective Medium Theory to obtain
theoretical resistivity vs. temperature curves corresponding to different fixed
ferromagnetic volume fraction values, assuming that the sample is a mixture of
typical metallic like and insulating manganites. By comparing this data with
our experimental resistivity curves we have obtained the relative ferromagnetic
volume fraction of our sample as a function of temperature. This result matches
with the corresponding magnetization data in excellent agreement, showing that
a mixed phase scenario is the key element to explain both the magnetic and
transport properties in the present compound.",1408.3599v1
2014-08-28,Room temperature giant baroresistance and magnetoresistance and its tunability in Pd doped FeRh,"We report room temperature giant baro-resistance ($\approx$128\%) in
$Fe_{49}(Rh_{0.93}Pd_{0.07})_{51}$. With the application of external pressure
and magnetic field the temperature range of giant baro-resistance
($\approx$600\% at 5K and 19.9 kbar and 8 Tesla) and magnetoresistance
($\approx$-85\% at 5K and 8 tesla) can be tuned from 5 K to well above room
temperature. As the AFM state is stabilized at room temperature under external
pressure, it shows giant room temperature magnetoresistance ($\approx$-55\%)
with magnetic field. Due to coupled magnetic and latticel changes, the
isothermal change in room temperature resistivity with pressure (in the absence
of applied magnetic field) as well as magnetic field (under various constant
pressure) can be scaled together to a single curve when plotted as a function
of X = T + 12.8*H - 7.2*P.",1408.6688v1
2017-01-18,Iron-based superconductivity extended to the novel silicide LaFeSiH,"We report the synthesis and characterization of the novel silicide LaFeSiH
displaying superconductivity with onset at 11 K. We find that this
pnictogen-free compound is isostructural to LaFeAsO, with a similar
low-temperature tetragonal to orthorhombic distortion. Using density functional
theory we show that this system is also a multiband metal in which the
orthorhombic distortion is likely related to single-stripe antiferromagnetic
order. Electrical resistivity and magnetic susceptibility measurements reveal
that these features occur side-by-side with superconductivity, which is
suppressed by external pressure.",1701.05010v3
2017-03-09,Oxygen migration during resistance switching and failure of hafnium oxide memristors,"While the recent establishment of the role of thermophoresis/diffusion-driven
oxygen migration during resistance switching in metal oxide memristors provided
critical insights required for memristor modeling, extended investigations of
the role of oxygen migration during ageing and failure remain to be detailed.
Such detailing will enable failure-tolerant design, which can lead to enhanced
performance of memristor-based next-generation storage-class memory. Here we
directly observed lateral oxygen migration using in-situ synchrotron x-ray
absorption spectromicroscopy of HfOx memristors during initial resistance
switching, wear over millions of switching cycles, and eventual failure,
through which we determined potential physical causes of failure. Using this
information, we reengineered devices to mitigate three failure mechanisms, and
demonstrated an improvement in endurance of about three orders of magnitude.",1703.03106v1
2018-10-09,Electron scattering by short range defects and resistivity of graphene,"The electron scattering by the short-range defects in the monolayer graphene
is considered in the framework of the flatland model. We analyze the effect of
this scattering on the electronic resistivity of the monolayer graphene (direct
problem) and develop a procedure for determination of the defect potential from
resistivity data (inverse problem). We use an approximation of the short-range
perturbation by the delta-shell potential that is reasonable since it
suppresses irrelevant short wavelength excitations. Our theoretical results
proved to be in a good agreement with experiment on suspended monolayer
graphene. It means that our model correctly describes essential features of the
physical problem under consideration. It gives possibility to consider the
inverse problem, i.e. on the basis of our results for direct problem to develop
a procedure for determination of parameters of the monolayer graphene sample
using experimental measurements for it. Thus the obtained results give new
important possibilities, which can be used in numerous applications.",1810.03897v1
2018-10-16,Studies of two-dimensional MoS2 on enhancing the electrical performance of ultrathin copper films,"Copper nanowires are widely used as on-chip interconnects due to superior
conductivity. However, with aggressive Cu interconnect scaling, the diffusive
surface scattering of electrons drastically increases the electrical
resistivity. In this work, we studied the electrical performance of Cu thin
films on different materials. By comparing the thickness dependence of Cu films
resistivity on MoS2 and SiO2, we demonstrated that two-dimensional MoS2 can be
used to enhance the electrical performance of ultrathin Cu films due to a
partial specular surface scattering. By fitting the experimental data with the
theoretical Fuchs Sondheimer model, we obtained the specularity parameter at
the Cu MoS2 interface in the temperature range 2K to 300K. Furthermore, first
principle calculations based on the density functional theory indicates that
there are more localized states at the Cu amorphous SiO2 interface than the Cu
MoS2 interface which is responsible for the higher resistivity in the Cu SiO2
heterostructure due to more severe electron scattering. Our results suggest
that Cu MoS2 hybrid is a promising candidate structure for the future
generations of CMOS interconnects.",1810.06772v1
2019-02-01,Graph Resistance and Learning from Pairwise Comparisons,"We consider the problem of learning the qualities of a collection of items by
performing noisy comparisons among them. Following the standard paradigm, we
assume there is a fixed ""comparison graph"" and every neighboring pair of items
in this graph is compared $k$ times according to the Bradley-Terry-Luce model
(where the probability than an item wins a comparison is proportional the item
quality). We are interested in how the relative error in quality estimation
scales with the comparison graph in the regime where $k$ is large. We prove
that, after a known transition period, the relevant graph-theoretic quantity is
the square root of the resistance of the comparison graph. Specifically, we
provide an algorithm that is minimax optimal. The algorithm has a relative
error decay that scales with the square root of the graph resistance, and
provide a matching lower bound (up to log factors). The performance guarantee
of our algorithm, both in terms of the graph and the skewness of the item
quality distribution, outperforms earlier results.",1902.00141v2
2019-02-06,AlGaN /GaN superlattice based p-channel field effect transistor (pFET) with TMAH treatment,"To realize the full spectrum of advantages that the III-nitride materials
system offers, the demonstration of p-channel III-nitride based devices is
valuable. Authors report the first p-type field effect transistor (pFET) based
on an AlGaN/GaN superlattice (SL), grown using MOCVD. Magnesium was used as the
p-type dopant. A sheet resistance of 11.6 k{\Omega}/sq, and a contact
resistance of 14.9{\Omega}.mm was determined using transmission line
measurements (TLM) for a Mg doping of 1.5e19cm^-3 of Mg. Mobilities in the
range of 7-10 cm\^2/Vs and a total sheet charge density in the range of
1e13-6e13 cm-2 were measured using room temperature Hall effect measurements.
Without Tetramethylammonium hydroxide (TMAH) treatment, the fabricated pFETs
had a maximum drain-source current (IDS) of 3mA/mm and an On-Resistance (RON)
of 3.48 k{\Omega}.mm, and did not turn-off completely. With TMAH treatment
during fabrication, a maximum IDS of 4.5mA/mm, RON of 2.2k{\Omega}.mm, and five
orders of current modulation was demonstrated, which is the highest achieved
for a p-type transistor based on (Al,Ga)N.",1902.02022v2
2019-02-26,Au-Ge alloys for wide-range low-temperature on-chip thermometry,"We present results of a Au-Ge alloy that is useful as a resistance-based
thermometer from room temperature down to at least \SI{0.2}{\kelvin}. Over a
wide range, the electrical resistivity of the alloy shows a logarithmic
temperature dependence, which simultaneously retains the sensitivity required
for practical thermometry while also maintaining a relatively modest and
easily-measurable value of resistivity. We characterize the sensitivity of the
alloy as a possible thermometer and show that it compares favorably to
commercially-available temperature sensors. We experimentally identify that the
characteristic logarithmic temperature dependence of the alloy stems from
Kondo-like behavior induced by the specific heat treatment it undergoes.",1902.10111v2
2019-07-11,DC Electrical Degradation of YSZ: Voltage Controlled Electrical Metallization of A Fast Ion Conducting Insulator,"DC electrical degradation as a form of dielectric and resistance breakdown is
a common phenomenon in thin-film devices including resistance-switching memory.
To obtain design data and to probe the degradation mechanism, highly
accelerated lifetime tests (HALT) are often conducted at higher temperatures
with thicker samples. While the mechanism is well established in semiconducting
oxides such as perovskite titanates, it is not in stabilized zirconia and other
fast oxygen-ion conductors that have little electronic conductivity. Here we
model the mechanism by an oxygen-driven, transport-limited, metal-insulator
transition, which finds support in rich experimental observations - including
in situ videos and variable temperature studies - of yttria-stabilized
zirconia. They are contrasted with the findings in semiconducting titanates and
resistance memory, and provide new insight into ceramic processing with
extremely rapid heating and cooling such as flash sintering and melt
processing.",1907.05479v2
2020-02-17,Transport mechanism in amorphous molybdenum silicide thin films,"Amorphous molybdenum silicide compounds have attracted significant interest
for potential device applications, particularly in single-photon detector. In
this work, the temperature-dependent resistance and magneto-resistance
behaviors were measured to reveal the charge transport mechanism, which is of
great importance for applications but is still insufficient. It is found that
Mott variable hopping conductivity dominates the transport of sputtered
amorphous molybdenum silicide thin films. Additionally, the observed
magneto-resistance crossover from negative to positive is ascribed to the
interference enhancement and the shrinkage of electron wave function, both of
which vary the probability of hopping between localized sites.",2002.06884v3
2020-09-17,Restored strange metal phase through suppression of charge density waves in underdoped YBa$_2$Cu$_3$O$_{7-δ}$,"The normal state of optimally doped cuprates is dominated by the ""strange
metal"" phase that shows a linear temperature ($T$) dependence of the
resistivity persisting down to the lowest $T$. For underdoped cuprates this
behavior is lost below the pseudogap temperature $T^*$, where Charge Density
Waves (CDW) together with other intertwined local orders characterize the
ground state. Here we show that the $T$-linear resistivity of highly strained,
ultrathin and underdoped YBa$_2$Cu$_3$O$_{7-\delta}$ films is restored when the
CDW amplitude, detected by Resonant Inelastic X-ray scattering, is suppressed.
This observation points towards an intimate connection between the onset of CDW
and the departure from $T$-linear resistivity in underdoped cuprates. Our
results illustrate the potential of using strain control to manipulate the
ground state of quantum materials.",2009.08398v3
2007-10-03,The effect of ozone oxidation on single-walled carbon nanotubes,"Exposing single-walled carbon nanotubes to room temperature UV-generated
ozone leads to an irreversible increase in their electrical resistance. We
demonstrate that the increased resistance is due to ozone oxidation on the
sidewalls of the nanotubes rather than at the end caps. Raman and x-ray
photoelectron spectroscopy show an increase in the defect density due to the
oxidation of the nanotubes. Using ultraviolet photoelectron spectroscopy we
show that these defects represent the removal of pi-conjugated electron states
near the Fermi level, leading to the observed increase in electrical
resistance. Oxidation of carbon nanotubes is an important first step in many
chemical functionalization processes. Since the oxidation rate is controllable
with short exposures, UV-generated ozone offers the potential for use as a
low-thermal budget processing tool.",0710.0803v1
2012-01-13,Intermediate state switching dynamics in magnetic double layer nanopillars grown by molecular beam epitaxy,"We observe a stable intermediate resistance switching state in the current
perpendicular to plane geometry for all Co/Cu/Co double layer nanopillar
junctions grown by molecular beam epitaxy. This novel state has a resistance
between the resistances of the parallel and antiparallel alignment of both
Co-layer magnetizations. The state, which originates from an additional
in-plane magnetic easy axis, can be reached by spin transfer torque switching
or by an external magnetic field. In addition to spin torque-induced coherent
small-angle spin wave modes we observe a broad microwave emission spectrum. The
latter is attributed to incoherent magnetic excitations that lead to a
switching between the intermediate state and the parallel or antiparallel
alignment of both ferromagnetic layers. We conclude that the additional
magnetic easy axis suppresses a stable trajectory of coherent large-angle
precession, which is not observed in our samples.",1201.2752v1
2012-01-14,Length dependence of the resistance in graphite: Influence of ballistic transport,"Using a linear array of voltage electrodes with a separation of several
micrometers on a $20 $nm thick and 30 $\mu$m long multigraphene sample we show
that the measured resistance does not follow the usual length dependence
according to Ohm's law. The deviations can be quantitatively explained taking
into account Sharvin-Knudsen formula for ballistic transport. This allows us to
obtain without free parameters the mean free path of the carriers in the sample
at different temperatures. In agreement with recently reported values obtained
with a different experimental method, we obtain that the carrier mean free path
is of the order of $\sim 2 \mu$m with a mobility $\mu \sim 10^7
$cm$^{2}$V$^{-1}$s$^{-1}$. The results indicate that the usual Ohm's law is not
adequate to calculate the absolute resistivity of mesoscopic graphite samples.",1201.3004v1
2012-01-14,Temperature dependence of the thermal boundary resistivity of glass-embedded metal nanoparticles,"The temperature dependence of the thermal boundary resistivity is
investigated in glass-embedded Ag particles of radius 4.5 nm, in the
temperature range from 300 to 70 K, using all-optical time-resolved
nanocalorimetry. The present results provide a benchmark for theories aiming at
explaining the thermal boundary resistivity at the interface between metal
nanoparticles and their environment, a topic of great relevance when tailoring
thermal energy delivery from nanoparticles as for applications in nanomedicine
and thermal management at the nanoscale",1201.3034v1
2014-01-07,Images of edge current in InAs/GaSb quantum wells,"Quantum spin Hall devices with edges much longer than several microns do not
display ballistic transport: that is, their measured conductances are much less
than $e^2/h$ per edge. We imaged edge currents in InAs/GaSb quantum wells with
long edges and determined an effective edge resistance. Surprisingly, although
the effective edge resistance is much greater than $h/e^2$, it is independent
of temperature up to 30 K within experimental resolution. Known candidate
scattering mechanisms do not explain our observation of an effective edge
resistance that is large yet temperature-independent.",1401.1531v2
2016-03-12,Spin Hall Effect and Origins of Nonlocal Resistance in Adatom-Decorated Graphene,"Recent experiments reporting unexpectedly large spin Hall effect (SHE) in
graphene decorated with adatoms have raised a fierce controversy. We apply
numerically exact Kubo and Landauer- Buttiker formulas to realistic models of
gold-decorated disordered graphene (including adatom clustering) to obtain the
spin Hall conductivity and spin Hall angle, as well as the nonlocal resistance
as a quantity accessible to experiments. Large spin Hall angles of 0.1 are
obtained at zero-temperature, but their dependence on adatom clustering differs
from the predictions of semiclassical transport theories. Furthermore, we find
multiple background contributions to the nonlocal resistance, some of which are
unrelated to SHE or any other spin-dependent origin, as well as a strong
suppression of SHE at room temperature. This motivates us to design a
multiterminal graphene geometry which suppresses these background contributions
and could, therefore, quantify the upper limit for spin current generation in
two-dimensional materials.",1603.03870v3
2016-03-17,Electrical Writing of Magnetic and Resistive Multistates in CoFe Films Deposited onto Pb[Zr$_x$Ti$_{1-x}$]O$_3$,"Electric control of magnetic properties is an important challenge for modern
magnetism and spintronic development. In particular, an ability to write
magnetic state electrically would be highly beneficial. Among other methods,
the use of electric field induced deformation of piezoelectric elements is a
promising low-energy approach for magnetization control. We investigate the
system of piezoelectric substrate Pb[Zr$_x$Ti$_{1-x}$]O$_3$ with CoFe
overlayers, extending the known reversible bistable electro-magnetic coupling
to surface and multistate operations, adding the initial state reset
possibility. Increasing the CoFe thickness improves the magnetoresistive
sensitivity, but at the expenses of decreasing the strain-mediated coupling,
with optimum magnetic thin film thickness of the order of 100 nm. The simplest
resistance strain gauge structure is realized and discussed as a multistate
memory cell demonstrating both resistive memory (RRAM) and magnetoresistive
memory (MRAM) functionalities in a single structure.",1603.05476v1
2018-08-26,Supercondutivity in SnSb with natural superlattice structure,"We report the results of electrical resistivity, magnetic and thermodynamic
measurements on polycrystalline SnSb, whose structure consists of stacks of Sb
bilayers and Sn4Sb3 septuple layers along the c-axis. The material is found to
be a weakly coupled, fully gapped, type-II superconductor with a bulk Tc of
1.50 K, while showing a zero resistivity transition at a significantly higher
temperature of 2.48 K. The Sommerfeld coefficient and upper critical field,
obtained from specific heat measurements, are 2.29 mJ/mol K and 520 Oe,
respectively. Compositional inhomogeneity and strain effect at the grain
boundaries are proposed as possible origins for the difference in resistive and
bulk superconducting transitions.In addition, a comparison with the rock-salt
structure SnAs superconductor is presented. Our results provide the first clear
evidence of bulk superconductivity in a natural superlattice derived from a
topological semimetal.",1808.08500v2
2019-03-03,Scaling parameters in anomalous and nonlinear Hall effects depend on temperature,"In the study of the anomalous Hall effect, the scaling relations between the
anomalous Hall and longitudinal resistivities play the central role. The
scaling parameters by definition are fixed as the scaling variable
(longitudinal resistivity) changes. Contrary to this paradigm, we unveil that
the electron-phonon scattering can result in apparent temperature-dependence of
scaling parameters when the longitudinal resistivity is tuned through
temperature. An experimental approach is proposed to observe this hitherto
unexpected temperature-dependence. We further show that this phenomenon also
exists in the nonlinear Hall effect in nonmagnetic inversion-breaking materials
and may help identify experimentally the presence of the side-jump contribution
besides the Berry-curvature dipole.",1903.00810v5
2019-03-19,Composition dependence of magnetoresistance in Fe$_{1-x}$Ni$_{x}$ alloys,"Resistance of Fe$_{1-x}$Ni$_x$(x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.9)
has been measured using four probe method from 5K to 300K with and without a
longitudinal magnetic field of 8T. The zero field resistivity of x=0.1 and 0.9
alloys, predominant contribution to resistivity above near room temperature is
due to electron-phonon scattering, whereas for x=05 and 0.7 alloys
electron-magnon scattering is dominant. Alloys with x=0.1 and 0.9 exhibit
positive magnetoresistance(MR) from 5K to 300K. For x=0.5 and 0.7 alloys,
magnetoresistance changes sign from positive to negative with increase in
temperature. The temperature at which sign changes increase with Ni
concentration in the alloy. The field dependent magnetoresistance is positive
for x=0.1, 0.7 and 0.9 alloys whereas it is negative for x=0.5 alloy. MR
follows linear behaviour with field for x=0.1 alloy. MR of all other alloys
follow a second order polynomial in field.",1903.08230v3
2019-03-26,Controlled inter-state switching between quantized conductance states in resistive devices for multilevel memory,"A detailed understanding of quantization conductance (QC), their correlation
with resistive switching phenomena and controlled manipulation of quantized
states is crucial for realizing atomic-scale multilevel memory elements. Here,
we demonstrate highly stable and reproducible quantized conductance states
(QC-states) in Al/Niobium oxide/Pt resistive switching devices. Three levels of
control over the QC-states, required for multilevel quantized state memories,
like, switching ON to different quantized states, switching OFF from quantized
states, and controlled inter-state switching among one QC states to another has
been demonstrated by imposing limiting conditions of stop-voltage and current
compliance. The well defined multiple QC-states along with a working principle
for switching among various states show promise for implementation of
multilevel memory devices.",1903.10688v1
2019-12-11,Current-induced fragmentation of antiferromagnetic domains,"Electrical and optical pulsing allow for manipulating the order parameter and
magnetoresistance of antiferromagnets, opening novel prospects for digital and
analog data storage in spintronic devices. Recent experiments in CuMnAs have
demonstrated giant resistive switching signals in single-layer
antiferromagnetic films together with analog switching and relaxation
characteristics relevant for neuromorphic computing. Here we report
simultaneous electrical pulsing and scanning NV magnetometry of
antiferromagnetic domains in CuMnAs performed using a pump-probe scheme. We
observe a nano-scale fragmentation of the antiferromagnetic domains, which is
controlled by the current amplitude and independent on the current direction.
The fragmented antiferromagnetic state conserves a memory of the pristine
domain pattern, towards which it relaxes. Domain fragmentation coexists with
permanent switching due to the reorientation of the antiferromagnetic moments.
Our simultaneous imaging and resistance measurements show a correlation between
the antiferromagnetic domain fragmentation and the largest resistive switching
signals in CuMnAs.",1912.05287v1
2019-12-12,Aharonov-Bohm oscillations of four-probe resistance in topological quantum rings in silicene and bilayer graphene,"We consider observation of Aharonov-Bohm oscillations in clean systems based
on the flow of topologically protected currents in silicene and bilayer
graphene. The chiral channels in these materials are defined by the flips of
the vertical electric field. The line of the flip confines chiral currents
flowing along it in the direction determined by the valley. We present an
electric field profile that forms a crossed ring to which four terminals can be
attached, and find that the conductance matrix elements oscillate in the
perpendicular magnetic field in spite of the absence of backscattering. We
propose a four-probe resistance measurement setup, and demonstrate that the
resistance oscillations have large visibility provided that the system is
prepared in such a way that a direct transfer of the chiral carriers between
the current probes is forbidden.",1912.05876v2
2021-01-13,Hinge Spin Polarization in Magnetic Topological Insulators Revealed by Resistance Switch,"We report on the possibility to detect hinge spin polarization in magnetic
topological insulators by resistance measurements. By implementing a
three-dimensional model of magnetic topological insulators into a
multi-terminal device with ferromagnetic contacts near the top surface, local
spin features of the chiral edge modes are unveiled. We find local spin
polarization at the hinges that inverts sign between top and bottom surfaces.
At the opposite edge, the topological state with inverted spin polarization
propagates in the reverse direction. Large resistance switch between forward
and backward propagating states is obtained, driven by the matching between the
spin polarized hinges and the ferromagnetic contacts. This feature is general
to the ferromagnetic, antiferromagnetic and canted-antiferromagnetic phases,
and enables the design of spin-sensitive devices, with the possibility of
reversing the hinge spin polarization of the currents.",2101.05293v2
2021-01-26,Demystifying strange metal and violation of Luttinger theorem in a doped Mott insulator,"Metallic states coined strange metal (SM), with robust linear-$T$
resistivity, have been widely observed in many quantum materials under strong
electron correlation, ranging from high-$T_{c}$ cuprate superconductor, organic
superconductor to twisted multilayer graphene and MoTe$_{2}$/WSe$_{2}$
superlattice. Despite decades of intensive studies, the mystery of strange
metal still defies any sensible theoretical explanation and has been the key
puzzle in modern condensed matter physics. Here, we solve a doped Mott
insulator model, which unambiguously exhibits SM phenomena accompanied with
quantum critical scaling in observables, e.g. resistivity, susceptibility and
specific heat. Closer look at SM reveals the breakdown of Landau's Fermi liquid
without any symmetry-breaking, i.e. the violation of Luttinger theorem.
Examining electron's self-energy extracted from numerical simulation provides
the explanation on the origin of linear-$T$ resistivity and suggests that the
long-overlooked static fluctuations in literature play an essential role in
non-Fermi liquid behaviors in correlated electron systems.",2101.10611v3
2012-06-15,A ferroelectric memristor,"Memristors are continuously tunable resistors that emulate synapses.
Conceptualized in the 1970s, they traditionally operate by voltage-induced
displacements of matter, but the mechanism remains controversial. Purely
electronic memristors have recently emerged based on well-established physical
phenomena with albeit modest resistance changes. Here we demonstrate that
voltage-controlled domain configurations in ferroelectric tunnel barriers yield
memristive behaviour with resistance variations exceeding two orders of
magnitude and a 10 ns operation speed. Using models of ferroelectric-domain
nucleation and growth we explain the quasi-continuous resistance variations and
derive a simple analytical expression for the memristive effect. Our results
suggest new opportunities for ferroelectrics as the hardware basis of future
neuromorphic computational architectures.",1206.3397v1
2015-04-30,Study of the Negative Magneto-Resistance of Single Proton-Implanted Lithium-Doped ZnO Microwires,"The magneto-transport properties of single proton-implanted ZnO and of
Li(7\%)-doped ZnO microwires have been studied. The as-grown microwires were
highly insulating and not magnetic. After proton implantation the Li(7\%) doped
ZnO microwires showed a non monotonous behavior of the negative
magneto-resistance (MR) at temperature above 150 K. This is in contrast to the
monotonous NMR observed below 50 K for proton-implanted ZnO. The observed
difference in the transport properties of the wires is related to the amount of
stable Zn vacancies created at the near surface region by the proton
implantation and Li doping. The magnetic field dependence of the resistance
might be explained by the formation of a magnetic/non magnetic heterostructure
in the wire after proton implantation.",1504.08230v1
2015-07-29,Integration of a 2D Periodic Nanopattern Into Thin Film Polycrystalline Silicon Solar Cells by Nanoimprint Lithography,"The integration of two-dimensional (2D) periodic nanopattern defined by
nanoimprint lithography and dry etching into aluminum induced crystallization
(AIC) based polycrystalline silicon (Poly-Si) thin film solar cells is
investigated experimentally. Compared to the unpatterned cell an increase of 6%
in the light absorption has been achieved thanks to the nanopattern which, in
turn, increased the short circuit current from 20.6 mA/cm2 to 23.8 mA/cm2. The
efficiency, on the other hand, has limitedly increased from 6.4% to 6.7%. We
show using the transfer length method (TLM) that the surface topography
modification caused by the nanopattern has increased the sheet resistance of
the antireflection coating (ARC) layer as well as the contact resistance
between the ARC layer and the emitter front contacts. This, in turn, resulted
in increased series resistance of the nanopatterned cell which has translated
into a decreased fill factor, explaining the limited increase in efficiency.",1507.08341v1
2019-06-03,Observations of zero electrical resistance of Au-Ag thin films near room temperature,"Recent observations of superconducting like transition at 286 K in Ag and Ag
nanostructures by Thapa et al. (arxiv: 1807.08572) have rekindled the hope for
room temperature superconductivity under ambient conditions. We also
investigated the electrical properties of Ag-Au nanostructure in the form of
thin film grown on SiO2/Si substrate by DC sputtering and observed signature of
zero resistance in the temperatures range of 243 K to 275 K. While the observed
electrical resistance of samples shows intriguing and perplexing behavior under
temperature cycling and external magnetic field; the large spatial
inhomogeneity present in thin film hampers the reproducibility indicating the
stability issues associated with superconducting like phase.",1906.00708v1
2019-06-24,Combination of informational storage and logical processing based on an all-oxide asymmetric multiferroic tunnel junction,"Multiferroic tunnel junctions (MFTJs) have already been proved to be
promising candidates for application in spintronics devices. The coupling
between tunnel magnetoresistance (TMR) and tunnel electroresistance (TER) in
MFTJs can provide four distinct resistive states in a single memory cell. Here
we show that in an all-oxide asymmetric MFTJ of La0.7Sr0.3MnO3 /PbZr0.2Ti0.8O3
/La0.7Te0.3MnO3 (LSMO/PZT/LTMO) with p-type and n-type electrodes, the
intrinsic rectification is observed and can be modified by the ferroelectric
polarization of PZT. Owing to the combined TMR, TER and diode effects, two
different groups of four resistive states under opposite reading biases are
performed. With two parallel asymmetric junctions and the appropriate series
resistance, the coexistence of logic units and quaternary memory cells can be
realized in the same array devices. The asymmetric MFTJ structure enables more
possibilities for designing next generation of multi-states memory and logical
devices with higher storage density, lower energy consumption and significantly
increased integration level.",1906.09993v1
2019-10-04,Nonvolatile Multilevel States in Multiferroic Tunnel Junctions,"Manipulation of tunneling spin-polarized electrons via a ferroelectric
interlayer sandwiched between two ferromagnetic electrodes, dubbed Multiferroic
Tunnel Junctions (MFTJs), can be achieved not only by the magnetic alignments
of two ferromagnets but also by the electric polarization of the ferroelectric
interlayer, providing great opportunities for next-generation multi-state
memory devices. Here we show that a La0.67Sr0.33MnO3
(LSMO)/PbZr0.2Ti0.8O3(PZT)/Co structured MFTJ device can exhibit multilevel
resistance states in the presence of gradually reversed ferroelectric domains
via tunneling electro-resistance and tunneling magnetoresistance, respectively.
The nonvolatile ferroelectric control in the MFTJ can be attributed to separate
contributions arising from two independent ferroelectric channels in the PZT
interlayer with opposite polarization. Our study shows the dominant role of
""mixed"" ferroelectric states on achieving accumulative electrical modulation of
multilevel resistance states in MFTJs, paving the way for multifunctional
device applications.",1910.02002v1
2020-06-02,Ultra-fast Kinematic Vortices in Mesoscopic Superconductors: The Effect of the Self-Field,"Within the framework of the generalized time-dependent Ginzburg-Landau
equations, we studied the influence of the magnetic self-field induced by the
currents inside a superconducting sample driven by an applied transport
current. The numerical simulations of the resistive state of the system show
that neither material inhomogeneity nor a normal contact smaller than the
sample width are required to produce an inhomogeneous current distribution
inside the sample, which leads to the emergence of a kinematic
vortex-antivortex pair (vortex street) solution. Further, we discuss the
behaviors of the kinematic vortex velocity, the annihilation rates of the
supercurrent, and the superconducting order parameters alongside the vortex
street solution. We prove that these two latter points explain the
characteristics of the resistive state of the system. They are the fundamental
basis to describe the peak of the current-resistance characteristic curve and
the location where the vortex-antivortex pair is formed.",2006.01335v1
2020-07-09,"Coupling-independent, Real-time Wireless Resistive Sensing through Nonlinear PT-symmetry","We report the realization of coupling-independent, robust wireless sensing of
fully-passive resistive sensors. PT-symmetric operation obviates sweeping,
permitting real-time, single-point sensing. Self-oscillation is achieved
through a fast-settling nonlinearity whose voltage amplitude is proportional to
the sensor's resistance. These advances markedly simplify the reader. A dual
time-scale theoretical framework generalizes system analysis to arbitrary
operating conditions and a correction strategy reduces errors due to detuning
from PT-symmetric conditions by an order of magnitude.",2007.05077v4
2020-07-29,An electro-thermal computational study of conducting channels in dielectric thin films using self-consistent phase-field methodology: A view toward the physical origins of resistive switching,"A large number of experimental studies suggest two-terminal resistive
switching devices made of a dielectric thin film sandwiched by a pair of
electrodes exhibit reversible multi-state switching behaviors; however coherent
understanding of physical and chemical origins of their electrical properties
needs to be further pursued to improve and customize the performance. In this
paper, phase-field methodology is used to study the formation and annihilation
of conductive channels resulting in reversible resistive switching behaviors
that can generally occur in any dielectric thin films. Our focus is on the
dynamical evolution of domains made of electrical charges under the influence
of spatially varying electric field and temperature resulting in distinctive
changes in electrical conductance.",2007.15123v1
2020-08-24,Peierls-type metal-insulator transition in carbon nanostructures,"We report the observation of Peierls-type metal-insulator transition in
carbon nanostructures formed by chemical vapor deposition inside the pore
network of the ZSM-5 zeolite. The Raman spectrum of this nanocarbon@ZSM-5
indicates a clear signature of the radial breathing mode (RBM) for (3,0) carbon
nanotubes that can constitute the carbon network segments. Electrical transport
measurements on multiple few-micron-sized nanocarbon@ZSM-5 crystals showed
metallic temperature of resistance dependence down to 30 K, at which point the
resistance exhibited a sharp upturn that is accompanied by the opening of a
quasigap at the Fermi level as indicated by the differential resistance
measurements. Further Hall measurements have yielded both the sign of the
charge carrier and its density. The latter demonstrated excellent consistency
with the quasigap data. We employed first-principles calculations to verify
that there can indeed be softening of the phonon modes in the (3,0) carbon
nanotubes.",2008.10160v1
2020-10-22,Electrical and Thermal Transport Properties of the beta-Pyrochlore Oxide CsW2O6,"We report the electrical resistivity, thermoelectric power, and thermal
conductivity of single-crystalline and sintered samples of the 5d pyrochlore
oxide CsW2O6. The electrical resistivity of the single crystal is 3 mohm cm at
295 K and gradually increases with decreasing temperature above 215 K (Phase
I). The thermoelectric power of the single-crystalline and sintered samples
shows a constant value of approximately -60 uV K-1 in Phase I. These results
reflect that the electron conduction by W 5d electrons in Phase I is incoherent
and in the hopping regime, although a band gap does not open at the Fermi
level. The thermal conductivity in Phase I of both samples is considerably low,
which might be due to the rattling of Cs+ ions. In Phase II below 215 K, the
electrical resistivity and the absolute value of thermoelectric power of both
samples strongly increase with decreasing temperature, corresponding to a
transition to a semiconducting state with a band gap open at the Fermi level,
while the thermal conductivity in Phase II is smaller than that in Phase I.",2010.11404v1
2020-11-11,Elastic turbulence generates anomalous flow resistance in porous media,"Diverse processes rely on the viscous flow of polymer solutions through
porous media. In many cases, the macroscopic flow resistance abruptly increases
above a threshold flow rate in a porous medium---but not in bulk solution. The
reason why has been a puzzle for over half a century. Here, by directly
visualizing the flow in a transparent 3D porous medium, we demonstrate that
this anomalous increase is due to the onset of an elastic instability. We
establish that the energy dissipated by the unstable flow fluctuations, which
vary across pores, generates the anomalous increase in flow resistance through
the entire medium. Thus, by linking the pore-scale onset of unstable flow to
macroscopic transport, our work provides generally-applicable guidelines for
predicting and controlling polymer solution flows.",2011.06036v1
2021-02-08,Double magnetic phase transitions and magnetotransport anomalies in a new compound Gd$_\textbf{2}$AgSi$_\textbf{3}$,"Dc and ac-magnetic susceptibility ($\chi$), specific heat ($C_\mathrm{P}$),
electrical resistivity ($\rho$) and magnetoresistance measurements performed on
the new polycrystalline compound $\mathrm{Gd_2AgSi_3}$, crystallizing in the
$\alpha$-$\mathrm{ThSi_2}$ tetragonal structure, are reported. Two magnetic
phase transitions were observed in dc and ac susceptibility, specific heat, and
resistivity measurements at temperatures $\mathrm{T_{N_1}} = 11$ K and
$\rm{T_{N_2}} = 20$ K, despite a single site occupied by Gd atom, which is an
indication of the complex magnetic behavior. $\mathrm{Gd_2AgSi_3}$ turns out to
be one of the rare Gd compound in which a minimum is observed in the
temperature dependence of resistivity in the paramagnetic state and also
negative magnetoresistance over a wide temperature range (above
$\rm{T_{N_2}}$), mimicking the behavior of exotic $\mathrm{Gd_2PdSi_3}$, in
this ternary family. The isothermal magnetic entropy and adiabatic temperature
changes reach a value of 9.5 J/kg-K and 7.5 K respectively for the field change
of 9 T.",2102.04096v2
2021-04-23,Ab initio inspection of thermophysical experiments for zirconium near melting,"We present quantum molecular dynamics calculations of thermophysical
properties of solid and liquid zirconium in the vicinity of melting. An
overview of available experimental data is also presented. We focus on the
analysis of thermal expansion, molar enthalpy, resistivity and normal spectral
emissivity of solid and liquid Zr. Possible reasons of discrepancies between
the first-principle simulations and experiments are discussed. Our calculations
reveal a significant volume change on melting in agreement with electrostatic
levitation experiments. Meanwhile, we confirm a low value of enthalpy of fusion
obtained in some pulse-heating experiments. Electrical resistivity of solid and
liquid Zr is systematically underestimated in our simulations, however the
slope of resistivity temperature dependencies agrees with experiment. Our
calculations predict almost constant normal spectral emissivity in liquid Zr.",2104.11521v2
2021-06-16,Statistical Analysis of Contacts to Synthetic Monolayer MoS2,"Two-dimensional (2D) semiconductors are promising candidates for scaled
transistors because they are immune to mobility degradation at the monolayer
limit. However, sub-10 nm scaling of 2D semiconductors, such as MoS2, is
limited by the contact resistance. In this work, we show for the first time a
statistical study of Au contacts to chemical vapor deposited monolayer MoS2
using transmission line model (TLM) structures, before and after dielectric
encapsulation. We report contact resistance values as low as 330 ohm-um, which
is the lowest value reported to date. We further study the effect of Al2O3
encapsulation on variability in contact resistance and other device metrics.
Finally, we note some deviations in the TLM model for short-channel devices in
the back-gated configuration and discuss possible modifications to improve the
model accuracy.",2106.08673v3
2021-06-19,Dopant Precursor Adsorption into Single-Dimer Windows: Towards Guided Self-Assembly of Dopant Arrays on Si(100),"Atomically precise dopant arrays in Si are being pursued for solid-state
quantum computing applications. We propose a guided self-assembly process to
produce atomically precise arrays of single dopant atoms in lieu of
lithographic patterning. We leverage the self-assembled c(4x2) structure formed
on Br- and I-Si(100) and investigate molecular precursor adsorption into the
generated array of single-dimer window (SDW) adsorption sites with density
functional theory (DFT). The adsorption of several technologically relevant
dopant precursors (PH$_3$, BCl$_3$, AlCl$_3$, GaCl$_3$) into SDWs formed with
various resists (H, Cl, Br, I) are explored to identify the effects of steric
interactions. PH$_3$ adsorbed without barrier on all resists studied, while
BCl$_3$ exhibited the largest adsorption barrier, 0.34 eV, with an I resist.
Dense arrays of AlCl$_3$ were found to form within experimentally realizable
conditions demonstrating the potential for the proposed use of guided
self-assembly for atomically precise fabrication of dopant-based devices.",2106.10556v1
2021-07-07,Large Magneto-Electric Resistance in the Topological Dirac Semimetal alpha Sn,"The spin-momentum locking of surface states in topological quantum materials
can produce a resistance that scales linearly with magnetic and electric
fields. Such a bilinear magneto-electric resistance (BMER) effect offers a
completely new approach for magnetic storage and magnetic field sensing
applications. The effects demonstrated so far, however, are relatively weak or
for low temperatures. Strong room-temperature BMER effects have now been found
in topological Dirac semimetal alpha-Sn thin films. The epitaxial alpha-Sn
films were grown by sputtering on silicon substrates. They showed BMER
responses that are 10^6 times larger than previously reported at room
temperature and also larger than that previously reported at low temperatures.
These results represent a major advance toward realistic BMER applications. The
data also made possible the first characterization of the three-dimensional,
Fermi-level spin texture of topological surface states in alpha-Sn.",2107.03472v1
2021-10-21,Magnetic critical behavior and anomalous Hall effect in 2H-Co$_{0.22}$TaS$_{2}$ single crystals,"We report ferromagnetism in 2H-Co$_{0.22}$TaS$_2$ single crystals where Co
atoms are intercalated in the van der Waals gap, and a systematic study of its
magnetic critical behavior in the vicinity of $T_c \sim 28$ K. The obtained
critical exponents $\beta$ = 0.43(2), $\gamma$ = 1.15(1), and $\delta =
3.54(1)$ fulfill the Widom scaling relation $\delta = 1+\gamma/\beta$ and
follow the scaling equation. This indicates that the spin coupling in
2H-Co$_{0.22}$TaS$_2$ is of three-dimensional Hersenberg type coupled with
long-range magnetic interaction, and that the exchange interaction decays with
distance as $J(r)\approx r^{-4.69}$. 2H-Co$_{0.22}$TaS$_2$ exhibits a weak
temperature-dependent metallic behavior in resistivity and negative values of
thermopower with dominant electron-type carriers, in which obvious anomalies
were observed below $T_c$ as well as the anomalous Hall effect (AHE). The
linear scaling behavior between the modified anomalous Hall resistivity
$\rho_{xy}/\mu_0H$ and longitudinal resistivity $\rho_{xx}^2M/\mu_0H$ implies
that the origin of AHE in 2H-Co$_{0.22}$TaS$_2$ should be dominated by the
extrinsic side-jump mechanism.",2110.11350v1
2022-01-21,"Anomalous metals: from ""failed superconductor"" to ""failed insulator""","Resistivity saturation is found on both superconducting and insulating sides
of an ""avoided"" magnetic-field-tuned superconductor-to-insulator transition
(H-SIT) in a two-dimensional In/InO$_x$ composite, where the anomalous metallic
behaviors cut off conductivity or resistivity divergence in the
zero-temperature limit. The granular morphology of the material implies a
system of Josephson junctions (JJ) with a broad distribution of Josephson
coupling E$_J$ and charging energy E$_C$ , with a H-SIT determined by the
competition between E$_J$ and E$_C$ . By virtue of self-duality across the true
H-SIT, we invoke macroscopic quantum tunneling effects to explain the
temperature-independent resistance where the ""failed superconductor"" side is a
consequence of phase fluctuations and the ""failed insulator"" side results from
charge fluctuations. While true self-duality is lost in the avoided transition,
its vestiges are argued to persist, owing to the incipient duality of the
percolative nature of the dissipative path in the underlying random JJ system.",2201.08801v1
2022-03-12,Quantifying active and resistive stresses in adherent cells,"To understand cell migration, it is crucial to gain knowledge on how cells
exert and integrate forces on/from their environment. A quantity of prime
interest for biophysicists interested in cell movements modeling is the
intracellular stresses. Up to now, three different methods have been proposed
to calculate it, they are all in the regime of the thin plate approximation.
Two are based on solving the mechanical equilibrium equation inside the cell
material (Monolayer Stress Microscopy, and Bayesian Inference Stress
Microscopy) and one is based on the continuity of displacement at the
cell/substrate interface (Intracellular Stress Microscopy). We show here using
3D FEM modeling that these techniques do not calculate the same quantities (as
was previously assumed), the first techniques calculate the sum of the active
and resistive stresses within the cell, whereas the last one only calculate the
resistive component. Combining these techniques should in principle permit to
get access to the active stress alone.",2203.06475v2
2022-03-23,Quantum oscillations and weak anisotropic resistivity in the chiral Fermion semimetal PdGa,"We perform a detailed analysis of the magnetotransport and de Haas-van Alphen
(dHvA) oscillations in crystal PdGa which is predicted to be a typical chiral
Fermion semimetal from CoSi family holding a large Chern number. The
unsaturated quadratic magnetoresistance (MR) and nonlinear Hall resistivity
indicate that PdGa is a multi-band system without electron-hole compensation.
Angle-dependent resistivity in PdGa shows weak anisotropy with twofold or
threefold symmetry when the magnetic field rotates within the (1$\bar{1}$0) or
(111) plane perpendicular to the current. Nine or three frequencies are
extracted after the fast Fourier-transform analysis (FFT) of the dHvA
oscillations with B//[001] or B//[011], respectively, which is confirmed to be
consistent with the Fermi surfaces (FSs) obtained from first-principles
calculations with spin-orbit coupling (SOC) considered.",2203.12772v1
2022-05-04,Percolative Superconductivity in Electron-Doped Sr$_{1-x}$Eu$_{x}$CuO$_{2+y}$ Films,"Electron-doped infinite-layer Sr$_{1-x}$Eu$_{x}$CuO$_{2+y}$ films over a wide
doping range have been prepared epitaxially on SrTiO$_3$(001) using reactive
molecular beam epitaxy. In-plane transport measurements of the single
crystalline samples reveal a dome-shaped nodeless superconducting phase
centered at $x$ $\sim$ 0.15, a Fermi-liquid behavior and pronounced upturn in
low temperature resistivity. We show that the resistivity upturn follows
square-root temperature dependence, suggesting the emergence of
superconductivity via a three-dimensional percolation process. The percolative
superconductivity is corroborated spectroscopically by imaging the electronic
phase separation between superconducting and metallic phases with
low-temperature scanning tunneling microscopy. Furthermore, we visualize
interstitial and apical oxygen anions that rapidly increase in number as $x>$
0.12, and elucidate their impacts on the superconductivity and normal-state
resistivity.",2205.01844v1
2022-05-10,Effect of substrate temperature on the optoelectronic properties of DC magnetron sputtered copper oxide films,"Copper oxide thin films are deposited on quartz substrates by DC magnetron
sputtering and the effect of deposition temperature on their optoelectronic
properties is examined in detail. Scanning Electron Microscopy (SEM), X-ray
diffraction (XRD) analysis, Raman spectroscopy, UV-Vis spectroscopy, and
four-probe sheet resistance measurements are used to characterize the surface
morphology, structural, optical, and electrical properties respectively.
Deposition is carried out at room temperature and between 200 and 300 {\deg}C.
XRD analysis indicates that the oxide formed is primarily Cu$_2$O and the
absorption spectra show the films have a critical absorption edge at around 300
nm. The sheet resistance gradually decreases with increase in deposition
temperature thereby increasing the conductivity of these thin films. Also
observed is the increase in band gap from 2.20 eV for room temperature
deposition to 2.35 eV at 300 {\deg}C. The optical band gap and the variation of
sheet resistance with temperature shows that the microstructure plays a vital
role in their behavior. These transformation characteristics are of huge
technological importance having variety of applications including transparent
solar cell fabrication.",2205.05615v1
2022-08-10,Spin-carrier coupling induced ferromagnetism and giant resistivity peak in EuCd$_2$P$_2$,"EuCd$_2$P$_2$ is notable for its unconventional transport: upon cooling the
metallic resistivity changes slope and begins to increase, ultimately 100-fold,
before returning to its metallic value. Surprisingly, this giant peak occurs at
18K, well above the N\'{e}el temperature ($T_N$) of 11.5K. Using a suite of
sensitive probes of magnetism, including resonant x-ray scattering and
magneto-optical polarimetry, we have discovered that ferromagnetic order onsets
above $T_N$ in the temperature range of the resistivity peak. The observation
of inverted hysteresis in this regime shows that ferromagnetism is promoted by
coupling of localized spins and itinerant carriers. The resulting carrier
localization is confirmed by optical conductivity measurements.",2208.05499v1
2022-10-04,Time-domain impedance method for transient photovoltage analysis,"In this work, we approximate the surface photovoltage (SPV) transients in
nm-sized ZnO films by the equivalent RC circuit model. The SPV rises in time in
time for about 90 mcs after the exciting light pulse at 275 nm is off at
different pulse widths ranging from 1.2 to 12 mcs. The key to this observation
is a considerable amount of defects in the films, which form a trap capacitance
in the equivalent circuit. The photogeneration of nonequilibrium electrons and
holes near the film surface is described by charging of a capacitance by the
current source whereas the rate of their spatial separation is determined by a
resistance. This resistance reflects an obstacle in the carrier movement while
another capacitance determines the charge separation distance. The
electron-hole recombination is account for a second resistance introduced into
the equivalent circuit. The resulting modeled SPV transient allows to reproduce
the observed experimental curve rather well.",2210.07928v1
2022-10-17,Multiscale modeling of resistive switching in gold nanogranular films,"Metallic nanogranular films display a complex dynamical response to a
constant bias, showing up as atypical resistive switching mechanism which could
be used to create electrical components for neuromorphic applications. To model
such a phenomenon we use a multiscale approach blending together an ab initio
treatment of the electric current at the nanoscale, a molecular dynamical
approach dictating structural rearrangements, and a finite-element solution of
the heat equation for heat propagation in the sample. We also consider
structural changes due to electromigration which are modelled on the basis of
experimental observations on similar systems. Within such an approach, we
manage to describe some distinctive features of the resistive switching
occurring in nanogranular film and provide a physical interpretation at the
microscopic level.",2210.09379v1
2022-10-27,Green's Functions For Random Resistor Networks,"We analyze random resistor networks through a study of lattice Green's
functions in arbitrary dimensions. We develop a systematic disorder
perturbation expansion to describe the weak disorder regime of such a system.
We use this formulation to compute ensemble averaged nodal voltages and bond
currents in a hierarchical fashion. We verify the validity of this expansion
with direct numerical simulations of a square lattice with resistances at each
bond exponentially distributed. Additionally, we construct a formalism to
recursively obtain the exact Green's functions for finitely many disordered
bonds. We provide explicit expressions for lattices with up to four disordered
bonds, which can be used to predict nodal voltage distributions for arbitrarily
large disorder strengths. Finally, we introduce a novel order parameter that
measures the overlap between the bond current and the optimal path (the path of
least resistance), for a given resistance configuration, which helps to
characterize the weak and strong disorder regimes of the system.",2210.15562v3
2022-12-19,"Anisotropic resistance with a 90-degree twist in a ferromagnetic Weyl semimetal, Co2MnGa","Co$_2$MnGa is a ferromagnetic semimetal with Weyl nodal lines identified by
ARPES. We studied electrical transport in thin Co$_2$MnGa lamellae (10 $\times$
10 $\times$ 0.4-5 microns) cut from single-crystals using a focused ion beam.
These crystals exhibit an unexpected and highly unusual planar resistance
anisotropy ($\sim$10 times) with principal axes that rotate by 90 degrees
between the upper and lower faces. Using symmetry arguments and simulations, we
find that the observed resistance anisotropy resembles that of an isotropic
conductor with anisotropic surface states that are impeded from hybridization
with bulk states. The origin of these states awaits further experiments that
can correlate the surface bands with the observed 90$^\circ$-twist geometry.",2212.09738v1
2022-12-29,Stateful Logic using Phase Change Memory,"Stateful logic is a digital processing-in-memory technique that could address
von Neumann memory bottleneck challenges while maintaining backward
compatibility with standard von Neumann architectures. In stateful logic,
memory cells are used to perform the logic operations without reading or moving
any data outside the memory array. Stateful logic has been previously
demonstrated using several resistive memory types, mostly by resistive RAM
(RRAM). Here we present a new method to design stateful logic using a different
resistive memory - phase change memory (PCM). We propose and experimentally
demonstrate four logic gate types (NOR, IMPLY, OR, NIMP) using commonly used
PCM materials. Our stateful logic circuits are different than previously
proposed circuits due to the different switching mechanism and functionality of
PCM compared to RRAM. Since the proposed stateful logic form a functionally
complete set, these gates enable sequential execution of any logic function
within the memory, paving the way to PCM-based digital processing-in-memory
systems.",2212.14377v1
2023-03-15,Two-fold anisotropic superconducting state in topological superconductor Sn$_4$Au,"Here we report the anisotropic magnetotransport properties in the
superconducting state of Sn$_4$Au single crystal. Sn$_4$Au single crystal is
synthesized through an easy melt growth method. Superconducting properties are
evidenced by resistivity vs. temperature and DC magnetization measurements.
Isothermal magnetization measurements hint toward type-II superconductivity in
Sn$_4$Au. In-plane and out-of-plane resistivity measurements show anisotropic
behavior of the upper critical field at temperatures below superconducting
transition (T$_c$ = 2.3 K). The observed anisotropy is more elucidated in
resistivity measurements performed below Tc at different tilt angles. The
anisotropy parameter is found to be 1.26. The observed results show the
presence two-fold anisotropic superconducting state in Sn$_4$Au single crystal,
which may be induced due to the layered structure of synthesized Sn$_4$Au
single crystal.",2303.08520v1
2023-03-28,Effect of atomic anti-site disorder on the AMR in FeCo alloys,"In order to understand the anti-site disorder effect on the anisotropic
magnetoresistance (AMR) effect in alloys, $\rm{Fe}_{50}Co_{50}$ alloys were
studied in this work using the fully relativistic spin-polarized screened (KKR)
method. The anti-site effect was modeled by interchanging Fe and Co atoms and
treated by the coherent potential approximation (CPA). We find that the
anti-site disorder broadens the spectral function and decreases the
conductivity. Our work emphasizes that the absolute variations of resistivity
under magnetic moment rotation are less affected by atomic disorders. The
annealing procedure improves the AMR by reduction of the total resistivity. At
the same time, we also find that the fourth-order term in the angular dependent
resistivity becomes weaker when the disorder increases, resulting from
increased scattering of the states around the band-crossing.",2303.15726v1
2023-03-28,Superconductivity in boron-doped carbon nanotube networks,"By using the five Angstrom diameter pores of calcined zeolite as the
template, we have fabricated boron doped carbon nanotube networks via the
chemical vapor deposition method. Raman data indicate the network to comprise
segments of interconnected carbon nano tubes. Transport measurements showed a
superconducting transition initiating at 40K, with a sharp downturn around 20K
to a low resistance state at 2K, accompanied by a low resistance plateau in the
current voltage characteristic, fluctuating around zero resistance. Magnetic
measurements exhibited the Meissner effect characteristic of thin
superconducting wire networks in which the superconducting wire radius is much
smaller than the London penetration length. At low magnetic field, the negative
diamagnetic susceptibility was observed to persist beyond 200K. The transport
and magnetic data are reconciled on the basis of a physical model based on weak
links comprising short, one-dimensional superconducting nano tubes, that govern
the global transport behavior.",2303.15980v1
2023-04-12,Measuring a Soft Resistive Strain Sensor Array by Solving the Resistor Network Inverse Problem,"Soft robotics is applicable to a variety of domains due to the adaptability
offered by the soft and compliant materials. To develop future intelligent soft
robots, soft sensors that can capture deformation with nearly infinite
degree-of-freedom are necessary. Soft sensor networks can address this problem,
however, measuring all sensor values throughout the body requires excessive
wiring and complex fabrication that may hinder robot performance. We circumvent
these challenges by developing a non-invasive measurement technique, which is
based on an algorithm that solves the inverse problem of resistor network, and
implement this algorithm on a soft resistive, strain sensor network. Our
algorithm works by iteratively computing the resistor values based on the
applied boundary voltage and current responses, and we analyze the
reconstruction error of the algorithm as a function of network size and
measurement error. We further develop electronics setup to implement our
algorithm on a stretchable resistive strain sensor network made of soft
conductive silicone, and show the response of the measured network to different
deformation modes. Our work opens a new path to address the challenge of
measuring many sensor values in soft sensors, and could be applied to soft
robotic sensor systems.",2304.05828v1
2023-05-22,Ion-selective scattering studied by the variable-energy electron irradiation of Ba$_{0.2}$K$_{0.8}$Fe$_2$As$_2$ superconductor,"Low-temperature variable-energy electron irradiation was used to induce
non-magnetic disorder in a single crystal of hole-doped iron-based
superconductor, Ba$_{1-x}$K$_x$Fe$_2$As$_2$, $x=$0.80. To avoid systematic
errors, the beam energy was adjusted non-consequently for five values between
1.0 and 2.5 MeV, whence sample resistance was measured in-situ at 22 K. For all
energies, the resistivity raises linearly with the irradiation fluence
suggesting the creation of uncorrelated dilute point-like disorder (confirmed
by simulations). The rate of the resistivity increase peaks at energies below
1.5 MeV. Comparison with calculated partial cross-sections points to the
predominant creation of defects in the iron sublattice. Simultaneously,
superconducting $T_c$, measured separately between the irradiation runs, is
monotonically suppressed as expected since it depends on the total scattering
rate, hence total cross-section, which is a monotonically increasing function
of energy. Our work confirms experimentally an often-made assumption of the
dominant role of the iron sub-lattice in iron-based superconductors.",2305.13217v1
2023-06-05,Multilayer GZ/YSZ Thermal Barrier Coating from Suspension and Solution Precursor Plasma Spray,"Gas turbines rely on thermal barrier coating (TBC) to thermally insulate the
nickel-based superalloys underneath during operation; however, current TBCs,
yttria stabilised zirconia (YSZ), limit the operating temperature and hence
efficiency. At an operating temperature above 1200{\deg}C, YSZ is susceptible
to failure due to phase instabilities and CMAS (Calcia-Magnesia-Alumina-Silica)
attack. Gadolinium zirconates (GZ) could overcome the drawback of YSZ,
complementing each other with the multi-layer approach. This study introduces a
novel approach utilising axial suspension plasma spray (ASPS) and axial
solution precursor plasma spray (ASPPS) to produce a double-layer and a
triple-layer TBCs with improved CMAS resistance. The former comprised
suspension plasma sprayed GZ and YSZ layers while the latter had an additional
dense layer deposited through a solution precursor to minimise the columnar
gaps that pre-existed in the SPS GZ layer, thus resisting CMAS infiltration.
Both coatings performed similarly in furnace cycling test (FCT) and burner rig
testing (BRT). In the CMAS test, triple-layer coating showed better CMAS
resistivity, as evidenced by the limited CMAS infiltration observed on the
surface.",2306.02720v1
2024-01-31,Effect of severe plastic deformation realized by rotary swaging on the mechanical properties and corrosion resistance of near-a-titanium alloy Ti-2.5Al-2.6Zr,"The research aims to analyze the impact that severe plastic deformation
arising during Rotary Swaging has on mechanical properties and corrosion
resistance of a near-a-titanium alloy Ti-2.5Al-2.6Zr (Russian industrial name
PT7M). The nature of corrosion decay in fine-grained alloys caused by hot salt
corrosion is known to vary from pit corrosion to intercrystalline corrosion at
the onset of recrystallization processes. Resistance to hot salt corrosion in a
fine-grained titanium alloy Ti-2.5Al-2.6Zr is shown to depend on the
structural-phase state of grain boundaries that varies during their migration
as a result of covering corrosive doping elements (aluminum, zirconium)
distributed in the crystal lattice of a titanium alloy.",2401.17672v1
2024-03-17,Observation of diamagnetic strange-metal phase in sulfur-copper codoped lead apatite,"By codoping sulfur and copper into lead apatite, the crystal grains are
directionally stacked and the room-temperature resistivity is reduced from
insulating to $2\times10^{-5}~\Omega\cdot$m. The resistance-temperature curve
exhibits a nearly linear relationship at low temperature suggesting the
presence of strange-metal phase, and a second-order phase transition is then
observed at around 230~K during cooling the samples. A possible Meissner effect
is present in dc magnetic measurements. Further hydrothermal lead-free
synthesis results in smaller resistance and stronger diamagnetism,
demonstrating the essential component might be sulfur-substituted copper
apatite and the alkalis matter as well. A clear pathway towards
superconductivity in this material is subsequently benchmarked.",2403.11126v3
2024-04-09,Transport resistance strikes back: unveiling its impact on fill factor losses in organic solar cells,"The fill factor ($FF$) is a critical parameter for solar cell efficiency, yet
its analytical description is challenging due to the interplay between
recombination and charge extraction processes. An often overlooked yet
significant factor contributing to $FF$ losses, beyond recombination, is the
influence of charge transport. In most state-of-the-art organic solar cells,
the primary limitation of the $FF$ arises not from recombination but rather
from low conductivity, highlighting the need for refined models to predict the
$FF$ accurately. Here, we extend the analytical model for transport resistance
to a more general case. Drawing from a large set of experimental
current-voltage and light intensity-dependent open-circuit voltage data, we
systematically incorporate crucial details previously omitted in the model.
Consequently, we introduce a straightforward set of equations to predict the
$FF$ of a solar cell, enabling the differentiation of losses attributed to
recombination and transport resistance. Our study provides valuable insights
into strategies for mitigating $FF$ losses based on the experimentally
validated analytical model, guiding the development of more efficient solar
cell designs and optimization strategies.",2404.06190v1
2024-05-09,Negative longitudinal resistance of monolayer graphene in the quantum Hall regime,"In the quantum Hall regime the charge current is carried by ideal
one-dimensional edge channels where the backscattering is prohibited by
topology. This results in the constant potential along the edge of the Hall bar
leading to zero 4-terminal longitudinal resistance r_xx. Finite scattering
between the counter-propagating edge states, when the topological protection is
broken, commonly results in r_xx > 0. However, a local disorder, if allowing
intersection of the edge states, can result in a counter-intuitive scenario
when r_xx<0. In this work we report the observation and a systematic study of
such unconventional negative longitudinal resistance seen in an encapsulated
monolayer graphene Hall bar device measured in the quantum Hall regime. We
supplement our findings with the numerical calculations which allow us to
outline the conditions necessary for the appearance of negative r_xx and to
exclude the macroscopic disorder (contamination bubble) as the main origin of
it.",2405.05515v2
2012-08-01,Spin-fluctuations in Ti$_{60}$V$_{40}$ alloy and its influence on the superconductivity,"We report experimental studies of the temperature and magnetic field
dependence of resistivity and dc magnetic susceptibility and the temperature
dependence of zero field heat capacity in a Ti$_{0.6}$V$_{0.4}$ alloy. The
temperature dependence of the normal state dc magnetic susceptibility in this
Ti$_{0.6}$V$_{0.4}$ alloy shows T$^2$lnT behavior. The temperature dependence
of resistivity follows a T$^2$ behaviour in the range 20-50 K. On the other
hand, a term $T^3$ lnT is needed in the expression containing the electronic
and lattice heat capacities to explain the temperature dependence of heat
capacity at temperatures where $T^2$ dependence of resistivity is observed.
Such temperature dependence of dc magnetic susceptibility, resistivity and heat
capacity are indications of the presence of spin-fluctuations in the system.
Further experimental evidence for the spin fluctuations is obtained in the form
of a negative value of T$^5$ term in the temperature dependence of resistivity.
The influence of spin-fluctuations on the superconducting properties of
Ti$_{0.6}$V$_{0.4}$ is discussed in detail. We show from our analysis of
resistivity and the susceptibility in normal and superconducting states that
the spin fluctuations present in Ti$_{0.6}$V$_{0.4}$ alloy are itinerant in
nature. There is some evidence of the existence of preformed Cooper-pairs in
the temperature range well above the superconducting transition temperature.
Our study indicates that the interesting correlations between spin-fluctuations
and superconductivity may actually be quite widespread amongst the
superconducting materials, and not necessarily be confined only to certain
classes of exotic compounds.",1208.0181v3
2016-06-14,On the multiferroic skyrmion-host GaV4S8,"The lacunar spinel GaV4S8 exhibits orbital ordering at 44 K and shows a
complex magnetic phase diagram below 12.7 K, which includes ferromagnetic and
cycloidal spin order. At low but finite external magnetic fields, N\'eel-type
skyrmions are formed in this material. Skyrmions are whirl-like spin vortices
that have received great theoretical interest because of their non-trivial spin
topology and that are also considered as basic entities for new data-storage
technologies. Interestingly, we found that the orbitally ordered phase shows
sizable ferroelectric polarization and that excess spin-driven polarizations
appear in all magnetic phases, including the skyrmion-lattice phase. Hence,
GaV4S8 shows simultaneous magnetic and polar order and belongs to the class of
multiferroics, materials that attracted enormous attention in recent years.
Here, we summarize the existing experimental information on the magnetic,
electronic, and dielectric properties of GaV4S8. By performing detailed
magnetic susceptibility, resistivity, specific heat, and dielectric
experiments, we complement the low-temperature phase diagram. Specifically, we
show that the low-temperature and low-field ground state of GaV4S8 seems to
have a more complex spin configuration than purely collinear ferromagnetic spin
order. In addition, at the structural Jahn-Teller transition the magnetic
exchange interaction changes from antiferromagnetic to ferromagnetic. We also
provide experimental evidence that the vanadium V4 clusters in GaV4S8 can be
regarded as molecular units with spin 1/2. However, at high temperatures
deviations in the susceptibility show up, indicating that either the magnetic
moments of the vanadium atoms fluctuate independently or excited states of the
V4 molecule become relevant.",1606.04511v1
2016-10-24,Self-aligned local electrolyte gating of 2D materials with nanoscale resolution,"In the effort to make 2D materials-based devices smaller, faster, and more
efficient, it is important to control charge carrier at lengths approaching the
nanometer scale. Traditional gating techniques based on capacitive coupling
through a gate dielectric cannot generate strong and uniform electric fields at
this scale due to divergence of the fields in dielectrics. This field
divergence limits the gating strength, boundary sharpness, and pitch size of
periodic structures, and restricts possible geometries of local gates (due to
wire packaging), precluding certain device concepts, such as plasmonics and
transformation optics based on metamaterials. Here we present a new gating
concept based on a dielectric-free self-aligned electrolyte technique that
allows spatially modulating charges with nanometer resolution. We employ a
combination of a solid-polymer electrolyte gate and an ion-impenetrable
e-beam-defined resist mask to locally create excess charges on top of the gated
surface. Electrostatic simulations indicate high carrier density variations of
$\Delta n =10^{14}\text{cm}^{-2}$ across a length of 10 nm at the mask
boundaries on the surface of a 2D conductor, resulting in a sharp depletion
region and a strong in-plane electric field of $6\times10^8 \text{Vm}^{-1}$
across the so-created junction. We apply this technique to the 2D material
graphene to demonstrate the creation of tunable p-n junctions for
optoelectronic applications. We also demonstrate the spatial versatility and
self-aligned properties of this technique by introducing a novel graphene
thermopile photodetector.",1610.07646v2
2020-09-22,Half-Metal Spin-Gapless Semiconductor Junctions as a Route to the Ideal Diode,"The ideal diode is a theoretical concept that completely conducts the
electric current under forward bias without any loss and that behaves like a
perfect insulator under reverse bias. However, real diodes have a junction
barrier that electrons have to overcome and thus they have a threshold voltage
$V_T$, which must be supplied to the diode to turn it on. This threshold
voltage gives rise to power dissipation in the form of heat and hence is an
undesirable feature. In this work, based on half-metallic magnets and
spin-gapless semiconductors we propose a diode concept that does not have a
junction barrier and the operation principle of which relies on the
spin-dependent transport properties of the HMM and SGS materials. We show that
the HMM and SGS materials form an Ohmic contact under any finite forward bias,
while for a reverse bias the current is blocked due to spin-dependent filtering
of the electrons. Thus, the HMM-SGS junctions act as a diode with zero
threshold voltage $V_T$, and linear $I-V$ characteristics as well as an
infinite on:off ratio at zero temperature. However, at finite temperatures,
non-spin-flip thermally excited high-energy electrons as well as low-energy
spin-flip excitations can give rise to a leakage current and thus reduce the
on:off ratio under a reverse bias. Furthermore, a zero threshold voltage allows
one to detect extremely weak signals and due to the Ohmic HMM-SGS contact, the
proposed diode has a much higher current drive capability and low resistance,
which is advantageous compared to conventional semiconductor diodes. We employ
the NEGF method combined with DFT to demonstrate the linear $I-V$
characteristics of the proposed diode based on two-dimensional half-metallic
Fe/MoS$_2$ and spin-gapless semiconducting VS$_2$ planar heterojunctions.",2009.10463v1
2020-11-22,"Quasi-two-dimensional heterostructures (K$M_{1-x}$Te)(LaTe$_{3}$) ($M$ = Mn, Zn) with charge density waves","Layered heterostructure materials with two different functional building
blocks can teach us about emergent physical properties and phenomena arising
from interactions between the layers. We report the intergrowth compounds
KLa$M$$_{1-x}$Te$_{4}$ ($M$ = Mn, Zn; $x\approx$ 0.35) featuring two chemically
distinct alternating layers [LaTe$_3$] and [K$M$$_{1-x}$Te]. Their crystal
structures are incommensurate, determined by single X-ray diffraction for the
Mn compound and transmission electron microscope (TEM) study for the Zn
compound. KLaMn$_{1-x}$Te$_{4}$ crystallizes in the orthorhombic superspace
group $Pmnm$(01/2${\gamma}$)$s$00 with lattice parameters $a$ = 4.4815(3)
{\AA}, $b$ = 21.6649(16) {\AA} and $c$ = 4.5220(3) {\AA}. It exhibits charge
density wave (CDW) order at room temperature with a modulation wave vector
$\mathbf{q}$ = 1/2$\mathbf{b}$* + 0.3478$\mathbf{c}$* originating from
electronic instability of Te-square nets in [LaTe$_{3}$] layers. The Mn analog
exhibits a cluster spin glass behavior with spin freezing temperature
$T_{\mathrm{f}}$ $\approx$ 5 K attributed to disordered Mn vacancies and
competing magnetic interactions in the [Mn$_{1-x}$Te] layers. The Zn analog
also has charge density wave order at room temperature with a similar
$\mathbf{q}$-vector having the $\mathbf{c}$* component ~ 0.346 confirmed by
selected-area electron diffraction (SAED). Electron transfer from
[K$M_{1-x}$Te] to [LaTe$_{3}$] layers exists in KLa$M_{1-x}$Te$_{4}$, leading
to an enhanced electronic specific heat coefficient. The resistivities of
KLa$M_{1-x}$Te$_{4}$ ($M$ = Mn, Zn) exhibit metallic behavior at high
temperatures and an upturn at low temperatures, suggesting partial localization
of carriers in the [LaTe$_{3}$] layers with some degree of disorder associated
with the $M$ atom vacancies in the [$M_{1-x}$Te] layers.",2011.11068v2
2021-06-09,Fracture Mechanics-Based Quantitative Matching of Forensic Evidence Fragments,"Fractured metal fragments with rough and irregular surfaces are often found
at crime scenes. Current forensic practice visually inspects the complex jagged
trajectory of fractured surfaces to recognize a ``match'' using comparative
microscopy and physical pattern analysis. We developed a novel computational
framework, utilizing the basic concepts of fracture mechanics and statistical
analysis to provide quantitative match analysis for match probability and error
rates. The framework employs the statistics of fracture surfaces to become
non-self-affine with unique roughness characteristics at relevant microscopic
length scale, dictated by the intrinsic material resistance to fracture and its
microstructure. At such a scale, which was found to be greater than two
grain-size or micro-feature-size, we establish that the material intrinsic
properties, microstructure, and exposure history to external forces on an
evidence fragment have the premise of uniqueness, which quantitatively
describes the microscopic features on the fracture surface for forensic
comparisons. The methodology utilizes 3D spectral analysis of overlapping
topological images of the fracture surface and classifies specimens with very
high accuracy using statistical learning. Cross correlations of image-pairs in
two frequency ranges are used to develop matrix variate statistical models for
the distributions among matching and non-matching pairs of images, and provides
a decision rule for identifying matches and determining error rates. A set of
thirty eight different fracture surfaces of steel articles were correctly
classified. The framework lays the foundations for forensic applications with
quantitative statistical comparison across a broad range of fractured materials
with diverse textures and mechanical properties.",2106.04809v1
2021-06-16,Role of surface termination in the metal-insulator transition of V$_2$O$_3$(0001) ultrathin films,"Surface termination is known to play an important role in determining the
physical properties of materials. It is crucial to know how surface termination
affects the metal-insulator transition (MIT) of V$_2$O$_3$ films for both
fundamental understanding and its applications. By changing growth parameters,
we achieved a variety of surface terminations in V$_2$O$_3$ films that are
characterized by low energy electron diffraction (LEED) and photoemission
spectroscopy techniques. Depending upon the terminations, our results show MIT
can be partially or fully suppressed near the surface region due to the
different filling of the electrons at the surface and sub-surface layers and
change of screening length compared to the bulk. Across MIT, a strong
redistribution of spectral weight and its transfer from high-to-low binding
energy regime is observed in a wide-energy-scale. Our results show total
spectral weight in the low-energy regime is not conserved across MIT,
indicating a breakdown of `sum rules of spectral weight', a signature of a
strongly correlated system. Such change in spectral weight is possibly linked
to the change in hybridization, lattice volume ({\it i.e.,} effective carrier
density), and spin degree of freedom in the system that happens across MIT. We
find that MIT in this system is strongly correlation-driven where the
electron-electron interactions play a pivotal role. Moreover, our results
provide a better insight in understanding the electronic structure of strongly
correlated systems and highlight the importance of accounting surface effects
during interpretation of the physical property data mainly using surface
sensitive probes, such as surface resistivity.",2106.08555v1
2022-03-24,Influence of generated defects by Ar-implantation on the thermoelectric properties of ScN,"Nowadays, making thermoelectric materials more efficient in energy conversion
is still a challenge. In this work, to reduce the thermal conductivity and thus
improve the overall thermoelectric performances, point and extended defects
were generated in epitaxial 111-ScN thin films by implantation using argon
ions. The films were investigated by structural, optical, electrical, and
thermoelectric characterization methods. The results demonstrated that argon
implantation leads to the formation of stable defects (up to 750 K operating
temperature) were identified as interstitial type defect clusters and so-called
argon-vacancy complexes. The insertion of those specific defects induces
acceptor-type deep levels in the bandgap yielding to a reduce of the free
carrier mobility. With a reduce electrical conductivity, the irradiated sample
exhibited higher Seebeck coefficient maintaining the power factor of the film.
The thermal conductivity is strongly reduced from 12 to 3 W.m-1.K-1 at 300 K,
showing the effect of defects in increasing phonon scattering. Subsequent high
temperature annealing, at 1573 K, leads to the progressive evolution of
defects: the initial clusters of interstitial evolved to the benefit of smaller
clusters and the formation of bubble. Thus, the number of free carriers, the
resistivity and the Seebeck coefficient are almost restored but the mobility of
the carriers remains low and a 30% drop in thermal conductivity is still
effective (8.5 W.m-1.K-1). This study shows that the control defect engineering
with defects introduced by irradiation using noble gases in a thermoelectric
coating can be an attractive method to enhance the figure of merit of
thermoelectric materials.",2203.13227v4
2022-03-29,Dose rate effects in radiation-induced changes to phenyl-based polymeric scintillators,"Results on the effects of ionizing radiation on the signal produced by
plastic scintillating rods manufactured by Eljen Technology company are
presented for various matrix materials, dopant concentrations, fluors (EJ-200
and EJ-260), anti-oxidant concentrations, scintillator thickness, doses, and
dose rates. The light output before and after irradiation is measured using an
alpha source and a photomultiplier tube, and the light transmission by a
spectrophotometer. Assuming an exponential decrease in the light output with
dose, the change in light output is quantified using the exponential dose
constant $D$. The $D$ values are similar for primary and secondary doping
concentrations of 1 and 2 times, and for antioxidant concentrations of 0, 1,
and 2 times, the default manufacturer's concentration. The $D$ value depends
approximately linearly on the logarithm of the dose rate for dose rates between
2.2 Gy/hr and 70 Gy/hr for all materials. For EJ-200 polyvinyltoluene-based
(PVT) scintillator, the dose constant is approximately linear in the logarithm
of the dose rate up to 3400 Gy/hr, while for polystyrene-based (PS)
scintillator or for both materials with EJ-260 fluors, it remains constant or
decreases (depending on doping concentration) above about 100 Gy/hr. The
results from rods of varying thickness and from the different fluors suggest
damage to the initial light output is a larger effect than color center
formation for scintillator thickness $\leq1$ cm. For the blue scintillator
(EJ-200), the transmission measurements indicate damage to the fluors. We also
find that while PVT is more resistant to radiation damage than PS at dose rates
higher than about 100 Gy/hr for EJ-200 fluors, they show similar damage at
lower dose rates and for EJ-260 fluors.",2203.15923v2
2022-04-11,Thermal insulation and heat guiding using nanopatterned MoS2,"In the modern electronics overheating is one of the major reasons for device
failure. Overheating causes irreversible damage to circuit components and can
also lead to fire, explosions, and injuries. Accordingly, in the advent of 2D
material-based electronics, an understanding of their thermal properties in
addition to their electric ones is crucial to enable efficient transfer of
excess heat away from the electronic components. In this work we propose
structures based on free-standing, few-layer, nanopatterned MoS2 that insulate
and guide heat in the in-plane direction. We arrive at these designs via a
thorough study of the in-plane thermal conductivity as a function of thickness,
porosity, and temperature in both pristine and nanopatterned MoS2 membranes.
Two-laser Raman thermometry was employed to measure the thermal conductivities
of a set of free-standing MoS2 flakes with diameters greater than 20 um and
thicknesses from 5 to 40 nm, resulting in values from 30 to 85 W/mK,
respectively. After nanopatterning a square lattice of 100-nm diameter holes
with a focused ion beam we have obtained a greater than 10-fold reduction of
the thermal conductivities for the period of 500 nm and values below 1 W/mK for
the period of 300 nm. The results were supported by equilibrium molecular
dynamic simulations for both pristine and nanopatterned MoS2. The selective
patterning of certain areas results in extremely large difference in thermal
conductivities within the same material. Exploitation of this effect enabled
for the first time thermal insulation and heat guiding in the few-layer MoS2.
The patterned regions act as high thermal resistors: we obtained a thermal
resistance of 4x10-6 m2K/W with only four patterned lattice periods of 300 nm,
highlighting the significant potential of MoS2 for thermal management
applications.",2204.04999v1
2022-08-04,"Epitaxial growth, magnetoresistance, and electronic band structure of GdSb magnetic semimetal films","Motivated by observations of extreme magnetoresistance (XMR) in bulk crystals
of rare-earth monopnictide (RE-V) compounds and emerging applications in novel
spintronic and plasmonic devices based on thin-film semimetals, we have
investigated the electronic band structure and transport behavior of epitaxial
GdSb thin films grown on III-V semiconductor surfaces. The Gd3+ ion in GdSb has
a high spin S=7/2 and no orbital angular momentum, serving as a model system
for studying the effects of antiferromagnetic order and strong exchange
coupling on the resulting Fermi surface and magnetotransport properties of
RE-Vs. We present a surface and structural characterization study mapping the
optimal synthesis window of thin epitaxial GdSb films grown on III-V
lattice-matched buffer layers via molecular beam epitaxy. To determine the
factors limiting XMR in RE-V thin films and provide a benchmark for band
structure predictions of topological phases of RE-Vs, the electronic band
structure of GdSb thin films is studied, comparing carrier densities extracted
from magnetotransport, angle-resolved photoemission spectroscopy (ARPES), and
density functional theory (DFT) calculations. ARPES shows hole-carrier rich
topologically-trivial semi-metallic band structure close to complete
electron-hole compensation, with quantum confinement effects in the thin films
observed through the presence of quantum well states. DFT predicted Fermi
wavevectors are in excellent agreement with values obtained from quantum
oscillations observed in magnetic field-dependent resistivity measurements. An
electron-rich Hall coefficient is measured despite the higher hole carrier
density, attributed to the higher electron Hall mobility. The carrier
mobilities are limited by surface and interface scattering, resulting in lower
magnetoresistance than that measured for bulk crystals.",2208.02648v2
2023-03-07,"Response to ""On the giant deformation and ferroelectricity of guanidinium nitrate"" by Marek Szafrański and Andrzej Katrusiak","Following a well-established practice of publishing commentaries to articles
of other authors who work on materials that were earlier studied by them (n.b.
six published comments[1-6]), Marek Szafra\'nski(MS) and Andrzej Katrusiak (AK)
have filed on the preprint server arXiv a manuscript entitled ""On the giant
deformation and ferroelectricity of guanidinium nitrate""[7] with comments on
our article ""Exceptionally high work density of a ferroelectric dynamic organic
crystal around room temperature"" published in Nature Communications (2022, 13,
2823).[8] Both in the submitted comment as well as in the required (by the
journal) direct communication with us preceding its posting, MS and AK have
expressed dissatisfaction with the choice of literature references in our
article, for which they felt that their previous work on this material has not
been cited to a sufficient extent. In their comment, they summarize their other
remarks on our article as ""the structural determinations of GN [guanidinium
nitrate] crystals, their phase transitions and associated giant deformation, as
well as its detailed structural mechanism, the molecular dynamics and
dielectric properties were reported before, while the semiconductivity,
ferroelectricity, and fatigue resistance of the GN [guanidinium nitrate]
crystals cannot be confirmed.""[7] Apart from the sentiments of MS and AK on our
choice of cited literature, we find their comments on the scientific content of
our article to be strongly biased towards their own results and unfounded.
Below, we provide a detailed response to their comments.",2303.04028v2
2023-05-12,Automated Grain Boundary (GB) Segmentation and Microstructural Analysis in 347H Stainless Steel Using Deep Learning and Multimodal Microscopy,"Austenitic 347H stainless steel offers superior mechanical properties and
corrosion resistance required for extreme operating conditions such as high
temperature. The change in microstructure due to composition and process
variations is expected to impact material properties. Identifying
microstructural features such as grain boundaries thus becomes an important
task in the process-microstructure-properties loop. Applying convolutional
neural network (CNN) based deep-learning models is a powerful technique to
detect features from material micrographs in an automated manner. Manual
labeling of the images for the segmentation task poses a major bottleneck for
generating training data and labels in a reliable and reproducible way within a
reasonable timeframe. In this study, we attempt to overcome such limitations by
utilizing multi-modal microscopy to generate labels directly instead of manual
labeling. We combine scanning electron microscopy (SEM) images of 347H
stainless steel as training data and electron backscatter diffraction (EBSD)
micrographs as pixel-wise labels for grain boundary detection as a semantic
segmentation task. We demonstrate that despite producing instrumentation drift
during data collection between two modes of microscopy, this method performs
comparably to similar segmentation tasks that used manual labeling.
Additionally, we find that na\""ive pixel-wise segmentation results in small
gaps and missing boundaries in the predicted grain boundary map. By
incorporating topological information during model training, the connectivity
of the grain boundary network and segmentation performance is improved.
Finally, our approach is validated by accurate computation on downstream tasks
of predicting the underlying grain morphology distributions which are the
ultimate quantities of interest for microstructural characterization.",2305.07790v1
2011-05-22,Optimal Three-Material Wheel Assemblage of Conducting and Elastic Composites,"We describe a new type of three material microstructures which we call wheel
assemblages, that correspond to extremal conductivity and extremal bulk modulus
for a composite made of two materials and an ideal material. The exact lower
bounds for effective conductivity and matching laminates was found in
(Cherkaev, 2009) and for anisotropic composites, in (Cherkaev, Zhang, 2011).
Here, we show different optimal structures that generalize the classical
Hashin-Shtrikman coated spheres (circles). They consist of circular inclusions
which contain a solid central circle (hub) and radial spikes in a surrounding
annulus, and (for larger volume fractions of the best material) an annulus
filled with it. The same wheel assemblages are optimal for the pair of dual
problems of minimal conductivity (resistivity) of a composite made from two
materials and an ideal conductor (insulator), in the problem of maximal
effective bulk modulus of elastic composites made from two linear elastic
material and void, and the dual minimum problem.",1105.4302v1
2015-10-10,Intrusion in heterogeneous materials: Simple global rules from complex micro-mechanics,"The interaction of intruding objects with deformable materials is a common
phenomenon, arising in impact and penetration problems, animal and vehicle
locomotion, and various geo-space applications. The dynamics of arbitrary
intruders can be simplified using Resistive Force Theory (RFT), an empirical
framework originally used for fluids but works surprisingly well, better in
fact, in granular materials. That such a simple model describes behavior in dry
grains, a complex nonlinear material, has invigorated a search to determine the
underlying mechanism of RFT. We have discovered that a straightforward
friction-based continuum model generates RFT, establishing a link between RFT
and local material behavior. Our theory reproduces experimental RFT data
without any parameter fitting and generates RFT's key simplifying assumption: a
geometry-independent local force formula. Analysis of the system explains why
RFT works better in grains than in viscous fluids, and leads to an analytical
criterion to predict RFT's in other materials.",1510.02966v1
2017-06-05,Dy$^{3+}$-doped Yttrium Complex Molecular Crystals for Two-color Thermometry in Heterogeneous Materials,"We develop Dy$^{3+}$-doped yttrium complexes for use as two-color thermometry
(TCT) phosphor molecular crystals in heterogeneous materials. These complexes
include: Dy:Y(acac)$_3$(phen), Dy:Y(hfa)$_3$(DPEPO), Dy:Y(4-BBA)$_3$(TPPO),
Dy:Y(acac)$_3$, and Dy:Y(acac)$_3$(DPEPO), where the Dy/Y ratio is 1:9. We
characterize the materials' photoluminescence at different temperatures to
determine the TCT calibration parameters and the degree to which thermal
quenching influences the emission. From this data we observe a link between the
excited state lifetime at room temperature and the degree to which the material
is susceptible to thermal quenching (i.e. materials having long room
temperature lifetimes are more resistant to thermal quenching than materials
with short room temperature lifetimes). Of the five complexes tested we find
that Dy:Y(acac)$_3$(DPEPO) has the best thermal performance, with the most
likely source of improvement being DPEPO's compact rigid structure. This
rigidity helps with energy transfer to the Dy$^{3+}$ ion, suppresses
non-radiative loss modes, and reduces exciplex formation.",1706.02658v1
1999-12-21,Three-dimensional spontaneous magnetic reconnection in neutral current sheets,"Magnetic reconnection in an antiparallel uniform Harris current sheet
equilibrium, which is initially perturbed by a region of enhanced resistivity
limited in all three dimensions, is investigated through compressible
magnetohydrodynamic simulations. Variable resistivity, coupled to the dynamics
of the plasma by an electron-ion drift velocity criterion, is used during the
evolution. A phase of magnetic reconnection amplifying with time and leading to
eruptive energy release is triggered only if the initial perturbation is
strongly elongated in the direction of current flow or if the threshold for the
onset of anomalous resistivity is significantly lower than in the corresponding
two-dimensional case. A Petschek-like configuration is then built up for \sim
100 Alfven times, but remains localized in the third dimension. Subsequently, a
change of topology to an O-line at the center of the system (``secondary
tearing'') occurs. This leads to enhanced and time-variable reconnection, to a
second pair of outflow jets directed along the O-line, and to expansion of the
reconnection process into the third dimension. High parallel current density
components are created mainly near the region of enhanced resistivity.",9912443v1
2007-03-05,MHD simulations of jet acceleration from Keplerian accretion disks: the effects of disk resistivity,"Accretion disks and astrophysical jets are used to model many active
astrophysical objects, viz., young stars, relativistic stars, and active
galactic nuclei. In this paper we present self-consistent time-dependent
simulations of supersonic jets launched from magnetized accretion disks, using
high resolution numerical techniques. In particular we study the effects of the
disk magnetic resistivity, parametrized through an alpha-prescription, in
determining the properties of the inflow-outflow system. Moreover we analyze
under which conditions steady state solutions of the type proposed in the self
similar models of Blandford and Payne can be reached and maintained in a self
consistent nonlinear stage. We use the resistive MHD FLASH code with adaptive
mesh refinement, allowing us to follow the evolution of the structure for a
time scale long enough to reach steady state. A detailed analysis of the
initial configuration state is given. We obtain the expected solutions in the
axisymmetric (2.5D) limit. Assuming a magnetic field around equipartition with
the thermal pressure of the disk, we show how the characteristics of the disk
jet system, as the ejection efficiency and the energetics, are affected by the
anomalous resistivity acting inside the disk.",0703064v1
1994-09-13,Mesoscopic quantum transport: Resonant tunneling in the presence of strong Coulomb interaction,"Coulomb blockade phenomena and quantum fluctuations are studied in mesoscopic
metallic tunnel junctions with high charging energies. If the resistance of the
barriers is large compared to the quantum resistance, transport can be
described by sequential tunneling. Here we study the influence of quantum
fluctuations. They are important when the resistance is small or the
temperature very low. A real-time approach is developed which allows the
diagrammatic classification of ``inelastic resonant tunneling'' processes where
different electrons tunnel coherently back and forth between the leads and the
metallic island. With the help of a nonperturbative resummation technique we
evaluate the spectral density which describes the charge excitations of the
system. From it physical quantities of interest like current and average charge
can be deduced. Our main conclusions are: An energy renormalization leads to a
logarithmic temperature dependence of the renormalized system parameters. A
finite lifetime broadening can change the classical picture drastically. It
gives rise to a strong flattening of the Coulomb oscillations for low
resistances, but in the Coulomb blockade regime inelastic electron cotunneling
persists. The temperature where these effects are important are accessible in
experiments.",9409051v1
1994-12-22,"""Scaling of an anomalous metal/insulator transition in a 2D system in silicon at zero magnetic field""","We have studied the temperature dependence of resistivity, $\rho$, for a
two-dimensional electron system in silicon at low electron densities,
$n_s\sim10^{11}$ cm$^{-2}$, near the metal/insulator transition. The
resistivity was empirically found to scale with a single parameter, $T_0$,
which approaches zero at some critical electron density, $n_c$, and increases
as a power $T_0\propto|n_s-n_c|^\beta$ with $\beta=1.6\pm0.1$ both in metallic
($n_s>n_c$) and insulating ($n_s<n_c$) regions. This dependence was found to be
sample-independent. We have also studied the diagonal resistivity at Landau
level filling factor $\nu=3/2$ where the system is known to be in a metallic
state at high magnetic field and in an insulating state at low magnetic field.
The temperature dependencies of resistivity at $B=0$ and at $\nu=3/2$ were
found to be identical. These behaviors suggest a true metal/insulator
transition in the two dimensional electron system in silicon at $B=0$, in
contrast with the well-known scaling theory.",9412103v1
1995-01-19,Resistivity as a function of temperature for models with hot spots on the Fermi surface.,"We calculate the resistivity $\rho$ as a function of temperature $T$ for two
models currently discussed in connection with high temperature
superconductivity: nearly antiferromagnetic Fermi liquids and models with van
Hove singularities on the Fermi surface. The resistivity is calculated
semiclassicaly by making use of a Boltzmann equation which is formulated as a
variational problem. For the model of nearly antiferromagnetic Fermi liquids we
construct a better variational solution compared to the standard one and we
find a new energy scale for the crossover to the $\rho\propto T^2$ behavior at
low temperatures. This energy scale is finite even when the spin-fluctuations
are assumed to be critical. The effect of additional impurity scattering is
discussed. For the model with van Hove singularities a standard ansatz for the
Boltzmann equation is sufficient to show that although the quasiparticle
lifetime is anomalously short, the resistivity $\rho\propto T^2\ln(1/T)$.",9501086v1
1996-06-05,Transport and magnetic properties in ferromagnetic manganese-oxide thin films,"The transport and magnetic properties in ferromagnetic manganese-oxide thin
films are studied based on the model of the coupling between the mobile
d-electrons and the core spins in Mn ions. The spontaneous magnetization and
the resistivity are obtained for various magnetic fields and temperature. The
resistivity in absence of magnetic field and the magnetoresistance exhibit
maxima near the Curie temperature, the applied magnetic field moves the
position of the resistivity peak to high temperature and suppresses the peak
value, which agree with the experimental results. The Hall resistivity is
predicted to exhibit maximum near the Curie point. The pressure effect of the
magnetoresistance can also be explained qualitatively in this mechanism. The
colossal magnetoresistance in ferromagnetic manganese-oxide thin films is
attributed to the spin-correlation fluctuation scattering and the low
dimensional effect.",9606029v1
1997-04-14,Temperature Dependent Resistivity of Single Wall Carbon Nanotubes,"Nonchiral single wall carbon nanotubes with an ""armchair"" wrapping are
theoretically predicted to be conducting, and high purity samples consisting
predominantly of these tubes exhibit metallic behavior with an intrinsic
resistivity which increases approximately linearly with temperature over a wide
temperature range. Here we study the coupling of the conduction electrons to
long wavelength torsional shape fluctuations, or twistons. A one dimensional
theory of the scattering of electrons by twistons is presented which predicts
an intrinsic resistivity proportional to the absolute temperature. Experimental
measurements of the temperature dependence of the resistivity are reported and
compared with the predictions of the twiston theory.",9704117v1
2002-05-24,The quantized Hall effect in the presence of resistance fluctuations,"We present an experimental study of mesoscopic, two-dimensional electronic
systems at high magnetic fields. Our samples, prepared from a low-mobility
InGaAs/InAlAs wafer, exhibit reproducible, sample specific, resistance
fluctuations. Focusing on the lowest Landau level we find that, while the
diagonal resistivity displays strong fluctuations, the Hall resistivity is free
of fluctuations and remains quantized at its $\nu=1$ value, $h/e^{2}$. This is
true also in the insulating phase that terminates the quantum Hall series.
These results extend the validity of the semicircle law of conductivity in the
quantum Hall effect to the mesoscopic regime.",0205513v2
2003-07-01,Effect of two bands on critical fields in MgB2 thin films with various resistivity values,"Upper critical fields of four MgB2 thin films were measured up to 28 Tesla at
Grenoble High Magnetic Field Laboratory. The films were grown by Pulsed Laser
Deposition and showed critical temperatures ranging between 29.5 and 38.8 K and
resistivities at 40 K varying from 5 to 50 mWcm. The critical fields in the
perpendicular direction turned out to be in the 13-24 T range while they were
estimated to be in 42-57 T the range in ab-planes. In contrast to the
prediction of the BCS theory, we did not observe any saturation at low
temperatures: a linear temperature dependence is exhibited even at lowest
temperatures at which we made the measurements. Moreover, the critical field
values seemed not to depend on the normal state resistivity value. In this
paper, we analyze these data considering the multiband nature of
superconductivity in MgB2 We will show how the scattering mechanisms that
determine critical fields and resistivity can be different.",0307013v2
2004-02-27,Possible Pairing Mechanisms of PuCoGa$_5$ Superconductor,"We examine possible pairing mechanisms of superconductivity in PuCoGa$_5$
based on spin-fluctuations or phonons as mediating bosons. We consider
experimental data of specific heat C(T) and resistivity $\rho(T)$ as input to
determine a consistent scattering boson with the superconducting transition
temperature of 18.5K in PuCoGa$_5$. Irrespective to the type of boson, the
characteristic boson frequency is found to be $\sim 150 K$ from the resistivity
fitting. The spin fluctuation model is most consistent with the experimental
resistivity, successfully explaining the anomalous temperature dependence
($\sim \frac{T^2}{150 K +T}$) at low temperatures as well as the saturation
behavior at high temperatures. Assuming that the pairing state is non s-wave,
the large residual resistivity $\rho_{imp} \sim 20 \mu \Omega cm \sim 120 K$
suggests that an ideally pure sample of PuCoGa$_5$ would have a maximum T$_c$
of 39 K.",0402685v2
2004-04-28,"How normal is the ""normal"" state of superconducting cuprates?","High magnetic field studies of the cuprate superconductors revealed a non-BCS
temperature dependence of the upper critical field $H_{c2}(T)$ determined
resistively by several groups. These determinations caused some doubts on the
grounds of the contrasting effect of the magnetic field on the in-plane,
$\rho_{ab}$, and out-of-plane, $\rho_{c}$ resistances reported for large sample
of Bi2212. Here we present careful measurements of both $\rho_{ab}(B)$ and
$\rho_{c}(B)$ of tiny Bi2212 crystals in magnetic fields up to 50 Tesla. None
of our measurements revealed a situation when on field increase $\rho_c$
reaches its maximum while $\rho_{ab}$ remains very small if not zero. The
resistive $H_{c2}(T)$ estimated from $\rho_{ab}(B)$ and $\rho_{c}(B)$ are
approximately the same. We also present a simple explanation of the unusual
Nernst signal in superconducting cuprates as a normal state phenomenon. Our
results support any theory of cuprates, which describes the state above the
resistive phase transition as perfectly 'normal' with a zero off-diagonal order
parameter.",0404678v1
2004-07-14,Investigation of the Field-Tuned Quantum Critical Point in CeCoIn_5,"The main properties and the type of the field-tuned quantum critical point in
the heavy-fermion metal CeCoIn$_5$ arisen upon applying magnetic fields $B$ are
considered within the scenario based on the fermion condensation quantum phase
transition. We analyze the behavior of the effective mass, resistivity,
specific heat, charge and heat transport as functions of applied magnetic
fields $B$ and show that in the Landau Fermi liquid regime these quantities
demonstrate the critical behavior which is scaled by the critical behavior of
the effective mass. We show that in the high-field non-Fermi liquid regime, the
effective mass exhibits very specific behavior, $M^*\sim T^{-2/3}$, and the
resistivity demonstrates the $T^{2/3}$ dependence. Finally, at elevated
temperatures, it changes to $M^*\sim T^{-1/2}$, while the resistivity becomes
linear in $T$. In zero magnetic field, the effective mass is controlled by
temperature $T$, and the resistivity is also linear in $T$. The obtained
results are in good agreement with recent experimental facts.",0407350v1
2005-04-02,Non-Ohmic variable-range hopping transport in one-dimensional conductors,"We investigate theoretically the effect of a finite electric field on the
resistivity of a disordered one-dimensional system in the variable-range
hopping regime. We find that at low fields the transport is inhibited by rare
fluctuations in the random distribution of localized states that create
high-resistance ``breaks'' in the hopping network. As the field increases, the
breaks become less resistive. In strong fields the breaks are overrun and the
electron distribution function is driven far from equilibrum. The logarithm of
the resistance initially shows a simple exponential drop with the field,
followed by a logarithmic dependence, and finally, by an inverse square-root
law.",0504047v2
2006-06-15,Crystalline-Electric-Field Effect on the Resistivity of Ce-based Heavy Fermion Systems,"The behavior of the resistivity of Ce-based heavy fermion systems is studied
using a 1/$N$-expansion method a la Nagoya, where $N$ is the spin-orbital
degeneracy of f-electrons. The 1/$N$-expansion is performed in terms of the
auxiliary particles, and a strict requirement of the local constraints is
fulfilled for each order of 1/N. The physical quantities can be calculated over
the entire temperature range by solving the coupled Dyson equations for the
Green functions self-consistently at each temperature. This 1/N-expansion
method is known to provide asymptotically exact results for the behavior of
physical quantities in both low- and high-energy regions when it is applied to
a single orbital periodic Anderson model (PAM). On the basis of a generalized
PAM including crystalline-electric-field splitting with a single conduction
band, the pressure dependence of the resistivity is calculated by
parameterizing the effect of pressure as the variation of the hybridization
parameter between the conduction electrons and f-electrons. The main result of
the present study is that the double-peak structure of the $T$-dependence of
the resistivity is shown to merge into a single-peak structure with increasing
pressure.",0606400v1
1996-10-07,Toroidal Vortices in Resistive Magnetohydrodynamic Equilibria,"Resistive steady states in toroidal magnetohydrodynamics (MHD), where Ohm's
law must be taken into account, differ considerably from ideal ones. Only for
special (and probably unphysical) resistivity profiles can the Lorentz force,
in the static force-balance equation, be expressed as the gradient of a scalar
and thus cancel the gradient of a scalar pressure. In general, the Lorentz
force has a curl directed so as to generate toroidal vorticity. Here, we
calculate, for a collisional, highly viscous magnetofluid, the flows that are
required for an axisymmetric toroidal steady state, assuming uniform scalar
resistivity and viscosity. The flows originate from paired toroidal vortices
(in what might be called a ``double smoke ring'' configuration), and are
thought likely to be ubiquitous in the interior of toroidally driven
magnetofluids of this type. The existence of such vortices is conjectured to
characterize magnetofluids beyond the high-viscosity limit in which they are
readily calculable.",9610006v1
2006-09-14,Comparison between resistive and collisionless double tearing modes for nearby resonant surfaces,"The linear instability and nonlinear dynamics of collisional (resistive) and
collisionless (due to electron inertia) double tearing modes (DTMs) are
compared with the use of a reduced cylindrical model of a tokamak plasma. We
focus on cases where two q = 2 resonant surfaces are located a small distance
apart. It is found that regardless of the magnetic reconnection mechanism,
resistivity or electron inertia, the fastest growing linear eigenmodes may have
high poloidal mode numbers m ~ 10. The spectrum of unstable modes tends to be
broader in the collisionless case. In the nonlinear regime, it is shown that in
both cases fast growing high-m DTMs lead to an annular collapse involving small
magnetic island structures. In addition, collisionless DTMs exhibit multiple
reconnection cycles due to reversibility of collisionless reconnection and
strong ExB flows. Collisionless reconnection leads to a saturated stable state,
while in the collisional case resistive decay keeps the system weakly dynamic
by driving it back towards the unstable equilibrium maintained by a source
term.",0609115v4
2006-12-08,RPC with low-resistive phosphate glass electrodes as a candidate for the CBM TOF,"Usage of electrodes made of glass with low bulk resistivity seems to be a
promising way to adapt the Resistive Plate Chambers (RPC) to the high-rate
environment of the upcoming CBM experiment. A pilot four-gap RPC sample with
electrodes made of phosphate glass, which has bulk resistivity in the order of
10^10 Ohm cm, has been studied with MIP beam for TOF applications. The tests
have yielded satisfactory results: the efficiency remains above 95% and the
time resolution stays within 120 ps up to the particle rate of 18 kHz/cm2. The
increase in rate from 2.25 to 18 kHz/cm2 leads to an increase of estimated
""tails"" fraction in the time spectrum from 1.5% to 4%.",0612083v1
2007-11-29,Resistively Detected NMR in Quantum Hall States: Investigation of the anomalous lineshape near $ν=1$,"A study of the resistively detected nuclear magnetic resonance (RDNMR)
lineshape in the vicinity of $\nu=1$ was performed on a high-mobility 2D
electron gas formed in GaAs/AlGaAs. In higher Landau levels, application of an
RF field at the nuclear magnetic resonance frequency coincides with an observed
minimum in the longitudinal resistance, as predicted by the simple hyperfine
interaction picture. Near $\nu=1$ however, an anomalous dispersive lineshape is
observed where a resistance peak follows the usual minimum. In an effort to
understand the origin of this anomalous peak we have studied the resonance
under various RF and sample conditions. Interestingly, we show that the
lineshape can be completely inverted by simply applying a DC current. We
interpret this as evidence that the minima and maxima in the lineshape
originate from two distinct mechanisms.",0711.4640v1
2008-09-06,Doping dependence of upper critical field and Hall resistivity in LaFeAsO1-xFx,"The electrical resistivity (Rxx) and Hall resistivity (Rxy) of LaFeAsO1-xFx
have been measured over a wide fluorine doping range 0 =< x =< 0.14 using 60 T
pulsed magnets. While the superconducting phase diagram (Tc, x) displays the
classic dome-shaped structure, we find that the resistive upper critical field
(Hc2) increases monotonically with decreasing fluorine concentration, with the
largest Hc2 >= 75 T for x = 0.05. This is reminiscent of the composition
dependence in high-Tc cuprates and might correlate with opening of a pseudo-gap
in the underdoped region. Further, the temperature dependence of Hc2(T) for
superconducting samples can be understood in terms of multi-band
superconductivity. Rxy data for non-superconducting samples show non-linear
field dependence, which is also consistent with a multi-carrier scenario.",0809.1133v3
2008-10-21,Nonlinear resistance of 2D electrons in crossed electric and magnetic fields,"The longitudinal resistivity of two dimensional (2D) electrons placed in
strong magnetic field is significantly reduced by applied electric field, an
effect which is studied in a broad range of magnetic fields and temperatures in
GaAs quantum wells with high electron density. The data are found to be in good
agreement with theory, considering the strong nonlinearity of the resistivity
as result of non-uniform spectral diffusion of the 2D electrons. Inelastic
processes limit the diffusion. Comparison with the theory yields the inelastic
scattering time of the two dimensional electrons. In the temperature range
T=2-10(K) for overlapping Landau levels, the inelastic scattering rate is found
to be proportional to T^2, indicating a dominant contribution of the
electron-electron scattering to the inelastic relaxation. In a strong magnetic
field, the nonlinear resistivity demonstrates scaling behavior, indicating a
specific regime of electron heating of well-separated Landau levels. In this
regime the inelastic scattering rate is found to be proportional to T^3,
suggesting the electron-phonon scattering as the dominant mechanism of the
inelastic relaxation.",0810.3713v2
2008-11-26,Temperature Dependence of Interlayer Magnetoresistance in Anisotropic Layered Metals,"Studies of interlayer transport in layered metals have generally made use of
zero temperature conductivity expressions to analyze angle-dependent
magnetoresistance oscillations (AMRO). However, recent high temperature AMRO
experiments have been performed in a regime where the inclusion of finite
temperature effects may be required for a quantitative description of the
resistivity. We calculate the interlayer conductivity in a layered metal with
anisotropic Fermi surface properties allowing for finite temperature effects.
We find that resistance maxima are modified by thermal effects much more
strongly than resistance minima. We also use our expressions to calculate the
interlayer resistivity appropriate to recent AMRO experiments in an overdoped
cuprate which led to the conclusion that there is an anisotropic, linear in
temperature contribution to the scattering rate and find that this conclusion
is robust.",0811.4442v1
2009-03-04,"Resistivity Anisotropy of $AE$Fe$_2$As$_2$ ($AE$ =Ca, Sr, Ba): direct versus Montgomery technique measurements","The anisotropy of electrical resistivity was measured in parent compounds of
the iron-arsenic high temperature superconductors, AEFe2As2 with Alkali Earth
elements AE=Ca,Sr, Ba. Measurements were performed using both the Montgomery
technique and direct resistivity measurements on samples cut along principal
crystallographic directions. The anisotropy ratio \gamma_\rho=\rho_c/\rho_a is
well below 10 for all compounds in the whole temperature range studied (4 to
300 K), in notable contrast to previous reports. The anisotropy at room
temperature increases from about 2 in Ca, to about 4 in Sr and Ba. In all
compounds the resistivity ratio decreases on cooling through the
structural/antiferromagnetic transition temperature T_{SM}, with the change
mainly coming from stronger variation in \rho_a as compared with \rho_c. This
suggests that the transitions stronger affect the two-dimensional parts of the
Fermi surface. We compare our experimental observations with band structure
calculations, and find similar trend in the evolution of anisotropy with the
size of AE ion. Our results show that the electronic structure of the iron
pnictides has large contribution from three-dimensional areas of the Fermi
surface.",0903.0820v1
2010-04-22,Studies of resistance switching effects in metal/YBa2Cu3O7-x interface junctions,"Current-voltage characteristics of planar junctions formed by an epitaxial
c-axis oriented YBa2Cu3O7-x thin film micro-bridge and Ag counter-electrode
were measured in the temperature range from 4.2 K to 300 K. A hysteretic
behavior related to switching of the junction resistance from a high-resistive
to a low-resistive state and vice-versa was observed and analyzed in terms of
the maximal current bias and temperature dependence. The same effects were
observed on a sub-micrometer scale YBa2Cu3O7-x thin film - PtIr point contact
junctions using Scanning Tunneling Microscope. These phenomena are discussed
within a diffusion model, describing an oxygen vacancy drift in YBa2Cu3O7-x
films in the nano-scale vicinity of the junction interface under applied
electrical fields.",1004.3909v1
2010-06-11,Mottness Collapse and T-linear Resistivity in Cuprate Superconductors,"Central to the normal state of cuprate high-temperature superconductors is
the collapse of the pseudogap, briefly reviewed here, at a critical point and
the subsequent onset of the strange-metal characterized by a resistivity that
scales linearly with temperature. A possible clue to the resolution of this
problem is the inter-relation between two facts: 1) A robust theory of T-linear
resistivity resulting from quantum criticality requires an additional length
scale outside the standard 1-parameter scaling scenario and 2) breaking the
Landau correspondence between the Fermi gas and an interacting system with
short-range repulsions requires non-fermionic degrees. We show that a
low-energy theory of the Hubbard model which correctly incorporates dynamical
spectral weight transfer has the extra degrees of freedom needed to describe
this physics. The degrees of freedom that mix into the lower band as a result
of dynamical spectral weight transfer are shown to either decouple beyond a
critical doping, thereby signaling Mottness collapse or unbind above a critical
temperature yielding strange metal behaviour characterised by $T-$linear
resistivity.",1006.2396v1
2011-01-04,The effect of varying Fe-content on transport properties of K intercalated iron selenide KxFe2-ySe2,"We report the successful growth of high-quality single crystals of potassium
intercalated iron selenide KxFe2-ySe2 by Bridgeman method. The effect of iron
vacancies on transport properties was investigated by electrical resistivity
and magnetic susceptibility measurements. With varying iron content, the system
passes from semiconducting/insulating to superconducting state. Comparing with
superconductivity, the anomalous ""hump"" effect in the normal state resistivity
is much more sensitive to the iron deficiency. The electrical resistivity
exhibits a perfect metallic behavior (R300K/R35K=42) for the sample with little
iron vacancies. Our results suggest that the anomalous ""hump"" effect in the
normal state resistivity may be due to the ordering process of the cation
vacancies in this non-stoichiometric compound rather than magnetic/structure
transition. A trace of superconductivity extending up to near 44 K was also
detected in some crystals of KxFe2-ySe2, which has the highest Tc of the
reported iron selenides.",1101.0789v1
2011-02-11,Enhancement of edge channel transport by a low frequency irradiation,"The magnetotransport properties of high mobility two dimensional electron gas
have recently attracted a significant interest due to the discovery of
microwave induced zero resistance states. Here we show experimentally that
microwave irradiation with a photon energy much smaller than the spacing
between Landau levels can induce a strong decrease in the four terminal
resistance. This effect is not predicted by the bulk transport models
introduced to explain zero resistance states, but can be naturally explained by
an edge transport model. This highlights the importance of edge channels for
zero resistance state physics that was proposed recently.",1102.2314v2
2011-05-11,"Systematics of the temperature-dependent inter-plane resistivity in Ba(Fe$_{1-x}$T$_x$)$_2$As$_2$ with T= Rh, Ni, and Pd","Temperature-dependent inter-plane resistivity, $\rho_c(T)$, was measured
systematically as a function of transition metal substitution in the
iron-arsenide superconductors Ba(Fe$_{1-x}$T$_x$)$_2$As$_2$, $T$= Ni, Pd, Rh.
The data are compared with the behavior found in
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, revealing resistive signatures of pseudogap. In
all compounds we find resistivity crossover at a characteristic pseudogap
temperature $T^*$ from non-metallic to metallic temperature dependence on
cooling. Suppression of $T^*$ proceeds very similar in cases of Ni and Pd
doping and much faster than in similar cases of Co and Rh doping. In cases of
Co and Rh doping an additional minimum in the temperature-dependent $\rho_c$
emerges for high dopings, when superconductivity is completely suppressed.
These features are consistent with the existence of a charge gap covering part
of the Fermi surface. The part of the Fermi surface affected by this gap is
notably larger for Ni and Pd doped compositions than in Co and Rh doped
compounds.",1105.2277v1
2011-09-08,Group velocity and causality in standard relativistic resistive magnetohydrodynamics,"Group velocity of electromagnetic waves in plasmas derived by standard
relativistic resistive MHD (resistive RMHD) equations is superluminal. If we
assume that the group velocity represents the propagation velocity of a signal,
we have to worry about the causality problem. That is, some acausal phenomena
may be induced, such that information transportation to the absolute past and
spontaneous decrease in the entropy. Here, we tried to find the acausal
phenomena using standard resistive RMHD numerical simulations in the suggested
situation of the acausal phenomena. The calculation results showed that even in
such situations no acausal effect happens. The numerical result with respect to
the velocity limit of the information transportation is consistent with a
linear theory of wave train propagation. Our results assure that we can use
these equations without problems of acausal phenomena.",1109.1856v1
2012-04-03,Resistive and magnetized accretion flows with convection,"We considered the effects of convection on the radiatively inefficient
accretion flows (RIAF) in the presence of resistivity and toroidal magnetic
field. We discussed the effects of convection on transports of angular momentum
and energy. We established two cases for the resistive and magnetized RIAFs
with convection: assuming the convection parameter as a free parameter and
using mixing-length theory to calculate convection parameter. A self-similar
method was used to solve the integrated equations that govern the behavior of
the presented model. The solutions showed that the accretion and rotational
velocities decrease by adding the convection parameter, while the sound speed
increases. Moreover, by using mixing-length theory to calculate convection
parameter, we found that the convection can be important in RIAFs with magnetic
field and resistivity.",1204.0743v1
2012-08-17,Cooperative dynamics in charge-ordered state of alpha-(BEDT-TTF)2I3,"Electric-field-dependent pulse measurements are reported in the
charge-ordered state of alpha-(BEDT-TTF)2I3. At low electric fields up to about
50 V/cm only negligible deviations from Ohmic behavior can be identified with
no threshold field. At larger electric fields and up to about 100 V/cm a
reproducible negative differential resistance is observed with a significant
change in shape of the measured resistivity in time. These changes critically
depend whether constant voltage or constant current is applied to the single
crystal. At high enough electric fields the resistance displays a dramatic drop
down to metallic values and relaxes subsequently in a single-exponential manner
to its low-field steady-state value. We argue that such an electric-field
induced negative differential resistance and switching to transient states are
fingerprints of cooperative domain-wall dynamics inherent to two-dimensional
bond-charge density wave with ferroelectric-like nature.",1208.3609v2
2012-11-05,Metastable Resistivity States and Conductivity Fluctuations in Low-doped La$_{1-x}$Ca$_{x}$MnO$_3$ Manganite Single Crystals,"Conductivity noise in dc current biased La_{0.82}Ca_{0.18}MnO_{3} single
crystals has been investigated in different metastable resistivity states
enforced by applying voltage pulses to the sample at low temperatures. Noise
measured in all investigated resistivity states is of 1/f-type and its
intensity at high temperatures and low dc bias scales as a square of the bias.
At liquid nitrogen temperatures for under bias exceeding a threshold value, the
behavior of the noise deviates from above quasi- equilibrium modulation noise
and depends in a non monotonic way on applied bias. The bias range of
nonequilibrium 1/f noise coincides with the range at which the conductance
increases linearly with bias voltage. This feature is attributed to a broad
continuity of states enabling indirect inelastic tunneling across intrinsic
tunnel junctions. The nonequilibrium noise has been ascribed to indirect
intrinsic tunneling mechanism while resistivity changes in metastable states to
variations in the energy landscape for charge carriers introduced by
microcracks created by the pulse procedures employed",1211.0838v1
2012-11-07,Exchange Field-Mediated Magnetoresistance in the Correlated Insulator Phase of Be Films,"We present a study of the proximity effect between a ferromagnet and a
paramagnetic metal of varying disorder. Thin beryllium films are deposited onto
a 5 nm-thick layer of the ferromagnetic insulator EuS. This bilayer arrangement
induces an exchange field, $H_{ex}$, of a few tesla in low resistance Be films
with sheet resistance $R\ll R_Q$, where $R_Q=h/e^2$ is the quantum resistance.
We show that $H_{ex}$ survives in very high resistance films and, in fact,
appears to be relatively insensitive to the Be disorder. We exploit this fact
to produce a giant low-field magnetoresistance in the correlated insulator
phase of Be films with $R\gg R_Q$.",1211.1663v1
2013-04-30,Mechanical resistance in unstructured proteins,"Single-molecule pulling experiments on unstructured proteins linked to
neurodegenerative diseases have measured rupture forces comparable to those for
stable folded proteins. To investigate the structural mechanisms of this
unexpected force resistance, we perform pulling simulations of the amyloid
{\beta}-peptide (A{\beta}) and {\alpha}-synuclein ({\alpha}S), starting from
simulated conformational ensembles for the free monomers. For both proteins,
the simulations yield a set of rupture events that agree well with the
experimental data. By analyzing the conformations right before rupture in each
event, we find that the mechanically resistant structures share a common
architecture, with similarities to the folds adopted by A{\beta} and {\alpha}S
in amyloid fibrils. The disease-linked Arctic mutation of A{\beta} is found to
increase the occurrence of highly force-resistant structures. Our study
suggests that the high rupture forces observed in A{\beta} and {\alpha}S
pulling experiments are caused by structures that might have a key role in
amyloid formation.",1304.7991v3
2013-06-11,Effect of pressure cycling on Iron: Signatures of an electronic instability and unconventional superconductivity,"High pressure electrical resistivity and x-ray diffraction experiments have
been performed on Fe single crystals. The crystallographic investigation
provides direct evidence that in the martensitic $bcc \rightarrow hcp$
transition at 14 GPa the $\lbrace 110\rbrace_{bcc}$ become the $\lbrace
002\rbrace_{hcp}$ directions. During a pressure cycle, resistivity shows a
broad hysteresis of 6.5 GPa, whereas superconductivity, observed between 13 and
31 GPa, remains unaffected. Upon increasing pressure an electronic instability,
probably a quantum critical point, is observed at around 19 GPa and, close to
this pressure, the superconducting $T_{c}$ and the isothermal resistivity
($0<T<300\,$K) attain maximum values. In the superconducting pressure domain,
the exponent $n = 5/3$ of the temperature power law of resistivity and its
prefactor, which mimics $T_{c}$, indicate that ferromagnetic fluctuations may
provide the glue for the Cooper pairs, yielding unconventional
superconductivity.",1306.2587v1
2013-09-14,Magnetic field tuned superconductor-to-insulator transition at the LaAlO$_3$ /SrTiO$_3$ interface,"We present a study of the magnetic field tuned superconductor-to-insulator
transition (SIT) in the electron gas that forms at the LaAlO$_3$/SrTiO$_3$
interface. We find that the magnetic field induces a transition into a weakly
insulating state, as is observed for the electrostatically tuned SIT at this
interface. Finite size scaling of the magnetoresistance yields the critical
exponent product $z\nu \simeq$ 7/3, indicating that the transition is governed
by quantum percolation effects. While such critical exponents have been
reported previously for high resistance films, they have not been reported for
a low resistance system like ours, with a maximum sheet resistance of $\approx$
1.5 k$\Omega$, much less than the quantum of resistance $R_Q \equiv h/4e^2 =
6.45$ k$\Omega$.",1309.3612v1
2013-11-11,Holographic duality and the resistivity of strange metals,"We present a strange metal, described by a holographic duality, which
reproduces the famous linear resistivity of the normal state of the copper
oxides, in addition to the linear specific heat. This holographic metal reveals
a simple and general mechanism for producing such a resistivity, which requires
only quenched disorder and a strongly interacting, locally quantum critical
state. The key is the minimal viscosity of the latter: unlike in a
Fermi-liquid, the viscosity is very small and therefore is important for the
electrical transport. This mechanism produces a resistivity proportional to the
electronic entropy.",1311.2451v2
2015-03-09,Effect of pressure on superconductivity in doped topological crystalline insulator Sn0.5In0.5Te,"We report on the impact of hydrostatic pressure on the superconductivity of
optimally (Indium) doped SnTe which is established to be derived from a
topological crystalline insulating phase. Single crystals of Sn1-xInxTe were
synthesized by a modified Bridgman method that exhibited maximum
superconducting Tc of 4.4 K for x= 0.5. Hydrostatic pressure upto 2.5 GPa was
applied on the crystals of Sn0.5In0.5Te and electrical resistivity as a
function of temperature and pressure was measured. We observed decrease in
onset superconducting transition temperature from 4.4 K to 2.8 K on increasing
pressure from ambient to 2.5 GPa. The normal state resistivity also decreased
abruptly by an order of magnitude at 0.5 GPa but for higher pressures, the same
decreased marginally. From onset, offset and zero resistivity values, dTc/dP of
-0.6K/GPa was confirmed. The low temperature normal state resistivity followed
T^2 dependence suggesting Fermi liquid behaviour both for ambient and high
pressure data. This increase in metallic characteristics accompanied by normal
state Fermi liquid behaviour is in accordance with a dome structure for Tc
variation with varying carrier concentration.",1503.02431v1
2015-03-24,Anisotropic Electronic Mobilities in the Nematic State of the Parent Phase NaFeAs,"Hall effect and magnetoresistance have been measured on single crystals of
the parent phase NaFeAs under a uniaxial pressure. Although significant
difference of the in-plane resistivity $\rho_{xx}(I\parallel a)$ and
$\rho_{xx}(I\parallel b)$ with the uniaxial pressure along $b$-axis was
observed, the transverse resistivity $\rho_{xy}$ shows a surprisingly isotropic
behavior. Detailed analysis reveals that the Hall coefficient $R_\mathrm{H}$
measured in the two orthogonal configurations ($I\parallel a$-axis and
$I\parallel b$-axis) coincide very well and exhibit a deviation from the high
temperature background at around the structural transition temperature
$T_{\mathrm{s}}$. Furthermore, the magnitude of $R_\mathrm{H}$ increases
remarkably below the structural transition temperature. This enhanced Hall
coefficient is accompanied by the non-linear transverse resistivity versus
magnetic field and enhanced magnetoresistance, which can be explained very well
by the two band model with anisotropic mobilities of each band. Our results
together with the two band model analysis clearly show that the anisotropic
in-plane resistivity in the nematic state is closely related to the distinct
quasiparticle mobilities when they are moving parallel or perpendicular to the
direction of the uniaxial pressure.",1503.07090v1
2015-10-13,"Global solvability, non-resistive limit and magnetic boundary layer of the compressible heat-conductive MHD equations","In general, the resistivity is inversely proportional to the electrical
conductivity, and is usually taken to be zero when the conducting fluid is of
extremely high conductivity (e.g., ideal conductors). In this paper, we first
establish the global well-posedness of strong solution to an initial-boundary
value problem of the one-dimensional compressible, viscous, heat-conductive,
non-resistive MHD equations with general heat-conductivity coefficient and
large data. Then, the non-resistive limit is justified and the convergence
rates are obtained, provided the heat-conductivity satisfies some growth
condition. Finally, we discuss the thickness of the magnetic boundary layer,
which is particularly in consistent with the Stokes-Blasius law in the
classical theory of laminar boundary layer.",1510.03529v2
2016-12-13,Strongly temperature dependent resistance of meander-patterned graphene,"We have studied the electronic properties of epitaxial graphene devices
patterned in a meander shape with the length up to a few centimeters and the
width of few tens of microns. These samples show a pronounced dependence of the
resistance on temperature. Accurate comparison with theory shows that this
temperature dependence originates from the weak localization effect observed
over a broad temperature range from 1.5 K up to 77 K. The comparison allows us
to estimate the characteristic times related to quantum interference. In
addition, a large resistance enhancement with temperature is observed at the
quantum Hall regime near the filling factor of 2. Record high resistance and
its strong temperature dependence are favorable for the construction of
bolometric photodetectors.",1612.04222v1
2016-12-15,Microscopic theory for radiation-induced Zero-Resistance States in 2D electron systems: Franck-Condon blockade,"We present a microscopic model on radiation-induced zero resistance states
according to a novel approach: Franck-Condon physics and blockade. Zero
resistance states rise up from radiation-induced magnetoresistance oscillations
when the light intensity is strong enough. The theory starts off with the {\it
radiation-driven electron orbit model} that proposes an interplay of the
swinging nature of the radiation-driven Landau states and the presence of
charged impurity scattering. When the intensity of radiation is high enough it
turns out that the driven-Landau states (vibrational states) involved in the
scattering process are spatially far from each other and the corresponding
electron wave functions do not longer overlap. As a result, it takes place a
drastic suppression of the scattering probability and then current and
magnetoresistance exponentially drop. Finally zero resistance states rise up.
This is an application to magnetotransport in two dimensional electron systems
of the Franck-Condon blockade, based on the Franck-Condon physics which in turn
stems from molecular vibrational spectroscopy.",1612.05247v1
2017-09-14,Simultaneous drop in mean free path and carrier density at the pseudogap onset in high-$T_c$ cuprates,"High-temperature superconducting cuprates are distinguished by an enigmatic
pseudogap which opens near optimal doping where the superconducting transition
temperature is highest. Key questions concern its origin and whether it is
essential in any way to superconductivity. Recent field-induced normal-state
transport experiments on hole-doped cuprates have measured abrupt changes in
the doping dependent Hall number and resistivity, consistent with a drop in
carrier density from $1+p$ to $p$ holes per copper atom, on entering the
pseudogap phase. In this work the change in resistivity is analyzed in terms of
an antiferromagnetic-order-induced Fermi surface reconstruction model that has
already successfully described the Hall number. In order for this model to
describe the resistivity we find that the zero-temperature mean free path must
also drop abruptly in proportion to the size of the Fermi surface. This
suggests that intrapocket scattering underlies the observed upturn in
resistivity in the pseudogap state.",1709.04590v1
2018-03-02,Robustness of the Insulating Bulk in the Topological Kondo Insulator SmB$_{6}$,"We used the inverted resistance method to extend the bulk resistivity of
SmB$_{6}$ to a regime where the surface conduction overwhelms the bulk.
Remarkably, the bulk resistivity shows an intrinsic thermally activated
behavior that changes ten orders of magnitude, suggesting that it is an ideal
insulator that is immune to disorder. Non-stoichiometrically-grown SmB$_{6}$
samples also show an almost identical thermally activated behavior. At low
temperatures, however, these samples show a mysterious high bulk resistivity
plateau, which may arise from extended defect conduction in a 3D TI.",1803.00959v1
2018-04-10,Purely electronic nanometallic ReRAM,"Resistance switching random access memory (ReRAM), with the ability to
repeatedly modulate electrical resistance, has been highlighted as a feasible
high-density memory with the potential to replace negative-AND (NAND) flash
memory. Such resistance modulation usually involves ion migration and filament
formation, which usually lead to relatively low device reliability and yield.
Resistance switching can also come from an entirely electronic origin, as in
nanometallic memory, by electron trapping and detrapping. Recent research has
revealed additional merits of its mechanism, which entails smart, atomic-sized
floating gates that can be easily engineered in amorphous Si, oxides, and
nitrides. This article addresses the basic ideas of nanometallic ReRAM, which
may also be a contender for analogue computing and non-von Neumann-type
computation.",1804.03302v1
2018-09-23,Resistive cooling of highly charged ions in a Penning trap to a fluid-like state,"We have performed a detailed experimental study of resistive cooling of large
ensembles of highly charged ions such as Ar$^{13+}$ in a cryogenic Penning
trap. Different from the measurements reported in [M. Vogel et al., Phys. Rev.
A, 043412 (2014)], we observe purely exponential cooling behavior when
conditions are chosen to allow collisional thermalization of the ions. We
provide evidence that in this situation, resistive cooling time constants and
final temperatures are independent of the initial ion energy, and that the
cooling time constant of a thermalized ion ensemble is identical to the
single-ion cooling time constant. For sufficiently high ion number densities,
our measurements show discontinuities in the spectra of motional resonances
which indicate a transition of the ion ensemble to a fluid-like state when
cooled to temperatures below approximately 14 K. With the final ion temperature
presently being 7.5 K, ions of the highest charge states are expected to form
ion crystals by mere resistive cooling, in particular not requiring the use of
laser cooling.",1809.08606v1
2019-09-13,Stabilizing effect of enhanced resistivity on peeling-ballooning instabilities on EAST,"Previous stability analysis of NSTX equilibrium with lithium-conditioning
demonstrates that the enhanced resistivity due to the increased effective
charge number Zeff (i.e. increased impurity level) can provide a stabilizing
effect on low-n edge localized modes (Banerjee et al 2017 Nucl. Fusion 24
054501). This paper extends the resistivity stabilizing effect to the
intermediate-n peeling-ballooning (PB) instabilities with the linear stability
analysis of EAST high-confinement mode equilibria in NIMROD two-fluid
calculations. However, the resistivity stabilizing effect on PB instabilities
in the EAST tokamak appears weaker than that found in NSTX. This work may give
better insight into the physical mechanism behind the beneficial effects of
impurity on the pedestal stability.",1909.06009v1
2020-03-10,Resonance peak shift in the photo-current of ultrahigh-mobility two-dimensional electron systems,"We report on a theoretical study on the rise of strong peaks at the harmonics
of the cyclotron resonance in the irradiated magnetoresistance in ultraclean
two-dimensional electron systems. The motivation is the experimental
observation of a totally unexpected strong resistance peak showing up at the
second harmonic. We extend the radiation-driven electron orbit model
(previously developed to study photocurrent oscillations and zero resistance
states) to a ultraclean scenario that implies longer scattering time and longer
mean free path. Thus, when the mean free path is equivalent, in terms of
energy, to twice the cyclotron energy ($2\hbar w_{c}$), the electron behaves as
under an effective magnetic field twice the one really applied. Then, at high
radiation power and/or low temperature, a resistance spike can be observed {\it
at the second harmonic}. For even cleaner samples the energy distance could
increase to three or four times the cyclotron energy giving rise to resistance
peaks at higher harmonics (third, fourth, etc.), i.e., a resonance peak shift
to lower magnetic fields as the quality of the sample increases. Thus, by
selecting the sample mobility one automatically would select the radiation
resonance response without altering the radiation frequency.",2003.04869v1
2020-03-22,Programmable quantum Hall bisector: towards a novel resistance standard for quantum metrology,"We demonstrate a programmable quantum Hall circuit that implements a novel
iterative voltage bisection scheme and allows obtaining any binary fraction
$(k/2^n)$ of the fundamental resistance quantum $R_K/2=h/2e^2$. The circuit
requires a number $n$ of bisection stages that only scales logarithmically with
the precision of the fraction. The value of $k$ can be set to any integer
between 1 and $2^n$ by proper gate configuration. The architecture exploits
gate-controlled routing, mixing and equilibration of edge modes of robust
quantum Hall states. The device does not contain {\em any} internal ohmic
contact potentially leading to spurious voltage drops. Our scheme addresses key
critical aspects of quantum Hall arrays of resistance standards, which are
today widely studied and used to create custom calibration resistances. The
approach is demonstrated in a proof-of-principle two-stage bisection circuit
built on a high-mobility GaAs/AlGaAs heterostructure operating at a temperature
of $260\,{\rm mK}$ and a magnetic field of $4.1\,{\rm T}$.",2003.10020v1
2014-08-27,DC resistivity at the onset of spin density wave order in two-dimensional metals,"The theory for the onset of spin density wave order in a metal in two
dimensions flows to strong coupling, with strong interactions not only at the
`hot spots', but on the entire Fermi surface. We advocate the computation of DC
transport in a regime where there is rapid relaxation to local equilibrium
around the Fermi surface by processes which conserve total momentum. The DC
resistivity is then controlled by weaker perturbations which do not conserve
momentum. We consider variations in the local position of the quantum critical
point, induced by long-wavelength disorder, and find a contribution to the
resistivity which is linear in temperature (up to logarithmic corrections) at
low temperature. Scattering of fermions between hot spots, by short-wavelength
disorder, leads to a residual resistivity and a correction which is linear in
temperature.",1408.6549v2
2017-01-26,Semi-analytical model of the contact resistance in two-dimensional semiconductors,"Contact resistance is a severe performance bottleneck for electronic devices
based on two-dimensional layered (2D) semiconductors, whose contacts are
Schottky rather than Ohmic. Although there is general consensus that the
injection mechanism changes from thermionic to tunneling with gate biasing,
existing models tend to oversimplify the transport problem, by neglecting the
2D transport nature and the modulation of the Schottky barrier height, the
latter being of particular importance in back-gated devices. In this work, we
develop a semi-analytical model based on Bardeen's transfer Hamiltonian
approach to describe both effects. Remarkably, our model is able to reproduce
several experimental observations of a metallic behavior in the contact
resistance, i.e., a decreasing resistance with decreasing temperature,
occurring at high gate voltage.",1701.07758v1
2018-10-05,A Deep Learning Approach to the Inversion of Borehole Resistivity Measurements,"We use borehole resistivity measurements to map the electrical properties of
the subsurface and to increase the productivity of a reservoir. When used for
geosteering purposes, it becomes essential to invert them in real time. In this
work, we explore the possibility of using Deep Neural Network (DNN) to perform
a rapid inversion of borehole resistivity measurements. Herein, we build a DNN
that approximates the following inverse problem: given a set of borehole
resistivity measurements, the DNN is designed to deliver a physically
meaningful and data-consistent piecewise one-dimensional layered model of the
surrounding subsurface. Once the DNN is built, we can perform the actual
inversion of the field measurements in real time. We illustrate the performance
of DNN of logging-while-drilling measurements acquired on high-angle wells via
synthetic data.",1810.04522v2
2020-09-21,A small-signal GFET equivalent circuit considering an explicit contribution of contact resistances,"A small-signal equivalent circuit for graphene field-effect transistors is
proposed considering the explicit contribution of effects at the metal-graphene
interfaces by means of contact resistances. A methodology to separate the
contact resistances from intrinsic parameters, obtained by a de-embedding
process, and extrinsic parameters of the circuit is considered. The
experimental high-frequency performance of three devices from two different
GFET technologies is properly described by the proposed small-signal circuit.
Some model parameters scale with the device footprint. The correct detachment
of contact resistances from the internal transistor enables to assess their
impact on the intrinsic cutoff frequency of the studied devices.",2009.09673v2
2014-01-30,Scale-invariant hyperscaling-violating holographic theories and the resistivity of strange metals with random-field disorder,"We compute the direct current resistivity of a scale-invariant,
$d$-dimensional strange metal with dynamic critical exponent $z$ and
hyperscaling-violating exponent $\theta$, weakly perturbed by a scalar operator
coupled to random-field disorder that locally breaks a $\mathbb{Z}_2$ symmetry.
Independent calculations via Einstein-Maxwell-Dilaton holography and memory
matrix methods lead to the same results. We show that random field disorder has
a strong effect on resistivity: charge carriers in the infrared are easily
depleted, as the relaxation time for momentum is surprisingly small. In the
course of our holographic calculation we use a non-trivial dilaton coupling to
the disordered scalar, allowing us to study a strongly-coupled scale invariant
theory with $\theta \ne 0$. Using holography, we are also able to determine the
disorder strength at which perturbation theory breaks down. Curiously, for
locally critical theories this breakdown occurs when the resistivity is
proportional to the entropy density, up to a possible logarithmic correction.",1401.7993v3
2017-04-24,Resistivity bound for hydrodynamic bad metals,"We obtain a rigorous upper bound on the resistivity $\rho$ of an electron
fluid whose electronic mean free path is short compared to the scale of spatial
inhomogeneities. When such a hydrodynamic electron fluid supports a non-thermal
diffusion process -- such as an imbalance mode between different bands -- we
show that the resistivity bound becomes $\rho \lesssim A \, \Gamma$. The
coefficient $A$ is independent of temperature and inhomogeneity lengthscale,
and $\Gamma$ is a microscopic momentum-preserving scattering rate. In this way
we obtain a unified and novel mechanism -- without umklapp -- for $\rho \sim
T^2$ in a Fermi liquid and the crossover to $\rho \sim T$ in quantum critical
regimes. This behavior is widely observed in transition metal oxides, organic
metals, pnictides and heavy fermion compounds and has presented a longstanding
challenge to transport theory. Our hydrodynamic bound allows phonon
contributions to diffusion constants, including thermal diffusion, to directly
affect the electrical resistivity.",1704.07384v1
2017-05-12,Resistive switching in MoSe$_{2}$/BaTiO$_{3}$ hybrid structures,"Here we study the resistive switching (RS) effect that emerges when
ferroelectric BaTiO$_{3}$ (BTO) and few-layers MoSe$_{2}$ are combined in one
single structure. The C-V loops reveal the ferroelectric nature of both
Al/Si/SiO$_{x}$/BTO/Au and Al/Si/SiO$_{x}$/MoSe$_{2}$/BTO/Au structures and the
high quality of the SiO$_{x}$/MoSe$_{2}$ interface in the
Al/Si/SiOx/MoSe$_{2}$/Au structure. Al/Si/SiO$_{x}$/MoSe$_{2}$/BTO/Au hybrid
structures show the electroforming free resistive switching that is explained
on the basis of the modulation of the potential distribution at the
MoSe$_{2}$/BTO interface via ferroelectric polarization flipping. This
structure shows promising resistive switching characteristics with switching
ratio of $\approx{}$10$^{2}$ and a stable memory window, which are highly
required for memory applications.",1705.04475v1
2019-03-04,On Resistive Memories: One Step Row Readout Technique and Sensing Circuitry,"Transistor-based memories are rapidly approaching their maximum density per
unit area. Resistive crossbar arrays enable denser memory due to the small size
of switching devices. However, due to the resistive nature of these memories,
they suffer from current sneak paths complicating the readout procedure. In
this paper, we propose a row readout technique with circuitry that can be used
to read {selector-less} resistive crossbar based memories. High throughput
reading and writing techniques are needed to overcome the memory-wall
bottleneck problem and to enable near memory computing paradigm. The proposed
technique can read the entire row of dense crossbar arrays in one cycle, unlike
previously published techniques. The requirements for the readout circuitry are
discussed and satisfied in the proposed circuit. Additionally, an approximated
expression for the power consumed while reading the array is derived. A figure
of merit is defined and used to compare the proposed approach with existing
reading techniques. Finally, a quantitative analysis of the effect of biasing
mismatch on the array size is discussed.",1903.01512v1
2011-04-22,Symmetry breaking as the origin of zero-differential resistance states of a 2DEG in strong magnetic fields,"Zero resistance differential states have been observed in two-dimensional
electron gases (2DEG) subject to a magnetic field and a strong dc current. In a
recent work we presented a model to describe the nonlinear transport regime of
this phenomenon. From the analysis of the differential resistivity and the
longitudinal voltage we predicted the formation of negative differential
resistivity states, although these states are known to be unstable. Based on
our model, we derive an analytical approximated expression for the
Voltage-Current characteristics, that captures the main elements of the
problem. The result allow us to construct an energy functional for the system.
In the zero temperature limit, the system presents a quantum phase transition,
with the control parameter given by the magnetic field. It is noted that above
a threshold value ($B>B_{th}$), the symmetry is spontaneously broken. At
sufficiently high magnetic field and low temperature the model predicts a phase
with a non-vanishing permanent current; this is a novel phase that has not been
observed so far.",1104.4476v1
2012-03-08,Precision quantization of Hall resistance in transferred graphene,"We show that quantum resistance standards made of transferred graphene reach
the uncertainty of semiconductor devices, the current reference system in
metrology. A large graphene device (150 \times 30 \mum2), exfoliated and
transferred onto GaAs, revealed a quantization with a precision of (-5.1 \pm
6.3) \times 10-9 accompanied by a vanishing longitudinal resistance at current
levels exceeding 10 \muA. While such performance had previously only been
achieved with epitaxially grown graphene, our experiments demonstrate that
transfer steps, inevitable for exfoliated graphene or graphene grown by
chemical vapor deposition (CVD), are compatible with the requirements of high
quality quantum resistance standards.",1203.1798v2
2012-03-23,Pressure effects on the heavy-fermion antiferromagnet CeAuSb2,"The f-electron compound CeAuSb2, which crystallizes in the ZrCuSi2-type
tetragonal structure, orders antiferromagnetically between 5 and 6.8 K, where
the antiferromagnetic transition temperature T_N depends on the occupancy of
the Au site. Here we report the electrical resistivity and heat capacity of a
high-quality crystal CeAuSb2 with T_N of 6.8 K, the highest for this compound.
The magnetic transition temperature is initially suppressed with pressure, but
is intercepted by a new magnetic state above 2.1 GPa. The new phase shows a
dome shape with pressure and coexists with another phase at pressures higher
than 4.7 GPa. The electrical resistivity shows a T^2 Fermi liquids behavior in
the complex magnetic state, and the residual resistivity and the T^2
resistivity coefficient increases with pressure, suggesting the possibility of
a magnetic quantum critical point at a higher pressure.",1203.5164v1
2015-06-03,Electronic resistances of multilayered two-dimensional crystal junctions,"We carry out a layer-by-layer investigation to understand electron transport
across metal-insulator-metal junctions. Interfacial structures of junctions
were studied and characterized using first-principles density functional theory
within the generalized gradient approximation. We found that as a function of
the number of crystal layers the calculated transmission coefficients of
multilayer silicene junctions decay much slower than for BN-based junctions We
revisited the semiclassical Boltzmann theory of electronic transport and
applied to multilayer silicene and BN-based junctions. The calculated
resistance in the high-transmission regime is smaller than that provided by the
Landauer formula. As the thickness of the barrier increases, results from the
Boltzmann and the Landauer formulae converge. We provide a upper limit in the
transmission coefficient below which, the Landauer method becomes valid.
Quantitatively, when the transmission coefficient is lower than $ \sim 0.05 $
per channel, the error introduced by the Landauer formula for calculating the
resistance is negligible. In addition, we found that the resistance of a
junction is not entirely determined by the averaged transmission, but also by
the distribution of the transmission over the first Brillouin zone.",1506.01397v1
2019-01-28,Quantifying Temperature-dependent Substrate Loss in GaN-on-Si RF Technology,"Intrinsic limits to temperature-dependent substrate loss for GaN-on-Si
technology, due to the change in resistivity of the substrate with temperature,
are evaluated using an experimentally validated device simulation framework.
Effect of room temperature substrate resistivity on temperature-dependent CPW
line loss at various operating frequency bands are then presented. CPW lines
for GaN-on-high resistivity Si are shown to have a pronounced
temperature-dependence for temperatures above 150{\deg}C and have lower
substrate losses for frequencies above the X-band. On the other hand,
GaN-on-low resistivity Si is shown to be more temperature-insensitive and have
lower substrate losses than even HR-Si for lower operating frequencies. The
effect of various CPW geometries on substrate loss is also presented to
generalize the discussion. These results are expected to act as a benchmark for
temperature dependent substrate loss in GaN-on-Si RF technology.",1901.09521v1
2019-01-29,Simultaneous prediction of multiple outcomes using revised stacking algorithms,"Motivation: HIV is difficult to treat because its virus mutates at a high
rate and mutated viruses easily develop resistance to existing drugs. If the
relationships between mutations and drug resistances can be determined from
historical data, patients can be provided personalized treatment according to
their own mutation information. The HIV Drug Resistance Database was built to
investigate the relationships. Our goal is to build a model using data in this
database, which simultaneously predicts the resistance of multiple drugs using
mutation information from sequences of viruses for any new patient.
  Results: We propose two variations of a stacking algorithm which borrow
information among multiple prediction tasks to improve multivariate prediction
performance. The most attractive feature of our proposed methods is the
flexibility with which complex multivariate prediction models can be
constructed using any univariate prediction models. Using cross-validation
studies, we show that our proposed methods outperform other popular
multivariate prediction methods.
  Availability: An R package will be made available.",1901.10153v1
2019-06-07,A resistive extension for ideal MHD,"We present an extension to the special relativistic, ideal
magnetohydrodynamics (MHD) equations, designed to capture effects due to
resistivity. The extension takes the simple form of an additional source term
which, when implemented numerically, is shown to emulate the behaviour produced
by a fully resistive MHD description for a range of initial data. The extension
is developed from first principle arguments, and thus requires no fine tuning
of parameters, meaning it can be applied to a wide range of dynamical systems.
Furthermore, our extension does not suffer from the same stiffness issues
arising in resistive MHD, and thus can be evolved quickly using explicit
methods, with performance benefits of roughly an order of magnitude compared to
current methods.",1906.03150v2
2019-06-19,Phonon scattering induced carrier resistivity in twisted double bilayer graphene,"In this work we carry out a theoretical study of the phonon-induced
resistivity in twisted double bilayer graphene (TDBG), in which two
Bernal-stacked bilayer graphene devices are rotated relative to each other by a
small angle $\theta$. We show that at small twist angles ($\theta\sim 1^\circ$)
the effective mass of the TDBG system is greatly enhanced, leading to a
drastically increased phonon-induced resistivity in the high-temperature limit
where phonon scattering leads to a linearly increasing resistivity with
increasing temperature. We also discuss possible implications of our theory on
superconductivity in such a system, and provide an order of magnitude
estimation of the superconducting transition temperature.",1906.08224v2
2021-02-16,Fast hierarchical inversion for borehole resistivity measurements in high-angle and horizontal wells using ADNN-AMLM,"With the rapid development of deep learning, intelligent scheme is gradually
introduced to solve various nolinear inverse problems. In this paper, we
combine an efficient adaptive deep neural network (ADNN) framework with
adaptive modified Levenberg-Marquardt (AMLM) algorithm based on three-layer
inversion model to exact formation resistivity and invasion depth from array
laterolog resistivity measurements. ADNN presented in this paper can realize
the 2D/3D fast forward modeling of array laterolog. AMLM algorithm and
hierarchical inversion scheme are adopted to improve the anti-noise ability and
convergence in complex logging environments, which realizing the fast and
accurate reconstruction of longitudinal resistivity profile in HA/HZ wells. The
numerical simulation shows that the ADNN forward modeling only takes 0.021s for
each logging point, and the maximum relative error is less than 2%. Three-layer
inversion model can eliminate the effect of surrounding bed and improve the
inversion accuracy in thinly layered formation. The error between inverted
results and truth model is less than 3%. The AMLM inversion algorithm can
effectively suppress the influence of noise, and takes only 10 steps to achieve
convergence.",2102.08038v1
2021-04-01,Towards high-rate RPC-based thermal neutron detectors using low-resistivity electrodes,"We present experimental results on the counting rate measurements for several
single-gap $^{10}$B lined resistive plate chambers ($^{10}$B-RPCs) with anodes
made from standard float glass, low resistivity glass and ceramic. The
measurements were performed at the V17 monochromatic neutron beamline (3.35
\.A) at the Helmholtz-Zentrum Berlin. For the $^{10}$B-RPCs with 0.28 mm thick
float glass a maximum counting rate density of about $8\times 10^{3}$
$Hz/cm^{2}$ was obtained. In the case of low resistivity glass and ceramic, the
counting rate density did not deviate from linear dependence on the neutron
flux up to the maximum flux available at this beamline and exceeded a value of
$3\times 10^{4}$ $Hz/cm^{2}$.",2104.00695v1
2021-09-14,Contactless Series Resistance Imaging of Perovskite Solar Cells via Inhomogeneous Illumination,"A contactless effective series resistance imaging method for large area
perovskite solar cells that is based on photoluminescence imaging with
non-uniform illumination is introduced and demonstrated experimentally. The
proposed technique is applicable to partially and fully processed perovskite
solar cells if laterally conductive layers are present. The capability of the
proposed contactless method to detect features with high effective series
resistance is validated by comparison with various contacted mode luminescence
imaging techniques. The method can reliably provide information regarding the
severeness of the detected series resistance through photo-excitation pattern
manipulation. Application of the method to sub-cells in monolithic tandem
devices, without the need for electrical contacting the terminals, appears
feasible.",2109.06971v1
2021-12-29,Wide-range $T^2$ resistivity and umklapp scattering in moiré graphene,"We argue that the unusually strong electron-electron interactions in the
narrow bands in moir\'e superlattices originate from compact Wannier orbitals.
Enhanced overlaps of electronic wavefunctions, enabled by such orbitals, result
in a strong el-el superlattice umklapp scattering. We identify the umklapp
scattering processes as a source of the strong temperature-dependent
resistivity observed in these systems. In a simple model, the umklapp
scattering predicts a $T$-dependent resistivity that grows as $T^2$ and is
getting bigger as the Wannier orbital radius decreases. We quantify the
enhancement in el-el scattering by the Kadowaki-Woods (KW) ratio, a quantity
that is sensitive to umklapp scattering but, helpfully, insensitive to the
effects due to the high density of electronic states. Our analysis predicts
anomalously large KW ratio values that clearly indicate the importance of the
umklapp el-el processes and their impact on the $T$-dependent resistivity.",2112.14745v2
2022-06-05,Simplicial effective resistance and enumeration of spanning trees,"A graph can be regarded as an electrical network in which each edge is a
resistor. This point of view relates combinatorial quantities, such as the
number of spanning trees, to electrical ones such as effective resistance. The
second and third authors have extended the combinatorics/electricity analogy to
higher dimension and expressed the simplicial analogue of effective resistance
as a ratio of weighted tree enumerators. In this paper, we first use that ratio
to prove a new enumeration formula for color-shifted complexes, confirming a
conjecture by Aalipour and the first author, and generalizing a result of
Ehrenborg and van Willigenburg on Ferrers graphs. We then use the same
technique to recover an enumeration formula for shifted complexes, first proved
by Klivans and the first and fourth authors. In each case, we add facets one at
a time, and give explicit expressions for simplicial effective resistances of
added facets by constructing high-dimensional analogues of currents and
voltages (respectively homological cycles and cohomological cocycles).",2206.02182v2
2022-11-25,Numerical study of SQUID array responses due to asymmetric junction parameters,"Superconducting quantum interference device arrays have been extensively
studied for their high magnetic field sensitivity. The performance of these
devices strongly depends on the characteristic parameters of their Josephson
junctions, i.e. their critical currents and shunt resistances. Using a
resistively shunted junction model and including thermal noise, we perform a
numerical investigation of the effects of asymmetric Josephson junctions by
independently studying variations in the critical currents and junction
resistances. We compare the voltage response of a dc-SQUID with a 1D parallel
SQUID array and study the maximum transfer function dependence on the number of
junctions in parallel, the screening parameter and thermal noise strength. Our
results show that the maximum transfer function and linearity increase with the
number of junctions in parallel for arrays with different junction resistances,
in contrast to SQUID arrays with identical junctions or with spreads in the
critical currents.",2211.13833v1
2023-01-08,Resistive Read-out in Thin Silicon Sensors with Internal Gain,"Two design innovations, low-gain avalanche (Low-Gain Avalance Diode, LGAD)
and resistive read-out (Resistive Silicon Detector, RSD), have brought strong
performance improvements to silicon sensors. Large signals, due to the added
gain mechanism, lead to improved temporal precision, while charge sharing,
introduced by resistive read-out, allows for achieving excellent spatial
resolution even with large pixels. LGAD- and RSD- based silicon sensors are now
adopted, or considered, in several future experiments and are the basis for
almost every next 4D-trackers. New results obtained with sensors belonging to
the second FBK production of RSD (RSD2) demonstrate how a combined resolution
of 30 ps and 30 \microns can be obtained with pixels as large as $1 \times 1 $
mm$^2$.",2301.02968v1
2023-06-09,Voltage-time dilemma and stochastic threshold voltage variation in pure silver atomic switches,"The formation and dissolution of silver nanowires plays a fundamental role in
a broad range of resistive switching devices, fundamentally relying on the
electrochemical metallization phenomenon. It was shown, however, that resistive
switching may also appear in pure metallic nanowires lacking any
silver-ion-hosting embedding environment, but this pure atomic switching
mechanism fundamentally differs from the conventional
electrochemical-metallization-based resistive switching. To facilitate the
quantitative description of the former phenomenon, we investigate broad range
of Ag atomic junctions with a special focus on the frequency-dependence and the
fundamentally stochastic cycle-to-cycle variation of the switching threshold
voltage. These devices are established in an ultra-high purity environment
where electrochemical metallization can be excluded. The measured
characteristics are successfully described by a vibrational pumping model,
yielding consistent predictions for the weak frequency dependence and the large
variance of the switching threshold voltage. We also demonstrate that
electrochemical-metallization-based resistive switching and pure atomic
switching may appear in the same device structure, and therefore the proper
understanding of the pure atomic switching mechanism has a distinguished
importance in silver-based electrochemical metallization cells.",2306.05736v1
2023-08-19,"Temperature, RF Field, and Frequency Dependence Performance Evaluation of Superconducting Niobium Half-Wave Cavity","Recent advancement in superconducting radio frequency cavity processing
techniques, with diffusion of impurities within the RF penetration depth,
resulted in high quality factor with increase in quality factor with increasing
accelerating gradient. The increase in quality factor is the result of a
decrease in the surface resistance as a result of nonmagnetic impurities doping
and change in electronic density of states. The fundamental understanding of
the dependence of surface resistance on frequency and surface preparation is
still an active area of research. Here, we present the result of RF
measurements of the TEM modes in a coaxial half wave niobium cavity resonating
at frequencies between 0.3-1.3 GHz. The temperature dependence of the surface
resistance was measured between 4.2 K and 1.6 K. The field dependence of the
surface resistance was measured at 2.0 K. The baseline measurements were made
after standard surface preparation by buffered chemical polishing.",2308.09859v1
2023-12-16,Negative differential resistance in Josephson junctions coupled to a cavity,"Regions with negative differential resistance can arise in the IV curve of
Josephson junctions and this phenomenon plays an essential role for
applications, in particular for THz radiation emission. For the measurement of
high frequency radiation from Josephson junctions, a cavity - either internal
or external - is often used. A cavity may also induce a negative differential
resistance region at the lower side of the resonance frequency. We investigate
the dynamics of Josephson junctions with a negative differential resistance in
the quasi particle tunnel current, i.e. in the McCumber curve. We find that
very complicated and unexpected interactions take place. This may be useful for
the interpretation of experimental measurements of THz radiation from intrinsic
Josephson junctions.",2312.14174v1
1995-01-26,Superconductivity and Stoichiometry in the BSCCO-family Materials,"We report on magnetization, c-axis and ab-plane resistivity, critical
current, electronic band structure and superconducting gap properties. Bulk
measurements and photoemission data were taken on similar samples.",9501124v1
2002-06-14,Electron scattering in multi-wall carbon-nanotubes,"We analyze two scattering mechanisms that might cause intrinsic electronic
resistivity in multi-wall carbon nanotubes: scattering by dopant impurities,
and scattering by inter-tube electron-electron interaction. We find that for
typically doped multi-wall tubes backward scattering at dopants is by far the
dominating effect.",0206264v1
2003-07-11,Magnetic and transport percolation in diluted magnetic semiconductors,"The ferromagnetic transition in a diluted magnetic semiconductor with
localized charge carriers is inevitably a percolation transition. In this work
we theoretically study the correlation between this magnetic percolation and
transport properties of the sample, including the possibility of a simultaneous
transport percolation. We find nontrivial signatures of the percolating
magnetic clusters in the transport properties of the system, including
interesting non-monotonic temperature dependence of the system resistivity.",0307294v1
2003-09-26,Vortex dynamics in dilute two dimensional Josephson junction arrays,"We have investigated the dynamics of vortices in a dilute two dimensional
Josephson junction array where a fraction of the superconducting islands is
missing. We have used the multiple trapping model to calculate the mobility of
vortices and the frequency dependence of the resistance and inductance of the
array.",0309620v1
2004-04-01,Hall anomaly in mixed state of superconductors and vortex dynamics,"The present author has long argued, with concrete predictions, that both
longitudinal and transverse (Hall) resistivities in the mixed state of
superconductors are dominated by vortex many-body effect. Hence there is no
need to introduce various ad hoc vortex dynamics theories. It is interesting to
note this point of view is now slowly creeping into the work of his most fierce
opponents.",0404009v1
2010-01-29,Cooper pairs under the action of disorder and strong magnetic field,"The zero temperature phase diagram of Cooper pairs exposed to disorder and
magnetic field is found to exhibit four distinct phases: a Bose and a Fermi
insulating, a metallic and a superconducting phase, respectively. The results
explain the giant negative magneto-resistance found experimentally in In-O,
TiN, Bi and high-$T_c$ materials.",1001.5431v2
2011-01-17,Localized superconductive pairs,"Different physical phenomena are discussed which should help to comprehend
and interpret the concept of localized superconductive pairs; these include
behavior of highly resistive granular materials with superconducting grains,
parity effect and the Berezinskii--Kosterlitz--Thouless transition.
Experimental arguments in support of localized pairs existence are presented
and conditions which promote their appearance are analyzed.",1101.3203v2
2016-07-06,Multilayer coating for higher accelerating fields in superconducting radio-frequency cavities: a review of theoretical aspects,"Theory of the superconductor-insulator-superconductor (S-I-S) multilayer
structure in superconducting accelerating cavity application is reviewed. The
theoretical field limit, optimum layer thicknesses and material combination,
and surface resistance are discussed. Those for the S-S bilayer structure are
also reviewed.",1607.01495v3
2023-05-25,Structure and properties of the films based on ternary transition metal borides: theory and experiment,"The review presents the results of theoretical and experimental studies of
the structure, bonding between atoms, mechanical properties, thermal stability,
and oxidation and corrosion resistance of films based on ternary transition
metal borides.",2305.15854v1
2005-12-19,Insulating transition in the flux-flow resistivity of a high temperature superconductor,"Measurements of the DC resistivity of under-doped cuprate superconductors
have revealed a metal--insulator transition at low temperatures when
superconductivity is suppressed by a very large magnetic field, with the
resistivity growing logarithmically in the low temperature limit. This
insulating behaviour has been associated not only with the large magnetic
fields, but also with the under-doped composition and intrinsic sample
inhomogeneity, and it is important to establish whether these factors are
essential to it. Here we report high resolution microwave measurements of the
flux-flow resistivity of optimally doped YBa_(2)Cu_(3)O_(6+x) in the mixed
state at temperatures down to 1.2 K. We find that the effective resistivity of
the vortex cores exhibits a metal-insulator transition, with a minimum at 13 K
and a logarithmically growing form below 5 K. The transition is seen in samples
of the highest quality and in magnetic fields as low as 1 T. Our work is the
first report of a metal-insulator transition in optimally doped
YBa_(2)Cu_(3)O_(6+x), and the first such transition to be seen in a system in
which superconductivity has not been globally suppressed.",0512459v1
2010-09-30,Resistivity-driven State Changes in Vertically Stratified Accretion Disks,"We investigate the effect of shear viscosity and Ohmic resistivity on the
magnetorotational instability (MRI) in vertically stratified accretion disks
through a series of local simulations with the Athena code. First, we use a
series of unstratified simulations to calibrate physical dissipation as a
function of resolution and background field strength; the effect of the
magnetic Prandtl number, Pm = viscosity/resistivity, on the turbulence is
captured by ~32 grid zones per disk scale height, H. In agreement with previous
results, our stratified disk calculations are characterized by a subthermal,
predominately toroidal magnetic field that produces MRI-driven turbulence for
|z| < 2 H. Above |z| = 2 H, magnetic pressure dominates and the field is
buoyantly unstable. Large scale radial and toroidal fields are also generated
near the mid-plane and subsequently rise through the disk. The polarity of this
mean field switches on a roughly 10 orbit period in a process that is
well-modeled by an alpha-omega dynamo. Turbulent stress increases with Pm but
with a shallower dependence compared to unstratified simulations. For
sufficiently large resistivity, on the order of cs H/1000, where cs is the
sound speed, MRI turbulence within 2 H of the mid-plane undergoes periods of
resistive decay followed by regrowth. This regrowth is caused by amplification
of toroidal field via the dynamo. This process results in large amplitude
variability in the stress on 10 to 100 orbital timescales, which may have
relevance for partially ionized disks that are observed to have high and low
accretion states.",1010.0005v2
2011-11-30,Self-Similar Solutions for Viscous and Resistive ADAF,"In this paper, the self-similar solution of resistive advection dominated
accretion flows (ADAF) in the presence of a pure azimuthal magnetic field is
investigated. The mechanism of energy dissipation is assumed to be the
viscosity and the magnetic diffusivity due to turbulence in the accretion flow.
It is assumed that the magnetic diffusivity and the kinematic viscosity are not
constant and vary by position and $\alpha$-prescription is used for them. In
order to solve the integrated equations that govern the behavior of the
accretion flow, a self-similar method is used. The solutions show that the
structure of accretion flow depends on the magnetic field and the magnetic
diffusivity. As, the radial infall velocity and the temperature of the flow
increase, and the rotational velocity decreases. Also, the rotational velocity
for all selected values of magnetic diffusivity and magnetic field is
sub-Keplerian. The solutions show that there is a certain amount of magnetic
field that the rotational velocity of the flow becomes zero. This amount of the
magnetic field depends on the gas properties of the disc, such as adiabatic
index and viscosity, magnetic diffusivity, and advection parameters. The
solutions show the mass accretion rate increases by adding the magnetic
diffusivity and in high magnetic pressure case, the ratio of the mass accretion
rate to the Bondi accretion rate decreases as magnetic field increases. Also,
the study of Lundquist and magnetic Reynolds numbers based on resistivity
indicates that the linear growth of magnetorotational instability (MRI) of the
flow decreases by resistivity. This property is qualitatively consistent with
resistive magnetohydrodynamics (MHD) simulations.",1111.7302v1
2016-11-09,Numerical integral of resistance coefficients in diffusion,"The resistance coefficients in screen Coulomb potential of stellar plasma are
evaluated in high accuracy. I have analyzed the possible singularities in the
integral of scattering angle. There are possible singularities in the case of
attractive potential. This may result in problem for numerical integral. In
order to avoid the problem, I have used a proper scheme, e.g., splitting into
many subintervals and the width of each subinterval is determined by the
variation of the integrand, to calculate the scattering angle. The collision
integrals are calculated by using Romberg's method therefore the accuracy is
high (i.e., $ \sim 10^{-12}$). The results of collision integrals and their
derivatives in $-12 \leq \psi \leq 5$ are listed. By using Hermite polynomial
interpolation from those data, the collision integrals can be obtained with an
accuracy of $10^{-10}$. For very weak coupled plasma ($\psi \geq 4.5$),
analytical fittings for collision integrals are available with an accuracy of
$10^{-11}$. I have compared the final results of resistance coefficients with
other works and found that, for repulsive potential, the results are basically
same to others, for attractive potential, the results in intermediate and
strong coupled case show significant differences. The resulting resistance
coefficients are tested in the solar model. Comparing with the widely used Cox
et al.(1989) and Thoul et al. (1994) models, the resistance coefficients in
screen Coulomb potential leads to a little weaker effect in solar model, which
is contrary to the expectation of attempts to solve the solar abundance
problem.",1611.03115v1
2019-03-28,Dynamic Streaming Spectral Sparsification in Nearly Linear Time and Space,"In this paper we consider the problem of computing spectral approximations to
graphs in the single pass dynamic streaming model. We provide a linear
sketching based solution that given a stream of edge insertions and deletions
to a $n$-node undirected graph, uses $\tilde O(n)$ space, processes each update
in $\tilde O(1)$ time, and with high probability recovers a spectral sparsifier
in $\tilde O(n)$ time. Prior to our work, state of the art results either used
near optimal $\tilde O(n)$ space complexity, but brute-force $\Omega(n^2)$
recovery time [Kapralov et al.'14], or with subquadratic runtime, but
polynomially suboptimal space complexity [Ahn et al.'14, Kapralov et al.'19].
  Our main technical contribution is a novel method for `bucketing' vertices of
the input graph into clusters that allows fast recovery of edges of
sufficiently large effective resistance. Our algorithm first buckets vertices
of the graph by performing ball-carving using (an approximation to) its
effective resistance metric, and then recovers the high effective resistance
edges from a sketched version of an electrical flow between vertices in a
bucket, taking nearly linear time in the number of vertices overall. This
process is performed at different geometric scales to recover a sample of edges
with probabilities proportional to effective resistances and obtain an actual
sparsifier of the input graph.
  This work provides both the first efficient $\ell_2$-sparse recovery
algorithm for graphs and new primitives for manipulating the effective
resistance embedding of a graph, both of which we hope have further
applications.",1903.12150v1
2019-06-20,Substrate mediated nitridation of niobium into superconducting Nb2N thin films for phase slip study,"Here we report a novel nitridation technique for transforming niobium into
hexagonal Nb2N which appears to be superconducting below 1K. The nitridation is
achieved by high temperature annealing of Nb films grown on Si3N4/Si (100)
substrate under high vacuum. The structural characterization directs the
formation of a majority Nb2N phase while the morphology shows granular nature
of the films. The temperature dependent resistance measurements reveal a wide
metal-to-superconductor transition featuring two distinct transition regions.
The region close to the normal state varies strongly with the film thickness,
whereas, the second region in the vicinity of the superconducting state remains
almost unaltered but exhibiting resistive tailing. The current-voltage
characteristics also display wide transition embedded with intermediate
resistive states originated by phase slip lines. The transition width in
current and the number of resistive steps depend on film thickness and they
both increase with decrease in thickness. The broadening in transition width is
explained by progressive establishment of superconductivity through proximity
coupled superconducting nano-grains while finite size effects and quantum
fluctuation may lead to the resistive tailing. Finally, by comparing with Nb
control samples, we emphasize that Nb2N offers unconventional superconductivity
with promises in the field of phase slip based device applications.",1906.08692v1
2021-04-28,Channel Models and Coding Solutions for 1S1R Crossbar Resistive Memory with High Line Resistance,"Crossbar resistive memory with the 1 Selector 1 Resistor (1S1R) structure is
attractive for nonvolatile, high-density, and low-latency storage-class memory
applications. As technology scales down to the single-nm regime, the increasing
resistivity of wordline/bitline becomes a limiting factor to device
reliability. This paper presents write/read communication channels while
considering the line resistance and device variabilities by statistically
relating the degraded write/read margins and the channel parameters. Binary
asymmetric channel (BAC) models are proposed for the write/read operations.
Simulations based on these models suggest that the bit-error rate of devices
are highly non-uniform across the memory array. These models provide
quantitative tools for evaluating the trade-offs between memory reliability and
design parameters, such as array size, technology nodes, and aspect ratio, and
also for designing coding-theoretic solutions that would be most effective for
crossbar memory. Method for optimizing the read threshold is proposed to reduce
the raw bit-error rate (RBER). We propose two schemes for efficient channel
coding based on Bose-Chaudhuri-Hocquenghem (BCH) codes. An interleaved coding
scheme is proposed to mitigate the non-uniformity of reliability and a location
dependent coding framework is proposed to leverage this non-uniformity. Both of
our proposed coding schemes effectively reduce the undetected bit-error rate
(UBER).",2104.14011v1
2022-05-13,The Relationship Between Insulin Resistance Neutrophil to Lymphocyte Ratio,"Aim: There is increasing interest in the role of chronic inflammation on
pathogenesis of various disease, and one of its markers, high NLR is associated
with various mortality and morbidity risk. Insulin resistance (IR) might be one
potential associate factors, as suggested in preclinical studies. However,
epidemiological studies are scarce which investigated the association between
NLR, and insulin resistance (IR) and they included only diabetes mellitus
patients, not the general population. This study aims to determine if there is
a direct correlation between NLR and IR in the US general population. Methods:
The sample consists of 3,307 from general population, provided by National
Health and Nutrition Examination Survey (NHANES). Homeostasis Model Assessment
of Insulin Resistance (HOMA-IR) value was calculated to evaluate insulin
resistance. We investigated the relationship between their NLR and HOMA-IR
values by bivariate and multivariate linear regression analyses. As insulin use
could results in inaccurate HOMA-IR estimation, we excluded them and ran the
analyses in subgroup analyses. Results: There was a relationship shown when
insulin users were included, having a beta coefficient value of 0.010 (95%
confidence interval [CI] of 0.003-0.017). However, when insulin users were
excluded, the beta value decreased to 0.004 (95% CI of -0.006-0.015). The
statistical significance was not reached when age, sex, and body mass index
were adjusted for in the multivariate analyses. Conclusion: There is no visible
relationship between IR and NLR in the general population. IR might not explain
the variation of NLR value in healthy people, and further studies are needed to
reveal the associated factor of high NLR.",2205.08308v2
2019-12-08,Multifilamentary character of anticorrelated capacitive and resistive switching in memristive structures based on (CoFeB)x(LiNbO3)100-x nanocomposite,"Resistive and capacitive switching in capacitor metal/nanocomposite/metal
(M/NC/M) structures based on (CoFeB)x(LiNbO3)100-x NC fabricated by ion-beam
sputtering with metal content x $\approx$ 8-20 at. % is studied. The
peculiarity of the structure synthesis was the use of increased oxygen content
($\approx$ 2*10^-5 Torr) at the initial stage of the NC growth. The NC films,
along with metal nanogranules of 3-6 nm in size, contained a large number of
dispersed Co (Fe) atoms (up to ~10^22 cm^-3). Measurements were performed both
in DC and AC (frequency range 5-13 MHz) regimes. When switching structures from
high-resistance (Roff) to low-resistance (Ron) state, the effect of a strong
increase in their capacity was found, which reaches 8 times at x $\approx$ 15
at. % and the resistance ratio Roff/Ron $\approx$ 40. The effect is explained
by the synergetic combination of the multifilamentary character of resistive
switching (RS) and structural features of the samples associated, in
particular, with the formation of high-resistance and strongly polarizable
LiNbO3 layer near the bottom electrode of the structures. The proposed model is
confirmed by investigations of RS of two-layer nanoscale M/NC/LiNbO3/M
structures as well as by studies of the magnetization of M/NC/M structures in
the pristine state and after RS.",1912.03726v3
2024-04-17,Stress analysis of functionally graded hyperelastic variable thickness rotating annular thin disk: A semi-analytic approach,"Functionally graded materials (FGMs) represent a promising class of advanced
materials designed with tailored microstructures to achieve optimized
mechanical, thermal, and functional properties across varying gradients. The
strategic integration of distinct materials within functionally graded
materials offers engineers unprecedented control over properties such as
strength, thermal conductivity, and corrosion resistance, enabling innovative
solutions for demanding applications in aerospace, automotive, and biomedical
industries. This study investigates a rotating annular thin disk with variable
thickness composed of incompressible hyperelastic material, made up of
functionally graded properties under large deformations. To elucidate these
phenomena, a power relation is employed to delineate the changes in
cross-sectional geometry m, the material property n, and the angular velocity w
of hyperelastic material. Constants used for hyperelastic material are obtained
from the experimental data. Equations are solved semi-analytically for
different values of m, n, and w, and the values of radial stresses, tangential
stresses, and elongation are calculated and compared for different conditions.
Results show that thickness and FG properties have a significant impact on the
behavior of disk, so that the expected behavior of the disk can be obtained by
an optimal selection of the disks geometry and material properties. By
selecting the optimum values for these variables, the location of maximum
stress can be controlled in large deformations, thereby furnishing significance
advantages in structural design and material selection.",2404.11365v1
2023-05-03,Universal sublinear resistivity in vanadium kagome materials hosting charge density waves,"The recent discovery of a charge density (CDW) state in ScV$_6$Sn$_6$ at
$T_{\textrm{CDW}}$ = 91 K offers new opportunities to understand the origins of
electronic instabilities in topological kagome systems. By comparing to the
isostructural non-CDW compound LuV$_6$Sn$_6$, we unravel interesting electrical
transport properties in ScV$_6$Sn$_6$, above and below the charge ordering
temperature. We observed that by applying a magnetic field along the $a$ axis,
the temperature behavior of the longitudinal resistivity in ScV$_6$Sn$_6$
changes from metal-like to insulator-like above the CDW transition. We show
that in the charge ordered state ScV$_6$Sn$_6$ follows the Fermi liquid
behavior while above that, it transforms into a non-Fermi liquid phase in which
the resistivity varies sublinearly over a broad temperature range. The
sublinear resistivity, which scales by $T^{3/5}$ is a common feature among
other vanadium-containing kagome compounds exhibiting CDW states such as
KV$_3$Sb$_5$, RbV$_3$Sb$_5$, and CsV$_3$Sb$_5$. By contrast, the non-Fermi
liquid behavior does not occur in LuV$_6$Sn$_6$. We explain the $T^{3/5}$
universal scaling behavior from the Coulomb scattering between Dirac electrons
and Van Hove singularities; common features in the electronic structure of
kagome materials. Finally, we show anomalous Hall-like behavior in
ScV$_6$Sn$_6$ below $T_{\textrm{CDW}}$, which is absent in the Lu compound.
Comparing the transport properties of ScV$_6$Sn$_6$ and LuV$_6$Sn$_6$ is
valuable to highlight the impacts of the unusual CDW in the Sc compound.",2305.02393v2
2014-06-24,The Origin of the X-ray Emission from the High-velocity Cloud MS30.7-81.4-118,"A soft X-ray enhancement has recently been reported toward the high-velocity
cloud MS30.7-81.4-118 (MS30.7), a constituent of the Magellanic Stream. In
order to investigate the origin of this enhancement, we have analyzed two
overlapping XMM-Newton observations of this cloud. We find that the X-ray
enhancement is $\sim$6' or $\sim$100 pc across, and is concentrated to the
north and west of the densest part of the cloud. We modeled the X-ray
enhancement with a variety of spectral models. A single-temperature equilibrium
plasma model yields a temperature of $(3.69^{+0.47}_{-0.44}) \times 10^6$ K and
a 0.4-2.0 keV luminosity of $7.9 \times 10^{33}$ erg s$^{-1}$. However, this
model underpredicts the on-enhancement emission around 1 keV, which may
indicate the additional presence of hotter plasma ($T \gtrsim 10^7$ K), or that
recombination emission is important. We examined several different physical
models for the origin of the X-ray enhancement. We find that turbulent mixing
of cold cloud material with hot ambient material, compression or shock heating
of a hot ambient medium, and charge exchange reactions between cloud atoms and
ions in a hot ambient medium all lead to emission that is too faint. In
addition, shock heating in a cool or warm medium leads to emission that is too
soft (for reasonable cloud speeds). We find that magnetic reconnection could
plausibly power the observed X-ray emission, but resistive
magnetohydrodynamical simulations are needed to test this hypothesis. If
magnetic reconnection is responsible for the X-ray enhancement, the observed
spectral properties could potentially constrain the magnetic field in the
vicinity of the Magellanic Stream.",1406.6363v1
2015-03-21,Graphene as a p-type metal for ultimate miniaturization,"We report macroscopic sheets of highly conductive bilayer graphene with
exceptionally high hole concentrations of ~ $10^{15}$ $cm^{-2}$ and
unprecedented sheet resistances of 20-25 {\Omega} per square over macroscopic
scales, and obtained in-situ over a thin cushion of molecular oxygen on a
silicon substrate. The electric and electronic properties of this specific
configuration remain stable upon thermal anneals and months of exposure to air.
We further report a complementary ab-initio study, predicting an enhancement of
graphene adhesion energy of up to a factor 20, also supported by experimental
fracture tests. Our results show that the remarkable properties of graphene can
be realized in a reliable fashion using a high-throughput process. In addition
to providing exceptional material properties, the growth process we employed is
scalable to large areas so that the outstanding conduction properties of
graphene can be harnessed in devices fabricated via conventional semiconductor
manufacturing processes. We anticipate that the approach will provide the
necessary scalability and reliability for future developments in the graphene
nanoscience and technology fields, especially in areas where further
miniaturization is hampered by size effects and electrical reliability of
classical conductors.",1503.06253v2
2018-04-06,Antisite pairs suppress the thermal conductivity of BAs,"BAs was predicted to have an unusually high thermal conductivity at room
temperature of 2000$\,$Wm$^{-1}$$\,$K$^{-1}$, comparable to that of diamond.
However, the experimentally measured thermal conductivity of BAs single
crystals is an order of magnitude lower. To identify the origin of this large
inconsistency, we investigated the lattice structure and potential defects in
BAs single crystals at atomic scale using aberration-corrected scanning
transmission electron microscopy (STEM). Rather than finding a large
concentration As vacancies ($V_\mathrm{As}$), as widely thought to dominate the
thermal resistance in BAs crystals, our STEM results showed enhanced intensity
of some B columns and reduced intensity of some As columns, suggesting the
presence of antisite defects with As$_\mathrm{B}$ (As-atom on B site) and
B$_\mathrm{As}$ (B-atom on As site) with significant concentrations. Further
calculations show that the antisite pair with As$_\mathrm{B}$ next to
B$_\mathrm{As}$ is preferred energetically among the different types of point
defects investigated, and confirm that such defects lower the thermal
conductivity for BAs. Using a concentration of
6.6$\pm$3$\times$10$^{20}$$\,$cm$^{-3}$ for the antisite pairs estimated from
STEM images, thermal conductivity is estimated to be
65-100$\,$Wm$^{-1}$$\,$K$^{-1}$, in reasonable agreement with our measured
value. Our study suggests that As$_\mathrm{B}$-B$_\mathrm{As}$ antisite pairs
are the primary lattice defects suppressing thermal conductivity of BAs.
Possible approaches are proposed for growth of high quality crystals or films
with high thermal conductivity.",1804.02381v1
2019-04-08,Characterizations of thermal stability and electrical performance of Au-Ni coating on CuCrZr substrate for high vacuum radio-frequency contact application,"Radio-frequency (RF) contacts-which are an example of electrical contacts-are
commonly employed on accelerators and nuclear fusion experimental devices. RF
contacts with a current load of 2 kA for steady-state operation were designed
for application to the International Thermonuclear Experimental Reactor (ITER)
device. In contrast to the typical working conditions of general commercial
electrical contacts, those of RF contacts employed on fusion devices include
high vacuum, high temperature, and neutron radiation. CuCrZr is currently of
interest as a base material for the manufacture of louvers of RF contacts,
which has excellent thermal and electrical properties and has low creep rate at
250 {\textdegree}C. In this study, a hard Au coating (Au-Ni) was electroplated
on CuCrZr samples and the samples were then subjected to thermal aging
treatment at 250 {\textdegree}C for 500 h in order to simulate the
vacuum-commissioning process of the ITER. The effects of thermal aging on the
hardness, elastic modulus, crystallite size, and compositions of the coating
were investigated via microstructural and mechanical characterizations of the
coating material. Metal atom migration in different coating layers during
thermal aging was characterized and evaluated via scanning electron
microscopy/energy dispersive X-ray spectroscopy observations of the
cross-sectional surfaces, and the obtained results could be used to directly
select the coating thickness for the final RF contact component. The contact
resistance-an important parameter of the RF contact-was measured in a dedicated
testbed built to simulate fusion reactor conditions between CuCrZr pins and
stainless steel plates coated with Au-Ni and Rh, respectively.",1907.07236v1
2020-07-03,Enhanced creep performance in a polycrystalline superalloy driven by atomic-scale phase transformation along planar faults,"Predicting the mechanical failure of parts in service requires understanding
their deformation behavior, and associated dynamic microstructural evolution up
to the near-atomic scale. Solutes are known to interact with defects generated
by plastic deformation, thereby affecting their displacement throughout the
microstructure and hence the material mechanical response to solicitation. This
effect is studied here in a polycrystalline Ni-based superalloy with two
different Nb contents that lead to a significant change in their creep
lifetime. Creep testing at 750C and 600 MPa shows that the high-Nb alloy
performs better in terms of creep strain rate. Considering the similar initial
microstructures, the difference in mechanical behavior is attributed to a phase
transformation that occurs along planar faults, controlled by the different
types of stacking faults and alloy composition. Electron channeling contrast
imaging reveals the presence of stacking faults in both alloys. Microtwinning
is observed only in the low-Nb alloy, rationalizing in part the higher creep
strain rate. In the high-Nb alloy, atom probe tomography evidences two
different types of stacking faults based on their partitioning behavior.
Superlattice intrinsic stacking faults (SISF) were found enriched in Nb, Co, Cr
and Mo while only Nb and Co was segregated at superlattice extrinsic stacking
faults. Based on their composition, a local phase transformation occurring
along the faults is suggested, resulting in slower creep strain rate in the
high-Nb alloy. In comparison, mainly SISF enriched in Co, Cr, Nb and Mo were
found in the low-Nb alloy. Following the results presented here, and those
available in the literature, an atomic-scale driven alloy design approach that
controls and promotes local phase transformation along planar faults at 750C is
proposed, aiming to design superalloys with enhanced creep resistance.",2007.01676v2
2022-03-15,Flexible terahertz photonic light-cage modules for in-core sensing and high temperature applications,"Terahertz (THz) technology is a growing and multi-disciplinary research
field, particularly for sensing and telecommunications. A number of THz
waveguides have emerged over the past years, which are set to complement the
capabilities of existing and bulky free space setups. In most designs however,
the guiding region is physically separated from the surroundings, making
interactions between light and the environment inefficient. We present photonic
THz light cages (THzLCs) operating at THz frequencies, consisting of
free-standing dielectric strands, which guide light within a hollow core with
immediate access to the environment. We show the versatility and design
flexibility of this concept, by 3D-printing several cm-length-scale modules
using a single design and four different polymer- and ceramic- materials, which
are either rigid, flexible, or resistant to high temperatures. We characterize
propagation- and bend-losses for straight- and curved- waveguides, which are of
order ~1 dB/cm in the former, and ~2-8 dB/cm in the latter for bend radii below
10 cm, and largely independent of the material. Our transmission experiments
are complemented by near-field measurements at the waveguide output, which
reveal antiresonant guidance for straight THzLCs, and a deformed fundamental
mode in the bent waveguides, in agreement with numerical conformal mapping
simulations. We show that these THzLCs can be used either as: (i) flexible,
reconfigurable, and bendable modular assemblies; (ii) in-core sensors of
structures contained directly inside the hollow core; (iii) high-temperature
sensors, with potential applications in industrial monitoring. These THzLCs are
a novel and useful addition to the growing library of THz waveguides, marrying
the waveguide-like advantages of reconfigurable, diffractionless propagation,
with the free-space-like immediacy of direct exposure to the surrounding
environment.",2203.08316v1
2022-10-21,Understanding The Reversible Electrodeposition of Al in Low-Cost Room Temperature Molten Salts,"Aluminum is the most earth-abundant metal, is trivalent, is inert in ambient
humid air, and has a density approximately four-times that of lithium at room
temperature. These attributes make it an attractive material for
cost-effective, long-duration storage of electrical energy in batteries.
Scientific discoveries in the past decade have established that secondary Al
batteries can be created by paring an Al anode with a graphite or transition
metal oxide cathode, in imidazolium-based, room-temperature
ionic-liquid-Aluminum chloride electrolytes. Here we report findings from a
systematic study that sheds light on the structural requirements,
physicochemical, and transport properties of the ionic liquid electrolytes
responsible for the high reversibility of Al battery anodes. We find that the
most important interfacial and transport properties of these electrolytes can
be achieved in other electrolytes, including ammonium-based molten salts that
are available at costs as much as twenty-times lower than the ionic
liquid-Aluminum chloride melt. High Al reversibility in ammonium- and
imidazolium-based electrolytes is specifically shown to require a critical
ratio of the solvation species, where Lewis acidity and beneficial interfacial
reactions continuously etch the alumina resistive interfacial layer and form
beneficial solid electrolyte interphase at the anode. We report further that
successful development of new electrolyte families that support high Al anode
reversibility also provides a good platform for detailed studies of the working
mechanisms of an intercalation graphite cathode using X-ray absorption
spectroscopy. Our findings therefore open new opportunities for developing
simple, cost-effective, room-temperature Al batteries that enable long-duration
electrical energy storage.",2210.12131v1
2024-01-18,Spreading of Low-viscosity Ink Filaments Driven by Bath Viscoelasticity in Embedded Printing,"Inks deposited in conventional direct ink writing need to be able to support
their own weight and that of the upper layers with minimal deformation to
preserve the structural integrity of the three-dimensional (3D) printed parts.
This constraint limits the range of usable inks to high-viscosity materials.
Embedded printing enables the use of much softer inks by depositing the
materials in a bath of another fluid that provides external support, thus
diversifying the types of 3D printable structures. The interactions between the
ink and bath fluids, however, give rise to a unique type of defect: spreading
of the dispensed ink behind the moving nozzle. By printing horizontal threads
made of dyed water in baths of Carbopol suspensions, we demonstrate that the
spreading can be attributed to the pressure field generated in the viscous bath
by the relative motion of the nozzle. As the pressure gradient increases with
the viscosity of the bath fluid while the viscosity of the ink resists the
flow, a larger bath-to-ink viscosity ratio results in more spreading for
low-concentration Carbopol baths. For high-concentration, yield-stress-fluid
baths, we find that the steady-state viscosity alone cannot account for the
spreading, as the elastic stress becomes comparable to the viscous stress and
the bath fluid around the dispensed ink undergoes fluidization and
resolidification. By parameterizing the transient rheology of the
high-concentration Carbopol suspensions using a simple viscoelastic model, we
suggest that the ink spreading is exacerbated by the elasticity but is
mitigated by the yield stress as long as the yield stress is low enough to
allow steady injection of the ink. These results help illuminate the link
between the bath rheology and the printing quality in embedded 3D printing.",2401.09684v1
2001-10-08,"Structural and electronic properties of the Nb$_4$-cluster compound Ga$_{1.33}$Nb$_4$X$_8$ (X = S, Se)","We report resistivity, thermopower and magnetic susceptibility measurements
on the Nb$_4$-cluster compounds Ga$_{1.33}$Nb$_4$X$_{8}$ (X = S, Se), derived
from vacancy ordered spinels A$_x$T$_4$X$_8$. The cubic selenide phase is
insulating and its resistivity crosses over from $\ln{\rho} \sim T^{-1}$ to
$\sim T^{-1/2}$ on cooling below 150 K, indicating variable range hopping (VRH)
conduction at low temperatures. This is similar to that previously reported for
V$_4$ and Mo$_4$ cluster compounds. The rhombohedrally distorted sulfide is
metallic and shows a minimum in resistance at $\sim $ 56 K below which the
resistivity varies as $\rho(T) \sim T^{-1/2}$. The thermopower of the selenide
becomes temperature independent below the crossover temperature. These Nb$_4$
compounds exhibit enhanced Pauli-paramagnetic magnetic susceptibility ($\chi$)
irrespective of their transport properties and both undergo a similar
transition in $\chi(T) \sim 30$ K. We discuss these properties in the model of
hopping conduction under long-range Coulomb repulsion effects and derive
consistency between some of the transport and magnetic parameters.",0110155v1
2001-11-06,Spin-dependent electrical transport in ion-beam sputter deposited Fe-Cr multilayers,"The temperature dependence of the electrical resistivity and
magnetoresistance of Xe-ion beam sputtered Fe-Cr multilayers has been
investigated. The electrical resistivity between 5 and 300 K in the fully
ferromagnetic state, obtained by applying a field beyond the saturation field
(H_sat) necessary for the antiferromagnetic(AF)-ferromagnetic(FM) field-induced
transition, shows evidence of spin-disorder resistivity as in crystalline Fe
and an s-d scattering contribution (as in 3d metals and alloys). The sublattice
magnetization m(T) in these multilayers has been calculated in terms of the
planar and interlayer exchange energies. The additional spin-dependent
scattering \Delta \rho (T) = \rho(T,H=0)_AF - \rho(T,H=H_sat)_FM in the AF
state over a wide range of temperature is found to be proportional to the
sublattice magnetization, both \Delta \rho(T) and m(T) reducing along with the
antiferromagnetic fraction. At intermediate fields, the spin-dependent part of
the electrical resistivity (\rho_s (T)) fits well to the power law \rho_s (T) =
b - cT^\alpha where c is a constant and b and \alpha are functions of H. At low
fields \alpha \approx 2 and the intercept b decreases with H much the same way
as the decrease of \Delta \rho (T) with T. A phase diagram (T vs. H_sat) is
obtained for the field- induced AF to FM transition. Comparisons are made
between the present investigation and similar studies using dc magnetron
sputtered and molecular beam epitaxy (MBE) grown Fe-Cr multilayers.",0111084v1
2002-10-29,Quantum Resistive Behaviors in the Vortex Liquid Regimes at Finite Temperatures,"Motivated by a {\it mean field-like} resistive behavior in magnetic fields
commonly seen in various superconducting (SC) cuprates and organics with strong
fluctuation, {\it quantum} SC fluctuation effects on resistive behaviors are
reexamined by putting emphasis on their roles in the so-called {\it thermal}
vortex liquid regime. By incorporating the quantum fluctuation and a vortex
pinning effect in the GL fluctuation theory, it is found that the resistivity
curve shows not a fan-shaped broadening but a sharp drop at a 3d vortex-glass
transition point far below an apparent upper critical field H_{c2}^*(T) as a
result of a quantm fluctuation enhanced by an adequately small condensation
energy or by a strong field. Fittings to data of cuprate and organic
superconductors are performed by including effects of SC pseudogap region. It
is argued on the cuprate materials that, irrespective of the presence of
fluctuations of competing non-SC orders, the in-plane coherence length of
hole-doped cuprates decreases on approaching the underdoped limit and that the
condensation energy density to be measured from the heat capacity data is
maximum near the optimal doping. The case of disordered quasi 2d s-wave films
showing the field-tuned superconductor-insulator transition (FSIT) behavior is
also studied for comparison, and an agreement with available data is found.",0210626v5
2002-11-22,Room Temperature Ballistic Conduction in Carbon Nanotubes,"Multiwalled carbon nanotubes are shown to be ballistic conductors at room
temperature, with mean free paths of the order of tens of microns. These
experiments follow and extend the original experiments by Frank et al (Science,
280 1744 1998) including in-situ electron microscopy experiments and a detailed
analysis of the length dependence of the resistance. The per unit length
resistance r < 100 Ohm/micron, indicating free paths l > 65 microns,
unambiguously demonstrate ballistic conduction at room temperature up to
macroscopic distances. The nanotube-metal contact resistances are in the range
0.1-1 kOhm micron. Contact scattering can explain why the measured conductances
are about half the expected theoretical value of 2 G0 . For V>0.1V the
conductance rises linearly (dG/dV~0.3 G0 /V) reflecting the linear increase in
the density-of-states in a metallic nanotube above the energy gap. Increased
resistances (r =2- 10 k Ohm/micron) and anomalous I-V dependences result from
impurities and surfactants on the tubes.Evidence is presented that ballistic
transport occurs in undoped and undamaged tubed for which the top layer is
metallic and the next layer is semiconducting. The diffusive properties of
lithographically contacted multiwalled nanotubes most likely result from
purification and other processing steps that damage and dope the nanotubes
thereby making them structurally and electronically different than the pristine
nanotubes investigated here.",0211515v1
2006-12-27,"Peculiarities of the transport properties of InMnAs layers, produced by the laser deposition, in strong magnetic fields","Magnetotransport properties of p-InMnAs layers are studied in pulsed magnetic
fields up to 30 T. Samples were prepared by the laser deposition and annealed
by ruby laser pulses. Well annealed samples show p-type conductivity while they
were n-type before the annealing. Surprisingly the anomalous Hall effect
resistance in paramagnetic state (T>40 K) and in strong magnetic fields (B > 20
T) appears to be greater than that in ferromagnetic state (T <= 40 K), while
the longitudinal resistance rises with the temperature decrease. The negative
magnetoresistance saturates in magnetic fields higher then 10T at T near 4 K
only, whereas the saturation fields of the anomalous Hall effect resistance are
much less (around 2 T at 30K). The total reduction of resistance exceeds 10
times in magnetic fields around of 10T. The obtained results are interpreted on
the base of the assumptions of the non-uniform distribution of Mn atoms acting
as acceptors, the local ferromagnetic transition and the percolation-like
character of the film conductivity, which prevailed under conditions of the
strong fluctuations of the exchange interaction. Characteristic scales of the
magneto-electric nonuniformity are estimated using analysis of the mesoscopic
fluctuations of the non-diagonal components of the magnetoresistivity tensor.",0612641v1
2007-06-28,Emergence of a flux tube through a partially ionised solar atmosphere,"For a magnetic flux tube, or indeed any flux, to emerge into the Solar corona
from the convection zone it must pass through the partially ionised layers of
the lower atmosphere: the photosphere and the chromosphere. In such regions the
ion-neutral collisions lead to an increased resistivity for currents flowing
across magnetic field lines. This Cowling resistivity can exceed the Spitzer
resistivity by orders of magnitude and in 2.5D simulations has been shown to be
sufficient to remove all cross field current from emerging flux. Here we extend
this modelling into 3D. Once again it is found that the Cowling resistivity
removes perpendicular current. However the presence of 3D structure prevents
the simple comparison possible in 2.5D simulations. With a fully ionised
atmosphere the flux emergence leads to an unphysically low temperature region
in the overlying corona, lifting of chromospheric material and the subsequent
onset of the Rayleigh-Taylor instability. Including neutrals removes the low
temperature region, lifts less chromospheric matter and shows no signs of the
Rayleigh-Taylor instability. Simulations of flux emergence therefore should
include such a neutral layer in order to obtain the correct perpendicular
current, remove the Rayleigh-Taylor instability and get the correct temperature
profile. In situations when the temperature is not important, i.e. when no
simulated spectral emission is required, a simple model for the neutral layer
is demonstrated to adequately reproduce the results of fully consistent
simulations.",0706.4223v1
2010-01-10,Anomalies of conductivity behavior near the paramagnetic-antiferromagnetic transition in single-crystals La_{2}CuO_{4+δ},"The temperature dependences of resistance, R(T), of two single-crystals
La_{2}CuO_{4+\delta} samples have been studied with the aim to detect a
possible change in the R(T) behavior induced by paramagnetic-antiferromagnetic
(PM-AFM) transition. One of the samples with \delta \lesssim 0.01, was fairly
homogeneous in oxygen distribution (not phase-separated) with Neel temperature
T_{N}\approx 266 K. Conductivity of this sample has been determined by Mott's
variable-range hopping below T_N. The other, far less resistive, sample with
\delta \approx 0.05, was inhomogeneous (phase-separated) showing both PM-AFM
(T_N\approx 205 K) and superconducting (T_c\approx 25 K) transitions. It is
found that for the homogeneous sample the resistivity decreases above T_N far
faster with temperature than below it (for both directions of measuring
current, parallel and perpendicular to basal CuO_2 planes). A similar behavior
of conductivity near PM-AFM transition is also found for the phase-separated
and less resistive sample. In this case a clear kink in R(T) curve near
T_N\approx 205 K can be seen. Furthermore, a transition to metallic (dR/dT>0)
behavior occurs far enough above T_N. The observed behavior of the samples
studied is related to increased delocalization of charge carriers above T_N.
This is in accordance with decrease in the AFM correlation length and
corresponding enhancement of the hole mobility above T_N known for low-doped
lanthanum cuprates.",1001.1518v1
2011-05-07,Effect of 50 MeV Li3+ irradiation on structural and electrical properties of Mn doped ZnO,"The present work aims to study the effect of ion irradiation on structural
and electrical properties and their correlation with the defects in Zn1-xMnxO
type system. Zn1-xMnxO (x = 0.02, 0.04) samples have been synthesized by
solid-state reaction method and have been irradiated with 50 MeV Li3+ ions. The
concomitant changes have been probed by x-ray diffraction (XRD), temperature
dependent electrical resistivity and positron annihilation lifetime (PAL)
spectroscopy. XRD result shows single phase wurtzite structure for
Zn0.98Mn0.02O, whereas for Zn0.96Mn0.04O sample an impurity phase has been
found apart from the usual peaks of ZnO. Ion irradiation dissolves this
impurity peak. Grain size of the samples found to be uniform. For
Zn0.98Mn0.02O, the observed sharp decrease in room temperature resistivity
(RhoRT) with irradiation is consistent with the lowering of FWHM of the XRD
peaks. However for Zn0.96Mn0.04O, RhoRT decreases for initial fluence but
increases for further increase of fluence. All the irradiated Zn0.98Mn0.02O
samples show metal-semiconductor transition in temperature dependent
resistivity measurement at low temperature. But all the irradiated
Zn0.96Mn0.04O samples show semiconducting nature in the whole range of
temperature. Results of room temperature resistivity, XRD and PAL measurements
are consistent with each other.",1105.1414v1
2013-01-07,Disorder-driven carrier transport in atomic layer deposited ZnO thin films,"This paper addresses the effect of disorder on the carrier transport
mechanism of atomic layer deposited ZnO thin films as has been investigated by
temperature dependent electrical resistivity measurements in the temperature
range of 4.2K to 300K. Films were grown on (0001) sapphire substrate at
different substrate temperatures varying from 150 to 350 C. The defects and
structural disorder in the films were found to be strongly dependent on their
growth temperature. The films grown at 150, 300 and 350 C were found to be
semiconductor-like in the whole measurement temperature range of resistivity
due to the enhanced disorder in these films. However, a metal to semiconductor
transition (MST) at low temperature has been observed in the films grown at 200
and 250 C. It was also observed that the film grown at 250 C with higher
residual resistivity, the transition temperature shifted towards the higher
value due to the increased disorder in this film as compared to that grown at
200 C. The upturn in resistivity below the transition temperature has been well
explained by considering quantum corrections to the Boltzmanns conductivity
which includes the effect of weak localization and coulomb electron-electron
interactions related to the existence of disorder in these films.",1301.1172v1
2014-11-27,Temperature dependence of electrical and thermal conduction in single silver nanowire,"Silver nanowires have great application potential in fields like flexible
electronic devices, solar cells and transparent electrodes. It is critical and
fundamental to study the thermal and electrical transport properties in a
single silver nanowire. In this work, the thermal and electrical transport in
an individual silver nanowire is characterized down to 35 K with the steady
state electro-thermal technique. The results indicate that, at room
temperature, the electrical resistivity increases by around 4 folds compared
from that of its bulk counterpart. After fitting the temperature dependent
electrical resistivity curves with the Bloch-Gr\""uneisen formula, the Debye
temperature (151 K) of the silver nanowire is found 36% lower than that (235 K)
of bulk silver, confirming strong phonon softening. The thermal conductivity is
reduced by 55% compared with that of its bulk counterpart at room temperature
and this reduction becomes larger as the temperature goes down. To explain the
opposite trends of thermal conductivity (\k{appa}) ~ temperature (T) of silver
nanowire and bulk silver, a unified thermal resistivity is used to elucidate
the electron scattering mechanism. A large residual unified thermal resistivity
for the silver nanowire is observed while that of the bulk silver is almost
zero. The same trend of variation against T indicates that the silver nanowire
and bulk silver share the same phonon-electron scattering mechanism.
Additionally, due to phonon-assisted electron energy transfer across the grain
boundaries, the Lorenz number of the silver nanowire is found much larger than
that of bulk silver and decreases with decreasing temperature.",1411.7659v2
2015-09-18,Evidence for hydrodynamic electron flow in PdCoO$_2$,"Electron transport is conventionally determined by the momentum-relaxing
scattering of electrons by the host solid and its excitations. The electrical
resistance is set by geometrical factors and the resistivity, which is a
microscopic property of the solid. Hydrodynamic fluid flow through channels, in
contrast, is determined by geometrical factors, boundary scattering and the
viscosity of the fluid, which is governed by momentum-conserving internal
collisions. A long-standing question in the physics of solids, brought into
focus by the advent of new calculational techniques, has been whether the
viscosity of the electron fluid plays an observable role in determining the
resistance. At first sight this seems unlikely, because in almost all known
materials the rate of momentum-relaxing collisions dominates that of the
momentum-conserving ones that give the viscous term. Here, we show this is not
always the case. We report experimental evidence that the resistance of
restricted channels of the ultra-pure two-dimensional metal PdCoO$_2$ has a
large viscous contribution. Comparison with theory allows an estimate of the
electronic viscosity in the range between $6\times 10^{-3}$~kg(ms)$^{-1}$ and
$3\times 10^{-4}$~kg(ms)$^{-1}$, which brackets that of water at room
temperature.",1509.05691v2
2015-10-31,The influence of system dynamics on the frictional resistance: insights from a discrete model,"In order to examine the influence of system dynamics on sliding friction, we
introduce the so-called micro-walking machine. This model consists of a rigid
body with a number of elastic contact spots that is pulled by a constantly
moving base. The system slides with dry friction on a rigid substrate. The
kinematic coupling of the rotation and the translation of the rigid body
results in varying normal and tangential forces at the contact spots. For
certain parameter ranges this leads to self-excited oscillations in the
vertical direction. A particular dynamic mode occurs which is characterized by
a strong correlation between low or even zero normal forces and a fast forward
motion. This effect is referred to as micro-walking. In addition to an
experimental rig we use numerical integration and an extensive parameter study
for the analysis. In theory, the reduction of the frictional resistance reaches
up to 98%. These results are confirmed by the experiments where the maximal
reduction was 73%. Our model shows that micro-vibrations play an important role
for the dynamic influences on the frictional resistance of systems that exhibit
apparently smooth sliding. The identification of the critical parameter range
enables the systematic control of frictional resistance through the adjustment
of attributes such as geometry and stiffness. In addition, it is possible to
deduce guidelines for how tribological test rigs should be designed in order to
get reliable results.",1511.00162v1
2016-05-02,Interfilament Resistance at 77 K in Striated HTS Coated Conductors,"Striating HTS coated conductor (CC) tapes into narrow filaments offers the
possibility of reducing the tapes' magnetization losses without unreasonably
decreasing their current-carrying capability. However, realizing well-separated
striations presents technological challenges, especially if the number of
filaments is large and/or if a thick layer of metallic stabilizer is present.
In these situations, the filaments can be easily coupled and their
effectiveness to reduce magnetization losses is strongly diminished or
eliminated. While the onset of coupling is well visible from magnetization loss
measurements, the actual path of the coupling current is unknown. In this
contribution we present a systematic study of the transverse resistance in HTS
CC samples in order to get a deeper understanding of those paths. The measured
samples differ in terms of manufacturer (SuperPower and SuperOx), and presence
and thickness of stabilizer material. In addition, oxidation is used as a means
to increase the resistance between the filaments in non-stabilized samples. The
results are interpreted with a chain network model. This work provides useful
insights on the factors determining the transverse resistance in striated HTS
CCs, thus indicating ways to improve the effectiveness of the striation process
for AC loss reduction.",1605.00401v2
2016-08-09,Disorder-sensitive pump-probe measurements on Nd$_{1.83}$Ce$_{0.17}$CuO$_{4\pmδ}$ films,"We find an unambiguous relationship between disorder-driven features in the
temperature dependence of the resistance and the behavior, as functions of the
temperature, of the parameters necessary to describe some of the relaxation
processes in the photoinduced differential time-resolved reflectivity of three
samples of Nd$_{1.83}$Ce$_{0.17}$CuO$_{4\pm\delta}$. The latter, sharing the
same Ce content, have been fabricated and annealed ad-hoc in order to differ
only for the degree of disorder, mainly related to oxygen content and location,
and, consequently, for the temperature dependence of the resistance: two of
them present a minimum in the resistance and behave as a superconductor and as
a metal, respectively, the third behaves as an insulator. The systematic
coherence between the resistance and the relaxation parameters behaviors in
temperature for all three samples is absolutely remarkable and shows that
pump-probe measurements can be extremely sensitive to disorder as it drives the
emergence of new excitations and of the related relaxation channels as in this
paradigmatic case.",1608.03006v1
2018-05-10,Activation Energy of Metastable Amorphous Ge2Sb2Te5 from Room Temperature to Melt,"Resistivity of metastable amorphous Ge2Sb2Te5 (GST) measured at device level
show an exponential decline with temperature matching with the steady-state
thin-film resistivity measured at 858 K (melting temperature). This suggests
that the free carrier activation mechanisms form a continuum in a large
temperature scale (300 K - 858 K) and the metastable amorphous phase can be
treated as a super-cooled liquid. The effective activation energy calculated
using the resistivity versus temperature data follow a parabolic behavior, with
a room temperature value of 333 meV, peaking to ~377 meV at ~465 K and reaching
zero at ~930 K, using a reference activation energy of 111 meV (3kBT/2) at
melt. Amorphous GST is expected to behave as a p-type semiconductor at Tmelt ~
858 K and transitions from the semiconducting-liquid phase to the
metallic-liquid phase at ~ 930 K at equilibrium. The simultaneous Seebeck (S)
and resistivity versus temperature measurements of amorphous-fcc mixed-phase
GST thin-films show linear S-T trends that meet S = 0 at 0 K, consistent with
degenerate semiconductors, and the dS/dT and room temperature activation energy
show a linear correlation. The single-crystal fcc is calculated to have dS/dT =
0.153 {\mu}V/K for an activation energy of zero and a Fermi level 0.16 eV below
the valance band edge.",1805.04054v1
2019-09-17,Algorithm for Training Neural Networks on Resistive Device Arrays,"Hardware architectures composed of resistive cross-point device arrays can
provide significant power and speed benefits for deep neural network training
workloads using stochastic gradient descent (SGD) and backpropagation (BP)
algorithm. The training accuracy on this imminent analog hardware however
strongly depends on the switching characteristics of the cross-point elements.
One of the key requirements is that these resistive devices must change
conductance in a symmetrical fashion when subjected to positive or negative
pulse stimuli. Here, we present a new training algorithm, so-called the
""Tiki-Taka"" algorithm, that eliminates this stringent symmetry requirement. We
show that device asymmetry introduces an unintentional implicit cost term into
the SGD algorithm, whereas in the ""Tiki-Taka"" algorithm a coupled dynamical
system simultaneously minimizes the original objective function of the neural
network and the unintentional cost term due to device asymmetry in a
self-consistent fashion. We tested the validity of this new algorithm on a
range of network architectures such as fully connected, convolutional and LSTM
networks. Simulation results on these various networks show that whatever
accuracy is achieved using the conventional SGD algorithm with symmetric
(ideal) device switching characteristics the same accuracy is also achieved
using the ""Tiki-Taka"" algorithm with non-symmetric (non-ideal) device switching
characteristics. Moreover, all the operations performed on the arrays are still
parallel and therefore the implementation cost of this new algorithm on array
architectures is minimal; and it maintains the aforementioned power and speed
benefits. These algorithmic improvements are crucial to relax the material
specification and to realize technologically viable resistive crossbar arrays
that outperform digital accelerators for similar training tasks.",1909.07908v1
2017-04-13,Light Induced Electron-Phonon Scattering Mediated Resistive Switching in Nanostructured Nb Thin Film Superconductor,"The elemental Nb is mainly investigated for its eminent superconducting
properties. In contrary, we report of a relatively unexplored property, namely,
its superior optoelectronic property in reduced dimension. We demonstrate here
that nanostructured Nb thin films (NNFs), under optical illumination, behave as
room temperature photo-switches and exhibit bolometric features below its
superconducting critical temperature. Both photo-switch and superconducting
bolometric behavior are monitored by its resistance change with light in
visible and near infrared (NIR) wavelength range. Unlike the conventional
photodetectors, the NNF devices switch to higher resistive states with light
and the corresponding resistivity change is studied with thickness and grain
size variations. At low temperature in its superconducting state, the light
exposure shifts the superconducting transition towards lower temperature. The
room temperature photon sensing nature of the NNF is explained by the photon
assisted electron-phonon scattering mechanism while the low temperature light
response is mainly related to the heat generation which essentially changes the
effective temperature for the device and the device is capable of sensing a
temperature difference of few tens of milli-kelvins. The observed
photo-response on the transport properties of NNFs can be very important for
future superconducting photon detectors, bolometers and phase slip based device
applications.",1704.04092v1
2017-07-05,Anomalous Hall effect in two-dimensional non-collinear antiferromagnetic semiconductor Cr0.68Se,"Cr0.68Se single crystals with two-dimensional (2D) character have been grown,
and the detailed magnetization M(T), electrical transport properties (including
longitudinal resistivity and Hall resistivity and thermal transport ones
(including heat capacity Cp(T) and thermoelectric power (TEP) S(T)) have been
measured. There are some interesting phenomena: (i) Cr0.68Se presents a
non-collinear antiferromagnetic (AFM) semiconducting behavior with the Neel
temperature TN = 42 K and the activated energy Eg=3.9 meV; (ii) It exhibits the
anomalous Hall effect (AHE) below TN and large negative magnetoresistance (MR)
about 83.7% (2 K, 8.5 T). The AHE coefficient RS is 0.385 cm-3/C at T=2 K and
the AHE conductivity {\sigma}H is about 1 ohm-1cm-1 at T=40 K, respectively;
(iii) The scaling behavior between the anomalous Hall resistivity and the
longitudinal resistivity is linear and further analysis implies that the origin
of the AHE in Cr0.68Se is dominated by the skew-scattering mechanism. Our
results may be helpful for exploring the potential application of these kind of
2D AFM semiconductors.",1707.01252v1
2017-07-20,Stochastic Dynamics of Resistive Switching: Fluctuations Lead to Optimal Particle Number,"Resistive switching is one of the foremost candidates for building novel
types of non-volatile random access memories. Any practical implementation of
such a memory cell calls for a strong miniaturization, at which point
fluctuations start playing a role that cannot be neglected. A detailed
understanding of switching mechanisms and reliability is essential. For this
reason, we formulate a particle model based on the stochastic motion of oxygen
vacancies. It allows us to investigate fluctuations in the resistance states of
a switch with two active zones. The vacancies' dynamics is governed by a master
equation. Upon the application of a voltage pulse, the vacancies travel
collectively through the switch. By deriving a generalized Burgers equation we
can interpret this collective motion as nonlinear traveling waves, and
numerically verify this result. Further, we define binary logical states by
means of the underlying vacancy distributions, and establish a framework of
writing and reading such memory element with voltage pulses. Considerations
about the dis- criminability of these operations under fluctuations together
with the markedness of the resistive switching effect itself lead to the
conclusion, that an intermediate vacancy number is optimal for performance.",1707.06648v1
2018-08-02,Non-Classical Longitudinal Magneto-Resistance in Anisotropic Black Phosphorus,"Resistivity measurements of a few-layer black phosphorus (bP) crystal in
parallel magnetic fields up to 45 T are reported as a function of the angle
between the in-plane field and the source-drain (S-D) axis of the device. The
crystallographic directions of the bP crystal were determined by Raman
spectroscopy, with the zigzag axis found within 5{\deg} of the S-D axis, and
the armchair axis in the orthogonal planar direction. A transverse
magneto-resistance (TMR) as well as a classically-forbidden longitudinal
magneto-resistance (LMR) are observed. Both are found to be strongly
anisotropic and non-monotonic with increasing in-plane field. Surprisingly, the
relative magnitude (in %) of the positive LMR is larger than the TMR above
$\sim$32 T. Considering the known anisotropy of bP whose zigzag and armchair
effective masses differ by a factor of approximately seven, our experiment
strongly suggests this LMR to be a consequence of the anisotropic Fermi surface
of bP.",1808.00858v2
2019-08-12,The role of graphitic filaments in resistive switching behaviour of amorphous silicon carbide thin films,"Resistive switching in amorphous silicon carbide (a-SiC) films deposited by a
single composite target magnetron sputtering process is reported. Switching
performance as a function of thickness of the films (50, 100 and 300 nm) as
well as different top metal electrodes (Cu, Pt and Ag) with the bottom
electrode fixed as Au, is investigated. The switching parameters (Forming
Voltage, Set and Reset voltages and corresponding currents) are found to be
dependent on thickness of SiC films and it is observed that 100 nm is the
optimal thickness for best endurance. The interface between metal electrode and
a-SiC films plays a more significant role in achieving switching performance.
Resistance Off/On ratios of 108, retention times >104 s and endurance of 50
cycles are achieved in the best devices. Cross-sectional scanning electron
microscopy provides evidence that the mechanism of switching involves the
formation of carbonaceous filaments and Raman spectroscopy indicates that these
filaments are nanocrystalline graphite in nature. The current work clearly
establishes that there is dissociation of SiC during the switching cycles
leading to formation of nanocrystalline graphitic filaments. These contribute
to switching, in addition to the metallic filaments, in the a-SiC based
resistive memory device.",1908.04079v1
2018-07-13,Tuning vortex fluctuations and the resistive transition in superconducting films with a thin overlayer,"It is shown that the temperature of the resistive transition $T_r$ of a
superconducting film can be increased by a thin superconducting or normal
overlayer. For instance, deposition of a highly conductive thin overlayer onto
a dirty superconducting film can give rise to an ""anti-proximity effect"" which
manifests itself in an initial increase of $T_r(d_2)$ with the overlayer
thickness $d_2$ followed by a decrease of $T_r(d_2)$ at larger $d_2$. Such a
nonmonotonic thickness dependence of $T_r(d_2)$ results from the interplay of
the increase of a net superfluid density mitigating phase fluctuations and the
suppression of the critical temperature $T_c$ due to the conventional proximity
effect. This behavior of $T_r(d_2)$ is obtained by solving the Usadel equations
to calculate the temperature of the Berezinskii-Kosterletz-Thouless transition,
and the temperature of the resistive transition due to thermally-activated
hopping of single vortices in dirty bilayers. The theory incorporates relevant
materials parameters such as thicknesses and conductivities of the layers,
interface contact resistance between them and the subgap quasiparticle states
which affect both phase fluctuations and the proximity effect suppression of
$T_c$. The transition temperature $T_r$ can be optimized by tuning the
overlayer parameters, which can significantly weaken vortex fluctuations and
nearly restore the mean-field critical temperature. The calculated behavior of
$T_r(d_2)$ may explain the nonmonotonic dependence of $T_r(d_2)$ observed on
(Ag, Au, Mg, Zn)-coated Bi films, Ag-coated Ga and Pb films or NbN and NbTiN
films on AlN buffer layers. These results suggest that bilayers can be used as
model systems for systematic investigations of optimization of fluctuations in
superconductors.",1807.04891v1
2020-01-02,Numerical investigation into fracture resistance of bone following adaptation,"Bone adapts in response to its mechanical environment. This evolution of bone
density is one of the most important mechanisms for developing fracture
resistance. A finite element framework for simulating bone adaptation, commonly
called bone remodelling, is presented. This is followed by a novel method to
both quantify fracture resistance and to simulate fracture propagation. The
authors' previous work on the application of configurational mechanics for
modelling fracture is extended to include the influence of heterogeneous bone
density distribution. The main advantage of this approach is that
configurational forces, and fracture energy release rate, are expressed
exclusively in terms of nodal quantities. This approach avoids the need for
post-processing and enables a fully implicit formulation for modelling the
evolving crack front. In this paper density fields are generated from both (a)
bone adaptation analysis and (b) subject-specific geometry and material
properties obtained from CT scans. It is shown that, in order to correctly
evaluate the configurational forces at the crack front, it is necessary to have
a spatially smooth density field with higher regularity than if the field is
directly approximated on the finite element mesh. Therefore, discrete density
data is approximated as a smooth density field using a Moving Weighted Least
Squares method. Performance of the framework is demonstrated using numerical
simulations for bone adaptation and subsequent crack propagation, including
consideration of an equine 3rd metacarpal bone. The degree of bone adaption is
shown to influence both fracture resistance and the resulting crack path.",2001.00647v1
2020-06-19,Contrasting physical properties of the trilayer nickelates Nd$_4$Ni$_3$O$_{10}$ and Nd$_4$Ni$_3$O$_8$,"We report the crystal structures and physical properties of trilayer
nickelates Nd$_4$Ni$_3$O$_{10}$ and Nd$_4$Ni$_3$O$_8$. Measurements of
magnetization and electrical resistivity display contrasting behaviors in the
two compounds. Nd$_4$Ni$_3$O$_{10}$ shows a paramagnetic metallic behavior with
a metal to metal phase transition($T^{\ast}$) at about 162 K, as revealed by
both magnetic susceptibility and resistivity. Further magnetoresistance and
Hall coefficient results show a negative magnetoresistance at low temperatures
and the carrier type of Nd$_4$Ni$_3$O$_{10}$ is dominated by hole-type charge
carriers. The significant enhancement of Hall coefficient and resistivity below
$T^{\ast}$ suggest that effective charge carrier density decreases when cooling
through the transition temperature. In contrast, Nd$_4$Ni$_3$O$_8$ shows an
insulating behavior despite small value of resistivity at room temperature. The
compound shows paramagnetic behavior, with the similar magnetic moments as in
Nd$_4$Ni$_3$O$_{10}$ derived from the Curie-Weiss fitting. This may suggest
that the magnetic moments in both systems are contributed by the Nd ions. By
applying pressures up to about 49 GPa, the insulating behavior is still present
and becomes even stronger. Our results suggest that the different Ni
configurations ($Ni^{1+/2+}$ or $Ni^{2+/3+}$) and competition between localized
and itinerant electrons may account for the contrasting behaviors in trilayer
nickelates Nd$_4$Ni$_3$O$_{10}$ and Nd$_4$Ni$_3$O$_8$.",2006.10988v1
2020-10-13,How to solve problems in micro- and nanofabrication caused by the emission of electrons and charged metal atoms during e-beam evaporation,"We discuss how the emission of electrons and ions during
electron-beam-induced physical vapor deposition can cause problems in micro-
and nanofabrication processes. After giving a short overview of different types
of radiation emitted from an electron-beam (e-beam) evaporator and how the
amount of radiation depends on different deposition parameters and conditions,
we highlight two phenomena in more detail: First, we discuss an unintentional
shadow evaporation beneath the undercut of a resist layer caused by the one
part of the metal vapor which got ionized by electron-impact ionization. These
ions first lead to an unintentional build-up of charges on the sample, which in
turn results in an electrostatic deflection of subsequently incoming ionized
metal atoms towards the undercut of the resist. Second, we show how low-energy
secondary electrons during the metallization process can cause cross-linking,
blisters, and bubbles in the respective resist layer used for defining micro-
and nanostructures in an e-beam lithography process. After the metal
deposition, the cross-linked resist may lead to significant problems in the
lift-off process and causes leftover residues on the device. We provide a
troubleshooting guide on how to minimize these effects, which e.g. includes the
correct alignment of the e-beam, the avoidance of contaminations in the
crucible and, most importantly, the installation of deflector electrodes within
the evaporation chamber.",2010.06459v2
2021-02-17,Optimization of epitaxial graphene growth for quantum metrology,"(See the complete abstract within the thesis in both English and German
versions)
  In this thesis, the process conditions of the epitaxial graphene growth
through a socalled polymer-assisted sublimation growth method are minutely
investigated. Atomic force microscopy (AFM) is used to show that the previously
neglected flow-rate of the argon process gas has a significant influence on the
morphology of the SiC substrate and atop carbon layers. The results can be well
explained using a simple model for the thermodynamic conditions at the layer
adjacent to the surface. The resulting control option of step-bunching on the
sub-nanometer scales is used to produce the ultra-flat, monolayer graphene
layers without the bilayer inclusions that exhibit the vanishing of the
resistance anisotropy. The comparison of four-point and scanning tunneling
potentiometry measurements shows that the remaining small anisotropy represents
the ultimate limit, which is given solely by the remaining resistances at the
SiC terrace steps. ... The precise control of step-bunching using the Ar flow
also enables the preparation of periodic non-identical SiC surfaces under the
graphene layer. Based on the work function measurements by Kelvin-Probe force
microscopy and X-ray photoemission electron microscopy, it is shown for the
first time that there is a doping variation in graphene, induced by a proximity
effect of the different near-surface SiC stacks. The comparison of the AFM and
low-energy electron microscopy measurements have enabled the exact assignment
of the SiC stacks, and the examinations have led to an improved understanding
of the surface restructuring in the framework of a step-flow mode. ...",2102.08691v1
2021-05-30,Enhanced electron-phonon coupling in doubly aligned hexagonal boron nitride bilayer graphene heterostructure,"The relative twist angle in heterostructures of two-dimensional (2D)
materials with similar lattice constants result in a dramatic alteration of the
electronic properties. Here, we investigate the electrical and magnetotransport
properties in bilayer graphene (BLG) encapsulated between two hexagonal boron
nitride (hBN) crystals, where the top and bottom hBN are rotationally aligned
with bilayer graphene with a twist angle $\theta_t\sim 0^{\circ} \text{and}~
\theta_b < 1^{\circ}$, respectively. This results in the formation of two
moir\'e superlattices, with the appearance of satellite resistivity peaks at
carrier densities $n_{s1}$ and $n_{s2}$, in both hole and electron doped
regions, together with the resistivity peak at zero carrier density.
Furthermore, we measure the temperature(T) dependence of the resistivity
($\rho$). The resistivity shows a linear increment with temperature within the
range 10K to 50K for the density regime $n_{s1} <n<n_{s2}$ with a large slope
d$\rho$/dT $\sim$ 8.5~$\Omega$/K. The large slope of d$\rho$/dT is attributed
to the enhanced electron-phonon coupling arising due to the suppression of
Fermi velocity in the reconstructed minibands, which was theoretically
predicted, recently in doubly aligned graphene with top and bottom hBN. Our
result establishes the uniqueness of doubly aligned moire system to tune the
strength of electron-phonon coupling and to modify the electronic properties of
multilayered heterostructures.",2105.14589v1
2021-09-01,"Thickness dependent transition from the 1T$^\prime$ to Weyl semimetal phase in ultrathin MoTe$ _{2} $: Electrical transport, Noise and Raman studies","Bulk 1T$^\prime$-MoTe$_2$ shows a structural phase transition from
1T$^\prime$ to Weyl semimetallic (WSM) $ T_{d} $ phase at $\sim$ 240 K. This
phase transition and transport properties in the two phases have not been
investigated on ultra-thin crystals. Here we report electrical transport, $1/f$
noise and Raman studies in ultra-thin 1T$^\prime$-MoTe$_2$ ($\sim$ 5 to 16 nm
thick) field-effect transistors (FETs) devices as a function of temperature.
The electrical resistivities for thickness 16 nm and 11 nm show maxima at
temperatures 208 K and 178 K, respectively, making a transition from
semiconducting to semi-metallic phase, hitherto not observed in bulk samples.
Raman frequencies and linewidths for 11nm thick crystal show change around 178
K, attributed to additional contribution to the phonon self-energy due to
enhanced electron-phonon interaction in the WSM phase. Further, the resistivity
at low-temperature shows an upturn below 20 K along with the maximum in the
power spectral density of the low frequency $1/f$ noise. The latter rules out
the metal-insulator transition (MIT) being responsible for the upturn of
resistivity below 20 K. The low temperature resistivity follows $\rho \propto
1/T$, changing to $\rho \propto T$ with increasing temperature supports
electron-electron interaction physics at electron-hole symmetric Weyl nodes
below 20 K. These observations will pave the way to unravel the properties of
WSM state in layered ultra-thin van der Waals materials.",2109.00504v2
2021-10-05,Carrier transport and performance limit of semi-transparent photovoltaics: CuIn$_{1-x}$Ga$_x$Se$_2$ as a case study,"Semi-transparent photovoltaic devices for building integrated applications
have the potential to provide simultaneous power generation and natural light
penetration. CuIn$_{1-x}$Ga$_x$Se$_2$ (CIGS) has been established as a mature
technology for thin-film photovoltaics, however, its potential for
Semi-Transparent Photovoltaics (STPV) is yet to be explored. In this paper, we
present its carrier transport physics explaining the trend seen in recently
published experiments. STPV requires deposition of films of only a few hundred
nanometers to make them transparent and manifests several unique properties
compared to a conventional thin-film solar cell. Our analysis shows that the
short-circuit current, Jsc is dominated by carriers generated in the depletion
region, making it nearly independent of bulk and back-surface recombination.
The bulk recombination, which limits the open-circuit voltage Voc, appears to
be higher than usual attributable to numerous grain boundaries. When the
absorber layer is reduced below 500 nm, grain size reduces resulting in more
grain boundaries and higher resistance. This produces an inverse relationship
between series resistance and absorber thickness. We also present a
thickness-dependent model of shunt resistance showing its impact in these
ultra-thin devices. For various scenarios of bulk and interface recombinations,
shunt and series resistances, AVT and composition of CuIn$_{1-x}$Ga$_x$Se$_2$,
we project the efficiency limit which - for most practical cases - is found to
be $\leq$10% for AVT $\geq$25%.",2110.02146v1
2022-01-11,Spectral Thermal Spreading Resistance of Wide Bandgap Semiconductors in Ballistic-Diffusive Regime,"To develop efficient thermal management strategies for wide bandgap (WBG)
semiconductor devices, it is essential to have a clear understanding of the
heat transport process within the device and accurately predict the junction
temperature. In this paper, we used the phonon Monte Carlo (MC) method with the
phonon dispersion of various typical WBG semiconductors, including GaN, SiC,
AlN, and \ce{\beta-Ga_2O_3}, to investigate the thermal spreading resistance in
a ballistic-diffusive regime. It was found that when compared with Fourier's
law-based predictions, the increase in the thermal resistance caused by
ballistic effects was strongly related to different phonon dispersions. Based
on the model deduced under the gray-medium approximation and the results of
dispersion MC, we obtained a thermal resistance model that can well address the
issues of thermal spreading and ballistic effects, and the influences of phonon
dispersion. The model can be easily coupled with FEM based thermal analysis and
applied to different materials. This paper can provide a clearer understanding
of the influences of phonon dispersion on the thermal transport process, and it
can be useful for the prediction of junction temperatures and the development
of thermal management strategies for WBG semiconductor devices.",2201.03788v1
2022-03-23,Improved Gradual Resistive Switching Range and 1000x On/Off Ratio in HfOx RRAM Achieved with a $Ge_2Sb_2Te_5$ Thermal Barrier,"Gradual switching between multiple resistance levels is desirable for analog
in-memory computing using resistive random-access memory (RRAM). However, the
filamentary switching of $HfO_x$-based conventional RRAM often yields only two
stable memory states instead of gradual switching between multiple resistance
states. Here, we demonstrate that a thermal barrier of $Ge_2Sb_2Te_5$ (GST)
between $HfO_x$ and the bottom electrode (TiN) enables wider and weaker
filaments, by promoting heat spreading laterally inside the $HfO_x$. Scanning
thermal microscopy suggests that $HfO_x+GST$ devices have a wider heating
region than control devices with only $HfO_x$, indicating the formation of a
wider filament. Such wider filaments can have multiple stable conduction paths,
resulting in a memory device with more gradual and linear switching. The
thermally-enhanced $HfO_x+GST$ devices also have higher on/off ratio ($>10^3$)
than control devices ($<10^2$), and a median set voltage lower by approximately
1 V (~35%), with a corresponding reduction of the switching power. Our
$HfO_x+GST$ RRAM shows 2x gradual switching range using fast (~ns) identical
pulse trains with amplitude less than 2 V.",2203.12190v1
2022-05-09,Reconciling scaling of the optical conductivity of cuprate superconductors with Planckian resistivity and specific heat,"Materials tuned to a quantum critical point display universal scaling
properties as a function of temperature $T$ and frequency $\omega$. A
long-standing puzzle regarding cuprate superconductors has been the observed
power-law dependence of optical conductivity with an exponent smaller than one,
in contrast to $T$-linear dependence of the resistivity and $\omega$-linear
dependence of the optical scattering rate. Here, we present and analyze
resistivity and optical conductivity of La$_{2-x}$Sr$_x$CuO$_4$ with $x=0.24$.
We demonstrate $\hbar\omega/k_{\mathrm{B}} T$ scaling of the optical data over
a wide range of frequency and temperature, $T$-linear resistivity, and optical
effective mass proportional to $\sim \ln T$ corroborating previous specific
heat experiments. We show that a $T,\omega$-linear scaling Ansatz for the
inelastic scattering rate leads to a unified theoretical description of the
experimental data, including the power-law of the optical conductivity. This
theoretical framework provides new opportunities for describing the unique
properties of quantum critical matter.",2205.04030v2
2022-05-23,Electrical Resistivity of Polycrystalline Graphene: Effect of Grain-Boundary-Induced Strain Fields,"We have revealed the decisive role of grain-boundary-induced strain fields in
electron scattering in polycrystalline graphene. To this end, we have
formulated the model based on Boltzmann transport theory which properly takes
into account the microscopic structure of grain boundaries (GB) as a repeated
sequence of heptagon-pentagon pairs. The effect of strain field is described
within the deformation potential theory. For comparison, we consider the
scattering due to electrostatic potential of charged grain boundary. We show
that at naturally low GB charges the deformation potential scattering dominates
and leads to physically reasonable and, what is important, experimentally
observable values of the electrical resistivity. It ranges from 0.1 to 10
k$\Omega $$\mu $m for different types of GBs with a size of 1 $\mu$m and has a
strong dependence on misorientation angle. For low-angle highly charged GBs,
two scattering mechanisms may compete. The resistivity increases markedly with
decreasing GB size and reaches values of 60 k$\Omega $$\mu $m and more. It is
also very sensitive to the presence of irregularities modeled by embedding of
partial disclination dipoles. With significant distortion, we found an increase
in resistance by more than an order of magnitude, which is directly related to
the destruction of diffraction on the GB. Our findings may be of interest both
in the interpretation of experimental data and in the design of electronic
devices based on poly- and nanocrystalline graphene.",2205.11270v1
2022-05-31,Anisotropic signatures of the electronic correlations in the electrical resistivity of UTe$_2$,"Multiple unconventional superconducting phases are suspected to be driven by
magnetic fluctuations in the heavy-fermion paramagnet UTe$_2$, and a challenge
is to identify the signatures of the electronic correlations, including the
magnetic fluctuations, in the bulk physical quantities. Here, we investigate
thoroughly the anisotropy of the electrical resistivity of UTe$_2$ under
intense magnetic fields up to 70~T, for different electrical-current and
magnetic-field configurations. Two characteristic temperatures and an
anisotropic low-temperature Fermi-liquid-like coefficient $A$, controlled by
the electronic correlations, are extracted. Their critical behavior near the
metamagnetic transition induced at $\mu_0H_m\simeq35$~T for
$\mathbf{H}\parallel\mathbf{b}$ is characterized. Anisotropic scattering
processes are evidenced and magnetic fluctuations are proposed to contribute,
via a Kondo hybridization, to the electrical resistivity. Our work appeals for
a microscopic modeling of the anisotropic contributions to the electrical
resistivity as a milestone for understanding magnetically-mediated
superconductivity in UTe$_2$.",2205.15789v2
2022-06-11,"On the Fermi gas, the Sommerfeld fine structure constant, and the electron-electron scattering in conductors","Electrical energy is considered as a fundamental parameter for inclusion in
Fermi gas theory, in addition to thermal energy. It is argued that electrical
energy can move some electrons to above the Fermi Level, providing free charges
to carry the electrical current, even at absolute zero temperature. The Drude
model, Ohm's law, quantum resistance, and the electrical resistivity due to
electron-electron scattering appear naturally as a consequence of the
theoretical description, which is based on the quantization of the angular
momentum and the Fermi-Dirac distribution, considering total energy as
${\epsilon}$ = k$_B$$T$ + ${\Phi}_0$$I$. The electrical and magnetic forces
acting on an electron are related to the ratio between the Fermi velocity and
the speed of light and show that the electron motion is due to helical paths.
Considering the center of mass description for the Bohr atom, it was possible
to show that the magnetic force is related to the electrical force as $F_M$ =
(${\alpha}$/${\pi}$) $F_E$, which demonstrates that the electrons move in
helical paths along the orbit. The helical motion naturally provides for
quantization of the magnetic flux, the spin of the electron, and the first
correction term of the anomalous magnetic moment. Applying the model to
describe the electron-electron scattering allows prediction of the behavior of
the electrical resistivity of many metals at low temperatures, which is in
excellent agreement with empirical observations.",2206.05393v2
2022-06-30,Antipolar transitions in GaNb$_4$Se$_8$ and GaTa$_4$Se$_8$,"We present dielectric, polarization, resistivity, specific heat, and magnetic
susceptibility data on single crystals of the lacunar spinels GaNb4Se8 and
GaTa4Se8, tetrahedral cluster-based materials with substantial spin-orbit
coupling. We concentrate on the possible occurrence of antipolar order in these
compounds, as previously reported for the isoelectronic GaNb4S8, where
spin-orbit coupling plays a less important role. Our broadband
dielectric-spectroscopy investigations reveal clear anomalies of the intrinsic
dielectric constant at the magneto-structural transitions in both systems that
are in accord with the expectations for antipolar transitions. A similar
anomaly is also observed at the cubic-cubic transition of the Nb compound
leading to an intermediate phase. Similar to other polar and antipolar lacunar
spinels, we find indications for dipolar relaxation dynamics at low
temperatures. Polarization measurements on GaNb4Se8 reveal weak ferroelectric
ordering below the magneto-structural transition, either superimposed to
antipolar order or emerging at structural domain walls. The
temperature-dependent dc resistivity evidences essentially thermally-activated
charge transport with different activation energies in the different phases. A
huge step-like increase of the resistivity at the magneto-structural transition
of the Ta compound points to a fundamental change in the electronic structure
or the mechanism of the charge transport. At low temperatures, charge transport
is governed by in-gap impurity states, as also invoked to explain the resistive
switching in these compounds.",2206.15200v2
2022-11-16,Decoupling the Roles of Defects/Impurities and Wrinkles in Thermal Conductivity of Wafer-scale hBN Films,"We demonstrate a non-monotonic evolution of thermal conductivity of
large-area hexagonal boron nitride films with thickness. Wrinkles and
defects/impurities are present in these films. Raman spectroscopy, an
optothermal non-contact technique, is employed to probe the temperature and
laser power dependence property of the Raman active E2ghigh phonon mode, which
in turn is used to estimate the rise in the temperature of the films under
different laser powers. As the conventional Fourier law of heat diffusion
cannot be directly employed analytically to evaluate the thermal conductivity
of these films with defects and wrinkles, finite element modeling is used
instead. In the model, average heat resistance is used to incorporate an
overall defect structure, and Voronoi cells with contact resistance at the cell
boundaries are constructed to mimic the wrinkled domains. The effective thermal
conductivity is estimated to be 87, 55, and 117 W/m.K for the 2, 10, and 30
nm-thick films, respectively. We also present a quantitative estimation of the
thermal resistance by defects and wrinkles individually to the heat flow. Our
study reveals that the defects/impurities render a much higher resistance to
heat transfer in the films than wrinkles.",2211.08683v2
2022-11-18,Magnetotransport induced by anomalous Hall effect,"In a magnetic metal, the Hall resistance is generally taken to be the sum of
the ordinary Hall resistance and the anomalous Hall resistance. Here it is
shown that this empirical relation is no longer valid when either the ordinary
Hall angle or the anomalous Hall angle is not small. Using the proper
conductivity relation, we reveal an unexpected magnetoresistance (MR) induced
by the anomalous Hall effect (AHE). A $B$-linear MR arises and the sign of the
slope depends on the sign of the anomalous Hall angle, giving rise to a
characteristic bowtie shape. The Hall resistance in a single-band system can
exhibit a nonlinearity which is usually considered as a characteristic of a
two-band system. A $B$-symmetric component appears in the Hall. These effects
reflect the fundamental difference between the ordinary Hall effect and the
AHE. Furthermore, we experimentally reproduce the unusual MR and Hall reported
before in Co$_3$Sn$_2$S$_2$ and show that these observations can be well
explained by the proposed mechanism. MR often observed in quantum anomalous
Hall insulators provides further confirmation of the picture. The effect may
also account for the large MR observed in non-magnetic three-dimensional
topological Dirac semimetals.",2211.10222v2
2022-12-08,Theory of the Little-Parks effect in spin-triplet superconductors,"The celebrated Little-Parks effect in mesoscopic superconducting rings has
recently gained great attention due to its potential to probe half-quantum
vortices in spin-triplet superconductors. However, despite the large number of
works reporting anomalous Little-Parks measurements attributed to
unconventional superconductivity, the general signatures of spin-triplet
pairing in the Little-Parks effect have not yet been systematically
investigated. Here we use Ginzburg-Landau theory to study the Little-Parks
effect in a spin-triplet superconducting ring that supports half-quantum
vortices; we calculate the field-induced Little-Parks oscillations of both the
critical temperature itself and the residual resistance resulting from thermal
vortex tunneling below the critical temperature. We observe two separate
critical temperatures with a single-spin superconducting state in between and
find that, due to the existence of half-quantum vortices, each minimum in the
upper critical temperature splits into two minima for the lower critical
temperature. From a rigorous calculation of the residual resistance, we confirm
that these two minima in the lower critical temperature translate into two
maxima in the residual resistance below and establish the general conditions
under which the two maxima can be practically resolved. In particular, we
identify a fundamental trade-off between sharpening each maximum and keeping
the overall magnitude of the resistance large. Our results will guide
experimental efforts in designing mesoscopic ring geometries for probing
half-quantum vortices in spin-triplet candidate materials on the device scale.",2212.04591v1
2023-04-16,Anomalous and Topological Hall Resistivity in Ta/CoFeB/MgO Magnetic Systems for Neuromorphic Computing Applications,"Topologically protected spin textures, such as magnetic skyrmions, have the
potential for dense data storage as well as energy-efficient computing due to
their small size and a low driving current. The evaluation of the writing and
reading of the skyrmion's magnetic and electrical characteristics is a key step
toward the implementation of these devices. In this paper, we present the
magnetic heterostructure Hall bar device and study the anomalous Hall and
topological Hall signals in the device. Using the combination of different
measurements like magnetometry at different temperatures, Hall effect
measurement from 2K to 300K, and magnetic force microscopy imaging, we
investigate the magnetic and electrical characteristics of the magnetic
structure. We measure the skyrmion topological resistivity at different
temperatures as a function of the magnetic field. The topological resistivity
is maximum around the zero magnetic field and it decreases to zero at the
saturating field. This is further supported by MFM imaging. Interestingly the
resistivity decreases linearly with the field, matching the behavior observed
in the corresponding micromagnetic simulations. We combine the experimental
results with micromagnetic simulations, thus propose a skyrmion-based synaptic
device and show spin-orbit torque-controlled potentiation/depression in the
device. The device performance as the synapse for neuromorphic computing is
further evaluated in a convolutional neural network CNN. The neural network is
trained and tested on the MNIST data set we show devices acting as synapses
achieving a recognition accuracy close to 90%, on par with the ideal
software-based weights which offer an accuracy of 92%.",2304.07742v1
2023-09-01,Multilayer Ferromagnetic Spintronic Devices for Neuromorphic Computing Applications,"Spintronics has gone through substantial progress due to its applications in
energy-efficient memory, logic and unconventional computing paradigms.
Multilayer ferromagnetic thin films are extensively studied for understanding
the domain wall and skyrmion dynamics. However, most of these studies are
confined to the materials and domain wall/skyrmion physics. In this paper, we
present the experimental and micromagnetic realization of a multilayer
ferromagnetic spintronic device for neuromorphic computing applications. The
device exhibits multilevel resistance states and the number of resistance
states increases with lowering temperature. This is supported by the multilevel
magnetization behavior observed in the micromagnetic simulations. Furthermore,
the evolution of resistance states with spin-orbit torque is also explored in
experiments and simulations. Using the multi-level resistance states of the
device, we propose its applications as a synaptic device in hardware neural
networks and study the linearity performance of the synaptic devices. The
neural network based on these devices is trained and tested on the MNIST
dataset using a supervised learning algorithm. The devices at the chip level
achieve 90\% accuracy. Thus, proving its applications in neuromorphic
computing. Furthermore, we lastly discuss the possible application of the
device in cryogenic memory electronics for quantum computers.",2309.00476v1
2024-01-30,Effect of the Sc/Zr ratio on the corrosion resistance of Al-Mg cast alloys,"The results of investigations of the corrosion resistance of Al-Mg-Sc-Zr
alloys with varying Mg content and different Sc/Zr ratios are presented. The
objects of investigations were the Al-Mg-Sc-Zr alloys with total Sc + Zr
content of 0.32 wt%. The concentration of Sc and Zr in the alloys varied with
the increments of 0.02 wt%. The alloys were produced by induction casting. The
effect of annealing temperature on the microhardness and electrical resistivity
of the Al-Mg-Sc-Zr alloys was investigated. Corrosion tests were carried out in
a medium simulating intergranular corrosion in aluminum alloys. Electrochemical
studies and mass loss tests were performed. An increase in the Sc concentration
and a decrease in the Zr one were shown to result in an increase in the
corrosion rate. The primary Al3(ScxZr1-x) particles were found to have the main
effect on the corrosion resistance of Al-Mg-Sc-Zr alloys. The dependence of the
corrosion current on the annealing temperature of the Al-Mg-Sc-Zr alloy was
found to have a non-monotonous character (with a maximum).",2401.17429v1
1997-02-27,High temperature anomaly of the conductance of a tunnel junction,"The linear conductance of a tunnel junction in series with an ohmic resistor
is determined in the high temperature limit. The tunneling current is treated
nonperturbatively by means of path integral techniques. Due to quantum effects
the conductance is smaller than the classical series conductance. The reduction
factor is found to be nonanalytic in the environmental resistance for vanishing
resistance. This behavior is a high temperature manifestation of the Coulomb
blockade effect.",9702242v3
2002-10-11,High-field side of Superconductor-Insulator Transition,"We report the experimental observation of a magnetic-field-tuned
superconductor-insulator transition (SIT) in ultrathin TiN films. The low
temperature transport properties of these films show scaling behavior
consistent with a transition driven by quantum phase fluctuations in
two-dimensional superconductor. The magnetoresistance reveals peak and a
subsequent decrease in fields higher than the critical field. The temperature
dependences of the isomagnetic resistance data on the high-field side of the
SIT have been analyzed and the transition from insulating to metallic phase is
found, with at high fields the zero-temperature asymptotic value of the
resistance being equal to h/e^2.",0210250v1
2003-11-11,Nonlocal effects in high energy charged particle beams,"Within the framework of the thermal wave model, an investigation is made of
the longitudinal dynamics of high energy charged particle beams. The model
includes the self-consistent interaction between the beam and its surroundings
in terms of a nonlinear coupling impedance, and when resistive as well as
reactive parts are included, the evolution equation becomes a generalised
nonlinear Schroedinger equation including a nonlocal nonlinear term. The
consequences of the resistive part on the propagation of particle bunches are
examined using analytical as well as numerical methods.",0311139v1
2008-11-05,"High-pressure, transport, and thermodynamic properties of CeTe3","We have performed high-pressure, electrical resistivity, and specific heat
measurements on CeTe3 single crystals. Two magnetic phases with nonparallel
magnetic easy axes were detected in electrical resistivity and specific heat at
low temperatures. We also observed the emergence of an additional phase at high
pressures and low temperatures and a possible structural phase transition
detected at room temperature and at 45 kbar, which can possibly be related with
the lowering of the charge-density wave transition temperature known for this
compound.",0811.0792v2
2009-07-30,High order fractional microwave induced resistance oscillations in 2D systems,"We report on the observation of microwave-induced resistance oscillations
associated with the fractional ratio n/m of the microwave irradiation frequency
to the cyclotron frequency for m up to 8 in a two-dimensional electron system
with high electron density. The features are quenched at high microwave
frequencies independent of the fractional order m. We analyze temperature,
power, and frequency dependencies of the magnetoresistance oscillations and
discuss them in connection with existing theories.",0907.5315v1
2010-11-24,A spark-resistant bulk-micromegas chamber for high-rate applications,"We report on the design and performance of a spark-resistant bulk-micromegas
chamber. The principle of this design lends itself to the construction of
large-area muon chambers for the upgrade of the detectors at the Large Hadron
Collider at CERN for luminosities in excess of 10**34/cm2/s or other high-rate
applications.",1011.5370v1
2012-12-10,Quantized escape and formation of edge channels at high Landau levels,"We present nonlocal resistance measurements in an ultra high mobility two
dimensional electron gas. Our experiments show that even at weak magnetic
fields classical guiding along edges leads to a strong non local resistance on
macroscopic distances. In this high Landau level regime the transport along
edges is dissipative and can be controlled by the amplitude of the voltage drop
along the edge. We report resonances in the nonlocal transport as a function of
this voltage that are interpreted as escape and formation of edge channels.",1212.2026v1
2019-06-26,Studies on small charge packet transport in high-resistivity fully-depleted CCDs,"In this work, we will present a physical model and measurements of the
transport of small charge packets in the bulk of thick high resistivity CCD
before being collected by the pixel potential wells. A new technique to measure
the lateral spread of the charge as a function of the ionization depth in the
bulk is presented. Results from measurements on CCD currently in use for
several scientific instruments are shown and validated with a new mathematical
algorithm to extend the current modeling based only on the diffusion of the
charge in silicon.",1906.11379v1
2011-07-09,Resistance to TB drugs in KwaZulu-Natal: causes and prospects for control,"In 2005 there was an outbreak of XDR (extensively drug resistant) TB in
Tugela Ferry, which is served by the Church of Scotland Hospital (COSH), in the
uMzinyathi District, KwaZulu-Natal, South Africa. An investigation was carried
out to determine if XDR TB was occurring elsewhere in the province, and to
develop hypotheses for the rise in drug resistance with a view to developing a
strategy for the control of MDR (multi-drug resistant) and XDR TB in the
province and elsewhere. TB incidence and treatment success rates, for each of
the 11 districts in the province, were obtained from the provincial electronic
TB register for the years 2002-2007. The results of culture and drug
sensitivity tests for the years 2002 to 2007 in each of the districts were
compiled and culture taking practices were compared to the number of MDR TB
cases. Interviews were conducted with key personnel in affected sites. In 2007,
2799, or 2.3% of 119,218 notified TB cases in the province were multi-drug
resistant (MDR), and of these 270 (9.6%) were XDR. The two worst affected
districts were uMzinyathi where 226 (4.1%) of 5522 notified TB cases were MDR,
and of these 120 (53%) were extensively drug resistant (XDR), and uMkhanyakude
where 337 (4.8%) of 6991 notified TB cases were MDR, but of these only four or
(1.2%) were XDR. The worst affected medical centre was COSH where 164 or 9.8%
of notified TB cases were MDR and of these 99 (60%) were XDR. Very high rates
of XDR TB in the province are only found in uMzinyathi district even though MDR
TB is common in most other districts. XDR may arisen at COSH because of the
early and effective integration of the TB and HIV programmes in overcrowded and
poorly ventilated facilities particular to COS.H To control XDR TB better
management of both susceptible and resistant forms of TB is needed including
treatment supervision, infection control and HIV management.",1107.1800v1
2012-02-06,Performances of Anode-resistive Micromegas for HL-LHC,"Micromegas technology is a promising candidate to replace Atlas forward muon
chambers -tracking and trigger- for future HL-LHC upgrade of the experiment.
The increase on background and pile-up event probability requires detector
performances which are currently under studies in intensive RD activities.
  We studied performances of four different resistive Micromegas detectors with
different read-out strip pitches. These chambers were tested using \sim120 GeV
momentum pions, at H6 CERN-SPS beam line in autumn 2010. For a strip pitch 500
micrometers we measure a resolution of \sim90 micrometers and a efficiency of
~98%. The track angle effect on the efficiency was also studied. Our results
show that resistive techniques induce no degradation on the efficiency or
resolution, with respect to the standard Micromegas. In some configuration the
resistive coating is able to reduce the discharge currents at least by a factor
of 100.Micromegas technology is a promising candidate to replace Atlas forward
muon chambers -tracking and trigger- for future HL-LHC upgrade of the
experiment. The increase on background and pile-up event probability requires
detector performances which are currently under studies in intensive RD
activities. We studied performances of four different resistive Micromegas
detectors with different read-out strip pitches. These chambers were tested
using \sim120 GeV momentum pions, at H6 CERN-SPS beam line in autumn 2010. For
a strip pitch 500 micrometers we measure a resolution of \sim90 micrometers and
a efficiency of \sim98%. The track angle effect on the efficiency was also
studied. Our results show that resistive techniques induce no degradation on
the efficiency or resolution, with respect to the standard Micromegas. In some
configuration the resistive coating is able to reduce the discharge currents at
least by a factor of 100.",1202.1074v1
2018-11-12,Phonon-induced giant linear-in-$T$ resistivity in magic angle twisted bilayer graphene: Ordinary strangeness and exotic superconductivity,"We study the effect of electron-acoustic phonon interactions in twisted
bilayer graphene on resistivity in the high-temperature transport and
superconductivity in the low-temperature phase diagram. We theoretically show
that twisted bilayer graphene should have an enhanced and strongly twist-angle
dependent linear-in-temperature resistivity in the metallic regime with the
resistivity magnitude increasing as the twist angle approaches the magic angle.
The slope of the resistivity versus temperature could approach one hundred ohms
per kelvin with a strong angle dependence, but with a rather weak dependence on
the carrier density. This higher-temperature density-independent linear-in-$T$
resistivity crosses over to a $T^4$ dependence at a low density-dependent
characteristic temperature, becoming unimportant at low temperatures. This
angle-tuned resistivity enhancement arises from the huge increase in the
effective electron-acoustic phonon coupling in the system due to the
suppression of graphene Fermi velocity induced by the flatband condition in the
moir\'e superlattice system. Our calculated temperature dependence is
reminiscent of the so-called `strange metal' transport behavior except that it
is arising from the ordinary electron-phonon coupling in a rather unusual
parameter space due to the generic moir\'e flatband structure of twisted
bilayer graphene. We also show that the same enhanced electron-acoustic phonon
coupling also mediates effective attractive interactions in $s$, $p$, $d$ and
$f$ pairing channels with a theoretical superconducting transition temperature
on the order of $\sim$5 K near magic angle. The fact that ordinary acoustic
phonons can produce exotic non-$s$-wave superconducting pairing arises from the
unusual symmetries of the system.",1811.04920v4
2017-03-07,A Strange Metal from Gutzwiller correlations in infinite dimensions,"Recent progress in extremely correlated Fermi liquid theory (ECFL) and
dynamical mean field theory (DMFT) enables us to compute in the $d \to \infty$
limit the resistivity of the $t-J$ model after setting $J\to0$. This is also
the $U=\infty$ Hubbard model. We study three densities $n=.75,.8,.85$ that
correspond to a range between the overdoped and optimally doped Mott insulating
state. We delineate four distinct regimes characterized by different behaviors
of the resistivity $\rho$. We find at the lowest $T$ a Gutzwiller Correlated
Fermi Liquid regime with $\rho \propto T^2$ extending up to an effective Fermi
temperature that is dramatically suppressed from the non-interacting value.
This is followed by a Gutzwiller Correlated Strange Metal regime with $\rho
\propto (T-T_0)$, i.e. a linear resistivity extrapolating back to $\rho=0$ at a
positive $T_0$. At a higher $T$ scale, this crosses over into the Bad Metal
regime with $\rho \propto (T+T_1)$ extrapolating back to a finite resistivity
at $T=0$, and passing through the Ioffe-Regel-Mott value where the mean free
path is a few lattice constants. This regime finally gives way to the High $T$
Metal regime, where we find $\rho \propto T$. The present work emphasizes the
first two, where the availability of an analytical ECFL theory is of help in
identifying the changes in related variables entering the resistivity formula
that accompany the onset of linear resistivity, and the numerically exact DMFT
helps to validate the results. We also examine thermodynamic variables such as
the magnetic susceptibility, compressibility, heat capacity and entropy, and
correlate changes in these with the change in resistivity. This exercise casts
valuable light on the nature of charge and spin correlations in the strange
metal regime, which has features in common with the physically relevant strange
metal phase seen in strongly correlated matters.",1703.02206v3
2019-07-16,General relativistic resistive magnetohydrodynamics with robust primitive variable recovery for accretion disk simulations,"Recent advances in black hole astrophysics, particularly the first visual
evidence of a supermassive black hole at the center of the galaxy M87 by the
Event Horizon Telescope (EHT), and the detection of an orbiting ""hot spot""
nearby the event horizon of Sgr A* in the Galactic center by the Gravity
Collaboration, require the development of novel numerical methods to understand
the underlying plasma microphysics. Non-thermal emission related to such hot
spots is conjectured to originate from plasmoids that form due to magnetic
reconnection in thin current layers in the innermost accretion zone.
Resistivity plays a crucial role in current sheet formation, magnetic
reconnection, and plasmoid growth in black hole accretion disks and jets. We
included resistivity in the three-dimensional general-relativistic
magnetohydrodynamics (GRMHD) code BHAC and present the implementation of an
Implicit-Explicit scheme to treat the stiff resistive source terms of the GRMHD
equations. The algorithm is tested in combination with adaptive mesh refinement
to resolve the resistive scales and a constrained transport method to keep the
magnetic field solenoidal. Several novel methods for primitive variable
recovery, a key part in relativistic magnetohydrodynamics codes, are presented
and compared for accuracy, robustness, and efficiency. We propose a new
inversion strategy that allows for resistive-GRMHD simulations of low
gas-to-magnetic pressure ratio and highly magnetized regimes as applicable for
black hole accretion disks, jets, and neutron star magnetospheres. We apply the
new scheme to study the effect of resistivity on accreting black holes,
accounting for dissipative effects as reconnection.",1907.07197v2
2020-06-23,Thermal interfacial resistance and nanolayer effect on the thermal conductivity of Al2O3-CO2 nanofluid: A Molecular Dynamics approach,"Nanofluids are known to have significantly different thermal properties
relative to the corresponding conventional fluids. Heat transfer at the
solid-fluid interface affects the thermal properties of nanofluids. The current
work helps in understanding the role of two nanoscale phenomena, namely
ordering of fluid layer around the nanoparticle (nanolayer) and thermal
resistance at the interface of solid-fluid in the enhancement of thermal
conductivity of Al2O3 - CO2 nanofluid. In this study, molecular dynamics (MD)
simulations have been used to study the thermal interfacial resistance by
transient non-equilibrium heat technique and nanolayer formed between Al2O3
nanoparticle (np) and surrounded CO2 molecules in the gaseous and supercritical
phase. The nanoparticle diameter (dNP) is varied between 2 and 5 nm to
investigate the size effect on thermal interfacial resistance (TIR) and thermal
conductivity of nanofluid and the results indicate that the TIR for larger
diameters is relatively high in both the phases. The study of the effect of
surface wettability and temperature on TIR reveals that the resistance
decreases with increase in interaction strength and temperature, but is
entirely independent at higher temperatures, in both gaseous and supercritical
nanofluid. A density distribution study of the nanolayer and the monolayer
around the nanoparticle revealed that the latter is more ordered in smaller
diameter with less thermal resistance. However, nanolayer study reveals that
the nanoparticle with bigger diameters are more suitable for the
cooling/heating purpose, as the system with larger diameters has higher thermal
conductivity. Results show that the nanolayer plays a significant role in
determining the effective thermal conductivity of the nanofluid, while the
influence of TIR appears negligible compared to the nanolayer.",2006.12805v2
2022-03-12,Parameterization of hydrodynamic friction in a model for sheared suspensions of rough particles,"We propose a method to parameterize a coarse grained model for the
hydrodynamic friction between nearly touching rough spheres in suspension
flows. The frictional resistance due to surface roughness primarily alters the
sliding and rolling modes of motion of rough particles. Stokesian dynamics
simulations incorporating a near-field pairwise resistance model accounting for
these enhanced frictional modes were employed to compute particle trajectories
in shear flow. In this model, the resistance to sliding and rolling modes of
motion are augmented from a weakly diverging log$(1/h)$ form for smooth spheres
to a strongly diverging $1/h$ form for rough spheres to account for the
additional resistance due to squeezing flows between surface asperities, where
$h$ is the mean surface separation between particles. We determine new bounds
on the relative magnitude of the augmentations to the resistance to different
modes of motion using inequality constraints reflecting the positive
definiteness of the Stokes resistance tensor for a pair of rough particles.
Using the simulations of a particle pair in a shear flow, a simple model for
angular rotation rate of the pair centerline is computed as a function of its
orientation in the shear flow and the free parameters of the hydrodynamic
resistance model: the friction coupling strength, $\alpha$, and friction
coupling range, $h_0$. Values of $\alpha$ and $h_0$ for real-world rough
particles can then be inferred by matching the pair rotation rate in the model
to experimental observations when a dilute rough particle suspension is
subjected to a linear shear flow. The same model is used to calculate the
hydrodynamic contribution to the high frequency viscosity of rough particle
suspensions. For different $\alpha$ and $h_0$, we observe that the viscosity
diverges differently depending on $h_0$.",2203.06300v1
2003-11-17,Collapse of Magnetized Singular Isothermal Toroids: I. Non-Rotating Case,"We study numerically the collapse of non-rotating, self-gravitating,
magnetized, singular isothermal toroids characterized by sound speed, $a$, and
level of magnetic to thermal support, $H_0$. In qualitative agreement with
previous treatments by Galli & Shu and other workers, we find that the
infalling material is deflected by the field lines towards the equatorial
plane, creating a high-density, flattened structure -- a pseudodisk. The
pseudodisk contracts dynamically in the radial direction, dragging the field
lines threading it into a highly pinched configuration that resembles a split
monopole. The oppositely directed field lines across the midplane and the large
implied stresses may play a role in how magnetic flux is lost in the actual
situation in the presence of finite resistivity or ambipolar diffusion. The
infall rate into the central regions is given to 5% uncertainty by the formula,
$\dot M = (1+H_0)a^3/G$, where $G$ is the universal gravitational constant,
anticipated by semi-analytical studies of the self-similar gravitational
collapses of the singular isothermal sphere and isopedically magnetized disks.
The introduction of finite initial rotation results in a complex interplay
between pseudodisk and true (Keplerian) disk formation that is examined in a
companion paper.",0311376v1
2006-02-01,From Protoplanets to Protolife: The Emergence and Maintenance of Life,"Despite great advances in our understanding of the formation of the Solar
System, the evolution of the Earth, and the chemical basis for life, we are not
much closer than the ancient Greeks to an answer of whether life has arisen and
persisted on any other planet. The origin of life as a planetary phenomenon
will probably resist successful explanation as long as we lack an early record
of its evolution and additional examples. It is widely thought that the
geologic record shows that life emerged quickly after the end of prolonged
bombardment of the Earth. New data and simulations contradict that view and
suggest that more than half a billion years of unrecorded Earth history may
have elapsed between the origin of life and LUCA. The impact-driven exchange of
material between the inner planets may have allowed earliest life to be more
cosmopolitan. Indeed, terrestrial life may not have originated on the Earth, or
even on any planet. Smaller bodies, e.g. the parent bodies of primitive
meteorites, offer alternative environments for the origin of life in our Solar
System. The search for past or present life on Mars is an obvious path to
greater enlightenment. The subsurface oceans of some icy satellites of the
outer planets represent the best locales to search for an independent origin of
life in the Solar System because of the high dynamical barriers for transfer,
intense radiation at their surfaces, and thick ice crusts. The ``ultimate''
answer to the abundance of life in the Cosmos will remain the domain of
speculation until we develop observatories capable of detecting habitable
planets - and signs of life - around the nearest million or so stars.",0602008v1
2000-05-10,"Magnetic, thermal, and transport properties on single crystals of antiferromagnetic Kondo-lattice Ce2PdSi3","Magnetization, heat capacity, electrical resistivity, thermoelectric power,
and Hall effect have been investigated on single-crystalline Ce_2PdSi_3. This
compound is shown to order antiferromagnetically below N'eel temperature (T_N)
\~3 K. The Sommerfeld coefficient far below T_N is found to be about 110 mJ/K^2
mol Ce, which indicates the heavy-fermion character of this compound. The
transport and magnetic properties exhibit large anisotropy with an interplay
between crystalline-electric-field (CEF) and Kondo effects. The sign of
thermoelectric power is opposite for different directions at high temperatures
and the ordinary Hall coefficient is anisotropic with opposite sign for
different geometries, indicating the anisotropic Fermi surface. The CEF
analysis from the temperature dependence of magnetic susceptibility suggests
that the ground state is |+/-1/2>. The first and the second excited CEF doublet
levels are found to be located at about 30 and 130 K, respectively. The Kondo
temperature is estimated to be the same order as T_N, indicating the presence
of a delicate competition between the Kondo effect and magnetic order.",0005164v1
2001-06-03,Transport processes in metal-insulator granular layers,"The non-equilibrium tunnel transport processes are considered in a square
lattice of metallic nanogranules embedded into insulating host. Based on a
simple model with three possible charging states (+,-, or 0) of a granule and
three kinetic processes (creation or recombination of a +- pair, and charge
transfer) between neighbor granules, the mean-field kinetic theory is
developed, which takes into account the interplay between the charging energy
and temperature and between the applied electric field and Coulomb fields by
non-compensated charge density. The resulting charge and current distributions
are found to depend essentially on the particular conditions in a granular
layer, namely, in a free area (FA) or in contact areas (CA) under macroscopic
metallic contacts. Thus, a steady state dc transport is only compatible with
zero charge density and ohmic resistivity within FA, but charge accumulation
and non-ohmic behavior are necessary for conduction over CA. The approximate
analytic solutions are obtained for characteristic regimes (low or high charge
density) of such conduction. Also non- stationary processes are considered,
displaying a peculiar combination of two strongly different relaxation times.
The comparison is done with the available transport data on similar
experimental systems.",0106034v2
2002-03-06,Concentration Dependence of Superconductivity and Order-Disorder Transition in the Hexagonal Rubidium Tungsten Bronze RbxWO3. Interfacial and bulk properties,"We revisited the problem of the stability of the superconducting state in
RbxWO3 and identified the main causes of the contradictory data previously
published. We have shown that the ordering of the Rb vacancies in the
nonstoichiometric compounds have a major detrimental effect on the
superconducting temperature Tc.The order-disorder transition is first order
only near x = 0.25, where it cannot be quenched effectively and Tc is reduced
below 1K. We found that the high Tc's which were sometimes deduced from
resistivity measurements, and attributed to compounds with .25 < x < .30, are
to be ascribed to interfacial superconductivity which generates spectacular
non-linear effects. We also clarified the effect of acid etching and set more
precisely the low-rubidium-content boundary of the hexagonal phase.This work
makes clear that Tc would increase continuously (from 2 K to 5.5 K) as we
approach this boundary (x = 0.20), if no ordering would take place - as its is
approximately the case in CsxWO3. This behaviour is reminiscent of the
tetragonal tungsten bronze NaxWO3 and asks the same question : what mechanism
is responsible for this large increase of Tc despite the considerable
associated reduction of the electron density of state ? By reviewing the other
available data on these bronzes we conclude that the theoretical models which
are able to answer this question are probably those where the instability of
the lattice plays a major role and, particularly, the model which call upon
local structural excitations (LSE), associated with the missing alkali atoms.",0203120v1
2003-04-19,Transport properties of granular metals at low temperatures,"We investigate transport in a granular metallic system at large tunneling
conductance between the grains, $g_T\gg 1$. We show that at low temperatures,
$T\leq g_T\delta $, where $\delta$ is the single mean energy level spacing in a
grain, the coherent electron motion at large distances dominates the physics,
contrary to the high temperature ($T>g_T\delta $) behavior where conductivity
is controlled by the scales of the order of the grain size. The conductivity of
one and two dimensional granular metals, in the low temperature regime, decays
with decreasing temperature in the same manner as that in homogeneous
disordered metals, indicating thus an insulating behavior. However, even in
this temperature regime the granular structure remains important and there is
an additional contribution to conductivity coming from short distances. Due to
this contribution the metal-insulator transition in three dimensions occurs at
the value of tunnel conductance $g_T^C=(1/6\pi)\ln (E_C/\delta)$, where $E_C$
is the charging energy of an isolated grain, and not at the generally expected
$g_T^C\propto 1$. Corrections to the density of states of granular metals due
to the electron-electron interaction are calculated. Our results compare
favorably with the logarithmic dependence of resistivity in the high-$T_c$
cuprate superconductors indicating that these materials may have a granular
structure.",0304448v1
2004-03-31,Correlation of microwave surface impedance of MgB_2 thin film with material parameters and a temperature niche for microwave applications,"Two issues related to the microwave surface impedance Z_s of MgB_2 thin film
are discussed in this Letter, both being significant for potential microwave
applications. At first, a correlation between Zs and Alpha = Xi/l was found,
where Xi is the coherence length, and l is the mean free path. The surface
resistance Rs decreases with Alpha at moderate and large values of Alpha and
saturates when Alpha approaches one. The values of the penetration depth at
zero temperature Lamda(0) for different films could be well fitted by Lamda_L
(1+Alpha)^(1/2), yielding a London penetration depth Lamda_L of 33.6 nm. The
second issue is to find a temperature niche for possible microwave
applications. Between 10K and 15K, our best MgB_2 films possess the lowest Rs
values compared with other superconductors such as NbN, Nb3Sn and the
high-temperature superconductor YBCO.",0403755v1
2004-10-21,Effect of nanometer-sized B powder on phase formation of polycrystalline MgB2,"The size effect of the raw B powder on the MgB2 phase formation has been
studied by the technique of in-situ high temperature resistivity (HT-rT)
measurement. The onset temperature, Tonset, and the completion temperature,
TPF, of the phase formation are determined directly during the ongoing thermal
process. These two temperatures, Tonset and TPF of the sample synthesized using
nanometer B and Mg powders (NanoB-MgB2) are 440 C and 490 C, respectively, the
same as those of the sample using micrometer B and nanometer Mg powders
(MicroB-MgB2). This indicates that the phase formation temperature of MgB2 do
not depend on the B powder size. On the other hand, the upper limit of the
sintering temperature, TN, above which the sample loses superconductivity, is
below 750 C for NanoB-MgB2, much lower than 980 C for the MgB2 prepared using
micron-sized B powder and millimeter sized Mg powder (DM-MgB2). In comparison
with the sample directly sintered at 650 C < TN, an interesting, irreversible
transformation in the crystal structure of the MgB2 phase was observed with the
sample going through the stages of initial sintering at 750 C, then
re-sintering at 650 C in an Mg-rich environment after the processes of
regrinding and pressing. Possible explanation of the observed properties is
discussed.",0410533v1
2005-03-18,Aharonov-Bohm electron interferometer in the integer quantum Hall regime,"We report experiments on a quantum electron interferometer fabricated from
high mobility, low density GaAs/AlGaAs heterostructure material. In this
device, a nearly circular electron island is defined by four front gates
deposited in etched trenches. The island is separated from the 2D electron bulk
by two nearly open constrictions. In the quantum Hall regime, two
counterpropagating edge channels are coupled by tunneling in the constrictions,
thus forming a closed electron interference path.For several fixed front gate
voltages, we observe periodic Aharonov-Bohm interference oscillations in
four-terminal resistance as a function of the enclosed flux. The oscillation
period DeltaB gives the area of the interference path S via quantization
condition S=h/eDeltaB. We experimentally determine the dependence of S on the
front gate voltage, and find that the Aharonov-Bohm quantization condition does
not require significant corrections due to the confining potential. These
results can be interpreted as a constant integrated compressibility of the
island with respect to the front gates. We also analyze experimental results
using two classical electrostatics models: one modeling the 2D electron density
due to depletion from an etch trench, and another modeling the gate voltage
dependence of the electron density profile in the island.",0503456v2
2006-09-05,Electrical and Thermal Transport in Metallic Single-Wall Carbon Nanotubes on Insulating Substrates,"We analyze transport in metallic single-wall carbon nanotubes (SWNTs) on
insulating substrates over the bias range up to electrical breakdown in air. To
account for Joule self-heating, a temperature-dependent Landauer model for
electrical transport is coupled with the heat conduction equation along the
nanotube. The electrical breakdown voltage of SWNTs in air is found to scale
linearly with their length, approximately as 5 V/um; we use this to deduce a
thermal conductance between SWNT and substrate g ~ 0.17 +/- 0.03 W/K/m per tube
length, which appears limited by the SWNT-substrate interface rather than the
thermal properties of the substrate itself. We examine the phonon scattering
mechanisms limiting electron transport, and find the strong temperature
dependence of the optical phonon absorption rate to have a remarkable influence
on the electrical resistance of micron-length nanotubes. Further analysis
reveals that unlike in typical metals, electrons are responsible for less than
15% of the total thermal conductivity of metallic nanotubes around room
temperature, and this contribution decreases at high bias or higher
temperatures. For interconnect applications of metallic SWNTs, significant
self-heating may be avoided if power densities are limited below 5 uW/um, or if
the SWNT-surrounding thermal interface is optimized.",0609075v2
2009-09-14,Progress in the development of a S RETGEM-based detector for an early forest fire warning system,"In this paper we present a prototype of a Strip Resistive Thick GEM
photosensitive gaseous detector filled with Ne and ethylferrocene vapours at a
total pressure of 1 atm for an early forest fire detection system. Tests show
that it is one hundred times more sensitive than the best commercial
ultraviolet flame detectors and therefore, it is able to reliably detect a
flame of 1.5x1.5x1.5 m3 at a distance of about 1km. An additional and unique
feature of this detector is its imaging capability, which in combination with
other techniques, may significantly reduce false fire alarms when operating in
an automatic mode.
  Preliminary results conducted with air filled photosensitive gaseous
detectors are also presented. The approach main advantages include both the
simplicity of manufacturing and affordability of construction materials such as
plastics and glues specifically reducing detector production cost. The
sensitivity of these air filled detectors at certain conditions may be as high
as those filled with Ne and EF. Long term test results of such sealed detectors
indicate a significant progress in this direction.
  We believe that our detectors utilized in addition to other flame and smoke
sensors will exceptionally increase the sensitivity of forest fire detection
systems. Our future efforts will be focused on attempts to commercialize such
detectors utilizing our aforementioned findings.",0909.2480v1
2009-09-28,Hall effect in superconducting Fe(Se0.5Te0.5) thin films,"The Hall effect is investigated for eight superconducting Fe(Se_0.5_Te_0.5_)
thin films grown on MgO and LaSrAlO_4_ substrates with different transition
temperatures (T_c_). The normal Hall coefficients (R_H_) have positive values
with magnitude of 1 - 1.5 x 10^-3^ cm^3^/C at room temperature for the all
samples. With decreasing temperature, we find two characteristic types of
behavior in R_H_(T) depending on T_c_. For thin films with lower T_c_
(typically T_c_ < 5 K), R_H_ start decreasing approximately below T = 250 K
toward a negative side, some of which shows sign reversal at T = 50 - 60 K, but
turns positive toward T = 0 K. On the other hand for the films with higher T_c_
(typically T_c_ > 9 K), R_ H_ leaves almost unchanged down to T = 100 K, and
then starts decreasing toward a negative side. Around the temperatures when
R_H_ changes its sign from positive to negative, obvious nonlinearity is
observed in the field-dependence of Hall resistance as to keep the low-field
R_H_ positive while the high-field R_H_ negative. Thus the electronic state
just above T_c_ is characterized by n_e_ (electron density) > n_h_ (hole
density) with keeping \mu_e_ < \mu_h_. These results suggest the dominance of
electron density to the hole density is an essential factor for the occurence
of superconductivity in Fe-chalcogenide superconductors.",0909.4985v3
2010-11-14,Tunneling anisotropic magnetoresistance of NiFe/IrMn/MgO/Pt stack: An antiferromagnet based spin-valve,"Spin-valve is a microelectronic device in which high and low resistance
states are realized by utilizing both charge and spin of carriers. Spin-valve
structures used in modern hard drive read-heads and magnetic random access
memories comprise two ferromagnetic (FM) electrodes whose relative
magnetization orientations can be switched between parallel and antiparallel
configurations, yielding the desired giant or tunneling magnetoresistance
effect. In this paper we demonstrate >100$% spin-valve-like signal in a
NiFe/IrMn/MgO/Pt stack with an antiferromagnet (AFM) on one side and a
non-magnetic metal on the other side of the tunnel barrier. FM moments in NiFe
are reversed by external fields <50mT and the exchange-spring effect of NiFe on
IrMn induces rotation of AFM moments in IrMn which is detected by the measured
tunneling anisotropic magnetoresistance (TAMR). Our work demonstrates a
spintronic element whose transport characteristics are governed by an AFM. It
demonstrates that sensitivity to low magnetic fields can be combined with
large, spin-orbit coupling induced magneto-transport anisotropy using a single
magnetic electrode. The AFM-TAMR provides means to study magnetic
characteristics of AFM films by an electronic transport measurement.",1011.3188v1
2011-09-09,Study of ageing in Al-Mg-Si alloys by positron annihilation spectroscopy,"In many common Al-Mg-Si alloys (6000 series) intermediate storage at or near
'room temperature' after solutionising leads to pronounced changes of the
precipitation kinetics during the ensuing artificial ageing step at \approx
180{\deg}C. This is not only an annoyance in production, but also a challenge
for researchers. We studied the kinetics of natural 'room temperature' ageing
(NA) in Al-Mg-Si alloys by means of various different techniques, namely
electrical resistivity and hardness measurement, thermoanalysis and positron
lifetime and Doppler broadening (DB) spectroscopy to identify the stages in
which the negative effect of NA on artificial ageing might appear. Positron
lifetime measurements were carried out in a fast mode, allowing us to measure
average lifetimes in below 1 minute. DB measurements were carried out with a
single detector and a 68Ge positron source by employing high momentum analysis.
The various measurements show that NA is much more complex than anticipated and
at least four different stages can be distinguished. The nature of these stages
cannot be given with certainty, but a possible sequence includes vacancy
diffusion to individual solute atoms, nucleation of solute clusters, Mg
agglomeration to clusters and coarsening or ordering of such clusters. Positron
lifetime measurements after more complex ageing treatments involving storage at
0{\deg}C, 20{\deg}C and 180{\deg}C have also been carried out and help to
understand the mechanisms involved.",1109.2019v2
2012-11-20,Enhanced superconducting performance of melt quenched Bi2Sr2CaCu2O8 (Bi-2212) superconductor,"We scrutinize the enhanced superconducting performance of melt quench Bismuth
based Bi2Sr2CaCu2O8 (Bi-2212) superconductor. The superconducting properties of
melt quenched Bi-2212 (Bi2212-MQ) sample are compared with non-melted Bi2212-NM
and Bi1.4Pb0.6Sr2Ca2Cu3O10 (Bi-2223). Crystal structure and morphology of the
samples are studied using X-ray diffraction and Scanning Electron Microscopy
(SEM) techniques. The high field (14T) magneto-transport and DC/AC magnetic
susceptibility techniques are extensively used to study the superconducting
properties of the investigated samples. The superconducting critical
temperature (Tc) and upper critical field (Hc2) as well as thermally activated
flux flow (TAFF) activation energy are estimated from the magneto-resistive
[R(T)H] measurements. Both DC magnetization and amplitude dependent AC
susceptibility measurements are used to determine the field and temperature
dependence of critical current density (Jc) for studied samples. On the other
hand, the frequency dependent AC susceptibility is used for estimating flux
creep activation energy. It is found that melt quenching significantly enhances
the superconducting properties of granular Bi-2212 superconductor. The results
are interpreted in terms of better alignment and inter-connectivity of the
grains along with reduction of grain boundaries for Bi2212-MQ sample.",1211.4681v2
2013-07-27,Strain-induced effects on the magnetic and electronic properties of epitaxial Fe$_{1-x}$Co$_{x}$Si thin films,"We have investigated the Co-doping dependence of the structural, transport,
and magnetic properties of \epsilon-FeCoSi epilayers grown by molecular beam
epitaxy on silicon (111) substrates. Low energy electron diffraction, atomic
force microscopy, X-ray diffraction, and high resolution transmission electron
microscopy studies have confirmed the growth of phase-pure, defect-free
\epsilon-FeCoSi epitaxial films with a surface roughness of ~1 nm. These
epilayers are strained due to lattice mismatch with the substrate, deforming
the cubic B20 lattice so that it becomes rhombohedral. The temperature
dependence of the resistivity changes as the Co concentration is increased,
being semiconducting-like for low $x$ and metallic-like for x \gtrsim 0.3. The
films exhibit the positive linear magnetoresistance that is characteristic of
\epsilon-FeCoSi below their magnetic ordering temperatures $T_\mathrm{ord}$, as
well as the huge anomalous Hall effect of order several \mu\Omega cm. The
ordering temperatures are higher than those observed in bulk, up to 77 K for x
= 0.4. The saturation magnetic moment of the films varies as a function of Co
doping, with a contribution of ~1 \mu_{B}/ Co atom for x \lesssim 0.25. When
taken in combination with the carrier density derived from the ordinary Hall
effect, this signifies a highly spin-polarised electron gas in the low x,
semiconducting regime.",1307.7301v1
2013-08-05,"Enhancement of superconductivity near the pressure-induced semiconductor-metal transition in BiS2-based compounds LnO(0.5)F(0.5)BiS2 (Ln = La, Ce, Pr, Nd)","Measurements of electrical resistivity were performed between 3 and 300 K at
various pressures up to 2.8 GPa on the BiS2-based superconductors
LnO0.5F0.5BiS2 (Ln = Pr, Nd). At lower pressures, PrO0.5F0.5BiS2 and
NdO0.5F0.5BiS2 exhibit superconductivity with critical temperatures Tc of 3.5
and3.9 K, respectively. As pressure is increased, both compounds undergo a
transition at a pressure Pt from a low Tc superconducting phase to a high Tc
superconducting phase in which Tc reaches maximum values of 7.6 and 6.4 K for
PrO0.5F0.5BiS2 and NdO0.5F0.5BiS2, respectively. The pressure-induced
transition is characterized by a rapid increase in Tc within a small range in
pressure of ~0.3 GPa for both compounds. In the normal state of PrO0.5F0.5BiS2,
the transition pressure Pt correlates with the pressure where the suppression
of semiconducting behaviour saturates. In the normal state of NdO0.5F0.5BiS2,
Pt is coincident with a semiconductor-metal transition. This behaviour is
similar to the results recently reported for the LnO0.5F0.5BiS2 (Ln = La, Ce)
compounds. We observe that Pt and the size of the jump in Tc between the two
superconducting phases both scale with the lanthanide element in LnO0.5F0.5BiS2
(Ln = La, Ce, Pr, Nd).",1308.1072v3
2014-02-13,"Colloidal pattern replication through contact photolithography operated in a ""Talbot-Fabry-Perot"" regime","We detail on a continuous colloidal pattern replication by using contact
photolithography. Chrome on quartz masks are fabricated using colloidal
nanosphere lithography and subsequently used as photolithography stamps.
Hexagonal pattern arrangements with different dimensions (980, 620 and 480 nm,
using colloidal particles with respective diameters) have been studied. When
the mask and the imaged resist layer were in intimate contact, a high fidelity
pattern replica was obtained after photolithography exposure and processing. In
turn, the presence of an air-gap in between has been found to affect the
projected image onto the photoresist layer, strongly dependent on the mask
feature size and air-gap height. Pattern replication, inversion and
hybridization was achieved for 980 nm-period mask; no hybridization for the 620
nm; and only pattern replication for the 480 nm. These results are interpreted
in the framework of a ""Talbot-Fabry-Perot"" effect. Numerical simulations
corroborate with the experimental findings providing insight into the involved
processes highlighting the important parameters affecting the exposure pattern.
The approach allows complex subwavelength patterning and is relevant for a 3D
layer-by-layer printing.",1402.3117v1
2014-02-28,Exploring of point-contact spectra of Ba1-xNaxFe2As2 in the normal and superconducting state,"We present study of derivatives of current-voltage I(V) characteristics of
point-contacts (PCs) based on Ba{1-x}Na{x}Fe2As2 (x=0.25) in the normal and
superconducting state. The detailed analysis of dV/dI(V) data (also given in
Appendix A) shows that the thermal regime, when temperature increases with a
voltage at a rate of about 1.8 K/mV, is realized in the investigated PCs at
least at high biases V above the superconducting (SC) gap \Delta. In this case,
specific resistivity \rho (T) in PC core is responsible for a peculiar dV/dI(V)
behavior, while a pronounced asymmetry of dV/dI(V) is caused by large value of
thermopower in this material. A reproducible zero-bias minima detected on
dV/dI(V) at low biases in the range \pm(6--9)mV well below the SC critical
temperature T_c could be connected with the manifestation of the SC gap \Delta.
Evaluation of these Andreev-reflection-like structures on dV/dI(V) points out
to the preferred value of 2\Delta/kT_c \approx 6. The expected second gap
features on dV/dI(V) are hard to resolve unambiguously, likely due to impurity
scattering, spatial inhomogeneity and transition to the mentioned thermal
regime as the bias further increases. Suggestions are made how to separate
spectroscopic features in dV/dI(V) from those caused by the thermal regime.",1402.7233v1
2014-03-16,Electrical Contacts to Three-Dimensional Arrays of Carbon Nanotubes,"We use numerical simulations to investigate the properties of metal contacts
to three-dimensional arrays of carbon nanotubes (CNTs). For undoped arrays
top-contacted with high or low work function metals, electrostatic screening is
very strong, resulting in a small Schottky barrier for current injection in the
top layer and large Schottky barriers for current injection in the deeper
layers. As a consequence, the majority of the current flows through the top
layer of the array. Our simulations show that doping of the CNT array can
alleviate this problem, even without direct contact to each tube in the array;
however, we find that the charge transfer length is unusually long in arrays
and increases with the number of CNT layers under the contact. We also show
that a bottom gate can modulate the contact resistance, but only very weakly.
These results are important for the design of electronic and optoelectronic
devices based on CNT arrays, because they suggest that increasing the thickness
of the array does little to improve the device performance unless the film is
strongly doped at the contacts and the contact is long, or unless each tube in
the array is directly contacted by the metal.",1403.3942v1
2014-06-05,Giant overlap between the magnetic and superconducting phases of CeAu2Si2 under pressure,"High pressure provides a powerful means for exploring unconventional
superconductivity which appears mostly on the border of magnetism. Here we
report the discovery of pressure-induced heavy fermion superconductivity up to
2.5 K in the antiferromanget CeAu2Si2 (TN ~ 10 K). Remarkably, the magnetic and
superconducting phases are found to overlap across an unprecedentedly wide
pressure interval from 11.8 to 22.3 GPa. Moreover, both the bulk Tc and TM are
strongly enhanced when increasing the pressure from 16.7 to 20.2 GPa. Tc
reaches a maximum at a pressure slightly below pc ~ 22.5 GPa, at which magnetic
order disappears. Furthermore, the scaling behavior of the resistivity provides
evidence for a continuous delocalization of the Ce 4f-electrons associated with
a critical endpoint lying just above pc. We show that the maximum Tc of
CeAu2Si2 actually occurs at almost the same unit-cell volume as that of
CeCu2Si2 and CeCu2Ge2, and when the Kondo and crystal field splitting energies
becomes comparable. Dynamical mean-filed theory calculations suggest that the
peculiar behavior in pressurized CeAu2Si2 might be related to its Ce 4f-orbital
occupancy. Our results not only provide a unique example of the interplay
between superconductivity and magnetism, but also underline the role of orbital
physics in understanding Ce-based heavy fermion systems.",1406.1438v2
2014-09-10,Proximity effects at the interface of a superconductor and a topological insulator in NbN - Bi_2Se_3 thin film bilayers,"In a search for a simple proximity system of a topological insulator and a
superconductor for studying the role of surface versus bulk effects by gating,
we report here on a first step toward this goal, namely the choice of such a
system and its characterization. We chose to work with thin film bilayers of
grainy 5 nm thick NbN films as the superconductor, overlayed with 20 nm thick
topological layer of $\rm Bi_2Se_3$ and compare the transport results to those
obtained on a 5 nm thick reference NbN film on the same wafer. Bilayers with
ex-situ and in-situ prepared $\rm NbN-Bi_2Se_3$ interfaces were studied and two
kinds of proximity effects were found. At high temperatures just below the
superconducting transition, all bilayers showed a conventional proximity effect
where the topological $\rm Bi_2Se_3$ suppresses the onset or mid-transition
$T_c$ of the superconducting NbN films by about 1 K. At low temperatures, a
cross-over of the resistance versus temperature curves of the bilayer and
reference NbN film occurs, where the bilayers show enhancement of $T_c(R=0)$,
$I_c$ (the supercurrent) and the Andreev conductance, as compared to the bare
NbN films. This indicates that superconductivity is induced in the $\rm
Bi_2Se_3$ layer at the interface region in between the NbN grains. Thus an
inverse proximity effect in the topological material is demonstrated.",1409.2975v1
2015-02-15,"Contact doping, Klein tunneling, and asymmetry of shot noise in suspended graphene","The inherent asymmetry of the electric transport in graphene is attributed to
Klein tunneling across barriers defined by $\textit{pn}$-interfaces between
positively and negatively charged regions. By combining conductance and shot
noise experiments we determine the main characteristics of the tunneling
barrier (height and slope) in a high-quality suspended sample with Au/Cr/Au
contacts. We observe an asymmetric resistance $R_{\textrm{odd}}=100-70$
$\Omega$ across the Dirac point of the suspended graphene at carrier density
$|n_{\rm G}|=0.3-4 \cdot 10^{11}$ cm$^{-2}$, while the Fano factor displays a
non-monotonic asymmetry in the range $F_{\textrm{odd}} \sim 0.03 - 0.1$. Our
findings agree with analytical calculations based on the Dirac equation with a
trapezoidal barrier. Comparison between the model and the data yields the
barrier height for tunneling, an estimate of the thickness of the
$\textit{pn}$-interface $d < 20$ nm, and the contact region doping
corresponding to a Fermi level offset of $\sim - 18$ meV. The strength of
pinning of the Fermi level under the metallic contact is characterized in terms
of the contact capacitance $C_c=19 \times 10^{-6}$ F/cm$^2$. Additionally, we
show that the gate voltage corresponding to the Dirac point is given by the
work function difference between the backgate material and graphene.",1502.04330v2
2015-10-06,Spin Hall magnetoresistance as a probe for surface magnetization in Pt/CoFe$_2$O$_4$ bilayers,"We study the spin Hall magnetoresistance (SMR) in Pt grown $\textit{in situ}$
on CoFe$_2$O$_4$ (CFO) ferrimagnetic insulating (FMI) films. A careful analysis
of the angle-dependent and field-dependent longitudinal magnetoresistance
indicates that the SMR contains a contribution that does not follow the bulk
magnetization of CFO but it is a fingerprint of the complex magnetism at the
surface of the CFO layer, thus signaling SMR as a tool for mapping surface
magnetization. A systematic study of the SMR for different temperatures and CFO
thicknesses gives us information impossible to obtain with any standard
magnetometry technique. On one hand, surface magnetization behaves
independently of the CFO thickness and does not saturate up to high fields,
evidencing that the surface has its own anisotropy. On the other hand,
characteristic zero-field magnetization steps are not present at the surface
while they are relevant in the bulk, strongly suggesting that antiphase
boundaries are the responsible of such intriguing features. In addition, a
contribution from ordinary magnetoresistance of Pt is identified, which is only
distinguishable due to the low resistivity of the $\textit{in-situ}$ grown Pt.",1510.01449v2
2015-11-25,Quantum oscillations of the topological surface states in low carrier concentration crystals of Bi$_{2-x}$Sb$_{x}$Te$_{3-y}$Se$_{y}$,"We report a high-field magnetotransport study on selected low-carrier
crystals of the topological insulator Bi$_{2-x}$Sb${_x}$Te$_{3-y}$Se$_{y}$.
Monochromatic Shubnikov - de Haas (SdH) oscillations are observed at 4.2~K and
their two-dimensional nature is confirmed by tilting the magnetic field with
respect to the sample surface. With help of Lifshitz-Kosevich theory, important
transport parameters of the surface states are obtained, including the carrier
density, cyclotron mass and mobility. For $(x,y)=(0.50,1.3)$ the Landau level
plot is analyzed in terms of a model based on a topological surface state in
the presence of a non-ideal linear dispersion relation and a Zeeman term with
$g_s = 70$ or $-54$. Input parameters were taken from the electronic dispersion
relation measured directly by angle resolved photoemission spectroscopy on
crystals from the same batch. The Hall resistivity of the same crystal
(thickness of 40~$\mu$m) is analyzed in a two-band model, from which we
conclude that the ratio of the surface conductance to the total conductance
amounts to 32~\%.",1511.08186v1
2016-05-06,Antiferromagnetism in trigonal SrMn2As2 and CaMn2As2 single crystals,"Crystallographic, electronic transport, thermal and magnetic properties are
reported for SrMn2As2 and CaMn2As2 single crystals grown using Sn flux.
Rietveld refinements of powder x-ray diffraction data show that the two
compounds are isostructural and crystallize in the trigonal CaAl2Si2-type
structure (space group P-3m1), in agreement with the literature. Electrical
resistivity rho versus temperature T measurements demonstrate insulating ground
states for both compounds with activation energies of 85 meV for SrMn2As2 and
61 meV for CaMn2As2. In a local-moment picture, the Mn^{+2} 3d^5 ions are
expected to have high-spin S = 5/2 with spectroscopic splitting factor g = 2.
Magnetic susceptibility chi and heat capacity measurements versus T reveal
antiferromagnetic (AFM) transitions at TN = 120(2) K and 62(3) K for SrMn2As2
and CaMn2As2, respectively. The anisotropic chi(T < TN) data indicate that the
hexagonal c axis is the hard axis and hence that the ordered Mn moments are
aligned in the ab plane. The chi(T) for both compounds and Cp(T) data for
SrMn2As2 show strong dynamic short-range AFM correlations from TN up to at
least 900 K, likely associated with quasi-two-dimensional connectivity of
strong AFM exchange interactions between the Mn spins within the corrugated
honeycomb Mn layers parallel to the ab plane.",1605.02052v2
2016-06-13,Observation of Spatial Charge and Spin Correlations in the 2D Fermi-Hubbard Model,"Strong electron correlations lie at the origin of transformative phenomena
such as colossal magneto-resistance and high-temperature superconductivity.
Already near room temperature, doped copper oxide materials display remarkable
features such as a pseudo-gap and a ""strange metal"" phase with unusual
transport properties. The essence of this physics is believed to be captured by
the Fermi-Hubbard model of repulsively interacting, itinerant fermions on a
lattice. Here we report on the site-resolved observation of charge and spin
correlations in the two-dimensional (2D) Fermi-Hubbard model realized with
ultracold atoms. Antiferromagnetic spin correlations are maximal at
half-filling and weaken monotonically upon doping. Correlations between singly
charged sites are negative at large doping, revealing the Pauli and correlation
hole\textemdash a suppressed probability of finding two fermions near each
other. However, as the doping is reduced below a critical value, correlations
between such local magnetic moments become positive, signaling strong bunching
of doublons and holes. Excellent agreement with numerical linked-cluster
expansion (NLCE) and determinantal quantum Monte Carlo (DQMC) calculations is
found. Positive non-local moment correlations directly imply potential energy
fluctuations due to doublon-hole pairs, which should play an important role for
transport in the Fermi-Hubbard model.",1606.04089v1
2016-06-24,Epitaxial graphene homogeneity and quantum Hall effect in millimeter-scale devices,"Quantized magnetotransport is observed in 5.6 x 5.6 mm^2 epitaxial graphene
devices, grown using highly constrained sublimation on the Si-face of SiC(0001)
at high temperature (1900 {\deg}C). The precise quantized Hall resistance of
Rxy = h/2e^2 is maintained up to record level of critical current Ixx = 0.72 mA
at T = 3.1 K and 9 T in a device where Raman microscopy reveals low and
homogeneous strain. Adsorption-induced molecular doping in a second device
reduced the carrier concentration close to the Dirac point(n ~ 1E10 (1/cm^2)),
where mobility of 43700 cm^2/Vs is measured over an area of 10 mm^2. Atomic
force, confocal optical, and Raman microscopies are used to characterize the
large-scale devices, and reveal improved SiC terrace topography and the
structure of the graphene layer. Our results show that the structural
uniformity of epitaxial graphene produced by face-to-graphite processing
contributes to millimeter-scale transport homogeneity, and will prove useful
for scientific and commercial applications.",1606.07720v1
2016-07-11,The electronic thermal conductivity of graphene,"Graphene, as a semimetal with the largest known thermal conductivity, is an
ideal system to study the interplay between electronic and lattice
contributions to thermal transport. While the total electrical and thermal
conductivity have been extensively investigated, a detailed first-principles
study of its electronic thermal conductivity is still missing. Here, we first
characterize the electron-phonon intrinsic contribution to the electronic
thermal resistivity of graphene as a function of doping using electronic and
phonon dispersions and electron-phonon couplings calculated from first
principles at the level of density-functional theory and many-body perturbation
theory (GW). Then, we include extrinsic electron-impurity scattering using
low-temperature experimental estimates. Under these conditions, we find that
the in-plane electronic thermal conductivity of doped graphene is ~300 W/mK at
room temperature, independently of doping. This result is much larger than
expected, and comparable to the total thermal conductivity of typical metals,
contributing ~10 % to the total thermal conductivity of bulk graphene. Notably,
in samples whose physical or domain sizes are of the order of few micrometers
or smaller, the relative contribution coming from the electronic thermal
conductivity is more important than in the bulk limit, since lattice thermal
conductivity is much more sensitive to sample or grain size at these scales.
Last, when electron-impurity scattering effects are included, we find that the
electronic thermal conductivity is reduced by 30 to 70 %. We also find that the
Wiedemann-Franz law is broadly satisfied at low and high temperatures, but with
the largest deviations of 20-50 % around room temperature.",1607.03037v1
2016-07-26,Interface-driven topological Hall effect in SrRuO$_3$-SrIrO$_3$ bilayer,"Electron transport coupled with magnetism has attracted attention over the
years as exemplified in anomalous Hall effect due to a Berry phase in momentum
space. Another type of unconventional Hall effect -- topological Hall effect,
originating from the real-space Berry phase, has recently become of great
importance in the context of magnetic skyrmions. We have observed topological
Hall effect in bilayers consisting of ferromagnetic SrRuO$_3$ and paramagnetic
SrIrO$_3$ over a wide region of both temperature and magnetic field. The
topological term rapidly decreases with the thickness of SrRuO$_3$, ending up
with the complete disappearance at 7 unit cells of SrRuO$_3$. Combined with
model calculation, we concluded that the topological Hall effect is driven by
interface Dzyaloshinskii-Moriya interaction, which is caused by both the broken
inversion symmetry and the strong spin-orbit coupling of SrIrO$_3$. Such
interaction is expected to realize the N\'{e}el-type magnetic skyrmion, of
which size is estimated to be $\sim$10 nm from the magnitude of topological
Hall resistivity. The results established that the high-quality oxide interface
enables us to tune the chirality of the system; this can be a step towards the
future topological electronics.",1607.07536v1
2016-08-25,Kelvin probe characterization of buried graphitic microchannels in single-crystal diamond,"In this work, we present an investigation by Kelvin Probe Microscopy (KPM) of
buried graphitic microchannels fabricated in single-crystal diamond by direct
MeV ion microbeam writing. Metal deposition of variable-thickness masks was
adopted to implant channels with emerging endpoints and high temperature
annealing was performed in order to induce the graphitization of the
highly-damaged buried region. When an electrical current was flowing through
the biased buried channel, the structure was clearly evidenced by KPM maps of
the electrical potential of the surface region overlying the channel at
increasing distances from the grounded electrode. The KPM profiling shows
regions of opposite contrast located at different distances from the endpoints
of the channel. This effect is attributed to the different electrical
conduction properties of the surface and of the buried graphitic layer. The
model adopted to interpret these KPM maps and profiles proved to be suitable
for the electronic characterization of buried conductive channels, providing a
non-invasive method to measure the local resistivity with a micrometer
resolution. The results demonstrate the potential of the technique as a
powerful diagnostic tool to monitor the functionality of all-carbon
graphite/diamond devices to be fabricated by MeV ion beam lithography.",1608.07126v1
2016-08-30,"Epitaxial thin films of pyrochlore iridate Bi_{2+x}Ir_{2-y}O_{7-delta}: structure, defects and transport properties","While pyrochlore iridate thin films are theoretically predicted to possess a
variety of emergent topological properties, experimental verification of these
predictions can be obstructed by the challenge in thin film growth. Here we
report on the pulsed laser deposition and characterization of thin films of a
representative pyrochlore compound Bi2Ir2O7. The films were epitaxially grown
on yttria-stabilized zirconia substrates and have lattice constants that are a
few percent larger than that of the bulk single crystals. The film composition
shows a strong dependence on the oxygen partial pressure.
Density-functional-theory calculations indicate the existence of Bi_Ir antisite
defects, qualitatively consistent with the high Bi: Ir ratio found in the
films. Both Ir and Bi have oxidation states that are lower than their nominal
values, suggesting the existence of oxygen deficiency. The iridate thin films
show a variety of intriguing transport characteristics, including multiple
charge carriers, logarithmic dependence of resistance on temperature,
antilocalization corrections to conductance due to spin-orbit interactions, and
linear positive magnetoresistance.",1608.08608v3
2017-10-04,"Formation, stratification, and mixing of the cores of Earth and Venus","Earth possesses a persistent, internally-generated magnetic field, whereas no
trace of a dynamo has been detected on Venus, at present or in the past,
although a high surface temperature and recent resurfacing events may have
removed paleomagnetic evidence. Whether or not a terrestrial body can sustain
an internally generated magnetic field by convection inside its metallic fluid
core is determined in part by its initial thermodynamic state and its
compositional structure, both of which are in turn set by the processes of
accretion and differentiation. Here we show that the cores of Earth- and
Venus-like planets should grow with stable compositional stratification unless
disturbed by late energetic impacts. They do so because higher abundances of
light elements are incorporated into the liquid metal that sinks to form the
core as the temperatures and pressures of metal-silicate equilibration increase
during accretion. We model this process and determine that this establishes a
stable stratification that resists convection and inhibits the onset of a
geodynamo. However, if a late energetic impact occurs, it could mechanically
stir the core creating a single homogenous region within which a long-lasting
geodynamo would operate. While Earth's accretion has been punctuated by a late
giant impact with likely enough energy to mix the core (e.g. the impact that
formed the Moon), we hypothesize that the accretion of Venus is characterized
by the absence of such energetic giant impacts and the preservation of its
primordial stratifications.",1710.01770v1
2018-03-30,Thermodynamics of Ion Separation by Electrosorption,"We present a simple, top-down approach for the calculation of minimum energy
consumption of electrosorptive ion separation using variational form of the
(Gibbs) free energy. We focus and expand on the case of electrostatic
capacitive deionization (CDI), and the theoretical framework is independent of
details of the double-layer charge distribution and is applicable to any
thermodynamically consistent model, such as the Gouy-Chapman-Stern (GCS) and
modified Donnan (mD) models. We demonstrate that, under certain assumptions,
the minimum required electric work energy is indeed equivalent to the free
energy of separation. Using the theory, we define the thermodynamic efficiency
of CDI. We explore the thermodynamic efficiency of current experimental CDI
systems and show that these are currently very low, less than 1% for most
existing systems. We applied this knowledge and constructed and operated a CDI
cell to show that judicious selection of the materials, geometry, and process
parameters can be used to achieve a 9% thermodynamic efficiency (4.6 kT energy
per removed ion). This relatively high value is, to our knowledge, by far the
highest thermodynamic efficiency ever demonstrated for CDI. We hypothesize that
efficiency can be further improved by further reduction of CDI cell series
resistances and optimization of operational parameters.",1803.11532v1
2018-05-22,Non-saturating large magnetoresistance in semimetals,"The rapidly expanding class of quantum materials known as {\emph{topological
semimetals}} (TSM) display unique transport properties, including a striking
dependence of resistivity on applied magnetic field, that are of great interest
for both scientific and technological reasons. However, experimental signatures
that can identify or discern the dominant mechanism and connect to available
theories are scarce. Here we present the magnetic susceptibility ($\chi$), the
tangent of the Hall angle ($\tan\theta_H$) along with magnetoresistance in four
different non-magnetic semimetals with high mobilities, NbP, TaP, NbSb$_2$ and
TaSb$_2$, all of which exhibit non-saturating large MR. We find that the
distinctly different temperature dependences, $\chi(T)$ and the values of
$\tan\theta_H$ in phosphides and antimonates serve as empirical criteria to
sort the MR from different origins: NbP and TaP being uncompensated semimetals
with linear dispersion, in which the non-saturating magnetoresistance arises
due to guiding center motion, while NbSb$_2$ and TaSb$_2$ being {\it
compensated} semimetals, with a magnetoresistance emerging from nearly perfect
charge compensation of two quadratic bands. Our results illustrate how a
combination of magnetotransport and susceptibility measurements may be used to
categorize the increasingly ubiquitous non-saturating large magnetoresistance
in TSMs.",1805.08797v2
2018-09-09,Efficient thermionic operation and phonon isolation by a semiconductor-superconductor junction,"Control of heat flux at small length scales is crucial for numerous
solid-state devices and systems. In addition to the thermal management of
information and communication devices the mastering of heat transfer channels
down to the nanoscale also enable, e.g., new memory concepts, high sensitivity
detectors and sensors, energy harvesters and compact solid-state refrigerators.
Electronic coolers and thermal detectors for electromagnetic radiation,
especially, rely on the maximization of electro-thermal response and blockade
of phonon transport. In this work, we propose and demonstrate that efficient
electro-thermal operation and phonon transfer blocking can be achieved in a
single solid-state thermionic junction. Our experimental demonstration relies
on suspended semiconductor-superconductor junctions where the electro-thermal
response arises from the superconducting energy gap, and the phonon blocking
naturally results from the transmission bottleneck at the junction. We suspend
different size degenerately doped silicon chips (up to macroscopic scale)
directly from the junctions and cool these by biasing the junctions. The
electronic cooling operation characteristics are accompanied by measurement and
analysis of the thermal resistance components in the structures indicating the
operation principle of phonon blocking in the junctions.",1809.02994v1
2018-11-02,Conformal printing of graphene for single and multi-layered devices on to arbitrarily shaped 3D surfaces,"Printing has drawn a lot of attention as a means of low per-unit cost and
high throughput patterning of graphene inks for scaled-up thin-form factor
device manufacturing. However, traditional printing processes require a flat
surface and are incapable of achieving patterning on to 3D objects. Here, we
present a conformal printing method to achieve functional graphene-based
patterns on to arbitrarily-shaped surfaces. Using experimental design, we
formulate a water-insoluble graphene ink with optimum conductivity. We then
print single and multi-layered electrically functional structures on to a
sacrificial layer using conventional screen printing. The print is then floated
on water, allowing the dissolution of the sacrificial layer, while retaining
the functional patterns. The single and multilayer patterns can then be
directly transferred on to arbitrarily-shaped 3D objects without requiring any
post deposition processing. Using this technique, we demonstrate conformal
printing of single and multilayer functional devices that include joule
heaters, resistive strain sensors and proximity sensors on hard, flexible and
soft substrates, such as glass, latex, thermoplastics, textiles, and even
candies and marshmallows. Our simple strategy offers great promises to add new
device and sensing functionalities to previously inert 3D surfaces.",1811.01073v2
2018-11-12,Homogeneous Large-area Quasi-freestanding Monolayer and Bilayer Graphene on SiC,"In this study, we first show that the argon flow during epitaxial graphene
growth is an important parameter to control the quality of the buffer and the
graphene layer. Atomic force microscopy (AFM) and low-energy electron
diffraction (LEED) measurements reveal that the decomposition of the SiC
substrate strongly depends on the Ar mass flow rate while pressure and
temperature are kept constant. Our data are interpreted by a model based on the
competition of the SiC decomposition rate, controlled by the Ar flow, with a
uniform graphene buffer layer formation under the equilibrium process at the
SiC surface. The proper choice of a set of growth parameters allows the growth
of defect-free, ultra-smooth and coherent graphene-free buffer layer and
bilayer-free monolayer graphene sheets which can be transformed into large-area
high-quality quasi-freestanding monolayer and bilayer graphene (QFMLG and
QFBLG) by hydrogen intercalation. AFM, scanning tunneling microscopy (STM),
Raman spectroscopy and electronic transport measurements underline the
excellent homogeneity of the resulting quasi-freestanding layers. Electronic
transport measurements in four-point probe configuration reveal a homogeneous
low resistance anisotropy on both {\mu}m- and mm scales.",1811.04998v1
2018-11-14,Giant anisotropy in superconducting single crystals of CsCa$_2$Fe$_4$As$_4$F$_2$,"CsCa$_2$Fe$_4$As$_4$F$_2$ is a newly discovered iron-based superconductor
with $T_\mathrm{c}\sim$ 30 K containing double Fe$_2$As$_2$ layers that are
separated by insulating Ca$_2$F$_2$ spacer layers. Here we report the transport
and magnetization measurements on CsCa$_2$Fe$_4$As$_4$F$_2$ single crystals
grown for the first time using the self flux of CsAs. We observed a huge
resistivity anisotropy $\rho_c(T)/\rho_{ab}(T)$, which increases with
decreasing temperature, from 750 at 300 K to 3150 at 32 K. The $\rho_c(T)$ data
exhibit a non-metallic behavior above $\sim$140 K, suggesting an incoherent
electronic state at high temperatures due to the dimension crossover. The
superconducting onset transition temperature in $\rho_{ab}$ is 0.7 K higher
than that in $\rho_c$, suggesting two-dimensional (2D) superconducting
fluctuations. The lower and upper critical fields also show an exceptional
anisotropy among iron-based superconductors. The $H_{c1}^\bot(T)$ data are well
fitted using the model with two $s$-wave-like superconducting gaps,
$\Delta_1(0)=6.75$ meV and $\Delta_2(0)=2.32$ meV. The inter-plane coherence
length $\xi_c(0)$ is $3.6$ \AA, remarkably smaller than the distance between
conducting layers (8.6 \AA), consolidating the 2D nature in the title material.",1811.05706v1
2019-02-01,Light Enhanced Blue Energy Generation using MoS$_2$ Nanopores,"Blue energy relies on the chemical potential difference generated between
solutions of high and low ionic strength and would provide a sun-and-wind
independent energy source at estuaries around the world. Converting this
osmotic energy through reverse-electrodialysis relies on ion-selective
membranes. A novel generation of these membranes is based on atomically thin
MoS$_2$ membranes to decrease the resistance to current flow to increase power
output. By modulating the surface charge by light we are able to raise the ion
selectivity of the membrane by a factor of 5 while staying at a neutral pH.
Furthermore, we find that the behavior of small nanopores is dominated by
surface conductance. We introduce a formalism based on the Dukhin number to
quantify these effects in the case of a concentration gradient system. As a
consequence, the charges created by light illumination provoke two important
changes. Increased surface charge at the pore rim enhances the ion selectivity
and therefore larger osmotic voltage (dominating in small pores), while the
increased surface charge of the overall membrane enhances the surface
conductance and therefore the osmotic current (dominating in larger pores). The
combination of these effects might be able to efficiently boost the energy
generation with arrays of nanopores with varying pore sizes.",1902.00410v1
2019-02-25,Synaptic Learning and Memory Functions Achieved in Self-rectifying BFO Memristor under Extreme Environmental Temperature,"Memristors have been intensively studied in recent years as promising
building blocks for next-generation non-volatile memory, artificial neural
networks and brain-inspired computing systems. Even though the environment
adaptability of memristor has been required in many application fields, it has
been rarely reported due to the underlying mechanism could become invalid
especially at an elevated temperature. Here, we focus on achieving synaptic
learning and memory functions in BiFeO3 memristor in a wide range of
temperature. We have proved the ferroelectricity of BFO films at a record-high
temperature of 500 {\deg}C by piezoresponse force microscopy (PFM) measurement.
Due to the robust ferroelectricity of BFO thin film, an analog-like resistance
switching behavior has been clearly found in a wide range of temperature, which
is attributed to the reversal of ferroelectric polarization. Various synaptic
functions including long-term potentiation (LTP), depression (LTD), consecutive
potentiation/depression (P/D) and spike-timing dependent plasticity (STDP) have
been realized from -170 to 300 {\deg}C, illustrating their potential for
electronic applications even under extreme environmental temperature.",1902.09081v1
2019-07-03,Probing defect states in few-layer MoS$_{2}$ by conductance fluctuation spectroscopy,"Despite the concerted effort of several research groups, a detailed
experimental account of defect dynamics in high-quality single- and few-layer
transition metal dichalcogenides remain elusive. In this paper we report an
experimental study of the temperature dependence of conductance and
conductance-fluctuations on several few-layer MoS$_{2}$ exfoliated on hexagonal
boron nitride and covered by a capping layer of high-$\kappa$ dielectric
HfO$_{2}$. The presence of the high-$\kappa$ dielectric made the device
extremely stable against environmental degradation as well as resistant to
changes in device characteristics upon repeated thermal cycling enabling us to
obtain reproducible data on the same device over a time-scale of more than one
year. Our device architecture helped bring down the conductance fluctuations of
the MoS$_2$ channel by orders of magnitude compared to previous reports. The
extremely low noise levels in our devices made in possible to detect the
generation-recombination noise arising from charge fluctuation between the
sulphur-vacancy levels in the band gap and energy-levels at the conductance
band-edge. Our work establishes conduction fluctuation spectroscopy as a viable
route to quantitatively probe in-gap defect levels in low-dimensional
semiconductors.",1907.01830v1
2020-04-11,High-field depinned phase and planar Hall effect in skyrmion-host Gd$_2$PdSi$_3$,"For the skyrmion-hosting intermetallic Gd$_2$PdSi$_3$ with centrosymmetric
hexagonal lattice and triangular net of rare earth sites, we report a thorough
investigation of the magnetic phase diagram. Our work reveals a new magnetic
phase with isotropic value of the critical field for all orientations, where
the magnetic ordering vector $\mathbf{q}$ is depinned from its preferred
directions in the basal plane. This is in contrast to the highly anisotropic
behavior of the low field phases, such as the skyrmion lattice (SkL), which are
easily destroyed by in-plane magnetic field. The bulk nature of the SkL and of
other magnetic phases was evidenced by specific-heat measurements. Resistivity
anisotropy, likely originating from partial gapping of the density of states
along $\mathbf{q}$ in this RKKY magnet, is picked up via the planar Hall effect
(PHE). The PHE confirms the single-$\mathbf{q}$ nature of the magnetic order
when the field is in the hexagonal plane, and allows to detect the preferred
directions of $\mathbf{q}$. For field aligned perpendicular to the basal plane,
several scenarios for the depinned phase (DP), such as tilted conical order,
are discussed on the basis of the data.",2004.05385v1
2020-09-11,Electronic nematic states tuned by isoelectronic substitution in bulk FeSe1-xSx,"Isoelectronic substitution is an ideal tuning parameter to alter electronic
states and correlations in iron-based superconductors. As this substitution
takes place outside the conducting Fe planes, the electronic behaviour is less
affected by the impurity scattering experimentally and relevant key electronic
parameters can be accessed. In this short review, I present the experimental
progress made in understanding the electronic behaviour of the nematic
electronic superconductors, FeSe1-xSx. A direct signature of the nematic
electronic state is in-plane anisotropic distortion of the Fermi surface
triggered by orbital ordering effects and electronic interactions that result
in multi-band shifts detected by ARPES. Upon sulphur substitution, the
electronic correlations and the Fermi velocities decrease in the tetragonal
phase. Quantum oscillations are observed for the whole series in ultra-high
magnetic fields and show a complex spectra due to the presence of many small
orbits. Effective masses associated to the largest orbit display non-divergent
behaviour at the nematic end point (x~0.175(5)), as opposed to critical
spin-fluctuations in other iron pnictides. Magnetotransport behaviour has a
strong deviation from the Fermi liquid behaviour and linear T resistivity is
detected at low temperatures inside the nematic phase, where scattering from
low energy spin-fluctuations are likely to be present. The superconductivity is
not enhanced in FeSe1-xSx and there are no divergent electronic correlations at
the nematic end point. These manifestations indicate a strong coupling with the
lattice in FeSe1-xSx and a pairing mechanism likely promoted by spin
fluctuations.",2009.05523v1
2020-09-23,Superconducting fluctuations in overdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$,"Fluctuating superconductivity - vestigial Cooper pairing in the resistive
state of a material - is usually associated with low dimensionality, strong
disorder or low carrier density. Here, we report single particle spectroscopic,
thermodynamic and magnetic evidence for persistent superconducting fluctuations
in heavily hole-doped cuprate superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$
($T_c$ = 66~K) despite the high carrier density. With a sign-problem free
quantum Monte Carlo calculation, we show how a partially flat band at ($\pi$,0)
can help enhance superconducting phase fluctuations. Finally, we discuss the
implications of an anisotropic band structure on the phase-coherence-limited
superconductivity in overdoped cuprates and other superconductors.",2009.10932v2
2020-09-29,Structural Phase Dependent Giant Interfacial Spin Transparency in W/CoFeB Thin Film Heterostructure,"Pure spin current has transfigured the energy-efficient spintronic devices
and it has the salient characteristic of transport of the spin angular
momentum. Spin pumping is a potent method to generate pure spin current and for
its increased efficiency high effective spin-mixing conductance (Geff) and
interfacial spin transparency (T) are essential. Here, a giant T is reported in
Sub/W(t)/Co20Fe60B20(d)/SiO2(2 nm) heterostructures in \beta-tungsten (\beta-W)
phase by employing all-optical time-resolved magneto-optical Kerr effect
technique. From the variation of Gilbert damping with W and CoFeB thicknesses,
the spin diffusion length of W and spin-mixing conductances are extracted.
Subsequently, T is derived as 0.81 \pm 0.03 for the \beta-W/CoFeB interface. A
sharp variation of Geff and T with W thickness is observed in consonance with
the thickness-dependent structural phase transition and resistivity of W. The
spin memory loss and two-magnon scattering effects are found to have negligible
contributions to damping modulation as opposed to spin pumping effect which is
reconfirmed from the invariance of damping with Cu spacer layer thickness
inserted between W and CoFeB. The observation of giant interfacial spin
transparency and its strong dependence on crystal structures of W will be
important for pure spin current based spin-orbitronic devices.",2009.14143v1
2017-04-20,Accretion powered AGN feedback in the cores of galaxy clusters,"Detection of the copious amount of X-ray emission from the dilute hot plasma
in galaxy clusters suggests that a substantial fraction of the central
intracluster medium (ICM) is cooling radiatively on a time scale much faster
than the Hubble time. Theoretical models predict the cooling rate as high as
about few hundred to few thousand solar mass per year, which would be then made
available for the formation of new stars in the core of these clusters.
However, systematic studies of the cores of such clusters failed to detect the
expected reservoirs of cooled gas. Thus, the gas in the cores of galaxy
clusters is losing substantial amount of energy in the form of X-rays but is
not cooling. This in turn point towards the famous cooling flow paradox and
hence demands some intermittent heating to balance the cooling over such a long
period. Several sources have been suggested to counteract on the cooling of the
ICM, however, the AGN feedback appeared to be the most promising and enough
energetic source to resist cooling of the ICM in the cores of such clusters. In
this presentation I will provide a brief overview on the feedback processes
that are involved in the cores of the galaxy clusters with an emphasis on the
AGN feedback and its observable signatures.",1704.06047v1
2017-04-23,Steep-slope Hysteresis-free Negative Capacitance MoS2 Transistors,"The so-called Boltzmann Tyranny defines the fundamental thermionic limit of
the subthreshold slope (SS) of a metal-oxide-semiconductor field-effect
transistor (MOSFET) at 60 mV/dec at room temperature and, therefore, precludes
the lowering of the supply voltage and the overall power consumption. Adding a
ferroelectric negative capacitor to the gate stack of a MOSFET may offer a
promising solution to bypassing this fundamental barrier. Meanwhile,
two-dimensional (2D) semiconductors, such as atomically thin transition metal
dichalcogenides (TMDs) due to their low dielectric constant, and ease of
integration in a junctionless transistor topology, offer enhanced electrostatic
control of the channel. Here, we combine these two advantages and demonstrate
for the first time a molybdenum disulfide (MoS2) 2D steep slope transistor with
a ferroelectric hafnium zirconium oxide layer (HZO) in the gate dielectric
stack. This device exhibits excellent performance in both on- and off-states,
with maximum drain current of 510 {\mu}A/{\mu}m, sub-thermionic subthreshold
slope and is essentially hysteresis-free. Negative differential resistance
(NDR) was observed at room temperature in the MoS2 negative capacitance
field-effect-transistors (NC-FETs) as the result of negative capacitance due to
the negative drain-induced-barrier-lowering (DIBL). High on-current induced
self-heating effect was also observed and studied.",1704.06865v2
2017-08-04,The cuprate phase diagram and the influence of nanoscale inhomogeneities,"The phase diagram associated with the high Tc superconductors is complicated
by an array of different ground states. The parent material represents an
antiferromagnetic insulator but with doping superconductivity becomes possible
with transition temperatures previously thought unattainable. The underdoped
region of the phase diagram is dominated by the so-called pseudogap phenomena
whereby in the normal state the system mimics superconductivity in its spectra
response but does not show the complete loss of resistivity associated with the
superconducting state. An understanding of this regime presents one of the
great challenges for the field. In the present study we revisit the structure
of the phase diagram as determined in photoemission studies. By careful
analysis of the role of nanoscale inhomogeneities in the overdoped region we
are able to more carefully separate out the gaps due to the pseudogap phenomena
from the gaps due to the superconducting transition. Within a mean field
description we are thus able to link the magnitude of the gap directly to the
Heisenberg exchange interaction term, $J\sum{s_i \cdot s_j}$, contained in the
$t-J$ model. This approach provides a clear indication that the pseudogap is
that associated with spin singlet formation.",1708.01558v2
2019-03-12,Precision Analysis of Evolved Stars,"Evolved stars dominate galactic spectra, enrich the galactic medium, expand
to change their planetary systems, eject winds of a complex nature, produce
spectacular nebulae and illuminate them, and transfer material between binary
companions. While doing this, they fill the HR diagram with diagnostic loops
that write the story of late stellar evolution. Evolved stars sometimes release
unfathomable amounts of energy in neutrinos, light, kinetic flow, and
gravitational waves. During these late-life times, stars evolve complexly, with
expansion, convection, mixing, pulsation, mass loss. Some processes have
virtually no spatial symmetries, and are poorly addressed with low-resolution
measurements and analysis. Even a ""simple"" question as how to model mass loss
resists solution. However, new methods offer increasingly diagnostic tools.
Astrometry reveals populations and groupings. Pulsations/oscillations support
study of stellar interiors. Optical/radio interferometry enable 2-3d imagery of
atmospheres and shells. Bright stars with rich molecular spectra and velocity
fields are a ripe opportunity for imaging with high spatial and spectral
resolution, giving insight into the physics and modeling of later stellar
evolution.",1903.05109v1
2019-04-14,Superconducting Praseodymium Superhydrides,"Superhydrides have complex hydrogenic sublattices and are important
prototypes for studying metallic hydrogen and high-temperature superconductors.
Encouraged by the results on LaH10, in consideration of the differences between
La and Pr, Pr-H system is especially worth studying because of the magnetism
and valence-band f-electrons in element Pr. Here we successfully synthesized
praseodymium superhydrides (PrH9) in laser-heated diamond anvil cells.
Synchrotron X-ray diffraction (XRD) analysis demonstrated the presence of
previously predicted F43m-PrH9 and unexpected P63/mmc-PrH9 phases. Moreover,
Fm3m-PrH3, P4/nmm-PrH(3-{\delta}) and Fm3m-PrH(1+x) were found below 52 GPa.
F43m-PrH9 and P63/mmc-PrH9 were stable above 100 GPa in experiment.
Experimental studies of electrical resistance in the PrH9 sample showed the
emergence of superconducting transition (Tc) below 9K and a dependent Tc on
applied magnetic field. Theoretical calculations indicate that magnetic order
and electron-phonon interaction coexist in a very close range of pressures in
the PrH9 sample which may contribute to its low superconducting temperature Tc.
Our results highlight the intimate connections among hydrogenic sublattices,
density of states, magnetism and superconductivity in Pr-based superhydrides.",1904.06643v2
2019-08-06,Hump-like structure in Hall signal from SrRuO$_3$ ultra-thin films without inhomogeneous anomalous Hall effect,"A controversy arose over the interpretation of the recently observed hump
features in Hall resistivity $\rho_{xy}$ from ultra-thin SrRuO$_3$ (SRO) film;
it was initially interpreted to be due to topological Hall effect but was later
proposed to be from existence of regions with different anomalous Hall effect
(AHE). In order to settle down the issue, we performed Hall effect as well as
magneto-optic Kerr-effect measurements on 4 unit cell SRO films grown on
SrTiO$_3$ (001) substrates. Clear hump features are observed in the measured
$\rho_{xy}$, whereas neither hump feature nor double hysteresis loop is seen in
the Kerr rotation which should be proportional to the magnetization. In
addition, magnetization measurement by superconducting quantum interference
device shows no sign of multiple coercive fields. These results show that
inhomogeneous AHE alone cannot explain the observed hump behavior in
$\rho_{xy}$ data from our SRO ultra-thin films. We found that emergence of the
hump structure in $\rho_{xy}$ is closely related to the growth condition, high
quality films having clear sign of humps.",1908.02083v1
2019-08-22,High-Pressure Synthesis of Magnetic Neodymium Polyhydrides,"The current search for room-temperature superconductivity is inspired by the
unique properties of the electron-phonon interaction in metal superhydrides.
Encouraged by the recently found highest-$T_C$ superconductor fcc-$LaH_{10}$,
here we discover several superhydrides of another lanthanide - neodymium. We
identify three novel metallic Nd-H phases at pressure range from 85 to 135 GPa:
$I4/mmm$-$NdH_4$, $C2/c$-$NdH_7$, $P6_3/mmc$-$NdH_9$, synthesized by
laser-heating metal samples in NH3BH3 media for in situ generation of hydrogen.
A lower trihydride $Fm\bar{3}m$-$NdH_3$ is found at pressures from 2 to 52 GPa.
$I4/mmm$-$NdH_4$ and $C2/c$-$NdH_7$ are stable from 135 down to 85 GPa, and
$P6_3/mmc$-$NdH_9$ from 110 to 130 GPa. Measurements of the electrical
resistance of NdH9 demonstrate a possible superconducting transition at ~4.5 K
in $P6_3/mmc$-$NdH_9$. Our theoretical calculations predict that all the
neodymium hydrides have antiferromagnetic order at pressures below 150 GPa and
represent one of the first discovered examples of strongly correlated
superhydrides with large exchange spin-splitting in the electron band structure
(> 450 meV). The critical N$\'e$el temperatures for new neodymium hydrides are
estimated using the mean-field approximation as about 4 K ($NdH_4$), 251 K
($NdH_7$) and 136 K ($NdH_9$).",1908.08304v3
2019-12-27,Localized spin waves at low temperatures in a Cobalt Carbide nanocomposite,"We study magnetic, transport and thermal properties of Cobalt carbide
nanocomposite with a mixture of Co2C and Co3C phases in 1:1 ratio, with an
average particle diameter of 40$\pm 15$ nm. We show that the behavior of the
nanocomposite is completely different from that of either Co3C or Co2C. We
observed that with decreasing temperature the saturation magnetization MS(T)
increases, however, below 100 K, there is a steep rise. A detail analysis shows
the increase in MS(T) down to 100 K is explained via the surface spin freezing
model. However, below 100 K the steep increase in MS(T) is explained by a
finite size effect related to a confinement of spin waves within the nano
particles. The measurement of heat capacity shows broad peak at 100 K along
with presence of another anomaly at a lower temperature 43 K(=Tex). Resistance
measurement in the nanocomposite shows metallic behavior at high T with an
unusual anomaly appearing at Tex, which is near the T regime where MS(T) begins
to increase steeply. A measurement of the temperature gradients across the
sample thickness indicates an abrupt change in thermal conductivity at Tex
which suggests a phase transition at Tex. Our results are explained in terms of
a transformation from a magnetically coupled state with a continuous spectrum
of spin waves into a magnetically decoupled state below 100 K with confined
spin waves.",1912.12085v1
2012-06-06,Irreversibility and time relaxation in electrostatic doping of oxide interfaces,"Two-dimensional electron gas (2DEG) confined in quantum wells at insulating
oxide interfaces have attracted much attention as their electronic properties
display a rich physics with various electronics orders such as
superconductivity and magnetism. A particularly exciting features of these
hetero-structures lies in the possibility to control their electronic
properties by electrostatic gating, opening up new opportunities for the
development of oxide based electronics. However, unexplained gating hysteresis
and time relaxation of the 2DEG resistivity have been reported in some bias
range, raising the question of the precise role of the gate voltage. Here we
show that in LaTiO3/SrTiO3 and LaAlO3/SrTiO3 heterostructures, above a filling
threshold, electrons irreversibly escape out of the well. This mechanism, which
is directly responsible for the hysteresis and time relaxation, can be entirely
described by a simple analytical model derived in this letter. Our results
highlight the crucial role of the gate voltage both on the shape and the
filling of the quantum well. They also demonstrate that it is possible to
achieve a low-carrier density regime in a semiconductor limit, whereas the
high-carrier density regime is intrinsically limited.",1206.1198v1
2018-07-04,Doping effects of Cr on the physical properties of BaFe$_{1.9-x}$Ni$_{0.1}$Cr$_{x}$As$_{2}$,"We present a systematic study on the heavily Cr doped iron pnictides
BaFe$_{1.9-x}$Ni$_{0.1}$Cr$_{x}$As$_{2}$ by using elastic neutron scattering,
high-resolution synchrotron X-ray diffraction (XRD), resistivity and Hall
transport measurements. When the Cr concentration increases from $x=$ 0 to 0.8,
neutron diffraction experiments suggest that the collinear antiferromagnetism
persists in the whole doping range, where the N\'{e}el temperature $T_N$
coincides with the tetragonal-to-orthorhombic structural transition temperature
$T_s$, and both of them keeps around 35 K. The magnetic ordered moment, on the
other hand, increases within increasing $x$ until $x=$ 0.5, and then decreases
with further increasing $x$. Detailed refinement of the powder XRD patterns
reveals that the Cr substitutions actually stretch the FeAs$_4$ tetrahedron
along the $c-$axis and lift the arsenic height away Fe-Fe plane. Transport
results indicate that the charge carriers become more localized upon Cr doping,
then changes from electron-type to hole-type around $x=$ 0.5. Our results
suggest that the ordered moment and the ordered temperature of static magnetism
in iron pnictides can be decoupled and tuned separately by chemical doping.",1807.01612v1
2018-07-26,Excitation and coherent control of spin qudit modes with sub-MHz spectral resolution,"Quantum bit or qubit is a two-level system, which builds the foundation for
quantum computation, simulation, communication and sensing. Quantum states of
higher dimension, i.e., qutrits (D = 3) and especially qudits (D = 4 or
higher), offer significant advantages. Particularly, they can provide
noise-resistant quantum cryptography, simplify quantum logic and improve
quantum metrology. Flying and solid-state qudits have been implemented on the
basis of photonic chips and superconducting circuits, respectively. However,
there is still a lack of room-temperature qudits with long coherence time and
high spectral resolution. The silicon vacancy centers in silicon carbide (SiC)
with spin S = 3/2 are quite promising in this respect, but until now they were
treated as a canonical qubit system. Here, we apply a two-frequency protocol to
excite and image multiple qudit modes in a SiC spin ensemble under ambient
conditions. Strikingly, their spectral width is about one order of magnitude
narrower than the inhomogeneous broadening of the corresponding spin resonance.
By applying Ramsey interferometry to these spin qudits, we achieve a spectral
selectivity of 600 kHz and a spectral resolution of 30 kHz. As a practical
consequence, we demonstrate absolute DC magnetometry insensitive to thermal
noise and strain fluctuations.",1807.10383v1
2018-12-16,Anti-fatigue-fracture hydrogels,"The emerging applications of hydrogels in devices and machines require these
soft materials to maintain robustness under cyclic mechanical loads. Whereas
hydrogels have been made tough to resist fracture under a single cycle of
mechanical load, these toughened gels still suffer from fatigue fracture under
multiple cycles of loads. The reported fatigue threshold (i.e., the minimal
fracture energy at which crack propagation occurs under cyclic loads) for
synthetic hydrogels is on the order of 1-100 J/m2, which is primarily
associated with the energy required to fracture a single layer of polymer
chains per unit area. Here, we demonstrate that the controlled introduction of
crystallinity in hydrogels can significantly enhance their fatigue thresholds,
since the process of fracturing crystalline domains for fatigue-crack
propagation requires much higher energy than fracturing a single layer of
polymer chains. The fatigue threshold of polyvinyl alcohol (PVA) with a
crystallinity of 18.9 wt.% in the swollen state can exceed 1,000 J/m2. We
further develop a strategy to enhance the anti-fatigue-fracture properties of
PVA hydrogels, but still maintain their high water contents and low moduli by
patterning highly-crystalline regions in the hydrogels. The current work not
only reveals an anti-fatigue-fracture mechanism in hydrogels but also provides
a practical method to design anti-fatigue-fracture hydrogels for diverse
applications.",1812.06403v1
2019-01-15,Use of Cernox thermometers in AC specific heat measurements under pressure,"We report on the resistance behavior of bare-chip Cernox thermometers under
pressures up to 2 GPa, generated in a piston-cylinder pressure cell. Our
results clearly show that Cernox thermometers, frequently used in
low-temperature experiments due to their high sensitivity, remain highly
sensitive even under applied pressure. We show that these thermometers are
therefore ideally suited for measurements of heat capacity under pressure
utilizing an ac oscillation technique up to at least 150 K. Our Cernox-based
system is very accurate in determining changes of the specific heat as a
function of pressure as demonstrated by measurements of the heat capacity on
three different test cases: (i) the superconducting transition in elemental Pb
(T_{c} = 7.2 K), (ii) the antiferromagnetic transition in the rare-earth
compound GdNiGe3 (T_{N} = 26 K) and (iii) the structural/magnetic transition in
the iron-pnictide BaFe2As2 (T_{s,N} = 130 K). The chosen examples demonstrate
the versatility of our technique for measuring the specific heat under pressure
of various condensed matter systems with very different transition temperatures
as well as amounts of removed entropy.",1901.05089v2
2019-10-07,High electrical conductivity of single metal-organic chains,"Molecular wires are essential components for future nanoscale electronics.
However, the preparation of individual long conductive molecules is still a
challenge. MMX metal-organic polymers are quasi-one-dimensional sequences of
single halide atoms (X) bridging subunits with two metal ions (MM) connected by
organic ligands. They are excellent electrical conductors as bulk macroscopic
crystals and as nanoribbons. However, according to theoretical calculations,
the electrical conductance found in the experiments should be even higher. Here
we demonstrate a novel and simple drop-casting procedure to isolate bundles of
few to single MMX chains. Furthermore, we report an exponential dependence of
the electrical resistance of one or two MMX chains as a function of their
length that does not agree with predictions based on their theoretical band
structure. We attribute this dependence to strong Anderson localization
originated by structural defects. Theoretical modeling confirms that the
current is limited by structural defects, mainly vacancies of iodine atoms,
through which the current is constrained to flow. Nevertheless, measurable
electrical transport along distances beyond 250 nm surpasses that of all other
molecular wires reported so far. This work places in perspective the role of
defects in one-dimensional wires and their importance for molecular
electronics.",1910.02834v1
2020-10-01,Universal limiting transition temperature for the high $T_\mathrm{c}$ superconductors,"Since their discovery three decades ago it has emerged that the physics of
high-$T_\mathrm{c}$ cuprate superconductors is characterised by multiple
temperature scales, and a phenomenology that deviates significantly from the
conventional paradigm of superconductivity. Below the ""pseudogap"" temperature,
$T^*$, a range of experiments indicate a reduction in the density of states.
Lower in temperature, $T_\mathrm{c}$ marks the onset of a bulk zero-resistance
state. Intermediate between these, numerous other temperature boundaries and
cross-overs have been identified, often postulated to be associated with
fluctuations of some kind. However, for the most part there is little consensus
either over their definitions or the physical mechanisms at play. One of these
temperature scales is the Nernst onset temperature, $T_\mathrm{onset}$, below
which thermoelectric phenomena characteristic of superconductivity are
observed. Depending on the material, the difference between $T_\mathrm{onset}$
and $T_\mathrm{c}$ ranges from almost nothing to over 100K. In this paper, we
identify $T_\mathrm{onset}$ from published experimental data according to a
consistent definition; this reveals a remarkable consistency of behaviour
across the whole high-$T_\mathrm{c}$ family, despite the appreciable variations
in other parameters. Our analysis suggests that in the cuprates there is an
inherent limit to $T_\mathrm{c} \sim 135$K. We compare this behaviour with
other strongly-correlated superconductors and propose a unified picture of
superconducting fluctuations close to the Mott state.",2010.00572v1
2020-11-17,Shallow Valence Band of Rutile GeO$_2$ and P-type Doping,"GeO$_2$ has an $\alpha$-quartz-type crystal structure with a very wide
fundamental band gap of 6.6 eV and is a good insulator. Here we find that the
stable rutile-GeO$_2$ polymorph with a 4.6 eV band gap has a surprisingly low
$\sim$6.8 eV ionization potential, as predicted from the band alignment using
first-principles calculations. Because of the short O$-$O distances in the
rutile structure containing cations of small effective ionic radii such as
Ge$^{4+}$, the antibonding interaction between O 2p orbitals raises the valence
band maximum energy level to an extent that hole doping appears feasible.
Experimentally, we report the flux growth of $1.5 \times 1.0 \times 0.8$ mm$^3$
large rutile GeO$_2$ single crystals and confirm the thermal stability for
temperatures up to $1021 \pm 10~^\circ$C. X-ray fluorescence spectroscopy shows
the inclusion of unintentional Mo impurities from the Li$_2$O$-$MoO$_3$ flux,
as well as the solubility of Ga in the r-GeO$_2$ lattice as a prospective
acceptor dopant. The resistance of the Ga- and Mo-codoped r-GeO$_2$ single
crystals is very high at room temperature, but it decreases by 2-3 orders of
magnitude upon heating to 300 $^\circ$C, which is attributed to
thermally-activated p-type conduction.",2011.08928v1
2020-11-25,Evidence for freezing of charge degrees of freedom across a critical point in CeCoIn$_5$,"The presence of a quantum critical point separating two distinct
zero-temperature phases is thought to underlie the `strange' metal state of
many high-temperature superconductors. The nature of this quantum critical
point, as well as a description of the resulting strange metal, are central
open problems in condensed matter physics. In large part, the controversy stems
from the lack of a clear broken symmetry to characterize the critical phase
transition, and this challenge is no clearer than in the example of the
unconventional superconductor CeCoIn$_5$. Through Hall effect and Fermi surface
measurements of CeCoIn$_5$, in comparison to ab initio calculations, we find
evidence for a critical point that connects two Fermi surfaces with different
volumes without apparent symmetry-breaking, indicating the presence of a
transition that involves an abrupt localization of one sector of the charge
degrees of freedom. We present a model for the anomalous electrical Hall
resistivity of this material based on the conductivity of valence charge
fluctuations.",2011.12951v1
2020-12-03,Effect of ageing on the properties of the W-containing IRIS-TiAl alloy,"The effects of ageing at 800 $^\circ$C on the properties of the IRIS alloy
(Ti$_{49.9}$Al$_{48}$W$_2$B$_{0.1}$) are studied. The initial microstructure of
this alloy densified by Spark Plasma Sintering (SPS) is mainly composed of
lamellar colonies which are surrounded by $\gamma$ grains. The evolutions of
the alloy strength and creep resistance resulting from this ageing treatment
are measured by the related mechanical tests. The microstructural changes are
investigated by scanning and transmission electron microscopies and by X-ray
diffraction. The main structural evolutions consist in a shrinkage of the
lamellar areas and in a precipitation of $\beta_0$ phase, which is accompanied
by a moderate segregation of tungsten and a decrease of the $\alpha_2$ lamellar
width. However, these evolutions are relatively limited and the microstructural
stability is found to result mainly from the low diffusivity of tungsten.
Conversely, a moderate effect of this ageing treatment on mechanical
properties, at room and high temperatures, is measured. Such experimental
results are interpreted and discussed in terms of the microstructural
evolutions and of the deformation mechanisms which are activated at different
temperatures under various solicitations.",2012.01760v1
2020-12-03,First order transition in trigonal structure ${\textbf{Ca}}{\textbf{Mn}}_{2}{\textbf{P}}_{2}$,"We report structural and physical properties of the single crystalline
${\mathrm{Ca}}{\mathrm{Mn}}_{2}{\mathrm{P}}_{2}$. The X-ray diffraction(XRD)
results show that ${\mathrm{Ca}}{\mathrm{Mn}}_{2}{\mathrm{P}}_{2}$ adopts the
trigonal ${\mathrm{Ca}}{\mathrm{Al}}_{2}{\mathrm{Si}}_{2}$-type structure.
Temperature dependent electrical resistivity $\rho(T)$ measurements indicate an
insulating ground state for ${\mathrm{Ca}}{\mathrm{Mn}}_{2}{\mathrm{P}}_{2}$
with activation energies of 40 meV and 0.64 meV for two distinct regions,
respectively. Magnetization measurements show no apparent magnetic phase
transition under 400 K. Different from other
${\mathrm{A}}{\mathrm{Mn}}_{2}{\mathrm{Pn}}_{2}$ (A = Ca, Sr, and Ba, and Pn =
P, As, and Sb) compounds with the same structure, heat capacity
$C_{\mathrm{p}}(T)$ and $\rho(T)$ reveal that
${\mathrm{Ca}}{\mathrm{Mn}}_{2}{\mathrm{P}}_{2}$ has a first-order transition
at $T$ = 69.5 K and the transition temperature shifts to high temperature upon
increasing pressure. The emergence of plenty of new Raman modes below the
transition, clearly suggests a change in symmetry accompanying the transition.
The combination of the structural, transport, thermal and magnetic
measurements, points to an unusual origin of the transition.",2012.01863v1
2021-02-10,Electropolishing of single crystal and polycrystalline aluminum to achieve high optical and mechanical surfaces,"Electropolishing has found wide application as the final surface treatment of
metal products in mechanical engineering and instrumentation, medicine and
reflective concentrators for PV cells. It was found that electropolishing (EP)
not only reduces the surface roughness and changes its appearance, but improves
many operational characteristics as well, such as corrosion resistance,
endurance, tensile strength, and many others, and also changes the
physicochemical properties, for example, reflectivity, electromagnetic
permeability and electronic emission of some ferro-magnetic metals. This fact
greatly expands the possibility of using this method in various fields of
science and technology. This work is part of a study, examining electro
polishing for reducing the crystalline defects adjacent to the surface, thus
improving its physical properties, contributing to higher optical efficiency,
when used in PV generation and storage devices. Five compositions were examined
using different temperature and current density parameters. The polished
samples were evaluated using reflectance spectrometry. The solution which was
composed of Phosphoric acid - 85%, Acetic acid - 10%, Nitric acid - 5% was
found to provide the best results. Another result obtained was that reflectance
increased as the current density increased up to 25 A/dm2. Further increasing
the current density resulted in deterioration of the surface and reduced
reflectance. It was shown that careful lapping and polishing followed by
electropolishing using the suggested solution may consist of an adequate
treatment for preparing reflective concentrators for PV cells.",2102.05752v1
2021-04-21,Electrically driven programmable phase-change meta-switch reaching 80% efficiency,"Despite recent advances in active metaoptics, wide dynamic range combined
with high-speed reconfigurable solutions is still elusive. Phase-change
materials (PCMs) offer a compelling platform for metasurface optical elements,
owing to the large index contrast and fast yet stable phase transition
properties. Here, we experimentally demonstrate an in situ electrically-driven
reprogrammable metasurface by harnessing the unique properties of a
phase-change chalcogenide alloy, Ge$_{2}$Sb$_{2}$Te$_{5}$ (GST), in order to
realize fast, non-volatile, reversible, multilevel, and pronounced optical
modulation in the near-infrared spectral range. Co-optimized through a
multiphysics analysis, we integrate an efficient heterostructure resistive
microheater that indirectly heats and transforms the embedded GST film without
compromising the optical performance of the metasurface even after several
reversible phase transitions. A hybrid plasmonic-PCM meta-switch with a record
electrical modulation of the reflectance over eleven-fold (an absolute
reflectance contrast reaching 80%), unprecedented quasi-continuous spectral
tuning over 250 nm, and switching speed that can potentially reach a few kHz is
presented. Our work represents a significant step towards the development of
fully integrable dynamic metasurfaces and their potential for beamforming
applications.",2104.10381v2
2021-07-01,Solid Source Metal-Organic Molecular Beam Epitaxy of Epitaxial RuO2,"A seemingly simple oxide with a rutile structure, RuO2 has been shown to
possess several intriguing properties ranging from strain-stabilized
superconductivity to a strong catalytic activity. Much interest has arisen
surrounding the controlled synthesis of RuO2 films but, unfortunately,
utilizing atomically-controlled deposition techniques like molecular beam
epitaxy (MBE) has been difficult due to the ultra-low vapor pressure and low
oxidation potential of Ru. Here, we demonstrate the growth of epitaxial,
single-crystalline RuO2 films on different substrate orientations using the
novel solid-source metal-organic (MO) MBE. This approach circumvents these
issues by supplying Ru using a pre-oxidized solid metal-organic precursor
containing Ru. High-quality epitaxial RuO2 films with bulk-like
room-temperature resistivity of 55 micro-ohm-cm were obtained at a substrate
temperature as low as 300 C. By combining X-ray diffraction, transmission
electron microscopy, and electrical measurements, we discuss the effect of
substrate temperature, orientation, film thickness, and strain on the structure
and electrical properties of these films. Our results illustrating the use of
novel solid-source MOMBE approach paves the way to the atomic-layer controlled
synthesis of complex oxides of stubborn metals, which are not only difficult to
evaporate but also hard to oxidize.",2107.00193v1
2021-08-02,PID-like active control strategy for electroacoustic resonators to design tunable single-degree-of-freedom sound absorbers,"Sound absorption at low frequencies still remains a challenge in both
scientific research and engineering practice. Natural porous materials are
ineffective in this frequency range, as well as acoustic resonators which
present too narrow bandwidth of absorption, thus requiring alternative
solutions based on active absorption techniques. In the present work, we
propose an active control framework applied on a closed-box loudspeaker to
enable the adjustment of the acoustic impedance at the loudspeaker diaphragm.
More specifically, based on the proportionality between the pressure inside the
enclosure and the axial displacement of the loudspeaker diaphragm at low
frequencies, we demonstrate both analytically and experimentally that a
PID-like feedback control approach allows tuning independently the compliance,
the resistance and the moving mass of the closed-box loudspeaker to implement a
prescribed impedance of a single-degree-of-freedom resonator. By considering
different control combinations to tailor the resonator characteristics, a
perfect absorption (with absorption coefficient equal to 1) is achievable at
the target resonance frequency, while enlarging the effective absorption
bandwidth. Moreover, the proposed feedback control strategy shows an excellent
control accuracy, especially compared to the feedforward-based control formerly
reported in the literature. The mismatches between the performance of
experimental prototype and the model, likely to result from the control time
delay and the inaccuracy in estimating the loudspeaker parameters, can be
compensated directly by tuning the control parameters in the control platform.
The active resonators implemented through the reported control scheme can be
used to build more complex acoustic devices/structures to enable
high-efficiency broadband sound absorption or other types of acoustic phenomena
such as wavefront shaping.",2108.00765v1
2021-10-29,Supercurrent diode effect and magnetochiral anisotropy in few-layer NbSe$_2$,"Nonreciprocal transport refers to charge transfer processes that are
sensitive to the bias polarity. Until recently, nonreciprocal transport was
studied only in dissipative systems, where the nonreciprocal quantity is the
resistance. Recent experiments have, however, demonstrated nonreciprocal
supercurrent leading to the observation of a supercurrent diode effect in
Rashba superconductors, opening the vision of dissipationless electronics. Here
we report on a supercurrent diode effect in NbSe$_2$ constrictions obtained by
patterning NbSe$_2$ flakes with both even and odd layer number. The observed
rectification is driven by valley-Zeeman spin-orbit interaction. We demonstrate
a rectification efficiency as large as 60%, considerably larger than the
efficiency of devices based on Rashba superconductors. In agreement with recent
theory for superconducting transition metal dichalcogenides, we show that the
effect is driven by an out-of-plane magnetic field component. Remarkably, we
find that the effect becomes field-asymmetric in the presence of an additional
in-plane field component transverse to the current direction. Supercurrent
diodes offer a further degree of freedom in designing superconducting quantum
electronics with the high degree of integrability offered by van der Waals
materials.",2110.15752v2
2021-11-28,CoFeVSb: A Promising Candidate for Spin Valve and Thermoelectric Applications,"We report a combined theoretical and experimental study of a novel quaternary
Heusler system CoFeVSb from the view point of room temperature spintronics and
thermoelectric applications. It crystallizes in cubic structure with small
DO$_3$-type disorder. The presence of disorder is confirmed by room temperature
synchrotron X-ray diffraction(XRD) and extended X-ray absorption fine structure
(EXAFS) measurements. Magnetization data reveal high ordering temperature with
a saturation magnetization of 2.2 $\mu_B$/f.u. Resistivity measurements reflect
half-metallic nature. Double hysteresis loop along with asymmetry in the
magnetoresistance(MR) data reveals room temperature spin-valve feature, which
remains stable even at 300 K. Hall measurements show anomalous behavior with
significant contribution from intrinsic Berry phase. This compound also large
room temperature power factor ($\sim0.62$ mWatt/m/K$^{2}$) and ultra low
lattice thermal conductivity ($\sim0.4$ W/m/K), making it a promising candidate
for thermoelectric application. Ab-initio calculations suggest weak
half-metallic behavior and reduced magnetization (in agreement with experiment)
in presence of DO$_3$ disorder. We have also found an energetically competing
ferromagnetic FM)/antiferromagnetic (AFM) interface structure within an
otherwise FM matrix: one of the prerequisites for spin valve behavior.
Coexistence of so many promising features in a single system is rare, and hence
CoFeVSb gives a fertile platform to explore numerous applications in future.",2111.14081v1
2021-12-16,Constrained multi-objective optimization of process design parameters in settings with scarce data: an application to adhesive bonding,"Adhesive joints are increasingly used in industry for a wide variety of
applications because of their favorable characteristics such as high
strength-to-weight ratio, design flexibility, limited stress concentrations,
planar force transfer, good damage tolerance, and fatigue resistance. Finding
the optimal process parameters for an adhesive bonding process is challenging:
the optimization is inherently multi-objective (aiming to maximize break
strength while minimizing cost), constrained (the process should not result in
any visual damage to the materials, and stress tests should not result in
failures that are adhesion-related), and uncertain (testing the same process
parameters several times may lead to different break strengths). Real-life
physical experiments in the lab are expensive to perform. Traditional
evolutionary approaches (such as genetic algorithms) are then ill-suited to
solve the problem, due to the prohibitive amount of experiments required for
evaluation. Although Bayesian optimization-based algorithms are preferred to
solve such expensive problems, few methods consider the optimization of more
than one (noisy) objective and several constraints at the same time. In this
research, we successfully applied specific machine learning techniques
(Gaussian Process Regression) to emulate the objective and constraint functions
based on a limited amount of experimental data. The techniques are embedded in
a Bayesian optimization algorithm, which succeeds in detecting Pareto-optimal
process settings in a highly efficient way (i.e., requiring a limited number of
physical experiments).",2112.08760v3
2022-01-08,Are Heavy Fermion Strange Metals Planckian?,"Strange metal behavior refers to a linear temperature dependence of the
electrical resistivity at temperatures below the Mott-Ioffe-Regel limit. It is
seen in numerous strongly correlated electron systems, from the heavy fermion
compounds, via transition metal oxides and iron pnictides, to magic angle
twisted bi-layer graphene, frequently in connection with unconventional or
""high temperature"" superconductivity. To achieve a unified understanding of
these phenomena across the different materials classes is a central open
problem in condensed matter physics. Tests whether the linear-in-temperature
law might be dictated by Planckian dissipation - scattering with the rate $\sim
k_{\rm B}T/\hbar$, are receiving considerable attention. Here we assess the
situation for strange metal heavy fermion compounds. They allow to probe the
regime of extreme correlation strength, with effective mass or Fermi velocity
renormalizations in excess of three orders of magnitude. Adopting the same
procedure as done in previous studies, i.e., assuming a simple Drude
conductivity with the above scattering rate, we find that for these strongly
renormalized quasiparticles, scattering is much weaker than Planckian, implying
that the linear temperature dependence should be due to other effects. We
discuss implications of this finding and point to directions for further work.",2201.02820v1
2022-03-04,"Character of the ""normal state"" of the nickelate superconductors","The occurrence of superconductivity in proximity to various strongly
correlated phases of matter has drawn extensive focus on their normal state
properties, to develop an understanding of the state from which
superconductivity emerges. The recent finding of superconductivity in layered
nickelates raises similar interests. However, transport measurements of doped
infinite-layer nickelate thin films have been hampered by materials limitations
of these metastable compounds - in particular, a relatively high density of
extended defects. Here, by moving to a substrate
(LaAlO$_{3}$)$_{0.3}$(Sr$_{2}$TaAlO$_{6}$)$_{0.7}$ which better stabilizes the
growth and reduction conditions, we can synthesize the doping series of
Nd$_{1-x}$Sr$_{x}$NiO$_{2}$ essentially free from extended defects. This
enables the first examination of the 'intrinsic' temperature and doping
dependent evolution of the transport properties. The normal state resistivity
exhibits a low-temperature upturn in the underdoped regime, linear behavior
near optimal doping, and quadratic temperature dependence for overdoping. This
is strikingly similar to the copper oxides, despite key distinctions - namely
the absence of an insulating parent compound, multiband electronic structure,
and a Mott-Hubbard orbital alignment rather than the charge-transfer insulator
of the copper oxides. These results suggest an underlying universality in the
emergent electronic properties of both superconducting families.",2203.02580v1
2022-03-22,Prediction of resistance induced by surface complexity in lubricating layers: Application to super-hydrophobic surfaces,"Super Hydrophobic (SH) coatings are widely used to mitigate drag in various
applications. Numerous studies have demonstrated that the beneficial wall-slip
effect produced by these materials disappears in laminar flow regimes. The main
mechanisms considered to be behind the decrease in performance are
Marangoni-induced stresses and air/liquid interface deformation. In the present
study, a new mechanism is proposed to explain the loss of performances of
SH-surfaces in laminar flow regimes. Here we consider the flow of air inside
the plastron and the associated momentum loses induced by roughness elements
with different geometric characteristics. The effects of air motion within the
plastron is coupled to the outer fluid with a homogenised boundary condition
approach. To this end, numerical simulations at the scale of the roughness
element were conducted as a function of the porosity and the tortuosity of the
domain to determine the slip velocity at the air-liquid interface.
  The homogenised boundary condition is then implemented in a theoretical model
for the outer flow to compute drag on SH-spheres at low $Re$ numbers.
Experiments of laminar SH falling spheres indicate that high values of the
tortuosity and low values of porosity lead to a loss of performances when
considering drag reduction. As anticipated, a 3D printed sphere with low
tortuosity and similar porosity demonstrated near-optimal drag reductions. A
comparative study between the predicted values and experiments shows that the
homogenised model is able to accurately predict the drag on SH surfaces for
values of the porosity and tortuosity estimated from microscopy images of the
SH textured surface.",2203.12039v1
2022-04-06,Thermal activation of low-density Ga implanted in Ge,"The nuclear spins of low-density implanted Ga atoms in Ge are interesting
candidates for solid state-based qubits. To date, activation studies of
implanted Ga in Ge have focused on high densities. Here we extend activation
studies into the low-density regime. We use spreading resistance profiling and
secondary ion mass spectrometry to derive electrical activation of Ga ions
implanted into Ge as a function of rapid thermal anneal temperature and implant
density. We show that for our implant conditions the activation is best for
anneal temperatures between 400 and 650 $^\circ$C, with a maximum activation of
64% at the highest fluence. Below 400 $^\circ$C, remaining implant damage
results in defects that act as superfluous carriers, and above 650 $^\circ$C,
surface roughening and loss of Ga ions are observed. The activation increased
monotonically from 10% to 64% as the implant fluence increased from
$6\times10^{10}$ to $6\times10^{12}$ cm$^{-2}$. The results provide thermal
anneal conditions to be used for initial studies of using low-density Ga atoms
in Ge as nuclear spin qubits.",2204.02878v1
2022-05-05,Intrinsic spin Hall torque in a moire Chern magnet,"In spin torque magnetic memories, electrically actuated spin currents are
used to switch a magnetic bit. Typically, these require a multilayer geometry
including both a free ferromagnetic layer and a second layer providing spin
injection. For example, spin may be injected by a nonmagnetic layer exhibiting
a large spin Hall effect, a phenomenon known as spin-orbit torque. Here, we
demonstrate a spin-orbit torque magnetic bit in a single two-dimensional system
with intrinsic magnetism and strong Berry curvature. We study AB-stacked
MoTe2/WSe2, which hosts a magnetic Chern insulator at a carrier density of one
hole per moire superlattice site. We observe hysteretic switching of the
resistivity as a function of applied current. Magnetic imaging using a
superconducting quantum interference device reveals that current switches
correspond to reversals of individual magnetic domains. The real space pattern
of domain reversals aligns precisely with spin accumulation measured near the
high-Berry curvature Hubbard band edges. This suggests that intrinsic spin- or
valley-Hall torques drive the observed current-driven magnetic switching in
both MoTe2/WSe2 and other moire materials. The switching current density of
10^3 Amps per square centimeter is significantly less than reported in other
platforms paving the way for efficient control of magnetic order.",2205.02823v1
2022-06-02,A multi-fidelity approach coupling parameter space reduction and non-intrusive POD with application to structural optimization of passenger ship hulls,"Nowadays, the shipbuilding industry is facing a radical change towards
solutions with a smaller environmental impact. This can be achieved with low
emissions engines, optimized shape designs with lower wave resistance and noise
generation, and by reducing the metal raw materials used during the
manufacturing. This work focuses on the last aspect by presenting a complete
structural optimization pipeline for modern passenger ship hulls which exploits
advanced model order reduction techniques to reduce the dimensionality of both
input parameters and outputs of interest. We introduce a novel approach which
incorporates parameter space reduction through active subspaces into the proper
orthogonal decomposition with interpolation method. This is done in a
multi-fidelity setting. We test the whole framework on a simplified model of a
midship section and on the full model of a passenger ship, controlled by 20 and
16 parameters, respectively. We present a comprehensive error analysis and show
the capabilities and usefulness of the methods especially during the
preliminary design phase, finding new unconsidered designs while handling high
dimensional parameterizations.",2206.01243v3
2022-06-08,Dielectric properties and impedance spectroscopy of NASICON type Na$_3$Zr$_2$Si$_2$PO$_{12}$,"We report the temperature dependent dielectric properties and impedance
spectroscopy investigation of Na$_3$Zr$_2$Si$_2$PO$_{12}$ in the frequency
range of 20 Hz--2 MHz. The Rietveld refinement of x-ray diffraction pattern
confirms the monoclinic phase with C2/c space group. The {\it d.c.} resistivity
behavior shows its strong insulating nature at low temperatures, and follows
Arrhenius law of thermal conduction with an activation energy of 0.68 eV. The
decrease in electric permittivity ($\epsilon_r$) with frequency is explained
based on the space polarization mechanism and its increment with temperature by
thermal activation of charge carriers. The dielectric loss (D=tan$\delta$) peak
follows the Arrhenius law of thermal activation with an energy of 0.25 eV. We
observe an enhancement in {\it a.c.} conductivity with frequency and
temperature due to the decrease in the activation energy, which results in
enhancing the conduction between defect states. Further, we observe an abrupt
increase in the {\it a.c.} conductivity at high frequencies, which is explained
using the universal Jonschers power law. The analysis of {\it a.c.}
conductivity shows two types of conduction mechanisms namely correlated barrier
hopping and non-overlapping small polaron tunnelling in the measured
temperature range. The imaginary part of the electric modulus confirms the
non-Debye type relaxation in the sample. The shifting of the relaxation peak
towards higher frequency side with an increase in temperature ensures its
thermally activated nature. The scaling behavior of the electric modulus shows
similar type of relaxation over the measured temperature range. The combined
analysis of electric modulus and impedance with frequency shows the short-range
mobility of charge carriers.",2206.03668v1
2022-11-18,Synthesis of infinite-layer nickelates and influence of the capping-layer on magnetotransport,"The recent discovery of a zero-resistance state in nickel-based compounds has
generated a re-excitement about the long-standing problem in condensed matter
of high-critical-temperature superconductivity, in light of the analogies
between infinite-layer nickelates and cuprates. However, despite some formal
valence and crystal symmetry analogies, the electronic properties of
infinite-layer nickelates are remarkably original accounting, among other
properties, of a unique Nd5d-Ni3d hybridization. This designates infinite-layer
nickelates as a new class of oxide superconductors which should be considered
on their own. Here we report about Nd1-xSrxNiO2 (x = 0, 0.05 and 0.2) thin
films synthesized with and without a SrTiO3 capping-layer, showing very smooth
and step-terraced surface morphologies. Angle-dependent anisotropic
magnetoresistance measurements performed with a magnetic field rotating
in-plane or out-of-plane with respect to the sample surface, rendered important
information about the magnetic properties of undoped SrTiO3-capped and uncapped
samples. The results point at a key role of the capping-layer in controlling
the magnitude and the anisotropy of the anisotropic magnetoresistance
properties. We discuss this control in terms of a combined effect between the
Nd-Ni hybridization and an intra-atomic exchange coupling between the Nd-4f and
Nd-5d states, the latter essentially contributing to the (magneto)transport.
Further studies foresee the influence of the capping layer on infinite-layer
nickelates with no magnetic rare-earth.",2211.10251v1
2022-12-12,Unconventional localization of electrons inside of a nematic electronic phase,"The magnetotransport behaviour inside the nematic phase of bulk FeSe reveals
unusual multiband effects that cannot be reconciled with a simple two-band
approximation proposed by surface-sensitive spectroscopic probes. In order to
understand the role played by the multiband electronic structure and the degree
of two-dimensionality we have investigated the electronic properties of
exfoliated flakes of FeSe by reducing their thickness. Based on
magnetotransport and Hall resistivity measurements, we assess the mobility
spectrum that suggests an unusual asymmetry between the mobilities of the
electrons and holes with the electron carriers becoming localized inside the
nematic phase. Quantum oscillations in magnetic fields up to 38 T indicate the
presence of a hole-like quasiparticle with a lighter effective mass and a
quantum scattering time three times shorter, as compared with bulk FeSe. The
observed localization of negative charge carriers by reducing dimensionality
can be driven by orbitally-dependent correlation effects, enhanced interband
spin-fluctuations or a Lifshitz-like transition which affect mainly the
electron bands. The electronic localization leads to a fragile two-dimensional
superconductivity in thin flakes of FeSe, in contrast to the two-dimensional
high-Tc induced with electron doping via dosing or using a suitable interface.",2212.06196v1
2023-01-19,Ab initio comparison of spin-transport properties in MgO-spaced ferrimagnetic tunnel junctions based on Mn$_3$Ga and Mn$_3$Al,"We report on first-principles spin-polarised quantum transport calculations
(from NEGF+DFT) in MgO-spaced magnetic tunnel junctions (MTJs) based on two
different Mn-based Heusler ferrimagnetic metals, namely Mn$_3$Al and Mn$_3$Ga
in their tetragonal DO$_{22}$ phase. The former is a fully compensated
half-metallic ferrimagnet, while the latter is a low-moment
high-spin-polarisation ferrimagnet, both with a small lattice mismatch from
MgO. In identical symmetric and asymmetric interface reconstructions across a
3-monolayer thick MgO barrier for both ferrimagets, the linear response
(low-voltage) spin-transfer torque (STT) and tunneling magneto-resistance (TMR)
effects are evaluated. A larger staggered in-plane STT is found in the Mn$_3$Ga
case, while the STT in Mn$_3$Al vanishes quickly away from the interface
(similarly to STT in ferromagnetic MTJs). The roles are reversed for the TMR,
which is practically 100\% in the half-metallic Mn$_3$Al-based MTJs (using the
conservative definition) as opposed to 60\% in the Mn$_3$Ga case. The weak
dependence on the exact interface reconstruction would suggest
Mn$_3$Ga-Mn$_3$Al solid solutions as a possible route towards optimal trade-off
of STT and TMR in the low-bias, low-temperature transport regime.",2301.08300v1
2023-05-09,Influence of Shape on Heteroaggregation of Model Microplastics: A Simulation Study,"Nano- and microplastics are a growing threat for the environment, especially
in aqueous habitats. For assessing the influence on the ecosystem and possible
solution strategies, it is necessary to investigate the fate of microplastics
(MP) in the environment. MPs are typically surrounded by natural organic
matter, which can cause them to aggregate. However, the effect of MP shape and
flow conditions on this heteroaggregation is not well understood. To address
this gap, we perform simulations of heteroaggregation of different MP shapes
with smaller spherical organic matter. We demonstrate that the shape had a
strong impact on the aggregate structure. MPs with mostly smooth surfaces
formed compact structures with a large number of neighbors with weak connection
strength and a higher fractal dimension. MPs with edges and corners aggregated
into more fractal structures with fewer neighbors, but with stronger
connections. Using MPCD, we investigated aggregates under shear flow. The
critical shear rate at which the aggregates break up is much larger for
spherical and rounded cube MPs, i.e, the compact aggregate structure of spheres
outweighs their weaker connection strength. Most notably, the rounded cube
exhibited unexpectedly high resistance against breakup under shear. We
attribute this to being fairly compact due to weaker, flexible neighbor
connections, which are still strong enough to prevent particles to break off
during shear flow. Irrespective of the stronger connections between
neighbouring MPs, the fractal aggregates of cubes break up at lower shear
rates. We find that cube aggregates reduced their radius of gyration
significantly, indicating restructuring, while most neighbor connections were
kept intact. Aggregates of spheres, however, kept their overall size while
undergoing local rearrangements, that broke a significant portion of their
neighbor interactions.",2305.05453v1
2023-06-08,Epitaxial thin films of binary Eu-compounds close to a valence transition,"Intermetallic binary compounds of europium reveal a variety of interesting
phenomena due to the interconnection between two different magnetic and 4f
electronic (valence) states, which are particularly close in energy. The
valence states or magnetic properties are thus particularly sensitive to
strain-tuning in these materials. Consequently, we grew epitaxial EuPd$_2$
(magnetic Eu$^{2+}$) and EuPd$_3$ (nonmagnetic Eu$^{3+}$) thin films on
MgO(001) substrates using molecular beam epitaxy. Ambient X-ray diffraction
confirms an epitaxial relationship of cubic Laves-type (C15) EuPd$_2$ with an
(111)-out-of-plane orientation, whereby eight distinct in-plane
crystallographic domains develop. For simple cubic EuPd$_3$ two different
out-of-plane orientations can be obtained by changing the substrate annealing
temperature under ultra-high vacuum conditions from 600 {\deg}C to 1000 {\deg}C
for one hour. A small resistance minimum evolves for EuPd$_3$ thin films grown
with low temperature substrate annealing, which was previously found even in
single crystals of EuPd$_3$ and might be attributed to a Kondo or weak
localization effect. Absence of influence of an applied magnetic fields and
magnetotransport measurements suggest a nonmagnetic ground state for EuPd$_3$
thin films, i. e., a purely trivalent Eu valence, as found in EuPd$_3$ single
crystals. For EuPd$_2$ magnetic ordering below ~72 K is observed, quite similar
to single crystal behavior. Field dependent measurements of the
magnetoresistance and the Hall effect show hysteresis effects below ~0.4 T and
an anomalous Hall effect below ~70 K, which saturates around 1.4 T, thus
proving a ferromagnetic ground state of the divalent Eu.",2306.05355v2
2023-06-26,Phase purity and surface morphology of high-Jc superconducting Bi2Sr2Ca1Cu2O8+δ thin films,"Bi2Sr2Ca1Cu2O8+d (Bi-2212) thin films with thicknesses less than 50 nm (<20
unit cells) are grown by pulsed laser deposition (PLD) onto (001) LaAlO3 (LAO)
single crystal substrates. Phase-pure and smooth c-axis oriented Bi-2212 films
with optimal oxygen doping, critical temperature Tc0 up to 86 K, and critical
current density Jc(60 K) above 1 MA/cm2 are obtained for samples that are
annealed in situ at temperatures below 700 {\deg}C. At higher temperature
Bi-2212 films on LAO substrates partially decompose to non-superconducting
impurity phases, while films on MgO and SrTiO3 substrates are stable. The
broadening of Tc of the metal-to-superconductor resistive phase transition in
magnetic fields is much larger for thin films of Bi-2212 as compared to
YBa2Cu3O7. The magnetic field-induced suppression of Tc0 is stronger for
Bi-2212 films containing impurity phases as compared to the phase-pure Bi-2212
films. The degradation of LAO substrate crystals after several steps of
deposition and chemical removal of the Bi-2212 layer is investigated. New,
commercially prepared substrates provide Bi-2212 films with smallest surface
roughness (3 nm) and strong out-of-plane texture. However, thin films of almost
the same quality are obtained on re-used LAO substrates that are mechanically
polished after the chemical etching.",2306.14481v1
2023-07-12,Coexistence of Competing Microbial Strains under Twofold Environmental Variability and Demographic Fluctuations,"Microbial populations generally evolve in volatile environments, under
conditions fluctuating between harsh and mild, e.g. as the result of sudden
changes in toxin concentration or nutrient abundance. Environmental variability
thus shapes the long-time population dynamics, notably by influencing the
ability of different strains of microorganisms to coexist. Inspired by the
evolution of antimicrobial resistance, we study the dynamics of a community
consisting of two competing strains subject to twofold environmental
variability. The level of toxin varies in time, favouring the growth of one
strain under low drug concentration and the other strain when the toxin level
is high. We also model time-changing resource abundance by a randomly switching
carrying capacity that drives the fluctuating size of the community. While one
strain dominates in a static environment, we show that species coexistence is
possible in the presence of environmental variability. By computational and
analytical means, we determine the environmental conditions under which
long-lived coexistence is possible and when it is almost certain. Notably, we
study the circumstances under which environmental and demographic fluctuations
promote, or hinder, the strains coexistence. We also determine how the make-up
of the coexistence phase and the average abundance of each strain depend on the
environmental variability.",2307.06314v3
2023-07-31,Synthesis of possible room temperature superconductor LK-99:Pb$_9$Cu(PO$_4$)$_6$O,"The quest for room-temperature superconductors has been teasing scientists
and physicists, since its inception in 1911 itself. Several assertions have
already been made about room temperature superconductivity but were never
verified or reproduced across the labs. The cuprates were the earliest high
transition temperature superconductors, and it seems that copper has done the
magic once again. Last week, a Korean group synthesized a Lead Apatite-based
compound LK-99, showing a T$_c$ of above 400$^\circ$K. The signatures of
superconductivity in the compound are very promising, in terms of resistivity
(R = 0) and diamagnetism at T$_c$. Although, the heat capacity (C$_p$) did not
show the obvious transition at T$_c$. Inspired by the interesting claims of
above room temperature superconductivity in LK-99, in this article, we report
the synthesis of polycrystalline samples of LK-99, by following the same heat
treatment as reported in [1,2] by the two-step precursor method. The phase is
confirmed through X-ray diffraction (XRD) measurements, performed after each
heat treatment. The room temperature diamagnetism is not evidenced by the
levitation of a permanent magnet over the sample or vice versa. Further
measurements for the confirmation of bulk superconductivity on variously
synthesized samples are underway. Our results on the present LK-99 sample,
being synthesized at 925$^\circ$C, as of now do not approve the appearance of
bulk superconductivity at room temperature. Further studies with different heat
treatments are though, yet underway.",2307.16402v2
2023-10-11,Temperature-Dependent Collective Excitations in a Three-Dimensional Dirac System ZrTe$_{5}$,"Zirconium pentatelluride (ZrTe$_{5}$), a system with a Dirac linear band
across the Fermi level and anomalous transport features, has attracted
considerable research interest for it is predicted to be located at the
boundary between strong and weak topological insulators separated by a
topological semimetal phase. However, the experimental verification of the
topological phase transition and the topological ground state in ZrTe$_{5}$ is
full of controversies, mostly due to the difficulty of precisely capturing the
small gap evolution with single-particle band structure measurements.
Alternatively, the collective excitations of electric charges, known as
plasmons, in Dirac systems exhibiting unique behavior, can well reflect the
topological nature of the band structure. Here, using reflective
high-resolution electron energy loss spectroscopy (HREELS), we investigate the
temperature-dependent collective excitations of ZrTe$_{5}$, and discover that
the plasmon energy in ZrTe$_{5}$ is proportional to the $1/3$ power of the
carrier density $n$, which is a unique feature of plasmons in three-dimensional
Dirac systems. Based on this conclusion, the origin of the resistivity anomaly
of ZrTe$_{5}$ can be attributed to the temperature-dependent chemical potential
shift in extrinsic Dirac semimetals.",2310.07232v2
2023-10-19,"Comparison of the Resistivities of Nanostructured Films Made from Silver, Copper-Silver and Copper Nanoparticle and Nanowire Suspensions","Spray deposition and inkjet printing of various nanostructures are emerging
complementary methods for creating conductive coatings on different substrates.
In comparison to established deposition techniques like vacuum metal coating
and lithography-based metallization processes, spray deposition and inkjet
printing benefit from significantly simplified equipment. However, there are
number of challenges related to peculiar properties and behaviour of
nanostructures that require additional studies. In present work, we investigate
electroconductive properties and sintering behaviour of thin films produced
from nanostructures of different metals (Ag, Cu and Cu-Ag) and different shapes
(nanowires and spherical nanoparticles), and compare them to the reference Ag
and Cu magnetron deposited films. Synthesized nanostructures were studied with
transmission electron microscopy. Morphology and crystallinity of produced
metal films were studied with scanning electron microscopy and X-ray
diffraction. The electrical parameters were measured by the van der Pauw
method. All nanowires-based films provided high conductivity and required only
modest thermal treatment (200 C). To achieve sufficient sintering and
conductivity of nanoparticles-based films, higher temperatures are required
(300 C for Ag nanoparticles and 350 C for Cu and Cu-Ag nanoparticles).
Additionally, stability of nanowires was studied by annealing the samples in
vacuum conditions inside a scanning electron microscope at 500 C.",2310.12506v1
2023-11-01,Active Noise Control Portable Device Design,"While our world is filled with its own natural sounds that we can't resist
enjoying, it is also chock-full of other sounds that can be irritating, this is
noise. Noise not only influences the working efficiency but also the human's
health. The problem of reducing noise is one of great importance and great
difficulty. The problem has been addressed in many ways over the years. The
current methods for noise reducing mostly rely on the materials and
transmission medium, which are only effective to some extent for the high
frequency noise. However, the effective reduction noise method especially for
low frequency noise is very limited.
  Here we come up with a noise reduction system consist of a sensor to detect
the noise in the environment. Then the noise will be sent to an electronic
control system to process the noise, which will generate a reverse phase
frequency signal to counteract the disturbance. Finally, the processed smaller
noise will be broadcasted by the speaker. Through this smart noise reduction
system, even the noise with low-frequency can be eliminated.
  The system is also integrated with sleep tracking and music player
applications. It can also remember and store settings for the same environment,
sense temperature, and smart control of home furniture, fire alarm, etc. This
smart system can transfer data easily by Wi-Fi or Bluetooth and controlled by
its APP.
  In this project, we will present a model of the above technology which can be
used in various environments to prevent noise pollution and provide a solution
to the people who have difficulties finding a peaceful and quiet environment
for sleep, work or study.",2311.00535v1
2023-11-13,Superconductivity in trilayer nickelate La4Ni3O10 under pressure,"Nickelate superconductors have attracted a great deal of attention over the
past few decades due to their similar crystal and electronic structures with
high-temperature cuprate superconductors. Here, we report the superconductivity
in a pressurized Ruddlesden-Popper phase single crystal, La4Ni3O10 (n = 3), and
its interplay with the density wave order in the phase diagram. With increasing
pressure, the density wave order as indicated by the anomaly in the resistivity
is progressively suppressed, followed by the emergence of the superconductivity
around 25 K. Our angle-resolved photoemission spectroscopy measurements reveal
that the electronic structure of La4Ni3O10 is very similar to that of La3Ni2O7,
suggesting unified electronic properties of nickelates in Ruddlesden-Popper
phases. Moreover, theoretical analysis unveils that antiferromagnetic (AFM)
super-exchange interactions can serve as the effective pairing interaction for
the emergence of superconductivity (SC) in pressurized La4Ni3O10. Our research
provides a new platform for the investigation of the unconventional
superconductivity mechanism in Ruddlesden-Popper trilayer perovskite
nickelates.",2311.07423v2
2023-11-15,Quantification of cell contractile behavior based on non-destructive macroscopic measurement of tension forces on bioprinted hydrogel,"Contraction assay based on surface measurement have been widely used to
evaluate cell contractility in 3D models. This method is straightforward and
requires no specific equipment, but it does not provide quantitative data about
contraction forces generated by cells. We expanded this method with a new
biomechanical model, based on the work-energy theorem, to provide
non-destructive longitudinal monitoring of contraction forces generated by
cells in 3D.We applied this method on hydrogels seeded with either fibroblasts
or osteoblasts. Hydrogel mechanical characteristics were modulated to enhance
(condition HCA$_{High}$: hydrogel contraction assay high contraction) or limit
(condition HCA$_{Low}$: hydrogel contraction assay low contraction) cell
contractile behaviors. Macroscopic measures were further correlated with cell
contractile behavior and descriptive analysis of their physiology in response
to different mechanical environments. Fibroblasts and osteoblasts contracted
their matrix up to 47% and 77% respectively. Contraction stress peaked at day 5
with 1.1 10$^{-14}$Pa for fibroblasts and 3.5 10$^{-14}$Pa for osteoblasts,
which correlated with cell attachment and spreading. Negligible contraction was
seen in HCA$_{Low}$. Both fibroblasts and osteoblasts expressed $\alpha$-SMA
contractile fibers in HCA$_{High}$ and HCA$_{Low}$. Failure to contract
HCA$_{Low}$ was attributed to increased cross-linking and resistance to
proteolytic degradation of the hydrogel.",2311.08773v1
2023-12-15,Plasma-enhanced atomic layer deposition of titanium nitride for superconducting devices,"This study presents a comprehensive investigation into the exceptional
superconducting attributes of titanium nitride (TiN) achieved through
plasma-enhanced atomic layer deposition (PEALD) on both planar and intricate
three-dimensional (3D) structures. We introduced an additional substrate
biasing cycle to densify the film and remove ligand residues, augmenting the
properties while minimizing impurities. While reactive-sputtered TiN films
exhibit high quality, our technique ensures superior uniformity by consistently
maintaining a desired sheet resistance greater than 95 percent across a 6inch
wafer, a critical aspect for fabricating extensive arrays of superconducting
devices and optimizing wafer yield. Moreover, our films demonstrate exceptional
similarity to conventional reactive-sputtered films, consistently reaching a
critical temperature (Tc) of 4.35 K with a thickness of around 40 nm. This
marks a notable achievement compared to previously reported ALD-based
superconducting TiN. Using the same process as for planar films, we obtained Tc
for aspect ratios (ARs) ranging from 2 to 40, observing a Tc of approximately 2
K for ARs between 2 and 10.5. We elucidate the mechanisms contributing to the
limitations and degradation of superconducting properties over these aggressive
3D structures. Our results seamlessly align with both current and
next-generation superconducting technologies, meeting stringent criteria for
thin-film constraints, large-scale deposition, conformality, 3D integration
schemes, and yield optimization.",2312.09984v1
2023-12-19,On the role of Grain Boundary Character in the Stress Corrosion Cracking of Nanoporous Gold Thin Films,"For its potential as a catalyst, nanoporous gold (NPG) prepared through
dealloying of bulk Ag-Au alloys has been extensively investigated. NPG thin
films can offer ease of handling, better tunability of the chemistry and
microstructure of the nanoporous structure, and represent a more sustainable
usage of scarce resources. These films are however prone to intergranular
cracking during dealloying, limiting their stability and potential
applications. Here, we set out to systematically investigate the grain
boundaries in Au28Ag72 thin films. We observe that a sample synthesized at 400
{\deg}C is at least 2.5 times less prone to cracking compared to a sample
synthesized at room temperature. This correlates with a higher density of
coincident site lattice grain boundaries, especially the density of coherent
sigma 3, increased, which appear resistant against cracking. Nanoscale
compositional analysis of random high-angle grain boundaries reveals prominent
Ag enrichment up to 77 at.%, whereas sigma 3 coherent twin boundaries show Au
enrichment of up to 30 at.%. The misorientation and the chemistry of grain
boundaries hence affect their dealloying behavior, which in turn controls the
cracking, and the possible longevity of NPG thin films for application in
electrocatalysis.",2312.12235v1
2024-02-26,Electronic phase transitions and superconductivity in ferroelectric Sn$_2$P$_2$Se$_6$ under pressure,"Since there is both strong electron-phonon coupling during a ferroelectric/FE
transition and superconducting/SC transition, it has been an important topic to
explore superconductivity from the FE instability. Sn$_2$P$_2$Se$_6$ arouses
broad attention due to its unique FE properties. Here, we reported the
electronic phase transitions and superconductivity in this compound based on
high-pressure electrical transport measurement, optical absorption spectroscopy
and Raman based structural analysis. Upon compression, the conductivity of
Sn$_2$P$_2$Se$_6$ was elevated monotonously, an electronic phase transition
occurred near 5.4 GPa, revealed by optical absorption spectroscopy, and the
insulating state is estimated to be fully suppressed near 15 GPa. Then, it
started to show the signature of superconductivity near 15.3 GPa. The
zero-resistance state was presented from 19.4 GPa, and the superconductivity
was enhanced with pressure continuously. The magnetic field effect further
confirmed the SC behavior and this compound had a $T_c$ of 5.4 K at 41.8 GPa
with a zero temperature upper critical field of 6.55 T. The Raman spectra
confirmed the structural origin of the electronic transition near 5.4 GPa,
which should due to the transition from the paraelectric phase to the
incommensurate phase, and suggested a possible first-order phase transition
when the sample underwent the semiconductor-metal transition near 15 GPa. This
work demonstrates the versatile physical properties in ferroelectrics and
inspires the further investigation on the correlation between FE instability
and SC in M$_2$P$_2$X$_6$ family.",2402.16427v1
2024-02-29,Anomalous frequency and temperature dependent scattering in the dilute metallic phase in lightly doped-SrTiO$_3$,"The mechanism of superconductivity in materials with aborted ferroelectricity
and the emergence of a dilute metallic phase in systems like doped-SrTiO$_3$
are outstanding issues in condensed matter physics. This dilute metal has
features both similar and different to those found in the normal state of other
unconventional superconductors. We have investigated the optical properties of
the dilute metallic phase in doped-SrTiO$_3$ using THz time-domain
spectroscopy. At low frequencies the THz response exhibits a Drude-like form as
expected for typical metal-like conductivity. We observed the frequency and
temperature dependencies to the low energy scattering rate $\Gamma(\omega, T)
\propto (\hbar\omega)^2 + (p \pi k_BT)^2 $ expected in a conventional Fermi
liquid, despite the fact that densities are too small to allow current decay
through electron-electron scattering. However we find the lowest known $p$
values of 0.39-0.72. As $p$ is 2 in a canonical Fermi liquid and existing
models based on energy dependent elastic scattering bound $p$ from below to 1,
our observation lies outside current explanation. Our data also gives insight
into the high temperature regime and shows that the temperature dependence of
the resistivity derives in part from strong T dependent mass renormalizations.",2402.18767v1
2024-03-06,"Crystal, ferromagnetism, and magnetoresistance with sign reversal in a EuAgP semiconductor","We synthesized the ferromagnetic EuAgP semiconductor and conducted a
comprehensive study of its crystalline, magnetic, heat capacity, band gap, and
magnetoresistance properties. Our investigation utilized a combination of X-ray
diffraction, optical, and PPMS DynaCool measurements. EuAgP adopts a hexagonal
structure with the $P6_3/mmc$ space group. As the temperature decreases, it
undergoes a magnetic phase transition from high-temperature paramagnetism to
low-temperature ferromagnetism. We determined the ferromagnetic transition
temperature to be $T_{\textrm{C}} =$ 16.45(1) K by fitting the measured
magnetic susceptibility using a Curie-Weiss law. Heat capacity analysis of
EuAgP considered contributions from electrons, phonons, and magnons, revealing
$\eta$ = 0.03 J/mol/$\textrm{K}^\textrm{2}$, indicative of semiconducting
behavior. Additionally, we calculated a band gap of $\sim$ 1.324(4) eV based on
absorption spectrum measurements. The resistivity versus temperature of EuAgP
measured in the absence of an applied magnetic field shows a pronounced peak
around $T_{\textrm{C}}$, which diminishes rapidly with increasing applied
magnetic fields, ranging from 1 to 14 T. An intriguing phenomenon emerges in
the form of a distinct magnetoresistance transition, shifting from positive
(e.g., 1.95\% at 300 K and 14 T) to negative (e.g., -30.73\% at 14.25 K and 14
T) as the temperature decreases. This behavior could be attributed to
spin-disordered scattering.",2403.03650v1
2024-03-20,Optimizing Transparent Electrodes: Interplay of High Purity SWCNTs network and a Polymer,"The discovery of transparent electrodes led to the development of
optoelectronic devices such as OLEDs, LCDs, touchscreens, IR sensors, etc.
Since ITO has many drawbacks in respect of its production cost and limited
transparency in IR, carbon nanotubes (CNTs) have been a potential replacement
for ITO due to their exceptional electrical and optical properties, especially
in the IR region. In this work, we present the development of a CNT-polymer
composite thin film that exhibits outstanding transparency across both visible
and IR spectra prepared by layer-by-layer (LbL) technique. This approach not
only ensures uniform integration and crosslinking of CNTs into lightweight
matrices, but also represents a cost-effective method for producing transparent
electrodes with remarkable optical and electrical properties. The produced
films achieved a transparency above 80% in the UV-VIS range and approximately
70% in the mid-IR range. The sheet resistance of the fabricated thin films was
measured at about 4 kOhm/sq, showing a tendency to decrease with the number of
bilayers. Furthermore, in this work we have investigated electrical properties
and transport mechanisms in more detail with computational analysis.
Computational analysis was performed to better understand the electrical
behavior of nanotube-polymer junctions in the interbundle structure. Based on
all results, we propose that the transparent electrodes with 4 and 6 bilayers
are the most optimal structures in terms of optical and electrical properties.",2403.13594v1
1996-10-01,Itinerant Antiferromagnetism in FeGe_2,"FeGe_2, and lightly doped compounds based on it, have a Fermi surface driven
instability which drive them into an incommensurate spin density wave state.
Studies of the temperature and magnetic field dependence of the resistivity
have been used to determine the magnetic phase diagram of the pure material
which displays an incommensurate phase at high temperatures and a commensurate
structure below 263 K in zero field. Application of a magnetic field in the
tetragonal basal plane decreases the range of temperatures over which the
incommensurate phase is stable. We have used inelastic neutron scattering to
measure the spin dynamics of FeGe_2. Despite the relatively isotropic transport
the magnetic dynamics is quasi-one dimensional in nature. Measurements carried
out on HET at ISIS have been used to map out the spin wave dispersion along the
c-axis up the 400 meV, more than an order of magnitude higher than the zone
boundary magnon for wavevectors in the basal plane.",9610009v1
1998-05-25,Metal-insulator transition induced by 16O -18O oxygen isotope exchange in colossal negative magnetoresistance manganites,"The effect of 16O-18O isotope exchange on the electric resistivity was
studied for (La(1-y)Pr(y))0.7Ca0.3MnO3 ceramic samples. Depending on y, this
mixed perovskite exhibited different types of low-temperature behavior ranging
from ferromagnetic metal (FM) to charge ordered (CO) antiferromagnetic
insulator. It was found that at y=0.75, the substitution of 16O by 18O results
in the reversible transition from a FM to a CO insulator at zero magnetic
field. The applied magnetic field (H >= 2 T) transformed the sample with 18O
again to the metallic state and caused the increase in the FM transition
temperature Tc of the 16O sample. As a result, the isotope shift of Tc at H = 2
T was as high as 63 K. Such unique sensitivity of the system to oxygen isotope
exchange, giving rise even to the metal-insulator transition, is discussed in
terms of the isotope dependence of the effective electron bandwidth which
shifts the balance between the CO and FM phases.",9805315v1
2001-04-13,Metal-insulator transition in 2D: a role of the upper Habbard band,"To explain the main features of the metal-insulator transition (MIT) in 2D we
suggest a simple model taking into account strongly localized states in the
band tail of 2D conductivity band with a specific emphasize of a role of
doubly-occupied states (upper Hubbard band). The metallic behavior of
resistance is explained as result of activation of localized electrons to
conductance band leading to a suppression of non-linear screening of the
disorder potential. The magnetoresistance (MR) in the critical region is
related to depopulation of double occupied localized states also leading to
partial suppression of the nonlinear screening. The most informative data are
related to nearly activated temperature dependence of MR in strongly insulating
limit (which can be in particular reached from the metallic state in high
enough fields). According to our model this behavior originates due to a
lowering of a position of chemical potential in the upper Hubbard band due to
Zeeman splitting. We compare the theoretical predictions to the existing
experimental data and demonstrate that the model explains such features of the
2D MIT as scaling behavior in the critical region, saturation of MR and H/T
scaling of MR in the insulating limit. The quantitative analysis of MR in
strongly insulating limit based on the model suggested leads to the values of
g-factors being in good agreement with known values for localized states in
corresponding materials.",0104254v1
2001-05-31,Anomalous Nonlinear Microwave Response of Epitaxial YBa2Cu3O7-x Films on MgO,"We have investigated the anomalous nonlinear microwave response of epitaxial
electron-beam coevaporated YBa2Cu3O7-x films on MgO. The power and temperature
dependent surface impedance and two-tone intermodulation distortion were
measured in stripline resonators at several frequencies between 2.3 and 11.2
GHz and at temperatures between 1.7 K and Tc. All of the eight films measured
to date show a decrease of the surface resistance Rs of up to one order of
magnitude as the microwave current is increased up to approximately 1 mA for T
< 20 K. The surface reactance Xs showed only a weak increase in the same
region. The usual nonlinear increase of Rs and Xs was observed at high currents
in the 100-mA range. The minimum of Rs correlates with a pronounced plateau in
the third-order intermodulation signal. We have developed a phenomenological
two-fluid model, incorporating a microwave current-dependent quasiparticle
scattering rate g and normal fraction fn. The model contains only three
adjustable parameters. We find good agreement with the measured data for
constant fn and a current-dependent scattering rate g whose magnitude increases
almost linearly with temperature and frequency. Obvious mechanisms leading to
nonlinear microwave response like Josephson coupling across grain boundaries,
nonlocal or nonequilibrium effects cannot explain the data. The anomalies could
rather reflect the specific charge and spin ordering and transport phenomena in
the low-dimensional cuprate superconductors.",0105613v1
2002-01-25,The influence of microstructures and crystalline defects on the superconductivity of MgB2,"This work studies the influence of microstructures and crystalline defects on
the superconductivity of MgB2, with the objective to improve its flux pinning.
A MgB2 sample pellet that was hot isostatic pressed (HIPed) was found to have
significantly increased critical current density (Jc) at high fields than its
un-HIPed counterpart. The HIPed sample had a Jc of 10000 A/cm2 in 50000 Oe (5
T) at 5K. This was 20 times higher than that of the un-HIPed sample, and the
same as the best Jc reported by other research groups. Microstructures observed
in scanning and transmission electron microscopy indicate that the HIP process
eliminated porosity present in the MgB2 pellet resulting in an improved
intergrain connectivity. Such improvement in intergrain connectivity was
believed to prevent the steep Jc drop with magnetic field H that occurred in
the un-HIPed MgB2 pellet at H > 45000 Oe (4.5 T) and T = 5 K. The HIP process
was also found to disperse the MgO that existed at the grain boundaries of the
un-HIPed MgB2 pellet and to generate more dislocations in the HIPed the
pellets. These dispersed MgO particles and dislocations improved flux pinning
also at H<45000 Oe. The HIPing process was also found to lower the resistivity
at room temperature.",0201486v2
2004-04-19,Low temperature transport in granular metals,"We investigate transport in a granular metallic system at large tunneling
conductance between the grains. We show that at low temperatures, $T\leq
g_T\delta $, where $\delta$ is the single mean energy level spacing in a grain,
the coherent electron motion at large distances dominates the physics, contrary
to the high temperature ($T > g_T \delta $) behavior where conductivity is
controlled by the scales of the order of the grain size. The conductivity of
one and two dimensional granular metals, in the low temperature regime, decays
with decreasing temperature in the same manner as that in homogeneous
disordered metals, indicating thus an insulating behavior. However, even in
this temperature regime the granular structure remains important and there is
an additional contribution to conductivity coming from short distances. Due to
this contribution the metal-insulator transition in three dimensions occurs at
the value of tunnel conductance $g_T^C=(1/6\pi)\ln (E_C/\delta)$, where $E_C$
is the charging energy of an isolated grain, and not at the generally expected
$g_T^C \propto 1$. Corrections to the density of states of granular metals due
to the electron-electron interaction are calculated. Our results compare
favorably with the logarithmic dependence of resistivity in the high-$T_c$
cuprate superconductors indicating that these materials may have a granular
structure.",0404443v2
2004-10-21,Novel magnetic behavior of single crystalline Er2PdSi3,"We report the results of ac and dc magnetic susceptibility (chi) and
electrical resistivity (rho) measurements on the single crystals of Er2PdSi3,
crystallizing in an AlB2-derived hexagonal structure, for two orientations
H//[0001] and H//[2 -1 -1 0]. For H//[0001], there are apparently two magnetic
transitions as revealed by the ac chi data, one close to 7 K attributable to
antiferromagnetic ordering and the other around 2 K. However, for H // [2 -1 -1
0], we observe additional features above 7 K (near 11 and 23 K) in the plot of
low-field chi(T); also, there is no corresponding anomaly in the rho(T) plot.
In this respect, the magnetic behavior of this compound is novel, particularly
while compared with other members of this series. The features in ac chi
respond differently to the application of a small dc magnetic field for the two
directions. As far as low temperature (T= 1.8 and 5 K) isothermal magnetization
(M) behaviour is concerned, it exhibits meta-magnetic-like features around 2
kOe saturating at high fields for the former orientation, whereas for the
latter, there is no saturation even at 120 kOe. The sign of paramagnetic Curie
temperature is different for these two directions. Thus, there is a strong
anisotropy in the magnetic behavior. However, interestingly, the rho(T) plots
are found to be essentially isotropic, with the data revealing possible
formation of magnetic superzone formation below 7 K.",0410532v1
2006-06-22,Metal-insulator transition in Nd$_{1-x}$Eu$_{x}$NiO$_{3}$ compounds,"Polycrystalline Nd$_{1-x}$Eu$_{x}$NiO$_3$ ($0 \leq x \leq 0.5$) compounds
were synthesized in order to investigate the character of the metal-insulator
(MI) phase transition in this series. Samples were prepared through the sol-gel
route and subjected to heat treatments at $\sim$1000 $^\circ$C under oxygen
pressures as high as 80 bar. X-ray Diffraction (XRD) and Neutron Powder
Diffraction (NPD), electrical resistivity $\rho(T)$, and Magnetization $M(T)$
measurements were performed on these compounds. The results of NPD and XRD
indicated that the samples crystallize in an orthorhombic distorted perovskite
structure, space group $Pbnm$. The analysis of the structural parameters
revealed a sudden and small expansion of $\sim$0.2% of the unit cell volume
when electronic localization occurs. This expansion was attributed to a small
increase of $\sim$0.003 \AA{} of the average Ni-O distance and a simultaneous
decrease of $\sim$$- 0.5^\circ$ of the Ni-O-Ni superexchange angle. The
$\rho(T)$ measurements revealed a MI transition occurring at temperatures
ranging from $T_{\rm MI}\sim 193$ to 336 K for samples with $x = 0$ and 0.50,
respectively. These measurements also show a large thermal hysteresis in
NdNiO$_{3}$ during heating and cooling processes suggesting a first-order
character of the phase transition at $T_{\rm MI}$. The width of this thermal
hysteresis was found to decrease appreciably for the sample
Nd$_{0.7}$Eu$_{0.3}$NiO$_{3}$. The results indicate that cation disorder
associated with increasing substitution of Nd by Eu is responsible for changing
the first order character of the transition in NdNiO$_{3}$.",0606573v1
2007-03-21,Dynamics of the Magnetic Flux Trapped in Fractal Clusters of a Normal Phase in Percolative Superconductors,"The effect of the fractal clusters of a normal phase, which act as pinning
centers, on the dynamics of magnetic flux in percolative type-II superconductor
is considered. The main features of these clusters are studied in detail: the
cluster statistics is analyzed; the fractal dimension of their boundary is
estimated; the distribution of critical currents is obtained, and its
peculiarities are explored. It is found that there is the range of fractal
dimension where this distribution has anomalous statistical properties,
specifically, its dispersion becomes infinite. It is examined how the finite
resolution capacity of the cluster geometric size measurement affects the
estimated value of fractal dimension. The effect of fractal properties of the
normal phase clusters on the electric field arisen from magnetic flux motion is
investigated for the cluster area distribution of different kinds. The
voltage-current characteristics of fractal superconducting structures in the
resistive state are obtained for an arbitrary fractal dimension. It is revealed
that the fractality of the boundaries of the normal phase clusters intensifies
the magnetic flux trapping and thereby raises the critical current of a
superconductor.",0703541v1
2007-03-27,Diffusion and activation of n-type dopants in germanium,"The diffusion and activation of $n$-type impurities (P and As) implanted into
$p$-type Ge(100) substrates were examined under various dose and annealing
conditions. The secondary ion mass spectrometry profiles of chemical
concentrations indicated the existence of a sufficiently high number of
impurities with increasing implanted doses. However, spreading resistance probe
profiles of electrical concentrations showed electrical concentration
saturation in spite of increasing doses and indicated poor activation of As
relative to P in Ge. The relationships between the chemical and electrical
concentrations of P in Ge and Si were calculated, taking into account the
effect of incomplete ionization. The results indicated that the activation of P
was almost the same in Ge and Si. The activation ratios obtained experimentally
were similar to the calculated values, implying insufficient degeneration of
Ge. The profiles of P in Ge substrates with and without damage generated by Ge
ion implantation were compared, and it was clarified that the damage that may
compensate the activated $n$-type dopants has no relationship with the
activation of P in Ge.",0703708v3
2008-10-14,Superconductivity in Fluorine-Arsenide Sr_{1-x}La_xFeAsF,"Since the discovery of superconductivity\cite{1} at 26 K in oxy-pnictide
$LaFeAsO_{1-x}F_x$, enormous interests have been stimulated in the fields of
condensed matter physics and material sciences. Among the five different
structures in this broad type of superconductors\cite{2,3,4,5,6}, the ZrCuSiAs
structure has received special attention since the $T_c$ has been quickly
promoted to 55-56 K\cite{7,8,9,10,11} in fluorine doped oxy-pnictides REFeAsO
(RE = rare earth elements). The superconductivity can also be induced by
applying a high pressure to the undoped samples\cite{12,13}. The mechanism of
superconductivity in the FeAs-based system remains unclear yet, but it turns
out to be clear that any change to the structure or the building blocks will
lead to a change of the superconducting transition temperatures. In this
Letter, we report the fabrication of the new family of compounds, namely
fluorine-arsenides DvFeAsF (Dv = divalent metals) with the ZrCuSiAs structure
and with the new building block DvF instead of the REO (both the layers DvF and
REO have the combined cation state of ""+1""). The undoped parent phase has a
Spin-Density-Wave like transition at about 173 K for SrFeAsF, 118 K for CaFeAsF
and 153 K for EuFeAsF. By doping electrons into the system the resistivity
anomaly associated with this SDW transition is suppressed and superconductivity
appears at 32 K in the fluorine-arsenide Sr$_{1-x}$La$_x$FeAsF (x = 0.4). Our
discovery here initiates a new method to obtain superconductors in the
FeAs-based system.",0810.2531v3
2009-07-09,Annular Spin-Transfer Memory Element,"An annular magnetic memory that uses a spin-polarized current to switch the
magnetization direction or helicity of a magnetic region is proposed. The
device has magnetic materials in the shape of a ring (1 to 5 nm in thickness,
20 to 250 nm in mean radius and 8 to 100 nm in width), comprising a reference
magnetic layer with a fixed magnetic helicity and a free magnetic layer with a
changeable magnetic helicity. These are separated by a thin non-magnetic layer.
Information is written using a current flowing perpendicular to the layers,
inducing a spin-transfer torque that alters the magnetic state of the free
layer. The resistance, which depends on the magnetic state of the device, is
used to read out the stored information. This device offers several important
advantages compared to conventional spin-transfer magnetic random access memory
(MRAM) devices. First, the ring geometry offers stable magnetization states,
which are, nonetheless, easily altered with short current pulses. Second, the
ring geometry naturally solves a major challenge of spin-transfer devices:
writing requires relatively high currents and a low impedance circuit, whereas
readout demands a larger impedance and magnetoresistance. The annular device
accommodates these conflicting requirements by performing reading and writing
operations at separate read and write contacts placed at different locations on
the ring.",0907.1600v1
2009-09-16,Band structure engineering of epitaxial graphene on SiC by molecular doping,"Epitaxial graphene on SiC(0001) suffers from strong intrinsic n-type doping.
We demonstrate that the excess negative charge can be fully compensated by
non-covalently functionalizing graphene with the strong electron acceptor
tetrafluorotetracyanoquinodimethane (F4-TCNQ). Charge neutrality can be reached
in monolayer graphene as shown in electron dispersion spectra from angular
resolved photoemission spectroscopy (ARPES). In bilayer graphene the band gap
that originates from the SiC/graphene interface dipole increases with
increasing F4-TCNQ deposition and, as a consequence of the molecular doping,
the Fermi level is shifted into the band gap. The reduction of the charge
carrier density upon molecular deposition is quantified using electronic Fermi
surfaces and Raman spectroscopy. The structural and electronic characteristics
of the graphene/F4-TCNQ charge transfer complex are investigated by X-ray
photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy
(UPS). The doping effect on graphene is preserved in air and is temperature
resistant up to 200\degree C. Furthermore, graphene non-covalent
functionalization with F4-TCNQ can be implemented not only via evaporation in
ultra-high vacuum but also by wet chemistry.",0909.2966v2
2010-01-07,"Anisotropic Connectivity and its Influence on Critical Current Densities, Irreversibility Fields, and Flux Creep in In-Situ-Processed MgB2 Strands","The anisotropy of the critical current density (Jc) and its influence on
measurement of irreversibility field (Birr) has been investigated for high
quality, in-situ MgB2 strands. Comparison of transport and magnetization
measurements has revealed the onset of a regime where large differences exist
between transport and magnetically measured values of the critical current
density and Birr. These effects, initially unexpected due to the lack of
crystalline texture in these in-situ processed strands, appear to be due to a
fibrous microstructure, connected with the details of the wire fabrication and
MgB2 formation reactions. Scanning electron micrographs of in-situ-processed
MgB2 monocore strands have revealed a fibrous microstructure. Grains (~100 nm)
are randomly oriented, and there is no apparent local texture of the grains.
However, this randomly oriented polycrystalline material has a fibrous texture
at a larger length scale, with stringers of MgB2 (~ 60 {\mu}m long and ~5
{\mu}m in diameter) partially separated by elongated pores -- the spaces
previously occupied by stringers of elemental Mg. This leads to an
interpretation of the differences observed in transport and magnetically
determined critical currents, in particular a large deviation between the two
at higher fields, in terms of different transverse and longitudinal
connectivities within the strand. The different values of connectivity also
lead to different resistive transition widths, and thus irreversibility field
values, as measured by transport and magnetic techniques. Finally, these
considerations are seen to influence estimated pinning potentials for the
strands.",1001.1030v1
2010-04-21,Determination of the intrinsic ferroelectric polarization in orthorhombic HoMnO3,"Whether large ferroelectric polarization P exists in the orthorhombic HoMnO3
with the E-type antiferromagnetic spin ordering or not remains as one of
unresolved, challenging issues in the physics of multiferroics. The issue is
closely linked to an intriguing experimental difficulty for determining P of
polycrystalline specimens that conventional pyroelectric current measurements
performed after a poling procedure under high dc electric fields are subject to
large errors due to the problems caused by leakage currents or space charges.
To overcome the difficulty, we employed the PUND method, which uses
successively the two positive and two negative electrical pulses, to directly
measure electrical hysteresis loops in several polycrystalline HoMnO3 specimens
below their N\'eel temperatures. We found that all the HoMnO3 samples had
similar remnant polarization Pr values at each temperature, regardless of their
variations in resistivity, dielectric constant, and pyroelectric current
levels. Moreover, Pr of ~0.07 \mu\C/cm2 at 6 K is consistent with the P value
obtained from the pyroelectric current measurement performed after a short
pulse poling. Our findings suggest that intrinsic P of polycrystalline HoMnO3
can be determined through the PUND method and P at 0 K may reach ~0.24
\mu\C/cm2 in a single crystalline specimen.",1004.3643v1
2010-07-26,Python Regius (Ball Python) shed skin: Biomimetic analogue for function-targeted design of tribo-surfaces,"A major concern in designing tribo-systems is to minimize friction, save
energy, and to reduce wear. Satisfying these requirements depends on the
integrity of the rubbing surface and its suitability to sliding conditions. As
such, designers currently focus on constructing surfaces that are an integral
part of the function of the tribo-system. Inspirations for such constructs come
from studying natural systems and from implementing natural design rules. One
species that may serve as an analogue for design is the Ball python. This is
because such a creature while depending on legless locomotion when sliding
against various surfaces, many of which are deemed tribologically hostile,
doesn't sustain much damage. Resistance to damage in this case originates from
surface design features. As such, studying these features and how do they
contribute to the control of friction and wear is very attractive for design
purposes. In this work we apply a multi scale surface characterization approach
to study surface design features of the Python regius that are beneficial to
design high quality lubricating surfaces (such as those obtained through
plateau honing). To this end, we studied topographical features by SEM and
through White Light Interferrometery (WLI). We further probe the roughness of
the surface on multi scale and as a function of location within the body. The
results are used to draw a comparison to metrological features of commercial
cylinder liners obtained by plateau honing.",1007.4419v1
2010-11-09,Phase diagram of iron-arsenide superconductors Ca(Fe1-xCox)2As2 (0 <= x <= 0.2),"Platelet-like single crystals of the Ca(Fe1-xCox)2As2 series having lateral
dimensions up to 15 mm and thickness up to 0.5 mm were obtained from the high
temperature solution growth technique using Sn flux. Upon Co doping, the c-axis
of the tetragonal unit cell decreases, while the a-axis shows a less
significant variation. Pristine CaFe2As2 shows a combined spin-density-wave and
structural transition near T = 166 K which gradually shifts to lower
temperatures and splits with increasing Co-doping. Both transitions terminate
abruptly at a critical Co-concentration of xc = 0.075. For x \geq 0.05,
superconductivity appears at low temperatures with a maximum transition
temperature TC of around 20 K. The superconducting volume fraction increases
with Co concentration up to x = 0.09 followed by a gradual decrease with
further increase of the doping level. The electronic phase diagram of
Ca(Fe1-xCox)2As2 (0 \leq x \leq 0.2) series is constructed from the
magnetization and electric resistivity data. We show that the low-temperature
superconducting properties of Co-doped CaFe2As2 differ considerably from those
of BaFe2As2 reported previously. These differences seem to be related to the
extreme pressure sensitivity of CaFe2As2 relative to its Ba counterpart.",1011.2085v1
2011-08-17,Impact of Protostellar Outflow on Star Formation: Effects of Initial Cloud Mass,"Star formation efficiency controlled by the protostellar outflow in a single
cloud core is investigated by three-dimensional resistive MHD simulations.
Starting from the prestellar cloud core, the star formation process is
calculated until the end of the main accretion phase. In the calculations, the
mass of the prestellar cloud is parameterized. During the star formation, the
protostellar outflow is driven by the circumstellar disk. The outflow extends
also in the transverse direction until its width becomes comparable to the
initial cloud scale, and thus, the outflow has a wide opening angle of >40
degrees. As a result, the protostellar outflow sweeps up a large fraction of
the infalling material and ejects it into the interstellar space. The outflow
can eject at most over half of the host cloud mass, significantly decreasing
star formation efficiency. The outflow power is stronger in clouds with a
greater initial mass. Thus, the protostellar outflow effectively suppresses
star formation efficiency in a massive cloud. The outflow weakens significantly
and disappears in several free-fall timescales of the initial cloud after the
cloud begins to collapse. The natal prestellar core influences the lifetime and
size of the outflow. At the end of the main accretion phase, a massive
circumstellar disk comparable in mass to the protostar remains. Calculations
show that typically, ~30% of the initial cloud mass is converted into the
protostar and ~20% remains in the circumstellar disk, while ~40% is ejected
into the interstellar space by the protostellar outflow. Therefore, a single
cloud core typically has a star formation efficiency of 30-50%.",1108.3564v1
2012-05-02,Negative thermal expansion and antiferromagnetism in the actinide oxypnictide NpFeAsO,"A neptunium analogue of the LaFeAsO tetragonal layered compound has been
synthesized and characterized by a variety of experimental techniques. The
occurrence of long-range magnetic order below a critical temperature T_N = 57 K
is suggested by anomalies in the temperature-dependent magnetic susceptibility,
electrical resistivity, Hall coefficient, and specific heat curves. Below T_N,
powder neutron diffraction measurements reveal an antiferromagnetic structure
of the Np sublattice, with an ordered magnetic moment of 1.70(0.07) \mu_B
aligned along the crystallographic c-axis. No magnetic order has been observed
on the Fe sublattice, setting an upper limit of about 0.3 \mu_B for the ordered
magnetic moment on the iron. High resolution x-ray powder diffraction
measurements exclude the occurrence of lattice transformations down to 5 K, in
sharp contrast to the observation of a tetragonal-to-orthorhombic distortion in
the rare-earth analogues, which has been associated with the stabilization of a
spin density wave on the iron sublattice. Instead, a significant expansion of
the NpFeAsO lattice parameters is observed with decreasing temperature below
T_N, corresponding to a relative volume change of about 0.2% and to an invar
behavior between 5 and 20 K. First-principle electronic structure calculations
based on the local-spin density plus Coulomb interaction and the local density
plus Hubbard-I approximations provide results in good agreement with the
experimental findings.",1205.0438v1
2012-09-13,Magnetic phase transitions in single crystals of the chiral helimagnet Cr1/3NbS2,"The chiral helimagnet Cr1/3NbS2 has been investigated by magnetic, transport
and thermal properties measurements on single crystals and by first principles
electronic structure calculations. From the measured field and temperature
dependence of the magnetization for fields applied perpendicular to the c axis,
the magnetic phase diagram has been constructed in the vicinity of the phase
transitions. A transition from a paramagnetic to a magnetically ordered phase
occurs near 120 K. With increasing magnetic field and at temperatures below 120
K, this material undergoes transitions from a helimagnetic to a soliton-lattice
phase near 900 Oe, and then to a ferromagnetic phase near 1300 Oe. The
transitions are found to strongly affect the electrical transport. The
resistivity decreases sharply upon cooling near 120 K, and the spin
reorientation from the helimagnetic ground state to the commensurate
ferromagnetic state is evident in the magnetoresistance. At high fields a large
magnetoresistance (55 % at 140 kOe) is observed near the magnetic transition
temperature. Heat capacity and electronic structure calculations show the
density of states at the Fermi level is low in the magnetically ordered state.
Effects of spin fluctuations are likely important in understanding the behavior
of Cr1/3NbS2 near and above the magnetic ordering transitions.",1209.2783v1
2013-04-15,Non-Fermi liquids and the Wiedemann-Franz law,"A general discussion of the ratio of thermal and electrical conductivities in
non-Fermi liquid metals is given. In metals with sharp Drude peaks, the
relevant physics is correctly organized around the slow relaxation of
almost-conserved momenta. While in Fermi liquids both currents and momenta
relax slowly, due to the weakness of interactions among low energy excitations,
in strongly interacting non-Fermi liquids typically only momenta relax slowly.
It follows that the conductivities of such non-Fermi liquids are obtained
within a fundamentally different kinematics to Fermi liquids. Among these
strongly interacting non-Fermi liquids we distinguish cases with only one
almost-conserved momentum, which we term hydrodynamic metals, and with many
patchwise almost-conserved momenta. For all these cases, we obtain universal
expressions for the ratio of conductivities that violate the Wiedemann-Franz
law. We further discuss the case in which long-lived `cold' quasiparticles, in
general with unconventional scattering rates, coexist with strongly interacting
hot spots, lines or bands. For these cases, we characterize circumstances under
which non-Fermi liquid transport, in particular a linear in temperature
resistivity, is and is not compatible with the Wiedemann-Franz law. We suggest
the likely outcome of future transport experiments on CeCoIn5, YbRh2Si2 and
Sr3Ru2O7 at their critical magnetic fields.",1304.4249v3
2014-05-15,Anomalous frequency and temperature dependent scattering and Hund's coupling in the almost quantum critical heavy fermion system CeFe$_2$Ge$_2$,"We present THz range optical conductivity data of a thin film of the near
quantum critical heavy fermion compound CeFe$_2$Ge$_2$. Our complex
conductivity measurements find a deviation from conventional Drude-like
transport in a temperature range previously reported to exhibit unconventional
behavior. We calculate the frequency dependent effective mass and scattering
rate using an extended Drude model analysis. We find the inelastic scattering
rate can be described by a temperature dependent power-law $\omega^{n(T)}$
where $n(T)$ approaches $\sim1.0 \pm 0.2$ at 1.5 K. This is compared to the
$\rho \sim T^{1.5}$ behavior claimed in dc resistivity data and the $\rho \sim
T^{2}$ expected from Fermi-liquid theory. In addition to a low temperature mass
renormalization, we find an anomalous mass renormalization that persists to
high temperature. We attribute this to a Hund's coupling in the Fe states in a
manner similar to that recently proposed in the ferro-pnictides. CeFe$_2$Ge$_2$
appears to be a very interesting system where one may study the interplay
between the usual $4f$ lattice Kondo effect and this Hund's enhanced Kondo
effect in the $3d$ states.",1405.4007v3
2014-05-23,Growth and characterization of heteroepitaxial La-substituted BaSnO$_3$ films on SrTiO$_3$ (001) and SmScO$_3$ (110) substrates,"Heteroepitaxial growth of BaSnO$_3$ (BSO) and Ba$_{1-x}$La$_x$SnO$_3$ (x = 7
%) (LBSO) thin films on different perovskite single crystal (SrTiO$_3$ (001)
and SmScO$_3$ (110)) substrates has been achieved by Pulsed Laser Deposition
(PLD) under optimized deposition conditions. X-ray diffraction measurements
indicate that the films on either of these substrates are relaxed due to the
large mismatch and present a high degree of crystallinity with narrow rocking
curves and smooth surface morphology while analytical quantification by proton
induced x-ray emission (PIXE) confirms the stoichiometric La transfer from a
polyphasic target, producing films with La contents above the bulk solubility
limit. The films show degenerate semiconducting behavior on both substrates,
with the observed room temperature resistivities, Hall mobilities and carrier
concentrations of 4.4 $m \Omega cm$, 10.11 $cm^2 V^{-1} s^{-1}$, and 1.38
$\cdot 10^{20} cm^{-3}$ on SmScO$_3$ and 7.8 $m \Omega cm$, 5.8 $cm^2 V^{-1}
s^{-1}$, and 1.36 $\cdot 10^{20} cm^{-3}$ on SrTiO$_3$ ruling out any extrinsic
contribution from the substrate. The superior electrical properties observed on
the SmScO3 substrate are attributed to reduction in dislocation density from
the lower lattice mismatch.",1405.6233v1
2014-05-31,Scale-Invariant Dissipationless Chiral Transport in Magnetic Topological Insulators beyond the Two-Dimensional Limit,"We investigate the quantum anomalous Hall Effect (QAHE) and related chiral
transport in the millimeter-size (Cr0.12Bi0.26Sb0.62)2Te3 films. With high
sample quality and robust magnetism at low temperatures, the quantized Hall
conductance of e2/h is found to persist even when the film thickness is beyond
the two-dimensional (2D) hybridization limit. Meanwhile, the Chern
insulator-featured chiral edge conduction is manifested by the non-local
transport measurements. In contrast to the 2D hybridized thin film, an
additional weakly field-dependent longitudinal resistance is observed in the 10
quintuple-layer film, suggesting the influence of the film thickness on the
dissipative edge channel in the QAHE regime. The extension of QAHE into the
three-dimensional thickness region addresses the universality of this quantum
transport phenomenon and motivates the exploration of new QAHE phases with
tunable Chern numbers. In addition, the observation of the scale-invariant
dissipationless chiral propagation on a macroscopic scale makes a major stride
towards ideal low-power interconnect applications.",1406.0106v2
2014-09-11,High performance solar cells based on graphene-GaAs heterostructures,"The honeycomb connection of carbon atoms by covalent bonds in a macroscopic
two-dimensional scale leads to fascinating graphene and solar cell based on
graphene/silicon Schottky diode has been widely studied. For solar cell
applications, GaAs is superior to silicon as it has a direct band gap of 1.42
eV and its electron mobility is six times of that of silicon. However,
graphene/GaAs solar cell has been rarely explored. Herein, we report
graphene/GaAs solar cells with conversion efficiency (Eta) of 10.4% and 15.5%
without and with anti-reflection layer on graphene, respectively. The Eta of
15.5% is higher than the state of art efficiency for graphene/Si system
(14.5%). Furthermore, our calculation points out Eta of 25.8% can be reached by
reasonably optimizing the open circuit voltage, junction ideality factor,
resistance of graphene and metal/graphene contact. This research strongly
support graphene/GaAs hetero-structure solar cell have great potential for
practical applications.",1409.3500v3
2014-10-13,Breakdown of Three-dimensional Dirac Semimetal State in pressurized Cd3As2,"We report the first observation of a pressure-induced breakdown of the 3D-DSM
state in Cd3As2, evidenced by a series of in-situ high-pressure synchrotron
X-ray diffraction (XRD) and single crystal transport measurements. We find that
Cd3As2 undergoes a structural phase transition from a metallic tetragonal (T)
phase in space group I41/acd to a semiconducting monoclinic (M) phase in space
group P21/c at critical pressure 2.57 GPa, above this pressure, an activation
energy gap appears, accompanied by distinct switches in Hall resistivity slope
and electron mobility. These changes of crystal symmetry and corresponding
transport properties manifest the breakdown of the 3D-DSM state in pressurized
Cd3As2.",1410.3213v4
2014-11-13,Analysis of viscoelastic soft dielectric elastomer generators operating in an electrical circuit,"A predicting model for soft Dielectric Elastomer Generators (DEGs) must
consider a realistic model of the electromechanical behaviour of the elastomer
filling, the variable capacitor and of the electrical circuit connecting all
elements of the device. In this paper such an objective is achieved by
proposing a complete framework for reliable simulations of soft energy
harvesters. In particular, a simple electrical circuit is realised by
connecting the capacitor, stretched periodically by a source of mechanical
work, in parallel with a battery through a diode and with an electrical load
consuming the energy produced. The electrical model comprises resistances
simulating the effect of the electrodes and of the conductivity current
invariably present through the dielectric film. As these devices undergo a high
number of electro-mechanical loading cycles at large deformation, the
time-dependent response of the material must be taken into account as it
strongly affects the generator outcome. To this end, the viscoelastic behaviour
of the polymer and the possible change of permittivity with strains are
analysed carefully by means of a proposed coupled electro-viscoelastic
constitutive model, calibrated on experimental data available in the literature
for an incompressible polyacrilate elastomer (3M VHB4910). Numerical results
showing the importance of time-dependent behaviour on the evaluation of
performance of DEGs for different loading conditions, namely equi-biaxial and
uniaxial, are reported in the final section.",1411.3613v2
2014-11-28,Growth control of the oxidation state in vanadium oxide thin films,"Precise control of the chemical valence or oxidation state of vanadium in
vanadium oxide thin films is highly desirable for not only fundamental
research, but also technological applications that utilize the subtle change in
the physical properties originating from the metal- insulator transition (MIT)
near room temperature. However, due to the multivalent nature of vanadium and
the lack of a good understanding on growth control of the oxidation state,
stabilization of phase pure vanadium oxides with a single oxidation state is
extremely challenging. Here, we systematically varied the growth conditions to
clearly map out the growth window for preparing phase pure epitaxial vanadium
oxides by pulsed laser deposition for providing a guideline to grow high
quality thin films with well-defined oxidation states of V2(+3)O3, V(+4)O2, and
V2(+5)O5. A well pronounced MIT was only observed in VO2 films grown in a very
narrow range of oxygen partial pressure P(O2). The films grown either in lower
(< 10 mTorr) or higher P(O2) (> 25 mTorr) result in V2O3 and V2O5 phases,
respectively, thereby suppressing the MIT for both cases. We have also found
that the resistivity ratio before and after the MIT of VO2 thin films can be
further enhanced by one order of magnitude when the films are further oxidized
by post-annealing at a well-controlled oxidizing ambient. This result indicates
that stabilizing vanadium into a single valence state has to compromise with
insufficient oxidation of an as grown thin film and, thereby, a subsequent
oxidation is required for an improved MIT behavior.",1411.7922v1
2014-12-05,Effects of Oxygen Adsorption on the Surface State of Epitaxial Silicene on Ag(111),"Epitaxial silicene, which is one single layer of silicon atoms packed in a
honeycomb structure, demonstrates a strong interaction with the substrate that
dramatically affects its electronic structure. The role of electronic coupling
in the chemical reactivity between the silicene and the substrate is still
unclear so far, which is of great importance for functionalization of silicene
layers. Here, we report the reconstructions and hybridized electronic
structures of epitaxial 4x4 silicene on Ag(111), which are revealed by scanning
tunneling microscopy and angle-resolved photoemission spectroscopy. The
hybridization between Si and Ag results in a metallic surface state, which can
gradually decay due to oxygen adsorption. X-ray photoemission spectroscopy
confirms the decoupling of Si-Ag bonds after oxygen treatment as well as the
relatively oxygen resistance of Ag(111) surface, in contrast to 4x4 silicene
[with respect to Ag(111)]. First-principles calculations have confirmed the
evolution of the electronic structure of silicene during oxidation. It has been
verified experimentally and theoretically that the high chemical activity of
4x4 silicene is attributable to the Si pz state, while the Ag(111) substrate
exhibits relatively inert chemical behavior.",1412.1887v1
2015-02-10,Ultrafast dynamic conductivity and scattering rate saturation of photoexcited charge carriers in silicon investigated with a midinfrared continuum probe,"We employ ultra-broadband terahertz-midinfrared probe pulses to characterize
the optical response of photoinduced charge-carrier plasmas in high-resistivity
silicon in a reflection geometry, over a wide range of excitation densities
(10^{15}-10^{19} cm^{-3}) at room temperature. In contrast to conventional
terahertz spectroscopy studies, this enables one to directly cover the
frequency range encompassing the resultant plasma frequencies. The intensity
reflection spectra of the thermalized plasma, measured using sum-frequency
(up-conversion) detection of the probe pulses, can be modeled well by a
standard Drude model with a density-dependent momentum scattering time of
approx. 200 fs at low densities, reaching approx. 20 fs for densities of
approx. 10^{19} cm^{-3}, where the increase of the scattering rate saturates.
This behavior can be reproduced well with theoretical results based on the
generalized Drude approach for the electron-hole scattering rate, where the
saturation occurs due to phase-space restrictions as the plasma becomes
degenerate. We also study the initial sub-picosecond temporal development of
the Drude response, and discuss the observed rise in the scattering time in
terms of initial charge-carrier relaxation, as well as the optical response of
the photoexcited sample as predicted by finite-difference time-domain
simulations.",1502.02829v1
2015-03-03,Construction of force measuring optical tweezers instrumentation and investigations of biophysical properties of bacterial adhesion organelles,"Optical tweezers are a technique in which microscopic-sized particles,
including living cells and bacteria, can be non-intrusively trapped with high
accuracy solely using focused light. The technique has therefore become a
powerful tool in the field of biophysics. Optical tweezers thereby provide
outstanding manipulation possibilities of cells as well as semi-transparent
materials, both non-invasively and non-destructively, in biological systems. In
addition, optical tweezers can measure minute forces (< 10-12 N), probe
molecular interactions and their energy landscapes, and apply both static and
dynamic forces in biological systems in a controlled manner. The assessment of
intermolecular forces with force measuring optical tweezers, and thereby the
biomechanical structure of biological objects, has therefore considerably
facilitated our understanding of interactions and structures of biological
systems. Adhesive bacterial organelles, so called pili, mediate adhesion to
host cells and are therefore crucial for the initial bacterial-cell contact.
Thus, they serve as an important virulence factor. The investigation of pili,
both their biogenesis and their expected in vivo properties, brings information
that can be of importance for the design of new drugs to prevent bacterial
infections, which is crucial in the era of increased bacterial resistance
towards antibiotics. In this thesis, an experimental setup of a force measuring
optical tweezers system and the results of a number of biomechanical
investigations of adhesive bacterial organelles are presented. Force measuring
optical tweezers have been used to characterize three different types of
adhesive organelles under various conditions, P, type 1, and S pili, which all
are expressed by uropathogenic Escherichia coli. A quantitative biophysical
force-extension model, built upon the structure and force response, has been
developed.",1503.00881v1
2015-03-30,Microbranching in mode-I fracture using large scale simulations of amorphous and perturbed lattice models,"We study the high-velocity regime mode-I fracture instability when small
microbranches start to appear near the main crack, using large scale
simulations. Some of the features of those microbranches have been reproduced
qualitatively in smaller scale studies (using ${\cal O}(10^4)$ atoms) on both a
model of an amorphous materials (via the continuous random network model) and
using perturbed lattice models. In this study, larger scale simulations (${\cal
O}(10^6)$ atoms) were performed using multi-threading computing on a GPU
device, in order to achieve more physically realistic results. First, we find
that the microbranching pattern appears to be converging with the lattice
width. Second, the simulations reproduce the growth of the size of a
microbranch as a function of the crack velocity, as well as the increase of the
amplitude of the derivative of the electrical resistance RMS with respect to
the time as a function of the crack velocity. In addition, the simulations
yield the correct branching angle of the microbranches, and the power law
governing the shape of the microbranches seems to be lower than one, so that
the side cracks turn over in the direction of propagation of the main crack as
seen in experiment.",1503.08616v2
2016-04-12,An invisible non-volatile solid-state memory,"Information technologies require entangling data stability with encryption
for a next generation of secure data storage. Current magnetic memories,
ranging from low-density stripes up to high-density hard drives, can ultimately
be detected using routinely available probes or manipulated by external
magnetic perturbations. Antiferromagnetic resistors feature unrivalled
robustness but the stable resistive states reported scarcely differ by more
than a fraction of a percent at room temperature. Here we show that the
metamagnetic (ferromagnetic to antiferromagnetic) transition in intermetallic
Fe0.50Rh0.50 can be electrically controlled in a magnetoelectric
heterostructure to reveal or cloak a given ferromagnetic state. From an aligned
ferromagnetic phase, magnetic states are frozen into the antiferromagnetic
phase by the application of an electric field, thus eliminating the stray field
and likewise making it insensitive to external magnetic field. Application of a
reverse electric field reverts the antiferromagnetic state to the original
ferromagnetic state. Our work demonstrates the building blocks of a feasible,
extremely stable, non-volatile, electrically addressable, low-energy
dissipation, magnetoelectric multiferroic memory.",1604.03383v2
2016-05-19,Robust two-dimensional superconductivity and vortex system in Bi2Te3/FeTe heterostructures,"The discovery of two-dimensional superconductivity in Bi2Te3/FeTe
heterostructure provides a new platform for the search of Majorana fermions in
condensed matter systems. Since Majorana fermions are expected to reside at the
core of the vortices, a close examination of the vortex dynamics in
superconducting interface is of paramount importance. Here, we report the
robustness of the interfacial superconductivity and 2D vortex dynamics in four
as-grown and aged Bi2Te3/FeTe heterostructure with different Bi2Te3 epilayer
thickness (3, 5, 7, 14 nm). After two years' air exposure, superconductivity
remains robust even when the thickness of Bi2Te3 epilayer is down to 3 nm.
Meanwhile, a new feature at ~13 K is induced in the aged samples, and the high
field studies reveal its relevance to superconductivity. The resistance of all
as-grown and aged heterostructures, just below the superconducting transition
temperature follows the Arrhenius relation, indicating the thermally activated
flux flow behavior at the interface of Bi2Te3 and FeTe. Moreover, the
activation energy exhibits a logarithmic dependence on the magnetic field,
providing a compelling evidence for the 2D vortex dynamics in this novel
system. The weak disorder associated with aging-induced Te vacancies is
possibly responsible for these observed phenomena.",1605.05903v1
2016-07-06,Chiral anomaly from strain-induced gauge fields in Dirac and Weyl semimetals,"Dirac and Weyl semimetals form an ideal platform for testing ideas developed
in high energy physics to describe massless relativistic particles. One such
quintessentially field-theoretic idea of chiral anomaly already resulted in the
prediction and subsequent observation of the pronounced negative
magnetoresistance in these novel materials for parallel electric and magnetic
fields. Here we predict that the chiral anomaly occurs - and has experimentally
observable consequences - when real electromagnetic fields E and B are replaced
by strain-induced pseudo-electromagnetic fields e and b. For example, a uniform
pseudomagnetic field b is generated when a Weyl semimetal nanowire is put under
torsion. In accord with the chiral anomaly equation we predict a negative
contribution to the wire resistance proportional to the square of the torsion
strength. Remarkably, left and right moving chiral modes are then spatially
segregated to the bulk and surface of the wire forming a ""topological coaxial
cable"". This produces hydrodynamic flow with potentially very long relaxation
time. Another effect we predict is the ultrasonic attenuation and
electromagnetic emission due to a time periodic mechanical deformation causing
pseudoelectric field e. These novel manifestations of the chiral anomaly are
most striking in the semimetals with a single pair of Weyl nodes but also occur
in Dirac semimetals such as Cd3As2 and Na3Bi and Weyl semimetals with unbroken
time reversal symmetry.",1607.01810v2
2016-11-17,Interfacial thermal conductance in graphene/black phosphorus heterogeneous structures,"Graphene, as a passivation layer, can be used to protect the black phosphorus
from the chemical reaction with surrounding oxygen and water. However, black
phosphorus and graphene heterostructures have low efficiency of heat
dissipation due to its intrinsic high thermal resistance at the interfaces. The
accumulated energy from Joule heat has to be removed efficiently to avoid the
malfunction of the devices. Therefore, it is of significance to investigate the
interfacial thermal dissipation properties and manipulate the properties by
interfacial engineering on demand. In this work, the interfacial thermal
conductance between few-layer black phosphorus and graphene is studied
extensively using molecular dynamics simulations. Two critical parameters, the
critical power Pcr to maintain thermal stability and the maximum heat power
density Pmax with which the system can be loaded, are identified. Our results
show that interfacial thermal conductance can be effectively tuned in a wide
range with external strains and interracial defects. The compressive strain can
enhance the interfacial thermal conductance by one order of magnitude, while
interface defects give a two-fold increase. These findings could provide
guidelines in heat dissipation and interfacial engineering for thermal
conductance manipulation of black phosphorus-graphene heterostructure-based
devices.",1611.05598v1
2017-06-08,Electronic and phonon excitations in α-RuCl$_3$,"We report on THz, infrared reflectivity and transmission experiments for wave
numbers from 10 to 8000 cm$^{-1}$ ($\sim$ 1 meV - 1 eV) and for temperatures
from 5 to 295 K on the Kitaev candidate material {\alpha}-RuCl$_3$. As reported
earlier, the compound under investigation passes through a first-order
structural phase transition, from a monoclinic high-temperature to a
rhombohedral low-temperature phase. The phase transition shows an extreme and
unusual hysteretic behavior, which extends from 60 to 166 K. In passing this
phase transition, in the complete frequency range investigated we found a
significant reflectance change, which amounts almost a factor of two. We
provide a broadband spectrum of dielectric constant, dielectric loss and
optical conductivity from the THz to the mid infrared regime and study in
detail the phonon response and the low-lying electronic density of states. We
provide evidence for the onset of an optical energy gap, which is of order 200
meV, in good agreement with the gap derived from measurements of the DC
electrical resistivity. Remarkably, the onset of the gap exhibits a strong blue
shift on increasing temperatures.",1706.02724v2
2017-10-03,Holographic model for the anomalous scalings of the cuprates,"We examine transport in a holographic model in which the dynamics of the
charged degrees of freedom is described by the nonlinear Dirac-Born-Infeld
(DBI) action. Axionic scalar fields are included to break translational
invariance and generate momentum dissipation in the system. Scaling exponents
are introduced by using geometries which are nonrelativistic and
hyperscaling-violating in the infrared. In the probe DBI limit the theory
reproduces the anomalous temperature dependence of the resistivity and Hall
angle of the cuprate strange metals, $\rho \sim T$ and $\cot\Theta_H \sim T^2$.
These scaling laws would not be present without the nonlinear dynamics encoded
by the DBI interactions. We further show that because of its richness the DBI
theory supports a wide spectrum of temperature scalings. This model provides
explicit examples in which transport is controlled by different relaxation
times. On the other hand, when only one quantity sets the temperature scale of
the system, the Hall angle and conductivity typically exhibit the same
temperature behavior. We illustrate this point using new fully backreacted
analytical dyonic black brane solutions.",1710.01326v2
2018-01-31,The origin of Mooij correlations in disordered metals,"Sufficiently disordered metals display systematic deviations from the
behavior predicted by semi-classical Boltzmann transport theory. Here the
scattering events from impurities or thermal excitations can no longer be
considered as additive independent processes, as asserted by Matthiessen's rule
following from this picture. In the intermediate region between the regime of
good conduction and that of insulation, one typically finds a change of sign of
the temperature coefficient of resistivity (TCR), even at elevated temperature
spanning ambient conditions, a phenomenology that was first identified by Mooij
in 1973. Traditional weak coupling approaches to identify relevant corrections
to the Boltzmann picture focused on long distance interference effects such as
""weak localization"", which are especially important in low dimensions (1D, 2D)
and close to the zero temperature limit. Here we formulate a strong-coupling
approach to tackle the interplay of strong disorder and lattice deformations
(phonons) in bulk three-dimensional metals at high temperatures. We identify a
polaronic mechanism of strong disorder renormalization, which describes how a
lattice locally responds to the relevant impurity potential. This mechanism,
which quantitatively captures the Mooij regime, is physically distinct and
unrelated to Anderson localization, but realizes early seminal ideas of
Anderson himself, concerning the interplay of disorder and lattice
deformations.",1802.00065v4
2018-05-30,Hikami-Larkin-Nagaoka (HLN) treatment of the Magneto Conductivity of Bi2Te3 Topological Insulator,"We report the magneto-conductivity analysis at different temperatures under
magnetic field of up to 5Tesla of a well characterized Bi2Te3 crystal. Details
of crystal growth and various physical properties including high linear magneto
resistance are already reported by some of us. To elaborate upon the transport
properties of Bi2Te3 crystal, the magneto conductivity is fitted to the known
HLN (Hikami Larkin Nagaoka) equation and it is found that the conduction
mechanism is dominated by both surface driven WAL (weak anti localization) and
the bulk WL states. The value of HLN equation coefficient signifying the type
of localization (WL, WAL or both WL and WAL) falls within the range of -0.5 to
-1.5. In our case, the low field (0.25Tesla) fitting of studied crystal
exhibited value close to -0.86 for studied temperatures of up to 50K,
indicating both WAL and WL contributions. The phase coherence length is found
to decrease from 98.266 to 40.314nm with increasing temperature. Summarily, the
short letter reports the fact that bulk Bi2Te3 follows the HLN equation and
quantitative analysis of the same facilitates to know the quality of studied
crystal in terms of WAL to WL contributions and thus the surface to bulk
conduction ratio.",1805.11822v1
2018-06-18,Band structure and Fermi surfaces of the reentrant ferromagnetic superconductor Eu(Fe0.86Ir0.14)2As2,"The electronic structure of the reentrant superconductor
Eu(Fe$_{0.86}$Ir$_{0.14}$)$_{2}$As$_{2}$ (T$_c$ = 22 K) with coexisting
ferromagnetic order (T$_M$ = 18 K) is investigated using angle-resolved
photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy (STS).
We study the in-plane and out-of-plane band dispersions and Fermi surface (FS)
of Eu(Fe$_{0.86}$Ir$_{0.14}$)$_{2}$As$_{2}$. The near E$_F$ Fe 3d-derived band
dispersions near the $\Gamma$ and X high-symmetry points show changes due to Ir
substitution, but the FS topology is preserved. From momentum dependent
measurements of the superconducting gap measured at T = 5 K, we estimate an
essentially isotropic s-wave gap ($\Delta\sim5.25\pm 0.25$ meV), indicative of
strong-coupling superconductivity with 2$\Delta$/k$_{B}$T$_{c}\simeq$ 5.8. The
gap gets closed at temperatures T $\geq$ 10 K, and this is attributed to the
resistive phase which sets in at T$_M$ = 18 K due to the Eu$^{2+}$-derived
magnetic order. The modifications of the FS with Ir substitution clearly
indicates an effective hole doping with respect to the parent compound.",1806.06563v1
2018-09-26,Nanoscale Intergranular Corrosion and Relation With Grain Boundary Character as Studied In Situ on Copper,"The initiation of intergranular corrosion at various types of grain
boundaries (GBs) was studied at the nanometer scale on microcrystalline copper
in 1 mM HCl aqueous solution. In situ Electrochemical Scanning Tunneling
Microscopy (ECSTM) and Electron Back-Scatter Diffraction analysis of the same
local microstructural region were combined using an innovative methodology
including micro marking performed with the STM tip. The results demonstrate
that electrochemically-induced intergranular dissolution, at the surface
termination of GBs, is dependent on the grain boundary character. It is found
that random high angle boundaries as well as sigma9 coincidence site lattice
(CSL) boundaries are susceptible to nanoscale initiation of intergranular
corrosion while for sigma3 CSL boundaries the behavior is dependent on the
deviation angle of the GB plane from the exact orientation. For the sigma3
twins, a transition from resistance to susceptibility occurs between 1{\deg}
and 1.7{\deg} of deviation as a result of the increase of the density of steps
(i.e. misorientation dislocations) in the coincidence boundary plane. The work
emphasizes the precision needed in the design of the grain boundary network in
applications where intergranular corrosion or its initiation must be controlled
at the nanoscale.",1809.09872v1
2018-11-14,Multifrequency Nanoscale Impedance Microscopy (m-NIM): A novel approach towards detection of selective and subtle modifications on the surface of polycrystalline boron-doped diamond electrodes,"In this paper, we describe the modification of Nanoscale Impedance Microscopy
(NIM), namely, a combination of contact-mode atomic force microscopy with local
impedance measurements. The postulated approach is based on the application of
multifrequency voltage perturbation instead of standard frequency-by-frequency
analysis, which among others offers more time-efficient and accurate
determination of the resultant impedance spectra with high spatial resolution.
Based on the impedance spectra analysis with an appropriate electric equivalent
circuit, it was possible to map surface resistance and contact capacitance.
Polycrystalline heavy boron-doped diamond (BDD) electrodes were the research
object. Recent studies have shown that the exposure of such electrodes to
oxidizing environment may result in the modification of termination type, and
thus it is a key factor in describing the electric and electrochemical
properties of BDD. We have successfully applied multifrequency NIM, which
allowed us to prove that the modification of termination type is selective and
occurs with different propensity on the grains having specific crystallographic
orientation. Furthermore, our approach enabled the detection of even subtle
submicroscopic surface heterogeneities, created as a result of various
oxidation treatments and to distinguish them from the surface heterogeneity
related to the local distribution of boron at the grain boundaries.",1811.05709v1
2019-05-12,Nodeless superconductivity and preserved time-reversal symmetry in the noncentrosymmetric Mo3P superconductor,"We report a comprehensive study of the noncentrosymmetric superconductor
Mo$_3$P. Its bulk superconductivity, with $T_c = 5.5$ K, was characterized via
electrical resistivity, magnetization, and heat-capacity measurements, while
its microscopic electronic properties were investigated by means of muon-spin
rotation/relaxation ($\mu$SR) and nuclear magnetic resonance (NMR) techniques.
In the normal state, NMR relaxation data indicate an almost ideal metallic
behavior, confirmed by band-structure calculations, which suggest a relatively
high electron density of states, dominated by the Mo $4d$-orbitals. The
low-temperature superfluid density, determined via transverse-field $\mu$SR and
electronic specific heat, suggest a fully-gapped superconducting state in
Mo$_3$P, with $\Delta_0= 0.83$ meV, the same as the BCS gap value in the
weak-coupling case, and a zero-temperature magnetic penetration depth
$\lambda_0 = 126$ nm. The absence of spontaneous magnetic fields below the
onset of superconductivity, as determined from zero-field $\mu$SR measurements,
indicates a preserved time-reversal symmetry in the superconducting state of
Mo$_3$P and, hence, spin-singlet pairing.",1905.04726v1
2019-05-28,Electronic structure and $H$-$T$ phase diagram of Eu(Fe$_{1-x}$Rh$_x$)$_2$As$_2$,"The iron-based superconductors represent a promising platform for
high-temperature superconductivity, but the interactions underpinning their
pairing present a puzzle. The EuFe$_2$As$_2$ family is unique among these
materials for having magnetic order which onsets within the superconducting
state, just below the superconducting transition. Superconductivity and
magnetic order are normally antagonistic and often vie for the same unpaired
electrons, but in this family the magnetism arises from largely localized Eu
moments and they coexist, with the competition between these evenly-matched
opponents leading to reentrant superconducting behavior. To help elucidate the
physics in this family and the interactions between the magnetic order and
superconductivity, we investigate the $H$--$T$ phase diagram near optimal Rh
doping through specific heat, resistivity, and magnetization measurements, and
study the electronic structure by angular-resolved photoemission spectroscopy.
The competition between the Eu and FeAs layers may offer a route to directly
accessing the electronic structure under effective magnetic fields via ARPES,
which is ordinarily a strictly zero-field technique.",1905.11554v2
2019-09-10,New and fast route to black TiO2 based on hollow cathode H2 plasma,"In this work, we demonstrate a new method to produce black TiO2 from pristine
anatase TiO2 films. It consists on the immersion of TiO2 films in a hollow
cathode H2 RF plasma for a few minutes, resulting in an efficient blackening of
TiO2. In this study, the pristine anatase TiO2 films were grown by magnetron
sputtering onto cover glass and c-Si substrates and then annealed at 450
{\deg}C for 2 h. Before and after the hollow cathode H2 plasma treatment, the
samples were characterized by profilometry, UV-Vis spectrophotometry, X-ray
diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field
emission scanning electron and atomic force microscopies, and four-point probe
measurements. The results show that the obtained black TiO2 thin films have a
significant light absorption on the whole solar spectrum, a very low sheet
resistance, and also a relatively high surface area when compared to the
pristine TiO2. All these characteristics lead to an important improvement on
their photocatalytic activity, as measured by the degradation rate of methylene
blue under UV irradiation.",1909.04623v1
2019-09-27,Superconducting proximity effect in InAsSb surface quantum wells with in-situ Al contact,"We demonstrate robust superconducting proximity effect in
InAs$_{0.5}$Sb$_{0.5}$ quantum wells grown with epitaxial Al contact, which has
important implications for mesoscopic and topological superconductivity. Unlike
more commonly studied InAs and InSb semiconductors, bulk InAs$_{0.5}$Sb$_{0.5}$
supports stronger spin-orbit coupling and larger $g$-factor. However, these
potentially desirable properties have not been previously measured in epitaxial
heterostructures with superconductors, which could serve as a platform for
fault-tolerant topological quantum computing. Through structural and transport
characterization we observe high-quality interfaces and strong spin-orbit
coupling. We fabricate Josephson junctions based on InAs$_{0.5}$Sb$_{0.5}$
quantum wells and observe strong proximity effect. These junctions exhibit
product of normal resistance and critical current, $I_{c}R_{N} =
\SI{270}{\micro V}$, and excess current, $I_{ex}R_{N} = \SI{200}{\micro V}$ at
contact separations of 500~nm. Both of these quantities demonstrate a robust
and long-range proximity effect with highly-transparent contacts.",1909.12571v2
2020-03-15,Vacancy diffusion in multi-principal element alloys: the role of chemical disorder in the ordered lattice,"Many of the purported virtues of Multi-Principal Element Alloys (MPEAs), such
as corrosion, high-temperature oxidation and irradiation resistance, are highly
sensitive to vacancy diffusivity. Similarly, solute interdiffusion is governed
by vacancy diffusion -- it is often unclear whether MPEAs are truly stable, or
effectively stabilized by slow interdiffusion. The considerable composition
space afforded to these alloys makes optimizing for desired properties a
daunting task; theoretical and computational tools are necessary to guide alloy
development. For diffusion, such tools depend on both a knowledge of the
vacancy migration barriers within a given alloy and an understanding of how
these barriers influence vacancy diffusivity. We present a generalized theory
of vacancy diffusion in rugged energy landscapes, paired with Kinetic Monte
Carlo simulations of MPEA vacancy diffusion. The barrier energy statistics are
informed by nudged elastic band calculations in the equiatomic CoNiCrFeMn
alloy. Theory and simulations show that vacancy diffusion in solid-solution
MPEAs is not necessarily sluggish, but can potentially be tuned, and that trap
models are an insufficient explanation for sluggish diffusion in the CoNiCrFeMn
HEA. These results also show that any model that endeavors to faithfully
represent diffusion-related phenomena must account for the full nature of the
energy landscape, not just the migration barriers.",2003.06900v2
2017-03-28,Indium substitution effect on the topological crystalline insulator family (Pb$_{1-x}$Sn$_{x}$)$_{1-y}$In$_{y}$Te: Topological and superconducting properties,"Topological crystalline insulators (TCIs) have been of great interest in the
area of condensed matter physics. We investigated the effect of indium
substitution on the crystal structure and transport properties in the TCI
system (Pb$_{1-x}$Sn$_{x}$)$_{1-y}$In$_{y}$Te. For samples with a tin
concentration $x\le50\%$, the low-temperature resisitivities show a dramatic
variation as a function of indium concentration: with up to ~2% indium doping
the samples show weak-metallic behavior, similar to their parent compounds;
with ~6% indium doping, samples have true bulk-insulating resistivity and
present evidence for nontrivial topological surface states; with higher indium
doping levels, superconductivity was observed, with a transition temperature,
Tc, positively correlated to the indium concentration and reaching as high as
4.7 K. We address this issue from the view of bulk electronic structure
modified by the indium-induced impurity level that pins the Fermi level. The
current work summarizes the indium substitution effect on (Pb,Sn)Te, and
discusses the topological and superconducting aspects, which can be provide
guidance for future studies on this and related systems.",1703.09836v1
2019-02-22,Development of transmon qubits solely from optical lithography on 300mm wafers,"Qubit information processors are increasing in footprint but currently rely
on e-beam lithography for patterning the required Josephson junctions (JJs).
Advanced optical lithography is an alternative patterning method, and we report
on the development of transmon qubits patterned solely with optical
lithography. The lithography uses 193 nm wavelength exposure and 300-mm large
silicon wafers. Qubits and arrays of evaluation JJs were patterned with process
control which resulted in narrow feature distributions: a standard deviation of
0:78% for a 220 nm linewidth pattern realized across over half the width of the
wafers. Room temperature evaluation found a 2.8-3.6% standard deviation in JJ
resistance in completed chips. The qubits used aluminum and titanium nitride
films on silicon substrates without substantial silicon etching. T1 times of
the qubits were extracted at 26 - 27 microseconds, indicating a low level of
material-based qubit defects. This study shows that large wafer optical
lithography on silicon is adequate for high-quality transmon qubits, and shows
a promising path for improving many-qubit processors.",1902.08501v1
2019-06-30,Evaluating Superconductors through Current Induced Depairing,"The phenomenon of superconductivity occurs in the phase space of three
principal parameters: temperature T, magnetic field B, and current density Jd .
The critical temperature Tc is one of the first parameters that is measured and
in a certain way defines the superconductor. From the practical applications
point of view, of equal importance is the upper critical magnetic field Bc2 and
conventional critical current density Jc (above which the system begins to show
resistance without entering the normal state). However, a seldom-measured
parameter, the depairing current density Jd , holds the same fundamental
importance as Tc and Bc2, in that it defines a boundary between the
superconducting and normal states. A study of Jd sheds unique light on other
important characteristics of the superconducting state such as the superfluid
density and the nature of the normal state below Tc, information that can play
a key role in better understanding newly-discovered superconducting materials.
From a measurement perspective, the extremely high values of Jd make it
difficult to measure, which is the reason why it is seldom measured. Here, we
will review the fundamentals of current-induced depairing and the fast-pulsed
current technique that facilitates its measurement and discuss the results of
its application to the topological-insulator/chalcogenide interfacial
superconducting system.
  Keywords: pairbreaking, pair-breaking, vortex, vortices, theory, tutorial,
RTS, room-temperature supeconductivity",1907.00427v1
2019-07-29,Imaging Nematic Transitions in Iron-Pnictide Superconductors with a Quantum Gas,"The SQCRAMscope is a recently realized Scanning Quantum CRyogenic Atom
Microscope that utilizes an atomic Bose-Einstein condensate to measure magnetic
fields emanating from solid-state samples. The quantum sensor does so with
unprecedented DC sensitivity at micron resolution from room-to-cryogenic
temperatures. An additional advantage of the SQCRAMscope is the preservation of
optical access to the sample: Magnetometry imaging of, e.g., electron transport
may be performed in concert with other imaging techniques. This multimodal
imaging capability can be brought to bear with great effect in the study of
nematicity in iron-pnictide high-temperature superconductors, where the
relationship between electronic and structural symmetry-breaking resulting in a
nematic phase is under debate. Here, we combine the SQCRAMscope with an in situ
microscope that measures optical birefringence near the surface. This enables
simultaneous and spatially resolved detection of both bulk and near-surface
manifestations of nematicity via transport and structural deformation channels,
respectively. By performing the first local measurement of emergent resistivity
anisotropy in iron pnictides, we observe sharp, nearly concurrent transport and
structural transitions. More broadly, these measurements demonstrate the
SQCRAMscope's ability to reveal important insights into the physics of complex
quantum materials.",1907.12601v2
2020-02-05,Impact of Residual Carbon Impurities and Gallium Vacancies on Trapping Effects in AlGaN/GaN MIS-HEMTs,"Effects of residual C impurities and Ga vacancies on the dynamic
instabilities of AlN/AlGaN/GaN metal insulator semiconductor high electron
mobility transistors are investigated. Secondary ion mass spectroscopy,
positron annihilation spectroscopy, steady state and time-resolved
photoluminescence (PL) measurements have been performed in conjunction with
electrical characterization and current transient analyses. The correlation
between yellow luminescence (YL), C- and Ga vacancy concentration is
investigated. Time-resolved PL indicating the C$_{\mathrm{N}}$O$_{\mathrm{N}}$
complex as the main source of the YL, while Ga vacancies or related complexes
with C seem not to play a major role. The device dynamic performance is found
to be significantly dependent on the C concentration close to the channel of
the transistor. Additionally, the magnitude of the YL is found to be in
agreement with the threshold voltage shift and with the on-resistance
degradation. Trap analysis of the GaN buffer shows an apparent activation
energy of $\sim$0.8eV for all samples, pointing to a common dominating trapping
process and that the growth parameters affect solely the density of trap
centres. It is inferred that the trapping process is likely to be directly
related to C based defects.",2002.01952v1
2020-04-17,Magnetic correlations in subsystems of the misfit [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$] cobaltate,"[Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$], a two dimensional misfit metallic
compound, is famous for its rich phases accessed by temperature, $i.e.$ high
temperature spin-state transition, metal-insulator transition (MIT) at
intermediate temperature ($\sim$ 100 K) and low temperature spin density wave
(SDW). It enters into SDW phase below T$_{MIT}$ which becomes long range at 27
K. Information on the independent role of misfit layers (rocksalt/Ca$_2$CoO$_3$
\& triangular/CoO$_2$) in these phases is scarce. By combining a set of
complementary macroscopic (DC magnetization and resistivity) and microscopic
(neutron diffraction and X-ray absorption fine structure spectroscopy)
measurements on pure (CCO) and Tb substituted in the rocksalt layer of CCO
(CCO1), magnetic correlations in both subsystems of this misfit compound are
unraveled. CCO is found to exhibit glassiness, as well as exchange bias (EB)
effects, while CCO1 does not exhibit glassiness, albeit it shows weaker EB
effect. By combining local structure investigations from extended X-ray
absorption fine structure (EXAFS) spectroscopy and neutron diffraction results
on CCO, we confirm that the SDW arises in the CoO$_2$ layer. Our results show
that the magnetocrystalline anisotropy associated with the rocksalt layer acts
as a source of pinning, which is responsible for EB effect. Ferromagnetic
clusters in the Ca$_2$CoO$_3$ affects SDW in CoO$_2$ and ultimately glassiness
arises.",2004.08319v2
2020-08-31,Electronic properties in itinerant ferromagnet SrRu$_{1-x}$Ti$_x$O$_3$,"Here, we study the electrical transport and specific heat in 4$d$ based
ferromagnetic material SrRuO$_3$ and its Ti substituted SrRu$_{1-x}$Ti$_x$O$_3$
series ($x$ $\le$ 0.7). The SrRuO$_3$ is a metal and shows itinerant
ferromagnetism with transition temperature $T_c$ $\sim$ 160 K. The nonmagnetic
Ti$^{4+}$ (3$d^0$) substitution would not only weaken the active Ru-O-Ru
channel but is also expected to tune the electronic density and electron
correlation effect. A metal to insulator transition has been observed around
$x$ $\sim$ 0.4. The nature of charge transport in paramagnetic-metallic state
($x$ $\leq$ 0.4) and in insulating state ($x$ $>$ 0.4) follows modified Mott's
variable range hopping model. In ferromagnetic-metallic state, resistivity
shows a $T^2$ dependence below $T_c$ which though modifies to $T^{3/2}$
dependence at low temperature. In Ti substituted samples, temperature range for
$T^{3/2}$ dependence extends to higher temperature. Interestingly, this
$T^{3/2}$ dependence dominates in whole ferromagnetic regime in presence of
magnetic field. This evolution of electronic transport behavior can be
explained within the framework of Fermi liquid theory and electron-magnon
scattering mechanism. The negative magnetoresistance exhibits a hysteresis and
a crossover between negative and positive value with magnetic field which is
connected with magnetic behavior in series. The decreasing electronic
coefficient of specific heat with $x$ supports the increasing insulating
behavior in present series. We calculate a high Kadowaki-Woods ratio ($x$
$\leq$ 0.3) for SrRuO$_3$ which increases with substitution concentration. This
signifies an increasing electronic correlation effect with substitution
concentration.",2009.00076v1
2007-10-21,Change of strength of vortex pinning in YBCO due to BaZrO_3 inclusions,"We probe the short-range pinning properties with the application of microwave
currents at very high driving frequencies (47.7 GHz) on
YBa$_2$Cu$_3$O$_{7-\delta}$ films with and without sub-micrometer BaZrO$_3$
inclusions. We explore the temperature and field ranges 60 K$<T<T_c$ and
0$<\mu_0H<$0.8 T, with the field applied along the c-axis. The magnetic field
induces a much smaller increase of the microwave resistivity, $\Delta
\rho_1(H)+\mathrm{i}\Delta \rho_2(H)$, in YBa$_2$Cu$_3$O$_{7-\delta}$/BaZrO$_3$
with respect to pure YBa$_2$Cu$_3$O$_{7-\delta}$. $\Delta \rho_1(H)$ is
slightly superlinear in pure YBa$_2$Cu$_3$O$_{7-\delta}$ (suggesting a possible
contribution of thermal activation), but linear or sublinear in
YBa$_2$Cu$_3$O$_{7-\delta}$/BaZrO$_3$ (suggesting a possible suppression of
thermal activation as a consequence of BaZrO$_3$ inclusions). These features
persist up to close to $T_c$. We discuss our data in terms of the ratio
$r=\Delta X_s'(H)/\Delta R_s'(H)$ in the framework of the models for the
microwave surface impedance in the mixed state. Large $r$ are found in
YBa$_2$Cu$_3$O$_{7-\delta}$/BaZrO$_3$, with little field dependence. By
contrast, smaller values and stronger field dependences are found in pure
YBa$_2$Cu$_3$O$_{7-\delta}$. We discuss the different field dependence of the
pinning constant.",0710.3943v1
2017-05-01,Selective mass enhancement close to the quantum critical point in BaFe$_2$(As$_{1-x}$P$_x$)$_2$,"A quantum critical point (QCP) is currently being conjectured for the
BaFe$_2$(As$_{1-x}$P$_x$)$_2$ system at the critical value $x_{\rm c} \approx$
0.3. In the proximity of a QCP, all thermodynamic and transport properties are
expected to scale with a single characteristic energy, given by the quantum
fluctuations. Such an universal behavior has not, however, been found in the
superconducting upper critical field $H_{\rm c2}$. Here we report $H_{\rm
c2}$-data for epitaxial thin films extracted from the electrical resistance
measured in very high magnetic fields up to 67 Tesla. Using a multi-band
analysis we find that $H_{\rm c2}$ is sensitive to the QCP, implying a
significant charge carrier effective mass enhancement at the doping-induced QCP
that is essentially band-dependent. Our results point to two qualitatively
different groups of electrons in BaFe$_2$(As$_{1-x}$P$_x$)$_2$. The first one
(possibly associated to hot spots or whole Fermi sheets) has a strong mass
enhancement at the QCP, and the second one is insensitive to the QCP. The
observed duality could also be present in many other quantum critical systems.",1705.00695v1
2017-07-31,Superconductivity at 5 K in quasi-one-dimensional Cr-based KCr3As3 single crystals,"Recently a new family of Cr-based A2Cr3As3 (A = K, Rb, Cs) superconductors
were reported, which own a rare quasi-one-dimensional (Q1D) crystal structure
with infinite (Cr3As3)2- chains and exhibit intriguing superconducting
characteristics possibly derived from spin-triplet electron pairing. The
crystal structure of A2Cr3As3 is actually a slight variation of the hexagonal
TlFe3Te3 prototype although they have different lattice symmetry. Here we
report superconductivity in a 133-type KCr3As3 compound that belongs to the
latter structure. The single crystals of KCr3As3 were prepared by the
deintercalation of K ions from K2Cr3As3 crystals which were grown from a
high-temperature solution growth method, and it owns a centrosymmetric lattice
in contrast to the non-centrosymmetric K2Cr3As3. After annealing at a moderate
temperature, the KCr3As3 crystals show bulk superconductivity at 5 K revealed
by electrical resistivity, magnetic susceptibility and heat capacity
measurements. The discovery of this KCr3As3 superconductor provides a different
structural instance to study the exotic superconductivity in these Q1D Cr-based
superconductors.",1707.09711v1
2019-12-23,Antimonene/Bismuthene Vertical Van-der Waals Heterostructure: A Computational Study,"In this paper, the structural, electronic, mechanical and optical properties
of antimonene-bismuthene Van-der Waals heterostructure (Sb-Bi HS) were
calculated based on the first principle density functional theory. We explored
different stacks of Sb-Bi HS to find the most and the least stable staking for
this heterostructure. At the GGA level of theory, the most stable model is a
semiconductor with an indirect band gap of 159 meV. However, when the
spin-orbit (SO) interaction is considered, the VBM and CBM touch the Fermi
level and the HS becomes a semimetal. Our results also show that the electronic
properties of the HS are robust against the external electric field and biaxial
strain. Young modulus was calculated as 64.3N/M which predicts this HS as a
resistant material against being stretched or compressed.
  The calculated optical properties, similar to monolayer antimonene, are
completely dependent on the polarization of incident light and differ when
parallel or perpendicular polarization is considered. Moreover, the absorption
coefficient for perpendicular polarization in the visible region is
significantly increased in comparison with the monolayer antimonene. High
structural stability, electronic and mechanical robustness against electric
field and strain, along with polarization-dependent optical properties of this
HS, promise for its applications in beam splitters and nano-scale mirrors.",1912.10978v2
2021-01-01,An Electronic Textile Embedded Smart Cementitious Composite,"Structural health monitoring (SHM) using self-sensing cement-based materials
has been reported before, where nano-fillers have been incorporated in
cementitious matrices as functional sensing elements. A percolation threshold
is always required in order for conductive nano-fillers modified concrete to be
useful for SHM. Nonetheless, the best pressure/strain sensitivity results
achieved for any self-sensing cementitious matrix are <0.01 MPa-1. In this
work, we introduce novel reduced graphene oxide (RGO) based electronic textile
(e-textile) embedded in plain and polymer-binder-modified cementitious matrix
for SHM applications. As a proof of concept, it was demonstrated that these
coated fabric-based sensors can be successfully embedded within the
cement-based structures, which are independent of any percolation threshold due
to the interconnected fabric inside the host matrix. The piezo-resistive
response was measured by applying direct and cyclic compressive loads (0.1 to
3.9 MPa). A pressure sensitivity of 1.5 MPa-1 and an ultra-high gauge factor of
2000 was obtained for the system of the self-sensing cementitious structure
with embedded e-textiles. The sensitivity of this new system with embedded
e-textile is many orders of magnitude higher than nanoparticle based
self-sensing of cementitious composites. The manufactured e-textile sensors
showed mechanical stability and functional durability over long-term cyclic
compression tests of 1000 cycles.",2101.00140v1
2021-01-13,A reusable pipeline for large-scale fiber segmentation on unidirectional fiber beds using fully convolutional neural networks,"Fiber-reinforced ceramic-matrix composites are advanced materials resistant
to high temperatures, with application to aerospace engineering. Their analysis
depends on the detection of embedded fibers, with semi-supervised techniques
usually employed to separate fibers within the fiber beds. Here we present an
open computational pipeline to detect fibers in ex-situ X-ray computed
tomography fiber beds. To separate the fibers in these samples, we tested four
different architectures of fully convolutional neural networks. When comparing
our neural network approach to a semi-supervised one, we obtained Dice and
Matthews coefficients greater than $92.28 \pm 9.65\%$, reaching up to $98.42
\pm 0.03 \%$, showing that the network results are close to the
human-supervised ones in these fiber beds, in some cases separating fibers that
human-curated algorithms could not find. The software we generated in this
project is open source, released under a permissive license, and can be freely
adapted and re-used in other domains. All data and instructions on how to
download and use it are also available.",2101.04823v2
2021-01-22,Structural and transport properties of 4f electron doped Y1-x(Dy)xPdBi topological semi-metallic thin films,"We report the effect of 4f electron doping on structural, electrical and
magneto-transport properties of Dy doped half Heusler Y1-x(Dy)xPdBi (x =0, 0.2,
0.5, 1) thin films grown by pulsed laser deposition. The Dy doping leads to
lattice contraction which increases from 0% for the parent x =0 sample to
approx 1.3% for x=1 sample with increase in Dy doping. The electrical transport
measurements show a typical semi-metallic behaviour in the temperature range 3K
to 300K and a sharp drop in resistivity at low temperatures (less than 3K) for
all the samples. Magnetotransport measurements and Shubnikov de-Hass
oscillations at high magnetic fields demonstrate that for these topologically
non-trivial samples, Dy doping induced lattice contraction plays an active role
in modifying the Fermi surface, carrier concentration and the effective
electron mass. There is an uniform suppression of the onset of
superconductivity with increased Dy doping which is possibly related to the
increasing local exchange field arising from the 4f electrons in Dy. Our
results indicate that we can tune various band structure parameters of YPdBi by
f electron doping and strained thin films of Y1-x(Dy)xPdBi show surface
dominated relativistic carrier transport at low temperatures.",2101.09185v2
2012-06-07,Anisotropic magnetothermoelectric power of ferromagnetic thin films,"We compare the behavior of the magnetothermoelectric power (MTEP)in metallic
ferromagnetic thin films of Ni80Fe20 (Permalloy; Py), Co and CrO2 at
temperatures in the range of 100 K to 400 K. In 25 nm thick Py films and 50 nm
thick Co films both the anisotropic magnetoresistance (AMR) and MTEP show a
relative change in resistance and thermoelectric power (TEP) of the order of
0.2% when the magnetic field is reversed, and in both cases there is no
significant change in AMR or MTEP any more after the saturation field has been
reached. Surprisingly, both Py and Co films have opposite MTEP behavior
although both have the same sign for AMR and TEP. The data on 100 nm films of
fully spin-polarized CrO2, grown both on TiO2 and on sapphire, show a different
picture. The MTEP behavior at low fields shows peaks similar to the AMR in
these films, with variations up to 1%. With increasing field both the MR and
the MTEP variations keeps growing, with MTEP showing relative changes of 1.5%
with the thermal gradient along the b-axis and even 20% with the gradient along
the c-axis, with an intermediate value of 3% for the film on sapphire. It
appears that the low-field effects are due to magnetic domain switching, while
the high-field effects are intrinsic to the electronic structure of CrO2.",1206.1527v2
2018-07-10,Influence of particle size and agglomeration in solid oxide fuel cell cathodes using manganite nanoparticles,"In this work we studied the influence of particle size and agglomeration in
the performance of solid oxide fuel cell cathodes made with nanoparticles of
La0.8Sr0.2MnO3. We followed two synthesis routes based on the Liquid Mix
method. In both procedures we introduced additional reagents in order to
separated the manganite particles. We evaluated cathodic performance by
Electrochemical Impedance Spectroscopy in symmetrical
(CATHODE/ELECTROLYTE/CATHODE) cells. Particle size was tuned by the temperature
used for cathode sintering. Our results show that deagglomeration of the
particles, serves to improve the cathodes performance. However, the dependence
of the performance with the size of the particles is not clear, as different
trends were obtained for each synthesis route. As a common feature, the
cathodes with the lowest area specific resistance are the ones sintered at the
largest temperature. This result indicates that an additional factor related
with the quality of the cathode/electrolyte sintering, is superimposed with the
influence of particle size, however further work is needed to clarify this
issue. The enhancement obtained by deagglomeration suggest that the use of this
kind of methods deserved to be considered to develop high performance
electrodes for solid oxide fuel cells.",1807.03816v1
2019-10-25,Interdiffusion between gadolinia doped ceria and yttria stabilized zirconia in solid oxide fuel cells: experimental investigation and kinetic modeling,"Interdiffusion between the yttria stabilized zirconia (YSZ) electrolyte and
the gadolinia doped ceria (CGO) barrier layer is one of the major causes to the
degradation of solid oxide fuel cells (SOFCs). We present in this work
experimental investigations on CGO-YSZ bi-layer electrolyte sintered at 1250 C
or 1315 C and element transport as a function of sintering temperature and
dwelling time. In order to quantitatively simulate the experimental
observations, the CALPHAD-type thermodynamic assessment of the CGO-YSZ system
is performed by simplifying the system to a CeO2-ZrO2 quasi-binary system, and
the kinetic descriptions (atomic mobilities) are constructed based on critical
review of literature data. The CGO-YSZ interdiffusion is then modeled with the
DICTRA software and the simulation results are compared with the experimental
data under different sintering or long-term operating conditions. The
corresponding ohmic resistance of the bi-layer electrolyte is predicted based
on the simulated concentration profile. The results implies that the
interdiffusion across the CGO-YSZ interface happens mainly during sintering at
high temperature, while during long-term operation at relatively lower
temperature the impact of interdiffusion on cell degradation is negligible.",1910.11947v2
2019-11-29,Ultrathin 2 nm gold as ideal impedance-matched absorber for infrared light,"Thermal detectors are a cornerstone of infrared (IR) and terahertz (THz)
technology due to their broad spectral range. These detectors call for suitable
broad spectral absorbers with minimalthermal mass. Often this is realized by
plasmonic absorbers, which ensure a high absorptivity butonly for a narrow
spectral band. Alternativly, a common approach is based on impedance-matching
the sheet resistance of a thin metallic film to half the free-space impedance.
Thereby, it is possible to achieve a wavelength-independent absorptivity of up
to 50 %, depending on the dielectric properties of the underlying substrate.
However, existing absorber films typicallyrequire a thickness of the order of
tens of nanometers, such as titanium nitride (14 nm), whichcan significantly
deteriorate the response of a thermal transducers. Here, we present the
application of ultrathin gold (2 nm) on top of a 1.2 nm copper oxide seed layer
as an effective IR absorber. An almost wavelength-independent and long-time
stable absorptivity of 47(3) %, ranging from 2 $\mu$m to 20 $\mu$m, could be
obtained and is further discussed. The presented gold thin-film represents
analmost ideal impedance-matched IR absorber that allows a significant
improvement of state-of-the-art thermal detector technology.",1911.13126v1
2020-08-01,Critical cooling rates for amorphous-to-ordered complexion transitions in Cu-rich nanocrystalline alloys,"Amorphous complexions in nanocrystalline metals have the potential to improve
mechanical properties and radiation tolerance, as well as resistance to grain
growth. In this study, the stability of amorphous complexions in binary and
ternary Cu-based alloys is investigated by observing the effect of cooling rate
from high temperature on the occurrence of amorphous-to-ordered complexion
transitions. Bulk Cu-Zr and Cu-Zr-Hf alloy samples were annealed to induce
boundary premelting and then quenched through a procedure that induces a
gradient of local cooling rate through the sample height. Amorphous complexion
thickness distributions were found to be invariant to local cooling rate in the
Cu-Zr-Hf alloy, demonstrating enhanced stability of the amorphous complexion
structure compared to the Cu-Zr alloy, which had thinner amorphous complexions
in the regions that were slowly cooled. The experimental results are used to
construct time-temperature-transformation diagrams of the amorphous-to-ordered
complexion transition for both the binary and ternary alloys, enabling a deeper
understanding of the influence of cooling rate and grain boundary chemistry on
complexion transitions. The critical cooling rate necessary to avoid complexion
transitions in the ternary alloy is found to be at least three orders of
magnitude slower than that for the binary alloy.",2008.00292v2
2020-10-26,Astability versus Bistability in van der Waals Tunnel Diode for Voltage Controlled Oscillator and Memory Applications,"Van der Waals (vdW) tunnel junctions are attractive due to their atomically
sharp interface, gate tunablity, and robustness against lattice mismatch
between the successive layers. However, the negative differential resistance
(NDR) demonstrated in this class of tunnel diodes often exhibits noisy
behaviour with low peak current density, and lacks robustness and
repeatability, limiting their practical circuit applications. Here we propose a
strategy of using a 1L-WS$_2$ as an optimum tunnel barrier sandwiched in a
broken gap tunnel junction of highly doped black phosphorus (BP) and SnSe$_2$.
We achieve high yield tunnel diodes exhibiting highly repeatable, ultra-clean,
and gate tunable NDR characteristics with a signature of intrinsic oscillation,
and a large peak-to-valley current ratio (PVCR) of 3.6 at 300 K (4.6 at 7 K),
making them suitable for practical applications. We show that the thermodynamic
stability of the vdW tunnel diode circuit can be tuned from astability to
bistability by altering the constraint through choosing a voltage or a current
bias, respectively. In the astable mode under voltage bias, we demonstrate a
compact, voltage controlled oscillator without the need for an external tank
circuit. In the bistable mode under current bias, we demonstrate a highly
scalable, single element one-bit memory cell that is promising for dense random
access memory applications in memory intensive computation architectures.",2010.13828v1
2020-12-14,"Magnetic, superconducting, and topological surface states on Fe$_{1+y}$Te$_{1-x}$Se$_{x}$","The idea of employing non-Abelian statistics for error-free quantum computing
ignited interest in recent reports of topological surface superconductivity and
Majorana zero modes (MZMs) in FeTe$_{0.55}$Se$_{0.45}$. An associated puzzle is
that the topological features and superconducting properties are not observed
uniformly across the sample surface. Understanding and practical control of
these electronic inhomogeneities present a prominent challenge for potential
applications. Here, we combine neutron scattering, scanning angle-resolved
photoemission spectroscopy (ARPES), and microprobe composition and resistivity
measurements to characterize the electronic state of
Fe$_{1+y}$Te$_{1-x}$Se$_{x}$. We establish a phase diagram in which the
superconductivity is observed only at sufficiently low Fe concentration, in
association with distinct antiferromagnetic correlations, while the coexisting
topological surface state occurs only at sufficiently high Te concentration. We
find that FeTe$_{0.55}$Se$_{0.45}$ is located very close to both phase
boundaries, which explains the inhomogeneity of superconducting and topological
states. Our results demonstrate the compositional control required for use of
topological MZMs in practical applications.",2012.07893v1
2021-02-16,Nodal superconductivity and superconducting domes in the topological Kagome metal CsV3Sb5,"Recently superconductivity was discovered in the Kagome metal AV3Sb5 (A = K,
Rb, and Cs), which has an ideal Kagome lattice of vanadium. These V-based
superconductors also host charge density wave (CDW) and topological nontrivial
band structure. Here we report the ultralow-temperature thermal conductivity
and high pressure resistance measurements on CsV3Sb5 with Tc = 2.5 K, the
highest among AV3Sb5. A finite residual linear term of thermal conductivity at
zero magnetic field and its rapid increase in fields suggest nodal
superconductivity. By applying pressure, the Tc of CsV3Sb5 increases first,
then decreases to lower than 0.3 K at 11.4 GPa, showing a clear first
superconducting dome peaked around 0.8 GPa. Above 11.4 GPa, superconductivity
re-emerges, suggesting a second superconducting dome. Both nodal
superconductivity and superconducting domes point to unconventional
superconductivity in this V-based superconductor. While our finding of nodal
superconductivity puts a strong constrain on the pairing state of the first
dome, which should be related to the CDW instability, the superconductivity of
the second dome may present another exotic pairing state in this ideal Kagome
lattice of vanadium.",2102.08356v2
2021-03-26,Liquid Reconfigurable Stealth Window Constructed by Metamaterial Absorber,"In this paper, a liquid reconfigurable stealth window constructed by
metamaterial absorber at microwave band is proposed. The stealth window
consists of an anti-reflection glass with indium tin oxide (ITO) as resistive
film and a liquid container made of polymethyl methacrylate (PMMA). Since the
materials constituting the window are all transparent, the metamaterials that
can be switched through the liquid control system can always maintain high
light transmission. The proposal can obtain a transmission passband from 2.3
GHz to 5 GHz with low insertion loss, especially at 2.45 GHz and 5 GHz with the
insertion loss of the passband reach 0.51 and 0.99 , by alcohol drainage. It
can also reflect electromagnetic waves at 2.45 GHz and absorb them from 4.5 GHz
to 10.5 GHz with a strong absorptivity over 90% by alcohol injection,
exhibiting the reconfigurable electromagnetic characteristic of switching
between transmission state and absorption state. Furthermore, the proposed
absorber shows its good transmission/absorption performance under different
polarizations and obtains absorptivity over 90% when alcohol injection in an
oblique incidence of 50{\deg}. Finally, the prototype window has been
fabricated to demonstrate the validity of the proposed structure, which
indicates that the proposal presents significant implications for smart stealth
systems and WLAN communication that require switching of working states in a
complex electromagnetic environment.",2103.14415v1
2021-05-05,Observation of current-induced switching in non-collinear antiferromagnetic IrMn$_3$ by differential voltage measurements,"There is accelerating interest in developing memory devices using
antiferromagnetic (AFM) materials, motivated by the possibility for
electrically controlling AFM order via spin-orbit torques, and its read-out via
magnetoresistive effects. Recent studies have shown, however, that high current
densities create non-magnetic contributions to resistive switching signals in
AFM/heavy metal (AFM/HM) bilayers, complicating their interpretation. Here we
introduce an experimental protocol to unambiguously distinguish current-induced
magnetic and nonmagnetic switching signals in AFM/HM structures, and
demonstrate it in IrMn$_3$/Pt devices. A six-terminal double-cross device is
constructed, with an IrMn$_3$ pillar placed on one cross. The differential
voltage is measured between the two crosses with and without IrMn$_3$ after
each switching attempt. For a wide range of current densities, reversible
switching is observed only when write currents pass through the cross with the
IrMn$_3$ pillar, eliminating any possibility of non-magnetic switching
artifacts. Micromagnetic simulations support our findings, indicating a complex
domain-mediated switching process.",2105.02277v1
2021-06-15,Unusual competition of superconductivity and charge-density-wave state in a compressed topological kagome metal,"Understanding the competition between superconductivity and other ordered
states (such as antiferromagnetic or charge-density-wave (CDW) state) is a
central issue in condensed matter physics. The recently discovered layered
kagome metal AV3Sb5 (A = K, Rb, and Cs) provides us a new playground to study
the interplay of superconductivity and CDW state by involving nontrivial
topology of band structures. Here, we conduct high-pressure electrical
transport and magnetic susceptibility measurements to study CsV3Sb5 with the
highest Tc of 2.7 K in AV3Sb5 family. While the CDW transition is monotonically
suppressed by pressure, superconductivity is enhanced with increasing pressure
up to P1~0.7 GPa, then an unexpected suppression on superconductivity happens
until pressure around 1.1 GPa, after that, Tc is enhanced with increasing
pressure again. The CDW is completely suppressed at a critical pressure P2~2
GPa together with a maximum Tc of about 8 K. In contrast to a common dome-like
behavior, the pressure-dependent Tc shows an unexpected double-peak behavior.
The unusual suppression of Tc at P1 is concomitant with the rapidly damping of
quantum oscillations, sudden enhancement of the residual resistivity and rapid
decrease of magnetoresistance. Our discoveries indicate an unusual competition
between superconductivity and CDW state in pressurized kagome lattice.",2106.07896v1
2021-07-31,Optical phonon modes assisted thermal conductivity in p-type ZrIrSb Half-Heusler alloy: A combined experimental and computational study,"Half Heusler (HH) alloys with 18 valence electron count have attracted
significant interest in the area of research related to thermoelectrics.
Understanding the novel transport properties exhibited by these systems with
semiconducting ground state is an important focus area in this field. Large
thermal conductivity shown by most of the HH alloy possesses a major hurdle in
improving the figure of merit (ZT). Additionally, understanding the mechanism
of thermal conduction in heavy constituents HH alloys is an interesting aspect.
Here, we have investigated the high temperature thermoelectric properties of
ZrIrSb through experimental studies, phonon dispersion and electronic band
structure calculations. ZrIrSb is found to exhibit substantially lower
magnitude of resistivity and Seebeck coefficient near room temperature, owing
to existence of anti-site disorder between Ir/Sb and vacant sites.
Interestingly, in ZrIrSb, lattice thermal conductivity is governed by coupling
between the acoustic and low frequency optical phonon modes, which originates
due to heavier Ir/Sb atoms. This coupling leads to an enhancement in the
Umklapp processes due to the optical phonon excitations near zone boundary,
resulting in a lower magnitude of \k{appa}L. Our studies point to the fact that
the simultaneous existence of two heavy mass elements within a simple unit cell
can substantially decrease the lattice degrees of freedom.",2108.00210v1
2021-08-18,Thermal Transport in Graphene Composites: The Effect of Lateral Dimensions of Graphene Fillers,"We report on the investigation of thermal transport in non-cured silicone
composites with graphene fillers of different lateral dimensions. Graphene
fillers are comprised of few-layer graphene flakes with lateral sizes in the
range from 400 nm to 1200 nm and number of atomic planes from one to ~100. The
distribution of the lateral dimensions and thicknesses of graphene fillers has
been determined via atomic force microscopy statistics. It was found that in
the examined range of the lateral dimensions the thermal conductivity of the
composites increases with the increasing size of the graphene fillers. The
observed difference in thermal properties can be related to the average gray
phonon mean free path in graphene, which has been estimated to be around ~800
nm at room temperature. The thermal contact resistance of composites with
graphene fillers of 1200-nm lateral dimensions was also smaller than that of
composites with graphene fillers of 400-nm lateral dimensions. The effects of
the filler loading fraction and the filler size on the thermal conductivity of
the composites were rationalized within the Kanari model. The obtained results
are important for optimization of graphene fillers for applications in thermal
interface materials for heat removal from high-power-density electronics.",2108.08409v1
2021-09-15,Superconductivity in In-doped AgSnBiTe3 with possible band inversion,"We investigated the chemical pressure effects on structural and electronic
properties of SnTe-based material using partial substitution of Sn by
Ag0.5Bi0.5, which results in lattice shrinkage. For Sn1-2x(AgBi)xTe,
single-phase polycrystalline samples were obtained with a wide range of x. On
the basis of band calculations, we confirmed that the Sn1-2x(AgBi)xTe system is
basically possessing band inversion and topologically preserved electronic
states. To explore new superconducting phases related to the topological
electronic states, we investigated the In-doping effects on structural and
superconducting properties for x = 0.33 (AgSnBiTe3). For (AgSnBi)(1-y)/3InyTe,
single-phase polycrystalline samples were obtained for y = 0-0.5 by
high-pressure synthesis. Superconductivity was observed for y = 0.2-0.5. For y
= 0.4, the transition temperature estimated from zero-resistivity state was 2.4
K, and the specific heat investigation confirmed the emergence of bulk
superconductivity. Because the presence of band inversion was theoretically
predicted, and the parameters obtained from specific heat analyses were
comparable to In-doped SnTe, we expect that the (AgSnBi)(1-y)/3InyTe and other
(Ag,In,Sn,Bi)Te phases are candidate systems for studying topological
superconductivity.",2109.07167v2
2021-09-17,Visualizing band selective enhancement of quasiparticle lifetime in a metallic ferromagnet,"Electrons navigate more easily in a background of ordered magnetic moments
than around randomly oriented ones. This fundamental quantum mechanical
principle is due to their Bloch wave nature and also underlies ballistic
electronic motion in a perfect crystal. As a result, a paramagnetic metal that
develops ferromagnetic order often experiences a sharp drop in the resistivity.
Despite the universality of this phenomenon, a direct observation of the impact
of ferromagnetic order on the electronic quasiparticles in a magnetic metal is
still lacking. Here we demonstrate that quasiparticles experience a significant
enhancement of their lifetime in the ferromagnetic state of the low-density
magnetic semimetal EuCd2As2, but this occurs only in selected bands and
specific energy ranges. This is a direct consequence of the magnetically
induced band splitting and the multi-orbital nature of the material. Our
detailed study allows to disentangle different electronic scattering mechanisms
due to non-magnetic disorder and magnon exchange. Such high momentum and energy
dependence quasiparticle lifetime enhancement can lead to spin selective
transport and potential spintronic applications.",2109.08538v1
2021-09-23,The Transfer Matrix Method and The Theory of Finite Periodic Systems. From Heterostructures to Superlattices,"Long-period systems and superlattices, with additional periodicity, have new
effects on the energy spectrum and wave functions. Most approaches adjust
theories for infinite systems, which is acceptable for large but not small
number of unit cells $n$. In the past 30 years, a theory based entirely on
transfer matrices was developed, where the finiteness of $n$ is an essential
condition. The theory of finite periodic systems (TFPS) is also valid for any
number of propagating modes, and arbitrary potential profiles (or refractive
indices). We review this theory, the transfer matrix definition, symmetry
properties, group representations, and relations with the scattering
amplitudes. We summarize the derivation of multichannel matrix polynomials
(which reduce to Chebyshev polynomials in the one-propagating mode limit), the
analytical formulas for resonant states, energy eigenvalues, eigenfunctions,
parity symmetries, and discrete dispersion relations, for superlattices with
different confinement characteristics. After showing the inconsistencies and
limitations of hybrid approaches that combine the transfer-matrix method with
Floquet's theorem, we review some applications of the TFPS to multichannel
negative resistance, ballistic transistors, channel coupling, spintronics,
superluminal, and optical antimatter effects. We review two high-resolution
experiments using superlattices: tunneling time in photonic band-gap and
optical response of blue-emitting diodes, and show extremely accurate
theoretical predictions.",2109.11640v4
2021-12-03,Multiscale simulation of injection-induced fracture slip and wing-crack propagation in poroelastic media,"In fractured poroelastic media under high differential stress, the shearing
of fractures and faults and the corresponding propagation of wing cracks can be
induced by fluid injection. Focusing on low-pressure stimulation with fluid
pressures below the minimum principal stress but above the threshold required
to overcome the fracture's frictional resistance to slip, this paper presents a
mathematical model and a numerical solution approach for coupling fluid flow
with fracture shearing and propagation. Numerical challenges are related to the
strong coupling between hydraulic and mechanical processes, the material
discontinuity the fractures represent in the medium, the wide range of spatial
scales involved, and the strong effect that fracture deformation and
propagation have on the physical processes. The solution approach is based on a
multiscale strategy. In the macroscale model, flow in and poroelastic
deformation of the matrix are coupled with the flow in the fractures and
fracture contact mechanics, allowing fractures to frictionally slide. Fracture
propagation is handled at the microscale, where the maximum tangential stress
criterion triggers the propagation of fractures, and Paris' law governs the
fracture growth processes. Simulations show how the shearing of a fracture due
to fluid injection is linked to fracture propagation, including cases with
hydraulically and mechanically interacting fractures.",2112.01811v2
2022-04-05,Tunable Energy Level Alignment in the Multilayers of Carboxylic Acids on Silver,"The precise energy level alignment between a metal electrode and an organic
semiconductor is required to reduce contact resistance and enhance the
efficiency of organic-semiconductor-based devices. One of the ways is to
include interlayers that mediate the energy level alignment, i.e., charge
injection layers (CILs). Here we introduce the monolayer thick CILs based on
the aromatic carboxylic acids that can induce the energy level shift in the
subsequent layers by up to 0.8 eV. By gradual chemical transformation of the
as-deposited molecules, we achieve a highly tunable energy level shift in the
range of 0.5 eV. We reveal that the position of both the work function and
energy-level position in the CIL increases linearly with the density of induced
dipoles. The energy level position of subsequent layers changes in the same way
as the CIL. Our results thus connect the energy alignment quantities, i.e.,
energy level positions of both CIL and subsequent layers and sample work
function. The high tunability would allow precise tuning of the active layers
deposited on the CIL, which marks the path towards efficient charge injection
layers on metal electrodes.",2204.02141v2
2022-05-11,Hierarchy of Symmetry Breaking Correlated Phases in Twisted Bilayer Graphene,"Twisted bilayer graphene (TBG) near the magic twist angle of $\sim1.1^{o}$
exhibits a rich phase diagram. However, the interplay between different phases
and their dependence on twist angle is still elusive. Here, we explore the
stability of various TBG phases and demonstrate that superconductivity near
filling of two electrons per moir\'e unit cell alongside Fermi surface
reconstructions, as well as entropy-driven high-temperature phase transitions
and linear-in-T resistance occur over a range of twist angles which extends far
beyond those exhibiting correlated insulating phases. In the vicinity of the
magic angle, we also find a metallic phase that displays a hysteretic anomalous
Hall effect and incipient Chern insulating behaviour. Such a metallic phase can
be rationalized in terms of the interplay between interaction-driven
deformations of TBG bands leading to Berry curvature redistribution and Fermi
surface reconstruction. Our results provide an extensive perspective on the
hierarchy of correlated phases in TBG as classified by their robustness against
deviations from the magic angle or, equivalently, their electronic interaction
requirements.",2205.05225v1
2022-06-16,Origin of Hole-Trapping States in Solution-Processed Copper(I) Thiocyanate (CuSCN) and Defect-Healing by I$_2$ Doping,"Solution-processed copper(I) thiocyanate (CuSCN) typically exhibits low
crystallinity with short-range order; the defects result in a high density of
trap states that limit the device performance. Despite the extensive electronic
applications of CuSCN, its defect properties have not been studied in detail.
Through X-ray absorption spectroscopy, pristine CuSCN prepared from the
standard diethyl sulfide-based recipe is found to contain under-coordinated Cu
atoms, pointing to the presence of SCN vacancies. A defect passivation strategy
is introduced by adding solid I$_2$ to the processing solution. At small
concentrations, the iodine is found to exist as I$^-$ which can substitute for
the missing SCN$^-$ ligand, effectively healing the defective sites and
restoring the coordination around Cu. Applying I$_2$-doped CuSCN as a p-channel
in thin-film transistors shows that the hole mobility increases by more than
five times at the optimal doping concentration of 0.5 mol%. Importantly, the
on/off current ratio and the subthreshold characteristics also improve as the
I$_2$ doping method leads to the defect healing effect while avoiding the
creation of detrimental impurity states. An analysis of the capacitance-voltage
characteristics corroborates that the trap state density is reduced upon I$_2$
addition. The contact resistance and bias-stress stability of the devices also
improve. This work shows a simple and effective route to improve hole transport
properties of CuSCN which is applicable to wide-ranging electronic and
optoelectronic applications.",2206.08040v1
2022-07-09,Diffusion-aware voltage source: An equivalent circuit network to resolve lithium concentration gradients in active particles,"Traditional equivalent circuit models (ECMs) have difficulties in estimating
battery internal states due to the lack of relevant physics, such as the
lithium diffusion in active particles. Here we configure a circuit network to
describe the lithium diffusion and define it as a new high-level circuit
element called diffusion-aware voltage source. The circuit representation is
proven equivalent to the discretized diffusion equation. The new voltage source
gives the electrode potential as a function of the surface concentration and
thus automatically incorporates the diffusion overpotential. We show that an
ECM with the proposed diffusion-aware voltage sources (called ""shell ECM"") can
reproduce the single particle model simulation results, making it a trustworthy
easy-to-implement substitute. Furthermore, the simplest shell ECM consisting of
a single diffusion-aware voltage source and a resistor is validated against
experimental constant-current discharges at various rates. The diffusion-aware
voltage source can be used to measure diffusivity by fitting the diffusion
resistance against experimental data. The viability of the shell ECM for
onboard usage is confirmed by implementation into a battery management system
of WAE Technologies. By tracking the internal concentration states, the shell
ECM demonstrates robustness to dynamic applied-current profiles.",2207.04249v2
2022-07-27,Effect on the Electronic and Magnetic Properties of Antiferromagnetic Topological Insulator MnBi$_2$Te$_4$ with Sn Doping,"We thoroughly investigate the effect of nonmagnetic Sn doping on the
electronic and magnetic properties of antiferromagnetic topological insulator
MnBi$_2$Te$_4$. We observe that Sn doping reduces the out-of-plane
antiferromagnetic (AFM) interactions in MnBi$_2$Te$_4$ up to 68\% of Sn
concentration and above the system is found to be paramagnetic. In this way,
the anomalous Hall effect observed at a very high field of 7.8 T in
MnBi$_2$Te$_4$ is reduced to 2 T with 68\% of Sn doping. Electrical transport
measurements suggest that all compositions are metallic in nature, while the
low-temperature resistivity is sensitive to the AFM ordering and to the
doping-induced disorder. Hall effect study demonstrates that Sn actually dopes
electrons into the system, thus, enhancing the electron carrier density almost
by two orders at 68\% of Sn. In contrast, SnBi$_2$Te$_4$ is found to be a
p-type system. Angle-resolved photoemission spectroscopy (ARPES) studies show
that the topological properties are intact at least up to 55\% of Sn as the
Dirac surface states are present in the valance band, but in SnBi$_2$Te$_4$ we
are unable to detect the topological states due to heavy hole doping. Overall,
Sn doping significantly affects the electronic and magnetic properties of
MnBi$_2$Te$_4$.",2207.13595v1
2022-08-01,Morphological Evolution of NMC Secondary Particles Through in situ electrochemical FIB/SEM experiment,"Microstructural evolution of NMC secondary particles during the battery
operation drives the electrochemical performance and impacts the Li-ion battery
lifetime. In this work, we develop an in situ methodology using the FIB/SEM
instrument to cycle single secondary particles of NMC active materials while
following the modifications of their 3D morphology. Two types of secondary
particles, i.e. low and high gradient NMC, were studied alongside morphological
investigations in both pristine state and different number of cycles. The
quantification of initial inner porosity and cracking evolution upon
electrochemical cycling reveals a clear divergence depending on the type of
gradient particles. An unexpected enhancement of the discharge capacity is
observed during the first cycles concurrently to the appearance of inner
cracks. At the first stages, impedance spectroscopy shows a charge transfer
resistance reduction that suggests a widening of the crack network connected to
the surface, which leads to an increase of contact area between liquid
electrolyte and NMC particle. 3D microstructure of individual secondary
particles after in situ cycles were investigated using FIB/SEM and nano-XCT.
The results suggest a strong impact of the initial porosity shape on the
degradation rate.",2208.00878v1
2022-10-06,Even-Denominator Fractional Quantum Hall State at Filling Factor ν = 3/4,"Fractional quantum Hall states (FQHSs) exemplify exotic phases of
low-disorder two-dimensional (2D) electron systems when electron-electron
interaction dominates over the thermal and kinetic energies. Particularly
intriguing among the FQHSs are those observed at even-denominator Landau level
filling factors, as their quasi-particles are generally believed to obey
non-Abelian statistics and be of potential use in topological quantum
computing. Such states, however, are very rare and fragile, and are typically
observed in the excited Landau level of 2D electron systems with the lowest
amount of disorder. Here we report the observation of a new and unexpected
even-denominator FQHS at filling factor {\nu} = 3/4 in a GaAs 2D hole system
with an exceptionally high quality (mobility). Our magneto-transport
measurements reveal a strong minimum in the longitudinal resistance at {\nu} =
3/4, accompanied by a developing Hall plateau centered at (h/e2)/(3/4). This
even-denominator FQHS is very unusual as it is observed in the lowest Landau
level and in a 2D hole system. While its origin is unclear, it is likely a
non-Abelian state, emerging from the residual interaction between composite
fermions.",2210.03226v1
2023-02-07,"Towards Flexible Biolaboratory Automation: Container Taxonomy-Based, 3D-Printed Gripper Fingers","Automation in the life science research laboratory is a paradigm that has
gained increasing relevance in recent years. Current robotic solutions often
have a limited scope, which reduces their acceptance and prevents the
realization of complex workflows. The transport and manipulation of laboratory
supplies with a robot is a particular case where this limitation manifests. In
this paper, we deduce a taxonomy of biolaboratory liquid containers that
clarifies the need for a flexible grasping solution. Using the taxonomy as a
guideline, we design fingers for a parallel robotic gripper which are developed
with a monolithic dual-extrusion 3D print that integrates rigid and soft
materials to optimize gripping properties. We design fine-tuned fingertips that
provide stable grasps of the containers in question. A simple actuation system
and a low weight are maintained by adopting a passive compliant mechanism. The
ability to resist chemicals and high temperatures and the integration with a
tool exchange system render the fingers usable for daily laboratory use and
complex workflows. We present the task suitability of the fingers in
experiments that show the wide range of vessels that can be handled as well as
their tolerance against displacements and their grasp stability.",2302.03644v2
2023-04-21,Revealing the higher-order spin nature of the Hall effect in non-collinear antiferromagnet $\mathrm{Mn_3Ni_{0.35}Cu_{0.65}N}$,"Ferromagnets generate an anomalous Hall effect even without the presence of a
magnetic field, something that conventional antiferromagnets cannot replicate
but noncollinear antiferromagnets can. The anomalous Hall effect governed by
the resistivity tensor plays a crucial role in determining the presence of time
reversal symmetry and the topology present in the system. In this work we
reveal the complex origin of the anomalous Hall effect arising in noncollinear
antiferromagnets by performing Hall measurements with fields applied in
selected directions in space with respect to the crystalline axes. Our coplanar
magnetic field geometry goes beyond the conventional perpendicular field
geometry used for ferromagnets and allows us to suppress any magnetic dipole
contribution. It allows us to map the in-plane anomalous Hall contribution and
we demonstrate a 120$^\circ$ symmetry which we find to be governed by the
octupole moment at high fields. At low fields we subsequently discover a
surprising topological Hall-like signature and, from a combination of
theoretical techniques, we show that the spins can be recast into dipole,
emergent octupole and noncoplanar effective magnetic moments. These co-existing
orders enable magnetization dynamics unachievable in either ferromagnetic or
conventional collinear antiferromagnetic materials.",2304.10747v1
2023-04-25,Effects of Oxidation on the Tribological Properties of Diamond Sliding Against Silica. Insights from Ab initio Molecular Dynamics,"Tribological phenomena such as adhesion, friction, and wear can undermine the
functionality of devices and applications based on the diamond-silica
interface. Controlling these phenomena is highly desirable, but difficult since
extrinsic factors, such as the surface termination by adsorbed species, can
deeply affect the reactivity of diamond and its resistance to wear. In this
work, we investigate the effects of diamond oxidation by massive ab initio
molecular dynamics simulations of silica sliding against diamond surfaces
considering different surface orientations, O-coverages, and tribological
conditions. Our findings reveal a dual role of oxygen that depends on coverage.
At full coverage, the adsorbed oxygen is very effective in friction and wear
reduction because the repulsion with the silica counter-surface prevents the
formation of chemical bonds across the interface. At reduced coverage and high
pressure, Si-O-C bonds are anyway established. In this situation the presence
of oxygen results detrimental as it weakens the surface C-C bonds making the
surface more vulnerable to wear. Indeed we observed atomic wear on the C(110)
surface at 50% O-coverage under harsh tribological conditions. The mechanisms
of friction reduction and atomistic wear are explained through the analysis of
the electronic properties and surface-surface interactions. Overall, our
accurate in silico experiments shed light into the effects of adsorbed oxygen
on the tribological behavior of diamond and show how oxidized diamond can be
worn by silica.",2304.12511v1
2023-05-03,Correlated Insulator and Chern Insulators in Pentalayer Rhombohedral Stacked Graphene,"Rhombohedral stacked multilayer graphene is an ideal platform to search for
correlated electron phenomena, due to its pair of flat bands touching at zero
energy and further tunability by an electric field. Furthermore, its
valley-dependent Berry phase at zero energy points to possible topological
states when the pseudospin symmetry is broken by electron correlation. However,
experimental explorations of these opportunities are very limited so far, due
to a lack of devices with optimized layer numbers and configurations. Here we
present electron transport measurements of hBN-encapsulated pentalayer graphene
at down to 100 milli-Kelvin. We observed a correlated insulating state with
>MOhm resistance at zero charge density and zero displacement field, where the
tight-binding calculation predicts a metallic ground state. By increasing the
displacement field, we observed a Chern insulator state with C = -5 and two
other states with C = -3 at a low magnetic field of ~1 Tesla. At high
displacement fields and charge densities, we observed isospin-polarized
quarter- and half-metals. Therefore, rhombohedral-stacked pentalayer graphene
is the first graphene system to exhibit two different types of Fermi-surface
instabilities: driven by a pair of flat bands touching at zero energy, and by
the Stoner mechanism in a single flat band. Our results demonstrate a new
direction to explore intertwined electron correlation and topology phenomena in
natural graphitic materials without the need of moir\'e superlattice
engineering.",2305.03151v2
2023-05-10,Strange metallicity in an antiferromagnetic quantum critical model: A sign-problem-free quantum Monte-Carlo study,"We compute transport and thermodynamic properties of a two-band spin-fermion
model describing itinerant fermions in two dimensions interacting via $Z_2$
antiferromagnetic quantum critical fluctuations by means of a sign-problem-free
quantum Monte-Carlo approach. We show that the phase diagram of this model
indeed contains a $d$-wave superconducting phase at low enough temperatures.
However, a crucial question that arises is whether a non-Fermi-liquid metallic
regime exists above $T_c$ exhibiting hallmark strange-metal transport
phenomenology. Interestingly, we find that this version of the model describes
a non-Fermi-liquid metallic regime that displays an approximately $T$-linear
resistivity above $T_c$ for a strong fermion-boson interaction. Using
Nernst-Einstein relation, our QMC results also show that this strange metal
phase exhibits a crossover from being characterized by a charge compressibility
given approximately by $\chi_{c}\sim 1/T$ at high temperatures to being
described by a charge diffusivity consistent with the scaling $D_{c}\sim 1/T$
at low temperatures. Therefore, our work adds support to the view that the
$Z_2$ antiferromagnetic spin-fermion model at strong coupling can be considered
a minimal model that describes both unconventional superconductivity and
strange metallicity, which are fundamentally interconnected in many important
strongly-correlated quantum materials.",2305.06421v2
2023-06-09,Giant Hall Switching by Surface-State-Mediated Spin-Orbit Torque in a Hard Ferromagnetic Topological Insulator,"Topological insulators (TI) and magnetic topological insulators (MTI) can
apply highly efficient spin-orbit torque (SOT) and manipulate the magnetization
with their unique topological surface states with ultra-high efficiency. Here,
we demonstrate efficient SOT switching of a hard MTI, V-doped (Bi,Sb)2Te3
(VBST) with a large coercive field that can prevent the influence of an
external magnetic field. A giant switched anomalous Hall resistance of 9.2
$k\Omega$ is realized, among the largest of all SOT systems. The SOT switching
current density can be reduced to $2.8\times10^5 A/cm^2$. Moreover, as the
Fermi level is moved away from the Dirac point by both gate and composition
tuning, VBST exhibits a transition from edge-state-mediated to
surface-state-mediated transport, thus enhancing the SOT effective field to
$1.56\pm 0.12 T/ (10^6 A/cm^2)$ and the interfacial charge-to-spin conversion
efficiency to $3.9\pm 0.3 nm^{-1}$. The findings establish VBST as an
extraordinary candidate for energy-efficient magnetic memory devices.",2306.05603v3
2023-06-26,CIMulator: A Comprehensive Simulation Platform for Computing-In-Memory Circuit Macros with Low Bit-Width and Real Memory Materials,"This paper presents a simulation platform, namely CIMulator, for quantifying
the efficacy of various synaptic devices in neuromorphic accelerators for
different neural network architectures. Nonvolatile memory devices, such as
resistive random-access memory, ferroelectric field-effect transistor, and
volatile static random-access memory devices, can be selected as synaptic
devices. A multilayer perceptron and convolutional neural networks (CNNs), such
as LeNet-5, VGG-16, and a custom CNN named C4W-1, are simulated to evaluate the
effects of these synaptic devices on the training and inference outcomes. The
dataset used in the simulations are MNIST, CIFAR-10, and a white blood cell
dataset. By applying batch normalization and appropriate optimizers in the
training phase, neuromorphic systems with very low-bit-width or binary weights
could achieve high pattern recognition rates that approach software-based CNN
accuracy. We also introduce spiking neural networks with RRAM-based synaptic
devices for the recognition of MNIST handwritten digits.",2306.14649v1
2023-07-03,Designing impact-resistant bio-inspired low-porosity structures using neural networks,"Biological structural designs in nature, like hoof walls, horns, and antlers,
can be used as inspiration for generating structures with excellent mechanical
properties. A common theme in these designs is the small percent porosity in
the structure ranging from 1 - 5\%. In this work, the sheep horn was used as an
inspiration due to its higher toughness when loaded in the radial direction
compared to the longitudinal direction. Under dynamic transverse compression,
we investigated the structure-property relations in low porosity structures
characterized by their two-dimensional (2D) cross-sections. A diverse design
space was created by combining polygonal tubules with different numbers of
sides placed on a grid with varying numbers of rows and columns. The volume
fraction and the orientation angle of the tubules were also varied. The finite
element (FE) method was used with a rate-dependent elastoplastic material model
to generate the stress-strain curves under plane strain conditions. A gated
recurrent unit (GRU) model was trained to predict the structures' stress-strain
response and energy absorption under different strain rates and applied
strains. The parameter-based model uses eight discrete parameters to
characterize the design space and as inputs to the model. The trained GRU model
can efficiently predict the response of a new design in as little as 0.16 ms
and allows rapid performance evaluation of 128000 designs in the design space.
The GRU predictions identified high-performance structures, and four design
trends that affect the specific energy absorption were extracted and discussed.",2307.00986v2
2023-07-07,Using electrical impedance spectroscopy to identify equivalent circuit models of lubricated contacts with complex geometry: in-situ application to mini traction machine,"Electrical contact resistance or capacitance as measured between a lubricated
contact has been used in tribometers, partially reflecting the lubrication
condition. In contrast, the electrical impedance provides rich information of
magnitude and phase, which can be interpreted using equivalent circuit models,
enabling more comprehensive measurements, including the variation of lubricant
film thickness and the asperity (metal to metal) contact area. An accurate
circuit model of the lubricated contact is critical as needed for the
electrical impedance analysis. However, existing circuit models are hand
derived and suited to interfaces with simple geometry, such as parallel plates,
concentric and eccentric cylinders. Circuit model identification of lubricated
contacts with complex geometry is challenging. This work takes the ball-on-disc
lubricated contact in a Mini Traction Machine (MTM) as an example, where screws
on the ball, grooves on the disc, and contact close to the disc edge make the
overall interface geometry complicated. The electrical impedance spectroscopy
(EIS) is used to capture its frequency response, with a group of load, speed,
and temperature varied and tested separately. The results enable an
identification of equivalent circuit models by fitting parallel
resistor-capacitor models, the dependence on the oil film thickness is further
calibrated using a high-accuracy optical interferometry, which is operated
under the same lubrication condition as in the MTM. Overall, the proposed
method is applicable to general lubricated interfaces for the identification of
equivalent circuit models, which in turn facilitates in-situ tribo-contacts
with electric impedance measurement of oil film thickness. It does not need
transparent materials as optical techniques do, or structural modifications for
piezoelectric sensor mounting as ultrasound techniques do.",2307.03668v1
2023-08-22,Magnetic Skyrmion: From Fundamental Physics to Pioneering Applications,"Skyrmionic devices exhibit energy-efficient and high-integration data storage
and computing capabilities due to their small size, topological protection, and
low drive current requirements. So, to realize these devices, an extensive
study, from fundamental physics to practical applications, becomes essential.
In this article, we present an exhaustive review of the advancements in
understanding the fundamental physics behind magnetic skyrmions and the novel
data storage and computing technologies based on them. We begin with an
in-depth discussion of fundamental concepts such as topological protection,
stability, statics and dynamics essential for understanding skyrmions,
henceforth the foundation of skyrmion technologies. For the realization of
CMOS-compatible skyrmion functional devices, the writing and reading of the
skyrmions are crucial. We discuss the developments in different writing schemes
such as STT, SOT, and VCMA. The reading of skyrmions is predominantly achieved
via two mechanisms: the Magnetoresistive Tunnel Junction (MTJ) TMR effect and
topological resistivity (THE). So, a thorough investigation into the Skyrmion
Hall Effect, topological properties, and emergent fields is also provided,
concluding the discussion on skyrmion reading developments. Based on the
writing and reading schemes, we discuss the applications of the skyrmions in
conventional logic, unconventional logic, memory applications, and neuromorphic
computing in particular. Subsequently, we present an overview of the potential
of skyrmion-hosting Majorana Zero Modes (MZMs) in the emerging Topological
Quantum Computation and helicity-dependent skyrmion qubits.",2308.11811v2
2023-09-11,"Ultrafast optical properties of stoichiometric and non-stoichiometric refractory metal nitrides TiNx, ZrNx, and HfNx","Refractory metal nitrides have recently gained attention in various fields of
modern photonics due to their cheap and robust production technology,
silicon-technology compatibility, high thermal and mechanical resistance, and
competitive optical characteristics in comparison to typical plasmonic
materials like gold and silver. In this work, we demonstrate that by varying
the stoichiometry of sputtered nitride films, both static and ultrafast optical
responses of refractory metal nitrides can efficiently be controlled. We
further prove that the spectral changes in ultrafast transient response are
directly related to the position of the epsilon-near-zero region. At the same
time, the analysis of the temporal dynamics allows us to identify three time
components - the ""fast"" femtosecond one, the ""moderate"" picosecond one, and the
""slow"" at the nanosecond time scale. We also find out that the
non-stoichiometry does not significantly decrease the recovery time of the
reflectance value. Our results show the strong electron-phonon coupling and
reveal the importance of both the electron and lattice temperature-induced
changes in the permittivity near the ENZ region and the thermal origin of the
long tail in the transient optical response of refractory nitrides.",2309.05593v1
2023-10-01,Effect of Spin Fluctuations on Magnetoresistance and Anomalous Hall Effect in the Chiral Magnet Co8Zn8Mn4,"The beta Mn type Co-Zn-Mn alloys have seized significant attention due to
their ability to host skyrmions at room temperature. Here we analyse the
unconventional magneto-transport properties of Co8Zn8Mn4 single crystals with a
Curie temperature of 275 K. A negative magnetoresistance is obtained over a
wide temperature range of 50K to 300K. The deviation of the isothermal
magnetoresistance (MR) curves from linearity to non-linearity as one approaches
higher temperatures points towards the transition from the dominance of magnons
to spin fluctuations. In the paramagnetic phase, the change in the shape of the
MR curve has been explained using the Khosla and Fischer model. The
relationship between the anomalous Hall effect (AHE) and longitudinal
resistivity reveals the dominance of the skew-scattering mechanism, which is
inexplicable based on the theories of semi-classical magneto-transport. We
experimentally determine that the spin fluctuation is the source of the
skew-scattering mechanism in Co8Zn8Mn4. In general skew-scattering mechanisms
predominate in compounds with high conductivity, but our findings demonstrate
that this is not always the case and that other aspects also require equal
consideration. Our work throws new light on the predominant scattering
mechanism in chiral magnets with skyrmionics phase at low conductivity.",2310.00739v1
2023-11-01,Annealing effects on the magnetic and magnetotransport properties of iron oxide nanoparticles self-assemblies,"In magnetic tunnel junctions based on iron oxide nanoparticles the disorder
and the oxidation state of the surface spin as well as the nanoparticles
functionalization play a crucial role in the magnetotransport properties. In
this work, we report a systematic study of the effects of vacuum annealing on
the structural, magnetic and transport properties of self-assembled ~10 nm
Fe3O4 nanoparticles. The high temperature treatment (from 573 to 873 K)
decomposes the organic coating into amorphous carbon, reducing the electrical
resistivity of the assemblies by 4 orders of magnitude. At the same time, the
3Fe2+/(Fe3++Fe2+) ratio is reduced from 1.11 to 0.13 when the annealing
temperature of the sample increases from 573 to 873 K, indicating an important
surface oxidation. Although the 2 nm physical gap remains unchanged with the
thermal treatment, a monotonous decrease of tunnel barrier width was obtained
from the electron transport measurements when the annealing temperature
increases, indicating an increment in the number of defects and hot-spots in
the gap between the nanoparticles. This is reflected in the reduction of the
spin dependent tunneling, which reduces the interparticle magnetoresistance.
This work shows new insights about influence of the nanoparticle interfacial
composition, as well their the spatial arrangement, on the tunnel transport of
self-assemblies, and evidence the importance of optimizing the nanostructure
fabrication for increasing the tunneling current without degrading the spin
polarized current.",2311.00700v1
2023-11-08,Incorporating temporal dynamics of mutations to enhance the prediction capability of antiretroviral therapy's outcome for HIV-1,"Motivation: In predicting HIV therapy outcomes, a critical clinical question
is whether using historical information can enhance predictive capabilities
compared with current or latest available data analysis. This study analyses
whether historical knowledge, which includes viral mutations detected in all
genotypic tests before therapy, their temporal occurrence, and concomitant
viral load measurements, can bring improvements. We introduce a method to weigh
mutations, considering the previously enumerated factors and the reference
mutation-drug Stanford resistance tables. We compare a model encompassing
history (H) with one not using it (NH). Results: The H-model demonstrates
superior discriminative ability, with a higher ROC-AUC score (76.34%) than the
NH-model (74.98%). Significant Wilcoxon test results confirm that incorporating
historical information improves consistently predictive accuracy for treatment
outcomes. The better performance of the H-model might be attributed to its
consideration of latent HIV reservoirs, probably obtained when leveraging
historical information. The findings emphasize the importance of temporal
dynamics in mutations, offering insights into HIV infection complexities.
However, our result also shows that prediction accuracy remains relatively high
even when no historical information is available. Supplementary information:
Supplementary material is available.",2311.04846v1
2024-03-12,Fragmentation of Dense Rotation-Dominated Structures Fed by Collapsing Gravomagneto-Sheetlets and Origin of Misaligned 100 au-Scale Binaries and Multiple Systems,"The majority of stars are in binary/multiple systems. How such systems form
in turbulent, magnetized cores of molecular clouds in the presence of non-ideal
MHD effects remains relatively under-explored. Through ATHENA++-based non-ideal
MHD AMR simulations with ambipolar diffusion, we show that the collapsing
protostellar envelope is dominated by dense gravomagneto-sheetlets, a
turbulence-warped version of the classic pseuodisk produced by anisotropic
magnetic resistance to the gravitational collapse, in agreement with previous
simulations of turbulent, magnetized single-star formation. The sheetlets feed
mass, magnetic fields, and angular momentum to a Dense ROtation-Dominated
(DROD) structure, which fragments into binary/multiple systems. This DROD
fragmentation scenario is a more dynamic variant of the traditional disk
fragmentation scenario for binary/multiple formation, with dense spiral
filaments created by inhomogeneous feeding from the highly structured
larger-scale sheetlets rather than the need for angular momentum transport,
which is dominated by magnetic braking. Collisions between the dense spiraling
filaments play a key role in pushing the local magnetic Toomre parameter
$Q_\mathrm{m}$ below unity, leading to gravitational collapse and stellar
companion formation provided that the local material is sufficiently
demagnetized, with a plasma-$\beta$ of order unity or more. This mechanism can
naturally produce {\it in situ} misaligned systems on the 100-au scale, often
detected with high-resolution ALMA observations. Our simulations also highlight
the importance of non-ideal MHD effects, which affect whether fragmentation
occurs and, if so, the masses and orbital parameters of the stellar companions
formed.",2403.07777v1
2024-03-17,Thickness effect on superconducting properties of niobium films for radio-frequency cavity applications,"Niobium-coated copper radio-frequency cavities are cost-effective
alternatives to bulk niobium cavities, given the lower material costs of copper
substrates and their operation in liquid helium at around 4.2 K. However, these
cavities historically exhibited a gradual degradation in performance with the
accelerating field. This phenomenon, not yet fully understood, limits the
application of niobium thin film cavities in accelerators where the real-estate
gradient needs to be maximized. Recent studies on niobium films deposited on
copper using high power impulse magnetron sputtering (HiPIMS) technique show
promising results in mitigating the performance degradation of niobium thin
film radio-frequency cavities. This paper examines the effect of film thickness
on the superconducting properties of niobium films deposited on copper using
HiPIMS. The study provides insights into how the critical temperature,
transition width, lower and upper critical fields, and critical current density
vary with the film thickness. Increasing the thickness of niobium films
deposited through HiPIMS is found to enhance superconducting properties and
reduce densities of defects and structural irregularities in the crystalline
lattice. This shows potential for enhancing overall performance and potentially
mitigating the observed performance degradation in niobium thin film
radio-frequency cavities. Additionally, the Ivry's scaling relation among
critical temperature, thickness, and sheet resistance at the normal state
appears applicable to niobium films up to approximately 4 $\mu$m. This extends
the previously confirmed validity for niobium films, which was limited to
around 300 nm thickness.",2403.11245v1
2024-04-15,Stiffness-Tuneable Limb Segment with Flexible Spine for Malleable Robots,"Robotic arms built from stiffness-adjustable, continuously bending segments
serially connected with revolute joints have the ability to change their
mechanical architecture and workspace, thus allowing high flexibility and
adaptation to different tasks with less than six degrees of freedom, a concept
that we call malleable robots. Known stiffening mechanisms may be used to
implement suitable links for these novel robotic manipulators; however, these
solutions usually show a reduced performance when bending due to structural
deformation. By including an inner support structure this deformation can be
minimised, resulting in an increased stiffening performance. This paper
presents a new multi-material spine-inspired flexible structure for providing
support in stiffness-controllable layer-jamming-based robotic links of large
diameter. The proposed spine mechanism is highly movable with type and range of
motions that match those of a robotic link using solely layer jamming, whilst
maintaining a hollow and light structure. The mechanics and design of the
flexible spine are explored, and a prototype of a link utilising it is
developed and compared with limb segments based on granular jamming and layer
jamming without support structure. Results of experiments verify the advantages
of the proposed design, demonstrating that it maintains a constant central
diameter across bending angles and presents an improvement of more than 203% of
resisting force at 180 degrees.",2404.09653v1
2024-04-23,Ultrafast nanocomposite scintillators based on Cd-enhanced CsPbCl3 nanocrystals in polymer matrix,"Lead halide perovskite nanocrystals (LHP-NCs) embedded in polymer matrices
are gaining traction for next-generation radiation detectors. While progress
has been made on green-emitting CsPbBr3 NCs, scant attention has been given to
the scintillation properties of CsPbCl3 NCs, which emit size-tunable UV-blue
light matching the peak efficiency of ultrafast photodetectors. In this study,
we explore the scintillation characteristics of CsPbCl3 NCs produced through a
scalable method and treated with CdCl2. Spectroscopic, radiometric and
theoretical analysis on both untreated and treated NCs uncover deep hole trap
states due to surface undercoordinated chloride ions, eliminated by Pb to Cd
substitution. This yields near-perfect efficiency and resistance to
polyacrylate mass-polymerization. Radiation hardness tests demonstrate
stability to high gamma doses while time-resolved experiments reveal ultrafast
radioluminescence with an average lifetime as short as 210 ps. These findings
enhance our comprehension of LHP NCs' scintillation properties, positioning
CsPbCl3 as a promising alternative to conventional fast scintillators.",2404.14813v1
1994-10-19,"$Pb_{0.4}Bi_{1.6}Sr_{2}Ca_{1}Cu_{2}O_{8+x}$ and Oxygen Stoichiometry: Structure, Resistivity, Fermi Surface Topology and Normal State Properties","$Pb_{0.4}Bi_{1.6}Sr_2CaCu_2O_{8+x}$ ($Bi(Pb)-$2212) single crystal samples
were studied using transmission electron microscopy (TEM), $ab-$plane
($\rho_{ab}$) and $c-$axis ($\rho_c$) resistivity, and high resolution
angle-resolved ultraviolet photoemission spectroscopy (ARUPS). TEM reveals that
the modulation in the $b-$axis for $Pb(0.4)-$doped $Bi(Pb)-$2212 is dominantly
of $Pb-$type that is not sensitive to the oxygen content of the system, and the
system clearly shows a structure of orthorhombic symmetry. Oxygen annealed
samples exhibit a much lower $c-$axis resistivity and a resistivity minimum at
$80-130$K. He-annealed samples exhibit a much higher $c-$axis resistivity and
$d\rho_c/dT<0$ behavior below 300K. The Fermi surface (FS) of oxygen annealed
$Bi(Pb)-$2212 mapped out by ARUPS has a pocket in the FS around the $\bar{M}$
point and exhibits orthorhombic symmetry. There are flat, parallel sections of
the FS, about 60\% of the maximum possible along $k_x = k_y$, and about 30\%
along $k_x = - k_y$. The wavevectors connecting the flat sections are about
$0.72(\pi, \pi)$ along $k_x = k_y$, and about $0.80(\pi, \pi)$ along $k_x = -
k_y$, rather than $(\pi,\pi)$. The symmetry of the near-Fermi-energy dispersing
states in the normal state changes between oxygen-annealed and He-annealed
samples.",9410069v1
2003-05-30,General expressions for the electrical resistivity and thermal conductivity of twinned crystals,"General expressions are derived for the electrical resisitivity and thermal
conductivity of a twinned single crystal. Particular attention is paid to the
effect of the structure of the twin domains on these transport coefficients.
Edge effects are also considered. The expression for the thermal conductivity
is used to fit data for a twinned single crystal of 0.8% Zn-doped YBa2Cu3O6.98.
The expression for the electrical resistivity is used to fit previously
published electrical resistivity data for a twinned single crystal of
YBa2Cu3O6.9. It is found that twin boundaries are not a significant source of
electron scattering in high-quality single crystals of Y-123. We cannot rule
out scattering of phonons by twin boundaries in these crystals, with up to 12%
suppression of the phonon component of the thermal conductivity. The related
problem of determining the electrical resistivity and thermal conductivity of a
crystal with oblique and alternating isotropic regions of different
conductivities is also solved.",0305698v5
2003-06-13,Behavior of the contacts of Quantum Hall Effect devices at high currents : an electronic thermometer,"This paper reports on an experimental study of the contact resistance of Hall
bars in the Quantum Hall Effect regime while increasing the current through the
sample. These measurements involve also the longitudinal resistance and they
have been always performed before the breakdown of the Quantum Hall Effect. Our
investigations are restricted to the $i=2$ plateau which is used in all
metrological measurements of the von Klitzing constant $R_K$. A particular care
has been taken concerning the configuration of the measurement. Four
configurations were used for each Hall bar by reversing the current and the
magnetic field polarities. Several samples with different width have been
studied and we observed that the critical current for the contact resistance
increases with the width of the Hall bar as previously observed for the
critical current of the longitudinal resistance. The critical currents exhibit
either a linear or a sublinear increase. All our observations are interpreted
in the current understanding of the Quantum hall effect brekdown. Our analysis
suggests that a heated region appears at the current contact, develops and then
extends in the whole sample while increasing the current. Consequently, we
propose to use the contact resistance as an electronic thermometer for the Hall
fluid.",0306368v3
2004-07-19,Resistivity studies under hydrostatic pressure on a low-resistance variant of the quasi-2D organic superconductor kappa-(BEDT-TTF)2Cu[N(CN)2]Br: quest for intrinsic scattering contributions,"Resistivity measurements have been performed on a low (LR)- and high
(HR)-resistance variant of the kappa-(BEDT-TTF)_2Cu[N(CN)_2]Br superconductor.
While the HR sample was synthesized following the standard procedure, the LR
crystal is a result of a somewhat modified synthesis route. According to their
residual resistivities and residual resistivity ratios, the LR crystal is of
distinctly superior quality. He-gas pressure was used to study the effect of
hydrostatic pressure on the different transport regimes for both variants. The
main results of these comparative investigations are (i) a significant part of
the inelastic-scattering contribution, which causes the anomalous rho(T)
maximum in standard HR crystals around 90 K, is sample dependent, i.e.
extrinsic in nature, (ii) the abrupt change in rho(T) at T* approx. 40 K from a
strongly temperature-dependent behavior at T > T* to an only weakly T-dependent
rho(T) at T < T* is unaffected by this scattering contribution and thus marks
an independent property, most likely a second-order phase transition, (iii)
both variants reveal a rho(T) proportional to AT^2 dependence at low
temperatures, i.e. for T_c < T < T_0, although with strongly sample-dependent
coefficients A and upper bounds for the T^2 behavior measured by T_0. The
latter result is inconsistent with the T^2 dependence originating from coherent
Fermi-liquid excitations.",0407478v1
2004-10-28,Transport properties in manganite thin films,"The resistivity of thin $La_{0.7}A_{0.3}MnO_{3}$ films ($A=Ca, Sr$) is
investigated in a wide temperature range. The comparison of the resistivities
is made among films grown by different techniques and on several substrates
allowing to analyze samples with different amounts of disorder. In the
low-temperature nearly half-metallic ferromagnetic state the prominent
contribution to the resistivity scales as $T^{\alpha}$ with $\alpha \simeq 2.5$
for intermediate strengths of disorder supporting the theoretical proposal of
single magnon scattering in presence of minority spin states localized by the
disorder. For large values of disorder the low-temperature behavior of the
resistivity is well described by the law $T^{3}$ characteristic of anomalous
single magnon scattering processes, while in the regime of low disorder the
$\alpha$ exponent tends to a value near 2. In the high temperature insulating
paramagnetic phase the resistivity shows the activated behavior characteristic
of polaronic carriers. Finally in the whole range of temperatures the
experimental data are found to be consistent with a phase separation scenario
also in films doped with strontium ($A=Sr$).",0410743v1
2008-12-22,Joule Heating and Anomalous Resistivity in the Solar Corona,"Recent radioastronomical observations of Faraday rotation in the solar corona
can be interpreted as evidence for coronal currents, with values as large as
$2.5 \times 10^9$ Amperes (Spangler 2007). These estimates of currents are used
to develop a model for Joule heating in the corona. It is assumed that the
currents are concentrated in thin current sheets, as suggested by theories of
two dimensional magnetohydrodynamic turbulence. The Spitzer result for the
resistivity is adopted as a lower limit to the true resistivity. The calculated
volumetric heating rate is compared with an independent theoretical estimate by
Cranmer et al (2007). This latter estimate accounts for the dynamic and
thermodynamic properties of the corona at a heliocentric distance of several
solar radii. Our calculated Joule heating rate is less than the Cranmer et al
estimate by at least a factor of $3 \times 10^5$. The currents inferred from
the observations of Spangler (2007) are not relevant to coronal heating unless
the true resistivity is enormously increased relative to the Spitzer value.
However, the same model for turbulent current sheets used to calculate the
heating rate also gives an electron drift speed which can be comparable to the
electron thermal speed, and larger than the ion acoustic speed. It is therefore
possible that the coronal current sheets are unstable to current-driven
instabilities which produce high levels of waves, enhance the resistivity and
thus the heating rate.",0812.4220v1
2009-06-24,Turbulent resistivity driven by the magnetorotational instability,"We measure the turbulent resistivity in the nonlinear regime of the MRI, and
evaluate the turbulent magnetic Prandtl number. We perform a set of numerical
simulations with the Eulerian finite volume codes Athena and Ramses in the
framework of the shearing box model. We consider models including explicit
dissipation coefficients and magnetic field topologies such that the net
magnetic flux threading the box in both the vertical and azimuthal directions
vanishes. We first demonstrate good agreement between the two codes by
comparing the properties of the turbulent states in simulations having
identical microscopic diffusion coefficients (viscosity and resistivity). We
find the properties of the turbulence do not change when the box size is
increased in the radial direction, provided it is elongated in the azimuthal
direction. To measure the turbulent resistivity in the disk, we impose a fixed
electromotive force on the flow and measure the amplitude of the saturated
magnetic field that results. We obtain a turbulent resistivity that is in rough
agreement with mean field theories like the Second Order Smoothing
Approximation. The numerical value translates into a turbulent magnetic Prandtl
number Pm_t of order unity. Pm_t appears to be an increasing function of the
forcing we impose. It also becomes smaller as the box size is increased in the
radial direction, in good agreement with previous results obtained in very
large boxes. Our results are in general agreement with other recently published
papers studying the same problem but using different methodology. Thus, our
conclusion that Pm_t is of order unity appears robust.",0906.4422v2
2009-07-08,Turbulent resistivity evaluation in MRI generated turbulence,"(abriged) MRI turbulence is a leading mechanism for the generation of an
efficient turbulent transport of angular momentum in an accretion disk through
a turbulent viscosity effect. It is believed that the same process could also
transport large-scale magnetic fields in disks, reshaping the magnetic
structures in these objects. This process, known as turbulent resistivity, has
been suggested and used in several accretion-ejection models and simulations to
produce jets. Still, the efficiency of MRI-driven turbulence to transport
large-scale magnetic fields is largely unknown.
  We investigate this problem both analytically and numerically. We introduce a
linear calculation of the MRI in the presence of a spatially inhomogeneous mean
magnetic field. We show that, in this configuration, MRI modes lead to an
efficient magnetic field transport, on the order of the angular momentum
transport. We next use fully non linear simulations of MRI turbulence to
compute the turbulent resistivity in several magnetic configurations.
  We find that the turbulent resistivity is on the order of the turbulent
viscosity in all our simulations, although somewhat lower. The turbulent
resistivity tensor is found to be highly anisotropic with a diffusion
coefficient 3 times greater in the radial direction than in the vertical
direction.
  These results support the possibility of driving jets from turbulent disks;
the resulting jets may not be steady.",0907.1393v1
2009-07-15,Transport properties and the anisotropy of Ba_{1-x}K_xFe_2As_2 single crystals in normal and superconducting states,"The transport and superconducting properties of Ba_{1-x}K_xFe_2As_2 single
crystals with T_c = 31 K were studied. Both in-plane and out-of plane
resistivity was measured by modified Montgomery method. The in-plane
resistivity for all studied samples, obtained in the course of the same
synthesis, is almost the same, unlike to the out-of plane resistivity, which
differ considerably. We have found that the resistivity anisotropy
\gamma=\rho_c /\rho_{ab} is almost temperature independent and lies in the
range 10-30 for different samples. This, probably, indicates on the extrinsic
nature of high out-of-plane resistivity, which may appear due to the presence
of the flat defects along Fe-As layers in the samples. This statement is
supported by comparatively small effective mass anisotropy, obtained from the
upper critical field measurements, and from the observation of the so-called
""Friedel transition"", which indicates on the existence of some disorder in the
samples in c-direction.",0907.2598v1
2010-12-31,In-plane anisotropy of electrical resistivity in the strain-detwinned SrFe2As2,"Intrinsic, in-plane anisotropy of electrical resistivity was studied on
mechanically detwinned single crystals of SrFe$_2$As$_2$ above and below the
temperature of the coupled structural/magnetic transition, $T_{\textrm{TO}}$.
Resistivity is smaller for electrical current flow along the orthorhombic $a_o$
direction (direction of antiferromagnetically alternating magnetic moments) and
is larger for transport along the $b_o$ direction (direction of ferromagnetic
chains), which is similar to CaFe$_2$As$_2$ and BaFe$_2$As$_2$ compounds. A
strongly first order structural transition in SrFe$_2$As$_2$ was confirmed by
high-energy x-ray measurements, with the transition temperature, and character
unaffected by moderate strain. For small strain levels, which are just
sufficient to detwin the sample, we find a negligible effect on the resistivity
above $T_{\textrm{TO}}$. With the increase of strain, the resistivity
anisotropy starts to develop above $T_{\textrm{TO}}$, clearly showing the
relation of anisotropy to an anomalously strong response to strain. Our study
suggests that electronic nematicity cannot be observed in the FeAs based
compounds in which the structural transition is strongly first order.",1101.0274v1
2012-12-05,Electric field driven destabilization of the insulating state in nominally pure LaMnO3,"We report an electric field driven destabilization of the insulating state in
nominally pure LaMnO3 single crystal with a moderate field which leads to a
resistive state transition below 300 K. The transition is between the
insulating state in LaMnO3 and a high resistance bad metallic state that has a
temperature independent resistivity. The transition occurs at a threshold field
(Eth) which shows a steep enhancement on cooling. While at lower temperatures
the transition is sharp and involves large change in resistance but it softens
on heating and eventually absent above 280K. When the Mn4+ content is increased
by Sr substitution up to x=0.1, the observed transition though observable in
certain temperature range, softens considerably. The observation has been
explained as bias driven percolation type transition between two coexisting
phases, where the majority phase is a charge and orbitally ordered polaronic
insulating phase and the minority phase is a bad metallic phase. The mobile
fraction f of the bad metallic phase deduced from the experimental data follows
an activated kinetics with the activation energy nearly equal to 200 meV and
the prefactor fo is a strong function of the field that leads to a rapid
enhancement of f on application of field leading to the resistive state
transition. We suggest likely scenarios for such co-existing phases in
nominally pure LaMnO3 that can lead to the bias driven percolation type
transition.",1212.1001v2
2013-09-21,A switch to reduce resistivity in smoothed particle magnetohydrodynamics,"Artificial resistivity is included in Smoothed Particle Magnetohydrodynamics
simulations to capture shocks and discontinuities in the magnetic field. Here
we present a new method for adapting the strength of the applied resistivity so
that shocks are captured but the dissipation of the magnetic field away from
shocks is minimised. Our scheme utilises the gradient of the magnetic field as
a shock indicator, setting {\alpha}_B = h|gradB|/|B|, such that resistivity is
switched on only where strong discontinuities are present. The advantage to
this approach is that the resistivity parameter does not depend on the absolute
field strength. The new switch is benchmarked on a series of shock tube tests
demonstrating its ability to capture shocks correctly. It is compared against a
previous switch proposed by Price & Monaghan (2005), showing that it leads to
lower dissipation of the field, and in particular, that it succeeds at
capturing shocks in the regime where the Alfv\'en speed is much less than the
sound speed (i.e., when the magnetic field is very weak). It is also simpler.
We also demonstrate that our recent constrained divergence cleaning algorithm
has no difficulty with shock tube tests, in contrast to other implementations.",1309.5437v1
2013-10-04,Piggyback resistive Micromegas,"Piggyback Micromegas consists in a novel readout architecture where the anode
element is made of a resistive layer on a ceramic substrate. The resistive
layer is deposited on the thin ceramic substrate by an industrial process which
provides large dynamic range of resistivity (10$^6$ to
10$^{10}$\,M$\Omega$/square). The particularity of this new structure is that
the active part is entirely dissociated from the read-out element. This gives a
large flexibility on the design of the anode structure and the readout scheme.
Without significant loss, signals are transmitted by capacitive coupling to the
read-out pads. The detector provides high gas gain, good energy resolution and
the resistive layer assures spark protection for the electronics. This assembly
could be combined with modern pixel array electronic ASICs. First tests with
different Piggyback detectors and configurations will be presented. This
structure is adequate for cost effective fabrication and low outgassing
detectors. It was designed to perform in sealed mode and its long term
stability has been extensively studied. In addition perspectives on the future
developments will be evoked.",1310.1242v1
2013-10-15,Recent advances with THGEM detectors,"The Thick Gaseous Electron Multiplier (THGEM) is a simple and robust
electrode suitable for large area detectors. In this work the results of
extensive comparative studies of the physical properties of different
THGEM-based structures are reviewed. The focus is on newly suggested THGEM-like
WELL configurations as well as on recently developed characterization methods.
The WELL structures are single-sided THGEM electrodes directly coupled to
different anode readout electrodes. The structures differ by the coupling
concept of the bottom THGEM electrode to the metallic readout pads: a Thick
WELL (THWELL) with direct coupling; the Resistive WELL (RWELL) and the
Segmented Resistive WELL (SRWELL) coupled through thin resistive films
deposited on insulating sheets and a Resistive-Plate WELL (RPWELL) coupled
through a plate of high bulk resistivity. The results are compared to that of
traditional double-sided THGEM electrodes followed by induction gaps - in some
cases with moderate additional multiplication within the gap. We compare the
different configurations in terms of gain, avalanche extension, discharge-rate
and magnitude as well as rate capabilities over a broad dynamic range -
exploiting a method that mimics highly ionizing particles in the laboratory. We
report on recent studies of avalanche distribution in THGEM holes using optical
readout.",1310.3912v1
2014-10-10,"On the bad metallicity and phase diagrams of Fe$_{1+δ}X$ ($X$ =Te, Se, S, solid solutions): an electrical resistivity study","Based on a systematic analysis of the thermal evolution of the resistivities
of Fe-based chalcogenides Fe$_{1+\delta }$Te$_{1-x}X_{x}$ ($X$= Se, S), it is
inferred that their often observed nonmetallic resistivities are related to a
presence of two resistive channels: one is a high-temperature
thermally-activated process while the other is a low-temperature log-in-$T$
process. On lowering temperature, there are often two metal-to-nonmetall
crossover events: one from the high-$T$ thermally-activated nonmetallic regime
into a metal-like phase and the other from the log-in-$T$ regime into a second
metal-like phase. Based on these events, together with the magnetic and
superconducting transitions, a phase diagram is constructed for each series. We
discuss the origin of both processes as well as the associated crossover
events. We also discuss how these resistive processes are being influenced by
pressure, intercalation, disorder, doping, or sample condition and, in turn,
how these modifications are shaping the associated phase diagrams.",1410.2676v1
2016-11-17,On the measurements of numerical viscosity and resistivity in Eulerian MHD codes,"We propose a simple ansatz for estimating the value of the numerical
resistivity and the numerical viscosity of any Eulerian MHD code. We test this
ansatz with the help of simulations of the propagation of (magneto)sonic waves,
Alfven waves, and the tearing mode instability using the MHD code Aenus. By
comparing the simu- lation results with analytical solutions of the
resistive-viscous MHD equations and an empirical ansatz for the growth rate of
tearing modes we measure the numerical viscosity and resistivity of Aenus. The
comparison shows that the fast-magnetosonic speed and wavelength are the
characteristic velocity and length, respectively, of the aforementioned
(relatively simple) systems. We also determine the dependance of the numerical
viscosity and resistivity on the time integration method, the spatial
reconstruction scheme and (to a lesser extent) the Riemann solver employed in
the simulations. From the measured results we infer the numerical resolution
(as a function of the spatial reconstruction method) required to properly
resolve the growth and saturation level of the magnetic field amplified by the
magnetorotational instability in the post-collapsed core of massive stars. Our
results show that it is to the best advantage to resort to ultra-high order
methods (e.g., 9th-order Monotonicity Preserving method) to tackle this problem
properly, in particular in three dimensional simulations.",1611.05858v2
2017-02-06,Rings and gaps produced by variable magnetic disk winds and avalanche accretion streams: I. Axisymmetric resistive MHD simulations,"Rings and gaps are being observed in an increasing number of disks around
young stellar objects. We illustrate the formation of such radial structures
through idealized, 2D (axisymmetric) resistive MHD simulations of coupled
disk-wind systems threaded by a relatively weak poloidal magnetic field
(plasma-$\beta \sim 10^3$). We find two distinct modes of accretion depending
on the resistivity and field strength. A small resistivity or high field
strength promotes the development of rapidly infalling `avalanche accretion
streams' in a vertically extended disk envelope that dominates the dynamics of
the system, especially the mass accretion. The streams are suppressed in
simulations with larger resistivities or lower field strengths, where most of
the accretion instead occurs through a laminar disk. In these simulations, the
disk accretion is driven mainly by a slow wind that is typically accelerated by
the pressure gradient from a predominantly toroidal magnetic field. Both
wind-dominated and stream-dominated modes of accretion create prominent
features in the surface density distribution of the disk, including rings and
gaps, with a strong spatial variation of the magnetic flux relative to the
mass. Regions with low mass-to-flux ratios accrete quickly, leading to the
development of gaps, whereas regions with higher mass-to-flux ratios tend to
accrete more slowly, allowing matter to accumulate and form dense rings. In
some cases, avalanche accretion streams are observed to produce dense rings
directly through continuous feeding. We discuss the implications of ring and
gap formation driven by winds and streams on grain growth and planet formation.",1702.01565v2
2017-09-18,Log-rise of the Resistivity in the Holographic Kondo Model,"We study a single-channel Kondo effect using a recently developed holographic
large-$N$ technique. In order to obtain resistivity of this model, we introduce
a probe field. The gravity dual of a localized fermionic impurity in
1+1-dimensional host matter is constructed by embedding a localized
2-dimensional Anti-de Sitter (\ads{2})-brane in the bulk of \ads{3}. This helps
us construct an impurity charge density which acts as a source to the bulk
equation of motion of the probe gauge field. The functional form of the charge
density is obtained independently by solving the equations of motion for the
fields confined to the \ads{2}-brane. The asymptotic solution of the probe
field is dictated by the impurity charge density, which in turn, affects the
current-current correlation functions, and hence the resistivity. Our choice of
parameters tunes the near-boundary impurity current to be marginal, resulting
in a $\log T$ behavior in the UV resistivity, as is expected for the Kondo
problem. The resistivity at the IR fixed point turns out to be zero, signaling
a complete screening of the impurity.",1709.06086v2
2019-07-11,First results of Resistive-Plate Well (RPWELL) detector operation at 163 K,"We present for the first time, discharge-free operation at cryogenic
conditions of a Resistive-Plate WELL (RPWELL) detector. It is a single-sided
Thick Gaseous Electron Multiplier (THGEM) coupled to a readout anode via a
plate of high bulk resistivity. The results of single- and double-stage RPWELL
detectors operated in stable conditions in Ne/5$\%$CH$_{4}$ at 163 K are
summarized. The RPWELL comprised a ferric-based (Fe$^{3+}$) ceramic composite
(""Fe-ceramic"") as the resistive plate, of volume resistivity $\sim$$10^{11}$
$\Omega$$\cdot$cm at this temperature. Gains of $\sim$$10^{4}$ and
$\sim$$10^{5}$ were reached with the single-stage RPWELL, with 6 keV X-rays and
single UV-photons, respectively. The double-stage detector, a THGEM followed by
the RPWELL, reached gains $\sim$$10^{5}$ and $\sim$$10^{6}$ with X-rays and
single UV-photons, respectively. The results were obtained with and without a
CsI photocathode on the first multiplying element. Potential applications at
these cryogenic conditions are discussed.",1907.05057v1
2020-04-10,Linear in temperature resistivity in the limit of zero temperature from the time reparameterization soft mode,"The most puzzling aspect of the 'strange metal' behavior of correlated
electron compounds is that the linear in temperature resistivity often extends
down to low temperatures, lower than natural microscopic energy scales. We
consider recently proposed deconfined critical points (or phases) in models of
electrons in large dimension lattices with random nearest-neighbor exchange
interactions. The criticality is in the class of Sachdev-Ye-Kitaev models, and
exhibits a time reparameterization soft mode representing gravity in dual
holographic theories. We compute the low temperature resistivity in a large $M$
limit of models with SU($M$) spin symmetry, and find that the dominant
temperature dependence arises from this soft mode. The resistivity is linear in
temperature down to zero temperature at the critical point, with a co-efficient
universally proportional to the product of the residual resistivity and the
co-efficient of the linear in temperature specific heat. We argue that the time
reparameterization soft mode offers a promising and generic mechanism for
resolving the strange metal puzzle.",2004.05182v4
2017-07-31,Universal linear-temperature resistivity: possible quantum diffusion transport in strongly correlated superconductors,"The strongly correlated electron fluids in high temperature cuprate
superconductors demonstrate an anomalous linear temperature ($T$) dependent
resistivity behavior, which persists to a wide temperature range without
exhibiting saturation. As cooling down, those electron fluids lose the
resistivity and condense into the superfluid. However, the origin of the
linear-$T$ resistivity behavior and its relationship to the strongly correlated
superconductivity remain a mystery. Here we report a universal relation
$d\rho/dT=(\mu_0k_B/\hbar)\lambda^2_L$, which bridges the slope of the
linear-$T$-dependent resistivity ($d\rho/dT$) to the London penetration depth
$\lambda_L$ at zero temperature among cuprate superconductor
Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ and heavy fermion superconductors
CeCoIn$_5$, where $\mu_0$ is vacuum permeability, $k_B$ is the Boltzmann
constant and $\hbar$ is the reduced Planck constant. We extend this scaling
relation to different systems and found that it holds for other cuprate,
pnictide and heavy fermion superconductors as well, regardless of the
significant differences in the strength of electronic correlations, transport
directions, and doping levels. Our analysis suggests that the scaling relation
in strongly correlated superconductors could be described as a hydrodynamic
diffusive transport, with the diffusion coefficient ($D$) approaching the
quantum limit $D\sim\hbar/m^*$, where $m^*$ is the quasi-particle effective
mass.",1707.09782v1
2019-03-28,Faster Spectral Sparsification in Dynamic Streams,"Graph sketching has emerged as a powerful technique for processing massive
graphs that change over time (i.e., are presented as a dynamic stream of edge
updates) over the past few years, starting with the work of Ahn, Guha and
McGregor (SODA'12) on graph connectivity via sketching. In this paper we
consider the problem of designing spectral approximations to graphs, or
spectral sparsifiers, using a small number of linear measurements, with the
additional constraint that the sketches admit an efficient recovery scheme.
  Prior to our work, sketching algorithms were known with near optimal $\tilde
O(n)$ space complexity, but $\Omega(n^2)$ time decoding (brute-force over all
potential edges of the input graph), or with subquadratic time, but rather
large $\Omega(n^{5/3})$ space complexity (due to their reliance on a rather
weak relation between connectivity and effective resistances). In this paper we
first show how a simple relation between effective resistances and edge
connectivity leads to an improved $\widetilde O(n^{3/2})$ space and time
algorithm, which we show is a natural barrier for connectivity based
approaches. Our main result then gives the first algorithm that achieves
subquadratic recovery time, i.e. avoids brute-force decoding, and at the same
time nontrivially uses the effective resistance metric, achieving
$n^{1.4+o(1)}$ space and recovery time.
  Our main technical contribution is a novel method for `bucketing' vertices of
the input graph into clusters that allows fast recovery of edges of high
effective resistance: the buckets are formed by performing ball-carving on the
input graph using (an approximation to) its effective resistance metric. We
feel that this technique is likely to be of independent interest.",1903.12165v1
2012-06-13,Current Challenges and Perspectives in Resistive Gaseous Detectors: a manifesto from RPC 2012,"Resistive gaseous detectors can be broadly defined as those operated in
conditions where virtually no field lines exist that connect any two metallic
electrodes sitting at different potential. This condition can be operationally
recognized as 'no gas gap being delimited by two metallic electrodes'. Since
early 70's, Resistive Plate Chambers (RPCs) are the most successful
implementation of this idea, that leads to fully spark-protected gaseous
detectors, with solid state-like reliability at working fields beyond 100kV/cm,
yet enjoying the general characteristics of gaseous detectors in terms of
flexibility, optimization and customization. We present a summary of the status
of the field of resistive gaseous detectors as discussed in a dedicated closing
session that took place during the XI Workshop for Resistive Plate Chambers and
Related Detectors celebrated in Frascati, and especially we review the
perspectives and ambitions towards the XII Workshop to be celebrated in Beijing
in year 2014. Due to the existence of two specific reviews ([1,2]) also at this
workshop, a minimum amount of overlap was found to be unavoidable. We have
realized, however, that the three works provide a look at the field from
different optics, so they can be largely considered to be complementary.
Contrary to the initial concerns, the overall appearance seems to be fairly
round, in our opinion.",1206.2735v2
2018-12-03,Resistive evolution of toroidal field configurations and their relation to magnetic clouds,"We study the resistive evolution of a localized self-organizing
magnetohydrodynamic equilibrium. In this configuration the magnetic forces are
balanced by a pressure force caused by a toroidal depression in the pressure.
Equilibrium is attained when this low pressure region prevents further
expansion into the higher-pressure external plasma. We find that, for the
parameters investigated, the resistive evolution of the structures follows a
universal pattern when rescaled to resistive time. The finite resistivity
causes both a decrease in the magnetic field strength and a finite slip of the
plasma fluid against the static equilibrium. This slip is caused by a
Pfirsch-Schl\""uter type diffusion, similar to what is seen in tokamak
equilibria. The net effect is that the configuration remains in Magnetostatic
equilibrium whilst it slowly grows in size. The rotational transform of the
structure becomes nearly constant throughout the entire structure, and
decreases according to a power law. In simulations this equilibrium is observed
when highly tangled field lines relax in a high-pressure (relative to the
magnetic field strength) environment, a situation that occurs when the twisted
field of a coronal loop is ejected into the interplanetary solar wind. In this
paper we relate this localized MHD equilibrium to magnetic clouds in the solar
wind.",1812.00005v1
2019-01-24,Parylene Based Memristive Devices with Multilevel Resistive Switching for Neuromorphic Applications,"In this paper, the resistive switching and neuromorphic behavior of
memristive devices based on parylene, a polymer both low-cost and safe for the
human body, is comprehensively studied. The Metal/Parylene/ITO sandwich
structures were prepared by means of the standard gas phase surface
polymerization method with different top active metal electrodes (Ag, Al, Cu or
Ti of about 500 nm thickness). These organic memristive devices exhibit
excellent performance: low switching voltage (down to 1 V), large OFF/ON
resistance ratio (about 10^3), retention (> 10^4 s) and high multilevel
resistance switching (at least 16 stable resistive states in the case of Cu
electrodes). We have experimentally shown that parylene-based memristive
elements can be trained by a biologically inspired spike-timing-dependent
plasticity (STDP) mechanism. The obtained results have been used to implement a
simple neuromorphic network model of classical conditioning. The described
advantages allow considering parylene-based organic memristors as prospective
devices for hardware realization of spiking artificial neuron networks capable
of supervised and unsupervised learning and suitable for biomedical
applications.",1901.08667v2
2020-01-24,Metal-to-metal transition and heavy-electron state in Nd$_4$Ni$_3$O$_{10-δ}$,"The trilayer nickelate Nd$_4$Ni$_3$O$_{10-\delta}$ ($\delta \approx$ 0.15)
was investigated by the measurements of x-ray diffraction, electrical
resistivity, magnetic susceptibility, and heat capacity. The crystal structure
data suggest a higher Ni valence in the inner perovskite-like layer. At ambient
pressure the resistivity shows a jump at 162 K, indicating a metal-to-metal
transition (MMT). The MMT is also characterized by a magnetic susceptibility
drop, a sharp specific-heat peak, and an isotropic lattice contraction. Below
$\sim$ 50 K, a resistivity upturn with a log$T$ dependence shows up,
accompanying with a negative thermal expansion. External hydrostatic pressure
suppresses the resistivity jump progressively, coincident with the diminution
of the log$T$ behavior. The low-temperature electronic specific-heat
coefficient is extracted to be $\sim$ 150 mJ K$^{-2}$ mol-fu$^{-1}$, equivalent
to $\sim$ 50 mJ K$^{-2}$ mol-Ni$^{-1}$, indicating an unusual heavy-electron
correlated state. The novel heavy-electron state as well as the logarithmic
temperature dependence of resistivity is explained in terms of the Ni$^{3+}$
centered Kondo effect in the inner layer of the (NdNiO$_3$)$_3$ trilayers.",2001.09059v2
2021-04-07,Functional annotation of creeping bentgrass protein sequences based on convolutional neural network,"Background: Creeping bentgrass (Agrostis soionifera) is a perennial grass of
Gramineae, belonging to cold season turfgrass, but has poor disease resistance.
Up to now, little is known about the induced systemic resistance (ISR)
mechanism, especially the relevant functional proteins, which is important to
disease resistance of turfgrass. Achieving more information of proteins of
infected creeping bentgrass is helpful to understand the ISR mechanism.
Results: With BDO treatment, creeping bentgrass seedlings were grown, and the
ISR response was induced by infecting Rhizoctonia solani. High-quality protein
sequences of creeping bentgrass seedlings were obtained. Some of protein
sequences were functionally annotated according to the database alignment while
a large part of the obtained protein sequences was left non-annotated. To treat
the non-annotated sequences, a prediction model based on convolutional neural
network was established with the dataset from Uniport database in three domains
to acquire good performance, especially the higher false positive control rate.
With established model, the non-annotated protein sequences of creeping
bentgrass were analyzed to annotate proteins relevant to disease-resistance
response and signal transduction. Conclusions: The prediction model based on
convolutional neural network was successfully applied to select good candidates
of the proteins with functions relevant to the ISR mechanism from the protein
sequences which cannot be annotated by database alignment. The waste of
sequence data can be avoided, and research time and labor will be saved in
further research of protein of creeping bentgrass by molecular biology
technology. It also provides reference for other sequence analysis of turfgrass
disease-resistance research.",2104.03139v2
2021-08-19,Resistive Hot Accretion Flows with Anisotropic Pressure,"Since the collisional mean free path of charged particles in hot accretion
flows can be significantly larger than the typical length-scale of the
accretion flows, the gas pressure is anisotropic to magnetic field lines. For
such a large collisional mean free path, the resistive dissipation can also
play a key role in hot accretion flows. In this paper, we study the dynamics of
resistive hot accretion flows in the presence of anisotropic pressure. We
present a set of self-similar solutions where the flow variables are assumed to
be a function only of radius. Our results show that the radial and rotational
velocities and the sound speed increase considerably with the strength of
anisotropic pressure. The increase in infall velocity and in sound speed are
more significant if the resistive dissipation is taken into account. We find
that such changes depend on the field strength. Our results indicate that the
resistive heating is $10\%$ of the heating by the work done by anisotropic
pressure when the strength of anisotropic pressure is 0.1. This value becomes
higher when the strength of anisotropic pressure reduces. The increase in disk
temperature can lead to heating and acceleration of the electrons in such
flows. It helps us to explain the origin of phenomena such as the flares in
Galactic Center Sgr A*.",2108.09829v1
2022-05-22,First Report of Susceptibility Status of the Invasive Vector: Aedes albopictus to insecticides used in vector control in Morocco,"Aedes albopictus has been newly recorded in Agdal district at Rabat in
Morocco. The establishment of this invasive mosquito could affect the public
health by causing serious epidemics despite of its high nuisance in urban and
sub-urban areas. Vector control is mainly based on environmental management but
chemical insecticides can be used to reduce adult mosquito densities during
peak periods. However, the level of susceptibility of this mosquito to
insecticides has not been studied yet in Morocco. This paper reports the
results of the first study conducted to monitor the insecticide resistance of
adult and larva Ae. albopictus to the insecticides currently used in the vector
control. The study was carried out during May-June 2018 at Rabat from the
north-west of the country. Adult susceptibility tests were performed following
the WHO test procedures. One organochlorate (DDT 4%), one pyrethroids
(cyfluthrin 0.15%), one carbamate (bendiocarb 0.1%) and one organophosphate
(fenithrothion 1%) were tested at diagnostic doses (DD). The five-fold DD of
bendiocarb were also used to yield information on the intensity of mosquito
adult resistance. The results of the performed susceptibility bioassay showed
that the vector is susceptible to cyfluthrin and resistant to DDT, bendiocarb
and fenithrothion. Larval bioassays to temephos were conducted according to WHO
standard operating protocol to establish the dose-mortality relationship and
deduct the LC50 and LC90 then resistance ratios. We show that larval
populations of Ae. albopictus are still sensible to this insecticide. This
information could help policy-makers to plan insecticide resistance management.",2205.11994v1
2023-09-15,Greedy Optimization of Resistance-based Graph Robustness with Global and Local Edge Insertions,"The total effective resistance, also called the Kirchhoff index, provides a
robustness measure for a graph $G$. We consider two optimization problems of
adding $k$ new edges to $G$ such that the resulting graph has minimal total
effective resistance (i.e., is most robust) -- one where the new edges can be
anywhere in the graph and one where the new edges need to be incident to a
specified focus node. The total effective resistance and effective resistances
between nodes can be computed using the pseudoinverse of the graph Laplacian.
The pseudoinverse may be computed explicitly via pseudoinversion; yet, this
takes cubic time in practice and quadratic space. We instead exploit
combinatorial and algebraic connections to speed up gain computations in an
established generic greedy heuristic. Moreover, we leverage existing randomized
techniques to boost the performance of our approaches by introducing a
sub-sampling step. Our different graph- and matrix-based approaches are indeed
significantly faster than the state-of-the-art greedy algorithm, while their
quality remains reasonably high and is often quite close. Our experiments show
that we can now process larger graphs for which the application of the
state-of-the-art greedy approach was impractical before.",2309.08271v1
2024-05-28,Differential Voltage Analysis and Patterns in Parallel-Connected Pairs of Imbalanced Cells,"Diagnosing imbalances in capacity and resistance within parallel-connected
cells in battery packs is critical for battery management and fault detection,
but it is challenging given that individual currents flowing into each cell are
often unmeasured. This work introduces a novel method useful for identifying
imbalances in capacity and resistance within a pair of parallel-connected cells
using only voltage and current measurements from the pair. Our method utilizes
differential voltage analysis (DVA) when the pair is under constant current
discharge and demonstrates that features of the pair's differential voltage
curve (dV/dQ), namely its mid-to-high SOC dV/dQ peak's height and skewness, are
sensitive to imbalances in capacity and resistance. We analyze and explain how
and why these dV/dQ peak shape features change in response to these imbalances,
highlighting that the underlying current imbalance dynamics resulting from
these imbalances contribute to these changes. Ultimately, we demonstrate that
dV/dQ peak shape features can identify the product of capacity imbalance and
resistance imbalance, but cannot uniquely identify the imbalances. This work
lays the groundwork for identifying imbalances in capacity and resistance in
parallel-connected cell groups in battery packs, where commonly only a single
current sensor is placed for each parallel cell group.",2405.17754v1
2018-02-05,Electrical-current-induced magnetic hysteresis in self-assembled vertically aligned La_{2/3}Sr_{1/3}MnO_3:ZnO-nanopillar composites,"Magnetoresistive random-access memory (MRAM) is poised to become a
next-generation information storage device. Yet, many materials challenges
remain unsolved before it can become a widely used memory storage solution.
Among them, an urgent need is to identify a material system that is suitable
for downscaling and is compatible with low-power logic applications.
Self-assembled, vertically-aligned La_{2/3}Sr_{1/3}MnO_3:ZnO nanocomposites, in
which La_{2/3}Sr_{1/3}MnO_3 (LSMO) matrix and ZnO nanopillars form an
intertwined structure with coincident-site-matched growth occurring between the
LSMO and ZnO vertical interfaces, may offer new MRAM applications by combining
their superior electric, magnetic (B), and optical properties. In this paper,
we show the results of electrical current induced magnetic hysteresis in
magneto-resistance measurements in these nano-pillar composites. We observe
that when the current level is low, for example, 1 uA, the magneto-resistance
displays a linear, negative, non-hysteretic B field dependence. Surprisingly,
when a large current is used, I > 10 uA, a hysteretic behavior is observed when
the B field is swept in the up and down directions. This hysteresis weakens as
the sample temperature is increased. A possible spin-valve mechanism related to
this electrical current induced magnetic hysteresis is proposed and discussed.",1802.01632v1
2018-03-05,Measurement of Elastoresistivity at Finite Frequency by Amplitude Demodulation,"Elastoresistivity, the relation between resistivity and strain, can elucidate
subtle properties of the electronic structure of a material and is an
increasingly important tool for the study of strongly correlated materials. To
date, elastoresistivity measurements have been predominantly performed with
quasi-static (DC) strain. In this work, we demonstrate a method for using AC
strain in elastoresistivity measurements. A sample experiencing AC strain has a
time-dependent resistivity, which modulates the voltage produced by an AC
current; this effect produces time-dependent variations in resisitivity that
are directly proportional to the elastoresistivity, and which can be measured
more quickly, with less strain on the sample, and with less stringent
requirements for temperature stability than the previous DC technique. Example
measurements between 10 Hz and 3 kHz are performed on a material with a large,
well-characterized and temperature dependent elastoresistivity: the
representative iron-based superconductor BaFe$_{1.975}$Co$_{0.025}$As$_2$.
These measurements yield a frequency independent elastoresistivity and
reproduce results from previous DC elastoresistivity methods to within
experimental accuracy. We emphasize that the dynamic (AC) elastoresistivity is
a distinct material-specific property that has not previously been considered.",1803.01909v2
2020-03-26,Fermi liquid behavior and colossal magnetoresistance in layered MoOCl2,"A characteristic of a Fermi liquid is the T^2 dependence of its resistivity,
sometimes referred to as the Baber law. However, for most metals, this behavior
is only restricted to very low temperatures, usually below 20 K. Here, we
experimentally demonstrate that for the single-crystal van der Waals layered
material MoOCl2, the Baber law holds in a wide temperature range up to ~120 K,
indicating that the electron-electron scattering plays a dominant role in this
material. Combining with the specific heat measurement, we find that the
modified Kadowaki-Woods ratio of the material agrees well with many other
strongly correlated metals. Furthermore, in the magneto-transport measurement,
a colossal magneto-resistance is observed, which reaches ~350% at 9 T and
displays no sign of saturation. With the help of first-principles calculations,
we attribute this behavior to the presence of open orbits on the Fermi surface.
We also suggest that the dominance of electron-electron scattering is related
to an incipient charge density wave state of the material. Our results
establish MoOCl2 as a strongly correlated metal and shed light on the
underlying physical mechanism, which may open a new path for exploring the
effects of electron-electron interaction in van der Waals layered structures.",2003.11905v1
2020-04-06,Microscopic Relaxation Channels in Materials for Superconducting Qubits,"Despite mounting evidence that materials imperfections are a major obstacle
to practical applications of superconducting qubits, connections between
microscopic material properties and qubit coherence are poorly understood.
Here, we perform measurements of transmon qubit relaxation times $T_1$ in
parallel with spectroscopy and microscopy of the thin polycrystalline niobium
films used in qubit fabrication. By comparing results for films deposited using
three techniques, we reveal correlations between $T_1$ and grain size, enhanced
oxygen diffusion along grain boundaries, and the concentration of suboxides
near the surface. Physical mechanisms connect these microscopic properties to
residual surface resistance and $T_1$ through losses arising from the grain
boundaries and from defects in the suboxides. Further, experiments show that
the residual resistance ratio can be used as a figure of merit for qubit
lifetime. This comprehensive approach to understanding qubit decoherence charts
a pathway for materials-driven improvements of superconducting qubit
performance.",2004.02908v1
2021-01-23,Field-effect at electrical contacts to two-dimensional materials,"The inferior electrical contact to two-dimensional (2D) materials is a
critical challenge for their application in post-silicon very large-scale
integrated circuits. Electrical contacts were generally related to their
resistive effect, quantified as contact resistance. With a systematic
investigation, this work demonstrates a capacitive
metal-insulator-semiconductor (MIS) field-effect at the electrical contacts to
2D materials: the field-effect depletes or accumulates charge carriers,
redistributes the voltage potential, and give rise to abnormal current
saturation and nonlinearity. On the one hand, the current saturation hinders
the devices' driving ability, which can be eliminated with carefully engineered
contact configurations. On the other hand, by introducing the nonlinearity to
monolithic analog artificial neural network circuits, the circuits' perception
ability can be significantly enhanced, as evidenced using a COVID-19 critical
illness prediction model. This work provides a comprehension of the
field-effect at the electrical contacts to 2D materials, which is fundamental
to the design, simulation, and fabrication of electronics based on 2D material.",2101.09487v1
2022-05-30,Mechanistic framework for reduced-order models in soft materials: Application to three-dimensional granular intrusion,"Soft materials often display complex behaviors that transition through
apparent solid- and fluid-like regimes. While a growing number of microscale
simulation methods exist for these materials, reduced-order models that
encapsulate the global-scale physics are often desired to predict how external
bodies interact with soft media, as occurs in diverse situations from impact
and penetration problems to locomotion over natural terrains. This work
proposes a systematic program to develop three-dimensional reduced-order models
for soft materials from a fundamental basis using continuum symmetries and
rheological principles. In particular, we derive a reduced-order technique for
modeling intrusion in granular media which we term three-dimensional Resistive
Force Theory (3D-RFT), which is capable of accurately and quickly predicting
the resistive stress distribution on arbitrary-shaped intruding bodies. Aided
by a continuum description of the granular medium, a comprehensive set of
spatial symmetry constraints, and a limited amount of reference data, we
develop a self-consistent and accurate 3D-RFT. We verify the model capabilities
in a wide range of cases and show it can be quickly recalibrated to different
media and intruder surface types. The premises leading to 3D-RFT anticipate
application to other soft materials with strongly hyperlocalized intrusion
behavior.",2205.14920v3
2023-01-27,Machine-guided Design of Oxidation Resistant Superconductors for Quantum Information Applications,"Decoherence in superconducting qubits has long been attributed to two level
systems arising from the surfaces and interfaces present in real devices. A
recent significant step in reducing decoherence was the replacement of
superconducting niobium by superconducting tantalum, resulting in a tripling of
transmon qubit lifetimes (T1). One of these surface variables, the identity,
thickness, and quality of the native surface oxide, is thought to play a major
role as tantalum only has one oxide whereas niobium has several. Here we report
the development of a thermodynamic metric to rank materials based on their
potential to form a well-defined, thin, surface oxide. We first compute this
metric for known binary and ternary metal alloys using data available from
Materials Project, and experimentally validate the strengths and limits of this
metric through preparation and controlled oxidation of 8 known metal alloys.
Then we train a convolutional neural network to predict the value of this
metric from atomic composition and atomic properties. This allows us to compute
the metric for materials that are not present in materials project, including a
large selection of known superconductors, and, when combined with Tc, allow us
to identify new candidate superconductors for quantum information science
(QISE) applications. We test the oxidation resistance of a pair of these
predictions experimentally. Our results are expected to lay the foundation for
tailored and rapid selection of improved superconductors for QISE.",2301.11543v1
2012-08-10,On the phase diagram of the itinerant helimagnet MnSi: does MnSi become quantum critical ?,"We performed a series of resistivity measurements of a MnSi single crystal at
high pressures, created by a piston-cylinder device with a liquid pressure
medium. The form of the resistivity curve at ambient pressure clearly indicates
a first order nature of the magnetic phase transition in MnSi. Application of
high pressure shows fast degradation of the first order features of the phase
transition. The temperature derivative of resistivity demonstrates two notable
features of the phase transition that disappear on pressure increasing. They
are a sharp peak marking the first order phase transition and a shallow
maximum, situated slightly above the critical temperature and pointing to the
domain of prominent helical fluctuations. The current experimental data rule
out any strong first order phase transition in MnSi at high pressures and low
temperatures, which would prevent development of a quantum critical region. On
the contrary, there should exist true quantum critical phenomena in MnSi at
high pressures because a tiny first order transition, if it survives at high
pressures to the lowest temperature, hardly could suppress the entire quantum
critical region.",1208.2174v1
2017-04-12,High temperature resistivity measured at ν = 5/2 as a predictor of 2DEG quality in the N=1 Landau level,"We report a high temperature (T = 0.3K) indicator of the excitation gap
$\Delta_{5/2}$ at the filling factor $ \nu=5/2$ fractional quantum Hall state
in ultra-high quality AlGaAs/GaAs two-dimensional electron gases. As the lack
of correlation between mobility $\mu$ and $\Delta_{5/2}$ has been well
established in previous experiments, we define, analyze and discuss the utility
of a different metric $\rho_{5/2}$, the resistivity at $\nu=5/2$, as a high
temperature predictor of $\Delta_{5/2}$. This high-field resistivity reflects
the scattering rate of composite fermions. Good correlation between
$\rho_{5/2}$ and $\Delta_{5/2}$ is observed in both a density tunable device
and in a series of identically structured wafers with similar density but
vastly different mobility. This correlation can be explained by the fact that
both $\rho_{5/2}$ and $\Delta_{5/2}$ are sensitive to long-range disorder from
remote impurities, while $\mu$ is sensitive primarily to disorder localized
near the quantum well.",1704.03794v1
2019-08-02,Realization of Ohmic-contact and velocity saturation in organic field-effect transistors by crystallized monolayer,"The contact resistance limits the down-scaling and operating range of OFETs.
With the monolayer (1L) organic crystals and non-destructive
metal/semiconductor interfaces, intrinsic mobility of 12.5 cm2V-1s-1 and Ohmic
contact resistance of 40 ohm-cm were achieved. The on/off ratio maintained at
10^3 even at a small VDS of -0.1 mV. High current density of 4.2 uA/um was
achieved with the 1L-crystal as the active layer. At such high current density,
the velocity saturation and channel self-heating effects are observed in OFETs
for the first time. In addition to the low contact resistance and
high-resolution lithography, we suggest the thermal management of the high
mobility OFETs will be the next major challenge to achieve high-speed densely
integrated flexible electronics.",1908.01032v1
2022-11-04,Relativistic resistive magneto-hydrodynamics code for high-energy heavy-ion collisions,"We construct a relativistic resistive magneto-hydrodynamic (RRMHD) numerical
simulation code for high-energy heavy-ion collisions. We split the system of
differential equations into two parts, a non-stiff and a stiff part. For the
non-stiff part, we evaluate the numerical flux using HLL approximated Riemann
solver and execute the time integration by the second-order of Runge-Kutta
algorithm. For the stiff part, which appears in Ampere's law, we integrate the
equations using semi-analytic solutions of the electric field. We employ the
generalized Lagrange multiplier method to ensure the divergence-free constraint
for the magnetic field and Gauss's law. We confirm that our code reproduces
well the results of standard RRMHD tests in the Cartesian coordinates. In the
Milne coordinates, the code with high conductivity is validated against
relativistic ideal MHD tests. We also verify the semi-analytic solutions of the
accelerating longitudinal expansion of relativistic resistive
magneto-hydrodynamics in high-energy heavy-ion collisions in a comparison with
our numerical result. Our numerical code reproduces these solutions.",2211.02310v1
2022-02-28,Mg-doping and free-hole properties of hot-wall MOCVD GaN,"The hot-wall metal-organic chemical vapor deposition (MOCVD), previously
shown to enable superior III-nitride material quality and high performance
devices, has been explored for Mg doping of GaN. We have investigated the Mg
incorporation in a wide doping range ($2.45\times{10}^{18}~cm^{-3}$ up to
$1.10\times{10}^{20}~cm^{-3}$) and demonstrate GaN:Mg with low background
impurity concentrations under optimized growth conditions. Dopant and impurity
levels are discussed in view of Ga supersaturation which provides a unified
concept to explain the complexity of growth conditions impact on Mg acceptor
incorporation and compensation. The results are analysed in relation to the
extended defects, revealed by scanning transmission electron microscopy (STEM),
X-ray diffraction (XRD), and surface morphology, and in correlation with the
electrical properties obtained by Hall effect and capacitance-voltage (C-V)
measurements. This allows to establish a comprehensive picture of GaN:Mg growth
by hot-wall MOCVD providing guidance for growth parameters optimization
depending on the targeted application. We show that substantially lower H
concentration as compared to Mg acceptors can be achieved in GaN:Mg without any
in-situ or post-growth annealing resulting in p-type conductivity in as-grown
material. State-of-the-art $p$-GaN layers with a low-resistivity and a high
free-hole density (0.77 $\Omega$.cm and $8.4\times{10}^{17}~cm^{-3}$,
respectively) are obtained after post-growth annealing demonstrating the
viability of hot-wall MOCVD for growth of power electronic device structures.",2202.13614v1
2019-11-21,Oxidized-monolayer Tunneling Barrier for Strong Fermi-level Depinning in Layered InSe Transistors,"In 2D-semiconductor-based field-effect transistors and optoelectronic
devices, metal-semiconductor junctions are one of the crucial factors
determining device performance. The Fermi-level (FL) pinning effect, which
commonly caused by interfacial gap states, severely limits the tunability of
junction characteristics, including barrier height and contact resistance. A
tunneling contact scheme has been suggested to address the FL pinning issue in
metal-2D-semiconductor junctions, whereas the experimental realization is still
elusive. Here, we show that an oxidized-monolayer-enabled tunneling barrier can
realize a pronounced FL depinning in indium selenide (InSe) transistors,
exhibiting a large pinning factor of 0.5 and a highly modulated Schottky
barrier height. The FL depinning can be attributed to the suppression of metal-
and disorder-induced gap states as a result of the high-quality tunneling
contacts. Structural characterizations indicate uniform and atomically thin
surface oxidation layer inherent from nature of van der Waals materials and
atomically sharp oxide-2D-semiconductor interfaces. Moreover, by effectively
lowering the Schottky barrier height, we achieve an electron mobility of 2160
cm$^2$/Vs and a contact barrier of 65 meV in two-terminal InSe transistors. The
realization of strong FL depinning in high-mobility InSe transistors with the
oxidized monolayer presents a viable strategy to exploit layered semiconductors
in contact engineering for advanced electronics and optoelectronics.",1911.09327v1
2023-12-11,Development of travelling heater method for growth of detector grade CdZnTe single crystals,"We report on the indigenous design and development of laboratory scale
travelling heater method (THM) system to grow detector grade Cd0.9Zn0.1Te
(CdZnTe) single crystals. THM system mainly consists of two-zone furnace with a
tuneable temperature gradient (30 - 80 C/cm), high precision translation (1 -
25 mm per day) and rotation (1 - 50 rpm) assemblies to meet the stringent
conditions that are essential to grow detector grade CdZnTe single crystals.
Further, a load cell in the THM system enables continuous monitoring of the
growth. Systematic growth experiments were performed to optimize the various
growth parameters in order to achieve large grain single crystals. Herein, the
effect of temperature gradient and growth rate on the increase in grain size is
discussed in detail. Each successful growth experiment yields a minimum of four
detector grade elements of dimensions 10 x 10 x 5 mm3 from a starting charge of
100 g of CdZnTe. The crystalline nature and quality of the detector elements
were evaluated using Laue, NIR transmission spectroscopy and I-V
characteristics. Crystals with resistivity greater than ~ 1-10 giga-ohm-cm were
identified for testing gamma ray detection. The photo peak of 137Cs was
resolved with an energy resolution of 4.2 % at 662 keV and its measured
electron mobility lifetime product is found to be ~ 3.3 x 10-3 cm2/V. The
demonstration of the gamma ray detection with a relatively high {\mu}{\tau}
product is the testimony to the successful growth of detector grade CdZnTe
single crystals by an indigenously developed THM system.",2312.06233v1
2020-09-10,Water Within a Permanently Shadowed Lunar Crater: Further LCROSS Modeling and Analysis,"The 2009 Lunar CRater Observation and Sensing Satellite (LCROSS) impact
mission detected water ice absorption using spectroscopic observations of the
impact-generated debris plume taken by the Shepherding Spacecraft, confirming
an existing hypothesis regarding the existence of water ice in permanently
shadowed regions within Cabeus crater. Ground-based observations in support of
the mission were able to further constrain the mass of the debris plume and the
concentration of the water ice ejected during the impact. In this work, we
explore additional constraints on the initial conditions of the pre-impact
lunar sediment required in order to produce a plume model that is consistent
with the ground-based observations. We match the observed debris plume
lightcurve using a layer of dirty ice with an ice concentration that increases
with depth, a layer of pure regolith, and a layer of material at about 6 meters
below the lunar surface that would otherwise have been visible in the plume but
has a high enough tensile strength to resist excavation. Among a few possible
materials, a mixture of regolith and ice with a sufficiently high ice
concentration could plausibly produce such a behavior. The vertical albedo
profiles used in the best fit model allows us to calculate a pre-impact mass of
water ice within Cabeus crater of $5 \pm 3.0 \times 10^{11}$ kg and a mass
concentration of water in the lunar sediment of $8.2 \pm 0.001$ %wt, assuming a
water ice albedo of 0.8 and a lunar regolith density of 1.5 g cm$^{-3}$, or a
mass concentration of water of $4.3 \pm 0.01$ %wt, assuming a lunar regolith
density of 3.0. These models fit to ground-based observations result in derived
masses of regolith and water ice within the debris plume that are consistent
with \emph{in situ} measurements, with a model debris plume ice mass of 108 kg.",2009.05080v1
2019-08-03,Real-time Deep Learning at the Edge for Scalable Reliability Modeling of Si-MOSFET Power Electronics Converters,"With the significant growth of advanced high-frequency power converters,
on-line monitoring and active reliability assessment of power electronic
devices are extremely crucial. This article presents a transformative approach,
named Deep Learning Reliability Awareness of Converters at the Edge (Deep
RACE), for real-time reliability modeling and prediction of high-frequency
MOSFET power electronic converters. Deep RACE offers a holistic solution which
comprises algorithm advances, and full system integration (from the cloud down
to the edge node) to create a near real-time reliability awareness. On the
algorithm side, this paper proposes a deep learning algorithmic solution based
on stacked LSTM for collective reliability training and inference across
collective MOSFET converters based on device resistance changes. Deep RACE also
proposes an integrative edge-to-cloud solution to offer a scalable
decentralized devices-specific reliability monitoring, awareness, and modeling.
The MOSFET convertors are IoT devices which have been empowered with edge
real-time deep learning processing capabilities. The proposed Deep RACE
solution has been prototyped and implemented through learning from MOSFET data
set provided by NASA. Our experimental results show an average miss prediction
of $8.9\%$ over five different devices which is a much higher accuracy compared
to well-known classical approaches (Kalman Filter, and Particle Filter). Deep
RACE only requires $26ms$ processing time and $1.87W$ computing power on Edge
IoT device.",1908.01244v1
2022-04-29,Quantitative Prediction of Fracture Toughness $(K_{{\rm I}c})$ of Polymer by Fractography Using Deep Neural Networks,"Fracture surfaces provide various types of information about fracture. The
fracture toughness $K_{{\rm I}c}$, which represents the resistance to fracture,
can be estimated using the three-dimensional (3D) information of a fracture
surface, i.e., its roughness. However, this is time-consuming and expensive to
obtain the 3D information of a fracture surface; thus, it is desirable to
estimate $K_{{\rm I}c}$ from a two-dimensional (2D) image, which can be easily
obtained. In recent years, methods of estimating a 3D structure from its 2D
image using deep learning have been rapidly developed. In this study, we
propose a framework for fractography that directly estimates $K_{{\rm I}c}$
from a 2D fracture surface image using deep neural networks (DNNs). Typically,
image recognition using a DNN requires a tremendous amount of image data, which
is difficult to acquire for fractography owing to the high experimental cost.
To compensate for the limited data, in this study, we used the transfer
learning (TL) method, and constructed high-performance prediction models even
with a small dataset by transferring machine learning models trained using
other large datasets. We found that the regression model obtained using our
proposed framework can predict $K_{{\rm I}c}$ in the range of approximately 1-5
[MPa$\sqrt{m}$] with a standard deviation of the estimation error of
approximately $\pm$0.37 [MPa$\sqrt{m}$]. The present results demonstrate that
the DNN trained with TL opens a new route for quantitative fractography by
which parameters of fracture process can be estimated from a fracture surface
even with a small dataset. The proposed framework also enables the building of
regression models in a few hours. Therefore, our framework enables us to screen
a large number of image datasets available in the field of materials science
and find candidates that are worth expensive machine learning analysis.",2204.13912v1
2023-06-26,Elucidating Interfacial Dynamics of Ti-Al Systems Using Molecular Dynamics Simulation and Markov State Modeling,"Due to their remarkable mechanical and chemical properties, Ti-Al based
materials are attracting considerable interest in numerous fields of
engineering, such as automotive, aerospace, and defense. With their low
density, high strength, and resistance to corrosion and oxidation, these
intermetallic alloys and compound metal-metallic composites have found diverse
applications. The present study delves into the interfacial dynamics of these
Ti-Al systems, particularly focusing on the behavior of Ti and Al atoms in the
presence of TiAl$_3$ grain boundaries under experimental heat treatment
conditions. Using a combination of Molecular Dynamics and Markov State Model
analyses, we scrutinize the kinetic processes involved in the formation of
TiAl$_3$. The Molecular Dynamics simulation indicates that at the early stage
of heat treatment, the predominating process is the diffusion of Al atoms
towards the Ti surface through the TiAl$_3$ grain boundaries. The Markov State
Modeling identifies three distinct dynamic states of Al atoms within the Ti/Al
mixture that forms during the process, each exhibiting a unique spatial
distribution. Using transition timescales as a qualitative measure of the
rapidness of the dynamics, it is observed that the Al dynamics is significantly
less rapid near the Ti surface compared to the Al surface. Put together, the
results offer a comprehensive understanding of the interfacial dynamics and
reveals a three-stage diffusion mechanism. The process initiates with the
premelting of Al, proceeds with the prevalent diffusion of Al atoms towards the
Ti surface, and eventually ceases as the Ti concentration within the mixture
progressively increases. The insights gained from this study could contribute
significantly to the control and optimization of manufacturing processes for
these high-performing Ti-Al based materials.",2306.14568v2
2024-01-17,Pressure-induced superconductivity in a novel germanium allotrope,"High-pressure studies on elements play an essential role in superconductivity
research, with implications for both fundamental science and applications. Here
we report the experimental discovery of surprisingly low pressure driving a
novel germanium allotrope into a superconducting state in comparison to that
for alpha-Ge. Raman measurements revealed structural phase transitions and
possible electronic topological transitions under pressure up to 58 GPa. Based
on pressure-dependent resistivity measurements, superconductivity was induced
above 2 GPa and the maximum Tc of 6.8 K was observed under 4.6 GPa.
Interestingly, a superconductivity enhancement was discovered during
decompression, indicating the possibility of maintaining pressure-induced
superconductivity at ambient pressure with better superconducting performance.
Density functional theory analysis further suggested that the electronic
structure of Ge (oP32) is sensitive to its detailed geometry and revealed that
disorder in the beta-tin structure leads to a higher Tc in comparison to the
perfect beta-tin Ge.",2401.09625v1
2012-01-09,Performances and ageing study of resistive-anodes Micromegas detectors for HL-LHC environment,"With the tenfold luminosity increase envisaged at the HL-LHC, the background
(photons, neutrons, ...) and the event pile-up probability are expected to
increase in proportion in the different experiments, especially in the forward
regions like, for instance, the muons chambers of the ATLAS detector. Detectors
based on the Micromegas principle should be good alternatives for the detector
upgrade in the HL-LHC framework because of a good spatial (<100 \mum) and time
(few ns) resolutions, high-rate capability, radiation hardness, good robustness
and the possibility to build large areas. The aim of this study is to
demonstrate that it is possible to reduce the discharge probability and protect
the electronics by using a resistive anode plane in a high flux hadrons
environment. Several prototypes of 10x10 cm2, with different pitches (0.5 to 2
mm) and different resistive layers have been tested at CERN (pi+@SPS). Several
tests have been performed with a telescope at different voltages to assess the
performances of the detectors in terms of position resolution and efficiency.
The spark behaviour in these conditions has also been evaluated. Resistive
coating has been shown to be a successful method to reduce the effect of sparks
on the efficiency of micromegas. A good spatial resolution (~80 \mum) can be
reached with a resistive strip coating detector of 1mm pitch and a high
efficiency (> 98%) can be achieved with resistive-anode micromegas detector. An
X-rays irradiation has been also performed, showing no ageing effect after more
than 21 days exposure and an integrated charge of almost 1C.",1201.1843v1
2003-09-01,Non-equilibrium and non-linear stationary state in thermoelectric materials,"Efficiency of thermoelectric materials is characterized by the figure of
merit Z. Z has been believed to be a peculiar material constant. However, the
accurate measurements in the present work reveal that Z has large size
dependence and a non-linear temperature distribution appears as stationary
state in the thermoelectric material. The observation of these phenomena is
achieved by the Harman method. This method is the most appropriate way to
investigate the thermoelectric properties because the dc and ac resistances are
measured by the same electrode configuration. We describe the anomalous
thermoelectric properties observed in mainly (Bi,Sb)2Te3 by the Harman method
and then insist that Z is not the peculiar material constant but must be
defined as the physical quantity dependent of the size and the position in the
material.",0309016v1
2006-11-27,Comparison of Methods for Characterizing Sound Absorbing Materials,"Sound absorbing materials are usually defined by five parameters: open
porosity, static airflow resistivity, tortuosity, and two characteristic
lengths. In recent decades, different methods have been developed in order to
characterize these parameters. These methods may be divided following three
approaches: i) inverse, ii) indirect and iii) direct. The inverse approach is
based on an optimisation problem where the material parameters are adjusted in
the acoustic model to reproduce acoustical measurements. The indirect approach
is based on the acoustical model from which analytical expressions linking the
material parameters to acoustical measurements are derived. Contrary to the
previous two approaches, the direct approach is not based on acoustical
measurements. It is based on the physical and mathematical definition of the
parameters and requires dedicated equipments. In this study, the five
parameters have been measured for different porous materials using some direct,
indirect and inverse methods. A comparison of the different results is carried
out, and shows that the different methods may yield large variability in the
found parameters. A discussion is given to explain the observed variability and
the limitations of the methods.",0611259v2
2007-08-14,Preliminary Results on Vibration Damping Properties of Nanoscale-Reinforced Composite Materials,"The focus in this paper is an analysis of existing state of the arts directed
toward the development of the next generation of vibration damping systems. The
research work concentrates on an investigation related to
nanoparticles/fibres/tubes-reinforced materials and coatings dynamic
characterization and modeling of the fundamental phenomena that control
relationships between structure and damping/mechanical properties of the
materials. We simulated composite materials using finite element and mesh free
methods, using a hollow shell representation of the individual nanotube/fiber.
Results of the research work will provide a platform for the development of
nanoparticle-reinforced damping materials that are light-weight, vibration and
shock resistant. The outcome of the research work is expected to have
wide-ranging technical benefits with direct relevance to industry in areas of
transportation (aerospace, automotive, rail), electronics and civil
infrastructure development.",0708.1821v1
2018-05-25,Imaging material functionality through 3D nanoscale tracking of energy flow,"The ability of energy carriers to move between atoms and molecules underlies
biochemical and material function. Understanding and controlling energy flow,
however, requires observing it on ultrasmall and ultrafast spatiotemporal
scales, where energetic and structural roadblocks dictate the fate of energy
carriers. Here we developed a non-invasive optical scheme that leverages
non-resonant interferometric scattering to track tiny changes in material
polarizability created by energy carriers. We thus map evolving energy carrier
distributions in four dimensions of spacetime with few-nanometer lateral
precision and directly correlate to material morphology. We visualize exciton,
charge, and heat transport in polyacene, silicon and perovskite semiconductors
and elucidate how disorder affects energy flow in 3D. For example, we show that
morphological boundaries in polycrystalline metal halide perovskites possess
lateral- and depth-dependent resistivities, blocking lateral transport for
surface but not bulk carriers. We furthermore reveal strategies to interpret
energy transport in disordered environments that will direct the design of
defect-tolerant materials for the semiconductor industry of tomorrow.",1805.09982v4
2020-03-30,A bioinspired optically transparent tough glass composite,"Glasses have numerous applications due to their exceptional transparency,
however, poor fracture and impact resistance limit their applications as an
engineering material. One relatively recent approach to improve the mechanical
properties of materials is through bio-inspiration. Structural biological
composites such as nacre, the protective inner layer of mollusk shells, offer
far superior mechanical properties relative to their constituents. This has
motivated researchers to mimic the design principles in natural composites to
create tough transparent materials. However, current bio-inspired materials
lack fabrication scalability or offer poor optical transmission. Here, an
efficient, scalable bulk process is developed for creating optically
transparent tough composites, resulting in a nacreous glass composite material
with a four-fold increase in fracture toughness and a three-fold increase in
flexural strength compared to conventional structural glasses, and with a 73%
of average optical transmittance. The composite consists of glass flakes and
poly (methyl methacrylate) (PMMA) assembled utilizing a centrifuge-based
fabrication method that aligns and compacts the flakes into layers. To optimize
the transparency of the structure, the refractive indices of the PMMA and glass
are matched. Based on the results, this nacreous glass composite is proposed as
a potential alternative in diverse architectural, vehicular, and electronics
applications.",2003.13863v1
2021-04-15,Towards A Process Model for Co-Creating AI Experiences,"Thinking of technology as a design material is appealing. It encourages
designers to explore the material's properties to understand its capabilities
and limitations, a prerequisite to generative design thinking. However, as a
material, AI resists this approach because its properties emerge as part of the
design process itself. Therefore, designers and AI engineers must collaborate
in new ways to create both the material and its application experience. We
investigate the co-creation process through a design study with 10 pairs of
designers and engineers. We find that design 'probes' with user data are a
useful tool in defining AI materials. Through data probes, designers construct
designerly representations of the envisioned AI experience (AIX) to identify
desirable AI characteristics. Data probes facilitate divergent thinking,
material testing, and design validation. Based on our findings, we propose a
process model for co-creating AIX and offer design considerations for
incorporating data probes in design tools.",2104.07595v2
2022-05-30,Progress and prospects in the quantum anomalous Hall effect,"The quantum anomalous Hall effect refers to the quantization of Hall effect
in the absence of applied magnetic field. The quantum anomalous Hall effect is
of topological nature and well suited for field-free resistance metrology and
low-power information processing utilizing dissipationless chiral edge
transport. In this Perspective, we provide an overview of the recent
achievements as well as the materials challenges and opportunities, pertaining
to engineering intrinsic/interfacial magnetic coupling, that are expected to
propel future development of the field.",2205.15226v3
2023-07-09,lcs4Foam -- An OpenFOAM Function Object to Compute Lagrangian Coherent Structures,"To facilitate the understanding and to quantitatively assess the material
transport in fluids, a modern characterisation method has emerged in fluid
dynamics in the last decades footed in dynamical systems theory. It allows to
examine the most influential material lines which are called Lagrangian
Coherent Structures (LCS) and order the material transport into dynamically
distinct regions at large scales which resist diffusion or mixing. LCS reveal
the robust skeleton of material surfaces and are essential to assess material
transport in time-dependent flows quantitatively. Candidates of LCS can be
estimated and visualised from finite-time stretching and folding fields by
calculating the Finite-Time Lyapunov Exponents (FTLE).
  In this contribution, we provide an OpenFOAM function object to compute FTLE
during CFD simulation. This enables the OpenFOAM community to assess the
geometry of the material transport in any flow quantitatively on-the-fly using
principally any OpenFOAM flow solver.",2307.04104v1
2023-11-23,Rate- and temperature-dependent ductile-to-brittle fracture transition: Experimental investigation and phase-field analysis for toffee,"The mechanical behaviour of many materials, including polymers or natural
materials, significantly depends on the rate of deformation. As a consequence,
a rate-dependent ductile-to-brittle fracture transition may be observed. For
toffee-like caramel, this effect is particularly pronounced. At room
temperature, this confectionery may be extensively deformed at low strain
rates, while it can behave highly brittle when the rate of deformation is
raised. Likewise, the material behaviour does significantly depend on
temperature, and even a slight cooling may cause a significant embrittlement.
  In this work, a thorough experimental investigation of the rate-dependent
deformation and fracture behaviour is presented. In addition, the influence of
temperature on the material response is studied. The experimental results form
the basis for a phase-field modelling of fracture. In order to derive the
governing equations of the model, an incremental variational principle is
introduced. By means of the validated model, an analysis of the experimentally
observed ductile-to-brittle fracture transition is performed. In particular,
the coupling between the highly dissipative deformation behaviour of the bulk
material and the rate-dependent fracture resistance is discussed.",2311.13869v1
2023-01-15,Inhomogeneous superconductivity onset in FeSe studied by transport properties,"Heterogeneous superconductivity onset is a common phenomenon in high-$T_c$
superconductors of both the cuprate and iron-based families. It is manifested
by a fairly wide transition from the metallic to zero-resistance state.
Usually, in these strongly anisotropic materials, superconductivity (SC) first
appears as isolated domains. This leads to anisotropic excess conductivity
above $T_c$, and the transport measurements provide valuable information about
the SC domain structure deep within the sample. In bulk samples, this
anisotropic SC onset gives an approximate average shape of SC grains, while in
thin samples it also indicates the average size of SC grains. In this work,
both interlayer and intralayer resistivity are measured as a function of
temperature in FeSe samples of various thickness. To measure the interlayer
resistivity, FeSe mesa structures oriented across the layers were fabricated
using FIB. As the sample thickness decreases, a significant increase in
superconducting transition temperature $T_c$ is observed : $T_c$ raises from 8
K in bulk material to 12 K in microbridges of thickness $\sim 40$ nm. We apply
analytical and numerical calculations to analyze these and earlier data and
find the aspect ratio and size of the SC domains in FeSe consistent with our
resistivity and diamagnetic response measurements. We propose a simple and
fairly accurate method for estimating the aspect ratio of SC domains from $T_c$
anisotropy in samples of various small thickness. The relationship between
nematic and superconducting domains in FeSe is discussed. We also generalize
the analytical formulas for conductivity in heterogeneous anisotropic
superconductors to the case of elongated SC domains of two perpendicular
orientations with equal volume fractions, corresponding to the nematic domain
structure in various Fe-based superconductors.",2301.06185v3
2023-11-28,Sputtered NbN Films for Ultrahigh Performance Superconducting Nanowire Single-Photon Detectors,"Nowadays ultrahigh performance superconducting nanowire single-photon
detectors are the key elements in a variety of devices from biological research
to quantum communications and computing. Accurate tuning of superconducting
material properties is a powerful resource for fabricating single-photon
detectors with a desired properties. Here, we report on the major theoretical
relations between ultrathin niobium nitride (NbN) films properties and
superconducting nanowire single-photon detectors characteristics, as well as
ultrathin NbN films properties dependence on reactive magnetron sputtering
recipes. Based on this study we formulate the exact requirements to ultrathin
NbN films for ultrahigh performance superconducting nanowire single-photon
detectors. Then, we experimentally study ultrathin NbN films properties
(morphology, crystalline structure, critical temperature, sheet resistance) on
silicon, sapphire, silicon dioxide and silicon nitride substrates sputtered
with various recipes. We demonstrate ultrathin NbN films (obtained with more
than 100 films deposition) with a wide range of critical temperature from 2.5
to 12.1 K and sheet resistance from 285 to 2000 ~$\Omega$/sq, as well as
investigate a sheet resistance evolution over for more than 40\% within two
years. Finally, we found out that one should use ultrathin NbN films with
specific critical temperature near 9 K and sheet resistance of 400 ~$\Omega$/sq
for ultrahigh performance SNSPD.",2311.17000v1
2009-03-27,Very High Order $\PNM$ Schemes on Unstructured Meshes for the Resistive Relativistic MHD Equations,"In this paper we propose the first better than second order accurate method
in space and time for the numerical solution of the resistive relativistic
magnetohydrodynamics (RRMHD) equations on unstructured meshes in multiple space
dimensions. The nonlinear system under consideration is purely hyperbolic and
contains a source term, the one for the evolution of the electric field, that
becomes stiff for low values of the resistivity. For the spatial discretization
we propose to use high order $\PNM$ schemes as introduced in \cite{Dumbser2008}
for hyperbolic conservation laws and a high order accurate unsplit time
discretization is achieved using the element-local space-time discontinuous
Galerkin approach proposed in \cite{DumbserEnauxToro} for one-dimensional
balance laws with stiff source terms. The divergence free character of the
magnetic field is accounted for through the divergence cleaning procedure of
Dedner et al. \cite{Dedneretal}. To validate our high order method we first
solve some numerical test cases for which exact analytical reference solutions
are known and we also show numerical convergence studies in the stiff limit of
the RRMHD equations using $\PNM$ schemes from third to fifth order of accuracy
in space and time. We also present some applications with shock waves such as a
classical shock tube problem with different values for the conductivity as well
as a relativistic MHD rotor problem and the relativistic equivalent of the
Orszag-Tang vortex problem. We have verified that the proposed method can
handle equally well the resistive regime and the stiff limit of ideal
relativistic MHD. For these reasons it provides a powerful tool for
relativistic astrophysical simulations involving the appearance of magnetic
reconnection.",0903.4832v1
2019-07-18,High-performance monolayer MoS2 field-effect transistor with large-scale nitrogen-doped graphene electrodes for Ohmic contact,"A finite Schottky barrier and large contact resistance between monolayer MoS2
and electrodes are the major bottlenecks in developing high-performance
field-effect transistors (FETs) that hinder the study of intrinsic quantum
behaviors such as valley-spin transport at low temperature. A gate-tunable
graphene electrode platform has been developed to improve the performance of
MoS2 FETs. However, intrinsic misalignment between the work function of
pristine graphene and the conduction band of MoS2 results in a large threshold
voltage for the FETs, because of which Ohmic contact behaviors are observed
only at very high gate voltages and carrier concentrations (~1013 cm-2). Here,
we present high-performance monolayer MoS2 FETs with Ohmic contact at a modest
gate voltage by using a chemical-vapor-deposited (CVD) nitrogen-doped graphene
with a high intrinsic electron carrier density. The CVD nitrogen-doped graphene
and monolayer MoS2 hybrid FETs platform exhibited a large negative shifted
threshold voltage of -54.2 V and barrier-free Ohmic contact under zero gate
voltage. Transparent contact by nitrogen-doped graphene led to a 214%
enhancement in the on-current and a four-fold improvement in the field-effect
carrier mobility of monolayer MoS2 FETs compared with those of a pristine
graphene electrode platform. The transport measurements, as well as Raman and
X-ray photoelectron spectroscopy analyses before and after thermal annealing,
reveal that the atomic C-N bonding in the CVD nitrogen-doped graphene is
responsible for the dominant effects of electron doping. Large-scale
nitrogen-doped graphene electrodes provide a promising device platform for the
development of high-performance devices and the study of unique quantum
behaviors.",1907.07883v1
2010-10-04,Defects induced ferromagnetism in Mn doped ZnO,"Single phase Mn doped (2 at %) ZnO samples have been synthesized by
solid-state reaction technique. Before the final sintering at 500 C, the mixed
powders have been milled for different milling periods (6, 24, 48 and 96
hours). The grain sizes of the samples are very close to each other (~ 32 \pm 4
nm). However, the defective state of the samples is different from each other
as manifested from the variation of magnetic properties and electrical
resistivity with milling time. All the samples have been found to be
ferromagnetic with clear hysteresis loops at room temperature. The maximum
value for saturation magnetization (0.11 {\mu}_B / Mn atom) was achieved for 96
hours milled sample. Electrical resistivity has been found to increase with
increasing milling time. The most resistive sample bears the largest saturation
magnetization. Variation of average positron lifetime with milling time bears a
close similarity with that of the saturation magnetization. This indicates the
key role played by open volume vacancy defects, presumably zinc vacancies near
grain surfaces, in inducing ferromagnetic order in Mn doped ZnO. To attain
optimum defect configuration favorable for ferromagnetism in this kind of
samples proper choice of milling period and annealing conditions is required.",1010.0547v1
2013-04-11,Sign-reversal of the in-plane resistivity anisotropy in iron pnictides,"The concept of an electronically-driven breaking of the rotational symmetry
of a crystal, without involving magnetic order, has found experimental support
in several systems, from semiconductor heterostructures and ruthenates, to
cuprate and iron-pnictide superconductors. In the pnictide BaFe$_{2}$As$_{2}$,
such an ""electronic nematic state"" appears above the magnetic transition dome,
over a temperature range that can be controlled by external strain. Here, by
measuring the in-plane resistivity anisotropy, we probe the electronic
anisotropy of this material over the entire nematic/magnetic dome, whose end
points coincide with the optimal superconducting transition temperatures.
Counter-intuitively, we find that, unlike other materials, the resistivity
anisotropy in BaFe$_{2}$As$_{2}$ changes sign across the doping phase diagram,
even though the signs of the magnetic, nematic, and orthorhombic order
parameters are kept fixed. This behavior is explained by the Fermi surface
reconstruction in the magnetic phase and spin-fluctuation scattering in the
nematic phase. The unique behavior of the transport anisotropy unveils that the
primary role is played by magnetic scattering in the normal state transport
properties of the iron pnictides, suggesting a close connection between
magnetism, nematicity, and unconventional superconductivity.",1304.3490v1
2013-09-20,Universal electric-field-driven resistive transition in narrow-gap Mott insulators,"One of today's most exciting research frontier and challenge in condensed
matter physics is known as Mottronics, whose goal is to incorporate strong
correlation effects into the realm of electronics. In fact, taming the Mott
insulator-to-metal transition (IMT), which is driven by strong electronic
correlation effects, holds the promise of a commutation speed set by a quantum
transition, and with negligible power dissipation. In this context, one
possible route to control the Mott transition is to electrostatically dope the
systems using strong dielectrics, in FET-like devices. Another possibility is
through resistive switching, that is, to induce the insulator-to-metal
transition by strong electric pulsing. This action brings the correlated system
far from equilibrium, rendering the exact treatment of the problem a difficult
challenge. Here, we show that existing theoretical predictions of the
off-equilibrium manybody problem err by orders of magnitudes, when compared to
experiments that we performed on three prototypical narrow gap Mott systems
V2-xCrxO3, NiS2-xSex and GaTa4Se8, and which also demonstrate a striking
universality of this Mott resistive transition (MRT). We then introduce and
numerically study a model based on key theoretically known physical features of
the Mott phenomenon in the Hubbard model. We find that our model predictions
are in very good agreement with the observed universal MRT and with a
non-trivial timedelay electric pulsing experiment, which we also report. Our
study demonstrates that the MRT can be associated to a dynamically directed
avalanche.",1309.5315v1
2016-04-23,"Giant magnetoresistance, three-dimensional Fermi surface and origin of resistivity plateau in YSb semimetal","Very strong magnetoresistance and a resistivity plateau impeding low
temperature divergence due to insulating bulk are hallmarks of topological
insulators and are also present in topological semimetals where the plateau is
induced by magnetic field, when time-reversal symmetry (protecting surface
states in topological insulators) is broken. Similar features were observed in
a simple rock-salt-structure LaSb, leading to a suggestion of the possible
non-trivial topology of 2D states in this compound. We show that its sister
compound YSb is also characterized by giant magnetoresistance exceeding one
thousand percent and low-temperature plateau of resistivity. We thus performed
in-depth analysis of YSb Fermi surface by band calculations, magnetoresistance,
and Shubnikov--de Haas effect measurements, which reveals only
three-dimensional Fermi sheets. Kohler scaling applied to magnetoresistance
data accounts very well for its low-temperature upturn behavior. The
field-angle-dependent magnetoresistance demonstrates a 3D-scaling yielding
effective mass anisotropy perfectly agreeing with electronic structure and
quantum oscillations analysis, thus providing further support for 3D-Fermi
surface scenario of magnetotransport, without necessity of invoking
topologically non-trivial 2D states. We discuss data implying that analogous
field-induced properties of LaSb can also be well understood in the framework
of 3D multiband model.",1604.06945v3
2017-02-23,Metallicity without quasi-particles in room-temperature strontium titanate,"Cooling oxygen-deficient strontium titanate to liquid-helium temperature
leads to a decrease in its electrical resistivity by several orders of
magnitude. The temperature dependence of resistivity follows a rough T$^{3}$
behavior before becoming T$^{2}$ in the low-temperature limit, as expected in a
Fermi liquid. Here, we show that the roughly cubic resistivity above 100K
corresponds to a regime where the quasi-particle mean-free-path is shorter than
the electron wave-length and the interatomic distance. These criteria define
the Mott-Ioffe-Regel limit. Exceeding this limit is the hallmark of strange
metallicity, which occurs in strontium titanate well below room temperature, in
contrast to other perovskytes. We argue that the T$^{3}$-resistivity cannot be
accounted for by electron-phonon scattering \`{a} la Bloch-Gruneisen and
consider an alternative scheme based on Landauer transmission between
individual dopants hosting large polarons. We find a scaling relationship
between the carrier mobility, the electric permittivity and the frequency of
transverse optical soft mode in this temperature range. Providing an account of
this observation emerges as a challenge to theory.",1702.07144v3
2018-02-26,Thermoelectric signatures of the electron-phonon fluid in PtSn4,"In most materials, transport can be described by the motion of distinct
species of quasiparticles, such as electrons and phonons. Strong interactions
between quasiparticles, however, can lead to collective behaviour, including
the possibility of viscous hydrodynamic flow. In the case of electrons and
phonons, an electron-phonon fluid is expected to exhibit strong phonon-drag
transport signatures and an anomalously low thermal conductivity. The Dirac
semi-metal PtSn4 has a very low resistivity at low temperatures and shows a
pronounced phonon drag peak in the low temperature thermopower; it is therefore
an excellent candidate for hosting a hydrodynamic electron-phonon fluid. Here
we report measurements of the temperature and magnetic field dependence of the
longitudinal and Hall electrical resistivities, the thermopower and the thermal
conductivity of PtSn4. We confirm a phonon drag peak in the thermopower near 14
K and observe a concurrent breakdown of the Lorenz ratio below the Sommerfeld
value. Both of these facts are expected for an electron-phonon fluid with a
quasi-conserved total momentum. A hierarchy between momentum-conserving and
momentum-relaxing scattering timescales is corroborated through measurements of
the magnetic field dependence of the electrical and Hall resistivity and of the
thermal conductivity. These results show that PtSn4 exhibits key features of
hydrodynamic transport.",1802.09468v1
2018-11-23,Neuromorphic MoS2 memtransistors fabricated by localised helium ion beam irradiation,"Two-dimensional layered semiconductors have recently emerged as attractive
building blocks for next-generation low-power non-volatile memories. However,
challenges remain in the controllable sub-micron fabrication of bipolar
resistively switching circuit components from these novel materials. Here we
report on the scalable experimental realisation of lateral on-dielectric
memtransistors from monolayer single-crystal molybdenum disulfide (MoS2)
utilising a focused helium ion beam. Site-specific irradiation with the probe
of a helium ion microscope (HIM) allows for the creation of charged defects in
the MoS2 lattice. The reversible drift of these locally seeded defects in the
applied electric field modulates the resistance of the semiconducting channel,
enabling versatile memristive functionality on the nanoscale. We find the
device can reliably retain its resistance ratios and set biases for hundreds of
switching cycles at sweep frequencies of up to 2.9 V/s with relatively low
drain-source biases. We also demonstrate long-term potentiation and depression
with sharp habituation that promises application in future neuromorphic
architectures. This work advances the down-scaling progress of memristive
devices without sacrificing key performance parameters such as power
consumption or its applicability for synaptic emulation.",1811.09545v1
2019-02-23,Quasi-ballistic thermal transport across MoS$_2$ thin films,"Layered two-dimensional (2D) materials have highly anisotropic thermal
properties between the in-plane and cross-plane directions. In general, it is
thought that cross-plane thermal conductivities ($\kappa_z$) are low, and
therefore c-axis phonon mean free paths (MFPs) are small. Here, we measure
$\kappa_z$ across MoS$_2$ films of varying thickness (20 to 240 nm) and uncover
evidence of very long c-axis phonon MFPs at room temperature in these layered
semiconductors. Experimental data obtained using time-domain thermoreflectance
(TDTR) are in good agreement with first-principles density functional theory
(DFT). These calculations reveal that ~50% of the heat is carried by phonons
with MFP >200 nm, exceeding kinetic theory estimates by nearly two orders of
magnitude. Because of quasi-ballistic effects, the $\kappa_z$ of nanometer thin
films of MoS$_2$ scales with their thickness and the volumetric thermal
resistance asymptotes to a non-zero value, ~10 m$^{2}$KGW$^{-1}$. This
contributes as much as 30% to the total thermal resistance of a 20 nm thick
film, the rest being limited by thermal interface resistance with the SiO$_2$
substrate and top-side aluminum transducer. These findings are essential for
understanding heat flow across nanometer-thin films of MoS$_2$ for
optoelectronic and thermoelectric applications.",1902.08713v2
2016-03-16,Coexistence of topological Dirac fermions in the surface and three-dimensional Dirac cone state in the bulk of ZrTe$_{5}$ single crystal,"Although, the long-standing debate on the resistivity anomaly in ZrTe$_{5}$
somewhat comes to an end, the exact topological nature of the electronic band
structure remains elusive till today. Theoretical calculations predicted that
bulk ZrTe$_{5}$ to be either a weak or a strong three-dimensional (3D)
topological insulator. However, the angle resolved photoemission spectroscopy
and transport measurements clearly demonstrate 3D Dirac cone state with a small
mass gap between the valence band and conduction band in the bulk. From the
magnetization and magneto-transport measurements on ZrTe$_{5}$ single crystal,
we have detected both the signature of helical spin texture from topological
surface state and chiral anomaly associated with the 3D Dirac cone state in the
bulk. This implies that ZrTe$_{5}$ is a novel 3D topological insulator having
massless Dirac fermionic excitation in its bulk gap state. Whereas, no 3D
topological insulator known in material science holds linear band dispersion in
its insulating bulk. Apart from the band topology, it is also apparent from the
resistivity and Hall measurements that the anomalous peak in the resistivity
can be shifted to a much lower temperature ($T$$<$2 K) by controlling impurity
and defects.",1603.05175v2
2018-12-03,Effect of structure and composition on the electronic excitation induced amorphization of La$_2$Ti$_{2-x}$Zr$_x$O$_7$ ceramics,"Understanding the response of ceramics operating in extreme environments is
of interest for a variety of applications. Ab initio molecular dynamic
simulations have been used to investigate the effect of structure and $B$-site
(=Ti, Zr) cation composition of lanthanum-based oxides (La$_2$$B_2$O$_7$) on
electronic-excitation-induced amorphization. We find that the amorphous
transition in monoclinic layered perovskite La$_2$Ti$_2$O$_7$ occurs for a
lower degree of electronic excitation than for cubic pyrochlore
La$_2$Zr$_2$O$_7$. While in each case the formation of O$_2$-like molecules
drives the structure to an amorphous state, an analysis of the polyhedral
connection network reveals that the rotation of TiO$_6$ octahedra in the
monoclinic phase can promote such molecule formation, while such octahedral
rotation is not possible in the cubic phase. However, once the symmetry of the
cubic structure is broken by substituting Ti for Zr, it becomes less resistant
to amorphization. A compound made of 50% Ti and 50% Zr (La$_2$TiZrO$_7$) is
found to be more resistant in the monoclinic than in the cubic phase, which may
be related to the lower bandgap of the cubic phase. These results illustrate
the complex interplay of structure and composition that give rise to the
radiation resistance of these important functional materials.",1812.01136v1
2019-11-09,Pulsed laser deposition of single phase n- and p-type Cu2O thin films with low resistivity,"Low resistivity (~3-24 mOhm.cm) with tunable n- and p-type phase pure Cu2O
thin films have been grown by pulsed laser deposition at 25-200 0C by varying
the background oxygen partial pressure (O2pp). Capacitance data obtained by
electrochemical impedance spectroscopy was used to determine the conductivity
(n- or p-type), carrier density, and flat band potentials for samples grown on
indium tin oxide (ITO) at 25 0C. The Hall mobility of the n- and p-type Cu2O
was estimated to be ~ 0.85 cm2.V-1s-1 and ~ 4.78 cm2.V-1s-1 respectively for
samples grown on quartz substrate at 25 0C. An elevated substrate temperature ~
200 0C with O2pp = 2 - 3 mTorr yielded p-type Cu2O films with six orders of
magnitude higher resistivities in the range ~ 9 - 49 kOhm.cm and mobilities in
the range ~ 13.5 - 22.2 cm2.V-1s-1. UV-Vis-NIR diffuse reflectance spectroscopy
showed optical bandgaps of Cu2O films in the range of 1.76 to 2.15 eV depending
on O2pp. Thin films grown at oxygen-rich conditions O2pp > 7 mTorr yielded
mixed-phase copper oxide irrespective of the substrate temperatures and upon
air annealing at 550 0C for 1 hour completely converted to CuO phase with
n-type semiconducting properties (~12 Ohm.cm, ~1.50 cm2.V-1s-1). The as-grown
p- and n-type Cu2O showed rectification and a photovoltaic (PV) response in
solid junctions with n-ZnO and p-Si electrodes respectively. Our findings may
create new opportunities for devising Cu2O based junctions requiring low
process temperatures.",1911.03727v2
2019-11-13,Light Intensity Modulated Impedance Spectroscopy (LIMIS) in All-Solid-State Solar Cells at Open Circuit,"Potentiostatic impedance spectroscopy (IS) is a well stablished
characterization technique for elucidating the electric resistivity and
capacitive features of materials and devices. In the case of solar cells, by
applying a small voltage perturbation the current signal is recorded and the
recombination processes and defect distributions are among the typical outcomes
in IS studies. In this work a photo-impedance approach, named light intensity
modulated impedance spectroscopy (LIMIS), is first tested in all-solid-state
photovoltaic cells by recording the individual photocurrent (IMPS) and
photovoltage (IMVS) responsivity signals due to a small light perturbation at
open-circuit (OC), and combining them: LIMIS=IMVS/IMPS. The experimental LIMIS
spectra from silicon, organic, and perovskite solar cells are presented and
compared with IS. An analysis of the equivalent circuit numerical models for
total resistive and capacitive features is discussed. Our theoretical findings
show a correction to the lifetimes evaluations by obtaining the total
differential resistances and capacitances combining IS and LIMIS measurements.
This correction addresses the discrepancies among different techniques, as
shown with transient photovoltage. The experimental differences between IS and
LIMIS (i) proves the unviability of the superposition principle, (ii) suggest a
bias-dependent photo-current correction to the empirical Shockley equation of
the steady-state current at different illumination intensities around OC and
(iii) are proposed as a potential figure of merit for characterizing
performance and stability of solar cells. In addition, new features are
reported for the low-frequency capacitance of perovskite solar cells, measured
by IS and LIMIS.",1911.05440v1
2020-01-19,Multilevel Resistance Switching and Enhanced Spin Transition Temperature in Single Molecule Spin Crossover Nanogap Devices,"Spin crossover (SCO) molecules are promising bi-stable magnetic switches with
applications in molecular spintronics. However, little is known about the
switching effects of a single SCO molecule when it is confined between two
metal electrodes. Here we examine the switching properties of a
[Fe(III)(EtOSalPet )(NCS)] SCO molecule that is specifically tailored for
surface deposition and binding to only one gold electrode in a nanogap device.
Temperature dependent conductivity measurements on SCO molecule containing
electromigrated gold break junctions show voltage independent telegraphic-like
switching between two resistance states at temperature below 200 K. The
transition temperature is very different from the transition temperature of 83
K that occurs in a bulk film of the same material. This indicates that the
bulk, co-operative SCO phenomenon is no longer preserved for a single molecule
and that the surface interaction drastically increases the temperature of the
SCO phenomenon. Another key finding of this work is that some devices show
switching between multiple resistance levels. We propose that in this case, two
SCO molecules are present within the nanogap with both participating in the
electronic transport and switching.",2001.06879v1
2020-05-18,Muiltiscale modeling of electrical conductivity of R-BAPB polyimide + carbon nanotubes nanocomposites,"The electrical conductivity of the polyimide R-BAPB polymer filled with
single-wall carbon nanotubes (CNT) with chirality (5,5) is modeled using a
multi-scale approach. The modeling starts with molecular dynamics simulations
of time-dependent fluctuating atomic configurations of polymer filled CNTs
junctions. Then the atomic positions obtained in the first step are used to
perform fully first-principles microscopic calculations of the CNTs junctions
contact resistances using the Green's function based quantum transport
technique. And finally, those contact resistances are supplied as an input to a
statistical calculation of a CNTs ensemble conductivity using a Monte Carlo
percolation model. The results of the first-principles calculations show a very
strong dependence of the polymer filled CNTs junctions contact resistance on
the geometry of CNTs junctions, including an angle $\varphi$ between nanotubes
axes and the positions of polymer atoms around CNTs. Incorporating into the
percolation model this strong dependence as well as CNTs agglomeration, pushed
the calculated values of electrical conductivity just above the percolation
threshold below 0.01 S/m, which is within the experimental range for composites
with various base polymers. Possible mechanisms for further reduction of
composites conductivity are discussed.",2005.09115v1
2020-07-09,Large magnetoresistance and non-zero Berry phase in the nodal-line semimetal MoO2,"We performed calculations of the electronic band structure and the Fermi
surface as well as measured the longitudinal resistivity rhoxx(T,H), Hall
resistivity rhoxy(T,H) and quantum oscillations of the magnetization as a
function of temperature at various magnetic fields for MoO2 with monoclinic
crystal structure. The band structure calculations show that MoO2 is a
nodal-line semimetal when spin-orbit coupling is ignored. It was found that a
large magnetoresistance reaching 5.03x10^4% at 2 K and 9 T, its nearly
quadratic field dependence and a field-induced up-turn behavior of rhoxx(T),
the characteristics common for many topologically non-trivial as well as
trivial semimetals, emerge also in MoO2. The observed properties are attributed
to a perfect charge-carrier compensation, evidenced by both calculations
relying on the Fermi surface topology and the Hall resistivity measurements.
Both the observation of negative magnetoresistance for magnetic field along the
current direction and the non-zero Berry phase in de Haas-van Alphen
measurements indicate that pairs of Weyl points appear in MoO2, which may be
due to the crystal symmetry breaking. These results highlight MoO2 as a new
platform materials for studying the topological properties of oxides.",2007.04814v1
2020-08-20,Origin of the hump anomalies in the Hall resistance loops of ultrathin SrRuO$_3$/SrIrO$_3$ multilayers,"The proposal that very small N\'eel skyrmions can form in SrRuO$_3$/SrIrO$_3$
epitaxial bilayers and that the electric field-effect can be used to manipulate
these skyrmions in gated devices strongly stimulated the recent research of
SrRuO$_3$ heterostructures. A strong interfacial Dzyaloshinskii-Moriya
interaction, combined with the breaking of inversion symmetry, was considered
as the driving force for the formation of skyrmions in SrRuO$_3$/SrIrO$_3$
bilayers. Here, we investigated nominally symmetric heterostructures in which
an ultrathin ferromagnetic SrRuO$_3$ layer is sandwiched between large
spin-orbit coupling SrIrO$_3$ layers, for which the conditions are not
favorable for the emergence of a net interfacial Dzyaloshinskii-Moriya
interaction. Previously the formation of skyrmions in the asymmetric
SrRuO$_3$/SrIrO$_3$ bilayers was inferred from anomalous Hall resistance loops
showing humplike features that resembled topological Hall effect contributions.
Symmetric SrIrO$_3$/SrRuO$_3$/SrIrO$_3$ trilayers do not show hump anomalies in
the Hall loops. However, the anomalous Hall resistance loops of symmetric
multilayers, in which the trilayer is stacked several times, do exhibit the
humplike structures, similar to the asymmetric SrRuO$_3$/SrIrO$_3$ bilayers.
The origin of the Hall effect loop anomalies likely resides in unavoidable
differences in the electronic and magnetic properties of the individual
SrRuO$_3$ layers rather than in the formation of skyrmions.",2008.09028v3
2021-09-28,Transport anomalies in the layered compound BaPt4Se6,"We report a layered ternary selenide BaPt4Se6 featuring sesqui-selenide
Pt2Se3 layers sandwiched by Ba atoms. The Pt2Se3 layers in this compound can be
derived from the Dirac-semimetal PtSe2 phase with Se vacancies that form a
honeycomb structure. This structure results in a Pt (VI) and Pt (II)
mixed-valence compound with both PtSe6 octahedra and PtSe4 square net
coordination configurations. Temperature dependent electrical transport
measurements suggest two distinct anomalies: a resistivity crossover, mimic to
the metal-insulator (M-I) transition at ~150K, and a resistivity plateau at
temperatures below 10K. The resistivity crossover is not associated with any
structural, magnetic or charge order modulated phase transitions.
Magnetoresistivity, Hall and heat capacity measurements concurrently suggest an
existing hidden state below 5K in this system. Angle-resolved photoemission
spectroscopy measurements reveal a metallic state and no dramatic
reconstruction of the electronic structure up to 200K.",2109.13902v1
2022-05-26,Is the optical conductivity of heavy fermion strange metals Planckian?,"Strange metal behavior appears across a variety of condensed matter settings
and beyond, and achieving a universal understanding is an exciting prospect.
The beyond-Landau quantum criticality of Kondo destruction has had considerable
success in describing the behavior of strange metal heavy fermion compounds,
and there is some evidence that the associated partial
localization-delocalization nature can be generalized to diverse materials
classes. Other potential overarching principles at play are also being
explored. An intriguing proposal is that Planckian scattering, with a rate of
$k_{\rm B}T/\hbar$, leads to the linear temperature dependence of the (dc)
electrical resistivity, which is a hallmark of strange metal behavior. Here we
extend a previously introduced analysis scheme based on the Drude description
of the dc resistivity to optical conductivity data. When they are well
described by a simple (ac) Drude model, the scattering rate can be directly
extracted. This avoids the need to determine the ratio of charge carrier
concentration to effective mass, which has complicated previous analyses based
on the dc resistivity. However, we point out that strange metals typically
exhibit strong deviations from Drude behavior, as exemplified by the
``extreme'' strange metal YbRh$_2$Si$_2$. This calls for alternative
approaches, and we point to the power of strange metal dynamical
(energy-over-temperature) scaling analyses for the inelastic part of the
optical conductivity. If such scaling extends to the low-frequency limit, a
strange metal relaxation rate can be estimated, and may ultimately be used to
test whether strange metals relax in a Planckian manner.",2205.13382v2
2023-01-01,Characteristic lengthscales of the electrically-induced insulator-to-metal transition,"Some correlated materials display an insulator-to-metal transition as the
temperature is increased. In most cases this transition can also be induced
electrically, resulting in volatile resistive switching due to the formation of
a conducting filament. While this phenomenon has attracted much attention due
to potential applications, many fundamental questions remain unaddressed. One
of them is its characteristic lengths: what sets the size of these filaments,
and how does this impact resistive switching properties. Here we use a
combination of wide-field and scattering-type scanning near-field optical
microscopies to characterize filament formation in NdNiO3 and SmNiO3 thin
films. We find a clear trend: smaller filaments increase the current density,
yielding sharper switching and a larger resistive drop. With the aid of
numerical simulations, we discuss the parameters controlling the filament width
and, hence, the switching properties.",2301.00456v1
2023-03-01,Piezoelectric composite cements: Towards the development of self-powered and self-diagnostic materials,"Piezoresistivity is the most commonly used sensing principle in cement-based
smart composites for strain-monitoring applications. Nonetheless, the need for
external electric power to conduct electrical resistivity measurements
restricts the scalability of this technology, especially when implemented in
remote structures. To address this issue, this manuscript thoroughly analyzes
the piezoelectric properties of cement composites doped with reduced graphene
oxide (rGO) and evaluates their potential as self-powered strain sensors. To do
so, a comprehensive methodology involving voltammetry measurements, open
circuit potential determination, and uniaxial compression testing is developed
to determine the piezoelectric coefficients of charge $d_{33}$ and voltage
$g_{33}$. Furthermore, a novel circuital model for signal processing of the
electromechanical response is developed and experimentally validated in terms
of time series of output voltage, resistance, and the generated electric power.
The developed methodology is applied to laboratory samples manufactured
following two different filler dispersion methods. The presented results
evidence that samples prepared by ultrasonic cleaner dispersion achieve optimal
properties, with a piezoelectric charge coefficient of
1122.28$\mathrm{\pm}$246.67 pC/N, about 47 times greater than previously
reported composites in the literature. Unlike piezoresistive cement-based
composites, a remarkable nonlinear correlation between the fractional change in
the intrinsic resistance of the material and the applied mechanical strain has
been observed. Instead, a considerable linearity ($\mathrm{R^2}=0.96$) between
the externally applied mechanical strain and the generated (piezoelectric)
electric power has been found, which suggests the great potential of the latter
for conducting off-the-grid strain monitoring applications.",2303.00352v1
2023-09-13,Anomalous Hall effect and magnetoresistance in micro-ribbons of the magnetic Weyl semimetal candidate PrRhC2,"PrRhC2 belongs to the rare-earth carbides family whose properties are of
special interest among topological semimetals due to the simultaneous breaking
of both inversion and time-reversal symmetry. The concomitant absence of both
symmetries grants the possibility to tune the Weyl nodes chirality and to
enhance topological effects like the chiral anomaly. In this work, we report on
the synthesis and compare the magnetotransport measurements of a poly- and
single crystalline PrRhC2 sample. Using a remarkable and sophisticated
technique, the PrRhC2 single crystal is prepared via focused ion beam cutting
from the polycrystalline material. Our magnetometric and specific heat analyses
reveal a non-collinear antiferromagnetic state below 20K, as well as
short-range magnetic correlations and/or magnetic fluctuations well above the
onset of the magnetic transition. The transport measurements on the PrRhC2
single crystal display an electrical resistivity peak at 3K and an anomalous
Hall effect below 6K indicative of a net magnetization component in the ordered
state. Furthermore, we study the angular variation of magnetoresistivities as a
function of the angle between the in-plane magnetic field and the injected
electrical current. We find that both the transverse and the longitudinal
resistivities exhibit fourfold angular dependencies due to higher-order terms
in the resistivity tensor, consistent with the orthorhombic crystal symmetry of
PrRhC2. Our experimental results may be interpreted as features of topological
Weyl semimetallic behavior in the magnetotransport properties.",2309.06963v1
2024-03-25,"Electrically tunable, rapid spin-orbit torque induced modulation of colossal magnetoresistance in Mn$_3$Si$_2$Te$_6$ nanoflakes","As a quasi-layered ferrimagnetic material, Mn$_3$Si$_2$Te$_6$ nanoflakes
exhibit magnetoresistance behaviour that is fundamentally different from their
bulk crystal counterparts. They offer three key properties crucial for
spintronics. Firstly, at least 10^6 times faster response comparing to that
exhibited by bulk crystals has been observed in current-controlled resistance
and magnetoresistance. Secondly, ultra-low current density is required for
resistance modulation (~ 5 A/cm$^2$). Thirdly, electrically gate-tunable
magnetoresistance has been realized. Theoretical calculations reveal that the
unique magnetoresistance behaviour in the Mn$_3$Si$_2$Te$_6$ nanoflakes arises
from a magnetic field induced band gap shift across the Fermi level. The rapid
current induced resistance variation is attributed to spin-orbit torque, an
intrinsically ultra-fast process (~nanoseconds). This study suggests promising
avenues for spintronic applications. In addition, it highlights
Mn$_3$Si$_2$Te$_6$ nanoflakes as a suitable platform for investigating the
intriguing physics underlying chiral orbital moments, magnetic field induced
band variation and spin torque.",2403.16684v1
2004-09-16,Oscillatory and Vanishing Resistance States in Microwave Irradiated 2D Electron Systems,"Giant-amplitude oscillations in dc magnetoresistance of a high-mobility
two-dimensional electron system can be induced by millimeterwave irradiations,
leading to zero-resistance states at the oscillation minima. Following a brief
overview of the now well-known phenomenon, this paper reports on aspects of
more recent experiments on the subject. These are: new zero-resistance states
associated with multi-photon processes; suppression of Shubnikov-de Haas
oscillations by high-frequency microwaves; and microwave photoconductivity of a
high-mobility two-dimensional hole system.",0409409v2
2010-02-09,Pressure-induced high-Tc superconducting phase in FeSe: correlation between anion height and Tc,"In this study, we performed high-pressure electrical resistivity measurements
of polycrystalline FeSe in the pressure range of 1-16.0 GPa at temperatures of
4-300 K. A precise evaluation of Tc from zero-resistivity temperatures revealed
that Tc shows a slightly distorted dome-shaped curve, with maximum Tc (30 K) at
6 GPa, which is lower than a previously reported Tc value (~37 K). With the
application of pressure, the temperature dependence of resistivity above Tc
changes dramatically to a linear dependence; a non-Fermi-liquid-like ""high-Tc""
phase appears above 3 GPa. We found a striking correlation between Tc and the
Se height: the lower the Se height, the more enhanced is Tc. Moreover, this
relation is broadly applicable to other iron pnictides, strongly indicating
that high-temperature superconductivity can appear only around the optimum
anion height (~1.38A). On the basis of these results, we suggest that the anion
height should be considered as a key determining factor of Tc of iron-based
superconductors containing various anions.",1002.1832v2
2017-06-22,Magneto-resistance oscillations induced by high-intensity terahertz radiation,"We report on observation of pronounced terahertz radiation-induced
magneto-resistivity oscillations in AlGaAs/GaAs two-dimensional electron
systems, the THz analog of the microwave induced resistivity oscillations
(MIRO). Applying high power radiation of a pulsed molecular laser we
demonstrate that MIRO, so far observed at low power only, are not destroyed
even at very high intensities. Experiments with radiation intensity ranging
over five orders of magnitude from $0.1$ W/cm$^2$ to $10^4$ W/cm$^2$ reveal
high-power saturation of the MIRO amplitude, which is well described by an
empirical fit function $I/(1 + I/I_s)^\beta$ with $\beta \sim 1$. The
saturation intensity Is is of the order of tens of W/cm$^2$ and increases by
six times by increasing the radiation frequency from $0.6$ to $1.1$ THz. The
results are discussed in terms of microscopic mechanisms of MIRO and compared
to nonlinear effects observed earlier at significantly lower excitation
frequencies.",1706.07239v1
2019-08-10,High-resistance YBa2Cu3O7-x grain-boundary Josephson junctions fabricated by electromigration,"[100]-tilt grain-boundary YBa2Cu3O7-x (YBCO) junctions are promising for
investigation of macroscopic quantum phenomena in high-Tc Josephson junctions.
However, fabrication of the [100]-tilt grain-boundary YBCO junctions with a
high resistance, which are required to study quantum effects, is difficult
because of a high transparency of a tunnel barrier in this type of junctions.
Here, we demonstrate a modification of grain-boundary barrier properties with a
new approach to an oxygen electromigration in the YBCO grain-boundary junctions
when the oxygen diffuses under an applied electric field from the
grain-boundary to a BaTbO3 layer deposited atop of an YBCO film. Using this
approach, we changed the normal-state resistance of the junctions from tens to
several hundred Ohms without a degradation of their characteristic voltage IcRn
and determined a barrier height and thickness by measuring the quasiparticle
tunnelling current.",1908.03784v1
1995-01-26,Study of the band--gap shift in CdS films: Influence of thermal annealing in different atmospheres,"We study by photoacoustic spectroscopy the band--gap shift effect of CdS
films. The CdS films were grown by chemical bath deposition and exposed to
different annealing atmospheres over a range of temperature in which the sample
structure is observed to change. We show the band--gap evolution as a function
of temperature of thermal annealing and determine the process which produces
the best combination of high band--gap energy and low resistivity. It allows us
to know a possible procedure to obtain low--resistivity CdS/CdTe solar cells
with high--quantum efficiency.",9501125v1
1995-07-14,Spin Conductivity and Spin-Charge Separation in the High $T_c$ Cuprates,"We study both the spin and electrical conductivities in models of relevance
to the high $T_c$ cuprates. These models describe metallic states with or
without spin-charge separation. We demonstrate that, given a linear in
temperature dependence of the electrical resistivity, the spin resistivity
should also be linear in temperature in the absence of spin-charge separation
and under conditions appropriate at least for the optimally doped cuprates, but
is in general {\it not} so in the presence of spin-charge separation. Based on
these results, we propose to use the temperature dependence of the electron
spin diffusion constant to diagnose spin-charge separation in the cuprates.",9507050v1
1997-08-15,Metal Insulator transition at B=0 in p-SiGe,"Observations are reported of a metal-insulator transition in a 2D hole gas in
asymmetrically doped strained SiGe quantum wells. The metallic phase, which
appears at low temperatures in these high mobility samples, is characterised by
a resistivity that decreases exponentially with decreasing temperature. This
behaviour, and the duality between resistivity and conductivity on the two
sides of the transition, are very similar to that recently reported for high
mobility Si-MOSFETs.",9708118v2
1999-07-08,High-Tc Superconductors in Applied Magnetic Fields Parallel to the CuO Planes: First Order Transition with Slow Onset of Resistivity,"The three dimensional uniformly frustrated XY model is used as a model of a
high temperature superconductor in an applied magnetic field parallel to the
CuO-planes. Through Monte Carlo simulations with anisotropy $\eta^2 = 10$ on
large lattices we find evidence for a first order transition. Earlier
simulations and theoretical treatments are discussed and the experimentally
found smooth onset of resistivity is suggested to be due to a large potential
barrier against vortex line motion above $T_c$ present for perfect alignment of
the applied field.",9907118v1
2001-03-08,Experimental observation of Frohlich superconductivity in high magnetic fields,"Resistivity and irreversible magnetisation data taken within the
high-magnetic-field CDWx phase of the quasi-two-dimensional organic metal
alpha-(BEDT-TTF)2KHg(SCN)4 are shown to be consistent with a field-induced
inhomogeneous superconducting phase. In-plane skin-depth measurements show that
the resistive transition on entering the CDWx phase is both isotropic and
representative of the bulk.",0103178v3
2001-07-26,Barkhausen-like conductance noise in polycrystalline high Tc superconductors immersed in a slowly varying magnetic field,"Analysis of the resistive transition of a polycristalline YBCO specimen
produced by an a.c. magnetic field, reveals the presence of a large conductance
noise signal which is repetitive over subsequent magnetization cycles. It is
shown that the noise arises from avalanche effects produced by the simultaneous
resistive transition of large groups of weak links. Owing to its repeatability,
the noise signal may be considered a sort of signature of the weak links
critical current distribution, making it an interesting new tool for the study
of high Tc ceramic superconductors, as reported measurements of noise
hysteresis show.",0107543v1
2003-09-05,Magnetothermal Conductivity of Highly Oriented Pyrolytic Graphite in the Quantum Limit,"We report on the magnetic field (0T$ \le B \le 9$T) dependence of the
longitudinal thermal conductivity $\kappa(T,B)$ of highly oriented pyrolytic
graphite in the temperature range 5 K $\le T\le$ 20 K for fields parallel to
the $c-$axis. We show that $\kappa(T,B)$ shows large oscillations in the
high-field region (B > 2 T) where clear signs of the Quantum-Hall effect are
observed in the Hall resistance. With the measured longitudinal electrical
resistivity we show that the Wiedemann-Franz law is violated in the high-field
regime.",0309129v1
2005-11-08,Magneto-transport and divergent screening of driven two dimensional electron gas in high Landau levels,"In two dimensional electron system in magnetic fields such that the Fermi
energy lies in high Landau levels and driven by microwave $ac$-field a
divergence of the Coulomb screening due to the Ryzhii photocurrent is
predicted. A model of magneto-transport with superposition of long range and
short range disorders is introduced. In this model the larger is the gradient
of the long range potential the smaller is the longitudinal
conductivity/resistivity. As a consequence a qualitative theory of the recently
discovered zero-resistance states is given.",0511195v1
2006-02-10,Quantum critical phase in BaVS$_3$,"We study the high-pressure metallic phase of high-purity single crystals of
BaVS$_3$ by measuring the temperature, pressure, and magnetic field dependence
of the resistivity. Above the critical pressure of $p_{\rm cr}=1.97$GPa an
extended non-Fermi liquid $p-T$ regime emerges with resistivity exponent $1.5
\le n<2$, crossing over to a FL only around $p=2.7$GPa. A hysteretic feature
indicates that close to the insulator--metal boundary, the system is
magnetically ordered. Our findings reveal a close analogy between the extended
partially ordered NFL state of non-conventional itinerant magnets and the
corresponding state of BaVS$_3",0602262v1
2007-08-16,Pressure-induced Superconductivity in CaLi2,"A search for superconductivity has been carried out on the hexagonal
polymorph of Laves-phase CaLi2, a compound for which Feng, Ashcroft, and
Hoffmann predict highly anomalous behavior under pressure. No superconductivity
is observed above 1.10 K at ambient pressure. However, high-pressure ac
susceptibility and electrical resistivity studies to 81 GPa reveal bulk
superconductivity in CaLi2 at temperatures as high as 13 K. The normal-state
resistivity shows a dramatic increase with pressure.",0708.2117v2
2011-02-02,Higher order finite difference schemes for the magnetic induction equations with resistivity,"In this paper, we design high order accurate and stable finite difference
schemes for the initial-boundary value problem, associated with the magnetic
induction equation with resistivity. We use Summation-By-Parts (SBP) finite
difference operators to approximate spatial derivatives and a Simultaneous
Approximation Term (SAT) technique for implementing boundary conditions. The
resulting schemes are shown to be energy stable. Various numerical experiments
demonstrating both the stability and the high order of accuracy of the schemes
are presented.",1102.0480v1
2011-10-10,Non-linear transport phenomena in a two-subband system,"We study non-linear transport phenomena in a high-mobility bilayer system
with two closely spaced populated electronic subbands in a perpendicular
magnetic field. For a moderate direct current excitation, we observe
zero-differential-resistance states with a characteristic 1/B periodicity. We
investigate, both experimentally and theoretically, the Hall field-induced
resistance oscillations which modulate the high-frequency magneto-intersubband
oscillations in our system if we increase the current. We also observe and
describe the influence of direct current on the magnetoresistance in the
presence of microwave irradiation.",1110.1953v1
2011-12-20,Phase of phonon-induced resistance oscillations in a high-mobility two-dimensional electron gas,"We report on experimental studies of magnetoresistance oscillations that
originate from the resonant interaction of two-dimensional electrons with
thermal transverse-acoustic phonons in very high-mobility GaAs/AlGaAs quantum
wells. We find that the oscillation maxima consistently occur when a frequency
of a phonon with twice the Fermi momentum exceeds an integer multiple of the
cyclotron frequency. This observation is in contrast to to all previous
experiments associating resistance maxima with magnetophonon resonance and its
harmonics. Our experimentally obtained resonant condition is in excellent
quantitative agreement with recent theoretical proposals.",1112.4766v1
2013-12-17,High-temperature thermoelectric properties of novel layered bismuth-sulfide LaO1-xFxBiS2,"We have investigated the high-temperature thermoelectric properties of the
layered compound LaO1-xFxBiS2. The electrical resistivity of LaOBiS2 showed an
anomalous behavior; a metal-semiconductor transition was observed around 270 K.
It was found that the value of the electrical resistivity decreased with F
substitution. The Seebeck coefficient decreased with increasing F
concentration. The highest power factor of 1.9 W/cmK2 at 480 C was obtained for
LaOBiS2.",1312.4694v1
2015-11-16,Spinless composite fermions in an ultra-high quality strained Ge quantum well,"We report on an observation of a fractional quantum Hall effect in an
ultra-high quality two-dimensional hole gas hosted in a strained Ge quantum
well. The Hall resistance reveals precisely quantized plateaus and vanishing
longitudinal resistance at filling factors $\nu = 2/3, 4/3$ and $5/3$. From the
temperature dependence around $\nu = 3/2$ we obtain the composite fermion mass
of $m^\star \approx 0.4\,m_e$, where $m_e$ is the mass of a free electron.
Owing to large Zeeman energy, all observed states are spin-polarized and can be
described in terms of spinless composite fermions.",1511.05164v1
2016-02-18,Resistive method for measuring the disintegration speed of Prince Rupert's drops,"We have successfully applied the resistance grid technique to measure the
disintegration speed in special type of glass objects, widely known as Prince
Rupert's drops. We use a digital oscilloscope and a simple electrical circuit,
glued to the surface of the drops, to detect the voltage changes, corresponding
to the breaks in the specific parts of the drops. The results obtained using
this method are in good qualitative and quantitative agreement with theoretical
predictions and previously published data. Moreover, the proposed experimental
setup doesn't include any expensive equipment (such as a high-speed camera) and
can therefore be widely used in high schools and universities.",1602.06801v1
2016-05-30,Comparison of CMS Resistive Plate Chambers performance during LHC RUN-1 and RUN-2,"The Resistive Plate Chambers detector system at the CMS experiment at the LHC
provides robustness and redundancy to the muon trigger. A total of 1056
double-gap chambers cover the pseudo-rapidity region < 1.6. The main detector
parameters and environmental conditions are constantly and closely monitored to
achieve operational stability and high quality data in the harsh conditions of
the second run period of the LHC with center-of-mass energy of 13 TeV. First
results of overall detector stability with 2015 data and comparisons with data
from the LHC RUN-1 period at 8 TeV are presented.",1605.09366v1
2017-03-01,Tunable Negative Differential Resistance in Planer Graphene Superlattice Resonant Tunneling Diode,"In this paper, we report on the controllable negative differential resistance
(NDR) in a proposed planar graphene superlattice structure. High value of peak
to valley ratio (PVR) is predicted. This is significant because of appearance
of NDR with high PVR at low biases. Our finding is important since beside the
other potential applications of the graphene, proposes implementation of the
graphene based superlattice in electronic devices such as resonant tunneling
diode and filters.",1703.00148v1
2019-01-09,Optical conductivity of granular aluminum films near the Mott metal-to-insulator transition,"We report measurements of the energy gap of granular aluminum films by THz
spectroscopy. We find that as the grains progressively decouple, the coupling
ratio $2\Delta(0)/k_{B}T_{c}$ increases above the BCS weak coupling ratio
$3.53$, and reaches values consistent with an approach to BCS-BEC crossover for
the high resistivity samples, expected from the short coherence length. The
Mattis-Bardeen theory describes remarkably well the behavior of
$\sigma_{1,s}/\sigma_{1,n}$ for all samples up to very high normal state
resistivities.",1901.02814v2
2020-05-26,CMS RPC Activities During LHC LS-2,"The second LHC long shutdown period (LS2) is an important opportunity for the
CMS Resistive Plate Chambers (RPC) to complete their consolidation and upgrade
projects. The consolidation includes detector maintenance for gas tightness, HV
(high voltage), LV (low voltage) and slow control operation. All services for
the RPC Phase-2 upgrade, namely RE3/1 and RE4/1, were anticipated for
installation to LS2. This paper summarises the RPC system maintenance and
upgrade activities.",2005.12534v1
2021-02-27,Spin polarization dynamics in the Bjorken-expanding resistive MHD background,"Evolution of spin polarization in the presence of external electric field is
studied for collision energies $\sqrt{s_{\rm NN}}=27\,{\rm GeV}$ and
$\sqrt{s_{\rm NN}}=200\,{\rm GeV}$. The numerical analysis is done in the
perfect-fluid Bjorken-expanding resistive magnetohydrodynamic background and
novel results are reported. In particular, we show that the electric field
plays a significant role in the competition between expansion and dissipation.",2103.02592v2
2023-01-01,High-resistivity niobium nitride films for unity-efficiency SMSPDs at telecom wavelengths and beyond,"The sensitive element of superconducting single-photon detectors made in the
form of a microstrip promise to resolve significant limitations caused by their
typical design. However, attention should be paid to the problem of
deterioration of the detection efficiency of devices with an increase of the
width of the superconducting strip from nano- to microscale. This article
demonstrates a possibility of achieving highly saturated detection efficiency
of superconducting microstrip single-photon detectors by using high-resistivity
niobium nitride films. The approach opens the way for employing fundamentally
improved experimental devices.",2301.00400v1
2023-08-18,Resistive relativistic MHD simulations of astrophysical jets,"Aims. The main goal of the present paper is to provide the first systematic
numerical study of the propagation of astrophysical relativistic jets, in the
context of high-resolution shock-capturing resistive relativistic
magnetohydrodynamics (RRMHD) simulations. We aim at investigating different
values and models for the plasma resistivity coefficient, and at assessing
their impact on the level of turbulence, the formation of current sheets and
reconnection plasmoids, the electromagnetic energy content, and the dissipated
power. Methods. We use the PLUTO code for simulations and we assume an
axisymmetric setup for jets, endowed with both poloidal and toroidal magnetic
fields, and propagating in a uniform magnetized medium. The gas is assumed to
be characterized by a realistic Synge-like equation of state (Taub equation),
appropriate for such type of astrophysical jets. The Taub equation is combined
here for the first time with the Implicit-Explicit Runge-Kutta time-stepping
procedure, as required in RRMHD simulations. Results. The main result is that
turbulence is clearly suppressed for the highest values of resistivity (low
Lundquist numbers), current sheets are broader, and plasmoids are barely
present, while for low values of resistivity results are very similar to ideal
runs, where dissipation is purely numerical. We find that recipes employing a
variable resistivity based on the advection of a jet tracer or on the
assumption of a uniform Lundquist number improve on the use of a constant
coefficient and are probably more realistic, preserving the development of
turbulence and of sharp current sheets, possible sites for the acceleration of
the non-thermal particles producing the observed high-energy emission.",2308.09477v2
2015-10-23,Origin of the turn-on temperature behavior in WTe$_2$,"A hallmark of materials with extremely large magnetoresistance (XMR) is the
transformative 'turn-on' temperature behavior: when the applied magnetic field
$H$ is above certain value, the resistivity versus temperature $\rho(T)$ curve
shows a minimum at a field dependent temperature $T^*$, which has been
interpreted as a magnetic-field-driven metal-insulator transition or attributed
to an electronic structure change. Here, we demonstrate that $\rho(T)$ curves
with turn-on behavior in the newly discovered XMR material WTe$_2$ can be
scaled as MR $\sim(H/\rho_0)^m$ with $m\approx 2$ and $\rho_0$ being the
resistivity at zero-field. We obtained experimentally and also derived from the
observed scaling the magnetic field dependence of the turn-on temperature $T^*
\sim (H-H_c)^\nu$ with $\nu \approx 1/2$, which was earlier used as evidence
for a predicted metal-insulator transition. The scaling also leads to a simple
quantitative expression for the resistivity $\rho^* \approx 2 \rho_0$ at the
onset of the XMR behavior, which fits the data remarkably well. These results
exclude the possible existence of a magnetic-field-driven metal-insulator
transition or significant contribution of an electronic structure change to the
low-temperature XMR in WTe$_2$. This work resolves the origin of the turn-on
behavior observed in several XMR materials and also provides a general route
for a quantitative understanding of the temperature dependence of MR in both
XMR and non-XMR materials.",1510.06976v2
2023-07-20,Nanoscale imaging of He-ion irradiation effects on amorphous TaO$_x$ toward electroforming-free neuromorphic functions,"Resistive switching in thin films has been widely studied in a broad range of
materials. Yet the mechanisms behind electroresistive switching have been
persistently difficult to decipher and control, in part due to their
non-equilibrium nature. Here, we demonstrate new experimental approaches that
can probe resistive switching phenomena, utilizing amorphous TaO$_x$ as a model
material system. Specifically, we apply Scanning Microwave Impedance Microscopy
(sMIM) and cathodoluminescence (CL) microscopy as direct probes of conductance
and electronic structure, respectively. These methods provide direct evidence
of the electronic state of TaO$_x$ despite its amorphous nature. For example CL
identifies characteristic impurity levels in TaO$_x$, in agreement with first
principles calculations. We applied these methods to investigate He-ion-beam
irradiation as a path to activate conductivity of materials and enable
electroforming-free control over resistive switching. However, we find that
even though He-ions begin to modify the nature of bonds even at the lowest
doses, the films conductive properties exhibit remarkable stability with large
displacement damage and they are driven to metallic states only at the limit of
structural decomposition. Finally, we show that electroforming in a nanoscale
junction can be carried out with a dissipated power of < 20 nW, a much smaller
value compared to earlier studies and one that minimizes irreversible
structural modifications of the films. The multimodal approach described here
provides a new framework toward the theory/experiment guided design and
optimization of electroresistive materials.",2307.11189v1
1998-03-09,Negative Domain Wall Contribution to the Resistivity of Microfabricated Fe Wires,"The effect of domain walls on electron transport has been investigated in
microfabricated Fe wires (0.65 to 20 $\mu m$ linewidths) with controlled stripe
domains. Magnetoresistance (MR) measurements as a function of domain wall
density, temperature and the angle of the applied field are used to determine
the low field MR contributions due to conventional sources in ferromagnetic
materials and that due to the erasure of domain walls. A negative domain wall
contribution to the resistivity is found. This result is discussed in light of
a recent theoretical study of the effect of domain walls on quantum transport.",9803102v1
1999-01-22,"Magnetoresistance, Micromagnetism, and Domain Wall Scattering in Epitaxial hcp Co Films","Large negative magnetoresistance (MR) observed in transport measurements of
hcp Co films with stripe domains were recently reported and interpreted in
terms of a novel domain wall (DW) scattering mechanism. Here detailed MR
measurements, magnetic force microscopy, and micromagnetic calculations are
combined to elucidate the origin of MR in this material. The large negative
room temperature MR reported previously is shown to be due to ferromagnetic
resistivity anisotropy. Measurements of the resistivity for currents parallel
(CIW) and perpendicular to DWs (CPW) have been conducted as a function of
temperature. Low temperature results show that any intrinsic effect of DWs
scattering on MR of this material is very small compared to the anisotropic MR.",9901245v1
2001-10-12,Large Thermopower in Metallic Oxides: Misfit Cobaltites and Mangano-Ruthenates,"Two different kinds of metal transition oxides have been studied for their
large thermopower values. The first one corresponds to the Tl-based misfit
cobaltite which is a hole-doped metal. We demonstrate that the partial
Bi-substitution for Tl in this phase induces an increase of the room
temperature (RT) thermopower (TEP) value. Same result is obtained with the new
Pb_{1/3}SrCoO_{3+delta} misfit corresponding to the Tl complete replacement by
lead. Simultaneously, the T dependence of their resistivity exhibits a
re-entrance below 70-90K where a large negative magnetoresistance is observed.
Magnetic measurements reveal a strong interplay between spins and charges for
this class of materials. Electron-doped (n-type) perovskite manganites are a
second class of potential candidates for applications. In particular, the
Ru^{4+/5+} substitution for Mn in the CaMnO_3 semi-conductor induces a drastic
drop of the resistivity values. Metals with large RT TEP values and not too
large thermal conductivities are generated. A comparison with best known
materials, Bi_2Te_3 and NaCo_2O_4 is made.",0110270v1
2001-11-05,Large Thermoelectric Power Factor in TiS2 Crystal with Nearly Stoichiometric Composition,"A TiS$_{2}$ crystal with a layered structure was found to have a large
thermoelectric power factor.The in-plane power factor $S^{2}/ \rho$ at 300 K is
37.1~$\mu$W/K$^{2}$cm with resistivity ($\rho$) of 1.7 m$\Omega$cm and
thermopower ($S$) of -251~$\mu$V/K, and this value is comparable to that of the
best thermoelectric material, Bi$_{2}$Te$_{3}$ alloy. The electrical
resistivity shows both metallic and highly anisotropic behaviors, suggesting
that the electronic structure of this TiS$_{2}$ crystal has a
quasi-two-dimensional nature. The large thermoelectric response can be ascribed
to the large density of state just above the Fermi energy and inter-valley
scattering. In spite of the large power factor, the figure of merit, $ZT$ of
TiS$_{2}$ is 0.16 at 300 K, because of relatively large thermal conductivity,
68~mW/Kcm. However, most of this value comes from reducible lattice
contribution. Thus, $ZT$ can be improved by reducing lattice thermal
conductivity, e.g., by introducing a rattling unit into the inter-layer sites.",0111063v1
2002-02-07,Resistivity extrema in double exchange ferromagnetic nondegenerate semiconductors,"A version of the magnetoimpurity theory of the colossal magnetoresistance
materials suitable for the double exchange ferromagnetic nondegenerate
semiconductors is presented. It provides an explanation of the nonmonotonic
temperature dependence for the charge carrier density in them when it displays
first a maximum and then a minimum, on increase in temperature. Respectively,
the resistivity displays first a minimum and then a maximum. The theory is
based on the relation between the charge carrier activation energy and the
change in the magnon free energy caused by the ionization of an impurity. This
is tantamount to the relation between the charge carrier density and the so
called giant red shift of the optical absorption edge.",0202126v1
2002-10-11,On the residual resistivity near a two dimensional metamagnetic quantum critical point,"The behavior of the residual (impurity-dominated) resistivity is computed for
a material near a two dimensional quantum critical point characterized by a
divergent $q=0$ susceptibility. A singular renormalization of the amplitude for
back-scattering of an electron off of a single impurity is found. When the
correlation length of the quantum critical point exceeds the mean free path,
the singular renormalization is found to convert the familiar
`Altshuler-Aronov' logarithmic correction to the conductivity into a
squared-logarithmic form. Impurities can induce unconventional Friedel
oscillations, which may be observable in scanning tunnelling microscope
experiments. Possible connections to the metamagnetic quantum critical end
point recently proposed for the material $Sr_{3}Ru_{2}O_{7}$ are discussed.",0210260v1
2003-01-27,Semiconductive and Photoconductive Properties of the Single Molecule Magnets Mn12-Acetate and Fe8Br8,"Resistivity measurements are reported for single crystals of Mn12-Acetate and
Fe8Br8. Both materials exhibit a semiconductor-like, thermally activated
behavior over the 200-300 K range. The activation energy, Ea, obtained for
Mn12-Acetate was 0.37 +/- 0.05 eV, which is to be contrasted with the value of
0.55 eV deduced from the earlier reported absorption edge measurements and the
range of 0.3-1 eV from intramolecular density of states calculations, assuming
2Ea = Eg, the optical band gap. For Fe8Br8, Ea was measured as 0.73 +/- 0.1 eV,
and is discussed in light of the available approximate band structure
calculations. Some plausible pathways are indicated based on the crystal
structures of both lattices. For Mn12-Acetate, we also measured
photoconductivity in the visible range; the conductivity increased by a factor
of about eight on increasing the photon energy from 632.8 nm (red) to 488 nm
(blue). X-ray irradiation increased the resistivity, but Ea was insensitive to
exposure.",0301515v1
2003-10-16,AC magnetic behavior of large grain magneto-resistive La0.78Ca0.22Mn0.90Ox materials,"We report a detailed set of AC magnetic measurements carried out on bulk
large grain La-Ca-Mn-O samples extracted from a floating zone method-grown rod.
Three samples with $La_{0.78}Ca_{0.22}Mn_{0.90}O_{x}$ stoichiometry but
differing in their microstructure were investigated by electrical resistivity
and AC susceptibility measurements: (i) a single grain sample, (ii) a sample
containing two grains and (iii) a polycrystalline sample. We show that the
superimposition of DC magnetic fields during AC magnetic susceptibility
measurements is an efficient way for characterizing the magnetic transition of
samples with different microstructures. Whereas both single grain and
polycrystalline samples display a single susceptibility peak, an additional
kink structure is observed in the case of the double grain sample. The
temperature dependence of the AC susceptibility measured with superimposed DC
magnetic fields is analyzed in the framework of second-order phase transition
ideas. The relations between the critical exponents ($\beta + \gamma$ ~ 1.5,
$\delta$ ~ 2.5) are found to be close to those of the mean-field model for all
samples. This is attributed to the disordering caused by unoccupied Mn sites.",0310376v1
2004-01-16,Study of the SmBaCuO solid solutions decomposition and its possible role for changing critical current,"We studied thermochemical characteristics of the Sm1+xBa2-xCu3Oy single
crystals by solution calorimetry. Dependences of formation enthalpies from
samarium content were constructed. It was established that solid solutions on
the bases of Sm123 could be decomposed both in inert and in oxygen atmosphere
into different mixtures. We supposed that solid solutions decomposition could
lead to increasing critical current density. We assumed from thermochemical
data that Jc could be greater for samples prepared in oxygen than for samples
synthesized in inert atmosphere. We confirmed these assumptions by comparison
of obtained thermochemical data with transport properties measured in
literature. We also investigated temperature dependences of resistance in the
temperature range of 300-550 K during slow heating. As it was shown there was
anomaly of resistance near 500 K. The origin of this anomaly was discussed.",0401277v1
2004-05-20,Tunnel Magneto-resistance in GaMnAs: going beyond Jullière formula,"The relation between tunnel magneto-resistance (TMR) and spin polarization is
explored for GaMnAs/GaAlAs/GaMnAs structures where the carriers experience
strong spin-orbit interactions. TMR is calculated using Landauer approach. The
materials are described in the 6 band $\bf {k}\cdot \bf{p}$ model which
includes spin orbit interaction. Ferromagnetism is described in the virtual
crystal mean field approximations. Our results indicate that TMR is a function
of of spin polarization and barrier thickness. As a result of the stong spin
orbit interactions, TMR also depends on the the angle between current flow
direction and the electrode magnetization. These results compromise the
validity of Julliere formula.",0405473v2
2004-06-21,Nonquasiparticle states in half-metallic ferromagnets,"Anomalous magnetic and electronic properties of the half-metallic
ferromagnets (HMF) have been discussed. The general conception of the HMF
electronic structure which take into account the most important correlation
effects from electron-magnon interactions, in particular, the spin-polaron
effects, is presented. Special attention is paid to the so called
non-quasiparticle (NQP) or incoherent states which are present in the gap near
the Fermi level and can give considerable contributions to thermodynamic and
transport properties. Prospects of experimental observation of the NQP states
in core-level spectroscopy is discussed. Special features of transport
properties of the HMF which are connected with the absence of one-magnon
spin-flip scattering processes are investigated. The temperature and magnetic
field dependences of resistivity in various regimes are calculated. It is shown
that the NQP states can give a dominate contribution to the temperature
dependence of the impurity-induced resistivity and in the tunnel junction
conductivity. First principle calculations of the NQP-states for the prototype
half-metallic material NiMnSb within the local-density approximation plus
dynamical mean field theory (LDA+DMFT) are presented.",0406487v1
2004-08-24,Current-induced metallic behavior in Pr$_{0.5}$Ca$_{0.5}$MnO$_3$ thin films: competition between Joule heating and nonlinear conduction mechanism,"Thin films of Pr0.5Ca0.5MnO3 manganites exhibiting charge/orbital-ordered
properties with colossal magnetoresistance have been synthesized by the pulsed
laser deposition technique on both (100)-SrTiO3 and (100)-LaAlO3 substrates.
The effects of current-induced metallic-behavior of the films are investigated
as a function of the temperature and the magnetic field. Calculations based on
a heat transfer model across the substrate, and our resistivity measurements
reveal effects of Joule heating on charge transport over certain ranges of
temperatures and magnetic fields. Our results also indicate that a nonlinear
conduction, which cannot be explained by homogeneous Joule heating of the film,
is observed when the material is less resistive (10-2 W.cm). The origin of this
behavior is explained with a model based on local thermal instabilities
associated with phase-separation mechanism and a change in the long range
charge-ordered state.",0408512v1
2004-10-04,What does intrinsic tunnelling spectroscopy really examine?,"The out-of-plane current-voltage (I-V) characteristics of Bi2212 are studied
in experimental environments of different heat transfer efficiency, allowing
practical separation of intrinsic and extrinsic phenomena. {\it Intrinsic}
(heating-free) response is Ohmic in the normal state of Bi2212, while its
resistance, R=V/I, is found to be a good practical measure of the mean
temperature of the sample in the overheated case. A self-heating model proposed
for the latter case provides a qualitative and quantitative description of key
findings of intrinsic tunnelling spectroscopy including (pseudo)gaps,
quasiparticle and normal state resistances. The model also naturally explains
the `superconducting' gap closure well below $T_c$ of the material as well as
its survival at a magnetic field significantly exceeding $H_{c2}$. The generic
shape of the individual branches of the brush-like part of I-V established
under conditions of negligible overheating suggests a phase-slip origin of the
so-called `intrinsic Josephson effect' (IJE).",0410069v1
2004-10-14,Carbon Nanotubes in Microelectronic Applications,"Carbon nanotubes with their outstanding electrical and mechanical properties
are suggested as interconnect material of the future and as switching devices,
which could outperform silicon devices. In this paper we will introduce
nanotubes, specify the applications, where nanotubes can contribute to the
advancement of Moore's law and show our progress of nanotube process
integration in a microelectronic compatible way. The growth of single
individual nanotubes at lithographically defined locations on whole wafers as a
key requirement for the successful implementation of nanotubes is shown. In
terms of nanotube transistors we propose a vertical nanotube transistor concept
which outperforms the ITRS requirements for the year 2016. The performance is
mainly limited by contact resistances, but by comparison with silicon devices
we show that fabricated nanotube transistors already today exceed the values
for transconductance, on-resistance and drive current of silicon devices.",0410360v1
2004-12-13,Unusual thermoelectric behavior of packed crystalline granular metals,"Loosely packed granular materials are intensively studied nowadays.
Electrical and thermal transport properties should reflect the granular
structure as well as intrinsic properties. We have compacted crystalline $CaAl$
based metallic grains and studied the electrical resistivity and the
thermoelectric power as a function of temperature ($T$) from 15 to 300K. Both
properties show three regimes as a function of temperature. It should be
pointed out : (i) The electrical resistivity continuously decreases between 15
and 235 K (ii) with various dependences, e.g. $\simeq$ $T^{-3/4}$ at low $T$,
while (iii) the thermoelectric power (TEP) is positive, (iv) shows a bump near
60K, and (v) presents a rather unusual square root of temperature dependence at
low temperature. It is argued that these three regimes indicate a competition
between geometric and thermal processes, - for which a theory seems to be
missing in the case of TEP. The microchemical analysis results are also
reported indicating a complex microstructure inherent to the phase diagram
peritectic intricacies of this binary alloy.",0412323v1
2005-07-01,Resistivity memory effect in La(1-x)Sr(x)MnO(3),"During the study of magnetoresistivity in La(1-x)Ca(x)MnO(3) it was found
that after cycling of the magnetic field, some kind of magnetic field memory
effect was observed. For La0.5Ca0.5MnO3 after cycling of the magnetic field to
13T and back to zero, ""frozen"" magnetoresistivity decreases about 20 times
comparing to zero field value, while for La(0.47)Ca(0.53)MnO(3) it is already
about four orders of magnitude. This effect can be observed only for
concentration region 0.45 < x < 0.55. In zero magnetic field, temperature
dependence of resistivity ro(T) shows semiconducting-like behavior, while after
magnetic field cycling it becomes metal-like. So it looks as we are dealing
with magnetic field induced semiconductor (or dielectric) to metal transition.
Such effect can be explained within phase-separation picture. In zero magnetic
field material consists of antiferromagnetic matrix (insulating phase) and
coexisting ferromagnetic, conducting phase. Magnetic field application causes
ferromagnetic phase to form some kind of conducting channels which shunts
semiconducting matrix phase. Such structure is preserved after reduction of
magnetic field, leaving the material conducting.",0507018v2
2005-08-06,Modelling the 0.6 - 0.7 power law of permittivity and admittance frequency responses in random R-C networks,"The dielectric response of complex materials is characterized, in many cases,
by a similar power law frequency dependence of both the real and the imaginary
parts of their complex dielectric constants. In the admittance representation,
this power law is often shown as the constant phase angle (CPA) response.
Apparently, the power that characterizes many different systems, when expressed
as the frequency dispersion of conductivity (the real part of admittance) is
often found to be in the range of 0.6 - 0.7 or having frequency independent,
constant phase angles (CPA) of about 54 - 63 deg. The model suggested here is
based on series-parallel mixing of resistors' and capacitors' responses in a
random R-C network. A geometric mean evaluation of the effective resistivity of
conductors having a uniform distribution of resistivity is used. In contrast to
models based on percolation arguments, the model suggested here can be applied
to both 2D and 3D systems.",0508170v2
2005-10-14,Superconducting transition in disordered granular superconductors in magnetic fields,"Motivated by a recent argument that the superconducting (SC) transition field
of three-dimensional (3D) disordered superconductors with granular structure in
a nonzero magnetic field should lie above $H_{c2}(0)$ in low $T$ limit, the
glass transition (or, in 2D, crossover) curve $H_g(T)$ of disordered quantum
Josephson junction arrays is examined by incorporating SC fluctuations. It is
found that the glass transition or crossover in the granular materials can be
described on the same footing as the vortex-glass (VG) transition in
amorphous-like (i.e., nongranular) materials. In most of 3D granular systems,
the vanishing of resistivity upon cooling should occur even above $H_{c2}(0)$,
while the corresponding sharp drop of the resistivity in 2D case may appear
only below $H_{c2}$ as a result of an enhanced quantum fluctuation.",0510380v5
2005-11-19,"Transport, thermal and magnetic properties of RuSr_2(Gd_{1.5}Ce_{0.5})Cu_2O_{10-δ}, a magnetic superconductor","Resistivity, thermoelectric power, heat capacity and magnetization for
samples of RuSr_2(Gd_{1.5}Ce_{0.5})Cu_{2}O_{10-\delta} were investigated in the
temperature range 1.8-300 K with a magnetic field up to 8 T. The resistive
transitions to the superconducting state are found to be determined by the
inhomogeneous (granular) structure, characterized by the intragranular, T_{c0},
and intergranular, T_{cg}, transition temperatures. Heat capacity, C(T), shows
a jump at the superconducting transition temperature T_{c0}\approx 37.5 K. A
Schottky-like anomaly is found in C(T) below 20 K. This low temperature anomaly
can be attributed to splitting of the ground term $^{8}S_{7/2}$ of paramagnetic
Gd^{3+} ions by internal and external magnetic fields.",0511489v1
2007-03-28,Comparison between experiment and calculated band structures for DyN and SmN,"We investigate the electronic band structure of two of the rare-earth
nitrides, DyN and SmN. Resistivity measurements imply that both materials have
a semiconducting ground state, and both show resistivity anomalies coinciding
with the magnetic transition, despite the different magnetic states in DyN and
SmN. X-ray absorption and emission measurements are in excellent agreement with
LSDA+U calculations, although for SmN the calculations predict a zero band gap.",0703740v3
2007-04-24,Impedance spectroscopy of epitaxial multiferroic thin films,"Temperature dependent impedance spectroscopy enables the many contributions
to the dielectric and resistive properties of condensed matter to be
deconvoluted and characterized separately. We have achieved this for
multiferroic epitaxial thin films of BiFeO3 (BFO) and BiMnO3 (BMO), key
examples of materials with strong magneto-electric coupling. We demonstrate
that the true film capacitance of the epitaxial layers is similar to that of
the electrode interface, making analysis of capacitance as a function of film
thickness necessary to achieve deconvolution. We modeled non-Debye impedance
response using Gaussian distributions of relaxation times and reveal that
conventional resistivity measurements on multiferroic layers may be dominated
by interface effects. Thermally activated charge transport models yielded
activation energies of 0.60 eV +- 0.05 eV (BFO) and 0.25 eV +- 0.03 eV (BMO),
which is consistent with conduction dominated by oxygen vacancies (BFO) and
electron hopping (BMO). The intrinsic film dielectric constants were determined
to be 320 +- 75 (BFO) and 450 +- 100 (BMO).",0704.3262v1
2007-08-09,Carbon nanotube array vias for interconnect applications,"The material and electrical properties of the CNT single vias and array vias
grown by microwave plasma-enhanced chemical vapor deposition were investigated.
The diameters of multiwall carbon nanotubes (MWNTs) grown on the bottom
electrode of Ta decrease with increasing pretreatment power and substrate
temperature while the effects of the growth power and methane flow ratio are
insignificant The decrease of CNT diameters leads to the decrease of the CNT
via diode devices. The increase of growth power enhances the CNT graphitization
degree and thue the conductivity of CNT via diode devices. In the same via
region, the MWNT diode resistances of the array vias are lower than those of
the single vias. The MWNT diode resistances on the bottom electrode of titanium
are lower than those on the bottom electrode of tantalum. It may be attributed
to the smaller tube diameters on the bottom electrode of Ti and the work
function difference between Ta and Ti films with respect to the work function
of CNTs.",0708.1298v1
2007-08-14,Suspension of Nanoparticles in SU-8 and Characterization of Nanocomposite Properties,"Gold nanospheres, single wall carbon nanotubes (SWNT), and diamonoids were
phyically incorporated into the negative photoresist SU-8. the mixtures were
spin cast onto silicon or aluminium coated silicon wafers. ASTM standard D638
tensile specimens were lithographically patterned in the materials and then
released from the substrate using Microchem'Omnicoat or an anodic metal
dissolution process. the residual stresses, elastic moduli, and viscosity of
the SU-8. Resistivity measurements of SU-8/SWNT nanocomposites were also
investigates. We found the effective modulus and viscosity of the SU-8 test
specimens decreases with the addition of diamantane and SWNTs. Additionally,
the SU-8/SWNT nanocomposites showed changes in resistivity with increased
strain, suggesting a gauge factor for the 1 wt% SU-8/SWNT nanocomposite of
approximately 2-4.",0708.1822v1
2007-12-07,Field Tuned Superconductor to Insulator Transitions in an Amorphous Film with an Imposed Multiply Connected Geometry,"We have observed multiple magnetic field driven superconductor to insulator
transitions (SIT) in amorphous Bi films perforated with a nano-honeycomb (NHC)
array of holes. The period of the magneto-resistance, H=H_M=h/2eS where S is
the area of a unit cell of holes, indicates the field driven transitions are
boson dominated. The field-dependent resistance follows
R(T)=R_0(H)exp(T_0(H)/T) on both sides of the transition so that the evolution
between these states is controlled by the vanishing of T_0 to0. We compare our
results to the thickness driven transition in NHC films and the field driven
transitions in unpatterned Bi films, other materials, and Josephson junction
arrays. Our results suggest a structural source for similar behavior found in
some materials and that despite the clear bosonic nature of the SITs,
quasiparticle degrees of freedom likely also play an important part in the
evolution of the SIT.",0712.1076v1
2008-07-02,Nano Imprint Lithography on Silica Sol-gels: a simple route to sequential patterning,"Since the pioneering work of S.Y. Chou et al.[1] Nano Imprint Lithography
(NIL) has emerged as a promising technique for surface patterning, opening for
numerous applications ranging from nanophotonics[2] to microfluidics[3]. NIL
basically consists in the stamping of deformable surfaces or films. Preferred
materials are thermoplastics[4] and UV curable resists[5]. So far, most papers
report on single imprinting methods for which the same surface is imprinted
only once. In the present paper, we report the imprinting of square silica
structures from simple line gratings and demonstrate how the specific
thermo-rheological behavior of ICSG resists can be harnessed to form complex
structures by sequential imprinting at low pressures.",0807.0378v1
2009-01-09,Stability of a Charged Particle Beam in a Resistive Plasma Channel,"A self-focusing of a coasting relativistic beam in a plasma channel that is
confined by an external magnetic field is studied as a means of reconditioning
the beam emerging from a beam injector [a radio frequency quadrupole (RFQ)] for
a linac. A detailed study of the beam stability in the self-focused beam has
been carried out. In order to explain beam filaments and the resistive hose
instability in a unified way, we treat all the azimuthal modes in the
derivation of the dispersion relation in a finite plasma channel that exhibit
many unstable modes, which are classified by Weinberg's scheme [Steven
Weinberg, J. Math. 8, 614 (1967)].",0901.1167v2
2009-07-21,"Anomalous transport properties of the halfmetallic ferromagnets Co2TiSi, Co2TiGe, and Co2TiSn","In this work the theoretical and experimental investigations of Co2TiZ (Z =
Si, Ge, or Sn) compounds are reported. Half-metallic ferromagnetism is
predicted for all three compounds with only two bands crossing the Fermi energy
in the majority channel. The magnetic moments fulfill the Slater-Pauling rule
and the Curie temperatures are well above room temperature. All compounds show
a metallic like resistivity for low temperatures up to their Curie temperature,
above the resistivity changes to semiconducting like behavior. A large negative
magnetoresistance of 55% is observed for Co2TiSn at room temperature in an
applied magnetic field of 4T which is comparable to the large negative
magnetoresistances of the manganites. The Seebeck coefficients are negative for
all three compounds and reach their maximum values at their respective Curie
temperatures and stay almost constant up to 950 K. The highest value achieved
is -52muV/K m for Co2TiSn which is large for a metal. The combination of
half-metallicity and the constant large Seebeck coefficient over a wide
temperature range makes these compounds interesting materials for
thermoelectric applications and further spincaloric investigations.",0907.3562v1
2009-08-27,"A low field technique for measuring magnetic and magneto-resistance anisotropy coefficients applied to (Ga,Mn)As","We demonstrate a simple, low cost, magneto-transport method for rapidly
characterizing the magnetic anisotropy and anisotropic magneto-resistance (AMR)
of ferromagnetic devices with uniaxial magnetic anisotropy. This transport
technique is the analogue of magnetic susceptibility measurements of bulk
material but is applicable to very small samples with low total moment. The
technique is used to characterize devices fabricated from the dilute magnetic
semiconductor (Ga,Mn)As. The technique allows us to probe the behavior of the
parameters close to the Curie temperature, in the limit of the applied magnetic
field tending to zero. This avoids the complications arising from the presence
of paramagnetism.",0908.3960v1
2010-01-20,Robust charge and magnetic order under electric field and current in the multiferroic LuFe(2)O(4),"We performed elastic neutron scattering measurements on the charge- and
magnetically-ordered multiferroic material LuFe(2)O(4). An external electric
field along the [001] direction with strength up to 20 kV/cm applied at low
temperature (~100 K) does not affect either the charge or magnetic structure.
At higher temperatures (~360 K), before the transition to three-dimensional
charge-ordered state, the resistivity of the sample is low, and an electric
current was applied instead. A reduction of the charge and magnetic peak
intensities occurs when the sample is cooled under a constant electric current.
However, after calibrating the real sample temperature using its own
resistance-temperature curve, we show that the actual sample temperature is
higher than the thermometer readings, and the ""intensity reduction"" is entirely
due to internal sample heating by the applied current. Our results suggest that
the charge and magnetic orders in LuFe(2)O(4) are unaffected by the application
of external electric field/current, and previously observed electric
field/current effects can be naturally explained by internal sample heating.",1001.3611v2
2010-10-07,Compensation-dependence of magnetic and electrical properties in Ga1-xMnxP,"We demonstrate the control of the hole concentration in Ga1-xMnxP over a wide
range by introducing compensating vacancies. The resulting evolution of the
Curie temperature from 51 K to 7.5 K is remarkably similar to that observed in
Ga1-xMnxAs despite the dramatically different character of hole transport
between the two material systems. The highly localized nature of holes in
Ga1-xMnxP is reflected in the accompanying increase in resistivity by many
orders of magnitude. Based on variable-temperature resistivity data we present
a general picture for hole conduction in which variable-range hopping is the
dominant transport mechanism in the presence of compensation.",1010.1368v2
2011-02-04,Low-Frequency Current Fluctuations in Graphene-like Exfoliated Thin-Films of Topological Insulators,"We report on the low-frequency current fluctuations and electronic noise in
thin-films made of bismuth selenide topological insulators. The films were
prepared via the graphene-like mechanical exfoliation and used as the current
conducting channels in the four- and two-contact devices. Analysis of the
resistance dependence on the film thickness indicates that the surface
contribution to conductance is dominant in our samples. It was established that
the current fluctuations have the noise spectrum close to the pure 1/f in the
frequency range from 1 to 10 kHz (f is the frequency). The relative noise
amplitude S/I^2 for the examined films was increasing from ~5x10^-8 to 5x10^-6
(1/Hz) as the resistance of the channels varied from ~10^3 to 10^5 Ohms. The
obtained noise data is important for understanding electron transport through
the surface and volume of topological insulators, and proposed applications of
this class of materials.",1102.0961v1
2011-05-04,Sondheimer Oscillation as a Fingerprint of Surface Dirac Fermions,"Topological states of matter challenge the paradigm of symmetry breaking,
characterized by gapless boundary modes and protected by the topological
property of the ground state. Recently, angle-resolved photoemission
spectroscopy (ARPES) has revealed that semiconductors of Bi$_{2}$Se$_{3}$ and
Bi$_{2}$Te$_{3}$ belong to such a class of materials. Here, we present
undisputable evidence for the existence of gapless surface Dirac fermions from
transport in Bi$_{2}$Te$_{3}$. We observe Sondheimer oscillation in
magnetoresistance (MR). This oscillation originates from the quantization of
motion due to the confinement of electrons within the surface layer. Based on
Sondheimer's transport theory, we determine the thickness of the surface state
from the oscillation data. In addition, we uncover the topological nature of
the surface state, fitting consistently both the non-oscillatory part of MR and
the Hall resistance.
  The side-jump contribution turns out to dominate around 1 T in Hall
resistance while the Berry-curvature effect dominates in 3 T $\sim$ 4 T.",1105.0731v1
2011-07-05,Evidence for filamentary superconductivity nucleated at antiphase domain walls in antiferromagnetic CaFe$_2$As$_2$,"Resistivity, magnetization and microscopic $^{75}$As nuclear magnetic
resonance (NMR) measurements in the antiferromagnetically ordered state of the
iron-based superconductor parent material CaFe$_2$As$_2$ exhibit anomalous
features that are consistent with the collective freezing of domain walls.
Below $T^*\approx 10$ K, the resistivity exhibits a peak and downturn, the bulk
magnetization exhibits a sharp increase, and $^{75}$As NMR measurements reveal
the presence of slow fluctuations of the hyperfine field. These features in
both the charge and spin response are strongly field dependent, are fully
suppressed by $H^*\approx 15$ T, and suggest the presence of filamentary
superconductivity nucleated at the antiphase domain walls in this material.",1107.0904v2
2011-08-22,Ferromagnetic Quantum Criticality in the Quasi-One-Dimensional Heavy Fermion Metal YbNi4P2,"We present a new Kondo-lattice system, YbNi4P2, which is a clean
heavy-fermion metal with a severely reduced ferromagnetic ordering temperature
at T_C=0.17K, evidenced by distinct anomalies in susceptibility, specific-heat,
and resistivity measurements. The ferromagnetic nature of the transition, with
only a small ordered moment of ~0.05mu_B, is established by a diverging
susceptibility at T_C with huge absolute values in the ferromagnetically
ordered state, severely reduced by small magnetic fields. Furthermore, YbNi4P2
is a stoichiometric system with a quasi-one-dimensional crystal and electronic
structure and strong correlation effects which dominate the low temperature
properties. This is reflected by a stronger-than-logarithmically diverging
Sommerfeld coefficient and a linear-in-T resistivity above T_C which cannot be
explained by any current theoretical predictions. These exciting
characteristics are unique among all correlated electron systems and make this
an interesting material for further in-depth investigations.",1108.4274v1
2012-10-18,Observation of a Large Photo-response in a Single Nanowire (Diameter ~30 nm) of Charge Transfer Complex Cu:TCNQ,"We report for the first time large photoresponse in a single NW of the charge
transfer complex Cu:TCNQ. We fabricate a metal-semiconductor-metal device with
a single NW and focus ion beam deposited Pt. We observe large photocurrent even
at zero bias. The spectral dependence of the photoresponse follows the main
absorption at ~ 405 nm which has the primarily responsible for photogenerated
carriers. We have quantitatively analyzed the bias dependent photocurrent by a
model of two back to back Schottky diodes connected by a series resistance. The
observation shows that the large photoresponse of the device primarily occurs
due to the reduction of the barrier at the contact regions due to illumination
along with the photoconductive contribution. There is also a bias driven
reduction of the nanowire resistance that is a unique feature for the material.",1210.5207v1
2013-01-16,Huge field-effect surface charge injection and conductance modulation in metallic thin films by electrochemical gating,"The field-effect technique, popular thanks to its application in common
field-effect transistors, is here applied to metallic thin films by using as a
dielectric a novel polymer electrolyte solution. The maximum injected surface
charge, determined by a suitable modification of a classic method of
electrochemistry called double-step chronocoulometry, reached some units in
10^15 charges/cm^2. At room temperature, relative variations of resistance up
to 8%, 1.9% and 1.6% were observed in the case of gold, silver and copper,
respectively and, if the films are thick enough (> 25 nm), results can be
nicely explained within a free-electron model with parallel resistive channels.
The huge charge injections achieved make this particular field-effect technique
very promising for a vast variety of materials such as unconventional
superconductors, graphene and 2D-like materials.",1301.3769v1
2013-02-05,Scaling of Non-Saturating MR and quantum oscillations in pristine and ion-implanted HOPG,"A wide variety of resistive and field dependent behaviors have been
previously observed in both doped and non-doped Highly Oriented Pyrolytic
Graphite (HOPG). We find HOPG samples to vary significantly in their
temperature dependent resistances, even between portions taken from the same
sample, yet they exhibit consistent non-saturating magnetoresistance (MR). The
scaling behavior of the MR is shown to be characteristic of a model based on
the Hall effect in granular materials. In addition to the large, field-linear
MR, all samples exhibit Shubnikov-de Haas (SdH) oscillations. Additional
samples were doped via ion-implantation by boron and phosphorous, but show no
signs of superconductivity nor any systematic change in their magnetoresistive
behavior. Analysis of the SdH data gives a 2D carrier density in agreement with
previous results, and a large mean-free path relative to crystallite size, even
in samples with thin ion-implanted surface layers.",1302.1229v1
2013-02-07,Thermoelectromotive force of hafnium at plastic deformation in regime of creep at temperature of 300 K,"The thermoelectromotive force and electrical resistivity of the
polycrystalline hafnium (Hf) with the grain size of 10 {\mu}m during the
process of plastic deformation in the regime of creep at the temperature of 300
K are precisely measured. It is shown that the thermoelectromotive force
depends on the deformation mechanism nature, because of the changing magnitude
of the electrons scattering on the different structural defects in the hafnium
crystal lattice at the deformation process. The main research conclusion is
that the method of thermoelectromotive force measurements is more informative,
comparing to the method of electric resistivity measurements in the process of
accurate characterization of the hafnium.",1302.1784v1
2013-03-11,Nanobatteries in redox-based resistive switches require extension of memristor theory,"Redox-based nanoionic resistive memory cells (ReRAMs) are one of the most
promising emerging nano-devices for future information technology with
applications for memory, logic and neuromorphic computing. Recently, the
serendipitous discovery of the link between ReRAMs and memristors and
memristive devices has further intensified the research in this field. Here we
show on both a theoretical and an experimental level that nanoionic-type
memristive elements are inherently controlled by non-equilibrium states
resulting in a nanobattery. As a result the memristor theory must be extended
to fit the observed non zerocrossing I-V characteristics. The initial
electromotive force of the nanobattery depends on the chemistry and the
transport properties of the materials system but can also be introduced during
ReRAM cell operations. The emf has a strong impact on the dynamic behaviour of
nanoscale memories, and thus, its control is one of the key factors for future
device development and accurate modelling.",1303.2589v1
2013-07-02,Non-volatile ferroelastic switching of the Verwey transition and resistivity of epitaxial Fe3O4/PMN-PT (011),"A central goal of electronics based on correlated materials or 'Mottronics'
is the ability to switch between distinct collective states with a control
voltage. Small changes in structure and charge density near a transition can
tip the balance between competing phases, leading to dramatic changes in
electronic and magnetic properties. In this work, we demonstrate that an
electric field induced two-step ferroelastic switching pathway in (011)
oriented 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-PT) substrates can be used to
tune the Verwey metal-insulator transition in epitaxial Fe3O4 films in a stable
and reversible manner. We also observe robust non-volatile resistance switching
in Fe3O4 up to room temperature, driven by ferroelastic strain. These results
provides a framework for realizing non-volatile and reversible tuning of order
parameters coupled to lattice-strain in epitaxial oxide heterostructures over a
broad range of temperatures, with potential device applications.",1307.0838v1
2014-06-01,Effect of carrier concentration on magnetism and magnetic order in the pyrochlore iridates,"We present resistivity, magnetization, and zero field muon spin relaxation
($\mu$SR) data for the pyrochlore iridate materials
Nd$_{2-x}$Ca$_{x}$Ir$_{2}$O$_{7}$ ($x = 0, 0.06$, and $0.10$) and
Sm$_2$Ir$_2$O$_7$. While Nd$_{2}$Ir$_{2}$O$_{7}$ (Nd227) is weakly conducting,
Sm$_{2}$Ir$_{2}$O$_{7}$ (Sm227) has slowly diverging resistivity at low
temperature. Nd227 and Sm227 exhibit magnetic anomalies at $T_{M} = 105 K$ and
$137 K$, respectively. However, zero-field $\mu$SR measurements show that
long-range magnetic order of the Ir$^{4+}$ sublattice sets in at much lower
temperatures ($T_{LRO} \sim 8 K$ for Nd227 and $70 K$ for Sm227); both
materials show heavily damped muon precession with a characteristic frequency
near 9 MHz. The magnetic anomaly at $T_{M}$ in Nd227 is not significantly
affected by the introduction of hole carriers by Ca-substitution in the
conducting Nd$_{2-x}$Ca$_{x}$Ir$_{2}$O$_{7}$ samples, but the muon precession
is fully suppressed for both.",1406.0194v1
2014-10-07,Thickness Scaling Effect on Interfacial Barrier and Electrical Contact to Two-Dimensional MoS2 Layers,"Understanding the interfacial electrical properties between metallic
electrodes and low dimensional semiconductors is essential for both fundamental
science and practical applications. Here we report the observation of thickness
reduction induced crossover of electrical contact at Au/MoS2 interfaces. For
MoS2 thicker than 5 layers, the contact resistivity slightly decreases with
reducing MoS2 thickness. By contrast, the contact resistivity sharply increases
with reducing MoS2 thickness below 5 layers, mainly governed by the quantum
confinement effect. It is found that the interfacial potential barrier can be
finely tailored from 0.3 to 0.6 eV by merely varying MoS2 thickness. A full
evolution diagram of energy level alignment is also drawn to elucidate the
thickness scaling effect. The finding of tailoring interfacial properties with
channel thickness represents a useful approach controlling the
metal/semiconductor interfaces which may result in conceptually innovative
functionalities.",1410.1943v2
2015-03-04,Observation of the chiral anomaly induced negative magneto-resistance in 3D Weyl semi-metal TaAs,"Weyl semi-metal is the three dimensional analog of graphene. According to the
quantum field theory, the appearance of Weyl points near the Fermi level will
cause novel transport phenomena related to chiral anomaly. In the present
paper, we report the first experimental evidence for the long-anticipated
negative magneto-resistance generated by the chiral anomaly in a newly
predicted time-reversal invariant Weyl semi-metal material TaAs. Clear
Shubnikov de Haas oscillations (SdH) have been detected starting from very weak
magnetic field. Analysis of the SdH peaks gives the Berry phase accumulated
along the cyclotron orbits to be {\pi}, indicating the existence of Weyl
points.",1503.01304v1
2015-03-12,"Shubnikov-de Haas oscillations, weak antilocalization effect and large linear magnetoresistance in the putative topological superconductor LuPdBi","We present electronic transport and magnetic properties of single crystals of
semimetallic half-Heusler phase LuPdBi, having theoretically predicted band
inversion requisite for nontrivial topological properties. The compound
exhibits superconductivity below a critical temperature $T_{\rm c}=1.8\,$K,
with a zero-temperature upper critical field $B_{\rm c2}\approx2.3\,$T.
Although superconducting state is clearly reflected in the electrical
resistivity and magnetic susceptibility data, no corresponding anomaly can be
seen in the specific heat. Temperature dependence of the electrical resistivity
suggests existence of two parallel conduction channels: metallic and
semiconducting, with the latter making negligible contribution at low
temperatures. The magnetoresistance is huge and clearly shows a weak
antilocalization effect in small magnetic fields. Above about 1.5 T, the
magnetoresistance becomes linear and does not saturate in fields up to 9 T. The
linear magnetoresistance is observed up to room temperature. Below 10 K, it is
accompanied by Shubnikov-de Haas oscillations. Their analysis reveals charge
carriers with effective mass of $0.06\,m_e$ and a Berry phase very close to
$\pi$, expected for Dirac-fermion surface states, thus corroborating
topological nature of the material.",1503.03697v1
2015-11-17,"Microstructure, mechanical properties and corrosion of friction stir welded 6061 Aluminum Alloy","The microstructure, mechanical properties, and corrosion behavior of friction
stir welded (FSW) AA6061 aluminum alloys were investigated. Dynamic
recrystallized structures were observed and grain sizes of nugget zone (NZ),
thermomechanically-affected zone (TMAZ), heat-affected zone (HAZ), and base
material (BM) were different. Hardness test indicated that the minimum and
maximum hardness values wereobtained in the HAZ and BM, respectively. Tensile
results showed that fracture occurred in the relatively weak regions in between
TMAZ and HAZ. Polarization tests illustrated that the FSW process improved the
corrosion resistance of AA6061-AA6061 and the HAZ had better corrosion
resistance than other regions. Raman characterizations revealed that aluminum
hydroxide was the main corrosion product formed on Al after immersion
experiments. Intergranular attack was observed in the NZ and downside by
scanning electron microscopy.",1511.05507v1
2015-11-20,Transmission conditions for thin curvilinear close to circular heat-resistant interphases in composite ceramics,"This paper considers the problem of heat transfer in a composite ceramic
material where the structural elements are bonded to the matrix via a thin heat
resistant adhesive layer. The layer has the form of a circular ring or close to
it. Using an asymptotic approach, the interphase is modeled by an infinitesimal
imperfect interface, preserving the main features of the temperature fields
around the interphase, and allowing a significant simplification where FEM
analysis is concerned. The nonlinear transmission conditions that accompany
such an imperfect interface are evaluated, and their accuracy is verified by
means of dedicated analytical examples as well as carefully designed FEM
simulations. The interphases of various geometries are analysed, with an
emphasis on the influence of the curvature of their boundaries on the accuracy
of the evaluated conditions. Numerical results demonstrate the benefits of the
approach and its limitations.",1511.06630v2
2015-11-29,Ultrafast electron-phonon-magnon interactions at noble metal-ferromagnet interfaces,"Ultrafast optical excitation of gold-cobalt bilayers triggers the nontrivial
interplay between the electronic, acoustic, and magnetic degrees of freedom.
Laser-heated electrons generated at the gold-air interface diffuse through the
layer of gold and strongly overheat the lattice in cobalt resulting in the
emission of ultrashort acoustic pulses and generation of exchange-coupled
magnons. Time-resolved optical measurements allow for extracting the thermal
boundary (Kapitza) resistances at metal/metal interfaces and the hot electron
diffusion length in ferromagnetic materials. Both the experimental data and the
analytical treatment of the two-temperature model reveal the role of the
Kapitza resistance in transient lattice overheating.",1511.09060v3
2016-04-05,Gap state charge induced spin-dependent negative differential resistance in tunnel junctions,"We propose and demonstrate through first-principles calculation a new
spin-dependent negative differential resistance (NDR) mechanism in magnetic
tunnel junctions (MTJ) with cubic cation disordered crystals (CCDC) AlO$_x$ or
Mg$_{1-x}$Al$_x$O as barrier materials. The CCDC is a class of insulators whose
band gap can be changed by cation doping. The gap becomes arched in an
ultrathin layer due to the space charge formed from metal-induced gap states.
With an appropriate combination of an arched gap and a bias voltage, NDR can be
produced in either spin channel. This mechanism is applicable to 2D and 3D
ultrathin junctions with a sufficiently small band gap that forms a large space
charge. It provides a new way of controlling the spin-dependent transport in
spintronic devices by an electric field. A generalized Simmons formula for
tunneling current through junction with an arched gap is derived to show the
general conditions under which ultrathin junctions may exhibit NDR.",1604.01364v1
2016-05-12,Thermoelectric performance of spin Seebeck effect in Fe3O4/Pt-based thin film heterostructures,"We report a systematic study on the thermoelectric performance of spin
Seebeck devices based on Fe3O4/Pt junction systems. We explore two types of
device geometries: a spin Hall thermopile and spin Seebeck multilayer
structures. The spin Hall thermopile increases the sensitivity of the spin
Seebeck effect, while the increase in the sample internal resistance has a
detrimental effect on the output power. We found that the spin Seebeck
multilayers can overcome this limitation since the multilayers exhibit the
enhancement of the thermoelectric voltage and the reduction of the internal
resistance simultaneously, therefore resulting in significant power
enhancement. This result demonstrates that the multilayer structures are useful
for improving the thermoelectric performance of the spin Seebeck effect.",1605.03752v1
2016-06-15,Response of Carbon Nanotube (CNT) Ply Subjected to a Pulsed Magnetic Field,"In this study, the possible deformation of a single Carbon Nanotube (CNT) ply
subjected to a pulsed magnetic field was investigated. In all tests the
capacitor bank was charged to 6kJ of energy. A Photon Doppler Velocimetry (PDV)
system was used to measure velocity or displacement of the CNT ply during the
experiments. The resistance of the CNT ply was measured using four-point probe
technique before and after the experiments. Preliminary results show that the
single CNT plies do not permanently deform in response to the pulsed magnetic
fields. However, they can be displaced, either by themselves a small amount
(0.6mm) or by a large amount using a driver material. Also, the resistance of
the CNT plies may increase or decrease depends on the lay-out (i.e., yarn) and
current flow directions.",1606.04893v2
2016-07-28,A 3D dislocation dynamics analysis of the size effect on the strength of [111] LiF micropillars at 300K and 600K,"The mechanical behavior in compression of [111] LiF micropillars with
diameters in the range 0.5 $\mu$m to 2.0 $\mu$m was analyzed by means of
discrete dislocation dynamics at ambient and elevated temperature. The
dislocation velocity was obtained from the Peach-Koehler force acting on the
dislocation segments from a thermally-activated model that accounted for the
influence of temperature on the lattice resistance. A size effect of the type
""smaller is stronger"" was predicted by the simulations, which was in
quantitative agreement with previous experimental results by the authors
\cite{SWC14}. The contribution of the different physical deformation mechanisms
to the size effect (namely, nucleation of dislocations, dislocation exhaustion
and forest hardening) could be ascertained from the simulations and the
dominant deformation mode could be assessed as a function of the specimen size
and temperature. These results shed light into the complex interaction among
size, lattice resistance and dislocation mobility in the mechanical behavior of
$\mu$m-sized single crystals.",1607.08642v1
2016-11-20,Uniform Benchmarking of Low Voltage Van Der Waals FETs,"Monolayer MoS2, MoSe2, MoTe2, WS2, WSe2, and black phosphorous field effect
transistors (FETs) operating in the low-voltage (LV) regime (0.3V) with
geometries from the 2019 and 2028 nodes of the 2013 International Technology
Roadmap for Semiconductors (ITRS) are benchmarked along with an ultra-thin-body
Si FET. Current can increase or decrease with scaling, and the trend is
strongly correlated with the effective mass. For LV operation at the 2028 node,
an effective mass of ~0.4 m0, corresponding to that of WSe2, gives the maximum
drive current. The short 6 nm gate length combined with LV operation is
forgiving in its requirements for material quality and contact resistances. In
this LV regime, device and circuit performance are competitive using currently
measured values for mobilities and contact resistances for the monolayer
two-dimensional materials.",1611.06480v1
2016-12-28,In-plane anisotropy of transport coefficients in the electronic nematic states: Universal origin of the nematicity in Fe-based superconductors,"The origin of the electronic nematicity and its remarkable
material-dependence are famous longstanding unsolved issues in Fe-based
superconductors. To attack these issues, we focus on the in-plane anisotropy of
the resistivity: In the nematic state in FeSe, the relation $\rho_x>\rho_y$
holds, where $\rho_{x(y)}$ is the resistivity along the longer (shorter) Fe-Fe
axis. In contrast, the opposite anisotropy $\rho_x<\rho_y$ is realized in other
undoped Fe-based superconductors. Such nontrivial material dependence is
naturally explained in terms of the strongly orbital-dependent inelastic
quasiparticle scattering realized in the orbital-ordered state. The opposite
anisotropy between FeSe ($\rho_x>\rho_y$) and other undoped compounds
($\rho_x<\rho_y$) reflects the difference in the number of hole-pockets. We
also explain the large in-plane anisotropy of the thermoelectric power in the
nematic state.",1612.08841v1
2017-02-03,"Evolution of structure, magnetism and electronic transport in doped pyrochlore iridate Y$_2$Ir$_{2-x}$Ru$_{x}$O$_7$","The interplay between spin-orbit coupling (SOC) and electron correlation
($U$) is considered for many exotic phenomena in iridium oxides. We have
investigated the evolution of structural, magnetic and electronic properties in
pyrochlore iridate Y$_2$Ir$_{2-x}$Ru$_{x}$O$_7$ where the substitution of Ru
has been aimed to tune this interplay. The Ru substitution does not introduce
any structural phase transition, however, we do observe an evolution of lattice
parameters with the doping level $x$. X-ray photoemission spectroscopy (XPS)
study indicates Ru adopts charge state of Ru$^{4+}$ and replaces the Ir$^{4+}$
accordingly. Magnetization data reveal both the onset of magnetic
irreversibility and the magnetic moment decreases with progressive substitution
of Ru. These materials show non-equilibrium low temperature magnetic state as
revealed by magnetic relaxation data. Interestingly, we find magnetic
relaxation rate increases with substitution of Ru. The electrical resistivity
shows an insulating behavior in whole temperature range, however, resistivity
decreases with substitution of Ru. Nature of electronic conduction has been
found to follow power-law behavior for all the materials.",1702.01023v1
2017-02-25,Compressive mechanical response of graphene foams and their thermal resistance with copper interfaces,"We report compressive mechanical response of graphene foams (GFs) and the
thermal resistance ($R_{TIM}$) between copper (Cu) and GFs, where GFs were
prepared by the chemical vapor deposition (CVD) method. We observe that Young's
modulus ($E_{GF}$) and compressive strength ($\sigma_{GF}$) of GFs have a power
law dependence on increasing density ($\rho_{GF}$) of GFs. The maximum
efficiency of absorbed energy ($\eta_{max}$) for all GFs during the compression
is larger than ~0.39. We also find that a GF with a higher $\rho_{GF}$ shows a
larger $\eta_{max}$. In addition, we observe that the measured $R_{TIM}$ of
Cu/GFs at room temperature with a contact pressure of 0.25 MP applied increases
from ~50 to ~90 $mm^2K/W$ when $\rho_{GF}$ increases from 4.7 to 31.9
$mg/cm^3$.",1702.07816v1
2017-11-22,Structural properties of Fe/Cu magnetic multilayers: a Monte Carlo approach,"Using atomistic Monte Carlo simulations, we investigated the impact of the
interface on the structural properties of iron and copper (Fe/Cu) magnetic
multilayers grown by Vorono\""i diagram. Interest in magnetic multilayers has
recently emerged as they are shown to be promising candidates for magnetic
storage media, magneto-resistive sensors, and personalized medical treatment.
As these artificial materials show large differences in properties compared to
conventional ones, many experimental and theoretical works have been dedicated
on shedding light on these differences and tremendous results have emerged.
However, little is known how the interfaces influence the structure of the
layers around them. By a numerical approach, we show that the structure of each
layer depends on its thickness and the interface morphology. The Fe and Cu
layers can adopt either the body-centered-cubic (bcc) or face-centered-cubic
(fcc) structure, while the interface can assume amorphous, bcc, fcc, or a
mixture of bcc and fcc structures depending on the layer thicknesses. These
results are in good agreement with the experiments. They could be helpful in
understanding effects such as giant magneto-resistance from the structural
viewpoint.",1711.08508v1
2017-11-24,Inter-layer and Intra-layer Heat Transfer in Bilayer/Monolayer Graphene van der Waals Heterostructure: Is There a Kapitza Resistance Analogous?,"Van der Waals heterostructures have exhibited interesting physical
properties. In this paper, heat transfer in hybrid coplanar bilayer/monolayer
(BL-ML) graphene, as a model layered van der Waals heterostructure, was studied
using non-equilibrium molecular dynamics (MD) simulations. Temperature profile
and inter- and intra-layer heat fluxes of the BL-ML graphene indicated that,
there is no fully developed thermal equilibrium between layers and the drop in
average temperature profile at the step-like BL-ML interface is not
attributable to the effect of Kapitza resistance. By increasing the length of
the system up to 1 $\mu$m in the studied MD simulations, the thermally
non-equilibrium region was reduced to a small area near the step-like
interface. All MD results were compared to a continuum model and a good match
was observed between the two approaches. Our results provide a useful
understanding of heat transfer in nano- and micro-scale layered 2D materials
and van der Waals heterostructures.",1711.09127v1
2018-04-20,Comparative study of the compensated semi-metals LaBi and LuBi : A first-principles approach,"We have investigated the electronic structures of LaBi and LuBi, employing
the full-potential all electron method as implemented in Wien2k. Using this, we
have studied in detail both the bulk and the surface states of these materials.
From our band structure calculations we find that LuBi, like LaBi, is a
compensated semi-metal with almost equal and sizable electron and hole pockets.
In analogy with experimental evidence in LaBi, we thus predict that LuBi will
also be a candidate for extremely large magneto-resistance (XMR), which should
be of immense technological interest. Our calculations reveal that LaBi,
despite being gapless in the bulk spectrum, displays the characteristic
features of a $\mathbb{Z}_{2}$ topological semi-metal, resulting in gapless
Dirac cones on the surface, whereas LuBi only shows avoided band inversion in
the bulk and is thus a conventional compensated semi-metal with extremely large
magneto-resistance.",1804.07652v1
2014-08-02,Destroyed quantum Hall effect in graphene with [0001] tilt grain boundaries,"The reason why the half-integer quantum Hall effect (QHE) is suppressed in
graphene grown by chemical vapor deposition (CVD) is unclear. We propose that
it might be connected to extended defects in the material and present results
for the quantum Hall effect in graphene with [0001] tilt grain boundaries
connecting opposite sides of Hall bar devices. Such grain boundaries contain
5-7 ring complexes that host defect states that hybridize to form bands with
varying degree of metallicity depending on grain boundary defect density. In a
magnetic field, edge states on opposite sides of the Hall bar can be connected
by the defect states along the grain boundary. This destroys Hall resistance
quantization and leads to non-zero longitudinal resistance. Anderson disorder
can partly recover quantization, where current instead flows along returning
paths along the grain boundary depending on defect density in the grain
boundary and on disorder strength. Since grain sizes in graphene made by
chemical vapor deposition are usually small, this may help explain why the
quantum Hall effect is usually poorly developed in devices made of this
material.",1408.0394v1
2019-02-21,Correlation in transport coefficients of hole-doped CuRhO$_2$ single crystals,"To clarify the origin of the nontrivial thermoelectric properties observed in
the delafossite oxide CuRhO$_2$ polycrystals, we have performed the systematic
transport measurements on the single-crystalline CuRhO$_2$ samples. In the
parent compound, we find a pronounced peak structure due to a phonon-drag
effect in the temperature dependence of the Seebeck coefficient, which is also
confirmed by the size effect experiments. In the Mg-substituted crystals, in
contrast to the results of the polycrystals, both the resistivity and the
Seebeck coefficient decrease with increasing Mg content $y$. In particular, the
coefficient $A$ for the $T^2$ term of the resistivity and the $T$-linear
coefficient for the Seebeck coefficient at low temperatures are well described
within a simple relationship expected for metals, which is also applicable to
the correlated materials with low carrier densities.",1902.08301v1
2020-04-14,Temperature overshoot as the cause of physical changes in resistive switching devices during electro-formation,"Resistive switching devices based on transition metal oxides require
formation of a conductive filament in order for the device to be able to
switch. Such filaments have been proposed to form by the reduction of the oxide
due to application of the electric field, but this report seeks to rebut that
interpretation. Frequently reported physical changes during electro-formation
include delamination of electrodes, crystallization of functional oxide,
intermixing of electrode and oxide materials, and extensive loss of oxygen
presumably to the ambient. Here we show that most of these effects are not
inherent to the formation and switching processes and instead are due to an
experimental artifact: the discharge of parasitic capacitances in the forming
circuit. Discharge of typical BNC cables can raise the temperature of the
filament to between 2,000 and 5,000 K resulting in extensive physical changes.
Discharge and associated effects mentioned above can be eliminated using an
on-chip load element without affecting the ability to switch.",2004.06571v1
2020-09-04,Effective Thermal Conductivity of SrBi$_4$Ti$_4$O$_{15}$-La$_{0.7}$Sr$_{0.3}$MnO$_3$ Oxide composite: Role of Particle Size and Interface Thermal Resistance,"We present a novel approach to reduce the thermal conductivity ($\kappa$) in
thermoelectric composite materials using acoustic impedance mismatch and the
Debye model. Also, the correlation between interface thermal resistance
(R$_{int}$) and the particle size of the dispersed phase on the k of the
composite is discussed. In particular, the $\kappa$ of an oxide composite which
consists of a natural superlattice Aurivillius phase (SrBi$_4$Ti$_4$O$_{15}$)
as a matrix and perovskite (La$_{0.7}$Sr$_{0.3}$MnO$_3$) as a dispersed phase
is investigated. A significant reduction in the $\kappa$ of composite, even
lower than the $\kappa$ of the matrix when the particle size of
La$_{0.7}$Sr$_{0.3}$MnO$_3$ is smaller than the Kapitza radius (a$_K$) is
observed, depicting that R$_{int}$ dominates for particle size lower than a$_K$
due to increased surface to volume ratio. The obtained results have the
potential to provide new directions for engineering composite thermoelectric
systems with desired thermal conductivity and promising in the field of energy
harvesting.",2009.02218v1
2022-02-25,Low-Temperature Thermal Conductivity of CeRh$_{2}$As$_{2}$,"CeRh$_2$As$_2$ is a rare unconventional superconductor ($T_c=0.26$ K)
characterized by two adjacent superconducting phases for a magnetic field $H
\parallel c$-axis of the tetragonal crystal structure. Antiferromagnetic order,
quadrupole-density-wave order ($T_0 = 0.4$ K) and the proximity of this
material to a quantum-critical point have also been reported: The coexistence
of these phenomena with superconductivity is currently under discussion. Here,
we present thermal conductivity and electrical resistivity measurements on a
single crystal of CeRh$_2$As$_2$ between 60 mK and 200 K and in magnetic fields
($H \parallel c$) up to 8 T. Our measurements at low $T$ verify the
Wiedemann-Franz law within the error bars. The $T$ dependence of the thermal
conductivity $\kappa(T)$ shows a pronounced drop below $T_c$ which is also
field dependent and thus interpreted as the signature of superconductivity.
However, the large residual resistivity and the lack of sharp anomalies in
$\kappa(T)$ at the expected transition temperatures clearly indicate that
samples of much higher purity are required to gain more information about the
superconducting gap structure.",2202.12667v1
2016-03-07,Pressure-resistant intermediate valence in Kondo insulator SmB6,"Resonant x-ray emission spectroscopy (RXES) was used to determine the
pressure dependence of the f-electron occupancy in the Kondo insulator SmB6.
Applied pressure reduces the f-occupancy, but surprisingly, the material
maintains a significant divalent character up to a pressure of at least 35 GPa.
Thus, the closure of the resistive activation energy gap and onset of magnetic
order are not driven by stabilization of an integer valent state. Over the
entire pressure range, the material maintains a remarkably stable intermediate
valence that can in principle support a nontrivial band structure.",1603.02207v1
2017-04-01,Small-signal model for 2D-material based field-effect transistors targeting radio-frequency applications: the importance of considering non-reciprocal capacitances,"A small-signal equivalent circuit of 2D-material based field-effect
transistors is presented. Charge conservation and non-reciprocal capacitances
have been assumed so the model can be used to make reliable predictions at both
device and circuit levels. In this context, explicit and exact analytical
expressions of the main radio-frequency figures of merit of these devices are
given. Moreover, a direct parameter extraction methodology is provided based on
S-parameter measurements. In addition to the intrinsic capacitances,
transconductance and output conductance, our approach allows extracting the
series combination of drain/source metal contact and access resistances.
Accounting for these extrinsic resistances is of upmost importance when dealing
with low dimensional field-effect transistors.",1704.00181v2
2017-04-05,An open-source platform to study uniaxial stress effects on nanoscale devices,"We present an automatic measurement platform that enables the
characterization of nanodevices by electrical transport and optical
spectroscopy as a function of uniaxial stress. We provide insights into and
detailed descriptions of the mechanical device, the substrate design and
fabrication, and the instrument control software, which is provided under
open-source license. The capability of the platform is demonstrated by
characterizing the piezo-resistance of an InAs nanowire device using a
combination of electrical transport and Raman spectroscopy. The advantages of
this measurement platform are highlighted by comparison with state-of-the-art
piezo-resistance measurements in InAs nanowires. We envision that the
systematic application of this methodology will provide new insights into the
physics of nanoscale devices and novel materials for electronics, and thus
contribute to the assessment of the potential of strain as a technology booster
for nanoscale electronics.",1704.01394v1
2017-08-09,Contact-Induced Semiconductor-to-Metal Transition in Single-Layer WS$_2$,"Low-resistance ohmic contacts are a challenge for electronic devices based on
two-dimensional materials. We show that an atomically precise junction between
a two-dimensional semiconductor and a metallic contact can lead to a
semiconductor-to-metal transition in the two-dimensional material--a finding
which points the way to a possible method of achieving low-resistance
junctions. Specifically, single-layer WS$_2$ undergoes a semiconductor-to-metal
transition when epitaxially grown on Ag(111), while it remains a direct band
gap semiconductor on Au(111). The metallicity of the single layer on Ag(111) is
established by lineshape analysis of core level photoemission spectra.
Angle-resolved photoemission spectroscopy locates the metallic states near the
Q point of the WS$_2$ Brillouin zone. Density functional theory calculations
show that the metallic states arise from hybridization between Ag bulk bands
and the local conduction band minimum of WS$_2$ near the Q point.",1708.02799v1
2019-08-26,Local electrodynamics of a disordered conductor model system measured with a microwave impedance microscope,"We study the electrodynamic impedance of percolating conductors with a
pre-defined network topology using a scanning microwave impedance microscope
(sMIM) at GHz frequencies. For a given percolation number we observe strong
spatial variations across a sample which correlate with the connected regions
(clusters) in the network when the resistivity is low such as in Aluminum. For
the more resistive material NbTiN the impedance becomes dominated by the local
structure of the percolating network (connectivity). The results can
qualitatively be understood and reproduced with a network current spreading
model based on the pseudo-inverse Laplacian of the underlying network graph.",1908.09810v1
2019-11-30,Structural relaxation in amorphous materials under cyclic tension-compression loading,"The process of structural relaxation in disordered solids subjected to
repeated tension-compression loading is studied using molecular dynamics
simulations. The binary glass is prepared by rapid cooling well below the glass
transition temperature and then periodically strained at constant volume. We
find that the amorphous system is relocated to progressively lower potential
energy states during hundreds of cycles, and the energy levels become deeper
upon approaching critical strain amplitude from below. The decrease in
potential energy is associated with collective nonaffine rearrangements of
atoms, and their rescaled probability distribution becomes independent of the
cycle number at sufficiently large time intervals. It is also shown that
yielding during startup shear deformation occurs at larger values of the stress
overshoot in samples that were cyclically loaded at higher strain amplitudes.
These results might be useful for mechanical processing of amorphous alloys in
order to reduce their energy and increase chemical resistivity and resistance
to crystallization.",1912.00221v1
2021-01-04,Twin Mechanical Metamaterials,"By mimicking the geometrical relation of nano-twin crystals, we propose novel
architected twin mechanical metamaterials (TMMs), which can impede local
shearing band formation under external loading, thus avoiding global
catastrophic failure. The effects of twin-space and twin angle on the
mechanical performance of TMMs were also explored, such as: energy absorption,
strength, and crack propagation resistance. The results showed that the twin
topology design can not only significantly improve the energy-absorption
efficiency but also remarkably improve the crack-propagation resistances of
stretching-dominant mechanical metamaterials. We also studied the effect of
twin-space and twin angle on the tensile strength of TMMs. This study is the
first to report on the inverse Hall-Petch effect of TMMs. Our findings open an
avenue for the design and fabrication of advanced materials with exceptionally
tuneable mechanical properties.",2101.00927v1
2012-06-04,Optimal Condition for Strong Terahertz Radiation from Intrinsic Josephson Junctions,"In order to enhance the radiation power in terahertz band based on the
intrinsic Josephson junctions of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ single
crystal, we investigate a long cylindrical sample embedded in a dielectric
material. Tuning the dielectric constant, the radiation power has a maximum
which is achieved when it equals the dissipation caused by Josephson plasma.
This yields the optimal dielectric constant of wrapping material in terms of
the properties of BSCCO single crystal. The maximal radiation power is found
proportional to the product of the typical superconducting current squared and
the typical normal resistance, or the gap energy squared divided by the typical
normal resistance, which offers a guideline for choosing superconductor as a
source of strong radiation. By introducing an anti-reflection layer, we can
build a compact device with the BSCCO cylinder and two wrapping dielectric
layers with finite thicknesses.",1206.0516v1
2012-06-15,Breakdown of the interlayer coherence in twisted bilayer graphene,"Coherent motion of the electrons in the Bloch states is one of the
fundamental concepts of the charge conduction in solid state physics. In
layered materials, however, such a condition often breaks down for the
interlayer conduction, when the interlayer coupling is significantly reduced by
e.g. large interlayer separation. We report that complete suppression of
coherent conduction is realized even in an atomic length scale of layer
separation in twisted bilayer graphene. The interlayer resistivity of twisted
bilayer graphene is much higher than the c-axis resistivity of Bernal-stacked
graphite, and exhibits strong dependence on temperature as well as on external
electric fields. These results suggest that the graphene layers are
significantly decoupled by rotation and incoherent conduction is a main
transport channel between the layers of twisted bilayer graphene.",1206.3410v1
2015-07-23,"Electronic, magnetic and transport properties of Fe intercalated 2H-TaS$_2$ studied by means of the KKR-CPA method","The electronic, magnetic and transport properties of Fe intercalated
2H-TaS$_2$ have been investigated by means of the Korringa-Kohn-Rostoker (KKR)
method. The non-stoichiometry and disorder in the system has been accounted for
using the Coherent Potential Approximation (CPA) alloy theory. A pronounced
influence of disorder on the spin magnetic moment has been found for the
ferro-magnetically ordered material. The same applies for the spin-orbit
induced orbital magnetic moment and magneto-crystalline anisotropy energy. The
temperature-dependence of the resistivity of disordered 2H-Fe$_{0.28}$TaS$_2$
investigated on the basis of the Kubo-St\v{r}eda formalism in combination with
the alloy analogy model has been found in very satisfying agreement with
experimental data. This also holds for the temperature dependent anomalous Hall
resistivity $ \rho_{\rm xy}(T) $. The role of thermally induced lattice
vibrations and spin fluctuations for the transport properties is discussed in
detail.",1507.06544v1
2018-07-18,Thermoelectric stack sample cooling modification of a commercial atomic force microscopy,"Enabling temperature dependent experiments in Atomic Force Microscopy is of
great interest to study materials and surface properties at the nanoscale. By
studying Curie temperature of multiferroic materials, temperature based phase
transition on crystalline structures or resistive switching phenomena are only
a few examples of applications. We present an equipment capable of cooling
samples using a thermoelectric cooling stage down to -61.4 C in a 15x15 mm
sample plate. The equipment uses a four-unit thermoelectric stack to achieve
maximum temperature range, with low electrical and mechanical noise. The
equipment is installed into a Keysight 5500LS Atomic Force Microscopy
maintaining its compatibility with all Electrical and Mechanical modes of
operation. We study the contribution of the liquid cooling pump vibration into
the cantilever static deflection noise and the temperature dependence of the
cantilever deflection. A La0.7Sr0.3MnO3-y thin film sample is used to
demonstrate the performance of the equipment and its usability by analysing the
resistive switching phenomena associated with this oxide perovskite.",1807.06876v1
2019-01-21,Ferromagnetic Kondo lattice behavior in Ce11Pd4In9,"We report on the low-temperature physical properties of a novel compound
Ce$_{11}$Pd$_4$In$_9$ that crystallizes with the orthorhombic
Nd$_{11}$Pd$_4$In$_9$-type crystal structure (space group $Cmmm$). The compound
exhibits ferromagnetic ordering at $T_{\rm {C}}$ = 18.6 K and an order-order
transition at $T_{\rm {t}}$ $\sim$~1.6 K, as inferred from the low-temperature
magnetic susceptibility, heat capacity and electrical resistivity data. In the
paramagnetic region, the electrical transport in Ce$_{11}$Pd$_4$In$_9$ is
dominated by Kondo effect. Below $T_{\rm {C}}$, a distinct contribution due to
ferromagnetic spin waves dominates the electrical resistivity data, while at
the lowest temperatures, the electrical transport and thermodynamic properties
are governed by strong electron-electron correlations. The features observed
conjointly hint at strongly correlated ground state in Ce$_{11}$Pd$_4$In$_9$ .",1901.06888v1
2019-11-14,Absence of evidence of spin transport through amorphous Y$_3$Fe$_5$O$_{12}$,"Long-distance transport of spin information in insulators without long-range
magnetic order has been recently reported. Here, we perform a complete
characterization of amorphous Y$_3$Fe$_5$O$_{12}$ (a-YIG) films grown on top of
SiO$_2$. We confirm a clear amorphous structure and paramagnetic behavior of
our a-YIG films, with semiconducting behavior resistivity that strongly decays
with increasing temperature. The non-local transport measurements show a signal
which is not compatible with spin transport and can be attributed to the drop
of the a-YIG resistivity caused by Joule heating. Our results emphasize that
exploring spin transport in amorphous materials requires careful procedures in
order to exclude the charge contribution from the spin transport signals.",1911.06061v2
2019-11-15,Design and Performance of Hafnium Optical and Near-IR Kinetic Inductance Detectors,"We report on the design and performance of Microwave Kinetic Inductance
Detectors (MKIDs) sensitive to single photons in the optical to near-infrared
range using hafnium as the sensor material. Our test device had a
superconducting transition temperature of 395 mK and a room temperature normal
state resistivity of 97 $\mu \Omega$ cm with an RRR = 1.6. Resonators on the
device displayed internal quality factors of around 200,000. Similar to the
analysis of MKIDs made from other highly resistive superconductors, we find
that modeling the temperature response of the detector requires an extra
broadening parameter in the superconducting density of states. Finally, we show
that this material and design is compatible with a full-array fabrication
process which resulted in pixels with decay times of about 40 $\mu$s and
resolving powers of ~9 at 800 nm.",1911.06434v1
2020-01-08,Effect of memory electrical switching in metal/vanadium oxide/silicon structures with VO2 films obtained by the sol-gel method,"Electrical switching and rectifying properties of the metal-VO2-Si
structures, on both p-type and n-type silicon, with vanadium dioxide films
obtained by an acetylacetonate sol-gel method, are studied. The switching
effect is shown to be due to the semiconductor-to-metal phase transition (SMPT)
in vanadium dioxide. The shift of the switching threshold voltage, accompanied
by the memory effect, in forward bias of the p-Si-VO2 anisotype heterojunction
is observed. To explain this effect, a model is proposed which suggests the
existence of an additional series resistance associated with a channel at the
VO2/Si interface, where a SiOx layer forms during the VO2 deposition process.
This resistance is responsible for both threshold switching characteristics,
and the memory effect, and the oxygen ion electromigration process is shown to
underlie this effect. Potential applications of the observed phenomena,
combining the effects of ReRAM and SMPT, in oxide electronics are discussed.",2001.03055v1
2020-05-24,"Schottky barriers, emission regimes and contact resistances in 2H-1T' MoS$_2$ lateral metal-semiconductor junctions from first-principles","We have studied the finite bias transport properties of a 2H-1T' MoS$_2$
lateral metal-semiconductor (M-S) junction by non-equilibrium Green's functions
calculations, aimed at contacting the 2D channel in a field effect transistor.
Our results indicate that (a) despite the fundamentally different
electrostatics of line and planar dipoles, the Schottky barrier heights respond
similarly to changes in doping and applied bias in 2D and 3D M-S junctions, (b)
2H-1T' MoS$_2$ lateral junctions are free from Fermi level pinning, (c)
armchair interfaces have superior contacting properties vs.\ zigzag interfaces,
(d) 1T' contacts to $p$ channels will present a reduced contact resistance by a
factor of 4-10 with respect to $n$ channels and (e) contacts to intermediately
doped $n$ ($p$) channels operate in the field (thermionic) emission regime. We
also provide an improved procedure to experimentally determine the emission
regime in 2D material junctions.",2005.11717v1
2020-06-12,Blocking of conducting channels widens window for ferroelectric resistive switching in interface-engineered Hf0.5Zr0.5O2 tunnel devices,"Films of Hf0.5Z0.5O2 (HZO) contain a network of grain boundaries. In (111)
HZO epitaxial films on (001) SrTiO3, for instance, twinned orthorhombic (o-HZO)
ferroelectric crystallites coexist with grain boundaries between o-HZO and a
residual paraelectric monoclinic (m-HZO) phase. These grain boundaries
contribute to the resistive switching response in addition to the genuine
ferroelectric polarization switching and have detrimental effects on device
performance. Here, it is shown that, by using suitable nanometric capping
layers deposited on HZO film, a radical improvement of the operation window of
the tunnel device can be achieved. Crystalline SrTiO3 and amorphous AlOx are
explored as capping layers. It is observed that these layers conformally coat
the HZO surface and allow to increase the yield and homogeneity of functioning
ferroelectric junctions while strengthening endurance. Data show that the
capping layers block ionic-like transport channels across grain boundaries. It
is suggested that they act as oxygen suppliers to the oxygen-getters grain
boundaries in HZO. In this scenario it could be envisaged that these and other
oxides could also be explored and tested for fully compatible CMOS
technologies.",2006.07048v1
2020-07-09,Fe3Se4: A Possible Ferrimagnetic Half-Metal?,"Half-metallic ferromagnets show 100% spin-polarization at the Fermi level and
are ideal candidates for spintronic applications. Despite the extensive
research in the field, very few materials have been discovered so far. Here we
present results of electronic band structure calculations based on density
functional theory and extensive physical-property measurements for Fe3Se4
revealing signatures of half-metallicity. The spin-polarized electronic band
structure calculations predict half-metallic ferrimagnetism for Fe3Se4. The
electrical resistivity follows exponentially suppressed electron-magnon
scattering mechanism in the low-temperature regime and show a magnetoresistance
effect that changes the sign from negative to positive with decreasing
temperature around 100 K. Other intriguing observations include the anomalous
behavior of Hall resistance below 100 K and an anomalous Hall coefficient that
roughly follows the \r{ho}2 behavior.",2007.04736v1
2020-07-29,Quasiparticle and Nonquasiparticle Transport in Doped Quantum Paraelectrics,"Charge transport in doped quantum paralectrics (QPs) presents a number of
puzzles, including a pronounced $T^2$ regime in the resistivity. We analyze
charge transport in a QP within a model of electrons coupled to a soft
transverse optical (TO) mode via a two-phonon mechanism. For $T$ above the
soft-mode frequency but below some characteristic scale ($E_0$), the
resistivity scales with the occupation number of phonons squared, i.e., as
$T^2$. The $T^2$ scattering rate does not depend on the carrier number density
and is not affected by a crossover between degenerate and non-degenerate
regimes, in agreement with the experiment. Temperatures higher than $E_0$
correspond to a non-quasiparticle regime, which we analyze by mapping the Dyson
equation onto a problem of supersymmetric quantum mechanics. The combination of
scattering by two TO phonons and by a longitudinal optical mode explains the
data quite well.",2007.14947v2
2020-08-06,"Magnetic, transport, and thermal properties of $δ$-phase UZr$_2$","Alloys of hexagonal $\delta$-phase UZr$_2$ have been synthesized and studied
by means of heat capacity, magnetic susceptibility, magnetization, electrical
resistivity, magnetoresistance, thermoelectric power, thermal conductivity
measurements, for the first time, at temperatures from 1.8 to 300 K and in
magnetic fields up to 8 T. The weak temperature dependence of the magnetic
susceptibility and the small value of both Seebeck (0.75 $\mu$V/K at room
temperature) and of the Sommerfeld coefficient (13.5 mJ mol$^{-1}$ K$^{-2}$)
point to 5$f$-electrons in this material having a delocalized nature. The
electrical resistivity and magnetoresistance indicate the presence of
significant electronic disorder in $\delta$-UZr$_2$, consistent with the
disorder in its crystal structure. Density functional theory calculations have
been performed and compared to experimental results.",2008.02746v1
2020-12-29,Magnetotransport signatures of chiral magnetic anomaly in the half-Heusler phase ScPtBi,"Study of magnetotransport properties of ScPtBi revealed simultaneously: a
negative contribution to the longitudinal magnetoresistance, the planar Hall
effect, and distinct angular narrowing of the longitudinal magnetoresistance {
three hallmarks of chiral magnetic anomaly (pumping of axial charge between
Weyl nodes), a distinct property of topological semimetals. Electronic
structure calculations show that structural defects, such as antisites and
vacancies, bring substantial density of states at the Fermi level of ScPtBi,
indicating that it is a semimetal, not a zero-gap semiconductor, as predicted
earlier. This is in accord with electrical resistivity in ScPtBi, showing no
characteristics of semiconductor. Moreover, below 0.7K we observed an onset of
a superconducting transition, with the resistivity disappearing completely
below 0.23 K.",2012.14819v2
2021-05-28,Projected mushroom-type phase-change memory,"Phase-change memory devices have found applications in in-memory computing
where the physical attributes of these devices are exploited to compute in
place without the need to shuttle data between memory and processing units.
However, non-idealities such as temporal variations in the electrical
resistance have a detrimental impact on the achievable computational precision.
To address this, a promising approach is projecting the phase configuration of
phase change material onto some stable element within the device. Here we
investigate the projection mechanism in a prominent phase-change memory device
architecture, namely mushroom-type phase-change memory. Using nanoscale
projected Ge2Sb2Te5 devices we study the key attributes of state-dependent
resistance, drift coefficients, and phase configurations, and using them reveal
how these devices fundamentally work.",2105.13693v2
2021-08-04,Current-induced breakdown of the quantum anomalous Hall effect,"The quantum anomalous Hall effect (QAHE) realizes dissipationless
longitudinal resistivity and quantized Hall resistance without the need of an
external magnetic field. However, when reducing the device dimensions or
increasing the current density, an abrupt breakdown of the dissipationless
state occurs with a relatively small critical current, limiting the
applications of the QAHE. We investigate the mechanism of this breakdown by
studying multi-terminal devices and identified that the electric field created
between opposing chiral edge states lies at the origin. We propose that
electric-field-driven percolation of two-dimensional charge puddles in the
gapped surface states of compensated topological-insulator films is the most
likely cause of the breakdown.",2108.02081v1
2021-10-08,Universal Non-Volatile Resistive Switching Behavior in 2D Metal Dichalcogenides Featuring Unique Conductive-Point Random Access Memory Effect,"Two-dimensional materials have been discovered to exhibit non-volatile
resistive switching (NVRS) phenomenon. In our work, we reported the universal
NVRS behavior in a dozen metal dichalcogenides, featuring low switching
voltage, large on/off ratio, fast switching speed and forming free
characteristics. A unique conductive-point random access memory (CPRAM) effect
is used to explain the switching mechanisms, supported by experimental results
from current-sweep measurements.",2110.03863v1
2021-10-27,Bound on resistivity in flat-band materials due to the quantum metric,"The quantum metric is a central quantity of band theory but has so far not
been related to many response coefficients due to its nonclassical origin.
However, within a newly developed Kubo formalism for fast relaxation, the
decomposition of the dc electrical conductivity into both classical (intraband)
and quantum (interband) contributions recently revealed that the interband part
is proportional to the quantum metric. Here, we show that interband effects due
to the quantum metric can be significantly enhanced and even dominate the
conductivity for semimetals at charge neutrality and for systems with highly
quenched bandwidth. This is true in particular for topological flat-band
materials of nonzero Chern number, where for intermediate relaxation rates an
upper bound exists for the resistivity due to the common geometrical origin of
quantum metric and Berry curvature. We suggest to search for these effects in
highly tunable rhombohedral trilayer graphene flakes.",2110.14658v3
2021-11-22,First-principles-based screening method for resistivity scaling of anisotropic metals,"The resistivity scaling of metals is a crucial limiting factor for further
downscaling of interconnects in nanoelectronic devices that affects signal
delay, heat production, and energy consumption. Here, we generalize a commonly
considered figure of merit for selecting promising candidate metals with highly
anisotropic Fermi surfaces in terms of their electronic transport properties at
the nanoscale. For this, we introduce a finite-temperature transport tensor,
based on band structures obtained from first principles. This transport tensor
allows for a straightforward comparison between highly anisotropic metals in
nanostructures with different lattice orientations and arbitrary transport
directions. By evaluating the temperature dependence of the tensor components,
we also assess the validity of a Fermi surface-based evaluation of the
transport properties at zero temperature, rather than considering standard
operating temperature conditions.",2111.11121v2
2021-12-17,Nanoscale laser flash measurements of diffuson transport in amorphous Ge and Si,"The thermal properties of amorphous materials have attracted significant
attention due to their technological importance in electronic devices.
Additionally, the disorder-induced breakdown of the phonon gas model makes
vibrational transport in amorphous materials a topic of fundamental interest.
In the past few decades, theoretical concepts such as propagons, diffusons, and
locons have emerged to describe different types of vibrational modes in
disordered solids. But experiments can struggle to accurately determine which
types of vibrational states carry the majority of the heat. In the present
study, we use nanoscale laser flash measurements (front/back time-domain
thermoreflectance) to investigate thermal transport mechanisms in amorphous Ge
and amorphous Si thin-films. We observe a nearly linear relationship between
the amorphous film's thermal resistance and the film's thickness. The slope of
the film's thermal resistance vs. thickness corresponds to a
thickness-independent thermal conductivity of 0.4 and 0.6 W/(m-K) for a-Ge and
a-Si, respectively. This result reveals that the majority of heat currents in
amorphous Si and Ge thin films prepared via RF sputtering at room temperature
are carried by diffusons and/or propagons with mean free paths less than a few
nanometers.",2112.09289v2
2022-01-06,Insights to negative differential resistance in \texorpdfstring{MoS\textsubscript{2}}{MoS2} Esaki diodes: a first-principles perspective,"\ce{MoS_2} is a two dimensional material with a band gap depending on the
number of layers and tunable by an external electric field. The experimentally
observed intralayer band-to-band tunneling and interlayer band-to-band
tunneling in this material present an opportunity for new electronic
applications in tunnel field effect transistors. However, such a widely
accepted concept has never been supported up by theoretical investigations
based on first principles. In this work, using density functional theory, in
conjunction with non-equilibrilibrium Green's function techniques and our
electric field gating method, enabled by a large-scale computational approach,
we study the relation between band alignment and transmission in planar and
side-stack \ce{MoS_2} $p$-$i$-$n$ junction configurations. We demonstrate the
presence of negative differential resistance for both in-plane and interlayer
current, a staple characteristic of tunnel diode junctions, and analyze the
physical origin of such an effect. Electrostatic potentials, the van der Waals
barrier, and complex band analysis are also examined for a thorough
understanding of Esaki Diodes.",2201.02178v1
2022-05-21,Increased Phase Coherence Length in a Porous Topological Insulator,"The surface area of Bi2Te3 thin films was increased by introducing nanoscale
porosity. Temperature dependent resistivity and magnetotransport measurements
were conducted both on as-grown and porous samples (23 and 70 nm). The
longitudinal resistivity of the porous samples became more metallic, indicating
the increased surface area resulted in transport that was more surface-like.
Weak antilocalization (WAL) was present in all samples, and remarkably the
phase coherence length doubled in the porous samples. This increase is likely
due to the large Fermi velocity of the Dirac surface states. Our results show
that the introduction of nanoporosity does not destroy the topological surface
states but rather enhances them, making these nanostructured materials
promising for low energy electronics, spintronics and thermoelectrics.",2205.10589v1
2022-07-11,Spin-Orbit Proximity Effect in Bi/Co Multilayer: The Role of Interface Scattering,"The Spin-Orbit Proximity Effect is the raise of Spin-Orbit Coupling at a
layer near to the interface with a strong spin-orbit material. It has been seen
in several system such as graphene and ferromagnetic layers. The control of the
Spin-Orbit Coupling can be a pathway to discover novel and exotic phases in
superconductor and semimetallic systems. Here, we study the magnetoelectrical
transport, i.e., magnetoresistance and anomalous Hall effect, in Cobalt/Bismuth
multilayers looking for traces of spin-orbit proximity effect and evaluate the
origin of such effect. Our results point for an increase of Spontaneous
Magnetic Anisotropy of Resistivity and Anomalous Hall Resistivity at very low
thicknesses of Cobalt. The analysis of the Anomalous Hall Resisitivity indicate
that the Bismuth layers change the scattering mechanism of Hall effect to the
extrinsic skew-scattering type, indicating that the spin-orbit proximity effect
could be related to the elastic scattering of cobalt free carriers by bismuth
sites at the interface.",2207.04937v1
2022-08-22,Unified intermediate coupling description of the pseudogap and the strange metal phases of cuprates,"A one band Hubbard model with intermediate coupling is shown to describe the
two most important unusual features of a normal state: linear resistivity
strange metal and the pseudogap. Both the spectroscopic and transport
properties of the cuprates are considered on the same footing by employing a
relatively simple postgaussian approximation valid for the intermediate
couplings $U/t=1.5-4$ in relevant temperatures $T>100{\rm K}.$ In the doping
range $\ p=0.1-0.3$, the value of $U$ is smaller than that in the parent
material. For a smaller doping, especially in the Mott insulator phase, the
coupling is large compared to the effective tight binding scale and a different
method is required. This scenario provides an alternative to the paradigm that
the coupling should be strong, say $U/t>6$, in order to describe the strange
metal. We argue that to obtain phenomenologically acceptable underdoped normal
state characteristics like $T^{\ast }$, pseudogap values, and spectral weight
distribution, a large value of $U$ is detrimental. Surprisingly the resistivity
in the above temperature range is linear $\rho =\rho_{0}+\alpha \frac{m^{\ast
}}{e^{2}n\hbar }T$ with the ""Planckian"" coefficient $\alpha $ of order one.",2208.10093v1
2022-09-05,Charge-Density Wave Driven Giant Thermionic-Current Switching in 1T-TaS$_{2}$/2H-TaSe$_{2}$/2H-MoS$_{2}$ Heterostructure,"1T-TaS$_2$ exhibits several resistivity phases due to the modulation of
charge density wave (CDW). The fact that such phase transition can be driven
electrically has attracted a lot of attention in the recent past towards
\emph{active-metal} based electronics. However, the bias-driven resistivity
switching is not very large ($<$ 5 fold), and an enhancement in the same will
highly impact such phase transition devices. One aspect that is often
overlooked is that such phase transition is also accompanied by a significant
change in the local temperature due to the low thermal conductivity of
1T-TaS$_2$. In this work, we exploit such electrically driven phase transition
induced temperature change to promote carriers over a thermionic barrier in a
1T-TaS$_{2}$/2H-TaSe$_{2}$/2H-MoS$_{2}$ T-Junction, achieving a $964$-fold
abrupt switching in the current through the MoS$_2$ channel. The device is
highly reconfigurable and exhibits an abrupt reduction in current as well when
the biasing configuration changes. The results are promising for several
electronic applications, including neuromorphic chips, switching, nonlinear
devices, and industrial electronics such as current and temperature sensing.",2209.02024v1
2022-11-18,Pressure-induced superconductivity in PdTeI with quasi-one-dimensional PdTe chains,"The quasi-one-dimensional material PdTeI exhibits unusual electronic
transport properties at ambient pressure. Here, we systematically investigate
both the structural and electronic responses of PdTeI to external pressure,
through a combination of electrical transport, synchrotron x-ray diffraction
(XRD), and Raman spectroscopy measurements. The charge density wave (CDW) order
in PdTeI is fragile and the transition temperature TCDW decreases rapidly with
the application of external pressure. The resistivity hump is indiscernible
when the pressure is increased to 1 GPa. Upon further compression, zero
resistance is established above 20 GPa, suggesting the occurrence of
superconductivity. Combined XRD and Raman data evidence that the emergence of
superconductivity is accompanied by a pressure-induced amorphization of PdTeI.",2211.10294v1
2023-02-21,Electron transport and scattering mechanisms in ferromagnetic monolayer Fe$_3$GeTe$_2$,"We study intrinsic charge-carrier scattering mechanisms and determine their
contribution to the transport properties of the two-dimensional ferromagnet
Fe$_3$GeTe$_2$. We use state-of-the-art first-principles calculations combined
with the model approaches to elucidate the role of the electron-phonon and
electron-magnon interactions in the electronic transport. Our findings show
that the charge carrier scattering in Fe$_3$GeTe$_2$ is dominated by the
electron-phonon interaction, while the role of magnetic excitations is
marginal. At the same time, the magnetic ordering is shown to effect
essentially on the electron-phonon coupling and its temperature dependence.
This leads to a sublinear temperature dependence of the electrical resistivity
near the Curie temperature, which is in line with experimental observations.
The room temperature resistivity is estimated to be $\sim$35 $\mu \Omega
\cdot$cm which may be considered as an intrinsic limit for monolayer
Fe$_3$GeTe$_2$.",2302.10974v1
2023-03-20,Thermal decomposition of the Kitaev material $α$-RuCl$_3$ and its influence on low-temperature behavior,"We explore the effect of heat treatment in argon atmosphere under various
temperatures up to $500^\circ$C on single crystals of $\alpha$-RuCl$_3$ by
study of the mass loss, microprobe energy dispersive x-ray spectroscopy, powder
x-ray diffraction, electrical resistance as well as low-temperature magnetic
susceptibility and specific heat. Clear signatures of dechlorination and
oxidation of Ru appear for annealing temperatures beyond $300^\circ$C. Analysis
of the specific heat below 2~K reveals a RuO$_2$ mass fraction of order $1\%$
for pristine $\alpha$-RuCl$_3$ which increases up to $20\%$ after thermal
annealing, fully consistent with mass-loss analysis. The small RuO$_2$
inclusions drastically reduce the global electrical resistance and may thus
significantly affect low-temperature thermal transport and Hall effect.",2303.11308v1
2023-09-08,Re-entrance of resistivity due to the interplay of superconductivity and magnetism in $\ce{Eu_{0.73}Ca_{0.27}(Fe_{0.87}Co_{0.13})2As2}$,"By simultaneous Co and Ca-doping we were able to obtain an
$\ce{EuFe2As2}$-based compound with superconductivity appearing above the
antiferromagnetic order of $\ce{Eu^{2+}}$ magnetic moments. However, as soon as
the antiferromagnetic order appears a re-entrance behavior is observed
\textemdash{} instead of zero resistivity and diamagnetic signal down to the
temperature of \unit[2]{K}. By investigating magnetization, ac susceptibility
and electrical transport properties of
$\ce{Eu_{0.73}Ca_{0.27}(Fe_{0.87}Co_{0.13})2As2}$ and comparing them to
previously studied M\""ossbauer effect and neutron scattering measurements of
this and similar compounds an explanation of such behavior is proposed.",2309.04308v2
2023-10-02,Crystallographic-dependent bilinear magnetoelectric resistance in a thin WTe$_2$ layer,"The recently reported Bilinear Magnetoeletric Resistance (BMR) in novel
materials with rich spin textures, such as bismuth selenide (Bi$_2$Se$_3$) and
tungsten ditelluride (WTe$_2$), opens new possibilities for probing the spin
textures via magneto-transport measurements. By its nature, the BMR effect is
directly linked to the crystal symmetry of the materials and its spin texture.
Therefore, understanding the crystallographic dependency of the effect is
crucial. Here we report the observation of crystallographic-dependent BMR in
thin WTe$_2$ layers and explore how it is linked to its spin textures. The
linear response measured in first harmonic signals and the BMR measured in
second harmonic signals are both studied under a wide range of magnitudes and
directions of magnetic field, applied current and at different temperatures. We
discover a three-fold symmetry contribution of the BMR when current is applied
along the a-axis of the WTe$_2$ thin layer at 10 K, which is absent for when
current is applied along the b-axis.",2310.01058v1
2023-11-23,Helicoidal Transformation Method for Finite Element Models of Twisted Superconductors,"This paper deals with the modelling of superconducting and resistive wires
with a helicoidal symmetry, subjected to an external field and a transport
current. Helicoidal structures are three-dimensional, and therefore yield
computationally intensive simulations in a Cartesian coordinate system. We show
in this paper that by working instead with a helicoidal system of coordinates,
the problem to solve can be made two-dimensional, drastically reducing the
computational cost. We first introduce the state-of-the-art approach and apply
it on the h-phi-formulation with helicoidally symmetric boundary conditions
(e.g., axial external magnetic field, with or without transport current), with
an emphasis on the function space discretization. Then, we extend the approach
to general boundary conditions (e.g., transverse external magnetic field) and
present numerical results with linear materials. In particular, we discuss the
frequency-dependent losses in composite wires made of superconducting filaments
embedded in a resistive matrix. Finally, we provide outlook to the application
of the generalized model with nonlinear materials.",2311.13919v2
2024-03-28,"Single-Crystal Growth and Characterization of Cuprate Superconductor (Hg,Re)Ba$_2$Ca$_2$Cu$_3$O$_{8+δ}$","We grew (Hg,Re)Ba$_2$Ca$_2$Cu$_3$O$_{8+\delta}$ ((Hg,Re)1223) single crystals
with good reproducibility via the single-step flux method using monoxides as
raw materials. A double-sealing method using a thick-walled quartz tube and a
stainless-steel container was adopted for explosion protection. The maximum
crystal size was approximately 1 mm x 1 mm in the ab plane and 0.04 mm in
thickness. The crystal was square-shaped, reflecting the tetragonal crystal
structure of (Hg,Re)1223. Magnetic susceptibility measurements indicated a
critical temperature of 130 K. The in-plane resistivity exhibited a linear
temperature dependence, indicating that the sample was close to optimal doping
level. The out-of-plane resistivity was also measured, and the anisotropy
parameter was 250-650 at 300 K.",2403.19182v1
2024-05-01,Tunable viscous layers in Corbino geometry using density junctions,"In sufficiently clean materials where electron-electron interactions are
strong compared to momentum-relaxing scattering processes, electron transport
resembles the flow of a viscous fluid. We study hydrodynamic electron transport
across density interfaces (n-n junctions) in a 2DEG in the Corbino geometry.
From numerical simulations in COMSOL using realistic parameters, we show that
we can produce tunable viscous layers at the density interface by varying the
density ratio of charge carriers. We quantitatively explain this observation
with simple analytic expressions together with boundary conditions at the
interface. We also show signatures of these viscous layers in the
magnetoresistance. Breaking down viscous and ohmic contributions, we find that
when outer radial region of the Corbino has higher charge density compared to
the inner region, the viscous layers at the interface serve to suppress the
magneto-resistance produced by momentum-relaxing scattering. Conversely, the
magneto-resistance is enhanced when the inner region has higher density than
the outer. Our results add to the repertoire of techniques for engineering
viscous electron flows, which hold a promise for applications in future
electronic devices.",2405.00381v1
2003-06-06,Collective transport and optical absorption near the stripe criticality,"Within the stripe quantum critical point scenario for high $T_c$
superconductors, we point out the possible direct contribution of charge
collective fluctuations to the optical absorption and to the d.c. resistivity.",0306176v1
2010-08-09,"Planes, Chains, and Orbits: Quantum Oscillations and High Magnetic Field Heat Capacity in Underdoped YBCO","The underlying physics of the magnetic-field-induced resistive state in high
temperature cuprate superconductors remains a mystery. One interpretation is
that the application of magnetic field destroys the d-wave superconducting gap
to uncover a Fermi surface that behaves like a conventional (i.e.Fermi Liquid)
metal (1). Another view is that an applied magnetic field destroys long range
superconducting phase coherence, but the superconducting gap amplitude survives
(2, 3). By measuring the specific heat of ultra-clean YBa2Cu3O6.56 (YBCO 6.56),
we obtain a measure of the quasi-particle density of states from the
superconducting state well into the magnetic-field-induced resistive state. We
have found that at very high magnetic fields the specific heat exhibits both
the conventional temperature dependence and quantum oscillations expected for a
Fermi Liquid. On the other hand, the magnetic field dependence of the
quasi-particle density of states follows a \sqrt{H} behavior that persists
right through the zero-resistance transition, evidencing the fully developed
d-wave superconducting gap over the entire magnetic field range measured. The
coexistence of these two phenomena pose a rigorous thermodynamic constraint on
theories of high-magnetic-field resistive state in the cuprates.",1008.1568v1
2011-02-09,Heavy Long-lived Mossbauer State of Niobium,"A heavy niobium state showing 1/3 residual resistance is discovered below the
superconducting transition temperature. This niobium sample contains
high-density long-lived Mossbauer excitation.",1102.1766v2
2015-12-21,"Kondo effect in CeX$_{c}$ (X$_{c}$=S, Se, Te) studied by electrical resistivity under high pressure","We have measured the electrical resistivity of cerium monochalcogenices, CeS,
CeSe, and CeTe, under high pressures up to 8 GPa. Pressure dependences of the
antiferromagnetic ordering temperature $T_{N}$, crystal field splitting, and
the $\ln T$ anomaly of the Kondo effect have been studied to cover the whole
region from the magnetic ordering regime at low pressure to the Fermi liquid
regime at high pressure. $T_{N}$ initially increases with increasing pressure,
and starts to decrease at high pressure as expected from the Doniach's diagram.
Simultaneously, the $\ln T$ behavior in the resistivity is enhanced, indicating
the enhancement of the Kondo effect by pressure. It is also characteristic in
CeX$_{c}$ that the crystal field splitting rapidly decreases at a common rate
of $-12.2$ K/GPa. This leads to the increase in the degeneracy of the $f$ state
and further enhancement of the Kondo effect. It is shown that the pressure
dependent degeneracy of the $f$ state is a key factor to understand the
pressure dependence of $T_{N}$, Kondo effect, magnetoresistance, and the peak
structure in the temperature dependence of resistivity.",1512.06530v1
2019-10-01,High transparency Bi2Se3 topological insulator nanoribbon Josephson junctions with low resistive noise properties,"Bi$_2$Se$_3$ nanoribbons, grown by catalyst-free Physical Vapour Deposition,
have been used to fabricate high quality Josephson junctions with Al
superconducting electrodes. The conductance spectra (dI/dV) of the junctions
show clear dip-peak structures characteristic of multiple Andreev reflections.
The temperature dependence of the dip-peak features reveals a highly
transparent Al/Bi$_2$Se$_3$ topological insulator nanoribbon interface and
Josephson junction barrier. This is supported by the high values of the
Bi$_2$Se$_3$ induced gap and of I$_c$R$_n$ (I$_c$ critical current, R$_n$
normal resistance of the junction) product both of the order of 160 $\mu$eV, a
value close to the Al gap. The devices present an extremely low relative
resistance noise below 1$\times$10$^{-12}$ $\mu$m$^2$/Hz comparable to the best
Al tunnel junctions, which indicates a high stability in the transmission
coefficients of transport channels. The ideal Al/Bi$_2$Se$_3$ interface
properties, perfect transparency for Cooper pair transport in conjunction with
low resistive noise make these junctions a suitable platform for further
studies of the induced topological superconductivity and Majorana bound states
physics.",1910.00280v2
2017-04-28,Electric Field Effect in Multilayer Cr2Ge2Te6: a Ferromagnetic Two-Dimensional Material,"The emergence of two-dimensional (2D) materials has attracted a great deal of
attention due to their fascinating physical properties and potential
applications for future nanoelectronic devices. Since the first isolation of
graphene, a Dirac material, a large family of new functional 2D materials have
been discovered and characterized, including insulating 2D boron nitride,
semiconducting 2D transition metal dichalcogenides and black phosphorus, and
superconducting 2D bismuth strontium calcium copper oxide, molybdenum
disulphide and niobium selenide, etc. Here, we report the identification of
ferromagnetic thin flakes of Cr2Ge2Te6 (CGT) with thickness down to a few
nanometers, which provides a very important piece to the van der Waals
structures consisting of various 2D materials. We further demonstrate the giant
modulation of the channel resistance of 2D CGT devices via electric field
effect. Our results illustrate the gate voltage tunability of 2D CGT and the
potential of CGT, a ferromagnetic 2D material, as a new functional quantum
material for applications in future nanoelectronics and spintronics.",1704.08862v1
2023-09-26,"The p-Laplace ""Signature"" for Quasilinear Inverse Problems with Large Boundary Data","This paper is inspired by an imaging problem encountered in the framework of
Electrical Resistance Tomography involving two different materials, one or both
of which are nonlinear. Tomography with nonlinear materials is in the early
stages of developments, although breakthroughs are expected in the
not-too-distant future.
  We consider nonlinear constitutive relationships which, at a given point in
the space, present a behaviour for large arguments that is described by
monomials of order p and q.
  The original contribution this work makes is that the nonlinear problem can
be approximated by a weighted p-Laplace problem. From the perspective of
tomography, this is a significant result because it highlights the central role
played by the $p-$Laplacian in inverse problems with nonlinear materials.
Moreover, when p=2, this provides a powerful bridge to bring all the imaging
methods and algorithms developed for linear materials into the arena of
problems with nonlinear materials.
  The main result of this work is that for ""large"" Dirichlet data in the
presence of two materials of different order (i) one material can be replaced
by either a perfect electric conductor or a perfect electric insulator and (ii)
the other material can be replaced by a material giving rise to a weighted
p-Laplace problem.",2309.15206v1
2024-04-23,An Accessible Instrument for Measuring Soft Material Mechanical Properties,"Soft material research has seen significant growth in recent years, with
emerging applications in robotics, electronics, and healthcare diagnostics
where understanding material mechanical response is crucial for precision
design. Traditional methods for measuring nonlinear mechanical properties of
soft materials require specially sized samples that are extracted from their
natural environment to be mounted on the testing instrument. This has been
shown to compromise data accuracy and precision in various soft and biological
materials. To overcome this, the Volume Controlled Cavity Expansion (VCCE)
method was developed. This technique tests soft materials by controlling the
formation rate of a liquid cavity inside the materials at the tip of an
injection needle, and simultaneously measuring the resisting pressure which
describes the material response. Despite VCCE's early successes, expansion of
its application beyond academia has been hindered by cost, size, and expertise.
In response to this, the first portable, bench-top instrument utilizing VCCE is
presented here. This device, built with affordable, readily available
components and open-source software, streamlines VCCE experimentation without
sacrificing performance or precision. It is especially suitable for
space-limited settings and designed for use by non-experts, promoting
widespread adoption. The instrument's efficacy was demonstrated through testing
Polydimethylsiloxane (PDMS) samples of varying stiffness. This study not only
validates instrument performance, but also sets the stage for further
advancements and broader applications in soft material testing. All data, along
with acquisition, control, and post-processing scripts, are made available on
GitHub.",2404.15036v1
2018-04-04,High-Performance Flexible Magnetic Tunnel Junctions for Smart Miniaturized Instruments,"Flexible electronics is an emerging field in many applications ranging from
in vivo biomedical devices to wearable smart systems. The capability of
conforming to curved surfaces opens the door to add electronic components to
miniaturized instruments, where size and weight are critical parameters. Given
their prevalence on the sensors market, flexible magnetic sensors play a major
role in this progress. For many high-performance applications, magnetic tunnel
junctions (MTJs) have become the first choice, due to their high sensitivity,
low power consumption etc. MTJs are also promising candidates for non-volatile
next-generation data storage media and, hence, could become central components
of wearable electronic devices. In this work, a generic low-cost regenerative
batch fabrication process is utilized to transform rigid MTJs on a 500 {\mu}m
silicon wafer substrate into 5 {\mu}m thin, mechanically flexible silicon
devices, and ensuring optimal utilization of the whole substrate. This method
maintains the outstanding magnetic properties, which are only obtained by
deposition of the MTJ on smooth high-quality silicon wafers. The flexible MTJs
are highly reliable and resistive to mechanical stress. Bending of the MTJ
stacks with a diameter as small as 500 {\mu}m is possible without compromising
their performance and an endurance of over 1000 cycles without fatigue has been
demonstrated. The flexible MTJs were mounted onto the tip of a cardiac catheter
with 2 mm in diameter without compromising their performance. This enables the
detection of magnetic fields and the angle which they are applied at with a
high sensitivity of 4.93 %/Oe and a low power consumption of 0.15 {\mu}W, while
adding only 8 {\mu}g and 15 {\mu}m to the weight and diameter of the catheter,
respectively.",1804.01298v1
2017-01-30,High quality factor manganese-doped aluminum lumped-element kinetic inductance detectors sensitive to frequencies below 100 GHz,"Aluminum lumped-element kinetic inductance detectors (LEKIDs) sensitive to
millimeter-wave photons have been shown to exhibit high quality factors, making
them highly sensitive and multiplexable. The superconducting gap of aluminum
limits aluminum LEKIDs to photon frequencies above 100 GHz. Manganese-doped
aluminum (Al-Mn) has a tunable critical temperature and could therefore be an
attractive material for LEKIDs sensitive to frequencies below 100 GHz if the
internal quality factor remains sufficiently high when manganese is added to
the film. To investigate, we measured some of the key properties of Al-Mn
LEKIDs. A prototype eight-element LEKID array was fabricated using a 40 nm
thick film of Al-Mn deposited on a 500 {\mu}m thick high-resistivity,
float-zone silicon substrate. The manganese content was 900 ppm, the measured
$T_c = 694\pm1$ mK, and the resonance frequencies were near 150 MHz. Using
measurements of the forward scattering parameter $S_{21}$ at various bath
temperatures between 65 and 250 mK, we determined that the Al-Mn LEKIDs we
fabricated have internal quality factors greater than $2 \times 10^5$, which is
high enough for millimeter-wave astrophysical observations. In the dark
conditions under which these devices were measured, the fractional frequency
noise spectrum shows a shallow slope that depends on bath temperature and probe
tone amplitude, which could be two-level system noise. The anticipated white
photon noise should dominate this level of low-frequency noise when the
detectors are illuminated with millimeter-waves in future measurements. The
LEKIDs responded to light pulses from a 1550 nm light-emitting diode, and we
used these light pulses to determine that the quasiparticle lifetime is 60
{\mu}s.",1701.08461v2
1997-08-21,Charge Dynamics from Copper Oxide Materials,"The charge dynamics of the copper oxide materials in the underdoped and
optimal doped regimes is studied within the framework of the fermion-spin
theory. The conductivity spectrum shows the non-Drude behavior at low energies
and unusual midinfrared peak, and the resistivity exhibits a linear behavior in
the temperature, which are consistent with experiments and numerical
simulations.",9708165v2
2000-07-06,Scaling of Crack Surfaces and Implications on Fracture Mechanics,"The scaling laws describing the roughness development of crack surfaces are
incorporated into the Griffith criterion. We show that, in the case of a
Family-Vicsek scaling, the energy balance leads to a purely elastic brittle
behavior. On the contrary, it appears that an anomalous scaling reflects a
R-curve behavior associated to a size effect of the critical resistance to
crack growth in agreement with the fracture process of heterogeneous brittle
materials exhibiting a microcracking damage.",0007100v1
2001-01-17,Negative Magnetoresistance Produced by Hall Fluctuations in a Ferromagnetic Domain Structure,"We present a model for a negative magnetoresistance (MR) that would develop
in a material with many ferromagnetic domains even if the individual domains
have no magnetoresistance and even if there is no boundary resistance. The
negative MR is due to a classical current-distortion effect arising from
spatial variations in the Hall conductivity, combined with a change in domain
structure due to an applied magnetic field. The negative MR can exceed 1000% if
the product of the carrier relaxation time and the internal magnetic field due
to spontaneous magnetization is sufficiently large.",0101268v2
2001-03-06,Rheology of a confined granular material,"We study the rheology of a granular material slowly driven in a confined
geometry. The motion is characterized by a steady sliding with a resistance
force increasing with the driving velocity and the surrounding relative
humidity. For lower driving velocities a transition to stick-slip motion
occurs, exhibiting a blocking enhancement whith decreasing velocity. We propose
a model to explain this behavior pointing out the leading role of friction
properties between the grains and the container's boundary.",0103143v1
2001-11-07,Crumpling a Thin Sheet,"Crumpled sheets have a surprisingly large resistance to further compression.
We have studied the crumpling of thin sheets of Mylar under different loading
conditions. When placed under a fixed compressive force, the size of a crumpled
material decreases logarithmically in time for periods up to three weeks. We
also find hysteretic behavior when measuring the compression as a function of
applied force. By using a pre-treating protocol, we control this hysteresis and
find reproducible scaling behavior for the size of the crumpled material as a
function of the applied force.",0111095v1
2003-10-23,Correlation between the Extraordinary Hall Effect and Resistivity,"We study the contribution of different types of scattering sources to the
extraordinary Hall effect. Scattering by magnetic nano-particles embedded in
normal-metal matrix, insulating impurities in magnetic matrix, surface
scattering and temperature dependent scattering are experimentally tested. Our
new data, as well as previously published results on a variety of materials,
are fairly interpreted by a simple modification of the skew scattering model.",0310551v1
2003-12-29,La0.95Sr0.05CoO3: An efficient room-temperature thermoelectric oxide,"We present measurements of electrical resistivity, thermal conductivity and
thermopower of polycrystalline Sr-doped LaCoO3 with composition
La0.95Sr0.05CoO3. Our data show that the investigated compound exhibits a very
respectable room temperature thermoelectric figure of merit value of 0.18. Our
results not only show that oxides are promising candidates for thermoelectric
cooling applications, but also point towards the need for careful theoretical
calculations that will serve as a guide in producing the next generation of
thermoelectric materials.",0312670v1
2004-01-06,"Superstructure, sodium ordering and antiferromagnetism in NaxCoO2 (0.75<x<1.0)","Transmission-electron-microscopy investigation reveals the presence of a
superstructure with a doubled period of 2d110 in the NaxCoO2 materials for x
ranging from 0.75 to 1.0. Systematic analyses suggest that this superstructure
in general appears just below a phase transition which could yield an anomalous
kink in resistivity. We herein interpret this superstructure in terms of sodium
ordering occurring at low temperatures. Measurements of magnetic susceptibility
for all NaxCoO2 (0.75<x<1.0) materials show an antiferromagetic state with Neel
temperature TN~4K.",0401052v1
2004-09-15,Drying model for porous material based on the dynamics of the evaporation front,"A receding-front model for drying of porous material is proposed that
explains their drying-rate curves based on the dynamics of the evaporation
front. The falling-rate regime is attributed to the slowing down of the front's
propagation inside the medium due to the resistance offered by the disorder
generated by porosity. The model is solved numerically and the resulting
drying-rate curve is obtained for the falling-rate period. The curve shows a
linear behavior at early times in conformance with experiment.",0409384v1
2004-10-20,Spin-polarized transport through carbon nanotubes,"Carbon nanotubes (CNT) belong to the most promising new materials which can
in the near future revolutionize the conventional electronics. When sandwiched
between ferromagnetic electrodes, the CNT behaves like a spacer in conventional
spin-valves, leading quite often to a considerable giant magneto-resistance
effect (GMR). This paper is devoted to reviewing some topics related to
electron correlations in CNT. The main attention however is directed to the
following effects essential for electron transport through nanotubes: (i)
nanotube/electrode coupling and (ii) inter-tube interactions.It is shown that
these effects may account for some recent experimental reports on GMR,
including those on negative (inverse) GMR.",0410507v1
2005-11-25,Decoupled magnetic and electrical switching in manganite trilayer,"We report magnetic and electrical transport studies of an epitaxially grown
trilayer thin film structure comprising La0.59Ca0.41MnO3 sandwiched between
La0.67Ca0.33MnO3 electrodes. Since La0.59Ca0.41MnO3 lies at the edge of the
thin film ferromagnetic metallic phase field, phase separation effects are
expected. These effects can explain the observed magnetic isotropy of the
middle layer. By contrast, the electrode material is magnetically uniaxial.
Easy axis magnetic field sweeps of the trilayer produce two sharp magnetic
transitions, but only one sharp transition in current-in-plane resistance
measurements.",0511632v1
2005-12-08,Charge order in photosensitive Bi0.4Ca0.6MnO3 films,"We report structural and electronic characterization of the charge order
phase in Bi0.4Ca0.6MnO3 films, in which photoinduced resistivity changes have
been observed at temperatures approaching room temperature. In all films,
lattice distortions associated with the charge order are observed, and both the
wavevectors and displacements of the distortions are in the plane of the film.
Films under compressive and tensile strain are observed to have different
resonant x-ray scattering characteristics-- a result that may shed light on the
mechanism responsible for the photosensitivity exhibited by this material.",0512179v1
2006-03-21,Effect of rolling on dissipation in fault gouge,"Sliding and rolling are two outstanding deformation modes in granular media.
The first one induces frictional dissipation whereas the latter one involves
deformation with negligible resistance. Using numerical simulations on
two-dimensional shear cells, we investigate the effect of the grain rotation on
the energy dissipation and the strength of granular materials under quasistatic
shear deformation. Rolling and sliding are quantified in terms of the so-called
Cosserat rotations. The observed spontaneous formation of vorticity cells and
clusters of rotating bearings may provide an explanation for the long standing
heat flow paradox of earthquake dynamics.",0603542v1
2006-06-20,Resonant Tunneling Magneto Resistance in Coupled Quantum Wells,"A three barrier resonant tunneling structure in which the two quantum wells
are formed by a dilute magnetic semiconductor material (ZnMnSe) with a giant
Zeeman splitting of the conduction band is theoretically investigated.
Self-consistent numerical simulations of the structure predict giant
magnetocurrent in the resonant bias regime as well as significant current spin
polarization for a considerable range of applied biases.",0606531v2
2006-08-07,Structure and Function of Window Glass and Pyrex,"Window glass is a ternary mixture, while pyrex (after window glass, the most
common form of commercial glass) is a quaternary. Building on our previous
success in deriving the composition of window glass (sodium calcium silicate)
without adjustable parameters, and borrowing from known reconstructed
crystalline surfaces, we model pyrex as silica clusters with a specific ternary
interface. Our global model explains the thermal expansivity contours of
ternary sodium borosilicates, and it is consistent with the optimized
resistance of pyrex to mechanical and thermal shocks. It suggests new
directions for studying the nanoscopic structure of these remarkable materials.",0608157v2
2006-08-28,A Novel Pyrochlore Ruthenate: Ca2Ru2O7,"Single crystals of a novel ruthenate, Ca2Ru2O7, were obtained. An X-ray
diffraction study on a single crystal revealed that this material crystallizes
in a pyrochlore structure with a lattice parameter, a = 10.197 Angstroms. The
magnetic susceptibility above 30 K is the summation of a Curie-Weiss
contribution and a constant term independent of temperature. The effective
moment per Ru atom is only 0.36 Bohr magnetons, one order of magnitude smaller
than that expected from a localized spin model with S=3/2 for Ru5+. Below 23 K,
the localized spins freeze in a spin-glass state. The resistivity at room
temperature is 2E-3 Ohm cm, comparable to that in metallic, highly correlated
oxides.}",0608593v1
2006-08-30,Electromagnetic shielding with polypyrrole-coated fabrics,"Several shielding applications, to protect human health and electronic
devices against dangerous effects of electromagnetic radiation, require
solutions that fabrics can suitably fulfill. Here, we will investigate the
electromagnetic interference shielding effectiveness of polypyrrole-coated
polyester textiles, in the frequency range 100-1000 MHz. Insertion losses for
several conductive fabrics with different surface resistivity ranging from 40
Ohm till the very low value of 3 Ohm were evaluated with a dual-tem cell.
Correlations between the shielding effectiveness and the conductivity of
composites are also discussed.",0608664v1
2007-03-19,Understanding the Branly effect,"At the end of the nineteenth century \'{E}douard Branly discovered that the
electrical resistance of a granular metallic conductor could drop by several
orders of magnitude when excited by the electromagnetic field emitted by an
electrical spark. Despite the fact that this effect has been used to detect
radio waves in the early times of wireless telegraphy and more recently studied
in the field of granular materials, no satisfactory explanation of the physical
origin of the effect has been given yet. In this contribution we propose to
relate the Branly effect to the induced tunnelling effect first described by
Fran\c{c}ois Bardou and Dominique Boos\'{e}.",0703495v1
2007-04-09,Electron Transport in Nanogranular Ferromagnets,"We study electronic transport properties of ferromagnetic nanoparticle arrays
and nanodomain materials near the Curie temperature in the limit of weak
coupling between the grains. We calculate the conductivity in the Ohmic and
non-Ohmic regimes and estimate the magnetoresistance jump in the resistivity at
the transition temperature. The results are applicable for many emerging
materials, including artificially self-assembled nanoparticle arrays and a
certain class of manganites, where localization effects within the clusters can
be neglected.",0704.1167v2
2007-07-06,Thermal rectification and negative differential thermal resistance in lattices with mass gradient,"We study thermal properties of one dimensional(1D) harmonic and anharmonic
lattices with mass gradient. It is found that the temperature gradient can be
built up in the 1D harmonic lattice with mass gradient due to the existence of
gradons. The heat flow is asymmetric in the anharmonic lattices with mass
gradient. Moreover, in a certain temperature region the {\it negative
differential thermal resistance} is observed. Possible applications in
constructing thermal rectifier and thermal transistor by using the graded
material are discussed.",0707.0977v1
2008-03-28,"On the electronic structure of the charge-ordered phase in epitaxial and polycrystalline La1-xCaxMnO3 (x = 0.55, 0.67) perovskite manganites","In this work the charge transport properties of charge ordered (CO)
La1-xCaxMnO3 (LCMO) (x= 0.55, 0.67) epitaxial thin films and polycrystals are
discussed following the recent controversy of localised electron states vs.
weakly or de- localised charge density wave (CDW) states in CO manganites. The
transport properties were investigated by current vs. voltage, direct current
resistivity vs. temperature, local activation energy vs. temperature,
magnetoresistance and admittance spectroscopy measurements, which all indicated
a localised electronic structure in the single CO phase. Delocalised charge
anomalies observed previously may be restricted to phase separated materials.",0803.4157v1
2008-11-02,Deposition of Diamond-like Carbon films using Dense Plasma Focus,"Diamond Like Carbon (DLC) films were deposited on quartz substrates using
Dense Plasma Focus (DPF) method. The formation of ${\rm sp^3}$ bonds as is it's
content in the film strongly depends on the substrate and it seems quartz is
not a suitable substrate. However, we report here the formation of DLC films on
quartz substrates that were maintained at elevated temperatures and show the
content of carbon atoms with ${\rm sp^3}$ bonds in the film is directly
proportional to the substrate's temperature. Not only does this give good
control of film fabrication, but also shows how to take advantage of DLC film's
anti-wear, scratch resistant properties on material surfaces that require
protection.",0811.0162v1
2009-05-03,Magnetic state electrical readout of Mn12 molecules,"We demonstrate that the different magnetic states of a Mn12 molecule can be
distinguished in a two-probe transport experiment from a complete knowledge of
the current-voltage curve. Our results, obtained with state-of-the-art
non-equilibrium transport methods combined with density functional theory,
demonstrate that spin configuration-specific negative differential resistances
(NDRs) appear in the I-V curves. These originate from the interplay between
electron localization and the re-hybridization of the molecular levels in an
external electric field and allow the detection of the molecule's spin-state.",0905.0281v1
2010-04-10,Extremely Low Drift in Amorphous Phase Change Nanowire Materials,"Time-dependent drift of resistance and threshold voltage in phase change
memory (PCM) devices is of concern as it leads to data loss. Electrical drift
in amorphous chalcogenides has been argued to be either due to electronic or
stress relaxation mechanisms. Here we show that drift in amorphized Ge2Sb2Te5
nanowires with exposed surfaces is extremely low in comparison to thin-film
devices. However, drift in stressed nanowires embedded under dielectric films
is comparable to thin-films. Our results shows that drift in PCM is due to
stress relaxation and will help in understanding and controlling drift in PCM
devices.",1004.1695v1
2010-06-30,Control of the structural and magnetic properties of perovskite oxide ultrathin films through the substrate symmetry effect,"Perovskite transition-metal oxides are networks of corner-sharing octahedra
whose tilts and distortions are known to affect their electronic and magnetic
properties. We report calculations on a model interfacial structure to avoid
chemical influences and show that the symmetry mismatch imposes an interfacial
layer with distortion modes that do not exist in either bulk material, creating
new interface properties driven by symmetry alone. Depending on the resistance
of the octahedra to deformation, the interface layer can be as small as one
unit cell or extend deep into the thin film.",1006.5758v1
2011-05-25,Non-Gaussian resistance noise in the ferromagnetic insulating state of a hole doped manganite,"We report the observation of a large 1/f noise in the ferromagnetic
insulating state (FMI) of a hole doped manganite single crystal of
La0.80Ca0.20MnO3 which manifests hopping conductivity in presence of a Coulomb
gap. The temperature dependent noise magnitude shows a deep within the FMI
state, there is a sharp freeze out of the noise magnitude with temperature on
cooling. As the material enters the FMI state, the noise becomes non-Gaussian
as seen through probability density function and second spectra. It is proposed
to arise from charge fluctuations in a correlated glassy phase of the polaronic
carriers which develop in these systems as reported in recent simulation
studies.",1105.5079v1
2013-12-03,Doped Polyaniline: A Possible Anode for Organic Electronics,"Polymer based printable organic thin film transistor (OTFT) is a viable low
cost alternative to amorphous silicon based thin film transistors and possesses
light-weight and flexibility advantage. In this paper, we report on the hole
injecting properties of doped PANI in OLED devices using it as an anode. From
these results we conclude that hole doped PANI layers can be used as a low
contact resistance source and drain electrode material for polymer OTFTs.",1312.0737v1
2013-12-28,Understanding Branly's effect through Induced Tunnelling,"At the end of the nineteenth century \'Edouard Branly discovered that the
electrical resistance of a granular metallic conductor could drop by several
orders of magnitude when excited by the electromagnetic field emitted by a
distant electrical spark [ ]. Despite the fact that this effect was used to
detect radio waves in the early days of wireless telegraphy and more recently,
studied in the field of granular materials, no satisfactory explanation of the
physical origin of the effect has been proposed. In this contribution, we
relate the Branly effect to the induced tunnelling effect first described by
Fran\c{c}ois Bardou and Dominique Boos\'e [ ].",1312.7464v2
2014-05-08,Inverse spin Hall effect in a closed loop circuit,"We present measurements of inverse spin Hall effects (ISHEs) in which the
conversion of a spin current into a charge current via the ISHE is detected not
as a voltage in a standard open circuit but directly as the charge current
generated in a closed loop. The method is applied to the ISHEs of Bi-doped Cu
and Pt. The derived expression of ISHE for the loop structure can relate the
charge current flowing into the loop to the spin Hall angle of the SHE material
and the resistance of the loop.",1405.2100v2
2014-09-23,Negative differential resistance: another banana?,"Just like the artefact found in ferroelectric hysteresis loops, the nearly
identical NDR effect shown in Sr3Co2Fe24O41, TiO2, Al2O3, glass and even banana
skins is confirmed to be a kind of water behavior. The combination of water
induced tunneling effect, water decomposition and absorption plays a crucial
role in the NDR effect. The results and mechanism demonstrated here illustrate
that much attention should be paid to the chemical environment when studying
electrical properties of materials / devices.",1409.6438v1
2015-01-13,The Electronic and Magnetic Properties of Magnetoresistant Nd1-xSrxMnAsO Oxyarsenides,"The oxypnictides Nd1-xSrxMnAsO have been successfully synthesised with x up
to 0.1. A synchrotron X-ray diffraction study demonstrates that there is no
change in crystal symmetry upon doping with Sr. An expansion of the inter-layer
distance between Nd-O-Nd and As-Mn-As blocks is observed with increasing x.
Results from variable temperature neutron diffraction and resistivity
measurements show that the local moment antiferromagnetic order of the Mn spins
is preserved as the [MnAs]- layers are hole doped and the materials are driven
metallic for x > 0.05. A sizeable positive magnetoresistance is observed at low
temperature which demonstrates that multiple MR mechanisms are possible in
LnMnAsO oxypnictides.",1501.02996v1
2015-03-02,Functional Materials for Information and Energy Technology: Insights by Photoelectron Spectroscopy,"The evolution of both information and energy technology is intimately
connected to complex condensed matter systems, the properties of which are
determined by electronic and chemical interactions and processes on a broad
range of length and time scales. Dedicated photoelectron spectroscopy and
spectromicroscopy experiments can provide important insights. We discuss some
recent methodological developments with application to relevant questions in
spintronics, and towards in-operando studies of resistive switching and
electrochemical processes.",1503.00464v2
2015-03-29,Cooperative Multiscale Aging in a Ferromagnet/Antiferromagnet Bilayer,"We utilize anisotropic magnetoresistance to study temporal evolution of the
magnetization state in epitaxial Ni$_{80}$Fe$_{20}$/Fe$_{50}$Mn$_{50}$
ferromagnet/antiferromagnet bilayers. The resistance exhibits power-law
evolution over a wide range of temperatures and magnetic fields, indicating
that aging is characterized by a wide range of activation time scales. We show
that aging is a cooperative process, i.e. the magnetic system is not a
superposition of weakly interacting subsystems characterized by simple
Arrhenius activation. The observed effects are reminiscent of avalanches in
granular materials, providing a conceptual link to a broad class of critical
phenomena in other complex condensed matter systems.",1503.08380v1
2015-11-17,On melting of boron phosphide under pressure,"Melting of cubic boron phosphide, BP has been studied at pressures to 9 GPa
using synchrotron X-ray diffraction and electrical resistivity measurements. It
has been found that above 2.6 GPa BP melts congruently, and the melting curve
exhibits negative slope -60(7) K/GPa, which is indicative of a higher density
of the melt as compared to the solid phase.",1511.05995v1
2015-11-30,Electronic Origins of Large Thermoelectric Power Factor of LaOBiS2-xSex,"We examined the electrical transport properties of densified LaOBiS2-xSex,
which constitutes a new family of thermoelectric materials. The power factor
increased with increasing concentration of Se, i.e., Se substitution led to an
enhanced electrical conductivity, without suppression of the Seebeck
coefficient. Hall measurements indicated that the low electrical resistivity
resulted from increases in the carrier mobility, and the decrease in carrier
concentration led to large absolute values of the Seebeck coefficient of the
system.",1511.09133v1
2016-04-04,Two-dimensional Dirac fermions in YbMnBi2 antiferromagnet,"We report two-dimensional quantum transport and Dirac fermions in YbMnBi2
single crystals. YbMnBi2 is a layered material with anisotropic conductivity
and magnetic order below 290 K. Magnetotransport properties, nonzero Berry
phase and small cyclotron mass indicate the presence of quasi two dimensional
Dirac fermions. Quantum oscillations in Hall resistivity suggest the presence
of both electron and hole parts of the Fermi surface whereas the Berry phase
suggests spin-orbit coupling.",1604.01009v1
2016-08-17,Field effect in stacked van der Waals heterostructures: Stacking sequence matters,"Stacked van der Waals (vdW) heterostructures where semi-conducting
two-dimensional (2D) materials are contacted by overlayed graphene electrodes
enable atomically-thin, flexible electronics. We use first-principles quantum
transport simulations of graphene-contacted MoS2 devices to show how the
transistor effect critically depends on the stacking configuration relative to
the gate electrode. We can trace this behavior to the stacking-dependent
response of the contact region to the capacitive electric field induced by the
gate. The contact resistance is a central parameter and our observation
establish an important design rule for devices based on 2D atomic crystals.",1608.05023v1
2017-06-30,Structural and dielectric characterization of Sm2MgMnO6,"The polycrystalline Sm2MgMnO6 (SMMO) was synthesized at 1173K by means of
sol-gel technique. Rietveld refine-ment of X-ray diffraction (XRD) pattern
confirmed the formation of a single phase monoclinic structure with space group
P21/n. The band gap achieved from UV-vis spectra shows the semiconducting
nature of the material. To observe the effect of grains and grain-boundaries in
the conduction process and dielectric relaxation measurements are carried out
on SMMO sample at different frequencies between 313 K and 673 K. An electrical
equivalent circuit consisting of the resistance and constant phase element is
used to clarify the impedance data.",1706.10038v1
2017-10-08,Hall effect spintronics for gas detection,"We present the concept of magnetic gas detection by the Extraordinary Hall
effect (EHE). The technique is compatible with the existing conductometric gas
detection technologies and allows simultaneous measurement of two independent
parameters: resistivity and magnetization affected by the target gas.
Feasibility of the approach is demonstrated by detecting low concentration
hydrogen using thin CoPd films as the sensor material. The Hall effect
sensitivity of the optimized samples exceeds 240% per 104 ppm at hydrogen
concentrations below 0.5% in the hydrogen/nitrogen atmosphere, which is more
than two orders of magnitude higher than the sensitivity of the conductance
detection.",1710.03700v1
2017-10-12,Martensitic relief observation by atomic force microscopy in yttria stabilized zirconia,"The tetragonal to monoclinic (t-m) phase transformation of zirconia has been
the object of extensive investigations of the last twenty years, and is now
recognised as being of martensitic nature. However, martensitic transformation
has only been observed by transmission electron microscopy or indirect methods.
Though the benefit on the fracture toughness and crack resistance was the main
interest, the transformation is now considered for its consequences on the
degradation of the material. The use of AFM reported here allowed the
observation of the first stages of martensite relief growth and of new
martensitic features.",1710.04442v1
2017-10-25,Ordered C vacancies in titanium carbides: a correlation between crystal structure and the effects on oxidation behavior at elevated temperature,"It has been widely accepted that the introduction of titanium carbides into
titanium-based alloys can significantly enhance the oxidation resistance due to
their superior physicochemical stability at elevated temperatures. The present
study reported for the first time that the ordered C vacancies within titanium
carbides could lead to an uncommon phenomenon particularly at the very initial
stage of oxidation. The intrinsic micro-to-macro oxidation mechanisms were
systematically clarified with the aids of transmission electron microscope and
ab-initio molecular dynamics simulation.",1710.09311v1
2017-12-28,Theoretical calculation of transport properties of oxide material using narrow band model,"We report about the results of theoretical calculations of temperature
dependence of resistivity ($\rho$) and Seebeck coefficient ($S$) for
thermoelectric (TE) and superconductivity (SC) phases by arithmetic equations
based on narrow band model with oxygen deficient structure, as the functions of
band-filling degree ($F$), and band width ratio of electron and spin states
($W$\sigma/$W$D). The phase diagrams of TE and SC states, and boundary were
imaged to the properties of $\rho$ and $S$ as a function of $F$ and
$W$\sigma/$W$D.",1712.09840v1
2018-01-12,Tunable elastic Parity-Time symmetric structure based on the shunted piezoelectric materials,"We theoretically and numerically report on tunable elastic Parity-Time (PT)
symmetric structure based on shunted piezoelectric units. We show that the
elastic loss and gain can be archived in piezoelectric materials when they are
shunted by external circuits containing positive and negative resistances. We
present and discuss, as an example, the strongly dependent relationship between
the exceptional points of a three-layered system and the impedance of their
external shunted circuit. The achieved results evidence the PT symmetric
structures based on this proposed concept can actively be tuned without any
change of their geometric configurations.",1801.04114v1
2018-02-12,Crack initiation in viscoelastic materials,"In viscoelastic materials, individually short-lived bonds collectively result
in a mechanical resistance which is long-lived but finite, as ultimately cracks
appear. Here we provide a microscopic mechanism by which cracks emerge from the
nonlinear local bond dynamics. This mechanism is different from crack
initiation in solids, which is governed by a competition between elastic and
adhesion energy. We provide and numerically verify analytical equations for the
dependence of the critical crack length on the bond kinetics and applied
stress.",1802.04017v1
2017-01-27,Delicate competing electronic states in ultrathin manganite films,"The coupling between the electrical transport properties of La2/3Sr1/3MnO3
(LSMO) thin films and structural phase transitions of SrTiO3 (STO) substrates
at Ts = 105 K has been investigated. We found that the electrical resistivity
of LSMO films exhibit a cusp at Ts, which is greatly amplified by tuning films
to the verge of metallic and insulating phases, i.e., to the boundary of two
delicate competing electronic states. Our results demonstrate that small
amounts of strain can tip the subtle balance of competing interactions and tune
the electronic properties in correlated electron materials.",1701.07933v1
2019-07-03,Precision measurements of the AC field dependence of the superconducting transition in strontium titanate,"Strontium titanate has resurfaced as a material prompting vigorous debate
about the origin of its superconductivity in the extremely low carrier
concentration regime. Here, we used simultaneous AC susceptibility and
transport methods to explore the superconducting phase transition region in
this material. We determined that strontium titanate is extremely sensitive to
even small AC fields, which also influence the resistive transition; we suggest
that extreme vortex sizes and mobilities contribute to this large effect. Our
findings will be of importance for accurately determining transition
temperature, informing the debate about the pairing mechanism in strontium
titanate, for which even millikelvin errors may be critical.",1907.01733v1
2020-04-14,Compaction Self-Assembly of Ultralow-Binder-Content Thermoplastic Composites Based on Lunar Soil Simulant,"In a recent study, we developed ultralow-binder-content (UBC) structural
materials based on lunar soil simulant and thermoset binders. In the current
research, we investigated thermoplastic binders. Compared to thermosets,
advanced thermoplastics could be more UV resistant, more durable, more robust,
and recyclable. Our main technology is the compaction self-assembly (CSA). By
using only ~4 wt% polyetherketoneketone (PEKK) binder, the thermoplastic-binder
UBC composite was stronger than typical steel-reinforced concrete. The CSA
operation was separate from the curing process. This study may provide an
important in-situ resource utilization method for large-scale construction on
Moon.",2004.06273v1
2017-05-01,On melting of boron subnitride B13N2 under pressure,"Melting of rhombohedral boron subnitride B13N2 has been studied in situ at
pressures to 8 GPa using synchrotron X-ray diffraction and electrical
resistivity measurements. It has been found that above 2.6 GPa B13N2 melts
incongruently, and the melting curve exhibits positive slope of 31(3) K/GPa
that points to a lower density of the melt as compared to the solid phase.",1705.03753v1
2019-03-25,Optical Hoovering on Plasmonic Rinks,"Excitation of surface waves on conducting materials provides a near
resistance-free interface capable of a material glissade either by plasmon
forces or optical beam tractors. Analogous to an ice hockey rink, as proof of
principle plasmon assisted optical traction, or hoovering, of water drops on a
gold surface is demonstrated. Variability in thresholds and movement is
observed and can be explained by the presence of significant roughness,
measured by SEM. The demonstration opens a path to directly integrate various
optical and plasmonic glissade technologies. Ways of improving transport and
potential applications spanning configurable microfluidics, antennas,
diagnostics,sensing and active devices are discussed.",1903.10106v1
2021-04-23,Microwave response in a topological superconducting quantum interference device,"Photon detection at microwave frequency is of great interest due to its
application in quantum computation information science and technology. Herein
are results from studying microwave response in a topological superconducting
quantum interference device (SQUID) realized in Dirac semimetal Cd3As2. The
temperature dependence and microwave power dependence of the SQUID junction
resistance are studied, from which we obtain an effective temperature at each
microwave power level. It is observed the effective temperature increases with
the microwave power. This observation of microwave response may pave the way
for single photon detection at the microwave frequency in topological quantum
materials.",2104.11841v1
2021-04-29,Thickness Dependence of Magneto-transport Properties in Tungsten Ditelluride,"We investigate the electronic structure of tungsten ditelluride (WTe$_2$)
flakes with different thicknesses in magneto-transport studies. The
temperature-dependent resistance and magnetoresistance (MR) measurements both
confirm the breaking of carrier balance induced by thickness reduction, which
suppresses the `turn-on' behavior and large positive MR. The Shubnikov-de-Haas
oscillation studies further confirm the thickness-dependent change of
electronic structure of WTe$_2$ and reveal a possible temperature-sensitive
electronic structure change. Finally, we report the thickness-dependent
anisotropy of Fermi surface, which reveals that multi-layer WTe$_2$ is an
electronic 3D material and the anisotropy decreases as thickness decreases.",2104.14464v1
2022-03-04,Impedance spectroscopy: Impedance spectroscopy of nanomaterials,"Solid state impedance spectroscopy enables the various contributions to the
resistive and capacitive properties of electronically inhomogeneous condensed
matter to be deconvoluted and characterized separately. The different
contributions arise from electronically distinct areas in the sample, which can
in an ideal case be represented each by one standard RC element. In the
following, the basic principles of impedance spectroscopy, different types of
experimental setups and several examples of experimental impedance data sets
from nanostructured materials are reviewed and discussed. The data analysis and
equivalent circuit modelling processes which are relevant for the application
of this technique to nanomaterials are emphasized. The different dimensions and
structure of nanomaterials as compared to macroscopic bulk samples leads to
quite different and sometimes more complex data that require detailed analysis
and advanced equivalent circuit models.",2203.02387v1
1998-12-08,Anomalous Low Temperature States in CeNi2Ge2,"Ambient pressure studies on high purity single crystals of the stoichiometric
4f-electron metal CeNi2Ge2 reveal anomalous low temperature forms of the
resistivity which challenge our understanding of the metallic state.
Comparisons are made with the isostructural and isoelectronic compound CePd2Si2
near the border of magnetism at high pressure, and possible reasons for this
novel non-Fermi liquid form of the resistivity are discussed. Phase diagrams of
further anomalies are presented, which involve a loss of resistance at low
temperature in some samples of CeNi2Ge2 and unexpected high pressure phases.",9812133v1
2003-03-20,Electrical resistivity and magnetization measurements on the heavy fermion superconductor PrOs4Sb12,"The filled skutterudite compound PrOs4Sb12, the first example of a Pr-based
heavy fermion superconductor, displays superconductivity with $T_c\sim 1.85$ K
and has an effective mass $m^* \sim$ {50 $m_e$}, where $m_e$ is the free
electron mass. For magnetic fields above 4.5 T, sharp features in the normal
state electrical resistivity, magnetization, specific heat, and thermal
expansion data suggest the occurrence of a phase transition at high fields.
This high field ordered phase in the normal state may originate from a
combination of crystalline electric field enhanced Zeeman splitting and
quadrupolar ordering. We present an investigation of the electrical resistivity
and magnetization of PrOs4Sb12 as a function of temperature between {350 mK}
and {3.5 K} and magnetic field up to {18 T}. The data reveal a detailed phase
boundary of the high field ordered phase as well as the lower critical field
$H_{c1}$ and the onset field of the peak effect in the superconducting state of
PrOs4Sb12.",0303405v1
2004-04-12,Universality of the Mott-Ioffe-Regel limit in metals,"The absence of resistivity saturation in many strongly correlated metals,
including the high-temperature superconductors, is critically examined from the
viewpoint of optical conductivity measurements. Coherent quasiparticle
conductivity, in the form of a Drude peak centred at zero frequency, is found
to disappear as the mean free path (at $\omega$ = 0) becomes comparable to the
interatomic spacing. This basic loss of coherence at the so-called
Mott-Ioffe-Regel (MIR) limit suggests that the universality of the MIR
criterion is preserved even in the presence of strong electron correlations. We
argue that the shedding of spectral weight at low frequencies, induced by
strong correlation effects, is the primary origin of the extended positive
slope of the resistivity to high temperatures observed in all so-called ""bad
metals"". Moreover, in common with those metals which exhibit resistivity
saturation at high temperatures, the scattering rate itself, as extracted from
optical spectra, saturates at a value consistent with the MIR limit. We
consider possible implications that this ceiling in the scattering rate may
have for our understanding of transport within a wide variety of bad metals and
suggest a better method for analysing their optical response.",0404263v1
2005-02-21,High pressure effects on the superconductivity of beta-pyrochlore oxides AOs2O6,"High pressure effects on the superconducting transitions of beta-pyrochlore
superconductors AOs2O6 (A = Cs, Rb, K) are studied by measuring resistivity
under high pressures up to 10 GPa. The superconducting transition temperature
Tc first increases with increasing pressure in all the compounds and then
exhibits a broad maximum at 7.6 K (6 GPa), 8.2 K (2 GPa) and 10 K (0.6 GPa) for
A = Cs, Rb and K, respectviely. Finally, the superconductivity is suppressed
completely at a critical pressure near 7 GPa and 6 GPa for A = Rb and K and
probably above 10 GPa for A = Cs. Characteristic changes in the coefficinet A
of the T2 term in resistivity and residual resistivity are observed, both of
which are synchronized with the corresponding change in Tc. It is suggested
that electron correlations and certain quantum fluctuations play important
roles in the occurrence or suppression of superconductivity in the
beta-pyrochlore oxides.",0502490v1
2003-07-30,Position Sensing from Charge Dispersion in Micro-Pattern Gas Detectors with a Resistive Anode,"Micro-pattern gas detectors, such as the Gas Electron Multiplier (GEM) and
the Micromegas need narrow high density anode readout elements to achieve good
spatial resolution. A high-density anode readout would require an unmanageable
number of electronics channels for certain potential micro-detector
applications such as the Time Projection Chamber. We describe below a new
technique to achieve good spatial resolution without increasing the electronics
channel count in a modified micro-detector outfitted with a high surface
resistivity anode readout structure. The concept and preliminary measurements
of spatial resolution from charge dispersion in a modified GEM detector with a
resistive anode are described below.",0307152v2
2008-09-30,High Pressure studies of the magnetic phase transition in MnSi: revisited,"New measurements of AC magnetic susceptibility and DC resistivity of a high
quality single crystal MnSi were carried out at high pressure making use of
helium as a pressure medium. The form of the AC magnetic susceptibility curves
at the magnetic phase transition suddenly changes upon helium solidification.
This implies strong sensitivity of magnetic properties of MnSi to non
hydrostatic stresses and suggests that the early claims on the existence of a
tricritical point at the phase transition line are probably a result of
misinterpretation of the experimental data. At the same time resistivity
behavior at the phase transition does not show such a significant influence of
helium solidification. The sharp peak at the temperature derivative of
resistivity, signifying the first order nature of the phase transition in MnSi
successfully survived helium crystallization and continued the same way to the
highest pressure.",0809.5117v1
2014-05-21,Waveguide-mode interference lithography technique for high contrast subwavelength structures in the visible region,"We explore possibilities of waveguide-mode interference lithography (WMIL)
technique for high contrast subwavelength structures in the visible region.
Selecting an appropriate waveguide-mode, we demonstrate high contrast resist
mask patterns for the first time. TM1 mode in the waveguide is shown to be
useful for providing a three-dimensional structure whose cross section is
checkerboard pattern. Applying our WMIL technique, we demonstrate 1D, 2D and 3D
subwavelength resist patterns that are widely used for the fabrication of
metamteterials in the visible region. In addition to the resist patterns, we
demonstrate a resonance at 1.9 eV for a split tube structure experimentally.",1405.5395v1
2015-10-28,Effect of ambient on the resistance fluctuations of graphene,"In this letter we present the results of systematic experimental
investigations of the effect of different chemical environments on the low
frequency resistance fluctuations of single layer graphene field effect
transistors (SLG-FET). The shape of the power spectral density of noise was
found to be determined by the energetics of the adsorption-desorption of
molecules from the graphene surface making it the dominant source of noise in
these devices. We also demonstrate a method of quantitatively determining the
adsorption energies of chemicals on graphene surface based on noise
measurements. We find that the magnitude of noise is extremely sensitive to the
nature and amount of the chemical species present. We propose that a chemical
sensor based on the measurement of low frequency resistance fluctuations of
single layer graphene field effect transistor devices will have extremely high
sensitivity, very high specificity, high fidelity and fast response times.",1510.08198v1
2016-07-09,In-beam evaluation of a medium-size Resistive-Plate WELL gaseous particle detector,"In-beam evaluation of a fully-equipped medium-size 30$\times$30 cm$^2$
Resistive Plate WELL (RPWELL) detector is presented. It consists here of a
single element gas-avalanche multiplier with Semitron ESD225 resistive plate, 1
cm$^2$ readout pads and APV25/SRS electronics. Similarly to previous results
with small detector prototypes, stable operation at high detection efficiency
(>98%) and low average pad multiplicity (~1.2) were recorded with 150 GeV muon
and high-rate pion beams, in Ne/(5%CH$_4$), Ar/(5%CH$_4$) and Ar/(7%CO$_2$).
This is an important step towards the realization of robust detectors suitable
for applications requiring large-area coverage; among them Digital Hadron
Calorimetry.",1607.02587v2
2017-12-26,Microwave-induced zero-resistance states in a high-mobility two-subband electron system,"In this study we used selectively-doped GaAs/AlAs heterostructure to
fabricate a high-mobility two-subband electronic system with substantially
different concentration of electrons in subbands. We observe microwave
photoresistance at high numbers of magneto-intersubband oscillations (MISO).
The system under study demonstrates microwave-induced resistance oscillations
(MIRO) and MISO interference. MIRO in the studied two-subband system appear in
lower magnetic fields comparing to MISO. This is an indication of some unknown
mechanism that exists in the two-subband system and is responsible for MISO
amplitude damping in low magnetic fields, while it does not affect the MIRO
amplitude. Zero resistance states (ZRS) appear in the system under study under
microwave irradiation in the narrow range of magnetic fields near the MISO
maximum.",1712.09244v1
2020-04-11,Characterisation of an RPC prototype with moderate resistivity plates using tetrafluoroethane ($C_2H_2F_4$),"Keeping in mind the requirements of high rate capable, cost effective, large
area detectors to be used in future high energy physics experiments,
commercially available bakelite plates having moderate bulk resistivity are
used to build an RPC module. The chamber is tested with cosmic rays in the
avalanche mode using 100\% Tetrafluoroethane ($C_2H_2F_4$). Standard NIM
electronics are used for this study. The efficiency, noise rate and time
resolution are measured. The detailed method of measurement and the first test
results are presented.",2004.05469v2
2019-08-29,Onset of phase diffusion in high kinetic inductance granular aluminum micro-SQUIDs,"Superconducting granular aluminum is attracting increasing interest due to
its high kinetic inductance and low dissipation, favoring its use in kinetic
inductance particle detectors, superconducting resonators or quantum bits. We
perform switching current measurements on DC-SQUIDs, obtained by introducing
two identical geometric constrictions in granular aluminum rings of various
normal-state resistivities in the range from $\rho_\mathrm{n} =
250\,\mu\Omega\mathrm{cm}$ to $5550\,\mu\Omega\mathrm{cm}$. The relative high
kinetic inductance of the SQUID loop, in the range of tens of nH, leads to a
suppression of the modulation in the measured switching current versus magnetic
flux, accompanied by a distortion towards a triangular shape. We observe a
change in the temperature dependence of the switching current histograms with
increasing normal-state film resistivity. This behavior suggests the onset of a
diffusive motion of the superconducting phase across the constrictions in the
two-dimensional washboard potential of the SQUIDs, which could be caused by a
change of the local electromagnetic environment of films with increasing
normal-state resistivities.",1908.11067v1
2019-12-18,"Multiplex stimulated Raman scattering imaging cytometry reveals cancer metabolic signatures in a spatially, temporally, and spectrally resolved manner","In situ measurement of cellular metabolites is still a challenge in biology.
Conventional methods, such as mass spectrometry or fluorescence microscopy,
would either destruct the sample or introduce strong perturbations to the
functions of target molecules. Here, we present multiplex stimulated Raman
scattering (SRS) imaging cytometry as a label-free single-cell analysis
platform with chemical specifity, and high-throughput capabilities. Cellular
compartments such as lipid droplets, endoplasmic reticulum, and nuclei are
seperated from the cytoplasm. Based on these chemical segmentations, 260
features from both morphology and molecular composition were generated and
analyzed for each cell. Using SRS imaging cytometry, we studied the metabolic
responses of human pancreatic cancer cells under stress by starvation and
chemotherapy drug treatments. We unveiled lipid-facilitated protrusion as a
metabolic marker for stress-resistant cancer cells through statistical analysis
of thousands of cells. Our findings also demonstrate the potential of targeting
lipid metabolism for selective treatment of starvation-resistant and
chemotherapy-resistant cancers. These results highlight our SRS imaging
cytometry as a powerful label-free tool for biological discoveries with a
high-throughput, high-content capacity.",1912.08340v1
2020-05-31,Towards a two-dimensional readout of the improved CMS Resistive Plate Chamber with a new front-end electronics,"As part of the Compact Muon Solenoid experiment Phase-II upgrade program, new
Resistive Plate Chambers will be installed in the forward region. High
background conditions are expected in this region during the high-luminosity
phase of the Large Hadron Collider, therefore an improved RPC design has been
proposed with a new front-end electronics to sustain a higher rate capability
and better time resolution. A new technology is used in the front-end
electronics resulting in very low achievable thresholds of the order of several
fC. Crucial in the design of the improved RPC is the capability of a
two-dimensional readout in order to improve the spatial resolution, mainly
motivated by trigger requirements. In this work, the first performance results
towards this two-dimensional readout are presented, based on data taken on a
real-size prototype chamber with two embedded orthogonal readout strips.
Furthermore, dedicated studies of the muon cluster size as a function of the
graphite resistivity are discussed.",2006.00576v1
2020-06-24,Microwave response of interacting oxide two-dimensional electron systems,"We present an experimental study on microwave illuminated high mobility
MgZnO/ZnO based two-dimensional electron systems with different electron
densities and, hence, varying Coulomb interaction strength. The photoresponse
of the low-temperature dc resistance in perpendicular magnetic field is
examined in low and high density samples over a broad range of illumination
frequencies. In low density samples a response due to cyclotron resonance (CR)
absorption dominates, while high density samples exhibit pronounced
microwave-induced resistance oscillations (MIRO). Microwave transmission
experiments serve as a complementary means of detecting the CR over the entire
range of electron densities and as a reference for the band mass unrenormalized
by interactions. Both CR and MIRO-associated features in the resistance permit
extraction of the effective mass of electrons but yield two distinct values.
The conventional cyclotron mass representing center-of-mass dynamics exhibits
no change with density and coincides with the band electron mass of bulk ZnO,
while MIRO mass reveals a systematic increase with lowering electron density
consistent with renormalization expected in interacting Fermi liquids.",2006.13627v1
2020-10-15,Extreme High-Field Superconductivity in Thin Re Films,"We report the high-field superconducting properties of thin, disordered Re
films via magneto-transport and tunneling density of states measurements. Films
with thicknesses in the range of 9 nm to 3 nm had normal state sheet
resistances of $\sim$0.2 k$\Omega$ to $\sim$1 k$\Omega$ and corresponding
transition temperatures in the range of 6 K to 3 K. Tunneling spectra were
consistent with those of a moderate coupling BCS superconductor.
Notwithstanding these unremarkable superconducting properties, the films
exhibited an extraordinarily high upper critical field. We estimate their
zero-temperature $H_{c2}$ to be more than twice the Pauli limit. Indeed, in 6
nm samples the estimated reduced critical field $H_{c2}/T_c\sim$ 5.6 T/K is
among the highest reported for any elemental superconductor. Although the sheet
resistances of the films were well below the quantum resistance $R_Q=h/4e^2$,
their $H_{c2}$'s approached the theoretical upper limit of a strongly
disordered superconductor for which $k_F\ell\sim1$.",2010.07674v2
2021-09-29,High-performance Ba1-xKxFe2As2 superconducting joints for persistent current operation,"Superconducting joints are one of the key technologies to make Ba1-xKxFe2As2
(Ba-122) superconducting wires or tapes for high-field applications. Herein,
superconducting joints were fabricated by a simple cold-pressing method, and
the joint resistance of the iron-based superconducting joint was estimated for
the first time. The superconducting properties, microstructures, and elements
distribution in the joint regions were investigated. At 4.2 K and 10 T, a
transport critical current Ic of 105 A for the joint was obtained, and the
critical current ratio (CCR= Ic-joint/Ic-tape) of the joint was 94.6%. On the
other hand, the joint show very low joint resistance of 2.7x10^-13 ohm in
self-field at 4.2 K. Among iron-based superconductors (IBS), this work is the
first to successfully realize a superconducting joint with such high CCR and
low joint resistance. This work shows great potential to apply Ba-122 in a
range of practical applications, where superconducting joints are essential.",2109.14300v1
2022-09-01,Directed flow in relativistic resistive magneto-hydrodynamic expansion for symmetric and asymmetric collision systems,"We construct a dynamical model for high-energy heavy-ion collision based on
the relativistic resistive magneto-hydrodynamic framework. Using our newly
developed (3+1)-dimensional relativistic resistive magneto-hydrodynamics code,
we investigate magneto-hydrodynamic expansion in symmetric and asymmetric
collision systems as a first application to high-energy heavy-ion collisions.
As a realistic initial condition for electromagnetic fields, we consider the
solutions of the Maxwell equations with the source term of point charged
particles moving in the direction of the beam axis, including finite constant
electrical conductivity of the medium. We evaluate the directed flow in the
symmetric and asymmetric collisions at RHIC energy. We find a significant
effect of finite electrical conductivity on the directed flow in the asymmetric
collision system. We confirm that a certain amount of energy transfer by
dissipation associated with Ohmic conduction occurs in the asymmetric collision
system because of asymmetry of the electric field produced by two different
colliding nuclei. Because this energy transfer makes the pressure gradient of
the medium flatter, the growth of directed flow decreases.",2209.00323v1
2023-02-21,A novel fast response and radiation-resistant scintillator detector for beam loss monitor,"At high luminosity areas, beam loss monitor with fast response and high
radiation resistance is crucial for accelerator operation. In this article, we
report the design and test results of a fast response and radiation-resistant
scintillator detector as the beam loss monitor for high luminosity colliders,
especially at low energy regions such as RFQ. The detector consists of a 2 cm*2
cm 0.5 cm LYSO crystal readout by a 6 mm*6 mm Silicon photomultiplier. Test
results from various radioactive sources show that the detector has good
sensitivity to photons from tens of keV to several MeV with good linearity and
energy resolution (23% for 60 keV {\gamma}-ray). For the field test, two such
detectors are installed outside of the vacuum chamber shell of an 800 MeV
electron storage ring. The details of the test and results are introduced.",2302.14662v1
2023-11-28,Transport properties of a half-filled Chern band at the electron and composite fermion phases,"We consider a half-filled Chern band and its transport properties in two
phases that it may form, the electronic Fermi liquid and the composite-fermion
Fermi liquid. For weak disorder, we show that the Hall resistivity for the
former phase is very small, while for the latter it is close to $2h/e^2$,
independent of the distribution of the Berry curvature in the band. At rising
temperature and high frequency, we expect the Hall resistivity of the
electronic phase to rise, and that of the composite-fermion phase to deviate
from $2h/e^2$. At high frequency, sign changes are expected as well.
Considering high-frequency transport, we show that the composite fermion phase
carries a gapped plasmon mode which does not originate from long ranged Coulomb
interaction, and we show how this mode, together with the reflection of
electro-magnetic waves off the Chern band, allow for a measurement of the
composite-fermion Drude weight and Berry curvature. Finally, we consider a
scenario of a mixed-phase transition between the two phases, for example as a
function of displacement-field, and show that such transition involves an
enhancement of the longitudinal resistivity, as observed experimentally.",2311.16761v1
2024-05-17,Possible spin-polarized Cooper pairing in high temperature FeSe superconductor,"Superconductivity and long-range ferromagnetism hardly coexist in a uniform
manner. The counter-example has been observed, in uranium-based superconductors
for instance, with a coexisting temperature limited to about 1 K. Here, we
report the coexistence of high temperature superconductivity and itinerant
ferromagnetism in lithium intercalated FeSe flakes. In superconducting samples
with transition temperature around 40 K, we observe the anomalous Hall effect
with a hysteresis loop in transverse resistivity and a butterfly-like pattern
of magneto-resistance. Intriguingly, such ferromagnetism persists down to a
temperature at which the zero-field resistance fully vanishes. Furthermore, the
superconductivity is enhanced under an in-plane magnetic field, suggestive of
the participation of spin-polarized Cooper pairs. The surprising finding
underscores a uniform coexistence of the two antagonistic phenomena on a
record-high energy scale.",2405.10482v1
2006-05-24,Tuning of magnetic and electronic states by control of oxygen content in lanthanum strontium cobaltites,"We report on the magnetic, resistive, and structural studies of perovskite
La$_{1/3}$Sr$_{2/3}$CoO$_{3-\delta}$. By using the relation of synthesis
temperature and oxygen partial pressure to oxygen stoichiometry obtained from
thermogravimetric analysis, we have synthesized a series of samples with
precisely controlled $\delta=0.00-0.49$. These samples show three structural
phases at $\delta=0.00-0.15$, $\approx0.25$, $\approx0.5$, and two-phase
behavior for other oxygen contents. The stoichiometric material with
$\delta=0.00$ is a cubic ferromagnetic metal with the Curie temperature $T_{\rm
C}=274$ K. The increase of $\delta$ to 0.15 is followed by a linear decrease of
$T_{\rm C}$ to $\approx$ 160 K and a metal-insulator transition near the
boundary of the cubic structure range. Further increase of $\delta$ results in
formation of a tetragonal $2a_p\times 2a_p \times 4a_p$ phase for
$\delta\approx 0.25$ and a brownmillerite phase for $\delta\approx0.5$. At low
temperatures, these are weak ferromagnetic insulators (canted antiferromagnets)
with magnetic transitions at $T_{\rm m}\approx230$ and 120 K, respectively. At
higher temperatures, the $2a_p\times 2a_p \times 4a_p$ phase is $G$-type
antiferromagnetic between 230 K and $\approx$360 K. Low temperature magnetic
properties of this system for $\delta<1/3$ can be described in terms of a
mixture of Co$^{3+}$ ions in the low-spin state and Co$^{4+}$ ions in the
intermediate-spin state and a possible spin transition of Co$^{3+}$ to the
intermediate-spin state above $T_{\rm C}$. For $\delta>1/3$, there appears to
be a combination of Co$^{2+}$ and Co$^{3+}$ ions, both in the high-spin state
with dominating antiferromagnetic interactions.",0605611v1
2008-06-23,"Phase transitions in LaFeAsO: structural, magnetic, elastic, and transport properties, heat capacity and Mossbauer spectra","We present results from a detailed experimental investigation of LaFeAsO, the
parent material in the series of ""FeAs"" based oxypnictide superconductors. Upon
cooling this material undergoes a tetragonal-orthorhombic crystallographic
phase transition at ~160 K followed closely by an antiferromagnetic ordering
near 145 K. Analysis of these phase transitions using temperature dependent
powder X-ray and neutron diffraction measurements is presented. A magnetic
moment of ~0.35 Bohr magnetons per iron is derived from Mossbauer spectra in
the low temperature phase. Evidence of the structural transition is observed at
temperatures well above the structural transition (up to near 200 K) in the
diffraction data as well as the polycrystalline elastic moduli probed by
resonant ultrasound spectroscopy measurements. The effects of the two phase
transitions on the transport properties (resistivity, thermal conductivity,
Seebeck coefficient, Hall coefficient), heat capacity, and magnetization of
LaFeAsO are also reported, including a dramatic increase in the magnitude of
the Hall coefficient below 160 K. The results suggest that the structural
distortion leads to a localization of carriers on Fe, producing small local
magnetic moments which subsequently order antiferromagnetically upon further
cooling. Evidence of strong electron-phonon interactions in the
high-temperature tetragonal phase is also observed.",0806.3878v2
2011-03-07,Reversibly tuning the insulating and superconducting state in KxFe2-ySe2 crystals by post-annealing,"Since the discovery of superconductivity at 26 K in oxy-pnictide
LaFeAsO1-xFx, enormous interests have been stimulated in the field of condensed
matter physics and material sciences. Among the many kind of structures in the
iron pnictide superconductors, FeSe with the PbO structure has received special
attention since there is not poisonous pnictogen element in chemical
composition and its structure is the simplest one. However, the superconducting
transition temperature (Tc) in iron chalcogenide compounds is not enhanced as
high as other iron pnictide superconductors under ambient pressure until the
superconductivity at above 30 K in potassium intercalated iron selenide
KxFe2-ySe2 was discovered. The insulating and the superconducting state are
both observed in KxFe2-ySe2 with different stoichiometries and some groups have
tuned the system from insulating to superconducting state by varying the ratio
of starting materials[10, 11]. The recent data from neutron scattering suggest
that the superconductivity may be built upon an ordered state of Fe vacancies
as well as the antiferromagnetic state with a very strong ordered magnetic
moment 3.4 B. Here we show that the superconductivity can actually be tuned on
a single sample directly from an insulating state by post-annealing and fast
quenching. Upon waiting for some days at room temperatures, the
superconductivity will disappear and the resistivity exhibits an insulating
behavior again. The spatial distribution of the compositions of the as-grown
sample and the post-annealed-quenched one was analyzed by the Energy Dispersive
X-ray Spectrum (EDXS) and found to be very close to each other. Therefore it is
tempting to conclude that the superconductivity is achieved when the
Fe-vacancies are in a random (disordered) state. Once they arrange in an
ordered state by relaxation or slow cooling, the system turns out to be an
insulator.",1103.1347v1
2014-09-16,Hydrogen Diffusion and Stabilization in Single-crystal VO2 Micro/nanobeams by Direct Atomic Hydrogenation,"We report measurements of the diffusion of atomic hydrogen in single
crystalline VO2 micro/nanobeams by direct exposure to atomic hydrogen, without
catalyst. The atomic hydrogen is generated by a hot filament, and the doping
process takes place at moderate temperature (373 K). Undoped VO2 has a
metal-to-insulator phase transition at ~340 K between a high-temperature,
rutile, metallic phase and a low-temperature, monoclinic, insulating phase with
a resistance exhibiting a semiconductor-like temperature dependence. Atomic
hydrogenation results in stabilization of the metallic phase of VO2
micro/nanobeams down to 2 K, the lowest point we could reach in our measurement
setup. Based on observing the movement of the hydrogen diffusion front in
single crystalline VO2 beams, we estimate the diffusion constant for hydrogen
along the c-axis of the rutile phase to be 6.7 x 10^{-10} cm^2/s at
approximately 373 K, exceeding the value in isostructural TiO2 by ~ 38x.
Moreover, we find that the diffusion constant along the c-axis of the rutile
phase exceeds that along the equivalent a-axis of the monoclinic phase by at
least three orders of magnitude. This remarkable change in kinetics must
originate from the distortion of the ""channels"" when the unit cell doubles
along this direction upon cooling into the monoclinic structure. Ab initio
calculation results are in good agreement with the experimental trends in the
relative kinetics of the two phases. This raises the possibility of a
switchable membrane for hydrogen transport.",1409.4661v1
2012-01-04,Synthesis and physical properties of the new potassium iron selenide superconductor K0.80Fe1.76Se2,"In this article we review our studies of the K0.80Fe1.76Se2 superconductor,
with an attempt to elucidate the crystal growth details and basic physical
properties over a wide range of temperatures and applied magnetic field,
including anisotropic magnetic and electrical transport properties,
thermodynamic, London penetration depth, magneto-optical imaging and Mossbauer
measurements. We find that: (i) Single crystals of similar stoichiometry can be
grown both by furnace-cooled and decanted methods; (ii) Single crystalline
K0.80Fe1.76Se2 shows moderate anisotropy in both magnetic susceptibility and
electrical resistivity and a small modulation of stoichiometry of the crystal,
which gives rise to broadened transitions; (iii) The upper critical field,
Hc2(T) is ~ 55 T at 2 K for H||c, manifesting a temperature dependent
anisotropy that peaks near 3.6 at 27 K and drops to 2.5 by 18 K; (iv) Mossbauer
measurements reveal that the iron sublattice in K0.80Fe1.76Se2 clearly exhibits
magnetic order, probably of the first order, from well below Tc to its Neel
temperature of Tn = 532 +/- 2 K. It is very important to note that, although,
at first glance there is an apparent dilemma posed by these data: high Tc
superconductivity in a near insulating, large ordered moment material, analysis
indicates that the sample may well consist of two phases with the minority
superconducting phase (that does not exhibit magnetic order) being finely
distributed, but connected with in an antiferromagnetic, poorly conducting,
matrix, essentially making a superconducting aerogel.",1201.0953v2
2019-04-24,Role of Oxygen Adsorption in Nanocrystalline ZnO Interfacial Layers for Polymer-Fullerene Bulk Heterojunction Solar Cells,"Colloidal zinc oxide (ZnO) nanoparticles are frequently used in the field of
organic photovoltaics for the realization of solution-producible,
electron-selective interfacial layers. Despite of the widespread use, there is
a lack of detailed investigations regarding the impact of structural properties
of the particles on the device performance. In this work, ZnO nanoparticles
with varying surface-area-to-volume ratio were synthesized and implemented into
polymer-fullerene bulk heterojunction solar cells with a gas-permeable top
electrode. By comparing the electrical characteristics before and after
encapsulation, it was found that the internal surface area of the ZnO layer
plays a crucial role under conditions where oxygen can penetrate the solar
cells. The adsorption of oxygen species at the nanoparticle surface causes band
bending and electron depletion next to the surface. Both effects result in the
formation of a barrier for electron injection and extraction at the ZnO/bulk
heterojunction interface and were more pronounced in case of small ZnO
nanocrystals (high surface-area-to-volume ratio). Different transport-related
phenomena in the presence of oxygen are discussed in detail, i.e., Ohmic
losses, expressed in terms of series resistance, as well as the occurrence of
space-charge-limited currents, related to charge accumulation in the
polymer-fullerene blend. Since absorption of UV light can cause desorption of
adsorbed oxygen species, the electrical properties depend also on the
illumination conditions. With the help of systematic investigations of the
current versus voltage characteristics of solar cells under different air
exposure and illumination conditions as well as studies of the
photoconductivity of pure ZnO nanoparticle layers, we gain detailed insight
into the role of the ZnO nanoparticle surface for the functionality of the
organic solar cells.",1904.10916v1
2020-10-12,Landau Quantization and Highly Mobile Fermions in an Insulator,"In strongly correlated materials, quasiparticle excitations can carry
fractional quantum numbers. An intriguing possibility is the formation of
fractionalized, charge-neutral fermions, e.g., spinons and fermionic excitons,
that result in neutral Fermi surfaces and Landau quantization in an insulator.
While previous experiments in quantum spin liquids, topological Kondo
insulators, and quantum Hall systems have hinted at charge-neutral Fermi
surfaces, evidence for their existence remains far from conclusive. Here we
report experimental observation of Landau quantization in a two dimensional
(2D) insulator, i.e., monolayer tungsten ditelluride (WTe$_{2}$), a large gap
topological insulator. Using a detection scheme that avoids edge contributions,
we uncover strikingly large quantum oscillations in the monolayer insulator's
magnetoresistance, with an onset field as small as ~ 0.5 tesla. Despite the
huge resistance, the oscillation profile, which exhibits many periods, mimics
the Shubnikov-de Haas oscillations in metals. Remarkably, at ultralow
temperatures the observed oscillations evolve into discrete peaks near 1.6
tesla, above which the Landau quantized regime is fully developed. Such a low
onset field of quantization is comparable to high-mobility conventional
two-dimensional electron gases. Our experiments call for further investigation
of the highly unusual ground state of the WTe$_{2}$ monolayer. This includes
the influence of device components and the possible existence of mobile
fermions and charge-neutral Fermi surfaces inside its insulating gap.",2010.05383v2
2021-07-29,Shearing Mechanisms of Co-Precipitates in IN718,"The Ni-base superalloy 718 is the most widely used material for
turbomachinery in the aerospace industry and land-based turbines. Although the
relationship between processing and the resulting properties is well known, an
understanding of the specific deformation mechanisms activated across its
application temperature range is required to create more mechanistically
accurate property models. Direct atomic-scale imaging observations with high
angle annular dark-field scanning transmission electron microscopy,
complemented by phase-field modeling informed by generalized stacking fault
surface calculations using density functional theory, were employed to
understand the shear process of ${\gamma}''$ and ${\gamma}'/{\gamma}''$
co-precipitates after 1 \% macroscopic strain at lower temperature (ambient and
$427 {\deg}C$). Experimentally, intrinsic stacking faults were observed in the
${\gamma}''$, whereas the ${\gamma}'$ was found to exhibit anti-phase
boundaries or superlattice intrinsic stacking faults. Additionally, the
atomically flat ${\gamma}'/{\gamma}''$ interfaces in the co-precipitates were
found to exhibit offsets after shearing, which can be used as tracers for the
deformation events. Phase-field modeling shows that the developing
fault-structure is dependent on the direction of the Burgers vector of the $a/2
\langle110\rangle$ matrix dislocation (or dislocation group) due to the lower
crystal symmetry of the ${\gamma''}$ phase. The interplay between ${\gamma}'$
and ${\gamma}''$ phases results in unique deformation pathways of the
co-precipitate and increases the shear resistance. Consistent with the
experimental observations, the simulation results indicate that complex
shearing mechanisms are active in the low-temperature deformation regime and
that multiple $a/2 \langle110\rangle$ dislocations of non-parallel Burgers
vectors may be active on the same slip plane.",2107.13840v1
2021-08-24,In Situ Photothermal Response of Single Gold Nanoparticles Through Hyperspectral Imaging AntiStokes Thermometry,"Several fields of applications require a reliable characterization of the
photothermal response and heat dissipation of nanoscopic systems, which remains
a challenging task both for modeling and experimental measurements. Here, we
present a new implementation of anti-Stokes thermometry that enables the in
situ photothermal characterization of individual nanoparticles (NPs) from a
single hyperspectral photoluminescence confocal image. The method is
label-free, applicable to any NP with detectable anti-Stokes emission, and does
not require any prior information about the NP itself or the surrounding media.
With it, we first studied the photothermal response of spherical gold NPs of
different sizes on glass substrates, immersed in water, and found that heat
dissipation is mainly dominated by the water for NPs larger than 50 nm. Then,
the role of the substrate was studied by comparing the photothermal response of
80 nm gold NPs on glass with sapphire and graphene, two materials with high
thermal conductivity. For a given irradiance level, the NPs reach temperatures
18% lower on sapphire and 24% higher on graphene than on bare glass. The fact
that the presence of a highly conductive material such as graphene leads to a
poorer thermal dissipation demonstrates that interfacial thermal resistances
play a very significant role in nanoscopic systems, and emphasize the need for
in situ experimental thermometry techniques. The developed method will allow
addressing several open questions about the role of temperature in
plasmon-assisted applications, especially ones where NPs of arbitrary shapes
are present in complex matrixes and environments.",2108.10954v1
2022-01-10,Superior enhancement in thermal conductivity of epoxy/graphene nanocomposites through use of dimethylformamide (DMF) relative to acetone as solvent,"In this work, we demonstrate that use of dimethylformamide (DMF) as a solvent
leads to better dispersion of graphene nanoplatelets in epoxy matrix compared
to acetone solvent, in turn leading to higher thermal conductivity
epoxy-graphene nanocomposites. While role of solvents in enabling superior
mechanical properties has been addressed before, outlined study is the first to
address the effect of solvents on thermal conductivity enhancement and provides
novel pathways for achieving high thermal conductivity polymer composite
materials. Uniform dispersion of graphene nanoparticles into epoxy can improve
thermal contact with polymer leading to superior interface thermal conductance
between polymer matrix and graphene. Organic solvents are typically employed to
achieve efficient dispersion of graphene into the epoxy matrix. In this study,
we compare the effect of two organic solvents, dimethylformamide (DMF) and
acetone, in terms of their efficiency in dispersing graphene into the epoxy
matrix and their effect on enhancing thermal conductivity of the composite. We
find that polymer-graphene composites made with DMF solvent show 44% higher
thermal conductivity compared to those made using acetone at 7 weight% filler
composition. Laser scanning confocal microscopy (LSCM) imaging reveals that
graphene-epoxy composites, prepared using DMF as solvent, exhibit more uniform
dispersion of graphene-nanoplatelets compared to the case of acetone with
acetone-based samples exhibiting up to 211% larger graphene agglomerations.
Comparison with effective medium theory reveals an almost 35% lower interface
thermal resistance between graphene and epoxy for DMF relative to acetone
prepared composite. These results provide fundamentally new avenues to achieve
higher thermal conductivity graphene-epoxy composites, of key importance for a
wide range of thermal management technologies.",2201.03527v2
2022-04-15,Universal Non-Polar Switching in Carbon-doped Transition Metal Oxides (TMOs) and Post TMOs,"Transition metal oxides (TMOs) and post-TMOs (PTMOs), when doped with Carbon,
show non-volatile current-voltage (I-V) characteristics, which are both
universal and repeatable. We have shown spectroscopic evidence of the
introduction of carbon-based impurity states inside the existing larger bandgap
effectively creating a smaller bandgap which we suggest could enable Mott-like
correlation effect. Our findings indicate new insights for yet to be understood
unipolar and nonpolar resistive switching in the TMOs and PTMOs. We have shown
that device switching is not thermal-energy dependent and have developed an
electronic-dominated switching model that allows for the extreme temperature
operation (from 1.5 K to 423 K) and state retention up to 673 K for a 1-hour
bake. Importantly, we have optimized the technology in an industrial process
and demonstrated integrated 1-transistor/1-resistor (1T1R) arrays up to 1 kbit
with 47 nm devices on 300 mm wafers for advanced node CMOS-compatible
correlated electron RAM (CeRAM). These devices are shown to operate with 2 ns
write pulses and retain the memory states up to 200 C for 24 hours. The
collection of attributes shown, including scalability to state-of-the-art
dimensions, non-volatile operation to extreme low and high temperatures, fast
write, and reduced stochasticity as compared to filamentary memories such as
ReRAMs show the potential for a highly capable two-terminal back-end-of-line
non-volatile memory.",2204.07656v1
2022-07-18,Room temperature spin-orbit torque efficiency in sputtered low-temperature superconductor delta-TaN,"In the course of searching for promising topological materials for
applications in future topological electronics, we evaluated spin-orbit torques
(SOTs) in high-quality sputtered ${\delta}-$TaN/Co20Fe60B20 devices through
spin-torque ferromagnetic resonance ST-FMR and spin pumping measurements. From
the ST-FMR characterization we observed a significant linewidth modulation in
the magnetic Co20Fe60B20 layer attributed to the charge-to-spin conversion
generated from the ${\delta}-$TaN layer. Remarkably, the spin-torque efficiency
determined from ST-FMR and spin pumping measurements is as large as ${\Theta}
=$ 0.034 and 0.031, respectively. These values are over two times larger than
for ${\alpha}-$Ta, but almost five times lower than for ${\beta}-$Ta, which can
be attributed to the low room temperature electrical resistivity $\sim
74{\mu}{\Omega}$ cm in ${\delta}-$TaN. A large spin diffusion length of at
least $\sim8$ nm is estimated, which is comparable to the spin diffusion length
in pure Ta. Comprehensive experimental analysis, together with density
functional theory calculations, indicates that the origin of the pronounced SOT
effect in ${\delta}-$TaN can be mostly related to a significant contribution
from the Berry curvature associated with the presence of a topically nontrivial
electronic band structure in the vicinity of the Fermi level (EF). Through
additional detailed theoretical analysis, we also found that an isostructural
allotrope of the superconducting ${\delta}-$TaN phase, the simple hexagonal
structure, ${\theta}-$TaN, has larger Berry curvature, and that, together with
expected reasonable charge conductivity, it can also be a promising candidate
for exploring a generation of spin-orbit torque magnetic random access memory
as cheap, temperature stable, and highly efficient spin current sources.",2207.08872v2
2023-03-30,Observation of non-superconducting phase changes in LuH$_{2\pm\text{x}}$N$_y$,"The recent report of near-ambient superconductivity in nitrogen doped
lutetium hydride has triggered a worldwide fanaticism and raised major
questions about the latest claims. An intriguing phenomenon of color changes in
pressurized samples from blue to pink to red was observed and correlated with
the claimed superconducting transition, but the origin and underlying physics
of these color changes have yet to be elucidated. Here we report synthesis and
characterization of high-purity nitrogen doped lutetium hydride
LuH$_{2\pm\text{x}}$N$_y$ with the same structure and composition as in the
main phase of near-ambient superconductor1. We find a new purple phase of
LuH$_{2\pm\text{x}}$N$_y$ between blue and pink phase, and reveal that the
sample color changes likely stem from pressure-driven redistribution of
nitrogen and its interaction with the LuH$_2$ framework. No superconducting
transition is found in all blue, purple, pink and red phases at temperatures
1.8-300 K and pressures 0-30 GPa. Instead, we identify a notable
temperature-induced resistance anomaly of structural and/or electronic origin
in LuH$_{2\pm\text{x}}$N$_y$, which is most pronounced in the pink phase and
may have been erroneously interpreted as a sign of superconducting transition.
This work establishes key benchmarks for nitrogen doped lutetium hydrides,
allowing an in-depth understanding of the novel pressure-induced phase changes.",2303.17587v2
2023-10-02,Resistless EUV lithography: photon-induced oxide patterning on silicon,"In this work, we show the feasibility of extreme ultraviolet (EUV) patterning
on an HF-treated Si(100) surface in the absence of a photoresist. EUV
lithography is the leading lithography technique in semiconductor manufacturing
due to its high resolution and throughput, but future progress in resolution
can be hampered because of the inherent limitations of the resists. We show
that EUV photons can induce surface reactions on a partially H-terminated Si
surface and assist the growth of an oxide layer, which serves as an etch mask.
This mechanism is different from the H-desorption in scanning tunneling
microscopy-based lithography. We achieve SiO2/Si gratings with 75 nm half-pitch
and 31 nm height, demonstrating the efficacy of the method and the feasibility
of patterning with EUV lithography without the use of a photoresist. Further
development of the resistless EUV lithography method can be a viable approach
to nm-scale lithography by overcoming the inherent resolution and roughness
limitations of photoresist materials.",2310.01268v1
2023-10-31,Signature of Topological Semimetal in Harmonic-honeycomb ReO3,"Transition-metal honeycomb compounds are capturing scientific attention due
to their distinctive electronic configurations, underscored by the
triangular-lattice spin-orbit coupling and competition between multiple
interactions, paving the way for potential manifestations of phenomena such as
Dirac semimetal, superconductivity, and quantum spin liquid states. These
compounds can undergo discernible pressure-induced alterations in their
crystallographic and electronic paradigms, as exemplified by our high-pressure
(HP) synthesis and exploration of the honeycomb polymorph of ReO3 (P6322). This
HP-P6322 polymorph bears a phase transition from P6322 to P63/mmc upon cooling
around Tp = 250 K, as evidenced by the evolution of temperature-dependent
magnetization (M-T curves), cell dimension, and conductivity initiated by an
inherent bifurcation of the oxygen position in the ab plane. Insightful
analysis of its band structure positions suggests this HP-P6322 polymorph being
a plausible candidate for Dirac semimetal properties. This phase transition
evokes anomalies in the temperature-dependent variation of paramagnetism
(non-linearity) and a crossover from semiconductor to temperature-independent
metal, showing a temperature independent conductivity behavior below ~200 K.
Under increasing external pressure, both the Tp and resistance of this
HP-polymorph is slightly magnetic-field dependent and undergo a ""V""-style
evolution (decreasing and then increasing) before becoming pressure independent
up to 20.2 GPa. Theoretical calculations pinpoint this anionic disorder as a
probable catalyst for the decrement in the conductive efficiency and muted
temperature-dependent conductivity response.",2310.20341v2
2024-01-13,Reliable operation of Cr$_2$O$_3$:Mg/ $β$-Ga$_2$O$_3$ p-n heterojunction diodes at 600$^\circ$C,"$\beta$-Ga$_2$O$_3$-based semiconductor heterojunctions have recently
demonstrated improved performance at high voltages and elevated temperatures
and are thus promising for applications in power electronic devices and
harsh-environment sensors. However, the long-term reliability of these
ultra-wide band gap (UWBG) semiconductor devices remains barely addressed and
may be strongly influenced by chemical reactions at the p-n heterojunction
interface. Here, we experimentally demonstrate operation and evaluate the
reliability of Cr$_2$O$_3$:Mg/ $\beta$-Ga$_2$O$_3$ p-n heterojunction diodes at
during extended operation at 600$^\circ$C, as well as after 30 repeated cycles
between 25-550$^\circ$C. The calculated pO2-temperature phase stability diagram
of the Ga-Cr-O material system predicts that Ga$_2$O$_3$ and Cr$_2$O$_3$ should
remain thermodynamically stable in contact with each other over a wide range of
oxygen pressures and operating temperatures. The fabricated Cr$_2$O$_3$:Mg /
$\beta$-Ga$_2$O$_3$ p-n heterojunction diodes show room-temperature on/off
ratios >10$^4$ at $\pm$5V and a breakdown voltage (V$_{Br}$) of -390V. The
leakage current increases with increasing temperature up to 600$^\circ$C, which
is attributed to Poole-Frenkel emission with a trap barrier height of 0.19 eV.
Over the course of a 140-hour thermal soak at 600$^\circ$C, both the device
turn-on voltage and on-state resistance increase from 1.08V and 5.34
m$\Omega$-cm$^2$ to 1.59V and 7.1 m$\Omega$-cm$^2$ respectively. This increase
is attributed to the accumulation of Mg and MgO at the Cr$_2$O$_3$/Ga$_2$O$_3$
interface as observed from TOF-SIMS analysis. These findings inform future
design strategies of UWBG semiconductor devices for harsh environment operation
and underscore the need for further reliability assessments for
$\beta$-Ga$_2$O$_3$ based devices.",2401.07166v1
2024-02-09,BaMn$_2$P$_2$: Highest magnetic ordering temperature 122-pnictide compound,"We report the growth of high-quality single crystals of ThCr$_2$Si$_2$-type
tetragonal BaMn$_2$P$_2$ and investigation of its structural, electrical
transport, thermal and magnetic properties. Our results of basal plane
electrical resistivity and heat capacity measurements show that the compound
has an insulating ground state with a small band gap. Anisotropic
susceptibility $\chi_{ab,c}(T)$ data infer a collinear local-moment N\'eel-type
antiferromagnetic (AFM) ground state below the ordering temperature $T_{\rm N}
= 795(15)$~K, which is highest among all the ThCr$_2$Si$_2$- and
CaAl$_2$Si$_2$-type 122-pnictide compounds reported so far suggesting that the
strength of magnetic exchange interactions is strongest in this material. The
magnetic transition temperatures of BaMn$_2$$Pn_{2}$ ($Pn$ = P, As, Sb, Bi)
compounds exhibit a monotonic decrease with the increase of tetragonal unit
cell parameters $a$ and $c$, suggesting a strong dependence of the strength of
the decisive magnetic exchange interactions on the separation between the
localized spins residing on the Mn-ions. The observed monotonic increase of
both $\chi_{ab}$ and $\chi_{c}$ for $T > T_{\rm N}$ suggests that short-range
dynamic quasi-two dimensional AFM correlations persist above the $T_{\rm N}$ up
to the highest temperature of the measurements. The large $T_{\rm N}$ of
BaMn$_2$P$_2$ demands for systematic hole-doping studies on this material as
similar investigations on related BaMn$_2$As$_{2}$ with $T_{\rm N} = 618$~K
have led to the discovery of an outstanding ground state where AFM of localized
Mn-spins and itinerant half-metallic ferromagnetism with $T_{\rm c} \approx
100$~K originating from the doped holes coexist together.",2402.06432v1
2016-07-07,Temperature dependence of the electrical resistivity and the anisotropic magnetoresistance (AMR) of electrodeposited Ni Co alloys,"The electrical resistivity and the anisotropic magnetoresistance (AMR) was
investigated for Ni Co alloys at and below room temperature. The Ni Co alloy
layers having a thickness of about 2 um were prepared by electrodeposition on
Si wafers with evaporated Cr and Cu underlayers. The alloy composition was
varied in the whole concentration range by varying the ratio of Ni sulfate and
Co sulfate in the electrolyte. The Ni Co alloy deposits were investigated first
in the as deposited state on the substrates and then, by mechanically stripping
them from the substrates, as self supporting layers both without and after
annealing. According to an X ray diffraction study, a strongly textured face
centered cubic (fcc) structure was formed in the as deposited state with an
average grain size of about 10 nm. Upon annealing, the crystal structure was
retained whereas the grain size increased by a factor of 3 to 5, depending on
alloy composition. The zero field resistivity decreased strongly by annealing
due to the increased grain size. The annealing hardly changed the AMR below 50
at.% Co but strongly decreased it above this concentration. The composition
dependence of the resistivity and the AMR of the annealed Ni Co alloy deposits
was in good quantitative agreement with the available literature data both at
13 K and at room temperature. Both transport parameters were found to exhibit a
pronounced maximum in the composition range between 20 and 30 at.% Co and the
data of the Ni Co alloys fit well to the limiting values of the pure component
metals (fcc Ni and fcc Co). The only theoretical calculation reported formerly
on fcc Ni Co alloys yielded at T=0K a resistivity value smaller by a factor of
5 and an AMR value larger by a factor of about 2 than the corresponding low
temperature experimental data, although the theoretical results properly
reproduced the composition dependence of both quantities.",1607.01960v1
2012-06-07,Resistive and magnetoresistive properties of CrO2 pressed powders with different types of inter-granular dielectric layers,"Resistive, magnetoresistive and magnetic properties of four kinds of pressed
CrO2 powders, synthesized by hydrothermal method of chromic anhydride have been
investigated. The particles in powders constituted of rounded particles
(diameter 120 nm) or needle-shaped crystals with an average diameter of 22.9 nm
and average length of 302 nm. All of the particles had a surface dielectric
shell of varying thickness and different types (such as oxyhydroxide -CrOOH or
chromium oxide Cr2O3). For all the samples at low temperatures we found
non-metallic temperature dependence of resistivity and giant negative
magnetoresistance (MR). The maximum value of MR at low temperatures (T \approx
5 K) is \approx 37% in relatively small fields (0.5 T). At higher temperatures
there was a rapid decrease of MR (up to \approx 1% / T at T \approx 200 K). The
main objective of this work was studying the influence of properties and
thickness of the intergranular dielectric layers, as well as CrO2 particle
shape, on the magnitude of the tunneling resistance and MR of the pressed
powder. The new results obtained in this study include: (1) detection at low
temperatures in powders with needle-like particles a new type of MR hysteresis,
and nonmonotonic MR behaviour with increasing magnetic field (absolute value of
the MR at first grows rather rapidly with the field, and then begins
diminishing markedly, forming a maximum), and (2) detection of non-monotonic
temperature dependence, where - a field in which the resistance in a magnetic
field has a maximum, as well as finding discrepancies in values of and
coercivity fields, (3) detection of the anisotropy of MR, depending on the
relative orientation of the transport current and the magnetic field, (4) a new
method of synthesis, to regulate the thickness of dielectric coating.",1206.1533v1
2021-07-23,Modeling the dynamical behavior of memristive {NiTi} alloy at constant stress for time-varying electric current input signals,"The dynamical electric behavior of a NiTi smart alloy thin filament when
driven by time varying current pulses is studied by a structure-based
phenomenological model that includes rate-based effects. The simulation model
relates the alloy's electrical resistivity to the relative proportions of the
three main structural phases namely Martensite, Austenite and R-phase,
experimentally known to exist in NiTi alloy lattice structure. The relative
proportions of the phases depend on temperature and applied stress. Temperature
varies due to the self-heating of the filament by the Joule effect when a
current pulse passes and also due to convective/radiative interchange with the
ambient. The temperature variation with time causes structural phase
transitions, which result in abrupt changes in the sample resistivity as the
proportions of each lattice phase vary. The model is described by a system of
four 1st-order nonlinear differential-algebraic equations yielding the temporal
evolution of resistivity and output voltage across the filament for any given
time-varying input current pulse. The model corresponds to a 4th-order extended
memristor, described by four state variables, which are the proportions of each
of the three NiTi lattice phases and temperature. Simulations are
experimentally verified by comparing to measurements obtained for samples
self-heated by triangular current input waveforms as well as for passively
samples with no current input. Numerical results reproduce very well
measurements of resistance vs. temperature at equilibrium as well as the full
dynamics of experimentally observed I-V characteristic curves and resistance
vs. driving current for time-varying current input waveforms of a wide range of
frequencies (0.01-10~Hz).",2107.11060v1
2024-05-06,Speckle pattern analysis of PVK:rGO composite based memristor device,"The memristors are expected to be fundamental devices for neuromorphic
systems and switching applications. For example, the device made of a
sandwiched layer of poly(N-vinylcarbazole) and reduced graphene composite
between asymmetric electrodes (ITO/PVK:rGO/Al) exhibits bistable resistive
switching behavior. Depending on the resistance state of the (ON-state or
OFF-state) at a constant applied voltage, it may show two different
resistivities. The performance of the memristor can be optimized by controlling
the doping amount of graphene oxide in the PVK polymer. To assess the
performance of the device, when it switches between ON and OFF states, optical
characterization approaches are highly promising due to their non-destructive
and remote nature. Here, we characterize the memristor device by the use of
speckle pattern (SP) analysis. The speckle pattern is the interference of
multiple light waves with random relative phases, which is generated via
different mechanisms such as scattering from diffusive materials. Therefore,
SPs can be used to investigate such samples as they include a huge amount of
information to be statistically elaborated. The experimental paradigm includes
\textit{in situ} acquisition of SPs of the PVK:rGO in different states followed
by statistical post-processing toward examining its conduction mechanism. The
variations in these statistical parameters are attributed to the resistance
state of the PVK:rGO samples under the applied voltage with regard to the
physical switching mechanism of the device. The resistance/conduction state, in
turn, depends on the activity and properties of PVK:rGO memristors as well as
the additional non-uniformities induced through the variations of density of
carriers. The present optical methodology can be potentially served as a
bench-top device for characterization purposes of similar devices while they
are operating.",2405.03369v1
2017-10-09,Superconductivity in the Nb-Ru-Ge $σ$-Phase,"We show that the previously unreported ternary $\sigma$-phase material
Nb$_{20.4}$Ru$_{5.7}$Ge$_{3.9}$ is a superconductor with a critical temperature
of 2.2 K. Temperature-dependent magnetic susceptibility, resistance, and
specific heat measurements were used to characterize the superconducting
transition. The Sommerfeld constant $\gamma$ for
Nb$_{20.4}$Ru$_{5.7}$Ge$_{3.9}$ is 91 mJ mol-f.u.$^{-1}$K$^{-2}$ and the
specific heat anomaly at the superconducting transition,
$\Delta$C/$\gamma$T$_c$, is approximately 1.38. The zero-temperature upper
critical field ($\mu_0$H$_{c2}$(0)) was estimated to be 2 T by resistance data.
Field-dependent magnetization data analysis estimated $\mu_0$H$_{c1}$(0) to be
5.5 mT. Thus, the characterization shows Nb$_{20.4}$Ru$_{5.7}$Ge$_{3.9}$ to be
a type II BCS superconductor. This material appears to be the first reported
ternary phase in the Nb-Ru-Ge system, and the fact that there are no previously
reported binary Nb-Ru, Nb-Ge, or Ru-Ge $\sigma$-phases shows that all three
elements are necessary to stabilize the material. A $\sigma$-phase in the
Ta-Ru-Ge system was synthesized but did not display superconductivity above 1.7
K, which suggests that electron count cannot govern the superconductivity
observed. Preliminary characterization of a possible superconducting
$\sigma$-phase in the Nb-Ru-Ga system is also reported.",1710.03347v1
2022-02-28,Colloquium: Quantum anomalous Hall effect,"The quantum Hall (QH) effect, quantized Hall resistance combined with zero
longitudinal resistance, is the characteristic experimental fingerprint of
Chern insulators - topologically non-trivial states of two-dimensional matter
with broken time-reversal symmetry. In Chern insulators, non-trivial bulk band
topology is expressed by chiral states that carry current along sample edges
without dissipation. The quantum anomalous Hall (QAH) effect refers to QH
effects that occur in the absence of external magnetic fields due to
spontaneously broken time-reversal symmetry. The QAH effect has now been
realized in four different classes of two-dimensional materials: (i) thin films
of magnetically (Cr- and/or V-) doped topological insulators in the (Bi,Sb)2Te3
family, (ii) thin films of the intrinsic magnetic topological insulator
MnBi2Te4, (iii) moir\'e materials formed from graphene, and (iv ) moir\'e
materials formed from transition metal dichalcogenides. In this Article, we
review the physical mechanisms responsible for each class of QAH insulator,
highlighting both differences and commonalities, and comment on potential
applications of the QAH effect.",2202.13902v4
2018-08-12,Low Temperature Specific Heat of Doped SrTiO$_3$: Doping Dependence of the Effective Mass and Kadowaki-Woods Scaling Violation,"We report wide-doping-range ($8 \times 10^{17}$ to $4 \times 10^{20}$
cm$^{-3}$ Hall electron density) low temperature specific heat measurements on
single crystal SrTiO$_3$:Nb, correlated with electronic transport data and
tight-binding modeling. Lattice dynamic contributions to specific heat are
shown to be well understood, albeit with unusual sensitivity to doping, likely
related to the behavior of soft modes. Electronic contributions to specific
heat provide effective masses that increase substantially, from $1.8$ to $4.8
m_e$, across the two SrTiO$_3$ Lifshitz transitions. It is shown that this
behavior can be quantitatively reconciled with quantum oscillation data and
calculated band structure, establishing a remarkably doping-independent mass
enhancement factor of $2.0$. Most importantly, with the doping-dependent $T^2$
resistivity prefactor and Sommerfeld coefficient known, Kadowaki-Woods scaling
has been tested over the entire doping range probed. Despite classic Fermi
liquid behavior in electronic specific heat, standard Kadowaki-Woods scaling is
dramatically violated, highlighting the need for new theoretical descriptions
of $T^2$ resistivity in SrTiO$_3$.",1808.03909v2
2015-06-07,Temperature dependent three-dimensional anisotropy of the magnetoresistance in WTe$_2$,"Extremely large magnetoresistance (XMR) was recently discovered in WTe$_2$,
triggering extensive research on this material regarding the XMR origin. Since
WTe$_2$ is a layered compound with metal layers sandwiched between adjacent
insulating chalcogenide layers, this material has been considered to be
electronically two-dimensional (2D). Here we report two new findings on
WTe$_2$: (1) WTe$_2$ is electronically 3D with a mass anisotropy as low as $2$,
as revealed by the 3D scaling behavior of the resistance
$R(H,\theta)=R(\varepsilon_\theta H)$ with $\varepsilon_\theta =(\cos^2 \theta
+ \gamma^{-2}\sin^2 \theta)^{1/2}$, $\theta$ being the magnetic field angle
with respect to c-axis of the crystal and $\gamma$ being the mass anisotropy;
(2) the mass anisotropy $\gamma$ varies with temperature and follows the
magnetoresistance behavior of the Fermi liquid state. Our results not only
provide a general scaling approach for the anisotropic magnetoresistance but
also are crucial for correctly understanding the electronic properties of
WTe$_2$, including the origin of the remarkable 'turn-on' behavior in the
resistance versus temperature curve, which has been widely observed in many
materials and assumed to be a metal-insulator transition.",1506.02214v2
2019-10-09,Preferential out-of-plane conduction and quasi-one-dimensional electronic states in layered 1T-TaS2,"Layered transition metal dichalcogenides (TMDs) are commonly classified as
quasi-two-dimensional materials, meaning that their electronic structure
closely resembles that of an individual layer, which results in resistivity
anisotropies reaching thousands. Here, we show that this rule does not hold for
1T-TaS2 - a compound with the richest phase diagram among TMDs. While the onset
of charge density wave order makes the in-plane conduction non-metallic, we
reveal that the out-of-plane charge transport is metallic and the resistivity
anisotropy is close to one. We support our findings with ab-initio calculations
predicting a pronounced quasi-one-dimensional character of the electronic
structure. Consequently, we interpret the highly debated metal-insulator
transition in 1T-TaS2 as a quasi-one-dimensional instability, contrary to the
long-standing Mott localisation picture. In a broader context, these findings
are relevant for the newly born field of van der Waals heterostructures, where
tuning interlayer interactions (e.g. by twist, strain, intercalation, etc.)
leads to new emergent phenomena.",1910.03817v2
2019-10-23,Complex Transport and Magnetism in Inhomogeneous Mixed Valence Ce$_3$Ir$_4$Ge$_{13}$,"We report the discovery of Ce$_3$Ir$_4$Ge$_{13}$, a new Remeika phase
compound with a complex array of structural, electronic, and magnetic
properties. Our single crystal x-ray diffraction measurements show that
Ce$_3$Ir$_4$Ge$_{13}$ forms in the tetragonally distorted $I4_1/amd$ space
group. The electrical resistivity is almost temperature independent over three
decades in temperature, from 0.4 K to 400 K, while the Hall coefficient
measurements are consistent with a low-carrier semimetal. Magnetic
susceptibility measurements reveal an effective moment of
$\mu^{\text{exp}}_{\text{eff}} = 1.87 \mu_B$/Ce, suggesting that this material
has a mixture of magnetic Ce$^{3+}$ and non-magnetic Ce$^{4+}$. Upon cooling,
Ce$_3$Ir$_4$Ge$_{13}$ first enters a short range magnetically ordered state
below $T_{\text{SRO}}=10$ K, marked by a deviation from Curie-Weiss behavior in
susceptibility and a broad field-independent heat capacity anomaly. At lower
temperatures, we observe a second, sharper peak in the heat capacity at $T^* =
1.7$ K, concurrent with a splitting of the field-cooled and zero-field-cooled
susceptibilities. A small resistivity drop at $T^*$ suggests a loss of spin
disorder scattering consistent with a magnetic ordering or spin freezing
transition. Ce$_3$Ir$_4$Ge$_{13}$ is therefore a rare example of an
inhomogeneous mixed valence compound with a complex array of thermodynamic and
transport properties.",1910.10764v1
2020-05-01,Characterisation of Cryogenic Material Properties of 3D-Printed Superconducting Niobium using a 3D Lumped Element Microwave Cavity,"We present an experimental characterisation of the electrical properties of
3D-printed Niobium. The study was performed by inserting a 3D-printed Nb post
inside an Aluminium cylindrical cavity, forming a 3D lumped element re-entrant
microwave cavity resonator. The resonator was cooled to temperatures below the
critical temperature of Niobium (9.25K) and then Aluminium (1.2K), while
measuring the quality factors of the electromagnetic resonances. This was then
compared with finite element analysis of the cavity and a measurement of the
same cavity with an Aluminium post of similar dimensions and frequency, to
extract the surface resistance of the Niobium post. The 3D-printed Niobium
exhibited a transition to the superconducting state at a similar temperature to
the regular Niobium, as well as a surface resistance of $3.1\times10^{-4}$
$\Omega$. This value was comparable to many samples of traditionally machined
Niobium previously studied without specialised surface treatment. Furthermore,
this study demonstrates a simple new method for characterizing the material
properties of a relatively small and geometrically simple sample of
superconductor, which could be easily applied to other materials, particularly
3D-printed materials. Further research and development in additive
manufacturing may see the application of 3D-printed Niobium in not only
superconducting cavity designs, but in the innovative technology of the future.",2005.00271v1
2021-09-30,Spin-flip-driven giant magneto-transport in A-type antiferromagnet NaCrTe2,"For anisotropic magneto-resistance (AMR) effect, its value synergistically
depends on the magnitudes of magneto-resistance (MR) and magneto-crystalline
anisotropy energy (MAE) simultaneously. In a magnetic material, the concurrence
of gigantic AMR and MR signals is rather difficult due to weak spin-lattice
coupling and small MAE. Here we report the considerable magneto-transport
effect in layered A-type antiferromagnetic (AFM) NaCrTe2 by realigning the spin
configurations. By applying H, the antiparallel spins of adjacent layers are
flipped to ferromagnetic (FM) coupling either Ising-type along c-axis or
XY-type within ab-plane. Theoretical calculations reveal that the energy
bandgap narrows from 0.39 eV to 0.11 eV, accompanying a transition from
semiconductor (high-R state) and half-semiconductor (low-R state),
respectively. Thus, gigantic negative MR ratio of -90% is obtained at 10 K.
More importantly, the decrement of R along H//c is far quicker than that of
H//ab because the MAE of Ising-FM state is 1017 {\mu}eV/Cr3+ lower than that of
XY-FM. The distinct trends result in the AMR ratio of 732% at 10 K, which is
the record value to our best knowledge. These findings unravel the intrinsic
origin of magneto in NaCrTe2 and will stimulate us to exploring the H-sensitive
transport property in more AFM materials.",2109.14923v1
2021-11-12,Recrystallization and Interdiffusion Processes in Laser-Annealed Strain-Relaxed Metastable Ge$_{0.89}$Sn0$_{.11}$,"The prospect of GeSn semiconductors for silicon-integrated infrared
optoelectronics brings new challenges related to the metastability of this
class of materials. As a matter of fact, maintaining a reduced thermal budget
throughout all processing steps of GeSn devices is essential to avoid possible
material degradation. This constraint is exacerbated by the need for higher Sn
contents along with an enhanced strain relaxation to achieve efficient
mid-infrared devices. Herein, as a low thermal budget solution for post-epitaxy
processing, we elucidate the effects of laser thermal annealing (LTA) on
strain-relaxed Ge$_{0.89}$Sn0$_{.11}$ layers and Ni-Ge$_{0.89}$Sn0$_{.11}$
contacts. Key diffusion and recrystallization processes are proposed and
discussed in the light of systematic microstructural studies. LTA treatment at
a fluence of 0.40 J/cm2 results in a 200-300 nm-thick layer where Sn atoms
segregate toward the surface and in the formation of Sn-rich columnar
structures in the LTA-affected region. These structures are reminiscent to
those observed in the dislocation-assisted pipe-diffusion mechanism, while the
buried GeSn layers remain intact. Moreover, by tailoring the LTA fluence, the
contact resistance can be reduced without triggering phase separation across
the whole GeSn multi-layer stacking. Indeed, a one order of magnitude decrease
in the Ni-based specific contact resistance was obtained at the highest LTA
fluence, thus confirming the potential of this method for the functionalization
of direct bandgap GeSn materials.",2111.06788v1
2022-04-18,Material properties of a low contraction and resistivity silicon-aluminum composite for cryogenic detectors,"We report on the cryogenic properties of a low-contraction silicon-aluminum
composite, namely Japan Fine Ceramics SA001, to use as a packaging structure
for cryogenic silicon devices. SA001 is a silicon--aluminum composite material
(75% silicon by volume) and has a low thermal expansion coefficient ($\sim$1/3
that of aluminum). The superconducting transition temperature of SA001 is
measured to be 1.18 K, which is in agreement with that of pure aluminum, and is
thus available as a superconducting magnetic shield material. The residual
resistivity of SA001 is 0.065 $\mathrm{\mu \Omega m}$, which is considerably
lower than an equivalent silicon--aluminum composite material. The measured
thermal contraction of SA001 immersed in liquid nitrogen is
$\frac{L_{293\mathrm{K}}-L_{77\mathrm{K}}}{L_{293\mathrm{K}}}=0.12$%, which is
consistent with the expected rate obtained from the volume-weighted mean of the
contractions of silicon and aluminum. The machinability of SA001 is also
confirmed with a demonstrated fabrication of a conical feedhorn array, with a
wall thickness of 100 $\mathrm{\mu m}$. These properties are suitable for
packaging applications for large-format superconducting detector devices.",2204.08111v2
2022-06-07,Phase-field modelling and analysis of rate-dependent fracture phenomena at finite deformation,"Fracture of materials with rate-dependent mechanical behaviour, e.g.
polymers, is a highly complex process. For an adequate modelling, the coupling
between rate-dependent stiffness, dissipative mechanisms present in the bulk
material and crack driving force has to be accounted for in an appropriate
manner. In addition, the fracture toughness, i.e. the resistance against crack
propagation, can depend on rate of deformation. In this contribution, an
energetic phase-field model of rate-dependent fracture at finite deformation is
presented. For the deformation of the bulk material, a formulation of finite
viscoelasticity is adopted with strain energy densities of Ogden type assumed.
The unified formulation allows to study different expressions for the fracture
driving force. Furthermore, a possibly rate-dependent toughness is
incorporated. The model is calibrated using experimental results from the
literature for an elastomer and predictions are qualitatively and
quantitatively validated against experimental data. Predictive capabilities of
the model are studied for monotonic loads as well as creep fracture.
Symmetrical and asymmetrical crack patterns are discussed and the influence of
a dissipative fracture driving force contribution is analysed. It is shown
that, different from ductile fracture of metals, such a driving force is not
required for an adequate simulation of experimentally observable crack paths
and is not favourable for the description of failure in viscoelastic rubbery
polymers. Furthermore, the influence of a rate-dependent toughness is discussed
by means of a numerical study. From a phenomenological point of view, it is
demonstrated that rate-dependency of resistance against crack propagation can
be an essential ingredient for the model when specific effects such as
rate-dependent brittle-to-ductile transitions shall be described.",2206.03460v1
2022-11-17,On universal butterfly and antisymmetric magnetoresistances,"Butterfly magnetoresistance (BMR) and antisymmetric magnetoresistance (ASMR)
are about a butterfly-cross curve and a curve with one peak and one valley when
a magnetic field is swept up and down along a fixed direction. Other than the
parallelogram-shaped magnetoresistance-curve (MR-curve) often observed in
magnetic memory devices, BMR and ASMR are two ubiquitous types of MR-curves
observed in diversified magnetic systems, including van der Waals materials,
strongly correlated systems, and traditional magnets. Here, we reveal the
general principles and the picture behind the BMR and the ASMR that do not
depend on the detailed mechanisms of magnetoresistance: 1) The systems exhibit
hysteresis loops, common for most magnetic materials with coercivities. 2) The
magnetoresistance of the magnetic structures in a large positive magnetic field
and in a large negative magnetic field is approximately the same. With the
generalized Ohm's law in magnetic materials, these principles explain why most
BMR appears in the longitudinal resistance measurements and is very rare in the
Hall resistance measurements. Simple toy models, in which the
Landau-Lifshitz-Gilbert equation governs magnetization, are used to demonstrate
the principles and explain the appearance and disappearance of BMR in various
experiments. Our finding provides a simple picture to understand
magnetoresistance-related experiments.",2211.09369v1
2009-03-16,Interplay between magnetism and superconductivity and appearance of a second superconducting transition in alpha-FeSe at high pressure,"We synthesized tetragonal alpha-FeSe by melting a powder mixture of iron and
selenium at high pressure. Subsequent annealing at normal pressure results in
removing traces of hexagonal beta- FeSe, formation of a rather sharp transition
to superconducting state at Tc ~ 7 K, and the appearance of a magnetic
transition near Tm = 120 K. Resistivity and ac-susceptibility were measured on
the annealed sample at hydrostatic pressure up to 4.5 GPa. A magnetic
transition visible in ac-susceptibility shifts down under pressure and the
resistive anomaly typical for a spin density wave (SDW) antiferromagnetic
transition develops near the susceptibility anomaly. Tc determined by the
appearance of a diamagnetic response in susceptibility, increases linearly
under pressure at a rate dTc/dP = 3.5 K/GPa. Below 1.5 GPa, the resistive
superconducting transition is sharp; the width of transition does not change
with pressure; and, Tc determined by a peak in drho/dT increases at a rate ~
3.5 K/GPa. At higher pressure, a giant broadening of the resistive transition
develops. This effect cannot be explained by possible pressure gradients in the
sample and is inherent to alpha-FeSe. The dependences drho(T)/dT show a
signature for a second peak above 3 GPa which is indicative of the appearance
of another superconducting state in alpha-FeSe at high pressure. We argue that
this second superconducting phase coexists with SDW antiferromagnetism in a
partial volume fraction and originates from pairing of charge carriers from
other sheets of the Fermi surface.",0903.2873v1
2022-05-19,High pressure structural and magneto-transport studies on type-II Dirac semimetal candidate Ir2In8S: Emergence of superconductivity upon decompression,"The structural and magneto-transport properties of type-II Dirac semimetal
candidate Ir2In8S have been investigated under high pressure. The ambient
tetragonal structure (P4_2/mnm) is found to be stable up to 7 GPa, above which
the system takes an orthorhombic Pnnm structure, possibly destroying the Dirac
cones due to the loss of the four-fold screw symmetry. In the tetragonal
structure, a gradual suppression of the transverse magneto-resistance and a
rapid change in the magnetic field dependence above 50K suggest possible
T-dependent Fermi surface modification. In the high pressure phase, the
metallic character increases marginally (as evident from the increased RRR
value) accompanied with suppressed magneto-resistance, without emergence of
superconductivity up to 20 GPa and down to 1.4K. Most surprisingly, upon
release of pressure to 0.2 GPa, a sharp resistance drop below 4K is observed,
field varying measurements confirm this as the onset of superconductivity. The
observed changes of the carrier density and mobility in the pressure-released
tetragonal phase indicate electronic structural modification resulting from the
irreversible polyhedral distortion. A simultaneous increase in the residual
resistivity and carrier density upon decompression indicates that an enhanced
impurity scattering play a key role in the emergence of superconductivity in
the tetragonal Ir2In8S, making it an ideal platform to study topological
superconductivity.",2205.09798v1
2022-11-08,Effective resistivity in relativistic collisionless plasmoid-mediated reconnection,"Magnetic reconnection can power spectacular high-energy astrophysical
phenomena by producing non-thermal energy distributions in highly magnetized
regions around compact objects. By means of two-dimensional fully kinetic
particle-in-cell (PIC) simulations we investigate relativistic collisionless
plasmoid-mediated reconnection in magnetically dominated pair plasmas with and
without guide field. In X-points, where diverging flows result in a
non-diagonal thermal pressure tensor, a finite residence time for particles
gives rise to a localized collisionless effective resistivity. Here, for the
first time for relativistic reconnection in a fully developed plasmoid chain we
identify the mechanisms driving the non-ideal electric field using a full Ohm's
law by means of a statistical analysis based on our PIC simulations. We show
that the non-ideal electric field is predominantly driven by gradients of
nongyrotropic thermal pressures. We propose a kinetic physics motivated
non-uniform effective resistivity model, which is negligible on global scales
and becomes significant only locally in X-points, that captures the properties
of collisionless reconnection with the aim of mimicking its essentials in
non-ideal magnetohydrodynamic descriptions. This effective resistivity model
provides a viable opportunity to design physically grounded global models for
reconnection-powered high-energy emission.",2211.04553v1
2023-10-23,Deep learning denoiser assisted roughness measurements extraction from thin resists with low Signal-to-Noise Ratio(SNR) SEM images: analysis with SMILE,"The technological advance of High Numerical Aperture Extreme Ultraviolet
Lithography (High NA EUVL) has opened the gates to extensive researches on
thinner photoresists (below 30nm), necessary for the industrial implementation
of High NA EUVL. Consequently, images from Scanning Electron Microscopy (SEM)
suffer from reduced imaging contrast and low Signal-to-Noise Ratio (SNR),
impacting the measurement of unbiased Line Edge Roughness (uLER) and Line Width
Roughness (uLWR). Thus, the aim of this work is to enhance the SNR of SEM
images by using a Deep Learning denoiser and enable robust roughness extraction
of the thin resist. For this study, we acquired SEM images of Line-Space (L/S)
patterns with a Chemically Amplified Resist (CAR) with different thicknesses
(15nm, 20nm, 25nm, 30nm), underlayers (Spin-On-Glass-SOG, Organic
Underlayer-OUL) and frames of averaging (4, 8, 16, 32, and 64 Fr). After
denoising, a systematic analysis has been carried out on both noisy and
denoised images using an open-source metrology software, SMILE 2.3.2, for
investigating mean CD, SNR improvement factor, biased and unbiased LWR/LER
Power Spectral Density (PSD). Denoised images with lower number of frames
present unaltered Critical Dimensions (CDs), enhanced SNR (especially for low
number of integration frames), and accurate measurements of uLER and uLWR, with
the same accuracy as for noisy images with a consistent higher number of
frames. Therefore, images with a small number of integration frames and with
SNR < 2 can be successfully denoised, and advantageously used in improving
metrology throughput while maintaining reliable roughness measurements for the
thin resist.",2310.14815v1
2023-04-13,Combining Electron-Phonon and Dynamical Mean-Field Theory Calculations of Correlated Materials: Transport in the Correlated Metal Sr$_2$RuO$_4$,"Electron-electron ($e$-$e$) and electron-phonon ($e$-ph) interactions are
challenging to describe in correlated materials, where their joint effects
govern unconventional transport, phase transitions, and superconductivity. Here
we combine first-principles $e$-ph calculations with dynamical mean field
theory (DMFT) as a step toward a unified description of $e$-$e$ and $e$-ph
interactions in correlated materials. We compute the $e$-ph self-energy using
the DMFT electron Green's function, and combine it with the $e$-$e$ self-energy
from DMFT to obtain a Green's function including both interactions. This
approach captures the renormalization of quasiparticle dispersion and spectral
weight on equal footing. Using our method, we study the $e$-ph and $e$-$e$
contributions to the resistivity and spectral functions in the correlated metal
Sr$_2$RuO$_4$. In this material, our results show that $e$-$e$ interactions
dominate transport and spectral broadening in the temperature range we study
(50$-$310~K), while $e$-ph interactions are relatively weak and account for
only $\sim$10\% of the experimental resistivity. We also compute effective
scattering rates, and find that the $e$-$e$ interactions result in scattering
several times greater than the Planckian value $k_BT$, whereas $e$-ph
interactions are associated with scattering rates lower than $k_BT$. Our work
demonstrates a first-principles approach to combine electron dynamical
correlations from DMFT with $e$-ph interactions in a consistent way, advancing
quantitative studies of correlated materials.",2304.06771v2
2011-07-13,SDW transition of Fe1 zigzag chains and metamagnetic transition of Fe2 in TaFe$_{1+y}$Te$_3$,"We systematically study the AFM order of Fe1 zigzag chains and spin-flop of
excess Fe2 under high magnetic field H through the susceptibility,
magnetoresistance (MR), Hall effect and specific heat measurements in
high-quality single crystal TaFe$_{1+y}$Te$_3$. These properties suggest that
the high temperature AFM transition of the TaFeTe$_3$ layers should be a
SDW-type AFM order. Below T$_N$, Fe1 antiferromangetic zigzag chains will
induce a inner magnetic field \textbf{H$_{int}$} to interstitial Fe2 and lead
Fe2 also forms an AFM alignment, in which the magnetic coupling strength
between Fe1 and Fe2 is enhanced by decreasing temperature. On the other hand,
the external magnetic field \textbf{H$_{ext}$} inclines to tune interstitial
Fe2 to form FM alignment along \textbf{H$_{ext}$}. When \textbf{H$_{ext}$}
arrives at the ""coercive"" field H$_C$, which is able to break the coupling
between Fe1 and Fe2, these interstitial Fe2 atoms take a spin-flop from AFM to
FM alignment. The local moment of Fe2 is about 4 $\mu_{\textrm{B}}$/Fe. From
low field ($<$H$_C$) AFM to high field ($>$H$_C$) FM for Fe2, it also induces
sharp drop on resistivity and an anomalous Hall effect. The possible magnetic
structure of TaFe$_{1+y}$Te$_3$ is proposed from the susceptibility and MR. The
properties related to the spin-flop of Fe2 supply a good opportunity to study
the coupling between Fe1 and Fe2 in these TaFe$_{1+y}$Te$_3$ or Fe$_{1+y}$Te
with interstitial Fe2 compounds.",1107.2561v1
2012-05-06,Free-Electron Laser-Powered Electron Paramagnetic Resonance Spectroscopy,"Electron paramagnetic resonance (EPR) spectroscopy interrogates unpaired
electron spins in solids and liquids to reveal local structure and dynamics;
for example, EPR has elucidated parts of the structure of protein complexes
that have resisted all other techniques in structural biology. EPR can also
probe the interplay of light and electricity in organic solar cells and
light-emitting diodes, and the origin of decoherence in condensed matter, which
is of fundamental importance to the development of quantum information
processors. Like nuclear magnetic resonance (NMR), EPR spectroscopy becomes
more powerful at high magnetic fields and frequencies, and with excitation by
coherent pulses rather than continuous waves. However, the difficulty of
generating sequences of powerful pulses at frequencies above 100 GHz has, until
now, confined high-power pulsed EPR to magnetic fields of 3.5 T and below. Here
we demonstrate that ~1 kW pulses from a free-electron laser (FEL) can power a
pulsed EPR spectrometer at 240 GHz (8.5 T), providing transformative
enhancements over the alternative, a state-of-the-art ~30 mW solid state
source. Using the UC Santa Barbara FEL as a source, our 240 GHz spectrometer
can rotate spin-1/2 electrons through pi/2 in only 6 ns (vs. 300 ns with the
solid state source). Fourier transform EPR on nitrogen impurities in diamond
demonstrates excitation and detection of EPR lines separated by ~200 MHz.
Decoherence times for spin-1/2 systems as short as 63 ns are measured, enabling
measurement of the decoherence time in a frozen solution of nitroxide
free-radicals at temperatures as high as 190 K. Both FELs and the quasi-optical
technology developed for the spectrometer are scalable to frequencies well in
excess of 1 THz, opening the possibility of high-power pulsed EPR spectroscopy
up to the highest static magnetic fields on earth.",1205.1186v1
2014-02-10,Development of CMOS pixel sensors for tracking and vertexing in high energy physics experiments,"CMOS pixel sensors (CPS) represent a novel technological approach to building
charged particle detectors. CMOS processes allow to integrate a sensing volume
and readout electronics in a single silicon die allowing to build sensors with
a small pixel pitch ($\sim 20 \mu m$) and low material budget ($\sim 0.2-0.3\%
X_0$) per layer. These characteristics make CPS an attractive option for
vertexing and tracking systems of high energy physics experiments. Moreover,
thanks to the mass production industrial CMOS processes used for the
manufacturing of CPS the fabrication construction cost can be significantly
reduced in comparison to more standard semiconductor technologies. However, the
attainable performance level of the CPS in terms of radiation hardness and
readout speed is mostly determined by the fabrication parameters of the CMOS
processes available on the market rather than by the CPS intrinsic potential.
  The permanent evolution of commercial CMOS processes towards smaller feature
sizes and high resistivity epitaxial layers leads to the better radiation
hardness and allows the implementation of accelerated readout circuits. The
TowerJazz $0.18 \mu m$ CMOS process being one of the most relevant examples
recently became of interest for several future detector projects. The most
imminent of these project is an upgrade of the Inner Tracking System (ITS) of
the ALICE detector at LHC. It will be followed by the Micro-Vertex Detector
(MVD) of the CBM experiment at FAIR. Other experiments like ILD consider CPS as
one of the viable options for flavour tagging and tracking sub-systems.",1402.2172v1
2020-04-23,SENSEI: Direct-Detection Results on sub-GeV Dark Matter from a New Skipper-CCD,"We present the first direct-detection search for eV-to-GeV dark matter using
a new ~2-gram high-resistivity Skipper-CCD from a dedicated fabrication batch
that was optimized for dark-matter searches. Using 24 days of data acquired in
the MINOS cavern at the Fermi National Accelerator Laboratory, we measure the
lowest rates in silicon detectors of events containing one, two, three, or four
electrons, and achieve world-leading sensitivity for a large range of sub-GeV
dark matter masses. Data taken with different thicknesses of the detector
shield suggest a correlation between the rate of high-energy tracks and the
rate of single-electron events previously classified as ""dark current."" We
detail key characteristics of the new Skipper-CCDs, which augur well for the
planned construction of the ~100-gram SENSEI experiment at SNOLAB.",2004.11378v3
2018-12-04,Superconductivity at 250 K in lanthanum hydride under high pressures,"The discovery of superconductivity at 203 K in H3S brought attention back to
conventional superconductors whose properties can be described by the
Bardeen-Cooper-Schrieffer (BCS) and the Migdal-Eliashberg theories. These
theories predict that high, and even room temperature superconductivity (RTSC)
is possible in metals possessing certain favorable parameters such as lattice
vibrations at high frequencies. However, these general theories do not suffice
to predict real superconductors. New superconducting materials can be predicted
now with the aid of first principles calculations based on Density Functional
Theory (DFT). In particular, the calculations suggested a new family of
hydrides possessing a clathrate structure, where the host atom (Ca, Y, La) is
at the center of the cage formed by hydrogen atoms. For LaH10 and YH10
superconductivity, with critical temperatures Tc ranging between 240 and 320 K
is predicted at megabar pressures. Here, we report superconductivity with a
record Tc ~ 250 K within the Fm-3m structure of LaH10 at a pressure P ~ 170
GPa. We proved the existence of superconductivity at 250 K through the
observation of zero-resistance, isotope effect, and the decrease of Tc under an
external magnetic field, which suggests an upper critical magnetic field of 120
T at zero-temperature. The pressure dependence of the transition temperatures
Tc (P) has a maximum of 250-252 K at the pressure of about 170 GPa. This leap,
by ~ 50 K, from the previous Tc record of 203 K indicates the real possibility
of achieving RTSC (that is at 273 K) in the near future at high pressures and
the perspective of conventional superconductivity at ambient pressure.",1812.01561v1
2021-09-18,Microstructural engineering of medium entropy NiCo(CrAl) alloy for enhanced room and high-temperature mechanical properties,"This work demonstrates the development of a strong and ductile medium entropy
alloy by employing conventional alloying and thermomechanical processing to
induce partial recrystallization (PR) and precipitation strengthening in the
microstructure. The combined usage of electron microscopy and atom probe
tomography reveals the sequence of microstructural evolution during the
process. First, the cold working of homogenized alloy resulted in a highly
deformed microstructure. On annealing at 700{\deg}C, B2 ordered precipitates
heterogeneously nucleate on the highly misoriented sites. These B2 promotes
particle stimulated nucleation (PSN) of new recrystallized strain-free grains.
The migration of recrystallized grain boundaries leads to discontinuous
precipitation of L12 ordered regions in highly dense lamellae structures.
Atomic-scale compositional analysis reveals a significant amount of Ni confined
to the GB regions between B2 and L12 precipitates, indicating Ni as a
rate-controlling element for coarsening the microstructure. On 20 hours of
annealing, the alloy comprises a composite microstructure of soft
recrystallized and hard non-recrystallized zones, B2 particles at the grain
boundaries (GBs), and coherent L12 precipitates inside the grains. The B2 pins
the GB movement during recrystallization while the latter provides high
strength. The microstructure results in a 0.2% yield stress (YS) value of 1030
MPa with 32% elongation at ambient temperature and retains up to 910 MPa at
670{\deg}C. Also, it shows exceptional microstructural stability at 700 {\deg}C
and resistance to deformation at high temperatures up to 770{\deg}C.
Examination of deformed microstructure reveals excessive twinning, formation of
stacking faults, shearing of L12 precipitates, and accumulation of dislocations
at around the B2 precipitates and GBs attributed to high strain hardening of
the alloy.",2109.08894v3
2022-10-07,Fast time-domain current measurement for quantum dot charge sensing using a homemade cryogenic transimpedance amplifier,"We developed a high-speed and low-noise time-domain current measurement
scheme using a homemade GaAs high-electron-mobility-transistor-based cryogenic
transimpedance amplifier (TIA). The scheme is versatile for broad cryogenic
current measurements, including semiconductor spin-qubit readout, owing to the
TIA's having low input impedance comparable to that of commercial
room-temperature TIAs. The TIA has a broad frequency bandwidth and a low noise
floor, with a trade-off between them governed by the feedback resistance
$R_{FB}$. A lower $R_{FB}$ of 50 k$\Omega$ enables high-speed current
measurement with a -3dB cutoff frequency $f_{-3dB}$ = 28 MHz and noise-floor
$NF = 8.5 \times 10^{-27}$ A$^{2}$/Hz, while a larger $R_{FB}$ of 400 k$\Omega$
provides low-noise measurement with $NF = 1.0 \times 10^{-27}$ A$^{2}$/Hz and
$f_{-3dB}$ = 4.5 MHz. Time-domain measurement of a 2-nA peak-to-peak square
wave, which mimics the output of the standard spin-qubit readout technique via
charge sensing, demonstrates a signal-to-noise ratio (SNR) of 12.7, with the
time resolution of 48 ns, for $R_{FB}$ = 200 k$\Omega$, which compares
favorably with the best-reported values for the radio-frequency (RF)
reflectometry technique. The time resolution can be further improved at the
cost of the SNR (or vice versa) by using an even smaller (larger) $R_{FB}$,
with a further reduction in the noise figure possible by limiting the frequency
band with a low-pass filter. Our scheme is best suited for readout electronics
for cryogenic sensors that require a high time resolution and current
sensitivity and thus provides a solution for various fundamental research and
industrial applications.",2210.03333v1
2001-03-20,Fully dense MgB_2 superconductor textured by hot deformation,"Bulk textured MgB_2 material of nearly full density showing a weak c-axis
alignment of the hexagonal MgB_2 grains parallel to the pressure direction was
obtained by hot deformation of a stoichiometric MgB_2 pellet prepared by a
gas-solid reaction. The texture of the material was verified by comparing the
x-ray diffraction patterns of the hot deformed material with isotropic MgB_2
powder. A small, but distinct anisotropy of the upper critical field up to
Hc2^{a,b}/Hc2^{c}~1.2 depending on degree of texture was found by resistance
and susceptibility measurements. No anisotropy of the critical current density
determined from magnetization measurements was found for the textured material.",0103408v2
2004-11-22,Quantized Failure Criteria and Indirect Observation for Predicting the Nanoscale Strength of Materials: The Example of the Ultra Nano Crystalline Diamond,"In this paper theoretical and statistical/experimental criteria for
determining the nanoscale strength of materials are proposed. In particular,
quantized criteria in fracture mechanics, dynamic fracture mechanics and
fatigue, as well as an experimental indirect observation of the nanoscale
strength, are proposed. The increasing of the dynamic resistance and the role
of a fractal crack surface formation are also rationalized. The analysis shows
that materials can be sensitive to flaws also at nanoscale (as demonstrated for
carbon nanotubes), in contrast to the conclusion of a recently published paper,
and that the surfaces are weaker than the inner parts of a solid by a factor of
about 10%. In addition, the proposed statistical/experimental procedure is
applied for predicting the nanoscale strength of the ultrananocrystalline
diamond (UNCD), an innovative material only recently developed.",0411556v1
2010-08-05,Evaluation of the acoustic and non-acoustic properties of sound absorbing materials using a three-microphone impedance tube,"This paper presents a straightforward application of an indirect method based
on a three-microphone impedance tube setup to determine the non-acoustic
properties of a sound absorbing porous material. First, a three-microphone
impedance tube technique is used to measure some acoustic properties of the
material (i.e., sound absorption coefficient, sound transmission loss,
effective density and effective bulk modulus) regarded here as an equivalent
fluid. Second, an indirect characterization allows one to extract its
non-acoustic properties (i.e., static airflow resistivity, tortuosity, viscous
and thermal characteristic lengths) from the measured effective properties and
the material open porosity. The procedure is applied to four different sound
absorbing materials and results of the characterization are compared with
existing direct and inverse methods. Predictions of the acoustic behavior using
an equivalent fluid model and the found non-acoustic properties are in good
agreement with impedance tube measurements.",1008.0975v1
2011-02-20,Intrinsic Correlation between Hardness and Elasticity in Polycrystalline Materials and Bulk Metallic Glasses,"Though extensively studied, hardness, defined as the resistance of a material
to deformation, still remains a challenging issue for a formal theoretical
description due to its inherent mechanical complexity. The widely applied
Teter's empirical correlation between hardness and shear modulus has been
considered to be not always valid for a large variety of materials. Here,
inspired by the classical work on Pugh's modulus ratio, we develop a
theoretical model which establishes a robust correlation between hardness and
elasticity for a wide class of materials, including bulk metallic glasses, with
results in very good agreement with experiment. The simplified form of our
model also provides an unambiguous theoretical evidence for Teter's empirical
correlation.",1102.4063v1
2014-07-05,Large-scale BN tunnel barriers for graphene spintronics,"We have fabricated graphene spin-valve devices utilizing scalable materials
made from chemical vapor deposition (CVD). Both the spin-transporting graphene
and the tunnel barrier material are CVD-grown. The tunnel barrier is realized
by h-BN, used either as a monolayer or bilayer and placed over the graphene.
Spin transport experiments were performed using ferromagnetic contacts
deposited onto the barrier. We find that spin injection is still greatly
suppressed in devices with a monolayer tunneling barrier due to resistance
mismatch. This is, however, not the case for devices with bilayer barriers. For
those devices, a spin relaxation time of 260 ps intrinsic to the CVD graphene
material is deduced. This time scale is comparable to those reported for
exfoliated graphene, suggesting that this CVD approach is promising for
spintronic applications which require scalable materials.",1407.1439v1
2017-02-16,Large elastic recovery of zinc dicyanoaurate,"We report the mechanical properties of the `giant' negative compressibility
material zinc(II) dicyanoaurate, as determined using a combination of
single-crystal nanoindentation measurements and \emph{ab initio} density
functional theory calculations. While the elastic response of zinc
dicyanoaurate is found to be intermediate to the behaviour of dense and open
framework structures, we discover the material to exhibit a particularly strong
elastic recovery, which is advantageous for a range of practical applications.
We attribute this response to the existence of supramolecular helices that
function as atomic-scale springs, storing mechanical energy during compressive
stress and hence inhibiting plastic deformation. Our results are consistent
with the relationship noted in [Cheng \& Cheng, \textit{Appl. Phys. Lett.},
1998, {\textbf{73}}, 614] between the magnitude of elastic recovery, on the one
hand, and the ratio of material hardness to Young's modulus, on the other hand.
Drawing on comparisons with other metal--organic frameworks containing helical
structure motifs, we suggest helices as an attractive supramolecular motif for
imparting resistance to plastic deformation in the design of functional
materials.",1702.05145v1
2018-06-19,Hydrodynamic Phonon Transport Perpendicular to Diffuse-Gray Boundaries,"In this paper, we examine the application of an ideal phonon-hydrodynamic
material as the heat transfer medium between two non-hydrodynamic contacts with
a finite temperature difference. We use the integral-equation approach to solve
a modified phonon Boltzmann transport equation with the displaced Bose-Einstein
distribution as the equilibrium distribution between two boundaries
perpendicular to the heat transfer direction. When the distance between the
boundaries is smaller than the phonon normal scattering mean free path, our
solution converges to the ballistic limit as expected. In the other limit, we
find that, although the local thermal conductivity in the bulk of the
hydrodynamic material approaches infinity, the thermal boundary resistance at
the hydrodynamic/non-hydrodynamic interfaces becomes dominant. Our study
provides insights to both the steady-state thermal characterization of
phonon-hydrodynamic materials and the practical application of
phonon-hydrodynamic materials for thermal management.",1806.07345v3
2019-08-26,One-pot synthesis: a simple and fast method to obtain ceramic superconducting materials,"The one-pot method focuses on the reduction of the number of steps or
chemical reactions in the synthesis of materials, and it is very appealing in
terms of sustainability. In addition to this point of view, superconductors are
desired materials due to their unusual properties, such as the zero resistivity
and the perfect diamagnetism. One-pot, Thus, in this work, we described the
one-pot synthesis of YBa2Cu3O7-{\delta} superconducting ceramic. In just two
steps and a few hours, a polymer composite solution was prepared, which
originates a powder after burning the polymer out with pure phase and with
superconducting properties better than those produced by other techniques.",1908.09923v1
2018-07-16,Tailoring Materials for Mottronics: Excess Oxygen Doping of a Prototypical Mott Insulator,"The Mott transistor is a paradigm for a new class of electronic
devices---often referred to by the term Mottronics---, which are based on
charge correlations between the electrons. Since correlation-induced insulating
phases of most oxide compounds are usually very robust, new methods have to be
developed to push such materials right to the boundary to the metallic phase in
order to enable the metal-insulator transition to be switched by electric
gating.
  Here we demonstrate that thin films of the prototypical Mott insulator
LaTiO$_3$ grown by pulsed laser deposition under oxygen atmosphere are readily
tuned by excess oxygen doping across the line of the band-filling controlled
Mott transition in the electronic phase diagram. The detected insulator to
metal transition is characterized by a strong change in resistivity of several
orders of magnitude. The use of suitable substrates and capping layers to
inhibit oxygen diffusion facilitates full control of the oxygen content and
renders the films stable against exposure to ambient conditions, making
LaTiO$_{3+x}$ a promising functional material for Mottronics devices.",1807.05724v1
2020-11-25,Reconstructing the thermal phonon transmission coefficient at solid interfaces in the phonon transport equation,"The ab initio model for heat propagation is the phonon transport equation, a
Boltzmann-like kinetic equation. When two materials are put side by side, the
heat that propagates from one material to the other experiences thermal
boundary resistance. Mathematically, it is represented by the reflection
coefficient of the phonon transport equation on the interface of the two
materials. This coefficient takes different values at different phonon
frequencies, between different materials. In experiments scientists measure the
surface temperature of one material to infer the reflection coefficient as a
function of phonon frequency. In this article, we formulate this inverse
problem in an optimization framework and apply the stochastic gradient descent
(SGD) method for finding the optimal solution. We furthermore prove the maximum
principle and show the Lipschitz continuity of the Fr\'echet derivative. These
properties allow us to justify the application of SGD in this setup.",2011.13047v2
2023-01-24,Using Arduino in Physics Experiments:Determining the Speed of Sound in Air,"Considering the 21st century skills and the importance of STEM education in
fulfilling these skills, it is clear that the course materials should be
materials that bring students together with technology and attract their
attention, apart from traditional materials. In addition, in terms of the
applicability of these materials, it is very important that the materials are
affordable and easily accessible. In this study two open ended resonance tube,
Computer and speaker for generate sound with different frequencies, Arduino
UNO, AR-054 Sound Sensor, Green LED and 220 ohm resistance were used for
measure the speed of sound in air at room tempature. With the help of sound
sensor, two consecutive harmonic frequency values were determined and the
fundamental frequency was calculated. Using the tube features and the
fundamental frequency value, the speed of sound propagation in the air at room
temperature was calculated as 386.42 m/s. This value is theoretically 346 m/s.
This study, in which the propagation speed of the sound is calculated with very
low cost and coding studies with 12% error margin, is important in terms of
hosting all STEM gains and can be easily applied in classrooms.",2301.10325v1
2023-09-14,Photo-induced reversible modification of the Curie-Weiss temperature in paramagnetic gadolinium compounds,"Gadolinium oxyhydride GdHO is a photochromic material that darkens under
illumination and bleaches back by thermal relaxation. As an inorganic
photochromic material that can be easily deposited by magnetron sputtering,
GdHO has very interesting potential applications as a functional material,
specially for smart glazing applications. However, the underlying reasons
behind the photochromic mechanism-which can be instrumental for the correct
optimisation of GdOH for different applications-are not completely understood.
In this paper, we rely on the well-stablished magnetic properties of Gd$^{3+}$
to shed light on this matter. GdOH thin films present paramagnetic behaviour
similar to other Gd$^{3+}$ compounds such as Gd$_2$O$_3$. Illumination of the
films result in a reversible increase of the Curie-Weiss temperature pointing
to RKKY interactions, which is consistent with the resistivity decrease
observed in the photo-darkened films.",2309.07978v1
2024-01-26,First-principles Methodology for studying magnetotransport in magnetic materials,"Unusual magnetotransport behaviors such as temperature dependent negative
magnetoresistance(MR) and bowtie-shaped MR have puzzled us for a long time.
Although several mechanisms have been proposed to explain them, the absence of
comprehensive quantitative calculations has made these explanations less
convincing. In our work, we introduce a methodology to study the
magnetotransport behaviors in magnetic materials. This approach integrates
anomalous Hall conductivity induced by Berry curvature, with a multi-band
ordinary conductivity tensor, employing a combination of first-principles
calculations and semi-classical Boltzmann transport theory. Our method
incorporates both the temperature dependency of relaxation time and anomalous
Hall conductivity, as well as the field dependency of anomalous Hall
conductivity. We initially test this approach on two-band models and then apply
it to a Weyl semimetal \CSS. The results, which align well with experimental
observations in terms of magnetic field and temperature dependencies,
demonstrate the efficacy of our approach. Additionally, we have investigated
the distinct behaviors of magnetoresistance (MR) and Hall resistivities across
various types of magnetic materials. This methodology provides a comprehensive
and efficient means to understand the underlying mechanisms of the unusual
behaviors observed in magneto-transport measurements in magnetic materials.",2401.15146v1
2024-03-29,Computational Shape Derivatives in Heat Conduction: An Optimization Approach for Enhanced Thermal Performance,"We analyze an optimization problem of the conductivity in a composite
material arising in a heat conduction energy storage problem. The model is
described by the heat equation that specifies the heat exchange between two
types of materials with different conductive properties with Dirichlet-Neumann
boundary conditions on the external part of the domain, and on the interface
characterized by the resisting coefficient between the highly conductive
material and the less conductive material. The main purpose of the paper is to
compute a shape gradient of an optimization functional in order to accurately
determine the optimal location of the conductive material using a classical
shape optimization strategy. We also present some numerical experiments to
illustrate the efficiency of the proposed method.",2403.20181v1
2002-05-30,Tunability of High-Dielectric-Constant Materials from First Principles,"A first-principles method, based on density functional perturbation theory,
is presented for computing the leading order tunability of
high-dielectric-constant materials.",0205655v1
2024-05-28,On the resistance regular graphs,"For a connected graph $G$, its resistance matrix is denoted by $R(G)$. If all
the row(column) sums of $R(G)$ are equal, then $G$ is said to be resistance
regular. In $[13]$, J. Zhou et al. posed the question regarding the existence
of a non-regular resistance regular graph. In this article, we establish that
all resistance regular graphs are regular, thus conclusively answering Zhou's
question by showing that no non-regular resistance regular graph exists. Also,
we compute the resistance energies of some resistance regular graphs.
Furthermore, we determine various bounds for the resistance energy and
resistance spectral radius of $G.$",2405.18177v1
2005-06-29,Galaxy formation and cosmic-ray acceleration in a magnetized universe,"We study the linear magneto-hydrodynamical behaviour of a Newtonian cosmology
with a viscous magnetized fluid of finite conductivity and generalise the Jeans
instability criterion. The presence of the field favors the anisotropic
collapse of the fluid, which in turn leads to further magnetic amplification
and to an enhanced current-sheet formation in the plane normal to the ambient
magnetic field. When the currents exceed a certain threshold, the resulting
electrostatic turbulence can dramatically amplify the resistivity of the medium
(anomalous resistivity). This could trigger strong electric fields and
subsequently the acceleration of ultra-high energy cosmic rays (UHECRs) during
the formation of protogalactic structures.",0506742v1
1998-10-21,Large scale instabilities in two-dimensional magnetohydrodynamics,"The stability of a sheared magnetic field is analyzed in two-dimensional
magnetohydrodynamics with resistive and viscous dissipation. Using a
multiple-scale analysis, it is shown that at large enough Reynolds numbers the
basic state describing a motionless fluid and a layered magnetic field, becomes
unstable with respect to large scale perturbations. The exact expressions for
eddy-viscosity and eddy-resistivity are derived in the nearby of the critical
point where the instability sets in. In this marginally unstable case the
nonlinear phase of perturbation growth obeys to a Cahn-Hilliard-like dynamics
characterized by coalescence of magnetic islands leading to a final new
equilibrium state. High resolution numerical simulations confirm quantitatively
the predictions of multiscale analysis.",9810026v1
1997-11-19,Intrinsic resistivity and the SO(5) theory of high-temperature superconductors,"The topological structure of the order parameter in Zhang's SO(5) theory of
superconductivity allows for an unusual type of dissipation mechanism via which
current-carrying states can decay. The resistivity due to this mechanism, which
involves orientation rather than amplitude order-parameter fluctuations, is
calculated for the case of a thin superconducting wire. The approach is a
suitably modified version of that pioneered by Langer and Ambegaokar for
conventional superconductors.",9711193v2
1998-05-22,reentrance effect in normal-metal/superconducting hybrid loops,"We have measured the transport properties of two mesoscopic hybrid loops
composed of a normal-metal arm and a superconducting arm. The samples differed
in the transmittance of the normal/superconducting interfaces. While the low
transmittance sample showed monotonic behavior in the low temperature
resistance, magnetoresistance and differential resistance, the high
transmittance sample showed reentrant behavior in all three measurements. This
reentrant behavior is due to coherent Andreev reflection at the
normal/superconducting interfaces. We compare the reentrance effect for the
three different measurements and discuss the results based on the theory of
quasiclassical Green's functions.",9805298v1
1998-12-20,"Comment on ""Charged impurity scattering limited low temperature resistivity of low density silicon inversion layers"" (Das Sarma and Hwang, cond-mat/9812216)","In a recent preprint cond-mat/9812216, Das Sarma and Hwang propose an
explanation of the sharp decrease in resistivity at low temperatures which has
been attributed to a transition to an unexpected conducting phase in dilute
high-mobility two-dimensional systems at B=0. In this Comment, we examine
whether their model is supported by the available experimental data.",9812331v1
1999-02-24,Charge Relaxation and Dephasing in Coulomb Coupled Conductors,"The dephasing time in coupled mesoscopic conductors is caused by the
fluctuations of the dipolar charge permitted by the long range Coulomb
interaction. We relate the phase breaking time to elementary transport
coefficients which describe the dynamics of this dipole: the capacitance, an
equilibrium charge relaxation resistance and in the presence of transport
through one of the conductors a non-equilibrium charge relaxation resistance.
The discussion is illustrated for a quantum point contact in a high magnetic
field in proximity to a quantum dot.",9902320v1
1999-03-31,Apparent Metallic Behavior at B = 0 of a two-dimensional electron system in AlAs,"We report the observation of metallic-like behavior at low temperatures and
zero magnetic field in two dimensional (2D) electrons in an AlAs quantum well.
At high densities the resistance of the sample decreases with decreasing
temperature, but as the density is reduced the behavior changes to insulating,
with the resistance increasing as the temperature is decreased. The effect is
similar to that observed in 2D electrons in Si-MOSFETs, and in 2D holes in SiGe
and GaAs, and points to the generality of this phenomenon.",9903443v1
1999-04-05,Spin Degree of Freedom in a Two-Dimensional Electron Liquid,"We have investigated correlation between spin polarization and
magnetotransport in a high mobility silicon inversion layer which shows the
metal-insulator transition. Increase in the resistivity in a parallel magnetic
field reaches saturation at the critical field for the full polarization
evaluated from an analysis of low-field Shubnikov-de Haas oscillations. By
rotating the sample at various total strength of the magnetic field, we found
that the normal component of the magnetic field at minima in the diagonal
resistivity increases linearly with the concentration of ``spin-up'' electrons.",9904058v1
1999-06-17,Systematic Evolution of the Magnetotransport Properties of Bi_{2}Sr_{2-x}La_{x}CuO_{6} with Carrier Concentration,"We report that it is possible to obtain a series of high-quality crystals of
La-doped Bi-2201, of which the transport properties have been believed to be
""dirtier"" than those of other cuprates. In our crystals, the normal-state
transport properties display behaviors which are in good accord with other
cuprates; for example, in the underdoped region the in-plane resistivity
\rho_{ab} shows the pseudogap feature and in the overdoped region the T
dependence of \rho_{ab} changes to T^n with n > 1. The characteristic
temperatures of the pseudogap deduced from the resistivity and the Hall
coefficient data are presented.",9906268v1
2000-02-08,Negative Pressure of Anisotropic Compressible Hall States : Implication to Metrology,"Pressure, compressibility, and Hall conductance of anisotropic states at
higher Landau levels are computed. Pressure and compressibility become
negative. Hall conductance is unquantized and varies with filling factor. These
facts agree with the recent experimental observations of highly anisotropic
compressible states at higher Landau levels. It is shown, as an implication of
negative pressure, that the quantum Hall effect has extraordinary stability,
that is, Hall resistance is quantized even when the longitudinal resistance
does not vanish.",0002108v3
2000-12-08,"Pressure, Resistance, and Current Activation of Anisotropic Compressible Hall States","Thermodynamic and electric properties of anisotropic compressible Hall states
at higher Landau levels are studied using a mean field theory on the von
Neumann lattice basis. It is shown that resistances agree with the recent
experiments of anisotropic compressible states and the states have negative
pressure. As implications, the collapse phenomena of the integer quantum Hall
effect are discussed.",0012133v1
2001-07-03,Scaling Behavior of Anomalous Hall Effect and Longitudinal Nonlinear Response in High-Tc Superconductors,"Based on existing theoretical model and by considering our longitudinal
nonlinear response function, we derive a nonliear equation in which the mixed
state Hall resistivity can be expressed as an analytical function of magnetic
field, temperature and applied current. This equation enables one to compare
quantitatively the experimental data with theoretical model. We also find some
new scaling relations of the temperature and field dependency of Hall
resistivity. The comparison between our theoretical curves and experimental
data shows a fair agreement.",0107045v1
2001-07-06,"Current-Driven Conformational Changes, Charging and Negative Differential Resistance in Molecular Wires","We introduce a theoretical approach based on scattering theory and total
energy methods that treats transport non-linearities, conformational changes
and charging effects in molecular wires in a unified way. We apply this
approach to molecular wires consisting of chain molecules with different
electronic and structural properties bonded to metal contacts. We show that
non-linear transport in all of these systems can be understood in terms of a
single physical mechanism and predict that negative differential resistance at
high bias should be a generic property of such molecular wires.",0107147v1
2001-07-17,Analysis of the resistance in p-SiGe over a wide temperature range,"The temperature dependence of a system exhibiting a `metal-insulator
transition in two dimensions at zero magnetic field' (MIT) is studied up to
90K. Using a classical scattering model we are able to simulate the
non-monotonic temperature dependence of the resistivity in the metallic high
density regime. We show that the temperature dependence arises from a complex
interplay of metallic and insulating contributions contained in the calculation
of the scattering rate $1/\td(E,T)$, each dominating in a limited temperature
range.",0107369v1
2001-09-27,Enhanced paramagnetism of the 4d itinerant electrons in the rhodium oxide perovskite SrRhO3,"Polycrystalline rhodium(IV) oxide perovskite SrRhO3 was obtained by
high-pressure synthesis techniques, followed by measurements of the magnetic
susceptibility, electrical resistivity, and specific heat. The title compound
has five 4d-electrons per perovskite unit and shows Fermi-liquid behavior in
its electrical resistivity. The magnetic susceptibility is large [chi(300K)
\~1.1*10^{-3} emu/mol-Rh] and proportional to 1/T^2 (< 380 K), while there is
no magnetic long-range order above 1.8 K. The specific heat measurements
indicate a probable magnetic contribution below ~ 15 K, which is not predicted
by the self-consistent renormalization theory of spin fluctuations for both
antiferro- and ferromagnetic 3D nearly-ordered metals.",0109522v2
2001-12-20,Fluctuation induced hopping and spin polaron transport,"We study the motion of free magnetic polarons in a paramagnetic background of
fluctuating local moments. The polaron can tunnel only to nearby regions of
local moments when these fluctuate into alignment. We propose this fluctuation
induced hopping as a new transport mechanism for the spin polaron. We calculate
the diffusion constant for fluctuation induced hopping from the rate at which
local moments fluctuate into alignment. The electrical resistivity is then
obtained via the Einstein relation. We suggest that the proposed transport
mechanism is relevant in the high temperature phase of the Mn pyrochlore
colossal magneto resistance compounds and Europium hexaboride.",0112385v1
2002-11-27,Indications of coherence-incoherence crossover in layered transport,"For many layered metals the temperature dependence of the interlayer
resistance has a different behavior than the intralayer resistance. In order to
better understand interlayer transport we consider a concrete model which
exhibits this behavior. A small polaron model is used to illustrate how the
interlayer transport is related to the coherence of quasi-particles within the
layers. Explicit results are given for the electron spectral function,
interlayer optical conductivity and the interlayer magnetoresistance. All these
quantities have two contributions: one coherent (dominant at low temperatures)
and one incoherent (dominant at high temperatures).",0211612v1
2002-11-28,Small polarons and c-axis transport in highly anisotropic metals,"Motivated by the anomalous c-axis transport properties of the quasi
two-dimensional metal, $\rm Sr_2 Ru O_4$, and related compounds, we have
studied the interlayer hopping of single electrons that are coupled strongly to
c-axis bosons. We find a c-axis resistivity that reflects the in-plane
electronic scattering in the low and very high temperature limits (relative to
the characteristic temperature of the boson $T_{\rm boson}$). For temperatures
near the $T_{\rm boson}$, a broad maximum in the resistivity can appear for
sufficiently strong electron-boson coupling. This feature may account for the
observed ``metallic to non-metallic crossover'' seen in these layered oxides,
where the boson may be a phonon.",0211675v1
2003-05-01,Negative differential resistance due to the resonance coupling of a quantum-dot dimer,"Electron tunneling through a coupled quantum-dot dimer under a dc-bias is
investigated. We find that a peak in the $I$-$V$ curve appears at low
temperature when two discrete electronic states in the two quantum dots are
aligned with each other -- resonance coupling. This leads to a negative
differential resistance. The peak height and width depend on the dot-dot
coupling. At high temperature, the peak disappears due to thermal smearing
effects.",0305018v1
2003-08-06,Measuring thermal conductivity in extreme conditions: sub-Kelvin temperatures and high (27 T) magnetic fields,"We present a one-heater-two-thermometer set-up for measuring thermal
conductivity and electric resistivity of a bulk sample at low temperatures down
to 0.1 K and in magnetic fields up to 27 Tesla. The design overcomes the
difficulties emerging in the context of large water-cooled resistive magnets.",0308106v1
2003-09-29,Fluxon dynamics by microwave surface resistance measurements in MgB2,"Field-induced variations of the microwave surface resistance, Rs(H), have
been investigated in high-density ceramic MgB2. At low temperatures, several
peculiarities of the Rs(H) curves cannot be justified in the framework of
models reported in the literature. We suggest that they are ascribable to the
unconventional vortex structure in MgB2, related to the presence of two gaps.
On the contrary, the results near Tc can be accounted for by the Coffey and
Clem model, with fluxons moving in the flux-flow regime, provided that the
anisotropy of the upper critical field is taken into due account.",0309654v1
2003-10-20,Evidence for a quantum phase transition in the electron-doped cuprate Pr2-xCexCuO4+d from Hall and resistivity measurements,"The doping and temperature dependence of the Hall coefficient, RH, and
ab-plane resistivity in the normal state down to 350mK is reported for oriented
films of the electron-doped high-Tc superconductor Pr2-xCexCuO4+d. The doping
dependence of b (r=r0+AT^b) and R_sub_H (at 350 mK) suggest a quantum phase
transition at a critical doping near x=0.165.",0310475v2
2004-01-15,Plasmon assisted transport through disordered array of quantum wires,"Phononless plasmon assisted thermally activated transport through a long
disordered array of finite length quantum wires is investigated analytically.
Generically strong electron plasmon interaction in quantum wires results in a
qualitative change of the temperature dependence of thermally activated
resistance in comparison to phonon assisted transport. At high temperatures,
the thermally activated resistance is determined by the Luttinger liquid
interaction parameter of the wires.",0401274v2
2004-01-26,Vanishing Hall Resistance at High Magnetic Field in a Double Layer Two-Dimensional Electron System,"At total Landau level filling factor $\nu_{tot}=1$ a double layer
two-dimensional electron system with small interlayer separation supports a
collective state possessing spontaneous interlayer phase coherence. This state
exhibits the quantized Hall effect when equal electrical currents flow in
parallel through the two layers. In contrast, if the currents in the two layers
are equal, but oppositely directed, both the longitudinal and Hall resistances
of each layer vanish in the low temperature limit. This finding supports the
prediction that the ground state at $\nu_{tot}=1$ is an excitonic superfluid.",0401521v1
2004-07-06,Spin characterization and control over the regime of radiation-induced zero-resistance states,"Over the regime of the radiation-induced zero-resistance states and
associated oscillatory magnetoresistance, we propose a low magnetic field
analog of quantum-Hall-limit techniques for the electrical detection of
electron spin- and nuclear magnetic- resonance, dynamical nuclear polarization
via electron spin resonance, and electrical characterization of the nuclear
spin polarization via the Overhauser shift. In addition, beats observed in the
radiation-induced oscillatory-magnetoresistance are developed into a method to
measure and control the zero-field spin splitting due to the Bychkov-Rashba and
bulk inversion asymmetry terms in the high mobility GaAs/AlGaAs system.",0407143v1
2004-08-03,Electrical resistivity and tunneling anomalies in CeCuAs2,"The compound CeCuAs2 is found to exhibit negative temperature (T) coefficient
of electrical resistivity (rho) under ambient pressure conditions in the entire
T-range of investigation (45 mK to 300 K), even in the presence of high
magnetic fields. Preliminary tunneling spectroscopic measurements indicate the
existence of a psuedo-gap at least at low temperatures, thereby implying that
this compound could be classified as a Kondo semi-conductor, though rho(T)
interestingly is not found to be of an activated type.",0408060v1
2005-01-05,Radiation-induced zero-resistance states with resolved Landau levels,"The microwave-photoexcited high mobility GaAs/AlGaAs two-dimensional electron
system exhibits an oscillatory-magnetoresistance with vanishing resistance in
the vicinity of magnetic fields $B = [4/(4j+1)] B_{f}$, where $B_{f} =
2\pi\textit{f}m^{*}/e$, m$^{*}$ is an the effective mass, e is the charge,
\textit{f} is the microwave frequency, and $j$ =1,2,3... Here, we report
transport with well-resolved Landau levels, and some transmission
characteristics.",0501091v1
2005-01-21,Metallic behavior in Si/SiGe 2D electron systems,"We calculate the temperature, density, and parallel magnetic field dependence
of low temperature electronic resistivity in 2D high-mobility Si/SiGe quantum
structures, assuming the conductivity limiting mechanism to be carrier
scattering by screened random charged Coulombic impurity centers. We obtain
comprehensive agreement with existing experimental transport data, compellingly
establishing that the observed 2D metallic behavior in low-density Si/SiGe
systems arises from the peculiar nature of 2D screening of long-range impurity
disorder. In particular, our theory correctly predicts the experimentally
observed metallic temperature dependence of 2D resistivity in the fully
spin-polarized system.",0501531v1
2005-05-10,Variable resistance at the boundary between semimetal and excitonic insulator,"We solve the two-band model for the transport across a junction between a
semimetal and an excitonic insulator. We analyze the current in terms of two
competing terms associated with neutral excitons and charged carriers,
respectively. We find a high value for the interface resistance, extremely
sensitive to the junction transparency. We explore favorable systems for
experimental confirmation.",0505247v1
2006-02-18,Anomalous Flux Pinning in ?-Pyrochlore Oxide Superconductor KOs2O6,"The superconducting transition of the ?-pyrochlore oxide KOs2O6 with Tc =
9.60 K is studied by resistivity measurements under various magnetic fields
using a high-quality single crystal. The reentrant behavior of
superconductivity is observed near Tc in low magnetic fields below 2 T. The
recovered resistance probably due to flux flow exhibits an anomalous angle
dependence, indicating that flux pinning is enhanced in magnetic fields along
certain crystallographic directions such as [110], [001] and [112]. It is
suggested that there is an intrinsic pinning mechanism coming from the specific
crystal structure of the ?-pyrochlore oxide.",0602433v1
2006-03-30,Joule heating induced negative differential resistance in free standing metallic carbon nanotubes,"The features of the $IV$ characteristics of metallic carbon nanotubes (m-NTs)
in different experimental setups are studied using semi-classical Boltzmann
transport equation together with the heat dissipation equation to account for
significant thermal effects at high electric bias. Our model predicts that the
shape of the m-NT characteristics is basically controlled by heat removal
mechanisms. In particular we show that the onset of negative differential
resistance in free standing nanotubes finds its origins in strong transport
nonlinearities associated with poor heat removal unlike in substrate-supported
nanotubes.",0603831v1
2007-03-27,Resistively shunted Josephson junctions: QFT predictions versus MC results,"During the last fourteen years several exact results were obtained for the
so-called boundary sine-Gordon model. In the case of a conformal bulk this 2D
boundary quantum field theory describes the universal scaling behavior of the
Caldeira-Leggett model of resistively shunted Josephson junctions. In this
work, we use a recently developed Monte Carlo technique to test some of the
analytical predictions.",0703712v2
1994-02-14,Fractal Dimension of Gauge-fixing Defects,"The fractal dimension $D_f$ of sites resisting Landau or maximal Abelian(MA)
gauge fixing in lattice $SU(3)$ gluodynamics is defined and computed. In Landau
gauge such sites clump into $D_f\sim 1$ clusters in the confining phase. In the
finite temperature phase their dimensionality drops to $D_f < 1$, that is,
clustering seems to dissipate. In contrast, MA gauge resistant sites fail to
exhibit a notable tendency to cluster at any temperature.",9402009v2
2002-07-09,Body Motion in a Resistive Medium at Temperature T,"We consider a macroscopic body propagating in a one-dimensional resistive
medium, consisting of an ideal gas at temperature $T$. For a whole family of
collisions with varying degree of inelasticity, we find an exact expression for
the effective force on the moving body as a function of the body's speed and
the value of the restitution coefficient. At low and high speeds it reduces to
the well-known Stoke's and Newton's law, respectively.",0207037v1
2002-11-29,Resistive plate chambers for time-of-flight measurements,"The applications of Resistive Plate Chambers (RPCs) have recently been
extended by the development of counters with time resolution below 100 ps sigma
for minimum ionising particles. Applications to HEP experiments have already
taken place and many further applications are under study. In this work we
address the operating principles of such counters along with some present
challenges, with emphasis on counter aging.",0211120v1
2007-05-04,Simultaneous recording of two- and four-probe resistive transitions in doped laser-processed Sr-Ru-O,"To confirm previously reported evidence of high-temperature superconductivity
in laser processed Sr-Ru-O, we performed simultaneous two-probe and four-probe
resistive measurements using bar-geometry samples. A superconducting-type
transition with an onset at about 250K was recorded in one of the samples,
consistent with our previously reported measurements in the X-bridge geometry.
Some compositional details of the samples are also provided which were not
known at the time of previous web-publication.",0705.0641v1
2007-07-18,"Synchnonization, zero-resistance states and rotating Wigner crystal","We show that rotational angles of electrons moving in two dimensions (2D) in
a perpendicular magnetic field can be synchronized by an external microwave
field which frequency is close to the Larmor frequency. The synchronization
eliminates collisions between electrons and thus creates a regime with zero
diffusion corresponding to the zero-resistance states observed in experiments
with high mobility 2D electron gas (2DEG). For long range Coulomb interactions
electrons form a rotating hexagonal Wigner crystal. Possible relevance of this
effect for planetary rings is discussed.",0707.2694v1
2007-11-06,Plasmon phenomena as origin of DC-current induced resistivity oscillations in two-dimensional electron systems,"We analyze theoretically the oscillations that the magnetoresistivity of
two-dimensional electron systems present when a high intensity direct current
is applied. In the model presented here we suggest that a plasma wave is
excited in the system producing an oscillating motion of the whole
two-dimensional electron gas at the plasma frequency. This scenario affects
dramatically the way that electrons interact with scatterers giving rise to
oscillations in the longitudinal resistivity. With this theoretical model
experimental results are well reproduced and explained.",0711.0927v1
2008-06-17,Electrical Resistivity and Specific Heat of EuFe2As2 Single Crystals: Magnetic homologue of SrFe2As2,"We have grown single crystals of EuFe2As2 and investigated its electrical
transport and thermodynamic properties. Electrical resistivity and specific
heat measurements clearly establish the intrinsic nature of magnetic phase
transitions at 20 K and 195 K. While the high temperature phase transition is
associated with the itinerant moment of Fe, the low temperature phase
transition is due to magnetic order of localized Eu-moments. Band structure
calculations point out a very close similarity of the electronic structure with
SrFe2As2. Magnetically, the Eu and Fe2As2 sublattice are nearly de-coupled.",0806.2876v2
2008-08-05,Suppression of Magnetic Order by Pressure in BaFe2As2,"We performed the dc resistivity and the ZF 75As-NMR measurement of BaFe2As2
under high pressure. The T-P phase diagram of BaFe2As2 determined from
resistivity anomalies and the ZF 75As-NMR clearly revealed that the SDW anomaly
is quite robust against P.",0808.0718v1
2008-10-14,Magnetic Field Induced Instabilities in Localised Two-Dimensional Electron Systems,"We report density dependent instabilities in the localised regime of
mesoscopic two-dimensional electron systems (2DES) with intermediate strength
of background disorder. They are manifested by strong resistance oscillations
induced by high perpendicular magnetic fields B_{\perp}. While the amplitude of
the oscillations is strongly enhanced with increasing B_{\perp}, their position
in density remains unaffected. The observation is accompanied by an unusual
behaviour of the temperature dependence of resistance and activation energies.
We suggest the interplay between a strongly interacting electron phase and the
background disorder as a possible explanation.",0810.2418v1
2009-08-02,Resistivity noise in crystalline magnetic nanowires and its implications to domain formation and kinetics,"We have investigated the time-dependent fluctuations in electrical
resistance, or noise, in high quality crystalline magnetic nanowires within
nanoporous templates. The noise increases exponentially with increasing
temperature and magnetic field, and has been analyzed in terms of domain wall
depinning within the Neel-Brown framework. The frequency-dependence of noise
also indicates a crossover from nondiffusive kinetics to long-range diffusion
at higher temperatures, as well as a strong collective depinning, which need to
be considered when implementing these nanowires in magnetoelectronic devices.",0908.0136v1
2010-07-07,Selfoscillations of Suspended Carbon Nanotubes with a Deflection Sensitive Resistance under Voltage Bias,"We theoretically investigate the electro-mechanics of a Suspended Carbon
Nanotube with a Deflection Sensitive Resistance subjected to a homogeneous
Magnetic Field and a constant Voltage Bias. We show that, (with the exception
of a singular case), for a sufficiently high magnetic field the
time-independent state of charge transport through the nanotube becomes
unstable to selfexcitations of the mechanical vibration accompanied by
oscialltions in the voltage drop and current across the nanotube.",1007.1139v1
2010-07-28,Inelastic contribution of the resistivity in the hidden order in URu2Si2,"In the hidden order of URu2Si2 the resistivity at very low temperature shows
no T^2 behavior above the transition to superconductivity. However, when
entering the antiferromagnetic phase, the Fermi liquid behavior is recovered.
We discuss the change of the inelastic term when entering the AF phase with
pressure considering the temperature dependence of the Grueneisen parameter at
ambient pressure and the influence of superconductivity by an extrapolation of
high field data.",1007.4905v1
2010-08-23,Field induced changes across magnetic compensation in Pr(1-x)Gd(x)Al(2) alloys,"The magnetic compensation phenomenon has been explored in the
Pr(1-x)Gd(x)Al(2) series. The contributions from Pr and Gd moments compensate
each other at a specific temperature in the ordered state (below (T(c)). At
high fields, the magnetic reorientation (with respect to the external field
direction) of the Pr and Gd moments appears as a minimum in the thermomagnetic
response. We demonstrate several interesting attributes related with the
magnetic reorienation phenomenon, viz., oscillatory behavior of the
magneto-resistance, sign change of the anamalous Hall resistivity, fingerprints
of field induced changes in the specific heat and ac-susceptibility data.",1008.3782v1
2011-01-14,Hall field-induced resistance oscillations in tilted magnetic fields,"We have studied the effect of an in-plane magnetic field on Hall
field-induced resistance oscillations in high mobility two-dimensional electron
systems. We have found that the oscillation frequency depends only on the
perpendicular component of the magnetic field but the oscillation amplitude
decays exponentially with an in-plane component. While these findings cannot be
accounted for by existing theories of nonlinear transport, our analysis
suggests that the decay can be explained by an in-plane magnetic field-induced
modification of the quantum scattering rate.",1101.2871v2
2011-02-24,Positive speed for high-degree automaton groups,"Mother groups are the basic building blocks for polynomial automaton groups.
We show that, in contrast with mother groups of degree 0 or 1, any bounded,
symmetric, generating random walk on the mother groups of degree at least 3 has
positive speed. The proof is based on an analysis of resistance in fractal
mother graphs. We give upper bounds on resistances in these graphs, and show
that infinite versions are tran- sient.",1102.4979v1
2011-03-09,An efficient multi-use multi-secret sharing scheme based on hash function,"In this paper, a renewable, multi-use, multi-secret sharing scheme for
general access structure based on one-way collision resistant hash function is
presented in which each participant has to carry only one share. By applying
collision-resistant one-way hash function, the proposed scheme is secure
against conspiracy attacks even if the pseudo-secret shares are compromised.
Moreover, high complexity operations like modular multiplication,
exponentiation and inversion are avoided to increase its efficiency. Finally,
in the proposed scheme, both the combiner and the participants can verify the
correctness of the information exchanged among themselves.",1103.1730v1
2011-05-28,Thermo-Resistive Instability in Magnetar Crusts,"We investigate a thermo-resistive instability in the outer crusts of
magnetars wherein a perturbation in temperature increases ohmic heating. We
show that magnetars of characteristic age {\tau}_{age} ~ 10^4 yr are unstable
over timescales as short as days if strong current sheets are present in the
outer crust. This instability could play an important role in the thermal and
magnetic field evolution of magnetars, and may be related to bursting activity
in magnetars.",1105.5712v1
2011-10-10,Non linear transport in drift-diffusion equations under magnetic field,"We analyze numerically and analytically the non linear transport properties
of a drift-diffusion equation in presence of a magnetic field and of a disorder
potential. For a wide range of parameters this model exhibits a plateau where
the drift velocity is almost independent on the applied electric field. This
behavior has strong similarities with the zero differential resistance states
observed experimentally in high mobility two dimensional systems. Performed
numerical simulations are in a good global agreement with the developed
analytical theory even if the later leads to overestimated negative
differential resistance values.",1110.2033v1
2012-08-09,Strange metals at finite 't Hooft coupling,"In this paper, we consider the AdS-Schwarzshild black hole in light-cone
coordinates which exhibits non-relativistic z=2 Schrodinger symmetry. Then, we
use the $AdS/CFT$ correspondence to investigate the effect of finite-coupling
corrections to two important properties of the strange metals which are the
Ohmic resistivity and the inverse Hall angle. It is shown that the Ohmic
resistivity and inverse Hall angle are linear and quadratic temperature
dependent in the case of $\mathcal{R}^4$ corrections, respectively. While in
the case of Gauss-Bonnet gravity, we find that the inverse Hall angle is
quadratic temperature dependent and the Ohmic conductivity can never be linear
temperature dependent.",1208.1855v1
2012-11-15,Microwave-induced resistance oscillations in tilted magnetic fields,"We have studied the effect of an in-plane magnetic field on microwave-induced
resistance oscillations in a high mobility two-dimensional electron system. We
have found that the oscillation amplitude decays exponentially with an in-plane
component of the magnetic field $B_\parallel$. While these findings cannot be
accounted for by existing theories, our analysis suggests that the decay can be
explained by a $B_\parallel$-induced correction to the quantum scattering rate,
which is quadratic in $B_\parallel$.",1211.3753v1
2013-07-25,"Negative differential resistance with graphene channels, interfacing distributed quantum dots in Field-Effect Transistors","Field effect transistors with channels made of graphene layer(s) were
explored. The graphene layer(s) contacted a distributed array of well-separated
semiconductor quantum dots (QDs). The dots were embedded in nano-structured
hole-array; each filled hole was occupied by one dot. Differential optical and
electrical conductance was observed. Since Negative Differential Resistance
(NDR) is key to high-speed elements, such construction may open the door for
new electro-photonic devices.",1307.6790v1
2013-09-04,Exploiting negative differential resistance in monolayer graphene FETs for high voltage gains,"Through self-consistent quantum transport simulations, we evaluate the RF
performance of monolayer graphene FETs in the bias region of negative output
differential resistance. We show that, compared to the region of
quasi-saturation, a voltage gain larger than 10 can be obtained, at the cost of
a decrease in the maximum oscillation frequency of about a factor of 1.5--3 and
the need for a careful circuit stabilization.",1309.1105v2
2013-11-01,Fermi liquid breakdown and evidence for superconductivity in YFe$_2$Ge$_2$,"In the d-electron system YFe$_2$Ge$_2$, an unusually high and temperature
dependent Sommerfeld ratio of the specific heat capacity $C/T \sim
100~\mathrm{mJ/(molK^2)}$ and an anomalous power law temperature dependence of
the electrical resistivity $\rho \simeq \rho_0 + AT^{3/2}$ signal Fermi liquid
breakdown, probably connected to a close-by quantum critical point. Full
resistive transitions, accompanied by DC diamagnetic screening fractions of up
to 80\% suggest that pure samples of YFe$_2$Ge$_2$ superconduct below
$1.8~\mathrm{K}$.",1311.0247v2
2014-04-28,Resistive Plate Chambers for Imaging Calorimetry - the DHCAL,"The DHCAL, the Digital Hadron Calorimeter, is a prototype calorimeter based
on Resistive Plate Chambers (RPCs). The design emphasizes the imaging
capabilities of the detector in an effort to optimize the calorimeter for the
application of Particle Flow Algorithms (PFAs) to the reconstruction of
hadronic jet energies in a colliding beam environment. The readout of the
chambers is segmented into 1 x 1 cm2 pads, each read out with a 1-bit (single
threshold) resolution. The prototype with approximately 500,000 readout
channels underwent extensive testing in both the Fermilab and CERN test beams.
This talk presents preliminary findings from the analysis of data collected at
the test beams.",1404.7046v2
2014-05-07,Thermal effects and switching kinetics in silver/manganite memristive systems: Probing oxygen vacancies diffusion,"We investigate the switching kinetics of oxygen vacancies (Ov) diffusion in
LPCMO-Ag memristive interfaces by performing experiments on the temperature
dependence of the high resistance (HR) state under thermal cycling.
Experimental results are well reproduced by numerical simulations based on
thermally activated Ov diffusion processes and fundamental assumptions relying
on a recent model proposed to explain bipolar resistive switching in manganite-
based cells. The confident values obtained for activation energies and
diffusion coefficient associated to Ov dynamics, constitute a validation test
for both model predictions and Ov diffusion mechanisms in memristive
interfaces.",1405.1585v1
2014-06-26,Signal Characteristics of a Resistive-Strip Micromegas Detector with an Integrated Two-Dimensional Readout,"In recent years, micropattern gaseous detectors, which comprise a
two-dimensional readout structure within one PCB layer, received significant
attention in the development of precision and cost-effective tracking detectors
in medium and high energy physics experiments. In this article, we present for
the first time a systematic performance study of the signal characteristics of
a resistive strip micromegas detector with a two-dimensional readout, based on
test-beam and X-ray measurements. In particular, comparisons of the response of
the two independent readout-layers regarding their signal shapes and signal
reconstruction efficiencies are discussed.",1406.6871v1
2016-06-25,Linear and quadratic in temperature resistivity from holography,"We present a new black hole solution in the asymptotic Lifshitz spacetime
with a hyperscaling violating factor. A novel computational method is
introduced to compute the DC thermoelectric conductivities analytically. We
find that both the linear-T and quadratic-T contributions to the resistivity
can be realized, indicating that a more detailed comparison with experimental
phenomenology can be performed in this scenario.",1606.07905v3
2017-02-18,Delta-doped Beta- Gallium Oxide Field Effect Transistor,"We report silicon delta doping in Gallium Oxide (\b{eta}-Ga2O3) grown by
plasma assisted molecular beam epitaxy using a shutter pulsing technique. We
describe growth procedures that can be used to realize high Si incorporation in
an oxidizing oxygen plasma environment. Delta doping was used to realize thin
(12 nm) low-resistance layers with sheet resistance of 320 Ohm/square (mobility
of 83 cm^2/Vs, integrated sheet charge of 2.4x10^14 cm^-2). A single
delta-doped sheet of carriers was employed as a channel to realize a field
effect transistor with current ID,MAX =292 mA/mm and transconductance gM = 27
mS/mm.",1702.06584v1
2017-11-17,An HLLC Riemann Solver for Resistive Relativistic Magnetohydrodynamics,"We present a new approximate Riemann solver for the augmented system of
equations of resistive relativistic magnetohydrodynamics (RRMHD) that belongs
to the family of Harten-Lax-van Leer contact wave (HLLC) solvers. In HLLC
solvers, the solution is approximated by two constant states flanked by two
shocks separated by a contact wave. The accuracy of the new approximate solver
is calibrated through one- and two-dimensional test problems.",1711.06691v2
2018-02-01,MHD simulations of resistive viscous accretion disk around millisecond pulsar,"We perform MHD simulations of a thin resistive and viscous accretion disk
around a neutron star with the surface dipolar magnetic field of 10$^8$ Gauss.
The system evolution is followed during the interval of 500 millisecond pulsar
rotations. Matter is accreted through a stable accretion column from the disk
onto the star. We also show propagation of the stellar wind through the corona.
Analysis of the mass accretion flux and torques on the star shows that the disk
reaches the quasi-stationary state.",1802.00261v1
2014-08-01,Nonmetallic Low-Temperature Normal State of K0.70Fe1.46Se1.85Te0.15,"The normal-state in-plane resistivity below the zero-field superconducting
transition temperature $T_c$ and the upper critical field Hc2 were measured by
suppressing superconductivity in pulsed magnetic fields for
K0.70Fe1.46Se1.85Te0.15. The normal-state resistivity $\rho_{ab}$ is found to
increase logarithmically with decrasing temperature as
$\frac{T}{T_c}\rightarrow 0$. Similar to granular metals, our results suggest
that a superconductor - insulator transition below zero-field T$_{c}$ may be
induced in high magnetic fields. This is related to the intrinsic real-space
phase-separated states common to all inhomogeneous superconductors.",1408.0271v1
2020-02-22,Accelerating longitudinal expansion of resistive relativistic-magneto-hydrodynamics in heavy ion collisions,"We study the evolution of the longitudinal expansion of an ideal fluid with
finite electrical conductivity, which is subject to the EM fields. In the
framework of resistive relativistic-magneto-hydrodynamic, we find an exact
analytical solution for the EM fields and for the acceleration of the fluid.",2002.09752v1
2012-01-03,Sub-Rayleigh lithography using high flux loss-resistant entangled states of light,"Quantum lithography achieves phase super-resolution using fragile,
experimentally challenging entangled states of light. We propose a scalable
scheme for creating features narrower than classically achievable, with reduced
use of quantum resources and consequently enhanced resistance to loss. The
scheme is an implementation of interferometric lithography using a mixture of
an SPDC entangled state with intense classical coherent light. We measure
coincidences of up to four photons mimicking multiphoton absorption. The
results show a narrowing of the interference fringes of up to 30% with respect
to the best analogous classical scheme using only 10% of the non-classical
light required for creating NOON states.",1201.0637v1
2017-08-02,Graphene membrane as a pressure gauge,"Straining graphene results in the appearance of a pseudo-magnetic field which
alters its local electronic properties. Applying a pressure difference between
the two sides of the membrane causes it to bend/bulge resulting in a resistance
change. We find that the resistance changes linearly with pressure for bubbles
of small radius while the response becomes non-linear for bubbles that stretch
almost to the edges of the sample. This is explained as due to the strong
interference of propagating electronic modes inside the bubble. Our
calculations show that high gauge factors can be obtained in this way which
makes graphene a good candidate for pressure sensing.",1708.00678v1
2019-12-18,Large responsivity of graphene radiation detectors with thermoelectric readout,"Simple estimations show that the thermoelectric readout in graphene radiation
detectors can be extremely effective even for graphene with modest
charge-carrier mobility ~1000 cm^2/(Vs). The detector responsivity depends
mostly on the residual charge-carrier density and split-gate spacing and can
reach competitive values of ~10^3 - 10^4 V/W at room temperature. The optimum
characteristics depend on a trade-off between the responsivity and the total
device resistance. Finding out the key parameters and their roles allows for
simple detectors and their arrays, with high responsivity and sufficiently low
resistance matching that of the radiation-receiving antenna structures.",1912.08489v1
2012-03-01,Magnetic and transport properties of iron-platinum arsenide Ca10(Pt4-δAs8)(Fe2-xPtxAs2)5 single crystal,"We report superconducting properties of single crystalline
Ca10(Pt4-{\delta}As8)(Fe2-xPtxAs2)5 by X-ray diffraction, magnetization,
resistivity, and magneto-optical imaging measurements. The magnetization
measurements reveal fish-tail hysteresis loop and relatively high critical
current density Jc ~ 0.8\times105 A/cm2 at low temperatures. The exponential
temperature dependence of Jc, which arises from nonlinear effective flux-creep
activation energy, has been observed. Upper critical field determined by
resistive transition shows a relatively large anisotropy. The magneto-optical
images reveal homogenous current flow within the crystal.",1203.0099v1
2012-03-22,Tungsten silicide films for microwave kinetic inductance detectors,"Microwave Kinetic Inductance Detectors (MKIDs) provide highly multiplexed
arrays of detectors that can be configured to operate from the sub-millimeter
to the X-ray regime. We have examined two tungsten silicide alloys (W5Si3 and
WSi2), which are dense alloys that provide a critical temperature tunable with
composition, large kinetic inductance fraction, and high normal-state
resistivity. We have fabricated superconducting resonators and provide
measurement data on critical temperature, surface resistance, quality factor,
noise, and quasiparticles lifetime. Tungsten silicide appears to be promising
for microwave kinetic inductance detectors.",1203.5064v2
2016-09-10,Angular resolution of stacked resistive plate chambers,"We present here detailed derivations of mathematical expressions for the
accuracy in the arrival direction of particles estimated using a set of stacked
resistive plate chambers (RPCs). The expressions are validated against
experimental results using data collected from the prototype detectors (without
magnet) of the upcoming India-based Neutrino Observatory (INO). We also present
a theoretical estimate of angular resolution of such a setup. In principle,
these expressions can be used for any other detector with an architecture
similar to that of RPCs.",1609.03071v2
2016-09-19,Scaling limits of stochastic processes associated with resistance forms,"We establish that if a sequence of spaces equipped with resistance metrics
and measures converge with respect to the Gromov-Hausdorff-vague topology, and
a certain non-explosion condition is satisfied, then the associated stochastic
processes also converge. This result generalises previous work on trees,
fractals, and various models of random graphs. We further conjecture that it
will be applicable to the random walk on the incipient infinite cluster of
critical bond percolation on the high-dimensional integer lattice.",1609.05666v1
2020-12-24,Backflow in simulated MHD accretion disks,"We perform resistive MHD simulations of accretion disk with alpha-viscosity,
accreting onto a rotating star endowed with a magnetic dipole. We find backflow
in the presence of strong magnetic field and large resistivity, and probe for
the dependence on Prandtl number. We find that in the magnetic case the
distance from the star at which backflow begins, the stagnation radius, is
different than in the hydrodynamic case, and the backflow shows non-stationary
behavior. We compare the results with hydrodynamics simulations.",2012.13194v1
2021-10-05,Density-Driven Resistance Response in $MnS_{2}$: Theory,"A colossal insulator-to-metal transition in high-spin pyrite phase of
$MnS_{2}$ has been experimentally observed \cite{colomns2}. There are two
possibilities behind this colossal insulator-to-metal transition: (1) migration
of $Mn$ electrons to unoccupied $S^{2-}_{2}$ antibonding states under pressure
which leads to conducting ligand states and hence metallic transition, and (2)
possibility of band crossing transition. We have analyzed this experimental
obervation theoretically using a toy statistical model and found that the
transition is due to the migration of electrons from the transition metal ions
to the ligand sites (i.e. the possibility (1)). The calculated resistivity
compares well with the experimental data within the fitting parameters of the
model.",2110.01902v1
2022-07-25,Superconductor--Insulator Transition in a non-Fermi Liquid,"We present a model of a strongly correlated system with a non-Fermi liquid
high temperature phase. Its ground state undergoes an insulator to
superconductor quantum phase transition (QPT) as a function of a pairing
interaction strength. Both the insulator and the superconductor are originating
from the same interaction mechanism. The resistivity in the insulating phase
exhibits the activation behavior with the activation energy, which goes to zero
at the QPT. This leads to a wide quantum critical regime with an algebraic
temperature dependence of the resistivity. Upon raising the temperature in the
superconducting phase, the model exhibits a finite temperature phase transition
to a Bose metal phase, which separates the superconductor from the non-Fermi
liquid metal.",2207.12307v1
2024-01-19,Asymptotic behavior of solution of the non-resistive 2D MHD equations on the half space,"In this paper, we obtain the global well-posedness and the asymptotic
behavior of solution of non-resistive 2D MHD problem on the half space. We
overcome the difficulty of zero spectrum gap by building the relationship
between half space and the whole space, and get the resolvent estimate for the
weak diffusion system. We use the two-tier energy method that couples the
boundedness of high-order $(H^3)$ energy to the decay of low-order energy, the
latter of which is necessary to control the growth of the highest energy.",2401.10456v1
2005-03-22,Theoretical current-voltage characteristics of ferroelectric tunnel junctions,"We present the concept of ferroelectric tunnel junctions (FTJs). These
junctions consist of two metal electrodes separated by a nanometer-thick
ferroelectric barrier. The current-voltage characteristics of FTJs are analyzed
under the assumption that the direct electron tunneling represents the dominant
conduction mechanism. First, the influence of converse piezoelectric effect
inherent in ferroelectric materials on the tunnel current is described. The
calculations show that the lattice strains of piezoelectric origin modify the
current-voltage relationship owing to strain-induced changes of the barrier
thickness, electron effective mass, and position of the conduction-band edge.
Remarkably, the conductance minimum becomes shifted from zero voltage due to
the piezoelectric effect, and a strain-related resistive switching takes place
after the polarization reversal in a ferroelectric barrier. Second, we analyze
the influence of the internal electric field arising due to imperfect screening
of polarization charges by electrons in metal electrodes. It is shown that, for
asymmetric FTJs, this depolarizing-field effect also leads to a considerable
change of the barrier resistance after the polarization reversal. However, the
symmetry of the resulting current-voltage loop is different from that
characteristic of the strain-related resistive switching. The crossover from
one to another type of the hysteretic curve, which accompanies the increase of
FTJ asymmetry, is described taking into account both the strain and
depolarizing-field effects. It is noted that asymmetric FTJs with dissimilar
top and bottom electrodes are preferable for the non-volatile memory
applications because of a larger resistance on/off ratio.",0503546v1
2013-04-09,Active control of magnetoresistance of organic spin valves using ferroelectricity,"Organic spintronic devices have been appealing because of the long spin life
time of the charge carriers in the organic materials and their low cost,
flexibility and chemical diversity. In previous studies, the control of
resistance of organic spin valves is generally achieved by the alignment of the
magnetization directions of the two ferromagnetic electrodes, generating
magnetoresistance.1 Here we employ a new knob to tune the resistance of organic
spin valves by adding a thin ferroelectric interfacial layer between the
ferromagnetic electrode and the organic spacer. We show that the resistance can
be controlled by not only the spin alignment of the two ferromagnetic
electrodes, but also by the electric polarization of the interfacial
ferroelectric layer: the MR of the spin valve depends strongly on the history
of the bias voltage which is correlated with the polarization of the
ferroelectric layer; the MR even changes sign when the electric polarization of
the ferroelectric layer is reversed. This new tunability can be understood in
terms of the change of relative energy level alignment between ferromagnetic
electrode and the organic spacer caused by the electric dipole moment of the
ferroelectric layer. These findings enable active control of resistance using
both electric and magnetic fields, opening up possibility for multi-state
organic spin valves and shed light on the mechanism of the spin transport in
organic spin valves.",1304.2446v2
2017-12-22,The Role of Oxygen in Ionic Liquid Gating on 2D Cr2Ge2Te6: a Non-Oxide Material,"Ionic liquid gating can markedly modulate the materials' carrier density so
as to induce metallization, superconductivity, and quantum phase transitions.
One of the main issues is whether the mechanism of ionic liquid gating is an
electrostatic field effect or an electrochemical effect, especially for oxide
materials. Recent observation of the suppression of the ionic liquid
gate-induced metallization in the presence of oxygen for oxide materials
suggests the electrochemical effect. However, in more general scenarios, the
role of oxygen in ionic liquid gating effect is still unclear. Here, we perform
the ionic liquid gating experiments on a non-oxide material: two-dimensional
ferromagnetic Cr2Ge2Te6. Our results demonstrate that despite the large
increase of the gate leakage current in the presence of oxygen, the oxygen does
not affect the ionic liquid gating effect (< 5 % difference), which suggests
the electrostatic field effect as the mechanism on non-oxide materials.
Moreover, our results show that the ionic liquid gating is more effective on
the modulation of the channel resistances compared to the back gating across
the 300 nm thick SiO2.",1712.08281v1
2022-11-30,Anomalous magneto-thermoelectric behavior in massive Dirac materials,"Extensive studies of electron transport in Dirac materials have shown
positive magneto-resistance (MR) and positive magneto-thermopower (MTP) in a
magnetic field perpendicular to the excitation current or thermal gradient. In
contrast, measurements of electron transport often show a negative longitudinal
MR and negative MTP for a magnetic field oriented along the excitation current
or thermal gradient; this is attributed to the chiral anomaly in Dirac
materials. Here, we report a very different magneto-thermoelectric transport
behavior in the massive Dirac material ZrTe5. Although thin flakes show a
commonly observed positive MR in a perpendicular magnetic field, distinct from
other Dirac materials, we observe a sharp negative MTP. In a parallel magnetic
field, we still observe a negative longitudinal MR, however, a remarkable
positive MTP is observed for the fields parallel to the thermal gradients. Our
theoretical calculations suggest that this anomalous magneto-thermoelectric
behavior can be attributed to the screened Coulomb scattering. This work
demonstrates the significance of impurity scattering in the electron transport
of topological materials and provides deep insight into the novel
magneto-transport phenomena in Dirac materials.",2211.17027v1
2022-12-01,Process parameter sensitivity of the energy absorbing properties of additively manufactured metallic cellular materials,"Additive Manufacturing (AM) has enabled the fabrication of metallic cellular
materials that are of interest in the design of lightweight impact resistant
structures. However, there is a need to understand the interactions between:
(i) the material architecture, (ii) the AM process parameters, and (iii) the
as-built geometry, microstructure and energy absorbing properties. In this
work, we investigate the quasi-static and dynamic behaviour of cellular
materials manufactured from 316L stainless steel using laser powder bed fusion
(LPBF). Four cellular architectures are considered (octet lattice,
lattice-walled square honeycomb, origami and square honeycomb), as well as
three sets of AM process parameters, characterised by laser powers of 50, 125
and 200 W. The exposure time is adjusted to deliver the same total heat input.
The 125 W case leads to material with the highest strength and ductility. The
cellular materials with this process variant match their nominal densities most
closely, and have the highest strength and energy absorption. Either reducing
(50 W) or increasing (200 W) the power leads to a significant increase in
porosity, reducing strength and energy absorption. However, we find that
changes due to process-induced porosity have a smaller influence than those
resulting from the choice of cellular architecture.",2212.00438v1
2023-09-11,Button Shear Testing for Adhesion Measurements of 2D Materials,"Two-dimensional (2D) materials are considered for numerous applications in
microelectronics, although several challenges remain when integrating them into
functional devices. Weak adhesion is one of them, caused by their chemical
inertness. Quantifying the adhesion of 2D materials on three-dimensional
surfaces is, therefore, an essential step toward reliable 2D device
integration. To this end, button shear testing is proposed and demonstrated as
a method for evaluating the adhesion of 2D materials with the examples of
graphene and hexagonal boron nitride (hBN), molybdenum disulfide, and tungsten
diselenide on silicon dioxide (SiO${_2}$) and silicon nitride substrates. We
propose a fabrication process flow for polymer buttons on the 2D materials and
establish suitable button dimensions and testing shear speeds. We show with our
quantitative data that low substrate roughness and oxygen plasma treatments on
the substrates before 2D material transfer result in higher shear strengths.
Thermal annealing increases the adhesion of hBN on SiO${_2}$ and correlates
with the thermal interface resistance between these materials. This establishes
button shear testing as a reliable and repeatable method for quantifying
adhesion of 2D materials.",2309.05852v3
1997-05-09,Small-q electron-phonon scattering and linear dc resistivity in high-T_c oxides,"We examine the effect on the DC resistivity of small-q electron-phonon
scattering, in a system with the electronic topology of the high-T_c oxides.
Despite the fact that the scattering is dominantly forward, its contribution to
the transport can be significant due to ``ondulations'' of the bands in the
flat region and to the umpklapp process. When the extended van-Hove
singularities are sufficiently close to $E_F$ the acoustic branch of the
phonons contribute significantly to the transport. In that case one can obtain
linear $T$ dependent resistivity down to temperatures as low as 10 K, even if
electrons are scattered also by optical phonons of about 500 K as reported by
Raman measurements.",9705085v1
1999-05-14,Universal scaling of Hall resistivity in clean and moderately clean limits for Hg- and Tl-based superconductors,"The mixed-state Hall resistivity and the longitudinal resistivity in
HgBa_{2}CaCu_{2}O_{6}, HgBa_{2}Ca_{2}Cu_{3}O_{8}, and Tl_{2}Ba_{2}CaCu_{2}O_{8}
thin films have been investigated as functions of the magnetic field up to 18
T. We observe the universal scaling behavior between \rho_{xy} and \rho_{xx} in
the regions of the clean and the moderately clean limit. The scaling exponent
\beta is 1.9 in the clean limit at high field and low temperature whereas \beta
is 1.0 in the moderately clean limit at low field and high temperature,
consistent with a theory based on the midgap states in the vortex cores. This
finding implies that the Hall conductivity is also universal in Hg- and
Tl-based superconductors.",9905201v1
1999-10-04,Normal State Resistivity of Underdoped YBa2Cu3Ox Thin Films and La2-xSrxCuO4 Ultra-Thin Films under Epitaxial Strain,"The normal state resistivity of high temperature superconductors can be
probed in the region below Tc by suppressing the superconducting state in high
magnetic fields. Here we present the normal state properties of YBa2Cu3Ox thin
films in the underdoped regime and the normal state resistance of La2-xSrxCuO4
thin films under epitaxial strain, measured below Tc by applying pulsed fields
up to 60 T. A universal rho(T) behaviour is reported. We interpret these data
in terms of the recently proposed 1D quantum transport model with the 1D paths
corresponding to the charge stripes.",9910033v1
2001-03-04,Effect of the In-Plane Magnetic Field on Conduction of the Si-inversion Layer: Magnetic Field Driven Disorder,"We compare the effects of temperature, disorder and parallel magnetic field
on the metallic-like temperature dependence of the resistivity. We found a
similarity between the effects of disorder and parallel field: the parallel
field weakens the metallic-like conduction in high mobility samples and make it
similar to that for low-mobility samples. We found a smooth continuous effect
of the in-plane field on conduction, without any threshold. While conduction
remains non-activated, the parallel magnetic field restores the same
resistivity value as the high temperature does. This matching sets substantial
constraints on the choice of the theoretical models developed to explain the
mechanism of the metallic conduction and parallel field magnetoresistance in 2D
carrier systems. We demonstrate that the data for magneto- and temperature
dependence of the resistivity of Si-MOS samples in parallel field may be well
described by a simple model of the magnetic field dependent disorder.",0103087v2
2001-11-20,High-pressure study on the superconducting pyrochlore oxide Cd2Re2O7,"Superconducting and structural phase transitions in a pyrochlore oxide
Cd2Re2O7 are studied under high pressure by x-ray diffraction and electrical
resistivity measurements. A rich P-T phase diagram is obtained, which contains
at least two phases with the ideal and slightly distorted pyrochlore
structures. It is found that the transition between them is suppressed with
increasing pressure and finally disappears at a critical pressure Pc = 3.5 GPa.
Remarkable enhancements in the residual resistivity as well as the coefficient
A of the AT 2 term in the resistivity are found around the critical pressure.
Superconductivity is detected only for the phase with the structural
distortion. It is suggested that the charge fluctuations of Re ions play a
crucial role in determining the electronic properties of Cd2Re2O7.",0111388v2
2002-10-02,Two-band effects in transport properties of MgB2,"We present resistivity and thermal conductivity measurements on bulk samples,
prepared either by a standard method or by a one-step technique. The latter
samples, due to their high density and purity, show residual resistivity values
as low as 0.5 mW cm and thermal conductivity values as high as 215 W/mK, higher
than the single crystal ones. Thermal and electrical data of all the samples
are analysed in the framework of the Bloch-Gruneisen equation giving reliable
parameter values. In particular the temperature resitivity coefficient,
obtained both from resistivity and thermal conductivity, in the dirty sample
comes out ten time larger than in the clean ones. This result supports the
hypothesis of ref. [1] that p and s bands conduct in parallel, prevailing p
conduction in clean samples and s conduction in dirty samples .",0210047v2
2003-07-31,Radiation-intensity and temperature dependence of microwave-induced magnetoresistance oscillations in high-mobility two-dimensional electron systems,"We present a detailed theoretical investigation on the radiation induced
giant magnetoresistance oscillations recently discovered in high-mobility
two-dimensional electron gas. Electron interactions with impurities, transverse
and longitudinal acoustic phonons in GaAs-based heterosystems are considered
simultaneously. Multiphoton-assisted impurity scatterings are shown to be the
primary origin of the resistance oscillation. Based on the balance-equation
theory developed for magnetotransport in Faraday geometry, we are able not only
to reproduce the observed period, phase and the negative resistivity of the
main oscillations, but also to predict the secondary peak/valley structures
relating to two-photon and three-photon processes. The dependence of the
magnetoresistance oscillation on microwave intensity, the role of dc bias
current and the effect of elevated electron temperature are discussed.
Furthermore, we propose that the temperature-dependence of the resistance
oscillation stems from the growth of the Landau level broadening due to the
enhancement of acoustic phonon scattering with increasing lattice temperature.
The calculated temperature-variation of the oscillation agrees well with
experimental observations.",0307757v1
2003-09-29,Andreev reflection and enhanced subgap conductance in NbN/Au/InGaAs-InP junctions,"We report on the fabrication of highly transparent superconductor/normal
metal/two-dimensional electron gas junctions formed by a superconducting NbN
electrode, a thin (10nm) Au interlayer, and a two-dimensional electron gas in a
InGaAs/InP heterostructure. High junction transparency has been achieved by
exploiting of a newly developed process of Au/NbN evaporation and rapid
annealing at 400C. This allowed us to observe for the first time a decrease in
the differential resistance with pronounced double-dip structure within the
superconducting energy gap in superconductor-2DEG proximity systems. The effect
of a magnetic field perpendicular to the plane of the 2DEG on the differential
resistance of the interface was studied. It has been found that the reduced
subgap resistance remains in high magnetic fields. Zero-field data are analyzed
within the previously established quasiclassical model for the proximity
effect.",0309682v2
2004-01-07,Large positive magneto-resistance in high mobility 2D electron gas : interplay of short and long range disorder,"We have observed a large positive quasi-classical magneto-resistance (MR) in
a high mobility 2D electron gas in AlGaAs/GaAs heterostructure. The
magneto-resistance is non-saturating and increases with magnetic field as
$\rho_{xx}\sim B^{\alpha} (\alpha=0.9-1.2)$. In antidot lattices a
non-monotonic MR is observed. We show that in both cases this MR can be
qualitatively described in terms of the theory recently advanced by Polyakov et
al (PRB, 64, 205306 (2001)). Their prediction is that such behavior as we
observe may be the consequence of a concurrent existence of short and long
range scattering potentials.",0401085v2
2004-03-01,Electronic Phase Diagram of High-T_c Cuprate Superconductors from a Mapping of the In-Plane Resistivity Curvature,"We propose that Resistivity Curvature Mapping (RCM) based on the in-plane
resistivity data is a useful way to objectively draw an electronic phase
diagrams of high-T_c cuprates, where various crossovers are important. In
particular, the pseudogap crossover line can be conveniently determined by RCM.
We show experimental phase diagrams obtained by RCM for
Bi_{2}Sr_{2-z}La_{z}CuO_{6+\delta}, La_{2-x}Sr_{x}CuO_{4}, and
YBa_{2}Cu_{3}O_{y}, and demonstrate the universal nature of the pseudogap
crossover. Intriguingly, the electronic crossover near optimum doping depicted
by RCM appears to occur rather abruptly, suggesting that the quantum critical
regime, if exists, must be very narrow.",0403032v2
2004-12-15,The resistive transition and Meissner effect in carbon nanotubes: Evidence for quasi-one-dimensional superconductivity above room temperature,"It is well known that copper-based perovskite oxides rightly enjoy consensus
as high-temperature superconductors on the basis of two signatures: the
resistive transition and the Meissner effect. We show that the resistive
transitions in carbon nanotubes agree quantitatively with the
Langer-Ambegaokar-McCumber-Halperin (LAMH) theory for quasi-1D superconductors
although the superconducting transition temperatures can vary from 0.4 K to 750
K for different samples. We have also identified the Meissner effect in the
field parallel to the tube axis up to room temperature for aligned and
physically separated multi-walled nanotubes (MWNTs). The magnitude of the
Meissner effect is in quantitative agreement with the predicted penetration
depth from the measured carrier density. Furthermore, the bundling of
individual MWNTs into closely packed bundles leads to a large enhancement in
the diamagnetic susceptibility, which is the hallmark of the Josephson coupling
among the tubes in bundles. These results consistently indicate quasi-1D
high-temperature superconductivity in carbon nanotubes.",0412382v2
2005-02-09,Low-temperature nodal-quasiparticle transport in lightly doped YBa_{2}Cu_{3}O_{y} near the edge of the superconducting doping regime,"In-plane transport properties of nonsuperconducting YBa_{2}Cu_{3}O_{y} (y =
6.35) are measured using high-quality untwinned single crystals. We find that
both the a- and b-axis resistivities show log(1/T) divergence down to 80 mK,
and accordingly the thermal conductivity data indicate that the nodal
quasiparticles are progressively localized with lowering temperature. Hence,
both the charge and heat transport data do not support the existence of a
""thermal metal"" in nonsuperconducting YBa_{2}Cu_{3}O_{y}, as opposed to a
recent report by Sutherland {\it et al.} [Phys. Rev. Lett. {\bf 94}, 147004
(2005)]. Besides, the present data demonstrate that the peculiar log(1/T)
resistivity divergence of cuprate is {\it not} a property associated with
high-magnetic fields.",0502223v2
2006-04-19,Transport Properties of Granular High-TC Superconductors,"We report on the application of the Resistively Shunted Junction (RSJ) model
to granular high-TC superconductors. Some derived predictions of the RSJ model
are applied to a set of superconducting granular samples which can be
considered as a network of Josephson junctions. The investigated samples belong
to both hole-doped Y1-xPrxBa2Cu3O7-d (x = 0.0, 0.35, and 0.45) and the
electron-doped Sm2-xCexCuO4-d (x = 0.18) systems which display the so-called
double resistive superconducting transition. We have performed several
transport measurements in these compounds including temperature and magnetic
field dependence of the electrical resistance, R(T,H), and I-V characteristics.
Several aspects of the I-V characteristics were quantitatively well described
by the RSJ model. The combined results strongly suggest that dissipation in
granular superconducting samples is a natural consequence of the normal current
flowing in parallel with the supercurrent current.",0604460v1
2006-10-05,Unconventional resistivity at the border of metallic antiferromagnetism in NiS2,"We report low-temperature and high-pressure measurements of the electrical
resistivity \rho(T) of the antiferromagnetic compound NiS_2 in its
high-pressure metallic state. The form of \rho(T) suggests that metallic
antiferromagnetism in NiS_2 is quenched at a critical pressure p_c=76+-5 kbar.
Near p_c the temperature variation of \rho(T) is similar to that observed in
NiS_{2-x}Se_x near the critical composition x=1 where the Neel temperature
vanishes at ambient pressure. In both cases \rho(T) varies approximately as
T^{1.5} over a wide range below 100 K. However, on closer analysis the
resistivity exponent in NiS_2 exhibits an undulating variation with temperature
not seen in NiSSe (x=1). This difference in behaviour may be due to the effects
of spin-fluctuation scattering of charge carriers on cold and hot spots of the
Fermi surface in the presence of quenched disorder, which is higher in NiSSe
than in stoichiometric NiS_2.",0610166v1
2009-05-29,Ferromagnetic quantum phase transition in Sr$_{1-x}$Ca$_x$RuO$_3$ thin films,"The ferromagnetic quantum phase transition in the perovskite ruthenate
Sr$_{1-x}$Ca$_x$RuO$_3$ is studied by low-temperature magnetization and
electrical resistivity measurements on thin films. The films were grown
epitaxially on SrTiO$_3$ substrates using metalorganic aerosol deposition and
characterized by X-ray diffraction and room temperature scanning tunneling
microscopy. High residual resistivity ratios of 29 and 16 for $x=0$ and $x=1$,
respectively, prove the high quality of the investigated samples. We observe a
continuous suppression of the ferromagnetic Curie temperature from $T_C=160$ K
at $x=0$ towards $T_C\to 0$ at $x_c\approx 0.8$. The analysis of the electrical
resistivity between 2 and 10 K reveals $T^2$ and $T^{3/2}$ behavior at $x\leq
0.6$ and $x\geq 0.7$, respectively. For undoped CaRuO$_3$, the measurement has
been extended down to 60 mK, revealing a crossover to $T^2$ behavior around 2
K, which suggests a Fermi-liquid ground state in this system.",0905.4885v1
2009-08-10,Temperature Dependence of Magnetophonon Resistance Oscillations in GaAs/AlAs Heterostructures at High Filling Factors,"The temperature dependence of phonon-induced resistance oscillations has been
investigated in two-dimensional electron system with moderate mobility at large
filling factors at temperature range T = 7.4 - 25.4 K. The amplitude of
phonon-induced oscillations has been found to be governed by quantum relaxation
time which is determined by electron-electron interaction effects. This is in
agreement with results recently obtained in ultra-high mobility two-dimensional
electron system with low electron density [A. T. Hatke et al., Phys. Rev. Lett.
102, 086808 (2009)]. The shift of the main maximum of the magnetophonon
resistance oscillations to higher magnetic fields with increasing temperature
is observed.",0908.1293v2
2009-10-09,Electromagnetic response of LaO_0.94F_0.06FeAs: AC susceptibility and microwave surface resistance,"We discuss on the electromagnetic response of a polycrystalline sample of
LaO_0.94F_0.06FeAs exposed to DC magnetic fields up to 10 kOe. The low- and
high-frequency responses have been investigated by measuring the AC
susceptibility at 100 kHz and the microwave surface resistance at 9.6 GHz. At
low as well as high DC magnetic fields, the susceptibility strongly depends on
the amplitude of the AC driving field, highlighting enhanced nonlinear effects.
The field dependence of the AC susceptibility exhibits a magnetic hysteresis
that can be justified considering the intragrain-field-penetration effects on
the intergrain critical current density. The microwave surface resistance
exhibits a clockwise magnetic hysteresis, which cannot be justified in the
framework of the critical-state models of the Abrikosov-fluxon lattice; it may
have the same origin as that detected in the susceptibility.",0910.1805v1
2010-08-04,High-Pressure Electrical Resistivity Measurements of EuFe2As2 Single Crystals,"High-pressure electrical resistivity measurements up to 3.0GPa have been
performed on EuFe2As2 single crystals with residual resistivity ratios RRR=7
and 15. At ambient pressure, a magnetic / structural transition related to
FeAs-layers is observed at T0 =190K and 194K for samples with RRR=7 and 15,
respectively. Application of hydrostatic pressure suppresses T0, and then
induces similar superconducting behavior in the samples with different RRR
values. However, the critical pressure 2.7GPa, where T0=0, for the samples with
RRR=15 is slightly but distinctly larger than 2.5GPa for the samples with
RRR=7.",1008.0684v1
2010-12-26,Superconductivity at 32 K in single crystal Rb$_{0.78}$Fe$_2$Se$_{1.78}$},"We successfully grew the high-quality single crystal of
Rb$_{0.78}$Fe$_2$Se$_{1.78}$, which shows sharp superconducting transition in
magnetic susceptibility and electrical resistivity. Resistivity measurements
show the onset superconducting transition ($T_{\rm c}$) at 32.1 K and zero
resistivity at 30 K. From the low-temperature iso-magnetic-field
magnetoresistance, large upper critical field $H_{\rm c2}$(0) has been
estimated as high as 180 T for in-plane field and 59 T for out-of-plane field.
The anisotropy $H^{ab}_{\rm c2}$(0)/$H^{c}_{\rm c2}$(0) is around 3.0, right
lying between those observed in K$_x$Fe$_2$Se$_2$ and Cs$_x$Fe$_2$Se$_2$.",1012.5525v1
2012-07-23,Quantum oscillations and high carrier mobility in the delafossite PdCoO$_2$,"We present de Haas-van Alphen and resistivity data on single crystals of the
delafossite PdCoO2. At 295 K we measure an in-plane resistivity of 2.6
\mu{\Omega}-cm, making PdCoO2 the most conductive oxide known. The
low-temperature in-plane resistivity has an activated rather than the usual T^5
temperature dependence, suggesting a gapping of effective scattering that is
consistent with phonon drag. Below 10 K, the transport mean free path is 20
\mum, approximately 10^5 lattice spacings and an astoundingly high value for
flux-grown crystals. We discuss the origin of these properties in light of our
data.",1207.5402v1
2012-10-02,Magnetotransport in graphene on silicon side of SiC,"We have studied the transport properties of graphene grown on silicon side of
SiC. Samples under study have been prepared by two different growth methods in
two different laboratories. Magnetoresistance and Hall resistance have been
measured at temperatures between 4 and 100 K in resistive magnet in magnetic
fields up to 22 T. In spite of differences in sample preparation, the field
dependence of resistances measured on both sets of samples exhibits two periods
of magneto-oscillations indicating two different parallel conducting channels
with different concentrations of carriers. The semi-quantitative agreement with
the model calculation allows for conclusion that channels are formed by
high-density and low-density Dirac carriers. The coexistence of two different
groups of carriers on the silicon side of SiC was not reported before.",1210.0744v2
2013-01-02,Plasmoid Instability in High-Lundquist-Number Magnetic Reconnection,"Our understanding of magnetic reconnection in resistive magnetohydrodynamics
has gone through a fundamental change in recent years. The conventional wisdom
is that magnetic reconnection mediated by resistivity is slow in laminar high
Lundquist ($S$) plasmas, constrained by the scaling of the reconnection rate
predicted by Sweet-Parker theory. However, recent studies have shown that when
$S$ exceeds a critical value $\sim10^{4}$, the Sweet-Parker current sheet is
unstable to a super-Alfv\'enic plasmoid instability, with a linear growth rate
that scales as $S^{1/4}$. In the fully developed statistical steady state of
two-dimensional resistive magnetohydrodynamic simulations, the normalized
average reconnection rate is approximately 0.01, nearly independent of $S$, and
the distribution function $f(\psi)$ of plasmoid magnetic flux $\psi$ follows a
power law $f(\psi)\sim\psi^{-1}$. When Hall effects are included, the plasmoid
instability may trigger onset of Hall reconnection even when the conventional
criterion for onset is not satisfied. The rich variety of possible reconnection
dynamics is organized in the framework of a phase diagram.",1301.0331v2
2013-02-09,mrPUF: A Memristive Device based Physical Unclonable Function,"Physical unclonable functions (PUFs) exploit the intrinsic complexity and
irreproducibility of physical systems to generate secret information. PUFs have
the potential to provide fundamentally higher security than traditional
cryptographic methods by preventing the cloning of identities and the
extraction of secret keys. One unique and exciting opportunity is that of using
the super-high information content (SHIC) capability of nanocrossbar
architecture as well as the high resistance programming variation of resistive
memories to develop a highly secure on-chip PUFs for extremely resource
constrained devices characterized by limited power and area budgets such as
passive Radio Frequency Identification (RFID) devices. We show how to implement
PUF based on nano-scale memristive (resistive memory) devices (mrPUF). Our
proposed architecture significantly increased the number of possible
challenge-response pairs (CRPs), while also consuming relatively lesser power
(around 70 uW). The presented approach can be used in other silicon-based PUFs
as well.",1302.2191v1
2013-04-24,A highly resistive layer within the crust of X-ray pulsars limits their spin periods,"The lack of X-ray pulsars with spin periods > 12 s raises the question of
where the population of evolved high magnetic field neutron stars has gone.
Unlike canonical radio pulsars, X-ray pulsars are not subject to physical
limits to the emission mechanism nor observational biases against the detection
of sources with longer periods. Here we show that a highly resistive layer in
the innermost part of the crust of neutron stars naturally limits the spin
period to a maximum value of about 10-20 s. This highly resistive layer is
expected if the inner crust is amorphous and heterogeneous in nuclear charge,
possibly due to the existence of a nuclear pasta phase. Our findings suggest
that the maximum period of isolated X-ray pulsars can be the first
observational evidence of an amorphous inner crust, which properties can be
further constrained by future X-ray timing missions combined with more detailed
models.",1304.6546v2
2014-05-05,Hall field-induced resistance oscillations in Ge/SiGe quantum wells,"We report on a magnetotransport study in a high-mobility 2D hole gas hosted
in a pure Ge/SiGe quantum well subject to dc electric fields and high frequency
microwave radiation. We find that under applied dc bias the differential
resistivity exhibits a pronounced maximum at a magnetic field which increases
linearly with the applied current. We associate this maximum with the
fundamental peak of Hall field-induced resistance oscillations (HIRO) which are
known to occur in 2D electron gases in GaAs/AlGaAs systems. After taking into
account the Dingle factor correction, we find that the position of the HIRO
peak is well described by the hole effective mass $m^\star \approx 0.09\,m_0$,
obtained from microwave photoresistance in the same sample.",1405.1093v1
2014-07-28,An apparent metal insulator transition in high mobility 2D InAs heterostructures,"We report on the first experimental observation of an apparent metal
insulator transition in a 2D electron gas confined in an InAs quantum well. At
high densities we find that the carrier mobility is limited by background
charged impurities and the temperature dependence of the resistivity shows a
metallic behavior with resistivity increasing with increasing temperature. At
low densities we find an insulating behavior below a critical density of $n_{c}
= 5 \times 10^{10}$ cm$^{-2}$ with the resistivity decreasing with increasing
temperature. We analyze this transition using a percolation model arising from
the failure of screening in random background charged impurities. We also
examine the percolation transition experimentally by introducing remote ionized
impurities at the surface. Using a bias during cool-down, we modify the
screening charge at the surface which strongly affects the critical density.
Our study shows that transition from a metallic to an insulating phase in our
system is due to percolation transition.",1407.7541v3
2014-11-01,Unusual resistance-voltage dependence of nanojunctions during electromigration in ultra-high vacuum,"The electrical resistance R of metallic nanocontacts subjected to controlled
cyclic electromigration in ultra-high vacuum has been investigated in-situ as a
function of applied voltage V. For sufficiently small contacts, i.e., large
resistance, a decrease of R(V) while increasing V is observed. This effect is
tentatively attributed to the presence of contacts separated by thin vacuum
barriers in parallel to ohmic nanocontacts. Simple model calculations indicate
that both thermal activation or tunneling can lead to this unusual behavior. We
describe our data by a tunneling model whose key parameter, i.e., the tunneling
distance, changes because of thermal expansion due to Joule heating and/or
electrostatic strain arising from the applied voltage. Oxygen exposure during
electromigration prevents the formation of negative R(V) slopes, and at the
same time enhances the probability of uncontrolled melting, while other gases
show little effects. In addition, indication for field emission has been
observed in some samples",1411.0105v1
2015-01-15,High Pressure Measurements of the Resistivity of $β$-YbAlB$_4$,"The electric resistivity $\rho(T)$ under hydrostatic pressure up to 8 GPa was
measured above 2 K using a high-quality single crystal of the Yb-based heavy
fermion system $\beta$-YbAlB$_4$. We found pressure-induced magnetic ordering
above the critical pressure $P_{\rm c} \approx $ 2.4 GPa. This phase transition
temperature $T_M$ is enhanced with pressure and reaches 30 K at a pressure of 8
GPa, which is the highest transition temperature for the Yb-based heavy fermion
compounds. In contrast, the resistivity is insensitive to pressure below $P_c$
and exhibits the $T$-linear behavior in the temperature range between 2 and 20
K. Our results indicate that quantum criticality for $\beta$-YbAlB$_4$ is also
located near $P_{\rm c}$ in addition to the ambient pressure.",1501.03852v1
2015-12-17,Alfvén Wave Heating of the Solar Chromosphere: 1.5D models,"Physical processes which may lead to solar chromospheric heating are analyzed
using high-resolution 1.5D non-ideal MHD modelling. We demonstrate that it is
possible to heat the chromospheric plasma by direct resistive dissipation of
high-frequency Alfv\'en waves through Pedersen resistivity. However this is
unlikely to be sufficient to balance radiative and conductive losses unless
unrealistic field strengths or photospheric velocities are used. The precise
heating profile is determined by the input driving spectrum since in 1.5D there
is no possibility of Alfv\'en wave turbulence. The inclusion of the Hall term
does not affect the heating rates. If plasma compressibility is taken into
account, shocks are produced through the ponderomotive coupling of Alfv\'en
waves to slow modes and shock heating dominates the resistive dissipation. In
1.5D shock coalescence amplifies the effects of shocks and for compressible
simulations with realistic driver spectra the heating rate exceeds that
required to match radiative and conductive losses. Thus while the heating rates
for these 1.5D simulations are an overestimate they do show that ponderomotive
coupling of Alfv\'en waves to sound waves is more important in chromospheric
heating than Pedersen dissipation through ion-neutral collisions.",1512.05816v1
2016-02-14,Ultra-sensitive nanoscale magnetic field sensors based on resonant spin filtering,"Solid state magnetic field sensors based on magneto-resistance modulation
find direct applications in communication devices, specifically in proximity
detection, rotational reference detection and current sensing. In this work, we
propose sensor structures based on the magneto-resistance physics of resonant
spin-filtering and present device designs catered toward exceptional magnetic
field sensing capabilities. Using the non-equilibrium Green's function spin
transport formalism self consistently coupled to the Poisson's equation, we
present highly-tunable pentalayer magnetic tunnel junction structures that are
capable of exhibiting an ultra-high peak tunnel magneto resistance $(\approx
2500 \%$). We show how this translates to device designs featuring an
ultra-high current sensitivity enhancement of over 300\% in comparison with
typical trilayer MTJ sensors, and a wider tunable range of field sensitivity.
We also demonstrate that a dynamic variation in sensor functionalities with the
structural landscape enables a superior design flexibility over typical
trilayer sensors. An optimal design exhibiting close to a 700\% sensitivity
increase as a result of angle dependent spin filtering is then presented.This
work sets a stage to engineer spintronic building blocks via the design of
functional structures tailored to exhibit ultra-sensitive spin filtering.",1602.04438v1
2016-04-10,Terahertz-induced resistance oscillations in high mobility two-dimensional electron systems,"We report on a theoretical work on magnetotransport under terahertz radiation
with high mobility two-dimensional electron systems. We focus on the
interaction between the obtained radiation-induced magnetoresistance
oscillations (RIRO) and the Shubnikov-de Haas (SdHO) oscillations. We study two
effects experimentally obtained with this radiation. First, the observed
disappearance of the SdHO oscillations simultaneously with the vanishing
resistance at the zero resistance states region. And secondly the strong
modulation of the SdHO oscillations at sufficient terahertz radiation power. We
conclude that both effects share the same physical origin, the interference
between the average advanced distance by the scattered electron between
irradiated Landau states, (RIRO), and the available initial density of states
at a certain magnetic field, (SdHO). Thus, from a physical standpoint, what the
terahertz experiments and theoretical simulations reveal is, on the one hand,
the oscillating nature of the Landau states subjected to radiation and, on the
other hand, how they behave in the presence of scattering.",1604.02721v1
2016-05-12,Improved Contacts to MoS2 Transistors by Ultra-High Vacuum Metal Deposition,"The scaling of transistors to sub-10 nm dimensions is strongly limited by
their contact resistance (Rc). Here we present a systematic study of scaling
MoS2 devices and contacts with varying electrode metals and controlled
deposition conditions, over a wide range of temperatures (80 to 500 K), carrier
densities (10^12 to 10^13 1/cm^2), and contact dimensions (20 to 500 nm). We
uncover that Au deposited in ultra-high vacuum (~10^-9 Torr) yields three times
lower Rc than under normal conditions, reaching 740 Ohm-um and specific contact
resistivity 3x10^-7 Ohm.cm2, stable for over four months. Modeling reveals
separate Rc contributions from the Schottky barrier and the series access
resistance, providing key insights on how to further improve scaling of MoS2
contacts and transistor dimensions. The contact transfer length is ~35 nm at
300 K, which is verified experimentally using devices with 20 nm contacts and
70 nm contact pitch (CP), equivalent to the ""14 nm"" technology node.",1605.03972v2
2016-10-03,A variational approach to resistive relativistic plasmas,"We develop an action principle to construct the field equations for a
multi-fluid system containing charge-neutral fluids, plasmas, and dissipation
(via resistive interactions), by combining the standard, Maxwell action and
minimal coupling of the electromagnetic field with a recently developed action
for relativistic dissipative fluids. We use a pull-back formalism from
spacetime to abstract matter spaces to build unconstrained variations for both
the charge-neutral fluids and currents making up the plasmas. Using basic
linear algebra techniques, we show that a general ""relabeling"" invariance
exists for the abstract matter spaces. With the field equations in place, a
phenomenological model for the resistivity is developed, using as constraints
charge conservation and the Second Law of Thermodynamics. A minimal model for a
system of electrons, protons, and heat is developed using the Onsager procedure
for incorporating dissipation.",1610.00445v1
2017-02-06,Semiempirical Modeling of Reset Transitions in Unipolar Resistive-Switching Based Memristors,"We have measured the transition process from the high to low resistivity
states, i.e., the reset process of resistive switching based memristors based
on Ni/HfO2/Si-n+ structures, and have also developed an analytical model for
their electrical characteristics. When the characteristic curves are plotted in
the current-voltage (I-V) domain a high variability is observed. In spite of
that, when the same curves are plotted in the charge-flux domain (Q-f), they
can be described by a simple model containing only three parameters: the charge
(Qrst) and the flux (frst) at the reset point, and an exponent, n, relating the
charge and the flux before the reset transition. The three parameters can be
easily extracted from the Q-f plots. There is a strong correlation between
these three parameters, the origin of which is still under study.",1702.01533v1
2017-02-28,Evidence for conventional superconductivity in Sr0.1Bi2Se3 from high pressure studies,"SrxBi2Se3 is recently reported to be a superconductor derived from
topological insulator Bi2Se3. It shows a maximum resistive Tc of 3.25 K at
ambient pressure. We report magnetic (upto 1 GPa) and transport properties
(upro 8 Gpa) under pressure for single crystalline Sr0.1Bi2Se3 superconductor.
Magnetic measurements show that Tc decreases from ~2.6 K (0 GPa) to ~1.9 K
(0.81 GPa). Similar behavior is observed in transport properties as well
without much change in the metallic characteristics in normal state
resistivity. No reentrant superconducting phase (Physical Review B 93, 144514
(2016)) is observed at high pressure. Normal state resistivity near Tc is
explained by Fermi liquid model. Above 100 K, a polaronic hopping conduction
mechanism with two parallel channels for current flow is indicated. Band
structure calculations indicate decreasing density of states at Fermi level
with pressure. In consonance with transition temperature suppression in
conventional BCS low Tc superconductors, the pressure effect in SrxBi2Se3 is
well accounted by pressure induced band broadening.",1702.08829v1
2017-12-21,"DC resistivity of quantum critical, charge density wave states from gauge-gravity duality","In contrast to metals with weak disorder, the resistivity of weakly-pinned
charge density waves (CDWs) is not controlled by irrelevant processes relaxing
momentum. Instead, the leading contribution is governed by incoherent,
diffusive processes which do not drag momentum and can be evaluated in the
clean limit. We compute analytically the dc resistivity for a family of
holographic charge density wave quantum critical phases and discuss its
temperature scaling. Depending on the critical exponents, the ground state can
be conducting or insulating. We connect our results to dc electrical transport
in underdoped cuprate high $T_c$ superconductors. We conclude by speculating on
the possible relevance of unstable, semi-locally critical CDW states to the
strange metallic region.",1712.07994v2
2018-09-27,p-GaAs nanowire MESFETs with near-thermal limit gating,"Difficulties in obtaining high-performance p-type transistors and gate
insulator charge-trapping effects present two major challenges for III-V
complementary metal-oxide semiconductor (CMOS) electronics. We report a p-GaAs
nanowire metal-semiconductor field-effect transistor (MESFET) that eliminates
the need for a gate insulator by exploiting the Schottky barrier at the
metal-GaAs interface. Our device beats the best-performing p-GaSb nanowire
metal-oxide-semiconductor field effect transistor (MOSFET), giving a typical
sub-threshold swing of 62 mV/dec, within 4% of the thermal limit, on-off ratio
$\sim 10^{5}$, on-resistance ~700 k$\Omega$, contact resistance ~30 k$\Omega$,
peak transconductance 1.2 $\mu$S/$\mu$m and high-fidelity ac operation at
frequencies up to 10 kHz. The device consists of a GaAs nanowire with an
undoped core and heavily Be-doped shell. We carefully etch back the nanowire at
the gate locations to obtain Schottky-barrier insulated gates whilst leaving
the doped shell intact at the contacts to obtain low contact resistance. Our
device opens a path to all-GaAs nanowire MESFET complementary circuits with
simplified fabrication and improved performance.",1809.10479v1
2018-10-07,High-resolution disruption halo current measurements using Langmuir probes in Alcator C-Mod,"Halo currents generated during disruptions on Alcator C-Mod have been
measured with Langmuir ""rail"" probes. These rail probes are embedded in a lower
outboard divertor module in a closely-spaced vertical (poloidal) array. The
dense array provides detailed resolution of the spatial dependence (~1 cm
spacing) of the halo current distribution in the plasma scrape-off region with
high time resolution (400 kHz digitization rate). As the plasma limits on the
outboard divertor plate, the contact point is clearly discernible in the halo
current data (as an inversion of current) and moves vertically down the
divertor plate on many disruptions. These data are consistent with filament
reconstructions of the plasma boundary, from which the edge safety factor of
the disrupting plasma can be calculated. Additionally, the halo current
""footprint"" on the divertor plate is obtained and related to the halo flux
width. The voltage driving halo current and the effective resistance of the
plasma region through which the halo current flows to reach the probes are also
investigated. Estimations of the sheath resistance and halo region resistivity
and temperature are given. This information could prove useful for modeling
halo current dynamics.",1810.03207v1
2020-04-27,The Resistivity of High-Tc Cuprates,"We show that the resistivity in each phase of the High-Tc cuprates is a
special case of a general expression derived from the Kubo formula. We obtain,
in particular, the T-linear behavior in the strange metal (SM) and upper
pseudogap (PG) phases, the pure $T^2$, Fermi liquid (FL) behavior observed in
the strongly overdoped regime as well as the $T^{1+\delta}$ behavior that
interpolates both in the crossover. We calculate the coefficients: a) of $T$ in
the linear regime and show that it is proportional to the PG temperature
$T^*(x)$; b) of the $T^2$-term in the FL regime, without adjusting any
parameter; and c) of the $T^{1.6}$ term in the crossover regime, all in
excellent agreement with the experimental data. From our model, we are able to
infer that the resistivity in cuprates is caused by the scattering of holes by
excitons, which naturally form as holes are doped into the electron background.",2004.12785v1
2012-01-05,Phonon-limited transport coefficients in extrinsic graphene,"The effect of electron-phonon scattering processes over the thermoelectric
properties of extrinsic graphene was studied. Electrical and thermal
resistivity, as well as the thermopower, were calculated within the Bloch
theory approximations. Analytical expressions for the different transport
coefficients were obtained from a variational solution of the Boltzmann
equation. The phonon-limited electrical resistivity \rho_{e-ph} shows a linear
dependence at high temperatures, and follows {\rho}_{e-ph} \sim T^{4} at low
temperatures, in agreement with experiments and theory previously reported in
the literature. The phonon-limited thermal resistivity at low temperatures
exhibits a \sim T dependence, and achieves a nearly constant value at high
temperatures. The predicted Seebeck coefficient at verylow temperatures is Q(T)
\sim -\pi 2 k_B T /(3 e E_F), which shows a n^{-1/2} dependence with the
density of carriers, in agreement with experimental evidence. Our results
suggest that thermoelectric properties can be controlled by adjusting the
Bloch-Gruneisen temperature through its dependence on the extrinsic carrier
density in graphene.",1201.1057v1
2012-01-27,Giant negative magnetoresistance in high-mobility 2D electron systems,"We report on a giant negative magnetoresistance in very high mobility
GaAs/AlGaAs heterostructures and quantum wells. The effect is the strongest at
$B \simeq 1$ kG, where the magnetoresistivity develops a minimum emerging at $T
\lesssim 2$ K. Unlike the zero-field resistivity which saturates at $T \simeq 2
$ K, the resistivity at this minimum continues to drop at an accelerated rate
to much lower temperatures and becomes several times smaller than the
zero-field resistivity. Unexpectedly, we also find that the effect is destroyed
not only by increasing temperature but also by modest in-plane magnetic fields.
The analysis shows that giant negative magnetoresistance cannot be explained by
existing theories considering interaction-induced or disorder-induced
corrections.",1201.5679v1
2019-03-12,DEM simulation of soil-tool interaction under extraterrestrial environmental effects,"In contrast to terrestrial environment, the harsh lunar environment
conditions include lower gravity acceleration, ultra-high vacuum and high (low)
temperature in the daytime (night-time). This paper focuses on the effects of
those mentioned features on soil cutting tests, a simplified excavation test,
to reduce the risk of lunar excavation missions. Soil behavior and blade
performance were analyzed under different environmental conditions. The results
show that: (1) the cutting resistance and the energy consumption increase
linearly with the gravity. The bending moment has a bigger increasing rate in
low gravity fields due to a decreasing moment arm; (2) the cutting
resistance,energy consumption and bending moment increase significantly because
of the raised soil strength on the lunar environment, especially in low gravity
fields. Under the lunar environment, the proportions of cutting resistance,
bending moment and energy consumption due to the effect of the van der Waals
forces are significant. Thus, they should be taken into consideration when
planning excavations on the Moon. Therefore, considering that the maximum
frictional force between the excavator and the lunar surface is proportional to
the gravity acceleration, the same excavator that works efficiently on the
Earth may not be able to work properly on the Moon.",1903.04821v1
2019-04-05,Superconductivity in the dilute single band limit in reduced Strontium Titanate,"We report on superconductivity in single crystals of SrTiO$_{3-\delta}$ with
carrier densities $\textit{n} < 1.4 \times10^{18}cm^{-3}$, where only a single
band is occupied. For all samples in this regime, the resistive transition
occurs at $T_{c} \approx 65 \pm 25 \ mK$. We observe a zero resistance state
for $\textit{n}$ as low as $1.03 \times10^{17}cm^{-3}$, and a partial resistive
transition for $\textit{n} = 3.85 \times10^{16}cm^{-3}$. We observe low
critical current densities, relatively high and isotropic upper critical
fields, and an absence of diamagnetic screening in these samples. Our findings
suggest an inhomogeneous superconducting state, embedded within a homogeneous
high-mobility 3-dimensional electron gas. $T_{c}$ does not vary appreciably
when $\textit{n}$ changes by more than an order of magnitude, inconsistent with
conventional superconductivity.",1904.03121v2
2012-06-25,A Study of Ni-Substitution Effects on Heavy-Fermion CeCu2Si2 - Similarities between Ni Substitution and High-Pressure Effects -,"The effects of Ni substitution on Ce(Cu1-xNix)2Si2 have been studied by
specific heat and electrical resistivity measurements. The specific heat
measurement has revealed that the enhanced quantum fluctuations around an
antiferromagnetic quantum critical point are markedly suppressed by Ni
substitution, and that the Fermi liquid state recovers in the Nirich region (x
> 0.12). The characteristic T-linear dependence of the resistivity has been
observed at approximately x ~ 0.10 together with a sign of superconductivity.
The variation of n in the form of rho - rho0 = aT^n against Tmax^1, at which
the resistivity peaks, coincides with the case of high-pressure experiments on
pure CeCu2Si2. The anomalous T-linear behavior appears to occur in the
crossover region from the Kondo regime to the valence fluctuation regime rather
than in the conventional antiferromagnetic quantum critical region.",1206.5747v1
2015-07-08,Future Large-Scale Memristive Device Crossbar Arrays: Limits Imposed by Sneak-Path Currents on Read Operations,"Passive crossbar arrays based upon memristive devices, at crosspoints, hold
great promise for the future high-density and non-volatile memories. The most
significant challenge facing memristive device based crossbars today is the
problem of sneak-path currents. In this paper, we investigate a memristive
device with intrinsic rectification behavior to suppress the sneak-path
currents in crossbar arrays. The device model is implemented in Verilog-A
language and is simulated to match device characteristics readily available in
the literature. Then, we systematically evaluate the read operation performance
of large-scale crossbar arrays utilizing our proposed model in terms of read
margin and power consumption while considering different crossbar sizes,
interconnect resistance values, HRS/LRS (High Resistance State/Low Resistance
State) values, rectification ratios and different read-schemes. The outcomes of
this study are understanding the trade-offs among read margin, power
consumption, read-schemes and most importantly providing a guideline for
circuit designers to improve the performance of a memory based crossbar
structure. In addition, read operation performance comparison of the intrinsic
rectifying memristive device model with other memristive device models are
studied.",1507.02077v1
2020-01-31,Dynamo in weakly collisional nonmagnetized plasmas impeded by Landau damping of magnetic fields,"We perform fully kinetic simulations of flows known to produce dynamo in
magnetohydrodynamics (MHD), considering scenarios with low Reynolds number and
high magnetic Prandtl number, relevant for galaxy cluster scale fluctuation
dynamos. We find that Landau damping on the electrons leads to a rapid decay of
magnetic perturbations, impeding the dynamo. This collisionless damping process
operates on spatial scales where electrons are nonmagnetized, reducing the
range of scales where the magnetic field grows in high magnetic Prandtl number
fluctuation dynamos. When electrons are not magnetized down to the resistive
scale, the magnetic energy spectrum is expected to be limited by the scale
corresponding to magnetic Landau damping or, if smaller, the electron
gyroradius scale, instead of the resistive scale. In simulations we thus
observe decaying magnetic fields where resistive MHD would predict a dynamo.",2001.11929v2
2020-07-24,Strange Metallic Transport in the Antiferromagnetic Regime of Electron Doped Cuprates,"We report magnetoresistance and Hall Effect results for electron-doped films
of the high-temperature superconductor La$_{2-x}$Ce$_x$CuO$_4$ (LCCO) for
temperatures from 0.7 to 45 K and magnetic fields up to 65 T. For x = 0.12 and
0.13, just below the Fermi surface reconstruction (FSR), the normal state
in-plane resistivity exhibits a well-known upturn at low temperature. Our new
results show that this resistivity upturn is eliminated at high magnetic field
and the resistivity becomes linear-in-temperature from $\sim$ 40 K down to 0.7
K. The magnitude of the linear coefficient scales with Tc and doping, as found
previously [1,2] for dopings above the FSR. In addition, the normal state Hall
coefficient has an unconventional field dependence for temperatures below 50K.
This anomalous transport data presents a new challenge to theory and suggests
that the strange metal normal state is also present in the antiferromagnetic
regime.",2007.12765v1
2020-08-26,An 8-bit In Resistive Memory Computing Core with Regulated Passive Neuron and Bit Line Weight Mapping,"The rapid development of Artificial Intelligence (AI) and Internet of Things
(IoT) increases the requirement for edge computing with low power and
relatively high processing speed devices. The Computing-In-Memory(CIM) schemes
based on emerging resistive Non-Volatile Memory(NVM) show great potential in
reducing the power consumption for AI computing. However, the device
inconsistency of the non-volatile memory may significantly degenerate the
performance of the neural network. In this paper, we propose a low power
Resistive RAM (RRAM) based CIM core to not only achieve high computing
efficiency but also greatly enhance the robustness by bit line regulator and
bit line weight mapping algorithm. The simulation results show that the power
consumption of our proposed 8-bit CIM core is only 3.61mW (256*256). The SFDR
and SNDR of the CIM core achieve 59.13 dB and 46.13 dB, respectively. The
proposed bit line weight mapping scheme improves the top-1 accuracy by 2.46%
and 3.47% for AlexNet and VGG16 on ImageNet Large Scale Visual Recognition
Competition 2012 (ILSVRC 2012) in 8-bit mode, respectively.",2008.11669v1
2022-04-29,Nonlocal thermoelectric resistance in vortical viscous transport,"The pursuit for clearly identifiable signatures of viscous electron flow in
the solid state systems has been a paramount task in the search of the
hydrodynamic electron transport behavior. In this work, we investigate
theoretically the nonlocal electric and thermal resistances for the generic
non-Galilean-invariant electron liquids in the multiterminal Hall-bar devices
in the hydrodynamic regime. The role of the device inhomogeneity is carefully
addressed in the model of the disorder potential with the long-range
correlation radius. We obtain analytic expressions for the thermoelectric
resistances that are applicable in the full crossover regime from charge
neutrality to high electron density. We show that the vortical component of the
electron flow manifests in the thermal transport mode close to the charge
neutrality where vorticity is already suppressed by the intrinsic conductivity
in the electric current. This behavior can be tested by the high-resolution
thermal imaging probes.",2204.14104v2
2022-11-04,In-plane anisotropy of electrical transport in Y$_{0.85}$Tb$_{0.15}$Ba$_2$Cu$_3$O$_{7-x}$ films,"We fabricate high-quality c-axis oriented epitaxial YBa$_2$Cu$_3$O$_{7-x}$
films with 15% of yttrium atoms replaced by terbium (YTBCO) and study their
electrical properties. The Tb substitution reduces the charge carrier density
resulting in increased resistivity and decreased critical current density
compared to the pure YBa$_2$Cu$_3$O$_{7-x}$ films. The electrical properties of
the YTBCO films show an in-plane anisotropy in both the superconducting and
normal state providing evidence for the twin-free film. Unexpectedly, the
resistive transition of the bridges also demonstrates the in-plane anisotropy
that can be explained within the framework of Tinkham's model of the resistive
transition and the Berezinskii-Kosterlitz-Thouless (BKT) model depending on the
sample parameters. We consider YTBCO films to be a promising platform for both
the fundamental research on the BKT transition in the cuprate superconductors
and for the fabrication of devices with high kinetic inductance.",2211.02564v2
2023-02-23,Anomalous Electronic Transport in High Mobility Corbino Rings,"We report low-temperature electronic transport measurements performed in two
multi-terminal Corbino samples formed in GaAs/Al-GaAs two-dimensional electron
gases (2DEG) with both ultra-high electron mobility ($\gtrsim 20\times 10^6$
$cm^2/Vs)$ and with distinct electron density of $1.7$ and $3.6\times
10^{11}~cm^{-2}$. In both Corbino samples, a non-monotonic behavior is observed
in the temperature dependence of the resistance below 1~$K$. Surprisingly, a
sharp {\it decrease} in resistance is observed with {\it increasing}
temperature in the sample with lower electron density, whereas an opposite
behavior is observed in the sample with higher density. To investigate further,
transport measurements were performed in large van der Pauw samples having
identical heterostructures, and as expected they exhibit resistivity that is
monotonic with temperature. Finally, we discuss the results in terms of various
lengthscales leading to ballistic and hydrodynamic electronic transport, as
well as a possible Gurzhi effect.",2302.12147v2
2024-01-01,"Debye temperature, electron-phonon coupling constant, and microcrystalline strain in highly-compressed La$_3$Ni$_2$O$_{7-δ}$","Recently Sun et al (Nature 621, 493 (2023)) reported on the discovery of
high-temperature superconductivity in highly-compressed
La$_3$Ni$_2$O$_{7-\delta}$. In addition to ongoing studies of the phase
structural transition, pairing mechanism, and other properties/parameters in
this highly-pressurized nickelate, here explore a possibility for the
electron-phonon pairing mechanism in the La$_3$Ni$_2$O$_{7-\delta}$. To do
this, we analyzed experimental data on temperature dependent resistance,
$R(T)$, and extracted pressure dependent Debye temperature, $\Theta_D$, for the
$Fmmm$-phase (high-pressure phase). Derived ballpark value is $\Theta_D(P = 25
GPa) = 550$ $K$. We also estimated the electron-phonon coupling constant,
$\lambda_{e-ph}(P=22.4 GPa) = 1.75$, for La$_3$Ni$_2$O$_{7-\delta}$ sample
exhibited zero-resistance transition. Performed analysis of XRD data showed
that the crystal lattice strain, $\epsilon(P)$, is higher in the $Fmmm$-phase
in comparison with the $Amam$-phase (low-pressure phase). Based on performed
$\epsilon(P)$ analysis, we proposed possible reason for the presence/absence of
the zero-resistance state in La$_3$Ni$_2$O$_{7-\delta}$.",2401.00804v2
2024-01-15,Comprehensive Joint Modeling of First-Line Therapeutics in Non-Small Cell Lung Cancer,"First-line antiproliferatives for non-small cell lung cancer (NSCLC) have a
relatively high failure rate due to high intrinsic resistance rates and
acquired resistance rates to therapy. 57% patients are diagnosed in late-stage
disease due to the tendency of early-stage NSCLC to be asymptomatic. For
patients first diagnosed with metastatic disease the 5-year survival rate is
approximately 5%. To help accelerate the development of novel therapeutics and
computer-based tools for optimizing individual therapy, we have collated data
from 11 different clinical trials in NSCLC and developed a semi-mechanistic,
clinical model of NSCLC growth and pharmacodynamics relative to the various
therapeutics represented in the study. In this study, we have produced
extremely precise estimates of clinical parameters fundamental to cancer
modeling such as the rate of acquired resistance to various pharmaceuticals,
the relationship between drug concentration and rate of cancer cell death, as
well as the fine temporal dynamics of anti-VEGF therapy. In the simulation sets
documented in this study, we have used the model to make meaningful
descriptions of efficacy gain in making bevacizumab-antiproliferative
combination therapy sequential, over a series of days, rather than concurrent.",2401.07719v1
2018-11-09,A Detailed Model of the Irish High Voltage Power Network for Simulating GICs,"Constructing a power network model for geomagnetically induced current (GIC)
calculations requires information on the DC resistances of elements within a
network. This information is often not known, and power network models are
simplified as a result, with assumptions used for network element resistances.
Ireland's relatively small, isolated network presents an opportunity to model a
complete power network in detail, using as much real-world information as
possible. A complete model of the Irish 400, 275, 220 and 110 kV network was
made for GIC calculations, with detailed information on the number, type and DC
resistances of transformers. The measured grounding resistances at a number of
substations were also included in the model, which represents a considerable
improvement on previous models of the Irish power network for GIC calculations.
Sensitivity tests were performed to show how calculated GIC amplitudes are
affected by different aspects of the model. These tests investigated: (1) How
the orientation of a uniform electric field affects GICs. (2) The effect of
including/omitting lower-voltage elements of the power network. (3) How the
substation grounding resistances assumptions affected GIC values. It was found
that changing the grounding resistance value had a considerable effect on
calculated GICs at some substations, and no discernible effect at others.
Finally, five recent geomagnetic storm events were simulated in the network. It
was found that heavy rainfall prior to the 26-28 August 2015 geomagnetic storm
event may have had a measurable impact on measured GIC amplitudes at a 400/220
kV transformer ground.",1811.04128v1
2020-03-09,Understanding the reduction of the edge safety factor during hot VDEs and fast edge cooling events,"In the present work a simple analytical approach is presented in order to
clarify the physics behind the edge current density behaviour of a hot plasma
entering in contact with a resistive conductor. When a plasma enters in contact
with a highly resistive wall, large current densities appear at the edge of the
plasma. The model shows that this edge current originates from the plasma
response, which attempts to conserve the poloidal magnetic flux ($\Psi$) when
the outer current is being lost. The loss of outer current is caused by the
high resistance of the outer current path compared to the plasma core
resistance. The resistance of the outer path may be given by plasma contact
with a very resistive structure or by a sudden decrease of the outer plasma
temperature (e.g. due to a partial thermal quench or due to a cold front
penetration caused by massive gas injection). For general plasma geometries and
current density profiles the model shows that given a small change of minor
radius ($\delta a$) the plasma current is conserved to first order ($\delta I_p
= 0 + \mathcal{O}(\delta a^2)$). This conservation comes from the fact that
total inductance remains constant ($\delta L = 0$) due to an exact compensation
of the change of external inductance with the change of internal inductance
($\delta L_\text{ext}+\delta L_\text{int} = 0$). As the total current is
conserved and the plasma volume is reduced, the edge safety factor drops
according to $q_a \propto a^2/I_p$. Finally the consistency of the resulting
analytical predictions is checked with the help of free-boundary MHD
simulations.",2003.04064v1
2019-07-24,GR-MHD disk winds and jets from black holes and resistive accretion disks,"We perform GR-MHD simulations of outflow launching from thin accretion disks.
As in the non-relativistic case, resistivity is essential for the mass loading
of the disk wind. We implemented resistivity in the ideal GR-MHD code HARM3D,
extending previous works (Qian et al. 2017, 2018) for larger physical grids,
higher spatial resolution, and longer simulation time. We consider an initially
thin, resistive disk orbiting the black hole, threaded by a large-scale
magnetic flux. As the system evolves, outflows are launched from the black hole
magnetosphere and the disk surface. We mainly focus on disk outflows,
investigating their MHD structure and energy output in comparison with the
Poynting-dominated black hole jet. The disk wind encloses two components -- a
fast component dominated by the toroidal magnetic field and a slower component
dominated by the poloidal field. The disk wind transitions from sub to
super-Alfv\'enic speed, reaching velocities $\simeq 0.1c$. We provide parameter
studies varying spin parameter and resistivity level, and measure the
respective mass and energy fluxes. A higher spin strengthens the
$B_{\phi}$-dominated disk wind along the inner jet. We disentangle a critical
resistivity level that leads to a maximum matter and energy output for both,
resulting from the interplay between re-connection and diffusion, which in
combination govern the magnetic flux and the mass loading. For counter-rotating
black holes the outflow structure shows a magnetic field reversal. We estimate
the opacity of the inner-most accretion stream and the outflow structure around
it. This stream may be critically opaque for a lensed signal, while the axial
jet funnel remains optically thin.",1907.10622v1
2017-05-23,The influence of outflow and global magnetic field on the structure and spectrum of resistive CDAFs,"We examine the effects of a global magnetic field and outflow on radiatively
inefficient accretion flow (RIAF) in the presence of magnetic resistivity. We
find a self-similar solutions for the height integrated equations that govern
the behavior of the flow. We use the mixing length mechanism for studying the
convection parameter. We adopt a radius dependent mass accretion rate as
$\dot{M}=\dot{M}_{out}{(\frac{r}{r_{out}})^{s}}$ with $s> 0$ to investigate the
influence of outflow on the structure of inflow where $s$ is a constant and
indication the effect of wind. Also, we have studied the radiation spectrum and
temperature of CDAFs. The thermal bermsstrahlung emission as a radiation
mechanism is taken into account for calculating the spectra emitted by the
CDAFs. The energy that powers bremsstrahlung emission at large radii is
provided by convective transport from small radii and viscous and resistivity
dissipation. Our results indicate that the disc rotates slower and accretes
faster, it becomes hotter and thicker for stronger wind. By increasing all
component of magnetic field, the disc rotates faster and accretes slower while
it becomes hotter and thicker. We show that the outflow parameter and all
component of magnetic field have the same effects on the luminosity of the
disc. We compare the dynamical structure of the disc in two different solutions
(with and without resistivity parameter). We show that only the radial infall
velocity and the surface density could changed by resistivity parameter
obviously. Increasing the effect of wind increases the disc's temperature and
luminosity of the disc. The effect of magnetic field is similar to the effect
of wind in the disc's temperature and luminosity of the disc, but the influence
of resistivity on the observational properties is not evident.",1705.08099v1
2020-01-21,Particle acceleration with anomalous pitch angle scattering in 3D separator reconnection,"Understanding how the release of stored magnetic energy contributes to the
generation of non-thermal high energy particles during solar flares is an
important open problem in solar physics. Magnetic reconnection plays a
fundamental role in the energy release and conversion processes taking place
during flares. A common approach for investigating particle acceleration is to
use test particles in fields derived from magnetohydrodynamic (MHD) simulations
of reconnection. These MHD simulations use anomalous resistivities that are
much larger than the Spitzer resistivity based on Coulomb collisions. The
processes leading to enhanced resistivity should also affect the test
particles. We explore the link between resistivity and particle orbits building
on a previous study using a 2D MHD simulation of magnetic reconnection. This
paper extends the previous investigation to a 3D magnetic reconnection
configuration and to study the effect on test particle orbits. We carried out
orbit calculations using a 3D MHD simulation of separator reconnection. We use
the relativistic guiding centre approximation including stochastic pitch angle
scattering. The effects of varying the resistivity and the models for pitch
angle scattering on particle orbit trajectories, final positions, energy
spectra, final pitch angle distribution, and orbit duration are all studied in
detail. Pitch angle scattering widens collimated beams of orbit trajectories,
allowing orbits to access previously unaccessible field lines; this causes
final positions to spread to topological structures that were previously
inaccessible. Scattered orbit energy spectra are found to be predominantly
affected by the level of anomalous resistivity, with the pitch angle scattering
model only playing a role in isolated cases. Scattering is found to play a
crucial role in determining the pitch angle and orbit duration distributions.",2001.07548v1
2021-07-27,Resistance distance distribution in large sparse random graphs,"We consider an Erdos-Renyi random graph consisting of N vertices connected by
randomly and independently drawing an edge between every pair of them with
probability c/N so that at N->infinity one obtains a graph of finite mean
degree c. In this regime, we study the distribution of resistance distances
between the vertices of this graph and develop an auxiliary field
representation for this quantity in the spirit of statistical field theory.
Using this representation, a saddle point evaluation of the resistance distance
distribution is possible at N->infinity in terms of an 1/c expansion. The
leading order of this expansion captures the results of numerical simulations
very well down to rather small values of c; for example, it recovers the
empirical distribution at c=4 or 6 with an overlap of around 90%. At large
values of c, the distribution tends to a Gaussian of mean 2/c and standard
deviation sqrt{2/c^3}. At small values of c, the distribution is skewed toward
larger values, as captured by our saddle point analysis, and many fine features
appear in addition to the main peak, including subleading peaks that can be
traced back to resistance distances between vertices of specific low degrees
and the rest of the graph. We develop a more refined saddle point scheme that
extracts the corresponding degree-differentiated resistance distance
distributions. We then use this approach to recover analytically the most
apparent of the subleading peaks that originates from vertices of degree 1.
Rather intuitively, this subleading peak turns out to be a copy of the main
peak, shifted by one unit of resistance distance and scaled down by the
probability for a vertex to have degree 1. We comment on a possible lack of
smoothness in the true N->infinity distribution suggested by the numerics.",2107.12561v2
2002-01-30,Activity in Very Cool Stars: Magnetic Dissipation in late-M and L Dwarf Atmospheres,"Recent observations show that chromospheric activity in late-M and L dwarfs
is much lower than in the earlier M types, in spite of comparatively rapid
rotation. We investigate the possibility that this drop-off in activity results
from the very high electrical resistivities in the dense, cool and
predominantly neutral atmospheres of late-M and L dwarfs. We calculate magnetic
field diffusivities in the atmospheres of objects with effective temperatures
in the range 3000-1500 (mid-M to L), using the atmospheric structure models of
Allard and Hauschildt. We find that the combination of very low ionization
fraction and high density in these atmospheres results in very large
resistivities due to neutral-charged particle collisions, and efficient field
diffusion. The resistivities are found to increase with both decreasing optical
depth, and decreasing effective temperature. As a result, any existing magnetic
fields are increasingly decoupled from atmospheric motions as one moves from
mid-M to L; we quantify this through a simple Reynolds number calculation.
This, coupled with the difficulty in transporting magnetic stresses through the
highly resistive atmosphere, can account for the observed drop in activity from
mid-M to L, assuming activity in these objects is magnetically driven. We also
examine the issue of acoustic heating, and find that this appears inadequate to
explain the observed H-alpha fluxes in mid-M to L dwarfs. Consequently,
magnetic heating does seem to be the most viable mechanism for generating
activity in these objects. Finally, we speculate on a possible flare mechanism
in these cool dwarfs.",0201518v1
1996-11-14,Vortex Quantum Nucleation and Tunneling in Superconducting Thin Films: Role of Dissipation and Periodic Pinning,"We investigate the phenomenon of decay of a supercurrent in a superconducting
thin film in the absence of an applied magnetic field. The resulting
zero-temperature resistance derives from two equally possible mechanisms: 1)
quantum tunneling of vortices from the edges of the sample; and 2) homogeneous
quantum nucleation of vortex-antivortex pairs in the bulk of the sample,
arising from the instability of the Magnus field's ``vacuum''. We study both
situations in the case where quantum dissipation dominates over the inertia of
the vortices. We find that the vortex tunneling and nucleation rates have a
very rapid dependence on the current density driven through the sample.
Accordingly, whilst normally the superconductor is essentially resistance-free,
for the high current densities that can be reached in high-$T_c$ films a
measurable resistance might develop. We show that edge-tunneling appears
favoured, but the presence of pinning centres and of thermal fluctuations leads
to an enhancement of the nucleation rates. In the case where a periodic pinning
potential is artificially introduced in the sample, we show that
current-oscillations will develop indicating an effect specific to the
nucleation mechanism where the vortex pair-production rate, thus the
resistance, becomes sensitive to the corrugation of the pinning substrate. In
all situations, we give estimates for the observability of the studied
phenomena.",9611112v1
1997-12-19,C-axis resistivity and high Tc superconductivity,"Recently we had proposed a mechanism for the normal-state C-axis resistivity
of the high-T$_c$ layered cuprates that involved blocking of the
single-particle tunneling between the weakly coupled planes by strong
intra-planar electron-electron scattering. This gave a C-axis resistivity that
tracks the ab-plane T-linear resistivity, as observed in the high-temperature
limit. In this work this mechanism is examined further for its implication for
the ground-state energy and superconductivity of the layered cuprates. It is
now argued that, unlike the single-particle tunneling, the tunneling of a
boson-like pair between the planes prepared in the BCS-type coherent trial
state remains unblocked inasmuch as the latter is by construction an eigenstate
of the pair annihilation operator. The resulting pair-delocalization along the
C-axis offers energetically a comparative advantage to the paired-up trial
state, and, thus stabilizes superconductivity. In this scheme the strongly
correlated nature of the layered system enters only through the blocking
effect, namely that a given electron is effectively repeatedly monitored
(intra-planarly scattered) by the other electrons acting as an environment, on
a time-scale shorter than the inter-planar tunneling time. Possible
relationship to other inter-layer pairing mechanisms proposed by several
workers in the field is also briefly discussed.",9712247v2
2000-07-03,Electron-Phonon Coupling Origin of the resistivity in YNi_{2}B_{2}C Single Crystals,"Resistivity measurements from 4.2 K up to 300 K were made on YNi_{2}B_{2}C
single crystals with Tc=15.5 K. The resulting rho(T) curve shows a perfect
Bloch-Grueneisen (BG) behavior, with a very small residual resistivity which
indicates the low impurity content and the high cristallographic quality of the
samples. The value lambda_{tr}=0.53 for the transport electron-phonon coupling
constant was obtained by using the high-temperature constant value of d(rho)/dT
and the plasma frequency reported in literature. The BG expression for the
phononic part of the resistivity rho_{ph}(T) was then used to fit the data in
the whole temperature range, by approximating alpha^{2}_{tr}F(Omega) with the
experimental phonon spectral density G(Omega) multiplied by a two-step
weighting function to be determined by the fit. The resulting fitting curve
perfectly agrees with the experimental points. We also solved the real-axis
Eliashberg equations in both s- and d-wave symmetries under the approximation
alpha^{2}F(Omega)= alpha^{2}_{tr}F(Omega). We found that the value of
lambda_{tr} here determined in single-band approximation is quite compatible
with Tc and the gap Delta experimentally observed. Finally, we calculated the
normalized tunneling conductance, whose comparison with break-junction tunnel
data gives indication of the possible s-wave symmetry for the order parameter
in YNi_{2}B_{2}C.",0007033v1
2010-12-10,High pressure study of transport properties in Co$_{1/3}$NbS$_2$,"This is the first study of the effect of pressure on transition metal
dichalcogenides intercalated by atoms that order magnetically.
Co$_{1/3}$NbS$_2$ is a layered system where the intercalated Co atoms order
antiferromagnetically at T$_N$ = 26 K at ambient pressure. We have conducted a
detailed study of dc-resistivity ($\rho$), thermoelectric power (S) and thermal
conductivity ($\kappa$). We found that at ambient pressure the magnetic
transition corresponds to a well pronounced peak in dS/dT, as well as to a kink
in the dc-resistivity. The effect of ordering on the thermal conductivity is
rather small but, surprisingly, more pronounced in the lattice contribution
than in the electronic contribution to $\kappa$. Under pressure, the
resistivity increases in the high temperature range, contrary to all previous
measurements in other layered transition metal dichalcogenides (TMD). In the
low temperature range, the strong dependences of thermopower and resistivity on
pressure are observed below TN, which, in turn, also depends on pressure at
rate of dT$_N$/dp $\approx$ -1 K/kbar. Several possible microscopic
explanations of the reduction of the ordering temperature and the evolution of
the transport properties with pressure are discussed.",1012.2408v1
2011-09-14,Evidence for a fractional quantum Hall state with anisotropic longitudinal transport,"At high magnetic fields, where the Fermi level lies in the N=0 lowest Landau
level (LL), a clean two-dimensional electron system (2DES) exhibits numerous
incompressible liquid phases which display the fractional quantized Hall effect
(FQHE) (Das Sarma and Pinczuk, 1997). These liquid phases do not break
rotational symmetry, exhibiting resistivities which are isotropic in the plane.
In contrast, at lower fields, when the Fermi level lies in the $N\ge2$ third
and several higher LLs, the 2DES displays a distinctly different class of
collective states. In particular, near half filling of these high LLs the 2DES
exhibits a strongly anisotropic longitudinal resistance at low temperatures
(Lilly et al., 1999; Du et al., 1999). These ""stripe"" phases, which do not
exhibit the quantized Hall effect, resemble nematic liquid crystals, possessing
broken rotational symmetry and orientational order (Koulakov et al., 1996;
Fogler et al., 1996; Moessner and Chalker, 1996; Fradkin and Kivelson, 1999;
Fradkin et al, 2010). Here we report a surprising new observation: An
electronic configuration in the N=1 second LL whose resistivity tensor
simultaneously displays a robust fractionally quantized Hall plateau and a
strongly anisotropic longitudinal resistance resembling that of the stripe
phases.",1109.3219v3
2011-10-18,A numerical model of resistive generation of intergalactic magnetic field at cosmic dawn,"Miniati and Bell (2011) proposed a mechanism for the generation of magnetic
seeds that is based the finite resistivity of the low temperature IGM in the
high redshift universe. In this model, cosmic-ray protons generated by the
first generation of galaxies, escape into the intergalactic medium carrying an
electric current that induces return currents, $j_t$, and associated electric
fields, $\vec E=\eta\vec j_t$ there. Because the resistivity, $\eta$, depends
on the IGM temperature, which is highly inhomogeneous due to adiabatic
contraction and shocks produced by structure formation, a non-vanishing curl of
the electric field exists which sustains the growth of magnetic field. In this
contribution we have developed an approximate numerical model for this process
by implementing the source terms of the resistive mechanism in the cosmological
code CHARM. Our numerical estimates substantiate the earlier analysis in
Miniati and Bell (2011) which found magnetic seeds between 10$^{-18}$ and
10$^{-16}$ Gauss throughout cosmic space at redshift z~6, consistent with
conservative estimates of magnetic fields in voids at z~0 from recent gamma-ray
experiments.",1110.4115v1
2017-02-18,Soft-proton exchange on Magnesium-oxide-doped substrates a route toward efficient and power-resistant nonlinear converters,"Despite its attractive features, Congruent-melted Lithium Niobate (CLN)
suffers from Photo-Refractive Damage (PRD). This light-induced refractive-index
change hampers the use of CLN when high-power densities are in play, a typical
regime in integrated optics. The resistance to PRD can be largely improved by
doping the lithium-niobate substrates with magnesium oxide. However, the
fabrication of waveguides on MgO-doped substrates is not as effective as for
CLN: either the resistance to PRD is strongly reduced by the waveguide
fabrication process (as it happens in Ti-indiffused waveguides) or the
nonlinear conversion efficiency is lowered (as it occurs in annealed-proton
exchange). Here we fabricate, for the first time, waveguides starting from
MgO-doped substrates using the Soft-Proton Exchange (SPE) technique and we show
that this third way represents a promising alternative. We demonstrate that SPE
allows to produce refractive-index profiles almost identical to those produced
on CLN without reducing the nonlinearity in the substrate. We also prove that
the SPE does not affect substantially the resistance to PRD. Since the
fabrication recipe is identical between CLN and MgO-doped substrates, we
believe that SPE might outperform standard techniques to fabricate robust and
efficient waveguides for high-intensity-beam confinement.",1702.05590v1
2019-04-11,Novel Resistive-Plate WELL sampling element for (S)DHCAL,"Digital and Semi-Digital Hadronic Calorimeters (S)DHCAL were suggested for
future Colliders as part of the particle-flow concept. Though studied mostly
with RPC-based techniques, investigations have shown that MPGD-based sampling
elements could outperform. An attractive, industry-produced, robust,
particle-tracking detector for large-area coverage, e.g. in (S)DHCAL, could be
the novel single-stage Resistive Plate WELL (RPWELL). It is a single-sided
THGEM coupled to the segmented readout electrode through a sheet of large bulk
resistivity. We summarize here the preliminary test-beam results obtained with
6.5 mm thick (incl. electronics) {$48 \times 48\,\mathrm{cm^2}$}~RPWELL
detectors. Two configurations are considered: a standalone RPWELL detector
studied with 150 GeV muons and high-rate pions beams and RPWELL sampling
element investigated within a small-(S)DHCAL prototype consisting of 7
resistive MICROMEGAS sampling elements followed by 5 RPWELL ones. The sampling
elements were equipped with a Semi-Digital readout electronics based on the
MICROROC chip.",1904.05545v2
2020-05-22,Accelerating Antimicrobial Discovery with Controllable Deep Generative Models and Molecular Dynamics,"De novo therapeutic design is challenged by a vast chemical repertoire and
multiple constraints, e.g., high broad-spectrum potency and low toxicity. We
propose CLaSS (Controlled Latent attribute Space Sampling) - an efficient
computational method for attribute-controlled generation of molecules, which
leverages guidance from classifiers trained on an informative latent space of
molecules modeled using a deep generative autoencoder. We screen the generated
molecules for additional key attributes by using deep learning classifiers in
conjunction with novel features derived from atomistic simulations. The
proposed approach is demonstrated for designing non-toxic antimicrobial
peptides (AMPs) with strong broad-spectrum potency, which are emerging drug
candidates for tackling antibiotic resistance. Synthesis and testing of only
twenty designed sequences identified two novel and minimalist AMPs with high
potency against diverse Gram-positive and Gram-negative pathogens, including
one multidrug-resistant and one antibiotic-resistant K. pneumoniae, via
membrane pore formation. Both antimicrobials exhibit low in vitro and in vivo
toxicity and mitigate the onset of drug resistance. The proposed approach thus
presents a viable path for faster and efficient discovery of potent and
selective broad-spectrum antimicrobials.",2005.11248v2
2020-10-22,Projecting the optimal control strategy on invasive plants combining effects of herbivores and native plants resistance,"Understanding how to limit biological invasion is critical, especially in the
context of accelerating anthropogenic ecological changes. Although biological
invasion success could be explained by the lack of natural enemies in new
regions, recent studies have revealed that resident herbivores often do have a
substantial effect on both native and invasive plants. Very few studies have
included consideration of native plant resistance while estimating methods of
controlling invasion; hence, it is unclear to what extent the interactive
effects of controlling approaches and native plants' resistance could slow down
or even inhibit biological invasion. We developed a spatial modeling framework,
using a paired logistic equation model, with considerations of the dispersal
processes, to capture the dynamics change of native and invasive plants under
various strategies of control. We found that when biocontrol agents could have
a strong effect on invasive plant, that could almost completely limit the
invasion, together with a high native plant resistance. However, a high
application frequency is needed make an efficient impact, whereas, a low
frequency treatment leads to nearly the same outcome as the no treatment case.
Lastly, we showed that evenly controlling a larger area with a weaker effect
still lead to a better outcome than focusing on small patches with a stronger
effect. Overall, this study has some management implications, such as how to
determine the optimal allocation strategy.",2010.14944v1
2021-10-14,Mitigation of parasitic losses in the quadrupole resonator enabling direct measurements of low residual resistances of SRF samples,"The quadrupole resonator (QPR) is a dedicated sample-test cavity for the RF
characterization of superconducting samples in a wide temperature, RF field and
frequency range. Its main purpose are high resolution measurements of the
surface resistance with direct access to the residual resistance thanks to the
low frequency of the first operating quadrupole mode. Besides the well-known
high resolution of the QPR, a bias of measurement data towards higher values
has been observed, especially at higher harmonic quadrupole modes. Numerical
studies show that this can be explained by parasitic RF losses on the adapter
flange used to mount samples into the QPR. Coating several micrometer of
niobium on those surfaces of the stainless steel flange that are exposed to the
RF fields significantly reduced this bias, enabling a direct measurement of a
residual resistance smaller than 5 n$\Omega$ at 2 K and 413 MHz. A constant
correction based on simulations was not feasible due to deviations from one
measurement to another. However, this issue is resolved given these new
results.",2110.07236v2
2022-01-27,On the Mitigation of Read Disturbances in Neuromorphic Inference Hardware,"Non-Volatile Memory (NVM) cells are used in neuromorphic hardware to store
model parameters, which are programmed as resistance states. NVMs suffer from
the read disturb issue, where the programmed resistance state drifts upon
repeated access of a cell during inference. Resistance drifts can lower the
inference accuracy. To address this, it is necessary to periodically reprogram
model parameters (a high overhead operation). We study read disturb failures of
an NVM cell. Our analysis show both a strong dependency on model
characteristics such as synaptic activation and criticality, and on the voltage
used to read resistance states during inference. We propose a system software
framework to incorporate such dependencies in programming model parameters on
NVM cells of a neuromorphic hardware. Our framework consists of a convex
optimization formulation which aims to implement synaptic weights that have
more activations and are critical, i.e., those that have high impact on
accuracy on NVM cells that are exposed to lower voltages during inference. In
this way, we increase the time interval between two consecutive reprogramming
of model parameters. We evaluate our system software with many emerging
inference models on a neuromorphic hardware simulator and show a significant
reduction in the system overhead.",2201.11527v1
2024-03-20,Picosecond Femtojoule Resistive Switching in Nanoscale VO$_{2}$ Memristors,"Beyond-Moore computing technologies are expected to provide a sustainable
alternative to the von Neumann approach not only due to their down-scaling
potential but also via exploiting device-level functional complexity at the
lowest possible energy consumption. The dynamics of the Mott transition in
correlated electron oxides, such as vanadium dioxide, has been identified as a
rich and reliable source of such functional complexity. However, its full
potential in high-speed and low-power operation has been largely unexplored. We
fabricated nanoscale VO$_{2}$ devices embedded in a broad-band test circuit to
study the speed and energy limitations of their resistive switching operation.
Our picosecond time-resolution, real-time resistive switching experiments and
numerical simulations demonstrate that tunable low-resistance states can be set
by the application of 20~ps long, $<$1.7~V amplitude voltage pulses at 15~ps
incubation times and switching energies starting from a few femtojoule.
Moreover, we demonstrate that at nanometer-scale device sizes not only the
electric field induced insulator-to-metal transition, but also the thermal
conduction limited metal-to-insulator transition can take place at timescales
of 100's of picoseconds. These orders of magnitude breakthroughs open the route
to the design of high-speed and low-power dynamical circuits for a plethora of
neuromorphic computing applications from pattern recognition to numerical
optimization.",2403.13530v1
2024-05-21,A lightweight PUF-based authentication protocol,"Lightweight authentication is essential for resource-constrained
Internet-of-Things (IoT). Implementable with low resource and operable with low
power, Physical Unclonable Functions (PUFs) have the potential as hardware
primitives for implementing lightweight authentication protocols. The arbiter
PUF (APUF) is probably the most lightweight strong PUF capable of generating
exponentially many challenge-response pairs (CRPs), a desirable property for
authentication protocols, but APUF is severely weak against modeling attacks.
Efforts on PUF design have led to many PUFs of higher resistance to modeling
attacks and also higher area overhead. There are also substantial efforts on
protocol development, some leverage PUFs' strength in fighting modeling
attacks, and some others employ carefully designed protocol techniques to
obfuscate either the challenges or the responses with modest increase of area
overhead for some or increased operations for some others. To attain both low
resource footprint and high modeling attack resistance, in this paper we
propose a co-design of PUF and protocol, where the PUF consists of an APUF and
a zero-transistor interface that obfuscates the true challenge bits fed to the
PUF. The obfuscated PUF possesses rigorously proven potential and
experimentally supported performance against modeling attacks when a condition
is met, and the protocol provides the condition required by the PUF and
leverages the PUF's modeling resistance to arrive at low resource overhead and
high operational simplicity, enabling lightweight authentications while
resisting modeling attacks.",2405.13146v1
2008-04-14,Phase Diagram and Quantum Critical Point in Newly Discovered Superconductors: SmO_{1-x}F_xFeAs,"The magnetic fluctuations associated with a quantum critical point (QCP) are
widely believed to cause the non-Fermi liquid behaviors and unconventional
superconductivities, for example, in heavy fermion systems and high temperature
cuprate superconductors. Recently, superconductivity has been discovered in
iron-based layered compound $LaO_{1-x}F_xFeAs$ with $T_c$=26 K\cite{yoichi},
and it competes with spin-density-wave (SDW) order\cite{dong}. Neutron
diffraction shows a long-rang SDW-type antiferromagnetic (AF) order at $\sim
134$ K in LaOFeAs\cite{cruz,mcguire}. Therefore, a possible QCP and its role in
this system are of great interests. Here we report the detailed phase diagram
and anomalous transport properties of the new high-Tc superconductors
$SmO_{1-x}F_xFeAs$ discovered by us\cite{chenxh}. It is found that
superconductivity emerges at $x\sim$0.07, and optimal doping takes place in the
$x\sim$0.20 sample with highest $T_c \sim $54 K. While $T_c$ increases
monotonically with doping, the SDW order is rapidly suppressed, suggesting a
QCP around $x \sim$0.14. As manifestations, a linear temperature dependence of
the resistivity shows up at high temperatures in the $x<0.14$ regime, but at
low temperatures just above $T_c$ in the $x>0.14$ regime; a drop in carrier
density evidenced by a pronounced rise in Hall coefficient are observed, which
mimic the high-$T_c$ cuprates. The simultaneous occurrence of order, carrier
density change and criticality makes a compelling case for a quantum critical
point in this system.",0804.2105v3
2008-07-07,Magnetoresistance and collective Coulomb blockade in super-lattices of ferromagnetic CoFe nanoparticles,"We report on transport properties of millimetric super-lattices of CoFe
nanoparticles surrounded by organic ligands. R(T)s follow R(T) =
R_0.exp(T/T_0)^0.5 with T_0 ranging from 13 to 256 K. At low temperature I(V)s
follow I=K[(V-V_T)/V_T]^ksi with ksi ranging 3.5 to 5.2. I(V) superpose on a
universal curve when shifted by a voltage proportional to the temperature.
Between 1.8 and 10 K a high-field magnetoresistance with large amplitude and a
strong voltage-dependence is observed. Its amplitude only depends on the
magnetic field/temperature ratio. Its origin is attributed to the presence of
paramagnetic states present at the surface or between the nanoparticles. Below
1.8 K, this high-field magnetoresistance abruptly disappears and inverse
tunnelling magnetoresistance is observed, the amplitude of which does not
exceed 1%. At this low temperature, some samples display in their I(V)
characteristics abrupt and hysteretic transitions between the Coulomb blockade
regime and the conductive regime. The increase of the current during these
transitions can be as high as a factor 30. The electrical noise increases when
the sample is near the transition. The application of a magnetic field
decreases the voltage at which these transitions occur so magnetic-field
induced transitions are also observed. Depending on the applied voltage, the
temperature and the amplitude of the magnetic field, the magnetic-field induced
transitions are either reversible or irreversible. These abrupt and hysteretic
transitions are also observed in resistance-temperature measurements. They
could be the soliton avalanches predicted by Sverdlov et al. [Phys. Rev. B 64,
041302 (R), 2001] or could also be interpreted as a true phase transition
between a Coulomb glass phase to a liquid phase of electrons.",0807.1060v3
2015-09-29,Simulation of radiation-induced defects,"Mainly due to their outstanding performance the position sensitive silicon
detectors are widely used in the tracking systems of High Energy Physics
experiments such as the ALICE, ATLAS, CMS and LHCb at LHC, the world's largest
particle physics accelerator at CERN, Geneva. The foreseen upgrade of the LHC
to its high luminosity (HL) phase (HL-LHC scheduled for 2023), will enable the
use of maximal physics potential of the facility. After 10 years of operation
the expected fluence will expose the tracking systems at HL-LHC to a radiation
environment that is beyond the capacity of the present system design. Thus, for
the required upgrade of the all-silicon central trackers extensive measurements
and simulation studies for silicon sensors of different designs and materials
with sufficient radiation tolerance have been initiated within the RD50
Collaboration.
  Supplementing measurements, simulations are in vital role for e.g. device
structure optimization or predicting the electric fields and trapping in the
silicon sensors. The main objective of the device simulations in the RD50
Collaboration is to develop an approach to model and predict the performance of
the irradiated silicon detectors using professional software. The first
successfully developed quantitative models for radiation damage, based on two
effective midgap levels, are able to reproduce the experimentally observed
detector characteristics like leakage current, full depletion voltage and
charge collection efficiency (CCE). Recent implementations of additional traps
at the SiO$_2$/Si interface or close to it have expanded the scope of the
experimentally agreeing simulations to such surface properties as the
interstrip resistance and capacitance, and the position dependency of CCE for
strip sensors irradiated up to $\sim$$1.5\times10^{15}$
n$_{\textrm{eq}}\textrm{cm}^{-2}$.",1509.08657v1
2015-10-14,"Elastic Composite, Reinforced Lightweight Concrete as a Type of Resilient Composite Systems",". A kind of ""Elastic Composite, Reinforced Lightweight Concrete (ECRLC)"" with
the mentioned specifics is a type of ""Resilient Composite Systems (RCS)"" in
which, contrary to the basic geometrical assumption of flexure theory in Solid
Mechanics, ""the strain changes in the beam height during bending"" is typically
""Non-linear"". . Through employing this integrated structure, with significant
high strain capability and modulus of resilience in bending, we could
constructively achieve high bearing capacities in beams with secure fracture
pattern, in less weight. . Due to the system particulars and its behavior in
bending, the usual calculation of the equilibrium steel amount to attain the
low-steel bending sections with secure fracture pattern in the beams and its
related limitations do not become propounded. Thereby, the strategic deadlock
of high possibility of brittle fracture pattern in the bending elements made of
the usual reinforced lightweight concretes, especially about the low-thickness
bending elements as slabs, is being unlocked. . This simple, applied technology
and the related components and systems can have several applications in ""the
Road and Building Industries"" too. . Regarding the ""strategic importance of the
Lightweight & Integrated Construction in practical increase of the resistance
and safety against earthquake"" and considering the appropriate behavior of this
resilient structure against the dynamic loads, shakes, impacts and shocks and
capability of making some lightweight and insulating, non-brittle, reinforced
sandwich panels and pieces, this system and its components could be also useful
in ""seismic areas"". . This system could be also employed in constructing the
vibration and impact absorber bearing pieces and slabs, which can be used in
""the Railroad & Subway Structures"" too. . Here, the ""RCS"" and ""ECRLC"" (as a
type of RCS) have been concisely presented.",1510.03933v1
2018-01-26,Enhanced moments of Eu in single crystals of the metallic helical antiferromagnet EuCo{2-y}As2,"The compound EuCo{2-y}As2 with the tetragonal ThCr2Si2 structure is known to
contain Eu{+2} ions with spin S = 7/2 that order below a temperature TN = 47 K
into an antiferromagnetic (AFM) proper helical structure with the ordered
moments aligned in the tetragonal ab plane, perpendicular to the helix axis
along the c axis, with no contribution from the Co atoms. Here we carry out a
detailed investigation of the properties of single crystals. Enhanced ordered
and effective moments of the Eu spins are found in most of our crystals.
Electronic structure calculations indicate that the enhanced moments arise from
polarization of the d bands, as occurs in ferromagnetic Gd metal. Electrical
resistivity measurements indicate metallic behavior. The low-field in-plane
magnetic susceptibilities chi{ab}(T < TN) for several crystals are reported
that are fitted well by unified molecular field theory (MFT), and the Eu-Eu
exchange interactions Jij are extracted from the fits. High-field magnetization
M data for magnetic fields H||ab reveal what appears to be a first-order
spin-flop transition followed at higher field by a second-order metamagnetic
transition of unknown origin, and then by another second-order transition to
the paramagnetic (PM) state. For H||c, the magnetization shows only a
second-order transition from the canted AFM to the PM state, as expected. The
critical fields for the AFM to PM transition are in approximate agreement with
the predictions of MFT. Heat capacity Cp measurements in zero and high H are
reported. Phase diagrams for H||c and H||ab versus T are constructed from the
high-field M(H,T) and Cp(H,T) measurements. The magnetic part Cmag(T, H = 0) of
Cp(T, H = 0) is extracted and is fitted rather well below TN by MFT, although
dynamic short-range AFM order is apparent in Cmag(T) up to about 70 K, where
the molar entropy attains its high-T limit of R ln8.",1801.08941v1
2018-09-10,High-performance InSe Transistors with Ohmic Contact Enabled by Nonrectifying-barrier-type Indium Electrodes,"The electrical contact to two-dimensional (2D)-semiconductor materials are
decisive to the electronic performance of 2D-semiconductor field-effect devices
(FEDs). The presence of a Schottky barrier often leads to a large contact
resistance, which seriously limits the channel conductance and carrier mobility
measured in a two-terminal geometry. In contrast, ohmic contact is desirable
and can be achieved by the presence of a nonrectifying or tunneling barrier.
Here, we demonstrate that an nonrectifying barrier can be realized by
contacting indium (In), a low work function metal, with layered InSe because of
a favorable band alignment at the In-InSe interface. The nonrectifying barrier
is manifested by ohmic contact behavior at T=2 K and a low barrier height,
{\Phi}$_B$=50 meV. This ohmic contact enables demonstration of an ON-current as
large as 410 {\mu}A/{\mu}m, which is among the highest values achieved in FEDs
based on layered semiconductors. A high electron mobility of 3,700 and 1,000
cm$^2$/Vs is achieved with the two-terminal In-InSe FEDs at T=2 K and room
temperature, respectively, which can be attributed to enhanced quality of both
conduction channel and the contacts. The improvement in the contact quality is
further proven by an X-ray photoelectron spectroscopy study, which suggests
that a reduction effect occurs at the In-InSe interface. The demonstration of
high-performance In-InSe FEDs indicates a viable interface engineering method
for next-generation, 2D-semiconductor-based electronics.",1809.03181v1
2018-11-19,Characterisation of AMS H35 HV-CMOS monolithic active pixel sensor prototypes for HEP applications,"Monolithic active pixel sensors produced in High Voltage CMOS (HV-CMOS)
technology are being considered for High Energy Physics applications due to the
ease of production and the reduced costs. Such technology is especially
appealing when large areas to be covered and material budget are concerned.
This is the case of the outermost pixel layers of the future ATLAS tracking
detector for the HL-LHC. For experiments at hadron colliders, radiation
hardness is a key requirement which is not fulfilled by standard CMOS sensor
designs that collect charge by diffusion. This issue has been addressed by
depleted active pixel sensors in which electronics are embedded into a large
deep implantation ensuring uniform charge collection by drift. Very first small
prototypes of hybrid depleted active pixel sensors have already shown a
radiation hardness compatible with the ATLAS requirements. Nevertheless, to
compete with the present hybrid solutions a further reduction in costs
achievable by a fully monolithic design is desirable. The H35DEMO is a large
electrode full reticle demonstrator chip produced in AMS 350 nm HV-CMOS
technology by the collaboration of Karlsruher Institut f\""ur Technologie (KIT),
Institut de F\'isica d'Altes Energies (IFAE), University of Liverpool and
University of Geneva. It includes two large monolithic pixel matrices which can
be operated standalone. One of these two matrices has been characterised at
beam test before and after irradiation with protons and neutrons. Results
demonstrated the feasibility of producing radiation hard large area fully
monolithic pixel sensors in HV-CMOS technology. H35DEMO chips with a substrate
resistivity of 200$\Omega$ cm irradiated with neutrons showed a radiation
hardness up to a fluence of $10^{15}$n$_{eq}$cm$^{-2}$ with a hit efficiency of
about 99% and a noise occupancy lower than $10^{-6}$ hits in a LHC bunch
crossing of 25ns at 150V.",1811.07817v3
2019-05-10,Vacuum electrical breakdown conditioning study in a parallel plate electrode pulsed DC system,"Conditioning of a metal structure in a high-voltage system is the progressive
development of resistance to vacuum arcing over the operational life of the
system. This is, for instance, seen during the initial operation of radio
frequency (rf) cavities in particle accelerators. It is a relevant topic for
any technology where breakdown limits performance, and where conditioning
continues for a significant duration of system runtime. Projected future linear
accelerators require structures with accelerating gradients of up to 100 MV/m.
Currently, this performance level is only achievable after a multi-month
conditioning period. In this work, a pulsed DC system applying voltage pulses
over parallel disk electrodes was used to study the conditioning process, with
the objective of obtaining insight into its underlying mechanics, and
ultimately, to find ways to shorten the conditioning process. Two kinds of
copper electrodes were tested: As-prepared machine-turned electrodes (""hard""
copper), and electrodes that additionally had been subjected to high
temperature treatments (""soft"" copper). The conditioning behaviour of the soft
electrodes was found to be similar to that of comparably treated accelerating
structures, indicating a similar conditioning process. The hard electrodes
reached the same ultimate performance as the soft electrodes much faster, with
a difference of more than an order of magnitude in the number of applied
voltage pulses. Two distinctly different distributions of breakdown locations
were observed on the two types of electrodes. Considered together, our results
support the crystal structure dislocation theory of breakdown, and suggest that
the conditioning of copper in high field systems such as rf accelerating
structures is dominated by material hardening.",1905.03996v1
2019-07-18,High-performance silicon-graphene hybrid plasmonic waveguide photodetectors beyond 1.55 μm,"A fast silicon-graphene hybrid plasmonic waveguide photodetectors beyond 1.55
{\mu}m is proposed and realized by introducing an ultra-thin wide
silicon-on-insulator ridge core region with a narrow metal cap. With this novel
design, the light absorption in graphene is enhanced while the metal absorption
loss is reduced simultaneously, which helps greatly improve the responsivity as
well as shorten the absorption region for achieving fast responses.
Furthermore, metal-graphene-metal sandwiched electrodes are introduced to
reduce the metal-graphene contact resistance, which is also helpful for
improving the response speed. When the photodetector operates at 2 {\mu}m, the
measured 3dB-bandwidth is >20 GHz (which is limited by the experimental setup)
while the 3dB-bandwith calculated from the equivalent circuit with the
parameters extracted from the measured S11 is as high as ~100 GHz. To the best
of our knowledge, it is the first time to report the waveguide photodetector at
2 {\mu}m with a 3dB-bandwidth over 20 GHz. Besides, the present photodetectors
also work very well at 1.55 {\mu}m. The measured responsivity is about 0.4 A/W
under a bias voltage of -0.3 V for an optical power of 0.16 mW, while the
measured 3dB-bandwidth is over 40 GHz (limited by the test setup) and the 3
dB-bandwidth estimated from the equivalent circuit is also as high as ~100 GHz,
which is one of the best results reported for silicon-graphene photodetectors
at 1.55 {\mu}m.",1907.12498v1
2020-07-01,Predicting Oxidation and Spin States by High-Dimensional Neural Networks: Applications to Lithium Manganese Oxide Spinels,"Lithium ion batteries often contain transition metal oxides like
Li$_{x}$Mn$_2$O$_4$ ($0\leq x\leq2$). Depending on the Li content different
ratios of Mn$^\text{III}$ to Mn$^\text{IV}$ ions are present. In combination
with electron hopping the Jahn-Teller distortions of the Mn$^\text{III}$O$_6$
octahedra can give rise to complex phenomena like structural transitions and
conductance. While for small model systems oxidation and spin states can be
determined using density functional theory (DFT), the investigation of
dynamical phenomena by DFT is too demanding. Previously, we have shown that a
high-dimensional neural network potential can extend molecular dynamics (MD)
simulations of Li$_{x}$Mn$_2$O$_4$ to nanosecond time scales, but these
simulations did not provide information about the electronic structure. Here we
extend the use of neural networks to the prediction of atomic oxidation and
spin states. The resulting high-dimensional neural network is able to predict
the spins of the Mn ions with an error of only 0.03 $\hbar$. We find that the
Mn e$_\text{g}$ electrons are correctly conserved and that the number of
Jahn-Teller distorted Mn$^\text{III}$O$_6$ octahedra is predicted precisely for
different Li loadings. A charge ordering transition is observed between 280 and
300 K, which matches resistivity measurements. Moreover, the activation energy
of the electron hopping conduction above the phase transition is predicted to
be 0.18 eV deviating only 0.02 eV from experiment. This work demonstrates that
machine learning is able to provide an accurate representation of both, the
geometric and the electronic structure dynamics of Li$_x$Mn$_2$O$_4$, on time
and length scales that are not accessible by ab initio MD.",2007.00335v2
2022-08-19,Superconductivity of Cs$_3$C$_{60}$ at atmosphere pressure,"Pressure as a clean and efficient tool can bring about unexpected
extraordinary physical and chemical properties of matters. The recent
discoveries of superconductivity at nearly room temperature in hydrides
highlight the power of pressure in this aspect. Capturing such Tc
superconductivity at atmosphere pressure for the technological applications is
highly desired. The large-scale growth of diamond through the chemical vapor
deposition away from the usual high-pressure and high-temperature conditions
fuels such a hope. Similar to hydrides, Cs-doped C$_{60}$ was also found to
exhibit superconductivity by the application of pressure with a comparable Tc
of 40 K as MgB$_2$. Here, we report the successful realization of
superconductivity in Cs-doped C$_{60}$ at atmosphere pressure. The phase is
characterized to have the primitive cubic structure in the space group of Pa-3
with the stoichiometry of Cs$_3$C$_{60}$. The superconductivity is evidenced
from the observations of both the Meissner effect and zero-resistance state.
Although the pressure effects on superconductivity are different for the newly
discovered Cs$_{3}$C$_{60}$ compared to the known two phases with fcc and A15
structure, the evolution of Tc with the volume for all these superconductors
follows the same universal trend, suggesting the same pairing mechanism of the
superconductivity. Such a trend together with the nearly linear Tc vs the
lattice constant in the structure with smaller unit-cell volumes and the
neighbouring antiferromagnetic state in the structure with larger unit-cell
volumes invites the electron-phonon coupling and the electron correlations
together to account for the superconductivity in Cs$_3$C$_{60}$. The present
results and findings suggest a new route to capturing the superconductivity
which takes place at high pressures to atmosphere pressure environment.",2208.09429v1
2022-11-02,High Temperature Ferromagnetism in Cr$_{1+x}$Pt$_{5-x}$P,"We present the growth and basic magnetic and transport properties of
Cr$_{1+x}$Pt$_{5-x}$P. We show that single crystals can readily be grown from a
high-temperature solution created by adding dilute quantities of Cr to Pt-P
based melts. Like other 1-5-1 compounds, Cr$_{1+x}$Pt$_{5-x}$P adopts a
tetragonal P4/mmm structure composed face-sharing CrPt$_3$ like slabs that are
broken up along the c-axis by sheets of P atoms. EDS and X-ray diffraction
measurements both suggest Cr$_{1+x}$Pt$_{5-x}$P has mixed occupancy between Cr
and Pt atoms, similar to what is found in the closely related compound
CrPt$_3$, giving real compositions of Cr$_{1.5}$Pt$_{4.5}$P (x = 0.5). We
report that Cr$_{1.5}$Pt$_{4.5}$P orders ferromagnetically at T$_C$ = 464.5 K
with a saturated moment of $\approx$ 2.1 $\mu_{\textit{B}}$/Cr at 1.8 K. Likely
owing to the strong spin-orbit coupling associated with the large quantity of
high Z Pt atoms, Cr$_{1.5}$Pt$_{4.5}$P has exceptionally strong planar
anisotropy with estimated anisotropy fields of 345 kOe and 220 kOe at 1.8 K and
300 K respectively. The resistance of Cr$_{1.5}$Pt$_{4.5}$P has a metallic
temperature dependence with relatively weak magnetoresistance. Electronic band
structure calculations show that CrPt$_5$P has a large peak in the density of
states near the Fermi level which is split into spin majority and minority
bands in the ferromagnetic state. Furthermore, the calculations suggest
substantial hybridization between Cr-3d and Pt-5d states near the Fermi level,
in agreement with the experimentally measured anisotropy.",2211.01491v1
2020-01-22,Spintronic superconductor in a bulk layered material with natural spin-valve structure,"Multi-layered materials provide fascinating platforms to realize various
functional properties, possibly leading to future electronic devices controlled
by external fields. In particular, layered magnets coupled with conducting
layers have been extensively studied recently for possible control of their
transport properties via the spin structure. Successful control of
quantum-transport properties in the materials with antiferromagnetic (AFM)
layers, so-called natural spin-valve structure, has been reported for the Dirac
Fermion and topological/axion materials. However, a bulk crystal in which
magnetic and superconducting layers are alternately stacked has not been
realized until now, and the search for functional properties in it is an
interesting yet unexplored field in material science. Here, we discover
superconductivity providing such an ideal platform in EuSn2As2 with the van der
Waals stacking of magnetic Eu layers and superconducting Sn-As layers, and
present the first demonstration of a natural spin-valve effect on the
superconducting current. Below the superconducting transition temperature (Tc),
the electrical resistivity becomes zero in the in-plane direction. In contrast,
it, surprisingly, remains finite down to the lowest temperature in the
out-of-plane direction, mostly due to the structure of intrinsic magnetic
Josephson junctions in EuSn2As2. The magnetic order of the Eu layers (or
natural spin-valve) is observed to be extremely soft, allowing one to easy
control of the out-of-plane to in-plane resistivities ratio from 1 to infinity
by weak external magnetic fields. The concept of multi-functional materials
with stacked magnetic-superconducting layers will open a new pathway to develop
novel spintronic devices with magnetically controllable superconductivity.",2001.07991v1
1997-02-26,"Stripes, Non-Fermi-Liquid Behavior, and High-Tc Superconductivity","The electronic structure of the high-Tc cuprates is studied in terms of
""large-U"" and ""small-U"" orbitals. A striped structure and three types of
quasiparticles are obtained, polaron-like ""stripons"" carrying charge, ""svivons""
carrying spin, and ""quasielectrons"" carrying both. The anomalous properties are
explained, and specifically the behavior of the resistivity, Hall constant, and
thermoelectric power. High-temperature superconductivity results from
transitions between pair states of quasielectrons and stripons.",9702232v1
2014-12-09,Materials Cartography: Representing and Mining Material Space Using Structural and Electronic Fingerprints,"As the proliferation of high-throughput approaches in materials science is
increasing the wealth of data in the field, the gap between
accumulated-information and derived-knowledge widens. We address the issue of
scientific discovery in materials databases by introducing novel analytical
approaches based on structural and electronic materials fingerprints. The
framework is employed to (i) query large databases of materials using
similarity concepts, (ii) map the connectivity of the materials space (i.e., as
a materials cartogram) for rapidly identifying regions with unique
organizations/properties, and (iii) develop predictive Quantitative Materials
Structure-Property Relation- ships (QMSPR) models for guiding materials design.
In this study, we test these fingerprints by seeking target material
properties. As a quantitative example, we model the critical temperatures of
known superconductors. Our novel materials fingerprinting and materials
cartography approaches contribute to the emerging field of materials
informatics by enabling effective computational tools to analyze, visualize,
model, and design new materials.",1412.4096v3
2013-10-14,High Pressure Effects on the Superconductivity in Rare-Earth Doped CaFe2As2,"High-pressure superconductivity in a rare-earth doped Ca0.86Pr0.14Fe2As2
single crystalline sample has been studied up to 12 GPa and temperatures down
to 11 K using designer diamond anvil cell under a quasi-hydrostatic pressure
medium. The electrical resistance measurements were complemented by high
pressure and low temperature x-ray diffraction studies at a synchrotron source.
The electrical resistance measurements show an intriguing observation of
superconductivity under pressure, with Tc as high as ~51 K at 1.9 GPa,
presenting the highest Tc reported in the intermetallic class of 1-2-2
iron-based superconductors. The resistive transition observed suggests a
possible existence of two superconducting phases at low pressures of 0.5 GPa:
one phase starting at Tc1 ~48 K, and the other starting at Tc2~16 K. The two
superconducting transitions show distinct variations with increasing pressure.
High pressure low temperature structural studies indicate that the
superconducting phase is a collapsed tetragonal ThCr2Si2-type (122) crystal
structure. Our high pressure studies indicate that high Tc state attributed to
non-bulk superconductivity in rare-earth doped 1-2-2 iron-based superconductors
is stable under compression over a broad pressure range.",1310.3842v2
2022-04-01,Magnetic Kagome Superconductor CeRu$_2$,"Materials with a kagome lattice provide a platform for searching for new
electronic phases and investigating the interplay between correlation and
topology. Various probes have recently shown that the kagome lattice can host
diverse quantum phases with intertwined orders, including charge density wave
states, bond density wave states, chiral charge order, and, rarely,
superconductivity. However, reports of the coexistence of superconductivity and
magnetic order in kagome materials remain elusive. Here we revisit a magnetic
superconductor CeRu$_2$ with a kagome network formed by Ru atoms. Our
first-principles calculations revealed a kagome flat band near the Fermi
surface, indicative of flat-band magnetism. At ambient pressure, CeRu$_2$
exhibits a superconducting transition temperature ($T_{\text{c}}$) up to ~ 6 K
and a magnetic order at ~ 40 K. Notably, superconductivity and related behavior
can be tuned by adjusting the amount of Ru. We conducted a systematic
investigation of the superconductivity and magnetic order in CeRu$_2$ via
magnetic, resistivity, and structural measurements under pressure up to ~ 168
GPa. An unusual phase diagram that suggests an intriguing interplay between the
compound's superconducting order parameters has been constructed. A
$T_{\text{c}}$ resurgence was observed above pressure of ~ 28 GPa, accompanied
by the sudden appearance of a secondary superconducting transition. Our
experiments have identified tantalizing phase transitions driven by high
pressure and suggest that the superconductivity and magnetism in CeRu$_2$ are
strongly intertwined.",2204.00553v2
2004-12-06,"Resistivity and Thermoelectric power of NaxCoO2 (x =1.0, 0.7 and 0.6) system","Results of thermo-electric power (S) and electrical resistivity (r)
measurements are reported on NaxCoO2 compounds with x = 1.0, 0.7 and 0.6. These
are single-phase compounds crystallizing in the hexagonal structure (space
group P63/mmc) at room temperature. Thermo-electric power values at 300K
(S300K) are, 80mV/K, 39mV/K and 37mV/K for x = 1.0, 0.7 and 0.6 samples,
respectively. The samples with x=0.7 and 1.0 are metallic down to 5 K, while
the x = 0.6 sample is semiconducting. The value of r300K for x = 1.0 sample is
\~0.895 mW-cm and the power factor (S2/r) is = 7.04 x 10-3 W/mK2 which
qualifies it as a good thermo-electric material. In x =1.0 sample, S(T) is
positive throughout 300-5K temperature range and decreases monotonically to
zero as temperature T= 0. In contrast, S(T) of x = 0.7 and 0.6 samples changes
sign and shows negative values between 90 K and 16 K before approaching zero as
T = 0. Anomalous S(T) behavior of x = 0.6 and 0.7 samples, which are
coincidentally the precursor materials to the reported superconductivity in
this class of materials, indicates a dramatic change in the electronic
structure of these compounds on lowering the Na content.",0412122v1
2011-11-21,"Anisotropic Magnetoresistance Effects in Fe, Co, Ni, Fe_4N, and Half-Metallic Ferromagnet: A Systematic Analysis","We theoretically analyze the anisotropic magnetoresistance (AMR) effects of
bcc Fe (+), fcc Co (+), fcc Ni (+), Fe$_4$N (-), and a half-metallic
ferromagnet (-). The sign in each ( ) represents the sign of the AMR ratio
observed experimentally. We here use the two-current model for a system
consisting of a spin-polarized conduction state and localized d states with
spin--orbit interaction. From the model, we first derive a general expression
of the AMR ratio. The expression consists of a resistivity of the conduction
state of the $\sigma$ spin ($\sigma=\uparrow$ or $\downarrow$), $\rho_{s
\sigma}$, and resistivities due to s--d scattering processes from the
conduction state to the localized d states. On the basis of this expression, we
next find a relation between the sign of the AMR ratio and the s--d scattering
process. In addition, we obtain expressions of the AMR ratios appropriate to
the respective materials. Using the expressions, we evaluate their AMR ratios,
where the expressions take into account the values of $\rho_{s
\downarrow}/\rho_{s \uparrow}$ of the respective materials. The evaluated AMR
ratios correspond well to the experimental results.",1111.4864v3
2013-09-25,Piezoresistance in Silicon and its nanostructures,"Piezoresistance is the change in the electrical resistance, or more
specifically the resistivity, of a solid induced by an applied mechanical
stress. The origin of this effect in bulk, crystalline materials like Silicon,
is principally a change in the electronic structure which leads to a
modification of the charge carriers effective mass. The last few years have
seen a rising interest in the piezoresistive properties of semiconductor
nanostructures, motivated in large part by claims of a giant piezoresistance
effect in Silicon nanowires that is more than two orders of magnitude bigger
than the known bulk effect. This review aims to present the controversy
surrounding claims and counter-claims of giant piezoresistance in Silicon
nanostructures by presenting a summary of the major works carried out over the
last 10 years. The main conclusions that can be drawn from the literature are
that i) reproducible evidence for a giant piezoresistance effect in un-gated
Silicon nanowires is limited, ii) in gated nanowires a giant effect has been
reproduced by several authors, iii) the giant effect is fundamentally different
from either the bulk Silicon piezoresistance or that due to quantum confinement
in accumulation layers and heterostructures, the evidence pointing to an
electrostatic origin for the piezoresistance, iv) released nanowires tend to
have slightly larger piezoresistance coefficients than un-released nanowires,
and v) insufficient work has been performed on bottom-up grown nanowires to be
able to rule out a fundamental difference in their properties when compared
with top-down nanowires. On the basis of this, future possible research
directions are suggested.",1309.6445v2
2014-09-25,Superconductivity in 122-type antimonide BaPt$_2$Sb$_2$,"The crystal structure, superconducting properties, and electronic structure
of a novel superconducting 122-type antimonide, BaPt$_2$Sb$_2$, have been
investigated by measurements of powder X-ray diffraction patterns, electrical
resistivity, ac magnetic susceptibility, specific heat as well as ab-initio
calculations. This material crystallizes in a new-type of monoclinic variant of
the CaBe$_2$Ge$_2$-type structure, in which Pt$_2$Sb$_2$ layers consisting of
PtSb$_4$ tetrahedra and Sb$_2$Pt$_2$ layers consisting of SbPt$_4$ tetrahedra
are stacked alternatively and Ba atoms are located between the layers.
Measurements of electrical resistivity, ac magnetic susceptibility and specific
heat revealed that BaPt$_2$Sb$_2$ is a superconducting material with a $T_{\rm
c}$ of 1.8 K. The electronic heat capacity coefficient $\gamma_{\rm n}$ and
Debye temperature $\theta_{\rm D}$ were 8.6(2) mJ/mol K$^2$ and 146(4) K, where
the figures in parentheses represent the standard deviation. The upper critical
field $\mu_{\rm 0}H_{\rm c2}(0)$ and the Ginzburg-Landau coherent length
$\xi(0)$ were determined to be 0.27 T and 35 nm. Calculations showed that it
has two three-dimensional Fermi surfaces (FSs) and two two-dimensional FSs,
leading to anisotropic transport properties. The d-states of the Pt atoms in
the Pt2Sb2 layers mainly contribute to $N(E_{\rm F})$. A comparison between
experimental and calculated results indicates that BaPt$_2$Sb$_2$ is a
superconducting material with moderate coupling.",1409.7147v1
2014-11-11,Tunable Cobalt Vacancies and Related Properties in LaCoxAs2,"The origin of transition metal vacancies and their effects on the properties
of ThCr2Si2-type compounds have been less studied and poorly understood. Here
we carefully investigate the structure, physical properties, and electronic
structure for a series of lanthanum cobalt arsenides with nominal composition
of LaCoxAs2 (1.6 < = x < = 2.1). It is revealed that the occupancy of Co can be
tuned between 1.98(1) and 1.61(1). The structural analyses based on X-ray and
neutron diffractions show the existence of Co vacancies results from charge
balance due to the formation of bond between As-As. These Co vacancies affect
the magnetic and electrical properties greatly, adjusting the Curie temperature
from 205 to 47 K and increasing the resistivity by more than 100%. First
principles calculations indicate that the Co vacancies weaken the spin
polarization and reduce the density of states at the Fermi level, resulting in
decreased Curie temperature and increased resistivity, respectively. Our
results address the importance of transition metal vacancies in ThCr2Si2-type
materials and offer a reliable route to tune the magnetism of ThCr2Si2-type
structure.",1411.2788v1
2017-10-02,Realization of the Axion Insulator State in Quantum Anomalous Hall Sandwich Heterostructures,"The 'magnetoelectric effect' arises from the coupling between magnetic and
electric properties in materials. The Z2 invariant of topological insulators
(TIs) leads to a quantized version of this phenomenon, known as the topological
magnetoelectric (TME) effect. This effect can be realized in a new topological
phase called an 'axion insulator' whose surface states are all gapped but the
interior still obeys time reversal symmetry. We demonstrate such a phase using
electrical transport measurements in a quantum anomalous Hall (QAH) sandwich
heterostructure, in which two compositionally different magnetic TI layers are
separated by an undoped TI layer. Magnetic force microscopy images of the same
sample reveal sequential magnetization reversals of the top and bottom layers
at different coercive fields, a consequence of the weak interlayer exchange
coupling due to the spacer. When the magnetization is antiparallel, both the
Hall resistance and Hall conductance show zero plateaus, accompanied by a large
longitudinal resistance and vanishing longitudinal conductance, indicating the
realization of an axion insulator state. Our findings thus show evidences for a
phase of matter distinct from the established QAH state and provide a promising
platform for the realization of the TME effect.",1710.00471v2
2018-04-20,Pressure induced superconductivity bordering a charge-density-wave state in NbTe4 with strong spinorbit coupling,"Transition-metal chalcogenides host various phases of matter, such as
charge-density wave (CDW), superconductors, and topological insulators or
semimetals. Superconductivity and its competition with CDW in low-dimensional
compounds have attracted much interest and stimulated considerable research.
Here we report pressure induced superconductivity in a strong spin-orbit (SO)
coupled quasi-one-dimensional (1D) transition-metal chalcogenide NbTe$_4$,
which is a CDW material under ambient pressure. With increasing pressure, the
CDW transition temperature is gradually suppressed, and superconducting
transition, which is fingerprinted by a steep resistivity drop, emerges at
pressures above 12.4 GPa. Under pressure $p$ = 69 GPa, zero resistance is
detected with a transition temperature $T_c$ = 2.2 K and an upper critical
field $H_{c2}$= 2 T. We also find large magnetoresistance (MR) up to 102\% at
low temperatures, which is a distinct feature differentiating NbTe$_4$ from
other conventional CDW materials.",1804.07448v1
2018-11-12,Laser writable high-K dielectric for van der Waals nano-electronics,"Like silicon-based semiconductor devices, van der Waals heterostructures will
require integration with high-K oxides. This is needed to achieve suitable
voltage scaling, improved performance as well as allowing for added
functionalities. Unfortunately, commonly used high-k oxide deposition methods
are not directly compatible with 2D materials. Here we demonstrate a method to
embed a multi-functional few nm thick high-k oxide within van der Waals devices
without degrading the properties of the neighbouring 2D materials. This is
achieved by in-situ laser oxidation of embedded few layer HfS2 crystals. The
resultant oxide is found to be in the amorphous phase with a dielectric
constant of k~15 and break-down electric fields in the range of 0.5-0.6 V/nm.
This transformation allows for the creation of a variety of fundamental
nano-electronic and opto-electronic devices including, flexible Schottky
barrier field effect transistors, dual gated graphene transistors as well as
vertical light emitting and detecting tunnelling transistors. Furthermore, upon
dielectric break-down, electrically conductive filaments are formed. This
filamentation process can be used to electrically contact encapsulated
conductive materials. Careful control of the filamentation process also allows
for reversible switching between two resistance states. This allows for the
creation of resistive switching random access memories (ReRAMs). We believe
that this method of embedding a high-k oxide within complex van der Waals
heterostructures could play an important role in future flexible
multi-functional van der Waals devices.",1811.04829v1
2018-10-09,"Magnetic behavior, Griffiths phase and magneto-transport study in 3$d$ based nano-crystalline double perovskite Pr$_2$CoMnO$_6$","Double perovskite (DP) oxide material receive extensive research interest due
to exciting physical properties with potential technological application. 3$d$
based DP oxides are promising for exciting physics like magnetodielectric,
ferroelectric, Griffith phase etc., specially Co/Mn DPs are gaining much
research interest. In this paper we present the study of magnetic phase and
transport properties in nano-crystalline Pr$_2$CoMnO$_6$ a 3$d$ based double
perovskite compound. This material shows a paramagnetic (PM) to ferromagnetic
(FM) phase transition below 173 K marked by a rapid increase in magnetic moment
due to spin ordering. We found divergence in inverse magnetic susceptibility
($\chi$$^{-1}$) from Curie weiss behavior around 206 K which indicates the
evolution of Griffiths phase before actual PM-FM transition. We found that the
Griffiths phase suppressed with increasing applied magnetic filed. For the
understanding of charge transport in this material we have measured temperature
dependent electrical resistivity. Pr$_2$CoMnO$_6$ is a strong insulator where
resistivity increase abruptly below magnetic phase transition. To understand
the effect of magnetic field on transport behavior we have also measured the
magnetoresistance (MR) at different temperatures. Sample shows the negative MR
with maximum value $\sim$22 $\%$ under applied magnetic field of 50 kOe at 125
K. MR follows quadratic field dependency above $T_c$ however below $T_c$ the MR
shows deviation from this field dependency at low field.",1810.03895v1
2020-02-11,A Multiscale Constitutive Model for Metal Forming of Dual Phase Titanium Alloys by Incorporating Inherent Deformation and Failure Mechanisms,"Ductile metals undergo a considerable amount of plastic deformation before
failure. Void nucleation, growth and coalescence is the mechanism of failure in
such metals. {\alpha}/{\beta} titanium alloys are ductile in nature and are
widely used for their unique set of properties like specific strength, fracture
toughness, corrosion resistance and resistance to fatigue failures. Voids in
these alloys were reported to nucleate on the phase boundaries between {\alpha}
and {\beta} phase. Based on the findings of crystal plasticity finite element
method (CPFEM) based investigation of the void growth at the interface of
{\alpha} and {\beta} phases [1], [2], a void nucleation, growth, and
coalescence model has been formulated. An existing single-phase crystal
plasticity theory is extended to incorporate underlying physical mechanisms of
deformation and failure in dual phase titanium alloys. Effects of various
factors (stress triaxiality, Lode parameter, deformation state (equivalent
strain), and phase boundary inclination) on void nucleation, growth and
coalescence are used to formulate the constitutive model while their
interaction with a conventional crystal plasticity theory is established. An
extensive parametric assessment of the model is carried out to quantify and
understand the effects of the material parameters on the overall material
response. Performance of the proposed model is then assessed and verified by
comparing the results of the proposed model with the RVE study results.
Application of the constitutive model for utilisation in the design and
optimisation of the forming process of {\alpha}/{\beta} titanium alloy
components is also demonstrated using experimental data.",2002.04459v1
2020-04-23,Hybrid Graphene/Carbon Nanofiber Wax Emulsion for Paper-based Electronics and Thermal Management,"Materials for electronics that function as electrical and/or thermal
conductors are often rigid, expensive, difficult to be sourced and sometimes
toxic. An electrically and thermally conductive nanocomposite that is
lightweight, flexible and eco-friendly could improve the environmental
friendliness of the electronics sector and enable new applications. Considering
this, we have fabricated electrically and thermally conductive flexible
materials by functionalizing paper with nanocarbon conductive inks. Carnauba
wax is emulsified in isopropyl alcohol and mixed with graphene nanoplatelets
(GNPs) or with hybrids of GNPs and carbon nanofibers (CNFs). The percolation
threshold of the hybrid samples is lowered compared with the pure GNPs
composites, due to their increased filler aspect ratio. The hybrid samples also
exhibit superior bending and folding stability. Densification of the coating to
decrease their sheet resistance enables them to achieve as low as ~ 50 {\Omega}
sq-1 for the GNP-based paper. The densification procedure improves the bending
stability, the abrasion resistance, and the electromagnetic interference
shielding of the paper-based conductors. Finally, the compressed samples show
an impressive enhancement of their thermal diffusivity. The flexible and
multifunctional nanocarbon coated paper is a promising electronic conductor and
thermally dissipative material and, at the same time, can increase the
environmental sustainability of the electronics sector.",2004.11476v1
2020-09-21,Photocurrent Imaging of Multi-Memristive Charge Density Wave Switching in Two-Dimensional 1T-TaS2,"Transport studies of atomically thin 1T-TaS2 have demonstrated the presence
of intermediate resistance states across the nearly commensurate (NC) to
commensurate (C) charge density wave (CDW) transition, which can be further
switched electrically. While this presents exciting opportunities for the
material in memristor applications, the switching mechanism has remained
elusive and could be potentially attributed to the formation of inhomogeneous C
and NC domains across the 1T-TaS2 flake. Here, we present simultaneous
electrical driving and scanning photocurrent imaging of CDWs in ultrathin
1T-TaS2 using a vertical heterostructure geometry. While micron-sized CDW
domains form upon changing temperature, electrically driven transitions result
in largely uniform changes, indicating that states of intermediate resistance
for the latter likely correspond to true metastable CDW states in between the
NC and C phases, which we then explain by a free energy analysis. Additionally,
we are able to perform repeatable and bidirectional switching across the
multiple CDW states without changing sample temperature, demonstrating that
atomically thin 1T-TaS2 can be further used as a robust and reversible
multi-memristor material.",2009.10179v1
2018-12-21,Transfer of mass and momentum at rough and porous surfaces,"The surface texture of materials plays a critical role in wettability,
turbulence and transport phenomena. In order to design surfaces for these
applications, it is desirable to characterise non-smooth and porous materials
by their ability to exchange mass and momentum with flowing fluids. While the
underlying physics of the tangential (slip) velocity at a fluid-solid interface
is well understood, the importance and treatment of normal (transpiration)
velocity and normal stress is unclear. We show that, when slip velocity varies
at an interface above the texture, a non-zero transpiration velocity arises
from mass conservation. The ability of a given surface texture to accommodate
for a normal velocity of this kind is quantified by a transpiration length. We
further demonstrate that normal momentum transfer gives rise to a pressure
jump. For a porous material, the pressure jump can be characterised by so
called resistance coefficients. By solving five Stokes problems, the introduced
measures of slip, transpiration and resistance can be determined for any
anisotropic non-smooth surface consisting of regularly repeating geometric
patterns. The proposed conditions are a subset of effective boundary conditions
derived from formal multi-scale expansion. We validate and demonstrate the
physical significance of the effective conditions on two canonical problems --
a lid-driven cavity and a turbulent channel flow, both with non-smooth bottom
surfaces.",1812.09401v2
2019-06-25,Titanium Contacts to MoS2 with Interfacial Oxide: Interface Chemistry and Thermal Transport,"The deposition of a thin oxide layer at metal/semiconductor interfaces has
been previously reported as a means of reducing contact resistance in 2D
electronics. Using X-ray photoelectron spectroscopy with in-situ Ti deposition,
we fabricate Au/Ti/TiOx/MoS2 samples as well as Au/Ti/MoS2 and Au/TiOx/MoS2 for
comparison. Elemental titanium reacts strongly with MoS2 whereas no interface
reactions are observed in the two types of samples containing TiOx/MoS2
interfaces. Using time domain thermoreflectance for the measurement of thermal
boundary conductance, we find that samples contacted with Ti and a thin TiOx
layer at the interface (less than or equal to 1.5 nm) exhibit the same behavior
as samples contacted solely with pure Ti. The Au/TiOx/MoS2 samples exhibit
approximately 20% lower thermal boundary conductance, despite having the same
MoS2 interface chemistry as the samples with thin oxide at the Ti/MoS2
interface. We identify the mechanism for this phenomenon, attributing it to the
different interfaces with the top Au contact. Our work demonstrates that the
use of thin interfacial oxide layers to reduce electrical contact resistance
does not compromise heat flow in 2D electronic devices. We note that the
thicknesses of the Ti and TiOx layers must be considered for optimal thermal
transport.",1906.10727v1
2019-06-27,The Essential Work of Fracture Parameters for 3D printed polymer sheets,"Additive manufacturing is becoming increasingly popular in academia and
industry. Accordingly, there has been a growing interest in characterizing 3D
printed samples to determine their structural integrity behaviour. We employ
the Essential Work of Fracture (EWF) to investigate the mechanical response of
polymer sheets obtained through additive manufacturing. Our goal is twofold;
first, we aim at gaining insight into the role of fibre reinforcement on the
fracture resistance of additively manufactured polymer sheets. Deeply
double-edge notched tensile (DDEN-T) tests are conducted on four different
polymers: Onyx, a crystalline, nylon-reinforced polymer, and three standard
polymers used in additive manufacturing - PLA, PP and ABS. Results show that
fibre-reinforcement translates into a notable increase in fracture resistance,
with the fracture energy of Onyx being an order of magnitude higher than that
reported for non-reinforced polymers. On the other hand, we propose the use of
a miniature test specimen, the deeply double-edge notched small punch specimens
(DDEN-SP), to characterize the mechanical response using a limited amount of
material. The results obtained exhibit good alignment with the DDEN-T data,
suggesting the suitability of the DDEN-SP test for measuring fracture
properties of additively manufactured polymers in a cost-effective manner.",1906.11512v1
2019-10-09,"The roles of adhesion, internal heat generation and elevated temperatures in normally loaded, sliding rough surfaces","The thermal effects of plastic and frictional heat generation and elevated
temperature were examined along with the role of adhesion in the context of
galling wear, using a representative crystal plasticity, normally loaded,
sliding surface model. Galling frequency behaviour was predicted for 316L
steel. Deformation of the surfaces was dominated by the surface geometry, with
no significant effect due to variations in frictional models. Plastic and
frictional heating were found to have a minimal effect on the deformation of
the surface, with the rapid conduction of heat preventing any highly localised
heating. There was no corresponding effect on the predicted galling frequency
response.
  Isothermal, elevated temperature conditions caused a decrease in galling
resistance, driven by the temperature sensitivity of the critical resolved
shear stress. The extent of deformation, as quantified by the area of
plastically deformed material and plastic reach, increased with temperature.
Comparisons were made with literature results for several surface amplitude and
wavelength conditions. Model results compared favourably with those in the
literature. However, the reduction in predicted galling resistance with
elevated temperature for a fixed surface was not as severe as observations in
the literature, suggesting other mechanisms (e.g. phase transformations,
surface coatings and oxides) are likely important.",1910.03830v1
2020-01-06,Two-dimensional antiferroelectric tunnel junction,"Ferroelectric tunnel junctions (FTJs), which consist of two metal electrodes
separated by a thin ferroelectric barrier, have recently aroused significant
interest for technological applications as nanoscale resistive switching
devices. So far, most of existing FTJs have been based on perovskite-oxide
barrier layers. The recent discovery of the two-dimensional (2D) van der Waals
ferroelectric materials opens a new route to realize tunnel junctions with new
functionalities and nm-scale dimensions. Due to the weak coupling between the
atomic layers in these materials, the relative dipole alignment between them
can be controlled by applied voltage. This allows transitions between
ferroelectric and antiferroelectric orderings, resulting in significant changes
of the electronic structure. Here, we propose to realize 2D antiferroelectric
tunnel junctions (AFTJs), which exploit this new functionality, based on
bilayer In$_2$X$_3$ (X = S, Se, Te) barriers and different 2D electrodes. Using
first-principles density functional theory calculations, we demonstrate that
the In$_2$X$_3$ bilayers exhibit stable ferroelectric and antiferroelectric
states separated by sizable energy barriers, thus supporting a non-volatile
switching between these states. Using quantum-mechanical modeling of the
electronic transport, we explore in-plane and out-of-plane tunneling across the
In$_2$S$_3$ van der Waals bilayers, and predict giant tunneling
electroresistance (TER) effects and multiple non-volatile resistance states
driven by ferroelectric-antiferroelectric order transitions. Our proposal opens
a new route to realize nanoscale memory devices with ultrahigh storage density
using 2D AFTJs.",2001.01639v3
2020-01-28,Interlayer band-to-band tunneling and negative differential resistance in van der Waals BP/InSe field effect transistors,"Atomically thin layers of van der Waals (vdW) crystals offer an ideal
material platform to realize tunnel field effect transistors (TFETs) that
exploit the tunneling of charge carriers across the forbidden gap of a vdW
heterojunction. This type of device requires a precise energy band alignment of
the different layers of the junction to optimize the tunnel current. Amongst
two-dimensional (2D) vdW materials, black phosphorus (BP) and indium selenide
(InSe) have a Brillouin zone-centered conduction and valence bands, and a type
II band offset, both ideally suited for band-to-band tunneling. Here, we
demonstrate TFETs based on BP/InSe heterojunctions with diverse electrical
transport characteristics: forward rectifying, Zener-tunneling and backward
rectifying characteristics are realized in BP/InSe junctions with different
thickness of the BP layer or by electrostatic gating of the junction.
Electrostatic gating yields a large on/off current ratio of up to 108 and
negative differential resistance at low applied voltages (V ~ 0.2V). These
findings illustrate versatile functionalities of TFETs based on BP and InSe,
offering opportunities for applications of these 2D materials beyond the device
architectures reported in the current literature.",2001.10273v1
2020-08-31,Creep deformation of WC hardmetals with iron-based binders,"Iron is a candidate to replace cobalt in WC hardmetals, due to its lower cost
and toxicity. A WC-FeCr hardmetal was compression tested at 900-1200 {\deg}C.
Particular attention is paid to the steady-state creep rates and
stress-exponents (n) during isostress treatments. Three regimes of stress
dependence are observed. Two of these were previously reported for WC-Co: power
law creep (n~3) at medium stresses; and grain boundary sliding (n~1) at higher
stresses, generally >100MPa. A previously unreported low stress (<10MPa) regime
with an exponent of n~2 is also observed. By combining electron microscopy with
X-ray diffraction texture measurements, the low stress regime is attributed to
viscous flow of the binder, which is accommodated by diffusional creep in the
WC skeleton. The mechanism may be applicable to other hardmetals. Compared to
analogous WC-Co materials, WC-FeCr shows improved creep resistance below 1000
{\deg}C, which can be explained by its lower self-diffusivity, and a lower
solubility for WC than Co. However, at temperatures corresponding to liquid
eutectic formation (~1140 {\deg}C), its creep resistance becomes inferior.
These results indicate FeCr may be a suitable replacement for Co provided the
eutectic temperature is not exceeded.",2008.13565v1
2020-10-06,Role of f-d exchange interaction and Kondo scattering in Nd doped pyrochlore Iridate (Eu1-xNdx)2Ir2O7,"We report study of magnetization, resistivity, magnetoresistance and specific
heat of the pyrochlore Iridate (Eu1-xNdx)2Ir2O7 with x=0.0, 0.5 and 1.0, where
spin orbit coupling, electronic correlation, magnetic frustration and Kondo
scattering coexists. Metal insulator transition temperature (T_MI) decrease
with increase in Nd content but always coincides with magnetic irreversibility
temperature (field induced moment). Resistivity below T_MI do not fit with
either activated (gap) or to any power law (gapless) dependence. The Curie
constant show surprising result, that Nd induces singlet correlation (reduction
of para-moment) in Ir sublattice. Magnetoresistance is negative at low
temperatures below 10 K and increases strongly with increase in x and vary
quadratically with field switching over to linear dependence above 50 kOe. Low
temperature specific heat shows Schottky peak, coming from Nd moments, showing
existence of doublet split in Nd energy level, arising from f-d exchange
interaction. All materials show presence of a linear specific heat in the
insulating region. The coefficient of linear specific heat for x= 0.0 does not
vary with external magnetic field but varies superlinearly for x = 1.0
materials. We argue that linear specific heat probably rules out weakly
correlated phases like Weyl fermions. We propose that with the introduction of
Nd at Eu site the system evolves from chiral spin liquid with gapless spinon
excitations with a very small charge gap to Kondo type interaction superposed
on chiral spin liquid coexisting with long range antiferromagnetic ordering.
Huge increase of magnetoresistance with increase in Nd concentrations shows
importance of Kondo scattering in the chiral spin liquid material by rare earth
moments.",2010.02685v1
2020-10-15,Multipurpose and Reusable Ultrathin Electronic Tattoos Based on PtSe2 and PtTe2,"Wearable bioelectronics with emphasis on the research and development of
advanced person-oriented biomedical devices have attracted immense interest in
the last decade. Scientists and clinicians find it essential to utilize
skin-worn smart tattoos for on-demand and ambulatory monitoring of an
individual's vital signs. Here we report on the development of novel ultrathin
platinum-based two-dimensional dichalcogenide (Pt-TMDs) based electronic
tattoos as advanced building blocks of future wearable bioelectronics. We made
these ultrathin electronic tattoos out of large-scale synthesized platinum
diselenide (PtSe2) and platinum ditelluride (PtTe2) layered materials and used
them for monitoring human physiological vital signs, such as the electrical
activity of the heart and the brain, muscle contractions, eye movements, and
temperature. We show that both materials can be used for these applications;
yet, PtTe2 was found to be the most suitable choice due to its metallic
structure. In terms of sheet resistance, skin-contact, and electrochemical
impedance, PtTe2 outperforms state-of-the-art gold and graphene electronic
tattoos and performs on par with medical-grade Ag/AgCl gel electrodes. The
PtTe2 tattoos show four times lower impedance and almost 100 times lower sheet
resistance compared to monolayer graphene tattoos. One of the possible prompt
implications of the work is perhaps in the development of advanced
human-machine interfaces. To display the application, we built a multi-tattoo
system that can easily distinguish eye movement and identify the direction of
an individual's sight.",2010.07534v1
2020-10-22,"Development, Processing and Applications of a UV-Curable Polymer with Surface Active Thiol Groups","We present here a novel resist formulation with active thiol groups at the
surface. The material is UV curable, and can be patterned at the micro- and
nanoscale by UV nanoimprint lithography. The resist formulation development,
its processing, patterning and surface characterization are presented here. In
addition, a possible application, including its use to modify the electrical
properties of graphene devices is shown. The cured material is highly
transparent, intrinsically hydrophilic and can be made more hydrophilic
following a UV-ozone or an O2 plasma activation. We evaluated the
hydrophilicity of the polymer for different polymer formulations and curing
conditions. In addition, a protocol for patterning of the polymer in the micro
and nanoscale by nanoimprinting is given and preliminary etching rates together
with the polymer selectivity are measured. The main characteristic and unique
advantage of the polymer is that it has thiol functional groups at the surface
and in the bulk after curing. These groups allow for direct surface
modifications with thiol-based chemistry e.g., thiol-ene reactions. We prove
the presence of the thiol groups by Raman spectroscopy and perform a thiol-ene
reaction to show the potential of the easy click chemistry. This opens the way
for very straightforward surface chemistry on nanoimprinted polymer samples.
Furthermore, we show how the polymer improves the electrical properties of a
graphene field effect transistor, allowing for optimal performance at ambient
conditions.",2010.11878v1
2021-04-02,"Crystal, local atomic and electronic structures of YbFe$_2$Zn$_{20-x}$Cd$_x$ ($0 \leq x \leq 1.4$): a multi-band system with possible coexistence of light and heavy fermions","The partial (up to 7 %) substitution of Cd for Zn in the Yb-based
heavy-fermion material YbFe$_2$Zn$_{20}$ is known to induce a slight ($\sim 20$
%) reduction of the Sommerfeld specific heat coefficient $\gamma$ and a huge
(up to two orders of magnitude) reduction of the $T^2$ resistivity coefficient
$A$, corresponding to a drastic and unexpected reduction of the Kadowaki-Woods
ratio $A/\gamma ^2$. Here, Yb $L_{3}$-edge X-ray absorption spectroscopy shows
that the Yb valence state is close to $3+$ for all $x$, whereas X-ray
diffraction reveals that Cd replace the Zn ions only at the $16c$ site of the
$Fd\bar{3}m$ cubic structure, leaving the $48f$ and $96g$ sites with full Zn
occupation. Ab-initio electronic structure calculations in pure and Cd-doped
materials, carried out without considering correlations, show multiple
conduction bands with only minor modifications of the band dispersions near the
Fermi level and therefore do not explain the resistivity drop introduced by Cd
substitution. We propose that the site-selective Cd substitution introduces
light conduction bands with substantial contribution of Cd($16c$) $5p$ levels
that have weak coupling to the Yb$^{3+}$ $4f$ moments. These light fermions
coexist with heavy fermions originated from other conduction bands with larger
participation of Zn($48f$ and $96g$) $4p$ levels that remain strongly coupled
with the Yb$^{3+}$ local moments.",2104.01050v1
2021-08-18,Robust narrow-gap semiconducting behavior in square-net La$_{3}$Cd$_{2}$As$_{6}$,"ABSTRACT: Narrow-gap semiconductors are sought-after materials due to their
potential for long-wavelength detectors, thermoelectrics, and more recently
non-trivial topology. Here we report the synthesis and characterization of a
new family of narrow-gap semiconductors, $R$$_{3}$Cd$_{2}$As$_{6}$ ($R=$ La,
Ce). Single crystal x-ray diffraction at room temperature reveals that the As
square nets distort and Cd vacancies order in a monoclinic superstructure. A
putative charge-density ordered state sets in at 279~K in
La$_{3}$Cd$_{2}$As$_{6}$ and at 136~K in Ce$_{3}$Cd$_{2}$As$_{6}$ and is
accompanied by a substantial increase in the electrical resistivity in both
compounds. The resistivity of the La member increases by thirteen orders of
magnitude on cooling, which points to a remarkably clean semiconducting ground
state. Our results suggest that light square net materials within a $I4/mmm$
parent structure are promising clean narrow-gap semiconductors.",2108.08006v1
2021-10-01,"Effects of nonmagnetic impurities and subgap states on the kinetic inductance, complex conductivity, quality factor and depairing current density","We investigate how a combination of a nonmagnetic-impurity scattering rate
$\gamma$ and finite subgap states parametrized by Dynes $\Gamma$ affects
various physical quantities relevant to to superconducting devices: kinetic
inductance $L_k$, complex conductivity $\sigma$, surface resistance $R_s$,
quality factor $Q$, and depairing current density $J_d$. All the calculations
are based on the Eilenberger formalism of the BCS theory. We assume the device
materials are extreme type-II $s$-wave superconductors. It is well known that
the optimum impurity concentration ($\gamma/\Delta_0 \sim 1$) minimizes $R_s$.
Here, $\Delta_0$ is the pair potential for the idealized ($\Gamma\to 0$)
superconductor for the temperature $T\to 0$. We find the optimum $\Gamma$ can
also reduce $R_s$ by one order of magnitude for a clean superconductor
($\gamma/\Delta_0 < 1$) and a few tens $\%$ for a dirty superconductor
($\gamma/\Delta_0 > 1$). Also, we find a nearly-ideal ($\Gamma/\Delta_0 \ll 1$)
clean-limit superconductor exhibits a frequency-independent $R_s$ for a broad
range of frequency $\omega$, which can significantly improve $Q$ of a very
compact cavity with a few tens of GHz frequency. As $\Gamma$ or $\gamma$
increases, the plateau disappears, and $R_s$ obeys the $\omega^2$ dependence.
The subgap-state-induced residual surface resistance $R_{\rm res}$ is also
studied, which can be detected by an SRF-grade high-$Q$ 3D resonator. We
calculate $L_k(\gamma, \Gamma,T)$ and $J_d(\gamma, \Gamma,T)$, which are
monotonic increasing and decreasing functions of $(\gamma, \Gamma,T)$,
respectively. Measurements of $(\gamma, \Gamma)$ of device materials can give
helpful information on engineering $(\gamma, \Gamma)$ via materials processing,
by which it would be possible to improve $Q$, engineer $L_k$, and ameliorate
$J_d$.",2110.00573v1
2021-10-21,Angular harmonic Hall voltage and magnetoresistance measurements of Pt/FeCoB and Pt-Ti/FeCoB bilayers for spin Hall conductivity determination,"Materials with significant spin-orbit coupling enable efficient
spin-to-charge interconversion, which can be utilized in novel spin electronic
devices. A number of elements, mainly heavy-metals (HM) have been identified to
produce a sizable spin current ($j_\mathrm{s}$), while supplied with a charge
current ($j$), detected mainly in the neighbouring ferromagnetic (FM) layer.
Apart from the spin Hall angle $\theta_\mathrm{SH}$ = $j_\mathrm{s}$/$j$, spin
Hall conductivity ($\sigma_\mathrm{SH}$) is an important parameter, which takes
also the resistivity of the material into account. In this work, we present a
measurement protocol of the HM/FM bilayers, which enables for a precise
$\sigma_\mathrm{SH}$ determination. Static transport measurements, including
resistivity and magnetization measurements are accompanied by the angular
harmonic Hall voltage analysis in a dedicated low-noise rotating probe station.
Dynamic characterization includes effective magnetization and magnetization
damping measurement, which enable HM/FM interface absorption calculation. We
validate the measurement protocol in Pt and Pt-Ti underlayers in contact with
FeCoB and present the $\sigma_\mathrm{SH}$ of up to 3.3$\times$10$^5$ S/m,
which exceeds the values typically measured in other HM, such as W or Ta.",2110.11483v1
2021-12-23,Hydrogen induced electronic transition within correlated perovskite nickelates with heavy rare-earth composition,"Although discovery in hydrogen induced electronic transition within
perovskite family of rare-earth nickelate (ReNiO3) opens up a new paradigm in
exploring both the new materials functionality and device applications, the
existing research stays at ReNiO3 with light rare-earth compositions. To
further extend the cognition towards heavier rare-earth, herein we demonstrate
the hydrogen induced electronic transitions for quasi-single crystalline
ReNiO3/LaAlO3 (001) heterostructures, covering a large variety of the
rare-earth composition from Nd to Er. The hydrogen induced elevations in the
resistivity of ReNiO3 (RH/R0) show an unexpected non-monotonic tendency with
the atomic number of the rare-earth composition, e.g., firstly increase from Nd
to Dy and afterwards decreases from Dy to Er. Although ReNiO3 with heavy
rare-earth composition (e.g. DyNiO3) exhibits large RH/R0 up to 107, their
hydrogen induced electronic transition is not reversible. Further probing the
electronic structures via near edge X-ray absorption fine structure analysis
clearly demonstrates the respective transition in electronic structures of
ReNiO3 from Ni3+ based electron itinerant orbital configurations towards the
Ni2+ based electron localized state. Balancing the hydrogen induced transition
reversibility with the abruption in the variations of material resistivity, we
emphasize that the ReNiO3 with middle rare-earth compositions (e.g. Sm) to be
most suitable that caters for the potential applications in correlated
electronic devices.",2112.12357v1
2022-12-01,Extrinsic to intrinsic mechanism crossover of anomalous Hall effect in the Ir-doped MnPtSn Heusler system,"Recent findings of large anomalous Hall signal in nonferromagnetic and
nonferrimagnetic materials suggest that the magnetization of the system is not
a critical component for the realization of the anomalous Hall effect (AHE).
Here, we present a combined theoretical and experimental study demonstrating
the evolution of different mechanisms of AHE in a cubic Heusler system
MnPt$_{1-x}$Ir$_x$Sn. With the help of magnetization and neutron diffraction
studies, we show that the substitution of nonmagnetic Ir in place of Pt
significantly reduces the net magnetic moment from 4.17 $ \mu _B$/f.u. in
MnPtSn to 2.78 $ \mu _B$/f.u. for MnPt$_{0.5}$Ir$_{0.5}$Sn. In contrast, the
anomalous Hall resistivity is enhanced by nearly three times from 1.6 $ \mu
\Omega $ cm in MnPtSn to about 5 $ \mu \Omega $ cm for
MnPt$_{0.5}$Ir$_{0.5}$Sn. The power law analysis of the Hall resistivity data
suggests that the extrinsic contribution of AHE that dominates in the case of
the parent MnPtSn almost vanishes for MnPt$_{0.5}$Ir$_{0.5}$Sn, where the
intrinsic mechanism plays the major role. The experimental results are well
supported by our theoretical study, which shows a considerable enhancement of
the spin-orbit coupling when Ir is introduced into the system. Our finding of a
crossover of the anomalous Hall effect with chemical engineering is a major
contribution toward the recent interest in controlling the band topology of
topological materials, both in bulk and thin-film forms.",2212.00360v1
2023-06-26,Large electro-opto-mechanical coupling in VO2 neuristors,"Biological neurons are electro-mechanical systems, where the generation and
propagation of an action potential is coupled to generation and transmission of
an acoustic wave. Neuristors, such as VO2, characterized by insulator-metal
transition (IMT) and negative differential resistance, can be engineered as
self-oscillators, which are good approximations of biological neurons in the
domain of electrical signals. In this study, we show that these
self-oscillators are coupled electro-opto-mechanical systems, with better
energy conversion coefficients than the conventional electromechanical or
electrooptical materials. This is due to the significant contrast in the
material's resistance, optical refractive index and density across the induced
temperature range in a Joule heating driven IMT. We carried out laser
interferometry to measure the opto-mechanical response while simultaneously
driving the devices electrically into self-oscillations of different kinds. We
analyzed films of various thicknesses, engineered device geometry and performed
analytical modelling to decouple the effects of refractive index change
vis-a-vis mechanical strain in the interferometry signal. We show that the
effective piezoelectric coefficient (d13*) for our neuristor devices is 660
pm/V, making them viable alternatives to Pb-based piezoelectrics for MEMS
applications. Furthermore, we show that the effective electro-optic coefficient
(r13*) is ~22 nm/V, which is much larger than that in thin-film and bulk
Pockels materials.",2306.14367v1
2023-08-28,Crystal-Chemical Origins of the Ultrahigh Conductivity of Metallic Delafossites,"Despite their highly anisotropic complex-oxidic nature, certain delafossite
compounds (e.g., PdCoO2, PtCoO2) are the most conductive oxides known, for
reasons that remain poorly understood. Their room-temperature conductivity can
exceed that of Au, while their low-temperature electronic mean-free-paths reach
an astonishing 20 microns. It is widely accepted that these materials must be
ultrapure to achieve this, although the methods for their growth (which produce
only small crystals) are not typically capable of such. Here, we first report a
new approach to PdCoO2 crystal growth, using chemical vapor transport methods
to achieve order-of-magnitude gains in size, the highest structural qualities
yet reported, and record residual resistivity ratios (>440). Nevertheless, the
first detailed mass spectrometry measurements on these materials reveal that
they are not ultrapure, typically harboring 100s-of-parts-per-million impurity
levels. Through quantitative crystal-chemical analyses, we resolve this
apparent dichotomy, showing that the vast majority of impurities are forced to
reside in the Co-O octahedral layers, leaving the conductive Pd sheets highly
pure (~1 ppm impurity concentrations). These purities are shown to be in
quantitative agreement with measured residual resistivities. We thus conclude
that a previously unconsidered ""sublattice purification"" mechanism is essential
to the ultrahigh low-temperature conductivity and mean-free-path of metallic
delafossites.",2308.14257v2
2023-10-26,Slow and Non-Equilibrium Dynamics due to Electronic Ferroelectricity in a Strongly-Correlated Molecular Conductor,"Using a combination of resistance fluctuation (noise) and dielectric
spectroscopy we investigate the nature of relaxor-type electronic
ferroelectricity in the organic conductor $\kappa$-(BETS)$_2$Mn[N(CN)$_2$]$_3$,
a system representative for a wider class of materials, where strong
correlations of electrons on a lattice of dimerized molecules results in an
insulating ground state. The two complementary spectroscopies reveal a distinct
low-frequency dynamics. By dielectric spectroscopy we detect an intrinsic
relaxation that is typical for relaxor ferroelectrics below the
metal-to-insulator transition at $T_{\rm{MI}}\sim 25\,$K. Resistance noise
spectroscopy reveals fluctuating two-level processes above $T_{\rm MI}$ which
strongly couple to the applied electric field, a signature of fluctuating polar
nanoregions (PNR), i.e. clusters of quantum electric dipoles fluctuating
collectively. The PNR preform above the metal insulator transition. Upon
cooling through $T_{\rm MI}$, a drastic increase of the low-frequency
$1/f$-type fluctuations and slowing down of the charge carrier dynamics is
accompanied by the onset of strong non-equilibrium dynamics indicating a glassy
transition of interacting dipolar clusters, the scaling properties of which are
consistent with a droplet model. The freezing of nano-scale polar clusters and
non-equilibrium dynamics is suggested to be a common feature of organic
relaxor-type electronic ferroelectrics and needs to be considered in
theoretical models describing these materials.",2310.17242v2
2024-01-01,Nonlinear charge transport induced by gate voltage oscillation in few-layer MnBi2Te4,"Nonlinear charge transport, including nonreciprocal longitudinal resistance
and nonlinear Hall effect, has garnered significant attention due to its
ability to explore inherent symmetries and topological properties of novel
materials. An exciting recent progress along this direction is the discovery of
significant nonreciprocal longitudinal resistance and nonlinear Hall effect in
the intrinsic magnetic topological insulator MnBi2Te4 induced by the quantum
metric dipole. Given the importance of this finding, the inconsistent response
with charge density, and conflicting requirement of C3z symmetry, it is
imperative to elucidate every detail that may impact the nonlinear transport
measurement. In this study, we reveal an intriguing experimental factor that
inevitably gives rise to sizable nonlinear transport signal in MnBi2Te4. We
demonstrate that this effect stems from the gate voltage oscillation caused by
the application of a large alternating current to the sample. Furthermore, we
propose a methodology to significantly suppress this effect by individually
grounding the voltage electrodes during the second-harmonic measurements. Our
investigation emphasizes the critical importance of thoroughly assessing the
impact of gate voltage oscillation before determining the intrinsic nature of
nonlinear transport in all 2D material devices with an electrically connected
operative gate electrode.",2401.00679v1
1997-12-15,Spin Tunneling in Conducting Oxides,"Direct tunneling in ferromagnetic junctions is compared with
impurity-assisted, surface state assisted, and inelastic contributions to a
tunneling magnetoresistance (TMR). Theoretically calculated direct tunneling in
iron group systems leads to about a 30% change in resistance, which is close to
experimentally observed values. It is shown that the larger observed values of
the TMR might be a result of tunneling involving surface polarized states. We
find that tunneling via resonant defect states in the barrier radically
decreases the TMR (down to 4% with Fe-based electrodes), and a resonant tunnel
diode structure would give a TMR of about 8%. With regards to inelastic
tunneling, magnons and phonons exhibit opposite effects: one-magnon emission
generally results in spin mixing and, consequently, reduces the TMR, whereas
phonons are shown to enhance the TMR. The inclusion of both magnons and phonons
reasonably explains an unusual bias dependence of the TMR.
  The model presented here is applied qualitatively to half-metallics with 100%
spin polarization, where one-magnon processes are suppressed and the change in
resistance in the absence of spin-mixing on impurities may be arbitrarily
large. Even in the case of imperfect magnetic configurations, the resistance
change can be a few 1000 percent. Examples of half-metallic systems are
CrO$_2$/TiO$_2$ and CrO$_2$/RuO$_2$, and an account of their peculiar band
structures is presented. The implications and relation of these systems to CMR
materials which are nearly half-metallic, are discussed.",9712170v2
2000-09-14,Experimental study of negative photoconductivity in n-PbTe(Ga) epitaxial films,"We report on low-temperature photoconductivity (PC) in n-PbTe(Ga) epitaxial
films prepared by the hot-wall technique on <111>-BaF_2 substrates. Variation
of the substrate temperature allowed us to change the resistivity of the films
from 10^8 down to 10_{-2} Ohm x cm at 4.2 K. The resistivity reduction is
associated with a slight excess of Ga concentration, disturbing the Fermi level
pinning within the energy gap of n-PbTe(Ga). PC has been measured under
continuous and pulse illumination in the temperature range 4.2-300 K. For films
of low resistivity, the photoresponse is composed of negative and positive
parts. Recombination processes for both effects are characterized by
nonexponential kinetics depending on the illumination pulse duration and
intensity. Analysis of the PC transient proves that the negative
photoconductivity cannot be explained in terms of nonequilibrium charge
carriers spatial separation of due to band modulation. Experimental results are
interpreted assuming the mixed valence of Ga in lead telluride and the
formation of centers with a negative correlation energy. Specifics of the PC
process is determined by the energy levels attributed to donor Ga III, acceptor
Ga I, and neutral Ga II states with respect to the crystal surrounding. The
energy level corresponding to the metastable state Ga II is supposed to occur
above the conduction band bottom, providing fast recombination rates for the
negative PC. The superposition of negative and positive PC is considered to be
dependent on the ratio of the densities of states corresponding to the donor
and acceptor impurity centers.",0009209v1
2002-04-20,Possible Magnetic separation in Ru doped La0.67Ca0.33MnO3,"X-ray diffraction, resistivity, ac susceptibility and magnetization studies
on La0.67Ca0.33Mn1-xRuxO3 (0 x < 0.1) were carried out. A significant increase
in the lattice parameters indicated the presence of mixed valance state of Ru:
Ru3+ and Ru4+. The resistivity of the doped compounds exhibited two features: a
broad maximum and a relatively sharp peak. While a para to ferromagnetic
transition could be observed for the latter peak, no magnetic signal either in
ac susceptibility or in magnetization measurements could be observed for the
broad maximum. The magnetic moment decreases non linearly from 3.55 to 3 mB
over the Ru composition from 0 to 8.5 at.%. Based on the results of the present
studies and on existing literature on the Mn-site substituted systems, we argue
that a magnetic phase separation occurs in the Ru doped system. While the sharp
peak in the resistivity corresponds to Ru4+ enriched region with a
ferromagnetic coupling with neighboring Mn ions, the broad peak corresponds to
a Ru3+ rich regions, with an antiferromagnetic coupling with neighboring Mn
ions.",0204441v1
2003-02-03,Metallicity and its low temperature behavior in dilute 2D carrier systems,"We theoretically consider the temperature and density dependent transport
properties of semiconductor-based 2D carrier systems within the RPA-Boltzmann
transport theory, taking into account realistic screened charged impurity
scattering in the semiconductor. We derive a leading behavior in the transport
property, which is exact in the strict 2D approximation and provides a zeroth
order explanation for the strength of metallicity in various 2D carrier
systems. By carefully comparing the calculated full nonlinear temperature
dependence of electronic resistivity at low temperatures with the corresponding
asymptotic analytic form obtained in the $T/T_F \to 0$ limit, both within the
RPA screened charged impurity scattering theory, we critically discuss the
applicability of the linear temperature dependent correction to the low
temperature resistivity in 2D semiconductor structures. We find quite generally
that for charged ionized impurity scattering screened by the electronic
dielectric function (within RPA or its suitable generalizations including local
field corrections), the resistivity obeys the asymptotic linear form only in
the extreme low temperature limit of $T/T_F \le 0.05$. We point out the
experimental implications of our findings and discuss in the context of the
screening theory the relative strengths of metallicity in different 2D systems.",0302047v3
2003-04-21,"Chemical, Structural, and Transport Properties of Na1-xCoO2","We report measurement of room-temperature compressibility, thermal expansion,
thermoelectric power a(T) at various pressures P < 20 kbar, basal-plane
resistivity rab (T), magnetic susceptibility and thermal conductivity k(T)
taken on single-crystal or cold-pressed Na0.57CoO2. An enhancement of a large
thermopower with a change of slope occurs on heating near 100 K, but this
enhancement is progressively suppressed by pressure. The c-axis thermal
expansion is large in the interval 150 K <T < 250 K where the c-axis
resistivity exhibits a smooth transition from a metallic to a non-metallic
temperature dependence; but the basal-plane thermal expansion remains
negligible for all temperatures T < 300 K. On the other hand, the basal-plane
room-temperature compressibility is large in the interval 0 < P < 22 kbar,
becoming negligible in the range 22 < P < 45 kbar, whereas the c-axis
room-temperature compressibility is anomalously large in the pressure range 22
< P < 35 kbar. The basal plane resistivity is prop. to T^(3/2) below 175 K
where there is 3D metallic conduction; it rises less rapidly with temperature
where the metallic conduction is confined to 2D. The phonon contribution to the
thermal conductivity of a cold-pressed ceramic sample is not suppressed, as
previously reported. These findings are rationalized with the aid of the virial
theorem, recognition of a pinning of the nominal Co(IV)/Co(III) redox couple at
the top of the O2-:2p6 bands, and a schematic location of the a1T and eT
antibonding bands of this couple with respect to the Fermi energy.",0304455v1
2004-11-04,"Electron transport, penetration depth and upper critical magnetic field of ZrB12 and MgB2","We report on the synthesis and measurements of the temperature dependence of
resistivity, R(T), the penetration depth, l(T), and upper critical magnetic
field, Hc2(T), for polycrystalline samples of dodecaboride ZrB12 and diboride
MgB2. We conclude that ZrB12 as well as MgB2 behave like simple metals in the
normal state with usual Bloch-Gruneisen temperature dependence of resistivity
and with rather low resistive Debye temperature, TR=280 K, for ZrB12 (as
compared to MgB2 with TR=900 K). The R(T) and l(T) dependencies of ZrB12 reveal
a superconducting transition at Tc=6.0 K. Although a clear exponential
l(T)dependence in MgB2 thin films and ceramic pellets was observed at low
temperatures, this dependence was almost linear for ZrB12 below Tc/2. These
features indicate s-wave pairing state in MgB2, whereas a d-wave pairing state
is possible in ZrB12. A fit to the data gives a reduced energy gap
2D(0)/kTc=1.6 for MgB2 films and pellets, in good agreement with published data
for 3D \pi - sheets of the Fermi surface. Contrary to conventional theories we
found a linear temperature dependence of Hc2(T) for ZrB12 (Hc2(0)=0.15 T).",0411116v1
2008-03-03,Phase separation and the effect of quenched disorder in $Pr_{0.5}Sr_{0.5}MnO_3$,"The nature of phase separation in $Pr_{0.5}Sr_{0.5}MnO_3$ has been probed by
linear as well as nonlinear magnetic susceptibilities and resistivity
measurements across the 2nd order paramagnetic to ferromagnetic transition
($T_C$) and 1st order ferromagnetic to antiferromagnetic transition ($T_N$). We
found that the ferromagnetic (metallic) clusters, which form with the onset of
long-range order in the system at $T_C$, continuously decrease their size with
the decrease in temperature and coexist with non-ferromagnetic (insulating)
clusters. These non-ferromagnetic clusters are identified to be
antiferromagnetic. Significantly, it is shown that they do not arise because of
the superheating effect of the lower temperature 1st order transition. Thus
reveals unique phase coexistence in a manganite around half-doping encompassing
two long-range order transitions. Both the ferromagnetic and antiferromagnetic
clusters form at $T_C$ and persist much below $T_N$. Substitution of quenched
disorder (Ga) at Mn-site promotes antiferromagnetism at the cost of
ferromagnetism without adding any magnetic interaction or introducing any
significant lattice distortion. Moreover, increase in disorder decreases the
ferromagnetic cluster size and with 7.5% Ga substitution clusters size reduces
to the single domain limit. Yet, all the samples show significant short-range
ferromagnetic interaction much above $T_C$. Resistivity measurements also
reveal the novel phase coexistence identified from the magnetic measurements.
It is significant that, increase in disorder up to 7.5% increases the
resistivity of the low temperature antiferromagnetic phase by about four
orders.",0803.0085v1
2008-04-16,Properties of the hole and electron doped perovskites LnCoO3,"Two extreme members of the cobaltite series, LaCoO3 and DyCoO3, were
investigated by the electrical resistivity and thermopower measurements up to
800-1000 K. Special attention was given to effects of extra holes or electrons,
introduced by light doping of Co sites by Mg2+ or Ti4+ ions. The experiments on
the La based compounds were complemented with magnetic measurements. The study
shows that both kinds of charge carriers induce magnetic states on surrounding
CoIII sites and form thus thermally stable polarons of large total spin. Their
itinerancy is characterized by low temperature resistivity, which is of
Arrhenius type r~exp(EA/kT) for the hole (CoIV) doped samples, while an unusual
dependence r~1/Tn (n=8-10) is observed for the electron (CoII) doped samples.
At higher temperatures, additional hole carriers are massively populated in the
CoIII background, leading to a resistivity drop. This transition become evident
at ~300 K and 450 K and culminates at TI-M=540 and 780 K for the La and Dy
based samples, respectively.
  The electronic behaviours of the cobaltites are explained considering two
excitation processes in parent compounds. The first one is related to a local
excitation from the diamagnetic LS CoIII to close-lying paramagnetic HS CoIII
state. Secondarily, a metallic phase of the IS CoIII character is formed
through a charge transfer mechanism between LS/HS pairs. The magnetic polarons
associated with doped carriers are interpreted as droplets of such IS phase.",0804.2685v3
2008-08-22,Single crystal growth and physical properties of the layered arsenide BaRh_2As_2,"Single crystals of BaRh_2As_2 have been synthesized from a Pb flux. We
present the room temperature crystal structure, single crystal x-ray
diffraction measurements as a function of temperature T, anisotropic magnetic
susceptibility \chi versus T, electrical resistivity in the ab-plane \rho
versus T, Hall coefficient versus T and magnetic field H, and heat capacity C
versus T measurements on the crystals. The single crystal structure
determination confirms that BaRh_2As_2 forms in the tetragonal ThCr_2Si_2 type
structure (space group I4/mmm) with lattice parameters a = b = 4.0564(6)\AA and
c = 12.797(4) \AA. Band structure calculations show that BaRh_2As_2 should be
metallic with a small density of states at the Fermi energy N(E_ F) = 3.49
states/eV f.u. (where f.u. \equiv formula unit) for both spin directions.
\rho(T) data in the ab-plane confirm that the material is indeed metallic with
a residual resistivity \rho(2K) = 29 \mu \Omega cm, and with a residual
resistivity ratio \rho(310K)/\rho(2K) = 5.3. The observed \chi(T) is small
(\sim 10^{-5} cm^3/mol) and weakly anisotropic with \chi_{ab}/\chi_ c \approx
2. The C(T) data indicate a small density of states at the Fermi energy with
the low temperature Sommerfeld coefficient \gamma = 4.7(9) mJ/mol K^2. There
are no indications of superconductivity, spin density wave, or structural
transitions between 2K and 300K. We compare the calculated density of states
versus energy of BaRh_2As_2 with that of BaFe_2As_2.",0808.3116v1
2009-04-24,Anisotropic magnetoresistance of spin-orbit coupled carriers scattered from polarized magnetic impurities,"Anisotropic magnetoresistance (AMR) is a relativistic magnetotransport
phenomenon arising from combined effects of spin-orbit coupling and broken
symmetry of a ferromagnetically ordered state of the system. In this work we
focus on one realization of the AMR in which spin-orbit coupling enters via
specific spin-textures on the carrier Fermi surfaces and ferromagnetism via
elastic scattering of carriers from polarized magnetic impurities. We report
detailed heuristic examination, using model spin-orbit coupled systems, of the
emergence of positive AMR (maximum resistivity for magnetization along
current), negative AMR (minimum resistivity for magnetization along current),
and of the crystalline AMR (resistivity depends on the absolute orientation of
the magnetization and current vectors with respect to the crystal axes)
components. We emphasize potential qualitative differences between pure
magnetic and combined electro-magnetic impurity potentials, between short-range
and long-range impurities, and between spin-1/2 and higher spin-state carriers.
Conclusions based on our heuristic analysis are supported by exact solutions to
the integral form of the Boltzmann transport equation in archetypical
two-dimensional electron systems with Rashba and Dresselhaus spin-orbit
interactions and in the three-dimensional spherical Kohn-Littinger model. We
include comments on the relation of our microscopic calculations to standard
phenomenology of the full angular dependence of the AMR, and on the relevance
of our study to realistic, two-dimensional conduction-band carrier systems and
to anisotropic transport in the valence band of diluted magnetic
semiconductors.",0904.3785v2
2011-01-28,Cooper pair insulator in amorphous films induced by nanometer-scale thickness variations,"Unusual transport properties of superconducting (SC) materials, such as the
under doped cuprates, low dimensional superconductors in strong magnetic
fields, and insulating films near the Insulator Superconductor Transition
(IST), have been attributed to the formation of inhomogeneous phases.
Difficulty correlating the behaviors with observations of the inhomogeneities
make these connections uncertain. Of primary interest here are proposals that
insulating films near the IST, which show an activated resistance and giant
positive magnetoresistance, contain islands of Cooper Pairs (CPs). Here we
present evidence that these types of inhomogeneities are essential to such an
insulating phase in amorphous Bi (a-Bi) films deposited on substrates patterned
with nanometer-sized holes. The patterning induces film thickness variations,
and corresponding coupling constant variations, that transform the composition
of the insulator from localized electrons to CPs. Analyses near the
thickness-tuned ISTs of films on nine different substrates show that weak links
between SC islands dominate the transport. In particular, the ISTs all occur
when the link resistance approaches the resistance quantum for pairs. These
observations lead to a detailed picture of CPs localized by spatial variations
of the superconducting coupling constant.",1101.5642v1
2011-09-15,Surface impedance of superconductors with magnetic impurities,"Motivated by the problem of the residual surface resistance of the
superconducting radio-frequency (SRF) cavities, we develop a microscopic theory
of the surface impedance of s-wave superconductors with magnetic impurities. We
analytically calculate the current response function and surface impedance for
a sample with spatially uniform distribution of impurities, treating magnetic
impurities in the framework of the Shiba theory. The obtained general
expressions hold in a wide range of parameter values, such as temperature,
frequency, mean free path, and exchange coupling strength. This generality, on
the one hand, allows for direct numerical implementation of our results to
describe experimental systems (SRF cavities, superconducting qubits) under
various practically relevant conditions. On the other hand, explicit analytical
expressions can be obtained in a number of limiting cases, which makes possible
further theoretical investigation of certain regimes. As a feature of key
relevance to SRF cavities, we show that in the regime of ""gapless
superconductivity"" the surface resistance exhibits saturation at zero
temperature. Our theory thus explicitly demonstrates that magnetic impurities,
presumably contained in the oxide surface layer of the SRF cavities, provide a
microscopic mechanism for the residual resistance.",1109.3395v2
2012-09-25,Sb concentration dependent structural and resistive properties of polycrystalline Bi-Sb alloys,"Polycrystalline Bi-Sb alloys have been synthesized over a wide range of
antimony concentration (8 at% to 20 at%) by solid state reaction method. In
depth structural analysis using X-Ray diffraction (XRD) and temperature
dependent resistivity measurement of synthesized samples have been performed.
XRD data confirmed single phase nature of polycrystalline samples and revealed
that complete solid solution is formed between bismuth and antimony. Rietveld
refinement technique, utilizing MAUD software, has been used to perform detail
structural analysis of the samples and lattice parameters of synthesized Bi-Sb
alloys have been estimated. Lattice parameter and unit cell volume decreases
monotonically with increasing antimony content. The variation of lattice
parameters with antimony concentration depicts a distinct slope change beyond
12 at% Sb content sample. Band gap has been estimated from the thermal
variation of resistivity data, with the 12% Sb content sample showing maximum
value. It has been observed that, with increasing antimony concentration the
transition from direct to indirect gap semiconductor is intimately related to
the variation of the estimated lattice parameters. Band diagram for the
polycrystalline Bi-Sb alloy system has also been proposed.",1209.5506v1
2012-12-18,Growth and physical property study of single nanowire (diameter ~ 45nm) of half doped Manganite,"We report here the growth and characterization of functional oxide nanowire
of hole doped manganite of La0.5Sr0.5MnO3 (LSMO). We also report four probe
electrical resistance measurement of single nanowire of LSMO (diameter ~ 45nm)
using FIB fabricated electrodes. The wires were fabricated by hydrothermal
method using autoclave at a temperature of 270 oC. The elemental analysis and
physical property like electrical resistivity were studied at individual
nanowire level. The quantitative determination of Mn valency and elemental
mapping of constituent elements was done by using Electron Energy Loss
Spectroscopy (EELS) in the Scanning Transmission Electron Microscopy (STEM)
mode. We addressed the important issue of whether as a result of size reduction
the nanowires can retain the desired composition, structure and physical
properties. The nanowires used were found to have a ferromagnetic transition
(TC) at around 325 K which is very close to the bulk value of around 330 K
found in single crystal of the same composition confirming that the functional
behavior is likely to be retained even after size reduction of the nanowires to
a diameter of 45 nm. The electrical resistivity shows insulating behavior
within the temperature range measured, which is very much similar to the bulk
system.",1212.4374v2
2013-10-16,Spin-Flipping in Pt and at Co/Pt Interfaces,"There has been recent controversy about the magnitude of spin-flipping in the
heavy metal Pt, characterized by the spin-diffusion length, lsf(Pt) We propose
a resolution of this controversy, and also present evidence for the importance
of a phenomenon neglected in prior studies of transport across sputtered
Ferromagnetic/Pt (F/Pt) interfaces, spin-flipping at the interface. The latter
is characterized by an interface spin-flipping parameter, delta(Co/Pt) that
specifies the probability P = [1 - exp(-delta)] of a conduction electron
flipping its spin direction as it traverses a Co/Pt interface. From studies of
the Current-Perpendicular-to-Plane (CPP) Resistances and Magnetoresistances of
sputtered ferromagnetically coupled Co/Pt multilayers by themselves, and
embedded within Py-based Double Exchange-biased Spin-Valves, we derive values
at 4.2K of delta(Co/Pt) = 0.9 (+0.5/-0.2), the interface specific resistance,
AR*(Co/Pt) = 0.74 +/- 0.15 fohm-m(2). and the interface spin-scattering
asymmetry, gamma(Co/Pt) = 0.58 +/- 0.12. This value of delta(Co/Pt) is much
larger than ones previously found for interfaces involving Co but not Pt. To
derive delta requires knowledge of the spin-diffusion length, lsf(Pt), for our
sputtered Pt. We derive lsf(Pt) from separate measurements. Combining our
results with those from others, we find that lsf(Pt) for Pt is approximately
proportional to the inverse resistivity, 1/rho(Pt).",1310.4364v2
2013-11-02,Experimental evidence for direct insulator-quantum Hall transition in multi-layer graphene,"We have performed magnetotransport measurements on a multi-layer graphene
flake. At the crossing magnetic field Bc, an approximately
temperature-independent point in the measured longitudinal resistivity, which
is ascribed to the direct insulator-quantum Hall (I-QH) transition, is
observed. By analyzing the amplitudes of the magnetoresistivity oscillations,
we are able to measure the quantum mobility of our device. It is found that at
the direct I-QH transition, the product of the quantum mobility and is about
0.37 which is considerably smaller than 1. In contrast, at Bc, the longitudinal
resistivity is close to the Hall resistivity, i.e., the product of the
classical mobility and the crossing field is about 1. Therefore our results
suggest that different mobilities need to be introduced for the direct I-QH
transition observed in multi-layered graphene. Combined with existing
experimental results obtained in various material systems, our data obtained on
graphene suggest that the direct I-QH transition is a universal effect in 2D.",1311.0353v1
2013-12-16,Which Memristor Theory is Best for Relating Devices Properties to Memristive Function?,"There are three theoretical models which purport to relate
experimentally-measurable or fabrication-controllable device properties to the
memristor's operation: 1. Strukov et al's phenomenological model; 2. Georgiou
et al's Bernoulli rewrite of that phenomenological model; 3. Gale's
memory-conservation model. They differ in their prediction of the effect on
memristance of changing the electrode size and factors that affect the
hysteresis. Using a batch of TiO$_2$ sol-gel memristors fabricated with
different top electrode widths we test and compare these three theories. It was
found that, contrary to model 2's prediction, the `dimensionless lumped
parameter', $\beta$, did not correlate to any measure of the hysteresis.
Contrary to model 1, memristance was found to be dependent on the three spatial
dimensions of the TiO$_2$ layer, as was predicted by model 3. Model 3 was found
to fit the change in resistance value with electrode size. Simulations using
model 3 and experimentally derived values for contact resistance gave
hysteresis values that were linearly related to (and only one order of
magnitude out) from the experimentally-measured values. Memristor hysteresis
was found to be related to the ON state resistance and thus the electrode size
(as those two are related). These results offer a verification of the
memory-conservation theory of memristance and its association of the vacancy
magnetic flux with the missing magnetic flux in memristor theory. This is the
first paper to experimentally test various theories pertaining to the operation
of memristor devices.",1312.4422v1
2015-11-13,Studies on proximity effect in Mo/Bi1.95Sb0.05Se3 hybrid structure,"Proximity effect in a mechanically exfoliated Bi1.95Sb0.05Se3 topological
insulator (TI) single crystal partially covered with disordered superconducting
(SC) Mo thin film is reported. Magnetotransport measurement was performed
simultaneously across three different regions of the sample viz. SC, TI and
SC/TI junction. Resistance measured across SC shows a TC at 4.3 K concomitantly
the resistance measurement on TI showed a metallic trend with a steep upturn at
TC. Magneto-resistance (MR) measurement on TI exhibit a positive MR with
Shubnikov-de Haas (SdH) oscillations, whereas on SC a positive MR superimposed
with steep cusp close to TC is observed. Across SC/TI junction both SdH
oscillation and the cusp were observed. The frequency of SdH oscillation on
SC/TI junction is found to be lesser (~ 125 T) as compared to a reference
Bi1.95Sb0.05Se3sample (~ 174 T). Upper critical field HC2 deduced from WHH fit
was found to be 17.14 T for a reference Mo film whereas Mo film deposited on TI
showed a decreased HC2 of 4.05 T. The coherence length for the former was found
to be 4.38 nm and for the latter 9.01 nm. The interaction between the spin-less
Cooper pairs in SC with the spin-momentum locked carriers on the surface of TI
is believed to cause such changes in transport properties.",1511.04213v1
2016-06-28,"Enhanced superconductivity, Kondo behavior and negative-curvature resistivity of oxygen-irradiated thin films of aluminium","We followed the evolution of the normal and superconducting properties of Al
thin films after each session of various successive oxygen irradiations at
ambient temperature. Such irradiated films, similar to the granular ones,
exhibit enhanced superconductivity, Kondo behavior and negative-curvature
resistivity. Two distinct roles of oxygen are identified: as a damage-causing
projectile and as an implanted oxidizing agent. The former gives rise to the
processes involved in the conventional recovery stages. The latter, considered
within the context of the Cabrera-Mott model, gives rise to a multistep process
which involves charges transfer and creation of stabilized vacancies and
charged defects. Based on the outcome of this multistep process, we consider
(i) the negative curvature resistivity as a manifestation of a
thermally-assisted liberation of trapped electric charges, (ii) the Kondo
contribution as a spin-flip scattering from paramagnetic, color-center-type
defects, and (iii) the enhancement of T_{c} as being due to a lattice softening
facilitated by the stabilized defects and vacancies. The similarity in the
phase diagrams of granular and irradiated films as well as the aging effects
are discussed along the same line of reasoning.",1606.08918v2
2016-06-30,Quadrupole-Driven Non-Fermi Liquid and Magnetic-Field Induced Heavy Fermion States in a Non-Kramers Doublet System,"Orbital degrees of freedom in condensed matters could play important roles in
forming a variety of exotic electronic states by interacting with conduction
electrons. In 4f electron systems, because of strong intra-atomic spin-orbit
coupling, an orbitally degenerate state inherently carries quadrupolar degrees
of freedom. The present work has focussed on a purely quadrupole-active system
PrIr2Zn20 showing superconductivity in the presence of an antiferroquadrupole
order at TQ = 0.11 K. We observed non-Fermi liquid (NFL) behaviors emerging in
the electrical resistivity and the 4f contribution to the specific heat, C_4f,
in the paramagnetic state at T > TQ. Moreover, in magnetic fields below 6 T,
all data set of the electrical resistivity and C_4f(T) are well scaled with
characteristic temperatures T0's. This is the first observation of the NFL
state in the nonmagnetic quadrupole-active system, whose origin is
intrinsically different from that observed in the vicinity of the conventional
quantum critical point. It implies possible formation of a quadrupole Kondo
lattice resulting from hybridization between the quadrupoles and the conduction
electrons. Below 0.13 K, the electrical resistivity and C_4f(T) exhibit
anomalies as B approaches 5 T. This is the manifestation of a field-induced
crossover toward a Fermi-liquid ground state in the quadrupole Kondo lattice.",1606.09571v1
2016-10-27,Magnetoresistance and robust resistivity plateau in MoAs2,"We have grown the MoAs$_2$ single crystal which crystallizes in a monoclinic
structure with C2/m space group. Transport measurements show that MoAs$_2$
displays a metallic behavior at zero field and undergoes a
metal-to-semiconductor crossover at low temperatures when the applied magnetic
field is over 5 T. A robust resistivity plateau appears below 18 K and persists
for the field up to 9 T. A large positive magnetoresistance (MR), reaching
about 2600\% at 2 K and 9 T, is observed when the field is perpendicular to the
current.The MR becomes negative below 40 K when the field is rotated to be
parallel to the current. The Hall resistivity shows the non-linear
field-dependence below 70 K. The analysis using two-band model indicates a
compensated electron-hole carrier density at low temperatures. A combination of
the breakdown of Kohler's rule, the abnormal drop and the cross point in Hall
data implies that a possible Lifshitz transition has occurred between 30 K and
60 K, likely driving the compensated electron-hole density, the large MR as
well as the metal-semiconductor transition in MoAs$_2$. Our results indicate
that the family of centrosymmetric transition-metal dipnictides has rich
transport behavior which can in general exhibit variable metallic and
topological features.",1610.08594v2
2017-10-24,Absence of Metallic Behavior in Epitaxial NiCo2O4 Thin Films: Role of Microstructural Disorder,"Despite the low resistivity (~ 1 mohm cm), the metallic electrical transport
has not been commonly observed in the inverse spinel NiCo2O4, except in certain
epitaxial thin films. Previous studies have stressed the effect of valence
mixing and degree of spinel inversion on the electric conduction of NiCo2O4
films. In this work, we have studied the effect of microstructure by comparing
the NiCo2O4 epitaxial films grown on MgAl2O4 (111) and on Al2O3 (0001)
substrates. Although the optimal growth condition and the magnetic properties
are similar for the NiCo2O4/MgAl2O4 and the NiCo2O4/Al2O3, they show metallic
and semiconducting electrical transport respectively. Despite similar
temperature and field dependence of magnetization, the NiCo2O4/Al2O3 show much
larger magnetoresistance at low temperature. Post-growth annealing decreases
the resistivity of NiCo2O4/Al2O3, but the annealed films are still
semiconducting. The correlation between the structural correlation length and
the resistivity suggests that the microstructural disorder, generated by the
dramatic mismatch between the NiCo2O4 and Al2O3 crystal structures, may be the
origin of the absence of the metallic electrical transport in NiCo2O4. These
results reveal microstructural disorder as another key factor in controlling
the electrical transport of NiCo2O4, with potentially large magnetoresistance
for spintronics application.",1710.08608v2
2017-12-05,Peculiarities of the electronic transport in half-metallic Co-based Heusler alloys,"Electrical, magnetic and galvanomagnetic properties of half-metallic Heusler
alloys of Co$_2$YZ (Y = Ti, V, Cr, Mn, Fe, Ni, and Z = Al, Si, Ga, Ge, In, Sn,
Sb) were studied in the temperature range 4.2--900 K and in magnetic fields of
up to 100 kOe. It was found that varying Y in affects strongly the electric
resistivity and its temperature dependence $\rho(T)$, while this effect is not
observed upon changing Z. When Y is varied, extrema (maximum or minimum) are
observed in $\rho(T)$ near the Curie temperature $T_C$. At $T < T_C$, the
$\rho(T)$ behavior can be ascribed to a change in electronic energy spectrum
near the Fermi level. The coefficients of the normal and anomalous Hall effect
were determined. It was shown that the latter coefficient, $R_S$, is related to
the residual resistivity $\rho_0$ by a power law $R_S \sim \rho_0^k/M_S$ with
$M_S$ the spontaneous magnetization. The exponent $k$ was found to be 1.8 for
Co$_2$FeZ alloys, which is typical for asymmetric scattering mechanisms, and
2.9 for Co$_2$YAl alloys, which indicates an additional contribution to the
anomalous Hall effect. The temperature dependence of resistivity at low
temperatures is analyzed and discussed in the framework of the two-magnon
scattering theory.",1712.01584v1
2017-12-25,Effects of nuclear spins on the transport properties of the edge of two-dimensional topological insulators,"The electrons in the edge channels of two-dimensional topological insulators
can be described as a helical Tomonaga-Luttinger liquid. They couple to nuclear
spins embedded in the host materials through the hyperfine interaction, and are
therefore subject to elastic spin-flip backscattering on the nuclear spins. We
investigate the nuclear-spin-induced edge resistance due to such backscattering
by performing a renormalization-group analysis. Remarkably, the effect of this
backscattering mechanism is stronger in a helical edge than in nonhelical
channels, which are believed to be present in the trivial regime of InAs/GaSb
quantum wells. In a system with sufficiently long edges, the disordered nuclear
spins lead to an edge resistance which grows exponentially upon lowering the
temperature. On the other hand, electrons from the edge states mediate an
anisotropic Ruderman-Kittel-Kasuya-Yosida nuclear spin-spin interaction, which
induces a spiral nuclear spin order below the transition temperature. We
discuss the features of the spiral order, as well as its experimental
signatures. In the ordered phase, we identify two backscattering mechanisms,
due to charge impurities and magnons. The backscattering on charge impurities
is allowed by the internally generated magnetic field, and leads to an
Anderson-type localization of the edge states. The magnon-mediated
backscattering results in a power-law resistance, which is suppressed at zero
temperature. Overall, we find that in a sufficiently long edge the nuclear
spins, whether ordered or not, suppress the edge conductance to zero as the
temperature approaches zero.",1712.09040v2
2018-01-26,Local Magnetic Measurements of Trapped Flux Through a Permanent Current Path in Graphite,"Temperature and field dependent measurements of the electrical resistance of
different natural graphite samples, suggest the existence of superconductivity
at room temperature in some regions of the samples. To verify whether
dissipationless electrical currents are responsible for the trapped magnetic
flux inferred from electrical resistance measurements, we localized them using
magnetic force microscopy on a natural graphite sample in remanent state after
applying a magnetic field. The obtained evidence indicates that at room
temperature a permanent current flows at the border of the trapped flux region.
The current path vanishes at the same transition temperature $T_c\approx370$~K
as the one obtained from electrical resistance measurements on the same sample.
This sudden decrease of the phase is different from what is expected for a
ferromagnetic material. Time dependent measurements of the signal show the
typical behavior of flux creep of a permanent current flowing in a
superconductor. The overall results support the existence of room-temperature
superconductivity at certain regions in the graphite structure and indicate
that magnetic force microscopy is suitable to localize them. Magnetic coupling
is excluded as origin of the observed phase signal.",1801.08836v1
2018-01-29,Observation of the Meissner effect at room temperature in single-layer graphene brought into contact with alkanes,"There are claims of synthesis of a room temperature superconductor. However,
these claims have not been officially accepted by scientific communities.
Currently, the highest transition temperature (Tc) recognized in scientific
articles is 135 K at 1 atm of Hg-Ba-Ca-Cu-O system which is a copper oxide
superconductor. We packed graphite flakes into a ring-shaped
polytetrafluoroethylene (PTFE) tube and further injected heptane or octane.
Then we generated circulating current in this ring tube by electromagnetic
induction and showed that this circulating current continues to flow
continuously at room temperature for 50 days. This experiment suggests that
bringing alkane into contact with graphite may result in a material with zero
resistance at room temperature. In addition, we showed by means of AC
resistance measurements using the two-terminal method that the resistances of
graphite fibers brought into contact with various alkanes suddenly change at
specific critical temperatures between 363 and 504 K. In this study, we show
that after a magnetic field is applied to a single-layer graphene at room
temperature, alkane is brought into contact with the single-layer graphene,
then the graphene excludes the magnetic field immediately. This phenomenon
demonstrates that the alkane-wetted single-layer graphene shows Meissner effect
at room temperature. Furthermore, we applied a magnetic field perpendicularly
to the annular single-layer graphene brought into contact with n-hexane and
immediately removed the magnetic field. After that we observed that a constant
magnetic field generates from this annular graphene for some time. In
conclusion, the single-layer graphene brought into contact with alkane shows
Meissner effect at room temperature, which provides definitive evidence for
room temperature superconductivity.",1801.09376v1
2019-05-10,Magnetic-Field-Induced Phenomena in the Paramagnetic Superconductor UTe$_{2}$,"We present magnetoresistivity measurements on the heavy-fermion
superconductor UTe$_{2}$ in pulsed magnetic fields $\mu_0H$ up to 68~T and
temperatures $T$ from 1.4 to 80~K. Magnetic fields applied along the three
crystallographic directions $\mathbf{a}$ (easy magnetic axis), $\mathbf{b}$,
and $\mathbf{c}$ (hard magnetic axes), are found to induce different phenomena
- depending on the field direction - beyond the low-field suppression of the
superconducting state. For $\mathbf{H}\parallel\mathbf{a}$, a broad anomaly in
the resistivity is observed at $\mu_0H^*\simeq10$~T and $T = 1.4$~K. For
$\mathbf{H}\parallel\mathbf{c}$, no magnetic transition nor crossover are
observed. For $\mathbf{H}\parallel\mathbf{b}$, a sharp first-order-like step in
the resistivity indicates a metamagnetic transition at the field $\mu_0H_m
\simeq 35$~T. When the temperature is raised signature of first-order
metamagnetism is observed up to a critical endpoint at $T_{CEP}\simeq7$~K. At
higher temperatures a crossover persists up to 28~K, i.e., below the
temperature $T_\chi^{max} = 35$~K where the magnetic susceptibility is maximal.
A sharp maximum in the Fermi-liquid quadratic coefficient $A$ of the
low-temperature resistivity is found at $H_m$. It indicates an enhanced
effective mass associated with critical magnetic fluctuations, possibly coupled
with a Fermi surface instability. Similarly to the URhGe case, we show that
UTe$_{2}$ is a candidate for field-induced reentrant superconductivity in the
proximity of $H_m$.",1905.03990v1
2019-05-13,Extending Policy from One-Shot Learning through Coaching,"Humans generally teach their fellow collaborators to perform tasks through a
small number of demonstrations. The learnt task is corrected or extended to
meet specific task goals by means of coaching. Adopting a similar framework for
teaching robots through demonstrations and coaching makes teaching tasks highly
intuitive. Unlike traditional Learning from Demonstration (LfD) approaches
which require multiple demonstrations, we present a one-shot learning from
demonstration approach to learn tasks. The learnt task is corrected and
generalized using two layers of evaluation/modification. First, the robot
self-evaluates its performance and corrects the performance to be closer to the
demonstrated task. Then, coaching is used as a means to extend the policy
learnt to be adaptable to varying task goals. Both the self-evaluation and
coaching are implemented using reinforcement learning (RL) methods. Coaching is
achieved through human feedback on desired goal and action modification to
generalize to specified task goals. The proposed approach is evaluated with a
scooping task, by presenting a single demonstration. The self-evaluation
framework aims to reduce the resistance to scooping in the media. To reduce the
search space for RL, we bootstrap the search using least resistance path
obtained using resistive force theory. Coaching is used to generalize the
learnt task policy to transfer the desired quantity of material. Thus, the
proposed method provides a framework for learning tasks from one demonstration
and generalizing it using human feedback through coaching.",1905.04841v1
2019-09-18,Blockade of vortex flow by thermal fluctuations in atomically thin clean-limit superconductors,"Resistance in superconductors arises from the motion of vortices driven by
flowing supercurrents or external electromagnetic fields and may be strongly
affected by thermal or quantum fluctuations. The common expectation borne out
in previous experiments is that as the temperature is lowered, vortex motion is
suppressed, leading to a decreased resistance. A new generation of materials
provides access to the previously inaccessible regime of clean-limit
superconductivity in atomically thin superconducting layers. We show
experimentally that for few-layer 2H-NbSe$_2$ the resistance below the
superconducting transition temperature may be non-monotonic, passing through a
minimum and then increasing again as temperature is decreased further. The
effects exists over a wide range of current and magnetic fields, but is most
pronounced in monolayer devices at intermediate currents. Analytical and
numerical calculations confirm that the findings can be understood in a
two-fluid vortex model, in which a fraction of vortices flow in channels while
the rest are pinned but thermally fluctuating in position. We show
theoretically that the pinned, fluctuating vortices effectively control the
mobility of the free vortices. The findings provide a new perspective on
fundamental questions of vortex mobility and dissipation in superconductors.",1909.08469v1
2019-09-19,Thermal rectification and interface thermal resistance in hybrid pillared-graphene and graphene: A molecular dynamics approach,"In this study, we investigate the thermal rectification and thermal
resistance in the hybrid pillared-graphene and graphene (PGG) system. This is
done through the classical molecular dynamics simulation (MD) and also with a
continuum model. At first, the thermal conductivity of both pillared-graphene
and graphene is calculated employing MD simulation and Fourier low. Our results
show that the thermal conductivity of the pillared-graphene is much smaller
than the graphene by an order of magnitude. Next, by applying positive and
negative temperature gradients along the longitudinal direction of PGG, the
thermal rectification is examined. The MD results indicate that for the lengths
in the range of 36 to 86nm, the thermal rectification remains almost constant
(~3-5%). We have also studied the phonon density of states (DOS) on both sides
of the interface of PGG. The DOS curves show that there is phonon scattering at
low frequencies (acoustic mode) that depends on the imposed temperature
gradient direction in the system. Therefore, we can introduce the PGG as a
promising thermal rectifier at room temperature. Furthermore, in the following
of this work, we also explore the temperature distribution over the PGG by
using the continuum model. The results that obtained from the continuum model
predict the MD results such as the temperature distribution in the upper half
layer and lower full layer graphene, the temperature gap and also the thermal
resistance at the interface.",1909.08971v1
2014-08-19,"Device Perspective for Black Phosphorus Field-Effect Transistors: Contact Resistance, Ambipolar and Scaling","Although monolayer black phosphorus (BP) or phosphorene has been successfully
exfoliated and its optical properties have been explored, most of electrical
performance of the devices is demonstrated on few-layer phosphorene and
ultra-thin BP films. In this paper, we study the channel length scaling of
ultra-thin BP field-effect transistors (FETs), and discuss a scheme for using
various contact metals to change transistor characteristics. Through studying
transistor behaviors with various channel lengths, the contact resistance can
be extracted from the transfer length method (TLM). With different contact
metals, we find out that the metal/BP interface has different Schottky barrier
heights, leading to a significant difference in contact resistance, which is
quite different from previous studies of transition metal dichalcogenides
(TMDs) such as MoS2 where Fermi-level is strongly pinned near conduction band
edge at metal/MoS2 interface. The nature of BP transistors are Schottky barrier
FETs, where the on and off states are controlled by tuning the Schottky
barriers at the two contacts. We also observe the ambipolar characteristics of
BP transistors with enhanced n-type drain current and demonstrate that the
p-type carriers can be easily shifted to n-type or vice versus by controlling
the gate bias and drain bias, showing the potential to realize BP CMOS logic
circuits.",1408.4206v2
2014-08-19,Exploring quantum phase transition in Pd_{1-x}Ni_x nanoalloys,"Pd$_{1-x}$Ni$_x$ alloy system is an established ideal transition metal system
possessing a composition induced paramagnetic to ferromagnetic quantum phase
transition (QPT) at the critical concentration $x_c \sim$ 0.026 in bulk. A
low-temperature non-Fermi liquid (NFL) behaviour around $x_c$ usually indicates
the presence of quantum criticality (QC) in this system. In this work, we
explore the existence of such a QPT in nanoparticles of this alloy system. We
synthesized single-phase, polydispersed and 40-50 nm mean diameter crystalline
nanoparticles of Pd$_{1-x}$Ni$_x$ alloys, with $x$ near $x_c$ and beyond, by a
chemical reflux method. In addition to the determination of the size,
composition, phase and crystallinity of the alloys by microscopic and
spectroscopic techniques, the existence of a possible QPT was explored by
resistivity and DC magnetization measurements. A dip in the value of the
exponent $n$ near $x_c$, and a concomitant peak in the constant $A$, of the
$AT^n$ dependence of the low temperature ($T$) resistivity indicate the
presence of a quantum-like phase transition in the system. The minimum value of
$n$, however, remains within the Fermi liquid regime ($n >$ 2). The DC
magnetization results suggest an anticipatory presence of a superparamagnetic
to ferromagnetic QPT in the mean-sized nanoparticles. The observation of a
possible quantum critical NFL behaviour ($n <$ 2) through resistivity is argued
to be inhibited by the electron-magnon scatterings present in the smaller
nanoparticles.",1408.4316v1
2017-01-03,Conduction Channel Formation and Dissolution Due to Oxygen Thermophoresis/Diffusion in Hafnium Oxide Memristors,"Transition metal oxide memristors, or resistive random-access memory (RRAM)
switches, are under intense development for storage-class memory because of
their favorable operating power, endurance, speed, and density. Their
commercial deployment critically depends on predictive compact models based on
understanding nanoscale physico-chemical forces, which remains elusive and
controversial owing to the difficulties in directly observing atomic motions
during resistive switching, Here, using scanning transmission synchrotron x-ray
spectromicroscopy to study in-situ switching of hafnium oxide memristors, we
directly observed the formation of a localized oxygen-deficiency-derived
conductive channel surrounded by a low-conductivity ring of excess oxygen.
Subsequent thermal annealing homogenized the segregated oxygen, resetting the
cells towards their as-grown resistance state. We show that the formation and
dissolution of the conduction channel are successfully modeled by radial
thermophoresis and Fick diffusion of oxygen atoms driven by Joule heating. This
confirmation and quantification of two opposing nanoscale radial forces that
affect bipolar memristor switching are important components for any future
physics-based compact model for the electronic switching of these devices.",1701.00864v1
2018-10-05,Effect of impurities on morphology and growth mode of (111) and (001) epitaxial-like ScN films,"ScN material is an emerging semiconductor with an indirect bandgap. It has
attracted attention for its thermoelectric properties, use as seed layers, and
for alloys for piezoelectric application. ScN or other transition metal nitride
semiconductors used for their interesting electrical properties are sensitive
to contaminants, such as oxygen or fluorine. In this present article, the
influence of depositions conditions on the amount of oxygen contaminants
incorporated in ScN films were investigated and their effects on the electrical
properties (electrical resistivity and Seebeck coefficient) were studied. The
epitaxial-like films of thickness 125 +-5 nm to 155 +-5 nm were deposited by
D.C.-magnetron sputtering on c-plane Al2O3, MgO(111) and r-plane Al2O3 at a
substrate temperature ranging from 700 to 950 degree C. The amount of oxygen
contaminants presents in the film, dissolved into ScN or as an oxide, was
related to the adatom mobility during growth, which is affected by the
deposition temperature and the presence of twin domain growth. The lowest
values of electrical resistivity of 50 micro-ohm cm were obtained on
ScN(111)/MgO(111) and on ScN(001)/r-plane Al2O3 grown at 950 degree C with no
twin domains and the lowest amount of oxygen contaminant. At the best, the
films exhibited an electrical resistivity of 50 micro-ohm cm with Seebeck
coefficient values maintained at -40 microV K-1, thus a power factor estimated
at 3.2 10-3 W m-1 K-2 (at room temperature).",1810.02593v1
2019-07-05,A post mortem analysis of the strain-induced crystallization effects on fatigue of elastomers,"Natural rubber (NR) is the most commonly used elastomer in the automotive
industry thanks to its outstanding fatigue resistance. Strain-induced
crystallization (SIC) is found to play a role of paramount importance in the
great crack growth resistance of NR [1]. Typically, NR exhibits a lifetime
reinforcement for non-relaxing loadings [2-3]. At the microscopic scale,
fatigue striations were observed on the fracture surface of Diabolo samples
tested in fatigue. They are the signature of SIC [2,4,5]. In order to provide
additional information on the role of SIC in the fatigue crack growth
resistance of NR, striations are investigated through post-mortem analysis
after fatigue experiments using loading ranging from-0.25 to 0.25. No striation
was observed in the case of tests performed at 90{\textdegree}C. This confirms
that the formation of striation requires a certain crystallinity level in the
material. At 23{\textdegree}C, two striation regimes were identified: small
striation patches with different orientations (Regime 1) and zones with large
and well-formed striations (Regime 2). Since fatigue striations are observed
for all the loading ratios applied, they are therefore not the signature of the
reinforcement. Nevertheless, increasing the minimum value of the strain
amplified the striation phenomenon and the occurrence of Regime 2.",1907.02688v1
2022-02-12,Expansion of Graphene-Based Device Technology for Resistance Metrology,"The field of Quantum Hall metrology had a strong start with the implemntation
of GaAs-based devices, given that 2D materials systems provided access to
interesting quantum phenomena, including the infrastructure associated with
making relevant measurements. With the technology laid out, further
improvements in both infrastructure and standards were achieved in the previous
two decades as EG-based quantized Hall resistance (QHR) devices became
established as national standards. Since the metrology community has reached
some understanding that a comparison against GaAs-based QHR devices had been
accomplished, the next steps became clearer as far as how the EG-based QHR with
a single Hall bar could be further developed. Since the early 90s, it has been
of modest interest that QHR devices have a means of interconnecting several
single Hall bar elements and has since been a subject of research. NMIs are now
presently at a juncture where consideration must be granted beyond just
simplicity of operation. A natural direction for resistance standards would be
to increase the total accessible parameter space. This means using EG-based QHR
devices to output more than the single value at the $\nu = 2$ plateau (about
12.9 k$\Omega$). A first natural question is whether one may use the $\nu = 6$
plateau or $\nu = 10$ plateau, and though some work has been done with these
Landau levels in graphene, they simply do not offer the same level of precision
as the $\nu = 2$ plateau.",2202.05954v1
2016-03-21,Influence of rhombohedral stacking order in the electrical resistance of bulk and mesoscopic graphite,"The electrical, in-plane resistance as a function of temperature $R(T)$ of
bulk and mesoscopic thin graphite flakes obtained from the same batch was
investigated. Samples thicker than $\sim 30$ nm show metalliclike contribution
in a temperature range that increases with the sample thickness, whereas a
semiconductinglike behavior was observed for thinner samples. The temperature
dependence of the in-plane resistance of all measured samples and several
others from literature can be very well explained between 2 K and 1100 K
assuming three contributions in parallel: a metalliclike conducting path at the
interfaces between crystalline regions, composed of two semiconducting phases,
i.e. Bernal and rhombohedral stacking. From the fits of $R(T)$ we obtain a
semiconducting energy gap of $110 \pm 20$meV for the rhombohedral and $38\pm 8
$meV for the Bernal phase. The presence of these crystalline phases was
confirmed by x-ray diffraction measurements. We review similar experimental
data from literature of the last 33 years and two more theoretical models used
to fit $R(T)$.",1603.06365v3
2017-04-03,Plasmonic heating in Au nanowires at low Temperatures: The role of thermal boundary resistance,"Inelastic electron tunneling and surface-enhanced optical spectroscopies at
the molecular scale require cryogenic local temperatures even under
illumination - conditions that are challenging to achieve with plasmonically
resonant metallic nanostructures. We report a detailed study of the laser
heating of plasmonically active nanowires at substrate temperatures from 5 to
60 K. The increase of the local temperature of the nanowire is quantified by a
bolometric approach and could be as large as 100 K for a substrate temperature
of 5 K and typical values of laser intensity. We also demonstrate that a $\sim
3\times$ reduction of the local temperature increase is possible by switching
to a sapphire or quartz substrate. Finite element modeling of the heat
dissipation reveals that the local temperature increase of the nanowire at
temperatures below $\sim$50 K is determined largely by the thermal boundary
resistance of the metal-substrate interface. The model reproduces the striking
experimental trend that in this regime the temperature of the nanowire varies
nonlinearly with the incident optical power. The thermal boundary resistance is
demonstrated to be a major constraint on reaching low temperatures necessary to
perform simultaneous inelastic electron tunneling and surface enhanced Raman
spectroscopies.",1704.00771v1
2017-05-18,Effects of the Functional Group on the Lithium Ions Across the Port of Carbon Nanotube,"The mean axial velocity of lithium irons across the entrance of carbon
nanotube VLi is an important factor for the charge-discharge performances of
rechargeable Lithium battery. The molecular dynamics simulation method is
adopted to evaluate the factors and their effects on VLi which include the
diameter of carbon nanotube, functional group type on the port and the number
of a given type of functional group. The statistical analysis of the
calculation results shows that: In the selected carbon nanotubes of four
different diameters, VLi will gradually rise with the increase of CNT diameter
due to lithium irons migration resistance decreasing; as the port of CNT is
successively modified to hydrogen (-H), hydroxyl (-OH), amino (-NH2) and
carboxyl (-COOH), the corresponding migration resistance of lithium ions is
enhanced resulting in the dropping of VLi; in comparison to the effect strength
of four types of functional groups on VLi, -COOH shows strongest, -NH2 and -OH
perform relatively weaker, and the effect difference between -NH2 and -OH is
very small, -H displays weakest; When the number of a given non-hydrogen
functional group on the port sequentially increases, it also shows a trend that
lithium ion migration resistance gradually increases which makes VLi decreases
in turn. The more influential the functional group, the greater the impact of
functional group number changes on VLi. The results of this paper have some
significance on the precise production of lithium-ion battery electrode
materials, enhancing the overall battery cycle efficiency and charging speed.",1705.06650v1
2017-08-24,Memory matrix theory of the dc resistivity of a disordered antiferromagnetic metal with an effective composite operator,"We perform the calculation of the dc resistivity as a function of temperature
of the ""strange-metal"" state that emerges in the vicinity of a
spin-density-wave phase transition in the presence of weak disorder. This
scenario is relevant to the phenomenology of many important correlated
materials, such as, e.g., the pnictides, the heavy-fermion compounds and the
cuprates. To accomplish this task, we implement the memory-matrix approach that
allows the calculation of the transport coefficients of the model beyond the
quasiparticle paradigm. Our computation is also inspired by the $\epsilon=3-d$
expansion in a hot-spot model embedded in $d$-space dimensions recently put
forth by Sur and Lee [Phys. Rev. B 91, 125136 (2015)], in which they find a new
low-energy non-Fermi liquid fixed point that is perturbatively accessible near
three dimensions. As a consequence, we are able to establish here the
temperature and doping dependence of the electrical resistivity at intermediate
temperatures of a two-dimensional disordered antiferromagnetic metallic model
with a composite operator that couples the order-parameter fluctuations to the
entire Fermi surface. We argue that our present theory provides a good basis in
order to unify the experimental transport data, e.g., in the cuprates and the
pnictide superconductors, within a wide range of doping regimes.",1708.07537v1
2019-04-03,Patterning of diamond like carbon films for sensor applications using silicon containing thermoplastic resist (SiPol) as a hard mask,"Patterning of diamond-like carbon (DLC) and DLC:metal nanocomposites is of
interest for an increasing number of applications. We demonstrate a nanoimprint
lithography process based on silicon containing thermoplastic resist combined
with plasma etching for straightforward patterning of such films. A variety of
different structures with few hundred nanometer feature size and moderate
aspect ratios were successfully realized. The quality of produced patterns was
directly investigated by the means of optical and scanning electron microscopy
(SEM). Such structures were further assessed by employing them in the
development of gratings for guided mode resonance (GMR) effect. Optical
characterization of such leaky waveguide was compared with numerical
simulations based on rigorous coupled wave analysis method with good agreement.
The use of such structures as refractive index variation sensors is
demonstrated with sensitivity up to 319 nm/RIU, achieving an improvement close
to 450% in sensitivity compared to previously reported similar sensors. This
pronounced GMR signal fully validates the employed DLC material, the technology
to pattern it and the possibility to develop DLC based gratings as corrosion
and wear resistant refractometry sensors that are able to operate under harsh
conditions providing great value and versatility.",1904.01880v1
2019-04-02,Filament mechanics in a half-space via regularised Stokeslet segments,"We present a generalisation of efficient numerical frameworks for modelling
fluid-filament interactions via the discretisation of a recently-developed,
non-local integral equation formulation to incorporate regularised Stokeslets
with half-space boundary conditions, as motivated by the importance of
confining geometries in many applications. We proceed to utilise this framework
to examine the drag on slender inextensible filaments moving near a boundary,
firstly with a relatively-simple example, evaluating the accuracy of resistive
force theories near boundaries using regularised Stokeslet segments. This
highlights that resistive force theories do not accurately quantify filament
dynamics in a range of circumstances, even with analytical corrections for the
boundary. However, there is the notable and important exception of movement in
a plane parallel to the boundary, where accuracy is maintained. In particular,
this justifies the judicious use of resistive force theories in examining the
mechanics of filaments and monoflagellate microswimmers with planar flagellar
patterns moving parallel to boundaries. We proceed to apply the numerical
framework developed here to consider how filament elastohydrodynamics can
impact drag near a boundary, analysing in detail the complex responses of a
passive cantilevered filament to an oscillatory flow. In particular, we
document the emergence of an asymmetric periodic beating in passive filaments
in particular parameter regimes, which are remarkably similar to the power and
reverse strokes exhibited by motile 9+2 cilia. Furthermore, these changes in
the morphology of the filament beating, arising from the fluid-structure
interactions, also induce a significant increase in the hydrodynamic drag of
the filament.",1904.02543v2
2015-07-23,Spatially resolved TiOx phases in RRAM conductive nanofilaments using soft X-ray spectromicroscopy,"Reduction in metal-oxide thin films has been suggested as the key mechanism
responsible for forming conductive nanofilaments within solid-state memory
devices, enabling their resistive switching capacity. The quantitative spatial
identification of such filaments is a daunting task, particularly for
metal-oxides capable of exhibiting multiple phases as in the case of TiOx.
Here, we spatially resolve and chemically characterize distinct TiOx phases in
localized regions of a TiOx-based memristive device by combining full-field
transmission X-ray microscopy with soft X-ray spectroscopic analysis that is
performed on lamella samples. We particularly show that electrically
pre-switched devices in low-resistive states comprise reduced disordered phases
with O/Ti ratios close to Ti2O3 stoichiometry that aggregate in a ~ 100 nm
filamentary region electrically conducting the top and bottom electrodes of the
devices. We have also identified crystalline rutile and orthorhombic-like TiO2
phases in the region adjacent to the filament, suggesting that the temperature
increases locally up to 1000 K, validating the role of Joule heating in
resistive switching. Contrary to previous studies, our approach enables to
simultaneously investigate morphological and chemical changes in a quantitative
manner without incurring difficulties imposed by interpretation of electron
diffraction patterns acquired via conventional electron microscopy techniques.",1507.06588v1
2019-01-16,Quantum oscillations in strongly correlated topological Kondo insulators,"The observation of quantum oscillations in topological Kondo insulators SmB6
and YbB12 is a recent puzzling experimental discovery. Quantum oscillations
observed in the resistivity and the magnetization are usually explained by the
existence of the Fermi surface. However, Kondo insulators do not have a Fermi
surface and thus should not show quantum oscillations. By performing dynamical
mean-field calculations for topologically nontrivial Kondo insulators in a
magnetic field, we analyze the effect of correlations on the emergence of
quantum oscillations in narrow-gap topological Kondo insulators and demonstrate
that the interplay between correlations and nonlocal hybridization,
ubiquitously occurring in topological Kondo insulators, can lead to observable
quantum oscillations without the necessity of a Fermi surface. Particularly, we
show that correlations make it easier to observe quantum oscillations in the
magnetization and the resistivity of the bulk material. The fundamental
mechanism for these quantum oscillations is a combination of correlation
effects and Landau levels coming very close to the Fermi energy. We furthermore
demonstrate that quantum oscillations in a three-dimensional system can be
understood by analyzing the physics on the two-dimensional planes in the
momentum space for which the hybridization in direction of the magnetic field
vanishes. We believe that this scenario is relevant to understanding the
observation of quantum oscillations in the magnetic torque for SmB6 as well as
oscillations in the resistivity and the magnetic torque of YbB12.",1901.05099v2
2019-10-18,Probing quantum spin liquids in equilibrium using the inverse spin Hall effect,"We propose an experimental method utilizing a strongly spin-orbit coupled
metal to quantum magnet bilayer that will probe quantum magnets lacking long
range magnetic order, e.g., quantum spin liquids, via examination of the
voltage noise spectrum in the metal layer. The bilayer is held in thermal and
chemical equilibrium, and spin fluctuations arising across the single interface
are converted into voltage fluctuations in the metal as a result of the inverse
spin Hall effect. We elucidate the theoretical workings of the proposed bilayer
system, and provide precise predictions for the frequency characteristics of
the enhancement to the ac electrical resistance measured in the metal layer for
three candidate quantum spin liquid models. Application to the Heisenberg
spin-$1/2$ kagom{\'e} lattice model should allow for the extraction of any
spinon gap present. A quantum spin liquid consisting of fermionic spinons
coupled to a $U(1)$ gauge field should cause subdominant $\W^{4/3}$ scaling of
the resistance of the coupled metal. Finally, if the magnet is well-captured by
the Kitaev model in the gapless spin liquid phase, then the proposed bilayer
can extract the two-flux gap which arises in spite of the gapless spectrum of
the fermions. We therefore show that spectral analysis of the ac resistance in
the metal in a single interface, equilibrium bilayer can test the relevance of
a quantum spin liquid model to a given candidate material.",1910.08610v2
2020-05-23,Mixed ground state in Fe-Ni Invar alloys,"We investigate the ground state properties of Invar alloys via detailed study
of the electronic structure of Fe$_{1-x}$Ni$_x$ alloys ($x$ = 0.2, 0.3, 0.4,
0.5, 0.6, 0.7, 0.9) employing $x$-ray photoelectron spectroscopy (XPS). While
all the alloys exhibit soft ferromagnetic behavior with Curie temperature much
higher than the room temperature, the results for invar alloy,
Fe$_{0.6}$Ni$_{0.4}$ exhibit anomalous behavior. Moreover, the
magneto-resistance of the Invar alloy becomes highly negative while the end
members possess positive magneto-resistance. The core level spectra of the
Invar alloy exhibit emergence of a distinct new feature below 20~K while all
other Fe-Ni alloys exhibit no temperature dependence down to 10~K.
Interestingly, the shallow core level spectra (3$s$, 3$p$) of Fe and Ni of the
Invar alloy reveal stronger deviation at low temperatures compared to the deep
core levels (2$s$, 2$p$) indicating crystal field effect. It appears that there
is a large precipitation of antiferromagnetic $\gamma^\prime$ phase below 20 K
possessing low magnetic moment (0.5$\mu_B$) on Fe within the $\alpha$ phase.
The discovery of negative magneto-resistance, anomalous magnetization at low
temperature and the emergence of unusual new features in the core levels at low
temperature provide an evidence of mixed phase in the ground state of Invar
alloys.",2005.11493v1
2020-07-01,"Impact of V substitution on the physical properties of Ni-Zn-Co ferrites: structural, magnetic, dielectric and electrical properties","We have investigated the Vanadium- (V) substituted Ni-Zn-Co ferrites where
the samples were prepared using solid-state reaction technique. The impact of
V5+ substitution on the structural, magnetic, dielectric and electrical
properties of Ni-Zn-Co ferrites has been studied. XRD analysis confirmed the
formation of a single-phase cubic spinel structure. The lattice constants have
been calculated both theoretically and experimentally along with other
structural parameters such as bulk density, X-ray density and porosity. The
FESEM images are taken to study the surface morphology. FTIR measurement is
also performed which confirms spinel structure formation. The saturation
magnetization (Ms), coercive field (Hc) and Bohr magneton (B) were calculated
from the obtained M-H loops. The temperature dependent permeability is studied
to obtain the Curie temperature. Frequency and composition dependence of
permeability was also analyzed. Dielectric behavior and ac resistivity are also
subjected to investigate the frequency dependency. An inverse relationship was
observed between the composition dependence of dielectric constant and ac
resistivity. The obtained results such as the electrical resistivity,
dielectric constants and magnetic properties suggest the appropriateness of the
studied ferrites in microwave device applications.",2007.00602v1
2020-07-20,Capping and gate control of anomalous Hall effect and hump structure in ultra-thin SrRuO$_3$ films,"Ferromagnetism and exotic topological structures in SrRuO$_3$ (SRO) induce
sign-changing anomalous Hall effect (AHE). Recently, hump structures have been
reported in the Hall resistivity of SRO thin films, especially in the
ultra-thin regime. We investigate the AHE and hump structure in the Hall
resistivity of SRO ultra-thin films with an SrTiO$_3$ (STO) capping layer and
ionic liquid gating. STO capping results in sign changes in the AHE and
modulation of the hump structure. In particular, the hump structure in the Hall
resistivity is strongly modulated and even vanishes in STO-capped 4 unit cell
(uc) films. In addition, the conductivity of STO-capped SRO ultra-thin films is
greatly enhanced with restored ferromagnetism. We also performed ionic liquid
gating to modulate the electric field at SRO/STO interface. Drastic changes in
the AHE and hump structure are observed with different gate voltages. Our study
shows that the hump structure as well as the AHE can be controlled by tuning
inversion symmetry and the electric field at the interface.",2007.09872v2
2020-07-23,Origin of gap-like behaviors in URu$_2$Si$_2$: Combined study via quasiparticle scattering spectroscopy and resistivity measurements,"We address two long-standing questions regarding the hidden order in URu2Si2:
Is it associated with the hybridization process, and what are the distinct
roles played by the localized and itinerant electrons? Our quasiparticle
scattering spectroscopy reveals a hybridization gap ubiquitous in the entire
phase space spanned by P and Fe substitutions in URu2Si2, including the
no-order and antiferromagnetic regions, with minimal change upon crossing the
phase boundary. This indicates its opening isn't associated with the ordering,
and thus localized electrons must be the major player. Towards a consistent
understanding of all the other gap-like behaviors observed only below
transition temperatures, we analyze the electrical resistivity using a model in
which gapped bosonic excitations are the dominant scattering source. With their
stiffness set to follow an unusual temperature dependence (decreasing with
decreasing temperature), this model fits all of our resistivity data well
including the jump at the transition. Remarkably, the extracted gap increases
slowly with increasing Fe content, similarly to the gap detected by inelastic
neutron scattering at Q1 = (1.4, 0, 0), suggesting a common origin. Such a
model can also naturally explain the Hall effect temperature dependence without
invoking Fermi surface gapping.",2007.12235v2
2020-10-11,Hydrothermal synthesis and complete phase diagram of FeSe$_{1-x}$S$_{x}$ $(0 \leq x \leq 1)$ single crystals,"We report the successful synthesis of FeSe$_{1-x}$S$_{x}$ single crystals
with $x$ ranging from 0 to 1 via a hydrothermal method. A complete phase
diagram of FeSe$_{1-x}$S$_{x}$ has been obtained based on resistivity and
magnetization measurements. The nematicity is suppressed with increasing $x$,
and a small superconducting dome appears within the nematic phase. Outside the
nematic phase, the superconductivity is continuously suppressed and reaches a
minimum $T_c$ at $x$ = 0.45; beyond this point, $T_c$ slowly increases until
$x$ = 1. Intriguingly, an anomalous resistivity upturn with a characteristic
temperature $T^*$ in the intermediate region of $0.31 \leq x \leq 0.71$ is
observed. $T^{*}$ shows a dome-like behavior with a maximum value at $x$ =
0.45, which is opposite the evolution of $T_c$, indicating competition between
$T^*$ and superconductivity. The origin of $T^*$ is discussed in detail.
Furthermore, the normal state resistivity evolves from non-Fermi-liquid to
Fermi-liquid behavior with S doping at low temperatures, accompanied by a
reduction in electronic correlations. Our study addresses the lack of single
crystals in the high-S doping region and provides a complete phase diagram,
which will promote the study of relations among nematicity, superconductivity,
and magnetism.",2010.05191v3
2021-03-12,Area-selective deposition and B $δ$-doping of Si(100) with BCl$_{3}$,"B-doped $\delta$-layers were fabricated in Si(100) using BCl$_{3}$ as a
dopant precursor in ultrahigh vacuum. BCl$_{3}$ adsorbed readily at room
temperature, as revealed by scanning tunneling microscopy (STM) imaging.
Annealing at elevated temperatures facilitated B incorporation into the Si
substrate. Secondary ion mass spectrometry (SIMS) depth profiling demonstrated
a peak B concentration $>$ 1.2(1) $\times$ 10$^{21}$ cm$^{-3}$ with a total
areal dose of 1.85(1) $\times$ 10$^{14}$ cm$^{-2}$ resulting from a 30 L
BCl$_{3}$ dose at 150 $^{\circ}$C. Hall bar measurements of a similar sample
were performed at 3.0 K revealing a sheet resistance of $R_{\mathrm{s}}$ = 1.91
k$\Omega\square^{-1}$, a hole concentration of $n$ = 1.90 $\times$ 10$^{14}$
cm$^{-2}$ and a hole mobility of $\mu$ = 38.0 cm$^{2}$V$^{-1}$s$^{-1}$ without
performing an incorporation anneal. Further, the conductivity of several
B-doped $\delta$-layers showed a log dependence on temperature suggestive of a
two-dimensional system. Selective-area deposition of BCl$_{3}$ was also
demonstrated using both H- and Cl-based monatomic resists. In comparison to a
dosed area on bare Si, adsorption selectivity ratios for H and Cl resists were
determined by SIMS to be 310(10):1 and 1529(5):1, respectively, further
validating the use of BCl$_{3}$ as a dopant precursor for atomic precision
fabrication of acceptor-doped devices in Si.",2103.07529v1
2021-05-21,"Convection, Heat Generation and Particle Deposition in Direct Laser Writing of Metallic Microstructures","Three-dimensional metallic microstructures find applications as stents in
medicine, as ultrabroadband antennas in communications, in micromechanical
parts or as structures of more fundamental interest in photonics like
metamaterials. Direct metal printing of such structures using three-dimensional
laser lithography is a promising approach, which is not extensively applied
yet, as fabrication speed, surface quality, and stability of the resulting
structures are limited so far. In order to identify the limiting factors, we
investigate the influence of light-particle interactions and varying scan speed
on heat generation and particle deposition in direct laser writing of silver.
We introduce a theoretical model which captures diffusion of particles and heat
as well as the fluid dynamics of the photo-resist. Chemical reactions are
excluded from the model but particle production is calibrated using
experimental data. We find that optical forces generally surmount those due to
convection of the photo-resist. Simulations predict overheating of the
photo-resist at laser powers similar to those found in experiments. The thermal
sensitivity of the system is essentially determined by the largest particles
present in the laser focus. Our results suggest that to improve particle
deposition and to achieve higher writing speeds in metal direct laser writing,
strong optical trapping of the emerging particles is desirable. Furthermore,
precise control of the particle size reduces the risk of spontaneous
overheating.",2105.10243v2
2021-10-29,Optimal asymmetry of transistor-based terahertz detectors,"Detectors of terahertz radiation based on field-effect transistors (FETs) are
among most promising candidates for low-noise passive signal rectification both
in imaging systems and wireless communications. However, it was not realised so
far that geometric asymmetry of common FET with respect to source-drain
interchange is a strong objective to photovoltage harvesting. Here, we break
the traditional scheme and reveal the optimally-asymmetric FET structure
providing the maximization of THz responsivity. We fabricate a series of
graphene transistors with variable top gate position with respect to
mid-channel, and compare their sub-THz responsivities in a wide range of
carrier densities. We show that responsivity is maximized for input gate
electrode shifted toward the source contact. Theoretical simulations show that
for large channel resistance, exceeding the gate impedance, such recipe for
responsivity maximisation is universal, and holds for both resistive
self-mixing and photo-thermoelectric detection pathways. In the limiting case
of small channel resistance, the thermoelectric and self-mixing voltages react
differently upon changing the asymmetry, which may serve to disentangle the
origin of nonlinearities in novel materials.",2110.15810v1
2021-12-06,"Dynamical Mean Field Theory of Moiré Bilayer Transition Metal Dichalcogenides: Phase Diagram, Resistivity, and Quantum Criticality","We present a comprehensive dynamical mean field study of the triangular
lattice moir\'e Hubbard model, which is believed to represent the physics of
moir\'e bilayer transition metal dichalcogenides. In these materials, important
aspects of the band structure including the bandwidth and the order and
location of van Hove singularities can be tuned by varying the interlayer
potential. We present a magnetic and metal-insulator phase diagram and a
detailed study of the dependence of the resistivity on temperature, band
filling and interlayer potential. We find that transport displays Fermi liquid,
strange metal and quantum critical behaviors in distinct regions of the phase
diagram. Specifically, we find that the cube-root van Hove singularity
($\rho(\epsilon) \sim|\epsilon|^{-1 / 3}$) gives a strange metal behavior with
a $T$-linear scattering rate and $\omega/T$ scaling. We show how magnetic order
affects the resistivity. Our results elucidate the physics of the correlated
states and the metal-insulator continuous transition recently observed in
twisted homobilayer WSe$_2$ and heterobilayer MoTe$_2$/WSe$_2$ experiments.",2112.03080v3
2022-03-15,Challenges and opportunities of srf theory for next generation particle accelerators,"We suggest a program to establish theoretical performance limits of srf
cavities using modern theories of nonequilibrium superconductivity under a
strong electromagnetic field. These theories will be used to calculate the main
parameter of merit of srf cavities: the quality factor Q and its dependencies
on the field amplitude, temperature and frequency, which would allow us to
understand how far the srf cavity performance could be pushed from the current
state of the art. Given that the quality factor is determined by multiple
mechanisms operating on very different length scales, we will address the
interconnected problems of a nonlinear surface resistance, rf losses of
vortices trapped in the cavity, the effect of materials defects and surface
topography, and the opportunities to boost the srf performance by surface
nano-structuring, impurity management and multilayers. We suggest the following
directions of theoretical srf research to address the goals of boosting the
performance of the next generation particle accelerators: 1. Establishing the Q
limit, mechanisms of nonlinear surface resistance and the residual resistance
in a nonequilibrium superconductor under a strong RF field. 2. Establishing the
srf breakdown field limit, dynamic superheating field and its dependencies on
frequency, temperature and concentration of impurities. 3. Losses due to
trapped vortices and extreme dynamics of ultrafast vortices driven by strong rf
Meissner currents in srf cavities. 4. Optimization of srf performance due to
surface nanostructuring of the cavity surface, multilayers and impurity
management.",2203.08315v1
2022-05-19,Electrical Circuit Modelling of Nanofluidic Systems,"Nanofluidic systems exhibit transport characteristics that have made
technological marvels such as desalination, energy harvesting, and highly
sensitive biomolecule sensing possible by virtue of their ability to influence
small currents due to the selective transport of ions. Traditionally many of
these applications have relied on the use of nanoporous membranes. The immense
complexities of membrane geometry often impede a comprehensive understanding of
the underlying physics. To bypass the associated difficulties, here we consider
the much simpler nanochannel array comprised of numerous nanochannels and
elucidate the effects of interchannel interactions on the Ohmic response of the
array. We demonstrate that a nanochannel array is equivalent to an array of
mutually independent but identical unit-cells whereby the array can be
represented by an equivalent electrical circuit of unit-cell resistances
connected in a parallel configuration. We show that the total resistance of the
system scales inversely to the number of channels. We further deconstruct the
unit-cell to be a combination of multiple contributing resistances connected in
series. We validate the theoretical model underlying these electrical
abstractions using numerical simulations and experiments. Our approach to
modeling realistic nanofluidic systems by their equivalent electrical circuit
provides an invaluable tool for analyzing and interpreting experimental
measurements, characterization of surface charge properties of newly developed
materials, and a method for the design and development of function-specific
nanofluidic devices.",2205.09437v3
2022-06-08,Phonon-limited resistivity of multilayer graphene systems,"We calculate the theoretical contribution to the doping and temperature ($T$)
dependence of electrical resistivity due to scattering by acoustic phonons in
Bernal bilayer graphene (BBG) and rhombohedral trilayer graphene (RTG). We
focus on the role of nontrivial geometric features of the detailed, anisotropic
$k\cdot p$ band structures of these systems - e.g. Van Hove singularities,
Lifshitz transitions, Fermi surface anisotropy, and band curvature near the gap
- whose effects on transport have not yet been systematically studied. We find
that these geometric features strongly influence the temperature and doping
dependencies of the resistivity. In particular, the band geometry leads to a
nonlinear $T$-dependence in the high-$T$ equipartition regime, complicating the
usual $T^4$ to $T$ Bloch-Gr\""{u}neisen crossover. Our focus on BBG and RTG is
motivated by recent experiments in these systems that have discovered several
exotic low-$T$ superconductivity proximate to complicated hierarchies of
isospin-polarized phases. These interaction-driven phases are intimately
related to the geometric features of the band structures, highlighting the
importance of understanding the influence of band geometry on transport. While
resolving the effects of the anisotropic band geometry on the scattering times
requires nontrivial numerical solution, our approach is rooted in intuitive
Boltzmann theory. We compare our results with recent experiment and discuss how
our predictions can be used to elucidate the relative importance of various
scattering mechanisms in these systems.",2206.04080v2
2022-07-18,Confinement-Induced Chiral Edge Channel Interaction in Quantum Anomalous Hall Insulators,"In quantum anomalous Hall (QAH) insulators, the interior is insulating but
electrons can travel with zero resistance along one-dimensional conducting
paths known as chiral edge channels (CECs). These CECs have been predicted to
be confined to the one-dimensional (1D) edges and exponentially decay in the
two-dimensional (2D) bulk. In this work, we present the results of a systematic
study of QAH devices fashioned in a Hall bar geometry of different widths. At
the charge neutral point, the QAH effect persists in a Hall bar device with a
width of only ~72 nm, implying the intrinsic decaying length of CECs is less
than ~36 nm. In the electron-doped regime, we find that the Hall resistance
deviates quickly from the quantized value when the sample width is less than 1
um. Our theoretical calculations suggest that the deviation from the quantized
Hall resistance in narrow QAH samples originates from the interaction between
two opposite CECs mediated by disorder-induced bulk states in QAH insulators,
consistent with our experimental observations.",2207.08371v1
2022-09-12,Robust design optimization for enhancing delamination resistance of composites,"Recent developments in the field of computational modeling of fracture have
opened up possibilities for designing structures against failure. A special
case, called interfacial fracture or delamination, can occur in loaded
composite structures where two or more materials are bonded together at
comparatively weak interfaces. Due to the potential crack growth along these
interfaces, the structural problem suffers from snap-back/snap-through
instabilities and bifurcations with respect to the model parameters, leading to
noisy and discontinuous responses. For such a case, the design optimization
problem for a selected quantity of interest is ill-posed, since small
variations in the design parameters can lead to large jumps in the structural
response. To this end, this paper presents a stochastic optimization approach
to maximize delamination resistance that is less sensitive to small
perturbations of the design and thereby leads to a robust solution. To overcome
the intractability of Monte Carlo methods for estimating the expected value of
the expensive-to-evaluate response function, a global, piecewise-constant
surrogate is constructed based on nearest-neighbor interpolation that is
iteratively refined during the optimization run. We found that by taking a
large stochastic region at the beginning of the optimization and gradually
reducing it to the desired one can help overcome poor local optima. Our results
demonstrate the effectiveness of the proposed framework using an example of
shape optimization of hard inclusions embedded in a double-cantilever beam,
which significantly enhances delamination resistance.",2209.05241v1
2022-10-25,Enhanced Thermoelectric Performance of Nanostructured Nickel Doped Ag2Te,"We report on the thermoelectric properties of nickel doped Ag2-xNixTe (x = 0,
0.015, 0.025 & 0.055, 0.115, 0.155) nanostructures in the temperature (T) range
of 5 K to 575 K. The electrical resistivity of Ag2Te nanostructure shows
metallic behaviour in 5 K to 300 K initially that evolves into two metal to
insulator transitions (MITs) at low and mid-temperature regimes with increasing
x due to Mott-variable range hopping (VRH) and Arrhenius transports,
respectively. Their Seebeck coefficient varies nearly in a linear fashion in
this temperature range, showing metallic or doped-degenerate semiconducting
behaviour. Notably, this behaviour of the Seebeck coefficient is in contrast to
Mott VRH conduction as observed in resistivity. The steady increase in
resistivity and S with the sharp decrease in thermal conductivity between 410 K
to 425 K associated with the structural phase transition accomplishes a maximum
thermoelectric figure of merit (ZT) of 0.86 near 480 K in x = 0.155. This is
about 83 % more compared to that of bulk Ag2Te, and shows a significant
improvement over the best value reported for Ag2Te nanostructures thus far.
This study, therefore, shows that simultaneous nanocomposite formation, doping
and nanostructuring could be an effective strategy for tuning the electron and
phonon transports to improve the thermoelectric properties of a material.",2210.13903v1
2022-12-28,An Atomistic Model of Field-Induced Resistive Switching in Valence Change Memory,"In Valence Change Memory (VCM) cells, the conductance of an insulating
switching layer is reversibly modulated by creating and redistributing point
defects under an external field. Accurate simulations of the switching dynamics
of these devices can be difficult due to their typically disordered atomic
structures and inhomogeneous arrangements of defects. To address this, we
introduce an atomistic framework for modelling VCM cells. It combines a
stochastic Kinetic Monte Carlo approach for atomic rearrangement with a quantum
transport scheme, both parameterized at the ab-initio level by using inputs
from Density Functional Theory (DFT). Each of these steps operates directly on
the underlying atomic structure. The model thus directly relates the energy
landscape and electronic structure of the device to its switching
characteristics. We apply this model to simulate non-volatile switching between
high- and low-resistance states in an TiN/HfO2/Ti/TiN stack, and analyze both
the kinetics and stochasticity of the conductance transitions. We also resolve
the atomic nature of current flow resulting from the valence change mechanism,
finding that conductive paths are formed between the undercoordinated Hf atoms
neighboring oxygen vacancies. The model developed here can be applied to
different material systems to evaluate their resistive switching potential,
both for use as conventional memory cells and as neuromorphic computing
primitives.",2212.14090v1
2023-05-02,Direct observations of spin fluctuations in spin-hedgehog-anti-hedgehog lattice states in MnSi$_{1-x}$Ge$_x$ ($x=0.6$ and $0.8$) at zero magnetic field,"The helimagnetic compounds MnSi$_{1-x}$Ge$_{x}$ show the three-dimensional
multiple-$q$ order as referred to as spin-hedgehog-anti-hedgehog (SHAH)
lattice. Two representative forms of SHAH are cubic-3$q$ lattice with $q \|
\langle100\rangle$ and tetrahedral-4$q$ lattice with $q \| \langle111\rangle$,
which show up typically for $x=1.0-~0.8$ and for $x=0.6$, respectively. Here,
we have investigated the spin fluctuations in the MnSi$_{1-x}$Ge$_{x}$
polycrystalline samples with $x=0.6$ and $0.8$ by using the time-of-flight
(TOF) neutron inelastic scattering and MIEZE-type neutron spin echo techniques
to elucidate the microscopic origin of the unconventional Hall effect in the
SHAH lattice states. This research is motivated by the observation of a sign
change in the unconventional Hall resistivity as a function of temperature [Y.
Fujishiro et al., Nat. Comm. $\textbf{10}$, 1059 (2019)]. The present results
reveal the correspondences between the temperature ranges where the positive
Hall resistivity and spin fluctuations are observed. These results agree well
with the theoretical model of the conduction electrons scattered by the
fluctuating spin clusters with a non-zero average of sign-biased scalar spin
chirality as a mechanism of the positive Hall resistivity [H. Ishizuka and N.
Nagaosa, Sci. Adv. $\textbf{4}$, eaap9962 (2018)].",2305.01172v1
2023-08-30,A Deep Dive into the Design Space of a Dynamically Reconfigurable Cryogenic Spiking Neuron,"Spiking neural network offers the most bio-realistic approach to mimic the
parallelism and compactness of the human brain. A spiking neuron is the central
component of an SNN which generates information-encoded spikes. We present a
comprehensive design space analysis of the superconducting memristor (SM)-based
electrically reconfigurable cryogenic neuron. A superconducting nanowire (SNW)
connected in parallel with an SM function as a dual-frequency oscillator and
two of these oscillators can be coupled to design a dynamically tunable spiking
neuron. The same neuron topology was previously proposed where a fixed
resistance was used in parallel with the SNW. Replacing the fixed resistance
with the SM provides an additional tuning knob with four distinct combinations
of SM resistances, which improves the reconfigurability by up to ~70%.
Utilizing an external bias current (Ibias), the spike frequency can be
modulated up to ~3.5 times. Two distinct spike amplitudes (~1V and ~1.8 V) are
also achieved. Here, we perform a systematic sensitivity analysis and show that
the reconfigurability can be further tuned by choosing a higher input current
strength. By performing a 500-point Monte Carlo variation analysis, we find
that the spike amplitude is more variation robust than spike frequency and the
variation robustness can be further improved by choosing a higher Ibias. Our
study provides valuable insights for further exploration of materials and
circuit level modification of the neuron that will be useful for system-level
incorporation of the neuron circuit",2308.15754v1
2023-12-03,Experimental apparatus for non-contact resistivity measurements of the rock core plug based on magnetic induction,"A new apparatus has been developed to measure the conductivity of rock
samples. The probe, which consists of multi-coil transmitters and receivers
doesn't require physical contact with the samples. The measurement is based on
the induction principle. The measurement system is validated by using saline
solutions and water-saturated sands of known conductivity. This work presents
details of the development of a system of magnetic resistivity measurements by
magnetic induction for petrophysical applications. The first application
consists of measuring the resistivity of the core plug which is 0.038 m in
diameter. Currently the system is operating properly at a frequency of 50 kHz
with a current of up to 500 mA at 20 {\deg}C. During the study two types of
samples were investigated: aqueous solutions with conductivities between 1 to
100 mS/cm and rocks. Several tests were carried out with the objective of
investigating the performance of the instrument, such as the experiment to
obtain sensitivity for the measurement system as a function of the current
applied to the transmitter coil.",2312.01375v1
2023-12-08,The Kernel Method for Electrical Resistance Tomography,"In this paper we consider the inverse problem of electrical conductivity
retrieval starting from boundary measurements, in the framework of Electrical
Resistance Tomography (ERT). In particular, the focus is on non-iterative
reconstruction algorithms, compatible with real-time applications. In this work
a new non-iterative reconstruction method for Electrical Resistance Tomography,
termed Kernel Method, is presented. The imaging algorithm deals with the
problem of retrieving the shape of one or more anomalies embedded in a known
background. The foundation of the proposed method is given by the idea that if
there exists a current flux at the boundary (Neumann data) able to produce the
same voltage measurements on two different configurations, with and without the
anomaly, respectively, then the corresponding electric current density for the
problem involving only the background material vanishes in the region occupied
by the anomaly. Coherently with this observation, the Kernel Method consists in
(i) evaluating a proper current flux at the boundary $g$, (ii) solving one
direct problem on a configuration without anomaly and driven by $g$, (iii)
reconstructing the anomaly from the spatial plot of the power density as the
region in which the power density vanishes. This new tomographic method has a
very simple numerical implementation at a very low computational cost. Beside
theoretical results and justifications of our method, we present a large number
of numerical examples to show the potential of this new algorithm.",2312.05059v1
2024-01-08,Microwave-assisted synthesis of LaMnO3+d: Tuning physical properties with microwave power,"Synthesis of transition metal oxides by microwave irradiation is a faster and
energy-saving method compared to conventional heating in an electrical furnace
because microwave energy is directly converted into heat within precursors.
However, not much is known about how the physical properties are modified by
the power of microwaves. We synthesized LaMnO3+d by irradiating oxide
precursors with microwaves and studied the impact of microwave power (P = 1000
W, 1200 W, 1400 W and 1600 W) on magnetism, resistivity, magnetoresistance,
thermopower, magnetic entropy change, magnetostriction, and electron spin
resonance. It is found that paramagnetic to ferromagnetic transition becomes
sharper, saturation magnetization increases, and electrical resistivity at low
temperatures dramatically decreases as P increases. While the resistivity of
samples irradiated with MW power of P less than or equal to 1400 W show
insulating-like behavior down to 50 K, an insulator-metal transition occurs in
the sample exposed to P = 1600 W and this sample also shows a maximum
magnetoresistance (= -55%), magneto-thermopower (=-87%), magnetostriction (-180
x10-6) for H = 50 kOe and magnetic entropy change of 4.78 J/kg. K for H = 30
kOe around the Curie temperature. The intensity of electron spin resonance
spectra at 300 K increases with P. We postulate that the much enhanced physical
properties observed for the P = 1600 W sample arise from the creation of higher
hole density, chemical homogeneity, and increased grain size. Our study shows
that microwave power can be used as a knob to tune magnetism and other physical
properties to our advantage.",2401.04087v1
2024-01-30,Two-Dimensional Phase-Fluctuating Superconductivity in Bulk-Crystalline NdO$_{0.5}$F$_{0.5}$BiS$_2$,"We present a combined growth and transport study of superconducting
single-crystalline NdO$_{0.5}$F$_{0.5}$BiS$_2$. Evidence of two-dimensional
superconductivity with significant phase fluctuations of preformed Cooper pairs
preceding the superconducting transition is reported. This result is based on
three key observations. (1) The resistive superconducting transition
temperature $T_c$ (defined by resistivity $\rho \rightarrow 0$) increases with
increasing disorder. (2) As $T\rightarrow T_c$, the conductivity diverges
significantly faster than what is expected from Gaussian fluctuations in two
and three dimensions. (3) Non-Ohmic resistance behavior is observed in the
superconducting state. Altogether, our observations are consistent with a
temperature regime of phase-fluctuating superconductivity. The crystal
structure with magnetic ordering tendencies in the NdO$_{0.5}$F$_{0.5}$ layers
and (super)conductivity in the BiS$_2$ layers is likely responsible for the
two-dimensional phase fluctuations. As such, NdO$_{0.5}$F$_{0.5}$BiS$_2$ falls
into the class of unconventional ``laminar"" bulk superconductors that include
cuprate materials and 4Hb-TaS$_2$.",2401.16980v2
2024-02-11,Reducing the metal-graphene contact resistance through laser-induced defects,"Graphene has been extensively studied for a variety of electronic and
optoelectronic applications. The reported contact resistance between metal and
graphene, or rather its specific contact resistance (R{_C}), ranges from a few
tens of {\Omega} {\mu}m up to a few k{\Omega} {\mu}m. Manufacturable solutions
for defining ohmic contacts to graphene remain a subject of research. Here, we
report a scalable method based on laser irradiation of graphene to reduce the
R{_C} in nickel-contacted devices. A laser with a wavelength of {\lambda} = 532
nm is used to induce defects at the contact regions, which are monitored
\textit{in-situ} using micro-Raman spectroscopy. Physical damage is observed
using \textit{ex-situ} atomic force and scanning electron microscopy. The
transfer line method (TLM) is used to extract R{_C} from back-gated graphene
devices with and without laser treatment under ambient and vacuum conditions. A
significant reduction in R{_C} is observed in devices where the contacts are
laser irradiated, which scales with the laser power. The lowest R{_C} of about
250 {\Omega} {\mu}m is obtained for the devices irradiated with a laser power
of 20 mW, compared to 900 {\Omega} {\mu}m for the untreated devices. The
reduction is attributed to an increase in defect density, which leads to the
formation of crystallite edges and in-plane dangling bonds that enhance the
injection of charge carriers from the metal into the graphene. Our work
suggests laser irradiation as a scalable technology for R{_C} reduction in
graphene and potentially other two-dimensional materials.",2402.07151v1
2024-04-19,A Soft e-Textile Sensor for Enhanced Deep Learning-based Shape Sensing of Soft Continuum Robots,"The safety and accuracy of robotic navigation hold paramount importance,
especially in the realm of soft continuum robotics, where the limitations of
traditional rigid sensors become evident. Encoders, piezoresistive, and
potentiometer sensors often fail to integrate well with the flexible nature of
these robots, adding unwanted bulk and rigidity. To overcome these hurdles, our
study presents a new approach to shape sensing in soft continuum robots through
the use of soft e-textile resistive sensors. This sensor, designed to
flawlessly integrate with the robot's structure, utilizes a resistive material
that adjusts its resistance in response to the robot's movements and
deformations. This adjustment facilitates the capture of multidimensional force
measurements across the soft sensor layers. A deep Convolutional Neural Network
(CNN) is employed to decode the sensor signals, enabling precise estimation of
the robot's shape configuration based on the detailed data from the e-textile
sensor. Our research investigates the efficacy of this e-textile sensor in
determining the curvature parameters of soft continuum robots. The findings are
encouraging, showing that the soft e-textile sensor not only matches but
potentially exceeds the capabilities of traditional rigid sensors in terms of
shape sensing and estimation. This advancement significantly boosts the safety
and efficiency of robotic navigation systems.",2404.12627v1
1996-01-23,"Transport Properties, Thermodynamic Properties, and Electronic Structure of SrRuO3","SrRuO$_3$ is a metallic ferromagnet. Its electrical resistivity is reported
for temperatures up to 1000K; its Hall coefficient for temperatures up to 300K;
its specific heat for temperatures up to 230K. The energy bands have been
calculated by self-consistent spin-density functional theory, which finds a
ferromagnetic ordered moment of 1.45$\mu_{{\rm B}}$ per Ru atom. The measured
linear specific heat coefficient $\gamma$ is 30mJ/mole, which exceeds the
theoretical value by a factor of 3.7. A transport mean free path at room
temperature of $\approx 10 \AA$ is found. The resistivity increases nearly
linearly with temperature to 1000K in spite of such a short mean free path that
resistivity saturation would be expected. The Hall coefficient is small and
positive above the Curie temperature, and exhibits both a low-field and a
high-field anomalous behavior below the Curie temperature.",9601106v1
1997-08-26,Scaling and the Metal-Insulator Transition in Si/SiGe Quantum Wells,"The existence of a metal-insulator transition at zero magnetic field in two-
dimensional electron systems has recently been confirmed in high mobility
Si-MOSFETs. In this work, the temperature dependence of the resistivity of
gated Si/SiGe/Si quantum well structures has revealed a similar metal-
insulator transition as a function of carrier density at zero magnetic field.
  We also report evidence for a Coulomb gap in the temperature dependence of
the resistivity of the dilute 2D hole gas confined in a SiGe quantum well.
  In addition, the resistivity in the insulating phase scales with a single
parameter, and is sample independent. These results are consistent with the
occurrence of a metal-insulator transition at zero magnetic field in SiGe
square quantum wells driven by strong hole-hole interactions.",9708201v1
1999-10-29,Neighbor-junction state effect on the fluxon motion in a Josephson stack,"We study experimentally and theoretically the influence of phase-whirling
(resistive) state in one junction of a two-fold Josephson stack on the fluxon
motion in the other junction. In experiment, we measure the fluxon velocity
versus current in one junction as a function of the state (Meissner or
resistive) of the neighboring junction. The analysis, made for the limit of
high fluxon density, shows that the interaction with the resistive state
results in an increase of the effective damping for the moving fluxon and,
therefore, in reduction of its velocity. Numerical simulations confirm this
result for various fluxon densities. The experimental data are in good
agreement with the theoretical predictions. In addition, the fluxon step
measured experimentally has a rather peculiar structure with back and forth
bending regions which is understood as a manifestation of the photon absorption
in the neighboring junction.",9910489v1
2000-03-02,Probing spin-charge separation using spin transport,"Pedagogical discussions are given on what constitutes a signature of
spin-charge separation. A proposal is outlined to probe spin-charge separation
in the normal state of the high $T_c$ cuprates using spin transport.
Specifically, the proposal is to compare the temperature dependences of the
spin resistivity and electrical resistivity: Spin-charge separation will be
manifested in the different temperature dependences of these two resistivities.
We also estimate the spin diffusion length and spin relaxation time scales, and
we argue that it should be experimentally feasible to measure the spin
transport properties in the cuprates using the spin-injection technique. The
on-going spin-injection experiments in the cuprates and related theoretical
issues are also discussed.",0003033v2
2000-06-01,Superconducting properties of [BaCuO_x]_2/[CaCuO_2]_n artificial structures with ultrathick CaCuO_2 blocks,"The electrical transport properties of [BaCuO_x]_2/[CaCuO_2]_n
(CBCCO-2xn)underdoped high temperature superconducting superlattices grown by
Pulsed Laser Deposition have been investigated. Starting from the optimally
doped CBCCO-2x2 superlattice, having three CuO_2 planes and T_c around 80 K, we
have systematically increased the number n up to 15 moving toward the
underdoped region and hence decreasing T_c. For n>11 the artificial structures
are no longer superconducting, as expected, for a uniformly distributed charge
carriers density inside the conducting block layer. The sheet resistance of
such artificial structures (n nearly equal to 11) turns out to be quite
temperature independent and close to the 2D quantum resistance 26 kOhm. A
further increase of the number of CuO_2 planes results in an insulator-type
dependence of R(T) in the wide range of temperatures from room temperature to 1
K. The value of the sheet resistance separating the Superconducting and the
Insulating regimes supports the fermionic scenario of the
Superconductor-Insulator transition in these systems.",0006023v2
2000-08-02,Evidence for small or intermediate-size polarons in the ferromagnetic state of manganites,"Oxygen-isotope effects on the intrinsic resistivity have been studied in
high-quality epitaxial thin films of La_{0.75}Ca_{0.25}MnO_{3} and
Nd_{0.7}Sr_{0.3}MnO_{3}. We found that the residual resistivity \rho_{o}
increases by about 15(3)% upon replacing ^{16}O by ^{18}O. This provides strong
evidence for the presence of small or intermediate-size polarons in the
metallic ferromagnetic state. Furthermore, the temperature dependent part of
the resistivity at low temperatures consists of an AT^{4.5} term contributed
from 2-magnon scattering, and a B\omega_{s}/\sinh^{2}(\hbar\omega_{s}/2k_{B}T)
term which arises from scattering by a soft optical phonon mode. The absolute
magnitudes of the coefficient A and the phonon frequency \hbar\omega_{s} for
both isotope samples are in quantitative agreement with theoretical
predictions.",0008029v1
2000-10-06,Fluctuation Effects in High Sheet Resistance Superconducting Films,"As the normal state sheet resistance, $R_n$, of a thin film superconductor
increases, its superconducting properties degrade. For $R_n\simeq h/4e^2$
superconductivity disappears and a transition to a nonsuperconducting state
occurs. We present electron tunneling and transport measurements on ultrathin,
homogeneously disordered superconducting films in the vicinity of this
transition. The data provide strong evidence that fluctuations in the amplitude
of the superconducting order parameter dominate the tunneling density of states
and the resistive transitions in this regime. We briefly discuss possible
sources of these amplitude fluctuation effects. We also describe how the data
suggest a novel picture of the superconductor to nonsuperconductor transition
in homogeneous 2D systems.",0010114v1
2001-07-29,Pressure-induced Superconductivity in a Ferromagnet UGe$_2$ -- Resistivity Measurements in Magnetic Field --,"The electrical resistivity measurements in the magnetic field are carried out
on the pressure-induced superconductor UGe$_2$. The superconductivity is
observed from 1.06 to 1.44 GPa. The upper critical field of $H_{C2}$ is
anisotropic where $H_{C2}(T)$ exhibits positive curvature for $H//b$ and
$c$-axis. The characteristic enhancement of $H_{C2}$ is reconfirmed for
$H//a$-axis. In the temperature and field dependence of resistivity at $P >
P_{C}$ where the ferromagnetic ordering disappears, it is observed that the
application of the external field along the {\it a}-axis increases the
coefficient of Fermi liquid behavior $AT^{2}$ correspondingly to the
metamagnetic transition.",0107584v1
2001-10-26,Two-dimensional metal in a parallel magnetic field,"We have investigated the effect of an in plane parallel magnetic field (B_||)
on two high mobility metallic-like dilute two-dimensional hole gas (2DHG)
systems in GaAs quantum wells. The experiments reveal that, while suppressing
the magnitude of the low temperature resistance drop, B_|| does not affect E_a,
the characteristic energy scale of the metallic resistance drop. The field B_c
at which the metallic-like resistance drop vanishes is dependent on both the
width of quantum well and the orientation of B_||. It is unexpected that E_a is
unaffected by B_|| up to Bc depite that the Zeeman energy at B_c is roughly
equal to E_a.",0110571v1
2002-05-07,Doping Dependence of Anisotropic Resistivities in Trilayered Superconductor Bi2Sr2Ca2Cu3O10+delta (Bi-2223),"The doping dependence of the themopower, in-plane resistivity rho_ab(T),
out-of-plane resistivity rho_c(T), and susceptibility has been systematically
measured for high-quality single crystal Bi2Sr2Ca2Cu3O10+delta. We found that
the transition temperature Tc and pseudogap formation temperature T_rho_c*,
below which rho_c shows a typical upturn, do not change from their optimum
values in the ""overdoped"" region, even though doping actually proceeds. This
suggests that, in overdoped region, the bulk $T_c$ is determined by the always
underdoped inner plane, which have a large superconducting gap, while the
carriers are mostly doped in the outer planes, which have a large phase
stiffness.",0205121v1
2002-09-19,Temperature dependence of electrical resistivity of high-Tc cuprates - from pseudogap to overdoped regions,"The effects of planar hole concentration, p, and in-plane disorder, Zn (y),
on the DC resistivity, r(T), of sintered samples of
Y_{1-x}Ca_xBa_2(Cu_{1-y}Zn_y)_3O_{7-d} were investigated over a wide doping
range by changing both the oxygen deficiency (d) and Ca content (x). From the
r(T,p) data we extracted characteristic crossover temperatures on the
underdoped and overdoped sides, T* and T_m respectively, above which r(T) is
linear. We compare our results with a number of other polycrystalline, thin
film and single crystal cuprate superconductors and find similar behavior in
the p-dependence of T*(p), T_m(p), and the resistivity exponent, m(p), in fits
to r(T) = r_0 + aT^m on the overdoped side. Our findings point towards the
possible existence of a quantum critical point (QCP) at the doping p=0.19 +/-
0.01.",0209457v1
2002-10-23,Crossover from coherent to incoherent electronic excitations in the normal state of Bi2Sr2CaCu2O8,"Angle resolved photoemission spectroscopy (ARPES) and resistivity
measurements are used to explore the overdoped region of the high temperature
superconductor Bi2Sr2CaCu2O8+delta. We find evidence for a new crossover line
in the phase diagram between a coherent metal phase for lower temperatures and
higher doping, and an incoherent metal phase for higher temperatures and lower
doping. The former is characterized by two well-defined spectral peaks in ARPES
due to coherent bilayer splitting and superlinear behavior in the resistivity,
whereas the latter is characterized by a single broad spectral feature in ARPES
and a linear temperature dependence of the resistivity.",0210531v1
2003-01-14,Resistance Noise Scaling in a Dilute Two-Dimensional Hole System in GaAs,"We have measured the resistance noise of a two-dimensional (2D)hole system in
a high mobility GaAs quantum well, around the 2D metal-insulator transition
(MIT) at zero magnetic field. The normalized noise power $S_R/R^2$ increases
strongly when the hole density p_s is decreased, increases slightly with
temperature (T) at the largest densities, and decreases strongly with T at low
p_s. The noise scales with the resistance, $S_R/R^2 \sim R^{2.4}$, as for a
second order phase transition such as a percolation transition. The p_s
dependence of the conductivity is consistent with a critical behavior for such
a transition, near a density p* which is lower than the observed MIT critical
density p_c.",0301222v2
2003-01-29,Radiation-Induced Magnetoresistance Oscillations in a 2D Electron Gas,"Recent measurements of a 2D electron gas subjected to microwave radiation
reveal a magnetoresistance with an oscillatory dependence on the ratio of
radiation frequency to cyclotron frequency. We perform a diagrammatic
calculation and find radiation-induced resistivity oscillations with the
correct period and phase. Results are explained via a simple picture of current
induced by photo-excited disorder-scattered electrons. The oscillations
increase with radiation intensity, easily exceeding the dark resistivity and
resulting in negative-resistivity minima. At high intensity, we identify
additional features, likely due to multi-photon processes, which have yet to be
observed experimentally.",0301569v3
2003-02-05,"A low density finite temperature apparent ""insulating"" phase in 2D systems","We propose that the observed low density ``insulating'' phase of a 2D
semiconductor system, with the carrier density being just below ($n < n_c$) the
so-called critical density where the derivative of resistivity changes sign at
low temperatures (i.e. resistivity $\rho(T)$ increases with increasing $T$ for
$n > n_c$ whereas it decreases with increasing $T$ for $n < n_c$), is in fact a
``high-temperature'' crossover version of the same effective metallic phase
seen at higher densities ($n>n_c$). This low density ($n<n_c$) finite
temperature crossover 2D effective insulating phase is characterized by
$\rho(T)$ with power law temperature dependence in contrast to the truly
insulating state (occurring at still lower densities) whose resistivity
increases exponentially with decreasing temperature.",0302112v1
2003-05-02,Quantum Gunn effect: Zero-resistance state in 2D electron gas,"Usually the conductivity is quantized as the inverse of the resistivity,
\rho=hc/ie^2, \sigma=ie^2/hc and the velocity versus the electric field is
linear, v=\mu E where \mu is the mobility of the electrons.However,when the
applied electric field exceeds a certain value, microwaves are emitted and the
relation v=\mu E breaks down so that the velocity actually reduces as E
increases. In this region, when magnetic field is applied, the conductivity
quantizes like the magnetic field, i.e., in units of hc/e which is different
from the usual quantization. Because of the flux quantization, the resistivity
will touch zero in the region of high electric field. Factors like 4/5 arise
due to new spin dependence of the effective charge.",0305032v1
2004-02-06,Counterflow measurements in strongly correlated GaAs hole bilayers: evidence for electron-hole pairing,"We study interacting GaAs bilayer hole systems, with very small interlayer
tunneling, in a counterflow geometry where equal currents are passed in
opposite directions in the two, independently contacted layers. At low
temperatures, both the longitudinal and Hall counterflow resistances tend to
vanish in the quantum Hall state at total bilayer filling $\nu=1$,
demonstrating the pairing of oppositely charged carriers in opposite layers.
The temperature dependence of the counterflow Hall resistance is anomalous
compared to the other transport coefficients: even at relatively high
temperatures ($\sim$600mK), it develops a very deep minimum, with a value that
is about an order of magnitude smaller than the longitudinal counterflow
resistivity.",0402186v2
2004-02-20,Chemical Control of Spin Chirality in $(Nd_{1-x} Dy_x)_2 Mo_2 O_7$,"Magnetization and Hall resistivity have been investigated for single crystals
of Dy-doped Nd$_{2}$Mo$_{2}$O$_{7}$. A sharp decrease of the Hall resistivity
upon a metamagnetic transition, perhaps associated with magnetic-field ($H$)
induced flop of Dy$^{3+}$ moments, has been observed in the Dy-doped crystals
only for $H \parallel [111]$ direction. In addition, the sign of the Hall
resistivity at a high field, both for $H \parallel [100]$ and for $H \parallel
[111]$, changes with the Dy-doping. These results are explained in terms of the
sign change of Mo spin chirality that is controlled by the Dy$^{3+}$ moments
with a different sign of $f$-$d$ interaction from the Nd$^{3+}$ moments.",0402510v1
2004-05-11,Probing Spin-Polarized Currents in the Quantum Hall Regime,"An experiment to probe spin-polarized currents in the quantum Hall regime is
suggested that takes advantage of the large Zeeman-splitting in the
paramagnetic diluted magnetic semiconductor zinc manganese selenide
(Zn$_{1-x}$Mn$_x$Se). In the proposed experiment spin-polarized electrons are
injected by ZnMnSe-contacts into a gallium arsenide (GaAs) two-dimensional
electron gas (2DEG) arranged in a Hall bar geometry. We calculated the
resulting Hall resistance for this experimental setup within the framework of
the Landauer-B\""uttiker formalism. These calculations predict for 100%
spininjection through the ZnMnSe-contacts a Hall resistance twice as high as in
the case of no spin-polarized injection of charge carriers into a 2DEG for
filling factor $\nu=2$. We also investigated the influence of the equilibration
of the spin-polarized electrons within the 2DEG on the Hall resistance. In
addition, in our model we expect no coupling between the contact and the 2DEG
for odd filling factors of the 2DEG for 100% spininjection, because of the
opposite sign of the g-factors of ZnMnSe and GaAs.",0405231v1
2004-08-27,Hall resistance and Lorenz ratio models in YBa2Cu3O7,"The 2D models of heat capacity, its conductivity ($\kappa$), Hall resistance
($R_H$) and the Lorenz ratio ($\mathcal{L}$) have been derived using the
ionization energy ($E_I$) based Fermi-Dirac statistics (iFDS). These models
reproduce the experimentally measured $\rho(T)$ and $R_H(T)$. The variation of
$\mathcal{L}$ is proportional to 1/T due to electron-phonon ($e$-$ph$)
scattering in $\kappa$. However, the $e$-$ph$ coupling in the electrical
resistivity has the polaronic effect that complies with iFDS, rather than the
$e$-$ph$ scattering that satisfies the Bloch-Gr\""{u}neisen formula. These
models are purely Fermi liquid and are not associated with any microscopic
theories of high-Tc superconductors.",0408613v6
2004-09-08,Non-linear Temperature Dependence of Resistivity in Single Crystalline Ag$_5$Pb$_2$O$_6$,"We measured electrical resistivity, specific heat and magnetic susceptibility
of single crystals of highly conductive oxide Ag_5Pb_2O_6, which has a layered
structure containing a Kagome lattice. Both the out-of-plane and in-plane
resistivity show T^2 dependence in an unusually wide range of temperatures up
to room temperature. This behavior cannot be accounted for either by electron
correlation or by electron-phonon scattering with high frequency optic phonons.
In addition, a phase transition with a large diamagnetic signal was found in
the ac susceptibility, which strongly suggests the existence of a
superconducting phase below 48 mK.",0409184v2
2004-09-08,High pressure investigation of the heavy-fermion antiferromagnet U_3Ni_5Al_19,"Measurements of magnetic susceptibility, specific heat, and electrical
resistivity at applied pressures up to 55 kbar have been carried out on single
crystals of the heavy-fermion antiferromagnet U_3Ni_5Al_19, which crystallizes
in the Gd_3Ni_5Al_19 orthorhombic structure with two inequivalent U sites. At
ambient pressure, a logarithmic T-dependence of the specific heat and T-linear
electrical resistivity below 5 K indicates non-Fermi liquid (NFL) behavior in
the presence of bulk antiferromagnetic order at T_N=23 K. Electrical
resistivity measurements reveal a crossover from non-Fermi liquid to Fermi
liquid behavior at intermediate pressures between 46 kbar and 51 kbar, followed
by a return to NFL T^{3/2} behavior at higher pressures. These results provide
evidence for an ambient pressure quantum critical point and an additional
antiferromagnetic instability at P_c=60 kbar.",0409202v1
2005-04-19,Nonmonotonic Temperature Dependence of the Hall Resistance for 2D Electron System in Si,"Weak field Hall resistance Rxy(T) of the 2D electron system in Si was
measured over the range of temperatures 1-35 K and densities, where the
diagonal resistivity exhibits a ``metallic'' behavior. The Rxy(T) dependence
was found to be non-monotonic with a maximum at temperatures Tm~0.16Tf. The
Rxy(T) variations in the low-temperature domain (T<Tm) agree qualitatively with
the semiclassical model, that takes into account a broadening of the
Fermi-distribution solely. The semiclassical result considerably exceeds an
interaction-induced quantum correction. In the ``high-temperature'' domain
(T>Tm), the Rxy(T) dependence can be qualitatively explained in terms of either
a semiclassical T-dependence of a transport time, or a thermal activation of
carries from a localized band.",0504475v1
2005-06-12,Classical Hall transition and magnetoresistance in strongly inhomogeneous planar systems,"The magneto-transport properties of planar and layered strongly inhomogeneous
two-phase systems are investigated, using the explicit expressions for the
effective conductivities and resistivities obtained by the exact dual
transformation, connecting effective conductivities of in-plane isotropic
two-phase systems with and without magnetic field. These expressions allow to
describe the effective resistivity of various inhomogeneous media at arbitrary
concentrations $x$ and magnetic fields $H$. The corresponding plots of the
$x$-dependence of the Hall constant $R_H(x,H)$ and the magnetoresistance
$R(x,H)$ are constructed for various values of magnetic field at some values of
inhomogeneity parameters. These plots for strongly inhomogeneous systems at
high magnetic fields show a sharp transition between partial Hall resistivities
(or Hall conductivities) with different dependencies of $R_H$ on the phase
concentrations. It is shown that there is a strong correlation between large
linear magnetoresistance effect and this sharp Hall transition. Both these
effects are a consequence of the exact duality symmetry. A possible physical
explanation of these effects and their correlation is proposed.",0506267v1
2005-07-08,Field-induced non-Fermi-liquid resistivity of stoichiometric YbAgGe single crystals,"We have investigated hexagonal YbAgGe down to 70 mK by measuring the
magnetic-field and temperature dependence of the resistivity rho of single
crystals in fields up to 14 T. Our results extend the H-T phase diagram to the
lowest temperatures for H applied in the basal plane and along the c-axis. In
particular, critical fields for the suppression of several magnetic phases are
determined. The temperature dependence of rho(T) is unusual: whereas at low H,
rho(T) reveals a temperature exponent n>=2, we find 1<=n<1.5 and strong
enhancement of the temperature dependence of rho(T) close to and beyond the
highest critical field for each field direction. For H applied in the basal
plane, at high fields a conventional T^2 dependence of rho(T) is reached above
10 T accompanied by an approach to saturation of a strong drop in the residual
resistivity. YbAgGe appears to be one of few Yb-based stoichiometric systems,
where quantum-critical behaviour may be induced by a magnetic field.",0507211v2
2005-08-12,The microwave induced resistance response of a high mobility 2DEG from the quasi-classical limit to the quantum Hall regime,"Microwave induced resistance oscillations (MIROs) were studied experimentally
over a very wide range of frequencies ranging from ~20 GHz up to ~4 THz, and
from the quasi-classical regime to the quantum Hall effect regime. At low
frequencies regular MIROs were observed, with a periodicity determined by the
ratio of the microwave to cyclotron frequencies. For frequencies below 150 GHz
the magnetic field dependence of MIROs waveform is well described by a
simplified version of an existing theoretical model, where the damping is
controlled by the width of the Landau levels. In the THz frequency range MIROs
vanish and only pronounced resistance changes are observed at the cyclotron
resonance. The evolution of MIROs with frequency are presented and discussed.",0508327v1
2005-11-15,1/f noise in a dilute GaAs two-dimensional hole system in the insulating phase,"We have measured the resistance and the 1/f resistance noise of a
two-dimensional low density hole system in a high mobility GaAs quantum well at
low temperature. At densities lower than the metal-insulator transition one,
the temperature dependence of the resistance is either power-like or simply
activated. The noise decreases when the temperature or the density increase.
These results contradict the standard description of independent particles in
the strong localization regime. On the contrary, they agree with the
percolation picture suggested by higher density results. The physical nature of
the system could be a mixture of a conducting and an insulating phase. We
compare our results with those of composite thin films.",0511375v1
2006-02-03,Observation of the quantized Hall insulator in the quantum critical regime of the two-dimensional electron gas,"We have investigated the Hall resistance $R_H$ near the plateau-insulator
transition of a two-dimensional electron gas in the quantum critical regime.
High-field magnetotransport data taken on a low-mobility InGaAs/InP
heterostructure with the plateau-insulator transition at a critical field $B_c$
of 17.2 T show that the Hall resistance $R_H$ is quantized at $h/e^2$ near the
critical filling fraction ($\nu_c$ = 0.55) when $T \to 0$. By making use of
universal scaling functions extracted from the magnetotransport data we show
that $R_H$ in the insulating phase in the limit $T \to 0$ is quantized at
$h/e^2$ for all values of the scaling parameter $\Delta\nu /(T/T_0)^\kappa$
with $\Delta\nu = \nu - \nu_c$. However, as a function of $\Delta\nu $ (or
magnetic field) the Hall resistance diverges in the limit $T \to 0$ for all
values $\nu < \nu_c$.",0602093v2
2006-12-18,Nonlinear Current of Strongly Irradiated Quantum Hall Gas,"Two dimensional electrons in weakly disordered high Landau levels are
considered. The current-field response in the presence of a strong microwave
field, is computed. The disordered Floquet evolution operator allows us to
treat the short range disorder perturbatively, at any strength of electric
fields. A simplifying Random Matrix Approximation reproduces the broadened
Landau levels density of states and structure factor. We derive the magnitude
of the Microwave Induced Resistivity Oscillations. The disorder short
wavelength cut-off determines the non-linear electric fields of the Zero
Resistance State and the Hall Induced Resistivity Oscillations. We discuss
wider implications of our results on experiments and other theories.",0612469v2
2007-12-13,Study of GEM-like detectors with resistive electrodes for RICH applications,"We have developed prototypes of GEM-like detectors with resistive electrodes
to be used as RICH photodetectors equipped with CsI photocathodes. The main
advantages of these detectors are their intrinsic spark protection and
possibility to operate at high gain (~10E5) in many gases including poorly
quenched ones, allowing for the adoption of windowless configurations in which
the radiator gas is also used in the chamber. Results of systematic studies of
the resistive GEMs combined with CsI photocathodes are presented: its quantum
efficiency, rate characteristics, long-term stability, etc. On the basis of the
obtained results, we believe that the new detector will be a promising
candidate for upgrading the ALICE RICH detector",0712.2179v1
2008-01-06,Scaling of Hall Resistivity in the Mixed State of MgB2 Films,"The longitudinal resistivity (rho_{xx}) and transverse resistivity (rho_{xy})
of MgB2 thin films in the mixed state were studied in detail. We found that the
temperature dependencies of rho_{xx} and \rho_{xy} at a fixed magnetic field
(H) satisfy the scaling law of $\rho_{xy}=A\rho_{xx}^\beta$, where the exponent
beta varies around 2.0 for different fields. In the low field region (below
1T), beta maintains a constant value of 2.0 due to the weak pinning strength of
the vortices, mainly from the superfluid of the pi band. When H>1T, beta drops
abruptly to its lowest value at about 2T because of the proliferation of
quasiparticles from the pi-band and, hence, the motion of the vortices from the
superfluid of the sigma-band dominates the dissipation. As the field is
increased further, the vortex pinning strength is weakened and beta increases
monotonically towards 2.0 at a high field. All the results presented here are
in good agreement with the expectation of the vortex physics of a multi-band
superconductor.",0801.0838v1
2008-02-05,Effect of small particles on the near-wall dynamics of a large particle in a highly bidisperse colloidal solution,"We consider the hydrodynamic effect of small particles on the dynamics of a
much larger particle moving normal to a planar wall in a highly bidisperse
dilute colloidal suspension of spheres. The gap $h_0$ between the large
particle and the wall is assumed to be comparable to the diameter $2a$ of the
smaller particles so there is a length-scale separation between the gap width
$h_0$ and the radius of the large particle $b<<h_0$. We use this length-scale
separation to develop a new lubrication theory which takes into account the
presence of the smaller particles in the space between the larger particle and
the wall. The hydrodynamic effect of the small particles on the motion of the
large particle is characterized by the short time (or high frequency)
resistance coefficient. We find that for small particle-wall separations $h_0$,
the resistance coefficient tends to the asymptotic value corresponding to the
large particle moving in a clear suspending fluid. For $h_0<<a$, the resistance
coefficient approaches the lubrication value corresponding to a particle moving
in a fluid with the effective viscosity given by the Einstein formula.",0802.0608v1
2008-07-16,Influence of doping on the Hall coefficient in Sr_{14-x}Ca_xCu_24O_41,"We present Hall-effect measurements of two-leg ladder compounds
Sr_{14-x}Ca_xCu_24O_41 (0 <= x <= 11.5) with the aim to determine the number of
carriers participating in dc transport. Distribution of holes between the
ladder and chain subsystems is one of the crucial questions important for
understanding the physics of these compounds. Our Hall effect and resistivity
measurements show typical semiconducting behavior for x < 11.5. However, for
x=11.5, the results are completely different, and the Hall coefficient and
resistivity behavior is qualitatively similar to that of high temperature
copper-oxide superconductors. We have determined the effective number of
carriers at room temperature and compared it to the number of holes in the
ladders obtained by other experimental techniques. We propose that going from
x=0 to x=11.5 less than 1 hole per formula unit is added to the ladders and is
responsible for a pronounced change in resistivity with Ca doping.",0807.2561v2
2008-08-04,Evidence for the Sr2RuO4 intercalations in the Sr3Ru2O7 region of the Sr3Ru2O7-Sr2RuO4 eutectic system,"Although Sr3Ru2O7 has not been reported to exhibit superconductivity so far,
ac susceptibility measurements revealed multiple superconducting transitions
occurring in the Sr3Ru2O7 region cut from Sr3Ru2O7-Sr2RuO4 eutectic crystals.
Based on various experimental results, some of us proposed the scenario in
which Sr2RuO4 thin slabs with a few layers of the RuO2 plane are embedded in
the Sr3Ru2O7 region as stacking faults and multiple superconducting transitions
arise from the distribution of the slab thickness. To examine this scenario, we
measured the resistivity along the ab plane (rho_ab) using a Sr3Ru2O7-region
sample cut from the eutectic crystal, as well as along the c axis (rho_c) using
the same crystal. As a result, we detected resistance drops associated with
superconductivity only in rho_ab, but not in rho_c. These results support the
Sr2RuO4 thin-slab scenario. In addition, we measured the resistivity of a
single crystal of pure Sr3Ru2O7 with very high quality and found that pure
Sr3Ru2O7 does not exhibit superconductivity down to 15 mK.",0808.0434v1
2008-08-18,Field Re-entrant Superconductivity Induced by the Enhancement of Effective Mass in URhGe,"High quality single crystals of a ferromagnetic superconductor URhGe were
successfully grown. The electrical resistivity was measured for the field along
b-axis in the orthorhombic crystal structure in order to study precisely its
field re-entrant superconductivity which occurs in the vicinity of the field
$H_{\rm R}$, where the easy magnetization switches from $c$ to b-axis. The
field re-entrant superconductivity of URhGe is analyzed with special focus on
its dependence with the value of residual resistivity $\rho_0$ and the
coefficient $A$ of $T^2$ term of the resistivity. The experimental results are
well explained by a crude model related with the field dependence of the
effective mass $m^\ast$, where the corresponding critical temperature
$T_{\mathrm{sc}}(m^\ast)$ and the upper critical field $H_{\rm c2}$ are
strongly enhanced. Discussion is made on the interplay between magnetic and
superconducting phase diagram as well as the link between $T_{\mathrm{sc}}$ and
$A$ in other heavy fermion superconductors.",0808.2500v1
2008-10-13,Observation of a Fractional Quantum Hall State at $ν=1/4$ in a Wide GaAs Quantum Well,"We report the observation of an even-denominator fractional quantum Hall
(FQH) state at $\nu=1/4$ in a high quality, wide GaAs quantum well. The sample
has a quantum well width of 50 nm and an electron density of
$n_e=2.55\times10^{11}$ cm$^{-2}$. We have performed transport measurements at
$T\sim35$ mK in magnetic fields up to 45 T. When the sample is perpendicular to
the applied magnetic field, the diagonal resistance displays a kink at
$\nu=1/4$. Upon tilting the sample to an angle of $\theta=20.3^o$ a clear FQH
state at emerges at $\nu=1/4$ with a plateau in the Hall resistance and a
strong minimum in the diagonal resistance.",0810.2274v1
2008-10-23,Jumps in current-voltage characteristics in disordered films,"We argue that giant jumps of current at finite voltages observed in
disordered samples of InO, TiN and YSi manifest a bistability caused by the
overheating of electrons. One of the stable states is overheated and thus
low-resistive, while the other, high-resistive state is heated much less by the
same voltage. The bistability occurs provided that cooling of electrons is
inefficient and the temperature dependence of the equilibrium resistance, R(T),
is steep enough. We use experimental R(T) and assume phonon mechanism of the
cooling taking into account its strong suppression by disorder. Our description
of details of the I-V characteristics does not involve adjustable parameters
and turns out to be in a quantitative agreement with the experiments. We
propose experiments for more direct checks of this physical picture.",0810.4312v2
2008-11-20,A novel non-Fermi-liquid state in the iron-pnictide FeCrAs,"We report transport and thermodynamic properties of stoichiometric single
crystals of the hexagonal iron-pnictide FeCrAs. The in-plane resistivity shows
an unusual ""non-metallic"" dependence on temperature T, rising continuously with
decreasing T from ~ 800 K to below 100 mK. The c-axis resistivity is similar,
except for a sharp drop upon entry into an antiferromagnetic state at T_N 125
K. Below 10 K the resistivity follows a non-Fermi-liquid power law, rho(T) =
rho_0 - AT^x with x<1, while the specific heat shows Fermi liquid behaviour
with a large Sommerfeld coefficient, gamma ~ 30 mJ/mol K^2. The high
temperature properties are reminiscent of those of the parent compounds of the
new layered iron-pnictide superconductors, however the T -> 0 properties
suggest a new class of non-Fermi liquid.",0811.3439v1
2009-02-25,Resistive relaxation of a magnetically confined mountain on an accreting neutron star,"Three-dimensional numerical magnetohydrodynamic (MHD) simulations are
performed to investigate how a magnetically confined mountain on an accreting
neutron star relaxes resistively. No evidence is found for non-ideal MHD
instabilities on a short time-scale, such as the resistive ballooning mode or
the tearing mode. Instead, the mountain relaxes gradually as matter is
transported across magnetic surfaces on the diffusion time-scale, which
evaluates to $\tau_\mathrm{I} \sim 10^5 - 10^8$ yr (depending on the
conductivity of the neutron star crust) for an accreted mass of $M_a = 1.2
\times 10^{-4} M_\odot$. The magnetic dipole moment simultaneously reemerges as
the screening currents dissipate over $\tau_\mathrm{I}$. For nonaxisymmetric
mountains, ohmic dissipation tends to restore axisymmetry by magnetic
reconnection at a filamentary neutral sheet in the equatorial plane. Ideal-MHD
oscillations on the Alfv\'{e}n time-scale, which can be excited by external
influences, such as variations in the accretion torque, compress the magnetic
field and hence decrease $\tau_\mathrm{I}$ by \change{one order of magnitude}
relative to its standard value (as computed for the static configuration). The
implications of long-lived mountains for gravitational wave emission from
low-mass X-ray binaries are briefly explored.",0902.4484v1
2009-12-09,Coulomb zero bias anomaly for fractal geometry and conductivity of granular systems near the percolation threshold,"A granular system slightly below the percolation threshold is a collection of
finite metallic clusters, characterized by wide spectrum of sizes, resistances,
and charging energies. Electrons hop from cluster to clusters via short
insulating ""links"" of high resistance. At low temperatures all clusters are
Coulomb blockaded and the dc-conductivity is exponentially suppressed. At
lowest T the leading transport mechanism is variable range cotunneling via
largest (critical) clusters, leading to the modified Efros-Shklovsky law. At
intermediate temperatures the principal suppression of the conductivity
originates from the Coulomb zero bias anomaly occurring, when electron tunnels
between adjacent large clusters with large resistances. Such clusters are
essentially extended objects and their internal dynamics should be taken into
account. In this regime the T-dependence of conductivity is stretched
exponential with a nontrivial index, expressed through the indices of
percolation theory. Due to the fractal structure of large clusters the anomaly
is strongly enhanced: it arises not only in low dimensions, but also in d=3
case.",0912.1701v1
2010-02-16,Pseudogap Phase Boundary in Overdoped Bi_2Sr_2CaCu_2O_8 Studied by Measuring Out-of-plane Resistivity under the Magnetic Fields,"The characteristic pseudogap temperature T* in Bi2Sr2CaCu2O8 system has been
systematically evaluated as a function of doping, especially focusing on its
overdoped region, by measuring the out-of-plane resistivity under the magnetic
fields. Overdoped samples have been prepared by annealing TSFZ-grown
Bi2Sr2CaCu2O8 single crystals under the high oxygen pressures (990 kgf/cm2). At
a zero field, the out-of-plane resistivity showed a metallic behavior down to
Tc (= 62 K), while under the magnetic fields of over 3 T,it showed typical
upturn behavior from around 65 K upon decreasing temperature. This result
suggests that the pseudogap and superconductivity are different phenomena.",1002.3014v1
2010-05-13,Probing top-gated field effect transistor of reduced graphene oxide monolayer made by dielectrophoresis,"We demonstrate top-gated field effect transistor made of reduced graphene
oxide (RGO) monolayer (graphene) by dielectrophoresis. Raman spectrum of RGO
flakes of typical size of 5{\mu}m x 5{\mu}m show a single 2D band at 2687 cm-1,
characteristic of a single layer graphene. The two probe current - voltage
measurements of RGO flakes, deposited in between the patterned electrodes with
a gap of 2.5 {\mu}m using a.c. dielectrophoresis show ohmic behavior with a
resistance of ~ 37k{\Omega}. The temperature dependence of the resistance (R)
of RGO measured between temperatures 305 K to 393 K yields temperature
coefficient of resistance [dR/dT]/R ~ -9.5x10-4 K-1, same as mechanically
exfoliated single layer graphene. The field effect transistor action was
obtained by electrochemical top-gating using solid polymer electrolyte (PEO +
LiClO4) and Pt wire. Ambipolar nature of graphene flakes is observed upto a
doping level of ~ 6x1012/cm2 and carrier mobility of ~ 50 cm2V-1sec-1. The
source - drain current characteristics shows a tendency of current saturation
at high source - drain voltage which is analyzed quantitatively by a diffusive
transport model.",1005.2258v1
2010-08-10,Temperature-dependent resistivity of suspended graphene,"In this paper we investigate the electron-phonon contribution to the
resistivity of suspended single layer graphene. In-plane as well as flexural
phonons are addressed in different temperature regimes. We focus on the
intrinsic electron-phonon coupling due to the interaction of electrons with
elastic deformations in the graphene membrane. The competition between screened
deformation potential vs fictitious gauge field coupling is discussed, together
with the role of tension in the suspended flake. In the absence of tension,
flexural phonons dominate the phonon contribution to the resistivity at any
temperature $T$ with a $T^{5/2}_{}$ and $T^{2}_{}$ dependence at low and high
temperatures, respectively. Sample-specific tension suppresses the contribution
due to flexural phonons, yielding a linear temperature dependence due to
in-plane modes. We compare our results with recent experiments.",1008.1631v1
2010-08-17,Heat capacity study of BaFe$_{2}$As$_{2}$: effects of annealing,"Heat-capacity, X-ray diffraction, and resistivity measurements on a
high-quality BaFe$_{2}$As$_{2}$ sample show an evolution of the
magneto-structural transition with successive annealing periods. After a 30-day
anneal the resistivity in the (ab) plane decreases by more than an order of
magnitude, to 12 $\mu\Omega$cm, with a residual resistance ratio $\sim$36; the
heat-capacity anomaly at the transition sharpens, to an overall width of less
than K, and shifts from 135.4 to 140.2 K. The heat-capacity anomaly in both the
as-grown sample and after the 30-day anneal shows a hysteresis of $\sim$0.15 K,
and is unchanged in a magnetic field $\mu_{0}$H = 14 T. The X-ray and
heat-capacity data combined suggest that there is a first order jump in the
structural order parameter. The entropy of the transition is reported.",1008.2967v2
2010-09-17,Anomalously strong pinning of the filling factor nu=2 in epitaxial graphene,"We explore the robust quantization of the Hall resistance in epitaxial
graphene grown on Si-terminated SiC. Uniquely to this system, the dominance of
quantum over classical capacitance in the charge transfer between the substrate
and graphene is such that Landau levels (in particular, the one at exactly zero
energy) remain completely filled over an extraordinarily broad range of
magnetic fields. One important implication of this pinning of the filling
factor is that the system can sustain a very high nondissipative current. This
makes epitaxial graphene ideally suited for quantum resistance metrology, and
we have achieved a precision of 3 parts in 10^10 in the Hall resistance
quantization measurements.",1009.3450v3
2010-10-14,Resistivity and Hall effect of LiFeAs: Evidence for electron-electron scattering,"LiFeAs is unique among the broad family of FeAs-based superconductors,
because it is superconducting with a rather large $T_c\simeq 18$ K under
ambient conditions although it is a stoichiometric compound. We studied the
electrical transport on a high-quality single crystal. The resistivity shows
quadratic temperature dependence at low temperature giving evidence for strong
electron-electron scattering and a tendency towards saturation around room
temperature. The Hall constant is negative and changes with temperature, what
most probably arises from a van Hove singularity close to the Fermi energy in
one of the hole-like bands. Using band structure calculations based on angular
resolved photoemission spectra we are able to reproduce all the basic features
of both the resistivity as well as the Hall effect data.",1010.2876v2
2010-10-20,Raychaudhuri's equation and aspects of relativistic charged collapse,"We use the Raychaudhuri equation to probe certain aspects related to the
gravitational collapse of a charged medium. The aim is to identify the stresses
the Maxwell field exerts on the fluid and discuss their potential implications.
Particular attention is given to those stresses that resist contraction. After
looking at the general case, we consider the two opposite limits of poor and
high electrical conductivity. In the former there are electric fields but no
currents, while in the latter the situation is reversed. When the conductivity
is low, we find that the main agents acting against the collapse are the
Coulomb forces triggered by the presence of an excess charge. At the ideal
Magnetohydrodynamic (MHD) limit, on the other hand, the strongest resistance
seems to come from the tension of the magnetic forcelines. In either case, we
discuss whether and how the aforementioned resisting stresses may halt the
contraction and provide a set of conditions making this likely to happen.",1010.4211v2
2010-12-30,Pressure-Driven Quantum Criticality in An Iron-Selenide Superconductor,"The discovery of superconductivity of about 30 K in iron selenides with very
large magnetic moments simulates the examination of completing orders. Here we
report a finding of pressure- induced suppression of the superconducting
transition temperature Tc and enhancement of the temperature of the resistance
hump TH through charge transfer between two iron sites with different
occupancies. The activation energy for the electric transport of the
high-temperature resistance is observed to go to zero at a critical pressure of
8.7 GPa, at which superconductivity tends to disappear and the
semiconductor-to-metal transition takes place. Beyond the critical point, the
resistance exhibits a metallic behavior over the whole temperature range
studied. All these features indicate the existence of quantum criticality in
iron-selenide superconductors.",1101.0092v3
2011-02-22,Charged Dilatonic Black Holes and their Transport Properties,"We briefly explain the consistency conditions imposed on the effective
holographic theories, which are parameterized by two real exponents
$(\gamma,\delta)$ that control the IR dynamics. The general scaling of DC
resistivity with temperature at low temperature and AC conductivity at low
frequency across the whole $(\gamma,\delta)$ plane are explained. There is a
codimension-one region where the DC resistivity is linear in the temperature.
For massive carriers, it is shown that when the scalar operator is not the
dilaton, the DC resistivity scales as the heat capacity (and entropy) for
$(2+1)$-dimensional systems. Regions are identified where the theory at finite
density is a Mott-like insulator. This contribution is based on arXiv:1005.4690
with emphasis on the transport properties of charged dilatonic black holes with
potential.",1102.4440v1
2011-03-24,Collective excitations and low temperature transport properties of bismuth,"We examine the influence of collective excitations on the transport
properties (resistivity, magneto- optical conductivity) for semimetals,
focusing on the case of bismuth. We show, using an RPA approximation, that the
properties of the system are drastically affected by the presence of an
acoustic plasmon mode, consequence of the presence of two types of carriers
(electrons and holes) in this system. We found a crossover temperature T*
separating two different regimes of transport. At high temperatures T > T* we
show that Baber scattering explains quantitatively the DC resistivity
experiments, while at low temperatures T < T* interactions of the carriers with
this collective mode lead to a T^5 behavior of the resistivity. We examine
other consequences of the presence of this mode, and in particular predict a
two plasmon edge feature in the magneto-optical conductivity. We compare our
results with the experimental findings on bismuth. We discuss the limitations
and extensions of our results beyond the RPA approximation, and examine the
case of other semimetals such as graphite or 1T-TiSe_2.",1103.4850v1
2011-03-29,Substrate Gating of Contact Resistance in Graphene Transistors,"Metal contacts have been identified to be a key technological bottleneck for
the realization of viable graphene electronics. Recently, it was observed that
for structures that possess both a top and a bottom gate, the electron-hole
conductance asymmetry can be modulated by the bottom gate. In this letter, we
explain this observation by postulating the presence of an effective thin
interfacial dielectric layer between the metal contact and the underlying
graphene. Electrical results from quantum transport calculations accounting for
this modified electrostatics corroborate well with the experimentally measured
contact resistances. Our study indicates that the engineering of metal-
graphene interface is a crucial step towards reducing the contact resistance
for high performance graphene transistors.",1103.5773v2
2011-05-28,A New numerical scheme for resistive relativistic MHD using method of characteristics,"We present a new numerical method of special relativistic resistive
magnetohydrodynamics with scalar resistivity that can treat a range of
phenomena, from nonrelativistic to relativistic (shock, contact discontinuity,
and Alfv\'en wave). The present scheme calculates the numerical flux of fluid
by using an approximate Riemann solver, and electromagnetic field by using the
method of characteristics. Since this scheme uses appropriate characteristic
velocities, it is capable of accurately solving problems that cannot be
approximated as ideal magnetohydrodynamics and whose characteristic velocity is
much lower than light velocity. The numerical results show that our scheme can
solve the above problems as well as nearly ideal MHD problems. Our new scheme
is particularly well suited to systems with initially weak magnetic field, and
mixed phenomena of relativistic and non-relativistic velocity; for example, MRI
in accretion disk, and super Alfv\'enic turbulence.",1105.5683v1
2011-06-02,High Lundquist Number Resistive MHD Simulations of Magnetic Reconnection: Searching for Secondary Island Formation,"Recently, secondary island formation due to the tearing instability of the
Sweet-Parker current sheet was identified as a possible mechanism that can lead
to fast reconnection (less sensitive dependence on Lundquist number $S$) both
in numerical simulations using Particle-in-Cell (PIC) method [Daughton et al.
2009], as well as using resistive magnetohydrodynamics (MHD) [Lapenta 2008;
Bhattacharjee et al. 2009]. This instability is thought to appear when $S$ is
greater than a certain threshold. These recent results prompt us to perform
more resistive MHD simulations of a basic reconnection configuration based on
the island coalescence instability, using much higher resolutions and larger
$S$. Our simulations are based on a fairly standard pseudo spectral code, which
has been tested for accuracy, convergence, and compared well with codes using
other methods [Ng et al. 2008]. In our simulations, formation of plasmoids were
not found, except when insufficient resolution was used, or when a small amount
of noise was added externally. The reconnection rate is found to follow the
Sweet-Parker scaling when no noise is added, but increases to a level
independent of $S$ with noise, when plasmoids form. Latest results with $S$ up
to $2 \times 10^5$ will be presented.",1106.0521v1
2011-08-03,Unusual Field-Insensitive Phase Transition and Kondo Behavior in SmTi$_2$Al$_{20}$,"Magnetization, electrical resistivity and specific heat measurements were
performed on high-quality single crystalline SmTi$_2$Al$_{20}$ (residual
resistivity ratio $\sim$ 40) grown by Al self-flux method. A Kondo-like $\log
T$ dependence in the resistivity is observed below 50 K. We discovered a
field-insensitive phase transition at $T_{x}$ = 6.5 K and a field-insensitive
heavy fermion behavior with the electronic specific heat coefficient $\gamma$ =
150 mJ/(K$^{2}$ mol). Specific heat analysis reveals that the ground state is a
$\Gamma_{8}$ quartet state and the Sm magnetic dipole moment $m_{{\rm Sm}}$
($\sim 0.5 \mu_{{\rm B}}$ at $T \simeq$ 0) orders below $T_{x}$ in spite of the
field-insensitive behavior. Possible reasons for the field insensitiveness will
be discussed.",1108.0751v1
2011-08-15,Current-Controlled Negative Differential Resistance due to Joule Heating in TiO2,"We show that Joule heating causes current-controlled negative differential
resistance (CC-NDR) in TiO2 by constructing an analytical model of the
voltage-current V(I) characteristic based on polaronic transport for Ohm's Law
and Newton's Law of Cooling, and fitting this model to experimental data. This
threshold switching is the 'soft breakdown' observed during electroforming of
TiO2 and other transition-metal-oxide based memristors, as well as a precursor
to 'ON' or 'SET' switching of unipolar memristors from their high to their low
resistance states. The shape of the V(I) curve is a sensitive indicator of the
nature of the polaronic conduction.",1108.3120v1
2011-08-25,Generalized four-point characterization method for resistive and capacitive contacts,"In this paper, a four-point characterization method is developed for
resistive samples connected to either resistive or capacitive contacts.
Provided the circuit equivalent of the complete measurement system is known
including coaxial cable and connector capacitances as well as source output and
amplifier input impedances, a frequency range and capacitive scaling factor can
be determined, whereby four-point characterization can be performed. The
technique is demonstrated with a discrete element test sample over a wide
frequency range using lock-in measurement techniques from 1 Hz - 100 kHz. The
data fit well with a circuit simulation of the entire measurement system. A
high impedance preamplifier input stage gives best results, since lock-in input
impedances may differ from manufacturer specifications. The analysis presented
here establishes the utility of capacitive contacts for four-point
characterizations at low frequency.",1108.5006v1
2011-09-09,Details of Sample Dependence and Transport Properties of URu2Si2,"Resistivity and specific heat measurements were performed in the low carrier
unconventional superconductor URu2Si2 on various samples with very different
qualities. The superconducting transition temperature (TSC) and the hidden
order transition temperature (THO) of these crystals were evaluated as a
function of the residual resistivity ratio (RRR). In high quality single
crystals the resistivity does not seem to follow a T2 dependence above TSC,
indicating that the Fermi liquid regime is restricted to low temperatures.
However, an analysis of the isothermal longitudinal magnetoresistivity points
out that the T2 dependence may be ""spoiled"" by residual inhomogeneous
superconducting contribution. We discuss a possible scenario concerning the
distribution of TSC related with the fact that the hidden order phase is very
sensitive to the pressure inhomogeneity.",1109.1953v1
2011-11-15,Phenomenology of retained refractoriness: On semi-memristive discrete media,"We study two-dimensional cellular automata, each cell takes three states:
resting, excited and refractory. A resting cell excites if number of excited
neighbours lies in a certain interval (excitation interval). An excited cell
become refractory independently on states of its neighbours. A refractory cell
returns to a resting state only if the number of excited neighbours belong to
recovery interval. The model is an excitable cellular automaton abstraction of
a spatially extended semi-memristive medium where a cell's resting state
symbolises low-resistance and refractory state high-resistance. The medium is
semi-memristive because only transition from high- to low-resistance is
controlled by density of local excitation. We present phenomenological
classification of the automata behaviour for all possible excitation intervals
and recovery intervals. We describe eleven classes of cellular automata with
retained refractoriness based on criteria of space-filling ratio, morphological
and generative diversity, and types of travelling localisations.",1111.3525v1
2011-12-06,Homogeneous bilayer graphene film based flexible transparent conductor,"Graphene is considered a promising candidate to replace conventional
transparent conductors due to its low opacity, high carrier mobility and
flexible structure. Multi-layer graphene or stacked single layer graphenes have
been investigated in the past but both have their drawbacks. The uniformity of
multi-layer graphene is still questionable, and single layer graphene stacks
require many transfer processes to achieve sufficiently low sheet resistance.
In this work, bilayer graphene film grown with low pressure chemical vapor
deposition was used as a transparent conductor for the first time. The
technique was demonstrated to be highly efficient in fabricating a conductive
and uniform transparent conductor compared to multi-layer or single layer
graphene. Four transfers of bilayer graphene yielded a transparent conducting
film with a sheet resistance of 180 {\Omega}_{\square} at a transmittance of
83%. In addition, bilayer graphene films transferred onto plastic substrate
showed remarkable robustness against bending, with sheet resistance change less
than 15% at 2.14% strain, a 20-fold improvement over commercial indium oxide
films.",1112.1378v1
2012-04-12,Nonequilibrium quasiparticles and electron cooling by normal metal - superconductor tunnel junctions,"We consider a model NISIN system with two junctions in series, where N is a
normal metal, S is a superconductor and I is an insulator. We assume that the
resistance of the first junction is high, while the resistance of the second
one is low. In this case the first junction cools the left normal electrode,
while the second junction partially removes excited quasiparticles from the
superconductor. We consider cooling properties of this double junction
structure. It is shown that the cooling power depends strongly on the ratio of
the resistances of the two junctions. In conclusion, we derive a generalized
expression for the cooling power of a NIS tunnel junction taking into account
charge imbalance effects.",1204.2719v1
2012-05-31,High-pressure study of non-Fermi liquid and spin-glass-like behavior in CeRhSn,"We present measurements of the temperature dependence of electrical
resistivity of CeRhSn up to ~ 27 kbar. At low temperatures, the electrical
resistivity varies linearly with temperature for all pressures, indicating
non-Fermi liquid behavior. Below a temperature Tf ~ 6 K, the electrical
resistivity deviates from a linear dependence. We found that the
low-temperature feature centered at T = Tf shows a pressure dependence dTf/dP ~
30 mK/kbar which is typical of canonical spin glasses. This interplay between
spin-glass-like and non-Fermi liquid behavior was observed in both CeRhSn and a
Ce0.9La0.1RhSn alloy.",1205.6997v1
2012-07-13,Effect of boron doping in the microwave surface resistance of neutron irradiated melt-textured Y_1.6Ba_2.3Cu_3.3O_7-x samples,"We report on the microwave surface resistance of melt-textured
Y_1.6Ba_2.3Cu_3.3O_7-x samples, doped with different amount of B_2O_3 and,
subsequently, irradiated by thermal neutrons at the fluence of 1.476 \times
10^17 cm^-2. The microwave surface resistance has been measured as a function
of temperature and DC magnetic field. The experimental results are
quantitatively discussed in the framework of the Coffey and Clem theory,
properly adapted to take into account the d-wave nature of cuprate
superconductors. By fitting the experimental data at zero DC field, we have
highlighted the effects of the induced defects in the general properties of the
samples, including the intergranular region. The analysis of the results
obtained at high DC fields allowed us to investigate the fluxon dynamics and
deduce the depinning frequency; in particular, we have shown that the addition
of B_2O_3 up to 0.1 wt% increases the effectiveness of the defects to hinder
the fluxon motion induced by the microwave current.",1207.3306v1
2012-08-31,A Piggyback resistive Micromegas,"A novel read-out architecture has been developed for the Micromegas detector.
The anode element is made of a resistive layer on a ceramic substrate. The
detector part is entirely separated from the read-out element. Without
significant loss, signals are transmitted by capacitive coupling to the
read-out pads. The detector provides high gas gain, good energy resolution and
the resistive layer assures spark protection to the electronics. This assembly
could be combined with modern pixel array electronic ASICs. This readout
organization is free on how the pixels are designed, arranged and connected. We
present first results taken with a MediPix read-out chip.",1208.6525v2
2012-10-18,Design and Simulation of Molecular Nonvolatile Single-Electron Resistive Switches,"We have carried out a preliminary design and simulation of a single-electron
resistive switch based on a system of two linear, parallel,
electrostatically-coupled molecules: one implementing a single-electron
transistor and another serving as a single-electron trap. To verify our design,
we have performed a theoretical analysis of this ""memristive"" device, based on
a combination of ab-initio calculations of the electronic structures of the
molecules and the general theory of single-electron tunneling in systems with
discrete energy spectra. Our results show that such molecular assemblies, with
a length below 10 nm and a footprint area of about 5 nm$^2$, may combine
sub-second switching times with multi-year retention times and high ($> 10^3$)
ON/OFF current ratios, at room temperature. Moreover, Monte Carlo simulations
of self-assembled monolayers (SAM) based on such molecular assemblies have
shown that such monolayers may also be used as resistive switches, with
comparable characteristics and, in addition, be highly tolerant to defects and
stray offset charges.",1210.5253v1
2012-12-11,"Anisotropic magnetization, resistivity and heat capacity of single crystalline R3Ni2-xSn7 (R = La, Ce, Pr and Nd)","We present a detailed study of R3Ni2-xSn7 (R = La, Ce, Pr and Nd) single
crystals by measurements of crystal structure, stoichiometry, temperature
dependent magnetic susceptibility, magnetization, electrical resistivity,
magnetoresistance, and specific heat. This series forms with partial Ni
occupancy with x varying from ~ 0.1 for R = La to ~0.7 for R = Nd. The
electrical resistivity of this series follows metallic behavior at high
temperatures. Determination of clear anisotropies as well as antiferromagnetic
ordering temperatures for R3Ni2-xSn7 (R = Ce, Pr and Nd) have been made. For
Pr3Ni1.56Sn7 and Nd3Ni1.34Sn7, multiple magnetic transitions take place upon
cooling. Metamagnetic transitions in this family (R = Ce, Pr and Nd) were
detected for applied magnetic fields below 70 kOe. An H-T phase diagram of
Ce3Ni1.69Sn7 was assembled to shed light on its low field properties and to
rule out possible quantum critical effects.",1212.2542v1
2013-01-21,Transparent conducting silver nanowire networks,"We present a transparent conducting electrode composed of a periodic
two-dimensional network of silver nanowires. Networks of Ag nanowires are made
with wire diameters of 45-110 nm and pitch of 500, 700 and 1000 nm. Anomalous
optical transmission is observed, with an averaged transmission up to 91% for
the best transmitting network and sheet resistances as low as 6.5 {\Omega}/sq
for the best conducting network. Our most dilute networks show lower sheet
resistance and higher optical transmittance than an 80 nm thick layer of ITO
sputtered on glass. By comparing measurements and simulations we identify four
distinct physical phenomena that govern the transmission of light through the
networks: all related to the excitation of localized surface plasmons and
surface plasmon polaritons on the wires. The insights given in this paper
provide the key guidelines for designing high-transmittance and low-resistance
nanowire electrodes for optoelectronic devices, including thin-film solar
cells. For these latter, we discuss the general design principles to use the
nanowire electrodes also as a light trapping scheme.",1301.4834v1
2013-01-25,The Role of the Equation of State in Resistive Relativistic Magnetohydrodynamics,"We have investigated the role of the equation of state in resistive
relativistic magnetohydrodynamics using a newly developed resistive
relativistic magnetohydrodynamic code. A number of numerical tests in
one-dimension and multi-dimensions are carried out in order to check the
robustness and accuracy of the new code. The code passes all the tests in
situations involving both small and large uniform conductivities. Equations of
state which closely approximate the single-component perfect relativistic gas
are introduced. Results from selected numerical tests using different equations
of state are compared. The main conclusion is that the choice of the equation
of state as well as the value of the electric conductivity can result in
considerable dynamical differences in simulations involving shocks,
instabilities, and magnetic reconnection.",1301.6052v1
2013-01-28,On conditions of negativity of friction resistance for non-stationary modes of blood flow and possible mechanism of affecting of environmental factors on energy effectiveness of cardio-vascular system functioning,"It is shown that initiated by action of molecular viscosity impulse flow,
directed usually from the moving fluid to limiting it solid surface, can, under
certain conditions, turn to zero and get negative values in the case of
non-stationary flow caused by alternating in time longitudinal (along the pipe
axis) pressure gradient. It is noted that this non-equilibrium mechanism of
negative friction resistance in the similar case of pulsating blood flow in the
blood vessels, in addition to the stable to turbulent disturbances swirled
blood flow structure providing, can also constitute hydro-mechanical basis of
the observed but not explained yet paradoxically high energy effectiveness of
the normal functioning of the cardio-vascular system (CVS). We consider
respective mechanism of affecting on the stability of the normal work of CVS by
environmental variable factors using shifting of hydro-dynamic mode with
negative resistance realization range boundaries and variation of linear
hydro-dynamic instability leading to the structurally stable swirled blood flow
organization.",1301.6603v1
2013-02-18,Resistive wall mode and neoclassical tearing mode coupling in rotating tokamak plasmas,"A model system of equations has been derived to describe a toroidally
rotating tokamak plasma, unstable to Resistive Wall Modes (RWMs) and metastable
to Neoclassical Tearing Modes (NTMs), using a linear RWM model and a nonlinear
NTM model. If no wall is present, the NTM growth shows the typical
threshold/saturation island widths, whereas a linearly unstable kink mode grows
exponentially in this model plasma system. When a resistive wall is present,
the growth of the linearly unstable RWM is accelerated by an unstable island: a
form of coupled RWM-NTM mode. Crucially, this coupled system has no threshold
island width, giving the impression of a triggerless NTM, observed in high beta
tokamak discharges. Increasing plasma rotation at the island location can
mitigate its growth, decoupling the modes to yield a conventional RWM with no
threshold width.",1302.4250v2
2013-03-21,On-sample water content measurement for a complete local monitoring in triaxial testing of unsaturated soils,"To provide a complete local monitoring of the state of an unsaturated soil
sample during triaxial testing, a local water content measurement device was
adapted to a triaxial device comprising the measurement of local displacements
(Hall effect transducers) and suction (High capacity transducer). Water content
was locally monitored by means of a resistivity probe. The water
content/resistivity calibration curves of an intact natural unsaturated loess
from Northern France extracted by block sampling at two depths (1 and 3.3 m)
were carefully determined, showing good accuracy and repeatability. The
validity of two models giving the resistivity of unsaturated soils with respect
to their water content was examined.",1303.5348v1
2013-07-02,Structure of Intratumor Heterogeneity: Is Cancer Hedging Its Bets?,"Development of resistance limits transferability of most anticancer therapies
into curative treatment and understanding mechanisms beyond it remains a big
challenge. Many high resolution experimental observations show enormous
intratumor heterogeneity at molecular, genetic and cellular levels which is
made responsible for emerging resistance to therapy. Therefore, researchers
search techniques to influence development of intratumor heterogeneity, which
requires understanding its role within the context of integrative, logically
consistent, framework, such as evolutionary theory. Although it is agreed that
intratumor heterogeneity increases probability of the emergence of therapy
resistant clones, more instructive role of its structure in the process of
cancer dynamics and metastasis is needed. In the paper, intratumor
heterogeneity is viewed as a product of two, in general stochastic, processes,
evolutionary optimization and changing environment, respectively. In
evolutionary theory, common risk-diversifying strategy displayed by isogenic
populations in unpredictably changing environments is bet-hedging. We suggest,
that the structure of intratumor heterogeneity is evolutionary trait evolving
to maximize the clonal fitness in changing (or uncertain) environment and that
its structure corresponds to bet-hedging strategy. We advocate our view by
reviewing and combining important cancer relevant concepts.",1307.0607v1
2013-07-25,Memory Effect and Triplet Pairing Generation in the Superconducting Exchange Biased Co/CoOx/Cu41Ni59/Nb/Cu41Ni59 Layered Heterostructure,"We fabricated a nanolayered hybrid superconductor-ferromagnet spin-valve
structure, the resistive state of which depends on the preceding magnetic field
polarity. The effect is based on a strong exchange bias (about -2 kOe) on a
diluted ferromagnetic copper-nickel alloy and generation of a long range odd in
frequency triplet pairing component. The difference of high and low resistance
states at zero magnetic field is 90% of the normal state resistance for a
transport current of 250 {\mu}A and still around 42% for 10 {\mu}A. Both logic
states of the structure do not require biasing fields or currents in the idle
mode.",1307.6742v1
2013-08-28,Tunneling at $ν_T=1$ in Quantum Hall Bilayers,"Interlayer tunneling measurements in the strongly correlated bilayer
quantized Hall phase at $\nu_T=1$ are reported. The maximum, or critical
current for tunneling at $\nu_T=1$, is shown to be a well-defined global
property of the coherent phase, insensitive to extrinsic circuit effects and
the precise configuration used to measure it, but also exhibiting a surprising
scaling behavior with temperature. Comparisons between the experimentally
observed tunneling characteristics and a recent theory are favorable at high
temperatures, but not at low temperatures where the tunneling closely resembles
the dc Josephson effect. The zero-bias tunneling resistance becomes extremely
small at low temperatures, vastly less than that observed at zero magnetic
field, but nonetheless remains finite. The temperature dependence of this
tunneling resistance is similar to that of the ordinary in-plane resistivity of
the quantum Hall phase.",1308.6269v2
2013-10-22,The Effect of Toroidal Magnetic Field on Thickness of a Viscose-Resistive Hot Accreting Flow,"By taking into account the effect of toroidal magnetic field and its
correspond heating, we determine the thickness of advection-dominated accretion
flows. We consider an axisymetric, rotating, steady viscous-resistive,
magnetized accretion flow under an advection dominated stage. The dominant
mechanism of energy dissipation is assumed to be turbulence viscosity and
magnetic diffusivity. We adopt a self-similar assumption in the radial
direction to obtain the dynamical quantities, that is, radial, azimuthal, sound
and Alfv\' en velocities. Our results show the vertical component of magnetic
force acts in the opposite direction of gravity and compresses the disc, thus
compared with the non-magnetic case, in general the disc half-thikness,
$\Delta\theta$, significantly is reduced. On the other hand, two parameters,
appearing due to action of magnetic field and reaction of the flow, affect the
disc thickness. The first one, $\beta_0$, showing the magnetic field strength
at the equatorial plane, decreases $\Delta\theta$. The other one, $\eta_0$ is
the magnetic resistivity parameter and when it increases, $\Delta\theta$
increases, too.",1310.6317v1
2014-02-13,Theory of measurements of d.c. and a.c. resistivity in anisotropic superconductors in tilted magnetic fields,"The vortex dynamics of uniaxial anisotropic superconductors with arbitrary
angles between the magnetic field, the applied current and the anisotropy axis
is theoretically studied, by focusing on the models for electrical transport
experiments in the linear regime. The vortex parameters, such as the viscous
drag, the vortex mobility and the pinning constant (in the weak point pinning
regime), together with the vortex motion resistivity, are derived in tensor
form by considering the very different free flux flow and pinned Campbell
regimes. The results are extended to high frequency regimes where additional
effects like thermal depinning/creep take place. The applicability to the
various tensor quantities of the well-known scaling laws for the angular
dependence on the field orientation is commented, illustrating when and with
which cautions the scaling approach can be used to discriminate between
intrinsic and extrinsic effects. It is shown that the experiments do not
generally yield the intrinsic values of the vortex parameters and vortex
resistivities. Explicit expressions relating measured and intrinsic quantities
are given and their use exemplified in data analyses of angular measurements.",1402.3164v1
2014-05-05,Colossal negative magnetoresistance in a 2D electron gas,"We report on a colossal negative magnetoresistance (MR) in GaAs/AlGaAs
quantum well which, at low temperatures, is manifested by a drop of the
resistivity by more than an order of magnitude at a magnetic field $B \approx
1$ kG. In contrast to MR effects discussed earlier, the MR reported here is not
parabolic, even at small $B$, and persists to much higher in-plane magnetic
fields and temperatures. Remarkably, the temperature dependence of the
resistivity at $B \approx 1$ kG is linear over the entire temperature range
studied (from 1 to 30 K) and appears to coincide with the high-temperature
limit of the zero-field resistivity, hinting on the important role of acoustic
phonons.",1405.1090v1
2014-09-30,Formation of magnetic moments and resistance upturn at grain boundaries of two-dimensional electron systems,"Electronic correlations control the normal state of bulk high-Tc cuprates.
Strong correlations also suppress the charge transport through cuprate grain
boundaries (GBs). The question then arises if these correlations can produce
magnetic states at cuprate GBs. We analyze the formation of local magnetic
moments at the GB of a correlated two-dimensional electron systems which is
represented by an inhomogeneous Hubbard model. The model Hamiltonian is
diagonalized after the implementation of a mean-field decoupling. The formation
of local magnetic moments is supported by a sufficiently strong variance in the
bond kinetic energies at the GB. Local scattering potentials can assist or
suppress the formation of a magnetic GB state, depending on the details of
their spacial distribution. Grain boundary induced stripes are formed in the
vicinity the GB and decay into the bulk. Moreover, we observe the build-up of
conducting channels which are confined by magnetic clusters. The grain boundary
resistance increases at decreasing temperatures. This low-temperature behavior
is caused by the suppression of current correlations in the state with local
magnetic GB moments. The resistance upturn at low temperatures is in
qualitative agreement with experiments.",1409.8559v1
2014-10-30,Magnetoresistance of layered conductors under conditions of topological phase transition,"The resistance of layered conductors with a multisheet Fermi surface (FS), in
a high magnetic field, in the immediate vicinity of Lifshic's topological
transition when the separate FS sheets are drown together by an external
action, pressure in part (and eventual change of the FS connectivity) is
studied theoretically. Analysis of magnetoresistance near topological
transition is illustrated for the case of FS in the shape of lightly corrugated
cylinder and two corrugated planes distributed with a repeated period in the
pulse space. It yields, that as the FS plane sheets approach sufficiently the
cylinder, the charge carriers produce a magnetic breakdown of one FS sheet to
another, decreasing a sharp anisotropy of magnetoresistance to the in-plane
current. Instead of square increase with a magnetic field, the slower
resistance growth remains linear in the field within a broad magnetic-field
range. In the intimate vicinity of topological transition, when the energy gap
between FS layers is negligibly small, the resistance is saturated.",1410.8330v1
2014-11-10,The Resistive-WELL detector: a compact spark-protected single amplification-stage MPGD,"In this work we present a novel idea for a compact spark-protected single
amplification stage Micro-Pattern Gas Detector (MPGD). The detector
amplification stage, realized with a structure very similar to a GEM foil, is
embedded through a resistive layer in the readout board. A cathode electrode,
defining the gas conversion/drift gap, completes the detector mechanics. The
new structure, that we call Resistive-WELL (R-WELL), has some characteristics
in common with previous MPGDs, such as C.A.T. and WELL, developed more than ten
years ago. The prototype object of the present study has been realized in the
2009 by TE-MPE-EM Workshop at CERN. The new architecture is a very compact
MPGD, robust against discharges and exhibiting a large gain
($\sim$6$\times$10$^3$), simple to construct and easy for engineering and then
suitable for large area tracking devices as well as huge calorimetric apparata.",1411.2466v1
2015-01-01,Fast Generation of Random Spanning Trees and the Effective Resistance Metric,"We present a new algorithm for generating a uniformly random spanning tree in
an undirected graph. Our algorithm samples such a tree in expected
$\tilde{O}(m^{4/3})$ time. This improves over the best previously known bound
of $\min(\tilde{O}(m\sqrt{n}),O(n^{\omega}))$ -- that follows from the work of
Kelner and M\k{a}dry [FOCS'09] and of Colbourn et al. [J. Algorithms'96] --
whenever the input graph is sufficiently sparse.
  At a high level, our result stems from carefully exploiting the interplay of
random spanning trees, random walks, and the notion of effective resistance, as
well as from devising a way to algorithmically relate these concepts to the
combinatorial structure of the graph. This involves, in particular,
establishing a new connection between the effective resistance metric and the
cut structure of the underlying graph.",1501.00267v1
2015-03-16,On Resistive Networks of Constant Power Devices,"This brief examines the behavior of DC circuits comprised of resistively
interconnected constant power devices, as may arise in DC microgrids containing
micro-sources and constant power loads. We derive a sufficient condition for
all operating points of the circuit to lie in a desirable set, where the
average nodal voltage level is high and nodal voltages are tightly clustered
near one another. Our condition has the elegant physical interpretation that
the ratio of resistive losses to total injected power should be small compared
to a measure of network heterogeneity, as quantified by a ratio of conductance
matrix eigenvalues. Perhaps surprisingly, the interplay between the circuit
topology, branch conductances and the constant power devices implicitly defines
a nominal voltage level for the circuit, despite the explicit absence of
voltage-regulated nodes.",1503.04769v1
2015-08-04,"Electron Viscosity, Current Vortices and Negative Nonlocal Resistance in Graphene","Quantum-critical states of diverse strongly correlated systems are predicted
to feature universal collision-dominated transport resembling that of viscous
fluids. However, investigation of these phenomena has been hampered by the lack
of known macroscopic signatures of the hydrodynamic regime at criticality. Here
we identify vorticity as such a signature and link it with an easily verifiable
striking macroscopic transport behavior. Produced by the viscous flow,
vorticity can drive electric current against an applied field, resulting in a
negative nonlocal voltage. We argue that the latter may play the same role for
the viscous regime as zero electrical resistance does for superconductivity.
Besides offering a diagnostic of viscous transport which distinguishes it from
ohmic currents, the sign-changing electrical response affords a robust tool for
directly measuring the viscosity-to-resistivity ratio. The strongly interacting
electron-hole plasma in high-mobility graphene provides a bridge between
quantum-criticality and the wealth of fluid mechanics phenomena.",1508.00836v2
2015-10-13,Charge order and suppression of superconductivity in HgBa2CuO4 at high pressures,"New insight into the superconducting properties of HgBa2CuO4 (Hg-1201)
cuprates is provided by combined measurements of the electrical resistivity and
single crystal X-ray diffraction under pressure. The changes induced by
increasing pressure up to 20GPa in optimally doped single crystals were
investigated. The resistivity measurements as a function of temperature show a
metallic behavior up to ~10GPa that gradually passes to an insulating state,
typical of charge ordering, that totally suppresses superconductivity above
13GPa. The changes in resistivity are accompanied by the apparition of sharp
Bragg peaks in the X-ray diffraction patterns indicating that the charge
ordering is accompanied by a 3D oxygen ordering appearing at 10GPa of
wavevector [0.25, 0, L]. As pressure induces a charge transfer of about 0.02 at
10GPa, our results are the first observation of charge order competing with
superconductivity that develops in the over-doped region of the phase diagram
of a cuprate.",1510.03750v1
2015-11-15,Synchronization of two memristive coupled van der Pol oscillators,"The objective of this paper is to explore the possibility to couple two van
der Pol (vdP) oscillators via a resistance-capacitance (RC) network comprising
a Ag-TiOx-Al memristive device. The coupling was mediated by connecting the
gate terminals of two programmable unijunction transistors (PUTs) through the
network. In the high resistance state (HRS) the memresistance was in the order
of MOhm leading to two independent selfsustained oscillators characterized by
the different frequencies f1 and f2 and no phase relation between the
oscillations. After a few cycles and in dependency of the mediated pulse
amplitude the memristive device switched to the low resistance state (LRS) and
a frequency adaptation and phase locking was observed. The experimental results
are underlined by theoretically considering a system of two coupled vdP
equations. The presented neuromorphic circuitry conveys two essentials
principle of interacting neuronal ensembles: synchronization and memory. The
experiment may path the way to larger neuromorphic networks in which the
coupling parameters can vary in time and strength and are realized by
memristive devices.",1511.06363v1
2015-12-07,Universality of DC Electrical Conductivity from Holography,"We propose a universal formula of dc electrical conductivity in rotational-
and translational- symmetries breaking systems via the holographic duality.
This formula states that the ratio of the determinant of the dc electrical
conductivities along any spatial directions to the black hole area density in
zero-charge limit has a universal value. As explicit illustrations, we give
several examples elucidating the validation of this formula: We construct an
anisotropic black brane solution, which yields linear in temperature for the
in-plane resistivity and insulating behavior for the out-of-plane resistivity;
We also construct a spatially isotropic black brane solution that both the
linear-T and quadratic-T contributions to the resistivity can be realized.",1512.01917v3
2016-01-26,Observation of An Anisotropic Wigner Crystal,"We report a new correlated phase of two-dimensional charged carriers in high
magnetic fields, manifested by an anisotropic insulating behavior at low
temperatures. It appears near Landau level filling factor $\nu=1/2$ in hole
systems confined to wide GaAs quantum wells when the sample is tilted in
magnetic field to an intermediate angle. The parallel field component
($B_{||}$) leads to a crossing of the lowest two Landau levels, and an
elongated hole wavefunction in the direction of $B_{||}$. Under these
conditions, the in-plane resistance exhibits an insulating behavior, with the
resistance along $B_{||}$ more than 10 times smaller than the resistance
perpendicular to $B_{||}$. We interpret this anisotropic insulating phase as a
two-component, striped Wigner crystal.",1601.07135v1
2016-02-05,Investigating Reliability Aspects of Memristor based RRAM with Reference to Write Voltage and Frequency,"In this paper, we report the effect of write voltage and frequency on
memristor based Resistive Random Access Memory (RRAM). The above said
parameters have been investigated on the linear drift model of memristor. With
a variation of write voltage from 0.2V to 1.2V and a subsequent frequency
modulation from 1, 2, 4, 10, 100 and 200 Hz the corresponding effects on memory
window, Low Resistance State (LRS) and High Resistance State (HRS) have been
reported. Thus the lifetime ({\tau}) reliability analysis of memristor based
RRAM is carried out using above results. It is found that, the HRS is
independent of write voltage, whereas LRS shows dependency on write voltage and
frequency. The simulation results showcase that the memristor possess higher
memory window and lifetime ({\tau}) in the higher voltage with lower frequency
region, which has been attributed to the fewer data losses in the memory
architecture.",1602.01947v1
2016-06-23,Device and Circuit Interaction Analysis of Stochastic Behaviors in Cross-Point RRAM Arrays,"Stochastic behaviors of resistive random access memory (RRAM) play an
important role in the design of cross-point memory arrays. A Monte Carlo
compact model of oxide RRAM is developed and calibrated with experiments on
various device stack configurations. With Monte Carlo SPICE simulations, we
show that an increase in array size and interconnect wire resistance will
statistically deteriorate write functionality. Write failure probability (WFP)
has an exponential dependency on device uniformity and supply voltage (VDD),
and the array bias scheme is a key knob. Lowering array VDD leads to higher
effective energy consumption (EEC) due to the increase in WFP when the
variation statistics are included in the analysis. Random-access simulations
indicate that data sparsity statistically benefits write functionality and
energy consumption. Finally, we show that a pseudo-sub-array topology with
uniformly distributed pre-forming cells in the pristine high resistance state
is able to reduce both WFP and EEC, enabling higher net capacity for memory
circuits due to improved variation tolerance.",1606.07457v3
2016-07-05,The Importance of the Electron Mean Free Path for Superconducting RF Cavities,"Impurity-doping is an exciting new technology in the field of SRF, producing
cavities with record-high quality factor $Q_0$ and BCS surface resistance that
decreases with increasing RF field. Recent theoretical work has offered a
promising explanation for this anti-Q-slope, but the link between the
decreasing surface resistance and the short mean free path of doped cavities
has remained elusive. In this work we investigate this link, finding that the
magnitude of this decrease varies directly with the mean free path: shorter
mean free paths correspond with stronger anti-Q-slopes. We draw a theoretical
connection between the mean free path and the overheating of the
quasiparticles, which leads to the reduction of the anti-Q-slope towards the
normal Q-slope of long-mean-free-path cavities. We also investigate the
sensitivity of the residual resistance to trapped magnetic flux, a property
which is greatly enhanced for doped cavities, and calculate an optimal doping
regime for a given amount of trapped flux.",1607.01411v2
2016-08-01,"Graphene-based, mid-infrared, room-temperature pyroelectric bolometers with ultrahigh temperature coefficient of resistance","Graphene is ideally suited for photonic and optoelectronic applications, with
a variety of photodetectors (PDs) in the visible, near-infrared (NIR), and THz
reported to date, as well as thermal detectors in the mid-infrared (MIR). Here,
we present a room temperature-MIR-PD where the pyroelectric response of a
LiNbO3 crystal is transduced with high gain (up to 200) into resistivity
modulation for graphene, leading to a temperature coefficient of resistance up
to 900%/K, two orders of magnitude higher than the state of the art, for a
device area of 300x300um2. This is achieved by fabricating a floating metallic
structure that concentrates the charge generated by the pyroelectric substrate
on the top-gate capacitor of the graphene channel. This allows us to resolve
temperature variations down to 15umK at 1 Hz, paving the way for a new
generation of detectors for MIR imaging and spectroscopy",1608.00569v1
2016-08-07,Anisotropic physical properties and pressure dependent magnetic ordering of CrAuTe$_4$,"Systematic measurements of temperature dependent magnetization, resistivity
and angle-resolved photoemission spectroscopy (ARPES) at ambient pressure as
well as resistivity under pressures up to 5.25 GPa were conducted on single
crystals of CrAuTe$_4$. Magnetization data suggest that magnetic moments are
aligned antiferromagnetically along the crystallographic $c$-axis below
$T_\textrm{N}$ = 255 K. ARPES measurements show band reconstruction due to the
magnetic ordering. Magnetoresistance data show clear anisotropy, and, at high
fields, quantum oscillations. The Neel temperature decreases monotonically
under pressure, decreasing to $T_\textrm{N}$ = 236 K at 5.22 GPa. The pressure
dependencies of (i) $T_\textrm{N}$, (ii) the residual resistivity ratio, and
(iii) the size and power-law behavior of the low temperature magnetoresistance
all show anomalies near 2 GPa suggesting that there may be a phase transition
(structural, magnetic, and/or electronic) induced by pressure. For pressures
higher than 2 GPa a significantly different quantum oscillation frequency
emerges, consistent with a pressure induced change in the electronic states.",1608.02213v2
2016-08-11,Anisotropic and strong negative magneto-resistance in the three-dimensional topological insulator Bi2Se3,"We report on high-field angle-dependent magneto-transport measurements on
epitaxial thin films of Bi2Se3, a three-dimensional topological insulator. At
low temperature, we observe quantum oscillations that demonstrate the
simultaneous presence of bulk and surface carriers. The magneto- resistance of
Bi2Se3 is found to be highly anisotropic. In the presence of a parallel
electric and magnetic field, we observe a strong negative longitudinal
magneto-resistance that has been consid- ered as a smoking-gun for the presence
of chiral fermions in a certain class of semi-metals due to the so-called axial
anomaly. Its observation in a three-dimensional topological insulator implies
that the axial anomaly may be in fact a far more generic phenomenon than
originally thought.",1608.03615v1
2016-08-15,Effect of electrical properties of glass electrodes on the performance of RPC detectors for the INO-ICAL experiment,"The India-based Neutrino Observatory (INO) collaboration has chosen glass
Resistive Plate Chambers (RPCs) as the active detector elements for the Iron
Calorimeter (ICAL) experiment. In the present work, we study the electrical
properties such as bulk resistivity and relative permittivity of the glasses
from two different manufacturers and compared the performances of RPCs built
using these glasses. We conclude that the glass electrodes with larger bulk
resistivy and permittivity are better suited for manufacturing RPCs for the
ICAL experiment, as these detectors could be operated at lower bias currents
and voltages, and produce better time resolutions compared to those built with
glass electrodes of smaller bulk resistivity and permittivity.",1608.04230v1
2016-12-02,Random walk hitting times and effective resistance in sparsely connected Erdős-Rényi random graphs,"We prove expectation and concentration results for the following random
variables on an Erd\H{o}s-R\'enyi random graph $\mathcal{G}\left(n,p\right)$ in
the sparsely connected regime $\log n + \log\log \log n \leq np < n^{1/10}$:
effective resistances, random walk hitting and commute times, the Kirchoff
index, cover cost, random target times, the mean hitting time and Kemeny's
constant. For the effective resistance between two vertices our concentration
result extends further to $np\geq c\log n, \; c>0$. To achieve these results,
we show that a strong connectedness property holds with high probability for
$\mathcal{G}(n,p)$ in this regime.",1612.00731v2
2016-12-26,Analysis of claims that the brain extracellular impedance is high and non-resistive,"Numerous measurements in the brain of the impedance between two extracellular
electrodes have shown that it is approximately resistive in the range of
biological interest, $<10\,$kHz, and has a value close to that expected from
the conductivity of physiological saline and the extracellular volume fraction
in brain tissue. Recent work from the group of Claude B\'edard and Alain
Destexhe has claimed that the impedance of the extracellular space is some
three orders of magnitude greater than these values and also displays a
$1/\sqrt{f}$ frequency dependence (above a low-frequency corner frequency).
Their measurements were performed between an intracellular electrode and an
extracellular electrode. It is argued that they incorrectly extracted the
extracellular impedance because of an inaccurate representation of the large,
confounding impedance of the neuronal membrane. In conclusion, no compelling
evidence has been provided to undermine the well established and physically
plausible consensus that the brain extracellular impedance is low and
approximately resistive",1612.08457v5
2017-02-02,Influence of thermal boundary conditions on the current-driven resistive transition in $\mathbf{VO_2}$ microbridges,"We investigate the resistive switching behaviour of $\mathrm{VO_2}$
microbridges under current bias as a function of temperature and thermal
coupling with the heat bath. Upon increasing the electrical current bias, the
formation of the metallic phase can progress smoothly or through sharp jumps.
The magnitude and threshold current values of these sharp resistance drops show
random behaviour and are dramatically influenced by thermal dissipation
conditions. Our results also evidence how the propagation of the metallic phase
induced by electrical current in $\mathrm{VO_2}$, and thus the shape of the
resulting high-conductivity path, are not predictable. We discuss the origin of
the switching events through a simple electro-thermal model based on the domain
structure of $\mathrm{VO_2}$ films that can be useful to improve the stability
and controllability of future $\mathrm{VO_2}$-based devices.",1702.00805v1
2017-06-05,Enhancement of superconductivity in NbN nanowires by negative electron-beam lithography with positive resist,"We performed comparative experimental investigation of superconducting NbN
nanowires which were prepared by means of positive-and negative electron-beam
lithography with the same positive tone Poly-methyl-methacrylate (PMMA) resist.
We show that nanowires with a thickness 4.9 nm and widths less than 100 nm
demonstrate at 4.2 K higher critical temperature and higher density of critical
and retrapping currents when they are prepared by negative lithography. Also
the ratio of the experimental critical-current to the depairing critical
current is larger for nanowires prepared by negative lithography. We associate
the observed enhancement of superconducting properties with the difference in
the degree of damage that nanowire edges sustain in the lithographic process. A
whole range of advantages which is offered by the negative lithography with
positive PMMA resist ensures high potential of this technology for improving
performance metrics of superconducting nanowire singe-photon detectors.",1706.01289v2
2017-09-26,Timing and Charge measurement of single gap Resistive Plate Chamber Detectors for INO-ICAL Experiment,"The recently approved India-based Neutrino Observatory will use the world's
largest magnet to study atmospheric muon neutrinos. The 50 kiloton Iron
Calorimeter consists of iron alternating with single-gap resistive plate
chambers. A uniform magnetic field of $\sim$1.5 T is produced in the iron using
toroidal-shaped copper coils. Muon neutrinos interact with the iron target to
produce charged muons, which are detected by the resistive plate chambers, and
tracked using orthogonal pick up strips. Timing information for each layer is
used to discriminate between upward and downward traveling muons. The design of
the readout electronics for the detector depends critically on an accurate
model of the charge induced by the muons, and the dependence on bias voltages.
In this paper, we present timing and charge response measurements using
prototype detectors under different operating conditions. We also report the
effect of varying gas mixture, particularly $SF_6$, on the timing response.",1709.08946v1
2017-10-30,Analysis of the measurements of anisotropic a.c. vortex resistivity in tilted magnetic fields,"Measurements of the high-frequency complex resistivity in superconductors are
a tool often used to obtain the vortex parameters, such as the vortex
viscosity, the pinning constant and the depinning frequency. In anisotropic
superconductors, the extraction of these quantities from the measurements faces
new difficulties due to the tensor nature of the electromagnetic problem. The
problem is specifically intricate when the magnetic field is tilted with
respect to the crystallographic axes. Partial solutions exist in the
free-flux-flow (no pinning) and Campbell (pinning dominated) regimes. In this
paper we develop a full tensor model for the vortex motion complex resistivity,
including flux-flow, pinning, and creep. We give explicit expressions for the
tensors involved. We obtain that, despite the complexity of the physics, some
parameters remain scalar in nature. We show that under specific circumstances
the directly measured quantities do not reflect the true vortex parameters, and
we give procedures to derive the true vortex parameters from measurements taken
with arbitrary field orientations. Finally, we discuss the applicability of the
angular scaling properties to the measured and transformed vortex parameters
and we exploit these properties as a tool to unveil the existence of
directional pinning.",1710.11485v1
2018-03-06,Effect of charge ordering on the electrical properties and magnetoresistance of manganites,"The Monte Carlo Ferromagnetic Ising model was used to study the electrical
properties of manganese oxides due to the charge ordering phase occurring at
doping, x = 0.5. The half-doped manganites have an insulator antiferromagnetic
ground state. We calculated the internal energy, specific heat, resistivity and
the magneto-resistance, MR, with parallel and anti-parallel applied magnetic
fields. Our simulation reveals that the resistivity decreases exponentially and
the electric current increases with increasing temperature according the free
charge increase, to transport from an insulator to conductor phase. The
magnetoresistance has negative small values with parallel magnetic field but
has positive high values with unti-parallel magnetic field. The obtained
semiconductor-metal transition behavior candidates the half-doped manganites to
be very good semiconductors diode junctions.",1803.02283v1
2018-05-21,Holographic DC Conductivity for Backreacted Nonlinear Electrodynamics with Momentum Dissipation,"We consider a holographic model with the charge current dual to a general
nonlinear electrodynamics (NLED) field. Taking into account the backreaction of
the NLED field on the geometry and introducing axionic scalars to generate
momentum dissipation, we obtain expressions for DC conductivities with a finite
magnetic field. The properties of the in-plane resistance are examined in
several NLED models. For Maxwell-Chern-Simons electrodynamics, negative
magneto-resistance and Mott-like behavior could appear in some parameter space
region. Depending on the sign of the parameters, we expect the NLED models to
mimic some type of weak or strong interactions between electrons. In the latter
case, negative magneto-resistance and Mott-like behavior can be realized at low
temperatures. Moreover, the Mott insulator to metal transition induced by a
magnetic field is also observed at low temperatures.",1805.07913v2
2018-06-23,Magnetic and magnetoresistive behavior of the ferromagnetic heavy fermion YbNi$_2$,"We present a study on the magnetic susceptibility $\chi(T)$ and electrical
resistance, as a function of temperature and magnetic field $R(T,H)$, of the
ferromagnetic heavy fermion YbNi$_2$. The X-ray diffraction analysis shows that
the synthesized polycrystalline samples crystallizes in the cubic Laves phase
structure C15, with a spatial group $Fd\overline{3}m$. The magnetic
measurements indicate a ferromagnetic behavior with transition temperature at 9
K. The electrical resistance is metallic-like at high temperatures and no
signature of Kondo effect was observed. In the ferromagnetic state, the
electrical resistance can be justified by electron-magnon scattering
considering the existence of an energy gap in the magnonic spectrum. The energy
gap was determined for various applied magnetic fields. Magnetoresistance as a
function of applied magnetic field, subtracted from the $R(T,H)$ curves at
several temperatures, is negative from 2 K until about 40 K for all applied
magnetic fields. The negative magnetoresistance originates from the suppression
of magnetic disorder by the magnetic field.",1806.08881v1
2018-09-17,Resisting Selfish Mining Attacks in the Bicomp,"Selfish mining, which is an attack on the integrity of the Bitcoin network,
was first proposed by Cornell researchers Emin Gun Sirer and Ittay Eyal in
2013. Selfish mining attack also exists in most Nakamoto consensus protocols.
Generally speaking, selfish mining strategy can comprise a Nakamoto consensus
system with less than 25% mining power of the whole system. We have discussed
how the Bicomp can resist selfish mining in our former paper ""Bicomp: A Bilayer
Scalable Nakamoto Consensus Protocol"". In this technical report, we give a
detailed derivation on the conditions a selfish attacker should meet to earn
more revenues through selfish mining. And we also get a conclusion that through
adjusting macroblock difficulties together with tenure lengths, the Bicomp
protocol has high resistant towards selfish mining.",1809.06289v1
2017-03-30,Deep Neural Network Optimized to Resistive Memory with Nonlinear Current-Voltage Characteristics,"Artificial Neural Network computation relies on intensive vector-matrix
multiplications. Recently, the emerging nonvolatile memory (NVM) crossbar array
showed a feasibility of implementing such operations with high energy
efficiency, thus there are many works on efficiently utilizing emerging NVM
crossbar array as analog vector-matrix multiplier. However, its nonlinear I-V
characteristics restrain critical design parameters, such as the read voltage
and weight range, resulting in substantial accuracy loss. In this paper,
instead of optimizing hardware parameters to a given neural network, we propose
a methodology of reconstructing a neural network itself optimized to resistive
memory crossbar arrays. To verify the validity of the proposed method, we
simulated various neural network with MNIST and CIFAR-10 dataset using two
different specific Resistive Random Access Memory (RRAM) model. Simulation
results show that our proposed neural network produces significantly higher
inference accuracies than conventional neural network when the synapse devices
have nonlinear I-V characteristics.",1703.10642v1
2019-02-01,Achieving sub-1 Ohm-mm Non-Recess S/D Contact Resistance in GaN HEMTs Utilizing Simple CMOS Compatible La/Ti/Al/Ti Metal Contacts,"In this paper, we report the use of lanthanum (La) in S/D contacts of GaN
HEMTs, achieving 0.97 Ohm-mm contact resistance without S/D recess. The HEMTs
show well-behaved electrical characteristics and satisfactory reliability. Our
studies show that La, a CMOS compatible metal, is promising to lower GaN HEMT
S/D contact resistance. La's low work function (3.5 eV) is beneficial for
reducing the barrier between the metals and GaN. The Ohmic contact formation
mechanism involved was shown to be different from conventional Ti/Al films.
Spherical-shaped high-La regions formed near the surface during annealing. La
diffuses into the AlGaN layer, and the overlap of La and Al peaks is
significantly increased compared with that before annealing.",1902.00227v1
2019-02-05,Resistive dissipative magnetohydrodynamics from the Boltzmann-Vlasov equation,"We derive the equations of motion of relativistic, resistive, second-order
dissipative magnetohydrodynamics from the Boltzmann-Vlasov equation using the
method of moments. We thus extend our previous work [Phys. Rev. D 98, 076009
(2018)], where we only considered the non-resistive limit, to the case of
finite electric conductivity. This requires keeping terms proportional to the
electric field $E^\mu$ in the equations of motions and leads to new transport
coefficients due to the coupling of the electric field to dissipative
quantities. We also show that the Navier-Stokes limit of the charge-diffusion
current corresponds to Ohm's law, while the coefficients of electrical
conductivity and charge diffusion are related by a type of Wiedemann-Franz law.",1902.01699v1
2019-07-23,Magnetotransport properties of granular oxide-segregated CoPtCr films for applications in future magnetic memory technology,"Magnetotransport properties of granular oxide-segregated CoPtCr films were
studied on both macroscopic and microscopic length scales by performing bulk
and point-contact magnetoresistance measurements, respectively. Such a
perpendicular magnetic medium is used in state-of-the-art hard disc drives and
if combined with magnetoresistive phenomena (for read/write operations) may
lead to a novel concept for magnetic recording with high areal density. While
the bulk measurements on the films showed only small variations in dc
resistance as a function of applied magnetic field (magnetoresistance of less
than 0.02 %), the point-contact measurements revealed
giant-magnetoresistance-like changes in resistance with up to 50,000 % ratios.
The observed magnetorestive effect could be attributed to a tunnel
magnetoresistance between CoPtCr grains with different coercivity. The
tunneling picture of electronic transport in our granular medium was confirmed
by the observation of tunneling-like current-voltage characteristics and bias
dependence of magnetoresistance; both the point-contact resistance and
magnetoresistance were found to decrease with the applied dc bias.",1907.09675v1
2020-02-01,Isotropically conducting (hidden) quantum Hall stripe phases in a two-dimensional electron gas,"Quantum Hall stripe (QHS) phases, predicted by the Hartree-Fock theory, are
manifested in GaAs-based two-dimensional electron gases as giant resistance
anisotropies. Here, we predict a ``hidden'' QHS phase which exhibits
\emph{isotropic} resistivity whose value, determined by the density of states
of QHS, is independent of the Landau index $N$ and is inversely proportional to
the Drude conductivity at zero magnetic field. At high enough $N$, this phase
yields to an Ando-Unemura-Coleridge-Zawadski-Sachrajda phase in which the
resistivity is proportional to $1/N$ and to the ratio of quantum and transport
lifetimes. Experimental observation of this border should allow one to find the
quantum relaxation time.",2002.00154v6
2007-10-25,Simulation Methodology for Analysis of Substrate Noise Impact on Analog / RF Circuits Including Interconnect Resistance,"This paper reports a novel simulation methodology for analysis and prediction
of substrate noise impact on analog / RF circuits taking into account the role
of the parasitic resistance of the on-chip interconnect in the impact
mechanism. This methodology allows investigation of the role of the separate
devices (also parasitic devices) in the analog / RF circuit in the overall
impact. This way is revealed which devices have to be taken care of (shielding,
topology change) to protect the circuit against substrate noise. The developed
methodology is used to analyze impact of substrate noise on a 3 GHz LC-tank
Voltage Controlled Oscillator (VCO) designed in a high-ohmic 0.18 $\mu$m 1PM6
CMOS technology. For this VCO (in the investigated frequency range from DC to
15 MHz) impact is mainly caused by resistive coupling of noise from the
substrate to the non-ideal on-chip ground interconnect, resulting in analog
ground bounce and frequency modulation. Hence, the presented test-case reveals
the important role of the on-chip interconnect in the phenomenon of substrate
noise impact.",0710.4723v1
2014-01-27,Transport near the Ising-nematic quantum critical point of metals in two dimensions,"We consider two-dimensional metals near a Pomeranchuk instability which
breaks 90$^\circ$ lattice rotation symmetry. Such metals realize
strongly-coupled non-Fermi liquids with critical fluctuations of an
Ising-nematic order. At low temperatures, impurity scattering provides the
dominant source of momentum relaxation, and hence a non-zero electrical
resistivity. We use the memory matrix method to compute the resistivity of this
non-Fermi liquid to second order in the impurity potential, without assuming
the existence of quasiparticles. Impurity scattering in the $d$-wave channel
acts as a random ""field"" on the Ising-nematic order. We find contributions to
the resistivity with a nearly linear temperature dependence, along with more
singular terms; the most singular is the random-field contribution which
diverges in the limit of zero temperature.",1401.7012v2
2016-03-21,Spin Hall effects in mesoscopic Pt films with high resistivity,"The energy efficiency of the spin Hall effects (SHE) can be enhanced if the
electrical conductivity is decreased without sacrificing the spin Hall
conductivity. The resistivity of Pt films can be increased to 150-300
{\mu}{\Omega}*cm by mesoscopic lateral confinement, thereby decreasing the
conductivity. The SHE and inverse spin Hall effects (ISHE) in these mesoscopic
Pt films are explored at 10 K by using the nonlocal spin injection/detection
method. All relevant physical quantities are determined in-situ on the same
substrate, and a quantitative approach is developed to characterize all
processes effectively. Extensive measurements with various Pt thickness values
reveal an upper limit for the Pt spin diffusion length: {\lambda}_pt<0.8 nm.
The average product of {\lambda}_pt and the Pt spin Hall angle {\alpha}_H is
substantial: {\alpha}_H*{\lambda}_pt=(0.142 +/- 0.040)nm for 4 nm thick Pt,
though a gradual decrease is observed at larger Pt thickness. The results
suggest enhanced spin Hall effects in resistive mesoscopic Pt films.",1603.06567v3
2017-05-07,Penetration of fast projectiles into resistant media: from macroscopic to subatomic projectiles,"The penetration of a fast projectile into a resistant medium is a complex
process that is suitable for simple modeling, in which basic physical
principles can be profitably employed. This study connects two different
domains: the fast motion of macroscopic bodies in resistant media and the
interaction of charged subatomic particles with matter at high energies, which
furnish the two limit cases of the problem of penetrating projectiles of
different sizes. These limit cases actually have overlapping applications; for
example, in space physics and technology. The intermediate or mesoscopic domain
finds application in atom cluster implantation technology. Here it is shown
that the penetration of fast nano-projectiles is ruled by a slightly modified
Newton's inertial quadratic force, namely, $F \sim v^{2-\beta}$, where $\beta$
vanishes as the inverse of projectile diameter. Factors essential to
penetration depth are ratio of projectile to medium density and projectile
shape.",1705.02337v2
2017-07-07,Resistance distance criterion for optimal slack bus selection,"We investigate the dependence of transmission losses on the choice of a slack
bus in high voltage AC transmission networks. We formulate a transmission loss
minimization problem in terms of slack variables representing the additional
power injection that each generator provides to compensate the transmission
losses. We show analytically that for transmission lines having small,
homogeneous resistance over reactance ratios ${r/x\ll1}$, transmission losses
are generically minimal in the case of a unique \textit{slack bus} instead of a
distributed slack bus. For the unique slack bus scenario, to lowest order in
${r/x}$, transmission losses depend linearly on a resistance distance based
indicator measuring the separation of the slack bus candidate from the rest of
the network. We confirm these results numerically for several IEEE and Pegase
testcases, and show that our predictions qualitatively hold also in the case of
lines having inhomogeneous ${r/x}$ ratios, with optimal slack bus choices
reducing transmission losses by ${10}\%$ typically.",1707.02845v1
2017-07-18,Umklapp scattering as the origin of $T$-linear resistivity in the normal state of high-$T_c$ cuprate superconductors,"The high-temperature normal state of the unconventional cuprate
superconductors has resistivity linear in temperature $T$, which persists to
values well beyond the Mott-Ioffe-Regel upper bound. At low-temperature, within
the pseudogap phase, the resistivity is instead quadratic in $T$, as would be
expected from Fermi liquid theory. Developing an understanding of these normal
phases of the cuprates is crucial to explain the unconventional
superconductivity. We present a simple explanation for this behavior, in terms
of umklapp scattering of electrons. This fits within the general picture
emerging from functional renormalization group calculations that spurred the
Yang-Rice-Zhang ansatz: umklapp scattering is at the heart of the behavior in
the normal phase.",1707.05666v4
2018-08-29,Resistivity of high pressure phosphorus phases,"Simple cubic (sc) black phosphorus (denoted BP), stable at P>10GPa, seems an
ordinary metal. It has electron-phonon-driven superconductivity with Tc 5-10 K.
The A17 phase, stable at atmospheric pressure, has a narrow gap, becomes
semimetallic at P=1 GPa, and has a smooth transition to topological metal
behavior at P ~ 5 GPa. The A7 phase, stable for 5<P<10 GPa, is metallic,
superconducting, and less conventional than the sc phase. Some insights are
extracted from analysis of resistivity versus temperature at various pressures.
A surprising order-of-magnitude disagreement between theory and experiment is
discussed.",1808.09914v2
2019-12-17,Defects Mitigation in Resistive Crossbars for Analog Vector Matrix Multiplication,"With storage and computation happening at the same place, computing in
resistive crossbars minimizes data movement and avoids the memory bottleneck
issue. It leads to ultra-high energy efficiency for data-intensive
applications. However, defects in crossbars severely affect computing accuracy.
Existing solutions, including re-training with defects and redundant designs,
but they have limitations in practical implementations. In this work, we
introduce row shuffling and output compensation to mitigate defects without
re-training or redundant resistive crossbars. We also analyzed the coupling
effects of defects and circuit parasitics. Moreover, We study different
combinations of methods to achieve the best trade-off between cost and
performance. Our proposed methods could rescue up to 10% of defects in
ResNet-20 application without performance degradation.",1912.07829v1
2012-03-08,CensorSpoofer: Asymmetric Communication with IP Spoofing for Censorship-Resistant Web Browsing,"A key challenge in censorship-resistant web browsing is being able to direct
legitimate users to redirection proxies while preventing censors, posing as
insiders, from discovering their addresses and blocking them. We propose a new
framework for censorship-resistant web browsing called {\it CensorSpoofer} that
addresses this challenge by exploiting the asymmetric nature of web browsing
traffic and making use of IP spoofing. CensorSpoofer de-couples the upstream
and downstream channels, using a low-bandwidth indirect channel for delivering
outbound requests (URLs) and a high-bandwidth direct channel for downloading
web content. The upstream channel hides the request contents using
steganographic encoding within email or instant messages, whereas the
downstream channel uses IP address spoofing so that the real address of the
proxies is not revealed either to legitimate users or censors. We built a
proof-of-concept prototype that uses encrypted VoIP for this downstream channel
and demonstrated the feasibility of using the CensorSpoofer framework in a
realistic environment.",1203.1673v2
2012-03-11,Ultrasound and Temperature Study of Non-Equilibrium Phase Transitions in Surface-Bound Liquid Layers,"The present research deals with the registration and study of temperature and
ultrasound parameters of non-equilibrium phase transitions occurring in the
layer ""liquid-solid surface"" in the process of slow heating and cooling of the
medium. Different resistive sensors have been used for taking measurements. As
a result there has been discovered a periodic stepped dependence of the
registered temperature with jumps ~7.5-13 K in water, water solutions and other
liquids. We have studied the conditions under which the stepped temperature
dependence of the resistive sensors indications is synchronous to the resonance
frequency variations of the liquid volume limited by the surface of the axial
piezoelectric resonator. The experiments showed that for studying temperature
transitions and ultrasound phase velocity variations the following conditions
are required: ac field in the area of the liquid surface layer. Assumed cause
of the temperature jumps occurrence is high heat conduction and heat capacity
of the surface-bound layer, causing local temperature variations on the surface
of the resistive sensor in the process of evolution of the two-dimensional
crystal liquid structure. Investigation of non-equilibrium transitions of the
surface-bound liquid layer may be of interest for studying molecular complexes
of liquid media, as well as cellular structures of living systems.",1203.2333v1
2012-06-11,Enhanced Dissipation Rate of Magnetic Field in Striped Pulsar Winds by the Effect of Turbulence,"In this letter we report on turbulent acceleration of the dissipation of
magnetic field in the postshock re- gion of a Poynting flux-dominated flow,
such as the Crab pulsar wind nebula. We have performed two- dimensional
resistive relativistic magnetohydrodynamics simulations of subsonic turbulence
driven by the Richtmyer-Meshkov instability at the shock fronts of the Poynting
flux-dominated flows in pulsar winds. We find that turbulence stretches current
sheets which substantially enhances the dissipation of magnetic field, and that
most of the initial magnetic field energy is dissipated within a few
eddy-turnover times. We also develop a simple analytical model for turbulent
dissipation of magnetic field that agrees well with our simulations. The
analytical model indicates that the dissipation rate does not depend on
resistivity even in the small resistivity limit. Our findings can possibly
alleviate the {\sigma}-problem in the Crab pulsar wind nebulae.",1206.2087v1
2015-04-22,Determination of the Riemann modulus and sheet resistivity by a six-point generalization of the van der Pauw method,"Six point generalization of the van der Pauw method is presented. The method
is applicable for two dimensional homogeneous systems with an isolated hole. A
single measurement performed on the contacts located arbitrarily on the sample
edge allows to determine the specific resistivity and a dimensionless parameter
related to the hole, known as the Riemann modulus. The parameter is invariant
under conformal mappings of the sample shape. The hole can be regarded as a
high resistivity defect. Therefore the method can be applied for experimental
determination of the sample inhomogeneity.",1504.05763v1
2015-07-30,Field-dependent surface resistance of a superconducting RF cavity caused by surface impurity,"Q-slope issue, which is caused by the field dependent surface resistance,
puzzled people for a long time in SRF fields. In this paper, we related the
Q-slope with surface treatments; and proposed a surface-impurity model to
explain the field-dependent of surface resistance of SRF cavities. Eighteen
cavity-test results have been analyzed to examine the model. These cavities
were treated by different recipes: Nitrogen-doping; BCP and HF-rinsing; EP with
120{\deg}C baking; and EP without 120{\deg}C baking. The performance of these
cavities, which is normally represented by cavity quality factor versus
accelerating gradient or surface magnetic field curves (Q0 vs. Eacc or Q0 vs.
B), has included all types of Q-slope, such as Low-field Q-slope, Medium-field
Q-slope, and Anti-Q-slope. The data fittings are quite successful; the fitting
results will be shown. The model can be used to evaluate the effectiveness of
the surface treatments. At last, the paper discussed the way to build a high-Q
high-gradient SRF cavity.",1507.08704v2
2016-09-29,Jet formation in solar atmosphere due to magnetic reconnection,"Using numerical simulations, we show that jets with features of type II
spicules and cold coronal jets corresponding to temperatures $10^{4}$ K can be
formed due to magnetic reconnection in a scenario in presence of magnetic
resistivity. For this we model the low chromosphere-corona region using the C7
equilibrium solar atmosphere model and assuming Resistive MHD rules the
dynamics of the plasma. The magnetic filed configurations we analyze correspond
to two neighboring loops with opposite polarity. The separation of the loops'
feet determines the thickness of a current sheet that triggers a magnetic
reconnection process, and the further formation of a high speed and sharp
structure. We analyze the cases where the magnetic filed strength of the two
loops is equal and different. In the first case, with a symmetric configuration
the spicules raise vertically whereas in an asymmetric configuration the
structure shows an inclination. With a number of simulations carried out under
a 2.5D approach, we explore various properties of excited jets, namely, the
morphology, inclination and velocity. The parameter space involves magnetic
field strength between 20 and 40 G, and the resistivity is assumed to be
uniform with a constant value of the order $10^{-2}\Omega\cdot m$",1609.09422v1
2018-07-03,Design of a New Stream Cipher: PALS,"In this paper, a new stream cipher is designed as a clock-controlled one, but
with a new mechanism of altering steps based on system theory in such a way
that the structures used in it are resistant to conventional attacks. Our
proposed algorithm (PALS) uses the main key with the length of 256 bits and a
32-bit message key. The most important criteria considered in designing the
PALS are resistance to known attacks, maximum period, high linear complexity,
and good statistical properties. As a result, the output keystream is very
similar to the perfectly random sequences and resistant to conventional attacks
such as correlation attacks, algebraic attack, divide & conquer attack,
time-memory tradeoff attack and AIDA/cube attacks. The base structure of the
PALS is a clock-controlled combination generator with memory and we obtained
all the features according to design criteria with this structure. PALS can be
used in many applications, especially in financial cryptography due to its
proper security features",1807.01115v2
2018-12-19,Coherent vs incoherent transport in holographic strange insulators,"Holographic strange metals are known to have a power law resistivity rising
with temperature, which is reminiscent of the strange metal phases in condensed
matter systems. In some holographic models, however, the exponent of the power
law in the resistivity can be negative. In this case one encounters phases with
diverging resistivity at zero temperature: holographic strange insulators.
  These states arise as a result of translational symmetry breaking in the
system, which can either be strong explicit and relevant in the IR, or
spontaneous, but pinned by a small explicit source. In some regards, one can
associate these two classes to the normal band insulators due to the strong
ionic potential, and Mott insulator due to the commensurate lock in of the
charge density wave.
  We study different features of these classes on the explicit example of a
holographic helical model with homogeneous Bianchy VII type translational
symmetry breaking, and uncover the main mechanisms underlying transport in
these two cases. We find that while transport in the explicit relevant case is
governed by the incoherent conductivity, in the pinned spontaneous case the
leading contribution comes from the coherent part.",1812.08132v2
2019-01-21,Possible pressure-induced topological quantum phase transition in the nodal line semimetal ZrSiS,"ZrSiS has recently gained attention due to its unusual electronic properties:
nearly perfect electron-hole compensation, large, anisotropic
magneto-resistance, multiple Dirac nodes near the Fermi level, and an extremely
large range of linear dispersion of up to 2 eV. We have carried out a series of
high pressure electrical resistivity measurements on single crystals of ZrSiS.
Shubnikov-de Haas measurements show two distinct oscillation frequencies. For
the smaller orbit, we observe a change in the phase of 0.5, which occurs
between 0.16 - 0.5 GPa. This change in phase is accompanied by an abrupt
decrease of the cross-sectional area of this Fermi surface. We attribute this
change in phase to a possible topological quantum phase transition. The phase
of the larger orbit exhibits a Berry phase of pi and remains roughly constant
up to 2.3 GPa. Resistivity measurements to higher pressures show no evidence
for pressure-induced superconductivity to at least 20 GPa.",1901.07043v1
2019-06-19,Comment on arXiv:1807.08572: a plausible explanation of the giant diamagnetism found in Au-Ag nanostructures,"In a recent comment (arXiv:1906.05742) on the preprint (arXiv:1807.08572)
entitled ""Coexistence of Diamagnetism and Vanishingly Small Electrical
Resistance at Ambient Temperature and Pressure in Nanostructures"", it is
pointed out that the reduction of the four-probe resistance ($R_{4P}$) to zero
value is accompanied by a rise in the two probe resistance ($R_{2P}$) in the
same temperature range. This curious correlation between $R_{4P}$ and $R_{2P}$
is said to be pointing towards a non-superconducting ""conductance percolation""
transition (rather than ""percolating superconducting transition"" as proposed in
the revised version of arxiv:1807.08572). The explanation offered in preprint
arXiv:1906.05742 is quite reasonable, but the author leaves open the question
of giant diamagnetism. In this short comment I suggest a plausible cause of the
giant diamagnetism found in nanostructures. It could be due to gapped
electronic energy spectrum of nanoparticles which is due to quantum confinement
effects, and that suppresses the electronic scattering mechanism leading to a
very high value of Langevin diamagnetism.",1906.08128v1
2019-10-05,Resistivity anisotropy of quantum Hall stripe phases,"Quantum Hall stripe phases near half-integer filling factors $\nu \ge 9/2$
were predicted by Hartree-Fock (HF) theory and confirmed by discoveries of
giant resistance anisotropies in high-mobility two-dimensional electron gases.
A theory of such anisotropy was proposed by MacDonald and Fisher, although they
used parameters whose dependencies on the filling factor, electron density, and
mobility remained unspecified. Here, we fill this void by calculating the
hard-to-easy resistivity ratio as a function of these three variables.
Quantitative comparison with experiment yields very good agreement which we
view as evidence for the ""plain vanilla"" smectic stripe HF phases.",1910.02260v3
2020-11-27,"Pinning, flux flow resistivity and anisotropy of Fe(Se,Te) thin films from microwave measurements through a bitonal dielectric resonator","We report on the anisotropy of the vortex motion surface impedance of a \fst
thin film grown on a CaF$_2$ substrate. The dependence on the magnetic field
intensity up to 1.2 T and direction, both parallel and perpendicular to the
sample $c$-axis, was explored at fixed temperature at two distinct frequencies,
$\sim16\;$GHz and $\sim27\;$GHz, by means of bitonal dielectric resonator. The
free flux flow resistivity $\rho_{ff}$ was obtained by exploiting standard
models for the high frequency dynamics, whereas the angle dependence was
studied in the framework of the well known and widely used
Blatter-Geshkenbein-Larkin (BGL) scaling theory for anistropic superconductors.
Excellent agreement with the scaling law prescription by the fluxon flux flow
resistivity was obtained. From the scaling analysis, a low-field mass
anisotropy $\sim1.8$ was obtained, well within the value ranges reported in
literature. The angular dependence of the pinning constant suggests that
pinning is dominated by random, isotropic point pins, consistently with
critical current density measurements.",2011.13819v1
2020-12-17,Low temperature $T$-linear resistivity due to umklapp scattering from a critical mode,"We consider the transport properties of a model of fermions scattered by a
critical bosonic mode. The mode is overdamped and scattering is mainly in the
forward direction. Such a mode appears at the quantum critical point for a
electronic nematic phase transition, and in gauge theories for a U(1) spin
liquid. It leads to a short fermion life-time, violating Landau's criterion for
a Fermi liquid. In spite of this, transport can be described by a Boltzmann
equation. We include momentum relaxation by umklapp scattering, supplemented by
weak impurity scattering. We find that above a very low temperature which
scales with $\Delta_q^3$, where $\Delta_q$ is the minimum umklapp scattering
vector, the resistivity is linear in $T$ with a coefficient which is
independent of the amount of disorder. We compare the relaxation time
approximation with an exact numerical solution of the Boltzmann equation.
Surprisingly we find that unlike the resistivity, the Hall Coefficient strongly
deviates from the relaxation time approximation and shows a strong reduction
with increasing temperature. We comment on possible comparisons with
experiments on high $T_c$ Cuprates.",2012.09339v1
2021-06-08,Transport in the 2D Fermi-Hubbard Model: Lessons from Weak Coupling,"We use quantum kinetic theory to calculate the thermoelectric transport
properties of the 2D single band Fermi-Hubbard model in the weak coupling
limit. For generic filling, we find that the high-temperature limiting
behaviors of the electrical ($\sim T$) and thermal ($\sim T^2$) resistivities
persist down to temperatures of order the hopping matrix element $T\sim t$,
almost an order of magnitude below the bandwidth. At half filling, perfect
nesting leads to anomalous low temperature scattering and nearly $T$-linear
electrical resistivity at all temperatures. We hypothesize that the $T$-linear
resistivity observed in recent cold atom experiments is continuously connected
to this weak coupling physics and suggest avenues for experimental
verification. We find a number of other novel thermoelectric results, such as a
low-temperature Wiedemann-Franz law with Lorenz coefficient $5\pi^2/36$.",2106.04479v2
2021-08-12,Spatio-temporal evolution of resistance state in simulated memristive networks,"Originally studied for their suitability to store information compactly,
memristive networks are now being analysed as implementations of neuromorphic
circuits. An extremely high number of elements is thus mandatory. To surpass
the limited achievable connectivity - due to the featuring size - exploiting
self-assemblies has been proposed as an alternative, in turn posing more
challenges. In an attempt for offering insight on what to expect when
characterizing the collective electrical response of switching assemblies, in
this work, networks of memristive elements are simulated. Collective electrical
behaviour and maps of resistance states are characterized upon different
electrical stimuli. By comparing the response of homogeneous and heterogeneous
networks, we delineate differences that might be experimentally observed when
the number of memristive units is scaled up and disorder arises as an
inevitable feature.",2108.05830v2
2021-12-15,Gaining Outlier Resistance with Progressive Quantiles: Fast Algorithms and Theoretical Studies,"Outliers widely occur in big-data applications and may severely affect
statistical estimation and inference. In this paper, a framework of
outlier-resistant estimation is introduced to robustify an arbitrarily given
loss function. It has a close connection to the method of trimming and includes
explicit outlyingness parameters for all samples, which in turn facilitates
computation, theory, and parameter tuning. To tackle the issues of nonconvexity
and nonsmoothness, we develop scalable algorithms with implementation ease and
guaranteed fast convergence. In particular, a new technique is proposed to
alleviate the requirement on the starting point such that on regular datasets,
the number of data resamplings can be substantially reduced. Based on combined
statistical and computational treatments, we are able to perform nonasymptotic
analysis beyond M-estimation. The obtained resistant estimators, though not
necessarily globally or even locally optimal, enjoy minimax rate optimality in
both low dimensions and high dimensions. Experiments in regression,
classification, and neural networks show excellent performance of the proposed
methodology at the occurrence of gross outliers.",2112.08471v3
2022-02-28,Structure from Voltage,"Effective resistance (ER) is an attractive way to interrogate the structure
of graphs. It is an alternative to computing the eigen-vectors of the graph
Laplacian. Graph laplacians are used to find low dimensional structures in high
dimensional data. Here too, ER based analysis has advantages over eign-vector
based methods. Unfortunately Von Luxburg et al. (2010) show that, when vertices
correspond to a sample from a distribution over a metric space, the limit of
the ER between distant points converges to a trivial quantity that holds no
information about the structure of the graph. We show that by using scaling
resistances in a graph with $n$ vertices by $n^2$, one gets a meaningful limit
of the voltages and of effective resistances. We also show that by adding a
""ground"" node to a metric graph one gets a simple and natural way to compute
all of the distances from a chosen point to all other points.",2203.00063v2
2022-03-31,Structural Phase Transition and Possible Valence Instability of Ce$-4f$ Electron Induced by Pressure in CeCoSi,"X-ray powder diffraction and electrical resistivity measurements were
performed on the tetragonal compound CeCoSi under pressure to elucidate the
phase boundary of the pressure-induced structural transition and the change in
the 4$f$ electronic state. The temperature-pressure phase diagram has been
determined from the shift of the Bragg peaks and from the anomaly in the
resistivity. The critical pressure, $P_{\rm s}$ $\sim$ 4.9 GPa at 300 K,
decreases to $P_{\rm s}$ $\sim$ 3.6 GPa at 10 K. The decrease of $P_{\rm s}$ is
due not only to the decrease in volume of the unit cell but also to an
anisotropic shrinkage by cooling. When crossing the boundary to the
high-pressure phase, the resistivity shows a significant drop to exhibit a
metallic temperature dependence. The results of this study strongly suggest
that the structural phase transition can be ascribed to valence instability of
Ce-$4f$ electron.",2203.16817v1
2022-05-05,MMINR: Multi-frame-to-Multi-frame Inference with Noise Resistance for Precipitation Nowcasting with Radar,"Precipitation nowcasting based on radar echo maps is essential in
meteorological research. Recently, Convolutional RNNs based methods dominate
this field, but they cannot be solved by parallel computation resulting in
longer inference time. FCN based methods adopt a multi-frame-to-single-frame
inference (MSI) strategy to avoid this problem. They feedback into the model
again to predict the next time step to get multi-frame nowcasting results in
the prediction phase, which will lead to the accumulation of prediction errors.
In addition, precipitation noise is a crucial factor contributing to high
prediction errors because of its unpredictability. To address this problem, we
propose a novel Multi-frame-to-Multi-frame Inference (MMI) model with Noise
Resistance (NR) named MMINR. It avoids error accumulation and resists
precipitation noise\'s negative effect in parallel computation. NR contains a
Noise Dropout Module (NDM) and a Semantic Restore Module (SRM). NDM
deliberately dropout noise simple yet efficient, and SRM supplements semantic
information of features to alleviate the problem of semantic information
mistakenly lost by NDM. Experimental results demonstrate that MMINR can attain
competitive scores compared with other SOTAs. The ablation experiments show
that the proposed NDM and SRM can solve the aforementioned problems.",2205.02457v1
2022-05-12,Tutorial: Analog Matrix Computing (AMC) with Crosspoint Resistive Memory Arrays,"Matrix computation is ubiquitous in modern scientific and engineering fields.
Due to the high computational complexity in conventional digital computers,
matrix computation represents a heavy workload in many data-intensive
applications, e.g., machine learning, scientific computing, and wireless
communications. For fast, efficient matrix computations, analog computing with
resistive memory arrays has been proven to be a promising solution. In this
Tutorial, we present analog matrix computing (AMC) circuits based on crosspoint
resistive memory arrays. AMC circuits are able to carry out basic matrix
computations, including matrix multiplication, matrix inversion, pseudoinverse
and eigenvector computation, all with one single operation. We describe the
main design principles of the AMC circuits, such as local/global or
negative/positive feedback configurations, with/without external inputs.
Mapping strategies for matrices containing negative values will be presented.
The underlying requirements for circuit stability will be described via the
transfer function analysis, which also defines time complexity of the circuits
towards steady-state results. Lastly, typical applications, challenges, and
future trends of AMC circuits will be discussed.",2205.05853v1
2022-08-17,Silicon sensors with resistive read-out: Machine Learning techniques for ultimate spatial resolution,"Resistive AC-coupled Silicon Detectors (RSDs) are based on the Low Gain
Avalanche Diode (LGAD) technology, characterized by a continuous gain layer,
and by the innovative introduction of resistive read-out. Thanks to a novel
electrode design aimed at maximizing signal sharing, RSD2, the second RSD
production by Fondazione Bruno Kessler (FBK), achieves a position resolution on
the whole pixel surface of about 8 $\mu m$ for 200-$\mu m$ pitch. RSD2 arrays
have been tested using a Transient Current Technique setup equipped with a
16-channel digitizer, and results on spatial resolution have been obtained with
machine learning algorithms.",2208.08294v2
2022-09-27,Clean-limit superconductivity in Im-3m H3S synthesized from sulfur and hydrogen donor ammonia borane,"We present detailed studies of the superconductivity in high-pressure H3S.
X-ray diffraction measurements show that cubic Im-3m H3S was synthesized from
elemental sulfur and hydrogen donor ammonia borane (NH3BH3). Our electrical
transport measurements confirm superconductivity with a transition temperature
Tc = 197 K at 153 GPa. From the analysis of both the normal state resistivity
and the slope of the critical field, we conclude that the superconductivity is
described by clean-limit behaviour. A significant broadening of the resistive
transition in finite magnetic field is found, as expected for superconductors.
We identify a linear temperature-over-field scaling of the resistance at the
superconducting transition which is not described by existing theories.",2209.13299v1
2022-12-02,Hybrid Tunable Magnet Actuator: Modeling and Design,"Reluctance actuators are preferred for high-precision applications. Due to
resistive losses in the coils, the accuracy of this type of actuator will
reduce in quasi-static operation mode within a vacuum environment. By using
soft permanent magnets whose magnetization states are in-situ tuned, no
constant power is needed to create a force and thereby the resistive losses
will reduce. In this paper, a new tuning method is investigated in order to
reduce the resistive losses. By using a history-dependent and non-linear
hysteresis model, a more efficient tuning algorithm is designed. Besides this,
the position accuracy and control simplicity of a variable reluctance tunable
magnet actuator are improved by linearizing the non-linear force-flux
relationship. This is achieved by using bias fluxes generated by hard permanent
magnets.",2212.01242v1
2022-12-14,Magnetic field evolution and reconnection in low resistivity plasmas,"The mathematics and physics of each of the three aspects of magnetic field
evolution -- topology, energy, and helicity -- is remarkably simple and clear.
When the resistivity $\eta$ is small compared to an imposed evolution, $a/v$,
timescale, which means $R_m\equiv\mu_0va/\eta>>1$, magnetic field line chaos
dominates the evolution of field-line topology in three-dimensional systems.
Chaos has no direct role in the dissipation of energy. A large current density,
$j_\eta\equiv vB/\eta$, is required for energy dissipation to be on a
comparable time scale to the topological evolution. Nevertheless, chaos plus
Alfv\'en wave damping explain why both timescales tend to be approximately an
order of magnitude longer than the evolution timescale $a/v$. Magnetic helicity
is injected onto tubes of field lines when boundary flows have vorticity. Chaos
can spread but not destroy magnetic helicity. Resistivity has a negligible
effect on helicity accumulation when $R_m>>1$. Helicity accumulates within a
tube of field lines until the tube erupts and moves far from its original
location.",2212.07487v3
2023-03-30,Partial condensation of mobile excitons in graphene multilayers,"At a large displacement field, in rhomboedral and Bernal-stacked graphene a
normal paramagnetic state transitions to a correlated state. Recent experiments
showed that such systems have several phase transitions as a function of the
carrier density. The phase adjacent to a paramagnetic state has anomalously
high resistance and reduced degeneracy of the Fermi sea. We show that both
phenomena can be explained through a concept of partial intervalley exciton
condensation: a fraction of particles condenses into excitons, and another
forms an intervalley coherent Fermi liquid. The exciton part of the system do
not contribute to the electrical current thus increasing the resistance. Within
this paradigm, the increase in the resistance has entirely geometrical origin.
We check validity of the phenomenological theory through numerical
calculations. We also show that the quantum oscillation data should not be very
different between the partial excitonic state and the intervalley coherent
states suggested by other authors. Further, we suggest STM/AFM or Raman
spectroscopy to have a conclusive evidence for the occurrence of the partial
exciton condensation that we suggest in this paper.",2303.17350v1
2023-05-11,Dendritic Computation through Exploiting Resistive Memory as both Delays and Weights,"Biological neurons can detect complex spatio-temporal features in spiking
patterns via their synapses spread across across their dendritic branches. This
is achieved by modulating the efficacy of the individual synapses, and by
exploiting the temporal delays of their response to input spikes, depending on
their position on the dendrite. Inspired by this mechanism, we propose a
neuromorphic hardware architecture equipped with multiscale dendrites, each of
which has synapses with tunable weight and delay elements. Weights and delays
are both implemented using Resistive Random Access Memory (RRAM). We exploit
the variability in the high resistance state of RRAM to implement a
distribution of delays in the millisecond range for enabling spatio-temporal
detection of sensory signals. We demonstrate the validity of the approach
followed with a RRAM-aware simulation of a heartbeat anomaly detection task. In
particular we show that, by incorporating delays directly into the network, the
network's power and memory footprint can be reduced by up to 100x compared to
equivalent state-of-the-art spiking recurrent networks with no delays.",2305.06941v2
2023-07-26,$N_{\rm eff}$ constraints on light mediators coupled to neutrinos: the dilution-resistant effect,"We investigate the impact of new light particles, carrying significant energy
in the early universe after neutrino decoupling, on the cosmological effective
relativistic neutrino species, $N_{{\rm eff}}$. If the light particles are
produced from decoupled neutrinos, $N_{{\rm eff}}$ is predominantly modified
through the dilution-resistant effect. This effect arises because the energy
stored in the mass of new particles is less diluted than the photon and
neutrino energy as the universe expands. Our study comprehensively explores
this effect, deriving $N_{{\rm eff}}$ constraints on the couplings of light
mediators with neutrinos, encompassing both scalar and vector mediators. We
find that the dilution-resistant effect can increase $N_{{\rm eff}}$ by 0.118
and 0.242 for scalar and vector mediators, respectively. These values can be
readily reached by forthcoming CMB experiments. Upon reaching these levels,
future $N_{{\rm eff}}$ constraints on the couplings will be improved by many
orders of magnitude.",2307.13967v2
2023-08-08,First order transition in Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O ($0.9<x<1.1$) containing Cu$_2$S,"Lee et al. reported that the compound LK99, with a chemical formula of
Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O ($0.9<x<1.1$), exhibits room-temperature
superconductivity under ambient pressure. In this study, we investigated the
transport and magnetic properties of pure Cu$_2$S and LK-99 containing Cu$_2$S.
We observed a sharp superconducting-like transition and a thermal hysteresis
behavior in the resistivity and magnetic susceptibility. However, we did not
observe zero-resistivity below the transition temperature. We argue that the
so-called superconducting behavior in LK-99 is most likely due to a reduction
in resistivity caused by the first order structural phase transition of Cu$_2$S
at around 385 K, from the $\beta$ phase at high temperature to the $\gamma$
phase at low temperature.",2308.04353v1
2023-11-19,Small-area Portable Resistive Plate Chambers for Muography,"Muography is finding applications in various domains such as volcanology,
archaeology, civil engineering, industry, mining, and nuclear waste surveys. To
simplify transportation and installation in remote locations after laboratory
testing, a fully portable and autonomous muon telescope based on Resistive
Plate Chambers (RPCs) is being developed. Two glass-RPC prototypes have been
created, sharing the same design goals but with different detector parameters,
and comparative studies are ongoing. Drawing from prototype experience, a
double-gap RPC with advanced features and improved spatial resolution is
constructed. Resistive electrodes are produced manually, and a new data
acquisition board is currently undergoing calibration. The results on prototype
performance, readout board comparisons and the technical progress on the
double-gap RPC are presented.",2311.11451v1
2023-12-21,Quantum Transport and Spectroscopy of Two-dimensional Perovskite/Graphene Interfaces,"Quantum transport properties in molecularly thin perovskite/graphene
heterostructure are experimentally investigated by Shubnikov-de Hass (SdH)
oscillation and photo-resistance spectroscopy. We find an efficient charge
transfer between the perovskite nanosheets and graphene, with a high hole
concentration in graphene of up to $\rm \sim 2.8 \times 10^{13}\ cm^{-2}$. The
perovskite layer also increases Fermi velocity lowering the effective mass of
graphene from expected $\rm \sim 0.12\ m_e$ to $\rm \sim 0.08\ m_e$. Combining
magneto-resistance and density functional theory calculations, we find that the
carrier density in graphene significantly depends on the perovskite termination
at the interface, affecting the charge transfer process and leading to a
coexistence of regions with different doping. We also investigate the
photo-response of the SdH oscillation under illumination. Using
photo-resistance spectroscopy, we find evidence of photo-assisted transport
across the perovskite layer between two graphene electrodes mediated by hot
carriers in perovskite. Our results provide a picture to understand the
transport behavior of 2D perovskite/graphene heterostructure and a reference
for the controlled design of interfaces in perovskite optoelectronic devices.",2312.13956v1
2023-12-23,A Hybrid Image Encryption Scheme based on Chaos and a DPA-Resistant Sbox,"Image encryption is one of the most common and effective methods to secure
digital images. Recently, Khalid M. Hosny presented an image encryption scheme
based on 6D hyper chaotic mapping and Q-Fibonacci matrix, which, despite its
remarkable theoretical and practical properties, has several weaknesses,
including inaccuracy of black image encryption, inappropriate white image
encryption (improper entropy parameters, correlation, chi-square test,
histogram, UACI, and NPCR), weak keys, inappropriate key usage. In this paper,
based on Khaled Hosny's design, a new effective design is presented that has
improved encryption security and efficiency. In addition, in the proposed
design, a secure key and a substitution box with a high degree of transparency
order, which is resistant to DPA attacks, have been added. Also, a method to
improve transferring chaos parameters is also proposed. The test results show
the improvement of the resistance of the proposed design against the common
attacks of image encryption schemes and improvement in bandwidth consumption.
Also it has been shown that the proposed scheme has produced better results in
terms of both security and efficiency compared to other similar new schemes.",2312.15280v1
2024-02-02,Constructing 100 MΩ and 1 GΩ Resistance Standards via Star-Mesh Transformations,"A recent mathematical framework for optimizing resistor networks to achieve
values in the M{\Omega} through G{\Omega} levels was employed for two specific
cases. Objectives here include proof of concept and identification of possible
apparatus limitations for future experiments involving graphene-based quantum
Hall array resistance standards. Using fractal-like, or recursive, features of
the framework allows one to calculate and implement network designs with
substantially lower-valued resistors. The cases of 100 M{\Omega} and 1
G{\Omega} demonstrate that, theoretically, one would not need more than 100
quantum Hall elements to achieve these high resistances.",2402.01496v1
2024-02-07,Stochastic modeling of Random Access Memories reset transitions,"Resistive Random Access Memories (RRAMs) are being studied by the industry
and academia because it is widely accepted that they are promising candidates
for the next generation of high density nonvolatile memories. Taking into
account the stochastic nature of mechanisms behind resistive switching, a new
technique based on the use of functional data analysis has been developed to
accurately model resistive memory device characteristics. Functional principal
component analysis (FPCA) based on Karhunen-Loeve expansion is applied to
obtain an orthogonal decomposition of the reset process in terms of
uncorrelated scalar random variables. Then, the device current has been
accurately described making use of just one variable presenting a modeling
approach that can be very attractive from the circuit simulation viewpoint. The
new method allows a comprehensive description of the stochastic variability of
these devices by introducing a probability distribution that allows the
simulation of the main parameter that is employed for the model implementation.
A rigorous description of the mathematical theory behind the technique is given
and its application for a broad set of experimental measurements is explained.",2402.05209v1
2024-02-16,Coherent states in microwave-induced resistance oscillations and zero resistance states,"We investigate irradiated high-mobility two-dimensional electron systems
(2DES) under low or moderated magnetic fields. These systems present
microwave-induced magnetoresistance oscillations (MIRO) which, as we
demonstrate, reveal the presence of coherent states of the quantum harmonic
oscillator. We also show that the principle of minimum uncertainty of coherent
states is at the heart of MIRO and zero resistance states (ZRS). Accordingly,
we are able to explain, based on coherent states, important experimental
evidence of these photo-oscillations. Such as their physical origin, their
periodicity with the inverse of the magnetic field and their peculiar
oscillations minima and maxima positions in regards of the magnetic field.
Thus, remarkably enough, we come to the conclusion that 2DES, under low
magnetic fields, become a system of quasiclassical states or coherent states
and MIRO would be the smoking gun of the existence of these peculiar states is
these systems.",2402.11002v1
2024-02-26,Improving the JPEG-resistance of Adversarial Attacks on Face Recognition by Interpolation Smoothing,"JPEG compression can significantly impair the performance of adversarial face
examples, which previous adversarial attacks on face recognition (FR) have not
adequately addressed. Considering this challenge, we propose a novel
adversarial attack on FR that aims to improve the resistance of adversarial
examples against JPEG compression. Specifically, during the iterative process
of generating adversarial face examples, we interpolate the adversarial face
examples into a smaller size. Then we utilize these interpolated adversarial
face examples to create the adversarial examples in the next iteration.
Subsequently, we restore the adversarial face examples to their original size
by interpolating. Throughout the entire process, our proposed method can smooth
the adversarial perturbations, effectively mitigating the presence of
high-frequency signals in the crafted adversarial face examples that are
typically eliminated by JPEG compression. Our experimental results demonstrate
the effectiveness of our proposed method in improving the JPEG-resistance of
adversarial face examples.",2402.16586v1
2024-02-23,Accelerating Dimensionality Reduction in Wave-Resistance Problems through Geometric Operators,"Reducing the dimensionality and uncertainty of design spaces is a key
prerequisite for shape optimisation in computationally intensive fluid
problems. However, running these analyses at an offline stage itself poses a
computationally demanding task. In this work, we propose a unique framework for
the inexpensive implementation of sensitivity analyses for reducing the
dimensionality of the design space in wave-resistance problems. At the heart of
our approach is the formulation of a geometric operator that leverages, via
high-order geometric moments, the underlying connection between geometry and
physics, specifically the wave-resistance coefficient ($C_w$), of ships using
the slender body theory based on the well-known Vossers' integral. The
resulting geometric operator is computationally inexpensive yet
physics-informed and can act as a geometry-based surrogate to drive parametric
sensitivities. To analytically demonstrate the capability of the proposed
approach, we use a well-known benchmark geometry, namely, the modified Wigley
hull. Its simple analytical formulation allows for closed expressions of the
geometric operators and exploration of computational domains that would
otherwise be inaccessible. In this context, the proposed geometric operator
outperforms existing similar approaches by achieving 100% similarity with $C_w$
at a fraction of the computational cost.",2403.06990v1
2024-03-14,Electronic diffusion in a normal state of high-Tc cuprate YBa$_2$Cu$_3$O$_{6+x}$,"The bad metallic phase with resistivity above the Mott-Ioffe-Regel limit,
which appears also in cuprate superconductors, was recently understood by cold
atom and computer simulations of the Hubbard model via charge susceptibility
and charge diffusion constant. However, since reliable simulations can be
typically done only at temperatures above the experimental temperatures, the
question for cuprate superconductors is still open. This paper addresses this
question by resorting to heat transport, which allows for the estimate of
electronic diffusion and it further combines it with the resistivity to
estimate the charge susceptibility. The doping and temperature dependencies of
diffusion constant and charge susceptibilities are shown and discussed for two
samples of YBa$_2$Cu$_3$O$_{6+x}$. Results indicate strongly incoherent
transport, mean free path corresponding to the Mott-Ioffe-Regel limit for the
underdoped sample at temperatures above ~200 K and significant effect of the
charge susceptibility on the resistivity.",2403.09241v1
2024-03-21,On the lineshapes of temperature-dependent transport measurements of superconductors under pressure,"Recent reports of superconductivity in the vicinity of room temperature have
been the subject of discussion by the community. Specifically, features in the
resistance-temperature (R-T) relations have raised questions. We show that many
of these features can arise from previously unaccounted-for dynamic effects
associated with the AC transport techniques often used in high-pressure
experiments. These dynamic AC effects can can cause the apparent resistance
(Rapparent) to diverge from the DC resistance (RDC), sharpen measured
superconducting transitions, and produce other features in the measured R-T
response. We also show that utilizing the full output of phase-sensitive
transport measurements provides a valuable probe of superconducting samples in
difficult to measure systems",2403.14075v2
2024-04-15,SpamDam: Towards Privacy-Preserving and Adversary-Resistant SMS Spam Detection,"In this study, we introduce SpamDam, a SMS spam detection framework designed
to overcome key challenges in detecting and understanding SMS spam, such as the
lack of public SMS spam datasets, increasing privacy concerns of collecting SMS
data, and the need for adversary-resistant detection models. SpamDam comprises
four innovative modules: an SMS spam radar that identifies spam messages from
online social networks(OSNs); an SMS spam inspector for statistical analysis;
SMS spam detectors(SSDs) that enable both central training and federated
learning; and an SSD analyzer that evaluates model resistance against
adversaries in realistic scenarios. Leveraging SpamDam, we have compiled over
76K SMS spam messages from Twitter and Weibo between 2018 and 2023, forming the
largest dataset of its kind. This dataset has enabled new insights into recent
spam campaigns and the training of high-performing binary and multi-label
classifiers for spam detection. Furthermore, effectiveness of federated
learning has been well demonstrated to enable privacy-preserving SMS spam
detection. Additionally, we have rigorously tested the adversarial robustness
of SMS spam detection models, introducing the novel reverse backdoor attack,
which has shown effectiveness and stealthiness in practical tests.",2404.09481v1
2024-04-23,Sharp ill-posedness for the non-resistive MHD equations in Sobolev spaces,"In this paper, we prove a sharp ill-posedness result for the incompressible
non-resistive MHD equations. In any dimension $d\ge 2$, we show the
ill-posedness of the non-resistive MHD equations in
$H^{\frac{d}{2}-1}(\mathbb{R}^d)\times H^{\frac{d}{2}}(\mathbb{R}^d)$, which is
sharp in view of the results of the local well-posedness in
$H^{s-1}(\mathbb{R}^d)\times H^{s}(\mathbb{R}^d)(s>\frac{d}{2})$ established by
Fefferman et al.(Arch. Ration. Mech. Anal., \textbf{223} (2), 677-691, 2017).
Furthermore, we generalize the ill-posedness results from
$H^{\frac{d}{2}-1}(\mathbb{R}^d)\times H^{\frac{d}{2}}(\mathbb{R}^d)$ to Besov
spaces $B^{\frac{d}{p}-1}_{p, q}(\mathbb{R}^d)\times B^{\frac{d}{p}}_{p,
q}(\mathbb{R}^d)$ and $\dot B^{\frac{d}{p}-1}_{p, q}(\mathbb{R}^d)\times \dot
B^{\frac{d}{p}}_{p, q}(\mathbb{R}^d)$ for $1\le p\le\infty, q>1$. Different
from the ill-posedness mechanism of the incompressible Navier-Stokes equations
in $\dot B^{-1}_{\infty, q}$ \cite{B,W}, we construct an initial data such that
the paraproduct terms (low-high frequency interaction) of the nonlinear term
make the main contribution to the norm inflation of the magnetic field.",2404.14825v1
2012-11-05,Structure and Thermodynamical Properties of Zirconium hydrides from first-principle,"Zirconium alloys are used as nuclear fuel cladding material due to their
mechanical and corrosion resistant properties together with their favorable
cross-section for neutron scattering. At running conditions, however, there
will be an increase of hydrogen in the vicinity of the cladding surface at the
water side of the fuel. The hydrogen will diffuse into the cladding material
and at certain conditions, such as lower temperatures and external load,
hydrides will precipitate out in the material and cause well known
embrittlement, blistering and other unwanted effects. Using phase-field methods
it is now possible to model precipitation build-up in metals, for example as a
function of hydrogen concentration, temperature and external load, but the
technique relies on input of parameters, such as the formation energy of the
hydrides and matrix. To that end, we have computed, using the density
functional theory (DFT) code GPAW, the latent heat of fusion as well as solved
the crystal structure for three zirconium hydride polymorphs: \delta-ZrH1.6,
\gamma-ZrH, and \epsilon-ZrH2.",1211.0858v1
2019-05-16,A multi-physics methodology for four-states of matter,"We propose a numerical methodology for the simultaneous numerical simulation
of four states of matter; gas, liquid, elastoplastic solids and plasma. The
distinct, interacting physical processes are described by a combination of
compressible, inert and reactive forms of the Euler equations, multiphase
equations, elastoplastic equations and resistive MHD equations. Combinations of
systems of equations are usually solved by coupling finite element for solid
modelling and CFD models for fluid modelling or including material effects
through boundary conditions rather than full material discretisation. Our
simultaneous solution methodology lies on the recasting of all the equations in
the same, hyperbolic form allowing their solution on the same grid with the
same finite-volume numerical schemes. We use a combination of sharp and diffuse
interface methods to track or capture material interfaces, depending on the
application. The communication between the distinct systems of equations (i.e.,
materials separated by sharp interfaces) is facilitated by means of
mixed-material Riemann solvers at the boundaries of the systems, which
represent physical material boundaries. To this end we derive approximate mixed
Riemann solvers for each pair of the above models based on characteristic
equations. To demonstrate the applicability of the new methodology we consider
a case study where we investigate the possibility of ignition of a combustible
gas that lies over a liquid in a metal container that is struck by a plasma-arc
akin to a lightning strike. We study the effect on the ignition of the metal
container material and conductivity, of the presence of a dielectric coating,
of insensitive combustible gases and sealed and pre-damaged metal surfaces.",1905.06620v1
2017-01-05,Graphene and its elemental analogue: A molecular dynamics view of fracture phenomenon,"Graphene and some graphene like two dimensional materials; hexagonal boron
nitride (hBN) and silicene have unique mechanical properties which severely
limit the suitability of conventional theories used for common brittle and
ductile materials to predict the fracture response of these materials. This
study revealed the fracture response of graphene, hBN and silicene nanosheets
under different tiny crack lengths by molecular dynamics (MD) simulations using
LAMMPS. The useful strength of these large area two dimensional materials are
determined by their fracture toughness. Our study shows a comparative analysis
of mechanical properties among the elemental analogues of graphene and
suggested that hBN can be a good substitute for graphene in terms of mechanical
properties. We have also found that the pre-cracked sheets fail in brittle
manner and their failure is governed by the strength of the atomic bonds at the
crack tip. The MD prediction of fracture toughness shows significant difference
with the fracture toughness determined by Griffth's theory of brittle failure
which restricts the applicability of Griffith's criterion for these materials
in case of nano-cracks. Moreover, the strengths measured in armchair and zigzag
directions of nanosheets of these materials implied that the bonds in armchair
direction has the stronger capability to resist crack propagation compared to
zigzag direction.",1701.01193v2
2022-08-04,Printing on particles: combining two-photon nanolithography and capillary assembly to fabricate multi-material microstructures,"Additive manufacturing at the micro- and nanoscale has seen a recent upsurge
to suit the increasing demand for more elaborate structures. However, the
integration and precise placement of multiple distinct materials at small
scales remain a challenge. To this end, we combine here the directed capillary
assembly of colloidal particles and two-photon direct laser writing (DLW) to
realize a new class of multi-material microstructures. We use DLW both to
fabricate 3D micro-templates to guide the capillary assembly of soft- and hard
colloids, and to link well-defined arrangements of polystyrene or silica
particles produced with capillary assembly, a process we term ""printing on
particles"". The printing process is based on automated particle recognition
algorithms and enables the user to connect colloids into one- and
two-dimensional tailored structures, including particle clusters and lattices
of varying symmetry and composition, using commercial photo-resists (IP-L or
IP-PDMS). Once printed and developed, the structures can be easily harvested
and re-dispersed in water. The flexibility of our method allows the combination
of a wide range of materials into complex structures, which we envisage will
boost the realization of new systems for a broad range of fields, including
microrobotics, micromanipulation and metamaterials.",2208.02635v1
2023-10-28,Making the cut: end effects and the benefits of slicing,"Cutting mechanics in soft solids have been a subject of study for several
decades, an interest fuelled by the multitude of its applications, including
material testing, manufacturing, and biomedical technology. Wire cutting is the
simplest model system to analyze the cutting resistance of a soft material.
However, even for this simple system, the complex failure mechanisms that
underpin cutting are still not completely understood. Several models that
connect the critical cutting force to the radius of the wire and the key
mechanical properties of the cut material have been proposed. An almost
ubiquitous simplifying assumption is a state of plane (and anti-plane) strain
in the material. In this paper, we show that this assumption can lead to
erroneous conclusions because even such a simple cutting problem is essentially
three-dimensional. A planar approximation restricts the analysis to the stress
distribution in the mid-plane. However, through finite element modeling, we
reveal that the maximal tensile stress - and thus the likely location of cut
initiation - is in fact located in the front plane. Friction reduces the
magnitude of this stress, but this detrimental effect can be counteracted by
large slice-to-push (shear-to-indentation) ratios. The introduction of these
end effects helps reconcile a recent controversy around the role of friction in
wire cutting, for it implies that slicing can indeed reduce required cutting
forces, but only if the slice-push ratio and the friction coefficient are
sufficiently large. Material strain-stiffening reduces the critical indentation
depth required to initiate the cut further and thus needs to be considered when
cutting non-linearly elastic materials.",2310.18595v1
1996-06-27,Temperature crossovers in cuprates,"We study the temperature crossovers seen in the magnetic and transport
properties of cuprates using a nearly antiferromagnetic Fermi liquid model
(NAFLM). For the overdoped cuprates, we find, in agreement with earlier work,
mean-field $z=2$ behavior of the magnetic variables associated with the fact
that the damping rate of their spin fluctuations is essentially independent of
temperature, while the resistivity exhibits a crossover from Fermi liquid
behavior at low temperature to linear-in-T above a certain temperature $T_0$,
due to the proximity of the quasiparticle Fermi surface to the magnetic
Brillouin zone boundary. For the underdoped cuprates we argue that the sequence
of crossovers identified by Barzykin and Pines in the low frequency magnetic
behavior (from mean field $z=2$ at high temperatures, $T>T_{cr}$, to
non-universal $z=1$ scaling behavior at intermediate $T$, $T_*<T<T_{cr}$, to
pseudogap behavior below $T_*$) reflects the development in the electronic
structure of a precursor to a spin-density-wave state. This development begins
at $T_{cr}$ with a thermal evolution of the quasiparticle spectral weight which
brings about temperature dependent spin-damping and ends at $T_*$ where the
Fermi surface has lost pieces near corners of the magnetic Brillouin zone. For
$T_*<T<T_{cr}$ the resistivity is linear in $T$ because this change in spectral
weight does not affect the resistivity significantly; below $T_*$ vertex
corrections act to bring about the measured downturn in $(\rho(T)-\rho(0))/T$
and approximately quadratic in $T$ resistivity for $T\ll T_*$.",9606208v3
2000-05-17,Coulomb blockade in one-dimensional arrays of high conductance tunnel junctions,"Properties of one-dimensional (1D) arrays of low Ohmic tunnel junctions (i.e.
junctions with resistances comparable to, or less than, the quantum resistance
$R_{\rm q}\equiv h/e^2\approx 25.8$ k$\Omega$) have been studied experimentally
and theoretically. Our experimental data demonstrate that -- in agreement with
previous results on single- and double-junction systems -- Coulomb blockade
effects survive even in the strong tunneling regime and are still clearly
visible for junction resistances as low as 1 k$\Omega$. We have developed a
quasiclassical theory of electron transport in junction arrays in the strong
tunneling regime. Good agreement between the predictions of this theory and the
experimental data has been observed. We also show that, due to both heating
effects and a relatively large correction to the linear relation between the
half-width of the conductance dip around zero bias voltage, $V_{1/2}$, and the
measured electronic temperature, such arrays are inferior to those
conventionally used in the Coulomb Blockade Thermometry (CBT). Still, the
desired correction to the half-width, $\Delta V_{1/2}$, can be determined
rather easily and it is proportional to the magnitude of the conductance dip
around zero bias voltage, $\Delta G$. The constant of proportionality is a
function of the ratio of the junction and quantum resistances, $R/R_{\rm q}$,
and it is a pure strong tunneling effect.",0005283v1
2001-09-04,Magnetotransport of CeRhIn5,"We report measurements of the temperature-dependent anisotropic resistivity
and in-plane magnetoresistance on single crystals of the tetragonal
heavy-fermion antiferromagnet (TN = 3.8 K) CeRhIn5. The measurements are
reported in the temperature range 1.4 K to 300 K and in magnetic fields to 18
tesla. The resistivity is moderately anisotropic, with a room-temperature
c-axis to in-plane resistivity ratio rho_c/rho_a(300 K) = 1.7. rho(T)
measurements on the non-magnetic analog LaRhIn5 indicate that the anisotropy in
the CeRhIn5 resistivity stems predominately from anisotropy in Kondo-derived
magnetic scattering. In the magnetically ordered regime an applied field H
reduces TN only slightly due to the small ordered moment (0.37mu_B) and
magnetic anisotropy. The magnetoresistance (MR) below TN is positive and varies
linearly with H. In the paramagnetic state a positive MR is present below 7.5
K, while a high-field negative contribution is evident at higher temperatures.
The positive contribution decreases in magnitude with increasing temperature.
Above 40 K the positive contribution is no longer observable, and the MR is
negative. The low-T positive MR results from interactions with the
Kondo-coherent state, while the high-T negative MR stems from single-impurity
effects. The H and T-dependent magnetotransport reflects the magnetic
anisotropy and Kondo interactions at play in CeRhIn5.",0109062v1
2002-07-16,"Resistivity, Hall effect and Shubnikov-de Haas oscillations in CeNiSn","The resistivity and Hall effect in CeNiSn are measured at temperatures down
to 35 mK and in magnetic fields up to 20 T with the current applied along the
{\it b} axis. The resistivity at zero field exhibits quadratic temperature
dependence below $\sim$0.16 K with a huge coefficient of the $T^2$ term (54
$\mu$$\Omega$cm/K$^2$). The resistivity as a function of field shows an
anomalous maximum and dip, the positions of which vary with field directions.
Shubnikov-de Haas (SdH) oscillations with a frequency {\it F} of $\sim$100 T
are observed for a wide range of field directions in the {\it ac} and {\it bc}
planes, and the quasiparticle mass is determined to be $\sim$10-20 {\it m}$_e$.
The carrier density is estimated to be $\sim10^{-3}$ electron/Ce. In a narrow
range of field directions in the {\it ac} plane, where the
magnetoresistance-dip anomaly manifests itself clearer than in other field
directions, a higher-frequency ($F=300\sim400\text{T}$) SdH oscillation is
found at high fields above the anomaly. This observation is discussed in terms
of possible field-induced changes in the electronic structure.",0207379v1
2003-03-03,Systematics in the superconducting and normal state properties in chemically substituted MgB$_{2}$,"The superconducting transition temperature, T$_{C}$, the residual resistivity
$\rho_{0}$ and the slope of resistivity curve at high temperature, d$\rho$/dT,
have been measured in a series of MgB$_{2}$ samples that have been chemically
substituted to varying degree with Li or Cu at the Mg-site and by Li or Cu at
the Mg-site along with C substitution at the B-site. DC resistivity and ac
susceptibility measurements were employed to extract the above parameters.
T$_{C}$ versus the electron count (estimated from simple chemical valence count
arguments) shows a universal behaviour, with T$_{C}$ being constant at the
MgB$_{2}$ value for electron counts lower than in MgB$_{2}$ but rapidly
decreasing for larger electron counts. The temperature dependence of
resistivity in the normal state fits to the Bloch- Gruneisen formula, from
which the Debye temperature, $\theta_{D}$, and the $\rho_{0}$ are extracted.
$\theta_{D}$ variation with T$_{C}$ is not systematic, whereas $\rho_{0}$
versus T$_{C}$ shows a systematic variation that depends on the type of the
chemical substituent. This dependence has a signature of the nature of the
intraband/interband scattering affected by the chemical substitutions.
d$\rho$/dT increases with C substitution, but decreases with Li and Cu
substitution, implying that C substitution leads to the domination of
conductivity by the $\sigma$ band, while in the Li/Cu substituted samples the
$\pi$ band dominates conduction.",0303022v1
2005-05-19,Non-Gaussian Fluctuations in Biased Resistor Networks: Size Effects versus Universal Behavior,"We study the distribution of the resistance fluctuations of biased resistor
networks in nonequilibrium steady states. The stationary conditions arise from
the competition between two stochastic and biased processes of breaking and
recovery of the elementary resistors. The fluctuations of the network
resistance are calculated by Monte Carlo simulations which are performed for
different values of the applied current, for networks of different size and
shape and by considering different levels of intrinsic disorder. The
distribution of the resistance fluctuations generally exhibits relevant
deviations from Gaussianity, in particular when the current approaches the
threshold of electrical breakdown. For two-dimensional systems we have shown
that this non-Gaussianity is in general related to finite size effects, thus it
vanishes in the thermodynamic limit, with the remarkable exception of highly
disordered networks. For these systems, close to the critical point of the
conductor-insulator transition, non-Gaussianity persists in the large size
limit and it is well described by the universal Bramwell-Holdsworth-Pinton
distribution. In particular, here we analyze the role of the shape of the
network on the distribution of the resistance fluctuations. Precisely, we
consider quasi-one-dimensional networks elongated along the direction of the
applied current or trasversal to it. A significant anisotropy is found for the
properties of the distribution. These results apply to conducting thin films or
wires with granular structure stressed by high current densities.",0505478v1
2007-01-05,Colossal electroresistance in ferromagnetic insulating state of single crystal Nd$_0.7$Pb$_0.3$MnO$_3$,"Colossal electroresistance (CER) has been observed in the ferromagnetic
insulating (FMI) state of a manganite. Notably, the CER in the FMI state occurs
in the absence of magnetoresistance (MR). Measurements of electroresistance
(ER) and current induced resistivity switching have been performed in the
ferromagnetic insulating state of a single crystal manganite of composition
Nd$_0.7$Pb$_0.3$MnO$_3$ (NPMO30). The sample has a paramagnetic to
ferromagnetic (Curie) transition temperature, Tc = 150 K and the ferromagnetic
insulating state is realized for temperatures, T <~ 130 K. The colossal
electroresistance, arising from a strongly nonlinear dependence of resistivity
($\rho$) on current density (j), attains a large value ($\approx 100%$) in the
ferromagnetic insulating state. The severity of this nonlinear behavior of
resistivity at high current densities is progressively enhanced with decreasing
temperature, resulting ultimately, in a regime of negative differential
resistivity (NDR, d$\rho$/dj < 0) for temperatures <~ 25 K. Concomitant with
the build-up of the ER however, is a collapse of the MR to a small value (<
20%) even in magnetic field, H = 7 T. This demonstrates that the mechanisms
that give rise to ER and MR are effectively decoupled in the ferromagnetic
insulating phase of manganites. We establish that, the behavior of
ferromagnetic insulating phase is distinct from the ferromagnetic metallic
(FMM) phase as well as the charge ordered insulating (COI) phase, which are the
two commonly realized ground state phases of manganites.",0701090v1
2005-09-05,Distribution of Return Periods of Rare Events in Correlated Time Series,"We study the effect on the distribution of return periods of rare events of
the presence in a time series of finite-term correlations with non-exponential
decay. Precisely, we analyze the auto-correlation function and the statistics
of the return intervals of extreme values of the resistance fluctuations
displayed by a resistor with granular structure in a nonequilibrium stationary
state. The resistance fluctuations, $\delta R$, are calculated by Monte Carlo
simulations using the SBRN model introduced some years ago by Pennetta,
Tref\'an and Reggiani and based on a resistor network approach. A rare event
occurs when $\delta R$ overcomes a threshold value $q$ significantly higher
than the average value of the resistance. We have found that for highly
disordered networks, when the auto-correlation function displays a
non-exponential decay but yet the resistance fluctuations are characterized by
a finite correlation time, the distribution of return intervals of the extreme
values is well described by a stretched exponential, with exponent largely
independent of the threshold $q$. We discuss this result and some of the main
open questions related to it, also in connection with very recent findings by
other authors concerning the observation of stretched exponential distributions
of return intervals of extreme events in long-term correlated time series.",0509037v2
2007-11-08,Study of Intrinsic Spin Hall Effect and Orbital Hall Effect in 4d- and 5d- Transition Metals,"We study the intrinsic spin Hall conductivity (SHC) in various
$5d$-transition metals (Ta, W, Re, Os, Ir, Pt, and Au) and 4d-transition metals
(Nb, Mo, Tc, Ru, Rh, Pd, and Ag) based on the Naval Research Laboratory
tight-binding model, which enables us to perform quantitatively reliable
analysis. In each metal, the obtained intrinsic SHC is independent of
resistivity in the low resistive regime ($\rho < 50 \mu\Omega\text{cm}$)
whereas it decreases in proportion to $\rho^{-2}$ in the high resistive regime.
In the low resistive regime, the SHC takes a large positive value in Pt and Pd,
both of which have approximately nine $d$-electrons per ion ($n_d=9$). On the
other hand, the SHC takes a large negative value in Ta, Nb, W, and Mo where
$n_d<5$. In transition metals, a conduction electron acquires the
trajectory-dependent phase factor that originates from the atomic wavefunction.
This phase factor, which is reminiscent of the Aharonov-Bohm phase, is the
origin of the SHC in paramagnetic metals and that of the anomalous Hall
conductivity in ferromagnetic metals. Furthermore, each transition metal shows
huge and positive $d$-orbital Hall conductivity (OHC), independently of the
strength of the spin-orbit interaction (SOI). Since the OHC is much larger than
the SHC, it will be possible to realize a {\it orbitronics device} made of
transition metals.",0711.1263v4
2008-03-06,Zinc adaptation and resistance to cadmium toxicity in mammalian cells. Molecular insight by proteomic analysis,"To identify proteins involved in cellular adaptive responses to zinc, a
comparative proteome analysis between a previously developed high zinc- and
cadmium- resistant human epithelial cell line (HZR) and the parental HeLa cells
has been carried out. Differentially produced proteins included co-chaperones,
proteins associated with oxido-reductase activities, and ubiquitin. Biochemical
pathways to which these proteins belong were probed for their involvement in
the resistance of both cell lines against cadmium toxicity. Among endoplasmic
reticulum stressors, thapsigargin sensitized HZR cells, but not HeLa cells, to
cadmium toxicity more acutely than tunicamycin, implying that these cells
heavily relied on proper intracellular calcium distribution. The similar
sensitivity of both HeLa and HZR cells to inhibitors of the proteasome, such as
MG-132 or lactacystin, excluded improved proteasome activity as a mechanism
associated with zinc adaptation of HZR cells. The enzyme
4-hydroxyphenylpyruvate dioxygenase was overproduced in HZR cells as compared
to HeLa cells. It transforms 4-hydroxyphenylpyruvate to homogentisate in the
second step of tyrosine catabolism. Inhibition of 4-hydroxyphenylpyruvate
dioxygenase decreased the resistance of HZR cells against cadmium, but not that
of HeLa cells, suggesting that adaptation to zinc overload and increased
4-hydroxyphenylpyruvate removal are linked in HZR cells",0803.0850v1
2008-03-24,Effect of static and dynamic disorder on electronic transport of $RCo_2$ compounds: a study of $Ho(Al_xCo_{1-x})_2$ alloys,"We present experimental results on thermoelectric power ({\em S}) and
electrical resistivity ($\rho $) of pseudobinary alloys
Ho(Al$_x$Co$_{1-x}$)$_2$ ($0 \leq x \leq 0.1 $), in the temperature range 4.2 K
to 300 K. The work focuses on the effects of static (induced by alloying) and
dynamic (induced by temperature) disorder on the magnetic state and electronic
transport in a metallic system with itinerant metamagnetic instability. Spatial
fluctuations of the local magnetic susceptibility in the alloys lead to a
development of a partially ordered magnetic ground state of the itinerant 3d
electron system. This results in a strong increase of the residual resistivity
and a suppression of the temperature-dependent resistivity. Thermopower
exhibits a complex temperature variation in both the magnetically ordered and
in the paramagnetic state. This complex temperature variation is referred to
the electronic density of states features in vicinity of Fermi energy and to
the interplay of magnetic and impurity scattering. Our results indicate that
the magnetic enhancement of the Co 3d-band in RCo$_{\rm 2}$--based alloys upon
a substitution of Co by non-magnetic elements is mainly related to a
progressive localization of the Co -- 3d electrons caused by disorder. We show
that the magnitude of the resistivity jump at the Curie temperature for
RCo$_{\rm 2}$ compounds exhibiting a first order phase transition is a
non-monotonic function of the Curie temperature due to a saturation of the
3d--band spin fluctuation magnitude at high temperatures.",0803.3380v3
2011-05-17,Linear-T scattering and pairing from antiferromagnetic fluctuations in the (TMTSF)_2X organic superconductors,"An exhaustive investigation of metallic electronic transport and
superconductivity of organic superconductors (TMTSF)_2PF_6 and (TMTSF)_2ClO_4
in the Pressure-Temperature phase diagram between T=0 and 20 K and a
theoretical description based on the weak coupling renormalization group method
are reported. The analysis of the data reveals a high temperature domain
(T\approx 20 K) in which a regular T^2 electron-electron Umklapp scattering
obeys a Kadowaki-Woods law and a low temperature regime (T< 8 K) where the
resistivity is dominated by a linear-in temperature component. In both
compounds a correlated behavior exists between the linear transport and the
extra nuclear spin-lattice relaxation due to antiferromagnetic fluctuations. In
addition, a tight connection is clearly established between linear transport
and T_c. We propose a theoretical description of the anomalous resistivity
based on a weak coupling renormalization group determination of
electron-electron scattering rate. A linear resistivity is found and its origin
lies in antiferromagnetic correlations sustained by Cooper pairing via
constructive interference. The decay of the linear resistivity term under
pressure is correlated with the strength of antiferromagnetic spin correlations
and T_c, along with an unusual build-up of the Fermi liquid scattering. The
results capture the key features of the low temperature electrical transport in
the Bechgaard salts.",1105.3322v2
2011-09-18,Vortex glass line and vortex liquid resistivity in doped BaFe2As2 single crystals,"The vortex liquid-to-glass transition has been studied in Ba0.72K0.28Fe2As2,
Ba0.9Co0.1Fe2As2, and Ba(Fe0.45Ni0.05)2As2 single crystal with superconducting
transition temperature, Tc = 31.7, 17.3, and 18 K, respectively, by
magnetoresistance measurements. For temperatures below Tc, the resistivity
curves were measured in magnetic fields within the range of 0 \leq B \leq 13 T,
and the pinning potential was scaled according to a modified model for vortex
liquid resistivity. Good scaling of the resistivity {\rho}(B, T) and the
effective pinning energy U0(B,T) was obtained with the critical exponents s and
B0. The vortex state is three-dimensional at temperatures lower than a
characteristic temperature T*. The vortex phase diagram was determined based on
the evolution of the vortex-glass transition temperature Tg with magnetic field
and the upper critical field, Hc2. We found that non-magnetic K doping results
in a high glass line close to the Hc2, while magnetic Ni and Co doping cause a
low glass line which is far away from the Hc2. Our results suggest that
non-magnetic induced disorder is more favourable for enhancement of pinning
strength compared to magnetic induced disorder. Our results show that the
pinning potential is responsible for the difference in the glass states.",1109.3837v1
2011-10-24,Manifestations of multiple-carrier charge transport in the magnetostructurally ordered phase of undoped BaFe$_2$As$_2$,"We investigated the transport properties of BaFe$_2$As$_2$ single crystals
before and after annealing with BaAs powder. The annealing remarkably improves
transport properties, in particular the magnitude of residual resistivity which
decreases by a factor of more than 10. From the resistivity measurement on
detwinned crystals we found that the anisotropy of the in-plane resistivity is
remarkably diminished after annealing, indicative of dominant contributions to
the charge transport from the carriers with isotropic and high mobility below
magnetostructural transition temperature $T_{\rm s}$ and the absence of nematic
state above $T_{\rm s}$. We found that the Hall resistivity shows strong
non-linearity against magnetic field and the magnetoresistance becomes very
large at low temperatures. These results give evidence for the manifestation of
multiple carriers with distinct characters in the ordered phase below $T_{\rm
s}$. By analyzing the magnetic field dependences, we found that at least three
carriers equally contribute to the charge transport in the ordered phase, which
is in good agreement with the results of recent quantum oscillation
measurements.",1110.5125v3
2012-02-14,Influence of e-e scattering on the temperature dependence of the resistance of a classical ballistic point contact in a two-dimensional electron system,"We experimentally investigate the temperature (T) dependence of the
resistance of a classical ballistic point contact (PC) in a two-dimensional
electron system (2DES). The split-gate PC is realized in a high-quality
AlGaAs/GaAs heterostructure. The PC resistance is found to drop by more than
10% as T is raised from 0.5 K to 4.2 K. In the absence of a magnetic field, the
T dependence is roughly linear below 2 K and tends to saturate at higher T.
Perpendicular magnetic fields on the order of a few 10 mT suppress the
T-dependent contribution dR. This effect is more pronounced at lower
temperatures, causing a crossover to a nearly parabolic T dependence in a
magnetic field. The normalized magnetic field dependencies dR(B) permit an
empiric single parameter scaling in a wide range of PC gate voltages. These
observations give strong evidence for the influence of electron-electron (e-e)
scattering on the resistance of ballistic PCs. Our results are in qualitative
agreement with a recent theory of the e-e scattering based T dependence of the
conductance of classical ballistic PCs [ Phys. Rev. Lett. 101 216807 (2008) and
Phys. Rev. B 81 125316 (2010)].",1202.2952v3
2012-07-06,Universal sheet resistance and revised phase diagram of the cuprate high-temperature superconductors,"Upon introducing charge carriers into the copper-oxygen sheets of the
enigmatic lamellar cuprates the ground state evolves from an insulator into a
superconductor, and eventually into a seemingly conventional metal (a Fermi
liquid). Much has remained elusive about the nature of this evolution and about
the peculiar metallic state at intermediate hole-carrier concentrations (p).
The planar resistivity of this unconventional metal exhibits a linear
temperature dependence (\rho $\propto$ T) that is disrupted upon cooling toward
the superconducting state by the opening of a partial gap (the pseudogap) on
the Fermi surface. Here we first demonstrate for the quintessential compound
HgBa$_2$CuO$_{4+\delta}$ a dramatic switch from linear to purely quadratic
(Fermi-liquid-like, \rho $\propto$ T$^2$) resistive behavior in the pseudogap
regime. Despite the considerable variation in crystal structures and disorder
among different compounds, our result together with prior work gives new
insight into the p-T phase diagram and reveals the fundamental resistance per
copper-oxygen sheet in both linear (\rho_S = A_{1S} T) and quadratic (\rho_S =
A_{2S} T$^2$) regimes, with A_{1S} $\propto$ A_{2S} $\propto$ 1/p. Theoretical
models can now be benchmarked against this remarkably simple universal
behavior. Deviations from this underlying behavior can be expected to lead to
new insights into the non-universal features exhibited by certain compounds.",1207.1504v2
2013-05-14,Differences in the effects of turns and constrictions on the resistive response in current-biased superconducting wire after single photon absorption,"We study how turns and constrictions affect the resistive response of the
superconducting wire after instant in time and local in space heating, which
models the absorption of the single photon by the wire. We find that the
presence of constriction favors detection of photons of various energies but
the presence of turn increases only ability to detect relatively ""low"" energy
photons. The main reason is that in case of constriction the current density is
increased over whole length and width of the constriction while in case of the
turn the current density is enhanced only near the inner corner of the turn. It
results in inhomogeneous Joule heating near the turn and worsens the conditions
for appearance of the normal domain at relatively small currents when the
""high"" energy photons already could create normal domain in straight part of
the wire. We also find that the amplitude of the voltage pulse depends on the
place where the photon is absorbed. It is the smallest one when photon is
absorbed near the turn and it is the largest one when photon is absorbed near
the constriction. This effect comes from the difference in resistance of
constriction and the turn in the normal state from the resistance of the rest
of the wire.",1305.3110v1
2013-05-31,Numerical Treatment of Anisotropic Radiation Field Coupling with the Relativistic Resistive Magnetofluids,"We develop a numerical scheme for solving a fully special relativistic
resistive radiation magnetohydrodynamics. Our code guarantees conservations of
total mass, momentum and energy. Radiation energy density and radiation flux
are consistently updated using the M-1 closure method, which can resolve an
anisotropic radiation fields in contrast to the Eddington approximation as well
as the flux-limited diffusion approximation. For the resistive part, we adopt a
simple form of the Ohm's law. The advection terms are explicitly solved with an
approximate Riemann solver, mainly HLL scheme, and HLLC and HLLD schemes for
some tests. The source terms, which describe the gas-radiation interaction and
the magnetic energy dissipation, are implicitly integrated, relaxing the
Courant-Friedrichs-Lewy condition even in optically thick regime or a large
magnetic Reynolds number regime. Although we need to invert $4\times 4$ (for
gas-radiation interaction) and $3\times 3$ (for magnetic energy dissipation)
matrices at each grid point for implicit integration, they are obtained
analytically without preventing massive parallel computing. We show that our
code gives reasonable outcomes in numerical tests for ideal
magnetohydrodynamics, propagating radiation, and radiation hydrodynamics. We
also applied our resistive code to the relativistic Petschek type magnetic
reconnection, revealing the reduction of the reconnection rate via the
radiation drag.",1306.0049v1
2014-02-06,Scattering mechanisms in textured FeGe thin films: magnetoresistance and the anomalous Hall effect,"A textured thin film of FeGe was grown by magnetron sputtering with a
helimagnetic ordering temperature of TN = 276 +/- 2 K. From 5 K to room
temperature a variety of scattering processes contribute towards the overall
longitudinal and Hall resistivities. These were studied by combining
magnetometry and magnetotransport measurements. The high-field
magnetoresistance (MR) displays three clear temperature regimes: Lorentz force
MR dominates at low temperatures, above T ~ 80 K scattering from spin-waves
predominates, whilst finally for T > 200 K scattering from fluctuating local
moments describes the MR. At low fields, where the magnetisation is no longer
technically saturated, we find a scaling of magnetoresistance with the square
of the magnetisation, indicating that the MR due to the unwinding of spins in
the conical phase arises from a similar mechanism to that in magnetic domain
walls. This MR is only visible up to a temperature of about 200 K. No features
can be found in the temperature or field dependence of the longitudinal
resistivity that belie the presence of the underlying magnetic phase transition
at TN: the marked changes in behavior are at much lower temperatures. The
anomalous Hall effect has a dramatic temperature dependence in which the
anomalous Hall resistivity scales quadratically with the longitudinal
resistivity: comparison with anomalous Hall scaling theory shows that our
system is in the intrinsic 'moderately dirty' regime. Lastly, we find evidence
of a topological Hall effect of size 100 ~Ohm cm.",1402.1276v2
2014-05-16,Extracting superconducting parameters from surface resistivity by using inside temperatures of SRF cavities,"The surface resistance of an RF superconductor depends on the surface
temperature, the residual resistance and various superconductor parameters,
e.g. the energy gap, and the electron mean free path. These parameters can be
determined by measuring the quality factor Q0 of a SRF cavity in helium-baths
of different temperatures. The surface resistance can be computed from Q0 for
any cavity geometry, but it is not trivial to determine the temperature of the
surface when only the temperature of the helium bath is known.
  Traditionally, it was approximated that the surface temperature on the inner
surface of the cavity was the same as the temperature of the helium bath. This
is a good approximation at small RF-fields on the surface, but to determine the
field dependence of Rs, one cannot be restricted to small field losses.
  Here we show the following: (1) How computer simulations can be used to
determine the inside temperature Tin so that Rs(Tin) can then be used to
extract the superconducting parameters. The computer code combines the
well-known programs, the HEAT code and the SRIMP code. (2) How large an error
is created when assuming the surface temperature is same as the temperature of
the helium bath? It turns out that this error is at least 10% at high RF-fields
in typical cases.",1405.4226v1
2014-05-23,Evolution of Anisotropic In-plane Resistivity with doping level in Ca$_{1-x}$Na$_x$Fe$_2$As$_2$ Single Crystals,"We measured the in-plane resistivity anisotropy in the underdoped
Ca$_{1-x}$Na$_x$Fe$_2$As$_2$ single crystals. The anisotropy (indicated by
$\rho_{\rm b} - \rho_{\rm a}$) appears below a temperature well above magnetic
transition temperature $T_{\rm N}$, being positive ($\rho_{\rm b} - \rho_{\rm
a} > 0$) as $x\leq$ 0.14. With increasing the doping level to $x$ = 0.19, an
intersection between $\rho_{\rm b}$ and $\rho_{\rm a}$ is observed upon
cooling, with $\rho_{\rm b} - \rho_{\rm a} < 0$ at low-temperature deep inside
a magnetically ordered state, while $\rho_{\rm b} - \rho_{\rm a}> 0$ at high
temperature. Subsequently, further increase of hole concentration leads to a
negative anisotropy $\rho_{\rm b} - \rho_{\rm a} < 0$ in the whole temperature
range. These results manifest that the anisotropic behavior of resistivity in
the magnetically ordered state depends strongly on the competition of the
contributions from different mechanisms, and the competition between the two
contributions results in a complicated evolution of the anisotropy of in-plane
resistivity with doping level.",1405.6199v1
2014-10-08,A Complementary Resistive Switch-based Crossbar Array Adder,"Redox-based resistive switching devices (ReRAM) are an emerging class of
non-volatile storage elements suited for nanoscale memory applications. In
terms of logic operations, ReRAM devices were suggested to be used as
programmable interconnects, large-scale look-up tables or for sequential logic
operations. However, without additional selector devices these approaches are
not suited for use in large scale nanocrossbar memory arrays, which is the
preferred architecture for ReRAM devices due to the minimum area consumption.
To overcome this issue for the sequential logic approach, we recently
introduced a novel concept, which is suited for passive crossbar arrays using
complementary resistive switches (CRSs). CRS cells offer two high resistive
storage states, and thus, parasitic sneak currents are efficiently avoided.
However, until now the CRS-based logic-in-memory approach was only shown to be
able to perform basic Boolean logic operations using a single CRS cell. In this
paper, we introduce two multi-bit adder schemes using the CRS-based
logic-in-memory approach. We proof the concepts by means of SPICE simulations
using a dynamical memristive device model of a ReRAM cell. Finally, we show the
advantages of our novel adder concept in terms of step count and number of
devices in comparison to a recently published adder approach, which applies the
conventional ReRAM-based sequential logic concept introduced by Borghetti et
al.",1410.2031v2
2014-10-13,Resistant Multiple Sparse Canonical Correlation,"Canonical Correlation Analysis (CCA) is a multivariate technique that takes
two datasets and forms the most highly correlated possible pairs of linear
combinations between them. Each subsequent pair of linear combinations is
orthogonal to the preceding pair, meaning that new information is gleaned from
each pair. By looking at the magnitude of coefficient values, we can find out
which variables can be grouped together, thus better understanding multiple
interactions that are otherwise difficult to compute or grasp intuitively.
  CCA appears to have quite powerful applications to high throughput data, as
we can use it to discover, for example, relationships between gene expression
and gene copy number variation. One of the biggest problems of CCA is that the
number of variables (often upwards of 10,000) makes biological interpretation
of linear combinations nearly impossible. To limit variable output, we have
employed a method known as Sparse Canonical Correlation Analysis (SCCA), while
adding estimation which is resistant to extreme observations or other types of
deviant data. In this paper, we have demonstrated the success of resistant
estimation in variable selection using SCCA. Additionally, we have used SCCA to
find multiple canonical pairs for extended knowledge about the datasets at
hand. Again, using resistant estimators provided more accurate estimates than
standard estimators in the multiple canonical correlation setting.
  R code is available and documented at https://github.com/hardin47/rmscca.",1410.3355v2
2014-12-19,Magnetoresistance near a quantum critical point,"In metals near a quantum critical point, the electrical resistance is thought
to be determined by the lifetime of the carriers of current, rather than the
scattering from defects. The observation of $T$-linear resistivity suggests
that the lifetime only depends on temperature, implying the vanishing of an
intrinsic energy scale and the presence of a quantum critical point. Our data
suggest that this concept extends to the magnetic field dependence of the
resistivity in the unconventional superconductor
BaFe$_2$(As$_{1-x}$P$_{x}$)$_2$ near its quantum critical point. We find that
the lifetime depends on magnetic field in the same way as it depends on
temperature, scaled by the ratio of two fundamental constants $\mu_B/k_B$.
These measurements imply that high magnetic fields probe the same quantum
dynamics that give rise to the $T$-linear resistivity, revealing a novel kind
of magnetoresistance that does not depend on details of the Fermi surface, but
rather on the balance of thermal and magnetic energy scales. This opens new
opportunities for the investigation of transport near a quantum critical point
by using magnetic fields to couple selectively to charge, spin and spatial
anisotropies.",1412.6484v2
2015-08-14,Lattice Boltzmann model for resistive relativistic magnetohydrodynamics,"In this paper, we develop a lattice Boltzmann model for relativistic
magnetohydrodynamics (MHD). Even though the model is derived for resistive MHD,
it is shown that it is numerically robust even in the high conductivity (ideal
MHD) limit. In order to validate the numerical method, test simulations are
carried out for both ideal and resistive limits, namely the propagation of
Alfv\'en waves in the ideal MHD and the evolution of current sheets in the
resistive regime, where very good agreement is observed comparing to the
analytical results. Additionally, two-dimensional magnetic reconnection driven
by Kelvin-Helmholtz instability is studied and the effects of different
parameters on the reconnection rate are investigated. It is shown that the
density ratio has negligible effect on the magnetic reconnection rate, while an
increase in shear velocity decreases the reconnection rate. Additionally, it is
found that the reconnection rate is proportional to $\sigma^{-\frac{1}{2}}$,
$\sigma$ being the conductivity, which is in agreement with the scaling law of
the Sweet-Parker model. Finally, the numerical model is used to study the
magnetic reconnection in a stellar flare. Three-dimensional simulation suggests
that the reconnection between the background and flux rope magnetic lines in a
stellar flare can take place as a result of a shear velocity in the
photosphere.",1508.03452v1
2015-10-12,First in-beam studies of a Resistive-Plate WELL gaseous multiplier,"We present the results of the first in-beam studies of a medium size
(10$\times$10 cm$^2$) Resistive-Plate WELL (RPWELL): a single-sided THGEM
coupled to a pad anode through a resistive layer of high bulk resistivity
($\sim$10$^9 \Omega$cm). The 6.2~mm thick (excluding readout electronics)
single-stage detector was studied with 150~GeV muons and pions. Signals were
recorded from 1$\times$1 cm$^2$ square copper pads with APV25-SRS readout
electronics. The single-element detector was operated in Ne\(5%
$\mathrm{CH_{4}}$) at a gas gain of a few times 10$^4$, reaching 99$\%$
detection efficiency at average pad multiplicity of $\sim$1.2. Operation at
particle fluxes up to $\sim$10$^4$ Hz/cm$^2$ resulted in $\sim$23$\%$ gain drop
leading to $\sim$5$\%$ efficiency loss. The striking feature was the
discharge-free operation, also in intense pion beams. These results pave the
way towards robust, efficient large-scale detectors for applications requiring
economic solutions at moderate spatial and energy resolutions.",1510.03116v2
2016-04-14,Magnetotransport of single crystalline YSb,"We report magnetic field dependent transport measurements on a single crystal
of cubic YSb together with first principles calculations of its electronic
structure. The transverse magnetoresistance does not saturate up to 9 T and
attains a value of 75,000 % at 1.8 K. The Hall coefficient is electron-like at
high temperature, changes sign to hole-like between 110 and 50 K, and again
becomes electron-like below 50 K. First principles calculations show that YSb
is a compensated semimetal with a qualitatively similar electronic structure to
that of isostructural LaSb and LaBi, but with larger Fermi surface volume. The
measured electron carrier density and Hall mobility calculated at 1.8 K, based
on a single band approximation, are 6.5$\times10^{20}/$cm$^{3}$ and
6.2$\times10^{4}$cm$^{2}$/Vs, respectively. These values are comparable with
those reported for LaBi and LaSb. Like LaBi and LaSb, YSb undergoes a magnetic
field-induced metal-insulator-like transition below a characteristic
temperature T$_{m}$, with resistivity saturation below 13 K. Thickness
dependent electrical resistance measurements show a deviation of the resistance
behavior from that expected for a normal metal; however, they do not
unambiguously establish surface conduction as the mechanism for the resistivity
plateau.",1604.04232v1
2017-02-14,A magnetic skyrmion as a non-linear resistive element - a potential building block for reservoir computing,"Inspired by the human brain, there is a strong effort to find alternative
models of information processing capable of imitating the high energy
efficiency of neuromorphic information processing. One possible realization of
cognitive computing are reservoir computing networks. These networks are built
out of non-linear resistive elements which are recursively connected. We
propose that a skyrmion network embedded in frustrated magnetic films may
provide a suitable physical implementation for reservoir computing
applications. The significant key ingredient of such a network is a
two-terminal device with non-linear voltage characteristics originating from
single-layer magnetoresistive effects, like the anisotropic magnetoresistance
or the recently discovered non-collinear magnetoresistance. The most basic
element for a reservoir computing network built from ""skyrmion fabrics"" is a
single skyrmion embedded in a ferromagnetic ribbon. In order to pave the way
towards reservoir computing systems based on skyrmion fabrics, here we simulate
and analyze i) the current flow through a single magnetic skyrmion due to the
anisotropic magneto-resistive effect and ii) the combined physics of local
pinning and the anisotropic magneto-resistive effect.",1702.04298v2
2017-06-15,MAGNUS: A new resistive MHD code with heat flow terms,"We present a new magnetohydrodynamic (MHD) code for the simulation of wave
propagation in the solar atmosphere, under the effects of electrical
resistivity, but not dominant, and heat transference in a uniform 3D grid. The
code is based on the finite volume method combined with the HLLE and HLLC
approximate Riemann solvers, which use different slope limiters like MINMOD,
MC, and WENO5. In order to control the growth of the divergence of the magnetic
field, due to numerical errors, we apply the Flux Constrained Transport method,
which is described in detail to understand how the resistive terms are included
in the algorithm. In our results, it is verified that this method preserves the
divergence of the magnetic fields within the machine round-off error. For the
validation of the accuracy and efficiency of the schemes implemented in the
code, we present some numerical tests in 1D and 2D for the ideal MHD. Later, we
show one test for the resistivity in a magnetic reconnection process and one
for the thermal conduction, where the temperature is advected by the magnetic
field lines. Moreover, we display two numerical problems associated with the
MHD wave propagation. The first one corresponds to a 3D evolution of a vertical
velocity pulse at the photosphere-transition-corona region, while the second
one consists in a 2D simulation of a transverse velocity pulse in a coronal
loop.",1706.05110v1
2018-02-06,Radiation resistant LGAD design,"In this paper, we report on the radiation resistance of 50-micron thick LGAD
detectors manufactured at the Fondazione Bruno Kessler employing several
different doping combinations of the gain layer. LGAD detectors with gain layer
doping of Boron, Boron low-diffusion, Gallium, Carbonated Boron and Carbonated
Gallium have been designed and successfully produced. These sensors have been
exposed to neutron fluences up to $\phi_n \sim 3 \cdot 10^{16}\; n/cm^2$ and to
proton fluences up to $\phi_p \sim 9\cdot10^{15}\; p/cm^2$ to test their
radiation resistance. The experimental results show that Gallium-doped LGADs
are more heavily affected by initial acceptor removal than Boron-doped LGAD,
while the presence of Carbon reduces initial acceptor removal both for Gallium
and Boron doping. Boron low-diffusion shows a higher radiation resistance than
that of standard Boron implant, indicating a dependence of the initial acceptor
removal mechanism upon the implant width. This study also demonstrates that
proton irradiation is at least twice more effective in producing initial
acceptor removal, making proton irradiation far more damaging than neutron
irradiation.",1802.01745v4
2018-04-14,Non-resistive dissipative magnetohydrodynamics from the Boltzmann equation in the 14-moment approximation,"We derive the equations of motion of relativistic, non-resistive,
second-order dissipative magnetohydrodynamics from the Boltzmann equation using
the method of moments. We assume the fluid to be composed of a single type of
point-like particles with vanishing dipole moment or spin, so that the fluid
has vanishing magnetization and polarization. In a first approximation, we
assume the fluid to be non-resistive, which allows to express the electric
field in terms of the magnetic field. We derive equations of motion for the
irreducible moments of the deviation of the single-particle distribution
function from local thermodynamical equilibrium. We analyze the Navier-Stokes
limit of these equations, reproducing previous results for the structure of the
first-order transport coefficients. Finally, we truncate the system of
equations for the irreducible moments using the 14-moment approximation,
deriving the equations of motion of relativistic, non-resistive, second-order
dissipative magnetohydrodynamics. We also give expressions for the new
transport coefficients appearing due to the coupling of the magnetic field to
the dissipative quantities.",1804.05210v2
2018-03-30,"Linearity Analysis of the Common Collector Amplifier, or Emitter Follower","A recently introduced Early modeling of transistors is applied to the study
of the common collector amplifier (or emitter follower), an important type of
electronic circuit typically employed as buffer, being characterized by near
unit voltage gain, high input resistance, and low output resistance. The Early
equivalent model is applied to derive a simple representation that is simple
and yet capable of incorporating the transistor non-linearities implied by the
Early effect. Mathematical expressions are obtained describing completely the
circuit operation in terms of currents and voltages, allowing accurate
estimation of the average voltage gain, total harmonic distortion (THD), and
average input and output resistances. Prototypes of small signal silicon
transistors of types NPN and PNP obtained in a previous work are used to
discuss the respectively implied properties of the common collector transistor.
In addition to confirming the importance of the trade-off of current gain for
the desired properties, it is also shown that sub-optimal performance can be
obtained in case the base and emitter resistances are not properly chosen. Even
so, the limited current gain implied by real-world NPN and PNP small signal
silicon devices implies some performance constraints. In particular, it has
been observed that the THD tends to be larger for PNP devices than NPN
counterparts with the same average current gain. The obtained results pave the
way not only to complementary analytical studies, but also provide guidance for
design and implementation of improved common collector configurations.",1805.02705v1
2018-11-23,Oxygen vacancies dynamics in redox-based interfaces: Tailoring the memristive response,"Redox-based memristive devices are among the alternatives for the next
generation of non volatile memories, but also candidates to emulate the
behavior of synapses in neuromorphic computing devices. It is nowadays well
established that the motion of oxygen vacancies (OV) at the nanoscale is the
key mechanism to reversibly switch metal/insulator/metal structures from
insulating to conducting, i.e. to accomplish the resistive switching effect.
The control of OV dynamics has a direct effect on the resistance changes, and
therefore on different figures of memristive devices, such as switching speed,
retention, endurance or energy consumption. Advances in this direction demand
not only experimental techniques that allow for measurements of OV dynamics,
but also of theoretical studies that shed light on the involved mechanisms.
Along this goal, we analize the OV dynamics in redox interfaces formed when an
oxidizable metallic electrode is in contact with the insulating oxide. We show
how the transfer of OV can be manipulated by using different electrical stimuli
protocols to optimize device figures such as the ON/OFF ratio or the energy
dissipation linked to the writing process. Analytical expressions for attained
resistance values, including the high and low resistance states are derived in
terms of total transferred OV in a nanoscale region of the interface. Our
predictions are validated with experiments performed in
Ti/La$_{1/3}$Ca$_{2/3}$MnO$_{3}$ redox memristive devices.",1811.09528v1
2014-08-14,"Crystal growth and annealing study of fragile, non-bulk superconductivity in YFe$_2$Ge$_2$","We investigated the occurrence and nature of superconductivity in single
crystals of YFe$_2$Ge$_2$ grown out of Sn flux by employing x-ray diffraction,
electrical resistivity, and specific heat measurements. We found that the
residual resistivity ratio (RRR) of single crystals can be greatly improved,
reaching as high as $\sim$60, by decanting the crystals from the molten Sn at
$\sim$350$^\circ$C and/or by annealing at temperatures between 550$^\circ$C and
600$^\circ$C. We found that samples with RRR $\gtrsim$ 34 showed resistive
signatures of superconductivity with the onset of the superconducting
transition $T_c\approx1.4$ K. RRR values vary between 35 and 65 with, on
average, no systematic change in $T_c$ value, indicating that systematic
changes in RRR do not lead to comparable changes in $T_c$. Specific heat
measurements on samples that showed clear resistive signatures of a
superconducting transition did not show any signature of a superconducting
phase transition, which suggests that the superconductivity observed in this
compound is either some sort of filamentary, strain stabilized
superconductivity associated with small amounts of stressed YFe$_2$Ge$_2$
(perhaps at twin boundaries or dislocations) or is a second crystallographic
phase present at levels below detection capability of conventional powder x-ray
techniques.",1408.3319v1
2019-07-17,A Nanomagnetic Voltage-Tunable Correlation Generator between Two Random Bit Streams for Stochastic Computing,"Graphical probabilistic circuit models of stochastic computing are more
powerful than the predominant deep learning models, but also have more
demanding requirements. For example, they require ""programmable stochasticity"",
e.g. generating two random binary bit streams with tunable amount of
correlation between the corresponding bits in the two streams. Electronic
implementation of such a system would call for several components leaving a
large footprint on a chip and dissipating excessive amount of energy. Here, we
show an elegant implementation with just two dipole-coupled magneto-tunneling
junctions (MTJ), with magnetostrictive soft layers, fabricated on a
piezoelectric film. The resistance states of the two MTJs (high or low) encode
the bits in the two streams. The first MTJ is driven to a random resistance
state via a current or voltage generating spin transfer torque and/or voltage
controlled magnetic anisotropy, while the second MTJ's resistance state is
determined solely by dipole coupling with the first. The effect of dipole
coupling can be varied with local strain applied to the second MTJ with a local
voltage (~0.2 V) and that varies the correlation between the resistance states
of the two MTJs and hence between the bits in the two streams (from 0% to
100%). This paradigm can be extended to arbitrary number of bit streams.",1907.07532v1
2017-04-26,Identifying Similarities in Epileptic Patients for Drug Resistance Prediction,"Currently, approximately 30% of epileptic patients treated with antiepileptic
drugs (AEDs) remain resistant to treatment (known as refractory patients). This
project seeks to understand the underlying similarities in refractory patients
vs. other epileptic patients, identify features contributing to drug resistance
across underlying phenotypes for refractory patients, and develop predictive
models for drug resistance in epileptic patients. In this study, epileptic
patient data was examined to attempt to observe discernable similarities or
differences in refractory patients (case) and other non-refractory patients
(control) to map underlying mechanisms in causality. For the first part of the
study, unsupervised algorithms such as Kmeans, Spectral Clustering, and
Gaussian Mixture Models were used to examine patient features projected into a
lower dimensional space. Results from this study showed a high degree of
non-linearity in the underlying feature space. For the second part of this
study, classification algorithms such as Logistic Regression, Gradient Boosted
Decision Trees, and SVMs, were tested on the reduced-dimensionality features,
with accuracy results of 0.83(+/-0.3) testing using 7 fold cross validation.
Observations of test results indicate using a radial basis function kernel PCA
to reduce features ingested by a Gradient Boosted Decision Tree Ensemble lead
to gains in improved accuracy in mapping a binary decision to highly non-linear
features collected from epileptic patients.",1704.08361v1
2019-06-24,Fully Dynamic Spectral Vertex Sparsifiers and Applications,"We study \emph{dynamic} algorithms for maintaining spectral vertex
sparsifiers of graphs with respect to a set of terminals $T$ of our choice.
Such objects preserve pairwise resistances, solutions to systems of linear
equations, and energy of electrical flows between the terminals in $T$. We give
a data structure that supports insertions and deletions of edges, and terminal
additions, all in sublinear time. Our result is then applied to the following
problems.
  (1) A data structure for maintaining solutions to Laplacian systems
$\mathbf{L} \mathbf{x} = \mathbf{b}$, where $\mathbf{L}$ is the Laplacian
matrix and $\mathbf{b}$ is a demand vector. For a bounded degree, unweighted
graph, we support modifications to both $\mathbf{L}$ and $\mathbf{b}$ while
providing access to $\epsilon$-approximations to the energy of routing an
electrical flow with demand $\mathbf{b}$, as well as query access to entries of
a vector $\tilde{\mathbf{x}}$ such that $\left\lVert
\tilde{\mathbf{x}}-\mathbf{L}^{\dagger} \mathbf{b} \right\rVert_{\mathbf{L}}
\leq \epsilon \left\lVert \mathbf{L}^{\dagger} \mathbf{b}
\right\rVert_{\mathbf{L}}$ in $\tilde{O}(n^{11/12}\epsilon^{-5})$ expected
amortized update and query time.
  (2) A data structure for maintaining All-Pairs Effective Resistance. For an
intermixed sequence of edge insertions, deletions, and resistance queries, our
data structure returns $(1 \pm \epsilon)$-approximation to all the resistance
queries against an oblivious adversary with high probability. Its expected
amortized update and query times are $\tilde{O}(\min(m^{3/4},n^{5/6}
\epsilon^{-2}) \epsilon^{-4})$ on an unweighted graph, and
$\tilde{O}(n^{5/6}\epsilon^{-6})$ on weighted graphs.
  These results represent the first data structures for maintaining key
primitives from the Laplacian paradigm for graph algorithms in sublinear time
without assumptions on the underlying graph topologies.",1906.10530v1
2019-11-18,Comparison of screening for methicillin-resistant Staphylococcus aureus (MRSA) at hospital admission and discharge,"Methicillin-resistant Staphylococcus aureus (MRSA) is a significant
contributor to the growing concern of antibiotic resistant bacteria, especially
given its stubborn persistence in hospitals and other health care facility
settings. In combination with this characteristic of S. aureus (colloquially
referred to as staph), MRSA presents an additional barrier to treatment and is
now believed to have colonized two of every 100 people worldwide. According to
the CDC, MRSA prevalence sits as high as 25-50% in countries such as the United
Kingdom and the United States. Given the resistant nature of staph as well as
its capability of evolving to compensate antibiotic treatment, controlling MRSA
levels is more a matter of precautionary and defensive measures. This study
examines the method of ""search and isolation,"" which seeks to isolate MRSA
positive patients in a hospital so as to decrease infection potential. Although
this strategy is straightforward, the question of just whom to screen is of
practical importance. We compare screening at admission to screening at
discharge. To do this, we develop a mathematical model and use simulations to
determine MRSA endemic levels in a hospital with either control measure
implemented. We found that screening at discharge was the more effective method
in controlling MRSA endemicity, but at the cost of a greater number of isolated
patients.",1911.07711v1
2020-07-02,Bloch-Grüneisen temperature and universal scaling of normalized resistivity in doped graphene revisited,"In this work, we resolved some controversial issues on the
Bloch-Gr\""{u}neisen (BG) temperature in doped graphene via analytical and
numerical calculations based on full inelastic electron-acoustic-phonon (EAP)
scattering rate and various approximation schemes. Analytic results for BG
temperature obtained by semi-inelastic (SI) approximation (which gives
scattering rates in excellent agreement with the full inelastic scattering
rates) are compared with those obtained by quasi-elastic (QE) approximation and
the commonly adopted value of $\Theta^{LA}_{F} = 2\hbar v_{LA} k_F/k_B$. It is
found that the commonly adopted BG temperature in graphene ($\Theta^{LA}_{F}$)
is about 5 times larger than the value obtained by the QE approximation and
about 2.5 times larger than that by the SI approximation, when using the
crossing-point temperature where low-temperature and high-temperature limits of
the resistivity meet. The corrected analytic relation based on SI approximation
agrees extremely well with the transition temperatures determined by fitting
the the low- and high-$T$ behavior of available experimental data of graphene's
resistivity. We also introduce a way to determine the BG temperature including
the full inelastic EAP scattering rate and the deviation of electron energy
from the chemical potential ($\mu$) numerically by finding the maximum of
$\partial \rho(\mu,T)/\partial T$. Using the analytic expression of
$\Theta_{BG,1}$ we can prove that the normalized resistivity defined as
$R_{1}=\rho(\mu,T)/\rho(\mu,\Theta_{BG,1})$ plotted as a function of
$(T/\Theta_{BG,1})$ is independent of the carrier density. Applying our results
to previous experimental data extracted shows a universal scaling behavior,
which is different from previous studies.",2007.00839v1
2020-11-16,Transition region from turbulent to dead zone in protoplanetary disks: local shearing box simulations,"The dynamical evolution of protoplanetary disks is of key interest for
building a comprehensive theory of planet formation and to explain the
observational properties of these objects. Using the magnetohydrodynamics code
Athena++, with an isothermal shearing box setup, we study the boundary between
the active and dead zone, where the accretion rate changes and mass can
accumulate. We quantify how the turbulence level is affected by the presence of
a non uniform ohmic resistivity in the radial-x direction that leads to a
region of inhibited turbulence (or dead zone). Comparing the turbulent activity
to that of ideal simulations, the turbulence inhibited area shows density
fluctuations and magnetic activity at its boundaries, driven by energy
injection from the active (ideal) zone boundaries. We find magnetic dissipation
to be significantly stronger in the ideal regions, and the turbulence
penetration through the boundary of the dead zone is determined by the value of
the resistivity itself, through the ohmic dissipation process, though the
thickness of the transition does not play a significant role in changing the
dissipation. We investigate the 1D spectra along the shearing direction:
magnetic spectra appear flat at large scales both in ideal as well as resistive
simulations, though a Kolmogorov scaling over more than one decade persists in
the dead zone, suggesting the turbulent cascade is determined by the
hydrodynamics of the system: MRI dynamo action is inhibited where sufficiently
high resistivity is present.",2011.08219v1
2021-10-21,E-DPNCT: An Enhanced Attack Resilient Differential Privacy Model For Smart Grids Using Split Noise Cancellation,"High frequency reporting of energy consumption data in smart grids can be
used to infer sensitive information regarding the consumer's life style and
poses serious security and privacy threats. Differential privacy (DP) based
privacy models for smart grids ensure privacy when analysing energy consumption
data for billing and load monitoring. However, DP models for smart grids are
vulnerable to collusion attack where an adversary colludes with malicious smart
meters and un-trusted aggregator in order to get private information from other
smart meters. We first show the vulnerability of DP based privacy model for
smart grids against collusion attacks to establish the need of a collusion
resistant model privacy model. Then, we propose an Enhanced Differential
Private Noise Cancellation Model for Load Monitoring and Billing for Smart
Meters (E-DPNCT) which not only provides resistance against collusion attacks
but also protects the privacy of the smart grid data while providing accurate
billing and load monitoring. We use differential privacy with a split noise
cancellation protocol with multiple master smart meters (MSMs) to achieve
colluison resistance. We did extensive comparison of our E-DPNCT model with
state of the art attack resistant privacy preserving models such as EPIC for
collusion attack. We simulate our E-DPNCT model with real time data which shows
significant improvement in privacy attack scenarios. Further, we analyze the
impact of selecting different sensitivity parameters for calibrating DP noise
over the privacy of customer electricity profile and accuracy of electricity
data aggregation such as load monitoring and billing.",2110.11091v4
2022-05-10,Disorder-enhanced effective masses and deviations from Matthiessen's rule in PdCoO$_2$ thin films,"The observation of hydrodynamic transport in the metallic delafossite
PdCoO$_2$ has increased interest in this family of highly conductive oxides,
but experimental studies so far have mostly been confined to bulk crystals. In
this work, the development of high-quality thin films of PdCoO$_2$ has enabled
a thorough study of the conductivity as a function of film thickness using both
dc transport and time-domain THz spectroscopy. With increasing film thickness
from 12 nm to 102 nm, the residual resistivity decreases and we observe a large
deviation from Matthiessen's rule (DMR) in the temperature dependence of the
resistivity. We find that the complex THz conductivity is well fit by a single
Drude term. We fit the data to extract the spectral weight and scattering rate
simultaneously. The temperature dependence of the Drude scattering rate is
found to be nearly independent of the residual resistivity and cannot be the
primary mechanism for the observed DMR. Rather, we observe large changes in the
spectral weight as a function of disorder, changing by a factor of 1.5 from the
most disordered to least disordered films. We believe this corresponds to a
mass enhancement of $\geq 2$ times the value of the bulk effective mass which
increases with residual disorder. This suggests that the mechanism behind the
DMR observed in dc resistivity is primarily driven by changes in the electron
mass. We discuss the possible origins of this behavior including the
possibility of disorder-enhanced electron-phonon scattering, which can be
systematically tuned by film thickness.",2205.05006v2
2022-08-05,Hall effect in Poiseuille flow of two-dimensional electron fluid,"The hydrodynamic regime of charge transport has been recently realized in
high-quality conductors. In the hydrodynamic as well as in the Ohmic regimes
the main part of the Hall resistance of a long sample is determined by the
balance between the Lorentz force and the electric force, acting on conduction
electrons. Experimentally observed deviations of the Hall resistance in
hydrodynamic samples from such the ''standard'' value are usually associated
with the Hall viscosity term in the Navier-Stokes equation. In this work we
theoretically study the Hall effect in a Poiseuille flow of a two-dimensional
electron fluid. We show that the near-edge semiballistic layers with the width
of the order of the inter-particle mean free path, which inevitably appear near
sample edges, give the contribution to the Hall resistance which is comparable
with the bulk contribution from the Hall viscosity. In this way, the measured
deviations of the Hall resistance from the ''standard'' one in hydrodynamic
samples by the usual contact techniques should be associated with both the Hall
viscosity in the bulk and the semiballistic effects in the near-edge layers",2208.03032v1
2022-10-28,Lattice effects on the physical properties of half doped perovskite ruthenates,"We investigate the unusual phase transitions in SrRuO$_{3}$ and
Sr$_{0.5}$Ca$_{0.5}$Ru$_{1-x}$Cr$_{x}$O$_{3}$ (x=0,0.05 and 0.1) employing
x-ray diffraction, resistivity, magnetic studies and x-ray photoemission
spectroscopy. Our results show the compounds undergo crossover from $itinerant$
ferromagnetism to $localised$ ferromagnetism. The combined studies suggests Ru
and Cr to be in 4+ valence state. A Griffith phase and an enhancement in Curie
temperature (Tc) from 38 K to 107 K is observed with Cr doping. A shift in the
chemical potential towards the valence band is observed with Cr doping. In the
metallic samples, interestingly, a direct link between the resistivity and
orthorhombic strain is observed. Detailed studies in this direction will be
helpful to understand the nature of interactions and hence manoeuvre its
properties. In the non metallic samples, the resistivity is mainly governed by
disorder and electron-electron correlation effects. The value of the
resistivity for the 5% Cr doped sample suggests semi metallic behaviour.
Understanding its nature in detail using electron spectroscopic techniques
could unravel the possibility of its utility in high mobility transistors at
room temperature and its combined property with ferromagnetism will be helpful
in making spintronic devices.",2210.16036v1
2022-12-05,DeAR: A Deep-learning-based Audio Re-recording Resilient Watermarking,"Audio watermarking is widely used for leaking source tracing. The robustness
of the watermark determines the traceability of the algorithm. With the
development of digital technology, audio re-recording (AR) has become an
efficient and covert means to steal secrets. AR process could drastically
destroy the watermark signal while preserving the original information. This
puts forward a new requirement for audio watermarking at this stage, that is,
to be robust to AR distortions. Unfortunately, none of the existing algorithms
can effectively resist AR attacks due to the complexity of the AR process. To
address this limitation, this paper proposes DeAR, a deep-learning-based audio
re-recording resistant watermarking. Inspired by DNN-based image watermarking,
we pioneer a deep learning framework for audio carriers, based on which the
watermark signal can be effectively embedded and extracted. Meanwhile, in order
to resist the AR attack, we delicately analyze the distortions that occurred in
the AR process and design the corresponding distortion layer to cooperate with
the proposed watermarking framework. Extensive experiments show that the
proposed algorithm can resist not only common electronic channel distortions
but also AR distortions. Under the premise of high-quality embedding
(SNR=25.86dB), in the case of a common re-recording distance (20cm), the
algorithm can effectively achieve an average bit recovery accuracy of 98.55%.",2212.02339v4
2023-04-18,Characterization of a Superconducting Microstrip Single-Photon Detector Shunted with an External Resistor,"A superconducting microstrip single-photon detector (SMSPD) generally
requires a shunt resistor to avoid latching, caused by its high
current-carrying capacity and low kinetic inductance. Here, the effect of the
shunt resistor on the behaviors of microbridge SMSPDs was investigated. We
analyzed the change in equivalent switching current at different shunt
resistances in two ways and determined the operating current range using
intrinsic dark count rate (iDCR) curves. We observed that the reduction in
shunt resistance can increase the operating current range, which helps to
improve the internal detection efficiency (IDE) and reduce the iDCR. However,
the reduction in the shunt resistance can reduce the pulse amplitude and
increase the pulse decay time, which can degrade the timing jitter and count
rate performance of the SMSPD. The trends of the experimental results can be
qualitatively reproduced using a circuit model for an SMSPD with a shunt
resistor, which provides useful information for the selection of shunt
resistors. Furthermore, we report the improved detection performance of a
helium-ion-irradiated SMSPD shunted with a small resistance of 5.2 {\Omega}. We
observed a weak IDE saturation with a bias current at a wavelength up to 2000
nm and a nonlinear relation between detection current and photon energy.",2304.08762v1
2023-05-18,Fabrication of Al/AlOx/Al junctions with high uniformity and stability on sapphire substrates,"Tantalum and aluminum on sapphire are widely used platforms for qubits of
long coherent time. As quantum chips scale up, the number of Josephson
junctions on Sapphire increases. Thus, both the uniformity and stability of the
junctions are crucial to quantum devices, such as scalable superconducting
quantum computer circuit, and quantum-limited amplifiers. By optimizing the
fabrication process, especially, the conductive layer during the electron beam
lithography process, Al/AlOx/Al junctions of sizes ranging from 0.0169 to 0.04
{\mu}m2 on sapphire substrates were prepared. The relative standard deviation
of room temperature resistances (RN) of these junctions is better than 1.7% on
15 mmx15 mm chips, and better than 2.66% on 2 inch wafers, which is the highest
uniformity on sapphire substrates has been reported. The junctions are robust
and stable in resistances as temperature changes. The resistances increase by
the ratio of 9.73% relative to RN as the temperature ramp down to 4K, and
restore their initial values in the reverse process as the temperature ramps
back to RT. After being stored in a nitrogen cabinet for 100 days, the
resistance of the junctions changed by1.16% in average. The demonstration of
uniform and stable Josephson junctions in large area paves the way for the
fabrication of superconducting chip of hundreds of qubits on sapphire
substrates.",2305.10956v2
2023-06-21,Coherent states and their superpositions (cat states) in microwave-induced resistance oscillations,"We report a novel theoretical approach on the microwave-induced resistance
oscillations based on the coherent states of the quantum harmonic oscillator.
We first obtain an expression for the coherent states of driven-quantum
harmonic oscillators that are used, in the model of microwaveinduced electron
orbits, to calculate magnetoresistance under radiation. Thus, we find that the
principle of minimum uncertainty of coherent states, involving time and energy,
is at the heart of photo-oscillations and zero resistance states. Accordingly,
we are able to explain important experimental evidence of this remarkable
effect. Such as the physical origin of oscillations, their periodicity with the
inverse of the magnetic field, their peculiar minima and maxima positions and
the existence of zero resistance states. We apply our theory to the case of
ultra-high mobility samples where we appeal to the principle of quantum
superposition of coherent states and obtain that Schrodinger cat states (even
and odd coherent states) are key to explain magnetoresistance at these extreme
mobilities. With them we explain the, experimentally obtained,
magnetoresistance resonance peak shift to a magnetic field where the cyclotron
frequency equals half the radiation frequency. This effect is similar to the
one described in quantum optics as a second harmonic generation process. We
also explain the magnetoresistance collapse, that take place in the dark and
with light. This effect is known as giant negative magnetoresistance. We
generalize our results to study the case of a three-component or triangular
Schrodinger cat state.",2306.12160v1
2023-08-28,Research on the Influence of Underwater Environment on the Dynamic Performance of the Mechanical Leg of a Deep-sea Crawling and Swimming Robot,"The performance of underwater crawling and adjustment of the body posture for
underwater manipulating of the deep-sea crawling and swimming robot (DCSR) is
directly influenced by the dynamic performance of the underwater mechanical
legs (UWML), as it serves as the executive mechanism of the DCSR. Compared with
the mechanical legs of legged robots working on land, the UWML of the DCSR not
only possesses the characteristics of the land used mechanical legs, but is
also affected by the influence of the deep-sea underwater working environment
(i.e., the hydrodynamic force, viscous resistance and dynamic seal resistance).
To reduce these influence, firstly, the hydrodynamic force of the UWML were
researched based on theory and experiment, and the hydrodynamic model was
established with the fitted hydrodynamic parameters. Secondly, the oil viscous
resistance and the dynamic seal resistance were studied experimentally, and the
change laws of both with respect to the joint speed and the ambient pressure
(depth of operation) were obtained. The results provide a basis for the
subsequent research on the structure optimization and high performance control
of the UWML and DCSR.",2308.14393v1
2023-11-17,Current manipulation of Giant tunneling altermagnetic resistance in collinear Antiferromagnetic RuO2/MgO/RuO2 sandwich structure,"As an emerging non-volatile memory technology, magnetic random access memory
(MRAM) has key features and advantages including non-volatility, high speed,
endurance, low power consumption and radiation tolerance. Conventional MRAM
utilizes magnetic tunnel junctions (MTJs), which consist of two ferromagnetic
layers separated by an insulating tunnel barrier. The orientation of the
magnetic layers represents the binary data (0 or 1), and electrical resistance
changes depending on the relative orientation of these magnetic layers. Despite
these advancements, the quest for a swifter, more stable magneto-resistive
random-access memory paradigm persists. In this vein, we present a
groundbreaking development: room-temperature antiferromagnetic tunnel junctions
devoid of any net magnetic moment. Over 200% tunneling altermagnetic resistance
(TAR) ratio was measured at RuO2 (110)/MgO/RuO2 (110)/W structure, which is
achieved by changing the antiferromagnetic Neel vector of RuO2 with an ultralow
current density 2 MA*cm-2.",2311.10288v2
2024-02-09,Wellposedness of the electron MHD without resistivity for large perturbations of the uniform magnetic field,"We prove the local wellposedness of the Cauchy problems for the electron
magnetohydrodynamics equations (E-MHD) without resistivity for possibly large
perturbations of nonzero uniform magnetic fields. While the local wellposedness
problem for (E-MHD) has been extensively studied in the presence of resistivity
(which provides dissipative effects), this seems to be the first such result
without resistivity. (E-MHD) is a fluid description of plasma in small scales
where the motion of electrons relative to ions is significant. Mathematically,
it is a quasilinear dispersive equation with nondegenerate but nonelliptic
second-order principal term. Our result significantly improves upon the
straightforward adaptation of the classical work of Kenig--Ponce--Rolvung--Vega
on the quasilinear ultrahyperbolic Schr\""odinger equations, as the regularity
and decay assumptions on the initial data are greatly weakened to the level
analogous to the recent work of Marzuola--Metcalfe--Tataru in the case of
elliptic principal term.
  A key ingredient of our proof is a simple observation about the relationship
between the size of a symbol and the operator norm of its quantization as a
pseudodifferential operator when restricted to high frequencies. This allows us
to localize the (non-classical) pseudodifferential renormalization operator
considered by Kenig--Ponce--Rolvung--Vega, and produce instead a classical
pseudodifferential renormalization operator. We furthermore incorporate the
function space framework of Marzuola--Metcalfe--Tataru to the present case of
nonelliptic principal term.",2402.06278v1
2024-03-21,Aging suppression in Multistrip Multigap Resistive Plate Chambers for high counting rate experiments,"A long term operation of Multi-Strip Multi-Gap Resistive Plate Chambers
(MSMGRPC) with gas mixtures based on C2H2F4 and SF6 leads to aging effects,
observed as depositions on the surface of the resistive electrodes. Moreover,
enhanced depositions and higher noise rates were evidenced around the nylon
spacers used for defining the gas gaps between the resistive electrodes. The
aging effects are reflected in an increase of the dark current and dark
counting rate, with negative impact on the long term performance of the chamber
and data volume in a free running readout mode operation. MSMGRPC prototypes
designed with a direct gas flow through the gas gaps and minimization of the
number of spacers in the active area were developed as mitigation solution.
Prototypes with this new design and different granularities were assembled
using fishing line as spacers and investigated for aging effects. Although a
significant reduction in the dark current and dark counting rate was evidenced,
dark counting rate localized around the fishing line spacers remains. In this
paper, a new generation of direct flow chambers based on discrete spacers is
presented. The results of their aging investigations show that, even at lower
gas flows, the aging effects become negligible.",2403.14190v1
2006-03-20,Unusual metamagnetism in CeIrIn$_5$,"We report a high field investigation (up to 45 T) of the metamagnetic
transition in CeIrIn$_5$ with resistivity and de-Haas-van-Alphen (dHvA) effect
measurements in the temperature range 0.03-1 K. As the magnetic field is
increased the resistivity increases, reaches a maximum at the metamagnetic
critical field, and falls precipitously for fields just above the transition,
while the amplitude of all measurable dHvA frequencies are significantly
attenuated near the metamagnetic critical field. However, the dHvA frequencies
and cyclotron masses are not substantially altered by the transition. In the
low field state, the resistivity is observed to increase toward low
temperatures in a singular fashion, a behavior that is rapidly suppressed above
the transition. Instead, in the high field state, the resistivity monotonically
increases with temperature with a dependence that is more singular than the
iconic Fermi-liquid, temperature-squared, behavior. Both the damping of the
dHvA amplitudes and the increased resistivity near the metamagnetic critical
field indicate an increased scattering rate for charge carriers consistent with
critical fluctuation scattering in proximity to a phase transition. The dHvA
amplitudes do not uniformly recover above the critical field, with some
hole-like orbits being entirely suppressed at high fields. These changes, taken
as a whole, suggest that the metamagnetic transition in CeIrIn$_5$ is
associated with the polarization and localization of the heaviest of
quasiparticles on the hole-like Fermi surface.",0603490v2
2022-11-10,"T-linear resistivity, optical conductivity and Planckian transport for a holographic local quantum critical metal in a periodic potential","High $T_c$ cuprate strange metals are noted for a DC-resistivity that scales
linearly with $T$ from the onset of superconductivity to the crystal melting
temperature, indicative of a Planckian dissipation life time
$\tau_{\hbar}\simeq \hbar /(k_B T)$. At the same time, the optical conductivity
ceases to be of Drude form at high temperatures, suggesting a change of the
underlying dynamics that surprisingly leaves the $T$-linear DC-resistivity
unaffected. We use the AdS/CFT correspondence that describes strongly coupled,
densely entangled metals to study DC thermo-electrical transport and the
optical conductivities of the local quantum critical Gubser-Rocha holographic
strange metal in the presence of a lattice potential, a prime candidate to
compare with experiment. We find that the DC-resistivity is linear in $T$ at
low temperatures for a range of lattice strengths and wavevectors, even as it
transitions between different dissipative regimes. At weak lattice potential
the optical conductivity evolves with increasing temperature from a Drude form
to a bad-metal characterized by a mid-IR resonance without changing the DC
transport, similar to that seen in cuprate strange metals. This mid-IR peak and
its temperature evolution can be understood as a consequence of Umklapp
hydrodynamics: hydrodynamic perturbations are Bloch modes in the presence of a
lattice. At strong lattice potential an incoherent metal is realized instead
where momentum conservation no longer plays a role in transport. In this regime
the thermal diffusivity can be explained by Planckian dissipation originating
in universal microscopic chaos, similar to holographic metals with strong
homogeneous momentum relaxation. The charge diffusivity does not submit to this
chaos explanation, even though the continuing linear-in-$T$ DC resistivity
saturates to an apparent universal slope, numerically equal to a Planckian
rate.",2211.05492v2
1998-05-20,A phenomenological model for magnetoresistance in granular polycrystalline colossal magnetoresistive materials: the role of spin polarised tunnelling at the grain boundaries,"It has been observed that in bulk and polycrystalline thin films of collossal
magnetoresistive (CMR) materials the magnetoresistance follows a different
behaviour compared to single crystals or single crystalline films below the
ferromagnetic transition temperature Tc. In this paper we develop a
phenomenological model to explain the magnetic field dependence of resistance
in granular CMR materials taking into account the spin polarised tunnelling at
the grain boundaries. The model has been fitted to two systems, namely,
La0.55Ho0.15Sr0.3MnO3 and La1.8Y0.5Ca0.7Mn2O7. From the fitted result we have
separated out, in La0.55Ho0.15Sr0.3MnO3, the intrinsic contribution from the
intergranular contribution to the magnetoresistance coming from spin polarised
tunnelling at the grain boundaries. It is observed that the temperature
dependence of the intrinsic contribution to the magnetoresistance in
La0.55Ho0.15Sr0.3MnO3 follows the prediction of double exchange model for all
values of field.",9805258v1
2000-11-21,Anomalous NMR Spin-Lattice Relaxation in SrB_{6} and Ca_{1-x}La_{x}B_{6},"We report the results of {11}B nuclear magnetic resonance (NMR) measurements
of SrB_{6} and Ca_{0.995}La_{0.05}B_{6} below room temperature. Although the
electrical resistivities of these two materials differ substantially, their
{11}B-NMR responses exhibit some strikingly common features. Both materials
exhibit ferromagnetic order, but their {11}B-NMR spectra reveal very small
hyperfine fields at the Boron sites. The spin lattice relaxation T_{1}^{-1}
varies considerably with external field but changes with temperature only below
a few K. We discuss these unusual results by considering various different
scenarios for the electronic structure of these materials.",0011352v2
2004-07-17,Magneto - transport characterization of Dy123 monodomain superconductors,"The following report considers textured materials of the DyBa2Cu3O7 type
seeded with a Nd123 seed as initiator. They are grown with an excess 20% Dy211
phase on a Dy2O3 substrate. We report chemical characterizations, electrical
resistivity, thermoelectric power and thermal conductivity over a broad
temperature range as a function of an applied magnetic field up to 6 T. We show
that specific features appear on the magneto thermal transport properties
different in these materials from those found in single crystals and
polycrystalline samples. We propose that two vortex regimes can be
distinguished in the mixed phase, - due to the intrinsic microstructure. We
calculate the viscosity, entropy and figure of merit of the samples.",0407463v1
2007-01-09,Pressure Study of Superconductivity and Magnetism in Pure and Rh-Doped RuSr2GdCu2O8 Materials,"A hydrostatic pressure study was made on pure and Rh-doped specimens of the
superconducting ferromagnetic compounds Ru1-xRhxSr2GdCu2O8 (x = 0-0.15) by
means of measurement of electrical resistivity vs temperature, in pressures up
to 2 GPa. Partial substitution of Rh for Ru decreases the magnetization of the
material, lowers both the magnetic ordering temperature Tm, and the
superconducting transition temperature Tc, and promotes granularity. The effect
of pressure for all compositions is an increase in both the intra- and
intergranular superconductivity transition temperatures, Tc and Tp
respectively, as well as Tm. The rate of change of each transition temperature
with pressure first drops for Rh concentrations near 5%, increasing latter for
higher concentrations. While the rate of increase of Tc with pressure for all
compositions is 2-3 times lower than in YBCO materials, the simultaneous
increase of Tc and Tm with pressure could support the notion of competition
between superconductivity and ferromagnetism in these materials. The effect of
pressure on the weak-links was a significant improvement of inter-granular
connectivity.",0701183v1
2007-04-25,Studies of the temperature and frequency dependent impedance of an electroceramic functional oxide thermistor,"The charge transport mechanism and the macroscopic dielectric constant in
polycrystalline device materials commonly exhibit several components such as
electrode-sample interface, grain boundary and bulk contributions. In order to
gain precise understanding of the functionality of polycrystalline
electroceramic device materials it is essential to deconvolute these
contributions. The paradigm of functional thermistor ceramics based on thick
film spinel manganates has been studied by temperature dependent alternating
current impedance spectroscopy. Three typical relaxation phenomena were
detected, which all showed a separated temperature dependence of resistivity
consistent with thermally activated charge transport. The dominating grain
boundary and the interface contributions exhibited distinctively different
capacitance allowing clear identification. The composite nature of the
dielectric properties in polycrystalline functional ceramics was emphasized,
and impedance spectroscopy was shown to be a powerful tool to account for and
model such behaviour.",0704.3378v1
2007-07-17,Gate-induced insulating state in bilayer graphene devices,"The potential of graphene-based materials consisting of one or a few layers
of graphite for integrated electronics originates from the large
room-temperature carrier mobility in these systems (approx. 10,000 cm2/Vs).
However, the realization of electronic devices such as field-effect transistors
will require controlling and even switching off the electrical conductivity by
means of gate electrodes, which is made difficult by the absence of a bandgap
in the intrinsic material. Here, we demonstrate the controlled induction of an
insulating state - with large suppression of the conductivity - in bilayer
graphene, by using a double-gate device configuration that allows an electric
field to be applied perpendicular to the plane. The dependence of the
resistance on temperature and electric field, and the absence of any effect in
a single-layer device, strongly suggest that the gate-induced insulating state
originates from the recently predicted opening of a bandgap between valence and
conduction bands.",0707.2487v2
2009-05-12,Large magnetic entropy change near room temperature in antipervoskite SnCMn3,"We report the observation of large magnetocaloric effect near room
temperature in antipervoskite SnCMn3. The maximal magnetic entropy change at
the first-order ferrimagnetic-paramagnetic transition temperature (TC 279 K) is
about 80.69mJ/cm3 K and 133mJ/cm3 K under the magnetic field of 20 kOe and 48
kOe, respectively. These values are close to those of typical magnetocaloric
materials. The large magnetocaloric effect is associated with the sharp change
of lattice, resistivity and magnetization in the vicinity of TC. Through the
measurements of Seebeck coefficient and normal Hall effect, the title system is
found to undergo a reconstruction of electronic structure at TC. Considering
its low-cost and innocuous raw materials, Mn-based antiperovskite compounds are
suggested to be appropriate for pursuing new materials with larger
magnetocaloric effect.",0905.1773v1
2009-06-28,Partial Kekule Ordering of Adatoms on Graphene,"Electronic and transport properties of Graphene, a one-atom thick crystalline
material, are sensitive to the presence of atoms adsorbed on its surface. An
ensemble of randomly positioned adatoms, each serving as a scattering center,
leads to the Bolzmann-Drude diffusion of charge determining the resistivity of
the material. An important question, however, is whether the distribution of
adatoms is always genuinely random. In this Article we demonstrate that a
dilute adatoms on graphene may have a tendency towards a spatially correlated
state with a hidden Kekule mosaic order. This effect emerges from the
interaction between the adatoms mediated by the Friedel oscillations of the
electron density in graphene. The onset of the ordered state, as the system is
cooled below the critical temperature, is accompanied by the opening of a gap
in the electronic spectrum of the material, dramatically changing its transport
properties.",0906.5174v1
2012-02-13,Nanostructured antimony tin oxide synthesized via chemical precipitation method: its characterization and application in humidity sensing,"In present investigation we report the synthesis of antimony tin oxide
nanoparticles via chemical precipitation method. The synthesized material was
characterized using X-ray diffractometer, Scanning Electron Microscope,
UV-visible absorption spectroscopy. XRD shows the crystalline nature of the
synthesized material and the crystallite size was estimated by using
Debye-Scherer equation and its minimum value was 3 nm. Pelletization of
synthesized material was done using hydraulic press machine under uniform
pressure of 616 MPa. Then the pellets were annealed at 200, 400 and 600{\deg}C.
Further each pellet was put in humidity sensing chamber and corresponding
variations in resistance with relative humidity (%RH) were measured. The
average sensitivity was calculated by taking the average of all sensitivities
ranging from 10 to 90% RH. The average sensitivity of the pellet annealed at
600{\deg}C was best among all the sensing pellets and was 2.18 K{\Omega}/%RH.
Results were reproducible {\pm}84% after 2 months.",1205.2336v1
2012-02-13,Effect of nanostructured zinc oxide additives on the humidity and temperature sensing properties of cuprous oxide,"Present paper reports the effect of ZnO additives on humidity and temperature
sensing properties of cuprous oxide. The cuprous oxide powder was mixed with
10% and 25% ZnO by weight and these samples were pelletized by using hydraulic
pressing machine. The sensing materials were also investigated by Scanning
Electron Microscope (SEM) and X-ray Diffraction (XRD). SEM images show
morphology and porosity of material. The average particles size of cuprous
oxide was found to be 1.2 micron. The sheet like structures of ZnO is evident
in micrographs. From XRD all peaks are well identified and crystallite size for
defferent peaks has also been calculated. The pellets of sensing materials were
subjected to annealing at temperatures 200, 400 and 600 degrees C respectively
and were exposed to humidity and temperature variations. Electrical resistances
of pellets were found to vary with humidity and temperature and were recorded.
The sensitivity of sensors at various temperature and humidity levels was
calculated.",1205.2707v1
2012-05-29,"Transport Properties of Ni, Co, Fe, Mn Doped Cu0.01Bi2Te2.7Se0.3 for Thermoelectric Device Applications","Bi2Te3 based thermoelectric devices typically use a nickel layer as a
diffusion barrier to block the diffusion of solder or copper atoms from the
electrode into the thermoelectric material. Previous studies have shown
degradation in the efficiency of these thermoelectric devices may be due to the
diffusion of the barrier layer into the thermoelectric material. In this work
Ni, Co, Fe, and Mn are intentionally doped into Cu0.01Bi2Te2.7Se0.3 in order to
understand their effects on the thermoelectric material. Thermoelectric
transport properties including the Seebeck coefficient, thermal conductivity,
electrical resistivity, carrier concentration, and carrier mobility of
Cu0.01Bi2Te2.7Se0.3 doped with 2 atomic percent M (M=Ni, Co, Fe, Mn) as
Cu0.01Bi2Te2.7Se0.3M0.02, are studied in a temperature range of 5-525 K.",1205.6377v1
2012-07-04,Colossal Magnetoresistance in the Mn2+ Oxypnictides NdMnAsO1-xFx,"Colossal magnetoresistance (CMR) is a rare phenomenon in which the electronic
resistivity of a material can be decreased by orders of magnitude upon
application of a magnetic field. Such an effect could be the basis of the next
generation of magnetic memory devices. Here we report CMR in the
antiferromagnetic oxypnictide NdMnAsO1-xFx as a result of competition between
an antiferromagnetic insulating phase with strong electron correlations and a
paramagnetic semiconductor upon application of a magnetic field. The discovery
of CMR in antiferromagnetic Mn2+ oxypnictide materials could open up an array
of materials for further investigation and optimisation for technological
applications.",1207.0958v1
2013-10-28,The d-p band-inversion topological insulator in bismuth-based skutterudites,"Skutterudites, a class of materials with cage-like crystal structure which
have received considerable research interest in recent years, are the breeding
ground of several unusual phenomena such as heavy fermion superconductivity,
exciton-mediated superconducting state and Weyl fermions. Here, we predict a
new topological insulator in bismuth-based skutterudites, in which the bands
involved in the topological band-inversion process are d- and p-orbitals, which
is distinctive with usual topological insulators, for instance in Bi2Se3 and
BiTeI the bands involved in the topological band-inversion process are only
p-orbitals. Due to the present of large d-electronic states, the electronic
interaction in this topological insulator is much stronger than that in other
conventional topological insulators. The stability of the new material is
verified by binding energy calculation, phonon modes analysis, and the finite
temperature molecular dynamics simulations. This new material can provide
nearly zero-resistivity signal current for devices and is expected to be
applied in spintronics devices.",1310.7413v2
2015-05-21,Ferromagnetism in Cr-doped topological insulator TlSbTe2,"We have synthesized a new ferromagnetic topological insulator by doping Cr to
the ternary topological-insulator material TlSbTe2. Single crystals of
Tl_{1-x}Cr_{x}SbTe2 were grown by a melting method and it was found that Cr can
be incorporated into the TlSbTe2 matrix only within the solubility limit of
about 1%. The Curie temperature \theta_c was found to increase with the Cr
content but remained relatively low, with the maximum value of about 4 K. The
easy axis was identified to be the c-axis and the saturation moment was 2.8
\mu_B (Bohr magneton) at 1.8 K. The in-plane resistivity of all the samples
studied showed metallic behavior with p-type carriers. Shubnikov-de Hass (SdH)
oscillations were observed in samples with the Cr-doping level of up to 0.76%.
We also tried to induce ferromagnetism in TlBiTe2 by doping Cr, but no
ferromagnetism was observed in Cr-doped TlBiTe2 crystals within the solubility
limit of Cr which turned out to be also about 1%.",1505.05631v1
2016-11-22,Statistical Methods for Thermal Index Estimation Based on Accelerated Destructive Degradation Test Data,"Accelerated destructive degradation test (ADDT) is a technique that is
commonly used by industries to access material's long-term properties. In many
applications, the accelerating variable is usually the temperature. In such
cases, a thermal index (TI) is used to indicate the strength of the material.
For example, a TI of 200C may be interpreted as the material can be expected to
maintain a specific property at a temperature of 200C for 100,000 hours. A
material with a higher TI possesses a stronger resistance to thermal damage. In
literature, there are three methods available to estimate the TI based on ADDT
data, which are the traditional method based on the least-squares approach, the
parametric method, and the semiparametric method. In this chapter, we provide a
comprehensive review of the three methods and illustrate how the TI can be
estimated based on different models. We also conduct comprehensive simulation
studies to show the properties of different methods. We provide thorough
discussions on the pros and cons of each method. The comparisons and discussion
in this chapter can be useful for practitioners and future industrial
standards.",1611.07412v1
2017-11-07,Fracture toughness characterization through notched small punch test specimens,"In this work a novel methodology for fracture toughness characterization by
means of the small punch test (SPT) is presented. Notched specimens are
employed and fracture resistance is assessed through a critical value of the
notch mouth displacement {\delta^SPT}. Finite element simulations and
interrupted experiments are used to track the evolution of {\delta^SPT} as a
function of the punch displacement. The onset of crack propagation is
identified by means of a ductile damage model and the outcome is compared to
the crack tip opening displacement estimated from conventional tests at crack
initiation. The proposed numerical-experimental scheme is examined with two
different grades of CrMoV steel and the differences in material toughness
captured. Limitations and uncertainties arising from the different damage
phenomena observed in the lowest toughness material examined are thoroughly
discussed.",1711.02406v1
2018-04-03,Combination of thermal and electric properties measurement techniques in a single setup suitable for radioactive materials in controlled environments and based on the 3-omega approach,"We have designed and developed a new experimental setup, based on the 3-omega
method, to measure thermal conductivity, heat capacity and electrical
resistivity of a variety of samples in a broad temperature range (2-550 K) and
under magnetic fields up to 9 T. The validity of this method is tested by
measuring various types of metallic (copper, platinum, and constantan) and
insulating (SiO_2) materials, which have a wide range of thermal conductivity
values (1-400 Wm-1K-1). We have successfully employed this technique for
measuring the thermal conductivity of two actinide single crystals, uranium
dioxide, and uranium nitride. This new experimental approach for studying
nuclear materials will help to advance reactor fuel development and
understanding. We have also shown that this experimental setup can be adapted
to the Physical Property Measurement System (Quantum Design) environment and/or
other cryocooler systems.",1804.00821v1
2018-11-02,Non-Equilibrium Phonon Transport Across Nanoscale Interfaces,"Despite the ubiquity of applications of heat transport across nanoscale
interfaces, including integrated circuits, thermoelectrics, and
nanotheranostics, an accurate description of phonon transport in these systems
remains elusive. Here we present a theoretical and computational framework to
describe phonon transport with position, momentum and scattering event
resolution. We apply this framework to a single material spherical nanoparticle
for which the multidimensional resolution offers insight into the physical
origin of phonon thermalization, and length-scale dependent anisotropy of
steady-state phonon distributions. We extend the formalism to handle interfaces
explicitly and investigate the specific case of semi-coherent materials
interfaces by computing the coupling between phonons and interfacial strain
resulting from aperiodic array of misfit dislocations. Our framework
quantitatively describes the thermal interface resistance within the
technologically relevant Si-Ge heterostructures. In future, this formalism
could provide new insight into coherent and driven phonon effects in nanoscale
materials increasingly accessible via ultrafast, THz and near-field
spectroscopies.",1811.01059v1
2018-11-07,Spin Hall effect in 2D metallic delafossite PtCoO$_2$ and vicinity topology,"The two-dimensional (2D) metal PtCoO$_2$ is renowned for the lowest room
temperature resistivity among all oxides, close to that of the top two
materials Ag and Cu. In addition, we theoretically predict a strong intrinsic
spin Hall effect. This originates from six strongly-tilted Dirac cones that we
find in the electronic structure near the Fermi surface, where a gap is opened
by large spin-orbit coupling (SOC). This is underpinned by rich topological
properties; in particular, the phenomenology of a mirror Chern metal is
realized not exactly, but very accurately, on account of an approximate
crystalline symmetry. We expect that such 'vicinity topology' to be a feature
of relevance well beyond this material. Our Wilson loop analysis indicates
further elaborate features such as fragile topology. These findings highlight
PtCoO$_2$ as a promising material for spintronic applications as well as a
platform to study the interplay of symmetry and topology.",1811.03105v1
2020-03-22,Thermoelectric probe of defect state induced by ionic liquid gating in vanadium dioxide,"Thermoelectric measurements detect the asymmetry between the density of
states above and below the chemical potential in a material. It provides
insights into small variations in the density of states near the chemical
potential, complementing electron transport measurements. Here, combined
resistance and thermoelectric power measurements are performed on vanadium
dioxide (VO2), a prototypical correlated electron material, under ionic-liquid
(IL) gating. With IL gating, charge transport below the
metal-to-insulator-transition (MIT) temperature remains in the thermally
activated regime, while the Seebeck coefficient exhibits an apparent transition
from semiconducting to metallic behavior. The contrasting behavior indicates
changes in electronic structure upon IL gating, due to the formation of oxygen
defect states. The experimental results are corroborated by numerical
simulations based on a model density of states incorporating a gating induced
defect band. This study reveals thermoelectric measurements to be a convenient
and sensitive probe for the role of defect states induced by IL gating in
suppressing the MIT in VO2, which remains benign in charge transport
measurements, and possibly for studying defect sates in other materials.",2003.09840v1
2017-03-10,Highly crystalline 2D superconductors,"Recent technological advances in controlling materials have developed methods
to produce idealized two-dimensional (2D) electron systems such as
heterogeneous interfaces, molecular-beam-epitaxy (MBE) grown atomic layers,
exfoliated thin flakes and field-effect devices. These 2D electron systems are
highly-crystalline with less disorder in common, some of which indeed show
sheet resistance more than one order of magnitude lower even in atomic layers
or single layers than that of conventional amorphous/granular thin films. Here,
we present a review on the recent developments of highly-crystalline 2D
superconductors and a series of unprecedented physical properties discovered in
these systems. In particular, we highlight the quantum metallic state (or
possible metallic ground state), the quantum Griffiths phase in out-of-plane
magnetic fields, and the superconducting state maintained in anomalously large
in-plane magnetic fields, which were observed in exfoliated 2D materials,
MBE-grown atomic-layer thin films and electric-double-layer (ion-gated)
interfaces. These phenomena are discussed on the basis of weakened disorder
and/or broken spatial inversion symmetry. These novel aspects suggest that
highly-crystalline 2D systems are promising platforms for exploring new quantum
physics and superconductors.",1703.03541v1
2018-10-07,Log-periodic quantum magneto-oscillations and discrete scale invariance in topological material HfTe5,"Discrete scale invariance (DSI) is a phenomenon featuring intriguing
log-periodicity which can be rarely observed in quantum systems. Here we report
the log-periodic quantum oscillations in the magnetoresistance (MR) and the
Hall traces of HfTe5 crystals, which reveals the appearance of DSI. The
oscillations show the same logB-periodicity in the behavior of MR and Hall,
indicating an overall effect of the DSI on the transport properties. Moreover,
the DSI feature in the Hall resistance signals its close relation to the
carriers. Combined with theoretical simulations, we further clarify the origin
of the log-periodic oscillations and the DSI in the topological materials. Our
work evidences the universality of the DSI in the Dirac materials and paves way
for the full understanding of the novel phenomenon.",1810.03109v1
2019-02-20,Structural origins of electronic conduction in amorphous copper-doped alumina,"We perform an {\it ab initio} modeling of amorphous copper-doped alumina
(a-Al$_2$O$_3$:Cu), a prospective memory material based on resistance
switching, and study the structural origin of electronic conduction in this
material. We generate molecular dynamics based models of a-Al$_2$O$_3$:Cu at
various Cu-concentrations and study the structural, electronic and vibrational
properties as a function of Cu-concentration. Cu atoms show a strong tendency
to cluster in the alumina host, and metallize the system by filling the band
gap uniformly for higher Cu-concentrations. We also study thermal fluctuations
of the HOMO-LUMO energy splitting and observe the time evolution of the size of
the band gap, which can be expected to have an important impact on the
conductivity. We perform a numerical computation of conduction pathways, and
show its explicit dependence on Cu connectivity in the host. We present an
analysis of ion dynamics and structural aspects of localization of classical
normal modes in our models.",1902.07559v1
2017-04-03,Superconducting Two-Dimensional Metal-Organic Framework,"Superconductivity is a fascinating quantum phenomenon characterized by zero
electrical resistance and the Meissner effect. To date, several distinct
families of superconductors (SCs) have been discovered. These include
three-dimensional (3D) bulk SCs in both inorganic and organic materials as well
as two-dimensional (2D) thin film SCs but only in $inorganic$ materials. Here
we predict superconductivity in 2D and 3D $organic$ metal-organic frameworks by
using first-principles calculations. We show that the highly conductive and
recently synthesized Cu-benzenehexathial (BHT) is a Bardeen-Cooper-Schrieffer
SC. Remarkably, the monolayer Cu-BHT has a critical temperature ($T_{c}$) of
4.43 K while $T_{c}$ of bulk Cu-BHT is 1.58 K. Different from the enhanced
$T_{c}$ in 2D inorganic SCs which is induced by interfacial effects, the
$T_{c}$ enhancement in this 2D organic SC is revealed to be the out-of-plane
soft-mode vibrations, analogous to surface mode enhancement originally proposed
by $Ginzburg$. Our findings not only shed new light on better understanding 2D
superconductivity, but also open a new direction to search for SCs by interface
engineering with organic materials.",1704.00490v1
2019-08-07,Transport phenomena in a free-standing two-dimensional sodium sheet,"The advances in the growth techniques provide numerous scope to explore the
possibilities of new 2D materials for potential applications. With the aid of
first-principle calculations we show that 2D Na can be a new addition to the
family of thermodynamically stable 2D materials for device applications. Not
surprisingly, due to half-occupied $3s$ orbital 2D Na possesses the features of
the 2D electron gas (2DEG). The transport properties are examined based on the
accurate solution of Boltzmann transport equation. With practically tunable
carrier density in 2D materials, the intrinsic electrical resistivity of
electron doped 2D Na is $\sim$ 1.4 times larger than that of graphene and falls
below the latter 450 K onwards. The Bloch-Gr\""uneisen temperature is almost
constant at 50 K, independent of the type or density of the charge carriers.
The electronic thermal conductivity of pure 2D Na is $\sim$ 1.24 times larger
than that of its bulk counterpart at 300 K. The Wiedemann-Franz law stands tall
in 2D Na with calculated Lorenz number 2.41 $\times 10^{-8} V^2/deg^2$ at room
temperature. The transport mechanism presented here is expected to occur in all
Na like systems with a clean Fermi surface.",1908.02431v1
2019-12-18,Observation of multiple Dirac states in a magnetic topological material EuMg2Bi2,"Initiated by the discovery of topological insulators, topologically
non-trivial materials, more specifically topological semimetals and metals have
emerged as new frontiers in the field of quantum materials. In this work, we
perform a systematic measurement of EuMg2Bi2, a compound with antiferromagnetic
transition temperature at 6.7 K, observed via electrical resistivity,
magnetization and specific heat capacity measurements. By utilizing
angle-resolved photoemission spectroscopy in concurrence with first-principles
calculations, we observe Dirac cones at the corner and the zone center of the
Brillouin zone. From our experimental data, multiple Dirac states at G and K
points are observed, where the Dirac nodes are located at different energy
positions from the Fermi level. Our experimental investigations of detailed
electronic structure as well as transport measurements of EuMg2Bi2 suggest that
it could potentially provide a platform to study the interplay between topology
and magnetism.",1912.08645v1
2012-03-28,Finite element modelling of shock-induced damages on ceramic hip prostheses,"The aim of this work was to simulate the behaviour of hip prostheses under
mechanical shocks. When hip joint is replaced by prosthesis, during the swing
phase of the leg, a microseparation between the prosthetic head and the cup
could occur. Two different sizes of femoral heads were studied: 28 and 32 mm
diameter, made, respectively, in alumina and zirconia. The shock-induced stress
was determined numerically using finite element analysis (FEA), Abaqus
software. The influence of inclination, force, material, and microseparation
was studied. In addition, an algorithm was developed from a probabilistic
model, Todinov's approach, to predict lifetime of head and cup. Simulations
showed maximum tensile stresses were reached on the cup's surfaces near to rim.
The worst case was the cup-head mounted at 30^{\circ}. All simulations and
tests showed bulk zirconia had a greater resistance to shocks than bulk
alumina. The probability of failure could be bigger than 0.9 when a porosity
greater than 0.7% vol. is present in the material. Simulating results showed
good agreement with experimental results. The tests and simulations are
promising for predicting the lifetime of ceramic prostheses.",1203.6154v1
2015-04-20,Giant reversible nanoscale piezoresistance at room temperature in Sr2IrO4 thin films,"Layered iridates have been the subject of intense scrutiny on account of
their unusually strong spin-orbit coupling, which opens up a narrow gap in a
material that would otherwise be a metal. This insulating state is very
sensitive to external perturbations. Here, we show that vertical compression at
the nanoscale, delivered using the tip of a standard scanning probe microscope,
is capable of inducing a five orders of magnitude change in the room
temperature resistivity of Sr2IrO4. The extreme sensitivity of the electronic
structure to anisotropic deformations opens up a new angle of interest on this
material, and the giant and fully reversible perpendicular piezoresistance
makes iridates a promising material for room temperature piezotronic devices.",1504.05245v1
2018-12-06,Crack Growth Behavior in NiTi Shape Memory Alloys Under Mode-I Isothermal Loading: Effect of Stress State,"Fracture behavior in nickel-titanium (NiTi) shape memory alloys (SMAs)
subjected to mode-I, isothermal loading is studied using finite element
analysis (FEA). Compact tension (CT) SMA specimen is modeled in Abaqus finite
element suite and crack growth under displacement boundary condition is
investigated for plane strain and plane stress conditions. Parameters for the
SMA material constitutive law implemented in the finite element setup are
acquired from characterization tests conducted on near-equiatomic NiTi SMA.
Virtual crack closure technique (VCCT) is implemented where crack is assumed to
extend when the energy release rate at the crack-tip becomes equal to the
experimentally obtained material-specific critical value. Load-displacement
curves and mechanical fields near the crack-tip in plane strain and plane
stress cases are examined. Moreover, a discussion with respect to the crack
resistance R-curves calculated using the load-displacement response for plane
strain and plane stress conditions is presented.",1812.02362v1
2018-12-24,Control of Spin Diffusion and Suppression of the Hanle Effect by the Coexistence of Spin and Valley Hall Effects,"In addition to spin, electrons in many materials possess an additional
pseudo-spin degree of freedom known as 'valley'. In materials where the spin
and valley degrees of freedom are weakly coupled, they can be both excited and
controlled independently. In this work, we study a model describing the
interplay of the spin and valley Hall effects in such two-dimensional
materials. We demonstrate the emergence of an additional longitudinal neutral
current that is both spin and valley polarized. The additional neutral current
allows to control the spin density by tuning the magnitude of the valley Hall
effect. In addition, the interplay of the two effects can suppress the Hanle
effect, that is, the oscillation of the nonlocal resistance of a Hall bar
device with in-plane magnetic field. The latter observation provides a possible
explanation for the absence of the Hanle effect in a number of recent
experiments. Our work opens also the possibility to engineer the conversion
between the valley and spin degrees of freedom in two-dimensional materials.",1812.09996v2
2019-06-24,Cross interface model for the thermal transport across interface between overlapped boron nitride nanoribbons,"The application of low-dimensional materials for heat dissipation requires a
comprehensive understanding of the thermal transport at the cross interface,
which widely exists in various composite materials and electronic devices. In
this work, we proposed an analytical model, named as cross interface model
(CIM), to accurately reveal the essential mechanism of the two-dimensional
thermal transport at the cross interface. The applicability of CIM is validated
through the comparison of the analytical results with molecular dynamics
simulations for a typical cross interface of two overlapped boron nitride
nanoribbons. Besides, it is figured out that the factor ({\eta}) has important
influence on the thermal transport besides the thermal resistance inside and
between the materials, which is found to be determined by two dimensionless
parameters from its expression. Our investigations deepen the understanding of
the thermal transport at the cross interface and also facilitate to guide the
applications of low-dimensional materials in thermal management.",1906.09751v1
2019-11-05,Molecular beam epitaxy of CuMnAs,"We present a detailed study of the growth of the tetragonal polymorph of
antiferromagnetic CuMnAs by the molecular beam epitaxy technique. We explore
the parameter space of growth conditions and their effect on the
microstructural and transport properties of the material. We identify its
typical structural defects and compare the properties of epitaxial CuMnAs
layers grown on GaP, GaAs and Si substrates. Finally, we investigate the
correlation between the crystalline quality of CuMnAs and its performance in
terms of electrically induced resistance switching.",1911.01794v1
2019-11-15,Flexoskeleton printing for versatile insect-inspired robots,"One of the many secrets to the success and prevalence of insects is their
versatile, robust, and complex exoskeleton morphology. A fundamental challenge
in insect-inspired robotics has been the fabrication of robotic exoskeletons
that can match the complexity of exoskeleton structural mechanics. Hybrid
robots composed of rigid and soft elements have previously required access to
expensive multi-material 3D printers, multi-step casting and machining
processes, or limited material choice when using consumer-grade fabrication
methods. Here we introduce a new design and fabrication process to rapidly
construct flexible exoskeleton-inspired robots called flexoskeleton printing.
We modify a consumer-grade fused deposition material (FDM) 3D printer to
deposit filament directly onto a heated thermoplastic base layer which provides
extremely strong bond strength between the deposited material and the
inextensible, flexible base layer. This process significantly improves the
fatigue resistance of printed components and enables a new class of
insect-inspired robot morphologies. We demonstrate these capabilities through
design and testing of a wide library of canonical flexoskeleton elements;
ultimately leading to the integration of elements into a flexoskeleton walking
legged robot.",1911.06897v2
2020-01-07,Molecular beam epitaxy of the magnetic kagome metal FeSn on LaAlO3 (111),"Materials with a layered Kagome lattice are expected to give rise to novel
physics arising from band structures with topological properties, spin liquid
behavior and the formation of skyrmions. Until now, most work on Kagome
materials has been performed on bulk samples due to difficulties in thin film
synthesis. Here, by using molecular beam epitaxy, layered Kagome-structured
FeSn films are synthesized on (111) oriented LaAlO3 substrate. Both in-situ and
ex-situ characterizations indicate these films are highly crystalline and
c-axis oriented, with atomically smooth surfaces. However, the films grow as
disconnected islands, with lateral dimensions on the micron scale. By
patterning Pt electrodes using a focused electron beam, longitudinal and
transverse resistance of single islands have been measured in magnetic fields.
Our work opens a pathway for exploring mesoscale transport properties in thin
films of Kagome materials and related devices.",2001.01820v2
2020-05-11,Highly flexible electromagnetic interference shielding films based on ultrathin Ni/Ag composites on paper substrates,"Highly flexible electromagnetic interference (EMI) shielding material with
excellent shielding performance is of great significance to practical
applications in next-generation flexible devices. However, most EMI materials
suffer from insufficient flexibility and complicated preparation methods. In
this study, we propose a new scheme to fabricate a magnetic Ni particle/Ag
matrix composite ultrathin film on a paper surface. For a ~2 micro meter thick
film on paper, the EMI shielding effectiveness (SE) was found to be 46.2 dB at
8.1 GHz after bending 200,000 times over a radius of ~2 mm. The sheet
resistance (Rsq) remained lower than 2.30 Ohm after bending 200,000 times.
Contrary to the change in Rsq, the EMI SE of the film generally increased as
the weight ratio of Ag to Ni increased, in accordance with the principle that
EMI SE is positively related with an increase in electrical conductivity.
Desirable EMI shielding ability, ultrahigh flexibility, and simple processing
provide this material with excellent application prospects.",2005.04875v1
2020-08-19,Observation of plateau-like magnetoresistance in twisted Fe3GeTe2/Fe3GeTe2 junction,"Controlling the stacking of van der Waals (vdW) materials is found to produce
exciting new findings, since hetero- or homo- structures have added the diverse
possibility of assembly and manipulated functionalities. However, so far, the
homostructure with a twisted angle based on the magnetic vdW materials remains
unexplored. Here, we achieved a twisted magnetic vdW Fe3GeTe2/Fe3GeTe2 junction
with broken crystalline symmetry. A clean and metallic vdW junction is
evidenced by the temperature-dependent resistance and the linear I-V curve.
Unlike the pristine FGT, a plateau-like magnetoresistance (PMR) is observed in
the magnetotransport of our homojunction due to the antiparallel magnetic
configurations of the two FGT layers. The PMR ratio is found to be ~0.05% and
gets monotonically enhanced as temperature decreases like a metallic giant
magnetoresistance (GMR). Such a tiny PMR ratio is at least three orders of
magnitude smaller than the tunneling magnetoresistance (TMR) ratio, justifying
our clean metallic junction without a spacer. Our findings demonstrate the
feasibility of the controllable homostructure and shed light on future
spintronics using magnetic vdW materials.",2008.08313v1
2020-10-24,Drawing WS2 thermal sensors on paper substrates,"Paper based thermoresistive sensors are fabricated by rubbing WS2 powder
against a piece of standard copier paper, like the way a pencil is used to
write on paper. The abrasion between the layered material and the rough paper
surface erodes the material, breaking the weak van der Waals interlayer bonds,
yielding a film of interconnected platelets. The resistance of WS2 presents a
strong temperature dependence, as expected for a semiconductor material in
which charge transport is due to thermally activated carriers. This strong
temperature dependence makes the paper supported WS2 devices extremely
sensitive to small changes in temperature. This exquisite thermal sensitivity,
and their fast response times to sudden temperature changes, is exploited
thereby demonstrating the usability of a WS2-on-paper thermal sensor in a
respiration monitoring device.",2010.12805v1
2021-04-08,Correlating Nanocrystalline Structure with Electronic Properties in 2D Platinum Diselenide,"Platinum diselenide (PtSe${_2}$) is a two-dimensional (2D) material with
outstanding electronic and piezoresistive properties. The material can be grown
at low temperatures in a scalable manner which makes it extremely appealing for
many potential electronics, photonics, and sensing applications. Here, we
investigate the nanocrystalline structure of different PtSe${_2}$ thin films
grown by thermally assisted conversion (TAC) and correlate them with their
electronic and piezoresistive properties. We use scanning transmission electron
microscopy for structural analysis, X-ray photoelectron spectroscopy (XPS) for
chemical analysis, and Raman spectroscopy for phase identification. Electronic
devices are fabricated using transferred PtSe${_2}$ films for electrical
characterization and piezoresistive gauge factor measurements. The variations
of crystallite size and their orientations are found to have a strong
correlation with the electronic and piezoresistive properties of the films,
especially the sheet resistivity and the effective charge carrier mobility. Our
findings may pave the way for tuning and optimizing the properties of TAC-grown
PtSe${_2}$ towards numerous applications.",2104.03636v1
2021-09-16,Analytic solution to pseudo-Landau levels in strongly bent graphene nanoribbons,"Nonuniform elastic strain is known to induce pseudo-Landau levels in Dirac
materials. But these pseudo-Landau levels are hardly resolvable in an analytic
fashion when the strain is strong, because of the emerging complicated space
dependence in both the strain-modulated Fermi velocity and the strain-induced
pseudomagnetic field. We analytically characterize the solution to the
pseudo-Landau levels in experimentally accessible strongly bent graphene
nanoribbons, by treating the effects of the nonuniform Fermi velocity and
pseudomagnetic field on equal footing. The analytic solution is detectable
through the angle-resolved photoemission spectroscopy (ARPES) and allows
quantitative comparison between theories and various transport experiments,
such as the Shubnikov-de Haas oscillation in the complete absence of magnetic
fields and the negative strain-resistivity resulting from the valley anomaly.
The analytic solution can be generalized to twisted two-dimensional materials
and topological materials and will shed a new light on the related experimental
explorations and straintronics applications.",2109.08182v2
2021-09-27,"Layered, Tunable Graphene Oxide-Nylon Heterostructures for Wearable Electrocardiogram Sensors","Nanoscale engineered materials combined with wearable wireless technologies
can deliver a new level of health monitoring. A reduced graphene oxide-nylon
composite material is developed and tested, demonstrating its usefulness as a
material for sensors in wearable, long-term electrocardiogram (ECG) monitoring
via a comparison to one of the widely used ECG sensors. The structural analysis
by scanning electron (SEM) and atomic force microscopy (AFM) shows a limited
number of defects on a macroscopic scale. Fourier Transform Infrared (FTIR) and
Raman spectroscopy confirm the presence of rGOx, and the ratio of D- and
G-features as a function of thickness correlates with the resistivity analysis.
The negligible effect of the defects and the tunability of electrical and
optical properties, together with live ECG data, demonstrate its signal
transduction capability.",2109.12739v2
2022-04-30,Scattering mechanisms in state-of-the-art GaAs/AlGaAs quantum wells,"Motivated by recent breakthrough in molecular beam epitaxy of GaAs/AlGaAs
quantum wells [Y. J. Chung \textit{et al.}, Nature Materials \textbf{20}, 632
(2021)], we examine contributions to mobility and quantum mobility from various
scattering mechanisms and their dependencies on the electron density. We find
that at lower electron densities, $n_e \lesssim 1 \times 10^{11}$ cm$^{-2}$,
both transport and quantum mobility are limited by unintentional background
impurities and follow a power law dependence, $\propto n_e^{\alpha}$, with
$\alpha \approx 0.85$. Our predictions for quantum mobility are in reasonable
agreement with an estimate obtained from the resistivity at filling factor
$\nu= 1/2$ in a sample of Y. J. Chung \textit{et al.} with $n_e = 1 \times
10^{11}$ cm$^{-2}$. Consideration of other scattering mechanisms indicates that
interface roughness (remote donors) is a likely limiting factor of transport
(quantum) mobility at higher electron densities. Future measurements of quantum
mobility should yield information on the distribution of background impurities
in GaAs and AlGaAs.",2205.00365v3
2023-07-20,Superconductivity in a van der Waals layered quasicrystal,"van der Waals (vdW) layered transition-metal chalcogenides are attracting
significant attention owing to their fascinating physical properties. This
group of materials consists of abundant members with various elements, having a
variety of different structures. However, all vdW layered materials studied to
date have been limited to crystalline materials, and the physical properties of
vdW layered quasicrystals have not yet been reported. Here, we report on the
discovery of superconductivity in a vdW layered quasicrystal of Ta1.6Te. The
electrical resistivity, magnetic susceptibility, and specific heat of the
Ta1.6Te quasicrystal fabricated by reaction sintering, unambiguously validated
the occurrence of bulk superconductivity at a transition temperature of ~1 K.
This discovery can pioneer new research on assessing the physical properties of
vdW layered quasicrystals as well as two-dimensional quasicrystals; moreover,
it paves the way toward new frontiers of superconductivity in thermodynamically
stable quasicrystals, which has been the predominant challenge facing condensed
matter physics since the discovery of quasicrystals almost four decades ago.",2307.10679v1
2023-08-21,Coupling Between Magnetic and Transport Properties in Magnetic Layered Material Mn2-xZnxSb,"We synthesized single crystals for Mn2-xZnxSb and studied their magnetic and
electronic transport properties. This material system displays rich magnetic
phase tunable with temperature and Zn composition. In addition, two groups of
distinct magnetic and electronic properties, separated by a critical Zn
composition of x = 0.6, are discovered. The Zn-less samples are metallic and
characterized by a resistivity jump at the magnetic ordering temperature, while
the Zn-rich samples lose metallicity and show a metal-to-insulator
transition-like feature tunable by magnetic field. Our findings establish
Mn2-xZnxSb as a promising material platform that offers opportunities to study
how the coupling of spin, charge, and lattice degrees of freedom governs
interesting transport properties in 2D magnets, which is currently a topic of
broad interest.",2308.10764v1
2023-10-08,An innovative clay metaBrick-based motif to enhance thermal and acoustic insulation,"Metamaterials have gained popularity in recent years as a promising avenue
for producing innovative materials with distinctive properties that offer
unprecedented features. In this study, we address the thermal and acoustic
challenges of building materials. We numerically and experimentally investigate
a clay metaBrick, which is an innovative metamaterial design based on the
existing hollow brick that has shown strong sound and thermal performances. We
evaluate the acoustic and thermal characteristics of the clay metaBrick,
including sound transmission and heat resistance, using the finite element
method. Furthermore, we validate the results experimentally by investigating
the behaviors of the wall built on metaBricks in two tests: sound and thermal.
We contrast the findings of the metaBrick based wall with performances of a
standard hollow brick wall. The metaBrick offers enhanced acoustic and thermal
insulation properties compared to the standard brick, with a compressive
strength above standards required in the building materials.",2310.05148v1
2024-03-18,The Role of Temperature on Irradiation Defect Evolution near Surfaces and Grain Boundaries in Tungsten,"This study explores the impact of temperature on defect dynamics in tungsten,
emphasizing its application in nuclear fusion reactors as Plasma Facing
Components (PFCs). Through atomistic simulations, the research elucidates the
intricate interplay of defect production, annihilation, and redistribution
under irradiation at room (300K) and elevated temperatures (1000K). It
demonstrates that higher temperatures significantly increase the number and
mobility of defects, leading to a substantial rise in the total number of
surviving Frenkel Pairs (FPs), with a notable preference for surface
distribution. This redistribution is attributed to energy gradient-driven
relocation processes, enhanced by the defects' increased mobility at elevated
temperatures. Moreover, the study reveals that elevated temperatures promote
biased accumulation of interstitial defects in grain boundaries, especially in
configurations that facilitate efficient interstitial migration, indicating a
strategy for minimizing lattice interstitial accumulation under irradiation.
These findings underscore the critical role of temperature in modulating
irradiation-induced defect dynamics in tungsten, providing valuable insights
for designing and selecting materials with optimized irradiation resistance for
use in extreme conditions of nuclear fusion reactors. The research suggests a
material design approach that accounts for temperature effects to enhance the
durability and performance of nuclear fusion materials.",2403.12259v1
2024-03-19,Unveiling the Reactivity of Oxygen and Ozone on C2N Monolayer: A First-Principles Study,"The process of environmental oxidation is pivotal in determining the physical
and chemical properties of two-dimensional (2D) materials. Its impact holds
great significance for the practical application of these materials in
nanoscale devices functioning under ambient conditions. This study delves into
the influence of O2 and O3 exposure on the structural and electronic
characteristics of the C2N monolayer, focusing on the kinetics of adsorption
and dissociation reactions. Employing first-principles density functional
theory calculations alongside climbing image nudged elastic band calculations,
we observe that the C2N monolayer exhibits resistance to oxidation and
ozonation, evidenced by energy barriers of 0.05 eV and 0.56 eV, respectively.
These processes are accompanied by the formation of epoxide (C-O-C) groups.
Furthermore, the dissociation mechanism involves charge transfers from the
monolayer to the molecules. Notably, the dissociated configurations demonstrate
higher bandgaps compared to the pristine C2N monolayer, attributed to robust
C-O hybridization. These findings suggest the robustness of C2N monolayers
against oxygen/ozone exposures, ensuring stability for devices incorporating
these materials.",2403.12454v1
2024-05-13,Significant improvement in sensitivity of an anomalous Nernst heat flux sensor by composite structure,"Heat flux sensors (HFS) have attracted significant interest for their
potential in managing waste heat efficiently. A recently proposed HFS, that
works on the basis of the anomalous Nernst effect (ANE), offers several
advantages in its simple structure leading to easy fabrication, low cost, and
reduced thermal resistance. However, enhancing sensitivity through traditional
material selection is now challenging due to a small number of materials
satisfying the required coexistence of a large transverse Seebeck coefficient
and low thermal conductivity. In this study, by utilizing composite structures
and optimizing the device geometry, we have achieved a substantial improvement
in the sensitivity of an ANE-based HFS. We developed composite structures
comprised of a plastic substrate with an uneven surface and three-dimensional
(3D) uneven TbCo films, fabricated using nanoimprint techniques and sputtering.
This approach resulted in a sensitivity that is approximately four times
greater than that observed in previous studies. Importantly, this method is
independent of the material properties and can significantly enhance the
sensitivity. Our findings could lead to the development of highly sensitive HFS
devices and open new avenues for the fabrication of 3D devices.",2405.07758v1
2003-08-25,Formation of Semi-relativisitc Jets from Magnetospheres of Accreting Neutron Stars: Injection of Hot Bubbles into a Magnetic Tower,"We present the results of 2.5-dimensional resistive magnetohydrodynamic (MHD)
simulations of the magnetic interaction between a weakly magnetized neutron
star and its accretion disk. General relativistic effects are simulated by
using the pseudo-Newtonian potential. We find that well-collimated jets
traveling along the rotation axis of the disk are formed by the following
mechanism: (1) The magnetic loops connecting the neutron star and the disk are
twisted due to the differential rotation between the neutron star and the disk.
(2) Twist injection from the disk initiates expansion of the loop. (3) The
expanding magnetic loops create a magnetic tower in which accelerated disk
material travel as collimated bipolar jets. The propagation speed of the
working surface of the jet is the order of 10% of the speed of light ($\sim
0.1c$). (4) Magnetic reconnection taking place inside the expanding magnetic
loops injects hot bubbles intermittently into the magnetic tower. The ejection
speed of the bubble is the order of the local Alfv\'{e}n speed of the launching
point and $\sim 0.2c$ in our simulations. (5) The hot bubbles moving inside the
tower catch up with the working surface of the jet. High energy electrons
created by the magnetic reconnection are a plausible source of radio emission.
Our model can explain the formation process of a narrow jet from a weakly
magnetized ($|{\boldmath$B_{*}$}|\le 10^{9}$ gauss) neutron star and the
correlation between radio flares of the core and of the lobe observed in Sco
X-1.",0308437v2
2009-01-28,Strong enhancement of Jc in binary and alloyed in-situ MgB2 wires by a new approach: Cold high pressure densification,"Cold high pressure densification (CHPD) is presented as a new way to
substantially enhance the critical current density of in situ MgB2 wires at 4.2
and 20 K at fields between 5 and 14 T. The results on two binary MgB2 wires and
an alloyed wire with 10 wt.% B4C are presented The strongest enhancement was
measured at 20K, where cold densification at 1.85 GPa on a binary Fe/MgB2 wire
raised both Jcpara and Jcperp by more than 300% at 5T, while Birr was enhanced
by 0.7 T. At 4.2K, the enhancement of Jc was smaller, but still reached 53% at
10 T. After applying pressures up to 6.5 GPa, the mass density dm of the
unreacted (B+Mg) mixture inside the filaments reached 96% of the theoretical
density. After reaction under atmospheric pressure, this corresponds to a
highest mass density df in the MgB2 filaments of 73%. After reaction, the
electrical resistance of wires submitted to cold densification was found to
decrease, reflecting an improved connectivity. A quantitative correlation
between filament mass density and the physical properties was established.
Monofilamentary rectangular wires with aspect ratios a/b < 1.25 based on low
energy ball milled powders exhibited very low anisotropy ratios, Gamma =
Jcpara/Jcperp being < 1.4 at 4.2 K and 10T. The present results can be
generalized to alloyed MgB2 wires, as demonstrated on a wire with B4C
additives. Based on the present data, it follows that cold densification has
the potential of further improving the highest Jcpara and Jcperp values
reported so far for in situ MgB2 tapes and wires with SiC and C additives.
Investigations are under work in our laboratory to determine whether the
densification method CHPD can be applied to longer wire or tape lengths.",0901.4546v1
2011-01-24,"Stabilization of an ambient pressure, collapsed tetragonal phase in CaFe2As2 and tuning of the orthorhombic / antiferromagnetic transition temperature by over 70 K by control of nano-precipitates","We have found a remarkably large response of the transition temperature of
CaFe2As2 single crystals grown out of excess FeAs to annealing / quenching
temperature. Whereas crystals that are annealed at 400 C exhibit a first order
phase transition from a high temperature tetragonal to a low temperature
orthorhombic and antiferromagnetic state near 170 K, crystals that have been
quenched from 960 C exhibit a transition from a high temperature tetragonal
phase to a low temperature, non-magnetic, collapsed tetragonal phase below 100
K. By use of temperature dependent electrical resistivity, magnetic
susceptibility, X-ray diffraction, Mossbauer spectroscopy and nuclear magnetic
resonance measurements we have been able to demonstrate that the transition
temperature can be reduced in a monotonic fashion by varying the annealing /
quenching temperature from 400 to 850 C with the low temperature state
remaining antiferromagnetic for transition temperatures larger than 100 K and
becoming collapsed tetragonal / non-magnetic for transition temperatures below
90 K. This suppression of the orthorhombic / antiferromagnetic phase transition
and its ultimate replacement with the collapsed tetragonal / non-magnetic phase
is similar to what has been observed for CaFe2As2 under hydrostatic pressure.
Transmission electron microscopy studies indicate that there is a temperature
dependent, width of formation of CaFe2As2 with a decreasing amount of excess Fe
and As being soluble in the single crystal at lower annealing temperatures. For
samples quenched from 960 C there is a fine (of order 10 nm), semi-uniform
distribution of precipitate that can be associated with an average strain field
whereas for samples annealed at 400 C the excess Fe and As form mesoscopic
grains that induce little strain throughout the CaFe2As2 lattice.",1101.4595v1
2011-10-14,Numerical Investigation of Design Strategies to Achieve Long-Life Pavements,"Increasing the HMA base thickness and modifying the HMA mixture properties to
improve the resistance to fatigue cracking are among the most popular methods
for achieving long-lasting pavements. Such methods are based on the idea of
reducing the tensile strain at the bottom of the HMA layer below the Fatigue
Endurance Limit (FEL), a level of strain below which no cumulative damage
occurs to the HMA mixture. This study investigates the effectiveness of several
design strategies involved in long-life, perpetual pavement design. A 3D Finite
Element model of the pavement involving a linear viscoelastic constitutive
model for HMA materials and non-uniform tire contact stresses is developed
using ABAQUS 6.11. The effects of asphalt base course thickness and mixture
type, rich binder layer, and aggregate subbase layer are examined. Four asphalt
base course mixture types, namely dense graded, polymer modified, high modulus,
and standard binder, are studied as a function of the asphalt base course
thickness. The results underline a better performance of the high-modulus
asphalt base, as compared to the other base course mixtures. The aggregate
subbase layer on top of subgrade soil showed a relatively minor effect on the
longitudinal and lateral strain response at the bottom of asphalt base course.
The addition of a rich binder layer at the bottom of the asphalt base course
showed a significant reduction in tensile strains. Tables are provided as a
guideline to assess the different alternatives in design of long-life perpetual
pavements.",1110.3318v7
2013-06-21,"Crystallographic, Electronic, Thermal and Magnetic Properties of Single-Crystal SrCo2As2","In tetragonal SrCo2As2 single crystals, inelastic neutron scattering
measurements demonstrated that strong stripe-type antiferromagnetic (AFM)
correlations occur at a temperature T = 5 K [W. Jayasekara et al.,
arXiv:1306.5174] that are the same as in the isostructural AFe2As2 (A = Ca, Sr,
Ba) parent compounds of high-Tc superconductors. This surprising discovery
suggests that SrCo2As2 may also be a good parent compound for high-Tc
superconductivity. Here, structural and thermal expansion, electrical
resistivity rho, angle-resolved photoemission spectroscopy (ARPES), heat
capacity Cp, magnetic susceptibility chi, 75As NMR and neutron diffraction
measurements of SrCo2As2 crystals are reported together with LDA band structure
calculations that shed further light on this fascinating material. The c-axis
thermal expansion coefficient alpha_c is negative from 7 to 300 K, whereas
alpha_a is positive over this T range. The rho(T) shows metallic character. The
ARPES measurements and band theory confirm the metallic character and in
addition show the presence of a flat band near the Fermi energy E_F. The band
calculations exhibit an extremely sharp peak in the density of states D(E_F)
arising from a flat d_{x^2 - y^2} band. A comparison of the Sommerfeld
coefficient of the electronic specific heat with chi(T = 0) suggests the
presence of strong ferromagnetic itinerant spin correlations which on the basis
of the Stoner criterion predicts that SrCo2As2 should be an itinerant
ferromagnet, in conflict with the magnetization data. The chi(T) does have a
large magnitude, but also exhibits a broad maximum at 115 K suggestive of
dynamic short-range AFM spin correlations, in agreement with the neutron
scattering data. The measurements show no evidence for any type of phase
transition between 1.3 and 300 K and we propose that metallic SrCo2As2 has a
gapless quantum spin-liquid ground state.",1306.5222v3
2014-02-17,Unravelling the effect of SrTiO3 antiferrodistortive phase transition on the magnetic properties of La0.7Sr0.3MnO3 thin films,"Epitaxial La0.7Sr0.3MnO3 (LSMO) thin films, with different thickness ranging
from 20 nm up to 330 nm, were deposited on (100)-oriented strontium titanate
(STO) substrates by pulsed laser deposition, and their structure and morphology
characterized at room temperature. Magnetic and electric transport properties
of the as-processed thin films reveal an abnormal behavior in the temperature
dependent magnetization M(T) below the antiferrodistortive STO phase transition
(TSTO) and also an anomaly in the magnetoresistance and electrical resistivity
close to the same temperature. Up to 100 nm LSMO thin films, an in-excess
magnetization and pronounced changes in the coercivity are evidenced, achieved
through the interface-mediated magnetoelastic coupling with antiferrodistortive
domain wall movement occurring below TSTO. Contrarily, for thicker LSMO thin
films, above 100 nm, an in-defect magnetization is observed. This reversed
behavior can be understood within the emergence in the upper layer of the film,
observed by high resolution transmission electron microscopy, of a branched
structure needed to relax elastic energy stored in the film which leads to
randomly oriented magnetic domain reconstructions. For enough high-applied
magnetic fields, as thermodynamic equilibrium is reached, a fully suppression
of the anomalous magnetization occurs, wherein the temperature dependence of
the magnetization starts to follow the expected Brillouin behavior.",1402.4040v1
2017-12-04,Effect of crystalline anisotropy on vertical (-201) and (010) beta-Ga2O3 Schottky barrier diodes on EFG single-crystal substrates,"Vertical (-201) and (010) beta-Ga2O3 Schottky barrier diodes (SBDs) were
fabricated on single-crystal substrates grown by edge-defined film-fed growth
(EFG) method. High resolution X-ray diffraction (HRXRD) and atomic force
microscopy (AFM) confirmed good crystal quality and surface morphology of the
substrates. The electrical properties of both devices, including
current-voltage (I-V) and capacitance-voltage (C-V) characteristics, were
comprehensively measured and compared. The (-201) and (010) SBDs exhibited
on-resistances (Ron) of 0.56 and 0.77 m{\Omega}cm2, turn-on voltages (Von) of
1.0 and 1.3 V, Schottky barrier heights (SBH) of 1.05 and 1.20 eV, electron
mobilities of 125 and 65 cm2/(Vs), respectively, with a high on-current of ~1.3
kA/cm2 and on/off ratio of ~109. The (010) SBD had a larger Von and SBH than
(-201) SBD due to anisotropic surface properties (i.e., surface Fermi level
pinning and band bending), as supported by X-ray photoelectron spectroscopy
(XPS) measurements. Temperature-dependent I-V also revealed the inhomogeneous
nature of the SBH in both devices, where (-201) SBD showed a more uniform SBH
distribution. The homogeneous SBH was also extracted: 1.33 eV for (-201) SBD
and 1.53 eV for (010) SBD. The reverse leakage current of the devices was well
described by the two-step trap-assisted tunneling model and the one-dimensional
variable range hopping conduction (1D-VRH) model. The (-201) SBD showed larger
leakage current due to its lower SBH and smaller activation energy. These
results indicate the crystalline anisotropy of beta-Ga2O3 can affect the
electrical properties of vertical SBDs and should be taken into consideration
when designing beta-Ga2O3 electronics.",1712.01318v1
2018-04-30,Detailed study on the Fermi surfaces of the type-II Dirac semimetallic candidates PdTe2 and PtTe2,"We present a detailed quantum oscillatory study on the Dirac type-II
semimetallic candidates PdTe$_{2}$ and PtTe$_{2}$ \emph{via} the temperature
and the angular dependence of the de Haas-van Alphen (dHvA) and Shubnikov-de
Haas (SdH) effects. In high quality single crystals of both compounds, i.e.
displaying carrier mobilities between $10^3$ and $10^4$ cm$^2$/Vs, we observed
a large non-saturating magnetoresistivity (MR) which in PtTe$_2$ at a
temperature $T = 1.3$ K, leads to an increase in the resistivity up to $5
\times 10^{4}$ % under a magnetic field $\mu_0 H = 62$ T. These high mobilities
correlate with their light effective masses in the range of 0.04 to 1 bare
electron mass according to our measurements. For PdTe$_{2}$ the experimentally
determined Fermi surface cross-sectional areas show an excellent agreement with
those resulting from band-structure calculations. Surprisingly, this is not the
case for PtTe$_{2}$ whose agreement between calculations and experiments is
relatively poor even when electronic correlations are included in the
calculations. Therefore, our study provides a strong support for the existence
of a Dirac type-II node in PdTe$_2$ and probably also for PtTe$_2$. Band
structure calculations indicate that the topologically non-trivial bands of
PtTe$_2$ do not cross the Fermi-level ($\varepsilon_F$). In contrast, for
PdTe$_2$ the Dirac type-II cone does intersect $\varepsilon_F$, although our
calculations also indicate that the associated cyclotron orbit on the Fermi
surface is located in a distinct $k_z$ plane with respect to the one of the
Dirac type-II node. Therefore it should yield a trivial Berry-phase.",1805.00087v1
2017-03-20,Pseudogap temperature $T^\star$ of cuprate superconductors from the Nernst effect,"We use the Nernst effect to delineate the boundary of the pseudogap phase in
the temperature-doping phase diagram of cuprate superconductors. New data for
the Nernst coefficient $\nu(T)$ of YBa$_{2}$Cu$_{3}$O$_{y}$ (YBCO),
La$_{1.8-x}$Eu$_{0.2}$Sr$_x$CuO$_4$ (Eu-LSCO) and
La$_{1.6-x}$Nd$_{0.4}$Sr$_x$CuO$_4$ (Nd-LSCO) are presented and compared with
previous data including La$_{2-x}$Sr$_x$CuO$_4$ (LSCO). The temperature $T_\nu$
at which $\nu/T$ deviates from its high-temperature behaviour is found to
coincide with the temperature at which the resistivity deviates from its
linear-$T$ dependence, which we take as the definition of the pseudogap
temperature $T^\star$- in agreement with gap opening detected in ARPES data. We
track $T^\star$ as a function of doping and find that it decreases linearly vs
$p$ in all four materials, having the same value in the three LSCO-based
cuprates, irrespective of their different crystal structures. At low $p$,
$T^\star$ is higher than the onset temperature of the various orders observed
in underdoped cuprates, suggesting that these orders are secondary
instabilities of the pseudogap phase. A linear extrapolation of $T^\star(p)$ to
$p=0$ yields $T^\star(p\to 0)\simeq T_N(0)$, the N\'eel temperature for the
onset of antiferromagnetic order at $p=0$, suggesting that there is a link
between pseudogap and antiferromagnetism. With increasing $p$, $T^\star(p)$
extrapolates linearly to zero at $p\simeq p_{\rm c2}$, the critical doping
below which superconductivity emerges at high doping, suggesting that the
conditions which favour pseudogap formation also favour pairing. We also use
the Nernst effect to investigate how far superconducting fluctuations extend
above $T_{\rm c}$, as a function of doping, and find that a narrow fluctuation
regime tracks $T_{\rm c}$, and not $T^\star$. This confirms that the pseudogap
phase is not a form of precursor superconductivity.",1703.06927v2
2022-02-06,Direct observation of vortices in an electron fluid,"Vortices are the hallmarks of hydrodynamic flow. Recent studies indicate that
strongly-interacting electrons in ultrapure conductors can display signatures
of hydrodynamic behavior including negative nonlocal resistance, Poiseuille
flow in narrow channels, and a violation of the Wiedemann-Franz law. Here we
provide the first visualization of whirlpools in an electron fluid. By
utilizing a nanoscale scanning superconducting quantum interference device on a
tip (SQUID-on-tip) we image the current distribution in a circular chamber
connected through a small aperture to an adjacent narrow current carrying strip
in high-purity type-II Weyl semimetal WTe2. In this geometry, the Gurzhi
momentum diffusion length and the size of the aperture determine the vortex
stability phase diagram. We find that the vortices are present only for small
apertures, whereas the flow is laminar (non-vortical) for larger apertures,
consistent with the theoretical analysis of the hydrodynamic regime and in
contrast to the expectations of ballistic transport in WTe2 at low
temperatures. Moreover, near the vortical-to-laminar transition, we observe a
single vortex in the chamber splitting into two vortices, a behavior that can
occur only in the hydrodynamic regime and cannot be sustained by ballistic
transport. These findings suggest a novel mechanism of hydrodynamic flow:
instead of the commonly considered electron-electron scattering at the bulk,
which becomes extremely weak at low temperatures, the spatial diffusion of
charge carriers' momenta is enabled by small-angle scattering at the planar
surfaces of thin pure crystals. This surface-induced para-hydrodynamics opens
new avenues for exploring and utilizing electron fluidics in high-mobility
electron systems.",2202.02798v1
2014-01-21,Random strain fluctuations as dominant disorder source for high-quality on-substrate graphene devices,"We have performed systematic investigations of transport through graphene on
hexagonal boron nitride (hBN) substrates, together with confocal Raman
measurements and a targeted theoretical analysis, to identify the dominant
source of disorder in this system. Low-temperature transport measurements on
many devices reveal a clear correlation between the carrier mobility $\mu$ and
the width $n^*$ of the resistance peak around charge neutrality, demonstrating
that charge scattering and density inhomogeneities originate from the same
microscopic mechanism. The study of weak-localization unambiguously shows that
this mechanism is associated to a long-ranged disorder potential, and provides
clear indications that random pseudo-magnetic fields due to strain are the
dominant scattering source. Spatially resolved Raman spectroscopy measurements
confirm the role of local strain fluctuations, since the line-width of the
Raman 2D-peak --containing information of local strain fluctuations present in
graphene-- correlates with the value of maximum observed mobility. The
importance of strain is corroborated by a theoretical analysis of the relation
between $\mu$ and $n^*$ that shows how local strain fluctuations reproduce the
experimental data at a quantitative level, with $n^*$ being determined by the
scalar deformation potential and $\mu$ by the random pseudo-magnetic field
(consistently with the conclusion drawn from the analysis of
weak-localization). Throughout our study, we compare the behavior of devices on
hBN substrates to that of devices on SiO$_2$ and SrTiO$_3$, and find that all
conclusions drawn for the case of hBN are compatible with the observations made
on these other materials. These observations suggest that random strain
fluctuations are the dominant source of disorder for high-quality graphene on
many different substrates, and not only on hexagonal boron nitride.",1401.5356v2
2018-12-07,Chemical Aspects of the Antiferromagnetic Topological Insulator MnBi$_{2}$Te$_{4}$,"Crystal growth of MnBi$_{2}$Te$_{4}$ has delivered the first experimental
corroboration of the 3D antiferromagnetic topological insulator state. Our
present results confirm that the synthesis of MnBi$_{2}$Te$_{4}$ can be
scaled-up and strengthen it as a promising experimental platform for studies of
a crossover between magnetic ordering and non-trivial topology. High-quality
single crystals of MnBi$_{2}$Te$_{4}$ are grown by slow cooling within a narrow
range between the melting points of Bi$_{2}$Te$_{3}$ (586 {\deg}C) and
MnBi$_{2}$Te$_{4}$ (600 {\deg}C). Single crystal X-ray diffraction and electron
microscopy reveal ubiquitous antisite defects in both cation sites and,
possibly, Mn vacancies. Powders of MnBi$_{2}$Te$_{4}$ can be obtained at
subsolidus temperatures, and a complementary thermochemical study establishes a
limited high-temperature range of phase stability. Nevertheless, quenched
powders are stable at room temperature and exhibit long-range antiferromagnetic
ordering below 24 K. The expected Mn(II) out-of-plane magnetic state is
confirmed by the magnetization, X-ray photoemission, X-ray absorption and
linear dichroism data. MnBi$_{2}$Te$_{4}$ exhibits a metallic type of
resistivity in the range 4.5-300 K. The compound is an n-type conductor that
reaches a thermoelectric figure of merit up to ZT = 0.17. Angle-resolved
photoemission experiments provide evidence for a surface state forming a gapped
Dirac cone.",1812.03106v1
2018-12-19,Universal relaxation in a holographic metallic density wave phase,"In this work, we uncover a universal relaxation mechanism of pinned density
waves, combining Gauge/Gravity duality and effective field theory techniques.
Upon breaking translations spontaneously, new gapless collective modes emerge,
the Nambu-Goldstone bosons of broken translations. When translations are also
weakly broken (eg by disorder or lattice effects), these phonons are pinned
with a mass $m$ and damped at a rate $\Omega$, which we explicitly compute.
This contribution to $\Omega$ is distinct from that of topological defects. We
show that $\Omega\simeq G m^2\Xi$, where $G$ is the shear modulus and $\Xi$ is
related to a diffusivity of the purely spontaneous state. This result follows
from the smallness of the bulk and shear moduli, as would be the case in a
phase with fluctuating translational order. At low temperatures, the collective
modes relax quickly into the heat current, so that late time transport is
dominated by the thermal diffusivity. In this regime, the resistivity in our
model is linear in temperature and the ac conductivity displays a significant
rearranging of the degrees of freedom, as spectral weight is shifted from an
off-axis, pinning peak to a Drude-like peak. These results could shed light on
transport properties in cuprate high $T_c$ superconductors, where quantum
critical behavior and translational order occur over large parts of the phase
diagram and transport shows qualitatively similar features.",1812.08118v3
2020-06-16,Topological Dirac states in a layered telluride TaPdTe$_5$ with quasi-one-dimensional PdTe$_2$ chains,"We report the synthesis and systematic studies of a new layered ternary
telluride TaPdTe5 with quasi-one-dimensional PdTe2 chains. This compound
crystalizes in a layered orthorhombic structure with space group Cmcm. Analysis
of its curved field-dependent Hall resistivity, using the two-band model,
indicates the hole-dominated transport with a high mobility ${\mu}_h$ = 2.38
$\times$ 10$^3$ cm$^2$ V$^{-1}$ s$^{-1}$ at low temperatures. The in-plane
magnetoresistance (MR) displays significant anisotropy with field applied along
the crystallographic $b$ axis. The MR with the current applied along the
$c$-axis is also measured in high magnetic fields up to 51.7 T. Remarkably, it
follows a power-law dependence and reaches (9.5 $\times$ 10$^3$)% at 2.1 K
without any signature of saturation. The De Haas-van Alphen oscillations show a
small Fermi-surface pocket with a nontrivial Berry phase. The Shubnikov-de Haas
(SdH) oscillations are detected at low temperatures and under magnetic fields
above 28.5 T. Two effective masses $m^*$ (0.26$m_e$ and 0.41$m_e$) are
extracted from the oscillatory SdH data. Our first-principles calculations
unveil a topological Dirac cone in its surface states, and, in particular, the
topological index indicates that TaPdTe$_5$ is a topologically nontrivial
material.",2006.09070v2
2020-11-03,Pressure induced superconductivity in MnSe,"The rich phenomena in the FeSe and related compounds have attracted great
interests as it provides fertile material to gain further insight into the
mechanism of high temperature superconductivity. A natural follow-up work was
to look into the possibility of superconductivity in MnSe. It was shown that
MnP becomes superconducting with Tc ~ 1 K under pressure. We demonstrated in
this work that high pressure can effectively suppress the complex magnetic
characters of MnSe crystal when observed at ambient condition. MnSe under
pressure is found to undergo several structural transformations: the cubic
phase first partially transforms to the hexagonal phase at about 12 GPa, the
crystal exhibits the coexistence of cubic, hexagonal and orthorhombic phases
from 16 GPa to 30 GPa, and above 30 GPa the crystal shows a single orthorhombic
phase. Superconductivity with Tc ~ 5 K was first observed at pressure ~12 GPa
by magnetic measurements (~16 GPa by resistive measurements). The highest Tc is
~ 9 K (magnetic result) at ~35 GPa. Our observations suggest the observed
superconductivity may closely relate to the pressure-induced structural change.
However, the interface between the metallic and insulating boundaries may also
play an important role to the pressure induced superconductivity in MnSe.",2011.01510v1
2020-12-24,"Structure, Electrical and Optical Properties of ITO Thin Films and their Influence on Performance of CdS/CdTe Thin-Film Solar Cells","In terms of mixing graded TiO2 and SnO2 powders by solid-state reaction
method, ITO was prepared. Using electron beam gun technology, ITO films with
different thicknesses were prepared. The influence of film thickness on
structure, electrical and optical properties was studied. The XRD patterns were
utilized to determine the structural parameters (lattice strain and crystallite
size) of ITO with different thicknesses. It is observed that the average
crystallite size increases as the film thickness increases, but the lattice
strain decreases. SEM shows that as the film thickness increases, the grain
size of ITO increases and improves. The electrical properties of ITO films with
different thicknesses were measured by the standard four-point probe method. It
can be seen that as the thickness of the ITO film increases from 75 nm to 325
nm, the resistivity decreases from 29x10^-4 Ohm/cm to 1.65x10^-4 Ohm/cm. This
means that ITO films with lower electrical properties will be more suitable for
high-efficiency CdTe solar cells. Three optical layer models (adhesive layer of
the substrate/B-spline layer of ITO film/surface roughness layer) are used to
calculate the film thickness with high-precision ellipsometry. In the higher
T(lambda) and R(lambda) absorption regions, the absorption coefficient is
determined to calculate the optical energy gap, which increases from 3.56 eV to
3.69 eV. Finally, the effects of ITO layers of various thicknesses on the
performance of CdS/CdTe solar cells are also studied. When the thickness of the
ITO window layer is 325 nm, Voc = 0.82 V, Jsc = 17 mA/cm2, and FF = 57.4%, the
highest power conversion efficiency (PCE) is 8.6%.",2012.13086v1
2021-12-26,The thickness dependence of quantum oscillations in ferromagnetic Weyl metal SrRuO$_{3}$,"Quantum oscillations in resistivity and magnetization at high magnetic fields
are a macroscopic fingerprint of the energy quantization due to the cyclotron
motion of quasiparticles. In a thin Weyl semimetal, a unique thickness
dependent Weyl-orbit quantum oscillation was proposed to exist, originating
from a nonlocal cyclotron orbit via the electron tunneling between the top and
bottom Fermi-arc surface states. Here, untwinned and high crystalline Weyl
metal SrRuO$_3$ thin films with different thicknesses were grown on miscut
SrTiO$_3$ (001) substrates. Magneto-transport measurements were carried out in
magnetic fields up to 35 T, and quantum oscillations with different frequencies
were observed and compared to the calculated band structure. In particular, we
discovered a frequency $F \approx$ 30 T at low temperatures and above 3 T that
corresponds to a small Fermi pocket with a light effective mass. Its
oscillation amplitude appears to be at maximum for film thicknesses in a range
of 10 to 20 nm, and the phase of the oscillation exhibits a systematic change
with the film thickness. After isolating the well separated frequencies, the
constructed Landau fan diagram shows an unusual concave downward curvature in
the 1/$\mu_0H_n$-$n$ curve, where $n$ is the Landau level index. Based on the
rigorous analysis of the thickness and field-orientation dependence of the
quantum oscillations, the oscillation with $F \approx$ 30 T is attributed to be
of surface origin, which is related to the Fermi-arc surface state originating
from non-overlapping Weyl nodes projected on the film's surface plane. Those
findings can be understood within the framework of the Weyl-orbit quantum
oscillation effect with non-adiabatic corrections.",2112.13331v2
2022-08-04,Strong-Coupling Superconductivity with $T_c$ $\sim$ 10.8 K Induced by P Doping in the Topological Semimetal Mo$_5$Si$_3$,"By performing P doping on the Si sites in the topological semimetal
Mo$_5$Si$_3$, we discover strong-coupling superconductivity in
Mo$_5$Si$_{3-x}$P$_x$ (0.5 $\le$ $x$ $\le$ 2.0). Mo$_5$Si$_3$ crystallizes in
the W$_5$Si$_3$-type structure with space group of $I4/mcm$ (No. 140), and is
not a superconductor itself. Upon P doping, the lattice parameter $a$ decreases
while $c$ increases monotonously. Bulk superconductivity is revealed in
Mo$_5$Si$_{3-x}$P$_x$ (0.5 $\le$ $x$ $\le$ 2.0) from resistivity,
magnetization, and heat capacity measurements. $T_c$ in
Mo$_5$Si$_{1.5}$P$_{1.5}$ reaches as high as 10.8 K, setting a new record among
the W$_5$Si$_3$-type superconductors. The upper and lower critical fields for
Mo$_5$Si$_{1.5}$P$_{1.5}$ are 14.56 T and 105 mT, respectively. Moreover,
Mo$_5$Si$_{1.5}$P$_{1.5}$ is found to be a fully gapped superconductor with
strong electron-phonon coupling. First-principles calculations suggest that the
enhancement of electron-phonon coupling is possibly due to the shift of the
Fermi level, which is induced by electron doping. The calculations also reveal
the nontrivial band topology in Mo$_5$Si$_3$. The $T_c$ and upper critical
field in Mo$_5$Si$_{3-x}$P$_x$ are fairly high among pseudobinary compounds.
Both of them are higher than those in NbTi, making future applications
promising. Our results suggest that the W$_5$Si$_3$-type compounds are ideal
platforms to search for new superconductors. By examinations of their band
topologies, more candidates for topological superconductors can be expected in
this structural family.",2208.02392v1
2023-05-19,Machine Learning Moment Tensor Potential for Modelling Dislocation and Fracture in L1$_0$-TiAl and D0$_{19}$-Ti$_3$Al Alloys,"Dual-phase $\gamma$-TiAl and $\alpha_2$-Ti$_{3}$Al alloys exhibit high
strength and creep resistance at high temperatures. However, they suffer from
low tensile ductility and fracture toughness at room temperature. Experimental
studies show unusual plastic behaviour associated with ordinary and
superdislocations, making it necessary to gain a detailed understanding on
their core properties in individual phases and at the two-phase interfaces.
Unfortunately, extended superdislocation cores are widely dissociated beyond
the length scales practical for routine first-principles density-functional
theory (DFT) calculations, while extant interatomic potentials are not
quantitatively accurate to reveal mechanistic origins of the unusual
core-related behaviour in either phases. Here, we develop a highly-accurate
moment tensor potential (MTP) for the binary Ti-Al alloy system using a DFT
dataset covering a broad range of intermetallic and solid solution structures.
The optimized MTP is rigorously benchmarked against both previous and new DFT
calculations, and unlike existing potentials, is shown to possess outstanding
accuracy in nearly all tested mechanical properties, including lattice
parameters, elastic constants, surface energies, and generalized stacking fault
energies (GSFE) in both phases. The utility of the MTP is further demonstrated
by producing dislocation core structures largely consistent with expectations
from DFT-GSFE and experimental observations. The new MTP opens the path to
realistic modelling and simulations of bulk lattice and defect properties
relevant to the plastic deformation and fracture processes in $\gamma$-TiAl and
$\alpha_2$-Ti$_{3}$Al dual-phase alloys.",2305.11825v2
2023-06-05,Imaging the Meissner effect and flux trapping in a hydride superconductor at megabar pressures using a nanoscale quantum sensor,"By directly altering microscopic interactions, pressure provides a powerful
tuning knob for the exploration of condensed phases and geophysical phenomena.
The megabar regime represents an exciting frontier, where recent discoveries
include novel high-temperature superconductors, as well as structural and
valence phase transitions. However, at such high pressures, many conventional
measurement techniques fail. Here, we demonstrate the ability to perform local
magnetometry inside of a diamond anvil cell with sub-micron spatial resolution
at megabar pressures. Our approach utilizes a shallow layer of Nitrogen-Vacancy
(NV) color centers implanted directly within the anvil; crucially, we choose a
crystal cut compatible with the intrinsic symmetries of the NV center to enable
functionality at megabar pressures. We apply our technique to characterize a
recently discovered hydride superconductor, CeH$_9$. By performing simultaneous
magnetometry and electrical transport measurements, we observe the dual
signatures of superconductivity: local diamagnetism characteristic of the
Meissner effect and a sharp drop of the resistance to near zero. By locally
mapping the Meissner effect and flux trapping, we directly image the geometry
of superconducting regions, revealing significant inhomogeneities at the micron
scale. Our work brings quantum sensing to the megabar frontier and enables the
closed loop optimization of superhydride materials synthesis.",2306.03122v1
2023-06-24,Exploration of strongly correlated states in SmB6 through a comparison of its two-coil pick-up response to that of Bi2Se3,"Earlier studies on the Kondo insulator SmB6 reveal the presence of a bulk
Kondo insulating gap between 30 - 50 K, and the emergence of a conducting
surface state only below 4 K. Here, we compare the two-coil mutual inductance
pick-up response of SmB6 single crystal with that of a conventional topological
insulator (TI), Bi2Se3 single crystal. From these studies we identify three
distinct temperature regimes for SmB6, viz., (i) T >= T*(~ 66 K), (ii) (40 K~)
T_g <= T < T*, and (iii) T < T_g. At T* in SmB6, we observe a peak in the
temperature-dependent AC pickup signal which corresponds to the peak in the
broad hump feature in the bulk DC susceptibility measurements and features in
the resistivity measurements. A dip in the pickup signal at T_g in SmB6
correlates with the evidence for the opening of a bulk Kondo gap in transport
measurements. Our study of the pickup signal in SmB6 suggests the presence of a
thin (submicron order thickness) high conducting surface layer from a
temperature just below T_g. In this T regime in SmB6, the pickup signal shows a
distinct square root frequency (f) dependence compared to the linear f
dependence found in Bi2Se3. Across all the different T regimes, distinct AC
frequency dependence and scaling properties are observed. Our results suggest
that above T*, weak exchange interactions cause electrons to scatter from
random ion sites. Electronic correlations gradually strengthen with the onset
of Kondo like hybridization, setting in from below T*, and at T_g, a strongly
correlated Kondo gap opens up in the bulk of the material. The appearance of
the thin high conducting surface layer is nearly coincident with the onset of
bulk Kondo insulating state below T_g in SmB6.",2306.13901v1
2024-01-07,Tantalum airbridges for scalable superconducting quantum processors,"The unique property of tantalum (Ta), particularly its long coherent lifetime
in superconducting qubits and its exceptional resistance to both acid and
alkali, makes it promising for superconducting quantum processors. It is a
notable advantage to achieve high-performance quantum processors with neat and
unified fabrication of all circuit elements, including coplanar waveguides
(CPW), qubits, and airbridges, on the tantalum film-based platform. Here, we
propose a reliable tantalum airbridges with separate or fully-capped structure
fabricated via a novel lift-off method, where a barrier layer with aluminium
(Al) film is first introduced to separate two layers of photoresist and then
etched away before the deposition of tantalum film, followed by cleaning with
piranha solution to remove the residual photoresist on the chip. We
characterize such tantalum airbridges as the control line jumpers, the ground
plane crossovers and even coupling elements. They exhibit excellent
connectivity, minimal capacitive loss, effectively suppress microwave and flux
crosstalk and offer high freedom of coupling. Besides, by presenting a
surface-13 tunable coupling superconducting quantum processor with median $T_1$
reaching above 100 $\mu$s, the overall adaptability of tantalum airbridges is
verified. The median single-qubit gate fidelity shows a tiny decrease from
about 99.95% for the isolated Randomized Benchmarking to 99.94% for the
simultaneous one. This fabrication method, compatible with all known
superconducting materials, requires mild conditions of film deposition compared
with the commonly used etching and grayscale lithography. Meanwhile, the
experimental achievement of non-local coupling with controlled-Z (CZ) gate
fidelity exceeding 99.2% may further facilitate qLDPC codes, laying a
foundation for scalable quantum computation and quantum error correction with
entirely tantalum elements.",2401.03537v1
2024-04-16,A Young Super Star Cluster Powering a Nebula of Retained Massive Star Ejecta,"We suggest that ""Godzilla"", an intriguing source in the lensed Sunburst
galaxy at $z=2.37$, is a young super star cluster powering a compact nebula
within gravitationally trapped stellar ejecta. Employing HST photometry and
spectroscopy from MUSE and X-Shooter at VLT, we infer physical and chemical
properties of the cluster and nebula, finding Godzilla is young (4-6 Myr),
massive ($\sim 10^{6-7}M_\odot$), a stellar metallicity $Z \simeq 0.25Z_\odot$,
and has the FUV component more compact than a few pc. The nebula gas is
significantly enriched with N and He, indicating stellar wind material, and has
highly elevated O relative to the sub-solar stellar metallicity, which
indicates entrainment of CCSNe ejecta. The high gas density $n_{\rm e} \simeq
10^{7-8}{\rm cm}^{-3}$ implies a highly pressurized intracluster environment.
We propose the high pressure is due to CCSN-driven supersonic turbulence in
warm, self-shielding gas, which has accumulated in the cluster center after
runaway radiative cooling and is dense enough to resist removal by CCSNe. The
nebula gas shows sub-solar C/O, Ne/O and Si/O values, which may reflect the
CCSN element yields for initial stellar masses $>40M_\odot$. A comparison to
element yield synthesis models for young star clusters shows that the gas
abundance pattern is consistent with complete retention and mixture of stellar
winds and CCSNe ejecta until the inferred cluster age. The O and He enhancement
we find may have implications for the formation of multiple stellar populations
in globular clusters, as Godzilla likely has already formed second-generation
stars prior to the onset of CCSNe and evolved star winds, in order not to
contradict the non-observation of O and large He enhancement in
second-generation stars.",2404.10755v2
2023-02-09,Scattering-dependent transport of SrRuO3 films: From Weyl fermion transport to hump-like Hall effect anomaly,"Recent observation of quantum transport phenomena of Weyl fermions has
brought much attention to 4d ferromagnetic perovskite SrRuO3 as a magnetic Weyl
semimetal. Besides, the hump-like Hall effect anomaly, which might have a
topological origin, has also been reported for this material. Here, we show
that the emergence of such phenomena is governed by the degree of scattering
determined by the defect density (Ru-deficiency- and/or interface-driven-defect
scattering) and measurement temperature (phonon scattering), where the former
is controlled by varying the growth conditions of the SrRuO3 films in molecular
beam epitaxy as well as the film thickness. The resulting electronic transport
properties can be classified into three categories: clean, intermediate, and
dirty regimes. The transport of Weyl fermions emerges in the clean regime,
whereas that of topologically trivial conduction electrons in the ferromagnetic
metal state prevail in the intermediate and dirty regimes. In the clean and
intermediate regimes, anomalous Hall resistivity obeys a scaling law
incorporating the intrinsic Karplus-Luttinger (Berry phase) and extrinsic
side-jump mechanisms. The hump-like Hall effect anomaly is observed only in the
dirty regime, which is contrary to the scaling law between anomalous Hall
resistivity and longitudinal resistivity. Hence, we conclude that this anomaly
is not inherent to the material and does not have a topological origin. We also
provide defect- and temperature-dependent transport phase diagrams of
stoichiometric SrRuO3 and Ru-deficient SrRu0.7O3 where the appearance of Weyl
fermions and hump-like Hall effect anomaly are mapped. These diagrams may serve
as a guideline for designing SrRu1-xO3-based spintronic and topological
electronic devices.",2302.04568v1
2024-02-29,"Magnetism, heat capacity and electronic structure of EuCd$_2$P$_2$ in view of its colossal magnetoresistance","The mechanism of the peculiar transport properties around the magnetic
ordering temperature of semiconducting antiferromagnetic EuCd$_2$P$_2$ is not
yet understood. With a huge peak in the resistivity observed above the N\'eel
temperature, $T_{\rm N}=10.6\,\rm K$, it exhibits a colossal magnetoresistance
effect. Recent reports on observations of ferromagnetic contributions above
$T_{\rm N}$ as well as metallic behavior below this temperature have motivated
us to perform a comprehensive characterization of this material, including its
resistivity, heat capacity, magnetic properties and electronic structure. Our
transport measurements revealed quite different temperature dependence of
resistivity with the maximum at $14\,\rm K$ instead of previously reported
$18\,\rm K$. Low-field susceptibility data support the presence of static
ferromagnetism above $T_{\rm N}$ and show a complex behavior of the material at
small applied magnetic fields. Namely, signatures of reorientation of magnetic
domains are observed up to $T=16\,\rm K$. Our magnetization measurements
indicate a magnetocrystalline anisotropy which also leads to a preferred
alignment of the magnetic clusters above $T_{\rm N}$. The momentum-resolved
photoemission experiments at temperatures from $24\,\rm K$ down to $2.5\,\rm K$
indicate the permanent presence of a fundamental band gap without change of the
electronic structure when going through $T_N$ that is in contradiction with
previous results. We performed \textit{ab initio} band structure calculations
which are in good agreement with the measured photoemission data when assuming
an antiferromagnetic ground state. Calculations for the ferromagnetic phase
show a much smaller bandgap, indicating the importance of possible
ferromagnetic contributions for the explanation of the colossal
magnetoresistance effect in the related EuZn$_2$P$_2$.",2402.18911v1
2023-01-14,Discovery of 2D materials using Transformer Network based Generative Design,"Two-dimensional (2D) materials have wide applications in superconductors,
quantum, and topological materials. However, their rational design is not well
established, and currently less than 6,000 experimentally synthesized 2D
materials have been reported. Recently, deep learning, data-mining, and density
functional theory (DFT)-based high-throughput calculations are widely performed
to discover potential new materials for diverse applications. Here we propose a
generative material design pipeline, namely material transformer
generator(MTG), for large-scale discovery of hypothetical 2D materials. We
train two 2D materials composition generators using self-learning neural
language models based on Transformers with and without transfer learning. The
models are then used to generate a large number of candidate 2D compositions,
which are fed to known 2D materials templates for crystal structure prediction.
Next, we performed DFT computations to study their thermodynamic stability
based on energy-above-hull and formation energy. We report four new
DFT-verified stable 2D materials with zero e-above-hull energies, including
NiCl$_4$, IrSBr, CuBr$_3$, and CoBrCl. Our work thus demonstrates the potential
of our MTG generative materials design pipeline in the discovery of novel 2D
materials and other functional materials.",2301.05824v1
2014-05-15,Effect of high pressure annealing on the normal state transport of LaO0.5F0.5BiS2,"We study normal state electrical, thermoelectrical and thermal transport in
polycrystalline BiS2-based compounds, which become superconducting by F doping
on the O site. In particular we explore undoped LaOBiS2 and doped
LaO0.5F0.5BiS2 samples, prepared either with or without high pressure
annealing, in order to evidence the roles of doping and preparation conditions.
The high pressure annealed sample exhibits room temperature values of
resistivity ro around 5 mohmcm, Seebeck coefficient S around -20 microV/K and
thermal conductivity k around 1.5 W/Km, while the Hall resistance RH is
negative at all temperatures and its value is -10-8 m3/C at low temperature.
The sample prepared at ambient pressure exhibits RH positive in sign and five
times larger in magnitude, and S negative in sign and slightly smaller in
magnitude. These results reveal a complex multiband evolution brought about by
high pressure annealing. In particular, the sign inversion and magnitude
suppression of RH, indicating increased electron-type carrier density in the
high pressure sample, may be closely related to previous findings about change
in lattice parameters and enhancement of superconducting Tc by high pressure
annealing. As for the undoped sample, it exhibits the 10 times larger
resistivity, 10 times larger |S| and 10 times larger |RH| than its doped
counterpart, consistently with its insulating nature. Our results point out the
dramatic effect of preparation conditions in affecting charge carrier density
as well as structural, band and electronic parameters in these systems.",1405.3832v2
2021-09-05,On the design of particle filters inspired by animal noses,"Passive filtering is a common strategy used to reduce airborne disease
transmission and particulate contaminants in buildings and individual covers.
The engineering of high-performance filters with relatively low flow resistance
but high virus- or particle-blocking efficiency is a nontrivial problem of
paramount relevance, as evidenced in the variety of industrial filtration
systems and the worldwide use of face masks. In this case, standard N95-level
covers have high virus-blocking efficiency, but they can cause breathing
discomfort. Next-generation industrial filters and masks should retain
sufficiently small droplets and aerosols while having low resistance. We
introduce a novel 3D printable particle filter inspired by animals' complex
nasal anatomy. Unlike standard random-media-based filters, the proposed concept
relies on equally spaced channels with tortuous airflow paths. These two
strategies induce distinct effects: a reduced resistance and a high likelihood
of particle trapping by altering their trajectories with tortuous paths and
induced local flow instability. The structures are tested for pressure drop and
particle filtering efficiency over a wide range of airflow rates. We have also
cross-validated the observed efficiency through numerical simulations. The
designed filters exhibit a lower pressure drop than the commercial mask and air
filters (N95, surgical, and high-efficiency particulate air (HEPA)). The
concept provides a new approach to developing scalable, flexible,
high-efficiency air filters for various engineering applications.",2109.08018v1
1997-09-27,"Low-temperature electrical transport and double exchange in La(Pb,Ca)MnO","The resistivity in the ferromagnetic state of flux-grown
La_{2/3}(Pb,Ca)_{1/3}MnO_3 single crystals, measured in magnetic fields up to 7
T, reveals a strong quadratic temperature dependence at and above 50 K. At
lower temperatures, this contribution drops precipitously leaving the
resistivity essentially temperature independent below 20 K. The Seebeck
coefficient also reflects a change of regime at the same temperature. We
attribute this behavior to a cut-off of single magnon scattering processes at
long wavelengths due to the polarized bands of a double-exchange ferromagnet.",9709305v3
1998-01-07,Theory of the Resistive Transition in Overdoped $Tl_2Ba_2CuO_{6+x}$: Implications for the angular dependence of the quasiparticle scattering rate in High-$T_c$ superconductors,"We show that recent measurements of the magnetic field dependence of the
magnetization, specific heat and resistivity of overdoped $T_c \sim 17K$
$Tl_{2}Ba_{2}CuO_{6+\delta}$ in the vicinity of the superconducting $H_{c2}$
imply that the vortex viscosity is anomalously small and that the material
studied is inhomogeneous with small, a few hundred $\AA$, regions in which the
local $T_{c}$ is much higher than the bulk $T_{c}$. The anomalously small
vortex viscosity can be derived from a microscopic model in which the
quasiparticle lifetime varies dramatically around the Fermi surface, being
small everywhere except along the zone diagonal (``cold spot''). We propose
experimental tests of our results.",9801059v1
1998-08-25,P-wave Pairing and Colossal Magnetoresistance in Manganese Oxides,"We point out that the existing experimental data of most manganese oxides
show the {\sl frustrated} p-wave superconducting condensation in the
ferromagnetic phase in the sense that the superconducting coherence is not long
enough to cover the whole system. The superconducting state is similar to the
$A_{1}$ state in superfluid He-3. The sharp drop of resistivity, the steep jump
of specific heat, and the gap opening in tunneling are well understood in terms
of the p-wave pairing. In addition, colossal magnetoresistance (CMR) is
naturally explained by the superconducting fluctuations with increasing
magnetic fields. The finite resistivity may be due to some magnetic
inhomogeneities. This study leads to the possibility of room temperature
superconductivity.",9808275v1
1998-10-30,"Hall Effect of La2/3(Ca,Pb)1/3MnO3 Single Crystals near the Critical Temperature","The Hall resistivity rho_{xy} of a La_{2/3}(Ca,Pb)_{1/3}MnO_3 single crystal
has been measured as a function of temperature and field. The overall behavior
is similar to that observed previously in thin-films. At 5 K, rho_{xy} is
positive and linear in field, indicating that the anomalous contribution $R_S$
is negligible. However, the effective carrier density in a free electron model
is n_{eff}=2.4 holes/Mn, even larger than the 0.85-1.9 holes/Mn reported for
thin-films and far larger than the 0.33 holes/Mn expected from the doping
level. As temperature increases, a strong, negative contribution to rho_{xy}
appears, that we ascribe to R_S. Using detailed magnetization data, we separate
the ordinary (\propto B) and anomalous (\propto M) contributions. Below T_C,
R_S \propto rho_{xx}, indicating that magnetic skew scattering is the dominant
mechanism in the metallic ferromagnetic regime. At and above the
resistivity-peak temperature, we find that rho_{xy}/rho_{xx}M is a constant,
independent of temperature and field. This implies that the anomalous Hall
coefficient is proportional to the magnetoresistance. A different explanation
based on two fluid model is also presented.",9810410v1
1998-11-28,Negative Differential Resistance in the Scanning Tunneling Spectroscopy of Organic molecules,"The conductance-voltage spectrum of molecular nanostructures measured by
scanning tunneling spectroscopy (STS) is generally assumed to reflect the local
density of states of the molecule. This excludes the possibility of observing
negative differential resistance (NDR). We report here the observation of NDR
in the scanning tunneling microscope (STM) current-voltage (I-V)
characteristics of self-assembled monolayer (SAM) of 4-p-Terphenylthiol
molecules on gold substrate measured using a platinum probe. We argue that the
NDR arises from narrow structures in the local density of states at the tip
apex atom and show that depending on the electrostatic potential profile across
the system, NDR could be observed in one or both bias directions.",9811402v1
1998-12-27,Field Induced Transition from Metal to Insulator in the CMR Manganites,"The gigantic reduction of the electric resistivity under the applied magnetic
field, CMR effect, is now widely accepted to appear in the vicinity of the
insulator to metal transition of the perovskite manganites. Recently, we have
discovered the first order transition from ferromagnetic metal to insulator in
$\rm La_{0.88}Sr_{0.12}MnO_3$ of the CMR manganite. This phase transition
induces the tremendous increase of the resistivity under the external magnetic
field just near above the phase transition temperature. We report here fairly
detailed results from the systematic experiments including neutron and
synchrotron X-ray scattering studies.",9812404v1
1999-01-25,Influence of Cu on spin-polaron tunneling in the ferromagnetic state of La(2/3)Ca(1/3)Mn(1-x)Cu(x)O(3) from the resistivity data,"Nearly a 50% decrease of resistivity \rho (T,x) due to just 4% Cu doping on
the Mn site of La(2/3)Ca(1/3)Mn(1-x)Cu(x)O(3) is observed. Attributing the
observed phenomenon to the substitution induced decrease of the spin polaron
energy E_s(x) below the Curie point T_C(x)=T_C(0)(1-x), all data are found to
be well fitted by the nonthermal coherent tunneling expression \rho (T,x) =
\rho_0*exp(-\gamma M^2(T,x)) assuming
M(T,x)=M_R(x)+M_0(x)*tanh{\sqrt{[T_C(x)/T]^2-1}} for the magnetization in the
ferromagnetic state. The best fits through all the data points yield M_0(x)=
\sqrt(1-x)M_0(0), M_R(x)=\sqrt(x)M_0(0), and E_s(x)=E_s(0)(1-x)^4 for the Cu
induced modifications of the Mn spins dominated zero-temperature spontaneous
magnetization, the residual paramagnetic contribution, and spin-polaron energy,
respectively, with E_s(0)=0.12 eV.",9901263v1
1999-03-03,c-axis Tunneling in Nb/Au/YBaCuO Structures,"We present the experimental results for Nb/Au/YBaCuO structures, in which the
current flows along (001) direction of YBaCuO film. The theoretical evaluations
show, that at the experimental values of the Au/YBaCuO interface transparency,
determined from the interface resistance D~10^-6, the critical current of the
structure is of the fluctuation order of magnitude due to the sharp decrease of
the amplitude potential of the superconducting carriers on this interface.
Obtained I-V-curves could be interpreted in terms of contact between d-type
pairing superconductor or gapless isotropic superconductor with normal metal.
No critical current was observed for investigated structures with
characteristic interface resistance RnS~10^-6 Ohm cm^2, 2 orders of magnitude
lower, than for known experimental data. PACS: 74.50.+r, 74.72.Bk",9903065v1
1999-03-15,Metal-insulator transition in CMR materials,"We report on resistivity measurements in La$_{0.67}$Ca$_{0.33}$MnO$_{3}$ and
Nd$_{0.7}$Sr$_{0.3}$MnO$_{3}$ thin films in order to elucidate the underlying
mechanism for the CMR behavior. The experimental results are analyzed in terms
of quantum phase transition ideas to study the nature of the metal-insulator
transition in manganese oxides. Resistivity curves as functions of
magnetization for various temperatures show the absence of scaling behavior
expected in a continuous quantum phase transition, which leads us to conclude
that the observed metal-insulator transition is most likely a finite
temperature crossover phenomenon.",9903238v2
2000-01-06,Time Dependent Effects and Transport Evidence for Phase Separation in La_{0.5}Ca_{0.5}MnO_{3},"The ground state of La_{1-x}Ca_{x}MnO_{3} changes from a ferromagnetic
metallic to an antiferromagnetic charge-ordered state as a function of Ca
concentration at x ~ 0.50. We present evidence from transport measurements on a
sample with x = 0.50 that the two phases can coexist, in agreement with other
observations of phase separation in these materials. We also observe that, by
applying and then removing a magnetic field to the mainly charge-ordered state
at some temperatures, we can ""magnetically anneal"" the charge order, resulting
in a higher zero-field resistivity. We also observe logarithmic time dependence
in both resistivity and magnetization after a field sweep at low temperatures.",0001064v1
2000-02-14,Transition Temperature and Magnetoresistance in Double-Exchange Compounds with Moderate Disorder,"We develop a variational mean-field theory of the ferromagnetic transition in
compounds like Lanthanum-Manganite within the framework of the Double-Exchange
Model supplemented by modest disorder. We obtain analytical expressions for the
transition temperature, its variation with the valence electron-density and its
decrease with disorder.
  We derive an expression for the conductivity for both the paramagnetic and
the ferromangetic metallic phases, and study its dependence on the temperature
and magnetic field. A simple relation between the resistivity in the
ferromagnetic phase and the spontaneous magnetization is found. Our results are
in a good agreement with the experimental data on transition temperatures and
resistivity in the manganite compounds with relatively small disorder. We
comment on the effects of increased disorder.",0002191v1
2000-03-11,Effect of γ-irradiation on superconducting transition temperature and resistive transition in polycrystalline YBa_{2}Cu_{3}O_(7-δ),"A bulk polycrystalline sample of YBa_(2)Cu_(3)O_(7-\delta) (\delta \approx
0.1) has been irradiated by \gamma-rays with ^{60}Co source. Non-monotonic
behavior of T_{c} with increasing irradiation dose \Phi (up to 220 MR) is
observed: T_{c} decreases at low doses (\Phi < 50 MR) from initial value
(\approx 93 K) by about 2 K and then rises, forming a minimum. At higher doses
(\Phi > 120 MR) T_{c} goes down again. The temperature width of resistive
transition increases rather sharply with dose below 75 MR and drops somewhat at
higher dose. The results observed are discussed, taking into account the
granular structure of sample studied and the influence of \gamma-rays on
intergrain Josephson coupling.",0003192v1
2000-06-07,Step-wise Behavior of Vortex-Lattice Melting Transition in Tilted Magnetic Fields in Single Crystals Bi2Sr2CaCu2O8+d,"The vortex lattice melting transition in single crystals Bi2Sr2CaCu2O8+d was
studied by the in-plane resistivity measurements in magnetic fields tilted away
from the c-axis to the ab-plane. In order to avoid the surface barrier effect
which hinders the melting transition in the conventional transport
measurements, we used the Corbino geometry of electric contacts. For the first
time, the complete Hc-Hab phase diagram of the melting-transition in
Bi2Sr2CaCu2O8+d is obtained. The c-axis melting field component Hc-melt
exhibits the novel, step-wise dependence on the in-plane magnetic fields Hab
which is discussed on the base of the crossing vortex lattice structure. The
sharp change of resistance behavior observed near the ab-plane suggests
transformation from first-order to second-order phase transition.",0006095v1
2000-08-07,Large two-level magnetoresistance effect in doped manganite grain boundary junctions,"We performed a systematic analysis of the tunneling magnetoresistance (TMR)
effect in single grain boundary junctions formed in epitaxial
La(2/3)Ca(1/3)MnO(3) films deposited on SrTiO(3) bicrystals. For magnetic
fields H applied parallel to the grain boundary barrier, an ideal two-level
resistance switching behavior with sharp transitions is observed with a TMR
effect of up to 300% at 4.2 K and still above 100% at 77 K. Varying the angle
between H and the grain boundary results in differently shaped resistance vs H
curves. The observed behavior is explained within a model of magnetic domain
pinning at the grain boundary interface.",0008105v1
2000-10-20,"Composite Spin Waves, Quasi-Particles and Low Temperature resistivity in Double Exchange Systems","We make a quantum description of the electron low temperature properties of
double exchange materials. In these systems there is a strong coupling between
the core spin and the carriers spin. This large coupling makes the low energy
spin waves to be a combination of ion and electron density spin waves. We study
the form and dispersion of these composite spin wave excitations. We also
analyze the spin up and down spectral functions of the temperature dependent
quasi-particles of this system. Finally we obtain that the thermally activated
composite spin waves renormalize the carriers effective mass and this gives
rise to a low temperature resistivity scaling as T ^{5/2}.",0010312v1
2000-12-13,Phase-coherence transition in granular superconductors with $π$ junctions,"We study the three-dimensional XY-spin glass as a model for the resistive
behavior of granular superconductors containing a random distribution of $\pi$
junctions, as in high-$T_c$ superconducting materials with d-wave symmetry. The
$\pi$ junctions leads to quenched in circulating currents (chiralities) and to
a chiral-glass state at low temperatures, even in the absence of an external
magnetic field. Dynamical simulations in the phase representation are used to
determine the nonlinear current-voltage characteristics as a function of
temperature. Based on dynamic scaling analysis, we find a phase-coherence
transition at finite temperature below which the linear resistivity should
vanish and determine the corresponding critical exponents. The results suggest
that the phase and chiralities may order simultaneously for decreasing
temperatures into a superconducting chiral-glass state.",0012238v1
2000-12-19,Resistance Spikes at Transitions between Quantum Hall Ferromagnets,"We report a new manifestation of first-order magnetic transitions in
two-dimensional electron systems. This phenomenon occurs in aluminum arsenide
quantum wells with sufficiently low carrier densities and appears as a set of
hysteretic spikes in the resistance of a sample placed in crossed parallel and
perpendicular magnetic fields, each spike occurring at the transition between
states with different partial magnetizations. Our experiments thus indicate
that the presence of magnetic domains at the transition starkly increases
dissipation, an effect also suspected in other ferromagnetic materials.
Analysis of the positions of the transition spikes allows us to deduce the
change in exchange-correlation energy across the magnetic transition, which in
turn will help improve our understanding of metallic ferromagnetism.",0012367v1
2001-01-30,Stress-induced metallic behavior under magnetic field in Pr$_{1-x}$Ca$_{x}$MnO$_{3}$ (x = 0.5 and 0.4) thin films,"We have investigated the role of the stress-induced by the presence of the
substrate in thin films of colossal magnetoresistive manganites on structural,
resistive and magnetic properties. Because of the strong coupling between the
small structural distortions related to the charge-ordering (CO) and the
resistive properties, the presence of the substrate prevents the full
developpement of the charge ordering in Pr$_{0.5}$Ca$_{0.5}$MnO$_{3}$,
especially in the very thin films. For thicker films, the CO state exists, but
is not fully developped. Correlatively, the magnetic field which is necessary
to suppress the CO is decreased drastically from 25 Tesla to about 5 Tesla on
SrTiO$_{3}$ substrates. We have also investigated the influence of the doping
level by studying the case of Pr$_{0.6}$Ca$_{0.4}$MnO$_{3}$.",0101448v1
2001-04-18,Electron Transport in Diborides: Observation of Superconductivity in ZrB2,"We report on syntheses and electron transport properties of polycrystalline
samples of diborides (AB2) with different transition metals atoms (A=Zr,Nb,Ta).
The temperature dependence of resistivity, \rho(T), and ac susceptibility of
these samples reveal superconducting transition of ZrB2 with Tc=5.5 K, while
NbB2 and TaB2 have been observed nonsuperconducting up to 0.37 K. Hc2(T) is
linear in temperature below Tc, leading to a rather low Hc2(0)= 0.1 T. At T
close to Tc, Hc2(T) demonstrates a downward curvature. We conclude that these
diborides as well as MgB2 samples behaves like a simple metals in the normal
state with usual Bloch-Gr\""uneisen temperature dependence of resistivity and
with Debye temperatures: 280 K, 460 K and 440 K, for ZrB2, NbB2 and MgB2,
respectively, rather than T^2 and T^3 as previously reported for MgB2.",0104323v1
2001-05-02,In-plane Hall effect in c-axis-oriented MgB2 thin films,"We have measured the longitudinal resistivity and the Hall resistivity in the
ab-plane of highly c-axis-oriented MgB2 thin films. In the normal state, the
Hall coefficient (R_H) behaves as R_H ~ T with increasing temperature (T) up to
130 K and then deviates from that linear T-dependence at higher temperatures.
The T^2 dependence of the cotangent of the Hall angle is only observed above
130 K. The mixed-state Hall effect reveals no sign anomaly over a wide range of
current densities from 10^2 to 10^4 A/cm^2 and for magnetic fields up to 5 T.",0105024v2
2001-05-04,A New Method of Probing the Phonon Mechanism in Superconductors including MgB$_{2}$,"Weak localization has a strong influence on both the normal and
superconducting properties of metals. In particular, since weak localization
leads to the decoupling of electrons and phonons, the temperature dependence of
resistance (i.e., $\lambda_{tr}$) is decreasing with increasing disorder, as
manifested by Mooij's empirical rule. In addition, Testardi's universal
correlation of $T_{c}$ (i.e., $\lambda$) and the resistance ratio (i.e.,
$\lambda_{tr}$) follows. This understanding provides a new means to probe the
phonon mechanism in superconductors including MgB$_{2}$. The merits of this
method are its applicability to any superconductors and its reliability because
the McMillan's electron-phonon coupling constant $\lambda$ and $\lambda_{tr}$
change in a broad range, from finite values to zero, due to weak localization.
Karkin et al's preliminary data of irradiated MgB$_{2}$ show the Testardi
correlation, indicating that the dominant pairing mechanism in MgB$_{2}$ is the
phonon-mediated interaction.",0105091v1
2002-01-25,Degradation of LaMnO{3-y} surface layer in LaMnO{3-y}/ metal interface,"We report electrical measurements showing the degradation processes of
LaMnO$_{3-y}$ (LaMnO) in LaMnO/normal metal interface in both point contact and
planar-type junctions. Immediately after the preparation of the interface, the
degradation process was followed by measuring the evolution of the junction
resistance versus time. This process is characterized by the appearance of a
second maximum in the resistance vs. temperature (R-T) dependence at
temperatures lower than the Curie temperature T$_c$, at which the
metal-insulator transition occurs in the bulk. These effects are explained in
terms of the formation of a depleted interface layer in LaMnO caused by an
out-diffusion of oxygen from the manganite surface to the normal metal. This
assumption is confirmed by XPS measurement. Similar results on LaSrMnO$_{3-y}$
interfaces are also obtained.",0201460v1
2002-02-06,Thermoelectric properties of the brownmillerite oxide Ca_{2-y}La_yCo_{2-x}Al_xO_5,"We prepared the brownmillerite oxide Ca_{2-y}La_yCo_{2-x}Al_xO_5, and found
that it was an n-type conductor. The thermopower and the resistivity of the
single crystal are -90 microV/K and 68 mOhm cm along the ab direction at 440 K,
which suggest relatively good thermoelectrical properties, compared with other
transition-metal oxides. Their temperature dependences are of activation type,
and the activation energies are 0.2 eV for the resistivity and 0.04 eV for the
thermopower. These energies differ by one order in magnitude, which implies
that a polaron dominates the charge transport. A sign of the thermopower of the
polycrystals changes from negative to positive at 500 K, indicating that holes
are excited thermally to decrease the magnitude of thermopower.",0202087v1
2002-04-29,Concentration of Charge Carriers and Anomalous Gap Parameter in the Normal State of High-$T_c$ Superconductors,"Fermi-Dirac statistics has been utilized by introducing the average
ionization energy ($E_I$) as an additional anomalous energy gap in order to
derive the two-dimensional concentration of charge carriers and the
phenomenological resistivity model for the superconducting polycrystalline
materials. The best fitted values of $E_I$ and the charge carriers'
concentration ranges in the vicinity of 4 to 9 meV and 10$^{16}$ m$^{-2}$
respectively for the superconducting single crystal samples and polycrystalline
compounds synthesized with various compositions via solid-state reactions. The
phenomenological resistivity model is further redefined here based on the
gapless nature of charge-carriers' dynamics within the Cu-O$_2$ planes that
corresponds to anomalous Fermi liquid behavior, which is in accordance with the
nested Fermi liquid theory.",0204601v1
2002-08-09,Quasi-one-dimensional superconductivity above 300 K and quantum phase slips in individual carbon nanotubes,"A great number of the existing data for electrical transport, the Altshuler
Aronov Spivak and Aharonov Bohm effects, as well as the tunneling spectra of
individual carbon nanotubes can be well explained by theories of the quantum
phase slips in quasi-one-dimensional superconductors. The existing data
consistently suggest that the mean-field superconducting transition temperature
T_{c0} in both single-walled and multi-walled carbon nanotubes could be higher
than 600 K. The quantum phase slip theories naturally explain why the on-tube
resistances in the closely packed nanotube bundles or in the individual
multi-walled nanotubes with large diameters approach zero at room temperature,
while a single tube with a small diameter has a substantial resistance.",0208198v4
2002-08-13,Characterization of one-dimensional quantum channels in InAs/AlSb,"We report the magnetoresistance characteristics of one-dimensional electrons
confined in a single InAs quantum well sandwiched between AlSb barriers. As a
result of a novel nanofabrication scheme that utilizes a 3nm-shallow wet
chemical etching to define the electrostatic lateral confinement, the system is
found to possess three important properties: specular boundary scattering, a
strong lateral confinement potential, and a conducting channel width that is
approximately the lithography width. Ballistic transport phenomena, including
the quenching of the Hall resistance, the last Hall plateau, and a strong
negative bend resistance, are observed at 4K in cross junctions with sharp
corners. In a ring geometry, we have observed Aharonov-Bohm interference that
exhibits characteristics different from those of the GaAs counterpart due to
the ballistic nature of electron transport and the narrowness of the conducting
channel width.",0208265v1
2002-08-27,Anomalous Hall Effect of Calcium-doped Lanthanum Cobaltite Films,"The Hall resistivity, magnetoresistance, and magnetization of
La_{1-x}Ca_{x}CoO_{3} epitaxial films with x between 0.25 and 0.4 grown on
lanthanum aluminate were measured in fields up to 7 T. The x=1/3 film, shows a
reentrant metal insulator transition. Below 100 K, the x=1/3 and 0.4 films have
significant coercivity which increases with decreasing temperature. At low
temperature the Hall resistivity remains large and essentially field
independent in these films, except for a sign change at the coercive field that
is more abrupt than the switching of the magnetization. A unique
magnetoresistance behavior accompanies this effect. These results are discussed
in terms of a percolation picture and the mixed spin state model for this
system. We propose that the low-temperature Hall effect is caused by
spin-polarized carriers scattering off of orbital disorder in the spin-ordered
clusters.",0208530v1
2003-01-24,Semiconductive and Photoconductive Properties of the Single Molecule Magnets Mn$_{12}$-Acetate and Fe$_8$Br$_8$,"Resistivity measurements are reported for single crystals of
Mn$_{12}$-Acetate and Fe$_8$Br$_8$. Both materials exhibit a
semiconductor-like, thermally activated behavior over the 200-300 K range. The
activation energy, $E_a$, obtained for Mn$_{12}$-Acetate was 0.37 $\pm$ 0.05
eV, which is to be contrasted with the value of 0.55 eV deduced from the
earlier reported absorption edge measurements and the range of 0.3-1 eV from
intramolecular density of states calculations, assuming $2E_a$= $E_g$, the
optical band gap. For Fe$_8$Br$_8$, $E_a$ was measured as 0.73 $\pm$ 0.1 eV,
and is discussed in light of the available approximate band structure
calculations. Some plausible pathways are indicated based on the crystal
structures of both lattices. For Mn$_{12}$-Acetate, we also measured
photoconductivity in the visible range; the conductivity increased by a factor
of about eight on increasing the photon energy from 632.8 nm (red) to 488 nm
(blue). X-ray irradiation increased the resistivity, but $E_a$ was insensitive
to exposure.",0301497v1
2003-02-12,Avoided Antiferromagnetic Order and Quantum Critical Point in CeCoIn$_5$,"We measured specific heat and resistivity of heavy fermion CeCoIn5 between
the superconducting critical field $H_{c2} = 5 T$ and 9 T, with field in the
[001] direction, and at temperatures down to 50mK. At 5T the data show Non
Fermi Liquid behavior down to the lowest temperatures. At field above 8T the
data exhibit crossover from the Fermi liquid to a Non Fermi Liquid behavior. We
analyzed the scaling properties of the specific heat, and compared both
resistivity and the specific heat with the predictions of a spin-fluctuation
theory. Our analysis leads us to suggest that the NFL behavior is due to
incipient antiferromagnetism (AF) in CeCoIn5, with the quantum critical point
in the vicinity of the $H_{c2}$. Below $H_{c2}$ the AF phase which competes
with the paramagnetic ground state is superseded by the superconducting
transition.",0302226v1
2003-02-21,Anomalous Hall Effect and Magnetoresistance of SrFe1-xCoxO3-d,"Transport and magnetic studies on polycrystalline samples of SrFe1-xCoxO3-d
have been carried out to investigate the relationship between the magnetic
structure and the anomalous Hall resistivity rH. The hysteretic behavior of the
magnetization observed in the measurements with varying temperature T up and
then down after zero field cooling indicates that the system has the reentrant
spin-glass phase, which is supported by the increasing width of the magnetic
reflections observed by neutron diffraction with decreasing T below the Curie
temperature TC. Detailed analyses of the observed Hall resistivity rH indicate
that the anomalous Hall coefficient exhibits unusual behavior in the reentrant
spin-glass phase. The magnetic field (H)- and T-dependence of the
magnetoresistance of the present system can be understood by a spin dependent
tunneling model.",0302436v1
2003-02-24,Spin-wave scattering at low temperatures in manganite films,"The temperature $T$ and magnetic field $H$ dependence of the resistivity
$\rho$ has been measured for La$_{0.8-y}$Sr$_{0.2}$MnO$_{3}$ (y=0 and 0.128)
films grown on (100) SrTiO$_{3}$ substrates. The low-temperature $\rho$ in the
ferromagnetic metallic region follows well $\rho (H,T)=\rho
_{0}(H)+A(H)\omega_{s}/\sinh (\hbar \omega_{s}/2k_{B}T)+B(H)T^{7/2}$ with $\rho
_{0}$ being the residual resistivity. We attribute the second and third term to
small-polaron and spin-wave scattering, respectively. Our analysis based on
these scattering mechanisms also gives the observed difference between the
metal-insulator transition temperatures of the films studied. Transport
measurements in applied magnetic field further indicate that spin-wave
scattering is a key transport mechanism at low temperatures.",0302486v1
2003-04-07,Thickness dependence of the properties of epitaxial MgB2 thin films grown by hybrid physical-chemical vapor deposition,"We have studied the effect of deposition rate and layer thickness on the
properties of epitaxial MgB2 thin films grown by hybrid physical-chemical vapor
deposition on 4H-SiC substrates. The MgB2 film deposition rate depends linearly
on the concentration of B2H6 in the inlet gas mixture. We found that the
superconducting and normal-state properties of the MgB2 films are determined by
the film thickness, not by the deposition rate. When the film thickness was
increased, the transition temperature, Tc, increased and the residual
resistivity, rho0, decreased. Above about 300 nm, a Tc of 41.8 K, a rho0 of
0.28 mikroOhm.cm, and a residual resistance ratio RRR of over 30 were obtained.
These values represent the best MgB2 properties reported thus far.",0304164v1
2003-06-05,Variable-range-hopping conductivity of half-doped bilayer manganite LaSr$_{2}$Mn$_{2}$O$_{7}$,"We report measurements of in-plane $\rho_{ab}$ and out-of-plane $\rho_{c}$
resistivities on a single crystal of the half-doped bilayer manganite
LaSr$_{2}$Mn$_{2}$O$_{7}$. In the temperature $T$ range 220 to 300 K, the
resistive anisotropy $\rho_{c}/\rho_{ab}=A+B/T$ ($A$ and $B$ constants), which
provides evidence for the variable-range-hopping conduction in the presence of
a Coulomb gap. This hopping mechanism also accounts for the quadratic magnetic
field $H$ and $\sin^{2}\phi$ dependences of the negative magnetoresistivity
$\ln [\rho_{i}(T,H,\phi)/\rho_{i}(T,H=0)]$ ($i=ab,c$), where $\phi$ is the
in-plane angle between the magnetic field and the current.",0306133v1
2003-06-11,"Enhanced electrical resistivity before Néel order in the metals, RCuAs$_2$ (R= Sm, Gd, Tb and Dy","We report an unusual temperature (T) dependent electrical resistivity($\rho$)
behavior in a class of ternary intermetallic compounds of the type RCuAs$_2$
(R= Rare-earths). For some rare-earths (Sm, Gd, Tb and Dy) with negligible
4f-hybridization, there is a pronounced minimum in $\rho$(T) far above
respective N\'eel temperatures (T$_N$). However, for the rare-earths which are
more prone to exhibit such a $\rho$(T) minimum due to 4f-covalent mixing and
the Kondo effect, this minimum is depressed. These findings, difficult to
explain within the hither-to-known concepts, present an interesting scenario in
magnetism.",0306266v1
2003-07-14,"Interplay between disorder, quantum and thermal fluctuations in ferromagnetic alloys: The case of UCu2Si(2-x)Ge(x)","We consider, theoretically and experimentally, the effects of structural
disorder, quantum and thermal fluctuations in the magnetic and transport
properties of certain ferromagnetic alloys.We study the particular case of
UCu2Si(2-x)Ge(x). The low temperature resistivity, rho(T,x), exhibits Fermi
liquid (FL) behavior as a function of temperature T for all values of x, which
can be interpreted as a result of the magnetic scattering of the conduction
electrons from the localized U spins. The residual resistivity, rho(0,x),
follows the behavior of a disordered binary alloy. The observed non-monotonic
dependence of the Curie temperature, Tc(x), with x can be explained within a
model of localized spins interacting with an electronic bath whose transport
properties cross-over from ballistic to diffusive regimes. Our results clearly
show that the Curie temperature of certain alloys can be enhanced due to the
interplay between quantum and thermal fluctuations with disorder.",0307328v2
2003-10-20,Studies of Current-Driven Excitations in Co/Cu/Co Trilayer Nanopillars,"We measure the dynamic resistance of a Co/Cu/Co trilayer nanopillar at varied
magnetic field $H$ and current $I$. The resistance displays the usual behavior,
almost symmetric in $H$, both when magnetization switching is hysteretic at
small $I,H$, and reversible at larger $I,H$. We show differences in the $I,H$
magnetization stability diagram measured by holding $I$ fixed and varying $H$
and vice versa. We also show how the peak in $dV/dI$ associated with telegraph
noise in the reversible switching regime, is calculated from the telegraph
noise variations with $I$. Lastly, we show data for a similar sample that
displays behavior asymmetric in $H$, and a negative reversible switching peak
instead of a usual positive one.",0310472v1
2003-11-17,The Normal State Resistivity of Grain Boundaries in YBa2Cu3O7-delta,"Using an optimized bridge geometry we have been able to make accurate
measurements of the properties of YBa2Cu3O7-delta grain boundaries above Tc.
The results show a strong dependence of the change of resistance with
temperature on grain boundary angle. Analysis of our results in the context of
band-bending allows us to estimate the height of the potential barrier present
at the grain boundary interface.",0311386v1
2004-02-09,Molecular electronics exploiting sharp structure in the electrode density-of-states. Negative differential resistance and Resonant Tunneling in a poled molecular layer on Al/LiF electrodes,"Density-functional calculations are used to clarify the role of an ultrathin
LiF layer on Al electrodes used in molecular electronics. The LiF layer creates
a sharp density of states (DOS), as in a scanning-tunneling microscope (STM)
tip. The sharp DOS, coupled with the DOS of the molecule leads to negative
differential resistance (NDR). Electron transfer between oriented molecules
occurs via resonant tunneling. The I-V characteristic for a thin-film of tris
(8-hydroxyquinoline)- aluminum (AlQ) molecules, oriented using electric-field
poling, and sandwiched between two Al/LiF electrodes is in excellent agreement
with theory. This molecular device presents a new paradigm for a convenient,
robust, inexpensive alternative to STM or mechanical break-junction structures.",0402257v1
2004-05-06,The antiferromagnetic transition of UPd2Al3 break-junctions: A new realization of N-shaped current-voltage characteristics,"We have investigated metallic break junctions of the heavy-fermion compound
UPd2Al3 at low temperatures between 0.1K and 9K and in magnetic fields up to
8T. Both the current-voltage I(V) characteristics and the dV/dI (V) spectra
clearly showed the superconducting ($T_{\rm c}\simeq$ 1.8K) as well as the
antiferromagnetic ($T_{\rm N}\simeq$14K) transition at low temperatures when
the bias voltage is raised. The junctions with lateral size of order 200nm had
huge critical current densities around $5\times 10^{10} A/m^2 at the
antiferromagnetic transition and hysteretic I(V) characteristics. Degrading the
quality of the contacts by in situ increasing the local residual resistivity
reduced the hysteresis. We show that those hysteretic I(V) curves can be
reproduced theoretically by assuming the constriction to be in the thermal
regime. It turns out that these point contacts represent non-linear devices
with N-shaped I(V) characteristics that have a negative differential resistance
like an Esaki tunnel diode.",0405118v1
2004-05-11,Weak links and phase slip centers in superconducting MgB2 wires,"MgB2 superconducting wires were produced by the Mg diffusion method. Scanning
electron microscopy (SEM), optical microscopy, dispersive x-ray analysis (EDS)
and XRD diffraction were used to study the physical structure and content of
the wires. Magnetic properties (Tcm, Hc1, Hc2, Jc by the Bean model) were
obtained with a SQUID magnetometer, and transport properties (Tcr, Hc2,
resistivity and residual resistivity ratio) were measured using a standard
four-lead configuration. The V-I characteristics of the wires close to the
critical temperature showed a staircase response, which was attributed to the
presence of weak links, creating phase slip centers. The origin of those weak
links is discussed in relation to their formation and structure.",0405219v1
2004-05-27,"Magnetic, electrical resistivity, heat-capacity and thermopower anomalies in CeCuAs2","The results of magnetic susceptibility, electrical resistivity ($\rho$),
heat-capacity (C) and thermopower (S) measurements on CeCuAs2, forming in
ZrCuSi2-type tetragonal structure, are reported. Our investigations reveal that
Ce is trivalent and there is no clear evidence for long range magnetic ordering
down to 45 mK. The $\rho$ behavior is notable in the sense that (i) the
temperature (T)-coefficient of $\rho$ is negative in the entire range of
measurement (45 mK to 300 K) with large values of $\rho$, while S behavior is
typical of metallic Kondo lattices, and (ii) $\rho$ is proportional to T-0.6 at
low temperatures, without any influence on the exponent by the application of a
magnetic field, which does not seem to classify this compound into
hither-to-known non-Fermi liquid (NFL) systems. In contrast to the logarithmic
increase known for NFL systems, C/T measured down to 0.5 K exhibits a fall
below 2 K. The observed properties of this compound are unusual among Ce
systems.",0405638v1
2004-06-24,"On Electron Transport in ZrB12, ZrB2 and MgB2","We report on measurements of the temperature dependence of resistivity,
$\rho(T)$, for single crystal samples of ZrB$_{12}$, ZrB$_{2}$ and
polycrystalline samples of MgB$_{2}$. It is shown that cluster compound
ZrB$_{12}$ behaves like a simple metal in the normal state, with a typical
Bloch -- Gr\""uneisen $\rho(T)$ dependence. However, the resistive Debye
temperature, $T_{R}=300 K$, is three times smaller than $T_{D}$ obtained from
specific heat data. We observe the $T^{2}$ term in $\rho(T)$ of these borides,
which could be interpreted as an indication of strong electron-electron
interaction. Although the $\rho (T)$ dependence of ZrB$_{12}$ reveals a sharp
superconductive transition at $T_{c}=6.0 K$, no superconductivity was observed
for single crystal samples of ZrB$_{2}$ down to $1.3 K$.",0406615v1
2004-07-07,Kondo Behavior of U in CaB$_6$,"Replacing U for Ca in semiconducting CaB$_6$ at the few at.% level induces
metallic behaviour and Kondo-type phenomena at low temperatures, a rather
unusual feature for U impurities in metallic hosts. For
Ca$_{0.992}$U$_{0.008}$B$_6$, the resistance minimum occurs at $T$ = 17 K. The
subsequent characteristic logarithmic increase of the resistivity with
decreasing temperature merges into the expected $T^2$ dependence below 0.8 K.
Data of the low-temperature specific heat and the magnetization are analyzed by
employing a simple resonance-level model. Analogous measurements on LaB$_6$
with a small amount of U revealed no traces of Kondo behavior, above 0.4 K.",0407158v1
2004-08-11,"Conductivity, weak ferromagnetism and charge instability in $α-MnS$ single crystal","The temperature dependence of resistivity, magnetization and electron-spin
resonance of the $\alpha- MnS $ single crystal were measured in temperature
range of $5 K < T < 550 K$. Magnetization hysteresis in applied magnetic field
up to 0.7 T at $T=5 K, 77 K, 300 K$, irreversible temperature behavior of
magnetization and resistivity were found . The obtained data were explained in
terms of degenerate tight binding model using random phase approximation. The
contribution of holes in $t_{2g}$ and $e_g$ bands of manganese ions to the
conductivity, optical absorbtion spectra and charge instability in $\alpha -MnS
$ were studied. Charge susceptibility maxima resulted from the competition of
the on-site Coulomb interaction between the holes in different orbitals and
small hybridization of sub-bands were calculated at $T=160 K, 250 K, 475 K$.",0408232v1
2004-08-26,Deviations from plastic barriers in Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ thin films,"Resistive transitions of an epitaxial Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ thin
film were measured in various magnetic fields ($H\parallel c$), ranging from 0
to 22.0 T. Rounded curvatures of low resistivity tails are observed in
Arrhenius plot and considered to relate to deviations from plastic barriers. In
order to characterize these deviations, an empirical barrier form is developed,
which is found to be in good agreement with experimental data and coincide with
the plastic barrier form in a limited magnetic field range. Using the plastic
barrier predictions and the empirical barrier form, we successfully explain the
observed deviations.",0408555v2
2004-08-27,Examination of the c-axis resistivity of Bi_{2}Sr_{2-x}La_xCuO_{6+δ} in magnetic fields up to 58 T,"We measure the magnetic-field dependence of the c-axis resistivity,
\rho_c(H), in a series of Bi_{2}Sr_{2-x}La_xCuO_{6+\delta} (BSLCO) single
crystals for a wide range of doping using pulsed magnetic fields up to 58 T.
The behavior of \rho_c(H) is examined in light of the recent determination of
the upper critical field H_{c2} for this material using Nernst effect
measurements. We find that the peak in \rho_c(H) shows up at a field H_p that
is much lower than H_{c2} and there is no discernable feature in \rho_c(H) at
H_{c2}. Intriguingly, H_p shows a doping dependence similar to that of T_c, and
there is an approximate relation k_{B}T_c \simeq {1/2}g\mu_{B}H_p. Moreover, we
show that the data for the lowest-T_c sample can be used to estimate the
pseudogap closing field H_{pg}, but the method to estimate H_{pg} proposed by
Shibauchi {\it et al.} [Phys. Rev. Lett. {\bf 86}, 5763 (2001)] must be
modified to apply to the BSLCO system.",0408603v1
2004-10-06,Ballistic resistivity in aluminum nanocontacts,"One of the major industrial challenges is to profit from some fascinating
physical features present at the nanoscale. The production of dissipationless
nanoswitches (or nanocontacts) is one of such attractive applications.
Nevertheless, the lack of knowledge of the real efficiency of electronic
ballistic/non dissipative transport limits future innovations. For multi-valent
metallic nanosystems -where several transport channels per atom are involved-
the only experimental technique available for statistical transport
characterization is the conductance histogram. Unfortunately its interpretation
is difficult because transport and mechanical properties are intrinsically
interlaced. We perform a representative series of semiclassical molecular
dynamics simulations of aluminum nanocontact breakages, coupled to full quantum
conductance calculations, and put in evidence a linear relationship between the
conductance and the contact minimum cross-section for the geometrically favored
aluminum nanocontact configurations. Valid in a broad range of conductance
values, such relation allows the definition of a transport parameter for
nanomaterials, that represents the novel concept of ballistic resistivity.",0410138v1
2004-12-01,Magnetoresistive Effects in Ferromagnet-Superconductor Multilayers,"We consider a nanoscale system consisting of Manganite-ferromagnet and
Cuprate-superconductor multilayers in a spin valve configuration. The
magnetization of the bottom Manganite-ferromagnet is pinned by a
Manganite-antiferromagnet. The magnetization of the top Manganite-ferromagnet
is coupled to the bottom one via indirect exchange through the superconducting
layers. We study the behavior of the critical temperature and the
magnetoresistance as a function of an externally applied parallel magnetic
field, when the number of Cuprate-superconductor layers are changed. There are
two typical behaviors in the case of a few monolayers of the Cuprates: a) For
small magnetic fields, the critical temperature and the magnetoresistance
change abruptly when the flipping field of the top Manganite-ferromagnet is
reached. b) For large magnetic fields, the multilayered system re-enters the
zero-resistance (superconducting) state after having become resistive (normal).",0412005v1
2004-12-12,Effect of oxygen content on the transport properties and magnetoresistance in [Ca$_{2}$CoO$_{3-δ}$]$_{0.62}$[CoO$_{2}$] single crystals,"Transport property is investigated in
[Ca$_{2}$CoO$_{3-\delta}$]$_{0.62}$[CoO$_{2}$] single crystals obtained by
varying annealing conditions. The $\rho_{ab}(T)$ exhibits a resistivity
minimum, and the temperature corresponding to this minimum increases with the
loss of oxygen content, indicative of the enhancement of spin density wave
(SDW). Large negative magnetoresistance (MR) was observed in all single
crystals [Ca$_{2}$CoO$_{3-\delta}$]$_{0.62}$[CoO$_{2}$], while a
magnetic-field-driven insulator-to-metal (IM) transition in oxygen annealed
samples. These results suggest a ferromagnetic correlation in system enhanced
by oxygen content. In addition, a low temperature thermal activation
resistivity induced by fields was observed in single crystals annealed in
oxygen atmosphere.",0412298v1
2004-12-27,Ferromagnetism and possible heavy fermion behavior in single crystals of NdOs$_4$Sb$_{12}$,"Single crystals of the filled-skutterudite compound NdOs$_4$Sb$_{12}$ have
been investigated by means of electrical resistivity, magnetization, and
specific heat measurements. The NdOs$_4$Sb$_{12}$ crystals have the
LaFe$_4$P$_{12}$-type cubic structure with a lattice parameter of 9.3 \AA.
Possible heavy-fermion behavior is inferred from specific heat measurements,
which reveal a large electronic specific heat coefficient $\gamma \approx 520$
mJ/mol-K$^2$, corresponding to an effective mass $m^* \sim$ 98 $m_e$. Features
related to a ferromagnetic transition at {$\sim$ 0.9 K} can be observed in
electrical resistivity, magnetization and specific heat. Conventional
Arrott-plot analysis indicates that NdOs$_4$Sb$_{12}$ conforms to mean-field
ferromagnetism.",0412713v3
2005-02-03,"Transverse ""resistance overshoot"" in a Si/SiGe two-dimensional electron gas in the quantum Hall effect regime","We investigate the peculiarities of the ""overshoot"" phenomena in the
transverse Hall resistance R_{xy} in Si/SiGe. Near the low magnetic field end
of the quantum Hall effect plateaus, when the filling factor \nu approaches an
integer i, R_{xy} overshoots the normal plateau value h/ie^2. However, if
magnetic field B increases further, R_{xy} decreases to its normal value. It is
shown that in the investigated sample n-Si/Si_{0.7}Ge_{0.3}, overshoots exist
for almost all \nu. Existence of overshoot in R_{xy} observed in different
materials and for different \nu, where splitting of the adjacent Landau bands
has different character, hints at the common origin of this effect. Comparison
of the experimental curves R_{xy}(\nu) for \nu = 3 and \nu = 5 with and without
overshoot showed that this effect exist in the whole interval between plateaus,
not only in the region where R_{xy} exceeds the normal plateau value.",0502094v1
2005-03-03,Transport properties of diluted magnetic semiconductors: Dynamical mean field theory and Boltzmann theory,"The transport properties of diluted magnetic semiconductors (DMS) are
calculated using dynamical mean field theory (DMFT) and Boltzmann transport
theory. Within DMFT we study the density of states and the dc-resistivity,
which are strongly parameter dependent such as temperature, doping, density of
the carriers, and the strength of the carrier-local impurity spin exchange
coupling. Characteristic qualitative features are found distinguishing weak,
intermediate, and strong carrier-spin coupling and allowing quantitative
determination of important parameters defining the underlying ferromagnetic
mechanism. We find that spin-disorder scattering, formation of bound state, and
the population of the minority spin band are all operational in DMFT in
different parameter range. We also develop a complementary Boltzmann transport
theory for scattering by screened ionized impurities. The difference in the
screening properties between paramagnetic ($T>T_c$) and ferromagnetic ($T<T_c$)
states gives rise to the temperature dependence (increase or decrease) of
resistivity, depending on the carrier density, as the system goes from the
paramagnetic phase to the ferromagnetic phase. The metallic behavior below
$T_c$ for optimally doped DMS samples can be explained in the Boltzmann theory
by temperature dependent screening and thermal change of carrier spin
polarization.",0503077v1
2005-04-22,Blue light-emitting diode based on ZnO,"A near-band-edge bluish electroluminescence (EL) band centered at around 440
nm was observed from ZnO p-i-n homojunction diodes through a semi-transparent
electrode deposited on the p-type ZnO top layer. The EL peak energy coincided
with the photoluminescence peak energy of an equivalent p-type ZnO layer,
indicating that the electron injection from the n-type layer to the p-type
layer dominates the current, giving rise to the radiative recombination in the
p-type layer. The imbalance in charge injection is considered to originate from
the lower majority carrier concentration in the p-type layer, which is one or
two orders of magnitude lower than that in the n-type one. The current-voltage
characteristics showed the presence of series resistance of several hundreds
ohms, corresponding to the current spread resistance within the bottom n-type
ZnO. The employment of conducting ZnO substrates may solve the latter problem.",0504587v1
2005-05-17,Transport properties of moderately disordered UCu$_4$Pd,"We present a detailed study on the (magneto)transport properties of as-cast
and heat treated material UCu$_4$Pd. We find a pronounced sample dependence of
the resistivity $\rho$ of as-cast samples, and reproduce the annealing
dependence of $\rho$. In our study of the Hall effect we determine a metallic
carrier density for all samples, and a temperature dependence of the Hall
constant which is inconsistent with the Skew scattering prediction. The
magnetoresistive response is very small and characteristic for spin disorder
scattering, suggesting that overall the resistivity is controlled mostly by
nonmagnetic scattering processes. We discuss possible sources for the
temperature and field dependence of the transport properties, in particular
with respect to quantum criticality and electronic localization effects.",0505418v1
2005-07-02,Drastic ground state changes induced by Ni substitution in NaxCoO2,"We report on the effect of Ni substitution at the Co site on the physical
properties of NaxCoO2 system by investigating the series NaxCo1-yNiyO2 (x=0.75,
0<y<0.15). An upturn in the resistivity is observed in all Ni substituted
samples as the temperature is lowered, suggestive of the occurrence of a
Metal-Insulator Transition (MIT). The temperature at which this transition
occurs increases with Ni content. The temperature dependence of the resistivity
in the metallic region in the Ni substituted samples shows a T2 dependence,
which is qualitatively different from that observed in the pristine sample. The
evolution of the Fano asymmetry parameter, extracted by analyzing the lineshape
of the IR active in-plane Co-O mode, both as a function of Ni concentration and
temperature corroborates the occurrence of the MIT. It is argued that the
progressive substitution of the Co4+ ions with Ni increases the probability of
double occupancy and therefore the on-site Coulomb interaction energy leading
to a shift in the thermodynamically driven MIT to higher temperatures.",0507045v1
2005-08-19,Determination of the intrinsic anomalous Hall effect of SrRuO$_3$,"The anomalous Hall effect (AHE) of epitaxial SrRuO$_3$ films with varying
lattice parameters is investigated, and analyzed according to the Berry-phase
scenario. SrRuO$_3$ thin films were deposited on SrTiO$_3$ substrates directly,
or using intermediate buffer layers, in order to finely control the epitaxial
strain. The AHE of the different films exhibits intrinsic features such as the
sign change of the Hall resistivity with the temperature, even for small
thicknesses of SrRuO$_3$. However, the anomalous Hall conductivity is greatly
reduced from its intrinsic value as the carrier scattering is increased when
the epitaxial strain is released. We argue that the AHE of fully strained
SrRuO$_3$ film with low residual resistivity represents the intrinsic AHE of
SrRuO$_3$.",0508443v1
2005-09-05,Magnetic and electronic transport percolation in epitaxial GeMn films,"Electronic transport and magnetic properties of Ge1-xMnx/Ge(100) films are
investigated as a function of Mn dilution. Depending on x, characteristic
temperatures separate different regimes in both properties. Resistivity
exhibits an insulator-like behavior in the whole temperature range and, below
about 80 K, two distinct activation energies are observed. At a higher
temperature value, TR, resistivity experiences a sudden reduction. Hall
coefficient shows a strong contribution from the anomalous Hall effect and, at
TR, a sign inversion, from positive to negative, is recorded. The magnetic
properties, inferred from magneto-optical Kerr effect, evidence a progressive
decrease of the ferromagnetic long range order as the temperature is raised,
with a Curie temperature TC not far from TR. The transport and magnetic results
are qualitatively consistent with a percolation mechanism due to bound magnetic
polarons in a GeMn diluted magnetic semiconductor, with localized holes [A.
Kaminski and S. Das Sarma, Phys. Rev. B 68, 235210 (2003)].",0509111v1
2005-10-07,Size Dependent Breakdown of Superconductivity in Ultranarrow Nanowires,"Below a certain temperature Tc (typically cryogenic), some materials lose
their electric resistance R entering a superconducting state. Folowing the
general trend toward a large scale integration of a greater number of
electronic components, it is desirable to use superconducting elements in order
to minimize heat dissipation. It is expected that the basic property of a
superconductor, i.e. dissipationless electric current, will be preserved at
reduced scales required by modern nanoelectronics. Unfortunately, there are
indications that for a certain critical size limit of the order of 10 nm, below
which a ""superconducting"" wire is no longer a superconductor in a sense that it
acquires a finite resistance even at temperatures close to absolute zero. In
the present paper we report an experimental evidence for a superconductivity
breakdown in ultranarrow quasi-1D aluminum nanowires.",0510181v1
2005-10-07,Evidence of ratchet effect in nanowires of a conducting polymer,"Ratchet effect, observed in many systems starting from living organism to
artificially designed device, is a manifestation of motion in asymmetric
potential. Here we report results of a conductivity study of Polypyrrole
nanowires, which have been prepared by a simple method to generate a variation
of doping concentration along the length. This variation gives rise to an
asymmetric potential profile that hinders the symmetry of the hopping process
of charges and hence the value of measured resistance of these nanowires become
sensitive to the direction of current flow. The asymmetry in resistance was
found to increase with decreasing nanowire diameter and increasing temperature.
The observed phenomena could be explained with the assumption that the spatial
extension of localized state involved in hopping process reduces as the doping
concentration reduces along the length of the nanowires.",0510188v1
2005-10-11,Highly oriented VO2 thin films prepared by sol-gel deposition method,"Highly oriented VO2 thin films were grown on sapphire substrates by the
sol-gel method that includes a low pressure annealing in an oxygen atmosphere.
This reduction process effectively promotes the formation of the VO2 phase over
a relatively wide range of pressures below 100 mTorr and temperatures above
400oC. X-ray diffraction analysis showed that as-deposited films crystallize
directly to the VO2 phase without passing through intermediate phases. VO2
films have been found to be with [100]- and [010]-preferred orientations on
Al2O3(1012) and Al2O3(1010) substrates, respectively. Both films undergo a
metal-insulator transition with an abrupt change in resistance, with different
transition behaviors observed for the differently oriented films. For the
[010]-oriented VO2 films a larger change in resistance of 1.2x10^4 and a lower
transition temperature are found compared to the values obtained for the
[100]-oriented films.",0510267v2
2005-11-10,"Thermoelectric properties of the layered Pd oxide R_2PdO_4 (R = La, Nd, Sm and Gd)","We prepared polycrystalline samples of R$_2$PdO$_4$ (R = La, Nd, Sm and Gd)
using a NaCl-flux technique. The measured resistivity is of the order of
10$^3-10^4$ $\Omega$cm at room temperature, which is two orders of magnitude
smaller than the values reported so far. We further studied the substitution
effects of Ce for Nd in Nd$_{1.9}$Ce$_{0.1}$PdO$_4$, where the substituted Ce
decreases the resistivity and the magnitude of the thermopower. The activation
energy gap of 70-80 meV and the effective mass of 15 evaluated from the
measured data are suitable for thermoelectric materials, but the mobility of
10$^{-6}$ cm$^2$/Vs is much lower than a typical value of 1-10 cm$^2$/Vs for
other thermoelectric oxides.",0511245v1
2005-11-10,Anderson localization in carbon nanotubes: defect density and temperature effects,"The role of irradiation induced defects and temperature in the conducting
properties of single-walled (10,10) carbon nanotubes has been analyzed by means
of a first-principles approach. We find that di-vacancies modify strongly the
energy dependence of the differential conductance, reducing also the number of
contributing channels from two (ideal) to one. A small number of di-vacancies
(5-9) brings up strong Anderson localization effects and a seemly universal
curve for the resistance as a function of the number of defects. It is also
shown that low temperatures, around 15-65 K, are enough to smooth out the
fluctuations of the conductance without destroying the exponential dependence
of the resistivity as a function of the tube length.",0511265v1
2005-11-17,Electrical Switching in Metallic Carbon Nanotubes,"We present first-principles calculations of quantum transport which show that
the resistance of metallic carbon nanotubes can be changed dramatically with
homogeneous transverse electric fields if the nanotubes have impurities or
defects. The change of the resistance is predicted to range over more than two
orders of magnitude with experimentally attainable electric fields. This novel
property has its origin that backscattering of conduction electrons by
impurities or defects in the nanotubes is strongly dependent on the strength
and/or direction of the applied electric fields. We expect this property to
open a path to new device applications of metallic carbon nanotubes.",0511447v1
2005-11-28,Laser microscopy of tunneling magnetoresistance in manganite grain-boundary junctions,"Using low-temperature scanning laser microscopy we directly image electric
transport in a magnetoresistive element, a manganite thin film intersected by a
grain boundary (GB). Imaging at variable temperature allows reconstruction and
comparison of the local resistance vs temperature for both, the manganite film
and the GB. Imaging at low temperature also shows that the GB switches between
different resistive states due to the formation and growth of magnetic domains
along the GB. We observe different types of domain wall growth; in most cases a
domain wall nucleates at one edge of the bridge and then proceeds towards the
other edge.",0511662v1
2006-03-16,Coordinate transformation in the model of long Josephson junctions: geometrically equivalent Josephson junctions,"The transition from the model of a long Josephson junction of variable width
to the model of a junction with a coordinate-dependent Josephson current
amplitude is effected through a coordinate transformation. This establishes the
correspondence between the classes of Josephson junctions of variable width and
quasi-one-dimensional junctions with a variable thickness of the barrier layer.
It is shown that for a junction of exponentially varying width the barrier
layer of the equivalent quasi-one-dimensional junction has a distributed
resistive inhomogeneity that acts as an attractor for magnetic flux vortices.
The curve of the critical current versus magnetic field for a Josephson
junction with a resistive microinhomogeneity is constructed with the aid of a
numerical simulation, and a comparison is made with the critical curve of a
junction of exponentially varying width. The possibility of replacing a
distributed inhomogeneity in a Josephson junction by a local inhomogeneity at
the end of the junction is thereby demonstrated; this can have certain
advantages from a technological point of view.",0603439v1
2006-03-28,Depolarizing-Field Effect in Strained Nanoscale Ferroelectric Capacitors and Tunnel Junctions,"The influence of depolarizing field on the magnitude and stability of a
uniform polarization in ferroelectric capacitors and tunnel junctions is
studied using a nonlinear thermodynamic theory. It is predicted that, in
heterostructures involving strained epitaxial films and metal electrodes, the
homogeneous polarization state may remain stable against transformations into
the paraelectric phase and into polydomain states down to the nanoscale. This
result supports the possibility of depolarizing-field-related resistive
switching in ferroelectric tunnel junctions with dissimilar electrodes. The
resistance on/off ratio in such junctions is shown to be governed by the
difference between the reciprocal capacitances of screening space charges in
the electrodes.",0603762v2
2006-03-31,Mechanism and Scalability in Resistive Switching of Metal-Pr0.7Ca0.3MnO3 Interface,"The polarity-dependent resistive-switching across metal-Pr0.7Ca0.3MnO3
interfaces is investigated. The data suggest that shallow defects in the
interface dominate the switching. Their density and fluctuation, therefore,
will ultimately limit the device size. While the defects generated/annihilated
by the pulses and the associated carrier depletion seem to play the major role
at lower defect density, the defect correlations and their associated hopping
ranges appear to dominate at higher defect density. Therefore, the switching
characteristics, especially the size-scalability, may be altered through
interface treatments.",0603832v1
2006-04-12,Influence of Domain Wall on Magnetocaloric Effect in GdPt$_{2}$,"The resistivity, magnetoresistance and in-field heat capacity measurements
were performed on GdPt$_{2}$ intermetallic compound. The magnetocaloric
parameters $\Delta T_{ad}$ and $-\Delta S$ were derived from the in-field heat
capacity data. Comparison has been made between the magnetocaloric effect
$-\Delta S$ and difference in resistivity $-\Delta \rho$ $(=\rho(H)-\rho(0))$
as a function of temperature. There is distinct difference in the temperature
dependence of $-\Delta S$ and $-\Delta \rho$ below the ferromagnetic transition
temperature. However after removing the domain wall contribution from $-\Delta
\rho$, the nature of $-\Delta S$ and $-\Delta \rho$ dependence as a function of
temperature are similar. Our observation indicates that the domain wall
contribution in magnetocaloric effect is negligible in spite of the fact that
it has significant contribution in magnetotransport.",0604297v1
2006-06-08,Weak localization correction to the anomalous Hall effect in polycrystalline Fe films,"In situ transport measurements have been made on ultrathin ($<$100 {\AA}
thick) polycrystalline Fe films as a function of temperature and magnetic field
for a wide range of disorder strengths. For sheet resistances $R_{xx}$ less
than $\sim 3k\Omega$, we find a logarithmic temperature dependence of the
anomalous Hall conductivity $\sigma_{xy}$ which is shown for the first time to
be due to a universal scale dependent weak localization correction within the
skew scattering model. For higher sheet resistance, granularity becomes
important and the break down of universal behavior becomes manifest as the
prefactors to $\sigma_{xx}$ and $\sigma_{xy}$ decrease at different rates with
increasing disorder.",0606215v2
2006-07-24,Magnetoresistance in Thin Permalloy Film (10nm-thick and 30-200nm-wide) Nanocontacts Fabricated by e-Beam Lithography,"In this paper we show spin dependent transport experiments in
nanoconstrictions ranging from 30 to 200nm. These nanoconstrictions were
fabricated combining electron beam lithography and thin film deposition
techniques. Two types of geometries have been fabricated and investigated. We
compare the experimental results with the theoretical estimation of the
electrical resistance. Finally we show that the magnetoresistance for the
different geometries does not scale with the resistance of the structure and
obtain drops in voltage of 20mV at 20Oe.",0607608v1
2006-07-28,Magnetic hysteresis in the microwave surface resistance of Nb samples in the critical state,"We discuss the hysteretic behavior of the field-induced variations of the
microwave surface resistance in superconductors in the critical state.
Measurements have been performed in a bulk sample of Nb and a powdered one at
different values of the temperature. We discuss a model, based on the Coffey
and Clem theory, in which we take into account the flux distribution inside the
sample, due to the critical state. The experimental results are justified
quantitatively in the framework of our model. We show that by fitting the
experimental data it is possible to determine the value of the critical current
density and its field dependence.",0607754v1
2006-09-25,Doping Dependence of Polaron Hopping Energies in La(1-x)Ca(x)MnO(3) (0<= x<= 0.15),"Measurements of the low-frequency (f<= 100 kHz) permittivity at T<= 160 K and
dc resistivity (T<= 430 K) are reported for La(1-x)Ca(x)MnO(3) (0<= x<= 0.15).
Static dielectric constants are determined from the low-T limiting behavior of
the permittivity. The estimated polarizability for bound holes ~ 10^{-22}
cm^{-3} implies a radius comparable to the interatomic spacing, consistent with
the small polaron picture established from prior transport studies near room
temperature and above on nearby compositions. Relaxation peaks in the
dielectric loss associated with charge-carrier hopping yield activation
energies in good agreement with low-T hopping energies determined from
variable-range hopping fits of the dc resistivity. The doping dependence of
these energies suggests that the orthorhombic, canted antiferromagnetic ground
state tends toward an insulator-metal transition that is not realized due to
the formation of the ferromagnetic insulating state near Mn(4+) concentration ~
0.13.",0609634v1
2006-10-10,Spin-polarized transport in ferromagnetic multilayered semiconductor nanostructures,"The occurrence of inhomogeneous spin-density distribution in multilayered
ferromagnetic diluted magnetic semiconductor nanostructures leads to strong
dependence of the spin-polarized transport properties on these systems. The
spin-dependent mobility, conductivity and resistivity in
(Ga,Mn)As/GaAs,(Ga,Mn)N/GaN, and (Si,Mn)/Si multilayers are calculated as a
function of temperature, scaled by the average magnetization of the diluted
magnetic semiconductor layers. An increase of the resistivity near the
transition temperature is obtained. We observed that the spin-polarized
transport properties changes strongly among the three materials.",0610275v1
2006-10-12,Domain wall magnetoresistance in a nanopatterned La(2/3)Sr(1/3)MnO3 track,"We have measured the contribution of magnetic domain walls (DWs) to the
electric resistance in epitaxial manganite films patterned by electron-beam
lithography into a track containing a set of notches. We find a DW
resistance-area (RA) product of ~2.5 10^(-13) Ohm/m^2 at low temperature and
bias, which is several orders of magnitude larger than the values reported for
3d ferromagnets. However, the current-voltage characteristics are highly linear
which indicates that the DWs are not phase separated but metallic. The DWRA is
found to increase upon increasing the injected current, presumably reflecting
some deformation of the wall by spin-transfer. When increasing temperature, the
DWRA vanishes at ~225K which is likely related to the temperature dependence of
the film anisotropy.",0610338v1
2006-10-25,Origin of negative differential resistance in molecular junctions of Rose Bengal,"Negative differential resistance (NDR) is tuned at junctions of
electronically different dimer and trimer of Rose Bengal on an atomic flat gold
(111) surface. Isolated molecule did not show any NDR. But it was induced to
show double NDR with large peak to valley ratio (1.8~3.1) in room temperature
via charging its neighbor reproducibly by an electrical pulse. In some sections
of junction by applying pulse one could destroy the phenomenon or regenerate it
by STM manipulation of molecules. NDR was also independent of polaronic nature.
It was possible to write bits 1 and 0 for cationic NDR (in dimer) and 00, 01,
10, 11 for di-anionic NDR (trimer) which generated 2/4 bit memory in a atomic
scale junction showing importance of junction electronics in future of
moletronics.",0610683v1
2006-11-13,Weak antilocalization in epitaxial graphene: evidence for chiral electrons,"Transport in ultrathin graphite grown on silicon carbide is dominated by the
electron-doped epitaxial layer at the interface. Weak anti-localization in 2D
samples manifests itself as a broad cusp-like depression in the longitudinal
resistance for magnetic fields 10 mT$< B <$ 5 T. An extremely sharp
weak-localization resistance peak at B=0 is also observed. These features
quantitatively agree with graphene weak-(anti)localization theory implying the
chiral electronic character of the samples. Scattering contributions from the
trapped charges in the substrate and from trigonal warping due to the graphite
layer on top are tentatively identified. The Shubnikov-de Haas oscillations are
remarkably small and show an anomalous Berry's phase.",0611339v2
2006-12-19,Semiconductors between spin-polarized source and drain,"Injecting spins into a semiconductor channel and transforming the spin
information into a significant electrical output signal is a long standing
problem in spintronics. Actually, this is the prerequisite of several concepts
of spin transistor. In this tutorial article, we discuss the general problem of
spin transport in a nonmagnetic channel between source and drain. Two problems
must be mastered: i) In the diffusive regime, the injection of a spin polarized
current from a magnetic metal beyond the ballistic transport zone requires the
insertion of a spin dependent and large enough interface resistance. ii) In
both the diffusive and ballistic regimes, and whatever the metallic or
semiconducting character of the source/drain, a small enough interface
resistance is the condition to keep the dwell time shorter than the spin
lifetime and thus to conserve the spin accumulation-induced output signal at an
optimum level. Practically, the main difficulties come from the second
condition. In our presentation of experimental results, we show why the
transformation of spin information into a large electrical signal has been more
easily achieved with carbon nanotubes than with semiconductors and we discuss
how the situation could be improved in the later case.",0612495v1
2007-01-17,Anomalous Hall effect in anatase Ti1-xCoxO2 at low temperature regime,"Anomalous Hall effect (AHE) of a ferromagnetic semiconductor anatase \cotio
thin film is studied from 10K to 300K. Magnetic field dependence of anomalous
Hall resistance is coincident with that of magnetization, while the anomalous
Hall resistance decreases at low temperature in spite of nearly
temperature-independent magnetization. Anomalous Hall conductivity sigma_AHE is
found to be proportional to the square of Hall mobility, suggesting that charge
scattering strongly affects the AHE in this system. The anatase Ti1-xCoxO2 also
follows a scaling relationship to conductivity sigma_xx as sigma_AHE ~
sigma_xx^1.6, which was observed for another polymorph rutile Ti1-xCoxO2,
suggesting an identical mechanism of their AHE.",0701395v2
2007-02-17,Room-Temperature Quantum Hall Effect in Graphene,"The quantum Hall effect (QHE), one example of a quantum phenomenon that occur
on a truly macroscopic scale, has been attracting intense interest since its
discovery in 1980 and has helped elucidate many important aspects of quantum
physics. It has also led to the establishment of a new metrological standard,
the resistance quantum. Disappointingly, however, the QHE could only have been
observed at liquid-helium temperatures. Here, we show that in graphene - a
single atomic layer of carbon - the QHE can reliably be measured even at room
temperature, which is not only surprising and inspirational but also promises
QHE resistance standards becoming available to a broader community, outside a
few national institutions.",0702408v1
2007-02-20,Anomalous electric conductions in KSbO3-type metallic rhenium oxides,"Single crystals of KSbO3-type rhenium oxides, La4Re6O$19, Pb6Re6O19, Sr2Re3O9
and Bi3Re3O11, were synthesized by a hydrothermal method. Their crystal
structures can be regarded as a network of three-dimensional orthogonal-dimer
lattice of edge-shared ReO6 octahedra. All of them exhibit small magnitude of
Pauli paramagnetism, indicating metallic electronic states without strong
electron correlations. The resistivity of these rhenates, except Bi3Re3O11,
have a temperature dependence of $rho(T)=\rho_{0}+AT^{n}$ $(n \approx 1.6)$ in
a wide temperature range between 5 K and 300 K, which is extraordinary for
three-dimensional metals without strong electron correlations. The resistivity
of Bi3Re3O11 shows an anomaly around at 50 K, where the magnetic susceptibility
also detects a deviation from ordinary Pauli paramagnetism.",0702451v1
2007-03-14,Electrical transport and percolation in magnetoresistive manganite / insulating oxide composites: case of La0.7Ca0.3MnO3 / Mn3O4,"We report the results of electrical resistivity measurements carried out on
well-sintered La0.7Ca0.3MnO3 / Mn3O4 composite samples with almost constant
composition of the magnetoresistive manganite phase (La0.7Ca0.3MnO3). A
percolation threshold (fc) occurs when the La0.7Ca0.3MnO3 volume fraction is ~
0.19. The dependence of the electrical resistivity as a function of
La0.7Ca0.3MnO3 volume fraction (fLCMO) can be described by percolation-like
phenomenological equations. Fitting the conducting regime (fLCMO > fc) by the
percolation power law returns a critical exponent t value of 2.0 +/- 0.2 at
room temperature and 2.6 +/-0.2 at 5 K. The increase of t is ascribed to the
influence of the grain boundaries on the electrical conduction process at low
temperature.",0703367v1
2007-03-25,"Origin of superconductivity in nominally ""undoped"" T'-La$_{2-x}$Y$_{x}$CuO$_{4}$ films","We have systematically studied the transport properties of the
La$_{2-x}$Y$_{x}$CuO$_{4}$(LYCO) films of T'-phase ($0.05\leq x \leq 0.30$). In
this nominally ""undoped"" system, superconductivity was acquired in certain Y
doping range ($0.10\leq x \leq 0.20$). Measurements of resistivity, Hall
coefficients in normal states and resistive critical field ($H^\rho_{c2}$)in
superconducting states of the T'-LYCO films show the similar behavior as the
known Ce-doped n-type cuprate superconductors, indicating the intrinsic
electron-doping nature. The charge carriers are induced by oxygen deficiency.
Non-superconducting Y-doped Pr- or Nd-based T'-phase cuprate films were also
investigated for comparison, suggesting the crucial role of the radii of A-site
cations in the origin of superconductivity in the nominally ""undoped"" cuptates.
Based on a reasonable scenario in the microscopic reduction process, we put
forward a self-consistent interpretation of these experimental observations.",0703643v1
2005-11-13,Non-radiating and radiating configurations driven by left-handed metamaterials,"It is shown that a pair of identical emitters (e.g. wire dipole antennas) in
the focal points of a disc, made of left-handed metamaterial (a ""perfect""
lens), form a non-radiating electromagnetic configuration. The emitters are fed
with voltages of equal magnitude and pi-out-of-phase. Detailed
finite-difference time-domain (FDTD) modeling shows that there are
non-propagating electromagnetic fields generated - fields that remain confined
within the region between the emitters and the lens. The energy balance of the
system shows that the radiation resistance of the system is very low. This
means that the input power is converted to heat in the volume of the lens and
only a small fraction of it is radiated. The system performance shows that
disturbing the configuration of the non-propagating electromagnetic fields with
the presence of an externally introduced object stimulates radiation. This
suggests possible detector applications. In-phase feeding voltages are also
studied with the consequence that the radiation resistance of the antennae is
increased.",0511113v1
2007-04-16,Memory function formalism approach to electrical conductivity and optical response of dilute magnetic semiconductors,"A combination of the memory function formalism and time-dependent
density-functional theory is applied to transport in dilute magnetic
semiconductors. The approach considers spin and charge disorder and
electron-electron interaction on an equal footing. Within the weak disorder
limit and using a simple parabolic approximation for the valence band we show
that Coulomb and exchange scattering contributions to the resistivity in GaMnAs
are of the same order of magnitude. The positional correlations of defects
result in a significant increase of Coulomb scattering, while the suppression
of localized spin fluctuations in the ferromagnetic phase contributes
substantially to the experimentally observed drop of resistivity below T_c. A
proper treatment of dynamical screening and collective excitations is essential
for an accurate description of infrared absorption.",0704.2061v1
2007-05-15,"Magnetic, magneto-thermal and magneto-transport properties in SmMn2Si2-xGex compounds","The effect of Ge substitution for Si in SmMMn2Si2-xGex compounds has been
studied. The Sm ordering temperature is found to be much larger in the compound
with x=2, as compared to the compounds with x=0 and 1. The increase in the
intra layer Mn-Mn distance is found to be responsible for this increase. Among
these three compounds, SmMn2Ge2 is found to show re-entrant ferromagnetism at
low temperatures. The magnetic contribution to the heat capacity has been found
in all the three compounds. The splitting of the ground state multiplet has
been estimated by fitting the magnetic part of the heat capacity data using the
Schottky formula. The isothermal magnetic entropy change is found to remain the
same for x=0 and 1, but decrease in the compound with x=2, though the nature of
magnetic transition changes from second order to first order, as x is increased
from 0 to 2. The electrical resistivity increases with Ge concentration. The
excess resistivity in the antiferromagnetic region has been calculated.",0705.2237v1
2007-06-01,Anomalous magnetoresistance of EuB$_{5.99}$C$_{0.01}$: Enhancement of magnetoresistance in systems with magnetic polarons,"We present results of measurements of electrical, magnetic and thermal
properties of EuB$_{5.99}$C$_{0.01}$. The observed anomalously large negative
magnetoresistance as above, so below the Curie temperature of ferromagnetic
ordering $T_C$ is attributed to fluctuations in carbon concentration. Below
$T_C$ the carbon richer regions give rise to helimagnetic domains, which are
responsible for an additional scattering term in the resistivity, which can be
suppressed by a magnetic field. Above $T_C$ these regions prevent the process
of percolation of magnetic polarons (MPs), acting as ""spacers"" between MPs. We
propose that such ""spacers"", being in fact volumes incompatible with existence
of MPs, may be responsible for the decrease of the percolation temperature and
for the additional (magneto)resistivity increase in systems with MPs.",0706.0091v1
2007-07-03,Spatial correlation of linear and nonlinear electron transport in superconducting microwave resonator: laser scanning microscopy analysis,"Spatially-resolved techniques of laser scanning microscopy (LSM) have been
used to image simultaneously the spatial variations of (i) rf current flow,
J$_RF$(x,y), of (ii) areas of resistive dissipation and (iii) the sources of
microwave nonlinearity (NL) in an operating superconducting resonator. The RF
power dependent spatial evolution of these linear and NL microwave properties
in the meander strip YBCO/LAO superconducting resonator have been LSM probed at
different temperatures below Tc. The influence of both topologies of the
twin-domain YBCO structure and of J$_RF$(x,y) peaks at the edges of
superconducting strip line on its NL properties was analyzed in detail with a
micron-scale spatial resolution. Result shows the resistive origin of the
dominant sources of microwave NLs",0707.0358v1
2007-07-04,Resistive Switching in Cr doped SrTiO3: An X-ray Absorption Spectroscopy study,"X-ray absorption spectroscopy was used to study the microscopic origin of
conductance and resistive switching in chromium doped strontium titanate
(Cr:SrTiO3). Differences in the x-ray absorption near edge spectroscopy (XANES)
at the Cr K-edge indicate that the valence of Cr changes from 3+ to 4+
underneath the anode of our sample device after the application of an electric
field. Spatially resolved x-ray fluorescence microscopy ($\mu$-XRF) maps show
that the Cr4+ region retracts from the anode-Cr:SrTiO3 interface after a
conducting state has been achieved. This interface region is studied with
extended x-ray absorption fine structure (EXAFS) and the results are compared
with structural parameters obtained from density functional theory (DFT)
calculations. They confirm that oxygen vacancies which are localized at the
octahedron with a Cr at its center are introduced at the interface. It is
proposed that the switching state is not due to a valence change of chromium
but caused by changes of oxygen vacancies at the interface.",0707.0655v1
2007-08-21,"Negative differential resistance of Styrene on an ideal Si[111] surface: dependence of the I-V characteristics on geometry, surface doping and shape of the STM-tip","We study the electron transport properties through a supported organic
molecule styrene (C8H8) on an ideal silicon surface Si[111] and probed by a
STM-tip. The I-V characteristics and the differential conductance of the
molecule are calculated using a self consistent approach based on non
equilibrium Green's functions. Two different adsorption configurations for the
molecule on the surface were considered which corresponds to a global and a
local minimum of the total energy. In both cases we find a negative
differential resistance (NDR) in a given interval of bias voltages. This effect
is controlled by the states available close to the Fermi level of the surface
and can be manipulated by properly doping the substrate. We also analyze the
influence of the tip-shape on the I-V characteristics.",0708.2834v1
2007-12-21,Vibronic polarons: comments on a model for the colossal field-resistance effects in manganites,"In addition to mechanisms already proposed to account for the formation in
manganites of a small-polaron superlattice above the Curie temperature Tc and
to a metallic-like sea of large polarons below Tc, we now consider other
observed colossal-resistance inducing fields, such as magnetic, electric,
photon, or strain fields. We attribute the charge-ordered phase formation to
the occurrence of strong dipolar binding of vibronic small polarons arising
from the phonon coupling of highly polarizable two-level orbital systems. These
species having associated inherent electric and magnetic off-center dipoles,
they couple to the external fields leading to the observed colossal effects.
The random phase appears due to polaron band widening in the external field.",0712.3803v1
2008-03-05,"The behavior of magnetic ordering and the KOndo effect in the alloys, Ce2Rh(1-x)Co(x)Si3: Evidence from bulk studies for Fermi-surface change during magnetic ordering - QCP transformation and applicability of SDW pictur","The results of magnetic susceptibility, electrical resistivity (rho), and
heat capacity measurements as a function of temperature are reported for the
alloys, Ce2Rh(1-x)Co(x)Si3, crystallizing in an AlB2-derived hexagonal
strcture. Ce2RhSi3 exhibits antiferromagnetic ordering at 7 K. The Neel
temperature decreases gradually with the increase in Co concentration. For x
greater than 0.6, no magnetic ordering is observed down to 0.5 K.
Interestingly, the x= 0.6 alloy exhibits signatutes of non-Fermi liquid
behavior, while the Co end member is a Fermi liquid. Thus, a transformation of
magnetic ordering state to non-magnetism via non-Fermiliquid state by
isoelectronic chemical doping is evident in this solid solution. The electrical
resistivity data for x= 0.2 and 0.3 alloys show an upturn at respective Neel
temperatures, establishing the formation of a magnetism-induced pseudo-gap for
these intermediate compositions alone as though there is a gradual Fermi
surface transformation as the quantum critical point is approached.",0803.0652v1
2008-03-09,"Upper critical field, Hall effect and magnetoresistance in the iron-based layered superconductor LaFeAsO_{0.9}F_{0.1-δ}","By using a two-step method, we successfully synthesized the iron based new
superconductor LaFeAsO_{0.9}F_{0.1-\delta}$. The resistive transition curves
under different magnetic fields were measured, leading to the determination of
the upper critical field Hc2(T) of this new superconductor. The value of Hc2 at
zero temperature is estimated to be about 50 Tesla roughly. In addition, the
Hall effect and magnetoresistance were measured in wide temperature region. A
negative Hall coefficient R_H has been found, implying a dominant conduction
mainly by electron-like charge carriers in this material. The charge carrier
density determined at 100 K is about 9.8E20cm^{-3}, which is close to the
cuprate superconductors. It is further found that the magnetoresistance does
not follow Kohler's law. Meanwhile, the different temperature dependence
behaviors of resistivity, Hall coefficient, and magnetoresistance have
anomalous properties at about 230 K, which may be induced by some exotic
scattering mechanism.",0803.1288v2
2008-03-12,Electron transport and thermoelectric properties of layered perovskite LaBaCo2O5.5,"We have investigated the systematic transport properties of the layered
112-type cobaltite LaBaCo2O5.5 by means of electrical resistivity,
magnetoresistance, electroresistance and thermoelectric measurements in various
conditions. In order to understand the complex conduction mechanism of
LaBaCo2O5.5, the transport data have been analyzed using different theoretical
models. The system shows semiconductor-semiconductor like transition (TSC)
around 326K, corresponding to ferromagnetic transition and in the low
temperature region resistivity data follows the Motts variable range hopping
model. Interestingly, near and below the room temperature this compound depicts
significant change in electro- and magnetoresistance behavior, the latter one
is noteworthy near the magnetic phase boundary. The temperature dependence of
thermopower, S(T), exhibits p-type polaronic conductivity in the temperature
range of 60-320K and reaches a maximum value of 303 uV/K (at 120K). In the low
temperature AFM region, the unusual S(T) behavior, generally observed for the
cobaltite series LnBaCo2O5.5 (Ln = Rare Earth), is explained by the electron
magnon scattering mechanism as previously described for perovskite manganites.",0803.1806v1
2008-03-14,From Ohmic to Ballistic Transport in Oriented Graphite,"In this work we show that for a quasi-2D system of size $\Omega$ and
thickness $t$ the resistance goes as $(2\rho/\pi t)\ln(\Omega/W)$, diverging
logarithmically with the size. Measurements in highly oriented pyrolytic
graphite (HOPG) as well as numerical simulations confirm this relation.
Furthermore, we present an experimental method that allows us to obtain the
carriers mean free path $l(T)$, the Fermi wavelength $\lambda(T)$ and the
mobility $\mu(T)$ directly from experiments without adjustable parameters.
Measuring the electrical resistance through microfabricated constrictions in
HOPG and observing the transition from ohmic to ballistic regime we obtain that
$0.2 \mu$m $\lesssim l \lesssim 10 \mu$m, $0.1 \mu$m $\lesssim \lambda \lesssim
2 \mu$m and a mobility $5 \times 10^4$ cm$^2$/Vs $ \lesssim \mu \lesssim 4
\times 10^7$ cm$^2$/Vs when the temperature decreases from 270K to 3K. A
comparison of these results with those from literature indicates that
conventional, multiband Boltzmann-Drude approaches are inadequate for oriented
graphite. The upper value obtained for the mobility is much larger than the
mobility graphene samples of micrometer size can have.",0803.2203v2
2008-03-19,Theory of quantum metal to superconductor transitions in highly conducting systems,"We derive the theory of the quantum (zero temperature) superconductor to
metal transition in disordered materials when the resistance of the normal
metal near criticality is small compared to the quantum of resistivity. This
can occur most readily in situations in which ``Anderson's theorem'' does not
apply. We explicitly study the transition in superconductor-metal composites,
in an s-wave superconducting film in the presence of a magnetic field, and in a
low temperature disordered d-wave superconductor. Near the point of the
transition, the distribution of the superconducting order parameter is highly
inhomogeneous. To describe this situation we employ a procedure which is
similar to that introduced by Mott for description of the temperature
dependence of the variable range hopping conduction. As the system approaches
the point of the transition from the metal to the superconductor, the
conductivity of the system diverges, and the Wiedemann-Franz law is violated.
In the case of d-wave (or other exotic) superconductors we predict the
existence of (at least) two sequential transitions as a function of increasing
disorder: a d-wave to s-wave, and then an s-wave to metal transition.",0803.2902v2
2008-03-23,Origin of negative differential resistance in a strongly coupled single molecule-metal junction device,"A new mechanism is proposed to explain the origin of negative differential
resistance (NDR) in a strongly coupled single molecule-metal junction. A
first-principles quantum transport calculation in a Fe-terpyridine linker
molecule sandwiched between a pair of gold electrodes is presented. Upon
increasing applied bias, it is found that a new phase in the broken symmetry
wavefunction of the molecule emerges from the mixing of occupied and unoccupied
molecular orbital. As a consequence, a non-linear change in the coupling
between molecule and lead is evolved resulting to NDR. This model can be used
to explain NDR in other class of metal-molecule junction device.",0803.3342v1
2008-04-13,Conductance of p-n-p graphene structures with 'air-bridge' top gates,"We have fabricated graphene devices with a top gate separated from the
graphene layer by an air gap--a design which does not decrease the mobility of
charge carriers under the gate. This gate is used to realise p-n-p structures
where the conducting properties of chiral carriers are studied. The band
profile of the structures is calculated taking into account the specifics of
the graphene density of states and is used to find the resistance of the p-n
junctions expected for chiral carriers. We show that ballistic p-n junctions
have larger resistance than diffusive ones. This is caused by suppressed
transmission of chiral carriers at angles away from the normal to the junction.",0804.2081v3
2008-06-16,"Metal-insulator transition and giant anisotropic magnetoresistance in ultra thin (Ga,Mn)As","MBE-grown, 5 nm-thick annealed Ga0.95Mn0.05As films with Tc~90K demonstrate
transition from metallic to insulating state below To~10K, where sheet
resistances Rsh~h/e2 and both longitudinal Rxx and transverse Rxy components
become comparable. Below metal-insulator transition we found giant anisotropic
magnetoresistance (GAMR), which depends on orientation of magnetization to
crystallographic axes and manifests itself in positive magnetoresistance near
50% for Rxx at T=1.7K, H//[110] crystallographic direction and parallel to
current in contrast to smaller and negative magnetoresistance for H//
direction. We connect GAMR with anisotropic spin-orbit interaction resulting in
formation of high- and low- resistance states with different localization along
non-equivalent easy axes.",0806.2590v1
2008-06-28,Theory of spin magnetohydrodynamics,"We develop a phenomenological hydrodynamic theory of coherent magnetic
precession coupled to electric currents. Exchange interaction between electron
spin and collective magnetic texture produces two reciprocal effects:
spin-transfer torque on the magnetic order parameter and the Berry-phase gauge
field experienced by the itinerant electrons. The dissipative processes are
governed by three coefficients: the ohmic resistance, Gilbert damping of the
magnetization, and the ""beta coefficient"" describing viscous coupling between
magnetic dynamics and electric current, which stems from spin mistracking of
the magnetic order. We develop general magnetohydrodynamic equations and
discuss the net dissipation produced by the coupled dynamics. The latter in
particular allows us to determine a lower bound on the magnetic-texture
resistivity.",0806.4656v2
2008-07-28,Transport anomalies across the quantum limit in semimetallic Bi$_{0.96}$Sb$_{0.04}$,"We report on a study of electronic transport in semi-metallic
Bi$_{0.96}$Sb$_{0.04}$. At zero field, the system is a very dilute Fermi liquid
displaying a T$^{2}$ resistivity with an enhanced prefactor. Quantum
oscillations in resistivity as well as in Hall, Nernst and Seebeck responses of
the system are detectable and their period quantifies the shrinking of the
Fermi surface with antimony doping. For a field along the trigonal axis, the
quantum limit was found to occur at a field as low as 3T. An ultraquantum
anomaly at twice this field was detected in both charge transport and Nernst
response. Its origin appears to lie beyond the one-particle picture and linked
to unidentified many-body effects.",0807.4432v1
2008-07-30,Ultra-Thin Silver Films obtained by Sequential Quench-Anneal Processing,"We have used the two-step growth technique, quench condensing followed by an
anneal, to grow ultra thin films of silver on glass substrates. As has been
seen with semiconductor substrates this process produces a metastable
homogeneous covering of silver. By measuring the in situ resistance of the film
during growth we are able to see that the low temperature growth onto
substrates held at 100 Kelvin produces a precursor phase that is insulating
until the film has been annealed. The transformation of the precursor phase
into the final, metallic silver film occurs at a characteristic temperature
near 150K where the sample reconstructs. This reconstruction is accompanied by
a decrease in resistance of up to 10 orders of magnitude.",0807.4948v1
2008-08-09,Electronic transport and specific heat of 1T- VSe2,"The results of low temperature thermoelectric power and the specific heat of
1T-VSe2 (Vanadium diselenide) have been reported along with the electrical
resistivity, and Hall coefficient of the compound. The Charge Density Wave
(CDW) transition is observed near 110K temperature in all these properties. The
Thermoelectric power has been measured from 15K to 300K spanning the
incommensurate and commensurate CDW regions. We observed a weak anomaly at the
CDW transition for the first time in the specific heat of VSe2. The linear
temperature dependence of resistivity and thermoelectric power at higher
temperatures suggests a normal metallic behavior and electron-phonon scattering
above the CDW transition. The positive thermoelectric power and negative Hall
coefficient along with strongly temperature dependent behavior in the CDW phase
suggest a mixed conduction related to the strongly hybridized s-p-d bands in
this compound.",0808.1332v2
2008-08-11,Non-trivial length dependence of the conductance and negative differential resistance in atomic molecular wires,"We study the electronic and transport properties of two novel molecular wires
made of atomic chains of carbon atoms (polyynes) capped with either,
benzene-thiols or pyridines. While both molecules are structurally similar, the
electrical conductance of benzene-thiol-capped chains attached to gold
electrodes is found to be much higher than that of pyridine-capped chains. We
predict that the conductance is almost independent of molecular length, which
suggests that these molecules could be ideal molecular wires for sub-10 nm
circuitry. Both systems exhibit negative differential resistance (NDR) but its
origin and characteristics depend on the type of molecule. We find a novel type
of NDR mechanism produced by the movement of the LUMO resonance with bias. We
also show that by gating the pyridine-capped molecules it is possible to make
the NDR disappear and dramatically modify the $I$-$V$ characteristics and the
length dependence.",0808.1494v2
2008-08-21,Electrons and holes in Si quantum well: a room-temperature transport and drag resistance study,"We investigate carrier transport in a single 22 nm-thick double-gated Si
quantum well device, which has independent contacts to electrons and holes.
Conductance, Hall density and Hall mobility are mapped in a broad double-gate
voltage window. When the gate voltage asymmetry is not too large only either
electrons or holes occupy the Si well and the Hall mobility shows the
fingerprints of volume inversion/accumulation. At strongly asymmetric
double-gate voltage an electric field induced electron-hole (EH) bi-layer is
formed inside the well. The EH drag resistance R_{he} is explored at balanced
carrier densities: R_{he} decreases monotonically from 860 to 37 Ohms when the
electron and hole density is varied between ~0.4-1.7x10^{16} m^{-2}.",0808.2914v1
2008-10-27,Abrupt Emergence of Pressure-Induced Superconductivity of 34 K in SrFe2As2: A Resistivity Study under Pressure,"We report resistivity measurement under pressure in single crystals of
SrFe_2As_2, which is one of the parent materials of Fe-based superconductors.
The structural and antiferromagnetic (AFM) transition of T_0 = 198 K at ambient
pressure is suppressed under pressure, and the ordered phase disappears above
P_c ~ 3.6-3.7 GPa. Superconductivity with a sharp transition appears
accompanied by the suppression of the AFM state. T_c exhibits a maximum of 34.1
K, which is realized close to the phase boundary at P_c. This T_c is the
highest among those of the stoichiometric Fe-based superconductors.",0810.4856v2
2008-12-11,Difference of Oxide Hetero-Structure Junctions with Semiconductor Electronic Devices,"Charge carrier injection performed in Pr0.7Ca0.3MnO3 (PCMO) hetero-structure
junctions exhibits stable without electric fields and dramatic changes in both
resistances and interface barriers, which are entirely different from behaviors
of semiconductor devices. Disappearance and reversion of interface barriers
suggest that the adjustable resistance switching of such hetero-structure oxide
devices should associate with motion of charge carriers across interfaces. The
results suggested that injected carriers should be still staying in devices and
resulted in changes in properties, which guided to a carrier self-trapping and
releasing picture in strongly correlated electronic framework. Observations in
PCMO and oxygen deficient CeO2 devices show that oxides as functional materials
could be used in microelectronics with some novel properties, in which
interface is very important.",0812.2071v1
2008-12-11,Evidence for Coexistence of Superconductivity and Magnetism in Single Crystals of Co-doped SrFe$_2$As$_2$,"In order to investigate whether magnetism and superconductivity coexist in
Co-doped SrFe$_2$As$_2$, we have prepared single crystals of
SrFe$_{2-x}$Co$_x$As$_2$, $x$ = 0 and 0.4, and characterized them via X-ray
diffraction, electrical resistivity in zero and applied field up to 9 T as well
as at ambient and applied pressure up to 1.6 GPa, and magnetic susceptibility.
At $x$ = 0.4, there is both magnetic and resistive evidence for a spin density
wave transition at 120 K, while $T_c$ = 19.5 K - indicating coexistent
magnetism and superconductivity. A discussion of how these results compare with
reported results, both in SrFe$_{2-x}$Co$_x$As$_2$ and in other doped 122
compounds, is given.",0812.2091v1
2009-01-10,"Wafer-Scale, Sub-5 nm Junction Formation by Monolayer Doping and Conventional Spike Annealing","We report the formation of sub-5 nm ultrashallow junctions in 4 inch Si
wafers enabled by the molecular monolayer doping of phosphorous and boron atoms
and the use of conventional spike annealing. The junctions are characterized by
secondary ion mass spectrometry and non-contact sheet resistance measurements.
It is found that the majority (~70%) of the incorporated dopants are
electrically active, therefore, enabling a low sheet resistance for a given
dopant areal dose. The wafer-scale uniformity is investigated and found to be
limited by the temperature homogeneity of the spike anneal tool used in the
experiments. Notably, minimal junction leakage currents (<1 uA/cm2) are
observed which highlights the quality of the junctions formed by this process.
The results clearly demonstrate the versatility and potency of the monolayer
doping approach for enabling controlled, molecular-scale ultrashallow junction
formation without introducing defects in the semiconductor.",0901.1396v1
2009-02-10,Spontaneous and low-field magnetoimpedance in La0.7Sr0.3CoO3 and La1-xSrxMnO3 (x = 0.18-0.5),"We report ac electrical transport in La0.7Sr0.3CoO3 and La1-xSrxMnO3 (x =
0.18- 0.5) as a function of temperature and frequency in H = 0 and 60 mT. Both
resistive (R) and reactive (X) components of impedance (Z = R+jX) were
measured. It is shown that a smooth decrease of the resistance around the Curie
temperautre in La0.7Sr0.3CoO3 transforms into an abrupt increase followed
closely by a peak in R with increasing frequency. Similar behavior in R was
also found in metallic compositions of the La-Sr-MnO3 series. The observed
anomaly at TC is suppressed by a small dc magnetic field of H = 60 mT which
rrsults in a huge ac magnetoreistance (= 30 % in manganite and =7 % in
cobaltite at f = 2 MHz). The anomaly in R in zero field is also accompanied by
a sudden incrases of X. While the ac magnetoresitance is negative as a function
of field from 100 Hz to 30 MHz, we show that the sign of X changes and a new
double peak structure develops in X for frequencies above 15 MHz.",0902.1780v1
2009-04-24,Evolution of orbital phases with particle size in nanoscale stoichiometric LaMnO3,"The thermodynamically stable long-range orbital order in bulk LaMnO3 becomes
metastable at nanoscale around a critical particle size d_C~20 nm. The orbital
order-disorder transition switches from reversible to irreversible at d_C while
the resistance in the orbital ordered state decays by 2-4% over a time scale of
~3000s. At well below d_C, of course, a stable orbital disordered phase
emerges. The orthorhombic distortion of the underlying crystallographic
structure (space group Pbnm) decreases systematically with the decrease in
particle size and at far below d_C (e.g., at ~10 nm), the structure becomes
cubic (space group Pm-3m). Using the crystallographic and electrical resistance
data, a phase diagram has been constructed showing the evolution of different
orbital phases as a function of particle size across ~10 nm to bulk for
stoichiometric LaMnO3.",0904.3878v3
2009-06-04,Sensitivity of Ag/Al Interface Specific Resistances to Interfacial Intermixing,"We have measured an Ag/Al interface specific resistance, 2AR(Ag/Al)(111) =
1.4 fOhm-m^2, that is twice that predicted for a perfect interface, 50% larger
than for a 2 ML 50%-50% alloy, and even larger than our newly predicted 1.3
fOhmm^2 for a 4 ML 50%-50% alloy. Such a large value of 2ARAg/Al(111) confirms
a predicted sensitivity to interfacial disorder and suggests an interface
greater than or equal to 4 ML thick. From our calculations, a predicted
anisotropy ratio, 2AR(Ag/Al)(001)/2AR(Ag/Al)(111), of more then 4 for a perfect
interface, should be reduced to less than 2 for a 4 ML interface, making it
harder to detect any such anisotropy.",0906.0934v1
2009-06-04,Perpendicular-current Studies of Electron Transport Across Metal/Metal Interfaces,"We review what we have learned about the scattering of electrons by the
interfaces between two different metals (M1/M2) in the
current-perpendicular-to-plane (CPP) geometry. In this geometry, the intrinsic
quantity is the specific resistance, AR, the product of the area through which
the CPP current flows times the CPP resistance. We describe results for both
non-magnetic/non-magnetic (N1/N2) and ferromagnetic/non-magnetic (F/N) pairs.
We focus especially upon cases where M1/M2 are lattice matched (i.e., have the
same crystal structure and the same lattice parameters to within ~ 1%), because
in these cases no-free-parameter calculations of 2AR agree surprisingly well
with measured values. But we also list and briefly discuss cases where M1/M2
are not lattice matched, either having different crystal structures, or lattice
parameters that differ by several percent. The published calculations of 2AR in
these latter cases do not agree so well with measured values.",0906.0936v1
2009-06-26,Upper bound for the conductivity of nanotube networks,"Films composed of nanotube networks have their conductivities regulated by
the junction resistances formed between tubes. Conductivity values are enhanced
by lower junction resistances but should reach a maximum that is limited by the
network morphology. By considering ideal ballistic-like contacts between
nanotubes we use the Kubo formalism to calculate the upper bound for the
conductivity of such films and show how it depends on the nanotube
concentration as well as on their aspect ratio. Highest measured conductivities
reported so far are approaching this limiting value, suggesting that further
progress lies with nanowires other than nanotubes.",0906.4906v2
2009-06-29,Upper critical fields of the 11-system iron-chalcogenide superconductor FeSe$_{0.25}$Te$_{0.75}$,"We have performed electrical resistivity measurements of a polycrystalline
sample of FeSe$_{0.25}$Te$_{0.75}$, which exhibits superconductivity at $T_{\rm
c} \sim 14$ K, in magnetic fields up to 55 T to determine the upper critical
field $\mu_{0}H_{\rm c2}$. In this compound, very large slopes of
$\mu_{0}H_{\rm c2}$ at the onset, the mid-point, the zero-resistivity
temperatures on superconductivity are determined to be -13.7, -10.1, and -6.9
T/K, respectively. The observed $\mu_{0}H_{\rm c2}(T)$s of this compound are
considerably smaller than those expected from the Werthamer-Helfand-Hohenberg
model, manifesting the Pauli limiting behavior. These results suggest that this
compound has a large Maki parameter, but it is smaller than that calculated for
a weak-coupling superconductor, indicating a large superconducting gap of this
compound as a strong-coupling superconductor.",0906.5248v1
2009-07-17,"Phase diagram of CeFeAs$_{1-x}$P$_{x}$O obtained from electric resistivity, magnetization, and specific heat measurements","We performed a systematic study on the properties of CeFeAs$_{1-x}$P$_{x}$O
($0\leq x\leq 1$) by electrical resistivity, magnetization and specific heat
measurements. The c-axis lattice constant decreases significantly with
increasing P content, suggesting a remarkable chemical pressure. The Fe-3d
electrons show the enhanced metallic behavior upon P-doping and undergo a
magnetic quantum phase transition around $x \approx 0.4$. Meanwhile, the Ce-4f
electrons develop a ferromagnetic order near the same doping level. The
ferromagnetic order is vanishingly small around $x=0.9$. The data suggest a
heavy-fermion-like behavior as $x\geq 0.95$. No superconductivity is observed
down to 2 K. Our results show the ferromagnetic ordered state as an
intermediate phase intruding between the antiferromagnetic bad metal and the
nonmagnetic heavy fermion metal and support the cerium-containing iron
pnictides as a unique layered Kondo lattice system.",0907.2961v2
2009-07-31,Top and side gated epitaxial graphene field effect transistors,"Three types of first generation epitaxial graphene field effect transistors
(FET) are presented and their relative merits are discussed. Graphene is
epitaxially grown on both the carbon and silicon faces of hexagonal silicon
carbide and patterned with electron beam lithography. The channels have a Hall
bar geometry to facilitate magnetoresistance measurements. FETs patterned on
the Si-face exhibit off-to-on channel resistance ratios that exceed 30. C-face
FETs have lower off-to-on resistance ratios, but their mobilities (up to 5000
cm2/Vs) are much larger than that for Si-face transistors. Initial
investigations into all-graphene side gate FET structures are promising.",0908.0017v1
2009-08-02,Spin-dependent transport in nanocomposite C:Co films,"The magneto-transport properties of nanocomposite C:Co (15 and 40 at.% Co)
thin films are investigated. The films were grown by ion beam co-sputtering on
thermally oxidized silicon substrates in the temperature range from 200 to 500
degC. Two major effects are reported: (i) a large anomalous Hall effect
amounting to 2 \mu ohm cm, and (ii) a negative magnetoresistance. Both the
field-dependent resistivity and Hall resistivity curves coincide with the
rescaled magnetization curves, a finding that is consistent with spin-dependent
transport. These findings suggest that C:Co nanocomposites are promising
candidates for carbon-based Hall sensors and spintronic devices.",0908.0127v1
2009-09-16,"Superconductivity at 39 K in New Iron Pnictide Oxide (Fe2As2)(Sr4(Mg,Ti)2O6)","We have discovered a new iron pnictide oxide superconductor
(Fe2As2)(Sr4(Mg,Ti)2O6). This material is isostructual with (Fe2As2)(Sr4M2O6)
(M = Sc, Cr), which was found in our previous study. The structure of this
compound is tetragonal with a space group of P4/nmm and consists of the
anti-fluorite type FeAs and perovskite-type blocking layers. The lattice
constants are a = 3.935 A and c = 15.952 A for (Fe2As2)(Sr4MgTiO6). In both
magnetization and resistivity measurements, this compound exhibits
superconductivity below 10 K. Moreover, ratio of Mg and Ti in this compound can
be changed toward Ti-rich composition. (Fe2As2)(Sr4Mg1-xTi1+xO6) phase is
obtained at 0 < x as a main phase, and Tc and superconducting volume fraction
increase with increasing x. The highest Tc(onset) was confirmed at 39 K for x =
0.6 in resistivity measurement.",0909.2945v3
2009-09-25,"Electrical, magnetic, magnetodielectric and magnetoabsorption studies in multiferroic GaFeO3","We report electrical, magnetic, magnetodielectric and magnetoabsorption
properties of a polycrystalline GaFeO3. The resistivity measurement shows that
the sample is highly insulating below 200 K and the resistivity above 200 K
obey the Arrhenius law with an activation energy of Ea = 0.67 eV. An anomaly
occurs in the temperature dependence of permittivity (e) near the ferrimagnetic
transition temperature (TC = 228 K) in a zero magnetic field and it is
suppressed under H = 60 mT which indicates a possible magnetoelectric coupling
in GaFeO3 with a fractional change of de/e = -1.8% at 60 mT around TC. The
coercivity (HC) of the sample increases dramatically with lowering temperature
below 200 K from 0.1 T at 200 K to 0.9 T at 5 K. Magnetoabsorption was studied
with a LC resonance technique and we found a close correlation between the
shift in the resonance frequency due to applied magnetic field and the coercive
field measured using dc magnetization measurements. Our results obtained with
multiple techniques suggest that GaFeO3 is an interesting ferrimagnet with
potential applications in future multiferroic devices.",0909.4609v1
2009-10-11,Anomalous Hall resistance in Ge:Mn systems with low Mn concentrations,"Taking Mn doped Germanium as an example, we evoke the consideration of a
two-band-like conduction in diluted ferromagnetic semiconductor (FMS). The main
argument for claiming Ge:Mn as a FMS is the occurrence of the anomalous Hall
effect (AHE). Usually, the reported AHE (1) is observable at temperatures above
10 K, (2) exhibits no hysteresis, and (3) changes the sign of slope. We
observed a similar Hall resistance in Mn implanted Ge with the Mn concentration
as low as 0.004%. We show that the puzzling AHE features can be explained by
considering a two-band-like conduction in Ge:Mn.",0910.1981v1
2009-10-20,"Sharp fall of electrical resistance for a small application of magnetic field on a metastable form of a compound, Tb5Si3, under pressure","We report an unusual sensitivity of electrical resistivity (rho) to an
application of a small magnetic field in an intermetallic compound, Tb5Si3,
under pressure. In this compound, there is a magnetic field-induced first-order
magnetic transition at 1.8 K. Under pressure, there is a metastable magnetic
phase after reducing the field to zero. This metastable phase is relatively of
higher rho and interestingly a small magnetic field (less than 2 kOe) in the
reverse direction results in a sharp fall of rho to restore virgin state rho.
The present finding could be relevant to spintronic applications.",0910.3794v1
2009-11-11,Neutron powder diffraction investigation of the structural and magnetic properties of (La1-yYy)FeAsO,"The structural, magnetic and resistive properties of (La1-yYy)FeAsO compounds
(y = 0.10, 0.20, 0.30) have been investigated by means of X-ray and neutron
powder diffraction as well as by resistivity measurements. The temperatures at
which the structural transition from tetragonal to orthorhombic and the
magnetic ordering take place progressively reduce by similar amounts with
increasing Y substitution on account of the progressive chemical pressure
increase. We propose that the structural transition could be originated by a
cooperative Jahn-Teller distortion involving the alignment of the fully
occupied Fe 3d(z2) orbitals in the Fe plane along the y axis, leading to the
branching of the cell parameters a and b. The magnetic structure develops after
the occurrence of the structural transition, but before its completion.",0911.2153v1
2009-11-23,Magnetic field and contact resistance dependence of non-local charge imbalance,"Crossed Andreev reflection (CAR) in metallic nanostructures, a possible basis
for solid-state electron entangler devices, is usually investigated by
detecting non-local voltages in multi-terminal superconductor/normal metal
devices. This task is difficult because other subgap processes may mask the
effects of CAR. One of these processes is the generation of charge imbalance
(CI) and the diffusion of non-equilibrium quasi-particles in the
superconductor. Here we demonstrate a characteristic dependence of non-local CI
on a magnetic field applied parallel to the superconducting wire, which can be
understood by a generalization of the standard description of CI to non-local
experiments. These results can be used to distinguish CAR and CI and to extract
CI relaxation times in superconducting nanostructures. In addition, we
investigate the dependence of non-local CI on the resistance of the injector
and detector contacts and demonstrate a quantitative agreement with a recent
theory using only material and junction characteristics extracted from separate
direct measurements.",0911.4427v1
2009-12-16,Cooling dynamics and thermal interface resistance of glass-embedded metal nanoparticles,"The cooling dynamics of glass-embedded noble metal nanoparticles with
diameters ranging from 4 to 26 nm were studied using ultrafast pump-probe
spectroscopy. Measurements were performed probing away from the surface plasmon
resonance of the nanoparticles to avoid spurious effects due to glass heating
around the particle. In these conditions, the time-domain data reflect the
cooling kinetics of the nanoparticle. Cooling dynamics are shown to be
controlled by both thermal resistance at the nanoparticule?glass interface, and
heat diffusion in the glass matrix. Moreover, the interface conductances are
deduced from the experiments and found to be correlated to the acoustic
impedance mismatch at the metal/glass interface.",0912.3058v1
2009-12-29,Interplay of bulk and interface effects in the electric-field driven transition in magnetite,"Contact effects in devices incorporating strongly-correlated electronic
materials are comparatively unexplored. We have investigated the
electrically-driven phase transition in magnetite (100) thin films by
four-terminal methods. In the lateral configuration, the channel length is less
than 2 $\mu$m, and voltage-probe wires $\sim$100 nm in width are directly
patterned within the channel. Multilead measurements quantitatively separate
the contributions of each electrode interface and the magnetite channel. We
demonstrate that on the onset of the transition contact resistances at both
source and drain electrodes and the resistance of magnetite channel decrease
abruptly. Temperature dependent electrical measurements below the Verwey
temperature indicate thermally activated transport over the charge gap. The
behavior of the magnetite system at a transition point is consistent with a
theoretically predicted transition mechanism of charge gap closure by electric
field.",0912.5374v1
2010-01-08,Low-magnetic-field control of dielectric constant at room temperature realized in Ba0.5Sr1.5Zn2Fe12O22,"We show that room temperature resistivity of Ba0.5Sr1.5Zn2Fe12O22 single
crystals increases by more than three orders of magnitude upon being subjected
to optimized heat treatments. The increase in the resistivity allows the
determination of magnetic field (H)-induced ferroelectric phase boundaries up
to 310 K through the measurements of dielectric constant at a frequency of 10
MHz. Between 280 and 310 K, the dielectric constant curve shows a peak centered
at zero magnetic field and thereafter decreases monotonically up to 0.1 T,
exhibiting a magnetodielectric effect of 1.1%. This effect is ascribed to the
realization of magnetic field-induced ferroelectricity at an H value of less
than 0.1 T near room temperature. Comparison between electric and magnetic
phase diagrams in wide temperature- and field-windows suggests that the
magnetic field for inducing ferroelectricity has decreased near its helical
spin ordering temperature around 315 K due to the reduction of spin anisotropy
in Ba0.5Sr1.5Zn2Fe12O22.",1001.1319v1
2010-03-05,Weak superconducting fluctuations and small anisotropy of the upper critical fields in an Fe1.05Te0.85Se0.15 single crystal,"We have investigated the temperature dependence of the resistive upper
critical fields ($\mu_{0}H_{\rm c2}(T)$) for an
Fe$_{1.05}$Te$_{0.85}$Se$_{0.15}$ single crystal, which exhibit
superconductivity at $T_{\rm c} \sim 14 K, in magnetic fields of up to 55 T.
Two-dimensional feature and superconducting fluctuations of the samples are
found to be weak, because the resistive broadening effect on applied magnetic
fields of up to 14 T is small. The Pauli paramagnetic effect is obviously
evidenced by the strong suppression of the $\mu_{0}H_{\rm c2}^{ab}(T)$ ($H
\parallel ab$) curve and nearly isotropic $\mu_{0}H_{\rm c2}(0) \approx 47 T is
seen for both $H \parallel ab$ and $H \parallel c$. This fact is almost
identical to the results of Fe$_{1+y}$Te$_{0.6}$Se$_{0.4}$ single crystals
reported previously. We have discussed that the small anisotropy of the upper
critical field at low temperatures in Fe$_{1+y}$(Te,Se) systems against the
variation of the Te/Se ratio.",1003.1171v3
2010-03-19,Lateral Spin Injection in Germanium Nanowires,"Electrical injection of spin-polarized electrons into a semiconductor, large
spin diffusion length, and an integration friendly platform are desirable
ingredients for spin-based devices. Here we demonstrate lateral spin injection
and detection in germanium nanowires, by using ferromagnetic metal contacts and
tunnel barriers for contact resistance engineering. Using data measured from
over 80 samples, we map out the contact resistance window for which lateral
spin transport is observed, manifestly showing the conductivity matching
required for spin injection. Our analysis, based on the spin diffusion theory,
indicates that the spin diffusion length is larger than 100 {\mu}m in germanium
nanowires at 4.2 K.",1003.3787v2
2010-03-28,Scanning Gate Microscopy on Graphene: Charge Inhomogeneity and Extrinsic Doping,"We have performed scanning gate microscopy (SGM) on graphene field effect
transistors (GFET), using a biased metallic nanowire coated with a dielectric
layer as a contact mode tip and local top gate. Electrical transport through
graphene at various back gate voltages is monitored as a function of tip
voltage and tip position. Near the Dirac point, the dependence of graphene
resistance on tip voltage shows a significant variation with tip position. SGM
imaging reveals mesoscopic domains of electron-doped and hole-doped regions.
Our measurements indicate a substantial spatial fluctuation (on the order of
10^12/cm^2) in the carrier density in graphene due to extrinsic local doping.
Important sources for such doping found in our samples include metal contacts,
edges of graphene, structural defects, and resist residues.",1003.5404v1
2010-04-07,Temperature dependence of the nonlocal voltage in an Fe/GaAs electrical spin injection device,"The nonlocal spin resistance is measured as a function of temperature in a
Fe/GaAs spin-injection device. For nonannealed samples that show minority-spin
injection, the spin resistance is observed up to room temperature and decays
exponentially with temperature at a rate of 0.018\,K$^{-1}$. Post-growth
annealing at 440\,K increases the spin signal at low temperatures, but the
decay rate also increases to 0.030\,K$^{-1}$. From measurements of the
diffusion constant and the spin lifetime in the GaAs channel, we conclude that
sample annealing modifies the temperature dependence of the spin transfer
efficiency at injection and detection contacts. Surprisingly, the spin transfer
efficiency increases in samples that exhibit minority-spin injection.",1004.1034v1
2010-05-01,Reversible Fluorination of Graphene: towards a Two-Dimensional Wide Bandgap Semiconductor,"We report the synthesis and evidence of graphene fluoride, a two-dimensional
wide bandgap semiconductor derived from graphene. Graphene fluoride exhibits
hexagonal crystalline order and strongly insulating behavior with resistance
exceeding 10 G$\Omega$ at room temperature. Electron transport in graphene
fluoride is well described by variable-range hopping in two dimensions due to
the presence of localized states in the band gap. Graphene obtained through the
reduction of graphene fluoride is highly conductive, exhibiting a resistivity
of less than 100 k$\Omega$ at room temperature. Our approach provides a new
path to reversibly engineer the band structure and conductivity of graphene for
electronic and optical applications.",1005.0113v1
2010-07-15,Quantum Hall Resistance Overshoot in 2-Dimensional Electron Gases - Theory and Experiment,"We present a systematical experimental investigation of an unusual transport
phenomenon observed in two dimensional electron gases in Si/SiGe
heterostructures under integer quantum Hall effect (IQHE) conditions. This
phenomenon emerges under specific experimental conditions and in different
material systems. It is commonly referred to as Hall resistance overshoot,
however, lacks a consistent explanation so far. Based on our experimental
findings we are able to develop a model that accounts for all of our
observations in the framework of a screening theory for the IQHE. Within this
model the origin of the overshoot is attributed to a transport regime where
current is confined to co-existing evanescent incompressible strips of
different filling factors.",1007.2586v1
2010-08-10,Transition from a ferromagnetic insulating to a ferromagnetic metallic state in nanoparticles of Nd0.8Sr0.2MnO3 : Study of the electronic - and magneto - transport properties,"A detailed investigation of the electronic - and magneto - transport
properties of Nd0.8Sr0.2MnO3 with the variation of grain size (down to 42 nm)
is presented here. Interestingly, we observe that the ferromagnetic insulating
state is suppressed and a metallic state is stabilized as the grain size of the
sample is reduced. As a result, metal insulator transition is observed in this
low doped manganite which is insulating in nature in its bulk form.
Destabilization of polaronic order in the ferromagnetic insulating state due to
enhanced surface disorder on grain size reduction has been attributed to this
effect. A phenomenological model has been proposed to represent the concept of
destabilization of polaron formation in the surface region of the nano grains.
Resistivity and magnetoresistance data have been carefully analyzed employing
different suitable models. Electrical third harmonic resistance has been
measured to directly probe the electrical nonlinearity in the samples.",1008.1693v1
2010-08-18,A New Strained-Silicon Channel Trench-gate Power MOSFET: Design and Analysis,"In this paper, we propose a new trench power MOSFET with strained Si channel
that provides lower on resistance than the conventional trench MOSFET. Using a
20% Ge mole fraction in the Si1-xGex body with a compositionally graded
Si1-xGex buffer in the drift region enables us to create strain in the channel
along with graded strain in the accumulation region. As a result, the proposed
structure exhibits 40% enhancement in current drivability, 28% reduction in the
on-resistance and 72% improvement in peak transconductance at the cost of only
12% reduction in the breakdown voltage when compared to the conventional trench
gate MOSFET. Furthermore, the graded strained accumulation region supports the
confinement of carriers near the trench sidewalls improving the field
distribution in the mesa structure useful for a better damage immunity during
inductive switching.",1008.3019v1
2010-08-24,Dominant role of impurity scattering over crystalline anisotropy for magnetotransport properties in the quasi-1D Hollandite Ba1.2Rh8O16,"Angular magnetotransport measurements have been performed to tackle the
origin of the magnetoresistance in the quasi-1D Hollandite Ba1.2Rh8O16. Three
samples of different impurities amount were measured. We observe that the low
temperature resistivity upturn is not due to a charge density wave transition,
and a dominant role of impurities scattering for low temperature transport
properties is instead demonstrated. The components of magnetoresistance were
separated by using the Kohler plot and the angular dependency of the resistance
under magnetic field. It shows the major contribution of an isotropic, likely
spin driven, negative magnetoresistance. Galvanomagnetic characteristics are
then consistent with a Kondo effect and appear to be essentially 3D at low
temperature.",1008.4040v1
2010-09-27,Effect of vertex corrections on the longitudinal transport through multilayered nanostructures: Exact dynamical mean-field theory approach applied to the inhomogeneous Falicov-Kimball model,"Inhomogeneous dynamical mean-field theory is employed to calculate the
vertex-corrected electronic charge transport for multilayered devices composed
of semi-infinite metallic lead layers coupled through a strongly correlated
material barrier region. The barrier region can be tuned from a metal to a Mott
insulator through adjusting the interaction strength and the particle filling.
We use the Falicov-Kimball model to describe the barrier region because an
exact expression for the vertex corrections is known, allowing us to determine
their effect on transport. The dc conductivity is calculated and we find the
effects of the vertex corrections are relatively small, manifesting themselves
in a small reduction in the resistance-area product. This reduction saturates
in absolute magnitude as the barrier layer becomes thick, as expected due to
the vanishing nature of the vertex corrections in bulk. The vertex corrections
have a larger relative effect on the resistance-area product for more metallic
and thinner devices.",1009.5299v1
2010-10-08,"A unified first-principles study of Gilbert damping, spin-flip diffusion and resistivity in transition metal alloys","Using a formulation of first-principles scattering theory that includes
disorder and spin-orbit coupling on an equal footing, we calculate the
resistivity $\rho$, spin flip diffusion length $l_{sf}$ and the Gilbert damping
parameter $\alpha$ for Ni$_{1-x}$Fe$_x$ substitutional alloys as a function of
$x$. For the technologically important Ni$_{80}$Fe$_{20}$ alloy, permalloy, we
calculate values of $\rho = 3.5 \pm 0.15$ $\mu$Ohm-cm, $l_{sf}=5.5 \pm 0.3$ nm,
and $\alpha= 0.0046 \pm 0.0001$ compared to experimental low-temperature values
in the range $4.2-4.8$ $\mu$Ohm-cm for $\rho$, $5.0-6.0$ nm for $l_{sf}$, and
$0.004-0.013$ for $\alpha$ indicating that the theoretical formalism captures
the most important contributions to these parameters.",1010.1626v3
2010-10-23,Silicon Oxide is a Non-Innocent Surface for Molecular Electronics and Nanoelectronics Studies,"Silicon oxide (SiOx) has been widely used in many electronic systems as a
supportive and insulating medium. Here we demonstrate various electrical
phenomena such as negative differential resistance, resistive switching and
current hysteresis intrinsic to a thin layer of SiOx. These behaviors can
largely mimic numerous electrical phenomena observed in molecules and other
nanomaterials, suggesting that substantial caution should be paid when studying
conduction in electronic systems with SiOx as a component. The actual switching
can be the result of SiOx and not the presumed molecular or nanomaterial
component. These electrical properties and the underlying mechanisms are
discussed in detail.",1010.4853v1
2010-11-17,Oxidation resistance of graphene-coated Cu and Cu/Ni alloy,"The ability to protect refined metals from reactive environments is vital to
many industrial and academic applications. Current solutions, however,
typically introduce several negative effects, including increased thickness and
changes in the metal physical properties. In this paper, we demonstrate for the
first time the ability of graphene films grown by chemical vapor deposition to
protect the surface of the metallic growth substrates of Cu and Cu/Ni alloy
from air oxidation. SEM, Raman spectroscopy, and XPS studies show that the
metal surface is well protected from oxidation even after heating at 200
\degree C in air for up to 4 hours. Our work further shows that graphene
provides effective resistance against hydrogen peroxide. This protection method
offers significant advantages and can be used on any metal that catalyzes
graphene growth.",1011.3875v1
2010-12-20,Conduction Electron Scattering and Spin-Flipping at Sputtered Co/Ni Interfaces,"Current-perpendicular-to-plane magnetoresistance (CPP-MR) measurements let us
quantify conduction electron scattering and spin-flipping at a sputtered
ferromagnetic/ferromagnetic (F1/F2 = Co/Ni) interface, with important
consequences for CPP-MR and spin-torque experiments with perpendicular
anisotropy. We use ferromagnetically coupled ([Ni/Co]xn)Ni multilayers, and
Py-based, symmetric double exchange-biased spin-valves (DEBSVs) containing
inserts of ferromagnetically coupled ([Co/Ni]xn)Co or ([Ni/Co]xn)Ni
multilayers, to derive Co/Ni interface specific resistances AR(Co/Ni)(Up) =
0.03 (+0.02)(-0.03) f-ohm-m^2 and AR(Co/Ni)(down) = 1.00 +/- 0.07 f-ohm-m^2,
and interface spin-flipping parameter delta(Co/Ni) = 0.35 +/- 0.05. The
specific resistances are consistent with our no-free-parameter calculations for
an interface thickness between 2 and 4 monolayers (ML) that is compatible with
expectations.",1012.4388v1
2011-01-19,Negative differential resistance in scanning tunneling microscopy: simulations on C$_{60}$-based molecular overlayers,"We determine the conditions in which negative differential resistance (NDR)
appears in the C$_{60}$-based molecular device of [Phys. Rev. Lett. {\bf 100},
036807 (2008)] by means of ab-initio electron-transport simulations. Our
calculations grant access to bias-dependent intrinsic properties of the
molecular device, such as electronic levels and their partial widths. We show
that these quantities depend on the molecule-molecule and molecule-electrode
interactions of the device. Hence, NDR can be tuned by modifying the bias
behavior of levels and widths using both types of interactions.",1101.3714v1
2011-01-26,Metal-insulator transition in ultrathin LaNiO3 films,"Transport in ultrathin films of LaNiO3 evolves from a metallic to a strongly
localized character as the film's thickness is reduced and the sheet resistance
reaches a value close to h/e2, the quantum of resistance in two dimensions. In
the intermediate regime, quantum corrections to the Drude low- temperature
conductivity are observed; they are accurately described by weak localization
theory. Remarkably, the negative magnetoresistance in this regime is isotropic,
which points to magnetic scattering associated with the proximity of the system
to either a spin glass state or the charge ordered antiferromagnetic state
observed in other rare earth nickelates.",1101.5111v2
2011-03-31,Aharonov-Casher effect in Bi$_{\rm 2}$Se$_{\rm 3}$ square-ring interferometers,"Electrical control of spin dynamics in Bi$_{\rm 2}$Se$_{\rm 3}$ was
investigated in ring-type interferometers. Aharonov-Bohm and
Altshuler-Aronov-Spivak resistance oscillations against magnetic field, and
Aharorov-Casher resistance oscillations against gate voltage were observed in
the presence of a Berry phase of $\pi$. A very large tunability of spin
precession angle by gate voltage has been obtained, indicating that Bi$_{\rm
2}$Se$_{\rm 3}$-related materials with strong spin-orbit coupling are promising
candidates for constructing novel spintronic devices.",1103.6115v1
2011-06-02,Evidence for semiconducting behavior with a narrow band gap of Bernal graphite,"We have studied the resistivity of a large number of highly oriented graphite
samples with areas ranging from several mm$^2$ to a few $\mu$m$^2$ and
thickness from $\sim 10 $nm to several tens of micrometers. The measured
resistance can be explained by the parallel contribution of semiconducting
graphene layers with low carrier density $< 10^9$ cm$^{-2}$ and the one from
metallic-like internal interfaces. The results indicate that ideal graphite
with Bernal stacking structure is a narrow-gap semiconductor with an energy gap
$E_g \sim 40 $meV.",1106.0437v3
2011-07-25,Unveiling a nematic quantum critical point in multi-orbital systems,"Electronic nematicity, proposed to exist in a number of transition metal
materials, can have different microscopic origins. In particular, the
anisotropic resistivity and meta-magnetic jumps observed in Sr3Ru2O7 are
consistent with an earlier proposal that the isotropic-nematic transition is
generically first order and accompanied by meta-magnetism when tuned by a
magnetic field. However, additional striking experimental features such as a
non-Fermi liquid resistivity and critical thermodynamic behavior imply the
presence of an unidentified quantum critical point (QCP). Here we show that
orbital degrees of freedom play an essential role in revealing a nematic QCP,
even though it is overshadowed by a nearby meta-nematic transition at low
temperature. We further present a finite temperature phase diagram including
the entropy landscape and discuss our findings in light of the phenomena
observed in Sr3Ru2O7.",1107.5052v5
2011-08-25,Structural and Electrical Characterization of Bi2Se3 Nanostructures Grown by Metalorganic Chemical Vapor Deposition,"We characterize nanostructures of Bi2Se3 that are grown via metalorganic
chemical vapor deposition using the precursors diethyl selenium and trimethyl
bismuth. By adjusting growth parameters, we obtain either single-crystalline
ribbons up to 10 microns long or thin micron-sized platelets. Four-terminal
resistance measurements yield a sample resistivity of 4 mOhm-cm. We observe
weak anti-localization and extract a phase coherence length l_phi = 178 nm and
spin-orbit length l_so = 93 nm at T = 0.29 K. Our results are consistent with
previous measurements on exfoliated samples and samples grown via physical
vapor deposition.",1108.4978v2
2011-09-14,Growth of atomically smooth thin films of the electronically phase separated manganite (La$_{0.5}$Pr$_{0.5}$)$_{0.67}$Ca$_{0.33}$MnO$_{3}$,"Atomically flat, epitaxial, and stoichiometric thin films of the
electronically phase separated compound
(La$_{0.5}$Pr$_{0.5}$)$_{0.67}$Ca$_{0.33}$MnO$_{3}$ were grown on as-received
and treated NdGaO$_{3}$ substrates by fine tuning of oxygen pressure during
deposition. Optimal thin films with step flow growth mode show superior
physical properties compared to thin films grown in off-optimal oxygen
pressures, {\em viz.} the highest maximum temperature coefficient of
resistance, the highest peak-resistivity temperature, and reduced coercive
fields. Transport, magnetization, and x-ray diffraction measurements indicate
that the oxygen pressure during growth plays a critical role in the formation
of oxygen vacancies, cation vacancies, and grain boundaries.",1109.3225v1
2011-09-23,A single layer hydrogen silsesquioxane (HSQ) based lift-off process for germanium and platinum,"Primarily used as etch mask, single layer hydrogen silsesquioxane has never
been investigated for lift-off technique. In this article, we propose a new
technique where a single layer of hydrogen silsesquioxane, a negative tone
electron beam resist, is used to make lift-off of germanium and platinum.
Removal of exposed hydrogen silsesquioxane is tested for various concentrations
of hydrofluoric acid. Ultrasonic agitation is also used to reduce the formation
of flakes due to accumulation of matter (evaporated metal in our case) along
the sidewalls of the lift-off narrow slots. Results demonstrate potential in
applying the hydrogen silsesquioxane as a negative tone lift-off resist to
pattern nanometer scale features into germanium and platinum layers.",1109.5187v1
2011-11-03,Estimation of the spin polarization for Heusler-compound thin films by means of nonlocal spin-valve measurements: Comparison of Co$_{2}$FeSi and Fe$_{3}$Si,"We study room-temperature generation and detection of pure spin currents
using lateral spin-valve devices with Heusler-compound electrodes, Co$_{2}$FeSi
(CFS) or Fe$_{3}$Si (FS). The magnitude of the nonlocal spin-valve (NLSV)
signals is seriously affected by the dispersion of the resistivity peculiarly
observed in the low-temperature grown Heusler compounds with ordered
structures. From the analysis based on the one-dimensional spin diffusion
model, we find that the spin polarization monotonically increases with
decreasing the resistivity, which depends on the structural ordering, for both
CFS and FS electrodes, and verify that CFS has relatively large spin
polarization compared with FS.",1111.0742v2
2011-11-27,A first-order magnetic phase transition near 15 K with novel magnetic-field-induced effects in Er5Si3,"We present magnetic characterization of a binary rare-earth intermetallic
compound Er5Si3, crystallizing in Mn5Si3-type hexagonal structure, through
magnetization, heat-capacity, electrical resistivity, and magnetoresistance
measurements. Our investigations confirm that the compound exhibits two
magnetic transitions with decreasing temperature, first one at 35 K and the
second one at 15 K. The present results reveal that the second magnetic
transition is a disorder-broadened first-order transition, as shown by thermal
hysteresis in the measured data. Another important finding is that, below 15 K,
there is a magnetic-field-induced transition with a hysteretic effect with the
electrical resistance getting unusually enhanced at this transition and the
magnetorsistance (MR) is found to exhibit intriguing magnetic-field dependence
indicating novel magnetic phase-co-existence phenomenon. It thus appears that
this compound is characterized by interesting magnetic anomalies in the
temperature-magnetic-field phase diagram.",1111.6240v1
2011-12-20,Approximate Theory of Temperature Coefficient of Resistivity of Amorphous Semiconductors,"In this paper, we develop an approximate theory of the temperature
coefficient of resistivity (TCR) and conductivity based upon the recently
proposed Microscopic Response Method. By introducing suitable approximations
for the lattice dynamics, localized and extended electronic states, we produce
new explicit forms for the conductivity and TCR, which depend on easily
accessible material parameters. The theory is in reasonable agreement with
experiments on a-Si:H and a-Ge:H. A long-standing puzzle, a \textquotedblleft
kink\textquotedblright\ in the experimental $% \log_{10}\sigma $ vs. 1/T curve,
is predicted by the theory and attributed to localized to extended transitions,
which have not been properly handled in earlier theories.",1112.4723v2
2011-12-23,Microscopic Details of the Integer Quantum Hall Effect in an Anti-Hall Bar,"Due to the lack of simulation tools that take into account the actual
geometry of complicated quantum Hall samples there are lots of experiments that
are not yet fully understood. Already some years ago R. G. Mani recorded a
shift of the Hall resistance transitions to lower magnetic fields in samples of
a Hall bar with embedded anti-Hall bar by using partial gating. We use a
Nonequilibrium Network Model (NNM) to simulate this geometry and find
qualitative agreement. Fitting the simulated resistance curves to the
experimental results we can not only determine the carrier concentration but
also obtain an estimate of the screened gating potential and especially the
amplitude and lengthscale of potential fluctuations from charge inhomogenities
which are not easily accessible by experiment.",1112.5673v1
2012-02-27,Coaxial Nanowire Resonant Tunneling Diodes from non-polar AlN/GaN on Silicon,"Resonant tunneling diodes are formed using AlN/GaN core-shell nanowire
heterostructures grown by plasma assisted molecular beam epitaxy on n-Si(111)
substrates. By using a coaxial geometry these devices take advantage of
non-polar (m-plane) nanowire sidewalls. Device modeling predicts non-polar
orientation should enhance resonant tunneling compared to a polar structure and
that AlN double barriers will lead to higher peak-to-valley current ratios
compared to AlGaN barriers. Electrical measurements of ensembles of nanowires
show negative differential resistance appearing only at cryogenic temperature.
Individual nanowire measurements show negative differential resistance at room
temperature with peak current density of 5*10^5 A/cm^2.",1202.6052v2
2012-04-09,Magnetic-field induced resistivity minimum with in-plane linear magnetoresistance of the Fermi liquid in SrTiO3-x single crystals,"We report novel magnetotransport properties of the low temperature Fermi
liquid in SrTiO3-x single crystals. The classical limit dominates the
magnetotransport properties for a magnetic field perpendicular to the sample
surface and consequently a magnetic-field induced resistivity minimum emerges.
While for the field applied in plane and normal to the current, the linear
magnetoresistance (MR) starting from small fields (< 0.5 T) appears. The large
anisotropy in the transverse MRs reveals the strong surface interlayer
scattering due to the large gradient of oxygen vacancy concentration from the
surface to the interior of SrTiO3-x single crystals. Moreover, the linear MR in
our case was likely due to the inhomogeneity of oxygen vacancies and oxygen
vacancy clusters, which could provide experimental evidences for the unusual
quantum linear MR proposed by Abrikosov [A. A. Abrikosov, Phys. Rev. B 58, 2788
(1998)].",1204.1901v1
2012-04-20,Size-dependent electronic-transport mechanism and sign reversal of magnetoresistance in Nd0.5Sr0.5CoO3,"A detailed investigation of electronic-transport properties of Nd0.5Sr0.5CoO3
has been carried out as a function of grain size ranging from micrometer order
down to an average size of 28 nm. Interestingly, we observe a size induced
metal-insulator transition in the lowest grain size sample while the bulk-like
sample is metallic in the whole measured temperature regime. An analysis of the
temperature dependent resistivity in the metallic regime reveals that the
electron-electron interaction is the dominating mechanism while other processes
like electron-magnon and electron-phonon scatterings are also likely to be
present. The fascinating observation of enhanced low temperature upturn and
minimum in resistivity on reduction of grain size is found due to
electron-electron interaction (quantum interference effect). This effect is
attributed to enhanced disorder on reduction of grain size. Interestingly, we
observed a cross over from positive to negative magnetoresistance in the low
temperature regime as the grain size is reduced. This observed sign reversal is
attributed to enhanced phase separation on decreasing the grain size of the
cobaltite.",1204.4572v1
2012-04-22,Anomalous ferromagnetism and non-Fermi-liquid behavior in the Kondo lattice CeRuSi2,"The structural, electronic and magnetic properties of the Kondo-lattice
system CeRuSi2 are experimentally investigated and analyzed in the series of
other ternary cerium compounds. This system is shown to be an excellent model
system demonstrating coexistence of the Kondo effect and anomalous
ferromagnetism with a small magnetic moment which is confirmed by magnetic and
\mu SR measurements. Data on specific heat, resistivity and Seebeck coefficient
are presented. Being deduced from the resistivity and specific heat data, the
non-Fermi-liquid behavior is observed at low temperatures, which is unusual for
a ferromagnetic Kondo system. A comparison with other magnetic Kondo lattices
is performed.",1204.4903v3
2012-07-02,Evolution of the magnetism of Tb(Co_{x}Ni_{1-x})_{2}B_{2}C,"The magnetic properties of polycrystalline Tb(Co_{x}Ni_{1-x})_{2}B_{2}C
(x=0.2,0.4,0.6,0.8) samples were probed by magnetization, specific heat, ac
susceptibility, and resistivity techniques. For x{\neq}0.4, the obtained curves
are consistent with the features expected for the corresponding magnetic modes,
namely k_{1}=(0.55,0,0) at x=0;
k_{2}=([nicefrac]\nicefrac{1}{2}</LaTeX>,0,[nicefrac]<LaTeX>\nicefrac{1}{2}) at
x= 0.2; k_{3}=(0,0,[nicefrac]\nicefrac{1}{3}) at x= 0.6, and k_{4}=(0,0,0) at
x= 0.8 and 1. For x=0.4, even though the neutron diffraction indicates a k_{2}
mode, but with a reduced magnetic moment, the magnetization, the ac
susceptibility, and resistivity indicate two magnetic events; furthermore,
deviation from Curie-Weiss behavior is observed below 150 K for this sample.
These features, together with the evolution of both magnetic moment and
critical temperature, are attributed to an interplay between competing magnetic
couplings; for the particular x=0.4 case, additional factors such as
crystalline electric field effects may be in operation.",1207.0519v1
2012-07-19,Mobility enhancement and highly efficient gating of monolayer MoS2 transistors with Polymer Electrolyte,"We report electrical characterization of monolayer molybdenum disulfide
(MoS2) devices using a thin layer of polymer electrolyte consisting of
poly(ethylene oxide) (PEO) and lithium perchlorate (LiClO4) as both a
contact-barrier reducer and channel mobility booster. We find that bare MoS2
devices (without polymer electrolyte) fabricated on Si/SiO2 have low channel
mobility and large contact resistance, both of which severely limit the
field-effect mobility of the devices. A thin layer of PEO/ LiClO4 deposited on
top of the devices not only substantially reduces the contact resistance but
also boost the channel mobility, leading up to three-orders-of-magnitude
enhancement of the field-effect mobility of the device. When the polymer
electrolyte is used as a gate medium, the MoS2 field-effect transistors exhibit
excellent device characteristics such as a near ideal subthreshold swing and an
on/off ratio of 106 as a result of the strong gate-channel coupling.",1207.4824v1
2012-07-20,"Magnetic, magnetocaloric and magnetotransport properties of RSn_{1+x}Ge_{1-x} compounds (R=Gd, Tb, Er; x=0.1)","We have studied the magnetic, magnetocaloric and magnetotransport properties
of RSn1+xGe1-x(R=Gd, Tb, Er; x=0.1) series by means of magnetization, heat
capacity and resistivity measurements. It has been found that all the compounds
crystallize in the orthorhombic crystal structure described by the
centrosymmetric space group Cmcm (No. 63). The magnetic susceptibility and heat
capacity data suggest that all the compounds are antiferromagnetic. Large
negative values of {\theta}p in case of GdSn1.1Ge0.9 and TbSn1.1Ge0.9 indicate
that strong antiferromagnetic interactions are involved, which is also
reflected in the magnetization isotherms. On the other hand ErSn1.1Ge0.9 shows
weak antiferromagnetic interaction. The heat capacity data have been analyzed
by fitting the temperature dependence and the values of {\theta}D and {\gamma}
have been estimated. Among these three compounds, ErSn1.1Ge0.9 shows
considerable magnetic entropy change of 9.5 J/kg K and an adiabatic temperature
change of 3.2 K for a field of 50 kOe. The resistivity data in different
temperature regimes have been analyzed and the dominant contributions have been
identified. All the compounds show small but positive magnetoresistance.",1207.4971v1
2012-07-30,The Effect of Electrode Size on Memristor Properties: An Experimental and Theoretical Study,"The width of the electrodes is not included in the current phenomenological
models of memristance, but is included in the memory-conservation (mem-con)
theory of memristance. An experimental study of the effect of changing the top
electrode width was performed on titanium dioxide sol-gel memristors. It was
demonstrated that both the on resistance, Ron, and the off resistance, Roff,
decreased with increasing electrode size. The memory function part of the
mem-con model could fit the relationship between Ron and electrode size.
Similarly, the conservation function fits the change in Roff. The
experimentally measured hysteresis did not fit the phenomenological model's
predictions. Instead the size of the hysteresis increased with increasing
electrode size, and correlated well to decreasing Ron.",1207.6933v1
2012-08-06,A Variant of the Point Defect Model for Passivity of Metals,"A variant of the point defect model originally enunciated by Macdonald and
co-workers is advanced and its theoretical implications for the steady state
current density, barrier layer thickness and the concentration of metal vacancy
at the metal/film interface are deduced. The differences between the original
point defect model and the present variant are also highlighted. The empirical
parameters alpha and beta in the original point defect model are replaced with
two physical parameters Rcont and Rhof which represent respectively the
electronic contact resistance at the metal/film interface and the electronic
resistivity of the oxide film. The present variant correctly describes the
annihilation of the metal vacancies at the metal/film interface and also
enforces the conservation of particle and defect volumes during the solid-state
reactions leading to the natural inclusion of the famous Pilling-Bedsworth
ratio RPB into the model. Diagnostics which help to check the model predictions
with experiments are given. Use of this variant to describe stress-induced
failure of the barrier oxide leading to pitting is also discussed.",1208.1096v1
2012-08-27,Suppression of superconductivity in layered Bi4O4S3 by Ag doping,"We report X-ray diffraction, magnetization and transport measurements for
polycrystalline samples of the new layered superconductor Bi4-xAgxO4S3
(0<x<0.2). The superconducting transition temperature (TC) decreases gradually
and finally suppressed for x>0.10. Accordingly, the resistivity changes from a
metallic behavior for x<0.1 to a semiconductor-like behavior for x>0.1. The
analysis of Seebeck coefficient shows there are two types of electron-like
carriers dominate at different temperature regions, indicative of a multiband
effect responsible for the transport properties. The suppression of
superconductivity and the increased resistivity can be attributed to a shift of
the Fermi level to the lower-energy side upon doping, which reduces the density
of states at EF. Further, our result indicates the superconductivity in the
parent Bi4O4S3 is intrinsic and the dopant Ag prefers to enter the BiS2 layers,
which may essentially modify the electronic structure.",1208.5307v1
2012-09-27,Theoretical investigation of direct and phonon-assisted tunneling currents in InAlGaAs-InGaAs bulk and quantum well interband tunnel junctions for multi-junction solar cells,"Direct and phonon-assisted tunneling currents in InAlGaAs-InGaAs bulk and
double quantum well interband tunnel heterojunctions are simulated rigorously
using the non-equilibrium Green's function formalism for coherent and
dissipative quantum transport in combination with a simple two-band
tight-binding model for the electronic structure. A realistic band profile and
associated built-in electrostatic field is obtained via self-consistent
coupling of the transport formalism to Poisson's equation. The model reproduces
experimentally observed features in the current-voltage characteristics of the
device, such as the structure appearing in the negative differential resistance
regime due to quantization of emitter states. Local maps of density of states
and current spectrum reveal the impact of quasi-bound states, electric fields
and electron-phonon scattering on the interband tunneling current. In this way,
resonances appearing in the current through the double quantum well structure
in the negative differential resistance regime can be related to the alignment
of subbands in the coupled quantum wells.",1209.6314v1
2012-10-11,Prediction of semi-metallic tetragonal Hf2O3 and Zr2O3 from first-principles,"A tetragonal phase is predicted for Hf2O3 and Zr2O3 using density functional
theory. Starting from atomic and unit cell relaxations of substoichiometric
monoclinic HfO2 and ZrO2, such tetragonal structures are only reached at zero
temperature by introducing the oxygen vacancy pair with the lowest formation
energy. The tetragonal Hf2O3 and Zr2O3 structures belong to space group P-4m2
and are more stable than their corundum structure counterparts. These phases
are semi-metallic, as confirmed through further G0W0 calculations. The carrier
concentrations are estimated to be 1.77E21 cm^{-3} for both electrons and holes
in tetragonal Hf2O3, and 1.75E21 cm^{-3} for both electrons and holes in
tetragonal Zr2O3. The tetragonal Hf2O3 phase is probably related to the low
resistivity state of hafnia-based resistive random access memory (RRAM).",1210.3348v1
2012-10-12,Superconducting LaAlO3/SrTiO3 Nanowires,"We report superconductivity in quasi-1D nanostructures created at the
LaAlO3/SrTiO3 interface. Nanostructures having line widths w~10 nm are formed
from the parent two-dimensional electron liquid using conductive atomic force
microscope lithography. Nanowire cross-sections are small compared to the
superconducting coherence length in LaAlO3/SrTiO3 (w<<xi~100 nm), placing them
in the quasi-1D regime. Broad superconducting transitions with temperature and
finite resistances in the superconducting state well below Tc~200 mK are
observed. V-I curves show switching between the superconducting and normal
states that are characteristic of superconducting nanowires. The four-terminal
resistance in the superconducting state shows an unusual dependence on the
current path, varying by as much as an order of magnitude.",1210.3606v1
2012-10-26,Spin injection from a half-metal at finite temperatures,"Spin injection from a half-metallic electrode in the presence of thermal spin
disorder is analyzed using a combination of random matrix theory,
spin-diffusion theory, and explicit simulations for the tight-binding s-d
model. It is shown that efficient spin injection from a half-metal is possible
as long as the effective resistance of the normal metal does not exceed a
characteristic value, which does not depend on the resistance of the
half-metallic electrode, but is rather controlled by spin-flip scattering at
the interface. This condition can be formulated as \alpha<(l/L)/T, where \alpha
is the relative deviation of the magnetization from saturation, l and L the
mean-free path and the spin-diffusion length in the non-magnetic channel, and T
the transparency of the tunnel barrier at the interface (if present). The
general conclusions are confirmed by tight-binding s-d model calculations. A
rough estimate suggests that efficient spin injection from true half-metallic
ferromagnets into silicon or copper may be possible at room temperature across
a transparent interface.",1210.7194v2
2012-12-03,Resistive switching in ferroelectric BiFeO3 by 1.7 eV change of the Schottky barrier height,"Using metal-ferroelectric junctions as switchable diodes was proposed several
decades ago. This was shown to actually work in PbZr(1-x)TixO3 (PZT) by Blom et
al. [P.W. M. Blom et al., Phys. Rev. Lett. 73, 2107 (1994)], who reported
switching in the rectification direction and changes of the current of about 2
orders of magnitude upon switching the polarization direction of the
ferroelectric layer. This form of resistive switching enables the read out of a
ferroelectric memory state at higher speed compared to the capacitive design,
without destroying the information in each reading cycle. Recently, Jiang and
coworkers have shown that these Schottky barrier effects are enormous in
BiFeO3, giving thousand times more switched charge than found by in PZT [A.Q.
Jiang. et al., Adv. Mat. 23, 1277 (2011)]. Here, by performing local
conductivity measurements, we attribute this to a large change of the Schottky
barrier height between the as-grown, down-polarized domains and the
up-polarized domains. These measurements allow to estimate the relative effect
of polarization charges and screening charges on the conduction through the
ferroelectric.",1212.0483v1
2012-12-18,Low temperature transport properties of multigraphene structures on 6H-SiC obtained by thermal graphitization: evidences of a presence of nearly perfect graphene layer,"Transport properties of multigraphene layers on 6H-SiC substrates fabricated
by thermal graphitization of SiC were studied. The principal result is that
these structures were shown to contain a nearly perfect graphene layer situated
between the SiC substrate and multgraphene layer. It was found that the curves
of magnetoresistance and Shubnikov- de Haas oscillations shown the features,
typical for single-layered graphene. The low temperature resistance
demonstrated an increase with temperature increase, which also corresponds to a
behavior typical for single-layered graphene (antilocalization). However at
higher temperatures the resistance decreased with an increase of temperature,
which corresponds to a weak localization. We believe that the observed behavior
can be explained by a parallel combination of contributions to the conductivity
of single-layered graphene and of multigraphene, the latter allowing to escape
damages of the graphene by atmosphere effect.",1212.4272v1
2013-01-07,Quantum Hall Effect in Hydrogenated Graphene,"The quantum Hall effect is observed in a two-dimensional electron gas formed
in millimeter-scale hydrogenated graphene, with a mobility less than 10
$\mathrm{cm^{2}/V\cdot s}$ and corresponding Ioffe-Regel disorder parameter
$(k_{F}\lambda)^{-1}\gg1$. In zero magnetic field and low temperatures, the
hydrogenated graphene is insulating with a two-point resistance of order of
$250 h/e^2$. Application of a strong magnetic field generates a negative
colossal magnetoresistance, with the two-point resistance saturating within
0.5% of $h/2e^{2}$ at 45T. Our observations are consistent with the opening of
an impurity-induced gap in the density of states of graphene. The interplay
between electron localization by defect scattering and magnetic confinement in
two-dimensional atomic crystals is discussed.",1301.1257v1
2013-01-12,Magnetic field-tuned Aharonov-Bohm oscillations and evidence for non-Abelian anyons at v=5/2,"We show that the resistance of the v=5/2 quantum Hall state, confined to an
interferometer, oscillates with magnetic field consistent with an Ising-type
non-Abelian state. In three quantum Hall interferometers of different sizes,
resistance oscillations at v=7/3 and integer filling factors have the magnetic
field period expected if the number of quasiparticles contained within the
interferometer changes so as to keep the area and the total charge within the
interferometer constant. Under these conditions, an Abelian state such as the
(3,3,1) state would show oscillations with the same period as at an integer
quantum Hall state. However, in an Ising-type non-Abelian state there would be
a rapid oscillation associated with the ""even-odd effect"" and a slower one
associated with the accumulated Abelian phase due to both the Aharonov-Bohm
effect and the Abelian part of the quasiparticle braiding statistics. Our
measurements at v=5/2 are consistent with the latter.",1301.2639v1
2013-02-07,Thermal Conductivity and Phonon Transport in Suspended Few-Layer Hexagonal Boron Nitride,"The thermal conductivity of suspended few-layer hexagonal boron nitride
(h-BN) was measured using a micro-bridge device with built-in resistance
thermometers. Based on the measured thermal resistance values of 11-12 atomic
layer h-BN samples with suspended length ranging between 3 and 7.5 um, the
room-temperature thermal conductivity of a 11-layer sample was found to be
about 360 Wm-1K-1, approaching the basal plane value reported for bulk h-BN.
The presence of a polymer residue layer on the sample surface was found to
decrease the thermal conductivity of a 5-layer h-BN sample to be about 250
Wm-1K-1 at 300 K. Thermal conductivities for both the 5 layer and the 11 layer
samples are suppressed at low temperatures, suggesting increasing scattering of
low frequency phonons in thin h-BN samples by polymer residue.",1302.1890v1
2013-02-08,"Comparative study of the electronic structure, phonon spectra and electron-phonon interaction of ZrB2 and TiB2","The electronic structure, optical and x-ray absorption spectra, angle
dependence of the cyclotron masses and extremal cross sections of the Fermi
surface, phonon spectra, electron-phonon Eliashberg and transport spectral
functions, temperature dependence of electrical resistivity of the MB2 (M=Ti
and Zr) diborides were investigated from first principles using the full
potential linear muffin-tin orbital method. The calculations of the dynamic
matrix were carried out within the framework of the linear response theory. A
good agreement with experimental data of optical and x-ray absorption spectra,
phonon spectra, electron-phonon spectral functions, electrical resistivity,
cyclotron masses and extremal cross sections of the Fermi surface was achieved.",1302.2144v1
2013-02-15,Storing magnetic information in IrMn/MgO/Ta tunnel junctions via field-cooling,"Tunneling junctions containing no ferromagnetic elements have been fabricated
and we show that distinct resistance states can be set by field cooling the
devices from above the N\'eel along different orientations. Variations of the
resistance up to 10% are found upon field cooling in applied fields of 2T,
in-plane or out of plane. Below TN, we found that the metastable states are
insensitive to magnetic fields thus constituting a memory element robust
against external magnetic fields. Our work provides the demonstration of an
electrically readable magnetic memory device, which contains no ferromagnetic
elements and stores the information in an antiferromagnetic active layer.",1302.3837v1
2013-03-06,Highly reproducible metal/graphene contacts and stable electrical performance by UV-Ozone treatment,"Resist residue from the device fabrication process is a general and
significant source of the metal/graphene contact interface contamination. In
this paper, Ultraviolet-Ozone (UVO) treatment is proven to be an effective way
of cleaning the metal/graphene interface. Electrical measurements of devices,
which were fabricated by using UVO treatment of the metal/graphene contact
region, show that stable and highly reproducible low contact resistance between
metal and graphene is obtained without affecting the electrical properties of
the graphene channel itself.",1303.1353v2
2013-03-15,Thermoelectric Properties of Polycrystalline NiSi3P4,"The Hall and Seebeck coefficients, electrical resistivity and thermal
conductivity of polycrystalline NiSi3P4 were characterized from 2 to 775K.
Undoped NiSi3P4 behaves like a narrow gap semiconductor, with activated
electrical resistivity \rho below room temperature and a large Seebeck
coefficient of ~400uV/K at 300K. Attempts to substitute boron for silicon
resulted in the production of extrinsic holes, yielding moderately-doped
semiconductor behavior with \rho increasing with increasing temperature above
~150\,K. Hall carrier densities are limited to approximately 5x10^{19}/cm^3 at
200K, which would suggest the solubility limit of boron is reached if boron is
indeed incorporated into the lattice. These extrinsic samples have a Hall
mobility of ~12cm^2/V/s at 300K, and a parabolic band equivalent effective mass
of ~3.5 times the free electron mass. At 700,K, the thermoelectric figure of
merit zT reaches ~0.1. Further improvements in thermoelectric performance would
require reaching higher carrier densities, as well as a mechanism to further
reduce the lattice thermal conductivity, which is ~5W/m/K at 700K. Alloying in
Ge results in a slight reduction of the thermal conductivity at low
temperatures, with little influence observed at higher temperatures.",1303.3772v1
2013-03-29,Hysteretic superconducting resistive transition in Ba0.07K0.93Fe2As2,"We have observed hysteresis in superconducting resistive transition curves of
Ba$_{0.07}$K$_{0.93}$Fe$_2$As$_2$ ($T_c\sim$8 K) below about 1 K for in-plane
fields. The hysteresis is not observed as the field is tilted away from the
$ab$ plane by 20$^{\circ}$ or more. The temperature and angle dependences of
the upper critical field indicate a strong paramagnetic effect for in-plane
fields. We suggest that the hysteresis can be attributed to a first-order
superconducting transition due to the paramagnetic effect. Magnetic torque data
are also shown.",1303.7281v4
2013-04-04,Benchtop Fabrication of Memristive Atomic Switch Networks,"Recent advances in nanoscale science and technology provide possibilities to
directly self-assemble and integrate functional circuit elements within the
wiring scheme of devices with potentially unique architectures. Electroionic
resistive switching circuits comprising highly interconnected fractal
electrodes and metal-insulator-metal interfaces, known as atomic switch
networks, have been fabricated using simple benchtop techniques including
solution-phase electroless deposition. These devices are shown to activate
through a bias-induced forming step that produces the frequency dependent,
nonlinear hysteretic switching expected for gapless-type atomic switches and
memristors. By eliminating the need for complex lithographic methods, such an
approach toward device fabrication provides a more accessible platform for the
study of ionic resistive switches and memristive systems.",1304.1243v2
2013-04-08,Ultra Low Power Associative Computing with Spin Neurons and Resistive Crossbar Memory,"Emerging resistive-crossbar memory (RCM) technology can be promising for
computationally-expensive analog pattern-matching tasks. However, the use of
CMOS analog-circuits with RCM would result in large power-consumption and poor
scalability, thereby eschewing the benefits of RCM-based computation. We
propose the use of low-voltage, fast-switching, magneto-metallic spin-neurons
for ultra low-power non-Boolean computing with RCM. We present the design of
analog associative memory for face recognition using RCM, where, substituting
conventional analog circuits with spin-neurons can achieve ~100x lower power.
This makes the proposed design ~1000x more energy-efficient than a 45nm-CMOS
digital ASIC, thereby significantly enhancing the prospects of RCM based
computational hardware.",1304.2281v1
2013-04-28,"Hidden Fermi Liquid, Scattering Rate Saturation and Nernst Effect: a DMFT Perspective","We investigate the transport properties of a correlated metal within
dynamical mean field theory. Canonical Fermi liquid behavior emerges only below
a very low temperature scale $T_{FL}$. Surprisingly the quasiparticle
scattering rate follows a quadratic temperature dependence up to much higher
temperatures and crosses over to saturated behavior around a temperature scale
$T_{sat}$. We identify these quasiparticles as constituents of the hidden Fermi
liquid. The non-Fermi liquid transport above $T_{FL}$, in particular the
linear-in-$T$ resistivity, is shown to be a result of a strongly temperature
dependent band dispersion. We derive simple expressions for resistivity, Hall
angle, thermoelectric power and Nernst coefficient in terms of a temperature
dependent renormalized band structure and the quasiparticle scattering rate. We
discuss possible tests of the DMFT picture of transport using ac measurements.",1304.7486v1
2013-05-10,Geometric treatment of conduction electron scattering by crystal lattice strains and dislocations,"A theory for conduction electron scattering by inhomogeneous crystal lattice
strains is developed, based on the differential geometric treatment of
deformations in solids. The resulting fully covariant Schr\""odinger equation
shows that the electrons can be described as moving in a non-Euclidean
background space in the continuum limit of the deformed lattice. Unlike
previous work, the formalism is applicable to cases involving purely elastic
strains as well as discrete and continuous distributions of dislocations --- in
the latter two cases it clearly demarcates the effects of the dislocation
strain field and core and differentiates between elastic and plastic strain
contributions respectively. The electrical resistivity due to the strain field
of edge dislocations is then evaluated using perturbation theory and the
Boltzmann transport equation. The resulting numerical estimate for Cu shows
good agreement with experimental values, indicating that the electrical
resistivity of edge dislocations is not entirely due to the core, contrary to
current models. Possible application to the study of strain effects in
constrained quantum systems is also discussed.",1305.2455v3
2013-05-15,Origin of Rigidity in Dry Granular Solids,"Solids are distinguished from fluids by their ability to resist shear. In
traditional solids, the resistance to shear is associated with the emergence of
broken translational symmetry as exhibited by a non-uniform density pattern. In
this work, we focus on the emergence of shear-rigidity in a class of solids
where this paradigm is challenged. Dry granular materials have no energetically
or entropically preferred density modulations. We show that, in contrast to
traditional solids, the emergence of shear rigidity in these granular solids is
a collective process, which is controlled solely by boundary forces, the
constraints of force and torque balance, and the positivity of the contact
forces. We develop a theoretical framework based on these constraints, which
connects rigidity to broken translational symmetry in the space of forces, not
positions of grains. We apply our theory to experimentally generated
shear-jammed (SJ) states and show that these states are indeed characterized by
a persistent, non-uniform density modulation in force space, which emerges at
the shear-jamming transition.",1305.3484v2
2013-06-24,Polarization Controlled Ohmic to Schottky Transition at a Metal/Doped Ferroelectric Interface,"Ferroelectric polar displacements have recently been observed in conducting
electron-doped BaTiO3. The co-existence of a ferroelectric phase and
conductivity opens the door to new functionalities which may provide a unique
route for novel device applications. Using first-principles methods and
electrostatic modeling we explore the effect that the switchable polarization
of electron-doped BaTiO3 (n-BaTiO3) has on the electronic properties of the
SrRuO3/n-BaTiO3 (001) interface. Ferroelectric polarization controls the
accumulation or depletion of electron charge at the interface, and the
associated bending of the n-BTO conduction band determines the transport regime
across the interface. The interface exhibits a Schottky tunnel barrier for one
polarization orientation, whereas an Ohmic contact is present for the opposite
polarization orientation, leading to a large change in interface resistance
associated with polarization reversal. Calculations reveal a large (five orders
of magnitude) change in the interface resistance as a result of polarization
switching.",1306.5763v2
2013-07-04,Impact of intrinsic deformations on the negative differential resistance of monolayer MoS$_2$ ultra-short channel MOSFET,"In this work we present a study on the impact of various intrinsic
deformations like ripples, twist, wrap on the electronic properties of
ultra-short monolayer MoS2 channels. The effect of deformation (3-7o twist or
wrap and 0.3-0.7 buckling amplitude) on a 3.5 nm planar monolayer MoS2 MOSFET
is evaluated by the density functional theory and the non-equilibrium Green`s
function (DFT-NEGF) approach. We study the channel density of states,
transmission spectra and the ID-VD characteristics under the varying
conditions, with focus on the negative differential resistance (NDR) behavior.
Our results show significant change in the NDR peak to valley ratio (PVR) and
the NDR window with such minor intrinsic deformations, especially with the
rippling.",1307.1306v2
2013-07-24,Extremely Large Magnetoresistance in the Nonmagnetic Metal PdCoO2,"Extremely large magnetoresistance is realized in the nonmagnetic layered
metal PdCoO2. In spite of a highly conducting metallic behavior with a simple
quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance
reaches up to 35000% for the field along the [1-10] direction. Furthermore, the
temperature dependence of the resistance becomes nonmetallic for this field
direction, while it remains metallic for fields along the [110] direction. Such
severe and anisotropic destruction of the interlayer coherence by a magnetic
field on a simple Fermi surface is ascribable to orbital motion of carriers on
the Fermi surface driven by the Lorentz force, but seems to have been largely
overlooked until now.",1307.6503v2
2013-08-08,Magneto-Transport Properties of Single Crystalline LaFeAsO,"Measurements of magnetization, specific heat, electrical resistivity, Hall
effect, and magnetoresistance on single crystalline samples of LaFeAsO grown in
a NaAs flux are reported. While this material is known to be a semimetal, the
temperature dependence of the electrical resistivity data presented herein is
reminiscent of semiconducting behavior and exhibits distinct features
associated with a structural transition and spin density wave (SDW) order.
Magnetoresistance and Hall coefficient measurements were performed in magnetic
fields up to 9 T applied perpendicular to the basal plane using a van der Pauw
configuration. The charge carrier density and mobility indicate that electrons
are the majority charge carriers and exhibit features indicative of the
structural transition and SDW formation. Low temperature X-ray diffraction
measurements have confirmed that the structural transition in these samples
occurs near 140 K, compared to a transition temperature of 156 K observed in
polycrystalline samples. Isotherms of magnetoresistivity measured as a function
of magnetic field can be scaled onto a single curve in which the scaling field
is a linear function of temperature between 2.2 K and 180 K.",1308.1885v1
2013-08-20,Probing long-range correlations in the Berezinskii-Kosterlitz-Thouless fluctuation regime of ultra-thin NbN superconducting films using transport noise measurements,"We probe the presence of long-range correlations in phase fluctuations by
analyzing the higher-order spectrum of resistance fluctuations in ultra-thin
NbN superconducting films. The non-Gaussian component of resistance
fluctuations is found to be sensitive to film thickness close to the
transition, which allows us to distinguish between mean field and
Berezinskii-Kosterlitz-Thouless (BKT) type superconducting transitions. The
extent of non-Gaussianity was found to be bounded by the BKT and mean field
transition temperatures and depend strongly on the roughness and structural
inhomogeneity of the superconducting films. Our experiment outlines a novel
fluctuation-based kinetic probe in detecting the nature of superconductivity in
disordered low-dimensional materials.",1308.4234v2
2013-09-04,Current-Induced Gap Suppression in the Mott Insulator Ca$_2$RuO$_4$,"We present nonlinear conduction phenomena in the Mott insulator Ca2RuO4
investigated with a proper evaluation of self-heating effects. By utilizing a
non-contact infrared thermometer, the sample temperature was accurately
determined even in the presence of large Joule heating. We find that the
resistivity continuously decreases with currents under an isothermal
environment. The nonlinearity and the resulting negative differential
resistance occurs at relatively low current range, incompatible with
conventional mechanisms such as hot electron or impact ionization. We propose a
possible current-induced gap suppression scenario, which is also discussed in
non-equilibrium superconducting state or charge-ordered insulator.",1309.0909v1
2013-09-06,Spin density wave order and fluctuations in Mn3Si: a transport study,"We present a comprehensive transport investigation of the itinerant
antiferromagnet Mn3Si which undergoes a spin density wave (SDW) order below
T_N~21.3K. The electrical resistivity, the Hall-, Seebeck and Nernst effects
exhibit pronounced anomalies at the SDW transition, while the heat conductivity
is phonon dominated and therefore is insensitive to the intrinsic electronic
ordering in this compound. At temperatures higher than T_N our data provide
strong evidence for a large fluctuation regime which extends up to ~200K in the
resistivity, the Seebeck effect and the Nernst effect. From the comparison of
our results with other prototype SDW materials, viz. LaFeAsO and Chromium, we
conclude that many of the observed features are of generic character.",1309.1636v1
2013-09-06,Metal-insulator transition induced in SrTi_{1-x}V_xO_3 thin films,"Epitaxial SrTi1-xVxO3 thin films with thicknesses of ~16 nm were grown on
(001)-oriented LSAT substrates using the pulsed electron-beam deposition
technique. The transport study revealed a temperature driven metal-insulator
transition (MIT) at 95 K for the film with x = 0.67. The films with higher
vanadium concentration (x > 0.67) were metallic, and the electrical resistivity
followed the T^2 law corresponding to a Fermi liquid system. In the insulating
region of x < 0.67, the temperature dependence of electrical resistivity for
the x = 0.5 and 0.33 films can be scaled with the variable range hopping model.
The possible mechanisms behind the observed MIT were discussed, including the
effects of electron correlation, lattice distortion and Anderson localization.",1309.1745v1
2013-09-10,Magnetoresistance evidence on surface state and field-dependent bulk gap in Kondo insulator SmB6,"Recently, the resistance saturation at low temperature in Kondo insulator
SmB6, a long-standing puzzle in condensed matter physics, was proposed to
originate from topological surface state. Here,we systematically studied the
magnetoresistance of SmB6 at low temperature up to 55 Tesla. Both temperature-
and angular-dependent magnetoresistances show a similar crossover behavior
below 5 K. Furthermore, the angular-dependent magnetoresistance on different
crystal face confirms a two-dimensional surface state as the origin of
magnetoresistances crossover below 5K. Based on two-channels model consisting
of both surface and bulk states, the field-dependence of bulk gap with critical
magnetic field (Hc) of 196 T is extracted from our temperature-dependent
resistance under different magnetic fields. Our results give a consistent
picture to understand the low-temperature transport behavior in SmB6,
consistent with topological Kondo insulator scenario.",1309.2378v3
2013-09-27,Evidence for a Kondo destroying quantum critical point in YbRh2Si2,"The heavy-fermion metal YbRh$_{2}$Si$_{2}$ is a weak antiferromagnet below
$T_{N} = 0.07$ K. Application of a low magnetic field $B_{c} = 0.06$ T ($\perp
c$) is sufficient to continuously suppress the antiferromagnetic (AF) order.
Below $T \approx 10$ K, the Sommerfeld coefficient of the electronic specific
heat $\gamma(T)$ exhibits a logarithmic divergence. At $T < 0.3$ K, $\gamma(T)
\sim T^{-\epsilon}$ ($\epsilon: 0.3 - 0.4$), while the electrical resistivity
$\rho(T) = \rho_{0} + aT$ ($\rho_{0}$: residual resistivity). Upon
extrapolating finite-$T$ data of transport and thermodynamic quantities to $T =
0$, one observes (i) a vanishing of the ""Fermi surface crossover"" scale
$T^{*}(B)$, (ii) an abrupt jump of the initial Hall coefficient $R_{H}(B)$ and
(iii) a violation of the Wiedemann Franz law at $B = B_{c}$, the field-induced
quantum critical point (QCP). These observations are interpreted as evidence of
a critical destruction of the heavy quasiparticles, i.e., propagating Kondo
singlets, at the QCP of this material.",1309.7260v1
2013-09-29,An Efficient Authorship Protection Scheme for Shared Multimedia Content,"Many electronic content providers today like Flickr and Google, offer space
to users to publish their electronic media (e.g. photos and videos) in their
cloud infrastructures, so that they can be publicly accessed. Features like
including other information, such as keywords or owner information into the
digital material is already offered by existing providers. Despite the useful
features made available to users by such infrastructures, the authorship of the
published content is not protected against various attacks such as compression.
In this paper we propose a robust scheme that uses digital invisible
watermarking and hashing to protect the authorship of the digital content and
provide resistance against malicious manipulation of multimedia content. The
scheme is enhanced by an algorithm called MMBEC, that is an extension of an
established scheme MBEC, towards higher resistance.",1309.7640v1
2013-10-11,Enhanced low-energy magnetic excitations via suppression of the itinerancy in Fe0.98-zCuzTe0.5Se0.5,"We have performed resistivity and inelastic neutron scattering measurements
on three samples of Fe0.98-zCuzTe0.5Se0.5 with z = 0, 0.02, and 0.1. It is
found that with increasing Cu doping the sample's resistivity deviates
progressively from that of a metal. However, in contrast to expectations that
replacing Fe with Cu would suppress the magnetic correlations, the low-energy
(no larger than 12 meV) magnetic scattering is enhanced in strength, with
greater spectral weight and longer dynamical spin-spin correlation lengths.
Such enhancements can be a consequence of either enlarged local moments or a
slowing down of the spin fluctuations. In either case, the localization of the
conduction states induced by the Cu doping should play a critical role. Our
results are not applicable to models that treat 3d transition metal dopants
simply as effective electron donors.",1310.3064v1
2013-10-28,Emergence of pressure-induced metamagnetic-like state in Mn-doped CdGeAs2 chalcopyrite,"The effect of hydrostatic pressure on resistivity and magnetic ac
susceptibility has been studied in Mn-doped CdGeAs2 room-temperature (RT)
ferromagnetic chalcopyrite with two types of MnAs micro-clusters. The slight
increase of temperature by about 30 K in the region between RT and Curie
temperature TC causes a significant change in the positions of pressure-induced
semiconductor-metal transition and magnetic phase transitions in low pressure
area. By conducting measurements of the anomalous Hall resistance in the field
H \leq 5 kOe, we present experimental evidence for pressure-induced
metamagnetic-like state during the paramagnetic phase at pressure P = 5 GPa.",1310.7451v1
2013-12-13,Temperature-dependent structural property and power factor of n type thermoelectric Bi0.90Sb0.10 and Bi0.86Sb0.14 alloys,"Thermal variation of structural property, linear thermal expansion
coefficient, resistivity, thermopower and power factor of polycrystalline
Bi1-xSbx (x=0.10, 0.14) samples are reported. Temperature-dependent powder
diffraction experiments indicate that samples do not undergo any structural
phase transition. Rietveld refinement technique has been used to perform
detailed structural analysis. Temperature dependence of thermal expansion
coefficient is found to be stronger for Bi0.90Sb0.10. Also, power factor for
direct band gap Bi0.90Sb0.10 is higher as compared to that for indirect band
gap Bi0.86Sb0.14. Role of electron-electron and electron-phonon scattering on
resistivity, thermopower and power factor have been discussed.",1312.3898v1
2014-02-11,Taming the resistive switching in Fe/MgO/V/Fe magnetic tunnel junctions: An ab initio study,"A possible mechanism for the resistive switching observed experimentally in
Fe/MgO/V/Fe junctions is presented. Ab initio total energy calculations within
the local density approximation and pseudopotential theory shows that by moving
the oxygen ions across the MgO/V interface one obtains a metastable state. It
is argued that this state can be reached by applying an electric field across
the interface. In addition, the ground state and the metastable state show
different electric conductances. The latter results are discussed in terms of
the changes of the density of states at the Fermi level and the charge transfer
at the interface due to the oxygen ion motion.",1402.2517v2
2014-02-24,Coplanar waveguide based ferromagnetic resonance in ultrathin film magnetic nanostructures: impact of conducting layers,"We report broadband ferromagnetic resonance (FMR) measurements based on a
coplanar waveguide (CPW) of ultrathin magnetic film structures that comprise
in-plane/out-of-plane decoupled layers deposited on nonmagnetic buffer layers
of various thickness or other buffer structures with a diverse sheet
resistance. We show that the excitation of the fundamental mode can be
substantially (up to 10 times) enhanced in the structures deposited on buffer
layers with a low sheet resistance in comparison to the structures deposited on
thin or weakly conducting buffer layers. The results are analyzed in terms of
shielding of the electromagnetic field of CPW by the conducting buffer layers.
The effect of enhancement of FMR absorption can be attractive for applications
in spintronic devices that utilize magnetization dynamics of ultrathin
ferromagnetic layers.",1402.5844v2
2014-03-05,Electrical and optical properties of fluid iron from compressed to expanded regime,"Using quantum molecular dynamics simulations, we show that the electrical and
optical properties of fluid iron change drastically from compressed to expanded
regime. The simulation results reproduce the main trends of the electrical
resistivity along isochores and are found to be in good agreement with
experimental data. The transition of expanded fluid iron into a nonmetallic
state takes place close to the density at which the constant volume derivative
of the electrical resistivity on internal energy becomes negative. The study of
the optical conductivity, absorption coefficient, and Rosseland mean opacity
shows that, quantum molecular dynamics combined with the Kubo-Greenwood
formulation provides a powerful tool to calculate and benchmark the electrical
and optical properties of iron from expanded fluid to warm dense region.",1403.1030v1
2014-03-06,Correlation between bulk thermodynamic measurements and the low temperature resistance plateau in SmB6,"Topological insulators are materials characterized by dissipationless,
spin-polarized surface states resulting from non-trivial band topologies.
Recent theoretical models and experiments suggest that SmB6 is the first
topological Kondo insulator, in which the topologically non-trivial band
structure results from electron-electron interactions via Kondo hybridization.
Here, we report that the surface conductivity of SmB6 increases systematically
with bulk carbon content. Further, addition of carbon is linked to an increase
in n-type carriers, larger low temperature electronic contributions to the
specific heat with a characteristic temperature scale of T* = 17 K, and a
broadening of the crossover to the insulating state. Additionally, X-ray
absorption spectroscopy shows a change in Sm valence at the surface. Our
results highlight the importance of phonon dynamics in producing a Kondo
insulating state and demonstrate a correlation between the bulk thermodynamic
state and low temperature resistance of SmB6.",1403.1462v2
2014-03-25,Quantum Resistor-Capacitor Circuit with Majorana Fermion Modes in Chiral Topological Superconductor,"We investigate the mesoscopic resistor-capacitor circuit consisting of a
quantum dot coupled to spatially separated Majorana fermion modes in a chiral
topological superconductor. We find substantially enhanced relaxation
resistance due to the nature of Majorana fermions, which are their own
anti-particles and composed of particle and hole excitations in the same
abundance. Further, if only a single Majorana mode is involved, the
zero-frequency relaxation resistance is completely suppressed due to a
destructive interference. As a result, the Majorana mode opens an exotic
dissipative channel on a superconductor which is typically regarded as
dissipationless due to its finite superconducting gap.",1403.6239v2
2014-04-26,Electric field control of magnetic properties and magneto-transport in composite multiferroics,"We study magnetic state and electron transport properties of composite
multiferroic system consisting of a granular ferromagnetic thin film placed
above the ferroelectric substrate. Ferroelectricity and magnetism in this case
are coupled by the long-range Coulomb interaction. We show that magnetic state
and magneto-transport strongly depend on temperature, external electric field,
and electric polarization of the substrate. Ferromagnetic order exists at
finite temperature range around ferroelectric Curie point. Outside the region
the film is in the superparamagnetic state. We demonstrate that magnetic phase
transition can be driven by an electric field and magneto-resistance effect has
two maxima associated with two magnetic phase transitions appearing in the
vicinity of the ferroelectric phase transition. We show that positions of these
maxima can be shifted by the external electric field and that the magnitude of
the magneto-resistance effect depends on the mutual orientation of external
electric field and polarization of the substrate.",1404.6671v2
2014-05-24,Visible light enhanced field effect at LaAlO3/SrTiO3 interface,"Electrical field and light-illumination have been two most widely used
stimuli in tuning the conductivity of semiconductor devices. Via capacitive
effect electrical field modifies the carrier density of the devices, while
light-illumination generates extra carriers by exciting trapped electrons into
conduction band1. Here, we report on an unexpected light illumination enhanced
field effect in a quasi-two-dimensional electron gas (q2DEG) confined at the
LaAlO3/SrTiO3 (LAO/STO) interface which has been the focus of emergent
phenomenon exploration2-14. We found that light illumination greatly
accelerates and amplifies the field effect, driving the field-induced
resistance growth which originally lasts for thousands of seconds into an
abrupt resistance jump more than two orders of magnitude. Also, the
field-induced change in carrier density is much larger than that expected from
the capacitive effect, and can even be opposite to the conventional
photoelectric effect. This work expands the space for novel effect exploration
and multifunctional device design at complex oxide interfaces.",1405.6250v1
2014-06-25,Compressive strain-induced metal-insulator transition in orthorhombic SrIrO3 thin films,"We have investigated the electronic properties of epitaxial orthorhombic
SrIrO3 thin-films under compressive strain. The metastable, orthorhombic SrIrO3
thin-films are synthesized on various substrates using an epi-stabilization
technique. We have observed that as in-plane lattice compression is increased,
the dc-resistivity (\r{ho}) of the thin films increases by a few orders of
magnitude, and the d\r{ho}/dT changes from positive to negative values.
However, optical absorption spectra show Drude-like, metallic responses without
an optical gap opening for all compressively-strained thin films. Transport
measurements under magnetic fields show negative magneto-resistance at low
temperature for compressively-strained thin-films. Our results suggest that
weak localization is responsible for the strain-induced metal-insulator
transition for the orthorhombic SrIrO3 thin-films.",1406.6640v1
2014-06-28,Exceptional Suppression of Flux-Flow Resistivity in FeSe$_{0.4}$Te$_{0.6}$ by Back-Flow from Excess Fe Atoms and Se/Te Substitutions,"We measured the microwave surface impedance of FeSe$_{0.4}$Te$_{0.6}$ single
crystals with- and without external magnetic fields. The superfluid density
exhibited a quadratic temperature dependence, indicating a strong pair-breaking
effect. The flux-flow resistivity behaved as $\rho_f(B\ll B_{\rm
c2})/\rho_n=\alpha B/B_{\rm c2}$. The observed $\alpha$ value of $\approx0.66$
was considerably smaller than that of other Fe-based materials ($\alpha\geq1$)
and was attributed to a back-flow of superfluids remarkable in disordered
superconductors. This is the first-time observation of the back-flow phenomenon
caused by an origin other than the vortex pinning in multiple-band systems.",1406.7383v2
2014-07-08,Non thermal and purely electronic resistive transition in narrow gap Mott insulators,"Mott insulator to metal transitions under electric field are currently the
subject of numerous fundamental and applied studies. This puzzling effect,
which involves non-trivial out-of-equilibrium effects in correlated systems, is
indeed at play in the operation of a new class of electronic memories, the Mott
memories. However the combined electronic and thermal effects are difficult to
disentangle in Mott insulators undergoing such transitions. We report here a
comparison between the properties under electric field of a canonical Mott
insulator and a model built on a realistic 2D resistor network able to capture
both thermal effects and electronic transitions. This comparison made
specifically on the family of narrow gap Mott insulators AM4Q8, (A = Ga or Ge;
M=V, Nb or Ta, and Q = S or Se) unambiguously establishes that the resistive
transition experimentally observed under electric field arises from a purely
electronic mechanism.",1407.2038v1
2014-12-08,Role of Se vacancies on Shubnikov de Haas oscillations in Bi2Se3: a combined magneto-resistance and positron annihilation study,"Magneto resistance measurements coupled with positron lifetime measurements,
to characterize the vacancy type defects, have been carried out on the
topological insulator (TI) system Bi2Se3, of varying Se/Bi ratio. Pronounced
Shubnikov de Haas (SdH) oscillations are seen in nominal Bi2Se3.1 crystals for
measurements performed in magnetic fields up to 15 T in the 4 K to 10 K
temperature range, with field applied perpendicular to the (001) plane of the
crystal. The quantum oscillations, characteristic of 2D electronic structure,
are seen only in the crystals that have a lower concentration of Se vacancies,
as inferred from positron annihilation spectroscopy.",1412.2466v1
2014-12-08,Effect of Electron-Phonon Coupling on Thermal Transport across Metal-Nonmetal Interface - A Second Look,"The effect of electron-phonon (e-ph) coupling on thermal transport across
metal-nonmetal interfaces is yet to be completely understood. In this paper, we
use a series of molecular dynamics (MD) simulations with e-ph coupling effect
included by Langevin dynamics to calculate the thermal conductance at a model
metal-nonmetal interface. It is found that while e-ph coupling can present
additional thermal resistance on top of the phonon-phonon thermal resistance,
it can also make the phonon-phonon thermal conductance larger than the pure
phonon transport case. This is because the e-ph interaction can disturb the
phonon subsystem and enhance the energy communication between different phonon
modes inside the metal. This facilitates redistributing phonon energy into
modes that can more easily transfer energy across the interfaces. Compared to
the pure phonon thermal conduction, the total thermal conductance with e-ph
coupling effect can become either smaller or larger depending on the coupling
factor. This result helps clarify the role of e-ph coupling in thermal
transport across metal-nonmetal interface.",1412.2791v3
2014-12-15,Percolation conductivity in hafnium sub-oxides,"In this study, we demonstrated experimentally that formation of chains and
islands of oxygen vacancies in hafnium sub-oxides (HfO$_x$, $x<2$) leads to
percolation charge transport in such dielectrics. Basing on the model of
\'{E}fros-Shklovskii percolation theory good quantitative agreement between the
experimental and theoretical data of current-voltage characteristics were
achieved. Based on the percolation theory suggested model shows that hafnium
sub-oxides consist of mixtures of metallic Hf nanoscale clusters of 1-2 nm
distributed onto non-stoichiometric HfO$_x$. It was shown that reported
approach might describe low resistance state current-voltage characteristics of
resistive memory elements based on HfO$_x$.",1412.4478v1
2015-01-07,Semimetallic transport properties of epitaxially stabilized perovskite CaIrO3 films,"We report on the synthesis and transport properties of perovskite (Pv) CaIrO3
thin films. The Pv phase of CaIrO3 was stabilized by epitaxial growth on
SrTiO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, and LaAlO3 substrates with strong tensile,
weak tensile, and compressive strains, respectively. The resistivity of these
films showed a poorly metallic behavior. The Hall resistivity exhibited a sign
change as a function of temperature and a nonlinear magnetic-field dependence,
which clearly indicated the coexistence of electrons and holes and hence
supported that Pv CaIrO3 films are semimetallic. The observed robustness of the
semimetallic ground state against tensile and compressive strains is consistent
with the presence of symmetry-protected Dirac points (nodes) around the Fermi
level that prohibits the system from becoming a band insulator.",1501.01433v1
2015-02-13,Surface state reconstruction in ion-damaged SmB_6,"We have used ion-irradiation to damage the (001) surfaces of SmB_6 single
crystals to varying depths, and have measured the resistivity as a function of
temperature for each depth of damage. We observe a reduction in the residual
resistivity with increasing depth of damage. Our data are consistent with a
model in which the surface state is not destroyed by the ion-irradiation, but
instead the damaged layer is poorly conducting and the initial surface state is
reconstructed below the damage. This behavior is consistent with a surface
state that is topologically protected.",1502.04103v1
2015-02-19,Occurrence of flat bands in strongly correlated Fermi systems and high-$T_c$ superconductivity of electron-doped compounds,"We consider a class of strongly correlated Fermi systems that exhibit an
interaction-induced flat band pinned to the Fermi surface, and generalize the
Landau strategy to accommodate a flat band and apply the more comprehensive
theory to electron systems of solids. The non-Fermi-liquid behavior that
emerges is compared with relevant experimental data on heavy-fermion metals and
electron-doped high-$T_c$ compounds. We elucidate how heavy-fermion metals have
extremely low superconducting transition temperature $T_c$, its maximum reached
in the heavy-fermion metal CeCoIn$_5$ does not exceed 2.3 K, and explain the
enhancement of $T_c$ observed in high-$T_c$ superconductors. We show that the
coefficient $A_1$ of the $T$-linear resistivity scales with $T_c$, in agreement
with the experimental behavior uncovered in the electron-doped materials. We
have also constructed schematic temperature-doping phase diagram of the copper
oxide superconductor $\rm La_{2-x}Ce_xCuO_4$ and explained the doping
dependence of its resistivity.",1502.05659v2
2015-03-05,Optical study of phase transitions in single-crystalline RuP,"RuP single crystals of MnP-type orthorhombic structure were synthesized by
the Sn flux method. Temperature-dependent x-ray diffraction measurements reveal
that the compound experiences two structural phase transitions, which are
further confirmed by enormous anomalies shown in temperature-dependent
resistivity and magnetic susceptibility. Particularly, the resistivity drops
monotonically upon temperature cooling below the second transition, indicating
that the material shows metallic behavior, in sharp contrast with the
insulating ground state of polycrystalline samples. Optical conductivity
measurements were also performed in order to unravel the mechanism of these two
transitions. The measurement revealed a sudden reconstruction of band structure
over a broad energy scale and a significant removal of conducting carriers
below the first phase transition, while a charge-density-wave-like energy gap
opens below the second phase transition.",1503.01544v1
2015-03-25,Nature of magnetotransport in metal/insulating-ferromagnet heterostructures: Spin Hall magnetoresistance or magnetic proximity effect,"We study the anomalous Hall-like effect (AHLE) and the effective anisotropic
magnetoresistance (EAMR) in antiferromagnetic {\gamma} -IrMn3/Y3Fe5O12(YIG) and
Pt/YIG heterostructures. For {\gamma} -IrMn3/YIG, the EAMR and the AHLE
resistivity change sign with temperature due to the competition between the
spin Hall magnetoresistance (SMR) and the magnetic proximity effect (MPE)
induced by the interfacial antiferromagnetic uncompensated magnetic moment. In
contrast, for Pt/YIG the AHLE resistivity changes sign with temperature whereas
no sign change is observed in the EAMR. This is because the MPE and the SMR
play a dominant role in the AHLE and the EAMR, respectively. As new types of
galvanomagnetic property, the AHLE and the EAMR have proved vital in
disentangling the MPE and the SMR in metal/insulating-ferromagnet
heterostructures.",1503.07388v2
2015-03-31,Persistence of two-dimensional topological insulator state in wide HgTe quantum well,"Our experimental studies of electron transport in wide (14 nm) HgTe quantum
wells confirm persistence of a two-dimensional topological insulator state
reported previously for narrower wells, where it was justified theoretically.
Comparison of local and nonlocal resistance measurements indicate edge state
transport in the samples of about 1 mm size at temperatures below 1 K.
Temperature dependence of the resistances suggests an insulating gap of the
order of a few meV. In samples with sizes smaller than 10 $\mu$m a
quasiballistic transport via the edge states is observed.",1503.08978v1
2015-05-19,Frequency-Independent Response of Self-Complementary Checkerboard Screens,"This research resolves a long-standing problem on the electromagnetic
response of self-complementary metallic screens with checkerboardlike geometry.
Although Babinet's principle implies that they show a frequency-independent
response, this unusual characteristic has not been observed yet due to the
singularities of the metallic point contacts in the checkerboard geometry. We
overcome this difficulty by replacing the point contacts with resistive sheets.
The proposed structure is prepared and characterized by terahertz time-domain
spectroscopy. It is experimentally confirmed that the resistive checkerboard
structures exhibit a flat transmission spectrum over 0.1--1.1 THz. It is also
demonstrated that self-complementarity can eliminate even the
frequency-dependent transmission characteristics of resonant metamaterials.",1505.04874v2
2015-05-22,Greedy Biomarker Discovery in the Genome with Applications to Antimicrobial Resistance,"The Set Covering Machine (SCM) is a greedy learning algorithm that produces
sparse classifiers. We extend the SCM for datasets that contain a huge number
of features. The whole genetic material of living organisms is an example of
such a case, where the number of feature exceeds 10^7. Three human pathogens
were used to evaluate the performance of the SCM at predicting antimicrobial
resistance. Our results show that the SCM compares favorably in terms of
sparsity and accuracy against L1 and L2 regularized Support Vector Machines and
CART decision trees. Moreover, the SCM was the only algorithm that could
consider the full feature space. For all other algorithms, the latter had to be
filtered as a preprocessing step.",1505.06249v1
2015-09-07,Optimization of Spatial Dose Distribution for Controlling Sidewall Shape in Electron-beam Lithography,"Electron-beam (e-beam) lithography is widely employed in fabrication of 2-D
patterns and 3-D structures. A certain type or shape of the sidewall in the
remaining resist profile may be desired in an application, e.g., an undercut
for lift-off and a vertical sidewall for etching, or required for a device.
Also, as the feature size is decreased well below a micron, a small variation
of the sidewall slope can lead to a significant (relative) CD error in certain
layers of resist. Therefore, it is important to understand effects of spatial
dose distribution on sidewall shape and be able to achieve the desired shape.
In this study, via simulation, the relationship among the total dose, spatial
distribution of dose, developing time and sidewall shape, and performance of
the method developed to optimize the dose distribution for a target sidewall
shape have been analyzed. The simulation results have been verified through
experiments.",1509.04694v1
2015-10-05,Magnetic oscillations of the anomalous Hall conductivity,"It is known that the Shubnikov--de Haas oscillations can be observed in the
Hall resistivity, although their amplitude is much weaker than the amplitude of
the diagonal resistivity oscillations. Employing a model of two-dimensional
massive Dirac fermions that exhibits anomalous Hall effect, we demonstrate that
the amplitude of the Shubnikov--de Haas oscillations of the anomalous Hall
conductivity is the same as that of the diagonal conductivity. We argue that
the oscillations of the anomalous Hall conductivity can be observed by studying
the valley Hall effect in graphene superlattices and the spin Hall effect in
the low-buckled Dirac materials.",1510.01360v2
2015-10-12,Weak ferromagnetism in non-centrosymmetric BiPd 4K superconductor,"We report synthesis of non-centrosymmetric BiPd single crystal by self flux
method. The BiPd single crystal is crystallized in monoclinic structure with
the P21 space group. Detailed SEM (Scanning Electron Microscopy) results show
that the crystals are formed in slab like morphology with homogenous
distribution of Bi and Pd. The magnetic susceptibility measurement confirmed
that the BiPd compound is superconducting below 4K. Further, BiPd exhibits weak
ferromagnetism near the superconducting transition temperature in isothermal
magnetization (MH) measurements. The temperature dependent electrical
resistivity also confirmed that the BiPd single crystal is superconducting at
Tc=4K. Magneto transport measurements showed that the estimated Hc2(0) value is
around 7.0kOe. We also obtained a sharp peak in heat capacity Cp(T)
measurements at below 4K due to superconducting ordering. The normalized
specific-heat jump, DC/{\gamma}Tc, is 1.52, suggesting the BiPd to be an
intermediate BCS coupled superconductor. The pressure dependent electrical
resistivity shows the Tc decreases with increasing applied pressure and the
obtained dTc/dP is -0.62K/Gpa.",1510.03217v2
2015-11-25,Andreev reflection at the edge of a two-dimentional semimetal,"We investigate electron transport through the interface between a niobium
superconductor and the edge of a two-dimensional semimetal, realized in a 20~nm
wide HgTe quantum well. Experimentally, we observe that typical behavior of a
single Andreev contact is complicated by both a pronounced zero-bias resistance
anomaly and shallow subgap resistance oscillations with $1/n$ periodicity.
These results are demonstrated to be independent of the superconducting
material and should be regarded as specific to a 2D semimetal in a proximity
with a superconductor. We interpret these effects to originate from the
Andreev-like correlated process at the edge of a two-dimensional semimetal.",1511.08085v1
2015-12-12,Low Temperature Structural and Transport Studies of La0.175Pr0.45Ca0.375MnO3,"The temperature (T) dependent x-ray diffraction (XRD) and resistivity
measurements of La0.175Pr0.45Ca0.375MnO3 (LPCMO) have been performed down to 2K
to understand the structural and transport properties. From room temperature
down to 220K, LPCMO exists in orthorhombic phase with Pnma structure and at
220K, it transforms to charge ordered (CO) monoclinic phase with P21/m
structure and remains as it is down to 2K. The CO phase is evident from the
occurrence of weak but well defined superlattice peaks in the XRD pattern. This
structural transformation is of first order in nature as evident from the phase
coexistence across the transition region. These results thus clearly illustrate
that LPCMO undergoes a first order structural phase transition from charge
disordered orthorhombic phase to CO monoclinic phase at 220K, consistent with
temperature dependent resistivity results. Our structural analysis of T
dependent XRD data using Rietveld refinement infers that below 220K, LPCMO
forms commensurate CO monoclinic P21/m structure with four times structural
modulation.",1512.03890v1
2015-12-17,A self-consistent spin-diffusion model for micromagnetics,"We propose a three-dimensional micromagnetic model that dynamically solves
the Landau-Lifshitz-Gilbert equation coupled to the full spin-diffusion
equation. In contrast to previous methods, we solve for the magnetization
dynamics and the electric potential in a self-consistent fashion. This
treatment allows for an accurate description of magnetization dependent
resistance changes. Moreover, the presented algorithm describes both spin
accumulation due to smooth magnetization transitions and due to material
interfaces as in multilayer structures. The model and its finite-element
implementation are validated by current driven motion of a magnetic vortex
structure. In a second experiment, the resistivity of a magnetic multilayer
structure in dependence of the tilting angle of the magnetization in the
different layers is investigated. Both examples show good agreement with
reference simulations and experiments respectively.",1512.05519v4
2015-12-18,Antiferromagnetism and superconductivity in the half-Heusler semimetal HoPdBi,"We observed the coexistence of superconductivity and antiferromagnetic order
in the single-crystalline ternary pnictide HoPdBi, a plausible topological
semimetal. The compound orders antiferromagnetically at $T_N =$1.9 K and
exhibits superconductivity below $T_c =$0.7 K, which was confirmed by magnetic,
electrical transport and specific heat measurements. The specific heat shows
anomalies corresponding to antiferromagnetic ordering transition and
crystalline field effect, but not to superconducting transition. Single-crystal
neutron diffraction indicates that the antiferromagnetic structure is
characterized by the (1/2, 1/2, 1/2) propagation vector. Temperature variation
of the electrical resistivity reveals two parallel conducting channels of
semiconducting and metallic character. In weak magnetic fields, the
magnetoresistance exhibits weak antilocalization effect, while in strong fields
and temperatures below 50 K it is large and negative. At temperatures below 7 K
Shubnikov-de Haas oscillations with two frequencies appear in the resistivity.
These oscillations have non-trivial Berry phase, which is a distinguished
feature of Dirac fermions.",1512.05972v1
2016-02-08,Phase separated behavior in Yttrium doped CaMnO3,"The effect of electron doping on the structural, transport, and magnetic
properties of Mn (IV) - rich Ca1-xYxMnO3 (x < 0.2) samples have been
investigated using neutron diffraction, neutron depolarization, magnetization
and resistivity techniques. The temperature dependence of resistivity follows
the small polaron model and the activation energy exhibits a minimum for x=0.1
sample. A phase separated magnetic ground state consisting of ferromagnetic
domains (~7microns) embedded in G-type antiferromagnetic matrix is observed in
the sample, x = 0.1. The transition to the long range magnetically ordered
state in this sample is preceded by a Griffiths phase. On lowering temperature
below 300K a structural transition from orthorhombic structure (Pnma) to a
monoclinic structure (P21/m) is observed in the case of x=0.2 sample. The
ferromagnetic behavior in this case is suppressed and the antiferromagnetic
ordering is described by coexisting C-type and G-type magnetic structures
corresponding to the monoclinic and orthorhombic phases, respectively.<",1602.02479v1
2016-02-08,Scaling behavior of temperature-dependent thermopower in CeAu2Si2 under pressure,"We report a combined study of in-plane resistivity and thermopower of the
pressure-induced heavy fermion superconductor CeAu2Si2 up to 27.8 GPa. It is
found that thermopower follows a scaling behavior in T/T* almost up to the
magnetic critical pressure pc ~ 22 GPa. By comparing with resistivity results,
we show that the magnitude and characteristic temperature dependence of
thermopower in this pressure range are governed by the Kondo coupling and
crystal-field splitting, respectively. Below pc, the superconducting transition
is preceded by a large negative thermopower minimum, suggesting a close
relationship between the two phenomena. Furthermore, thermopower of a variety
of Ce-based Kondo-lattices with different crystal structures follows the same
scaling relation up to T/T* ~ 2.",1602.02498v2
2016-02-22,Quantum Oscillations at Integer and Fractional Landau Level Indices in ZrTe5,"A three-dimensional (3D) Dirac semimetal (DS) is an analogue of graphene, but
with linear energy dispersion in all (three) momentum directions.3D DSs have
been a fertile playground in discovering novel quantum particles, for example
Weyl fermions, in solid state systems.Many 3D DSs (e.g., ZrTe5) were
theoretically predicted. We report here the results from the studies of
aberration-corrected scanning transmission electron microscopy and low
temperature magneto-transport measurements in exfoliated ZrTe5 thin
flakes.Several unique results were observed. First, an
anomalous-Hall-effect-like behavior was observed around zero magnetic field
(B).Second, a non-trivial Berry's phase of \pi\ was obtained from the Landau
level fan diagram of the Shubnikov-de Haas oscillations in the longitudinal
resistivity. Third, the longitudinal resistivity shows linear B field
dependence in the quantum limit. Most surprisingly, quantum oscillations were
observed at fractional Landau level indices N = 2/3 and 2/5, demonstrating
strong electron-electron interactions effects in ZrTe5.",1602.06824v3
2016-02-26,Eigenanalysis of morphological diversity in silicon random nanostructures formed via resist collapse,"This paper demonstrates eigenanalysis to quantitatively reveal the diversity
and capacity of identities offered by the morphological diversity in silicon
nanostructures formed via random collapse of resist. The analysis suggests that
approximately 10^115 possible identities are provided per 0.18-um^2 area of
nanostructures, indicating that nanoscale morphological signatures will be
extremely useful for future information security applications where securing
identities is critical. The eigenanalysis provides an intuitive physical
picture and quantitative characterization of the diversity of structural
fluctuations while unifying measurement stability concerns, which will be
widely applicable to other materials, devices, and system architectures.",1602.08205v2
2016-04-29,Ca$_3$Ir$_4$Sn$_{13}$: A weakly correlated nodeless superconductor,"We report detailed Seebeck coefficient, Hall resistivity as well as specific
heat measurement on Ca$_3$Ir$_4$Sn$_{13}$ single crystals. The Seebeck
coefficient exhibits a peak corresponding to the anomaly in resistivity at
$T^*$, and the carrier density is suppressed significantly below $T^*$. This
indicates a significant Fermi surface reconstruction and the opening of the
charge density wave gap at the supperlattice transition. The magnetic field
induced enhancement of the residual specific heat coefficient $\gamma(H)$
exhibits a nearly linear dependence on magnetic field, indicating a nodeless
gap. In the temperature range close to $T_c$ the Seebeck coefficient can be
described well by the diffusion model. The zero-temperature extrapolated
thermoelectric power is very small, implying large normalized Fermi
temperature. Consequently the ratio $\frac{T_c}{T_F}$ is very small. Our
results indicate that Ca$_3$Ir$_4$Sn$_{13}$ is a weakly correlated nodeless
superconductor.",1604.08948v1
2016-06-06,First-principles calculation of the stabilities of LMP/LAMP lithium superionic conductors against sodium-ion exchange in seawater,"Electronic structure calculations carried out to estimate the free energies
of Na(aq)+ exchange for lithium in LiM2(PO4)3 (LMP, M=Si4+,Ge4+,Ti4+,Sn4+,Zr4+)
and Li1+xAlxM2-x(PO4)3 (LAMP; M=Ge4+,Ti4+, between 0 and 0.5) compounds in
seawater. The calculations show that resistance to sodium-ion exchange
increases with decreasing cell volume. For the pure LMP compounds, only the
hypothetical LiSi2(PO4)3 is predicted to be stable against sodium ion exchange
in aqueous solution. The calculations indicate that increasing the extent of
Al3+ substitution for M4+ in the LAMP compounds increases the resistance to
exchange, and that both LAGP and LATP can be stabilized against sodium exchange
for x greater than or equal to approximately 0.5 Li1+xAlxM2-x(PO4)3.",1606.02177v1
2016-06-09,Giant Linear Magneto-resistance in Nonmagnetic PtBi2,"We synthesized nonmagnetic PtBi$_2$ single crystals and observed a giant
linear magneto-resistance (MR) up to 684\% under a magnetic field $\mu_0H$ = 15
T at $T$ = 2 K. The linear MR decreases with increasing temperature, but it is
still as large as 61\% under $\mu_0H$ of 15 T at room temperature. Such a giant
linear MR is unlikely to be described by the quantum model as the quantum
condition is not satisfied. Instead, we found that the slope of MR scales with
the Hall mobility, and it can be well explained by a classical disorder model.",1606.02847v1
2016-07-13,Tuning the electronic and the crystalline structure of LaBi by pressure,"Extreme magnetoresistance (XMR) in topological semimetals is a recent
discovery which attracts attention due to its robust appearance in a growing
number of materials. To search for a relation between XMR and
superconductivity, we study the effect of pressure on LaBi taking advantage of
its simple structure and simple composition. By increasing pressure we observe
the disappearance of XMR followed by the appearance of superconductivity at
P=3.5 GPa.The suppression of XMR is correlated with increasing zero-field
resistance instead of decreasing in-field resistance. At higher pressures, P=11
GPa, we find a structural transition from the face center cubic lattice to a
primitive tetragonal lattice in agreement with theoretical predictions. We
discuss the relationship between extreme magnetoresistance, superconductivity,
and structural transition in LaBi.",1607.03560v1
2016-07-20,Performance of Topological Insulator Interconnects,"The poor performance of copper interconnects at the nanometer scale calls for
new material solutions for continued scaling of integrated circuits. We propose
the use of three dimensional time-reversal-invariant topological insulators
(TIs), which host backscattering-protected surface states, for this purpose.
Using semiclassical methods, we demonstrate that nanoscale TI interconnects
have a resistance 1-3 orders of magnitude lower than copper interconnects and
graphene nanoribbons at the nanometer scale. We use the nonequilibrium Green
function (NEGF) formalism to measure the change in conductance of nanoscale TI
and metal interconnects caused by the presence of impurity disorder. We show
that metal interconnects suffer a resistance increase, relative to the clean
limit, in excess of 500% due to disorder while the TI's surface states increase
less than 35% in the same regime.",1607.06131v2
2016-08-03,Prominent metallic surface conduction and the singular magnetic response of topological Dirac fermion in three-dimensional topological insulator Bi$_{1.5}$Sb$_{0.5}$Te$_{1.7}$Se$_{1.3}$,"We report semiconductor to metal-like crossover in temperature dependence of
resistivity ($\rho$) due to the switching of charge transport from bulk to
surface channel in three-dimensional topological insulator
Bi$_{1.5}$Sb$_{0.5}$Te$_{1.7}$Se$_{1.3}$. Unlike earlier studies, a much
sharper drop in $\rho$($T$) is observed below the crossover temperature due to
the dominant surface conduction. Remarkably, the resistivity of the conducting
surface channel follows a rarely observable $T^2$ dependence at low temperature
as predicted theoretically for a two-dimensional Fermi liquid system. The field
dependence of magnetization shows a cusp-like paramagnetic peak in the
susceptibility ($\chi$) at zero field over the diamagnetic background. The peak
is found to be robust against temperature and decays linearly with field from
its zero-field value. This unique behavior of $\chi$ is associated with the
spin-momentum locked topological surface state of
Bi$_{1.5}$Sb$_{0.5}$Te$_{1.7}$Se$_{1.3}$. The reconstruction of surface state
with time is clearly reflected through the reduction of peak height with the
age of the sample.",1608.01203v2
2016-08-11,Magnetoresistance generated from charge-spin conversion by anomalous Hall effect in metallic ferromagnetic/nonmagnetic bilayers,"A theoretical formulation of magnetoresistance effect in a metallic
ferromagnetic/nonmagnetic bilayer originated from the charge-spin conversion by
the anomalous Hall effect is presented. Analytical expressions of the
longitudinal and transverse resistivities in both nonmagnet and ferromagnet are
obtained by solving the spin diffusion equation. The magnetoresistance
generated from charge-spin conversion purely caused by the anomalous Hall
effect in the ferromagnet is found to be proportional to the square of the spin
polarizations in the ferromagnet and has fixed sign. We also find additional
magnetoresistances in both nonmagnet and ferromagnet arising from the mixing of
the spin Hall and anomalous Hall effects. The sign of this mixing resistance
depends on those of the spin Hall angle in the nonmagnet and the spin
polarizations of the ferromagnet.",1608.03359v2
2016-08-12,Growth of ultra thin vanadium dioxide thin films using magnetron sputtering,"In this work, the results of fabricating ultra thin VO$_2$ films on the
technologically relevant amorphous SiO$_2$ surface using reactive DC magnetron
sputtering are presented. Results indicate that a post deposition anneal in low
partial pressures of oxygen is an effective way at stabilizing the
VO$_2$(M$_{1}$) phase on the SiO$_2$ surface. VO$_2$ films with a thickness of
42nm show a continuous microstructure, and undergo a resistivity change of more
than a factor of 200 as the temperature of the film increases above 72$^{o}C$.
The film shows hysteresis in the metal-insulator transition temperature upon
heating and cooling with a width of approximately 8$^o$C. The resistivity of
the low temperature semiconducting phase is found to be thermally activated
with an activation energy 0.16$\pm$0.03 $ev$. Stress measurements using X-ray
diffraction indicate that the ultra thin VO$_2$ film has a large tensile stress
of 2.0$\pm$0.2 $GPa$. This value agrees well with the calculated thermal stress
due to differential thermal expansion between the VO$_2$ thin film and silicon
substrate. The stress leads to a shift of the metal-insulator transition
temperature by approximately 4$^{o}C$.",1608.03911v1
2016-08-31,Spin polarization ratios of resistivity and density of states estimated from anisotropic magnetoresistance ratio for nearly half-metallic ferromagnets,"We derive a simple relational expression between the spin polarization ratio
of resistivity, $P_\rho$, and the anisotropic magnetoresistance ratio $\Delta
\rho/\rho$, and that between the spin polarization ratio of the density of
states at the Fermi energy, $P_{\rm DOS}$, and $\Delta \rho/\rho$ for nearly
half-metallic ferromagnets. We find that $P_\rho$ and $P_{\rm DOS}$ increase
with increasing $|\Delta \rho/\rho|$ from 0 to a maximum value. In addition, we
roughly estimate $P_\rho$ and $P_{\rm DOS}$ for a Co$_2$FeGa$_{0.5}$Ge$_{0.5}$
Heusler alloy by substituting its experimentally observed $\Delta \rho/\rho$
into the respective expressions.",1608.08888v1
2016-10-17,Anomalous Hall effect of ferromagnetic Fe3Sn2 single crystal with geometrically frustrated kagome lattice,"The anomalous Hall effect is investigated for ferromagnetic Fe3Sn2 single
crystal with geometrically frustrated kagome bilayer of Fe. The scaling
behavior between anomalous Hall resistivity rho_{xy}^{A} and longitudinal
resistivity rho_{xx} is quadratic and further analysis implies that the AHE in
Fe3Sn2 single crystal should be dominated by the intrinsic Karplus-Luttinger
mechanism rather than extrinsic skew-scattering or side-jump mechanisms.
Moreover, there is a sudden jump of anomalous Hall conductivity sigma_{xy}^{A}
appearing at about 100 K where the spin-reorientation transition from the c
axis to the ab plane is completed. This change of sigma_{xy}^{A} might be
related to the evolution of Fermi surface induced by the spin-reorientation
transition.",1610.04970v1
2016-11-11,MgGa2O4 spinel barrier for magnetic tunnel junctions: coherent tunneling and low barrier height,"Epitaxial Fe/magnesium gallium spinel oxide (MgGa2O4)/Fe(001) magnetic tunnel
junctions (MTJs) were fabricated by magnetron sputtering. Tunnel
magnetoresistance (TMR) ratio up to 121% at room temperature (196% at 4 K) was
observed, suggesting a TMR enhancement by the coherent tunneling effect in the
MgGa2O4 barrier. The MgGa2O4 layer had a spinel structure and it showed good
lattice matching with the Fe layers owing to slight tetragonal lattice
distortion of MgGa2O4. Barrier thickness dependence of the tunneling resistance
and current-voltage characteristics revealed that the barrier height of the
MgGa2O4 barrier is much lower than that in an MgAl2O4 barrier. This study
demonstrates the potential of Ga-based spinel oxides for MTJ barriers having a
large TMR ratio at a low resistance area product.",1611.03606v1
2016-11-28,Doping of metal-organic frameworks towards resistive sensing,"Coordination polymerization leads to various metal-organic frameworks (MOFs)
in which symmetrical metal nodes exposed to nano voids lead to unique physical
properties and chemical functionalities. One of the challenges towards their
applications as porous materials is to make MOFs optimally conductive to be
used as electronic components. Here, we demonstrate that Co-MOF-74, a honeycomb
nano{framework with one{dimensionally arranged cobalt atoms advances its
physical properties by accommodating Tetracyanochinodimethan (TCNQ), an
acceptor molecule. Strong intermolecular charge transfer narrows the optical
band gap down to 1.5 eV of divalent TCNQ and enhances the electrical
conduction, which allows the MOF to be utilized for resistive gas- and
photo-sensing. Our result provides insight into electronic interactions in
doped MOFs and paves the way towards their electronic applications.",1611.09138v1
2016-12-02,Stokes paradox in electronic Fermi liquids,"The Stokes paradox is the statement that in a viscous two dimensional fluid,
the ""linear response"" problem of fluid flow around an obstacle is ill-posed. We
present a simple consequence of this paradox in the hydrodynamic regime of a
Fermi liquid of electrons in two-dimensional metals. Using hydrodynamics and
kinetic theory, we estimate the contribution of a single cylindrical obstacle
to the global electrical resistance of a material, within linear response.
Momentum relaxation, present in any realistic electron liquid, resolves the
classical paradox. Nonetheless, this paradox imprints itself in the resistance,
which can be parametrically larger than predicted by Ohmic transport theory. We
find a remarkably rich set of behaviors, depending on whether or not the
quasiparticle dynamics in the Fermi liquid should be treated as diffusive,
hydrodynamic or ballistic on the length scale of the obstacle. We argue that
all three types of behavior are observable in present day experiments.",1612.00856v2
2017-02-08,Ironwood Meta Key Agreement and Authentication Protocol,"Number theoretic public-key solutions, currently used in many applications
worldwide, will be subject to various quantum attacks, making them less
attractive for longer-term use. Certain group theoretic constructs are now
showing promise in providing quantum-resistant cryptographic primitives, and
may provide suitable alternatives for those looking to address known quantum
attacks. In this paper, we introduce a new protocol called a Meta Key Agreement
and Authentication Protocol (MKAAP) that has some characteristics of a
public-key solution and some of a shared-key solution. Specifically it has the
deployment benefits of a public-key system, allowing two entities that have
never met before to authenticate without requiring real-time access to a
third-party, but does require secure provisioning of key material from a
trusted key distribution system (similar to a symmetric system) prior to
deployment. We then describe a specific MKAAP instance, the Ironwood MKAAP,
discuss its security, and show how it resists certain quantum attacks such as
Shor's algorithm or Grover's quantum search algorithm. We also show Ironwood
implemented on several ``internet of things'' (IoT devices), measure its
performance, and show how it performs significantly better than ECC using fewer
device resources.",1702.02450v2
2017-06-08,Scale-invariant large nonlocality in polycrystalline graphene,"The observation of large nonlocal resistances near the Dirac point in
graphene has been related to a variety of intrinsic Hall effects, where the
spin or valley degrees of freedom are controlled by symmetry breaking
mechanisms. Engineering strong spin or valley Hall signals on scalable graphene
devices could stimulate further practical developments of spin- and
valleytronics. Here we report on scale-invariant nonlocal transport in
large-scale chemical vapour deposition graphene under an applied external
magnetic field. Contrary to previously reported Zeeman spin Hall effect, our
results are explained by field-induced spin-filtered edge states whose
sensitivity to grain boundaries manifests in the nonlocal resistance. This
phenomenon, related to the emergence of the quantum Hall regime, persists up to
the millimeter scale, showing that polycrystalline morphology can be imprinted
in nonlocal transport. This suggests that topological Hall effects in
large-scale graphene materials are highly sensitive to the underlying
structural morphology, limiting practical realizations.",1706.02539v2
2017-09-01,Reproducibility and off-stoichiometry issues in nickelate thin films grown by pulsed laser deposition,"Rare-earth nickelates are strongly correlated oxides displaying a
metal-to-insulator transition at a temperature tunable by the rare-earth ionic
radius. In PrNiO$_3$ and NdNiO$_3$, the transition is very sharp and shows an
hysteretic behavior akin to a first-order transition. Both the temperature at
which the transition occurs and the associated resistivity change are extremely
sensitive to doping and therefore to off-stoichiometry issues that may arise
during thin film growth. Here we report that strong deviations in the transport
properties of NdNiO$_3$ films can arise in films grown consecutively under
nominally identical conditions by pulsed laser deposition; some samples show a
well-developed transition with a resistivity change of up to five orders of
magnitude while others are metallic down to low temperatures. Through a
detailed analysis of \textit{in-situ} X-ray photoelectron spectroscopy data, we
relate this behavior to large levels of cationic off-stoichoimetry that also
translate in changes in the Ni valence and bandwidth. Finally, we demonstrate
that this lack of reproducibility can be remarkably alleviated by using
single-phase NdNiO$_3$ targets.",1709.00240v1
2017-09-05,Temperature Dependent n-p Transition of 3 Dimensional Dirac Semimetal Na$_3$Bi Thin Film,"We study the temperature dependence ($77$ K - $475$ K) of the longitudinal
resistivity and Hall coefficient of thin films (thickness $20$ nm) of three
dimensional topological Dirac semimetal Na$_3$Bi grown via molecular beam
epitaxy (MBE). The temperature-dependent Hall coefficient is electron-like at
low temperature, but transitions to hole-like transport around $200$ K. We
develop a model of a Dirac band with electron-hole asymmetry in Fermi velocity
and mobility (assumed proportional to the square of Fermi velocity) which
explains well the magnitude and temperature dependence of the Hall resistivity.
We find that the hole mobility is about $7$ times larger than the electron
mobility. In addition, we find that the electron mobility decreases
significantly with increasing temperature, suggesting electron-phonon
scattering strongly limits the room temperature mobility.",1709.01209v1
2017-09-05,Superconducting and normal-state properties of the noncentrosymmetric superconductor Re6Zr,"We systematically investigate the normal and superconducting properties of
non-centrosymmetric Re$_{6}$Zr using magnetization, heat capacity, and
electrical resistivity measurements. Resistivity measurements indicate
Re$_{6}$Zr has poor metallic behavior and is dominated by disorder. Re$_6$Zr
undergoes a superconducting transition at $T_{\mathrm{c}} =
\left(6.75\pm0.05\right)$ K. Magnetization measurements give a lower critical
field, $\mu_{0}H_{\mathrm{c1}} = \left(10.3 \pm 0.1\right)$ mT. The
Werthamer-Helfand-Hohenberg model is used to approximate the upper critical
field $\mu_{0}H_{\mathrm{c2}} = \left(11.2 \pm 0.2\right)$ T which is close to
the Pauli limiting field of 12.35 T and which could indicate singlet-triplet
mixing. However, low-temperature specific-heat data suggest that Re$_{6}$Zr is
an isotropic, fully gapped s-wave superconductor with enhanced electron-phonon
coupling. Unusual flux pinning resulting in a peak effect is observed in the
magnetization data, indicating an unconventional vortex state.",1709.01328v1
2017-09-11,Tuning electrical properties of silicon dioxide through intrinsic nano-patterns,"The inherent network of nanopores and voids in silicon dioxide (SiO2) is
generally undesirable for aspects of film quality, electrical insulation and
dielectric performance. However, if we view these pores as natural
nano-patterns embedded in a dielectric matrix then that opens up new vistas for
exploration. The nano-pattern platform can be used to tailor electrical,
optical, magnetic and mechanical properties of the carrier film. In this
article we report the tunable electrical properties of thermal SiO2 thin-film
achieved through utilization of the metal-nanopore network where the pores are
filled with metallic Titanium (Ti). Without any intentional chemical doping, we
have shown that the electrical resistivity of the oxide film can be controlled
through physical filling up of the intrinsic oxide nanopores with Ti. The
electrical resistance of the composite film remains constant even after
complete removal of the metal from the film surface except the pores. Careful
morphological, electrical and structural analyses are carried out to establish
that the presence of Ti in the nanopores play a crucial role in the observed
conductive nature of the nanoporous film.",1709.03259v1
2017-09-14,Towards Universal Non-Volatile Resistance Switching in Non-metallic Monolayer Atomic Sheets,"Here, we report the intriguing observation of stable non-volatile resistance
switching (NVRS) in single-layer atomic sheets sandwiched between metal
electrodes. NVRS is observed in the prototypical semiconducting (MX2, M=Mo, W;
and X=S, Se) transitional metal dichalcogenides (TMDs), and insulating
hexagonal boron nitride (h-BN), which alludes to the universality of this
phenomenon in non-metallic 2D monolayers, and features forming-free switching.
This observation of NVRS phenomenon, widely attributed to ionic diffusion,
filament and interfacial redox in bulk oxides and electrolytes, inspires new
studies on defects, ion transport and energetics at the sharp interfaces
between atomically-thin sheets and conducting electrodes. From a contemporary
perspective, switching is all the more unexpected in monolayers since leakage
current is a fundamental limit in ultra-thin oxides. Emerging device concepts
in non-volatile flexible memory fabrics, and brain-inspired (neuromorphic)
computing could benefit substantially from the pervasive NVRS effect and the
associated wide materials and engineering co-design opportunity.
Experimentally, a 50 GHz radio-frequency (RF) monolayer switch is demonstrated,
which opens up a new application for electronic zero-static power RF switching
technology.",1709.04592v1
2017-11-06,Negative to Positive Magnetoresistance transition in Functionalization of Carbon nanotube and Polyaniline Composite,"Electrical resistivity and magnetoresistance(MR) in polyaniline(PANI) with
carbon nanotube(CNT) and functionalized carbon nanotube(fCNT) composites have
been studied for different weight percentage down to the temperature 4.2K and
up to magnetic field 5T. Resistivity increases significantly in composite at
low temperature due to functionalization of CNT compare to only CNT.
Interestingly transition from negative to positive magnetoresistance has been
observed for 10wt% of composite as the effect of disorder is more in fCNT/PANI.
This result depicts that the MR has strong dependency on disorder in the
composite system. The transition of MR has been explained in the basis of
polaron-bipolaron model. The long range Coulomb interaction between two
polarons screened by disorder in the composite of fCNT/PANI, increases the
effective on-site Coulomb repulsion energy to form bipolaron which leads to
change the sign of MR from negative to positive.",1711.01957v2
2017-11-27,Effect of RF Sputtering Process Parameters on Silicon Nitride Thin Film Deposition,"The objective of this work was to study the RF sputtering process parameters
optimisation for deposition of Silicon Nitride thin films. The process
parameters chosen to be varied were deposition power, deposition duration, flow
rate of argon and flow rate of nitrogen. The parameters were varied at three
levels according to Taguchi L9 orthogonal array. Surface topology, film
composition, coating thickness, coating resistivity and refractive index were
determined using SEM, XRD, profilometer, Semiconductor device analyser and UV
spectrometer respectively. The measured film thickness values ranged from
127.8nm to 908.3nm with deposition rate varying from 1.47nm/min to a maximum
value of 10.1nm/min. The resistivity of the film varied between 1.53x1013ohm-m
to 7.85 x1013ohm-m. Refractive index of the film was calculated to be between
1.84 to 2.08. From the results, it was seen that film properties tend to be
poor when there is no nitrogen flow and tend to improve with small input of
nitrogen. Also, SEM images indicated amorphous structure of silicon nitride
which was confirmed by XRD pattern.",1711.09556v2
2017-12-29,Non-stoichiometry effects on the extreme magnetoresistance in Weyl semimetal WTe2,"Non-stoichiometry effect on the extreme magnetoresistance is systematically
investigated for the Weyl semimetal WTe2. Magnetoresistance and Hall
resistivity are measured for the as-grown samples with a slight difference in
Te vacancies and the annealed samples with increased Te vacancies. The fittings
to a two-carrier model show that the magnetoresistance is strongly dependent on
the residual resistivity ratio (i.e., the degree of non-stoichiometry), which
is eventually understood in terms of electron doping which not only breaks the
balance between electron-type and hole-type carrier densities but also reduces
the average carrier mobility. Thus, compensation effect and ultrahigh mobility
are probably the main driving force of the extreme magnetoresistance in WTe2.",1712.10200v2
2018-03-03,Giant Planar Hall Effect in the Dirac Semimetal ZrTe5,"Recently, giant planar Hall effect originating from chiral anomaly has been
predicted in nonmagnetic Dirac/Weyl semimetals. ZrTe5 is considered to be an
intriguing Dirac semimetal at the boundary of weak topological insulators and
strong topological insulators, though this claim still remains controversial.
Here, we report the observation in ZrTe5 of the giant planar Hall resistivity
that shows two different magnetic-field dependences as predicted by theory and
a maximum at the Lifshitz transition temperature. We found that the giant
planar Hall resistivity fades out with decreasing the thickness of ZrTe5
nanoplates, which may be ascribed to the vanishing of the 3D nature of the
samples. In addition, we have observed a nontrivial Berry phase,
chiral-anomaly-induced negative longitudinal magnetoresistance, and a giant
in-plane anisotropic magnetoresistance in these ZrTe5 nanoplates. All the
experimental observations demonstrated coherently that ZrTe5 is a Dirac
semimetal.",1803.01213v2
2018-03-18,Bulk transport properties of Bismuth selenide thin films approaching the two-dimensional limit,"We have investigated the transport properties of topological insulator Bi2Se3
thin films grown using magnetron sputtering with an emphasis on understanding
the behavior as a function of thickness. We show that thickness has a strong
influence on all aspects of transport as the two-dimensional limit is
approached. Bulk resistivity and Hall mobility show disproportionately large
changes below 6 quintuple layer which we directly correlate to an increase in
the bulk band gap of few-layer Bi2Se3, an effect that is concomitant with
surface gap opening. A tendency to crossover from a metallic to an insulating
behavior in temperature-dependent resistivity measurements in ultra-thin Bi2Se3
is also consistent with an increase in the bulk band gap along with enhanced
disorder at the film-substrate interface. Our work highlights that the
properties of few-layer Bi2Se3 are tunable that may be attractive for a variety
of device applications in areas such as optoelectronics, nanoelectronics and
spintronics.",1803.06593v1
2018-03-30,Growth of Thin Oxidation-Resistive Crystalline Si Nanostructures on Graphene,"We report the growth of Si nanostructures, either as thin films or
nanoparticles, on graphene substrates. The Si nanostructures are shown to be
single crystalline, air stable and oxidation resistive, as indicated by the
observation of a single crystalline Si Raman mode at around 520 cm-1, a STM
image of an ordered surface structure under ambient condition, and a Schottky
junction with graphite. Ultra-thin silicon regions exhibit silicene-like
behavior, including a Raman mode at around 550 cm-1, a triangular lattice
structure in STM that has distinctly different lattice spacing from that of
either graphene or thicker Si, and metallic conductivity of up to 500 times
higher than that of graphite. This work suggests a bottom-up approach to
forming a Si nanostructure array on a large scale patterned graphene substrate
for fabricating nanoscale Si electronic devices.",1804.00072v1
2018-03-31,Quantum Wires and Waveguides Formed in Graphene by Strain,"Confinement of electrons in graphene to make devices has proven to be a
challenging task. Electrostatic methods fail because of Klein tunneling, while
etching into nanoribbons requires extreme control of edge terminations, and
bottom-up approaches are limited in size to a few nanometers. Fortunately, its
mechanical flexibility raises the possibility of using strain to alter
graphene's properties and create novel straintronic devices. Here, we report
transport studies of nanowires created by linearly-shaped strained regions
resulting from individual folds formed by layer transfer onto hexagonal boron
nitride. Conductance measurements across the folds reveal Coulomb blockade
signatures, indicating confined charges within these structures, which act as
quantum dots. Along folds, we observe sharp features in traverse resistivity
measurements, attributed to an amplification of the dot conductance modulations
by a resistance bridge incorporating the device. Our data indicates ballistic
transport up to ~1 um along the folds. Calculations using the Dirac model
including strain are consistent with measured bound state energies and predict
the existence of valley-polarized currents. Our results show that graphene
folds can act as straintronic quantum wires.",1804.00207v1
2018-04-05,Two-Stage Proximity-Induced Gap-Opening in Topological Insulator - Insulating Ferromagnet (Bi$_x$Sb$_{1-x}$)$_2$Te$_3$ - EuS Bilayers,"To further investigate the interplay between ferromagnetism and topological
insulators, thin films of the low-carrier topological insulator
(Bi$_x$Sb$_{1-x}$)$_2$Te$_3$ were deposited on the insulating ferromagnet EuS
(100) in situ. AC susceptibility indicates magnetic anomalies between
$T\approx30~\mathrm{K}$ and $T\approx60~\mathrm{K}$, well above the Curie
temperature $T_C \approx 15~\mathrm{K}$ of EuS. When the Fermi level is close
to the Dirac point and the surface state dominates the electric conduction,
sharp increases in resistance with decreasing temperatures were observed
concurrently with the magnetic anomalies. Positive-negative magnetoresistance
crossovers were observed at the Curie temperature, which seem only to appear
when the sheet resistance exceeds the Mott-Ioffe-Regel limit $h/e^2$. A
two-stage gap-opening process due to magnetic proximity is proposed.",1804.02061v2
2018-04-16,Structural and magnetic properties of CeZnAl$_3$ single crystals,"We have synthesized single crystals of CeZnAl$_3$, which is a new member of
the family of the Ce-based intermetallics Ce$TX_3$ ($T$ = transition metal,
$X$= Si, Ge, Al), crystallizing in the non-centrosymmetric tetragonal
BaNiSn$_3$-type structure. Magnetization, specific heat and resistivity
measurements all show that CeZnAl$_3$ orders magnetically below around 4.4 K.
Furthermore, magnetization measurements exhibit a hysteresis loop at low
temperatures and fields, indicating the presence of a ferromagnetic component
in the magnetic state. This points to a different nature of the magnetism in
CeZnAl$_3$ compared to the other isostructural Ce$T$Al$_3$ compounds.
Resistivity measurements under pressures up to 1.8 GPa show a moderate
suppression of the ordering temperature with pressure, suggesting that
measurements to higher pressures are required to look for quantum critical
behavior.",1804.05477v1
2018-05-11,Unveiling the mechanisms of the spin Hall effect in Ta,"Spin-to-charge current interconversions are widely exploited for the
generation and detection of pure spin currents and are key ingredients for
future spintronic devices including spin-orbit torques and spin-orbit logic
circuits. In case of the spin Hall effect, different mechanisms contribute to
the phenomenon and determining the leading contribution is peremptory for
achieving the largest conversion efficiencies. Here, we experimentally
demonstrate the dominance of the intrinsic mechanism of the spin Hall effect in
highly-resistive Ta. We obtain an intrinsic spin Hall conductivity for
$\beta$-Ta of -820$\pm$120 ($\hbar$/e) $\Omega^{-1}cm^{-1}$ from spin
absorption experiments in a large set of lateral spin valve devices. The
predominance of the intrinsic mechanism in Ta allows us to linearly enhance the
spin Hall angle by tuning the resistivity of Ta, reaching up to -35$\pm$3%, the
largest reported value for a pure metal.",1805.04475v1
2018-06-04,Nodeless superconductivity in the SnAs-based van der Waals type superconductor NaSn2As2,"We grew the single crystals of the SnAs-based van der Waals (vdW)-type
superconductor NaSn$_2$As$_2$ and systematically measured its resistivity,
specific heat, and ultralow-temperature thermal conductivity. The
superconducting transition temperature $T_c$ = 1.60 K of our single crystal is
0.3 K higher than that previously reported. A weak but intrinsic anomaly
situated at 193 K is observed in both resistivity and specific heat, which
likely arises from a charge-density-wave (CDW) instability.
Ultralow-temperature thermal conductivity measurements reveal a fully-gapped
superconducting state with a negligible residual linear term in zero magnetic
field, and the field dependence of $\kappa_0 / T$ further suggests
NaSn$_2$As$_2$ is an $s$-wave superconductor.",1806.01141v1
2018-06-20,Heat transport in pristine and polycrystalline single-layer hexagonal boron nitride,"We use a phase field crystal model to generate large-scale bicrystalline and
polycrystalline single-layer hexagonal boron nitride (h-BN) samples and employ
molecular dynamics (MD) simulations with the Tersoff many-body potential to
study their heat transport properties. The Kapitza thermal resistance across
individual h-BN grain boundaries is calculated using the inhomogeneous
nonequilibrium MD method. The resistance displays strong dependence on the tilt
angle, the line tension and the defect density of the grain boundaries. We also
calculate the thermal conductivity of pristine h-BN and polycrystalline h-BN
with different grain sizes using an efficient homogeneous nonequilibrium MD
method. The in-plane and the out-of-plane (flexural) phonons exhibit different
grain size scalings of the thermal conductivity in polycrystalline h-BN and the
extracted Kapitza conductance is close to that of large-tilt-angle grain
boundaries in bicrystals.",1806.07936v2
2018-09-17,Phase transformations and compatibility in helical structures,"We systematically study phase transformations from one helical structure to
another. Motivated in part by recent work that relates the presence of
compatible interfaces with properties such as the hysteresis and reversibility
of a phase transformation [35, 33, 12, 28], we give necessary and sufficient
conditions on the structural parameters of two helical phases such that they
are compatible. We show that, locally, four types of compatible interface are
possible: vertical, horizontal, helical and elliptical. We discuss the mobility
of these interfaces and give examples of systems of interfaces that are mobile
and could be used to fully transform a helical structure from one phase to
another.
  These results provide a basis for the tuning of helical structural parameters
so as to achieve compatibility of phases. In the case of transformations in
crystals, this kind of tuning has led to materials with exceptionally low
hysteresis and dramatically improved resistance to transformational fatigue.
Compatible helical transformations with low hysteresis and fatigue resistance
would exhibit an unusual shape memory effect involving both twist and
extension, and may have potential applications as new artificial muscles and
actuators.",1809.06282v2
2019-05-01,Hydrodynamic Coulomb drag and bounds on diffusion,"We study Coulomb drag between an active layer with a clean electron liquid
and a passive layer with a pinned electron lattice in the regime of fast
intralayer equilibration. Such a two-fluid system offers an experimentally
realizable way to disentangle the fast rate of intralayer electron-electron
interactions from the much slower rate of momentum transfer between both
layers. We identify an intermediate temperature range above the Fermi energy of
the electron fluid but below the Debye energy of the electronic crystal where
the hydrodynamic drag resistivity is directly proportional to a fast
electron-electron scattering rate. The results are compatible with the
conjectured scenario for strong electron-electron interactions which poses that
a linear temperature dependence of resistivity originates from a ""Planckian""
electron relaxation time $\tau_{eq}\sim \hbar/k_BT$. We compare this to the
better known semiclassical case, where the diffusion constant is found to be
not proportional to the microscopic timescale.",1905.00317v2
2019-05-03,Supersonic flow and negative local resistance in hydrodynamic Dirac electron nozzles,"In clean Dirac electron systems such as graphene, electron-electron
interactions can dominate over other relaxation mechanisms such as phonon or
impurity scattering. It has been predicted that in this limit, collective
electron dynamics can be described by hydrodynamic equations. The prerequisites
for electron liquids are already fulfilled in current experiments and hints of
electron hydrodynamics have been identified in transport measurements. Here, we
show that a nozzle geometry, implemented for example in a graphene sample, can
cause a transition from subsonic to supersonic flow and provides an interesting
probe for the hydrodynamic regime of Dirac electrons. In particular, we predict
two distinct transport features that can be seen in the experimentally
measurable voltage characteristics on the exit side of the nozzle: a pronounced
negative local resistance, and an abrupt change of the electrostatic potential
induced by an electron shock wave. Our results pave the way for an experimental
identification of supersonic hydrodynamic electron flow and for the
experimental study of electron shock waves.",1905.01247v2
2019-05-21,Thermal Boundary Resistance Measurement and Analysis Across SiC/SiO2 Interface,"Silicon Carbide (SiC) is a typical material for third-generation
semiconductor. The thermal boundary resistance (TBR) of 4H-SiC/SiO2 interface,
was investigated by both experimental measurements and theoretical
calculations. The structure of 4H-SiC/SiO2 was characterized by using
transmission electron microscopy and X-ray diffraction. The TBR is measured as
8.11*10-8 m2K/W by 3-omega method. Furthermore, the diffuse mismatch model was
employed to predict the TBR of different interfaces which is in good agreement
with measurements. Heat transport behavior based on phonon scattering
perspective was also discussed to understand the variations of TBR across
different interfaces. Besides, the intrinsic thermal conductivity of SiO2 thin
films (200~1,500 nm in thickness) on 4H-SiC substrates was measured by 3 omega
procedure, as 1.42 W/mK at room temperature. It is believed the presented
results could provide useful insights on the thermal management and heat
dissipation for SiC devices.",1905.08570v1
2019-05-29,The effect of atomic structure on the electrical response of aluminium oxide tunnel junctions,"Many nanoelectronic devices rely on thin dielectric barriers through which
electrons tunnel. For instance, aluminium oxide barriers are used as Josephson
junctions in superconducting electronics. The reproducibility and drift of
circuit parameters in these junctions are affected by the uniformity,
morphology, and composition of the oxide barriers. To improve these circuits
the effect of the atomic structure on the electrical response of aluminium
oxide barriers must be understood. We create three-dimensional atomistic models
of aluminium oxide tunnel junctions and simulate their electronic transport
properties with the non-equilibrium Green's function formalism. Increasing the
oxide density is found to produce an exponential increase in the junction
resistance. In highly oxygen-deficient junctions we observe metallic channels
which decrease the resistance significantly. Computing the charge and current
density within the junction shows how variation in the local potential
landscape can create channels which dominate conduction. An atomistic approach
provides a better understanding of these transport processes and guides the
design of junctions for nanoelectronics applications.",1905.12214v1
2019-09-06,"Structural, Surface Morphology and Magneto-Transport properties of Self Flux Grown Eu Doped Bi2Se3 Single Crystal","Here, we report the effect of europium (Eu) doping in Bi2Se3 topological
insulator (TI) by using different characterization techniques viz. X-ray
diffraction (XRD), scanning electron microscopy (SEM) coupled with energy
dispersive X-ray analysis (EDXA) and magneto-transport measurements.
Temperature dependent electrical resistivity curves revealed a metallic
behaviour both in the presence and absence of applied magnetic field.
Magneto-transport measurements showed a decrease in the magneto-resistance (MR)
value of the Eu0.1Bi1.9Se3 sample (32% at 5K) in comparison to the pure Bi2Se3
sample (80% at 5K). For, Eu0.1Bi1.9Se3 sample, a complex crossover between WL
and WAL phenomenon was observed at lower applied magnetic fields, whereas the
same was absent in case of the pristine one. Further, HLN (Hikami Larkin
Nagaoka) fitted magneto-conductivity (MC) analysis revealed a competing weak
anti localization (WAL) and weak localization (WL) behaviour. Summarily, in the
present work we study the structural, surface morphology and magneto-transport
properties of as grown Eu0.1Bi1.9Se3 single crystals.",1909.02713v1
2019-09-12,Magneto-transport and Shubnikov-de Haas oscillations in the layered ternary telluride Ta3SiTe6 topological semimetal,"Topological semimetals characterize a novel class of quantum materials
hosting Dirac/Weyl fermions. The important features of topological fermions can
be exhibited by quantum oscillations. Here we report the magnetoresistance and
Shubnikov-de Haas (SdH) quantum oscillation of longitudinal resistance in the
single crystal of topological semimetal Ta3SiTe6 with the magnetic field up to
38 T. Periodic amplitude of the oscillations reveals related information about
the Fermi surface. The fast Fourier transformation spectra represent a single
oscillatory frequency. The analysis of the oscillations shows the Fermi pocket
with a cross-section area of 0.13 angstrom power minus 2. Combining
magneto-transport measurements and the first-principles calculation, we find
that these oscillations come from the hole pocket. Hall resistivity and the SdH
oscillations recommend that Ta3SiTe6 is a hole dominated system.",1909.05564v1
2019-09-17,A Thermal Resistance Network Model for Heat Conduction of Amorphous Polymers,"Thermal conductivities (TCs) of the vast majority of amorphous polymers are
in a very narrow range, 0.1 $\sim$ 0.5 Wm$^{-1}$K$^{-1}$, although single
polymer chains possess TC of orders-of-magnitude higher. Entanglement of
polymer chains plays an important role in determining the TC of bulk polymers.
We propose a thermal resistance network (TRN) model for TC in amorphous
polymers taking into account the entanglement of molecular chains. Our model
explains well the physical origin of universally low TC observed in amorphous
polymers. The empirical formulae of pressure and temperature dependence of TC
can be successfully reproduced from our model not only in solid polymers but
also in polymer melts. We further quantitatively explain the anisotropic TC in
oriented polymers.",1909.07607v1
2019-09-17,"A ""road-map"" of Nickelate superconductivity","We comment on the electronic structure of Nickelate system $Nd Ni O_2$ which
shows superconductivity on doping. The doped system $Nd_{0.8}Sr_{0.2}NiO_2$
shows (most probably unconventional) superconductivity with transition
temperatures ranging from $9~K$ to $15~K$\cite{dang}. The resistivity of the
parent compound $Nd NiO_2$ shows a minimum at around 60K, and an up-turn at
lower temperatures. In the current understanding it is thought to be
originating from a Kondo like coupling between mobile d-states of the $Nd~5d$
bands and un-paired electrons in $Ni 3d_{x^2-y^2}-O2p$ hybrid orbitals of
$Ni^{1+}$ and $O^{2-}$ions. In this note we offer alternative possibilities of
the observed resistance minimum in $LaNiO_2$. We attempt to construct a
""road-map"" of various possibilities to comprehend the observed behaviour and
suggest further experiments to prove or disprove a given explanation. We also
compare and contrast Nickelates with Cuprates. Comparison points towards
unconventional superconductivity in Nickelates.",1909.07688v1
2019-09-23,Nanostructured La0.5Ba0.5CoO3 as cathode for solid oxide fuel cells,"A simple method has been used to synthesize nanostructured La0.5Ba0.5CoO3
(LBCO) powders, by confining chemical precursors into the pores of
polycarbonate filters. The proposed method allows us to obtain powders formed
by crystallites of different sizes, it is scalable and does not involve the use
of sophisticated deposition techniques. The area specific polarization
resistance of symmetrical cells was studied to analyze the electrochemical
behavior of the LBCO nanostructures as cathodes for Solid-Oxide Fuel Cells. We
show that the performance is improved by reducing the size of the crystallites,
obtaining area specific resistance values of 0.2 Wcm2 at 700C, comparable with
newly developed cathodes using novel deposition techniques.",1909.10611v1
2020-03-31,In-situ grown single crystal aluminum as a non-alloyed ohmic contact to n-ZnSe by molecular beam epitaxy (MBE),"Novel ohmic contacts to n-ZnSe are demonstrated using single crystal Al films
deposited on epitaxially grown ZnSe (100) by molecular beam epitaxy (MBE).
Electron Backscatter Diffraction (EBSD) confirmed the single crystalline
structure of the Al films. The (110)-oriented Al layer was rotated rotated
45$^\circ$ relative to substrate to match the ZnSe (100) lattice constant. The
as-grown Al-ZnSe contact exhibited nearly ideal ohmic characteristics over a
large doping range of n-ZnSe without any additional treatment. The contact
resistances are in a range of 10$^{-3}$ $\Omega$-cm$^{2}$ for even lightly
doped ZnSe ($\sim$10$^{17}$ cm$^{-3}$). Leaky Schottky behavior in lightly
doped ZnSe samples suggested Al-ZnSe formed a low barrier height, Schottky
limit contact. In-situ grown Al could act as a simple metal contact to n-ZnSe
regardless of carrier concentration with lower resistance compared to other
reported contacts in literatures. The reported novel metallization method could
greatly simplify the ZnSe-based device fabrication complexity as well as lower
the cost",2003.14411v2
2014-08-16,Control of InGaAs facets using metal modulation epitaxy (MME),"Control of faceting during epitaxy is critical for nanoscale devices. This
work identifies the origins of gaps and different facets during regrowth of
InGaAs adjacent to patterned features. Molecular beam epitaxy (MBE) near SiO2
or SiNx led to gaps, roughness, or polycrystalline growth, but metal modulated
epitaxy (MME) produced smooth and gap-free ""rising tide"" (001) growth filling
up to the mask. The resulting self-aligned FETs were dominated by FET channel
resistance rather than source-drain access resistance. Higher As fluxes led
first to conformal growth, then pronounced {111} facets sloping up away from
the mask.",1408.3714v1
2014-08-20,Fluctuation Effects on the Transport Properties of Unitary Fermi Gases,"In this letter, we investigate the fluctuation effects on the transport
properties of unitary Fermi gases in the vicinity of the superfluid transition
temperature $T_c$. Based on the time-dependent Ginzburg-Landau formalism of the
BEC-BCS crossover, we investigate both the residual resistivity below $T_c$
induced by phase slips and the paraconductivity above $T_c$ due to pair
fluctuations. These two effects have been well studied in the weak coupling BCS
superconductor, and here we generalize them to the unitary regime of ultracold
Fermi gases. We find that while the residual resistivity below $T_c$ increases
as one approaches the unitary limit, consistent with recent experiments, the
paraconductivity exhibits non-monotonic behavior. Our results can be verified
with the recently developed transport apparatus using mesoscopic channels.",1408.4557v1
2017-01-11,Morphology and mechanical properties of nanocrystalline Cu/Ag alloy,"Hybrid Monte Carlo (MC)/molecular dynamics (MD) simulations are conducted to
study the microstructures of nanocrystalline (nc) Cu/Ag alloys with various Ag
concentrations. When the Ag concentration is below 50 Ag atoms/nm!, an increase
in Ag concentration leads to a gradual growth of monolayer grain boundary (GB)
complexions into nanolayer complexions. Above the concentration of 50 Ag
atoms/nm!, wetting layers with a bulk crystalline phase are observed. The
effects of Ag on mechanical properties and deformation mechanisms of nc Cu/Ag
alloys are investigated in MD simulations of uniaxial tension. GB sliding
resistance is found to first increase and then decrease with an increase in Ag
concentration. Surprisingly, we also find that the dislocation density
decreases monotonically with an increase in Ag concentration, which suggests
that the grain interiors are softened by the introduction of Ag dopants at GBs.
In addition, there is a critical Ag concentration that maximizes flow stress of
nc Cu/Ag alloys. The flow stress, GB sliding resistance, and the intragranular
dislocation densities become less sensitive to Ag dopants when the grain
diameter increases from 5nm to 40nm.",1701.03013v1
2017-01-15,Heat generation due to spin transport in spin valves,"Using a macroscopic approach, we studied theoretically the heat generation
due to spin transport in a typical spin valve with nonmagnetic spacer layer of
finite thickness. Our analysis shows that the spin-dependent heat generation
can also be caused by another mechanism, the spin-conserving scattering in the
presence of spin accumulation gradient, in addition to the well-known spin-flip
scattering. The two mechanisms have equal contributions in semi-infinite
layers, such as the ferromagnetic layers of the spin valve. However, in the
nonmagnetic layer of a thickness much smaller than its spin-diffusion length,
the spin-dependent heat generation is dominated by the spin-flip scattering in
the antiparallel configuration, and by the spin-conserving scattering in the
parallel configuration. We also proved that the spin-dependent heat generation
cannot be interpreted as the Joule heating of the spin-coupled interface
resistance in each individual layer. An effective resistance is proposed as an
alternative so that the heat generation can still be described simply by
applying Joule's law to an equivalent circuit.",1701.03984v1
2017-01-17,Conditions for $T^2$ resistivity from electron-electron scattering,"Many complex oxides (including titanates, nickelates and cuprates) show a
regime in which resistivity follows a power law in temperature ($\rho\propto
T^2$). By analogy to a similar phenomenon observed in some metals at low
temperature, this has often been attributed to electron-electron (Baber)
scattering. We show that Baber scattering results in a $T^2$ power law only
under several crucial assumptions which may not hold for complex oxides. We
illustrate this with sodium metal ($\rho_\text{el-el}\propto T^2$) and
strontium titanate ($\rho_\text{el-el}\not\propto T^2$). We conclude that an
observation of $\rho\propto T^2$ is not sufficient evidence for
electron-electron scattering.",1701.04744v1
2017-01-30,Negative differential resistance and magnetoresistance in zigzag borophene nanoribbons,"We investigate the transport properties of pristine zigzag-edged borophene
nanoribbons (ZBNRs) of different widths, using the fist-principles
calculations. We choose ZBNRs with widths of 5 and 6 as odd and even widths.
The differences of the quantum transport properties are found, where even-N
BNRs and odd-N BNRs have different current-voltage relationships. Moreover, the
negative differential resistance (NDR) can be observed within certain bias
range in 5-ZBNR, while 6-ZBNR behaves as metal whose current rises with the
increase of the voltage. The spin filter effect of 36% can be revealed when the
two electrodes have opposite magnetization direction. Furthermore, the
magnetoresistance effect appears to be in even-N ZBNRs, and the maximum value
can reach 70%.",1701.08501v1
2017-01-27,Dynamics of a capacitive electret-based microcantilever for energy harvesting,"In this paper, a novel electret-based capacitive energy harvesting device has
been developed according to out-of-plane gap closing scheme. The device is
composed of a micro cantilever and a substrate which form a variable capacitor
and is in series with a resistance. An electret material is used to provide the
bias voltage which is needed in capacitive energy harvesters in order to
scavenge energy from ambient vibration. The ambient vibration is applied to the
system as a harmonic base excitation. The motion equations and the
corresponding boundary conditions are derived using Hamilton's principle based
on Euler-Bernoulli beam theory and the Kirchhoff's voltage law is employed to
couple the mechanical and electrical fields. The equations of motion are
discretized using Galerkin procedure and integrated numerically over time.
Pull-in instability of the system is investigated in both static and dynamic
cases. The effect of various parameters on the behavior of the device is
studied. The maximum theoretical harvested power is resistance in the order of
1 micro-watt.",1701.08843v1
2017-03-07,Possible devil's staircase in the Kondo lattice CeSbSe,"The temperature ($T$) - magnetic field ($H$) phase diagram for the tetragonal
layered compound CeSbSe, is determined from magnetization, specific heat, and
electrical resistivity measurements. This system exhibits complex magnetic
ordering at $T_{\rm{M}}$ $=$ 3 K and the application of a magnetic field
results in a cascade of magnetically ordered states for $H$ $\lesssim$ 1.8 T
which are characterized by fractional integer size steps: i.e., a possible
Devil's staircase is observed. Electrical transport measurements show a weak
temperature dependence and large residual resistivity which suggest a small
charge carrier density and strong scattering from the $f$-moments. These
features reveal Kondo lattice behavior where the $f$-moments are incompletely
screened, resulting in a fine balanced magnetic interaction between different
Ce neighbors that is mediated by the RKKY interaction. This produces the nearly
degenerate magnetically ordered states that are accessed under an applied
magnetic field.",1703.02204v3
2017-03-07,Strong Electron-Phonon Interaction and Colossal Magnetoresistance in EuTiO$_3$,"At low temperatures, EuTiO$_3$ system has very large resistivities and
exhibits colossal magnetoresistance. Based on a first principle calculation and
the dynamical mean-field theory for small polaron we have calculated the
transport properties of EuTiO$_3$. It is found that due to electron-phonon
interaction the conduction band may form a tiny subband which is close to the
Fermi level. The tiny subband is responsible for the large resistivity.
Besides, EuTiO$_3$ is a weak antiferromagnetic material and its magnetization
would slightly shift the subband via exchange interaction between conduction
electrons and magnetic atoms. Since the subband is close to the Fermi level, a
slight shift of its position gives colossal magnetoresistance.",1703.02238v4
2018-10-06,Impact of Angular Deviation from Coincidence Site Lattice Grain Boundaries on Hydrogen Segregation and Diffusion in Alpha-iron,"Coincidence Site Lattice (CSL) grain boundaries (GBs) are believed to be
low-energy, resistant to intergranular fracture, as well as to hydrogen
embrittlement. Nevertheless, the behavior of CSL-GBs are generally confused
with their angular deviations. In the current study, the effect of angular
deviation from the perfect sigma3 (111) [1-10] GBs in Alpha-iron on the
hydrogen diffusion and the susceptibility of the GB to hydrogen embrittlement
is investigated through molecular static and dynamics simulations. By utilizing
Rice-Wang model it is shown that the ideal GB shows the highest resistance to
decohesion below the hydrogen saturation limit. Finally, the hydrogen
diffusivity along the ideal GB is observed to be the highest.",1810.02988v1
2018-10-07,Thermal properties of NbN single-photon detectors,"We investigate thermal properties of a NbN single-photon detector capable of
unit internal detection efficiency. Using an independent calibration of the
coupling losses we determine the absolute optical power absorbed by the NbN
film and, via a resistive superconductor thermometry, the thermal resistance
Z(T) of the NbN film in dependence of temperature. In principle, this approach
permits a simultaneous measurement of the electron-phonon and phonon-escape
contributions to the energy relaxation, which in our case is ambiguous for
their similar temperature dependencies. We analyze the Z(T) within the
two-temperature model and impose an upper bound on the ratio of electron and
phonon heat capacities in NbN, which is surprisingly close to a recent
theoretical lower bound for the same quantity in similar devices.",1810.03134v2
2018-10-16,Quantitative and systematic analysis of bias dependence of spin accumulation voltage in a non-degenerate Si spin valve,"Spin accumulation voltages in a non-degenerate Si spin valve are discussed
quantitatively as a function of electric bias current using systematic
experiments and model calculations. As an open question in semiconductor
spintronics, the origin of the deviation of spin accumulation voltages measured
experimentally in a non-degenerate Si spin valve is clarified from that
obtained by model calculation using the spin drift diffusion equation including
the effect of the spin-dependent interfacial resistance of tunneling barriers.
Unlike the case of metallic spin valves, the bias dependence of the
resistance-area product for a ferromagnet/MgO/Si interface, resulting in the
reappearance of the conductance mismatch, plays a central role to induce the
deviation.",1810.06879v1
2019-02-19,Nanoelectromechanical resonators from high-T$_c$ superconducting crystals of Bi$_2$Sr$_2$Ca$_1$Cu$_2$O$_{8+δ}$,"In this report, we present nanoelectromechanical resonators fabricated with
thin exfoliated crystals of a high-T$_c$ cuprate superconductor
Bi$_2$Sr$_2$Ca$_1$Cu$_2$O$_{8+\delta}$. The mechanical readout is performed by
capacitively coupling their motion to a coplanar waveguide microwave cavity
fabricated with a superconducting alloy of molybdenum-rhenium. We demonstrate
mechanical frequency tunability with external dc-bias voltage, and quality
factors up to 36600. Our spectroscopic and time-domain measurements show that
mechanical dissipation in these systems is limited by the contact resistance
arising from resistive outer layers. The temperature dependence of dissipation
indicates the presence of tunneling states, further suggesting that their
intrinsic performance could be as good as other two-dimensional atomic crystals
such as graphene.",1902.06896v1
2020-02-10,Structural and magneto-transport studies of iron intercalated Bi2Se3 single crystals,"A detailed investigation on the structural and magneto-transport properties
of iron intercalated Bi2Se3 single crystals have been presented. The x-ray
diffraction and Raman studies confirm the intercalation of Fe in the van der
Waals gaps between the layers. The electrical resistivity of the compounds
decreases upon intercalation, and Hall resistivity shows the enhancement of the
charge carriers upon intercalation. The magnetoresistance shows the
non-saturating linear behavior at higher magnetic field and low temperature.
Intercalation of Fe increases the onset of the linear magnetoresistance
behavior, indicating the reduction in quantum effects. The Kohler scaling
employed on the magnetoresistance data indicates single scattering process for
all these compounds in the measured temperature range of 3- 300 K.",2002.03609v2
2020-02-20,Tunable correlation-driven symmetry breaking in twisted double bilayer graphene,"A variety of correlated phases have recently emerged in select twisted van
der Waals (vdW) heterostructures owing to their flat electronic dispersions. In
particular, heterostructures of twisted double bilayer graphene (tDBG) manifest
electric field-tunable correlated insulating (CI) states at all quarter
fillings of the conduction band, accompanied by nearby states featuring
signatures suggestive of superconductivity. Here, we report electrical
transport measurements of tDBG in which we elucidate the fundamental role of
spontaneous symmetry breaking within its correlated phase diagram. We observe
abrupt resistivity drops upon lowering the temperature in the correlated
metallic phases neighboring the CI states, along with associated nonlinear
$I$-$V$ characteristics. Despite qualitative similarities to superconductivity,
concomitant reversals in the sign of the Hall coefficient instead point to
spontaneous symmetry breaking as the origin of the abrupt resistivity drops,
while Joule heating appears to underlie the nonlinear transport. Our results
suggest that similar mechanisms are likely relevant across a broader class of
semiconducting flat band vdW heterostructures.",2002.08904v1
2020-03-31,Efficiency Increase in Multijunction Monochromatic Photovoltaic Devices Due to Luminescent Coupling,"We present a multijunction detailed balance model that includes the effects
of luminescent coupling, light trapping and nonradiative recombination,
suitable for treatment of multijunction solar cells and photonic power
converters -- photovoltaic devices designed to convert narrow-band light. The
model includes both specular and Lambertian reflections using a ray-optic
formalism and treats nonradiative processes using an internal radiative
efficiency. Using this model, we calculate and optimize the efficiency of
multijunction photonic power converters for a range of material qualities and
light-trapping schemes. Multijunction devices allow increased voltage with
lower current, decreasing series resistance losses. We show that efficiency
increases significantly with increased number of junctions, even without series
resistance, when the device has an absorbing substrate. Such an increase does
not occur when the device has a back reflector. We explain this effect using a
simplified model, which illustrates the origin of the decreased radiative
losses in multijunction devices on substrates.",2004.00081v1
2020-04-15,Theory for Non-Fermi Liquid Temperature Dependence in Resistivity of Ce_xLa_{1-x} Cu_{5.62} Au_{0.38} (x=0.02-0.10) on the Local Quantum Valence Criticality of Ce Impurities,"It was reported by Shiino et al in J. Phys. Soc. Jpn. 86, 123705 (2017) that
Ce_xLa_{1-x} Cu_{5.62} Au_{0.38} (x=0.02-0.10) exhibits a new type of quantum
criticality in both magnetic and thermal properties, which is the same as that
observed in a series of materials exhibiting quantum critical valence
fluctuations (QCVF), such as \beta-YbAlB_4, Yb_{15}Al_{34}Au_{51}, and so on.
However, the temperature (T) dependence in the resistivity rho(T) for T<0.5K is
quite anomalous, i.e., \rho(T)\propto (const.-T^{n}) with n \simeq 0.75 at
x=0.05. We find that this anomalous exponent is given by n=2(1-\zeta), with
zeta being the weakly temperature dependent (0.5 \lsim \zeta \lsim 0.7)
critical exponent for the QCVF.The observed critical exponent n\simeq 0.75 at
x=0.05 is reproduced by choosing \zeta\simeq 0.63 which is consistent with the
divergent behavior observed in the uniform magnetic susceptibility \chi\propto
T^{-\zeta} with \zeta\simeq 0.67 at x=0.02.",2004.06869v1
2020-04-20,Anomalous pressure dependence of the electronic transport and anisotropy in SrIrO3 films,"Iridate oxides display exotic physical properties that arise from the
interplay between a large spin-orbit coupling and electron correlations. Here,
we present a comprehensive study of the effects of hydrostatic pressure on the
electronic transport properties of SrIrO3 (SIO), a system that has recently
attracted a lot of attention as potential correlated Dirac semimetal. Our
investigations on untwinned thin films of SIO reveal that the electrical
resistivity of this material is intrinsically anisotropic and controlled by the
orthorhombic distortion of the perovskite unit cell. These effects provide
another evidence for the strong coupling between the electronic and lattice
degrees of freedom in this class of compounds. Upon increasing pressure, a
systematic increase of the transport anisotropies is observed. The anomalous
pressure-induced changes of the resistivity cannot be accounted for by the
pressure dependence of the density of the electron charge carriers, as inferred
from Hall effect measurements. Moreover, pressure-induced rotations of the IrO6
octahedra likely occur within the distorted perovskite unit cell and affect
electron mobility of this system.",2004.09116v1
2022-02-07,Time-correlation functions for odd Langevin systems,"We investigate the statistical properties of fluctuations in active systems
that are governed by non-symmetric responses. Both an underdamped Langevin
system with an odd resistance tensor and an overdamped Langevin system with an
odd elastic tensor are studied. For a system in thermal equilibrium, the
time-correlation functions should satisfy time-reversal symmetry and the
anti-symmetric parts of the correlation functions should vanish. For the odd
Langevin systems, however, we find that the anti-symmetric parts of the
time-correlation functions can exist and that they are proportional to either
the odd resistance coefficient or the odd elastic constant. This means that the
time-reversal invariance of the correlation functions is broken due to the
presence of odd responses in active systems. Using the short-time asymptotic
expressions of the time-correlation functions, one can estimate an odd elastic
constant of an active material such as an enzyme or a motor protein.",2202.03225v3
2022-02-24,Resistivity anisotropy from the multiorbital Boltzmann equation in nematic FeSe,"We compute the resistivity anisotropy in the nematic phase of FeSe from the
static solution of the multiorbital Boltzmann equation. By introducing disorder
at the level of the microscopic multiorbital model we show that even elastic
scattering by localized impurities may lead to non-trivial anisotropic
renormalization of the electronic velocities, challenging the usual
understanding of transport based only on cold- and hot-spots effects. Our model
takes into account both the $xz/yz$ and the recently proposed $xy$ nematic
ordering. We show that the latter one has a crucial role in order to reproduce
the experimentally-measured anisotropy, providing a direct fingerprint of the
different nematic scenarios on the bulk transport property of FeSe.",2202.12070v2
2007-10-05,Strain-induced insulator state in La_0.7Sr_0.3CoO_3,"We report on the observation of a strain-induced insulator state in
ferromagnetic La_0.7Sr_0.3CoO_3 films. Tensile strain above 1% is found to
enhance the resistivity by several orders of magnitude. Reversible strain of
0.15% applied using a piezoelectric substrate triggers huge resistance
modulations, including a change by a factor of 10 in the paramagnetic regime at
300 K. However, below the ferromagnetic ordering temperature, the magnetization
data indicate weak dependence on strain for the spin state of the Co ions. We
interpret the changes observed in the transport properties in terms of a
strain-induced splitting of the Co e_g levels and reduced double exchange,
combined with a percolation-type conduction in an electronic cluster state.",0710.1306v1
2012-01-10,Giant resistance change across the phase transition in spin crossover molecules,"The electronic origin of a large resistance change in nanoscale junctions
incorporating spin crossover molecules is demonstrated theoretically by using a
combination of density functional theory and the non-equilibrium Green's
functions method for quantum transport. At the spin crossover phase transition
there is a drastic change in the electronic gap between the frontier molecular
orbitals. As a consequence, when the molecule is incorporated in a two terminal
device, the current increases by up to four orders of magnitude in response to
the spin change. This is equivalent to a magnetoresistance effect in excess of
3,000 %. Since the typical phase transition critical temperature for spin
crossover compounds can be extended to well above room temperature, spin
crossover molecules appear as the ideal candidate for implementing spin devices
at the molecular level.",1201.2028v2
2014-01-08,The features of contact resistivity behavior at helium temperatures for InP- and GaAs-based ohmic contacts,"Contact resistivity rc of InP and GaAs based ohmic contacts was measured in
the 4.2/300 K temperature range. Nonmonotonic dependences rc(T), with a minimum
at temperature 50 K (150 K) for InP (GaAs) based contacts were obtained. The
results can be explained within the framework of the mechanism of current flow
through metal shunts (associated with dislocations) penetrating into the
semiconductor bulk, with allowance being made for electron freeze-out at helium
temperatures. Contact ohmicity in the 4.2/30K temperature range is due to
accumulation band bending near shunt ends at the metal/semiconductor interface.",1401.1658v1
2016-03-16,Mathematical Modeling of CRISPR-CAS system effects on biofilm formation,"Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR), linked
with CRISPR associated (CAS) genes, play a profound role in the interactions
between phage and their bacterial hosts. It is now well understood that
CRISPR-CAS systems can confer adaptive immunity against bacteriophage
infections. However, the possibility of failure of CRISPR immunity may lead to
a productive infection by the phage (cell lysis) or lysogeny. Recently,
CRISPR-CAS genes have been implicated in changes to group behaviour, including
biofilm formation, of the bacterium Pseudomonas aeruginosa when lysogenized.
For lysogens with a CRISPR system, another recent experimental study suggests
that bacteriophage re-infection of previously lysogenized bacteria may lead to
cell death. Thus CRISPR immunity can have complex effects on phage-host-lysogen
interactions, particularly in a biofilm. In this contribution, we develop and
analyse a series of models to elucidate and disentangle these interactions.
From a therapeutic standpoint, CRISPR immunity increases biofilm resistance to
phage therapy. Our models predict that lysogens may be able to displace
CRISPR-immune bacteria in a biofilm, and thus suggest strategies to eliminate
phage resistant biofilms.",1603.05311v1
2017-04-10,Experimental determination of phonon thermal conductivity and Lorenz ratio of single crystal bismuth telluride,"We use a magnetothermal resistance method to measure the lattice thermal
conductivity of a single crystal of Bi$_2$Te$_3$ from 5 to 60 K. We apply a
large transverse magnetic field to suppress the electronic thermal conduction
while measuring thermal conductivity and electrical resistivity. The lattice
thermal conductivity is then calculated by extrapolating the thermal
conductivity versus electrical conductivity curve to a zero electrical
conductivity value. Our results show that the measured phonon thermal
conductivity follows the $e^{({\Delta}_{min}/T)}$ temperature dependence and
the Lorenz ratio corresponds to the modified Sommerfeld value in the
intermediate temperature range. Our low-temperature experimental data and
analysis on Bi$_2$Te$_3$ are an important compliment to previous measurements
of Goldsmid [14] and theoretical calculations by Broido $\textit{et al.}$ [21]
at higher temperature 100 - 300 K.",1704.03029v1
2017-04-12,Metal-Insulator Transition in Ga doped ZnO via Controlled Thickness,"We report thickness dependent metal insulator transition in Ga doped ZnO
(Ga:ZnO) thin films grown by pulsed laser deposition technique. From the
electrical transport measurements, we find that while the thinnest film
exhibits a resistivity of 0.05 $\Omega$-cm, lying in the insulating regime, the
thickest has resistivity of $6.6\times10^{-4}\Omega$-cm which shows metallic
type of conduction. Our analysis reveals that the Mott's variable range hopping
(VRH) model governs the insulating behavior in the thinner Ga:ZnO whereas the
2D weak localization phenomena is appropriate to explain the electron transport
in the thicker Ga:ZnO. Magnetoresistance study further confirms the presence of
strong localization in 6 nm film while weak localization is observed in 20 nm
and above thicker films. From the density functional calculations, it is found
that due to surface reconstruction and Ga doping, strong crystalline disorder
sets in very thin films to introduce localized states and thereby, restricts
the donor electron mobility.",1704.03846v1
2017-04-24,Spin injection into silicon detected by broadband ferromagnetic resonance spectroscopy,"We studied the spin injection in a NiFe(Py)/Si system using broadband
ferromagnetic resonance spectroscopy. The Gilbert damping parameter of the Py
layer on top of the Si channel was determined as a function of the Si doping
concentration and Py layer thickness. For fixed Py thickness we observed an
increase of the Gilbert damping parameter with decreasing resistivity of the Si
channel. For a fixed Si doping concentration we measured an increasing Gilbert
damping parameter for decreasing Py layer thickness. No increase of the Gilbert
damping parameter was found Py/Si samples with an insulating interlayer. We
attribute our observations to an enhanced spin injection into the
low-resistivity Si by spin pumping.",1704.07006v1
2017-05-27,Magnetic and magnetotransport properties of ThCr2Si2-type Ce2O2Bi composed of conducting Bi2- square net and magnetic Ce-O layer,"ThCr2Si2-type Ce2O2Bi epitaxial thin films were grown by recently developed
multilayer solid phase epitaxy. The ionic state of Ce was confirmed to be 3+ by
x-ray photoelectron spectroscopy, corresponding to the electronic configuration
of [Xe]4f1. Electrical resistivity showed the nonmonotonic temperature
dependence with a sharp resistivity maximum, concomitant with a magnetization
kink at 10 K, suggesting antiferromagnetic transition. In addition,
magnetoresistance showed a large angular-dependent magnetoresistance. These
results imply that carrier transport in the Bi2- square net could be influenced
by magnetic ordering in the Ce-O layer owing to its unique layered structure
[Bi2-/(Ce2O2)2+], particularly in the form of epitaxial thin films.",1705.09774v1
2017-07-03,Inverse spin Hall effect in Nd doped SrTiO3,"Conversion of spin to charge current was observed in SrTiO3 doped with Nd
(Nd:STO), which exhibited a metallic behavior even with low concentration
doping. The obvious variation of DC voltages for Py/Nd:STO, obtained by
inverting the spin diffusion direction, demonstrated that the detected signals
contained the contribution from the inverse spin Hall effect (ISHE) induced by
the spin dependent scattering from Nd impurities with strong spin-orbit
interaction. The DC voltages of the ISHE for Nd:STO were measured at different
microwave frequency and power, which revealed that spin currents were
successfully injected into doped STO layer by spin pumping. The linear relation
between the ISHE resistivity and the resistivity induced by impurities implied
that the skew scattering was the dominant contribution in this case, and the
spin Hall angle was estimated to be 0.17%. This work demonstrated that
extrinsic spin dependent scattering in oxides can be used in spintroics besides
that in heavy elements doped metals.",1707.00444v1
2017-07-27,Chiral transport along magnetic domain walls in the quantum anomalous Hall effect,"The recent prediction, and subsequent discovery, of the quantum anomalous
Hall (QAH) effect in thin films of the three-dimensional ferromagnetic
topological insulator (MTI) (Cr$_y$Bi$_x$Sb$_{1-x-y}$)$_2$Te$_3$ has opened new
possibilities for chiral-edge-state-based devices in zero external magnetic
field. Like the $\nu=1$ quantum Hall system, the QAH system is predicted to
have a single chiral edge mode circulating along the boundary of the film.
Backscattering of the chiral edge mode should be suppressed, as recently
verified by the observation of well-quantized Hall resistivities $\rho_{yx} =
\pm h/e^2$, along with longitudinal resistivities as low as a few ohms.
Dissipationless 1D conduction is also expected along magnetic domain walls.
Here, we intentionally create a magnetic domain wall in a MTI and study
electrical transport along the domain wall. We present the first observation of
chiral transport along domain walls, in agreement with theoretical predictions.
We present further evidence that two modes equilibrate and co-propagate along
the length of the domain wall.",1707.08677v1
2018-08-20,Theory of bilinear magneto-electric resistance from topological-insulator surface states,"We theoretically investigate a new kind of nonlinear magnetoresistance on the
surface of three-dimensional topological insulators (TIs). At variance with the
unidirectional magnetoresistance (UMR) effect in magnetic bilayers, this
nonlinear magnetoresistance does not rely on a conducting ferromagnetic layer
and scales linearly with both the applied electric and magnetic fields; for
this reason, we name it bilinear magneto-electric resistance (BMER). We show
that the sign and the magnitude of the BMER depends sensitively on the
orientation of the current with respect to the magnetic field as well as the
crystallographic axes -- a property that can be utilized to map out the spin
texture of the topological surface states via simple transport measurement,
alternative to the angle-resolved photoemission spectroscopy (ARPES).",1808.06339v1
2018-08-28,Impact of antiferromagnetic order on Landau level splitting of quasi-two-dimensional Dirac fermions in EuMnBi$_2$,"We report spin-split Landau levels of quasi-two-dimensional Dirac fermions in
a layered antiferromagnet EuMnBi$_2$, as revealed by interlayer resistivity
measurements in a tilted magnetic field up to $\sim$35 T. The amplitude of
Shubnikov-de Haas (SdH) oscillation in interlayer resistivity is strongly
modulated by changing the tilt angle of the field, i.e., the
Zeeman-to-cyclotron energy ratio. The effective $g$ factor estimated from the
tilt angle, where the SdH oscillation exhibits a phase inversion, differs by
approximately 50% between two antiferromagnetic phases. This observation
signifies a marked impact of the magnetic order of Eu sublattice on the
Dirac-like band structure. The origin may be sought in strong exchange coupling
with the local Eu moments, as verified by the first-principles calculation.",1808.09424v1
2018-08-31,Absence of superconductivity in pulsed laser deposited Au/Ag modulated nanostructured thin films,"We have grown Au/Ag modulated nanostructured thin films by pulsed laser
deposition using metallic targets. The growths performed at room temperature
involved deposition of alternate layers of the two metals with larger thickness
of Au and much lower thickness of Ag (two cases) on crystalline silicon (100)
and quartz substrates. However, the characterization revealed that
nanostructured configuration is realized in the film. We characterized the
films by x-ray diffraction (XRD), Field emission scanning electron microscopy
(FESEM) with energy dispersive analysis of x-rays (EDAX), magnetization (M-T)
and resistivity (Rho-T) measurements. The magnetization and resistivity
measurements confirm that there is no signature of superconducting transition
within the temperature range of 5K to 300K studied in these films.",1808.10699v1
2019-03-02,Turning ZrTe5 into semiconductor through atomic intercalation,"In this work, we use the liquid ammonia method to successfully intercalate
potassium atoms into ZrTe5 single crystal, and find a transition from semimetal
to semiconductor at low temperature in the intercalated ZrTe5. The resistance
anomalous peak is gradually suppressed and finally disappears with increasing
potassium concentration. Whilst, the according sign reversal is always observed
in the Hall resistance measurement. We tentatively attribute the
semimetal-semiconductor transition to the lattice expansion induced by atomic
intercalation and thereby a larger energy band gap.",1903.00644v1
2019-03-23,An In-situ Annealing effect of Graphene-Graphene Interlayer Conduction,"An interlayer distance modulation in twisted bilayer graphene is reported.
This is achieved by an in-situ annealing technique. The transformation of
systematic vacuum and hydrogen annealing effects in twisted bilayer CVD
graphene on SiO2 surface is reported based on experimental results. Incoherent
interlayer conduction is observed in the twisted bilayer device. In-situ
annealing efficiently removes the residues in the graphene-to-graphene
interface and enhances the interlayer conduction. We demonstrate
graphene-to-graphene interlayer resistance modulated by an order of magnetite
at 5 K. We also report on the behavior of molecular hydrogen on graphene
interlayer using the gate voltage-dependent resistance as a function of
temperature at atmospheric pressure. It was observed that interlayer conduction
in hydrogen/argon gas ambient is reduced. Results imply that modulation in the
interlayer distance of graphene-to-graphene junction, as determined by the
transport measurement investigation. Overall this result leads to the
possibility of making electrically tunable devices using twisted bilayer
graphene.",1903.09899v2
2019-04-05,Effect of density on microwave-induced resistance oscillations in back-gated GaAs quantum wells,"We report on microwave-induced resistance oscillations (MIROs) in a
tunable-density 30-nm-wide GaAs/AlGaAs quantum well. We find that the MIRO
amplitude increases dramatically with carrier density. Our analysis shows that
the anticipated increase in the effective microwave power and quantum lifetime
with density is not sufficient to explain the observed growth of the amplitude.
We further observe that the fundamental oscillation extrema move towards
cyclotron resonance with increasing density, which also contradicts theoretical
predictions. These findings reveal that the density dependence is not properly
captured by existing theories, calling for further studies.",1904.03140v1
2019-04-18,Determining Phonon Mean Free Path Spectrum by Ballistic Phonon Resistance within a Nanoslot-Patterned Thin Film,"At micro- to nano-scales, classical size effects in heat conduction play an
important role in suppressing the thermal transport process. Such effects occur
when the characteristic lengths become commensurate to the mean free paths
(MFPs) of heat carriers that are mainly phonons for nonmetallic crystals.
Beyond existing experimental efforts on thin films using laser-induced thermal
gratings, this work provides the complete theoretical analysis for a new
approach to extract the effective phonon MFP distribution for the in-plane heat
conduction within a thin film or flake-like sample. In this approach, nanoslots
are patterned on a suspended thin film. Phonons will transport ballistically
through the neck region between adjacent nanoslots if the phonon MFPs are much
longer than the neck width. The associated ""ballistic thermal resistance"" for
varied neck dimensions can then be used to reconstruct the phonon MFP
distribution within the film. The technique can be further extended to
two-dimensional materials when the relaxation time approximation is reasonably
accurate.",1904.08956v2
2019-08-23,Anomalous Kerr Effect in SrRuO$_3$ Thin Films,"We study the magneto-optical Kerr effect (MOKE) in SrRuO$_3$ thin films,
uncovering wide regimes of wavelength, temperature, and magnetic field where
the Kerr rotation is not simply proportional to the magnetization but instead
displays two-component behavior. One component of the MOKE signal tracks the
average magnetization, while the second ""anomalous"" component bears a
resemblance to anomalies in the Hall resistivity which have been previously
reported in skyrmion materials. We present a theory showing that the MOKE
anomalies arise from the non-monotonic relation between the Kerr angle and the
magnetization, when we average over magnetic domains which proliferate near the
coercive field. Our results suggest that inhomogeneous domain formation, rather
than skyrmions, may provide a common origin for the observed MOKE and Hall
resistivity anomalies.",1908.08974v2
2019-08-29,Evidence for weak antilocalization-weak localization crossover and metal-insulator transition in CaCu$_{3}$Ru$_{4}$O$_{12}$ thin films,"Artificial confinement of electrons by tailoring the layer thickness has
turned out to be a powerful tool to harness control over competing phases in
nano-layers of complex oxides. We investigate the effect of dimensionality on
transport properties of $d$-electron based heavy-fermion metal
CaCu$_{3}$Ru$_{4}$O$_{12}$. Transport behavior evolves from metallic to
localized regime upon reducing thickness and a metal insulator transition is
observed below 3 nm film thickness for which sheet resistance crosses $h/e^{2}
\sim 25~$k$\Omega$, the quantum resistance in 2D. Magnetotransport study
reveals a strong interplay between inelastic and spin-orbit scattering lengths
upon reducing thickness, which results in weak antilocalization (WAL) to weak
localization (WL) crossover in magnetoconductance.",1908.11128v2
2021-01-17,Surface-Wave Propagation on Non-Hermitian Metasurfaces with Extreme Anisotropy,"Electromagnetic metasurfaces enable the advanced control of surface-wave
propagation by spatially tailoring the local surface reactance. Interestingly,
tailoring the surface resistance distribution in space provides new, largely
unexplored degrees of freedom. Here, we show that suitable spatial modulations
of the surface resistance between positive (i.e., loss) and negative (i.e.,
gain) values can induce peculiar dispersion effects, far beyond a mere
compensation. Taking inspiration from the parity-time symmetry concept in
quantum physics, we put forward and explore a class of non-Hermitian
metasurfaces that may exhibit extreme anisotropy mainly induced by the
gain-loss interplay. Via analytical modeling and full-wave numerical
simulations, we illustrate the associated phenomenon of surface-wave
canalization, explore nonlocal effects and possible departures from the ideal
conditions, and address the feasibility of the required constitutive
parameters. Our results suggest intriguing possibilities to dynamically
reconfigure the surface-wave propagation, and are of potential interest for
applications to imaging, sensing and communications.",2101.06641v1
2012-06-11,Multiorbital effects on the transport and the superconducting fluctuations in LiFeAs,"The resistivity, Hall effect and transverse magnetoresistance (MR) have been
measured in low residual resistivity single crystals of LiFeAs. A comparison
with angle resolved photoemission spectroscopy and quantum oscillation data
implies that four carrier bands unevenly contribute to the transport. However
the scattering rates of the carriers all display the T^2 behavior expected for
a Fermi liquid. Near Tc low field deviations of the MR with respect to a H^2
variation permit us to extract the superconducting fluctuation contribution to
the conductivity. Though below Tc the anisotropy of superconductivity is rather
small, the superconducting fluctuations display a quasi ideal two-dimensional
behavior which persists up to 1.4 Tc. These results call for a refined
theoretical understanding of the multiband behavior of superconductivity in
this pnictide.",1206.2278v2
2015-04-27,Two types of nematicity in the phase diagram of the cuprate superconductor YBa$_2$Cu$_3$O$_y$,"Nematicity has emerged as a key feature of cuprate superconductors, but its
link to other fundamental properties such as superconductivity, charge order
and the pseudogap remains unclear. Here we use measurements of transport
anisotropy in YBa$_2$Cu$_3$O$_y$ to distinguish two types of nematicity. The
first is associated with short-range charge-density-wave modulations in a
doping region near $p = 0.12$. It is detected in the Nernst coefficient, but
not in the resistivity. The second type prevails at lower doping, where there
are spin modulations but no charge modulations. In this case, the onset of
in-plane anisotropy - detected in both the Nernst coefficient and the
resistivity - follows a line in the temperature-doping phase diagram that
tracks the pseudogap energy. We discuss two possible scenarios for the latter
nematicity.",1504.06972v3
2015-06-29,Magnetization and magneto-transport studies on Fe$_2$VAl$_{1-x}$Si$_x$,"We report on magnetoresistance, Hall and magnetization measurements of
Fe2VAl1-xSix Heusler compounds for x= 0.005, 0.015, 0.02. There is a systematic
change in the temperature coefficient of resistance (TCR) from negative to
positive as the Si composition is increased. The Hall co-efficient shows that
the carriers are electron like and the carrier density increases with Si
concentration. Resistance measurements under magnetic field indicate a
decreasing behavior under the application of magnetic field at low temperature
region (T< 60 K), suggesting the suppression of scattering by magnetic field.
Temperature and field dependent magnetization measurements did not show any
significant change apart from the fact that the presence of super paramagnetic
(SPM) cluster and its ordering at low temperatures. Arrott plot analysis of
magnetization versus field also indicates the magnetic ordering with applied
field below 60 K.",1506.08516v1
2015-07-07,Two-dimensional superconductor-insulator quantum phase transitions in an electron-doped cuprate,"We use ionic liquid-assisted electric field effect to tune the carrier
density in an electron-doped cuprate ultrathin film and cause a two-dimensional
superconductor-insulator transition (SIT). The low upper critical field in this
system allows us to perform magnetic field (B)-induced SIT in the liquid-gated
superconducting film. Finite-size scaling analysis indicates that SITs induced
both by electric and magnetic field are quantum phase transitions and the
transitions are governed by percolation effects - quantum mechanical in the
former and classical in the latter case. Compared to the hole-doped cuprates,
the SITs in electron-doped system occur at critical sheet resistances (Rc) much
lower than the pair quantum resistance RQ=h/(2e)2=6.45 k{\Omega}, suggesting
the possible existence of fermionic excitations at finite temperature at the
insulating phase near SITs.",1507.01668v1
2015-07-07,S-wave Superconductivity in Optimally Doped SrTi$_{1-x}$Nb$_x$O$_3$ Unveiled by Electron Irradiation,"We report on a study of electric resistivity and magnetic susceptibility
measurements in electron irradiated SrTi$_{0.987}$Nb$_{0.013}$O$_3$ single
crystals. Point-like defects, induced by electron irradiation, lead to an
almost threefold enhancement of the residual resistivity, but barely affect the
superconducting critical temperature ($T_c$). The pertinence of Anderson's
theorem provides strong evidence for a s-wave superconducting order parameter.
Stronger scattering leads to a reduction of the effective coherence length
($\xi$) and the deduced coherence length in the clean limit ($\xi_0$) is around
the BCS coherence length ($\xi_{BCS}$). Combined with thermal conductivity data
pointing to multiple nodeless gaps, the current results identify optimally
doped SrTi$_{1-x}$Nb$_x$O$_3$ as a multi-band s-wave superconductor.",1507.01867v2
2015-07-15,Depinning of Trapped Magnetic Flux in Bulk Niobium SRF Cavities,"Trapped magnetic flux is known to be a significant contribution to the
residual resistance of superconducting radio frequency (SRF) cavities. The
additional losses depend strongly if the vortices are depinned by the RF. The
depinning is affected by the purity of the material, and the size of the
pinning centers, as well as the cavity operation frequency. One may define a
depinning frequency, above which significant depinning occurs. This publication
presents a derivation of the depinning frequency from experimental data. We
find a depinning frequency of 673 MHz for RRR 110 niobium. On this basis the
currently used model is extended to describe the trapped flux sensitivity as
function of residual resistance ratio (RRR) and operation frequency while also
accounting for the pinning center size and the treatment history of the cavity.
Moreover, the model offers an explanation for the significantly higher trapped
flux sensitivity reported for nitrogen doped and 120 C baked cavities.",1507.04105v1
2016-09-08,Pressure-induced topological phase transition in polar semiconductor BiTeBr,"We performed X-ray diffraction and electrical resistivity measurement up to
pressures of 5 GPa and the first-principles calculations utilizing experimental
structural parameters to investigate the pressure-induced topological phase
transition in BiTeBr having a noncentrosymmetric layered structure (space group
P3m1). The P3m1 structure remains stable up to pressures of 5 GPa; the ratio of
lattice constants, c/a, has a minimum at pressures of 2.5 - 3 GPa. In the same
range, the temperature dependence of resistivity changes from metallic to
semiconducting at 3 GPa and has a plateau region between 50 and 150 K in the
semiconducting state. Meanwhile, the pressure variation of band structure shows
that the bulk band-gap energy closes at 2.9 GPa and re-opens at higher
pressures. Furthermore, according to the Wilson loop analysis, the topological
nature of electronic states in noncentrosymmetric BiTeBr at 0 and 5 GPa are
explicitly revealed to be trivial and non-trivial, respectively. These results
strongly suggest that pressure-induced topological phase transition in BiTeBr
occurs at the pressures of 2.9 GPa.",1609.02274v1
2016-09-27,Anomalous Feedback and Negative Domain Wall Resistance,"Magnetic induction can be regarded as a negative feedback effect, where the
motive-force opposes the change of magnetic flux that generates the
motive-force. In artificial electromagnetics emerging from spintronics,
however, this is not necessarily the case. By studying the current-induced
domain wall dynamics in a cylindrical nanowire, we show that the spin
motive-force exerting on electrons can either oppose or support the applied
current that drives the domain wall. The switching into the anomalous feedback
regime occurs when the strength of the dissipative torque {\beta} is about
twice the value of the Gilbert damping constant {\alpha}. The anomalous
feedback manifests as a negative domain wall resistance, which has an analogy
with the water turbine.",1609.08250v1
2018-07-19,General theory of topological Hall effect in systems with chiral spin textures,"We present a consistent theory of the topological Hall effect (THE) in 2D
magnetic systems with disordered array of chiral spin textures, such as
magnetic skyrmions. We focus on the scattering regime when the mean-free path
of itinerant electrons exceeds the spin texture size, and THE arises from the
asymmetric carrier scattering on individual chiral spin textures. We calculate
the resistivity tensor on the basis of the Boltzmann kinetic equation taking
into account the asymmetric scattering on skyrmions via the collision integral.
Our theory describes both the adiabatic regime, when THE arises from a spin
Hall effect and the non-adiabatic scattering when THE is due to purely charge
transverse currents. We analyze the dependence of THE resistivity on a chiral
spin texture structure,as well as on material parameters. We discuss the
crossover between spin and charge regimes of THE driven by the increase of
skyrmion size, the features of THE due to the variation of the Fermi energy,
and the exchange interaction strength; we comment on the sign and magnitude of
THE",1807.07396v1
2018-12-21,Thermoelectric transport in two-dimensional topological insulator state based on HgTe quantum well,"The thermoelectric response of HgTe quantum wells in the state of
two-dimensional topological insulator (2D TI) has been studied experimentally.
Ambipolar thermopower, typical for an electron-hole system, has been observed
across the charge neutrality point, where the carrier type changes from
electrons to holes according to the resistance measurements. The hole-type
thermopower is much stronger than the electron-type one. The thermopower
linearly increases with temperature. We present a theoretical model which
accounts for both the edge and bulk contributions to the electrical
conductivity and thermoelectric effect in a 2D TI, including the effects of
edge to bulk leakage. The model, contrary to previous theoretical studies,
demonstrates that the 2D TI is not expected to show anomalies of thermopower
near the band conductivity threshold, which is consistent with our experimental
results. Based on the experimental data and theoretical analysis, we conclude
that the observed thermopower is mostly of the bulk origin, while the
resistance is determined by both the edge and bulk transport.",1812.09226v1
2019-01-09,Crystal structures and the sign reversal Hall resistivity in iron-based superconductors Lix(C3H10N2)0.32FeSe (0.15<x<0.4),"We report the crystal structure, superconductivity and normal state
properties of two iron-based materials, Li0.15(C3H10N2)0.32FeSe(P-4) and
Lix(C3H10N2)0.32FeSe(P4/nmm, 0.25<x<0.4) with superconducting transition
temperature from 40~46K. The determined crystal structures revealed a coupling
between Li concentration and the oritation of 1,2-Diaminopropane molecules
within the hyper expanded FeSe layers. Further fitting on resistivity in terms
of the Lawence-Doniach model suggests the two superconductors belong to the
quasi-two dimonsional system. With increasing temperature, a differences in
crystal structures and doping levels. First principle calculations revealed the
increase in FeSe layer diatance will restruct the Fermi surface and generate a
new hole pocket around Gamma point in the Brillouin Zone. Our findings support
that the increase in two dimensionalities will leads to a temperature induced
Lifshitz transition in electron doped FeSe superconductors.",1901.02580v1
2019-01-18,Tuning electric charge scattering in YBCO single crystals via irradiation with MeV electrons,"Irradiation with electrons is an efficient approach to inducing a large
number of defects with a minimal impact on the material itself. Analysis of the
energy transfer from an accelerated particle smashing into the crystal lattice
shows that only electrons with MeV energies produce point defects in the form
of interstitial ions and vacancies that form perfect scattering centers. Here,
we investigate the changes in the resistive characteristics of YBCO single
crystals from the 1-2-3 system after several steps of low-temperature
irradiation with $0.5-2.5$\,MeV electrons and irradiation doses of up to
$8.8\times10^{18}$\,cm$^{-2}$. The penetration depth of such electrons is much
larger than the crystal thickness. We reveal that defects appearing in
consequence of such electron irradiation not only increase the residual
resistance, but they affect the phonon spectrum of the system and lower the
superconducting transition temperature linearly with increase of the
irradiation dose. Furthermore, the irradiation-induced defects are distributed
non-uniformly, that manifests itself via a broadening of the superconducting
transition. Interestingly, the excess conductivity remains almost unaffected
after such electron irradiation.",1901.06293v1
2019-06-11,Characterisation of Li in the surface film of a corrosion resistant Mg-Li(-Al-Y-Zr) alloy,"The surface film formed upon Mg-Li(-Al-Y-Zr) following aqueous immersion and
air-exposure was investigated. This alloy (which contains 30.3 at. % Li)
possesses a bcc crystal structure and has been reported as being corrosion
resistant. It was determined that the principal components of the surface film
were Li2CO3 and Mg(OH)2 as characterised by grazing incidence X-ray diffraction
(GIXRD). The detection of hcp grains near the alloy surface was observed by
GIXRD and selected area electron diffraction (SAED). The spatial distribution
of Li and Mg in the surface film was characterised by electron energy loss
spectroscopy (EELS) and the distribution of other major elements in the alloy
was characterised by scanning transmission electron microscopy (STEM) and
energy dispersive X-ray spectroscopy (EDXS). It was observed that Li was
distributed throughout the alloy surface film and with an elevated
concentration in the so-called outer layer.",1906.04508v1
2019-06-11,Electrical Switching of Tristate Antiferromagnetic Néel Order in $α$-Fe$_{2}$O$_{3}$ Epitaxial Films,"The ability to manipulate antiferromagnetic (AF) moments is a key requirement
for the emerging field of antiferromagnetic spintronics. Electrical switching
of bi-state AF moments has been demonstrated in metallic AFs, CuMnAs and
Mn$_2$Au. Recently, current-induced ""saw-tooth"" shaped Hall resistance was
reported in Pt/NiO bilayers, while its mechanism is under debate. Here, we
report the first demonstration of convincing, non-decaying, step-like
electrical switching of tri-state N\'eel order in Pt/$\alpha$-Fe$_2$O$_3$
bilayers. Our experimental data, together with Monte-Carlo simulations, reveal
the clear mechanism of the switching behavior of $\alpha$-Fe$_2$O$_3$ N\'eel
order among three stable states. We also show that the observed ""saw-tooth""
Hall resistance is due to an artifact of Pt, not AF switching, while the
signature of AF switching is step-like Hall signals. This demonstration of
electrical control of magnetic moments in AF insulator (AFI) films will greatly
expand the scope of AF spintronics by leveraging the large family of AFIs.",1906.04694v2
2019-10-01,Valley Hall Effect and Non-Local Resistance in Locally Gapped Graphene,"We report on the emergence of bulk, valley-polarized currents in
graphene-based devices, driven by spatially varying regions of broken
sublattice symmetry, and revealed by non-local resistance ($R_\mathrm{NL}$)
fingerprints. By using a combination of quantum transport formalisms, giving
access to bulk properties as well as multi-terminal device responses, the
presence of a non-uniform local bandgap is shown to give rise to
valley-dependent scattering and a finite Fermi surface contribution to the
valley Hall conductivity, related to characteristics of $R_\mathrm{NL}$. These
features are robust against disorder and provide a plausible interpretation of
controversial experiments in graphene/hBN superlattices. Our findings suggest
both an alternative mechanism for the generation of valley Hall effect in
graphene, and a route towards valley-dependent electron optics, by materials
and device engineering.",1910.00489v2
2019-11-14,Free-standing silicon shadow masks for transmon qubit fabrication,"Nanofabrication techniques for superconducting qubits rely on resist-based
masks patterned by electron-beam or optical lithography. We have developed an
alternative nanofabrication technique based on free-standing silicon shadow
masks fabricated from silicon-on-insulator wafers. These silicon shadow masks
not only eliminate organic residues associated with resist-based lithography,
but also provide a pathway to better understand and control surface-dielectric
losses in superconducting qubits by decoupling mask fabrication from substrate
preparation. We have successfully fabricated aluminum 3D transmon
superconducting qubits with these shadow masks and found coherence quality
factors comparable to those fabricated with standard techniques.",1911.05924v2
2019-11-21,Experimental Realization of a Reconfigurable Electroacoustic Topological Insulator,"A substantial challenge in guiding elastic waves is the presence of
reflection and scattering at sharp edges, defects, and disorders. Recently,
mechanical topological insulators have sought to overcome this challenge by
supporting back-scattering resistant wave transmission. In this Letter, we
propose and experimentally demonstrate the first \emph{reconfigurable
electroacoustic} topological insulator exhibiting an analog to the quantum
valley Hall effect (QVHE). Using programmable switches, this phononic structure
allows for rapid reconfiguration of domain walls and thus the ability to
control back-scattering resistant wave propagation along dynamic interfaces for
phonons lying in static and finite-frequency regimes. Accordingly, a
graphene-like Polyactic Acid (PLA) layer serves as the host medium, equipped
with periodically arranged and bonded piezoelectric patches, resulting in two
Dirac cones at the $K-$points. The PZT patches are then connected to negative
capacitance external circuits to break inversion symmetry and create nontrivial
topologically-protected bandgaps. As such, topologically protected interface
waves are demonstrated numerically and validated experimentally for different
predefined trajectories over a broad frequency range.",1911.09608v1
2020-01-07,Joule heating in the normal-superconductor phase transition in a magnetic field,"Joule heating is a non-equilibrium dissipative process that occurs in a
normal metal when an electric current flows, in an amount proportional to the
metal's resistance. When it is induced by eddy currents resulting from a change
in magnetic flux, it is also proportional to the rate at which the magnetic
flux changes. Here we show that in the phase transformation between normal and
superconducting states of a metal in a magnetic field, the total amount of
Joule heating is determined by the thermodynamic properties of the system and
is independent of the resistivity of the normal metal. We also show that Joule
heating only occurs in the normal region of the material. The conventional
theory of superconductivity however predicts that Joule heating occurs also in
the superconducting region within a London penetration depth of the phase
boundary. This implies that there is a problem with the conventional theory of
superconductivity.",2001.07509v2
2020-05-05,Study of single crystalline SrAgSb and SrAuSb semimetals,"Given renewed interest in the electronic properties of semimetallic compounds
with varying degrees of spin orbit coupling we have grown single crystals of
SrAgSb and SrAuSb, measured their temperature and field dependent electrical
resistivity and magnetization and performed density functional theory (DFT)
band structure calculations. Magnetization measurements are consistent with a
diamagnetic host with a small amount of local moment bearing impurities.
Although the residual resistivity ratio (RRR) for all samples studied was
relatively low, ranging between 2.4 and 3.4, the compounds had non-saturating
magnetoresistance (MR), reaching values of $\sim$ 17% and $\sim$ 70% at 4 K and
9 T for SrAgSb and SrAuSb respectively. Band structure calculations, using the
experimentally determined Wyckoff positions for the Sr, Ag/Au, and Sb atoms,
show that whereas SrAgSb is a topologically trivial, but compensated,
semimetal; SrAuSb is a topologically non-trivial, Dirac semimetal.",2005.02323v1
2020-05-12,Large anisotropic topological Hall effect in a hexagonal non-collinear magnet Fe5Sn3,"We report the observation of a large anisotropic topological Hall effect
(THE) in the hexagonal non-collinear magnet Fe5Sn3 single crystals. It is found
that the sign of the topological Hall resistivity is negative when a magnetic
field H perpendicular to the bc-plane (H\perp bc-plane), however, it changes
form negative to positive when H parallel to the c-axis (H\parallel c-axis).
The value of topological Hall resistivity increased with the increasing
temperature and reached approximately -2.12 \mu\Omega cm (H\perp bc-plane) and
0.5 \mu\Omega cm (H\parallel c-axis) at 350 K, respectively. Quantitative
analyses of the measured data suggest that the observed anisotropic THE may
originate from the opposite scalar spin chirality induced by the magnetic
fields perpendicular and parallel to the c-axis, respectively.",2005.05709v1
2020-05-16,Defect Level Switching for Highly-Nonlinear and Hysteretic Electronic Devices,"Nonlinear and hysteretic electrical devices are needed for applications from
circuit protection to next-generation computing. Widely-studied devices for
resistive switching are based on mass transport, such as the drift of ions in
an electric field, and on collective phenomena, such as insulator-metal
transitions. We ask whether the large photoconductive response known in many
semiconductors can be stimulated in the dark and harnessed to design electrical
devices. We design and test devices based on photoconductive CdS, and our
results are consistent with the hypothesis that resistive switching arises from
point defects that switch between deep- and shallow-donor configurations:
defect level switching (DLS). This new electronic device design principle -
photoconductivity without photons - leverages decades of research on
photoconductivity and defect spectroscopy. It is easily generalized and will
enable the rational design of new nonlinear, hysteretic devices for future
electronics.",2005.07935v1
2020-06-04,Competition between ferromagnetic and antiferromagnetic states in Al8.5-xFe23Ge12.5+x (0<=x<=3),"Polycrystalline Al7+xFe23Ge14-x-type orthorhombic Al8.5-xFe23Ge12.5+x
(0<=x<=3) compounds were studied by X-ray diffraction measurement,
metallographic examination, and magnetization and electrical resistivity
measurements. The lattice parameters show anisotropic x dependences, reflecting
a lower symmetry of rather complex crystal structure. In the x=0 sample, a
ferromagnetic (FM) transition occurs at the Curie temperature TC of 255 K,
which is systematically reduced with increasing x and disappears at x=2.5 where
an antiferromagnetic (AFM) ground state is realized. The Neel temperature TN
seems to appear at x>=1, and grows to 143 K at x=3 with the increment of x. In
the intermediate range of x (1<=x<=2), a FM to AFM phase transition occurs
below TC. In the AFM phase, the electrical resistivity rho shows a Fermi
surface instability characterized by the upturn of rho below approximately TN.
The competition between the FM and AFM states would be ascribed to the
anisotropic x dependences of Fe-Fe bond lengths.",2006.03152v1
2020-06-08,Anisotropic physical properties and large critical current density in KCa${_2}$Fe${_4}$As${_4}$F${_2}$ single crystal,"We present a systematic study of electrical resistivity, Hall coefficient,
magneto-optical imaging, magnetization, and STEM analyses of
KCa${_2}$Fe${_4}$As${_4}$F${_2}$ single crystals. Sharp diamagnetic transition
and magneto-optical imaging reveal homogeneity of single crystal and prominent
Bean-like penetrations of vortices. Large anisotropy of electrical resistivity,
with ${\rho _c / \rho _{ab}}$ > 100, and semiconductor-like ${\rho _c}$ suggest
that the electronic state is quasi two-dimensional. Hall effect measurements
indicate that KCa${_2}$Fe${_4}$As${_4}$F${_2}$ is a multiband system with holes
as main carriers. Magnetization measurements reveal significantly larger J$_c$
compared with that in other iron-based superconductors with different values of
J$_c$ depending on the direction of magnetic field. Origin of these J$_c$
characteristics is discussed based on microstructural observations using STEM.
In addition, further enhancement of J$_c$ in KCa${_2}$Fe${_4}$As${_4}$F${_2}$
for future application is demonstrated in terms of heavy-ion irradiation.",2006.04478v1
2020-06-12,Unraveling ferroelectric polarization and ionic contributions to electroresistance in epitaxial Hf0.5Zr0.5O2 tunnel junctions,"Tunnel devices based on ferroelectric Hf0.5Zr0.5O2 (HZO) barriers hold great
promises for emerging data storage and computing technologies. The resistance
state of the device can be changed by a suitable writing voltage. However, the
microscopic mechanisms leading to the resistance change are an intricate
interplay between ferroelectric polarization controlled barrier properties and
defect-related transport mechanisms. Here is shown the fundamental role of the
microstructure of HZO films setting the balance between those contributions.
The oxide film presents coherent or incoherent grain boundaries, associated to
the existence of monoclinic and orthorhombic phases in HZO films, which are
dictated by the mismatch with the substrates for epitaxial growth. These grain
boundaries are the toggle that allows to obtain either large (up to 450 %) and
fully reversible genuine polarization controlled electroresistance when only
the orthorhombic phase is present or an irreversible and extremely large
(1000-100000 %) electroresistance when both phases coexist.",2006.07093v1
2020-06-30,2D MoSe2 as a Promising Chemo-resistive Sensor for N2O Detection: A DFT Approach,"We have investigated the impact of toxic N2O gas upon structural and
electronic properties of 2D MoSe2 monolayer using DFT approach. In this work,
as a result of N2O gas absorption, charge transfer, band gap and density of
states (DOS) are changed and these parameters are extracted as electronic
properties of 2D MoSe2 monolayer nano-gas sensor. Moreover, the band gap is
tunable upon the N2O gas absorption for pristine and adsorbed MoSe2 in both Top
Mo (Top Se) structures. Also, the spin up and down states in the DOS results
considerable magnetic moment altering the magnetic property of the 2D MoSe2
monolayer. Later, the desorption property of the 2D MoSe2 monolayer towards the
target N2O gas molecule at three different temperature are calculated. Thus,
the paper concludes with outcomes of the structural and electronic properties
aligning its behavior as a chemo-resistive nano-gas sensor and showing it as a
potential applicant for sensing of toxic N2O gas molecule. The nature of toxic
N2O gas molecule is not explored till date using 2D monolayer, thus, in this
work it is estimated through simulated results and the experimental
verification is awaited.",2006.16698v2
2020-07-09,"Magnetoresistance scaling, disorder, `hot spots' and the origin of $T$-linear resistivity in BaFe$_2$(As$_{1-x}$P$_x$)$_2$","The scaling of $H$-linear magnetoresistance in field and temperature was
measured in under-doped (x = 0.19) and optimally-doped
(x=0.31)~BaFe$_2$(As$_{1-x}$P$_x$)$_2$. We analyze the data based on an orbital
model in the presence of strongly anisotropic quasiparticle spectra and
scattering time due to antiferromagnetism. The magnetoresistance is dominated
by the properties of small regions of the Fermi surface called `hot spots'
where antiferromagnetic excitations induce a large quasiparticle scattering
rate. Approximate temperature-magnetic field scaling relations are derived and
shown to be consistent with the experimental data. We argue that these results
link the origin of linear-in-temperature resistivity to hot spots arising from
an antiferromagnetic critical point, and magnetoresistance measurements provide
a route to quantify this link.",2007.04970v1
2020-07-28,A Novel Compact Si-B-N Barrier on Mg-Li Alloys via Plasma Treatment,"Mg-Li alloys have attracted much attention due to their superior properties.
However, it is a great challenge to improve their inferior oxidation and
corrosion resistance. We report a novel Si-B-N ceramic film deposited on the
Mg-9.6Li alloy surface as an effective barrier against oxidation and corrosion.
The films were deposited by using plasma enhanced chemical vapor deposition
from a N2-B2H6-SiH4 gas mixtures, showing compact structure and adhesive
attachment to the alloy surface. The barrier revealed excellent protection
against oxidation in humid air for 500 days, and no observable changes were
found in immersion test of the 3.5 wt.% NaCl solution for 10 min. The superior
oxidation and corrosion resistance are attributed to the excellent material
property of Si-B-N coatings with compact structure via plasma treatment.
Moreover, it is found that moderate proportion of B_2 H_6 in the source gas
mixture is beneficial to the protection of alloys, where the hydrogen release
reaction nearly disappeared and no bubbles were generated on the surface in the
immersion test.",2007.14170v1
2020-08-13,Resistivity saturation in Kondo insulators,"Resistivities of heavy-fermion insulators typically saturate below a
characteristic temperature $T^*$. For some, metallic surface states,
potentially from a non-trivial bulk topology, are a likely source of residual
conduction. Here, we establish an alternative mechanism: At low temperature, in
addition to the charge gap, the scattering rate turns into a relevant energy
scale, invalidating the semiclassical Boltzmann picture. Finite lifetimes of
intrinsic carriers limit conduction, impose the existence of a crossover $T^*$,
and control - now on par with the gap - the quantum regime emerging below it.
We showcase the mechanism with realistic many-body simulations and elucidate
how the saturation regime of the Kondo insulator Ce$_3$Bi$_4$Pt$_3$, for which
residual conduction is a bulk property, evolves under external pressure and
varying disorder. Using a phenomenological formula we derived for the quantum
regime, we also unriddle the ill-understood bulk conductivity of SmB$_6$ -
demonstrating that our mechanism is widely applicable to correlated narrow-gap
semiconductors.",2008.05846v1
2020-08-21,"Growth and anisotropy evaluation of NbBiCh$_3$ (Ch = S, Se) misfit-layered superconducting single crystals","NbBiCh$_3$ (Ch = S, Se) misfit-layered superconducting single crystals were
successfully grown using a CsCl/KCl flux for the first time. The obtained
crystals had a well-developed habit parallel to the c-plane with a typical
width of 1-2 mm and thickness of 10-40 um. The superconducting transition
temperatures with zero resistivity of NbBiS$_3$ single crystals obtained from
the nominal composition of Nb0.9Bi1.2S3 was 0.31 K, and that value of the
NbBiSe$_3$ single crystals grown from the stoichiometry composition
(NbBiSe$_3$) was 2.3 K. Sharp decreases in electric resistivity and magnetic
susceptibility at approximately 3 K suggested a possible superconducting
transition temperature of NbBiSe$_3$. The normal-state anisotropy values of
grown NbBiS$_3$ and NbBiSe$_3$ single crystals were 2.2-2.4 and 1.5-1.6,
respectively.",2008.09322v1
2020-08-27,Core-structure and lattice resistance of twinning dislocations in fcc metals,"Metals with fcc structure may exhibit deformation twinning under specific
conditions, which is an interesting but somewhat elusive aspect of their
deformation behavior. It is well acknowledged that the phenomenon occurs
through the activities of twinning partial dislocations. However, the lack of a
comprehensive understanding of their fundamental properties obstructs the
development of detailed multiscale models of crystal plasticity in the fcc
metals. Here we explore the core-structures and lattice friction of twinning
partials through atomistically informed numerical modeling. To this end, we
choose four fcc crystals with widely differing stacking fault energies. Using
the semi-discrete variational Peierls Nabarro model, we compute the core-widths
and Peierls stresses of edge and screw twinning dislocations. Apart from the
conventional layer-by-layer model of twin nucleation, the recently proposed
alternate-shear model has also been examined. In the latter case, a negative
stable fault energy has been observed, which is large enough to overcome the
Peierls barrier. This study also highlights the significance of incorporating
the surface correction, the absence of which leads to an overestimation of the
intrinsic lattice resistance of the twinning dislocations.",2008.11937v1
2020-10-11,Electrical properties of thermal oxide scales on pure iron in liquid lead-bismuth eutectic,"The impedance behavior of pre-oxidized iron in liquid lead-bismuth eutectic
(LBE) at 200 oC is studied using electrochemical impedance spectroscopy. The
structures and resistance of oxide grown on iron oxidized in air at different
temperatures and durations are compared. The results show that the resistance
of the oxide film increases with increasing oxidizing temperature, due to the
formation of a thicker scale and fewer defects. At the same temperature (600
oC), increasing the oxidation time can also reduce the defect concentration in
the oxide film and improve the impedance of the oxide scale in LBE.",2010.05372v1
2020-10-14,Competing spin modulations in a magnetically frustrated semimetal EuCuSb,"The competing magnetic ground states of the itinerant magnet EuCuSb, which
has a hexagonal layered structure, were studied via magnetization, resistivity,
and neutron diffraction measurements on single-crystal samples. EuCuSb has a
three-dimensional semimetallic band structure as confirmed by band calculation
and angle-resolved photoelectron spectroscopy, consistent with the nearly
isotropic metallic conductivity in the paramagnetic state. However, below the
antiferromagnetic transition temperature of TN1 (8.5 K), the resistivity,
especially along the hexagonal axis, increases significantly. This implies the
emergence of anisotropic magnetic ordering coupled to the conducting electrons.
Neutron diffraction measurements show that the Eu spins, which order
ferromagnetically within each layer, are collinearly modulated
(up-up-down-down) along the hexagonal axis below TN1, followed by the partial
emergence of helical spin modulation below TN2 (6 K). Based on the observation
of anomalous magnetoresistance with hysteretic behavior, we discuss the
competing nature of the ground state inherent in a frustrated Heisenberg-like
spin system with a centrosymmetric structure.",2010.06841v1
2020-10-20,Strange metals as ersatz Fermi liquids,"A long standing mystery of fundamental importance in correlated electron
physics is to understand strange non-Fermi liquid metals that are seen in
diverse quantum materials. A striking experimental feature of these metals is a
resistivity that is linear in temperature ($T$). In this paper we ask what it
takes to obtain such non-Fermi liquid physics down to zero temperature in a
translation invariant metal. If in addition the full frequency ($\omega$)
dependent conductivity satisfies $\omega/T$ scaling, we argue that the
$T$-linear resistivity must come from the intrinsic physics of the low energy
fixed point. Combining with earlier arguments that compressible translation
invariant metals are `ersatz Fermi liquids' with an infinite number of emergent
conserved quantities, we obtain powerful and practical conclusions. We show
that there is necessarily a diverging susceptibility for an operator that is
odd under inversion/time reversal symmetries, and has zero crystal momentum. We
discuss a few other experimental consequences of our arguments, as well as
potential loopholes which necessarily imply other exotic phenomena.",2010.10523v3
2020-11-06,Molecular Dynamic Study of Local Interfacial Thermal Resistance of Solid-Liquid and Solid-Solid Interfaces: Water and Nanotextured Surface,"Degradation in performances of air conditioners and refrigerators is caused
by a frost formation and adhesion on the surface. In the present study, by
means of the classical molecular dynamics simulation, we investigate how and
how much the nanotextured surface characteristics, such as surface wettability
and geometry, influenced the interfacial thermal resistance (ITR) between the
solid wall and the water/ice. The ITR of the interfacial region was comparable
in both the water and the ice states. As the nanostructure gaps became
narrower, the ITR of the interfacial region decreased. The local ITR had a weak
negative correlation with the local H2O molecule density regardless of the
phase of the H2O molecules. The local ITR decreased as the local density
increased. The greater amount of the thermal energy was transferred through the
material interface by means of the intermolecular interaction when more the H2O
molecules were located in the proximity area, which was closer to the Pt solid
wall than the first adsorption layer peak. When the H2O molecules were in the
crystal form on the solid wall, the proximity molecules decreased, and then the
local ITR significantly increased.",2011.03184v2
2020-11-10,Thickness induced metal to insulator charge transport and unusual hydrogen response in granular palladium nanofilms,"This work reports a systematic study of the evolution of charge transport
mechanism in granular ultra-thin films of palladium of thickness varying
between 6nm and 2nm. While the films with thickness > 4nm exhibit metallic
behaviour, that at 3nm thickness undergoes a metal-insulator transition at
19.5K. In contrast, the 2nm thick film remained insulating at all temperatures.
with transport following Mott's variable range hopping. At room temperature,
while the thicker film exhibit resistance decrease on H$_2$ exposure. the
insulating film showed an anomalous initial resistance increase before
switching to a subsequent decrease. The nanostructure dependent transport and
the ensuing H$_2$ response is modeled on a percolation model, which also
explores the relevance of film thickness as a macroscopic control parameter to
engineer the desired system response in granular metal films.",2011.05123v1
2020-11-23,From hidden metal-insulator transition to Planckian-like dissipation by tuning disorder in a nickelate,"Heavily oxygen deficient NdNiO$_3$ (NNO) films, which are insulating due to
electron localization, contain pristine regions that undergo a hidden
metal-insulator transition. Increasing oxygen content increases the
connectivity of the metallic regions and the metal-insulator transition is
first revealed, upon reaching the percolation threshold, by the presence of
hysteresis. Only upon further oxygenation is the global metallic state (with a
change in the resistivity slope) eventually achieved. It is shown that
sufficient oxygenation leads to linear temperature dependence of resistivity in
the metallic state, with a scattering rate directly proportional to
temperature. Despite the known difficulties to establish the proportionality
constant, the experiments are consistent with a relationship 1/$\tau$= $\alpha
k_B T/\hbar$, with $\alpha$ not far from unity. These results could provide
experimental support for recent theoretical predictions of disorder in a
two-fluid model as a possible origin of Planckian dissipation.",2011.11535v2
2020-11-26,All-MOCVD-Grown Gallium Nitride Diodes with Ultra-Low Resistance Tunnel Junctions,"We carefully investigate three important effects including postgrowth
activation annealing, delta ({\delta}) dose and p+-GaN layer thickness and
experimentally demonstrate their influence on the electrical properties of GaN
p-n homojunction diodes with a tunnel junction (TJ)-based p-contact. The p-n
diodes and TJ structures were monolithically grown by metalorganic chemical
vapor deposition (MOCVD) in a single growth step. By optimizing the annealing
time and temperature for magnesium (Mg) activation and introducing
{\delta}-doses for both donors and acceptors at TJ interfaces, a significant
improvement in electrical properties is achieved. For the continuously-grown,
all-MOCVD GaN homojunction TJs, ultra-low forward voltage penalties of 158 mV
and 490 mV are obtained at current densities of 20 A/cm2 and 100 A/cm2,
respectively. The p-n diode with an engineered TJ shows a record-low normalized
differential resistance of 1.6 x 10-4 {\Omega}-cm2 at 5 kA/cm2.",2011.13431v1
2020-12-29,Efficient partitioning of surface Green's function: toward ab initio contact resistance study,"In this work, we propose an efficient computational scheme for
first-principle quantum transport simulations to evaluate the open-boundary
conditions. Its partitioning differentiates from conventional methods in that
the contact self-energy matrices are constructed on smaller building blocks,
principal layers (PL), while conventionally it was restricted to have the same
lateral dimensions of the adjoining atoms in a channel region. Here, we obtain
the properties of bulk electrodes through non-equilibrium Green's function
(NEGF) approach with significant improvements in the computational efficiency
without sacrificing the accuracy of results. To exemplify the merits of the
proposed method we investigate the carrier density dependency of contact
resistances in silicon nanowire devices connected to bulk metallic contacts.",2012.14903v1
2020-12-30,Anomalous thermal transport and violation of Wiedemann-Franz law in the critical regime of a charge density wave transition,"ErTe$_3$ is studied as a model system to explore thermal transport in a
layered charge density wave (CDW) material. We present data from thermal
diffusivity, resistivity, and specific heat measurements: There is a sharp
decrease in thermal conductivity both parallel and perpendicular to the primary
CDW at the CDW transition temperature. At the same time, the resistivity
changes more gradually. Correspondingly, while well above and below $T_c$, a
consistent description of the thermal transport applies with essentially
independent electron and phonon contributions (estimated using the Wiedemann
Franz law), in the critical regime no such description is possible; the
observed behavior corresponds to a strongly coupled electron-phonon critical
`soup.'",2012.15048v1
2021-02-05,"A Colossal Electroresistance response, accompanied by metal-insulator transition, in a mixed-valent vanadate","Colossal electroresistance (CER) in manganites, i.e., a large change in
electrical resistance under the influence of either an applied electric field
or an applied electric current, has often been described as complimentary to
the colossal magnetoresistance (CMR) effect. Mixed valent vanadates with active
t2g and empty eg orbitals, unlike manganites, have not naturally been discussed
in this context, as double exchange based CMR is not realizable in them.
However, presence of coupled spin and orbital degrees of freedom,
metal-insulator transition (MIT) accompanied by orbital order-disorder
transition, etc., anyway make the vanadates an exciting group of materials.
Here we probe a Fe-doped hollandite lead vanadate PbFe1.75V4.25O11 (PFVO),
which exhibits a clear MIT as a function of temperature. Most importantly, a
giant fall in the resistivity, indicative of a CER, as well as a systematic
shift in the MIT towards higher temperature are observed as a function of
applied electric current. Detailed structural, magnetic, thermodynamic and
transport studies point towards a complex interplay between orbital
order/disorder effect, MIT and double exchange in this system.",2102.03128v1
2021-02-02,Fabrication of astronomical x-ray reflection gratings using thermally activated selective topography equilibration,"Thermally activated selective topography equilibration (TASTE) enables the
creation of 3D structures in resist using grayscale electron-beam lithography
followed by a thermal treatment to induce a selective polymer reflow. A blazed
grating topography can be created by reflowing repeating staircase patterns in
resist into wedge-like structures. Motivated by astronomical applications, such
patterns with periodicities 840 nm and 400 nm have been fabricated in 130
nm-thick PMMA using TASTE to provide a base for X-ray reflection gratings. A
path forward to integrate this alternative blazing technique into grating
fabrication recipes is discussed.",2102.12359v1
2021-03-04,Uncovering Thermal and Electrical Properties of Sb2Te3/GeTe Superlattice Films,"Superlattice-like phase change memory (SL-PCM) promises lower switching
current than conventional PCM based on Ge2Sb2Te5 (GST). However, a fundamental
understanding of SL-PCM requires detailed characterization of the interfaces
within such a SL. Here, we explore the electrical and thermal transport of SLs
with deposited Sb2Te3 and GeTe alternating layers of various thicknesses. We
find up to ~4X reduction of the effective cross-plane thermal conductivity of
the SL stack (as-deposited polycrystalline) compared to polycrystalline GST
(as-deposited amorphous and later annealed) due to the thermal interface
resistances within the SL. Thermal measurements with varying periods of our SLs
show a signature of phonon coherence with a transition from wave-like to
particle-like phonon transport, further described by our modeling. Electrical
resistivity measurements of such SLs reveal strong anisotropy (~2000X) between
the in-plane and cross-plane directions due to the weakly interacting van der
Waals gaps. This work uncovers electro-thermal transport in SLs based on Sb2Te3
and GeTe, for improved design of low-power PCM.",2103.02867v3
2021-04-01,Unconventional satellite resistance peaks in moiré superlattice of h-BN/ AB-stacked tetralayer-graphene heterostructure,"Most studies on moir\'e superlattices formed from a stack of h-BN and
graphene have focused on single layer graphene; graphene with multiple layers
is less understood. Here, we show that a moir\'e superlattice of multilayer
graphene shows new features arising from the anisotropic Fermi surface affected
by the superlattice structure. The moir\'e superlattice of a h-BN/AB-stacked
tetralayer graphene heterostructure exhibited resistivity peaks showing a
complicated dependence on the perpendicular electric field. The peaks were not
due to secondary Dirac cones forming, but rather opening of the energy gap due
to folding of the anisotropic Fermi surface. In addition, superlattice peaks
resulted from mixing of light- and heavy-mass bilayer-like bands via the
superlattice potential. The gaps did not open on the boundary of the
superlattice Brillouin zone, but rather opened inside it, which reflected the
anisotropy of the Fermi surface of multilayer graphene.",2104.00261v1
2021-07-07,Structural and WAL analysis of Topological single-crystal SnSb2Te4,"Here, we report successful single crystal growth of SnSb2Te4 using the
self-flux method. Unidirectional crystal growth is confirmed through X Ray
Diffraction (XRD) pattern taken on mechanically cleaved crystal flake while the
rietveld refined Powder XRD (PXRD) pattern confirms the phase purity of the
grown crystal. Scanning Electron Microscopy (SEM) image and Energy Dispersive
X-Ray analysis (EDAX) confirm crystalline morphology and exact stoichiometry of
constituent elements. Vibrational Modes observed in Raman spectra also confirm
the formation of the SnSb2Te4 phase. DC resistivity measurements confirm the
metallic character of the grown crystal. Magneto-transport measurements up to
5T show a nonsaturating low magneto-resistance percentage. V type cusp and
Hikami Larkin Nagaoka (HLN) fitting at lower field confirms the Weak
Anti-localization (WAL) effect in SnSb2Te4. Density Functional Theory (DFT)
calculations were showing topological non-trivial electronic band structure. It
is the first-ever report on MR study and WAL analysis of SnSb2Te4 single
crystal.",2107.03014v1
2021-07-13,"First-principles study of the crystal structure, electronic structure, and transport properties of NiTe$_2$ under pressure","Recent experiments showed the distinct observations on the transition metal
ditelluride NiTe$_2$ under pressure: one reported a superconducting phase
transition at 12 GPa, whereas another observed a sign reversal of Hall
resistivity at 16 GPa without the appearance of superconductivity. To clarify
the controversial experimental phenomena, we have carried out first-principles
electronic structure calculations on the compressed NiTe$_2$ with structure
searching and optimization. Our calculations show that the pressure can
transform NiTe$_2$ from a layered P-3m1 phase to a cubic Pa-3 phase at $\sim$10
GPa. Meanwhile, both the P-3m1 and Pa-3 phases possess nontrivial topological
properties. The calculated superconducting $T_c$'s for these two phases based
on the electron-phonon coupling theory both approach 0 K. Further magnetic
transport calculations reveal that the sign of Hall resistance for the Pa-3
phase is sensitive to the pressure and the charge doping, in contrast to the
case of the P-3m1 phase. Our theoretical predictions on the compressed NiTe$_2$
wait for careful experimental examinations.",2107.05922v1
2021-07-14,A fast-converging scheme for the Phonon Boltzmann equation with dual relaxation times,"Callaway's dual relaxation times model, which takes into account the normal
and resistive scatterings of phonon, is used to describe the heat conduction in
materials like graphene. For steady-state problems, the Callaway model is
usually solved by the conventional iterative scheme (CIS), which is efficient
in the ballistic regime, but inefficient in the diffusive/hydrodynamic regime.
In this paper, a general synthetic iterative scheme (GSIS) is proposed to
expedite the convergence to steady-state solutions. First, macroscopic
synthetic equations are designed to guide the evolution of equilibrium
distribution functions for normal and resistive scatterings, so that fast
convergence can be achieved even in the diffusive/hydrodynamic regime. Second,
the Fourier stability analysis is conducted to find the convergence rate for
both CIS and GSIS, which rigorously proves the efficiency of GSIS over CIS.
Finally, several numerical simulations are carried out to demonstrate the
accuracy and efficiency of GSIS, where up to three orders of magnitude of
convergence acceleration is achieved.",2107.06688v1
2021-07-26,Statistical analysis of spin switching in coupled spin-crossover molecules,"We study the switching behavior of two spin-crossover molecules residing in a
nanojunction device consisting of two closely spaced gold electrodes. The spin
states are monitored through a real-time measurement of the resistance of the
junction. A statistical analysis of the resistance values, the occupation
probabilities, and the lifetimes of the respective spin states shows that the
two spin-crossover molecules are coupled to each other. We extract the
parameters for a minimal model describing the two coupled spin-crossover
molecules. Finally, we use the time dependence of factorial cumulants to
demonstrate that the measured data indicates the presence of interactions
between the two spin-crossover molecules.",2107.11935v1
2021-09-29,Physical and one-dimensional properties of single crystalline La$_{5}$AgPb$_{3}$,"We report here the properties of single crystals of La$_{5}$AgPb$_{3}$, which
is a member of the $R_5MX_3$ ($R$ = rare earth, $M$ = transition metal or main
group element, $X$ = Pb, Sn, Sb, In, Bi) family of chain-like compounds.
Measurements of the electrical resistivity, specific heat and magnetic
susceptibility are compared to the results of density functional calculations,
finding that La$_{5}$AgPb$_{3}$ is a non-magnetic metal with moderate
correlations. The analysis of the electrical resistivity and specific heat
measurements highlight the importance of lattice vibrations in the material,
while the calculated electron density suggests the presence of localized La and
well-hybridized Ag atoms that extend along the c-axis in the La$_{5}$AgPb$_{3}$
structure. The temperature dependence of the magnetic susceptibility is
consistent with a possible one-dimensional character of La$_{5}$AgPb$_{3}$,
where the strength of correlations is much weaker than in one-dimensional
conductors that have been previously reported.",2109.14716v1
2021-10-20,Anomalous Hall effect from gapped nodal line in Co2FeGe Heusler compound,"Full Heusler compounds with Cobalt as a primary element show anomalous
transport properties owing to the Weyl fermions and broken time-reversal
symmetry. We present here the study of anomalous Hall effect (AHE) in Co2FeGe
Heusler compound. The experiment reveals anomalous Hall conductivity (AHC) 100
S/cm at room temperature with an intrinsic contribution of 78 S/cm . The
analysis of anomalous Hall resistivity suggests the scattering independent
intrinsic mechanism dominates the overall behaviour of anomalous Hall
resistivity. The first principles calculation reveals that the Berry curvature
originated by gapped nodal line near EF is the main source of AHE in Co2FeGe
Heusler compound. The theoretically calculated AHC is in agreement with the
experiment.",2110.10677v1
2021-11-06,GdV6Sn6: a Multi-carrier Metal with Non-magnetic 3d-electron Kagome Bands and 4f-electron Magnetism,"Electronic properties of the single crystal of GdV6Sn6, where non-magnetic
V-kagome layers are separated by magnetic Gd-triangular lattice, are
investigated. GdV6Sn6 exhibits unique magnetotransport properties at
low-temperature such as non-linear Hall resistivity and increase of resistance
R in magnetic field H as R ~ H^0.75 up to 56 T with Shubnikov-De Haas
oscillations. Investigation of the non-magnetic analogue YV6Sn6 and the first
principles calculations reveal these properties are relevant to the bands
arising from the V-kagome layer. A magnetic transition at 5 K in GdV6Sn6
modifies the transport properties, pointing to a coupling between Gd-spins on
the triangular lattice and carriers in the V-kagome layer.",2111.03806v1
2021-11-14,Modelling photothermal induced resonance microscopy: the role of interface thermal resistances,"Infrared (IR) nanospectroscopy by photothermal induced resonance (PTIR) is a
novel experimental technique that combines the nanoscale resolution granted by
atomic force microscopy (AFM) and the chemical labelling made possible by IR
absorption spectroscopy. While the technique has developed enormously over the
last decade from an experimental point of view, the theoretical modelling of
the signal still varies significantly throughout the literature and misses a
solid benchmark. Here, we report an analysis focused on the electromagnetic and
thermal simulations of a PTIR experiment. Thanks to a control experiment where
the signal is acquired as a function of the thickness of a polymer film and for
different tip geometries, we find clear evidence that the interface thermal
resistances play a key role in the determination of the measured signal and
should therefore always be accounted for by any quantitative modelling.",2111.07303v1
2021-12-01,Immobilization of the rare earth fraction in lanthanide phosphates LnPO4. Radiation and hydrolytic resistance of the matrix,"Radiation and hydrolytic resistance of
Eu0.054Gd0.014Y0.05La0.111Ce0.2515Pr0.094Nd0.3665Sm0.059PO4 with monazite
structure has been studied. The powders were obtained by deposition from
solutions. Ceramic specimens with relative density ~97% were obtained by Spark
Plasma Sintering (heating rate Vh = 50 {\deg}C/min, sintering temperature Ts =
1070 {\deg}C, sintering time ts = 18 min). Irradiation by accelerated electrons
up to dose of 10^9 Ge was found not to result in a destruction of the target
phase. After the irradiation, an increasing of the leaching rate by an order of
magnitude (up to ~10^{-8} g/(cm2*day)) and a reduction of the mechanical
properties by 32% as compared to the non-irradiated ceramic specimen were
observed.",2112.00844v1
2021-12-24,Measured potential profile in a quantum anomalous Hall system suggests bulk-dominated current flow,"Ideally, quantum anomalous Hall systems should display zero longitudinal
resistance. Yet in experimental quantum anomalous Hall systems elevated
temperature can make the longitudinal resistance finite, indicating dissipative
flow of electrons. Here, we show that the measured potentials at multiple
locations within a device at elevated temperature are well-described by
solution of Laplace's equation, assuming spatially-uniform conductivity,
suggesting non-equilibrium current flows through the two-dimensional bulk.
Extrapolation suggests that at even lower temperatures current may still flow
primarily through the bulk rather than, as had been assumed, through edge
modes. An argument for bulk current flow previously applied to quantum Hall
systems supports this picture.",2112.13123v3
2022-01-24,Nonconventional Quantized Hall Resistances Obtained with $ν= 2$ Equilibration in Epitaxial Graphene $p-n$ Junctions,"We have demonstrated the millimeter-scale fabrication of monolayer epitaxial
graphene $p-n$ junction devices using simple ultraviolet photolithography,
thereby significantly reducing device processing time compared to that of
electron beam lithography typically used for obtaining sharp junctions. This
work presents measurements yielding nonconventional, fractional multiples of
the typical quantized Hall resistance at $\nu=2$ ($R_H\approx 12906 {\Omega}$)
that take the form: $\frac{a}{b}R_H$. Here, $a$ and $b$ have been observed to
take on values such 1, 2, 3, and 5 to form various coefficients of $R_H$.
Additionally, we provide a framework for exploring future device configurations
using the LTspice circuit simulator as a guide to understand the abundance of
available fractions one may be able to measure. These results support the
potential for drastically simplifying device processing time and may be used
for many other two-dimensional materials.",2201.09791v1
2022-03-11,Toward accurate polarization estimation in nanoscopic systems,"The nanoscopic characterization of ferroelectric thin films is crucial from
their device application point of view. Standard characterization techniques
are based on detecting the nanoscopic charge compensation current (switching
current) caused by the polarization reversal in the ferroelectric. Owing to
various surface and bulk limited mechanisms, leakage currents commonly appear
during such measurements, which are frequently subtracted using the device I-V
characteristic by employing positive-up-negative-down (PUND) measurement
scheme. By performing nanoscopic switching current measurements on a commonly
used ferroelectric, BiFeO3, we show that such characterization methods may be
prone to large errors in the polarization estimation on ferro-resistive
samples, due to current background subtraction issues. Especially, when
ferro-resistive behavior is associated with the polarization reversal of the
ferroelectric thin film, background current subtraction is not accurate due to
the mismatch of the I-V characteristics for the two polarization states. We
show instead that removing the background current by an asymmetric least
squares subtraction method, though not perfect, gives a much better estimation
of the ferroelectric properties of the sample under study.",2203.06157v1
2022-05-11,Self-heating Effect in Silicon-Photomultipliers,"The main effect of radiation damage in a Silicon-Photolumtiplier (SiPM) is a
dramatic increase in the dark current. The power dissipated, if not properly
cooled, heats the SiPM, whose performance parameters depend on temperature.
Heating studies were performed with a KETEK SiPM, glued on an Al$_2$O$_3$
substrate, which is either directly connected to the temperature-controlled
chuck of a probe station, or through layers of material with well-known thermal
resistance. The SiPM is illuminated by a LED operated in DC-mode. The SiPM
current is measured and used to determine the steady-state temperature as a
function of power dissipated in the multiplication region of the SiPM and
thermal resistance, as well as the time dependencies for heating and cooling.
This information can be used to correct the parameters determined for
radiation-damaged SiPM for the effects of self-heating. The method can also be
employed for packaged SiPMs with unknown thermal contact to a heat sink. The
results presented in this paper are preliminary.",2205.05504v2
2022-05-31,A Novel Readout Scheme for Muon Tomography Application in Material Identification,"This work reports a cost-effective, multi-parameter readout and
data-acquisition system for a muon scattering tomography system based on
Resistive Plate Chambers (RPCs). Initial test measurements with a prototype
Resistive Plate Chamber were performed using a low-cost FPGA coupled to the
NINO ASIC for the event selection and handling data. The Time over-Threshold
(TOT) property of NINO ASICs has been used to achieve better position
information and achieve precise tracking capability. In our test setup, we try
to build an imaging setup using a single RPC and lead block, which covers some
areas of RPC. A glass RPC of dimension 30cm x 30cm, filled with a gas mixture
of 95% Freon and 5% Isobutane, equipped with two orthogonal panels of readout
strips of width 3 cm and pitch 3.2 cm, has been operated.",2205.15966v1
2022-06-04,How to recognize the universal aspects of Mott criticality?,"In this paper we critically discuss several examples of two-dimensional
electronic systems displaying interaction-driven metal-insulator transitions of
the Mott (or Wigner--Mott) type, including dilute two-dimension electron gases
(2DEG) in semiconductors, Mott organic materials, as well as the recently
discovered transition-metal dichalcogenide (TMD) moir\'e bilayers. Remarkably
similar behavior is found in all these systems, which is starting to paint a
robust picture of Mott criticality. Most notable, on the metallic side a
resistivity maximum is observed whose temperature scale vanishes at the
transition. We compare the available experimental data on these systems to
three existing theoretical scenarios: spinon theory, Dynamical Mean Field
Theory (DMFT) and percolation theory. We show that the DMFT and percolation
pictures for Mott criticality can be distinguished by studying the origins of
the resistivity maxima using an analysis of the dielectric response.",2206.02055v2
2022-06-28,Negative Differential Resistance in Spin-Crossover Molecular Devices,"We demonstrate, based on low-temperature scanning tunneling microscopy (STM)
and spectroscopy, a pronounced negative differential resistance (NDR) in
spin-crossover (SCO) molecular devices, where a Fe$^{\text{II}}$ SCO molecule
is deposited on surfaces. The STM measurements reveal that the NDR is robust
with respect to substrate materials, temperature, and the number of SCO layers.
This indicates that the NDR is intrinsically related to the electronic
structure of the SCO molecule. Experimental results are supported by density
functional theory (DFT) with non-equilibrium Green's functions (NEGF)
calculations and a generic theoretical model. While the DFT+NEGF calculations
reproduce NDR for a special atomically-sharp STM tip, the effect is attributed
to the energy-dependent tip density of states rather than the molecule itself.
We, therefore, propose a Coulomb blockade model involving three molecular
orbitals with very different spatial localization as suggested by the molecular
electronic structure.",2206.13767v2
2022-07-26,Understanding the Mechanism of the Performance Improvement in Nitrogen-doped Niobium Superconducting Radio Frequency Cavity,"Niobium superconducting radiofrequency cavities enable applications in modern
accelerators and quantum computers. However, the surface resistance
significantly deteriorates the cavities performance. Nitrogen doping surface
treatment can consistently increase cavity performance by reducing surface
resistance, but the improvement mechanism is not fully understood. Herein, we
employed transmission electron microscopy and spectroscopy to uncover the
structural and chemical differences of the Nb-air interface between the
non-doped and nitrogen-doped cavities. The results indicate that nitrogen
doping passivates the Nb surface by introducing a compressive strain close to
the Nb/air interface, which impedes the oxygen diffusion and hydrogen atoms and
reduces surface oxide thickness.",2207.13171v1
2022-08-31,Possible origin of extremely large magnetoresistance in the topological insulator CaBi2 single crystal,"CaBi2 has been experimentally found to be a superconductor with a transition
temperature of 2 K and identified as a topological insulator via spin- and
angle-resolved photoemission spectroscopy, which makes it a possible platform
to study the interplay between superconductivity and topology. But the detailed
transport properties for CaBi2 single crystal remain unexplored in experiments.
Here, we systematically studied the magneto-transport properties of CaBi2
single crystal grown by a flux method. CaBi2 shows a magnetic-field-induced
upturn behavior with a plateau in resistivity at low temperature. An extremely
large and non-saturating magnetoresistance up to ~15000% at 3 K and 12 T was
achieved. The possible reason for the magnetic field and temperature dependence
of resistivity and extremely large magnetoresistance at low temperature was
discussed by adopting the Kohler's scaling law, which can be understood by the
compensation effect confirmed by the Hall Effect measurement.",2208.14595v1
2022-09-16,Ferroelectricity and resistive switching in BaTiO$_3$ thin films with liquid electrolyte top contact for bioelectronic devices,"We investigate ferroelectric- and resistive switching behavior in 18-nm-thick
epitaxial BaTiO$_3$ (BTO) films in a model
electrolyte-ferroelectric-semiconductor (EFS) configuration. The system is
explored for its potential as a ferroelectric microelectrode in bioelectronics.
The BTO films are grown by pulsed laser deposition (PLD) on semiconducting
Nb-doped (0.5 wt\%) SrTiO$_{3}$ (Nb:STO) single crystal substrates. The
ferroelectric properties of the bare BTO films are demonstrated by
piezoresponse force microscopy (PFM) measurements. Cyclic voltammetry (CV)
measurements in EFS configuration, with phosphate buffered saline (PBS) acting
as the liquid electrolyte top contact, indicate characteristic ferroelectric
switching peaks in the bipolar current-voltage loop. The ferroelectric nature
of the observed switching peaks is confirmed by analyzing the current response
of the EFS devices to unipolar voltage signals. Moreover, electrochemical
impedance spectroscopy (EIS) measurements indicate bipolar resisitive switching
behavior of the EFS devices, which is controlled by the remanent polarization
state of the BTO layer. Our results represent a constitutive step towards the
realization of neuroprosthetic implants and hybrid neurocomputational systems
based on ferroelectric microelectrodes.",2209.08020v1
2022-09-21,Colossal Spontaneous Hall Effect and Emergent Magnetism in KTaO$_3$ Two-Dimensional Electron Gases,"There has been intense recent interest in the two-dimensional electron gases
(2DEGs) that form at the surfaces and interfaces of KTaO$_3$ (KTO), with the
discovery of superconductivity at temperatures significantly higher than those
of similar 2DEGs based on SrTiO$_3$ (STO). Here we demonstrate that KTO 2DEGs
fabricated under conditions that suppress the superconductivity show a large
spontaneous Hall effect at low temperatures. The transverse response is
asymmetric in an applied perpendicular magnetic field and becomes hysteretic at
millikelvin temperatures. The hysteresis is due to long range magnetic order
arising from local Ta$^{4+}$ moments. However, the most striking features of
the data are the asymmetry of the transverse response and the large spontaneous
transverse resistance at zero field, which can be a significant fraction of the
longitudinal resistance and depends on crystal orientation. Both effects are
due to the presence of a dominant contribution to the transverse response that
is symmetric in perpendicular field, suggesting that its origin is topological
in nature. We argue that this contribution arises from Berry curvature dipoles
coupled with nonequilibrium conditions induced by the measuring current.",2209.10534v2
2022-09-30,Remote Surface Optical Phonon Scattering in Ferroelectric Ba$_{0.6}$Sr$_{0.4}$TiO$_{3}$ Gated Graphene,"We report the effect of remote surface optical (RSO) phonon scattering on
carrier mobility in monolayer graphene gated by ferroelectric oxide. We
fabricate monolayer graphene transistors back-gated by epitaxial (001)
Ba$_{0.6}$Sr$_{0.4}$TiO$_{3}$ films, with field effect mobility up to 23,000
cm$^{2}$V$^{-1}$s$^{-1}$ achieved. Switching the ferroelectric polarization
induces nonvolatile modulation of resistance and quantum Hall effect in
graphene at low temperatures. Ellipsometry spectroscopy studies reveal four
pairs of optical phonon modes in Ba$_{0.6}$Sr$_{0.4}$TiO$_{3}$, from which we
extract the RSO phonon frequencies. The temperature dependence of resistivity
in graphene can be well accounted for by considering the scattering from the
intrinsic longitudinal acoustic phonon and the RSO phonon, with the latter
dominated by the mode at 35.8 meV. Our study reveals the room temperature
mobility limit of ferroelectric-gated graphene transistors imposed by RSO
phonon scattering.",2209.15527v1
2022-10-06,Kinetically Decoupled Electrical and Structural Phase Transitions in VO2,"Vanadium dioxide (VO2) has drawn significant attention for its near room
temperature insulator to metal transition and associated structural phase
transition. The underlying Physics behind the temperature induced insulator to
metal and concomitant structural phase transition in VO2 is yet to be fully
understood. We have investigated the kinetics of the above phase transition
behaviors of VO2 with the help of resistivity measurements and Raman
spectroscopy. Resistance thermal hysteresis scaling and relaxation measurements
across the temperature induced insulator to metal transition reveal the unusual
behaviour of this first-order phase transition, whereas Raman relaxation
measurements show that the temperature induced structural phase transition in
VO2 follows usual behaviour and is consistent with mean field prediction. At
higher temperature sweeping rates decoupling of insulator to metal transition
and structural phase transition have been confirmed. The observed anomalous
first order phase transition behavior in VO2 is attributed to the
unconventional quasi particle dynamics, i.e. significantly lowered electronic
thermal conductivity across insulator to metal transition, which is confirmed
by ultrafast optical pump-probe time domain thermoreflectance measurements.",2210.02691v1
2022-11-06,Triclinic BiFeO3: A room-temperature multiferroic phase with enhanced magnetism and resistivity,"The magnetic and transport properties of BiFeO3/La2NiMnO6 (BFO/LNMO)
composite have been investigated both experimentally and theoretically. Unlike
the normal rhombohedral (R3c) phase, BFO in the composites is crystallized in
the triclinic phase (P1). Interestingly, the composites demonstrate a
significant enhancement in the magnetization, magnetoelectric coupling and show
higher resistivity than that of the regular BFO (R3c). As LNMO has its Curie
temperature at 280 K, the room temperature and above room temperature magnetic
contribution in the composites is expected to be from the triclinic BFO phase.
Experimentally observed enhancement in magnetization is validated using
classical Monte Carlo simulation and density functional theory (DFT)
calculations. The calculations reveal higher magnetic moments in triclinic BFO
as compared to the rhombohedral BFO. Overall, this study reveals triclinic BFO
as the promising room temperature multiferroic phase which is helpful to
optimize the multiferroicity of BFO and achieve wider applications in future.",2211.03123v3
2022-11-11,Synthesis and physical properties of uranium thin-film hydrides UH2 and \b{eta}-UH3,"Formation of thin uranium hydrides films, UH2 and \b{eta}-UH3, synthesized by
a reactive dc sputtering of uranium metal, was explored using variable
deposition conditions. Obtained stable oxygen-free hydride films were studied
by a variety of methods, both in situ (photoelectron spectroscopy - XPS), and
ex-situ (x-ray diffraction - XRD, transmission electron microscopy - TEM),
electrical resistivity, and magnetometry). Both types of hydrides are
ferromagnetic, the Curie temperatures of UH2 and \b{eta}-UH3 are approx. 120
and 170 K, respectively. Ferromagnetism in the thin films is robust and does
not depend on structure details while electrical resistivity data reflect
disorder in both types of hydrides.",2211.06144v1
2023-01-03,Supercurrent in Bi$_4$Te$_3$ Topological Material-Based Three-Terminal Junctions,"In an in-situ prepared three-terminal Josephson junction based on the
topological insulator Bi$_4$Te$_3$ and the superconductor Nb the transport
properties are studied. The differential resistance maps as a function of two
bias currents reveal extended areas of Josephson supercurrent including
coupling effects between adjacent superconducting electrodes. The observed
dynamics for the coupling of the junctions is interpreted using a numerical
simulation of a similar geometry based on a resistively and capacitively
shunted Josephson junction model. The temperature dependency indicates that the
device behaves similar to prior experiments with single Josephson junctions
comprising topological insulators weak links. Irradiating radio frequencies to
the junction we find a spectrum of integer Shapiro steps and an additional
fractional step, which is interpreted by a skewed current-phase relationship.
In a perpendicular magnetic field we observe Fraunhofer-like interference
patterns of the switching currents.",2301.01115v1
2023-01-06,Berry curvature induced valley Hall effect in non-encapsulated hBN/Bilayer graphene heterostructure aligned with near-zero twist angle,"Valley Hall effect has been observed in asymmetric single-layer and bilayer
graphene systems. In single-layer graphene systems, asymmetry is introduced by
aligning graphene with hexagonal boron nitride (hBN) with a near-zero twist
angle, breaking the sub-lattice symmetry. Although a similar approach has been
used in bilayer graphene to break the layer symmetry and thereby observe the
valley Hall effect, the bilayer graphene was sandwiched with hBN on both sides
in those studies. This study looks at a much simpler, non-encapsulated
structure where hBN is present only at the top of graphene. The
crystallographic axes of both hBN and bilayer graphene are aligned. A clear
signature of the valley Hall effect through non-local resistance measurement
($R_{\rm{NL}}$) was observed. The observed non-local resistance could be
manipulated by applying a displacement field across the heterostructure.
Furthermore, the electronic band structure and Berry curvature calculations
validate the experimental observations.",2301.02358v2
2023-01-29,Anisotropic magnetic and magnetotransport properties in morphologically distinct Nd0.6Sr0.4MnO3 thin films,"We investigate the magnetic and magnetotransport properties of nanostructured
Nd0.6Sr0.4MnO3 (NSMO) thin films grown on (100) oriented SrTiO3 (STO)
substrates. The thin films fabricated using the pulsed laser deposition
technique have been found to possess two distinct surface morphologies:
granular and nano rod type. Magnetization measurements have revealed that the
films with rod-type morphology exhibit improved in-plane magnetic anisotropy.
Magnetotransport studies have revealed that the granular thin films display a
characteristic butterfly-shaped low-field magneto-resistive (LFMR) behavior.
Furthermore, we investigate the anisotropic magneto-resistive (AMR) phenomenon
in the samples and we find that morphology greatly affects AMR. Thin films with
rod-type morphology show an enhanced AMR %. Such morphology dependent
tunability in magnetoresistance properties over a wide temperature range is
potentially interesting for developing oxide-based sensors and devices.",2301.12406v1
2023-02-10,Electrical characterization of the azimuthal anisotropy of $(\mathrm{Ni}_x\mathrm{Co}_{1-x})\mathrm{B}$-based ferromagnetic nanotubes,"We report on the structural, electric and magnetic properties of
$(\mathrm{Ni}_x\mathrm{Co}_{1-x})\mathrm{B}$ ferromagnetic nanotubes,
displaying azimuthal magnetization. The tubes are fabricated using electroless
plating in polycarbonate porous templates, with lengths several tens of
micrometers, diameters from 100nm to 500nm and wall thicknesses from 10nm to
80nm. The resistivity is $\sim 1.5\times10^{-6}\mathrm{\Omega/m}$, and the
anisotropic magnetoresistance~(AMR) of 0.2-0.3%, one order of magnitude
larger~(resp. smaller) than in the bulk material, which we attribute to the
resistance at grain boundaries. We determined the azimuthal anisotropy field
from M(H) AMR loops of single tubes contacted electrically. Its magnitude is
around 10mT, and tends to increase with the tube wall thickness, as well as the
Co content. However, surprisingly it does not dependent much on the diameter
nor on the curvature.",2302.05246v1
2023-02-14,Microscopic mechanism of tunable thermal conductivity in carbon nanotube-geopolymer nanocomposites,"Geopolymer has been considered as a green and low-carbon material with great
potential application due to its simple synthesis process, environmental
protection, excellent mechanical properties, good chemical resistance and
durability. In this work, the molecular dynamics simulation is employed to
investigate the effect of the size, content and distribution of carbon
nanotubes on the thermal conductivity of geopolymer nanocomposites, and the
microscopic mechanism is analyzed by the phonon density of states, phonon
participation ratio and spectral thermal conductivity, etc. The results show
that there is a significant size effect in geopolymer nanocomposites system due
to the carbon nanotubes. In addition, when the content of carbon nanotubes is
16.5%, the thermal conductivity in carbon nanotubes vertical axial direction
(4.85 W/(mk)) increases 125.6% compared with the system without carbon
nanotubes (2.15 W/(mk)). However, the thermal conductivity in carbon nanotubes
vertical axial direction (1.25 W/(mk)) decreases 41.9%, which is mainly due to
the interfacial thermal resistance and phonon scattering at the interfaces. The
above results provide theoretical guidance for the tunable thermal conductivity
in carbon nanotube-geopolymer nanocomposites.",2302.07195v1
2023-02-18,Fractional Marcus-Hush-Chidsey-Yakopcic current-voltage model for redox-based resistive memory devices,"We propose a circuit-level model combining the Marcus-Hush-Chidsey electron
current equation and the Yakopcic equation for the state variable for
describing resistive switching memory devices of the structure metal-ionic
conductor-metal. We extend the dynamics of the state variable originally
described by a first-order time derivative by introducing a fractional
derivative with an arbitrary order between zero and one. We show that the
extended model fits with great fidelity the current-voltage characteristic data
obtained on a Si electrochemical metallization memory device with Ag-Cu alloy.",2302.09407v2
2023-03-01,Electronic Transport Studies of Ag-doped Bi2Se3 Topological Insulator,"The structural, magnetotransport, and angle-resolved photoemission
spectroscopy (ARPES) of Ag-doped Bi2Se3 single crystals are presented.
Temperature dependent resistivity exhibits metallic behavior with a slope
change above 200 K for Ag-doped Bi2Se3. The magnetoresistance shows positive
quadratic dependence at low fields satisfying Kohler's rule. Hall resistivity
measurement shows that electrons are dominant charge carriers. Furthermore,
these results agree well with the ARPES spectra observed at T = 20 K, where the
Fermi level lies inside the bulk conduction band. The Dirac point of the
topological surface states is shifted toward higher binding energy (~ 0.12 eV)
for Ag-doped samples as compared to pristine Bi2Se3.",2303.00296v1
2023-02-21,Electronic Transport in the Silicon Carbide Semiconductor in Phase 3C,"In this work we study, theoretically, electronic mobility of the silicon
carbide semiconductor in the 3C phase, named 3C-SiC. 3C-SiC has shown great
potential for applications in extreme conditions. Thus, the study of the
electronic mobility of this semiconductor is of great interest. In this work
were theoretically deduced: drift velocity, displacement and mobility of the
charge carriers in the n-type doped 3C-SiC semiconductor, subjected to a
constant electric field. The dependence of these transport properties as a
function of the intensity of the electric field and temperature was analyzed.
For this, a differential equation of motion was used with a source term (low
intensity electric fields) and a term of resistance to movement (electrical
resistance).",2303.09457v1
2023-03-19,The fluidic memristor: collective phenomena in elastohydrodynamic networks,"Fluid flow networks are ubiquitous and can be found in a broad range of
contexts, from human-made systems such as water supply networks to living
systems like animal and plant vasculature. In many cases, the elements forming
these networks exhibit a highly non-linear pressure-flow relationship. Although
we understand how these elements work individually, their collective behavior
remains poorly understood. In this work, we combine experiments, theory, and
numerical simulations to understand the main mechanisms underlying the
collective behavior of soft flow networks with elements that exhibit negative
differential resistance. Strikingly, our theoretical analysis and experiments
reveal that a minimal network of nonlinear resistors, which we have termed a
`fluidic memristor', displays history-dependent resistance. This new class of
element can be understood as a collection of hysteresis loops that allows this
fluidic system to store information. Our work provides insights that may inform
new applications of fluid flow networks in soft materials science, biomedical
settings, and soft robotics, and may also motivate new understanding of the
flow networks involved in animal and plant physiology.",2303.10777v1
2023-03-20,Engineering Higher-Order Dirac and Weyl Semimetallic phase in 3D Topolectrical Circuits,"We propose a 3D topolectrical (TE) network that can be tuned to realize
various higher-order topological gapless and chiral phases. We first study a
higher-order Dirac semimetal phase that exhibits a hinge-like Fermi arc linking
the Dirac points. This circuit can be extended to host highly tunable first-
and second-order Weyl semimetal phases by introducing a non-reciprocal
resistive coupling in the x-y plane that breaks time reversal symmetry. The
first- and second-order Weyl points are connected by zero-admittance surface
and hinge states, respectively. We also study the emergence of first- and
second-order chiral modes induced by resistive couplings between similar nodes
in the z-direction. These modes respectively occur in the midgap of the surface
and hinge admittance bands in our circuit model without the need for any
external magnetic field.",2303.10911v2
2023-03-20,Electronic and magnetic properties of Lu and LuH$_2$,"Clarifying the electronic and magnetic properties of lutetium, lutetium
dihydride, and lutetium oxide is very helpful to understand the emergent
phenomena in lutetium-based compounds (such as room-temperature
superconductivity). However, this kind of study is still scarce at present.
Here, we report on the electronic and magnetic properties of lutetium metals,
lutetium dihydride powders, and lutetium oxide powders. Crystal structures and
chemical compositions of these samples were characterized by X-ray diffraction
and X-ray photoemission spectroscopy, respectively. Electrical transport
measurements show that the resistance of lutetium has a linear behavior
depending on temperature, whereas the resistance of lutetium dihydride powders
is independent of temperature. More interestingly,
paramagnetism-ferromagnetism-spin glass transitions were observed at near 240
and 200 K, respectively, in lutetium metals. Our work uncovered the complex
magnetic properties of Lu-based compounds.",2303.11063v2
2023-04-22,A Deep Neural Network Deployment Based on Resistive Memory Accelerator Simulation,"The objective of this study is to illustrate the process of training a Deep
Neural Network (DNN) within a Resistive RAM (ReRAM) Crossbar-based simulation
environment using CrossSim, an Application Programming Interface (API)
developed for this purpose. The CrossSim API is designed to simulate neural
networks while taking into account factors that may affect the accuracy of
solutions during training on non-linear and noisy ReRAM devices. ReRAM-based
neural cores that serve as memory accelerators for digital cores on a chip can
significantly reduce energy consumption by minimizing data transfers between
the processor and SRAM and DRAM. CrossSim employs lookup tables obtained from
experimentally derived datasets of real fabricated ReRAM devices to digitally
reproduce noisy weight updates to the neural network. The CrossSim directory
comprises eight device configurations that operate at different temperatures
and are made of various materials. This study aims to analyse the results of
training a Neural Network on the Breast Cancer Wisconsin (Diagnostic) dataset
using CrossSim, plotting the innercore weight updates and average training and
validation loss to investigate the outcomes of all the devices.",2304.11337v1
2023-05-16,The kinetic theory of ultra-subsonic fermion systems and applications to flat band magic angle twisted bilayer graphene,"The only kinematically-allowed phonon-scattering events for bands of subsonic
fermions ($v_F < v_p$) are interband transitions, leading to different low-$T$
transport physics than in the typical supersonic case. We apply a kinetic
theory of phonon-limited transport to a generic two-band system of subsonic
fermions, deriving formulae for relaxation times and resistivity that are
accurate in the limit of close bands and small $v_F/v_p$. We predict regimes of
$\rho \propto T$, $\rho \propto T^2$, and perfect conductivity. Our theory
predicts linear-in-$T$ resistivity down to a crossover temperature that is
suppressed from its supersonic analogue by a factor of $v_F/v_p$, offering a
new explanation for low-$T$ ""strange metal"" behavior observed in flat band
systems.",2305.09120v1
2023-05-31,Supercurrent through a single transverse mode in nanowire Josephson junctions,"Hybrid superconductor-semiconductor materials are fueling research in
mesoscopic physics and quantum technology. Recently demonstrated smooth
$\beta$-Sn superconductor shells, due to the increased induced gap, are
expanding the available parameter space to new regimes. Fabricated on
quasiballistic InSb nanowires, with careful control over the hybrid interface,
Sn shells yield critical current-normal resistance products exceeding
temperature by at least an order of magnitude even when nanowire resistance is
of order 10k$\Omega$. In this regime Cooper pairs travel through a purely 1D
quantum wire for at least part of their trajectory. Here, we focus on the
evolution of supercurrent in magnetic field parallel to the nanowire. Long
decay up to fields of 1T is observed. At the same time, the decay for higher
occupied subbands is notably faster in some devices but not in others. We
analyze this using a tight-binding numerical model that includes the Zeeman,
orbital and spin-orbit effects. When the first subband is spin polarized, we
observe a dramatic suppression of supercurrent, which is also confirmed by the
model and suggests an absence of significant triplet supercurrent generation.",2306.00146v1
2023-06-26,Origin of magnetic ordering in half-Heusler RuMnGa,"The half-Heusler alloy RuMnGa having valence electron count (VEC) 18 has
recently been theoretically proposed to exhibit compensated ferrimagnetic
(CFiM) character instead of the expected nonmagnetic ground state. On the other
hand, a preliminary experimental study proposed ferromagnetic (FM) ordering. As
no half-Heusler system with VEC 18 is known to exhibit magnetic ordering, we
have investigated the details of crystal structure and magnetic properties of
RuMnGa using a combination of experimental tools, viz., x-ray and neutron
diffraction techniques, dc and ac susceptibility, isothermal magnetisation,
heat capacity, resistivity and neutron depolarisation measurements. Rietveld
refinements of x-ray and neutron diffraction data suggest single phase nature
of the compound with elemental composition RuMn$_{0.86}$Ga$_{1.14}$. We have
shown that the system exhibits FM-type ordering owing to the inherent presence
of this minor off-stoichiometry, showing very low magnetic moment. The system
also exhibits reentrant canonical spin-glass behaviour, which is rarely
observed in half-Heusler alloys. The temperature coefficient of resistivity
changes its sign from negative to positive and further to negative as the
temperature decreases.",2306.14836v1
2023-07-02,"Giant coercivity, resistivity upturn, and anomalous Hall effect in ferrimagnetic FeTb","Despite the blooming interest, the transition-metal rare-earth ferrimagnets
have not been comprehensively understood in terms of their coercivity and
transport properties. Here, we report a systematic study of the magnetic and
transport properties of ferrimagnetic FeTb alloy by varying the layer thickness
and temperature. The FeTb is tuned from the Tb-dominated regime to the
Fe-dominated regime via the layer thickness, without varying the composition.
The coercivity closely follows the $1/\cos\theta_H$ scaling (where $\theta_H$
is the polar angle of the external magnetic field) and increases
quasi-exponentially upon cooling (exceeding 90 kOe at low temperatures),
revealing that the nature of the coercivity is the thermally-assisted domain
wall depinning field. The resistivity exhibits a quasi-linear upturn upon
cooling possibly due to thermal vibrations of the structure factor of the
amorphous alloy. The existing scaling laws of the anomalous Hall effect in the
literature break down for the amorphous FeTb that are either Fe- or
Tb-dominated. These findings should advance the understanding of the
transition-metal-rare-earth ferrimagnets and the associated ferrimagnetic
phenomena in spintronics.",2307.00475v1
2023-07-19,Observation of large intrinsic anomalous Hall conductivity in polycrystalline Mn$_3$Sn films,"We report the observation of anomalous Hall effect in Mn$_3$Sn
polycrystalline thin films deposited on Pt coated Al$_2$O$_3$ substrate with a
large anomalous Hall conductivity of 65($\Omega$cm)$^{-1}$ at 3K. The Hall and
magnetic measurements show a very small hysteresis owing to a weak
ferromagnetic moment in this material. The longitudinal resistivity decreases
sufficiently for the thin films as compared to the polycrystalline bulk sample
used as the target for the film deposition. The anomalous Hall resistivity and
conductivity decreases almost linearly with the increase in the temperature. A
negative magnetoresistance is observed for all the measured temperatures with
the negative decrease in the magnitude with the increase in temperature.",2307.09808v1
2023-10-27,A diamond anvil microassembly for Joule heating and electrical measurements up to 150 GPa and 4000 K,"When diamond anvil cell (DAC) sample chambers are outfitted with both thermal
insulation and electrodes, two cutting-edge experimental methods are enabled:
Joule heating with spectroradiometric temperature measurement, and electrical
resistance measurements of samples heated to thousands of kelvin. The accuracy
of temperature and resistance measurements, however, often suffers from poor
control of the shape and location of the sample, electrodes, and thermal
insulation. Here, we present a recipe for the reproducible and precise
fabrication of DAC sample, electrodes, and thermal insulation using a
three-layer microassembly. The microassembly contains two potassium chloride
thermal insulation layers, four electrical leads, a sample, and a buttressing
layer made of polycrystalline alumina. The sample, innermost electrodes, and
buttress layer are fabricated by focused-ion-beam milling. Three iron samples
are presented as proof of concept. Each is successfully compressed and pulsed
Joule heated while maintaining a four-point probe configuration. The highest
pressure-temperature condition achieved is $\sim 150$ GPa and $\sim 4000$ K.",2310.18176v1
2023-11-02,Disentangling transport mechanisms in a correlated oxide by photoinduced charge injection,"We present a novel heterostructured approach to disentangle the mechanism of
electrical transport of the strongly correlated PrNiO3, by placing the
nickelate under the photoconductor CdS. This enables the injection of carriers
into PrNiO3 in a controlled way, which can be used to interrogate its intrinsic
transport mechanism. We find a non-volatile resistance decrease when
illuminating the system at temperatures below the PrNiO3 metal-insulator
transition. The photoinduced change becomes more volatile as the temperature
increases. These data help understand the intrinsic transport properties of the
nickelate-CdS bilayer. Together with data from a bare PrNiO3 film, we find that
the transport mechanism includes a combination of mechanisms including both
thermal activation and variable range hopping. At low temperatures without
photoinduced carriers the transport is governed by hopping, while at higher
temperatures and intense illumination the activation mechanism becomes
relevant. This work shows a new way to optically control the low-temperature
resistance of PrNiO3.",2311.00904v1
2023-11-13,Metallic conductivity on Na-deficient structural domain walls in the spin-orbit Mott insulator Na$_2$IrO$_3$,"Honeycomb Na$_2$IrO$_3$ is a prototype spin-orbit Mott insulator and Kitaev
magnet. We report a combined structural and electrical resistivity study of
Na$_2$IrO$_3$ single crystals. Laue back-scattering diffraction indicates
twinning with $\pm 120^\circ$ rotation around the $c^*$-axis while scanning
electron microscopy displays nanothin lines parallel to all three b-axis
orientations of twin domains. Energy dispersive x-ray analysis line-scans
across such domain walls indicate no change of the Ir signal intensity, i.e.
intact honeycomb layers, while the Na intensity is reduced down to $\sim 2/3$
of its original value at the domain walls, implying significant hole doping.
Utilizing focused-ion-beam micro-sectioning, the temperature dependence of the
electrical resistance of individual domain walls is studied. It demonstrates
the tuning through the metal-insulator transition into a correlated-metal
ground state by increasing hole doping.",2311.07275v1
2023-11-30,Electrical resistance associated with the scattering of optically oriented electrons in n-GaAs,"In a bulk GaAs crystal, an unusual magnetoresistance effect, which takes
place when a spin-polarized current flows through the sample, was detected.
Under conditions of optical pumping of electron spins, an external magnetic
field directed along the electric current and perpendicular to the oriented
spins decreases the resistance of the material. The phenomenon is due to the
spin-dependent scattering of electrons by neutral donors. It was found that the
sign of the magnetoresistance does not depend on the sign of the exciting light
circular polarization, the effect is even with respect to the sign of the spin
polarization of the carriers, which indicates a correlation between the spins
of optically oriented free electrons and electrons localized on donors.",2311.18713v1
2023-12-01,Comparative study of Kondo effect in Vanadium dichalcogenides VX$_2$ (X=Se & Te),"We report on the electrical transport, magnetotransport, and magnetic
properties studies on the transition metal dichalcogenides VSe$_2$ and VTe$_2$
and draw a comprehensive comparison between them. We observe Kondo effect in
both systems induced by the exchange interaction between localized moments and
conduction electrons at low temperature, resulting into resistance upturn at 6
K for VSe$_2$ and 17 K for VTe$_2$. From the field dependent resistance
measurements we find that the data is fitted best with modified Hamann equation
corrected by the quantum Brillouin function for VSe$_2$, while the data is
fitted best with modified Hamann equation corrected by the classical Langevin
function for VTe$_2$. Interestingly, we observe a contrasting magnetoresistance
(MR) property between these systems across the Kondo temperature. That means,
negative MR is found in both systems in the Kondo state. In the normal state MR
is positive for VSe$_2$, while it is negligible for VTe$_2$. In addition, both
systems show weak ferromagnetism at low temperature due to intercalated V
atoms.",2312.09258v1
2023-12-28,Memristive behavior of functionalized graphene quantum dot and polyaniline nanocomposites,"Zero-dimensional graphene quantum dots (GQD) dispersed in conducting polymer
matrix display a striking range of optical, mechanical, and thermoelectric
properties which can be utilized to design next-generation sensors and low-cost
thermoelectric. This exotic electrical property in GQDs is achieved by
exploiting the concentration of the GQDs and by tailoring the functionalization
of the GQDs. However, despite extensive investigation, the nonlinear
resistivity behavior leading to memristive like characteristic has not been
explored much. Here, we report electrical characterisation of nitrogen
functionalized GQD (NGQD) embedded in a polyaniline (PANI) matrix. We observe a
strong dependence of the resistance on current and voltage history, the
magnitude of which depends on the NGQD concentration and temperature. We
explain this memristive property using a phenomenological model of the
alignment of PANI rods with a corresponding charge accumulation arising from
the NGQD on its surface. The NGQD-PANI system is unique in its ability to
matrix offers a unique pathway to design neuromorphic logic and synaptic
architectures with crucial advantages over existing systems.",2312.16759v1
2024-01-04,Anomalous upper critical field in the quasicrystal superconductor Ta$_{1.6}$Te,"Superconductivity in quasicrystals poses a new challenge in condensed matter
physics. We measured the resistance and ac magnetic susceptibility of a
Ta$_{1.6}$Te dodecagonal quasicrystal, which is superconducting below $T_c
\sim$ 1 K. We show that the upper critical field increases linearly with a
large slope of $-$4.4 T/K with decreasing temperature down to 0.04 K, with no
tendency to level off. The extrapolated zero-temperature critical field exceeds
the Pauli limit by a factor of 2.3. We also observed flux-flow resistance with
thermally activated behavior and an irreversibility field that is distinct from
the upper critical field. We discuss these peculiarities in terms of the
nonuniform superconducting gap and spin--orbit interaction in quasicrystal
structures.",2401.02079v1
2024-01-07,Advancing Noise-Resilient Twist Angle Characterization in Bilayer Graphene through Raman Spectroscopy via GAN-CNN Modeling,"In this study, we introduce an innovative methodology for robust twist angle
identification in bilayer graphene using Raman spectroscopy, featuring the
integration of generative adversarial network and convolutional neural network
(GAN-CNN). Our proposed approach showcases remarkable resistance to noise
interference, particularly in ultra-low Signal-to-Noise Ratio (SNR) conditions.
We demonstrate the GAN-CNN model's robust learning capability, even when SNR
reaches minimal levels. The model's exceptional noise resilience negates the
necessity for preprocessing steps, facilitating accurate classification, and
substantially reducing computational expenses. Empirical results reveal the
model's prowess, achieving heightened accuracy in twist angle identification.
Specifically, our GAN-CNN model achieves a test accuracy exceeding 99.9% and a
recall accuracy of 99.9%, relying on an augmented dataset containing 4209
spectra. This work not only contributes to the evolution of noise-resistant
spectral analysis methodologies but also provides crucial insights into the
application of advanced deep learning techniques for bilayer graphene
characterization through Raman spectroscopy. The findings presented herein have
broader implications for enhancing the precision and efficiency of material
characterization methodologies, laying the foundation for future advancements
in the field.",2401.03371v1
2024-01-10,Superconductivity in Ternary Zirconium Telluride Zr6MTe2 with 3d Transition Metals,"We report the synthesis, electronic properties, and electronic states of
Zr6MTe2 (M = Cr, Mn, Fe, and Co), which is isostructural to a recently
discovered superconductor family Sc6MTe2. Based on the electrical resistivity
and heat capacity data measured at low temperatures, Zr6FeTe2 is found to show
bulk superconductivity below Tc = 0.76 K. Zr6CoTe2 also exhibited zero
resistivity due to superconductivity below 0.13 K. In contrast, Zr6+dMn1-dTe2
does not show superconductivity but instead exhibits strong magnetism, which
most likely prevents the formation of superconductivity in this material. The
electronic properties and electronic states of Zr6MTe2 are discussed in
comparison with those of Sc6MTe2.",2401.04870v1
2024-01-25,Non-zero crossing current-voltage characteristics of interface-type resistive switching devices,"A number of memristive devices, mainly ReRAMs, have been reported to exhibit
a unique non-zero crossing hysteresis attributed to the interplay of resistive
and not yet fully understood `capacitive', and `inductive' effects. This work
exploits a kinetic simulation model based on the stochastic cloud-in-a-cell
method to capture these effects. The model, applied to Au/BiFeO$_{3}$/Pt/Ti
interface-type devices, incorporates vacancy transport and capacitive
contributions. The resulting nonlinear response, characterized by hysteresis,
is analyzed in detail, providing an in-depth physical understanding of the
virtual effects. Capacitive effects are modeled across different layers,
revealing their significant role in shaping the non-zero crossing hysteresis
behavior. Results from kinetic simulations demonstrate the impact of
frequency-dependent impedance on the non-zero crossing phenomenon. This model
provides insights into the effects of various device material properties, such
as Schottky barrier height, device area and oxide layer on the non-zero
crossing point.",2401.14507v1
2024-01-27,Electronic structure and physical properties of candidate topological material GdAgGe,"We grew needle-shaped single crystals of GdAgGe, which crystallizes in a
noncentrosymmetric hexagonal crystal structure with space group
P$\overline{6}$2$m$ (189). The magnetic susceptibility data for $H \perp c$
reveal two pronounced antiferromagnetic transitions at $T_{N1}$ = 20 K and
$T_{N2}$ = 14.5 K. The magnetic susceptibility anomalies are less prominent for
$H \parallel c$. The transition at $T_{N1}$ is accompanied by a pronounced heat
capacity anomaly confirming the bulk nature of the magnetic transition. Below
$T_{N1}$, the electrical resistivity data follows a $T^{3/2}$ dependence. In
the magnetically ordered state, GdAgGe shows positive transverse
magnetoresistance, which increases with decreasing temperature and increasing
field, reaching a value of $\sim$ 27% at 9 T and 10 K. The Hall resistivity
data and electronic band structure calculations suggest that both the hole and
electron charge carriers contribute to the transport properties. The electronic
band structure displays linear band crossings near the Fermi level. The
calculations reveal that GdAgGe has a nodal line with drumhead surface states
coupled with a nonzero Berry phase, making it a nontrivial nodal-line
semimetal.",2401.15464v1
2024-02-29,First-principles electron-phonon interactions and electronic transport in large-angle twisted bilayer graphene,"Twisted bilayer graphene (tBLG) has emerged as an exciting platform for novel
condensed matter physics. However, electron-phonon ($e$-ph) interactions in
tBLG and their effects on electronic transport are not completely understood.
Here we show first-principles calculations of $e$-ph interactions and
resistivity in commensurate tBLG with large twist angles of 13.2 and 21.8
degrees. These calculations overcome key technical barriers, including large
unit cells of up to 76 atoms, Brillouin-zone folding of the $e$-ph
interactions, and unstable lattice vibrations due to the AA-stacked domains. We
show that $e$-ph interactions due to layer-breathing (LB) phonons enhance
intervalley scattering in large-angle tBLG. This interaction effectively
couples the two layers, which are otherwise electronically decoupled at such
large twist angles. As a result, the phonon-limited resistivity in tBLG
deviates from the temperature-linear trend characteristic of monolayer graphene
and tBLG near the magic angle. Taken together, our work quantifies $e$-ph
interactions and scattering mechanisms in tBLG, revealing subtle interlayer
coupling effects at large twist angles.",2402.19453v1
2024-03-04,Tuning charge density wave of kagome metal ScV6Sn6,"Compounds with a kagome lattice exhibit intriguing properties and the charge
density wave (CDW) adds an additional layer of interest to research on them. In
this study, we investigate the temperature and magnetic field dependent
electrical properties under a chemical substitution and hydrostatic pressure of
ScV6Sn6, a non-magnetic charge density wave (CDW) compound. Substituting 5 % Cr
at the V site or applying 1.5 GPa of pressure shifts the CDW to 50 K from 92 K.
This shift is attributed to the movement of the imaginary phonon band, as
revealed by the phonon dispersion relation. The longitudinal and Hall
resistivities respond differently under these stimuli. The magnetoresistance
(MR) maintains its quasilinear behavior under pressure, but it becomes
quadratic after Cr substitution. The anomalous Hall-like behavior of the parent
compound persists up to the respective CDW transition under pressure, after
which it sharply declines. In contrast, the longitudinal and Hall resistivities
of Cr substituted compounds follow a two-band model and originates from the
multi carrier effect. These results clearly highlight the role of phonon
contributions in the CDW transition and call for further investigation into the
origin of the anomalous Hall-like behavior in the parent compound.",2403.02463v1
2024-03-05,A Reduced-Order Resistive Force Model for Robotic Foot-Mud Interactions,"Legged robots are well-suited for broad exploration tasks in complex
environments with yielding terrain. Understanding robotic foot-terrain
interactions is critical for safe locomotion and walking efficiency for legged
robots. This paper presents a reduced-order resistive-force model for
robotic-foot/mud interactions. We focus on vertical robot locomotion on mud and
propose a visco-elasto-plastic analog to model the foot/mud interaction forces.
Dynamic behaviors such as mud visco-elasticity, withdrawing cohesive suction,
and yielding are explicitly discussed with the proposed model. Besides
comparing with dry/wet granular materials, mud intrusion experiments are
conducted to validate the force model. The dependency of the model parameter on
water content and foot velocity is also studied to reveal in-depth model
properties under various conditions. The proposed force model potentially
provides an enabling tool for legged robot locomotion and control on muddy
terrain.",2403.02617v1
2024-03-20,The influence of hydrogen on the electronic structure in transition metallic glasses,"We investigate the influence of hydrogen on the electronic structure of a
binary transition metallic glass of V$_{80}$Zr$_{20}$. We examine the
hybridization between the hydrogen and metal atoms with the aid of hard x-ray
photoelectron spectroscopy. Combined with ab initio density functional theory,
we are able to show and predict the formation of $s$-$d$ hybridized energy
states. With optical transmission and resistivity measurements, we investigate
the emergent electronic properties formed out of those altered energy states,
and together with the theoretical calculations of the frequency-dependent
conductivity tensor, we qualitatively support the observed strong
wavelength-dependency of the hydrogen-induced changes on the optical absorption
and a positive parabolic change in resistivity with hydrogen concentration.",2403.13371v1
2024-04-07,Morphological stability of electrostrictive thin films,"A large electric field is typically present in anodic or passive oxide films.
Stresses induced by such a large electric field are critical in understanding
the breakdown mechanism of thin oxide films and improving their corrosion
resistance. In this work, we consider electromechanical coupling through the
electrostrictive effect. A continuum model incorporating lattice misfit and
electric field-induced stresses is developed. We perform a linear stability
analysis of the full coupled model and show that, for typical oxides,
neglecting electrostriction underestimates the film's instability, especially
in systems with a large electric field. Moreover, a region where
electrostriction can potentially provide a stabilizing effect is identified,
allowing electrostriction to enhance corrosion resistance. We identified an
equilibrium electric field intrinsic to the system and the corresponding
equilibrium film thickness. The film's stability is very sensitive to the
electric field: a 40 percent deviation from the equilibrium electric field can
change the maximum growth rate by nearly an order of magnitude. Moreover, our
model reduces to classical morphological instability models in the limit of
misfit-only, electrostatic-only, and no-electrostriction cases. Finally, the
effect of various parameters on the film's stability is studied.",2404.05093v1
2024-04-11,Respective Roles of Electron-Phonon and Electron-Electron Interactions in the Transport and Quasiparticle Properties of SrVO$_3$,"The spectral and transport properties of strongly correlated metals, such as
SrVO$_3$ (SVO), are widely attributed to electron-electron ($e$-$e$)
interactions, with lattice vibrations (phonons) playing a secondary role. Here,
using first-principles electron-phonon ($e$-ph) and dynamical mean field theory
calculations, we show that $e$-ph interactions play an essential role in SVO:
they govern the electron scattering and resistivity in a wide temperature range
down to 30 K, and induce an experimentally observed kink in the spectral
function. In contrast, the $e$-$e$ interactions control quasiparticle
renormalizations and low temperature transport, and enhance the $e$-ph
coupling. We clarify the origin of the near $T^2$ temperature dependence of the
resistivity by analyzing the $e$-$e$ and $e$-ph limited transport regimes. Our
work disentangles the electronic and lattice degrees of freedom in a
prototypical correlated metal, revealing the dominant role of $e$-ph
interactions in SVO.",2404.07772v1
2024-04-16,Strain-dependent Insulating State and Kondo Effect in Epitaxial SrIrO$_{3}$ Films,"The large spin-orbit coupling in iridium oxides plays a significant role in
driving novel physical behaviors, including emergent phenomena in the films and
heterostructures of perovskite and Ruddlesden-Popper iridates. In this work, we
study the role of epitaxial strain on the electronic behavior of thin SrIrO$_3$
films. We find that compressive epitaxial strain leads to metallic transport
behavior, but a slight tensile strain shows gapped behavior.
Temperature-dependent resistivity measurements are used to examine different
behaviors in films as a function of strain. We find Kondo contributions to the
resistivity, with stronger effects in films that are thinner and under less
compressive epitaxial strain. These results show the potential to tune
SrIrO$_3$ into Kondo insulating states and open possibilities for a quantum
critical point that can be controlled with strain in epitaxial films.",2404.10909v1
2024-04-24,Low thermal boundary resistance at bonded GaN/diamond interface by controlling ultrathin heterogeneous amorphous layer,"Thermal boundary resistance (TBR) in semiconductor-on-diamond structure
bottlenecks efficient heat dissipation in electronic devices. In this study, to
reduce the TBR between GaN and diamond, surface-activated bonding with a hybrid
SiOx-Ar ion source was applied to achieve an ultrathin interfacial layer. The
simultaneous surface activation and slow deposition of the SiOx binder layer
enabled precise control over layer thickness (2.5-5.3 nm) and formation of an
amorphous heterogeneous nanostructure comprising a SiOx region between two
inter-diffusion regions. Crucially, the 2.5-nm-thick interfacial layer achieved
a TBR of 8.3 m2-W/GW, a record low for direct-bonded GaN/diamond interface. A
remarkable feature is that the TBR is extremely sensitive to the interfacial
thickness; rapidly increasing to 34 m2-K/GW on doubling the thickness to 5.3
nm. Theoretical analysis revealed the origin of this increase: a diamond/SiOx
interdiffusion layer extend the vibrational frequency, far-exceeding that of
crystalline diamond, which increases the lattice vibrational mismatch and
suppresses phonon transmission.",2404.15738v1
2024-05-03,Local insulator-to-superconductor transition in amorphous InO$_x$ films modulated by e-beam irradiation,"We present a novel method enabling precise post-fabrication modulation of the
electrical resistance in micrometer-scale regions of amorphous indium oxide
(a-InO$_x$) films. By subjecting initially insulating films to an electron beam
at room temperature, we demonstrate that the exposed region of the films
becomes superconducting. The resultant superconducting transition temperature
($T_c$) is adjustable up to 2.8 K by changing the electron dose and
accelerating voltage. This technique offers a compelling alternative to
traditional a-InO$_x$ annealing methods for both fundamental investigations and
practical applications. Moreover, it empowers independent adjustment of
electrical properties across initially identical a-InO$_x$ samples on the same
substrate, facilitating the creation of superconducting microstructures with
precise $T_c$ control at the micrometer scale. The observed resistance
modifications likely stem from photoreduction induced by X-ray and/or UV
radiation emitted during electron beam interactions with the film and
substrate.",2405.02276v1
2024-05-27,Resistance Distribution of Decoherent Quantum Hall-Superconductor Edges,"We study the probability distribution of the resistance, or equivalently the
charge transmission, of a decoherent quantum Hall-superconductor edge, with the
decoherence coming from metallic puddles along the edge. Such metallic puddles
may originate from magnetic vortex cores or other superconductivity suppressing
perturbations. In contrast to the distribution of a coherent edge which is
peaked away from zero charge transmission, we show analytically and numerically
that the distribution of a decoherent edge with metallic puddles is always
peaked at zero charge transmission, which serves as a probe of coherence of
superconducting chiral edge states. We further show that the distribution width
decays exponentially in magnetic field and temperature. Our theoretical
decoherent distribution agrees well with the recent experimental observation in
graphene with superconducting proximity.",2405.17550v1
2017-12-13,Magnetotransport in a model of a disordered strange metal,"Despite much theoretical effort, there is no complete theory of the 'strange'
metal state of the high temperature superconductors, and its
linear-in-temperature, $T$, resistivity. Recent experiments showing an
unexpected linear-in-field, $B$, magnetoresistivity have deepened the puzzle.
We propose a simple model of itinerant electrons, interacting via random
couplings with electrons localized on a lattice of quantum 'dots' or 'islands'.
This model is solvable in a large-$N$ limit, and can reproduce observed
behavior. The key feature of our model is that the electrons in each quantum
dot are described by a Sachdev-Ye-Kitaev model describing electrons without
quasiparticle excitations. For a particular choice of the interaction between
the itinerant and localized electrons, this model realizes a controlled
description of a diffusive marginal-Fermi liquid (MFL) without momentum
conservation, which has a linear-in-$T$ resistivity and a $T \ln T$ specific
heat as $T\rightarrow 0$. By tuning the strength of this interaction relative
to the bandwidth of the itinerant electrons, we can additionally obtain a
finite-$T$ crossover to a fully incoherent regime that also has a linear-in-$T$
resistivity. We show that the MFL regime has conductivities which scale as a
function of $B/T$; however, its magnetoresistance saturates at large $B$. We
then consider a macroscopically disordered sample with domains of MFLs with
varying densities of electrons. Using an effective-medium approximation, we
obtain a macroscopic electrical resistance that scales linearly in the magnetic
field $B$ applied perpendicular to the plane of the sample, at large $B$. The
resistance also scales linearly in $T$ at small $B$, and as $T f(B/T)$ at
intermediate $B$. We consider implications for recent experiments reporting
linear transverse magnetoresistance in the strange metal phases of the
pnictides and cuprates.",1712.05026v3
2018-10-05,Static and Dynamic Signatures of Anisotropic Electronic Phase Separation in La2/3Ca1/3MnO3 Thin Films under Anisotropic Strain,"The electronic phase separation (EPS) of optimally doped La2/3Ca1/3MnO3
(LCMO) thin films under various degrees of anisotropic strain is investigated
by static magnetotransport and dynamic relaxation measurements. Three LCMO
films were grown simultaneously on (001) NdGaO3 (NGO) substrates by pulsed
laser deposition, and then post-growth annealed at 780 oC in O2 for different
durations of time. With increasing annealing time, the films developed
significant strains of opposite signs along the two orthogonal in-plane
directions. The static temperature-dependent resistivity, R(T), was measured
simultaneously along the two orthogonal directions. With increasing annealing
time, both zero-field-cooled and field-cooled R(T) show significant increases,
suggesting strain-triggered EPS and appearance of antiferromagnetic insulating
(AFI) phases in a ferromagnetic metallic (FMM) ground state. Meanwhile, R(T)
along the tensile-strained [010] direction becomes progressively larger than
that along the compressive-strained [100]. The enhanced resistivity anisotropy
indicates that the EPS is characterized by phase-separated FMM entities with a
preferred orientation along [100], possibly due to the cooperative deformation
and rotation/tilting of the MnO6 octahedra under the enhanced anisotropic
strain. The anisotropic EPS can also be tuned by an external magnetic field.
During a field-cycle at several fixed temperatures, the AFI phases are melted
at high fields and recovered at low fields, resulting in sharp resistance
changes of the ratio as high as 104. Furthermore, the resistivity was found to
exhibit glass-like behavior, relaxing logarithmically in the phase-separated
states. Fitting the data to a phenomenological model, the resulting resistive
viscosity and characteristic relaxation time are found to evolve with
temperature, showing a close correlation with the static measurements in the
EPS states.",1810.02516v1
2023-07-13,Hydrodynamic magnetotransport in two-dimensional electron systems with macroscopic obstacles,"In high-quality conductors, the hydrodynamic regime of electron transport has
been recently realized. In this work we theoretically investigate
magnetotransport of a viscous electron fluid in samples with
electron-impermeable obstacles. We use the two approaches to describe the fluid
flow. The first one is based on the equations of hydrodynamics of a charged
fluid, which assume that the kinetic equation takes into account the two
harmonics of the electron distribution function. The second approach is based
on the equations that are obtained by taking into account three harmonics of
the distribution function (''quasi-hydrodynamics''). Within the hydrodynamic
approach, we consider the cases of the rough and the smooth edges of the disks,
on which the electron scattering is diffusive or specular, respectively. The
longitudinal magnetoresistivity turns out to be strong and negative, the same
for both rough and smooth discs edges to within small corrections. For rough
discs, the Hall resistivity is equal to its standard value. For smooth discs
the Hall resistance acquire a small correction to the standard value,
proportional to the Hall viscosity. In the quasi-hydrodynamic approach, we
considered the case of smooth discs and small magnetic fields. In the regime
when the flow is substantially different from the hydrodynamic one, the
longitudinal resistivity does not depend on the shear stress relaxation time
(but depends on the relaxation time of the third angular harmonic), while the
correction to the standard Hall resistivity does not depend on both relaxation
times. We compare the results of the hydrodynamic calculation of the
longitudinal resistance with the experimental data on magnetotransport in
high-quality GaAs quantum wells with macroscopic defects. A good agreement of
theory and experiment evidences in favor of the realization of the hydrodynamic
transport regime in such systems.",2307.06705v2
2023-11-13,Pruning random resistive memory for optimizing analogue AI,"The rapid advancement of artificial intelligence (AI) has been marked by the
large language models exhibiting human-like intelligence. However, these models
also present unprecedented challenges to energy consumption and environmental
sustainability. One promising solution is to revisit analogue computing, a
technique that predates digital computing and exploits emerging analogue
electronic devices, such as resistive memory, which features in-memory
computing, high scalability, and nonvolatility. However, analogue computing
still faces the same challenges as before: programming nonidealities and
expensive programming due to the underlying devices physics. Here, we report a
universal solution, software-hardware co-design using structural
plasticity-inspired edge pruning to optimize the topology of a randomly
weighted analogue resistive memory neural network. Software-wise, the topology
of a randomly weighted neural network is optimized by pruning connections
rather than precisely tuning resistive memory weights. Hardware-wise, we reveal
the physical origin of the programming stochasticity using transmission
electron microscopy, which is leveraged for large-scale and low-cost
implementation of an overparameterized random neural network containing
high-performance sub-networks. We implemented the co-design on a 40nm 256K
resistive memory macro, observing 17.3% and 19.9% accuracy improvements in
image and audio classification on FashionMNIST and Spoken digits datasets, as
well as 9.8% (2%) improvement in PR (ROC) in image segmentation on DRIVE
datasets, respectively. This is accompanied by 82.1%, 51.2%, and 99.8%
improvement in energy efficiency thanks to analogue in-memory computing. By
embracing the intrinsic stochasticity and in-memory computing, this work may
solve the biggest obstacle of analogue computing systems and thus unleash their
immense potential for next-generation AI hardware.",2311.07164v1
2022-06-09,Identification of High-Dielectric Constant Compounds from Statistical Design,"The discovery of high-dielectric materials is crucial to increasing the
efficiency of electronic devices and batteries. Here, we report three
previously unexplored materials with very high dielectric constants (69 $<$
$\epsilon$ $<$ 101) and large band gaps (2.9$<$ $E_{\text{g}}$(eV) $<$ 5.5)
obtained by screening materials databases using statistical optimization
algorithms aided by artificial neural networks (ANN). Two of these new
dielectrics are mixed-anion compounds (Eu$_5$SiCl$_6$O$_4$ and HoClO), and are
shown to be thermodynamically stable against common semiconductors via
phase-diagram analysis. We also uncovered four other materials with relatively
large dielectric constants (20$<$$\epsilon$$<$40) and band gaps
(2.3$<$$E_{\text{g}}$(eV)$<$2.7). While the ANN training data is obtained from
Materials Project, the search-space consists of materials from Open Quantum
Materials Database (OQMD) - demonstrating a successful implementation of
cross-database materials design. Overall, we report dielectric properties of 17
materials calculated using ab-initio calculations, that were selected in our
design workflow. The dielectric materials with high dielectric properties
predicted in this work open up further experimental research opportunities.",2206.04750v1
1997-10-23,"Stripes, Non-Fermi-Liquid Behavior, and Two-Component Transport in the High-Tc Cuprates","Non-Fermi-liquid features of the high-Tc cuprates, and specifically the
systematic behavior of the resistivity, Hall constant, and thermoelectric
power, are shown to result from an electronic structure based on ""large-U"" and
""small-U"" orbitals, and the resulting striped structure.",9710254v1
1998-12-03,Anomalous Magnetothermal Resistance of High-Tc Superconductors: Anomalous Cyclotron Orbits at a Dirac Point,"I derive equations of motion for quasiparticles near the nodes in the d-wave
gap of high Tc superconductors. Previous versions have not properly taken into
account the spatial dependence of the gap parameter phase. The results are
compatible with magnetothermal conductivity measurements in the superconducting
phase by Ong and Krishana.",9812063v1
1999-05-18,On Anisotropic Transport in High Landau Levels,"We would like to point out that: (i) according to the edge-bulk transport
models for the quantum Hall regime, the direction of low bulk conductance is
actually perpendicular to that expected naively; and (ii) the values of
experimental ""high resistance"" peaks correspond to value of bulk conductance
$\approx 1 e^{2}/h$.",9905237v1
2001-11-03,Stability of antiferromagnetism at high magnetic fields in Mn3Si,"We report low temperature measurements of the specific heat, resistivity and
magnetisation of the itinerant antiferromagnet Mn3Si. The unprecedented
stability of the magnetic state to high magnetic field up to 14 T inferred from
the invariance of these bulk properties is incompatible with itinerant
magnetism expected of a conventional Fermi liquid.",0111048v1
2003-11-12,The Driving Force of Superconducting Transition in High Temperature Superconductors,"We show that both the kinetic energy and the exchange energy of the t-J model
can be read off from the optical data. We show that the optical data indicates
that the superconducting transition in high temperature superconductors is
kinetic energy driven and the exchange energy resist the transition. We also
show that kinetic energy may also be the driving force of the pseudogap
phenomenon.",0311282v1
2009-04-10,Linear in temperature resistivity of scalar fermions: application to high Tc cuprates,no longer applicable,0904.1746v4
2024-01-06,The 4-adic complexity of quaternary sequences with low autocorrelation and high linear complexity,"Recently, Jiang et al. proposed several new classes of quaternary sequences
with low autocorrelation and high linear complexity by using the inverse Gray
mapping (JAMC, \textbf{69} (2023): 689--706). In this paper, we estimate the
4-adic complexity of these quaternary sequences. Our results show that these
sequences have large 4-adic complexity to resist the attack of the rational
approximation algorithm.",2401.03204v1
2020-08-27,Modeling cross-field demagnetization of superconducting stacks and bulks for up to 100 tapes and 2 million cycles,"Superconducting stacks and bulks can act as very strong magnets (more than 17
T), but they lose their magnetization in the presence of alternating (or
ripple) transverse magnetic fields, due to the dynamic magneto-resistance. This
demagnetization is a major concern for applications requiring high run times,
such as motors and generators, where ripple fields are of high amplitude and
frequency. We have developed a numerical model based on dynamic
magneto-resistance that is much faster than the conventional
Power-Law-resistivity model, enabling us to simulate high number of cycles with
the same accuracy. We simulate demagnetization behavior of superconducting
stacks made of 10-100 tapes for up to 2 million cycles of applied ripple field.
We found that for high number of cycles, the trapped field reaches non-zero
stationary values for both superconducting bulks and stacks; as long as the
ripple field amplitudes are below the parallel penetration field, being
determined by the penetration field for a single tape in stacks. Bulks keep
substantial stationary values for much higher ripple field amplitudes than the
stacks, being relevant for high number of cycles. However, for low number of
cycles, stacks lose much less magnetization as compared to bulks.",2008.12006v2
2021-03-07,130 mA/mm $β$-Ga$_2$O$_3$ MESFET with Low-Temperature MOVPE-Regrown Ohmic Contacts,"We report on the demonstration of metalorganic vapor phase epitaxy-regrown
(MOVPE) ohmic contacts in an all MOVPE-grown $\beta$-Ga$_2$O$_3$
metal-semiconductor field effect transistor (MESFET). The low-temperature
(600$^{\circ}$C) heavy (n$^{+}$) Si-doped regrown layers exhibit extremely high
conductivity with sheet resistance of 73 $\Omega$/$\square$ and record low
metal/n$^{+}$-Ga$_2$O$_3$ contact resistance of 80 m$\Omega$.mm and specific
contact resistivity of 8.3$\times$10$^{-7}$ $\Omega$.cm$^{2}$ were achieved.
The fabricated MESFETs exhibit a maximum drain-to-source current of 130 mA/mm,
a high I$_{ON}$/I$_{OFF}$ of $>$10$^{10}$ with a high power FOM of 25
MW/cm$^{2}$ were achieved without any field plates. Nanoparticle-assisted Raman
thermometry, thermal modeling, and infrared thermography were performed to
assess the device self-heating under the high current and power conditions.
This demonstration shows the promise of MOVPE technique for the realization of
high-performance lateral $\beta$-Ga$_2$O$_3$ devices and also highlights the
need for device-level thermal management.",2103.04275v2
2010-08-31,Uniaxial linear resistivity of superconducting La(1.905)Ba(0.095)CuO(4) induced by an external magnetic field,"We present an experimental study of the anisotropic resistivity of
superconducting La(2-x)Ba(x)CuO(4) with x=0.095 and transition temperature
Tc=32 K. In a magnetic field perpendicular to the CuO(2) layers, H(perp), we
observe that the resistivity perpendicular to the layers, \rho(perp), becomes
finite at a temperature consistent with previous studies on very similar
materials; however, the onset of finite parallel resistivity, \rho(par), occurs
at a much higher temperature. This behavior contradicts conventional theory,
which predicts that \rho(perp) and \rho(par) should become finite at the same
temperature. Voltage vs. current measurements near the threshold of voltage
detectability indicate linear behavior perpendicular to the layers, becoming
nonlinear at higher currents, while the behavior is nonlinear from the onset
parallel to the layers. These results, in the presence of moderate H(perp),
appear consistent with superconducting order parallel to the layers with
voltage fluctuations between the layers due to thermal noise. In search of
uncommon effects that might help to explain this behavior, we have performed
diffraction measurements that provide evidence for H(perp)-induced charge and
spin stripe order. The field-induced decoupling of superconducting layers is
similar to the decoupled phase observed previously in La(2-x)Ba(x)CuO(4) with
x=1/8 in zero field.",1009.0031v4
2014-07-03,"Phonon-limited resistivity of graphene by first-principle calculations: electron-phonon interactions, strain-induced gauge field and Boltzmann equation","Electron-phonon coupling in graphene is extensively modeled and simulated
from first principles. We find that using an accurate model for the
polarizations of the acoustic phonon modes is crucial to obtain correct
numerical results. The interactions between electrons and acoustic phonon
modes, the gauge field and deformation potential, are calculated at the DFT
level in the framework of linear response. The zero-momentum limit of acoustic
phonons is interpreted as a strain pattern, allowing the calculation of the
acoustic gauge field parameter in the GW approximation. The role of electronic
screening on the electron-phonon matrix elements is investigated. We then solve
the Boltzmann equation semi-analytically in graphene, including both acoustic
and optical phonon scattering. We show that, in the Bloch-Gr\""uneisen and
equipartition regimes, the electronic transport is mainly ruled by the
unscreened acoustic gauge field, while the contribution due to the deformation
potential is negligible and strongly screened. By comparing with experimental
data, we show that the contribution of acoustic phonons to resistivity is
doping- and substrate-independent. The DFT+GW approach underestimates this
contribution to resistivity by about 30 %. Above 270K, the calculated
resistivity underestimates the experimental one more severely, the
underestimation being larger at lower doping. We show that, beside remote
phonon scattering, a possible explanation for this disagreement is the
electron-electron interaction that strongly renormalizes the coupling to
intrinsic optical-phonon modes. Finally, after discussing the validity of the
Matthiessen rule in graphene, we derive simplified analytical solutions of the
Boltzmann equation to extract the coupling to acoustic phonons, related to the
strain-induced gauge field, directly from experimental data.",1407.0830v2
2015-08-10,Fracture resistance of zigzag single walled carbon nanotubes,"Brittle fracture is one of the important failure modes of Single-Walled
Carbon Nanotube (SWNT) due to mechanical loading. In this paper, the fracture
resistance of zigzag SWNTs with preexisting defects is calculated using
fracture mechanics concepts based on atomistic simulations. The problem of
unstable crack growth at finite temperature, presumably caused by lattice
trapping effect, is circumvented by computing the strain energy release rate
through a series of displacement-controlled tensile loading of SWNTs (applied
through moving the outermost layer of atoms at one end at constant strain rate
of 9.4x10-4/ps) with pre-existing crack-like defects of various lengths. The
strain energy release rate, G, is computed for (17,0), (28,0) and (35,0) SWNTs
(each with aspect ratio 4) with pre-existing cracks up to 29.5{\AA} long. The
fracture resistance, Gc, is determined as a function of crack length for each
tube at three different temperatures (1K, 300K and 500K). A significant
dependence of Gc on crack length is observed reminiscent of the rising R curve
behavior of metals at the macroscale: for the zigzag nanotubes Gc increases
with crack length at small length, and tends to reach a constant value if the
tube diameter is large enough. We suspect that the lattice trapping effect
plays the role of crack tip plasticity at the atomic scale. For example, at 300
Kelvin, Gc for the (35,0) tube with aspect ratio 4 converges to 6 Joule/m2 as
the crack length exceeds 20 Angstrom. This value is comparable with the
fracture toughness of graphite and Silicon. The fracture resistance of the
tubes is found to decrease significantly as the temperature increases. To study
the length effects, the computations are repeated for zigzag nanotubes with the
same three chiralities but with aspect ratio 8 at 1K.",1508.02129v1
2015-11-23,CPP Magnetoresistance of Magnetic Multilayers: A critical review,"We present a comprehensive review of data and analysis of Giant (G)
Magnetoresistance (MR) with Current-flow Perpendicular-to-layer-Planes (CPP-MR)
of magnetic multilayers [F/N]n (n = number of repeats) with alternating
nanoscale layers of ferromagnetic (F) and non-magnetic (N) metals. GMR, a large
change in resistance when an applied magnetic field changes the moment ordering
of adjacent F-layers from anti-parallel (AP) to parallel (P), was discovered in
1988 in the Current-flow-in-layer-Planes (CIP) geometry. The CPP-MR has two
advantages over the CIP-MR: (1) it allows more direct access to the underlying
physics; and (2) it is usually larger, which should be advantageous for
devices. When the first CPP-MR data were published in 1991, it was not clear
whether electronic transport in GMR multilayers is fully diffusive or at least
partly ballistic. It was not known whether the properties of layers and
interfaces would vary with layer thickness or number. It was not known if the
CPP-MR would be dominated by scattering within the F-metals or at the F/N
interfaces. Nothing was known about: (1) spin-flipping within F-metals,
characterized by a spin-diffusion length, l(F)sf; (2) interface specific
resistances (AR = area A times resistance R) for N1/N2 interfaces; (3)
interface specific resistances and spin-dependent scattering asymmetry at F/N
and F1/F2 interfaces; and (4) spin-flipping at F/N, F1/F2 and N1/N2 interfaces.
Knowledge of spin-dependent scattering asymmetries in F-metals and F-alloys,
and of spin-flipping in N-metals and N-alloys was limited. We show how CPP-MR
measurements have quantified the scattering and spin-flipping parameters that
determine CPP-MR for a wide range of F- and N-metals and alloys and of F/N
pairs. We also review progress in finding techniques and F-alloys and F/N pairs
to enhance the CPP-MR to make it more competitive for devices.",1511.07387v1
2016-07-01,Size-dependence of nanosecond-scale spin-torque switching in perpendicularly magnetized tunnel junctions,"We time-resolve the spin-transfer-torque-induced switching in perpendicularly
magnetized tunnel junctions of diameters from 50 to 250 nm in the thermally
activated regime. When the field and the spin-torque concur to favor the P to
AP transition, the reversal yields monotonic resistance ramps that can be
interpreted as a domain wall propagation through the device at velocities of 17
to 30 nm/ns; smaller cells switch hence faster. When the field hinders the P to
AP transition, the switching is preceded by repetitive switching attempts,
during which the resistance transiently increases until successful reversal
occurs. At 50 nm, the P to AP switching proceeds reproducibly in 3 ns, with a
monotonic increase of the device resistance. In the reverse transition (AP to
P), several reversal paths are possible even in the smallest junctions.
Besides, the non uniform nature of the response seems still present at
nanoscale, with sometimes electrical signatures of strong disorder during the
reversal. The AP to P transition is preceded by a strong instability of the AP
state in devices above 100 nm. The resistance becomes extremely agitated before
switching to P in a path yielding a slow (20-50 ns) irregular increase of the
conductance with variability. Unreversed bubbles of 60 nm can persist a few
microseconds in the largest junctions. The complexity of the AP to P switching
is reduced but not suppressed when the junctions are downsized below 60 nm. The
instability of the initial AP state is no longer detected but the other
features remain. In the smallest junctions (50 nm) we occasionally observe much
faster (sub-1 ns) switching events. We discuss the origin of the switching
asymmetry and its size dependence, with an emphasis on the role of the non
uniformities of the stray field emanating from the reference layers, which
affects the zones in which nucleation is favored.",1607.00260v1
2018-03-08,Helical magnetic structure and the anomalous and topological Hall effects in epitaxial B20 Fe$_{1-y}$Co$_y$Ge films,"Epitaxial films of the B20-structure alloy Fe$_{1-y}$Co$_y$Ge were grown by
molecular beam epitaxy on Si (111) substrates. The magnetization varied
smoothly from the bulk-like values of one Bohr magneton per Fe atom for FeGe to
zero for non-magnetic CoGe. The chiral lattice structure leads to a
Dzyaloshinskii-Moriya interaction (DMI), and the films' helical magnetic ground
state was confirmed using polarized neutron reflectometry measurements. The
pitch of the spin helix, measured by this method, varies with Co content $y$
and diverges at $y \sim 0.45$. This indicates a zero-crossing of the DMI, which
we reproduced in calculations using first principle methods. We also measured
the longitudinal and Hall resistivity of our films as a function of magnetic
field, temperature, and Co content $y$. The Hall resistivity is expected to
contain contributions from the ordinary, anomalous, and topological Hall
effects. Both the anomalous and topological Hall resistivities show peaks
around $y \sim 0.5$. Our first principles calculations show a peak in the
topological Hall constant at this value of $y$, related to the strong
spin-polarisation predicted for intermediate values of $y$. Half-metallicity is
predicted for $y = 0.6$, consistent with the experimentally observed linear
magnetoresistance at this composition. Whilst it is possible to reconcile
theory with experiment for the various Hall effects for FeGe, the large
topological Hall resistivities for $y \sim 0.5$ are much larger then expected
when the very small emergent fields associated with the divergence in the DMI
are taken into account.",1803.03281v2
2020-07-09,Physical properties revealed by transport measurements on superconducting Nd$_{0.8}$Sr$_{0.2}$NiO$_{2}$ thin films,"The newly found superconductivity in infinite-layer nickelate superconducting
films has attracted much attention, because their crystalline and electronic
structures are similar to high-$T_c$ cuprate superconductors. The upper
critical field can provide much information on superconductivity, but detailed
experimental data are still lacking in these films. Here we present temperature
and angle dependence of resistivity measured under different magnetic fields
($H$) in Nd$_{0.8}$Sr$_{0.2}$NiO$_{2}$ thin films. The onset superconducting
transition occurs at about 16.2 K at 0 T. Temperature dependent upper critical
fields determined by using a criterion very close to the onset transition show
a clear negative curvature near the critical transition temperature, which is
explained as the consequence of the paramagnetically limited effect on
superconductivity. The temperature dependent anisotropy of the upper critical
field is obtained from resistivity data, which yields a value decreasing from 3
to 1.2 with lowering temperature. This can be explained by a variable
contribution from the orbital limit effect on upper critical field. The angle
dependent resistivity at a fixed temperature and different magnetic fields
cannot be scaled to one curve, which deviates from the prediction of the
anisotropic Ginzburg-Landau theory. However, at low temperatures, the increased
resistivity by magnetic field can be scaled by the parameter $H^\beta
|\cos\theta|$ ($1<\beta<6$) with $\theta$ the angle enclosed between $c$-axis
and the applied magnetic field. As the first detailed study on the upper
critical field of the nickelate thin films, our results clearly indicate a
small anisotropy and paramagnetically limited effect of superconductivity in
nickelate superconductors.",2007.04884v2
2020-11-11,Interface controlled thermal properties of ultra-thin chalcogenide-based phase change memory devices,"Phase change memory (PCM) is a rapidly growing technology that not only
offers advancements in storage-class memories but also enables in-memory data
storage and processing towards overcoming the von Neumann bottleneck. In PCMs,
the primary mechanism for data storage is thermal excitation. However, there is
a limited body of research regarding the thermal properties of PCMs at length
scales close to the memory cell dimension and, thus, the impact of interfaces
on PCM operation is unknown. Our work presents a new paradigm to manage thermal
transport in memory cells by manipulating the interfacial thermal resistance
between the phase change unit and the electrodes without incorporating
additional insulating layers. Experimental measurements show a substantial
change in thermal boundary resistance as GST transitions from one
crystallographic structure (cubic) to another (hexagonal) and as the thickness
of tungsten contacts is reduced from five to two nanometers. Simulations reveal
that interfacial resistance between the phase change unit and its adjacent
layer can reduce the reset current for 20 and 120 nm diameter devices by up to
~40% and ~50%, respectively. The resultant phase-dependent and geometric
effects on thermal boundary resistance dictate that the effective thermal
conductivity of the phase change unit can be reduced by a factor of four,
presenting a new opportunity to reduce operating currents in PCMs.",2011.05492v1
2022-03-22,"Effect of ECAP and heat treatment on mechanical properties, stress relaxation behavior and corrosion resistance of a 321-type austenitic steel with increased delta-ferrite content","Hot rolled commercial metastable austenitic steel 0.8C-18Cr-10Ni-0.1Ti
(Russian industrial name 08X18H10T, analog 321L) with strongly elongated thin
delta-ferrite particles in its microstructure was the object of investigations.
The lengths of these delta-particles were up to 500 mkm, the thickness was 10
mkm. The formation of the strain-induced martensite as well as the grinding of
the austenite and of the delta-ferrite grains take place during ECAP. During
the annealing of the UFG steel, the formation of the delta-phase particles
takes place. These particles affect the grain boundary migration and the
strength of the steel. However, a reduction of the Hall-Petch coefficient as
compared to the coarse-grained (CG) steel due to the fragmentation of the
delta-ferrite particles was observed. The samples of the UFG steel were found
to have 2-3 times higher stress relaxation resistance as compared to the CG
steel (a higher macroelasticity stress and a lower stress relaxation
magnitude). The differences in the stress relaxation resistance of the UFG and
CG steels were investigated. ECAP was shown to result in an increase in the
corrosion rate and in an increased tendency to the intergranular corrosion
(IGC). The reduction of the corrosion resistance of the UFG steel was found to
originate from the increase in the fraction of the strain-induced martensite
during ECAP.",2203.12102v1
2022-10-18,Sensing Remote Bulk Defects Through Resistance Noise in a Large Area Graphene Field Effect Transistor,"Substrate plays a crucial role in determining transport and low frequency
noise behavior of graphene field effect devices. Typically, heavily dope
Si/SiO$_2$ substrate is used to fabricate these devices for efficient gating.
Trapping-detrapping processes closed to the graphene/substrate interface are
the dominant sources of resistance fluctuations in the graphene channel, while
Coulomb fluctuations arising due to any remote charge fluctuations inside the
bulk of the substrate are effectively screened by the heavily doped substrate.
Here, we present electronic transport and low frequency noise characteristics
of large area CVD graphene field effect transistor (FET) prepared on a lightly
doped Si/SiO$_2$ substrate (N$_A$ $\sim$ 10$^{15}$cm$^{-3}$). Through a
systematic characterization of transport, noise and capacitance at various
temperature, we reveal that remote Si/SiO$_2$ interface can affect the charge
transport in graphene severely and any charge fluctuations inside bulk of the
silicon substrate can be sensed by the graphene channel. The resistance (R) vs.
back gate voltage (V$_{bg}$) characteristics of the device shows a hump around
the depletion region formed at the SiO$_2$/Si interface, confirmed by the
capacitance (C) - Voltage (V) measurement. Low frequency noise measurement on
these fabricated devices shows a peak in the noise amplitude close to the
depletion region. This indicates that due to the absence of any charge layer at
Si/SiO$_2$ interface, screening ability decreases and as a consequence, any
fluctuations in the deep level coulomb impurities inside the silicon substrate
can be observed as a noise in resistance in graphene channel via mobility
fluctuations. Noise behavior on ionic liquid gated graphene on the same
substrate exhibits no such peak in noise and can be explained by the
interfacial trapping - detrapping processes closed to the graphene channel.",2210.09851v1
2023-11-24,Multi-tap Resistive Sensing and FEM Modeling enables Shape and Force Estimation in Soft Robots,"We address the challenge of reliable and accurate proprioception in soft
robots, specifically those with tight packaging constraints and relying only on
internally embedded sensors. While various sensing approaches with single
sensors have been tried, often with a constant curvature assumption, we look
into sensing local deformations at multiple locations of the sensor. In our
approach, we multi-tap an off-the-shelf resistive sensor by creating multiple
electrical connections onto the resistive layer of the sensor and we insert the
sensor into a soft body. This modification allows us to measure changes in
resistance at multiple segments throughout the length of the sensor, providing
improved resolution of local deformations in the soft body. These measurements
inform a model based on a finite element method (FEM) that estimates the shape
of the soft body and the magnitude of an external force acting at a known
arbitrary location. Our model-based approach estimates soft body deformation
with approximately 3% average relative error while taking into account internal
fluidic actuation. Our estimate of external force disturbance has an 11%
relative error within a range of 0 to 5 N. The combined sensing and modeling
approach can be integrated, for instance, into soft manipulation platforms to
enable features such as identifying the shape and material properties of an
object being grasped. Such manipulators can benefit from the inherent softness
and compliance while being fully proprioceptive, relying only on embedded
sensing and not on external systems such as motion capture. Such proprioception
is essential for the deployment of soft robots in real-world scenarios.",2311.14566v1
2024-04-05,Direct Electrical Detection of Spin Chemical Potential Due to Spin Hall Effect in $β$-Tungsten and Platinum Using a Pair of Ferromagnetic and Normal Metal Voltage probes,"The phenomenon of Spin Hall Effect (SHE) generates a pure spin current
transverse to an applied current in materials with strong spin-orbit coupling,
although not detectable through conventional electrical measurement. An
intuitive Hall effect like measurement configuration is implemented to directly
measure pure spin chemical potential of the accumulated spins at the edges of
heavy metal (HM) channels that generates large SHE. A pair of transverse
linearly aligned voltage probes in placed in ohmic contact with the top surface
of HM , one being a ferromagnetic metal (FM) with non-zero spin polarization
and other is the reference metal (RM) with zero polarization of carriers. This
combination of FM/RM electrodes is shown to induce an additional voltage
proportional to a spin accumulation potential, which is anti symmetric with
respect to opposite orientations of FM controlled by a 2D vector magnet. Proof
of concept of the measurement scheme is verified by comparing the signs of
voltages for HM channels of Tungsten (W) and Platinum (Pt) which are known to
generate opposite spin accumulation under similar conditions of applied
current. The same devices are also able to detect the reciprocal effect,
inverse spin Hall effect (ISHE) by swapping the current and voltage leads and
the results are consistent with reciprocity principle. Further, exploiting a
characteristic feature of W thin film deposition, a series of devices were
fabricated with W resistivity varying over a wide range of 10 - 750 $\mu
\Omega$-cm and the calculated spin Hall resistivity exhibits a pronounced power
law dependence on resistivity. Our measurement scheme combined with almost two
decades of HM resistivity variation provides the ideal platform required to
test the underlying microscopic mechanism responsible for SHE/ISHE.",2404.03934v1
2013-02-11,Feedback from Winds and Supernovae in Massive Stellar Clusters. I: Hydrodynamics,"We use 3D hydrodynamical models to investigate the effects of massive star
feedback from winds and supernovae on inhomogeneous molecular material left
over from the formation of a massive stellar cluster. We simulate the
interaction of the mechanical energy input from a cluster with 3 O-stars into a
giant molecular cloud (GMC) clump containing 3240 solar masses of molecular
material within a 4 pc radius. The cluster wind blows out of the molecular
clump along low-density channels, into which denser clump material is
entrained. We find that the densest molecular regions are surprisingly
resistant to ablation by the cluster wind, in part due to shielding by other
dense regions closer to the cluster. Nonetheless, molecular material is
gradually removed by the cluster wind during which mass-loading factors in
excess of several 100 are obtained. Because the clump is very porous, 60-75 per
cent of the injected wind energy escapes the simulation domain, with the
difference being radiated. After 4.4 Myr, the massive stars in our simulation
begin to explode as supernovae. The highly structured environment into which
the SN energy is released allows even weaker coupling to the remaining dense
material and practically all of the SN energy reaches the wider environment.
The molecular material is almost completely dispersed and destroyed after 6
Myr. The escape fraction of ionizing radiation is estimated to be about 50 per
cent during the first 4 Myr of the cluster's life. A similar model with a
larger and more massive GMC clump reveals the same general picture, though more
time is needed for it to be destroyed.",1302.2443v1
2016-12-22,Insight into the Role of Oxygen in Phase-Change Material GeTe,"Oxygen is widely used to tune the performance of chalcogenide phase-change
materials in the usage of phase-Change random access memory (PCRAM) which is
considered as the most promising next-generation non-volatile memory. However,
the microscopic role of oxygen in the write-erase process, i.e., the reversible
phase transition between crystalline and amorphous state of phase-change
materials is not clear yet. Using oxygen doped GeTe as an example, this work
unravels the role of oxygen at the atomic scale by means of ab initio total
energy calculations and ab initio molecular dynamics simulations. Our main
finding is that after the amorphization and the subsequent re-crystallization
process simulated by ab initio molecular dynamics, oxygen will drag one Ge atom
out of its lattice site and both atoms stay in the interstitial region near the
Te vacancy that was originally occupied by the oxygen, forming a
""dumbbell-like"" defect (O-VTe-Ge), which is in sharp contrast to the results of
ab initio total energy calculations at 0 K showing that the oxygen prefers to
substitute Te in crystalline GeTe. This specific defect configuration is found
to be responsible for the slower crystallization speed and hence the improved
data retention of oxygen doped GeTe as reported in recent experimental work.
Moreover, we find that the oxygen will increase the effective mass of the
carrier and thus increases the resistivity of GeTe. Our results unravel the
microscopic mechanism of the oxygen-doping optimization of phase-change
material GeTe, and the present reported mechanism can be applied to other
oxygen doped ternary chalcogenide phase-change materials.",1612.07467v1
2013-12-20,Lessons from a Large-Scale Assessment: Results from Conceptual Inventories,"We report the conceptual inventory results of a large-scale assessment
project at a large university. We studied an attempt at introducing materials
and instructional methods informed by physics education research (PER-informed
materials) into a department where most instruction has been traditional and a
significant number of faculty are hesitant, ambivalent or even resistant about
the introduction of such reforms. The changes were made in the laboratories and
recitation sections of the introductory classes, both calculus-based and
algebra-based, introducing PER-informed materials and training the teaching
assistants in student-centered instructional methods. In addition to the
results found in the large lecture classes, we present the results of a small
PER-informed, inquiry-based, laboratory-based class that has been taught as a
special section of the algebra-based course for about 10 years. The assessment
reported in this paper was done using available PER-developed assessment
instruments. The results of other assessment instruments used in the project,
such as free-response pre- and post-tests, are reported in subsequent papers.
The results in this paper inform researchers in PER of the use of PER-informed
materials and instructional methods in a department not unified in the
introduction and implementation of these materials and the results of the
implementation as assessed by PER-based conceptual inventories. We found that
our conceptual inventory scores were lower than many results reported elsewhere
in the literature. However, we did see a statistically significant increase in
the conceptual inventory scores with the implementation of PER-informed
laboratories and the use of student-centered pedagogy in the labs and
recitations. The increase was much greater, if the lecture instructor also used
PER-informed materials.",1312.6000v1
2017-11-19,Elastomeric focusing enables application of hydraulic principles to solid materials in order to create micromechanical actuators with giant displacements,"A continuing challenge in material science is how to create active materials
in which shape changes or displacements can be generated electrically or
thermally. Here we borrow principles from hydraulics, in particular that
confined geometries can be used to focus expansion into large displacements, to
create solid materials with amplified shape changes. Specifically, we confined
an elastomeric poly(dimethylsiloxane) sheet between two more rigid layers and
caused focused expansion into embossed channels by local resistive heating,
resulting in a 10x greater relative displacement than the unconfined geometry.
We used this effect to create electrically controlled microfluidic valves that
open and close in less than 100 ms, can cycle >10,000 times, and operate with
as little as 20 mW of power. We investigate this mechanism and establish design
rules by varying dimensions, configurations, and materials. We show the
generality of elastomeric focusing by creating additional devices where local
heating and expansion are generated either wirelessly through inductive
coupling or optically with a laser, allowing arbitrary and dynamic positioning
of a microfluidic valve along the channels.",1711.07102v1
2020-04-29,Superconducting Materials for Microwave Kinetic Inductance Detectors,"The superconducting materials that make up an MKID have a significant effect
on its performance. The $T_\textrm{c}$ and normal state resistivity
$\rho_\textrm{N}$ of the film determine the penetration depth $\lambda$ and
therefore how much kinetic inductance it has. The ratio of kinetic inductance
to total inductance ($\alpha$), the volume of the inductor, and $Q_\textrm{m}$
determines the magnitude of the response to incoming energy. The quasiparticle
lifetime $\tau_\textrm{qp}$ is the characteristic time during which the MKID's
surface impedance is modified by the incoming energy. Many materials have been
explored for use in superconducting resonators and MKIDs, but that information
is often not published or scattered around the literature. This chapter
contains information and references on the work that has been done with thin
film lithographed circuits for MKIDs over the last two decades. Note that
measured material properties such as the internal loss quality factor
$Q_\textrm{i}$ and quasiparticle lifetime $\tau_\textrm{qp}$ vary significantly
depending on how the MKID superconducting thin film is made and the system they
are measured in, so it is best to interpret all stated values as typical but
not definitive. Values are omitted in cases when there aren't enough
measurements or there is too much disagreement in the literature to estimate a
typical value. In order to be as complete as possible some unpublished results
from the author's lab are included and can be identified by the lack of a
reference. Unless noted all films are polycrystalline or amorphous.",2004.14576v1
2018-12-20,Dynamics of Fluid Driven Autonomous Materials: Interconnected Fluid Filled Cavities to Realize Autonomous Materials,"The study of elastic structures embedded with fluid-filled cavities received
considerable attention in fields such as autonomous materials, sensors,
actuators, and smart systems. This work studies an elastic beam embedded with a
set of fluid-filled bladders, similar to a honeycomb structure, which are
interconnected via an array of slender tubes. The configuration of the
connecting tubes is arbitrary, and each tube may connect any two bladders. Beam
deformation both creates, and is induced by, the internal viscous flow- and
pressure-fields which deform the bladders and thus the surrounding solid.
Applying concepts from poroelasticity, and leveraging Cosserat beam
large-deformation models, we obtain a set of three coupled equations relating
the fluidic pressure within the bladders to the large transverse and
longitudinal displacements of the beam. We show that by changing the viscous
resistance of the connecting tubes we are able to modify the amplitude of
oscillatory deformation modes created due to external excitations on the
structure. In addition, rearranging tube configuration in a given bladder
system is shown to add an additional degree of control, and generate varying
mode shapes for the same external excitation. The presented modified Cosserat
model is applied to analyze a previously suggested energy harvester
configuration and estimate the efficiency of such a device. The results of this
work are validated by a transient three-dimensional numerical study of the full
fluid-structure-interaction problem. The presented model allows for the
analysis and design of soft smart-metamaterials with unique mechanical
properties.
  Keywords: autonomous materials, adaptive materials, programmed materials,
smart systems, autonomous systems, soft matter, soft robotics, energy
harvesting, fluid dynamics, fluid-structure interaction, large deformation.",1812.08717v2
2019-01-14,Anomalous relation between in-plane and out-of-plane stiffnesses in 2D networked materials,"For thin networked materials, which are spatial discrete structures
constructed by continuum components, a paradox on the effective thickness
defined by the in-plane and out-of-plane stiffnesses is found, i.e. the
effective thickness is not a constant but varies with loading modes. To reveal
the mechanism underneath the paradox, we have established a micromechanical
framework to investigate the deformation mechanism and predict the stiffness
matrix of the networked materials. It is revealed that the networked materials
can carry in-plane loads by axial stretching/compression of the components in
the networks and resist out-of-plane loading by bending and torsion of the
components. The bending deformation of components has a corresponding relation
to the axial stretching/compression through the effective thickness, as the
continuum plates do, while the torsion deformation has no relation to the axial
stretching/compression. The isolated torsion deformation breaks the classical
stiffness relation between the in-plane stiffness and the out-of-plane
stiffness, which can even be further distorted by the stiffness threshold
effect in randomly networked materials. Accordingly, a new formula is
summarized to describe the anomalous stiffness relation. This network model can
also apply in atomic scale 2D nanomaterials when combining with the molecular
structural mechanics model. This work gives an insight into the understanding
of the mechanical properties of discrete materials/structures ranging from
atomic scale to macro scale.",1901.04203v1
2019-10-16,"Stumbling Through the Research Wilderness, Standard Methods to Shine Light on Electrically Conductive Nanocomposites for Future Health-Care Monitoring","Electrically conductive nanocomposites are an exciting ever expanding area of
research that has yielded many new technologies for wearable health devices.
Acting as strain sensing materials, they have paved the way towards real time
medical diagnostic tools that may very well lead to a golden age of healthcare.
Currently, the goal in research is to create a material that simultaneously has
both a large gauge factor G and sensing range. However, a weakness in the area
of electromechanical research is the lack of standardisation in the reporting
of the figure of merit, i.e. G, and the need for new metrics to give
researchers a more complete view of the research landscape of resistive type
sensors. A paradigm shift in the way in which data is reported is required, to
push research in the right direction and to facilitate achieving research
goals. Here, we report a standardised method for reporting strain sensing
performance and the introduction of the working factor W and the Young's
modulus Y of a material as two new material criteria. Using this new method, we
can now for the first time define the benchmarks for an optimum sensing
material, G > 7, W > 1, Y < 300 kPa, using limits set by standard commercial
materials and the human body. Using extrapolated data from 200 publications
normalised to this standard method, we can review what composite types meet
these benchmark limits, what governs composite performances, the literary
trends in composites and individual nanomaterial performance and the future
prospects of research.",1910.07249v1
2022-04-11,Electron transport in the single-layer semiconductor,"Two-dimensional (2D) materials are a new class of materials with interesting
physical properties and applications ranging from nanoelectronics to sensing
and photonics. In addition to graphene, the most studied 2D material,
monolayers of other layered materials such as semiconducting dichalcogenides
MoS2 or WSe2 are gaining in importance as promising channel materials for
field-effect transistors (FETs) and phototransistors. However, it is unclear
that how the specific process of electron transport is affected by temperature.
So, nowadays the electron dynamics of single-layer semiconductor cannot be
understood fundamentally. Here, we develop an analytical theory distinguishing
from traditional energy band theory, backed up by Monte-Carlo simulations, that
predicts the process of electron transport and the effect of temperature on the
electron transport in the single-layer semiconductor. In this paper, A new
model is built to deal with electron transporting in the sing-layer
semiconductor. The resistance is decided by the barrier rather than the
electron scattering in the single-layer semiconductor, which is macroscopic
quantum effect. Electron transport in FETs with different dielectric
configurations are investigated at different temperatures and a new control
factor that is decided by top-gate voltage or bottom-gate voltage is introduced
to describe the effect of gate voltage on the electron transport in 2D
semiconductor. The results of simulation show the drain current is mainly
determined by some elements, such as temperature, top-gate voltage, bottom-gate
voltage and source-drain voltage.",2204.04850v1
2022-12-15,Physics-Informed Neural Networks for Material Model Calibration from Full-Field Displacement Data,"The identification of material parameters occurring in constitutive models
has a wide range of applications in practice. One of these applications is the
monitoring and assessment of the actual condition of infrastructure buildings,
as the material parameters directly reflect the resistance of the structures to
external impacts. Physics-informed neural networks (PINNs) have recently
emerged as a suitable method for solving inverse problems. The advantages of
this method are a straightforward inclusion of observation data. Unlike
grid-based methods, such as the least square finite element method (LS-FEM)
approach, no computational grid and no interpolation of the data is required.
In the current work, we propose PINNs for the calibration of constitutive
models from full-field displacement and global force data in a realistic regime
on the example of linear elasticity. We show that conditioning and
reformulation of the optimization problem play a crucial role in real-world
applications. Therefore, among others, we identify the material parameters from
initial estimates and balance the individual terms in the loss function. In
order to reduce the dependency of the identified material parameters on local
errors in the displacement approximation, we base the identification not on the
stress boundary conditions but instead on the global balance of internal and
external work. We demonstrate that the enhanced PINNs are capable of
identifying material parameters from both experimental one-dimensional data and
synthetic full-field displacement data in a realistic regime. Since
displacement data measured by, e.g., a digital image correlation (DIC) system
is noisy, we additionally investigate the robustness of the method to different
levels of noise.",2212.07723v2
2022-07-15,Screening 0D materials for 2D nanoelectronics applications,"As nanoelectronic devices based on two-dimensional (2D) materials are moving
towards maturity, optimization of the properties of the active 2D material must
be accompanied by equal attention to optimizing the properties of and the
interfaces to the other materials around it, such as electrodes, gate
dielectrics, and the substrate. While these are usually either 2D or 3D
materials, recently K. Liu et al. [Nat. Electron. 4, 906 (2021)] reported on
the use of zero-dimensional (0D) material, consisting of vdW-bonded Sb$_2$O$_3$
clusters, as a highly promising insulating substrate and gate dielectric. Here,
we report on computational screening study to find promising 0D materials for
use in nanoelectronics applications, in conjunction with 2D materials in
particular. By combining a database and literature searches, we found 16
materials belonging to 6 structural prototypes with high melting points and
high band gaps, and a range of static dielectric constants. We carried out
additional first-principles calculations to evaluate selected technologically
relevant material properties, and confirmed that all these materials are van
der Waals-bonded, thus allowing for facile separation of 0D clusters from the
3D host and also weakly perturbing the electronic properties of the 2D material
after deposition.",2207.07364v1
2015-08-07,"Pressure Effects on Superconducting Properties of the BiS2-Based Superconductor Bi2(O,F)S2","Pressure effects on a recently discovered BiS2-based superconductor
Bi2(O,F)S2 (Tc = 5.1 K) were examined via two different methods; high pressure
resistivity measurement and high pressure annealing. The effects of these two
methods on the superconducting properties of Bi2(O,F)S2 were significantly
different although in both methods hydrostatic pressure is applied to the
sample by the cubic-anvil-type apparatus. In high pressure resistivity
measurement, Tc linearly decreased at the rate of -1.2 K GPa-1. In contrast,
the Tc of 5.1 K is maintained after high pressure annealing under 2 GPa and
470{\deg}C of optimally doped sample despite significant change of lattice
parameters. In addition, superconductivity was observed in fluorine-free Bi2OS2
after high pressure annealing. These results suggest that high pressure
annealing would cause a unique effect on physical properties of layered
compounds.",1508.01656v1
2018-09-11,Atomic positions independent descriptor for machine learning of material properties,"The high-throughput screening of periodic inorganic solids using machine
learning methods requires atomic positions to encode structural and
compositional details into appropriate material descriptors. These atomic
positions are not available {\it a priori} for new materials which severely
limits exploration of novel materials. We overcome this limitation by using
only crystallographic symmetry information in the structural description of
materials. We show that for materials with identical structural symmetry,
machine learning is trivial and accuracies similar to that of density
functional theory calculations can be achieved by using only atomic numbers in
the material description. For machine learning of formation energies of bulk
crystalline solids, this simple material descriptor is able to achieve
prediction mean absolute errors of only 0.07 eV/atom on a test dataset
consisting of more than 85,000 diverse materials. This atomic-position
independent material descriptor presents a new route of materials discovery
wherein millions of materials can be screened by training a machine learning
model over a drastically reduced subspace of materials.",1809.03960v2
2019-01-14,Materials discovery and properties prediction in thermal transport via materials informatics: a mini-review,"There has been an increasing demand for materials with special thermal
properties, whereas experimental discovery is high-cost and time-consuming. The
emerging discipline `Materials Informatics' is an effective approach that can
accelerate materials development by combining material science and big data
technique. Recently materials informatics has been applied to the design of
novel materials such as thermal interface materials for heat-dissipation, and
thermoelectric materials for power generation. This mini-review summarized the
research progress on the applications of materials informatics for the thermal
transport properties prediction and discovery of materials with special thermal
properties, including optimal thermal conductivity, interfacial thermal
conductance and thermoelectricity efficiency. In addition, some perspectives
are given for the outlook of materials informatics in the field of thermal
transport.",1901.04133v1
2024-02-07,Are LLMs Ready for Real-World Materials Discovery?,"Large Language Models (LLMs) create exciting possibilities for powerful
language processing tools to accelerate research in materials science. While
LLMs have great potential to accelerate materials understanding and discovery,
they currently fall short in being practical materials science tools. In this
position paper, we show relevant failure cases of LLMs in materials science
that reveal current limitations of LLMs related to comprehending and reasoning
over complex, interconnected materials science knowledge. Given those
shortcomings, we outline a framework for developing Materials Science LLMs
(MatSci-LLMs) that are grounded in materials science knowledge and hypothesis
generation followed by hypothesis testing. The path to attaining performant
MatSci-LLMs rests in large part on building high-quality, multi-modal datasets
sourced from scientific literature where various information extraction
challenges persist. As such, we describe key materials science information
extraction challenges which need to be overcome in order to build large-scale,
multi-modal datasets that capture valuable materials science knowledge.
Finally, we outline a roadmap for applying future MatSci-LLMs for real-world
materials discovery via: 1. Automated Knowledge Base Generation; 2. Automated
In-Silico Material Design; and 3. MatSci-LLM Integrated Self-Driving Materials
Laboratories.",2402.05200v1
1997-11-19,Inter-Band Pairing Theory of Superconductivity,"A model for high temperature superconductors based on the idea of Cooper
pairs comprised of electrons from different bands is studied. We propose that
the two bands relevant for the cuprates are comprised of Cu dx2-y2, dz2, planar
O psigma, and apical O pz orbitals. Along the diagonal, kx=ky in the Brillouin
zone, the two band Fermi surfaces may cross. We associate the optimal doping
for the highest Tc with this point because only in the vicinity of this
touching point are inter-band Cooper pairs energetically possible. Due to the
lack of time reversal invariance of an inter-band Cooper pair with itself, the
standard interpretation of Josephson tunneling is altered such that the
detailed nature of the single particle tunneling matrix elements contributes to
the supercurrent. The dx2-y2 gap observations from Josephson tunneling are
shown to arise from our model with pairing due to phonons. A Hubbard model is
written down for the two bands at the Fermi energy with realistic parameters
for LaSrCuO. The anomalous normal state features in the nmr are calculated and
qualitatively explained as due to the character of the two bands in the
vicinity of the crossing point. The Hall effect is calculated using standard
Bloch-Boltzmann transport theory. The observed strong temperature dependence of
the Hall coefficient is reproduced and is due to the strong reshaping of the
current carrying band Fermi surface due to band repulsion with the other band
for dopings very close to the Fermi surface touching point. Reasonable
quantitative agreement is also obtained for the nmr and Hall effect. A linear
resistivity at optimal doping is expected due to the proximity of the second
band in k space which can strongly relax the current and the ""smallness"" of the
current carrying Fermi surface.",9711170v2
2001-02-01,The electronic state of vortices in YBa2Cu3Oy investigated by complex surface impedance measurement,"The electromagnetic response to microwaves in the mixed state of
YBa2Cu3Oy(YBCO) was measured in order to investigate the electronic state
inside and outside the vortex core. The magnetic-field dependence of the
complex surface impedance at low temperatures was in good agreement with a
general vortex dynamics description assuming that the field-independent viscous
damping force and the linear restoring force were acting on the vortices. In
other words, both real and imaginary parts of the complex resistivity, \rho_1,
and \rho_2, were linear in B. This is explained by theories for d-wave
superconductors. Using analysis based on the Coffey-Clem description of the
complex penetration depth, we estimated that the vortex viscosity \eta at 10 K
was (4 \sim 5) \times 10^{-7} Ns/m^2. This value corresponds to \omega_0 \tau
\sim 0.3 - 0.5, where \omega_0 and \tau are the minimal gap frequency and the
quasiparticle lifetime in the vortex core, respectively. These results suggest
that the vortex core in YBCO is in the moderately clean regime. Investigation
of the moderately clean vortex core in high-temperature superconductors is
significant because physically new effects may be expected due to d-wave
characteristics and to the quantum nature of cuprate superconductors. The
behavior of Z_s as a function of B across the first order transition (FOT) of
the vortex lattice was also investigated. Unlike Bi2Sr2CaCu2Oy (BSCCO), no
distinct anomaly was observed around the FOT in YBCO. Our results suggest that
the rapid increase of X_s due to the change of superfluid density at the FOT
would be observed only in highly anisotropic two-dimensional vortex systems
like BSCCO. We discuss these results in terms of the difference of the
interlayer coupling and the energy scale between the two materials.",0102021v2
2010-06-23,Physical properties of FeSe$_{0.5}$Te$_{0.5}$ single crystals grown under different conditions,"We report on structural, magnetic, conductivity, and thermodynamic studies of
FeSe$_{0.5}$Te$_{0.5}$ single crystals grown by self-flux and Bridgman methods.
The samples were prepared from starting materials of different purity at
various temperatures and cooling rates. The lowest values of the susceptibility
in the normal state, the highest transition temperature $T_c$ of 14.5 K, and
the largest heat-capacity anomaly at $T_c$ were obtained for pure (oxygen-free)
samples. The critical current density $j_c$ of $8 \times 10^4$ A/cm$^2$ (at 2
K) achieved in pure samples is attributed to intrinsic inhomogeneity due to
disorder at the cation and anion sites. The impure samples show increased $j_c$
up to $2.3 \times 10^5$ A/cm$^2$ due to additional pinning centers of
Fe$_3$O$_4$. The upper critical field $H_{c2}$ of $\sim 500$ kOe is estimated
from the resistivity study in magnetic fields parallel to the \emph{c}-axis.
The anisotropy of the upper critical field $\gamma_{H_{c2}} =
H_{_{c2}}^{ab}/H_{_{c2}}^{c}$ reaches a value $\sim 6$ at $T\longrightarrow
T_c$. Extremely low values of the residual Sommerfeld coefficient for pure
samples indicate a high volume fraction of the superconducting phase (up to
97%). The electronic contribution to the specific heat in the superconducting
state is well described within a single-band BCS model with a temperature
dependent gap $\Delta_0 = 27(1)$ K. A broad cusp-like anomaly in the electronic
specific heat of samples with suppressed bulk superconductivity is ascribed to
a splitting of the ground state of the interstitial Fe$^{2+}$ ions. This
contribution is fully suppressed in the ordered state in samples with bulk
superconductivity.",1006.4453v2
2011-01-25,Extreme 54Cr-rich nano-oxides in the CI chondrite Orgueil -Implication for a late supernova injection into the Solar System,"Systematic variations in 54Cr/52Cr ratios between meteorite classes (Qin et
al., 2010a; Trinquier et al., 2007) point to large scale spatial and/or
temporal isotopic heterogeneity in the solar protoplanetary disk. Two
explanations for these variations have been proposed, with important
implications for the formation of the Solar System: heterogeneous seeding of
the disk with dust from a supernova, or energetic-particle irradiation of dust
in the disk. The key to differentiating between them is identification of the
carrier(s) of the 54Cr anomalies. Here we report the results of our recent
NanoSIMS imaging search for the 54Cr-rich carrier in the acid-resistant residue
of the CI chondrite Orgueil. A total of 10 regions with extreme 54Cr-excesses
({\delta}54Cr values up to 1500 %) were found. Comparison between SEM, Auger
and NanoSIMS analyses showed that these 54Cr-rich regions are associated with
one or more sub-micron (typically less than 200 nm) Cr oxide grains, most
likely spinels. Because the size of the NanoSIMS primary O- ion beam is larger
than the typical grain size on the sample mount, the measured anomalies are
lower limits, and we estimate that the actual 54Cr enrichments in three grains
are at least 11 times Solar and in one of these may be as high as 50 times
Solar. Such compositions strongly favor a Type II supernova origin. The
variability in bulk 54Cr/52Cr between meteorite classes argues for a
heterogeneous distribution of the 54Cr carrier in the solar protoplanetary disk
following a late supernova injection event. Such a scenario is also supported
by the O-isotopic distribution and variable abundances in different planetary
materials of other presolar oxide and silicate grains from supernovae.",1101.4949v1
2011-12-02,Surviving the hole I: Spatially resolved chemistry around Sgr A*,"The interstellar region within the few central parsecs around the
super-massive black hole, Sgr A* at the very Galactic center is composed by a
number of overlapping molecular structures which are subject to one of the most
hostile physical environments in the Galaxy. We present high resolution
(4""x3""~0.16x0.11 pc) interferometric observations of CN, 13CN, H2CO, SiO,
c-C3H2 and HC3N emission at 1.3 mm towards the central ~4 pc of the Galactic
center region. Strong differences are observed in the distribution of the
different molecules. The UV resistant species CN, the only species tracing all
previously identified circumnuclear disk (CND) structures, is mostly
concentrated in optically thick clumps in the rotating filaments around Sgr A*.
H2CO emission traces a shell-like structure that we interpret as the expansion
of Sgr A East against the 50 km/s and 20 km/s giant molecular clouds (GMCs). We
derive isotopic ratios 12C/13C~15-45 across most of the CND region. The densest
molecular material, traced by SiO and HC3N, is located in the southern CND. The
observed c-C3H2/HC3N ratio observed in the region is more than an order of
magnitude lower than in Galactic PDRs. Toward the central region only CN was
detected in absorption. Apart from the known narrow line-of-sight absorptions,
a 90 km/s wide optically thick spectral feature is observed. We find evidences
of an even wider (>100 km/s) absorption feature. Around 70-75% of the gas mass,
concentrated in just the 27% densest molecular clumps, is associated with
rotating structures and show evidences of association with each of the arcs of
ionized gas in the mini-spiral structure. Chemical differentiation has been
proven to be a powerful tool to disentangle the many overlapping molecular
components in this crowded and heavily obscured region.",1112.0566v1
2012-09-17,"Transport, Thermal, and Magnetic Properties of the Narrow-Gap Semiconductor CrSb2","Resistivity, Hall effect, Seebeck coefficient, thermal conductivity, heat
capacity, and magnetic susceptibility data are reported for CrSb2 single
crystals. In spite of some unusual features in electrical transport and Hall
measurements below 100 K, only one phase transition is found in the temperature
range from 2 to 750 K corresponding to long-range antiferromagnetic order below
T_N ~ 273 K. Many of the low temperature properties can be explained by the
thermal depopulation of carriers from the conduction band into a low mobility
band located approximately 16 meV below the conduction band edge, as deduced
from the Hall effect data. In analogy with what occurs in Ge, the low mobility
band is likely an impurity band. The Seebeck coefficient, S, is large and
negative for temperatures from 2 to 300 K ranging from ~ -70\muV/K at 300 K to
-4500\muV/K at 18 K. A large maximum in |S| at 18 K is likely due to phonon
drag with the abrupt drop in |S| below 18 K due to the thermal depopulation of
the high mobility conduction band. The large thermal conductivity between 10
and 20 K (~350 W/m/K) is consistent with this interpretation, as are detailed
calculations of the Seebeck coefficient made using the complete calculated
electronic structure. These data are compared to data reported for FeSb2, which
crystallizes in the same marcasite structure, and FeSi, another unusual
narrow-gap semiconductor.",1209.3676v2
2013-11-13,"Thermodynamic and transport properties of single crystalline RCo$_{2}$Ge$_{2}$ (R = Y, La-Nd, Sm-Tm)","Single crystals of RCo$_{2}$Ge$_{2}$ (R = Y, La-Nd, Sm-Tm) were grown using a
self-flux method and were characterized by room-temperature powder x-ray
diffraction; anisotropic, temperature and field dependent magnetization;
temperature and field dependent, in-plane resistivity; and specific heat
measurements. In this series, the majority of the moment-bearing members order
antiferromagnetically; YCo$_{2}$Ge$_{2}$ and LaCo$_{2}$Ge$_{2}$ are
non-moment-bearing. Ce is trivalent in CeCo$_{2}$Ge$_{2}$ at high temperatures,
and exhibits an enhanced electronic specific heat coefficient due to Kondo
effect at low temperatures. In addition, CeCo$_{2}$Ge$_{2}$ shows two
low-temperature anomalies in temperature-dependent magnetization and specific
heat measurements. Three members (R = Tb-Ho) have multiple phase transitions
above 1.8 K. Eu appears to be divalent with total angular momentum L = 0. Both
EuCo$_{2}$Ge$_{2}$ and GdCo$_{2}$Ge$_{2}$ manifest essentially isotropic
paramagnetic properties consistent with J = S = 7/2. Clear magnetic anisotropy
for rare-earth members with finite L was observed, with ErCo$_{2}$Ge$_{2}$ and
TmCo$_{2}$Ge$_{2}$ manifesting planar anisotropy and the rest members
manifesting axial anisotropy. The experimentally estimated crystal electric
field (CEF) parameters B$_{2}^{0}$ were calculated from the anisotropic
paramagnetic $\theta_{ab}$ and $\theta_{c}$ values and follow a trend that
agrees well with theoretical predictions. The ordering temperatures, T$_{N}$,
as well as the polycrystalline averaged paramagnetic Curie-Weiss temperature,
$\Theta_{avg}$, for the heavy rare-earth members deviate from the de Gennes
scaling, as the magnitude of both are the highest for Tb, which is sometimes
seen for extremely axial systems. Except for SmCo$_{2}$Ge$_{2}$, metamagnetic
transitions were observed at 1.8 K for all members that ordered
antiferromagnetically.",1311.3321v1
2014-07-19,Ferromagnetic cluster spin-glass behavior in PrRhSn3,"We report the synthesis, structure, and magnetic and transport properties of
a new ternary intermetallic compound PrRhSn3 which crystallizes in LaRuSn3-type
cubic structure (space group Pm-3n). At low applied fields the dc magnetic
susceptibility exhibits a sharp anomaly below 6~K with an irreversible behavior
in zero field cooled (ZFC) and field cooled (FC) susceptibility below 5.5 K.
The ac susceptibility exhibits a frequency dependent anomaly revealing a
spin-glass behavior with a freezing temperature, T_f = 4.3 K. The observation
of spin-glass behavior is further supported by a very slow decay of
thermo-remnant magnetization (mean relaxation time tau = 2149 s). However, a
small jump at very low field in the isothermal magnetization at 2 K and a weak
anomaly in the specific heat near 5.5 K reveal the presence of ferromagnetic
clusters. The frequency dependence of the transition temperature T_f in the ac
susceptibility obeys the Vogel-Fulcher law, nu = nu_0exp[-E_a/k_B(T_f-T_0)]
with activation energy E_a/k_B = 19.1 K. This together with an intermediate
value of the parameter delta T_f = Delta T_f/T_f Delta(log nu) = 0.086 provide
an evidence for the formation of a cluster-glass state in PrRhSn3. The magnetic
contribution of the specific heat reveals a broad Schottky-type anomaly
centered around 10 K and the analysis based on the crystal electric field model
indicates a singlet ground state. Further, below T_f the magnetic part of the
specific heat exhibits a T^{3/2} temperature dependence. The strong influence
of the crystal electric field and a T^{3/2} temperature dependence are also
seen in the electrical resistivity which reveals a metallic character and a
high magnetoresistance. We also obtain a surprisingly large value of
Sommerfeld-Wilson ratio R_W ~ 247$.",1407.5201v1
2015-10-01,"Are quantum spin Hall edge modes more resilient to disorder, sample geometry and inelastic scattering than quantum Hall edge modes?","On the surface of 2D Topological insulators occur 1D quantum spin Hall(QSH)
edge modes with Dirac like dispersion. Unlike quantum Hall(QH) edge modes which
occur at high magnetic fields in 2DEGs, the occurrence of QSH edge modes is
because of spin-orbit scattering in the bulk of the material. These QSH edge
modes are spin dependent and chiral- opposite spins move in opposing
directions. Electronic spin has larger decoherence and relaxation time than
charge- in view of this its expected that QSH edge modes will be more robust to
disorder and inelastic scattering than QH edge modes which are charge dependent
and spin unpolarized. However, we notice no such advantage accrues to QSH edge
modes when subjected to same degree of contact disorder and/or inelastic
scattering in similar setups as QH edge modes. In fact we observe that QSH edge
modes are more susceptible to inelastic scattering and contact disorder than QH
edge modes. Further, while a single disordered contact has no effect on QH edge
modes it leads to a finite charge Hall current in case of quantum spin Hall
edge modes and thus vanishing of pure quantum spin Hall effect. For more than a
single disordered contact while quantum Hall states continue to remain immune
to disorder, quantum spin Hall edge modes become more susceptible- the Hall
resistance for quantum spin Hall effect changes sign with increasing disorder.
In case of many disordered contacts with inelastic scattering included while
quantization of Hall edge modes holds, for quantum spin Hall edge modes- a
finite charge Hall current still flows. For quantum spin Hall edge modes in the
inelastic scattering regime we distinguish between two cases: with spin-flip
and without spin-flip scattering. Finally, while asymmetry in sample geometry
can have a deleterious effect on quantum spin Hall case it has no impact in
quantum Hall case.",1510.00105v2
2015-10-06,Conservative regularization of compressible flow and ideal magnetohydrodynamics,"Ideal systems like MHD and Euler flow may develop singularities in vorticity
(w = curl v). Viscosity and resistivity are dissipative regularizations. We
propose a minimal, local, conservative, nonlinear, dispersive regularization of
compressible flow and ideal MHD, in analogy with the KdV regularization of the
1D Hopf equation. This work significantly extends earlier work on
incompressible Euler and ideal MHD. It involves a cut-off lambda inversely
proportional to square-root of density rho, which is like a position-dependent
mean free path. In MHD, lambda can be taken of order the electron collisionless
skin depth. The regularizing `twirl' term is - lambda w x curl w. Such a term
could be important in high speed flows with vorticity and arise in an expansion
of kinetic equations in Knudsen number. A magnetic analogue of the twirl term -
(B x curl B)/(rho mu_0), arises as the Lorentz force in ideal MHD. Our
regularization preserves symmetries of the ideal systems, and with appropriate
boundary conditions, implies associated conservation laws. Energy and enstrophy
are subject to a priori bounds determined by initial data. A Hamiltonian and
Poisson bracket formulation is developed and used to generalize the
constitutive relation to bound higher moments of w and curl w. A `swirl'
velocity field is shown to transport w/rho and B/rho, generalizing the
Kelvin-Helmholtz and Alfv\'en theorems. The steady regularized equations are
used to model a rotating vortex, MHD pinch, plane vortex sheet, channel flow,
plane flow and propagating spherical and cylindrical vortices; solutions are
more regular than corresponding Eulerian ones. The proposed regularization
could facilitate simulations of fluid/MHD equations and provide a consistent
statistical mechanics of vortices/current filaments in 3D, without blowup of
enstrophy. Implications for detailed analyses of fluid and plasma systems are
discussed.",1510.01606v2
2015-10-20,Photoconversion in the HIT solar cells: Theory vs experiment,"We obtain theoretical expressions for the photocurrent in the Heterojunction
solar cells with Intrinsic Thin layer (HIT cells). Our calculations take into
account tunneling of electrons and holes through wide-bandgap layers of
$\alpha$-Si:H or $\alpha$-SiC:H. We introduce the criteria, under which
tunneling does not lead to the deterioration of solar cell characteristics, in
particular, to the reduction of the short-circuit current and open-circuit
voltage. We propose an algorithm to compute the photoconversion efficiency of
HIT elements, taking into account the peculiarities of the open-circuit voltage
generation, in particular, its rather high values. We test our theoretical
predictions against the experimental results. For this, we fabricate HIT
elements with the efficiency of about $20\,\%$. We measured the temperature
dependence of the short-circuit current, open-circuit voltage, photoconversion
power, and fill factor of the current-voltage curve of these elements in a wide
temperature range from 80 to 420\,K. In the low-temperature range, the
open-circuit voltage and the photoconversion power decrease on cooling. At $T
\ge 200$\,K, the theoretical expressions and the experimental curves agree
rather well. The behavior of the fill factor and output power at low
temperatures is explained by the increase of the series resistance on cooling.
We discuss the reasons behind the reduction of the power temperature
coefficient in HIT elements. We show that they are related to the low value of
the combined surface and volume recombination rate. Finally, we derive a
theoretical expression for the HIT element's operation temperature under
natural working conditions.",1510.06007v2
2016-01-16,Signatures of the Adler-Bell-Jackiw chiral anomaly in a Weyl Fermion semimetal,"Weyl semimetals provide the realization of Weyl fermions in solid-state
physics. Among all the physical phenomena that are enabled by Weyl semimetals,
the chiral anomaly is the most unusual one. Here, we report signatures of the
chiral anomaly in the magneto-transport measurements on the first Weyl
semimetal TaAs. We show negative magnetoresistance under parallel electric and
magnetic fields, that is, unlike most metals whose resistivity increases under
an external magnetic field, we observe that our high mobility TaAs samples
become more conductive as a magnetic field is applied along the direction of
the current for certain ranges of the field strength. We present systematically
detailed data and careful analyses, which allow us to exclude other possible
origins of the observed negative magnetoresistance. Our transport data,
corroborated by photoemission measurements, first-principles calculations and
theoretical analyses, collectively demonstrate signatures of the Weyl fermion
chiral anomaly in the magneto-transport of TaAs.",1601.04208v2
2016-08-15,"Physical properties of single crystalline $R$Mg$_{2}$Cu$_{9}$ ($R$ = Y, Ce-Nd, Gd-Dy, Yb) and the search for in-plane magnetic anisotropy in hexagonal systems","Single crystals of $R$Mg$_{2}$Cu$_{9}$ ($R$=Y, Ce-Nd, Gd-Dy, Yb) were grown
using a high-temperature solution growth technique and were characterized by
measurements of room-temperature x-ray diffraction, temperature-dependent
specific heat and temperature-, field-dependent resistivity and anisotropic
magnetization. YMg$_{2}$Cu$_{9}$ is a non-local-moment-bearing metal with an
electronic specific heat coefficient, $\gamma \sim$ 15 mJ/mol K$^2$. Yb is
divalent and basically non-moment bearing in YbMg$_{2}$Cu$_{9}$. Ce is
trivalent in CeMg$_{2}$Cu$_{9}$ with two magnetic transitions being observed at
2.1 K and 1.5 K. PrMg$_{2}$Cu$_{9}$ does not exhibit any magnetic phase
transition down to 0.5 K. The other members being studied ($R$=Nd, Gd-Dy) all
exhibits antiferromagnetic transitions at low-temperatures ranging from 3.2 K
for NdMg$_{2}$Cu$_{9}$ to 11.9 K for TbMg$_{2}$Cu$_{9}$. Whereas
GdMg$_{2}$Cu$_{9}$ is isotropic in its paramagnetic state due to zero angular
momentum ($L$=0), all the other local-moment-bearing members manifest an
anisotropic, planar magnetization in their paramagnetic states. To further
study this planar anisotropy, detailed angular-dependent magnetization was
carried out on magnetically diluted (Y$_{0.99}$Tb$_{0.01}$)Mg$_{2}$Cu$_{9}$ and
(Y$_{0.99}$Dy$_{0.01}$)Mg$_{2}$Cu$_{9}$. Despite the strong, planar
magnetization anisotropy, the in-plane magnetic anisotropy is weak and
field-dependent. A set of crystal electric field parameters are proposed to
explain the observed magnetic anisotropy.",1608.04310v1
2017-06-19,"Chronic neural probe for simultaneous recording of single-unit, multi-unit, and local field potential activity from multiple brain sites","Drug resistant focal epilepsy can be treated by resecting the epileptic focus
requiring a precise focus localization using stereoelectroencephalography
(SEEG) probes. As commercial SEEG probes offer only a limited spatial
resolution, probes of higher channel count and design freedom enabling the
incorporation of macro and microelectrodes would help increasing spatial
resolution and thus open new perspectives for investigating mechanisms
underlying focal epilepsy and its treatment. This work describes a new
fabrication process for SEEG probes with materials and dimensions similar to
clinical probes enabling recording single neuron activity at high spatial
resolution. Polyimide is used as a biocompatible flexible substrate into which
platinum electrodes and leads are...
  The resulting probe features match those of clinically approved devices.
Tests in saline solution confirmed the probe stability and functionality.
Probes were implanted into the brain of one monkey (Macaca mulatta), trained to
perform different motor tasks. Suitable configurations including up to 128
electrode sites allow the recording of task-related neuronal signals. Probes
with 32 and 64 electrode sites were implanted in the posterior parietal cortex.
Local field potentials and multi-unit activity were recorded as early as one
hour after implantation. Stable single-unit activity was achieved for up to 26
days after implantation of a 64-channel probe. All recorded signals showed
modulation during task execution. With the novel probes it is possible to
record stable biologically relevant data over a time span exceeding the usual
time needed for epileptic focus localization in human patients. This is the
first time that single units are recorded along cylindrical polyimide probes
chronically implanted 22 mm deep into the brain of a monkey, which suggests the
potential usefulness of this probe for human applications.",1706.05899v1
2017-06-29,Effects of Incomplete Ionization on Beta - Ga2O3 Power Devices: Unintentional Donor with Energy 110 meV,"Understanding the origin of unintentional doping in Ga2O3 is key to
increasing breakdown voltages of Ga2O3 based power devices. Therefore,
transport and capacitance spectroscopy studies have been performed to better
understand the origin of unintentional doping in Ga2O3. Previously unobserved
unintentional donors in commercially available (-201) Ga2O3 substrates have
been electrically characterized via temperature dependent Hall effect
measurements up to 1000 K and found to have a donor energy of 110 meV. The
existence of the unintentional donor is confirmed by temperature dependent
admittance spectroscopy, with an activation energy of 131 meV determined via
that technique, in agreement with Hall effect measurements. With the
concentration of this donor determined to be in the mid to high 10^16 cm^-3
range, elimination of this donor from the drift layer of Ga2O3 power
electronics devices will be key to pushing the limits of device performance.
Indeed, analytical assessment of the specific on-resistance (Ronsp) and
breakdown voltage of Schottky diodes containing the 110 meV donor indicates
that incomplete ionization increases Ronsp and decreases breakdown voltage as
compared to Ga2O3 Schottky diodes containing only the shallow donor. The
reduced performance due to incomplete ionization occurs in addition to the
usual tradeoff between Ronsp and breakdown voltage. To achieve 10 kV operation
in Ga2O3 Schottky diode devices, analysis indicates that the concentration of
110 meV donors must be reduced below 5x10^14 cm^-3 to limit the increase in
Ronsp to one percent.",1706.09960v2
2018-01-24,Superconductivity in the vicinity of a ferroelectric quantum phase transition,"Superconductivity has been observed in doped SrTiO$_3$ at charge-carrier
densities below 10$^{18}$ cm$^{-3}$, where the density of states at the Fermi
level of the itinerant electrons is several orders of magnitude lower than that
of conventional metals. In terms of the Bardeen-Cooper-Schrieffer description,
this implies the existence of an extraordinarily strong interaction driving the
formation of Cooper pairs, potentially comparable in order of magnitude to that
in some high Tc superconductors. Under suitable conditions the interaction
might remain effective at densities approaching metallic densities, leading to
the possibility of pair formation at elevated temperatures. Here we investigate
the pressure dependence of the resistivity and superconducting transition
temperature, Tc, of SrTiO$_3$ at a carrier density near to optimal doping. Our
experiments show that Tc collapses rapidly with pressure and hence with
increasing frequency of the soft transverse-optical phonon mode connected to
the ferroelectric quantum critical point. We show that the superconductivity
phase diagram can be understood in terms of the coupling of electrons via two
hybrid longitudinal polar modes, based on a model of dipolar fluctuations of
the charge carrier-ion system. In particular, we predict that for carrier
densities above the order of 10$^{18}$ cm$^{-3}$, Tc can be strongly enhanced
on approaching the ferroelectric quantum critical point, as seen in our
measurements of SrTiO$_3$ and as found in many electrically conducting magnetic
analogues. However below this density we predict the reverse behaviour, namely
that Tc is suppressed on approaching the ferroelectric quantum critical point.
Our model is also relevant to superconductivity found in gated ferroelectric
quantum critical systems such as KTaO$_3$ and can guide searches for new
superconductors in a diversity of materials.",1801.08121v2
2018-03-01,Conductance relaxation in GeBiTe - slow thermalization in an open quantum system,"This work describes the microstructure and transport properties of GeBiTe
films with emphasis on their out-of-equilibrium behavior.
Persistent-photoconductivity (PPC), previously studied in the phase-change
compound GeSbTe is also quite prominent in this system. Much weaker PPC
response is observed in the pure GeTe compound and when alloying GeTe with
either In or Mn. Films made from these compounds share the same
crystallographic structure, the same p-type conductivity, a similar
compositional disorder extending over mesoscopic scales, and similar mosaic
morphology. The enhanced PPC response exhibited by the Sb and Bi alloys may
therefore be related to their common chemistry. PPC is observable in GeBiTe
films at the entire range of sheet resistances studied in this work. The excess
conductance produced by a brief exposure to infrared illumination decays with
time as a stretched-exponential (Kohlrausch law). Intrinsic electron-glass
effects on the other hand, are observable in thin films of GeBiTe only for
samples that are strongly-localized just like it was noted with the seven
electron-glasses previously studied. These include a memory-dip which is the
defining attribute of the phenomenon. The memory-dip in GeBiTe is the widest
among the germanium-telluride alloys studied to date consistent with the high
carrier-concentration of this compound. The thermalization process exhibited in
either, the PPC-state or in the electron-glass regime is sluggish but the
temporal law of the relaxation from the out-of-equilibrium state is distinctly
different. Coexistence of the two phenomena give rise to some non-trivial
effects, in particular, the visibility of the memory-dip is enhanced in the
PPC-state. The relation between this effect and the dependence of the
memory-effect magnitude on the ratio between the interparticle-interaction and
quench-disorder is discussed.",1803.00564v1
2018-04-12,Bulk and surface characterization of In$_2$O$_3$(001) single crystals,"A comprehensive bulk and surface investigation of high-quality
In$_2$O$_3$(001) single crystals is reported. The transparent-yellow,
cube-shaped single crystals were grown using the flux method. Inductively
coupled plasma mass spectrometry (ICP-MS) reveals small residues of Pb, Mg, and
Pt in the crystals. Four-point-probe measurements show a resistivity of 2.0
$\pm$ 0.5 $\times$ 10$^5$ {\Omega} cm, which translates into a carrier
concentration of $\approx$10$^{12}$ cm$^{-3}$. The results from x-ray
diffraction (XRD) measurements revise the lattice constant to 10.1150(5) {\AA}
from the previously accepted value of 10.117 {\AA}. Scanning tunneling
microscopy (STM) images of a reduced (sputtered/annealed) and oxidized
(exposure to atomic oxygen at 300 {\deg}C) surface show a step height of 5
{\AA}, which indicates a preference for one type of surface termination. The
surfaces stay flat without any evidence for macroscopic faceting under any of
these preparation conditions. A combination of low-energy ion scattering (LEIS)
and atomically resolved STM indicates an indium-terminated surface with small
islands of 2.5 {\AA} height under reducing conditions, with a surface structure
corresponding to a strongly distorted indium lattice. Scanning tunneling
spectroscopy (STS) reveals a pronounced surface state at the Fermi level
($E_F$). Photoelectron spectroscopy (PES) shows additional, deep-lying band gap
states, which can be removed by exposure of the surface to atomic oxygen.
Oxidation also results in a shoulder at the O 1s core level at a higher binding
energy, possibly indicative of a surface peroxide species. A downward band
bending of 0.4 eV is observed for the reduced surface, while the band bending
of the oxidized surface is of the order of 0.1 eV or less.",1804.04478v1
2018-04-19,Modelling massive-star feedback with Monte Carlo radiation hydrodynamics: photoionization and radiation pressure in a turbulent cloud,"We simulate a self-gravitating, turbulent cloud of 1000 Msol with
photoionization and radiation pressure feedback from a 34 Msol star. We use a
detailed Monte Carlo radiative transfer scheme alongside the hydrodynamics to
compute photoionization and thermal equilibrium with dust grains and multiple
atomic species. Using these gas temperatures, dust temperatures, and ionization
fractions, we produce self-consistent synthetic observations of line and
continuum emission. We find that all material is dispersed from the (15.5
pc)$^3$ grid within 1.6 Myr or 0.74 free-fall times. Mass exits with a peak
flux of $2 \times 10^{-3}$ Msol/yr, showing efficient gas dispersal. The model
without radiation pressure has a slight delay in the breakthrough of
ionization, but overall its effects are negligible. 85 per cent of the volume,
and 40 per cent of the mass, become ionized -- dense filaments resist
ionization and are swept up into spherical cores with pillars that point
radially away from the ionizing star. We use free-free emission at 20 cm to
estimate the production rate of ionizing photons. This is almost always
underestimated: by a factor of a few at early stages, then by orders of
magnitude as mass leaves the volume. We also test the ratio of dust continuum
surface brightnesses at 450 and 850 micron to probe dust temperatures. This
underestimates the actual temperature by more than a factor of 2 in areas of
low column density or high line-of-sight temperature dispersion; the HII region
cavity is particularly prone to this discrepancy. However, the probe is
accurate in dense locations such as filaments.",1804.07309v1
2016-06-06,Origin and magnitude of 'designer' spin-orbit interaction in graphene on semiconducting transition metal dichalcogenides,"We use a combination of experimental techniques to demonstrate a general
occurrence of spin-orbit interaction (SOI) in graphene on transition metal
dichalcogenide (TMD) substrates. Our measurements indicate that SOI is
ultra-strong and extremely robust, despite it being merely
interfacially-induced, with neither graphene nor the TMD substrates changing
their structure. This is found to be the case irrespective of the TMD material
used, of the transport regime, of the carrier type in the graphene band, and of
the thickness of the graphene multilayer. Specifically, we perform weak
antilocalization measurements as the simplest and most general diagnostic of
SOI, and show that the spin relaxation time is very short in all cases
regardless of the elastic scattering time. Such a short spin-relaxation time
strongly suggests that the SOI originates from a modification of graphene band
structure. We confirmed this expectation by measuring a gate-dependent beating,
and a corresponding frequency splitting, in the low-field Shubnikov-de Haas
magneto-resistance oscillations in high quality bilayer graphene on WSe$_2$.
These measurements provide an unambiguous diagnostic of a SOI-induced splitting
in the electronic band structure, and their analysis allows us to determine the
SOI coupling constants for the Rashba term and the so-called spin-valley
coupling term, i.e., the terms that were recently predicted theoretically for
interface-induced SOI in graphene. The magnitude of the SOI splitting is found
to be on the order of 10 meV, more than 100 times greater than the SOI
intrinsic to graphene. Both the band character of the interfacially induced
SOI, as well as its robustness and large magnitude make graphene-on-TMD a
promising system to realize and explore a variety of spin-dependent transport
phenomena, such as, in particular, spin-Hall and valley-Hall topological
insulating states.",1606.01789v1
2019-02-14,Quantum magnetic imaging of iron biomineralisation in teeth of the chiton Acanthopleura hirtosa,"Iron biomineralisation is critical for life. Nature capitalises on the
physical attributes of iron biominerals for a variety of functional, structural
and sensory applications. Although magnetism is an integral property of iron
biominerals, the role it plays in their nano-assembly remains a fundamental,
unanswered question. This is well exemplified by the magnetite-bearing radula
of chitons. Chitons, a class of marine mollusc, create the hardest biomineral
of any animal in their abrasion-resistant, self-sharpening teeth4. Despite this
system being subjected to a range of high resolution imaging studies, the
mechanisms that drive mineral assembly remain unresolved. However, the advent
of quantum imaging technology provides a new avenue to probe magnetic
structures directly. Here we use quantum magnetic microscopy, based on
nitrogen-vacancy centres in diamond, to attain the first subcellular magnetic
profiling of a eukaryotic system. Using complementary magnetic imaging
protocols, we spatially map the principal mineral phases (ferrihydrite and
magnetite) in the developing teeth of Acanthopleura hirtosa with submicron
resolution. The images reveal previously undiscovered long-range magnetic
order, established at the onset of magnetite mineralisation. This is in
contrast to electron microscopy studies that show no strong common
crystallographic orientation. The quantum-based magnetic profiling techniques
presented in this work have broad application in biology, earth science,
chemistry and materials engineering and can be applied across the range of
systems for which iron is vital.",1902.09637v2
2019-05-24,Interference measurements of non-Abelian e/4 & Abelian e/2 quasiparticle braiding,"The quantum Hall states at filling factors $\nu=5/2$ and $7/2$ are expected
to have Abelian charge $e/2$ quasiparticles and non-Abelian charge $e/4$
quasiparticles. The non-Abelian statistics of the latter has been predicted to
display a striking interferometric signature, the even-odd effect. By measuring
resistance oscillations as a function of magnetic field in Fabry-P\'erot
interferometers using new high purity heterostructures, we for the first time
report experimental evidence for the non-Abelian nature of excitations at
$\nu=7/2$. At both $\nu=5/2$ and $7/2$ we also examine, for the first time, the
fermion parity, a topological quantum number of an even number of non-Abelian
quasiparticles. The phase of observed $e/4$ oscillations is reproducible and
stable over long times (hours) near both filling factors, indicating stability
of the fermion parity. At both fractions, when phase fluctuations are observed,
they are predominantly $\pi$ phase flips, consistent with either fermion parity
change or change in the number of the enclosed $e/4$ quasiparticles. We also
examine lower-frequency oscillations attributable to Abelian interference
processes in both states. Taken together, these results constitute new evidence
for the non-Abelian nature of $e/4$ quasiparticles; the observed life-time of
their combined fermion parity further strengthens the case for their utility
for topological quantum computation.",1905.10248v5
2020-03-21,Fluctuation dynamo in a weakly collisional plasma,"The turbulent amplification of cosmic magnetic fields depends upon the
material properties of the host plasma. In many hot, dilute astrophysical
systems, such as the intracluster medium (ICM) of galaxy clusters, the rarity
of particle--particle collisions allows departures from local thermodynamic
equilibrium. These departures exert anisotropic viscous stresses on the plasma
motions that inhibit their ability to stretch magnetic-field lines. We present
a numerical study of the fluctuation dynamo in a weakly collisional plasma
using magnetohydrodynamic (MHD) equations endowed with a field-parallel viscous
(Braginskii) stress. When the stress is limited to values consistent with a
pressure anisotropy regulated by firehose and mirror instabilities, the
Braginskii-MHD dynamo largely resembles its MHD counterpart. If instead the
parallel viscous stress is left unabated -- a situation relevant to recent
kinetic simulations of the fluctuation dynamo and to the early stages of the
dynamo in a magnetized ICM -- the dynamo changes its character, amplifying the
magnetic field while exhibiting many characteristics of the saturated state of
the large-Prandtl-number (${\rm Pm}\gtrsim{1}$) MHD dynamo. We construct an
analytic model for the Braginskii-MHD dynamo in this regime, which successfully
matches magnetic-energy spectra. A prediction of this model, confirmed by our
simulations, is that a Braginskii-MHD plasma without pressure-anisotropy
limiters will not support a dynamo if the ratio of perpendicular and parallel
viscosities is too small. This ratio reflects the relative allowed rates of
field-line stretching and mixing, the latter of which promotes resistive
dissipation of the magnetic field. In all cases that do exhibit a dynamo, the
generated magnetic field is organized into folds that persist into the
saturated state and bias the chaotic flow to acquire a scale-dependent spectral
anisotropy.",2003.09760v2
2020-09-30,OMC-1 dust polarisation in ALMA Band 7: Diagnosing grain alignment mechanisms in the vicinity of Orion Source I,"We present ALMA Band 7 polarisation observations of the OMC-1 region of the
Orion molecular cloud. We find that the polarisation pattern observed in the
region is likely to have been significantly altered by the radiation field of
the $>10^{4}$ L$_{\odot}$ high-mass protostar Orion Source I. In the
protostar's optically thick disc, polarisation is likely to arise from dust
self-scattering. In material to the south of Source I - previously identified
as a region of 'anomalous' polarisation emission - we observe a polarisation
geometry concentric around Source I. We demonstrate that Source I's extreme
luminosity may be sufficient to make the radiative precession timescale shorter
than the Larmor timescale for moderately large grains ($> 0.005-0.1\,\mu$m),
causing them to precess around the radiation anisotropy vector (k-RATs) rather
than the magnetic field direction (B-RATs). This requires relatively unobscured
emission from Source I, supporting the hypothesis that emission in this region
arises from the cavity wall of the Source I outflow. This is one of the first
times that evidence for k-RAT alignment has been found outside of a
protostellar disc or AGB star envelope. Alternatively, the grains may remain
aligned by B-RATs and trace gas infall onto the Main Ridge. Elsewhere, we
largely find the magnetic field geometry to be radial around the BN/KL
explosion centre, consistent with previous observations. However, in the Main
Ridge, the magnetic field geometry appears to remain consistent with the
larger-scale magnetic field, perhaps indicative of the ability of the dense
Ridge to resist disruption by the BN/KL explosion.",2009.14758v2
2016-03-22,Strongly Anisotropic Thermal and Electrical Conductivities of Self-assembled Silver Nanowire Network,"Heat dissipation issues are the emerging challenges in the field of flexible
electronics. Thermal management of flexible electronics creates a demand for
flexible materials with highly anisotropic thermal conductivity, which work as
heat spreaders to remove excess heat in the in-plane direction and as heat
shields to protect human skin or device components under them from heating.
This study proposes a self-assembled silver nanowire network with high thermal
and electrical anisotropy with the potential to solve these challenges. The
in-plane thermal conductivity of the network along the axial direction of
silver nanowires is measured as 37 W/m-K while the cross-plane thermal
conductivity is only 0.36 W/m-K. The results of measurements of electrical and
thermal conductivities suggest that abundant wire-wire contacts strongly impede
thermal transport. The excellent alignment of nanowires results in the same
anisotropy ratio of 3 for both thermal and electrical conduction in the two
in-plane directions. The ratio remains unchanged as the temperature decrease to
50 K, which indicates that wire-wire contacts lower the thermal and electrical
conduction in the two directions to the same extent and their effect is
independent of temperature. In addition, phonon softening markedly reduces the
Debye temperatures of the network, which are fitted from the electrical
resistivity data. As a result of phonon thermal conduction, the Lorenz numbers
of the film in the two directions, which are approximately the same, are larger
than the Sommerfeld value at room temperature and decrease as temperature
decreases because of small angle scattering and the reduced phonon
contribution. This nanowire network provides a solution to the emerging
challenges of thermal management of flexible electronics.",1603.06845v1
2017-05-18,Superconductivity and charge carrier localization in ultrathin $\mathbf{{La_{1.85}Sr_{0.15}CuO_4}/{La_2CuO_4}}$ bilayers,"$\mathrm{La_{1.85}Sr_{0.15}CuO_4}$/$\mathrm{La_2CuO_4}$ (LSCO15/LCO) bilayers
with a precisely controlled thickness of N unit cells (UCs) of the former and M
UCs of the latter ([LSCO15\_N/LCO\_M]) were grown on (001)-oriented {\slao}
(SLAO) substrates with pulsed laser deposition (PLD). X-ray diffraction and
reciprocal space map (RSM) studies confirmed the epitaxial growth of the
bilayers and showed that a [LSCO15\_2/LCO\_2] bilayer is fully strained,
whereas a [LSCO15\_2/LCO\_7] bilayer is already partially relaxed. The
\textit{in situ} monitoring of the growth with reflection high energy electron
diffraction (RHEED) revealed that the gas environment during deposition has a
surprisingly strong effect on the growth mode and thus on the amount of
disorder in the first UC of LSCO15 (or the first two monolayers of LSCO15
containing one $\mathrm{CuO_2}$ plane each). For samples grown in pure
$\mathrm{N_2O}$ gas (growth type-B), the first LSCO15 UC next to the SLAO
substrate is strongly disordered. This disorder is strongly reduced if the
growth is performed in a mixture of $\mathrm{N_2O}$ and $\mathrm{O_2}$ gas
(growth type-A). Electric transport measurements confirmed that the first UC of
LSCO15 next to the SLAO substrate is highly resistive and shows no sign of
superconductivity for growth type-B, whereas it is superconducting for growth
type-A. Furthermore, we found, rather surprisingly, that the conductivity of
the LSCO15 UC next to the LCO capping layer strongly depends on the thickness
of the latter. A LCO capping layer with 7~UCs leads to a strong localization of
the charge carriers in the adjacent LSCO15 UC and suppresses superconductivity.
The magneto-transport data suggest a similarity with the case of weakly hole
doped LSCO single crystals that are in a so-called {""{cluster-spin-glass
state}""}",1705.06587v1
2017-07-18,"Extremely large magnetoresistance and Kohler's rule in PdSn4: a complete study of thermodynamic, transport and band structure properties","The recently discovered material PtSn$_4$ is known to exhibit extremely large
magnetoresistance (XMR) that also manifests Dirac arc nodes on the surface.
PdSn$_4$ is isostructure to PtSn$_4$ with same electron count. We report on the
physical properties of high quality single crystals of PdSn$_4$ including
specific heat, temperature and magnetic field dependent resistivity and
magnetization, and electronic band structure properties obtained from angle
resolved photoemission spectroscopy (ARPES). We observe that PdSn$_4$ has
physical properties that are qualitatively similar to those of PtSn$_4$, but
find also pronounced differences. Importantly, the Dirac arc node surface state
of PtSn$_4$ is gapped out for PdSn$_4$. By comparing these similar compounds,
we address the origin of the extremely large magnetoresistance in PdSn$_4$ and
PtSn$_4$; based on detailed analysis of the magnetoresistivity, $\rho(H,T)$, we
conclude that neither carrier compensation nor the Dirac arc node surface state
are primary reason for the extremely large magnetoresistance. On the other
hand, we find that surprisingly Kohler's rule scaling of the
mangnetoresistance, which describes a self-similarity of the field induced
orbital electronic motion across different length scales and is derived for a
simple electronic response of metals to applied in a magnetic field is obeyed
over the full range of temperatures and field strengths that we explore.",1707.05706v2
2019-03-19,Pressure-induced superconductivity in layered pnictogen diselenide NdO$_{0.8}$F$_{0.2}$Sb$_{1-x}$Bi$_x$Se$_2$ (x = 0.3 and 0.7),"Polycrystalline samples of layered pnictogen diselenide NdO0.8F0.2Sb1-xBixSe2
(x = 0 to 0.8) were successfully synthesized by solid-state reactions.
Electrical resistivity in the synthesized samples was systematically decreased
with an increase in Bi content x. Crystal structure analysis using synchrotron
X-ray diffraction suggests that insulator to metal transition upon Bi doping
correlates with anomalous change in c-axis length and/or corrugation in
conducting layer. The emergence of superconductivity under high pressure is
demonstrated using diamond anvil cell (DAC) with boron-doped diamond
electrodes, for x = 0.3 and 0.7 as the representative samples. For Sb-rich one
(x = 0.3), we observed a superconducting transition with Tconset = 5.3 K at 50
GPa, which is the first-ever report of the superconductivity in layered
SbCh2-based (Ch: chalcogen) compounds. The Tconset of x = 0.3 increased with
increasing pressure and reached 7.9 K at 70.8 GPa, followed by the gradual
decrease in Tc up to 90 GPa. For Bi-rich one (x = 0.7), a superconducting
transition with Tconset = 5.9 K was observed at 43.5 GPa, which is the almost
comparable to that of x = 0.3; besides, upper critical field (Hc2) is evaluated
to be ~10 T for x = 0.7, which is higher than that of x = 0.3 (Hc2 = 6.7 T at
50 GPa).",1903.07791v3
2015-06-18,Evolution of electronic states in n-type copper oxide superconductor via electric double layer gating,"Since the discovery of n-type copper oxide superconductors, the evolution of
electron- and hole-bands and its relation to the superconductivity have been
seen as a key factor in unveiling the mechanism of high-Tc superconductors. So
far, the occurrence of electrons and holes in n-type copper oxides has been
achieved by chemical doping, pressure, and/or deoxygenation. However, the
observed electronic properties are blurred by the concomitant effects such as
change of lattice structure, disorder, etc. Here, we report on successful
tuning the electronic band structure of n-type Pr2-xCexCuO4 (x = 0.15)
ultrathin films, via the electric double layer transistor technique. Abnormal
transport properties, such as multiple sign reversals of Hall resistivity in
normal and mixed states, have been revealed within an electrostatic field in
range of -2 V to +2 V, as well as varying the temperature and magnetic field.
In the mixed state, the intrinsic anomalous Hall conductivity invokes the
contribution of both electron and hole-bands as well as the energy dependent
density of states near the Fermi level. The two-band model can also describe
the normal state transport properties well, whereas the carrier concentrations
of electrons and holes are always enhanced or depressed simultaneously in
electric fields. This is in contrast to the scenario of Fermi surface
reconstruction by antiferromagnetism, where an anti-correlation between
electrons and holes is commonly expected. Our findings paint the picture where
Coulomb repulsion plays an important role in the evolution of the electronic
states in n-type cuprate superconductors.",1506.05727v1
2019-01-08,Thermal bridging of graphene nanosheets via covalent molecular junctions. a Non-Equilibrium Green Functions Density Functional Tight-Binding study,"Despite the uniquely high thermal conductivity of graphene is well known, the
exploitation of graphene into thermally conductive nanomaterials and devices is
limited by the inefficiency of thermal contacts between the individual
nanosheets. A fascinating yet experimentally challenging route to enhance
thermal conductance at contacts between graphene nanosheets is through
molecular junctions, allowing covalently connecting nanosheets otherwise
interacting only via weak Van der Waals forces. Beside the bare existence of
covalent connections, the choice of molecular structures to be used as thermal
junctions should be guided by their vibrational properties, in terms of phonon
transfer through the molecular junction. In this paper, density functional
tight-binding combined with Green functions formalism was applied for the
calculation of thermal conductance and phonon spectra of several different
aliphatic and aromatic molecular junctions between graphene nanosheets. Effect
of molecular junction length, conformation, and aromaticity were studied in
detail and correlated with phonon tunnelling spectra. The theoretical insight
provided by this work can guide future experimental studies to select suitable
molecular junctions in order to enhance the thermal transport by suppressing
the interfacial thermal resistances, particularly attractive for various
systems, including graphene nanopapers and graphene polymer nanocomposites, as
well as related devices. In a broader view, the possibility to design molecular
junctions to control phonon transport currently appears as an efficient way to
produce phononic devices and controlling heat management in nanostructures.",1901.02396v2
2019-01-09,Printing surface charge as a new paradigm to program droplet transport,"Directed, long-range and self-propelled transport of droplets on solid
surfaces, especially on water repellent surfaces, is crucial for many
applications from water harvesting to bio-analytical devices. One appealing
strategy to achieve the preferential transport is to passively control the
surface wetting gradients, topological or chemical, to break the asymmetric
contact line and overcome the resistance force. Despite extensive progress, the
directional droplet transport is limited to small transport velocity and short
transport distance due to the fundamental trade-off: rapid transport of droplet
demands a large wetting gradient, whereas long-range transport necessitates a
relatively small wetting gradient. Here, we report a radically new strategy
that resolves the bottleneck through the creation of an unexplored gradient in
surface charge density (SCD). By leveraging on a facile droplet printing on
superamphiphobic surfaces as well as the fundamental understanding of the
mechanisms underpinning the creation of the preferential SCD, we demonstrate
the self-propulsion of droplets with a record-high velocity over an ultra-long
distance without the need for additional energy input. Such a Leidenfrost-like
droplet transport, manifested at ambient condition, is also genetic, which can
occur on a variety of substrates such as flexible and vertically placed
surfaces. Moreover, distinct from conventional physical and chemical gradients,
the new dimension of gradient in SCD can be programmed in a rewritable fashion.
We envision that our work enriches and extends our capability in the
manipulation of droplet transport and would find numerous potential
applications otherwise impossible.",1901.02612v1
2019-11-06,Absence of superconductivity in bulk Nd$_{1-x}$Sr$_x$NiO$_2$,"Recently superconductivity at 9 - 15 K was discovered in an infinite-layer
nickelate (Nd$_{0.8}$Sr$_{0.2}$NiO$_2$ films), which has received enormous
attention. Since the $Ni^{1+}$ ionic state in NdNiO$_2$ may have the $3d^9$
outer-shell electronic orbit which resembles that of the cuprates, it is very
curious to know whether superconductivity discovered here has similar mechanism
as that in the cuprates. By using a three-step method, we successfully
synthesize the bulk samples of Nd$_{1-x}$Sr$_x$NiO$_2$ (x=0, 0.2, 0.4). The
X-ray diffractions reveal that all the samples contain mainly the infinite
layer phase of 112 with some amount of segregated Ni. This has also been well
proved by the SEM image and the EDS composition analysis. The resistive
measurements on the Sr doped samples show insulating behavior without the
presence of superconductivity. Temperature dependence of the magnetic moment
under high magnetic fields exhibits a Curie-Weiss law feature with the
paramagnetic moment of about 2$\mu_B$/f.u.. By applying pressure on
Nd$_{0.8}$Sr$_{0.2}$NiO$_2$ up to about 50.2 GPa, we find that the strong
insulating behavior at ambient pressure is significantly suppressed, but
superconductivity has not been observed either. Since the lattice constants
derived from our XRD data are very close to those of the reported
superconducting films, we argue that the superconductivity in the reported film
may not originate from the expected Nd$_{0.8}$Sr$_{0.2}$NiO$_2$, but arise from
the interface or the stress effect.",1911.02420v3
2019-11-12,Absence of Superconductivity in Nd$_{0.8}$Sr$_{0.2}$NiO$_x$ Thin Films without Chemical Reduction,"The recently reported superconductivity 9-15 K in Nd0.8Sr0.2NiO2/SrTiO3
heterostructures that were fabricated by a soft-chemical topotactic reduction
approach based on precursor Nd0.8Sr0.2NiO3 thin films deposited on SrTiO3
substrates, has excited an immediate surge of research interest. To explore an
alternative physical path instead of chemical reduction for realizing
superconductivity in this compound, using pulsed laser deposition, we
systematically fabricated 63 Nd0.8Sr0.2NiOx (NSNO) thin films at a wide range
of oxygen partial pressures on various different oxide substrates. Transport
measurements did not find any signature of superconductivity in all the 63
thin-film samples. With reducing the oxygen content in the NSNO films by
lowering the deposition oxygen pressure, the NSNO films are getting more
resistive and finally become insulating. Furthermore, we tried to cap a
20-nm-thick amorphous LaAlO3 layer on a Nd0.8Sr0.2NiO3 thin film deposited at a
high oxygen pressure of 150 mTorr to create oxygen vacancies on its surface and
did not succeed in higher conductivity either. Our experimental results
together with the recent report on the absence of superconductivity in
synthesized bulk Nd0.8Sr0.2NiO2 crystals suggest that the chemical reduction
approach could be unique for yielding superconductivity in NSNO/SrTiO3
heterostructures. However, SrTiO3 substrates could be reduced to generate
oxygen vacancies during the chemical reduction process as well, which may thus
partially contribute to conductivity.",1911.04662v2
2019-11-19,Multi-GMR sensors controlled by additive dipolar coupling,"Vertical packaging of multiple Giant Magnetoresistance (multi-GMR) stacks is
a very interesting noise reduction strategy for local magnetic sensor
measurements, which has not been reported experimentally so far. Here, we have
fabricated multi-GMR sensors (up to 12 repetitions) keeping good GMR ratio,
linearity and low roughness. From magnetotransport measurements, two different
resistance responses have been observed with a crossover around 5 GMR
repetitions: step-like (N<5) and linear (N>5) behavior, respectively. With the
help of micromagnetic simulations, we have analyzed in detail the two main
magnetic mechanisms: the Neel coupling distribution induced by the roughness
propagation and the additive dipolar coupling between the N free layers.
Furthermore we have correlated the dipolar coupling mechanism, controlled by
the number of GMRs (N) and lateral dimensions (width), to the sensor
performance (sensitivity, noise and detectivity) in good agreement with
analytical theory. The noise roughly decreases in multi-GMRs as 1/\sqrt{N} in
both regimes (low frequency 1/f and thermal noise). The sensitivity is even
stronger reduced, scaling as 1/N, in the strong dipolar regime (narrow devices)
while converges to a constant value in the weak dipolar regime (wide devices).
Very interestingly, they are more robust against undesirable RTN noise than
single GMRs at high voltages and the linearity can be extended towards much
larger magnetic field range without dealing with the size and the reduction of
GMR ratio. Finally, we have identified the optimal conditions for which
multi-GMRs exhibit lower magnetic field detectivity than single GMRs: wide
devices operating in the thermal regime where much higher voltage can be
applied without generating remarkable magnetic noise.",1911.08592v1
2020-07-30,The effect of structural and magnetic disorder on the 3$d$-5$d$ exchange interactions of La$_{2-x}$Ca$_{x}$CoIrO$_{6}$,"The delicate balance between spin-orbit coupling, Coulomb repulsion and
crystalline electric field interactions observed in Ir-based oxides is usually
manifested as exotic magnetic behavior. Here we investigate the evolution of
the exchange coupling between Co and Ir for partial La substitution by Ca in
La$_{2}$CoIrO$_6$. A great advantage of the use of Ca$^{2+}$ as replacement for
La$^{3+}$ is the similarity of its ionic radii. Thus, the observed magnetic
changes can more easily be associated to electronic variations. A thorough
investigation of the structural, electronic and magnetic properties of the
La$_{2-x}$Ca$_{x}$CoIrO$_6$ system was carried out by means of synchrotron
x-ray powder diffraction, muon spin rotation and relaxation ($\mu$SR), AC and
DC magnetization, XAS, XMCD, Raman spectroscopy, electrical resistivity and
dielectric permittivity. Our XAS results show that up to 25% of Ca substitution
at the La site results in the emergence of Co$^{3+}$, possibly in high spin
state, while the introduction of larger amount of Ca leads to the increase of
Ir valence. The competing magnetic interactions resulting from the mixed
valences lead to a coexistence of a magnetically ordered and an emerging spin
glass (SG) state for the doped samples. Our $\mu$SR results indicate that for
La$_{2}$CoIrO$_6$ a nearly constant fraction of a paramagnetic (PM) phase
persists down to low temperature, possibly related to the presence of a small
amount of Ir$^{3+}$ and to the anti-site disorder at Co/Ir sites. For the doped
compounds the PM phase freezes below 30 K, but there is still some dynamics
associated with the SG. The dielectric data obtained for the parent compound
and the one with 25% of Ca-doping indicate a possible magnetodielectric effect,
which is discussed in terms of the electron hopping between the TM ions, the
anti-site disorder and the distorted crystalline structure.",2007.15318v1
2020-09-30,A model for atomic precision p-type doping with diborane on Si(100)-2$\times$1,"Diborane (B$_2$H$_6$) is a promising molecular precursor for atomic precision
p-type doping of silicon that has recently been experimentally demonstrated [T.
{\v{S}}kere{\v{n}}, \textit{et al.,} Nature Electronics (2020)]. We use density
functional theory (DFT) calculations to determine the reaction pathway for
diborane dissociating into a species that will incorporate as electrically
active substitutional boron after adsorbing onto the Si(100)-2$\times$1
surface. Our calculations indicate that diborane must overcome an energy
barrier to adsorb, explaining the experimentally observed low sticking
coefficient ($< 10^{-4}$ at room temperature) and suggesting that heating can
be used to increase the adsorption rate. Upon sticking, diborane has an $\sim
50\%$ chance of splitting into two BH$_3$ fragments versus merely losing
hydrogen to form a dimer such as B$_2$H$_4$. As boron dimers are likely
electrically inactive, whether this latter reaction occurs is shown to be
predictive of the incorporation rate. The dissociation process proceeds with
significant energy barriers, necessitating the use of high temperatures for
incorporation. Using the barriers calculated from DFT, we parameterize a
Kinetic Monte Carlo model that predicts the incorporation statistics of boron
as a function of the initial depassivation geometry, dose, and anneal
temperature. Our results suggest that the dimer nature of diborane inherently
limits its doping density as an acceptor precursor, and furthermore that
heating the boron dimers to split before exposure to silicon can lead to poor
selectivity on hydrogen and halogen resists. This suggests that while diborane
works as an atomic precision acceptor precursor, other non-dimerized acceptor
precursors may lead to higher incorporation rates at lower temperatures.",2010.00129v1
2020-10-26,Solubility limit of Ge Dopants in AlGaN: a Chemical and Microstructural Investigation down to the Nanoscale,"Attaining low resistivity AlGaN layers is the keystone to improve the
efficiency of light emitting devices in the ultraviolet spectral range. Here,
we present a microstructural analysis of Ge-doped AlGaN samples with Al mole
fraction from x=0 to 1, and nominal doping level in the range of 1E20 cm-3,
together with the measurement of Ge concentration and its spatial distribution
down to the nm scale. AlGaN:Ge samples with x smaller or equal to 0.2 do not
present any sign of inhomogeneity. However, samples with x > 0.4 display
micrometer-size Ge crystallites at the surface. Ge segregation is not
restricted to the surface: Ge-rich regions with a size of tens of nanometers
are observed inside the AlGaN:Ge layers, generally associated with Ga-rich
regions around structural defects. With this local exceptions, the AlGaN:Ge
matrix present an homogenous Ge composition which can be significantly lower
than the nominal doping level. Precise measurements of Ge in the matrix provide
a view of the solubility diagram of Ge in AlGaN as a function of the Al mole
fraction. The solubility of Ge in AlN is extremely low. Between AlN and GaN,
the solubility increases linearly with the Ga mole fraction in the ternary
alloy, which suggests that the Ge incorporation takes place by substitution of
Ga atoms only. The maximum percentage of Ga sites occupied by Ge saturates
around 1%. The solubility issues and Ge segregation phenomena at different
length scales likely play a role in the efficiency of Ge as n-type AlGaN
dopant, even at Al concentrations where Ge DX centers are not expected to
manifest. Therefore, this information can have direct impact in the performance
of Ge-doped AlGaN light emitting diodes, particularly in the spectral range for
disinfection (around 260 nm), which requires heavily-doped alloys with high Al
mole fraction.",2010.13577v1
2020-10-26,Domain Wall-Magnetic Tunnel Junction Spin Orbit Torque Devices and Circuits for In-Memory Computing,"There are pressing problems with traditional computing, especially for
accomplishing data-intensive and real-time tasks, that motivate the development
of in-memory computing devices to both store information and perform
computation. Magnetic tunnel junction (MTJ) memory elements can be used for
computation by manipulating a domain wall (DW), a transition region between
magnetic domains. But, these devices have suffered from challenges: spin
transfer torque (STT) switching of a DW requires high current, and the multiple
etch steps needed to create an MTJ pillar on top of a DW track has led to
reduced tunnel magnetoresistance (TMR). These issues have limited experimental
study of devices and circuits. Here, we study prototypes of three-terminal
domain wall-magnetic tunnel junction (DW-MTJ) in-memory computing devices that
can address data processing bottlenecks and resolve these challenges by using
perpendicular magnetic anisotropy (PMA), spin-orbit torque (SOT) switching, and
an optimized lithography process to produce average device tunnel
magnetoresistance TMR = 164%, resistance-area product RA = 31
{\Omega}-{\mu}m^2, close to the RA of the unpatterned film, and lower switching
current density compared to using spin transfer torque. A two-device circuit
shows bit propagation between devices. Device initialization variation in
switching voltage is shown to be curtailed to 7% by controlling the DW initial
position, which we show corresponds to 96% accuracy in a DW-MTJ full adder
simulation. These results make strides in using MTJs and DWs for in-memory and
neuromorphic computing applications.",2010.13879v1
2020-12-30,Cooperation in a fluid swarm of fuel-free micro-swimmers,"Cooperation is vital for the survival of a swarm$^1$. Large scale cooperation
allows murmuring starlings to outmaneuver preying falcons$^2$, shoaling
sardines to outsmart sea lions$^3$, and homo sapiens to outlive their
Pleistocene peers$^4$. On the micron-scale, bacterial colonies show excellent
resilience thanks to the individuals' ability to cooperate even when densely
packed, mitigating their internal flow pattern to mix nutrients, fence the
immune system, and resist antibiotics$^{5-14}$. Production of an artificial
swarm on the micro-scale faces a serious challenge $\frac{\;\;}{\;\;}$ while an
individual bacterium has an evolutionary-forged internal machinery to produce
propulsion, until now, artificial micro-swimmers relied on the precise chemical
composition of their environment to directly fuel their drive$^{14-23}$. When
crowded, artificial micro-swimmers compete locally for a finite fuel supply,
quenching each other's activity at their greatest propensity for cooperation.
Here we introduce an artificial micro-swimmer that consumes no chemical fuel
and is driven solely by light. We couple a light absorbing particle to a fluid
droplet, forming a colloidal chimera that transforms light energy into
propulsive thermo-capillary action. The swimmers' internal drive allows them to
operate and remain active for a long duration (days) and their effective
repulsive interaction allows for a high density fluid phase. We find that above
a critical concentration, swimmers form a long lived crowded state that
displays internal dynamics. When passive particles are introduced, the dense
swimmer phase can re-arrange and spontaneously corral the passive particles. We
derive a geometrical, depletion-like condition for corralling by identifying
the role the passive particles play in controlling the effective concentration
of the micro-swimmers.",2012.15087v1
2021-02-09,Evidence for multiband superconductivity and charge density waves in Ni-doped ZrTe$_2$,"We carried out a comprehensive study of the electronic, magnetic, and
thermodynamic properties of Ni-doped ZrTe$_2$. High quality
Ni$_{0.04}$ZrTe$_{1.89}$ single crystals show a possible coexistence of charge
density waves (CDW, T$_{CDW}\approx287$\,K) with superconductivity (T$_c\approx
4.1$\,K), which we report here for the first time. The temperature dependence
of the lower (H$_{c_1}$) and upper (H$_{c_2}$) critical magnetic fields both
deviate significantly from the behaviors expected in conventional single-gap
s-wave superconductors. However, the behaviors of the normalized superfluid
density $\rho_s(T)$ and H$_{c_2}(T)$ can be described well using a two-gap
model for the Fermi surface, in a manner consistent with conventional multiband
superconductivity. Electrical resistivity and specific heat measurements show
clear anomalies centered near 287\,K consistent with a CDW phase transition.
Additionally, electronic-structure calculations support the coexistence of
electron-phonon multiband superconductivity and CDW order due to the
compensated disconnected nature of the electron- and hole-pockets at the Fermi
surface. Our electronic structure calculations also suggest that ZrTe$_2$ could
reach a non-trivial topological type-II Dirac semimetallic state. These
findings highlight that Ni-doped ZrTe2 can be uniquely important for probing
the coexistence of superconducting and CDW ground states in an electronic
system with non-trivial topology.",2102.04812v3
2021-02-18,$f$-electron hybridised metallic Fermi surface in magnetic field-induced metallic YbB$_{12}$,"The nature of the Fermi surface observed in the recently discovered family of
unconventional insulators starting with SmB$_6$ and subsequently YbB$_{12}$ is
a subject of intense inquiry. Here we shed light on this question by comparing
quantum oscillations between the high magnetic field-induced metallic regime in
YbB$_{12}$ and the unconventional insulating regime. In the field-induced
metallic regime beyond 47 T, we find prominent quantum oscillations in the
contactless resistivity characterised by multiple frequencies up to at least
3000 T and heavy effective masses up to at least 17 $m_\text{e}$,
characteristic of an $f$-electron hybridised metallic Fermi surface. The growth
of quantum oscillation amplitude at low temperatures in electrical transport
and magnetic torque in insulating YbB$_{12}$ is closely similar to the
Lifshitz-Kosevich low temperature growth of quantum oscillation amplitude in
field-induced metallic YbB$_{12}$, pointing to an origin of quantum
oscillations in insulating YbB$_{12}$ from in-gap neutral low energy
excitations. The field-induced metallic regime of YbB$_{12}$ is characterised
by more Fermi surface sheets of heavy quasiparticle effective mass that emerge
in addition to the heavy Fermi surface sheets yielding multiple quantum
oscillation frequencies below 1000 T observed in both insulating and metallic
regimes. We thus observe a heavy multi-component Fermi surface in which
$f$-electron hybridisation persists from the unconventional insulating to the
field-induced metallic regime of YbB$_{12}$, which is in distinct contrast to
the unhybridised conduction electron Fermi surface observed in the case of the
unconventional insulator SmB$_6$. Our findings require a different theoretical
model of neutral in-gap low energy excitations in which the $f$-electron
hybridisation is retained in the case of the unconventional insulator
YbB$_{12}$.",2102.09545v2
2021-05-18,Microwave response of a metallic superconductor subject to a high-voltage gate electrode,"Processes that lead to the critical-current suppression and change of
impedance of a superconductor under the application of an external voltage is
an active area of research, especially due to various possible technological
applications. In particular, field-effect transistors and radiation detectors
have been developed in the recent years, showing the potential for precision
and sensitivity exceeding their normal-metal counterparts. In order to describe
the phenomenon that leads to the critical-current suppression in metallic
superconducting structures, a field-effect hypothesis has been formulated,
stating that an electric field can penetrate the metallic superconductor and
affect its characteristics. The existence of such an effect would imply the
incompleteness of the underlying theory, and hence indicate an important gap in
the general comprehension of superconductors. In addition to its theoretical
value, a complete understanding of the phenomenon underneath the electric-field
response of the superconductor is important in the light of the related
technological applications. In this paper, we study the change of the
characteristics of a superconductor implementing a coplanar-waveguide resonator
as a tank circuit, by relating our measurements to the reactance and resistance
of the material. Namely, we track the state of the superconductor at different
voltages and resulting leakage currents of a nearby gate electrode which is not
galvanically connected to the resonator. By comparing the effects of the
leakage current and of a change in the temperature of the system, we conclude
that the observed behaviour in the superconductor is [...]",2105.08322v4
2021-05-24,A new ideality factor for perovskite solar cells and an analytical theory for their impedance spectroscopy response,"Impedance spectroscopy (IS) is a relatively straightforward experimental
technique that is commonly used to obtain information about the physical and
chemical characteristics of photovoltaic devices. However, the non-standard
physical behaviour of perovskite solar cells (PSC), which are heavily
influenced by the motion of mobile ion vacancies, has hindered efforts to
obtain a consistent theory to interpret PSC impedance data. This work rectifies
this omission by deriving a simple analytic model of the impedance response of
a PSC from the underlying drift-diffusion model of charge carrier dynamics and
ion vacancy motion. Extremely good agreement is shown between the analytic
model and the much more complex drift-diffusion model in regimes (including
maximum power point) where the applied voltage is close to the open circuit
voltage $V_{oc}$. Both models show good qualitative agreement to experimental
IS data in the literature and predict many of the observed anomalous features
found in impedance measurements on PSCs, such as `the giant low frequency
capacitance` and `inductive arcs' in the Nyquist plots. Where the physical
properties of the PSC are already known the analytic model can be used to
predict the recombination current $j_{rec}$ and the high and low frequency
resistances and capacitances of the cell, $R_{HF}$, $C_{HF}$, $R_{LF}$ and
$C_{LF}$. In scenarios where the physical properties of the cell are unknown
the analytic model can also used to extract physical parameters from
experimental PSC impedance data. {A novel physical parameter of particular
significance to PSC physics is identified. This is termed the electronic
ideality factor, $n_{el}$, and (as opposed to the standard ideality factor) can
be used to deduce the dominant source of recombination in a PSC, independent of
its ionic properties.",2105.11226v1
2021-05-27,Van der Waals interaction affects wrinkle formation in two-dimensional materials,"Nonlinear mechanics of solids is an exciting field that encompasses both
beautiful mathematics, such as the emergence of instabilities and the formation
of complex patterns, as well as multiple applications. Two-dimensional crystals
and van der Waals (vdW) heterostructures allow revisiting this field on the
atomic level, allowing much finer control over the parameters and offering
atomistic interpretation of experimental observations. In this work, we
consider the formation of instabilities consisting of radially-oriented
wrinkles around mono- and few-layer ""bubbles"" in two-dimensional vdW
heterostructures. Interestingly, the shape and wavelength of the wrinkles
depend not only on the thickness of the two-dimensional crystal forming the
bubble, but also on the atomistic structure of the interface between the bubble
and the substrate, which can be controlled by their relative orientation. We
argue that the periodic nature of these patterns emanates from an energetic
balance between the resistance of the top membrane to bending, which favors
large wavelength of wrinkles, and the membrane-substrate vdW attraction, which
favors small wrinkle amplitude. Employing the classical ""Winkler foundation""
model of elasticity theory, we show that the number of radial wrinkles conveys
a valuable relationship between the bending rigidity of the top membrane and
the strength of the vdW interaction. Armed with this relationship, we use our
data to demonstrate a nontrivial dependence of the bending rigidity on the
number of layers in the top membrane, which shows two different regimes driven
by slippage between the layers, and a high sensitivity of the vdW force to the
alignment between the substrate and the membrane.",2105.13229v1
2021-08-04,System Modelling of Very Low Earth Orbit Satellites for Earth Observation,"The operation of satellites in very low Earth orbit (VLEO) has been linked to
a variety of benefits to both the spacecraft platform and mission design.
Critically, for Earth observation (EO) missions a reduction in altitude can
enable smaller and less powerful payloads to achieve the same performance as
larger instruments or sensors at higher altitude, with significant benefits to
the spacecraft design. As a result, renewed interest in the exploitation of
these orbits has spurred the development of new technologies that have the
potential to enable sustainable operations in this lower altitude range. In
this paper, system models are developed for (i) novel materials that improve
aerodynamic performance enabling reduced drag or increased lift production and
resistance to atomic oxygen erosion and (ii) atmosphere-breathing electric
propulsion (ABEP) for sustained drag compensation or mitigation in VLEO.
Attitude and orbit control methods that can take advantage of the aerodynamic
forces and torques in VLEO are also discussed. These system models are
integrated into a framework for concept-level satellite design and this
approach is used to explore the system-level trade-offs for future EO
spacecraft enabled by these new technologies. A case-study presented for an
optical very-high resolution spacecraft demonstrates the significant potential
of reducing orbital altitude using these technologies and indicates possible
savings of up to 75% in system mass and over 50% in development and
manufacturing costs in comparison to current state-of-the-art missions. For a
synthetic aperture radar (SAR) satellite, the reduction in mass and cost with
altitude were shown to be smaller, though it was noted that currently available
cost models do not capture recent commercial advancements in this segment...",2108.01945v2
2021-09-10,One-Dimensional Luttinger Liquids in a Two-Dimensional Moiré Lattice,"The Luttinger liquid (LL) model of one-dimensional (1D) electronic systems
provides a powerful tool for understanding strongly correlated physics
including phenomena such as spin-charge separation. Substantial theoretical
efforts have attempted to extend the LL phenomenology to two dimensions (2D),
especially in models of closely packed arrays of 1D quantum wires, each being
described as a LL. Such coupled-wire models have been successfully used to
construct 2D anisotropic non-Fermi liquids, quantum Hall states, topological
phases, and quantum spin liquids. However, an experimental demonstration of
high-quality arrays of 1D LLs suitable for realizing these models remains
absent. Here we report the experimental realization of 2D arrays of 1D LLs with
crystalline quality in a moir\'e superlattice made of twisted bilayer tungsten
ditelluride (tWTe$_{2}$). Originating from the anisotropic lattice of the
monolayer, the moir\'e pattern of tWTe$_{2}$ hosts identical, parallel 1D
electronic channels, separated by a fixed nanoscale distance, which is tunable
by the interlayer twist angle. At a twist angle of ~ 5 degrees, we find that
hole-doped tWTe$_{2}$ exhibits exceptionally large transport anisotropy with a
resistance ratio of ~ 1000 between two orthogonal in-plane directions. The
across-wire conductance exhibits power-law scaling behaviors, consistent with
the formation of a 2D anisotropic phase that resembles an array of LLs. Our
results open the door for realizing a variety of correlated and topological
quantum phases based on coupled-wire models and LL physics.",2109.04637v3
2021-09-16,MEAM parameterization for cyclic and tensile deformations of Gold-Silver core-shell systems,"Gold-Silver (Au-Ag) core-shell nanostructures are gaining importance in
stretchable electronics where high tensile and fatigue resistance is of
paramount importance. This work proposes the parameterization of a modified
embedded atomic model (MEAM) interatomic potential through density functional
theory (DFT) calculations for investigating the role of dislocations and defect
interaction governing the mechanical behavior of Au-Ag and Ag-Au Core-shell
nanostructures under tensile and fatigue loading using molecular dynamics (MD)
simulations. A comparative analysis between the Core-shell structures and their
pristine counterparts is also conducted. Throughout this work, pseudo-potential
and all-electron full potential DFT schemes are used for parameterizing MEAM by
calculating cohesive energy, lattice parameter, and bulk modulus of pure Au, Ag
and their alloy. Using the new force-field for MD simulations, the tensile
behavior of pristine and core-shell nanowires is explored for temperatures
between 300K to 600K. The fatigue properties of two pristine and two core-shell
nanowires in a strain range of -15% to 15% for 10 cycles is also conducted. Our
results suggest that Ag-Au Core-shell nanowire shows the best reversibility
under fatigue loading among the structures examined. Moreover, Ag-Au exhibit
the highest dislocation formation and complete annihilation of defects
consistently. While, Au-Ag present improved fatigue properties than its
pristine counterparts but have some residual defects leading to lower
reversibility when compared to Ag-Au. For tensile loading, all four structures
exhibited deterioration in strength with increasing temperature. Thermal
softening is seen to be more prominent in Au-Ag core-shell nanowires compared
to Ag-Au.",2109.08196v2
2021-10-08,Synthesis and study of ScN thin films,"To contemplate an alternative approach for the minimization of diffusion at
high temperature depositions, present findings impart viability of
room-temperature deposited reactively sputtered ScN thin film samples. The
adopted room temperature route endows precise control over the $R_{N_2}$ flow
for a methodical structural phase evolution from Sc$\to$ScN and probe the
correlated physical aspects of the highly textured ScN samples. In the nitrided
regime i.e. at $R_{N_2}$ = 2.5-100% flow, incorporation of unintentional oxygen
defects were evidenced from surface sensitive soft x-ray absorption
spectroscopy study, though less compared to their metal ($R_{N_2} = 0\%$) and
interstitial ($R_{N_2} = 1.6\%$) counterparts, due to higher Gibb's free energy
for Sc-O-N formation with no trace of ligand field splitting around the O
K-edge spectra. To eradicate the sceptism of appearance of N K-edge (401.6 eV)
and Sc L-edge (402.2 eV) absorption spectra adjacent to each other, the nascent
Sc K-edge study has been adopted for the first time to validate complementary
insight on the metrical parameters of the Sc-N system taken into consideration.
Optical bandgaps of the polycrystalline ScN thin film samples were found to
vary between 2.25-2.62 eV as obtained from the UV-Vis spectroscopy, whereas,
the nano-indentation hardness and modulus of the as-deposited samples lie
between 15-34GPa and 152-476GPa, respectively following a linearly increasing
trend of resistance to plastic deformations. Besides, contrary to other early
3d transition metal nitrides (TiN, VN, CrN), a comprehensive comparison of
noticeably large homogeneity range in Sc-N has been outlined to apprehend the
minuscule lattice expansion over the large $R_{N_2}$ realm.",2110.04008v1
2021-12-28,Highly sensitive fire alarm system based on cellulose paper with low temperature response and wireless signal conversion,"Highly sensitive smart sensors for early fire detection with remote warning
capabilities are urgently required to improve the fire safety of combustible
materials in diverse applications. The highly-sensitive fire alarm can detect
fire situation within a short time quickly when a fire disaster is about to
occur, which is conducive to achieve fire tuned. Herein, a novel fire alarm is
designed by using flame-retardant cellulose paper loaded with graphene oxide
(GO) and two-dimensional titanium carbide (Ti3C2, MXene). Owing to the
excellent temperature dependent electrical resistance switching effect of GO,
it acts as an electrical insulator at room temperature and becomes electrically
conductive at high temperature. During a fire incident, the partial
oxygen-containing groups on GO will undergo complete removal, which results in
the conductivity transformation.Besides the use of GO feature, this work also
introduces conductive MXene to enhance fire detection speed and warning at low
temperature, especially below 300 {\deg}C. The designed flame-retardant fire
alarm is sensitive enough to detect fire incident, showing a response time of 2
s at 250 {\deg}C, which is calculated by a novel and quantifiable technique.
More importantly, the designed fire alarm sensor is coupled to a wireless
communication interface to conveniently transmit fire signal remotely.
Therefore, when an abnormal temperature is detected, the signal is wirelessly
transmitted to a liquid crystal display (LCD) screen when displays a message
such as ""FIRE DANGER"". The designed smart fire alarm paper is promising for use
as a smart wallpaper for interior house decoration and other applications
requiring early fire detection and warning.",2201.05442v1
2022-10-24,Anomalous Hall effect and two-dimensional Fermi surfaces in the charge-density-wave state of kagome metal RbV$_3$Sb$_5$,"AV$_3$Sb$_5$ (A=Cs, K, Rb) are recently discovered superconducting systems
($T_{\rm c}\sim0.9-2.5$ K) in which the vanadium atoms adopt the kagome
structure. Intriguingly, these systems enter a charge-density-wave (CDW) phase
($T_{\rm CDW}\sim80-100$ K), and further evidence shows that the time-reversal
symmetry is broken in the CDW phase. Concurrently, the anomalous Hall effect
has been observed in KV$_3$Sb$_5$ and CsV$_3$Sb$_5$ inside the novel CDW phase.
Here, we report a comprehensive study of a high-quality RbV$_3$Sb$_5$ single
crystal with magnetotransport measurements. Our data demonstrate the emergence
of anomalous Hall effect in RbV$_3$Sb$_5$ when the charge-density-wave state
develops. The magnitude of anomalous Hall resistivity at the low temperature
limit is comparable to the reported values in KV$_3$Sb$_5$ and CsV$_3$Sb$_5$.
The magnetoresistance channel further reveals a rich spectrum of quantum
oscillation frequencies, many of which have not been reported before. In
particular, a large quantum oscillation frequency (2235 T), which occupies
$\sim$56% of the Brillouin zone area, has been recorded. For the quantum
oscillation frequencies with sufficient signal-to-noise ratio, we further
perform field-angle dependent measurements and our data indicate
two-dimensional Fermi surfaces in RbV$_3$Sb$_5$. Our results provide
indispensable information for understanding the anomalous Hall effect and band
structure in kagome metals AV$_3$Sb$_5$.",2210.13250v2
2022-11-17,An effective anisotropic visco-plastic model dedicated to high contrast ductile laminated microstructures: Application to lath martensite substructure,"In particular types of layer- or lamellar-like microstructures such as
pearlite and lath martensite, plastic slip occurs favorably in directions
parallel to inter-lamellar boundaries. This may be due to the interplay between
morphology and crystallographic orientation or, more generally, due to
constraints imposed on the plastic slip due to the lamellar microstructural
geometry. This paper proposes a micromechanics based, computationally
efficient, scale independent model for particular type of lamellar
microstructures containing softer lamellae, which are sufficiently thin to be
considered as discrete slip planes embedded in a matrix representing the harder
lamellae. Accordingly, the model is constructed as an isotropic visco-plastic
model which is enriched with an additional orientation-dependent planar plastic
deformation mechanism. This additional mode is activated when the applied load,
projected on the direction of the soft films, induces a significant amount of
shear stress. Otherwise, the plastic deformation is governed solely by the
isotropic part of the model. The response of the proposed model is assessed via
a comparison to direct numerical simulations (DNS) of an infinite periodic
two-phase laminate. It is shown that the yielding behavior of the model follows
the same behavior as the reference model. It is observed that the proposed
model is highly anisotropic, and the degree of anisotropy depends on the
contrast between the slip resistance (or yield stress) of the planar mode
versus that of the isotropic part. The formulation is then applied to model the
substructure of lath martensite with inter-layer thin austenite films. It is
exploited in a mesoscale simulation of a dual-phase (DP) steel
microstructure.The results are compared with those of a standard isotropic
model and a full crystal plasticity model.",2211.09754v1
2022-11-19,Density-tuned effective metal-insulator transitions in 2D semiconductor layers: Anderson localization or Wigner crystallization,"Electrons (or holes) confined in 2D semiconductor layers have served as model
systems for studying disorder and interaction effects for almost 50 years. In
particular, strong disorder drives the metallic 2D carriers into a strongly
localized Anderson insulator (AI) at low densities whereas pristine 2D
electrons in the presence of no (or little) disorder should solidify into a
Wigner crystal at low carrier densities. Since the disorder in 2D
semiconductors is mostly Coulomb disorder arising from random charged
impurities, the applicable physics is complex as the carriers interact with
each other as well as with the random charged impurities through the same
long-range Coulomb coupling. By critically theoretically analyzing the
experimental transport data in depth using a realistic transport theory to
calculate the low-temperature 2D resistivity as a function of carrier density
in 11 different experimental samples covering 9 different materials, we
establish, utilizing the Ioffe-Regel-Mott criterion for strong localization, a
direct connection between the critical localization density for the 2D
metal-insulator transition (MIT) and the sample mobility deep into the metallic
state, which for clean samples could lead to a localization density low enough
to make the transition appear to be a Wigner crystallization. We believe that
the insulating phase is always an effective Coulomb disorder-induced localized
AI, which may have short-range WC-like correlations at low carrier densities.
Our theoretically calculated disorder-driven critical MIT density agrees with
experimental findings in all 2D samples, even for the ultra-clean samples. In
particular, the extrapolated critical density for the 2D MIT seems to vanish
when the high-density mobility goes to infinity, indicating that transport
probes a disorder-localized insulating ground state independent of how low the
carrier density might be.",2211.10673v2
2023-01-18,Probing electron-electron interaction along with superconducting fluctuations in disordered TiN thin films,"Here, we demonstrate an interplay between superconducting fluctuations and
electron-electron interaction (EEI) by low temperature magnetotransport
measurements for a set of 2D disordered TiN thin films. While cooling down the
sample, a characteristic temperature T* is obtained from the R(T) at which
superconducting fluctuations start to appear. The upturn in R(T) above T*
corresponds to weak localization (WL) and/or EEI. By the temperature and field
dependences of the observed resistance, we show that the upturn in R(T)
originates mainly from EEI with a negligible contribution from WL. Further, we
have used the modified Larkins electron-electron attraction strength
beta(T/Tc), containing a field induced pair breaking parameter, in the
Maki-Thompson (MT) superconducting fluctuation term. Here, the temperature
dependence of the beta(T/Tc) obtained from the magnetoresistance analysis shows
a diverging behavior close to Tc and it remains almost constant at higher
temperature within the limit of ln(T/Tc) < 1. Interestingly, the variation of
beta(T/Tc) on the reduced temperature (T/Tc) offers a common trend which has
been closely followed by all the concerned samples presented in this study.
Finally, the temperature dependence of inverse phase scattering time , as
obtained from the magnetoresistance analysis, clearly shows two different
regimes; the first one close to Tc follows the Ginzburg-Landau relaxation rate
, whereas, the second one at high temperature varies almost linearly with
temperature indicating the dominance of inelastic electron-electron scattering
for the dephasing mechanism. These two regimes are followed in a generic way by
all the samples in spite of being grown under different growth conditions.",2301.07648v1
2023-02-08,Bioabsorbable WE43 Mg alloy wires modified by continuous plasma electrolytic oxidation for implant applications. Part II: degradation and biological performance,"The corrosion, mechanical degradation and biological performance of
cold-drawn WE43 Mg wires were analyzed as a function of thermo-mechanical
processing and the presence of a protective oxide layer created by continuous
plasma electrolytic oxidation (PEO). It was found that the corrosion properties
of the non-surface-treated wire could be optimized by means of thermal
treatment within certain limits, but the corrosion rate remained very high.
Hence, strength and ductility of these wires vanished after 24 h of immersion
in simulated body fluid at 37$^\circ$C and, as a result of that rather quick
degradation, direct tests did not show any MC3T3-E1 preosteoblast cell
attachment on the surface of the Mg wires. In contrast, surface modification of
the annealed WE43 Mg wires by a continuous PEO process led to the formation of
a homogeneous oxide layer of $\approx$ 8$\mu$m and significantly improved the
corrosion resistance and hence the biocompatibility of the WE43 Mg wires. It
was found that a dense layer of Ca/P was formed at the early stages of
degradation on top of the Mg(OH)2 layer and hindered the diffusion of the
Cl-ions which dissolve Mg(OH)2 and accelerate the corrosion of Mg alloys. As a
result, pitting corrosion was suppressed and the strength of the Mg wires was
above 100 MPa after 96 h of immersion in simulated body fluid at 37$^\circ$C.
Moreover, many cells were able to attach on the surface of the PEO
surface-modified wires during cell culture testing. These results demonstrate
the potential of thin Mg wires surface-modified by continuous PEO in terms of
mechanical, degradation and biological performance for bioabsorbable wire-based
devices.",2302.13778v1
2023-02-28,Quantifying interaction mechanism in infinite layer nickelate superconductors,"The relationship between the long-range antiferromagnetic order in cuprates
and the high-temperature superconductivity in these compounds represents
unresolved, nearly four-decades long scientific problem. Because recently
discovered nickelate superconductors are crystallographical counterparts of
cuprates, many properties and difficulties into describing these compounds are
common to both families. Recently, Fowlie et al (2022 Nature Physics 18 1043)
aimed to detect the antiferromagnetic order in $R_{1-x}Sr_{x}NiO_{2}$ (R = Nd,
Pr, La, x ~ 0.2) films by using the muon spin rotation (muSR) technique. This
research group reported on the existence of short-range antiferromagnetic order
in all studied nickelates. Here, we aimed to reveal the existence of this
interaction in the same nickelate films by analyzing the temperature dependent
resistivity, $\rho(T)$, reported by the same research group. Global $\rho(T)$
data fits to the advanced Bloch-Gr\""uneisen model showed that each of
R1-xSrxNiO2 compounds can be characterized by a unique power-law exponent, p
(where p=2 for the electron-electron scattering, p=3 for the electron-magnon
scattering, and p=5 for the electron-phonon scattering), and global
characteristic temperature, $T_{\omega}$ (which has the meaning of the Debye
temperature at p=5). We found that p=2.0 in Nd- and Pr-based compounds, and
p=1.3 for La-based compound. The latter value does not have any interpretation
within established theoretical models. We also analyzed $\rho(T)$ data for
$Nd_{1-x}Sr_{x}NiO_{2}$ (0.125 < x < 0.325) reported by Lee et al (2022
arXiv2203.02580). Because our analysis showed that p-values in nickelates are
remarkably different from p=3, we call for the developent of a new theoretical
model to describe $\rho(T)$ in materials exhibiting a short-range
antiferromagnetic order.",2302.14729v3
2023-03-11,Non-Fermi-Liquid Behavior of Superconducting SnH$_4$,"We studied chemical interaction of Sn with H$_2$ by X-ray diffraction methods
at pressures of 180-210 GPa. A previously unknown tetrahydride SnH$_4$ with a
cubic structure (${fcc}$) exhibiting superconducting properties below ${T}$$_C$
= 72 K was obtained; the formation of a high molecular ${C2/m}$-SnH$_{14}$
superhydride and several lower hydrides, ${fcc}$ SnH$_2$ and
${C2}$-Sn$_{12}$H$_{18}$, was also detected. The temperature dependence of
critical current density ${J}$$_C$(T) in SnH$_4$ yields the superconducting gap
2$\Delta$(0) = 23 meV at 180 GPa. SnH$_4$ has unusual behavior in strong
magnetic fields: ${B,T}$-linear dependences of magnetoresistance and the upper
critical magnetic field ${B}$$_{C2}$(T) $\propto$ (${T}$$_C$ - ${T}$). The
latter contradicts the Wertheimer-Helfand-Hohenberg model developed for
conventional superconductors. Along with this, the temperature dependence of
electrical resistance of ${fcc}$ SnH$_4$ in non-superconducting state exhibits
a deviation from what is expected for phonon-mediated scattering described by
the Bloch-Gr\""uneisen model, and is beyond the framework of the Fermi liquid
theory. Such anomalies occur for many superhydrides, making them much closer to
cuprates than previously believed.",2303.06339v2
2023-06-16,Tailoring defects and nanocrystal transformation for optimal heating power in bimagnetic $Co_yFe_{1-y}O@Co_xFe_{3-x}O_4$ particles,"The effects of cobalt incorporation in spherical heterostructured iron oxide
nanocrystals (NCs) of sub-critical size have been explored by colloidal
chemistry methods. Synchrotron X-ray total scattering methods suggest that
cobalt (Co) substitution in rock salt iron oxide NCs tends to remedy its vacant
iron sites, offering a higher degree of resistance to oxidative conversion.
Self-passivation still creates a spinel-like shell, but with higher volume
fraction of the rock salt Co-containing phase in the core. The higher divalent
metal stoichiometry in the rock salt phase, with increasing Co content, results
in a population of unoccupied tetrahedral metal sites in the spinel part,
likely through oxidative shell creation, involving an ordered defect-clustering
mechanism, directly correlated to the core stabilization. To shed light on the
effects of Co-substitution and atomic-scale defects (vacant sites), Monte Carlo
simulations suggest that designed NCs, with desirable, enhanced magnetic
properties (cf. exchange bias and coercivity), are developed with
magnetocrystalline anisotropy raised at relatively low content of Co ions in
the lattice. Growth of optimally performing candidates combines also a strongly
exchange-coupled system, secured through a high volumetric ratio rock salt
phase, interfaced by a not so defective spinel shell. In view of these
requirements, Specific Absorption Rate (SAR) calculations demonstrate that the
sufficiently protected from oxidation rock salt core and preserved over time
heterostructure, play a key role in magnetically-mediated heating efficacies,
for potential use of such NCs in magnetic hyperthermia applications.",2306.09684v1
2023-11-19,Discovery of Superconductivity and Electron-Phonon Drag in the Non-Centrosymmetric Weyl Semimetal LaRhGe$_3$,"We present an exploration of the effect of electron-phonon coupling and
broken inversion symmetry on the electronic and thermal properties of the
semimetal LaRhGe$_3$. Our transport measurements reveal evidence for
electron-hole compensation at low temperatures, resulting in a large
magnetoresistance of 3000% at 1.8 K and 14 T. The carrier concentration is on
the order of $10^{21}\rm{/cm}^3$ with high carrier mobilities of
$2000~\rm{cm}^2/\rm{Vs}$. When coupled to our theoretical demonstration of
symmetry-protected $\textit{almost movable}$ Weyl nodal lines, we conclude that
LaRhGe$_3$ supports a Weyl semimetallic state. We discover superconductivity in
this compound with a $T_{\text c}$ of 0.39(1) K and $B_{\rm{c}}(0)$ of 2.2(1)
mT, with evidence from specific heat and transverse-field muon spin relaxation.
We find an exponential dependence in the normal state electrical resistivity
below $\sim50$ K, while Seebeck coefficient and thermal conductivity
measurements each reveal a prominent peak at low temperatures, indicative of
strong electron-phonon interactions. To this end, we examine the
temperature-dependent Raman spectra of LaRhGe$_3$ and find that the lifetime of
the lowest energy $A_1$ phonon is dominated by phonon-electron scattering
instead of anharmonic decay. We conclude that LaRhGe$_3$ has strong
electron-phonon coupling in the normal state, while the superconductivity
emerges from weak electron-phonon coupling. These results open up the
investigation of electron-phonon interactions in the normal state of
superconducting non-centrosymmetric Weyl semimetals.",2311.11402v2
2024-01-10,Droplet morphology-based wettability tuning and design of fog harvesting mesh to minimize mesh-clogging,"Fog harvesting relies on intercepting atmospheric or industrial fog by
placing a porous obstacle, e.g., a mesh and collecting the deposited water. In
the face of global water scarcity, such fog harvesting has emerged as a viable
alternative source of potable water. Typical fog harvesting meshes suffer from
poor collection efficiency due to aerodynamic bypassing of the oncoming fog
stream and poor collection of the deposited water from the mesh. One pestering
challenge in this context is the frequent clogging up of mesh pores by the
deposited fog water, which not only yields low drainage efficiency but also
generates high aerodynamic resistance to the oncoming fog stream, thereby
negatively impacting the fog collection efficiency. Minimizing the clogging is
possible by rendering the mesh fiber superhydrophobic, but that entails other
detrimental effects like premature dripping and flow-induced re-entrainment of
water droplets into the fog stream from the mesh fiber. Herein, we improvise on
the traditional interweaved metal mesh designs by defining critical parameters,
viz., mesh pitch, shade coefficient, and fiber wettability, and deduce their
optimal values from numerically and experimentally observed morphology of
collected fog-water droplets under various operating scenarios. We extend our
investigations over a varying range of mesh-wettability, including
superhydrophilic and hydrophobic fibers, and go on to find optimal shade
coefficients which would theoretically render clog-proof fog harvesting meshes.
The aerodynamic, deposition, and overall collection efficiencies are
characterized. Hydrophobic meshes with square pores, having fiber diameters
smaller than the capillary length scale of water, and an optimal shade
coefficient, are found to be the most effective design of such clog-proof
meshes.",2401.05284v2
2024-02-18,Impact of the La2NiO4+δ oxygen content on the synaptic properties of the TiN/La2NiO4+δ/Pt memristive devices,"The rapid development of brain-inspired computing requires new artificial
components and architectures for its hardware implementation. In this regard,
memristive devices emerged as potential candidates for artificial synapses
because of their ability to emulate the plasticity of the biological synapses.
In this work, the synaptic behavior of the TiN/La2NiO4+{\delta}/Pt memristive
devices based on thermally annealed La2NiO4+{\delta} films is thoroughly
investigated. Using electron energy loss spectroscopy, we show that annealing
using reducing (Ar) or oxidizing (O2) atmospheres affects the interstitial
oxygen content ({\delta}) in the La2NiO4+{\delta} films. Electrical
characterization shows that both devices exhibit long-term
potentiation/depression and spike-timing-dependent plasticity, which makes them
suitable for neuromorphic applications. At the same time, the Ar annealed
TiN/La2NiO4+{\delta}/Pt device demonstrates non-volatile properties with low
energy consumption during the learning process. On the other hand, in the O2
annealed TiN/La2NiO4+{\delta}/Pt device the resistive switching behavior is
more volatile and requires more energy for synaptic learning. Finally, the
simulation tools show that spiking neural network architectures with
unsupervised learning rules based on the experimental data achieve high
inference accuracy in the digit recognition task, which proves the potential of
TiN/La2NiO4+{\delta}/Pt devices for artificial synapse applications.",2402.11612v1
2024-03-12,Electronic and dynamical properties of cobalt monogermanide CoGe phases under pressure,"We present the pressure dependence of the electronic and dynamical properties
of six different CoGe phases: orthorhombic Cmmm, hexagonal P6/mmm and
P$\bar{6}$2m, monoclinic C2/m, cubic P2$_{1}$3, and orthorhombic Pnma. Using
first-principles DFT calculations and the direct force-constants method, we
study the dynamical stability of individual phases under external pressure. We
show that the orthorombic Cmmm and hexagonal P6/mmm structures are unstable
over a broad pressure range and most pronounced imaginary phonon soft mode in
both cases leads to a stable hexagonal P$\bar{6}$2m structure of the lowest
ground-state energy of all studied phases at ambient and low (below $\sim 3$
GPa) external pressure. Under these conditions, the cubic P2$_{1}$3 phase has
the highest energy, however, together with monoclinic C2/m and orthorombic Pnma
it is dynamically stable and all these three structures can potentially coexist
as meta-stable phases. Above $\sim 3$ GPa, the cubic P2$_{1}$3 phase becomes
the most energetically favorable. Fitting the Birch--Murnaghan equation of
state we derive bulk modulus for all mentioned phases, which indicate
relatively high resistance of CoGe to compression. Such conclusions are
confirmed by band structure calculations. Additionally, we show that electronic
bands of the hexagonal P$\bar{6}$2m phase reveal characteristic features of the
kagome-like structure, while in the cubic P2$_{1}$3 phase spectrum, one can
locate spin-1 and double Weyl fermions. In both cases, the external pressure
induces the Lifshitz transition, related to the modification of the Fermi
surface topology.",2403.07580v1
1996-07-09,Anomalous magnetic response of the valence-fluctuating compound YbInCu4,"The exact solution of the spin one-half Falicov-Kimball model, with random
hopping between the lattice sites, is used to explain the anomalous magnetic
response of Yb-based valence-fluctuating intermetallic compounds. The anomalous
behavior arises from an entropy-driven local-moment--nonmagnetic transition of
unhybridized Yb ions in these materials which can also be used to explain the
observed metamagnetism and resistivity anomalies.",9607068v1
1996-09-27,Magnetoresistance in La(1-x)SrxCoO3 for 0.05 - x - 0.25,"The dc resistivity, magnetoresistance and magnetic susceptibility of
La(1-x)SrxCoO3 compounds have been investigated in the temperature range of 4K
to 300K for magnetic fields up to 7 T. In the doping range studied (0.05 - x -
0.25) the electronic properties of the material exhibit a crossover from
semiconducting to metallic behavior. The magnetoresistance is highest in the
semiconducting state. A correlation was found between the energy gap determined
from the dc conductivity and the energy scale identified from neutron
scattering data. The results are interpreted in terms of a double exchange
model.",9609274v1
1997-07-01,e-h Coherence and Charging Effects in Ultrasmall Metallic Grains,"We consider a model for electron tunneling between a pair of ultrasmall
metallic grains. Under appropriate circumstances, non-equilibrium final state
effects can strongly enhance tunneling and produce electron-hole coherence
between the grains. The model displays a quantum phase transition between a
Coulomb blockaded state to a coherent state exhibiting subohmic tunneling
conductance. The critical state of the junction exhibits a temperature
independent resistance of order $h/e^2$. Finally we discuss the possible
relevance to granular materials and quantum dots. In particular, similarities
between the quantum transition in our model and the metal-insulator transition
in granular wires observed by Herzog et al. are described in detail.",9707014v1
1997-07-18,Shearing the Vacuum - Quantum Friction,"We consider two perfectly smooth featureless surfaces at T=0, defined only by
their respective dielectric functions, separated by a finite distance, and ask
the question whether they can experience any friction when sheared parallel to
their interface. We find large frictional effects comparable to everyday
frictional forces provided that the materials have resistivities of the order
of 1 m-Ohm and that the surfaces are in close proximity. The friction depends
solely on the reflection coefficients of the surfaces to electromagnetic waves
and its detailed behaviour with shear velocity and separation is dictated by
the dispersion of the reflectivity with frequency.",9707190v2
1998-02-25,Magnetization Controlled Superconductivity in a Film with Magnetic Dots,"We consider a superconducting film with Magnetic Dots Array (MDA) placed on
it. Magnetic moments of these dots are supposed to be normal to the film and
strong enough to create vortices in the superconducting film. Magnetic
interaction between dots is negligible. Below the superconducting transition
temperature of the film in zero magnetic field the MDA with randomly magnetized
dots produces resistive state of the film. Paradoxically, in a finite magnetic
field the film with MDA is superconductive.",9802276v1
1998-03-28,Anomalous Hall Effect in Double Exchange Magnets,"We investigate the possible origin of anomalous Hall effect in the CMR
(colossal magnetoresistance) materials - the doped rare earth manganites -
observed recently by Matl et al. It is demonstrated that the spin-orbit
interaction in the double exchange model couples magnetization to the Berry
phase associated with three dimensional spin textures and induces a non-zero
average topological flux which in turn generates an anomalous contribution to
transverse resistivity. The same effect, but involving the orbital Berry phase,
occurs in the model with orbital degeneracy and Coulomb repulsion.",9803350v1
1998-07-13,Magnetoresistance of Epitaxial Fe Wires with Varied Domain Wall Structure,"The low temperature negative domain wall (DW) contribution to the resistivity
observed in expitaxial Fe microstructures has been investigated as a function
of film thickness. The DW spin structure changes from Bloch to Neel-like with
decreasing film thickness. Results suggest that an interplay between orbital
effects in the internal magnetic fields near DWs and thin film surface
scattering are at the origin of the observed negative wall contribution.",9807183v1
1998-09-02,Rolling friction of a hard cylinder on a viscous plane,"The resistance against rolling of a rigid cylinder on a flat viscous surface
is investigated. We found that the rolling-friction coefficient reveals
strongly non-linear dependence on the cylinder's velocity. For low velocity the
rolling-friction coefficient rises with velocity due to increasing deformation
rate of the surface. For larger velocity, however, it decreases with velocity
according to decreasing contact area and deformation of the surface.",9809053v1
1998-12-10,Electric field and potential around localized scatterers in thin metal films studied by scanning tunneling potentiometry,"Direct observation of electric potential and field variation near local
scatterers like grain boundaries, triple points and voids in thin platinum
films studied by scanning tunneling potentiometry is presented. The field is
highest at a void, followed by a triple point and a grain boundary. The local
field near a void can even be four orders of magnitude higher than the
macroscopic field. This indicates that the void is the most likely place for an
electromigration induced failure. The field build up near a scatterer strongly
depends on the grain connectivity which is quantified by the average grain
boundary reflection coefficient, estimated from the resistivity.",9812167v1
1999-01-11,Effect of disorder on the Kondo behavior of thin Cu(Mn) films,"We have studied the influence of disorder on the Kondo effect in thin films
of Cu(Mn), i.e., Cu doped with a small amount of Mn. We find that the Kondo
contribution to the resistivity is suppressed when the elastic mean-free-path,
$\lambda$, is reduced. While this is qualitatively similar to results found
previously by our group in a different material, our new experiments reveal in
detail how this suppression depends on both film thickness and $\lambda$. These
results are compared with the theory of Martin, Wan, and Phillips. While there
is general qualitative agreement with this theory, there appear to be some
quantitative discrepancies.",9901092v1
1999-03-10,Large Thermopower in a Layered Oxide NaCo_2O_4,"A transition-metal oxide NaCo_2O_4 is a layered oxide in which CoO_2 and Na
alternately stack along the c axis. Recently we have found that this compound
shows unusually large thermopower with low resistivity, which is comparable to
those of Bi_2Te_3. The negative transverse magnetoresistance and the strongly
temperature-dependent Hall coefficient suggest that electron correlation
dominates the conduction mechanism in NaCo_2O_4.",9903162v1
1999-07-05,Chiral Glass Phase in Ceramic Superconductors,"A three-dimensional lattice of the Josephson junctions with a finite
self-conductance is employed to model the ceramic superconductors. By Monte
Carlo simulations it is shown that the chiral glass phase is stable in three
dimensions even under the influence of screening. The nonlinear ac
susceptibility and the compensation effect are also studied. The compensation
effect is shown to be due to the existence of the chiral glass phase. In
agreement with experiments, this effect is demonstrated to be present in the
ceramic superconductors which show the paramagnetic Meissner effect.",9907060v1
1999-09-01,Polyethylene under tensile load: strain energy storage and breaking of linear and knotted alkanes probed by first-principles molecular dynamics calculations,"The mechanical resistance of a polyethylene strand subject to tension and the
way its properties are affected by the presence of a knot is studied using
first-principles molecular dynamics calculations. The distribution of strain
energy for the knotted chains has a well-defined shape that is very different
from the one found in the linear case. The presence of a knot significantly
weakens the chain in which it is tied. Chain rupture invariably occurs just
outside the entrance to the knot, as is the case for a macroscopic rope.",9909013v1
1999-11-09,Heat capacity and transport studies of the ferromagnetic superconductor RuSr2GdCu2O8,"Resistivity, thermoelectric power and heat capacity are investigated in the
ferromagnetic superconductor RuSr2GdCu2O8 with and without Zn substitution. The
thermodynamic signatures of the ordering of the Ru moments and the paramagnetic
Gd moments as well as the onset of superconductivity are all clearly seen and
quantified. The materials are shown to exhibit bulk superconductivity which
coexists with spatially-uniform ferromagnetism. They appear to be typical
underdoped superconducting cuprates in which the pseudogap dominates
normal-state transport, thermodynamic and substitutional properties. However, a
field-induced increase in Tc could suggest some degree of triplet pairing.",9911135v1
2000-02-14,Scanned Probe Microscopy of Electronic Transport in Carbon Nanotubes,"We use electrostatic force microscopy and scanned gate microscopy to probe
the conducting properties of carbon nanotubes at room temperature. Multi-walled
carbon nanotubes are shown to be diffusive conductors, while metallic
single-walled carbon nanotubes are ballistic conductors over micron lengths.
Semiconducting single-walled carbon nanotubes are shown to have a series of
large barriers to conduction along their length. These measurements are also
used to probe the contact resistance and locate breaks in carbon nanotube
circuits.",0002209v1
2000-03-27,Current and power spectrum in a magnetic tunnel device with an atomic size spacer,"Current and its noise in a ferromagnetic double tunnel barrier device with a
small spacer particle were studied in the framework of the sequential tunneling
approach. Analytical formulae were derived for electron tunneling through the
spacer particle containing only a single energy level. It was shown that
Coulomb interactions of electrons with a different spin orientation lead to an
increase of the tunnel magnetoresistance. Interactions can also be responsible
for the negative differential resistance. A current noise study showed, which
relaxation processes can enhance or reduce fluctuations leading either to a
super-Poissonian or a sub-Poissonian shot noise.",0003418v1
2000-05-25,Magnetic-Field-Driven Superconductor-Insulator-Type Transition in Graphite,"A magnetic-field-driven transition from metallic- to semiconducting-type
behavior in the basal-plane resistance takes place in highly oriented pyrolytic
graphite at a field $H_c \sim 1~$kOe applied along the hexagonal c-axis. The
analysis of the data reveals a striking similarity between this transition and
that measured in thin-film superconductors and Si MOSFET's. However, in
contrast to those materials, the transition in graphite is observable at almost
two orders of magnitude higher temperatures.",0005439v1
2000-11-29,Giant Magnetoresistance at the Interface of Iron Thin Films,"Ag/Fe/Ag and Cr/Fe/Cr trilayers with a single $25 nm$ thick ferromagnetic
layer exhibit giant magnetoresistance (GMR) type behavior. The resistance
decreases for parallel and transversal magnetic field alignements with a
Langevin-type magnetic field dependence up to B=12 T. The phenomenon is
explained by a granular interface structure. Results on Fe/Ag multilayers are
also interpreted in terms of a granular interface magnetoresistance.",0011491v1
2001-01-22,Orbital Correlations in the Ferromagnetic Half-Metal $CrO_{2},"We deduce a model relevant for the description of the ferromagnetic
half-metal Chromium dioxide ($CrO_{2}$), widely used in magnetic recording
technology. The model describes the effect of dynamical, local orbital
correlations arising from local quantum chemistry of the material. A finite
temperature solution of the model in $d=\infty$ provides a natural explanation
of the optical response, photoemission, resistivity and the large Woods-Saxon
ratio observed in experiments. Our study confirms the important role of many
body dynamical correlation effects for a proper understanding of the metallic
phase of $CrO_{2}$.",0101335v1
2001-03-06,Coherent description of electrical and thermal impurity-and-phonon limited transport in simple metals,"The electrical resistivity, thermoelectric power and electronic thermal
conductivity of simple (isotropic) metals are studied in a uniform way.
Starting from results of a variational solution of the Boltzmann equation, a
generalized Matthiessen rule is used in order to superpose the inelastic (or
not) electron-phonon and elastic electron-impurity scattering cross sections
(""matrix elements""). The temperature dependence relative to these processes is
given through simple functions and physical parameters over the usually
investigated range of temperature for each transport coefficient. The coherence
of such results is emphasized.",0103138v1
2001-03-08,Localization corrections to the anomalous Hall effect in a ferromagnet,"We calculate the localization corrections to the anomalous Hall conductivity
related to the contribution of spin-orbit scattering into the current vertex
(side-jump mechanism). We show that in contrast to the ordinary Hall effect,
there exists a nonvanishing localization correction to the anomalous Hall
resistivity. The correction to the anomalous Hall conductivity vanishes in the
case of side-jump mechanism, but is nonzero for the skew scattering. The total
correction to the nondiagonal conductivity related to both mechanisms, does not
compensate the correction to the diagonal conductivity.",0103182v1
2001-03-23,Premartensitic Transition in Ni2+xMn1-xGa Heusler Alloys,"The temperature dependencies of the resistivity and magnetization of a series
of Ni2+XMn1-XGa (X = 0 - 0.09) alloys were investigated. Along with the
anomalies associated with ferromagnetic and martensitic transitions,
well-defined anomalies were observed at the temperature of premartensitic
transformation. The premartensitic phase existing in a temperature range 200 -
260 K in the stoichiometric Ni2MnGa is suppressed by the martensitic phase with
increasing Ni content and vanishes in Ni2.09Mn0.91Ga composition.",0103483v1
2001-04-24,Electrical current distribution across a metal-insulator-metal structure during bistable switching,"Combining scanning electron microscopy (SEM) and electron-beam-induced
current (EBIC) imaging with transport measurements, it is shown that the
current flowing across a two-terminal oxide-based capacitor-like structure is
preferentially confined in areas localized at defects. As the thin-film device
switches between two different resistance states, the distribution and
intensity of the current paths, appearing as bright spots, change. This implies
that switching and memory effects are mainly determined by the conducting
properties along such paths. A model based on the storage and release of charge
carriers within the insulator seems adequate to explain the observed memory
effect.",0104452v1
2001-04-24,A simple one-dimensional model of heat conduction which obeys Fourier's law,"We present the computer simulation results of a chain of hard point particles
with alternating masses interacting on its extremes with two thermal baths at
different temperatures. We found that the system obeys Fourier's law at the
thermodynamic limit. This result is against the actual belief that one
dimensional systems with momentum conservative dynamics and nonzero pressure
have infinite thermal conductivity. It seems that thermal resistivity occurs in
our system due to a cooperative behavior in which light particles tend to
absorb much more energy than the heavier ones.",0104453v1
2001-06-29,Landau diamagnetism revisited,"The problem of diamagnetism, solved by Landau, continues to pose fascinating
issues which have relevance even today. These issues relate to inherent quantum
nature of the problem, the role of boundary and dissipation, the meaning of
thermodynamic limits, and above all, the quantum-classical crossover occasioned
by environment-induced decoherence. The Landau Diamagnetism provides a unique
paradigm for discussing these issues, the significance of which are
far-reaching. Our central result is a remarkable one as it connects the mean
orbital magnetic moment, a thermodynamic property, with the electrical
resistivity, which characterizes transport properties of materials.",0106646v1
2001-07-12,Theory of Angular Magnetoresistance in CPP spin valves,"The resistance of CPP spin valve is a continuous function of the angle
$\theta $ between the magnetizations of both ferromagnets. We use the cicuit
theory for non-collinear magnetoelectronics to compute the angular
magnetoresistance of CPP spin valves taking the spin accumulation in the
ferromagnetic layers into account.",0107250v1
2001-07-27,Large magnetoresistance using hybrid spin filter devices,"A magnetic ""spin filter"" tunnel barrier, sandwiched between a non-magnetic
metal and a magnetic metal, is used to create a new magnetoresistive tunnel
device, somewhat analogous to an optical polarizer-analyzer configuration. The
resistance of these trilayer structures depends on the relative magnetization
orientation of the spin filter and the ferromagnetic electrode. The spin
filtering in this configuration yields a previously unobserved
magnetoresistance effect, exceeding 100%.",0107571v1
2001-08-17,Negative Magneto-Resistance Beyond Weak Localization in Three-Dimensional Billiards: Effect of Arnold Diffusion,"We investigate a semiclassical conductance for ballistic open
three-dimensional (3-d) billiards. For partially or completely broken-ergodic
3-d billiards such as SO(2) symmetric billiards, the dependence of the
conductance on the Fermi wavenumber is dramatically changed by the lead
orientation. Application of a symmetry-breaking weak magnetic field brings
about mixed phase-space structures of 3-d billiards which ensures a novel
Arnold diffusion that cannot be seen in 2-d billiards. In contrast to the 2-d
case, the anomalous increment of the conductance should inevitably include a
contribution arising from Arnold diffusion as well as a weak localization
correction. Discussions are devoted to the physical condition for observing
this phenomenon.",0108276v1
2001-08-29,Anomalous Co-site substitution effects on the physical properties of the thermoelectric oxide NaCo2O4,"We prepared polycrystalline samples of NaCo2-xMxO4 substituted for the Co
site by other 3d or 4d elements (M=Mn,Cu, Zn, Ru, Rh, and Pd). While some of
the elements (M=Mn,Ru and Rh) act as a strong scatterer to give rise to a rapid
increase in resistivity, the others (M=Cu, Zn and Pd) do not deteriorate the
electric conduction of the host. Most unusually, the Cu substitution
significantly enhances the thermopower, which increases the figure of merit by
several times at 100 K.",0108485v1
2001-10-05,Successive Phase Transitions in a Metal-Ordered Manganite Perovskite YBaMn2O6,"Structural, magnetic and electric properties of a metal-ordered perovskite
YBaMn2O6 have been studied by means of powder X-ray diffraction, DSC, magnetic
susceptibility, and electric resistivity. It is found that this material
undergoes a 1st order structural phase transition at Tc1=520 K, from a pseudo
orthorhombic (monoclinic) phase to a pseudo tetragonal (monoclinic) one.
Accompanied by this transition, the susceptibility exhibits a sharp drop, where
ferromagnetic exchange interaction becomes antiferromagnetic. Furthermore, two
more transitions, a metal-insulator transition at Tc2=480 K and an
antiferromagnetic ordering at Tc3=200 K, have been observed respectively.",0110114v1
2002-04-29,"Nonlinear charging, and transport times in doped nanotubes junctions","The nonlinear capacitance in doped nanotube junctions is calculated self
consistently. It decreases as a function of the applied bias when the latter
becomes larger than the pseudogap of the nanotube. For this device, one can
deduce a relaxation time of about 0.1 femtosecond. Because of its negative
differential resistance (NDR), a switching time of less than a fs can also be
deduced.",0204609v3
2002-06-24,"Boltzmann theory of engineered anisotropic magnetoresistance in (Ga,Mn)As","We report on a theoretical study of dc transport coefficients in (Ga,Mn)As
diluted magnetic semiconductor ferromagnets that accounts for quasiparticle
scattering from ionized Mn$^{2+}$ acceptors with a local moment $S=5/2$ and
from non-magnetic compensating defects. In metallic samples Boltzmann transport
theory with Golden rule scattering rates accounts for the principle trends of
the measured difference between resistances for magnetizations parallel and
perpendicular to the current. We predict that the sign and magnitude of the
anisotropic magnetoresistance can be changed by strain engineering or by
altering chemical composition.",0206416v1
2002-07-16,Carbon Nanotubes as Schottky Barrier Transistors,"We show that carbon nanotube transistors operate as unconventional ""Schottky
barrier transistors"", in which transistor action occurs primarily by varying
the contact resistance rather than the channel conductance. Transistor
characteristics are calculated for both idealized and realistic geometries, and
scaling behavior is demonstrated. Our results explain a variety of experimental
observations, including the quite different effects of doping and adsorbed
gases. The electrode geometry is shown to be crucial for good device
performance.",0207397v1
2002-09-13,Some Thermal and Electrical Properties of Candelilla Wax,"We report the values of some thermal and electrical properties of Candelilla
Wax (euphorbia cerifera). The open-cell photoacoustic technique and another
photothermic technique - based on the measure of the temperature decay of a
heated sample - were employed to obtain the thermal diffusivity ($\alpha_{s} =
0.026 \pm 0.00095 {cm}^{2}{/sec}$) as well as the thermal conductivity
($k=2.132 \pm 0.16 {W/mK}$) of this wax. The Kelvin null method was used to
measure the dark decay of the surface potential of the sample after a Corona
Discharge, obtaining a resistivity of $\rho_e=5.98 \pm 0.19 \times 10^{17}
{ohm-cm}$.",0209328v1
2002-09-25,Magnetic properties of Ni2.18Mn0.82Ga Heusler alloys with a coupled magnetostructural transition,"Polycrystalline Ni2.18Mn0.82Ga Heusler alloys with a coupled
magnetostructural transition are studied by differential scanning calorimetry,
magnetic and resistivity measurements. Coupling of the magnetic and structural
subsystems results in unusual magnetic features of the alloy. These uncommon
magnetic properties of Ni2.18Mn0.82Ga are attributed to the first-order
structural transition from a tetragonal ferromagnetic to a cubic paramagnetic
phase.",0209574v1
2002-10-04,The Effects of the Misfit Structure on Thermoelectric Properties of Bi2-xPbxSr2Co2Oy Single Crystals,"In-plane anisotropy of the resistivity and thermopower was measured for
single crystal Bi2-xPbxSr2Co2Oy. There is large in-plane anisotropy, which is
attributed to the anisotropic pseudogap formation due to the different crystal
symmetry between the square Bi2Sr2O4 layer and the triangular CuO2 layer. The
magnitude of the thermopower both along a- and b-axis direction increases with
Pb doping from x=0 to 0.4, where we observe discontinuous shrink of b-axis
length. We attribute this to the enhancement of the misfitness. Thus, we can
improve the thermoelectric properties by tuning the misfitness.",0210087v1
2002-10-21,Competing SDW Phases and Quantum Oscillations in (TMTSF)2ClO4 in Magnetic Field,"We propose a new approach for studying spin density waves (SDW) in the
Bechgaard salt (TMTSF)2ClO4 where lattice is dimerized in transverse direction
due to anion ordering. The SDW response is calculated in the matrix formulation
that rigorously treats the hybridization of inter-band and intra-band SDW
correlations. Since the dimerization gap is large, of the order of transverse
bandwidth, we also develop an exact treatment of magnetic breakdown in the
external magnetic field. The obtained results agree with the experimental data
on the fast magneto-resistance oscillations. Experimentally found 260T rapid
oscillations and the characteristic Tc dependance on magnetic field of relaxed
material are fitted with our results for anion potential of the order of
interchain hopping.",0210452v1
2002-10-28,"Fine ""mist"" vs large droplets in phase separated manganites","The properties of phase-separated systems, e.g. manganites, close to a I
order phase transition between charge-ordered insulator and ferromagnetic
metal, are usually described by the percolation picture. We argue that the
correlated occupation of metallic sites leads to the preferential formation of
larger metallic clusters, which explains the often observed inverse, or
``overshot'' hysteresis in manganites (when the resistivity with increasing
temperature is larger than with decreasing T). It also explains the recently
discovered thermal cycling effect in manganites. Thus in treating this and
similar systems in percolation picture, not only the total concentration of
metallic phase, but also the distribution of metallic clusters by shape and
size may significantly influence the properties of such systems.",0210616v1
2002-11-12,Infrared properties of W-doped charge-density-wave material K$_{0.3}$MoO$_3$,"The optical conductivity spectra of quasi-one dimensional compounds
K$_{0.3}$Mo$_{1-x}$W$_x$O$_3$ (x=0, 0.03 and 0.15) have been studied over broad
frequencies. While the dc resistivity measurements indicate no sign of CDW
transition in heavily W-doped blue bronze, the optical conductivity spectra
still show a single particle gap at around 0.2 eV for \textbf{E} parallel to
the chain direction. Such impurity effect challenges our understanding about
the occurrence of the optical gap with the CDW transition.",0211225v1
2002-11-18,Anomalous Hall Effect of Reentrant Spin Glass System Fe1-xAlx (x ~ 0.3),"The anomalous Hall coefficient Rs has been studied for the reentrant spin
glass system Fe0.7Al0.3 by measuring the magnetization M and the Hall
resistivity r_H. We have found that R_s exhibits anomalous temperature
dependence at the spin-glass transition temperature T_G, indicating that an
additional term appears along with the beginning of the spin glass phase. The
result is discussed in relation to the recent proposal of the chirality
mechanism of the Hall effect in the spin glass phase.",0211368v1
2002-12-01,The superconducting gap of \QTR{em}{in situ} $MgB_{2}$ thin films by microwave surface impedance measurements,"Precision measurements of the microwave surface resistance $R_{s}$ of in situ
$MgB_{2}$ films directly reveal an exponential behavior of $R_{s}$ at low
temperature indicating a fully-gapped order parameter. The entire temperature
dependence of $R_{s}$ is well described by a Mattis-Bardeen formalism but with
a small gap ratio of $\Delta (0)/kT_{c}=0.72$, corresponding to $\Delta
(0)=1.9meV$.",0212009v1
2002-12-09,Conductance switching in a molecular device: the role of sidegroups and intermolecular interactio,"We report first-principles studies of electronic transport in monolayers of
Tour wires functionalized with different side groups. An analysis of the
scattering states and transmission eigenchannels suggests that the
functionalization does not strongly affect the resonances responsible for
current flow through the monolayer. However, functionalization has a
significant effect on the interactions within the monolayer, so that monolayers
with NO$_2$ side groups exhibit local minima associated with twisted
conformations of the molecules. We use our results to interpret observations of
negative differential resistance and molecular memory in monolayers of NO$_2$
functionalized molecules in terms of a twisting of the central ring induced by
an applied bias potential.",0212191v1
2003-04-24,The spin-torque transistor,"A magnetoelectronic thin-film transistor is proposed that can display
negative differential resistance and gain. The working principle is the
modulation of the soure-drain current in a spin valve by the magnetization of a
third electrode, which is rotated by the spin-torque created by a control
spin-valve. The device can operate at room temperature, but in order to be
useful, ferromagnetic materials with polarizations close to unity are required.",0304550v1
2003-05-27,Double Magnetic Transition in Pr0.5Sr0.5CoO3,"We report studies of polycrystalline samples of the metallic ferromagnet
Pr0.5Sr0.5CoO3 through measurements of the magnetization, a.c. magnetic
susceptibility, resistivity, and specific heat. We find an unusual anomaly
around TA = 120 K, much below the ferromagnetic transition (TC = 226 K). The
anomaly is manifested in field cooled magnetization as a downward step in low
fields (H less than or equal to 0.01 T) but is transformed into an upward step
for H greater than or equal to 0.05 T. The anomaly cannot be easily attributed
to antiferromagnetic ordering, but may correspond to a second ferromagnetic
transition or an alteration of the ferromagnetic state associated with orbital
ordering.",0305621v1
2003-06-08,Analysis Of Critical Power Loss In A Superconductor,"A critical power dissipation resulting from an oscillating magnetic field, Hp
cos wt, can produce a magnetic breakdown field, H <Hc, the critical field of
the superconductor. The analysis shows, for example, why the breakdown field of
a superconducting microwave cavity can be well below Hc in some cases, and
indicates what the functional dependence of the cavity Q may be for values of
Hp near H . The effective resistivity of a single isolated oscillating fluxoid,
as well as that of a stationary normal region, is also derived for both type I
and type Il superconductors.",0306202v1
2003-07-11,Enhanced thermoelectric properties of NaxCoO2 whisker crystals,"Single-crystalline whiskers of thermoelectric cobalt oxide, NaxCoO2, have
been grown by an unconventional method from potassium-containing compositions,
and their transport properties, and chemical compositions were determined. The
growth mechanism was analyzed and interpreted by means of thermogravimetric
analysis. At 300 K, electrical resistivity r and thermoelectric power S of the
whisker are 102 u ohm cm and 83 uV/K, respectively. The power-factor, S2/r,
thus is enhanced up to ~ 68 uW/K2 cm.",0307277v1
2003-07-31,Reflection of electrons from a domain wall in magnetic nanojunctions,"Electronic transport through thin and laterally constrained domain walls in
ferromagnetic nanojunctions is analyzed theoretically. The description is
formulated in the basis of scattering states. The resistance of the domain wall
is calculated in the regime of strong electron reflection from the wall. It is
shown that the corresponding magnetoresistance can be large, which is in a
qualitative agreement with recent experimental observations. We also calculate
the spin current flowing through the wall and the spin polarization of electron
gas due to reflections from the domain wall.",0307765v1
2003-08-16,Frequency Dependence of Superconducting Cavity Q and Magnetic Breakdown Field,"A theoretical explanation is given to account for the unexpected observation
that L- and S-band Nb superconducting cavities were found to have lower Q and
lower magnetic breakdown field than those of the higher X-band frequencies.
Both effects can be related to the trapping of magnetic flux in the cavity
walls. The frequency dependence arises from the frequency dependence of the
resistivity of oscillating fluxoids. Calculations based on this model are in
agreement with experimental observations.",0308324v1
2003-08-22,Relevance of Cooperative Lattice Effects and Correlated Disorder in Phase-Separation Theories for CMR Manganites,"Previous theoretical investigations of colossal magnetoresistance (CMR)
materials explain this effect using a ``clustered'' state with preformed
ferromagnetic islands that rapidly align their moments with increasing external
magnetic fields. While qualitatively successful, explicit calculations indicate
drastically different typical resistivity values in two- and three-dimensional
lattices, contrary to experimental observations. This conceptual bottleneck in
the phase-separated CMR scenario is resolved here considering the cooperative
nature of the Mn-oxide lattice distortions. This induces power-law correlations
in the quenched random fields used in toy models with phase competition. When
these effects are incorporated, resistor-network calculations reveal very
similar results in two and three dimensions, solving the puzzle.",0308456v1
2003-09-13,Metal-insulator transition in Ca_{1-x}Li_xPd_3O_4,"Metal-insulator transition in Ca_{1-x}Li_xPd_3O_4 has been studied through
charge transport measurements. The resistivity, the Seebeck coefficient, and
the Hall coefficient are consistently explained in terms of a simple one-band
picture, where a hole with a moderately enhanced mass is itinerant
three-dimensionally. Contrary to the theoretical prediction [Phys. Rev. B62,
13426 (2000)], CaPd_3O_4 is unlikely to be an excitonic insulator, and holds a
finite carrier concentration down to 4.2 K. Thus the metal-insulator transition
in this system is basically driven by localization effects.",0309335v1
2003-10-10,"Charge transport in l-DNA probed by conducting-AFM, and relationship with its structure","We studied the electrical conductivity of DNA samples as function of the
number of DNA molecules. We showed that the insulating gap (no current at low
voltage) increases from ~1-2 V for bundles and large ropes to ~4-7 V for few
DNA molecules. From the distance dependent variation of the current, a unique
hopping distance of ~3 nm is calculated (polaron-hopping model) independently
of the number of DNA in the sample. The highly resistive behavior of the single
DNA is correlated with its flattened conformation on the surface (reduced
thickness, ~0.5-1.5 nm, compared to its nominal value, ~2 nm).",0310242v1
2003-12-18,Spin momentum transfer in current perpendicular to the plane spin valves,"We present experimental and numerical micromagnetic data on the effect of
spin momentum transfer in current perpendicular to the plane spin valves.
Starting from a configuration with orthogonal free and pinned layer
magnetizations, the free layer magnetization exhibits abrupt current induced
switching that is qualitatively consistent with the spin torque model. When
operating the spin valve as a field sensor, spin transfer can produce a change
in resistance that mimics an effective magnetic field and induce magnetic
instability that requires a larger bias field in order to stabilize the device.",0312505v1
2004-03-24,New Pyrochlore Oxide Superconductor RbOs2O6,"We report the discovery of a new pyrochlore oxide superconductor RbOs2O6. The
compound crystallizes in the same beta-pyrochlore structure as the recently
discovered superconductor KOs2O6, where Os atoms form a corner-sharing
tetrahedral network called the pyrochlore lattice with Rb or K atoms in the
cage. Resistivity, magnetic susceptibility and specific heat measurements on
polycrystalline samples evidence a bulk superconductivity with Tc = 6.3 K.",0403601v2
2004-04-16,Quenched growth of nanostructured lead thin films on insulating substrates,"Lead island films were obtained via vacuum vapor deposition on glass and
ceramic substrates at 80 K. Electrical conductance was measured during vapor
condensation and further annealing of the film up to room temperature. The
resistance behavior during film formation and atomic force microscopy of
annealed films were used as information sources about their structure. A model
for the quenched growth, based on ballistic aggregation theory, was proposed.
The nanostructure, responsible for chemiresistive properties of thin lead films
and the mechanism of sensor response are discussed.",0404393v2
2004-04-28,"Current-induced magnetization reversal in a (Ga,Mn)As-based magnetic tunnel junction","We report current-induced magnetization reversal in a ferromagnetic
semiconductor-based magnetic tunnel junction (Ga,Mn)As/AlAs/(Ga,Mn)As prepared
by molecular beam epitaxy on a p-GaAs(001) substrate. A change in
magneto-resistance that is asymmetric with respect to the current direction is
found with the excitation current of 10^6 A/cm^2. Contributions of both
unpolarized and spin-polarized components are examined, and we conclude that
the partial magnetization reversal occurs in the (Ga,Mn)As layer of smaller
magnetization with the spin-polarized tunneling current of 10^5 A/cm^2.",0404663v1
2004-04-30,Spin-dependent transport in molecular tunnel junctions,"We present measurements of magnetic tunnel junctions made using a
self-assembled-monolayer molecular barrier. Ni/octanethiol/Ni samples were
fabricated in a nanopore geometry. The devices exhibit significant changes in
resistance as the angle between the magnetic moments in the two electrodes is
varied, demonstrating that low-energy electrons can traverse the molecular
barrier while maintaining spin coherence. An analysis of the voltage and
temperature dependence of the data suggests that the spin-coherent transport
signals can be degraded by localized states in the molecular barriers.",0404740v1
2004-08-07,Hystersis like behaviour in Thin Films with heating-cooling cycle,"The expression of temperature distribution along a film thickness is derived
and distribution of temperature in the film as the substrate is heated is
shown. The variation of film resistance with different substrate temperature is
calculated and the existence of temperature gradient along the film thickness
with finite thermal conductivity leads to hysteresis like behaviour on
heating-cooling the film.",0408163v1
2004-10-12,Quasi-ballistic electron transport in double-wall carbon nanotubes,"Room-temperature quasi-ballistic electron transport in double-wall carbon
nanotubes (DWNT) is demonstrated. Conductance dependence on the length was
measured by submerging DWNTs into liquid mercury. The conductance plots show
plateaus, indicating weak dependence of the electrode-tube-electrode electrical
resistance on the length of the connecting nanotube. We infer a mean free path
between 0.6 and 10 micron meters for around 80% of the DWNTs, which is in good
agreement with calculations based on the electron scattering by acoustic
phonons and by disorder.",0410310v1
2004-11-07,Sub 20 nm Short Channel Carbon Nanotube Transistors,"Carbon nanotube field-effect transistors with sub 20 nm long channels and
on/off current ratios of > 1000000 are demonstrated. Individual single-walled
carbon nanotubes with diameters ranging from 0.7 nm to 1.1 nm grown from
structured catalytic islands using chemical vapor deposition at 700 degree
Celsius form the channels. Electron beam lithography and a combination of HSQ,
calix[6]arene and PMMA e-beam resists were used to structure the short channels
and source and drain regions. The nanotube transistors display on-currents in
excess of 15 microA for drain-source biases of only 0.4 Volt.",0411177v1
2004-11-11,Ferromagnetic-superconducting hybrid films and their possible applications: A direct study in a model combinatorial film,"Model combinatorial films (CFs) which host a pure superconductor adjacent to
a ferromagneticsuperconducting hybrid film (HF) are manufactured for the study
of the influence of ferromagnetic nanoparticles (FNs) on the nucleation of
superconductivity. Careful resistance measurements were performed
simultaneously on two different sites of the CFs. Enhancement of
superconductivity and magnetic memory effects were observed only on the hybrid
site of the CFs but were absent on their purely superconducting part. Our
results give direct proof that the FNs modulate the superconducting order
parameter in an efficient and controlled way giving us the possibility of
miscellaneous practical applications.",0411311v1
2004-12-20,Carbon Nanotubes for Interconnect Applications,"We briefly review the status of the application of carbon nanotubes (CNTs)
for future interconnects and present results concerning possible integration
schemes. Growth of single nanotubes at lithographically defined locations
(vias) has been achieved which is a prerequisite for the use of CNTs as future
interconnects. For the 20 nm node, a current density of 5 10^8 A/cm^2 and a
resistance of 7.8 kOhm could be achieved for a single multi-walled CNT vertical
interconnect.",0412537v1
2005-01-12,Nanoengineered Curie Temperature in Laterally-Patterned Ferromagnetic Semiconductor Heterostructures,"We demonstrate the manipulation of the Curie temperature of buried layers of
the ferromagnetic semiconductor (Ga,Mn)As using nanolithography to enhance the
effect of annealing. Patterning the GaAs-capped ferromagnetic layers into
nanowires exposes free surfaces at the sidewalls of the patterned (Ga,Mn)As
layers and thus allows the removal of Mn interstitials using annealing. This
leads to an enhanced Curie temperature and reduced resistivity compared to
unpatterned samples. For a fixed annealing time, the enhancement of the Curie
temperature is larger for narrower nanowires.",0501298v2
2005-01-29,Spin accumulation and decay in magnetic Schottky barriers,"The theory of charge and spin transport in forward-biased Schottky barriers
reveals characteristic and experimentally relevant features. The conductance
mismatch is found to enhance the current induced spin-imbalance in the
semiconductor. The GaAs|MnAs interface resistance is obtained from an analysis
of the magnetic field dependent Kerr rotation experiments by Stephens et al.
and compared with first-principles calculations for intrinsic interfaces. With
increasing current bias, the interface transparency grows towards the
theoretical values, reflecting increasingly efficient Schottky barrier
screening.",0501726v1
2005-02-01,Adsorption of Oxygen Molecules on Individual Carbon Single-walled Nanotubes,"Our study of the adsorption of oxygen molecules on individual semiconductiong
single-walled carbon nanotubes at ambient conditions reveals that the
adsorption is physisorption, that the resistance without O2 increases by ~two
orders of magnitude as compared to that with O2, and that the sensitive
response is due to the pinning of the Fermi level near the top of the valence
band of the tube resulting from impurity states of O2 appearing above the
valence band.",0502012v1
2005-03-07,"Physical properties, strontium ordering and structural modulation in layered hexagonal Sr0.35CoO2","Layered Sr0.35CoO2 has been synthesized by means of an ion exchange reaction
from Na0.7CoO2. Resistivity measurements show that this material can be either
metallic or semiconducting depending on the annealing conditions. Magnetic
susceptibility, following the Curie-Weiss law, increases with lowering
temperature and shows a small anomalous kink at around 30 K.
Transmission-electron-microscopy observations reveal the presence of two
superstructures arising respectively from the intercalated Sr-ordering (a
compositional modulation) with q1 = a* / 3 + b* / 3 and a periodic structural
distortion (a transverse structural modulation) with q2 = a* / 2.",0503136v1
2005-04-12,Polaron Transport in the Paramagnetic Phase of Electron-Doped Manganites,"The electrical resistivity, Hall coefficient, and thermopower as functions of
temperature are reported for lightly electron-doped Ca(1-x)La(x)MnO(3)(0 <= x
<= 0.10). Unlike the case of hole-doped ferromagnetic manganites, the magnitude
and temperature dependence of the Hall mobility for these compounds is found to
be inconsistent with small-polaron theory. The transport data are better
described by the Feynman polaron theory and imply intermediate coupling (alpha
\~ 5.4) with a band effective mass, m*~4.3 m_0, and a polaron mass, m_p ~ 10
m_0.",0504303v1
2005-04-26,Spin filtering through ferromagnetic BiMnO3 tunnel barriers,"We report on experiments of spin filtering through ultra-thin single-crystal
layers of the insulating and ferromagnetic oxide BiMnO3 (BMO). The spin
polarization of the electrons tunneling from a gold electrode through BMO is
analyzed with a counter-electrode of the half-metallic oxide La2/3Sr1/3MnO3
(LSMO). At 3 K we find a 50% change of the tunnel resistances according to
whether the magnetizations of BMO and LSMO are parallel or opposite. This
effect corresponds to a spin filtering effciency of up to 22%. Our results thus
show the potential of complex ferromagnetic insulating oxides for spin
filtering and injection.",0504667v1
2005-05-16,Electronic mean free path in as-produced and purified single-wall carbon nanotubes,"The effect of purification on room temperature electronic transport
properties of single-wall carbon nanotubes (SWNT) was studied by submerging
samples into liquid mercury. The conductance plots of purified SWNTs showed
plateaus, indicating weak dependence of the electrical resistance on the length
of the tube connecting the electrodes, providing evidence of quasi-ballistic
conduction in SWNTs. The electronic mean free path of the purified SWNTs
reached a few microns, which is longer than that of the as-produced SWNTs, and
which is consistent with the calculation based on the scattering by acoustic
phonons.",0505377v1
2005-06-03,Magnetic and Transport Properties of Fe-Ag granular multilayers,"Results of magnetization, magnetotransport and Mossbauer spectroscopy
measurements of sequentially evaporated Fe-Ag granular composites are
presented. The strong magnetic scattering of the conduction electrons is
reflected in the sublinear temperature dependence of the resistance and in the
large negative magnetoresistance. The simultaneous analysis of the magnetic
properties and the transport behavior suggests a bimodal grain size
distribution. A detailed quantitative description of the unusual features
observed in the transport properties is given.",0506072v2
2005-07-06,A single molecule switch based on two Pd nanocrystals linked by a conjugated dithiol,"Tunneling spectroscopy measurements have been carried out on a single
molecule device formed by two Pd nanocrystals (dia, $\sim$5 nm) electronically
coupled by a conducting molecule, dimercaptodiphenylacetylene. The I-V data,
obtained by positioning the tip over a nanocrystal electrode, exhibit negative
differential resistance (NDR) on a background M-I-M characteristics. The NDR
feature occurs at $\sim$0.67 V at 300 K and shifts to a higher bias of 1.93 V
at 90 K. When the tip is held in the middle region of the device, a coulomb
blockade region is observed ($\pm\sim$0.3 V).",0507147v1
2005-07-15,Spin transference and magnetoresistance amplification in a transistor,"A current problem in semiconductor spin-based electronics is the difficulty
of experimentally expressing the effect of spin-polarized current in electrical
circuit measurements. We present a theoretical solution with the principle of
transference of the spin diffusion effects in the semiconductor channel of a
system with three magnetic terminals. A notable result of technological
consequences is the room temperature amplification of the magneto-resistive
effect, integrable with electronics circuits, demonstrated by computation of
current dependence on magnetization configuration in such a system with
currently achievable parameters.",0507378v2
2005-09-27,Electron-Hole Asymmetry in GdBaCo_{2}O_{5+x}: Evidence for Spin Blockade of Electron Transport in a Correlated Electron System,"In RBaCo_{2}O_{5+x} compounds (R is rare earth) variability of the oxygen
content allows precise doping of CoO_2 planes with both types of charge
carriers. We study transport properties of doped GdBaCo_{2}O_{5+x} single
crystals and find a remarkable asymmetry in the behavior of holes and electrons
doped into a parent insulator GdBaCo_{2}O_{5.5}. Doping dependences of
resistivity, Hall response, and thermoelectric power reveal that the doped
holes greatly improve the conductivity, while the electron-doped samples always
remain poorly conducting. This doping asymmetry provides strong evidence for a
spin blockade of the electron transport in RBaCo_{2}O_{5+x}.",0509673v1
2005-10-13,The electrical current effect in phase separated La5/8-yPryCa3/8MnO3: Charge order melting vs. Joule heating,"We have studied the effect of electric field on transport properties of the
prototypical phase separated manganite La5/8-yPryCa3/8MnO3 with y=0.34. Our
results show that the suggested image in which the charge ordered state is
melted by the appliance of an electric current and/or voltage has to be
revised. We were able to explain the observed resistivity drop in terms of an
artifact related to Joule heating and the particular hysteresis that the system
under study display, common to many other phase separated manganites.",0510366v1
2005-12-16,A possible minimum toy model with negative differential capacitance for self-sustained current oscillation,"We generalize a simple model for superlattices to include the effect of
differential capacitance. It is shown that the model always has a stable
steady-state solution (SSS) if all differential capacitances are positive. On
the other hand, when negative differential capacitance is included, the model
can have no stable SSS and be in a self-sustained current oscillation behavior.
Therefore, we find a possible minimum toy model with both negative differential
resistance and negative differential capacitance which can include the
phenomena of both self-sustained current oscillation and $I-V$ oscillation of
stable SSSs.",0512370v2
2006-01-13,Gamma radiation exposure of MCT diode arrays,"Investigations of electrical properties of long-wavelength infrared (LWIR)
mercury cadmium telluride (MCT) arrays exposed to gamma-radiation have been
performed. Resistance-area product characteristics of LWIR n{+}-p photodiodes
have been investigated using microprobe technique at T=78 K before and after an
exposure to various doses of gamma-radiation. The current transport mechanisms
for those structures are described within the framework of the balance equation
model taking into account the occupation of the trap states in the band gap.",0601276v1
2006-01-13,Influence of Roughness and Disorder on Tunneling Magnetoresistance,"A systematic, quantitative study of the effect of interface roughness and
disorder on the magnetoresistance of FeCo$|$vacuum$|$FeCo magnetic tunnel
junctions is presented based upon parameter-free electronic structure
calculations. Surface roughness is found to have a very strong effect on the
spin-polarized transport while that of disorder in the leads (leads consisting
of a substitutional alloy) is weaker but still sufficient to suppress the huge
tunneling magneto-resistance (TMR) predicted for ideal systems.",0601291v2
2006-02-09,Strong Pinning Enhancement in MgB2 Using Very Small Dy2O3 Additions,"0.5 to 5.0 wt.% Dy2O3 was in-situ reacted with Mg + B to form pinned MgB2.
While Tc remained largely unchanged, Jc was strongly enhanced. The best sample
(only 0.5 wt.% Dy2O3) had a Jc of 6.5 x 10^5 A/cm^2 at 6K, 1T and 3.5 x 10^5
A/cm^2 at 20K, 1T, around a factor of 4 higher compared to the pure sample, and
equivalent to hot-pressed or nano-Si added MgB2 at below 1T. Even distributions
of nano-scale precipitates of DyB4 and MgO were observed within the grains. The
room temperature resistivity decreased with Dy2O3 indicative of improved grain
connectivity.",0602234v1
2006-02-27,"Origin of the large thermoelectric power in oxygen-variable RBaCo_{2}O_{5+x} (R=Gd, Nd)","Thermoelectric properties of GdBaCo_{2}O_{5+x} and NdBaCo_{2}O_{5+x} single
crystals have been studied upon continuous doping of CoO_2 planes with either
electrons or holes. The thermoelectric response and the resistivity behavior
reveal a hopping character of the transport in both compounds, providing the
basis for understanding the recently found remarkable divergence of the Seebeck
coefficient at x=0.5. The doping dependence of the thermoelectric power evinces
that the configurational entropy of charge carriers, enhanced by their spin and
orbital degeneracy, plays a key role in the origin of the large thermoelectric
response in these correlated oxides.",0602618v1
2006-03-27,Modeling transient absorption and thermal conductivity in a simple nanofluid,"Molecular dynamics simulations are used to simulate the thermal properties of
a model fluid containing nanoparticles (nanofluid). By modelling transient
absorption experiments, we show that they provide a reliable determination of
interfacial resistance between the particle and the fluid. The flexibility of
molecular simulation allows us to consider separately the effect of
confinement, particle mass and Brownian motion on the thermal transfer between
fluid and particle. Finally, we show that in the absence of collective effects,
the heat conductivity of the nanofluid is well described by the classical
Maxwell Garnet equation model.",0603704v1
2006-05-04,Optical conductivity of charge carriers interacting with a two-level systems reservoir,"Using the functional-integral method we investigate the effective dynamics of
a charged particle coupled to a set of two-level systems as a function of
temperature and external electric field. The optical conductivity and the
direct current (dc) resistivity induced by the reservoir are computed. Three
different regimes are found depending on the two-level system spectral
function, which may lead to a non-Drude optical conductivity in a certain range
of parameters. Our results contrast to the behavior found when considering the
usual bath of harmonic oscillators which we are able to recover in the limit of
very low temperatures.",0605105v1
2006-05-24,Controlling charge injection in organic field-effect transistors using self-assembled monolayers,"We have studied charge injection across the metal/organic semiconductor
interface in bottom-contact poly(3-hexylthiophene) (P3HT) field-effect
transistors, with Au source and drain electrodes modified by self-assembled
monolayers (SAMs) prior to active polymer deposition. By using the SAM to
engineer the effective Au work function, we markedly affect the charge
injection process. We systematically examine the contact resistivity and
intrinsic channel mobility, and show that chemically increasing the injecting
electrode work function significantly improves hole injection relative to
untreated Au electrodes.",0605605v1
2006-08-10,Gate-controlled nuclear magnetic resonance in an AlGaAs/GaAs quantum Hall device,"We study the resistively detected nuclear magnetic resonance (NMR) in an
AlGaAs/GaAs quantum Hall device with a side gate. The strength of the hyperfine
interaction between electron and nuclear spins is modulated by tuning a
position of the two-dimensional electron systems with respect to the polarized
nuclear spins using the side-gate voltages. The NMR frequency is systematically
controlled by the gate-tuned technique in a semiconductor device.",0608237v1
2006-08-27,Magnetic Switching of Phase-Slip Dissipation in NbSe2 Nanobelts,"The stability of the superconducting dissipationless and resistive states in
single-crystalline NbSe2 nanobelts is characterized by transport measurements
in an external magnetic field (H). Current-driven electrical measurements show
voltage steps, indicating the nucleation of phase-slip structures. Well below
the critical temperature, the position of the voltage steps exhibits a sharp,
periodic dependence as a function of H. This phenomenon is discussed in the
context of two possible mechanisms: the interference of the order parameter and
the periodic rearrangement of the vortex lattice within the nanobelt.",0608586v1
2006-08-28,Inverse Spin Hall Effect by Spin Injection,"Motivated by a recent experiment[Nature {\bf 442}, 176 (2006)], we present a
quantitative microscopic theory to investigate the inverse spin-Hall effect
with spin injection into aluminum considering both intrinsic and extrinsic
spin-orbit couplings using the orthogonalized-plane-wave method. Our
theoretical results are in good agreement with the experimental data. It is
also clear that the magnitude of the anomalous Hall resistivity is mainly due
to contributions from extrinsic skew scattering, while its spatial variation is
determined by the intrinsic spin-orbit coupling.",0608594v2
2006-08-31,Atomic and electronic structure of ultra-thin Al/AlOx/Al interfaces,"Interfaces between metals based on AlO$_{x}$ represent the most popular basis
for Josephson junctions or, more recently, also for junctions exhibiting
substantial tunneling magneto-resistance. We have performed a computational
study of possible local geometric structures of such interfaces at the
ab-initio DFT/GGA level of approximation to complement recent experimental data
on ultra-thin AlO$_{x}$-based interfaces. We present two competing structures
that we characterise with their electronic properties: fragmentation and
interface energies.",0608718v1
2006-09-01,Nonlinear screening of charge impurities in graphene,"It is shown that a ``vacuum polarization'' induced by Coulomb potential in
graphene leads to a strong suppression of electric charges even for undoped
case (no charge carriers). A standard linear response theory is therefore not
applicable to describe the screening of charge impurities in graphene. In
particular, it overestimates essentially the contributions of charge impurities
into the resistivity of graphene.",0609026v3
2006-09-14,Strain induced pressure effect in pulsed laser deposited thin films of the strongly correlated oxide V2O3,"V2O3 thin films about 10 nm thick were grown on Al2O3 (0001) by pulsed laser
deposition. The XRD analysis is in agreement with R-3c space group. Some of
them exhibit the metal / insulator transition characteristic of V2O3 bulk
material and others samples exhibit a metallic behavior. For the latter, the
XPS analysis indicates an oxidation state of +III for vanadium. There is no
metal / insulator transition around 150 K in this sample and a strongly
correlated Fermi liquid rho = AT2 behavior of the resistivity at low
temperature is observed, with a value of A of 1.2 10-4 ohm cm, 3 times larger
than the bulk value at 25 kbar.",0609342v1
2006-09-19,Adaptive Programming of Unconventional Nano-Architectures,"Novel assembly processes for nanocircuits could present compelling
alternatives to the detailed design and placement currently used for computers.
The resulting architectures however may not be programmable by standard means.
In this paper, nanocomputers with unconventional architectures are programmed
using adaptive methods. The internals of the device are treated as a ""black
box"" and programming is achieved by manipulating ""control voltages"". Learning
algorithms are used to set the controls. As examples, logic gates and simple
arithmetic circuits are implemented. Additionally, similar methods allow for
reconfiguration of the devices, and makes them resistant to certain kinds of
faults.",0609489v1
2006-09-20,Spin Injection and Nonlocal Spin Transport in Magnetic Nanostructures,"We theoretically study the nonlocal spin transport in a device consisting of
a nonmagnetic metal (N) and ferromagnetic injector (F1) and detector (F2)
electrodes connected to N. We solve the spin-dependent transport equations in a
device with arbitrary interface resistance from a metallic-contact to tunneling
regime, and obtain the conditions for efficient spin injection, accumulation,
and transport in the device. In a device containing a superconductor (F1/S/F2),
the effect of superconductivity on the spin transport is investigated. The
spin-current induced spin Hall effect in nonmagnetic metals is also discussed.",0609508v1
2006-09-21,Resistive and rectifying effects of pulling gold atoms at thiol-gold nano-contacts,"We investigate, by means of first-principles calculations, structural and
transport properties of junctions made of symmetric dithiolated molecules
placed between Au electrodes. As the electrodes are pulled apart, we find that
it becomes energetically favorable that Au atoms migrate to positions between
the electrode surface and thiol terminations, with junction structures
alternating between symmetric and asymmetric. As a result, the calculated
$\emph{IV}$ curves alternate between rectifying and non-rectifying behaviors as
the electrodes are pulled apart, which is consistent with recent experimental
results.",0609558v1
2006-11-15,Tunneling anisotropic magnetoresistance and spin-orbit coupling in Fe/GaAs/Au tunnel junctions,"We report the observation of tunneling anisotropic magnetoresistance effect
(TAMR) in the epitaxial metal-semiconductor system Fe/GaAs/Au. The observed
two-fold anisotropy of the resistance can be switched by reversing the bias
voltage, suggesting that the effect originates from the interference of the
spin-orbit coupling at the interfaces. Corresponding model calculations
reproduce the experimental findings very well.",0611406v1
2006-11-28,Energy Transport between Hole Gas and Crystal Lattice in Diluted Magnetic Semiconductor,"The temperature dependent energy transfer rate between charge carriers and
lattice has been experimentally investigated in ferromagnetic semiconductors.
Studied 100 nm thick low-temperature MBE grown Mn_{x}Ga_{1-x}As samples had
manganese concentrations x=3.7 % and 4.0 %. Curie temperatures estimated from
temperatures of peak resistivities were 60 K and 62 K, respectively.",0611704v1
2006-12-01,Vortex motion in chilarity-controlled pair of magnetic disks,"We investigate the influence of the vortex chirality on the magnetization
processes of a magnetostatically coupled pair of magnetic disks. The magnetic
vortices with opposite chiralities are realized by introducing asymmetry into
the disks. The motion of the paired vortices are studied by measuring the
magnetoresistance with lock-in resistance bridge technique. The vortex
annihilation process is found to depend on the moving directions of the
magnetic vorticies. The experimental results are well reproduced by the
micromagnetic simulation.",0612023v1
2006-12-01,Microscopic and Macroscopic Signatures of Antiferromagnetic Domain Walls,"Magnetotransport measurements on small single crystals of Cr, the elemental
antiferromagnet, reveal the hysteretic thermodynamics of the domain structure.
The temperature dependence of the transport coefficients is directly correlated
with the real-space evolution of the domain configuration as recorded by x-ray
microprobe imaging, revealing the effect of antiferromagnetic domain walls on
electron transport. A single antiferromagnetic domain wall interface resistance
is deduced to be of order $5\times10^{-5}\mathrm{\mu\Omega\cdot cm^{2}}$ at a
temperature of 100 K.",0612039v1
2006-12-06,Plasma-Like Negative Capacitance in Nano-Colloids,"A negative capacitance has been observed in a nano-colloid between 0.1 and
10^-5 Hz. The response is linear over a broad range of conditions. The
low-omega dispersions of both the resistance and capacitance are consistent
with the free-carrier plasma model, while the transient behavior demonstrates
an unusual energy storage mechanism. A collective excitation, therefore, is
suggested.",0612160v1
2006-12-11,Theoretical study of doped-Tl$_{2}$Mn$_{2}$O$_{7}$ and Tl$_{2}$Mn$_{2}$O$_{7}$ under pressure,"Using first-principles density functional based calculations, we study the
effect of doping and pressure in manganese based pyrochlore
compound,Tl$_{2}$Mn$_{2}$O$_{7}$ that exhibits colossal magneto-resistive
behavior. The theoretical study is motivated by the counter-intuitive
experimental observation of suppression of ferromagnetic transition temperature
upon application of pressure and its enhancement upon substitution of Mn by
moderate amount of nonmagnetic Sb ion. We also attempt to resolve the issue
related to crystal structure changes that may occur upon application of
pressure.",0612245v2
2006-12-31,Thermal rectifying effect in two dimensional anharmonic lattices,"We study thermal rectifying effect in two dimensional (2D) systems consisting
of the Frenkel Kontorva (FK) lattice and the Fermi-Pasta-Ulam (FPU) lattice. It
is found that the rectifying effect is related to the asymmetrical interface
thermal resistance. The rectifying efficiency is typically about two orders of
magnitude which is large enough to be observed in experiment. The dependence of
rectifying efficiency on the temperature and temperature gradient is studied.
The underlying mechanism is found to be the match and mismatch of the spectra
of lattice vibration in two parts.",0701015v1
2007-01-18,On the origin of unusual transport properties observed in densely packed polycrystalline CaAl_{2},"A possible origin of unusual temperature behavior of transport coefficients
observed in densely packed polycrystalline CaAl_{2} compound [M. Ausloos et
al., J. Appl. Phys. 96, 7338 (2004)] is discussed, including a power-like
dependence of resistivity with $\rho \propto T^{-3/4}$ and N-like form of the
thermopower. All these features are found to be in good agreement with the
Shklovskii-Efros localization scenario assuming polaron-mediated hopping
processes controlled by the Debye energy.",0701456v1
2007-01-24,Graphene Nano-Ribbon Electronics,"We have fabricated graphene nano-ribbon field-effect transistor devices and
investigated their electrical properties as a function of ribbon width. Our
experiments show that the resistivity of a ribbon increases as its width
decreases, indicating the impact of edge states. Analysis of temperature
dependent measurements suggests a finite quantum confinement gap opening in
narrow ribbons. The electrical current noise of the graphene ribbon devices at
low frequency is found to be dominated by the 1/f noise.",0701599v1
2007-03-07,Current sharing between superconducting film and normal metal,"A two-dimensional model is introduced that describes current sharing between
the superconducting and normal metal layers in configuration typical of
YBCO-coated conductors. The model is used to compare the effectiveness of
surround stabilizer and more conventional one-sided stabilizer. When the
resistance of the interface between the superconductor and stabilizer is low
enough, the surround stabilizer is less effective than the one-sided stabilizer
in stabilizing a hairline crack in the superconducting film.",0703193v1
2007-03-12,Effect of Polarized Current on the Magnetic State of Antiferromagnet,"We provide evidence for the effects of spin polarized current on a
nanofabricated antiferromagnet incorporated into a spin-valve structure.
Signatures of current-induced effects include bipolar steps in differential
resistance, current-induced changes of exchange bias correlated with these
steps, and deviations from the statistics expected for thermally activated
switching of spin valves. We explain our observations by a combination of spin
torque exerted on the interfacial antiferromagnetic moments, and
electron-magnon scattering in antiferromagnet.",0703281v2
2007-04-14,Biased Structural Fluctuations due to Electron Wind Force,"Direct correlation between temporal structural fluctuations and electron wind
force is demonstrated, for the first time, by STM imaging and analysis of
atomically-resolved motion on a thin film surface under large applied current
(10e5 Amp/sqare cm). The magnitude of the momentum transfer between current
carriers and atoms in the fluctuating structure is at least five to fifteen
times (plus or minus one sigma range) larger than for freely diffusing adatoms.
The corresponding changes in surface resistivity will contribute significant
fluctuation signature to nanoscale electronic properties.",0704.1852v1
2007-04-25,Pressure induced magnetic ordering in Yb2Pd2Sn with two quantum critical points,"Pressure induced long range antiferromagnetic order is discovered in Yb2Pd2Sn
by measuring the electrical resistivity under pressure up to 5.0 GPa. Magnetic
ordering is observed above about 1.0 GPa, being the lowest pressure in
Yb-intermetallics showing pressure induced magnetic ordering, Unexpectedly,
ordering disappears above about 4.0 GPa, giving rise to the first observation
of the appearance of two quantum critical points persisting in a broad range of
pressure within a single material.",0704.3307v2
2007-06-10,Scattering of charge carriers by point defects in bilayer graphene,"Theory of scattering of massive chiral fermions in bilayer graphene by radial
symmetric potential is developed. It is shown that in the case when the
electron wavelength is much larger than the radius of the potential the
scattering cross-section is proportional to the electron wavelength. This leads
to the mobility independent on the electron concentration. In contrast with the
case of single-layer, neutral and charged defects are, in general, equally
relevant for the resistivity of the bilayer graphene.",0706.1351v2
2007-06-19,Resistive state of quasi-one-dimensional superconductors: fluctuations vs. sample inhomogeneity,"The shape of experimentally observed R(T) transition of thin superconducting
wires is analyzed. Broadening of the transition in quasi-1-dimensional
superconducting channels is typically associated with phase slip mechanism
provided by thermal or quantum fluctuations. It is shown that consideration of
inevitable geometrical inhomogeneity and finite dimensions of real samples
studied in experiments is of primary importance for interpretation of results.
The analysis is based on experimental fact that for many superconducting
materials the critical temperature is a function of characteristic dimension of
a low-dimensional system: film thickness or wire cross section",0706.2779v1
2007-08-03,Nonlocal Charge Transport Mediated by Spin Diffusion in the Spin-Hall Effect Regime,"A nonlocal electric response in the spin-Hall regime, resulting from spin
diffusion mediating charge conduction, is predicted. The spin-mediated
transport stands out due to its long-range character, and can give dominant
contribution to nonlocal resistance. The characteristic range of nonlocality,
set by the spin diffusion length, can be large enough to allow detection of
this effect in materials such as GaAs despite its small magnitude. The
detection is facilitated by a characteristic nonmonotonic dependence of
transresistance on the external magnetic field, exhibiting sign changes and
decay.",0708.0455v1
2007-09-11,Co/Nb/Co low field superconducting spin switch,"We report experiments on a superconducting spin switch based on
technologically relevant materials as elemental ferromagnetic Co and elemental
superconducting Nb. The Co/Nb/Co structure exhibits inverse spin switch effect,
can be operated at liquid helium temperature and can switch from
superconductive to normal state in rather weak applied magnetic fields.
Relevant critical currents as a function of temperature and magnetic field as
well as preparation of superconductive or resistive state are addressed here.",0709.1687v1
2007-09-12,Dynamic Thermal Analysis of a Power Amplifier,"This paper presents dynamic thermal analyses of a power amplifier. All the
investigations are based on the transient junction temperature measurements
performed during the circuit cooling process. The presented results include the
cooling curves, the structure functions, the thermal time constant distribution
and the Nyquist plot of the thermal impedance. The experiments carried out
demonstrated the influence of the contact resistance and the position of the
entire cooling assembly on the obtained results.",0709.1818v1
2007-09-20,A Kondo lattice antiferromagnet CePd5Al2,"We report on the electrical resistivity, magnetic susceptibility and
heat-capacity measurements on a new intermetallic compound CePd5Al2,
crystallizing in the ZrNi2Al5-type tetragonal structure, with lattice
parameters a = 4.156 A and c = 14.883 A. The compound presents Kondo lattice
behavior and an easy-plane antiferromagnetic ground state with two magnetic
transitions at 2.9 K and 3.9 K. The Sommerfeld coefficient is estimated as 60
mJ/mol K^2.",0709.3135v1
2007-09-24,Magnetoresistance in an all-manganite heterostructure,"We study the magnetic and transport properties of all-manganite
heterostructures consisting of ferromagnetic metallic electrodes separated by
an antiferromagnetic barrier. We find that the magnetic ordering in the barrier
is influenced by the relative orientation of the electrodes magnetization
producing a large difference in resistance between the parallel and
antiparallel orientations of the ferromagnetic layers. The external application
of a magnetic field in a parallel configuration also leads to large
magnetoresistance.",0709.3720v1
2007-11-06,Barrier breakdown in a multiple quantum well structure,"We explore a regime of unipolar electronic transport in a multiple quantum
well structure with very large current discontinuities - up to five orders of
magnitude. Magneto-transport experiments reveal different transport regimes.
Quantum well impact ionization shifts the structure from a resistive down
state, where the current flows through inter-well quantum tunneling, to a
highly conductive up state. In the latter regime, the current leaks through a
barrier suddenly broken down because of an efficient ionization of the first
quantum well.",0711.0890v1
2007-11-08,Substrate limited electron dynamics in graphene,"We study the effects of polarizable substrates such as SiO2 and SiC on the
carrier dynamics in graphene. We find that the quasiparticle spectrum acquires
a finite broadening due to the long-range interaction with the polar modes at
the interface between graphene and the substrate. This mechanism results in a
density dependent electrical resistivity, that exhibits a sharp increase around
room temperature, where it can become the dominant limiting factor of electron
transport. The effects are weaker in doped bilayer graphene, due to the more
conventional parabolic band dispersion.",0711.1303v3
2007-11-28,Evidence for Two Current Conduction in Iron,"Measurements of resistivities of dilute iron based alloys show strong
deviations from Matthiessen's rule. These deviations can be explained by a
model in which spin up and spin down electrons conduct in parallel. The results
are consistent with the theory of impurity shielding in these alloys. [This
1967 paper provides the first experimental demonstration of two current
conduction at low temperatures in a ferromagnetic metal. One direct consequence
of this property is the Giant Magnetoresistance discovered in 1988 by the
groups of Albert Fert and of Peter Gr\""unberg].",0711.4478v1
2007-12-12,Magnetic phase transition and magnetocaloric effect in PrCo9Si4 and NdCo9Si4,"The compounds, PrCo9Si4 and NdCo9Si4, have been recently reported to exhibit
first-order ferromagnetic transitions near 24 K. We have subjected this
compound for further characterization by magnetization, heat-capacity and
electrical resistivity measurements at low temperatures in the presence of
magnetic fields, particularly to probe magnetocaloric effect and
magnetoresistance. The compounds are found to exhibit rather modest
magnetocaloric effect at low temperatures peaking at Curie temperature,
tracking the behavior of magnetoresistance. The magnetic transition does not
appear to be first order in its character.",0712.1989v1
2008-01-09,Colossal Positive Magnetoresistance in a Doped Nearly Magnetic Semiconductor,"We report on a positive colossal magnetoresistance (MR) induced by
metallization of FeSb$_{2}$, a nearly magnetic or ""Kondo"" semiconductor with 3d
ions. We discuss contribution of orbital MR and quantum interference to
enhanced magnetic field response of electrical resistivity.",0801.1354v1
2008-03-27,Current-induced persistent magnetization in a relaxorlike manganite,"A single crystal of 7% Fe-doped
(La$_{0.7}$Pr$_{0.3}$)$_{0.65}$Ca$_{0.35}$MnO$_3$ shows up as a typical relaxor
ferromagnet, where ferromagnetic metallic and charge-orbital-ordered insulating
clusters coexist with controllable volume fraction by external stimuli. There,
the persistent ferromagnetic metallic state can be produced by an
electric-current excitation as the filamentary region, the magnetization in
which is increased by ~0.4$\mu_{\rm B}$ per Mn. A clear distinction from the
current heating effect in a magnetic field, which conversely leads to a
decrease in ferromagnetic fraction, enables us to bi-directionally switch both
the magnetization and resistance by applying the voltages with different
magnitudes.",0803.3922v1
2008-03-30,Organized Current Patterns in Disordered Conductors,"We present a general theory of current deviations in straight current
carrying wires with random imperfections, which quantitatively explains the
recent observations of organized patterns of magnetic field corrugations above
micron-scale evaporated wires. These patterns originate from the most efficient
electron scattering by Fourier components of the wire imperfections with
wavefronts along the $\pm 45^{\circ}$ direction. We show that long range
effects of surface or bulk corrugations are suppressed for narrow wires or
wires having an electrically anisotropic resistivity.",0803.4307v1
2008-05-16,Frictional Duality Observed during Nanoparticle Sliding,"One of the most fundamental questions in tribology concerns the area
dependence of friction at the nanoscale. Here, experiments are presented where
the frictional resistance of nanoparticles is measured by pushing them with the
tip of an atomic force microscope. We find two coexisting frictional states:
While some particles show finite friction increasing linearly with the
interface areas of up to 310,000nm^2, other particles assume a state of
frictionless sliding. The results further suggest a link between the degree of
surface contamination and the occurrence of this duality.",0805.2448v2
2008-05-28,Extraordinary sensitivity of the electronic structure and properties of single-walled carbon nanotubes to molecular charge-transfer,"Interaction of single-walled carbon nanotubes with electron donor and
acceptor molecules causes significant changes in the electronic and Raman
spectra, the relative proportion of the metallic species increasing on electron
donation through molecular charge transfer, as also verified by electrical
resistivity measurements.",0805.4239v1
2008-06-10,Thermal contact resistance between two nanoparticles,"We compute the thermal conductance between two nanoparticles in contact based
on the Molecular Dynamics technique. The contact is generated by letting both
particles stick together under van der Waals attractions. The thermal
conductance is derived from the fluctuation-dissipation theorem and the time
fluctuations of the exchanged power. We show that the conductance is
proportional to the atoms involved in the thermal interaction. In the case of
silica, the atomic contribution to the thermal conductance is in the range of
0.5 to 3 nW.K-1. This result fits to theoretical predictions based on
characteristic times of the temperature fluctuation. The order of magnitude of
the contact conductance is 1 \mu W.K-1 when the cross section ranges from 1 to
10nm2.",0806.1609v1
2008-06-25,Morphology and flexibility of graphene and few-layer graphene on various substrates,"We report on detailed microscopy studies of graphene and few-layer-graphene
produced by mechanical exfoliation on various semi-conducting substrates. We
demonstrate the possibility to prepare and analyze graphene on (001)-GaAs,
manganese p-doped (001)-GaAs and InGaAs substrates. The morphology of graphene
on these substrates was investigated by scanning electron and atomic force
microscopy and compared to layers on silicon oxide. It was found that graphene
sheets strongly follow the texture of the sustaining substrates independent on
doping, polarity or roughness. Furthermore resist residues exist on top of
graphene after a lithographic step. The obtained results provide the
opportunity to research the graphene-substrate interactions.",0806.4074v1
2008-06-25,Hidden Orbital Liquid State Within Ferromagnetically Ordered Metallic SrRuO3,"We have experimentally found related anomalies in electrical resistivity, dc
and ac magnetic susceptibility, appearing deeply within ferromagnetically
ordered state in SrRuO3. Lack of Jahn-Teller distortion in this regime rules
out conventional orbital order, forcing one to describe these in terms of an
orbital liquid ground state coexisting with ferromagnetic spin order. We
suggest that weak spin-orbit coupling in such an unusual state underpins the
observed anomalies.",0806.4198v1
2008-07-29,Control of heat transport in quantum spin systems,"We study heat transport in quantum spin systems analytically and numerically.
First, we demonstrate that heat current through a two-level quantum spin system
can be modulated from zero to a finite value by tuning a magnetic field.
Second, we show that a spin system, consisting of two dissimilar parts - one is
gapped and the other is gapless, exhibits current rectification and negative
differential thermal resistance. Possible experimental realizations by using
molecular junctions or magnetic materials are discussed.",0807.4575v1
2008-07-31,Superconductivity in nickel-based compound GdONiBi and hole doped Gd0.9Sr0.1ONiBi,"We successfully synthesized the nickel-based compound GdONiBi with
superconducting transition temperature about 4.5 K. By partially substituting
the element Gd with Sr to introduce holes into the material, we got new
superconductor Gd0.9Sr0.1ONiBi with critical temperature about 4.7 K. The
normal state resistivity in nickel-based samples shows a metallic behavior. The
magnetoresistance measurements show a different behavior compared to those in
iron-based compounds which indicates that the mechanism in the two kinds of
superconductors maybe different.",0807.5045v1
2008-09-11,Koshino-Taylor effect in graphene,"We discuss the phonon-assisted scattering of electrons by defects, i.e., the
so-called Koshino-Taylor effect, in graphene. The two-dimensional character of
graphene implies that the strength of the Koshino-Taylor effect can be
considerably larger than in ordinary metals. We show that at finite
temperatures the defect-induced resistivity formally diverges in the
thermodynamic limit, having a non-analytic $T\ln T$ component when finite size
effects are taken into account.",0809.1996v2
2008-10-10,Hysteresis in the electronic transport of V2O3 thin films: non-exponential kinetics and range scale of phase coexistence,"The thermal hysteresis of the electronic transport properties were studied
for V2O3 thin films. The temporal evolution of the resistance shows the
out-of-equilibrium nature of this hysteresis with a very slow relaxation.
Partial cycles reveal not only a behavior consistent with phase coexistence,
but also the presence of spinodal temperatures which are largely separated. The
temperature spreading of phase coexistence is consistent with the bulk phase
diagram in the pressure-temperature plane, confirming that the film is
effectively under an effective pressure induced by the substrate.",0810.1868v1
2008-11-19,Nonlocal Spin Transport in Lateral Spin Valves with Multiple Ferromagnetic Electrodes,"We study the nonlocal spin transport in a lateral spin valve with multiple
ferromagnetic (FM) electrodes. When two current-injecting and two spin
current-detecting electrodes are all ferromagnetic, the number of possible
nonlocal spin signal states is four at maximum. In reality, this number is
reduced, depending on the inter-probe distance and the relative magnitudes of
the spin resistances. Our theoretical results are in agreement with recent
experiments of spin injection into an Al island, a carbon nanotube, and
graphene.",0811.3138v1
2009-02-24,Analysis of the Conduction Heat Transfer in Cantilevers under Steady State Cryogenic Conditions,"An accurate analysis of the conduction heat transfer in a cryogenic flask is
made and some useful formulae are derived. Taking into account the temperature
dependence of conductivity and tensile strength of the supporting rods for a
helium cryostat, these formulae may provide more exact results than the the
formulae based on simpler models. This allows the design of the supporting
elements of a liquid helium cryostat with minimum cross-section (for minimizing
the heat transfer)and proper mechanical resistance. Some examples of numerical
results and tables are also presented.",0902.4144v1
2009-03-23,Spin-polarized electronic structures and transport properties of Fe-Co alloys,"The electrical resistivities of Fe-Co alloys owing to random alloy disorder
are calculated using the Kubo-Greenwood formula. The obtained electrical
esistivities agree well with experimental data quantitatively at low
temperature. The spin-polarization of Fe50Co50 estimated from the conductivity
(86%) has opposite sign to that from the densities of the states at the Fermi
level (-73%). It is found that the conductivity is governed mainly by
s-electrons, and the s-electrons in the minority spin states are less
conductive due to strong scattering by the large densities of the states of
d-electrons than the majority spin electrons.",0903.3842v1
2009-04-15,Nonvolatile memory effects in hybrid devices of few-layer graphene and ferroelectric polymer films,"We report on the fabrication and electrical characterization of few-layer
graphene (FLG) devices coated with a ferroelectric polymer layer of
poly(vinylidene fluoride/trifluoroethylene) [P(VDF/TrFE)]. Highly stable and
reliable resistance changes were observed under floating conditions, which were
dependent on the back gate voltage applied beforehand. Nonvolatile memory
functionality in the hybrid FLG-P(VDF/TrFE) devices is attributed to a remanent
electric field induced by the ferroelectric polarization of the P(VDF/TrFE)
layer.",0904.2242v1
2009-04-15,Quasiparticle Transformation During a Metal-Insulator Transition in Graphene,"Here we show, with simultaneous transport and photoemission measurements,
that the graphene terminated SiC(0001) surface undergoes a metal-insulator
transition (MIT) upon dosingwith small amounts of atomic hydrogen. We find the
room temperature resistance increases by about 4 orders of magnitude, a
transition accompanied by anomalies in the momentum-resolved spectral function
including a non-Fermi Liquid behaviour and a breakdown of the quasiparticle
picture. These effects are discussed in terms of a possible transition to a
strongly (Anderson) localized ground state.",0904.2249v1
2009-05-14,Galvanomagnetic properties and noise in a barely metallic film of V2O3,"We have measured the magnetotransport properties of a strained metallic V2O3
thin film. Most of the properties are similar to V2O3 single crystals that have
been submitted to a large pressure. In addition, resistance noise analysis
indicates that conductivity fluctuations are freezing out at T\approx 10K.
Examination of a range of measurements leads to the conclusion that
spins-configuration fluctuations dominate in the low temperature regime.",0905.2290v1
2009-05-25,Photocurrent Properties of Freely Suspended Carbon Nanotubes under Uniaxial Strain,"The photocurrent properties of freely suspended single-walled carbon
nanotubes (CNTs) are investigated as a function of uniaxial strain. We observe
that at low strain, the photocurrent signal of the CNTs increases for
increasing strain, while for large strain, the signal decreases, respectively.
We interpret the non-monotonous behavior by a superposition of the influence of
the uniaxial strain on the resistivity of the CNTs and the effects caused by
Schottky contacts between the CNTs and the metal contacts.",0905.3952v1
2009-06-23,Breakdown Current Density of Graphene Nano Ribbons,"Graphene nanoribbons (GNRs) with widths down to 16 nm have been characterized
for their current-carrying capacity. It is found that GNRs exhibit an
impressive breakdown current density, on the order of 10^8 A/cm2. The breakdown
current density is found to have a reciprocal relationship to GNR resistivity
and the data fit points to Joule heating as the likely mechanism of breakdown.
The superior current-carrying capacity of GNRs will be valuable for their
application in on-chip electrical interconnects. The thermal conductivity of
sub-20 nm graphene ribbons is found to be more than 1000 W/m-K.",0906.4156v1
2009-07-07,Quantum oscillations in a topological insulator Bi_{1-x}Sb_{x},"We have studied transport and magnetic properties of Bi_{1-x}Sb_x, which is
believed to be a topological insulator - a new state of matter where an
insulating bulk supports an intrinsically metallic surface. In nominally
insulating Bi_{0.91}Sb_{0.09} crystals, we observed strong quantum oscillations
of the magnetization and the resistivity originating from a Fermi surface which
has a clear two-dimensional character. In addition, a three-dimensional Fermi
surface is found to coexist, which is possibly due to an unusual coupling of
the bulk to the surface. This finding demonstrates that quantum oscillations
can be a powerful tool to directly probe the novel electronic states in
topological insulators.",0907.1125v1
2009-07-17,Calculation of Cu/Ta interface electron transmission and effect on conductivity in nanoscale interconnect technology,"Resistivity augmentation in nanoscale metal interconnects is a performance
limiting factor in integrated circuits. Here we present calculations of
electron scattering and transmission at the interface between Cu interconnects
and their barrier layers, in this case Ta. We also present a semiclassical
model to predict the technological impact of this scattering and find that a
barrier layer can significantly decrease conductivity, consistent with
previously published measurements.",0907.2999v2
2009-07-22,Magnetoresistive junctions based on epitaxial graphene and hexagonal boron nitride,"We propose monolayer epitaxial graphene and hexagonal boron nitride (h-BN) as
ultimate thickness covalent spacers for magnetoresistive junctions. Using a
first-principles approach, we investigate the structural, magnetic and spin
transport properties of such junctions based on structurally well defined
interfaces with (111) fcc or (0001) hcp ferromagnetic transition metals. We
find low resistance area products, strong exchange couplings across the
interface, and magnetoresistance ratios exceeding 100% for certain chemical
compositions. These properties can be fine tuned, making the proposed junctions
attractive for nanoscale spintronics applications.",0907.3952v1
2009-08-20,Scattering of charge carriers in graphene induced by topological defects,"We study the scattering of graphene quasiparticles by topological defects,
represented by holes, pentagons and heptagons. For holes, we found that at low
concentration they give a negligible contribution to the resistivity. Whenever
pentagons or heptagons are introduced we realize that a fermionic current is
scattered by defects.",0908.2979v2
2009-08-31,Tuning the graphene work function by electric field effect,"We report variation of the work function for single and bi-layer graphene
devices measured by scanning Kelvin probe microscopy (SKPM). Using the electric
field effect, the work function of graphene can be adjusted as the gate voltage
tunes the Fermi level across the charge neutrality point. Upon biasing the
device, the surface potential map obtained by SKPM provides a reliable way to
measure the contact resistance of individual electrodes contacting graphene.",0909.0020v2
2009-09-25,A large magnetoinductance effect in La0.67Ba0.33MnO3,"We report four probe impedance of La0.67Ba0.33MnO3 at f = 100 kHz under
different dc bias magnetic fields. The ac resistance (R) exhibits a peak around
Tp = 325 K which is accompanied by a rapid increase and a peak in the reactance
(X) in a zero field. The magnetoreactance exhibits a sharp peak close to Tp and
its magnitude (= 60% in H = 1 kG) exceeds that of the ac magnetoresistance (= 5
% inH = 1 kG). It is suggested that the magnetoreactance arises from changes in
the self inductance of the sample rather than the capacitance.",0909.4614v1
2009-10-04,Theory of thermally activated vortex bundles flow over the directional-dependent potential barriers in type-II superocnductors,"The thermally activated vortex bundle flow over the directional-dependent
energy barrier in type-II superconductors is investigated. The coherent
oscillation frequency and the mean direction of the random collective pinning
force of the vortex bundles are evaluated by applying the random walk theorem.
The thermally activated vortex bundle flow velocity is obtained.The
temperature- and field-dependent Hall and longitudinal resistivities induced by
the bundle flow for type-II superconducting bulk materials and thin films are
calculated. All the results are in agreement with the experiments.",0910.0581v3
2009-10-13,Voltage Asymmetry of Spin-Transfer Torques,"We present a Non-Equilibrium Green's Function based model for spin torque
transfer (STT) devices which provides quantitative agreement with
experimentally measured (1) differential resistances, (2) Magnetoresistance
(MR), (3) In-plane torque and (4) out-of-plane torque over a range of bias
voltages, using a single set of three adjustable parameters. We believe this is
the first theoretical model that is able to cover this diverse range of
experiments and a key aspect of our model is the inclusion of multiple
transverse modes. We also provide a simple explanation for the asymmetric bias
dependence of the in-plane torque, based on the polarization of the two
contacts in energy range of transport.",0910.2489v1
2009-10-21,Low-temperature ballistic transport in nanoscale epitaxial graphene cross junctions,"We report on the observation of inertial-ballistic transport in nanoscale
cross junctions fabricated from epitaxial graphene grown on SiC(0001).
Ballistic transport is indicated by a negative bend resistance of R12,43 ~ 170
ohm which is measured in a non-local, four-terminal configuration at 4.2 K and
which vanishes as the temperature is increased above 80 K.",0910.4010v1
2009-10-24,Inducing Chalcogenide Phase Change with Ultra-Narrow Carbon Nanotube Heaters,"Carbon nanotube (CNT) heaters with sub-5 nm diameter induce highly localized
phase change in Ge2Sb2Te5 (GST) chalcogenide. A significant reduction in
resistance of test structures is measured as the GST near the CNT heater
crystallizes. Effective GST heating occurs at currents as low as 25 uA,
significantly lower than in conventional phase change memory with metal
electrodes (0.1-0.5 mA). Atomic force microscopy reveals nucleation sites
associated with phase change in GST around the CNT heater. Finite element
simulations confirm electrical characteristics consistent with the experiments,
and reveal the current and phase distribution in GST.",0910.4672v2
2009-11-09,Anomalous Nernst effect and heat transport by vortex vacancies in granular superconductors,"We study the Nernst effect due to vortex motion in two-dimensional granular
superconductors using simulations with Langevin or resistively shunted
Josephson-junction dynamics. In particular, we show that the geometric
frustration of both regular and irregular granular materials can lead to
thermally driven transport of vortices from colder to hotter regions, resulting
in a sign reversal of the Nernst signal. We discuss the underlying mechanisms
of this anomalous behavior in terms of heat transport by mobile vacancies in an
otherwise pinned vortex lattice.",0911.1628v2
2010-01-19,Competing contributions of superconducting and insulating states in Ag5Pb2O6/CuO composite,"The composite material, consisting of metallic particles Ag5Pb2O6 diluted in
insulating CuO matrix, has been investigated in a narrow concentration range
separating ballistic tunnel transport from hopping conductivity. The formation
of intergrain conducting bridges between metallic particles has been avoided by
a careful metallurgic treatment. Resistivity is indicated by temperature
dependence lnR~(T0/T)^1/2, and this dependence appeals an attention for
possible one dimensional conductivity which could be looked upon as a property
uniquely associated with an onset of the superconductivity extending up to Tc ~
356 K.",1001.3185v1
2010-01-28,Electrical observation of a tunable band gap in bilayer graphene nanoribbons at room temperature,"We investigate the transport properties of double-gated bilayer graphene
nanoribbons at room temperature. The devices were fabricated using conventional
CMOS-compatible processes. By analyzing the dependence of the resistance at the
charge neutrality point as a function of the electric field applied
perpendicular to the graphene surface, we show that a band gap in the density
of states opens, reaching an effective value of ~sim50 meV. This demonstrates
the potential of bilayer graphene as FET channel material in a conventional
CMOS environment.",1001.5213v1
2010-01-30,Magnetoresistance of a spin MOSFET with ferromagnetic MnAs source and drain contacts,"Spin-dependent transport was investigated in a spin metal-oxide-semiconductor
field-effect transistors (spin MOSFET) with ferromagnetic MnAs source and drain
(S/D) contacts. The spin MOSFET of bottom-gate type was fabricated by
photolithography using an epitaxial MnAs film grown on a silicon-on-insulator
(SOI) substrate. In-plane magnetoresistance showed spin-valve-type hysteretic
behavior, when the measurements were performed with constant source-drain and
source-gate biases. By comparing with the magnetization-related resistance
change resulting from the MnAs contacts, we conclude that the spin-polarized
electrons are injected from the MnAs source into the Si MOS inversion channel,
and detected by the MnAs drain.",1002.0057v1
2010-02-03,Dislocation Mobility in a Quantum Crystal: the Case of Solid 4He,"We investigate the structure and mobility of dislocations in hcp 4He
crystals. In addition to fully characterizing the five elastic constants of
this system, we obtain direct insight into dislocation core structures on the
basal plane, which demonstrates a tendency toward dissociation into partial
dislocations. Moreover, our results suggest that intrinsic lattice resistance
is an essential factor in the mobility of these dislocations. This insight
sheds new light on the possible correlation between dislocation mobility and
the observed macroscopic behavior of crystalline 4He.",1002.0704v1
2010-03-15,Electron localization near Mott transition in organic superconductor $κ$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}]$Br,"The effect of disorder on the electronic properties near the Mott transition
is studied in an organic superconductor
$\kappa$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br, which is systematically irradiated
by X-ray. We observe that X-ray irradiation causes Anderson-type electron
localization due to molecular disorder. The resistivity at low temperatures
demonstrates variable range hopping conduction with Coulomb interaction. The
experimental results show clearly that the electron localization by disorder is
enhanced by the Coulomb interaction near the Mott transition.",1003.2890v2
2010-03-25,Columnar Fluctuations as a Source of Non-Fermi-Liquid Behavior in Weak Metallic Magnets,"It is shown that columnar fluctuations, in conjunction with weak quenched
disorder, lead to a T^{3/2} temperature dependence of the electrical
resistivity. This is proposed as an explanation of the observed
non-Fermi-liquid behavior in the helimagnet MnSi, with one possible realization
of the columnar fluctuations provided by skyrmion lines that have independently
been proposed to be present in this material.",1003.4809v3
2010-03-28,Giant magnetic broadening of ferromagnetic resonance in a GMR Co/Ag/Co/Gd quadlayer,"Both magnetic-resonance damping and the giant magnetoresistance effect have
been predicted to be strongly affected by the local density of states in thin
ferromagnetic films. We employ the antiferromagnetic coupling between Co and Gd
to provide a spontaneous change from parallel to antiparallel alignment of two
Co films. A sharp increase in magnetic damping accompanies the change from
parallel to antiparallel alignment, analogous to resistivity changes in giant
magnetoresistance.",1003.5344v1
2010-04-05,Non-monotonic variation of anomalous Hall effect with spin orbit coupling strength,"For L1(0) FePt films, the anomalous Hall resistivity is found to be
proportional to spontaneous magnetization $M_{\mathrm{S}}$. After the
$M_{\mathrm{S}}$ temperature effect is eliminated, $\rho_{\mathrm{xyo}}$ can be
fitted by $\rho_{\mathrm{xyo}}=a_{\mathrm{o}}\rho_{\mathrm{xx}}+
b_{\mathrm{o}}\rho_{\mathrm{xx}}^{\mathrm{2}}$. $a_{\mathrm{o}}$ and
$b_{\mathrm{o}}$ change non-monotonically with chemical long range ordering
degree $S$. Accordingly, it is indicated that for L1(0) FePt films the spin
orbit coupling strength increases monotonically with increasing $S$.",1004.0548v4
2010-04-29,Designing multifunctional chemical sensors using Ni and Cu doped carbon nanotubes,"We demonstrate a ""bottom up"" approach to the computational design of a
multifunctional chemical sensor. General techniques are employed for describing
the adsorption coverage and resistance properties of the sensor based on
density functional theory (DFT) and non-equilibrium Green's function
methodologies (NEGF), respectively. Specifically, we show how Ni and Cu doped
metallic (6,6) single-walled carbon nanotubes (SWNTs) may work as effective
multifunctional sensors for both CO and NH3.",1004.5334v1
2010-05-19,Electron properties of fluorinated single-layer graphene transistors,"We have fabricated transistor structures using fluorinated single-layer
graphene flakes and studied their electronic properties at different
temperatures. Compared with pristine graphene, fluorinated graphene has very
large and strongly temperature dependent resistance in the electro-neutrality
region. We show that fluorination creates a mobility gap in graphene's spectrum
where electron transport takes place via localised electron states.",1005.3474v3
2010-06-22,Hall carrier density and magnetoresistance measurements in thin film vanadium dioxide across the metal-insulator transition,"Temperature dependent magneto-transport measurements in magnetic fields of up
to 12 Tesla were performed on thin film vanadium dioxide (VO2) across the
metal-insulator transition (MIT). The Hall carrier density increases by 4
orders of magnitude at the MIT and accounts almost entirely for the resistance
change. The Hall mobility varies little across the MIT and remains low,
~0.1cm2/V sec. Electrons are found to be the major carriers on both sides of
the MIT. Small positive magnetoresistance in the semiconducting phase is
measured.",1006.4376v1
2010-08-15,Limits on electron quality in suspended graphene due to flexural phonons,"The temperature dependence of the mobility in suspended graphene samples is
investigated. In clean samples, flexural phonons become the leading scattering
mechanism at temperature $T \gtrsim 10\,\,$K, and the resistivity increases
quadratically with $T$. Flexural phonons limit the intrinsic mobility down to a
few $\text{m}^2/\text{Vs}$ at room $T$. Their effect can be eliminated by
applying strain or placing graphene on a substrate.",1008.2522v1
2010-08-29,Shubnikov-de Haas oscillations in SrTiO3\LaAlO3 interface,"Quantum magnetic oscillations in SrTiO3/\LaAlO3 interface are observed. The
evolution of their frequency and amplitude at various gate voltages and
temperatures is studied. The data are consistent with the Shubnikov de-Haas
theory. The Hall resistivity rho exhibits nonlinearity at low magnetic field.
It is fitted assuming multiple carrier contributions. The comparison between
the mobile carrier density inferred from the Hall data and the oscillation
frequency suggests multiple valley and spin degeneracy. The small amplitude of
the oscillations is discussed in the framework of the multiple band scenario.",1008.4975v1
2010-09-01,Two distinct quasiparticle inelastic scattering rates in the $t-J$ model and their relevance for high-$T_c$ cuprates superconductors,"The recent findings about two distinct quasiparticle inelastic scattering
rates in angle-dependent magnetoresistance (ADMR) experiments in overdoped
high-$T_c$ cuprates superconductors have motivated many discussions related to
the link between superconductivity, pseudogap, and transport properties in
these materials. After computing dynamical self-energy corrections in the
framework of the $t-J$ model the inelastic scattering rate was introduced as
usual. Two distinct scattering rates were obtained showing the main features
observed in ADMR experiments. Predictions for underdoped cuprates are
discussed. The implicances of these two scattering rates on the resistivity
were also studied as a function of doping and temperature and confronted with
experimental measurements.",1009.0158v1
2010-10-15,Theory of I-V Characteristics of Magnetic Josephson Junctions,"We analyze the electrical characteristics of a circuit consisting of a free
thin-film magnetic layer and source and drain electrodes that have opposite
magnetization orientations along the free magnet's two hard directions. We find
that when the circuit's current exceeds a critical value there is a sudden
resistance increase which can be large in relative terms if the currents to
source or drain are strongly spin polarized and the free magnet is thin. This
behavior can be partly understood in terms of a close analogy between the
magnetic circuit and a Josephson junction.",1010.3073v1
2010-10-29,The Structural and Magnetic ordering in $La{}_{0.5-x}Nd_{x}Ca_{0.5}MnO_{3}$ (0.1 \ensuremath{\le} x \ensuremath{\le} 0.5) Manganites,"The crystal and magnetic structure of polycrystalline
$La{}_{0.5-x}Nd{}_{x}Ca_{0.5}MnO{}_{3}$ (0.0 \ensuremath{\le} x
\ensuremath{\le} 0.5) samples have been investigated using magnetization,
resistivity, transmission electron microscope, and neutron diffraction
techniques. The samples are isostructural and possess orthorhombic structure in
\textit{Pnma} space group. On lowering of temperature, the samples exhibit CE -
type antiferromagnetic structure coexisting with a weak ferromagnetic ordering.
The charge and orbitally ordered antiferromagnetic phase is weakened by the
growth of ferromagnetic phase. The evolution of structural distortions and
magnetic structure at low temperature as a function of Nd doping exhibit a
strong correlation with A - site disorder ($\sigma{}^{2}$).",1010.6124v1
2010-12-15,Giant Tunneling Electroresistance Effect Driven by an Electrically Controlled Spin Valve at a Complex Oxide Interface,"A giant tunneling electroresistance effect may be achieved in a ferroelectric
tunnel junction by exploiting the magnetoelectric effect at the interface
between a ferroelectric barrier and magnetic La1-xSrxMnO3 electrode. Using
first-principles density functional theory we demonstrate that a few magnetic
monolayers of La1-xSrxMnO3 near the interface act, in response to ferroelectric
polarization reversal, as an atomic scale spin-valve by filtering
spin-dependent current. This effect produces more than an order of magnitude
change in conductance, and thus constitutes a giant resistive switching effect.",1012.3421v2
2010-12-17,Electro thermal simulation of superconducting nanowire avalanche photodetectors,"We developed an electro thermal model of NbN superconducting nanowire
avalanche photodetectors (SNAPs) on sapphire substrates. SNAPs are single
photon detectors consisting of the parallel connection of N superconducting
nanowires. We extrapolated the physical constants of the model from
experimental data and we simulated the time evolution of the device resistance,
temperature and current by solving two coupled electrical and thermal
differential equations describing the nanowires. The predictions of the model
were in good quantitative agreement with the experimental results.",1012.3964v1
2010-12-17,Ternary Tetradymite Compounds as Topological Insulators,"Ternary tetradymites Bi2Te2S, Bi2Te2Se and Bi2Se2Te are found to be stable,
bulk topological insulators via theory, showing band inversion between group V
and VI pz orbitals. We identify Bi2Se2Te as a good candidate to study massive
Dirac Fermions, with a (111) cleavage-surface-derived Dirac point (DP) isolated
in the bulk band gap at the Fermi energy Ef like Bi2Se3 but with a spin texture
alterable by layer chemistry. In contrast, Bi2Te2S and Bi2Te2Se (111) behave
like Bi2Te3, with a DP below Ef buried in bulk bands. Bi2Te2S offers large bulk
resistivity needed for devices.",1012.3974v3
2011-01-18,Metal-insulator transition and electrically-driven memristive characteristics of SmNiO3 thin films,"The correlated oxide SmNiO3 (SNO) exhibits an insulator to metal transition
(MIT) at 130 {\deg}C in bulk form. We report on synthesis and electron
transport in SNO films deposited on LaAlO3 (LAO) and Si single crystals. X-ray
diffraction studies show that compressively strained single-phase SNO grows
epitaxially on LAO while on Si, mixed oxide phases are observed. MIT is
observed in resistance-temperature measurements in films grown on both
substrates, with charge transport in-plane for LAO/SNO films and out-of-plane
for Si/SNO films. Electrically-driven memristive behavior is realized in
LAO/SNO films, suggesting that SNO may be relevant for neuromorphic devices.",1101.3538v1
2011-01-25,Ferron Type of Coductivity in Metal CuFeSe2,"It is pointed out, that the charge transfer in the compound in paramagnetic
region has a ferron type of transport with ferrons of a small radius, predicted
by N. Mott. For some another specimen the charge transfer may be carried out by
ferrons of a large radius at very low temperatures. The results are well
confirmed by the temperature dependence of resistivity and by metal type of the
compound.",1101.4904v2
2011-02-04,Anisotropy in transport and magnetic properties of K0.64Fe1.44Se2,"We report a study of anisotropy in transport and magnetic properties of
K0.64Fe1.44Se2.00 single crystals. The anisotropy in resistivity is up to one
order of magnitude between 1.8 K and 300 K. Magnetic susceptibility exhibits
weak temperature dependence in the normal state with decrease in temperature
with no significant anomalies. The lower critical fields Hc1 of
K0.64Fe1.44Se2.00 are only about 3 Oe and the anisotropy of Hc1,c/Hc1,ab is
about 1. The critical currents for H||ab and H||c are about 10-10^3 A/cm2,
smaller than in iron pnictides and in FeTe_{1-x}Se_{x} and nearly isotropic.",1102.1010v3
2011-03-01,Experimental Spin Ratchet,"Spintronics relies on the ability to transport and utilize the spin
properties of an electron rather than its charge. We describe a spin rachet at
the single-electron level that produces spin currents with no net bias or
charge transport. Our device is based on the ground state energetics of a
single electron transistor comprising a superconducting island connected to
normal leads via tunnel barriers with different resistances that break spatial
symmetry. We demonstrate spin transport and quantify the spin ratchet
efficiency using ferromagnetic leads with known spin polarization. Our results
are modeled theoretically and provide a robust route to the generation and
manipulation of pure spin currents.",1103.0105v1
2011-03-15,Quantum transport in oxide nanostructures,"We describe magnetotransport experiments performed on Hall crosses made from
quantum wires at LaAlO3/SrTiO3 interfaces. Shubnikov-de Haas oscillations
measured in a 14-nm wide structure exhibit modulations that are consistent with
spin-orbit coupling or valley degeneracies. Hall measurements performed on the
6 nm-wide Hall cross reveal dissipative coupling to magnetic phases. Hall
plateaus are observed that deviate significantly from two-dimensional quantum
Hall counterparts. Non-monotonic dips in the Hall resistance are attributed to
one-dimensional confinement and spin-orbit coupling.",1103.3036v1
2011-03-29,Atomistic calculation of the thermal conductance of large scale bulk-nanowire junctions,"We have developed an efficient scalable kernel method for thermal transport
in open systems, with which we have computed the thermal conductance of a
junction between bulk silicon and silicon nanowires with diameter up to 10 nm.
We have devised scaling laws for transmission and reflection spectra, which
allow us to predict the thermal resistance of bulk-nanowire interfaces with
larger cross sections than those achievable with atomistic simulations. Our
results indicate the characteristic size beyond which atomistic systems can be
treated accurately by mesoscopic theories.",1103.5581v1
2011-03-30,"Anomalous conductivity dependence of plasticized PVC for different modificator ""A"" concentrations and film thicknesses","The dependences of electrical conductivity of plasticized PVC films on mass
fraction of plasticizer ""A"" and the film thickness are experimentally
investigated. Non-monotonic dependence of conductivity on the concentration of
plasticizer and strongly nonlinear dependence of the resistance of the film on
its thickness are found. Possibility of construction of the models describing
received results is shown and also discussed.",1103.5975v1
2011-05-12,Coulomb drag in graphene single layers separated by a thin spacer,"Motivated by very recent studies of Coulomb drag in grahene-BN-graphene
system we develop a theory of Coulomb drag for the Fermi liquid regime, for the
case when the ratio of spacer thickness $d$ to the Fermi wavelength of
electrons is arbitrary. The concentration ($n$) and thickness dependence of the
drag resistivity is changed from $n^{-3}d^{-4}$ for the thick spacer to
$n^{-1}|\ln{(nd^2)}|$ for the thin one.",1105.2534v2
2011-05-30,A ferromagnetic-like phase transition in new oxychalcogenide HgOCuSe,"We report the synthesis of a new oxychalcogenide HgOCuSe sample. The
resistivity decreases as a function of $T^{1.75}$ with decreasing temperature
from room temperature down to around 80 K. There exists a very sharp
ferromagnetic-like phase transition at around 60 K under a field of $H$ = 100
Oe. Contrary to the usual ferromagnetic materials, the descending and ascending
branches of the magnetic hysteresis curve, at 30 K, are reversed in the whole
irreversible field range and the reverse irreversibility decreases at 5 K.",1105.5868v1
2011-06-20,A fully woven touchpad sensor based on soft capacitor fibers,"A novel, highly flexible capacitor fiber (with 100 nF m-1 typical capacitance
per length) having a multilayer periodic structure of dielectric and conductive
polymer composite films is fabricated by drawing technique. The fiber is used
to build a woven touchpad sensor. Then, we study the influence of the fiber
length, capacitance and volume resistivity on the touch sensing performance. A
theoretical ladder network model of a fiber network is developed. A fully woven
textile sample incorporating one-dimension array of the capacitor fibers is
fabricated. Finally we show that such an array functions as a two-dimensional
touch sensor.",1106.3881v1
2011-06-24,Coexistence of bulk superconductivity and charge density wave in CuxZrTe3,"We report coexistence of bulk superconductivity and charge density wave (CDW)
with superconducting critical temperature Tc = 3.8 K in Cu intercalated
quasi-two-dimensional crystals of ZrTe3. The Cu intercalation results in the
expansion of the unit cell orthogonal to the Zr-Zr metal chains (b - axis) and
partial filling of CDW energy bandgap without obvious shift of CDW transition
temperature. b - axis resistivity ?Rhob is not related to CDW, and its dominant
scattering mechanism for both ZrTe3 and Cu0.05ZrTe3 is the electron - electron
Umklapp scattering.",1106.5047v1
2011-08-01,Enhancement of Spin Injection into Graphene by Water Dipping,"We immerse single layer graphene spin valves into purified water for a short
duration (<1 min) and investigate the effect on spin transport. Following water
immersion, we observe an enhancement in nonlocal magnetoresistance.
Additionally, the enhancement of spin signal is correlated with an increase in
junction resistance, which produces an increase in spin injection efficiency.
This study provides a simple way to improve the signal magnitude and
establishes the robustness of graphene spin valves to water exposure, which
enables future studies involving chemical functionalization in aqueous
solution.",1108.0380v1
2011-08-12,Magnetic noise induced by dc current in a micron-size magnetic wire,"The magnetic noise spectra induced by direct-current (dc) current flowing
through a micron-scale ferromagnetic wire have been investigated. We have
observed the noise spectra with a resonance frequency. Under the application of
the magnetic field in the plane, the magnetic field dependences of the
resonance frequency and amplitude were well interpreted by the analytical
calculation based on the stochastic model. The noise spectra are attributable
to the resistance oscillation reflecting the uniform magnetization precession
which is produced by the Joule heating due to the dc current.",1108.2548v1
2011-09-29,Sources of negative tunneling magneto-resistance in multilevel quantum dots with ferromagnetic contacts,"We analyze distinct sources of spin-dependent energy level shifts and their
impact on the tunneling magnetoresistance (TMR) of interacting quantum dots
coupled to collinearly polarized ferromagnetic leads. Level shifts due to
virtual charge fluctuations can be quantitatively evaluated within a
diagrammatic representation of our transport theory. The theory is valid for
multilevel quantum dot systems and we exemplarily apply it to carbon nanotube
quantum dots, where we show that the presence of many levels can qualitatively
influence the TMR effect.",1109.6599v1
2011-10-13,Tuning the structural instability of SrTiO_3 by Eu doping: The phase diagram of Sr_1-xEu_xTiO_3,"The phase diagram of Sr_1-xEu_xTiO_3 is determined experimentally by electron
paramagnetic resonance and resistivity measurements and analyzed theoretically
within the self-consistent phonon approximation as a function of x
([0.03-1.0]). The transition temperature of the structural instability of the
system increases nonlinearly to higher temperatures with increasing x. This is
interpreted theoretically by a substantial alteration in the dynamics caused by
a change in the double-well potential from broad and shallow to narrow and
deep.",1110.2922v2
2011-11-21,Ink-Jet Printed Graphene Electronics,"We demonstrate ink-jet printing as a viable method for large area fabrication
of graphene devices. We produce a graphene-based ink by liquid phase
exfoliation of graphite in N-Methylpyrrolidone. We use it to print thin-film
transistors, with mobilities up to~95cm^2V^(-1)s(-1), as well as transparent
and conductive patterns, with~80 % transmittance and~30kOhm/sq sheet
resistance. This paves the way to all-printed, flexible and transparent
graphene devices on arbitrary substrates",1111.4970v1
2011-11-24,Domain wall attraction and repulsion during spin-torque-induced coherent motion,"We calculate the interaction between two magnetic domain walls during their
current-induced motion. This interaction produces a separation-dependent
resistance and also a differential velocity, causing domains in motion to
experience an effective attraction at large separations and an effective
repulsion at short separations. In an intermediate range of currents the two
domain walls will reach a natural equilibrium spacing that depends on the
magnitude of the current flowing through the material.",1111.5868v1
2011-12-09,Characterization and Predictive Modeling of Epitaxial Silicon-Germanium Thermistor Layers,"The thermal coefficient of resistance (TCR) for epitaxial silicon-germanium
(SiGe) layers has been analyzed by experiment and simulation. Predictive
simulation using drift-diffusion formalism and self-consistent
quantum-mechanical solutions yielded similar results, TCR around 2%/K at 300 K.
This modeling approach can be used for different, graded and constant, SiGe
profiles,. It is also capable of predicting the influence of background
auto-doping on the TCR of the detectors",1112.2043v1
2011-12-14,Possibility of a zero-temperature metallic phase in granular two-band superconducting films,"A variational approach is used to study the superconductor-insulator
transition in two-band granular superconducting films using a
resistance-shunted Josephson junction array model in this letter. We show that
a zero-temperature metallic phase may exist between the superconducting and
insulator phases which is absent in normal single band granular superconducting
films. The metallic phase may be observable in some dirty pnictide
superconductor films.",1112.3132v2
2012-02-08,Seismic Waveguide of Metamaterials,"We have developed a new method of an earthquake-resistant design to support
conventional aseismic designs using acoustic metamaterials. We suggest a simple
and practical method to reduce the amplitude of a seismic wave exponentially.
Our device is an attenuator of a seismic wave. Constructing a cylindrical
shell-type waveguide that creates a stop-band for the seismic wave, we convert
the wave into an evanescent wave for some frequency range without touching the
building we want to protect.",1202.1586v1
2012-04-10,"Modeling the underlying mechanisms for organic memory devices: Tunneling, electron emission and oxygen adsorbing","We present a combined experimental and theoretical study to get insight into
both memory and negative differential resistance (NDR) effect in organic memory
devices. The theoretical model we propose is simply a one-dimensional metallic
island array embedding within two electrodes. We use scattering operator method
to evaluate the tunneling current among the electrode and islands to establish
the basic bistable I-V curves for several devices. The theoretical results
match the experiments very well, and both memory and NDR effect could be
understood comprehensively. The experimental correspondence, say, the
experiment of changing the pressure of oxygen, is addressed as well.",1204.2022v1
2012-04-18,Magnetoresistance Relaxation in (La0.5Eu0.5)0.7Pb0.3MnO3 Single Crystals under the Action of a Pulse Magnetic Field,"Magnetoresistance of substituted lanthanum manganite (La0.5Eu0.5)0.7Pb0.3MnO3
in the pulse magnetic field H = 25 T was measured at different temperatures.
Magnetoresistance relaxation with a characteristic time of 10 -3 s was found.
It has been established that the temperature dependence of the relaxation
parameter {\tau}(t) at different temperatures correlates with the temperature
dependence of electrical resistance R(T). The proposed relaxation mechanism is
related to relaxation of conducting and dielectric phases in the sample volume
under phase stratification conditions. It is shown that relaxation parameter
{\tau} reflects the number of boundaries in the volume and not the ratio
between phase fractions.",1204.3987v1
2012-05-18,Metal-to-insulator transition in anatase TiO2 thin films induced by growth rate modulation,"We demonstrate control of the carrier density of single phase anatase TiO2
thin films by nearly two orders of magnitude by modulating the growth kinetics
during pulsed laser deposition, under fixed thermodynamic conditions. The
resistivity and the intensity of the photoluminescence spectra of these TiO2
samples, both of which correlate with the number of oxygen vacancies, are shown
to depend strongly on the growth rate. A quantitative model is used to explain
the carrier density changes.",1205.4065v1
2012-05-30,Type-I superconductivity in ScGa3 and LuGa3 single crystals,"We present evidence of type-I superconductivity in single crystals of ScGa3
and LuGa3, from magnetization, specific heat, and resistivity measurements: low
critical temperatures Tc = 2.1-2.2 K; field-induced secondto first-order phase
transition in the specific heat, critical fields less than 240 Oe; and low
Ginzburg-Landau coefficients {\kappa} approx 0.23 and 0.30 for ScGa3 and LuGa3,
respectively, are all traits of a type-I superconducting ground state. These
observations render ScGa3 and LuGa3 two of only several type-I superconducting
compounds, with most other superconductors being type II (compounds and alloys)
or type I (elemental metals and metaloids).",1205.6836v1
2012-07-20,Superconducting state in the metastable binary bismuthide Rh3Bi14 single crystals,"We report detailed magnetic, transport and thermodynamic properties of
metastable Rh3Bi14 single crystals in superconducting and normal state. We show
that Rh3Bi14 is nearly isotropic, weak to intermediately coupled BCS
superconductor, whereas the electronic resistivity above superconducting Tc =
2.94 K is dominated by the phonon scattering in the large unit cell with pores
filled by Bi atoms. Superconductivity is strongly influenced by the nature of
atoms that fill the voids in the crystal structure.",1207.5043v1
2012-08-23,Evolution of c-f hybridization and two component Hall effect in β-YbAlB_4,"\beta-YbAlB_4 is the unique heavy fermion superconductor that exhibits
unconventional quantum criticality without tuning in a strongly intermediate
valence state. Despite the large coherence temperature, set by the peak of the
longitudinal resistivity, our Hall effect measurements reveal that resonant
skew scattering from incoherent local moments persists down to at least ~40 K,
where the Hall coefficient exhibits a distinct minimum signaling another
formation of coherence. The observation strongly suggests that the
hybridization between f-moments and conduction electrons has a two component
character with distinct Kondo or coherence scales T_K of ~40 K and 200 K; this
is confirmed by the magnetic field dependence of \rho_xy.",1208.4680v1
2012-08-28,Trench Gate Power MOSFET: Recent Advances and Innovations,"The trench gate MOSFET has established itself as the most suitable power
device for low to medium power applications by offering the lowest possible ON
resistance among all MOS devices. The evolution of the trench gate power MOSFET
has been discussed in this chapter, starting right from its beginnings to the
recent trends. The innovations in the structural improvements to meet the
requirements for an efficient operation, the progress in the fabrication
technology, the characterization methods and various reliability issues have
been emphasized.",1208.5553v1
2012-09-26,Effect of rotation of the polarization of linearly polarized microwaves on the radiation-induced magnetoresistance oscillations,"Light-matter coupling is investigated by rotating, by an angle \theta, the
polarization of linearly polarized microwaves with respect to the long-axis of
GaAs/AlGaAs Hall-bar electron devices. At low microwave power, P, experiments
show a strong sinusoidal variation in the diagonal resistance R_{xx} vs. \theta
at the oscillatory extrema, indicating a linear polarization sensitivity in the
microwave radiation-induced magnetoresistance oscillations. Surprisingly, the
phase shift \theta_{0} for maximal oscillatory R_{xx} response under
photoexcitation appears dependent upon the radiation-frequency f, the extremum
in question, and the magnetic field orientation or sgn(B).",1209.5808v1
2012-09-27,Interaction effects and transport properties of Pt capped Co nanoparticles,"We studied the magnetic and transport properties of Co nanoparticles (NPs)
being capped with varying amounts of Pt. Beside field and temperature dependent
magnetization measurements we performed delta-M measurements to study the
magnetic interactions between the Co NPs. We observe a transition from
demagnetizing towards magnetizing interactions between the particles for an
increasing amount of Pt capping. Resistivity measurements show a crossover from
giant magnetoresistance towards anisotropic magnetoresistance.",1209.6255v1
2012-10-18,Possibility of Exciton Mediated Superconductivity in Nano-Sized Sn/Si Core-Shell Clusters: A Process Technology towards Heterogeneous Material in Nano-Scale,"We have produced Sn/Si core-shell cluster assemblies by a
plasma-gas-condensation cluster beam deposition apparatus. For the sample with
Si content = 12 at.%, the temperature dependence of electrical resistivity
exhibits a metallic behavior above 10K and the onset of superconducting
transition below 6.1 K. With decreasing temperature, the thermomagnetic curve
for the sample with Si content = 8 at.% begins to decrease steadily toward
negative value below 7.7 K, indicating the Meissner effect. An increase in the
transition temperature, TC is attributable to exciton-typesuperconductivity.",1210.5027v1
2012-10-29,Optical Absorption Measurements on Crystalline Silicon at 1550nm,"Crystalline silicon is currently being discussed as test-mass material for
future generations of gravitational wave detectors that will operate at
cryogenic temperatures. We present optical absorption measurements on a
large-dimension sample of crystalline silicon at a wavelength of 1550nm at room
temperature. The absorption was measured in a monolithic cavity setup using the
photo-thermal self-phase modulation technique. The result for the absorption
coefficient of this float-zone sample with a specific resistivity of 11kOhm cm
was measured to be \alpha_A=(264 +/- 39)ppm/cm.",1210.7763v2
2012-12-17,Anomalous Hall Effect in perpendicularly magnetized Mn(_{3-x})Ga thin films,"Mn$_{3-x}$Ga (x = 0.1, 0.4, 0.7) thin films on MgO and SrTiO$_3$ substrates
were investigated with magnetic anisotropy perpendicular to the film plane. An
anomalous Hall-effect was observed for the tetragonal distorted lattice in the
crystallographic D0$_{22}$ phase. The Hall resistivity $\varrho_{xy}$ was
measured in a temperature range from 20 to 330 K. The determined skew
scattering and side jump coefficients are discussed with regard to the film
composition and used substrate and compared to the crystallographic and
magnetic properties.",1212.4019v1
2013-03-07,Thickness dependence of the degree of spin polarization of the electrical current in permalloy thin films,"Spin-polarized electrical transport is investigated in $
Al_{2}O_{3}/Ni_{80}Fe_{20}/Al_{2}O_{3}$ thin films for permalloy thickness
between 6 and 20nm. The degree of spin-polarization of the current flowing in
the plane of the film is measured through the current induced spin wave Doppler
shift. We find that it decreases as the film thickness decreases, from 0.72 at
20nm to 0.46 at 6nm. This decrease is attributed to a spin depolarization
induced by the film surfaces. A model is proposed which takes into account the
contributions of the different sources of electron scattering (alloy disorder,
phonons, thermal magnons, grain boundaries, film surfaces) to the measured
spin-dependent resistivities.",1303.1692v1
2013-06-12,Electron transport across a metal-organic interface,"We simulate the electron transport across the Au(111)-pentacene interface
using non-equilibrium Green's functions and density-functional theory
(NEGF-DFT), and calculate the bias-dependent electron transmission. We find
that the electrical contact resistance is dominated by the formation of a
Schottky barrier at the interface, and show that the conventional semiconductor
transport models across Schottky barriers need to be modified in order to
describe the simulation data. We present an extension of the conventional
Schottky barrier transport model, which can describe our simulation results and
rationalize recent experimental data.",1306.2731v1
2013-06-26,A singularly perturbed non-ideal transmission problem and application to the effective conductivity of a periodic composite,"We investigate the effective thermal conductivity of a two-phase composite
with thermal resistance at the interface. The composite is obtained by
introducing into an infinite homogeneous matrix a periodic set of inclusions of
a different material. The diameter of each inclusion is assumed to be
proportional to a positive real parameter \epsilon. Under suitable assumptions,
we show that the effective conductivity can be continued real analytically in
the parameter \epsilon around the degenerate value \epsilon=0, in
correspondence of which the inclusions collapse to points.",1306.6176v1
2013-07-12,Observation of Longitudinal Spin Seebeck Effect with Various Transition Metal Films,"We evaluated the thermoelectric properties of longitudinal spin Seebeck
devices by using ten different transition metals (TMs). Both the intensity and
sign of spin Seebeck coefficients were noticeably dependent on the degree of
the inverse spin Hall effect and the resistivity of each TM film. Spin
dependent behaviors were also observed under ferromagnetic resonance. These
results indicate that the output of the spin Seebeck devices originates in the
spin current.",1307.3320v1
2013-08-08,Planar Superconducting Whispering Gallery Mode Resonators,"We introduce a microwave circuit architecture for quantum signal processing
combining design principles borrowed from high-Q 3D resonators in the quantum
regime and from planar structures fabricated with standard lithography. The
resulting '2.5D' whispering-gallery mode resonators store 98% of their energy
in vacuum. We have measured internal quality factors above 3 million at the
single photon level and have used the device as a materials characterization
platform to place an upper bound on the surface resistance of thin film
aluminum of less than 250nOhms.",1308.1743v2
2013-09-02,Model of the Electrostatics and Tunneling Current of Metal-Graphene Junctions and Metal-Insulator-Graphene Heterostructures,"In this paper we present a comprehensive model for the tunneling current of
the metal-insulator-graphene heterostructure, based on the Bardeen Transfer
Hamiltonian method, of the metal-insulator-graphene heterostructure. As a
particular case we have studied the metal-graphene junction, unveiling the role
played by different electrical and physical parameters in determining the
differential contact resistance.",1309.0390v1
2013-09-19,Giant electroresistance and tunable magnetoelectricity in a multiferroic junction,"First-principles density functional calculations show that the
$\textrm{SrRuO}_{3}/\textrm{PbTiO}_{3}/\textrm{SrRuO}_{3}$ multiferroic
junction with asymmetric (RuO$_{2}$/PbO and TiO$_{2}$/SrO) interfaces has a
large ferroelectric depolarizing field, whose switching changes the interface
transmission probabilities for tunneling electrons, leading to
electroresistance modulation over several orders of magnitude. The switching
further affects the interface spin density, naturally driving magnetoresistance
as well as modulated spin-dependent in-plane resistivity, which may be
exploited in field-effect devices.",1309.4883v2
2013-11-28,Gate controlled spin pumping at a quantum spin Hall edge,"We propose a four-terminal device designed to manipulate by all electrical
means the spin of a magnetic adatom positioned at the edge of a quantum spin
Hall insulator. We show that an electrical gate, able to tune the interface
resistance between a quantum spin Hall insulator and the source and drain
electrodes, can switch the device between two regimes: one where the system
exhibits spin pumping and the other where the adatom remains in its ground
state. This demonstrates an all-electrical route to control single spins by
exploiting helical edge states of topological materials.",1311.7329v1
2014-03-02,Spin disorder in an Ising honeycomb chain cobaltate,"We report on a member of the spin-disordered honeycomb lattice
antiferromagnet in a quasi-one-dimensional cobaltate Ba_3Co_2O_6(CO_3)_0.7.
Resistivity exhibits as semimetallic along the face-sharing CoO6 chains.
Magnetic susceptibility shows strongly anisotropic Ising-spin character with
the easy axis along the chain due to significant spin-orbit coupling and a
trigonal crystal field. Nevertheless, ^135Ba NMR detects no indication of the
long-range magnetic order down to 0.48 K. Marginally itinerant electrons
possess large entropy and low-lying excitations with a Wilson ratio R_W = 116,
which highlight interplays of charge, spin, and orbital in the disordered
ground state.",1403.0208v1
2014-03-18,Quantum longitudinal and Hall transport at the LaAlO3/SrTiO3 interface at low electron densities,"We examined the magneto-transport behavior of electrons confined at the
conducting LaAlO3/SrTiO3 interface in the low sheet carrier density regime. We
observed well resolved Shubnikov-de Haas quantum oscillations in the
longitudinal resistance, and a plateau-like structure in the Hall conductivity.
The Landau indices of the plateaus in the Hall conductivity data show spacing
close to 4, in units of the quantum of conductance. These experimental features
can be explained by a magnetic breakdown transition, which quantitatively
explains the area, structure, and degeneracy of the measured Fermi surface.",1403.4343v1
2014-03-18,31P NMR Investigation of the Superconductor LiFeP (Tc = 5 K),"We investigate the static and dynamic spin susceptibility of the 111 type
Fe-based superconductor LiFeP with Tc ~ 5 K through the measurement of Knight
shift 31K and the spin-lattice relaxation rate 1/T1 at 31P site by nuclear
magnetic resonance. The constant 31K, small magnitudes of 1/T1T, along with the
resistivity rho ~ T^2 all point to the weak spin correlations in LiFeP. 1/T1T
display small enhancement toward Tc, indicating that the superconductivity is
intimately correlated with the antiferromagnetic spin fluctuations.",1403.4458v1
2014-03-21,Field induced large magnetocaloric effect and magnetoresistance in ErNiSi,"Large magnetocaloric effect (MCE) and magnetoresistance (MR) together with
negligible hysteresis loss has been observed in ErNiSi compound, which
undergoes metamagnetic transition at low temperatures. Magnetization, heat
capacity and resistivity measurements confirm the metamagnetic transition. The
maximum value of isothermal entropy change and MR for a field change of 50 kOe
are found to be 19.1 J/kg K and -34 %. Large MCE with negligible magnetic
hysteresis loss could make this material promising for low temperature magnetic
refrigeration.",1403.5396v1
2014-06-17,Phenomenological Modeling of Memristive Devices,"We present a computationally inexpensive yet accurate phenomenological model
of memristive behavior in titanium dioxide devices by fitting experimental
data. By design, the model predicts most accurately I-V relation at small
non-disturbing electrical stresses, which is often the most critical range of
operation for circuit modeling. While the choice of fitting functions is
motivated by the switching and conduction mechanisms of particular titanium
dioxide devices, the proposed modeling methodology is general enough to be
applied to different types of memory devices which feature smooth non-abrupt
resistance switching.",1406.4219v2
2014-12-21,A brief introduction to giant magnetoresistance,"Giant magnetoresistance (GMR) is a quantum mechanical magnetoresistance
effect observed in thin film structures composed of alternating ferromagnetic
and nonmagnetic layers. The effect manifests itself as a significant decrease
(typically 10-80%) in electrical resistance in the presence of a magnetic
field. The effect is exploited commercially by manufacturers of hard disk
drives. The 2007 Nobel Prize in physics was awarded to Albert Fert and Peter
Grunberg for the discovery of GMR.",1412.7691v1
2015-02-10,Preventing Buckling of Slender Cylindrical Structures by Internal Viscous Flows,"Viscous flows within an elastic structure apply stress on the solid-liquid
interface. The stress-field created by the viscous flow can be utilized to
counter stress created by external forces and thus may be applied as a tool for
delaying the onset of structural failure. To illustrate this concept we study
viscous flow within an elastic cylinder under compressive axial force. We
obtain a closed-form expression showing an approximately linear relation
between the critical buckling load and the liquid inlet pressure. Our results
are validated by numerical computations. We discuss future research directions
of fluid-solid composite materials which create flow under external stress,
yielding enhanced resistance to structural failure.",1502.02814v1
2015-03-04,Adiabatic Joule Heating of Copper from 4 K to the Melting Temperature,"Considering a copper wire heated by Joule effect and the variation of its
resistivity and specific heat with temperature, we established numerical and
analytical solutions (between 293 and 1356 K for the latter) for the evolution
of its temperature over time. The Temperature vs. Time evolution follows a
Lambertian function. The calculations are based on the assumption of adiabatic
heating and uniform current distribution within the wire. We demonstrate that
at very low temperature the heating rate is strongly dependent on copper
purity.",1503.01279v1
2015-08-17,Evidence for resonant scattering of electrons by spin fluctuations in $LaNiO_3/LaAlO_3$ heterostructures grown by pulsed laser deposition,"We present measurements of resistivity $\rho$ in highly oriented $LaNiO_3$
films grown on $LaAlO_3$ substrates by using a pulsed laser deposition
technique. The experimental data are found to follow a universal $\rho (T)
\propto T^{3/2}$ dependence for the entire temperature interval ($20K<T<300K$).
The observed behavior has been attributed to a resonant scattering of electrons
on antiferromagnetic fluctuations (with a characteristic energy $\hbar \omega
_{sf}\simeq 2.1meV$) triggered by spin-density wave propagating through the
interface boundary of $LaNiO_3/LaAlO_3$ sandwich.",1508.04063v1
2015-09-14,Multi-Fields Modulation of Physical Properties of Oxide Thin Films,"Oxide thin films exhibit versatile physical properties such as magnetism,
ferroelectricity, piezoelectricity, metal-insulator transition (MIT),
multiferroicity, colossal magnetoresistivity, switchable resistivity, etc. More
importantly, the exhibited multifunctionality could be tuned by various
external fields, which has enabled demonstration of novel electronic devices.
In this article, recent studies of the multi-fields modulation of physical
properties in oxide thin films have been reviewed. Some of the key issues and
prospects about this field are also addressed.",1509.03939v1
2015-11-24,Structural Properties and Thermodynamics of Hafnium sub-oxides in RRAM,"We study the structural and electronic properties of various hafnium
sub-oxides HfzO from z = 9 to z = 0.5, by ab initio simulation using Density
Functional Theory. The stability of these sub-oxides is studied against
monoclinic HfO2. The progressive oxidation of a given HfzO is also envisaged
toward stoichiometric HfO2. The analogy with a conductive region of electrons
inside a HfO2 matrix is discussed within the context of Oxide-based Resistive
Random Access Memories (OxRRAM) devices which employ hafnium dioxide as an
insulator.",1511.07665v1
2016-01-01,Reverse degradation of nickel graphene junction by hydrogen annealing,"Metal contacts are fundamental building components for graphene based
electronic devices and their properties are greatly influenced by interface
quality during device fabrication, leading to resistance variation. Here we
show that nickel graphene junction degrades after air exposure, due to
interfacial oxidation, thus creating a tunneling barrier. Most importantly, we
demonstrate that hydrogen annealing at moderate temperature (300 0C) is an
effective technique to reverse the degradation.",1601.00109v2
2016-01-06,Electronic transport through a silicene-based zigzag and armchair junction,"Using density functional theory and non-equilibrium Greens function
technique, we performed theoretical investigations on the transport properties
of several ZAZ SiNRs junctions,a similar kind of silicene molecules junction
combined by zigzag and armchair silicene nanoribbons. It is found that the
differential conductances of the three systems decrease with an order of
5-ZAZ>4-ZAZ>3-ZAZ.Particularly,the Negative differential resistance can be
observed within certain bias voltage range only in 3-ZAZ SiNRs. In order to
elucidate the mechanism the NDR behavior, the transmission spectra and
molecular projected selfconsistent Hamiltonian states are discussed in details.",1601.01066v1
2016-01-18,Investigation of ITO based liquid sensor for ammonia hydroxide detection,"We proposed an Indium Tin Oxide (ITO) sensor for detecting the NH4OH in
seawater and carried out a series of experiments to investigate the feasibility
of it as a hazardous and noxious substance (HNS) sensor. The ITO layer revealed
a distinct resistance change ({\delta}R) which is linearly correlated with the
NH4OH concentration. Sensing mechanism of the porous ITO layer has been
explained in terms of reduction and electrical double layer (EDL) formation.
Also, the chemical stability of ITO as a HNS sensor has verified.",1601.04446v1
2016-01-18,Low temperature phase diagram of hydrogen at pressures up to 380 GPa. A possible metallic phase at 360 GPa and 200 K,"Two new phases of hydrogen have been discovered at room temperature in Ref.1:
phase IV above 220 GPa and phase V above ~270 GPa. In the present work we have
found a new phase VI at P~360 GPa and T<200 K. This phase is likely metallic as
follows from the featureless Raman spectra, a strong drop in resistance, and
absence of a photoconductive response. We studied hydrogen at low temperatures
with the aid of Raman, infrared absorption, and electrical measurements at
pressures up to 380 GPa, and have built a new phase diagram of hydrogen.",1601.04479v1
2016-05-17,Insulator to metal transition of WO3 epitaxial films induced by electrochemical Li-ion intercalation,"We investigated systematic evolutions of structural and electronic properties
of LixWO3 films, induced by Li-ion electrochemical reactions.
Chronoamperometric Li-ion intercalation could control the amount of Li content
up to x ~ 0.5. The resistivity abruptly decreased with increasing x and the
films underwent an insulator to metal transition (IMT) within a range of 0.2 <
x < 0.24, which was consistent with IMT of cubic NaxWO3. The X-ray diffraction
analyses revealed the coexistence of tetragonal and cubic phases across IMT,
suggesting that the alkaline-ion content was a primary factor for metallic
conductivity in the ReO3-type WO3 system.",1605.04997v1
2016-07-19,Specific Heat and Electrical Transport Properties of Sn0.8Ag0.2Te Superconductor,"Sn0.8Ag0.2Te is a new superconductor with Tc ~ 2.4 K. The superconducting
properties of Sn0.8Ag0.2Te have been investigated by specific heat measurements
under magnetic fields. Bulk nature of superconductivity was confirmed from the
amplitude of the specific heat jump at the superconducting transition, and the
amplitude is consistent with fully-gapped superconductivity. Upper critical
field was estimated from specific heat and electrical resistivity measurements
under magnetic fields. The Hall coefficient was positive, suggesting that the
Ag acts as a p-type dopant in Sn0.8Ag0.2Te.",1607.05474v1
2016-10-21,Electromotive forces generated in 3d-transition ferromagnetic metal films themselves under their ferromagnetic resonance,"We report the electromotive force (EMF) properties generated in 3d-transition
ferromagnetic metal (FM = Fe, Co, and Ni80Fe20) films themselves under their
ferromagnetic resonance (FMR). For Fe and Co films, the EMF due to the
anomalous-Hall effect is dominantly generated under their FMR. Meanwhile, for a
Ni80Fe20 film, the EMF due to the inverse spin-Hall effect in the Ni80Fe20 film
itself under the FMR is mainly generated. This tendency is qualitatively
explained with differences of the spin polarization, the spin Hall
conductivity, the anomalous Hall conductivity, the magnetization saturation,
and the resistivity of the FM films.",1610.06695v2
2016-11-27,Probing Electron Spin Resonance in Monolayer Graphene,"The precise value of the $g$-factor in graphene is of fundamental interest
for all spin-related properties and their application. We investigate monolayer
graphene on a Si/SiO2 substrate by resistively detected electron spin resonance
(ESR). Surprisingly, the magnetic moment and corresponding g-factor of
1.952+/-0.002 is insensitive to charge carrier type, concentration, and
mobility.",1611.08782v1
2016-12-14,Dielectric geometric phase optical elements from femtosecond direct laser writing,"We propose to use femtosecond direct laser writing technique to realize
dielectric optical elements from photo-resist materials for the generation of
structured light from purely geometrical phase transformations. This is
illustrated by the fabrication and characterization of spin-to-orbital optical
angular momentum couplers generating optical vortices of topological charge
from 1 to 20. In addition, the technique is scalable and allows obtaining
microscopic to macroscopic flat optics. These results thus demonstrate that
direct 3D photopolymerization technology qualifies for the realization of
spin-controlled geometric phase optical elements.",1612.04487v1
2016-12-06,Development of an Experimental Setup to Analyze Carbon/Epoxy Composite Subjected to Current Impulses,"In this paper, variation in electrical properties of CFRP caused by
relatively low magnitude current impulses discharged through CFRP coupons are
reported, and internal changes of the composite, due to current impulses, are
studied. Based on electrical resistance measurements caused by these currents,
property changes in CFRP composite coupons of two different carbon ply
orientations are compared. Furthermore, it will be investigated if the changes
caused by current impulses are mainly focused in the region of the current
injection at the edges of composite coupons, or are they distributed uniformly
through the bulk of the composite.",1612.07204v1
2016-12-28,Tomonaga-Luttinger liquid and localization in Weyl semimetals,"We study both noncentrosymmetric and time-reversal breaking Weyl semimetal
systems under a strong magnetic field with the Coulomb interaction. The
three-dimensional bulk system is reduced to many mutually interacting
quasi-one-dimensional wires. Each strongly correlated wire can be approached
within the Tomonaga-Luttinger liquid formalism. Including impurity scatterings,
we inspect the localization effect and the temperature dependence of the
electrical resistivity. The effect of a large number of Weyl points in real
materials is also discussed.",1612.08905v2
2018-03-22,Vortex liquid phase in the p-wave ferromagnetic superconductor UCoGe,"The upper critical field for field along the b-axis of the p-wave
ferromagnetic superconductor UCoGe has a particular S-shape, akin to the
re-entrant superconducting phase of URhGe. To explore the evolution of the
superconducting phase under this transverse magnetic field, we report the
thermal conductivity and resistivity measurements, revealing a possible
field-induced vortex liquid phase, and supporting a field-induced change of the
superconducting order parameter.",1803.08468v3
2018-04-20,Redox reaction enhanced Schottky contact at a \LNO{}(001)/Al interface,"Emergent phenomena at interfaces between oxides and metals can appear due to
charge transfer and mass transport that modify the bulk properties. By coating
the metallic oxide LaNiO$_3$ by aluminium, we fabricated a junction exhibiting
a diode-like behaviour. At the equilibrium, the interface is insulating. The
metallic behaviour can be recovered by applying a voltage drop across the
junction in one polarity only. The electrical properties in direct and reverse
bias are investigated. The observed electro-resistive effect rises up to $10^5$
\% and can be interpreted in terms of (i) a spontaneous redox reaction
occurring at the interface and (ii) its reversal induced by charge injection in
direct bias.",1804.07574v1
2018-06-13,Vortex spin-valve on a topological insulator,"Spin-valve structures are usually associated with the ability to modify the
resistance of electrical currents. We here demonstrate a profoundly different
effect of a spin-valve. In combination with a topological insulator and
superconducting materials, we show that a spin-valve can be used to toggle
quantum vortices in and out of existence. In the antiparallel configuration,
the spin-valve causes superconducting vortex nucleation. In the parallel
configuration, however, no vortices appear. This switching effect suggests a
new way to control quantum vortices.",1806.05184v1
2018-09-25,Anomalous Transport Behavior in Quantum Magnets,"Transport behavior characterized by a low-temperature electrical resistivity
that displays a power-law behavior $\rho(T\to 0) \propto T^s$ with an exponent
$s<2$, is commonly observed in magnetic materials in both the magnetic and
nonmagnetic phases. We give a pedagogical overview of this phenomenon that
summarizes both the experimental situation and the state of its theoretical
understanding. We also put it in context by drawing parallels with unusual
power-law transport behavior in other systems.",1809.09675v1
2018-09-28,Magneto-dielectric and Magneto-resistive in the Mixed Spinel MgFe2O4,"The mixed spinel, MgFe2O4 has been synthesized by ball-milling assisted
sintering method. X-ray diffraction study confirms formation of cubic MgFe2O4
and the lattice parameter values calculated are a = b = c = 8.369(3) {\AA}.
Vibrating sample magnetometer measurements at room temperature shows a soft
ferrimagnetic nature. Magneto-Dielectric and Magneto-Restive plots confirm
coupling at room temperature in the prepared MgFe2O4. The peak at 500 Oe in the
MD plot is due to the canting of Fe3+ ions distributed in octahedral and
tetrahedral sites.",1809.10968v1
2014-08-21,Simulation of Schottky-Barrier Phosphorene Transistors,"Schottky barrier field-effect transistors (SBFETs) based on few and mono
layer phosphorene are simulated by the non-equilibrium Green's function
formalism. It is shown that scaling down the gate oxide thickness results in
pronounced ambipolar I-V characteristics and significant increase of the
minimal leakage current. The problem of leakage is especially severe when the
gate insulator is thin and the number of layer is large, but can be effectively
suppressed by reducing phosphorene to mono or bilayer. Different from
two-dimensional graphene and layered dichalcogenide materials, both the
ON-current of the phosphorene SBFETs and the metal-semiconductor contact
resistance between metal and phosphorene strongly depend on the transport
crystalline direction.",1408.5013v1
2004-06-10,Magnetic and orbital blocking in Ni nanocontacts,"We address the fundamental question of whether magneto-resistance (MR) of
atomic-sized contacts of Nickel is very large because of the formation of a
domain wall (DW) at the neck. Using {\em ab initio} transport calculations we
find that, as in the case of non-magnetic electrodes, transport in Ni
nanocontacts depends very much on the orbital nature of the electrons. Our
results are in agreement with several experiments in the average value of the
conductance. On the other hand, contrary to existing claims, DW scattering does
{\em not} account for large MR in Ni nanocontacts.",0406249v2
2004-06-25,Strong electron correlation effects in non-volatile electronic memory devices,"We investigate hysteresis effects in a model for non-volatile memory devices.
Two mechanisms are found to produce hysteresis effects qualitatively similar to
those often experimentally observed in heterostructures of transition metal
oxides. One of them is a novel switching effect based on a metal-insulator
transition due to strong electron correlations at the dielectric/metal
interface. The observed resistance switching phenomenon could be the
experimental realisation of a novel type of strongly correlated electron
device.",0406646v1
2011-07-20,Effect of pressure on the electronic structure of hcp Titanium,"The effect of pressure on the hexagonal close-packed structure of titanium is
investigated. The lattice parameters of the equilibrium structure were
determined in terms of the Gibbs free energy using the Epitaxial Bain Path
method. When this process was repeated for several pressures, the effect of
pressure on the lattice parameters was revealed. The calculated lattice
parameters were in good agreement with the experimental and theoretical
results. The effects of pressure on parameters depending on the electronic
structure such as conductivity and resistivity in the ground state were also
investigated up to 30 GPa using density functional theory.",1107.3948v1
2014-10-03,Enhanced spin-orbit coupling and charge carrier density suppression in LaAl1-xCrxO3/SrTiO3 heterointerfaces,"We report a gradual suppression of the two-dimensional electron gas (2DEG) at
the LaAlO3/SrTiO3 interface on substitution of chromium at the Al sites. The
sheet carrier density at the interface (ns) drops monotonically from 2.2x10(14)
cm-2 to 2.5x10(13) cm-2 on replacing nearly 60 percent of Al sites by Cr and
the sheet resistance (Rs) exceeds the quantum limit for localization (h/2e2) in
the concentrating range 40 to 60 percent of Cr.",1410.0876v1
2014-10-05,Planar Hall effect in Y3Fe5O12(YIG)/IrMn films,"The planar Hall effect of IrMn on an yttrium iron garnet (YIG = Y3Fe5O12) was
measured in the magnetic field rotating in the film plane. The magnetic field
angle dependence of planar Hall resistance (PHR) has been observed in YIG/IrMn
bilayer at different temperatures, while the GGG/IrMn (GGG= Gd3Ga5O12) shows
constant PHR for different magnetic field angles at both 10 K and 300 K. This
provides evidence that IrMn has interfacial spins which can be led by FM in
YIG/IrMn structure. A hysteresis can be observed in PHR-magnetic field angle
loop of YIG/IrMn films at 10 K, indicating the irreversible switching of IrMn
interfacial spins at low temperature.",1410.1112v1
2014-11-08,"Correlations among magnetic, magnetocaloric and magneto-transport properties in HoNiSi","Magnetic, magnetocaloric and magneto-transport properties of polycrystalline
HoNiSi have been studied. The compound crystallizes in orthorhombic crystal
structure and orders antiferromagnetically at TN=4.6 K. Magnetization isotherms
show curvature at small fields, revealing a field induced metamagnetic
transition. Magnetocalroic effect (MCE) has been estimated using magnetization
data and is found to be 12.8 J/kg K for a field of 50 kOe. Application of field
reduces the resistivity near TN, which results in a large negative MR. The
maximum value of MR has been found to be -24% at 4 K for 50 kOe. Below 4 K, the
compound shows positive MR with shape changing with field.",1411.2135v1
2017-01-29,Yielding Transitions and Grain-Size Effects in Dislocation Theory,"The statistical-thermodynamic dislocation theory developed in previous papers
is used here in an analysis of yielding transitions and grain-size effects in
polycrystalline solids. Calculations are based on the 1995 experimental results
of Meyers et al. for polycrystalline copper under strain-hardening conditions.
The main assertion is that the well known Hall-Petch effects are caused by
enhanced strengths of dislocation sources at the edges of grains instead of the
commonly assumed resistance to dislocation flow across grain boundaries. The
theory describes rapid transitions between elastic and plastic deformation at
yield points; thus it can be used to predict grain-size dependence of both
yield stresses and flow stresses",1701.08336v1
2017-11-08,Rattler-induced aging dynamics in jammed granular systems,"Granular materials jam when developing a network of contact forces able to
resist the applied stresses. Through numerical simulations of the dynamics of
the jamming process, we show that the jamming transition does not occur when
the kinetic energy vanishes. Rather, as the system jams, the kinetic energy
becomes dominated by rattlers particles, that scatter withing their cages. The
relaxation of the kinetic energy in the jammed configuration exhibits a double
power-law decay, which we interpret in terms of the interplay between backbone
and rattlers particles.",1711.03045v1
2017-12-04,A two-channel model for Spin-relaxation noise,"We develop a two-channel resistor model for simulating spin transport with
general applicability. Using this model, for the case of graphene as a
prototypical material, we calculate the spin signal consistent with
experimental values. Using the same model we also simulate the charge and spin-
dependent 1/f noise, both in the local and nonlocal four-probe measurement
schemes, and identify the noise from the spin-relaxation resistances as the
major source of spin-dependent 1/f noise.",1712.01414v1
2018-10-17,Interface enhanced magnetic anisotropy in Pt/EuO films,"We report proximity effects of spin-orbit coupling in EuO$_{1-x}$ films
capped with a Pt overlayer. Transport measurements suggest that current flows
along a conducting channel at the interface between the Pt and EuO. The
temperature dependence of the resistivity picks up the critical behaviors of
EuO, i.e., the metal-to-insulator transition. We also find an unusual
enhancement of the magnetic anisotropy in this structure from its bulk value
which results from strong spin-orbit coupling across the Pt/EuO interface.",1810.07336v1
2018-10-18,Superconductivity of platinum hydride,"We report the ac magnetic susceptibility, electrical resistance, and X-ray
diffraction measurements of platinum hydride (PtHx) in diamond anvil cells,
which reveal its superconducting transition. At 32 GPa, when PtHx is in a
P63/mmc structure, PtHx exhibits superconducting transition at 6.7 K and
superconducting transition temperature (Tc) decreases with pressure to 4.8 K at
36 GPa. The observed T c is higher than that of powdered Pt by more than three
orders of magnitude. It is suggested that hydrides of noble metals have higher
Tc than the elements.",1810.08191v1
2018-10-23,Perfect absorption of water waves by linear or nonlinear critical coupling,"We report on experiments of perfect absorption for surface gravity waves
impinging a wall structured by a subwavelength resonator. By tuning the
geometry of the resonator, a balance is achieved between the radiation damping
and the intrinsic viscous damping, resulting in perfect absorption by critical
coupling. Besides, it is shown that the resistance of the resonator, hence the
intrinsic damping, can be controlled by the wave amplitude, which provides a
way for perfect absorption tuned by nonlinear mechanisms. The perfect absorber
that we propose, without moving parts or added material, is simple, robust and
it presents a deeply subwavelength ratio wavelength/size $\simeq 18$.",1810.09884v1
2018-10-24,On the effect of Ti on Oxidation Behaviour of a Polycrystalline Nickel-based Superalloy,"Titanium is commonly added to nickel superalloys but has a well-documented
detrimental effect on oxidation resistance. The present work constitutes the
first atomistic-scale quantitative measurements of grain boundary and bulk
compositions in the oxide scale of a current generation polycrystalline nickel
superalloy performed through atom probe tomography. Titanium was found to be
particularly detrimental to oxide scale growth through grain boundary
diffusion.",1810.10444v1
2018-10-31,Domain formation and self-sustained oscillations in quantum cascade lasers,"We study oscillations in quantum cascade lasers due to traveling electric
field domains, which are observed both in simulations and experiments. These
oscillations occur in a range of negative differential resistance and we
clarify the condition determining whether the boundary between domains of
different electric field can become stationary.",1810.13207v2
2019-05-01,Degenerately Doped Transition Metal Dichalcogenides as Ohmic Homojunction Contacts to Transition Metal Dichalcogenide Semiconductors,"In search of an improved strategy to form low resistance contacts to MoS2 and
related semiconducting transition metal dichalcogenides, we use ab initio
density functional electronic structure calculations in order to determine the
equilibrium geometry and electronic structure of MoO3/MoS2 and MoO2/MoS2
bilayers. Our results indicate that, besides a rigid band shift associated with
charge transfer, the presence of molybdenum oxide modifies the electronic
structure of MoS2 very little. We find that the charge transfer in the bilayer
provides a sufficient degree of hole doping to MoS2, resulting in a highly
transparent contact region.",1905.00285v1
2019-07-08,Effect of elasto-plastic compatibility of grains on the void initiation criteria in low carbon steel,"The present study evidences the role of ferrite grain size distributions on
the occurrence of void initiation in a low carbon steel. Various
thermomechanical treatments were done to create ultrafine, bimodal and coarse
range of ferrite grain distributions. A two parameter characterization of
probable void initiation sites is proposed; elastic modulus difference and
difference in Schmid factor of the grains surrounding the void. All
microstructures were categorized based on the ability to ease or resist void
nucleation. For coarse grains, elastic modulus difference as well as the Schmid
factor difference is highest, intermediate for ultrafine and lowest for bimodal
microstructure.",1907.03703v1
2020-09-26,"Heat vortexes of ballistic, diffusive and hydrodynamic phonon transport in two-dimensional materials","In this work, the heat vortexes in two-dimensional porous or ribbon
structures are investigated based on the phonon Boltzmann transport equation
(BTE) under the Callaway model. First, the separate thermal effects of normal
(N) scattering and resistive (R) scattering are investigated with
frequency-independent assumptions. And then the heat vortexes in graphene are
studied as a specific example. It is found that the heat vortexes can appear in
both ballistic (rare R/N scattering) and hydrodynamic (N scattering dominates)
regimes but disappear in the diffusive (R scattering dominates) regime. As long
as there is not sufficient R scattering, the heat vortexes can appear in
present simulations.",2009.12587v1
2007-10-17,"Input Impedance, Nanocircuit Loading, and Radiation Tuning of Optical Nanoantennas","Here we explore the radiation features of optical nanoantennas, analyzing the
concepts of input impedance, optical radiation resistance, impedance matching
and loading of plasmonic nanodipoles. We discuss how the concept of antenna
impedance may be applied to optical frequencies, and how its quantity may be
properly defined and evaluated. We exploit these concepts in optimization of
nanoantenna loading by optical nanocircuit elements, extending classic concepts
of radio-frequency antenna theory to the visible regime for the proper design
and matching of plasmonic nanoantennas.",0710.3411v1
2012-01-06,Bi(111) thin film with insulating interior but metallic surfaces,"The electrical conductance of molecular beam epitaxial Bi on BaF2(111) was
measured as a function of both film thickness (4-540 nm) and temperature (5-300
K). Unlike bulk Bi as a prototype semimetal, the Bi thin films up to 90 nm are
found to be insulating in the interiors but metallic on the surfaces. This
result has not only resolved unambiguously the long controversy about the
existence of semimetal-semiconductor transition in Bi thin film but also
provided a straightforward interpretation for the long-puzzled temperature
dependence of the resistivity of Bi thin films, which in turn might suggest
some potential applications in spintronics.",1201.1480v1
2012-01-30,Thermoelectric Properties of Ho-doped Bi1-xSbx,"The Seebeck coefficients, electrical resistivities, total thermal
conductivities, and magnetization are reported for temperatures between 5 and
350 K for n-type Bi0.88Sb0.12 nano-composite alloys made by Ho-doping at the 0,
1 and 3% atomic levels. The alloys were prepared using a dc hot-pressing
method, and are shown to be single phase for both Ho contents with grain sizes
on the average of 900 nm. We find the parent compound has a maximum of ZT =
0.28 at 231 K, while doping 1% Ho increases the maximum ZT to 0.31 at 221 K and
the 3% doped sample suppresses the maximum ZT = 0.24 at a temperature of 260 K.",1201.6304v1
2016-03-21,Multi-scale modelling of supercapacitors: From molecular simulations to a transmission line model,"We perform molecular dynamics simulations of a typical nanoporous-carbon
based supercapacitors. The organic electrolyte consists in
1-ethyl-3-methyl--imidazolium and hexafluorophosphate ions dissolved in
acetonitrile. We simulate systems at equilibrium, for various applied voltages.
This allows us to determine the relevant thermodynamic (capacitance) and
transport (in-pore resistivities) properties. These quantities are then
injected in a transmission line model for testing its ability to predict the
charging properties of the device. The results from this macroscopic model are
in good agreement with non-equilibrium molecular dynamics simulations, which
validates its use for interpreting electrochemical impedance experiments.",1603.06640v1
2017-05-11,Tunable spin dynamics in chiral soliton lattice,"We study dynamics of a chiral soliton lattice (CSL) in a classical
one-dimensional spin chain coupled to the conduction electrons under an
electric field. The CSL has attracted much interest because its period can be
easily controlled by an external magnetic field. We clarify the dependence of
the CSL dynamics on its period. A collective coordinate and an SU(2) gauge
method are used for the analysis. It turns out that the velocity of the CSL
becomes slower as the period becomes longer. We also mention a relation between
the velocity and the magnetic resistance.",1705.04086v2
2017-07-05,Surfing Liquid Metal Droplet on the Same Metal Bath via Electrolyte Interface,"We reported a phenomenon that when exerting an electric field gradient across
a liquid metal/electrolyte interface, a droplet of the same liquid metal can
persistently surf on the interface without coalescence. A thin layer of the
intermediate solution, which separates the droplet from direct metallic
contacting and provides the levitating force, is responsible for such surfing
effect. The electric resistance of this solution film is measured and the film
thickness is further theoretically calculated. The fact that the levitating
state can be switched on and off via a controlled manner paves a way for
reliable manipulation of liquid metal droplet.",1707.01498v1
2018-08-04,Toward a Spectral Theory of Cellular Sheaves,"This paper outlines a program in what one might call spectral sheaf theory
--- an extension of spectral graph theory to cellular sheaves. By lifting the
combinatorial graph Laplacian to the Hodge Laplacian on a cellular sheaf of
vector spaces over a regular cell complex, one can relate spectral data to the
sheaf cohomology and cell structure in a manner reminiscent of spectral graph
theory. This work gives an exploratory introduction, and includes results on
eigenvalue interlacing, sparsification, effective resistance, and sheaf
approximation. These results and subsequent applications are prefaced by an
introduction to cellular sheaves and Laplacians.",1808.01513v2
2018-08-05,Role of Doping Ratio on The Sensing Properties of ZnO:SnO2 Thin Films,"Thin films of ZnO:SnO2 were deposited on different substrates like glass and
c-Si using spray pyrolysis method .The structures and morphology of the
prepared samples films were cheeked using X-ray diffraction and atomic force
microscope. Gas sensing measurements provided from resistance measurement in
the absent and exposure to NO2 gas . The results showed that good enhancement
of sensitivity take place after doping with tin oxide. Maximum sensitivity
obtained at 9% doping ratio and operating temperature 200oC.",1808.04235v1
2018-08-14,"Short commentary on comparing previous claim of RT superconductivity with the data of arXiv:1807.08572, ""Evidence for Superconductivity at Ambient Temperature and Pressure in Nanostructures""","I briefly mention a previous claim of room temperature superconductivity (
arXiv:0905.3524) in Ag-based oxide material and compare their results with the
most recent claim of ambient temperature superconductivity in arXiv:1807.08572.
In both cases, an electrical transition to low resistance state and
diamagnetism are observed. Silver is a common ingredient in both claims. Does
it mean that silver holds the key to RT superconductivity or, the missing field
cool data (in both reports) hint of some other physical phenomenon than
superconductivity.",1808.04912v1
2019-03-08,Ti surface modification for biomedical applications,"Micro Arc Oxidation (MAO) is an electrochemical approach for the surface
treatment usually applied on so called valve metals such as Al, Mg and Ti. MAO
is usually carried out an aqueous electrolyte, which involves a bath cooling
and leads to the creation of surface contained components originated in the
electrolyte. In current work, we applied a different approach of ceramic
surface formation on Ti alloy used in biomedical applications. Here, MAO
process conducted in molten nitrate salt at 280 deg C. The developed surface
morphology, chemical and phase composition, and corrosion resistance were
investigated and described in the work.",1903.03507v1
2019-08-22,Anomalous Hall effect at the spontaneously electron-doped polar surface of PdCoO2 ultrathin films,"We revealed the electrical transport through surface ferromagnetic states of
a nonmagnetic metal PdCoO2. Electronic reconstruction at the Pd-terminated
surface of PdCoO2 induces Stoner-like ferromagnetic states, which could lead to
spin-related phenomena among the highly conducting electrons in PdCoO2.
Fabricating a series of nanometer-thick PdCoO2 thin films, we detected a
surface-magnetization-driven anomalous Hall effect via systematic thickness-
and termination-dependent measurements. Besides, we discuss that finite
magnetic moments in electron doped CoO2 triangular lattices may have given rise
to additional unconventional Hall resistance.",1908.08173v1
2011-04-12,Upper critical fields and superconducting anisotropy of K0.70Fe1.55Se1.01S0.99 and K0.76Fe1.61Se0.96S1.04 single crystals,"We have investigated temperature and angular dependence of resistivity of
K0.70(7)Fe1.55(7)Se1.01(2)S0.99(2) and K0.76(5)Fe1.61(5)Se0.96(4)S1.04(5)
single crystals. The upper critical fields Hc2(T) for both field directions
decrease with the increase in S content. On the other hand, the angle-dependent
magnetoresistivity for both compounds can be scaled onto one curve using the
anisotropic Ginzburg-Landau theory. The obtained anisotropy of Hc2(T) increases
with S content, implying that S doping might decrease the dimensionality of
certain Fermi surface parts, leading to stronger two dimensional character.",1104.2318v2
2012-03-10,Large thermal Hall coefficient in bismuth,"We present a systematical study of thermal Hall effect on a bismuth single
crystal by measuring resistivity, Hall coefficient, and thermal conductivity
under magnetic field, which shows a large thermal Hall coefficient comparable
to the largest one in a semiconductor HgSe. We discuss that this is mainly due
to a large mobility and a low thermal conductivity comparing theoretical
calculations, which will give a route for controlling heat current in
electronic devices.",1203.2237v1
2012-06-12,Evidence of Josephson-coupled superconducting regions at the interfaces of Highly Oriented Pyrolytic Graphite,"Transport properties of a few hundreds of nanometers thick (in the graphene
plane direction) lamellae of highly oriented pyrolytic graphite (HOPG) have
been investigated. Current-Voltage characteristics as well as the temperature
dependence of the voltage at different fixed input currents provide evidence
for Josephson-coupled superconducting regions embedded in the internal
two-dimensional interfaces, reaching zero resistance at low enough
temperatures. The overall behavior indicates the existence of superconducting
regions with critical temperatures above 100 K at the internal interfaces of
oriented pyrolytic graphite.",1206.2463v2
2012-06-20,Enhanced thermoelectric properties by Ir doping of PtSb2 with pyrite structure,"The effects of Ir doping on the thermoelectric properties of Pt1-xIrxSb2 (x =
0, 0.01, 0.03, and 0.1) with pyrite structure were studied. Measurements of
electrical resistivity rho, Seebeck coefficient S, and thermal conductivity
kappa were conducted. The results showed an abrupt change from semiconducting
behavior without Ir (x = 0) to metallic behavior at x = 0.01. The sample with x
= 0.01 exhibited large S and low rho, resulting in a maximum power factor
(S^2/rho) of 43 muW/cmK^2 at 400 K. The peculiar ""pudding mold""-type electronic
band dispersion could explain the enhanced thermoelectric properties in the
metallic state.",1206.4482v1
2012-06-28,Electron backscattering from stacking faults in SiC by means of \textit{ab initio} quantum transport calculations,"We study coherent backscattering phenomena from single and multiple stacking
faults (SFs) in 3C- and 4H-SiC within density functional theory quantum
transport calculations. We show that SFs give rise to highly dispersive bands
within both the valance and conduction bands that can be distinguished for
their enhanced density of states at particular wave number subspaces. The
consequent localized perturbation potential significantly scatters the
propagating electron waves and strongly increases the resistance for $n$-doped
systems. We argue that resonant scattering from SFs should be one of the
principal degrading mechanisms for device operation in silicon carbide.",1206.6600v1
2015-04-28,Optical loss by surface transfer doping in silicon waveguides,"We show that undoped silicon waveguides may suffer of up to 1.8 dB/cm
free-carrier absorption caused by improper surface passivation. To verify the
effects of free-carriers we apply a gate field to the waveguides. Smallest
losses correspond to higher electrical sheet resistances and are generally
obtained with non-zero gate fields. The presence of free carriers for zero gate
field is attributed to surface transfer doping. These results open new
perspectives for minimizing propagation losses in silicon waveguides and for
obtaining low-loss and highly conductive silicon films without applying a gate
voltage.",1504.07613v1
2015-07-04,Evidence for defect-mediated tunneling in hexagonal boron nitride-based junctions,"We investigate tunneling in metal-insulator-metal junctions employing few
atomic layers of hexagonal boron nitride (hBN) as the insulating barrier. While
the low-bias tunnel resistance increases nearly exponentially with barrier
thickness, subtle features are seen in the current-voltage curves, indicating
marked influence of the intrinsic defects present in the hBN insulator on the
tunneling transport. In particular, single electron charging events are
observed, which are more evident in thicker-barrier devices where direct
tunneling is substantially low. Furthermore, we find that annealing the devices
modifies the defect states and hence the tunneling signatures.",1507.01058v1
2015-07-13,Defect induced structural and thermoelectric properties of Sb2Te3 alloy,"Structural and thermoelectric properties of metallic and semiconducting
Sb2Te3 are reported. X-Ray diffraction and Raman spectroscopy studies reveal
that semiconducting sample have higher defect density. Nature and origin of
possible defects are highlighted. Semiconducting Sb2Te3 hosts larger numbers of
defects, which act as scattering center and give rise to the increased value of
resistivity, thermopower and power factor. Thermopower data indicates p-type
nature of the synthesized samples. It is evidenced that the surface states are
often mixed with the bulk state, giving rise to metallicity in Sb2Te3. Role of
different scattering mechanism on the thermoelectric property of Sb2Te3 is
discussed.",1507.03337v1
2015-07-22,Theoretical Study of Coulomb Correlations and Spin-Orbit Coupling in SrIrO3,"Given that energy scales associated with crystal field splitting, spin orbit
coupling and coulomb correlations in iridates are comparable, hence leading to
exotic properties, we investigate the physical properties of orthorhombic
SrIrO3 using density functional theory. Our calculations, however, show that
SrIrO 3 is a bad metal with no long range magnetic ordering, unlike its sister
compounds Sr2IrO4 and Sr3Ir2O7. Moreover, despite having large band width, it
appears conclusive that the larger resistivity in SrIrO 3 is due to spin orbit
interactions. Besides, the effects of electron-electron correlations on its
electronic structure and magnetic properties are also discussed.",1507.06058v1
2016-09-21,Spin Hall magnetoresistance in antiferromagnet/normal metal bilayers,"We predict the emergence of spin Hall magnetoresistance in a magnetic bilayer
composed of a normal metal adjacent to an antiferromagnet. Based on a recently
derived drift-diffusion equation, we show that the resistance of the bilayer
depends on the relative angle between the direction transverse to the current
flow and the N\'eel order parameter. Although this effect presents striking
similarities with the spin Hall magnetoresistance recently reported in
ferromagnetic bilayers, in the present case its physical origin is attributed
to the anisotropic spin relaxation of itinerant spins in the antiferromagnet.",1609.06521v1
2018-12-26,Probing the Relationship between Anisotropic Magnetoresistance and Magnetization of ferromagnetic films,"The anisotropic magnetoresistance (AMR) in thin permalloy strips was
calculated at each steps during magnetization by the finite element method. The
magnetization at equilibrium under different external fields was obtained by
micromagnetic simulations, while the resistance with different magnetization
was obtained by solving the Poisson equations iteratively until
self-consistence. We find that the relation between magnetization and AMR
deviates from the Stoner-Wohlfarth prediction when the magnetization is reduced
from saturation. The reason is that the demagnetization is not necessarily from
coherent rotation of the magnetic moment. We conclude that it is necessary to
use numeric simulations to optimize the responses of AMR sensors.",1812.10294v1
2019-03-02,Reconfigurable Electromagnetic Structures: X-Band and Beyond,"Developing reconfigurable millimeter-wave (mmWave) antennas and devices is an
outstanding challenge, with switch technologies being a primary impediment.
Recently, it has been shown that vanadium dioxide (VO2), a thermochromic
material whose resistance changes with temperature, could provide a path
forward in developing reconfigurable mmWave devices. As an initial step towards
this vision, we investigate the integration of VO2 switches in reconfigurable
components at 15 GHz. In particular, a frequency reconfigurable antenna and a
reconfigurable phase shifter are shown. The low loss and minimal parasitics of
VO2 technology have the potential to enable devices at 15 GHz and beyond.",1906.03034v1
2019-06-18,The Poole-Frenkel laws and a pathway to multi-valued memory,"We revisit the mechanism of Poole-Frenkel non-ohmic conduction in materials
of non-volatile memory. Percolation theory is shown to explain both the Poole
and Frenkel dependencies corresponding to the cases of respectively small and
large samples compared to the correlation radii of their percolation clusters.
The applied bias modifies a limited number of microscopic resistances forming
the percolation pathways. That understanding opens a pathway to multi-valued
non-volatile memory and related neural network applications.",1906.07677v2
2019-11-06,Disclosing antiferromagnetism in tetragonal Cr2O3 by electrical measurements,"The tetragonal phase of chromium (III) oxide, although unstable in the bulk,
can be synthesized in epitaxial heterostructures. The theoretical investigation
by density functional theory predicts an antiferromagnetic ground state for
this compound. We demonstrate experimentally antiferromagnetism up to 40 K in
ultrathin films of t-Cr2O3 by electrical measurements exploiting interface
effect within a neighboring ultrathin Pt layer. We show that magnetotransport
in Pt is affected by both spin-Hall magnetoresistance and magnetic proximity
effect while we exclude any role of magnetism for the low-temperature
resistance anomaly observed in Pt.",1911.02596v1
2020-06-14,Ideal memristor based on viscous magnetization dynamics driven by spin torque,"We show that ideal memristors - devices whose resistance is proportional to
the charge that flows through them - can be realized using spin torque-driven
viscous magnetization dynamics. The latter can be accomplished in the spin
liquid state of thin-film heterostructures with frustrated exchange, where
memristive response is tunable by proximity to the glass transition, while
current-induced Joule heating facilitates nonvolatile operation and
second-order memristive functionality beneficial for neuromorphic applications.
Ideal memristive behaviors can be achieved in other systems characterized by
viscous dynamics of physical, electronic, or magnetic degrees of freedom.",2006.07996v1
2020-08-17,Surface Conductivity in Antiferromagnetic Semiconductor CrSb$_2$,"The contribution of bulk and surface to the electrical resistance along
crystallographic \textit{b}- and \textit{c}-axes as a function of crystal
thickness gives evidence for a temperature independent surface states in an
antiferromagnetic narrow-gap semiconductor CrSb$_{2}$. ARPES shows a clear
electron-like pocket at $\Gamma$-$Z$ direction which is absent in the bulk band
structure. First-principles calculations also confirm the existence of metallic
surface states inside the bulk gap. Whereas combined experimental probes point
to enhanced surface conduction similar to topological insulators, surface
states are trivial since CrSb$_2$ exhibits no band inversion.",2008.07521v1
2020-08-23,Rigidity and fracture of fibrous double networks,"Tunable mechanics and fracture resistance are hallmarks of biological tissues
and highly desired in engineered materials. To elucidate the underlying
mechanisms, we study a rigidly percolating double network (DN) made of a stiff
and a flexible network. The DN shows remarkable tunability in mechanical
response when the stiff network is just above its rigidity percolation
threshold and minimal changes far from this threshold. Further, the DN can be
modulated to either be extensible, breaking gradually, or stronger, breaking in
a more brittle fashion by varying the flexible network's concentration.",2008.09934v1
2020-12-23,"Superconducting properties of the non-centrosymmetric Superconductors TaXSi (X= Re, Ru)","We have investigated the ternary noncentrosymmetric superconductors TaXSi
(X=Re, Ru) by magnetization, resistivity, and specific heat measurements. The
samples crystallize in orthorhombic TiFeSi structure having superconducting
transition Tc = 5.32 K and 3.91 K, for TaReSi and TaRuSi respectively. Specific
heat measurements indicated an s-wave nature of both materials with a
moderately coupled nature. However, a low value of specific heat jump and the
concave nature of the upper critical field suggests a nontrivial
superconducting gap.",2012.12596v1
2021-01-30,Nearly ideal memristive functionality based on viscous magnetization dynamics,"We experimentally demonstrate a proof-of-principle implementation of an
almost ideal memristor - a two-terminal circuit element whose resistance is
approximately proportional to the integral of the input signal over time. The
demonstrated device is based on a thin-film ferromagnet/antiferromagnet
bilayer, where magnetic frustration results in viscous magnetization dynamics
enabling memristive functionality, while the external magnetic field plays the
role of the driving input. The demonstrated memristor concept is amenable to
downscaling and can be adapted for electronic driving, making it attractive for
applications in neuromorphic circuits.",2102.00123v1
2021-09-18,Berry curvature induced nonlinear magnetoresistivity in two dimensional systems,"The band geometric properties of quantum materials play an elemental role in
the linear and nonlinear transport of electrons. In this paper, we propose that
the interplay of the Berry curvature, the orbital magnetic moment and the
Lorentz force can induce a finite nonlinear resistivity in two dimensional
systems in presence of a perpendicular magnetic field. The induced nonlinear
magnetoresistivity scales linearly with the magnetic field and is purely
quantum mechanical in origin. This novel transport signature can be used as an
additional experimental probe for the geometric quantities in intrinsically
time reversal symmetric systems.",2109.08979v2
2021-10-28,Prandtl-Tietjens intermittency in transitional pipe flows,"Pipe flow often traverses a regime where laminar and turbulent flow co-exist.
Prandtl and Tietjens explained this intermittency as a feedback between the
fluctuations of the internal flow resistance and the constant pressure drop
driving the flow. However, because the focus has moved towards studying
intermittency without flow fluctuations near the universal critical Reynolds
number, their explanation has largely disappeared. Here we refine the
mechanism, which has never been put to a quantitative test, to develop a model
that agrees with experiments at higher Reynolds numbers, enabling us to
demonstrate that Prandtl and Tietjens' mechanism is, in fact, intrinsic to
flows where both the pressure gradient and perturbation are constant.",2110.14983v2
2021-11-09,Lattice structure design optimization under localized linear buckling constraints,"An optimization method for the design of multi-lattice structures satisfying
local buckling constraints is proposed in this paper. First, the concept of
free material optimization is introduced to find an optimal elastic tensor
distribution among all feasible elastic continua. By approximating the elastic
tensor under the buckling-containing constraint, a matching lattice structure
is embedded in each macro element. The stresses in local cells are especially
introduced to obtain a better structure. Finally, the present method obtains a
lattice structure with excellent overall stiffness and local buckling
resistance, which enhances the structural mechanical properties.",2111.05294v1
2021-11-16,Have Mysterious Topological Valley Currents Been Observed in Graphene Superlattices?,"We provide a critical discussion concerning the claim of topological valley
currents, driven by a global Berry curvature and valley Hall effect proposed in
recent literature. After pointing out a major inconsistency of the theoretical
scenario proposed to interpret giant nonlocal resistance, we discuss various
possible alternative explanations and open directions of research to solve the
mystery of nonlocal transport in graphene superlattices.",2111.08506v1
2021-12-23,Metal Oxide Nanoparticles and Their Applications: A Report,"Herein, we report a brief introduction of metal oxide nanoparticles and their
diverse applications in different scientific and medical fields. This report
will be updated frequently to give a complete review in similar fields of
nanotechnology. In the present version of the report, an introduction to
nanotechnology and nanomaterials with some synthesis routes (such as
Hydrothermal synthesis and Sol-Gel synthesis etc.) to prepare the metal oxide
nanoparticles is given. In this version we have primarily included the basic
introduction of application of metal oxide nanoparticles in the fields of
biomedical, resistive switching and photovoltaic etc.",2201.04938v1
2022-04-14,Cohesive zone modelling of hydrogen assisted fatigue crack growth: the role of trapping,"We investigate the influence of microstructural traps in hydrogen-assisted
fatigue crack growth. To this end, a new formulation combining multi-trap
stress-assisted diffusion, mechanism-based strain gradient plasticity and a
hydrogen- and fatigue-dependent cohesive zone model is presented and
numerically implemented. The results show that the ratio of loading frequency
to effective diffusivity governs fatigue crack growth behaviour. Increasing the
density of \emph{beneficial} traps, not involved in the fracture process,
results in lower fatigue crack growth rates. The combinations of loading
frequency and carbide trap densities that minimise embrittlement susceptibility
are identified, providing the foundation for a rational design of
hydrogen-resistant alloys.",2204.07079v1
2022-06-10,Magneto-Seebeck coefficient of Fermi-liquid in three-dimensional Dirac/Weyl semimetal,"We investigate dissipationless magneto-Seebeck effect in three-dimensional
Dirac/Weyl semimetal. The Hall resistivity $\rho_{yx}$ and thermoelectric Hall
coefficient $\alpha_{xy}$ exhibit plateaus at the quantum limit, where
electrons occupy only the zeroth Landau level. In this condition, quantum
oscillation in the Seebeck coefficient $S_{xx}\approx \rho_{yx}\alpha_{xy} $ is
suppressed, and the massless fermions are transformed into a Fermi liquid
system. We show that the Seebeck coefficient at the quantum limit is expressed
by the harmonic sum of Fermi wavelength and thermal de Broglie wavelength
scaled by magnetic length.",2206.04957v1
2022-06-13,LinReTraCe: The Linear Response Transport Centre,"We describe the ""Linear Response Transport Centre"" (LinReTraCe), a package
for the simulation of transport properties of solids. LinReTraCe captures
quantum (in)coherence effects beyond semi-classical Boltzmann techniques, while
incurring similar numerical costs. The enabling algorithmic innovation is a
semi-analytical evaluation of Kubo formulae for resistivities and the
coefficients of Hall, Seebeck and Nernst. We detail the program's architecture,
its interface and usage with electronic-structure packages such as WIEN2k,
VASP, and Wannier90, as well as versatile tight-binding settings.",2206.06097v2
2022-08-03,Electrical transport and magnetic properties of the triangular-lattice compound Zr$_2$NiP$_2$,"We report the first investigation of the electrical and magnetic properties
of the triangular-lattice compound Zr$_2$NiP$_2$ (space group $P$6$_3$/$mmc$).
The temperature evolution of electrical resistivity follows the
Bloch-Gr\""uneisen-Mott law, and exhibits a typically metallic behavior. No
transition is visible by both electrical and magnetic property measurements,
and nearly no magnetization is detected ($M_0$ $<$ 0.002$\mu_\mathrm{B}$/Ni)
down to 1.8 K up to 7 T. The metallic and nonmagnetic characters are well
understood by the first-principles calculations for Zr$_2$NiP$_2$.",2208.01799v1
2022-08-09,Rapid suppression of charge density wave transition in LaSb2 under pressure,"LaSb2 is found to be an example of an exceptionally pressure sensitive and
tunable, two dimensional compound. In-plane electrical resistivity of LaSb2
under pressure up to 12.9 kbar was measured in zero and applied magnetic field.
The charge density wave transition (observed at ~ 350 K at ambient pressure) is
completely suppressed by 6-7 kbar with significant (in comparison with the
ambient pressure) increase in Fermi surface gapping and transition hysteresis
just above ambient pressure.",2208.04997v1
2023-03-12,Pressure-induced color change in the lutetium dihydride LuH2,"The lutetium dihydride LuH2 is stable at ambient conditions. Here we show
that its color undergoes sequential changes from dark blue at ambient pressure
to pink at ~2.2 GPa and then to bright red at ~4 GPa upon compression in a
diamond anvil cell. Such a pressure-induced color change in LuH2 is reversible
and it is very similar to that recently reported in the N-doped lutetium
hydride. However, our preliminary resistance measurements on LuH2 under
pressures up to 7.7 GPa evidenced no superconductivity down to 1.5 K.",2303.06718v1
2023-06-27,Enhancing interfacial thermal conductance of amorphous interface by optimized interfacial mass distribution,"Interfacial thermal resistance arises challenges for the thermal management
as the modern semiconductors are miniatured to nanoscale. Previous studies
found that graded mass distribution in interface can maximumly enhance the
interfacial thermal conductance of crystalline interface, however, whether this
strategy is effective for amorphous interface is less explored. In this work,
graded mass distribution in the amorphous interface between crystalline Si and
crystalline Ge is optimized to increase the interfacial thermal conductance by
the extended atomistic Greens function method.",2306.15254v1
2023-06-30,Magnetotransport in Weyl semimetal WTe2 single crystal,"A WTe2 single crystal was grown by the chemical vapor transport method, and
its electrical resistivity and galvanomagnetic properties were investigated.
Single-band and two-band models were used to estimate the concentration and
mobility of charge carriers in WTe2 at temperatures from 4.2 to 150 K.",2307.08676v1
2023-09-22,Using superconductivity to control magnetism: a facet of superconducting spintronics,"Magnets are used in electronics to store and read information. A magnetic
moment is rotated to a desired direction, so that information can later be
retrieved by reading this orientation. Controlling the moment via electric
currents causes resistive losses and heating, a major bottleneck in advancing
computing technologies. Superconducting spintronics can resolve this using the
unique features of superconductors.",2309.12836v1
2024-04-19,Ca substituion instead of Sr in La$_{0.58}$Sr$_{0.4}$Co$_{0.2}$Fe$_{0.8}$O$_{3-δ}$ as a cathode electrode for IT-SOFCs,"La$_{0.58}$Ca$_{0.4}$Co$_{0.2}$Fe$_{0.8}$O$_{3-\delta}$ (L58CCF) was
synthesized and evaluated as a cathode electrode for intermediate temperature
solid oxide fuel cells (IT-SOFC) based on the Y$_2$O$_3$-stabilized ZrO$_2$
(YSZ) electrolyte. The effect of sintering temperature on the L58CCF
performance was investigated. The best Area specific resistances (ASRs) for the
L58CCF sintered at 950 $^{\circ}$C were 1.218, 0.447, 0.228, 0.156, 0.099
$\Omega.cm^{2}$ at 600, 650, 700, 750, 800 $^{\circ}$C, respectively.",2404.12972v1
2024-04-25,Hall response in interacting bosonic and fermionic ladders,"We use bosonization, retaining band curvature terms, to analyze the Hall
response of interacting bosonic and fermionic two-leg ladders threaded by a
flux. We derive an explicit expression of the Hall imbalance in a perturbative
expansion in the band curvature, retaining fully the interactions. We show that
the flux dependence of the Hall imbalance allows to distinguish the two phases
(Meissner and Vortex) that are present for a bosonic ladder. For small magnetic
field we relate the Hall resistance, both for bosonic and fermionic ladders, to
the density dependence of the charge sitffness of the system in absence of
flux. Our expression unveil a universal interaction-independent behavior in the
Galilean invariant case.",2404.16973v1
2004-07-18,Kubo formula for Floquet states and photoconductivity oscillations in a 2D electron gas,"The recent discovery of the microwave induced vanishing resistance states in
a two dimensional electron system (2DES) is an unexpected and surprising
phenomena. In these experiments the magnetoresistance of a high mobility 2DES
under the influence of microwave radiation of frequency $\omega$ at moderate
values of the magnetic field, exhibits strong oscillations with zero-resistance
states (ZRS) governed by the ratio $\omega /\omega_c$, where $\omega_c$ is the
cyclotron frequency. In this work we present a model for the photoconductivity
of a two dimensional electron system (2DES) subjected to a magnetic field. The
model includes the microwave and Landau contributions in a non-perturbative
exact way, impurity scattering effects are treated perturbatively. In our
model, the Landau-Floquet states act coherently with respect to the oscillating
field of the impurities, that in turn induces transitions between these levels.
Based on this formalism, we provide a Kubo-like formula that takes into account
the oscillatory Floquet structure of the problem. We study the effects of both
short-range and long-range disorder on the photoconductivity. Our calculation
yields a magnetoresistance oscillatory behavior with the correct period and
phase. It is found that, in agreement with experiment, negative dissipation can
only be induced in very high mobility samples. We analyze the dependence of the
results on the microwave power and polarization. For high-intensity radiation
multi-photon processes take place predicting new negative-resistance states
centered at $ \omega / \omega_c=1/2$, and $ \omega / \omega_c= 3/2$.",0407468v3
2021-11-22,"Characterization of the (Cu,C)Ba$_2$Ca$_3$Cu$_4$O$_{11+δ}$ single crystals grown under high pressure","By using high pressure and high temperature (3.7 GPa, 1120 $^{\circ}$C)
synthesis technique, we have grown (Cu,C)Ba$_2$Ca$_3$Cu$_4$O$_{11+\delta}$
single crystals. X-ray diffraction, scanning electron microscopy, resistivity
and magnetization measurements are carried out and all show that the samples
have good quality. The single crystal has onset and zero-resistance transition
temperatures of about 111 K and 109.6 K, indicating a very narrow transition
width, which is consistent with a rather sharp magnetization transition.
Magnetization hysteresis loops (MHLs) are also measured, showing a pronounced
second peak effect in the intermediate temperature region. The magnetic
critical current density calculated from the MHLs at 77 K and 1.5 T is about
6.4$\times$10$^4$ A/cm$^2$. By using a criterion of 1$\%$ normal state
resistivity, we have determined the irreversibility line which exhibits an
irreversibility field of about 8 T at 77 K. Compared with other layered
systems, it is easy to find that the irreversibility line is rather high and
could be further improved with the optimized transition temperature of about
118 K as previously discovered in polycrystalline samples.",2111.11255v1
2022-11-28,Non-linear Transport Phenomena and Current-induced Hydrodynamics in Ultra-high Mobility Two-dimensional Electron Gas,"We report on non-linear transport phenomena at high filling factor and DC
current-induced electronic hydrodynamics in an ultra-high mobility (mu=20x10^6
cm^2/Vs) two-dimensional electron gas in a narrow (15 micron wide) GaAs/AlGaAs
Hall bar for DC current densities reaching 0.67 A/m. The various phenomena and
the boundaries between the phenomena are captured together in a two-dimensional
differential resistivity map as a function of magnetic field (up to 250 mT) and
DC current. This map, which resembles a phase diagram, demarcate distinct
regions dominated by Shubnikov-de Haas (SdH) oscillations (and phase inversion
of these oscillations) around zero DC current; negative magnetoresistance and a
double-peak feature (both ballistic in origin) around zero field; and Hall
field-induced resistance oscillations (HIROs) radiating out from the origin.
From a detailed analysis of the data near zero field, we show that increasing
the DC current suppresses the electron-electron scattering length that drives a
growing hydrodynamic contribution to both the differential longitudinal and
transverse (Hall) resistivities. Our approach to induce hydrodynamics with DC
current differs from the more usual approach of changing the temperature. We
also find a significant (factor of two to four) difference between the quantum
lifetime extracted from SdH oscillations, and the quantum lifetime extracted
from HIROs. In addition to observing HIRO peaks up to the seventh order, we
observe an unexpected HIRO-like feature close to mid-way between the
first-order and the second-order HIRO maxima at high DC current.",2211.15551v1
2023-06-27,Investigation of high resistivity p-type FZ silicon diodes after 60Co γ-irradiation,"In this work, the effects of $^\text{60}$Co $\gamma$-ray irradiation on high
resistivity $p$-type diodes have been investigated. The diodes were exposed to
dose values of 0.1, 0.2, 1, and \SI{2}{\mega Gy}. Both macroscopic ($I$--$V$,
$C$--$V$) and microscopic (Thermally Stimulated Current~(TSC)) measurements
were conducted to characterize the radiation-induced changes. The investigated
diodes were manufactured on high resistivity $p$-type Float Zone (FZ) silicon
and were further classified into two types based on the isolation technique
between the pad and guard ring: $p$-stop and $p$-spray. After irradiation, the
macroscopic results of current-voltage and capacitance-voltage measurements
were obtained and compared with existing literature data. Additionally, the
microscopic measurements focused on the development of the concentration of
different radiation-induced defects, including the boron interstitial and
oxygen interstitial (B$_\text{i}$O$_\text{i}$) complex, the carbon interstitial
and oxygen interstitial C$_\text{i}$O$_\text{i}$ defect, the H40K, and the
so-called I$_\text{P}^*$. To investigate the thermal stability of induced
defects in the bulk, isochronal annealing studies were performed in the
temperature range of \SI{80}{\celsius} to \SI{300}{\celsius}. These annealing
processes were carried out on diodes irradiated with doses of 1 and
\SI{2}{\mega Gy} and the corresponding TSC spectra were analysed. Furthermore,
in order to investigate the unexpected results observed in the $C$-$V$
measurements after irradiation with high dose values, the surface conductance
between the pad and guard ring was measured as a function of both dose and
annealing temperature.",2306.15336v1
2009-06-30,Viscous and Resistive Effects on the MRI with a Net Toroidal Field,"Resistivity and viscosity have a significant role in establishing the energy
levels in turbulence driven by the magnetorotational instability (MRI) in local
astrophysical disk models. This study uses the Athena code to characterize the
effects of a constant shear viscosity \nu and Ohmic resistivity \eta in
unstratified shearing box simulations with a net toroidal magnetic flux. A
previous study of shearing boxes with zero net magnetic field performed with
the ZEUS code found that turbulence dies out for values of the magnetic Prandtl
number, P_m = \nu/\eta, below P_m \sim 1; for P_m \gtrsim 1, time- and
volume-averaged stress levels increase with P_m. We repeat these experiments
with Athena and obtain consistent results. Next, the influence of viscosity and
resistivity on the toroidal field MRI is investigated both for linear growth
and for fully-developed turbulence. In the linear regime, a sufficiently large
\nu or \eta can prevent MRI growth; P_m itself has little direct influence on
growth from linear perturbations. By applying a range of values for \nu and
\eta to an initial state consisting of fully developed turbulence in the
presence of a background toroidal field, we investigate their effects in the
fully nonlinear system. Here, increased viscosity enhances the turbulence, and
the turbulence decays only if the resistivity is above a critical value;
turbulence can be sustained even when P_m < 1, in contrast to the zero net
field model. While we find preliminary evidence that the stress converges to a
small range of values when \nu and \eta become small enough, the influence of
dissipation terms on MRI-driven turbulence for relatively large \eta and \nu is
significant, independent of field geometry.",0906.5352v2
2010-06-10,$c$-axis charge gap and its critical point in the heavily doped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$,"Temperature-dependent inter-plane resistivity, $\rho _c(T)$, was used to
characterise the normal state of the iron-arsenide superconductor
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ over a broad doping range $0\leq x<0.50$. The
data were compared with in-plane resistivity, $\rho _a(T)$, and magnetic
susceptibility, $\chi (T)$, taken in $H \bot c$, as well as Co NMR Knight
shift, $^{59}K$, and spin relaxation rate, $1/T_1T$. The inter-plane
resistivity data show a clear correlation with the NMR Knight shift, assigned
to the formation of the pseudo-gap. Evolution of $\rho _c(T)$ with doping
reveals two characteristic energy scales. The temperature of the cross-over
from non-metallic, increasing on cooling, behavior of $\rho _c(T)$ at
high-temperatures to metallic behavior at low temperatures, $T^*$, correlates
well with an anomaly in all three magnetic measurements. This characteristic
temperature, equal to approximately 200~K in the parent compound, $x$=0,
decreases with doping and vanishes near $x^* \approx$0.25. For doping levels $x
\geq 0.166$, an additional feature appears above $T^*$, with metallic behavior
of $\rho _c (T)$ found above the low-temperature resistivity increase. The
characteristic temperature of this charge-gap formation, $T_{\rm CG}$, vanishes
at $x_{\rm CG} \simeq$0.30, paving the way to metallic, $T$-linear, $\rho_c
(T)$ close to $x_{\rm CG}$ and super-linear $T$-dependence for $x>x_{\rm CG}$.
None of these features are evident in the in-plane resistivity $\rho_a(T)$. For
doping levels $x <x_{\rm CG}$, $\chi (T)$ shows a known, anomalous, $T$-linear
dependence, which disappears for $x>x_{\rm CG}$.",1006.2087v1
2011-03-22,Phase Diagram of Pressure-Induced Superconductivity in EuFe2As2 Probed by High-Pressure Resistivity up to 3.2 GPa,"We have constructed a pressure$-$temperature ($P-T$) phase diagram of
$P$-induced superconductivity in EuFe$_2$As$_2$ single crystals, via
resistivity ($\rho$) measurements up to 3.2 GPa. As hydrostatic pressure is
applied, an antiferromagnetic (AF) transition attributed to the FeAs layers at
$T_\mathrm{0}$ shifts to lower temperatures, and the corresponding resistive
anomaly becomes undetectable for $P$ $\ge$ 2.5 GPa. This suggests that the
critical pressure $P_\mathrm{c}$ where $T_\mathrm{0}$ becomes zero is about 2.5
GPa. We have found that the AF order of the Eu$^{2+}$ moments survives up to
3.2 GPa without significant changes in the AF ordering temperature
$T_\mathrm{N}$. The superconducting (SC) ground state with a sharp transition
to zero resistivity at $T_\mathrm{c}$ $\sim$ 30 K, indicative of bulk
superconductivity, emerges in a pressure range from $P_\mathrm{c}$ $\sim$ 2.5
GPa to $\sim$ 3.0 GPa. At pressures close to but outside the SC phase, the
$\rho(T)$ curve shows a partial SC transition (i.e., zero resistivity is not
attained) followed by a reentrant-like hump at approximately $T_\mathrm{N}$
with decreasing temperature. When nonhydrostatic pressure with a uniaxial-like
strain component is applied using a solid pressure medium, the partial
superconductivity is continuously observed in a wide pressure range from 1.1
GPa to 3.2 GPa.",1103.4209v4
2017-06-13,Understanding breaks in solar flares x-ray spectra: Evaluation of a co-spatial return-current model,"Hard x-ray spectral breaks are explained in terms of a 1D model with a
co-spatial return current. We study 19 flares observed by RHESSI (Ramaty High
Energy Solar Spectroscopic Imager) with strong spectral breaks at energies
around a few deka-keV, that cannot be explained by isotropic albedo or
non-uniform ionization alone. We identify these breaks at the HXR peak time,
but we obtain 8 s-cadence spectra of the entire impulsive phase. Electrons with
an initially power-law distribution and a sharp low-energy cutoff lose energy
through return-current losses until they reach the thick target, where they
lose their remaining energy through collisions. Our main results are: (1) The
return-current collisional thick-target model (RCCTTM) provides acceptable fits
for spectra with strong breaks. (2) Limits on the plasma resistivity are
derived from the fitted potential drop and deduced electron-beam flux density,
assuming the return-current is a drift current in the ambient plasma. These
resistivities are typically 2-3 orders of magnitude higher than the Spitzer
resistivity at the fitted temperature, and provide a test for the adequacy of
classical resistivity and the stability of the return current. (3) Using the
upper limit of the low-energy cutoff, the return current is always stable to
the generation of ion acoustic and electrostatic ion cyclotron instabilities
when the electron temperature is lower than 9 times the ion temperature. (4) In
most cases the return current is most likely primarily carried by runaway
electrons from the tail of the thermal distribution rather than the bulk
drifting thermal electrons. For these cases, anomalous resistivity is not
required.",1706.03897v2
2018-01-09,Structure Entropy and Resistor Graphs,"We propose the notion of {\it resistance of a graph} as an accompanying
notion of the structure entropy to measure the force of the graph to resist
cascading failure of strategic virus attacks. We show that for any connected
network $G$, the resistance of $G$ is
$\mathcal{R}(G)=\mathcal{H}^1(G)-\mathcal{H}^2(G)$, where $\mathcal{H}^1(G)$
and $\mathcal{H}^2(G)$ are the one- and two-dimensional structure entropy of
$G$, respectively. According to this, we define the notion of {\it security
index of a graph} to be the normalized resistance, that is, $\theta
(G)=\frac{\mathcal{R}(G)}{\mathcal{H}^1(H)}$. We say that a connected graph is
an $(n,\theta)$-{\it resistor graph}, if $G$ has $n$ vertices and has security
index $\theta (G)\geq\theta$. We show that trees and grid graphs are
$(n,\theta)$-resistor graphs for large constant $\theta$, that the graphs with
bounded degree $d$ and $n$ vertices, are $(n,\frac{2}{d}-o(1))$-resistor
graphs, and that for a graph $G$ generated by the security model
\cite{LLPZ2015, LP2016}, with high probability, $G$ is an $(n,\theta)$-resistor
graph, for a constant $\theta$ arbitrarily close to $1$, provided that $n$ is
sufficiently large. To the opposite side, we show that expander graphs are not
good resistor graphs, in the sense that, there is a global constant
$\theta_0<1$ such that expander graphs cannot be $(n,\theta)$-resistor graph
for any $\theta\geq\theta_0$. In particular, for the complete graph $G$, the
resistance of $G$ is a constant $O(1)$, and hence the security index of $G$ is
$\theta (G)=o(1)$. Finally, we show that for any simple and connected graph
$G$, if $G$ is an $(n, 1-o(1))$-resistor graph, then there is a large $k$ such
that the $k$-th largest eigenvalue of the Laplacian of $G$ is $o(1)$, giving
rise to an algebraic characterization for the graphs that are secure against
intentional virus attack.",1801.03404v1
2017-12-13,Increased hepatic PDGF-AA signaling mediates liver insulin resistance in obesity associated type 2 diabetes,"Type 2 diabetes (T2D) is closely linked with non-alcoholic fatty liver
disease (NAFLD) and hepatic insulin resistance, but the involved mechanisms are
still elusive. Using DNA methylome and transcriptome analyses of livers from
obese individuals, we found that both hypomethylation at a CpG site in PDGFA
(encoding platelet derived growth factor alpha) and PDGFA overexpression are
associated with increased T2D risk, hyperinsulinemia, increased insulin
resistance and increased steatohepatitis risk. Both genetic risk score studies
and human cell modeling pointed to a causative impact of high insulin levels on
PDGFA CpG site hypomethylation, PDGFA overexpression, and increased PDGF-AA
secretion from liver. We found that PDGF-AA secretion further stimulates its
own expression through protein kinase C activity and contributes to insulin
resistance through decreased expression of both insulin receptor substrate 1
and of insulin receptor. Importantly, hepatocyte insulin sensitivity can be
restored by PDGF-AA blocking antibodies, PDGF receptor inhibitors and by
metformin opening therapeutic avenues. Conclusion: Therefore, in the liver of
obese patients with T2D, the increased PDGF-AA signaling contributes to insulin
resistance, opening new therapeutic avenues against T2D and NAFLD.",1712.04680v1
2022-09-22,Deep learning based sferics recognition for AMT data processing in the dead band,"In the audio magnetotellurics (AMT) sounding data processing, the absence of
sferic signals in some time ranges typically results in a lack of energy in the
AMT dead band, which may cause unreliable resistivity estimate. We propose a
deep convolutional neural network (CNN) to automatically recognize sferic
signals from redundantly recorded data in a long time range and use them to
compensate for the resistivity estimation. We train the CNN by using field time
series data with different signal to noise rations that were acquired from
different regions in mainland China. To solve the potential overfitting problem
due to the limited number of sferic labels, we propose a training strategy that
randomly generates training samples (with random data augmentations) while
optimizing the CNN model parameters. We stop the training process and data
generation until the training loss converges. In addition, we use a weighted
binary cross-entropy loss function to solve the sample imbalance problem to
better optimize the network, use multiple reasonable metrics to evaluate
network performance, and carry out ablation experiments to optimally choose the
model hyperparameters. Extensive field data applications show that our trained
CNN can robustly recognize sferic signals from noisy time series for subsequent
impedance estimation. The subsequent processing results show that our method
can significantly improve S/N and effectively solve the problem of lack of
energy in dead band. Compared to the traditional processing method without
sferic compensation, our method can generate a smoother and more reasonable
apparent resistivity-phase curves and depolarized phase tensor, correct the
estimation error of sudden drop of high-frequency apparent resistivity and
abnormal behavior of phase reversal, and finally better restore the real
shallow subsurface resistivity structure.",2209.13647v1
2023-02-23,Differential Multi-probe Thermal Transport Measurements of Multi-walled Carbon Nanotubes grown by Chemical Vapor Deposition,"Carbon nanotubes (CNTs) are quasi-1D nanostructures that display both high
thermal conductivity and intriguing low-dimensional phonon transport phenomena.
In comparison to the advances made in the theoretical calculation of the
lattice thermal conductivity of CNTs, thermal transport measurements of CNTs
have been limited by either the poor temperature sensitivity of Raman
thermometry technique or the presence of contact thermal resistance errors in
sensitive two-probe resistance thermometry measurements. Here we report
advances in a multi-probe measurement of the intrinsic thermal conductivity of
individual multi-walled CNT samples that are transferred from the growth
substrate onto the measurement device. The sample-thermometer thermal interface
resistance is directly measured by this multi-probe method and used to model
the temperature distribution along the contacted sample segment. The detailed
temperature profile helps to eliminate the contact thermal resistance error in
the obtained thermal conductivity of the suspended sample segment. A
differential electro-thermal bridge measurement method is established to
enhance the signal-to-noise ratio and reduce the measurement uncertainty by
over 40%. The obtained thermal resistances of multiple suspended segments of
the same MWCNT sample increase linearly with increasing length, revealing
diffusive phonon transport as a result of phonon-defect scattering in these
MWCNTs. The measured thermal conductivity increases with temperature and
reaches up to 390+- 20 W m-1 K-1 at room temperature for a 9-walled MWCNT.
Theoretical analysis of the measurement results suggests submicron phonon mean
free paths due to extrinsic phonon scattering by extended defects such as grain
boundaries. The obtained thermal conductivity is decreased by a factor of 3
upon electron beam damage and surface contamination of the CNT sample.",2302.11778v4
2024-05-27,Even- and Odd-denominator Fractional Quantum Anomalous Hall Effect in Graphene Moire Superlattices,"Fractional quantum anomalous hall effect (FQAHE), a transport effect with
fractionally quantized Hall plateau emerging under zero magnetic field,
provides a radically new opportunity to engineer topological quantum
electronics. By construction of topological flat band with moire engineering,
intrinsic FQAHE has been observed in twisted MoTe2 system and rhombohedral
pentalayer graphene/hBN moire superlattices with anomalous Hall resistivity
quantization number C <= 2/3 including the gapless composite Fermi-liquid state
with C = 1/2. Here we experimentally demonstrate a new system of rhombohedral
hexalayer graphene (RHG)/hBN moire superlattices showing both fractional and
integer quantum anomalous Hall effects when the lowest flat Chern band is
fractionally and fully filled at zero magnetic field. The zero-field Hall
resistance Rho_xy = h/Ce2 is quantized to values corresponding to C = 3/5, 2/3,
5/7, 3/4, 7/9 and 1 at moire filling factors v = 3/5, 2/3, 5/7, 3/4, 7/9 and 1,
respectively. Particularly, the C = 3/4 FQAHE state at v = 3/4 moire filling
featuring a minimum of longitudinal resistance Rho_xx and fractionally
quantized Hall resistance Rho_xy = 4h/3e2, is observed for the first time under
zero magnetic field. Such a state may be similar to the C = 3/4 fractional
quantum hall (FQHE) state recently observed at high magnetic fields9,10 and
possibly host fractional charge excitations obeying non-Abelian statistics. By
tuning the electrical and magnetic fields at 0 < v < 1, we have observed a sign
reversal of the Hall resistivity for v = 2/3 state, indicating a transition
from quasi-electron-like excitations to quasi-hole ones. Our experiment has
established RHG/hBN moire superlattices a promising platform to explore
quasi-particles with fractional charge excitations and non-Abelian anyons at
zero magnetic field.",2405.16944v1
2023-08-04,Quench Risk Increase With Radiation Damage,"Superconducting magnets are often proposed to confine plasma in fusion
reactors. Superconducting material enables the magnets to carry current
densities that would melt materials with non-zero resistance. Quench occurs
when superconductivity is lost and the current starts to generate heat. Unless
prevented with a fast enough control system, the heat generated during a quench
can cause catastrophic damage to the coils. This work describes a less-studied
heating mechanism that increases the likelihood and aggressiveness of fusion
magnet quenches. Defects accumulate in the magnet structural material under
irradiation by the fusion process. The defects store energy in the material and
change thermal and normal state electrical properties. Wigner energy is
released when defects anneal. After a 0.9 mDPA neutron irradiation, a 10 K
disturbance from 20 K is predicted to release enough energy to result in a
final temperature of 40 K. Irradiation damage also reduces the quench time
constant by increasing normal state resistivity and thus Ohmic heating. The
continuous operation of a fusion reactor produces an increasingly unstable
thermodynamic system in superconducting magnets by changing electrical and
thermal properties with irradiation damage. The temperature margin between
operation and quench runaway reduces with irradiation. The next steps are to
include these observations in quench models and validate the predictions
experimentally. Implications of this work is felt by all fusion powerplant
projects planning to leverage superconducting magnets. Designs will recognize
this risk with more stringent specifications on quench control systems and
maximum duration of coil operation at cryogenic temperature between periodic
releases of Wigner energy to avoid catastrophic quench failures.",2308.03794v2
2024-03-09,New Directions for Thermoelectrics: A Roadmap from High-Throughput Materials Discovery to Advanced Device Manufacturing,"Thermoelectric materials, which can convert waste heat into electricity or
act as solid-state Peltier coolers, are emerging as key technologies to address
global energy shortages and environmental sustainability. However, discovering
materials with high thermoelectric conversion efficiency is a complex and slow
process. The emerging field of high-throughput material discovery demonstrates
its potential to accelerate the development of new thermoelectric materials
combining high efficiency and low cost. The synergistic integration of
high-throughput material processing and characterization techniques with
machine learning algorithms can form an efficient closed-loop process to
generate and analyze broad data sets to discover new thermoelectric materials
with unprecedented performances. Meanwhile, the recent development of advanced
manufacturing methods provides exciting opportunities to realize scalable,
low-cost, and energy-efficient fabrication of thermoelectric devices. This
review provides an overview of recent advances in discovering thermoelectric
materials using high-throughput methods, including processing,
characterization, and screening. Advanced manufacturing methods of
thermoelectric devices are also introduced to realize the broad impacts of
thermoelectric materials in power generation and solid-state cooling. In the
end, this paper also discusses the future research prospects and directions.",2403.05952v1
2023-07-28,Self-optimization wavelet-learning method for predicting nonlinear thermal conductivity of highly heterogeneous materials with randomly hierarchical configurations,"In the present work, we propose a self-optimization wavelet-learning method
(SO-W-LM) with high accuracy and efficiency to compute the equivalent nonlinear
thermal conductivity of highly heterogeneous materials with randomly
hierarchical configurations. The randomly structural heterogeneity,
temperature-dependent nonlinearity and material property uncertainty of
heterogeneous materials are considered within the proposed self-optimization
wavelet-learning framework. Firstly, meso- and micro-structural modeling of
random heterogeneous materials are achieved by the proposed computer
representation method, whose simulated hierarchical configurations have
relatively high volume ratio of material inclusions. Moreover,
temperature-dependent nonlinearity and material property uncertainties of
random heterogeneous materials are modeled by a polynomial nonlinear model and
Weibull probabilistic model, which can closely resemble actual material
properties of heterogeneous materials. Secondly, an innovative stochastic
three-scale homogenized method (STSHM) is developed to compute the macroscopic
nonlinear thermal conductivity of random heterogeneous materials. Background
meshing and filling techniques are devised to extract geometry and material
features of random heterogeneous materials for establishing material databases.
Thirdly, high-dimensional and highly nonlinear material features of material
databases are preprocessed and reduced by wavelet decomposition technique. The
neural networks are further employed to excavate the predictive models from
dimension-reduced low-dimensional data.",2307.15403v2
2002-09-19,"Magnetic Interactions and Transport in (Ga,Cr)As","The magnetic, transport, and structural properties of (Ga,Cr)As are reported.
Zincblende Ga$_{1-x}$Cr$_{x}$As was grown by low-temperature molecular beam
epitaxy (MBE). At low concentrations, x$\sim$0.1, the materials exhibit unusual
magnetic properties associated with the random magnetism of the alloy. At low
temperatures the magnetization M(B) increases rapidly with increasing field due
to the alignment of ferromagnetic units (polarons or clusters) having large
dipole moments of order 10-10$^2$$\mu_B$. A standard model of
superparamagnetism is inadequate for describing both the field and temperature
dependence of the magnetization M(B,T). In order to explain M(B) at low
temperatures we employ a distributed magnetic moment (DMM) model in which
polarons or clusters of ions have a distribution of moments. It is also found
that the magnetic susceptibility increases for decreasing temperature but
saturates below T=4 K. The inverse susceptibility follows a linear-T
Curie-Weiss law and extrapolates to a magnetic transition temperature
$\theta$=10 K. In magnetotransport measurements, a room temperature resistivity
of $\rho$=0.1 $\Omega$cm and a hole concentration of $\sim10^{20}$ cm$^{-3}$
are found, indicating that Cr can also act as a acceptor similar to Mn. The
resistivity increases rapidly for decreasing temperature below room
temperature, and becomes strongly insulating at low temperatures. The
conductivity follows exp[-(T$_1$/T)$^{1/2}$] over a large range of
conductivity, possible evidence of tunneling between polarons or clusters.",0209477v2
2011-03-24,Effect of hydrogen plasma treatment and oxygen deficiency on conducting properties of In$_2$O$_3$:Sn thin films,"Electrical conductivity, Hall effect and magnetoresistance of In$_2$O$_3$:Sn
thin films deposited on a glass substrates at different temperatures and oxygen
pressures, as well as the films treated in a hydrogen plasma, have been
investigated in the temperature range 1.5-300 K. The observed temperature
dependences of resistivity were typical for metallic transport of electrons
except temperature dependence of resistivity of the In$_2$O$_3$:Sn film
deposited in the oxygen deficient atmosphere. The electron concentration and
mobility for the film deposited at 230$^\circ$C was larger than that for the
film deposited nominally at room temperature. Short (5 minutes) treatment of
the films in hydrogen plasma leads to the enhancement of electrical
conductivity while longer (30 minute) treatment has the opposite effect. The
electrical measurements were accompanied by AFM and SEM studies of structural
properties, as well as by XPS analysis. Basic on structural and electrical
measurements we conclude the reduction process initiated by the hydrogen plasma
provides essential modification of the ITO films surface. At the same time,
electrical properties of the remaining (located beneath the surface layer)
parts of the ITO films remain mostly unchangeable. XPS analysis shows that
grown in situ oxygen deficient ITO films have enhanced DOS between the Fermi
level and the valence band edge. The extra localized states behave as acceptors
leading to a compensation of $n$-type ITO. That can explain lower $n$-type
conductivity in this material crossing over to a Mott-type hopping.",1103.4792v1
2011-06-14,Evaluation of nano-frictional and mechanical properties of a novel Langmuir-Blodgett monolayer/self-assembly monolayer composite structure,"A novel stearic acid (SA)/3-aminopropyltrethoxysilane (APS) composite
structure was fabricated using the combined method of the Langmuir-Blodgett
technique and self-assembly monolayer (SAM) technique. Its frictional, adhesive
properties and interface contact types between the atomic force microscope tip
and the samples were evaluated based on Amonton's laws and the general
Carpick's transition equation, respectively. The results showed that the
tip-sample contacts corresponded to the
Johnson-Kendall-Robert/Derjaguin-Muller-Toporov (DMT) transition model for
SiO2, APS-SAMs, and the unheated SA-APS composite structure, and for the heated
SA-APS bilayer to the DMT model. Frictional forces for the four samples were
linearly dependent on external loads at higher loads, and at lower loads they
were significantly affected by adhesive forces. Frictional and scratching tests
showed that the heated SA-APS composite structure exhibited the best
lubricating properties and adhesion resistance ability, and its wear resistance
capacity was greatly improved due to the binding-mode conversion from hydrogen
bonds to covalent bonds. Thus, this kind of composite bilayer might be
promising for applications in the lubrication of nano/microelectromechanical
systems. I.",1106.2596v1
2012-08-06,Weak antilocalization and disorder-enhanced electron interactions in crystalline GeSbTe,"Phase change materials can be reversibly switched between amorphous and
crystalline states and often show strong contrast in the optical and electrical
properties of these two phases. They are now in widespread use for optical data
storage, and their fast switching and a pronounced change of resistivity upon
crystallization are also very attractive for nonvolatile electronic data
storage. Nevertheless there are still several open questions regarding the
electronic states and charge transport in these compounds. In this work we
study electrical transport in thin metallic films of the disordered,
crystalline phase change material Ge$_1$Sb$_2$Te$_4$. We observe weak
antilocalization and disorder enhanced Coulomb interaction effects at low
temperatures, and separate the contributions of these two phenomena to the
temperature dependence of the resistivity, Hall effect, and magnetoresistance.
Strong spin-orbit scattering causes positive magnetoresistance at all
temperatures, and a careful analysis of the low-field magnetoresistance allows
us to extract the temperature dependent electron dephasing rate and study other
scattering phenomena. We find electron dephasing due to inelastic
electron-phonon scattering at higher temperatures, electron-electron scattering
dephasing at intermediate temperatures, and a crossover to weak temperature
dependence below 1 K.",1208.1104v2
2012-10-24,Temperature-composition Phase Diagrams for Ba1-xSrxFe2As2 and Ba0.5Sr0.5(Fe1-yCoy)2As2,"Single crystals of mixed alkaline earth metal iron arsenide materials of
Ba1-xSrxFe2As2 and Ba0.5Sr0.5(Fe1-yCoy)2As2 are synthesized via the self-flux
method. Ba1-xSrxFe2As2 display spin-density wave features (TN) at temperatures
intermediate to the parent materials, x = 0 and 1, with TN(x) following an
approximately linear trend. Cobalt doping of the 1 to 1 Ba:Sr mixture,
Ba0.5Sr0.5(Fe1-yCoy)2As2, results in a superconducting dome with maximum
transition temperature of TC = 19 K at y = 0.092, close to the maximum
transition temperatures observed in unmixed A(Fe1-yCoy)2As2; however, an
annealed crystal with y = 0.141 showed a TC increase from 11 to 16 K with a
decrease in Sommerfeld coefficient from 2.58(2) to 0.63(2) mJ/(K2 mol atom).
For the underdoped y = 0.053, neutron diffraction results give evidence that TN
and structural transition (To) are linked at 78 K, with anomalies observed in
magnetization, resistivity and heat capacity data, while a superconducting
transition at TC ~ 6 K is seen in resistivity and heat capacity data. Scanning
tunneling microscopy measurements for y = 0.073 give Dynes broadening factor of
1.15 and a superconducting gap of 2.37 meV with evidence of surface
inhomogeneity.",1210.6638v1
2012-11-19,The effect of simultaneous substitution on the electronic band structure and thermoelectric properties of Se-doped Co3SnInS2 with the Kagome lattice,"The thermoelectric properties and electronic band structures for Se-doped
Co3SnInS2 were examined. The parent compound of this material (Co3Sn2S2) has
two kinds of Sn sites (Sn1 and Sn2 sites). The density functional theory (DFT)
calculations show that the indium substitution at the Sn2 site induces a
metallic band structure, on the other hand, a semiconducting band structure is
obtained from substitution at the Sn1 site. However, according to the previous
reports, since the indium atom prefers to replace the tin atom at the Sn1 site
rather than the Sn2 site, the resistivity of Co3SnInS2 shows
semiconducting-like behavior. In this study we have demonstrated that metallic
behavior and a decrease in resistivity for Se-doped Co3SnInS2 occurs without
suppression of the Seebeck coefficient. From the DFT calculations, when the
selenium content is above 0.5, the total crystallographic energy shows that a
higher indium occupancy at Sn2 site is more stable. Therefore, it is suggested
that the selenium doping suppress the site preference for indium substitution.
This is one of the possible explanations for the metallic conductivity observed
in Se-doped Co3SnInS2",1211.4467v3
2016-01-21,Anomalous electronic structure and magnetoresistance in TaAs$_2$,"The resistance of a metal in a magnetic field can be very illuminating about
its ground state. Some famous examples include the integer and fractional
quantum Hall effects\cite{Klitzing-QHE,Tsui-FQHE}, Shubnikov-de Haas
oscillations\cite{SdH}, and weak localization\cite{Lee-WL} \emph{et al}. In
non-interacting metals the resistance typically increases upon the application
of a magnetic field\cite{Pippard-MR}. In contrast, in some special
circumstances metals, with anisotropic Fermi surfaces\cite{Kikugawa-PdCoO2LMR}
or a so-called Weyl semimetal for instance\cite{Nielsen-ABJ,Son-ChirAnom}, may
have negative magnetoresistance. Here we show that semimetallic TaAs$_2$
possesses a gigantic negative magnetoresistance ($-$98\% in a field of 3 T at
low temperatures), with an unknown mechanism. Density functional calculations
illustrate that TaAs$_2$ is a new topological semimetal [$\mathbb{Z}_2$
invariant (0;111)] without a Dirac dispersion. This demonstrates that the
presence of negative magnetoresistance in non-magnetic semimetals cannot be
uniquely attributed to the Adler-Bell-Jackiw anomaly of bulk Dirac/Weyl
fermions. Our results also imply that the OsGe$_2$-type monoclinic dipnictides
are likely a material basis where unconventional topological semimetals may be
found.",1601.05524v2
2016-11-09,Theory of Coulomb Drag in Spatially Inhomogeneous Materials,"Coulomb drag between parallel two-dimensional electronic layers is an
excellent tool for the study of electron-electron interactions. In actual
experiments, the layers display spatial charge density fluctuations due to
imperfections such as external charged impurities. However, at present a
systematic way of taking these inhomogeneities into account in drag
calculations has been lacking, making the interpretation of experimental data
problematic. On the other hand, there exists a highly successful and widely
accepted formalism describing transport within single inhomogeneous layers
known as effective medium theory. In this work, we generalize the standard
effective medium theory to the case of Coulomb drag between two inhomogeneous
sheets and demonstrate that inhomogeneity in the layers has a strong impact on
drag transport. In the case of exciton condensation between the layers, we show
that drag resistivity takes on a value determined by the amplitude of density
fluctuation. Next we consider drag between graphene sheets, in which the
existence of spatial charge density fluctuations is well-known. We show that
these inhomogeneities play a crucial role in explaining existing experimental
data. In particular, the temperature dependence of the experimentally observed
peaks in drag resistivity can only be explained by taking the layer density
fluctuations into account. We also propose a method of extracting information
on the correlations between the inhomogeneities of the layers. The effective
medium theory of Coulomb drag derived here is general and applies to all
two-dimensional materials.",1611.03089v2
2016-12-21,Magnetothermopower and magnetoresistance of single Co-Ni/Cu multilayered nanowires,"The magnetothermopower and the magnetoresistance of single Co Ni/Cu
multilayered nan-owires with various thicknesses of the Cu spacer are
investigated. Both kinds of measurement have been performed as a function of
temperature (50 K to 325 K) and under applied magnetic fields perpendicular to
the nanowire axis, with magnitudes up to 15 % at room temperature. A linear
relation between thermopower S and electrical conductivity {\sigma} of the
nanowires is found, with the magnetic field as an implicit variable. Combining
the linear behavior of the S vs. {\sigma} and the Mott formula, the energy
derivative of the resistivity has been determined. In order to extract the true
nanowire materials parameters from the measured thermopower, a simple model
based on the Mott formula is employed to distinguish the individual thermopower
contributions of the sample. By assuming that the non-diffusive thermopower
contributions of the nanowire can be neglected, it was found that the magnetic
field induced changes of thermopower and resistivity are equivalent. The
emphasis in the present paper is on the comparison of the magnetoresistance and
magnetothermopower results and it is found that the same correlation is valid
between the two sets of data for all samples, irrespective of the relative
importance of the giant magnetoresistance or anisotropic magnetoresistance
contributions in the various individual nanowires.",1612.07078v1
2018-01-17,Rules for Phase Shifts of Quantum Oscillations in Topological Nodal-line Semimetals,"Nodal-line semimetals are topological semimetals in which band touchings form
nodal lines or rings. Around a loop that encloses a nodal line, an electron can
accumulate a nontrivial $\pi$ Berry phase, so the phase shift in the
Shubnikov-de Haas (SdH) oscillation may give a transport signature for the
nodal-line semimetals. However, different experiments have reported
contradictory phase shifts, in particular, in the WHM nodal-line semimetals
(W=Zr/Hf, H=Si/Ge, M=S/Se/Te). For a generic model of nodal-line semimetals, we
present a systematic calculation for the SdH oscillation of resistivity under a
magnetic field normal to the nodal-line plane. From the analytical result of
the resistivity, we extract general rules to determine the phase shifts for
arbitrary cases and apply them to ZrSiS and Cu$_3$PdN systems. Depending on the
magnetic field directions, carrier types, and cross sections of the Fermi
surface, the phase shift shows rich results, quite different from those for
normal electrons and Weyl fermions. Our results may help exploring transport
signatures of topological nodal-line semimetals and can be generalized to other
topological phases of matter.",1801.05709v2
2018-05-03,Transport measurements in twisted bilayer graphene: Electron-phonon coupling and Landau level crossing,"We investigate electronic transport in twisted bilayer graphene (tBLG) under
variable temperatures ($T$), carrier densities ($n$), and transverse magnetic
fields, focusing on samples with small-twist-angles ($\theta$). These samples
show prominent signatures associated with the van Hove singularities (VHSs) and
superlattice-induced mini-gaps (SMGs). Temperature-dependent field effect
measurement shows that the difference between temperature-dependent resistivity
and residual resistivity, $\rho_{xx}(n,T) - \rho_{0}(n)$, follows $~T^\beta$
for $n$ between the main Dirac point (DP) and SMG. The evolution of the
temperature exponent $\beta$ with $n$ exhibits a W-shaped dependence, with
minima of $\beta$ ~0.9 near the VHSs and maxima of $\beta$ ~1.7 toward the
SMGs. This W-shaped behavior can be qualitatively understood with a theoretical
picture that considers both the Fermi surface smearing near the VHSs and
flexural-acoustic phonon scattering. In the quantum Hall regime, we observe
only Landau level crossings in the massless Dirac spectrum originating from the
main DP but not in the parabolic band near the SMG. Such crossings enable the
measurement of an enhanced interlayer dielectric constant, attributed to a
reduced Fermi velocity. Moreover, we measure the Fermi velocity, interlayer
coupling strength, VHS energy relative to the DP, and gap size of SMG, four
important parameters used to describe the peculiar band structure of the
small-$\theta$ tBLG.",1805.01454v3
2018-05-29,The effect of energy-dependent electron scattering on thermoelectric transport in novel topological semimetal CoSi,"These compounds have long been known as promising thermoelectric materials.
Recently it was revealed, that they also have unconventional electronic
topology. This renewed interest to the investigation of their transport
properties. In order to improve theoretical description of thermoelectric
transport in these compounds, we take into account electron scattering beyond
commonly used constant relaxation time approximation. Using first principle
calculations, we investigate the scattering of charge carriers by phonons and
point defects. The dependence of the scattering rate on the energy correlates
with that for the total density of states. This implies that in this material
not only the intraband, but also the interband scattering is important,
especially for bands with low density of states. The Seebeck coefficient and
the electrical resistivity of CoSi and of dilute solid solutions
Co$_{1-x}$M$_x$Si (M=Fe or Ni, $x<0.1$) are calculated as a function of
temperature and the alloy composition. We show that the account of strong
energy dependence of relaxation time is important for the description of
experimentally observed rapid increase of the resistivity and qualitative
change of its temperature dependence with the substitution of cobalt for iron,
as well as for the description of the magnitude of the Seebeck coefficient, its
temperature and composition dependence.",1805.11334v4
2018-06-11,Investigation of anomalous thermodynamic and transport properties of Sr$_{1-x}$Ca$_x$RuO$_3$ ($x \geq 0.8$),"Thermodynamic and transport properties of Sr$_{1-x}$Ca$_x$RuO$_3$ with a
calcium concentration $x \geq 0.8$ were investigated at low temperatures and in
external magnetic field. The investgations revealed a Landau Fermi liquid (LFL)
behaviour characterized by specific heat $C/T = const$ and resistivity
$\rho\sim T^2$ and an anomalous non-Fermi liquid (NFL) behaviour with $\rho
\sim T^{5/3}$ and a quasi-logarithmic increase of $C/T$ with decreasing
temperature. The $T$--$x$ and $T$--$B$ phase diagrams which separate both
regions were prepared for the investigated materials. Then, the experimental
behaviour of $C/T$ and $\rho(T)$ were compared with predictions of the
self-consistent renormalization (SCR) theory of spin fluctuations. Within this
approach, $C/T(T)$ was well described up to 20 K. The SCR parameters $y_0$,
$y_1$ and $T_0$ inferred from specific heat analysis allowed to describe
properly $\rho(T)$ up to approximately 5 K. In addition, the resistivity data
were analysed within the `hidden Fermi liquid' theory of Anderson, obtaining
very good descritption of the experimental behaviour up to about 25 K. An
anomalous increase of the $C/T$ ratio already in the LFL region below 2 K in
very weak magnetic fields (0.2--0.3 T) was identified as caused by the Schottky
anomaly induced by ferromagnetic clusters embodied into the essentially
paramagnetic materials.",1806.03923v1
2018-09-16,Unraveling hagfish slime,"Hagfish slime is a unique predator defense material containing a network of
long fibrous threads each ~ 10 cm in length. Hagfish release the threads in a
condensed coiled state known as thread cells, or skeins (~ 100 microns), which
must unravel within a fraction of a second to thwart a predator attack. Here we
consider the hypothesis that viscous hydrodynamics can be responsible for this
rapid unraveling, as opposed to chemical reaction kinetics alone. Our main
conclusion is that, under reasonable physiological conditions, unraveling due
to viscous drag can occur within a few hundred milliseconds, and is accelerated
if the skein is pinned at a surface such as the mouth of a predator. We model a
single thread cell unspooling as the fiber peels away due to viscous drag. We
capture essential features by considering one-dimensional scenarios where the
fiber is aligned with streamlines in either uniform flow or uniaxial
extensional flow. The peeling resistance is modeled with a power-law dependence
on peeling velocity. A dimensionless ratio of viscous drag to peeling
resistance appears in the dynamical equations and determines the unraveling
timescale. Our modeling approach is general and can be refined with future
experimental measurements of peel strength for skein unraveling. It provides
key insights into the unraveling process, offers potential answers to lingering
questions about slime formation from threads and mucous vesicles, and will aid
the growing interest in engineering similar bioinspired material systems.",1809.05914v1
2019-09-24,Two-band superconductivity with unconventional pairing symmetry in HfV$_2$Ga$_4$,"In this letter, we have examined the superconducting ground state of the
HfV$_2$Ga$_4$ compound using resistivity, magnetization, zero-field (ZF) and
transverse-field (TF) muon-spin relaxation and rotation ($\mu$SR) measurements.
Resistivity and magnetization unveil the onset of bulk superconductivity with
$T_{\bf c}\sim$ 3.9~K, while TF-$\mu$SR measurements show that the temperature
dependence of the superfluid density is well described by a nodal two-gap
$s$+$d$-wave order parameter model. In addition, ZF muon relaxation rate
increases with decreasing temperature below 4.6 K, indicating the presence of
weak spin fluctuations. These observations suggest an unconventional multiband
nature of the superconductivity possibly arising from the distinct $d$-bands of
V and Hf ions with spin fluctuations playing an important role. To better
understand these findings, we carry out first-principles electronic-structure
calculations, further highlighting that the Fermi surface consists of multiple
disconnected sheets with very different orbital weights and spin-orbit
coupling, bridging the way for a nodal multiband superconductivity scenario. In
this vein, therefore, HfV$_2$Ga$_4$-family stands out as an open avenue to
novel unexplored unconventional superconducting compounds, such as
ScV$_2$Ga$_4$ and ZrV$_2$Ga$_4$, and other many rare earths based materials.",1909.10712v1
2014-08-22,Composition-spread Growth and the Robust Topological Surface State of Kondo insulator SmB6 Thin Films,"Topological insulators are a class of materials with insulating bulk but
protected conducting surfaces due to the combination of spin-orbit interactions
and time-reversal symmetry. The surface states are topologically non-trivial
and robust against non-magnetic backscattering, leading to interesting physics
and potential quantum computing applications1, 2. Recently there has been a
fast growing interest in samarium hexboride (SmB6), a Kondo insulator predicted
to be the first example of a correlated topological insulator3, 4. Here we
fabricated smooth thin films of nanocrystalline SmB6 films. Their transport
behavior indeed shows that SmB6 is a bulk insulator with topological surface
states. Upon decreasing the temperature, the resistivity \r{ho} of Sm0.14B0.86
(SmB6) films display significant increase below 50 K due to hybridization gap
formation, and it shows a saturation behavior below 10 K. The saturated
resistance of our textured films is similar to that of the single crystals,
suggesting that this conduction is from the surface and robust against grain
boundary scatterings. Point contact spectroscopy (PCS) of the film using a
superconducting tip displays both a Kondo Fano resonance and Andreev
reflection, suggesting the existence of both an insulating Kondo lattice and
metallic surface states.",1408.5413v1
2017-01-12,Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method,"The determination of the longitudinal spin Seebeck effect (LSSE) coefficient
is currently plagued by a large uncertainty due to the poor reproducibility of
the experimental conditions used in its measurement. In this work we present a
detailed analysis of two different methods used for the determination of the
LSSE coefficient. We have performed LSSE experiments in different laboratories,
by using different setups and employing both the temperature difference method
and the heat flux method. We found that the lack of reproducibility can be
mainly attributed to the thermal contact resistance between the sample and the
thermal baths which generate the temperature gradient. Due to the variation of
the thermal resistance, we found that the scaling of the LSSE voltage to the
heat flux through the sample rather than to the temperature difference across
the sample greatly reduces the uncertainty. The characteristics of a single
YIG/Pt LSSE device obtained with two different setups was $(1.143\pm0.007)\cdot
10^{-7}$ Vm/W and $(1.101\pm0.015)\cdot 10^{-7}$ Vm/W with the heat flux method
and $(2.313\pm0.017)\cdot 10^{-7}$ V/K and $(4.956\pm0.005)\cdot 10^{-7}$ V/K
with the temperature difference method. This shows that systematic errors can
be considerably reduced with the heat flux method.",1701.03285v3
2017-01-23,Three-dimensionality of the bulk electronic structure in WTe2,"We use temperature- and field-dependent resistivity measurements
[Shubnikov--de Haas (SdH) quantum oscillations] and ultrahigh resolution,
tunable, vacuum ultraviolet (VUV) laser-based angle-resolved photoemission
spectroscopy (ARPES) to study the three-dimensionality (3D) of the bulk
electronic structure in WTe2, a type-II Weyl semimetal. The bulk Fermi surface
(FS) consists of two pairs of electron pockets and two pairs of hole pockets
along the X-Gamma-X direction as detected by using an incident photon energy of
6.7 eV, which is consistent with the previously reported data. However, if
using an incident photon energy of 6.36 eV, another pair of tiny electron
pockets is detected on both sides of the Gamma point, which is in agreement
with the small quantum oscillation frequency peak observed in the
magnetoresistance. Therefore, the bulk, 3D FS consists of three pairs of
electron pockets and two pairs of hole pockets in total. With the ability of
fine tuning the incident photon energy, we demonstrate the strong
three-dimensionality of the bulk electronic structure in WTe2. The combination
of resistivity and ARPES measurements reveal the complete, and consistent,
picture of the bulk electronic structure of this material.",1701.06667v1
2017-11-02,A Comparative Study on Spin-Orbit Torque Efficiencies from W/ferromagnetic and W/ferrimagnetic Heterostructures,"It has been shown that W in its resistive form possesses the largest
spin-Hall ratio among all heavy transition metals, which makes it a good
candidate for generating efficient dampinglike spin-orbit torque (DL-SOT)
acting upon adjacent ferromagnetic or ferrimagnetic (FM) layer. Here we provide
a systematic study on the spin transport properties of W/FM magnetic
heterostructures with the FM layer being ferromagnetic
Co$_{20}$Fe$_{60}$B$_{20}$ or ferrimagnetic Co$_{63}$Tb$_{37}$ with
perpendicular magnetic anisotropy. The DL-SOT efficiency $|\xi_{DL}|$, which is
characterized by a current-induced hysteresis loop shift method, is found to be
correlated to the microstructure of W buffer layer in both
W/Co$_{20}$Fe$_{60}$B$_{20}$ and W/Co$_{63}$Tb$_{37}$ systems. Maximum values
of $|\xi_{DL}|\approx 0.144$ and $|\xi_{DL}|\approx 0.116$ are achieved when
the W layer is partially amorphous in the W/Co$_{20}$Fe$_{60}$B$_{20}$ and
W/Co$_{63}$Tb$_{37}$ heterostructures, respectively. Our results suggest that
the spin Hall effect from resistive phase of W can be utilized to effectively
control both ferromagnetic and ferrimagnetic layers through a DL-SOT mechanism.",1711.00630v2
2017-12-28,"Aspects of electron scattering, the elastic, and the inelastic","A electron of mass $m$, when electrically scatters of nucleus, of mass $M$,
transfers momentum $q$ to the nucleus. The energy lost by electron is more than
the energy gained by the nucleus. The resulting energy goes in exciting the
atom to a higher energy state as in Frank Hertz experiment and sodium, neon,
mercury vapor lamps, or ionization of atom as in bubble and cloud chamber
experiments, or just production of X-rays as in Bremsstraulung. In this paper,
we study these phenomenon. These experiments are inelastic scattering
experiments. We remark, why neutrinos donot scatter and can penetrate earth,
why muons travel further than electrons in materials and why a material like
lead plate can slow down electrons and positrons efficiently. We look at the
elastic scattering of electrons as in electron diffraction and electron
microscopes. We look at scattering of electrons in the condensed matter, these
phenomenon range from scattering of electrons of periodic potential, to give
Bloch waves, scattering of electrons of phonons and impurities to give
resistance, scattering of electrons of lattice to give cooper pairs and
superconductivity. We study electron scattering from exchange potential as in
Fermi liquid theory and resulting $T^2$ resistance at low temperatures.
Electron scattering of exchange potential resulting in chemical reactions. We
turn our attention to electron-proton scattering both eleastic and inelastic,
as in deep inelastic scattering experiments and understand the independence of
ineleastic cross-section of with respect to transferred momentum. We see, why
we can just say that there are three quarks in proton from elastic
cross-section. Our main contribution in this article is we are detailed at
places, we find literature terse.",1712.09868v3
2018-10-10,Charge transfer and tunable built-in electric fields across semiconductor-crystalline oxide interfaces,"Built-in electric fields across heterojunctions between semiconducting
materials underpin the functionality of modern device technologies.
Heterojunctions between semiconductors and epitaxially grown crystalline oxides
provide a rich setting in which built-in fields can be explored. Here, we
present an electrical transport and hard X-ray photoelectron spectroscopy study
of epitaxial SrNbxTi1-xO3-{\delta} / Si heterojunctions. A non-monotonic
anomaly in the sheet resistance is observed near room temperature, which is
accompanied by a crossover in sign of the Hall resistance. The crossover is
consistent with the formation of a hole gas in the Si and the presence of a
built-in field. Hard X-ray photoelectron spectroscopy measurements reveal
pronounced asymmetric features in both the SrNbxTi1-xO3-{\delta} and Si
core-level spectra that we show arise from built-in fields. The extended probe
depth of hard X-ray photoelectron spectroscopy enables band bending across the
SrNbxTi1-xO3-{\delta} / Si heterojunction to be spatially mapped. Band
alignment at the interface and surface depletion in SrNbxTi1-xO3-{\delta} are
implicated in the formation of the hole gas and built-in fields. Control of
charge transfer and built-in electric fields across semiconductor-crystalline
oxide interfaces opens a pathway to novel functional heterojunctions.",1810.04648v1
2018-11-09,Static and sliding contact of rough surfaces: effect of asperity-scale properties and long-range elastic interactions,"Friction in static and sliding contact of rough surfaces is important in
numerous physical phenomena. We seek to understand macroscopically observed
static and sliding contact behavior as the collective response of a large
number of microscopic asperities. We develop an efficient numerical framework
that can be used to investigate how the macroscopic response of multiple
frictional contacts depends on long-range elastic interactions, different
constitutive assumptions about the deforming contacts and their local shear
resistance, and surface roughness. We approximate the contact between two rough
surfaces as that between a regular array of discrete deformable elements
attached to a elastic block and a rigid rough surface. The deformable elements
are viscoelastic or elasto/viscoplastic with a range of relaxation times, and
the elastic interaction between contacts is long-range. We find that the model
reproduces main macroscopic features of evolution of contact and friction for a
range of constitutive models of the elements, suggesting that macroscopic
frictional response is robust with respect to the microscopic behavior.
Viscoelasticity/viscoplasticity contributes to the increase of friction with
contact time and leads to a subtle history dependence. Interestingly,
long-range elastic interactions only change the results quantitatively compared
to the meanfield response. We find that sustained increase in the static
friction coefficient during long hold times suggests viscoelastic response of
the underlying material with multiple relaxation time scales. We also find that
the experimentally observed proportionality of the direct effect in velocity
jump experiments to the logarithm of the velocity jump points to a complex
material-dependent shear resistance at the microscale.",1811.03811v1
2019-07-01,Eshelby tensors and overall properties of nano-composites considering both interface stretching and bending effects,"In this study, the fundamental framework of analytical micromechanics is
generalized to consider nano-composites with both interface stretching and
bending effects. The interior and exterior Eshelby tensors for a spherical
nano-inclusion, with an interface defined by the Steigmann-Ogden model,
subjected to an arbitrary uniform eigenstrain are derived for the first time.
Correspondingly, the stress/strain concentration tensors for a spherical
nano-inhomogeneity subjected to arbitrary uniform far-field stress/strain
loadings are also derived. Using the obtained concentration tensors, the
effective bulk and shear moduli are derived by employing the dilute
approximation and the Mori-Tanaka method, respectively, which can be used for
both nano-composites and nano-porous materials. An equivalent interface
curvature parameter reflecting the influence of the interface bending
resistance is found, which can significantly simplify the complex expressions
of the effective properties. In addition to size-dependency, the closed form
expressions show that the effective bulk modulus is invariant to interface
bending resistance parameters, in contrast to the effective shear modulus. We
also put forward for the first time a characteristic interface curvature
parameter, near which the effective shear modulus is affected significantly.
Numerical results show that the effective shear moduli of nano-composites and
nano-porous materials can be greatly improved by an appropriate surface
modification. Finally, the derived effective modulus with the Steigmann-Ogden
interface model is provided in the supplemental MATLAB code, which can be
easily executed, and used as a benchmark for semi-analytical solutions and
numerical solutions in future studies.",1907.00591v3
2019-07-24,Interlayer quantum transport in Dirac semimetal BaGa$_2$,"Quantum limit is quite easy to achieve once the band crossing exists exactly
at the Fermi level ($E_F$) in topological semimetals. In multilayered Dirac
fermion system, the density of Dirac fermions on the zeroth Landau levels (LLs)
increases in proportion to the magnetic field, resulting in intriguing angle-
and field-dependent interlayer tunneling conductivity near the quantum limit.
BaGa$_2$ is an example of multilayered Dirac semimetal with anisotropic Dirac
cone close to $E_F$, providing a good platform to study its interlayer
transport properties. In this paper, we report the negative interlayer
magnetoresistance (NIMR, I//c and B//c) induced by the tunneling of Dirac
fermions on the zeroth LLs of neighbouring Ga layers in BaGa$_2$. When the
field deviates from the c-axis, the interlayer resistivity $\rho_{zz}(\theta)$
increases and finally results in a peak with the field perpendicular to the
c-axis. These unusual interlayer transport properties (NIMR and resistivity
peak with B$\perp$c) are observed together for the first time in Dirac
semimetal under ambient pressure and are well explained by the model of
tunneling between Dirac fermions in the quantum limit.",1907.10702v1
2020-03-10,Approaching Three-Dimensional Quantum Hall effect in Bulk HfTe5,"The discovery of quantum Hall effect in two-dimensional (2D) electronic
systems inspired the topological classifications of electronic systems1,2. By
stacking 2D quantum Hall effects with interlayer coupling much weaker than the
Landau level spacing, quasi-2D quantum Hall effects have been experimentally
observed3~7, due to the similar physical origin of the 2D counterpart.
Recently, in a real 3D electronic gas system where the interlayer coupling is
much stronger than the Landau level spacing, 3D quantum Hall effect has been
observed in ZrTe58. In this Letter, we report the electronic transport features
of its sister bulk material, i.e., HfTe5, under external magnetic field. We
observe a series of plateaus in Hall resistance \r{ho}xy as magnetic field
increases until it reaches the quantum limit at 1~2 Tesla. At the plateau
regions, the longitudinal resistance \r{ho}xx exhibits local minima. Although
\r{ho}xx is still nonzero, its value becomes much smaller than \r{ho}xy at the
last few plateaus. By mapping the Fermi surface via measuring the Shubonikov-de
Haas oscillation, we find that the strength of Hall plateau is proportional to
the Fermi wavelength, suggesting that its formation may be attributed to the
gap opening from the interaction driven Fermi surface instability. By comparing
the bulk band structures of ZrTe5 and HfTe5, we find that there exists an extra
pocket near the Fermi level of HfTe5, which may lead to the finite but nonzero
longitudinal conductance.",2003.04519v1
2022-02-17,Consecutive topological phase transitions and colossal magnetoresistance in a magnetic topological semimetal,"The combination of magnetic symmetries and electronic band topology provides
a promising route for realizing topologically nontrivial quasiparticles, and
the manipulation of magnetic structures may enable the switching between
topological phases, with the potential for achieving functional physical
properties. Here, we report measurements of the electrical resistivity of
EuCd$_2$As$_2$ under pressure, which show an intriguing insulating dome at
pressures between $p_{\rm c1}\sim1.0$~GPa and $p_{\rm c2}\sim2.0$~GPa, situated
between two regimes with metallic transport. The insulating state can be fully
suppressed by a small magnetic field, leading to a colossal negative
magnetoresistance on the order of $10^5$\%, accessible via a modest field of
$\sim0.2$~T. First-principles calculations reveal that the dramatic evolution
of the resistivity under pressure is due to consecutive transitions of
EuCd$_2$As$_2$ from a magnetic topological insulator to a trivial insulator,
and then to a Weyl semimetal, with the latter resulting from a pressure-induced
change in the magnetic ground state. Similarly, the colossal magnetoresistance
results from a field-induced polarization of the magnetic moments, transforming
EuCd$_2$As$_2$ from a trivial insulator to a Weyl semimetal. These findings
underscore weak magnetic exchange couplings and spin anisotropy as ingredients
for discovering tunable magnetic topological materials with desirable
functionalities.",2202.08454v1
2014-01-10,Development of a NbN Deposition Process for Superconducting Quantum Sensors,"We have carried out a detailed programme to explore the superconducting
characteristics of reactive DC-magnetron sputtered NbN. The basic principle is
to ignite a plasma using argon, and then to introduce a small additional
nitrogen flow to achieve the nitridation of a Nb target. Subsequent sputtering
leads to the deposition of NbN onto the host substrate. The characteristics of
a sputtered film depend on a number of parameters: argon pressure, nitrogen
flow rate and time-evolution profile, substrate material, etc. Crucially, the
hysteresis in the target voltage as a function of the nitrogen flow can be used
to provide a highly effective monitor of nitrogen consumption during the
reactive process. By studying these dependencies we have been able to achieve
highly reproducible film characteristics on sapphire, silicon dioxide on
silicon, and silicon nitride on silicon. Intrinsic film stress was minimised by
optimising the argon pressure, giving NbN films having Tc = 14.65 K. In the
paper, we report characteristics such as deposition rate, Residual Resistance
Ratio (RRR), film resistivity, transition temperature, and stress, as a
function of deposition conditions. In order to enhance our understanding of the
microwave properties of the films, we fabricated a wide range of microstrip NbN
resonators (half wavelength, quarter wavelength, ring resonators). In the
paper, we provide an illustrative result from this work showing a 2.1097 GHz
resonator having a Q of 15,962 at 3.3 K.",1401.2276v1
2014-01-10,Development of a NbN Deposition Process for Superconducting Quantum Sensors,"We have carried out a detailed programme to explore the superconducting
characteristics of reactive DC-magnetron sputtered NbN. The basic principle is
to ignite a plasma using argon, and then to introduce a small additional
nitrogen flow to achieve the nitridation of a Nb target. Subsequent sputtering
leads to the deposition of NbN onto the host substrate. The characteristics of
a sputtered film depend on a number of parameters: argon pressure, nitrogen
flow rate and time-evolution profile, substrate material, etc. Crucially, the
hysteresis in the target voltage as a function of the nitrogen flow can be used
to provide a highly effective monitor of nitrogen consumption during the
reactive process. By studying these dependencies we have been able to achieve
highly reproducible film characteristics on sapphire, silicon dioxide on
silicon, and silicon nitride on silicon. Intrinsic film stress was minimised by
optimising the argon pressure, giving NbN films having Tc = 14.65 K. In the
paper, we report characteristics such as deposition rate, Residual Resistance
Ratio (RRR), film resistivity, transition temperature, and stress, as a
function of deposition conditions. In order to enhance our understanding of the
microwave properties of the films, we fabricated a wide range of microstrip NbN
resonators (half wavelength, quarter wavelength, ring resonators). In the
paper, we provide an illustrative result from this work showing a 2.1097 GHz
resonator having a Q of 15,962 at 3.3 K.",1401.2292v1
2017-05-08,Investigation of a possible electronic phase separation in the magnetic semiconductors Ga$_{1-x}$Mn$_{x}$As and Ga$_{1-x}$Mn$_{x}$P by means of fluctuation spectroscopy,"We present systematic temperature-dependent resistance noise measurements on
a series of ferromagnetic Ga$_{1-x}$Mn$_{x}$As epitaxial thin films covering a
large parameter space in terms of the Mn content $x$ and other variations
regarding sample fabrication. We infer that the electronic noise is dominated
by switching processes related to impurities in the entire temperature range.
While metallic compounds with $x>2$ % do not exhibit any significant change in
the low-frequency resistance noise around the Curie temperature $T_\mathrm{C}$,
we find indications for an electronic phase separation in films with $x<2$ % in
the vicinity of $T_\mathrm{C}$, manifesting itself in a maximum in the noise
power spectral density. These results are compared with noise measurements on
an insulating Ga$_{1-x}$Mn$_{x}$P reference sample, for which the evidence for
an electronic phase separation is even stronger and a possible percolation of
bound magnetic polarons is discussed. Another aspect addressed in this work is
the effect of ion-irradiation induced disorder on the electronic properties of
Ga$_{1-x}$Mn$_{x}$As films and, in particular, whether any electronic
inhomogeneities can be observed in this case. Finally, we put our findings into
the context of the ongoing debate on the electronic structure and the
development of spontaneous magnetization in these materials.",1705.02963v3
2017-07-26,Emergent Strain-Stiffening in Interlocked Granular Chains,"Granular chain packings exhibit a striking emergent strain-stiffening
behavior despite the individual looseness of the constitutive chains. Using
indentation experiments on such assemblies, we measure an exponential increase
in the collective resistance force $F$ with the indentation depth $z$, and with
the square root of the number $\mathcal{N}$ of beads per chain. These two
observations are respectively reminiscent of the self-amplification of friction
in a capstan or in interleaved books, as well as the physics of polymers. The
experimental data are well captured by a novel model based on these two
ingredients. Specifically, the resistance force is found to vary according to
the universal relation: $\log F \sim \mu \sqrt{\mathcal{N}} \Phi^{11/8}z/ b $,
where $\mu$ is the friction coefficient between two elementary beads, $b$ is
their size, and $\Phi$ is the volume fraction of chain beads when semi-diluted
in a surrounding medium of unconnected beads. Our study suggests that theories
normally confined to the realm of polymer physics at a molecular level can be
used to explain phenomena at a macroscopic level. This class of systems enables
the study of friction in complex assemblies, with practical implications for
the design of new materials, the textile industry, and biology.",1707.08547v2
2019-04-09,Detection mechanism in highly sensitive ZnO nanowires network gas sensors,"Metal-oxide nanowires are showing a great interest in the domain of gas
sensing due to their large response even at a low temperature, enabling
low-power gas sensors. However their response is still not fully understood,
and mainly restricted to the linear response regime, which limits the design of
appropriate sensors for specific applications. Here we analyse the non-linear
response of a sensor based on ZnO nanowires network, both as a function of the
device geometry and as a response to oxygen exposure. Using an appropriate
model, we disentangle the contribution of the nanowire resistance and of the
junctions between nanowires in the network. The applied model shows a very good
consistency with the experimental data, allowing us to demonstrate that the
response to oxygen at room temperature is dominated by the barrier potential at
low bias voltage, and that the nanowire resistance starts to play a role at
higher bias voltage. This analysis allows us to find the appropriate device
geometry and working point in order to optimize the sensitivity. Such analysis
is important for providing design rules, not only for sensing devices, but also
for applications in electronics and opto-electronics using nanostructures
networks with different materials and geometries.",1904.04591v1
2019-12-07,Substrate Dependent Resistive Switching in Amorphous-HfOx Memristors: An Experimental and Computational Investigation,"While two-terminal HfOX (x<2) memristor devices have been studied for ion
transport and current evolution, there have been limited reports on the effect
of the long-range thermal environment on their performance. In this work,
amorphous-HfOX based memristor devices on two different substrates, thin
SiO2(280 nm)/Si and glass, with different thermal conductivities in the range
from 1.2 to 138 W/m-K were fabricated. Devices on glass substrates exhibit
lower reset voltage, wider memory window and, in turn, a higher performance
window. In addition, the devices on glass show better endurance than the
devices on the SiO2/Si substrate. These devices also show non-volatile
multi-level resistances at relatively low operating voltages which is critical
for neuromorphic computing applications. A Multiphysics COMSOL computational
model is presented that describes the transport of heat, ions and electrons in
these structures. The combined experimental and COMSOL simulation results
indicate that the long-range thermal environment can have a significant impact
on the operation of HfOx-based memristors and that substrates with low thermal
conductivity can enhance switching performance.",1912.03545v2
2019-12-12,Cable bacteria as long-range biological semiconductors,"Filamentous cable bacteria exhibit unprecedented long-range biological
electron transport, which takes place in a parallel fibre structure that shows
an extraordinary electrical conductivity for a biological material. Still, the
underlying electron transport mechanism remains undisclosed. Here we determine
the intrinsic electrical properties of individual cable bacterium filaments. We
retrieve an equivalent electrical circuit model, characterising cable bacteria
as resistive biological wires. Temperature dependent experiments reveal that
the charge transport is thermally activated, and can be described with an
Arrhenius-type relation over a broad temperature range (-196{\deg}C to
+50{\deg}C), thus excluding metal-like electron transport. Furthermore, when
cable bacterium filaments are utilized as the channel in a field-effect
transistor, they show n-type transport, indicating that electrons rather than
holes are the charge carriers. Electron mobilities are in the order of
10$^{-1}$ cm$^2$/Vs, comparable to many organic semiconductors. This new type
of biological centimetre-range semiconductor with low resistivity offers new
perspectives for both fundamental studies and applications in (bio)electronics.",1912.06224v1
2019-01-10,Experimentally determined correlation between direct and inverse Edelstein effects at Bi2O3/Cu interface by means of spin absorption method using lateral spin valve structure,"We have experimentally elucidated the correlation between inverse and direct
Edelstein Effects (EEs) at Bi2O3/Cu interface by means of spin absorption
method using lateral spin valve structure. The conversion coefficient {\lambda}
for the inverse EE is determined by the electron momentum scattering time in
the interface, whereas the coefficient q for the direct EE is by the spin
ejection time from the interface. For the Bi2O3/Cu interface, the spin ejection
time was estimated to be ~ 53 fs and the momentum scattering time ~ 13 fs at
room temperature, both of which contribute to the total momentum relaxation
time that defines the resistivity of the interface. The effective spin Hall
angle for the Bi2O3/Cu interface amounts to ~ 10% which is comparable to
commonly used spin Hall material such as platinum. Interesting to note is that
the experimentally obtained Edelstein resistances given by the output voltage
divided by the injection current for direct and inverse effects are the same.
Analysis based on our phenomenological model reveals that the larger the
momentum scattering time, the more efficient direct EE; and the smaller spin
ejection time, the more efficient inverse EE.",1901.03095v1
2019-01-30,Modeling of the interaction of rigid wheels with dry granular media,"We analyze the capabilities of various recently developed techniques, namely
Resistive Force Theory (RFT) and continuum plasticity implemented with the
Material Point Method (MPM), in capturing dynamics of wheel--dry granular media
interactions. We compare results to more conventionally accepted methods of
modeling wheel locomotion. While RFT is an empirical force model for
arbitrarily-shaped bodies moving through granular media, MPM-based continuum
modeling allows the simulation of full granular flow and stress fields. RFT
allows for rapid evaluation of interaction forces on arbitrary shaped intruders
based on a local surface stress formulation depending on depth, orientation,
and movement of surface elements. We perform forced-slip experiments for three
different wheel types and three different granular materials, and results are
compared with RFT, continuum modeling, and a traditional terramechanics
semi-empirical method. Results show that for the range of inputs considered,
RFT can be reliably used to predict rigid wheel granular media interactions
with accuracy exceeding that of traditional terramechanics methodology in
several circumstances. Results also indicate that plasticity-based continuum
modeling provides an accurate tool for wheel-soil interaction while providing
more information to study the physical processes giving rise to resistive
stresses in granular media.",1901.10667v1
2019-06-07,Strategy for enhanced thermoelectric performance of Bi2S3 nanorods by Bi nanoinclusions,"This is the first report on the enhanced thermoelectric (TE) properties of
novel Bi2S3-Bi nanocomposites synthesized using a one-step polyol method at
different reaction temperatures (TRe) and time. They are well-characterized as
nanorod-composites, coexistent with orthorhombic Bi2S3 and rhombohedral Bi
phases together in which the latter coats the former forming Bi2S3-Bi
core-shell type structures along with independent Bi nanoparticles (NPs). There
is a very significant observation of systematic reduction in electri-cal
resistivity \r{ho} with reaction temperature and time duration increase,
revealing a promising approach for reduction of \r{ho} in this highly resistive
Bi2S3 and hence resolving the earlier obstacles for its thermoelectric
application potentials for the past few decades. Most astonishingly, TE power
factor at 300 K of highest Bi content nanocomposite pellet, made at 27 oC using
~900 MPa pressure, is 3 orders of magnitude greater than that of hot-pressed
Bi2S3, or even 23% better than that of spark plasma-sintered core-shell
Bi2S3@Bi sample reported earlier (Tarachand et al. Nano Res. 2016, 9, 3291; Ge
et al. ACS Appl. Mater. Interfaces 2017, 9, 4828). Considering the probable
greatly reduced thermal conductivity due to their complex nanostructures, the
significantly improved TE performance potential near 300 K is highly
anticipated for these toxic- and rare earth element-free TE nanocomposites,
making the present synthesis method as a pioneering approach for developing
enhanced thermoelectric properties of Bi2S3-based materials without using extra
sintering steps.",1906.03003v1
2020-06-15,Room-temperature quantum spin Hall phase in laser-patterned few-layer 1T'- MoS2,"The quantum-spin-Hall (QSH) phase of 2D topological insulators has attracted
increased attention since the onset of 2D materials research. While large bulk
gaps with vanishing edge gaps in atomically thin layers have been reported,
verifications of the QSH phase by resistance measurements are comparatively
few. This is partly due to the poor uniformity of the bulk gap induced by the
substrate over a large sample area and/or defects induced by oxidation. Here,
we report the observation of the QSH phase at room-temperature in the 1T'-phase
of few-layer MoS2 patterned onto the 2H semiconducting phase using low-power
and short-time laser beam irradiation. Two different resistance measurements
reveal hallmark transport conductance values, ~e2/2h and e2/4h, as predicted by
the theory. Magnetic-field dependence, scanning tunneling spectra, and
calculations support the emergence of the room-temperature QSH phase. Although
further experimental verification is still desirable, our results provide
feasible application to room-temperature topological devices.",2006.08125v2
2020-07-07,A switchable two-dimensional electron gas based on ferroelectric Ca:SrTiO$_3$,"Two-dimensional electron gases (2DEGs) can form at the surface of oxides and
semiconductors or in carefully designed quantum wells and interfaces. Depending
on the shape of the confining potential, 2DEGs may experience a finite electric
field, which gives rise to relativistic effects such as the Rashba spin-orbit
coupling. Although the amplitude of this electric field can be modulated by an
external gate voltage, which in turn tunes the 2DEG carrier density, sheet
resistance and other related properties, this modulation is volatile. Here, we
report the design of a ''ferroelectric'' 2DEG whose transport properties can be
electrostatically switched in a non-volatile way. We generate a 2DEG by
depositing a thin Al layer onto a SrTiO$_3$ single crystal in which 1 percent
of Sr is substituted by Ca to make it ferroelectric. Signatures of the
ferroelectric phase transition at 25 K are visible in the Raman response and in
the temperature dependences of the carrier density and sheet resistance that
shows a hysteretic dependence on electric field as a consequence of
ferroelectricity. We suggest that this behavior may be extended to other oxide
2DEGs, leading to novel types of ferromagnet-free spintronic architectures.",2007.03344v1
2020-07-07,Multigap superconductivity in the new BiCh$_{2}$-based layered superconductor La$_\mathrm{0.7}$Ce$_\mathrm{0.3}$OBiSSe,"The layered bismuth oxy-sulfide materials, which are structurally related to
the Fe-pnictides/chalcogenides and cuprates superconductors, have brought
substantial attention for understanding the physics of reduced dimensional
superconductors. We have examined the pairing symmetry of recently discovered
BiCh$_2$-based superconductor, La$_\mathrm{1-x}$Ce$_\mathrm{x}$OBiSSe with $x$
= 0.3, through transverse field (TF) muon spin rotation measurement, in
addition we present the results of magnetization, resistivity and zero field
(ZF) muon spin relaxation measurements. Bulk superconductivity has been
observed below 2.7 K for $x$ = 0.3, verified by resistivity and magnetization
data. The temperature dependence of the magnetic penetration depth has been
determined from TF-$\mu$SR data can be described by an isotropic two-gap $s+s$
wave model compared to a single gap $s$- or anisotropic $s$-wave models, the
resemblance with Fe-pnictides/chalcogenides and MgB$_2$. Furthermore, from the
TF-$\mu$SR data, we have determined the London's penetration depth
$\lambda_\mathrm{L}(0)$ = 452(3) nm, superconducting carrier's density
$n_\mathrm{s}$ = 2.18(1) $\times$10$^{26}$ carriers/m$^{3}$ and effective mass
enhancement $m^{*}$ = 1.66(1) $m_\mathrm{e}$, respectively. No signature of
spontaneous internal field is found down to 100 mK in ZF-$\mu$SR measurement
suggest that time-reversal symmetry is preserved in this system.",2007.03752v1
2020-10-28,Nanoscale plasticity and neuromorphic dynamics in silicon suboxide RRAM,"Resistive random-access memories, also known as memristors, whose resistance
can be modulated by the electrically driven formation and disruption of
conductive filaments within an insulator, are promising candidates for
neuromorphic applications due to their scalability, low-power operation and
diverse functional behaviours. However, understanding the dynamics of
individual filaments, and the surrounding material, is challenging, owing to
the typically very large cross-sectional areas of test devices relative to the
nanometre scale of individual filaments. In the present work, conductive atomic
force microscopy is used to study the evolution of conductivity at the
nanoscale in a fully CMOS-compatible silicon suboxide thin film. Distinct
filamentary plasticity and background conductivity enhancement are reported,
suggesting that device behaviour might be best described by composite core
(filament) and shell (background conductivity) dynamics. Furthermore, constant
current measurements demonstrate an interplay between filament formation and
rupture, resulting in current-controlled voltage spiking in nanoscale regions,
with an estimated optimal energy consumption of 25 attojoules per spike. This
is very promising for extremely low-power neuromorphic computation and suggests
that the dynamic behaviour observed in larger devices should persist and
improve as dimensions are scaled down.",2010.15184v1
2021-02-11,Large topological Hall effect near room temperature in noncollinear ferromagnet LaMn2Ge2 single crystal,"Non-trivial spin structures in itinerant magnets can give rise to topological
Hall effect (THE) due to the interacting local magnetic moments and conductive
electrons. While, in series of materials, THE has mostly been observed at low
temperatures far below room temperature (RT) limiting its potential
applications. Here, we report the anisotropic anomalous Hall effect (AHE) near
RT in LaMn2Ge2, a noncollinear ferromagnetic (FM) with Curie temperature TC=325
K. Large topological Hall resistivity of ~1.0 10-6 ohmcm in broad temperature
range (190 K <T< 300 K) is realized as field (H) parallel to the ab-plane (H //
ab) and current along c axis (I // c), in contrast to the conventional AHE for
H // c and I // ab. The emergence of THE is attributed to the spin chirality of
noncoplanar spin configurations stabilized by thermal fluctuation during spin
flop process. Moreover, the constructed temperature-field (H-T) phase diagrams
based on the isothermal topological Hall resistivity reveal a field-induced
transition from the noncoplanar spin configuration to polarized ferromagnetic
states. Our experimental realization of large THE near RT highlights LaMn2Ge2
as a promising system for functional applications in novel spintronic devices.",2102.05837v1
2021-03-01,Directional ballistic transport in the two-dimensional metal PdCoO2,"In an idealized infinite crystal, the material properties are constrained by
the symmetries of its unit cell. Naturally, the point-group symmetry is broken
by the sample shape of any finite crystal, yet this is commonly unobservable in
macroscopic metals. To sense the shape-induced symmetry lowering in such
metals, long-lived bulk states originating from anisotropic Fermi surfaces are
needed. Here we show how strongly facetted Fermi surfaces and long
quasiparticle mean free paths present in microstructures of PdCoO2 yield an
in-plane resistivity anisotropy that is forbidden by symmetry on an infinite
hexagonal lattice. Bar shaped transport devices narrower than the mean free
path are carved from single crystals using focused ion beam (FIB) milling, such
that the ballistic charge carriers at low temperatures frequently collide with
both sidewalls defining a channel. Two symmetry-forbidden transport signatures
appear: the in-plane resistivity anisotropy exceeds a factor of 2, and
transverse voltages appear in zero magnetic field. We robustly identify the
channel direction as the source of symmetry breaking via ballistic Monte- Carlo
simulations and numerical solution of the Boltzmann equation.",2103.01332v1
2021-04-13,Oblique and asymmetric Klein tunneling across smooth NP junctions or NPN junctions in 8-Pmmn borophene,"The tunneling of electrons and holes in quantum structures plays a crucial
role in studying the transport properties of materials and the related devices.
8-Pmmn borophene is a new two-dimensional Dirac material, which hosts tilted
Dirac cone and chiral, anisotropic massless Dirac fermions. We develop the
transfer matrix method to investigate the Klein tunneling of massless fermions
across the smooth NP junctions and NPN junctions of 8-Pmmn borophene. Like the
sharp NP junctions of 8-Pmmn borophene, the tilted Dirac cones induce the
oblique Klein tunneling. The angle of perfect transmission to the normal
incidence is 20.4 degrees, a constant determined by the Hamiltonian of 8-Pmmn
borophene. For the NPN junction, there are branches of the Klein tunneling in
the phase diagram. We find that the asymmetric Klein tunneling is induced by
the chirality and anisotropy of the carriers. Furthermore, we show the
oscillation of electrical resistance related to the Klein tunneling in the NPN
junctions. One may analyze the pattern of electrical resistance and verify the
existence of asymmetric Klein tunneling experimentally.",2104.07450v3
2021-08-04,Quasi-HfO$_x$/ AlO$_y$ and AlO$_y$/ HfO$_x$ Based Memristor Devices: Role of Bi-layered Oxides in Digital Set and Analog Reset Switching,"Understanding the resistive switching behavior, or the resistance change, of
oxide-based memristor devices, is critical to predicting their responses with
known electrical inputs. Also, with the known electrical response of a
memristor, one can confirm its usefulness in non-volatile memory and/or in
artificial neural networks. Although bi- or multi-layered oxides have been
reported to improve the switching performance, compared to the single oxide
layer, the detailed explanation about why the switching can easily be improved
for some oxides combinations is still missing. Herein, we fabricated two types
of bi-layered heterostructure devices, quasi-HfO$_x$/AlO$_y$ and
AlO$_y$/HfO$_x$ sandwiched between Au electrodes, and their electrical
responses are investigated. For a deeper understanding of the switching
mechanism, the performance of a HfOx only device is also considered, which
serves as a control device. The role of bi-layered heterostructures is
investigated using both the experimental and simulated results. Our results
suggest that synergistic switching performance can be achieved with a proper
combination of these materials and/or devices. These results open the avenue
for designing more efficient double- or multi-layers memristor devices for an
analog response.",2108.02247v2
2021-08-12,"Strength, corrosion resistance and cellular response of interfaces in bioresorbable poly-lactic acid/Mg fiber composites for orthopedic applications","The shear strength and the corrosion resistance of the fiber/matrix interface
after immersion in simulated body fluid was studied in poly-lactic acid/Mg
fiber composites. The shear strength of the interface was measured by means of
push-out tests in thin slices of the composite perpendicular to the fibers. It
was found that the interface strength dropped from 15.2 \pm 1.4 MPa to 7.8 \pm
3.7 MPa after the composite was immersed in simulated body fluid for 148 hours.
The reduction of the interface strength was associated to the fast corrosion of
the fibers as water diffused to the interface through the polymer. The
expansion of the fibers due to the formation of corrosion products was enough
to promote radial cracks in the polymer matrix which facilitate the ingress of
water and the development of corrosion pitting in the fibers. Moreover, cell
culture testing on the material showed that early degradation of the Mg fibers
affected the proliferation of pre-osteoblasts near the Mg fibers due to the
local changes in the environment produced by the fiber corrosion. Thus, surface
modification of Mg fibers to delay degradation seems to be a critical point for
further development of Mg/PLA composites for biomedical applications.",2108.05782v1
2021-08-17,A pH-based bio-rheostat: a proof-of-concept,"New science and new technology need new materials and new concepts. In this
respect, biological matter can play a primary role because it is a material
with interesting and innovative features that have found several applications
in technology, from highly sensitive sensors for medical treatments to devices
for energy harvesting. Furthermore, most of its phenomenology remains unclear
thus giving new hints for speculative investigations. In this letter, we
explore the possibility to use a well-known photosensitive protein, the
Reaction Center of Rhodobacter Sphaeroides, to build up an electrical pH
sensor, i.e., a device able to change its resistance depending on the pH of the
solution in which it crystalizes. By using a microscopic model successfully
tested on analogue proteins, we investigate the electrical response of the
Reaction Center single protein under different conditions of applied bias,
showing the feasibility of the bio-rheostat hypothesis. As a matter of facts,
the calculated resistance of this protein grows of about 100% when going from a
pH = 10 to a pH = 6.5. Moreover, calculations of the current voltage
characteristics well agree with available experiments performed with a current
atomic force microscopy under neutral conditions. All findings are in
qualitative agreement with the known role of pH in biochemical activities of
Reaction Center and similar proteins, therefore supporting a proof-of-concept
for the development of new electron devices based on biomaterials.",2108.07541v2
2021-10-22,A viscous active shell theory of the cell cortex,"The cell cortex is a thin layer beneath the plasma membrane that gives animal
cells mechanical resistance and drives most of their shape changes, from
migration, division to multicellular morphogenesis. It is mainly composed of
actin filaments, actin binding proteins, and myosin molecular motors.
Constantly stirred by myosin motors and under fast renewal, this material may
be well described by viscous and contractile active-gel theories. Here, we
assume that the cortex is a thin viscous shell with non-negligible curvature
and use asymptotic expansions to find the leading-order equations describing
its shape dynamics, starting from constitutive equations for an incompressible
viscous active gel. Reducing the three-dimensional equations leads to a
Koiter-like shell theory, where both resistance to stretching and bending rates
are present. Constitutive equations are completed by a kinematical equation
describing the evolution of the cortex thickness with turnover. We show that
tension and moment resultants depend not only on the shell deformation rate and
motor activity but also on the active turnover of the material, which may also
exert either contractile or extensile stress. Using the finite-element method,
we implement our theory numerically to study two biological examples of drastic
cell shape changes: osmotic shocks and cell division. Our work provides a
numerical implementation of thin active viscous layers and a generic
theoretical framework to develop shell theories for slender active biological
structures.",2110.12089v2
2022-05-03,Electrical Switching of the Edge Current Chirality in Quantum Anomalous Hall Insulators,"A quantum anomalous Hall (QAH) insulator is a topological state of matter, in
which the interior is insulating but electrical current flows along the edges
of the sample, in either clockwise (right-handed) or counter-clockwise
(left-handed) direction dictated by the spontaneous magnetization orientation.
Such chiral edge current (CEC) eliminates any backscattering, giving rise to
quantized Hall resistance and zero longitudinal resistance. In this work, we
fabricate mesoscopic QAH sandwich (i.e. magnetic topological insulator
(TI)/TI/magnetic TI) Hall bar devices and succeed in switching the CEC
chirality in QAH insulators through spin-orbit torque (SOT) by applying a
current pulse and suitably controlled gate voltage. The well-quantized QAH
states with opposite CEC chiralities are demonstrated through four- and
three-terminal measurements before and after SOT switching. Our theoretical
calculations show that the SOT that enables the magnetization switching can be
generated by both bulk and surface carriers in QAH insulators, in good
agreement with experimental observations. Current pulse-induced switching of
the CEC chirality in QAH insulators will not only advance our knowledge in the
interplay between magnetism and topological states but also expedite easy and
instantaneous manipulation of the QAH state in proof-of-concept
energy-efficient electronic and spintronic devices as well as quantum
information applications.",2205.01581v1
2022-06-20,Joule heating and the thermal conductivity of a two-dimensional electron gas at cryogenic temperatures studied by modified 3$ω$ method,"During the standard ac lock-in measurement of the resistance of a
two-dimensional electron gas (2DEG) applying an ac current $I = \sqrt{2} I_0
\sin(\omega t)$, the electron temperature $T_e$ oscillates with the angular
frequency $2 \omega$ due to the Joule heating $\propto I^2$. We have shown that
the highest ($T_\mathrm{H}$) and the lowest ($T_\mathrm{L}$) temperatures
during a cycle of the oscillations can be deduced, at cryogenic temperatures,
exploiting the third-harmonic (3$\omega$) component of the voltage drop
generated by the ac current $I$ and employing the amplitude of the Shubnikov-de
Haas oscillations as the measure of $T_e$. The temperatures $T_\mathrm{H}$ and
$T_\mathrm{L}$ thus obtained allow us to roughly evaluate the thermal
conductivity $\kappa_{xx}$ of the 2DEG via the modified 3$\omega$ method, in
which the method originally devised for bulk materials is modified to be
applicable to a 2DEG embedded in a semiconductor wafer. The $\kappa_{xx}$ thus
deduced is found to be consistent with the Wiedemann-Franz law. The method
provides a convenient way to access $\kappa_{xx}$ using only a standard
Hall-bar device and the simple experimental setup for the resistance
measurement.",2206.09702v2
2022-09-18,Control of chiral orbital currents in a colossal magnetoresistance material,"Colossal magnetoresistance (CMR) is an extraordinary enhancement of the
electric conductivity in the presence of a magnetic field. It is conventionally
associated with a field-induced spin polarization, which drastically reduces
spin scattering and thus electric resistance. However, ferrimagnetic Mn3Si2Te6
is an intriguing exception to this rule: it exhibits a 7-order-of-magnitude
reduction in ab-plane resistivity with a 13-Tesla anisotropy field which occur
only when a magnetic polarization is avoided [1]. Here we report an exotic
quantum state that is driven by ab-plane chiral orbital currents (COC) flowing
along edges of MnTe6 octahedra. The c-axis orbital moments of ab-plane COC
couple to the ferrimagnetic Mn spins to drastically increase the ab-plane
conductivity (CMR) when an external magnetic field is aligned along the
magnetic hard c-axis. Both the COC state and its CMR are extraordinarily
susceptible to small DC currents exceeding a critical threshold, and a hallmark
of this COC state is an exotic time-dependent, bistable switching mimicking a
first-order melting transition. The control of the COC-enabled CMR and bistable
switching offers a fundamentally new paradigm for quantum technologies.",2209.08672v1
2022-09-27,Single crystal growth of iridates without platinum impurities,"Iridates have attracted much interest in the last decade for their novel
magnetism emerging in the limit of strong spin-orbit coupling and possible
unconventional superconductivity. A standard for growing iridate single
crystals has been the flux method using platinum crucibles. Here, we show that
this widely used method compromises the sample quality by inclusion of platinum
impurities. We find that Sr2IrO4 single crystals grown in iridium crucibles
show remarkable differences from those grown in platinum crucibles in their
sample characterizations using Raman spectroscopy, resistivity, magnetization,
optical third harmonic generation, resonant X-ray diffraction, and resonant
inelastic X-ray scattering measurements. In particular, we show that several
peaks of sizable intensities disappear in the Raman spectra of samples free of
platinum impurities, and a significantly larger activation energy is extracted
from the resistivity data compared to previously reported values. Furthermore,
we find no evidence of the previously reported glide symmetry breaking
structural distortions and confirm the I41/acd space group of the lattice
symmetry. Although the platinum impurities are not apparent in the magnetic
properties and thus went unnoticed in the stoichiometric insulating phase for a
long time, their effects can be much more detrimental to transport properties
in chemically doped compounds. Therefore, our result suggests using growth
methods that avoid platinum impurities for an investigation of intrinsic
physical properties of iridates, and possible superconducting phases.",2209.13506v1
2022-11-02,Utilizing the sensitization effect for direct laser writing in a novel photoresist based on the chitin monomer N-acetyl-D-glucosamine,"The great flexibility of direct laser writing arises from the possibility to
fabricate precise three-dimensional structures on very small scales as well as
the broad range of applicable materials. However, there is still a vast number
of promising materials which are currently inaccessible requiring the
continuous development of novel photoresists. Here, a new bio-sourced resist is
reported which relies on the monomeric unit of chitin, N-acetyl-D-glucosamine,
expanding the existing plant-based biopolymer resists by a bio-based monomer
from the animal kingdom. In addition it is shown that combined use of two
photoinitiators is advantageous over the use of a single one. In our approach,
the first photoinitator is a good two-photon absorber at the applied
wavelength, while the second photoinitiator exhibits poor two-photon absorbtion
abilities, but is better suited for crosslinking of the monomer. The first
photoinitiator absorbs the light acting as a sensitizer and transfers the
energy to the second initiator, which subsequently forms a radical and
initializes the polymerization. This sensitization effect enables a new route
to utilize reactive photointiators with a small two-photon absorption
cross-section for direct laser writing without changing their chemical
structure.",2211.01193v1
2022-11-15,Drag resistance mediated by quantum spin liquids,"Recent advances in material synthesis made it possible to realize
two-dimensional monolayers of candidate materials for a quantum spin liquid
(QSL) such as $\alpha$-RuCl$_3$,1T-TaSe$_2$ and 1T-TaS$_2$. In this work, we
propose an experimental setup that exploits nonlocal electrical probes to gain
information on the transport properties of a gapless QSL. The proposed setup is
a spinon-mediated drag experiment: a current is injected in one of the two
layers and a voltage is measured on the second metallic film. The overall
momentum transfer mechanism is a two-step process mediated by Kondo interaction
between the local moments in the quantum spin liquid and the spins of the
electrons. In the limit of negligible momentum relaxed within the QSL layer, we
calculate the drag relaxation rate for Kitaev, $\mathbb{Z}_2$, and U(1) QSLs
using Aslamazov-Larkin diagrams. We find, however, that the case of dominant
momentum relaxation within the QSL layer is far more relevant and thus develop
a model based on the Boltzmann kinetic equation to describe the proposed setup.
Within this framework we calculate the low temperature scaling behavior of the
drag resistivity, both for U(1) and $\mathbb{Z}_2$ QSLs with Fermi surfaces. In
some regimes we find a crossover in the temperature scaling that is different
between the $\mathbb{Z}_2$ and U(1) QSL both because of the non-Fermi liquid
nature of the U(1) QSL, and because of the qualitatively different momentum
relaxation mechanism within the QSL layer. Our findings suggest that parameters
of the system can be tuned to make the spinon-mediated drag a significant
fraction of the total transresistance.",2211.08421v1
2023-01-31,"Superconducting Diode Effect -- Fundamental Concepts, Material Aspects, and Device Prospects","Superconducting diode effect, in analogy to the nonreciprocal resistive
charge transport in semiconducting diode, is a nonreciprocity of
dissipationless supercurrent. Such an exotic phenomenon originates from
intertwining between symmetry-constrained supercurrent transport and intrinsic
quantum functionalities of helical/chiral superconductors. In this article,
research progress of superconducting diode effect including fundamental
concepts, material aspects, device prospects, and theoretical/experimental
development is reviewed. First, fundamental mechanisms to cause superconducting
diode effect including simultaneous space-inversion and time-reversal symmetry
breaking, magnetochiral anisotropy, interplay between spin-orbit interaction
energy and the characteristic energy scale of supercurrent carriers, and
finite-momentum Cooper pairing are discussed. Second, the progress of
superconducting diode effect from theoretical predictions to experimental
observations are reviewed. Third, interplay between various system parameters
leading to superconducting diode effect with optimal performance is presented.
Then, it is explicitly highlighted that nonreciprocity of supercurrent can be
characterized either by current-voltage relation obtained from resistive
direct-current measurements in the metal-superconductor fluctuation region
($T\approx T_c$) or by current-phase relation and nonreciprocity of superfluid
inductance obtained from alternating-current measurements in the
superconducting phase ($T<T_c$). Finally, insight into future directions in
this active research field is provided with a perspective analysis on
intertwining between band-topology and helical superconductivity, which could
be useful to steer the engineering of emergent topological superconducting
technologies.",2301.13564v1
2023-02-09,Structural changes induced by electric currents in a single crystal of Pr$_2$CuO$_4$,"We demonstrate a novel approach to the structural and electronic property
modification of perovskites, focusing on Pr$_2$CuO$_4$, an undoped parent
compound of a class of electron-doped copper-oxide superconductors. Currents
were passed parallel or perpendicular to the copper-oxygen layers with the
voltage ramped up until a rapid drop in the resistivity was achieved, a process
referred to as ""flash"". The current was then further increased tenfold in
current-control mode. This state was quenched by immersion into liquid
nitrogen. Flash can drive many compounds into different atomic structures with
new properties, whereas the quench freezes them into a long-lived state.
Single-crystal neutron diffraction of as-grown and modified Pr$_2$CuO$_4$
revealed a $\sqrt{10}$x$\sqrt{10}$ superlattice due to oxygen-vacancy order.
The diffraction peak intensities of the superlattice of the modified sample
were significantly enhanced relative to the pristine sample. Raman-active
phonons in the modified sample were considerably sharper. Measurements of
electrical resistivity, magnetization and two-magnon Raman scattering indicate
that the modification affected only the Pr-O layers, but not the Cu-O planes.
These results point to enhanced oxygen-vacancy order in the modified samples
well beyond what can be achieved without passing electrical current. Our work
opens a new avenue toward electric field/quench control of structure and
properties of layered perovskite oxides.",2302.04385v2
2023-03-20,Topological monopole's gauge field induced anomalous Hall effect in artificial honeycomb lattice,"Vortex magnetic structure in artificial honeycomb lattice provides a unique
platform to explore emergent properties due to the additional Berry phase
curvature imparted by chiral magnetization to circulating electrons via direct
interaction. We argue that while the perpendicularly-aligned magnetic component
leads to the quantized flux of monopole at the center of the Berry sphere, the
in-plane vortex circulation of magnetization gives rise to unexpected
non-trivial topological Berry phase due to the gauge field transformation. The
unprecedented effect signifies the importance of vector potential in
multiply-connected geometrical systems. Experimental confirmations to proposed
hypotheses are obtained from Hall resistance measurements on permalloy
honeycomb lattice. Investigation of the topological gauge transformation due to
the in-plane chirality reveals anomalous quasi-oscillatory behavior in Hall
resistance $R_{xy}$ as function of perpendicular field. The oscillatory nature
of $R_{xy}$ is owed to the fluctuation in equilibrium current as a function of
Fermi wave-vector $k_F$, envisaged under the proposed new formulation in this
article. Our synergistic approach suggests that artificially tunable
nanostructured material provides new vista to the exploration of topological
phenomena of strong fundamental importance.",2303.11506v1
2023-09-23,Enhanced radiation damage tolerance of amorphous interphase and grain boundary complexions in Cu-Ta,"Amorphous interfacial complexions are particularly resistant to radiation
damage and have been primarily studied in alloys with good glass-forming
ability, yet recent reports suggest that these features can form even in
immiscible alloys such as Cu-Ta under irradiation. In this study, the
mechanisms of damage production and annihilation due to primary knock-on atom
collisions are investigated for amorphous interphase and grain boundaries in a
Cu-Ta alloy using atomistic simulations. Amorphous complexions, in particular
amorphous interphase complexions that separate Cu and Ta grains, result in less
residual defect damage than their ordered counterparts. Stemming from the
nanophase chemical separation in this alloy, the amorphous complexions exhibit
a highly heterogeneous distribution of atomic excess volume, as compared to a
good glass former like Cu-Zr. Complexion thickness, a tunable structural
descriptor, plays a vital role in damage resistance. Thicker interfacial films
are more damage-tolerant because they alter the defect production rate due to
differences in intrinsic displacement threshold energies during the collision
cascade. Overall, the findings of this work highlight the importance of
interfacial engineering in enhancing the properties of materials operating in
radiation-prone environments and the promise of amorphous complexions as
particularly radiation damage-tolerant microstructural features.",2309.13474v2
2024-01-05,Quest for a solution to drift in phase change memory devices,"The goal of this thesis is to gain new insights into the drift phenomenon and
identify strategies to mitigate it. An extensive experimental characterization
of PCM devices and in particular drift forms the foundation of each chapter.
With respect to time-scales, ambient temperature, device dimensions, and
combinations thereof, drift is studied under unprecedented conditions. In three
studies, different aspects of drift are examined.
  (1) The origin of structural relaxation: Drift measurements over 9 orders of
magnitude in time reveal the onset of relaxation in a melt-quenched state. The
data is used to appraise two models, the Gibbs relaxation model and the
collective relaxation model. Additionally, a refined version of the collective
relaxation model is introduced and the consequences of a limited number of
structural defects are discussed.
  (2) Exploiting nanoscale effects in phase change memories: Scaling devices to
ever-smaller dimensions is incentivized by the requirement to achieve higher
storage densities and less power consumption. Eventually, confinement and
interfacial effects will govern the device characteristics. Anticipating these
consequences, the feasibility to use a single element, Antimony, is assessed
for the first time. The power efficiency, stability against crystallization,
and drift are characterized under different degrees of confinement.
  (3) State-dependent drift in a projected memory cell: New device concepts are
aiming to reduce drift by decoupling the cell resistance from the electronic
properties of the amorphous phase. A shunt resistor scaling with the amount of
amorphous material is added. Simulations and the drift characteristics of a
projected device put the idealized concept to the test. The contact resistance
between the phase change material and the shunt resistor is identified as a
decisive parameter to achieve the desired device properties.",2401.09462v1
2024-02-20,Low frequency resistance fluctuations in an ionic liquid gated channel probed by cross-correlation noise spectroscopy,"A system in equilibrium keeps ``exploring"" nearby states in the phase space
and consequently, fluctuations can contain information, that the mean value
does not. However, such measurements involve a fairly complex interplay of
effects arising in the device and measurement electronics, that are non-trivial
to disentangle. In this paper, we briefly analyse some of these issues and show
the relevance of a two-amplifier cross-correlation technique for semiconductors
and thin films commonly encountered. We show that by using home-built
amplifiers costing less than $10$ USD/piece one can measure spectral densities
as low as $\sim 10^{-18}-10^{-19}~ {\rm {V^2}{Hz^{-1}}}$. We apply this method
to an ionic liquid gated Ga:ZnO channel and show that the glass transition of
the ionic liquid brings about a change in the exponent of the low frequency
resistance fluctuations. Our analysis suggests that a log-normal distribution
of the Debye relaxation times of the fluctuations and an increased weight of
the long timescale relaxations can give a semi-quantitative explanation of the
observed change in the exponent.",2402.13363v1
2024-03-04,Nature of point defects in monolayer MoS2 and the MoS2/(111)Au heterojunction,"Deposition of MoS2 on (111)-Au alters the electronic properties of MoS2. In
this study, we investigate the free-standing MoS2 monolayer and the
MoS2~\(111)-Au heterostructure, with and without strain, as well as defects of
interest in memristive and neuromorphic applications. We focus on so-called
atomristor devices based on monolayer materials that achieve resistive
switching characteristics with the adsorption and desorption of metal adatoms.
Our study confirms that the formation of midgap states is the primary mechanism
behind the resistive switching. Our results show that strain lowers the
adsorption~\desorption energies of Au+defect structures of interest, leading to
more favorable switching energies, but simultaneously reduces the switching
ratio between states of differing conductivities. The presence of the (111)-Au
substrate additionally introduces non-uniform amounts of strain throughout and
charge transfer to the MoS2 monolayer. We propose that the induced strain can
contribute to the experimentally observed n- to p-type transition and Ohmic to
Schottky transition in the MoS2 monolayer. The charge transfer leads to a
permanent polarization at the interface, which can be tuned by strain. Our
study has important implications on the role of the electrode as being a source
of the observed variability in memristive devices and as serving as an
additional degree of freedom for tuning the switching characteristics of the
memristor device.",2403.01708v1
2006-10-04,Electric Field Effect Analysis of Thin PbTe films on high-epsilon SrTiO3 Substrate,"Thin PbTe films (thickness 500 - 600 angstrom), deposited on SrTiO3, have
been investigated by electric field effect (EFE). The high resistivity of such
thin films warrants a high sensitivity of the EFE method. The SrTiO3 substrate
serves as the dielectric layer in the Gate-Dielectric-PbTe structure. Due to
the large dielectric constant of SrTiO3, particularly at low temperatures, the
electric displacement D in the film reaches the high value of about 10^8 V/cm,
and the EFE introduced charge into the PbTe film amounts to ~ 8 microC/cm2. The
high D permits to measure the EFE resistance and Hall constant over a wide
region of D, revealing the characteristic features of their D-dependence. An
appropriate theoretical model has been formulated, showing that, for such
films, one can measure the dependence of the Fermi level on D. In fact, we
demonstrate that shifting the Fermi level across the gap by varying D, the
density-of-states of the in-gape states can be mapped out. Our results show,
that the PbTe layers studied, possess a mobility gap exceeding the gap of bulk
PbTe.",0610107v1
2007-02-21,Soliton Wall Superlattice in Quasi-One-Dimensional Conductor (Per)2Pt(mnt)2,"We suggest a model to explain the appearance of a high resistance high
magnetic field charge-density-wave (CDW) phase, discovered by D. Graf et al.
[Phys. Rev. Lett. v. 93, 076406 (2004)] in (Per)2Pt(mnt)2. In particular, we
show that the Pauli spin-splitting effects improve the nesting properties of a
realistic quasi-one-dimensional electron spectrum and, therefore, a high
resistance Peierls CDW phase is stabilized in high magnetic fields. In low and
very high magnetic fields, a periodic soliton wall superlattice (SWS) phase is
found to be a ground state. We suggest experimental studies of the predicted
phase transitions between the Peierls and SWS CDW phases in (Per)2Pt(mnt)2 to
discover a unique SWS phase.",0702500v2
2011-09-26,Superconductivity and Rattling under High Pressure in the beta-Pyrochlore Oxide RbOs2O6,"Rattling-induced superconductivity in the beta-pyrochlore oxide RbOs2O6 is
investigated under high pressures up to 6 GPa. Resistivity measurements in a
high-quality single crystal show that the superconducting transition
temperature Tc increases gradually from 6.3 K at ambient pressure to 8.8 K at
3.5 GPa, surprisingly remains almost constant at 8.8 \pm 0.1 K in a wide
pressure range between 3.5 (Po) and 4.8 GPa, and suddenly drops to 6.3 K at Ps
= 4.9 GPa, followed by a gradual decrease with further pressure increase. Two
anomalies in the temperature dependence of the normal-state resistivity are
observed at Po < P < Ps and P > Ps, revealing the presence of two high-pressure
phases corresponding to the changes in Tc. The rattling of the Rb ion inside a
cage made of Os and O atoms may be slightly and seriously modified in these
high-pressure phases that probably have cages of reduced symmetry,
respectively, so that electron-rattler interactions that govern the
superconducting and transport properties of beta-RbOs2O6 are significantly
affected.",1109.5422v1
2018-06-29,RPC upgrade project for CMS Phase II,"The Muon Upgrade Phase II of the Compact Muon Solenoid (CMS) aims to
guarantee the optimal conditions of the present system and extend the $\eta$
coverage to ensure a reliable system for the High Luminosity Large Hadron
Collider (HL-LHC) period. The Resistive Plate Chambers (RPCs) system will
upgrade the off-detector electronics (called link system) of the chambers
currently installed chambers and place improved RPCs (iRPCs) to cover the high
pseudo$-$rapidity region, a challenging region for muon reconstruction in terms
of background and momentum resolution. In order to find the best option for the
iRPCs, an R\&D program for new detectors was performed and real size prototypes
have been tested in the Gamma Irradiation Facility (GIF++) at CERN. The results
indicated that the technology suitable for the high background conditions is
based on High Pressure Laminate (HPL) double-gap RPC. The RPC Upgrade Phase II
program is planned to be ready after the Long Shutdown 3 (LS3).",1806.11503v3
2019-06-25,Fast charge sensing of Si/SiGe quantum dots via a high-frequency accumulation gate,"Quantum dot arrays are a versatile platform for the implementation of spin
qubits, as high-bandwidth sensor dots can be integrated with single-, double-
and triple-dot qubits yielding fast and high-fidelity qubit readout. However,
for undoped silicon devices, reflectometry off sensor ohmics suffers from the
finite resistivity of the two-dimensional electron gas (2DEG), and alternative
readout methods are limited to measuring qubit capacitance, rather than qubit
charge. By coupling a surface-mount resonant circuit to the plunger gate of a
high-impedance sensor, we realized a fast charge sensing technique that is
compatible with resistive 2DEGs. We demonstrate this by acquiring at high speed
charge stability diagrams of double- and triple-dot arrays in Si/SiGe
heterostructures as well as pulsed-gate single-shot charge and spin readout
with integration times as low as 2.4 $\mu$s.",1906.10584v2
2023-01-25,Modeling of mouse experiments suggests that optimal anti-hormonal treatment for breast cancer is diet-dependent,"Estrogen receptor positive breast cancer is frequently treated with
anti-hormonal treatment such as aromatase inhibitors (AI). Interestingly, a
high body mass index has been shown to have a negative impact on AI efficacy,
most likely due to disturbances in steroid metabolism and adipokine production.
Here, we propose a mathematical model based on a system of ordinary
differential equations to investigate the effect of high-fat diet on tumor
growth. We inform the model with data from mouse experiments, where the animals
are fed with high-fat or control (normal) diet. By incorporating AI treatment
with drug resistance into the model and by solving optimal control problems we
found differential responses for control and high-fat diet. To the best of our
knowledge, this is the first attempt to model optimal anti-hormonal treatment
for breast cancer in the presence of drug resistance. Our results underline the
importance of considering high-fat diet and obesity as factors influencing
clinical outcomes during anti-hormonal therapies in breast cancer patients.",2301.10553v3
2003-09-08,Temperature Dependence of Zero-Bias Resistances of a Single Resistance-Shunted Josephson Junction,"Zero-bias resistances of a single resistance-shunted Josephson junction are
calculated as a function of the temperature by means of the path-integral Monte
Carlo method in case a charging energy $E_{\rm C}$ is comparable with a
Josephson energy $E_{\rm J}$. The low-temperature behavior of the zero-bias
resistance changes around $\alpha=R_{\rm Q}/R_{\rm S}=1$, where $R_{\rm S}$ is
a shunt resistance and $R_{\rm Q}=h/(2e)^2$. The temperature dependence of the
zero-bias resistance shows a power-law-like behavior whose exponent depends on
$E_{\rm J}/E_{\rm C}$. These results are compared with the experiments on
resistance-shunted Josephson junctions.",0309177v1
2019-09-10,Charge Transport in a Polar Metal,"The fate of electric dipoles inside a Fermi sea is an old issue, yet
poorly-explored. Sr$_{1-x}$Ca$_x$TiO$_{3}$ hosts a robust but dilute
ferroelectricity in a narrow ($0.002<x<0.02$) window of substitution. This
insulator becomes metallic by removal of a tiny fraction of its oxygen atoms.
Here, we present a detailed study of low-temperature charge transport in
Sr$_{1-x}$Ca$_x$TiO$_{3-\delta}$, documenting the evolution of resistivity with
increasing carrier concentration ($n$). Below a threshold carrier
concentration, $n^*(x)$, the polar structural phase transition has a clear
signature in resistivity and Ca substitution significantly reduces the 2 K
mobility at a given carrier density. For three different Ca concentrations, we
find that the phase transition fades away when one mobile electron is
introduced for about $7.9\pm0.6$ dipoles. This threshold corresponds to the
expected peak in anti-ferroelectric coupling mediated by a diplolar counterpart
of Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. Our results imply that the
transition is driven by dipole-dipole interaction, even in presence of a dilute
Fermi sea. Charge transport for $n < n^*(x)$ shows a non-monotonic temperature
dependence, most probably caused by scattering off the transverse optical
phonon mode. A quantitative explanation of charge transport in this polar metal
remains a challenge to theory. For $n\geq n^*(x)$, resistivity follows a
T-square behavior together with slight upturns (in both Ca-free and
Ca-substituted samples). The latter are reminiscent of Kondo effect and most
probably due to oxygen vacancies.",1909.04278v2
2020-09-08,Disorder and magnetic field induced Bose-metal state in two-dimensional Ta$_x$(SiO$_2$)$_{1-x}$ granular films,"The origin of the intermediate anomalous metallic state in two-dimensional
superconductor materials remains enigmatic. In the present paper, we observe
such a state in a series of $\sim$9.0 nm thick Ta$_x$(SiO$_2$)$_{1-x}$ ($x$
being the volume fraction of Ta) nanogranular films. At zero field, the $x$
$\gtrsim$ 0.75 films undergo a Berezinskii-Kosterlitz-Thouless transition as
transform from normal to superconducing states upon cooling. For the $x$
$\lesssim$ 0.71 films, the resistance increases with decreasing temperature
from 2 K down to 40 mK. A normal state to anomalous metallic state transition
is observed in the $x$ $\simeq$ 0.73 film, i.e., near the transition
temperature, the resistance of the film decreases sharply upon cooling as if
the system would cross over to superconducting state, but then saturates to a
value far less than that in normal state. When a small magnetic field
perpendicular to the film plane is applied, the anomalous metallic state occurs
in the $x$ $\gtrsim$ 0.75 films. It is found that both disorder and magnetic
field can induce the transition from superconductor to anomalous metal and
their influences on the transition are similar. For the the magnetic field
induced case, we find the sheet resistance $R_{\square}(T,H)$ ($T$ and $H$
being the temperature and the magnitude of magnetic field) data near the
crossover from the anomalous metal to superconductor and in the vicinity of the
anomalous metal to insulator transition, respectively, obey unique scaling laws
deduced from the Bose-metal model. Our results strongly suggest that the
anomalous metallic state in the Ta$_x$(SiO$_2$)$_{1-x}$ granular films is
bosonic and dynamical gauge field fluctuation resulting from superconducting
quantum fluctuations plays a key role in its formation.",2009.03511v1
2019-01-11,Superconductivity in an organometallic compound,"Organometallic compounds constitute a very large group of substances that
contain at least one metal-to-carbon bond in which the carbon is part of an
organic group. They have played a major role in the development of the science
of chemistry. These compounds are used to a large extent as catalysts
(substances that increase the rate of reactions without themselves being
consumed) and as intermediates in the laboratory and in industry. Recently,
novel quantum phenormena such as topological insulators and superconductors
were also suggested in these materials. However, there has been no report on
the experimental exploration for the topological state. Evidence for
superconductivity from the zero-resistivity state in any organometallic
compound has not been achieved yet, though much efforts have been devoted. Here
we report the experimental realization of superconductivity with the critical
temperature of 3.6 K in a potassium-doped organometallic compound, $ i.e.$
tri-$o$-tolylbismuthine with the evidence of both the Meissner effect and the
zero-resistivity state through the $dc$ and $ac$ magnetic susceptibility and
resistivity measurements. The obtained superconducting parameters classify this
compound as a type-II superconductor. The benzene ring is identified to be the
essential superconducting unit in such a phenyl organometallic compound. The
superconducting phase and its composition are determined by the combined
studies of the X-ray diffraction and theoretical calculations as well as the
Raman spectroscopy measurements. These findings enrich the applications of
organometallic compounds in superconductivity and add a new electron-acceptor
family for organic superconductors. This work also points to a large pool for
finding superconductors from organometallic compounds.",1901.03572v1
2022-03-23,Large anomalous Hall effect in layered antiferromagnet Co$_{0.29}$TaS$_2$,"We present a study on the magnetization, anomalous Hall effect (AHE) and
novel longitudinal resistivity in layered antiferromagnet Co$_{0.29}$TaS$_{2}$.
Of particular interests in Co$_{0.29}$TaS$_{2}$ are abundant magnetic
transitions, which show that the magnetic structures are tuned by temperature
or magnetic field. With decreasing temperature, Co$_{0.29}$TaS$_{2}$ undergoes
two transitions at T$_{t1}\sim$ 38.3 K and T$_{t2}\sim$ 24.3 K. Once the
magnetic field is applied, another transition T$_{t3}\sim$ 34.3 K appears
between 0.3 T and 5 T. At 2 K, an obvious ferromagnetic hysteresis loop within
H$_{t1}\sim\pm$ 6.9 T is observed, which decreases with increasing temperature
and eventually disappears at T$_{t2}$. Besides, Co$_{0.29}$TaS$_{2}$ displays
step-like behavior as another magnetic transition around H$_{t2}\sim\pm$ 4 T,
which exists until $\sim$ T$_{t1}$. These characteristic temperatures and
magnetic fields mark complex magnetic phase transitions in
Co$_{0.29}$TaS$_{2}$, which are also evidenced in transport results. Large AHE
dominates in the Hall resistivity with the conspicuous value of
R$_{s}$/R$_{0}\sim 10^{5}$, considering that the tiny net magnetization
(0.0094$\mu_{B}$/Co) alone would not lead to this value, thus the contribution
of Berry curvature is necessary. The longitudinal resistivity illustrates a
prominent irreversible behavior within H$_{t1}$. The abrupt change at H$_{t2}$
below T$_{t1}$, corresponding to the step-like magnetic transitions, is also
observed. Synergy between the magnetism and topological properties, both
playing a crucial role, may be the key factor of large AHE in antiferromagnet,
which also offers a new perspective in magnetic topological materials with the
platform of Co$_{0.29}$TaS$_{2}$.",2203.12771v1
2023-03-07,Colossal nonreciprocal Hall effect and broadband frequency mixing due to a room temperature nonlinear Hall effect,"Nonreciprocal (NR) charge transport in quantum materials has attracted
enormous interest since it offers an avenue to investigate quantum symmetry
related physics and holds many prospective applications such as rectification
and photodetection over a wide range of frequencies. The NR transport reported
to date occurs along the longitudinal direction with the NR resistance limited
to a few percent of the ohmic resistance. Here we report a transverse
nonreciprocal transport phenomenon with divergent nonreciprocity - colossal NR
Hall effect. This is revealed in direct current (DC) measurements on the
microscale Hall devices made of the Pt wires deposited by focused ion beam
(FIB) on Si substrates and the Weyl semimetal NbP with FIB-deposited Pt
electrodes at 0 magnetic field. When a DC is applied along the x-axis of the
devices Ix, it generates a voltage along the y-axis Vy near room temperature,
with Vy quadratically scaling with Ix. The transverse resistance, which shows a
sign reversal upon switching the current direction, results from a colossal
extrinsic nonlinear Hall effect (NLHE) rooted in the disorder scatterings in
the Pt wires. While NbP was not found to show NLHE, the NLHE generated in the
Pt electrodes can be transmitted to the NbP Hall devices, which yields a
surprisingly large nonlinear anomalous Hall effect in NbP with the Hall angle
(${\Theta_H}$) far exceeding the record value of the anomalous Hall angle of
magnetic conductors at room temperature. Furthermore, we find such a strong
NLHE can lead to broadband frequency mixing, with the frequency spectrum of the
Hall voltage including 2nd-harmonic generation, sum & difference frequency
generations, and other multiple wave mixing components. These results not only
demonstrate the concept of the NRHE for the first time but also pave the way
for exploring NLHE's applications in Thz communication, imaging, and energy
harvesting.",2303.03738v2
1999-10-22,Carrier density change in Colossal Magnetoresistive Pyrochlore Tl2Mn2O7,"Hall resistivity and magneto-thermopower have been measured for colossal
magnetoresistive Tl2Mn2O7 over wide temperature and magnetic-field ranges.
These measurements revealed that a small number of free electron-like carriers
is responsible for the magneto-transport properties. In contrast to perovskite
CMR materials, the anomalous Hall coefficient is negligible even in the
ferromagnetic state due to negligibly small skew scattering. The characteristic
feature in Tl2Mn2O7 is that the carrier density changes with temperature and
the magnetic field. The carrier density increases around TC as the temperature
is lowered or as the magnetic field is increased, which explains the CMR of
this material. The conduction-band-edge shift, which is caused by the strong
s-d interaction between localized Mn moments and s-like conduction electrons,
is a possible mechanism for the carrier density change.",9910345v1
2003-12-05,Measuring Dielectric Properties and Surface Resistance of Microwave PCBs in the K-band,"The theoretical model is fully developed and the test rig is designed for the
measurements of microwave parameters of unclad and laminated dielectric
substrates. The geometry of the electromagnetic field in the resonator allows
dielectric measurements with electric field component orthogonal to the sample
surface. The test rig was completely automatized for measurements of the
following parameters: (i) dielectric constant of the dielectric substrate in
the range from 2 to 10, (ii) loss tangent of the dielectric substrate in the
range from 10^-4 to 10^-2, and (iii) microwave ohmic loss at the interface
between the metal layer and the dielectric material in the range from 0.01 to
0.2 Ohm.Measurements for a number of commonly-used microwave PCB materials were
performed in the frequency range from 30 to 40 GHz and over a temperature range
from -50C to +70C.",0312151v2
2005-01-07,The Spot Model for random-packing dynamics,"The diffusion and flow of amorphous materials, such as glasses and granular
materials, has resisted a simple microscopic description, analogous to defect
theories for crystals. Early models were based on either gas-like inelastic
collisions or crystal-like vacancy diffusion, but here we propose a cooperative
mechanism for dense random-packing dynamics, based on diffusing ``spots'' of
interstitial free volume. Simulations with the Spot Model can efficiently
generate realistic flowing packings, and yet the model is simple enough for
mathematical analysis. Starting from a non-local stochastic differential
equation, we derive continuum equations for tracer diffusion, given the
dynamics of free volume (spots). Throughout the paper, we apply the model to
granular drainage in a silo, and we also briefly discuss glassy relaxation. We
conclude by discussing the prospects of spot-based multiscale modeling and
simulation of amorphous materials.",0501130v1
2005-06-10,Rolling friction and bistability of rolling motion,"The rolling motion of a rigid cylinder on an inclined flat viscous surface is
investigated and the nonlinear resistance force against rolling, $F_R(v)$, is
derived. For small velocities $F_R(v)$ increases with velocity due to
increasing deformation rate of the surface material. For larger velocity it
decreases with velocity due to decreasing contact area between the rolling
cylinder and the deformed surface. The cylinder is, moreover, subjected to a
viscous drag force and stochastic fluctuations due to a surrounding medium
(air). For this system, in a wide range of parameters we observe bistability of
the rolling motion. Depending on the material parameters, increasing the noise
level may lead to increasing or decreasing average velocity.",0506255v1
2005-08-21,"Superconductivity, charge ordering and structural properties of alpha and beta-NaxCoO2.y(H2O, D2O)","Two series of &#61537;alpha and beta-NaxCoO2 materials have been prepared by
means of Na deintercalation from the parent &#61537;alpha-NaCoO2 and
&#61538;beta-Na0.6CoO2 phases, respectively. The &#61537;alpha-NaxCoO2
materials undergo a clear phase transition from the hexagonal to the beta-phase
like monoclinic structure along with Na deintercalation. Measurements of
resistivity and magnetization demonstrated the presence notable charge ordering
transitions in both alpha and beta-NaxCoO2 with 0.4 < x < 0.5 below 100K. Bulk
Superconductivity has been observed in the hydrated
&#61537;alpha-NaxCoO2.1.3H2O at ~4.5K and in &#61538;beta-NaxCoO2.1.3H2O at
\~4.3K. Intercalation of D2O in alpha and beta-Na0.33CoO2 also yields
superconductivity at slightly lower temperatures. It is worthy to note that,
despite of the structural difference, the alpha-, beta- and gamma-NaxCoO2 .yH2O
materials show up notable commonalities in their essential physical properties,
e.g. superconductivity and charge ordering transitions.",0508502v1
2005-10-18,Modulated optical reflectance measurements on La2/3Sr1/3MnO3 thin films,"The modulated optical reflectance (MOR) measurement technique was applied to
colossal magnetoresistive materials, in particular, La2/3Sr1/3MnO3 (LSMO) thin
films. The contactless measurement scheme is prospective for many applications
spanning from materials characterization to new devices like reading heads for
magnetically recorded media. A contrasted room temperature surface scan of a
100 microns wide 400 microns long bridge patterned into LSMO film provided
preliminary information about the film homogeneity. Then the temperature was
varied between 240 and 400 K, i.e. through the ferromagnetic to paramagnetic
transition. A clear relation between the MOR signal measured as function of the
temperature and the relative derivative of the resistivity up to the Curie
temperature was observed. This relationship is fundamental for the MOR
technique and its mechanism was explored in the particular case of LSMO.
Analysis in the framework of the Drude model showed that, within certain
conditions, the measured MOR signal changes are correlated to changes in the
charge carrier concentration.",0510475v1
2005-12-22,Laser Scanning Microscopy of HTS Films and Devices,"The work describes the capabilities of Laser Scanning Microscopy (LSM) as a
spatially resolved method of testing high_Tc materials and devices. The earlier
results obtained by the authors are briefly reviewed. Some novel applications
of the LSM are illustrated, including imaging the HTS responses in rf mode,
probing the superconducting properties of HTS single crystals, development of
twobeam laser scanning microscopy. The existence of the phase slip lines
mechanism of resistivity in HTS materials is proven by LSM imaging.",0512582v1
2004-01-19,Laser Generated Magnetic Pulses: Hot Electron Propagation in Conducting and Dielectric Material,"We report experimental evidence of electrostatic inhibition of fast
electrons, generated in a highly resistive material upon irradiation with an
intense ultra-short ($10^{16} W/cm^{2}$, $100 fmsec$) laser pulse. The
experiment involves measurement of temporal evolution of self-generated
magnetic pulses using pump-probe polarimetry. A comparison is made between the
temporal behaviour of magnetic pulses generated with Aluminum and Glass
targets. It is found that in contrast to Aluminium, self-generated magnetic
pulse decays much faster in glass. This is attributed to the absence of return
shielding currents in glass, which results in build up of electrostatic field,
which in turn inhibits the movement of fast electrons. Fitting of experimental
measurements using a one dimensional model, yields estimate of conductivity of
Aluminium and glass, and penetration depth of hot electrons in these materials.",0401084v1
2007-09-12,Reducing the Possibility of Subjective Error in the Determination of the Structure-Function-Based Effective Thermal Conductivity of Boards,"The thermal response function given to a unit-step dissipation accurately
characterizes the thermal system. Instead of the thermal response function the
so-called structure function describing three-dimensional as the equivalent
model of one-dimensional heat-spreading, created from the thermal response
function with the help of complex mathematical procedures, is often used. Using
the structure function the partial thermal capacity and partial heat resistance
of certain elements of the thermal system can be identified. If the geometrical
measurements of a thermal system of simple geometry and homogeneous material
(such as a homogeneous rod or board, etc.) are known, the coefficient of
thermal conductivity of the material in question can be determined from two
points of the structure function at 2-5 per cent of accuracy. In this paper a
method is presented which applies a wide range/section instead of two points of
the cumulative structure function to determine the thermal coefficient, thus
reducing the subjective error deriving from the selection of the two points.
The above method is presented and illustrated in simulated as well as measured
thermal transient responses.",0709.1863v1
2008-01-22,"Phase coherent transport in (Ga,Mn)As","Quantum interference effects and resulting quantum corrections of the
conductivity have been intensively studied in disordered conductors over the
last decades. The knowledge of phase coherence lengths and underlying dephasing
mechanisms are crucial to understand quantum corrections to the resistivity in
the different material systems. Due to the internal magnetic field and the
associated breaking of time-reversal symmetry quantum interference effects in
ferromagnetic materials have been scarcely explored. Below we describe the
investigation of phase coherent transport phenomena in the newly discovered
ferromagnetic semiconductor (Ga,Mn)As. We explore universal conductance
fluctuations in mesoscopic (Ga,Mn)As wires and rings, the Aharonov-Bohm effect
in nanoscale rings and weak localization in arrays of wires, made of the
ferromagnetic semiconductor material. The experiments allow to probe the phase
coherence length L_phi and the spin flip length L_SO as well as the temperature
dependence of dephasing.",0801.3363v1
2008-08-03,Use of a nanoindentation fatigue test to characterize the ductile-brittle transition,"When considering grinding of minerals, scaling effect induces competition
between plastic deformation and fracture in brittle solids. The competition can
be sketched by a critical size of the material, which characterizes the
ductile-brittle transition. A first approach using Vickers indentation gives a
good approximation of the critical size through an extrapolation from the
macroscopic to the microscopic scales. Nanoindentation tests confirm this
experimental value. According to the grain size compared to the indent size, it
can reasonably be said that the mode of damage is deformation-induced
intragranular microfracture. This technique also enables to perform cyclic
indentations to examine calcite fatigue resistance. Repeated loadings with a
nanoindenter on CaCO3 polycrystalline samples produce cumulative mechanical
damage. It is also shown that the transition between ductile and brittle
behaviour depends on the number of indentation cycles. The ductile domain can
be reduced when the material is exposed to a fatigue process.",0808.0329v1
2008-10-02,Metallic conduction at organic charge-transfer interfaces,"The electronic properties of interfaces between two different solids can
differ strikingly from those of the constituent materials. For instance,
metallic conductivity, and even superconductivity, have been recently
discovered at interfaces formed by insulating transition metal oxides. Here we
investigate interfaces between crystals of conjugated organic molecules, which
are large gap undoped semiconductors, i.e. essentially insulators. We find that
highly conducting interfaces can be realized with resistivity ranging from 1 to
30 kOhm square, and that, for the best samples, the temperature dependence of
the conductivity is metallic. The observed electrical conduction originates
from a large transfer of charge between the two crystals that takes place at
the interface, on a molecular scale. As the interface assembly process is
simple and can be applied to crystals of virtually any conjugated molecule, the
conducting interfaces described here represent the first examples of a new
class of electronic systems.",0810.0361v1
2009-11-13,Internal relaxation time in immersed particulate materials,"We study the dynamics of the solid to liquid transition for a model material
made of elastic particles immersed in a viscous fluid. The interaction between
particle surfaces includes their viscous lubrication, a sharp repulsion when
they get closer than a tuned steric length and their elastic deflection induced
by those two forces. We use Soft Dynamics to simulate the dynamics of this
material when it experiences a step increase in the shear stress and a constant
normal stress. We observe a long creep phase before a substantial flow
eventually establishes. We find that the typical creep time relies on an
internal relaxation process, namely the separation of two particles driven by
the applied stress and resisted by the viscous friction. This mechanism should
be relevant for granular pastes, living cells, emulsions and wet foams.",0911.2531v1
2010-02-18,The influence of Ga$^+$-irradiation on the transport properties of mesoscopic conducting thin films,"We studied the influence of 30keV Ga$^+$-ions -- commonly used in focused ion
beam (FIB) devices -- on the transport properties of thin crystalline graphite
flake, La$_{0.7}$Ca$_{0.3}$MnO$_3$ and Co thin films. The changes of the
electrical resistance were measured in-situ during irradiation and also the
temperature and magnetic field dependence before and after irradiation. Our
results show that the transport properties of these materials strongly change
at Ga$^+$ fluences much below those used for patterning and ion beam induced
deposition (IBID), limiting seriously the use of FIB when the intrinsic
properties of the materials of interest are of importance. We present a method
that can be used to protect the sample as well as to produce selectively
irradiation-induced changes.",1002.3565v1
2010-09-24,Photoemission induced gating of topological insulator,"The recently discovered topological insulators exhibit topologically
protected metallic surface states which are interesting from the fundamental
point of view and could be useful for various applications if an appropriate
electronic gating can be realized. Our photoemission study of Cu intercalated
Bi2Se3 shows that the surface states occupancy in this material can be tuned by
changing the photon energy and understood as a photoemission induced gating
effect. Our finding provides an effective tool to investigate the new physics
coming from the topological surface states and suggests the intercalation as a
recipe for synthesis of the material suitable for electronic applications.",1009.4855v2
2011-08-23,Single-Crystal and Powder Neutron Diffraction Study of FeXMn1-XS Solid Solutions,"FeXMn1-XS (0 <x< 0.3) synthesized on the basis of {\alpha}-MnS are the novel
Mott-type substances with the rock salt structure. Neutron diffraction study
shows that the shift of the Neel temperature of these materials from 150 (x =
0) to 200 K (x = 0.29) under the action of chemical pressure (x) is accompanied
by a decrease in the cubic NaCl lattice parameters. The structural transition
with a change in crystal symmetry and a decrease in resistance before the
magnetic transition at x = 0.25 is found. Therefore, FeXMn1-XS are interesting
materials for both fundamental study of the interrelation between the magnetic,
electrical, and structural properties in systems with the strong electron
correlations of a MnO-type and application.",1108.4537v2
2012-02-11,Temperature dependence of the conductivity of graphene on boron nitride,"The substrate material of monolayer graphene influences the charge carrier
mobility by various mechanisms. At room temperature, the scattering of
conduction electrons by phonon modes localized at the substrate surface can
severely limit the charge carrier mobility. We here show that for substrates
made of the piezoelectric hexagonal boron nitride (hBN), in comparison to the
widely used SiO$_2$, this mechanism of remote phonon scattering is --at room
temperature-- weaker by almost an order of magnitude, and causes a resistivity
of approximately 3\,$\Omega$. This makes hBN an excellent candidate material
for future graphene based electronic devices operating at room temperature.",1202.2440v2
2012-10-15,Theory of Charge Order and Heavy-Electron Formation in the Mixed-Valence Compound KNi$_2$Se$_2$,"The material KNi$_2$Se$_2$ has recently been shown to possess a number of
striking physical properties, many of which are apparently related to the mixed
valency of this system, in which there is on average one quasi-localized
electron per every two Ni sites. Remarkably, the material exhibits a charge
density wave (CDW) phase that disappears upon cooling, giving way to a
low-temperature coherent phase characterized by an enhanced electron mass,
reduced resistivity, and an enlarged unit cell free of structural distortion.
Starting from an extended periodic Anderson model and using the slave-boson
formulation, we develop a model for this system and study its properties within
mean-field theory. We find a reentrant first-order transition from a CDW phase,
in which the localized moments form singlet dimers, to a heavy Fermi liquid
phase as temperature is lowered. The magnetic susceptibility is Pauli-like in
both the high- and low-temperature regions, illustrating the lack of a
single-ion Kondo regime such as that usually found in heavy-fermion materials.",1210.4041v3
2012-10-24,Magnetic phase diagram of CePt3B1-xSix,"We present a study of the main bulk properties (susceptibility,
magnetization, resistivity and specific heat) of CePt_3B_(1-x)Si-x, an alloying
system that crystallizes in a noncentrosymmetric lattice, and derive the
magnetic phase diagram. The materials at the end point of the alloying series
have previously been studied, with CePt_3B established as a material with two
different magnetic phases at low temperatures (antiferromagnetic below T_N =
7.8 K, weakly ferromagnetic below T_C ~ 5 K), while CePt3Si is a heavy fermion
superconductor (T_c = 0.75 K) coexisting with antiferromagnetism (T_N = 2.2 K).
From our experiments we conclude that the magnetic phase diagram is divided
into two regions. In the region of low Si content (up to x ~ 0.7) the material
properties resemble those of CePt3B. Upon increasing the Si concentration
further the magnetic ground state continuously transforms into that of CePt3Si.
In essence, we argue that CePt_3B can be understood as a low pressure variant
of CePt3Si.",1210.6489v3
2013-04-26,Preparation and characterization of Bismaleimide resin/titania nanocomposites via sol-gel process,"Bismaleimide (BMI) resin/ titania nanocomposites were synthesized from
allylated-phenolic modified bismaleimide resin and TiO2 via the sol-gel process
of tetrabutyltitanate (Ti(OnBu)4, TBT). These nanocomposite materials were
characterized by FT-IR, XRD, FE-SEM, TGA and DMA. It was found that the
nano-scale TiO2 particles were formed in the AP-BMI resin matrix, and the
average primary particle size of the dispersed phase in the nanocomposites was
less than 100nm, but the particle aggregates with bigger size existed. Obvious
improvements of glass transition temperature and heat resistance properties of
the AP-BMI resins were achieved by the introduction of nano-sized TiO2
inorganic phase, and the modulus of the material was also improved.",1304.7082v1
2013-10-05,Engineered spin-valve type magnetoresistance in Fe$_3$O$_4$-CoFe$_2$O$_4$ core-shell nanoparticles,"Naturally occurring spin-valve-type magnetoresistance (SVMR), recently
observed in Sr2FeMoO6 samples, suggests the possibility of decoupling the
maximal resistance from the coercivity of the sample. Here we present the
evidence that SVMR can be engineered in specifically designed and fabricated
core-shell nanoparticle systems, realized here in terms of soft magnetic Fe3O4
as the core and hard magnetic insulator CoFe2O4 as the shell materials. We show
that this provides a magnetically switchable tunnel barrier that controls the
magnetoresistance of the system, instead of the magnetic properties of the
magnetic grain material, Fe3O4, and thus establishing the feasibility of
engineered SVMR structures.",1310.1469v1
2013-10-23,A simple method to characterize the electrical and mechanical properties of micro-fibers,"A procedure to characterize the electrical and mechanical properties of
micro-fibers is presented here. As the required equipment can be found in many
teaching laboratories, it can be carried out by physics and
mechanical/electrical engineering students. The electrical resistivity, mass
density and Young's modulus of carbon micro-fibers have been determined using
this procedure, obtaining values in very good agreement with the reference
values. The Young's modulus has been obtained by measuring the resonance
frequency of carbon fiber based cantilevers. In this way, one can avoid common
approaches based on tensile or bending tests which are difficult to implement
for microscale materials. Despite the simplicity of the experiments proposed
here, they can be used to trigger in the students interest on the electrical
and mechanical properties of microscale materials.",1310.6134v1
2014-07-31,Quantum Criticality Based on Large Ising Spins: YbCo$_2$Ge$_4$ with New 1-2-4 Structure Type,"We present a new type of quantum critical material YbCo$_2$Ge$_4$, having the
largest quantum-critical pseudospin size ever. The YbCo$_2$Ge$_4$-type
structure is new, forms in the orthorhombic $Cmcm$ system, and is related to
the well-known ThCr$_2$Si$_2$ structure. Heavy rare earth (Tm,Yb,Lu, or Y)
members are also possible to be grown. YbCo$_2$Ge$_4$ possesses the Ising-type
ground-state doublet, namely the simplest ones of uniaxially up or down, $|\pm
\sim 7/2\rangle$. It is clearly manifested through comprehensive resistivity,
magnetization, specific heat, and NQR/NMR experiments. Large pseudospin state
usually tends to order in simple magnetisms, or hard to be screened by Kondo
effect. Therefore, the discovery of the quantum criticality of the fluctuating
large spins opens a new door to new-material search and theoretical studies.",1407.8274v1
2014-09-19,Analysis of the internal heat losses in a thermoelectric generator,"A 3D thermoelectric numerical model is used to investigate different internal
heat loss mechanisms for a thermoelectric generator with bismuth telluride p-
and n-legs. The model considers all thermoelectric effects, temperature
dependent material parameters and simultaneous convective, conductive and
radiative heat losses, including surface to surface radiation. For radiative
heat losses it is shown that for the temperatures considered here, surface to
ambient radiation is a good approximation of the heat loss. For conductive heat
transfer the module efficiency is shown to be comparable to the case of
radiative losses. Finally, heat losses due to internal natural convection in
the module is shown to be negligible for the millimetre sized modules
considered here. The combined case of radiative and conductive heat transfer
resulted in the lowest efficiency. The optimized load resistance is found to
decrease for increased heat loss. The leg dimensions are varied for all heat
losses cases and it is shown that the ideal way to construct a TEG module with
minimal heat losses and maximum efficiency is to either use a good insulating
material between the legs or evacuate the module completely, and use small and
wide legs closely spaced.",1409.6743v1
2015-01-17,Superconductivity in the orthorhombic phase of thermoelectric CsPbxBi4-xTe6 with 0.3=<x=<1.0,"Experimental measurements clearly reveal the presence of bulk
superconductivity in the CsPbxBi4-xTe6 (0.3=<x=<1.0) materials, i.e. the first
member of the thermoelectric series of Cs[PbmBi3Te5+m], these materials have
the layered orthorhombic structure containing infinite anionic [PbBi3Te6]-
slabs separated with Cs+ cations. Temperature dependences of electrical
resistivity, magnetic susceptibility, and specific heat have consistently
demonstrated that the superconducting transition in CsPb0.3Bi3.7Te6 occurs at
Tc=3.1K, with a superconducting volume fraction close to 100% at 1.8 K.
Structural study using aberration-corrected STEM/TEM reveals a rich variety of
microstructural phenomena in correlation with the Pb-ordering and chemical
inhomogeneity. The superconducting material CsPb0.3Bi3.7Te6 with the highest Tc
shows a clear ordered structure with a modulation wave vector of q=a*/2+
c*/1.35 on the a-c plane. Our study evidently demonstrates that
superconductivity deriving upon doping of narrow-gap semiconductor is a viable
approach for exploration of novel superconductors.",1501.04184v1
2015-01-22,DFT+U simulation of the Ti${}_4$O${}_7$-TiO${}_2$ interface,"The formation of conducting channels of Ti${}_4$O${}_7$ inside
TiO${}_2$-based memristors is believed to be the origin for the change in
electric resistivity of these devices. While the properties of the bulk
materials are reasonably known, the interface between them has not been studied
up to now mostly due to their different crystalline structures. In this work we
present a way to match the interfaces between TiO${}_2$ and Ti${}_4$O${}_7$ and
subsequently the band offset between these materials is obtained from density
functional theory based calculations. The results show that while the valence
band is located at the Ti${}_4$O${}_7$, the conduction band is found at the
TiO${}_2$ structure, resulting into a type II interface. In this case, the
Ti${}_4$O${}_7$ would act as a donor to the TiO${}_2$ matrix.",1501.05564v1
2015-02-09,A theory of finite deformation magneto-viscoelasticity,"This paper deals with the mathematical modelling of large strain
magneto-viscoelastic deformations. Energy dissipation is assumed to occur both
due to the mechanical viscoelastic effects as well as the resistance offered by
the material to magnetisation. Existence of internal damping mechanisms in the
body is considered by decomposing the deformation gradient and the magnetic
induction into `elastic' and `viscous' parts. Constitutive laws for material
behaviour and evolution equations for the non-equilibrium fields are derived
that agree with the laws of thermodynamics. To illustrate the theory the
problems of stress relaxation, magnetic field relaxation, time dependent
magnetic induction and strain are formulated and solved for a specific form of
the constitutive law. The results, that show the effect of several modelling
parameters on the deformation and magnetisation process, are illustrated
graphically.",1502.02482v1
2015-08-06,Odd-parity magnetoresistance in pyrochlore iridate thin films with broken time-reversal symmetry,"A new class of materials termed topological insulators have been intensively
investigated due to their unique Dirac surface state carrying dissipationless
edge spin currents. Recently, it has been theoretically proposed that the three
dimensional analogue of this type of band structure, the Weyl Semimetal phase,
is materialized in pyrochlore oxides with strong spin-orbit coupling,
accompanied by all-in-all-out spin ordering. Here, we report on the fabrication
and magnetotransport of Eu2Ir2O7 single crystalline thin films. We reveal that
one of the two degenerate all-in-all-out domain structures, which are connected
by time-reversal operation, can be selectively formed by the polarity of the
cooling magnetic field. Once formed, the domain is robust against an oppositely
polarised magnetic field, as evidenced by an unusual odd field dependent term
in the magnetoresistance and an anomalous term in the Hall resistance. Our
findings pave the way for exploring the predicted novel quantum transport
phenomenon at the surfaces/interfaces or magnetic domain walls of pyrochlore
iridates.",1508.01318v1
2015-09-04,Hall effect in the extremely large magnetoresistance semimetal WTe$_2$,"We systematically measured the Hall effect in the extremely large
magnetoresistance semimetal WTe$_2$. By carefully fitting the Hall resistivity
to a two-band model, the temperature dependencies of the carrier density and
mobility for both electron- and hole-type carriers were determined. We observed
a sudden increase of the hole density below $\sim$160~K, which is likely
associated with the temperature-induced Lifshitz transition reported by a
previous photoemission study. In addition, a more pronounced reduction in
electron density occurs below 50~K, giving rise to comparable electron and hole
densities at low temperature. Our observations indicate a possible electronic
structure change below 50~K, which might be the direct driving force of the
electron-hole ``compensation'' and the extremely large magnetoresistance as
well. Numerical simulations imply that this material is unlikely to be a
perfectly compensated system.",1509.01463v2
2015-11-19,`Ferroelectric' Metals Reexamined: Fundamental Mechanisms and Design Considerations for New Materials,"The recent observation of a ferroelectric-like structural transition in
metallic LiOsO$_3$ has generated a flurry of interest in the properties of
polar metals. Such materials are thought to be rare because free electrons
screen out the long-range electrostatic forces that favor a polar structure
with a dipole moment in every unit cell. In this work, we question whether
long-range electrostatic forces are always the most important ingredient in
driving polar distortions. We use crystal chemical models, in combination with
first-principles Density Functional Theory calculations, to explore the
mechanisms of inversion-symmetry breaking in LiOsO$_3$ and both insulating and
electron-doped ATiO$_3$ perovskites, A = Ba, Sr, Ca. Although electrostatic
forces do play a significant role in driving the polar instability of BaTiO$_3$
(which is suppressed under electron doping), the polar phases of CaTiO$_3$ and
LiOsO$_3$ emerge through a mechanism driven by local bonding preferences and
this mechanism is `resistant' to the presence of charge carriers. Hence, our
results suggest that there is no fundamental incompatibility between
metallicity and polar distortions. We use the insights gained from our
calculations to suggest design principles for new polar metals and promising
avenues for further research.",1511.06187v2
2016-01-12,Superconductivity in Tl_{0.6}Bi_{2}Te_{3} Derived from a Topological Insulator,"Bulk superconductivity has been discovered in Tl_{0.6}Bi_{2}Te_{3}, which is
derived from the topological insulator Bi2Te3. The superconducting volume
fraction of up to 95% (determined from specific heat) with Tc of 2.28 K was
observed. The carriers are p-type with the density of ~1.8 x 10^{20} cm^{-3}.
Resistive transitions under magnetic fields point to an unconventional
temperature dependence of the upper critical field B_{c2}. The crystal
structure appears to be unchanged from Bi2Te3 with a shorter c-lattice
parameter, which, together with the Rietveld analysis, suggests that Tl ions
are incorporated but not intercalated. This material is an interesting
candidate of a topological superconductor which may be realized by the strong
spin-orbit coupling inherent to topological insulators.",1601.02877v1
2016-05-06,Intrinsic Negative Poisson's Ratio for Single-Layer Graphene,"Negative Poisson's ratio (NPR) materials have drawn significant interest
because the enhanced toughness, shear resistance and vibration absorption that
typically are seen in auxetic materials may enable a range of novel
applications. In this work, we report that single-layer graphene exhibits an
intrinsic NPR, which is robust and independent of its size and temperature. The
NPR arises due to the interplay between two intrinsic deformation pathways (one
with positive Poisson's ratio, the other with NPR), which correspond to the
bond stretching and angle bending interactions in graphene. We propose an
energy-based deformation pathway criteria, which predicts that the pathway with
NPR has lower energy and thus becomes the dominant deformation mode when
graphene is stretched by a strain above 6%, resulting in the NPR phenomenon.",1605.01827v2
2016-03-24,"Isotoxal star-shaped polygonal voids and rigid inclusions in nonuniform antiplane shear fields. Part II: Singularities, annihilation and invisibility","Notch stress intensity factors and stress intensity factors are obtained
analytically for isotoxal star-shaped polygonal voids and rigid inclusions (and
also for the corresponding limit cases of star-shaped cracks and stiffeners),
when loaded through remote inhomogeneous (self-equilibrated, polynomial)
antiplane shear stress in an infinite linear elastic matrix. Usually these
solutions show stress singularities at the inclusion corners. It is shown that
an infinite set of geometries and loading conditions exist for which not only
the singularity is absent, but the stress vanishes ('annihilates') at the
corners. Thus the material, which even without the inclusion corners would have
a finite stress, remains unstressed at these points in spite of the applied
remote load. Moreover, similar conditions are determined in which a star-shaped
crack or stiffener leaves the ambient stress completely unperturbed, thus
reaching a condition of 'quasi-static invisibility'. Stress annihilation and
invisibility define optimal loading modes for the overall strength of a
composite and are useful for designing ultra-resistant materials.",1605.04942v1
2016-10-30,"Characteristics of Interlayer Tunneling Field Effect Transistors Computed by a ""DFT-Bardeen"" Method","Theoretical predictions are made for the current-voltage characteristics of
two-dimensional heterojunction interlayer tunneling field-effect transistors
(Thin-TFETs), focusing on the magnitude of the current that is achievable in
such devices. A theory based on the Bardeen tunneling method is employed, using
wavefunctions from first-principles density-functional theory. This method
permits convenient incorporation of differing materials into the source and
drain electrodes, i.e. with different crystal structures, lattice constants,
and/or band structures. Large variations in the tunnel currents are found,
depending on the particular two-dimensional materials used for the source and
drain electrodes. Tunneling between states derived from the center
(Gamma-point) of the Brillouin zone (BZ) is found, in general, to lead to
larger current than for zone-edge (e.g. K-point) states. Differences, as large
as an order of magnitude, between the present results and various prior
predictions are discussed. Predicted values for the tunneling currents,
including subthreshold swing, are compared with benchmark values for low-power
digital applications. Contact resistance is considered and its effect on the
tunneling currents is demonstrated.",1610.09695v1
2016-10-31,Signature of Hanle Precession in Trilayer MoS2: Theory and Experiment,"Valley-spin coupling in transition-metal dichalcogenides (TMDs) can result in
unusual spin transport behaviors under an external magnetic field. Nonlocal
resistance measured from 2D materials such as TMDs via electrical Hanle
experiments are predicted to exhibit nontrivial features, compared with results
from conventional materials due to the presence of intervalley scattering as
well as a strong internal spin-orbit field. Here, for the first time, we report
the all-electrical injection and non-local detection of spin polarized carriers
in trilayer MoS_2 films. We calculate the Hanle curves theoretically when the
separation between spin injector and detector is much larger than spin
diffusion length, \lamda_s. The experimentally observed curve matches the
theoretically-predicted Hanle shape under the regime of slow intervalley
scattering. The estimated spin life-time was found to be around 110 ps at 30 K.",1611.00059v1
2016-11-23,"Electron interactions, spin-orbit coupling, intersite correlations in pyrochlore iridates","We perform combined density functional and dynamical mean-field calculations
to study the pyrochlore iridates Lu$_2$Ir$_2$O$_7$, Y$_2$Ir$_2$O$_7$ and
Eu$_2$Ir$_2$O$_7$. Both single-site and cluster dynamical mean-field
calculations are performed and spin-orbit coupling is included. Paramagnetic
metallic phases, antiferromagnetic metallic phases with tilted Weyl cones and
antiferromagnetic insulating phases are found. The magnetic phases display
all-in/all-out magnetic ordering, consistent with previous studies. Unusually
for electronically three dimensional materials, the single-site dynamical
mean-field approximation fails to reproduce qualitative material trends,
predicting in particular that the paramagnetic phase properties of
Y$_2$Ir$_2$O$_7$ and Eu$_2$Ir$_2$O$_7$ are almost identical, although in
experiments the Y compound has a much higher resistance than the Eu compound.
This qualitative failure is attributed to the importance of intersite magnetic
correlations in the physics of these materials.",1611.07997v2
2017-02-27,Quantum critical scaling and fluctuations in Kondo lattice materials,"We propose a new phenomenological framework for three classes of Kondo
lattice materials that incorporates the interplay between the fluctuations
associated with the antiferromagnetic quantum critical point and those produced
by the hybridization quantum critical point that marks the end of local moment
behavior. We show that these fluctuations give rise to two distinct regions of
quantum critical scaling: hybridization fluctuations are responsible for the
logarithmic scaling in the density of states of the heavy electron Kondo liquid
that emerges below the coherence temperature T*; while the unconventional power
law scaling in the resistivity that emerges at lower temperatures below T_QC
may reflect the combined effects of hybridization and antiferromagnetic quantum
critical fluctuations. Our framework is supported by experimental measurements
on CeCoIn5, CeRhIn5 and other heavy electron materials.",1702.08132v2
2017-06-30,Two-Dimensional h-BN and MoS2 as Diffusion Barriers for Ultra-Scaled Copper Interconnects,"Copper interconnects in modern integrated circuits require ultra-thin
barriers to prevent intermixing of Cu with surrounding dielectric materials.
Conventional barriers rely on metals like TaN, however their finite thickness
reduces the cross-sectional area and significantly increases the resistivity of
nanoscale interconnects. In this study, a new class of two-dimensional (2D) Cu
diffusion barriers, hexagonal boron nitride (h-BN) and molybdenum disulfide
(MoS2), is demonstrated for the first time. Using time-dependent dielectric
breakdown measurements and scanning transmission electron microscopy coupled
with energy dispersive X-ray spectroscopy and electron energy loss
spectroscopy, these 2D materials are shown to be promising barrier solutions
for ultra-scaled interconnect technology. The predicted lifetime of devices
with directly deposited 2D barriers can achieve three orders of magnitude
improvement compared to control devices without barriers.",1706.10178v1
2017-08-31,Nonmonotonic dependence of polymer glass mechanical response on chain bending stiffness,"We investigate the mechanical properties of amorphous polymers by means of
coarse-grained simulations and nonaffine lattice dynamics theory. A small
increase of polymer chain bending stiffness leads first to softening of the
material, while hardening happens only upon further strengthening of the
backbones. This nonmonotonic variation of the storage modulus $G'$ with bending
stiffness is caused by a competition between additional resistance to
deformation offered by stiffer backbones and decreased density of the material
due to a necessary decrease in monomer-monomer coordination. This
counter-intuitive finding suggests that the strength of polymer glasses may in
some circumstances be enhanced by softening the bending of constituent chains.",1709.00024v2
2017-12-31,Geometry Effects on Switching Currents in Superconducting Ultra Thin Films,"Vortex dynamics is strongly connected with the mechanisms responsible for the
photon detection of superconducting devices. Indeed, the local suppression of
superconductivity by photon absorption may trigger vortex nucleation and motion
effects, which can make the superconducting state unstable. In addition,
scaling down the thickness of the superconducting films and/or the width of the
bridge geometry can strongly influence the transport properties of
superconducting films, e.g. affecting its critical current as well as its
switching current into the normal state. Understanding such instability can
boost the performances of those superconducting devices based on nanowire
geometries. We present an experimental study on the resistive switching in NbN
and NbTiN ultra-thin films with a thickness of few nanometers. Despite both
films were patterned with the same microbridge geometry, the two
superconducting materials show different behaviors at very low applied magnetic
fields. A comparison with other low temperature superconducting materials
outlines the influence of geometry effects on the superconducting transport
properties of these materials particularly useful for devices applications.",1801.00306v1
2018-02-22,Shear strength of wet granular materials: macroscopic cohesion and effective stress,"Rheometric measurements on assemblies of wet polystyrene bead assemblies, in
steady uniform quasistatic shear flow, for varying liquid content within the
small saturation (pendular) range of isolated liquid bridges, are supplemented
with a systematic study by discrete numerical simulations. Numerical results
and experimental ones agree quantitatively is the intergranular friction
coefficient is set to 0.09, suitable for the dry material. Shear resistance and
solid fraction are recorded as functions of the reduced pressure p, comparing
normal stress to capillary bridge tensile strength. The Mohr-Coulomb relation
with p-independent cohesion c applies for p above 2. The assumption that
contact force contributions to stress act as effective stresses predicts shear
strength quite well throughout the numerically investigated range of
parameters.. A generalized Mohr-Coulomb cohesion c is defined, which relates to
the dry material internal friction, coordination numbers and capillary force
network anisotropy. The Rumpf formula approximation, ignoring capillary shear
stress is correct for the larger saturation range within the pendular regime,
but fails to describe its decrease for small liquid contents.",1802.08172v1
2018-09-12,Elastoresistive and Elastocaloric Anomalies at Magnetic and Electronic-Nematic Critical Points,"Using Ba(Fe$_{0.975}$Co$_{0.025}$)$_2$As$_{2}$ as an exemplar material
exhibiting second order electronic-nematic and antiferromagnetic transitions,
we present measurements that reveal anomalies in the elastoresistance
$\left(\frac{\partial \rho_{ij}}{\partial\varepsilon_{kl}}\right)$ and
elastocaloric effect $\left(\frac{\partial T}{\partial\varepsilon_{kl}}\right)$
at both phase transitions. Both effects are understood to arise from the effect
of strain on the transition temperatures; in the region close to the phase
transitions this leads to (1) similarity between the strain and temperature
derivatives of the resistivity and (2) similarity between the elastocaloric
effect and the singular part of the specific heat. These mechanisms for
elastoresistance and elastocaloric effect should be anticipated for any
material in which mechanical deformation changes the transition temperature.
Furthermore, these measurements provide evidence that the Fisher-Langer
relation $\rho^{(c)} \propto U^{(c)}$ between the scattering from critical
degrees of freedom and their energy-density, respectively, holds near each of
the Ne\'{e}l and electronic nematic transitions in the material studied.",1809.04582v1
2018-09-17,Electric-Field Control of Magnetic Order: From FeRh to Topological Antiferromagnetic Spintronics,"Using an electric field instead of an electric current (or a magnetic field)
to tailor the electronic properties of magnetic materials is promising for
realizing ultralow energy-consuming memory devices because of the suppression
of Joule heating, especially when the devices are scaled to the nanoscale. In
the review, we summarize recent results on the giant magnetization and
resistivity modulation in a metamagnetic intermetallic alloy - FeRh, which is
achieved by electric-field-controlled magnetic phase transitions in
multiferroic heterostructures. Furthermore, the approach is extended to
topological antiferromagnetic spintronics, which is currently receiving
attention in the magnetic society, and the antiferromagnetic order parameter
has been able to switch back and forth by a small electric field. In the end,
we envision the possibility of manipulating exotic physical phenomena in the
emerging topological antiferromagnetic spintronics field via the electric-field
approach.",1809.06011v1
2017-03-02,Morphology and properties evolution upon ring-opening polymerization during extrusion of cyclic butylene terephthalate and graphene-related-materials into thermally conductive nanocomposites,"In this work, the study of thermal conductivity before and after in-situ
ring-opening polymerization of cyclic butylene terephthalate into poly
(butylene terephthalate) in presence of graphene-related materials (GRM) is
addressed, to gain insight in the modification of nanocomposites morphology
upon polymerization. Five types of GRM were used: one type of graphite
nanoplatelets, two different grades of reduced graphene oxide (rGO) and the
same rGO grades after thermal annealing for 1 hour at 1700{\deg}C under vacuum
to reduce their defectiveness. Polymerization of CBT into pCBT, morphology and
nanoparticle organization were investigated by means of differential scanning
calorimetry, electron microscopy and rheology. Electrical and thermal
properties were investigated by means of volumetric resistivity and bulk
thermal conductivity measurement. In particular, the reduction of nanoflake
aspect ratio during ring-opening polymerization was found to have a detrimental
effect on both electrical and thermal conductivities in nanocomposites.",1703.00805v2
2015-05-18,Unique opportunity to harness polarization in GaN to override the conventional power electronics figure-of-merits,"Owing to the large breakdown electric field, wide bandgap semiconductors such
as SiC, GaN, Ga2O3 and diamond based power devices are the focus for next
generation power switching applications. The unipolar trade-off relationship
between the area specific-on resistance and breakdown voltage is often employed
to compare the performance limitation among various materials. The GaN material
system has a unique advantage due to its prominent spontaneous and
piezoelectric polarization effects in GaN, AlN, InN, AlxInyGaN alloys and
flexibility in inserting appropriate heterojunctions thus dramatically broaden
the device design space.",1505.04651v1
2015-05-21,Impedance Matching of Atomic Thermal Interfaces Using Primitive Block Decomposition,"We explore the physics of thermal impedance matching at the interface between
two dissimilar materials by controlling the properties of a single atomic mass
or bond. The maximum thermal current is transmitted between the materials when
we are able to decompose the entire heterostructure solely in terms of
primitive building blocks of the individual materials. Using this approach, we
show that the minimum interfacial thermal resistance arises when the
interfacial atomic mass is the arithmetic mean, while the interfacial spring
constant is the harmonic mean of its neighbors. The contact induced broadening
matrix for the local vibronic spectrum, obtained from the self-energy matrices,
generalizes the concept of acoustic impedance to the nonlinear phonon
dispersion or the short-wavelength (atomic) limit.",1505.05564v1
2017-11-06,"On the relation between plasticity, friction, and geometry","Plasticity refers to thermodynamically irreversible deformation associated
with a change of configuration of materials. Friction is a phenomenological law
that describes the forces resisting sliding between two solids or across an
embedded dislocation. These two types of constitutive behaviors explain the
deformation of a wide range of engineered and natural materials. Yet, they are
typically described with distinct physical laws that cloud their inherent
connexion. Here, I introduce a multiplicative form of kinematic friction that
closely resembles the power-law flow of viscoplastic materials and that
regularizes the constitutive behavior at vanishing velocity, with important
implications for rupture dynamics. Using a tensor-valued state variable that
describes the degree of localization, I describe a constitutive framework
compatible with viscoplastic theories that captures the continuum between
distributed and localized deformation and for which the frictional response
emerges when the deformed region collapses from three to two dimensions.",1711.01954v2
2018-10-12,Non-volatile ferroelectric memory effect in ultrathin α-In2Se3,"Recent experiments on layered {\alpha}-In2Se3 have confirmed its
room-temperature ferroelectricity under ambient condition. This observation
renders {\alpha}-In2Se3 an excellent platform for developing two-dimensional
(2D) layered-material based electronics with nonvolatile functionality. In this
letter, we demonstrate non-volatile memory effect in a hybrid 2D ferroelectric
field effect transistor (FeFET) made of ultrathin {\alpha}-In2Se3 and graphene.
The resistance of graphene channel in the FeFET is tunable and retentive due to
the electrostatic doping, which stems from the electric polarization of the
ferroelectric {\alpha}-In2Se3. The electronic logic bit can be represented and
stored with different orientations of electric dipoles in the top-gate
ferroelectric. The 2D FeFET can be randomly re-written over more than $10^5$
cycles without losing the non-volatility. Our approach demonstrates a protype
of re-writable non-volatile memory with ferroelectricity in van de Waals 2D
materials.",1810.05328v1
2018-10-17,From plastic flow to brittle fracture: role of microscopic friction in amorphous solids,"Plasticity in soft amorphous materials typically involves collective
deformation patterns that emerge upon intense shearing. The microscopic basis
of amorphous plasticity has been commonly established through the notion of
""Eshelby""-type events, localized abrupt rearrangements that induce flow in the
surrounding material via non-local elastic-type interactions. This universal
mechanism in flowing disordered solids has been proposed despite their
diversity in terms of scales, microscopic constituents, or interactions.
However, we argue that the presence of frictional interactions in granular
solids alters the dynamics of flow by nucleating micro shear cracks that
continually coalesce to build up system-spanning fracture-like formations on
approach to failure. The plastic-to-brittle failure transition is uniquely
controlled by the degree of frictional resistance which is in essence similar
to the role of heterogeneities that separate the abrupt and smooth yielding
regimes in glassy structures.",1810.07418v1
2018-10-17,Modeling Heterogeneous Melting in Phase Change Memory Devices,"We present thermodynamic crystallization and melting models and calculate
phase change velocities in $Ge_2 Sb_2 Te_5$ based on kinetic and thermodynamic
parameters. The calculated phase change velocities are strong functions of
grain size, with smaller grains beginning to melt at lower temperatures. Phase
change velocities are continuous functions of temperature which determine
crystallization and melting rates. Hence, set and reset times as well as power
and peak current requirements for switching are strong functions of grain size.
Grain boundary amorphization can lead to a sufficient increase in cell
resistance for small-grain phase change materials even if the whole active
region does not completely amorphize. Isolated grains left in the amorphous
regions, the quenched-in nuclei, facilitate templated crystal growth and
significantly reduce set times for phase change memory cells. We demonstrate
the significance of heterogeneous melting through 2-D electrothermal
simulations coupled with a dynamic materials phase change model. Our results
show reset and set times on the order of ~1 ns for 30 nm wide confined
nanocrystalline (7.5 nm - 25 nm radius crystals) phase change memory cells.",1810.07764v1
2018-11-08,Magnetically-driven orbital-selective insulator-metal transition in double perovskite oxides,"Interaction-driven metal-insulator transitions or Mott transitions
  are widely observed in condensed-matter systems. In multi-orbital
  systems, many-body physics is richer in which an orbital-selective
  metal-insulator transition is an intriguing and unique
  phenomenon. Here we use first-principles calculations to show that a
  magnetic transition (from paramagnetic to long-range magnetically
  ordered) can simultaneously induce an orbital-selective
  insulator-metal transition in rock-salt ordered double perovskite
  oxides $A_2BB'$O$_6$ where $B$ is a non-magnetic ion (Y$^{3+}$ and
  Sc$^{3+}$) and $B'$ a
  magnetic ion with a $d^3$ electronic configuration (Ru$^{5+}$ and
  Os$^{5+}$). The orbital selectivity originates from
  geometrical frustration of a face-centered-cubic lattice on which
  the magnetic ions $B'$ reside. Including realistic structural
  distortions and spin-orbit interaction do
  not affect the transition. The predicted orbital-selective transition
  naturally explains the anomaly observed in the electric resistivity
  of Sr$_2$YRuO$_6$. Implications of other available experimental data
  are also discussed. Our work shows that by exploiting
  geometrical frustration on non-bipartite lattices, novel
  electronic/magnetic/orbital-coupled phase transitions can occur in
  correlated materials that are in the vicinity of metal-insulator phase
  boundary.",1811.03465v1
2018-11-08,Giant anomalous Nernst effect in the magnetic Weyl semimetal Co3Sn2S2,"In ferromagnetic solids, even in absence of magnetic field, a transverse
voltage can be generated by a longitudinal temperature gradient. This
thermoelectric counterpart of the Anomalous Hall effect (AHE) is dubbed the
Anomalous Nernst effect (ANE). Expected to scale with spontaneous
magnetization, both these effects arise because of the Berry curvature at the
Fermi energy. Here, we report the observation of a giant ANE in a
newly-discovered magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$ crystal. Hall
resistivity and Nernst signal both show sharp jumps at a threshold field and
exhibit a clear hysteresis loop below the ferromagnetic transition temperature.
The ANE signal peaks a maximum value of about 5 miuV/K which is comparable to
the largest seen in any magnetic material. Moreover, the anomalous transverse
thermoelectric conductivity becomes as large as about 10 A/K.m at 70 K, the
largest in known semimetals. The observed ANE signal is much larger than what
is expected according to the magnetization.",1811.03485v2
2018-11-23,Extremely large magnetoresistance induced by hidden three-dimensional Dirac bands in nonmagnetic semimetal InBi,"Extremely large positive magnetoresistance (XMR) was found in a nonmagnetic
semimetal InBi. Using several single crystals with different residual
resistivity ratios (RRRs), we revealed that the XMR strongly depended on the
RRR (sample quality). Assuming that there were no changes in effective mass m*
and carrier concentrations in these single crystals, this dependence was
explained by a semiclassical two-carrier model. First-principle calculations
including the spin-orbit interactions (SOI) unveiled that InBi had a
compensated carrier balance and SOI-induced ""hidden"" three-dimensional (3D)
Dirac bands at the M and R points. Because the small m* and the large carrier
mobilities will be realized, these hidden 3D Dirac bands should play an
important role for the XMR in InBi. We suggest that this feature can be
employed as a novel strategy for the creation of XMR semimetals.",1811.09383v2
2019-02-07,In situ control of diamagnetism by electric current in Ca$_3$(Ru$_{1-x}$Ti$_x$)$_2$O$_7$,"Non-equilibrium steady state (NESS) conditions induced by DC current can
alter the physical properties of strongly correlated electron systems (SCES).
In this regard, it was recently shown that DC current can trigger novel
electronic states, such as current-induced diamagnetism, which cannot be
realized in equilibrium conditions. However, reversible control of diamagnetism
has not been achieved yet. Here, we demonstrate reversible in situ control
between a Mott insulating state and a diamagnetic semimetal-like state by DC
current in the Ti-substituted bilayer ruthenate
Ca$_3$(Ru$_{1-x}$Ti$_x$)$_2$O$_7$ ($x=0.5$%). By performing simultaneous
magnetic and resistive measurements, we map out the temperature vs
current-density phase diagram in the NESS of this material. The present results
open up the possibility of creating novel electronic states in a variety of
SCES under DC current.",1902.02515v1
2019-05-15,Unconventional Hall Effect induced by Berry Curvature,"Berry phase and Berry curvature play a key role in the development of
topology in physics and do contribute to the transport properties in solid
state systems. In this paper, we report the finding of novel nonzero Hall
effect in topological material ZrTe5 flakes when in-plane magnetic field is
parallel and perpendicular to the current. Surprisingly, both symmetric and
antisymmetric components with respect to magnetic field are detected in the
in-plane Hall resistivity. Further theoretical analysis suggests that the
magnetotransport properties originate from the anomalous velocity induced by
Berry curvature in a tilted Weyl semimetal. Our work not only enriches the Hall
family but also provides new insights into the Berry phase effect in
topological materials.",1905.06040v2
2020-02-13,Guest-Tunable Dielectric Sensing Using a Single Crystal of HKUST-1,"There is rising interest on low-k dielectric materials based on porous
metal-organic frameworks (MOFs) for improved electrical insulation in
microelectronics. Herein, we demonstrate the concept of MOF dielectric sensor
built from a single crystal of HKUST-1. We study guest encapsulation effects of
polar and non-polar molecules, by monitoring the transient dielectric response
and AC conductivity of the crystal exposed to different vapors (water, I2,
methanol, ethanol). The dielectric properties were measured along the <100>
crystal direction in the frequency range of 100 Hz to 2 MHz. The dielectric
data show the efficacy of MOF dielectric sensor for discriminating the guest
analytes. The time-dependent transient response reveals dynamics of the
molecular inclusion and exclusion processes in the nanoscale pores. Since
dielectric response is ubiquitous to all MOF materials (unlike DC conductivity
and fluorescence), our results demonstrate the potential of dielectric MOF
sensors compared to resistive sensors and luminescence-based approaches.",2002.05705v1
2020-04-08,Nonreciprocal thermal transport in a multiferroic helimagnet,"Breaking of spatial inversion symmetry (SIS) induces unique phenomena in
condensed matter. Besides the classic examples such as natural optical activity
and piezoelectricity, the spin-orbit interaction further enriches the effect of
SIS breaking, as exemplified by the Rashba effect. In particular, by combining
this symmetry with magnetic fields or another type of time-reversal symmetry
(TRS) breaking, noncentrosymmetric materials can be made to exhibit
nonreciprocal responses, which are responses that differ for rightward and
leftward stimuli. For example, resistivity becomes directionally dependent;
that is to say, rectification appears in noncentrosymmetric materials in a
magnetic field. However, the effect of SIS breaking on thermal transport
remains to be elucidated. Here we show nonreciprocal thermal transport in the
multiferroic helimagnet TbMnO3. The longitudinal thermal conductivity depends
on whether the thermal current is parallel or antiparallel to the vector
product of the electric polarization and magnetization. This phenomenon is
thermal rectification that is controllable with external fields in a uniform
crystal. This discovery may pave the way to thermal diodes with controllability
and scalability.",2004.03801v1
2012-01-13,Ferroelectric PbTiO$_{3}$/SrRuO$_{3}$ superlattices with broken inversion symmetry,"We have fabricated PbTiO$_{3}$/SrRuO$_{3}$ superlattices with ultra-thin
SrRuO$_{3}$ layers. Due to the superlattice geometry, the samples show a large
anisotropy in their electrical resistivity, which can be controlled by changing
the thickness of the PbTiO$_{3}$ layers. Therefore, along the ferroelectric
direction, SrRuO$_{3}$ layers can act as dielectric, rather than metallic,
elements. We show that, by reducing the concentration of PbTiO$_{3}$, an
increasingly important effect of polarization asymmetry due to compositional
inversion symmetry breaking occurs. The results are significant as they
represent a new class of ferroelectric superlattices, with a rich and complex
phase diagram. By expanding our set of materials we are able to introduce new
behaviors that can only occur when one of the materials is not a perovskite
titanate. Here, compositional inversion symmetry breaking in bi-color
superlattices, due to the combined variation of A and B site ions within the
superlattice, is demonstrated using a combination of experimental measurements
and first principles density functional theory.",1201.2893v2
2012-01-31,Effect of starting materials on the superconducting properties of SmFeAsO1-xFx tapes,"SmFeAsO1-xFx tapes were prepared using three kinds of starting materials. It
shows that the starting materials have an obvious effect on the impurity phases
in final superconducting tapes. Compared with the other samples, the samples
fabricated by SmAs, FeO, Fe2As, and SmF3 have the smallest arsenide impurity
phase and voids. As a result, these samples possess much denser structure and
better grain connectivity. Moreover, among the three kinds of samples
fabricated in this work, this kind of sample has the highest zero-resistivity
temperature ~40 K and largest critical current density ~4600 A/cm^2 in
self-field at 4.2 K. This is the highest Jc values reported so far for
SmFeAsO1-xFx wires and tapes.",1201.6522v1
2014-01-05,Phase-coexistence and glass-like behavior in magnetic and dielectric solids with long range order,"Phase-coexistence in the manganese-oxide compounds or manganites with
colossal magneto-resistance (CMR) has been generally considered to be an
inhomogeneous ground state. An alternative explanation of phase-coexistence as
the manifestation of a disorder-broadened first order magnetic phase transition
being interrupted by the glasslike arrest of kinetics is now gradually gaining
ground. This kinetic arrest of a first order phase transitions, between two
states with long-range magnetic order, has actually been observed in various
other classes of magnetic materials in addition to the CMR manganites. The
underlying common features of this kinetic arrest of a first order phase
transition are discussed in terms of the phenomenology of glasses. The possible
manifestations of such glass-like arrested states across disorder-influenced
first order phase transitions in dielectric solids and in multiferroic
materials, are also discussed.",1401.0891v2
2017-04-04,Mechanics of disordered auxetic metamaterials,"Auxetic materials are of great engineering interest not only because of their
fascinating negative Poisson's ratio, but also due to their increased toughness
and indentation resistance. These materials are typically synthesized polyester
foams with a very heterogeneous structure, but the role of disorder in auxetic
behavior is not fully understood. Here, we provide a systematic theoretical and
experimental investigation in to the effect of disorder on the mechanical
properties of a paradigmatic auxetic lattice with a re-entrant hexagonal
geometry. We show that disorder has a marginal effect on the Poisson's ratio
unless the lattice topology is altered, and in all cases examined the disorder
preserves the auxetic characteristics. Depending on the direction of loading
applied to these disordered auxetic lattices, either brittle or ductile failure
is observed. It is found that brittle failure is associated with a
disorder-dependent tensile strength, whereas in ductile failure disorder does
not affect strength. Our work thus provides general guidelines to optimize
elasticity and strength of disordered auxetic metamaterials.",1704.00943v3
2017-05-31,Tuning of Magnetic and Electrical Properties in Complex oxide Thin Films Deposited By Pulsed Laser Deposition,"Lanthanum manganite, LaMnO (LMO) is the parent compound for a class of hole
doped(e.g. La1-xCaxMnO3, La1-xSrxMnO3) and electron doped (e.g. . La1-xCexMnO3,
La1-xSnxMnO3) perovskite complex oxide materials. Strong correlation between
the spin,lattice, charge and orbital degrees of freedom is a hallmark of these
class of materials (popularly known as manganites). Competition and interplay
of these degrees of freedom lead to a wide range of interesting electronic
behavior including half-metallicity, colossal magneto-resistivity, etc.
Although a lot of experimental research has been carried out on the hole doped
and the electron doped counterparts, the parent system LMO remains less
investigated. This could be attributed to the difficulty in making
stoichiometric LMO (whether in bulk polycrystalline, single crystals or thin
films). There exists phenomenon like double-exchange (DE) and
anti-ferromagnetic super-exchange (SE) interactions which leads to
ferromagnetism in LMO thin films. This project work is aimed at the fabrication
and characterization of thin films of stoichiometric LMO and their structural,
magnetic and electrical studies.",1705.11003v1
2017-07-04,"Time-temperature superposition in grain and grain boundary response regime of A2HoRuO6 (A = Ba, Sr, Ca) double perovskite ceramics: A Conductivity Spectroscopic Analysis","The pursuit for an appropriate universal scaling factor to satisfy the
time-temperature superposition principle for grain and grain boundary responses
has been explored in the ac conductivity domain for polycrystalline double
perovskite oxides A2HoRuO6 (AHR; A = Ba, Sr, Ca). The samples show different
structural phases ranging from cubic to monoclinic with decreasing ionic radii.
The degree of distortion in the materials is correlated to the strength of
bonding through the bond valence sum (BVS). The conductivity spectra for all
the samples obey the power law behaviour. The contribution of different
microstructural features to the conduction process is established. Thermal
variation of dc resistivity points towards a gradual crossover from nearest
neighbour to variable range hopping. The activation energies obtained from dc
conductivity, hopping frequency and relaxation frequency show close correlation
between the conduction and relaxation mechanisms. The scaled conductivity
curves for AHR showed the presence of two different conduction processes with
dissimilar activation energies in the grain boundary and grain response
regimes. It is thus concluded that a single scaling parameter is insufficient
to satisfy the time temperature superposition principle universally when two
different thermally activated regions are present simultaneously in the
materials.",1707.00881v1
2017-07-18,Insulator to Metal Transition in WO$_3$ Induced by Electrolyte Gating,"Tungsten oxide and its associated bronzes (compounds of tungsten oxide and an
alkali metal) are well known for their interesting optical and electrical
characteristics. We have modified the transport properties of thin WO$_3$ films
by electrolyte gating using both ionic liquids and polymer electrolytes. We are
able to tune the resistivity of the gated film by more than five orders of
magnitude, and a clear insulator-to-metal transition is observed. To clarify
the doping mechanism, we have performed a series of incisive operando
experiments, ruling out both a purely electronic effect (charge accumulation
near the interface) and oxygen-related mechanisms. We propose instead that
hydrogen intercalation is responsible for doping WO$_3$ into a highly
conductive ground state and provide evidence that it can be described as a
dense polaronic gas.",1707.05748v1
2019-04-02,Solid Propellants,"Solid propellants are energetic materials used to launch and propel rockets
and missiles. Although their history dates to the use of black powder more than
two millennia ago, greater performance demands and the need for ""insensitive
munitions"" that are resistant to accidental ignition have driven much research
and development over the past half-century. The focus of this review is the
material aspects of propellants, rather than their performance, with an
emphasis on the polymers that serve as binders for oxidizer particles and as
fuel for composite propellants. The prevalent modern binders are discussed
along with a discussion of the limitations of state-of-the-art modeling of
composite motors.",1904.01510v1
2019-04-08,Superhydrophobic frictions,"Contrasting with its sluggish behavior on standard solids, water is extremely
mobile on superhydrophobic materials, as shown for instance by the continuous
acceleration of drops on tilted water-repellent leaves. For much longer
substrates, however, drops reach a terminal velocity that results from a
balance between weight and friction, allowing us to question the nature of this
friction. We report that the relationship between force and terminal velocity
is non-linear. This is interpreted by showing that classical sources of
friction are minimized, so that the aerodynamical resistance to motion becomes
dominant, which eventually explains the matchless mobility of water. Our
results are finally extended to viscous liquids, also known to be unusually
quick on these materials.",1904.03913v1
2019-04-23,Hydrated lithium intercalation into the Kitaev spin liquid candidate material $α-$RuCl$_3$,"We study on transport and magnetic properties of hydrated and
lithium-intercalated $\alpha$-RuCl$_3$, Li$_x$RuCl$_3 \cdot y$H$_2$O, for
investigating the effect on mobile-carrier doping into candidate materials for
a realization of a Kitaev model. From thermogravitometoric and one-dimensional
electron map analyses, we find two crystal structures of this system, that is,
mono-layer hydrated Li$_x$RuCl$_3 \cdot y$H$_2$O~$(x\approx0.56, y\approx1.3)$
and bi-layer hydrated Li$_x$RuCl$_3 \cdot y$H$_2$O~$(x\approx0.56,
y\approx3.9)$. The temperature dependence of the electrical resistivity shows a
temperature hysteresis at 200-270 K, which is considered to relate with a
formation of a charge order. The antiferromagnetic order at 7-13 K in pristine
$\alpha$-RuCl$_3$~ is successfully suppressed down to 2 K in bi-layer hydrated
Li$_x$RuCl$_3 \cdot y$H$_2$O, which is sensitive to not only an electronic
state of Ru but also an interlayer distance between Ru-Cl planes.",1904.10231v2
2019-12-03,Large Resistance Change on Magnetic Tunnel Junction based Molecular Spintronics Devices,"Molecular bridges covalently bonded to two ferromagnetic electrodes can
transform ferromagnetic materials and produce intriguing spin transport
characteristics. This paper discusses the impact of molecule induced strong
coupling on spin transport. To study the molecular coupling effect
organometallic molecular complex (OMC) was bridged between two ferromagnetic
electrodes of a magnetic tunnel junction (Ta/Co/NiFe/AlOx/NiFe/Ta) along the
exposed side edges. OMCs induced strong iter-ferromagnetic electrode coupling
to yield drastic changes in transport properties of the magnetic tunnel
junction testbed at the room temperature. These OMCs also transformed the
magnetic properties of magnetic tunnel junctions. SQUID and ferromagnetic
resonance studies provided insightful data to explain transport studies on the
magnetic tunnel junction based molecular spintronics devices.",1912.01305v1
2021-01-04,Unraveling the optical contrast in Sb2Te and AgInSbTe phase-change materials,"Chalcogenide phase-change materials (PCMs) show a significant contrast in
optical reflectivity and electrical resistivity upon crystallization from the
amorphous phase and are leading candidates for non-volatile photonic and
electronic applications. In addition to the flagship Ge2Sb2Te5 phase-change
alloy, doped Sb2Te alloys, in particular AgInSbTe used in rewritable optical
discs, have been widely investigated for decades, and nevertheless the
theoretical insights on the optical properties of this important family of PCMs
are scarce. Here, we carry out thorough ab initio simulations to gain an
atomistic understanding of the optical properties of Sb2Te and AgInSbTe. We
show that the large optical contrast between the amorphous and crystalline
phase stems from the change in bond type in the parent compound Sb2Te. Ag and
In impurities serve mostly the purpose of stabilization of the amorphous phase,
and have marginal impact on the large variation in the dielectric function upon
the phase transitions.",2101.00789v2
2011-04-05,Viscoelastic Fracture of Biological Composites,"Soft constituent materials endow biological composites, such as bone, dentin
and nacre, with viscoelastic properties that may play an important role in
their remarkable fracture resistance. In this paper we calculate the scaling
properties of the quasi-static energy release rate and the viscoelastic
contribution to the fracture energy of various biological composites, using
both perturbative and non-perturbative approaches. We consider coarse-grained
descriptions of three types of anisotropic structures: (i) Liquid-crystal-like
composites (ii) Stratified composites (iii) Staggered composites, for different
crack orientations. In addition, we briefly discuss the implications of
anisotropy for fracture criteria. Our analysis highlights the dominant
lengthscales and scaling properties of viscoelastic fracture of biological
composites. It may be useful for evaluating crack velocity toughening effects
and structure-dissipation relations in these materials.",1104.0814v1
2012-03-12,Circuital model for the Maxwell Fish Eye perfect drain,"Perfect drain for the Maxwell Fish Eye (MFE) is a non-magnetic dissipative
region placed in the focal point to absorb all the incident radiation without
reflection or scattering. The perfect drain was recently designed as a material
with complex electrical permittivity that depends on frequency. However, this
material is only a theoretical material, so it can not be used in practical
devices. Recently, the perfect drain has been claimed as necessary to achieve
super-resolution [Leonhard 2009, New J. Phys. 11 093040], which has increased
the interest for practical perfect drains suitable for manufacturing. Here, we
analyze the super-resolution properties of a device equivalent to the MFE,
known as Spherical Geodesic Waveguide (SGW), loaded with the perfect drain. In
the SGW the source and drain are implemented with coaxial probes. The perfect
drain is realized using a circuit (made of a resistance and a capacitor)
connected to the drain coaxial probes. Super-resolution analysis for this
device is done in Comsol Multiphysics. The results of simulations predict the
super-resolution up to wavelength/3000 and optimum power transmission from the
source to the drain.",1203.2424v1
2015-06-22,Fracture Toughness of Silicate Glasses: Insights from Molecular Dynamics Simulations,"Understanding, predicting and eventually improving the resistance to fracture
of silicate materials is of primary importance to design new glasses that would
be tougher, while retaining their transparency. However, the atomic mechanism
of the fracture in amorphous silicate materials is still a topic of debate. In
particular, there is some controversy about the existence of ductility at the
nano-scale during the crack propagation. Here, we present simulations of the
fracture of three archetypical silicate glasses using molecular dynamics. We
show that the methodology that is used provide realistic values of fracture
energy and toughness. In addition, the simulations clearly suggest that
silicate glasses can show different degrees of ductility, depending on their
composition.",1506.06441v1
2015-06-26,Conduction through subsurface cracks in bulk topological insulators,"Topological insulators (TIs) have the singular distinction of being
electronic insulators while harboring metallic, conductive surfaces. In
ordinary materials, defects such as cracks and deformations are barriers to
electrical conduction, intuitively making the material more electrically
resistive. Peculiarly, 3D TIs should become better conductors when they are
cracked because the cracks themselves, which act as conductive topological
surfaces, provide additional paths for the electrical current. Significantly,
for a TI material, any surface or extended defect harbors such conduction. In
this letter, we demonstrate that small subsurface cracks formed within the
predicted 3D TI samarium hexaboride (SmB$_{6}$) via systematic scratching or
sanding results in such an increase in the electrical conduction. SmB$_{6}$ is
in a unique position among TIs to exhibit this effect because its
single-crystals are thick enough to harbor cracks, and because it remarkably
does not appear to suffer from conduction through bulk impurities. Our results
not only strengthen the building case for SmB$_{6}$'s topological nature, but
are relevant to all TIs with cracks, including TI films with grain boundaries.",1506.08233v1
2018-12-14,VI3 - a new layered ferromagnetic semiconductor,"Two-dimensional (2D) materials are promising candidates for next-generation
electronic devices. In this regime, insulating 2D ferromagnets, which remain
rare, are of special importance due to their potential for enabling new device
architectures. Here we report the discovery of ferromagnetism in a layered van
der Waals semiconductor, VI3, which is based on honeycomb vanadium layers
separated by an iodine-iodine van der Waals gap. It has a BiI3-type structure
(R-3, No.148) at room temperature, and our experimental evidence suggests that
it may undergo a subtle structural phase transition at 78 K. VI3 becomes
ferromagnetic at 49 K, below which magneto-optical Kerr effect imaging clearly
shows ferromagnetic domains, which can be manipulated by the applied external
magnetic field. The optical band gap determined by reflectance measurements is
0.6 eV, and the material is highly resistive.",1812.05982v1
2019-01-06,Low-Frequency Noise Spectroscopy of Charge-Density-Wave Phase Transitions in Vertical Quasi-2D Devices,"We report results regarding the electron transport in vertical quasi-2D
layered 1T-TaS2 charge-density-wave devices. The low-frequency noise
spectroscopy was used as a tool to study changes in the cross-plane electrical
characteristics of the quasi-2D material below room temperature. The noise
spectral density revealed strong peaks - changing by more than an
order-of-magnitude - at the temperatures closely matching the electrical
resistance steps. Some of the noise peaks appeared below the temperature of the
commensurate to nearly-commensurate charge-density-wave transition, possibly
indicating the presence of the debated ""hidden"" phase transitions. These
results confirm the potential of the noise spectroscopy for investigations of
electron transport and phase transitions in novel materials.",1901.01475v1
2019-06-12,"Simulation and experimental studies of induction hardening behavior of a new medium-carbon, low-alloy wear resistance steel","Flux2D commercial software together with a Gleeble thermomechanical simulator
has been employed to numerically and physically simulate the material
properties profile of an induction hardened slurry transportation pipe made of
a recently developed 0.4 wt.% C, Nb-microalloyed steel. After calculating the
thermal history of a 400 mm diameter, 10 mm thick pipe at various positions
through the thickness, different heating and cooling paths were physically
simulated using the Gleeble machine to predict the through-thickness material
microstructure and hardness profiles. The results showed that by coupling a
phase transformation model considering the effect of heating rate on the
austenite transformation temperatures which allows calculations for arbitrary
cooling paths with calculated induction heating and quenching thermal cycles,
it has been possible to design induction hardening parameters for a slurry
transport pipe material.",1906.05007v1
2019-06-15,Nonlinear planar Hall effect,"An intriguing property of three-dimensional (3D) topological insulator (TI)
is the existence of surface states with spin-momentum locking, which offers a
new frontier of exploration in spintronics. Here, we report the observation of
a new type of Hall effect in a 3D TI Bi2Se3 film. The Hall resistance scales
linearly with both the applied electric and magnetic fields and exhibits a
{\pi}/2 angle offset with respect to its longitudinal counterpart, in contrast
to the usual angle offset of {\pi}/4 between the linear planar Hall effect and
the anisotropic magnetoresistance. This novel nonlinear planar Hall effect
originates from the conversion of a nonlinear transverse spin current to a
charge current due to the concerted actions of spin-momentum locking and time
reversal symmetry breaking, which also exists in a wide class of
non-centrosymmetric materials with a large span of magnitude. It provides a new
way to characterize and utilize the nonlinear spin-to-charge conversion in a
variety of topological quantum materials.",1906.06462v1
2019-06-15,Effect of tungsten on vacancy behaviors in Ta-W alloys from first-principles,"Alloying elements play an important role in the design of plasma facing
materials with good comprehensive properties. Based on first-principles
calculations, the stability of alloying element W and its interaction with
vacancy defects in Ta-W alloys are studied. The results show that W tends to
distribute dispersedly in Ta lattice, and is not likely to form precipitation
even with the coexistence of vacancy. The aggregation behaviors of W and
vacancy can be affected by their concentration competition. The increase of W
atoms has a negative effect on the vacancy clustering, as well as delays the
vacancy nucleation process, which is favorable to the recovery of point
defects. Our results are in consistent with the defect evolution observed in
irradiation experiments in Ta-W alloys. Our calculations suggest that Ta is a
potential repairing element that can be doped into Ta-based materials to
improve their radiation resistance.",1906.06610v1
2019-06-24,Electrical and magnetic properties of thin films of the spin-filter material CrVTiAl,"The spin-filter material CrVTiAl is a promising candidate for producing
highly spin-polarized currents at room temperature in a nonmagnetic
architecture. Thin films of compensated-ferrimagnetic CrVTiAl have been grown
and their electrical and magnetic properties have been studied. The resistivity
shows two-channel semiconducting behavior with one disordered gapless channel
and a gapped channel with activation energy $\Delta E$=~0.1~-~0.2~eV.
Magnetoresistance measurements to B~=~35~T provide values for the mobilities of
the gapless channel, leading to an order of magnitude difference in the carrier
effective masses, which are in reasonable accord with our
density-functional-theory based results. The density of states and electronic
band structure is computed for permutations of the four sublattices arranged
differently along the (111) body diagonal, yielding metallic (Cr-V-Al-Ti),
spin-gapless (Cr-V-Ti-Al) and spin-filtering (Cr-Ti-V-Al) phases. Robustness of
the spin-gapless phase to substitutional disorder is also considered.",1906.10222v1
2019-11-25,Fracturing of polycrystalline MoS$_2$ nanofilms,"The possibility of tailoring the critical strain of 2D materials will be
crucial for the fabrication of flexible devices. In this paper, the fracture in
polycrystalline MoS2 films with two different grain orientations is studied at
the micro- and nanoscale using electron microscopy. The critical uniaxial
strain is determined to be approximately 5% and independent of the sample
morphology. However, electron beam irradiation is found to enhance the
interaction between the MoS2 and the PDMS substrates, leading to an increased
critical strain that can exceed 10%. This enhancement of strain resistance was
used to fabricate a mechanically robust array of lines 1 mm in length. Finally,
nanoscale crack propagation studied by transmission electron microscopy showed
that cracks propagate along the grain boundaries as well as through the grains,
preferentially along van der Waals bonding. These results provide insight
regarding the fracture of polycrystalline 2D materials and a new method to
tailor the critical strain and nanofabrication of ultra-thin MoS2 devices using
well-developed tools, which will be of great interest to the flexible
electronics industry.",1911.10769v1
2019-11-27,Large topological Hall effect in a geometrically frustrated kagome magnet Fe$_3$Sn$_2$,"We report on the observation of a large topological Hall effect (THE) over a
wide temperature region in a geometrically frustrated Fe3Sn2 magnet with a
kagome-bilayer structure. We found that the magnitude of the THE resistivity
increases with temperature and reaches -0.875 {\mu}{\Omega}.cm at 380 K.
Moreover, the critical magnetic fields with the change of THE are consistent
with the magnetic structure transformation, which indicates that the real-space
fictitious magnetic field is proportional to the formation of magnetic
skyrmions in Fe3Sn2. The results strongly suggest that the large THE originates
from the topological magnetic spin textures and may open up further research
opportunities in exploring emergent phenomena in kagome materials.",1911.12214v1
2020-01-21,Huge linear magnetoresistance due to open orbits in $γ$-PtBi$_2$,"Some single-crystalline materials present an electrical resistivity which
decreases between room temperature and low temperatures at zero magnetic field
as in a good metal and switches to a nearly semiconductinglike behavior at low
temperatures with the application of a magnetic field. Often, this is
accompanied by a huge and nonsaturating linear magnetoresistance which remains
difficult to explain. Here we present a systematic study of the
magnetoresistance in single-crystal $\gamma$-PtBi$_2$. We observe that the
angle between the magnetic field and the crystalline $c$ axis fundamentally
changes the magnetoresistance, going from a saturating to a nonsaturating
magnetic field dependence. In between, there is one specific angle where the
magnetoresistance is perfectly linear with the magnetic field. We show that the
linear dependence of the nonsaturating magnetoresistance is due to the
formation of open orbits in the Fermi surface of $\gamma$-PtBi$_2$.",2001.07674v2
2020-01-22,Chemical segregation in Ge2Sb2Te5 thin films during in-situ heating,"Germanium antimony telluride has been the most used and studied phase-change
material for electronic memory due to its suitable crystallization temperature,
amorphous to crystalline resistance contrast, and stability of the amorphous
phase. In this work, the segregation of Ge in a Ge2Sb2Te5 film of 30 nm
thickness during heating inside the transmission electron microscope was
observed and characterized. The Ge2Sb2Te5 film was deposited using sputtering
on a Protochips Fusion holder and left uncapped in atmosphere for about four
months. Oxygen incorporated within the film played a significant role in the
chemical segregation observed which resulted in amorphous Ge-O grain boundaries
and Sb and Te rich crystalline domains. Such composition changes can occur when
the phase-change material interfaces insulating oxide layers in an integrated
device and would significantly impact its electrical and thermal properties.",2001.08100v1
2020-05-10,Determination of the magnetocaloric effect from thermophysical parameters and their relationships near magnetic phase transition in doped manganites,"We present the results of a comparative analysis of the magnetocaloric effect
(MCE) in Pr0.7Sr0.2Ca0.1MnO3, through direct and indirect measurements, using
experimentally measured magnetization, specific heat, magnetostriction,
resistivity, thermal diffusivity and thermal conductivity parameters. We have
demonstrated that the change in each parameter in response to a magnetic field
near the ferromagnetic-paramagnetic phase transition temperature of the
material correlates with the change in magnetic entropy. These findings allow
us to interrelate these parameters and provide an alternative, effective
approach for accessing the usefulness of magnetocaloric materials.",2005.04569v1
2020-07-05,Deep Learning based Dimple Segmentation for Quantitative Fractography,"In this work, we try to address the challenging problem of dimple detection
and segmentation in Titanium alloys using machine learning methods, especially
neural networks. The images i.e. fractographs are obtained using a Scanning
Election Microscope (SEM). To determine the cause of fracture in metals we
address the problem of segmentation of dimples in fractographs i.e. the
fracture surface of metals using supervised machine learning methods.
Determining the cause of fracture would help us in material property,
mechanical property prediction and development of new fracture-resistant
materials. This method would also help in correlating the topography of the
fracture surface with the mechanical properties of the material. Our proposed
novel model achieves the best performance as compared to other previous
approaches. To the best of our knowledge, this is one the first work in
fractography using fully convolutional neural networks with self-attention for
supervised learning of dimple fractography, though it can be easily extended to
account for brittle characteristics as well.",2007.02267v3
2020-07-10,Canted Spin Texture and Quantum Spin Hall Effect in WTe2,"We report an unconventional quantum spin Hall phase in the monolayer
T$_\text{d}$-WTe$_2$, which exhibits hitherto unknown features in other
topological materials. The low-symmetry of the structure induces a canted spin
texture in the $yz$ plane, which dictates the spin polarization of
topologically protected boundary states. Additionally, the spin Hall
conductivity gets quantized ($2e^2/h$) with a spin quantization axis parallel
to the canting direction.
  These findings are based on large-scale quantum simulations of the spin Hall
conductivity tensor and nonlocal resistances in multi-probe geometries using a
realistic tight-binding model elaborated from first-principle methods.
  The observation of this canted quantum spin Hall effect, related to the
formation of topological edge states with nontrivial spin polarization, demands
for specific experimental design and suggests interesting alternatives for
manipulating spin information in topological materials.",2007.05626v1
2020-07-14,Tuning Conductivity and Spin Dynamics in Few-Layer Graphene via In Situ Potassium Exposure,"Chemical modification, such as intercalation or doping of novel materials is
of great importance for exploratory material science and applications in
various fields of physics and chemistry. In the present work, we report the
systematic intercalation of chemically exfoliated few-layer graphene with
potassium while monitoring the sample resistance using microwave conductivity.
We find that the conductivity of the samples increases by about an order of
magnitude upon potassium exposure. The increased of number of charge carriers
deduced from the ESR intensity also reflects this increment. The doped phases
exhibit two asymmetric Dysonian lines in ESR, a usual sign of the presence of
mobile charge carriers. The width of the broader component increases with the
doping steps, however, the narrow components seem to have a constant line
width.",2007.07057v1
2020-07-31,Quantum breakdown of superconductivity in low-dimensional materials,"In order to understand the emergence of superconductivity it is useful to
study and identify the various pathways leading to the destruction of
superconductivity. One way is to use the increase in Coulomb-repulsion due to
the increase in disorder, which overpowers the attractive interaction
responsible for Cooper-pair formation. A second pathway, applicable to
uniformly disordered materials, is the competition between superconductivity
and Anderson localization, which leads to electronic granularity in which phase
and amplitude fluctuations of the superconducting order parameter play a role.
Finally, a third pathway is an array of superconducting islands coupled by some
form of proximity-effect, due to Andreev-reflections, and which leads from a
superconducting state to a state with finite resistivity, which appears like a
metallic groundstate. This review summarizes recent progress in understanding
of these different pathways, including experiments in low dimensional materials
and application in superconducting quantum devices.",2007.15870v1
2020-08-06,Creep in reactive colloidal gels: a nanomechanical study of cement hydrates,"From soft polymeric gels to hardened cement paste, amorphous solids under
constant load exhibit a pronounced time-dependent deformation called creep. The
microscopic mechanism of such a phenomenon is poorly understood in amorphous
materials and constitutes an even greater challenge in densely packed and
chemically reactive granular systems. Both features are prominently present in
hydrating cement pastes composed of calcium silicate hydrate (C-S-H)
nanoparticles, whose packing density increases as a function of time, while
cement hydration is taking place. Performing nano-indentation tests and
porosity measurements on a large collection of samples at various stages of
hydration, we show that the creep response of hydrating cement paste is mainly
controlled by the inter-particle distance and results from slippage between
(C-S-H) nanoparticles. Our findings provide a unique insight into the
microscopic mechanism underpinning the creep response in aging granular
materials, thus paving the way for the design of concrete with improved creep
resistance.",2008.02617v3
2020-12-04,Epitaxial stabilization of SrCu$_3$O$_4$ with infinite Cu$_{3/2}$O$_2$ layers,"We report the epitaxial thin film synthesis of SrCu$_3$O$_4$ with infinitely
stacked Cu$_3$O$_4$ layers composed of edge-sharing CuO$_4$ square-planes,
using molecular beam epitaxy. Experimental and theoretical characterizations
showed that this material is a metastable phase that can exist by applying
tensile biaxial strain from the (001)-SrTiO$_3$ substrate. SrCu$_3$O$_4$ shows
an insulating electrical resistivity in accordance with the Cu$^{2+}$ valence
state revealed X-ray photoelectron spectroscopy. First-principles calculations
also indicated that the unoccupied $d_{3z^2-r^2}$ band becomes substantially
stabilized owing to the absence of apical anions, in contrast to
$A_2$Cu$_3$O$_4$Cl$_2$ ($A = $Sr, Ba) with an $A_2$Cl$_2$ block layer and
therefore a trans-CuO$_4$Cl$_2$ octahedron. These results suggest that
SrCu$_3$O$_4$ is a suitable parent material for electron-doped
superconductivity based on the Cu$_3$O$_4$ plane.",2012.02433v1
2021-03-02,Bioinspired approaches to toughen calcium phosphate-based ceramics for bone repair,"To respond to the increasing need for bone repair strategies, various types
of biomaterials have been developed. Among those, calcium phosphate ceramics
(CPCs) are promising since they possess a chemical composition similar to that
of bones. To be suitable for implants, CPCs need to fulfill a number of
biological and mechanical requirements. Fatigue resistance and toughness are
two key mechanical properties that are still challenging to obtain in CPCs.
This paper thus reviews and discusses current progress in the processing of
CPCs with bioinspired microstructures for load-bearing applications. First,
methods to obtain CPCs with bioinspired structure at individual lengthscales,
namely nano-, micro-, and macroscale are discussed. Then, approaches to attain
synergetic contribution of all lengthscales through a complex and biomimetic
hierarchical structure are reviewed. The processing methods and their design
capabilities are presented and the mechanical properties of the materials they
can produce are analysed. Their limitations and challenges are finally
discussed to suggest new directions for the fabrication of biomimetic bone
implants with satisfactory properties. The paper could help biomedical
researchers, materials scientists and engineers to join forces to create the
next generation of bone implants.",2103.01443v1
2021-04-14,Combining AFM imaging and elementally resolved spectro-electrochemistry for understanding stability and quality of passive films formed on Alloy 600,"Understanding elemental corrosion currents and visualizing corroding
topographies provide a detailed insight into corrosion mechanisms at the
nano-scale. Here, we develop a strategy to understand the elemental
composition, corrosion resistivity and local stability of passive materials.
Specifically, we utilize a pulse voltammetry approach in a novel
electrochemical AFM cell and complement this data by real-time dissolution
currents based on spectro-electrochemical online analysis in an ICP-MS flow
cell. We study the oxide properties and their protective behaviour, when formed
under different applied potentials using alloy 600 as model sample. Both AFM
and ICP-MS data show that passive films formed on alloy 600 at around +0.3 to
+0.4~V in neutral 1 mM NaCl solution are most stable during anodic corrosion at
+1.0~V, while AFM further demonstrates that local dissolution occurs,
indicating locally varying defect levels in the passive film. In combination of
both techniques, our approach provide real-time elementally resolved and
localized information of passive film quality under corrosive conditions, and
it may prove useful for other corroding materials.",2104.07100v1
2021-06-11,Measurement of onset of structural relaxation in melt-quenched phase change materials,"Chalcogenide phase change materials enable non-volatile, low-latency
storage-class memory. They are also being explored for new forms of computing
such as neuromorphic and in-memory computing. A key challenge, however, is the
temporal drift in the electrical resistance of the amorphous states that encode
data. Drift, caused by the spontaneous structural relaxation of the newly
recreated melt-quenched amorphous phase, has consistently been observed to have
a logarithmic dependence in time. Here, we show that this observation is valid
only in a certain observable timescale. Using threshold-switching voltage as
the measured variable, based on temperature-dependent and short timescale
electrical characterization, we experimentally measure the onset of drift. This
additional feature of the structural relaxation dynamics serves as a new
benchmark to appraise the different classical models to explain drift.",2106.06270v1
2021-08-08,Strong-coupling superconductivity of SrIr2 and SrRh2: Phonon engineering of metallic Ir and Rh,"Experimental and theoretical studies on superconductivity in SrIr$_2$ and
SrRh$_2$ Laves phases are presented. The measured resistivity, heat capacity,
and magnetic susceptibility confirm the superconductivity of these compounds
with $T_c$ = 6.07 K and 5.41 K, respectively. Electronic structure calculations
show that the Fermi surface is mostly contributed by 5$d$ (4$d$) electrons of
Ir (Rh), with Sr atoms playing the role of electron donors. The effect of the
spin-orbit coupling is analyzed and found to be important in both materials.
Lattice dynamics and electron-phonon coupling (EPC) are studied and the strong
electron-phonon interaction is found, contributed mostly by the low-frequency
Ir and Rh vibrations. The enhancement of EPC when compared to weakly-coupled
metallic Ir and Rh is explained by the strong modifications in the propagation
of phonons in the network of Ir (Rh) tetrahedrons, which are the building
blocks of the Laves phase, and originate from the metallic fcc structures of
elemental iridium and rhodium.",2108.03692v1
2021-08-06,Manipulating thermal fields with inhomogeneous heat spreaders,"We design a class of spatially inhomogeneous heat spreaders in the context of
steady-state thermal conduction leading to spatially uniform thermal fields
across a large convective surface. Each spreader has a funnel-shaped design,
either in the form of a trapezoidal prism or truncated cone, and is forced by a
thermal source at its base. We employ transformation-based techniques, commonly
used to study metamaterials, to determine the require thermal conductivity for
the spreaders. The obtained materials, although strongly anisotropic and
inhomogeneous, can be accurately approximated by assembling isotropic,
homogeneous layers, rendering them realisable. An alternative approach is then
considered for the conical and trapezoidal spreaders by dividing them into two
or three isotropic, homogeneous components respectively. We refer to these
simple configurations as neutral layers. All designs are validated numerically
both with and without the effects of thermal contact resistance between
interfaces. Such novel designs pave the way for future materials that can
manipulate and control the flow of heat, helping to solve traditional heat
transfer problems such as controlling the temperature of an object and energy
harvesting.",2108.04881v2
2021-08-20,Peak in the superconducting transition temperature of the nonmagnetic topological line-nodal material CaSb$_2$ under pressure,"Investigating the pressure dependence of the superconducting (SC) transition
temperature $T_{\rm c}$ is crucial for understanding the SC mechanism. Herein,
we report on the pressure dependence of $T_{\rm c}$ in the nonmagnetic
topological line-nodal material CaSb$_2$, based on measurements of electric
resistance and alternating current magnetic susceptibility. $T_{\rm c}$
initially increases with increasing pressure and peaks at $\sim$ 3.1~GPa. With
a further increase in pressure, $T_{\rm c}$ decreases and finally becomes
undetectable at 5.9~GPa. Because no signs of phase transition or Lifshitz
transition are observed in the normal state, the peculiar peak structure of
$T_{\rm c}$ suggests that CaSb$_2$ has an unconventional SC character.",2108.08992v1
2021-09-09,Bias factor of dislocation loops in quasicrystalline materials,"Vacancy swelling of quasicrystals under irradiation is considered. In
quasicrystals, the evolution of dislocations is accompanied by the formation of
phasons which are localized topological defects of the vacancy and interstitial
types. At moderate temperatures the diffusivity of phasons is low which leads
to the formation of ring-or disk-shaped phason trails inside dislocation loops.
To find the capture efficiency of point defects by a dislocation loop with the
complementary ring of phasons the steady-state drift-diffusional problem is
solved in the toroidal geometry by the successive overrelaxation method. It is
shown that phasons significantly reduce the bias of dislocations towards
absorption of interstitial atoms. For this reason, quasicrystalline materials
are predicted to exhibit increased resistance to vacancy swelling.",2109.04136v2
2021-09-20,Coexistence of superconductivity and weak anti-localization at KTaO3 (111) interfaces,"The intersection of two-dimensional superconductivity and topologically
nontrivial states hosts a wide range of quantum phenomena, including Majorana
fermions. Coexistence of topologically nontrivial states and superconductivity
in a single material, however, remains elusive. Here, we report on the
observation of two-dimensional superconductivity and weak anti-localization at
the TiOx/KTaO3(111) interfaces. A remnant, saturating resistance persists below
the transition temperature as superconducting puddles fail to reach phase
coherence. Signatures of weak anti-localization are observed below the
superconducting transition, suggesting the coexistence of superconductivity and
weak anti-localization. The superconducting interfaces show roughly one order
of magnitude larger weak anti-localization correction, compared to
non-superconducting interfaces, alluding to a relatively large coherence length
in these interfaces.",2109.09786v1
2021-09-23,Plastic deformation of the CaMg$_{2}$ C14-Laves phase from 50-250$^\circ$C,"Intermetallic phases can significantly improve the creep resistance of
magnesium alloys, extending their use to higher temperatures. However, little
is known about the deformation behaviour of these phases at application
temperatures, which are commonly below their macroscopic
brittle-to-ductile-transition temperature. In this study, we therefore
investigate the activation of different slip systems of the CaMg$_2$ phase and
the occurrence of serrated yielding in the temperature range from 50$^\circ$C
to 250$^\circ$C. A decreasing amount of serrated flow with increasing
temperature suggests that solute atoms govern the flow behaviour when the
CaMg$_{2}$ phase is off-stoichiometric.",2109.11367v1
2021-11-08,Microstructure and the Boson-peak in thermally-treated In_{x}O films,"We report on the correlation between the boson-peak and structural changes
associated with thermally-treating amorphous indium-oxide films. In this
process, the resistance of a given sample may decrease by a considerable margin
while its amorphous structure is preserved. In the present study, we focus on
the changes that result from the heat-treatment by employing
electron-microscopy, X-ray, and Raman spectroscopy. These techniques were used
on films with different stoichiometry and thus different carrier-concentration.
The main effect of heat-treatment is material densification, which presumably
results from elimination of micro-voids. The densified system presents better
wavefunction-overlap and more efficient connectivity for the current flow.
X-ray, and electron-beam diffraction experiments indicate that the heat-treated
samples show significantly less spatial heterogeneity with only a moderate
change of the radial-distribution function metrics. These results are
consistent with the changes that occur in the boson-peak characteristics due to
annealing as observed in their Raman spectra.",2111.04277v1
2021-11-11,NbReSi: A Noncentrosymetric Superconductor with Large Upper Critical Field,"We report the discovery of superconductivity in noncentrosymmetric NbReSi,
which crystallizes in a hexagonal ZrNiAl-type crystal structure with space
group $P\bar{6}2m$ (No.~189). Bulk superconductivity, with $T_c$ = 6.5 K was
characterized via electrical-resistivity, magnetization, and heat-capacity
measurements. The low-temperature electronic specific heat suggests a fully
gapped superconducting state in NbReSi, while a large upper critical field of
$\mu_0H_\mathrm{c2}(0)$ $\sim$ 12.6 T is obtained, which is comparable to the
weak-coupling Pauli limit. The electronic band-structure calculations show that
the density of states at the Fermi level are dominated by Re and Nb
$d$-orbitals, with a sizeable band splitting induced by the antisymmetric
spin-orbit coupling. NbReSi represents another candidate material for revealing
the puzzle of time-reversal symmetry breaking observed in some Re-based
superconductors and its relation to the lack of inversion symmetry.",2111.06010v1
2021-11-14,Superconductivity in noncentrosymmetric NbReSi investigated by muon spin rotation and relaxation,"Noncentrosymmetric materials are promising paradigm to explore unconventional
superconductivity. In particular, several Re containing noncentrosymmetric
materials have attracted considerable attention due to a superconducting state
with a broken time reversal symmetry. A comprehensive study on the
superconducting ground state of NbReSi was investigated using magnetization,
resistivity, and muon spin rotation/relaxation measurements. Zero field muon
spectroscopy results showed the absence of any spontaneous magnetic field below
the superconducting transition temperature, T$ _{c} $ = 6.29 K, indicating the
preserved time-reversal symmetry. Transverse field muon spin rotation
measurements confirms a s-wave nature of the sample with $\Delta(0)/k_{B}T_{c}
$ = 1.726. This study urges further investigation on more noncentrosymmetric
materials to elucidate the selective appearance of unconventional nature and
unveil its dependence on antisymmetric spin-orbit coupling strength.",2111.07247v1
2021-12-26,Tuning Ferroelectrics to Antiferroelectrics in Multiferroic LaxSr1-xFe12O19 Ceramics,"The combination of antiferroelectricity (AFE) and ferromagnetism (FM) in one
structure would allow the development of new type of multiferroic candidates,
which be applicable not only in magnetoelectric memories but also in novel
energy storage devices. Here we propose a novel type of multiferroic candidate
LaxSr1-xFe12O19, whose room temperature state could betuned from ferroelectrics
(FE) to antiferroelectrics by changing x from 0 to 0.5. The emphasis of this
paper will be focused on the La0.5Sr0.5Fe12O19 system, in which full AFE and FM
coexist. The pure antiferroelectric behavior in La0.5Sr0.5Fe12O19 ceramics is
demonstrated by double polarization-electric field (P-E) hysteresis loops,
which are fully separated by a linear antiferroelectric AFE component with zero
net polarization. The material of La0.2Sr0.7Fe12O19 with the intermediate
composition exhibits a hybrid ferroelectric/antiferroelectric state. The
recoverable energy density of the antiferroelectric La0.5Sr0.5Fe12O19 phase
reaches 14.3 J/cm3. This material demonstrates strong magnetoelectric coupling
and giant magnetoresistance (GMR) effect. A 1.1T magnetic field generates
electronic polarization up to 0.95uC/cm2, reduce the resistance by 117%,
enhances dielectric constants by 540% and right shifts the maximum dielectric
loss peak by 208 kHz. The combined functional responses provide an opportunity
to develop novel multifunctional electric and energy storage devices.",2112.13307v1
2022-01-03,Aerogel from sustainably grown bacterial cellulose pellicle as thermally insulative film for building envelope,"Improving building energy performance requires the development of new highly
insulative materials. An affordable retrofitting solution comprising a thin
film could improve the resistance to heat flow in both residential and
commercial buildings and reduce overall energy consumption. Here we propose
cellulose aerogel films formed from pellicles produced by the bacteria
Gluconacetobacter hansenii as insulation materials. We studied the impact of
density and nanostructure on the aerogels' thermal properties. Thermal
conductivity as low as 13 mW/(K*m) was measured for native pellicle-based
aerogels dried as-is with minimal post-treatment. The use of waste from the
beer brewing industry as a solution to grow the pellicle maintained the
cellulose yield obtained with standard Hestrin-Schramm medium, making our
product more affordable and sustainable. In the future, our work can be
extended through further diversification of the sources of substrate among food
wastes, facilitating larger potential production and applications.",2201.00449v1
2022-03-13,Electronic and topological properties of the van der Waals layered superconductor PtTe,"We report the crystal growth and structural and electronic properties of
superconducting, van der Waals layered PtTe. Easily cleavable crystals with a
plate-like morphology consistent with the layered structure were grown from a
platinum rich flux. A consistent determination of $T_c = 0.57$ K is made from
the onset of diamagnetism, the zero of resistivity, and the midpoint of the
heat capacity jump. The observed behavior is consistent with type-II
superconductivity, with upper critical field at $T=0$ estimated using the
Werthamer-Helfand-Hohenberg theory to be 143 and 65 Oe for fields out of and in
the plane, respectively. The heat capacity discontinuity is close to the weak
coupling BCS value. Density functional theory calculations and analysis of the
electronic structure finds that PtTe is a topological semimetal with numerous
surface states, but suggests the superconducting state itself may be
topologically trivial. Angle resolved photoemission spectroscopy reveals a
normal-state Fermi surface in remarkable agreement with theory, and confirms
the overall topological nature of the material by experimental identification
of the surface bands. Together, these findings identify PtTe as an interesting
example of a cleavable, topological, and superconducting material.",2203.06655v1
2022-04-28,Vacancy formation energies and migration barriers in multi-principal element alloys,"Multi-principal element alloys (MPEAs) continue to garner interest as
structural and plasma-facing materials due to their structure stability and
increased resistance to radiation damage. Despite sensitivity of mechanical
behavior to irradiation and point-defect formation, there has been scant
attention on understanding vacancy stability and diffusion in refractory-based
MPEAs. Using density-functional theory, we examine vacancy stability and
diffusion barriers in body-centered cubic (Mo0.95W0.05)0.85Ta0.10(TiZr)0.05.
The results in this MPEA show strong dependence on environment, originating
from local lattice distortion associated with charge-transfer between
neighboring atoms that vary with different chemical environments. We find a
correlation between degree of lattice distortion and migration barrier: (Ti,
Zr) with less distortion have lower barriers, while (Mo, W) with larger
distortion have higher barriers, depending up local environments. Under
irradiation, our findings suggest that (Ti, Zr) are significantly more likely
to diffuse than (Mo, W) while Ta shows intermediate effect. As such, material
degradation caused by vacancy diffusion can be controlled by tuning composition
of alloying elements to enhance creep strength at extreme operating
temperatures and harsh conditions.",2204.13616v1
2022-08-01,Boundary scattering in micro-size crystal of topological Kondo insulator SmB$_6$,"We have studied the effects of phonon-boundary scattering on the thermal
transport in topological Kondo insulator, SmB$_6$. The studies have been
performed by using the $3\omega$ method in the temperature range 300K - 3K. We
show that the observed thermal conductivity of micro-size SmB$_6$ is of the
order of magnitude smaller than for a bulk single-crystal. Using the Callaway
model we analyzed the low-temperature lattice thermal conductivity of the micro
crystal and show that phonon scattering by sample boundaries plays a major role
in the thermal resistance in this topological material. In addition, we show
that the temperature dependence of the lattice thermal conductivity shows a
double peak structure that suggests complex phonon-phonon or phonon-defects
interactions in SmB$_6$. These findings provide guidance for the understanding
of the thermal transport of advanced materials and devices at a micro-scale.",2208.01145v1
2022-08-09,Pressure-Independent Through-Plane Electrical Conductivity Measurements of Highly Filled Conductive Polymer Composites,"Highly filled conductive polymer composites (CPCs) are widely used in
applications such as bipolar plate materials for polymer electrolyte membrane
fuel cells and redox flow batteries, electromagnetic interference shielding and
sensors due to their useful electrical properties. A common method for
determining through-plane electrical conductivities $\left(\sigma_{\rm tp}
\right)$ of such highly filled CPCs applies a conductive carbon paper between
electrodes and sample with application of external pressure to improve
electrical contact. We show the pressure-dependence of the measured
$\sigma_{\rm tp}$ can be eliminated by using a liquid metal such as the
gallium-indium eutectic alloy (EGaIn) as contact material. Results indicate
that EGaIn reduces contact resistances and cause three to five times larger
$\sigma_{\rm tp}$ compared to measurements with carbon paper contacts and
pressures up to 20 bar.",2208.04643v1
2023-01-18,Paper-based Flexible Supercapacitors with drawn van der Waals materials,"Two-dimensional (2D) materials are widely used in various applications due to
their extraordinary properties. In particular, their electrochemical stability,
low electrical resistance, and huge specific surface area make them very
interesting active materials for supercapacitors. Herein, flexible,
biodegradable, and low-cost supercapacitors are introduced in a very simple way
based on hand-drawing pencil traces or -rubbing molybdenum disulfide (MoS2),
titanium trisulfide (TiS3) and franckeite traces on the paper. Results
demonstrate that pencil-drawn paper has higher capacitance performance (~6.39
F/g) among the suggested electrodes. Interestingly, the introduced MoS2/pencil,
TiS3/pencil, and franckeite/pencil drawn paper electrodes reveal dramatic
improvements with long cyclic life thanks to the occurrence of synergetic
effects and higher available active cites within the heterostructures.
Moreover, the assembled symmetric solid-state supercapacitors retain their
performance even under applied bending, indicating their excellent potential
for wearable/flexible applications.",2301.07759v1
2023-02-18,Magnetoresistance signature of two-dimensional electronic states in Co$_3$Sn$_2$S$_2$,"Two-dimensional (2D) Dirac bands and flat bands are characteristics of a
kagome lattice. However, experimental studies on their electrical transport are
few, because three-dimensional (3D) bulk bands of kagome materials, consisting
of stacked 2D kagome layers, dominate the transport. We report a
magnetoresistance (MR) study of a kagome material, Co$_3$Sn$_2$S$_2$. Based on
analysis of the temperature, magnetic field, and field angle dependence of the
resistivity, we obtain a complete anatomy of MR. Besides a magnon MR, a
chirality-dependent MR, and a chiral-anomaly-induced MR, the most intriguing
feature is an orbital MR that scales only with the out-of-plane field, which
strongly indicates its 2D nature. We attribute it to the Dirac band of the
kagome lattice.",2302.09229v1
2023-03-01,Thermodynamic determination of the equilibrium first-order phase-transition line hidden by hysteresis in a phase diagram,"Phase diagrams form the basis for the study of material science, and the
profiles of phase-transition lines separating different thermodynamic phases
include comprehensive information about thermodynamic quantities, such as
latent heat. However, in some materials exhibiting field-induced first-order
transitions (FOTs), the equilibrium phase-transition line is hidden by the
hysteresis region associated with the FOT; thus, it cannot be directly
determined from measurements of resistivity, magnetization, etc. Here, we
demonstrate a thermodynamics-based method for determining the hidden
equilibrium FOT line. This method is verified for the FOT between
antiferromagnetic and ferrimagnetic states in magneto-electric compounds
(Fe$_{0.95}$Zn$_{0.05}$)$_{2}$Mo$_{3}$O$_{8}$. The equilibrium FOT line
determined based on the Clausius-Clapeyron equation exhibits a reasonable
profile in terms of the third law of thermodynamics, and it shows marked
differences from the midpoints of the hysteresis region. Our findings highlight
that care should be taken for referring to the hysteresis midpoint line when
discussing field-induced latent heat or magnetocaloric effects.",2303.00327v1
2023-03-21,"Structure, physical properties, and magnetically tunable topological phases in topological semimetal EuCuBi","A single material achieving multiple topological phases can provide potential
application for topological spintronics, whereas the candidate materials are
very limited. Here, we report the structure, physical properties, and possible
emergence of multiple topological phases in the newly discovered, air-stable
EuCuBi single crystal. EuCuBi crystallizes in a hexagonal space group P63/mmc
(No. 194) in ZrBeSi-type structure with an antiferromagnetic (AFM) ground state
below TN = 11.2 K. There is a competition between AFM and ferromagnetic (FM)
interactions below TN revealed by electrical resistivity and magnetic
susceptibility measurements. With the increasing magnetic field, EuCuBi evolves
from the AFM ground state with a small amount of FM component, going through
two possible metamagnetic phases, finally reaches the field-induced FM phase.
Based on the first-principles calculations, we demonstrate that the Dirac,
Weyl, and possible mirror Chern insulator can be achieved in EuCuBi by tuning
the temperature and applying magnetic field, making EuCuBi a promising
candidate for exploring multiple topological phases.",2303.11894v1
2023-04-20,"Magnetic behavior of cubic Dy4RhAl with respect to isostructural Dy4PtAl, revealing a novel 4f d-band interaction","We have investigated for the first time the magnetic behaviour of an
intermetallic compound, Dy4RhAl, crystallizing in Gd4RhIn type cubic structure
containing 3 sites for rare-earth (R), by several bulk measurements down to 1.8
K. This work is motivated by the fact that the isostructural Dy compound in the
R4PtAl family surprisingly orders ferromagnetically unlike other members of
this series, which order antiferromagnetically. The results reveal that the
title compound undergoes antiferromagnetic order at about 18 K, similar to
other heavy R members of R4RhAl family, unlike its Pt counterpart, indicating a
subtle difference in the role of conduction electrons to decide magnetism of
these compounds. Besides, spin-glass features coexisting with antiferromagnetic
order could be observed, which could mean cluster antiferromagnetism. The
electrical resistivity and magnetoresistance behaviours in the magnetically
ordered state are typical of magnetic materials exhibiting antiferromagnetic
gap. Features attributable to spin-reorientation as a function of temperature
and magnetic field can be seen in the magnetization data.",2304.10122v1
2023-08-07,Oxide layer formation prevents deteriorating ion migration in thermoelectric Cu$_2$Se during operation in air,"Cu$_2$Se is a mixed ionic-electronic conductor with outstanding
thermoelectric performance originally envisioned for space missions.
Applications were discontinued due to material instability, where elemental Cu
grows at the electrode interfaces during operation in vacuum. Here, we show
that when Cu$_2$Se is operating in air, formation of an oxide surface layer
suppresses Cu$^+$ migration along the current direction. In operando X-ray
scattering and electrical resistivity measurements quantify Cu$^+$ migration
through refinement of atomic occupancies and phase composition analysis. Cu
deposition can be prevented during operation in air, irrespective of a critical
voltage, if the thermal gradient is applied along the current direction.
Maximum entropy electron density analysis provides experimental evidence that
Cu$^+$ migration pathways under thermal and electrical gradients differ
substantially from equilibrium diffusion. The study establishes new promise for
inexpensive sustainable Cu$_2$Se in thermoelectric applications, and it
underscores the importance of atomistic insight into materials during
thermoelectric operating conditions.",2308.03559v1
2023-09-01,Denture reinforcement via topology optimization,"We present a computational design method that optimizes the reinforcement of
dental prostheses and increases the durability and fracture resistance of
dentures. Our approach optimally places reinforcement, which could be
implemented by modern multi-material, three-dimensional printers. The study
focuses on reducing deformation by identifying regions within the structure
that require reinforcement (E-glass material). Our method is applied to a
three-dimensional removable lower jaw dental prosthesis and aims to improve the
living quality of denture patients and pretend fracture of dental reinforcement
in clinical studies. To do this, we compare the deformation results of a
non-reinforced denture and a reinforced denture that has two materials. The
results indicate the maximum deformation is lower and node-based displacement
distribution demonstrates that the average displacement distribution is much
better in the reinforced denture.",2309.00396v1
2023-09-06,Magnetic order in the $S_{\mathrm{eff}}$ = 1/2 triangular-lattice compound NdCd$_3$P$_3$,"We present and characterize a new member of the $R$Cd$_3$P$_3$ ($R$= rare
earth) family of materials, NdCd$_3$P$_3$, which possesses Nd$^{3+}$ cations
arranged on well-separated triangular lattice layers. Magnetic susceptibility
and heat capacity measurements demonstrate a likely $S_{\mathrm{eff}}$ = 1/2
ground state, and also reveal the formation of long-range antiferromagnetic
order at $T_{N} = 0.34$ K. Via measurements of magnetization, heat capacity,
and electrical resistivity, we characterize the electronic properties of
NdCd$_3$P$_3$ and compare results to density functional theory calculations.",2309.03332v1
2023-09-18,Ferroelectric Schottky diodes of CuInP$_2$S$_6$ nanosheet,"Ferroelectricity in van der Waals (vdW) layered material has attracted a
great deal of interest recently. CuInP$_2$S$_6$ (CIPS), the only vdW layered
material whose ferroelectricity in the bulk was demonstrated by direct
polarization measurements, was shown to remain ferroelectric down to a
thickness of a few nanometers. However, its ferroelectric properties have just
started to be explored in the context of potential device applications. We
report here the preparation and measurements of metal-ferroelectric
semiconductor-metal heterostructures using nanosheets of CIPS obtained by
mechanical exfoliation. Four bias voltage and polarization dependent resistive
states were observed in the current-voltage characteristics, which we attribute
to the formation of ferroelectric Schottky diode, along with switching
behavior.",2309.10045v1
2023-10-25,Super-resolution imaging reveals resistance to mass transfer in functionalized stationary phases,"Chemical separations are costly in terms of energy, time, and money.
Separation methods are optimized with inefficient trial-and-error approaches
that lack insight into the molecular dynamics that lead to the success or
failure of a separation and, hence, ways to improve the process. We perform
super-resolution imaging of fluorescent analytes in four different commercial
liquid chromatography materials. Surprisingly, we observe that chemical
functionalization can block over fifty percent of the porous interior of the
material, rendering it inaccessible to small molecule analytes. Only in situ
imaging unveils the inaccessibility when compared to the industry-accepted ex
situ characterization methods. Selectively removing some of the
functionalization with solvent restores pore access without significantly
altering the single-molecule kinetics that underlie the separation and agree
with bulk chromatography measurements. Our molecular results determine that
commercial stationary phases, marketed as fully porous, are over-functionalized
and provide a new avenue to characterize and direct separation material design
from the bottom-up.",2310.16266v1
2023-11-17,Fabrication of damage-free and/or contamination-free sub-um electrodes using PMMA masks,"Quality of the electrical contacts and interfaces in various
metal/semiconductor/insulator heterostructures is one of the pivotal aspects in
both applied and fundamental research areas. For instance, non-optimal contact
resistance can limit the overall efficiency of a certain developed technology
and thus considerably narrow the range or fully block its practical
application. On the other hand in fundamental research it is often the case
that the manifestation of targeted phenomenon crucially depends on the level of
contamination in the fabricated experimental samples. Here we offer a set of
recipes that are aimed at contamination-free and damage-free fabrication of the
devices, mostly developed for the two dimensional materials, but nevertheless
applicable for a wider range of the systems, where the quality of the
interfaces and/or non-invasiveness of the fabrication recipes are important.
Our recipes are based on the preparation of the flexible PMMA membranes, with
the help of which we can prepare residue-free or damage-free electrical
connections to the studied material.",2311.10340v1
2023-11-20,Spontaneous supercrystal formation during a strain-engineered metal-insulator transition,"Mott metal-insulator transitions possess electronic, magnetic, and structural
degrees of freedom promising next generation energy-efficient electronics. We
report a previously unknown, hierarchically ordered state during a Mott
transition and demonstrate correlated switching of functional electronic
properties. We elucidate in-situ formation of an intrinsic supercrystal in a
Ca2RuO4 thin film. Machine learning-assisted X-ray nanodiffraction together
with electron microscopy reveal multi-scale periodic domain formation at and
below the film transition temperature (TFilm ~ 200-250 K) and a separate
anisotropic spatial structure at and above TFilm. Local resistivity
measurements imply an intrinsic coupling of the supercrystal orientation to the
material's anisotropic conductivity. Our findings add an additional degree of
complexity to the physical understanding of Mott transitions, opening
opportunities for designing materials with tunable electronic properties.",2311.11842v1
2023-12-10,Characterization of Semiconducting Materials Using the Van der Pauw Method,"Semiconductors are currently an active topic of study due to the endless
range of applications in electronic hardware and computer engineering. In this
experiment, the material properties (i.e. resistivity $\rho$, Hall coefficient
$R_{H}$, and mobility $\mu$) of a doped GaAs sheet is described by utilizing
Hall Effect and the Van der Pauw method with varying temperature $T$ and
magnetic field values $B$. It is determined that the sample is an $n$-type
semiconductor using the sign of $R_H$, which is measured to be $R_H = -2.9
\times 10^{-12} \pm 0.1 \times 10^{-14} ~ \text{m}^{3} \text{C}^{-1}$, at $T =
303 ~\text{K}$ and $B = 3.3 ~\text{kGs}$. Furthermore, the rate of change for
the slope $R_H$ and $T$ is increasing along $B$ at the rate of $\Delta k/
\Delta B = \left(3.6 \pm 0.5 \right) \times 10^{-16} ~\text{m}^3 (\text{CK}
\cdot \text{kGs})^{-1}$, meaning the charge accumulation caused by the current
and Lorentz force is quadratic in $B$. It is also discovered that $\mu$, and
therefore the electron drift velocity is reduced proportionally at higher
$T$-values. This method provides a potential analogue in quantum scales with
the Quantum Hall Effect and characterisation of quantum dots.",2312.05744v1
2023-12-15,Smart sensing of the multifunctional properties of magnetron sputtered $MoS_2$ across the amorphous-crystalline transition,"Molybdenum disulfide, $MoS_2$, is a next-generation semiconductor and is
frequently integrated into emergent optoelectronic technologies based on
two-dimensional materials. Here, we present a method that provides direct
optical feedback on the thickness and crystallinity of sputter-deposited
$MoS_2$ down to the few-layer regime. This smart sensing enables tracking the
material's functional properties, such as excitonic response, sheet resistance,
and hardness across the amorphous-crystalline transition. To illustrate the
potential of such feedback-controlled fabrication, we realized $MoS_2$-based
hyperbolic metamaterials (HMM) with controllable optical topological
transitions and hardness.",2312.10180v2
2024-01-10,A Universal Scaling Law for Intrinsic Fracture Energy of Networks,"Networks of interconnected materials permeate throughout nature, biology, and
technology due to exceptional mechanical performance. Despite the importance of
failure resistance in network design and utility, no existing physical model
effectively links strand mechanics and connectivity to predict bulk fracture.
Here, we reveal a universal scaling law that bridges these levels to predict
the intrinsic fracture energy of diverse networks. Simulations and experiments
demonstrate its remarkable applicability to a breadth of strand constitutive
behaviors, topologies, dimensionalities, and length scales. We show that local
strand rupture and nonlocal energy release contribute synergistically to the
measured intrinsic fracture energy in networks. These effects coordinate such
that the intrinsic fracture energy scales independent of the energy to rupture
a strand; it instead depends on the strand rupture force, breaking length, and
connectivity. Our scaling law establishes a physical basis for understanding
network fracture and a framework for fabricating tough materials from networks
across multiple length scales.",2401.05564v1
2024-01-23,Berezinskii-Kosterlitz-Thouless transition in rhenium nitride films,"The quest to manipulate and understand superconductivity demands exploring
diverse materials and unconventional behaviors. Here, we investigate the BKT
transition in synthesized ReN$_x$ thin films, demonstrating their emergence as
a compelling platform for studying this pivotal phenomenon. By systematically
varying synthesis parameters, we achieve ReN$_x$ films exhibiting a BKT
transition comparable or even surpassing the archetypal NbN$_x$ system.
Detailed current-voltage measurements unlock the intrinsic parameters of the
BKT transition, revealing the critical role of suppressed superconducting
volume in pushing ReN$_x$ towards the two-dimensional limit. Utilizing this
two-dimensional electron system, we employ Beasley-Mooij-Orlando (BMO) theory
to extract the vortex unbinding transition temperature and superelectron
density at the critical point. Further confirmation of the BKT transition is
obtained through temperature-dependent resistivity, current-voltage, and
magnetoresistance measurements. Our findings suggest that native disorder and
inhomogeneity within ReN$_x$ thin films act to suppress long-range coherence,
ultimately driving the system towards the BKT regime. This work establishes
ReN$_x$ as a promising material for exploring BKT physics and paves the way for
tailoring its properties for potential applications in superconducting devices.",2401.12628v1
2024-02-11,Cooperating Cracks in Two-Dimensional Crystals,"The pattern development of multiple cracks in extremely anisotropic solids
such as bilayer or multilayer two-dimensional (2D) crystals contains rich
physics, which, however, remains largely unexplored. We studied crack
interaction across neighboring 2D layers by transmission electron microscopy
and molecular dynamics simulations. Parallel and anti-parallel ('En-Passant')
cracks attract and repel each other in bilayer 2D crystals, respectively, in
stark contrast to the behaviors of co-planar cracks. We show that the misfit
between in-plane displacement fields around the crack tips results in
non-uniform interlayer shear, which modifies the crack driving forces by
creating an antisymmetric component of the stress intensity factor. The
cross-layer interaction between cracks directly leads to material toughening,
the strength of which increases with the shear stiffness and decreases with the
crack spacings. Backed by the experimental findings and simulation results, a
theory that marries the theory of linear elastic fracture mechanics and the
shear-lag model is presented, which guides the unconventional approach to
engineer fracture patterns and enhance material resistance to cracking.",2402.07088v1
2024-03-26,Microscale Morphology Driven Thermal Transport in Fiber Reinforced Polymer Composites,"Fiber-reinforced polymer composite (FRPC) materials are used extensively in
various industries, such as aerospace, automobiles, and electronics packaging,
due to their remarkable specific strength and desirable properties, such as
enhanced durability and corrosion resistance. The evolution of thermal
properties in FRPCs is crucial for advancing thermal management systems,
optimizing material performance, and enhancing energy efficiency across these
diverse sectors. Despite significant research efforts to develop new materials
with improved thermal properties and reduced thermal degradation, there is a
lack of understanding of the thermal transport phenomena considering the
influence of microscale reinforcement morphology in these composites. In the
current study, we performed experimental investigations complemented by
computations to determine the thermal transport properties and associated
phenomena in epoxy and carbon fiber-reinforced epoxy composites. The
experimental findings were utilized as input data for numerical analysis to
examine the impact of fiber morphology and volume fraction in thermal transport
phenomena. Our results revealed that composites incorporating non-circular
fibers manifested higher thermal conductivity than traditional circular fibers
in the transverse direction. This can be attributed to increased interconnected
heat flow pathways facilitated by the increased surface area of non-circular
fibers with the same cross-sectional areas, resulting in efficient heat
transfer.",2403.17650v1
2024-04-24,Synthesis of layered gold tellurides AuSbTe and Au$_2$Te$_3$ and their semiconducting and metallic behavior,"Previous studies on natural samples of pampaloite (AuSbTe) revealed the
crystal structure of a potentially cleavable and/or exfoliable material, while
studies on natural and synthetic montbrayite (Sb-containing Au$_2$Te$_3$)
claimed various chemical compositions for this low symmetry compound. Few
investigations of synthetic samples have been reported for both materials,
leaving much of their chemical, thermal and electronic characteristics unknown.
Here, we investigate the stability, electronic properties and synthesis of the
gold antimony tellurides AuSbTe and Au$_{1.9}$Sb$_{0.46}$Te$_{2.64}$
(montbrayite). Differential thermal analysis and $\textit{in situ}$ powder
x-ray diffraction revealed that AuSbTe is incongruently melting, while
Au$_{1.9}$Sb$_{0.46}$Te$_{2.64}$ is congruently melting. Calculations of the
band structures and four-point resistivity measurements showed that AuSbTe is a
semiconductor and Au$_{1.9}$Sb$_{0.46}$Te$_{2.64}$ a metal. Various synthesis
attempts confirmed the limited stable chemical composition of
Au$_{1.9}$Sb$_{0.46}$Te$_{2.64}$, identified successful methods to synthesize
both compounds, and highlighted the challenges associated with single crystal
synthesis of AuSbTe.",2404.16239v1
2024-05-03,Piezoresistivity as an Order Parameter for Ferroaxial Transitions,"Recent progress in the understanding of the collective behavior of electrons
and ions have revealed new types of ferroic orders beyond ferroelectricity and
ferromagnetism, such as the ferroaxial state. The latter retains only
rotational symmetry around a single axis and reflection symmetry with respect
to a single mirror plane, both of which are set by an emergent electric
toroidal dipole moment. Due to this unusual symmetry-breaking pattern, it has
been challenging to directly measure the ferroaxial order parameter, despite
the increasing attention this state has drawn. Here, we show that off-diagonal
components of the piezoresistivity tensor (i.e., the linear change in
resistivity under strain) transform the same way as the ferroaxial moments,
providing a direct probe of such order parameters. We identify two new proper
ferroaxial materials through a materials database search, and use
first-principles calculations to evaluate the piezoconductivity of the
double-perovskite CaSnF$_6$, revealing its connection to ferroaxial order and
to octahedral rotation modes.",2405.02149v1
2004-11-16,Upper Critical Fields up to 60T in Dirty Magnesium Diboride Thin Films,"Upper critical fields of several magnesium diboride thin films were measured
up to 28 T at the Grenoble High Magnetic Field Laboratory (GHMFL) in Grenoble
and up to 60 T at the Laboratoire National des Champs Magnetiques Pulses
(LNCMP) in Toulouse. The samples were prepared both by pulsed laser deposition
(PLD) and hybrid physical chemical vapour deposition (HPCVD) technique; they
have critical temperatures between 29 and 39 K and normal state resistivities
between 5 and 250 &#956;ohmcm; one of them has been intentionally doped with
carbon. The measured critical fields were exceptionally high; we obtained the
record value of 52 T at 4.2 K in the parallel orientation. In contrast with the
BCS predictions, no saturation in Hc2 at low temperature was observed.
Furthermore, films with a wide range of resistivity values showed similar
critical fields, suggesting that in a two band system resistivity and Hc2 are
not trivially linked. The high Hc2 values seem to be related with the expanded
c-axis. The structure of one of the samples was carefully investigated with
X-ray diffraction at European Synchrotron Radiation Facility (ESRF) in
Grenoble.",0411404v1
2008-07-22,"Microphysical dissipation, turbulence and magnetic fields in hyper-accreting discs","Hyper-accreting discs occur in compact-object mergers and collapsars, and may
power gamma-ray bursts (GRBs). We calculate the microscopic viscosity and
resistivity of plasma in these discs, and discuss the implications for their
global structure and evolution. In the neutrino-cooled innermost regions, the
viscosity is provided mainly by mildly degenerate electrons, while the
resistivity is modified from the Spitzer value due to the effects of both
relativity and degeneracy. The plasma behaves as an almost ideal MHD fluid.
Among the non-ideal MHD effects the Hall term is relatively the most important,
while the magnetic Prandtl number, Pr (the ratio of viscosity to resistivity),
is typically larger than unity: 10 < Pr < 6000. The outer radiatively
inefficient regions also display high Pr. Numerical simulations of the
magneto-rotational instability indicate that the saturation level and angular
momentum transport efficiency may be greatly enhanced at high Pr. If this
behaviour persists in the presence of a strong Hall effect we would expect that
hyper-accreting discs should be strongly magnetised and highly variable. The
expulsion of magnetic field that cannot be dissipated at small scales may also
favour a magnetic outflow. We note the similaries between the Prandtl number in
hyper-accreting discs and X-ray binary discs, which suggests that a comparison
between late-time activity in GRBs and X-ray binary accretion states may be
fruitful. Our results imply that the behavior of high Prandtl number MHD flows
needs to be considered in studies of hyper-accreting discs.",0807.3547v2
2011-11-16,Optical tuning and ultrafast dynamics of high-temperature superconducting terahertz metamaterials,"Through the integration of semiconductors or complex oxides into metal
resonators, tunable metamaterials have been achieved by a change of environment
using an external stimulus. Metals provide high conductivity to realize a
strong resonant response in metamaterials; however, they contribute very little
to the tunability. The complex conductivity in high-temperature superconducting
films is highly sensitive to external perturbations, which provides new
opportunities in achieving tunable metamaterials resulting directly from the
resonant elements. Here we demonstrate ultrafast dynamical tuning of resonance
in the terahertz (THz) frequency range in YBa_2Cu_3O_7-\delta (YBCO) split-ring
resonator arrays excited by near-infrared femtosecond laser pulses. The
photoexcitation breaks the superconducting Cooper pairs to create the
quasiparticle state. This dramatically modifies the imaginary part of the
complex conductivity and consequently the metamaterial resonance in an
ultrafast timescale. We observed resonance switching accompanied with a wide
range frequency tuning as a function of photoexcitation fluence, which also
strongly depend on the nano-scale thickness of the superconducting films. All
of our experimental results are well reproduced through calculations using an
analytical model, which takes into account the SRR resistance and kinetic
inductance contributed from the complex conductivity of YBCO films. The
theoretical calculations reveal that the increasing SRR resistance upon
increasing photoexcitation fluence is responsible for the reduction of
resonance strength, and both the resistance and kinetic inductance contribute
to the tuning of resonance frequency.",1111.3917v1
2012-05-14,A fully covariant mean-field dynamo closure for numerical 3+1 resistive GRMHD,"The powerful high-energy phenomena typically encountered in astrophysics
invariably involve physical engines, like neutron stars and black hole
accretion disks, characterized by a combination of highly magnetized plasmas,
strong gravitational fields, and relativistic motions. In recent years
numerical schemes for General Relativistic MHD (GRMHD) have been developed to
model the multidimensional dynamics of such systems, including the possibility
of an evolving spacetime. Such schemes have been also extended beyond the ideal
limit including the effects of resistivity, in an attempt to model dissipative
physical processes acting on small scales (sub-grid effects) over the global
dynamics. Along the same lines, magnetic fields could be amplified by the
presence of turbulent dynamo processes, as often invoked to explain the high
values of magnetization required in accretion disks and neutron stars. Here we
present, for the first time, a further extension to include the possibility of
a mean-field dynamo action within the framework of numerical 3+1 (resistive)
GRMHD. A fully covariant dynamo closure is proposed, in analogy with the
classical theory, assuming a simple alpha-effect in the comoving frame. Its
implementation into a finite-difference scheme for GRMHD in dynamical
spacetimes [the X-ECHO code: (Bucciantini and Del Zanna 2011)] is described,
and a set of numerical test is presented and compared with analytical solutions
wherever possible.",1205.2951v3
2013-01-31,An ageing study of resistive micromegas for the HL-LHC environment,"Resistive-anode micromegas detectors are in development since several years,
in an effort to solve the problem of sparks when working at high flux and high
ionizing radiation like in the HL-LHC (up to ten times the luminosity of the
LHC). They have been chosen as one of the technologies that will be part of the
ATLAS New Small Wheel project (forward muon system). An ageing study is
mandatory to assess their capabilities to handle the HL-LHC environment on a
long-term period. A prototype has been exposed to several types of irradiation
(X-rays, cold neutrons, $^{60}$Co gammas and alphas) above the equivalent
charge produced at the detector in five HL-LHC running years without showing
any degradation of the performances in terms of gain and energy resolution.
This study has been completed with the characterization of the tracking
performances in terms of efficiency and spatial resolution, verifying the
compatibility of results obtained with both resistive micromegas detectors,
irradiated and non-irradiated one.",1301.7648v1
2014-03-20,High Electron Mobility in Epitaxial Graphene on 4H-SiC(0001) via post-growth annealing under hydrogen,"We investigate the magneto-transport properties of epitaxial graphene
single-layer on 4H-SiC(0001), grown by atmospheric pressure graphitization in
Ar, followed by H2 intercalation. We directly demonstrate the importance of
saturating the Si dangling bonds at the graphene/SiC(0001) interface to achieve
high carrier mobility. Upon successful Si dangling bonds elimination, carrier
mobility increases from 3 000 cm^2/Vs to > 11 000 cm^2/Vs at 0.3 K.
Additionally, graphene electron concentration tends to decrease from a few
10^12 cm^-2 to less than 10^12 cm^-2. For a typical large (30x280 um^2) Hall
bar, we report the observation of the integer quantum Hall states at 0.3 K with
well developed transversal resistance plateaus at Landau level fillings factors
of nu = 2, 6, 10, 14.. 42 and Shubnikov de Haas oscillation of the longitudinal
resistivity observed from about 1 T. In such a device, the Hall state
quantization at nu=2, at 19 T and 0.3 K, can be very robust: the dissipation in
electronic transport can stay very low, with the longitudinal resistivity lower
than 5 mOhm, for measurement currents as high as 250 uA. This is very promising
in the view of an application in metrology.",1403.5059v1
2015-02-16,(Li0.84Fe0.16)OHFe0.98Se superconductor: Ion-exchange synthesis of large single crystal and highly two-dimensional electron properties,"A large and high-quality single crystal (Li0.84Fe0.16)OHFe0.98Se, the optimal
superconductor of newly reported (Li1-xFex)OHFe1-ySe system, has been
successfully synthesized via a hydrothermal ion-exchange technique. The
superconducting transition temperature (Tc) of 42 K is determined by magnetic
susceptibility and electric resistivity measurements, and the zero-temperature
upper critical magnetic fields are evaluated as 79 and 313 Tesla for the field
along the c-axis and the ab-plane, respectively. The ratio of out-of-plane to
in-plane electric resistivity,\r{ho}c/\r{ho}ab, is found to increases with
decreasing temperature and to reach a high value of 2500 at 50 K, with an
evident kink occurring at a characteristic temperature T*=120 K. The negative
in-plane Hall coefficient indicates that electron carriers dominate in the
charge transport, and the hole contribution is significantly reduced as the
temperature is lowered to approach T*. From T* down to Tc, we observe the
linear temperature dependences of the in-plane electric resistivity and the
magnetic susceptibility for the FeSe layers. Our findings thus reveal that the
normal state of (Li0.84Fe0.16)OHFe0.98Se becomes highly two-dimensional and
anomalous prior to the superconducting transition, providing a new insight into
the mechanism of high-Tc superconductivity.",1502.04688v2
2015-09-29,"Design, development and performance study of six-gap glass MRPC detectors","The Multigap Resistive Plate Chambers (MRPCs) are gas ionization detectors
with multiple gas sub-gaps made of resistive electrodes. The high voltage (HV)
is applied on the outer surfaces of outermost resistive plates only, while the
interior plates are left electrically floating. The presence of multiple narrow
sub--gaps with high electric field results in faster signals on the outer
electrodes, thus improving the detector's time resolution. Due to their
excellent performance and relatively low cost, the MRPC detector has found
potential application in Time-of-Flight (TOF) systems. Here we present the
design, fabrication, optimization of the operating parameters such as the HV,
the gas mixture composition, and, performance of six--gap glass MRPC detectors
of area 27cm $\times$ 27 cm, which are developed in order to find application
as trigger detectors, in TOF measurement etc. The design has been optimized
with unique spacers and blockers to ensure a proper gas flow through the narrow
sub-gaps, which are 250 $\mu$m wide. The gas mixture consisting of R134A,
Isobutane and SF$_{6}$, and the fraction of each constituting gases has been
optimized after studying the MRPC performance for a set of different
concentrations. The counting efficiency of the MRPC is about 95% at $17.9$ kV.
At the same operating voltage, the time resolution, after correcting for the
walk effect, is found to be about $219$ ps.",1509.08586v2
2017-02-21,Pressure induced half-collapsed-tetragonal phase in CaKFe$_4$As$_4$,"We report the temperature-pressure phase diagram of CaKFe$_4$As$_4$
established using high pressure electrical resistivity, magnetization and high
energy x-ray diffraction measurements up to 6 GPa. With increasing pressure,
both resistivity and magnetization data show that the bulk superconducting
transition of CaKFe$_4$As$_4$ is suppressed and then disappears at $p$
$\gtrsim$ 4 GPa. High pressure x-ray data clearly indicate a phase transition
to a collapsed tetragonal phase in CaKFe$_4$As$_4$ under pressure that
coincides with the abrupt loss of bulk superconductivity near 4 GPa. The x-ray
data, combined with resistivity data, indicate that the collapsed tetragonal
transition line is essentially vertical, occuring at 4.0(5) GPa for
temperatures below 150 K. Band structure calculations also find a sudden
transition to a collapsed tetragonal state near 4 GPa, as As-As bonding takes
place across the Ca-layer. Bonding across the K-layer only occurs for $p$
$\geq$ 12 GPa. These findings demonstrate a new type of collapsed tetragonal
phase in CaKFe$_4$As$_4$: a half-collapsed-tetragonal phase.",1702.06622v1
2016-06-30,Identification of a possible superconducting transition above room temperature in natural graphite crystals,"Measuring with high precision the electrical resistance of highly ordered
natural graphite samples from a Brazil mine, we have identified a transition at
$\sim$350~K with $\sim$40~K transition width. The step-like change in
temperature of the resistance, its magnetic irreversibility and time dependence
after a field change, consistent with trapped flux and flux creep, and the
partial magnetic flux expulsion obtained by magnetization measurements, suggest
the existence of granular superconductivity below 350~K. The zero-field virgin
state can only be reached again after zero field cooling the sample from above
the transition. Paradoxically, the extraordinarily high transition temperature
we found for this and several other graphite samples is the reason why this
transition remained undetected so far. The existence of well ordered
rhombohedral graphite phase in all measured samples has been proved by x-rays
diffraction measurements, suggesting its interfaces with the Bernal phase as a
possible origin for the high-temperature superconductivity, as theoretical
studies predicted. The localization of granular superconductivity at these two
dimensional interfaces prevents the observation of a zero resistance state or
of a full Meissner state.",1606.09425v1
2022-02-04,Fabrication of Surface Ion Traps with Integrated Current Carrying Wires enabling High Magnetic Field Gradients,"A major challenge for quantum computers is the scalable simultaneous
execution of quantum gates. One approach to address this in trapped ion quantum
computers is the implementation of quantum gates based on static magnetic field
gradients and global microwave fields. In this paper, we present the
fabrication of surface ion traps with integrated copper current carrying wires
embedded inside the substrate below the ion trap electrodes, capable of
generating high magnetic field gradients. The copper layer's measured sheet
resistance of 1.12 m$\Omega$/sq at room temperature is sufficiently low to
incorporate complex designs, without excessive power dissipation at high
currents causing a thermal runaway. At a temperature of 40 K the sheet
resistance drops to 20.9 $\mu\Omega$/sq giving a lower limit for the residual
resistance ratio of 100. Continuous currents of 13 A can be applied, resulting
in a simulated magnetic field gradient of 144 T/m at the ion position, which is
125 $\mu$m from the trap surface for the particular anti-parallel wire pair in
our design.",2202.02313v2
2019-03-15,Hyper-Resistive Model of Ultra High Energy Cosmic Ray Acceleration by Magnetically Collimated Jets Created by Active Galactic Nuclei,"This is the fourth in a series of companion papers showing that, when an
efficient dynamo can be maintained by accretion disks around supermassive black
holes in Active Galactic Nuclei (AGNs), it will lead to the formation of a
powerful, magnetically-collimated helix that could explain both the observed
jet/radiolobe structures on very large scales and ultimately the enormous power
inferred from the observed ultra high energy cosmic rays (UHECRs) with energies
> 10^19 eV. Many timescales are involved in this process. Our hyper-resistive
magnetohydrodynamic (MHD) model provides a bridge between General Relativistic
MHD simulations of dynamo formation, on the short accretion timescale, and
observational evidence of magnetic collimation of large-scale jets on
astrophysical timescales. Given the final magnetic structure, we apply
hyper-resistive kinetic theory to show how instability causes slowly-evolving
magnetically-collimated jets to become the most powerful relativistic
accelerators in the Universe. The model yields nine observables in reasonable
agreement with observations: the jet length, radiolobe radius and apparent
opening angle as observed by synchrotron radiation; the synchrotron total
power, synchrotron wavelengths and maximum electron energy (TeVs); and the
maximum UHECR energy, the cosmic ray energy spectrum and the cosmic ray
intensity on Earth.",1903.06839v2
2019-01-23,Josephson junctions and SQUIDs created by focused helium ion beam irradiation of YBa$_2$Cu$_3$O$_7$,"By scanning with a $30\, \mathrm{keV}$ focused He ion beam (He-FIB) across
YBa$_2$Cu$_3$O$_7$ (YBCO) thin film microbridges, we create Josephson barriers
with critical current density $j_\mathrm{c}$ adjustable by irradiation dose
$D$. The dependence $j_\mathrm{c} (D)$ yields an exponential decay. At $4.2\,
\mathrm{K}$, a transition from flux-flow to Josephson behavior occurs when
$j_\mathrm{c}$ decreases below $\approx 2\, \mathrm{MA/cm^2}$. The Josephson
junctions exhibit current-voltage characteristics (IVCs) that are well
described by the resistively and capacitively shunted junction model, without
excess current for characteristic voltages $V_\mathrm{c} \lesssim 1\,
\mathrm{mV}$. Devices on MgO and LSAT substrates show non-hysteretic IVCs,
while devices on SrTiO$_3$ show a small hysteresis. For all junctions an
approximate scaling $V_\mathrm{c} \propto j_\mathrm{c}^{1/2}$ is found. He-FIB
irradiation with high dose produces barriers with $j_\mathrm{c}=0$ and high
resistances of $10\, \mathrm{k\Omega} \ldots 1\, \mathrm{G\Omega}$. This
provides the possibility to write highly resistive walls or areas into YBCO
using a He-FIB. Transmission electron microscopy reveals an amorphous phase
within the walls, whereas for lower doses the YBCO stays crystalline. We have
also ``drawn'' superconducting quantum interference devices (SQUIDs) by using a
He-FIB for definition of the SQUID hole and the junctions. The SQUIDs show high
performance, with flux noise $< 500\, \mathrm{n \Phi_0/Hz^{1/2}}$ in the
thermal white noise limit for a device with $19\, \mathrm{pH}$ inductance.",1901.08039v3
2023-02-14,The current unbalance in stacked REBCO tapes -- simulations based on a circuit grid model,"Unlike low temperature superconducting cables, there is so far no perfect
solution for REBCO coated conductors to form a fully transposed high current
cable. Every REBCO cable concept must import a stack of tapes to achieve an
operating current as high as tens of kiloamperes. The stacked REBCO tapes, no
matter whether they are twisted or not, however, have a nature of
non-transposing and therefore could result in current unbalance. In this
manuscript, the current unbalance and the related electrical characteristics of
a cable made of 40 stacked REBCO tapes are studied with an electrical circuit
simulation. The differences in splice resistances and tape inductances that are
both related to the non-transposed structure of a REBCO stack are considered.
Results show that for a 40 cm long termination, a proper method to keep the
contact resistivity between each tape and the copper termination around 1e-8
ohmm is crucial to totally avoid current unbalance lowering the cable
performance. Surprisingly, the inter-tape current transfer is found to be able
to further exacerbate local high current though it does make the overall
distribution more balanced. The inductance difference induced current unbalance
is only important if local defects exist at long REBCO tapes, which on the
other hand can be cured by good inter-tape current transfer. For a
fast-charging rate of 1 kA/s, the inter-tape contact resistivity should also be
low to a level of 1e-8 ohmm to ensure a short current transfer length of around
1 m.",2302.06817v1
2024-04-25,Conductivity of lattice bosons at high temperatures,"Quantum simulations are quickly becoming an indispensable tool for studying
particle transport in correlated lattice models. One of the central topics in
the study of transport is the bad-metal behavior, characterized by the direct
current (dc) resistivity linear in temperature. In the fermionic Hubbard model,
optical conductivity has been studied extensively, and a recent optical lattice
experiment has demonstrated bad metal behavior in qualitative agreement with
theory. Far less is known about transport in the bosonic Hubbard model. We
investigate the conductivity in the Bose-Hubbard model, and focus on the regime
of strong interactions and high-temperatures. We use numerically exact
calculations for small lattice sizes. At weak tunneling, we find multiple peaks
in the optical conductivity that stem from the Hubbard bands present in the
many-body spectrum. This feature slowly washes out as the tunneling rate gets
stronger. At high temperature, we identify a regime of $T$-linear resistivity,
as expected. When the interactions are very strong, the leading
inverse-temperature coefficient in conductivity is proportional to the
tunneling amplitude. As the tunneling becomes stronger, this dependence takes
quadratic form. At very strong coupling and half filling, we identify a
separate linear resistivity regime at lower temperature, corresponding to the
hard-core boson regime. Additionally, we unexpectedly observe that at half
filling, in a big part of the phase diagram, conductivity is an increasing
function of the coupling constant before it saturates at the hard-core-boson
result. We explain this feature based on the analysis of the many-body energy
spectrum and the contributions to conductivity of individual eigenstates of the
system.",2404.16559v1
2004-10-22,Observation of double resistance anomalies and excessive resistance in mesoscopic superconducting Au$_{0.7}$In$_{0.3}$ rings with phase separation,"We have measured mesoscopic superconducting Au$_{0.7}$In$_{0.3}$ rings
prepared by e-beam lithography and sequential deposition of Au and In at room
temperature followed by a standard lift-off procedure. In samples showing no
Little-Parks resistance oscillations, highly unusual double resistance
anomalies, two resistance peaks found near the onset of superconductivity, were
observed. Although resistance anomaly featuring a single resistance peak has
been seen in various mesoscopic superconducting samples, double resistance
anomalies have never been observed previously. The dynamical resistance
measurements suggest that there are two critical currents in these samples. In
addition, the two resistance peaks were found to be suppressed at different
magnetic fields. We attribute the observed double resistance anomalies to an
underlying phase separation in which In-rich grains of intermetallic compound
of AuIn precipitate in a uniform In-dilute matrix of Au$_{0.9}$In$_{0.1}$. The
intrinsic superconducting transition temperature of the In-rich grains is
substantially higher than that of the In-dilute matrix. The suppression of the
conventional Little-Parks resistance oscillation is explained in the same
picture by taking into consideration a strong variation in the $T_c$ of the
In-rich grains. We also report the observation of an unusual
magnetic-field-induced metallic state with its resistance higher than the
normal-state resistance, referred to here as excessive resistance, and an h/2e
resistance oscillation with the amplitude of oscillation depends extremely
weakly on temperature.",0410567v2
2022-09-17,Superfunctional materials by ultra-severe plastic deformation,"Superfunctional materials are defined as materials with specific properties
being superior to the functions of engineering materials. Numerous studies
introduced severe plastic deformation (SPD) as an effective process to improve
the functional and mechanical properties of various metallic and non-metallic
materials. Moreover, the concept of ultra-SPD - introducing shear strains over
1000 to reduce the thickness of sheared phases to levels comparable to atomic
distances - was recently utilized to synthesize novel superfunctional
materials. In this article, the application of ultra-SPD for controlling atomic
diffusion and phase transformation and synthesizing new materials with
superfunctional properties is discussed. The main properties achieved by
ultra-SPD include: (i) high-temperature thermal stability in new immiscible
age-hardenable aluminum alloys; (ii) room-temperature superplasticity for the
first time in magnesium and aluminum alloys; (iii) high strength and high
plasticity in nanograined intermetallics; (iv) low elastic modulus and high
hardness in biocompatible binary and high-entropy alloys; (v) superconductivity
and high strength in the Nb-Ti alloys; (vi) room-temperature hydrogen storage
for the first time in magnesium alloys; and (vii) superior photocatalytic
hydrogen production, oxygen production, and carbon dioxide conversion on
high-entropy oxides and oxynitrides as a new family of photocatalysts.",2209.08295v3
2020-06-08,Data-driven topology design using a deep generative model,"In this paper, we propose a sensitivity-free and multi-objective structural
design methodology called data-driven topology design. It is schemed to obtain
high-performance material distributions from initially given material
distributions in a given design domain. Its basic idea is to iterate the
following processes: (i) selecting material distributions from a dataset of
material distributions according to eliteness, (ii) generating new material
distributions using a deep generative model trained with the selected elite
material distributions, and (iii) merging the generated material distributions
with the dataset. Because of the nature of a deep generative model, the
generated material distributions are diverse and inherit features of the
training data, that is, the elite material distributions. Therefore, it is
expected that some of the generated material distributions are superior to the
current elite material distributions, and by merging the generated material
distributions with the dataset, the performances of the newly selected elite
material distributions are improved. The performances are further improved by
iterating the above processes. The usefulness of data-driven topology design is
demonstrated through numerical examples.",2006.04559v3
2024-04-03,Wenzhou TE: a first-principles calculated thermoelectric materials database,"Since the implementation of the Materials Genome Project by the Obama
administration in the United States, the development of various computational
materials databases has fundamentally expanded the choices of industries such
as materials and energy. In the field of thermoelectric materials, the
thermoelectric figure of merit ZT quantifies the performance of the material.
From the viewpoint of calculations for vast materials, the ZT values are not
easily obtained due to their computational complexity. Here, we show how to
build a database of thermoelectric materials based on first-principles
calculations for the electronic and heat transport of materials. Firstly, the
initial structures are classified according to the values of bandgap and other
basic properties using the clustering algorithm K-means in machine learning,
and high-throughput first principles calculations are carried out for
narrow-bandgap semiconductors which exhibiting potential thermoelectric
application. The present framework of calculations mainly includes deformation
potential module, electrical transport performance module, mechanical and
thermodynamic properties module. We have also set up a search webpage for the
calculated database of thermoelectric materials, providing searching and
viewing the related physical properties of materials. Our work may inspire the
construction of more computational databases of first-principle thermoelectric
materials and accelerate research progress in the field of thermoelectrics.",2404.02571v1
2023-12-13,The Milky Way shines in high-energy neutrinos,"The most energetic astrophysical sources in the Milky Way, cosmic
accelerators capable of producing high-energy cosmic rays, have resisted
discovery for over a century. Up to now, astrophysicists sought these sources
mainly by scouring the Galaxy for the gamma rays they are expected to emit. In
2023, the IceCube Neutrino Observatory discovered high-energy neutrinos from
the Milky Way, inaugurating a telltale stream of evidence of cosmic-ray
production and interaction in the Galaxy.",2312.08102v1
1998-10-21,Inverse Cascade of Primordial Magnetic Field in MHD Turbulence,"The feature of the spectrum of primordial magnetic field is studied by using
renormalization group analysis in magnetohydrodynamics. Taking account of the
renormalized resistivity at the fixed point, we show that the scaling of the
typical scale with time obeys $L(t) \sim t^{2/5}$ for random initial condition.",9810339v1
1999-06-10,Luttinger liquid behavior in single wall nanotubes,"Transport properties of metallic single-wall nanotubes are examined based on
the Luttinger liquid theory. Focusing on a nanotube transistor setup, the
linear conductance is computed from the Kubo formula using perturbation theory
in the lead-tube tunnel conductances. For sufficiently long nanotubes and high
temperature, phonon backscattering should lead to an anomalous temperature
dependence of the resistivity.",9906150v1
2002-01-07,Temperature-dependent $H_{c2}$ anisotropy in MgB$_2$ as inferred from measurements on polycrystals,"We present data on temperature-dependent anisotropy of the upper critical
field of MgB$_2$ obtained from the analysis of measurements on high purity, low
resistivity polycrystals. The anisotropy decreases in a monotonic fashion with
increase of temperature.",0201085v1
2003-05-29,Imaging the charge transport in arrays of CdSe nanocrystals,"A novel method to image charge is used to measure the diffusion coefficient
of electrons in films of CdSe nanocrystals at room temperature. This method
makes possible the study of charge transport in films exhibiting high
resistances or very small diffusion coefficients.",0305684v1
2003-06-03,Intrinsic tunneling or Joule heating?,"It is shown that the `tunnelling spectra' reported by Yurgens et al. could be
reproduced qualitatively and quantitatively using the experimental out-of-plane
normal state resistance R(T) and assuming that the heating of the mesa, caused
by the Joule dissipation, is the only reason for effects observed at high bias.",0306081v2
2004-10-09,"Comment on cond-mat/0409228 ""Microwave photoresponse in the 2D electron system caused by intra-Landau level transitions""","We provide an article-extract which points out that a microwave-induced
modification in the resistance occurs at relatively ""high"" magnetic fields
where the radiation is incapable of producing inter-Landau level excitations
and, therefore, that the microwave radiation must be producing intra Landau
level excitations as well.",0410227v1
2005-11-22,Quantum phase slip junctions,"In this paper we demonstrate that, if it exists, coherent quantum phase slip
is the exact dual to Josephson tunneling. We use the duality to predict kinetic
capacitance and a sharp resonance in narrow wires. Biased resistively and
driven at high frequency, quantum phase slip junctions should exhibit current
plateaus of interest for a fundamental standard.",0511535v1
2003-04-13,"Comment on ""Phase Transition-Like Behavior in a Low-Pass Filter""","This is a reminder that an infinite series can be defined other than as the
limit of a sequence of finite series. An example is provided in which a circuit
element comprised of an infinite series of resistors has negative resistance.",0304051v1
2005-01-24,Nonlocal Gate Of Quantum Network Via Cavity Quantum Electrodynamics,"We propose an experimentally feasible scheme to realize the nonlocal gate
between two different quantum network nodes. With an entanglement-qubit (ebit)
acts as a quantum channel, our scheme is resistive to actual environment noise
and can get high fidelity in current cavity quantum electrodynamics (C-QED)
system.",0501125v2
2008-03-16,Asymmetric exclusion processes with constrained dynamics,"Asymmetric exclusion processes with locally reversible kinetic constraints
are introduced to investigate the effect of non-conservative driving forces in
athermal systems. At high density they generally exhibit rheological-like
behavior, negative differential resistance, two-step structural relaxation,
dynamical heterogeneity and, possibly, a jamming transition driven by the
external field.",0803.2287v2
2010-04-05,Superconducting plasmonics and extraordinary transmission,"Negative dielectric constant and dominant kinetic resistance make
superconductors an intriguing plasmonic media. Here we report on the first
study of one of the most important and disputed manifestations of plasmonics,
the effect of extraordinary transmission through an array of sub-wavelength
holes, using a perforated film of high-temperature superconductor.",1004.0729v1
2010-05-03,Construction of a Digital Hadron Calorimeter,"The DHCAL collaboration is assembling a large scale prototype Digital Hadron
Calorimeter (DHCAL). The calorimeter utilizes Resistive Plate Chambers (RPCs)
as active medium and features of the order of 400,000 1 \times 1 cm2 pads with
binary (or digital) electronic readout. The purpose of the prototype is to
provide detailed measurements of hadronic showers and to prove the concept of a
DHCAL with RPCs as active elements.",1005.0410v1
2010-07-16,Indications of room-temperature superconductivity at a metal-PZT interface,"We report the observation of an exceptionally large room-temperature
electrical conductivity in silver and aluminum layers deposited on a lead
zirconate titanate (PZT) substrate. The surface resistance of the silver-coated
samples also shows a sharp change near 313 K. The results are strongly
suggestive of a superconductive interfacial layer, and have been interpreted in
the framework of Bose-Einstein condensation of bipolarons as the suggested
mechanism for high-temperature superconductivity in cuprates.",1007.2736v1
2010-07-18,Test Beam Results Using an RPC Semi-Digital HCAL,"We report on the development of an GRPCs (Glass Resistive Plate chambers)
Semi- Digital hadron calorimeter for the future International Linear Collider
(ILC).Two types of GRPCs (small and 1m2) were tested in PS beam at CERN.
Detector performances are presented here in terms of efficiency, pad
multiplicity, homogeneity and stability in time.",1007.3009v3
2011-12-14,Superconductivity in Single-Crystal YIn3,"We measure the superconducting transition of YIn$_3$ by resistivity,
susceptibility, and specific heat. Despite using high-quality single-crystal
samples, the transitions detected by the three techniques are shifted from each
other in temperature, suggesting a region of filamentary superconductivity. We
discuss the possible implications for filamentary superconductivity in
unconventional superconductors.",1112.3083v1
2013-03-05,Unusual suppression of superconductivity in YNi2B2C under neutron irradiation,"The behavior of electrical resistivity rho(T), temperature of superconducting
transition Tc, and upper critical field Hc2(T) of polycrystalline YNi2B2C after
irradiation with thermal neutron and subsequent high-temperature isochronous
annealings in the temperature range Tann = 100 - 1000C has been studied.",1303.0929v1
2015-01-11,Resistance of a Rotating-Moving Brane with Background Fields Against Collapse,"Using the boundary state formalism we investigate the effect of tachyon
condensation process on a rotating and moving D$p$-brane with various
background fields in the bosonic string theory. The rotation and motion are
inside the brane volume. We demonstrate that some specific rotations and/or
motions can preserve the brane from instability and collapse.",1501.02453v1
2017-02-12,Optimal doping of the diode current interrupters,"An analytical solution to the problem of decreasing the energy losses
$\Omega$ in diode current interrupters during recovery of the blocking ability
by optimizing dopant distribution $N(x)$ over structure thickness has been
obtained. It was found the distribution $N(x)$ close to optimal one that
decreases $\Omega$ by 30-55% compared with standard interrupters with uniformly
doped high-resistivity layers.",1702.03496v1
2016-03-24,"A note on ""achieving security, robust cheating resistance, and high-efficiency for outsourcing large matrix multiplication computation to a malicious cloud""","We show that the Lei et al.'s scheme [Information Sciences, 280 (2014),
205-217] fails, because the verifying equation does not hold over the infinite
field R. For the field R, the computational errors should be considered
seriously. We also remark that the incurred communication cost in the scheme
could be overtake the computational gain, which makes it somewhat artificial.",1603.07399v1
2020-06-07,Asymmetric Jet launching,"In resistive and viscous magnetohydrodynamical (MHD) simulations we obtain
axial jets launched from the innermost magnetosphere of a star-disk system. We
found that in a part of the parameter space continuous asymmetric jets, which
are propagating in opposite directions, are launched. We compare the speed of
propagation and rotation of obtained jets with recent observational results.",2006.04083v1
2021-12-30,Two Instances of Interpretable Neural Network for Universal Approximations,"This paper proposes two bottom-up interpretable neural network (NN)
constructions for universal approximation, namely Triangularly-constructed NN
(TNN) and Semi-Quantized Activation NN (SQANN). Further notable properties are
(1) resistance to catastrophic forgetting (2) existence of proof for
arbitrarily high accuracies (3) the ability to identify samples that are
out-of-distribution through interpretable activation ""fingerprints"".",2112.15026v2
2022-02-20,High-throughput computational screening of nanoporous materials in targeted applications,"Due to their chemical and structural diversity, nanoporous materials can be
used in a wide variety of applications, including fluid separation, gas
storage, heterogeneous catalysis, drug delivery, etc. Given the large and
rapidly increasing number of known nanoporous materials, and the even bigger
number of hypothetical structures, computational screening is an efficient
method to find the current best-performing materials and to guide the design of
future materials. This review highlights the potential of high-throughput
computational screenings in various applications. The achievements and the
challenges associated to the screening of several material properties are
discussed to give a broader perspective on the future of the field.",2202.09886v2
2020-08-29,High-throughput Design of Magnetic Materials,"Materials design based on density functional theory (DFT) calculations is an
emergent field of great potential to accelerate the development and employment
of novel materials. Magnetic materials play an essential role in green energy
applications as they provide efficient ways of harvesting, converting, and
utilizing energy. In this review, after a brief introduction to the major
functionalities of magnetic materials, we demonstrated the fundamental
properties which can be tackled via high-throughput DFT calculations, with a
particular focus on the current challenges and feasible solutions. Successful
case studies are summarized on several classes of magnetic materials, followed
by bird-view perspectives for the future.",2008.12907v1
2021-02-03,High-throughput discovery of novel cubic crystal materials using deep generative neural networks,"High-throughput screening has become one of the major strategies for the
discovery of novel functional materials. However, its effectiveness is severely
limited by the lack of quantity and diversity of known materials deposited in
the current materials repositories such as ICSD and OQMD. Recent progress in
machine learning and especially deep learning have enabled a generative
strategy that learns implicit chemical rules for creating chemically valid
hypothetical materials with new compositions and structures. However, current
materials generative models have difficulty in generating structurally diverse,
chemically valid, and stable materials. Here we propose CubicGAN, a generative
adversarial network (GAN) based deep neural network model for large scale
generation of novel cubic crystal structures. When trained on 375,749 ternary
crystal materials from the OQMD database, we show that our model is able to not
only rediscover most of the currently known cubic materials but also generate
hypothetical materials of new structure prototypes. A total of 506 such new
materials (all of them are either ternary or quarternary) have been verified by
DFT based phonon dispersion stability check, several of which have been found
to potentially have exceptional functional properties. Considering the
importance of cubic materials in wide applications such as solar cells and
lithium batteries, our GAN model provides a promising approach to significantly
expand the current repository of materials, enabling the discovery of new
functional materials via screening. The new crystal structures finally verified
by DFT are freely accessible at our Carolina Materials Database
http://www.carolinamatdb.org.",2102.01880v2
2020-08-25,Cathode Materials for Lithium Ion Batteries (LIBs): A Review on Materials related aspects towards High Energy Density LIBs,"This article reviews the development of cathode materials for secondary
lithium ion batteries since its inception with the introduction of lithium
cobalt oxide in early 1980s. The time has passed and numerous cathode materials
are designed and developed to realize not only the enhanced capacity but also
the power density simultaneously. However, there are numerous challenges such
as the cyclic stability of cathode materials, their structural and thermal
stability, higher operating voltage together with high ionic and electronic
conductivity for efficient ion and charge transport during charging and
discharging. This article will cover the development of materials in
chronological order classifying as the lithium ion cathode materials in
different generations. The ternary oxides such as LiTMOx (TM=Transition Metal)
are considered as the first generation materials, whereas modified ternary and
quaternary oxide systems are considered as the second generation materials. The
current i.e. third generation includes complex oxide systems with higher
lithium content such as Li2TMSiO4 aiming for higher energy density. Further,
developments are heading towards lithium metal based batteries with a
possibility for very high energy densities.",2008.10896v2
1999-11-15,Comparison of the Transport Mechanism in Underdoped High Temperature Superconductors and in Spin Ladders,"Recently, the normal state resistivity of high temperature superconductors
(in particular in La2-xSrxCuO4 single crystals) has been studied extensively in
the region below Tc by suppressing the superconducting state in high magnetic
fields. In the present work we report on the normal state resistance of
underdoped La2-xSrxCuO4 thin films under epitaxial strain, measured far below
Tc by applying pulsed fields up to 60 T. We will compare the transport
measurements on these high temperature superconductors with transport data
reported for the Sr2.5Ca11.5Cu24O41 spin ladder compound. This comparison leads
to an interpretation of the data in terms of the recently proposed 1D quantum
transport model and the charge-stripe models.",9911217v1
2007-11-13,High-resolution intracellular recordings using a real-time computational model of the electrode,"Intracellular recordings of neuronal membrane potential are a central tool in
neurophysiology. In many situations, especially in vivo, the traditional
limitation of such recordings is the high electrode resistance, which may cause
significant measurement errors. We introduce a computer-aided technique, Active
Electrode Compensation (AEC), based on a digital model of the electrode
interfaced in real time with the electrophysiological setup. The
characteristics of this model are first estimated using white noise current
injection. The electrode and membrane contribution are digitally separated, and
the recording is then made by online subtraction of the electrode contribution.
Tests comparing AEC to other techniques demonstrate that it yields recordings
with improved accuracy. It enables high-frequency recordings in demanding
conditions, such as injection of conductance noise in dynamic-clamp mode, not
feasible with a single high resistance electrode until now. AEC should be
particularly useful to characterize fast phenomena in neurons, in vivo and in
vitro.",0711.2075v1
2010-08-19,Josephson Coupling and Fiske Dynamics in Ferromagnetic Tunnel Junctions,"We report on the fabrication of Nb/AlO_x/Pd_{0.82}Ni_{0.18}/Nb
superconductor/insulator/ferromagnetic metal/superconductor (SIFS) Josephson
junctions with high critical current densities, large normal resistance times
area products, high quality factors, and very good spatial uniformity. For
these junctions a transition from 0- to \pi-coupling is observed for a
thickness d_F ~ 6 nm of the ferromagnetic Pd_{0.82}Ni_{0.18} interlayer. The
magnetic field dependence of the \pi-coupled junctions demonstrates good
spatial homogeneity of the tunneling barrier and ferromagnetic interlayer.
Magnetic characterization shows that the Pd_{0.82}Ni_{0.18} has an out-of-plane
anisotropy and large saturation magnetization, indicating negligible dead
layers at the interfaces. A careful analysis of Fiske modes provides
information on the junction quality factor and the relevant damping mechanisms
up to about 400 GHz. Whereas losses due to quasiparticle tunneling dominate at
low frequencies, the damping is dominated by the finite surface resistance of
the junction electrodes at high frequencies. High quality factors of up to 30
around 200 GHz have been achieved. Our analysis shows that the fabricated
junctions are promising for applications in superconducting quantum circuits or
quantum tunneling experiments.",1008.3341v1
2010-09-02,Superconducting and Structural Transitions in the β-Pyrochlore Oxide KOs2O6 under High Pressure,"Rattling-induced superconductivity in the {\beta}-pyrochlore oxide KOs2O6 is
investigated under high pressure up to 5 GPa. Resistivity measurements in a
high-quality single crystal reveal a gradual decrease in the superconducting
transition temperature Tc from 9.7 K at 1.0 GPa to 6.5 K at 3.5 GPa, followed
by a sudden drop to 3.3 K at 3.6 GPa. Powder X-ray diffraction experiments show
a structural transition from cubic to monoclinic or triclinic at a similar
pressure. The sudden drop in Tc is ascribed to this structural tran-sition, by
which an enhancement in Tc due to a strong electron-rattler interaction present
in the low-pressure cubic phase is abrogated as the rattling of the K ion is
completely suppressed or weakened in the high-pressure phase of reduced
symmetry. In addition, we find two anomalies in the temperature dependence of
resistivity in the low-pressure phase, which may be due to subtle changes in
rattling vibration.",1009.0355v1
2010-09-03,Test beam studies for a highly granular GRPC Semi-Digital HCAL,"The Particle Flow Analysis approach retained for the future ILC detectors
requires high granularity and compact particle energy deposition. A Glass
Resistive Plate Chamber based Semi-Digital calorimeter can offer both at a low
price for the hadronic section. This paper presents some recent developments
and results near test beam in the use of Glass Resistive Plate Chamber with
embedded front-end electronics to build a prototype based on this principle.
All the critical parameters such as the spatial and angular uniformity of the
response as well as the noise level have been measured on small chambers and
found to be appropriate. Small semi-conductive chambers allowing for high rates
and a large chamber have also been tested.",1009.0719v1
2016-10-19,Gossamer bulk high-temperature superconductivity in FeSe,"The cuprates and iron-based high-temperature superconductors share many
common features: layered strongly anisotropic crystal structure, strong
electronic correlations, interplay between different types of electronic
ordering, the intrinsic spatial inhomogeneity due to doping. The understanding
of complex interplay between these factors is crucial for a directed search of
new high-temperature superconductors. Here we show the appearance of
inhomogeneous gossamer superconductivity in bulk FeSe compound at ambient
pressure and at temperature 5 times higher than its zero-resistance $T_c$. This
discovery helps to understand numerous remarkable superconducting properties of
FeSe. We also find and prove a general property: if inhomogeneous
superconductivity in a anisotropic conductor first appears in the form of
isolated superconducting islands, it reduces electric resistivity
anisotropically with maximal effect along the least conducting axis. This gives
a simple and very general tool to detect inhomogeneous superconductivity in
anisotropic compounds, which is critically important to study the onset of
high-temperature superconductivity.",1610.06117v1
2016-12-09,Graphenic Carbon-Silicon Contacts for Reliability Improvement of Metal-Silicon Junctions,"Contact resistance and thermal degradation of metal-silicon contacts are
challenges in nanoscale CMOS as well as in power device applications. Titanium
silicide (TiSi) contacts are commonly used metal-silicon contacts, but are
known to diffuse into the active region under high current stress. In this
paper we show that a graphenic carbon (C) contact deposited on n-type silicon
(C-Si) by CVD, has the same low Schottky barrier height of 0.45 eV as TiSi, but
a much improved reliability against high current stress. The C-Si contact is
over 100 million times more stable against high current stress pulses than the
conventionally used TiSi junction. The C-Si contact properties even show
promise to establish an ultra-low, high temperature stable contact resistance.
The finding has important consequences for the enhancement of reliability in
power devices as well as in Schottky-diodes and electrical contacts to silicon
in general.",1612.06362v1
2018-10-05,Superconducting proximity effect in epitaxial Al-InAs heterostructures,"Semiconductor-based Josephson junctions provide a platform for studying
proximity effect due to the possibility of tuning junction properties by gate
voltage and large-scale fabrication of complex Josephson circuits. Recently
Josephson junctions using InAs weak link with epitaxial aluminum contact have
improved the product of normal resistance and critical current, $I_cR_N$, in
addition to fabrication process reliability. Here we study similar devices with
epitaxial contact and find large supercurrent and substantial product of
$I_cR_N$ in our junctions. However we find a striking difference when we
compare these samples with higher mobility samples in terms of product of
excess current and normal resistance, $I_{ex}R_N$. The excess current is
negligible in lower mobility devices while it is substantial and independent of
gate voltage and junction length in high mobility samples. This indicates that
even though both sample types have epitaxial contacts only the high-mobility
one has a high transparency interface. In the high mobility short junctions, we
observe values of $I_cR_N/\Delta \sim 2.2$ and $I_{ex}R_N/\Delta \sim 1.5$ in
semiconductor weak links.",1810.02514v4
2019-07-23,High-Chern-Number and High-Temperature Quantum Hall Effect without Landau Levels,"The quantum Hall effect (QHE) with quantized Hall resistance of h/{\nu}e2
starts the research on topological quantum states and lays the foundation of
topology in physics. Afterwards, Haldane proposed the QHE without Landau
levels, showing nonzero Chern number |C|=1, which has been experimentally
observed at relatively low temperatures. For emerging physics and
low-power-consumption electronics, the key issues are how to increase the
working temperature and realize high Chern numbers (C>1). Here, we report the
experimental discovery of high-Chern-number QHE (C=2) without Landau levels and
C=1 Chern insulator state displaying nearly quantized Hall resistance plateau
above the N\'eel temperature in MnBi2Te4 devices. Our observations provide a
new perspective on topological matter and open new avenues for exploration of
exotic topological quantum states and topological phase transitions at higher
temperatures.",1907.09947v4
2021-01-08,Superconductivity at ~70 K in Tin Hydride SnHx under High Pressure,"Various tin hydrides SnHx (x = 4, 8, 12, 14) have been theoretically
predicted to be stable at high pressures and to show high-critical-temperature
superconductivity with Tc ranging from about 70 to 100 K. However, experimental
verifications for any of these phases are still lacking to date. Here, we
report on the in-situ synthesis, electrical resistance, and synchrotron x-ray
diffraction measurements of SnHx at ~ 200 GPa. The main phase of the obtained
sample can be indexed with the monoclinic C2/m SnH12 via comparison with the
theoretical structural modes. A sudden drop of resistance and the systematic
downward shift under external magnetic fields signals the occurrence of
superconductivity in SnHx at Tc = ~ 70 K with an upper critical field u0Hc2(0)
= ~ 11.2 T, which is relatively low in comparison with other reported high-Tc
superhydrides. Various characteristic superconducting parameters are estimated
based on the BCS theory.",2101.02846v1
2021-07-20,Performance of a fast timing micro-pattern gaseous detector for future collider experiments,"The fast timing MPGD is a micro-pattern gaseous detector conceived for
achieving sub-nanosecond time resolution while maintaining the ability to
instrument large areas in high-rate environments; applications of such
technology are perspected in high-energy physics experiments at future
colliders and medical diagnostics with time-of-flight methods. This work shows
the systematic studies carried on an FTM prototype on the performance of GEM
foils coated with resistive DLC films, whose development is essential for the
FTM operation. The resistive foil performance has been tested with several gas
mixtures and compared with the results obtained on conductive foils. The
results show that the performance of the FTM is presently limited by the
technology of manufacturing of DLC-coated GEM foils, with high gains reachable
exclusively in isobuthane-based mixtures.",2107.09439v1
2021-10-27,Robust genuine high-dimensional steering with many measurements,"Quantum systems of high dimensions are attracting a lot of attention because
they feature interesting properties when it comes to observing entanglement or
other forms of correlations. In particular, their improved resistance to noise
is favourable for experiments in quantum communication or quantum cryptography.
However, witnessing this high-dimensional nature remains challenging,
especially when the assumptions on the parties involved are weak, typically
when one of them is considered as a black box. In this context, the concept of
genuine high-dimensional steering has been recently introduced and
experimentally demonstrated [Phys. Rev. Lett. 126, 200404 (2021)]; it allows
for a one-sided device-independent certification of the dimension of a
bipartite shared state by only using two measurements. Here I overcome this
limitation by developing, for more than two measurements, universal bounds on
the incompatibility robustness, turned into meaningful dimension certificates.
Interestingly, even though the resulting bounds are quite loose, they still
often offer an increased resistance to noise and could then be advantageously
employed in experiments.",2110.14435v2
2022-03-10,Large output voltage to magnetic flux change in nanoSQUIDs based on direct-write Focused Ion Beam Induced Deposition technique,"NanoSQUIDs are quantum sensors that excel in detecting a small change in
magnetic flux with high sensitivity and high spatial resolution. Here, we
employ resist-free direct-write Ga+ Focused Ion Beam Induced Deposition (FIBID)
techniques to grow W-C nanoSQUIDs, and we investigate their electrical response
to changes in the magnetic flux. Remarkably, FIBID allows the fast
($3~\mathrm{nm}$) growth of $700~\mathrm{nm}\times 300~\mathrm{nm}$
Dayem-bridge nanoSQUIDs based on narrow nanowires ($50~\mathrm{nm}$ wide) that
act as Josephson junctions. The observed transfer coefficient (output voltage
to magnetic flux change) is very high (up to $1301~\mathrm{\mu V/\Phi_0}$),
which correlates with the high resistivity of W-C in the normal state. We
discuss here the potential of this approach to reduce the active area of the
nanoSQUIDs to gain spatial resolution as well as their integration on
cantilevers for scanning-SQUID applications.",2203.05278v1
2008-08-07,Thermal strain-induced enhancement of electromagnetic properties in SiC-MgB2 composites,"Strain engineering has been used to modify materials properties in
ferroelectric, superconducting, and ferromagnetic thin films. The advantage of
strain engineering is that it can achieve unexpected enhancement in certain
properties, such as an increase in ferroelectric critical temperature, Tc, by
300 to 500K, with a minimum detrimental effect on the intrinsic properties of
the material. The strain engineering has been largely applied to the materials
in thin film form, where the strain is generated as a result of lattice
mismatch between the substrate and component film or between layers in
multilayer structures. Here, we report the observation of residual thermal
stress/strain in dense SiC-MgB2 superconductor composites prepared by a
diffusion method. We demonstrate that the thermal strain caused by the
different thermal expansion coefficients between the MgB2 and SiC phases is
responsible for the significant improvement in the critical current density,
Jc, the irreversibility field, Hirr, and the upper critical field, Hc2, in the
SiC-MgB2 composite where the carbon substitution level is low. In contrast to
the common practice of improving the Jc and Hc2 of MgB2 through chemical
substitution, by taking advantage of residual thermal strains we are able to
design a composite, which shows only a small drop in Tc and little increase in
resistivity, but a significant improvement over the Jc and Hc2 of MgB2. The
present findings open up a new direction for manipulation of materials
properties through strain engineering for materials in various forms.",0808.1136v1
2008-08-26,Thermoelectric Effects in Anisotropic Systems: Measurement and Applications,"The Harman method for measuring the thermal conductivity of a sample using
the Peltier effect, may also be used to determine the dimensionless figure of
merit from just two electrical resistance measurements. We consider a modified
version of the Harman method where the current contacts are much smaller than
the contact faces of the sample. We calculate the voltage and temperature
distributions in a rectangular sample of a material having anisotropy in all of
its transport coefficients. The thermoelectric anisotropy has important
consequences in the form of thermoelectric eddy currents and the Bridgman
effect. We prove that in the limit of a very thin sample of arbitrary shape,
there exist van der Pauw formulae relating particular linear combinations of
the potential and temperature differences between points on the edges of the
sample. We show that the Harman figure of merit can be radically different from
the intrinsic figures of merit of the material, and can often be substantially
enhanced. By defining an effective figure of merit in terms of the rate of
entropy production, we show that the increase in the Harman figure of merit
does indicate an improvement in the thermoelectric performance of an
anisotropic sample having small current contacts. However, we also prove that
in the case of a material with tetragonal symmetry, the effective figure of
merit is always bounded from above by the largest intrinsic figure of merit of
the material.",0808.3526v1
2015-02-27,Electrically Tunable Band Gap in Antiferromagnetic Mott Insulator Sr2IrO4,"The electronic band gap in conventional semiconductor materials, such as
silicon, is fixed by the material's crystal structure and chemical composition.
The gap defines the material's transport and optical properties and is of great
importance for performance of semiconductor devices like diodes, transistors
and lasers. The ability to tune its value would allow enhanced functionality
and flexibility of future electronic and optical devices. Recently, an
electrically tunable band gap was realized in a 2D material - electronically
gated bilayer graphene [1-3]. Here we demonstrate the realization of an
electrically tunable band gap in a 3D antiferromagnetic Mott insulator Sr2IrO4.
Using nano-scale contacts between a sharpened Cu tip and a single crystal of
Sr2IrO4, we apply a variable external electric field up to a few MV/m and
demonstrate a continuous reduction in the band gap of Sr2IrO4 by as much as
16%. We further demonstrate the feasibility of reversible resistive switching
and electrically tunable anisotropic magnetoresistance,which provide evidence
of correlations between electronic transport, magnetic order, and orbital
states in this 5d oxide. Our findings suggest a promising path towards band gap
engineering in 5d transition-metal oxides that could potentially lead to
appealing technical solutions for next-generation electronic devices.",1502.07982v1
2016-11-28,Synthesis of low-moment CrVTiAl: a potential room temperature spin filter,"The efficient production of spin-polarized currents at room temperature is
fundamental to the advancement of spintronics. Spin-filter materials ---
semiconductors with unequal band gaps for each spin channel --- can generate
spin-polarized current without the need for spin-polarized contacts. In
addition, a spin-filter material with zero magnetic moment would have the
advantage of not producing strong fringing fields that would interfere with
neighboring electronic components and limit the volume density of devices. The
quaternary Heusler compound CrVTiAl has been predicted to be a zero-moment
spin-filter material with a Curie temperature in excess of 1000 K. In this
work, CrVTiAl has been synthesized with a lattice constant of $a = 6.15 \AA$.
Magnetization measurements reveal an exceptionally low moment of $\mu = 2.3
\times 10^{-3} \mu_B/f.u.$ at a field of $\mu_0 H = 2 T$, that is independent
of temperature between T = 10 K and 400 K, consistent with the predicted
zero-moment ferrimagnetism. Transport measurements reveal a combination of
metallic and semiconducting components to the resistivity. Combining a
zero-moment spin-filter material with nonmagnetic electrodes would lead to an
essentially nonmagnetic spin injector. These results suggest that CrVTiAl is a
promising candidate for further research in the field of spintronics.",1611.09307v3
2016-10-19,Lattice of infinite bending-resistant fibers,"This article present the double-periodical lattice made of infinite elastic
fibers that withstand bending and tension. The model describes the elastic
properties of flat periodic structure. With this model the behavior of a
two-dimensional array of infinite fibers is simulated. The material that
contains a row of broken fibers is considered. These broken fibers form the
failure in the material that shapes like a long straight crack. The lattice is
tensioned in the direction, which is orthogonal to the direction of straight
crack. The conditions of fracture of this lattice are investigated. The closed
form expression for the stress in the first unbroken fiber and the expression
for fracture toughness are given. These values are the functions of mechanical
parameters of lattice and tensions in both families of fibers. The closed form
solution demonstrates a notable behavior of the material. Namely, the fracture
behavior of two-dimensional lattice is cardinally depends upon the pre-stress
in the material in the direction, parallel to crack direction. If the tension
in fibers that parallel to the crack direction exists, it stabilizes the crack
growth and makes the load distribution in the unbroken fibers more even. The
two-dimensional lattice behaves in the presence of tension in both directions
similarly to the plane elastic media. The finite length crack assumes the shape
of the elongated elliptic split. Another behavior of lattice occurs if the
fibers, parallel to crack direction, are unstressed. The character of stress
concentration near the crack differs. The load distribution at the crack tip
varies considerably. The first unbroken fiber carries higher load. The crack is
lens-shaped and the crack borders form at the tip the finite angle.",1612.00274v1
2017-06-20,Coulomb drag in topological materials,"Dirac fermions are at the forefront of modern condensed matter physics
research. They are known to occur in materials as diverse as graphene,
topological insulators, and transition metal dichalcogenides, while closely
related Weyl fermions have been discovered in other materials. They have been
predicted to lend themselves to a variety of technological applications, while
the recent prediction and discovery of the quantized anomalous Hall effect of
massive Dirac fermions is regarded as a potential gateway towards low-energy
electronics. Some materials hosting Dirac fermions are natural platforms for
interlayer coherence effects such as Coulomb drag and exciton condensation. The
top and bottom surfaces of a thin topological insulator film provide such a
prototype system. Here we describe recent insights into Coulomb drag between
two layers of Dirac fermions relying primarily on topological insulator films
as a minimal model. We consider both non-magnetic topological insulators,
hosting massless Dirac fermions, and magnetic topological insulators, in which
the fermions are massive. We discuss in general terms the dynamics of the
thin-film spin density matrix, outlining numerical results and approximate
analytical expressions where appropriate for the drag resistivity \r{ho}D at
low temperatures and low electron densities. In magnetic topological insulators
with out-of-plane magnetizations in both the active and passive layers we
analyze the role of the anomalous Hall effect in Coulomb drag.",1706.07291v2
2019-02-11,Large area photoelectrodes based on hybrids of CNT fibres and ALD grown TiO2,"Hybridisation is a powerful strategy towards the next generation of
multifunctional materials for environmental and sustainable energy
applications. Here, we report a new inorganic nanocarbon hybrid material
prepared with atomically controlled deposition of a monocrystalline TiO2 layer
that conformally coats a macroscopic carbon nanotube (CNT) fiber. Through X-ray
diffraction, Raman spectroscopy and photoemission spectroscopy we detect the
formation of a covalent Ti-O-C bond at the TiO2/CNT interface and a residual
strain of approximately 0.7-2 \%, which is tensile in TiO2 and compressive in
the CNT. It arises after deposition of the amorphous oxide onto the CNT surface
previously functionalized by the oxygen plasma used in ALD. These features are
observed in samples of different TiO2 thickness, in the range from 10 to 80 nm.
Ultraviolet photoemission spectroscopy on a 20 nm-thick TiO2 coated sample
gives a work function of 4.27 eV, between that of TiO2 (4.23 eV) and the CNT
fiber (4.41 eV), and the presence of new interband gap states that shift the
valence band maximum to 1.05 eV below the Fermi level. Photoelectrochemical
measurements demonstrate electron transfer from TiO2 to the CNT fiber network
under UV irradiation. Electrochemical impedance spectroscopy measurements
reveal a low resistance for charge transfer and transport, as well as a large
capacitance. Our results point to the fact that these hybrids, in which each
phase has nanometric thickness and the current collector is integrated into the
material, are very different from conventional electrodes and can provide a
number of superior properties.",1902.04137v1
2020-09-15,Correlated electron metal properties of the honeycomb ruthenate Na$_2$RuO$_3$,"We report the synthesis and characterisation of polycrystalline
Na$_2$RuO$_3$, a layered material in which the Ru$^{4+}$ ($4d^4$ configuration)
form a honeycomb lattice. The optimal synthesis condition was found to produce
a nearly ordered Na$_2$RuO$_3$ ($C2/c$ phase), as assessed from the refinement
of the time-of-flight neutron powder diffraction. Magnetic susceptibility
measurements reveal a large temperature-independent Pauli paramagnetism
($\chi_0 \sim 1.42(2)\times10^{-3}$ emu/mol Oe) with no evidence of magnetic
ordering down to 1.5 K, and with an absence of dynamic magnetic correlations,
as evidenced by neutron scattering spectroscopy. The intrinsic susceptibility
($\chi_0$) together with the Sommerfeld coeficient of $\gamma=11.7(2)$ mJ/Ru
mol K$^2$ estimated from heat capacity measurements, gives an enhanced Wilson
ratio of $R_W\approx8.9(1)$, suggesting that magnetic correlations may be
present in this material. While transport measurements on pressed pellets show
nonmetallic behaviour, photoemission spectrocopy indicate a small but finite
density of states at the Fermi energy, suggesting that the bulk material is
metallic. Except for resistivity measurements, which may have been compromised
by near surface and interface effects, all other probes indicate that
Na$_2$RuO$_3$ is a moderately correlated electron metal. Our results thus stand
in contrast to earlier reports that Na$_2$RuO$_3$ is an antiferromagnetic
insulator at low temperatures.",2009.07105v1
2019-04-08,Ideal isotropic auxetic networks from random networks,"Auxetic materials are characterized by a negative Poisson's ratio,
$\mathrm{\nu}$. As the Poisson's ratio becomes negative and approaches the
lower isotropic mechanical limit of $\mathrm{\nu = -1}$, materials show
enhanced resistance to impact and shear, making them suitable for applications
ranging from robotics to impact mitigation. Past experimental efforts aimed at
reaching the $\mathrm{\nu = -1}$ limit have resulted in highly anisotropic
materials, which show a negative Poisson's ratio only when subjected to
deformations along specific directions. Isotropic designs have only attained
moderately auxetic behavior, or have led to structures that cannot be
manufactured in 3D. Here, we present a design strategy to create isotropic
structures from disordered networks that leads to Poisson's ratios as low as
$\mathrm{\nu = -0.98}$. The materials conceived through this approach are
successfully fabricated in the laboratory and behave as predicted. The
Poisson's ratio $\mathrm{\nu}$ is found to depend on network structure and bond
strengths; this sheds light on the structural motifs that lead to auxetic
behavior. The ideas introduced here can be generalized to 3D, a wide range of
materials, and a spectrum of length scales, thereby providing a general
platform that could impact technology.",1904.04359v1
2019-08-22,Size dependent yield hardness induced by surface energy,"Size dependent hardness has long been reported in nanosized indentations,
however the corresponding explanation is still in exploration. In this paper,
we examine the influence of surface energy on the hardness of materials under
spherical indentation. To evaluate the ability of materials to resist
indentation, a yield hardness is defined here as the contact pressure at the
inception of material yield. It is found that this defined hardness is an
intrinsic material property depending only on the yield strength and Poisson
ratio in conventional continuum mechanics. Then, the impact of surface energy
on the yield hardness is analyzed through finite element simulations. By using
the dimensional analysis, the dependences of the yield hardness and critical
indent depth at yield initiation on surface energy have been achieved. When the
yield strength is comparable to the ratio of surface energy density to indenter
radius, surface energy will alter the yield hardness and the critical indent
depth. As the size of indenter decreases to nanoscale, both the yield hardness
and the indent depth will increase significantly. This study provides a
possible clarification to the size dependence of hardness and a potential
approach to measure the yield strength and surface energy of solids through
nanosized indentations.",1908.08175v1
2020-07-25,Industrial manufacturing and characterization of multiscale CFRP laminates made from prepregs containing graphene-related materials,"The introduction of graphene-related materials (GRMs) in carbon
fibre-reinforced polymers (CFRP) has been proved to enhance their mechanical
and electrical properties. However, methodologies to produce the 3-phase
materials (multiscale composites) at an industrial scale and in an efficient
manner are still lacking. In this paper, multiscale CFRP composites containing
different GRMs have been manufactured following standard procedures currently
used in the aerospace industry with the aim to evaluate its potential
application. Graphite nanoplateletelets (GNPs), in situ exfoliated graphene
oxide (GO) and reduced graphene oxide (rGO) have been dispersed into an epoxy
resin to subsequently impregnate aeronautical grade carbon fibre tape. The
resulting prepregs have been used for manufacturing laminates by hand lay-up
and autoclave curing at 180 {\deg}C. Abroad characterization campaign has been
carried out to understand the behaviour of the different multiscale laminates
manufactured. The degree of cure, glass transition temperature and degradation
temperature have been evaluated by thermal evolution techniques. Similarly,
their mechanical properties (tensile, flexural, in-plane shear, interlaminar
shear and mode I interlaminar fracture toughness) have been analysed together
with their electrical conductivity. The manufacturing process resulted
appropriated for producing three-phase laminates and their quality was as good
as in conventional CFRPs. The addition ofGOand rGO resulted in an enhancement
of the in-plane shear properties and delamination resistance while the addition
ofGNPimproved the electrical conductivity.",2007.12902v1
2021-04-06,Phase Change Memory by GeSbTe Electrodeposition in Crossbar Arrays,"Phase change memories (PCM) is an emerging type of non-volatile memory that
has shown a strong presence in the data-storage market. This technology has
recently attracted significant research interest in the development of non-Von
Neumann computing architectures such as in-memory and neuromorphic computing.
Research in these areas has been primarily motivated by the scalability
potential of phase change materials and their compatibility with industrial
nanofabrication processes. In this work, we are presenting our development of
crossbar phase change memory arrays through the electrodeposition of GeSbTe
(GST). We show that GST can be electrodeposited in microfabricated TiN crossbar
arrays using a scalable process. Our phase switching test of the
electrodeposited materials have shown that a SET/RESET resistance ratio of 2-3
orders of magnitude is achievable with a switching endurance of around 80
cycles. These results represent the first phase switching of electrodeposited
GeSbTe in microfabricated crossbar arrays. Our work paves the way towards
developing large memory arrays involving electrodeposited materials for passive
selectors and phase switching devices. It also opens opportunities for
developing a variety of different electronic devices using electrodeposited
materials.",2104.02340v2
2021-07-29,Magnetic frustration in a van der Waals metal CeSiI,"The realization of magnetic frustration in a metallic van der Waals (vdW)
coupled material has been sought as a promising platform to explore novel
phenomena both in bulk matter and in exfoliated devices. However, a suitable
material platform has been lacking so far. Here, we demonstrate that CeSiI
hosts itinerant electrons coexisting with exotic magnetism. In CeSiI, the
magnetic cerium atoms form a triangular bilayer structure sandwiched by van der
Waals stacked iodine layers. From resistivity and magnetometry measurements, we
confirm the coexistence of itinerant electrons with magnetism with dominant
antiferromagnetic exchange between the strongly Ising-like Ce moments below 7
K. Neutron diffraction directly confirms magnetic order with an incommensurate
propagation vector k ~ (0.28, 0, 0.19) at 1.6 K, which points to the importance
of further neighbor magnetic interactions in this system. The presence of a
two-step magnetic-field-induced phase transition along c axis further suggests
magnetic frustration in the ground state. Our findings provide a novel material
platform hosting a coexistence of itinerant electron and frustrated magnetism
in a vdW system, where exotic phenomena arising from rich interplay between
spin, charge and lattice in low dimension can be explored.",2107.13810v1
2022-03-31,Catapulting of topological defects through elasticity bands in active nematics,"Active materials are those in which individual, uncoordinated local stresses
drive the material out of equilibrium on a global scale. Examples of such
assemblies can be seen across scales from schools of fish to the cellular
cytoskeleton and underpin many important biological processes. Synthetic
experiments that recapitulate the essential features of such active systems
have been the object of study for decades as their simple rules allow us to
elucidate the physical underpinnings of collective motion. One system of
particular interest has been active nematic liquid crystals (LCs). Because of
their well understood passive physics, LCs provide a rich platform to
interrogate the effects of active stress. The flows and steady state structures
that emerge in an active LCs have been understood to result from a competition
between nematic elasticity and the local activity. However most investigations
of such phenomena consider only the magnitude of the elastic resistance and not
its peculiarities. Here we investigate a nematic liquid crystal and selectively
change the ratio of the material's splay and bend elasticities. We show that
increases in the nematic's bend elasticity specifically drives the material
into an exotic steady state where elongated regions of acute bend distortion or
""elasticity bands"" dominate the structure and dynamics. We show that these
bands strongly influence defect dynamics, including the rapid motion or
""catapulting"" along the disintegration of one of these bands thus converting
bend distortion into defect transport. Thus, we report a novel dynamical state
resultant from the competition between nematic elasticity and active stress.",2204.00113v1
2023-09-15,"Emergence of partially disordered antiferromagnetism and isothermal magnetization plateau due to geometrical frustration in a metallic compound, Er2RhSi3","Partially disordered antiferro (PDA) magnetism (in which one of the three
magnetic ions in a triangular network remains magnetically disordered), has
been known commonly among geometrically frustrated insulating materials. The
one-third plateau in isothermal magnetization (M) of such materials has been of
great theoretical interest. Here, we report these properties in a
AlB2-structure derived metallic material, Er2RhSi3 in which Er sublattice has
triangular networks. The presence of a well-defined lamda anomaly in the
temperature (T) dependence of heat capacity and its magnetic-field (H)
dependence, and the loss of spin-disorder contribution in electrical
resistivity (rho) confirm antiferromagnetic order below (TN=) 5 K. On the other
hand, the separation of zero-field-cooled and field-cooled dc magnetic
susceptibility (chi) curves, decay of isothermal remnant magnetization and the
frequency dependence of real and imaginary components of ac chi suggest the
onset of spin-glass freezing concomitant with the antiferromagnetic order. In
addition, interestingly, we observe one-third plateau in M(H) below 20 kOe for
T less than TN. The change in rho as a function of H at a given temperature
well below TN is also revealing, with this compound exhibiting a plateau below
20 kOe, with complexities at higher fields. Therefore, this compound serves as
a prototype for theoretical understanding of transport behavior across
one-third plateau due to PDA magnetism in a metal without any interference from
the 4f delocalization phenomena.",2309.08176v1
2023-10-18,Moire synaptic transistor for homogeneous-architecture reservoir computing,"Reservoir computing has been considered as a promising intelligent computing
paradigm for effectively processing complex temporal information. Exploiting
tunable and reproducible dynamics in the single electronic device have been
desired to implement the reservoir and the readout layer of reservoir computing
system. Two-dimensional moire material, with an artificial lattice constant
many times larger than the atomic length scale, is one type of most studied
artificial quantum materials in community of material science and
condensed-matter physics over the past years. These materials are featured with
gate-tunable periodic potential and electronic correlation, thus varying the
electric field allows the electrons in the moire potential per unit cell to
exhibit distinct and reproducible dynamics, showing great promise in robust
reservoir computing. Here, we report that a moire synaptic transistor can be
used to implement the reservoir computing system with a homogeneous
reservoir-readout architecture. The synaptic transistor is fabricated based on
a h-BN/bilayer graphene/h-BN moire heterostructure, exhibiting
ferroelectricity-like hysteretic gate voltage dependence of resistance. Varying
the magnitude of the gate voltage enables the moire transistor to be switched
between long-term memory and short-term memory with nonlinear dynamics. By
employing the short- and long-term memory as the reservoir nodes and weights of
the readout layer, respectively, we construct a full-moire physical neural
network and demonstrate that the classification accuracy of 90.8% can be
achieved for the MNIST handwritten digit database. Our work would pave the way
towards the development of neuromorphic computing based on the moire materials.",2310.11743v1
2024-05-06,Band structure engineering using a moiré polar substrate,"Applying long wavelength periodic potentials on quantum materials has
recently been demonstrated to be a promising pathway for engineering novel
quantum phases of matter. Here, we utilize twisted bilayer boron nitride (BN)
as a moir\'e substrate for band structure engineering. Small-angle-twisted
bilayer BN is endowed with periodically arranged up and down polar domains,
which imprints a periodic electrostatic potential on a target two-dimensional
(2D) material placed on top. As a proof of concept, we use Bernal bilayer
graphene as the target material. The resulting modulation of the band structure
appears as superlattice resistance peaks, tunable by varying the twist angle,
and Hofstadter butterfly physics under a magnetic field. Additionally, we
demonstrate the tunability of the moir\'e potential by altering the dielectric
thickness underneath the twisted BN. Finally, we find that
near-60{\deg}-twisted bilayer BN provides a unique platform for studying the
moir\'e structural effect without the contribution from electrostatic moir\'e
potentials. Tunable moir\'e polar substrates may serve as versatile platforms
to engineer the electronic, optical, and mechanical properties of 2D materials
and van der Waals heterostructures.",2405.03761v1
2001-11-01,"To the problem of electron-phonon interaction and ""d-wave pairing"" in high-Tc oxides","It is supported a recent proposal by Maksimov that electron-phonon
interaction (EPI) (Gruneisen-Bloch formulae) determines the linearity of
temperature dependence of resistivity for both HTSC-cuprates and most of metals
at T near above 0.2 of their characteristic Debye temperature (normal state for
HTSC). However, it is emphasized here that in this T-region the resistivity is
not proportional to T but is only linear in T. This fact indicates to
T-independent contribution to normal-state resistivity in HTSC-cuprates
(magnetic contribution, in our treatment) which behavior, in its turn,
indicates to possible magnetic (SDW-like) phase transition before SC transition
in HTSC-system. SDW-gap (measured as pseudogap with d-wave symmetry, in our
treatment) is formed at the symmetrical parts of the Fermi surface above Tc and
persists in SC state. The magnitude of SDW-gap is essentially larger than that
for SC-gap. So, SDW formed can mimic d-wave symmetry of the order parameter
measured below Tc (which is now attributed to d-wave pairing). On the other
hand, since the Gruneisen-Bloch curve appears to be (in approach used) a
geometric locus for the Tc(onset)(H) (as in LTSC) this fact evidents about
EPI-nature (BCS) of SC transition (s-wave) in high-Tc oxides. The proposal to
increase Tc using above (SDW/CDW/SC) model (and possible realization) is
presented.",0111015v1
2004-05-31,"Transport Properties in the ""Strange Metal Phase"" of High Tc Cuprates: Spin-Charge Gauge Theory Versus Experiments","The SU(2)xU(1) Chern-Simons spin-charge gauge approach developed earlier to
describe the transport properties of the cuprate superconductors in the
``pseudogap'' regime, in particular, the metal-insulator crossover of the
in-plane resistivity, is generalized to the ``strange metal'' phase at higher
temperature/doping. The short-range antiferromagnetic order and the gauge field
fluctuations, which were the key ingredients in the theory for the pseudogap
phase, also play an important role in the present case. The main difference
between these two phases is caused by the existence of an underlying
statistical $\pi$-flux lattice for charge carriers in the former case, whereas
the background flux is absent in the latter case. The Fermi surface then
changes from small ``arcs'' in the pseudogap to a rather large closed line in
the strange metal phase. As a consequence the celebrated linear in T dependence
of the in-plane and out-of-plane resistivity is shown explicitly to recover.
The doping concentration and temperature dependence of theoretically calculated
in-plane and out-of-plane resistivity, spin-relaxation rate and AC conductivity
are compared with experimental data, showing good agreement.",0405704v2
2007-05-03,Mean-Field Magnetohydrodynamics of Accretion Disks,"We consider the accretion process in a disk with magnetic fields that are
dragged in from the interstellar medium by gravitational collapse. Two
diffusive processes are at work in the system: (1) ""viscous"" torques exerted by
turbulent and magnetic stresses, and (2) ""resistive"" redistribution of mass
with respect to the magnetic flux arising from the imperfect conduction of
current. In steady state, self-consistency between the two rates of drift
requires that a relationship exists between the coefficients of turbulent
viscosity and turbulent resistivity. Ignoring any interactions with a stellar
magnetosphere, we solve the steady-state equations for a magnetized disk under
the gravitational attraction of a mass point and threaded by an amount of
magnetic flux consistent with calculations of magnetized gravitational collapse
in star formation. Our model mean-field equations have an exact analytical
solution that corresponds to magnetically diluted Keplerian rotation about the
central mass point. The solution yields the strength of the magnetic field and
the surface density as functions of radial position in the disk and their
connection with the departure from pure Keplerian rotation in representative
cases. We compare the predictions of the theory with the available observations
concerning T Tauri stars, FU Orionis stars, and low- and high-mass protostars.
Finally, we speculate on the physical causes for high and low states of the
accretion disks that surround young stellar objects. One of the more important
results of this study is the physical derivation of analytic expressions for
the turbulent viscosity and turbulent resistivity.",0705.0421v1
2008-08-27,The quantum critical point in CeRhIn_5: a resistivity study,"The pressure--temperature phase diagram of CeRhIn_5 has been studied under
high magnetic field by resistivity measurements. Clear signatures of a quantum
critical point has been found at a critical pressure of p_c = 2.5 GPa. The
field induced magnetic state in the superconducting state is stable up to the
highest field. At p_c the antiferromagnetic ground-state under high magnetic
field collapses very rapidly. Clear signatures of p_c are the strong
enhancement of the resistivity in the normal state and of the inelastic
scattering term. No clear T2 temperature dependence could be found for
pressures above T_c. From the analysis of the upper critical field within a
strong coupling model we present the pressure dependence of the coupling
parameter lambda and the gyromagnetic ratio g. No signatures of a spatially
modulated order parameter could be evidenced. A detailed comparison with the
magnetic field--temperature phase diagram of CeCoIn_5 is given. The comparison
between CeRhIn_5 and CeCoIn_5 points out the importance to take into account
the field dependence of the effective mass in the calculation of the
superconducting upper critical field H_c2. It suggests also that when the
magnetic critical field H_(0) becomes lower than H_c2 (0)$, the persistence of
a superconducting pseudo-gap may stick the antiferromagnetism to H_c2 (0).",0808.3687v1
2009-07-13,Enhanced Critical parameters of nano-Carbon doped MgB2 Superconductor,"The high field magnetization and magneto transport measurements are carried
out to determine the critical superconducting parameters of MgB2-xCx system.
The synthesized samples are pure phase and the lattice parameters evaluation is
carried out using the Rietveld refinement. The R-T(H) measurements are done up
to a field of 140 kOe. The upper critical field values, Hc2 are obtained from
this data based upon the criterion of 90% of normal resistivity i.e. Hc2=H at
which Rho=90%Rho; where RhoN is the normal resistivity i.e., resistivity at
about 40 K in our case. The Werthamer-Helfand-Hohenberg (WHH) prediction of
Hc(0) underestimates the critical field value even below than the field up to
which measurement is carried out. After this the model, the Ginzburg Landau
theory (GL equation) is applied to the R-T(H) data which not only calculates
the Hc2(0) value but also determines the dependence of Hc2 on temperature in
the low temperature high field region. The estimated Hc(0)=157.2 kOe for pure
MgB2 is profoundly enhanced to 297.5 kOe for the x=0.15 sample in MgB2-xCx
series. Magnetization measurements are done up to 120 kOe at different
temperatures and the other parameters like irreversibility field, Hirr and
critical current density Jc(H) are also calculated. The nano carbon doping
results in substantial enhancement of critical parameters like Hc2, Hirr and
Jc(H) in comparison to the pure MgB2 sample.",0907.2129v2
2009-12-08,"Anisotropy of upper critical field in one-dimensional organic system, (TMTTF)$_2$PF$_6$ under extremely high pressure","We have measured the temperature dependent resistivity of (TMTTF)$_2$PF$_6$
to 7 GPa using a turnbuckle DAC (diamond anvil cell) and in magnetic field up
to 5 T. Unlike many other organic conductors, a zero resistance was observed in
the superconducting state even under high pressures. Superconductivity was
observed over a range of $P$ = 4.18 GPa to 6.03 GPa and showed a peak $T_c$ of
2.25 K at 4.58 GPa. The temperature dependence of the upper critical magnetic
field $H_{c2}(T)$ was determined via resistivity at $P$ = 4.58 GPa, for the
intrachain ($a$), interchain ($b'$), and interlayer ($c^*$) configurations and
the $H_{c2}(T)$ displays positive curvature without saturation, which may be
originated by a FFLO state, for magnetic field along a-axis and $b'$-axis in T
$\ge$ 0.5 K for $P$ = 4.48 GPa. This feature is suppressed with increasing
pressure and the orbital pair breaking mechanism becomes dominant. The values
of the Ginzberg-Landau coherence length for three different axes obtained from
this work shows that (TMTTF)$_2$PF$_6$ is an anisotropic three - dimensional
superconductor.",0912.1391v1
2011-01-06,Pressure effect on superconductivity of $A_{x}$Fe$_2$Se$_2$ ($A$ = K and Cs),"We performed the high hydrostatic pressure resistivity measurements (up to
1.7 GPa) on the newly discovered superconductors $A_{x}$Fe$_2$Se$_2$ ($A$ = K
and Cs) single crystals. Two batches of single crystals $K_xFe_2Se_2$ with
different transition temperatures ($T_c$) were used to study the effect of
pressure. The $T_c$ of the first one gradually decreases with increasing
pressure from 32.6 K at ambient pressure. While a dome-like behavior was
observed for the crystal with $T_c=31.1$ K, and $T_c$ reaches its maximum value
of 32.7 K at the pressure of 0.48 GPa. It indicates that there exists a optimal
doping with maximum $T_c$ of 32.7K in $K_xFe_2Se_2$ system. The behavior of
$T_c$ vs. pressure for $Cs_xFe_2Se_2$ also shows a dome-like behavior, and
$T_c$ reaches its maximum value of 31.1 K at the pressure of 0.82 GPa. The hump
observed in temperature dependence of resistivity for all the samples tends to
shift to high temperature with increasing pressure. The resistivity hump could
arise from the vacancy of Fe or Se.",1101.1234v1
2011-08-08,Sub-micrometer epitaxial Josephson junctions for quantum circuits,"We present a fabrication scheme and testing results for epitaxial
sub-micrometer Josephson junctions. The junctions are made using a
high-temperature (1170 K) ""via process"" yielding junctions as small as 0.8 mu m
in diameter by use of optical lithography. Sapphire (Al2O3) tunnel-barriers are
grown on an epitaxial Re/Ti multilayer base-electrode. We have fabricated
devices with both Re and Al top electrodes. While room-temperature (295 K)
resistance versus area data are favorable for both types of top electrodes, the
low-temperature (50 mK) data show that junctions with the Al top electrode have
a much higher subgap resistance. The microwave loss properties of the junctions
have been measured by use of superconducting Josephson junction qubits. The
results show that high subgap resistance correlates to improved qubit
performance.",1108.1830v2
2011-09-29,"Comparative Survival Analysis of Deinococcus Radiodurans and the Haloarchaea Natrialba Magadii and Haloferax Volcanii, Exposed to Vacuum Ultraviolet Irradiation","The haloarchaea Natrialba magadii and Haloferax volcanii, as well as the
radiation-resistant bacterium Deinococcus radiodurans, were exposed to
vacuum-UV (V-UV) radiation at the Brazilian Synchrotron Light Laboratory
(LNLS). Cell monolayers (containing 105 - 106 cells per sample) were prepared
over polycarbonate filters and irradiated under high vacuum (10-5 Pa) with
polychromatic synchrotron radiation. N. magadii was remarkably resistant to
high vacuum with a survival fraction of ((3.77 \pm 0.76) x 10-2), larger than
the one of D. radiodurans ((1.13 \pm 0.23) x 10-2). The survival fraction of
the haloarchaea H. volcanii, of ((3.60 \pm 1.80) x 10-4), was much smaller.
Radiation resistance profiles were similar between the haloarchaea and D.
radiodurans for fluencies up to 150 J m-2. For fluencies larger than 150 J m-2
there was a significant decrease in the survival of haloarchaea, and in
particular H. volcanii did not survive. Survival for D. radiodurans was 1%
after exposure to the higher V-UV fluency (1350 J m-2) while N. magadii had a
survival lower than 0.1%. Such survival fractions are discussed regarding the
possibility of interplanetary transfer of viable micro-organisms and the
possible existence of microbial life in extraterrestrial salty environments
such as the planet Mars and the Jupiter's moon Europa. This is the first work
reporting survival of haloarchaea under simulated interplanetary conditions.",1109.6590v1
2013-08-06,"Impurity effect and suppression to superconductivity in Na(Fe$_{0.97-x}$Co$_{0.03}$T$_x$)As (T=Cu, Mn)","We report the successful growth and the impurity scattering effect of single
crystals of Na(Fe$_{0.97-x}$Co$_{0.03}$T$_x$)As (T=Cu, Mn). The temperature
dependence of DC magnetization at high magnetic fields is measured for
different concentrations of Cu and Mn. Detailed analysis based on the
Curie-Weiss law indicates that the Cu doping weakens the average magnetic
moments, while doping Mn enhances the local magnetic moments greatly,
suggesting that the former may be non- or very weak magnetic impurities, and
the latter give rise to magnetic impurities. However, it is found that both
doping Cu and Mn will enhance the residual resistivity and suppress the
superconductivity at the same rate in the low doping region, being consistent
with the prediction of the S$^{\pm}$ model. For the Cu-doped system, the
superconductivity is suppressed completely at a residual resistivity $\rho_0$ =
0.87 m$\Omega$ cm at which a strong localization effect is observed. However,
in the case of Mn doping, the behavior of suppression to \emph{T}$_{c}$ changes
from a fast speed to a slow one and keeps superconductive even up to a residual
resistivity of 2.86 m$\Omega$ cm. Clearly the magnetic Mn impurities are even
not as detrimental as the non- or very weak magnetic Cu impurities to
superconductivity in the high doping regime.",1308.1356v1
2013-10-31,A Technique for Write-endurance aware Management of Resistive RAM Last Level Caches,"Due to increasing cache sizes and large leakage consumption of SRAM device,
conventional SRAM caches contribute significantly to the processor power
consumption. Recently researchers have used non-volatile memory devices to
design caches, since they provide high density, comparable read latency and low
leakage power dissipation. However, their high write latency may increase the
execution time and hence, leakage energy consumption. Also, since their write
endurance is small, a conventional energy saving technique may further
aggravate the problem of write-variations, thus reducing their lifetime. In
this paper, we present a cache energy saving technique for non-volatile caches,
which also attempts to improve their lifetime by making writes equally
distributed to the cache. Our technique uses dynamic cache reconfiguration to
adjust the cache size to meet program requirement and turns off the remaining
cache to save energy. Microarchitectural simulations performed using an x86-64
simulator, SPEC2006 benchmarks and a resistive-RAM LLC (last level cache) show
that over an 8MB baseline cache, our technique saves 17.55% memory subsystem
(last level cache + main memory) energy and improves the lifetime by 1.33X.
Over the same resistive-RAM baseline, an SRAM of similar area with no cache
reconfiguration leads to an energy loss of 186.13%.",1311.0041v2
2014-06-11,Signatures of localization in the effective metallic regime of high mobility Si MOSFETs,"Combining experimental data, numerical transport calculations, and
theoretical analysis, we study the temperature-dependent resistivity of
high-mobility 2D Si MOSFETs to search for signatures of weak localization
induced quantum corrections in the effective metallic regime above the critical
density of the so-called two-dimensional metal-insulator transition (2D MIT).
The goal is to look for the effect of logarithmic insulating localization
correction to the metallic temperature dependence in the 2D conductivity so as
to distinguish between the 2D MIT being a true quantum phase transition versus
being a finite-temperature crossover. We use the Boltzmann theory of
resistivity including the temperature dependent screening effect on charged
impurities in the system to fit the data. We analyze weak perpendicluar field
magnetoresistance data taken in the vicinity of the transition and show that
they are consistent with weak localization behavior in the strongly disordered
regime $k_F\ell\gtrsim1$. Therefore we supplement the Botzmann transport theory
with a logarithmic in temperature quantum weak localization correction and
analyze the competition of the insulating temperature dependence of this
correction with the metallic temperature dependence of the Boltzmann
conductivity. Using this minimal theoretical model we find that the logarithmic
insulating correction is masked by the metallic temperature dependence of the
Botzmann resistivity and therefore the insulating $\log T$ behavior may be
apparent only at very low temperatures which are often beyond the range of
temperatures accessible experimentally. Analyzing the low-$T$ experimental Si
MOSFET transport data we identify signatures of the putative insulating
behavior at low temperature and density in the effective metallic phase.",1406.3024v2
2016-04-13,Remarkable magnetostructural coupling around the magnetic transition in CeCo$_{0.85}$Fe$_{0.15}$Si,"We report a detailed study of the magnetic properties of
CeCo$_{0.85}$Fe$_{0.15}$Si under high magnetic fields (up to 16 Tesla)
measuring different physical properties such as specific heat, magnetization,
electrical resistivity, thermal expansion and magnetostriction.
CeCo$_{0.85}$Fe$_{0.15}$Si becomes antiferromagnetic at $T_N \approx$ 6.7 K.
However, a broad tail (onset at $T_X \approx$ 13 K) in the specific heat
precedes that second order transition. This tail is also observed in the
temperature derivative of the resistivity. However, it is particularly
noticeable in the thermal expansion coefficient where it takes the form of a
large bump centered at $T_X$. A high magnetic field practically washes out that
tail in the resistivity. But surprisingly, the bump in the thermal expansion
becomes a well pronounced peak fully split from the magnetic transition at
$T_N$. Concurrently, the magnetoresistance also switches from negative to
positive just below $T_X$. The magnetostriction is considerable and
irreversible at low temperature ($\frac {\Delta L}{L} \left(16 T\right) \sim$
4$\times$10$^{-4}$ at 2 K) when the magnetic interactions dominate. A broad
jump in the field dependence of the magnetostriction observed at low $T$ may be
the signature of a weak ongoing metamagnetic transition. Taking altogether, the
results indicate the importance of the lattice effects in the development of
the magnetic order in these alloys.",1604.03985v1
2018-01-19,High pressure effects on non-fluorinated BiS2-based superconductors La$_{1-x}$M$_x$OBiS$_2$ (M = Ti and Th),"Layered \textit{Ln}OBiS$_2$ compounds with \textit{Ln} = La, Ce, Pr, Nd, and
Yb can be rendered conducting and superconducting via two routes, substitution
of F for O or the tetravalent ions Ti, Zr, Hf, and Th for trivalent \textit{Ln}
ions. Electrical resistivity measurements on non-fluorinated
La$_{0.80}$Ti$_{0.20}$OBiS$_2$ and La$_{0.85}$Th$_{0.15}$OBiS$_2$
superconductors were performed between $\sim$1.5 K and 300 K and under pressure
up to 2.4 GPa. For both compounds, the superconducting transition temperature
$T_c$, which is $\sim$2.9 K at ambient pressure, gradually increases with
pressure to 3.2-3.7 K at $\sim$1 GPa, above which it is suppressed and the
superconducting transitions become very broad. Measurements of the normal state
electrical resistivity of the two compounds reveal discontinuous changes of the
resistivity as a function of pressure at $\sim$0.6 GPa. Surprisingly, above 1.3
GPa, semiconducting-like behavior reappears in La$_{0.80}$Ti$_{0.20}$OBiS$_2$.
This study reveals a new high-pressure phase of La$_{1-x}$$M$$_x$OBiS$_2$
containing the tetravalent ions $M$ = Ti, Th which does not favor
superconductivity. In contrast, application of pressure to fluorinated
LaO$_0.5$F$_0.5$BiS$_2$ produces an abrupt tetragonal-monoclinic transition to
a metallic phase with an enhanced $T_c$. These results demonstrate that the
response of the normal and superconducting properties of LaOBiS$_2$-based
compounds depends strongly on the atomic site where the electron donor ions are
substituted.",1801.06568v1
2018-05-23,Discovery of a new nontoxic cuprate superconducting system Ga-Ba-Ca-Cu-O,"Superconductivity is observed in a new nontoxic cuprate system Ga-Ba-Ca-Cu-O,
with Tc = 82K for GaBa2Ca5Cu6O14+{\delta} (Ga-1256) and Tc = 116K probably for
GaBa2Ca3Cu4O10+{\delta} (Ga-1234) or GaBa2Ca2Cu3O8+{\delta} (Ga-1223),
respectively. All compounds are fabricated by solid state reaction method under
high pressure and high temperature. Samples are characterized by resistivity,
magnetization and X-ray diffraction (XRD) measurements. The temperature
dependence of magnetization measured in both zero-field-cooled and field-cooled
processes on one sample (S1) shows two superconducting transitions at about 82K
and 113K. The estimated shielding fraction for the phase with Tc of 82K is
about 67%, while the fraction for another phase with Tc of 113K is quite small.
The XRD Rietveld refinement for S1 indicates two main phases existing in the
sample, Ga-1256 with fraction of about 58% and non-superconducting Ca0.85CuO2
with fraction of about 42%, respectively. Thus, we can conclude the
superconducting phase with transition temperature of 82K is due to Ga-1256. The
resistivity measurement also confirms the superconductivity for S1, and the
resistivity reaches zero at about 82K. The temperature dependence of
magnetization for another sample (S2) shows much higher superconducting
shielding fraction for the phase with Tc of 116K, which may be a promising
prospective for the synthesis of Ga-1234 or Ga-1223 phase.",1805.09268v1
2018-06-11,Development of a new Front End electronics in Silicon and Silicon-Germanium technology for the Resistive Plate Chamber detector for high rate experiments,"The upgrade of the Resistive Plate Chamber (RPC) detector, in order to
increase the detector rate capability and to be able to work efficiently in
high rate environment, consists in the reduction of the operating voltage along
with the detection of signals which are few hundred {\mu}V small. The approach
chosen by this project to achieve this objective is to develop a new kind of
Front End electronics which, thanks to a mixed technology in Silicon and
Silicon-Germanium, enhance the detector performances increasing its rate
capability. The Front End developed is composed by a preamplifier in Silicon
BJT technology with a very low inner noise (1000 $e^{-}$ rms) and an
amplification factor of 0.3-0.4 mV/fC and a new kind of discriminator in SiGe
HJT technology which allows a minimum threshold of the order of 0.5 mV. The
performances of this kind of Front End will be shown. The results are obtained
by using the CERN H8 beamline with a full-size RPC chamber of 1 mm gas gap and
1.2 mm thickness of electrodes equipped with this kind of Front End
electronics.",1806.04113v1
2019-09-16,High-Throughput In-Memory Computing for Binary Deep Neural Networks with Monolithically Integrated RRAM and 90nm CMOS,"Deep learning hardware designs have been bottlenecked by conventional
memories such as SRAM due to density, leakage and parallel computing
challenges. Resistive devices can address the density and volatility issues,
but have been limited by peripheral circuit integration. In this work, we
demonstrate a scalable RRAM based in-memory computing design, termed XNOR-RRAM,
which is fabricated in a 90nm CMOS technology with monolithic integration of
RRAM devices between metal 1 and 2. We integrated a 128x64 RRAM array with CMOS
peripheral circuits including row/column decoders and flash analog-to-digital
converters (ADCs), which collectively become a core component for scalable
RRAM-based in-memory computing towards large deep neural networks (DNNs). To
maximize the parallelism of in-memory computing, we assert all 128 wordlines of
the RRAM array simultaneously, perform analog computing along the bitlines, and
digitize the bitline voltages using ADCs. The resistance distribution of low
resistance states is tightened by write-verify scheme, and the ADC offset is
calibrated. Prototype chip measurements show that the proposed design achieves
high binary DNN accuracy of 98.5% for MNIST and 83.5% for CIFAR-10 datasets,
respectively, with energy efficiency of 24 TOPS/W and 158 GOPS throughput. This
represents 5.6X, 3.2X, 14.1X improvements in throughput, energy-delay product
(EDP), and energy-delay-squared product (ED2P), respectively, compared to the
state-of-the-art literature. The proposed XNOR-RRAM can enable intelligent
functionalities for area-/energy-constrained edge computing devices.",1909.07514v1
2019-05-01,"Measurement of azimuthal dependent muon flux by 2\,m\,$\times$\,2\,m RPC stack at IICHEP-Madurai","The proposed 50 \,kton\, INO-ICAL experiment is an upcoming underground high
energy physics experiment planned to be commissioned at Bodi hills near Theni,
India ($9^{\circ}57'N$, $77^{\circ}16'E$) to study various properties of
neutrino oscillations using atmospheric neutrinos produced by extensive air
shower phenomenon. The resistive plate chamber has been chosen as the active
detector element for the proposed INO-ICAL. An experimental setup consisting a
stack of 12 layers of glass resistive plate chambers each with a size of
$\sim$2\,m$\times$2\,m has been built at IICHEP, Madurai to study the
performance and long-term stability of the resistive plate chambers(RPCs)
commercially produced in large quantities by the Indian industries as well as
its electronics for the front-end and subsequent signal processing. In this
study, the azimuthal dependence of muon flux at various zenith angles at
Madurai (9$^{\circ}$56'N, 78$^{\circ}$00'E and at an altitude of 160\,m above
mean sea level) has been presented along with the comparison of Monte Carlo
from CORSIKA and HONDA predictions.",1905.00739v2
2019-05-20,Imaging and monitoring the Reykjanes supercritical geothermal reservoir in Iceland with time-lapse CSEM and MT measurements,"We have investigated the benefits and drawbacks of active EM surveying
(Controlled-Source EM or CSEM) for monitoring geothermal reservoirs in the
presence of strong industrial noise with an actual time-lapse survey over the
Reykjanes geothermal field in Iceland before and after the thermal stimulation
of the supercritical RN-15/IDDP-2 geothermal well. It showed that a high CSEM
survey repeatability can be achieved with electric field measurements (within a
few percent) but that time-lapse MT survey is a challenging task because of the
high level of cultural noise in this industrialized environment. To assess the
quality of our CSEM dataset, we inverted the data and confronted the resulting
resistivity model with the resistivity logged in the RN-15/IDDP-2 well. We
obtained a good match up to 2-3km depth, i.e. enough to image the caprock and
the liquid-dominated reservoir but not deep enough to image the reservoir in
supercritical conditions. To obtain such an image, we had to jointly invert
legacy MT data with our CSEM data. On the monitoring aspects, the analysis of
changes in electric fields did not allow to identify any CSEM signal related to
the thermal stimulation of the RN-15/IDDP-2 well. One possible explanation is
the weakness of the time-lapse CSEM signal compared the achieved CSEM survey
repeatability as a result of a limited resistivity change over a limited volume
within the reservoir.",1905.07899v1
2020-03-10,High performance picosecond- and micron-level 4D particle tracking with 100% fill-factor Resistive AC-Coupled Silicon Detectors (RSD),"In this paper we present a complete characterization of the first batch of
Resistive AC-Coupled Silicon Detectors, called RSD1, designed at INFN Torino
and manufactured by Fondazione Bruno Kessler (FBK) in Trento. With their 100%
fill-factor, RSD represent the new enabling technology for high-precision
4D-tracking. Indeed, being based on the well-known charge multiplication
mechanism of Low-Gain Avalanche Detectors (LGAD), they benefit from the very
good timing performances of such technology together with an unprecedented
resolution of the spatial tracking, which allows to reach the micron-level
scale in the track reconstruction. This is essentially due to the absence of
any segmentation structure between pads (100% fill-factor) and to other two
innovative key-features: the first one is a properly doped n+ resistive layer,
slowing down the charges just after being multiplied, and the second one is a
dielectric layer grown on Silicon, inducing a capacitive coupling on the metal
pads deposited on top of the detector. The very good spatial resolution
(micron-level) we measured experimentally - higher than the nominal pad pitch -
comes from the analogical nature of the readout of signals, whose amplitude
attenuates from the pad center to its periphery, while the outstanding results
in terms of timing (less than 14 ps, even better than standard LGAD) are due to
a combination of very-fine pitch, analogical response and charge
multiplication.",2003.04838v2
2023-02-14,Resistive Heating Induced by Streaming Cosmic Rays Around a Galaxy in the Early Universe,"It is expected that cosmic rays (CRs) escape from high-redshift galaxies at
redshift $z\sim 10 \, - \, 20$ because CRs are accelerated by supernova
remnants of the first stars. Although ultraviolet and X-ray photons are widely
considered the main source of heating of the intergalactic medium, CRs can also
contribute to it. When the CRs propagate in the intergalactic medium, in
addition to the heating process due to CR ionization, resistive heating occurs
due to the electron return current induced by the streaming CRs. We evaluate
the heating rate around a galaxy as a function of the distance from the galaxy.
We find that the resistive heating induced by CRs dominates over the other
heating processes in the vicinity of the galaxy $r \lesssim 10^2 \,
\mathrm{kpc}$ until the temperature reaches $T\sim 10^4 \, \mathrm{K}$. We also
recalculate the strength of the magnetic field generated by streaming CRs under
the presence of X-ray heating and show that achieved strength can be about $1$
order of magnitude smaller when the X-ray heating is included. The presence of
the ""first"" CRs could be confirmed from the characteristic signature of CR
heating imprinted on the $21$-$\mathrm{cm}$ line map in future radio
observations.",2302.07028v1
2023-04-21,"Bragg's law for X-ray scattering by quantum thermodynamic time crystals, Q-balls, as manifestation of the mechanism of High-T$_c$ superconductivity","Proposed by the author Q-ball mechanism of the pseudogap state and high-Tc
superconductivity in cuprates was recently supported by micro X-ray diffraction
data in HgBa$_2$CuO$_{4+y}$. This provides a remarkable opportunity to
investigate X-ray diffraction produced by the quantum thermodynamic time
crystals, a direct embodiment of those are just the Euclidean Q-balls
considered in the aforementioned theory. Simultaneously, it is also
demonstrated that T-linear temperature dependence of electrical resistivity in
the Q-ball phase arises due to scattering of electrons on the condensed
charge/spin fluctuations inside the Q-balls. This gives a clue concerning
possible mechanism of T-linear behaviour of electrical resistivity in the
strange metal phase of high-T$_c$ cuprates. For this purpose the Green's
functions of X-ray photons and fermions scattered by the Q-balls in the
pseudogap phase of high-Tc superconductors are calculated using the Feynman
diagrammatic technique. The Bragg's peaks intensity, provided by the imaginary
part of the retarded photon Green's function, is calculated. In total, obtained
results describe X-ray and electron scattering on the finite size Q-ball of
CDW/SDW density, that oscillates with bosonic frequency $\Omega=2\pi nT$ in
Matsubara time, i.e. the quantum thermodynamic time crystal. It is found, that
theoretical results are in good correspondence with X-ray diffraction data in
HgBa$_2$CuO$_{4+y}$ reported recently. The T-linear dependence of electrical
resistivity arises due to inverse temperature dependence of the Q-ball radius
as function of temperature.",2304.10874v2
2023-07-09,Design Space Exploration and Comparative Evaluation of Memory Technologies for Synaptic Crossbar Arrays: Device-Circuit Non-Idealities and System Accuracy,"In-memory computing (IMC) utilizing synaptic crossbar arrays is promising for
deep neural networks to attain high energy efficiency and integration density.
Towards that end, various CMOS and post-CMOS technologies have been explored as
promising synaptic device candidates which include SRAM, ReRAM, FeFET,
SOT-MRAM, etc. However, each of these technologies has its own pros and cons,
which need to be comparatively evaluated in the context of synaptic array
designs. For a fair comparison, such an analysis must carefully optimize each
technology, specifically for synaptic crossbar design accounting for device and
circuit non-idealities in crossbar arrays such as variations, wire resistance,
driver/sink resistance, etc. In this work, we perform a comprehensive design
space exploration and comparative evaluation of different technologies at 7nm
technology node for synaptic crossbar arrays, in the context of IMC robustness
and system accuracy. Firstly, we integrate different technologies into a
cross-layer simulation flow based on physics-based models of synaptic devices
and interconnects. Secondly, we optimize both technology-agnostic design knobs
such as input encoding and ON-resistance as well as technology-specific design
parameters including ferroelectric thickness in FeFET and MgO thickness in
SOT-MRAM. Our optimization methodology accounts for the implications of device-
and circuit-level non-idealities on the system-level accuracy for each
technology. Finally, based on the optimized designs, we obtain inference
results for ResNet-20 on CIFAR-10 dataset and show that FeFET-based crossbar
arrays achieve the highest accuracy due to their compactness, low leakage and
high ON/OFF current ratio.",2307.04261v1
2023-09-28,Study of Bulk Damage of High Dose Gamma Irradiated p-type Silicon Diodes with Various Resistivities,"The bulk damage of p-type silicon detectors caused by high doses of gamma
irradiation has been studied. The study was carried out on three types of
n$^{+}$-in-p silicon diodes with comparable geometries but different initial
resistivities. This allowed to determine how different initial parameters of
studied samples influence radiation-induced changes in the measured
characteristics. The diodes were irradiated by a Cobalt-60 gamma source to
total ionizing doses ranging from 0.50 up to 8.28 MGy, and annealed for 80
minutes at 60 {\deg}C. The Geant4 toolkit for simulation of the passage of
particles through matter was used to simulate the deposited energy homogeneity,
to verify the equal distribution of total deposited energies through all the
layers of irradiated samples, and to calculate the secondary electron spectra
in the irradiation box. The main goal of the study was to characterize the
gamma-radiation induced displacement damage by measuring current-voltage
characteristics (IV), and the evolution of the full depletion voltage with the
total ionizing dose, by measuring capacitance-voltage characteristics (CV). It
has been observed that the bulk leakage current increases linearly with total
ionizing dose, and the damage coefficient depends on the initial resistivity of
the silicon diode. The effective doping concentration and therefore full
depletion voltage significantly decreases with increasing total ionizing dose,
before starting to increase again at a specific dose. We assume that this
decrease is caused by the effect of acceptor removal. Another noteworthy
observation of this study is that the IV and CV measurements of the gamma
irradiated diodes do not reveal any annealing effect.",2309.16293v1
2023-10-17,Improving Interface Physics Understanding in High-Frequency Cryogenic Normal Conducting Cavities,"As progress towards real implementations of cryogenic high gradient normal
conducting accelerating cavities continues, a more mature understanding of the
surface physics in this novel environment becomes increasingly necessary. To
this end, we here focus on developing a deeper understanding of one cavity
figure of merit, the radiofrequency (RF) surface resistivity, $R_s$. A
combination of experimental measurements and theory development form the basis
of this work. For many cases, existing theory is sufficient but there are
nuances leading to systemic errors in prediction which we address here. In
addition, for certain cases there exist unexpected local minimum in $R_s$ found
at temperatures above 0K. We compare here several alternative models for RF
surface resistivity those which incorporate thin film like behavior which we
use to predict the location of the local minimum in surface resistivity. Our
experimental results focus on C-band frequencies for the benefit of several
future cryogenic linear accelerator concepts intended to operate in this
regime. To this end we have measured factor of $2.89\pm 0.05$ improvements in
quality factor at $77$K and $4.61\pm 0.05$ at 45K. We further describe the test
setup and cooling capabilities to address systematic issues associated with the
measurements as well as a comparison of RF cavity preparation and the
significant effect on $R_s$. Some implications of our measurements to linear
accelerators combined with the theoretical considerations are extended to a
wider range of frequencies especially the two additional aforementioned bands.
Additional possible implications for condensed matter physics studies are
mentioned.",2310.11578v1
2024-01-18,Hazard resistance-based spatiotemporal risk analysis for distribution network outages during hurricanes,"Blackouts in recent decades show an increasing prevalence of power outages
due to extreme weather events such as hurricanes. Precisely assessing the
spatiotemporal outages in distribution networks, the most vulnerable part of
power systems, is critical to enhance power system resilience. The Sequential
Monte Carlo (SMC) simulation method is widely used for spatiotemporal risk
analysis of power systems during extreme weather hazards. However, it is found
here that the SMC method can lead to large errors by directly applying the
fragility function or failure probability of system components in
time-sequential analysis, particularly overestimating damages under evolving
hazards with high-frequency sampling. To address this issue, a novel hazard
resistance-based spatiotemporal risk analysis (HRSRA) method is proposed. This
method converts the time-varying failure probability of a component into a
hazard resistance as a time-invariant value during the simulation of evolving
hazards. The proposed HRSRA provides an adaptive framework for incorporating
high-spatiotemporal-resolution meteorology models into power outage
simulations. By leveraging the geographic information system data of the power
system and a physics-based hurricane wind field model, the superiority of the
proposed method is validated using real-world time-series power outage data
from Puerto Rico during Hurricane Fiona 2022.",2401.10418v1
2024-02-06,Characterisation of resistive MPGDs with 2D readout,"Micro-Pattern Gaseous Detectors (MPGDs) with resistive anode planes provide
intrinsic discharge robustness while maintaining good spatial and time
resolutions. Typically read out with 1D strips or pad structures, here the
characterisation results of resistive anode plane MPGDs with 2D strip readout
are presented. A uRWELL prototype is investigated in view of its use as a
reference tracking detector in a future gaseous beam telescope. A MicroMegas
prototype with a fine-pitch mesh (730 line-pairs-per-inch) is investigated,
both for comparison and to profit from the better field uniformity and thus the
ability to operate the detector more stable at high gains. Furthermore, the
measurements are another application of the RD51 VMM3a/SRS electronics.",2402.03899v1
2019-01-24,Materials Informatics for Heat Transfer: Recent Progresses and Perspectives,"With the advances in materials and integration of electronics and
thermoelectrics, the demand for novel crystalline materials with ultimate
high/low thermal conductivity is increasing. However, search for optimal
thermal materials is challenge due to the tremendous degrees of freedom in the
composition and structure of crystal compounds and nanostructures, and thus
empirical search would be exhausting. Materials informatics, which combines the
simulation/experiment with machine learning, is now gaining great attention as
a tool to accelerate the search of novel thermal materials. In this review, we
discuss recent progress in developing materials informatics for heat transport:
the exploration of crystals with high/low thermal conductivity via
high-throughput screening, and nanostructure design for high/low thermal
conductance using the Bayesian optimization and Monte Carlo tree search. The
progresses show that the materials informatics method are useful for designing
thermal functional materials. We end by addressing the remaining issues and
challenges for further development.",1901.08504v1
2011-01-20,"Optical and DC conductivity of the two-dimensional Hubbard model in the pseudogap regime and across the antiferromagnetic quantum critical point, including vertex corrections","The conductivity of the two-dimensional Hubbard model is particularly
relevant for high-temperature superconductors. Vertex corrections are expected
to be important because of strongly momentum dependent self-energies. We use
the Two-Particle Self-Consistent approach that satisfies crucial constraints
such as the Mermin-Wagner theorem, the Pauli principle and sum rules in order
to reach non-perturbative regimes. This approach is reliable from weak to
intermediate coupling. A functional derivative approach ensures that vertex
corrections are included in a way that satisfies the f sum-rule. The two types
of vertex corrections that we find are the antiferromagnetic analogs of the
Maki-Thompson and Aslamasov-Larkin contributions of superconducting
fluctuations to the conductivity but, contrary to the latter, they include
non-perturbative effects. The resulting analytical expressions must be
evaluated numerically. The calculations are impossible unless a number of
advanced numerical algorithms are used. A maximum entropy approach is specially
developed for analytical continuation of our results. The numerical results are
for nearest neighbor hoppings. In the pseudogap regime induced by
two-dimensional antiferromagnetic fluctuations, the effect of vertex
corrections is dramatic. Without vertex corrections the resistivity increases
as we enter the pseudogap regime. Adding vertex corrections leads to a drop in
resistivity, as observed in some high temperature superconductors. At high
temperature, the resistivity saturates at the Ioffe-Regel limit. At the quantum
critical point and beyond, the resistivity displays both linear and quadratic
temperature dependence and there is a correlation between the linear term and
the superconducting transition temperature. A hump is observed in the
mid-infrared range of the optical conductivity in the presence of
antiferromagnetic fluctuations.",1101.4037v2
2022-10-26,Bolometric detection of Josephson inductance in a highly resistive environment,"The Josephson junction is a building block of quantum circuits. Its behavior,
well understood when treated as an isolated entity, is strongly affected by
coupling to an electromagnetic environment. In 1983, Schmid predicted that a
Josephson junction shunted by a resistance exceeding the resistance quantum
$\mathbf{\textit{R}}_\mathrm{Q} = h/4e^2 \approx 6.45$ k$\mathbf{\Omega}$ for
Cooper pairs would become insulating since the phase fluctuations would destroy
the coherent Josephson coupling. However, recent microwave measurements have
questioned this interpretation. Here, we insert a small Josephson junction in a
Johnson-Nyquist-type setup where it is driven by weak current noise arising
from thermal fluctuations. Our heat probe minimally perturbs the junction's
equilibrium, shedding light on features not visible in charge transport. We
find that the Josephson critical current completely vanishes in DC charge
transport measurement, and the junction demonstrates Coulomb blockade in
agreement with the theory. Surprisingly, thermal transport measurements show
that the Josephson junction acts as an inductor at high frequencies,
unambiguously demonstrating that a supercurrent survives despite the Coulomb
blockade observed in DC measurements. The discrepancy between these two
measurements highlights the difference between the low and the high frequency
response of a junction and calls for further theoretical and experimental
inputs on the dynamics of Josephson junctions \textcolor{black}{operating at
high frequencies in highly resistive environments.",2210.14953v4
2019-09-09,High Dielectric Ternary Oxides from Crystal Structure Prediction and High-throughput Screening,"The development of new high dielectric materials is essential for advancement
in modern electronics. Oxides are generally regarded as the most promising
class of high dielectric materials for industrial applications as they possess
both high dielectric constants and large band gaps. Most previous researches on
high dielectrics were limited to already known materials. In this study, we
conducted an extensive search for high dielectrics over a set of ternary oxides
by combining crystal structure prediction and density functional perturbation
theory calculations. From this search, we adopted multiple stage screening to
identify 440 new low-energy high dielectric materials. Among these materials,
33 were identified as potential high dielectrics favorable for modern device
applications. Our research has opened an avenue to explore novel high
dielectric materials by combining crystal structure prediction and high
throughput screening.",1909.04195v1
2003-06-17,Materials Aspects of High-Temperature Superconductors for Applications,"Materials aspects of cuprate high-temperature superconductors (HTS) are
reviewed with respect to technical applications. The structural chemistry
common to all HTS and their critical temperatures for the onset of
superconductivity are presented. Intrinsic problems for the production of
technically applicable HTS materials are discussed and how these problems have
been overcome for a number of technically applicable HTS materials.",0306442v1
2010-05-20,Non Super-Cell SuperConductivity Of High Tc Materials,"Recently we have described materials interface transport coupling rigorously
utilizing NEGF nonequilibrium Green's functions, and have discussed the
Hamiltonian terms that from Green's theorem and boundary conditions can be
rewritten as Self Energy. We derive the application of our theory to the high
$Tc$ Superconducting materials interfaces that are the composition of the high
temperature superconducting materials. The derivation models a non super-cell
geometry of plaquettes that will describe the superconducting 2D material in
abrupt coupling with the material of insulating or normal conducting
composition.",1005.3618v1
2012-05-24,CuBr2-A New Multiferroic Material with High Critical Temperature,"A new multiferroic material, CuBr2, is reported for the first time. CuBr2 has
not only a high transition temperature (close to liquid nitrogen temperature)
but also low dielectric loss and strong magnetoelectric coupling. These
findings reveal the importance of anion effects in the search for the high
temperature multiferroics materials among these low-dimensional spin systems.",1205.5318v1
1998-07-24,Destruction of localized electron pairs above the magnetic-field-driven superconductor-insulator transition in amorphous InO films,"We have investigated the field-induced superconductivity-destroying quantum
transition in amorphous indium oxide films at low temperatures down to 30 mK.
It has been found that, on the high-field side of the transition, the
magnetoresistance reaches a maximum and the phase can be insulating as well as
metallic. With further increasing magnetic field the film resistance drops and
approaches in the high-field limit the resistance value at transition point so
that at high fields the metallic phase occurs for both cases. We give a
qualitative account of this behavior in terms of field-induced destruction of
localized electron pairs.",9807332v2
1999-10-22,"Weak localisation, hole-hole interactions and the ""metal""-insulator transition in two dimensions","A detailed investigation of the metallic behaviour in high quality
GaAs-AlGaAs two dimensional hole systems reveals the presence of quantum
corrections to the resistivity at low temperatures. Despite the low density
($r_{s}>10$) and high quality of these systems, both weak localisation
(observed via negative magnetoresistance) and weak hole-hole interactions
(giving a correction to the Hall constant) are present in the so-called
metallic phase where the resistivity decreases with decreasing temperature. The
results suggest that even at high $r_{s}$ there is no metallic phase at T=0 in
two dimensions.",9910368v2
2000-08-28,Josephson-Vortex-Glass Transition in Strong Fields,"A vortex-glass transition due to point disorder in layered superconductors is
studied for the case with an applied field {\it parallel} to the layers. Our
calculation of tilt responses indicates that, irrespective of the magnitude of
the field, the resulting glass phase, Josephson-vortex-glass (JG), should have
a transverse Meissner effect, as in a planar splayed glass phase, only for a
tilt perpendicular to the layers. Further, focusing on the high field (and/or
high anisotropy) region $B \sqrt{\Gamma} > \phi_0/d^2$, where $\Gamma$ is the
mass anisotropy in the Lawrence-Doniach model, the JG transition line
$T_{JG}(B)$ is shown to have a similar form to a $B$-$T$ line following from
the {\it disorder-free} Lindemann criterion and to decrease with increasing $B
\sqrt{\Gamma}$, in marked contrast to the disorder-free melting line {\it
insensitive to} $B \sqrt{\Gamma}$ in such the high field region. This
$T_{JG}(B)$ line seems to have been recently observed in a.c. susceptibility
and in-plane resistivity measurements in BSCCO and qualitatively explains a
field dependence at lower temperatures of previous BSCCO resistivity data
showing the so-called in-plane Lorentz force-free behavior.",0008397v1
2005-06-01,Spin polarization induced tenfold magneto-resistivity of highly metallic 2D holes in a narrow GaAs quantum well,"We observe that an in-plane magnetic field ($B_{||}$) can induce an order of
magnitude enhancement in the low temperature ($T$) resistivity ($\rho$) of
metallic 2D holes in a narrow (10nm) GaAs quantum well. Moreover, we show the
first observation of saturating behavior of $\rho(B_{||})$ at high $B_{||}$ in
GaAs system, which suggests our large positive $\rho(B_{||})$ is due to the
spin polarization effect alone. We find that this tenfold increase in
$\rho(B_{||})$ even persists deeply into the 2D metallic state with the high
$B_{||}$ saturating values of $\rho$ lower than 0.1$\times$h/e$^2$. The
dramatic effect of $B_{||}$ we observe on the highly conductive 2D holes (with
$B$=0 conductivity as high as 75e$^2$/h) sets strong constraint on models for
the spin dependent transport in dilute metallic 2D systems.",0506031v3
2005-09-06,Conduction anisotropy and Hall effect in the organic conductor (TMTTF)2AsF6: evidence for Luttinger liquid and charge ordering,"We present the high-temperature (70 K < T < 300 K) resistivity anisotropy and
Hall effect measurements of the quasi-one-dimensional (1D) organic conductor
(TMTTF)2AsF6. The temperature variations of the resistivity are pronouncedly
different for the three different directions, with metallic-like at high
temperatures for the a-axis only. Above 220 K the Hall coefficient R_H is
constant, positive and strongly enhanced over the expected value; and the
corresponding carrier concentration is almost 100 times lower than calculated
for one hole/unit cell. Our results give evidence for the existence of a
high-temperature regime above 200 K where the 1D Luttinger liquid features
appear in the transport properties. Our measurements also give strong evidence
of charge ordering in (TMTTF)2AsF6. At the charge-ordering transition T_{CO}
\approx 100 K, R_H(T) abruptly changes its behavior, switches sign and rapidly
increases with further temperature decrease.",0509147v1
2003-08-19,Nanolithography with metastable helium atoms in a high-power standing-wave light field,"We have created periodic nanoscale structures in a gold substrate with a
lithography process using metastable triplet helium atoms that damage a
hydrofobic resist layer on top of the substrate. A beam of metastable helium
atoms is transversely cooled and guided through an intense standing-wave light
field. Compared to commonly used low-power optical masks, a high-power light
field (saturation parameter of 10E7) increases the confinement of the atoms in
the standing-wave considerably, and makes the alignment of the experimental
setup less critical. Due to the high internal energy of the metastable helium
atoms (20 eV), a dose of only one atom per resist molecule is required. With an
exposure time of only eight minutes, parallel lines with a separation of 542 nm
and a width of 100 nm (1/11th of the wavelength used for the optical mask) are
created.",0308076v1
2007-05-10,Manifestations of fine features of the density of states in the transport properties of KOs2O6,"We performed high-pressure transport measurements on high-quality single
crystals of KOs2O6, a beta-pyrochlore superconductor. While the resistivity at
high temperatures might approach saturation, there is no sign of saturation at
low temperatures, down to the superconducting phase. The anomalous resistivity
is accompanied by a nonmetallic behavior in the thermoelectric power (TEP) up
to temperatures of at least 700 K, which also exhibits a broad hump with a
maximum at 60 K. The pressure influences mostly the low-energy electronic
excitations. A simple band model based on enhanced density of states in a
narrow window around the Fermi energy (EF) explains the main features of this
unconventional behavior in the transport coefficients and its evolution under
pressure.",0705.1401v1
2008-05-06,Coherence-incoherence crossover in the normal state of iron-oxypnictides and importance of the Hund's rule coupling,"A new class of high temperature superconductors based on iron and arsenic was
recently discovered, with superconducting transition temperature as high as 55
K. Here we show, using microscopic theory, that the normal state of the iron
pnictides at high temperatures is highly anomalous, displaying a Curie Weiss
susceptibility and a linear temperature dependence of the resistivity. Below a
coherence scale T*, the resistivity sharply drops and susceptibility crosses
over to Pauli-like temperature dependence. Remarkably, the
coherence-incoherence crossover temperature is a very strong function of the
strength of the Hund's rule coupling J_Hund. On the basis of the normal state
properties, we estimate J_Hund to be 0.35-0.4 eV. In the atomic limit, this
value of J_Hund leads to the critical ratio of the exchange constants
J_1/J_2~2. While normal state incoherence is in common to all strongly
correlated superconductors, the mechanism for emergence of the incoherent state
in iron-oxypnictides, is unique due to its multiorbital electronic structure.",0805.0722v2
2009-06-11,The enigma of the nu=0 quantum Hall effect in graphene,"We apply Laughlin's gauge argument to analyze the $\nu=0$ quantum Hall effect
observed in graphene when the Fermi energy lies near the Dirac point, and
conclude that this necessarily leads to divergent bulk longitudinal resistivity
in the zero temperature thermodynamic limit. We further predict that in a
Corbino geometry measurement, where edge transport and other mesoscopic effects
are unimportant, one should find the longitudinal conductivity vanishing in all
graphene samples which have an underlying $\nu=0$ quantized Hall effect. We
argue that this $\nu=0$ graphene quantum Hall state is qualitatively similar to
the high field insulating phase (also known as the Hall insulator) in the
lowest Landau level of ordinary semiconductor two-dimensional electron systems.
We establish the necessity of having a high magnetic field and high mobility
samples for the observation of the divergent resistivity as arising from the
existence of disorder-induced density inhomogeneity at the graphene Dirac
point.",0906.2209v2
2009-09-21,Epitaxial LaFeAsOF thin films grown by pulsed laser deposition,"Superconducting and epitaxially grown LaFeAsOF thin films were successfully
prepared on (001)-oriented LaAlO3 substrates using pulsed laser deposition. The
prepared thin films show exclusively a single in-plane orientation with
epitaxial relation (001)[100] parallel to (001)[100] and a FWHM value of 1deg.
Furthermore, resistive measurement of the superconducting transition
temperature revealed a Tc90 of 25K with a high residual resistive ratio of 6.8.
The applied preparation technique, standard thin film pulsed laser deposition
at room temperature in combination with a subsequent post annealing process, is
suitable for fabrication of high quality LaFeAsO1-xFx thin films. A high upper
critical field of 76.2 T was evaluated for magnetic fields applied
perpendicular to the c-axis and the anisotropy was calculated to be 3.3
assuming single band superconductivity.",0909.3788v1
2010-01-31,Saturation of the Anomalous Hall Effect in Critically Disordered Ultra-thin CNi3 Films,"We demonstrate that a distinct high-disorder anomalous Hall effect phase
emerges at the correlated insulator threshold of ultra-thin, amorphous,
ferromagnetic CNi3 films. In the weak localization regime, where the sheet
conductance G >> e^2/h, the anomalous Hall resistance of the films increases
with increasing disorder and the Hall conductance scales as Gxy ~ G^1.6.
However, at sufficiently high disorder the system begins to enter the 2D
correlated insulator regime, at which point the Hall resistance Rxy abruptly
saturates and the scaling exponent becomes 2. Tunneling measurements show that
the saturation behavior is commensurate with the emergence of the 2D Coulomb
gap, suggesting that e-e interactions mediate the high-disorder phase.",1002.0099v1
2012-07-16,Pressure effects on the superconducting thin film Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$,"We report electrical resistivity measurements on a high-quality
Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ thin film ($x=0.4$) under pressure. The
superconducting transition temperature (=39.95 K) of the optimally-doped thin
film shows a dome shape with pressure, reaching a maximal value 40.8 K at 11.8
kbar. The unusually high superconducting transition temperature and its
anomalous pressure dependence are ascribed to a lattice mismatch between the
LaAlO$_3$ substrate and the thin film. The local temperature exponent of the
resistivity ($n=d\text{ln}\Delta\rho/d\text{ln}T$) shows a funnel shape around
the optimal pressure, suggesting that fluctuations associated with the
anomalous normal state are responsible for high-temperature superconductivity.",1207.3826v1
2012-10-09,Quantum oscillations in a d-wave vortex liquid,"The observation of quantum oscillations in underdoped cuprates has generated
intense debate about the nature of the field-induced resistive state and its
implications for the `normal state' of high T_c superconductors. Quantum
oscillations suggest an underlying Fermi liquid state at high magnetic fields H
and low temperatures, in contrast with the high-temperature, zero-field
pseudogap state seen in spectroscopy. Recent heat capacity measurements show
quantum oscillations together with a large and singular field-dependent
suppression of the electronic density of states (DOS), which suggests a
resistive state that is affected by the d-wave superconducting gap. We present
a theoretical analysis of the electronic excitations in a vortex-liquid state,
with short range pairing correlations in space and time, that is able to
reconcile these seemingly contradictory observations. We show that phase
fluctuations lead to large suppression of the DOS that goes like $\sqrt{H}$ at
low fields, in addition to quantum oscillations with a period determined by a
Fermi surface reconstructed by a competing order parameter.",1210.2466v1
2013-04-07,Ageing studies of resistive Micromegas detectors for the HL-LHC,"Resistive-anode Micromegas detectors are in development since several years,
in an effort to solve the problem of sparks when working in high flux and high
radiations environment like in the HL-LHC (ten times the luminosity of the
LHC). They have been chosen as one of the technologies that will be part of the
ATLAS New Small Wheel project (forward muon system). An ageing study is
mandatory to assess their capabilities to handle the HL-LHC environment on a
long-term period. A prototype has been exposed to several types of irradiations
(X-rays, cold neutrons, 60 Co gammas) up to an equivalent HL-LHC time of more
than five years without showing any degradation of the performances in terms of
gain and energy resolution. Beam test studies took place in October 2012 to
assess the tracking performances (efficiency, spatial resolution,...). Results
of ageing studies and beam test performances are reported in this paper.",1304.2053v1
2013-07-31,Quartz Capillary Cladding Anthracene and Polycyclic Aromatic Hydrocarbon(PAH)-Core Scintillating/WLS Fibers for High Rates and Radiation Damage Resistance,"Quartz capillary tube/fibers have been filled with anthracene by a melt and
vacuum inbibition process to fabricate a scintillating core fiber. Other
polcyclic aromatic hydrocarbons(PAH), such as p-Terphenyl (pTP), stilbene or
naphthalene are also well-suited to scintillating/shifting fiber cores. The
resulting scintillating core with quartz cladding capillary fibers (250-750
micron cores) had a high specific light output when tested with muons (8 p.e.
per MIP). These PAH core quartz capillary cladding scintillating/shifting
optical fibers have the potential of high radiation resistance, fast response,
and are applicable to many energy and intensity frontier experiments.",1307.8376v1
2013-08-08,"Ultra-low Energy, High Performance and Programmable Magnetic Threshold Logic","We propose magnetic threshold-logic (MTL) design based on non-volatile
spin-torque switches. A threshold logic gate (TLG) performs summation of
multiple inputs multiplied by a fixed set of weights and compares the sum with
a threshold. MTL employs resistive states of magnetic tunnel junctions as
programmable input weights, while, a low-voltage domain-wall shift based
spin-torque switch is used for thresholding operation. The resulting MTL gate
acts as a low-power, configurable logic unit and can be used to build fully
pipelined, high-performance programmable computing blocks. Multiple stages in
such a MTL design can be connected using energy-efficient ultralow swing
programmable interconnect networks based on resistive switches. Owing to
memory-based compact logic and interconnect design and low-voltage, high-speed
spintorque based threshold operation, MTL can achieve more than two orders of
magnitude improvement in energy-delay product as compared to look-up table
based CMOS FPGA.",1308.4169v1
2015-09-28,High resolution experimental parameter space of a chaotic circuit,"We have obtained a high resolution parameter space of an experimental Chua's
circuit and shown that the topology of the chaotic and periodic regions present
not only expected features previously observed from high resolution numerical
simulations of idealised Chua's circuit, but also novel unexpected features.
Unmatched feedback resistances cause the formation of at least two competing
spirals with consequent disrupted or malformed shrimps. We have also confirmed
experimentally that the period-adding bifurcation route is formed by periodic
regions whose size decrease exponentially with their period, and consequently,
periodic behaviour with higher period is unlikely to be observed. The
higher-resolution span of parameters was possible by the use of a newly
designed potentiometer that could be potentially used in other electronic
equipments to reveal hidden behaviours. To have such resistances we developed
in series arrays of resistors short-circuited by relays as discrete
potentiometers with 1024 steps, and resolutions of 0.100 $\Omega$ for $r_L$ in
series with the inductor, and 0.200 $\Omega$ for R connecting the two
capacitors.",1509.08425v2
2015-10-01,"Comment on ""Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system"" (A. P. Drozdov et al., Nature 525, 73 (2015))","It is demonstrated that resistive transition at 203 K observed in metallic
sulfur hydride system at high pressure can be magnetic (rather than
superconducting (SC)) in nature. The onset temperature of genuine
superconducting transition in these compounds appears to be essentially lower
on temperature. The normal-state magnetic (AF SDW) phase transition preceding a
superconducting one (Tc < Tm) is characteristic for HTSC cuprates, pnictides
(selenides) and organic superconductors. The resistive drop is provided by
disappearing of magnetic (AF spin fluctuation) scattering of conduction
electrons and hence formation of AF SDW order in the normal state. The
formation of such modulated magnetic structure in sulfur hydride seems to be
possible because of magnetic properties of metallic hydrogen at high densities
(in analogy with iron). Such unconventional picture with two successive phase
transitions: magnetic (AF SDW) and only then superconducting one is naturally
described by Keldysh-Kopaev theory of dielectric (metal-insulator) phase
transition in systems with coexistence of superconducting (e-e) and dielectric
(e-h)pairings.",1510.00123v1
2016-11-24,Puddle-induced resistance oscillations in the breakdown of the graphene quantum Hall effect,"We report on the stability of the quantum Hall plateau in wide Hall bars made
from a chemically gated graphene film grown on SiC. The $\nu=2$ quantized
plateau appears from fields $B \simeq 5$ T and persists up to $B \simeq 80$ T.
At high current density, in the breakdown regime, the longitudinal resistance
oscillates with a $1/B$ periodicity and an anomalous phase, which we relate to
the presence of additional electron reservoirs. The high field experimental
data suggest that these reservoirs induce a continuous increase of the carrier
density up to the highest available magnetic field, thus enlarging the quantum
plateaus. These in-plane inhomogeneities, in the form of high carrier density
graphene pockets, modulate the quantum Hall effect breakdown and decrease the
breakdown current.",1611.08179v1
2017-02-08,Fine structure of high-power microwave-induced resistance oscillations,"We report on observation of a fine structure of microwave-induced resistance
oscillations in an ultraclean two-dimensional electron gas. This fine structure
is manifested by multiple secondary sharp extrema, residing beside the primary
ones, which emerge at high radiation power. Theoretical considerations reveal
that this fine structure originates from multiphoton-assisted scattering off
short-range impurities. Unique properties of the fine structure allow us to
access all experimental parameters, including microwave power, and to separate
different contributions to photoresistance. Furthermore, we show that the fine
structure offers a convenient means to quantitatively assess the correlation
properties of the disorder potential in high-quality systems, allowing
separation of short- and long-range disorder contributions to the electron
mobility.",1702.02556v1
2018-04-20,Sensitivity optimization of micro-machined thermo-resistive flow-rate sensors on silicon substrates,"We report on an optimized micro-machined thermal flow-rate sensor as part of
an autonomous multi-parameter sensing device for water network monitoring. The
sensor has been optimized under the following constraints: low power
consumption and high sensitivity, while employing a large thermal conductivity
substrate, namely silicon. The resulting device consists of a platinum
resistive heater deposited on a thin silicon pillar ~ 100 $\mu$m high and 5
$\mu$m wide in the middle of a nearly 100 $\mu$m wide cavity. Operated under
the anemometric scheme, the reported sensor shows a larger sensitivity in the
velocity range up to 1 m/s compared to different sensors based on similar high
conductivity substrates such as bulk silicon or silicon membrane with a power
consumption of 44 mW. Obtained performances are assessed with both CFD
simulation and experimental characterization.",1804.07524v1
2014-10-24,"Doping dependence of the upper critical field, superconducting current density and thermally activated flux flow activation energy in polycrystalline CeFeAsO1-xFx superconductors","We report the results from resistivity and magnetic measurements on
polycrystalline Ce oxypnictide (CeFeAsO1-xFx) samples where x spans from 0.13
to 0.25. We find that the orbital limiting field is as high as 150 T and it
systematically decreases with increasing doping. The Maki parameter is greater
than one across the phase diagram and the large Maki parameter suggests that
orbital and Pauli limiting effects contribute to the upper critical field. The
broadening of the superconducting transition in the resistivity data was
interpreted using the thermally activated flux flow (TAFF) model where we find
that the TAFF activation energy, U0(B), is proportional to B^{-(gamma)} from 1
T to high fields, and (gamma) does not significantly change with doping.
However, U0 and the superconducting critical current, Jc, are peaked in the
mid-doping region (x = 0.15 to x = 0.20), and not in the low (x < 0.15) or high
doping (x > 0.20) regions. Furthermore, U0 is correlated with Jc and follows
the two fluid model for granular samples.",1410.6546v1
2015-05-22,Growth and Characterization of Millimeter-sized Single Crystals of CaFeAsF,"High-quality and sizable single crystals are crucial for studying the
intrinsic properties of unconventional superconductors, which are lacking in
the 1111 phase of the Fe-based superconductors. Here we report the successful
growth of CaFeAsF single crystals with the sizes of 1-2 mm using the self-flux
method. Owning to the availability of the high-quality single crystals, the
structure and transport properties were investigated with a high reliability.
The structure was refined by using the single-crystal x-ray diffraction data,
which confirms the reports earlier on the basis of powder data. A clear anomaly
associated with the structural transition was observed at 121 K from the
resistivity, magnetoresistance, and magnetic susceptibility measurements.
Another kink-feature at 110 K, most likely an indication of the
antiferromagnetic transition, was also detected in the resistivity data. Our
results supply a basis to propel the physical investigations on the 1111 phase
of the Fe-based superconductors.",1505.06014v1
2020-04-01,Characterization of sputtered hafnium thin films for high quality factor microwave kinetic inductance detectors,"Hafnium is an elemental superconductor which crystallizes in a hexagonal
close packed structure, has a transition temperature $T_{C} \simeq 400 mK$, and
has a high normal state resistivity around $90 \mu \Omega. cm$. In Microwave
Kinetic Inductance Detectors (MKIDs), these properties are advantageous since
they allow for creating detectors sensitive to optical and near infra-red
radiation. In this work, we study how sputter conditions and especially the
power applied to the target during the deposition, affect the hafnium $T_{C}$,
resistivity, stress, texture and preferred crystal orientation. We find that
the position of the target with respect to the substrate strongly affects the
orientation of the crystallites in the films and the internal quality factor,
$Q_{i}$, of MKIDs fabricated from the films. In particular, we demonstrate that
a DC magnetron sputter deposition at a normal angle of incidence, low pressure,
and low plasma power promotes the growth of compressive (002)-oriented films
and that such films can be used to make high quality factor MKIDs with $Q_{i}$
up to 600,000.",2004.00736v1
2007-10-03,Scaling analysis of normal state properties of high-temperature superconductors,"We propose a model-independent scaling method to study the physical
properties of high-temperature superconductors in the normal state. We have
analyze the experimental data of the c-axis resistivity, the in-plane
resistivity, the Hall coefficient, the magnetic susceptibility, the
spin-lattice relaxation rate, and the thermoelectric power using this method.
It is shown that all these physical quantities exhibit good scaling behaviors,
controlled purely by the pseudogap energy scale in the normal state. The doping
dependence of the pseudogap obtained from this scaling analysis agrees with the
experimental results of angle-resolved photoemission and other measurements. It
sheds light on the understanding of the basic electronic structure of high-Tc
oxides.",0710.0693v3
2007-10-18,Transport and percolation in a low-density high-mobility two-dimensional hole system,"We present a study of the temperature and density dependence of the
resistivity of an extremely high quality two-dimensional hole system grown on
the (100) surface of GaAs. For high densities in the metallic regime ($p\agt 4
\times 10^{9}$ cm$^{-2}$), the nonmonotonic temperature dependence ($\sim
50-300$ mK) of the resistivity is consistent with temperature dependent
screening of residual impurities. At a fixed temperature of $T$= 50 mK, the
conductivity vs. density data indicates an inhomogeneity driven
percolation-type transition to an insulating state at a critical density of
$3.8\times 10^9$ cm$^{-2}$.",0710.3542v1
2014-01-16,High-quality multi-terminal suspended graphene devices,"We introduce a new scheme to realize suspended, multi-terminal graphene
structures that can be current annealed successfully to obtain uniform, very
high quality devices. A key aspect is that the bulky metallic contacts are not
connected directly to the part of graphene probed by transport measurements,
but only through etched constriction, which prevents the contacts from acting
invasively. The device high quality and uniformity is demonstrated by a
reproducibly narrow (delta_n ~ 10^9 cm^-2) resistance peak around charge
neutrality, by carrier mobility values exceeding 10^6 cm^2/V/s, by the
observation of integer quantum Hall plateaus starting at 30 mT and of symmetry
broken states at about 200 mT, and by the occurrence of a negative
multi-terminal resistance directly proving the occurrence of ballistic
transport. As these multi-terminal devices enable measurements that cannot be
done in a simpler two-terminal configuration, we anticipate that their use in
future studies of graphene-based systems will be particularly relevant.",1401.4033v1
2019-08-30,Pressure-induced suppression of charge density wave and emergence of Superconductivity in 1T-VSe2,"We report pressure evolution of charge density wave (CDW) order and emergence
of superconductivity (SC) in 1T-VSe2 single crystal by studying resistance and
magnetoresistance behavior under high pressure. With increasing
quasi-hydrostatic pressure the CDW order enhances with increase ofthe ordering
temperature up to 240K at 12 GPa. Upon further increase of pressure, the
resistance anomaly due to CDW order gets suppressed drastically and
superconductivity emerges at ~15 GPa, with the onset critical temperature (Tc)
~ 4K. The pressure dependence of Tc is found negligible, different from the
significant increase or a dome-shape seen in iso-structural layered diselenide
superconductors. The high pressure magnetoresistance and Hall measurements
suggest successive electronic structural changes with Fermi surface
modifications at 6 GPa and 12GPa. From the observed negative magnetoresistance
in this pressure range and absence of coexisting CDW and SC phases, we propose
that intra-layer spin-fluctuation can play a role in the emergence of
superconductivity in the high pressure phase.",1908.11678v1
2015-04-16,Phonon-limited carrier mobility and resistivity from carbon nanotubes to graphene,"Under which conditions do the electrical transport properties of
one-dimensional (1D) carbon nanotubes (CNTs) and 2D graphene become equivalent?
We have performed atomistic calculations of the phonon-limited electrical
mobility in graphene and in a wide range of CNTs of different types to address
this issue. The theoretical study is based on a tight-binding method and a
force-constant model from which all possible electron-phonon couplings are
computed. The electrical resistivity of graphene is found in very good
agreement with experiments performed at high carrier density. A common
methodology is applied to study the transition from 1D to 2D by considering
CNTs with diameter up to 16 nm. It is found that the mobility in CNTs of
increasing diameter converges to the same value, the mobility in graphene. This
convergence is much faster at high temperature and high carrier density. For
small-diameter CNTs, the mobility strongly depends on chirality, diameter, and
existence of a bandgap.",1504.04206v2
2019-08-15,Analysis of Skin Effect in High Frequency Isolation Transformers,"In this paper, a high frequency transformer with different conductors and
winding arrangements, at presence of eddy currents and skin effect, is studied.
By using different winding structures, and conductor types, such as circular,
square shaped, and foil wires, the skin effect in the windings is studied and
current density within the conductors at a high frequency of 20 MHz and a lower
frequency of 20 kHz are investigated using finite element method (FEM)
simulation. Moreover, magnetic field distribution in the transformers at 20 MHz
is obtained and displayed. Also, magnetizing inductance, leakage inductance and
AC winding resistance for all of the transformer types are found and compared,
and frequency response for the transformers are obtained and shown. Lastly,
based on the results, the skin effect increases the AC winding resistance and
decreases the leakage inductance as the frequency increases. Furthermore,
different winding arrangements, conductors, and transformer types show a wide
range of parasitic and loss behavior, which enable the designers to compromise
between various parameters in different applications, especially new fast
switches such as SiC and GaN.",1910.01983v1
2020-08-31,An Integrated Approach to Produce Robust Models with High Efficiency,"Deep Neural Networks (DNNs) needs to be both efficient and robust for
practical uses. Quantization and structure simplification are promising ways to
adapt DNNs to mobile devices, and adversarial training is the most popular
method to make DNNs robust. In this work, we try to obtain both features by
applying a convergent relaxation quantization algorithm, Binary-Relax (BR), to
a robust adversarial-trained model, ResNets Ensemble via Feynman-Kac Formalism
(EnResNet). We also discover that high precision, such as ternary (tnn) and
4-bit, quantization will produce sparse DNNs. However, this sparsity is
unstructured under advarsarial training. To solve the problems that adversarial
training jeopardizes DNNs' accuracy on clean images and the struture of
sparsity, we design a trade-off loss function that helps DNNs preserve their
natural accuracy and improve the channel sparsity. With our trade-off loss
function, we achieve both goals with no reduction of resistance under weak
attacks and very minor reduction of resistance under strong attcks. Together
with quantized EnResNet with trade-off loss function, we provide robust models
that have high efficiency.",2008.13305v4
2021-11-19,Resistance-Time Co-Modulated PointNet for Temporal Super-Resolution Simulation of Blood Vessel Flows,"In this paper, a novel deep learning framework is proposed for temporal
super-resolution simulation of blood vessel flows, in which a
high-temporal-resolution time-varying blood vessel flow simulation is generated
from a low-temporal-resolution flow simulation result. In our framework,
point-cloud is used to represent the complex blood vessel model,
resistance-time aided PointNet model is proposed for extracting the time-space
features of the time-varying flow field, and finally we can reconstruct the
high-accuracy and high-resolution flow field through the Decoder module. In
particular, the amplitude loss and the orientation loss of the velocity are
proposed from the vector characteristics of the velocity. And the combination
of these two metrics constitutes the final loss function for network training.
Several examples are given to illustrate the effective and efficiency of the
proposed framework for temporal super-resolution simulation of blood vessel
flows.",2111.10372v1
2021-11-27,Longevity Study on the CMS Resistive Plate Chambers for HL-LHC,"The CMS Resistive Plate Chamber (RPC) system has been certified for 10 years
of LHC operation. In the next years, during the High luminosity LHC (HL-LHC)
phase, the LHC instantaneous luminosity will increase to a factor five more
than the existing LHC luminosity. This will subject the present CMS RPC system
to background rates and operating conditions much higher with respect to those
for which the detectors have been designed. Those conditions could affect the
detector properties and introduce nonrecoverable aging effects. A dedicated
longevity test is set up in the CERN Gamma Irradiation Facility (GIF++) to
determine if the present RPC detectors can survive the hard background
conditions during the HL-LHC running period. During the irradiation test, the
RPC detectors are exposed to a high gamma radiation for a long period and the
detector main parameters are monitored as a function of the integrated charge.
Based on collecting a large fraction of the expected integrated charge at the
LH-LHC, The results of the irradiation test will be presented.",2111.13995v1
2022-08-24,Multi-mode Analysis of Surface Losses in a Superconducting Microwave Resonator in High Magnetic Fields,"This paper reports on a surface impedance measurement of a niobium titanium
superconducting radio frequency (SRF) cavity in a magnetic field (up to
$10\,{\rm T}$). A novel method is employed to decompose the surface resistance
contributions of the cylindrical cavity end caps and walls using measurements
from multiple $TM$ cavity modes. The results confirm that quality factor
degradation of a NbTi SRF cavity in a high magnetic field is primarily from
surfaces perpendicular to the field (the cavity end caps), while parallel
surface resistances (the walls) remain relatively constant. This result is
encouraging for applications needing high Q cavities in strong magnetic fields,
such as the Axion Dark Matter eXperiment (ADMX), because it opens the
possibility of hybrid SRF cavity construction to replace conventional copper
cavities.",2208.11799v1
2022-12-19,Eco-friendly Resistive Plate Chambers for detectors in future HEP applications,"Resistive Plate Chamber detectors are largely used in current High Energy
Physics experiments, typically operated in avalanche mode with large fractions
of Tetrafluoroethane (C2H2F4), a gas recently banned by the European Union due
to its high Global Warming Potential (GWP). An intense R&D activity is ongoing
to improve RPC technology in view of future HEP applications. In the last few
years the RPC EcoGas@GIF++ Collaboration has been putting in place a joint
effort between the ALICE, ATLAS, CMS, LHCb/SHiP and EP-DT Communities to
investigate the performance of present and future RPC generations with
eco-friendly gas mixtures. Detectors with different layout and electronics have
been operated with ecological gas mixtures, with and without irradiation at the
CERN Gamma Irradiation Facility (GIF++). Results of these performance studies
together with plans for an aging test campaign are discussed in this article.",2212.09572v1
2023-01-02,Noise-resistant quantum memory enabled by Hamiltonian engineering,"Nuclear spins in quantum dots are promising candidates for fast and scalable
quantum memory. By utilizing the hyperfine interaction between the central
electron and its surrounding nuclei, quantum information can be transferred to
the collective state of the nuclei and be stored for a long time. However,
nuclear spin fluctuations in a partially polarized nuclear bath deteriorate the
quantum memory fidelity. Here we introduce a noise-resistant protocol to
realize fast and high-fidelity quantum memory through Hamiltonian engineering.
With analytics and numerics, we show that high-fidelity quantum state transfer
between the electron and the nuclear spins is achievable at relatively low
nuclear polarizations, due to the strong suppression of nuclear spin noises.
For a realistic quantum dot with $10^4$ nuclear spins, a fidelity surpassing
80% is possible at a polarization as low as 30%. Our approach reduces the
demand for high nuclear polarization, making experimentally realizing quantum
memory in quantum dots more feasible.",2301.00575v1
2023-11-06,Persistent Homology for High-dimensional Data Based on Spectral Methods,"Persistent homology is a popular computational tool for analyzing the
topology of point clouds, such as the presence of loops or voids. However, many
real-world datasets with low intrinsic dimensionality reside in an ambient
space of much higher dimensionality. We show that in this case traditional
persistent homology becomes very sensitive to noise and fails to detect the
correct topology. The same holds true for existing refinements of persistent
homology. As a remedy, we find that spectral distances on the
$k$-nearest-neighbor graph of the data, such as diffusion distance and
effective resistance, allow to detect the correct topology even in the presence
of high-dimensional noise. Moreover, we derive a novel closed-form formula for
effective resistance, and describe its relation to diffusion distances.
Finally, we apply these methods to high-dimensional single-cell RNA-sequencing
data and show that spectral distances allow robust detection of cell cycle
loops.",2311.03087v2
2023-05-01,"Leveraging Language Representation for Material Recommendation, Ranking, and Exploration","Data-driven approaches for material discovery and design have been
accelerated by emerging efforts in machine learning. However, general
representations of crystals to explore the vast material search space remain
limited. We introduce a material discovery framework that uses natural language
embeddings derived from language models as representations of compositional and
structural features. The discovery framework consists of a joint scheme that
first recalls relevant candidates, and next ranks the candidates based on
multiple target properties. The contextual knowledge encoded in language
representations conveys information about material properties and structures,
enabling both representational similarity analysis for recall, and multi-task
learning to share information across related properties. By applying the
framework to thermoelectrics, we demonstrate diversified recommendations of
prototype structures and identify under-studied high-performance material
spaces. The recommended materials are corroborated by first-principles
calculations and experiments, revealing novel materials with potential high
performance. Our framework provides a task-agnostic means for effective
material recommendation and can be applied to various material systems.",2305.01101v2
2019-07-12,"Data-driven materials science: status, challenges and perspectives","Data-driven science is heralded as a new paradigm in materials science. In
this field, data is the new resource, and knowledge is extracted from materials
data sets that are too big or complex for traditional human reasoning -
typically with the intent to discover new or improved materials or materials
phenomena. Multiple factors, including the open science movement, national
funding, and progress in information technology, have fueled its development.
Such related tools as materials databases, machine learning, and
high-throughput methods are now established as parts of the materials research
toolset. However, there are a variety of challenges that impede progress in
data-driven materials science: data veracity, integration of experimental and
computational data, data longevity, standardization, and the gap between
industrial interests and academic efforts. In this perspective article, we
discuss the historical development and current state of data-driven materials
science, building from the early evolution of open science to the rapid
expansion of materials data infrastructures. We also review key successes and
challenges so far, providing a perspective on the future development of the
field.",1907.05644v2
2024-04-09,Predicting the future applications of any stoichiometric inorganic material through learning from past literature,"Through learning from past literature, artificial intelligence models have
been able to predict the future applications of various stoichiometric
inorganic materials in a variety of subfields of materials science. This
capacity offers exciting opportunities for boosting the research and
development (R&D) of new functional materials. Unfortunately, the previous
models can only provide the prediction for existing materials in past
literature, but cannot predict the applications of new materials. Here, we
construct a model that can predict the applications of any stoichiometric
inorganic material (regardless of whether it is a new material). Historical
validation confirms the high reliability of our model. Key to our model is that
it allows the generation of the word embedding of any stoichiometric inorganic
material, which cannot be achieved by the previous models. This work constructs
a powerful model, which can predict the future applications of any
stoichiometric inorganic material using only a laptop, potentially
revolutionizing the R&D paradigm for new functional materials",2404.06120v1
2019-10-29,Observation of spin-momentum locked surface states in amorphous Bi$_{2}$Se$_{3}$,"Crystalline symmetries have played a central role in the identification of
topological materials. The use of symmetry indicators and band representations
have enabled a classification scheme for crystalline topological materials,
leading to large scale topological materials discovery. In this work we address
whether amorphous topological materials, which lie beyond this classification
due to the lack of long-range structural order, exist in the solid state. We
study amorphous Bi$_2$Se$_3$ thin films, which show a metallic behavior and an
increased bulk resistance. The observed low field magnetoresistance due to weak
antilocalization demonstrates a significant number of two dimensional surface
conduction channels. Our angle-resolved photoemission spectroscopy data is
consistent with a dispersive two-dimensional surface state that crosses the
bulk gap. Spin resolved photoemission spectroscopy shows this state has an
anti-symmetric spin texture resembling that of the surface state of crystalline
Bi$_2$Se$_3$. These experimental results are consistent with theoretical
photoemission spectra obtained with an amorphous tight-binding model that
utilizes a realistic amorphous structure. This discovery of amorphous materials
with topological properties uncovers an overlooked subset of topological matter
outside the current classification scheme, enabling a new route to discover
materials that can enhance the development of scalable topological devices.",1910.13412v4
2022-04-26,Unusually strong electronic correlation and field-induced ordered phase in YbCo$_2$,"We report the first study of electrical resistivity, magnetization, and
specific heat on YbCo$_2$. The measurements on a single-phased sample of
YbCo$_2$ bring no evidence of magnetic ordering down to 0.3 K in a zero
magnetic field. The manifestations of low Kondo temperature are observed. The
specific heat value divided by temperature, C/T, keeps increasing
logarithmically beyond 7 J/mol.K2 with decreasing temperature down to 0.3 K
without no sign of magnetic ordering, suggesting a very large electronic
specific heat. Analysis of the magnetic specific heat indicates that the large
portion of the low-temperature specific heat is not explained simply by the low
Kondo temperature but is due to the strong intersite magnetic correlation in
both the 3d and 4f electrons. Temperature-dependent measurements under static
magnetic fields up to 7 T are carried out, which show the evolution of
field-induced transition above 2 T. The transition temperature increases with
increasing field, pointing to a ferromagnetic character. The extrapolation of
the transition temperature to zero field suggests that YbCo$_2$ is in the very
proximity of the quantum critical point. These results indicate that in the
unique case of YbCo$_2$, the itinerant electron magnetism of Co 3d-electrons
and the Kondo effect within the vicinity of quantum criticality of Yb 4f-local
moments can both play a role.",2204.12025v2
2019-10-02,"High-throughput Density Functional Perturbation Theory and Machine Learning Predictions of Infrared, Piezoelectric and Dielectric Responses","Many technological applications depend on the response of materials to
electric fields, but available databases of such responses are limited. Here,
we explore the infrared, piezoelectric and dielectric properties of inorganic
materials by combining high-throughput density functional perturbation theory
and machine learning approaches. We compute {\Gamma}-point phonons, infrared
intensities, Born-effective charges, piezoelectric, and dielectric tensors for
5015 non-metallic materials in the JARVIS-DFT database. We find 3230 and 1943
materials with at least one far and mid-infrared mode, respectively. We
identify 577 high-piezoelectric materials, using a threshold of 0.5 C/m2. Using
a threshold of 20, we find 593 potential high-dielectric materials.
Importantly, we analyze the chemistry, symmetry, dimensionality, and geometry
of the materials to find features that help explain variations in our datasets.
Finally, we develop high-accuracy regression models for the highest infrared
frequency and maximum Born-effective charges, and classification models for
maximum piezoelectric and average dielectric tensors to accelerate discovery.",1910.01183v2
2022-06-21,A method to computationally screen for tunable properties of crystalline alloys,"Conventionally, high-throughput computational materials searches start from
an input set of bulk compounds extracted from material databases, and this set
is screened for candidate materials for specific applications. In contrast,
many functional materials, and especially semiconductors, are heavily
engineered alloys or solid solutions of multiple compounds rather than a single
bulk compound. To improve our ability to design functional materials, in this
work we propose a framework and open-source code to automatically construct
possible ""alloy pairs"" and ""alloy systems"" and detect ""alloy members"" from a
set of existing, experimental or calculated ordered compounds, without
requiring any additional metadata beyond their crystal structure. We provide
analysis tools to estimate stability across each alloy. As a demonstration, we
apply this framework to all inorganic materials in the Materials Project
database to create a new database of over 600,000 unique alloy pair entries
that can then be used in materials discovery studies to search for materials
with tunable properties. This new database has been incorporated into the
Materials Project website and linked with corresponding material identifiers
for any user to query and explore. Using an example of screening for p-type
transparent conducting materials, we demonstrate how using this methodology
reveals candidate material systems that might otherwise have been excluded by a
traditional screening. This work lays a foundation from which materials
databases can go beyond stoichiometric compounds, and approach a more realistic
description of compositionally tunable materials.",2206.10715v3
2023-05-20,PhotoMat: A Material Generator Learned from Single Flash Photos,"Authoring high-quality digital materials is key to realism in 3D rendering.
Previous generative models for materials have been trained exclusively on
synthetic data; such data is limited in availability and has a visual gap to
real materials. We circumvent this limitation by proposing PhotoMat: the first
material generator trained exclusively on real photos of material samples
captured using a cell phone camera with flash. Supervision on individual
material maps is not available in this setting. Instead, we train a generator
for a neural material representation that is rendered with a learned relighting
module to create arbitrarily lit RGB images; these are compared against real
photos using a discriminator. We then train a material maps estimator to decode
material reflectance properties from the neural material representation. We
train PhotoMat with a new dataset of 12,000 material photos captured with
handheld phone cameras under flash lighting. We demonstrate that our generated
materials have better visual quality than previous material generators trained
on synthetic data. Moreover, we can fit analytical material models to closely
match these generated neural materials, thus allowing for further editing and
use in 3D rendering.",2305.12296v2
2015-06-30,"Strong, Tough and Stiff Bioinspired Ceramics from Brittle Constituents","High strength and high toughness are usually mutually exclusive in
engineering materials. Improving the toughness of strong but brittle materials
like ceramics thus relies on the introduction of a metallic or polymeric
ductile phase to dissipate energy, which conversely decreases the strength,
stiffness, and the ability to operate at high temperature. In many natural
materials, toughness is achieved through a combination of multiple mechanisms
operating at different length scales but such structures have been extremely
difficult to replicate. Building upon such biological structures, we
demonstrate a simple approach that yields bulk ceramics characterized by a
unique combination of high strength (470 MPa), high toughness (22 MPa.m1/2),
and high stiffness (290 GPa) without the assistance of a ductile phase. Because
only mineral constituents were used, this material retains its mechanical
properties at high temperature (600{\deg}C). The bioinspired,
material-independent design presented here is a specific but relevant example
of a strong, tough, and stiff material, in great need for structural,
transportations, and energy-related applications.",1506.08979v1
2014-03-02,A comprehensive scenario of the single crystal growth and doping dependence of resistivity and anisotropic upper critical fields in (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$ ($0.22 \leq x \leq 1$),"Large high-quality single crystals of hole-doped iron-based superconductor
(Ba$_{1-x}$K$_x$)Fe$_2$As$_2$ were grown over a broad composition range $0.22
\leq x \leq 1$ by inverted temperature gradient method. We found that high
soaking temperature, fast cooling rate, and adjusted temperature window of the
growth are necessary to obtain single crystals of heavily K doped crystals
(0.65$\leq x \leq$ 0.92) with narrow compositional distributions as revealed by
sharp superconducting transitions in magnetization measurements and close to
100% superconducting volume fraction. The crystals were extensively
characterized by x-ray and compositional analysis, revealing monotonic
evolution of the $c$-axis crystal lattice parameter with K substitution.
Quantitative measurements of the temperature-dependent in-plane resistivity,
$\rho(T)$ found doping-independent, constant within error bars, resistivity at
room temperature, $\rho(300K)$, in sharp contrast with significant doping
dependence in electron and isovalent substituted BaFe$_2$As$_2$ based
compositions. The shape of the temperature dependent resistivity, $\rho(T)$,
shows systematic doping-evolution, being close to $T^2$ in overdoped and
revealing significant contribution of the $T$-linear component at optimum
doping. The slope of the upper critical field, $d H_{c2}/dT$, scales linearly
with $T_c$ for both $H\parallel c$, $ H_{c2,c}$, and $H \parallel ab$,
$H_{c2,ab}$. The anisotropy of the upper critical field, $\gamma \equiv
H_{c2,ab} / H_{c2,c}$ determined near zero-field $T_c$ increases from $\sim$2
to 4-5 with increasing K doping level from optimal $x \sim$0.4 to strongly
overdoped $x$=1.",1403.0227v1
2017-12-07,"Effects of high energy proton irradiation on the superconducting properties of Fe(Se,Te) thin films","In this paper we explore the effects of 3.5 MeV proton irradiation on
Fe(Se,Te) thin films grown on CaF2. In particular, we carry out a systematic
experimental investigation with different irradiation fluences up to 7.30x10^16
cm^-2 and different proton implantation depths, in order to clarify whether and
to what extent the critical current is enhanced or suppressed, what are the
effects of irradiation on the critical temperature, the resistivity and the
critical magnetic fields, and finally what is the role played by the substrate
in this context. We find that the effect of irradiation on superconducting
properties is generally small as compared to the case of other iron-based
superconductors. Such effect is more evident on the critical current density
Jc, while it is minor on the transition temperature Tc, on the normal state
resistivity and on the upper critical field Hc2 up to the highest fluences
explored in this work. In addition, our analysis shows that when protons
implant in the substrate far from the superconducting film, the critical
current can be enhanced up to 50% of the pristine value at 7 T and 12 K, while
there is no appreciable effect on critical temperature and critical fields
together with a slight decrease in resistivity. On the contrary, when the
implantation layer is closer to the film-substrate interface, both critical
current and temperature show a decrease accompanied by an enhancement of the
resistivity and the lattice strain. This result evidences that possible
modifications induced by irradiation in the substrate may affect the
superconducting properties of the film via lattice strain. The robustness of
the Fe(Se,Te) system to irradiation induced damage makes it a promising
compound for the fabrication of magnets in high-energy accelerators.",1712.02558v1
2020-04-29,Self-similar structure of resistive ADAFs with outflow and large-scale magnetic field,"The observations and simulations have revealed that large-scale magnetic
field and outflows can exist in the inner regions of an advection-dominated
accretion disc where the resistive diffusion may also be important. In the
present paper, the roles of large-scale magnetic field and outflows in the
structure of resistive advection-dominated accretion discs are explored by
assuming that the accretion flow is radially self-similar. In the non-ideal
magnetohydrodynamic (MHD) approximation, the results show that the angular
velocity is always sub-Keplerian when both the outflow and the large-scale
magnetic field are taken into account. A stronger toroidal field component
leads to faster rotation, while the disc rotates with faster rate if the
vertical field component is weaker. The increase of magnetic diffusivity causes
the infall velocity to be close to Keplerian velocity. Although the previous
studies in the ideal MHD approximation have shown that the disc temperature
decreases due to the vertical field component, we find that the effect of
vertical field component on the temperature of a resistive disc depends on the
magnetic diffusivity. When the magnetic diffusivity is high, the more efficient
mechanism for decreasing the disc temperature can be the outflows, and not the
large-scale magnetic field. In such a limit of the magnetic diffusivity, the
components of the large-scale magnetic field enhance the gas temperature. The
increase of temperature can lead to heating and acceleration of the electrons
and help us to explain the origin of phenomena such as the flares in Sgr A*. On
the other hand, the infall velocity in such a limit rises as the temperature
increases, and therefore the surface density falls to too low values. Any
change in the density profile can alter the structure and the emitted spectrum
of disc.",2004.14757v1
2022-02-28,Ultra-Efficient Resistance Switching between Charge Ordered Phases in 1T-TaS$_2$ with a Single Picosecond Electrical Pulse,"Progress in high-performance computing demands significant advances in memory
technology. Among novel memory technologies that promise efficient device
operation on a sub-ns timescale, resistance switching between charge ordered
phases of the 1T-TaS$_2$ has shown to be potentially useful for the development
of high-speed, energy efficient non-volatile memory device. While ultrafast
switching was previously reported with optical pulses, determination of the
intrinsic speed limits of actual devices that are triggered by electrical
pulses is technically challenging and hitherto still largely unexplored. A new
optoelectronic laboratory-on-a-chip, designed for measurements of ultrafast
memory switching, enables an accurate measurement of the electrical switching
parameters with 100 fs temporal resolution. A photoconductive response is used
for ultrashort electrical pulse generation, while its propagation along a
coplanar transmission line is detected using electro-optical sampling using a
purpose-grown highly-resistive electro-optic (Cd,Mn)Te crystal substrate. By
combining the transmission line and the 1T-TaS$_2$ device in a single
optoelectronic circuit a non-volatile resistance switching with a single 1.9 ps
electrical pulse is demonstrated, with an extremely small switching energy
density per unit area E$_A$ = 9.4 fJ/$\mu$m$^2$. The experiments demonstrate
ultrafast, energy-efficient circuits utilizing switching between non-volatile
charge-ordered states offers a new technological platform for cryogenic memory
devices.",2202.13831v3
2021-10-15,MHD simulations of small ELMs at low triangularity in ASDEX Upgrade,"The development of small- and no-ELM regimes for ITER is a high priority
topic due to the risks associated to type-I ELMs. By considering non-linear
extended MHD simulations of the ASDEX Upgrade tokamak with the JOREK code, we
probe a regime that avoids type-I ELMs completely provided that the separatrix
density is high enough. The dynamics of the pedestal in this regime are
observed to be qualitatively similar to the so-called quasi-continuous exhaust
(QCE) regime in several ways. Repetitive type-I ELMs are substituted by roughly
constant levels of outwards transport caused by peeling-ballooning modes (with
dominant ballooning characteristics) which are localised in the last 5\% of the
confined region (in normalised poloidal flux). The simulated low triangularity
plasma transitions to a type-I ELMy H-mode if the separatrix density is
sufficiently reduced or if the input heating power is sufficiently increased.
The stabilising factors that play a role in the suppression of the small ELMs
are also investigated by analysing the simulations, and the importance of
including diamagnetic effects in the simulations is highlighted. By considering
a scan in the pedestal resistivity and by measuring the poloidal velocity of
the modes (and comparing to theoretical estimates for ideal and resistive
modes), we identify the underlying instabilities as resistive
peeling-ballooning modes. Decreasing the resistivity below
experimentally-relevant conditions (i.e., going towards ideal MHD), the
peeling-ballooning modes that constrain the pedestal below the type-I ELM
stability boundary display sharply decreasing growth rates.",2110.07908v1
2022-01-05,Superconducting $I$$\overline{4}$3$m$ CSH$_7$ model applied to resistive transition temperature data for compressed C-S-H at high pressure,"This article updates version 1 by restricting consideration to only the
resistive data and excluding the questioned 287.7-K datum reported for
carbonaceous sulfur hydride in Snider et al., Nature $\textbf{585}$, 373
(2020). The superconducting transitions are considered in terms of the
theoretically-discovered compressed $I$$\overline{\textrm{4}}$3$m$ CSH$_7$
structure of Sun et al., Phys. Rev. B $\textbf{101}$, 174102 (2020), which
comprises a sublattice similar to $Im$$\overline{\textrm{3}}$$m$ H$_3$S with
CH$_4$ intercalates. Positing an electronic genesis of the superconductivity, a
model is presented in analogy with earlier work on superconductivity in
$Im$$\overline{\textrm{3}}$$m$ H$_3$S, in which pairing is induced via purely
electronic Coulomb interactions across the mean distance $\zeta$ between the S
and H$_4$ tetrahedra enclosing C. Theoretical superconducting transition
temperatures for $I$$\overline{\textrm{4}}$3$m$ CSH$_7$ are derived as
$T$$_{\textrm{C0}}$ = (2/3)$^{1/2}$ $\sigma^{1/2}$ $\beta$/$a$$\zeta$, where
$\beta$ = 1247.4 $\mathring{\mathrm{A}}$$^2$K is a universal constant, $\sigma$
is the participating charge fraction, and $a$ is the lattice parameter.
Analysis suggests persistent bulk superconductivity with a pressure-dependent
$\sigma$, increasing from $\sigma$ = 3.5, determined previously for
$Im$$\overline{3}$$m$ H$_3$S, to $\sigma$ = 7.5 at high pressure owing to
additionally participating C-H bond electrons. With $a$ and $\zeta$ determined
by theoretical structure, calculations of $T$$_{\textrm{C0}}$ at the highest
pressures, 258 and 271 GPa, are in agreement with resistive transitions to
within an overall uncertainty of $\pm$ 3.5 K.",2201.01860v3
2021-12-02,Mechanistic Data Science for Modeling and Design of Aerospace Composite Materials,"Polymer matrix composites exhibit remarkable lightweight and high strength
properties that make them attractive for aerospace applications. Constituents'
materials such as advanced polymers and fibers or fillers with their
hierarchical structure embed these exceptional properties to the composite
materials. This hierarchical structure in multiple length scales provides an
opportunity for designing the composite materials for optimized properties.
However, the high dimensional design space for the constituents' materials and
architectures choice of the composites makes it a challenging design problem.
To tackle this high dimensional design space, a systematic, efficient approach
named mechanistic data science framework is proposed in this work to identify
the governing mechanisms of materials systems from the limited available data
and create a composite knowledge database. Our composite knowledge database
comprises the knowledge of polymers at the nanoscale with nano reinforcement,
the unidirectional structure at the microscale, and woven structure at
mesoscale mechanisms that can be further used for the part scale composite
design and analysis. The mechanistic data science framework presented in this
work can be further extended to other materials systems that will provide the
materials designer with the necessary tools to evaluate a new materials system
design rapidly.",2112.00968v1
2024-01-31,Incorporating quasiparticle and excitonic properties into material discovery,"In recent years, GW-BSE has been proven to be extremely successful in
studying the quasiparticle (QP) bandstructures and excitonic effects in the
optical properties of materials. However, the massive computational cost
associated with such calculations restricts their applicability in
high-throughput material discovery studies. Recently, we developed a Python
workflow package, $py$GWBSE, to perform high-throughput GW-BSE simulations. In
this work, using $py$GWBSE we create a database of various QP properties and
excitonic properties of over 350 chemically and structurally diverse materials.
Despite the relatively small size of the dataset, we obtain highly accurate
supervised machine learning (ML) models via the dataset. The models predict the
quasiparticle gap with an RMSE of 0.36 eV, exciton binding energies of
materials with an RMSE of 0.29 eV, and classify materials as high or low
excitonic binding energy materials with classification accuracy of 90%. We
exemplify the application of these ML models in the discovery of 159
visible-light and 203 ultraviolet-light photoabsorber materials utilizing the
Materials Project database.",2401.17831v1
2020-12-10,"Growth of Two-dimensional Compound Materials: Controllability, Material Quality, and Growth Mechanism","CONSPECTUS: Two-dimensional (2D) compound materials are promising materials
for use in electronics, optoelectronics, flexible devices, etc. because they
are ultrathin and cover a wide range of properties. Among all methods to
prepare 2D materials, chemical vapor deposition (CVD) is promising because it
produces materials with a high quality and reasonable cost. So far, much
efforts have been made to produce 2D compound materials with large domain size,
controllable number of layers, fast-growth rate, and high quality features,
etc. However, due to the complicated growth mechanism like sublimation and
diffusion processes of multiple precursors, maintaining the controllability,
repeatability, and high quality of CVD grown 2D binary and ternary materials is
still a big challenge, which prevents their widespread use. Here, taking 2D
transition metal dichalcogenides (TMDCs) as examples, we review current
progress and highlight some promising growth strategies for the growth of 2D
compound materials. The key technology issues which affect the CVD process,
including non-metal precursor, metal precursor, substrate engineering,
temperature, and gas flow, are discussed. Also, methods in improving the
quality of CVD-grown 2D materials and current understanding on their growth
mechanism are highlighted. Finally, challenges and opportunities in this field
are proposed. We believe this review will guide the future design of
controllable CVD systems for the growth of 2D compound materials with good
controllability and high quality, laying the foundations for their potential
applications.",2012.05486v1
2022-03-17,Quasi-solid-state electrolyte for ultra-high safety and cycle stability battery,"All-solid-state lithium batteries (ASSLB) have been regarded as the most
promising candidate to achieve the next generation energy storage with high
energy and high safety. However, some bottlenecks, including high interfacial
resistance, bad electrochemical stability, and low conductivity, have hindered
its further development. Here, we developed a Pyr13FSI/LiFSI-based gel
electrolyte and used it in the LFP/LTO full battery system to achieve a
lithium-ion battery with high safety and cycle stability. The presence of ionic
liquid in the electrolyte reduces the crystallinity of PVDF-HFP polymer matrix,
increases the ion conductivity of the electrolyte, and greatly improves the
electrode-electrolyte interface contact. These advantages enable the battery to
work at room temperature and reach a specific capacity of 123mAh/g at the
current of 1C. The slightly change in interfacial resistances between the gel
electrolyte and electrodes with the increase of the cycle numbers is confirmed
through electrochemical impedance spectroscopy. The high electrochemical
stability of the electrolyte in the LFP/LTO system makes the battery exhibit
good cycle stability, and the battery maintains 80% of its initial capacity
after 2000 cycles at the current of 1C. In addition, benefitting from the
excellent properties of ionic liquids, such as non-flammability, negligible
vapour pressure, and high conductivity, the obtained gel electrolyte based
LFP/LTO pouch battery exhibits high safety and cycle stability.",2203.09269v1
2012-11-25,HIV drug resistance: problems and perspectives,"Access to combination antiretroviral treatment (ART) has improved greatly
over recent years. At the end of 2011, more than eight million HIV infected
people were receiving antiretroviral therapy in low-income and middle-income
countries. ART generally works well in keeping the virus suppressed and the
patient healthy. However, treatment only works as long as the virus is not
resistant against the drugs used. In the last decades, HIV treatments have
become better and better at slowing down the evolution of drug resistance, so
that some patients are treated for many years without having any resistance
problems. However, for some patients, especially in low-income countries, drug
resistance is still a serious threat to their health. This essay will review
what is known about transmitted and acquired drug resistance, multi-class drug
resistance, resistance to newer drugs, resistance due to treatment for the
prevention of mother-to-child transmission, the role of minority variants
(low-frequency drug-resistance mutations), and resistance due to pre-exposure
prophylaxis.",1211.5807v2
2022-07-16,Random 2D nanowire networks: Finite-size effect and the effect of busbar/nanowire contact resistance on their electrical conductivity,"We have studied the resistance of two-dimensional random percolating networks
of zero-width metallic nanowires (rings or sticks). We toke into account the
nanowire resistance per unit length, the junction (nanowire/nanowire contact)
resistance, and the busbar/nanowire contact resistance. Using a mean-field
approximation (MFA), we derived the total resistance of the nanoring-based
networks as a function of their geometrical and physical parameters. We have
proposed a way of accounting for the contribution of the busbar/nanowire
contact resistance toward the network resistance. The MFA predictions have been
confirmed by our Monte Carlo (MC) numerical simulations. Our study evidenced
that the busbar/nanowire contact resistance has a significant effect on the
electrical conductivity when the junction resistance dominates over wire
resistance.",2207.07841v2
1995-01-09,"Resonant Tunneling and Charging Effects, a Path Integral Approach","Electron tunneling through small metallic islands with low capacitance is
studied. The large charging energy in these systems is responsible for
nonperturbative Coulomb blockade effects. We further consider the effect of
electron interactions in the electrodes. In junctions with high resistance
compared to the quantum resistance transport can be described by sequential
tunneling. If the resistance is lower, quantum fluctuations, higher order
coherent processes, and eventually resonant tunneling become important. We
present a path integral real-time approach, which allows a systematic
diagrammatic classification of these processes. An important process is
``inelastic resonant tunneling'', where different electrons tunnel coherently
between the electrodes and the island. Physical quantities like the current and
the average charge on the island can be deduced. We find a strong
renormalization of the system parameters and, in addition, a finite lifetime
broadening. It results in a pronounced broadening and smearing of the Coulomb
oscillations of the conductance. These effects are important in an
experimentally accessible range of temperatures. The electron interaction in
the electrodes is modeled by a Luttinger liquid. It leads to non-analytic
kernels in the effective action. The diagrammatic expansions can be performed
also in this case, resulting in power-law current-voltage characteristics.",9501028v1
1997-11-11,Transport Properties of Heavy Fermion Compounds,"A technique for measuring the electrical resistivity and absolute thermopower
is presented for pressures up to 30 GPa, temperatures down to 25 mK and
magnetic fields up to 10 T. With the examples of CeCu2Ge2 and CeCu2Si2 we focus
on the interplay of normal phase and superconducting properties. With
increasing pres- sure, the behaviour of CeCu2Ge2 evolves from that of an
antiferromagnetically ordered Kondo system to that characteristic of an
intermediate valence compound as the Kondo temperature increases by about two
orders of magnitude. In the pressure window 8-10 < P < 20 GPa, a
superconducting phase occurs which com- petes at low pressure with magnetic
ordering. For CeCu2Si2 the effective mass of carriers is probed by both the
coefficient of the Fermi liquid law and the ini- tial slope of the upper
critical field. The magnetic instability is studied no- tably for CeRu2Ge2 and
Yb-based compounds for which pressure-induced magnetic ordering tends to
develop. Finally, contrary to conventional wisdom, we argue that in heavy
fermions a large part of the residual resistivity is most likely not
independent of temperature; tentatively ascribed to Kondo hole, it can be very
pressure as well as sample dependent. [electrical resistivity, thermoelectric
power, heavy fermion, magnetic order, superconductivity]",9711089v1
1999-01-14,Multiple Andreev reflections in diffusive SNS structures,"We report new measurements on sup-gap energy structure originating from
multiple Andreev reflections in mesoscopic SNS junctions. The junctions were
fabricated in a planar geometry with high transparency superconducting contacts
of Al deposited on highly diffusive and surface d-doped n++-GaAs. For samples
with a normal GaAs region of active length 0.3um the Josephson effect with a
maximal supercurrent Ic=3mA at T=237mK was observed. The sub-gap structure was
observed as a series of local minima in the differential resistance at dc bias
voltages V=2D/ne with n=1,2,4 i.e. only the even sub-gap positions. While at
V=2D/e (n=1) only one dip is observed, the n=2, and the n=4 sub-gap structures
each consists of two separate dips in the differential resistance. The mutual
spacing of these two dips is independent of temperature, and the mutual spacing
of the n=4 dips is half of the spacing of the n=2 dips. The voltage bias
positions of the sub-gap differential resistance minima coincide with the
maxima in the oscillation amplitude when a magnetic field is applied in an
interferometer configuration, where one of the superconducting electrodes has
been replaced by a flux sensitive open loop.",9901140v2
2000-07-13,Josephson junction array type I-V characteristics of quench-condensed ultra thin films of Bi,"In this communication we report studies of d.c current-voltage (I-V)
characteristics of ultra thin films of Bi, quench condensed on single crystal
sapphire substrates at T = 15K. The hysteretic I-V characteristics are
explained using a resistively and capacitively shunted junction (RCSJ) model of
Josephson junction arrays. The Josephson coupling energy($E_J$) and the
charging energy($E_c$) are calculated for different thickness($d$) values. A
low resistance state is found in the low current regime below the critical
current, $I_c$. This resistance $R_0$ is found to have a minimum at a
particular thickness ($d_c$) value. Reflection High Energy Electron Diffraction
(RHEED) studies are done on these films. A distinct appearance of a diffuse
ring near $d_c$ is observed in the diffraction images, consistent with the
recent STM studies(Ekinci and Valles, PRL {\bf 82}(1999) 1518). These films
show an irreversible annealing when temperature is increased. The annealing
temperature ($T_a$) also has a maximum at the same thickness. Althoguh the
R$_s$ vs T of quench condensed Bi films suggest that the films are uniform, our
results indicate that even in thick films, the order parameter is not fully
developed over the complete area of the film. These results are discussed
qualitatively.",0007222v1
2001-04-26,Electron Quasiparticles Drive the Superconductor-to-Insulator Transition in Homogeneously Disordered Thin Films,"Transport data on Bi, MoGe, and PbBi/Ge homogeneously-disordered thin films
demonstrate that the critical resistivity, $R_c$, at the nominal
insulator-superconductor transition is linearly proportional to the normal
sheet resistance, $R_N$. In addition, the critical magnetic field scales
linearly with the superconducting energy gap and is well-approximated by
$H_{c2}$. Because $R_N$ is determined at high temperatures and $H_{c2}$ is the
pair-breaking field, the two immediate consequences are: 1)
electron-quasiparticles populate the insulating side of the transition and 2)
standard phase-only models are incapable of describing the destruction of the
superconducting state. As gapless electronic excitations populate the
insulating state, the universality class is no longer the 3D XY model. The lack
of a unique critical resistance in homogeneously disordered films can be
understood in this context. In light of the recent experiments which observe an
intervening metallic state separating the insulator from the superconductor in
homogeneously disordered MoGe thin films, we argue that the two transitions
that accompany the destruction of superconductivity are 1) superconductor to
Bose metal in which phase coherence is lost and 2) Bose metal to localized
electron insulator via pair-breaking.",0104504v2
2001-05-24,Dilute electron gas near the metal-insulator transition in two dimensions,"In recent years systematic experimental studies of the temperature dependence
of the resistivity in a variety of dilute, ultra clean two dimensional
electron/hole systems have revived the fundamental question of localization or,
alternatively, the existence of a metal-insulator transition in the presence of
strong electron-electron interactions in two dimensions. We argue that under
the extreme conditions of ultra clean systems not only is the electron-electron
interaction very strong but the role of other system specific properties are
also enhanced. In particular, we emphasize the role of valleys in determining
the transport properties of the dilute electron gas in silicon inversion layers
(Si-MOSFETs). It is shown that for a high quality sample the temperature
behavior of the resistivity in the region close to the critical region of the
metal-insulator transition is well described by a renormalization group
analysis of the interplay of interaction and disorder if the electron band is
assumed to have two distinct valleys. The decrease in the resistivity up to
five times has been captured in the correct temperature interval by this
analysis, without involving any adjustable parameters. The considerable
variance in the data obtained from different Si-MOSFET samples is attributed to
the sample dependent scattering rate across the two valleys, presenting thereby
with a possible explanation for the absence of universal behavior in Si-MOSFET
samples of different quality.",0105471v1
2002-03-06,c-Axis Transport and Resistivity Anisotropy of Lightly- to Moderately-Doped La_{2-x}Sr_{x}CuO_{4} Single Crystals: Implications on the Charge Transport Mechanism,"Both the in-plane and the out-of-plane resistivities (\rho_{ab} and \rho_{c})
are measured in high-quality La_{2-x}Sr_{x}CuO_{4} (LSCO) single crystals in
the lightly- to moderately-doped region, x = 0.01 to 0.10, and the resistivity
anisotropy is determined. In all the samples studied, the anisotropy ratio \rho
_{c}/\rho_{ab} quickly increases with decreasing temperature, although in
non-superconducting samples the strong localization effect causes \rho
_{c}/\rho_{ab} to decrease at low temperatures. Most notably, it is found that
\rho_{c}/\rho_{ab} at moderate temperatures (100 - 300 K) is almost completely
independent of doping in the non-superconducting regime (x = 0.01 to 0.05);
this indicates that the same charge confinement mechanism that renormalizes the
c-axis hopping rate is at work down to x = 0.01. It is discussed that this
striking x-independence of \rho_{c}/\rho_{ab} is consistent with the idea that
holes form a self-organized network of hole-rich regions, which also explains
the unusually metallic in-plane transport of the holes in the lightly-doped
region. Furthermore, the data for x > 0.05 suggest that the emergence of the
superconductivity is related to an increase in the c-axis coupling.",0203107v1
2002-05-15,Evolution of the resistivity anisotropy in Bi_{2}Sr_{2-x}La_{x}CuO_{6+δ} single crystals for a wide range of hole doping,"To elucidate how the temperature dependence of the resistivity anisotropy of
the cuprate superconductors changes with hole doping, both the in-plane and the
out-of-plane resistivities (\rho_{ab} and \rho_{c}) are measured in a series of
high-quality Bi_{2}Sr_{2-x}La_{x}CuO_{6+\delta} (BSLCO) single crystals for a
wide range of x (x = 0.23 - 1.02), which corresponds to the hole doping per Cu,
p, of 0.03 - 0.18. The anisotropy ratio, \rho_{c}/\rho_{ab}, shows a systematic
increase with decreasing p at moderate temperatures, except for the most
underdoped composition where the localization effect enhances \rho_{ab} and
thus lowers \rho_{c}/\rho_{ab}. The exact p dependence of \rho_{c}/\rho_{ab} at
a fixed temperature is found to be quite peculiar, which is discussed to be due
to the effect of the pseudogap that causes \rho_{c}/\rho_{ab} to be
increasingly more enhanced as p is reduced. The pseudogap also causes a rapid
growth of \rho_{c}/\rho_{ab} with decreasing temperature, and, as a result, the
\rho_{c}/\rho_{ab} value almost reaches 10^6 in underdoped samples just above
T_c. Furthermore, it is found that the temperature dependence of \rho_{c} of
underdoped samples show two distinct temperature regions in the pseudogap
phase, which suggests that the divergence of \rho_{c} below the pseudogap
temperature is governed by two different mechanisms.",0205305v2
2003-05-08,"Anisotropic magnetization, specific heat and resistivity of RFe2Ge2 single crystals","We have grown RFe2Ge2 single crystals for R = Y and ten members of the
lanthanide series (Pr, Nd, Sm, Gd-Tm, Lu) using Sn flux as the solvent. The
method yields clean, high quality crystal plates as evidenced by residual
resistivities and RRR values in the range of 3-12 uOhm cm and 20-90
respectively. The crystals are also virtually free of magnetic impurities or
secondary phases, allowing the study of the intrinsic anisotropic magnetic
behavior of each compound. Characterization was made with X-Ray diffraction,
and temperature and field dependent magnetization, specific heat and
resistivity. Very strong anisotropies arising mostly from CEF effects were
observed for all magnetic rare earths except Gd. Antiferromagnetic ordering
occurred at temperatures between 16.5 K (Nd) and 1.1 K (Ho) that roughly scale
with the de Gennes factor for the heavy rare earths. For some members there is
also a lower temperature transition associated with changes in the magnetic
structure. Tm did not order down to 0.4 K, and appears to be a van Vleck
paramagnet. All members which ordered above 2 K showed a metamagnetic
transition at 2 K for fields below 70 kOe. The calculated effective moments per
rare earth atom are close to the expected free ion values of R^3+ except for Sm
which displays anomalous behavior in the paramagnetic state. The non-magnetic
members of this series (Y, Lu) are characterized by an unusually large
electronic specific heat coefficient (gamma ~ 60 mJ/mol K^2) and
temperature-independent susceptibility term (chi_0 ~ 0.003 emu/mol), indicative
of a relatively large density of states at the Fermi surface.",0305173v1
2004-09-15,Current-Induced Pair Breaking in Magnesium Diboride,"The transport of electrical current through a superconductor falls into three
broad regimes: non-dissipative, dissipative but superconducting, and normal or
non-superconducting. These regimes are demarkated by two definitions of
critical current: one is the threshold current above which the superconductor
enters a dissipative (resistive) state; the other is the thermodynamic
threshold above which the superconductivity itself is destroyed and the
superconducting order parameter vanishes. The first threshold defines the
conventional critical current density Jc and the second defines the depairing
(or pair-breaking) current Jd. Type II superconductors in the mixed state have
quantized flux vortices, which tend to move when acted upon by the Lorentz
driving force of an applied transport current. In such a mixed state the
resistance vanishes only when vortices are pinned in place by defects and the
applied current is below the threshold Jc required to overcome pinning and
mobilize the vortices. Typically Jd >> Jc and a direct experimental measurement
of Jd over the entire temperature range (0 < T < Tc) is prohibited by the
enormous power dissipation densities (p ~ 10^10 -- 10^12 W/cm^3) needed to
reach the normal state. In this work, intense pulsed signals were used to
extend transport measurements to unprecedented power densities (p ~ 10^9 --
10^10 W/cm^3). This together with MgB2's combination of low normal-state
resistivity and high transition temperature have permitted a direct estimation
of \jd over the entire temperature range. This review describes our
experimental investigation of current-induced depairing in MgB2, and provides
an introduction to the phenomenological theories of superconductivity and how
the observations fit in their context.",0409402v1
2005-06-09,Pressure-induced valence change in the rare earth metals:The case of Praseodymium,"The rare earth metal praseodymium (Pr) transforms from the d-fcc crystal
structure (Pr-III) to {$\alpha$}-U one (Pr-IV) at 20 GPa with a large volume
collapse (${\rm\Delta} V/V$ = 0.16), which is associated with the valence
change of the Pr ion. The two 4{\it f} electrons in the Pr ion is supposed to
be itinerant in the Pr-IV phase. In order to investigate the electronic state
of the phase IV, we performed the high pressure electrical resistance
measurement using the diamond anvil cell up to 32 GPa. In the Pr-IV phase, the
temperature dependence of the resistance shows an upward negative curvature,
which is similar to the itinerant 5{\it f} electron system in actinide metals
and compounds. This suggests the narrow quasiparticle band of the 4{\it f}
electrons near the Fermi energy. A new phase boundary is found at $T_{0}$ in
the Pr-IV phase. From the temperature and magnetic field dependences of the
resistance at 26 GPa, the ground state of the Pr-IV phase is suggested to be
magnetic. Several possibilities for the origin of $T_{0}$ are discussed.",0506222v1
2004-10-20,The penetration of plasma clouds across magnetic boundaries : the role of high frequency oscillations,"Experiments are reported where a collisionfree plasma cloud penetrates a
magnetic barrier by self-polarization. We here focus on the resulting anomalous
magnetic field diffusion into the plasma cloud, two orders of magnitude faster
than classical, which is one important aspect of the plasma cloud penetration
mechanism. Without such fast magnetic diffusion, clouds with kinetic beta below
unity would not be able to penetrate magnetic barriers at all. Tailor-made
diagnostics has been used for measurements in the parameter range with the
kinetic beta ? 0.5 to 10, and with normalized width w/r(gi) of the order of
unity. Experimental data on hf fluctuations in density and in electric field
has been combined to yield the effective anomalous transverse resistivity
eta(EFF). It is concluded that they are both dominated by highly nonlinear
oscillations in the lower hybrid range, driven by a strong diamagnetic current
loop that is set up in the plasma in the penetration process. The anomalous
magnetic diffusion rate, calculated from the resistivity eta(EFF), is
consistent with single-shot multi-probe array measurements of the diamagnetic
cavity and the associated quasi-dc electric structure. An interpretation of the
instability measurements in terms of the resistive term in the generalized (low
frequency) Ohm's law is given.",0410168v1
2007-12-13,Andreev reflections at large ferromagnet/high-T_C superconductor area junctions with rough interface,"Sub-gap conductance at a large area junction with a rough interface of a
ferromagnet and a high-T$_{C}$ superconductor is superimposed by multiple peaks
which is not expected from an ideal point contact Andreev reflection process.
We demonstrate this phenomenon by measuring resistance as a function of bias
voltage of a Co/Y$_{1}$Ba$_{2}$Cu$_{3}$O$_{7-\delta}$ junction with contact
area 50 x 70 $\mu$ $m^{2}$ at various temperatures. In order to analyze such
Andreev reflection data, the interface is assumed to have random potentials
which can create local electric fields. The Blonder-Tinkham-Klapwijk theory is
modified with the inclusion of a broadening parameter due to finite life time
effects of quasi particles. An additional voltage drop due to local electric
fields at the rough interface has been included in terms of an extra energy
shift which may be related to the asymmetry of normalized resistance data. Spin
polarization has been introduced for the ferromagnet. The presented model
explains the multi-peak nature and asymmetry of Andreev reflection data
experimentally observed at large area junctions. Extension of the model also
interprets the experimentally observed anomalous enhancement of resistance
peaks in the sub-gap region which may result from crossing the critical current
limit across the junction.",0712.2131v2
2008-06-11,Anisotropic thermodynamic and transport properties of single crystalline (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$ (x = 0 and 0.45),"Single crystals of BaFe$_2$As$_2$ and (Ba$_{0.55}$K$_{0.45}$)Fe$_2$As$_2$
have been grown out of excess Sn with 1% or less incorporation of solvent. The
crystals are exceptionally micaceous, are easily exfoliated and can have
dimensions as large as 3 x 3 x 0.2 mm$^3$. The BaFe$_2$As$_2$ single crystals
manifest a structural phase transition from a high temperature tetragonal phase
to a low temperature orthorhombic phase near 85 K and do not show any sign of
superconductivity down to 1.8 K. This transition can be detected in the
electrical resistivity, Hall resistivity, specific heat and the anisotropic
magnetic susceptibility. In the (Ba$_{0.55}$K$_{0.45}$)Fe$_2$As$_2$ single
crystals this transition is suppressed and instead superconductivity occurs
with a transition temperature near 30 K. Whereas the superconducting transition
is easily detected in resistivity and magnetization measurements, the change in
specific heat near $T_c$ is small, but resolvable, giving $\Delta C_p/\gamma
T_c \approx 1$. The application of a 140 kOe magnetic field suppresses $T_c$ by
only $\sim 4$ K when applied along the c-axis and by $\sim 2$ K when applied
perpendicular to the c-axis. The ratio of the anisotropic upper critical
fields, $\gamma = H_{c2}^{\perp c} / H_{c2}^{\| c}$, varies between 2.5 and 3.5
for temperatures down to $\sim 2$ K below $T_c$.",0806.1874v2
2008-06-16,"Transport and anisotropy in single-crystalline SrFe$_2$As$_2$ and $A_{0.6}$K$_{0.4}$Fe$_2$As$_2$ ($A$ = Sr, Ba) superconductors","We have successfully grown high quality single crystals of SrFe$_2$As$_2$ and
A$_{0.6}$K$_{0.4}$Fe$_2$As$_2$(A=Sr, Ba) using flux method. The resistivity,
specific heat and Hall coefficient have been measured. For parent compound
SrFe$_2$As$_2$, an anisotropic resistivity with $\rho_c$ / $\rho_{ab}$ as large
as 130 is obtained at low temperatures. A sharp drop in both in-plane and
out-plane resistivity due to the SDW instability is observed below 200 K. The
angular dependence of in-plane magnetoresistance shows 2-fold symmetry with
field rotating within ab plane below SDW transition temperature. This is
consistent with a stripe-type spin ordering in SDW state. In K doped
A$_{0.6}$K$_{0.4}$Fe$_2$As$_2$(A=Sr. Ba), the SDW instability is suppressed and
the superconductivity appears with T$_c$ above 35 K. The rather low anisotropy
in upper critical field between H$\parallel$ab and H$\parallel$c indicates
inter-plane coupling play an important role in hole doped Fe-based
superconductors.",0806.2648v3
2008-07-03,Pressure induced superconductivity in CaFe$_2$As$_2$,"CaFe$_2$As$_2$ has been found to be exceptionally sensitive to the
application of hydrostatic pressure and superconductivity has been found to
exist in a narrow pressure region that appears to be at the interface between
two different phase transitions. The pressure - temperature ($P - T$) phase
diagram of CaFe$_2$As$_2$ reveals that this stoichiometric, highly ordered,
compound can be easily tuned to reveal all the salient features associated with
FeAs-based superconductivity without introducing any disorder. Whereas at
ambient pressure CaFe$_2$As$_2$ does not superconduct for $T > 1.8$ K and
manifests a first order structural phase transition near $T \approx 170$ K, the
application of $\sim 5$ kbar hydrostatic pressure fully suppresses the
resistive signature of the structural phase transition and instead
superconductivity is detected for $T < 12$ K. For $P \ge 5.5$ kbar a different
transition is detected, one associated with a clear reduction in resistivity
and for $P > 8.6$ kbar superconductivity is no longer detected. This higher
pressure transition temperature increases rapidly with increasing pressure,
exceeding 300 K by $P \sim 17$ kbar. The low temperature, superconducting dome
is centered around 5 kbar, extending down to 2.3 kbar and up to 8.6 kbar. This
superconducting phase appears to exist when the low pressure transition is
suppressed sufficiently, but before the high pressure transition has reduced
the resistivity, and possibly the associated fluctuations, too dramatically.",0807.0616v2
2008-08-06,Divergent resistance at the Dirac point in graphene: Evidence for a transition in a high magnetic field,"We have investigated the behavior of the resistance of graphene at the $n=0$
Landau Level in an intense magnetic field $H$. Employing a low-dissipation
technique (with power $P<$3 fW), we find that, at low temperature $T$, the
resistance at the Dirac point $R_0(H)$ undergoes a 1000-fold increase from
$\sim$10 k$\Omega$ to 40 M$\Omega$ within a narrow interval of field. The
abruptness of the increase suggests that a transition to an insulating, ordered
state occurs at the critical field $H_c$. Results from 5 samples show that
$H_c$ depends systematically on the disorder, as measured by the offset gate
voltage $V_0$. Samples with small $V_0$ display a smaller critical field $H_c$.
Empirically, the steep increase in $R_0$ fits acccurately a
Kosterlitz-Thouless-type correlation length over 3 decades. The curves of $R_0$
vs. $T$ at fixed $H$ approach the thermal-activation form with a gap
$\Delta\sim$15 K as $H\to H_c^{-}$, consistent with a field-induced insulating
state.",0808.0906v3
2009-09-22,Experimental study on the cyclic resistance of a natural loess from Northern France,"In order to analyze the instability phenomenon observed along the Northern
High Speed Line of R\'eseau Ferr\'e de France (RFF), soil blocks were taken at
a site near the railway, at four different depths (1.2, 2.2, 3.5 and 4.9 m).
Cyclic triaxial tests were carried out on saturated and unsaturated soil
specimens. The results from tests on initially saturated specimens showed that
the soil taken at 2.2 m depth has the lowest resistance to cyclic loading, in
relation to its highest porosity and lowest clay fraction. This soil was then
studied at unsaturated state with various initial water contents. Unsaturated
soil specimens were first subjected to cyclic loadings to decrease their
volume. These cyclic loadings was stopped when the volume decrease was
approximately equal to the initial pore air volume, or when the pores filled by
air were eliminated and the soil was considered to become saturated.
Afterwards, the back-pressure tubing was saturated with de-aired water and
cycles were applied under undrained condition. Significant effect of initial
water content was evidenced: the lower the initial water content, the higher
the cyclic resistance. This can be explained by the densification of the soil
during the initial cyclic loadings.",0909.3932v1
2011-03-23,"On the origin of non-monotonic doping dependence of the in-plane resistivity anisotropy in Ba(Fe$_{1-x}T_x$)$_2$As$_2$, $T$ = Co, Ni and Cu","The in-plane resistivity anisotropy has been measured for detwinned single
crystals of Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$ and Ba(Fe$_{1-x}$Cu$_x$)$_2$As$_2$.
The data reveal a non-monotonic doping dependence, similar to previous
observations for Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$. Magnetotransport measurements
of the parent compound reveal a non-linear Hall coefficient and a strong linear
term in the transverse magnetoresistance. Both effects are rapidly suppressed
with chemical substitution over a similar compositional range as the onset of
the large in-plane resistivity anisotropy. It is suggested that the relatively
small in-plane anisotropy of the parent compound in the spin density wave state
is due to the presence of an isotropic, high mobility pocket of reconstructed
Fermi surface. Progressive suppression of the contribution to the conductivity
arising from this isotropic pocket with chemical substitution eventually
reveals the underlying in-plane anisotropy associated with the remaining FS
pockets.",1103.4535v2
2011-11-21,Coulomb drag in monolayer and bilayer graphene,"We theoretically calculate the interaction-induced frictional Coulomb drag
resistivity between two graphene monolayers as well as between two graphene
bilayers, which are spatially separated by a distance ""$d$"". We show that the
drag resistivity between graphene monolayers can be significantly affected by
the intralayer momentum-relaxation mechanism. For energy independent intralayer
scattering, the frictional drag induced by inter-layer electron-electron
interaction goes asymptotically as $\rho_D \sim T^2/n^4d^6$ and $\rho_D \sim
T^2/n^2d^2$ in the high-density ($k_F d \gg 1$) and low-density ($k_F d \ll 1$)
limits, respectively. When long-range charge impurity scattering dominates
within the layer, the monolayer drag resistivity behaves as $\rho_D \sim
T^2/n^3d^4$ and $T^2 \ln (\sqrt{n} d) /n$ for $k_F d \gg 1$ and $k_F d \ll 1$,
respectively. The density dependence of the bilayer drag is calculated to be
$\rho_D \propto T^2/n^{3}$ both in the large and small layer separation limit.
In the large layer separation limit, the bilayer drag has a strong $1/d^4$
dependence on layer separation, whereas this goes to a weak logarithmic
dependence in the strong inter-layer correlation limit of small layer
separation. In addition to obtaining the asymptotic analytical formula for
Coulomb drag in graphene, we provide numerical results for arbitrary values of
density and layer separation interpolating smoothly between our asymptotic
theoretical results.",1111.5022v2
2011-12-12,Self-similar solutions of viscous and resistive ADAFs with thermal conduction,"We have studied the effects of thermal conduction on the structure of viscous
and resistive advection-dominated accretion flows (ADAFs). The importance of
thermal conduction on hot accretion flow is confirmed by observations of hot
gas that surrounds Sgr A$^*$ and a few other nearby galactic nuclei. In this
research, thermal conduction is studied by a saturated form of it, as is
appropriated for weakly-collisional systems. It is assumed the viscosity and
the magnetic diffusivity are due to turbulence and dissipation in the flow. The
viscosity also is due to angular momentum transport. Here, the magnetic
diffusivity and the kinematic viscosity are not constant and vary by position
and $\alpha$-prescription is used for them. The govern equations on system have
been solved by the steady self-similar method. The solutions show the radial
velocity is highly subsonic and the rotational velocity behaves sub-Keplerian.
The rotational velocity for a specific value of the thermal conduction
coefficient becomes zero. This amount of conductivity strongly depends on
magnetic pressure fraction, magnetic Prandtl number, and viscosity parameter.
Comparison of energy transport by thermal conduction with the other energy
mechanisms implies that thermal conduction can be a significant energy
mechanism in resistive and magnetized ADAFs. This property is confirmed by
non-ideal magnetohydrodynamics (MHD) simulations.",1112.2678v1
2012-02-14,Viscous and resistive accretion flows with radially self-similar and outflows,"The existence of outflow in accretion flows is confirmed by observations and
magnetohydrodynamics (MHD) simulations. In this paper, we study outflows of
accretion flows in the presence of resistivity and toroidal magnetic field. The
mechanism of energy dissipation in the flow is assumed to be the viscosity and
the magnetic diffusivity due to turbulence in the accretion flow. It is also
assumed that the magnetic diffusivity and the kinematic viscosity are not
constant and vary by position and $\alpha$-prescription is used for them. The
influence of outflow emanating from accretion disc is considered as a sink for
mass, angular momentum and energy. The self-similar method is used to solve the
integrated equations that govern the behavior of the accretion flow in the
presence of outflow. The solutions represent the disc which rotates faster and
becomes cooler for stronger outflows. Moreover, by adding the magnetic
diffusivity, the surface density and rotational velocity decrease, while the
radial velocity and temperature increase. The study of present model with the
magnitude of magnetic field implies that the disc rotates and accretes faster
and becomes hotter, while the surface density decreases. The disc thickness
increases by adding the magnetic field or resistivity, while it becomes thinner
for more losses of mass and energy due to the outflows.",1202.3095v1
2012-05-17,Viscous-Resistive ADAF with a general Large-Scale Magnetic Field,"We have studied the structure of hot accretion flow bathed in a general
large-scale magnetic field. We have considered magnetic parameters $
\beta_{r,\varphi,z}[=c^2_{r,\varphi,z}/(2c^2_{s})] $, where $ c^2_{r, \varphi,
z} $ are the Alfv\'{e}n sound speeds in three direction of cylindrical
coordinate $ (r,\varphi,z) $. The dominant mechanism of energy dissipation is
assumed to be the magnetic diffusivity due to turbulence and viscosity in the
accretion flow. Also, we adopt a more realistic model for kinematic viscosity $
(\nu=\alpha c_{s} H) $, with both $ c_{s} $ and $ H $ as a function of magnetic
field. As a result in our model, the kinematic viscosity and magnetic
diffusivity $ (\eta=\eta_{0}c_{s} H) $ are not constant. In order to solve the
integrated equations that govern the behavior of the accretion flow, a
self-similar method is used. It is found that the existence of magnetic
resistivity will increase the radial infall velocity as well as sound speed and
vertical thickness of the disk. However the rotational velocity of the disk
decreases by the increase of magnetic resistivity. Moreover, we study the
effect of three components of global magnetic field on the structure of the
disk. We found out that the radial velocity and sound speed are Sub-Keplerian
for all values of magnetic field parameters, but the rotational velocity can be
Super-Keplerian by the increase of toroidal magnetic field. Also, Our numerical
results show that all components of magnetic field can be important and have a
considerable effect on velocities and vertical thickness of the disk.",1205.3888v1
2012-10-29,Numerical Study of Charge Transport of Overdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$ within Semiclassical Boltzmann Transport Theory,"The in-plane resistivity of the high-temperature oxide superconductor
La$_{2-x}$Sr$_{x}$CuO$_{4}$ [LSCO] shows a strong growth of a contribution
linear in temperature as the doping is reduced in the overdoped region toward
optimal. This linear term is a signature of non-Fermi liquid behavior. We find
that the appearance of a linear term in the resistivity can arise in a
semiclassical Boltzmann transport theory which uses renormalized quasiparticle
scattering rates and an empirical band structure fitted to ARPES data on LSCO.
The linearized Boltzmann equation is solved numerically by discretizing the
Brillouin zone in a way that fits best to the Fermi surface geometry. The main
trends in the development of the anomalous temperature dependence are well
reproduced. There is a substantial underestimation of the magnitude of the
resistivity which is expected in view of the moderate to weak values we chose
for the onsite repulsion to stay within the one-loop renormalization group
approximation. The analysis was extended to the Seebeck coefficient with
similar agreement with the main trends in the data.",1210.7668v2
2012-11-07,"c-axis resistivity, pseudogap, superconductivity and Widom line in doped Mott insulators","Layered doped Mott insulators, such as the cuprates, show unusual temperature
dependence of the resistivity. Intriguingly, the resistivity perpendicular to
the CuO$_2$ planes, $\rho_c(T)$, shows both metallic ($d\rho_c/dT > 0$) and
semi-conducting ($d\rho_c/dT<0$) behavior. We shed light on this puzzle by
calculating $\rho_c$ for the two-dimensional Hubbard model within plaquette
cellular dynamical mean-field theory and strong-coupling continuous-time
quantum Monte Carlo as the impurity solver. The temperature, $T$, and doping,
$\delta$, dependencies of $\rho_c$ are controlled by the first-order transition
between pseudogap and correlated metal phases from which superconductivity can
emerge. On the large doping side of the transition $\rho_c(T)$ is metallic,
while on the low-doping side $\rho_c(T)$ changes from metallic to
semi-conducting behavior with decreasing $T$. As a function of doping, the jump
in $\rho_c$ across the first-order transition evolves into a sharp crossover at
higher temperatures. This crossover coincides with the pseudogap temperature
$T^*$ in the single-particle density of states, the spin susceptibility and
other observables. Such coincidence in crossovers is expected along the
continuation of the first-order transition into the super-critical regime,
called the Widom line. This implies that not only the dynamic and the
thermodynamic properties but also the DC transport in the normal state are
governed by the hidden first-order transition. $\rho_c(T)$ has a
high-temperature quasi-linear regime where it can exceed the Mott-Ioffe-Regel
limit and when it has a minimum it is nearly parallel to the Widom line.",1211.1702v1
2013-04-24,"Anisotropic transport and magnetic properties, and magnetic-field tuned states of CeZn11 single crystals","We present detailed temperature and field dependent data obtained from
magnetization, resistivity, heat capacity, Hall resistivity and thermoelectric
power measurements performed on single crystals of CeZn11. The compounds orders
antiferromagnetically at $\sim$ 2 K. The zero-field resistivity and TEP data
show features characteristic of a Ce-based intermetallic with crystal electric
field splitting and possible correlated, Kondo lattice effects. We constructed
the T-H phase diagram for the magnetic field applied along the easy, [110],
direction which shows that the magnetic field required to suppress T_N below
0.4 K is in the range of 45-47.5 kOe. A linear behavior of the rho(T) data,
H||[110], was observed only for H=45 kOe for 0.46 K<T<1.96 K followed by the
Landau-Fermi-liquid regime for a limited range of fields, 47.5 kOe< H<60 kOe.
From the analysis of our data, it appears that CeZn11 is a weakly to moderately
correlated local moment compound with rather small Kondo temperature. The
thermoelectric and transport properties of CeZn11 are mostly governed by the
CEF effects. Given the very high quality of our single crystals, quantum
oscillations are found for both CeZn11 and its non-magnetic analogue, LaZn11.",1304.6752v1
2013-07-12,Optical properties and electronic structure of the nonmetallic metal FeCrAs,"The complex optical properties of a single crystal of hexagonal FeCrAs ($T_N
\simeq 125$ K) have been determined above and below $T_N$ over a wide frequency
range in the planes (along the $b$ axis), and along the perpendicular ($c$
axis) direction. At room temperature, the optical conductivity
$\sigma_1(\omega)$ has an anisotropic metallic character. The electronic band
structure reveals two bands crossing the Fermi level, allowing the optical
properties to be described by two free-carrier (Drude) contributions consisting
of a strong, broad component and a weak, narrow term that describes the
increase in $\sigma_1(\omega)$ below $\simeq 15$ meV. The dc-resistivity of
FeCrAs is ``non-metallic'', meaning that it rises in power-law fashion with
decreasing temperature, without any signature of a transport gap. In the
analysis of the optical conductivity, the scattering rates for both Drude
contributions track the dc-resistivity quite well, leading us to conclude that
the non-metallic resistivity of FeCrAs is primarily due to a scattering rate
that increases with decreasing temperature, rather than the loss of free
carriers. The power law $\sigma_1(\omega) \propto \omega^{-0.6}$ is observed in
the near-infrared region and as $T\rightarrow T_N$ spectral weight is
transferred from low to high energy ($\gtrsim 0.6$ eV); these effects may be
explained by either the two-Drude model or Hund's coupling. We also find that a
low-frequency in-plane phonon mode decreases in frequency for $T < T_N$,
suggesting the possibility of spin-phonon coupling.",1307.3528v2
2013-09-26,Anomalous Fermi liquid phase in metallic Skyrmion crystals,"In non-centrosymmetric crystals such as MnSi, magnetic order can take the
form of a skyrmion crystal (SkX) . In this phase, conduction electrons coupled
to the local magnetic moments acquire a Berry's phase, leading to an emergent
electromagnetism. Motivated by experimental reports of a non-Fermi liquid phase
in MnSi, in which resistivity is observed to scale as $\Delta \rho \sim
T^{3/2}$, here we examine the effect of coupling phonons of an incommensurate
SkX to electrons. Despite the formal similarity to a system consisting of a
Fermi surface coupled to an electromagnetic field, the Berry phase fluctuations
do not lead to non-Fermi liquid behavior. Instead, we propose a different
mechanism in which electrons scatter off columnar fluctuation in a
three-dimensional SkX. When the effects of lattice induced anisotropy are
neglected, these fluctuations are ultra-soft and induce an `anomalous Fermi
liquid' in which Landau quasiparticles survive but with an anomalous $\Delta
\rho(T)\sim T^{7/4}$ resistivity perpendicular to the columns, and a Fermi
liquid resistivity along them.",1309.7047v3
2014-07-11,Self-consistent stationary MHD shear flows in the solar atmosphere as electric field generators,"Magnetic fields and flows in coronal structures, for example, in gradual
phases in flares, can be described by 2D and 3D magnetohydrostatic (MHS) and
steady magnetohydrodynamic (MHD) equilibria. Within a physically simplified,
but exact mathematical model, we study the electric currents and corresponding
electric fields generated by shear flows. Starting from exact and analytically
calculated magnetic potential fields, we solveid the nonlinear MHD equations
self-consistently. By applying a magnetic shear flow and assuming a nonideal
MHD environment, we calculated an electric field via Faraday's law. The formal
solution for the electromagnetic field allowed us to compute an expression of
an effective resistivity similar to the collisionless Speiser resistivity. We
find that the electric field can be highly spatially structured, or in other
words, filamented. The electric field component parallel to the magnetic field
is the dominant component and is high where the resistivity has a maximum. The
electric field is a potential field, therefore, the highest energy gain of the
particles can be directly derived from the corresponding voltage. In our
example of a coronal post-flare scenario we obtain electron energies of tens of
keV, which are on the same order of magnitude as found observationally. This
energy serves as a source for heating and acceleration of particles.",1407.3227v1
2014-07-22,Rapid Change of Field Line Connectivity and Reconnection in Stochastic Magnetic Fields,"Magnetic fields without a direction of continuous symmetry have the generic
feature that neighboring field lines exponentiate away from each other and
become stochastic, hence the ideal constraint of preserving magnetic field line
connectivity becomes exponentially sensitive to small deviations from ideal
Ohm's law. The idea of breaking field line connectivity by stochasticity as a
mechanism for fast reconnection is tested with numerical simulations based on
reduced magnetohydrodynamics equations with a strong guide field line-tied to
two perfectly conducting end plates. Starting from an ideally stable force-free
equilibrium, the system is allowed to undergo resistive relaxation. Two
distinct phases are found in the process of resistive relaxation. During the
quasi-static phase, rapid change of field line connectivity and strong induced
flow are found in regions of high field line exponentiation. However, although
the field line connectivity of individual field lines can change rapidly, the
overall pattern of field line mapping appears to deform gradually. From this
perspective, field line exponentiation appears to cause enhanced diffusion
rather than reconnection. In some cases, resistive quasi-static evolution can
cause the ideally stable initial equilibrium to cross a stability threshold,
leading to formation of intense current filaments and rapid change of field
line mapping into a qualitatively different pattern. It is in this onset phase
that the change of field line connectivity is more appropriately designated as
magnetic reconnection. Our results show that rapid change of field line
connectivity appears to be a necessary, but not a sufficient condition for fast
reconnection.",1407.6069v1
2014-12-17,Contacts for organic switches with carbon-nanotube leads,"Molecular devices, as future electronics, seek low-resistivity contacts for
the energy saving. At the same time, the contacts should intensify desired
properties of tailored electronic elements. In this work, we focus our
attention on two classes of organic switches connected to carbon-nanotube leads
and operating due to photo- or field-induced proton transfer (PT) process. By
means of the first-principles atomistic simulations of the ballistic
conductance, we search for atomic contacts which strengthen diversity of the
two swapped I-V characteristics between two tautomers of a given molecular
system. We emphasize, that the low-resistive character of the contacts is not
necessarily in accordance with the switching properties. Very often, the
higher-current flow makes it more difficult to distinguish between the logic
states of the molecular device. Instead, the resistive contacts multiply a
current gear at the tautomeric transition to a larger extent. The low- and
high-bias work regimes set additional conditions, which are fulfilled by
different contacts. In some cases, the peroxide contacts or the direct
connection to the tube perform better than the popular sulfur contact.
Additionally, we find that the switching-bias value is not an inherent property
of the conducting molecule, but it strongly depends on the chosen contacts.",1412.5667v3
2015-09-07,Finite Size Effect in Amorphous Indium oxide,"We study the low temperature magneto-transport properties of several highly
disordered amorphous Indium oxide(a:InO) samples. Simultaneously fabricated
devices comprising a 2-dimensional (2D) film and 10 $\mu$m long wires of
different widths were measured to investigate the effect of size as we approach
the 1D limit, which is around 4 times the correlation length, and happens to be
around 100 nm for a:InO. The film and the wires showed magnetic field ({\it B})
induced superconductor to insulator transition (SIT). In the superconducting
side, the resistance increased with decrease in wire width, whereas, an
opposite trend is observed in the insulating side. We find that this effect can
be explained in light of charge-vortex duality picture of the SIT. Resistance
of the 2D film follows an activated behavior over the temperature ($T$),
whereas, the wires show a crossover from the high-$T$ activated to a
$T$-independent behavior. At high temperature regime the wires' resistance
follow the film's until they deviate and became independent of $T$. We find
that temperature at which this deviation occurs evolve with magnetic field and
the width of the wire, which show the effect of finite size on the transport.",1509.02033v2
2015-09-18,Effect of Strain on Ferroelectric Field Effect in Strongly Correlated Oxide Sm$_{0.5}$Nd$_{0.5}$NiO$_3$,"We report the effect of epitaxial strain on the magnitude and retention of
the ferroelectric field effect in high quality PbZr$_{0.3}$Ti$_{0.7}$O$_3$
(PZT)/3.8-4.3 nm Sm$_{0.5}$Nd$_{0.5}$NiO$_3$ (SNNO) heterostructures grown on
(001) LaAlO$_3$ (LAO) and SrTiO$_3$ (STO) substrates. For SNNO on LAO, which
exhibits a first-order metal-insulator transition (MIT), switching the
polarization of PZT induces a 10 K shift in the transition temperature
$T_{MI}$, with a maximum resistance change between the on and off states of
$\Delta$$R$/$R_{on}$ ~75%. In sharp contrast, only up to 5% resistance change
has been induced in SNNO on STO, where the MIT is second-order, with the
modulation of $T_{MI}$ negligibly small. We also observe thermally activated
retention of the off state resistance $R_{off}$ in both systems, with the
activation energy of 22 meV (28 meV) for devices on LAO (STO). The time
dynamics and thermal response of the field effect instability points to
phonon-assisted interfacical trapping of charged mobile defects, which are
attributed to strain induced oxygen vacancies. At room temperature, $R_{off}$
stabilizes at ~55% and ~19% of the initial switching levels for SNNO on LAO and
STO, respectively, reflecting the significantly different oxygen vacancy
densities in these two systems. Our results reveal the critical role of strain
in engineering and modeling the complex oxide composite structures for
nanoelectronic and spintronic applications.",1509.05493v2
2015-09-19,Collapse of the low temperature insulating state in Cr-doped V$_2$O$_3$ thin films,"We have grown epitaxial Cr-doped V$_2$O$_3$ thin films with Cr concentrations
between $0$ and $20\%$ on $(0001)$-Al$_2$O$_3$ by oxygen-assisted molecular
beam epitaxy. For the highly doped samples (> $3\%$), a regular and monotonous
increase of the resistance with decreasing temperature is measured. Strikingly,
in the low doping samples (between $1\%$ and $3\%$), a collapse of the
insulating state is observed with a reduction of the low temperature
resistivity by up to 5 orders of magnitude. A vacuum annealing at high
temperature of the films recovers the low temperature insulating state for
doping levels below $3\%$ and increases the room temperature resistivity
towards the values of Cr-doped V$_2$O$_3$ single crystals. It is well-know that
oxygen excess stabilizes a metallic state in V$_2$O$_3$ single crystals. Hence,
we propose that Cr doping promotes oxygen excess in our films during deposition
leading to the collapse of the low temperature insulating state at low Cr
concentrations. These results suggest that slightly Cr-doped V$_2$O$_3$ films
can be interesting candidates for field effect devices.",1509.05866v1
2015-10-23,Identifying lineage effects when controlling for population structure improves power in bacterial association studies,"Bacteria pose unique challenges for genome-wide association studies (GWAS)
because of strong structuring into distinct strains and substantial linkage
disequilibrium across the genome. While methods developed for human studies can
correct for strain structure, this risks considerable loss- of-power because
genetic differences between strains often contribute substantial phenotypic
variability. Here we propose a new method that captures lineage-level
associations even when locus-specific associations cannot be fine-mapped. We
demonstrate its ability to detect genes and genetic variants underlying
resistance to 17 antimicrobials in 3144 isolates from four taxonomically
diverse clonal and recombining bacteria: Mycobacterium tuberculosis,
Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae. Strong
selection, recombination and penetrance confer high power to recover known
antimicrobial resistance mechanisms, and reveal a candidate association between
the outer membrane porin nmpC and cefazolin resistance in E. coli. Hence our
method pinpoints locus-specific effects where possible, and boosts power by
detecting lineage-level differences when fine-mapping is intractable.",1510.06863v3
2016-07-26,Resistive Tearing Instability in Electron-MHD: Application to Neutron Star Crusts,"We study a resistive tearing instability developing in a system evolving
through the combined effect of Hall drift in the Electron-MHD limit and Ohmic
dissipation. We explore first the exponential growth of the instability in the
linear case and we find the fastest growing mode, the corresponding eigenvalues
and dispersion relation. The instability growth rate scales as $\gamma \propto
B^{2/3} \sigma^{-1/3}$ where $B$ is the magnetic field and $\sigma$ the
electrical conductivity. We confirm the development of the tearing resistive
instability in the fully non-linear case, in a plane parallel configuration
where the magnetic field polarity reverses, through simulations of systems
initiating in Hall equilibrium with some superimposed perturbation. Following a
transient phase, during which there is some minor rearrangement of the magnetic
field, the perturbation grows exponentially. Once the instability is fully
developed the magnetic field forms the characteristic islands and X-type
reconnection points, where Ohmic decay is enhanced. We discuss the implications
of this instability for the local magnetic field evolution in neutron stars'
crusts, proposing that it can contribute to heating near the surface of the
star, as suggested by models of magnetar post-burst cooling. In particular, we
find that a current sheet a few meters thick, covering as little as $1\%$ of
the total surface can provide $10^{42}~$erg in thermal energy within a few
days. We briefly discuss applications of this instability in other systems
where the Hall effect operates such as protoplanetary discs and space plasmas.",1607.07874v2
2016-07-29,Using a terrestrial laser scanner to characterize vegetation-induced flow resistance in a controlled channel,"Vegetation characteristics providing spatial heterogeneity at the channel
reach scale can produce complex flow patterns and the relationship between
plant patterns morphology and flow resistance is still an open question (Nepf
2012). Unlike experiments in laboratory, measuring the vegetation
characteristics related to flow resistance on open channel in situ is
difficult. Thanks to its high resolution and light weight, scanner lasers allow
now to collect in situ 3D vegetation characteristics. In this study we used a
1064 nm usual Terrestrial Laser Scanner (TLS) located 5 meters at nadir above a
8 meters long equipped channel in order to both i) characterize the vegetation
structure heterogeneity within the channel form a single scan (blockage factor,
canopy height) and ii) to measure the 2D water level all over the channel
during steady flow within a few seconds scan. This latter measuring system was
possible thanks to an additive dispersive product sprinkled at the water
surface. Vegetation characteristics and water surfaces during steady flows from
6 different plant spatial design on channel bottom for 4 plant species were
thus measured. Vegetation blockage factors at channel scale were estimated from
TLS points clouds and analyzed.",1608.02483v1
2016-10-09,Chaos-based Wireless Communication Resisting Multipath Effects,"In additive white gaussian noise (AWGN) channel, chaos has been proved to be
the optimal coherent communication waveform in the sense of using very simple
matched filter to maximize the signal-to-noise ratio (SNR). Recently, Lyapunov
exponent spectrum of the chaotic signals after being transmitted through a
wireless channel has been shown to be unaltered, paving the way for wireless
communication using chaos. In wireless communication systems, inter-symbol
interference (ISI) caused by multipath propagation is one of the main obstacles
to achieve high bit transmission rate and low bit error rate (BER). How to
resist multipath effect is a fundamental problem in a chaos-based wireless
communication system (CWCS). In this paper, implementation of a CWCS is
presented. It is built to transmit chaotic signals generated by a hybrid
dynamical system and then to filter the received signals by using the
corresponding matched filter to decrease the noise effect and to detect the
binary information. We find that the multipath effect can be effectively
resisted by regrouping the return map of the received signal and by setting the
corresponding threshold based on the available information. We show that the
optimal threshold is a function of the channel parameters and of the
transmitted information symbols. Practically, the channel parameters are
time-variant, and the future information symbols are unavailable. In this case,
a suboptimal threshold (SOT) is proposed, and the BER using the SOT is derived
analytically. Simulation results show that the CWCS achieves a remarkable
competitive performance even under inaccurate channel parameters.",1611.02325v3
2016-11-22,Sampling Random Spanning Trees Faster than Matrix Multiplication,"We present an algorithm that, with high probability, generates a random
spanning tree from an edge-weighted undirected graph in
$\tilde{O}(n^{4/3}m^{1/2}+n^{2})$ time (The $\tilde{O}(\cdot)$ notation hides
$\operatorname{polylog}(n)$ factors). The tree is sampled from a distribution
where the probability of each tree is proportional to the product of its edge
weights. This improves upon the previous best algorithm due to Colbourn et al.
that runs in matrix multiplication time, $O(n^\omega)$. For the special case of
unweighted graphs, this improves upon the best previously known running time of
$\tilde{O}(\min\{n^{\omega},m\sqrt{n},m^{4/3}\})$ for $m \gg n^{5/3}$ (Colbourn
et al. '96, Kelner-Madry '09, Madry et al. '15).
  The effective resistance metric is essential to our algorithm, as in the work
of Madry et al., but we eschew determinant-based and random walk-based
techniques used by previous algorithms. Instead, our algorithm is based on
Gaussian elimination, and the fact that effective resistance is preserved in
the graph resulting from eliminating a subset of vertices (called a Schur
complement). As part of our algorithm, we show how to compute
$\epsilon$-approximate effective resistances for a set $S$ of vertex pairs via
approximate Schur complements in $\tilde{O}(m+(n + |S|)\epsilon^{-2})$ time,
without using the Johnson-Lindenstrauss lemma which requires $\tilde{O}(
\min\{(m + |S|)\epsilon^{-2}, m+n\epsilon^{-4} +|S|\epsilon^{-2}\})$ time. We
combine this approximation procedure with an error correction procedure for
handing edges where our estimate isn't sufficiently accurate.",1611.07451v2
2016-11-30,Reconnection and particle acceleration in interacting flux ropes I. Magnetohydrodynamics and test particles in 2.5D,"Magnetic reconnection and non-thermal particle distributions associated with
current-driven instabilities are investigated by means of resistive
magnetohydrodynamics (MHD) simulations combined with relativistic test particle
methods. We propose a system with two parallel, repelling current channels in
an initially force-free equilibrium, as a simplified representation of flux
ropes in a stellar magnetosphere. The current channels undergo a rotation and
separation on Alfv\'enic timescales, forming secondary islands and (up to
tearing unstable) current sheets in which non-thermal energy distributions are
expected to develop. Using the recently developed particle module of our
open-source grid-adaptive MPI-AMRVAC software, we simulate MHD evolution
combined with test particle treatments in MHD snapshots. We explore under which
plasma-$\beta$ conditions the fastest reconnection occurs in two-and-a-half
dimensional (2.5D) scenarios and in these settings test particles are evolved.
We quantify energy distributions, acceleration mechanisms, relativistic
corrections to the particle equations of motion and effects of resistivity in
magnetically dominated proton-electron plasmas. Due to large resistive electric
fields and indefinite acceleration of particles in the infinitely long current
channels, hard energy spectra are found in 2.5D configurations. Solutions to
these numerical artifacts are proposed for both 2.5D setups and future 3D work.
We discuss the magnetohydrodynamics of an additional kink instability in 3D
setups and the expected effects on energy distributions. The obtained results
hold as a proof-of-principle for test particle approaches in MHD simulations,
relevant to explore less idealised scenarios like solar flares and more exotic
astrophysical phenomena, like black hole flares, magnetar magnetospheres and
pulsar wind nebulae.",1611.09966v2
2016-12-06,Pressure-induced magnetic transition exceeding 30 K in the Yb-based heavy fermion superconductor $β$-YbAlB$_4$,"Measurements of the electric resistivity $\rho(T)$ under pressure up to 8 GPa
were performed on high-quality single-crystals of the Yb-based heavy fermion
system $\beta$-YbAlB$_4$ in the temperature range $2<T<$ 300 K. In the
resistivity data, we observed pressure-induced magnetic ordering above the
critical pressure $P_{\rm c} \sim$ 2 GPa. Clear difference in the phase diagram
under pressure using two types of pressure mediums indicates that the
transition temperature may be further enhanced under application of uniaxial
pressure. With pressure, this phase transition temperature $T_{\rm M}$ is
enhanced reaching 32 K at 8 GPa, which is the highest transition temperature so
far recorded for the Yb-based heavy fermion compounds. The power-law exponent
$\alpha$ in $\rho=\rho_0+ AT^{\alpha}$ below $T_{\rm M}$ gradually changes from
3/2 to 5/2 with increasing pressure from 2 to 8 GPa. In contrast, the
resistivity exhibits a $T$-linear behavior in the temperature range 2 $\le T
\le$ 20 K and is insensitive to pressure below $P_{\rm c}$. In this pressure
regime, the magnetization is also nearly independent of pressure and shows no
anomaly above 2 K. Our results indicate that a quantum critical point for
$\beta$-YbAlB$_4$ is also located near $P_{\rm c}$ in addition to the strange
metal region near the ambient pressure.",1612.01800v2
2017-10-07,Intrinsically shunted Josephson junctions for electronics applications,"Conventional Josephson metal-insulator-metal devices are inherently
underdamped and exhibit hysteretic current-voltage response due to a very high
subgap resistance compared to that in the normal state. At the same time,
overdamped junctions with single-valued characteristics are needed for most
superconducting digital applications. The usual way to overcome the hysteretic
behavior is to place an external low-resistance normal-metal shunt in parallel
with each junction. Unfortunately, such solution results in a considerable
complication of the circuitry design and introduces parasitic inductance
through the junction. This paper provides a concise overview of some generic
approaches that have been proposed in order to realize internal shunting in
Josephson heterostructures with a barrier that itself contains the desired
resistive component. The main attention is paid to self-shunted devices with
local weak-link transmission probabilities so strongly disordered in the
interface plane that transmission probabilities are tiny for the main part of
the transition region between two superconducting electrodes, while a small
part of the interface is well transparent. We consider the possibility of
realizing a universal bimodal distribution function and emphasize advantages of
such junctions that can be considered as a new class of self-shunted Josephson
devices promising for practical applications in superconducting electronics
operating at 4.2 K.",1710.02707v1
2018-03-13,Graph Ranking and the Cost of Sybil Defense,"Ranking functions such as PageRank assign numeric values (ranks) to nodes of
graphs, most notably the web graph. Node rankings are an integral part of
Internet search algorithms, since they can be used to order the results of
queries. However, these ranking functions are famously subject to attacks by
spammers, who modify the web graph in order to give their own pages more rank.
We characterize the interplay between rankers and spammers as a game. We define
the two critical features of this game, spam resistance and distortion, based
on how spammers spam and how rankers protect against spam. We observe that all
the ranking functions that are well-studied in the literature, including the
original formulation of PageRank, have poor spam resistance, poor distortion,
or both. Finally, we study Min-PPR, the form of PageRank used at Google itself,
but which has received no (theoretical or empirical) treatment in the
literature. We prove that Min-PPR has low distortion and high spam resistance.
A secondary benefit is that Min-PPR comes with an explicit cost function on
nodes that shows how important they are to the spammer; thus a ranker can focus
their spam-detection capacity on these vulnerable nodes. Both Min-PPR and its
associated cost function are straightforward to compute.",1803.05001v5
2018-04-25,Jet launching in resistive GR-MHD black hole - accretion disk systems,"We investigate the launching mechanism of relativistic jets from black hole
sources, in particular the strong winds from the surrounding accretion disk.
Numerical investigations of the disk wind launching - the simulation of the
accretion-ejection transition - have so far almost only been done for
non-relativistic systems. From these simulations we know that resistivity, or
magnetic diffusivity, plays an important role for the launching process. Here,
we extend this treatment to general relativistic magnetohydrodynamics (GR-MHD)
applying the resistive GR-MHD code rHARM. Our model setup considers a thin
accretion disk threaded by a large-scale open magnetic field. We run a series
of simulations with different Kerr parameter, field strength and diffusivity
level. Indeed we find strong disk winds with, however, mildly relativistic
speed, the latter most probably due to our limited computational domain.
Further, we find that magnetic diffusivity lowers the efficiency of accretion
and ejection, as it weakens the efficiency of the magnetic lever arm of the
disk wind. As major driving force of the disk wind we disentangle the toroidal
magnetic field pressure gradient, however,magneto-centrifugal driving may also
contribute. Black hole rotation in our simulations suppresses the accretion
rate due to an enhanced toroidal magnetic field pressure that seems to be
induced by frame-dragging. Comparing the energy fluxes from the
Blandford-Znajek-driven central spine and the surrounding disk wind, we find
that the total electromagnetic energy flux is dominated by the total matter
energy flux of the disk wind (by a factor 20). The kinetic energy flux of the
matter outflow is comparatively small and comparable to the Blandford-Znajek
electromagnetic energy flux.",1804.09652v1
2018-05-18,Radio frequency performance projection and stability trade-off of h-BN encapsulated graphene field-effect transistors,"Hexagonal boron nitride (h-BN) encapsulation significantly improves carrier
transport in graphene. This work investigates the benefit of implementing the
encapsulation technique in graphene field-effect transistors (GFET) in terms of
their radio frequency (RF) performance. For such a purpose, a drift-diffusion
self-consistent simulator is prepared to get the GFET electrical
characteristics. Both the mobility and saturation velocity information are
obtained by means of an ensemble Monte Carlo simulator upon considering the
relevant scattering mechanisms that affect carrier transport. RF figures of
merit are simulated using an accurate small-signal model that includes
non-reciprocal capacitances. Results reveal that the cutoff frequency could
scale up to the physical limit given by the inverse of the transit time.
Projected maximum oscillation frequencies, in the order of few THz, are
expected to exceed the values demonstrated by InP and Si based RF transistors.
The existing trade-off between power gain and stability and the role played by
the gate resistance are also studied. High power gain and stability are
feasible even if the device is operated far away from current saturation.
Finally, the benefits of device unilateralization and the exploitation of the
negative differential resistance region to get negative-resistance gain are
discussed.",1805.07138v4
2018-06-21,Development and Characterization of 6-gap Bakelite Multi-gap Resistive Plate Chamber,"The Multi-gap Resistive Plate Chamber (MRPC) is an advanced form of Resistive
Plate Chamber (RPC) detector where the gas gap is divided into sub-gaps. MRPCs
are known for their good time resolution and detection efficiency for charged
particles. They have found suitable applications in several high energy physics
experiments like ALICE in LHC, CERN, Geneva, Switzerland, and STAR in RHIC,
BNL, USA. As they have very good time resolution and are of low cost, they can
be a suitable replacement for very expensive scintillators used in Positron
Emission Tomography Imaging. The MRPCs that are being used nowadays are
developed with glass electrodes. We have made an attempt to develop a 6-gap
MRPC using bakelite electrodes. The outer electrodes are of dimensions 15 cm
$\times$ 15 cm $\times$ 0.3 cm and the inner electrodes are of dimension 14 cm
$\times$ 14 cm $\times$ 0.05 cm. The glossy finished electrode surfaces have
not been treated with any oil like linseed, silicone for smoothness. The
performance of the detector has been studied measuring the efficiency, noise
rate and time resolution with cosmic rays. This effort is towards the
development of a prototype for Positron Emission Tomography with the
Time-Of-Flight technique using MRPCs. Details of the development procedure and
performance studies have been presented here.",1806.08265v1
2018-06-23,Bilayer h-BN Barriers for Tunneling Contacts in Fully-Encapsulated Monolayer $\mathbf{MoSe_2}$ Field-Effect Transistors,"The performance of electronic and spintronic devices based on two-dimensional
semiconductors (2D SC) is largely dependent on the quality and resistance of
the metal/SC electrical contacts, as well as preservation of the intrinsic
properties of the SC channel. Direct Metal/SC interaction results in highly
resistive contacts due to formation of large Schottky barriers and considerably
affects the properties of the 2D SC. In this work, we address these two
important issues in monolayer $\mathrm{MoSe_2}$ Field-Effect transistors
(FETs). We encapsulate the $\mathrm{MoSe_2}$ channel with hexagonal Boron
Nitride (h-BN), using bilayer h-BN at the metal/SC interface. The bilayer h-BN
eliminates the metal/$\mathrm{MoSe_2}$ chemical interactions, preserves the
electrical properties of $\mathrm{MoSe_2}$ and reduces the contact resistances
by prevention of Fermi-level pinning. We investigate electrical transport in
the monolayer $\mathrm{MoSe_2}$ FETs that yields close to intrinsic electron
mobilities ($\approx 26\ \mathrm{cm^2 V^{-1} s^{-1}}$) even at room
temperature. Moreover, we experimentally study the charge transport through
Metal/h-BN/$\mathrm{MoSe_2}$ tunnel contacts and we explicitly show that the
dielectric bilayer of h-BN provides highly efficient gating (tuning the Fermi
energy) of the $\mathrm{MoSe_2}$ channel at the contact regions even with small
biases. Also we provide a theoretical model that allows to understand and
reproduce the experimental $I-V$ characteristics of the contacts. These
observations give an insight into the electrical behavior of the metal/h-BN/2D
SC heterostructure and introduce bilayer h-BN as a suitable choice for high
quality tunneling contacts that allows for low energy charge and spin
transport.",1806.08954v1
2018-09-25,Neural Networks with Structural Resistance to Adversarial Attacks,"In adversarial attacks to machine-learning classifiers, small perturbations
are added to input that is correctly classified. The perturbations yield
adversarial examples, which are virtually indistinguishable from the
unperturbed input, and yet are misclassified. In standard neural networks used
for deep learning, attackers can craft adversarial examples from most input to
cause a misclassification of their choice.
  We introduce a new type of network units, called RBFI units, whose non-linear
structure makes them inherently resistant to adversarial attacks. On
permutation-invariant MNIST, in absence of adversarial attacks, networks using
RBFI units match the performance of networks using sigmoid units, and are
slightly below the accuracy of networks with ReLU units. When subjected to
adversarial attacks, networks with RBFI units retain accuracies above 90% for
attacks that degrade the accuracy of networks with ReLU or sigmoid units to
below 2%. RBFI networks trained with regular input are superior in their
resistance to adversarial attacks even to ReLU and sigmoid networks trained
with the help of adversarial examples.
  The non-linear structure of RBFI units makes them difficult to train using
standard gradient descent. We show that networks of RBFI units can be
efficiently trained to high accuracies using pseudogradients, computed using
functions especially crafted to facilitate learning instead of their true
derivatives. We show that the use of pseudogradients makes training deep RBFI
networks practical, and we compare several structural alternatives of RBFI
networks for their accuracy.",1809.09262v1
2019-09-22,Ship resistance when operating in floating ice floes: a combined CFD&DEM approach,"Whilst climate change is transforming the Arctic into a navigable ocean where
small ice floes are floating on the sea surface, the effect of such ice
conditions on ship performance has yet to be understood. The present work
combines a set of numerical methods to simulate the ship-wave-ice interaction
in such ice conditions. Particularly, Computational Fluid Dynamics is applied
to provide fluid solutions for the floes and it is incorporated with the
Discrete Element Method to govern ice motions and account for ship-ice/ice-ice
collisions, by which, the proposed approach innovatively includes wave effects
in the interaction. In addition, this work introduces two algorithms that can
implement computational models with natural ice-floe fields, which takes
randomness into consideration thus achieving high-fidelity modelling of the
problem. Following validation against experiments, the model is shown accurate
in predicting the ice-floe resistance of a ship, and then a series of
simulations are performed to investigate how the resistance is influenced by
ship speed, ice concentration, ice thickness and floe diameter. This paper
presents a useful approach that can provide power estimates for Arctic shipping
and has the potential to facilitate other polar engineering purposes.",1909.10018v1
2014-08-26,Mean-field dynamics of tumor growth and control using low-impact chemoprevention,"Cancer poses danger because of its unregulated growth, development of
resistant subclones, and metastatic spread to vital organs. Although the major
transitions in cancer development are increasingly well understood, we lack
quantitative theory for how chemoprevention is predicted to affect survival. We
employ master equations and probability generating functions, the latter well
known in statistical physics, to derive the dynamics of tumor growth as a
mean-field approximation. We also study numerically the associated stochastic
birth-death process. Our findings predict exponential tumor growth when a
cancer is in its early stages of development and hyper-exponential growth
thereafter. Numerical simulations are in general agreement with our analytical
approach. We evaluate how constant, low impact treatments affect both
neoplastic growth and the frequency of chemoresistant clones. We show that
therapeutic outcomes are highly predictable for treatments starting either
sufficiently early or late in terms of initial tumor size and the initial
number of chemoresistant cells, whereas stochastic dynamics dominate therapies
starting at intermediate neoplasm sizes, with high outcome sensitivity both in
terms of tumor control and the emergence of resistant subclones. The outcome of
chemoprevention can be understood in terms of both minimal physiological
impacts resulting in long-term control and either preventing or slowing the
emergence of resistant subclones. We argue that our model and results can also
be applied to the management of early, clinically detected cancers after tumor
excision.",1408.6052v1
2011-07-22,Ferromagnetic Quantum Critical Endpoint in UCoAl,"Resistivity and magnetostriction measurements were performed at high magnetic
fields and under pressure on UCoAl. At ambient pressure, the 1st order
metamagnetic transition at H_m ~ 0.7 T from the paramagnetic ground state to
the field-induced ferromagnetic state changes to a crossover at finite
temperature T_0 ~11 K. With increasing pressure, H_m linearly increases, while
T_0 decreases and is suppressed at the quantum critical endpoint (QCEP, P_QCEP
~ 1.5 GPa, H_m ~ 7 T). At higher pressure, the value of H_m identified as a
crossover continuously increases, while a new anomaly appears above P_QCEP at
higher field H* in resistivity measurements. The field dependence of the
effective mass (m*) obtained by resistivity and specific heat measurements
exhibits a step-like drop at H_m at ambient pressure. With increasing pressure,
it gradually changes into a peak structure and a sharp enhancement of m* is
observed near the QCEP. Above P_QCEP, the enhancement of m* is reduced, and a
broad plateau is found between H_m and H*. We compare our results on UCoAl with
those of the ferromagnetic superconductor UGe2 and the itinerant metamagnetic
ruthenate Sr3Ru2O7.",1107.4590v1
2013-12-02,Revisiting heat capacity of bulk polycrystalline YBa2Cu3O7-δ,"In this letter, we present the superconducting property characterization of a
phase pure reasonably good quality YBa2Cu3O7-{\delta} sample. Studied compound
is crystallized in orthorhombic Pmmm space group with lattice parameters a, b,
and c are 3.829(2) {\AA}, 3.887(1) {\AA} and 11.666(3) {\AA} respectively. Bulk
superconductivity is observed below 90K as evidenced by resistivity and dc/ac
magnetization measurements. The resistivity under magnetic field ({\rho}TH)
measurements showed clearly both the intra-grain and inter-grain transitions,
which are supplemented by detailed (varying frequency and amplitude) ac
susceptibility studies as well. The upper critical field at 0K i.e., Hc2(0)
being determined from {\rho}TH measurements with 50% criteria of resistivity
drope is ~ 70 Tesla. Studied polycrystalline YBa2Cu3O7-{\delta} is subjected to
detailed heat capacity (CP) studies. Cp exhibited well defined anomaly at below
90 K, which decreases with applied field. Though the Cp anomaly/peak at Tc
reduces with applied field, the same is not completely suppressed in high
applied fields of up to 12 Tesla. The Sommerfeld constant ({\gamma}) and Debye
temperature ({\Theta}D) as determined from low temperature fitting of CP(T)
data to Sommerfeld-Debye model, are 10.65 mJ/mole-K2 and 312.3 K respectively.
The results are compared with existing literature on bulk polycrystalline
superconducting YBa2Cu3O7-{\delta} sample",1312.0417v2
2013-12-22,"Crystal growth, transport phenomena and two gap superconductivity in the mixed alkali metal $(K_{1-z}Na_z)_{x}Fe_{2-y}Se_2$ iron selenide","Using the self-flux technique we grew superconducting
$(K_{1-z}Na_z)_{x}Fe_{2-y}Se_2$ (z = 0.3) single crystals. The EDX mapping
revealed the uniform elements distribution on the crystal surface while the XRD
measurements indicate that the crystals are compositionally inhomogenous on
nanoscale. The physical properties of the as-prepared sample are characterized
by electrical resistivity, magnetization and specific heat measurements.
Resistivity measurements show the onset of the superconducting transition at 33
K and zero resistivity at 31.7 K. The large upper critical field $H_{c2}$(0)
was estimated as high as about of 140 T for the in-plane field and 38 T for the
out-of-plane field. The anisotropy of $H_{c2}^{ab}(0)/H_{c2}^{c}(0)$ and
coherence lengths $\xi^{ab}(0)/\xi^{c}$(0) was found to be around 3.7. The
pioneer studies by multiple Andreev reflections effect spectroscopy
(""break-junction"" technique) revealed the presence of two anisotropic
superconducting gaps $\Delta_L\,=\,(9.3\pm1.5)\,meV$,
$\Delta_S\,=\,(1.9\pm0.4)\,meV$, and provided measuring of the $\Delta_L$(T)
temperature dependence. The BCS-ratio for the large gap
$2\Delta_L/k_BT_c^{bulk}\,\approx\,6.3$ points to a strong electron-boson
coupling in the ""driving"" condensate characterized by $\Delta_L$ order
parameter.",1312.6441v2
2014-11-27,Electron-phonon interaction in a spin-orbit coupled quantum wire with a gap,"Interaction between electron and acoustic phonon in an in-plane magnetic
field induced gapped quantum wire with Rashba spin-orbit interaction is
studied. We calculate acoustic phonon limited resistivity ($\rho$) and
phonon-drag thermopower ($S_g$) due to two well known mechanisms of
electron-phonon interaction namely, deformation potential (DP) and
piezoelectric (PE) scattering. In the so called Bloch-Gruneisen temperature
limit both $\rho$ and $S_g$ depend on temperature ($T$) in a power law fashion
i.e. $\rho$ or $S_g\sim T^{\nu_T}$. For resistivity, $\nu_T$ takes the value
$5$ and $3$ due to DP and PE scattering respectively. On the other hand,
$\nu_T$ is $4$ and $2$ due to DP and PE scattering, respectively for
phonon-drag thermopower. Additionally, we find numerically that $\nu_T$ depends
on Rashba parameter ($\alpha$) and electron density ($n$). The dependence of
$\nu_T$ on $\alpha$ becomes more prominent at lower density. We also study the
variations of $\rho$ and $S_g$ with carrier density in the Bloch-Gruneisen
regime. Through a numerical analysis a similar power law dependence $\rho$ or
$S_g\sim n^{-\nu_n}$ is established in which the effective exponent $\nu_n$
undergoes a smooth transition from a low density behavior to a high density
behavior. At a higher density regime, $\nu_n$ matches excellently with the
value obtained from theoretical arguments. Approximate analytical expressions
for both resistivity and phonon-drag thermopower in the Bloch-Gruneisen regime
are given.",1411.7620v1
2019-02-01,Observation of Two Collapsed Phases in CaRbFe4As4,"We report the observation of the pressure-induced, fully-collapsed tetragonal
phase of CaRbFe4As4 for P~ 22 GPa via high-pressure x-ray diffraction and
magnetotransport measurements. The x-ray measurements, along with resistivity
measurements, show that there is an initial half-collapsed tetragonal phase for
6 < P < 22 GPa, in which superconductivity is continuously suppressed from Tc=
35K at P= 3.1 GPa to Tc <2K for P >17.2 GPa, as well as signs of the
fully-collapsed tetragonal phase near P=22 GPa. Density functional calculations
suggest that both of these transitions are driven by increased As-As bonding,
first across the Ca layer, and then at the second transition, across the Rb
layer. Although electrical resistivity measurements in the fully-collapsed
tetragonal phase do not show superconductivity, there is a change in the slope
of both the Hall coefficient and the longitudinal resistance near 22 GPa,
suggesting a strong correlation between the electronic and lattice degrees of
freedom in this new iron-based superconductor.",1902.00472v3
2019-02-04,Gauge phonon dominated resistivity in twisted bilayer graphene near magic angle,"Recent experiments on twisted bilayer graphene (tBG) close to magic angle
show that a small relative rotation in a van der Waals heterostructure greatly
alters its electronic properties. We consider various scattering mechanisms and
show that the carrier transport in tBG is dominated by a combination of charged
impurities and acoustic gauge phonons. Charged impurities still dominate at low
temperature and densities because of the inability of Dirac fermions to screen
long-range Coulomb potentials at charge neutrality; however, the gauge phonons
dominate for most of the experimental regime because although they couple to
current, they do not induce charge and are therefore unscreened by the large
density of states close to magic angle. We show that the resistivity has a
strong monotonically decreasing carrier density dependence at low temperature
due to charged impurity scattering, and weak density dependence at high
temperature due to gauge phonons. Away from charge neutrality, the resistivity
increases with temperature, while it does the opposite close to the Dirac
point. A non-monotonic temperature dependence observed only at low temperature
and carrier density is a signature of our theory that can be tested in
experimentally available samples.",1902.01405v1
2019-05-06,A Differential Game Approach to Decentralized Virus-Resistant Weight Adaptation Policy over Complex Networks,"Increasing connectivity of communication networks enables large-scale
distributed processing over networks and improves the efficiency for
information exchange. However, malware and virus can take advantage of the high
connectivity to spread over the network and take control of devices and servers
for illicit purposes. In this paper, we use an SIS epidemic model to capture
the virus spreading process and develop a virus-resistant weight adaptation
scheme to mitigate the spreading over the network. We propose a differential
game framework to provide a theoretic underpinning for decentralized mitigation
in which nodes of the network cannot fully coordinate, and each node determines
its own control policy based on local interactions with neighboring nodes. We
characterize and examine the structure of the Nash equilibrium, and discuss the
inefficiency of the Nash equilibrium in terms of minimizing the total cost of
the whole network. A mechanism design through a penalty scheme is proposed to
reduce the inefficiency of the Nash equilibrium and allow the decentralized
policy to achieve social welfare for the whole network. We corroborate our
results using numerical experiments and show that virus-resistance can be
achieved by a distributed weight adaptation scheme.",1905.02237v2
2020-03-29,Deficiency of the scaling collapse as an indicator of a superconductor-insulator quantum phase transition,"Finite-size scaling analysis is a well-accepted method for identification and
characterization of quantum phase transitions (QPTs) in superconducting,
magnetic and insulating systems. We formally apply this analysis in the form
suitable for QPTs in 2-dimensional superconducting films to magnetic-field
driven superconductor-metal transition in 1-dimensional MoGe nanowires. Despite
being obviously inapplicable to nanowires, the 2d scaling equation leads to a
high-quality scaling collapse of the nanowire resistance in the temperature and
resistance ranges comparable or better to what is accepted in the analysis of
the films. Our results suggest that the appearance and the quality of the
scaling collapse by itself is not a reliable indicator of a QPT. We have also
observed a sign-change of the zero-bias anomaly (ZBA) in the non-linear
resistance, occurring exactly at the critical field of the accidental QPT. This
behavior is often taken as an additional confirmation of the transition. We
argue that in nanowires, the non-linearity is caused by electron heating and
has no relation to the critical fluctuations. Our observation suggests that
similar to the scaling collapse, the sign-change of ZBA can be a misleading
indicator of QPT.",2003.13157v2
2016-03-05,Stationary Axisymmetric Configuration of the Resistive Thick Accretion Tori around a Schwarzschild Black Hole,"We examine a thick accretion disc in the presence of external gravity and
intrinsic dipolar magnetic field due to a non-rotating central object. In this
paper, we generalize the Newtonian theory of stationary axisymmetric resistive
tori of Tripathy, Prasanna $\&$ Das (1990) by including the fully general
relativistic features. If we are to obtain the steady state configuration, we
have to take into account the finite resistivity for the magnetofluid in order
to avoid the piling up of the field lines anywhere in the accretion discs. The
efficient value of conductivity must be much smaller than the classical
conductivity to be astrophysically interesting. The accreting plasma in the
presence of an external dipole magnetic field gives rise to a current in the
azimuthal direction. The azimuthal current produced due to the motion of the
magnetofluid modifies the magnetic field structure inside the disc and
generates a poloidal magnetic field for the disc. The solutions we have found
show that the radial inflow, pressure and density distributions are strongly
modified by the electrical conductivity both in relativistic and Newtonian
regimes. However, the range of conductivity coefficient is different for both
regimes, as well as that of the angular momentum parameter and the radius of
the innermost stable circular orbit. Furthermore, it is shown that the
azimuthal velocity of the disc which is not dependent on conductivity is
sub-Keplerian in all radial distances for both regimes. Owing to the presence
of pressure gradient and magnetic forces. This work may also be important for
the general relativistic computational magnetohydrodynamics that suffers from
the lack of exact analytic solutions that are needed to test computer codes.",1603.01712v1
2016-03-15,The Resistive-Plate WELL with Argon mixtures - a robust gaseous radiation detector,"A thin single-element THGEM-based, Resistive-Plate WELL (RPWELL) detector was
operated with 150 GeV/c muon and pion beams in Ne/(5%CH$_4$), Ar/(5%CH$_4$) and
Ar/(7%CO$_2$); signals were recorded with 1 cm$^2$ square pads and SRS/APV25
electronics. Detection efficiency values greater than 98% were reached in all
the gas mixtures, at average pad multiplicity of 1.2. The use of the
10$^9${\Omega}cm resistive plate resulted in a completely discharge-free
operation also in intense pion beams. The efficiency remained essentially
constant at 98-99% up to fluxes of $\sim$10$^4$Hz/cm$^2$, dropping by a few %
when approaching 10$^5$ Hz/cm$^2$. These results pave the way towards
cost-effective, robust, efficient, large-scale detectors for a variety of
applications in future particle, astro-particle and applied fields. A potential
target application is digital hadron calorimetry.",1603.04820v1
2017-07-27,Reconnection and particle acceleration in interacting flux ropes -- II. 3D effects on test particles in magnetically dominated plasmas,"We analyze particle acceleration in explosive reconnection events in
magnetically dominated proton-electron plasmas. Reconnection is driven by
large-scale magnetic stresses in interacting current-carrying flux tubes. Our
model relies on development of current-driven instabilities on macroscopic
scales. These tilt-kink instabilities develop in an initially force-free
equilibrium of repelling current channels. Using MHD methods we study a 3D
model of repelling and interacting flux tubes in which we simultaneously evolve
test particles, guided by electromagnetic fields obtained from MHD. We identify
two stages of particle acceleration; Initially particles accelerate in the
current channels, after which the flux ropes start tilting and kinking and
particles accelerate due to reconnection processes in the plasma. The explosive
stage of reconnection produces non-thermal energy distributions with slopes
that depend on plasma resistivity and the initial particle velocity. We also
discuss the influence of the length of the flux ropes on particle acceleration
and energy distributions. This study extends previous 2.5D results to 3D
setups, providing all ingredients needed to model realistic scenarios like
solar flares, black hole flares and particle acceleration in pulsar wind
nebulae: formation of strong resistive electric fields, explosive reconnection
and non-thermal particle distributions. By assuming initial energy
equipartition between electrons and protons, applying low resistivity in
accordance with solar corona conditions and limiting the flux rope length to a
fraction of a solar radius we obtain realistic energy distributions for solar
flares with non-thermal power law tails and maximum electron energies up to 11
MeV and maximum proton energies up to 1 GeV.",1707.08920v2
2016-09-23,Parallelization of JOREK-STARWALL for non-linear MHD simulations including resistive walls (Report of the EUROfusion High Level Support Team Projects JORSTAR/JORSTAR2),"Large scale plasma instabilities inside a tokamak can be influenced by the
currents flowing in the conducting vessel wall. This involves non linear plasma
dynamics and its interaction with the wall current. In order to study this
problem the code that solves the magneto-hydrodynamic (MHD) equations, called
JOREK [Huysmans G.T.A. and Czarny O. NF 47, 659 (2007); Czarny O. and Huysmans
G. JCP 227, 7423 (2008)], was coupled [Hoelzl M., et al. Journal of Physics:
Conference Series, 401, 012010 (2012)] with the model for the vacuum region and
the resistive conducting structure named STARWALL [Merkel P., Strumberger E.,
arXiv:150804911 (2015)]. The JOREK-STARWALL model has been already applied to
perform simulations of Vertical Displacement Events (VDEs), Resistive Wall
Modes (RWMs), Quiescent H-Mode, and vertical kick ELM triggering. At the
beginning of the project it was not possible to resolve the realistic wall
structure with a large number of finite element triangles due to the huge
consumption of memory and wall clock time by STARWALL and the corresponding
coupling routine in JOREK. Moreover, both the STARWALL code and the JOREK
coupling routine were only partially parallelized via OpenMP. The aim of this
project is to implement an MPI parallelization to reduce memory consumption and
execution time such that simulations with large resolutions become possible.",1609.07441v2
2018-07-03,Weak anti-localization of two-dimensional holes in germanium beyond the diffusive regime,"Gate-controllable spin-orbit coupling is often one requisite for spintronic
devices. For practical spin field-effect transistors, another essential
requirement is ballistic spin transport, where the spin precession length is
shorter than the mean free path such that the gate-controlled spin precession
is not randomized by disorder. In this letter, we report the observation of a
gate-induced crossover from weak localization to weak anti-localization in the
magneto-resistance of a high-mobility two-dimensional hole gas in a strained
germanium quantum well. From the magneto-resistance, we extract the
phase-coherence time, spin-orbit precession time, spin-orbit energy splitting,
and cubic Rashba coefficient over a wide density range. The mobility and the
mean free path increase with increasing hole density, while the spin precession
length decreases due to increasingly stronger spin-orbit coupling. As the
density becomes larger than $\sim6\times 10^{11}$cm$^{-2}$, the spin precession
length becomes shorter than the mean free path, and the system enters the
ballistic spin transport regime. We also report here the numerical methods and
code developed for calculating the magneto-resistance in the ballistic regime,
where the commonly used HLN and ILP models for analyzing weak localization and
anti-localization are not valid. These results pave the way toward
silicon-compatible spintronic devices.",1807.01400v1
2019-01-21,"Charge, lattice and magnetism across the valence crossover in EuIr$_2$Si$_2$ single crystals","We present a detailed study of the temperature evolution of the crystal
structure, specific heat, magnetic susceptibility and resistivity of single
crystals of the paradigmatic valence-fluctuating compound EuIr$_2$Si$_2$. A
comparison to stable-valent isostructural compounds EuCo$_2$Si$_2$ (with
Eu$^{3+}$), and EuRh$_2$Si$_2$, (with Eu$^{2+}$) reveals an anomalously large
thermal expansion indicative of the lattice softening associated to valence
fluctuations. A marked broad peak at temperatures around 65-75 K is observed in
specific heat, susceptibility and the derivative of resistivity, as thermal
energy becomes large enough to excite Eu into a divalent state, which localizes
one f electron and increases scattering of conduction electrons. In addition,
the intermediate valence at low temperatures manifests in a moderately
renormalized electron mass, with enhanced values of the Sommerfeld coefficient
in the specific heat and a Fermi-liquid-like dependence of resistivity at low
temperatures. The high residual magnetic susceptibility is mainly ascribed to a
Van Vleck contribution. Although the intermediate/fluctuating valence duality
is to some extent represented in the interconfiguration fluctuation model
commonly used to analyze data on valence-fluctuating systems, we show that this
model cannot describe the different physical properties of EuIr$_2$Si$_2$ with
a single set of parameters.",1901.06826v1
2019-06-12,Influence of 3D plasmoid dynamics on the transition from collisional to kinetic reconnection,"Within the resistive magnetohydrodynamic model, high-Lundquist number
reconnection layers are unstable to the plasmoid instability, leading to a
turbulent evolution where the reconnection rate can be independent of the
underlying resistivity. However, the physical relevance of these results
remains questionable for many applications. First, the reconnection electric
field is often well above the runaway limit, implying that collisional
resistivity is invalid. Furthermore, both theory and simulations suggest that
plasmoid formation may rapidly induce a transition to kinetic scales, due to
the formation of thin current sheets. Here, this problem is studied for the
first time using a first-principles kinetic simulation with a Fokker-Planck
collision operator in 3D. The low-$\beta$ reconnecting current layer thins
rapidly due to Joule heating before onset of the oblique plasmoid instability.
Linear growth rates for standard ($k_y = 0$) tearing modes agree with
semi-collisional boundary layer theory, but the angular spectrum of oblique
($|k_y|>0$) modes is significantly narrower than predicted. In the non-linear
regime, flux-ropes formed by the instability undergo complex interactions as
they are advected and rotated by the reconnection outflow jets, leading to a
turbulent state with stochastic magnetic field. In a manner similar to previous
2D results, super-Dreicer fields induce a transition to kinetic reconnection in
thin current layers that form between flux-ropes. These results may be testable
within new laboratory experiments.",1906.04867v1
2019-06-17,Non-equilibrium Green's Function and First Principle Approach to Modeling of Multiferroic Tunnel Junctions,"Recently, multiferroic tunnel junctions (MFTJs) have gained significant
spotlight in the literature due to its high tunneling electro-resistance
together with its non-volatility. In order to analyze such devices and to have
insightful understanding of its characteristics, there is a need for developing
a multi-physics modeling and simulation framework. The simulation framework
discussed in this paper is motivated by the scarcity of such multi-physics
studies in the literature. In this study, a theoretical analysis of MFTJs is
demonstrated using self-consistent analysis of spin-based non-equilibrium
Green's function (NEGF) method to estimate the tunneling current,
Landau-Khalatnikov (LK) equation to model the ferroelectric polarization
dynamics, together with landau-Lifshitz-Gilbert's (LLG) equations to capture
the magnetization dynamics. The spin-based NEGF method is equipped with a
magnetization dependent Hamiltonian that eases the modeling of the tunneling
electro-resistance (TER), tunneling magneto-resistance (TMR), and the
magnetoelectric effect (ME) in MFTJs. Moreover, we apply the first principle
calculations to estimate the screening lengths of the MFTJ electrodes that are
necessary for estimation of tunneling current. The simulation results of the
proposed framework are in good agreement with the experimental results.
Finally, a comprehensive analysis of TER and TMR of MFTJs and their dependence
on various device parameters is illustrated.",1906.06986v1
2020-05-02,All-electrical monitoring of bacterial antibiotic susceptibility in a microfluidic device,"The lack of rapid antibiotic susceptibility tests adversely affects the
treatment of bacterial infections and contributes to increased prevalence of
multidrug resistant bacteria. Here, we describe an all-electrical approach that
allows for ultra-sensitive measurement of growth signals from only tens of
bacteria in a microfluidic device. Our device is essentially a set of
microfluidic channels, each with a nano-constriction at one end and
cross-sectional dimensions close to that of a single bacterium. Flowing a
liquid bacteria sample (e.g., urine) through the microchannels rapidly traps
the bacteria in the device, allowing for subsequent incubation in drugs. We
measure the electrical resistance of the microchannels, which increases (or
decreases) in proportion to the number of bacteria in the microchannels. The
method and device allow for rapid antibiotic susceptibility tests in about two
hours. Further, the short-time fluctuations in the electrical resistance during
an antibiotic susceptibility test are correlated with the morphological changes
of bacteria caused by the antibiotic. In contrast to other electrical
approaches, the underlying geometric blockage effect provides a robust and
sensitive signal, which is straightforward to interpret without electrical
models. The approach also obviates the need for a high-resolution microscope
and other complex equipment, making it potentially usable in resource-limited
settings.",2005.00846v1
2020-05-04,Environment-friendly gas mixtures for Resistive Plate Chambers: an experimental and simulation study,"Resistive Plate Chambers (RPC) have shown stable operation at the Large
Hadron Collider and satisfactory efficiency for the entire Run 1 (2010-2013)
and Run 2 (2015-2018) with C$_{2}$H$_{2}$F$_{4}$-based gas mixtures and the
addition of SF$_{6}$ and i-C$_{4}$H$_{10}$. Since its global warming potential
(GWP) is high, C$_{2}$H$_{2}$F$_{4}$ is phasing out of production due to recent
European Union regulations and as a result its cost is progressively
increasing. Therefore, finding a new RPC gas mixture with a low GWP has become
extremely important. This contribution describes the simulation of the RPC
efficiency with tetrafluoropropene C$_{3}$H$_{2}$F$_{4}$ (HFO1234ze), a
hydrofluoroolefin with very low GWP. Simulation results are systematically
compared with measurements of RPC efficiency in C$_{3}$H$_{2}$F$_{4}$-based gas
mixtures with the addition of different combinations of Ar, He, CO$_{2}$,
O$_{2}$ and i-C$_{4}$H$_{10}$ in various concentrations. This simulation allows
the study of the interplay between C$_{3}$H$_{2}$F$_{4}$ and the other gas
components in the mixture as well as may allow the identification of the most
promising environment-friendly gas mixtures with C$_{3}$H$_{2}$F$_{4}$ for
RPCs.",2005.01476v1
2020-05-04,Evidence for a pressure-induced antiferromagnetic quantum critical point in intermediate valence UTe2,"UTe$_2$ is a recently discovered unconventional superconductor that has
attracted much interest due to its many intriguing properties - a large
residual density-of-states in the superconducting state, re-entrant
superconductivity in high magnetic fields, and potentially spin-triplet
topological superconductivity. Our ac calorimetry, electrical resistivity, and
x-ray absorption study of UTe$_2$ under applied pressure reveals key new
insights on the superconducting and magnetic states surrounding
pressure-induced quantum criticality at P$_{c1}$ = 1.3 GPa. First, our specific
heat data at low pressures, combined with a phenomenological model, show that
pressure alters the balance between two closely competing superconducting
orders. Second, near 1.5 GPa we detect two bulk transitions that trigger
changes in the resistivity which are consistent with antiferromagnetic order,
rather than ferromagnetism. The presence of both bulk magnetism and
superconductivity at pressures above P$_{c2}$ = 1.4 GPa results in a
significant temperature difference between resistively and thermodynamically
determined transitions into the superconducting state, which indicates a
suppression of the superconducting volume fraction by magnetic order. Third,
the emergence of magnetism is accompanied by an increase in valence towards a
U$^{4+}$ (5f2) state, which indicates that UTe$_2$ exhibits intermediate
valence at ambient pressure. Our results suggest that antiferromagnetic
fluctuations may play a more significant role on the superconducting state of
UTe$_2$ than previously thought.",2005.01659v2
2020-05-22,Improved-RPC for the CMS muon system upgrade for the HL-LHC,"During Phase-2 of the LHC, known as the High Luminosity LHC (HL-LHC), the
accelerator will increase its instantaneous luminosity to 5 $\times$ 10$^{34}$
cm$^{-2}$ s$^{-1}$, delivering an integrated luminosity of 3000 fb$^{-1}$ over
10 years of operation starting from 2027. In view of the HL-LHC, the CMS muon
system will be upgraded to sustain efficient muon triggering and reconstruction
performance. Resistive Plate Chambers (RPCs) serve as dedicated detectors for
muon triggering due to their excellent timing resolution, and will extend
$|\eta|$ (pseudorapidity) up to a region of 2.4. Before Long Shutdown 3 (LS3),
the RE3/1 and RE4/1 stations of the endcap will be equipped with new improved
Resistive Plate Chambers (iRPCs) having different design and geometry than the
present RPC system. The iRPC geometry configuration improves the detector's
rate capability and its ability to survive the harsh background conditions of
the HL-LHC. Also, new electronics equipped with excellent timing precision
measurements with a resolution of less than 150 ps are developed to readout the
RPC detectors from both sides of the strips to allow for good spatial
resolution along them. The performance of the iRPC has been studied with gamma
radiation at the Gamma Irradiation Facility (GIF++) at CERN. Ongoing longevity
studies will help to certify the iRPCs for the HL-LHC running period. The main
detector parameters such as the currents, rate and resistivity are regularly
monitored as a function of the integrated charge. Preliminary results of the
detector performance will be presented.",2005.11396v4
2020-06-08,Flow through three-dimensional self-affine fractures,"We investigate through numerical simulations of the Navier-Stokes equations
the influence of the surface roughness on the fluid flow through fracture
joints. Using the Hurst exponent $H$ to characterize the roughness of the
self-affine surfaces that constitute the fracture, our analysis reveal the
important interplay between geometry and inertia on the flow. Precisely, for
low values of Reynolds numbers Re, we use Darcy's law to quantify the hydraulic
resistance $G$ of the fracture and show that its dependence on $H$ can be
explained in terms of a simple geometrical model for the tortuosity $\tau$ of
the channel. At sufficiently high values of Re, when inertial effects become
relevant, our results reveal that nonlinear corrections up to third-order to
Darcy's law are aproximately proportional to $H$. These results imply that the
resistance $G$ to the flow follows a universal behavior by simply rescaling it
in terms of the fracture resistivity and using an effective Reynolds number,
namely, Re/$H$. Our results also reveal the presence of quasi-one-dimensional
channeling, even considering the absence of shear displacement between upper
and lower surfaces of the self-affine fracture.",2006.04846v1
2020-06-22,Effect of Landau quantization on linear magnetoresistance of periodically modulated two-dimensional electron gas,"The linear response of two-dimensional electron gas in a perpendicular
magnetic field in the presence of a spatially dependent classically smooth
electrostatic potential is studied theoretically, by application of the Kubo
formula for nonlocal conductivity tensor. In the classical transport regime, a
general expression for the conductivity tensor through the correlation
functions of the homogeneous electron gas is derived. The quantum transport
regime, when Landau quantization is essential, is studied for the case of
unidirectional periodic potential modulation. Apart from the Shubnikov-de Haas
oscillations, the resistivity can demonstrate quantum oscillations with larger
periods and smaller amplitudes, which survive when temperature increases. These
oscillations exist when the modulation amplitude considerably exceeds the
cyclotron energy so the Landau subbands, formed out of the Landau levels by the
modulation potential, overlap in the energy domain. Both diagonal components of
the resistivity tensor demonstrate oscillations related to modification of the
density of states by the modulation. In addition, the resistivity component
perpendicular to the modulation axis, which is caused by the
scattering-assisted hopping transport, shows another kind of oscillations
related to enhancement of the hopping probability when the guiding center of
cyclotron orbit shifts by the doubled cyclotron radius. It is suggested that
such high-temperature oscillations can be detected under conditions when the
modulation period considerably exceeds the cyclotron radius.",2006.12351v1
2020-11-06,(Quasi-)Real-Time Inversion of Airborne Time-Domain Electromagnetic Data via Artificial Neural Network,"The possibility to have results very quickly after, or even during, the
collection of electromagnetic data would be important, not only for quality
check purposes, but also for adjusting the location of the proposed flight
lines during an airborne time-domain acquisition. This kind of readiness could
have a large impact in terms of optimization of the Value of Information of the
measurements to be acquired. In addition, the importance of having fast tools
for retrieving resistivity models from airborne time-domain data is
demonstrated by the fact that Conductivity-Depth Imaging methodologies are
still the standard in mineral exploration. In fact, they are extremely
computationally efficient, and, at the same time, they preserve a very high
lateral resolution. For these reasons, they are often preferred to inversion
strategies even if the latter approaches are generally more accurate in terms
of proper reconstruction of the depth of the targets and of reliable retrieval
of true resistivity values of the subsurface. In this research, we discuss a
novel approach, based on neural network techniques, capable of retrieving
resistivity models with a quality comparable with the inversion strategy, but
in a fraction of the time. We demonstrate the advantages of the proposed novel
approach on synthetic and field datasets.",2011.03522v1
2020-11-30,Discovering novel cancer bio-markers in acquired lapatinib resistance using Bayesian methods,"Genes/Proteins do not work alone within our body, rather as a group they
perform certain activities indicated as pathways. Signalling transduction
pathways (STPs) are some of the important pathways that transmit biological
signals from protein-to-protein controlling several cellular activities.
However, many diseases such as cancer target some of these signalling pathways
for their growth and malignance, but demystifying their underlying mechanisms
are a very complicated tasks. In this study, we use a fully Bayesian approach
to develop methodologies in discovering novel driver bio-markers in aberrant
STPs given two-conditional high-throughput gene expression data. This project,
namely PathTurbEr (Pathway Perturbation Driver), is applied on a global gene
expression dataset derived from the lapatinib (an EGFR/HER dual inhibitor)
sensitive and resistant samples from breast cancer cell lines (SKBR3).
Differential expression analysis revealed 512 differentially expressed genes
(DEGs) and their signalling pathway enrichment analysis revealed 22 singalling
pathways as aberrated including PI3K-AKT, Hippo, Chemokine, and TGF-beta
singalling pathway as highly dysregulated in lapatinib resistance. Next, we
model the aberrant activities in TGF-beta STP as a causal Bayesian network (BN)
from given observational datasets using three Markov Chain Monte Carlo (MCMC)
sampling methods, i.e. Neighbourhood sampler (NS) and Hit-and-Run (HAR)
sampler, which has already proven to have more robust inference with lower
chances of getting stuck at local optima and faster convergence compared to
other state-of-art methods. Next, we examined the structural features of the
optimal BN as a statistical process that generates the global structure using,
$p_1$-model, a special class of Exponential Random Graph Models (ERGMs) and
MCMC methods for their hyper-parameter sampling....",2012.00566v1
2021-02-02,Long-term evolution of a merger-remnant neutron star in general relativistic magnetohydrodynamics I: Effect of magnetic winding,"Long-term ideal and resistive magnetohydrodynamics (MHD) simulations in full
general relativity are performed for a massive neutron star formed as a remnant
of binary neutron star mergers. Neutrino radiation transport effects are taken
into account as in our previous papers. The simulation is performed in axial
symmetry and without considering dynamo effects as a first step. In the ideal
MHD, the differential rotation of the remnant neutron star amplifies the
magnetic-field strength by the winding in the presence of a seed poloidal field
until the electromagnetic energy reaches $\sim 10\%$ of the rotational kinetic
energy, $E_{\rm kin}$, of the neutron star. The timescale until the maximum
electromagnetic energy is reached depends on the initial magnetic-field
strength and it is $\sim 1$ s for the case that the initial maximum
magnetic-field strength is $\sim 10^{15}$ G. After a significant amplification
of the magnetic-field strength by the winding, the magnetic braking enforces
the initially differentially rotating state approximately to a rigidly rotating
state. In the presence of the resistivity, the amplification is continued only
for the resistive timescale, and if the maximum electromagnetic energy reached
is smaller than $\sim 3\%$ of $E_{\rm kin}$, the initial differential rotation
state is approximately preserved. In the present context, the post-merger mass
ejection is induced primarily by the neutrino irradiation/heating and the
magnetic winding effect plays only a minor role for the mass ejection.",2102.01346v1
2021-03-15,Electron Collision Cross Sections in Tetrafluoropropene HFO1234ze(E) for Gas Mixtures in Resistive Plate Chambers,"In recent years, there has been growing interest in tetrafluoropropene
HFO1234ze(E) (C$_{3}$H$_{2}$F$_{4}$) for Resistive Plate Chambers (RPCs). This
novel gas is considered a promising alternative to the standard mixtures
currently used in RPCs, thanks to its low global warming potential. The
knowledge of electron collision cross sections in C$_{3}$H$_{2}$F$_{4}$ enables
reliable predictions of electron transport coefficients and reaction rates in
C$_{3}$H$_{2}$F$_{4}$-based gas mixtures. This allows for optimizing the
C$_{3}$H$_{2}$F$_{4}$-based gas mixtures to achieve the desired performance in
RPCs.
  From measurements of electron transport coefficients and reaction rates, a
complete set of scattering cross sections for electrons in
C$_{3}$H$_{2}$F$_{4}$ has been derived. Validation of the electron collision
cross sections is achieved through systematic comparisons of electron swarm
parameters with experimental data in both pure C$_{3}$H$_{2}$F$_{4}$ and
C$_{3}$H$_{2}$F$_{4}$/CO$_{2}$ gas mixtures. Given the influence of electron
attachment in C$_{3}$H$_{2}$F$_{4}$ by the gas density, this work also includes
precise calculations of the critical electric field strength in such mixtures.
This set of cross sections has been further utilized to compute the effective
ionization Townsend coefficient in gas mixtures containing
C$_{3}$H$_{2}$F$_{4}$, potentially applicable for RPCs.",2103.08643v2
2021-03-31,Cascade-Forward Neural Network Based on Resilient Backpropagation for Simultaneous Parameters and State Space Estimations of Brushed DC Machines,"A sensorless speed, average temperature and resistance estimation technique
based on Neural Network (NN) for brushed DC machines is proposed in this paper.
The literature on parameters and state spaces estimations of the Brushed DC
machines, shows a variety of approaches. However, these observers are sensitive
to a noise, on the model accuracy also are difficult to stabilize and to
converge. Furthermore, the majority of earlier works, estimate either the speed
or the temperature or the winding resistance. According to the literatures, the
Resilient backpropagation (RBP) as is the known as the faster BP algorithm,
Cascade-Forward Neural Network (CFNN), is known as the among accelerated
learning backpropagation algorithms, that's why where it is found in several
researches, also in several applications in these few years. The main objective
of this paper is to introduce an intelligent sensor based on resilient BP to
estimate simultaneously the speed, armature temperature and resistance of
brushed DC machines only from the measured current and voltage. A comparison
between the obtained results and the results of traditional estimator has been
made to prove the ability of the proposed method. This method can be embedded
in thermal monitoring systems, in high performance motor drives.",2104.04348v1
2021-04-25,Relativistic resistive dissipative magnetohydrodynamics from the relaxation time approximation,"Here we derive the relativistic resistive dissipative second-order
magnetohydrodynamic evolution equations using the Boltzmann equation, thus
extending our work from the previous paper
\href{https://link.springer.com/article/10.1007/JHEP03(2021)216}{JHEP 03 (2021)
216} where we considered the non-resistive limit. We solve the Boltzmann
equation for a system of particles and antiparticles using the relaxation time
approximation and the Chapman-Enskog like gradient expansion for the
off-equilibrium distribution function, truncating beyond second-order. In the
first order, the bulk and shear stress are independent of the electromagnetic
field, however, the diffusion current, shows a dependence on the electric
field. In the first order, the transport coefficients~(shear and bulk stress)
are shown to be independent of the electromagnetic field. The diffusion
current, however, shows a dependence on the electric field. In the
second-order, the new transport coefficients that couple electromagnetic field
with the dissipative quantities appear, which are different from those obtained
in the 14-moment approximation~\cite{Denicol:2019iyh} in the presence of the
electromagnetic field. Also we found out the various components of conductivity
in this case.",2104.12179v2
2021-05-17,Strange Metals from Melting Correlated Insulators in Twisted Bilayer Graphene,"Even as the understanding of the mechanism behind correlated insulating
states in magic-angle twisted bilayer graphene converges towards various kinds
of spontaneous symmetry breaking, the metallic ""normal state"" above the
insulating transition temperature remains mysterious, with its excessively high
entropy and linear-in-temperature resistivity. In this work, we focus on the
effects of fluctuations of the order-parameters describing correlated
insulating states at integer fillings of the low-energy flat bands on charge
transport. Motivated by the observation of heterogeneity in the order-parameter
landscape at zero magnetic field in certain samples, we conjecture the
existence of frustrating extended range interactions in an effective Ising
model of the order-parameters on a triangular lattice. The competition between
short-distance ferromagnetic interactions and frustrating extended range
antiferromagnetic interactions leads to an emergent length scale that forms
stripe-like mesoscale domains above the ordering transition. The gapless
fluctuations of these heterogeneous configurations are found to be responsible
for the linear-in-temperature resistivity as well as the enhanced low
temperature entropy. Our insights link experimentally observed
linear-in-temperature resistivity and enhanced entropy to the strength of
frustration, or equivalently, to the emergence of mesoscopic length scales
characterizing order-parameter domains.",2105.08069v3
2021-07-21,On the explosive phase of the tearing mode in double current sheet plasmas: effect of the equilibrium magnetic configuration on the onset threshold and growth rate,"Magnetic reconnection associated with the tearing instability occurring in
double-current sheet systems is investigated within the framework of reduced
resistive magnetohydrodynamics (MHD) in a two-dimensional Cartesian geometry.
The explosive non linear phase is particularly explored using the adaptive
finite-element FINMHD code. The critical aspect ratio, that is defined as the
minimum $L/x_s$ ratio (with $L$ and $x_s$ being the periodic system length and
half-distance between the two current layers respectively) necessary for non
linear destabilization after the linear and early non linear saturation phases,
is obtained. The latter threshold is independent of the details of the chosen
initial equilibrium (double Harris-like magnetic profile) and of the
resistivity. Its value is shown to be $4.7$, that is close and slightly smaller
than the value of order $5$ deduced using a more particular equilibrium
configuration in previous studies. The time dependence of the kinetic energy
($E_K$) is shown to follow a double exponential law, $E_K \propto \exp \
[e^{(\gamma^* t)} ]$, with a pseudo-growth rate $\gamma^* \simeq 0.1 \ t_A^
{-1}$ ($t_A$ being the characteristic Alfv\'en time) that is again independent
of the configuration and resistivity. The mechanism offers a possible
explanation for the sudden onset of explosive magnetic energy release occurring
on the fast Alfv\'en time scale in disruptive events of astrophysical plasmas
with pre-existing double current sheets like in the solar corona.",2107.10069v2
2021-11-22,Magnetic attractive interaction induced superconductivity in metals,"The BCS theory has described the conventional superconductors
successfully.However,it is still not clear when the superconductivity occurs
and why the resistance is zero.Also,there is no simple formula to calculate
Tc,and it is not well understood about how to improve Tc. Therefore,a theory of
superconductivity caused by magnetic attractive interactions is
presented.(1)The magnetic attractive interaction leads to
superconductivity.This interactions happen only when the electron velocity
reaches up to 106 m/s and the distance between two electrons is about 0.0529
nm. The number of superconducting electrons is about 10-5 of the number of free
electrons.(2)Resistance is redefined as the ratio of magnetic flux to electric
quantity. The resistance equals to zero, when the magnetic flux is 0. This is
why superconductors show Meissner effect.(3)Tc is determined by the magnetic
attractive energy. A simple formula to estimate Tc is derived and it is related
not only to the electron density n and Bc, but also to electronic degrees of
freedom i.(4)The Tc can be increased with increasing the ratio of the
superconducting electrons to total electrons. Mankowsky realized the transient
room temperature superconductivity in YBCO by illuminating in 2014. Bilayer
graphene superconductor was realized by Cao via applied a voltage in 2018. In
2020, roomtemperature superconductor was reported under high pressure for the
CSH system. Another way to improve Tc is to reduce electronic degrees of
freedom i. By forming Al""super atoms""to reduce i, Tc was further increased
experimentally to more than 100 K in 2015. We believe that room temperature
superconductors can be realized in Li by applied a voltage at atmospheric
pressure.",2111.11048v1
2022-01-28,Generalized statistics: applications to data inverse problems with outlier-resistance,"The conventional approach to data-driven inversion framework is based on
Gaussian statistics that presents serious difficulties, especially in the
presence of outliers in the measurements. In this work, we present maximum
likelihood estimators associated with generalized Gaussian distributions in the
context of R\'enyi, Tsallis and Kaniadakis statistics. In this regard, we
analytically analyse the outlier-resistance of each proposal through the
so-called influence function. In this way, we formulate inverse problems by
constructing objective functions linked to the maximum likelihood estimators.
To demonstrate the robustness of the generalized methodologies, we consider an
important geophysical inverse problem with high noisy data with spikes. The
results reveal that the best data inversion performance occurs when the
entropic index from each generalized statistic is associated with objective
functions proportional to the inverse of the error amplitude. We argue that in
such a limit the three approaches are resistant to outliers and are also
equivalent, which suggests a lower computational cost for the inversion process
due to the reduction of numerical simulations to be performed and the fast
convergence of the optimization process.",2201.12173v1
2022-04-02,Mechanical and electrical properties of MWCNT/PP films and structural health monitoring of GF/PP joints,"While welding of thermoplastic composites (TPCs) is a promising rivetless
method to reduce weight, higher confidence in joints' structural integrity and
failure prediction must be achieved for widespread use in industry. In this
work, we present an innovative study on damage detection for ultrasonically
welded TPC joints with multiwalled carbon nanotubes (MWCNTs) and embedded
buckypaper films. MWCNTs show promise for structural health monitoring (SHM) of
composite joints, assembled by adhesive bonding or fusion bonding, through
electrical resistance changes. This study focuses on investigating
multifunctional films and their suitability for ultrasonic welding (USW) of
TPCs, using two approaches: 1) MWCNT/filled polypropylene (PP) nanocomposites
prepared via solvent dispersion, and 2) high conductivity MWCNT buckypaper
embedded between PP films by hot pressing. Nanocomposite formulations
containing 5 wt and 10 wt MWCNTs were synthesized using solvent dispersion
method, followed by compression molding to manufacture films. The effect of
MWCNT concentration on electrical and dynamic mechanical behavior of
multifunctional films was examined with a Sourcemeter and Dynamic Mechanical
Analyzer, and a comparison was made between 5 to 20 wt MWCNT-PP films based on
previous research. Glass fiber/polypropylene (GF/PP) composite joints were
ultrasonically welded in a single lap shear configuration using buckypaper and
MWCNT/PP films. Furthermore, electrical resistance measurements were carried
out for joints under bending loads. It was observed that 15 wt and 20 wt
MWCNT/PP films had higher stability and sensitivity for resistance response
than embedded buckypaper and films with low MWCNT contents, demonstrating their
suitability for USW and potential for SHM.",2204.00909v1
2022-05-09,ResSFL: A Resistance Transfer Framework for Defending Model Inversion Attack in Split Federated Learning,"This work aims to tackle Model Inversion (MI) attack on Split Federated
Learning (SFL). SFL is a recent distributed training scheme where multiple
clients send intermediate activations (i.e., feature map), instead of raw data,
to a central server. While such a scheme helps reduce the computational load at
the client end, it opens itself to reconstruction of raw data from intermediate
activation by the server. Existing works on protecting SFL only consider
inference and do not handle attacks during training. So we propose ResSFL, a
Split Federated Learning Framework that is designed to be MI-resistant during
training. It is based on deriving a resistant feature extractor via
attacker-aware training, and using this extractor to initialize the client-side
model prior to standard SFL training. Such a method helps in reducing the
computational complexity due to use of strong inversion model in client-side
adversarial training as well as vulnerability of attacks launched in early
training epochs. On CIFAR-100 dataset, our proposed framework successfully
mitigates MI attack on a VGG-11 model with a high reconstruction
Mean-Square-Error of 0.050 compared to 0.005 obtained by the baseline system.
The framework achieves 67.5% accuracy (only 1% accuracy drop) with very low
computation overhead. Code is released at:
https://github.com/zlijingtao/ResSFL.",2205.04007v1
2022-06-18,Quantifying the value of transient voltage sources,"Some voltage sources are transient, lasting only for a moment of time, such
as the voltage generated by converting a human motion into electricity. Such
sources moreover tend to have a degree of randomness as well as internal
resistance. We investigate how to put a number to how valuable a given
transient source is. We derive several candidate measures via a systematic
approach. We establish an inter-convertibility hierarchy between such sources,
where inter-conversion means adding passive interface circuits to the sources.
Resistors at the ambient temperature are at the bottom of this hierarchy and
sources with low internal resistance and high internal voltages are at the top.
We provide three possible measures for a given source that assign a number to
the source respecting this hierarchy. One measure captures how much ``unitdc""
the source contains, meaning $1$ V dc with $1\Omega$ internal resistance for
$1$s. Another measure relates to the signal-to-noise ratio of the voltage
time-series whereas a third is based on the relative entropy between the
voltage probability distribution and a thermal noise resistor. We argue that
the unitdc measure is particularly useful by virtue of its operational
interpretation in terms of the number of unit dc sources that one needs to
combine to create the source or that can be distilled from the source.",2206.09126v2
2022-09-14,Accretion disc backflow in resistive MHD simulations,"We investigate accretion onto a central star, with the size, rotation rate,
and magnetic dipole of a young stellar object, to study the flow pattern
(velocity and density) of the fluid within and outside of the disc. We perform
resistive MHD simulations of thin $\alpha$-discs, varying the parameters such
as the stellar rotation rate and magnetic field, and (anomalous) coefficients
of viscosity and resistivity in the disc. To provide a benchmark for the
results and to compare with known analytic results, we also perform purely
hydrodynamic simulations (HD) for the same problem. Although obtained for a
different situation with differing inner boundary condition, the disc structure
in the HD simulations closely follows the analytic solution of Klu\'zniak and
Kita (2000) -- in particular a region of ""midplane"" backflow exists in the
right range of radii, depending on the viscosity parameter. In the MHD
solutions, whenever the magnetic Prandtl number does not exceed a certain
critical value, the midplane backflow exists throughout the accretion disc,
extending all the way down to the inner transition zone where the disc
transitions to a magnetic funnel flow. For values of the magnetic Prandtl
number close to the critical value the backflow and the inner disc undergo a
quasiperiodic radial oscillation, otherwise the backflow is steady, as is the
disc solution. From our results, supplemented by our reading of the literature,
we conclude that midplane backflow is a real feature of at least some accretion
discs, whether HD $\alpha$-discs or MHD discs, including ones driven by MRI
turbulence.",2209.06526v1
2022-11-02,"Weak antilocalization induced by Se substitution in layered BiCh$_2$-based (Ch = S, Se) superconductors LaO$_{1-x}$F$_x$BiS$_{2-y}$Se$_y$","We report transport properties for layered BiCh2-based (Ch = S, Se)
superconductors LaO1-xFxBiS2-ySey (x = 0.2, 0.5, y = 0-1.05) and the
observation of weak antilocalization (WAL). Electrical resistivity and Hall
coefficients for the Se-poor samples increase with decreasing temperature. The
increase becomes less pronounced with increasing Se concentration indicating a
loss of insulating behavior. Interestingly, the moderately Se-substituted
samples exhibit metallic behavior in the high-temperature region and a weak
increase in the resistivity in the low-temperature regions, which indicates the
existence of carrier localization. The heavily Se-substituted compounds show
metallic behavior in the entire-temperature region. Sign changes of the Hall
coefficients are observed for the x = 0.2 samples, which possibly is related to
a charge-density wave (CDW). Magnetoresistance measurements indicate that WAL
is realized in the heavily Se-substituted systems. The WAL behavior is weakened
by the changes in F and Se concentrations. A crossover state of the WAL and WL
emerges around the moderately F-doped and Se-free LaO0.8F0.2BiS2. The change of
the resistivity behavior by the F and Se substitution clearly correlates to the
difference of the magnetoconductance. Moreover, the localization regions of the
WAL-WL crossover and weak WAL states are possibly associated with the CDW. We
propose that the BiCh2-based system is a good platform for studying
relationship between WAL, superconductivity, and electronic ordering because
those states are tunable by element substitutions with bulk single crystals.",2211.00843v1
2022-11-17,Charge diffusion in relativistic resistive second-order dissipative magnetohydrodynamics,"We study charge diffusion in relativistic resistive second-order dissipative
magnetohydrodynamics. In this theory, charge diffusion is not simply given by
the standard Navier-Stokes form of Ohm's law, but by an evolution equation
which ensures causality and stability. This, in turn, leads to transient
effects in the charge diffusion current, the nature of which depends on the
particular values of the electrical conductivity and the charge-diffusion
relaxation time. The ensuing equations of motion are of so-called stiff
character, which requires special care when solving them numerically. To this
end, we specifically develop an implicit-explicit Runge-Kutta method for
solving relativistic resistive second-order dissipative magnetohydrodynamics
and subject it to various tests. We then study the system's evolution in a
simplified 1+1-dimensional scenario for a heavy-ion collision, where matter and
electromagnetic fields are assumed to be transversely homogeneous, and
investigate the cases of an initially non-expanding fluid and a fluid initially
expanding according to a Bjorken scaling flow. In the latter case, the scale
invariance is broken by the ensuing self-consistent dynamics of matter and
electromagnetic fields. However, the breaking becomes quantitatively important
only if the electromagnetic fields are sufficiently strong. The breaking of
scale invariance is larger for smaller values of the conductivity. Aspects of
entropy production from charge diffusion currents and stability are also
discussed.",2211.09459v2
2023-08-21,Neuromorphic Hebbian learning with magnetic tunnel junction synapses,"Neuromorphic computing aims to mimic both the function and structure of
biological neural networks to provide artificial intelligence with extreme
efficiency. Conventional approaches store synaptic weights in non-volatile
memory devices with analog resistance states, permitting in-memory computation
of neural network operations while avoiding the costs associated with
transferring synaptic weights from a memory array. However, the use of analog
resistance states for storing weights in neuromorphic systems is impeded by
stochastic writing, weights drifting over time through stochastic processes,
and limited endurance that reduces the precision of synapse weights. Here we
propose and experimentally demonstrate neuromorphic networks that provide
high-accuracy inference thanks to the binary resistance states of magnetic
tunnel junctions (MTJs), while leveraging the analog nature of their stochastic
spin-transfer torque (STT) switching for unsupervised Hebbian learning. We
performed the first experimental demonstration of a neuromorphic network
directly implemented with MTJ synapses, for both inference and
spike-timing-dependent plasticity learning. We also demonstrated through
simulation that the proposed system for unsupervised Hebbian learning with
stochastic STT-MTJ synapses can achieve competitive accuracies for MNIST
handwritten digit recognition. By appropriately applying neuromorphic
principles through hardware-aware design, the proposed STT-MTJ neuromorphic
learning networks provide a pathway toward artificial intelligence hardware
that learns autonomously with extreme efficiency.",2308.11011v1
2023-10-02,Breaking Through the Plasma Wavelength Barrier to Extend the Transparency Range of Ultrathin Indium Tin Oxide Films into the Far Infrared,"Indium tin oxide (ITO) film, which is the most commonly used transparent
conductive film (TCF), has traditionally been believed to be transparent in the
visible spectrum but to reflect infrared (IR) light beyond the plasma
wavelength (${\lambda}_p$). However, our theoretical analysis challenges this
notion by demonstrating that an ultrathin ITO TCF that is thinner than the
light's penetration depth, can overcome the transmission barrier at
${\lambda}_p$. To validate the theoretical modeling, we have successfully
fabricated ITO films that, despite having ${\lambda}_p \approx$ 1 ${\mu}$m,
remain transparent from 400 nm to 20 ${\mu}$m. This represents the broadest
transparency range ever reported for any In$_2$O$_3$-based TCF. The 10-nm-thick
ITO TCFs have high visible transmittance (91.0% at 550 nm), low resistivity (5
$\times$ 10$^{-4}$ ${\Omega}\cdot$ cm), and good IR transmittance (averaging
60% over 1.35 $\unicode{x2013}$ 18.35 ${\mu}$m). Their IR transparency
facilitates radiative cooling of the underlying circuitry. When an operational
resistor is enclosed by commercial ITO TCFs that are 140 nm thick, its
temperature increases. However, using 10-nm-thick ITO TCFs instead of the
commercial ones can completely avoid this temperature rise. Moreover, attaching
a silver grid to a 10-nm-thick ITO TCF can reduce the effective sheet
resistance to ~10 ${\Omega}/\square$ at the expense of only ~3% transmittance.
This development paves the way for large-scale applications that require low
sheet resistance and far-IR transparency.",2310.00984v1
2024-01-31,Large amplitude traveling waves for the non-resistive MHD system,"We prove the existence of large amplitude bi-periodic traveling waves
(stationary in a moving frame) of the two-dimensional non-resistive
Magnetohydrodynamics (MHD) system with a traveling wave external force with
large velocity speed $\lambda (\omega_1, \omega_2)$ and of amplitude of order
$O(\lambda^{1^+})$ where $\lambda \gg 1$ is a large parameter. For most values
of $\omega = (\omega_1, \omega_2)$ and for $\lambda \gg 1$ large enough, we
construct bi-periodic traveling wave solutions of arbitrarily large amplitude
as $\lambda \to + \infty$. More precisely, we show that the velocity field is
of order $O(\lambda^{0^+})$, whereas the magnetic field is close to a constant
vector as $\lambda \to + \infty$. Due to the presence of small divisors, the
proof is based on a nonlinear Nash-Moser scheme adapted to construct nonlinear
waves of large amplitude. The main difficulty is that the linearized equation
at any approximate solution is an unbounded perturbation of large size of a
diagonal operator and hence the problem is not perturbative. The invertibility
of the linearized operator is then performed by using tools from micro-local
analysis and normal forms together with a sharp analysis of high and low
frequency regimes w.r. to the large parameter $\lambda \gg 1$. To the best of
our knowledge, this is the first result in which global in time, large
amplitude solutions are constructed for the 2D non-resistive MHD system with
periodic boundary conditions and also the first existence results of large
amplitude quasi-periodic solutions for a nonlinear PDE in higher space
dimension.",2401.17943v1
2024-02-29,Quantum transport properties of the topological Dirac Semimetal $α$-Sn,"We report measurements of the electrical resistivity ($\rho$) and
thermoelectric power (S) in a thin film of strained single-crystalline
$\alpha$-Sn grown by molecular beam epitaxy on an insulating substrate. The
temperature (T) dependence of the resistivity of $\alpha$-Sn can be divided
into two regions:below T* $\approx$ 135 K $\rho$(T) shows a metallic-like
behaviour, while above this temperature an increasing contribution from
thermally excited holes to electrical transport is observed. However, it is
still dominated by highly mobile electrons, resulting in a negative sign of the
Seebeck coefficient above T = 47 K. In the low temperature limit, a small
positive S likely reflects the persistent contribution from low-mobility holes
or the positive phonon-drag thermopower. In the presence of the magnetic field
(B) applied along an electric field or thermal gradient, we note a negative
magnetoresistance or a negative slope of S(B), respectively. The theoretical
prediction for the former (calculated using density functional theory) agrees
well with the experiment. However, these characteristics quickly disappear when
the magnetic field is deviated from an orientation parallel to the electrical
field or the thermal gradient. We indicate that the behaviour of the electrical
resistivity and thermoelectric power can be explained in terms of the chiral
current arising from the topologically non-trivial electronic structure of
$\alpha$-Sn. Its decay at high temperature is a consequence of the decreasing
ratio between the intervalley Weyl relaxation time to the Drude scattering
time.",2403.00083v1
2024-05-06,Physical properties and electronic structure of the two-gap superconductor V$_{2}$Ga$_{5}$,"We present a thorough investigation of the physical properties and
superconductivity of the binary intermetallic V2Ga5. Electrical resistivity and
specific heat measurements show that V2Ga5 enters its superconducting state
below Tsc = 3.5 K, with a critical field of Hc2,perp c(Hc2,para c) = 6.5(4.1)
kOe. With H perp c, the peak effect was observed in resistivity measurements,
indicating the ultrahigh quality of the single crystal studied. The resistivity
measurements under high pressure reveal that the Tsc is suppressed linearly
with pressure and reaches absolute zero around 20 GPa. Specific heat and muon
spin relaxation measurements both indicate that the two-gap s-wave model best
describes the superconductivity of V2Ga5. The spectra obtained from
angle-resolved photoemission spectroscopy measurements suggest that two
superconducting gaps open at the Fermi surface around the Z and {\Gamma}
points. These results are verified by first-principles band structure
calculations. We therefore conclude that V2Ga5 is a phonon-mediated two-gap
s-wave superconductor",2405.03499v1
2013-12-03,Materials Design by Quantum-Chemical and other Theoretical/Computational Means: Applications to Energy Storage and Photoemissive Materials,"The present paper discusses some recent developments in the field of rational
design for energy storage and photoemissive materials. Recent and new examples
of designer materials for Li-ion and Li-air type batteries with high capacity
and energy/power density as well as photoemissive materials with low
workfunctions and improved brightness are discussed as illustrative examples of
how quantum-chemical and other theoretical computational means can be used for
rational materials design.",1312.0699v2
2015-10-05,Low frequency sound attenuation in a flow duct using a thin slow sound material,"We present a thin subwavelength material that can be flush mounted to a duct
and which gives a large wide band attenuation at remarkably low frequencies in
air flow channels. To decrease the material thickness, the sound is slowed in
the material using folded side branch tubes. The impedance of the material is
compared to the optimal value, which differs greatly from the characteristic
impedance. In particular, the viscous and thermal effects have to be very small
to have high transmission losses. Grazing flow on this material increases the
losses at the interface between the flow and the material.",1606.01877v1
2005-06-06,Fast high--voltage amplifiers for driving electro-optic modulators,"We describe five high-voltage (60 to 550V peak to peak), high-speed (1-300ns
rise time; 1.3-300MHz bandwidth) linear amplifiers for driving capacitive or
resistive loads such as electro-optic modulators. The amplifiers use bipolar
transistors in various topologies. Two use electron tubes to overcome the speed
limitations of high-voltage semiconductors. All amplifiers have been built.
Measured performance data is given for each.",0506050v1
2016-02-26,Resistively detected high-order magnetoplasmons in a high-quality 2D electron gas,"We report on high-order magnetoplasmon resonances detected in photoresistance
in high-mobility GaAs quantum wells. These resonances manifest themselves as a
series of photoresistance extrema in the regime of Shubnikov-de Haas
oscillations. Extending to orders above 20, the extrema exhibit alternating
strength, being less (more) pronounced at even (odd) order magnetoplasmon
modes. This experimental technique provides sensitive and elegant means to
detect and investigate multiple magnetoplasmon modes and could be applied to
other systems.",1602.08407v1
2023-01-17,High Speed Parallel Signal Crosstalk Cancellation Concept,"High performance computing (HPC) systems make extensive use of high speed
electrical interconnects, in routing signals among processing elements, or
between processing elements and memory. Increasing bandwidth demands result in
high density, parallel I/O exposed to crosstalk due to tightly coupled
transmission lines. The crosstalk cancellation signaling concept discussed in
this paper utilizes the known, predictable theory of coupled transmission lines
to cancel crosstalk from neighboring traces with carefully chosen resistive
cross-terminations between them. Through simulation and analysis of practical
bus architectures, we explore the merits of crosstalk cancellation which could
be used in dense interconnect HPC (or other) applications.",2301.10170v1
2017-10-04,A Characterization of Effective Resistance Metrics,"We produce a characterization of finite metric spaces which are given by the
effective resistance of a graph. This characterization is applied to the more
general context of resistance metrics defined by Kigami. A countably infinite
resistance metric gives rise to a sequence of finite, increasing graphs with
invariant effective resistance. We show that these graphs have a unique limit
graph in terms of the convergence of edge weights and that their associated
random walks converge weakly to the random walk on the limit graph. If the
limit graph is recurrent, its effective resistance is identified as the initial
resistance metric.",1710.01587v2
2017-12-22,Bacterial cooperation leads to heteroresistance,"By challenging E. coli with sublethal norfloxacin for 10 days, Henry Lee and
James Collins suggests the bacterial altruism leads to the population-wide
resistance. By detailedly analyzing experiment data, we suggest that bacterial
cooperation leads to population-wide resistance under norfloxacin pressure and
simultaneously propose the bacteria shield is the possible feedback mechanism
of less resistant bacteria. The bacteria shield is that the less resistant
bacteria sacrifice the large number of themselves to consume norfloxacin and
then to relieve the norfloxacin burden from highly resistant bacteria. Thus,
due to highly resistant bacteria and less resistant bacteria extracted from the
same bacteria population, bacterial cooperation leads to heteroresistance.",1712.08309v1
2005-08-31,Spinel ferrites: old materials bring new opportunities for spintronics,"Over the past few years, intensive studies of ultrathin epitaxial films of
perovskite oxides have often revealed exciting properties like giant
magnetoresistive tunnelling and electric field effects. Spinel oxides appear as
even more versatile due to their more complex structure and the resulting many
degrees of freedom. Here we show that the epitaxial growth of nanometric
NiFe2O4 films onto perovskite substrates allows the stabilization of novel
ferrite phases with properties dramatically differing from bulk ones. Indeed,
NiFe2O4 films few nanometres thick have a saturation magnetization at least
twice that of the bulk compound and their resistivity can be tuned by orders of
magnitude, depending on the growth conditions. By integrating such thin NiFe2O4
layers into spin-dependent tunnelling heterostructures, we demonstrate that
this versatile material can be useful for spintronics, either as a conductive
electrode in magnetic tunnel junctions or as a spin-filtering insulating
barrier in the little explored type of tunnel junction called spin-filter. Our
findings are thus opening the way for the realisation of monolithic spintronics
architectures integrating several layers of a single material, where the layers
are functionalised in a controlled manner.",0508764v1
2007-05-10,"Influence of oxygen partial pressure on structural, transport and magnetic properties of Co doped TiO2 films","Thin films of Co-TiO2 are deposited on silicon and quartz substrates using
Pulse Laser Deposition (PLD) process at various oxygen partial pressures
ranging from 6.6 x 10-3 Pascals (Pa) to 53 Pa. Crystal structure, transport and
magnetic properties of reduced CoxTi(1-x)O2 (0 <x< 0.03) thin films are
investigated and are found to have a strong dependence on the oxygen partial
pressure. X-ray diffraction (XRD) data reveals the presence of mixed phase
material containing both anatase and rutile. However, these phases
intertransform with the change in the oxygen partial pressure in the chamber
during the growth of the films. X-ray Photoelectron Spectroscopy (XPS) shows no
Co or CoO related peaks for samples with Co concentration up to x=0.03.
However, the oxygen 1s peaks are asymmetric suggesting the presence of oxygen
vacancies. The transport and magnetic measurements show a clear dependence on
the concentration of oxygen vacancies. There is an enhancement in the
electrical conductivity and the magnetization as more vacancies are created in
the material. The resistivity as a function of temperature rho(T) follows the
polaronic behavior and the activation energies obtained, ~100 to 150meV, are
within the range that is typical for semiconducting materials.",0705.1527v1
2008-11-25,Structural and physical properties of $SrMn_{1-x}Ru_xO_3$ perovskites,"We combine the results of magnetic and transport measurements with neutron
diffraction data to construct the structural and magnetic phase diagram of the
entire family of SrMn$_{1-x}$Ru$_{x}$O$_3$ ($0 \leqslant x \leqslant 1$)
perovskites. We have found antiferromagnetic ordering of the C type for lightly
Ru-substituted materials ($0.06 \leqslant x \leqslant 0.5$) in a similar manner
to $R_{y}$Sr$_{1-y}$MnO$_3$ ($R$=La, Pr), due to the generation of Mn$^{3+}$ in
both families of manganite perovskites by either $B$-site substitution of
Ru$^{5+}$ for Mn$^{4+}$ or $A$-site substitution of $R^{3+}$ for Sr$^{2+}$.
This similarity is driven by the same ratio of $d^4$ / $d^3$ ions in both
classes of materials for equivalent substitution level. In both cases, a
tetragonal lattice distortion is observed, which for some compositions ($0.06
\leqslant x \leqslant 0.2$) is coupled to a C-type AF transition and results in
a first order magnetic and resistive transition. Heavily substituted
SrMn$_{1-x}$Ru$_{x}$O$_3$ materials are ferromagnetic due to dominating
exchange interactions between the Ru$^{4+}$ ions. Intermediate substitution
($0.6 \leqslant x \leqslant 0.7$) leads to a spin-glass behavior instead of a
quantum critical point reported previously in single crystals, due to enhanced
disorder.",0811.4181v1
2009-10-09,Three-dimensional jamming and flows of soft glassy materials,"Various disordered dense systems such as foams, gels, emulsions and colloidal
suspensions, exhibit a jamming transition from a liquid state (they flow) to a
solid state below a yield stress. Their structure, thoroughly studied with
powerful means of 3D characterization, exhibits some analogy with that of
glasses which led to call them soft glassy materials. However, despite its
importance for geophysical and industrial applications, their rheological
behavior, and its microscopic origin, is still poorly known, in particular
because of its nonlinear nature. Here we show from two original experiments
that a simple 3D continuum description of the behaviour of soft glassy
materials can be built. We first show that when a flow is imposed in some
direction there is no yield resistance to a secondary flow: these systems are
always unjammed simultaneously in all directions of space. The 3D jamming
criterion appears to be the plasticity criterion encountered in most solids. We
also find that they behave as simple liquids in the direction orthogonal to
that of the main flow; their viscosity is inversely proportional to the main
flow shear rate, as a signature of shear-induced structural relaxation, in
close similarity with the structural relaxations driven by temperature and
density in other glassy systems.",0910.1821v2
2012-08-04,Microscopic theory of the glassy dynamics of passive and active network materials,"Signatures of glassy dynamics have been identified experimentally for a rich
variety of materials in which molecular networks provide rigidity. Here we
present a theoretical framework to study the glassy behavior of both passive
and active network materials. We construct a general microscopic network model
that incorporates nonlinear elasticity of individual filaments and steric
constraints due to crowding. Based on constructive analogies between structural
glass forming liquids and random field Ising magnets implemented using a
heterogeneous self-consistent phonon method, our scheme provides a microscopic
approach to determine the mismatch surface tension and the configurational
entropy, which compete in determining the barrier for structural rearrangements
within the random first order transition theory of escape from a local energy
minimum. The influence of crosslinking on the fragility of inorganic network
glass formers is recapitulated by the model. For active network materials, the
mapping, which correlates the glassy characteristics to the network
architecture and properties of nonequilibrium motor processes, is shown to
capture several key experimental observations on the cytoskeleton of living
cells: Highly connected tense networks behave as strong glass formers; intense
motor action promotes reconfiguration. The fact that our model assuming a
negative motor susceptibility predicts the latter suggests that on average the
motorized processes in living cells do resist the imposed mechanical load. Our
calculations also identify a spinodal point where simultaneously the mismatch
penalty vanishes and the mechanical stability of amorphous packing disappears.",1208.0880v1
2014-09-24,Field tunable spin density wave phases in Sr3Ru2O7,"The conduction electrons in a metal experience competing interactions with
each other and the atomic nuclei. This competition can lead to many types of
magnetic order in metals. For example, in chromium the electrons order to form
a spin-density-wave (SDW) antiferromagnetic state. A magnetic field may be used
to perturb or tune materials with delicately balanced electronic interactions.
Here we show that the application of a magnetic field can induce SDW magnetic
order in a metal, where none exists in the absence of the field. We use
magnetic neutron scattering to show that the application of a large (~8T)
magnetic field to the metamagnetic perovskite metal Sr3Ru2O7 can be used to
tune the material through two magnetically-ordered SDW states. The ordered
states exist over relatively small ranges in field (<0.4T) suggesting that
their origin is due to a new mechanism related to the electronic fine structure
near the Fermi energy, possibly combined with the stabilising effect of
magnetic fluctuations. The magnetic field direction is shown to control the SDW
domain populations which naturally explains the strong resistivity anisotropy
or electronic nematic behaviour observed in this material.",1409.7054v2
2014-12-12,Magnetoresistance from broken spin helicity,"The propensity of some materials and multilayers to have a magnetic field
dependent resistance, called magnetoresistance, has found commercial
applications such as giant magnetoresistance harddisk read heads. But
magnetoresistance can also be a powerful probe of electronic and magnetic
interactions in matter. For example, magnetoresistance can be used to analyze
multiband conductivity, conduction inhomogeneity, localized magnetic moments,
and (fractional) Landau level structure. For materials with strong spin-orbit
interaction, magnetoresistance can be used as a probe for weak antilocalization
or a nontrivial Berry phase, such as in topological insulator surface states.
For the three dimensional topological insulators a large and linear
magnetoresistance is often used as indication for underlying non-trivial
topology, although the origin of this effect has not yet been established.
Here, we observe a large magnetoresistance in the conducting bulk state of
Bi$_2$Te$_3$. We show that this type of large magnetoresistance is due to the
competition between helical spin-momentum locking (i.e. spin rotates with
momentum direction) and the unidirectional spin alignment by an applied
magnetic field. Warping effects are found to provide the (quasi) linear
dependence on magnetic field. We provide a quantitative model for the helicity
breaking induced magnetoresistance that can be applied to a vast range of
materials, surfaces or interfaces with weak to strong spin-orbit interactions,
such as the contemporary oxide interfaces, bulk Rashba systems, and topological
insulator surface states.",1412.4065v1
2015-09-16,Photoinduced Kondo effect in CeZn$_{3}$P$_{3}$,"The Kondo effect, which originates from the screening of a localized magnetic
moment by a spin-spin interaction, is widely observed in non-artificial
magnetic materials, artificial quantum dots, and carbon nanotubes. In devices
based on quantum dots or carbon nanotubes that target quantum information
applications, the Kondo effect can be tuned by a gate voltage, a magnetic
field, or light. However, the manipulation of the Kondo effect in
non-artificial materials has not been thoroughly studied; in particular, the
artificial creation of the Kondo effect remains unexplored. Per this subject
study, however, a new route for the optical creation of the Kondo effect in the
non-artificial material $p$-type semiconductor CeZn$_{3}$P$_{3}$ is presented.
The Kondo effect emerges under visible-light illumination of the material by a
continuous-wave laser diode and is ultimately revealed by photoinduced
electrical resistivity, which clearly exhibits a logarithmic temperature
dependency. By contrast, a La-based compound (LaZn$_{3}$P$_{3}$) displays only
normal metallic behavior under similar illumination. The photoinduced Kondo
effect, which occurs at higher temperatures when compared with the Kondo effect
in artificial systems, provides a potential new range of operation for not only
quantum information/computation devices but also for operation of magneto-optic
devices thereby expanding the range of device applications based on the Kondo
effect.",1509.04909v2
2015-11-06,"Finite size effects on crack front pinning at heterogeneous planar interfaces: Experimental, finite elements and perturbation approaches","Understanding the role played by the microstructure of materials on their
macroscopic failure properties is an important challenge in solid mechanics.
Indeed, when a crack propagates at a heterogeneous brittle interface, the front
is trapped by tougher regions and deforms. This pinning induces non-linearities
in the crack propagation problem, even within Linear Elastic Fracture Mechanics
theory, and modifies the overall failure properties of the material. For
example crack front pinning by tougher places could increase the fracture
resistance of multilayer structures, with interesting technological
applications. Analytical perturbation approaches, based on Bueckner-Rice
elastic line models, focus on the crack front perturbations, hence allow for a
description of these phenomena. Here, they are applied to experiments
investigating the propagation of a purely interfacial crack in a simple
toughness pattern: a single defect strip surrounded by homogeneous interface.
We show that by taking into account the finite size of the body, quantitative
agreement with experimental and finite elements results is achieved. In
particular this method allows to predict the toughness contrast, i.e. the
toughness difference between the single defect strip and its homogeneous
surrounding medium. This opens the way to a more accurate use of the
perturbation method to study more disordered heterogeneous materials, where the
finite elements method is less adequate. From our results, we also propose a
simple method to determine the adhesion energy of tough interfaces by measuring
the crack front deformation induced by known interface patterns.",1511.02050v1
2016-05-26,Measurement Techniques for Thermal Conductivity and Interfacial Thermal Conductance of Bulk and Thin Film Materials,"Thermal conductivity and interfacial thermal conductance play crucial roles
in the design of engineering systems where temperature and thermal stress are
of concerns. To date, a variety of measurement techniques are available for
both bulk and thin film solid-state materials with a broad temperature range.
For thermal characterization of bulk material, the steady-state absolute
method, laser flash diffusivity method, and transient plane source method are
most used. For thin film measurement, the 3{\omega} method and transient
thermoreflectance technique including both frequency-domain and time-domain
analysis are employed widely. This work reviews several most commonly used
measurement techniques. In general, it is a very challenging task to determine
thermal conductivity and interface contact resistance with less than 5% error.
Selecting a specific measurement technique to characterize thermal properties
need to be based on: 1) knowledge on the sample whose thermophysical properties
is to be determined, including the sample geometry and size, and preparation
method; 2) understanding of fundamentals and procedures of the testing
technique and equipment, for example, some techniques are limited to samples
with specific geometrics and some are limited to specific range of
thermophysical properties; 3) understanding of the potential error sources
which might affect the final results, for example, the convection and radiation
heat losses.",1605.08469v2
2016-04-02,Modeling Mechanical Properties of Aluminum Composite Produced Using Stir Casting Method,"ANN (Artificial Neural Networks) modeling methodology was adopted for
predicting mechanical properties of aluminum cast composite materials. For this
purpose aluminum alloy were developed using conventional foundry method. The
composite materials have complex nature which posses the nonlinear relationship
among heat treatment, processing parameters, and composition and affects their
mechanical properties. These nonlinear relation ships with properties can more
efficiently be modeled by ANNs. Neural networks modeling needs sufficient data
base consisting of mechanical properties, chemical composition and processing
parameters. Such data base is not available for modeling. Therefore, a large
range of experimental work was carried out for the development of aluminum
composite materials. Alloys containing Cu, Mg and Zn as matrix were reinforced
with 1- 15% Al2O3 particles using stir casting method. Alloys composites were
cast in a metal mold. More than eighty standard samples were prepared for
tensile tests. Sixty samples were given solution treatments at 580oC for half
an hour and tempered at 120oC for 24 hours. The samples were characterized to
investigate mechanical properties using Scanning Electron Microscope, X-Ray
Spectrometer, Optical Metallurgical Microscope, Vickers Hardness, Universal
Testing Machine and Abrasive Wear Testing Machine. A MLP (Multilayer
Perceptron) feedforward was developed and used for modeling purpose. Training,
testing and validation of the model were carried out using back propagation
learning algorithm. The modeling results show that an architecture of 14 inputs
with 9 hidden neurons and 4 outputs which includes the tensile strength,
elongation, hardness and abrasive wear resistance gives reasonably accurate
results with an error within the range of 2-7 % in training, testing and
validation.",1605.09691v1
2016-07-26,Superconductivity in CaBi$_{2}$,"Superconductivity is observed with critical temperature $T_{c}$ = 2.0 K in
self-flux-grown single crystals of $CaBi_{2}$. This material adopts the
$ZrSi_{2}$ structure type with lattice parameters a = 4.696(1) $\AA$, b =
7.081(2) $\AA$ and c = 4.611(1) $\AA$. The crystals of $CaBi_{2}$ were studied
by means of magnetic susceptibility, specific heat and electrical resistivity
measurements. The heat capacity jump at $T_{c}$ is $\Delta C/\gamma T_{c}$ =
1.41, confirming bulk superconductivity; the Sommerfeld coefficient $\gamma$ =
4.1 $mJ\: mol^{-1}\, K^{-2}$ and the Debye temperature $\Theta_{D}$ = 157 K.
The electron-phonon coupling strength is $\lambda_{el-ph}$ = 0.59, and the
thermodynamic critical field $H_{c}$ is low, between 111 and 124 Oe $CaBi_{2}$
is a moderate coupling type-I superconductor. Results of electronic structure
calculations are reported and charge densities, electronic bands, densities of
states and Fermi surfaces are discussed, focusing on the effects of
spin\textendash orbit coupling and electronic property anisotropy. We find a
mixed quasi-2D + 3D character in the electronic structure, which reflects the
layered crystal structure of the material.",1607.07603v1
2016-08-21,Unusual interlayer quantum transport behavior caused by the zeroth Landau level in YbMnBi2,"Relativistic fermions in topological quantum materials are characterized by
linear energy-momentum dispersion near band crossing points. Under magnetic
field, relativistic fermions acquire Berry phase of {\pi} in cyclotron motion,
leading to a zeroth Landau level (LL) at the crossing point. Such
field-independent zeroth LL, which distinguishes relativistic fermions from
conventional electron systems, is hardly probed in transport measurements since
the Fermi energy (EF) is usually not right at the band crossing points in most
topological materials. Here we report the observation of exotic quantum
transport behavior resulting from the zeroth LL in a multiband topological
semimetal YbMnBi2 which possesses linear band crossings both at and away from
the Fermi level (FL). We show that the Dirac bands with the crossing points
being above or below the FL leads to Shubnikov de-Haas oscillations in the
in-plane magnetoresistance, whereas the Dirac bands with the crossing points
being at the FL results in unusual angular dependences of the out-of-plane
magnetoresistance and in-plane Hall resistivity due to the dependence of the
zeroth LL's degeneracy on field orientation. Our results shed light on the
transport mechanism of the zeroth LL's relativistic fermions in layered
materials.",1608.05956v1
2016-10-18,"Light emission, light detection and strain sensing with nanocrystalline graphene","Graphene is of increasing interest for optoelectronic applications exploiting
light detection, light emission and light modulation. Intrinsically light
matter interaction in graphene is of a broadband type. However by integrating
graphene into optical micro cavities also narrow band light emitters and
detectors have been demonstrated. The devices benefit from the transparency,
conductivity and processability of the atomically thin material. To this end we
explore in this work the feasibility of replacing graphene by nanocrystalline
graphene, a material which can be grown on dielectric surfaces without catalyst
by graphitization of polymeric films. We have studied the formation of
nanocrystalline graphene on various substrates and under different
graphitization conditions. The samples were characterized by resistance,
optical transmission, Raman, X-ray photoelectron spectroscopy, atomic force
microscopy and electron microscopy measurements. The conducting and transparent
wafer-scale material with nanometer grain size was also patterned and
integrated into devices for studying light-matter interaction. The measurements
show that nanocrystalline graphene can be exploited as an incandescent emitter
and bolometric detector similar to crystalline graphene. Moreover the material
exhibits piezoresistive behavior which makes nanocrystalline graphene
interesting for transparent strain sensors.",1610.05513v1
2017-02-01,Pore ordering in mesoporous matrices induced by different directing agents,"Mesoporous silica particles of MCM-41 type were synthesized by sol-gel method
from tetraethyl orthosilicate (TEOS) in 2-methoxyethanol and deionized water
mixture in base conditions at room temperature. Ammonia or sodium hydroxides
were used as catalysts and cetyl-trimethylammonium bromide (CTAB) and
n-dodecyl-trimethylammonium bromide (DTAB) as structure directing agents. The
porosities and the ordered structure have been analyzed using transmission and
scanning electron microscopy, small angle neutron and X-ray diffraction,
nitrogen adsorption, thermal analysis and FTIR spectroscopy. The samples
consist of spherical particles of sub-micrometer size, with radially arranged
pores. The comparison of the effect of the different surfactants and catalysts
shows that by varying the surfactant type and their proportion, the pore sizes
can be controlled. As compared to the commonly used ammonia catalyst, the use
of NaOH as catalyst results in a much smaller porosity of the as-prepared
materials. These materials are not resisting to the heat treatment at 700 C
used for the template removal, and the ordered porous structure is completely
lost.",1702.00366v1
2017-10-27,Materials considerations for forming the topological insulator phase in InAs/GaSb heterostructures,"In an ideal InAs/GaSb bilayer of appropriate dimension in-plane electron and
hole bands overlap and hybridize, and a topologically non-trivial, or quantum
spin Hall (QSH) insulator, phase is predicted to exist. The in-plane
dispersion's potential landscape, however, is subject to microscopic
perturbations originating from material imperfections. In this work, the effect
of disorder on the electronic structure of InAs/GaSb bilayers was studied by
the temperature and magnetic field dependence of the resistance of a dual-gated
heterostructures gate-tuned through the inverted to normal gap regimes.
Conduction in the inverted (predicted topological) regime was qualitatively
similar to behavior in a disordered two-dimensional system. The impact of
charged impurities and interface roughness on the formation of topologically
protected edge states and an insulating bulk was estimated. The experimental
evidence and estimates of disorder in the potential landscape indicated the
potential fluctuations in state-of-the-art films are sufficiently strong such
that conduction in the predicted topological insulator (TI) regime was
dominated by a symplectic metal phase rather than a TI phase. The implications
are that future efforts must address disorder in this system and focus must be
placed on the reduction of defects and disorder in these heterostructures if a
TI regime is to be achieved.",1710.10095v1
2014-08-05,Emergent surface superconductivity of nanosized Dirac puddles in a topological insulator,"Surfaces of three-dimensional topological insulators have emerged as one of
the most remarkable states of condensed quantum matter1-5 where exotic
electronic phases of Dirac particles should arise1,6-8. Here we report a
discovery of surface superconductivity in a topological material (Sb2Te3) with
resistive transition at a temperature of ~9 K induced through a minor tuning of
growth chemistry that depletes bulk conduction channels. The depletion shifts
Fermi energy towards the Dirac point as witnessed by about two orders of
magnitude reduction of carrier density and by very large (~25,000 cm^2/Vs)
carrier mobility. Direct evidence from scanning tunneling spectroscopy and from
magnetic response show that the superconducting condensate forms in surface
puddles at unprecedentedly higher temperatures, near 60 K and above. The new
superconducting state we observe to emerge in puddles can be tuned by the
topological material's parameters such as Fermi velocity and mean free path
through band engineering; it could potentially become a hunting ground for
Majorana modes6 and lead to a disruptive paradigm change9 in how quantum
information is processed.",1408.1046v1
2019-07-31,"Coexisting 1T/2H polymorphs, reentrant resistivity behavior, and charge distribution in MoS2-hBN 2D/2D composite thin films","In view of their immensely intriguing properties, two dimensional materials
are being intensely researched in search of novel phenomena and diverse
application interests, however, studies on the realization of nanocomposites in
the application-worthy thin-film platform are rare. Here we have grown MoS2-hBN
composite thin films on different substrates by the pulsed laser deposition
technique and made comparative studies with the pristine MoS2 and hBN films.
The Raman, XPS and HRTEM confirm the concomitant presence of both the 1T
(conducting) and 2H (semiconducting) polymorphs of MoS2 in the composite film.
Interestingly, a peculiar reentrant semiconductor-metal-insulator transition is
seen in the composite film which is absent in the MoS2 film, and it correlates
well with the signatures of phonon softening seen in temperature-dependent
Raman spectroscopy. Furthermore, electrostatic force microscopy reveals the
presence of three distinct regions (metallic, semiconducting, and insulating)
in the composite film with differing contact potentials and enhanced propensity
for charge transfer with respect to pristine MoS2. A triboelectric
nanogenerator device containing biphasic composite film as an electron acceptor
exhibits more than twofold (sixfold) enhancement in peak-to-peak output voltage
as compared to the pristine MoS2 (hBN) film. These observations bring out the
potential of nanocomposite thin films for unfolding emergent phenomena and
technological applications.",1907.13522v1
2022-02-21,Towards fully two-dimensional spintronic devices,"Within the field of spintronics major efforts are directed towards developing
applications for spin-based transport devices made fully out of two-dimensional
(2D) materials. In this work we present an experimental realization of a
spin-valve device where the generation of the spin signal is exclusively
attributed to the spin-dependent conductivity of the magnetic graphene
resulting from the proximity of an interlayer antiferromagnet, CrSBr. We
clearly demonstrate that the usage of the conventional 3D magnetic contacts,
that are commonly air-sensitive and incompatible with practical technologies,
can be fully avoided when graphene/CrSBr heterostructures are employed.
Moreover, apart from providing exceptionally long spin relaxation length, the
usage of graphene for both generation and transport of the spin allows to
automatically avoid the conductivity mismatch between the source and the
channel circuits that has to be considered when using conventional
low-resistive contacts. Our results address a necessary step in the engineering
of spintronic circuitry out of layered materials and precede further
developments in the area of complex spin-logic devices. Moreover, we introduce
a fabrication procedure where we designed and implemented a recipe for the
preparation of electrodes via a damage-free technique that offers an immediate
advantage in the fields of air-sensitive and delicate organic materials.",2202.09972v1
2016-03-10,Möbius Kondo Insulators,"Heavy fermion materials have recently attracted attention for their potential
to combine topological protection with strongly correlated electron physics. To
date, the ideas of topological protection have been restricted to the heavy
fermion or ""Kondo"" insulators with the simplest point-group symmetries. Here we
argue that the presence of nonsymmorphic crystal symmetries in many heavy
fermion materials opens up a new family of topologically protected heavy
electron systems. Re-examination of archival resistivity measurements in
nonsymmorphic heavy fermion insulators Ce$_3$Bi$_4$Pt$_3$ and CeNiSn reveals
the presence of low temperature conductivity plateau, making them candidate
members of the new class of material. We illustrate our ideas with a specific
model for CeNiSn, showing how glide symmetries generate surface states with a
novel Mobius braiding that can be detected by ARPES or non-local conductivity
measurements. One of the interesting effects of strong correlation, is the
development of partially localization or ""Kondo breakdown"" on the surfaces,
which transforms Mobius surface states into quasi-one dimensional conductors,
with the potential for novel electronic phase transitions.",1603.03435v4
2017-07-14,Mesoscale simulations of confined Nafion thin films,"The morphology and transport properties of thin films of the ionomer Nafion,
with thicknesses on the order of the bulk cluster size, have been investigated
as a model system to explain the anomalous behaviour of
catalyst/electrode-polymer interfaces in membrane-electrode assemblies. We have
employed dissipative particle dynamics (DPD) to investigate the interaction of
water and fluorocarbon chains with carbon and quartz as confining materials for
a wide range of operational water contents and film thicknesses. We found
confinement-induced clustering of water perpendicular to the thin film.
Hydrophobic carbon forms a water depletion zone near the film interface,
whereas hydrophilic quartz results in a zone with excess water. There are, on
average, oscillating water-rich and fluorocarbon-rich regions, in agreement
with experimental results from neutron reflectometry. Water diffusivity shows
increasing directional anisotropy of up to 30% with decreasing film thickness,
depending of the confining material. The percolation analysis revealed
significant differences in water clustering and connectivity with the confining
material. These findings indicate the fundamentally different nature of ionomer
thin films, compared to membranes, and suggest explanations for increased ionic
resistances observed in the catalyst layer.",1707.04604v3
2017-07-27,SRF Theory Developments from the Center for Bright Beams,"We present theoretical studies of SRF materials from the Center for Bright
Beams. First, we discuss the effects of disorder, inhomogeneities, and
materials anisotropy on the maximum parallel surface field that a
superconductor can sustain in an SRF cavity, using linear stability in
conjunction with Ginzburg-Landau and Eilenberger theory. We connect our
disorder mediated vortex nucleation model to current experimental developments
of Nb$_3$Sn and other cavity materials. Second, we use time-dependent
Ginzburg-Landau simulations to explore the role of inhomogeneities in
nucleating vortices, and discuss the effects of trapped magnetic flux on the
residual resistance of weakly- pinned Nb$_3$Sn cavities. Third, we present
first-principles density-functional theory (DFT) calculations to uncover and
characterize the key fundamental materials processes underlying the growth of
Nb$_3$Sn. Our calculations give us key information about how, where, and when
the observed tin-depletedregions form. Based on this we plan to develop new
coating protocols to mitigate the formation of tin depleted regions.",1707.09025v1
2019-12-13,"Strength, transformation toughening and fracture dynamics of rocksalt-structure Ti1-xAlxN (0 <= x <= 0.75) alloys","Ab initio-calculated ideal strength and toughness describe the upper limits
for mechanical properties attainable in real systems and can, therefore, be
used in selection criteria for materials design. We employ density-functional
ab initio molecular dynamics (AIMD) to investigate the mechanical properties of
defect-free rocksalt-structure (B1) TiN and B1 Ti1-xAlxN (x = 0.25, 0.5, 0.75)
solid solutions subject to [001], [110], and [111] tensile deformation at room
temperature. We determine the alloys' ideal strength and toughness, elastic
responses, and ability to plastically deform up to fracture as a function of
the Al content. Overall, TiN exhibits greater ideal moduli of resilience and
tensile strengths than TiAlN solid solutions. Nevertheless, AIMD modelingshows
that, irrespective of the strain direction, the binary compound systematically
fractures by brittle cleavage at its yield point. The simulations also indicate
that Ti0.5Al0.5N and Ti0.25Al0.75N solid solutions are inherently more
resistant to fracture and possess much greater toughness than TiN, due to the
activation of local structural transformations (primarily of B1 -> wurtzite
type) beyond the elastic-response regime. In sharp contrast, TiAlN alloys with
25% Al exhibit similar brittleness as TiN. The results of this work are
examples of the limitations of elasticity-based criteria for prediction of
strength, brittleness, ductility, and toughness in materials able to undergo
phase transitions with loading. Furthermore, comparing present and previous
findings, we suggest a general principle for design of hard ceramic solid
solutions that are thermodynamically inclined to dissipate extreme mechanical
stresses via transformation toughening mechanisms.",1912.06367v2
2015-04-02,Thermoelectric Signal Enhancement by Reconciling the Spin Seebeck and Anomalous Nernst Effects in Ferromagnet/Non-magnet Multilayers,"The utilization of ferromagnetic (FM) materials in thermoelectric devices
allows one to have a simpler structure and/or independent control of electric
and thermal conductivities, which may further remove obstacles for this
technology to be realized. The thermoelectricity in FM/non-magnet (NM)
heterostructures using an optical heating source is studied as a function of NM
materials and a number of multilayers. It is observed that the overall
thermoelectric signal in those structures which is contributed by spin Seebeck
effect and anomalous Nernst effect (ANE) is enhanced by a proper selection of
NM materials with a spin Hall angle that matches to the sign of the ANE.
Moreover, by an increase of the number of multilayer, the thermoelectric
voltage is enlarged further and the device resistance is reduced,
simultaneously. The experimental observation of the improvement of
thermoelectric properties may pave the way for the realization of magnetic-(or
spin-) based thermoelectric devices.",1504.00642v1
2018-07-02,Electron-electron interactions of the multi-Cooper-pairs in the 1D limit and their role in the formation of global phase coherence in quasi-one-dimensional superconducting nanowire arrays,"Nanostructuring of superconducting materials to form dense arrays of thin
parallel nanowires with significantly large transverse Josephson coupling has
proven to be an effective way to increase the upper critical field of
superconducting elements by as much as two orders of magnitude as compared to
the corresponding bulk materials and, in addition, may cause considerable
enhancements in their critical temperatures. Such materials have been realized
in the linear pores of mesoporous substrates or exist intrinsically in the form
of various quasi-1D crystalline materials. The transverse coupling between the
superconducting nanowires is determined by the size-dependent coherence length
E0. In order to obtain E0 over the Langer-Ambegaokar- McCumber-Halperin (LAMH)
theory, extensive experimental fitting parameters have been required over the
last 40 years. We propose a novel Monte Carlo algorithm for determining E0 of
the multi-Cooper pair system in the 1D limit. The concepts of uncertainty
principle, Pauli-limit, spin flip mechanism, electrostatic interaction, thermal
perturbation and co-rotating of electrons are considered in the model. We use
Pb nanowires as an example to monitor the size effect of E0 as a result of the
modified electron-electron interaction without the need for experimental
fitting parameters. We investigate how the coherence length determines the
transverse coupling of nanowires in dense arrays. This determines whether or
not a global phase-coherent state with zero resistance can be formed in such
arrays. Our Monte Carlo results are in very good agreement with experimental
data from various types of superconducting nanowire arrays",1807.00611v1
2018-07-30,Tunable Thermal Energy Transport across Diamond Membranes and Diamond-Si Interfaces by Nanoscale Graphoepitaxy,"The development of electronic devices, especially those that involve
heterogeneous integration of materials, has led to increased challenges in
addressing their thermal operational-temperature demands. The heat flow in
these systems is significantly influenced or even dominated by thermal boundary
resistance at interface between dissimilar materials. However, controlling and
tuning heat transport across an interface and in the adjacent materials has so
far drawn limited attention. In this work, we grow chemical-vapor-deposited
(CVD) diamond on silicon substrates by graphoepitaxy and experimentally
demonstrate tunable thermal transport across diamond membranes and
diamond-silicon interfaces. We observed the highest diamond-silicon thermal
boundary conductance (TBC) measured to date and increased diamond thermal
conductivity due to strong grain texturing in the diamond near the interface.
Additionally, non-equilibrium molecular-dynamics (NEMD) simulations and a
Landauer approach are used to understand the diamond-silicon TBC. These
findings pave the way for tuning or increasing thermal conductance in
heterogeneously integrated electronics that involve polycrystalline materials
and will impact applications including electronics thermal management and
diamond growth.",1807.11400v2
2019-10-28,Tailored Graphenic Structures Directly Grown on Titanium Oxide Boost the Interfacial Charge Transfer,"The successful application of titanium oxide-graphene hybrids in the fields
of photocatalysis, photovoltaics and photodetection strongly depends on the
interfacial contact between both materials. The need to provide a good coupling
between the enabling conductor and the photoactive phase prompted us to
directly grow conducting graphenic structures on TiO2 crystals. We here report
on the direct synthesis of tailored graphenic structures by using Plasma
Assisted Chemical Vapour Deposition that present a clean junction with the
prototypical titanium oxide (110) surface. Chemical analysis of the interface
indicates chemical bonding between both materials. Photocurrent measurements
under UV light illumination manifest that the charge transfer across the
interface is efficient. Moreover, the influence of the synthesis atmosphere,
gas precursor (C2H2) and diluents (Ar, O2), on the interface and on the
structure of the as-grown graphenic material is assessed. The inclusion of O2
promotes vertical growth of partially oxidized carbon nanodots/rods with
controllable height and density. The deposition with Ar results in continuous
graphenic films with low resistivity (6.8x10-6 ohm x m). The synthesis
protocols developed here are suitable to produce tailored carbon-semiconductor
structures on a variety of practical substrates as thin films, pillars or
nanoparticles.",1910.12667v1
2020-08-23,Nanofibril-mediated Fracture Resistance of Bone,"Natural hard composites like human bone possess a combination of strength and
toughness that exceeds that of their constituents and of many engineered
composites. This augmentation is attributed to their complex hierarchical
structure, spanning multiple length scales; in bone, characteristic dimensions
range from nanoscale fibrils to microscale lamellae to mesoscale osteons and
macroscale organs. The mechanical properties of bone have been studied, with
the understanding that the isolated microstructure at micro- and nano-scales
gives rise to superior strength compared to that of whole tissue, and the
tissue possesses an amplified toughness relative to that of its nanoscale
constituents. Nanoscale toughening mechanisms of bone are not adequately
understood at sample dimensions that allow for isolating salient
microstructural features, because of the challenge of performing fracture
experiments on small-sized samples. We developed an in-situ three-point bend
experimental methodology that probes site-specific fracture behavior of
micron-sized specimens of hard material. Using this, we quantify crack
initiation and growth toughness of human trabecular bone with sharp fatigue
pre-cracks and blunt notches. Our findings indicate that bone with fatigue
cracks is two times tougher than that with blunt cracks. In-situ
data-correlated electron microscopy videos reveal this behavior arises from
crack-bridging by nanoscale fibril structure. The results reveal a transition
between fibril-bridging (~1 $\mu$m) and crack deflection/twist (~500 $\mu$m) as
a function of length-scale, and quantitatively demonstrate hierarchy-induced
toughening in a complex material. This versatile approach enables quantifying
the relationship between toughness and microstructure in various complex
material systems and provides direct insight for designing biomimetic
composites.",2008.09955v1
2020-10-28,"Statistical analysis of the material, geometrical and imperfection characteristics of structural stainless steels and members","Traditional member-based two-step design approaches included in current
structural codes for steel structures, as well as more recent system-based
direct-design alternatives, require building rigorous structural reliability
frameworks for the calibration of partial coefficients (resistance factors) to
achieve specified target reliability requirements. Key design parameters
affecting the strength of structures and their random variations are generally
modelled by nominal or characteristic values in design standards, which are
combined with partial coefficients that need to be calibrated from measurements
on real samples. While the statistical characterization of material and
geometric properties of structural steels has been consolidated over the last
decades, information about the characterization of structural stainless steels
is virtually non-existent due to the limited pool of available data. Thus, this
paper presents the basic ingredient for developing reliability frameworks for
stainless steel structures and components by statistically characterizing the
main random parameters affecting their strength through a comprehensive
database collected from the literature. Based on the collected data,
appropriate probabilistic models are proposed for geometric properties,
material properties, imperfections and residual stresses of different stainless
steel alloys and cross-section or product types. The data is equally applicable
to member-based reliability analyses as described in existing codes and
system-based analyses targeted at the direct-design of stainless steel
structures by advanced analysis.",2010.14777v2
2020-11-03,Fully-Compensated Ferrimagnetic Spin Filter Materials within the Cr$\textit{M}\textit{N}$Al Equiatomic Quaternary Heusler Alloys,"XX'YZ equiatomic quaternary Heusler alloys (EQHA's) containing Cr, Al, and
select Group IVB elements ($\textit{M}$ = Ti, Zr, Hf) and Group VB elements
($\textit{N}$ = V, Nb, Ta) were studied using state-of-the-art density
functional theory to determine their effectiveness in spintronic applications.
Each alloy is classified based on their spin-dependent electronic structure as
a half-metal, a spin gapless semiconductor, or a spin filter material. We
predict several new fully-compensated ferrimagnetic spin filter materials with
small electronic gaps and large exchange splitting allowing for robust spin
polarization with small resistance. CrVZrAl, CrVHfAl, CrTiNbAl, and CrTiTaAl
are identified as particularly robust spin filter candidates with an exchange
splitting of $\sim 0.20$ eV. In particular, CrTiNbAl and CrTiTaAl have
exceptionally small band gaps of $\sim 0.10$ eV. Moreover, in these compounds,
a spin asymmetric electronic band gap is maintained in 2 of 3 possible atomic
arrangements they can take, making the electronic properties less susceptible
to random site disorder. In addition, hydrostatic stress is applied to a subset
of the studied compounds in order to determine the stability and tunability of
the various electronic phases. Specifically, we find the CrAlV$\textit{M}$
subfamily of compounds to be exceptionally sensitive to hydrostatic stress,
yielding transitions between all spin-dependent electronic phases.",2011.01389v1
2020-12-02,Strain-induced anion ordering in perovskite oxyfluoride films,"Anionic ordering is a promising route to engineer physical properties in
functional heteroanionic materials. A central challenge in the study of
anion-ordered compounds lies in developing robust synthetic strategies to
control anion occupation and in understanding the resultant implications for
electronic structure. Here, we show that epitaxial strain induces preferential
occupation of F and O on the anion sites in perovskite oxyfluoride SrMnO2.5-dFg
films grown on different substrates. Under compressive strain, F tends to take
the apical-like sites, which was revealed by F and O K-edge linearly polarized
x-ray absorption spectroscopy and density functional theory calculations,
resulting in an enhanced c-axis expansion. Under tensile strain, F tends to
take the equatorial-like sites, enabling the longer Mn-F bonds to lie within
the plane. The anion ordered oxyfluoride films exhibit a significant orbital
polarization of the 3d electrons, distinct F-site dependence to their valence
band density of states, and an enhanced resistivity when F occupies the
apical-like anion site compared to the equatorial-like site. By demonstrating a
general strategy for inducing anion-site order in oxyfluoride perovskites, this
work lays the foundation for future materials design and synthesis efforts that
leverage this greater degree of atomic control to realize new polar or
quasi-two-dimensional materials.",2012.01221v1
2021-02-06,Multiple charge density waves and superconductivity nucleation at antiphase domain walls in the nematic pnictide Ba$_{1-x}$Sr$_{x}$Ni$_{2}$As$_{2}$,"How superconductivity interacts with charge or nematic order is one of the
great unresolved issues at the center of research in quantum materials.
Ba$_{1-x}$Sr$_{x}$Ni$_{2}$As$_{2}$ (BSNA) is a charge ordered pnictide
superconductor recently shown to exhibit a six-fold enhancement of
superconductivity due to nematic fluctuations near a quantum phase transition
(at $x_c=0.7$). The superconductivity is, however, anomalous, with the
resistive transition for $0.4 < x< x_c$ occurring at a higher temperature than
the specific heat anomaly. Using x-ray scattering, we discovered a new charge
density wave (CDW) in BSNA in this composition range. The CDW is commensurate
with a period of two lattice parameters, and is distinct from the two CDWs
previously reported in this material. We argue that the anomalous transport
behavior arises from heterogeneous superconductivity nucleating at antiphase
domain walls in this CDW. We also present new data on the incommensurate CDW,
previously identified as being unidirectional, showing that is a rotationally
symmetric, ""4$Q$"" state with $C_4$ symmetry. Our study establishes BSNA as a
rare material containing three distinct CDWs, and an exciting testbed for
studying coupling between CDW, nematic, and SC orders.",2102.03592v2
2021-04-29,"Competing magnetic interactions and magnetoresistance anomalies in cubic intermetallic compounds, Gd4RhAl and Tb4RhAl, and enhanced magnetocaloric effect for the Tb case","We report complex magnetic, magnetoresistance (MR) and magnetocaloric
properties of Gd4RhAl and Tb4RhAl forming in the Gd4RhIn type cubic structure.
Though the synthesis of the compounds was reported long ago, to our knowledge,
no attempt was made to investigate the properties of these compounds. The
present results of ac and dc magnetization, electrical resistivity and
heat-capacity measurements down to 1.8 K establish that these compounds undergo
antiferromagnetic order initially, followed by complex spin-glass features with
decreasing temperature. These characteristic temperatures are: For Gd case, TN
is about 46K and TG is about 21 K, and for Tb, about 32 and 28 K respectively.
Additionally, there are field induced magnetic effects, interestingly leading
to non-monotonic variations in MR. There is a significant MR over a wide
temperature range above TN, similar to the behavior of magnetocaloric effect
(MCE) as measured by isothermal entropy change (DeltaS). An intriguing finding
we made is that DeltaS at the onset of magnetic order is significantly larger
for the Tb compound than that observed for the Gd analogue near its TN. On the
basis of this observation in a cubic material, we raise a question whether
aspherical nature of the 4f orbital can play a role to enhance MCE under
favorable circumstances, a clue that could be useful to find materials for
magnetocaloric applications.",2104.14521v1
2021-10-12,Bridging the Band Gap: What Device Physicists Need to Know About Machine Learning,"This article surveys the landscape of semiconductor materials and devices
research for the acceleration of machine learning (ML) algorithms. We observe a
disconnect between the semiconductor and device physics and engineering
communities, and the digital logic and computer hardware architecture
communities. The article first provides an overview of the principles of
computational complexity and fundamental physical limits to computing and their
relation to physical systems. The article then provides an introduction to ML
by presenting three key components of ML systems: representation, evaluation,
and optimisation. The article then discusses and provides examples of the
application of emerging technologies from the demiconductor and device physics
domains as solutions to computational problems, alongside a brief overview of
emerging devices for computing applications. The article then reviews the
landscape of ML accelerators, comparing fixed-function and reprogrammable
digital logic with novel devices such as memristors, resistive memories,
magnetic memories, and probabilistic bits. We observe broadly lower performance
of ML accelerators based on novel devices and materials when compared to those
based on digital complimentary metal-oxide semiconductor (CMOS) technology,
particularly in the MNIST optical character recognition task, a common ML
benchmark, and also highlight the lack of a trend of progress in approaches
based on novel materials and devices. Lastly, the article proposes figures of
merit for meaningful evaluation and comparison of different ML implementations
in the hope of fostering a dialogue between the materials science, device
physics, digital logic, and computer architecture communities by providing a
common frame of reference for their work.",2110.05910v2
2021-11-15,In situ Bragg coherent X-ray diffraction imaging of corrosion in a Co-Fe alloy microcrystal,"Corrosion is a major concern for many industries, as corrosive environments
can induce structural and morphological changes that lead to material
dissolution and accelerate material failure. The progression of corrosion
depends on nanoscale morphology, stress, and defects present. Experimentally
monitoring this complex interplay is challenging. Here we implement in situ
Bragg coherent X-ray diffraction imaging (BCDI) to probe the dissolution of a
Co-Fe alloy microcrystal exposed to hydrochloric acid (HCl). By measuring five
Bragg reflections from a single isolated microcrystal at ambient conditions, we
compare the full three-dimensional (3D) strain state before corrosion and the
strain along the [111] direction throughout the corrosion process. We find that
the strained surface layer of the crystal dissolves to leave a progressively
less strained surface. Interestingly, the average strain closer to the centre
of the crystal increases during the corrosion process. We determine the
localised corrosion rate from BCDI data, revealing the preferential dissolution
of facets more exposed to the acid stream, highlighting an experimental
geometry effect. These results bring new perspectives to understanding the
interplay between crystal strain, morphology, and corrosion; a prerequisite for
the design of more corrosion-resistant materials.",2111.07903v5
2021-12-16,Observation and manipulation of a phase separated state in a charge density wave material,"The 1T polytype of TaS$_\textrm{2}$ has been studied extensively as a
strongly correlated system. As 1T-TaS$_\textrm{2}$ is thinned towards the 2D
limit, its phase diagram shows significant deviations from that of the bulk
material. Optoelectronic maps of ultrathin 1T-TaS$_\textrm{2}$ have indicated
the presence of non-equilibrium charge density wave phases within the
hysteresis region of the nearly commensurate (NC) to commensurate (C)
transition. We perform scanning tunneling microscopy on exfoliated ultrathin
flakes of 1T-TaS$_\textrm{2}$ within the NC-C hysteresis window, finding
evidence that the observed non-equilibrium phases consist of intertwined,
irregularly shaped NC-like and C-like domains. After applying lateral
electrical signals to the sample we image changes in the geometric arrangement
of the different regions. We use a phase separation model to explore the
relationship between electronic inhomogeneity present in ultrathin
1T-TaS$_\textrm{2}$ and its bulk resistivity. These results demonstrate the
role of phase competition morphologies in determining the properties of 2D
materials.",2112.09240v1
2022-03-17,Quasi-static crack front deformations in cohesive materials,"When a crack interacts with material heterogeneities, its front distorts and
adopts complex tortuous configurations that are reminiscent of the energy
barriers encountered during crack propagation. As such, the study of crack
front deformations is key to rationalize the effective failure properties of
micro-structured solids and interfaces. Yet, the impact of a localized
dissipation in a finite region behind the crack front, called the process zone,
has often been overlooked. In this work, we derive the equation ruling 3D
coplanar crack propagation in heterogeneous cohesive materials where the
opening of the crack is resisted by some traction in its wake. We show that the
presence of a process zone results in two competing effects on the deformation
of crack fronts: (i) it makes the front more compliant to small-wavelength
perturbations, and (ii) it smooths out local fluctuations of strength and
process zone size, from which emerge heterogeneities of fracture energy. Their
respective influence on front deformations is shown to strongly impact the
stability of perturbed crack fronts, as well as their stationary shapes when
interacting with arrays of tough obstacles. Overall, our theory provides a
unified framework to predict the variety of front profiles observed in
experiments, even when the small-scale yielding hypothesis of linear elastic
fracture mechanics breaks down.",2203.09317v2
2022-05-11,Reversible Tuning of Superconductivity in Ion-Gated NbN Ultrathin Films by Self-Encapsulation with a High-$κ$ Dielectric Layer,"Ionic gating is a powerful technique for tuning the physical properties of a
material via electric field-induced charge doping, but is prone to introduce
extrinsic disorder and undesired electrochemical modifications in the gated
material beyond pure electrostatics. Conversely, reversible, volatile and
electrostatic modulation is pivotal in the reliable design and operation of
novel device concepts enabled by the ultrahigh induced charge densities
attainable via ionic gating. Here we demonstrate a simple and effective method
to achieve reversible and volatile gating of surface-sensitive ultrathin
niobium nitride films via controlled oxidation of their surface. The resulting
niobium oxide encapsulation layer exhibits a capacitance comparable to that of
non-encapsulated ionic transistors, withstands gate voltages beyond the
electrochemical stability window of the gate electrolyte, and enables a
fully-reversible tunability of both the normal-state resistivity and the
superconducting transition temperature of the encapsulated films. Our approach
should be transferable to other materials and device geometries where more
standard encapsulation techniques are not readily applicable.",2205.05491v3
2022-06-07,Observation of surface superconductivity in a three-dimensional Dirac material,"Superconductivity becomes more interesting when it encounters dimensional
constraint or topology, because it is of importance for exploring exotic
quantum phenomena or developing superconducting electronics. Here we report the
coexistence of naturally formed surface superconducting state and
three-dimensional topological Dirac state in single crystals of BaMg$_2$Bi$_2$.
The electronic structure obtained from the first-principles calculations
demonstrates that BaMg$_2$Bi$_2$ is an ideal Dirac material, in which the Dirac
point is very close to the Fermi level and no other energy band crosses the
Fermi level. Superconductivity up to 4.77 K can be observed under ambient
pressure in the measurements of resistivity. The angle dependent
magnetoresistance reveals the two-dimensional characteristic of
superconductivity, indicating that superconductivity occurs on the surface of
the sample and is absent in the bulk state. Our study not only provides
BaMg$_2$Bi$_2$ as a suitable platform to study the interplay between
superconductivity and topological Dirac state, but also indicates that
MgBi-based materials may be a promising system for exploring new
superconductors.",2206.03405v1
2022-10-03,Interwoven atypical quantum states in CeLiBi$_2$,"We report the discovery of CeLiBi$_2$, the first example of a material in the
tetragonal Ce$TX_2$ ($T$ = transition metal; $X$ = pnictogen) family wherein an
alkali cation replaces the typical transition metal. Magnetic susceptibility
and neutron powder diffraction measurements are consistent with a crystal-field
$\Gamma_6$ ground state Kramers doublet that orders antiferromagnetically below
$T_N = 3.4$ K with an incommensurate propagation wave vector ${\bf{k}} = (0,
0.0724(4), 0.5)$ that generates a nanometric modulation of the magnetic
structure. The best model of the ordered state is an elliptical cycloid with Ce
moments primarily residing in the $ab$ plane. This is highly unusual, as all
other $\Gamma_6$ Ce$TX_2$ members order ferromagnetically. Further, we observe
an atypical hard-axis metamagnetic transition at $2$ T in magnetostriction,
magnetization, and resistivity measurements. CeLiBi$_2$ is a rare example of a
highly conductive material with dominant skew scattering leading to a large
anomalous Hall effect. Quantum oscillations with five frequencies arise in
magnetostriction and magnetic susceptibility data to $T = 30$ K and $\mu_0H =
55$ T, which indicate small Fermi pockets of light carriers with effective
masses as low as 0.07$m_e$. Density functional theory calculations indicate
that square-net Dirac-like Bi$-p$ bands are responsible for these ultralight
carriers. Together, our results show that CeLiBi$_2$ enables multiple atypical
magnetic and electronic properties in a single clean material.",2210.01031v2
2022-11-27,Ionic Peltier Effect in Li-Ion Electrolytes,"The coupled transport of charge and heat provide fundamental insights into
the microscopic thermodynamics and kinetics of materials. We describe a
sensitive ac differential resistance bridge that enables measurements of the
temperature difference on two sides of a coin cell with a resolution of better
than 10 uK. We use this temperature difference metrology to determine the ionic
Peltier coefficients of symmetric Li-ion electrochemical cells as a function of
Li salt concentration, solvent composition, electrode material, and
temperature. The Peltier coefficients {\Pi} are negative, i.e., heat flows in
the direction opposite to the drift of Li ions in the applied electric field,
large, 30 kJ mol-1, and increase with increasing temperature at T > 300 K. The
Peltier coefficient is approximately constant on time scales that span the
characteristic time for mass diffusion across the thickness of the electrolyte,
suggesting that heat of transport plays a minor role in comparison to the
changes in partial molar entropy of Li at the interface between the electrode
and electrolyte. Our work demonstrates a new platform for studying the
non-equilibrium thermodynamics of electrochemical cells and provides a window
into the transport properties of electrochemical materials through measurements
of temperature differences and heat currents that complement traditional
measurements of voltages and charge currents.",2211.14949v2
2023-03-28,A model for critical current effects in point-contact Andreev-reflection spectroscopy,"It is well known that point-contact Andreev reflection spectroscopy provides
reliable measurements of the energy gap(s) in a superconductor when the contact
is in the ballistic or nearly-ballistic regime. However, especially when the
mean free path of the material under study is small, obtaining ballistic
contacts can be a major challenge. One of the signatures of a Maxwell
contribution to the contact resistance is the presence of ""dips"" in the
differential conductance, associated to the sudden appearance of a Maxwell
term, in turn due to the attainment of the critical current of the material in
the contact region. Here we show that, using a proper model for the $R(I)$ of
the material under study, it is possible to fit the experimental curves
(without the need of normalization) obtaining the correct values of the gap
amplitudes even in the presence of such dips, as well as the temperature
dependence of the critical current in the contact. We present a test of the
procedure in the case of Andreev-reflection spectra in
Mg$_{0.85}$Al$_{0.15}$B$_2$ single crystals.",2303.15968v2
2023-05-12,Striation lines in intermittent fatigue crack growth in an Al alloy,"Fatigue failure of crystalline materials is a difficult problem in science
and engineering, and recent results have shown that fatigue crack growth can
occur in intermittent jumps which have fat-tailed distributions. As fatigue
crack propagation is known to leave markings -- called striations -- on the
fracture surface, the distances between these should also have fat-tailed
distributions, if the crack propagation is intermittent. Here, we combine
macroscale crack tip tracking in fatigue crack growth measurements of aluminum
5005 samples with \emph{post-mortem} scanning electron microscopy imaging of
the striation lines. We introduce two different methods for extracting the
striation line spacing from the images. What we find is a similar distribution
of striation spacings as jump sizes using one of our methods, but the average
striation spacing does not correlate with the crack growth rate. We conclude
that we observe avalanche-like crack propagation, reflected in both the
macroscale crack tip tracking as well as the analysis of the fracture surfaces.
Our results show that the fracture surfaces can be used to study the
intermittency of fatigue crack propagation and in development of
crack-resistant materials. The advantages and disadvantages of the two methods
introduced are discussed.",2305.07460v1
2023-07-07,Observation of the anomalous Hall effect in a layered polar semiconductor,"Progress in magnetoelectric materials is hindered by apparently contradictory
requirements for time-reversal symmetry broken and polar ferroelectric
electronic structure in common ferromagnets and antiferromagnets. Alternative
routes could be provided by recent discoveries of a time-reversal symmetry
breaking anomalous Hall effect in noncollinear magnets and altermagnets, but
hitherto reported bulk materials are not polar. Here, we report the observation
of a spontaneous anomalous Hall effect in doped AgCrSe$_2$, a layered polar
semiconductor with an antiferromagnetic coupling between Cr spins in adjacent
layers. The anomalous Hall resistivity 3 $\mu\Omega$ cm is comparable to the
largest observed in compensated magnetic systems to date, and is rapidly
switched off when the angle of an applied magnetic field is rotated to $\sim
80^{\circ}$ from the crystalline $c$-axis. Our ionic gating experiments show
that the anomalous Hall conductivity magnitude can be enhanced by modulating
the $p$-type carrier density. We also present theoretical results that suggest
the anomalous Hall effect is driven by Berry curvature due to noncollinear
antiferromagnetic correlations among Cr spins, which are consistent with the
previously suggested magnetic ordering in AgCrSe$_2$. Our results open the
possibility to study the interplay of magnetic and ferroelectric-like responses
in this fascinating class of materials.",2307.03541v1
2023-08-23,"Plastic deformation mechanisms during nanoindentation of W, Mo, V body-centered cubic single crystals and their corresponding W-Mo, W-V equiatomic random solid solutions","Deformation plasticity mechanisms in alloys and compounds may unveil the
material capacity towards optimal mechanical properties. We conduct a series of
molecular dynamics (MD) simulations to investigate plasticity mechanisms due to
nanoindentation in pure tungsten, molybdenum and vanadium body-centered cubic
single crystals, as well as the also body-centered cubic, equiatomic, random
solid solutions (RSS) of tungsten--molybdenum and tungsten--vanadium alloys.
Our analysis focuses on a thorough, side-by-side comparison of dynamic
deformation processes, defect nucleation, and evolution, along with
corresponding stress--strain curves. We also check the surface morphology of
indented samples through atomic shear strain mapping. As expected, the presence
of Mo and V atoms in W matrices introduces lattice strain and distortion,
increasing material resistance to deformation and slowing down dislocation
mobility of dislocation loops with a Burgers vector of 1/2 $\langle 111
\rangle$. Our side-by-side comparison displays a remarkable suppression of the
plastic zone size in equiatomic W--V RSS, but not in equiatomic W--Mo RSS
alloys, displaying a clear prediction for optimal hardening response equiatomic
W--V RSS alloys. If the small-depth nanoindentation plastic response is
indicative of overall mechanical performance, it is possible to conceive a
novel MD-based pathway towards material design for mechanical applications in
complex, multi-component alloys.",2308.12206v1
2023-09-08,Intralayer Negative Poisson's Ratio in Two-Dimensional Black Arsenic by Strain Engineering,"Negative Poisson's ratio as the anomalous characteristic generally exists in
artificial architectures, such as re-entrant and honeycomb structures. The
structures with negative Poisson's ratio have attracted intensive attention due
to their unique auxetic effect and many promising applications in shear
resistant and energy absorption fields. However, experimental observation of
negative Poisson's ratio in natural materials barely happened, although various
two-dimensional layered materials are predicted in theory. Herein, we report
the anisotropic Raman response and the intrinsic intralayer negative Poisson's
ratio of two-dimensional natural black arsenic (b-As) via strain engineering
strategy. The results were evident by the detailed Raman spectrum of b-As under
uniaxial strain together with density functional theory calculations. It is
found that b-As was softer along the armchair than zigzag direction. The
anisotropic mechanical features and van der Waals interactions play essential
roles in strain-dependent Raman shifts and negative Poisson's ratio in the
natural b-As along zigzag direction. This work may shed a light on the
mechanical properties and potential applications of two-dimensional puckered
materials.",2309.04058v1
2023-10-04,Three-Sensor 2ω Method with Multi-directional Layout: A General Methodology for Measuring Thermal Conductivity of Solid Materials,"Anisotropic thermal transport plays a key role in both theoretical study and
engineering practice of heat transfer, but accurately measuring anisotropic
thermal conductivity remains a significant challenge. To address this issue, we
propose the three-sensor 2{\omega} method in this study, which is capable of
accurately measuring the isotropic or anisotropic thermal conductivity of solid
materials. In this method, several three-sensor groups following the design
guidelines are fabricated upon the sample along different characteristic
directions, and each group consists of three parallel metal sensors with
unequal widths and distances optimally designed based on sensitivity analysis.
Among the three sensors, the outer two serve as AC heaters and the middle one
as a DC detector. The 2{\omega} voltage signals across the detector in each
three-sensor group are measured, and then the data are processed by the
proposed Intersection Method to derive the thermal conductivities along
directions of interest. The application of the detector's 2{\omega} instead of
the heater's 3{\omega} voltage signals eliminates the errors introduced by the
uncertainties of thermal resistance in superficial structures (metal layer,
insulation layer, interface, etc.). Meanwhile, by replacing the fitting
algorithm with the Intersection Method, the local optimum trap of multivariate
fitting is avoided. To verify the accuracy and reliability, four typical
monocrystalline semiconductors, i.e., Si, GaN, AlN, and {\beta -Ga _2 O _3},
are measured, and the results are consistent with the literature. This method
will provide a comprehensive and versatile solution for the thermal
conductivity measurements of solid materials.",2310.02846v1
2023-10-25,Non-Destructive Imaging of Breakdown Process in Ferroelectric Capacitors Using \textit{In-situ} Laser-Based Photoemission Electron Microscopy,"HfO$_2$-based ferroelectrics are one of the most actively developed
functional materials for memory devices. However, in HfO$_2$-based
ferroelectric devices, dielectric breakdown is a main failure mechanism during
repeated polarization switching. Elucidation of the breakdown process may
broaden the scope of applications for the ferroelectric HfO$_2$. Here, we
report direct observations of a breakdown process in HfO$_2$-based
ferroelectric capacitors, by \textit{in-situ} laser-based photoemission
electron microscopy (laser-PEEM). We have not only clearly visualized the hard
dielectric breakdown (HDB) spot, but also observed the regions responsible for
the soft dielectric breakdown (SDB) which is a precursor phenomenon to HDB. It
was found that the low-resistance region formed after SDB is wider than the
conduction path formed after HDB. Furthermore, our spectromicroscopic analysis
revealed that the photoelectron spectrum after SDB shows an enhancement in
intensity without spectral-shape modulation, interpreted that the initially
existed defects are increased. In the HDB spot, however, an additional shoulder
structure was observed. These results provide spectroscopic evidence that the
electronic states responsible for the conduction path after SDB are different
from those after HDB. Through this work, we propose this microscopic approach
as a versatile tool for studying buried materials as they are, accelerating the
development of material engineering for advanced electronic devices.",2310.16275v1
2023-11-16,Properties of Nb\_xTi\_{(1-x)}N thin films deposited on 300 mm silicon wafers for upscaling superconducting digital circuits,"Scaling superconducting digital circuits requires fundamental changes in the
current material set and fabrication process. The transition to 300 mm wafers
and the implementation of advanced lithography are instrumental in facilitating
mature CMOS processes, ensuring uniformity, and optimizing the yield. This
study explores the properties of NbxTi(1-x)N films fabricated by magnetron DC
sputtering on 300 mm Si wafers. As a promising alternative to traditional Nb in
device manufacturing, NbxTi(1-x)N offers numerous advantages, including
enhanced stability and scalability to smaller dimensions, in both processing
and design. As a ternary material, NbxTi(1-x)N allows engineering material
parameters by changing deposition conditions. The engineered properties can be
used to modulate device parameters through the stack and mitigate failure
modes. We report characterization of NbxTi(1-x)N films at less than 2%
thickness variability, 2.4% Tc variability and 3% composition variability. The
films material properties such as resistivity (140-375 {\Omega}cm) and critical
temperature Tc (4.6 K - 14.1 K) are correlated with stoichiometry and
morphology of the films. Our results highlight the significant influence of
deposition conditions on crystallographic texture along the films and its
correlation with Tc.",2311.09772v2
2024-03-18,Primary Defect Production in Doped Iron Grain Boundaries during Low Energy Collision Cascades,"This study explores the intricate interactions between grain boundaries (GBs)
and irradiation-induced defects in nanocrystalline iron, highlighting the role
of dopants like copper. Utilizing molecular dynamics simulations, the research
delineates how GB properties, such as GB energy and defect formation energies,
influence the formation and evolution of defects in low energy collision
cascades. It reveals that GBs not only augment defect production but also show
a marked preference for interstitials over vacancies, a behavior significantly
modulated by the cascade's proximity to the GB. The presence of dopants is
shown to alter GB properties, affecting both the rate and type of defect
production, thereby underscoring the complex interplay between GB
characteristics, dopant elements, and defect dynamics. Moreover, the
investigation uncovers that the structural characteristics of GBs play a
crucial role in cascade evolution and defect generation, with certain GB
configurations undergoing reconfiguration in response to cascades. For
instance, the reconfiguration of one pure Fe twist GB suggests that GB geometry
can significantly influence defect generation mechanisms. These findings point
to the potential of GB engineering in developing materials with enhanced
radiation tolerance, advocating for a nuanced approach to material design. By
tailoring GB properties and selectively introducing dopant elements, materials
can be optimized to exhibit superior resistance to radiation-induced damage,
offering insights for applications in nuclear reactors and other
radiation-prone environments.",2403.12257v1
2024-05-21,Engineering band structures of two-dimensional materials with remote moire ferroelectricity,"The stacking order and twist angle provide abundant opportunities for
engineering band structures of two-dimensional materials, including the
formation of moire bands, flat bands, and topologically nontrivial bands. The
inversion symmetry breaking in rhombohedral-stacked transitional metal
dichalcogenides (TMDCs) endows them with an interfacial ferroelectricity
associated with an out-of-plane electric polarization. By utilizing twist angle
as a knob to construct rhombohedral-stacked TMDCs, antiferroelectric domain
networks with alternating out-of-plane polarization can be generated. Here, we
demonstrate that such spatially periodic ferroelectric polarizations in
parallel-stacked twisted WSe2 can imprint their moire potential onto a remote
bilayer graphene. This remote moire potential gives rise to pronounced
satellite resistance peaks besides the charge-neutrality point in graphene,
which are tunable by the twist angle of WSe2. Our observations of ferroelectric
hysteresis at finite displacement fields suggest the moire is delivered by a
long-range electrostatic potential. The constructed superlattices by moire
ferroelectricity represent a highly flexible approach, as they involve the
separation of the moire construction layer from the electronic transport layer.
This remote moire is identified as a weak potential and can coexist with
conventional moire. Our results offer a comprehensive strategy for engineering
band structures and properties of two-dimensional materials by utilizing moire
ferroelectricity.",2405.12811v1
1996-07-08,Dynamic Conductance in Quantum Hall Systems,"In the framework of the edge-channel picture and the scattering approach to
conduction, we discuss the low frequency admittance of quantized Hall samples
up to second order in frequency. The first-order term gives the leading order
phase-shift between current and voltage and is associated with the displacement
current. It is determined by the emittance which is a capacitance in a
capacitive arrangement of edge channels but which is inductive-like if edge
channels predominate which transmit charge between different reservoirs. The
second-order term is associated with the charge relaxation. We apply our
results to a Corbino disc and to two- and four-terminal quantum Hall bars, and
we discuss the symmetry properties of the current response. In particular, we
calculate the longitudinal resistance and the Hall resistance as a function of
frequency.",9607051v1
1997-02-12,Kondo Effect in High-T_c Cuprates,"We study the Kondo effect due to the nonmagnetic impurity, e.g., Zn, in
high-T_c cuprates based on the spin-change separated state. In the optimal or
overdoped case with the Kondo screening, the residual resistivity is dominated
by the spinons while the T-dependent part determined by the holons. This gives
$\rho(T) = { {4 \hbar} /{e^2}} { { n_{imp.}} /{(1-x)}} + {{\alpha T} / x}$ (x:
hole concentration,$n_{imp.}$: impurity concentration, $\alpha$: constant ),
which is in agreement with experiments. In the underdoped region with the
pseudo spin gap, an SU(2) formulation predicts that the holon phase shift is
related to the formation of the local spin moment, and hence the residual
resistivity is given by $\rho_{res.} = { {4 \hbar} /{ e^2}} { { n_{imp.}}/{x}}
$, which is also consistent with the experiments. The magnetic impurity case,
e.g., Ni, is also discussed.",9702103v2
1999-03-11,Anisotropic States of Two-Dimensional Electron Systems in High Landau Levels: Effect of an In-Plane Magnetic Field,"We report the observation of an acute sensitivity of the anisotropic
longitudinal resistivity of two-dimensional electron systems in half-filled
high Landau levels to the magnitude and orientation of an in-plane magnetic
field. In the third and higher Landau levels, at filling fractions nu=9/2,
11/2, etc., the in-plane field can lead to a striking interchange of the ""hard""
and ""easy"" transport directions. In the second Landau level the normally
isotropic resistivity and the weak nu=5/2 quantized Hall state are destroyed by
a large in-plane field and the transport becomes highly anisotropic.",9903196v2
1999-06-23,Micro-Raman and resistance measurements of epitaxial La0.7Sr0.3MnO3 films,"The Channel-Spark method was used for deposition of highly oriented
ferromagnetic La0.7Sr0.3MnO3 films on NdGaO3 substrates. It was found that
additional oxygen decreases the film quality suppressing the Curie temperature
and metal-insulator transition below the room temperature. To achieve the best
quality of the films the samples were either annealed in high vacuum at
deposition temperature or even deposited in argon atmosphere with no oxygen
annealing. For such films the resistive measurements showed a metallic
behaviour in the interval 10-300 K in accordance with the high Curie point (Tc
350 K). Micro-Raman analysis indicate that the La0.7Sr0.3MnO3 films are well
ordered, while some outgrowths show stoichiometrical deviations.",9906348v1
1999-07-19,Quantum Theory of Quantum-Hall Smectics,"We propose a quantum stripe (smectic) coupled-Luttinger-liquid model for the
anisotropic states which occur in two-dimensional electron systems with
high-index partial Landau level filling, $\nu^{*} = \nu - \lbrack\nu\rbrack$.
Perturbative renormalization group calculations establish that interaction
terms neglected in this model are relevant - probably driving the system into
an anisotropic Wigner crystal---but for $0.4 \lesssim \nu^{*} \lesssim 0.6$
only below temperatures which are outside of the experimentally accessible
range. We argue that the Hall conductance of the ground state flows toward
$\lbrack\nu\rbrack e^{2}/h$ and $(\lbrack\nu\rbrack + 1) e^{2}/h$ respectively,
on the low and high filling factor sides of this range, consistent with recent
observations. A semiclassical theory of smectic state transport properties,
which incorporates Luttinger liquid effects in the evaluation of scattering
amplitudes, accounts for the magnitude of the dissipative resistivities at
$\nu^{*}=1/2$, for their $\nu^{*}$-dependence, and for the observation of
non-linearities of opposite sign in easy and hard direction resistivities.",9907278v1
1999-10-14,Electrical Noise From Phase Separation In Pr2/3Ca1/3MnO3 Single Crystal,"Low frequency electrical noise measurements have been used to probe the
electronic state of the perovskite-type manganese oxide Pr2/3Ca1/3MnO3 versus
temperature and in the vicinity of the field-induced transition from the
insulating, charge-ordered state (I-CO) to the metallic, ferromagnetic state
(M-F). At high temperature we have observed a high level of the excess noise
with mainly a gaussian distribution of the resistance fluctuations, and the
associated power spectral density has a standard 1/f dependence. However, in
the hysteretic region, where the electrical resistance depends dramatically on
the sample history, we have observed a huge non-gaussian noise characterized by
two level fluctuator-like switching (TLS) in the time domain. We discuss the
origin of the noise in terms of percolative behavior of the conductivity. We
speculate that the dominant fluctuators are manganese clusters switching
between the M-F and the I-CO phases.",9910204v1
1999-12-20,Oxygen isotope effects in high-quality thin films of manganites: Quantitative constraints on the physics of manganites,"Oxygen isotope effects on the transport properties have been studied in
high-quality epitaxial thin films of La_{0.75}Ca_{0.25}MnO_{3} and
Nd_{0.7}Sr_{0.3}MnO_{3}. In the paramagnetic state, the resistivity can be well
fitted by \rho (T) = (A/\sqrt{T})\exp(E_{\rho}/k_{B}T) with the parameters A
and E_{a} depending strongly on the oxygen isotope mass. The resistivity below
80 K almost perfectly follows \rho = \rho_{o}+
B\omega_{s}/\sinh^{2}(\hbar\omega_{s}/2k_{B}T) with \hbar\omega_{s}/k_{B} \sim
100 K. Both \rho_{o} and B increase by about 15(3)% upon raplacing $^{16}$O by
$^{18}$O. The results provide quantitative constraints on the basic physics of
manganites.",9912355v1
2000-05-03,The doping dependence of T* - what is the real high-Tc phase diagram?,"Underdoped high-Tc superconductors are frequently characterised by a
temperature, T*, below which the normal-state pseudogap opens. Two different
""phase diagrams"" based on the doping (p) dependence of T* are currently
considered: one where T* falls to zero at a critical doping state and the other
where T* merges with Tc in the overdoped region. By examining the temperature
dependence of the NMR Knight shift and relaxation rate, entropy, resistivity,
infrared conductivity, Raman scattering, ARPES and tunnelling data it is
concluded that the second scenario is not at all supported. Neither can one
distinguish a small and a large pseudogap as is often done. T* is an energy
scale which falls abruptly to zero at p=0.19.",0005063v2
2000-07-13,Exclusion of quantum coherence as the origin of the 2D metallic state in high-mobility silicon inversion layers,"The temperature and density dependence of the phase coherence time
$\tau_\phi$ in high-mobility silicon inversion layers was determined from the
magnetoresistivity due to weak localization. The upper temperature limit for
single-electron quantum interference effects was delineated by comparing
$\tau_\phi$ with the momentum relaxation time $\tau$. A comparison between the
density dependence of the borders for quantum interference effects and the
strong resistivity drop reveals that theses effects are not related to each
other. As the strong resistivity drop occurs in the Drude regime, the apparent
metallic behavior can not be caused by quantum coherent effects.",0007230v3
2001-02-22,Magnetoresistivity and Complete $H_{c2}(T)$ in $MgB_2$,"Detailed magneto-transport data on dense wires of $MgB_2$ are reported for
applied magnetic fields up to 18 T. The temperature and field dependencies of
the electrical resistivity are consistent with $MgB_2$ behaving like a simple
metal and following a generalized form of Kohler's rule. In addition, given the
generally high $T_c$ values and narrow resistive transition widths associated
with $MgB_2$ synthesized in this manner, combined with applied magnetic fields
of up to 18 T, an accurate and complete $H_{c2}(T)$ curve could be determined.
This curve agrees well with curves determined from lower field measurements on
sintered pellets and wires of $MgB_2$. $H_{c2}(T)$ is linear in $T$ over a wide
range of temperature (7 K $\le~T~\le$ 32 K) and has an upward curvature for $T$
close to $T_c$. These features are similar to other high $\kappa$, clean limit,
boron-bearing intermetallics: $YNi_2B_2C$ and $LuNi_2B_2C$.",0102413v2
2001-08-17,Entropy of vortex cores on the border of the superconductor-to-insulator transition in an underdoped cuprate,"We present a study of Nernst effect in underdoped $La_{2-x}Sr_xCuO_4$ in
magnetic fields as high as 28T. At high fields, a sizeable Nernst signal was
found to persist in presence of a field-induced non-metallic resistivity. By
simultaneously measuring resistivity and the Nernst coefficient, we extract the
entropy of vortex cores in the vicinity of this field-induced
superconductor-insulator transition. Moreover, the temperature dependence of
the thermo-electric Hall angle provides strong constraints on the possible
origins of the finite Nernst signal above $T_c$, as recently discovered by Xu
et al.",0108277v2
2002-03-07,Pseudogap and Conduction Dimensionalities in High-T_c Superconductors,"The nature of normal state charge-carriers' dynamics and the transition in
conduction and gap dimensionalities between 2D and 3D for YBa_2 Cu_3
O_{7-delta} and Bi_2 Sr_2 Ca_{1-x} Y_x Cu_2 O_8 high-T_c superconductors were
described by computing and fitting the resistivity curves, rho(T,delta,x).
These were carried out by utilizing the 2D and 3D Fermi liquid (FL) and
ionization energy (E_I) based resistivity models coupled with charge-spin (CS)
separation based t-J model [Phys. Rev. B 64, 104516 (2001)]. rho(T,delta,x)
curves of Y123 and Bi2212 samples indicate the beginning of the transition of
conduction and gap from 2D to 3D with reduction in oxygen content (7-delta) and
Ca^{2+} (1-x) as such, c-axis pseudogap could be a different phenomenon from
superconductor and spin gaps. These models also indicate that the recent MgB_2
superconductor is at least not Y123 or Bi2212 type.",0203164v8
2002-03-07,The Onset of Anisotropic Transport of Two-Dimensional Electrons in High Landau Levels: An Isotropic-to-Nematic Liquid Crystal Phase Transition?,"The recently discovered anisotropy of the longitudinal resistance of
two-dimensional electrons near half filling of high Landau levels is found to
persist to much higher temperatures T when a large in-plane magnetic field B||
is applied. Under these conditions we find that the longitudinal resistivity
scales quasi-linearly with B||/T. These observations support the notion that
the onset of anisotropy at B||=0 does not reflect the spontaneous development
of charge density modulations but may instead signal an isotropic-to-nematic
liquid crystal phase transition.",0203174v1
2003-05-21,Magnetoresistive response of a high mobility 2DES under electromagnetic wave excitation,"Oscillations of the resistance observed under electromagnetic wave excitation
in the high mobility GaAs/AlGaAs 2DES are examined as a function of the
radiation frequency and the power, utilizing an empirical lineshape based on
exponentially damped sinusoids. The fit-analysis indicates the resistance
oscillation frequency, F, increases with the radiation frequency, n, at the
rate dF/dn = 2.37 mTesla/GHz; the damping parameter, a, is approximately
independent of n at constant power; and the amplitude, A, of the oscillations
grows slowly with the incident power, at a constant temperature and frequency.
The lineshape appears to provide a good description of the data.",0305507v2
2003-07-15,Bolometric technique for high-resolution broadband microwave spectroscopy of ultra-low-loss samples,"A novel low temperature bolometric method has been devised and implemented
for high-precision measurements of the microwave surface resistance of small
single-crystal platelet samples having very low absorption, as a continuous
function of frequency. The key to the success of this non-resonant method is
the in-situ use of a normal metal reference sample that calibrates the absolute
rf field strength. The sample temperature can be controlled independently of
the 1.2 K liquid helium bath, allowing for measurements of the temperature
evolution of the absorption. However, the instrument's sensitivity decreases at
higher temperatures, placing a limit on the useful temperature range. Using
this method, the minimum detectable power at 1.3 K is 1.5 pW, corresponding to
a surface resistance sensitivity of $\approx$1 $\mu\Omega$ for a typical 1
mm$\times$1 mm platelet sample.",0307340v1
2003-09-26,Metastable Resistance Anisotropy Orientation of Two-Dimensional Electrons in High Landau Levels,"In half-filled high Landau levels, two-dimensional electron systems possess
collective phases which exhibit a strongly anisotropic resistivity tensor. A
weak, but as yet unknown, rotational symmetry-breaking potential native to the
host semiconductor structure is necessary to orient these phases in macroscopic
samples. Making use of the known external symmetry-breaking effect of an
in-plane magnetic field, we find that the native potential can have two
orthogonal local minima. It is possible to initialize the system in the higher
minimum and then observe its relaxation toward equilibrium.",0309625v2
2003-12-31,Single-electron transistors in electromagnetic environments,"The current-voltage (I-V) characteristics of single-electron transistors
(SETs) have been measured in various electromagnetic environments. Some SETs
were biased with one-dimensional arrays of dc superconducting quantum
interference devices (SQUIDs). The purpose was to provide the SETs with a
magnetic-field-tunable environment in the superconducting state, and a
high-impedance environment in the normal state. The comparison of SETs with
SQUID arrays and those without arrays in the normal state confirmed that the
effective charging energy of SETs in the normal state becomes larger in the
high-impedance environment, as expected theoretically. In SETs with SQUID
arrays in the superconducting state, as the zero-bias resistance of the SQUID
arrays was increased to be much larger than the quantum resistance R_K = h/e^2
= 26 kohm, a sharp Coulomb blockade was induced, and the current modulation by
the gate-induced charge was changed from e periodic to 2e periodic at a bias
point 0<|V|<2D_0/e, where D_0 is the superconducting energy gap. The author
discusses the Coulomb blockade and its dependence on the gate-induced charge in
terms of the single Josephson junction with gate-tunable junction capacitance.",0312726v2
2004-08-19,Charge dynamics of Ca_{2-x}Na_{x}CuO_{2}Cl_{2} as a correlated electron system with the ideal tetragonal lattice,"We report the reflectivity and the resistivity measurement of
Ca_{2-x}Na_{x}CuO_{2}Cl_{2} (CNCOC), which has a single-CuO2-plane lattice with
no orthorhombic distortion. The doping dependence of the in-plane optical
conductivity spectra for CNCOC is qualitatively the same to those of other
cuprates, but a slight difference between CNCOC and LSCO, i.e., the absence of
the 1.5 eV peak in CNCOC, can be attributed to the smaller charge-stripe
instability in CNCOC. The temperature dependence of the optical onductivity
spectra of CNCOC has been analyzed both by the two-component model
(Drude+Lorentzian) and by the one-component model (extended-Drude analysis).
The latter analysis gives a universal trend of the scattering rate Gamma(omega)
with doping. It was also found that Gamma(omega) shows a saturation behavior at
high frequencies, whose origin is the same as that of resistivity saturation at
high temperatures.",0408423v1
2004-11-17,Spin-fluctuation dominated electrical transport of Ni3Al at high pressure,"We present the first study of a magnetic quantum phase transition in the
itinerant-electron ferromagnet Ni3Al at high pressures. Electrical resistivity
measurements in a diamond anvil cell at hydrostatic pressures up to 100 kbar
and temperatures as low as 50 mK indicate that the Curie temperature collapses
towards absolute zero at a critical pressure pc=82(2) kbar. Over wide ranges in
pressure and temperature, both in the ferromagnetic and paramagnetic states,
the temperature variation of the resistivity is found to deviate from the
conventional Fermi-liquid form. We consider the extent to which this deviation
can be understood in terms of a mean-field model of enhanced spin fluctuations
on the border of ferromagnetism in three dimensions.",0411451v1
2004-12-27,Fiske steps studied with flux-flow resistance oscillation in a narrow stack of Bi2Sr2CaCu2O8+d junctions,"We have experimentally investigated the fluxon dynamics in a narrow
Bi2Sr2CaCu2O8+d stack with junction length L~1.8 um. As an evidence of
high-frequency excitation by a collective cavity mode, under an (in-plane)
external magnetic field, the current-voltage characteristics show prominent
Fiske steps with the corresponding resonance frequencies of 75-305 GHz. Further
study of flux-flow resistance oscillation with various c-axis currents
clarifies the correlation with Fiske steps by distinguishing two different
regions i.e., static flux-flow region at low bias current level and dynamic
Fiske step region at high bias current level.",0412690v3
2005-03-07,Quantum Hall Effect at 40 kelvin: Evidence of MacroscopicQuantization in the Extreme Soft Limit,"Evidence of both fractional and integer quantum hall effects (QHE) in three
dimensional bulk replica opal (250nm diameter) structures of non-crystalline
carbon are presented. In a remarkably soft quantum limit of ~ 40K temperature
and about one tesla of magnetic field clear hall steps, such as n= 2/3, 4/5, 1
and others were observed to be coordinated with the minima of longitudinal
magneto-resistance. This behavior is indicative of macroscopic quantum
phenomenon associated with electronic condensation into a strongly correlated
quantum liquid (QL). For other systems, such as very high mobility,
two-dimensional, electron (hole)-gas or (TDEG) these effects typically arise
under high magnetic fields (B) and at low temperatures (T), i.e., in the
extreme quantum limit (B/T>1). Currently, QHE is applied as calibration
benchmark, international resistance standard, and a characterization technique
for semiconductor heterostructures. We believe that applications can be
widespread if the devices and the operating conditions were more accessible.",0503166v1
2005-04-01,On the origin of multiple ordered phases in PrFe4P12,"The nature of multiple electronic orders in skutterudite PrFe_4P_{12} is
discussed on the basis of a model with antiferro-quadrupole (AFQ) interaction
of \Gamma_3 symmetry. The high-field phase can be reproduced qualitatively
provided (i) ferro-type interactions are introduced between the dipoles as well
as between the octupoles of localized f-electrons, and (ii) separation is
vanishingly small between the \Gamma_1-\Gamma_4^{(1)} crystalline electric
field (CEF) levels. The high-field phase can have either the same ordering
vector q=(1,0,0) as in the low-field phase, or a different one q=0 depending on
the parameters. In the latter case, distortion of the crystal perpendicular to
the (111) axis is predicted. The corresponding anomaly in elastic constants
should also appear. The electrical resistivity is calculated with account of
scattering within the CEF quasi-quartet. It is found that the resistivity as a
function of the direction of magnetic field shows a sharp maximum around the
(111) axis at low temperatures because of the level crossing.",0504014v2
2005-04-27,Influence of a Parallel Magnetic Field on Microwave Photoconductivity in a High-Mobility 2D Electron System,"We have studied experimentally the influence of a parallel magnetic field
($B_{//}$) on microwave-induced resistance oscillations (MIRO) and
zero-resistance states (ZRS) previously discovered in a high-mobility 2D
electron system. We have observed a strong suppression of MIRO/ZRS by a modest
$B_{//}\sim 0.5$ T. In Hall bar samples, magnetoplasmon resonance (MPR) has
also been observed concurrently with the MIRO/ZRS. In contrast to the
suppression of MIRO/ZRS, the MPR peak is found to be enhanced by $B_{//}$.
These findings have not been addressed by current models proposed to explain
the microwave-induced effects.",0504715v1
2005-05-25,"Anisotropy, disorder, and superconductivity in CeCu2Si2 under high pressure","Resistivity measurements were carried out up to 8 GPa on single crystal and
polycrystalline samples of CeCu2Si2 from differing sources in the homogeneity
range. The anisotropic response to current direction and small uniaxial
stresses was explored, taking advantage of the quasi-hydrostatic environment of
the Bridgman anvil cell. It was found that both the superconducting transition
temperature Tc and the normal state properties are very sensitive to uniaxial
stress, which leads to a shift of the valence instability pressure Pv and a
small but significant change in Tc for different orientations with respect to
the tetragonal c-axis. Coexistence of superconductivity and residual
resistivity close to the Ioffe-Regel limit around 5 GPa provides a compelling
argument for the existence of a valence-fluctuation mediated pairing
interaction at high pressure in CeCu2Si2.",0505613v1
2005-07-06,Magnetoresistance and spin polarization in the insulating regime of a Si two-dimensional electron system,"We have studied the magnetoresistance in a high-mobility Si inversion layer
down to low electron concentrations at which the longitudinal resistivity
$\rho_{xx}$ has an activated temperature dependence. The angle of the magnetic
field was controlled so as to study the orbital effect proportional to the
perpendicular component $B_\perp$ for various total strengths $B_{\rm tot}$. A
dip in $\rho_{xx}$, which corresponds to the Landau level filling factor of
$\nu=4$, survives even for high resistivity of $\rho_{xx} \sim 10^8 \Omega$ at
$T= 150 {\rm mK}$. The linear $B_{\rm tot}$-dependence of the value of
$B_\perp$ at the dip for low $B_{\rm tot}$ indicates that a ferromagnetic
instability does not occur even in the far insulating regime.",0507136v1
2006-05-22,Radiation-induced magnetoresistance oscillations in two-dimensional electron systems under bichromatic irradiation,"We analyze the magnetoresistance $R_{xx}$ oscillations in high-mobility
two-dimensional electron systems induced by the combined driving of two
radiation fields of frequency $\omega_1$ and $\omega_2$, based on the
balance-equation approach to magnetotransport for high-carrier-density systems
in Faraday geometry. It is shown that under bichromatic irradiation of
$\omega_2\sim 1.5 \omega_1$, most of the characterstic peak-valley pairs in the
curve of $R_{xx}$ versus magnetic field in the case of monochromatic
irradiation of either $\omega_1$ or $\omega_2$ disappear, except the one around
$\omega_1/\omega_c\sim 2$ or $\omega_2/\omega_c\sim 3$. $R_{xx}$ oscillations
show up mainly as new peak-valley structures around other positions related to
multiple photon processes of mixing frequencies $\omega_1+\omega_2$,
$\omega_2-\omega_1$, etc. Many minima of these resistance peak-valley pairs can
descend down to negative with enhancing radiation strength, indicating the
possible bichromaticzero-resistance states.",0605521v1
2006-06-19,Metallic State in Cubic FeGe beyond its Quantum Phase Transition,"We report on results of electrical resistivity and structural investigations
on the cubic modification of FeGe under high pressure. The long-wavelength
helical order ($T_C=280$ K) is suppressed at a critical pressure $p_c\approx
19$ GPa. An anomaly in the resistivity data at $T_X(p)$ and strong deviations
from a Fermi-liquid behavior in a wide pressure range above $p_c$ suggest that
the suppression of $T_C$ disagrees with the standard notion of a quantum
critical phase transition. The metallic ground state persisting at high
pressure can be described by band-structure calculations if structural disorder
due to zero-point motion is included. Discontinuous changes in the pressure
dependence of the shortest Fe-Ge interatomic distance occurring close to the
$T_C(p)$ phase line could be interpreted as a symmetry-conserving transition of
first order.",0606493v1
2007-03-23,Giant asymmetry of the longitudinal magnetoresistance in high-mobility two-dimensional electron gas on a cylindrical surface,"A giant asymmetry in the magnetoresistance was revealed in high-mobility,
two-dimensional electron gas on a cylindrical surface. The longitudinal
resistance along the magnetic-field gradient impressed by the surface curvature
was found to vanish if measured along one of the edges of the curved Hall bar.
If the external magnetic field is reversed, then the longitudinal resistance
vanishes at the opposite edge of the Hall bar. This asymmetry is analyzed
quantitatively in terms of the Landauer-Buettiker formalism.",0703623v1
2006-12-17,A New GEM-like Imaging Detector with Electrodes Coated with Resistive Layers,"We have developed and tested several prototypes of GEM-like detectors with
electrodes coated with resistive layers: CuO or CrO. These detectors can
operate stably at gains close to 10E5 and they are very robust. We discovered
that the cathodes of these detectors could be coated by CsI layers and in such
a way the detectors gain high efficiency for the UV photons. We also
demonstrated that such detectors can operate stably in the cascade mode and
high overall gains (~10E6) are reachable. This opens applications in several
areas, for example in RICH or in noble liquid TPCs. Results from the first
applications of these devices for UV photon detection at room and cryogenic
temperatures are given.",0612166v1
1997-02-07,The Landauer Resistance and Band Spectra for the Counting Quantum Turing Machine,"The generalized counting quantum Turing machine (GCQTM) is a machine which,
for any N, enumerates the first $2^{N}$ integers in succession as binary
strings. The generalization consists of associating a potential with read-1
steps only. The Landauer Resistance (LR) and band spectra were determined for
the tight binding Hamiltonians associated with the GCQTM for energies both
above and below the potential height. For parameters and potentials in the
electron region, the LR fluctuates rapidly between very high and very low
values as a function of momentum. The rapidity and extent of the fluctuations
increases rapidly with increasing N. For N=18, the largest value considered,
the LR shows good transmission probability as a function of momentum with
numerous holes of very high LR values present. This is true for energies above
and below the potential height. It is suggested that the main features of the
LR can be explained by coherent superposition of the component waves reflected
from or transmitted through the $2^{N-1}$ potentials in the distribution. If
this explanation is correct, it provides a dramatic illustration of the effects
of quantum nonlocality.",9702021v1
2008-06-17,Structural transition and anisotropic properties of single crystalline SrFe2As2,"Plate-like single crystals of SrFe2As2 as large as 3x3x0.5 mm3 have been
grown out of Sn flux. The SrFe2As2 single crystals show a structural phase
transition from a high temperature tetragonal phase to a low temperature
orthorhombic phase at To = 198 K, and do not show any sign of superconductivity
down to 1.8 K. The structural transition is accompanied by an anomaly in the
electrical resistivity, Hall resistivity, specific heat, and the anisotropic
magnetic susceptibility. In an intermediate temperature range from 198 K to 160
K, single crystal X-ray diffraction suggests a coexistence of the
high-temperature tetragonal and the low-temperature orthorhombic phases.",0806.2711v1
2008-08-29,On collisions driven negative energy waves and Weibel instability of a relativistic electron beam in a quasi-neutral plasma,"A new quasi-neutral model describing the Weibel instability of a high-current
relativistic beam propagating through a resistive plasma is developed. It
treats beam electrons as kinetic particles, and ambient plasma as a
non-relativistic fluid. For a finite-temperature beam, a new class of negative
energy magneto-sound waves is identified, which can possess negative energy.
Their growth due to collisional dissipation in the cold return current
destabilizes the beam-plasma system even for high beam temperatures. We perform
detailed two- and three-dimensional particle-in-cell (PIC) simulations of the
thermal beam and collisional plasma. It is shown that in three dimensions, the
Weibel instability persists even for physically collisionless background
plasma. The anomalous plasma resistivity is then caused by the two-stream
instability.",0808.4078v2
2008-10-05,Anisotropic magnetic and superconducting properties of pure and Co-doped CaFe$_2$As$_2$ single crystals,"We report anisotropic dc magnetic susceptibility $\chi(T)$, electrical
resistivity $\rho(T)$, and heat capacity $C(T)$ measurements on the single
crystals of CaFe$_{2-x}$Co$_x$As$_2$ for $x$ = 0 and 0.06. Large sized single
crystals were grown by the high temperature solution method with Sn as the
solvent. For the pure compound with $x$ = 0, a high temperature transition at
170 K is observed which is attributed to a combined spin density wave (SDW)
ordering and a structural phase transition. On the other hand, for the Co-doped
samples for $x$ = 0.06, the SDW transition is suppressed while
superconductivity is observed at $\simeq$17 K. The superconducting transition
has been confirmed from the magnetization and electrical resistivity studies.
The $^{57}$Fe M\""ossbauer spectrum in CaFe$_2$As$_2$ indicates that the SDW
ordering is incommensurate. In the Co-doped sample, a prominent paramagnetic
line at 4.2 K is observed indicating a weakening of the SDW state.",0810.0848v2
2008-11-17,Possible superconductivity above 25 K in single crystalline Co-doped BaFe$_{2}$As$_{2}$,"We present superconducting properties of single crystalline
Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$ by measuring magnetization, resistivity,
upper critical field, Hall coefficient, and magneto-optical images. The
magnetization measurements reveal fish-tail hysteresis loop at high
temperatures and relatively high critical current density above $J_{c}=10^{5}$
A/cm$^{2}$ at low temperatures. Upper critical field determined by resistive
transition is anisotropic with anisotropic parameter $\sim$ 3.5. Hall effect
measurements indicate that Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$ is a
multiband system and the mobility of electron is dominant. The magneto-optical
imaging reveals prominent Bean-like penetration of vortices although there is a
slight inhomogeneity in a sample. Moreover, we find a distinct
superconductivity above 25 K, which leads us to speculate that higher
transition temperature can be realized by fine tuning Co-doping level.",0811.2621v1
2008-12-05,High-T_c superconductivity induced by doping rare earth elements into CaFeAsF,"We have successfully synthesized the fluoride-arsenide compounds
Ca$_{1-x}$RE$_x$FeAsF (RE=Nd, Pr; x=0, 0.6). The x-ray powder diffraction
confirmed that the main phases of our samples are Ca$_{1-x}$RE$_x$FeAsF with
the ZrCuSiAs structure. By measuring resistivity, superconductivity was
observed at 57.4 K in Nd-doped and 52.8 K in Pr-doped samples with x=0.6. Bulk
superconductivity was also proved by the DC magnetization measurements in both
samples. Hall effect measurements revealed hole-like charge carriers in the
parent compound CaFeAsF with a clear resistivity anomaly below 118 K, while the
Hall coefficient $R_H$ in the normal state is negative for the superconducting
samples Ca$_{0.4}$Nd$_{0.6}$FeAsF and Ca$_{0.4}$Pr$_{0.6}$FeAsF. This indicates
that the rare earth element doping introduces electrons into CaFeAsF which
induces the high temperature superconductivity.",0812.1192v1
2009-01-14,AC Josephson effect in the long voltage-biased SINIS junction,"Theory of non-stationary coherent effects is developed for
superconductor-normal-superconductor (SNS) structures with relatively strong
normal scattering on S/N interfaces (interface resistance is large compared to
intrinsic resistance of N metal). Analitical expressions are found for the
time-dependent anomalous Green functions induced in the N region under the
fixed-voltage-bias. The amplitude of the current oscillations is determined in
non-equilibrium conditions. Non-stationary correction to the distribution
function is calculated in high-temperature limit and found to be slowly
decreasing with the temperature, leading to the dominance of the
second-harmonic term in the Josepshon current at high temperatures and low
voltage.",0901.1966v2
2009-03-04,Observation of a non-Ohmic Hall resistivity above the critical temperature in the high-temperature superconductor YBa$_{2}$Cu$_{3}$O$_{7-δ}$,"Investigations of the resistivity and the Hall effect as a function of
electric field and temperature in the normal state and upper part of the
superconducting transition of an optimally doped, very thin film of
YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ are reported. Using a fast pulsed-current
technique allowed to reduce the self-heating of the sample and to reach
electric fields up to 1 kV/cm. An intrinsic non-Ohmic behavior of the Hall
conductivity above the critical temperature that appears to originate from two
different, partially counteracting effects is revealed. The major contribution
stems from the suppression of Aslamazov-Larkin superconducting fluctuations in
high electric fields.",0903.0725v1
2009-04-17,EuFe$_2$As$_2$ under high pressure: an antiferromagnetic bulk superconductor,"We report the ac magnetic susceptibility $\chi_{ac}$ and resistivity $\rho$
measurements of EuFe$_2$As$_2$ under high pressure $P$. By observing nearly
100% superconducting shielding and zero resistivity at $P$ = 28 kbar, we
establish that $P$-induced superconductivity occurs at $T_c \sim$~30 K in
EuFe$_2$As$_2$. $\rho$ shows an anomalous nearly linear temperature dependence
from room temperature down to $T_c$ at the same $P$. $\chi_{ac}$ indicates that
an antiferromagnetic order of Eu$^{2+}$ moments with $T_N \sim$~20 K persists
in the superconducting phase. The temperature dependence of the upper critical
field is also determined.",0904.2618v2
2009-06-29,Spontaneous non-steady magnetic reconnection within the solar environment,"This work presents a 2.5-dimensional simulation study of the instability of
current-sheets located in a medium with a strong density variation along the
current layer. The initial force-free configuration is observed to undergo a
two-stage evolution consisting of an abrupt regime transition from a slow to a
fast reconnection process leading the system to a final chaotic configuration.
Yet, the onset of the fast phase is not determined by the presence of any
anomalous enhancement in plasma's local resistivity, but rather is the result
of a new mechanism discovered in Lapenta (2008)* and captured only when
sufficient resolution is present. Hence, the effects of the global resistivity,
the global viscosity and the plasma beta on the overall dynamics are
considered. This mechanism allowing the transition from slow to fast
reconnection provides a simple but effective model of several processes taking
place within the solar atmosphere from the high chromosphere up to the low
corona. In fact, the understanding of a spontaneous transition to a
self-feeding fast reconnection regime as well as its macroscopic evolution is
the first and fundamental step to produce realistic models of all those
phenomena requiring fast (and high power) triggering events (* Lapenta G. 2008,
Phys. Rev. Lett., 100, 235001).",0906.5382v1
2009-07-17,Performances of linseed oil-free bakelite RPC prototypes with cosmic ray muons,"A comparative study has been performed on Resistive Plate Chambers (RPC) made
of two different grades of bakelite paper laminates, produced and commercially
available in India. The chambers, operated in the streamer mode using argon,
tetrafluroethane and isobutane in 34:59:7 mixing ratio, are tested for the
efficiency and the stability with cosmic rays. A particular grade of bakelite
(P-120, NEMA LI-1989 Grade XXX), used for high voltage insulation in humid
conditions, was found to give satisfactory performance with stable efficiency
of > 96% continuously for more than 130 days. A thin coating of silicone fluid
on the inner surfaces of the bakelite RPC is found to be necessary for
operation of the detector.",0907.2976v1
2009-10-21,"""Bad Metal"" Conductivity of Hard Core Bosons","Two dimensional hard core bosons suffer strong scattering in the high
temperature resistive state at half filling. The dynamical conductivity is
calculated using non perturbative tools such as continued fractions, series
expansions and exact diagonalization. We find a large temperature range with
linearly increasing resistivity and broad dynamical conductivity, signaling a
breakdown of Boltzmann-Drude quasiparticle transport theory. At zero
temperature, a high frequency peak in the dynamical conductivity appears above
a ""Higgs mass"" gap, and corresponds to order parameter magnitude fluctuations.
We discuss the apparent similarity between conductivity of hard core bosons and
phenomenological characteristics of cuprates, including the universal scaling
of Homes et. al. (Nature 430, 539 (2004)).",0910.4158v2
2009-12-16,Distributed control of reactive power flow in a radial distribution circuit with high photovoltaic penetration,"We show how distributed control of reactive power can serve to regulate
voltage and minimize resistive losses in a distribution circuit that includes a
significant level of photovoltaic (PV) generation. To demonstrate the
technique, we consider a radial distribution circuit with a single branch
consisting of sequentially-arranged residential-scale loads that consume both
real and reactive power. In parallel, some loads also have PV generation
capability. We postulate that the inverters associated with each PV system are
also capable of limited reactive power generation or consumption, and we seek
to find the optimal dispatch of each inverter's reactive power to both maintain
the voltage within an acceptable range and minimize the resistive losses over
the entire circuit. We assume the complex impedance of the distribution circuit
links and the instantaneous load and PV generation at each load are known. We
compare the results of the optimal dispatch with a suboptimal local scheme that
does not require any communication. On our model distribution circuit, we
illustrate the feasibility of high levels of PV penetration and a significant
(20% or higher) reduction in losses.",0912.3281v1
2010-03-26,Strong carrier-scattering in iron-pnictide superconductors with highest Tc obtained from charge transport experiments,"Characteristic normal-state charge transport is found in the oxygen-deficient
iron-arsenides LnFeAsO1-y (Ln: La and Nd) with the highest Tc's among known
Fe-based superconductors. The effect of ""doping"" in this system is mainly on
the carrier scattering, quite distinct from that in high-Tc cuprates. In the
superconducting regime of the La system with maximum Tc = 28 K, the
low-temperature resistivity is dominated by a T^2 term. On the other hand, in
the Nd system with Tc higher than 40 K, the carriers are subject to stronger
scattering showing T-linear resistivity and small magnetoresistance. Such
strong scattering appears crucial for high-Tc superconductivity in the
iron-based system.",1003.5039v1
2010-04-14,Electron-hole coexistence in disordered graphene probed by high-field magneto-transport,"We report on magneto-transport measurement in disordered graphene under
pulsed magnetic field of up to 57T. For large electron or hole doping, the
system displays the expected anomalous Integer Quantum Hall Effect (IQHE)
specific to graphene up to filling factor $\nu=2$. In the close vicinity of the
charge neutrality point, the system breaks up into co-existing puddles of holes
and electrons, leading to a vanishing Hall and finite longitudinal resistance
with no hint of divergence at very high magnetic field. Large resistance
fluctuations are observed near the Dirac point. They are interpreted as the the
natural consequence of the presence of electron and hole puddles. The magnetic
field at which the amplitude of the fluctuations are the largest is directly
linked to the mean size of the puddles.",1004.2356v1
2010-05-30,Loss-resistant state teleportation and entanglement swapping using a quantum-dot spin in an optical microcavity,"We present a scheme for efficient state teleportation and entanglement
swapping using a single quantum-dot spin in an optical microcavity based on
giant circular birefringence. State teleportation or entanglement swapping is
heralded by the sequential detection of two photons, and is finished after the
spin measurement. The spin-cavity unit works as a complete Bell-state analyzer
with a built-in spin memory allowing loss-resistant repeater operation. This
device can work in both the weak coupling and the strong coupling regime, but
high efficiencies and high fidelities are only achievable when the side leakage
and cavity loss is low. We assess the feasibility of this device, and show it
can be implemented with current technology. We also propose a spin manipulation
method using single photons, which could be used to preserve the spin coherence
via spin echo techniques.",1005.5545v2
2010-09-28,Vortex Phase Diagram of Layered Superconductor Cu0.03TaS2 for H || c,"The magnetization and anisotropic electrical transport properties have been
measured in high quality Cu0.03TaS2 single crystal. A pronounced peak effect
has been observed, indicating that the high quality and homogeneity are vital
to peak effect. A kink has been observed in the magnetic field H dependence of
the in-plane resistivity {\rho}ab for H || c, which corresponds to a transition
from activated to diffusive behavior of vortex liquid phase. In the diffusive
regime of the vortex liquid phase, the in-plane resistivity {\rho}ab shows
{\rho}ab $\propto$ H0.3 relation, which does not follow the Bardeen-Stephen law
for free flux flow. Finally, a simplified vortex phase diagram of Cu0.03TaS2
for H || c is given.",1009.5449v2
2010-11-27,Performance of Glass Resistive Plate Chambers for a high granularity semi-digital calorimeter,"A new design of highly granular hadronic calorimeter using Glass Resistive
Plate Chambers (GRPCs) with embedded electronics has been proposed for the
future International Linear Collider (ILC) experiments. It features a 2-bit
threshold semi-digital read-out. Several GRPC prototypes with their electronics
have been successfully built and tested in pion beams. The design of these
detectors is presented along with the test results on efficiency, pad
multiplicity, stability and reproducibility.",1011.5969v2
2010-12-13,Self-consistent calculation of the single particle scattering rate in high $Tc$ cuprates,"The linear temperature dependence of the resistivity above the optimal doping
is a longstanding problem in the field of high temperature superconductivity in
cuprates. In this paper, we investigate the effect of gauge fluctuations on the
momentum relaxation time and the transport scattering rate within the slave
boson method. We use a more general slave treatment to resolve the ambiguity of
decomposing the Heisenberg exchange term. We conclude that this term should be
decomposed only in the Cooper channel. This results in the spinon mass
inversely proportional to the doping. It is showed that solving the equation
for the transport scattering rate self-consistently, we find a crossover
temperature above which we obtain the linear temperature dependence of the
electrical resistivity as well as the single particle scattering rate. It is
also shown that this linear temperature dependence of the scattering rate in
the pseudogap region explains the existence of the Fermi arcs with a length
that linearly varies with temperature.",1012.2764v1
2011-03-17,Quantum-Classical Crossover and Apparent Metal-Insulator Transition in a Weakly Interacting 2D Fermi Liquid,"We report the observation of a parallel magnetic field induced
metal-insulator transition (MIT) in a high-mobility two-dimensional electron
gas (2DEG) for which spin and localization physics most likely play no major
role. The high-mobility metallic phase at low field is consistent with the
established Fermi liquid transport theory including phonon scattering, whereas
the insulating phase at higher field shows a large negative temperature
dependence at resistances much smaller than the quantum of resistance, $h/e^2$.
We argue that this observation is a direct manifestation of a quantum-classical
crossover arising predominantly from the magneto-orbital coupling between the
finite width of the 2DEG and the in-plane magnetic field.",1103.3496v2
2011-05-05,Pairing Fluctuations and Anomalous Transport Above the BCS-BEC Crossover in the Two Dimensional Attractive Hubbard Model,"A Fermi liquid with weak attractive interaction undergoes a BCS transition to
a superconductor with reducing temperature. With increasing interaction
strength, the thermal transition is progressively modified as the high
temperature `metallic' phase develops a pseudogap due to pairing fluctuations
and the resistivity above T_c shows insulating behaviour. The crossover to
insulating character occurs much before the system can be considered to be in
the BEC regime of preformed fermion pairs. We use a new Monte Carlo tool to map
out the BCS-BEC crossover in the attractive Hubbard model on large two
dimensional lattices and explicitly compute the resistivity to demonstrate how
the metal to superconductor (MS) thermal transition at weak coupling crosses
over to an insulator to superconductor (IS) transition at intermediate
coupling. Our high resolution access to the single particle and optical
spectrum at finite temperature allows us to completely describe the transport
crossover in this longstanding problem.",1105.1156v1
2011-11-28,Evolution of a metastable phase with a magnetic phase coexistence phenomenon and its unusual sensitivity to magnetic field cycling in the alloys Tb5-xLuxSi3 (x <= 0.7),"Recently, we reported an anomalous enhancement of the positive
magnetoresistance beyond a critical magnetic field in Tb5Si3 in the
magnetically ordered state, attributable to 'inverse metamagnetism'. This
results in unusual magnetic hysteresis loops for the pressurized specimens,
which are relevant to the topic of 'electronic phase separation'. In this
paper, we report the influence of small substitutions of Lu for Tb, to show the
evolution of these magnetic anomalies. We find that, at low temperatures, the
high-field high-resistivity phase could be partially stabilized on returning
the magnetic field to zero in many of these Lu substituted alloys, as measured
through the electrical resistivity ({\rho}). Also, the relative fractions of
this phase and the virgin phase appear to be controlled by a small tuning of
the composition and temperature. Interestingly, at 1.8 K a sudden 'switch-over'
of the value of {\rho} for this mixed phase to that for the virgin phase for
some compositions is observed at low fields after a few field cycles,
indicating metastability of this mixed phase.",1111.6368v1
2012-10-09,Interdependence of Electric Discharge and The Magnetorotational Instability in Protoplanetary Disks,"We study how the magnetorotational instability (MRI) in protoplanetary disks
is affected by the electric discharge caused by the electric field in the
resistive MHD. We have performed three-dimensional shearing box simulations
with various values of plasma beta and electrical breakdown models. We find the
self-sustainment of the MRI in spite of the high resistivity. The instability
gives rise to the large electric field that causes the electrical breakdown,
and the breakdown maintains the high ionization degree required for the
instability.
  The condition for this self-sustained MRI is set by the balance between the
energy supply from the shearing motion and the energy consumed by the Ohmic
dissipation. We apply the condition to various disk models and study where the
active, self-sustained, and dead zones of MRI are. In the fiducial minimum-mass
solar nebula (MMSN) model, the newly-found sustained zone occupies only the
limited volume of the disk. In the late-phase gas-depleted disk models,
however, the sustained zone occupies larger volume of the disk.",1210.2508v2
2012-12-18,Microwave properties of superconducting atomic-layer deposited TiN films,"We have grown superconducting TiN films by atomic layer deposition with
thicknesses ranging from 6 to 89 nm. This deposition method allows us to tune
the resistivity and critical temperature by controlling the film thickness. The
microwave properties are measured, using a coplanar-waveguide resonator, and we
find internal quality factors above a million, high sheet inductances (5.2-620
pH), and pulse response times up to 100 \mu s. The high normal state
resistivity of the films (> 100 \mu\Omega cm) affects the superconducting state
and thereby the electrodynamic response. The microwave response is modeled
using a quasiparticle density of states modified with an effective
pair-breaker,consistently describing the measured temperature dependence of the
quality factor and the resonant frequency.",1212.4434v1
2013-04-22,Persistent non-metallic behavior in Sr2IrO4 and Sr3Ir2O7 at high pressures,"Iridium-based 5d transition-metal oxides are attractive candidates for the
study of correlated electronic states due to the interplay of enhanced
crystal-field, Coulomb and spin-orbit interaction energies. At ambient
pressure, these conditions promote a novel Jeff = 1/2 Mott insulating state,
characterized by a gap of the order of ~0.1 eV. We present high-pressure
electrical resistivity measurements of single crystals of Sr2IrO4 and Sr3Ir2O7.
While no indications of a pressure-induced metallic state up to 55 GPa were
found in Sr2IrO4, a strong decrease of the gap energy and of the resistance of
Sr3Ir2O7 between ambient pressure and 104 GPa confirm that this compound is in
the proximity of a metal-insulator transition.",1304.5864v2
2013-08-28,Normal-state charge dynamics in doped BaFe2As2: Roles of doping and necessary ingredients for superconductivity,"We carried out a comparative study of the in-plane resistivity and optical
spectrum of doped BaFe2As2 and investigated the doping evolution of the charge
dynamics. For BaFe2As2, charge dynamics is incoherent at high temperatures.
Electron (Co) and isovalent (P) doping into BaFe2As2 increase coherence of the
system and transform the incoherent charge dynamics into highly coherent one.
On the other hand, charge dynamics remains incoherent for hole (K) doping. It
is found in common with any type of doping that superconductivity with high
transition temperature emerges when the normal-state charge dynamics maintains
incoherence and when the resistivity associated with the coherent channel
exhibits dominant temperature-linear dependence.",1308.6133v1
2014-04-07,Crystal structure and physical properties of EuPtIn$_{4}$ intermetallic antiferromagnet,"We report the synthesis of EuPtIn$_{4}$ single crystalline platelets by the
In-flux technique. This compound crystallizes in the orthorhombic Cmcm
structure with lattice parameters $a=4.542(1)$ \AA, $b=16.955(2)$ \AA$\,$ and
$c=7.389(1)$ \AA. Measurements of magnetic susceptibility, heat capacity,
electrical resistivity, and electron spin resonance (ESR) reveal that
EuPtIn$_{4}$ is a metallic Curie-Weiss paramagnet at high temperatures and
presents antiferromagnetic (AFM) ordering below $T_{N}=13.3$ K. In addition, we
observe a successive anomaly at $T^{*} = 12.6$ K and a spin-flop transition at
$H_{c} \sim 2.5$ T applied along the $ac$-plane. In the paramagnetic state, a
single Eu$^{2+}$ Dysonian ESR line with a Korringa relaxation rate of $b =
4.1(2)$ Oe/K is observed. Interestingly, even at high temperatures, both ESR
linewidth and electrical resistivity reveal a similar anisotropy. We discuss a
possible common microscopic origin for the observed anisotropy in these
physical quantities likely associated with an anisotropic magnetic interaction
between Eu$^{2+}$ 4$f$ electrons mediated by conduction electrons.",1404.1660v1
2014-04-14,High temperature superconducting FeSe films on SrTiO3 substrates,"Interface enhanced superconductivity at two dimensional limit has become one
of most intriguing research directions in condensed matter physics. Here, we
report the superconducting properties of ultra-thin FeSe films with the
thickness of one unit cell (1-UC) grown on conductive and insulating SrTiO3
(STO) substrates. For the 1-UC FeSe on conductive STO substrate (Nb-STO), the
magnetization versus temperature (M-T) measurement shows a diamagnetic signal
at 85 K, suggesting the possibility of superconductivity appears at this high
temperature. For the FeSe films on insulating STO substrate, systematic
transport measurements were carried out and the sheet resistance of FeSe films
exhibits Arrhenius TAFF behavior with a crossover from a single-vortex pinning
region to a collective creep region. More intriguing, sign reversal of Hall
resistance with temperature is observed, demonstrating a crossover from hole
conduction to electron conduction above Tc in 1-UC FeSe films.",1404.3464v2
2014-04-16,Magnetic Ordering at Anomalously High Temperatures in Dy at Extreme Pressures: a New Kondo-Lattice State?,"In an attempt to destabilize the magnetic state of the heavy lanthanides Dy
and Gd, extreme pressures were applied in an electrical resistivity measurement
to 157 GPa over the temperature range 5 - 295 K. The magnetic ordering
temperature $T_{\text{o}}$ and spin-disorder resistance $R_{sd}$ of Dy, as well
as the superconducting pair-breaking effect $\Delta T_{c}$ in Y(1 at.\% Dy),
are found to track each other in a highly non-monotonic fashion as a function
of pressure, all three increasing sharply above 73 GPa, the critical pressure
for a 6\% volume collapse in Dy. At 157 GPa $T_{\text{o}}$ is estimated to
reach temperatures in the range 370 - 500 K, the highest magnetic ordering
temperature of any lanthanide. In contrast, $T_{\text{o}% }(P)$ for Gd shows no
such sharp increase to 105 GPa. Taken together, these results suggest that
pressures greater than 73 GPa transform Dy from a conventional magnetic
lanthanide into a Kondo lattice system with an anomalously high magnetic
ordering temperature.",1404.4256v3
2014-05-14,Theory of universal incoherent metallic transport,"In an incoherent metal, transport is controlled by the collective diffusion
of energy and charge rather than by quasiparticle or momentum relaxation. We
explore the possibility of a universal bound $D \gtrsim \hbar v_F^2/(k_B T)$ on
the underlying diffusion constants in an incoherent metal. Such a bound is
loosely motivated by results from holographic duality, the uncertainty
principle and from measurements of diffusion in strongly interacting
non-metallic systems. Metals close to saturating this bound are shown to have a
linear in temperature resistivity with an underlying dissipative timescale
matching that recently deduced from experimental data on a wide range of
metals. This bound may be responsible for the ubiquitous appearance of high
temperature regimes in metals with $T$-linear resistivity, motivating direct
probes of diffusive processes and measurements of charge susceptibilities.",1405.3651v3
2014-05-14,Linear Resistivity from Non-Abelian Black Holes,"Starting with the holographic p-wave superconductor, we show how to obtain a
finite DC conductivity through a non-abelian gauge transformation. The
translational symmetry is preserved. We obtain phenomenological similarities
with high temperature cuprate superconductors. Our results suggest that a
lattice or impurities are not essential to produce a finite DC resistivity with
a linear temperature dependence. An analogous field theory calculation for free
fermions, presented in the appendix, indicates our results may be a special
feature of strong interactions.",1405.3714v4
2014-06-10,Nonlinear transport and noise thermometry in quasi-classical ballistic point contacts,"We study nonlinear transport and non-equilibrium current noise in
quasi-classical point contacts (PCs) defined in a low-density high-quality
two-dimensional electron system in GaAs. At not too high bias voltages $V$
across the PC the noise temperature is determined by a Joule heat power and
almost independent on the PC resistance that can be associated with a
self-heating of the electronic system. This commonly accepted scenario breaks
down at increasing $V$, where we observe extra noise accompanied by a strong
decrease of the PC's differential resistance. The spectral density of the extra
noise is roughly proportional to the nonlinear current contribution in the PC
$\delta S\approx2F^*|e\delta I|\sim V^2$ with the effective Fano factor
$F^*<1$, indicating that a random scattering process is involved. A small
perpendicular magnetic field is found to suppress both $\delta I$ and $\delta
S$. Our observations are consistent with a concept of a drag-like mechanism of
the nonlinear transport mediated by electron-electron scattering in the leads
of quasi-classical PCs.",1406.2481v2
2014-12-11,Transition-Metal Substitutions in Iron Chalcogenides,"The $ab$-plane resistivity and Hall effect are studied in
Fe$_{1-y}$M$_y$Te$_{0.65}$Se$_{0.35}$ single crystals doped with two transition
metal elements, M = Co or Ni, over a wide doping range, $0 \leq y \leq 0.2$.
The superconducting transition temperature, $T_{c}$, reaches zero for Co at $y
\simeq 0.14$ and for Ni at $y \simeq 0.032$, while the resistivity at the
$T_{c}$ onset increases weakly with Co doping, and strongly with Ni doping. The
Hall coefficient $R_H$, positive for $y$ = 0, remains so at high temperatures
for all $y$, while it changes sign to negative at low $T$ for $y > 0.135$ (Co)
and $y > 0.06$ (Ni). The analysis based on a two band model suggests that at
high $T$ residual hole pockets survive the doping, but holes get localized upon
the lowering of $T$, so that the effect of the electron doping on the transport
becomes evident. The suppression of the $T_c$ by Co impurity is related to
electron doping, while in case of the Ni impurity strong electron localization
most likely contributes to fast decrease of the $T_c$.",1412.3599v1
2015-10-01,"'Metal'-like transport in high-resistance, high aspect ratio two-dimensional electron gases","We investigate the striking absence of strong localisation observed in
mesoscopic two-dimensional electron gases (2DEGs) (Baenninger et al 2008 Phys.
Rev. Lett. 100 1016805, Backes et al 2015 Phys. Rev. B 92 235427) even when
their resistivity $\rho >> h/e^2$. In particular, we try to understand whether
this phenomenon originates in quantum many-body effects, or simply percolative
transport through a network of electron puddles. To test the latter scenario,
we measure the low temperature (low-$T$) transport properties of long and
narrow 2DEG devices in which percolation effects should be heavily suppressed
in favour of Coulomb blockade. Strikingly we find no indication of Coulomb
blockade and that the high-$\rho$, low-$T$ transport is exactly similar to that
previously reported in mesoscopic 2DEGs with different geometries. Remarkably,
we are able to induce a `metal'-insulator transition (MIT) by applying a
perpendicular magnetic field $B$. We present a picture within which these
observations fit into the more conventional framework of the 2D MIT.",1510.00236v2
2016-07-28,A Second-order Divergence-constrained Multidimensional Numerical Scheme for Relativistic Two-Fluid Electrodynamics,"A new multidimensional simulation code for relativistic two-fluid
electrodynamics (RTFED) is described. The basic equations consist of the full
set of Maxwell's equations coupled with relativistic hydrodynamic equations for
separate two charged fluids, representing the dynamics of either an
electron-positron or an electron-proton plasma. It can be recognized as an
extension of conventional relativistic magnetohydrodynamics (RMHD). Finite
resistivity may be introduced as a friction between the two species, which
reduces to resistive RMHD in the long wavelength limit without suffering from a
singularity at infinite conductivity. A numerical scheme based on HLL
(Harten-Lax-Van Leer) Riemann solver is proposed that exactly preserves the two
divergence constraints for Maxwell's equations simultaneously. Several
benchmark problems demonstrate that it is capable of describing RMHD
shocks/discontinuities at long wavelength limit, as well as dispersive
characteristics due to the two-fluid effect appearing at small scales. This
shows that the RTFED model is a promising tool for high energy astrophysics
application.",1607.08487v1
2016-12-14,Successive spatial symmetry breaking under high pressure in the spin-orbit-coupled metal Cd2Re2O7,"The 5d-transition metal pyrochlore oxide Cd2Re2O7, which was recently
suggested to be a prototype of the spin-orbit-coupled metal [Phys. Rev. Lett.
115, 026401 (2015)], exhibits an inversion-symmetry breaking (ISB) transition
at 200 K and a subsequent superconductivity below 1 K at ambient pressure. We
study the crystal structure at high pressures up to 5 GPa by means of
synchrotron X-ray powder diffraction. A rich structural phase diagram is
obtained, which contains at least seven phases and is almost consistent with
the electronic phase diagram determined by previous resistivity measurements.
Interestingly, the ISB transition vanishes at ~4 GPa, where the enhancement of
the upper critical field was observed in resistivity. Moreover, it is shown
that the point groups at 8 K, probably kept in the superconducting phases,
sequentially transform into piezoelectric, ferroelectric, and centrosymmetric
structures on the application of pressure.",1612.04577v2
2016-12-25,Effects of Interstitial Oxygen and Carbon on Niobium Superconducting Cavities,"We present results on the effects of interstitial oxygen and carbon on a
bulk-niobium superconducting radio-frequency cavity. Previous experiments have
shown that high-temperature (~800 $^\circ\text{C}$) nitrogen-doping plays the
dominant role in the reduction of the electron mean free path in the RF
penetration layer of niobium that leads to a decrease in microwave surface
resistance and a suppression the temperature-dependent component of the surface
resistance with increasing accelerating gradient. In this work, we show that
oxygen and carbon-doping has very similar effects on cavity performance,
demonstrating that these effects are not unique to nitrogen. The preparation
method used in the introduction of interstitial oxygen and carbon has the
advantage that it is done at lower temperatures than that of high-temperature
nitrogen-doping and does not require post-treatment electro-polishing.",1612.08291v2
2017-06-06,Topological Phase Transition Under Pressure in the Topological Nodal Line Superconductor PbTaSe$_2$,"A first-order-like resistivity hysteresis is induced by a subtle structural
transition under hydrostatic pressure in the topological nodal-line
superconductor PbTaSe$_2$. This structure transition is quickly suppressed to
zero at pressure $\sim$0.25 GPa. As a result, superconductivity shows a marked
suppression, accompanied with fundamental changes in the magnetoresistance and
Hall resistivity, suggesting a Lifshitz transition around $\sim$0.25 GPa. The
first principles calculations show that the spin-orbit interactions partially
gap out the Dirac nodal line around $K$ point in the Brillouin zone upon
applying a small pressure, whilst the Dirac states around $H$ point are
completely destroyed. The calculations further reveal a second structural phase
transition under a pressure as high as $\sim$30 GPa, through which a transition
from a topologically nontrivial phase to a trivial phase is uncovered, with a
superconducting dome emerging under this high-pressure phase.",1706.01744v1
2018-02-21,Optical transparency and electrical conductivity of single-wall carbon nanotubes and of intermediate filaments of porcine Müller cells,"In the present study, we continue investigation of the high-contrast vision
in the inverted retina of the vertebrates eyes. We report a method of
separation and purification of porcine (Sus scrofa domestica) intermediate
filaments (IFs), extracted from the retinal M\""uller cells (MCs). We also
report experimental and theoretical methods of measurements and calculations of
the reduced resistivity and light transmission by the IFs and single-wall
carbon nanotubes (SWCNTs). The measured reduced resistivity values were
(3.1+-0.3)*10^-4 and (2.8+-0.2)*10^-4 Ohm m^-1 cm^2, respectively, being quite
close to those of typical metals. We report a method for measuring the light
energy transmission by the intermediate filaments and single-wall carbon
nanotubes. We found that these structures efficiently transfer light energy
along its axis, with the light reemitted at the other end of the structure. We
also report spectral selectivity of the IFs. The reported results demonstrate
that the assumptions we made in deducing the theory of high-contrast vision in
an inverted retina were correct and fully supported by the presently reported
experimental results.",1803.07124v1
2018-04-27,Effect of uniaxial stress on the magnetic phases of CeAuSb$_2$,"We present results of measurements of resistivity of \CAS{} under the
combination of $c$-axis magnetic field and in-plane uniaxial stress. In
unstressed \CAS{} there are two magnetic phases. The low-field A phase is a
single-component spin-density wave (SDW), with $\mathbf{q} = (\eta, \pm \eta,
1/2)$, and the high-field B phase consists of microscopically coexisting
$(\eta, \eta, 1/2)$ and $(\eta, -\eta, 1/2)$ spin-density waves. Pressure along
a $\langle 100 \rangle$ lattice direction is a transverse field to both of
these phases, and so initially has little effect, however eventually induces
new low- and high-field phases in which the principal axes of the SDW
components appear to have rotated to the $\langle 100 \rangle$ directions.
Under this strong $\langle 100 \rangle$ compression, the field evolution of the
resistivity is much smoother than at zero strain: In zero strain, there is a
strong first-order transition, while under strong $\langle 100 \rangle$ it
becomes much broader. We hypothesize that this is a consequence of the uniaxial
stress lifting the degeneracy between the (100) and (010) directions.",1804.10539v2
2018-05-29,Resisting collapse: How matter inside a black hole can withstand gravity,"How can a Schwarzschild-sized matter system avoid a fate of gravitational
collapse? To address this question, we critically reexamine the arguments that
led to the ""Buchdahl bound"", which implies that the minimal size of a stable,
compact object must be larger than nine eighths of its own Schwarzschild
radius. Following Mazur and Mottola, and in line with other counterexamples to
the singularity theorems, we identify large negative radial pressure extending
to the gravitational radius as the essential ingredient for evading the
Buchdahl bound. Our results are novel although consistent with many other
investigations of models of non-singular black holes. It is shown in particular
that a large negative pressure in the framework of classical GR translates into
a large positive pressure once quantum physics is incorporated. In this way, a
Schwarzschild-sized bound state of closed, interacting fundamental strings in
its high-temperature Hagedorn phase can appear to have negative pressure and
thus the ability to resist gravitational collapse.",1805.11667v2
2018-06-08,Fluidity Onset in Graphene,"Viscous electron fluids have emerged recently as a new paradigm of
strongly-correlated electron transport in solids. Here we report on a direct
observation of the transition to this long-sought-for state of matter in a
high-mobility electron system in graphene. Unexpectedly, the electron flow is
found to be interaction-dominated but non-hydrodynamic (quasiballistic) in a
wide temperature range, showing signatures of viscous flows only at relatively
high temperatures. The transition between the two regimes is characterized by a
sharp maximum of negative resistance, probed in proximity to the current
injector. The resistance decreases as the system goes deeper into the
hydrodynamic regime. In a perfect darkness-before-daybreak manner, the
interaction-dominated negative response is strongest at the transition to the
quasiballistic regime. Our work provides the first demonstration of how the
viscous fluid behavior emerges in an interacting electron system.",1806.03231v2
2018-06-25,"Noise Measurements of High-Speed, Light-Emitting GaN Resonant-Tunneling Diodes","We report here the first RF noise measurements on two designs of n-doped
GaN/AlN double-barrier resonant tunneling diodes (RTDs), each having a
room-temperature negative differential resistance (NDR) and also strong near-UV
light emission. The measurements are made with a standard, un-isolated RF
receiver and calibration is made using a substitution-resistor/hot-cold
radiometric technique which works in the positive differential resistance (PDR)
region but not the NDR region. A high-quality InGaAs/AlAs double-barrier RTD is
used as a control sample and displays shot noise suppression down to
$\Gamma\approx$0.5 in the PDR region, as expected. The GaN/AlN RTDs display
both shot-noise enhancement and suppression in the PDR regions, but no obvious
sign of sudden shot-noise enhancement in the threshold bias region of light
emission. This supports the hypothesis that the holes required for light
emission are created by electronic (Zener) interband tunneling, not impact
ionization. Further the minimum shot-noise factor of $\Gamma\sim$ 0.34 suggests
that the GaN/AlN RTDs are acting like triple-barrier devices.",1806.09270v1
2019-09-04,High-field moment polarization in the itinerant ferromagnet URhSi,"We report a high-magnetic-field study of the itinerant ferromagnet URhSi.
Magnetization and electrical resistivity were measured under magnetic fields
$\mu_0H$ up to 58~T applied along the directions $\mathbf{a}$, $\mathbf{b}$,
and $\mathbf{c}$ of the orthorhombic structure and temperatures $T$ ranging
from 1.5 to 50 K. For $\mathbf{H}\parallel\mathbf{b}$, pseudo-metamagnetism at
$\mu_0H_m\simeq30-40$~T is associated with a broad step in the magnetization
and a maximum in the resistivity. The properties of URhSi are discussed and
compared with those of the isostructural superconducting ferromagnets URhGe and
UCoGe and of the superconducting paramagnet UTe$_2$.",1909.01810v2
2019-09-30,Hall coefficient diagnostics of surface state in pressurized SmB6,"In this study, we report the first results of the high-pressure Hall
coefficient (RH) measurements in the putative topological Kondo insulator SmB6
up to 37 GPa. Below 10 GPa, our data reveal that RH(T) exhibits a prominent
peak upon cooling below 20 K. Remarkably, the temperature at which surface
conduction dominates coincides with the temperature of the peak in RH(T). The
temperature dependent resistance and Hall coefficient can be well fitted by a
two-channel model with contributions from the metallic surface and the
thermally activated bulk states. When the bulk of SmB6 becomes metallic and
magnetic at ~ 10 GPa, both the RH(T) peak and the resistance plateau disappear
simultaneously. Our results indicate that the RH(T) peak is a fingerprint to
diagnose the presence of a metallic surface state in SmB6. The high-pressure
magnetic state of SmB6 is robust to 180 GPa, and no evidence of
superconductivity is observed in the metallic phase.",1909.13462v1
2014-10-06,Memristive Threshold Logic Circuit Design of Fast Moving Object Detection,"Real-time detection of moving objects involves memorisation of features in
the template image and their comparison with those in the test image. At high
sampling rates, such techniques face the problems of high algorithmic
complexity and component delays. We present a new resistive switching based
threshold logic cell which encodes the pixels of a template image. The cell
comprises a voltage divider circuit that programs the resistances of the
memristors arranged in a single node threshold logic network and the output is
encoded as a binary value using a CMOS inverter gate. When a test image is
applied to the template-programmed cell, a mismatch in the respective pixels is
seen as a change in the output voltage of the cell. The proposed cell when
compared with CMOS equivalent implementation shows improved performance in
area, leakage power, power dissipation and delay.",1410.1267v1
2014-11-11,Frequency-dependent phonon mean free path in carbon nanotubes from non-equilibrium molecular dynamics,"Owing to their long phonon mean free paths (MFPs) and high thermal
conductivity, carbon nanotubes (CNTs) are ideal candidates for, e.g., removing
heat from electronic devices. It is unknown, however, how the intrinsic phonon
MFPs depend on vibrational frequency in non-equilibrium. We determine the
spectrally resolved phonon MFPs in isotopically pure CNTs from the spectral
phonon transmission function calculated using non-equilibrium molecular
dynamics, fully accounting for the resistive phonon-phonon scattering processes
through the anharmonic terms of the interatomic potential energy function. Our
results show that the effective room temperature MFPs of low-frequency phonons
($f<0.5$ THz) exceed $10$ $\mu$m, while the MFP of high-frequency phonons
($f\gtrsim 20$ THz) is in the range 10--100 nm. Because the determined MFPs
directly reflect the resistance to energy flow, they can be used to accurately
predict the thermal conductivity for arbitrary tube lengths by calculating a
single frequency integral. The presented results and methods are expected to
significantly improve the understanding of non-equilibrium thermal transport in
low-dimensional nanostructures.",1411.2838v2
2014-11-12,"Acoustic (Ultrasonic) Non-Diffracting Beams: Some theory, and Proposals of Acoustic Antennas for several purposes","On the basis of suitable theoretical grounds, we study and propose Antennas
for the generation, in Acoustics, of Non-Diffracting Beams of ultrasound. We
start considering for instance a frequency of about 40 kHz, and foresee fair
results even for finite apertures endowed with reasonable diameters (e.g., of 1
m), having in mind various possible applications, including remote sensing.
Then, we discuss the production in lossy media of ultrasonic beams resisting
both diffraction and attenuation. Everything is afterward investigated for the
cases in which high-power acoustic transducers are needed (for instance, for
detection at a distance -or even explosion- of buried objects, like mines).
  Keywords: Acoustic Non-Diffracting Beams; Truncated Beams of Ultrasound;
Remote sensing; Diffraction, Attenuation, Annular transducers, Bessel beam
superposition, High-power ultrasound emitters, Beams resisting diffraction and
attenuation, Acoustic Frozen Waves, Detection of buried objects, Explosion of
Mines at a distance",1411.3340v1
2016-06-07,Oscillatory Localization of Quantum Walks Analyzed by Classical Electric Circuits,"We examine an unexplored quantum phenomenon we call oscillatory localization,
where a discrete-time quantum walk with Grover's diffusion coin jumps back and
forth between two vertices. We then connect it to the power dissipation of a
related electric network. Namely, we show that there are only two kinds of
oscillating states, called uniform states and flip states, and that the
projection of an arbitrary state onto a flip state is bounded by the power
dissipation of an electric circuit. By applying this framework to states along
a single edge of a graph, we show that low effective resistance implies
oscillatory localization of the quantum walk. This reveals that oscillatory
localization occurs on a large variety of regular graphs, including
edge-transitive, expander, and high degree graphs. As a corollary, high
edge-connectivity also implies localization of these states, since it is
closely related to electric resistance.",1606.02136v3
2016-12-17,Contact resistance between two REBCO tapes under load and load-cycles,"No-insulation (NI) REBCO magnets have many advantages. They are
self-protecting, therefore do not need quench detection and protection which
can be very challenging in a high Tc superconducting magnet. Moreover, by
removing insulation and allowing thinner copper stabilizer, NI REBCO magnets
have significantly higher engineering current density and higher mechanical
strength. On the other hand, NI REBCO magnets have drawbacks of long magnet
charging time and high field-ramp-loss. In principle, these drawbacks can be
mitigated by managing the turn-to-turn contact resistivity (Rc). Evidently the
first step toward managing Rc is to establish a reliable method of accurate Rc
measurement. In this paper, we present experimental Rc measurements of REBCO
tapes as a function of mechanical load up to 144 MPa and load cycles up to 14
times. We found that Rc is in the range of 26-100 uOhm-cm2; it decreases with
increasing pressure, and gradually increases with number of load cycles. The
results are discussed in the framework of Holm's electric contact theory.",1701.00447v2
2017-01-07,A quantitative description of Nernst effect in high-temperature superconductors,"A quantitative vortex-fluid model for flux-flow resistivity $\rho$ and Nernst
signal $e_N$ in high-temperature superconductors (HTSC) is proposed. Two kinds
of vortices, magnetic and thermal, are considered, and the damping viscosity
$\eta$ is modeled by extending the Bardeen-Stephen model to include the
contributions of flux pinning at low temperature and in weak magnetic fields,
and vortex-vortex collisions in strong magnetic fields. Remarkably accurate
descriptions for both Nernst signal of six samples and flux flow resistivity
are achieved over a wide range of temperature $T$ and magnetic field $B$. A
discrepancy of three orders of magnitude between data and Anderson's model of
Nernst signal is pointed out and revised using experimental values of $\eta$
from magnetoresistance. Furthermore, a two-step procedure is developed to
reliably extract, from the Nernst signal, a set of physical parameters
characterizing the vortex dynamics, which yields predictions of local
superfluid density $n_s$, the Kosterlitz coefficient $b$ of thermal vortices,
and upper critical field and temperature. Application of the model and
systematic measurement of relevant physical quantities from Nernst signal in
other HTSC samples are discussed.",1701.01832v1
2018-11-08,Temperature dependence of side-jump spin Hall conductivity,"In the conventional paradigm of the spin Hall effect, the side-jump
conductivity due to electron-phonon scattering is regarded to be temperature
independent. To the contrary, we draw the distinction that, while this
side-jump conductivity is temperature independent in the classical
equipartition regime where the longitudinal resistivity is linear in
temperature, it is temperature dependent below the equipartition regime. The
mechanism resulting in this temperature dependence differs from the familiar
one of the longitudinal resistivity. In the concrete example of Pt, we show
that the change of the spin Hall conductivity with temperature can be as high
as 50%. Experimentally accessible high-purity Pt is proposed to be suitable for
observing this prominent variation below 80 K.",1811.03229v6
2019-07-28,"Quantum critical fluctuations, Planckian dissipation, and compactification scale","The most striking result here is that the notion of Planckian dissipation is
also applicable to the $c$-axis resistivity of the high temperature cuprate
superconductors, and to my knowledge this aspect has not been previously
addressed. The derivation involves Kubo formula and does not require any
mechanism beyond a non-Fermi liquid assumption. The $c$-axis resistivity, in
its essential aspects, is discussed in the context of quantum critical point.
Finally, I consider a zero temperature problem with one of its spatial
dimensions compactified. The warning is that this compatification scale at the
quantum critical point behaves similarly to the finite temperature problem, but
obviously being at zero temperature there is no dissipation.",1907.12163v2
2020-02-10,Anomalous Nematic States in High Half-Filled Landau Levels,"It is well established that the ground states of a two-dimensional electron
gas with half-filled high ($N \ge 2$) Landau levels are compressible
charge-ordered states, known as quantum Hall stripe (QHS) phases. The generic
features of QHSs are a maximum (minimum) in a longitudinal resistance $R_{xx}$
($R_{yy}$) and a non-quantized Hall resistance $R_H$. Here, we report on
emergent minima (maxima) in $R_{xx}$ ($R_{yy}$) and plateau-like features in
$R_H$ in half-filled $N \ge 3$ Landau levels. Remarkably, these unexpected
features develop at temperatures considerably lower than the onset temperature
of QHSs, suggesting a new ground state.",2002.03964v2
2020-02-16,Study of Position Sensitive Silicon Detector (PSD) for SiW-ECAL at ILC,"We are developing position sensitive silicon detectors (PSDs) which have an
electrode at each of four corners so that incident position of a charged
particle can be obtained with signal from the electrodes. It is expected that
the position resolution of the electromagnetic calorimeter (ECAL) of the ILD
detector will be improved by introducing PSDs to detection layers. We have been
developing the PSDs for several years. In the previous production we found that
the charge separation is not optimally done due to the readout impedance. To
solve the issue, we produced new PSDs with higher surface resistance with an
additional resistive layer on the surface. We also implemented several
techniques to decrease position distortion and increase signal-to-noise ratio
which are essential for the optimal position resolution. The measurements on
the prototype sensors are ongoing, including radiation source measurement and
laser measurement using an ASIC for silicon pad detectors.",2002.06534v2
2020-03-23,Multi-Terminal DC Fault Identification for MMC-HVDC Systems based on Modal Analysis -- A Localized Protection Scheme,"We propose a localized protection scheme based on modal analysis in
multi-terminal modular multilevel converter (MMC) based high voltage DC (HVDC)
systems. The paper addresses the issues of localized protection scheme based DC
fault identification, such as differentiating between external and internal
faults, classification of type of fault contingency i.e., pole to pole
(\textit{PTP}) or pole to ground (\textit{PTG}) for high impedance faults
(HIFs) in the system. The scheme works on equivalent network of multi-terminal
MMC-HVDC system for a DC fault, using phase-modal transformation to analyse
line-mode and zero-mode voltage across the current limiting reactor (CLR) for
different possible contingencies in the presence of fault resistance. The
protection scheme is validated to be reliable for HIFs and in the presence of
White Gaussian Noise (WGN) in measurement. The scheme operation is validated to
be intact for varying fault location, fault resistances and system transients.",2003.10145v2
2022-01-31,Accelerated 3D Electrical Resistivity Tomography with a Scalable Jacobian-free Approach,"A Jacobian-free inversion method is presented to accelerate Electrical
Resistivity Tomography (ERT) for shallow aquifer characterization. The ERT
problem typically implements the adjoint state method to efficiently compute
Jacobian during the inversion. However, the adjoint state method needs
intrusive forward model code changes and may not be computationally scalable
with many observations especially when one performs 3D ERT surveys with dense
multi-electrode arrays. Here the Principal Component Geostatistical Approach
(PCGA), a fast and scalable Jacobian-free inverse modeling method, is applied
to solve a high dimensional data-intensive ERT problem. The PNNL's ERT
simulation software E4D was linked to the python interface pyPCGA without
intrusive code change and the example code is upload in a public repository.
The result in this study shows that high-resolution 3D subsurface
characterization is computationally feasible, which would have a great
potential for implementations in practice.",2202.00059v1
2014-01-02,Electrolyte gate dependent high-frequency measurement of graphene field-effect transistor for sensing applications,"We performed radiofrequency (RF) reflectometry measurements at 2.4 GHz on
electrolyte-gated graphene field-effect transistors (GFETs) utilizing a tunable
stub-matching circuit for impedance matching. We demonstrate that the gate
voltage dependent RF resistivity of graphene can be deduced even in the
presence of the electrolyte which is in direct contact with the graphene layer.
The RF resistivity is found to be consistent with its DC counterpart in the
full gate voltage range. Furthermore, in order to access the potential of
high-frequency sensing for applications, we demonstrate time-dependent gating
in solution with nanosecond time resolution.",1401.0381v1
2016-03-16,"The ""ideal"" tearing mode: theory and resistive MHD simulations","Classical MHD reconnection theories, both the stationary Sweet-Parker model
and the tearing instability, are known to provide rates which are too slow to
explain the observations. However, a recent analysis has shown that there
exists a critical threshold on current sheet's thickness, namely a/L~S^(-1/3),
beyond which the tearing modes evolve on fast macroscopic Alfvenic timescales,
provided the Lunquist number S is high enough, as invariably found in solar and
astrophysical plasmas. Therefore, the classical Sweet-Parker scenario, for
which the diffusive region scales as a/L~S^(-1/2) and thus can be up to ~100
times thinner than the critical value, is likely to be never realized in
nature, as the current sheet itself disrupts in the elongation process. We
present here two-dimensional, compressible, resistive MHD simulations, with S
ranging from 10^5 to 10^7, that fully confirm the linear analysis. Moreover, we
show that a secondary plasmoid instability always occurs when the same critical
scaling is reached on the local, smaller scale, leading to a cascading
explosive process, reminiscent of the flaring activity.",1603.04995v1
2017-05-15,Mathematical Analysis of the Probability of Spontaneous Mutations in HIV-1 Genome and Their Role in the Emergence of Resistance to Anti-Retroviral Therapy,"$\textbf{Background:}$ High mutability of HIV is the driving force of
antiretroviral drug resistance, which represents a medical care challenge.
  $\textbf{Method and Model Equation:}$ To detect the mutability of each gene
in the HIV-1 genome; a mathematical analysis of HIV-1 genome is performed,
depending on a linear relation wherein the probability of spontaneous mutations
emergence is directly proportional to the ratio of the gene length to the whole
genome length. \begin{equation*} {P_g}{S_i} =\frac{g}{G} \end{equation*}
  $\textbf{Results:}$ $\textbf{tat}$, $\textbf{vpr}$ and $\textbf{vpu}$ are the
least mutant genes in HIV-1 genome. Protease $\textbf{PROT}$ gene is the least
mutant gene component of the polymerases $\textbf{pol}$.
  $\textbf{Conclusion:}$ $\textbf{tat}$, $\textbf{vpr}$ and $\textbf{vpu}$ are
the best candidates for HIV-1 recombinant subunit vaccines or as a part of
$\textit{prime and boost}$ vaccine combinations. Also; the protease
inhibitor-based regime represents a high genetic barrier for HIV to overcome.",1705.06132v1
2017-08-05,Copper-oxide Nanowires based Humidity Sensor,"This paper presents investigated results of copper-oxide nanowires used as a
humidity sensor. Copper-oxide nanowires films were grown over cross-comb type
gold electrodes on a SiO2 substrate using thermal annealing technique, and its
humidity sensitive characteristics were investigated through resistance across
the gold electrodes. These copper-oxide nanowires films revealed high
sensitivity and long-term stability with fast response time. It was found that
resistance across gold electrodes of the fabricated sensor decreases with
increase in humidity almost linearly on a logarithmic scale. It appears that
copper-oxide nanowires can be used as low-cost humidity sensor with high output
reliability and reproduction rate. The observations were carried out at room
temperature (RT) and relative humidity (RH) in the range of 6% to 97%.",1708.01720v1
2018-08-03,An All-Electric Single-Molecule Hybridisation Detector for short DNA Fragments,"In combining DNA nanotechnology and high-bandwidth single-molecule detection
in nanopipettes, we demonstrate an all-electric, label-free hybridisation
sensor for short DNA sequences (< 100 nt). Such short fragments are known to
occur as circulating cell-free DNA in various bodily fluids, such as blood
plasma and saliva, and have been identified as disease markers for cancer and
infectious diseases. To this end, we use as a model system a 88-mer target from
the RV1910c gene in Mycobacterium tuberculosis that is associated with
antibiotic (isoniazid) resistance in TB. Upon binding to short probes attached
to long carrier DNA, we show that resistive pulse sensing in nanopipettes is
capable of identifying rather subtle structural differences, such as the
hybridisation state of the probes, in a statistically robust manner. With
significant potential towards multiplexing and high-throughput analysis, our
study points towards a new, single-molecule DNA assay technology that is fast,
easy to use and compatible with point of care environments.",1808.01168v1
2018-08-23,An explicit divergence-free DG method for incompressible magnetohydrodynamics,"We extend the recently introduced explicit divergence-free DG scheme for
incompressible hydrodynamics [arXiv:1808.04669]. to the incompressible
magnetohydrodynamics (MHD). A globally divergence-free finite element space is
used for both the velocity and the magnetic field. Highlights of the scheme
includes global and local conservation properties, high-order accuracy,
energy-stability, pressure-robustness. When forward Euler time stepping is
used, we need two symmetric positive definite (SPD) hybrid-mixed Poisson
solvers (one for velocity and one for magnetic field) to advance the solution
to the next time level. Since we treat both viscosity in the momentum equation
and resistivity in the magnetic induction equation explicitly, the method shall
be best suited for inviscid or high-Reynolds number, low resistivity flows so
that the CFL constraint is not too restrictive.",1808.08119v1
2019-08-13,Study of Particle Multiplicity of Cosmic Ray Events using 2m$\times$2m Resistive Plate Chamber Stack at IICHEP-Madurai,"An experimental setup consisting of 12 layers of glass Resistive Plate
Chambers (RPCs) of size 2\,m\,$\times$\,2\,m has been built at IICHEP-Madurai
(\ang{9;56;14.5}\,N \ang{78;00;47.9}\,E, on the surface) to study the long term
performance and stability of RPCs produced on large scale in Indian industry.
This setup has been collecting data triggered by the passage of charged
particles. The measurement of the multiplicity of charged particles due to
cosmic ray interactions are presented here. Finally, the results are compared
with different hadronic models of the CORSIKA simulation.",1908.04589v5
2011-04-11,Resistively detected nuclear magnetic resonance via a single InSb two-dimensional electron gas at high temperature,"We report on the demonstration of the resistively detected nuclear magnetic
resonance (RDNMR) of a single InSb two-dimensional electron gas (2DEG) at
elevated temperatures up to 4 K. The RDNMR signal of 115In in the simplest
pseudospin quantum Hall ferromagnet triggered by a large direct current shows a
peak-dip line shape, where the nuclear relaxation time T1 at the peak and the
dip is different but almost temperature independent. The large Zeeman,
cyclotron, and exchange energy scales of the InSb 2DEG contribute to the
persistence of the RDNMR signal at high temperatures.",1104.1826v1
2012-03-23,Transport Measurements on Nano-engineered Two Dimensional Superconducting Wire Networks,"Superconducting triangular Nb wire networks with high normal-state resistance
are fabricated by using a negative tone hydrogen silsesquioxane (HSQ) resist.
Robust magnetoresistance oscillations are observed up to high magnetic fields
and maintained at low temperatures, due to the eective reduction of wire
dimensions. Well-defined dips appear at integral and rational values (1/2, 1/3,
1/4) of the reduced flux f = Phi/Phi_0, which is the first observation in the
triangular wire networks. These results are well consistent with theoretical
calculations for the reduced critical temperature as a function of f.",1203.5163v1
2015-04-03,Energy-efficient hybrid spintronic-straintronic reconfigurable bit comparator,"We propose a reconfigurable bit comparator implemented with a nanowire spin
valve whose two contacts are magnetostrictive with bistable magnetization.
Reference and input bits are ""written"" into the magnetization states of the two
contacts with electrically generated strain and the spin-valve's resistance is
lowered if they match. Multiple comparators can be interfaced in parallel with
a magneto-tunneling junction to determine if an N-bit input stream matches an
N-bit reference stream bit by bit. The system is robust against thermal noise
at room temperature and a 16-bit comparator can operate at roughly 416 MHz
while dissipating at most 420 aJ per cycle.",1504.00952v2
2020-01-09,Coupling loss at the end connections of REBCO stacks: 2D modelling and measurement,"In high power density superconducting motors, superconducting tapes are
usually stacked and connected together at terminals to improve the current
capacity. When a parallel sinusoidal magnetic field is applied on this
partially coupled stack, the coupling current is induced and causes additional
coupling loss. Usually 3D modeling is needed to calculate the coupling loss but
it takes too much computing resource and time. In this paper, a numerical 2D
modeling by minimum electromagnetic entropy production (MEMEP) method is
developed to speed up the calculation. The presented MEMEP model shows good
accuracy and the capability to take the realistic resistance between tapes into
account for coupling loss calculation with a high number of mesh element, which
agrees to measurements.Thanks to the model, a systemic study of coupling loss
on amplitude-dependence, frequency-dependence, resistance-dependence, and
length-dependence, is presented and discussed. The results reveal the features
of coupling loss which is very helpful devices with multi-tape conductors, such
as the stator or rotor windings of motors.",2001.02866v1
2020-05-22,Aging Study on Resistive Plate Chambers of the CMS Muon Detector for HL-LHC,"In the High Luminosity Large Hadron Collider (HL-LHC) program, during the
next years, the instantaneous luminosity will increase up to 5 $\times$
10$^{34}$ cm$^{-2}$ s$^{-1}$ which means a factor five higher than the nominal
LHC. In that period, the present CMS Resistive Plate Chambers (RPC) system will
be subjected to background rates higher than those for which the detectors have
been designed, which could affect the detector properties and induce aging
effects. To study whether the present RPC system can sustain the hard
background conditions during the HL-LHC running period, a dedicated longevity
test is ongoing at the CERN Gamma Irradiation Facility, where a few spare RPCs
are exposed to high gamma radiation for a long term period to mimic the HL-LHC
operational conditions. During the longevity test, the main detector parameters
are continuously monitored as a function of the integrated charge. Preliminary
results of the study, after having collected a sufficient amount of the
expected integrated charge at HL-LHC, will be presented.",2005.11397v2
2020-06-03,Suppression of Gate Screening on Edge Magnetoplasmons by Highly Resistive ZnO Gate,"We investigate a way to suppress high-frequency coupling between a gate and
low-dimensional electron systems in the gigahertz range by measuring the
velocity of edge magnetoplasmons (EMPs) in InAs quantum Hall systems.We compare
the EMPvelocity in three samples with different electromagnetic
environments-one has a highly resistive zinc oxide (ZnO) top gate, another has
a normal metal (Ti/Au) top gate, and the other does not have a gate. The
measured EMP velocity in the ZnO gate sample is one order of magnitude larger
than that in the Ti/Au gate sample and almost the same as that in the ungated
sample. As is well known, the smaller velocity in the Ti/Au gate sample is due
to the screening of the electric field in EMPs. The suppression of the gate
screening effect in the ZnO gate sample allows us to measure the velocity of
unscreened EMPs while changing the electron density. It also offers a way to
avoid unwanted high-frequency coupling between quantum Hall edge channels and
gate electrodes.",2006.01996v1
2020-06-05,PLANS: Robust Program Learning from Neurally Inferred Specifications,"Recent years have seen the rise of statistical program learning based on
neural models as an alternative to traditional rule-based systems for
programming by example. Rule-based approaches offer correctness guarantees in
an unsupervised way as they inherently capture logical rules, while neural
models are more realistically scalable to raw, high-dimensional input, and
provide resistance to noisy I/O specifications. We introduce PLANS (Program
LeArning from Neurally inferred Specifications), a hybrid model for program
synthesis from visual observations that gets the best of both worlds, relying
on (i) a neural architecture trained to extract abstract, high-level
information from each raw individual input (ii) a rule-based system using the
extracted information as I/O specifications to synthesize a program capturing
the different observations. In order to address the key challenge of making
PLANS resistant to noise in the network's output, we introduce a filtering
heuristic for I/O specifications based on selective classification techniques.
We obtain state-of-the-art performance at program synthesis from diverse
demonstration videos in the Karel and ViZDoom environments, while requiring no
ground-truth program for training. We make our implementation available at
github.com/rdang-nhu/PLANS.",2006.03312v1
2020-07-15,Model predictive control of resistive wall mode for ITER,"Active feedback stabilization of the dominant resistive wall mode (RWM) for
an ITER H-mode scenario at high plasma pressure using infinite-horizon model
predictive control (MPC) is presented. The MPC approach is closely-related to
linear-quadratic-Gaussian (LQG) control, improving the performance in the
vicinity of constraints. The control-oriented model for MPC is obtained with
model reduction from a high-dimensional model produced by CarMa code. Due to
the limited time for on-line optimization, a suitable MPC formulation
considering only input (coil voltage) constraints is chosen, and the primal
fast gradient method is used for solving the associated quadratic programming
problem. The performance is evaluated in simulation in comparison to LQG
control. Sensitivity to noise, robustness to changes of unstable RWM dynamics,
and size of the domain of attraction of the initial conditions of the unstable
modes are examined.",2007.07544v2
2021-03-02,Numerical Qualification of Eco-Friendly Gas Mixtures for Avalanche-Mode Operation of Resistive Plate Chambers in INO-ICAL,"Numerical qualification of an eco-friendly alternative gas mixture for
avalanche mode operation of Resistive Plate Chambers is the soul of this work.
To identify the gas mixture, a numerical model developed elsewhere by the
authors has been first established by comparing the simulated figure of merits
(efficiency and streamer probability) with the experimental data for the gas
mixture used in INO-ICAL. Then it has been used to simulate the same properties
of a gas mixture based on argon, carbon di-oxide and nitrogen, identified as
potential replacement by studying its different properties. Efficacy of this
eco-friendly gas mixture has been studied by comparing the simulated result
with the standard gas mixture used in INO-ICAL as well as with experimental
data of other eco-friendly hydrofluorocarbon (HFO1234ze) based potential
replacements. To increase the efficacy of the proposed gas mixture, studies of
the traditional way (addition of a little amount of SF$_6$) and an alternative
approach (exploring the option of high-end electronics) were carried out.",2103.01906v2
2021-03-17,Comprehensive study of out-of-plane transport properties in BaFe$_{2}$As$_{2}$: Three-dimensional electronic state and effect of chemical substitution,"We investigated the out-of-plane transport properties of parent and
chemically substituted BaFe$_{2}$As$_{2}$ for various types of substitution.
Based on the studies of Hall coefficient and chemical-substitution effect, we
have clarified the origin for the unusual temperature dependence of
out-of-plane resistivity $\rho_c(T)$ in the high-temperature
paramagnetic-tetragonal phase. Electron (hole) carriers have an incoherent
(coherent) character, which is responsible for non-metallic (metallic)
$\rho_c(T)$. Although both of electron and hole contributions are almost
comparable, a slightly larger contribution comes from electrons at high
temperatures, while from holes at low temperatures, resulting in a maximum in
$\rho_c(T)$. In the low-temperature antiferromagnetic-orthorhombic phase, the
major effect of substitution is to increase the residual-resistivity component,
as in the case for the in-plane transport. In particular, Co atoms substituted
for Fe give rise to strong scattering with large $\mathit{ac}$ anisotropy. We
found that K substitution induces a non-metallic behavior in $\rho_c(T)$ at low
temperatures, which is likely due to a weakly localized nature along the
$c$-axis direction.",2103.09700v1
2021-04-30,Open-Source Memory Compiler for Automatic RRAM Generation and Verification,"The lack of open-source memory compilers in academia typically causes
significant delays in research and design implementations. This paper presents
an open-source memory compiler that is directly integrated within the Cadence
Virtuoso environment using physical verification tools provided by Mentor
Graphics (Calibre). It facilitates the entire memory generation process from
netlist generation to layout implementation, and physical implementation
verification. To the best of our knowledge, this is the first open-source
memory compiler that has been developed specifically to automate Resistive
Random Access Memory (RRAM) generation. RRAM holds the promise of achieving
high speed, high density and non-volatility. A novel RRAM architecture,
additionally is proposed, and a number of generated RRAM arrays are evaluated
to identify their worst case control line parasitics and worst case settling
time across the memristors of their cells. The total capacitance of lines SEL,
N and P is 5.83 fF/cell, 3.31 fF/cell and 2.48 fF/cell respectively, while the
total calculated resistance for SEL is 1.28 Ohm/cell and 0.14 Ohm/cell for both
N and P lines.",2104.14885v1
2021-08-19,Monarch: A Durable Polymorphic Memory For Data Intensive Applications,"3D die stacking has often been proposed to build large-scale DRAM-based
caches. Unfortunately, the power and performance overheads of DRAM limit the
efficiency of high-bandwidth memories. Also, DRAM is facing serious scalability
challenges that make alternative technologies more appealing. This paper
examines Monarch, a resistive 3D stacked memory based on a novel reconfigurable
crosspoint array called XAM. The XAM array is capable of switching between
random access and content-addressable modes, which enables Monarch (i) to
better utilize the in-package bandwidth and (ii) to satisfy both the random
access memory and associative search requirements of various applications.
Moreover, the Monarch controller ensures a given target lifetime for the
resistive stack. Our simulation results on a set of parallel memory-intensive
applications indicate that Monarch outperforms an ideal DRAM caching by 1.21x
on average. For in-memory hash table and string matching workloads, Monarch
improves performance up to 12x over the conventional high bandwidth memories.",2108.08497v1
2021-08-19,Induced superconducting pairing in integer quantum Hall edge states,"Indium Arsenide (InAs) near surface quantum wells (QWs) are promising for the
fabrication of semiconductor-superconductor heterostructures given that they
allow for a strong hybridization between the two-dimensional states in the
quantum well and the ones in the superconductor. In this work we present
results for InAs QWs in the quantum Hall regime placed in proximity of
superconducting NbTiN. We observe a negative downstream resistance with a
corresponding reduction of Hall (upstream) resistance, consistent with a very
high Andreev conversion. We analyze the experimental data using the
Landauer-B\""{u}ttiker formalism, generalized to allow for Andreev reflection
processes. We attribute the high efficiency of Andreev conversion in our
devices to the large transparency of the InAs/NbTiN interface and the
consequent strong hybridization of the QH edge modes with the states in the
superconductor.",2108.08899v3
2021-12-26,Self-discharge by streaming cosmic rays,"A new nonthermal phenomenon caused by streaming cosmic rays (CRs) in the
universe is proposed. The streaming CRs drive the return current of thermal
electrons to compensate for the CR current. Then, electric fields are induced
by the resistivity of the return current. It is shown that the resistive
electric fields can accelerate secondary electrons generated by the streaming
CRs. This is the self-discharge by streaming CRs. In this work, the
self-discharge condition and the condition for runaway acceleration of
secondary electrons are presented. The self-discharge makes high-energy
secondary electrons, resulting in enhancements of ionization and nonthermal
emission including K$\alpha$ emission line of neutral irons. After the
self-discharge, the return current of thermal electrons is replaced by the
electric current of secondary electrons. Since some magnetic field generations
and amplifications are driven by the return current of thermal electrons, the
self-discharge can significantly influence them.",2112.13395v2
2022-01-03,Performance of a prototype bakelite RPC at GIF++ using self-triggered electronics for the CBM Experiment at FAIR,"The Muon Chamber (MuCh) is a sub-system of the Compressed Baryonic Matter
(CBM) experiment for the detection of low-mass-vector mesons produced in high
energy heavy-ion collisions at beam energies ranging from 2 AGeV to 11 AGeV and
decaying in the di-muon channel. MuCh consists of a segmented absorber and four
detector triplet stations sandwiched between the absorber segments. At the 3rd
and 4th stations of MuCh, Resistive Plate Chambers (RPCs) have been conceived
for muon tracking. We have tested the performance of a low resistivity bakelite
RPC prototype equipped with self-triggered front end electronics (MuCh-XYTER)
for the CBM Muon Chamber. A systematic study on the muon detection efficiency
and time resolution has been carried out in a high-rate photon background at
the Gamma Irradiation Facility (GIF++) at CERN. The details of the measurement
setup and the results are presented here.",2201.00661v1
2022-01-21,Multidimensional minimum-work control of a 2D Ising model,"A system's configurational state can be manipulated using dynamic variation
of control parameters, such as temperature, pressure, or magnetic field; for
finite-duration driving, excess work is required above the equilibrium
free-energy change. Minimum-work protocols in multidimensional
control-parameter space have potential to significantly reduce work relative to
one-dimensional control. By numerically minimizing a linear-response
approximation to the excess work, we design protocols in control-parameter
spaces of a 2D Ising model that efficiently drive the system from the all-down
to all-up configuration. We find that such designed multidimensional protocols
take advantage of more flexible control to avoid control-parameter regions of
high system resistance, heterogeneously input and extract work to make use of
system relaxation, and flatten the energy landscape, making accessible many
configurations that would otherwise have prohibitively high energy and thus
decreasing spin correlations. Relative to one-dimensional protocols, this
speeds up the rate-limiting spin-inversion reaction, thereby keeping the system
significantly closer to equilibrium for a wide range of protocol durations, and
significantly reducing resistance and hence work.",2201.08925v2
2022-03-14,Planckian Dissipation and non-Ginzburg-Landau Type Upper Critical Field in Bi2201,"Resistivity and Hall effect measurements have been carried out on a
micro-fabricated bridge of Bi2201 single crystal at low temperatures down to
0.4 K under high magnetic fields. When superconductivity is crashed by a high
magnetic field, the recovered ""normal state"" resistivity still shows a linear
temperature dependence in low temperature region. Combining with the effective
mass and the charge carrier density, we get a linear scattering rate $1/\tau =
\alpha k_{B} T/\hbar$ with $0.77<\alpha<1.16$, which gives a strong evidence of
the Planckian dissipation. Furthermore, our results reveal a new type of
temperature dependence of upper critical field,
$H_{c2}(T)=H^*\sqrt{(1-t)/(t+0.154)}$, which is totally different from the
expectation of the Ginzburg-Landau theory, and suggests uncondensed Cooper
pairs above $H_{c2}(T)$ line.",2203.06879v3
2022-04-04,Optimisation of Operating High Voltage of the large area Resistive Plate Chamber for ICAL experiment,"The Resistive Plate Chamber is a widely used detector in high energy physics.
The operating potential of this chamber is determined by the optimisation of
the efficiency and noise rate of the device. This optimisation is based on the
assumption that the performance of the device over the whole surface area is
uniform. The INO-ICAL experiment is going to use $\sim$ 30000 RPC of size
$\sim$2\,m$\times$2\,m. All the RPC will have to pass a minimum quality
assurance criteria, but may not be able to maintain a good uniformity over the
whole surface area, particularly for the whole running period of about twenty
years. This paper describes the choice of the optimum operating HV for an RPC
of non-uniform response.",2204.01251v1
2022-04-05,An optical transition-edge sensor with high energy resolution,"Optical transition-edge sensors have shown energy resolution for resolving
the number of incident photons at the telecommunication wavelength. Higher
energy resolution is required for biological imaging and microscope
spectroscopy. In this paper, we report on a Au/Ti (10/20 nm) bilayer TES that
showed high energy resolution. This was achieved by lowering the critical
temperature Tc to 115 mK and the resultant energy resolution was 67 meV full
width at half maximum (FWHM) at 0.8 eV. When Tc was lowered to 115 mK, the
theoretical resolution would scaled up to 30 meV FWHM, considering that the
typical energy resolution of optical TESs is 150 meV and Tc is 300 mK. To
investigate the gap between the theoretical expectation (30 meV) and the
measured value (67 meV), we measured its complex impedance and current noise.
We found excess Johnson noise in the TES and an excess Johnson term M was 1.5
at a bias point where the resistance was 10% of normal resistance. For
reference, the TES was compared with a TES showing typical energy resolution
(156 meV FWHM). We will discuss what improved the energy resolution and what
might have been the limiting factor on it.",2204.01903v1
2022-05-05,Precursor superconducting effects in the optimally doped YBa$_2$Cu$_3$O$_{7-δ}$ superconductor: the confrontation between superconducting fluctuations and percolative effects revisited,"The confrontation between the superconducting fluctuations and percolation
effects as the origin of the in-plane paraconductivity in cuprate
superconductors was earlier addressed at a quantitative level in the case of
the optimally doped YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) compound. Using in-plane
resistivity data from a high-quality YBCO thin film, we will extend these
analyses to high reduced temperatures, in the case of the
Gaussian-Ginzburg-Landau (GGL) approach for the conventional superconducting
fluctuations, by considering the total energy cutoff. These data will also be
analysed in terms of the mean field-approach of the effective-medium theory, to
probe if emergent percolative effects may account for the resistivity rounding
above $T_c$. Our analyses confirm earlier conclusions: the measured
paraconductivity cannot be explained in terms of emergent percolation
processes, but it may be accounted for in terms of the GGL approach. These
results also call into question alternative scenarios, including a recent
proposal derived from emergent percolative effects.",2205.02812v1
2022-08-31,"Ferroelectric FET-based strong physical unclonable function: a low-power, high-reliable and reconfigurable solution for Internet-of-Things security","Hardware security has been a key concern in modern information technologies.
Especially, as the number of Internet-of-Things (IoT) devices grows rapidly, to
protect the device security with low-cost security primitives becomes
essential, among which Physical Unclonable Function (PUF) is a widely-used
solution. In this paper, we propose the first FeFET-based strong PUF exploiting
the cycle-to-cycle (C2C) variation of FeFETs as the entropy source. Based on
the experimental measurements, the proposed PUF shows satisfying performance
including high uniformity, uniqueness, reconfigurability and reliability. To
resist machine-learning attack, XOR structure was introduced, and simulations
show that our proposed PUF has similar resistance to existing attack models
with traditional arbiter PUFs. Furthermore, our design is shown to be
power-efficient, and highly robust to write voltage, temperature and device
size, which makes it a competitive security solution for Internet-of-Things
edge devices.",2208.14678v1
2023-04-28,The Volume of Healthy Red Blood Cells is Optimal for Advective Oxygen Transport in Arterioles,"Red blood cells (RBCs) are vital for transporting oxygen from the lungs to
the body's tissues through the intricate circulatory system. They achieve this
by binding and releasing oxygen molecules to the abundant hemoglobin within
their cytosol. The volume of RBCs affects the amount of oxygen they can carry,
yet whether this volume is optimal for transporting oxygen through the
circulatory system remains an open question. This study explores, through
high-fidelity numerical simulations, the impact of RBC volume on advectve
oxygen transport efficiency through arterioles which form the area of greatest
flow resistance in the circulatory system. The results show that, strikingly,
RBCs with volumes similar to those found in vivo are most efficient to
transport oxygen through arterioles. The flow resistance is related to the
cell-free layer thickness, which is influenced by the shape and the motion of
the RBCs: at low volumes RBCs deform and fold while at high volumes RBCs
collide and follow more diffuse trajectories. In contrast, RBCs with a healthy
volume maximize the cell-free layer thickness, resulting in a more efficient
advectve transport of oxygen.",2305.02197v2
2023-06-04,Observations of the Current Sheet Heating in X-ray during a Solar Flare,"In the solar corona, magnetic reconnection occurs due to the finite
resistivity of the plasma. At the same time, resistivity leads to ohmic
heating. Therefore, the reconnecting current sheet should heat the surrounding
plasma. This paper presents experimental evidence of such plasma heating caused
by magnetic reconnection. We observed the effect during a C1.4 solar flare on
16 February 2003 at the active region NOAA 10278, near the solar limb. Thanks
to such a location, we successfully identified all the principal elements of
the flare: the flare arcade, the fluxrope, and, most importantly, the presumed
position of the current sheet. By analyzing the monochromatic X-ray images of
the Sun obtained by the CORONAS-F/SPIRIT instrument in the Mg XII 8.42 A
spectral line, we detected a high-temperature ($T \geq$ 4 MK) emission at the
predicted location of the current sheet. The high-temperature emission appeared
during the CME impulsive acceleration phase. We believe that this additionally
confirms that the plasma heating around the current sheet and magnetic
reconnection inside the current sheet are strongly connected.",2306.02355v1
2023-10-18,Thermo-electric Transport of Dyonic Gubser-Rocha Black Holes,"We study the thermo-electric transport coefficients of an extended version of
the Gubser-Rocha model. After reviewing the two relaxation time model from
holography and studying the effect of the magnetic field on thermo-electric
transports from hydrodynamic theory, we present a new dilatonic dyonic
asymptotically AdS black hole solution. Notice that S-duality plays an
important role in finding the analytic solution with the magnetic field. Using
the AdS/CMT dictionary, we analyze the electric and thermo-electric transport
properties of the dual field theory. The resistivity exhibits T-linearity in
the low-temperature regime. However, in the strong momentum relaxation and a
strong magnetic field limit, the resistivitiy shows explicit deviation from the
linear-in-T resistivity. The Hall angle is linear-in-T for both the
low-temperature regime and the high-temperature regime for fixed momentum
dissipation strength. The Nernst signal is a bell-shaped function in terms of
the magnetic field even when the momentum relaxation is strong. Finally, we
discuss the possibility of getting a semi-realistic strange metal description
from our model.",2310.12067v1
2024-01-24,Heterogeneously Integrated Laser on Silicon with Non-Volatile Wavelength Tuning,"The von-Neumann bottleneck has constrained computing systems from efficiently
operating on the increasingly large demand in data from networks and devices.
Silicon (Si) photonics offers a powerful solution for this issue by providing a
platform for high-bandwidth, energy-efficient interconnects. Furthermore,
memristors have emerged as a fundamental building block for non-volatile data
storage and novel computing architectures with powerful in-memory processing
capabilities. In this paper, we integrate an Al2O3 memristor into a
heterogeneous Si quantum dot microring laser to demonstrate the first laser
with non-volatile optical memory. The memristor alters the effective optical
modal index of the microring laser cavity by the plasma dispersion effect in
the high resistance state (HRS) or Joule heating in the low resistance state
(LRS), subsequently controlling the output wavelength of the laser in a
non-volatile manner. This device enables a novel pathway for future
optoelectronic neuromorphic computers and optical memory chips.",2401.13757v1
2024-03-29,Deepfake Sentry: Harnessing Ensemble Intelligence for Resilient Detection and Generalisation,"Recent advancements in Generative Adversarial Networks (GANs) have enabled
photorealistic image generation with high quality. However, the malicious use
of such generated media has raised concerns regarding visual misinformation.
Although deepfake detection research has demonstrated high accuracy, it is
vulnerable to advances in generation techniques and adversarial iterations on
detection countermeasures. To address this, we propose a proactive and
sustainable deepfake training augmentation solution that introduces artificial
fingerprints into models. We achieve this by employing an ensemble learning
approach that incorporates a pool of autoencoders that mimic the effect of the
artefacts introduced by the deepfake generator models. Experiments on three
datasets reveal that our proposed ensemble autoencoder-based data augmentation
learning approach offers improvements in terms of generalisation, resistance
against basic data perturbations such as noise, blurring, sharpness
enhancement, and affine transforms, resilience to commonly used lossy
compression algorithms such as JPEG, and enhanced resistance against
adversarial attacks.",2404.00114v1
2011-03-05,Physics and measurements of magnetic materials,"Magnetic materials, both hard and soft, are used extensively in several
components of particle accelerators. Magnetically soft iron-nickel alloys are
used as shields for the vacuum chambers of accelerator injection and extraction
septa; Fe-based material is widely employed for cores of accelerator and
experiment magnets; soft spinel ferrites are used in collimators to damp
trapped modes; innovative materials such as amorphous or nanocrystalline core
materials are envisaged in transformers for high-frequency polyphase resonant
convertors for application to the International Linear Collider (ILC). In the
field of fusion, for induction cores of the linac of heavy-ion inertial fusion
energy accelerators, based on induction accelerators requiring some 107 kg of
magnetic materials, nanocrystalline materials would show the best performance
in terms of core losses for magnetization rates as high as 105 T/s to 107 T/s.
After a review of the magnetic properties of materials and the different types
of magnetic behaviour, this paper deals with metallurgical aspects of
magnetism. The influence of the metallurgy and metalworking processes of
materials on their microstructure and magnetic properties is studied for
different categories of soft magnetic materials relevant for accelerator
technology. Their metallurgy is extensively treated. Innovative materials such
as iron powder core materials, amorphous and nanocrystalline materials are also
studied. A section considers the measurement, both destructive and
non-destructive, of magnetic properties. Finally, a section discusses magnetic
lag effects.",1103.1069v1
2021-03-14,JAMIP: an artificial-intelligence aided data-driven infrastructure for computational materials informatics,"Materials informatics has emerged as a promisingly new paradigm for
accelerating materials discovery and design. It exploits the intelligent power
of machine learning methods in massive materials data from experiments or
simulations to seek for new materials, functionality, principles, etc.
Developing specialized facility to generate, collect, manage, learn and mine
large-scale materials data is crucial to materials informatics. We herein
developed an artificial-intelligence-aided data-driven infrastructure named
Jilin Artificial-intelligence aided Materials-design Integrated Package
(JAMIP), which is an open-source Python framework to meet the research
requirements of computational materials informatics. It is integrated by
materials production factory, high-throughput first-principles calculations
engine, automatic tasks submission and monitoring progress, data extraction,
management and storage system, and artificial intelligence machine learning
based data mining functions. We have integrated specific features such as
inorganic crystal structure prototype database to facilitate high-throughput
calculations and essential modules associated with machine learning studies of
functional materials. We demonstrated how our developed code is useful in
exploring materials informatics of optoelectronic semiconductors by taking
halide perovskites as typical case. By obeying the principles of automation,
extensibility, reliability and intelligence, the JAMIP code is a promisingly
powerful tool contributing to the fast-growing field of computational materials
informatics.",2103.07957v1
2010-07-08,A Model of the Number of Antibiotic Resistant Bacteria in Rivers,"The large reservoir of antibiotic resistant bacteria in raw and treated water
supplies is a matter of public health concern. Currently, the National
Antimicrobial Resistance Monitoring Systems, a collaborative effort of the
Centers for Disease Control, the US Department of Agriculture, and the US Food
and Drug Administration, does not monitor antimicrobial resistance in surface
waters. Given the serious nature of antibiotic resistance in clinical settings,
and the likelihood that antibiotic resistant bacteria can be transmitted to
humans from large environmental reservoirs via drinking water, explanations for
the distribution of antibiotic resistant bacteria and tools for studying this
distribution must be found. Here we focus on mathematical modeling of
cultivable bacteria in a river, which will be used to study the distribution of
antibiotic resistant bacteria in the environment. We consider both antibiotic
resistant and non-antibiotic resistant bacteria in the model, and, taking into
account the strong correlation between land use and antibiotic resistant
bacteria in rivers, we include a function for the influx of bacteria into the
river from the shore. We simulate the model for two different time scales and
show that if there is too many bacteria from the land entering the river, the
river entirely fills with antibiotic resistant bacteria, while less frequent
influxes allows time for the bacteria to lose the antibiotic resistant gene.
This mathematically verifies that reduction in antibiotic use near the banks of
rivers, will reduce the counts of antibiotic resistant bacteria in rivers.",1007.1383v1
2024-01-02,A comparative study of resistivity models for simulations of magnetic reconnection in the solar atmosphere. II. Plasmoid formation,"Plasmoid-mediated reconnection plays a fundamental role in different solar
atmospheric phenomena. Numerical reproduction of this process is therefore
essential for developing robust solar models. Our goal is to assess
plasmoid-mediated reconnection across various numerical resistivity models in
order to investigate how plasmoid numbers and reconnection rates depend on the
Lundquist number. We used the Bifrost code to drive magnetic reconnection in a
2D coronal fan-spine topology, carrying out a parametric study of several
experiments with different numerical resolution and resistivity models. We
employed three anomalous resistivity models: (1) the original hyper-diffusion
from Bifrost, (2) a resistivity proportional to current density, and (3) a
resistivity quadratically proportional to electron drift velocity. For
comparisons, experiments with uniform resistivity were also run.
Plasmoid-mediated reconnection is obtained in most of the experiments. With
uniform resistivity, increasing the resolution reveals higher plasmoid
frequency with weaker scaling to the Lundquist number, obtaining 7.9-12
plasmoids per minute for $S_L\in[1.8 \times 10^4, 2.6\times 10^5]$ with a
scaling of $S_L^{0.210}$ in the highest-resolution resistivity cases,
transcending into Petschek reconnection in the high-$S_L$ limit and
Sweet-Parker reconnection in the low-$S_L$ limit. Anomalous resistivity leads
to similar results even with lower resolution. The drift-velocity-dependent
resistivity excellently reproduces Petschek reconnection for any Lundquist
number, and similar results are seen with resistivity proportional to
current-density. Among the different resistivity models applied on the given
numerical resolution, the hyper-diffusion model reproduced plasmoid
characteristics in closest resemblance to those obtained with uniform
resistivity at a significantly higher resolution.",2401.01177v1
2007-11-20,Induction of nuclear fission by high-voltage application,"In nuclear power generation, fissile materials are mainly used. For example,
$U^{235}$ is fissile and therefore quite essential for use of nuclear energy.
However, the material $U^{235}$ has very small natural abundance less than 1 %.
We should seek possibility of utilizing fissionable materials such as $U^{238}$
because natural abundance of such fissionable materials is generally much
larger than fissile ones. In this paper, we show that thermal neutrons with
vanishing kinetic energy can induce nuclear fission when high voltage is
applied to fissionable materials. To obtain this result, we use the liquid-drop
model for nuclei. Finally, we propose how fissionable materials can be
utilized.",0711.3153v1
2020-06-17,Simulation of Particle-Material Interactions,"This paper gives an overview of the particle transport theory essentials, the
basics of particle-material interaction simulation, physical quantities needed
to simulate particle transport and interactions in materials, Monte Carlo
simulation flow, response of additive detectors, statistical weights and other
techniques to minimize statistical errors. Effects in materials under
irradiation, materials response related to component lifetime and performance
are considered with a focus on high-energy and high-power accelerator
applications. Implementation of simulation of particle-material interactions in
the modern Monte Carlo codes along with the code s main features and results of
recent benchmarking are described.",2006.09866v1
2003-03-04,Accretion of low angular momentum material onto black holes: 2D magnetohydrodynamical case,"We report on the second phase of our study of slightly rotating accretion
flows onto black holes. We consider magnetohydrodynamical (MHD) accretion flows
with a spherically symmetric density distribution at the outer boundary, but
with spherical symmetry broken by the introduction of a small,
latitude-dependent angular momentum and a weak radial magnetic field. We study
accretion flows by means of numerical 2D, axisymmetric, MHD simulations with
and without resistive heating. Our main result is that the properties of the
accretion flow depend mostly on an equatorial accretion torus which is made of
the material that has too much angular momentum to be accreted directly. The
torus accretes, however, because of the transport of angular momentum due to
the magnetorotational instability (MRI). Initially, accretion is dominated by
the polar funnel, as in the hydrodynamic inviscid case, where material has zero
or very low angular momentum. At the later phase of the evolution, the torus
thickens towards the poles and develops a corona or an outflow or both.
Consequently, the mass accretion through the funnel is stopped. The accretion
of rotating gas through the torus is significantly reduced compared to the
accretion of non-rotating gas (i.e., the Bondi rate). It is also much smaller
than the accretion rate in the inviscid, weakly rotating case.Our results do
not change if we switch on or off resistive heating. Overall our simulations
are very similar to those presented by Stone, Pringle, Hawley and Balbus
despite different initial and outer boundary conditions. Thus, we confirm that
MRI is very robust and controls the nature of radiatively inefficient accretion
flows.",0303093v1
2002-05-17,"A systematic study of four series of electron-doped rare earth manganates, LnxCa1-xMnO3 (Ln=La, Nd, Gd and Y) over the x=0.02-0.25 composition range","Electrical and magnetic properties of four series of manganates LnxCa1-xMnO3
(Ln=La, Nd, Gd and Y) have been studied in the electron doped regime
(x=0.02-0.25) in order to investigate the various inter-dependent phenomena
such as ferromagnetism, phase separation and charge ordering. The general
behavior of all the four series of manganates is similar, with some of the
properties showing dependence on the average radius of the A-site cations, <rA>
and cation size disorder. Thus, all the compositions show increase in
magnetization at 100-120 K (TM) for x<xmax, the magnetization increasing with
increasing x. The value of xmax increases with decreasing <rA>, probably due to
the increased phase separation induced by site disorder. This is also reflected
in the larger width of the hysteresis loops at T<TM for small x or <rA>. In
this regime, the electrical resistivity decreases with increasing x, but
remains low and nearly constant T>TM. The percolative nature of the conduction
mechanism at T<TM is substantiated by the fit of the conductivity data to the
scaling law, s \mu |xc-x|p where p is in the 2-4 range. When x>xmax, the
materials become antiferromagnetic and charge-ordered at a temperature TCA,
accompanied by a marked increase in resistivity. The value of TCA increases
with increase in <rA> and x (upto x=0.3). Thus, all the four series of
manganates are characterized by a phase-separated regime between x=0.02 and
0.1-0.15 and an antiferromagnetic charge-ordered regime at x>0.1-0.15.",0205370v2
2017-10-25,NaSn2As2: An Exfoliatable Layered van der Waals Zintl Phase,"The discovery of new families of exfoliatable 2D crystals that have diverse
sets of electronic, optical, and spin-orbit coupling properties, enables the
realization of unique physical phenomena in these few-atom thick building
blocks and in proximity to other materials. Herein, using NaSn2As2 as a model
system, we demonstrate that layered Zintl phases having the stoichiometry
ATt2Pn2 (A = Group 1 or 2 element, Tt = Group 14 tetrel element and Pn = Group
15 pnictogen element) and feature networks separated by van der Waals gaps can
be readily exfoliated with both mechanical and liquid-phase methods. We
identified the symmetries of the Raman active modes of the bulk crystals via
polarized Raman spectroscopy. The bulk and mechanically exfoliated NaSn2As2
samples are resistant towards oxidation, with only the top surface oxidizing in
ambient conditions over a couple of days, while the liquid-exfoliated samples
oxidize much more quickly in ambient conditions. Employing angle-resolved
photoemission spectroscopy (ARPES), density functional theory (DFT), and
transport on bulk and exfoliated samples, we show that NaSn2As2 is a highly
conducting 2D semimetal, with resistivities on the order of 10-6 {\Omega} m.
Due to peculiarities in the band structure, the dominating p-type carriers at
low temperature are nearly compensated by the opening of n-type conduction
channels as temperature increases. This work further expands the family of
exfoliatable 2D materials to layered van der Waals Zintl phases, opening up
opportunities in electronics and spintronics.",1710.09059v1
2017-12-06,Interfacial Strain Effects on Lithium Diffusion Pathways in the Spinel Solid Electrolyte Li-Doped MgAl$_2$O$_4$,"(Li,Al)-co-doped magnesium spinel (Li$_x$Mg$_{1-2x}$Al$_{2+x}$O$_4$) is a
solid lithium-ion electrolyte with potential use in all-solid-state lithium-ion
batteries. Interfaces with spinel electrodes, such as Li$_y$Mn$_2$O$_4$ and
Li$_{4+3z}$Ti$_5$O$_{12}$, may be lattice-matched, with potentially low
interfacial resistances. Small lattice parameter differences across a
lattice-matched interface are unavoidable, causing residual epitaxial strain.
This strain potentially modifies lithium diffusion near the interface,
contributing to interfacial resistance. Here we report a density functional
theory study of strain effects on lithium diffusion pathways for
(Li,Al)-co-doped magnesium spinel, for $x_\mathrm{Li} = 0.25$ and
$x_\mathrm{Li} = 0.5$. We have calculated diffusion profiles for the
un-strained materials, and for isotropic and biaxial tensile strains of up to
6%, corresponding to {100} epitaxial interfaces with Li$_y$Mn$_2$O$_4$ and
Li$_{4+3z}$Ti$_5$O$_{12}$. We find that isotropic tensile strain reduces
lithium diffusion barriers by as much as 0.32 eV, with typical barriers reduced
by ~0.1 eV. This effect is associated with increased volumes of transitional
octahedral sites, and broadly follows local electrostatic potentials. For
biaxial (epitaxial) strain changes in octahedral site volumes and in lithium
diffusion barriers are much smaller than under isotropic strain. Typical
barriers are reduced by only ~ 0.05 eV. Individual effects, however, depend on
the pathway considered and the relative strain orientation. These results
predict that isotropic strain strongly affects ionic conductivities in
(Li,Al)-co-doped magnesium spinel electrolytes, and that tensile strain is a
potential route to enhanced lithium transport. For a lattice-matched interface
with candidate spinel-structured electrodes epitaxial strain has a small, but
complex, effect on lithium diffusion barriers.",1712.02156v3
2022-01-20,Pseudo-hydrodynamic flow of quasiparticles in semimetal WTe2 at room temperature,"Recently, much interest has emerged in fluid-like electric charge transport
in various solid-state systems. The hydrodynamic behavior of the electronic
fluid reveals itself as a decrease of the electrical resistance with increasing
temperature (the Gurzhi effect) in narrow conducting channels, polynomial
scaling of the resistance as a function of the channel width, substantial
violation of the Wiedemann-Franz law supported by the emergence of the
Poiseuille flow. Similarly to whirlpools in flowing water, the viscous
electronic flow generates vortices, resulting in abnormal sign-changing
electrical response driven by the backflow of electrical current.
Experimentally, the presence of the hydrodynamic vortices was observed in
low-temperature graphene as a negative voltage drop near the current-injecting
contacts. However, the question of whether the long-ranged sign-changing
electrical response can be produced by a mechanism other than hydrodynamics has
not been addressed so far. Here we use polarization-sensitive laser microscopy
to demonstrate the emergence of visually similar abnormal sign-alternating
patterns in charge density in multilayer tungsten ditelluride at room
temperature where this material does not exhibit true electronic hydrodynamics.
We argue that this pseudo-hydrodynamic behavior appears due to a subtle
interplay between the diffusive transport of electrons and holes. In
particular, the sign-alternating charge accumulation in WTe2 is supported by
the unexpected backflow of compressible neutral electron-hole current, which
creates charge-neutral whirlpools in the bulk of this nearly compensated
semimetal. We demonstrate that the exceptionally large spatial size of the
charge domains is sustained by the long recombination time of electron-hole
pairs.",2201.08331v1
2022-08-19,Electron transport properties of a narrow-bandgap semiconductor Bi$_2$O$_2$Te nanosheet,"A thin, narrow-bandgap semiconductor Bi$_2$O$_2$Te nanosheet is obtained via
mechanical exfoliation and a Hall-bar device is fabricated from it on a heavily
doped Si/SiO$_2$ substrate and studied at low temperatures. Gate transfer
characteristic measurements show that the transport carriers in the nanosheet
are of $n$-type. The carrier density, mobility, and mean free path in the
nanosheet are determined by measurements of the Hall resistance and the
longitudinal resistance of the Hall-bar device and it is found that the
electron transport in the nanosheet is in a quasi-two-dimensional (2D),
strongly disordered regime. Magnetotransport measurements for the device at
magnetic fields applied perpendicular to the nanosheet plane show dominantly
weak antilocalization (WAL) characteristics at low fields and a linear
magnetoresistance (LMR) behavior at large fields. We attribute the WAL
characteristics to strong spin-orbit interaction (SOI) and the LMR to the
classical origin of strong disorder in the nanosheet. Low-field
magnetoconductivity measurements are also performed and are analyzed based on
the multi-channel Hikami-Larkin-Nagaoka theory with the LMR correction being
taken into account. The phase coherence length, spin relaxation length,
effective 2D conduction channel number and coefficient in the linear term due
to the LMR in the nanosheet are extracted. It is found that the spin relaxation
length in the Bi$_2$O$_2$Te nanosheet is several times smaller than it in its
counterpart Bi$_2$O$_2$Se nanosheet and thus an ultra-strong SOI is present in
the Bi$_2$O$_2$Te nanosheet. Our results reported in this study would greatly
encourage further studies and applications of this emerging narrow-bandgap
semiconductor 2D material.",2208.09361v1
2022-10-20,Seebeck coefficient in a nickelate superconductor: electronic dispersion in the strange metal phase,"Superconducting nickelates are a new family of materials that combine
strongly-correlated magnetism with unconventional superconductivity. While
comparisons with the superconducting cuprates are natural, very little is known
about the metallic state of the nickelates, making these comparisons difficult.
We probe the electronic dispersion of thin-film superconducting 5-layer ($n=5$)
and metallic 3-layer ($n=3$) nickelates by measuring the Seebeck coefficient,
$S$. We find a temperature independent and negative $S/T$ for both the $n=5$
nickelate, with strange metal resistivity, and the $n=3$ compound, with more
conventional Fermi liquid resistivity. These results are in stark contrast with
the strongly temperature-dependent $S/T$ measured at similar electron filling
in the cuprate La$_{1.36}$Nd$_{0.4}$Sr$_{0.24}$CuO$_4$. We reproduce the
temperature dependence, sign, and amplitude of $S/T$ in the nickelates using
Boltzmann transport theory combined with the electronic structure calculated
from density functional theory. This demonstrates that the electronic structure
obtained from first-principles calculations is a good starting point for
calculating the transport properties of superconducting nickelates, and
suggests that, despite indications of strong electronic correlations, there are
well-defined quasiparticles in the metallic state of this family of materials.
Finally, we explain the differences in the Seebeck coefficient between
nickelates and cuprates as originating in strong dissimilarities in impurity
concentrations. Beyond establishing a baseline understanding of how the
electronic structure relates to transport coefficients in these new materials,
this work demonstrates the power of the semi-classical approach to
quantitatively describe transport measurements, even in the strange-metallic
state.",2210.10987v2
2023-04-19,Realization of Z$_2$ Topological Metal in Single-Crystalline Nickel Deficient NiV$_2$Se$_4$,"Temperature-dependent electronic and magnetic properties are reported for a
Z2 topological metal single-crystalline nickel-deficient NiV$_2$Se$_4$. It is
found to crystallize in the monoclinic Cr3S4 structure type with space group
I2=m. From single-crystal x-ray diffraction, we find that there are vacancies
on the Ni site, resulting in the composition Ni0:85V2Se4 in agreement with our
electron-probe microanalysis. The electrical resistivity shows metallic
behavior with a broad anomaly around 150{200 K that is also observed in the
heat capacity data. This anomaly indicates a change of state of the material
below 150 K. We believe that this anomaly could be due to spin fluctuations or
charge-density-wave (CDW) fluctuations, where the lack of long-range order is
caused by vacancies at the Ni site of Ni0:85V2Se4. Although we fail to observe
any structural distortion in this crystal down to 1.5 K, its electronic and
thermal properties are anomalous. The observation of non-linear temperature
dependence of resistivity as well as an enhanced value of the Sommerfeld
coefficient = 104.0(1) mJ/molK2 suggests strong electron-electron correlations
in this material. The first-principles calculations performed for
NiV$_2$Se$_4$, which are also applicable to Ni0:85V2Se4, classify this material
as a topological metal with Z2 = (1; 110) and coexisting electron and hole
pockets at the Fermi level. The phonon spectrum lacks any soft phonon mode,
consistent with the absence of periodic lattice distortion in the present
experiments.",2304.09357v1
2024-05-17,Unconventional Unidirectional Magnetoresistance in vdW Heterostructures,"Electrical readout of magnetic states is a key to realize novel spintronics
devices for efficient computing and data storage. Unidirectional
magnetoresistance (UMR) in bilayer systems, consisting of a spin source
material and a magnetic layer, refers to a change in the longitudinal
resistance upon the reversal of magnetization, which typically originates from
the interaction of spin-current and magnetization at the interface. Because of
UMR s linear dependence on applied charge current and magnetization, it can be
used to electrically read the magnetization state. However, in conventional
spin source materials, the spin polarization of an electric field induced spin
current is restricted to be in the film plane and hence the ensuing UMR can
only respond to the in plane component of the magnetization. On the other hand,
magnets with perpendicular magnetic anisotropy (PMA) are highly desired for
magnetic memory and spin-logic devices, while the electrical read out of PMA
magnets through UMR is critically missing. Here, we report the discovery of an
unconventional UMR in bilayer heterostructures of a topological semimetal
(WTe2) and a PMA ferromagnetic insulator (Cr2Ge2Te6, CGT), which allows to
electrically read the up and down magnetic states of the CGT layer by measuring
the longitudinal resistance. Our theoretical calculations based on a tight
binding model show that the unconventional UMR originates from the interplay of
crystal symmetry breaking in WTe2 and magnetic exchange interaction across the
WTe2 and CGT interface. Combining with the ability of WTe2 to obtain magnetic
field free switching of the PMA magnets, our discoveries open an exciting
pathway to achieve two terminal magnetic memory devices that operate solely on
the spin orbit torque and UMR, which is critical for developing next-generation
non volatile and low power consumption data storage technologies.",2405.10889v1
2024-05-21,Spin-polarized p-wave superconductivity in the kagome material RbV$_3$Sb$_5$,"The study of kagome materials has attracted much attention in the past few
years due to the presence of many electron-electron interaction-driven phases
in a single material.In this work, we report the discovery of intrinsic
spin-polarized p-wave superconductivity in the thin-flake kagome material
RbV$_3$Sb$_5$. Firstly, when an in-plane magnetic field is swept in opposite
directions, we observe a unique form of hysteresis in magnetoresistance which
is different from the hysteresis induced by extrinsic mechanisms such as
flux-trapping or superheating and supercooling effects. The unconventional
hysteresis indicates the emergence of an intrinsic time-reversal
symmetry-breaking superconducting phase. Strikingly, at a fixed magnetic field,
the finite-resistance state can be quenched to the zero-resistance state by
applying a large current. Secondly, at temperatures around 400 mK, the
re-entrance of superconductivity occurs during an in-plane field-sweeping
process with a fixed sweeping direction. This kind of re-entrance is asymmetric
about the zero field axis and observed in all field directions for a fixed
current direction, which is different from the re-entrance observed in
conventional superconductors. Moreover, the angle-dependent in-plane critical
field measurements reveal a two-fold symmetry that deviates from the original,
centrosymmetric D$_{6h}$ point group symmetry of the crystal. These findings
put very strong constraints on the possible superconducting pairing symmetry of
RbV$_3$Sb$_5$. We point out that the pairing symmetry, which is consistent with
the crystal symmetry and all the observed novel properties, is a time-reversal
symmetry-breaking, p-wave pairing with net spin polarization. Importantly, this
p-wave pairing gives rise to a nodal topological superconducting state with
Majorana flat bands on the sample edges.",2405.12592v1
2003-10-07,Study of coupling loss on bi-columnar BSCCO/Ag tapes by a.c. susceptibility measurements,"Coupling losses were studied in composite tapes containing superconducting
material in the form of two separate stacks of densely packed filaments
embedded in a metallic matrix of Ag or Ag alloy. This kind of sample geometry
is quite favorable for studying the coupling currents and in particular the
role of superconducting bridges between filaments. By using a.c. susceptibility
technique, the electromagnetic losses as function of a.c. magnetic field
amplitude and frequency were measured at the temperature T = 77 K for two tapes
with different matrix composition. The length of samples was varied by
subsequent cutting in order to investigate its influence on the dynamics of
magnetic flux penetration. The geometrical factor $\chi_0$ which takes into
account the demagnetizing effects was established from a.c. susceptibility data
at low amplitudes. Losses vs frequency dependencies have been found to agree
nicely with the theoretical model developed for round multifilamentary wires.
Applying this model, the effective resistivity of the matrix was determined for
each tape, by using only measured quantities. For the tape with pure silver
matrix its value was found to be larger than what predicted by the theory for
given metal resistivity and filamentary architecture. On the contrary, in the
sample with a Ag/Mg alloy matrix, an effective resistivity much lower than
expected was determined. We explain these discrepancies by taking into account
the properties of the electrical contact of the interface between the
superconducting filaments and the normal matrix. In the case of soft matrix of
pure Ag, this is of poor quality, while the properties of alloy matrix seem to
provoke an extensive creation of intergrowths which can be actually observed in
this kind of samples.",0310158v1
2007-05-11,Electrical transport and optical studies of ferromagnetic Cobalt doped ZnO nanoparticles exhibiting a metal-insulator transition,"The observed correlation of oxygen vacancies and room temperature
ferromagnetic ordering in Co doped ZnO1-o nanoparticles reported earlier (Naeem
et al Nanotechnology 17, 2675-2680) has been further explored by transport and
optical measurements. In these particles room temperature ferromagnetic
ordering had been observed to occur only after annealing in forming gas. In the
current work the optical properties have been studied by diffuse reflection
spectroscopy in the UV-Vis region and the band gap of the Co doped compositions
has been found to decrease with Co addition. Reflections minima are observed at
the energies characteristic of Co+2 d-d (tethrahedral symmetry) crystal field
transitions, further establishing the presence of Co in substitutional sites.
Electrical transport measurements on palletized samples of the nanoparticles
show that the effect of a forming gas is to strongly decrease the resistivity
with increasing Co concentration. For the air annealed and non-ferromagnetic
samples the variation in the resistivity as a function of Co content are
opposite to those observed in the particles prepared in forming gas. The
ferromagnetic samples exhibit an apparent change from insulator to metal with
increasing temperatures for T>380K and this change becomes more pronounced with
increasing Co content. The magnetic and resistive behaviors are correlated by
considering the model by Calderon et al [M. J. Calderon and S. D. Sarma, Annals
of Physics 2007 (Accepted doi: 10.1016/j.aop.2007.01.010] where the
ferromagnetism changes from being mediated by polarons in the low temperature
insulating region to being mediated by the carriers released from the weakly
bound states in the higher temperature metallic region.",0705.1593v3
2008-01-08,"Impact of silver addition on room temperature magneto-resistance in La0.7Ba0.3MnO3 (LBMO): Agx (x = 0.0, 0.1, 0.2, 0.3, 0.4)","La0.7Ba0.3MnO3 (LBMO):Agx (x = 0.0, 0.1, 0.2, 0.3, and 0.4) composites are
synthesized by solid-state reaction route, the final sintering temperatures are
varied from 1300 (LBMO1300Ag) to 1400 0C (LBMO1400Ag), and their physical
properties are compared as a function of temperature and Ag content. All
samples are crystallized in single phase accompanied by some distortion in main
structural phase peaks at higher angles with increase in silver content. Though
the lattice parameters (a, c) decrease, the b increases slightly with an
increase in Ag content. The scanning electron micrographs (SEM) showed better
grains morphology in terms of size and diffusion of grain boundaries with an
increase in Ag content. In both LBMO1300Ag and LBMO1400Ag series the metal
insulator transition (TMI) and accompanied paramagnetic-ferromagnetic
transition (TC) temperatures are decreased with increase in Ag content. The
sharpness of MI transition, defined by temperature coefficient of resistance
(TCR), is improved for Ag added samples. At a particular content of Ag(0.3),
the TMI and TC are tuned to 300K and maximum magneto-resistance at 7Tesla
applied field (MR7T) of up to 55% is achieved at this temperature, which is
more than double to that as observed for pure samples of the both 1300 and 1400
0C series at same temperature. The MR7T is further increased to above 60% for
LBMOAg(0.4) samples, but is at 270K. The MR7T is measured at varying
temperatures of 5, 100, 200, 300, and 400K in varying fields from +/- 7 Tesla,
which exhibits U and V type shapes. Summarily, the addition of Ag in LBMO
improves significantly the morphology of the grains and results in better
physical properties of the parent manganite system.",0801.1162v1
2011-05-31,Evidence of electronic phase arrest and glassy ferromagnetic behaviour in (Nd0.4Gd0.3)Sr0.3MnO3 manganite : Comparative study between bulk and nanometric samples,"The effect of doping of rare earth Gd 3+ ion replacing Nd 3+ in
Nd0.7Sr0.3MnO3 is investigated in details. Measurements of resistivity,
magnetoresistance, magnetization, linear and non linear ac magnetic
susceptibility on chemically synthesized (Nd0.7-xGdx)Sr0.3MnO3 shows various
interesting features with doping level x=0.3. Comparative study has been
carried out between a bulk and a nanometric sample (grain size ~ 60 nm)
synthesized from the same as prepared powder to maintain identical
stoichiometry. Resistivity of the samples shows strong dependence on the
magnetic field - temperature history. The magnetoresistance of the samples also
show strong irreversibility with respect to sweeping of the field between
highest positive and negative values. Moreover, resistivity is found to
increase with time after field cooling and then switching off the field. All
these phenomena have been attributed to phase separation effect and arrest of
phases in the samples. Furthermore, the bulk sample displays a spin glass like
behaviour as evident from frequency dependence of linear ac magnetic
susceptibility and critical divergence of the nonlinear ac magnetic
susceptibility. The experimentally obtained characteristic time t after
dynamical scaling analysis of the frequency dependence of the ac susceptibility
is found to be t=10-17 s which implies that the system is different from a
canonical spin glass. An unusual frequency dependence of the second harmonic of
ac susceptibility around the magnetic transition temperature led us to
designate the magnetic state of the sample to be glassy ferromagnetic. On
reduction of grain size low field magnetoresistance and phase arrest phenomena
are found to enhance but the glassy state is observed to be destabilized in the
nanometric sample.",1105.6284v2
2013-06-11,Generation of concentration density maxima of small dispersive coal dust particles in horizontal iodine air filter at air-dust aerosol blow,"The spatial distributions of the small dispersive coal dust particles with
the nano and micro sizes in the granular filtering medium with the cylindrical
coal granules in the absorber in the horizontal iodine air filter during its
long term operation at the nuclear power plant are researched. It is shown that
the concentration density maxima of the small dispersive coal dust particles
appear in the granular filtering medium with the cylindrical coal absorbent
granules in the horizontal iodine air filter at an action by the air dust
aerosol blow. The comparison of the measured aerodynamic resistances of the
horizontal and vertical iodine air filters is conducted. The main conclusion is
that the magnitude of the aerodynamic resistance of the horizontal iodine air
filters is much smaller in comparison with the magnitude of the aerodynamic
resistance of the vertical iodine air filters at the same loads of the air dust
aerosol volumes. It is explained that the direction of the air dust aerosol
blow and the direction of the gravitation force in the horizontal iodine air
filter are orthogonal, hence the effective accumulation of the small dispersive
coal dust particles takes place at the bottom of absorber in the horizontal
iodine air filter. It is found that the air dust aerosol stream flow in the
horizontal iodine air filter is not limited by the appearing structures, made
of the precipitated small dispersive coal dust particles, in distinction from
the vertical iodine air filter, in the process of long term operation of the
iodine air filters at the nuclear power plant.",1306.2853v1
2019-09-19,Improving wafer-scale Josephson junction resistance variation in superconducting quantum coherent circuits,"Quantum bits, or qubits, are an example of coherent circuits envisioned for
next-generation computers and detectors. A robust superconducting qubit with a
coherent lifetime of $O$(100 $\mu$s) is the transmon: a Josephson junction
functioning as a non-linear inductor shunted with a capacitor to form an
anharmonic oscillator. In a complex device with many such transmons, precise
control over each qubit frequency is often required, and thus variations of the
junction area and tunnel barrier thickness must be sufficiently minimized to
achieve optimal performance while avoiding spectral overlap between neighboring
circuits. Simply transplanting our recipe optimized for single, stand-alone
devices to wafer-scale (producing 64, 1x1 cm dies from a 150 mm wafer)
initially resulted in global drifts in room-temperature tunneling resistance of
$\pm$ 30%. Inferring a critical current $I_{\rm c}$ variation from this
resistance distribution, we present an optimized process developed from a
systematic 38 wafer study that results in $<$ 3.5% relative standard deviation
(RSD) in critical current ($\equiv \sigma_{I_{\rm c}}/\left\langle I_{\rm c}
\right\rangle$) for 3000 Josephson junctions (both single-junctions and
asymmetric SQUIDs) across an area of 49 cm$^2$. Looking within a 1x1 cm moving
window across the substrate gives an estimate of the variation characteristic
of a given qubit chip. Our best process, utilizing ultrasonically assisted
development, uniform ashing, and dynamic oxidation has shown $\sigma_{I_{\rm
c}}/\left\langle I_{\rm c} \right\rangle$ = 1.8% within 1x1 cm, on average,
with a few 1x1 cm areas having $\sigma_{I_{\rm c}}/\left\langle I_{\rm c}
\right\rangle$ $<$ 1.0% (equivalent to $\sigma_{f}/\left\langle f
\right\rangle$ $<$ 0.5%). Such stability would drastically improve the yield of
multi-junction chips with strict critical current requirements.",1909.09165v2
2014-08-11,"Synchronization of pairwise-coupled, identical, relaxation oscillators based on metal-insulator phase transition devices: A Model Study","Computing with networks of synchronous oscillators has attracted wide-spread
attention as novel materials and device topologies have enabled realization of
compact, scalable and low-power coupled oscillatory systems. Of particular
interest are compact and low-power relaxation oscillators that have been
recently demonstrated using MIT (metal- insulator-transition) devices using
properties of correlated oxides. This paper presents an analysis of the
dynamics and synchronization of a system of two such identical coupled
relaxation oscillators implemented with MIT devices. We focus on two
implementations of the oscillator: (a) a D-D configuration where complementary
MIT devices (D) are connected in series to provide oscillations and (b) a D-R
configuration where it is composed of a resistor (R) in series with a
voltage-triggered state changing MIT device (D). The MIT device acts like a
hysteresis resistor with different resistances in the two different states. The
synchronization dynamics of such a system has been analyzed with purely charge
based coupling using a resistive (Rc) and a capacitive (Cc) element in
parallel. It is shown that in a D-D configuration symmetric, identical and
capacitively coupled relaxation oscillator system synchronizes to an anti-phase
locking state, whereas when coupled resistively the system locks in phase.
Further, we demonstrate that for certain range of values of Rc and Cc, a
bistable system is possible which can have potential applications in
associative computing. In D-R configuration, we demonstrate the existence of
rich dynamics including non-monotonic flows and complex phase relationship
governed by the ratios of the coupling impedance. Finally, the developed
theoretical formulations have been shown to explain experimentally measured
waveforms of such pairwise coupled relaxation oscillators.",1408.2582v1
2014-08-13,"Ferromagnetism, insulator-metal transition and magnetotransport in Pr0.58Ca0.42MnO3 films: role of microstructural perturbations","Magnetic and magnetotransport properties of oriented polycrystalline
Pr0.58Ca0.42MnO3 thin films prepared in flowing oxygen and air ambient has been
investigated. The magnetic ground state of both the films is a frozen cluster
glass. In the air annealed film charge order (CO) is quenched and ferromagnetic
(FM) transition, which appears at TC=148 K is followed by antiferromagnetic
(AFM) transition at TN=104 K. This film shows self-field hysteretic
insulator-metal transition (IMT) at TIMC=89 K and TIMW=148 K in the cooling and
warming cycle, respectively. Application of magnetic field (H) gradually
enhances TIMC and TIMW, reduces the thermoresistive hysteresis and TIM
diminishes. In contrast, the film annealed in flowing oxygen shows a CO
transition, which is followed by FM and AFM transitions. This film shows
appreciably smaller magnetic moment and does not show IMT upto H=20 kOe. As H
is increased to H=30 kOe, IMT having strong thermoresistive hysteresis and
sharp resistivity jumps appears in the cooling and warming cycles. As H
increases to higher values the thermoresistive hysteresis is reduced,
resistivity jumps are observed to disappear and TIM decreases. In the lower
temperature regime the resistivity first decreases slowly with H and then shows
sharp drop. The virgin cycle is not recoverable in subsequent cycles. The
decrement far more pronounced in the oxygen annealed film and occurs at much
higher H suggesting that the frozen cluster glass state is more robust in this
film. The microstructural analysis of the two set of films shows CO quenching,
FM transition and self-field IMT in air annealed film is caused by higher
density of microstructural disorder and lattice defects. The difference in
growth ambience of the two films could give rise to such microstructural
perturbations.",1408.2979v1
2019-12-17,Metal-to-insulator transition in Pt-doped TiSe$_2$ driven by emergent network of narrow transport channels,"Metal-to-insulator transitions (MIT) can be driven by a number of different
mechanisms, each resulting in a different type of insulator -- Change in
chemical potential can induce a transition from a metal to a band insulator;
strong correlations can drive a metal into a Mott insulator with an energy gap;
an Anderson transition, on the other hand, due to disorder leads to a localized
insulator without a gap in the spectrum. Here we report the discovery of an
alternative route for MIT driven by the creation of a network of narrow
channels. Transport data on Pt substituted for Ti in TiSe$_2$ shows a dramatic
increase of resistivity by five orders of magnitude for few % of Pt
substitution, with a power-law dependence of the temperature-dependent
resistivity $\rho(T)$. Our scanning tunneling microscopy data show that Pt
induces an irregular network of nanometer-thick domain walls (DWs) of charge
density wave (CDW) order, which pull charge carriers out of the bulk and into
the DWs. While the CDW domains are gapped, the charges confined to the narrow
DWs interact strongly, with pseudogap-like suppression in the local density of
states, even when they were weakly interacting in the bulk, and scatter at the
DW network interconnects thereby generating the highly resistive state.
Angle-resolved photoemission spectroscopy spectra exhibit pseudogap behavior
corroborating the spatial coexistence of gapped domains and narrow domain walls
with excess charge carriers.",1912.08246v2
2020-06-23,Electron doping of the layered nickelate La$_4$Ni$_3$O$_{10}$ by aluminum substitution: A combined experimental and DFT study,"The physical properties of La$_4$Ni$_3$O$_{10}$ with a 2D-like
Ruddlesden-Popper-type crystal structure are extraordinarily dependent on
temperature and chemical substitution. By introducing Al$^{3+}$ atoms ($x$)
randomly at the Ni-sites, the average oxidation state for the two
non-equivalent Ni-cations is tuned and adopt values below the average of +2.67
in La$_4$Ni$_3$O$_{10}$. La$_4$Ni$_{3-x}$Al$_x$O$_{10}$ is a solid solution for
$x=0.00$ to 1.00, and are prepared by the citric acid method. The samples adopt
a slightly distorted monoclinic structure (P21/a), evidenced by peak broadening
of the (117) reflection. We report on a remarkable effect on the electronic
properties induced by tiny amounts of homogeneously distributed Al-cations,
with clear correspondence between resistivity, magnetization, diffraction, and
DFT data. DFT shows that electronically there is no significant difference
between the non-equivalent Ni atoms and no tendency towards any
Ni$^{3+}$/Ni$^{2+}$ charge ordering. The electron doping via Al-substitution
has a profound effect on electric and magnetic properties. The resistivity
changes from metallic to semiconducting with increasing band-gap at higher
Al-levels, consistent with results from DFT. The metal-to-metal transition
reported for La$_4$Ni$_3$O$_{10}$, which is often interpreted as a charge
density wave, is maintained until $x = 0.15$ Al-level. However, the temperature
characteristics of the resistivity change already at very low Al-levels (below
0.03). A coupling of the metal-to-metal transition to the lattice is evidenced
by an anomaly in the unit cell dimensions. No long-range magnetic order is
detected by powder neutron diffraction. The introduction of the non-magnetic
Al$^{3+}$ changes the Ni$^{3+}$/Ni$^{2+}$ ratio and is likely to block
double-exchange pathways by means of -Ni-O-Al-O-Ni- fragments into the network
of corner shared octahedra with the emergence of possible short-range order in
ferromagnetic like islands.",2006.12854v1
2021-06-03,A data mining approach for improved interpretation of ERT inverted sections using the DBSCAN clustering algorithm,"SUMMARY Geophysical imaging using the inversion procedure is a powerful tool
for the exploration of the Earth's subsurface. However, the interpretation of
inverted images can sometimes be difficult, due to the inherent limitations of
existing inversion algorithms, which produce smoothed sections. In order to
improve and automate the processing and interpretation of inverted geophysical
models, we propose an approach inspired from data mining. We selected an
algorithm known as DBSCAN (Density-Based Spatial Clustering of Applications
with Noise) to perform clustering of inverted geophysical sections. The
methodology relies on the automatic sorting and clustering of data. DBSCAN
detects clusters in the inverted electrical resistivity values, with no prior
knowledge of the number of clusters. This algorithm has the advantage of being
defined by only two parameters: the neighbourhood of a point in the data space,
and the minimum number of data points in this neighbourhood. We propose an
objective procedure for the determination of these two parameters. The proof of
concept described here is applied to simulated ERT (electrical resistivity
tomography) sections, for the following three cases: two layers with a step,
two layers with a rebound, and two layers with an anomaly embedded in the upper
layer. To validate this approach, sensitivity studies were carried out on both
of the above parameters, as well as to assess the influence of noise on the
algorithm's performance. Finally, this methodology was tested on real field
data. DBSCAN detects clusters in the inverted electrical resistivity models,
and the former are then associated with various types of earth materials, thus
allowing the structure of the prospected area to be determined. The proposed
data-mining algorithm is shown to be effective, and to improve the
interpretation of the inverted ERT sections. This new approach has considerable
potential, as it can be applied to any geophysical data represented in the form
of sections or maps.",2106.01673v1
2022-03-13,Colossal transverse magnetoresistance due to nematic superconducting phase fluctuations in a copper oxide,"Electronic anisotropy (or `nematicity') has been detected in all main
families of cuprate superconductors by a range of experimental techniques --
electronic Raman scattering, THz dichroism, thermal conductivity, torque
magnetometry, second-harmonic generation -- and was directly visualized by
scanning tunneling microscope (STM) spectroscopy. Using angle-resolved
transverse resistance (ARTR) measurements, a very sensitive and background-free
technique that can detect 0.5$\%$ anisotropy in transport, we have observed it
also in La$_{2-x}$Sr$_{x}$CuO$_{4}$ (LSCO) for $0.02 \leq x \leq 0.25$.
Arguably the key enigma in LSCO is the rotation of the nematic director with
temperature; this has not been seen before in any material. Here, we address
this puzzle by measuring the angle-resolved transverse magnetoresistance
(ARTMR) in LSCO. We report a discovery of colossal transverse magnetoresistance
(CTMR) -- an order-of-magnitude drop in the transverse resistivity in the
magnetic field of $6\,$T, while none is seen in the longitudinal resistivity.
We show that the apparent rotation of the nematic director is caused by
superconducting phase fluctuations, which are much more anisotropic than the
normal-electron fluid, and their respective directors are not parallel. This
qualitative conclusion is robust and follows straight from the raw experimental
data. We quantify this by modelling the measured (magneto-)conductivity by a
sum of two conducting channels that correspond to distinct anisotropic Drude
and Cooper-pair effective mass tensors. Strikingly, the anisotropy of
Cooper-pair stiffness is significantly larger than that of the normal
electrons, and it grows dramatically on the underdoped side, where the
fluctuations become effectively quasi-one dimensional.",2203.06769v1
2022-04-06,Planckian properties of 2D semiconductor systems,"We describe and discuss the low-temperature resistivity (and the
temperature-dependent inelastic scattering rate) of several different doped 2D
semiconductor systems from the perspective of the Planckian hypothesis
asserting that $\hbar/\tau =k_\mathrm{B}T$ provides a scattering bound, where
$\tau$ is the appropriate relaxation time. The regime of transport considered
here is well-below the Bloch-Gruneisen regime so that phonon scattering is
negligible. The temperature-dependent part of the resistivity is almost
linear-in-$T$ down to arbitrarily low temperatures, with the linearity arising
from an interplay between screening and disorder, connected with carrier
scattering from impurity-induced Friedel oscillations. The temperature
dependence disappears if the Coulomb interaction between electrons is
suppressed. The temperature coefficient of the resistivity is enhanced at lower
densities, enabling a detailed study of the Planckian behavior both as a
function of the materials system and carrier density. Although the precise
Planckian bound never holds, we find somewhat surprisingly that the bound seems
to apply approximately with the scattering rate never exceeding $k_\mathrm{B}
T$ by more than an order of magnitude either in the experiment or in the
theory. In addition, we calculate the temperature-dependent electron-electron
inelastic scattering rate by obtaining the temperature-dependent self-energy
arising from Coulomb interaction, also finding it to obey the Planckian bound
within an order of magnitude at all densities and temperatures. We introduce
the concept of a generalized Planckian bound where $\hbar/\tau$ is bounded by
$\alpha k_\mathrm{B} T$ with $\alpha\sim 10$ or so in the super-Planckian
regime with the strict Planckian bound of $\alpha$=1 being a nongeneric
finetuned situation.",2204.02982v3
2022-06-18,Radiation resistance in simulated metallic core-shell nanoparticles,"We present molecular dynamics (MD) simulations of radiation damage in pure Fe
nanoparticles (NP) and bimetallic FeCu core-shell nanoparticles (CSNP). The
CSNP includes a perfect body centered cubic (bcc) Fe core coated with a
face-centered cubic (fcc) Cu shell. Irradiation with Fe Primary Knock-on Atoms
(PKA) with energies between 1 and 7 keV leads to point defects, without
clustering beyond divacancies and very few slightly larger vacancy clusters,
and without interstitial clusters, unlike what happens in bulk at the same PKA
energies. The Fe-Cu interface and shell can act as a defect sink, absorbing
radiation-induced damage and, therefore, the final number of defects in the Fe
core is significantly lower than in the Fe NP. In addition, the Cu shell
substantially diminishes the number of sputtered Fe atoms, acting as a barrier
for recoil ejection. Structurally, the Cu shell responds to the stress
generated by the collision cascade by creating and destroying stacking faults
across the shell width, which could also accommodate further irradiation
defects. Sputtering yield (Y) is underestimated by BCA, which is also expected
since the simulation is for a thin film at normal incidence. We also compare MD
defect production to bulk predictions of the analytic Athermal Recombination
Corrected Displacements Per Atom (arc-dpa) model. The number of vacancies in
the Fe core is only slightly lower than arc-dpa predictions, but the number of
interstitials is reduced by about one order of magnitude compared to vacancies,
at 5 keV. According to the radiation resistance found for FeCu CSNP in our
simulations, this class of nanomaterial could be suitable for developing new
radiation resistant coatings, nanostructured components, and shields for use in
extreme environments, for instance, in nuclear energy and astrophysical
applications.",2206.09063v2
2022-10-31,Modeling disks and magnetic outflows around a forming massive star: I. Investigating the two layer-structure of the accretion disk,"Like their lower mass siblings, massive protostars can be expected to: a) be
surrounded by circumstellar disks and b) launch magnetically-driven jets and
outflows. The disk formation and global evolution is thereby controlled by
advection of angular momentum from large scales, the efficiency of magnetic
braking and the resistivity of the medium, and the internal thermal and
magnetic pressures of the disk. We perform a series of 30 simulations of a
massive star forming from the gravitational collapse of a molecular cloud
threaded by an initially-uniform magnetic field, starting from different values
for the mass of the cloud, its initial density and rotation profiles, its
rotational energy content, the magnetic field strength, and the resistivity of
the material. The gas and dust is modeled with the methods of resistive
magnetohydrodynamics, also considering radiation transport of thermal emission
and self-gravity. After the initial infall phase dominated by the gravitational
collapse, an accretion disk is formed, shortly followed by the launching of
magnetically-driven outflows. Two layers can be distinguished in the accretion
disk: a thin layer, vertically supported by thermal pressure, and a thick
layer, vertically supported by magnetic pressure. We observe the effects of
magnetic braking in the inner ~50 au of the disk at late times in our fiducial
case. The parameter study reveals that the size of the disk is mostly
determined by the density and rotation profiles of the initial mass reservoir
and not by the magnetic field strength. Magnetic pressure can slightly increase
the size of the accretion disk, while magnetic braking is more relevant in the
innermost parts of the disk as opposed to the outer disk. From the parameter
study, we infer that multiple initial conditions for the onset of gravitational
collapse are able to produce a given disk size and protostellar mass.",2210.17220v1
2023-01-05,Self-Assembly of Soot Nanoparticles on the Surface of Resistively Heated Carbon Microtubes in Near-Hexagonal Arrays of Micropyramids,"Almost regular hexagonal arrays of a few micrometers tall and wide
micropyramids consisting of soot nano-particles are formed on the surface of
graphitized hollow filaments, which are resistively heated to
~1800$^\circ$C-2400$^\circ$C in an Ar atmosphere containing trace amounts of
oxygen (~300 p.p.m.). At the higher temperatures (T>2300$^\circ$C,
approximately) the soot particles are represented mainly by multi-shell carbon
nano-onions. The height and the width of the pyramids is strongly dependent on
the temperature of the resistive heating, diminishing from 5-10mkm at
T=1800$^\circ$C to 1mkm at 2300-2400$^\circ$C. Quasi-hexagonal arrays of the
micropyramids are organized in the convex ``craters'' on the surface of the
microtubes, which grow with the time of the thermal treatment. The pyramids are
pointing always normally to the surface of the craters, except at the
boundaries between the craters, where the normal direction is not well defined.
The pyramids are soft and can be easy destroyed by touching them, but can be
hardened by heating them in the oxygen-free atmosphere. The pyramids are
observed only on the exterior surface of the microtubes, but not on their inner
surface. This suggests that the thermophoretic force generated by a strong
temperature gradient near the external surface of the tubes may be the cause of
the micropyramids formation. Electrostatic charging of the soot nanoparticles
due to thermionic emission may also be relevant to this phenomenon. The
micropyramids can function as field emission point sources, as demonstrated
with the use of a micro-nanoprobing station, mounted in a scanning electron
microscope.",2301.05023v1
2023-03-19,Disentangling superconductor and dielectric microwave losses in sub-micron $\rm Nb$/$\rm TEOS-SiO_2$ interconnects using a multi-mode microstrip resonator,"Understanding the origins of power loss in superconducting interconnects is
essential for the energy efficiency and scalability of superconducting digital
logic. At microwave frequencies, power dissipates in both the dielectrics and
superconducting wires, and these losses can be of comparable magnitude. A novel
method to accurately disentangle such losses by exploiting their frequency
dependence using a multi-mode transmission line resonator, supported by a
geometric factor concept and a 3D superconductor finite element method (FEM)
modeling, is described. Using the method we optimized a planarized fabrication
process of reciprocal quantum logic (RQL) for the interconnect loss at 4.2 K
and GHz frequencies. The interconnects are composed of niobium ($\rm Nb$)
insulated by silicon dioxide made with a tetraethyl orthosilicate precursor
($\rm TEOS-SiO_2$). Two process generations use damascene fabrication, and the
third one uses Cloisonn\'{e} fabrication. For all three, $\rm TEOS-SiO_2$
exhibits a dielectric loss tangent $\tan \delta = 0.0012 \pm 0.0001$,
independent of $\rm Nb$ wire width over $0.25 - 4 \: \mu m$. The $\rm Nb$ loss
varies with both the processing and the wire width. For damascene fabrication,
scanning transmission electron microscopy (STEM) and energy dispersive X-ray
spectroscopy (EDS) reveal that Nb oxide and Nb grain growth orientation
increase the loss above the Bardeen Cooper Schrieffer (BCS) minimum theoretical
resistance $R _{BCS}$. For Cloisonn\'{e} fabrication, the $0.25 \: \mu m$ wide
$\rm Nb$ wires exhibit an intrinsic resistance $R_s = 13 \pm 1.4 \: \mu \Omega$
at 10 GHz, which is below $R_{BCS} \approx 17 \: \mu \Omega$. That is arguably
the lowest resistive loss reported for $\rm Nb$.",2303.10685v1
2023-07-31,Semiconducting transport in Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O sintered from Pb$_2$SO$_5$ and Cu$_3$P,"The very recent claim on the discovery of ambient-pressure room-temperature
superconductivity in modified lead-apatite has immediately excited sensational
attention in the entire society, which is fabricated by sintering lanarkite
(Pb2SO5) and copper(I) phosphide (Cu$_3$P). To verify this exciting claim, we
have successfully synthesized Pb$_2$SO$_5$, Cu$_3$P, and finally the modified
lead-apatite Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O. Detailed electrical transport and
magnetic properties of these compounds were systematically analyzed. It turns
out that Pb$_2$SO$_5$ is a highly insulating diamagnet with a room-temperature
resistivity of ~7.18x10$^9$ Ohm.cm and Cu$_3$P is a paramagnetic metal with a
room-temperature resistivity of ~5.22x10$^{-4}$ Ohm.cm. In contrast to the
claimed superconductivity, the resulting Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O
compound sintered from Pb$_2$SO$_5$ and Cu$_3$P exhibits semiconductor-like
transport behavior with a large room-temperature resistivity of ~1.94x10$^4$
Ohm.cm although our compound shows greatly consistent x-ray diffraction
spectrum with the previously reported structure data. In addition, when a
pressed Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O pellet is located on top of a commercial
Nd$_2$Fe$_{14}$B magnet at room temperature, no repulsion could be felt and no
magnetic levitation was observed either. These results imply that the claim of
a room-temperature superconductor in modified lead-apatite may need more
careful re-examination, especially for the electrical transport properties.",2307.16802v1
2023-08-11,Observation of integer and fractional quantum anomalous Hall effects in twisted bilayer MoTe2,"The interplay between strong correlations and topology can lead to the
emergence of intriguing quantum states of matter. One well-known example is the
fractional quantum Hall effect, where exotic electron fluids with fractionally
charged excitations form in partially filled Landau levels. The emergence of
topological moir\'e flat bands provides exciting opportunities to realize the
lattice analogs of both the integer and fractional quantum Hall states without
the need for an external magnetic field. These states are known as the integer
and fractional quantum anomalous Hall (IQAH and FQAH) states. Here, we present
direct transport evidence of the existence of both IQAH and FQAH states in
twisted bilayer MoTe2 (AA stacked). At zero magnetic field, we observe
well-quantized Hall resistance of h/e2 around moir\'e filling factor {\nu} = -1
(corresponding to one hole per moir\'e unit cell), and nearly-quantized Hall
resistance of 3h/2e2 around {\nu} = -2/3, respectively. Concomitantly, the
longitudinal resistance exhibits distinct minima around {\nu} = -1 and -2/3.
The application of an electric field induces topological quantum phase
transition from the IQAH state to a charge transfer insulator at {\nu} = -1,
and from the FQAH state to a generalized Wigner crystal state, further
transitioning to a metallic state at {\nu} = -2/3. Our study paves the way for
the investigation of fractionally charged excitations and anyonic statistics at
zero magnetic field based on semiconductor moir\'e materials.",2308.06177v3
2023-10-15,Structural and physical properties of the chiral antiferromagnet CeRhC$_2$,"We report a study of the structural, magnetic, transport, and thermodynamic
properties of polycrystalline samples of CeRhC$_2$. CeRhC$_2$ crystallizes in a
tetragonal structure with space group $P4_1$ and it orders
antiferromagnetically below $T_\textrm{N1} \approx$ 1.8 K. Powder neutron
diffraction measurements reveal a chiral magnetic structure with a single
propagation vector $Q_m = (1/2,1/2,0.228(5))$, indicating an antiferromagnetic
arrangement of Ce magnetic moments in the $ab$-plane and incommensurate order
along the $c$-axis with a root-mean-square ordered moment of $m_\textrm{ord}$=
0.68 $\mu_\textrm{B}$/Ce. Applying a magnetic field suppresses the N\'{e}el
temperature $T_\textrm{N1}$ to zero near $\mu_0H_\textrm{c1}\sim$0.75 T. A
second antiferromagnetic phase ($T_\textrm{N2}$), however, becomes apparent in
electrical resistivity, Hall and heat capacity measurements in fields above 0.5
T and extrapolates to zero temperature at $\mu_0H_\textrm{c2}\sim$ 1 T.
Electrical resistivity measurements reveal that LaRhC$_2$ is a semiconductor
with a bandgap of $E_\textrm{g}\sim24$ meV; whereas, resistivity and Hall
measurements indicate that CeRhC$_2$ is a semimetal with a low carrier
concentration of $n\sim10^{20}$ cm$^{-3}$. With applied hydrostatic pressure,
the zero-field antiferromagnetic transition of CeRhC$_2$ is slightly enhanced
and CeRhC$_2$ becomes notably more metallic up to 1.36 GPa. The trend toward
metallicity is in line with density-functional calculations that indicate that
both LaRhC$_2$ and CeRhC$_2$ are semimetals, but the band overlap is larger for
CeRhC$_2$, which has a smaller unit cell volume that its La counterpart. This
suggests that the bandgap closes due to a lattice contraction when replacing La
with Ce in RRhC$_2$ (R = rare-earth), in agreement with experimental results.",2310.09904v1
2023-12-16,"Multiple magnetic transitions, metamagnetism and large magnetoresistance in GdAuGe single crystals","We report the physical properties of GdAuGe single crystals, which were grown
using Bi flux. The powder x-ray diffraction data shows that the compound
crystallizes in hexagonal NdPtSb-type structure (space group P63mc).
Magnetization measurements performed for field configuration H||c and H||ab
show that GdAuGe orders antiferromagnetically at the Neel temperature, TN =
17.2 K. Around this temperature, heat capacity and electrical resistivity data
exhibit prominent anomaly due to the antiferromagnetic (AFM) transition. In
addition to an AFM phase transition, the magnetization data for H||c display
the signature of field-induced metamagnetic (MM) transitions below TN. The
critical field range for these transitions vary from 0.2 to 6.2 T. The critical
fields for the MM transitions decrease with increasing temperature and approach
zero value for temperature approaching TN. Interestingly, the magnetoresistance
(MR) data (for H||c) record a sharp increase in values at the critical fields
that coincide with those seen in magnetization data, tracking the presence of
MM transitions. MR is positive and large (169% at 9 T and 2 K) at low
temperatures. Above TN, MR becomes small and switches to negative values. Hall
resistivity data reveal the predominance of hole charge carriers in the system.
In addition, we observe an emergence of step-like feature in the Hall
resistivity data within the field range of second MM, and a significantly large
anomalous Hall conductivity of 1270 {\Omega}-1 cm-1 at 2 K. The H-T phase
diagram constructed from our detailed magnetization and magnetotransport
measurements reveals multiple intricate magnetic phase transitions. The
electronic and magnetic structure of GdAuGe are also thoroughly investigated
using first-principles methods. The electronic band structure calculations
reveal that GdAuGe is a Dirac nodal-line semimetal.",2312.10352v1
2024-01-31,Effect of annealing on the corrosion-fatigue strength and hot salt corrosion resistance of fine-grained titanium near-α alloy Ti-5Al-2V obtained by Rotary Swaging,"The corrosion-fatigue strength in 3% aqueous NaCl solution and the resistance
against hot salt corrosion (HSC) of the fine-grained near-a alloy Ti-5Al-2V
(Russian analog of Grade 9 titanium alloy with increased aluminum content) has
been studied. The properties of the Ti-5Al-2V alloy in the coarse-grained
state, in the fine-grained after cold Rotary Swaging (RS), in partly
recrystallized state, and in fully recrystallized one have been investigated.
The mechanical properties of the alloy were characterized using compression
tests and microhardness measurements. The effects of RS and of the annealing
temperature and time on the character of corrosion destruction of the surface
and on the composition of the products of the HSC were studied. RS was shown to
result in an increase in the depth of the intergranular corrosion defects while
the recrystallization annealing promotes the increasing of the corrosion
resistance of the Ti-5Al-2V titanium alloy. The parameters of the Basquin
equation for the corrosion-fatigue curves for the near-a Ti-5Al-2V alloy in the
coarse-grained state, in the severely strained one, and after recrystallization
annealing were determined for the first time. An effect of nonmonotonous
dependencies of the slopes of the corrosion-fatigue curves for the strained
near-a Ti-5Al-2V alloy on the recrystallization annealing temperature has been
observed.",2401.17659v1
2024-02-18,"Combined X-ray diffraction, electrical resistivity, and $ab$ $initio$ study of (TMTTF)$_2$PF$_6$ under pressure: implications to the unified phase diagram","We present a combined experimental and theoretical study on the
quasi-one-dimensional organic conductor (TMTTF)$_2$PF$_6$, and elucidate the
variation of its physical properties under pressure. We fully resolve the
crystal structure by single crystal x-ray diffraction measurements using a
diamond anvil cell up to 8 GPa, and based on the structural data, we perform
first-principles density-functional theory calculations and derive the $ab$
$initio$ extended Hubbard-type Hamiltonians. Furthermore, we compare the
behavior of the resistivity measured up to 3 GPa using a BeCu clamp-type cell
and the ground state properties of the obtained model numerically calculated by
the many-variable variational Monte Carlo method. Our main findings are as
follows: i) The crystal was rapidly compressed up to about 3 GPa where the
volume drops to 80% and gradually varies down to 70% at 8 GPa. The transfer
integrals increase following such behavior whereas the screened Coulomb
interactions decrease, resulting in a drastic reduction of correlation effect.
ii) The degree of dimerization in the intrachain transfer integrals, as the
result of the decrease in structural dimerization together with the change in
the intermolecular configuration, almost disappears above 4 GPa; the interchain
transfer integrals also show characteristic variations under pressure. iii) The
results of identifying the characteristic temperatures in the resistivity and
the charge and spin orderings in the calculations show an overall agreement:
The charge ordering sensitively becomes unstable above 1 GPa, while the spin
ordering survives up to higher pressures. These results shed light on the
similarities and differences between applying external pressure and
substituting the chemical species (chemical pressure).",2403.13816v1
2024-03-29,Heat Transfer Coefficients of Moving Particle Beds from Flow-Dependent Particle Bed Thermal Conductivity and Near-Wall Resistance,"Determination of heat transfer coefficients for flowing packed particle beds
is essential to the design of particle heat exchangers, and other thermal
processes. While such dense granular flows fall into the well-known plug-flow
regime, the discrete nature of granular materials alters the thermal transport
processes in both the near-wall and bulk regions of flowing particle beds from
their stationary counterparts. As a result, heat transfer correlations based on
the stationary particle bed thermal conductivity could be inadequate for
flowing particles in a heat exchanger. Earlier works have achieved reasonable
agreement with experiments by treating granular media as a plug-flow continuum
with a near-wall thermal resistance in series. However, the properties of the
continuum were often obtained from measurements on stationary beds owing to the
difficulty of flowing bed measurements. In this work, it was found that the
properties of a stationary bed are highly sensitive to the method of particle
packing and there is a decrease in the particle bed thermal conductivity and
increase in the near-wall thermal resistance, measured as an effective air gap
thickness, on the onset of particle flow. These variations in the
thermophysical properties of stationary and flowing particle beds can lead to
errors in heat transfer coefficient calculations. Therefore, the heat transfer
coefficients for granular flows were calculated using experimentally determined
flowing particle bed thermal conductivity and near-wall air gap for ceramic
particles -CARBOCP40/100(275 um), HSP40/70(404um) and HSP16/30(956um); at
velocities of 5-15mms-1; and temperatures of 300-650C. The thermal conductivity
and air gap values for CP40/100 and HSP40/70 were further used to calculate
heat transfer coefficients across different particle bed temperatures and
velocities for different parallel-plate heat exchanger dimensions.",2403.19892v2
2024-04-03,Bacterial cell death: Atomistic simulations reveal pore formation as a mode of action of structurally nano engineered star peptide polymers,"Multidrug resistance (MDR) to conventional antibiotics is one of the most
urgent global health threats, necessitating the development of effective and
biocompatible antimicrobial agents that are less inclined to provoke
resistance. Structurally Nanoengineered Antimicrobial Peptide Polymers (SNAPPs)
are a novel and promising class of such alternatives. These star-shaped
polymers are made of a dendritic core with multiple arms made of co-peptides
with varying amino acid sequences. Through a comprehensive set of in vivo
experiments, we (Nature Microbiology, 1, 16162, 2016) showed that SNAPPs with
arms made of random blocks of lysine (K) and valine (V) residues exhibit
sub-micron M efficacy against Gram-negative and Gram-positive bacteria tested.
Cryo-TEM images suggested pore formation by SNAPP with random block co-peptide
arms as one of their mode of actions. However, the molecular mechanisms
responsible for this mode of action of SNAPP were not fully understood. To
address this gap, we employed atomistic molecular dynamics simulation technique
to investigate the influence of three different sequences of amino acids,
namely 1) alternating block KKV 2) random block and 3) di-block motifs on
secondary structure of their arms and SNAPP's overall configuration as well as
their interactions with lipid bilayer. We, for the first time identified a
step-by-step mechanism through which alternating block and random SNAPPs
interact with lipid bilayer and leads to pore formation, hence cell death.
These insights provide a strong foundation for further optimization of the
chemical structure of SNAPPs for maximum performance against MDR bacteria,
therefore offering a promising avenue for addressing antibiotic resistance and
development of effective antibacterial agents.",2404.02501v3
2019-07-30,Investigating radiation damage in nuclear energy materials using JANNuS multiple ion beams,"Ion accelerators have been used by material scientists for decades to
investigate radiation damage formation in nuclear materials and thus to emulate
neutron-induced changes. The versatility of conditions in terms of particle
energy, dose rate, fluence, etc., is a key asset of ion beams allowing for
fully instrumented analytical studies. In addition, very short irradiation
times and handling of non-radioactive samples dramatically curtail the global
cost and duration as compared to in-reactor testing. Coupling of two or more
beams, use of heated/cooled sample holders, and implementation of in situ
characterization and microscopy pave the way to real time observation of
microstructural and property evolution in various extreme radiation conditions
more closely mimicking the nuclear environments. For these reasons, multiple
ion beam facilities have been commissioned worldwide. In France, under the
auspices of the Universit{\'e} Paris-Saclay, the JANNuS platform for 'Joint
Accelerators for Nanosciences and Nuclear Simulation' comprises five ion
implanter and electrostatic accelerators with complementary performances. At
CSNSM (CNRS \& Univ Paris-Sud, Orsay), a 200 kV Transmission Electron
Microscope is coupled to an accelerator and an implanter for in situ
observation of microstructure modifications induced by ion beams in a material,
making important contribution to the understanding of physical phenomena at the
nanoscale. At CEA Paris-Saclay, the unique triple beam facility in Europe
allows the simultaneous irradiation with heavy ions (like Fe, W) for nuclear
recoil damage and implantation of a large array of ions including gasses for
well-controlled modelling-oriented experiments. Several classes of materials
are of interest for the nuclear industry ranging from metals and alloys, to
oxides or glasses and carbides. This paper gives selected examples that
illustrate the use of JANNuS ion beams in investigating the radiation
resistance of structural materials for today's and tomorrow's nuclear reactors.",1908.00627v1
1997-05-20,Low-temperature resistivity of single crystals YBa_2Cu_3O_{6+x} in the normal state,"A scan of the superconductor -- nonsuperconductor transformation in single
crystals YBa_2Cu_3O_{6+x} (x about 0.37) was done in two alternative ways,
namely, by applying the magnetic field and by reducing the hole concentration
through the oxygen rearrangement. The in-plane normal-state resistivity
\rho_{ab} obtained in both cases was quite similar; its temperature dependence
can be fitted by logarithmic law in the temperature range of almost two
decades. However, a different representation of the \sigma_{ab}=1/\rho_{ab} by
a power law typical for a 3D-material near a metal -- insulator transition is
also plausible. The vertical conductivity \sigma_c=1/\rho_c followed the power
law and neither \sigma_c(T), nor \rho_c(T) could be fitted by log(T). It
follows from the \rho_c measurements that the transformation at T=0 is split
into two transitions: superconductor -- normal-metal and normal-metal --
insulator. In our samples, they are distanced in the oxygen content by \Delta
x\approx0.025.",9705197v2
1999-06-18,First-Order Phase Transition in a Quantum Hall Ferromagnet,"The single-particle energy spectrum of a two-dimensional electron gas in a
perpendicular magnetic field consists of equally-spaced spin-split Landau
levels, whose degeneracy is proportional to the magnetic field strength. At
integer and particular fractional ratios between the number of electrons and
the degeneracy of a Landau level (filling factors n) quantum Hall effects
occur, characterised by a vanishingly small longitudinal resistance and
quantised Hall voltage. The quantum Hall regime offers unique possibilities for
the study of cooperative phenomena in many-particle systems under
well-controlled conditions. Among the fields that benefit from quantum-Hall
studies is magnetism, which remains poorly understood in conventional material.
Both isotropic and anisotropic ferromagnetic ground states have been predicted
and few of them have been experimentally studied in quantum Hall samples with
different geometries and filling factors. Here we present evidence of
first-order phase transitions in n = 2 and 4 quantum Hall states confined to a
wide gallium arsenide quantum well. The observed hysteretic behaviour and
anomalous temperature dependence in the longitudinal resistivity indicate the
occurrence of a transition between the two distinct ground states of an Ising
quantum-Hall ferromagnet. Detailed many-body calculations allowed the
identification of the microscopic origin of the anisotropy field.",9906294v4
2000-01-19,Microscopic self-consistent theory of Josephson junctions including dynamical electron correlations,"We formulate a fully self-consistent, microscopic model to study the
retardation and correlation effects of the barrier within a Josephson junction.
The junction is described by a series of planes, with electronic correlation
included through a local self energy for each plane. We calculate current-phase
relationships for various junctions, which include non-magnetic impurities in
the barrier region, or an interfacial scattering potential. Our results
indicate that the linear response of the supercurrent to phase across the
barrier region is a good, but not exact indicator of the critical current. Our
calculations of the local density of states show the current-carrying Andreev
bound states and their energy evolution with the phase difference across the
junction.
  We calculate the figure of merit for a Josephson junction, which is the
product of the critical current, Ic, and the normal state resistance, R(N), for
junctions with different barrier materials. The normal state resistance is
calculated using the Kubo formula, for a system with zero current flow and no
superconducting order. Semiclassical calculations would predict that these two
quantities are determined by the transmission probabilities of electrons in
such a way that the product is constant for a given superconductor at fixed
temperature. Our self-consistent solutions for different types of barrier
indicate that this is not the case. We suggest some forms of barrier which
could increase the Ic.R(N) product, and hence improve the frequency response of
a Josephson device.",0001269v1
2000-10-31,Lattice Resistance and Peierls Stress in Finite-size Atomistic Dislocation Simulations,"Atomistic computations of the Peierls stress in fcc metals are relatively
scarce. By way of contrast, there are many more atomistic computations for bcc
metals, as well as mixed discrete-continuum computations of the Peierls-Nabarro
type for fcc metals. One of the reasons for this is the low Peierls stresses in
fcc metals. Because atomistic computations of the Peierls stress take place in
finite simulation cells, image forces caused by boundaries must either be
relaxed or corrected for if system size independent results are to be obtained.
One of the approaches that has been developed for treating such boundary forces
is by computing them directly and subsequently subtracting their effects, as
developed by V. B. Shenoy and R. Phillips [Phil. Mag. A, 76 (1997) 367]. That
work was primarily analytic, and limited to screw dislocations and special
symmetric geometries. We extend that work to edge and mixed dislocations, and
to arbitrary two-dimensional geometries, through a numerical finite element
computation. We also describe a method for estimating the boundary forces
directly on the basis of atomistic calculations. We apply these methods to the
numerical measurement of the Peierls stress and lattice resistance curves for a
model aluminum (fcc) system using an embedded-atom potential.",0010503v1
2000-12-04,Semiconducting Characteristics of Magnesium-Doped Al2O3 Single Crystals,"DC and AC electrical measurements were performed to investigate the
electrical conductivity of alpha-Al2O3:Mg samples with different concentrations
of [Mg]^0 centers .The concentration of [Mg]^0 centers was monitored by the
opticalabsorption peak at 2.56 eV. At low electrical fields, DC measurements
reveal blocking contacts. Steady electroluminescence is emitted at the negative
electrodeindicating that the majority of carriers are holes. Low voltage AC
measurements show that the equivalent circuit for the sample is the bulk
resistance in series with the junction capacitance connected in parallel with a
capacitance, which represents the dielectric constant of the sample. The values
determined for the bulk resistance in both DC and AC experiments are in good
agreement. The electrical conductivity of Al2O3:Mg crystals increases linearly
with the concentration of [Mg]^0 centers, regardless of the amount of other
impurities also present in the crystals, and is four times higher in the
$c_{\perpendicular}$ than in the $c_{\parallel}$ direction. The conductivity is
thermally activated with an activation energy of 0.68 eV, which is independent
of: 1) the [Mg]^0 content, 2) the crystallographic orientation, and 3) the
concentration of other impurities. These results favor the {\it
small-polaron-motion} mechanism.",0012037v1
2001-04-10,Electron-vibration coupling constants in positively charged fullerene,"Recent experiments have shown that C60 can be positively field-doped. In that
state, fullerene exhibits a higher resistivity and a higher superconducting
temperature than the corresponding negatively doped state. A strong
intramolecular hole-phonon coupling, connected with the Jahn-Teller effect of
the isolated positive ion, is expected to be important for both properties, but
the actual coupling strengths are so far unknown. Based on density functional
calculations, we determine the linear couplings of the two a_g, six g_g, and
eight h_g vibrational modes to the H_u HOMO level of the C60 molecule. The
couplings predict a D_5 distortion, and an H_u vibronic ground state for C60^+.
They are also used to generate the dimensionless coupling constant <lambda>
which controls the superconductivity and the phonon contribution to the
electrical resistivity in the crystalline phase. We find that <lambda> is 1.4
times larger in positively-charged C60 than in the negatively-doped case. These
results are discussed in the context of the available transport data and
superconducting temperatures. The role of higher orbital degeneracy in
superconductivity is also addressed.",0104177v4
2001-06-08,Efficient Switching and Domain Interlocking Observed in Polyaxial Ferroelectrics,"We present in-situ transmission electron microscopy observations of domain
wall motion in thin freestanding potassium niobate single-crystals. We observe
that not all domains of a given polarization orientation are equally switchable
in applied electric fields. Tilted and curved 90 degree domain walls are common
and display field-induced mobility, whereas untilted domain boundaries resist
such motion. The sensitivity of the domain wall response to field direction
suggests that electrostatic energy contributions play a crucial role in the
observed switching properties. We can explain our results in terms of the
polarization charges and the resulting depolarization fields associated with
angled domain walls. A phenomenological Landau-Ginzburg analysis of a tilted
domain boundary indicates that such electrostatic effects reduce its local
switching barrier, thereby enhancing its field-induced mobility compared to
that of its untilted counterpart. Consequently not all domain walls are equally
mobile. Furthermore the switching efficiency of a particular domain is
determined by its allowed final states, as defined by its neighbors. Switching
will be inhibited if the relative energetics are unfavorable, and we call this
phenomenon domain interlocking. Any increase in density of such field-resistant
wall configurations with cycle time represents an inherent contribution to
ferroelectric fatigue. Uniaxial ferroelectrics, with polarizations parallel to
the field, should not support such interlocked domains.",0106173v1
2001-10-18,Weak localization in InSb thin films heavily doped with lead,"The paper reports on the investigations of the weak localization (WL) effects
in 3D polycrystalline thin films of InSb. The films are closely compensated
showing the electron concentration n>10^{16} cm^{-3} at the total concentration
of the donor and acceptor type structural defects >10^{18} cm^{-3}. Unless
Pb-doped, the InSb films do not show any measurable or show very small WL
effect at 4.2 K. The Pb-doping to the concentration of the order of 10^{18}
cm^{-3} leads to pronounced WL effects below 7 K. In particular, a clearly
manifested SO scattering is observed. From the comparison of the experimental
data on temperature dependence of the magnetoresistivity and sample resistance
with the WL theory, the temperature dependence of the phase destroying time is
determined. The determination is performed by fitting theoretical terms
obtained from Kawabata's theory to experimental data on magnetoresistance. It
is concluded that the dephasing process is connected to three separate
interaction processes. The first is due to the SO scatterings and is
characterized by temperature-independent relaxation time. The second is
associated with the electron-phonon interaction. The third dephasing process is
characterized by independent on temperature relaxation time tau_c. This
relaxation time is tentatively ascribed to inelastic scattering at extended
structural defects, like grain boundaries. The resulting time dephasing time
shows saturation in its temperature dependence. The temperature dependence of
the resistance of the InSb<Pb> films can be explained by the electron-electron
interaction for T<1 K, and by the WL effect for T>2 K.",0110367v1
2004-05-24,"Conductivity of DNA probed by conducting-atomic force microscopy: effects of contact electrode, DNA structure, surface interactions","We studied the electrical conductivity of DNA molecules with conducting
atomic force microscopy as a function of the chemical nature of the substrate
surfaces, the nature of the electrical contact, and the number of DNA molecules
(from a few molecules, to ropes and large fibers containing up to ~ 106
molecules). Independent of the chemical nature of the surface (hydrophobic or
hydrophilic, electrically neutral or charged), we find that DNA is highly
resistive. From a large number of current-voltage curves measured at several
distance along the DNA, we estimate a conductivity of about 10-6-10-5 S.cm-1
per DNA molecule. For single DNA molecules, this highly resistive behavior is
correlated with its flattened conformation on the surface (reduced thickness,
\~0.5-1.5 nm, compared to its nominal value, ~2.4 nm). We find that
intercalating an organic semiconductor buffer film between the DNA and the
metal electrode improves the reliability of the contact, while direct metal
evaporation usually destroys the DNA and prevents any current measurements.
After long exposure under vacuum or dry nitrogen, the conductivity strongly
decreases, leading to the conclusion that water molecules and ions in the
hydration shell of the DNA play a major role.",0405547v1
2004-10-21,Realization of an N-shaped IVC of nanoscale metallic junctions using the antiferromagnetic transition,"We have observed at low temperatures (<8K) hysteretic I(V) characteristics
for sub-mkm (~200nm) metallic break-junctions based on the heavy-fermion
compound UPd2Al3. Degrading the quality of the contacts by in situ increasing
the local residual resistivity or temperature rise reduces the hysteresis. We
demonstrate that those hysteretic I(V) curves can be reproduced theoretically
by assuming the constriction to be in the thermal regime. Our calculations show
that such anomalous I(V) curves are due to the sharp increase of \rho(T) of
UPd2Al3 near the Neel temperature T_N ~ 14K. From this point of view each metal
with similar \rho(T) should produce similar hysteretic I(V) curves. As example
we show calculations for the rare-earth manganite La{0.75}Sr{0.25}MnO3, a
system with colossal magnetoresistance. In this way we demonstrate that
nano-sized point contacts can be non-linear devices with N-shaped I(V)
characteristics, i. e. with negative differential resistance, that could serve
like Esaki tunnel diodes or Gunn diodes as amplifiers, generators, and
switching units. Their characteristic response time is estimated to be less
than 1ns for the investigated contacts.",0410535v1
2005-01-12,Current induced magnetization switching in exchange biased spin-valves for CPP-GMR heads,"In contrast to earlier studies performed on simple Co/Cu/Co sandwiches, we
have investigated spin transfer effects in complex spin-valve pillars with a
diameter of 130nm developed for current-perpendicular to the plane (CPP)
magneto-resistive heads. The structure of the samples included an exchange
biased synthetic pinned layer and a free layer both laminated by insertion of
several ultrathin Cu layers. Despite the small thickness of the polarizing
layer, our results show that the free layer can be switched between the
parallel (P) and the antiparallel (AP) states by applying current densities of
the order of 10^7 A/cm^2. A strong asymmetry is observed between the two
critical currents IcAP-P and IcP-AP, as predicted by the model of Slonczewski
model. Thanks to the use of exchange biased structures, the stability phase
diagrams could be obtained in the four quadrants of the (H, I) plan. The
critical lines derived from the magnetoresistance curves measured with
different sense currents, and from the resistance versus current curves
measured for different applied fields, match each other very well. The main
features of the phase diagrams can be reproduced by investigating the stability
of the solutions of the Landau Lifshitz Gilbert equation including spin torque
term within a macrospin model. A spin-transfer saturation effect was observed
in the positive currents range. We attribute it to a de-depolarization effect
which appears as a consequence of the asymmetric heating of the pillars, whose
top and the bottom leads are made of different materials.",0501281v1
2005-05-10,The static and dynamic conductivity of warm dense Aluminum and Gold calculated within a density functional approach,"The static resistivity of dense Al and Au plsmas are calculated where all the
needed inputs are obtained from density functional theory (DFT). This is used
as input for a study of the dynamic conductivity. These calculations involve a
self-consistent determination of (i) the equation of state (EOS) and the
ionization balance, (ii) evaluation of the ion-ion, and ion-electron
pair-distribution functions, (iii) Determination of the scattering amplitudes,
and finally the conductivity. We present data for the static resistivity of Al
for compressions 0.1-2.0, and in the temperature range T= 0.1 - 10 eV. Results
for Au in the same temperature range and for compressions 0.1-1.0 is also
given. In determining the dynamic conductivity for a range of frequencies
consistent with standard laser probes, a knowledge of the electronic
eigenstates and occupancies of Al- or Au plasma becomes necessary. They are
calculated using a neutral-pseudoatom model. We examine a number of
first-principles approaches to the optical conductivity, including many-body
perturbation theory, molecular-dynamics evaluations, and simplified
time-dependent DFT. The modification to the Drude conductivity that arises from
the presence of shallow bound states in typical Al-plasmas is examined and
numerical results are given at the level of the Fermi Golden rule and an
approximate form of time-dependent DFT.",0505226v1
2005-07-05,Valence instability of cerium under pressure in the Kondo-like perovskite La$_{0.1}$Ce$_{0.4}$Sr$_{0.5}$MnO$_3$,"Effect of hydrostatic pressure and magnetic field on electrical resistance of
the Kondo-like perovskite manganese oxide,
La$_{0.1}$Ce$_{0.4}$Sr$_{0.5}$MnO$_3$ with a ferrimagnetic ground state, have
been investigated up to 2.1 GPa and 9 T. In this compound, the Mn-moments
undergo double exchange mediated ferromagnetic ordering at $T_{\rm C}$ $\sim$
280 K and there is a resistance maximum, $T_{\rm max}$ at about 130 K which is
correlated with an antiferromagnetic ordering of {\it cerium} with respect to
the Mn-sublattice moments. Under pressure, the $T_{\rm max}$ shifts to lower
temperature at a rate of d$T_{max}$/d$P$ = -162 K/GPa and disappears at a
critical pressure $P_{\rm c}$ $\sim$ 0.9 GPa. Further, the coefficient, $m$ of
$-logT$ term due to Kondo scattering decreases linearly with increase of
pressure showing an inflection point in the vicinity of $P_{\rm c}$. These
results suggest that {\it cerium} undergoes a transition from Ce$^{3+}$ state
to Ce$^{4+}$/Ce$^{3+}$ mixed valence state under pressure. In contrast to
pressure effect, the applied magnetic field shifts $T_{\rm max}$ to higher
temperature presumably due to enhanced ferromagnetic Mn moments.",0507094v1
2005-08-22,"Magnetoresistance, specific heat and magnetocaloric effect of equiatomic rare-earth transition-metal magnesium compounds","We present a study of the magnetoresistance, the specific heat and the
magnetocaloric effect of equiatomic $RET$Mg intermetallics with $RE = {\rm
La}$, Eu, Gd, Yb and $T = {\rm Ag}$, Au and of GdAuIn. Depending on the
composition these compounds are paramagnetic ($RE = {\rm La}$, Yb) or they
order either ferro- or antiferromagnetically with transition temperatures
ranging from about 13 to 81 K. All of them are metallic, but the resistivity
varies over 3 orders of magnitude. The magnetic order causes a strong decrease
of the resistivity and around the ordering temperature we find pronounced
magnetoresistance effects. The magnetic ordering also leads to well-defined
anomalies in the specific heat. An analysis of the entropy change leads to the
conclusions that generally the magnetic transition can be described by an
ordering of localized $S=7/2$ moments arising from the half-filled $4f^7$
shells of Eu$^{2+}$ or Gd$^{3+}$. However, for GdAgMg we find clear evidence
for two phase transitions indicating that the magnetic ordering sets in
partially below about 125 K and is completed via an almost first-order
transition at 39 K. The magnetocaloric effect is weak for the antiferromagnets
and rather pronounced for the ferromagnets for low magnetic fields around the
zero-field Curie temperature.",0508528v1
2006-01-19,Quantum supercurrent transistors in carbon nanotubes,"Electronic transport through nanostructures is greatly affected by the
presence of superconducting leads. If the interface between the nanostructure
and the superconductors is sufficiently transparent, a dissipationless current
(supercurrent) can flow through the device due to the Josephson effect. A
Josephson coupling, as measured via the zero-resistance supercurrent, has been
obtained via tunnel barriers, superconducting constrictions, normal metals, and
semiconductors. The coupling mechanisms vary from tunneling to Andreev
reflection. The latter process has always occurred via a normal-type system
with a continuous density of states. Here we investigate a supercurrent flowing
via a discrete density of states, i.e., the quantized single particle energy
states of a quantum dot, or artificial atom, placed in between superconducting
electrodes. For this purpose, we exploit the quantum properties of finite-sized
carbon nanotubes (CNTs). By means of a gate electrode, successive discrete
energy states are tuned ON and OFF resonance with the Fermi energy in the
superconducting leads, resulting in a periodic modulation of the critical
current and a non-trivial correlation between the conductance in the normal
state and the supercurrent. We find, in good agreement with existing theory,
that the product of the critical current and the normal state resistance
becomes an oscillating function, in contrast to being constant as in previously
explored regimes.",0601434v1
2006-03-17,"Comment on 'Hysteresis, Switching, and Negative Differential Resistance in Molecular Junctions: a Polaron Model', by M. Galperin, M.A. Ratner, and A. Nitzan, Nano Lett. 5, 125 (2005)","It is shown that the ``hysteresis'' in a polaron model of electron transport
through the molecule found by M.Galperin et al. [Nano Lett. 5, 125 (2005)] is
an artefact of their ``mean-field'' approximation. The reason is trivial: after
illegitimate replacement $\hat{n}^{2}=\hat{n}n_{0},$ where \hat{n} is the
electron number operator, n_{0} the average molecular level occupation,
Galperin et al. obtained non-physical dependence of a renormalized molecular
energy level on the non-integer mean occupation number n_{0} (i.e. the electron
self-interaction) and the resulting non-linearity of current. The exact theory
of correlated polaronic transport through molecular quantum dots (MQDs) that we
proposed earlier [Phys. Rev. B67, 235312 (2003)] proved that there is no
hysteresis or switching in current-voltage characteristics of non-degenerate,
d=1, or double degenerate, d=2, molecular bridges, contrary to the mean-field
result. Switching could only appear in multiply degenerate MQDs with d>2 due to
electron correlations. Most of the molecular quantum dots are in the regime of
weak coupling to the electrodes addressed in our formalism.",0603467v3
2006-09-10,"Magnetic and magnetoresistance behavior of Tb7Rh3, an intermetallic compound with a negative temperature coefficient of electrical resistivity in the paramagnetic state, and Paramagnetic Giant Magnetoresistance Phenomenon","The results of dc magnetization, electrical and magnetoresistance and heat
capacity measurements (2-300 K) on Tb7Rh3, crystallizing in Th7Fe3-type
hexagonal structure, are reported. In this compound, magnetic ordering sets in
around 90 K with additional transitions at low temperatures and the temperature
coefficient of resistivity (R), dR/dT, is negative over a wide temperature
range in the paramagnetic state. The present magnetization results reveal that
this compound is apparently characterized by rich features in the
magnetic-field-temperature phase diagram. A point of major emphasis is that the
sign of dR/dT in the paramagnetic state can be gradually changed by the
application of magnetic field. As a result, the magnitude of the
magnetoresistance (MR) is rather large even in the vicinity of room temperature
(far above magnetic ordering temperature), in addition to giant MR behavior in
the magnetically ordered state. Viewed together With similar behavior for other
heavy rare-earth members of this series, this class of compounds can be
classified as Paramagnetic Giant Magnetoresistance Systems. A new theoretical
approach is warranted to understand this phenomenon.",0609231v1
2007-03-29,Easy-plane magnetocrystalline anisotropy in the multi-step metamagnet CeIr3Si2,"Highly anisotropic properties of CeIr$_3$Si$_2$ have been observed by the
magnetization $M$($B$), electrical resistivity $\rho$, and specific heat
measurements on a single-crystalline sample. This compound with an orthorhombic
structure having zigzag chains of Ce ions along the a-axis undergos magnetic
transitions at 3.9 K and 3.1 K. At 0.3 K, metamagnetic transitions occur at
0.68 T and 1.3 T for $B$$//$$b$ and 0.75 T for $B$$//$$c$. Easy-plane
magnetocrystalline anisotropy is manifested as $M$($B//b$) $\cong$ $M$($B//c$)
$\cong$ 11$M$($B//a$) at $B$ = 5 T. Electrical resistivity is also anisotropic;
$\rho_{b}$ $\cong$ $\rho_{c}$ $\ge$ 2$\rho_{a}$. The magnetic part of $\rho$
exhibits a double-peak structure with maxima at 15 K and 250 K. The magnetic
entropy at $T$$\rm_{N1}$ = 3.9 K is a half of $R$ln2. These observations are
ascribable to the combination of the Kondo effect with $T$$\rm_{K}$ $\sim$ 20 K
and a strong crystal field effect. The analysis of $M$($B$) and paramagnetic
susceptibility revealed unusually large energy splitting of 500 K and 1600 K
for the two excited doublets, respectively.",0703776v1
2004-01-28,Matter and Light in Flatland,"Using a non-material current through three new dimensions. It was possible to
build a particle-space model (a higher dimensional object intersecting a lower
dimensional world). The new dimensions solve the old problem of equal sign
walls huge electric repulsion force in the electric sphere model, since these
curved dimensions confine these walls, preventing them from coming apart. The
flat-fermion, which is a toroid, is resistant to be moved, intersects the space
(flatland) in two places at the same time (non-local) while moving, leaving a
sinusoidal electric field that uses the two dimensions of flatland and adopt a
toroidal intersection at rest, avoiding the information about its momentum. It
also has an anapole moment, which time consuming intersection in flatland
produces the flat-fermion magnetic dipole moment. The flat-fermion has an
enantiomer and both undergo a separation under an external magnetic field. On
the other hand, flat-photon, is also a toroid, is not resistant to be moved,
also intersects flatland in two places at the same time, but its sinusoidal
electric field uses one dimension less from the two available. Therefore, in
order to have mass the object should touch all the dimensions of flatland. Pure
quantum phenomena such as Self-Interference, the number of turns before being
identical and the uncertainty principle, as well as, fermion geometric
properties and its magnetic dipole moment are explained and derived.",0401153v1
2007-05-09,Inter comparison of the magneto transport of La2/3Ca1/3MnO3: Ag/In polycrystalline composites,"In this article, we report the synthesis, magneto transport features, and
magnetization of polycrystalline La2/3Ca1/3MnO3:Agx/Inx composites with x = 0,
0.1, 0.2, 0.3 and 0.4. In case of Ag the temperature coefficient of resistance
(TCR) near ferromagnetic (FM) transition enhances significantly with addition
of Ag. The FM transition temperature (TFM) is also increased slightly with Ag
doping. Magneto-transport measurements revealed that magneto-resistance (MR) is
found to be maximum near TFM. Very sharp TCR is seen near TFM with highest
value of up to 15 % for Ag (0.4) sample, which is an order of magnitude higher
than as for pristine sample and is the best value yet reported for any
polycrystalline LCMO compound. Increased TCR, TFM and significant above room
temperature MR of La2/3Ca1/3MnO3:Agx composites is explained on the basis of
improved grains size. Interestingly the La2/3Ca1/3MnO3:Inx composites behaved
exactly in opposite way resulting in decreased TFM, and TCR compared to
pristine LCMO compound. In fact the grains morphology of LCMO:Inx composites is
seen inferior to pristine LCMO which is opposite to the LCMO:Agx case.",0705.1212v1
2007-12-12,Magnetic anomalies in single crystalline ErPd2Si2,"Considering certain interesting features in the previously reported 166Er
Moessbauer effect and neutron diffraction data on the polycrystalline form of
ErPd2Si2 crystallizing in ThCr2Si2-type tetragonal structure, we have carried
out magnetic measurements (1.8 to 300 K) on the single crystalline form of this
compound. We observe significant anisotropy in the absolute values of
magnetization (indicating that the easy axis is c-axis) as well as in the
features due to magnetic ordering in the plot of magnetic susceptibility (chi)
versus temperature (T) at low temperatures. The chi(T) data reveal that there
is a pseudo-low dimensional magnetic order setting in at 4.8 K, with a
three-dimensional antiferromagnetic ordering setting in at a lower temperature
(3.8 K). A new finding in the chi(T) data is that, for H//<110>, but not for
H//<001>, there is a broad shoulder in the range 8-20 K, indicative of the
existence of magnetic correlations above 5 K as well, which could be related to
the previously reported slow-relaxation-dominated Moessbauer spectra.
Interestingly, the temperature coefficient of electrical resistivity is found
to be isotropic; no feature due to magnetic ordering could be detected in the
electrical resistivity data at low temperatures, which is attributed to
magnetic Brillioun-zone boundary gap effects. The results reveal complex nature
of the magnetism of this compound.",0712.2002v1
2008-11-14,Reduction of the field-dependent microwave surface resistance in YBa_2Cu_3O_7 with sub-micrometric BaZrO_3 inclusions as a function of BaZrO_3 concentration,"In order to study the vortex pinning determined by artificially introduced
pinning centers in the small-vortex displacement regime, we measured the
microwave surface impedance at 47.7 GHz in the mixed state of
YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin films, where sub-micrometric BaZrO$_3$
particles have been incorporated. As a function of the BaZrO$_3$ content, we
observe that the absolute losses slightly decrease up to a BaZrO$_3$ content of
5%, and then increase. We found that the magnetic-field-induced losses behave
differently, in that they are not monotonic with increasing BaZrO$_3$
concentration: at small concentration (2.5%) the field-induced losses increase,
but large reduction of the losses themselves, by factors up to 3, is observed
upon further increasing the BaZrO$_3$ concentration in the target up to 7%.
Using measurements of both surface resistance and surface reactance we estimate
vortex pinning-related parameters. We find that BaZrO$_3$ inclusions introduce
deep and steep pinning wells. In particular, the minimum height of the energy
barrier for single vortices is raised. At larger BaZrO$_3$ content (5% and 7%)
the phenomenon is at its maximum, but it is unclear whether it shows a
saturation or not, thus leaving room for further improvements.",0811.2351v1
2008-12-12,Diffusive Charge Transport in Graphene on SiO2,"We review our recent work on the physical mechanisms limiting the mobility of
graphene on SiO2. We have used intentional addition of charged scattering
impurities and systematic variation of the dielectric environment to
differentiate the effects of charged impurities and short-range scatterers. The
results show that charged impurities indeed lead to a conductivity linear in
density in graphene, with a scattering magnitude that agrees quantitatively
with theoretical estimates [1]; increased dielectric screening reduces
scattering from charged impurities, but increases scattering from short-range
scatterers [2]. We evaluate the effects of the corrugations (ripples) of
graphene on SiO2 on transport by measuring the height-height correlation
function. The results show that the corrugations cannot mimic long-range
(charged impurity) scattering effects, and have too small an
amplitude-to-wavelength ratio to significantly affect the observed mobility via
short-range scattering [3, 4]. Temperature-dependent measurements show that
longitudinal acoustic phonons in graphene produce a resistivity linear in
temperature and independent of carrier density [5]; at higher temperatures,
polar optical phonons of the SiO2 substrate give rise to an activated, carrier
density-dependent resistivity [5]. Together the results paint a complete
picture of charge carrier transport in graphene on SiO2 in the diffusive
regime.",0812.2504v1
2008-12-22,Magnetoresistance in paramagnetic heavy fermion metals,"A theoretical study of magnetic field (h) effects on single-particle spectra
and transport quantities of heavy fermion metals in the paramagnetic phase is
carried out. We have employed a non-perturbative local moment approach (LMA) to
the asymmetric periodic Anderson model within the dynamical mean field
framework. The lattice coherence scale $\om_L$, which is proportional within
the LMA to the spin-flip energy scale, and has been shown in earlier studies to
be the energy scale at which crossover to single impurity physics
occurs,increases monotonically with increasing magnetic field. The many body
Kondo resonance in the density of states at the Fermi level splits into two
with the splitting being proportional to the field itself. For h$\geq$ 0, we
demonstrate adiabatic continuity from the strongly interacting case to a
corresponding non-interacting limit, thus establishing Fermi liquid behaviour
for heavy fermion metals in the presence of magnetic field. In the Kondo
lattice regime, the theoretically computed magnetoresistance is found to be
negative in the entire temperature range. We argue that such a result could be
understood at $T\gtrsim \om_L$ by field-induced suppression of spin-flip
scattering and at $T\lesssim \om_L$ through lattice coherence. The coherence
peak in the heavy fermion resistivity diminishes and moves to higher
temperatures with increasing field. Direct comparison of the theoretical
results to the field dependent resistivity measurements in CeB$_6$ yields good
agreement.",0812.4101v2
2009-01-28,"Magnetic, Thermal, and Transport Properties of Layered Arsenides BaRu2As2 and SrRu2As2","The magnetic, thermal and transport properties of polycrystalline BaRu2As2
and SrRu2As2 samples with the ThCr2Si2 structure were investigated by means of
magnetic susceptibility chi(T), electrical resistivity rho(T), and heat
capacity Cp(T) measurements. The temperature (T) dependence of rho indicates
metallic character for both compounds with residual resistivity ratios rho(310
K)/rho(2 K) of 17 and 5 for the Ba and Sr compounds, respectively. The Cp(T)
results reveal a low-T Sommerfeld coefficient gamma = 4.9(1) and 4.1(1) mJ/mol
K^2 and Debye temperature \Theta_D = 271(7) K and 271(4) K for the Ba and Sr
compounds, respectively. The chi (T) was found to be diamagnetic with a small
absolute value for both compounds. No transitions were found for BaRu2As2 above
1.8 K. The chi(T) data for SrRu2As2 exhibit a cusp at \sim 200 K, possibly an
indication of a structural and/or magnetic transition. We discuss the
properties of BaRu2As2 and SrRu2As2 in the context of other ThCr2Si2-type and
ZrCuSiAs-type transition metal pnictides.",0901.4582v2
2009-12-03,Two and single superconductive capacitor paradox,"In this work we consider a new version of the remarkable two capacitor
paradox, concretely its simpler form called single capacitor paradox in
realistic case when all capacitors plates, conductors and switch are made by
the same kind of superconductive material. In non-superconductive regime (when
temperature is larger than critical) electric circuit holds non-zero residual
electric resistance by means of which decrease of the initial electric field
energy in closed circuit by single capacitor discharge can be explained. (Also
it will be supposed that within mentioned electric circuit any residual
inductivity can be effectively neglected.) But in superconductive regime (when
temperature is smaller than critical) electric circuit exactly does not hold
any residual resistance and we consider what then appears. It is shown that
here, according to London law, electric field energy in closed circuit
oscillates during time between its initial value and zero what seemingly
represents new single (two) superconductive capacitor paradox (of electric
field energy oscillation). Precisely, it is shown that here electric charge and
current harmonically oscillate during time in such way that mentioned electric
circuit can be considered as a typical LC circuit with inductivity defined by
superconductivity, i.e. London parameter and capacitor characteristics. In this
way total energy of the capacitor variable electric field and electric current
variable magnetic field stands constant which represents solution of mentioned
paradox.",0912.0648v6
2010-01-05,Spatial and frequency dependencies of local photoresponse of HTS strip-line resonator in regime of two-tone microwave intermodulation excitation,"A new phenomenological approach to spatially-resolved research of nonlinear
(NL) microwave properties of operating thin-film superconducting resonators is
proposed. The approach is based on frequency and spatial singularity of Laser
Scanning Microscopy (LSM) images that can be extracted from a set of 2-D
patterns representing x-y distribution of the LSM photoresponse, PR(x, y), at
fixed third-order intermodulation (IMD) frequencies 2f1-f2 and 2f2-f1 as a
result of two-tone resonator microwave excitation at equidistant frequencies f1
and f2 relative to the fundamental resonance, f0. It was shown by us earlier
that the total LSM PR(x, y) originates from two independent (resistive, PRR(x,
y), and inductive, PRX(x, y)) contributions which can be extracted directly
from the LSM images acquired at f1 and f2 by using a method of
spatially-resolved complex impedance partition [1]. Here, we show that
practically the same manipulation of LSM images at 2f1-f2 and 2f2-f1 can be
used to present NL components of IMD LSM PR(x, y) in terms of its independent
spatial variations of (i) inductive IMD_IND(x, y) and (ii) resistive IMD_RES(x,
y) contributions reflecting the origin of the local sources of microwave NL.
[1] A.P. Zhuravel, S.M. Anlage, and A.V. Ustinov, Appl. Phys. Lett., vol. 88,
p. 212503, 2006.",1001.0677v1
2010-02-18,Growth and characterization of epitaxial LuNi2B2C thin films on MgO single crystals,"Biaxially textured LuNi2BC thin films with Tc up to 15.8 K and a residual
resistivity ratio up to 15 have been prepared. The films were deposited on
MgO(110) substrates using pulsed laser deposition from a stoichiometric target.
Via the precise control of the deposition rate, a biaxial texture is favored
within a broad range of the deposition temperature. The full epitaxial
relationship between the borocarbide film, the \luo interface layer and the
substrate is (110)[001]MgO II (110)[001]Lu2O3 II (001)[100]LuNi2B2C. A very
sharp in--plane alignment of about 1\textdegree and an out--of--plane order of
about 2.5\textdegree was achieved in the \luni layer. However, a systematic
study using different deposition temperatures shows that the temperature is
crucial for phase formation and appealing superconducting properties. Applying
optimized deposition conditions, critical temperatures of up to 15.8 K and
steep superconducting transitions of about 0.3 K are reproducibly obtained. We
further analyzed the upper critical field Hc2 of one film deposited under
optimized conditions. It was resistively measured along the [001] direction and
fitted with a power law. The value of Hc2(0) = 9.82 T obtained from that fit is
in very good agreement with single crystal data and the power exponent
describing the positive curvature for small external magnetic fields of about
0.19 indicates a relatively low intraband scattering in the films.",1002.3584v2
2010-02-19,Uniaxial strain detwinning of CaFe2As2 and BaFe2As2: optical and transport study,"TThe parent compounds of iron-arsenide superconductors, $A$Fe$_{2}$As$_{2}$
($A$=Ca, Sr, Ba), undergo a tetragonal to orthorhombic structural transition at
a temperature $T_{\mathrm{TO}}$ in the range 135 to 205K depending on the
alkaline earth element. Below $T_{\mathrm{TO}}$ the free standing crystals
split into equally populated structural domains, which mask intrinsic,
in-plane, anisotropic properties of the materials. Here we demonstrate a way of
mechanically detwinning CaFe$_{2}$As$_{2}$ and BaFe$_{2}$As$_{2}$. The
detwinning is nearly complete, as demonstrated by polarized light imaging and
synchrotron $X$-ray measurements, and reversible, with twin pattern restored
after strain release. Electrical resistivity measurements in the twinned and
detwinned states show that resistivity, $\rho$, decreases along the
orthorhombic $a_{o}$-axis but increases along the orthorhombic $b_{o}$-axis in
both compounds. Immediately below $T_{\mathrm{TO}}$ the ratio $\rho_{bo}/
\rho_{ao}$ = 1.2 and 1.5 for Ca and Ba compounds, respectively. Contrary to
CaFe$_{2}$As$_{2}$, BaFe$_{2}$As$_{2}$ reveals an anisotropy in the nominally
tetragonal phase, suggesting that either fluctuations play a larger role above
$T_{\mathrm{TO}}$ in BaFe$_{2}$As$_{2}$ than in CaFe$_{2}$As$_{2}$, or that
there is a higher temperature crossover or phase transition.",1002.3801v3
2010-10-14,Pressure dependence of Curie temperature and resistivity in complex Heusler alloys,"Using first-principles electronic structure calculations, we have studied the
dependence of the Curie temperature on external hydrostatic pressure for random
Ni2MnSn Heusler alloys doped with Cu and Pd atoms, over the entire range of
dopant concentrations. The Curie temperatures are calculated by applying
random-phase approximation to the Heisenberg Hamiltonian whose parameters are
determined using the linear response and multiple scattering methods, based on
density-functional theory. In (Ni1-x,Pdx)2MnSn alloys, the Curie temperature is
found to increase with applied pressure over the whole concentration range. The
crossover from the increase to the decrease of the Curie temperature with
pressure takes place for Cu concentrations larger than about 70% in
(Ni1-x,Cux)2MnSn Heusler alloys. The results for the reference Ni2MnSn Heusler
alloy agree well with a previous theoretical study of E. Sasioglu, L. M.
Sandratskii and P. Bruno Phys. Rev. B 71 214412 (2005) and also reasonably well
with available experimental data. Results for the spin-disorder-induced part of
the resistivity in (Ni1-x,Pdx)2MnSn Heusler alloys, calculated by using the
disordered local moment model, are also presented. Finally, a qualitative
understanding of the results, based on Anderson's superexchange interaction and
Stearn's model of the indirect exchange interaction between localized and
itinerant d electrons, is provided.",1010.3025v2
2010-12-25,Charge inhomogeneities and transport in semiconductor heterostructures with a manganese $δ$-layer,"We study experimentally and theoretically the effects of disorder, nonlinear
screening, and magnetism in semiconductor heterostructures containing a
$\delta$-layer of Mn, where the charge carriers are confined within a quantum
well and hence both ferromagnetism and transport are two-dimensional (2D) and
differ qualitatively from their bulk counterparts. Anomalies in the electrical
resistance observed in both metallic and insulating structures can be
interpreted as a signature of significant ferromagnetic correlations. The
insulating samples turn out to be the most interesting as they can give us
valuable insights into the mechanisms of ferromagnetism in these
heterostructures. At low charge carrier densities, we show how the interplay of
disorder and nonlinear screening can result in the organization of the carriers
in the 2D transport channel into charge droplets separated by insulating
barriers. Based on such a droplet picture and including the effect of magnetic
correlations, we analyze the transport properties of this set of droplets,
compare it with experimental data, and find a good agreement between the model
calculations and experiment. Our analysis shows that the peak or shoulder-like
features observed in temperature dependence of resistance of 2D
heterostructures $\delta$-doped by Mn lie significantly below the Curie
temperature $T_{C}$ unlike the three-dimensional case, where it lies above and
close to $T_{C}$. We also discuss the consequences of our description for
understanding the mechanisms of ferromagnetism in the heterostructures under
study.",1012.5456v1
2011-02-11,Mutual Friction in Superfluid He^4 Near the λ-line,"We present experimental results for the thermal resistivity {\rho} of
superfluid He^4 along several isobars between saturated vapor pressure and the
melting pressure. The measurements are for the temperature range 1 -
T_c(q)/T_{\lambda} < t < 2{\times}10^{-5} and the heat-flux range 3 < q < 70
{\mu}W/cm^2. Here t {\equiv} 1-T/T_{\lambda}, T_{\lambda} is the transition
temperature in the limit of zero q, and T_c is the transition temperature at
finite q. The data suggest that the resistivity has an incipient singularity at
T_{\lambda} which can be described by the power law {\rho} =
(t/t0)^{-(m{\nu}+{\alpha})} where t0 = (q/q0)^x. However, the singularity is
supplanted by the transition to a more highly dissipative phase at T_c(q) <
T_{\lambda}. The results suggest a mild dependence of m{\nu} + {\alpha} on P,
but can be described quite well by m{\nu} + {\alpha} = 2.76, x = 0.89, and q_0
= q_{0,0} - q_{0,1}P with q_{0,0} = 401 W/cm^2 and q_{0,1} = -5.0 W
/{cm^2-bar}. The results imply that the Gorter-Mellink mutual friction exponent
m has a value close to 3.46 and is distinctly larger than the classical value m
= 3. We suggest that the reason for this may be found in the nature of the
counterflow close to T_{\lambda}, which is expected to involve turbulent
normalfluid flow.",1102.2373v1
2011-03-10,Buckling instability of a thin-layer rectilinear Couette flow,"We analyse the buckling stability of a thin, viscous sheet when subject to
simple shear, providing conditions for the onset of the dominant out-of-plane
modes using two models: (i) an asymptotic theory for the dynamics of a viscous
plate and (ii) the full Stokes equations. In either case, the plate is
stabilised by a combination of viscous resistance, surface tension and buoyancy
relative to an underlying denser fluid. In the limit of vanishing thickness,
plates buckle at a shear rate $\gamma/(\mu d)$ independent of buoyancy, where
2d is the plate thickness, $\gamma$ is the average surface tension between the
upper and lower surfaces and $\mu$ is the fluid viscosity. For thicker plates
stabilised by an equal surface tension at the upper and lower surfaces, at and
above onset, the most unstable mode has moderate wavelength, is stationary in
the frame of the centre-line, spans the width of the plate with crests and
troughs aligned at approximately $45^\circ$ to the walls and closely resembles
elastic shear modes. The thickest plates that can buckle have an aspect ratio
(thickness/width) approximately $\EC$ and are stabilised only by internal
viscous resistance. We show that the viscous plate model can only accurately
describe the onset of buckling for vanishingly thin plates but provides an
excellent description of the most unstable mode above onset. Finally, we show
that by modifying the plate model to incorporate advection and make the model
material frame-invariant, it is possible to extend its predictive power to
describe relatively short, travelling waves.",1103.1925v1
2011-08-03,Origin of conductivity cross over in entangled multi-walled carbon nanotube network filled by iron,"A realistic transport model showing the interplay of the hopping transport
between the outer shells of iron filled entangled multi-walled carbon nanotubes
(MWNT) and the diffusive transport through the inner part of the tubes, as a
function of the filling percentage, is developed. This model is based on
low-temperature electrical resistivity and magneto-resistance (MR)
measurements. The conductivity at low temperatures showed a crossover from
Efros-Shklovski (E-S) variable range hopping (VRH) to Mott VRH in 3 dimensions
(3D) between the neighboring tubes as the iron weight percentage is increased
from 11% to 19% in the MWNTs. The MR in the hopping regime is strongly
dependent on temperature as well as magnetic field and shows both positive and
negative signs, which are discussed in terms of wave function shrinkage and
quantum interference effects, respectively. A further increase of the iron
percentage from 19% to 31% gives a conductivity crossover from Mott VRH to 3D
weak localization (WL). This change is ascribed to the formation of long iron
nanowires at the core of the nanotubes, which yields a long dephasing length
(e.g. 30 nm) at the lowest measured temperature. Although the overall transport
in this network is described by a 3D WL model, the weak temperature dependence
of inelastic scattering length expressed as L_phi ~T^-0.3 suggests the
possibility for the presence of one-dimensional channels in the network due to
the formation of long Fe nanowires inside the tubes, which might introduce an
alignment in the random structure.",1108.0881v1
2011-08-24,Carrier-independent ferromagnetism and giant anomalous Hall effect in magnetic topological insulator,"Breaking the time-reversal symmetry of a topological insulator (TI) by
ferromagnetism can induce exotic magnetoelectric phenomena such as quantized
anomalous Hall (QAH) effect. Experimental observation of QAH effect in a
magnetically doped TI requires ferromagnetism not relying on the charge
carriers. We have realized the ferromagnetism independent of both polarity and
density of carriers in Cr-doped BixSb2-xTe3 thin films grown by molecular beam
epitaxy. Meanwhile, the anomalous Hall effect is found significantly enhanced
with decreasing carrier density, with the anomalous Hall angle reaching
unusually large value 0.2 and the zero field Hall resistance reaching one
quarter of the quantum resistance (h/e2), indicating the approaching of the QAH
regime. The work paves the way to ultimately realize QAH effect and other
unique magnetoelectric phenomena in TIs.",1108.4754v2
2011-09-10,Role of ambient air on photoluminescence and electrical conductivity of assembly of ZnO Nanoparticles,"Effect of ambient gases on photoluminescence (PL) and electrical conductivity
of films prepared using ZnO nanoparticles (NPs) have been investigated. It is
observed that NPs of size below 20 nm kept inside a chamber exhibit complete
reduction in their visible PL when oxygen partial pressure of the surrounding
gases is decreased by evacuation. However the visible PL from ZnO NPs is
insensitive to other major gases present in the ambient air. The rate of change
of PL intensity with pressure is inversely proportional to the ambient air
pressure and increases when particle size decreases due to the enhanced surface
to volume ratio. On the other hand an assembly of ZnO NPs behaves as a complete
insulator in the presence of dry air and its major components like N2, O2 and
CO2. Electrical conduction having resistivity ~102 - 103 {\Omega}m is observed
in the presence of humid air. The depletion layer formed at the NP surface
after acquiring donor electrons of ZnO by the adsorbed oxygen, has been found
to control the visible PL and increases the contact potential barrier between
the NPs which in turn enhances the resistance of the film.",1109.2253v1
2011-10-07,Reversible metal-insulator transition in LaAlO3 thin films mediated by intragap defects: An alternative mechanism for resistive switching,"We report on the electric-field-induced reversible metal-insulator transition
(MIT) of the insulating LaAlO3 thin films observed in metal/LaAlO3/Nb-SrTiO3
heterostructures. The switching voltage depends strongly on the thickness of
the LaAlO3 thin film which indicates that a minimum thickness is required for
the MIT. A constant opposing voltage is required to deplete the charges from
the defect states. Our experimental results exclude the possibility of
diffusion of the metal electrodes or oxygen vacancies into the LaAlO3 layer.
Instead, the phenomenon is attributed to the formation of a quasi-conduction
band (QCB) in the defect states of LaAlO3 that forms a continuum state with the
conduction band of the Nb-SrTiO3. Once this continuum (metallic) state is
formed, the state remains stable even when the voltage bias is turned off. The
thickness dependent reverse switch-on voltage and the constant forward
switch-off voltage are consistent with our model. The viewpoint proposed here
can provide an alternative mechanism for resistive switching in complex oxides.",1110.1595v1
2012-02-07,Effect of internal chemical pressure on transport properties and TCR for sensors applications,"In this work, the structural and transport properties of
(Nd0.7-xLax)Sr0.3MnO3 manganites with x = 0, 0.1 and 0.2 prepared by solid
state reaction route are studied. These compounds are found to be crystallized
in orthorhombic structural form. The influence of La substitution in place of
Nd at A-site shifts the metal to semiconductor/insulator transition temperature
(TMI) peak towards room temperature with x = 0, 0.1 and 0.2. A composition
prepared with the value of x = 0.2 in (Nd0.7-xLax)0.7Sr0.3MnO3 manganites (i.e.
(Nd0.5La0.2)0.7Sr0.3MnO3), TMI was observed at 289 K which is close to room
temperature. The maximum percentage of TCR values of compounds are increasing
with average radius <r_A> but %TCR are slightly equal in x = 0.1 and 0.2 as
compared to the parent compound. The maximum %TCR value is almost independent
with A-site average radius <r_A> in x = 0.1 and 0.2. The electrical resistivity
data are explored by different theoretical models and it has been concluded
that at low temperature (ferromagnetic metallic region) conduction mechanism
presumably due to the combined effect of electron-electron, electron-phonon and
electron-magnon scattering, while in paramagnetic semiconducting regime, the
variation of resistivity with temperature are explained by (1) Mott variable
range hopping mechanism, (2) Adiabatic small polaron hopping and (3) Thermally
activated hopping. The polaron hopping and thermal activation energies are
decreasing with increase of an average A-site ionic radius (<rA>). An
appropriate enlightenment for the observed behavior is discussed in detail.",1202.1355v1
2012-07-02,Evolution of superconducting correlations within magnetic-field-decoupled CuO(2) layers of La(1.905)Ba(0.095)CuO(4),"We explore the evolution of superconductivity in La(2-x)Ba(x)CuO(4) with
x=0.095 in magnetic fields of up to 35 T applied perpendicular to the CuO(2)
planes. Previous work on this material has shown that perpendicular fields
enhance both charge and spin stripe order within the planes. We present
measurements of the resistivity parallel and perpendicular to the planes, as
well as the Hall effect. Measurements of magnetic susceptibility for fields of
up to 15 T applied both parallel and perpendicular to the planes provide
complementary measures of the superconductivity. We show that fields sufficient
to destroy pair tunneling between the planes do not disrupt the superconducting
correlations within the planes. In fact, we observe an onset of large amplitude
but phase disordered superconductivity within the planes at approximately 30 K
that is remarkably insensitive to field. With further cooling, we observe a
phase-transition-like drop in the in-plane resistivity to an apparent state of
superconductivity, despite the lack of phase coherence between the layers.
These observations raise interesting questions concerning the identification of
the upper critical field, where pairing is destroyed, in underdoped cuprates.",1207.0528v2
2012-07-26,Kinetic impedance and depairing in thin and narrow superconducting films,"We use both Eilenberger-Usadel and Ginzburg-Landau (GL) theory to calculate
the superfluid's temperature-dependent kinetic inductance for all currents up
to the depairing current in thin and narrow superconducting films. The
calculations apply to BCS weak-coupling superconductors with isotropic gaps and
transport mean-free paths much less than the BCS coherence length. The kinetic
inductance is calculated for the response to a small alternating current when
the film is carrying a dc bias current. In the slow-experiment/fast-relaxation
limit, in which the superconducting order parameter quasistatically follows the
time-dependent current, the kinetic inductance diverges as the bias current
approaches the depairing value. However, in the
fast-experiment/slow-relaxiation limit, in which the the superconducting order
parameter remains fixed at a value corresponding to the dc bias current, the
kinetic inductance rises to a finite value at the depairing current. We then
use time-dependent GL theory to calculate the kinetic impedance of the
superfluid, which includes not only the kinetic reactance but also the kinetic
resistance of the superfluid arising from dissipation due to order-parameter
relaxation. The kinetic resistance is largest for angular frequencies $\omega$
obeying $\omega \tau_s > 1$, where $\tau_s$ is the order-parameter relaxation
time, and for bias currents close to the depairing current. We also include the
normal fluid's contribution to dissipation in deriving an expression for the
total kinetic impedance. The Appendices contain many details about the
temperature-dependent behavior of superconductors carrying current up to the
depairing value.",1207.6421v2
2012-11-27,Electronic phase separation due to magnetic polaron formation in the semimetallic ferromagnet EuB$_6$ - A weakly-nonlinear-transport study,"We report measurements of weakly nonlinear electronic transport, as measured
by third-harmonic voltage generation $V_{3\omega}$, in the low-carrier density
semimetallic ferromagnet EuB$_6$, which exhibits an unusual magnetic ordering
with two consecutive transitions at $T_{c_1} = 15.6$\,K and $T_{c_2} =
12.5$\,K. Upon cooling in zero magnetic field through the ferromagnetic
transition, the dramatic drop in the linear resistivity at the upper transition
$T_{c_1}$ coincides with the onset of nonlinearity, and upon further cooling is
followed by a pronounced peak in $V_{3 \omega}$ at the lower transition
$T_{c_2}$. Likewise, in the paramagnetic regime, a drop of the material's
magnetoresistance $R(H)$ precedes a magnetic-field-induced peak in nonlinear
transport. A striking observation is a linear temperature dependence of
$V_{3\omega}^{\rm peak}(H)$. We suggest a picture where at the upper transition
$T_{c_1}$ the coalescing MP form a conducting path giving rise to a strong
decrease in the resistance. The MP formation sets in at around $T^\ast \sim
35$\,K below which these entities are isolated and strongly fluctuating, while
growing in number. The MP then start to form links at $T_{c_1}$, where
percolative electronic transport is observed. The MP merge and start forming a
continuum at the threshold $T_{c_2}$. In the paramagnetic temperature regime
$T_{c_1} < T < T^\ast$, MP percolation is induced by a magnetic field, and the
threshold accompanied by charge carrier delocalization occurs at a single
critical magnetization.",1211.6305v1
2013-04-05,Anisotropic Magneto Resistance and Planar Hall Effect at the LaAlO$_3$/SrTiO$_3$ Heterointerfaces: Effect of Carrier Confinement on Magnetic Interactions,"The confinement of the two dimensional electron gas (2DEG), preferential
occupancy of the Ti 3d orbital and strong spin-orbit coupling at the
LaAlO$_3$/SrTiO$_3$ interface play a significant role in its emerging
properties. Here we report a fourfold oscillation in the anisotropic magneto
resistance (AMR) and the observation of planar Hall effect (PHE) at the
LaAlO$_3$/SrTiO$_3$ heterointerface. We evaluate the carrier confinement
effects on the AMR and find that the fourfold oscillation appears only for the
case of 2DEG system while it is twofold for the 3D system. As the fourfold
oscillation fits well to the phenomenological model for a cubic symmetry
system, we attribute this oscillation to the anisotropy in the magnetic
scattering arising from the interaction of electrons with the localized
magnetic moments coupled to the crystal symmetry. The AMR behavior is further
found to be sensitive to applied gate electric field, emphasizing the
significance of spin-orbit coupling at the interface. These confinement effects
suggest that the magnetic interactions are predominant at the interface, and
the gate electric field modulation of AMR suggest the possible gate tunable
magnetic interactions in these systems. The observed large PHE further
indicates that the in plane nature of magnetic ordering arises from the
in-plane Ti 3dxy orbitals.",1304.1619v1
2013-09-24,Wiedemann-Franz law and non-vanishing temperature scale across the field-tuned quantum critical point of YbRh2Si2,"The in-plane thermal conductivity kappa(T) and electrical resistivity rho(T)
of the heavy-fermion metal YbRh2Si2 were measured down to 50 mK for magnetic
fields H parallel and perpendicular to the tetragonal c axis, through the
field-tuned quantum critical point, Hc, at which antiferromagnetic order ends.
The thermal and electrical resistivities, w(T) and rho(T), show a linear
temperature dependence below 1 K, typical of the non-Fermi liquid behavior
found near antiferromagnetic quantum critical points, but this dependence does
not persist down to T = 0. Below a characteristic temperature T* ~ 0.35 K,
which depends weakly on H, w(T) and rho(T) both deviate downward and converge
in the T = 0 limit. We propose that T* marks the onset of short-range magnetic
correlations, persisting beyond Hc. By comparing samples of different purity,
we conclude that the Wiedemann-Franz law holds in YbRh2Si2, even at Hc,
implying that no fundamental breakdown of quasiparticle behavior occurs in this
material. The overall phenomenology of heat and charge transport in YbRh2Si2 is
similar to that observed in the heavy-fermion metal CeCoIn5, near its own
field-tuned quantum critical point.",1309.6315v1
2014-03-01,Sudden reversal in the pressure dependence of Tc in the iron-based superconductor CsFe2As2: A possible link between inelastic scattering and pairing symmetry,"We report a sudden reversal in the pressure dependence of Tc in the
iron-based superconductor CsFe2As2, similar to that discovered recently in
KFe2As2 [Tafti et al., Nat. Phys. 9, 349 (2013)]. As in KFe2As2, we observe no
change in the Hall coefficient at the zero temperature limit, again ruling out
a Lifshitz transition across the critical pressure Pc. We interpret the Tc
reversal in the two materials as a phase transition from one pairing state to
another, tuned by pressure, and investigate what parameters control this
transition. Comparing samples of different residual resistivity, we find that a
6-fold increase in impurity scattering does not shift Pc. From a study of X-ray
diffraction on KFe2As2 under pressure, we report the pressure dependence of
lattice constants and As-Fe-As bond angle. The pressure dependence of these
lattice parameters suggests that Pc should be significantly higher in CsFe2As2
than in KFe2As2, but we find on the contrary that Pc is lower in CsFe2As2.
Resistivity measurements under pressure reveal a change of regime across Pc,
suggesting a possible link between inelastic scattering and pairing symmetry.",1403.0110v3
2014-03-18,Superconductivity and Physical Properties of CaPd2Ge2 Single Crystals,"We present the superconducting and normal state properties of CaPd2Ge2 single
crystal investigated by magnetic susceptibility \chi, isothermal magnetization
M, heat capacity C_p, in-plane electrical resistivity \rho and London
penetration depth \lambda versus temperature T and magnetic field H
measurements. Bulk superconductivity is inferred from the \rho(T) and C_p(T)
data. The \rho(T) data exhibit metallic behavior and undergoes a
superconducting transition with T_c onset = 1.98 K and zero resistivity state
at T_c 0 = 1.67 K. The \chi(T) reveal the onset of superconductivity at 2.0 K.
For T>2.0 K, the \chi(T) and M(H) are weakly anisotropic paramagnetic with
\chi_ab > \chi_c. The C_p(T) confirm the bulk superconductivity below T_c =
1.69(3) K. The superconducting state electronic heat capacity is analyzed
within the framework of a single-band \alpha-model of BCS superconductivity and
various normal and superconducting state parameters are estimated. Within the
\alpha-model, the C_p(T) data and the ab plane \lambda(T) data consistently
indicate a moderately anisotropic s-wave gap with \Delta(0)/k_B T_c ~ 1.6,
somewhat smaller than the BCS value of 1.764. The relationship of the heat
capacity jump at T_c and the penetration depth measurement to the anisotropy in
the s-wave gap is discussed.",1403.4595v1
2014-05-23,Bio-inspired design of ice-retardant devices based on benthic marine invertebrates: the effect of surface texture,"Growth of ice on surfaces poses a challenge for both organisms and for
devices that come into contact with liquids below the freezing point.
Resistance of some organisms to ice formation and growth, either in subtidal
environments (e.g. Antarctic anchor ice), or in environments with moisture and
cold air (e.g. plants, intertidal) begs examination of how this is
accomplished. Several factors may be important in promoting or mitigating ice
formation. As a start, here we examine the effect of surface texture alone. We
tested four candidate surfaces, inspired by hard-shelled marine invertebrates
and constructed using a three-dimensional printing process. We screened
biological and artifical samples for ice formation and accretion in submerged
conditions using previous methods, and developed a new test to examine ice
formation from surface droplets as might be encountered in environments with
moist, cold air. It appears surface texture plays only a small role in delaying
the onset of ice formation: a stripe feature (corresponding to patterning found
on valves of blue mussels, Crassostrea gigas, or on the spines of the Antarctic
sea urchin, Sterechinus neumayeri) slowed ice formation an average of 25%
compared to a grid feature (corresponding to patterning found on sub-polar
butterclams, Saxidomas). The geometric dimensions of the features have only a
small (~6%) effect on ice formation. Surface texture affects ice formation, but
does not explain by itself the large variation in ice formation and
species-specific ice resistance observed in other work. This suggests future
examination of other factors, such as material elastic properties and coatings,
and their interaction with surface pattern.",1405.6048v2
2014-06-16,Tunable Semimetallic State in Compressive-strained SrIrO3 Films Revealed by Transport Behaviors,"Orthorhombic SrIrO3 is a typical spin-orbit-coupling correlated metal that
shows diversified physical properties under the external stimuli. Here
nonlinear Hall effect and weakly temperature-dependent resistance are observed
in a SrIrO3 film epitaxially grown on SrTiO3 substrate. It infers that
orthorhombic SrIrO3 is a semimetal oxide. However, linear Hall effect and
insensitive-temperature-dependent resistance are observed in SrIrO3 films grown
on (La,Sr)(Al,Ta)O3 (LSAT) substrates, suggesting a tunable semimetallic state
due to band structure change in SrIrO3 films under different compressive
strain. The mechanism of this evolution is explored in detail through
strain-state analysis by reciprocal space mapping and electron diffraction,
carrier density and mobility calculations, as well as electronic band structure
evolution under compressive strain (predicted by tight-binding approximation).
It might suggest that the strain-induced band shift leads to the semimetallic
tuning in the SrIrO3 film grown on from SrTiO3 to LSAT substrates. Our findings
illustrate the tunability of SrIrO3 properties and pave the way to induce novel
physical states in SrIrO3 such as the proposed topological insulator state in
heterostructures.",1406.3878v2
2014-06-17,"Magnetic and transport properties of i-$R$-Cd icosahedral quasicrystals ($R$ = Y, Gd-Tm)","We present a detailed characterization of the recently discovered i-$R$-Cd
($R$ = Y, Gd-Tm) binary quasicrystals by means of x-ray diffraction,
temperature-dependent dc and ac magnetization, temperature-dependent resistance
and temperature-dependent specific heat measurements. Structurally, the
broadening of x-ray diffraction peaks found for i-$R$-Cd is dominated by
frozen-in phason strain, which is essentially independent of $R$. i-Y-Cd is
weakly diamagnetic and manifests a temperature-independent susceptibility.
i-Gd-Cd can be characterized as a spin-glass below 4.6 K via dc magnetization
cusp, a third order non-linear magnetic susceptibility peak, a
frequency-dependent freezing temperature and a broad maximum in the specific
heat. i-$R$-Cd ($R$ = Ho-Tm) is similar to i-Gd-Cd in terms of features
observed in thermodynamic measurements. i-Tb-Cd and i-Dy-Cd do not show a clear
cusp in their zero-field-cooled dc magnetization data, but instead show a more
rounded, broad local maximum. The resistivity for i-$R$-Cd is of order 300 $\mu
\Omega$ cm and weakly temperature-dependent. The characteristic freezing
temperatures for i-$R$-Cd ($R$ = Gd-Tm) deviate from the de Gennes scaling, in
a manner consistent with crystal electric field splitting induced local moment
anisotropy.",1406.4522v1
2014-07-16,"Velocity-strengthening friction significantly affects interfacial dynamics, strength and dissipation","Frictional interfaces are abundant in natural and manmade systems and their
dynamics still pose challenges of fundamental and technological importance. A
recent extensive compilation of multiple-source experimental data has revealed
that velocity-strengthening friction, where the steady-state frictional
resistance increases with sliding velocity over some range, is a generic
feature of such interfaces. Moreover, velocity-strengthening friction has very
recently been linked to slow laboratory earthquakes and stick-slip motion. Here
we elucidate the importance of velocity-strengthening friction by theoretically
studying three variants of a realistic rate-and-state friction model. All
variants feature identical logarithmic velocity-weakening friction at small
sliding velocities, but differ in their higher velocity behaviors. By
quantifying energy partition (e.g. radiation and dissipation), the selection of
interfacial rupture fronts and rupture arrest, we show that the presence or
absence of velocity-strengthening friction can significantly affect the global
interfacial resistance and the total energy released during frictional
instabilities (""event magnitude""). Furthermore, we show that different forms of
velocity-strengthening friction (e.g. logarithmic vs. linear) may result in
events of similar magnitude, yet with dramatically different dissipation and
radiation rates. This happens because the events are mediated by interfacial
rupture fronts with vastly different propagation velocities, where stronger
velocity-strengthening friction promotes slower rupture. These theoretical
results may have significant implications on our understanding of frictional
dynamics.",1407.4253v1
2014-09-11,Quantum Hall Effect on Top and Bottom Surface States of Topological Insulator (Bi1-xSbx)2Te3 Films,"The three-dimensional (3D) topological insulator (TI) is a novel state of
matter as characterized by two-dimensional (2D) metallic Dirac states on its
surface. Bi-based chalcogenides such as Bi2Se3, Bi2Te3, Sb2Te3 and their
combined/mixed compounds like Bi2Se2Te and (Bi1-xSbx)2Te3 are typical members
of 3D-TIs which have been intensively studied in forms of bulk single crystals
and thin films to verify the topological nature of the surface states. Here, we
report the realization of the Quantum Hall effect (QHE) on the surface Dirac
states in (Bi1-xSbx)2Te3 films (x = 0.84 and 0.88). With electrostatic
gate-tuning of the Fermi level in the bulk band gap under magnetic fields, the
quantum Hall states with filling factor \nu = \pm 1 are resolved with quantized
Hall resistance of Ryx = h/e2 and zero longitudinal resistance, owing to chiral
edge modes at top/bottom surface Dirac states. Furthermore, the appearance of a
\nu = 0 state (\sigma xy = 0) reflects a pseudo-spin Hall insulator state when
the Fermi level is tuned in between the energy levels of the non-degenerate top
and bottom surface Dirac points. The observation of the QHE in 3D TI films may
pave a way toward TI-based electronics.",1409.3326v1
2014-09-22,Crystal growth and magnetic properties of equiatomic CeAl,"Single crystal of CeAl has been grown by flux method using Ce-Al self-flux.
Several needle like single crystals were obtained and the length of the needle
corresponds to the [001] crystallographic direction. Powder x-ray diffraction
revealed that CeAl crystallizes in orthorhombic CrB-type structure with space
group ${Cmcm}$ (no. 63). The magnetic properties have been investigated by
means of magnetic susceptibility, isothermal magnetization, electrical
transport, and heat capacity measurements. CeAl is found to order
antiferromagnetically with a N$\grave{\rm e}$el temperature $T_{\rm N}$ = 10K.
The magnetization data below the ordering temperature reveals two metamagentic
transitions for fields less than 20kOe. From the inverse magnetic
susceptibility an effective moment of $2.66\mu_{\rm B}$/Ce has been estimated,
which indicates that Ce is in its trivalent state. Electrical resistivity data
clearly shows a sharp drop at 10K due to the reduction of spin disorder
scattering of conduction electrons thus confirming the magnetic ordering. The
estimated residual resistivity ratio (RRR) is 33, thus indicating a good
quality of the single crystal. The bulk nature of the magnetic ordering is also
confirmed by heat capacity data. From the Schottky anomaly of the heat capacity
we have estimated the crystal field level splitting energies of the $(2J+1)$
degenerate ground state as 25K and 175K respectively for the fist and second
excited states.",1409.6079v1
2014-09-29,Verwey transition in Fe$_{3}$O$_{4}$ thin films: Influence of oxygen stoichiometry and substrate-induced microstructure,"We have carried out a systematic experimental investigation to address the
question why thin films of Fe$_3$O$_4$ (magnetite) generally have a very broad
Verwey transition with lower transition temperatures as compared to the bulk.
We observed using x-ray photoelectron spectroscopy, x-ray diffraction and
resistivity measurements that the Verwey transition in thin films is
drastically influenced not only by the oxygen stoichiometry but especially also
by the substrate-induced microstructure. In particular, we found (1) that the
transition temperature, the resistivity jump, and the conductivity gap of fully
stoichiometric films greatly depends on the domain size, which increases
gradually with increasing film thickness, (2) that the broadness of the
transition scales with the width of the domain size distribution, and (3) that
the hysteresis width is affected strongly by the presence of antiphase
boundaries. Films grown on MgO (001) substrates showed the highest and sharpest
transitions, with a 200 nm film having a T$_V$ of 122K, which is close to the
bulk value. Films grown on substrates with large lattice constant mismatch
revealed very broad transitions, and yet, all films show a transition with a
hysteresis behavior, indicating that the transition is still first order rather
than higher order.",1409.8195v1
2014-12-02,"Structural, electrical and magnetic properties of nanostructured Mn2Ni1.6Sn0.4 melt spun ribbons","Nanocrystalline ribbons of inverse Heusler alloy Mn2Ni1.6Sn0.4 have been
synthesised by melt spinning of the arc melted bulk precursor. The single phase
ribbons crystallize into a cubic structure and exhibit very fine crystallite
size of < 2 nm. Temperature dependent magnetization (M-T) measurements reveal
that austenite (A)-martensite (M) phase transition begins at T~248 K and
finishes at T~238 K during cooling cycle and these values increase to T~267 K
and T~259 K while warming. In cooling cycle, the A-phase shows ferromagnetic
(FM) ordering with a Curie temperature T~267 K, while both the
FM-antiferromagnetic (AFM) and M-transitions occur at T~242 K. The M-phase
undergoes FM transition at T~145 K. These transitions are also confirmed by
temperature dependent resistivity measurements. The observed hysteretic
behaviour of magnetization and resistivity in the temperature regime spanned by
the A-M transition is a manifestation of the first order phase transition.
Magnetization and susceptibility data also provide unambiguous evidence in
favour of spin glass . The scaling of the glass freezing temperature (Tf) with
frequency, extracted from the frequency dependent AC susceptibility
measurements, confirms the existence of canonical spin glass at T<145 K. The
occurrence of canonical spin glass has been explained in terms of the
nanostructuring modified interactions between the FM correlations in the
martensitic phase and the coexisting AFM.",1412.0859v1
2015-02-01,"Enhanced conduction band density of states in intermetallic EuTSi$_3$ (T=Rh, Ir)","We report on the physical properties of single crystalline EuRhSi$_3$ and
polycrystalline EuIrSi$_3$, inferred from magnetisation, electrical transport,
heat capacity and $^{151}$Eu M\""ossbauer spectroscopy. These previously known
compounds crystallise in the tetragonal BaNiSn$_3$-type structure. The single
crystal magnetisation in EuRhSi$_3$ has a strongly anisotropic behaviour at 2 K
with a spin-flop field of 13 T, and we present a model of these magnetic
properties which allows the exchange constants to be determined. In both
compounds, specific heat shows the presence of a cascade of two close
transitions near 50 K, and the $^{151}$Eu M\""ossbauer spectra demonstrate that
the intermediate phase has an incommensurate amplitude modulated structure. We
find anomalously large values, with respect to other members of the series, for
the RKKY N\'eel temperature, for the spin-flop field (13 T), for the spin-wave
gap ($\simeq$ 20-25 K) inferred from both resistivity and specific heat data,
for the spin-disorder resistivity in EuRhSi$_3$ ($\simeq 35$ $\mu$Ohm.cm) and
for the saturated hyperfine field (52 T). We show that all these quantities
depend on the electronic density of states at the Fermi level, implying that
the latter must be strongly enhanced in these two materials. EuIrSi$_3$
exhibits a giant magnetoresistance ratio, with values exceeding 600 % at 2 K in
a field of 14 T.",1502.00285v1
2015-09-02,Shear-induced rigidity of frictional particles: Analysis of emergent order in stress space,"Solids are distinguished from fluids by their ability to resist shear. In
traditional solids, the resistance to shear is associated with the emergence of
broken translational symmetry as exhibited by a non-uniform density pattern,
which results from either minimizing the energy cost or maximizing the entropy
or both. In this work, we focus on a class of systems, where this paradigm is
challenged. We show that shear-driven jamming in dry granular materials is a
collective process controlled solely by the constraints of mechanical
equilibrium. We argue that these constraints lead to a broken translational
symmetry in a dual space that encodes the statistics of contact forces and the
topology of the contact network. The shear-jamming transition is marked by the
appearance of this broken symmetry. We extend our earlier work, by comparing
and contrasting real space measures of rheology with those obtained from the
dual space. We investigate the structure and behavior of the dual space as the
system evolves through the rigidity transition in two different shear
protocols. We analyze the robustness of the shear-jamming scenario with respect
to protocol and packing fraction, and demonstrate that it is possible to define
a protocol-independent order parameter in this dual space, which signals the
onset of rigidity.",1509.00678v2
2015-09-15,Domain-resolved room-temperature magneto-electric coupling in manganite-titanate heterostructures,"We present a model artificial multiferroic system consisting of a
(011)-oriented ferroelectric Pb(Mg,Nb,Ti)O$_3$ substrate intimately coupled to
a ferromagnetic (La,Sr)MnO$_3$ film through epitaxial strain and converse
piezoelectric effects. Electric field pulse sequences of less than 6 kV/cm were
shown to induce large reversible and bistable remanent strains in the manganite
film. Magnetic hysteresis loops demonstrate that the changes in strain states
result in significant changes in magnetic anisotropy from a highly anisotropic
two-fold magnetic symmetry to a more isotropic one. Such changes in magnetic
anisotropy are reversible upon multiple cycles and are stable at zero applied
electric field, and are accompanied by large changes in resistivity. We
directly image the change between the two-fold and isotropic magnetic
configurations at the scale of a single ferromagnetic domain using X-ray
photoemission electron microscopy as a function of applied electric field
pulses. Imaging the domain reversal process as a function of electric field
shows that the energy barrier for magnetization reversal is drastically
lowered, by up to 70% as determined from free energy calculations, through the
anisotropic strain change generated by the ferroelectric substrate. Thus, an
electric field pulse can be used to 'set' and 'reset' the magnetic anisotropy
orientation and resistive state in the film, as well as lowering the coercive
field required to reverse magnetization, showing a promising route towards
electric-field manipulation of multifunctional nanostructures at room
temperature.",1509.04775v1
2015-11-05,Characteristics of undulatory locomotion in granular media,"Undulatory locomotion is ubiquitous in nature and observed in different
media, from the swimming of flagellated microorganisms in biological fluids, to
the slithering of snakes on land, or the locomotion of sandfish lizards in
sand. Despite the similarity in the undulating pattern, the swimming
characteristics depend on the rheological properties of different media.
Analysis of locomotion in granular materials is relatively less developed
compared with fluids partially due to a lack of validated force models but
recently a resistive force theory in granular media has been proposed and shown
useful in studying the locomotion of a sand-swimming lizard. Here we employ the
proposed model to investigate the swimming characteristics of a slender
filament, of both finite and infinite length, undulating in a granular medium
and compare the results with swimming in viscous fluids. In particular, we
characterize the effects of drifting and pitching in terms of propulsion speed
and efficiency for a finite sinusoidal swimmer. We also find that, similar to
Lighthill's results using resistive force theory in viscous fluids, the
sawtooth swimmer is the optimal waveform for propulsion speed at a given power
consumption in granular media. The results complement our understanding of
undulatory locomotion and provide insights into the effective design of
locomotive systems in granular media.",1511.01925v1
2016-02-19,Heat transport study of field-tuned quantum criticality in CeIrIn5,"The in-plane electrical resistivity, rho, and thermal conductivity, kappa, of
the heavy-fermion superconductor CeIrIn5 were measured down to 40mK in magnetic
fields up to 11 T applied along the c axis. For all fields above Hc2=4T of
filamentary superconductivity, we find that the ratio of heat and charge
conductivities in the T to 0 limit obeys the Wiedemann-Franz law,
kappa/T=L0/rho, where L0 = 2.45*10^-8 WOhmK^-2 is the Sommerfeld value of the
Lorenz number. The temperature-dependent parts of both the electrical and
thermal resistivity,w = T/L0 kappa, follow the functional dependence expected
for the Fermi liquid theory of metals with rho - rho_0 = AT^2, w - w_0 = BT^2,
with rho0 = w0 and B ~ 2A. The coefficient B does not show a significant field
dependence even upon approaching Hc2 = 0.4 T of the bulk superconducting state.
The weak response to the magnetic field is in stark contrast with the behavior
found in the closely related CeCoIn5, in which the field-tuned quantum critical
point coincides with Hc2. The value of the electron-electron mass enhancement,
as judged by the A and B coefficients, is about one order of magnitude reduced
in CeIrIn5 as compared to CeCoIn5 (in spite of the fact that the zero field
gamma_0 in CeIrIn5 is twice as large as gamma_0 in CeCoIn5), which suggests
that the material is significantly farther away from the magnetic quantum
critical point at bulk Hc2 and at all of the studied fields. A suppressed
Kadowaki-Woods ratio in CeIrIn5 compared to CeCoIn5 suggests a notably more
localized nature of f electrons in the compound.",1602.06311v1
2016-02-26,"Spin dynamics, electronic and thermal transport properties of two-dimensional CrPS4 single crystal","2-Dimensional (2D) CrPS4 single crystals have been grown by the chemical
vapor transport method. The crystallographic, magnetic, electronic and thermal
transport properties of the single crystals were investigated by the
room-temperature X-ray diffraction, electrical resistivity \r{ho}(T), specific
heat CP(T) and the electronic spin response (ESR) measurements. CrPS4 crystals
crystallize into a monoclinic structure. The electrical resistivity \r{ho}(T)
shows a semiconducting behavior with an energy gap Ea=0.166 eV. The
antiferromagntic (AFM) transition temperature is about TN=36 K. The spin
flipping induced by the applied magnetic field is observed along the c axis.
The magnetic phase diagram of CrPS4 single crystal has been discussed. The
extracted magnetic entropy at TN is about 10.8 J/mol K, which is consistent
with the theoretical value R ln(2S + 1) for S = 3/2 of the Cr3+ ion. Based on
the mean-field theory, the magnetic exchange constants J1 and Jc corresponding
to the interactions of the intralayer and between layers are about 0.143 meV
and -0.955 meV are obtained based on the fitting of the susceptibility above
TN, which agree with the results obtained from the ESR measurements. With the
help of the strain for tuning the magnetic properties, monolayer CrPS4 may be a
promising candidate to explore 2D magnetic semiconductors.",1602.08174v1
2016-05-25,Probing chiral superconductivity in Sr$_{2}$RuO$_{4}$ underneath the surface by point contact measurements,"Sr$_{2}$RuO$_{4}$ (SRO) is the prime candidate for chiral $p$-wave
superconductor with critical temperature $T_{c}(SRO)\sim$1.5 K. Chiral domains
with opposite chiralities $p_{x}\pm ip_{y}$ were proposed, but yet to be
confirmed. We measure the field dependence of the point contact (PC) resistance
between a tungsten tip and the SRO-Ru eutectic crystal, where micrometer-sized
Ru inclusions are embedded in SRO with atomic sharp interface. Ruthenium is an
$s$-wave superconductor with $T_{c}(Ru)\sim$0.5 K, flux pinned near the Ru
inclusions can suppress its superconductivity as reflected from the PC
resistance and spectra. This flux pinning effect is originated from SRO
\textit{underneath} the surface and is very strong. To fully remove it, one has
to thermal cycle the sample above $T_{c}(SRO)$. This resembles the thermal
demagnetization for a ferromagnet, where ferromagnetic domains are randomized
above its Curie temperature. Another way is by applying alternating fields with
decreasing amplitude, resembling field demagnetization for the ferromagnet. The
observed hysteresis in magnetoresistance can be explained by domain dynamics,
providing support for the existence of chiral domains. The origin of strong
pinning \textit{underneath} the surface is also discussed.",1605.07712v2
2016-05-27,The role of ion transport phenomena in memristive double barrier devices,"In this work we report on the role of ion transport for the dynamic behavior
of a double barrier quantum mechanical
Al/Al$_2$O$_3$/Nb$_{\text{x}}$O$_{\text{y}}$/Au memristive device based on
numerical simulations in conjunction with experimental measurements. The device
consists of an ultra-thin Nb$_{\text{x}}$O$_{\text{y}}$ solid state electrolyte
between an Al$_2$O$_3$ tunnel barrier and a semiconductor metal interface at an
Au electrode. It is shown that the device provides a number of interesting
features for potential applications such as an intrinsic current compliance, a
relatively long retention time, and no need for an initialization step.
Therefore, it is particularly attractive for applications in highly dense
random access memories or neuromorphic mixed signal circuits. However, the
underlying physical mechanisms of the resistive switching are still not
completely understood yet. To investigate the interplay between the current
transport mechanisms and the inner atomistic device structure a lumped element
circuit model is consistently coupled with 3D kinetic Monte Carlo model for the
ion transport. The simulation results indicate that the drift of charged point
defects within the Nb$_{\text{x}}$O$_{\text{y}}$ is the key factor for the
resistive switching behavior. It is shown in detail that the diffusion of
oxygen modifies the local electronic interface states resulting in a change of
the interface properties of the double barrier device.",1605.08564v2
2016-05-27,Space Charge Limited Current with Self-heating in Pr$_{0.7}$Ca$_{0.3}$MnO$_3$ based RRAM,"Space Charge Limited Current (SCLC) based conduction has been identified for
PCMO-based RRAM devices based on the observation that $I \propto V^{\alpha}$
where $\alpha \approx 2$. A critical feature of the IV characteristics is a
sharp rise in current ($\alpha \gg 2$) which has been widely attributed to
trap-filled limit (TFL) followed by an apparent trap-free SCLC conduction. In
this paper, we show by TCAD analysis that trap-filled limit (TFL) is
insufficient to explain the sharp current rise ($\alpha \gg 2$). As an
alternative, we propose a shallow trap SCLC model with selfheating effect based
thermal runaway to explain the sharp current rise followed by a series
resistance dominated regime. Experimental results over a range of
25{\deg}C-125{\deg}C demonstrate all 4 regimes (i) Ohmic ($\alpha = 1$), (ii)
shallow trap SCLC ($\alpha \approx 2$), (iii) current shoot up ($\alpha \gg 2$)
and (iv) series resistance ($\alpha = 1$). Further, TCAD simulations with
thermal modeling are able to match the experimental IV characteristics in all
the regimes. Thus, a current conduction mechanism in PCMO-based RRAM supported
by detailed TCAD model is presented. Such a model is essential for further
quantitative understanding and design for PCMO-based RRAM.",1605.08755v1
2016-07-23,"Influence of Al-doping on the structural, magnetic, and electrical properties of La$_{1-x}$Ba$_x$Mn$_{1-x}$Al$_x$O$_3$ ($0\leq x \leq 0.25$) manganites","We have studied the effect of Al doping on the structural, magnetic and
electrical properties of La$_{1-x}$Ba$_x$Mn$_{1-x}$Al$_x$O$_3$ ($0\leq x \leq
0.25$) manganite, annealed in two 750$^oC$ and 1350$^oC$ temperatures. The XRD
analysis shows that the structures in all samples have single phase
rhombohedral structure with R$\bar{3}$c space group. The unit cell volume
almost decrease with increasing the Al doping in all samples. The grain growth
with increasing annealing temperature and Al doping also have been studied. We
observed that, T$_c$ temperature decreases when the Al ion substitute in Mn ion
site. The magnetic study of the samples via magnetic susceptibility results in
Griffiths and spin-glass phase for samples doped with aluminium. Along the
resistivity measurement results, the $T_{MIT}$ (metal-insulator) transition
temperatures decrease and the system become an insulator. The insulator-metal
transition occurs for L0 sample in near 165K, while this transition is weak for
H0 sample due to oxygen non-stoichiometry.Using three models viz. 1. Adiabatic
small polaron hoping, 2.Variable range hopping, and 3. Percolation model, the
resistance have been studied.",1607.06908v1
2016-08-07,Imaging Electron Motion in a Few Layer MoS2 Device,"Ultrathin sheets of MoS2 are a newly discovered 2D semiconductor that holds
great promise for nanoelectronics. Understanding the pattern of current flow
will be crucial for developing devices. In this talk, we present images of
current flow in MoS2 obtained with a Scanned Probe Microscope (SPM) cooled to 4
K. We previously used this technique to image electron trajectories in
GaAs/AlGaAs heterostructures and graphene. The charged SPM tip is held just
above the sample surface, creating an image charge inside the device that
scatters electrons. By measuring the change in resistance {\Delta}R while the
tip is raster scanned above the sample, an image of electron flow is obtained.
We present images of electron flow in an MoS2 device patterned into a hall bar
geometry. A three-layer MoS2 sheet is encased by two hBN layers, top and
bottom, and patterned into a hall-bar with multilayer graphene contacts. An SPM
image shows the current flow pattern from the wide contact at the end of the
device for a Hall density n = 1.3x10^12 cm^-2. The SPM tip tends to block flow,
increasing the resistance R. The pattern of flow was also imaged for a narrow
side contact on the sample. At density n = 5.4x10^11 cm^-2; the pattern seen in
the SPM image is similar to the wide contact. The ability to image electron
flow promises to be very useful for the development of ultrathin devices from
new 2D materials.",1608.02250v1
2016-10-07,Surface Conductivity of Si(100) and Ge(100) Surfaces Determined from Four-Point Transport Measurements Using an Analytical N-Layer Conductance Model,"An analytical N-layer model for charge transport close to a surface is
derived from the solution of Poisson's equation and used to describe
distance-dependent electrical four-point measurements on the microscale. As the
N-layer model comprises a surface channel, multiple intermediate layers and a
semi-infinite bulk, it can be applied to semiconductors in combination with a
calculation of the near-surface band-bending to model very precisely the
measured four-point resistance on the surface of a specific sample and to
extract a value for the surface conductivity. For describing four-point
measurements on sample geometries with mixed 2D-3D conduction channels often a
very simple parallel-circuit model has so far been used in the literature, but
the application of this model is limited, as there are already significant
deviations, when it is compared to the lowest possible case of the N-layer
model, i.e. the 3-layer model. Furthermore, the N-layer model is applied to
published distance-dependent four-point resistance measurements obtained with a
multi-tip scanning tunneling microscope (STM) on Germanium(100) and
Silicon(100) with different bulk doping concentrations resulting in the
determination of values for the surface conductivities of these materials.",1610.02239v1
2016-11-28,Graphene Contacts to a HfSe2/SnS2 Heterostructure,"Placing graphene on SnS2 results in significant charge transfer, on the order
of 10^13/cm^2, from the graphene to the SnS2, and the charge transfer results
in a negative Schottky barrier contact for electron injection from the graphene
into the SnS2 conduction band. However, due to the s-px,y composition of the
SnS2 conduction band, the coupling between the SnS2 and the graphene is
relatively weak. A third layer, HfSe2, placed between the SnS2 and the
graphene, serves as a matrix element matching layer, since it has strong
coupling to both the graphene and the SnS2. It increases the coupling to the
graphene by a factor of 10, and it has little effect on the negative Schottky
barrier height, since the conduction band wavefucntion of the SnS2 / HfSe2 is a
coherent superposition of the orbitals from the two individual layers, such
that there is no energy barrier for an electron to move between the two layers.
This paper first investigates the electronic properties of the heterostructure
bilayer SnS2 / HfSe2 in the presence of an applied vertical electric field, and
then it investigates the trilayer systems of BN / SnS2 / HfSe2 and graphene /
SnS2 / HfSe2. A tunneling Hamiltonian estimate of the the contact resistance of
the graphene to the SnS2 / HfSe2 heterostructure indicates an excellent
low-resistance contact.",1611.08941v1
2016-12-07,Magnetoresistance of compensated semimetals in confined geometries,"Two-component conductors -- e.g., semi-metals and narrow band semiconductors
-- often exhibit unusually strong magnetoresistance in a wide temperature
range. Suppression of the Hall voltage near charge neutrality in such systems
gives rise to a strong quasiparticle drift in the direction perpendicular to
the electric current and magnetic field. This drift is responsible for a strong
geometrical increase of resistance even in weak magnetic fields. Combining the
Boltzmann kinetic equation with sample electrostatics, we develop a microscopic
theory of magnetotransport in two and three spatial dimensions. The compensated
Hall effect in confined geometry is always accompanied by electron-hole
recombination near the sample edges and at large-scale inhomogeneities. As the
result, classical edge currents may dominate the resistance in the vicinity of
charge compensation. The effect leads to linear magnetoresistance in two
dimensions in a broad range of parameters. In three dimensions, the
magnetoresistance is normally quadratic in the field, with the linear regime
restricted to rectangular samples with magnetic field directed perpendicular to
the sample surface. Finally, we discuss the effects of heat flow and
temperature inhomogeneities on the magnetoresistance.",1612.02439v2
2017-02-10,Mesoscopic transport in electrostatically-defined spin-full channels in quantum Hall ferromagnets,"In this work we use electrostatic control of quantum Hall ferromagnetic
transitions in CdMnTe quantum wells to study electron transport through
individual domain walls (DWs) induced at a specific location. These DWs are
formed due to hybridization of two counter-propagating edge states with
opposite spin polarization. Conduction through DWs is found to be symmetric
under magnetic field direction reversal, consistent with the helical nature of
these DWs. We observe that long domain walls are in the insulating regime with
localization length 4 - 6~$\mu$m. In shorter DWs the resistance saturates to a
non-zero value at low temperatures. Mesoscopic resistance fluctuations in a
magnetic field are investigated. The theoretical model of transport through
impurity states within the gap induced by spin-orbit interactions agrees well
with the experimental data. Helical DWs have required symmetry for the
formation of synthetic p-wave superconductors. Achieved electrostatic control
of a single helical domain wall is a milestone on the path to their
reconfigurable network and ultimately to a demonstration of braiding of
non-Abelian excitations.",1702.03279v2
2017-06-06,"Structural, electronic, magnetic and transport properties of equiatomic quaternary Heusler Alloy CoRhMnGe: Theory and Experiment","In this work, we present structural, electronic, magnetic, mechanical and
transport properties of equiatomic quaternary Heusler alloy, CoRhMnGe using
both theoretical and experimental techniques. A detailed structural analysis is
performed using X-ray diffraction(XRD) and extended X-ray absorption fine
structure(EXAFS) spectroscopy. The alloy is found to crystallize in Y-type
structure having space group $F\bar{4}3m$ (\# 216). The ab-initio simulation
pedict half-metallic ferromagnetic characteristics leading to large spin
polarization. The calculated magnetization is found to be in fair agreement
with experiment as well as those predicted by the Slater-Pauling rule, which is
a prerequisite for half-metallicity. The magnetic transition
temperature($\mathrm{T_{C}}$) is found to be $\sim 760$ K. Measured electrical
resistivity in the temperature range 2-400 K also gives an indication of
half-metallic behavior. Simulated resistivity matches fairly well with those
measured, with the temperature dependant carrier relaxation time lying in the
range $1-2$ fs. Effect of hydrostatic pressure on electronic structure,
magnetic and mechanical properties are investigated in detail. The alloy is
found to preserve half-metallic characteristics upto 30.27 GPa beyond which it
transit to metallic phase. No magnetic phase transition is found to occur in
the whole range of pressure. The system also satisfies the Born-Huang criteria
for mechanical stability upto a limited range of pressure. All these properties
make CoRhMnGe alloy promising for spintronics devices.",1706.01624v1
2017-06-14,Impurity band conduction in group-IV ferromagnetic semiconductor Ge1-xFex with nanoscale fluctuations in Fe concentration,"We study the carrier transport and magnetic properties of group-IV-based
ferromagnetic semiconductor Ge1-xFex thin films (Fe concentration x = 2.3 - 14
%) with and without boron (B) doping, by measuring their transport
characteristics; the temperature dependence of resistivity, hole concentration,
mobility, and the relation between the anomalous Hall conductivity versus
conductivity. At relatively low x (= 2.3 %), the transport in the undoped
Ge1-xFex film is dominated by hole hopping between Fe-rich hopping sites in the
Fe impurity band, whereas that in the B-doped Ge1-xFex film is dominated by the
holes in the valence band in the degenerated Fe-poor regions. As x increases (x
= 2.3 - 14 %), the transport in the both undoped and B-doped Ge1-xFex films is
dominated by hole hopping between the Fe-rich hopping sites of the impurity
band. The magnetic properties of the Ge1-xFex films are studied by various
methods including magnetic circular dichroism, magnetization and anomalous Hall
resistance, and are not influenced by B-doping. We show band profile models of
both undoped and B-doped Ge1-xFex films, which can explain the transport and
the magnetic properties of the Ge1-xFex films.",1706.04445v2
2017-06-19,Steady \& unsteady fluidised granular flows down slopes,"Fluidisation is the process by which the weight of a bed of particles is
supported by a gas flow passing through it from below. When fluidised materials
flow down an incline, the dynamics of the motion differ from their
non-fluidised counterparts because the granular agitation is no longer required
to support the weight of the flowing layer. Instead, the weight is borne by the
imposed gas flow and this leads to a greatly increased flow mobility. In this
paper, a framework is developed to model this two phase motion by incorporating
a kinetic theory description for the particulate stresses generated by the
flow. In addition to calculating numerical solutions for fully developed flows,
it is shown that for sufficiently thick flows there is often a local balance
between the production and dissipation of the granular temperature. This
phenomenon permits an asymptotic reduction of the full governing equations and
the identification of a simple state in which the volume fraction of the flow
is uniform. The results of the model are compared with new experimental
measurements of the internal velocity profiles of steady granular flows down
slopes. The distance covered with time by unsteady granular flows down slopes
and along horizontal surfaces and their shapes are also measured and compared
with theoretical predictions developed for flows that are thin relative to
their streamwise extent. For the horizontal flows, it was found that resistance
from the sidewalls was required in addition to basal resistance to capture
accurately the unsteady evolution of the front position and the depth of the
current and for situations in which side-wall drag dominates, similarity
solutions are found for the experimentally-measured motion.",1706.05997v1
2017-06-28,Origin of nonlocal resistance in multiterminal graphene on hexagonal-boron-nitride: Fermi surface edge currents rather than Fermi sea topological valley currents,"The recent observation [R. V. Gorbachev et al., Science {\bf 346}, 448
(2014)] of nonlocal resistance $R_\mathrm{NL}$ near the Dirac point (DP) of
multiterminal graphene on aligned hexagonal boron nitride (G/hBN) has been
interpreted as the consequence of topological valley Hall currents carried by
the Fermi sea states just beneath the bulk gap $E_g$ induced by the inversion
symmetry breaking. However, the valley Hall conductivity $\sigma^v_{xy}$,
quantized inside $E_g$, is not directly measurable. Conversely, the
Landauer-B\""{u}ttiker formula, as numerically exact approach to observable
nonlocal transport quantities, yields $R_\mathrm{NL} \equiv 0$ for the same
simplistic Hamiltonian of gapped graphene that generates $\sigma^v_{xy} \neq
0$. We combine ab initio with quantum transport calculations to demonstrate
that G/hBN wires with zigzag edges host dispersive edge states near the DP that
are absent in theories based on the simplistic Hamiltonian. Although such edge
states exist also in isolated zigzag graphene wires, aligned hBN is required to
modify their energy-momentum dispersion and generate $R_\mathrm{NL} \neq 0$
near the DP persisting in the presence of edge disorder. Concurrently, the edge
states resolve the long-standing puzzle of why the highly insulating state of
G/hBN is rarely observed. We conclude that the observed $R_\mathrm{NL}$ is
unrelated to Fermi sea topological valley currents conjectured for gapped Dirac
spectra.",1706.09361v2
2017-09-15,Reentrant Metallic Behavior in the Weyl Semimetal NbP,"We report the occurrence of reentrant metallic behavior in the Weyl semimetal
NbP. When the applied magnetic field $H$ is above a critical value $H_c$, a
reentrance appears as a peak in the temperature dependent resistivity
$\rho_{xx}(T)$ at $T$ = $T_p$, similar to that observed in graphite where it
was attributed to local superconductivity. The $T_p(H)$ relationship follows a
power-law dependence $T_p\sim(H-H_c)^{1/v}$ where $v$ can be derived from the
temperature dependence of the zero-field resistivity $\rho_0(T) \sim T^v$. From
concurrent measurements of the transverse $\rho_{xx}(T)$ and Hall
$\rho_{xy}(T)$ magnetoresistivities, we reveal a clear correlation between the
rapidly increasing $\rho_{xy}(T)$ and the occurrence of a peak in the
$\rho_{xx}(T)$ curve. Quantitative analysis indicates that the reentrant
metallic behavior arises from the competition of the magneto conductivity
$\sigma_{xx}(T)$ with an additional component
$\Delta\sigma_{xx}(T)=\kappa_H\sigma_{xx}(T)$ where
$\kappa_H=[\rho_{xy}(T)/\rho_{xx}(T)]^2$ is the Hall factor. We find that the
Hall factor ($\kappa_H \approx 0.4$) at peak temperature $T_p$ is nearly
field-independent, leading to the observed $T_p(H)$ relationship. Furthermore,
the reentrant metallic behavior in $\rho_{xx}(T)$ also is reflected in the
behavior of $\rho_{xx}(H)$ that ranges from non-saturating at $T>70$ K to
saturation at liquid helium temperatures. The latter can be explained with the
magnetic field dependence of the Hall factor $\kappa_H(H)$. Our studies
demonstrate that a semiclassical theory can account for the 'anomalies' in the
magnetotransport phenomena of NbP without invoking an exotic mechanism.",1709.05041v1
2018-01-04,Photocorrosion-limited maximum efficiency of solar photoelectrochemical water splitting,"Photoelectrochemical (PEC) water splitting to generate hydrogen is one of the
most studied methods for converting solar energy into clean fuel because of its
simplicity and potentially low cost. Despite over 40 years of intensive
research, PEC water splitting remains in its early stages with stable
efficiencies far less than 10%, a benchmark for commercial applications. Here,
we revealed that the desired photocorrosion stability sets a limit of 2.48 eV
(relative to the normal hydrogen electrode (NHE)) for the highest possible
potential of the valence band (VB) edge of a photocorrosion-resistant
semiconducting photocatalyst. We further demonstrated that such limitation has
a deep root in underlying physics after deducing the relation between energy
position of the valence band edge and free-energy for a semiconductor. The
disparity between the stability-limited VB potential at 2.48 V and the oxygen
evolution reaction (OER) potential at 1.23 V vs NHE reduces the maximum STH
conversion efficiency to approximately 8% for long-term stable single-bandgap
PEC water splitting cells. Based on this understanding, we suggest that the
most promising strategy to overcome this 8% efficiency limit is to decouple the
requirements of efficient light harvesting and chemical stability by protecting
the active semiconductor photocatalyst surface with a photocorrosion-resistant
oxide coating layer.",1801.01334v2
2018-01-09,Advanced Environmentally Resistant Lithium Fluoride Mirror Coatings for the Next-Generation of Broadband Space Observatories,"Recent advances in the physical vapor deposition (PVD) of protective fluoride
films have raised the far-ultraviolet (FUV: 912-1600 {\AA}) reflectivity of
aluminum-based mirrors closer to the theoretical limit. The greatest gains, at
more than 20%, have come for lithium fluoride-protected aluminum, which has the
shortest wavelength cutoff of any conventional overcoat. Despite the success of
the NASA FUSE mission, the use of lithium fluoride (LiF)-based optics is rare,
as LiF is hygroscopic and requires handling procedures that can drive risk.
With NASA now studying two large mission concepts for astronomy, Large
UV-Optical-IR Surveyor (LUVOIR) and the Habitable Exoplanet Imaging Mission
(HabEx), which mandate throughput down to 1000 {\AA}, the development of
LiF-based coatings becomes crucial. This paper discusses steps that are being
taken to qualify these new enhanced LiF-protected aluminum (eLiF) mirror
coatings for flight. In addition to quantifying the hygroscopic degradation, we
have developed a new method of protecting eLiF with an ultrathin (10-20 {\AA})
capping layer of a non-hygroscopic material to increase durability. We report
on the performance of eLiF-based optics and assess the steps that need to be
taken to qualify such coatings for LUVOIR, HabEx, and other FUV-sensitive space
missions.",1801.03102v1
2018-01-28,"Temperature-Dependence of the Solid-Electrolyte Interphase Overpotential: Part I. Two Parallel Mechanisms, One Phase Transition","It has been shown recently that the overpotential originating from ionic
conduction of alkali-ions through the inner dense solid-electrolyte interphase
(SEI) is strongly non-linear. An empirical equation was proposed to merge the
measured resistances from both galvanostatic cycling (GS) and electrochemical
impedance spectroscopy (EIS) at 25$^{\circ}$C. Here, this analysis is extended
to the full temperature range of batteries from -40$^{\circ}$C to
+80$^{\circ}$C for Li, Na, K and Rb-metal electrodes in carbonate electrolytes.
Two different transport mechanisms are found. The first one conducts
alkali-ions at all measured temperatures. The second transport mechanism
conducts ions for all seven measured Li-ion electrolytes and one out of four
Na-ion electrolytes, however, only above a certain critical temperature $T_C$.
At $T_C$ a phase transition is observed switching-off the more efficient
transport mechanism and leaving only the general ion conduction mechanism. The
associated overpotentials increase rapidly below $T_C$ depending on alkali-ion,
salt and solvent and become a limiting factor during galvanostatic operation of
all Li-ion electrolytes at low temperature. In general, the current analysis
merges the SEI resistances measured by EIS ranging from 26 $\Omega$cm$^2$ for
the best Li up to 292 M$\Omega$cm$^2$ for Rb electrodes to its galvanostatic
response over seven orders of magnitude. The determined critical temperatures
are between 0-25$^{\circ}$C for the tested Li and above 50$^{\circ}$C for Na
electrolytes.",1801.09676v1
2018-03-02,Structures and Physical Properties of CsV$_2$Se$_{2-x}$O and V$_2$Se$_2$O,"By using solid-state reactions, we successfully synthesize new oxyselenides
CsV$_2$Se$_{2-x}$O (x = 0, 0.5). These compounds containing V$_2$O planar
layers with a square lattice crystallize in the CeCr$_2$Si$_2$C structure with
the space group of $P4/mmm$. Another new compound V$_2$Se$_2$O which
crystallizes in space group $I4/mmm$ is fabricated by topochemical
deintercalation of cesium from CsV$_2$Se$_2$O powder with iodine in
tetrahydrofuran(THF). Resistivity measurements show a semiconducting behavior
for CsV$_2$Se$_2$O, while a metallic behavior for CsV$_2$Se$_{1.5}$O, and an
insulating feature for V$_2$Se$_2$O. A charge- or spin-density wave-like
anomaly has been observed at 168 K for CsV$_2$Se$_2$O and 150 K for
CsV$_2$Se$_{1.5}$O, respectively. And these anomalies are also confirmed by the
magnetic susceptibility measurements. The resistivity in V$_2$Se$_2$O exhibits
an anomalous log(1/$T$) temperature dependence, which is similar to the case in
parent phase or very underdoped cuprates indicating the involvement of strong
correlation. Magnetic susceptibility measurements show that the magnetic moment
per V-site in V$_2$Se$_2$O is much larger than that of CsV$_2$Se$_{2-x}$O,
which again suggests the correlation induced localization effect in the former.",1803.00703v1
2018-02-21,Optical Receiver with Helicity Dependent Switching of Magnetization,"In this work, we propose helicity-dependent switching (HDS) of magnetization
of Co/Pt for energy efficient optical receiver. Designing a low power optical
receiver for optical-to-electrical signal conversion has proven to be very
challenging. Current day receivers use a photodiode that produces a
photocurrent in response to input optical signals, and power hungry
trans-impedance amplifiers are required to amplify the small photocurrents.
Here, we propose light helicity induced switching of magnetization to overcome
the requirement of photodiodes and subsequent trans-impedance amplification by
sensing the change in magnetization with a magnetic tunnel junction (MTJ).
Magnetization switching of a thin ferromagnet layer using circularly polarized
laser pulses have recently been demonstrated which shows one-to-one
correspondence between light helicity and the magnetization state. We propose
to utilize this phenomena by using digital input dependent circularly polarized
laser pulses to directly switch the magnetization state of a thin Co/Pt
ferromagnet layer at the receiver. The Co/Pt layer is used as the free layer of
an MTJ, the resistance of which is modified by the laser pulses. With the
one-to-one dependence between input data and output magnetization state, the
MTJ resistance is directly converted to digital output signal. Our device to
circuit level simulation results indicate that, HDS based optical receiver
consumes only 0.124 pJ/bit energy, which is much lower than existing
techniques.",1803.07148v1
2018-04-05,Symmetry breaking and unconventional charge ordering in single crystal Na$_{2.7}$Ru$_4$O$_9$,"The interplay of charge, spin, and lattice degrees of freedom in matter leads
to various forms of ordered states through phase transitions. An important
subclass of these phenomena of complex materials is charge ordering (CO),
mainly driven by mixed-valence states. We discovered by combining the results
of electrical resistivity ($\rho$), specific heat, susceptibility $\chi$
(\textit{T}), and single crystal x-ray diffraction (SC-XRD) that
Na$_{2.7}$Ru$_4$O$_9$ with the monoclinic tunnel type lattice (space group
$C$2/$m$) exhibits an unconventional CO at room temperature while retaining
metallicity. The temperature-dependent SC-XRD results show successive phase
transitions with super-lattice reflections at \textbf{q}$_1$=(0, $\frac{1}{2}$,
0) and \textbf{q}$_2$=(0, $\frac{1}{3}$, $\frac{1}{3}$) below $T_{\textrm{C2}}$
(365 K) and only at \textbf{q}$_1$=(0, $\frac{1}{2}$, 0) between
$T_{\textrm{C2}}$ and $T_{\textrm{C1}}$ (630 K). We interpreted these as an
evidence for the formation of an unconventional CO. It reveals a strong
first-order phase transition in the electrical resistivity at $T_{\textrm{C2}}$
(cooling) = 345 K and $T_{\textrm{C2}}$ (heating) = 365 K. We argue that the
origin of the phase transition is due to the localized 4$d$ Ru-electrons. The
results of our finding reveal an unique example of Ru$^{3+}$/Ru$^{4+}$ mixed
valance heavy \textit{d}$^4$ ions.",1804.02012v1
2018-06-08,Interface chemical and electronic properties of LaAlO3/SrVO3 heterostructures,"We have studied the chemical and electronic properties of LaAlO3/SrVO3
ultrathin films by combining hard x-ray photoemission spectroscopy and
transport measurements. We compare single SrVO3 (SVO) ultrathin films and SrVO3
buried below a polar LaAlO3 (LAO) thin layer, both epitaxially grown on SrTiO3.
While ultrathin films (4 unit cells) of SVO do show insulating behavior over
the entire temperature range, the LAO/SVO interface has a resistivity minimum
at 250 K. When increasing the SVO layer thickness, the minimum is observed to
shift to higher temperatures, but the resistivity stays always smaller than
that of comparable SVO single films. Hard x-ray photoemission spectroscopy
reveals a surface or interface related V5+ component in the V 2p spectra for
SVO films and LAO/SVO heterostructures, respectively, attributed to a strongly
oxidized component. This chemical reconstruction is weaker in LAO/SVO
heterostructures compared to single SVO films. We show that this dead layer in
SVO ultrathin films has to be considered when the film thickness reaches the
few unit-cells limit and propose solutions on how to prevent this detrimental
effect.",1806.03066v1
2018-06-20,Unusual phonon density of states and response to the superconducting transition in the In-doped topological crystalline insulator Pb$_{0.5}$Sn$_{0.5}$Te,"We present inelastic neutron scattering results of phonons in
(Pb$_{0.5}$Sn$_{0.5}$)$_{1-x}$In$_x$Te powders, with $x=0$ and 0.3. The $x=0$
sample is a topological crystalline insulator, and the $x=0.3$ sample is a
superconductor with a bulk superconducting transition temperature $T_c$ of 4.7
K. In both samples, we observe unexpected van Hove singularities in the phonon
density of states at energies of 1--2.5 meV, suggestive of local modes. On
cooling the superconducting sample through $T_c$, there is an enhancement of
these features for energies below twice the superconducting-gap energy. We
further note that the superconductivity in
(Pb$_{0.5}$Sn$_{0.5}$)$_{1-x}$In$_x$Te occurs in samples with normal-state
resistivities of order 10 m$\Omega$~cm, indicative of bad-metal behavior.
Calculations based on density functional theory suggest that the
superconductivity is easily explainable in terms of electron-phonon coupling;
however, they completely miss the low-frequency modes and do not explain the
large resistivity. While the bulk superconducting state of
(Pb$_{0.5}$Sn$_{0.5}$)$_{0.7}$In$_{0.3}$Te appears to be driven by phonons, a
proper understanding will require ideas beyond simple BCS theory.",1806.07531v1
2017-03-18,Coexistence of non-Fermi liquid and Fermi liquid self-energies at all dopings in cuprates,"Various angle-dependent measurements in hole-doped cuprates suggested that
Non-Fermi liquid (NFL) and Fermi-liquid (FL) self-energies coexist in the
Brillouin zone. Moreover, it is also found that NFL self-energies survive up to
the overdoped region where the resistivity features a global FL-behavior. To
address this problem, here we compute the momentum dependent self-energy from a
single band Hubbard model. The self-energy is calculated self-consistently by
using a momentum-dependent density-fluctuation (MRDF) method. One of our main
result is that the computed self-energy exhibits a NFL-like frequency
dependence only in the antinodal region, and FL-like behavior elsewhere, and
retains its analytic form at all momenta and dopings. The dominant source of
NFL self-energy in the antinodal region stems from the self-energy-dressed
fluctuations between the itinerant and localized densities as self-consistency
is invoked. We also calculate the DC conductivity by including the full
momentum dependent self-energy. We find that the resistivity-temperature
exponent n becomes 1 near the optimal doping, while the NFL self-energy
occupies largest momentum-space volume. Surprisingly, even in the NFL state
near the optimal doping, the nodal region contains FL-like self-energies; while
in the under- and over-dopings (n ~ 2), the antinodal region remains NFL-like.
These results highlight the non-local correlation physics in cuprates and in
other similar intermediately correlated materials, where a direct link between
the microscopic single-particle spectral properties and the macroscopic
transport behavior can not be well established.",1703.06280v4
2013-12-27,Space charge dynamics in solid electrolytes with steric effect and Vegard stresses: resistive switching and ferroelectric-like hysteresis of electromechanical response,"We performed self-consistent modelling of electrotransport and
electromechanical response of solid electrolyte thin films allowing for steric
effects of mobile charged defects (ions, protons or vacancies), electron
degeneration and Vegard stresses. We establish correlations between the
features of the space-charge dynamics, current-voltage and bending-voltage
curves in the wide frequency range of applied electric voltage. The pronounced
ferroelectric-like hysteresis of bending-voltage loops and current maxima on
double hysteresis current-voltage loops appear for the electron-open
electrodes. The double hysteresis loop with pronounced humps indicates the
resistance switching of memristor-type. The switching occurs due to the strong
coupling between electronic and ionic subsystem. The sharp meta-stable maximum
of the electron density appears near one open electrode and moves to another
one during the periodic change of applied voltage. Our results can explain the
nature and correlation of electrical and mechanical memory effects in thin
films of solid electrolytes. The analytical expression proving that the
electrically induced bending of solid electrolyte films can be detected by
interferometric methods is derived.",1312.7300v1
2014-10-08,Kondo-hole substitution in heavy fermions: dynamics and transport,"Kondo-hole substitution is a unique probe for exploring the interplay of
interactions, f-electron dilution and disorder in heavy fermion materials.
Within the diluted periodic Anderson model, we investigate the changes in
single-particle dynamics as well as response functions, as a function of Kondo
hole concentration ($x$) and temperature. We show that the spectral weight
transfers due to Kondo hole substitution has characteristics that are different
from those induced by temperature; The dc resistivity crosses over from a
highly non-monotonic form with a coherence peak in the $x\rightarrow 0$ limit
to a monotonic single-impurity like form that saturates at low temperature. The
thermopower exhibits a characteristic maximum as a function of temperature, the
value of which changes sign with increasing $x$, and its location is shown to
correspond to a low energy scale of the system. The Hall coefficient also
changes sign with increasing $x$ at zero temperature and is highly temperature
dependent for all $x$. As $x$ is increased beyond a certain $x_c$, the Drude
peak and the mid-infrared peak in the optical conductivity vanish almost
completely; A peak in the optical scattering rate melts and disappears
eventually. We discuss the above-mentioned changes in the properties in terms
of a crossover from coherent, Kondo lattice behaviour to single impurity like,
incoherent behaviour with increasing $x$. A comparison of theory with
experiments carried out for the dc resistivity and the thermopower of
Ce$_{1-x}$La$_x$B$_6$ yields good agreement.",1410.2475v1
2016-06-01,Combined effects of Sr substitution and pressure on the ground states in CaFe$_2$As$_2$,"We present a detailed study of the combined effects of Sr substitution and
hydrostatic pressure on the ground-state properties of CaFe$_2$As$_2$.
Measurements of the electrical resistance and magnetic susceptibility, both at
ambient and finite pressure $P$ $\leq$ 2$\,$GPa, were performed on
Ca$_{1-x}$Sr$_x$Fe$_2$As$_2$ single crystals grown out of Sn flux. We find that
upon Sr substitution the ranges of stability of both the structural-magnetic
transition and the transition into the non-magnetic collapsed tetragonal phase
are shifted to higher pressure levels with the latter moving at a higher rate.
This suggests the possibility of separating the two phase lines, which
intersect already at elevated temperatures for $x$ = 0 and low Sr concentration
levels. For $x$ = 0.177 we find strong evidence that both phases remain
separated down to lowest temperature and that a zero-resistance state emerges
in this intermediate pressure window. This observation indicates that
Sr-substitution combined with hydrostatic pressure provides another route for
stabilizing superconductivity in CaFe$_2$As$_2$. Our results are consistent
with the notion that (i) preserving the fluctuations associated with the
structural-magnetic transition to low temperatures is vital for
superconductivity to form in this material and that (ii) the non-magnetic
collapsed tetragonal phase is detrimental for superconductivity.",1606.00141v1
2016-06-06,Duality and reciprocity of fluctuation-dissipation relations in conductors,"By analogy with linear-response we formulate the duality and reciprocity
properties of current and voltage fluctuations expressed by Nyquist relations
including the intrinsic bandwidths of the respective fluctuations. For this
purpose we individuate total-number and drift-velocity fluctuations of carriers
inside a conductor as the microscopic sources of noise. The spectral densities
at low frequency of the current and voltage fluctuations and the respective
conductance and resistance are related in a mutual exclusive way to the
corresponding noise-source. The macroscopic variance of current and voltage
fluctuations are found to display a dual property via a plasma conductance that
admits a reciprocal plasma resistance. Analogously, the microscopic
noise-sources are found to obey a dual property and a reciprocity relation. The
formulation is carried out in the frame of the grand canonical (for current
noise) and canonical (for voltage noise) ensembles and results are derived
which are valid for classical as well as for degenerate statistics including
fractional exclusion statistics. The unifying theory so developed sheds new
light on the microscopic interpretation of dissipation and fluctuation
phenomena in conductors. In particular it is proven that, as a consequence of
the Pauli principle, for Fermions non-vanishing single-carrier velocity
fluctuations at zero temperature are responsible for diffusion but not for
current noise, which vanishes in this limit.",1606.01659v1
2017-01-25,Evidence for an excitonic insulator phase in a zero-gap InAs/GaSb bilayer,"Many-body interactions can produce novel ground states in a condensed-matter
system. For example, interacting electrons and holes can spontaneously form
excitons, a neutral bound state, provided that the exciton binding energy
exceeds the energy separation between the single particle states. Here we
report on electrical transport measurements on spatially separated
two-dimensional electron and hole gases with nominally degenerate energy
subbands, realized in an InAs(10 nm)/GaSb(5 nm) coupled quantum well. We
observe a narrow and intense maximum (~500 k\Omega) in the four-terminal
resistivity in the charge neutrality region, separating the electron-like and
hole-like regimes, with a strong activated temperature-dependence above T = 7 K
and perfect stability against quantizing magnetic fields. By quantitatively
comparing our data with early theoretical predictions, we show that such
unexpectedly large resistance in our nominally zero-gap semi-metal system is
probably due to the formation of an excitonic insulator state.",1701.07417v1
2017-11-29,Thermal contribution to the spin-orbit torque in metallic/ferrimagnetic systems,"We report a systematic study of current-induced perpendicular magnetization
switching in W/Co$_{x}$Tb$_{1-x}$/Al thin films with strong perpendicular
magnetic anisotropy. Various Co$_{x}$Tb$_{1-x}$ ferrimagnetic alloys with
different magnetic compensation temperatures are presented. The systems are
characterized using MOKE, SQUID and anomalous Hall resistance at different
cryostat temperature ranging from 10 K to 350 K. The current-switching
experiments are performed in the spin-orbit torque geometry where the current
pulses are injected in plane and the magnetization reversal is detected by
measuring the Hall resistance. The full reversal magnetization has been
observed in all samples. Some experimental results could only be explained by
the strong sample heating effect during the current pulses injection. We have
found that, for a given composition $x$ and switching polarity, the devices
always reach the same temperature $\textit{T}_{switch}(x)$ before switching
independently of the cryostat temperature. $\textit{T}_{switch}$ seems to scale
with the Curie temperature of the Co$_{x}$Tb$_{1-x}$ ferrimagnetic alloys. This
explains the evolution of the critical current (and critical current density)
as a function of the alloy concentration. Future application could take
advantages of this heating effect which allows reducing the in-plane external
field. Unexpected double magnetization switching has been observed when the
heat generated by the current allows crosses the compensation temperature.",1711.10790v1
2018-10-01,Electrical detection of current generated spin in topological insulator surface states: Role of interface resistance,"Current generated spin polarization in topological insulator (TI) surface
states due to spin-momentum locking has been detected recently using
ferromagnet/tunnel barrier contacts, where the projection of the TI spin onto
the magnetization of the ferromagnet is measured as a voltage. However,
opposing signs of the spin voltage have been reported, which had been
tentatively attributed to the coexistence of trivial two-dimensional electron
gas states on the TI surface which may exhibit opposite current-induced
polarization than that of the TI Dirac surface states. Models based on
electrochemical potential have been presented to determine the sign of the spin
voltage expected for the TI surface states. However, these models neglect
critical experimental parameters which also affect the sign measured. Here we
present a Mott two-spin current resistor model which takes into account these
parameters such as spin-dependent interface resistances, and show that such
inclusion can lead to a crossing of the voltage potential profiles for the
spin-up and spin-down electrons within the channel, which can lead to measured
spin voltages of either sign. These findings offer a resolution of the ongoing
controversy regarding opposite signs of spin signal reported in the literature,
and highlight the importance of including realistic experimental parameters in
the model.",1810.00757v2
2018-10-24,"On the interactions of Ti${_2}$AlC, Ti${_3}$AlC${_2}$, Ti${_3}$SiC${_2}$ and Cr${_2}$AlC with palladium at 900 °C","Herein we report on the reactivity between palladium, Pd, and the MAX phases,
Ti${_2}$AlC, Ti${_3}$AlC${_2}$, Ti${_3}$SiC${_2}$ and Cr${_2}$AlC. Diffusion
couples of Pd/MAX were heated to 900 {\deg}C under uniaxial stress of ~20 MPa
for 2, 4, and 10 h in a vacuum (<1 Pa) hot press. The diffusion couples were
examined using X-ray diffraction, scanning electron microscopy and
energy-dispersive X-ray spectroscopy. After heating to 900 {\deg}C for 10 h,
the diffusion layer thicknesses in the Ti${_2}$AlC/Pd, Cr${_2}$AlC/Pd,
Ti${_3}$AlC${_2}$/Pd and Ti${_3}$SiC${_2}$/Pd couples were found to be 35, 45,
105 and 410 mm, respectively. Thus, Ti${_2}$AlC is the most resistant to
reaction, while Ti${_3}$SiC${_2}$ is least resistant, with Cr${_2}$AlC and
Ti${_3}$AlC${_2}$, in between. In all cases, the reaction occurred by the
diffusion of the A-group element into Pd, concomitant with Pd diffusion into
the MAX phase. No diffusion of the M and X atoms was detected.",1811.00098v1
2018-11-27,"Thermoelectric properties of (Ba,K)Cd2As2 crystallized in the CaAl2Si2-type structure","As-Based Zintl compounds Ba1-xKxCd2As2 crystallized in the CaAl2Si2-type
structure (space group P3-m1) were prepared using solid-state reactions
followed by hot-pressing. We have successfully substituted K for Ba up to x =
0.08, producing hole-carrier doping with concentrations up to 1.60*1020 cm-3.
We have determined the band-gap value of non-doped BaCd2As2 to be 0.40 eV from
the temperature dependence of the electrical resistivity. Both the electrical
resistivity and the Seebeck coefficient decrease with hole doping, leading to a
power factor value of 1.28 mW m-1 K-2 at 762 K for x = 0.04. A first-principles
band calculation shows that the relatively large power factor mainly originates
from the two-fold degeneracy of the bands comprising As px,y orbitals and from
the anisotropic band structure at the valence-band maximum. The lattice thermal
conductivity is suppressed by the K doping to 0.46 W m-1 K-1 at 773 K for x =
0.08, presumably due to randomness. The effect of randomness is compensated by
an increase in the electronic thermal conductivity, which keeps the total
thermal conductivity approximately constant. In consequence, the dimensionless
figure-of-merit ZT reaches a maximum value of 0.81 at 762 K for x = 0.04.",1811.10867v1
2018-11-29,Application of an extended van der Pauw method to anisotropic magnetoresistance measurements of ferromagnetic films,"We demonstrate anisotropic resistivity measurements using the extended van
der Pauw (vdP) method in ferromagnetic Ni80Fe20 (Py) films. We apply it to
measure anisotropic magnetoresistance (AMR) and compare the results of the vdP
method with the more conventional Hall-bar method along the hard and easy axis
of the film and show that the vdP method gives more reliable AMR result. For
instance, the AMR result along the hard and easy axis of the film are in close
agreement. Further, we applied the vdP method to study AMR in a series of Py
films with thicknesses ranging between 10-250 nm. The films were grown by
sputtering deposition at an angle with respect to the substrate normal and with
an in-situ magnetic field, both conditions assisting in the definition of
in-plane uniaxial anisotropy. The microstructure of Py films was characterized
using X-ray reflectivity, diffraction and polar mapping of (111) planes. We
detected no off-normal texture and negligible surface roughness, which
indicates that self-shadowing is not dominating in our growth. Yet the films
have well defined uniaxial anisotropy. Abrupt changes in the average
resistivity vs. film thickness were observed, which cannot be explained by the
models accounting for the thickness and grain size but strongly correlate with
the changes in (111) texture in the films. We compared our results with the
literature and show that independent of growth method, substrate and deposition
temperature, the AMR value presents a saturation behavior with thickness at
about 100 nm.",1811.12029v1
2019-05-27,Unidirectional planar Hall voltages induced by surface acoustic waves in ferromagnetic thin films,"The electromotive forces induced by surface acoustic waves (SAWs) are
investigated in ferromagnetic thin films. CoFeB thin films deposited on
LiNbO$_3$ substrates are patterned into Hall-bars to study the acoustoelectric
transport properties of the device. The longitudinal and transverse dc voltages
that develop in the Hall bars, which are parallel and orthogonal to the flow of
the SAW, respectively, are measured under application of an in-plane magnetic
field. The longitudinal voltage scales linearly with the SAW power and reverses
its polarity upon changing the direction to which the SAW propagates,
suggesting generation of a dc acoustic current via the SAW excitation. The
magnetic field has little influence on the acoustic current. In contrast, the
SAW induced transverse voltage shows significant dependence on the relative
angle between the magnetic field and the SAW propagation direction. Such field
angle dependent voltage resembles that of the planar Hall voltage induced by
electric current. Interestingly, the angle dependent acoustic transverse
voltage does not depend on the SAW propagation direction. Moreover, the
magnitude of the equivalent angle dependent acoustic transverse resistance is
more than one order of magnitude larger than that of the planar Hall
resistance. These results show the unique acoustoelectric transport properties
of ferromagnetic thin films.",1905.11224v1
2019-07-04,Thick adherent diamond films on AlN with low thermal barrier resistance,"Growth of $>$100 $\mu$m thick diamond layer adherent on aluminium nitride is
presented in this work. While thick films failed to adhere on untreated AlN
films, hydrogen/nitrogen plasma treated AlN films retained the thick diamond
layers. Clear differences in zeta potential measurement confirms the surface
modification due to hydrogen/nitrogen plasma treatment. Areal Raman maps showed
an increase in non-diamond carbon in the initial layers of diamond grown on
pre-treated AlN. The presence of non-diamond carbon has minimal effect on the
interface between diamond and AlN. The surfaces studied with x-ray
photoelectron spectroscopy (XPS) revealed a clear distinction between
pre-treated and untreated samples. The surface aluminium goes from nitrogen
rich environment to an oxygen rich environment after pre-treatment. Cross
section transmission electron microscopy shows a clean interface between
diamond and AlN. Thermal barrier resistance between diamond and AlN was found
to be in the range of 16 m$^2$K/GW which is a large improvement on the current
state-of-the-art.",1907.02481v1
2019-07-23,"Electrical characteristics of vertical-geometry Schottky junction to magnetic insulator (Ga,Mn)N heteroepitaxially grown on sapphire","Schottky barrier height and the ideality factor $\eta$ are established for
the first time in the single phase (Ga,Mn)N using a vertical geometry device.
The material has been heteroepitaxially grown on commercially available low
threading dislocation density GaN:Si template. The observed above 10M$\Omega$
resistances already at room temperature are indicative that a nearly
conductive-dislocation-free electrical properties are achieved. The analysis of
temperature dependence of the forward bias I-V characteristics in the frame of
the thermionic emission model yields Ti-(Ga,Mn)N Schottky barrier height to be
slightly lower but close in character to other metal/GaN junctions. However,
the large magnitudes of the ideality factor $\eta$>1.5 for T$\leqslant$300K,
point to a sizable current blocking in the structure. While it remains to be
seen whether it is due to the presence of (Ga,Mn)N barrier or due to other
factors which reduce the effective area of the junction, an existence of a
substantial serial resistance may hold the key to explain similar observations
in other devices of a corresponding structure and technological relevance.",1907.09757v1
2020-02-11,Cation controlled wetting properties of vermiculite membranes and its potential for fouling resistant oil-water separation,"The surface free energy is one of the most fundamental properties of solids,
hence, manipulating the surface energy and thereby the wetting properties of
solids, has tremendous potential for various physical, chemical, biological as
well as industrial processes. Typically, this is achieved by either chemical
modification or by controlling the hierarchical structures of surfaces. Here we
report a phenomenon whereby the wetting properties of vermiculite laminates are
controlled by the hydrated cations on the surface and in the interlamellar
space. We find that by exploiting this mechanism, vermiculite laminates can be
tuned from superhydrophillic to hydrophobic simply by exchanging the cations;
hydrophilicity decreases with increasing cation hydration free energy, except
for lithium. Lithium, which has a higher hydration free energy than potassium,
is found to provide a superhydrophilic surface due to its anomalous hydrated
structure at the vermiculite surface. Building on these findings, we
demonstrate the potential application of superhydrophilic lithium exchanged
vermiculite as a thin coating layer on microfiltration membranes to resist
fouling, and thus, we address a major challenge for oil-water separation
technology.",2002.04522v1
2020-02-20,Predictive Crystal Plasticity Modeling of Single Crystal Nickel Based on First-Principles Calculations,"To reduce reliance on experimental fitting data within the crystal plasticity
finite element method (CPFEM), an approached is proposed that integrates
first-principles calculations based on density functional theory (DFT) to
predict the strain hardening behavior of pure Ni single crystals. Flow
resistance was evaluated through the Peierls-Nabarro equation using the ideal
shear strength and elastic properties calculated by DFT-based methods, with
hardening behavior modeled by imposing strains on supercells in
first-principles calculations. Considered alone, elastic interactions of pure
edge dislocations capture hardening behavior for small strains on single slip
systems. For larger strains, hardening is captured through a strain-weighted
linear combination of edge and screw flow resistance components. The rate of
combination is not predicted in the present framework, but agreement with
experiments through large strains (~0.4) for multiple loading orientations
demonstrates a possible route for more predictive crystal plasticity modeling
through incorporation of analytical models of mesoscale physics.",2002.08552v5
2020-03-13,"Structural, magnetic and insulator-to-metal transitions under pressure in the GaV4S8 Mott insulator: A rich phase diagram up to 14.7 GPa","In addition to its promising potential for applications, GaV4S8 shows very
interesting physical properties with temperature and magnetic field. These
properties can be tuned by applying hydrostatic pressure in order to reveal and
understand the physics of these materials. Not only pressure induces an
insulator-to-metal transition in GaV4S8 but it also has an interesting effect
on the structural and magnetic transitions. Using a combination of AC
calorimetry, capacitance, and resistivity measurements under pressure, we
determine the evolution of the structural and magnetic transitions with
pressure and thus establish the T-P phase diagram of GaV4S8. To detect the
insulator-to-metal transition, we use optical conductivity and DC resistivity
measurements and we follow the evolution of the Mott gap under pressure. The
structural transition temperature increases with pressure and a second
transition appears above 6 GPa indicating a possible new phase with a very
small gap. Pressure has surprisingly a very weak effect on the ferromagnetic
transition that persists even very close to the IMT that occurs at around 14
GPa, implying that the metallic state may also be magnetic.",2003.06358v1
2020-03-26,Sub-THz momentum drag and violation of Matthiessen's rule in an ultraclean ferromagnetic SrRuO$_3$ metallic thin film,"SrRuO$_3$, a ferromagnet with an approximately 160\,K Curie temperature,
exhibits a $T^2$ dependent dc resistivity below $\approx$ 30 K. Nevertheless,
previous optical studies in the infrared and terahertz range show non-Drude
dynamics at low temperatures which seem to contradict a Fermi-liquid picture
with long-lived quasiparticles. In this work, we measure the low-frequency THz
range response of thin films with residual resistivity ratios, $\rho_{300K}/
\rho_{4K} \approx$ 74. Such low disorder samples allow an unprecedented look at
the effects of electron-electron interactions on low-frequency transport. At
temperatures below 30 K, we found both a very sharp zero-frequency mode which
has a width narrower than $k_BT/\hbar$ as well as a broader zero frequency
Lorentzian that has at least an order of magnitude larger scattering rate. Both
features have temperature dependencies consistent with a Fermi-liquid with the
wider feature explicitly showing a T$^2$ scaling. Such two -Drude transport
sheds light on previous reports of the violation of Mathielssen's rule and
extreme sensitivity to disorder in metallic ruthenates. We consider a number of
possibilities for the origin of the two feature optical conductivity including
multiband effects that arise from momentum conserving interband scattering and
the approximate conservation of a pseudo-momentum that arises from quasi-1D
Fermi surfaces.",2003.12024v1
2020-09-07,Effect of interface resistance on thermoelectric properties in (1-x)La$_{0.95}$Sr$_{0.05}$Co$_{0.95}$Mn$_{0.05}$O$_3$/(x)WC composite,"In this study, the synergistic effect of the particle size of the dispersed
phase and the interface thermal resistance (R$_{int}$) between the phases on
the phonon thermal conductivity ($\kappa_{ph}$) of the
(1-x)La$_{0.95}$Sr$_{0.05}$Co$_{0.95}$Mn$_{0.05}$O$_3$/(x)WC thermoelectric
composite, is demonstrated. Further, the correlation between the R$_{int}$ and
the Kapitza radius is discussed using the Bruggeman's asymmetrical model. In
particular, the polycrystalline
La$_{0.95}$Sr$_{0.05}$Co$_{0.95}$Mn$_{0.05}$O$_3$ sample is synthesized using a
standard-solid state route. The presence of WC nanoparticle is confirmed from
the electron microscopy images. Electrical conductivity ($\sigma$) increases,
and the Seebeck coefficient ($\alpha$) decreases with the increase in
conducting WC volume fraction in the composite. The simultaneous increase in
$\sigma$ and a decrease in $\kappa_{ph}$ with the WC volume fraction results in
an increased figure of merit (zT) for
(1-x)La$_{0.95}$Sr$_{0.05}$Co$_{0.95}$Mn$_{0.05}$O$_3$/(x)WC composite. A
maximum zT $\sim$ 0.20 is obtained for
(1-x)La$_{0.95}$Sr$_{0.05}$Co$_{0.95}$Mn$_{0.05}$O$_3$/(x)WC composite for
x=0.010 at 463 K. The results obtained in the present study shows promise to
design thermoelectric composites with desired phonon thermal conductivity
considering the elastic properties between the phases.",2009.03236v3
2020-09-24,Phonon hydrodynamics in crystalline GeTe at low temperature,"A first-principles density functional method along with the direct solution
of linearized Boltzmann transport equations are employed to systematically
analyze the low-temperature thermal transport in crystalline GeTe. The
extensive thermal transport simulations, ranging from room temperature to
cryogenic temperatures, reveal the emergence of a phonon hydrodynamic regime in
GeTe at low temperature. The reduction of grain boundary scattering is found to
play a crucial role along with the divergent trend of umklapp and normal
scattering at low temperatures in accommodating the hydrodynamic regime.
Average scattering rates for normal, umklapp, and other resistive processes are
distinguished for a wide range (4-300 K) of temperatures and used for
identifying various phonon transport regimes. Therefore, the variations of
lattice thermal conductivity, phonon propagation length, and thermal
diffusivity with temperature, related to these transport regimes (ballistic,
hydrodynamic, and kinetic), have been thoroughly investigated. The modewise
decomposition of lattice thermal conductivity and the distinction of thermal
diffusivity according to different scattering processes reveal rich information
on the dominant phonon modes and phonon scattering processes in GeTe at low
temperature. Further, the kinetic-collective model is used to elucidate the
hydrodynamic behavior of phonon scattering through the relative study of
collective and kinetic contributions to the thermal transport properties. In
this context, the Knudsen number is estimated through the characteristic
nonlocal length and the grain size, which further quantifies the consistent
hydrodynamic behavior of phonon thermal transport for GeTe. Finally,
phonon-vacancy scattering for GeTe is realized, and vacancies are found
strongly to influence the hydrodynamic window while incorporating the other
resistive scattering mechanisms.",2009.11962v1
2020-09-30,Domain Control by Adjusting Anisotropic Stress in Pyrochlore Oxide Cd2Re2O7,"The 5d pyrochlore oxide Cd2Re2O7 exhibits successive phase transitions from a
cubic pyrochlore structure (phase I) to a tetragonal structure without
inversion symmetry below Ts1 of ~200 K (phase II) and further to another
noncentrosymmetric tetragonal structure below Ts2 of ~120 K (phase III). The
two low-temperature phases may be characterized by odd-parity multipolar orders
induced by the Fermi liquid instability of the spin-orbit-coupled metal. To
control the tetragonal domains generated by the transitions and to obtain a
single-domain crystal for the measurements of anisotropic properties, we
prepared single crystals with the (0 0 1) surface and applied biaxial and
uniaxial stresses along the plane. Polarizing optical microscopy observations
revealed that inducing a small strain of approximately 0.05% could flip the
twin domains ferroelastically in a reversible fashion at low temperatures,
which evidences that the tetragonal deformation switches at Ts2 between c > a
for phase II and c < a for phase III. Resistivity measurements using
single-domain crystals under uniaxial stress showed that the anisotropy was
maximum at around Ts2 and turned over across Ts2: resistivity along the c axis
is larger (smaller) than that along the a axis by ~25% for phase II (III) at
around Ts2. These large anisotropies probably originate from spin-dependent
scattering in the spin-split Fermi surfaces of the cluster electric toroidal
quadrupolar phases of Cd2Re2O7.",2009.14443v1
2012-01-10,"Microscopic theory for a ferromagnetic-nanowire/superconductor heterostructure: Transport, fluctuations and topological superconductivity","Motivated by the recent experiment of Wang et al. [Nature Physics 6, 389
(2010)], who observed a highly unusual transport behavior of ferromagnetic
Cobalt nanowires proximity-coupled to superconducting electrodes, we study
proximity effect and temperature-dependent transport in such a mesoscopic
hybrid structure. It is assumed that the asymmetry in the tunneling barrier
gives rise to the Rashba spin-orbit-coupling in the barrier that enables
induced p-wave superconductivity in the ferromagnet to exist. We first develop
a microscopic theory of Andreev scattering at the spin-orbit-coupled interface,
derive a set of self-consistent boundary conditions, and find an expression for
the p-wave minigap in terms of the microscopic parameters of the contact.
Second, we study temperature-dependence of the resistance near the
superconducting transition and find that it should generally feature a
fluctuation-induced peak. The upturn in resistance is related to the
suppression of the single-particle density of states due to the formation of
fluctuating pairs, whose tunneling is suppressed. In conclusion, we discuss
this and related setups involving ferromagnetic nanowires in the context of
one-dimensional topological superconductors. It is argued that to realize
unpaired end Majorana modes, one does not necessarily need a half-metallic
state, but a partial spin polarization may suffice. Finally, we propose yet
another related class of material systems -- ferromagnetic semiconductor wires
coupled to ferromagnetic superconductors -- where direct realization of
Kitaev-Majorana model should be especially straightforward.",1201.2180v2
2016-03-14,Lifshitz scaling effects on holographic paramagnetism/ferromagneism phase transition,"In the probe limit, we investigate holographic paramagnetism-ferromagnetism
phase transition in the four-dimensional (4D) and five-dimensional(5D) Lifshitz
black holes by means of numerical and semi-analytical methods, which is
realized by introducing a massive 2-form field coupled to the Maxwell field. We
find that the Lifshitz dynamical exponent $z$ contributes evidently to magnetic
moment and hysteresis loop of single magnetic domain quantitatively not
qualitatively. Concretely, in the case without external magnetic field, the
spontaneous magnetization and ferromagnetic phase transition happen when the
temperature gets low enough, and the critical exponent for the magnetic moment
is always $1/2$, which is in agreement with the result from mean field theory.
And the increasing $z$ enhances the phase transition and increases the DC
resistivity which behaves as the colossal magnetic resistance effect in some
materials. Furthermore, in the presence of the external magnetic field, the
magnetic susceptibility satisfies the Cure-Weiss law with a general $z$. But
the increase of $z$ will result in shortening the period of the external
magnetic field.",1603.04149v1
2016-03-14,Double-phase transition and giant positive magnetoresistance in the quasi-skutterudite Gd$_3$Ir$_4$Sn$_{13}$,"The magnetic, thermodynamic and electrical/thermal transport properties of
the caged-structure quasi-skutterudite Gd$_3$Ir$_4$Sn$_{13}$ are
re-investigated. The magnetization $M(T)$, specific heat $C_p(T)$ and the
resistivity $\rho(T)$ reveal a double-phase transition -- at $T_{N1}\sim$ 10~K
and at $T_{N2}\sim$ 8.8~K -- which was not observed in the previous report on
this compound. The antiferromagnetic transition is also visible in the thermal
transport data, thereby suggesting a close connection between the electronic
and lattice degrees of freedom in this Sn-based quasi-skutterudite. The
temperature dependence of $\rho(T)$ is analyzed in terms of a power-law for
resistivity pertinent to Fermi liquid picture. Giant, positive
magnetoresistance (MR) $\approx$ 80$\%$ is observed in Gd$_3$Ir$_4$Sn$_{13}$ at
2~K with the application of 9~T. The giant MR and the double magnetic
transition can be attributed to the quasi-cages and layered antiferromagnetic
structure of Gd$_3$Ir$_4$Sn$_{13}$ vulnerable to structural distortions and/or
dipolar or spin-reorientation effects. The giant value of MR observed in this
class of 3:4:13 type alloys, especially in a Gd-compound, is the highlight of
this work.",1603.04377v1
2016-03-29,Electronic and transport properties of the Mn-doped topological insulator Bi$_{2}$Te$_{3}$: A first-principles study,"We present a first-principles study of the electronic, magnetic, and
transport properties of the topological insulator Bi$_{2}$Te$_{3}$ doped with
Mn atoms in substitutional (Mn$_{\rm Bi}$) and interstitial van der Waals gap
positions (Mn$_{\rm i}$), which act as acceptors and donors, respectively. The
effect of native Bi$_{\rm Te}$- and Te$_{\rm Bi}$-antisite defects and their
influence on calculated electronic transport properties is also investigated.
We have studied four models representing typical cases, namely (i)
Bi$_{2}$Te$_{3}$ with and without native defects, (ii) Mn$_{\rm Bi}$ defects
with and without native defects, (iii) the same but for Mn$_{\rm i}$ defects,
and (iv) the combined presence of Mn$_{\rm Bi}$ and Mn$_{\rm i}$. It was found
that lattice relaxations around Mn$_{\rm Bi}$ defects play an important role
for both magnetic and transport properties. The resistivity is strongly
influenced by the amount of carriers, their type, and by the relative positions
of the Mn-impurity energy levels and the Fermi energy. Our results indicate
strategies to tune bulk resistivities, and also help to uncover the location of
Mn atoms in measured samples. Calculations indicate that at least two of the
considered defects have to be present simultaneously in order to explain the
experimental observations, and the role of interstitials may be more important
than expected.",1603.08811v2
2017-04-03,Thickness-dependent Kapitza resistance in multilayered graphene and other two-dimensional crystals,"The Kapitza or thermal boundary resistance (TBR), which limits heat
dissipation from a thin film to its substrate, is a major factor in the thermal
management of ultrathin nanoelectronic devices and is widely assumed to be a
property of only the interface. However, data from experiments and molecular
dynamics simulations suggest that the TBR between a multilayer 2-dimensional
(2D) crystal and its substrate decreases with increasing film thickness. To
explain this thickness dependence, we generalize the recent theory for
single-layer 2D crystals by Ong, Cai and Zhang [Phys. Rev. B 94, 165427
(2016)], which is derived from the theory by Persson, Volokitin, and Ueba [J.
Phys.: Condens. Matter 23, 045009 (2011)], and use it to evaluate the TBR
between bare $N$-layer graphene and SiO$_{2}$. Our calculations reproduce
quantitatively the TBR thickness dependence seen in experiments and simulations
as well as its asymptotic convergence, and predict that the low-temperature TBR
scales as $T^{-4}$ in few-layer graphene. Analysis of the interfacial
transmission coefficient spectrum shows that the TBR reduction in few-layer
graphene is due to the additional contribution from higher flexural phonon
branches. Our theory sheds light on the role of flexural phonons in
substrate-directed heat dissipation and provides the framework for optimizing
the thermal management of multilayered 2D devices.",1704.00435v2
2017-04-23,Quantum limit transport and destruction of the Weyl nodes in TaAs,"Weyl fermions are a new ingredient for correlated states of electronic
matter. A key difficulty has been that real materials also contain non-Weyl
quasiparticles, and disentangling the experimental signatures has proven
challenging. We use magnetic fields up to 95 tesla to drive the Weyl semimetal
TaAs far into its quantum limit (QL), where only the purely chiral 0th Landau
levels (LLs) of the Weyl fermions are occupied. We find the electrical
resistivity to be nearly independent of magnetic field up to 50 tesla: unusual
for conventional metals but consistent with the chiral anomaly for Weyl
fermions. Above 50 tesla we observe a two-order-of-magnitude increase in
resistivity, indicating that a gap opens in the chiral LLs. Above 80 tesla we
observe strong ultrasonic attenuation below 2 kelvin, suggesting a
mesoscopically-textured state of matter. These results point the way to
inducing new correlated states of matter in the QL of Weyl semimetals.",1704.06944v3
2017-05-01,Arbitrary control of the polarization and intensity profiles of diffraction-attenuation-resistant beams along their propagation direction,"We report on the theory and experimental generation of a class of
diffraction-attenuation-resistant beams with state of polarization (SoP) and
intensity that can be controlled on demand along the propagation direction.
This is achieved by a suitable superposition of Bessel beams, whose parameters
are systematically chosen based on closed-form analytic expressions provided by
the Frozen Waves (FWs) method. Using an amplitude-only spatial light modulator,
we experimentally demonstrate three scenarios. In the first, the SoP of a
horizontally polarized beam evolves to radial polarization and is then changed
to vertical polarization, with the beam intensity held constant. In the second,
we simultaneously control the SoP and the longitudinal intensity profile, which
was chosen such that the beam's central ring can be switched-off over
predefined space regions, thus generating multiple foci with different SoP and
at different intensity levels along the propagation. Finally, the ability to
control the SoP while overcoming attenuation inside lossy fluids is shown
experimentally for the first time in the literature (to the best of our
knowledge). Therefore, we envision our proposed method to be of great interest
for many applications, such as optical tweezers, atom guiding, material
processing, microscopy, and optical communications.",1705.00408v3
2019-03-02,Topological Valley Currents in Bilayer Graphene/Hexagonal Boron Nitride Superlattices,"Graphene superlattices have recently been attracting growing interest as an
emergent class of quantum metamaterials. In this paper, we report the
observation of nonlocal transport in bilayer graphene (BLG) superlattices
encapsulated between two hexagonal boron nitride (hBN) layers, which formed
hBN/BLG/hBN moir\'e superlattices. We then employed these superlattices to
detect a long-range charge-neutral valley current using an all-electrical
method. The moir\'e superlattice with broken inversion symmetry leads to a hot
spot with Berry curvature accumulating at the charge neutral point (CNP), and
it harbors satellites of the CNP. We observed nonlocal resistance on the order
of 1 $\text{k}\Omega$, which obeys a scaling relation. This nonlocal resistance
evolves from the quantum Hall effect but without magnetic field/time-reversal
symmetry breaking, which is associated with a hot-spot-induced topological
valley current. This study should pave the way to developing a
Berry-phase-sensitive probe to detect hot spots in gapped Dirac materials with
inversion-symmetry breaking.",1903.00625v2
2019-04-05,Explicit relationship between electrical and topological degradation of polymer-supported metal films subjected to mechanical loading,"For a comprehensive characterization of mechanical reliability of
metallization layers on polymer substrates both electrical and mechanical
degradation should be taken into account. Although it is evident that cracking
of a conductive film should lead to electrical degradation, the quantitative
relationship between the growth of electric resistance and parameters of the
induced crack pattern has remained thus far unexplored. With the help of finite
element modelling we were able to find an explicit and concise expression which
shows that electrical resistance grows with the fourth order of the crack
length and second order of the areal crack density. The discovered relationship
was verified by comparison with the experimental results of tensile testing of
polymer-supported thin metal films. Presented model is independent of the
length scale and can be applied to films with different thicknesses as long as
Ohm's law is valid. It is demonstrated that linear crack density is an
ambiguous parameter which does not properly capture the development of a crack
pattern. For the unambiguous characterization of the intensity of a crack
pattern a universal dimensionless factor is proposed. Presented results show
that there is a wide range of possible crack patterns which do not lead to
electrical failure of a conductive film that can be used for failure-free
design of flexible electronic devices.",1904.03007v1
2015-04-09,Quantum oscillations with non-zero Berry phase from a complex three dimensional Fermi surface in Bi2Te3,"We performed angle dependent magnetoresistance study of a metallic single
crystal sample of Bi2Te3. We find that the magnetoresistance is highly
asymmetric in positive and negative magnetic fields for small angles between
the magnetic field and the direction perpendicular to the plane of the sample.
The magnetoresistance becomes symmetric as the angle approaches 90 degree. The
quantum Shubnikov de-Haas oscillations are symmetric and show signatures of
topological surface states with Dirac dispersion in the form of non-zero Berry
phase. However, the angular dependence of these oscillations suggests a complex
three dimensional Fermi surface as the source of these oscillations, which does
not exactly conform with the six ellipsoidal model of the Fermi surface of
Bi2Te3. We attribute the asymmetry in the magnetoresistance to a mixing of the
Hall voltage in the longitudinal resistance due to the comparable magnitude of
the Hall and longitudinal resistance in our samples. This provides a clue to
understanding the asymmetric magnetoresistance often seen in this and similar
materials. Moreover, the asymmetric nature evolves with exposure to atmosphere
and thermal cycling, which we believe is either due to exposure to atmosphere
or thermal cycling, or both affecting the carrier concentration and hence the
Hall signal in these samples. However, the quantum oscillations seem to be
robust against these factors which suggests that the two have different
origins.",1504.02386v1
2015-06-17,Origin of the glass-like dynamics in molecular metals $\pmbκ$-(BEDT-TTF)$_{\textbf{2}}$X: implications from fluctuation spectroscopy and $\pmb{\textit{ab initio}}$ calculations,"We have studied the low-frequency dynamics of the charge carriers in
different organic charge-transfer salts $\kappa$-(BEDT-TTF)$_2$X with polymeric
anions X by using resistance noise spectroscopy. Our aim is to investigate the
structural, glass-like transition caused by the conformational degrees of
freedom of the BEDT-TTF molecules' terminal ethylene groups. Although of
fundamental importance for studies of the electronic ground-state properties,
the phenomenology of the glassy dynamics is only scarcely investigated and its
origin is not understood. Our systematic studies of fluctuation spectroscopy of
various different compounds reveal a universal, pronounced maximum in the
resistance noise power spectral density related to the glass transition. The
energy scale of this precess can be identified with the activation energy of
the glass-like ethylene endgroup structural dynamics as determined from
thermodynamic and NMR measurements. For the first time for this class of
'plastic crystals', we report a typical glassy property of the relaxation time,
namely a Vogel-Fulcher-Tammann law, and are able to determine the degree of
fragility of the glassy system. Supporting $\textit{ab initio}$ calculations
provide an explanation for the origin and phenomenology of the glassy dynamics
in different systems in terms of a simple two-level model, where the relevant
energy scales are determined by the coupling of the ethylene endgroups to the
anions.",1506.05191v1
2015-07-13,"Structural, and Magnetic properties of flux free large FeTe Single crystal","We report synthesis of non superconducting parent compound of iron
chalcogenide, i.e., FeTe single crystal by self flux method. The FeTe single
crystal is crystallized in tetragonal structure with the P4/nmm space group.
The detailed SEM (scanning electron microscopy) results showed that the
crystals are formed in slab like morphology and are near (slight deficiency of
Te) stoichiometric with homogenous distribution of Fe and Te. The coupled
structural and magnetic phase transition is seen at around 70K in both
electrical resistivity and magnetization measurements, which is hysteric
(deltaT = 5K) in nature with cooling and warming cycles. Magnetic
susceptibility (chi-T) measurements showed the magnetic transition to be of
antiferromagnetic nature, which is substantiated by isothermal magnetization
(M-H) plots as well. The temperature dependent electrical resistivity measured
in 10kOe field in both in plane and out of plane field directions showed that
the hysteric width nearly becomes double to deltaT = 10K, and is maximum for
the out of plane field direction for the studied FeTe single crystal. We also
obtained a sharp spike like peak in heat capacity Cp(T) measurement due to the
coupled structural and magnetic order phase transitions.",1507.03320v2
2018-12-06,Covalent-bonding-induced strong phonon scattering in the atomically thin WSe2 layer,"In nano-device applications using 2D van der Waals materials, a heat
dissipation through nano-scale interfaces can be a critical issue for
optimizing device performances. By using a time-domain thermoreflectance
measurement technique, we examine a cross-plane thermal transport through
mono-layered (n=1) and bi-layered (n=2) WSe2 flakes which are sandwiched by top
metal layers of Al, Au, and Ti and the bottom Al2O3 substrate. In these
nanoscale structures with hetero- and homo-junctions, we observe that the
thermal boundary resistance (TBR) is significantly enhanced as the number of
WSe2 layers increases. In particular, as the metal is changed from Al, to Au,
and to Ti, we find an interesting trend of TBR depending on the WSe2 thickness;
when referenced to TBR for a system without WSe2, TBR for n=1 decreases, but
that for n=2 increases. This result clearly demonstrates that the stronger
bonding for Ti leads to a better thermal conduction between the metal and the
WSe2 layer, but in return gives rise to a large mismatch in the phonon density
of states between the first and second WSe2 layers so that the WSe2-WSe2
interface becomes a major thermal resistance for n=2. By using photoemission
spectroscopy and optical second harmonic generation technique, we confirm that
the metallization induces a change in the valence state of W-ions, and also
recovers a non-centrosymmetry for the bi-layered WSe2.",1812.02383v1
2018-12-25,Quantum Transport in Topological Semimetals under Magnetic Fields (II),"We review our recent works on the quantum transport, mainly in topological
semimetals and also in topological insulators, organized according to the
strength of the magnetic field. At weak magnetic fields, we explain the
negative magnetoresistance in topological semimetals and topological insulators
by using the semiclassical equations of motion with the nontrivial Berry
curvature. We show that the negative magnetoresistance can exist without the
chiral anomaly. At strong magnetic fields, we establish theories for the
quantum oscillations in topological Weyl, Dirac, and nodal-line semimetals. We
propose a new mechanism of 3D quantum Hall effect, via the ""wormhole"" tunneling
through the Weyl orbit formed by the Fermi arcs and Weyl nodes in topological
semimetals. In the quantum limit at extremely strong magnetic fields, we find
that an unexpected Hall resistance reversal can be understood in terms of the
Weyl fermion annihilation. Additionally, in parallel magnetic fields,
longitudinal resistance dips in the quantum limit can serve as signatures for
topological insulators.",1812.10120v2
2019-06-11,Observation of Large Unidirectional Rashba Magnetoresistance in Ge(111),"Relating magnetotransport properties to specific spin textures at surfaces or
interfaces is an intense field of research nowadays. Here, we investigate the
variation of the electrical resistance of Ge(111) grown epitaxially on
semi-insulating Si(111) under the application of an external magnetic field. We
find a magnetoresistance term which is linear in current density j and magnetic
field B, hence odd in j and B, corresponding to a unidirectional
magnetoresistance. At 15 K, for I = 10 $\mu$A (or j = 0.33 A/m) and B = 1 T, it
represents 0.5 % of the zero field resistance, a much higher value compared to
previous reports on unidirectional magnetoresistance. We ascribe the origin of
this magnetoresistance to the interplay between the externally applied magnetic
field and the current-induced pseudo-magnetic field in the spin-splitted
subsurface states of Ge(111). This unidirectional magnetoresistance is
independent of the current direction with respect to the Ge crystal axes. It
progressively vanishes, either using a negative gate voltage due to carrier
activation into the bulk (without spin-splitted bands), or by increasing the
temperature due to the Rashba energy splitting of the subsurface states lower
than $\sim$58 k$_B$. The highly developed technologies on semiconductor
platforms would allow the rapid optimization of devices based on this
phenomenon.",1906.04457v1
2019-06-11,Thermal conductivity and thermal rectification of nanoporous graphene: A molecular dynamics simulation,"Using non-equilibrium molecular dynamics (NEMD) simulation, we study thermal
properties of the so-called nanoporous graphene (NPG) sheet which contains a
series of nanoporous in an ordered way and was synthesized recently (Science
360 (2018), 199). The dependence of thermal conductivity on sample size, edge
chirality, and porosity concentration are investigated. Our results indicate
that the thermal conductivity of NPG is about two orders smaller compared with
of pristine graphene. Therefore this sheet can be used as a thermoelectric
material. Also, the porosity concentration helps us to tune the thermal
conductivity. Moreover, the results show that the thermal conductivity
increases with growing sample length due to ballistic transport. On the other
hand, along the armchair direction, the thermal conductivity is larger than
zigzag direction. We also examined the thermal properties of the interface of
NPG and graphene. The temperature drops significantly through the interface
leading to the thermal resistance. The thermal resistance changes with imposed
heat flux direction, and this difference cause significantly large thermal
rectification factor, and heat current prefers one direction to another.
Besides, to investigate those quantities fundamentally, we study the phonon
density of states and scattering of them.",1906.04696v1
2019-06-12,Spin transport and Spin Tunnelling Magneto-Resistance (STMR) of F$|$NCSC$|$F spin valve,"In this work, we study the spin transport at the
Ferromagnet$|$Noncentrosymmetric Superconductor (F$|$NCSC) junction of a
Ferromagnet$|$Noncentrosymmetric Superconductor$|$Ferromagnet (F$|$NCSC$|$F)
spin valve. We investigate the Tunnelling Spin-Conductance (TSC), spin current
and Spin Tunnelling Magneto-Resistance (STMR), and their dependence on various
important parameters like Rashba Spin-Orbit Coupling (RSOC), strength and
orientation of magnetization, an external in-plane magnetic field, barrier
strength and a significant Fermi Wavevector Mismatch (FWM) at the ferromagnetic
and superconducting regions. The study has been carried out for different
singlet-triplet mixing of the NCSC gap parameter. We develop Bogoliubov-de
Gennes (BdG) Hamiltonian and use the extended Blonder - Tinkham - Klapwijk
(BTK) approach along with the scattering matrix formalism to calculate the
scattering coefficients. Our results strongly suggest that the TSC is highly
dependent on RSOC, magnetization strength and its orientation, and
singlet-triplet mixing of the gap parameter. It is observed that NCSC with
moderate RSOC shows maximum conductance for a partially opaque barrier in
presence of low external magnetic field. For a strongly opaque barrier and a
nearly transparent barrier a moderate value and a low value of field
respectively are found to be suitable. Moreover, NCSC with large singlet
component is appeared to be useful. In addition, for NCSC with large RSOC and
low magnetization strength, a giant STMR ($\%$) is observed. We have also seen
that the spin current is strongly magnetization orientation dependent. With the
increase in bias voltage spin current increases in transverse direction, but
the component along the direction of flow is almost independent.",1906.05081v1
2019-06-13,Passivation-induced physicochemical alterations of the native surface oxide film on 316L austenitic stainless steel,"Time of Flight Secondary Ion Mass Spectroscopy, X-Ray Photoelectron
Spectroscopy, in situ Photo-Current Spectroscopy and electrochemical analysis
were combined to characterize the physicochemical alterations induced by
electrochemical passivation of the surface oxide film providing corrosion
resistance to 316L stainless steel. The as-prepared surface is covered by a ~2
nm thick, mixed (Cr(III)-Fe(III)) and bi-layered hydroxylated oxide. The inner
layer is highly enriched in Cr(III) and the outer layer less so. Molybdenum is
concentrated, mostly as Mo(VI), in the outer layer. Nickel is only present at
trace level. These inner and outer layers have band gap values of 3.0 and
2.6-2.7 eV, respectively, and the oxide film would behave as an insulator.
Electrochemical passivation in sulfuric acid solution causes the preferential
dissolution of Fe(III) resulting in the thickness decrease of the outer layer
and its increased enrichment in Cr(III) and Mo(IV-VI). The further Cr(III)
enrichment of the inner layer causes loss of photoactivity and improved
corrosion protection with the anodic shift of the corrosion potential and the
increase of the polarization resistance by a factor of ~4. Aging in the passive
state promotes the Cr enrichment in the inner barrier layer of the passive
film.",1906.05544v1
2019-06-21,Crystal Growth and basic transport and magnetic properties of MnBi2Te4,"We report successful growth of magnetic topological insulator (MTI) MnBi2Te4.
The heating schedule basically deals with growth of the crystal from melt at
900C and very slow cooling (1C/hr) to around 600C with 24 hours hold time,
followed by cooling to room temperature. Our detailed, PXRD Reitveld analysis
showed that the resultant crystal is dominated mainly by MnBi2Te4 and minor
phases of Bi2Te3 and MnTe. The transport measurements showed a step like
behavior at around 150K followed by cusp like structure in resistivity at
around 25K (TP) due reported anti-ferromagnetic ordering of Mn. Both the
resistivity transitions are seen clearly in dR/dT measurements at 150K and 20K
respectively. The 25K transition of the compound is also seen in magnetic
susceptibility. Low temperature (5K) magnetoresistance (MR) in applied field of
up to 6 Tesla exhibited negative ve MR below 3 Tesla and +ve for higher fields.
Also, seen are steps in MR below one Tesla. The studied MnBi2Te4 MTI crystal
could be a possible candidate for Quantum Anomalous Hall (QAH) effect.",1906.09038v3
2019-10-03,Nonlinear transport of ballistic Dirac electrons tunneling through a tunable potential barrier in graphene,"Dirac-electronic tunneling and nonlinear transport properties with both
finite and zero energy bandgap are investigated for graphene with a tilted
potential barrier under a bias. For validation, results from a
finite-difference based numerical approach, which is developed for calculating
transmission and reflection coefficients with a dynamically-tunable
(time-dependent bias field) barrier-potential profile, are compared with those
of both an analytical model for a static square-potential barrier and a
perturbation theory using Wentzel-Kramers-Brillouin (WKB) approximation. For a
biased barrier, both transmission coefficient and tunneling resistance are
computed and analyzed, indicating a full control of the peak in tunneling
resistance by bias field for a tilted barrier, gate voltage for barrier height,
and energy for incoming electrons. Moreover, a finite energy gap in graphene is
found to suppress head-on transmission as well as skew transmission with a
large transverse momentum. For a gapless graphene, on the other hand, filtering
of Dirac electrons outside of normal incidence is found and can be used for
designing electronic lenses. All these predicted attractive transport
properties are expected extremely useful for the development of novel
electronic and optical graphene-based devices.",1910.01295v1
2019-10-09,Decoupling of itinerant and localized $d$-orbital electrons in the compound Sc$_{0.5}$Zr$_{0.5}$Co,"By using the arc-melting method, we successfully synthesized the compound
Sc$_{0.5}$Zr$_{0.5}$Co with the space group of $Pm$-$3m$. Both the resistivity
and magnetic susceptibility measurements reveal a phase transition at about 86
K. This transition might be attributed to the establishment of an
antiferromagnetic order. The magnetization hysteresis loop measurements in wide
temperature region show a weak ferromagnetic feature, which suggests a possible
canted arrangement of the magnetic moments. Bounded by the phase transition
temperature, the resistivity at ambient pressure shows a change from Fermi
liquid behavior to a super-linear behavior as temperature increases. By
applying pressures up to 32.1 GPa, the transition temperature does not show a
clear change and no superconductivity is observed above 2 K. The density
functional theory (DFT) calculations confirm the existence of the
antiferromagnetic order and reveal a gap between the spin-up and spin-down
$d$-orbital electrons. This kind of behavior may suggest that the
antiferromagnetic order in this compound originates from the localized
$d$-electrons which do not contribute to the conductance. Thus the itinerant
and localized $d$-orbital electrons in the compound are decoupled.",1910.03966v1
2019-10-10,AFM manipulation of gold nanowires to build electrical circuits,"We introduce scanning-probe-assisted nanowire circuitry (SPANC) as a new
method to fabricate electrodes for the characterization of electrical transport
properties at the nanoscale. SPANC uses an atomic force microscope (AFM) to
manipulate nanowires to create complex and highly conductive nanostructures
(paths) that work as nanoelectrodes, allowing connectivity and electrical
characterization of other nano-objects. The paths are formed by the spontaneous
cold welding of gold nanowires upon mechanical contact, leading to an excellent
contact resistance of about 9 Ohms/junction. SPANC is an easy to use and
cost-effective technique that fabricates clean nanodevices. Hence, this new
method can complement and/or be an alternative to other well-established
methods to fabricate nanocircuits such as electron beam lithography (EBL). The
circuits made by SPANC are easily reconfigurable, and their fabrication does
not require the use of polymers and chemicals. In this work, we present a few
examples that illustrate the capabilities of this method, allowing robust
device fabrication and electrical characterization of several nano-objects with
sizes down to aprox. 10 nm, well below the current smallest size able to be
contacted in a device using the standard available technology (around 30 nm).
Importantly, we also provide the first experimental determination of the sheet
resistance of thin antimonene flakes.",1910.04801v1
2019-10-21,"A report of (topological) Hall anomaly two decades ago in Gd2PdSi3, and its relevance to the history of the field of Topological Hall Effect due to magnetic skyrmions","The area of magnetic skyrmions, with potential revolution in certain
applications, in condensed matter physics is considered about a decade old. In
this article, we draw the attention of the community to the recent work of
Kurumaji et al [Science 365, 914 (2019)] establishing magnetic skyrmion lattice
behavior in Gd2PdSi3. We consider it important to bring out the two decades old
history, in particular Hall transport anomalies characterizing magnetic
skyrmions. The key experimental data in support of the skyrmion lattice that
Kurumaji et al present is the observation of topological Hall resistivity in an
intervening field range, following two metamagnetic transitions. In addition,
the values are giant, compared to those known for other magnetic skyrmions. We
point out here that such features in Hall resistivity data, arising from Gd 4f
magnetism, can be found in our publication in 1999 (along with the metamagnetic
transitions) and we expressed difficulties in explaining the results at that
time. In view of above, we propose to the scientific community that the
compound Gd2PdSi3, ex post facto, can be considered as the first experimental
demonstration for giant topological Hall effect in this field, discovered about
two decades ago. We take this opportunity to share some thoughts, offering
clues for further investigations, in particular to identify novel magnetic
skyrmions and to find the same to enable applications.",1910.09194v2
2019-10-25,Energy-efficient ultrafast SOT-MRAMs based on low-resistivity spin Hall metal Au0.25Pt0.75,"Many key electronic technologies (e.g., large-scale computing, machine
learning, and superconducting electronics) require new memories that are fast,
reliable, energy-efficient, and of low-impedance at the same time, which has
remained a challenge. Non-volatile magnetoresistive random access memories
(MRAMs) driven by spin-orbit torques (SOTs) have promise to be faster and more
energy-efficient than conventional semiconductor and spin-transfer-torque
magnetic memories. This work reports that the spin Hall effect of
low-resistivity Au0.25Pt0.75 thin films enables ultrafast antidamping-torque
switching of SOT-MRAM devices for current pulse widths as short as 200 ps. If
combined with industrial-quality lithography and already-demonstrated
interfacial engineering, our results show that an optimized MRAM cell based on
Au0.25Pt0.75 can have energy-efficient, ultrafast, and reliable switching, e.g.
a write energy of < 1 fJ (< 50 fJ) for write error rate of 50% (<1e-5) for 1 ns
pulses. The antidamping torque switching of the Au0.25Pt0.75 devices is 10
times faster than expected from a rigid macrospin model, most likely because of
the fast micromagnetics due to the enhanced non-uniformity within the free
layer. These results demonstrate the feasibility of Au0.25Pt0.75-based
SOT-MRAMs as a candidate for ultrafast, reliable, energy-efficient,
low-impedance, and unlimited-endurance memory.",1910.11896v2
2019-11-15,Resist and Transfer Free Patterned CVD Graphene Growth on ALD Molybdenum Carbide Nano Layers,"Multilayer graphene (MLG) films were grown by chemical vapour deposition
(CVD) on molybdenum carbide ($MoC_{x}$) substrates. We fabricated the catalytic
$MoC_{x}$ films by plasma enhanced atomic layer deposition (PEALD). The
mechanism of graphene growth is studied and analysed for amorphous and
crystalline $MoC_{x}$ films. In addition, the unique advantages of catalytic
substrate PEALD are demonstrated in two approaches to graphene device
fabrication. First, we present a complete bottom up, resist-free patterned
graphene growth (GG) on pre-patterned $MoC_{x}$ PEALD performed at
50$^{\circ}C$. Selective CVD GG eliminates the need to pattern or transfer the
graphene film to retain its pristine, as grown, qualities. Furthermore, we
fabricated MLG directly on PEALD $MoC_{x}$ on 100 nm suspended SiN membrane. We
characterise the MLG qualities using Raman spectroscopy, and analyse the
samples by optical microscopy, scanning electron microscopy and X-ray
diffraction measurements. The techniques of graphene device manufacturing
demonstrated here pave the path for large scale production of graphene
applications.",1911.06490v3
2020-05-30,Tribocorrosion under galvanic interaction of Ti6Al4V and NiCr implant alloys,"Micromovements that occur in the joint between dental prostheses and implants
can lead to wear-induced degradation. This process can be enhanced by corrosion
in the oral environment influenced by the presence of solutions containing
fluoride. Moreover, the eventual galvanic interactions between NiCr and Ti
alloys can accelerate the wear-corrosion process. In this work, the
tribocorrosion process of Ti6Al4V and NiCr alloys used in dental implant
rehabilitations immersed in fluoride solutions at different pH values was
investigated. The galvanic interaction effect between the alloys was also
assessed. Tribocorrosion tests in corrosive media were performed with isolated
Ti6Al4V and NiCr alloys, followed by testing with both alloys in contact. The
media selected were based on fluoride concentrations and pH values that are
possible to be found in oral environments. Analysis of the surfaces after the
tribocorrosion tests was carried out using confocal laser microscopy. The wear
profile and volume losses were determined by confocal measurements. It was
concluded that the galvanic interaction between the alloys increased the
tribocorrosion resistance of Ti6Al4V, compared with that of the isolated
Ti6Al4V alloy. Ti6Al4V coupled with NiCr reduced the electrochemical potential
decay during sliding. The increased resistance was explained by the
electrochemical shift of the Ti6Al4V potential from active dissolution to the
passive domain.",2006.00270v1
2020-10-16,Multiscale studies of nanoconfined charging dynamics in supercapacitors bridged by machine learning,"The energy-delivery performance of supercapacitors is fundamentally
determined by the dynamics of ions confined in nanoporous materials, which has
attracted intensive interest in nanoscopic research. Many nanoscopic
understandings, including changes in in-pore ion concentration and mobility
during dynamical processes, are continuously reported. However, quantitative
scale-up of these nanoscopic understandings for evaluation of the macroscopic
performance of supercapacitors is difficult due to the absence of links between
these scales. Here we demonstrate that machine learning can be used to
establish such links. Starting from nanoscale, we first reveal a
diffusion-enhanced migration of ions in nanopores using primarily modified
Poisson-Nernst-Planck model, unlike in bulk electrolyte where diffusion
counteracts migration. Using machine learning, we discover a dynamically
varying ionic resistance and its equation, resulting from the in-pore ion
concentration change contributed by diffusion-enhanced migration. The obtained
equation is used to construct a nano-circuitry model (NCM), which describes
both the macroscopic performance of supercapacitors and nanometre-resolved
ionic behaviour. We demonstrate that NCM can provide additional perspectives to
understand cyclic voltammograms. A Faradaic-like current peak can show in
non-Faradaic processes, and an asymmetric charging/discharging can occur
without ion desolvation. These is because the dynamically varying resistance
delivers ions effectively for storage. The demonstrated use of machine learning
could extend to other ionic systems including batteries and desalination,
paving the route towards rational design.",2010.08151v1
2020-10-31,A Non-Volatile Cryogenic Random-Access Memory Based on the Quantum Anomalous Hall Effect,"The interplay between ferromagnetism and topological properties of electronic
band structures leads to a precise quantization of Hall resistance without any
external magnetic field. This so-called quantum anomalous Hall effect (QAHE) is
born out of topological correlations, and is oblivious of low-sample quality.
It was envisioned to lead towards dissipationless and topologically protected
electronics. However, no clear framework of how to design such an electronic
device out of it exists. Here we construct an ultra-low power, non-volatile,
cryogenic memory architecture leveraging the QAHE phenomenon. Our design
promises orders of magnitude lower cell area compared with the state-of-the-art
cryogenic memory technologies. We harness the fundamentally quantized Hall
resistance levels in moir\'e graphene heterostructures to store non-volatile
binary bits (1, 0). We perform the memory write operation through controlled
hysteretic switching between the quantized Hall states, using nano-ampere level
currents with opposite polarities. The non-destructive read operation is
performed by sensing the polarity of the transverse Hall voltage using a
separate pair of terminals. We custom design the memory architecture with a
novel sensing mechanism to avoid accidental data corruption, ensure highest
memory density and minimize array leakage power. Our design is transferrable to
any material platform exhibiting QAHE, and provides a pathway towards realizing
topologically protected memory devices.",2011.00170v1
2021-02-11,Microscopic metallic air-bridge arrays for connecting quantum devices,"We present a single-exposure fabrication technique for a very large array of
microscopic air-bridges using a tri-layer resist process with electron-beam
lithography. The technique is capable of forming air-bridges with strong
metal-metal or metal-substrate connections. This was demonstrated by its
application in an electron tunnelling device consisting of 400 identical
surface gates for defining quantum wires, where the air-bridges are used as
suspended connections for the surface gates. This technique enables us to
create a large array of uniform one-dimensional channels that are open at both
ends. In this article, we outline the details of the fabrication process,
together with a study and the solution of the challenges present in the
development of the technique, which includes the use of water-IPA (isopropyl
alcohol) developer, calibration of resist thickness and numerical simulation of
the development.",2102.06123v2
2021-03-29,In Situ Phase-Transition Crystallization of All-Inorganic Water-Resistant Exciton-Radiative Heteroepitaxial CsPbBr3-CsPb2Br5 Core-Shell Perovskite Nanocrystals,"The instability of metal halide perovskites upon exposure to moisture or heat
strongly hampers their applications in optoelectronic devices. Here, we report
the large-yield synthesis of highly water-resistant total-inorganic green
luminescent CsPbBr3/CsPb2Br5 core/shell heteronanocrystals (HNCs) by developing
an in situ phase transition approach. It is implemented via water-driven phase
transition of the original monoclinic CsPbBr3 nanocrystal and the resultant
tetragonal CsPb2Br5 nanoshell has small lattice mismatch with the CsPbBr3 core,
which ensures formation of an epitaxial interface for the yielded
CsPbBr3/CsPb2Br5 HNCs. These HNCs maintain nearly 100% of the original
luminescence intensity after immersion in water for eleven months and the
luminescence intensity drops only to 81.3% at 100 {\deg}C. The transient
luminescence spectroscopy and density functional theory calculation reveal that
there are double radiative recombination channels in the core CsPbBr3
nanocrystal, and the electron potential barrier provided by the CsPb2Br5
nanoshell significantly improves the exciton recombination rate. A prototype
quasi-white light-emitting device based on these robust CsPbBr3/CsPb2Br5 HNCs
is realized, showing their strong competence in solid-state lighting and wide
color-gamut displays.",2103.15491v2
2021-05-31,Ab initio Molecular Dynamics Simulation of Threshold Displacement Energies and Defect Formation Energies in Y4Zr3O12,"Ab initio molecular dynamics simulations using VASP was employed to calculate
threshold displacement energies and defect formation energies of Y4Zr3O12
{\delta}-phase, which is the most commonly found phase in newly developed Zr
and Al-containing ODS steels. The Threshold displacement energy (Ed) values are
determined to be 28 eV for Zr3a primary knock-on atom along [111] direction, 40
eV for Zr18f atoms along [111] direction and 50 eV for Y recoils along [110]
direction. Minimum Ed values for O and O' atoms are 13 eV and 16 eV
respectively. The displacement energies of anions are much smaller compared to
cations, thus suggesting that anion disorder is more probable than cation
disorder. All directions except the direction in which inherent structural
vacancies are aligned, cations tend to occupy another cation site. The
threshold displacement energies are larger than that of Y2Ti2O7, the
conventional precipitates in Ti containing ODS steels. Due to the partial
occupancy of Y and Zr in the 18f position, the antisite formation energy is
negligibly small, and it may help the structure to withstand more disorder upon
irradiation. These results convey that Zr/Al ODS alloys, which have better
corrosion resistance properties compared to the conventional Ti-ODS alloys, may
also possess superior radiation resistance.",2105.15066v1
2021-06-10,Multilayer Capacitances: How Selective Contacts Affect Capacitance Measurements of Perovskite Solar Cells,"Capacitance measurements as a function of voltage, frequency and temperature
are useful tools to identify fundamental parameters that affect solar cell
operation. Techniques such as capacitance-voltage (CV), Mott-Schottky analysis
and thermal admittance spectroscopy (TAS) measurements are therefore frequently
employed to obtain relevant parameters of the perovskite absorber layer in
perovskite solar cells. However, state-of-the-art perovskite solar cells employ
thin electron and hole transport layers that improve contact selectivity. These
selective contacts are often quite resistive in nature, which implies that
their capacitances will contribute to the total capacitance and thereby affect
the extraction of the capacitance of the perovskite layer. Based on this
premise, we develop a simple multilayer model that considers the perovskite
solar cell as a series connection of the geometric capacitance of each layer in
parallel with their voltage-dependent resistances. Analysis of this model
yields fundamental limits to the resolution of spatial doping profiles and
minimum values of doping/trap densities, built-in voltages and activation
energies. We observe that most of the experimental
capacitance-voltage-frequency-temperature data, calculated doping/trap
densities and activation energies reported in literature are within these
cut-off values derived, indicating that the capacitance response of the
perovskite solar cell is indeed strongly affected by the capacitance of its
selective contacts.",2106.05758v2
2021-06-25,Blistering Failure of Elastic Coatings with Applications to Corrosion Resistance,"A variety of polymeric surfaces, such as anti-corrosion coatings and
polymer-modified asphalts, are prone to blistering when exposed to moisture and
air. As water and oxygen diffuse through the material, dissolved species are
produced, which generate osmotic pressure that deforms and debonds the
coating.These mechanisms are experimentally well-supported; however,
comprehensive macroscopic models capable of predicting the formation osmotic
blisters, without extensive data-fitting, is scant. Here, we develop a general
mathematical theory of blistering and apply it to the failure of anti-corrosion
coatings on carbon steel. The model is able to predict the irreversible,
nonlinear blister growth dynamics, which eventually reaches a stable state,
ruptures, or undergoes runaway delamination, depending on the mechanical and
adhesion properties of the coating. For runaway delamination, the theory
predicts a critical delamination length, beyond which unstable corrosion-driven
growth occurs. The model is able to fit multiple sets of blister growth data
with no fitting parameters. Corrosion experiments are also performed to observe
undercoat rusting on carbon steel, which yielded trends comparable with model
predictions. The theory is used to define three dimensionless numbers which can
be used for engineering design of elastic coatings capable of resisting visible
deformation, rupture, and delamination.",2106.13371v1
2021-07-29,Thermal Contribution in the Electrical Switching Experiments with Heavy Metal / Antiferromagnet Structures,"We examine the thermal origin of the detected ""saw-tooth"" shaped Hall
resistance (Rxy) signals in the spin-orbit torque switching experiment for
antiferromagnetic MnN. Compared with the results of the heavy metal /
antiferromagnet bilayers (MnN/Ta), the qualitatively same ""saw-tooth"" shaped
signals also appear in the samples with the heavy metal layer alone (either Ta
or Pt) without MnN layer. In addition, The Rxy signal changes oppositely in the
devices with Ta and Pt, due to the opposite temperature coefficient of
resistivity (TCR) of the two materials. All those results are consistent with
the ""localized Joule heating"" mechanism in devices with Hall crosses geometry.
Moreover, by utilizing a structure with separated writing current paths and
Hall cross area, the quadratic relationship between delta-Rxy and the writing
current's amplitude is observed, which provides quantitative evidence of the
thermal contribution. These results reveal the dominant thermal artifact in the
widely used Hall crosses geometry for Neel vector probing, and also provide a
strategy to semi-quantitatively evaluate the thermal effect, which can shed
light on a more conclusive experiment design.",2107.13859v1
2021-08-26,Direct thermal infrared vision via nanophotonic detector design,"Detection of infrared (IR) photons in a room-temperature IR camera is carried
out by a two-dimensional array of microbolometer pixels which exhibit
temperature-sensitive resistivity. When IR light coming from the far-field is
focused onto this array, microbolometer pixels are heated up in proportion to
the temperatures of the far-field objects. The resulting resistivity change of
each pixel is measured via on-chip electronic readout circuit followed by
analog to digital (A/D) conversion, image processing, and presentation of the
final IR image on a separate information display screen. In this work, we
introduce a new nanophotonic detector as a minimalist alternative to
microbolometer such that the final IR image can be presented without using the
components required for A/D conversion, image processing and display. In our
design, the detector array is illuminated with visible laser light and the
reflected light itself carries the IR image which can be directly viewed. We
realize and numerically demonstrate this functionality using a resonant
waveguide grating structure made of typical materials such as silicon carbide,
silicon nitride, and silica for which lithography techniques are
well-developed. We clarify the requirements to tackle the issues of fabrication
nonuniformities and temperature drifts in the detector array. We envision a
potential near-eye display device for IR vision based on timely use of
diffractive optical waveguides in augmented reality headsets and tunable
visible laser sources. Our work indicates a way to achieve direct thermal IR
vision for suitable use cases with lower cost, smaller form factor, and reduced
power consumption compared to the existing thermal IR cameras.",2108.11583v1
2021-08-26,Effects of minor alloying on the mechanical properties of Al based metallic glasses,"Minor alloying is widely used to control mechanical properties of metallic
glasses (MGs). The present understanding of how a small amount of alloying
element changes strength is that the additions lead to more efficient packing
of atoms and increased local topological order, which then increases the
barrier for shear transformations and the resistance to plastic deformation.
Here, we discover that minor alloying can improve the strength of MGs by
increasing the chemical bond strength alone and show that this strengthening is
distinct from changes in topological order. The results were obtained using
Al-Sm based MGs minor alloyed with transition metals (TMs). The addition of TMs
led to an increase in the hardness of the MGs which, however, could not be
explained based on changes in the topological ordering in the structure.
Instead we found that it was the strong bonding between TM and Al atoms which
led to a higher resistance to shear transformation that resulted in higher
strength and hardness, while the topology around the TM atoms had no influence
on their mechanical response. This finding demonstrates that the effects of
topology and chemistry on mechanical properties of MGs are independent of each
other and that they should be understood as separate, sometimes competing
mechanisms of strengthening. This understanding lays a foundation for design of
MGs with improved mechanical properties.",2108.12028v1
2021-09-13,Ray Optics for Gliders,"Control of self-propelled particles is central to the development of many
microrobotic technologies, from dynamically reconfigurable materials to
advanced lab-on-a-chip systems. However, there are few physical principles by
which particle trajectories can be specified and can be used to generate a wide
range of behaviors. Within the field of ray optics, a single principle for
controlling the trajectory of light -- Snell's law -- yields an intuitive
framework for engineering a broad range of devices, from microscopes to cameras
and telescopes. Here we show that the motion of self-propelled particles
gliding across a resistance discontinuity is governed by a variant of Snell's
law, and develop a corresponding ray optics for gliders. Just as the ratio of
refractive indexes sets the path of a light ray, the ratio of resistance
coefficients is shown to determine the trajectories of gliders. The magnitude
of refraction depends on the glider's shape, in particular its aspect ratio,
which serves as an analog to the wavelength of light. This enables the demixing
of a polymorphic, many-shaped, beam of gliders into distinct monomorphic,
single-shaped, beams through a friction prism. In turn, beams of monomorphic
gliders can be focused by spherical and gradient friction lenses.
Alternatively, the critical angle for total internal reflection can be used to
create shape-selective glider traps. Overall our work suggests that furthering
the analogy between light and microscopic gliders will result in a wide range
of new devices for sorting, concentrating, and analyzing self-propelled
particles.",2109.06360v5
2021-10-11,Topological phonons in an inhomogeneously strained silicon-2: Evidence of spin-momentum locking,"In this study, we report first experimental evidence of spin-momentum locking
in the topological phonons in an inhomogeneously strained Si thin film. The
spin-momentum locking in the topological phonons lead to a longitudinal spin
texture or spatially inhomogeneous spin distribution in the freestanding sample
structure. The spin texture was uncovered using location dependent Hall effect
and planar Hall effect measurement. The charge carrier density and anomalous
Hall resistance showed a linear behavior along the length of the sample.
Similarly, the planar Hall resistance related with the spin dependent
scattering was also found to be different at two different location along the
length of the sample. The spin-momentum locking also gave rise to transverse
thermal spin current and spin-Nernst magneto thermopower response, which was
uncovered using angle dependent longitudinal second harmonic measurement. The
magneto thermopower response was also a function of crystallography of the Si
sample where the sign of the response was opposite for <110> and <100> aligned
samples. The spin-momentum locking in topological phonons may give rise to
large spin dependent response at and above room temperature, which can pave the
way for energy efficient spintronics and spin-caloritronics devices.",2110.04937v1
2021-10-11,Bi kagome sublattice distortions by quenching and flux pinning in superconducting RbBi$_2$,"The properties of RbBi$_2$, a 4.15 K superconductor, were investigated using
magnetic field, pressure and neutron diffraction. Under hydrostatic pressure,
an almost 50 % reduction of T$_c$ is observed, linked to a low Debye
temperature estimated at 165 K. The resistivity and magnetic susceptibility
were measured on quenched and slow-cooled polycrystalline samples. The
resistivity follows a low temperature power-law dependence in both types of
samples, while the diamagnetic susceptibility, $\chi$, is dependent on the
sample cooling history. Slow-cooled samples have a $\chi= -1$ while quenched
samples have $\chi< -1$ due to grain size differences. Evidence of the effects
of the cooling rate is also discerned from the local structure, obtained by
neutron diffraction and the pair density function analysis. Slow-cooled samples
have structurally symmetric Bi hexagons, in contrast to quenched samples in
which disorder is manifested in periodic distortions of the Bi hexagonal rings
of the kagome sublattice. Disorder may lead to flux pinning that reduces vortex
mobility, but T$_c$ remains unaffected by the cooling rate.",2110.05452v1
2021-10-18,Magnetic field induced transition from a vortex liquid to Bose metal in ultrathin a-MoGe thin film,"We identify a magnetic field induced transition from a vortex liquid to Bose
metal in a 2-dimensional amorphous superconductor, a-MoGe, using a combination
of magnetotransport and scanning tunnelling spectroscopy (STS). Below the
superconducting transition, Tc ~ 1.36 K, the magnetoresistance isotherms cross
at a nearly temperature independent magnetic field, H_c^*~ 36 kOe. Above this
field, the temperature coefficient of resistance is weakly negative, but the
resistance remains finite as T --> 0, as expected in a bad metal. From STS
conductance maps at 450 mK we observe a very disordered vortex lattice at very
low fields that melts into a vortex liquid above 3 kOe. Up to H_c^* the
tunnelling spectra display superconducting gap and coherence peak over a broad
background caused by electron-electron interactions, as expected in a vortex
liquid. However, above H_c^* the tunnelling spectra continue to display the gap
but the coherence peak gets completely suppressed, suggesting that Cooper pairs
lose their phase coherence. We conclude that H_c^* demarcates a transition from
a vortex liquid to Bose metal, that eventually transforms to a regular metal at
a higher field H* where the gap vanishes in the electronic spectrum.",2110.09335v3
2021-12-18,Infrared Absorption and its Sources of CdZnTe at Cryogenic Temperature,"To reveal the infrared absorption causes in the wavelength region between
electronic and lattice absorptions, we measured the temperature dependence of
the absorption coefficient of $p$-type low-resistivity ($\sim 10^2~{\rm \Omega
cm}$) CdZnTe crystals. We measured the absorption coefficients of CdZnTe
crystals in four-wavelength bands ($\lambda=6.45$, 10.6, 11.6, 15.1$~\mu$m)
over the temperature range of $T=8.6-300$ K with an originally developed
system. The CdZnTe absorption coefficient was measured to be $\alpha=0.3-0.5$
${\rm cm^{-1}}$ at $T=300$ K and $\alpha=0.4-0.9$ ${\rm cm^{-1}}$ at $T=8.6$ K
in the investigated wavelength range. With an absorption model based on
transitions of free holes and holes trapped at an acceptor level, we conclude
that the absorption due to free holes at $T=150-300$ K and that due to
trapped-holes at $T<50$ K are dominant absorption causes in CdZnTe. We also
discuss a method to predict the CdZnTe absorption coefficient at cryogenic
temperature based on the room-temperature resistivity.",2112.09879v1
2022-01-02,Role of surface functional groups to superconductivity in Nb$_2$C-MXene: Experiments and density functional theory calculations,"The recently discovered surface-group-dependent superconductivity in
Nb$_2$C-MXene fabricated by the molten salts method is attracting wide
attention. However, regarding the superconductivity of Nb$_2$C-MXene with
functional F groups (Nb$_2$CF$_x$), there were some conflicting results in
experimental and theoretical studies. Herein, we systematically carried out
experimental and theoretical investigations on the superconductivity in
Nb$_2$C-MXene with the Cl functional group (Nb$_2$CCl$_x$) and Nb$_2$CF$_x$.
The experimental results of the Meissner effect and zero resistivity have
proved that Nb$_2$CClx is superconducting with the transition temperature (Tc)
~ 5.2 K. We extract its superconducting parameters from the temperature
dependence of resistivity and the field dependence of the magnetization. The
Ginzburg-Landau parameter K$_G$$_L$ is estimated to be 2.41, indicating that
Nb$_2$CClx is a typical type-II superconductor. Conversely, both magnetic and
electrical transport measurements demonstrate that Nb$_2$CF$_x$ is not
superconducting. The first-principles density functional theory (DFT)
calculations show that the Tc of Nb$_2$Cl$_x$ is ~ 5.2 K, while Nb$_2$CF$_x$ is
dynamically unstable with imaginary frequency in phonon spectrum, which is in
good agreement with the experimental results. Our studies not only are useful
for clarifying the present inconsistency but also offer referential
significance for future investigations on the superconductivity of MXenes.",2201.00298v1
2022-01-13,Charge-Density-Wave Proximity Effects in Graphene,"Certain layered transition metal dichalcogenides (TMDCs), such as 1T-TaS2,
show a rich collection of charge density wave (CDW) phases at different
temperatures, and their atomic structures and electron conductions have been
widely studied. However, the properties of CDW systems that are integrated with
other electronic materials have not yet been investigated. Here, we incorporate
the CDW properties of TMDCs into the electronic transport of graphene for the
first time. During CDW phase transitions, anomalous transport behaviors that
are closely related to the formation of correlated disorder in TMDCs were
observed in the graphene sample used in this study. In particular, the
commensurate CDW phase forms a periodic charge distribution with potential
fluctuations, and thus constitutes correlated charged impurities, which
decreases resistivity and enhances carrier mobility in graphene. The
CDW-graphene heterostructure system demonstrated here paves the way to
controlling the temperature-dependent carrier mobility and resistivity of
graphene and to developing novel functional electronic devices such as
graphene-based sensors and memory devices.",2201.04844v2
2022-01-25,Charge-4e and charge-6e flux quantization and higher charge superconductivity in kagome superconductor ring devices,"The flux quantization is a key indication of electron pairing in
superconductors. For example, the well-known h/2e flux quantization is
considered strong evidence for the existence of the charge-2e, two-electron
Cooper pairs. Here we report evidence for multi-charge flux quantization in
mesoscopic ring devices fabricated using the transition-metal kagome
superconductor CsV3Sb5. We perform systematic magneto-transport measurements
and observe unprecedented quantization of magnetic flux in units of h/4e and
h/6e in magnetoresistance oscillations. Specifically, at low temperatures,
magnetoresistance oscillations with period h/2e are detected, as expected from
the flux quantization for charge-2e superconductivity. We find that the h/2e
oscillations are suppressed and replaced by resistance oscillations with h/4e
periodicity when temperature is increased. Increasing the temperature further
suppresses the h/4e oscillations and robust resistance oscillations with h/6e
periodicity emerge as evidence for charge-6e flux quantization. Our
observations provide the first experimental evidence for the existence of
multi-charge flux quanta and emergent quantum matter exhibiting higher-charge
superconductivity in the strongly fluctuating region above the charge-2e Cooper
pair condensate, revealing new insights into the intertwined and vestigial
electronic order in kagome superconductors.",2201.10352v3
2022-03-09,The drastic effect of the impurity scattering on the electronic and superconducting properties of Cu-doped FeSe,"Non-magnetic impurities in iron-based superconductors can provide an
important tool to understand the pair symmetry and they can influence
significantly the transport and the superconducting behaviour. Here, we present
a study of the role of strong impurity potential in the Fe plane, induced by Cu
substitution, on the electronic and superconducting properties of single
crystals of FeSe. The addition of Cu quickly suppresses both the nematic and
superconducting states, and increases the residual resistivity due to enhanced
impurity scattering. Using magnetotransport data up to 35 T for a small amount
of Cu impurity, we detect a significant reduction in the mobility of the charge
carriers by a factor of ~3. While the electronic conduction is strongly
disrupted by Cu substitution, we identify additional signatures of anisotropic
scattering which manifest in linear resistivity at low temperatures and
$H^{1.6}$ dependence of magnetoresistance. The suppression of superconductivity
by Cu substitution is consistent with a sign-changing $s_{\pm}$ order
parameter. Additionally, in the presence of compressive strain, the
superconductivity is enhanced, similar to FeSe.",2203.04624v1
2022-04-21,Ferrous Metal Matrix Composites Status Scope and Challenges,"The present paper is an effort to culminate the status, scopes and challenges
in the development of ferrous metal matrix composites (FMMCs). The FMMCs are
old but less in use than the non-ferrous metal matrix composites (NFMMCs), as
far as literature and actual applications are concerned. Therefore, this
stimulates the exploration of the reasons behind the scarcity of literature and
field applications of the FMMCs, which must be investigated scientifically. The
powder metallurgy route is the most used process for fabricating iron and steel
based FMMCs by reinforcing particulates. At the same time, the in-situ method
has been used for the fabrication and cast iron-based FMMCs. The main
characteristics being considered during the designing and fabrication of FMMCs
are wear resistance and improved specific mechanical properties. To fabricate
cheaper and eco-friendly FMMCs, traditionally used costly reinforcements such
as SiC, WC, TiC, SiO2, TiO2, TiB2 are required to be replaced by inexpensive
industrial wastes like red-mud, fly-ashes and grinding swarf. The data
extracted from the web of science exhibited that the FMMCs have been researched
less than the NFMMCs. The increasing number of research papers on FMMCs
indicates a bright future. FMMCs are going to be a favourite topic among
researchers and manufacturers. Higher strengths, wear resistance, dimensional
stability at elevated temperatures, and, most importantly, the lower cost will
put forward the FMMCs as a stiff competitor of NFMMCs. In developing and mass
production of FMMCs for field applications, challenges like oxidation and
higher weight still require special research efforts.",2204.09999v2
2022-05-12,"Investigation of lattice dynamics, magnetism and electronic transport in $β$-Na$_{0.33}$V$_2$O$_{5}$","We investigate the electronic and magnetic properties as well as lattice
dynamics and spin-phonon coupling of $\beta$-Na$_{0.33}$V$_2$O$_5$ using
temperature-dependent Raman scattering, dc-magnetization and dc-resistivity,
x-ray photoemission, and absorption spectroscopy. The Rietveld refinement of
XRD pattern with space group C2/m confirms the monoclinic structure. The
analysis of temperature-dependent Raman spectra in a temperature range of
13--673~K reveals an anharmonic dependence of the phonon frequency and full
width at half maximum, which is accredited to the symmetric phonon decay.
However, below about 40 K, the hardening of the phonon frequency beyond
anharmonicity is attributed to the spin-phonon coupling. Interestingly, the
estimated effective magnetic moment $\mu_{\rm eff}=$ 0.63~$\mu_B$ from the
magnetization data manifests a mixed-valence state of V ions in 4+ (18$\pm$1\%)
and 5+ (82$\pm$1\%). A similar ratio of V$^{4+}$ to V$^{5+}$ is also observed
in the x-ray photoemission and x-ray absorption near-edge spectra and that is
found to be consistent with the sample stoichiometry. In addition, the V$^{4+}$
ions are distributed between different vanadium (V1 and V3) sites. The analysis
of extended x-ray absorption fine structure at different V-sites gives the
corresponding V--O bond lengths, which are utilized in the assignment of Raman
modes. Moreover, the temperature-dependent resistivity resembles a
semiconducting behavior where the charge carrier transport is facilitated by
the band conduction at higher temperatures and via hopping $\le$260~K.",2205.06019v2
2022-05-04,Graphene/fluorinated graphene systems for a wide spectrum of electronics application,"Heterostructures prepared from graphene and fluorographene (FG) using the
technology of 2D printing on solid and flexible substrates were fabricated and
studied. Excellent stability of printed graphene layers and, to a lesser
degree, composite graphene: PEDOT: PSS layers were shown. Extraordinary
properties of FG as an insulating layer for graphene-based heterostructures at
fluorination degree above 30% were demonstrated. It is shown that the leakage
current in thin (20-40 nm) films is normally smaller than 10^-8 A/cm2, the
breakdown field being greater than 108 V/cm. In hybrid structures with printed
FG layers in which graphene was transferred onto, or capsulated with, an FG
layer, an increase in charge-carrier mobility and material conductivity
amounting to 5-6 times was observed. The spectrum of future applications of FG
layers can be further extended due to the possibility of obtaining, from weakly
fluorinated graphene (< 20%), functional layers exhibiting a negative
differential resistance behavior and, at fluorination degrees of 20-23%,
field-effect-transistor channels with current modulation reaching several
orders. Composite or bilayer films based on fluorographene and V2O5 or
polyvinyl alcohol exhibit a stable resistive switching behavior. On the whole,
graphene/FG heterostructures enjoy huge potential for their use in a wide
spectrum of application, including flexible electronics.",2205.07602v1
2022-07-14,Magnetron Sputtered Non-Toxic and Precious Element-Free Ti-Zr-Ge Metallic Glass Nanofilms with Enhanced Biocorrosion Resistance,"The chemical composition and structural state of advanced alloys are the
decisive factors in optimum biomedical performance. This contribution presents
unique Ti-Zr-Ge metallic glass thin-film compositions fabricated by magnetron
sputter deposition targeted for nanocoatings for biofouling prevention. The
amorphous nanofilms with nanoscale roughness exhibit a large relaxation and
supercooled liquid regions as revealed by flash differential scanning
calorimetry. Ti\textsubscript{68}Zr\textsubscript{8}Ge\textsubscript{24} shows
the lowest corrosion (0.17 \textmu A cm\textsuperscript{\textminus2}) and
passivation (1.22 \textmu A cm\textsuperscript{\textminus2}) current densities,
with the lowest corrosion potential of \textminus0.648 V and long-range
stability against pitting, corroborating its excellent performance in phosphate
buffer solution at 37 {\textdegree}C. The oxide layer is comprised of
TiO\textsubscript{2}, TiO\textsubscript{\emph{x}} and
ZrO\textsubscript{\emph{x}}, as determined using X-ray photoelectron
spectroscopy by short-term ion-etching of the surface layer. The two orders of
magnitude increase in the oxide and interface resistance (from 14 to 1257
{\textOmega} cm\textsuperscript{2}) along with an order of magnitude decrease
in the capacitance parameter of the oxide interface (from 1.402 x
10\textsuperscript{\textminus5} to 1.677 x 10\textsuperscript{\textminus6} S
s\textsuperscript{n} cm\textsuperscript{\textminus2}) of the same composition
is linked to the formation of carbonyl groups and reduction of the native oxide
layer during linear sweep voltammetry.",2207.07000v2
2022-08-09,"Structural, magnetic and transport properties of Co$_2$CrAl epitaxial thin films","We report the physical properties of Co$_2$CrAl Heusler alloy epitaxial thin
films grown on single crystalline MgO(001) substrate using pulsed laser
deposition technique. The x-ray diffraction pattern in $\theta$-2$\theta$ mode
showed the film growth in single phase B2-type ordered cubic structure with the
presence of (002) and (004) peaks, and the film oriented along the MgO(001)
direction. The $\phi$~scan along the (220) plane confirms the four-fold
symmetry and the epitaxial growth relation found to be
Co$_2$CrAl(001)[100]$\vert$$\vert$MgO(001)[110]. The thickness of about 12~nm
is extracted through the analysis of x-ray reflectivity data. The isothermal
magnetization (M--H) curves confirm the ferromagnetic (FM) nature of the thin
film having significant hysteresis at 5 and 300~K. From the in-plane M--H
curves, the saturation magnetization values are determined to be
2.1~$\mu$$_{\rm B}$/f.u.~at 5~K and 1.6~$\mu$$_{\rm B}$/f.u. at 300~K, which
suggests the soft FM behavior in the film having the coercive field $\approx$
522~Oe at 5~K. The thermo-magnetization measurements at 500~Oe magnetic field
show the bifurcation between field-cooled and zero-field-cooled curves below
about 100~K. The normalized field-cooled magnetization curve follows the T$^2$
dependency, and the analysis reveal the Curie temperature around 335$\pm$11~K.
Moreover, the low-temperature resistivity indicates semiconducting behavior
with the temperature, and we find a negative temperature coefficient of
resistivity (5.2 $\times$ 10$^{-4}$ /K).",2208.04687v1
2022-10-21,Effect of Pressure on Electrical and optical Properties of Metal Doped TiO$_2$,"A comparative study of the electrical and optical properties has been done on
3d-doped TiO$_2$. Ti$_{1-x}$M$_x$O$_2$ (M= Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn)
powder and its corresponding pellets, with doping concentration $x= 0.05$. The
samples were prepared using the solid-state route. Optical and electrical
measurements have been performed for all prepared samples and interestingly, it
is observed that due to external pressure (i.e. strain) both the properties
change significantly. A rigorous theoretical calculation has also been carried
out to verify the experimental band gap obtained from optical absorption
spectroscopy. In case of pellet sample band gap decreases as compared to the
powder sample due to variation of pressure inside the structures. Role of
doping has also been investigated both in pellet and powder forms and we found
that the band gap decreases as the atomic number of dopants increases. A
cross-over behavior is seen in pellet samples on doping with Ni, Cu and Zn
(i.e. band gap increases with an increase in the atomic number of dopant).
Electrical resistivity measurements have been carried out for both pellet and
powder samples and it is found that in the case of strained samples the value
of resistivity is smaller while in the case of strain-free samples it is quite
large. We believe that the present study suggests a novel approach for tuning
the electrical and optical properties of semiconducting oxides either from
doping or from applied pressure (or strain).",2210.11687v1
2022-10-28,Optimal Inverter-Based Resources Placement in Low-Inertia Power Systems,"An increase in the integration of Inverter Based Resources (IBRs) to the
electric grid, will lead to a corresponding decrease in the amount of connected
synchronous generators, resulting in a decline in the available rotational
inertia system-wide. This can lead to pronounced frequency deviations when
there are disturbances and faults in the grid. This decline in available
rotational inertia can be compensated for by fast acting IBRs participating in
frequency response services, by rapidly injecting into or removing power from
the grid. Currently, there are still relative small number of sizable IBRs in
the grid. Therefore, the placement of the IBRs in the system, as well as the
inverter configuration type and controller, will have a material impact on the
frequency response of the grid. In this work, we present an optimal placement
algorithm that maximizes the benefits of utilizing IBRs in providing frequency
response services. That is, we minimize the overall system frequency deviation
while using a minimal amount of electric power injection from the IBRs. The
proposed algorithm uses the resistance distance to place the IBRs at nodes that
are central to the rest of the nodes in the network thus minimizing the
distance of power flow. The proposed greedy algorithm achieves a near optimal
performance and relies on the supermodularity of the resistance distances. We
validate the performance of the placement algorithm on three IEEE test systems
of varying sizes, by comparing its performance to an exhaustive search
algorithm. We further evaluate the performance of the placed IBRs on an IEEE
test system, to determine their impact on frequency stability. The IBRs are
configured in a grid-forming mode and equipped with a model predictive control
(MPC)-based inverter power control.",2210.15839v1
2022-12-16,Environmental Doping-Induced Degradation of the Quantum Anomalous Hall Insulators,"The quantum anomalous Hall (QAH) insulator is a topological quantum state
with quantized Hall resistance and zero longitudinal resistance in the absence
of an external magnetic field. The QAH insulator carries spin-polarized
dissipation-free chiral edge current and thus provides a unique opportunity to
develop energy-efficient transformative information technology. Despite
promising advances on the QAH effect over the past decade, the QAH insulator
has thus far eluded any practical applications. In addition to its low working
temperature, the QAH state in magnetically doped topological insulator (TI)
films/heterostructures usually deteriorates with time in ambient conditions. In
this work, we prepare three QAH devices with similar initial properties and
store them in different environments to investigate the evolution of their
transport properties. The QAH device without a protection layer in air show
clear degradation and becomes hole-doped with the charge neutral point shifting
significantly to positive gate voltages. The QAH device kept in an argon glove
box without a protection layer shows no measurable degradation after 560 hours
and the device protected by a 3 nm AlOx protection layer in air shows minimal
degradation with stable QAH properties. Our work shows a route to preserve the
dissipation-free chiral edge state in QAH devices for potential applications in
quantum information technology.",2212.08538v1
2023-01-13,Exploring the substrate-driven morphological changes in Nd0.6Sr0.4MnO3 thin films,"Manganite thin films are promising candidates for studying the strongly
correlated electron systems. Understanding the growth-and morphology-driven
changes in the physical properties of manganite thin films is vital for their
applications in oxitronics. This work reports the morphological, structural,
and electrical transport properties of nanostructured Nd0.6Sr0.4MnO3 (NSMO)
thin films fabricated using the pulsed laser deposition technique. Scanning
electron microscopy (SEM) imaging of the thin films revealed two prominent
surface morphologies: a granular and a unique crossed-nano-rod-type morphology.
From X-ray diffraction (XRD) and atomic force microscopy (AFM) analysis, we
found that the observed nanostructures resulted from altered growth modes
occurring on the terraced substrate surface. Furthermore, investigations on the
electrical-transport properties of thin films revealed that the films with
crossed-nano-rod type morphology showed a sharp resistive transition near the
metal-to-insulator transition (MIT). An enhanced temperature coefficient of
resistance (TCR) of up to one order of magnitude was also observed compared to
the films with granular morphology. Such enhancement in TCR % by tuning the
morphology makes these thin films promising candidates for developing
oxide-based temperature sensors and detectors.",2301.05513v1
2023-01-30,Percolation and electrical conduction in random systems of curved linear objects on a plane: computer simulations along with a mean-field approach,"Using computer simulations, we have studied the percolation and the
electrical conductance of two-dimensional, random percolating networks of
curved, zero-width metallic nanowires. We mimicked the curved nanowires using
circular arcs. The percolation threshold decreased as the aspect ratio of the
arcs increased. Comparison with published data on the percolation threshold of
symmetric quadratic B\'{e}zier curves suggests that, when the percolation of
slightly curved wires is simulated, the particular choice of curve to mimic the
shape of real-world wires is of little importance. Considering the electrical
properties, we took into account both the nanowire resistance per unit length
and the junction (nanowire/nanowire contact) resistance. Using a mean-field
approximation (MFA), we derived the total electrical conductance of the
nanowire-based networks as a function of their geometrical and physical
parameters. The MFA predictions have been confirmed by our Monte Carlo
numerical simulations. For our random homogeneous and isotropic systems of
conductive curved wires, the electric conductance decreased as the wire shape
changed from a stick to a ring when the wire length remained fixed.",2301.12795v1
2023-01-31,Platinum contacts for 9-atom-wide armchair graphene nanoribbons,"Creating a good contact between electrodes and graphene nanoribbons (GNRs)
has been a longstanding challenge in searching for the next GNR-based
nanoelectronics. This quest requires the controlled fabrication of sub-20 nm
metallic gaps, a clean GNR transfer minimizing damage and organic contamination
during the device fabrication, as well as work function matching to minimize
the contact resistance. Here, we transfer 9-atom-wide armchair-edged GNRs
(9-AGNRs) grown on Au(111)/mica substrates to pre-patterned platinum
electrodes, yielding polymer-free 9-AGNR field-effect transistor devices. Our
devices have a resistance in the range of $10^6$ to $10^8$ $\Omega$ in the
low-bias regime, which is 2 to 4 orders of magnitude lower than previous
reports. Density functional theory (DFT) calculations combined with the
non-equilibrium Green's function method (NEGF) explain the observed p-type
electrical characteristics and further demonstrate that platinum gives strong
coupling and higher transmission in comparison to other materials such as
graphene.",2301.13814v1
2023-02-13,Growth of Zr/ZrO2 core-shell structures by Fast Thermal Oxidation,"This research has been conducted to characterize and validate the resistive
heating as a synthesis method for zirconium oxides (ZrO$_2$). A wire of Zr has
been oxidized to form a core shell structure, in which the core is the metal
wire, and the shell is an oxide layer around 10${\mu}$m thick. The
characterization This research has been conducted to characterize and validate
the resistive heating as a synthesis method for zirconium oxides (ZrO$_2$). A
wire of Zr has been oxidized to form a core shell structure, in which the core
is the metal wire, and the shell is an oxide layer around 10${\mu}$m thick. The
characterization of the samples has been performed by means of Scanning
Electron Microscopy (SEM). The chemical composition was analysed by X-ray
spectroscopy (EDX). X-ray diffraction (XRD) and Raman spectroscopy have been
used to assess crystallinity and crystal structure. Photoluminescence (PL) and
cathodoluminescence (CL) measurements have allowed us to study the distribution
of defects along the shell, and to confirm the degree of uniformity. The oxygen
vacancies, either as isolated defects or forming complexes with impurities,
play a determinant role in the luminescent processes. Colour centres, mainly
electron centres as F, F$_A$ and F$_{AA}$, give rise to several visible
emissions extending from blue to green, with main components around 2eV,
2.4-2.5eV and 2.7eV. The differences between PL and CL are also discussed.",2302.06296v1
2023-03-15,Magnetic phase diagram and multiple field-induced states in the intermetallic triangular-lattice antiferromagnet NdAuAl$_4$Ge$_2$ with Ising-like spins,"Geometrical frustration and the enhancement of strong quantum fluctuations in
two-dimensional triangular antiferromagnets can lead to various intriguing
phenomena. Here, we studied the spin-1/2 triangular lattice antiferromagnet
NdAuAl$_4$Ge$_2$. Thermodynamic and transport properties, such as magnetization
and specific heat together with the resistivity measurements were performed. In
zero field, two successive phase transitions were observed at $T_{\rm
N1}=1.75\pm 0.02$ K and $T_{\rm N2}=0.49\pm 0.02$ K, respectively. Under
magnetic field, $\rm XXZ$-type anisotropy was revealed, with the moments
pointing along the easy $c$ axis. For $B\parallel c$, multiple field-induced
states were observed, and the magnetic phase diagram was established based on
the specific heat and magnetization data. The temperature-dependent resistivity
measurements indicate that NdAuAl$_4$Ge$_2$ is a good metal. It is very likely
that both the long-range RKKY interactions and the geometrical frustration play
an important roles in this case.",2303.08661v1
2023-04-07,Effect of Pt vacancies on magnetotransport of Weyl semimetal candidate GdPtSb epitaxial films,"We examine the effects of Pt vacancies on the magnetotransport properties of
Weyl semimetal candidate GdPtSb films, grown by molecular beam epitaxy on
c-plane sapphire. Rutherford backscattering spectrometry (RBS) and x-ray
diffraction measurements suggest that phase pure GdPt$_{x}$Sb films can
accommodate up to $15\%$ Pt vacancies ($x=0.85$), which act as acceptors as
measured by Hall effect. Two classes of electrical transport behavior are
observed. Pt-deficient films display a metallic temperature dependent
resistivity (d$\rho$/dT$>$0). The longitudinal magnetoresistance (LMR, magnetic
field $\mathbf{B}$ parallel to electric field $\mathbf{E}$) is more negative
than transverse magnetoresistance (TMR, $\mathbf{B} \perp \mathbf{E}$),
consistent with the expected chiral anomaly for a Weyl semimetal. The
combination of Pt-vacancy disorder and doping away from the expected Weyl
nodes; however, suggests conductivity fluctuations may explain the negative LMR
rather than chiral anomaly. Samples closer to stoichiometry display the
opposite behavior: semiconductor-like resistivity (d$\rho$/dT$<$0) and more
negative transverse magnetoresistance than longitudinal magnetoresistance.
Hysteresis and other nonlinearities in the low field Hall effect and
magnetoresistance suggest that spin disorder scattering, and possible
topological Hall effect, may dominate the near stoichiometric samples. Our
findings highlight the complications of transport-based identification of Weyl
nodes, but point to possible topological spin textures in GdPtSb.",2304.03811v1
2023-05-22,Development of Fe$_2$O$_3$/YSZ ceramic plates for cryogenic operation of resistive-protected gaseous detectors,"We present a ceramic material based on hematite (Fe$_2$O$_3$) and zirconia
stabilized with yttria at 8% molar (YSZ), that exhibits stable electrical
properties with transported charge and that can be tuned to the resistivities
necessary to induce spark-quenching in gaseous detectors ($\rho = 10^9-10^{12}$
$\Omega \cdot$cm), from room temperature down to the liquid-vapor coexistence
point of nitrogen (77 K). It, thus, allows covering the operating temperatures
of most immediate interest to gaseous instrumentation. The ceramics have been
produced in a region of mass concentrations far from what has been usually
explored in literature: optimal characteristics are achieved for Fe$_2$O$_3$
concentrations of 75%wt (LAr boiling temperature), 35%wt (LXe boiling
temperature), and 100%wt (room temperature). The nine order of magnitude
enhancement observed for the electrical conductivity of the mixed phases
relative to that of pure Fe$_2$O$_3$ is startling, however it can be
qualitatively understood based on existing literature. Plates of 4 cm x 4 cm
have been manufactured and, prior to this work, operated in-detector at the LXe
boiling point (165 K), demonstrating spark-free operation. Preliminary results
obtained for the first time on a spark-protected amplification structure
(RP-WELL) at around the LAr boiling point (90 K) are now presented, too.",2305.12899v2
2023-07-05,An efficient approach to include transport effects in thin coating layers in electrochemo-mechanical models for all-solid-state batteries,"A novel approach is presented to efficiently include transport effects in
thin active material coating layers of all-solid-state batteries using a
dimensionally reduced formulation embedded into a three-dimensionally resolved
coupled electrochemo-mechanical continuum model. In the literature, the effect
of coating layers is so far captured by additional zero-dimensional resistances
to circumvent the need for an extremely fine mesh resolution. However, a
zero-dimensional resistance cannot capture transport phenomena along the
coating layer, which can become significant, as we will show in this work.
Thus, we propose a model which resolves the thin coating layer in a
two-dimensional manifold based on model assumptions in the direction of the
thickness. This two-dimensional formulation is monolithically coupled with a
three-dimensional model representing the other components of a battery cell.
The approach is validated by showing conservation properties and convergence
and by comparing the results with those computed with a fully resolved model.
Results for realistic microstructures of a battery cell, including coating
layers as well as design recommendations for a preferred coating layer, are
presented. Based on those results, we show that existing modeling approaches
feature remarkable errors when transport along the coating layer is
significant, whereas the novel approach resolves this.",2307.02424v1
2023-08-04,"Effect of Pb addition on microstructure, transport properties and the critical current density in a polycrystalline FeSe0.5Te0.5","We have investigated the effects of lead (Pb) additions (x) up to 40 wt.% (x
= 0-0.4) on the structure, electrical properties, and magnetic properties of
FeSe0.5Te0.5 superconductor. The samples were prepared by the solid-state
reaction method and characterized by various techniques. The parent compound (x
= 0) showed the onset temperature Tc onset of 15 K, and zero-resistance
temperature, Tc offset of 12 K. The addition of Pb enhances the metallic
characteristics of FeSe0.5Te0.5, but both Tc onset and Tc offset are decreased
to the lower temperature with the broadened transition width. The Tc onset is
nearly the same (10.3 K) at higher additions, such as x = 0.3 and 0.4, but zero
resistivity is not observed up to 7 K. Microstructural analysis and transport
studies suggest that for x > 0.05, Pb additions weakened the coupling between
grains and suppressed the superconducting percolation, leading to a broad
transition. More importantly, the inclusion of a relatively small amount of Pb
(x = 0.05) increased the critical current density, Jc, in the entire magnetic
field, which might be attributable to better phase uniformity as well as good
grain connectivity.",2308.02128v1
2023-08-07,Single crystal growth and characterization of antiferromagnetically ordering EuIn$_2$,"We report the single crystal growth and characterization of EuIn$_2$, a
magnetic topological semimetal candidate according to our density functional
theory (DFT) calculations. We present results from electrical resistance,
magnetization, M\""ossbauer spectroscopy, and X-ray resonant magnetic scattering
(XRMS) measurements. We observe three magnetic transitions at
$T_{\text{N}1}\sim 14.2~$K, $T_{\text{N}2}\sim12.8~$K and $T_{\text{N}3}\sim
11~$K, signatures of which are consistently seen in anisotropic temperature
dependent magnetic susceptibility and electrical resistance data. M\""ossbauer
spectroscopy measurements on ground crystals suggest an incommensurate
sinusoidally modulated magnetic structure below the transition at
$T_{\text{N}1}\sim 14~$K, followed by the appearance of higher harmonics in the
modulation on further cooling roughly below $T_{\text{N}2}\sim13~$K, before the
moment distribution squaring up below the lowest transition around
$T_{\text{N}3}\sim 11~$K. XRMS measurements showed the appearance of magnetic
Bragg peaks below $T_{\text{N}1}\sim14~$K, with a propagation vector of
$\bm{\tau}$ $=(\tau_h,\bar{\tau}_h,0)$, with $\tau_h$varying with temperature,
and showing a jump at $T_{\text{N}3}\sim11$~K. The temperature dependence of
$\tau_h$ between $\sim11$~K and $14$~K shows incommensurate values consistent
with the M\""{o}ssbauer data. XRMS data indicate that $\tau_h$ remains
incommensurate at low temperatures and locks into $\tau_h=0.3443(1)$.",2308.03600v1
2023-08-10,Ferromagnetism and insulating behavior with a logarithmic temperature dependence of resistivity in $Pb_{10-x}Cu_x\left( PO_4 \right) _6O$,"Recent claim of discovering above-room-temperature superconductivity (Tc
about 400 K) at ambient pressure in copper doped apatite $Pb_{10}\left( PO_4
\right) _6O$ has stimulated world-wide enthusiasm and impulse of motion. A lot
of follow-up works have been carried out with controversial conclusions. To
check whether superconductivity is really present or absent in the material, we
need samples which should have a rather pure phase of $Pb_{10-x}Cu_x\left( PO_4
\right) _6O$. Here we report the characterization results from the
$Pb_{10-x}Cu_x\left( PO_4 \right) _6O$ with a fraction of about 97 wt.%
inferred from the fitting to the x-ray diffraction pattern. The resistivity
measurements show that it is a semiconductor characterized roughly by a ln(1/T)
temperature dependence in wide temperature region without trace of
superconductivity. Magnetization measurements show that it has a general
ferromagnetic signal with a weak superparamagnetic background. Many grains of
the sample show clear interactions with a NbFeB magnet. The detected Cu
concentration is much lower than the expected nominal one and the conduction
may be improved if more Cu atoms are successfully doped into the system. Our
results show the absence of metallicity and superconductivity in
$Pb_{10-x}Cu_x\left( PO_4 \right) _6O$ at ambient pressure, and suggest the
presence of strong correlation effect.",2308.05786v3
2023-08-15,Thermoelectric response across the semiconductor-semimetal transition in black phosphorus,"In spite of intensive studies on thermoelectricity in metals, little is known
about thermoelectric response in semiconductors at low temperature. An even
more fascinating and unanswered question is what happens to the Seebeck
coefficient when the semiconductor turns to a metal. By precisely tuning the
ground state of black phosphorus with pressure from the semiconducting to
semimetallic state, we track a systematic evolution of the Seebeck coefficient.
Thanks to a manifest correlation between the Seebeck coefficient and
resistivity, the Seebeck response in each conduction regime, i.e., intrinsic,
saturation, extrinsic, and variable range hopping (VRH) regimes, is identified.
In the former two regimes, the Seebeck coefficient behaves in accordance with
the present theories, whereas in the later two regimes available theories do
not give a satisfactory account for its response. However, by eliminating the
extrinsic sample dependence in the resistivity $\rho$ and Seebeck coefficient
$S$, the Peltier conductivity $\alpha=S/\rho$ allows to unveil the intrinsic
thermoelectric response, revealing vanishing fate for $\alpha$ in the VRH
regime. The emerged ionized impurity scattering on entry to the semimetallic
state is easily surpassed by electron-electron scattering due to squeezing of
screening length accompanied by an increase of carrier density with pressure.
In the low temperature limit, a small number of carriers enhances a prefactor
of $T$-linear Seebeck coefficient as large as what is observed in prototypical
semimetals. A crucial but largely ignored role of carrier scattering in
determining the magnitude and sign of the Seebeck coefficient is indicated by
the observation that a sign reversal of the $T$-linear prefactor is concomitant
with a change in dominant scattering mechanism for carriers.",2308.07900v1
2023-08-18,Anomalous Hall effect induced by Berry curvature in topological nodal-line van der Waals ferromagnet Fe$_4$GeTe$_2$,"The exploration of nontrivial transport phenomena associated with the
interplay between magnetic order and spin-orbit coupling (SOC), particularly in
van der Waals (vdW) systems has gained a resurgence of interest due to their
easy exfoliation, ideal for two-dimensional (2D) spintronics. We report the
near room temperature quasi-2D ferromagnet, Fe$_4$GeTe$_2$ from the iron-based
vdW family (Fe$_n$GeTe$_2$, $n$=3,4,5), exhibiting a large anomalous Hall
conductivity (AHC), $\sigma^A_{xy}$ $\sim$ 490 $\Omega^{-1}\textrm{cm}^{-1}$ at
2 K. The near quadratic behavior of anomalous Hall resistivity
($\rho^{A}_{xy}$) with the longitudinal resistivity ($\rho_{xx}$) suggests that
a dominant AHC contribution is coming from an intrinsic Berry curvature (BC)
mechanism. Concomitantly, the electronic structure calculations reveal a large
BC arising from SOC induced gaped nodal lines around the Fermi level, governing
such large AHC property. Moreover, we also report an exceptionally large
anomalous Hall angle ($\simeq$ 10.6\%) and Hall factor ($\simeq$ 0.22 V$^{-1}$)
values which so far, are the largest in compared to those for other members in
this vdW family.",2308.09695v1
2023-08-25,Evidence of the Coulomb gap in the density of states of MoS$_2$,"$\mathrm{MoS_2}$ is an emergent van der Waals material that shows promising
prospects in semiconductor industry and optoelectronic applications. However,
its electronic properties are not yet fully understood. In particular, the
nature of the insulating state at low carrier density deserves further
investigation, as it is important for fundamental research and applications. In
this study, we investigate the insulating state of a dual-gated exfoliated
bilayer $\mathrm{MoS_2}$ field-effect transistor by performing magnetotransport
experiments. We observe positive and non-saturating magnetoresistance, in a
regime where only one band contributes to electron transport. At low electron
density ($\sim 1.4\times 10^{12}~\mathrm{cm^{-2}}$) and a perpendicular
magnetic field of 7 Tesla, the resistance exceeds by more than one order of
magnitude the zero field resistance and exponentially drops with increasing
temperature. We attribute this observation to strong electron localization.
Both temperature and magnetic field dependence can, at least qualitatively, be
described by the Efros-Shklovskii law, predicting the formation of a Coulomb
gap in the density of states due to Coulomb interactions. However, the
localization length obtained from fitting the temperature dependence exceeds by
more than one order of magnitude the one obtained from the magnetic field
dependence. We attribute this discrepancy to the presence of a nearby metallic
gate, which provides electrostatic screening and thus reduces long-range
Coulomb interactions. The result of our study suggests that the insulating
state of $\mathrm{MoS_2}$ originates from a combination of disorder-driven
electron localization and Coulomb interactions.",2308.13337v2
2023-09-05,Localized f-electron magnetism in the semimetal Ce3Bi4Au3,"Ce$_{3}$Bi$_{4}$Au$_{3}$ crystallizes in the same non-centrosymmetric cubic
structure as the prototypical Kondo insulator Ce$_{3}$Bi$_{4}$Pt$_{3}$. Here we
report the physical properties of Ce$_{3}$Bi$_{4}$Au$_{3}$ single crystals
using magnetization, thermodynamic, and electrical-transport measurements.
Magnetic-susceptibility and heat-capacity data reveal antiferromagnetic (AFM)
order below $T_N=3.2$ K. The magnetic entropy $S_{\rm mag}$ reaches $R$ln2
slightly above $T_N$, which suggests localized $4f$-moments in a doublet ground
state. Multiple field-induced magnetic transitions are observed at temperatures
below $T_N$, which indicate a complex spin structure with competing
interactions. Ce$_{3}$Bi$_{4}$Au$_{3}$ shows semimetallic behavior in
electrical resistivity measurements in contrast to the majority of reported
Cerium-based 343 compounds. Electrical-resistivity measurements under
hydrostatic pressure reveal a slight enhancement of $T_N$ under pressures up to
2.3 GPa, which supports a scenario wherein Ce$_{3}$Bi$_{4}$Au$_{3}$ belongs to
the far left of the Doniach phase diagram dominated by
Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. Using realistic many-body
simulations, we confirm the semi-metallic electronic structure of
Ce$_{3}$Bi$_{4}$Au$_{3}$ and quantitatively reproduce its local moment behavior
in the paramagnetic state.",2309.02559v1
2023-09-27,Design of Passive and Structural Conductors for Tokamaks Using Thin-Wall Eddy Current Modeling,"A new three-dimensional electromagnetic modeling tool ThinCurr has been
developed using the existing PSI-Tet finite-element code in support of
conducting structure design work for both the SPARC and DIII-D tokamaks. Within
this framework a 3D conducting structure model was created for both the SPARC
and DIII-D tokamaks in the thin-wall limit. This model includes accurate
details of the vacuum vessel and other conducting structural elements with
realistic material resistivities. This model was leveraged to support the
design of a passive runaway electron mitigation coil (REMC), studying the
effect of various design parameters, including coil resistivity, current quench
duration, and plasma vertical position, on the effectiveness of the coil. The
REMC is a non-axisymmetric coil designed to passively drive large
non-axisymmetric fields during the plasma disruption thereby destroying flux
surfaces and deconfining RE seed populations. These studies indicate that
current designs should apply substantial 3D fields at the plasma surface during
future plasma current disruptions as well as highlight the importance of having
the REMC conductors away from the machine midplane in order to ensure they are
robust to off-normal disruption scenarios.",2309.15336v1
2023-10-02,Dielectric Detection of Single Nanoparticles Using a Microwave Resonator Integrated with a Nanopore,"The characterization of individual nanoparticles in a liquid constitutes a
critical challenge for environmental, material, and biological sciences. To
detect nanoparticles, electronic approaches are especially desirable owing to
their compactness and lower costs. Indeed, for single-molecule and
single-nanoparticle detection, resistive pulse sensing has advanced
significantly during the last two decades. While resistive pulse sensing was
widely used to obtain the geometric size information, impedimetric measurements
to obtain dielectric signatures of nanoparticles have scarcely been reported.
To explore this orthogonal sensing modality, we developed an impedimetric
sensor based on a microwave resonator with a nanoscale sensing gap surrounding
a nanopore. The approach of single nanoparticles near the sensing region and
their translocation through the nanopore induced sudden changes in the
impedance of the structure. The impedance changes in turn were picked up by the
phase response of the microwave resonator. We worked with 100 nm and 50 nm
polystyrene nanoparticles to observe single-particle events. Our current
implementation was limited by the non-uniform electric field at the sensing
region. The work provides a complementary sensing modality for nanoparticle
characterization where the dielectric response, rather than the ionic current,
determines the signal.",2310.00910v1
2023-10-16,Growth and characterization of the magnetic topological insulator candidate Mn$_2$Sb$_2$Te$_5$,"We report a new member of topological insulator (TI) family i.e.,
Mn$_2$Sb$_2$Te$_5$, which belongs to MnSb$_2$Te$_4$ family and is a sister
compound of Mn$_2$Bi$_2$Te$_5$. An antiferromagnetic layer of (MnTe)$_2$ has
been inserted between quintuple layers of Sb$_2$Te$_3$. The crystal structure
and chemical composition of as grown Mn$_2$Sb$_2$Te$_5$ crystal is
experimentally visualized by single crystal XRD (SCXRD) and field emission
scanning electron microscopy (FESEM). The valence states of individual
constituents i.e., Mn, Sb and Te are ascertained through X ray photo electron
spectroscopy (XPS). Different vibrational modes of Mn$_2$Sb$_2$Te$_5$ are
elucidated through Raman spectroscopy. Temperature-dependent resistivity of
Mn$_2$Sb$_2$Te$_5$ resulted in metallic behaviour of the same with an up-turn
at below around 20K. Further, the magneto-transport R(T) vs H of the same
exhibited negative magneto-resistance (MR) at low temperatures below 20K and
small positive at higher temperatures. The low Temperature -ve MR starts
decreasing at higher fields. The magnetic moment as a function of temperature
at 100Oe and 1kOe showed AFM like down turn cusps at around 20K and 10K. The
isothermal magnetization (MH) showed AFM like loops with some embedded FM/PM
domains at 5K and purely paramagnetic (PM) like at 100K. The studied
Mn$_2$Sb$_2$Te$_5$ clearly exhibited the characteristics of a magnetic TI
(MTI).",2310.10163v1
2023-10-22,Investigation of the mechanism of the anomalous Hall effects in Cr2Te3/(BiSb)2(TeSe)3 heterostructure,"The interplay between ferromagnetism and the non-trivial topology has
unveiled intriguing phases in the transport of charges and spins. For example,
it is consistently observed the so-called topological Hall effect (THE)
featuring a hump structure in the curve of the Hall resistance (Rxy) vs. a
magnetic field (H) of a heterostructure consisting of a ferromagnet (FM) and a
topological insulator (TI). The origin of the hump structure is still
controversial between the topological Hall effect model and the multi-component
anomalous Hall effect (AHE) model. In this work, we have investigated a
heterostructure consisting of BixSb2-xTeySe3-y (BSTS) and Cr2Te3 (CT), which
are well-known TI and two-dimensional FM, respectively. By using the so-called
minor-loop measurement, we have found that the hump structure observed in the
CT/BSTS is more likely to originate from two AHE channels. Moreover, by
analyzing the scaling behavior of each amplitude of two AHE with the
longitudinal resistivities of CT and BSTS, we have found that one AHE is
attributed to the extrinsic contribution of CT while the other is due to the
intrinsic contribution of BSTS. It implies that the proximity-induced
ferromagnetic layer inside BSTS serves as a source of the intrinsic AHE,
resulting in the hump structure explained by the two AHE model.",2310.14259v1
2023-11-09,Lithium-ion battery degradation: using degradation mode analysis to validate lifetime prediction modelling,"Predicting lithium-ion battery lifetime is one of the greatest unsolved
problems in battery research right now. Recent years have witnessed a surge in
lifetime prediction papers using physics-based, empirical, or data-driven
models, most of which have been validated against the remaining capacity
(capacity fade) and sometimes resistance (power fade). However, there are many
different combinations of degradation mechanisms in lithium-ion batteries that
can result in the same patterns of capacity and power fade, making it
impossible to find a unique validated solution. Experimentally, degradation
mode analysis involving measuring the loss of lithium inventory, loss of active
material at both electrodes, and electrode drift/slippage has emerged as a
state-of-the-art requirement for cell degradation studies. In this paper we
coupled five degradation mechanisms together for the first time. We also showed
how three models with different levels of complexity can all fit the remaining
capacity and resistance well, but only the model with five coupled degradation
mechanisms could also fit the degradation modes at all temperatures. This work
proves that validating only against capacity and power fade is no longer
sufficient, and state-of-the-art experimental and modelling degradation studies
should include degradation mode analysis for validation in the future.",2311.05482v2
2023-11-19,Non-Hermitian effect to the ballistic transport and quantized Hall conductivity in 2H-MoS$_{2}$,"By designing a multi-channel millimeter Hall measurement configuration, we
realize the carrier-density (locally) controllable measurement on the transport
property in 2H MoS$_{2}$. We observe a linearly increased Hall conductivity and
exponentially decreased resistivity as the increase of dc current. The
intrinsically large band gap does not exhibit too much effect on our
measurement, as far as the magnetic field is above the critical value, which is
$B=6$ T for 2H-MoS$_{2}$. Instead, the edge effect which emerge as a result of
one-dimensional channels. This is different from the Corbino geometry which is
widely applied on semiconductors, where the edges are absent. At room
temperature, we observe that the emergent quantized quantum Hall plateaus are
at the same value for both the two measurements, which implies that the
quantized conductivity does not depends on the non-Hermitian interactions, but
the number of partially filled Landau levels, and this is in consistent with
the previous theoretical works\cite{Siddiki}. At low-temperature limit, the
Hall plateaus are destroyed due to the filtered contribution from the electrons
above fermi energy, and in this case, the two measuremens exhibits stronger
distinction, where we observe stronger fluctuations (of voltage, conductivity,
and resistivity) at the currents between where there are Hall plateaus at
higher temperature.",2311.11276v3
2023-11-24,Even-in-magnetic-field part of transverse resistivity as a probe of magnetic order,"The detection of a voltage transverse to both an applied current and a
magnetic field is one of the most common characterization techniques in
solid-state physics. The corresponding component of the resistivity tensor
$\rho_{ij}$ can be separated into odd and even parts with respect to the
applied magnetic field. The former contains information, for example, about the
ordinary or anomalous Hall effect. The latter is typically ascribed to
experimental artefacts and ignored. We here show that upon suppressing these
artefacts in carefully controlled experiments, useful information remains. We
first investigate the well-explored ferromagnet CoFeB, where the even part of
$\rho_{yx}$ contains a contribution from the anisotropic magnetoresistance,
which we confirm by Stoner-Wohlfarth modelling. We then apply our approach to
magnetotransport measurements in $\rm Mn_5Si_3$ thin films with a complex
compensated magnetic order. In this material, the even part of the transverse
signal is sizable only in the low-spin-symmetry phase below $\approx 80$ K and
thus offers a simple and readily available probe of the magnetic order.",2311.14498v1
2023-12-10,Radiation resistance of fine-grained ceramics Y2.5Nd0.5Al5O12 under Xe-ions irradiation,"Oxide Y2.5Nd0.5Al5O12 (YAG:Nd) with garnet structure was synthesized in the
powder and ceramics forms. Fine-grained YAG:Nd ceramics with a relative density
of ~99% were obtained by the Spark Plasma Sintering method (SPS). The radiation
resistance of ceramics was studied under irradiation with swift Xe-ions (E =
146 MeV). A gradient defect structure is formed in irradiated ceramics, varying
from layer to layer. The strained YAG phase formed as a result of Xe ions
irradiation is localized in a near-surface layer with a thickness of ~5 {\mu}m.
Full amorphization of the samples was observed under irradiation with a fluence
of 1x10^13 cm-2. The calculated critical fluence was 6.5x10^12 cm-2, which
corresponded to 0.03 dpa. The microhardness of the surface layers of irradiated
ceramics is less than the central layers, and, in general, decreases with
increasing ion fluence.",2312.05820v1
2024-01-16,Thermoelectric power of overdoped Tl2201 crystals: Charge density waves and $T^1$ and $T^2$ resistivities,"We report measurements of the in-plane thermoelectric power (TEP) for an
overdoped (OD) crystal of the single layer cuprate superconductor
Tl$_2$Ba$_2$CuO$_{6+x}$ (Tl2201) at several hole concentrations ($p$), from 300
or 400 K to below the superconducting transition temperature ($T_c$). For $p$ =
0.192 and 0.220, small upturns in the TEP below 150 K are attributed to the
presence of charge density waves (CDW) detected by resonant inelastic X-ray
scattering studies. This suggests that measurement of the TEP could provide a
simple and effective guide to the presence of a CDW. Over a certain temperature
range, often strongly restricted by the CDW, the TEP is consistent with the
Nordheim-Gorter rule and the $T^1$ and $T^2$ terms in the in-plane resistivity
of similar crystals observed below 160 K. Two scenarios in which the $T^1$
scattering term is uniform or non-uniform around the Fermi surface are
discussed. As found previously by others, for uniform scattering the $T^1$
terms give scattering rates ($\tau^{-1}$) at lower $p$ that are somewhat larger
than the Planckian value $k_B T/\hbar$ and fall to zero for heavily OD
crystals. Near 160 K, $\tau^{-1}$ from the $T^2$ terms corresponds to the
Planckian value.",2401.08380v1
2024-01-25,Unveiling a Novel Metal-to-Metal Transition in LuH2: Critically Challenging Superconductivity Claims in Lutetium Hydrides,"Following the recent report by Dasenbrock-Gammon et al. (2023) of
near-ambient superconductivity in nitrogen-doped lutetium trihydride
(LuH3-{\delta}N{\epsilon}), significant debate has emerged surrounding the
composition and interpretation of the observed sharp resistance drop. Here, we
meticulously revisit these claims through comprehensive characterization and
investigations. We definitively identify the reported material as lutetium
dihydride (LuH2), resolving the ambiguity surrounding its composition. Under
similar conditions (270-295 K and 1-2 GPa), we replicate the reported sharp
decrease in electrical resistance with a 30% success rate, aligning with
Dasenbrock-Gammon et al.'s observations. However, our extensive investigations
reveal this phenomenon to be a novel, pressure-induced metal-to-metal
transition intrinsic to LuH2, distinct from superconductivity. Intriguingly,
nitrogen doping exerts minimal impact on this transition. Our work not only
elucidates the fundamental properties of LuH2 and LuH3 but also critically
challenges the notion of superconductivity in these lutetium hydride systems.
These findings pave the way for future research on lutetium hydride systems
while emphasizing the crucial importance of rigorous verification in claims of
ambient temperature superconductivity.",2401.13958v2
2024-02-06,Homogeneity problem for basis expansion of functional data with applications to resistive memories,"The homogeneity problem for testing if more than two different samples come
from the same population is considered for the case of functional data. The
methodological results are motivated by the study of homogeneity of electronic
devices fabricated by different materials and active layer thicknesses. In the
case of normality distribution of the stochastic processes associated with each
sample, this problem is known as Functional ANOVA problem and is reduced to
test the equality of the mean group functions (FANOVA). The problem is that the
current/voltage curves associated with Resistive Random Access Memories (RRAM)
are not generated by a Gaussian process so that a different approach is
necessary for testing homogeneity. To solve this problem two different
parametric and nonparametric approaches based on basis expansion of the sample
curves are proposed. The first consists of testing multivariate homogeneity
tests on a vector of basis coefficients of the sample curves. The second is
based on dimension reduction by using functional principal component analysis
of the sample curves (FPCA) and testing multivariate homogeneity on a vector of
principal components scores. Different approximation numerical techniques are
employed to adapt the experimental data for the statistical study. An extensive
simulation study is developed for analyzing the performance of both approaches
in the parametric and non-parametric cases. Finally, the proposed methodologies
are applied on three samples of experimental reset curves measured in three
different RRAM technologies.",2402.04321v1
2024-02-17,Fourier Electron Optics with Massless Dirac Fermions Scattered by Quantum Dot Lattice,"The field of electron optics exploits the analogy between the movement of
electrons or charged quasiparticles, primarily in two-dimensional materials
subjected to electric and magnetic (EM) fields and the propagation of
electromagnetic waves in a dielectric medium with varied refractive index. We
significantly extend this analogy by introducing Fourier electron optics (FEO)
with massless Dirac fermions (MDF), namely the charge carriers of single-layer
graphene under ambient conditions, by considering their scattering from a
two-dimensional quantum dot lattice (TDQDL) treated within Lippmann-Schwinger
formalism. By considering the scattering of MDF from TDQDL with a cavity, as
well as the moir\'{e} pattern of twisted TDQDLs, we establish an electronic
analogue of Babinet's principle in optics. Exploiting the similarity of the
resulting differential scattering cross-section with the Fraunhofer diffraction
pattern, we construct a dictionary for such FEO. Subsequently, we evaluate the
resistivity of such scattered MDF using the Boltzmann approach as a function of
the angle made between the direction of propagation of these charge-carriers
and the symmetry axis of the dot-lattice, and Fourier analyze them to show that
the spatial frequency associated with the angle-resolved resistivity gets
filtered according to the structural changes in the dot lattice, indicating
wider applicability of FEO of MDF.",2402.11259v1
2024-04-01,Electronic structure and thermoelectric properties of epitaxial Sc1-xVxNy thin films grown on MgO(001),"The electronic structure of Sc1-xVxNy epitaxial films with different alloying
concentrations of V are investigated with respect to effects on thermoelectric
properties. Band structure calculations on Sc0.75V0.25N indicate that V 3d
states lie in the band gap of the parent ScN compound in the vicinity of the
Fermi level. Thus, theoretically the presence of light (dispersive) bands at
the {\Gamma}-point with band multiplicity is expected to lead to lower
electrical resistivity while flat (heavy) bands at X-W-K symmetry points are
associated with higher Seebeck coefficient than that of ScN. With this aim,
epitaxial Sc1-xVxNy thin film samples were deposited on MgO(001) substrates.
All the samples showed N substoichiometry and pseudocubic crystal structure.
The N-vacancy-induced states were visible in the Sc 2p XAS spectra. The
reference ScN and Sc1-xVxNy samples up to x = 0.12 were n type, exhibiting
carrier concentration of 1021 cm-3, typical for degenerate semiconductors. For
the highest V alloying of x = 0.15, holes became the majority charge carrier as
indicated by the positive Seebeck coefficient. The underlying electronic
structure and bonding mechanism in Sc1-xVxNy influence the electrical
resistivity, Seebeck coefficient, and Hall effect. Thus, the work contributes
to the fundamental understanding of the correlated defects and thermoelectric
properties to the electronic structure in Sc-N system with V alloying.",2404.01417v1
2024-05-01,"Metamagnetism and anomalous magnetotransport properties in rare-earth-based polar semimetals $R$AuGe ($R =$ Dy, Ho, and Gd)","We report the magnetic, magnetoelastic, and magnetotransport properties of
single crystals of polar magnets $R$AuGe ($R=$ Dy, Ho, and Gd), grown by Au-Ge
self-flux. Magnetization and magnetostriction measurements reveal multi-step
metamagnetic transitions for the $c$-axis magnetic field ($H\parallel c$) for
DyAuGe and HoAuGe, suggesting magnetic frustration in the triangular lattice of
$R$ ions. The magnetic phase diagrams have clarified a close connection between
the magnetoelastic property and the emergence of the intermediate metamagentic
phase. The magnetic-field dependence of the resistivity and Hall resistivity
reveal the semimetallic transport dominated by hole-type carriers, consistent
with the behavior in a nonmagnetic analogue YAuGe. We also identify a signature
of an anomalous Hall effect (AHE) proportional to the field-induced
magnetization in $R=$ Dy, Ho, and Gd. GdAuGe shows magnetic and transport
behavior as reported in a previous study using Bi-flux grown single crystals,
while the self-flux grown crystal shows larger magnetoresistance ($\sim$ 345\%,
at 1.8 K and 9 T) due to higher hole-type carrier mobility ($\sim$ 6400
cm$^2$/Vs). Using the two-band model analysis considering the mobility change
during the magnetization process, we extract the anomalous Hall conductivity:
$\sim 1200$ S/cm and $\sim 530$ S/cm for $R=$ Dy and Ho, respectively, at 1.8 K
with 9 T for $H\parallel c$. The magnitude of conductivity suggests a
contribution of intrinsic origin, possibly related to the Berry curvature in
the electron bands induced by the time-reversal symmetry breaking and the polar
lattice.",2405.00628v2
1995-10-03,Theory of the Normal State of Cuprate Superconducting Materials,"We have proposed a model Hamiltonian, which describes a simple physical
picture that the holes with single occupation constraint introduced by doping
move in the antiferromagnetic background of the copper spins, to describe the
normal state of the cuprate superconducting materials, and used the
renormalization group method to calculate its anomalous magnetic and transport
properties. The anomalous magnetic behavior of the normal state is controlled
by both the copper spin and the spin part of the doping hole residing on the O
sites. The physical resistivity is determined by both the
quasiparticle-spin-fluctuation and the quasiparticle-gauge-fluctuation
scatterings and the Hall coefficient is determined by the parity-odd gauge
interaction deriving from the nature of the hard-core boson which describes the
charge part of the doping holes.",9510015v1
1999-03-04,Transport in Materials with Disclination Dipoles: Applications to Polycrystals and Amorphous Dielectrics,"The problem of both electron and phonon scattering by wedge disclination
dipoles (WDD) is studied in the framework of the deformation potential
approach. The exact analytical results for the mean free path are obtained
within the Born approximation. The WDD-induced contribution to the residual
resistivity in nanocrystalline metals is estimated. Using the WDD-based model
of a grain boundary, the thermal conductivity, kappa, of polycrystals and
amorphous dielectrics is studied. It is shown that the low-temperature
crossover of kappa experimentally observed in LiF, NaCl, and sapphire can be
explained by the grain-boundary phonon scattering. A combination of two
scattering processes, the phonon scattering due to biaxial WDD and the
Rayleigh-type scattering, is suggested to be of importance in amorphous
dielectrics. Our results are in a good agreement with the experimentally
observed kappa in a-SiO_2, a-GeO_2 a-Se, and polystyrene over a wide
temperature range.",9903072v1
1999-05-06,Role of Orbitals in Manganese Oxides - Ordering and Fluctuation,"We study the manganese oxides from the viewpoint of the strongly correlated
doped Mott insulator. The magnetic ordering and the charge transport are
governed by the orbital degrees of freedom, and their dimensionality is
controlled by the anisotropic transfer integrals between the $e_g$ orbitals. As
x increases the magnetic structure is predicted to change as $A \to F \to A \to
C \to G$ (F: ferromagnet, A: layered antiferromagnet, C: rod-type
antiferromagnet, G: usual antiferromagnet), in agreement with experiments.
Especially the orbital is aligned as $d_{x^2-y^2}$ in the metallic A state,
which explains the quasi 2D transport and no canting of the spin observed
experimentally. Next we discuss the ferromagnetic state without the orbital
ordering due to the quantum fluctuation. Here the interplay between the
electron repulsion U and the Jahn-Teller electron-phonon interation $E_{LR}$ is
studied with a large d model. In addition to this strong correlation, we
propose that the dynamical phase separation could explain the specific heat as
well as the various anomalous physical properties, e.g., resistivity,
photo-emission, etc.",9905072v1
1999-11-16,Magneto-impedance of glass-coated Fe-Ni-Cu microwires,"The magneto-impedance (MI) of glass-coated Fe-Ni-Cu microwires was
investigated for longitudinal radio-frequency (RF) currents up to a frequency
of 200 MHz using an RF lock-in amplifier method. The MI, defined as DZ/Z =
[Z(H)-Z(H=0.3T)]/Z(H=0.3T), displays a peak structure (negative MI) at zero
field for RF currents with frequencies less than 20MHz and this crosses over to
a sharp dip (positive MI) at higher frequencies. This crossover behavior is
ascribed to the skin-depth-limited response primarily governed by the
field-dependence of the permeability. Large saturation fields (300 to 600 Oe)
and other anomalies indicate the possible influence of giant magneto-resistance
(GMR) on the MI.",9911241v1
2000-11-18,Magneto-electronic Properties of a Ferrimagnetic Semiconductor: The Hybrid Cupromanganite CaCu3Mn4O12,"The mixed manganite-cuprate CaCu3Mn4O12 is found, using density functional
methods, to be a narrow gap (90 meV calculated) ferrimagnetic semiconductor. Cu
(formally S=1/2) antialigns with Mn (formally S=3/2), and the net spin moment
is 9 \mu_B consistent with the formal spins. Holes have Cu d_{xy}-O p_{\sigma}
(i.e. antibonding dp\sigma) character with spins aligned antiparallel to the
net magnetization; electrons have the opposite spin and have mixed Cu d_{xy} -
Mn e_g character. Thermally excited electrons and holes will each be fully spin
polarized, but in opposite directions. The properties of this material are
strongly tied to the distorted quadruple perovskite structure, which is closely
related to the skutterudite structure. The observed resistivity,
magnetoresistance, and magnetization are discussed in terms of our results.",0011316v1
2001-06-15,Pressure-induced recovery of the Fermi-liquid state in the non-Fermi liquid material U2Pt2In,"In the study of non-Fermi-liquid (NFL) phenomena in correlated metals,
U2Pt2In is of special interest as it is one of the rare stoichiometric
(undoped) materials that show NFL behaviour at ambient pressure. Here we report
on the stability of the NFL phase with respect to hydrostatic pressure (p< 1.8
GPa). Electrical resistivity data under pressure, taken on a single-crystalline
sample for a current in the tetragonal plane, show that T_FL, i.e. the
temperature below which the Fermi-liquid T^2-term is observed, increases with
pressure as T_FL ~ (p-p_c), where p_c~0 is a critical pressure. This provides
strong evidence for the location of U2Pt2In at an antiferromagnetic quantum
critical point.",0106292v1
2002-04-25,Interpretation of large room-temperature diamagnetism at low magnetic fields in films of oxidised atactic polypropylene in terms of superconducting current loops,"A simple model is used to analyse published results on large room-temperature
diamagnetism for two films of oxidised atactic polypropylene (OAPP) at low
magnetic fields. The model involves induced currents expected in circular
closed loops of superconductors in fields below the lower critical field H_{c1}
at which flux penetration would first occur if a metamagnetic transition did
not intervene as in OAPP, and the assumption that resistance would be restored
at H_{c1} (negligible pinning). Fits to the data for the more strongly magnetic
sample with the model, allowing two different types of loops with different
loop radii b_1 and b_2, but with the same cross section a of loop material
yield H_{c1} is approximately equal to 5260 Oe, and fits to the data for the
less strongly magnetic sample with two loop sizes and with the same value of
H_{c1}, combined with the knowledge that the minimum number of closed loops of
any type is one, requires that the radius a of the cross section of the
material should be less than about 0.8 micrometres, in fair agreement with a
maximum radius of 1 micrometre obtained previously from other data.",0204556v1
2002-08-28,Low frequency 1/f noise in doped manganite grain-boundary junctions,"We have performed a systematic analysis of the low frequency 1/f-noise in
single grain boundary junctions in the colossal magnetoresistance material
La_{2/3}Ca_{1/3}MnO_{3-delta}. The grain boundary junctions were formed in
epitaxial La_{2/3}Ca_{1/3}MnO_{3-delta} films deposited on SrTiO_3 bicrystal
substrates and show a large tunneling magnetoresistance of up to 300% at 4.2 K
as well as ideal, rectangular shaped resistance versus applied magnetic field
curves. Below the Curie temperature T_C the measured 1/f noise is dominated by
the grain boundary. The dependence of the noise on bias current, temperature
and applied magnetic field gives clear evidence that the large amount of low
frequency noise is caused by localized sites with fluctuating magnetic moments
in a heavily disordered grain boundary region. At 4.2 K additional temporally
unstable Lorentzian components show up in the noise spectra that are most
likely caused by fluctuating clusters of interacting magnetic moments. Noise
due to fluctuating domains in the junction electrodes is found to play no
significant role.",0208556v1
2002-11-14,Variable-Range Hopping of Spin Polarons: Magnetoresistance in a Modified Mott Regime,"We analize electrical conductivity controlled by hopping of bound spin
polarons in disordered solids with wide distributions of electron energies and
polaron shifts (barriers). By means of percolation theory and Monte Carlo
simulations we have shown that in such materials at low temperatures, when
hopping occurs in the vicinity of the Fermi level, a hard polaron gap does not
manifest itself in the transport properties. This happens because as
temperature decreases the hopping polaron trades the decreasing electron and
polaron barriers for increasing hopping distance. As a result, in the absence
of the Coulomb correlation effects, in this variable-range variable-barrier
hopping regime, the electrical resistivity as a function of temperature obeys a
non-activation law, which differs from the standard Mott law.",0211301v1
2002-11-15,Ultra-sharp magnetization steps in perovskite manganites,"We report a detailed study of step-like metamagnetic transitions in the
magnetization and resistivity of polycrystalline Pr0.5Ca0.5Mn0.95Co0.05O3. The
steps have a sudden onset below a critical temperature, are extremely sharp
(width < 0.2 mT), and occur at critical fields which are linearly dependent on
the absolute value of the cooling field in which the sample is prepared.
Similar transitions are also observed at low temperature in non-Co doped
manganites, including single crystal samples. These data show that the steps
are an intrinsic property, qualitatively different from either previously
observed higher temperature metamagnetic transitions in the manganites or
metamagnetic transitions observed in other materials.",0211337v1
2003-04-02,Low Friction Flows of Liquids at Nanopatterned Interfaces,"With the recent important development of microfluidic systems,
miniaturization of flow devices has become a real challenge. Microchannels,
however, are characterized by a large surface to volume ratio, so that surface
properties strongly affect flow resistance in submicrometric devices. We
present here results showing that the concerted effect of wetting . properties
and surface roughness may considerably reduce friction of the fluid past the
boundaries. The slippage of the fluid at the channel boundaries is shown to be
drastically increased by using surfaces that are patterned at the nanometer
scale. This effect occurs in the regime where the surface pattern is partially
dewetted, in the spirit of the 'superhydrophobic' effects that have been
recently discovered at the macroscopic scales. Our results show for the first
time that, in contrast to the common belief, surface friction may be reduced by
surface roughness. They also open the possibility of a controlled realization
of the 'nanobubbles' that have long been suspected to play a role in
interfacial slippage",0304037v1
2003-05-30,A Low-Temperature Atomic Layer Deposition Liftoff Method for Microelectronic and Nanoelectronic Applications,"We report a novel method for depositing patterned dielectric layers with
sub-micron features using atomic layer deposition (ALD). The patterned films
are superior to sputtered or evaporated films in continuity, smoothness,
conformality, and minimum feature size. Films were deposited at 100-150C using
several different precursors and patterned using either PMMA or photoresist.
The low deposition temperature permits uniform film growth without significant
outgassing or hardbaking of resist layers. A liftoff technique presented here
gives sharp step edges with edge roughness as low as ~10 nm. We also measure
dielectric constants (k) and breakdown fields for the high-k materials aluminum
oxide (k ~ 8-9), hafnium oxide (k ~ 16-19) and zirconium oxide (k ~ 20-29),
grown under similar low temperature conditions.",0305711v2
2003-11-13,"Structural, magnetic and transport properties of thin films of the Heusler alloy Co2MnSi","Thin films of Co2MnSi have been grown on a-plane sapphire substrates from
three elemental targets by dc magnetron co-sputtering. These films are single
phase, have a strong (110) texture and a saturation magnetization of 4.95
uB/formula unit at 10 K. Films grown at the highest substrate temperature of
715 K showed the lowest resistivity (47 uOhm cm at 4.2 K) and the lowest
coercivity (18 Oe). The spin polarization of the transport current was found to
be of the order of 54% as determined by point contact Andreev reflection
spectroscopy. A decrease in saturation magnetization with decreasing film
thickness and different transport behaviour in thinner films indicate a graded
disorder in these films grown on non-lattice matched substrates.",0311316v1
2004-05-17,Itinerant Ferromagnetism and Superconductivity,"Superconductivity has again become a challenge following the discovery of
unconventional superconductivity. Resistance-free currents have been observed
in heavy-fermion materials, organic conductors and copper oxides. The discovery
of superconductivity in a single crystal of $UGe_2$, $ZrZn_2$ and $URhGe$
revived the interest in the coexistence of superconductivity and
ferromagnetism. The experiments indicate that: i)The superconductivity is
confined to the ferromagnetic phase. ii)The ferromagnetic order is stable
within the superconducting phase (neutron scattering experiments). iii) The
specific heat anomaly associated with the superconductivity in these materials
appears to be absent. The specific heat depends on the temperature linearly at
low temperature.
  I present a review of the recent experimental results and the basic
theoretical ideas concerning ferromagnetic superconductivity
(FM-superconductivity) induced by the ferromagnetic spin fluctuations. A
particular attention is paid to the magnon exchange mechanism of
FM-superconductivity.",0405371v2
2005-01-08,Silver paint as a soldering agent for DyBaCuO single-domains welding,"Silver paint has been tested as a soldering agent for DyBaCuO single-domain
welding. Junctions have been manufactured on Dy-Ba-Cu-O single-domains cut
either along planes parallel to the c-axis or along the ab-planes.
Microstructural and superconducting characterisations of the samples have been
performed. For both types of junctions, the microstructure in the joined area
is very clean: no secondary phase or Ag particles segregation has been
observed. Electrical and magnetic measurements for all configurations of
interest are reported $\rho(T)$ curves, and Hall probe mapping). The narrow
resistive superconducting transition reported for all configurations shows that
the artificial junction does not affect significantly the measured
superconducting properties of the material.",0501163v1
2005-01-19,Magnetism and Transport in YbMn2Sb2,"A new ternary intermetallic compound, namely, YbMn2Sb2, has been synthesized
and its magnetic and electrical transport properties have been studied in the
temperature range of 2 to 300 K. This compound crystallizes in a trigonal,
La2O2S type structure (space group P3bm1, No. 164) and is found to be
ferromagnetically ordered at room temperature. The magnetism is attributed to
the ordering of Mn sublattice. M5 xray absorption spectrum of YbMn2Sb2 obtained
at room temperature suggests that the valency of Yb in this compound is close
to 2. Electrical resistivity of this compound is metal like and a positive
magnetoresistance of 13 percent is observed at 5 K in an applied field of 9T.
Key words Rare earth intermetallics and alloys, Magnetic properties, Xray
absorption spectroscopy, Electrical transport.",0501450v1
2005-03-08,Ultra low threshold current THz quantum cascade lasers based on buried strip-waveguides,"THz quantum cascade lasers based on a novel buried cavity geometry are
demonstrated by combining double-metal waveguides with proton implantation.
Devices are realised with emission at 2.8 THz, displaying ultra low threshold
currents of 19 mA at 4K in both pulsed and continuous wave operation. Thanks to
the semiconductor material on both sides of the active region and to the narrow
width of the top metal strip, the thermal properties of these devices have been
greatly improved. A decrease of the thermal resistance by over a factor of two
compared to standard ridge double-metal lasers of similar size has been
measured.",0503186v1
2005-06-17,Theory of spin-polarized transport in ferromagnet-semiconductor structures: Unified description of ballistic and diffusive transport,"A theory of spin-polarized electron transport in ferromagnet-semiconductor
heterostructures, based on a unified semiclassical description of ballistic and
diffusive transport in semiconductors, is outlined. The aim is to provide a
framework for studying the interplay of spin relaxation and transport mechanism
in spintronic devices. Transport inside the (nondegenerate) semiconductor is
described in terms of a thermoballistic current, in which electrons move
ballistically in the electric field arising from internal and external
electrostatic potentials, and are thermalized at randomly distributed
equilibration points. Spin relaxation is allowed to take place during the
ballistic motion. For arbitrary potential profile and arbitrary values of the
momentum and spin relaxation lengths, an integral equation for a spin transport
function determining the spin polarization in the semiconductor is derived. For
field-driven transport in a homogeneous semiconductor, the integral equation
can be converted into a second-order differential equation that generalizes the
spin drift-diffusion equation. The spin-polarization in ferromagnet
semiconductor structures is obtained by matching the spin-resolved chemical
potentials at the interfaces, with allowance for spin-selective interface
resistances. Illustrative examples are considered.",0506441v1
2006-02-06,Non-collinear Magnetoelectronics,"The electron transport properties of hybrid ferromagnetic|normal metal
structures such as multilayers and spin valves depend on the relative
orientation of the magnetization direction of the ferromagnetic elements.
Whereas the contrast in the resistance for parallel and antiparallel
magnetizations, the so-called Giant Magnetoresistance, is relatively well
understood for quite some time, a coherent picture for non-collinear
magnetoelectronic circuits and devices has evolved only recently. We review
here such a theory for electron charge and spin transport with general
magnetization directions that is based on the semiclassical concept of a vector
spin accumulation. In conjunction with first-principles calculations of
scattering matrices many phenomena, e.g. the current-induced spin-transfer
torque, can be understood and predicted quantitatively for different material
combinations.",0602151v1
2006-02-27,"Relating supercooling and glass-like arrest of kinetics for phase separated systems: studies on doped CeFe$_2$ and (La,Pr,Ca)MnO$_3$","Coexisting ferromagnetic and antiferromagnetic phases over a range of
temperature as well as magnetic field have been reported in many materials of
current interest, showing disorder-broadened 1st order transitions. Anomalous
history effects observed in magnetization and resistivity are being explained
invoking the concepts of kinetic arrest akin to glass transitions. From
magnetization measurements traversing novel paths in field-temperature space,
we obtain the intriguing result that the regions of the sample which can be
supercooled to lower temperatures undergo kinetic-arrest at higher
temperatures, and vice versa. Our results are for two diverse systems viz. the
inter-metallic doped CeFe$_2$ which has an antiferromagnetic ground state, and
the oxide La-Pr-Ca-Mn-O which has a ferromagnetic ground state, indicating the
possible universality of this effect of disorder on the widely encountered
phenomenon of glass-like arrest of kinetics.",0602627v1
2006-06-09,The magnetotransport properties of La0.7Sr0.3MnO3/BaTiO3 superlattices grown by pulsed laser deposition technique,"We have investigated the magnetotransport properties of La0.7Sr0.3MnO3/BaTiO3
superlattices, grown on SrTiO3 substrate by pulsed laser deposition technique,
both with current-in-plane and current-perpendicular-to-the-plane directions.
Several features indicate the presence of magnetic inhomogeneities at the
interfaces which is independent of BaTiO3 layer thickness variation. First, the
magnetic property in the superlattices decreases. Second, a hysteresis in
magnetoresistance due to the relaxation of the resistive state is observed.
Third, a threshold under an applied magnetic field in the magnetoresistance is
seen. Such behaviors are in agreement with the phase separation scenario which
could be the possible reason for these magnetic inhomogeneities at the
interfaces. On the contrary, the magnetoresistance with the
current-perpendicular-to-the-plane direction is mostly attributed to the
tunneling effect along with the ordering of the spin at the interface. This
study confirms the importance of the interfaces in superlattices that can be
used to control novel physical properties in oxide materials.",0606232v1
2006-06-30,Synthesis of VO_2 Nanowire and Observation of the Metal-Insulator Transition,"We have fabricated crystalline nanowires of VO_2 using a new synthetic
method. A nanowire synthesized at 650^oC shows the semiconducting behavior and
a nanowire at 670^oC exhibits the first-order metal-insulator transition which
is not the one-dimensional property. The temperature coefficient of resistance
in the semiconducting nanowire is 7.06 %/K at 300 K, which is higher than that
of commercial bolometer.",0606793v1
2006-11-17,Evolution in Materio: Exploiting the Physics of Materials for Computation,"We describe several techniques for using bulk matter for special purpose
computation. In each case it is necessary to use an evolutionary algorithm to
program the substrate on which the computation is to take place. In addition,
the computation comes about as a result of nearest neighbour interactions at
the nano- micro- and meso-scale. In our first example we describe evolving a
saw-tooth oscillator in a CMOS substrate. In the second example we demonstrate
the evolution of a tone discriminator by exploiting the physics of liquid
crystals. In the third example we outline using a simulated magnetic quantum
dot array and an evolutionary algorithm to develop a pattern matching circuit.
Another example we describe exploits the micro-scale physics of charge density
waves in crystal lattices. We show that vastly different resistance values can
be achieved and controlled in local regions to essentially construct a
programmable array of coupled micro-scale quasiperiodic oscillators. Lastly we
show an example where evolutionary algorithms could be used to control density
modulations, and therefore refractive index modulations, in a fluid for optical
computing.",0611462v1
2006-12-23,Magnetic phase diagram of Ce2Fe17,"Rare-earth-based permanent-magnet materials rich in iron have relatively low
ferromagnetic ordering temperatures. This is believed to be due to the presence
of antiferromagnetic exchange interactions, besides the ferromagnetic
interactions responsible for the magnetic order. The magnetic properties of
Ce2Fe17 are anomalous. Instead of ferromagnetic, it is antiferromagnetic, and
instead of one ordering temperature, it shows two, at the Neel temperature TN ~
208 K and at TT ~ 124 K. Ce2Fe17, doped by 0.5% Ta, also shows two ordering
temperatures, one to an antiferromagnetic phase, at TN ~ 214 K, and one to a
ferromagnetic phase, at T0 ~ 75 K. In order to clarify this behavior,
single-crystalline samples were prepared by solution growth, and characterized
by electron microscopy, single crystal x-ray diffraction, temperature-dependent
specific heat, and magnetic field and temperature-dependent electrical
resistivity and magnetization. From these measurements, magnetic H-T phase
diagrams were determined for both Ta-doped Ce2Fe17 and undoped Ce2Fe17. These
phase diagrams can be very well described in terms of a theory that gives
magnetic phase diagrams of systems with competing antiferro- and
ferromagnetism.",0612603v1
2006-05-06,Radiation enhancement and radiation suppression by a left-handed metamaterial,"The perfect lens property of a dispersive and lossy left-handed metamaterial
(LHM) disk is exploited to superimpose a source of electromagnetic radiation
onto its mirror image, formed as a result of reflection from a perfect electric
conductor (PEC) or a perfect magnetic conductor (PMC). The superposition of a
vertical wire-dipole antenna with its PEC-image results in an increase of the
radiation resistance of the antenna compared to that of an antenna emitting in
free space. On the other hand, if the same antenna is coupled to a PMC-image it
is shown that the result is the formation of a non-radiating configuration. The
finite-difference time-domain (FDTD) analysis is performed and this allows a
detailed characterization of the systems. It is shown that the non-radiating
system allows relatively large amounts of electromagnetic energy to be stored
in the LHM-disk and that is indicative of strong electromagnetic fields inside
the material. This property is employed in a second-harmonic generation (SHG)
process and the potential of a non-radiating configuration as an efficient
nonlinear device is demonstrated.",0605055v1
2006-07-25,"Superconductivity: coherent ""tunnelling"" by a dielectric array of charge-carriers","Superconduction manifests when a steady-state current flows through a
material without an electric field being present. It is argued here that the
absence of scattering of the charge-carriers, although absolutely necessary, is
not sufficient to explain why an electric field is zero when a current flows
between two contacts to a superconducting material. It is concluded that an
electric field, and thus a resistance, must manifest unless (i) the
charge-carriers form part of an array of dielectric charge centres, and (ii)
the charge-carriers can increase their velocities without increasing their
kinetic energies. A model is propoased which allows these requirements to
manifest. The model is fitted to selected experimental results which have been
published for low temperature metals, YBCO, and highly-doped p-type diamond. In
each case a satisfactory description of the experimental results is
demonstrated.",0607227v1
2005-04-05,Reduction of Magnetic Noise in Atom Chips by Material Optimization,"We discuss the contribution of the material type in metal wires to the
electromagnetic fluctuations in magnetic microtraps close to the surface of an
atom chip. We show that significant reduction of the magnetic noise can be
achieved by replacing the pure noble metal wires with their dilute alloys. The
alloy composition provides an additional degree of freedom which enables a
controlled reduction of both magnetic noise and resistivity if the atom chip is
cooled. In addition, we provide a careful re-analysis of the magnetically
induced trap loss observed by Yu-Ju Lin et al. [Phys. Rev. Lett. 92, 050404
(2004)] and find good agreement with an improved theory.",0504027v2
2007-04-20,Transport measurements across a tunable potential barrier in graphene,"The peculiar nature of electron scattering in graphene is among many exciting
theoretical predictions for the physical properties of this material. To
investigate electron scattering properties in a graphene plane, we have created
a gate-tunable potential barrier within a single-layer graphene sheet. We
report measurements of electrical transport across this structure as the
tunable barrier potential is swept through a range of heights. When the barrier
is sufficiently strong to form a bipolar junctions (npn or pnp) within the
graphene sheet, the resistance across the barrier sharply increases. We compare
these results to predictions for both diffusive and ballistic transport, as the
barrier rises on a length scale comparable to the mean free path. Finally, we
show how a magnetic field modifies transport across the barrier.",0704.2626v2
2007-05-16,Ab initio estimate of temperature dependence of electrical conductivity in a model amorphous material: hydrogenated amorphous silicon,"We present an ab initio calculation of the DC conductivity of amorphous
silicon and hydrogenated amorphous silicon. The Kubo-Greenwood formula is used
to obtain the DC conductivity, by thermal averaging over extended dynamical
simulation. Its application to disordered solids is discussed. The conductivity
is computed for a wide range of temperatures and doping is explored in a naive
way by shifting the Fermi level. We observed the Meyer-Neldel rule for the
electrical conductivity with E_MNR = 0.06 eV and a temperature coefficient of
resistance, TCR ~ -2.0% K^-1 for a-Si:H. In general, experimental trends are
reproduced by these calculations, and this suggests the possible utility of the
approach for modeling carrier transport in other disordered systems.",0705.2384v3
2007-07-08,Tensoresistive Effect in Single Crystal Microwires of Pbte Doped with Tl,"Results of room temperature measurements of tensoresistive effect of thin
single crystal microwires of Pb1-xTlxTe (x=0.0000 - 0.0025, d = 5 - 20
micrometers) obtained from the melted compound of corresponding composition by
the filling of quartz capillary with the following crystallization of material
are presented. For the samples corresponding to chemical composition with
concentration of thallium x ~0,0025 an essential increase of tensoresistive
effect (resistance changes for elastic elongations per unit length of a
crystal) in comparison with nondoped samples is observed. Various mechanisms
which can lead to observable anomalies, including resonance scattering are
discussed. Obtained experimental results allow us to suppose that the observed
peculiarities can be interpreted on the basis of model of an impurity band of
Tl in PbTe.",0707.1124v1
2007-08-13,"Orbital Ordering Structures in (Nd,Pr)0.5Sr0.5MnO3 Manganite Thin Films on Perovskite (011) Substrates","Structural study of orbital-ordered manganite thin films has been conducted
using synchrotron radiation, and a ground state electronic phase diagram is
made. The lattice parameters of four manganite thin films, Nd0.5Sr0.5MnO3
(NSMO) or Pr0.5Sr0.5MnO3 (PSMO) on (011) surfaces of SrTiO3 (STO) or
[(LaAlO3){0.3}(SrAl0.5Ta0.5O3){0.7}] (LSAT), were measured as a function of
temperature. The result shows, as expected based on previous knowledge of bulk
materials, that the films' resistivity is closely related to their structures.
Observed superlattice reflections indicate that NSMO thin films have an
antiferro-orbital-ordered phase as their low-temperature phase while PSMO film
on LSAT has a ferro-orbital-ordered phase, and that on STO has no
orbital-ordered phase. A metallic ground state was observed only in films
having a narrow region of A-site ion radius, while larger ions favor
ferro-orbital-ordered structure and smaller ions stabilize
antiferro-orbital-ordered structure. The key to the orbital-ordering transition
in (011) film is found to be the in-plane displacement along [0-1 1] direction.",0708.1693v1
2007-08-16,The nanostructural origin of the ac conductance in dielectric granular metals: the case study of Co_20(ZrO_2)_80,"We show which is the nanostructure required in granular Co20(ZrO2)80 thin
films to produce an ac response such as the one that is universally observed in
a very wide variety of dielectric materials. A bimodal size distribution of Co
particles yields randomly competing conductance channels which allow both
thermally assisted tunneling through small particles and capacitive conductance
among larger particles that are further apart. A model consisting on a simple
cubic random resistance-capacitor network describes quantitatively the
experimental results as functions of temperature and frequency, and enables the
determination of the microscopic parameters controlling the ac response of the
samples.",0708.2140v1
2007-08-16,Spin-transfer torques in anti-ferromagnetic metals from first principles,"In spite of the absence of a macroscopic magnetic moment, an anti-ferromagnet
is spin-polarized on an atomic scale. The electric current passing through a
conducting anti-ferromagnet is polarized as well, leading to spin-transfer
torques when the order parameter is textured, such as in anti-ferromagnetic
non-collinear spin valves and domain walls. We report a first principles study
on the electronic transport properties of anti-ferromagnetic systems. The
current-induced spin torques acting on the magnetic moments are comparable with
those in conventional ferromagnetic materials, leading to measurable angular
resistances and current-induced magnetization dynamics. In contrast to
ferromagnets, spin torques in anti-ferromagnets are very nonlocal. The torques
acting far away from the center of an anti-ferromagnetic domain wall should
facilitate current-induced domain wall motion.",0708.2143v2
2007-12-11,Frequency- and electric-field-dependent conductivity of single-walled carbon nanotube networks of varying density,"We present measurements of the frequency and electric field dependent
conductivity of single walled carbon nanotube(SWCNT) networks of various
densities. The ac conductivity as a function of frequency is consistent with
the extended pair approximation model and increases with frequency above an
onset frequency $\omega_0$ which varies over seven decades with a range of film
thickness from sub-monolayer to 200 nm. The nonlinear electric field-dependent
DC conductivity shows strong dependence on film thickness as well. Measurement
of the electric field dependence of the resistance R(E) allows for the
determination of a length scale $L_{E}$ possibly characterizing the distance
between tube contacts, which is found to systematically decrease with
increasing film thickness. The onset frequency $\omega_0$ of ac conductivity
and the length scale $L_{E}$ of SWCNT networks are found to be correlated, and
a physically reasonable empirical formula relating them has been proposed. Such
studies will help the understanding of transport properties and benefit the
applications of this material system.",0712.1733v3
2007-12-21,Kinks in the electronic specific heat,"We find that the heat capacity of a strongly correlated metal presents
striking changes with respect to Landau Fermi liquid theory. In contrast with
normal metals, where the electronic specific heat is linear at low temperature
(with a T^3 term as a leading correction), a dynamical mean-field study of the
correlated Hubbard model reveals a clear kink in the temperature dependence,
marking a rapid change from a low-temperature linear behavior and a second
linear regime with a reduced slope. Experiments on LiV2O4 support our findings,
implying that correlated materials are more resistive to cooling at low T than
expected from the intermediate temperature behavior.",0712.3723v2
2008-01-07,Utility of transient testing to characterize thermal interface materials,"This paper analyzes a transient method for the characterization of
low-resistance thermal interfaces of microelectronic packages. The transient
method can yield additional information about the package not available with
traditional static methods at the cost of greater numerical complexity,
hardware requirements, and sensitivity to noise. While the method is
established for package-level thermal analysis of mounted and assembled parts,
its ability to measure the relatively minor thermal impedance of thin thermal
interface material (TIM) layers has not yet been fully studied. We combine the
transient thermal test with displacement measurements of the bond line
thickness to fully characterize the interface.",0801.1009v1
2008-03-05,Giant room temperature piezoresistance in a metal/silicon hybrid,"Metal/semiconductor hybrids are artificially created structures presenting
novel properties not exhibited by either of the component materials alone. Here
we present a giant piezoresistance effect in a hybrid formed from silicon and
aluminum. The maximum piezoresistive gage factor (GF) of 843, measured at room
temperature, compares with a GF of -93 measured in the bulk homogeneous
silicon. This piezoresistance boost is not due to the silicon/aluminum
interface, but results from a stress induced anisotropy in the silicon
conductivity that acts to switch current away from the highly conductive
aluminum for uniaxial tensile strains. Its magnitude is shown, via the
calculation of hybrid resistivity weighting functions, to depend only on the
geometrical arrangement of the component parts of the hybrid.",0803.0655v1
2008-04-02,"Physical properties of the new Uranium ternary compounds U3Bi4M3 (M=Ni, Rh)","We report the properties of two new isostructural compounds, U3Bi4Ni3 and
U3Bi4Rh3. The first of these compounds is non-metallic, and the second is a
nearly ferromagnetic metal, both as anticipated from their electron count
relative to other U-based members of the larger 3-4-3 family. For U3Bi4Rh3, a
logarithmic increase of C/T below 3 K, a resistivity proportional to T^4/3, and
the recovery of Fermi-liquid behavior in both properties with applied fields
greater than 3T, suggest that U3Bi4Rh3 may be a new example of a material
displaying ferromagnetic quantum criticality.",0804.0393v1
2008-11-19,Intrinsic Response of Graphene Vapor Sensors,"Graphene is a purely two-dimensional material that has extremely favorable
chemical sensor properties. It is known, however, that conventional
nanolithographic processing typically leaves a resist residue on the graphene
surface, whose impact on the sensor characteristics of the system has not yet
been determined. Here we show that the contamination layer both degrades the
electronic properties of the graphene and masks graphene s intrinsic sensor
responses. The contamination layer chemically dopes the graphene, enhances
carrier scattering, and acts as an absorbent layer that concentrates analyte
molecules at the graphene surface, thereby enhancing the sensor response. We
demonstrate a cleaning process that verifiably removes the contamination on the
device structure and allows the intrinsic chemical responses of graphene to be
measured.",0811.3091v1
2009-03-19,Superconductivity at 17 K in (Fe2P2)(Sr4Sc2O6): a new superconducting layered pnictide oxide with a thick perovskite oxide layer,"A new layered oxypnictide (Fe2P2)(Sr4Sc2O6) have been synthesized by
solid-state reaction. This material has an alternating layer stacking structure
of anti-fluorite Fe2P2 and perovskite-based Sr4Sc2O6 oxide layers. Space group
of the material is P4/nmm and lattice constants a and c are 4.016 A and 15.543
A, respectively. The interlayer Fe-Fe distance corresponding to the c-axis
length is the longest ever reported in the iron-based oxypnictide systems. In
both magnetization and resistivity measurements, the present compound exhibited
superconductivity below 17 K, which is much higher than that of LaFePO and the
highest in arsenic-free iron-based oxypnictide systems under ambient pressure.",0903.3314v3
2009-05-27,Precision Cutting and Patterning of Graphene with Helium Ions,"We report nanoscale patterning of graphene using a helium ion microscope
configured for lithography. Helium ion lithography is a direct-write
lithography process, comparable to conventional focused ion beam patterning,
with no resist or other material contacting the sample surface. In the present
application, graphene samples on Si/SiO2 substrates are cut using helium ions,
with computer controlled alignment, patterning, and exposure. Once suitable
beam doses are determined, sharp edge profiles and clean etching are obtained,
with little evident damage or doping to the sample. This technique provides
fast lithography compatible with graphene, with ~15 nm feature sizes.",0905.4407v2
2009-06-08,Tunneling electroresistance effect in ferroelectric tunnel junctions at the nanoscale,"Stable and switchable polarization of ferroelectric materials opens a
possibility to electrically control their functional behavior. A particularly
promising approach is to employ ferroelectric tunnel junctions where the
polarization reversal in a ferroelectric barrier changes the tunneling current
across the junction. Here, we demonstrate the reproducible tunneling
electroresistance effect using a combination of Piezoresponse Force Microscopy
(PFM) and Conducting Atomic Force Microscopy (C-AFM) techniques on
nanometer-thick epitaxial BaTiO3 single crystal thin films on SrRuO3 bottom
electrodes. Correlation between ferroelectric and electronic transport
properties is established by the direct nanoscale visualization and control of
polarization and tunneling current in BaTiO3 films. The obtained results show a
change in resistance by about two orders of magnitude upon polarization
reversal on a lateral scale of 20 nm at room temperature. These results are
promising for employing ferroelectric tunnel junctions in non-volatile memory
and logic devices, not involving charge as a state variable.",0906.1521v1
2009-06-30,"Electric field effects, Mott insulator, Surface patterning, Scanning tunneling microscopy, Transition metal chalcogenides","We report the first experimental evidence for a strong electromechanical
coupling in the Mott insulator GaTa4Se8 allowing a highly reproducible
nano-writing with a Scanning Tunneling Microscope (STM). The local electric
field across the STM junction is observed to have a threshold value above which
the clean (100) surface of GaTa4Se8 becomes mechanically instable: At voltage
biases V > 1.1V the surface suddenly inflates and comes in contact with the STM
tip, resulting in nanometer size craters. The formed pattern can be
indestructibly ""read"" by STM at lower voltage bias, thus allowing a 5
Tdots/inch2 dense writing/reading at room temperature. The discovery of the
electromechanical coupling in GaTa4Se8 might give new clues in the
understanding of the Electric Pulse Induced Resistive Switching recently
observed in this stoechiometric Mott insulator.",0906.5473v1
2009-11-30,Kondo-like behaviors in magnetic and thermal properties of single crystal Tm5Si2Ge2,"We grew the single crystal of stoichiometric Tm5Si2.0Ge2.0 using a Bridgeman
method and performed XRD, EDS, magnetization, ac and dc magnetic
susceptibilities, specific heat, electrical resistivity and XPS experiments. It
crystallizes in orthorhombic Sm5Ge4-type structure. The mean valence of Tm ions
in Tm5Si2.0Ge2.0 is almost trivalent. The 4f states is split by the crystalline
electric field. The ground state exhibits the long range antiferromagnetic
order with the ferromagnetically coupled magnetic moments in the ac plane below
8.01 K, while the exited states exhibit the reduction of magnetic moment and
magnetic entropy and -log T-behaviors observed in Kondo materials.",0911.5640v1
2009-12-05,Theory and Simulation of Spin Transport in Antiferromagnetic Semiconductors: Application to MnTe,"We study in this paper the parallel spin current in an antiferromagnetic
semiconductor thin film where we take into account the interaction between
itinerant spins and lattice spins. The spin model is an anisotropic Heisenberg
model. We use here the Boltzmann's equation with numerical data on cluster
distribution obtained by Monte Carlo simulations and cluster-construction
algorithms. We study the cases of degenerate and non-degenerate semiconductors.
The spin resistivity in both cases is shown to depend on the temperature with a
broad maximum at the transition temperature of the lattice spin system. The
shape of the maximum depends on the spin anisotropy and on the magnetic field.
It shows however no sharp peak in contrast to ferromagnetic materials. Our
method is applied to MnTe. Comparison to experimental data is given.",0912.0989v4
2010-05-14,Effect of phonon dispersion on thermal conduction across Si/Ge interfaces,"We report finite-volume simulations of the phonon Boltzmann transport
equation (BTE) for heat conduction across the heterogeneous interfaces in SiGe
superlattices. The diffuse mismatch model incorporating phonon dispersion and
polarization is implemented over a wide range of Knudsen numbers. The results
indicate that the thermal conductivity of a Si/Ge superlattice is much lower
than that of the constitutive bulk materials for superlattice periods in the
submicron regime. We report results for effective thermal conductivity of
various material volume fractions and superlattice periods. Details of the
non-equilibrium energy exchange between optical and acoustic phonons that
originate from the mismatch of phonon spectra in silicon and germanium are
delineated for the first time. Conditions are identified for which this effect
can produce significantly more thermal resistance than that due to boundary
scattering of phonons.",1005.2578v1
2010-07-22,Anisotropic weakly localized transport in nitrogen-doped ultrananocrystalline diamond films,"We establish the dominant effect of anisotropic weak localization (WL) in
three dimensions associated with a propagative Fermi surface, on the
conductivity correction in heavily nitrogen doped ultrananocrystalline diamond
(UNCD) films based on magneto-resistance studies at low temperatures. Also, low
temperature electrical conductivity can show weakly localized transport in 3D
combined with the effect of electron-electron interactions in these materials,
which is remarkably different from the conductivity in 2DWL or strong
localization regime. The corresponding dephasing time of electronic
wavefunctions in these systems described as ~ T^-p with p < 1, follows a
relatively weak temperature dependence compared to the generally expected
nature for bulk dirty metals having $p \geq 1$. The temperature dependence of
Hall (electron) mobility together with an enhanced electron density has been
used to interpret the unusual magneto-transport features and show delocalized
electronic transport in these n-type UNCD films, which can be described as
low-dimensional superlattice structures.",1007.3918v2
2010-09-01,Anomalous scattering in superconducting indium-doped tin telluride,"Results of resistivity, Hall effect, magnetoresistance, susceptibility and
heat capacity measurements are presented for single crystals of indium-doped
tin telluride with compositions Sn$_{.988-x}$In$_x$Te where $0 \leq x \leq 8.4
%$, along with microstructural analysis based on transmission electron
microscopy. For small indium concentrations, $x \leq 0.9 %$ the material does
not superconduct above 0.3 K, and the transport properties are consistent with
simple metallic behavior. For $x \geq 2.7 %$ the material exhibits anomalous
low temperature scattering and for $x \geq 6.1 %$ bulk superconductivity is
observed with critical temperatures close to 2 K. Intermediate indium
concentrations $2.7% \leq x \leq 3.8%$ do not exhibit bulk superconductivity
above 0.7 K. Susceptibility data indicate the absence of magnetic impurities,
while magnetoresistance data are inconsistent with localization effects,
leading to the conclusion that indium-doped SnTe is a candidate charge Kondo
system, similar to thallium-doped PbTe.",1009.0090v1
2010-09-06,Understanding adhesion at as-deposited interfaces from ab initio thermodynamics of deposition growth: thin-film alumina on titanium carbide,"We investigate the chemical composition and adhesion of chemical vapour
deposited thin-film alumina on TiC using and extending a recently proposed
nonequilibrium method of ab initio thermodynamics of deposition growth (AIT-DG)
[Rohrer J and Hyldgaard P 2010 Phys. Rev. B 82 045415]. A previous study of
this system [Rohrer J, Ruberto C and Hyldgaard P 2010 J. Phys.: Condens. Matter
22 015004] found that use of equilibrium thermodynamics leads to predictions of
a non-binding TiC/alumina interface, despite the industrial use as a
wear-resistant coating. This discrepancy between equilibrium theory and
experiment is resolved by the AIT-DG method which predicts interfaces with
strong adhesion. The AIT-DG method combines density functional theory
calculations, rate-equation modelling of the pressure evolution of the
deposition environment and thermochemical data. The AIT-DG method was
previously used to predict prevalent terminations of growing or as-deposited
surfaces of binary materials. Here we extent the method to predict surface and
interface compositions of growing or as-deposited thin films on a substrate and
find that inclusion of the nonequilibrium deposition environment has important
implications for the nature of buried interfaces.",1009.1027v1
2010-09-07,Phase coherent transport in SrTiO3/LaAlO3 interfaces,"The two dimensional electron gas formed between the two band insulators
SrTiO3 and LaAlO3 exhibits a variety of interesting physical properties which
make it an appealing material for use in future spintronics and/or quantum
computing devices. For this kind of applications electrons have to retain their
phase memory for sufficiently long times or length. Using a mesoscopic size
device we were able to extract the phase coherence length, and its temperature
variation. We find the dephasing rate to have a power law dependence on
temperature. The power depends on the temperature range studied and sheet
resistance as expected from dephasing due to strong electron-electron
interactions.",1009.1273v1
2010-10-11,Restoring the electrical conductivity of graphene oxide films by UV light induced oxygen desorption,"We report a chemical free method for the reduction of graphene oxide (GO)
thin films. It was observed how for GO films annealed in air the oxygen species
desorb from the GO surface upon exposure to UV light and how the surface
resistivity of such deoxygenated GO films decreases with increasing the
exposure to the UV light. The obtained results open a clean as well as easy
route for the integration of GO based materials into optoelectronic devices.",1010.2108v4
2010-11-12,Memory effects in complex materials and nanoscale systems,"Memory effects are ubiquitous in nature and are particularly relevant at the
nanoscale where the dynamical properties of electrons and ions strongly depend
on the history of the system, at least within certain time scales. We review
here the memory properties of various materials and systems which appear most
strikingly in their non-trivial time-dependent resistive, capacitative and
inductive characteristics. We describe these characteristics within the
framework of memristors, memcapacitors and meminductors, namely memory circuit
elements whose properties depend on the history and state of the system. We
examine basic issues related to such systems and critically report on both
theoretical and experimental progress in understanding their functionalities.
We also discuss possible applications of memory effects in various areas of
science and technology ranging from digital to analog electronics,
biologically-inspired circuits, and learning. We finally discuss future
research opportunities in the field.",1011.3053v1
2010-12-13,The split-ring Josephson resonator as an artificial atom,"Using the resistive-shunted-junction model we show that a split-ring
Josephson oscillator or radio-frequency SQUID in the hysteretic regime is
similar to an atomic system. It has a number of stationary states that we
characterize. Applying a short magnetic pulse we switch the system from one
state to another. These states can be detected via the reflection of a small
amplitude signal forming the base of a new spectroscopy.",1012.2833v1
2010-12-23,Memristive Systems Analysis of 3-Terminal Devices,"Memristive systems were proposed in 1976 by Leon Chua and Sung Mo Kang as a
model for 2-terminal passive nonlinear dynamical systems which exhibit memory
effects. Such systems were originally shown to be relevant to the modeling of
action potentials in neurons in regards to the Hodgkin-Huxley model and, more
recently, to the modeling of thin film materials such as TiO2-x proposed for
non-volatile resistive memory. However, over the past 50 years a variety of
3-terminal non-passive dynamical devices have also been shown to exhibit memory
effects similar to that predicted by the memristive system model. This article
extends the original memristive systems framework to incorporate 3-terminal,
non-passive devices and explains the applicability of such dynamic systems
models to 1) the Widrow-Hoff memistor, 2) floating gate memory cells, and 3)
nano-ionic FETs.
  Keywords-memristive systems, memistor, transconductance, synaptic transistor,
non-linear dynamic systems",1012.5124v1
2011-01-14,Ni-Mn-Ga films in the austenite and the martensite structures at room temperature: Uniaxial texturation and epitaxial growth,"Ni-Mn-Ga films in the austenite and the martensite structures at room
temperature have been obtained using the DC magnetron sputtering technique. Two
elaboration processes were studied. A first batch of samples was deposited
using a resist sacrificial layer in order to release the film from the
substrate before vacuum annealing. This process leads to polycrystalline films
with a strong (022) fiber texture. The martensitic phase transformation of such
polycrystalline freestanding films has been studied by optical and scanning
electron microscopy. A second batch of samples was grown epitaxially on
(100)MgO substrates using different deposition temperatures. The texture has
been analyzed with four-circle X-ray diffraction. Epitaxial films crystallized
both in the austenite and the martensite structures at room temperature have
been studied.",1101.2811v1
2011-01-31,Yielding and irreversible deformation below the microscale: Surface effects and non-mean-field plastic avalanches,"Nanoindentation techniques recently developed to measure the mechanical
response of crystals under external loading conditions reveal new phenomena
upon decreasing sample size below the microscale. At small length scales,
material resistance to irreversible deformation depends on sample morphology.
Here we study the mechanisms of yield and plastic flow in inherently small
crystals under uniaxial compression. Discrete structural rearrangements emerge
as series of abrupt discontinuities in stress-strain curves. We obtain the
theoretical dependence of the yield stress on system size and geometry and
elucidate the statistical properties of plastic deformation at such scales. Our
results show that the absence of dislocation storage leads to crucial effects
on the statistics of plastic events, ultimately affecting the universal scaling
behavior observed at larger scales.",1102.0019v2
2011-05-11,Linear magnetoresistance in commercial n-type silicon due to inhomogeneous doping,"Free electron theory tells us that resistivity is independent of magnetic
field. In fact, most observations match the semiclassical prediction of a
magnetoresistance that is quadratic at low fields before saturating. However, a
non-saturating linear magnetoresistance has been observed in exotic
semiconductors such as silver chalcogenides, lightly-doped InSb, N-doped InAs,
MnAs-GaAs composites, PrFeAsO, and epitaxial graphene. Here we report the
observation of a large linear magnetoresistance in the ohmic regime in
commonplace commercial n-type silicon wafer. It is well-described by a
classical model of spatially fluctuating donor densities, and may be amplified
by altering the aspect ratio of the sample to enhance current-jetting:
increasing the width tenfold increased the magnetoresistance at 8 T from 445 %
to 4707 % at 35 K. This physical picture may well offer insights into the large
magnetoresistances recently observed in n-type and p-type Si in the non-ohmic
regime.",1105.2174v1
2011-05-27,Development of correlated quasiparticle conductance peak as molecule-linked gold nanoparticle films transition from Mott-insulator to metal phases,"We have studied conductance ($\it{g}$) of butanedithiol-linked gold
nanoparticle films across a percolation insulator-to-metal transition. As the
transition proceeds, electrons become itinerant (i.e. Coulomb charging and
kinetic effects are both significant), and films exhibit a previously
unobserved zero-bias conductance peak (ZBCP). The peak is much more pronounced
and easily observed using electromigration-induced break junction (BJ) contacts
rather than macroscopic 4-probe electrodes. We attribute this ZBCP to quantum
correlations amongst electrons, in view of other temperature- ($\it{T}$-) and
magnetic ($\it{B}$-) dependent measurements as well as predictions of the
Hubbard model and dynamic mean field theory in this transition regime. Metallic
film resistances ($\it{R}$'s) increase linearly with $\it{T}$, but with
suggested scattering lengths that, anomalously, are shorter than inter-atomic
distances. Similar so-called ""bad-metallic"" behaviour has been observed in
several studies of correlated systems, and is still being understood. We find
here that the anomalous $\it{R}$ behaviours are associated with the ZBCP. This
system can serve as a new test bed for studying correlated electrons and points
to a nano building-block strategy for fashioning novel correlated materials.",1105.5647v1
2011-07-31,Observation of Quantized Hall Effect and Shubnikov-de Hass Oscillations in Highly Doped Bi2Se3: Evidence for Layered Transport of Bulk Carriers,"Bi2Se3 is an important semiconductor thermoelectric material and a prototype
topological insulator. Here we report observation of Shubnikov-de Hass (SdH)
oscillations accompanied by quantized Hall resistances (Rxy) in highly-doped
n-type Bi2Se3 with bulk carrier concentrations of few 10^19 cm^-3. Measurements
under tilted magnetic fields show that the magnetotransport is 2D-like, where
only the c-axis component of the magnetic field controls the Landau level
formation. The quantized step size in 1/Rxy is found to scale with the sample
thickness, and average ~e2/h per quintuple layer (QL). We show that the
observed magnetotransport features do not come from the sample surface, but
arise from the bulk of the sample acting as many parallel 2D electron systems
to give a multilayered quantum Hall effect. Besides revealing a new electronic
property of Bi2Se3, our finding also has important implications for electronic
transport studies of topological insulator materials.",1108.0204v2
2011-08-30,"Linear magnetoresistivity in the ternary AM2B2 and A3Rh8B6 phases (A = Ca, Sr; M = Rh, Ir)","We studied the magnetoresistivity of the AM2B2 and A3Rh8B6 (A = Ca, Sr; M =
Rh, Ir) compounds within the ranges 1.8<=T<=300 K and 0<=H<=50 kOe. The
zero-field resistivity {\rho}0(T) is metallic and follows closely the
Bloch-Gr\""uneisen description. A positive, nonsaturating, and dominantly
linear-in-H magnetoresistivity was observed in all samples, including the ones
with a superconducting ground state. Such {\Delta}{\rho}T(H)/{\rho}T(0),
reaching 1200% in favorable cases, was found to be much stronger for the AM2B2
compounds and to decrease with temperature as well as when Ca is replaced by
Sr, or Rh is replaced by Ir. Finally, the general features of the observed
magnetoresistivity will be discussed in terms of the Abrikosov model for the
linear magnetoresistivity in inhomogeneous materials.",1108.5803v1
2011-09-22,Microscopic model for the ferroelectric field effect in oxide heterostructures,"A microscopic model Hamiltonian for the ferroelectric field effect is
introduced for the study of oxide heterostructures with ferroelectric
components. The long-range Coulomb interaction is incorporated as an
electrostatic potential, solved self-consistently together with the charge
distribution. A generic double-exchange system is used as the conducting
channel, epitaxially attached to the ferroelectric gate. The observed
ferroelectric screening effect, namely the charge accumulation/depletion near
the interface, is shown to drive interfacial phase transitions that give rise
to robust magnetoelectric responses and bipolar resistive switching, in
qualitative agreement with previous density functional theory calculations. The
model can be easily adapted to other materials by modifying the Hamiltonian of
the conducting channel, and it is useful in simulating ferroelectric field
effect devices particularly those involving strongly correlated electronic
components where ab-initio techniques are difficult to apply.",1109.4791v1
2011-10-09,Optimizing the Bi_(2-x)Sb_(x)Te_(3-y)Se_(y) solid solutions to approach the intrinsic topological insulator regime,"To optimize the bulk-insulating behavior in the topological insulator
materials having the tetradymite structure, we have synthesized and
characterized single-crystal samples of Bi_(2-x)Sb_(x)Te_(3-y)Se_(y) (BSTS)
solid solution at various compositions. We have elucidated that there are a
series of ""intrinsic"" compositions where the acceptors and donors compensate
each other and present a maximally bulk-insulating behavior. At such
compositions, the resistivity can become as large as several Ohmcm at low
temperature and one can infer the role of the surface-transport channel in the
non-linear Hall effect. In particular, the composition of Bi1.5Sb0.5Te1.7Se1.3
achieves the lowest bulk carrier density and appears to be best suited for
surface transport studies.",1110.1788v1
2011-10-24,Ni(111)|Graphene|h-BN Junctions as Ideal Spin Injectors,"Deposition of graphene on top of hexagonal boron nitride (h-BN) was very
recently demonstrated while graphene is now routinely grown on Ni. Because the
in-plane lattice constants of graphite, h-BN, graphite-like BC2N and of the
close-packed surfaces of Co, Ni and Cu match almost perfectly, it should be
possible to prepare ideal interfaces between these materials which are
respectively, a semimetal, insulator, semiconductor, ferromagnetic and
nonmagnetic metals. Using parameter-free energy minimization and electronic
transport calculations, we show how h-BN can be combined with the perfect spin
filtering property of Ni|graphite and Co|graphite interfaces to make perfect
tunnel junctions or ideal spin injectors (SI) with any desired resistance-area
product.",1110.5291v1
2011-11-30,"Synthesis, Characterization, and Finite Size Effects on Electrical Transport of Nanoribbons of the Charge-Density Wave Conductor NbSe3","NbSe3 exhibits remarkable anisotropy in most of its physical properties and
has been a model system for studies of quasi-one-dimensional
charge-density-wave (CDW) phenomena. Herein, we report the synthesis,
characterization, and electrical transport of single-crystalline NbSe3
nanoribbons by a facile one-step vapour transport process involving the
transport of selenium powder onto a niobium foil substrate. Our investigations
aid the understanding of the CDW nature of NbSe3 and the growth process of the
material. They also indicate that NbSe3 nanoribbons have enhanced CDW
properties compared to those of the bulk phase due to size confinement effects,
thus expanding the search for new mesoscopic phenomena at the nanoscale level.
Single nanoribbon measurements on the electrical resistance as a function of
temperature show charge-density wave transitions at 59 K and 141 K. We also
demonstrate significant enhancement in the depinning effect and sliding regimes
mainly attributed to finite size effects.",1112.0039v1
2012-04-02,"Phase Stability, Structures and Properties of the (Bi2)m(Bi2Te3)n Natural Superlattices","The phase stability of the (Bi2)m(Bi2Te3)n natural superlattices has been
investigated through the low temperature solid state synthesis of a number of
new binary BixTe1-x compositions. Powder X-ray diffraction revealed that an
infinitely adaptive series forms for 0.44 < x < 0.70, while an unusual 2-phase
region with continuously changing compositions is observed for 0.41 < x < 0.43.
For x > 0.70, mixtures of elemental Bi and an almost constant composition
(Bi2)m(Bi2Te3)n phase are observed. Rietveld analysis of synchrotron X-ray
powder diffraction data collected on Bi2Te (m = 2, n = 1) revealed substantial
interchange of Bi and Te between the Bi2 and Bi2Te3 blocks, demonstrating that
the block compositions are variable. All investigated phase pure compositions
are degenerate semiconductors with low residual resistivity ratios and moderate
positive magnetoresistances (R/R0 = 1.05 in 9 T). The maximum Seebeck
coefficient is +80 muV K-1 for x = 0.63, leading to an estimated thermoelectric
figure of merit, zT = 0.2 at 250 K.",1204.0356v1
2012-05-16,Spin transport and spin dephasing in zinc oxide,"The wide bandgap semiconductor ZnO is interesting for spintronic applications
because of its small spin-orbit coupling implying a large spin coherence
length. Utilizing vertical spin valve devices with ferromagnetic electrodes
(TiN/Co/ZnO/Ni/Au), we study the spin-polarized transport across ZnO in
all-electrical experiments. The measured magnetoresistance agrees well with the
prediction of a two spin channel model with spin-dependent interface
resistance. Fitting the data yields spin diffusion lengths of 10.8nm (2K),
10.7nm (10K), and 6.2nm (200K) in ZnO, corresponding to spin lifetimes of 2.6ns
(2K), 2.0ns (10K), and 31ps (200K).",1205.3666v3
2012-05-28,Visualizing Landau levels of Dirac electrons in a one dimensional potential,"Using scanning tunneling spectroscopy we have measured the response of Dirac
electrons in a magnetic field to the presence of a well-defined smoothly
varying 1D periodic potential. We find that the lower index Landau level
energies reliably trace the potential variations, while the higher index levels
appear surprisingly homogeneous. Modeling the effects of the periodic potential
on the Landau level spectra, we show that the Landau level behavior encodes
information on the spatial extent of the wavefunctions. The lower index maps
reveal Landau level stripes, which would act as traps for chiral
one-dimensional modes. Our findings have important implications for transport
and magneto-resistance measurements in Dirac materials with engineered
potential landscapes.",1205.6230v2
2012-07-14,Topological phase transition induced by random substitution,"The transition from topologically nontrivial to a trivial state is studied by
first-principles calculations on bulk zinc-blende type
(Hg$_{1-x}$Zn$_x$)(Te$_{1-x}$S$_x$) disordered alloy series. The random
chemical disorder was treated by means of the Coherent Potential Approximation.
We found that although the phase transition occurs at the strongest disorder
regime (${x\approx 0.5}$), it is still manifested by well-defined Bloch states
forming a clear Dirac cone at the Fermi energy of the bulk disordered material.
The computed residual resistivity tensor confirm the topologically-nontrivial
state of the HgTe-rich (${x<0.5}$), and the trivial state of the ZnS-rich alloy
series (${x>0.5}$) by exhibiting the quantized behavior of the off-diagonal
spin-projected component, independently on the concentration $x$.",1207.3463v1
2012-07-23,Superconducting and thermoelectric properties of new layered Superconductor Bi4O4S3,"Polycrystalline sample of the new layered superconductor Bi4O4S3 is
successfully synthesized by solid-state reaction method by using Bi, S and
Bi2O3 powders with one step reaction. The superconducting transition
temperature (Tconset=4.5 K), the zero resistance transition temperature
(Tc0=4.07 K) and the diamagnetic transition temperature (4.02 K at H=10 Oe)
were confirmed by electrical transport and magnetic measurements. Also, our
results indicate a typical type II-superconductor behavior. In addition, a
large thermoelectric effect was observed with a dimensionless thermoelectric
figure of merit (ZT) of about 0.03 at 300K, indicating Bi4O4S3 can be a
potential thermoelectric material.",1207.5395v1
2012-09-13,Topological-Metal to Band-Insulator Transition in (Bi1-xInx)2Se3 Thin Films,"By combining transport and photo emission measurements on (Bi1-xInx)2Se3 thin
films, we report that this system transforms from a topologically non-trivial
metal into a topologically trivial band insulator through three quantum phase
transitions. At x = 3-7%, there is a transition from a topologically
non-trivial metal to a trivial metal. At x = 15%, the metal becomes a
variable-range-hopping insulator. Finally, above x = 25%, the system becomes a
true band insulator with its resistance immeasurably large even at room
temperature. This material provides a new venue to investigate topologically
tunable physics and devices with seamless gating/tunneling insulators.",1209.2840v1
2012-11-01,Spin Hall Magnetoresistance Induced by a Non-Equilibrium Proximity Effect,"We report anisotropic magnetoresistance in Pt|Y3Fe5O12 bilayers. In spite of
Y3Fe5O12 being a very good electrical insulator, the resistance of the Pt layer
reflects its magnetization direction. The effect persists even when a Cu layer
is inserted between Pt and Y3Fe5O12, excluding the contribution of induced
equilibrium magnetization at the interface. Instead, we show that the effect
originates from concerted actions of the direct and inverse spin Hall effects
and therefore call it ""spin Hall magnetoresistance.""",1211.0098v1
2012-11-07,Tuning the thermoelectric properties of SrTiO3 by controlled oxygen doping,"We report the thermoelectric properties (Seebeck coefficient, thermal
conductivity, and electrical resistivity) of lightly doped single crystals of
(001)-oriented SrTiO3 (STO). Hall effect measurements show that electron doping
around 10^-5 carriers per unit cell can be achieved by vacuum annealing of the
crystals under carefully controlled conditions. The steep density of states
near the Fermi energy of STO at this doping level (confirmed by ab initio
calculations) retains an unusually large Seebeck coefficient, in spite of an
increase in the electronic conductivity by several orders of magnitude. This
effect, combined with a decrease in thermal conductivity due to vacancy
disorder scattering makes intrinsic doping in STO (and other materials) an
alternative strategy to optimize its thermoelectric figure of merit.",1211.1615v1
2012-12-21,Multigap RPC for PET: development and optimisation of the detector design,"Transforming the resistive plate chambers from charged-particle into
gamma-quanta detectors opens the way towards their application as a basic
element of a hybrid imaging system, which combines positron emission tomography
(PET) with magnetic resonance imaging (MRI) in a single device and provides
non- and minimally- invasive quantitative methods for diagnostics. To this end,
we performed detailed investigations encompassing the whole chain from the
annihilation of the positron in the body, through the conversion of the created
photons into electrons and to the optimization of the electron yield in the
gas. GEANT4 based simulations of the efficiency of the RPC photon detectors
with different converter materials and geometry were conducted for optimization
of the detector design. The results justify the selection of a sandwich-type
gas-insulator-converter design, with Bi or Pb as converter materials.",1212.5551v1
2013-02-18,Comparative Measurements of Inverse Spin Hall and Magnetoresistance in YIG|Pt and YIG|Ta,"We report on a comparative study of spin Hall related effects and
magnetoresistance in YIG|Pt and YIG|Ta bilayers. These combined measurements
allow to estimate the characteristic transport parameters of both Pt and Ta
layers juxtaposed to YIG: the spin mixing conductance $G_{\uparrow \downarrow}$
at the YIG$|$normal metal interface, the spin Hall angle $\Theta_{SH}$, and the
spin diffusion length $\lambda_{sd}$ in the normal metal. The inverse spin Hall
voltages generated in Pt and Ta by the pure spin current pumped from YIG
excited at resonance confirm the opposite signs of spin Hall angles in these
two materials. Moreover, from the dependence of the inverse spin Hall voltage
on the Ta thickness, we extract the spin diffusion length in Ta, found to be
$\lambda_{sd}^\text{Ta}=1.8\pm0.7$ nm. Both the YIG|Pt and YIG|Ta systems
display a similar variation of resistance upon magnetic field orientation,
which can be explained in the recently developed framework of spin Hall
magnetoresistance.",1302.4416v1
2013-02-20,Anomalous metallic state above the upper critical field of the conventional three-dimensional superconductor AgSnSe2 with strong intrinsic disorder,"We report superconducting properties of AgSnSe2 which is a conventional
type-II superconductor in the very dirty limit due to intrinsically strong
electron scatterings. While this material is an isotropic three-dimensional
(3D) superconductor with a not-so-short coherence length where strong vortex
fluctuations are NOT expected, we found that the magnetic-field-induced
resistive transition at fixed temperatures becomes increasingly broader toward
zero temperature and, surprisingly, that this broadened transition is taking
place largely ABOVE the upper critical field determined thermodynamically from
the specific heat. This result points to the existence of an anomalous metallic
state possibly caused by quantum phase fluctuations in a strongly-disordered 3D
superconductor.",1302.4787v1
2013-03-06,Li$_2$RhO$_3$: A spin-glassy relativistic Mott insulator,"Motivated by the rich interplay among electronic correlation, spin-orbit
coupling (SOC), crystal-field splitting, and geometric frustrations in the
honeycomb-like lattice, we systematically investigated the electronic and
magnetic properties of Li$_2$RhO$_3$. The material is semiconducting with a
narrow band gap of $\Delta\sim$78 meV, and its temperature dependence of
resistivity conforms to 3D variable range hopping mechanism. No long-range
magnetic ordering was found down to 0.5 K, due to the geometric frustrations.
Instead, single atomic spin-glass behavior below the spin-freezing temperature
($\sim$6 K) was observed and its spin dynamics obeys the universal critical
slowing down scaling law. First principle calculations suggested it to be a
relativistic Mott insulator mediated by both electronic correlation and SOC.
With moderate strength of electronic correlation and SOC, our results shed new
light to the research of Heisenberg-Kitaev model in realistic materials.",1303.1235v2
2013-06-13,Combinatorial search of superconductivity in Fe-B composition spreads,"We have fabricated Fe-B thin film composition spreads in search of possible
superconducting phases following a theoretical prediction by Kolmogorov et
al.^1 Co-sputtering was used to deposit spreads covering a large compositional
region of the Fe-B binary phase diagram. A trace of superconducting phase was
found in the nanocrystalline part of the spread, where the film undergoes a
metal to insulator transition as a function of composition in a region with the
average composition of FeB_2. The resistance drop occurs at 4K, and a
diamagnetic signal has also been detected at the same temperature. The
superconductivity is suppressible in the magnetic field up to 2 Tesla.",1306.3024v1
2013-07-16,Correlating toughness and roughness in ductile fracture,"Three dimensional calculations of ductile crack growth under mode I plane
strain, small scale yielding conditions are carried out using an
elastic-viscoplastic constitutive relation for a progres- sively cavitating
plastic solid with two populations of void nucleating second phase particles.
Full field solutions are obtained for three dimensional material
microstructures characterized by ran- dom distributions of void nucleating
particles. Crack growth resistance curves and fracture surface roughness
statistics are calculated using standard procedures. The range of void
nucleating particle volume fractions considered give rise to values of
toughness, JIC, that vary by a factor of four. For all volume fractions
considered, the computed fracture surfaces are self-affine over a size range of
about two orders of magnitude with a roughness exponent of 0.54 $\pm$ 0.03. For
small void nucleating particle volume fractions, the mean large particle
spacing serves as a single dominant length scale. In this regime, the
correlation length of the fracture surface corresponding to the cut-off of the
self-affine behavior is found to be linearly related to JIC thus quantitatively
correlating toughness and fracture surface roughness.",1307.4413v1
2013-08-30,A linear nonequilibrium thermodynamics approach to optimization of thermoelectric devices,"Improvement of thermoelectric systems in terms of performance and range of
applications relies on progress in materials science and optimization of device
operation. In this chapter, we focuse on optimization by taking into account
the interaction of the system with its environment. For this purpose, we
consider the illustrative case of a thermoelectric generator coupled to two
temperature baths via heat exchangers characterized by a thermal resistance,
and we analyze its working conditions. Our main message is that both electrical
and thermal impedance matching conditions must be met for optimal device
performance. Our analysis is fundamentally based on linear nonequilibrium
thermodynamics using the force-flux formalism. An outlook on mesoscopic systems
is also given.",1308.6735v1
2013-09-24,Efficient Gate-tunable light-emitting device made of defective boron nitride nanotubes: from ultraviolet to the visible,"Boron nitride is a promising material for nanotechnology applications due to
its two-dimensional graphene-like, insulating, and highly-resistant structure.
Recently it has received a lot of attention as a substrate to grow and isolate
graphene as well as for its intrinsic UV lasing response. Similar to carbon,
one-dimensional boron nitride nanotubes (BNNTs) have been theoretically
predicted and later synthesised. Here we use first principles simulations to
unambiguously demonstrate that i) BN nanotubes inherit the highly efficient UV
luminescence of hexagonal BN; ii) the application of an external perpendicular
field closes the electronic gap keeping the UV lasing with lower yield; iii)
defects in BNNTS are responsible for tunable light emission from the UV to the
visible controlled by a transverse electric field (TEF). Our present findings
pave the road towards optoelectronic applications of BN-nanotube-based devices
that are simple to implement because they do not require any special doping or
complex growth.",1309.6117v1
2013-10-11,Dropping the Ball: The effect of anisotropic granular materials on ejecta and impact crater shape,"In this fluid dynamics video, we present an experimental investigation of the
shape of impact craters in granular materials. Complex crater shapes, including
polygons, have been observed in many terrestrial planets as well as moons and
asteroids. We release spherical projectiles from different heights above a
granular bed (sand). The experiments demonstrate two different techniques to
create non-circular impact craters, which we measure by digitizing the final
crater topography. In the first method, we create trenches in the sand to mimic
fault lines or valleys on a planetary target. During impact, ejecta move faster
in the direction of the trenches, creating nearly elliptical craters with the
major axis running parallel to the trench. Larger trenches lead to more oblong
craters. In the second method, a hose beneath the surface of the sand injects
nitrogen gas. The pressure of the gas counters the hydrostatic pressure of the
sand, greatly reducing static friction between grains above the injection
point, without disturbing the surface. The affected sand has lower resistance
to impact, creating a knob in the otherwise circular crater rim.",1310.3290v1
2013-10-20,Impurity effects in Cu$_2$O,"The doping of wide gap semiconductors is an interesting problem both from the
scientific and technological point of view. A well known example of this
problem is the doping of Cu$_2$O. The only element which has produced an order
of magnitude increase in the conductivity of Cu$_2$O bulk samples is chlorine,
as previously reported by us and others. However the solar cells produced with
this material do not show any improvement in performances because of the
reduction in the minority carrier diffusion length. In this paper we
investigate the effect of other impurities in order to check their possible use
as dopants and to assess their effects on the minority carrier diffusion
length. Seven impurities have been introduced by evaporation on the starting
copper sheet before the oxidation used to produce Cu$_2$O: chromium (Cr), iron
(Fe), silver (Ag), silicon (Si), sodium (Na), sulfur (S) and phosphorus (P).
The experiments show that a 20 ppm of concentration of these dopants does not
give any relevant effect neither on the resistivity, nor on the mobility. The
effect on minority carrier diffusion length is also negligible except for
sodium which produces a slight degradation of the samples.",1310.5341v1
2013-11-07,Magnetic domain and magnetic resistance phase transition in strongly correlated electronic material of perovskites junction,"The junction magnetoresistivity and domain phase transition were studied
between ZnO and La0.4Gd0.1Sr0.5CoO3 thin films grown on LaAlO3 (100) substrates
epitaxially by pulse laser deposit. The ferromagnetic transformation into
phase-separated (two phase) state was displayed below Tc~127 and has observed
that the lattice change discontinuously in the doped cobalt perovskites
La0.4Gd0.1Sr0.5CoO3. The Ginzburg-Landau phase field is introduced to deduce
antiferroelectric domain structure in LGSCO thin film. On the basis of the
domain structures, the phase boundary of thin film is strongly dependent on the
combination of electric-mechanical coupling. The phase transformation into
phase separated state occurs below Tc~127-128K, and have displayed that the
lattice constants change discontinuously at the transformation. The positive MR
of ZnO/LGSCO heterojunction exhibited the MIT behavior at 0.2 T is 4.86%, at
0.5 T is 6.05% for approximately 140K.",1311.1650v1
2013-11-17,First-principle study of octahedral tilting and Ferroelectric like transition in metallic LiOsO3,"The octahedral tilting and ferroelectric-like structural transition of LiOsO3
metallic perovskite [Nature Materials 12, 1024 (2013)] was examined using
first-principles density-functional theory. In LiOsO3, a-a-a- octahedral
titling mode is responsible for the cubic to rhombohedral structural
transition, which is stable phase at room temperature. At low temperatures, a
non-centrosymmetric transition to a rhombohedra phase was realized due to zone
center phonon softening. The phase transition behavior of LiOsO3 can be
explained fully by density functional calculations and phonon calculations. The
electronic structure and Fermi surface changes due to the electron lattice
coupling effect are also presented. The carrier density of state across the
phase transition is associated with the resistivity, heat capacity, and
susceptibility.",1311.4139v1
2014-02-24,Experimental realization of a semiconducting full Heusler compound: Fe2TiSi,"Single-phase films of the full Heusler compound Fe2TiSi have been prepared by
magnetron sputtering. The compound is found to be a semiconductor with a gap of
0.4eV. The electrical resistivity has a logarithmic temperature dependence up
to room temperature due to Kondo scattering of a dilute free electron gas off
superparamagnetic impurities. The origin of the electron gas is extrinsic due
to disorder or off-stoichiometry. Density functional theory calculations of the
electronic structure are in excellent agreement with electron energy loss,
optical, and x-ray absorption experiments. Fe2TiSi may find applications as a
thermoelectric material.",1402.5755v1
2014-03-12,Magnetoresistance of double layer hybrid system in tilted magnetic field,"Magnetoresistance and Hall coefficient of a graphene layer are investigated
in the presence of a tilted magnetic field. We consider the graphene layer is
assembled by either another graphene layer or a two-dimensional electron gas
(2DEG) and an interlayer electron-electron interaction is modeled within Random
Phase Approximation. Our calculated magnetoresistances show different
interlayer screening effects between decoupled graphene-graphene and
graphene-2DEG systems. We also analyze the dependence of dielectric materials
as well as the distance between layers on magnetoresistances. The angle
dependence of the Hall coefficient is studied and we show that a quite large
Hall resistivity occurs in the graphene layer.",1403.2857v2
2014-03-28,Doping nature of native defects in 1T-TiSe2,"The transition metal dichalcogenide 1T-TiSe2 is a quasi two-dimensional
layered material with a charge density wave (CDW) transition temperature of
TCDW 200 K. Self-doping effects for crystals grown at different temperatures
introduce structural defects, modify the temperature dependent resistivity and
strongly perturbate the CDW phase. Here we study the structural and doping
nature of such native defects combining scanning tunneling
microscopy/spectroscopy and ab initio calculations. The dominant native single
atom dopants we identify in our single crystals are intercalated Ti atoms, Se
vacancies and Se substitutions by residual iodine and oxygen.",1403.7339v2
2014-04-08,Modulation of pure spin currents with a ferromagnetic insulator,"We propose and demonstrate spin manipulation by magnetically controlled
modulation of pure spin currents in cobalt/copper lateral spin valves,
fabricated on top of the magnetic insulator Y$_3$Fe$_5$O$_{12}$ (YIG). The
direction of the YIG magnetization can be controlled by a small magnetic field.
We observe a clear modulation of the non-local resistance as a function of the
orientation of the YIG magnetization with respect to the polarization of the
spin current. Such a modulation can only be explained by assuming a finite
spin-mixing conductance at the Cu/YIG interface, as it follows from the
solution of the spin-diffusion equation. These results open a new path towards
the development of spin logics.",1404.2311v2
2014-04-10,Tunable chiral spin texture in magnetic domain-walls,"Magnetic domain-walls (DWs) with a preferred chirality exhibit very efficient
current-driven motion. Since structural inversion asymmetry (SIA) is required
for their stability, the observation of chiral domain walls in highly symmetric
Pt/Co/Pt is intriguing. Here, we tune the layer asymmetry in this system and
observe, by current-assisted DW depinning experiments, a small chiral field
which sensitively changes. Moreover, we convincingly link the observed
efficiency of DW motion to the DW texture, using DW resistance as a direct
probe for the internal orientation of the DW under the influence of in-plane
fields. The very delicate effect of capping layer thickness on the chiral field
allows for its accurate control, which is important in designing novel
materials for optimal spin-orbit-torque-driven DW motion.",1404.2945v1
2014-04-17,Extreme thermopower anisotropy and interchain transport in the quasi-one-dimensional metal Li(0.9)Mo(6)O(17),"Thermopower and electrical resistivity measurements transverse to the
conducting chains of the quasi-one-dimensional metal Li(0.9)Mo(6)O(17) are
reported in the temperature range 5 K <= T <= 500 K. For T>= 400 K the
interchain transport is determined by thermal excitation of charge carriers
from a valence band ~ 0.14 eV below the Fermi level, giving rise to a large,
p-type thermopower that coincides with a small, n-type thermopower along the
chains. This dichotomy -- semiconductor-like in one direction and metallic in a
mutually perpendicular direction -- gives rise to substantial transverse
thermoelectric (TE) effects and a transverse TE figure of merit among the
largest known for a single compound.",1404.4576v3
2014-05-15,Damage nucleation from repeated dislocation absorption at a grain boundary,"Damage nucleation from repeated dislocation absorption at a grain boundary is
simulated with molecular dynamics. At the grain boundary-dislocation
intersection site, atomic shuffling events determine how the free volume
brought by the incoming dislocation is accommodated. This process in turn
determines the crack nucleation mechanism, as well as the critical strain and
number of dislocations that can be absorbed before cracking. Slower strain
rates promote earlier crack nucleation and a damage nucleation mode where
cracking is preceded by dislocation emission. The simulation methodology
presented here can be used to probe other types of boundaries as well, although
multiple thermodynamically equivalent starting configurations are required to
quantify the damage resistance of a given grain boundary.",1405.3974v2
2014-06-04,Magnetic-Field Induced Semimetal in Topological Crystalline Insulator Thin Films,"We investigate electromagnetic properties of a topological crystalline
insulator (TCI) thin film under external electromagnetic fields. The TCI thin
film is a topological insulator indexed by the mirror-Chern number. It is
demonstrated that the gap closes together with the emergence of a pair of
gapless cones carrying opposite chirarities by applying in-plane magnetic
field. A pair of gapless points have opposite vortex numbers. This is a
reminiscence of a pair of Weyl cones in 3D Weyl semimetal. We thus present an a
magnetic-field induced semimetal-semiconductor transition in 2D material. This
is a giant-magnetoresistance, where resistivity is controlled by magnetic
field. Perpendicular electric field is found to shift the gapless points and
also renormalize the Fermi velocity in the direction of the in-plane magnetic
field.",1406.1009v2
2014-06-05,"Magnetotransport in ferromagnetic Mn5Ge3, Mn5Ge3C0.8, and Mn5Si3C0.8 thin films","The electrical resistivity, anisotropic magnetoresistance (AMR), and
anomalous Hall effect of ferromagnetic Mn5Ge3, Mn5Ge3C0.8, and Mn5Si3C0.8 thin
films has been investigated. The data show a behavior characteristic for a
ferromagnetic metal, with a linear increase of the anomalous Hall coefficient
with Curie temperature. While for ferromagnetic Mn5Si3C0.8 the normal Hall
coefficient R0 and the AMR ratio are independent of temperature, these
parameters strongly increase with temperature for the germanide films. This
difference is attributed to the different hybridization of electronic states in
the materials due different lattice parameters and different atomic
configurations (Ge vs. Si metalloid). The concomitant sign change of R0 and the
AMR ratio with temperature observed for the germanide films is discussed in a
two-current model indicating an electron-like minority-spin transport at low
temperatures.",1406.1442v1
2014-07-16,Mesoscale Imperfections in MoS2 Atomic Layers Grown by Vapor Transport Technique,"The success of isolating small flakes of atomically thin layers through
mechanical exfoliation has triggered enormous research interest in graphene and
other two-dimensional materials. For device applications, however, controlled
large-area synthesis of highly crystalline monolayers with a low density of
electronically active defects is imperative. Here, we demonstrate the
electrical imaging of dendritic ad-layers and grain boundaries in monolayer
molybdenum disulfide (MoS2) grown by vapor transport technique using microwave
impedance microscopy. The micrometer-sized precipitates in our films, which
appear as a second layer of MoS2 in conventional height and optical
measurements, show 2 orders of magnitude higher conductivity than that of the
single layer. The zigzag grain boundaries, on the other hand, are shown to be
more resistive than the crystalline grains, consistent with previous studies.
Our ability to map the local electrical properties in a rapid and
nondestructive manner is highly desirable for optimizing the growth process of
large-scale MoS2 atomic layers.",1407.4188v1
2014-07-30,Synthesis and transport properties of ternary type-I Si clathrate K8Al7Si39,"A ternary type-I Si clathrate, K8AlxSi46-x, which is a candidate functional
material composed of abundant non-toxic elements, was synthesized and its
transport properties were investigated at temperatures ranging from 10 to 320
K. The synthesized compound is confirmed to be the ternary type-I Si clathrate
K8Al7Si39 with a lattice parameter of a = 10.442 A using neutron powder
diffractometry and inductively coupled plasma optical emission spectrometry.
Electrical resistivity and Hall coefficient measurements revealed that
K8Al7Si39 is a metal with electrons as the dominant carriers at a density of
approximately 1x10^27 /m3. The value of Seebeck coefficient for K8Al7Si39 is
negative and its absolute value increases with the temperature. The temperature
dependence of the thermal conductivity is similar to that for a crystalline
solid. The dimensionless figure of merit is approximately 0.01 at 300 K, which
is comparable to that for other ternary Si clathrates.",1407.7911v2
2014-08-30,Chemical Pressure effect at the boundary of Mott insulator and itinerant electron limit of Spinel Vanadates,"The chemical pressure effect on the structural, transport, magnetic and
electronic properties (by measuring X-ray photoemission spectroscopy) of ZnV2O4
has been investigated by doping Mn and Co on the Zinc site of ZnV2O4. With Mn
doping the V-V distance increases and with Co doping it decreases. The
resistivity and thermoelectric power data indicate that as the V-V distance
decreases the system moves towards Quantum Phase Transition. The transport data
also indicate that the conduction is due to the small polaron hopping. The
chemical pressure shows the non-monotonous behaviour of charge gap and
activation energy. The XPS study also supports the observation that with
decrease of the V-V separation the system moves towards Quantum Phase
Transition. On the other hand when Ti is doped on the V-site of ZnV2O4 the
metal-metal distance decreases and at the same time the TN also increases.",1409.0106v1
2014-12-23,Temperature controlled motion of an antiferromagnet-ferromagnet interface within a dopant-graded FeRh epilayer,"Chemically ordered B2 FeRh exhibits a remarkable
antiferromagnetic-ferromagnetic phase transition that is first order. It thus
shows phase coexistence, usually by proceeding though nucleation at random
defect sites followed by propagation of phase boundary domain walls. The
transition occurs at a temperature that can be varied by doping other metals
onto the Rh site. We have taken advantage of this to yield control over the
transition process by preparing an epilayer with oppositely directed doping
gradients of Pd and Ir throughout its height, yielding a gradual transition
that occurs between 350~K and 500~K. As the sample is heated, a horizontal
antiferromagnetic-ferromagnetic phase boundary domain wall moves gradually up
through the layer, its position controlled by the temperature. This mobile
magnetic domain wall affects the magnetisation and resistivity of the layer in
a way that can be controlled, and hence exploited, for novel device
applications.",1412.7346v1
2015-01-21,Efficient Linear Scaling Approach for Computing the Kubo Hall Conductivity,"We report an order-N approach to compute the Kubo Hall conductivity for
disorderd two-dimensional systems reaching tens of millions of orbitals, and
realistic values of the applied external magnetic fields (as low as a few
Tesla). A time-evolution scheme is employed to evaluate the Hall conductivity
$\sigma_{xy}$ using a wavepacket propagation method and a continued fraction
expansion for the computation of diagonal and off-diagonal matrix elements of
the Green functions. The validity of the method is demonstrated by comparison
of results with brute-force diagonalization of the Kubo formula, using
(disordered) graphene as system of study. This approach to mesoscopic system
sizes is opening an unprecedented perspective for so-called reverse engineering
in which the available experimental transport data are used to get a deeper
understanding of the microscopic structure of the samples. Besides, this will
not only allow addressing subtle issues in terms of resistance standardization
of large scale materials (such as wafer scale polycrystalline graphene), but
will also enable the discovery of new quantum transport phenomena in complex
two-dimensional materials, out of reach with classical methods.",1501.05100v2
2015-01-26,Raman scattering investigation of large positive magnetoresistance material WTe$_2$,"We have performed polarized Raman scattering measurements on WTe$_2$, for
which an extremely large positive magnetoresistance has been reported recently.
We observe 5 A$_1$ phonon modes and 2 A$_2$ phonon modes out of 33 Raman active
modes, with frequencies in good accordance with first-principles calculations.
The angular dependence of the intensity of the peaks observed is consistent
with the Raman tensors of the $C_{2v}$ point group symmetry attributed to
WTe$_2$. Although the phonon spectra suggest neither strong electron-phonon nor
spin-phonon coupling, the intensity of the A$_1$ phonon mode at 160.6 cm$^{-1}$
shows an unconventional decrease with temperature decreasing, for which the
origin remains unclear.",1501.06321v3
2015-02-17,Superconducting Dome and Crossover to an Insulating State in [Tl4]Tl1-xSnxTe3,"The structural, superconducting, and electronic phase diagram of
[Tl4]Tl1-xSnxTe3 is reported. Magnetization and specific heat measurements show
bulk superconductivity exists for 0 < x < 0.4. Resistivity measurements
indicate a crossover from a metallic state for low dopings to a doped insulator
at x = 1. Universally, there is a large non-Debye specific heat contribution,
characterized by an Einstein temperature of {\theta}E ~ 35 K. Density
functional theory calculations predict x = 0 to be a topological metal, while x
= 1 is a topological crystalline insulator. The disappearance of
superconductivity correlates with the transition between these distinct
topological states.",1502.05059v2
2015-02-24,Room temperature magnetodielectric studies on Mn doped LaGaO3,"The polycrystalline samples of LaGa1-xMnxO3 (0<x<0.3) has been prepared by
solid state reaction route. The phase purity of these samples has been
confirmed by powder x-ray diffraction experiments carried out on BL-12 at
Indus-2 synchrotron radiation source. The sample with x=0.2 shows significant
change in the value of capacitance with the application of magnetic field. The
observed results were understood by systematically analyzing
magneto-capacitance (MC), magneto resistance (MR) and dielectric loss as a
function of frequency. Our results and analysis suggests that the observed
magneto dielectric (MD) coupling may be due to the MR effect of Maxwell-Wagner
type and/or field induced dipolar relaxation. Further it is observed that the
oxygen stoichiometry plays a very crucial role in observed MD coupling.",1502.06887v2
2015-03-18,Atomically Thin Resonant Tunnel Diodes built from Synthetic van der Waals Heterostructures,"Vertical integration of two-dimensional van der Waals materials is predicted
to lead to novel electronic and optical properties not found in the constituent
layers. Here, we present the direct synthesis of two unique, atomically thin,
multi-junction heterostructures by combining graphene with the monolayer
transition-metal dichalocogenides: MoS2, MoSe2, and WSe2.The realization of
MoS2-WSe2-Graphene and WSe2-MoSe2-Graphene heterostructures leads toresonant
tunneling in an atomically thin stack with spectrally narrow room temperature
negative differential resistance characteristics.",1503.05592v1
2015-09-17,Microwave Loss Reduction in Cryogenically Cooled Conductors,"Measurements of microwave attenuation at room temperature and 4.2 K have been
performed on some conductors commonly used in receiver input circuits. The
reduction in loss on cooling is substantial, particularly for copper and plated
gold, both of which showed a factor of 3 loss reduction. Copper passivated with
benzotriazole shows the same loss as without passivation. The residual
resistivity ratio between room temperature and 4.2 K, deduced from the
measurements using the classical skin effect formula, was smaller than the
measured DC value to a degree consistent with conduction in the extreme
anomalous skin effect regime at cryogenic temperatures. The measurements were
made in the 5-10 GHz range. The materials tested were: aluminum alloys 1100-T6
and 6061-O, C101 copper, benzotriazole treated C101 copper, and brass plated
with electroformed copper, Pur-A-Gold 125-Au soft gold, and BDT200 bright gold.",1509.05273v1
2015-09-17,Symmetry constraints on the elastoresistivity tensor,"The elastoresistivity tensor $m_{ij,kl}$ characterizes changes in a
material's resistivity due to strain. As a fourth-rank tensor,
elastoresistivity can be a uniquely useful probe of the symmetries and
character of the electronic state of a solid. We present a symmetry analysis of
$m_{ij,kl}$ (both in the presence and absence of a magnetic field) based on the
crystalline point group, focusing for pedagogic purposes on the $D_{4h}$ point
group (of relevance to several materials of current interest). We also discuss
the relation between $m_{ij,kl}$ and various thermodynamic susceptibilities,
particularly where they are sensitive to critical fluctuations proximate to a
critical point at which a point group symmetry is spontaneously broken.",1509.05462v1
2015-10-19,"Structure, Energy, and Thermal Transport Properties of Si-SiO$_2$ Nanostructures using an Ab initio based Parameterization of a Charge-Optimized Many-Body Forcefield","In an effort to extend the reach of current ab initio calculations to
simulations requiring millions of configurations for complex systems such as
heterostructures, we have parameterized the third-generation Charge Optimized
Many-Body (COMB3) potential using solely ab initio total energies, forces, and
stress tensors as input. The quality and the predictive power of the new
forcefield is assessed by computing properties including the cohesive energy
and density of SiO$_2$ polymorphs, surface energies of alpha-quartz, and phonon
densities of states of crystalline and amorphous phases of SiO$_2$. Comparison
with data from experiments, ab initio calculations, and molecular dynamics
simulations using published forcefields including BKS (van Beest, Kramer, and
van Santen), ReaxFF, and COMB2 demonstrate an overall improvement of the new
parameterization. The computed temperature dependence of the thermal
conductivity of crystalline alpha-quartz and the Kapitza resistance of the
interface between crystalline Si(001) and amorphous silica are in excellent
agreement with experiment, setting the stage for simulations of complex
nanoscale heterostructures.",1510.05416v1
2015-11-07,Anomalous magneto-elastic and charge doping effects in thallium-doped BaFe2As2,"Within the BaFe2As2 crystal lattice, we partially substitute thallium for
barium and report the effects of interlayer coupling in Ba1-xTlxFe2As2
crystals. We demonstrate the unusual effects of magneto-elastic coupling and
charge doping in this iron-arsenide material, whereby Neel temperature rises
with small x, and then falls with additional x. Specifically, we find that Neel
and structural transitions in BaFe2As2 (TN =Ts= 133 K) increase for x=0.05 (TN
= 138 K, Ts = 140 K) from magnetization, heat capacity, resistivity, and
neutron diffraction measurements. Evidence from single crystal X-ray
diffraction and first principles calculations attributes the stronger magnetism
in x=0.05 to magneto-elastic coupling related to the shorter intraplanar Fe-Fe
bond distance. With further thallium substitution, the transition temperatures
decrease for x = 0.09 (TN = Ts = 131 K), and this is due to charge doping. We
illustrate that small changes related to 3d transition-metal state can have
profound effects on magnetism.",1511.02400v1
2015-11-24,Transport and thermodynamic properties under anharmonic motion in type-I Ba8Ga16Sn30 clathrate,"Anharmonic guest atom oscillation has direct connection to the thermal
transport and thermo- electric behavior of type-I Ba8Ga16Sn30 clathrates. This
behavior can be observed through several physical properties, with for example
the heat capacity providing a measure of the overall excita- tion level
structure. Localized anharmonic excitations also influence the low-temperature
resistivity, as we show in this paper. By combining heat capacity, transport
measurements and our previous NMR relaxation results, we address the
distribution of local oscillators in this material, as well as the shape of the
confining potential and the excitation energies for Ba(2) ions in the cages. We
also compare to the soft-potential model and other models used for similar
systems. The results show good agreement between the previously deduced
anharmonic rattler potential and experimental data.",1511.07594v1
2015-11-28,Extremely large magnetoresistance in few-layer graphene/boron-nitride heterostructures,"Understanding magnetoresistance, the change in electrical resistance upon an
external magnetic field, at the atomic level is of great interest both
fundamentally and technologically. Graphene and other two-dimensional layered
materials provide an unprecedented opportunity to explore magnetoresistance at
its nascent stage of structural formation. Here, we report an extremely large
local magnetoresistance of ~ 2,000% at 400 K and a non-local magnetoresistance
of > 90,000% in 9 T at 300 K in few-layer graphene/boron-nitride
heterostructures. The local magnetoresistance is understood to arise from large
differential transport parameters, such as the carrier mobility, across various
layers of few-layer graphene upon a normal magnetic field, whereas the
non-local magnetoresistance is due to the magnetic field induced
Ettingshausen-Nernst effect. Non-local magnetoresistance suggests the
possibility of a graphene based gate tunable thermal switch. In addition, our
results demonstrate that graphene heterostructures may be promising for
magnetic field sensing applications.",1511.08867v1
2015-12-22,Large-signal model of the bilayer graphene field-effect transistor targeting radio-frequency applications: theory versus experiment,"Bilayer graphene is a promising material for radio-frequency transistors
because its energy gap might result in a better current saturation than the
monolayer graphene. Because the great deal of interest in this technology,
especially for flexible radio-frequency applications, gaining control of it
requires the formulation of appropriate models for the drain current, charge
and capacitance. In this work we have developed them for a dual-gated bilayer
graphene field-effect transistor. A drift-diffusion mechanism for the carrier
transport has been considered coupled with an appropriate field-effect model
taking into account the electronic properties of the bilayer graphene.
Extrinsic resistances have been included considering the formation of a
Schottky barrier at the metal-bilayer graphene interface. The proposed model
has been benchmarked against experimental prototype transistors, discussing the
main figures of merit targeting radio-frequency applications.",1512.07159v1
2016-01-21,Saturation of ion irradiation effects in Cr2AlC,"Cr2AlC materials were irradiated with 7 MeV Xe26+ ions and 500 keV He2+ ions
at room temperature. A structural transition with an increased c lattice
parameter and a decreased a lattice parameter occurs after irradiation to doses
above 1 dpa. Nevertheless, the modified structure is stable up to the dose of
5.2 dpa without obvious lattice disorder. The three samples irradiated to doses
above 1 dpa have comparable lattice parameters and hardness values, suggesting
a saturation of irradiation effects in Cr2AlC. The structural transition and
irradiation effects saturation are ascribed to irradiation-induced antisite
defects (CrAl and AlCr) and C interstitials, which is supported by the
calculations of the formation energies of various defects in Cr2AlC. The
irradiation-induced antisite defects and C interstitials may be critical to
understand the excellent resistance to irradiation-induced amorphization of MAX
phases.",1601.05514v1
2016-02-02,Fast synthesis of Fe1.1Se1-xTex superconductors in a self-heating and furnace-free way,"A fast and furnace-free method of combustion synthesis is employed for the
first time to synthesize iron-based superconductors. Using this method,
Fe1.1Se1-xTex (0<=x<=1) samples can be prepared from self-sustained reactions
of element powders in only tens of seconds. The obtained Fe1.1Se1-xTex samples
show clear zero resistivity and corresponding magnetic susceptibility drop at
around 10-14 K. The Fe1.1Se0.33Te0.67 sample shows the highest onset Tc of
about 14 K, and its upper critical field is estimated to be approximately 54 T.
Compared with conventional solid state reaction for preparing polycrystalline
FeSe samples, combustion synthesis exhibits much-reduced time and energy
consumption, but offers comparable superconducting properties. It is expected
that the combustion synthesis method is available for preparing plenty of
iron-based superconductors, and in this direction further related work is in
progress.",1602.00880v1
2016-02-11,A multiscale model of distributed fracture and permeability in solids in all-round compression,"We present a microstructural model of permeability in fractured solids, where
the fractures are described in terms of recursive families of parallel,
equidistant cohesive faults. Faults originate upon the attainment of a tensile
or shear resistance in the undamaged material. Secondary faults may form in a
hierarchical orga- nization, creating a complex network of connected fractures
that modify the permeability of the solid. The undamaged solid may possess
initial porosity and permeability. The particular geometry of the superposed
micro-faults lends itself to an explicit analytical quantification of the
porosity and permeability of the dam- aged material. The approach is
particularly appealing as a means of modeling low permeability oil and gas
reservoirs stimulated by hydraulic fracturing.",1602.03801v2
2016-04-04,Universal scaling for the spin-electricity conversion on surface states of topological insulators,"We have investigated spin-electricity conversion on surface states of
bulk-insulating topological insulator (TI) materials using a spin pumping
technique. The sample structure is Ni-Fe|Cu|TI trilayers, in which magnetic
proximity effects on the TI surfaces are negligibly small owing to the inserted
Cu layer. Voltage signals produced by the spin-electricity conversion are
clearly observed, and enhanced with decreasing temperature in line with the
dominated surface transport at lower temperatures. The efficiency of the
spin-electricity conversion is greater for TI samples with higher resistivity
of bulk states and longer mean free path of surface states, consistent with the
surface spin-electricity conversion.",1604.00751v1
2016-04-06,Enhanced Thermoelectric Power and Electronic Correlations in RuSe$_2$,"We report the electronic structure, electric and thermal transport properties
of Ru$_{1-x}$Ir$_{x}$Se$_2$ ($x \leq 0.2$). RuSe$_2$ is a semiconductor that
crystallizes in a cubic pyrite unit cell. The Seebeck coefficient of RuSe$_2$
exceeds -200 $\mu$V/K around 730 K. Ir substitution results in the suppression
of the resistivity and the Seebeck coefficient, suggesting the removal of the
peaks in density of states near the Fermi level. Ru$_{0.8}$Ir$_{0.2}$Se$_{2}$
shows a semiconductor-metal crossover at about 30 K. The magnetic field
restores the semiconducting behavior. Our results indicate the importance of
the electronic correlations in enhanced thermoelectricity of RuSb$_{2}$.",1604.01755v1
2016-04-12,"EPW: Electron-phonon coupling, transport and superconducting properties using maximally localized Wannier functions","The EPW (Electron-Phonon coupling using Wannier functions) software is a
Fortran90 code that uses density-functional perturbation theory and maximally
localized Wannier functions for computing electron-phonon couplings and related
properties in solids accurately and efficiently. The EPW v4 program can be used
to compute electron and phonon self-energies, linewidths, electron-phonon
scattering rates, electron-phonon coupling strengths, transport spectral
functions, electronic velocities, resistivity, anisotropic superconducting gaps
and spectral functions within the Migdal-Eliashberg theory. The code now
supports spin-orbit coupling, time-reversal symmetry in non-centrosymmetric
crystals, polar materials, and $\mathbf{k}$ and $\mathbf{q}$-point
parallelization. Considerable effort was dedicated to optimization and
parallelization, achieving almost a ten times speedup with respect to previous
releases. A computer test farm was implemented to ensure stability and
portability of the code on the most popular compilers and architectures. Since
April 2016, version 4 of the EPW code is fully integrated in and distributed
with the Quantum ESPRESSO package, and can be downloaded through QE-forge at
http://qe-forge.org/gf/project/q-e.",1604.03525v2
2016-05-09,A non-volatile memory based on nonlinear magnetoelectric effects,"The magnetoelectric effects in multiferroics have a great potential in
creating next-generation memory devices. We conceive a new concept of
non-volatile memories based on a type of nonlinear magnetoelectric effects
showing a butterfly-shaped hysteresis loop. The principle is to utilize the
states of the magnetoelectric coefficient, instead of magnetization, electric
polarization or resistance, to store binary information. Our experiments in a
device made of the PMN-PT/Terfenol-D multiferroic heterostructure clearly
demonstrate that the sign of the magnetoelectric coefficient can be repeatedly
switched between positive and negative by applying electric fields, confirming
the feasibility of this principle. This kind of non-volatile memory has
outstanding practical virtues such as simple structure, easy operations in
writing and reading, low power, fast speed, and diverse materials available.",1605.02505v1
2016-05-17,Pressure-induced gap closing and metallization of MoSe$_{2}$ and MoTe$_{2}$,"Layered molybdenum dichalchogenides are semiconductors whose gap is
controlled by delicate interlayer interactions. The gap tends to drop together
with the interlayer distance, suggesting collapse and metallization under
pressure. We predict, based on first principles calculations, that layered
semiconductors 2H$_c$-MoSe$_2$ and 2H$_c$-MoTe$_2$ should undergo metallization
at pressures between 28 and 40 GPa (MoSe$_2$) and 13 and 19 GPa (MoTe$_2$).
Unlike MoS$_2$ where a 2H$_c$ $\to$ 2H$_a$ layer sliding transition is known to
take place, these two materials appear to preserve the original 2H$_c$ layered
structure at least up to 100 GPa and to increasingly resist lubric layer
sliding under pressure. Similar to metallized MoS$_2$ they are predicted to
exhibit a low density of states at the Fermi level, and presumably very modest
superconducting temperatures if any. We also study the $\beta$-MoTe$_2$
structure, metastable with a higher enthalpy than 2H$_c$-MoTe$_2$. Despite its
ready semimetallic and (weakly) superconducting character already at zero
pressure, metallicity is not expected to increase dramatically with pressure.",1605.05111v1
2016-07-26,Experimental Observation of Topological Superconductivity and Majorana Zero Modes on beta-Bi2Pd Thin Films,"Using a cryogenic scanning tunneling microscopy, we report the observation of
topologically nontrivial superconductivity on a single material of \beta-Bi2Pd
films grown by molecular beam epitaxy. The superconducting gap associated with
spinless odd-parity pairing opens on the surface and appears much larger than
the bulk one due to the Dirac-fermion enhanced parity mixing of surface pair
potential. Majorana zero modes (MZMs), supported by such superconducting
states, are identified at magnetic vortices. The superconductivity and MZMs
exhibit resistance to nonmagnetic defects, characteristic of
time-reversal-invariant topological superconductors. Our results demonstrate a
simple platform to generate, manipulate and braid MZMs for quantum computation.",1607.07551v4
2016-07-28,Imaging current-induced switching of antiferromagnetic domains in CuMnAs,"The magnetic order in antiferromagnetic (AF) materials is hard to control
with external magnetic fields. However, recent advances in detecting and
manipulating AF order electrically have opened up new prospects for these
materials in basic and applied spintronics research. Using x-ray magnetic
linear dichroism microscopy, we show here that staggered effective fields
generated by electrical current can induce reproducible and reversible
modification of the antiferromagnetic domain structure in microdevices
fabricated from a tetragonal CuMnAs thin film. The current-induced domain
switching is inhomogeneous at the submicron level. A clear correlation between
the average domain orientation and the anisotropy of the electrical resistance
is demonstrated.",1607.08478v2
2016-08-11,Evolution of Insulator-Metal Phase Transitions in Epitaxial Tungsten Oxide Films during Electrolyte-Gating,"An interface between an oxide and an electrolyte gives rise to various
processes as exemplified by electrostatic charge accumulation/depletion and
electrochemical reactions such as intercalation/decalation under electric
field. Here we directly compare typical device operations of those in electric
double layer transistor geometry by adopting ${A}$-site vacant perovskite
WO$_3$ epitaxial thin films as a channel material and two different
electrolytes as gating agent. $\textit{In situ}$ measurements of x-ray
diffraction and channel resistance performed during the gating revealed that in
both the cases WO$_3$ thin film reaches a new metallic state through multiple
phase transitions, accompanied by the change in out-of-plane lattice constant.
Electrons are electrostatically accumulated from the interface side with an
ionic liquid, while alkaline metal ions are more uniformly intercalated into
the film with a polymer electrolyte. We systematically demonstrate this
difference in the electrostatic and electrochemical processes, by comparing
doped carrier density, lattice deformation behavior, and time constant of the
phase transitions.",1608.03357v1
2016-10-15,Dynamical Conductivity of Dirac Materials,"For graphene (a Dirac material) it has been theoretically predicted and
experimentally observed that DC resistivity is proportional to $ T^4$ when the
temperature is much less than Bloch- Gr\""{u}neisen ($\Theta_{BG}$) temperature
and T linear in opposite case ($T>>\Theta_{BG}$). Going beyond the DC case, we
investigate the dynamical conductivity in graphene using the powerful method of
memory function formalism. In the DC (zero frequency regime) limit, we obtained
the above mention behavior which was previously obtained using the
Bloch-Boltzmann kinetic equation. In the finite frequency regime, we obtained
several new results: (1) the generalized Drude scattering rate, in the zero
temperature limit, shows $\omega^4 $ behavior at low frequencies ($\omega <<
k_B \Theta_{BG}/ \hbar$) and saturates at higher frequencies. We also observed
the Holstein Mechanism, however, with different power laws from that in the
case of metals; (2) At higher frequencies, $\omega>>k_B \Theta_{BG}/ \hbar$,
and higher temperatures $T>>\Theta_{BG}$, we observed that the generalized
Drude scattering rate is linear in temperature. In addition, several other
results are also obtained. With the experimental advancement of this field,
these results should be experimentally tested.",1610.04697v1
2016-10-18,Magnetic properties of low-moment ferrimagnetic Heusler Cr2CoGa thin films grown by molecular beam epitaxy,"Recently, theorists have predicted many materials with a low magnetic moment
and large spin-polarization for spintronic applications. These compounds are
predicted to form in the inverse Heusler structure, however, many of these
compounds have been found to phase segregate. In this study, ordered Cr2CoGa
thin films were synthesized without phase segregation using molecular beam
epitaxy. The present as-grown films exhibit a low magnetic moment from
antiferromagnetically coupled Cr and Co atoms as measured with SQUID
magnetometry and soft X-ray magnetic circular dichroism. Electrical
measurements demonstrated a thermally-activated semiconductor-like resistivity
with an activation energy of 87 meV. These results confirm spin gapless
semiconducting behavior, which makes these thin films well positioned for
future devices.",1610.05808v1
2016-10-21,On the impact of strain on the electronic properties of InAs/GaSb quantum well systems,"Electron-hole hybridization in InAs/GaSb double quantum well structures leads
to the formation of a mini band gap. We experimentally and theoretically
studied the impact of strain on the transport properties of this material
system. Thinned samples were mounted to piezo electric elements to exert strain
along the [011] and [001] crystal directions. When the Fermi energy is tuned
through the mini gap, a dramatic impact on the resistivity at the charge
neutrality point is found which depends on the amount of applied external
strain. In the electron and hole regimes, strain influences the Landau level
structure. By analyzing the intrinsic strain from the epitaxial growth, the
external strain from the piezo elements and combining our experimental results
with numerical simulations of strained and unstrained quantum wells, we
compellingly illustrate why the InAs/GaSb material system is regularly found to
be semimetallic.",1610.06776v1
2016-11-09,Parallel and series conduction model in Topological Insulators,"In the past few years there has been a surge in the material science
engineering in order to synthesize bulk insulating and surface metallic
Topological Insulating (TI) materials. This quest is not only theoretically
important but also promising from the novel application perspective. The
dependence of temperature on resistance (R-T) of a particular sample reveals a
plethora of information about the electronic properties especially in a unique
sample like TI where there are two components comprising of an insulating bulk
and metallic surface states. Depending on the amount of intrinsic doping during
the sample formation, the bulk can either couple or remain decoupled with the
surface. The former leads to a metallic R-T profile whereas the latter is
captured by an insulating R-T behavior. These two behaviors can be represented
by series and parallel resistor models respectively. In this work we study the
R-T behavior in the framework of resistor models capturing the essential
features of our sample.",1611.02856v1
2016-12-11,Superconductivity in Se-doped new materials EuSr2Bi2S4F4 and Eu2SrBi2S4F4,"From our powder x ray diffraction pattern, electrical transport and magnetic
studies we report the effect of isovalent Se substitution at S sites in the
newly discovered systems EuSr2Bi2S4F4 and Eu2SrBi2S4F4. We have synthesized two
new variants of 3244 type superconductor with Eu replaced by Sr which is
reported elsewhere [Z. Haque et. al.]. We observe superconductivity at Tc 2.9 K
(resistivity) and 2.3 K (susceptibility) in EuSr2Bi2S4-xSexF4 series for x = 2.
In the other series Eu2SrBi2S4-xSexF4, two materials (x= 1.5; Tc = 2.6 K and x
= 2; Tc = 2.75 K) exhibit superconductivity.",1612.03415v1
2017-02-16,Millimeter-scale layered MoSe2 grown on sapphire and evidence for negative magnetoresistance,"Molecular beam epitaxy technique has been used to deposit a single layer and
a bilayer of MoSe 2 on sapphire. Extensive characterizations including in-situ
and ex-situ measurements show that the layered MoSe 2 grows in a scalable
manner on the substrate and reveals characteristics of a stoichiometric
2H-phase. The layered MoSe 2 exhibits polycrystalline features with domains
separated by defects and boundaries. Temperature and magnetic field dependent
resistivity measurements unveil a carrier hopping character described within
two-dimensional variable range hopping mechanism. Moreover, a negative
magnetoresistance was observed, stressing a fascinating feature of the charge
transport under the application of a magnetic field in the layered MoSe 2
system. This negative magnetoresistance observed at millimeter-scale is similar
to that observed recently at room temperature inWS2 flakes at a micrometer
scale [Zhang et al., Appl. Phys. Lett. 108, 153114 (2016)]. This scalability
highlights the fact that the underlying physical mechanism is intrinsic to
these two-dimensional materials and occurs at very short scale.",1702.05121v1
2017-06-16,Gate-tunable large magnetoresistance in an all-semiconductor spin-transistor-like device,"A large spin-dependent and electric field-tunable magnetoresistance of a
two-dimensional electron system (2DES) is a key ingredient for the realization
of many novel concepts for spin-based electronic devices. The low
magnetoresistance observed during the last decades in devices with lateral
semiconducting (SC) transport channels between ferromagnetic (FM) source (S)
and drain (D) contacts has been the main obstacle for realizing spin field
effect transistor proposals. Here, we show both, a large two terminal
magnetoresistance in lateral 2DES-based spin valve geometry, with up to 80%
resistance change, and tunability of the magnetoresistance by an electric gate.
The large magnetoresistance is due to finite electric field effects at the
FM/SC interface, which boost spin-to-charge conversion. The gating scheme we
use is based on switching between uni- and bi-directional spin diffusion,
without resorting to the spin-orbit coupling.",1706.05239v1
2017-06-19,Electrical signature of individual magnetic skyrmions in multilayered systems,"Magnetic skyrmions are topologically protected whirling spin textures that
can be stabilized in magnetic materials in which a chiral interaction is
present. Their limited size together with their robustness against the external
perturbations promote them as the ultimate magnetic storage bit in a novel
generation of memory and logic devices. Despite many examples of the signature
of magnetic skyrmions in the electrical signal, only low temperature
measurements, mainly in magnetic materials with B20 crystal structure, have
demonstrated the skyrmions contribution to the electrical transport properties.
Using the combination of Magnetic Force Microscopy (MFM) and Hall resistivity
measurements, we demonstrate the electrical detection of sub-100 nm skyrmions
in multilayered thin film at room temperature (RT). We furthermore analyse the
room temperature Hall signal of a single skyrmion which contribution is mainly
dominated by anomalous Hall effect.",1706.05809v1
2017-06-26,The Sobering Reality of Perovskite/Si Tandem Solar Cells under Realistic Operating Conditions,"Perovskite/Si tandem solar cells have the potential to considerably
out-perform conventional solar cells. Under standard test conditions,
perovskite/Si tandem solar cells already outperform the Si single junction.
Under realistic conditions, however, as we show, those tandem solar cells are
hardly more efficient than the Si cell alone. We model the performance of
realistic perovskite/Si tandem solar cells under real-world climate conditions,
by incorporating parasitic cell resistances, non-radiative recombination, and
optical losses into the detailed-balance limit. We show quantitatively that
optimizing these parameters in the perovskite top cell, perovskite/Si tandem
solar cells reach an efficiency advantage of up to 14% absolute, even while
leaving the Si cell untouched. Despite the rapid efficiency increase of
perovskite solar cells, our results emphasize the need for further material
development, careful device design, and light management strategies, all
necessary for highly efficient perovskite/Si tandem solar cells.",1706.08610v1
2017-09-11,Signature of growth-deposition technique on the properties of PECVD and thermal SiO2,"In this article, we report the process induced variation in the
characteristics of PECVD deposited and thermally grown silicon dioxide (SiO2)
thin film. We find key differences in the porosity, arrangement of the
nano-pores, surface roughness, refractive index and electrical resistivity of
the SiO2 thin films obtained by the two methods. While the occurrence of the
nanoporous structure is an inherent property of the material and independent of
the process of film growth or deposition, the arrangements of these nano-pores
in the oxide film is process dependent. The distinct arrangements of the
nano-pores are signatures of the deposition/growth processes. Morphological
analysis has been carried out to demonstrate the difference between oxides
either grown by thermal oxidation or through PECVD deposition. The tunable
conductive behavior of the metal filled nano-porous oxides is also
demonstrated, which has potential to be used as conductive oxides in various
applications.",1709.03257v1
2017-10-10,Evidence of a topological Hall effect in Eu$_{1-x}$Sm$_x$TiO$_3$,"We report on the observation of a possible topological Hall effect in thin
films of the itinerant ferromagnet Eu1-xSmxTiO3. EuTiO3 and Eu0.955Sm0.045TiO3
films were grown by molecular beam epitaxy. The EuTiO3 film is insulating. The
Hall resistivity of the Eu0.955Sm0.045TiO3 films exhibits the anomalous Hall
effect below the Curie temperature of ~ 5 K as well as additional features that
appear at 2 K. It is shown that these features are magnetic in origin and
consistent with the topological Hall effect seen in materials systems with
topologically nontrivial spin textures, such as skyrmions. The results open up
interesting possibilities for epitaxial hybrid heterostructures that combine
topological magnetic states, tunable carrier densities, and other phenomena.",1710.03729v1
2017-10-12,Thermal conductivity reduction in rough silicon nanomembranes,"Nanostructured silicon is a promising material for thermoelectric conversion,
because the thermal conductivity in silicon nanostructures can be strongly
reduced with respect to that of bulk materials. We present thermal conductivity
measurements, performed with the 3$\omega$ technique, of suspended
monocrystalline silicon thin films (nanomembranes or nanoribbons) with smooth
and rough surfaces. We find evidence for a significant effect of surface
roughness on phonon propagation: the measured thermal conductivity for the
rough structures is well below that predicted by theoretical models which take
into account diffusive scattering on the nanostructure walls. Conversely, the
electrical conductivity appears to be substantially unaffected by surface
roughness: the measured resistance of smooth and rough nanostructures are
comparable, if we take into account the geometrical factors. Nanomembranes are
more easily integrable in large area devices with respect to nanowires and are
mechanically stronger and able to handle much larger electrical currents (thus
enabling the fabrication of thermoelectric devices that can supply higher power
levels with respect to current existing solutions).",1710.04403v1
2017-10-17,XPS study of the chemical stability of DyBa2Cu3O6+δ superconductor,"The chemical stability of the powder DyBa2Cu3O6+{\delta} has been studied by
X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and thermal
analysis at ambient conditions. The powder was subjected to mechanical
processing in a ball mill-activator to accelerate chemical degradation. The
kinetic regularities of hydrolytic decomposition of DyBa2Cu3O6+{\delta} under
the influence of air moisture have been determined. The resistive properties of
DyBa2Cu3O6+{\delta} to water have been found to be better, but not much
different from analogous properties of YBa2Cu3O6+{\delta} which is unstable in
a wet environment. Chemical degradation of the material is triggered by crucial
concentrating of water particles near the free surface of the solid reactant
(due to their low diffusibility in the bulk) leading to rapid chemical
decomposition of the respective regions.",1710.06271v1
2017-10-27,Percolative nature of the dc paraconductivity in the cuprate superconductors,"We present an investigation of the planar direct-current (dc)
paraconductivity of the model cuprate material HgBa$_2$CuO$_{4+\delta}$ in the
underdoped part of the phase diagram. The simple quadratic
temperature-dependence of the Fermi-liquid normal-state resistivity enables us
to extract the paraconductivity above the macroscopic $T_c$ with great
accuracy. The paraconductivity exhibits unusual exponential temperature
dependence, with a characteristic temperature scale that is distinct from
$T_c$. In the entire temperature range where it is discernable, the
paraconductivity is quantitatively explained by a simple superconducting
percolation model, which implies that underlying gap disorder dominates the
emergence of superconductivity.",1710.10220v1
2017-10-31,Suppression of vacancies boosts thermoelectric performance in type-I clathrates,"Intermetallic type-I clathrates continue to attract attention as promising
thermoelectric materials. Here we present structural and thermoelectric
properties of single crystalline Ba8(Cu,Ga,Ge,v)46, where v denotes a vacancy.
By single crystal X-ray diffraction on crystals without Ga we find clear
evidence for the presence of vacancies at the 6c site in the structure. With
increasing Ga content, vacancies are successively filled. This increases the
charge carrier mobility strongly, even within a small range of Ga substitution,
leading to reduced electrical resistivity and enhanced thermoelectric
performance. The largest figure of merit ZT =0.9 at 900 K is found for a single
crystal of approximate composition Ba8Cu4.6Ga1.0Ge40.4. This value, that may
further increase at higher temperatures, is one of the largest to date found in
transition metal element-based clathrates.",1710.11536v1
2018-01-02,Edge-Grafted Molecular Junctions between Graphene Nanoplatelets: Applied Chemistry to Enhance Heat Transfer in Nanomaterials,"The edge-functionalization of graphene nanoplatelets (GnP) was carried out
exploiting diazonium chemistry, aiming at the synthesis of edge decorated
nanoparticles to be used as building blocks in the preparation of engineered
nanostructured materials for enhanced heat transfer. Indeed, both phenol
functionalized and dianiline-bridged GnP (GnP-OH and E-GnP, respectively) were
assembled in nanopapers exploiting the formation of non-covalent and covalent
molecular junctions, respectively. Molecular dynamics allowed to estimate the
thermal conductance for the two different types of molecular junction,
suggesting a factor 6 between conductance of covalent vs. non-covalent
junctions. Furthermore, the chemical functionalization was observed to drive
the self-organization of the nanoflakes into the nanopapers, leading to a 20%
enhancement of the thermal conductivity for GnP-OH and E-GnP while the cross
plane thermal conductivity was boosted by 150% in the case of E-GnP. The
application of chemical functionalization to the engineering of contact
resistance in nanoparticles network was therefore validated as a fascinating
route for the enhancement of heat exchange efficiency on nanoparticle networks,
with great potential impact in low-temperature heat exchange and recovery
applications",1801.00859v1
2018-01-03,Ion-exchange synthesis and superconductivity at 8.6 K of Na2Cr3As3 with quasi-one-dimensional crystal structure,"A new Cr-based quasi-one-dimensional superconductor Na2Cr3As3 was synthesized
by an ion-exchange method in sodium naphthalenide solution. The crystals are
thread-like and the structure was analyzed by X-ray diffraction with a
noncentrosymmetric hexagonal space group P-6m2 (No. 187), in which the
(Cr3As3)2- linear chains are separated by Na+ ions, and the refined lattice
parameters are a = 9.239(2) {\AA} and c = 4.209(6) {\AA}. The measurements for
electrical resistivity, magnetic susceptibility, and heat capacity reveal a
superconducting transition with unconventional characteristic at the Tc of 8.6
K, which exceeds that of all previously reported Cr-based superconductors.",1801.01010v1
2018-01-04,Crystal growth and magnetic anisotropy in the spin-chain ruthenate Na$_2$RuO$_4$,"We report single crystal growth, electrical resistivity $\rho$, anisotropic
magnetic susceptibiltiy $\chi$, and heat capacity $C_p$ measurements on the
one-dimensional spin-chain ruthenate Na$_2$RuO$_4$. We observe variable range
hopping (VRH) behaviour in $\rho(T)$. The magnetic susceptibility with magnetic
field perpendicular ($\chi_\perp$) and parallel ($\chi_\parallel$) to the
spin-chains is reported. The magnetic properties are anisotropic with
$\chi_\perp > \chi_\parallel$ in the temperature range of measurements T
$\approx 2$ to $305$ K with $\chi_\perp / \chi_\parallel$ $\approx 1.4$ at
$305$ K. Analysis of the $\chi(T)$ data reveals an anisotropy in the $g$-factor
and Van-Vleck paramagnetic contribution. An anomaly in $\chi(T)$ and a
corresponding lambda-like anomaly in $C_p$ at $T_N = 37$ K confirms long-range
antiferromagnetic ordering. This temperature is an order of magnitude smaller
than the Weiss temperature $\theta \sim -250$ K and points to suppression of
long range magnetic order due to low dimensionality. However, we were unable to
get a satisfactory fit of the experimental $\chi(T)$ by an isolated
one-dimensional spin-chain model, suggesting the importance of inter-chain
interactions in Na$_2$RuO$_4$.",1801.01524v1
2018-01-17,The simultaneous discharge of liquid and grains from a silo,"The flow rate of water through an orifice at the bottom of a container
depends on the hydrostatic pressure whereas for a dry granular material is
nearly constant. But what happens during the simultaneous discharge of grains
and liquid from a silo? By measuring the flow rate as a function of time, we
found that: (i) different regimes appear, going from constant flow rate
dominated by the effective fluid viscosity to a hydrostatic-like discharge
depending on the aperture and grain size, (ii) the mixed material is always
discharged faster than dry grains but slower than liquid, (iii) for the
mixture, the liquid level drops faster than the grains level but they are
always linearly proportional to one another, and (iv) a sudden growth in the
flow rate happens during the transition from a biphasic to a single phase
discharge. These results are associated to the competition between the decrease
of hydrostatic pressure above the granular bed and the hydrodynamic resistance.
A model combining the Kozeny-Carman, Bernoulli and mass conservation equations
is proposed and the numerical results are in good agreement with experiments.",1801.05747v1
2018-02-16,Levitated electromechanics: all-electrical cooling of charged nano- and micro-particles,"We show how charged levitated nano- and micro-particles can be cooled by
interfacing them with an $RLC$ circuit. All-electrical levitation and cooling
is applicable to a wide range of particle sizes and materials, and will enable
state-of-the-art force sensing within an electrically networked system.
Exploring the cooling limits in the presence of realistic noise we find that
the quantum regime of particle motion can be reached in cryogenic environments
both for passive resistive cooling and for an active feedback scheme, paving
the way to levitated quantum electromechanics.",1802.05928v3
2018-02-21,Design of Chern Insulating Phases in Honeycomb Lattices,"The search for robust examples of the magnetic version of topological
insulators, referred to as quantum anomalous Hall insulators or simply Chern
insulators, so far lacks success. Our groups have explored two distinct
possibilities based on multiorbital 3d oxide honeycomb lattices. Each has a
Chern insulating phase near the ground state, but materials parameters were not
appropriate to produce a viable Chern insulator. Further exploration of one of
these classes, by substituting open shell 3d with 4d and 5d counterparts, has
led to realistic prediction of Chern insulating ground states. Here we recount
the design process, discussing the many energy scales that are active in
participating (or resisting) the desired Chern insulator phase.",1802.07411v1
2018-02-21,Meta-screening and permanence of polar distortion in metallized ferroelectrics,"Ferroelectric materials are characterized by a spontaneous polar distortion.
The behavior of such distortions in the presence of free charge is the key to
the physics of metallized ferroelectrics in particular, and of
structurally-polar metals more generally. Using first-principles simulations,
here we show that a polar distortion resists metallization and the attendant
suppression of long-range dipolar interactions in the vast majority of a sample
of 11 representative ferroelectrics. We identify a meta-screening effect,
occurring in the doped compounds as a consequence of the charge rearrangements
associated to electrostatic screening, as the main factor determining the
survival of a non-centrosymmetric phase. Our findings advance greatly our
understanding of the essentials of structurally-polar metals, and offer
guidelines on the behavior of ferroelectrics upon field-effect charge injection
or proximity to conductive device elements.",1802.07464v1
2018-04-09,Canted antiferromagnetism in phase-pure CuMnSb,"We report the low-temperature properties of phase-pure single crystals of the
half-Heusler compound CuMnSb grown by means of optical float-zoning. The
magnetization, specific heat, electrical resistivity, and Hall effect of our
single crystals exhibit an antiferromagnetic transition at $T_{\mathrm{N}} =
55~\mathrm{K}$ and a second anomaly at a temperature $T^{*} \approx
34~\mathrm{K}$. Powder and single-crystal neutron diffraction establish an
ordered magnetic moment of $(3.9\pm0.1)~\mu_{\mathrm{B}}/\mathrm{f.u.}$,
consistent with the effective moment inferred from the Curie-Weiss dependence
of the susceptibility. Below $T_{\mathrm{N}}$, the Mn sublattice displays
commensurate type-II antiferromagnetic order with propagation vectors and
magnetic moments along $\langle111\rangle$ (magnetic space group $R[I]3c$).
Surprisingly, below $T^{*}$, the moments tilt away from $\langle111\rangle$ by
a finite angle $\delta \approx 11^{\circ}$, forming a canted antiferromagnetic
structure without uniform magnetization consistent with magnetic space group
$C[B]c$. Our results establish that type-II antiferromagnetism is not the
zero-temperature magnetic ground state of CuMnSb as may be expected of the
face-centered cubic Mn sublattice.",1804.03223v1
2018-04-24,Electrical and thermal transport in coplanar polycrystalline graphene-hBN heterostructures,"We present a theoretical study of electronic and thermal transport in
polycrystalline heterostructures combining graphene (G) and hexagonal boron
nitride (hBN) grains of varying size and distribution. By increasing the hBN
grain density from a few percents to $100\%$, the system evolves from a good
conductor to an insulator, with the mobility dropping by orders of magnitude
and the sheet resistance reaching the M$\Omega$ regime. The Seebeck coefficient
is suppressed above $40\%$ mixing, while the thermal conductivity of
polycrystalline hBN is found to be on the order of $30-120\,{\rm W}{\rm
m}^{-1}{\rm K}^{-1}$. These results, agreeing with available experimental data,
provide guidelines for tuning G-hBN properties in the context of
two-dimensional materials engineering. In particular, while we proved that both
electrical and thermal properties are largely affected by morphological
features (like e.g. by the grain size and composition), we find in all cases
that nm-sized polycrystalline G-hBN heterostructures are not good
thermoelectric materials.",1804.09272v2
2018-05-08,Relativistic Gurzhi effect in channels of Dirac materials,"Charge transport in channel-shaped 2D Dirac systems is studied employing the
Boltzmann equation. The dependence of the resistivity on temperature and
chemical potential is investigated. An accurate understanding of the influence
of electron-electron interaction and material disorder allows us to identify a
parameter regime, where the system reveals hydrodynamic transport behavior. We
point out the conditions for three Dirac fermion specific features: heat flow
hydrodynamics, pseudo\-diffusive transport, and the electron-hole scattering
dominated regime. It is demonstrated that for clean samples the relativistic
Gurzhi effect, a definite indicator of hydrodynamic transport, can be observed.",1805.02987v2
2018-05-28,Phonon Fingerprints of CsPb2Br5 Single Crystals,"CsPb2Br5 is a stable, water-resistant, material derived from CsPbBr3
perovskite and featuring two-dimensional Pb-Br framework separated by Cs
layers. Both compounds can coexist at nano- length scale, which often produces
conflicting optical spectroscopy results. We present a complete set of
polarized Raman spectra of nonluminescent CsPb2Br5 single crystals that reveals
the symmetry and frequency of nondegenerate Raman active phonons accessible
from the basal (001) plane. The experimental results are in good agreement with
density functional perturbation theory simulations, which suggests that the
calculated frequencies of yet unobserved double degenerate Raman and infrared
phonons are also reliable. Unlike CsPbBr3, the lattice dynamics of CsPb2Br5 is
stable as evidenced by the calculated phonon dispersion. The sharp Raman lines
and lack of a dynamic- disorder-induced central peak in the spectra at room
temperature indicate that the coupling of Cs anharmonic motion to Br atoms,
known to cause the dynamic disorder in CsPbBr3, is absent in CsPb2Br5.",1805.11181v1
2018-06-01,Flat bands and the physics of strongly correlated Fermi systems,"Some materials can have the dispersionless parts in their electronic spectra.
These parts are usually called flat bands and generate the corps of unusual
physical properties of such materials. These flat bands are induced by the
condensation of fermionic quasiparticles, being very similar to the Bose
condensation. The difference is that fermions to condense, the Fermi surface
should change its topology, leading to violation of time-reversal (T) and
particle-hole (C) symmetries. Thus, the famous Landau theory of Fermi liquids
does not work for the systems with fermion condensate (FC) so that several
experimentally observable anomalies have not been explained so far. Here we use
FC approach to explain recent observations of the asymmetric tunneling
conductivity in heavy-fermion compounds and graphene and its restoration in
magnetic fields, as well as the violation of Leggett theorem, recently observed
experimentally in overdoped cuprates, and recent observation of the challenging
universal scaling connecting linear-$T$-dependent resistivity to the
superconducting superfluid density.",1806.00438v1
2018-06-19,Influence of Interfaces on the Transport Properties of Graphite revealed by Nanometer Thickness Reduction,"We investigated the influence of thickness reduction on the transport
properties of graphite microflakes. Using oxygen plasma etching we decreased
the thickness of highly oriented pyrolytic graphite (HOPG) microflakes from
$\sim 100$~nm to $\sim 20$~nm systematically. Keeping current and voltage
electrodes intact, the electrical resistance $R(T)$, the magnetoresistance (MR)
and Raman spectra were measured in every individual sample and after each
etching step of a few nm. The results show that $R(T)$ and MR can increase or
decrease with the sample thickness in a non-systematic way. The results
indicate that HOPG samples are inhomogeneous materials, in agreement with
scanning transmission electron microscopy images and X-ray diffraction data.
Our results further indicate that the quantum oscillations in the MR are not an
intrinsic property of the ideal graphite structure but their origin is related
to internal conducting interfaces.",1806.07417v3
2018-06-20,Concurrent transitions in wear rate and surface microstructure in nanocrystalline Ni-W,"Nanocrystalline metals are promising materials for wear-resistant
applications due to their superior strength and hardness, but prior work has
shown that cyclic loading can lead to coarsening. In this study, scratch wear
tests were carried out on nanocrystalline Ni-19 at.% W films with an
as-deposited grain size of 3 nm, with systematic characterization performed
after different wear cycles. A new gradient nanograined microstructure is
observed and a direct connection between wear rate and subsurface
microstructure is discovered. A second Ni-W specimen with the same composition
and a 45 nm average grain size is produced by annealing the original specimen.
Subsequent wear testing shows that an identical subsurface microstructure is
produced in this sample, emphasizing the importance of the cross-over in
deformation mechanisms for determining the steady-state grain size during wear.",1806.07919v2
2018-06-27,Spin splitting induced in a superconductor by an antiferromagnetic insulator,"Inspired by recent feats in exchange coupling antiferromagnets to an adjacent
material, we demonstrate the possibility of employing them for inducing spin
splitting in a superconductor, thereby avoiding the detrimental, parasitic
effects of ferromagnets employed to this end. We derive the Gor'kov equation
for the matrix Green's function in the superconducting layer, considering a
microscopic model for its disordered interface with a two-sublattice magnetic
insulator. We find that an antiferromagnetic insulator with effectively
uncompensated interface induces a large, disorder-resistant spin splitting in
the adjacent superconductor. In addition, we find contributions to the
self-energy stemming from the interfacial disorder. Within our model, these
mimic impurity and spin-flip scattering, while another breaks the symmetries in
particle-hole and spin spaces. The latter contribution, however, drops out in
the quasi-classical approximation and thus, does not significantly affect the
superconducting state.",1806.10356v2
2019-08-30,Efficient Pourbaix diagrams of many-element compounds,"Pourbaix diagrams have long been an essential tool for determining the phase
stability of solids and their associated ionic species under electrochemical
conditions. In recent years, Pourbaix diagrams have been used for applications
ranging from corrosion-resistance alloy design to electrocatalysis, and the
data from which they are generated has been enhanced by the availability of
materials data in various online databases. However, generation of
multi-element Pourbaix diagrams has a critical bottleneck which makes 3-element
systems difficult to analyze quickly, and 4 and 5 element systems intractable.
In this work, we present a method for constructing Pourbaix diagrams which uses
a pre-processing step to circumvent the most egregious computational bottleneck
and make many-element Pourbaix diagrams computationally efficient.",1909.00035v1
2019-09-02,Nematic properties of FeSe$_{1-x}$Te$_{x}$ crystals with a low Te content,"We report on the synthesis and physical properties of FeSe$_{1-x}$Te$_x$
single crystals with a low Te content (x = 0.17, 0.21, 0.25), where the
replacement of Se with Te partially suppresses superconductivity. Resistivity
and Hall effect measurements indicate weak anomalies at elevated temperatures
ascribed to nematic transitions. A quasi-classical analysis of transport data,
including in a pulsed magnetic field of up to 25 T, confirms the inversion of
majority carriers type from holes in FeSe to electrons in FeSe$_{1-x}$Te$_x$ at
x $>$ 0.17. The temperature-dependent term in the elastoresistance of the
studied compositions has a negative sign, which means that for substituted FeSe
compositions, the elastoresistance is positive for hole-doped materials and
negative for electron-doped materials just like in semiconductors such as
silicon and germanium.",1909.00711v1
2019-09-10,Ferroelectric enhancement of superconductivity in compressively strained SrTiO$_3$ films,"SrTiO$_3$ is an incipient ferroelectric on the verge of a polar instability,
which is avoided at low temperatures by quantum fluctuations. Within this
unusual quantum paraelectric phase, superconductivity persists despite
extremely dilute carrier densities. Ferroelectric fluctuations have been
suspected to play a role in the origin of superconductivity by contributing to
electron pairing. To investigate this possibility, we used optical second
harmonic generation to measure the doping and temperature dependence of the
ferroelectric order parameter in compressively strained SrTiO$_3$ thin films.
At low temperatures, we uncover a spontaneous out-of-plane ferroelectric
polarization with an onset that correlates perfectly with normal-state
electrical resistivity anomalies. These anomalies have previously been
associated with an enhancement of the superconducting critical temperature in
doped SrTiO$_3$ films, directly linking the ferroelectric and superconducting
phases. We develop a long-range mean-field Ising model of the ferroelectric
phase transition to interpret the data and extract the relevant energy scales
in the system. Our results support a long-suspected connection between
ferroelectricity and superconductivity in SrTiO$_3$, but call into question the
role played by ferroelectric fluctuations.",1909.04782v1
2014-08-07,Magneto-transport properties of oriented Mn2CoAl films sputtered on thermally oxidized Si substrates,"Spin gapless semiconductors are interesting novel class of materials by
embracing both magnetism and semiconducting. Its potential application in
future spintronics requires realization in thin film form. In this letter, we
report a successful growth of spin gapless Mn2CoAl films on thermally oxidized
Si substrates by magnetron sputtering deposition. The films deposited at 673K
are well oriented to (001) direction and display a uniform-crystalline surface.
Magnetotransport measurements on the oriented films reveal a
semiconducting-like resistivity, small anomalous Hall conductivity and linear
magnetoresistance (MR) representative of the transport signatures of spin
gapless semiconductors. The magnetic properties of the films have also been
investigated and compared to that of bulk Mn2CoAl, with small discrepancy
induced by the composition deviation.",1408.1547v1
2017-03-06,Pressure-Induced Insulator-to-Metal Transition Provides Evidence for Negative-$U$ Centers in Large-Gap Disordered Insulators,"Attractive negative-$U$ interactions between electrons facilitated by strong
electron-phonon interaction are common in highly polarizable and disordered
materials such as amorphous chalcogenides, but there is no direct evidence for
them in large-band-gap insulators. Here we report how such negative-$U$ centers
are responsible for widespread insulator-to-metal transitions in amorphous
HfO$_2$ and Al$_2$O$_3$ thin films with a 10$^9$-fold resistance drop.
Triggered by a static hydraulic pressure or a 0.1 ps impulse of magnetic
pressure, the transition can proceed at such low pressure that there is very
little overall deformation (strain~10$^{-5}$). Absent a significant energy
change overall, the transition is attributed to the reversal of localized
electron-phonon interaction: By reversing the sign of $U$, trapped electrons
are destabilized and released, thus clearing conduction paths previously
blocked by charged traps. The results also suggest that Mott insulators when
disordered may become Anderson insulators with strong electron-phonon
interactions regulating incipient conduction paths, a novel finding of
technological significance for electronic devices.",1703.02003v1
2017-03-20,Optimized spin-injection efficiency and spin MOSFET operation based on low-barrier ferromagnet/insulator/n-Si tunnel contact,"We theoretically investigate the spin injection in different FM/I/n-Si tunnel
contacts by using the lattice NEGF method. We find that the tunnel contacts
with low barrier materials such as TiO$_2$ and Ta$_{2}$O$_{5}$, have much lower
resistances than the conventional barrier materials, resulting in a wider and
attainable optimum parameters window for improving the spin injection
efficiency and MR ratio of a vertical spin MOSFET. Additionally, we find the
spin asymmetry coefficient of TiO$_2$ tunnel contact has a negative value,
while that of Ta$_{2}$O$_{5}$ contact can be tuned between positive and
negative values, by changing the parameters.",1703.06835v3
2013-12-24,All-Metallic Electrically-Gated Tantalum Diselenide Switches and Logic Circuits,"We report the fabrication and performance of all-metallic three-terminal
devices with tantalum diselenide thin-film conducting channels. For this
proof-of-concept demonstration, the layers of 2H-TaSe2 were exfoliated
mechanically from single crystals grown by the chemical vapor transport method.
Devices with nanometer-scale thicknesses exhibit strongly non-linear
current-voltage characteristics, unusual optical response, and electrical
gating at room temperature. We have found that the drain-source current in
thin-film 2H-TaSe2-Ti/Au devices reproducibly shows an abrupt transition from a
highly resistive to a conductive state, with the threshold tunable via the gate
voltage. Such current-voltage characteristics can be used in principle for
implementing radiation-hard all-metallic logic circuits. These results may open
new application space for thin films of van der Waals materials.",1312.6863v1
2014-10-27,Giant supercurrent states in a superconductor-InAs/GaSb-superconductor junction,"Superconductivity in topological materials has attracted a great deal of
interest in both electron physics and material sciences since the theoretical
predictions that Majorana fermions can be realized in topological
superconductors [1-4]. Topological superconductivity could be realized in a
type II, band-inverted, InAs/GaSb quantum well if it is in proximity to a
conventional superconductor. Here we report observations of the proximity
effect induced giant supercurrent states in an InAs/GaSb bilayer system that is
sandwiched between two superconducting tantalum electrodes to form a
superconductor-InAs/GaSb-superconductor junction. Electron transport results
show that the supercurrent states can be preserved in a surprisingly large
temperature-magnetic field (T-H) parameter space. In addition, the evolution of
differential resistance in T and H reveals an interesting superconducting gap
structure.",1410.7342v3
2014-10-30,Kondo effect and non-Fermi liquid behavior in Dirac and Weyl semimetals,"We study the Kondo effect in three-dimensional (3D) Dirac materials and Weyl
semimetals. We find the scaling of the Kondo temperature with respect to the
doping $n$ and the coupling $J$ between the moment of the magnetic impurity and
the carriers of the semimetal. We find that when the temperature is much
smaller than the Kondo temperature the resistivity due to the Kondo effect
scales as the $n^{-4/3}$.We also study the effect of the interplay of
long-range scalar disorder and Kondo effect. In the presence of
disorder-induced long-range carrier density inhomogeneities the Kondo effect is
not characterized by a Kondo temperature but by a distribution of Kondo
temperatures. We obtain the expression of such distribution and show that its
features cause the appearance of strong non-Fermi liquid behavior. Finally we
compare the properties of the Kondo effect in 3D Dirac materials and 2D Dirac
systems like graphene and topological insulators.",1410.8532v2
2014-11-07,Temperature evolution of magnetic and transport behavior in 5\textit{d} Mott insulator Sr$_2$IrO$_4$: Significance of magneto-structural coupling,"We have investigated the temperature evolution of magnetism and its
interrelation with structural parameters in perovskite-based layered compound
Sr$_2$IrO$_4$, which is believed to be a $J_{eff}$ = 1/2 Mott insulator. The
structural distortion plays an important role in this material which induces a
weak ferromagnetism in otherwise antiferromagnetically ordered magnetic state
with transition temperature around 240 K. Interestingly, at low temperature
below around 100 K, a change in magnetic moment has been observed. Temperature
dependent x-ray diffraction measurements show sudden changes in structural
parameters around 100 K are responsible for this. Resistivity measurements show
insulating behavior throughout the temperature range across the magnetic phase
transition. The electronic transport can be described with Mott's
two-dimensional variable range hopping (VRH) mechanism, however, three
different temperature ranges are found for VRH, which is a result of varying
localization length with temperature. A negative magnetoresistance (MR) has
been observed at all temperatures in contrast to positive behavior generally
observed in strongly spin-orbit coupled materials. The quadratic field
dependence of MR implies a relevance of a quantum interference effect.",1411.1946v1
2014-11-19,Electronic structure and transport properties of Cu-deficient kuramite Cu3-xSnS4,"Electrical and thermal transport properties of Cu-deficient kuramite
Cu3-xSnS4 (CTS) was examined as a possible earth-abundant thermoelectric
material. Crystallographic structure of CTS was characterized by partial
disorder between Cu and Sn. In contrast to semiconducting electrical transport
of related compounds, such as Cu2ZnSnS4 and Cu3SbS4, metallic conduction with
an electrical resistivity of 0.4 mohmcm and a carrier concentration of 3 \times
10^21 cm-3 was observed at 300 K. Lattice thermal conductivity was calculated
at 2.6 Wm^-1K^-1, which was probably reduced by Cu-deficiency and or partial
cation disorder. Density functional theory calculation indicates valence band
was composed of hybridization between Cu 3d orbitals and S 3p orbitals.",1411.5122v2
2015-05-20,"III-V/Si Wafer Bonding Using Transparent, Conductive Oxide Interlayers","We present a method for low temperature plasma-activated direct wafer bonding
of III-V materials to Si using a transparent, conductive indium zinc oxide
interlayer. The transparent, conductive oxide (TCO) layer provides excellent
optical transmission as well as electrical conduction, suggesting suitability
for Si/III-V hybrid devices including Si-based tandem solar cells. For bonding
temperatures ranging from 100$^{\circ}$C to 350$^{\circ}$C, Ohmic behavior is
observed in the sample stacks, with specific contact resistivity below 1
$\Omega$cm$^2$ for samples bonded at 200$^{\circ}$C. Optical absorption
measurements show minimal parasitic light absorption, which is limited by the
III-V interlayers necessary for Ohmic contact formation to TCOs. These results
are promising for Ga$_{0.5}$In$_{0.5}$P/Si tandem solar cells operating at one
sun or low concentration conditions.",1505.05453v2
2016-06-10,Pressure sensing using vertically aligned carbon nanotubes on a flexible substrate,"Sensing technologies have been under research and development for their
varied applications from microelectronics to space exploration. With the end of
Moores law in sight, there is growing demand for shrinking materials and
improving sensitivity and range of sensing of sensors. Carbon nanotubes (CNTs)
offer an excellent combination of small size (in the order of nanometers in two
dimensions and micrometers in the third dimension), varied current conductivity
(from insulating to metallic), flexibility, mechanical strength and feasibility
of mass production. Here we used CNTs to fabricate pressure sensors to sense
static loads of pressure and studied the characteristics of different methods
of building the sensors. We offer an adhesive-absorption technique of
fabrication of pressure sensors that tackles the issue of endurance of the
sensors to repeated operation. We demonstrate a significant change in
resistance of a vertically aligned forest of nanotubes upon application of
static loads. This study will enable building of better pressure sensors for
several applications.",1606.03190v1
2016-06-18,Failure mechanisms of single-crystal silicon electrodes in lithium-ion batteries,"Long-term durability is a major obstacle limiting the widespread use of
lithium ion batteries (LIBs) in heavy-duty applications and others demanding
extended lifetime. As one of the root causes of degradation and failure of
battery performance, the electrode failure mechanisms are still unknown. Here,
we reveal the fundamental fracture mechanisms of single-crystal silicon
electrodes over extended lithiation/delithiation cycles, using electrochemical
testing, microstructure characterization, fracture mechanics, and finite
element analysis. Anisotropic lithium invasion causes crack initiation
perpendicular to the electrode surface, followed by growth through the
electrode thickness. The low fracture energy of the lithiated/unlithiated
silicon interface provides a weak microstructural path for crack deflection,
accounting for the crack patterns and delamination observed after repeated
cycling. Based on this physical understanding, we demonstrate how electrolyte
additives can heal electrode cracks and provide strategies to enhance the
fracture resistance in future LIBs from surface chemical, electrochemical, and
material science perspectives.",1606.06283v1
2016-06-26,(CaO)(FeSe): A Layered Wide Gap Oxychalcogenide Semiconductor,"A new iron-oxychalcogenide (CaO)(FeSe) was obtained which crystallizes in the
orthorhombic space group Pnma (No. 62) with a = 5.9180(12) {\AA}, b = 3.8802(8)
{\AA}, c = 13.193(3) {\AA}. The unique structure of (CaO)(FeSe) is built up of
a quasi-two-dimensional network of corrugated infinite layers of corner-shared
FeSe2O2 tetrahedra that extend in the ab-plane. The corrugated layers composed
of corner-shared FeSe2O2 tetrahedra stack along the c-axis with Ca2+ cations
sandwiched between the layers. Optical spectroscopy and resistivity
measurements reveal semiconducting behavior with an indirect optical band gap
of around 1.8 eV and an activation energy of 0.19(1) eV. Electronic band
structure calculations at the density function level predict a magnetic
configuration as ground state and confirm the presence of an indirect wide gap
in (CaO)(FeSe).",1606.08000v1
2017-01-17,Strange metal state near a heavy-fermion quantum critical point,"Recent experiments on quantum criticality in the Ge-substituted
heavy-electron material YbRh2Si2 under magnetic field have revealed a possible
non-Fermi liquid (NFL) strange metal (SM) state over a finite range of fields
at low temperatures, which still remains a puzzle. In the SM region, the
zero-field antiferromagnetism is suppressed. Above a critical field, it gives
way to a heavy Fermi liquid with Kondo correlation. The T (temperature)-linear
resistivity and the T-logarithmic followed by a power-law singularity in the
specific heat coefficient at low T, salient NFL behaviours in the SM region,
are un-explained. We offer a mechanism to address these open issues
theoretically based on the competition between a quasi-2d fluctuating
short-ranged resonant- valence-bonds (RVB) spin-liquid and the Kondo
correlation near criticality. Via a field-theoretical renormalization group
analysis on an effective field theory beyond a large-N approach to an anti-
ferromagnetic Kondo-Heisenberg model, we identify the critical point, and
explain remarkably well both the crossovers and the SM behaviour.",1701.04599v1
2017-01-17,Lifshitz transition mediated electronic transport anomaly in bulk ZrTe5,"Zirconium pentatelluride ZrTe$_5$, a fascinating topological material
platform, hosts exotic chiral fermions in its highly anisotropic
three-dimensional Dirac band and holds great promise advancing the
next-generation information technology. However, the origin underlying its
anomalous resistivity peak has been under debate for decades. Here we provide
transport evidence substantiating the anomaly to be a direct manifestation of a
Lifshitz transition in the Dirac band with an ultrahigh carrier mobility
exceeding 3$\times$10$^5$ cm$^2$ V$^{-1}$ s$^{-1}$. We demonstrate that the
Lifshitz transition is readily controllable by means of carrier doping, which
sets the anomaly peak temperature $T_p$. $T_p$ is found to scale approximately
as $n_H^{0.27}$, where the Hall carrier concentration $n_H$ is linked with the
Fermi level by $\epsilon_F$ $\propto$ $n_H^{1/3}$ in a linearly dispersed Dirac
band. This relation indicates $T_p$ monotonically increases with $\epsilon_F$,
which serves as an effective knob for fine tuning transport properties in
pentatelluride-based Dirac semimetals.",1701.04737v2
2017-01-26,Spin mediated magneto-electro-thermal transport behavior in Ni80Fe20/MgO/p-Si thin films,"In Si, spin-phonon interaction is the primary spin relaxation mechanism. At
low temperatures, the absence of spin-phonon relaxation will lead to enhanced
spin accumulation. Spin accumulation may change the electro-thermal transport
within the material, and thus may serve as an investigative tool for
characterizing spin-mediated behavior. Here we present the first experimental
proof of spin accumulation induced electro-thermal transport behavior in a Pd
(1 nm)/Ni80Fe20 (25 nm)/MgO (1 nm)/p-Si (2 um) specimen. The spin accumulation
originates from the spin-Hall effect. The spin accumulation changes the
phononic thermal transport in p-Si causing the observed magneto-electro-thermal
transport behavior. We also observe the inverted switching behavior in
magnetoresistance measurement at low temperatures in contrast to magnetic
characterization, which is attributed to the canted spin states in p-Si due to
spin accumulation. The spin accumulation is elucidated by current dependent
anomalous Hall resistance measurement, which shows a decrease as the electric
current is increased. This result may open a new paradigm in the field of
spin-mediated transport behavior in semiconductor and semiconductor
spintronics.",1701.07854v2
2017-11-27,Extreme magnetoresistance induced by Zeeman effect-driven electron-hole compensation and topological protection in MoSi$_2$,"The magnetoresistance is the magnetic field induced change of electrical
resistivity of a material. Recent studies have revealed extremely large
magnetoresistance in several non-magnetic semimetals, which has been explained
on the basis of either electron-hole compensation or the Fermi surface
topology, or the combination of both. Here, we present a single crystal study
on MoSi$_2$, which exhibits extremely large magnetoresistance, approaching
almost 10$^7$ % at 2 K and 14 T magnetic field. It is found that the
electron-hole compensation level in MoSi$_2$ evolves with magnetic field, which
is resulted from strong Zeeman effect, and found beneficial in boosting the
large non-saturating magnetoresistance. The non-trivial Berry phase in the de
Haas-van Alphen oscillations and the moderate suppression of backward
scattering of the charge carriers lend support for the topological nature of
this semimetal. The ultra-large carrier mobility of the topologically protected
charge carriers reinforces the magnetoresistance of MoSi2 to an unprecedented
large value.",1711.09646v1
2017-11-30,Experimental observation of node-line-like surface states in LaBi,"In a Dirac nodal line semimetal, the bulk conduction and valence bands touch
at extended lines in the Brillouin zone. To date, most of the theoretically
predicted and experimentally discovered nodal lines derive from the bulk bands
of two- and three-dimensional materials. Here, based on combined angle-resolved
photoemission spectroscopy measurements and first-principles calculations, we
report the discovery of node-line-like surface states on the (001) surface of
LaBi. These bands derive from the topological surface states of LaBi and bridge
the band gap opened by spin-orbit coupling and band inversion. Our
first-principles calculations reveal that these ""nodal lines"" have a tiny gap,
which is beyond typical experimental resolution. These results may provide
important information to understand the extraordinary physical properties of
LaBi, such as the extremely large magnetoresistance and resistivity plateau.",1711.11174v2
2017-12-19,"Synthesis, Crystal Structure, and Physical Properties of New Layered Oxychalcogenide La2O2Bi3AgS6","We have synthesized a new layered oxychalcogenide La2O2Bi3AgS6. From
synchrotron X-ray diffraction and Rietveld refinement, the crystal structure of
La2O2Bi3AgS6 was refined using a model of the P4/nmm space group with a =
4.0644(1) {\AA} and c = 19.412(1) {\AA}, which is similar to the related
compound LaOBiPbS3, while the interlayer bonds (M2-S1 bonds) are apparently
shorter in La2O2Bi3AgS6. The tunneling electron microscopy (TEM) image
confirmed the lattice constant derived from Rietveld refinement (c ~ 20 {\AA}).
The electrical resistivity and Seebeck coefficient suggested that the
electronic states of La2O2Bi3AgS6 are more metallic than those of LaOBiS2 and
LaOBiPbS3. The insertion of a rock-salt-type chalcogenide into the van der
Waals gap of BiS2-based layered compounds, such as LaOBiS2, will be a useful
strategy for designing new layered functional materials in the layered
chalcogenide family.",1712.06726v1
2017-12-05,A Holistic Approach to Evaluate EMI Shielding Characteristics of Carbon Nanotube-based Polymer Composites,"The work presents a comprehensive methodology to determine the Shielding
Effectiveness (SE) of single-walled carbon nanotubes (SWCNTs)/polymer
nanocomposites. Here, an algorithm based on Ant Colony Optimization (ACO) was
employed to determine the electrical conductivity ({\sigma}) of these
nanocomposites as a function of SWCNT concentration. Then, these {\sigma}
values were used to compute the SE values as a function of frequency and
concentration. Specifically, a pseudo three-dimensional (3D) percolation model
was developed to study the effects of random connectivity of SWCNTs to one
another on the {\sigma} values of the nanocomposites. Both intrinsic and
tunneling resistances were taken into account. The consequences of the presence
of both well-exfoliated and aggregated SWCNTs with varying lengths distributed
inhomogeneously on {\sigma} and SE values were investigated.",1712.08188v1
2018-10-13,Tuning the electronic structures and transport properties of zigzag blue phosphorene nanoribbons,"In recent years, single element two-dimensional atom crystal materials have
aroused extensive interest in many applications. Blue phosphorus, successfully
synthesized on Au substrate by molecular beam epitaxy not long ago, shows
unusual geometrical and electronic structures. We investigate the electronic
structures and transport properties of zigzag blue phosphorene nanoribbons by
using a first-principles method, which can be obviously tuned via different
groups passivation on the both edges. The ZBPNRs-H and ZBPNRs-OH present a wide
gap semiconductor property. While the ZBPNRs-O are metallic. Interestingly, the
current-voltage curves of ZBPNRs-O show a negative differential resistive
effect, which is independent on the ribbon width. The electric current through
the ZBPNRs-O is mainly flowing along the both outside zigzag phosphorus chains
via the way of P-P bond current. Through modifying the both edges with various
functional groups, the ZBPNRs can display some important functional
characteristics and become a candidate of NDR devices.",1810.05792v1
2018-10-18,Coating of Aluminum Alloys by Micro Arc Oxidation in Nitrate Salt,"Plasma electrolytic oxidation (PEO) is a process for obtaining oxide coatings
on valve metals. Mostly PEO is done in an aqueous solution electrolyte which
limits the size of treated parts due to the system heating up. In presented
work an alternative method of PEO processing applied in aluminum 1050 alloy in
nitrate molten salt was investigated. The morphology, phase and chemical
compositions, micro-hardness, and corrosion resistance were examined using. The
obtained results showed that formed coating contains from two sub-layers, outer
soft layer with the thickness of 4 micrometer and inner, denser layer with the
thickness of 5 micrometer. The formed coating consists of corundum, {\gamma} -
Al2O3, {\theta} - Al2O3 and is free of any contaminants originated from the
electrolyte.",1810.08018v1
2018-11-26,Synthesis of Oxidation-Resistant Electrochemical-Active Copper Nanowires Using Phenylenediamine Isomers,"Phenylenediamine (PDA) was chosen as a coordinating, reducing, and capping
agent to effectively direct growth and protect against oxidation of Cu
nanowires (Cu NWs) in an aqueous solution. PDA was found to reduce Cu (II) to
Cu (I) at room temperature, and stabilize the resulting Cu (I) by forming a
coordination complex. The presence of a stable Cu (I) complex is the key step
in the synthesis of Cu NWs under mild conditions. Different PDA isomers lead to
different growth paths of forming Cu NWs. Both pPDA and mPDA-synthesized Cu NWs
were covered with a thin layer of polyphenylenediamine and show excellent
anti-oxidation properties, even in the presence of water. The usefulness of the
present and electrochemical active Cu NWs for a variety of nanotechnology
applications is discussed.",1811.10510v1
2019-01-31,Unconventional Bloch-Grüneisen scattering in hybrid Bose-Fermi systems,"We report on the novel mechanism of electron scattering in hybrid Bose-Fermi
systems consisting of a two-dimensional electron gas in the vicinity of an
exciton condensate: We show that a pair-of-bogolons--mediated scattering proves
to be dominating over the conventional acoustic phonon channel and over the
single-bogolon scattering, even if the screening is taken into account. We
develop a microscopic theory of this effect, focusing on GaAs and MoS$_2$
materials, and find the principal temperature dependence of resistivity,
distinct from the conventional phonon--mediated processes. Further, we
scrutinize parameters and suggest a way to design composite samples with
predefined electron mobilities and propose a mechanism of electron pairing for
superconductivity.",1902.01214v1
2019-02-14,Charge transport in oxygen-deficient EuTiO$_3$: the emerging picture of dilute metallicity in quantum-paraelectric perovskite oxides,"We report on a study of charge transport in EuTiO$_{3-\delta}$ single
crystals with carrier density tuned across several orders of magnitude.
Comparing this system with other quasi-cubic perovskites, in particular
strontium titanate, we draw a comprehensive picture of metal-insulator
transition and dilute metallicity in this $AB$O$_3$ family. Because of a lower
electric permittivity, the metal-insulator transition in EuTiO$_{3-\delta}$
occurs at higher carrier densities compared to SrTiO$_3$. At low temperature, a
distinct $T^2$ resistivity is visible. Its prefactor $A$ smoothly decreases
with increasing carrier concentration in a similar manner in three different
perovskites. Our results draw a comprehensive picture of charge transport in
doped quantum paraelectrics.",1902.05512v2
2019-02-27,Stokes flow analogous to viscous electron current in graphene,"Electron transport in two-dimensional conducting materials such as graphene,
with dominant electron-electron interaction, exhibits unusual vortex flow that
leads to a nonlocal current-field relation (negative resistance), distinct from
the classical Ohm's law. The transport behavior of these materials is best
described by low Reynolds number hydrodynamics, where the constitutive
pressure-speed relation is Stoke's law. Here we report evidence of such
vortices observed in a viscous flow of Newtonian fluid in a microfluidic device
consisting of a rectangular cavity$-$analogous to the electronic system. We
extend our experimental observations to elliptic cavities of different
eccentricities, and validate them by numerically solving bi-harmonic equation
obtained for the viscous flow with no-slip boundary conditions. We verify the
existence of a predicted threshold at which vortices appear. Strikingly, we
find that a two-dimensional theoretical model captures the essential features
of three-dimensional Stokes flow in experiments.",1902.10383v1
2019-06-30,Dissipative-regime measurements as a tool for confirming and characterizing near-room-temperature superconductivity,"The search for new superconducting materials approaching room temperature
benefits from having a variety of testing methodologies to confirm and
characterize the presence of superconductivity. Often the first signatures of
new superconducting species occur incompletely and in very small volume
fractions. These trace amounts may be too weak to produce an observable
Meissner effect and the resistance may not go completely to zero if the
percolation threshold is not met. Under these conditions, secondary
behavior--such as transitions or cross overs in the temperature dependence of
magnetoresistance, magnetic irreversibility, or thermopower--are often used as
indications for the presence of superconductivity. Our group has developed a
rather unique set of fast-timescale and dissipative transport measurements that
can provide another tool set for confirming and characterizing suspected
superconductivity. Here we provide some background for these methods and
elucidate their collaborative value in the search for new superconducting
materials. Keywords: pairbreaking, pair-breaking, vortex, vortices, theory,
tutorial, RTS, room-temperature superconductivity, superconductor, detection,
characterization",1907.00425v1
2019-07-08,Theory of Spin Injection in Two-dimensional Metals with Proximity-Induced Spin-Orbit Coupling,"Spin injection is a powerful experimental probe into a wealth of
nonequilibrium spin-dependent phenomena displayed by materials with spin-orbit
coupling (SOC). Here, we develop a theory of coupled spin-charge diffusive
transport in two-dimensional spin-valve devices. The theory describes a
realistic proximity-induced SOC with both spatially uniform and random
components of the SOC due to adatoms and imperfections, and applies to the two
dimensional electron gases found in two-dimensional materials and van der Walls
heterostructures. The various charge-to-spin conversion mechanisms known to be
present in diffusive metals, including the spin Hall effect and several
mechanisms contributing current-induced spin polarization are accounted for.
Our analysis shows that the dominant conversion mechanisms can be discerned by
analyzing the nonlocal resistance of the spin-valve for different polarizations
of the injected spins and as a function of the applied in-plane magnetic field.",1907.03727v1
2019-07-09,Low-Temperature Dielectric Anomalies at the Mott Insulator-Metal Transition,"The correlation-driven Mott transition is commonly characterized by a drop in
resistivity across the insulator-metal phase boundary; yet, the complex
permittivity provides a deeper insight into the microscopic nature. We
investigate the frequency- and temperature-dependent dielectric response of the
Mott insulator $\kappa$-(BEDT-TTF)$_{2}$-Cu$_2$(CN)$_3$ when tuning from a
quantum spin liquid into the Fermi-liquid state by applying external pressure
and chemical substitution of the donor molecules. At low temperatures the
coexistence region at the first-order transition leads to a strong enhancement
of the quasi-static dielectric constant $\epsilon_1$ when the effective
correlations are tuned through the critical value. Several dynamical regimes
are identified around the Mott point and vividly mapped through pronounced
permittivity crossovers. All experimental trends are captured by dynamical
mean-field theory of the single-band Hubbard model supplemented by percolation
theory.",1907.04437v2
2019-07-20,Generating Optimal Grasps Under A Stress-Minimizing Metric,"We present stress-minimizing (SM) metric, a new metric of grasp qualities.
Unlike previous metrics that ignore the material of target objects, we assume
that target objects are made of homogeneous isotopic materials. SM metric
measures the maximal resistible external wrenches without causing fracture in
the target objects. Therefore, SM metric is useful for robot grasping valuable
and fragile objects. In this paper, we analyze the properties of this new
metric, propose grasp planning algorithms to generate globally optimal grasps
maximizing the SM metric, and compare the performance of the SM metric and a
conventional metric. Our experiments show that SM metric is aware of the
geometries of target objects while the conventional metric are not. We also
show that the computational cost of the SM metric is on par with that of the
conventional metric.",1907.08749v1
2019-07-23,Electronic transport in thin films of BaPbO$_3$: Unraveling two-dimensional quantum effects,"Recently, perovskite related BaPbO$_3$ has attracted attention due to its
hidden topological properties and, moreover, has been used as a thin layer in
heterostructures to induce two-dimensional superconductivity. Here we
investigate the normal state electronic transport properties of thin films of
BaPbO$_3$. Temperature and magnetic field dependent sheet resistances are
strongly affected by two-dimensional quantum effects. Our analysis decodes the
interplay of spin--orbit coupling, disorder, and electron--electron interaction
in this compound. Similar to recently discussed topological materials, we find
that weak antilocalization is the dominant protagonist in magnetotransport,
whereas electron--electron interactions play a pronounced role in the
temperature dependence. A systematic understanding of these quantum effects is
essential to allow for an accurate control of properties not only of thin films
of BaPbO$_3$, but also of topological heterostructures.",1907.09839v2
2019-07-28,Magneto-ionic control of spin polarization in magnetic tunnel junctions,"Magnetic tunnel junctions (MTJs) with Hf0.5Zr0.5O2 barriers are reported to
show both tunneling magnetoresistance effect (TMR) and tunneling
electroresistance effect (TER), displaying four resistance states by magnetic
and electric field switching. Here we show that, under electric field cycling
of large enough magnitude, the TER can reach values as large as 10^6%.
Moreover, concomitant with this TER enhancement, the devices develop electrical
control of spin polarization, with sign reversal of the TMR effect. Currently,
this intermediate state exists for a limited number of cycles and understanding
the origin of these phenomena is key to improve its stability. The experiments
presented here point to the magneto-ionic effect as the origin of the large TER
and strong magneto-electric coupling, showing that ferroelectric polarization
switching of the tunnel barrier is not the main contribution.",1907.12111v1
2020-02-11,On the Mechanical and Thermal Stability of Free-standing Monolayer Amorphous Carbon,"Recently (C.-T. Toh et al., Nature 577, 199 (2020)), the first synthesis of
free-standing monolayer amorphous carbon (MAC) was achieved. MAC is a pure
carbon structure composed of five, six, seven and eight atom rings randomly
distributed. MAC proved to be surprisingly stable and highly fracture
resistant. Its electronic properties are similar to boron nitride. In this
work, we have investigated the mechanical properties and thermal stability of
MAC models using fully-atomistic reactive molecular dynamics simulations. For
comparison purposes, the results are contrasted against pristine graphene (PG)
models of similar dimensions. Our results show that MAC and PG exhibit distinct
mechanical behavior and fracture dynamics patterns. While PG after a critical
strain threshold goes directly from elastic to brittle regimes, MAC shows
different elastic stages between these two regimes. Remarkably, MAC is
thermally stable up to 3600 K, which is close to the PG melting point. These
exceptional physical properties make MAC-based materials promising candidates
for new technologies, such as flexible electronics.",2002.04682v1
2020-02-28,Evidence for metastable photo-induced superconductivity in K$_3$C$_{60}$,"Far and mid infrared optical pulses have been shown to induce non-equilibrium
unconventional orders in complex materials, including photo-induced
ferroelectricity in quantum paraelectrics, magnetic polarization in
antiferromagnets and transient superconducting correlations in the normal state
of cuprates and organic conductors. In the case of non-equilibrium
superconductivity, femtosecond drives have generally resulted in electronic
properties that disappear immediately after excitation, evidencing a state that
lacks intrinsic rigidity. Here, we make use of a new optical device to drive
metallic K$_3$C$_{60}$ with mid-infrared pulses of tunable duration, ranging
between one picosecond and one nanosecond. The same superconducting-like
optical properties observed over short time windows for femtosecond excitation
are shown here to become metastable under sustained optical driving, with
lifetimes in excess of ten nanoseconds. Direct electrical probing becomes
possible at these timescales, yielding a vanishingly small resistance. Such a
colossal positive photo-conductivity is highly unusual for a metal and, when
taken together with the transient optical conductivities, it is rather
suggestive of metastable light-induced superconductivity.",2002.12835v1
2020-03-20,Quantum Fluctuations in the Non-Fermi Liquid System CeCo$_{2}$Ga$_{8}$ Investigated Using $μ$SR,"Reduced dimensionality offers a crucial information in deciding the type of
the quantum ground state in heavy fermion materials. Here we have examined
stoichiometric CeCo$_{2}$Ga$_{8}$ compound, which crystallizes in a
quasi-one-dimensional crystal structure with Ga-Ce-Co chains along the
$c$-axis. The low-temperature behavior of magnetic susceptibility
($\chi\sim-\ln T$), heat capacity ($C_p/T\sim-\ln T$), and resistivity
($\rho\sim T^{n}$) firmly confirm the non-Fermi liquid ground state of
CeCo$_{2}$Ga$_{8}$. We studied the low-energy spin dynamics of
CeCo$_{2}$Ga$_{8}$ compound utilizing zero field (ZF-) and longitudinal field
(LF-) muon spin relaxation ($\mu$SR) measurements. ZF-$\mu$SR measurement
reveals the absence of long-range magnetic ordering down to 70 mK, and
interestingly below 1 K, the electronic relaxation rate sharply rises,
intimating the appearance of low energy quantum spin fluctuations in
CeCo$_{2}$Ga$_{8}$.",2003.09104v1
2020-03-28,Superconductivity in the nonsymmorphic line-nodal compound CaSb$_2$,"We found superconductivity in CaSb$_2$ with the transition temperature of 1.7
K by means of electrical-resistivity, magnetic-susceptibility, and
specific-heat measurements. This material crystallizes in a nonsymmorphic
structure and is predicted to have multiple Dirac nodal lines in the bulk
electronic band structure protected by symmetry even in the presence of
spin-orbit coupling. We discuss a possible topological superconductivity for
the quasi-2-dimensional band originating mainly from one of the antimony sites.",2003.12800v1
2020-02-25,Advanced protection against environmental degradation of silver mirror stacks for space application,"Protection of silver mirror stacks from environmental degradation before
launching is crucial for space applications. Hereby, we report a comparative
study of the advanced protection of silver mirror stacks for space telescopes
provided by SiO2 and Al2O3 coatings in conditions of accelerated aging by
sulfidation. The model silver stack samples were deposited by cathodic
magnetron sputtering on a reference silica substrate for optical applications
and a surface-pretreated SiC substrate. Accelerated aging was performed in dry
and more severe wet conditions. Optical micrographic observations, surface and
interface analysis by Time-of Flight Secondary Ion Mass Spectrometry (ToF-SIMS)
and reflectivity measurements were combined to comparatively study the effects
of degradation. The results show a lower kinetics of degradation by accelerated
aging of the stacks protected by the alumina coating in comparable test
conditions.",2004.06590v1
2020-04-20,Lindemann unjamming of emulsions,"We study the bulk and shear elastic properties of barely-compressed,
""athermal"" emulsions and find that the rigidity of the jammed solid fails at
remarkably large critical osmotic pressures. The minuscule yield strain and
similarly small Brownian particle displacement of solid emulsions close to this
transition suggests that this catastrophic failure corresponds to a
plastic-entropic instability: the solid becomes too soft and weak to resist the
thermal agitation of the droplets that compose it and fails. We propose a
modified Lindemann stability criterion to describe this transition and derive a
scaling law for the critical osmotic pressure that agrees quantitatively with
experimental observations.",2004.09594v2
2020-09-07,Quantum Sensing of Insulator-to-Metal Transitions in a Mott Insulator,"Nitrogen vacancy (NV) centers, optically-active atomic defects in diamond,
have attracted tremendous interest for quantum sensing, network, and computing
applications due to their excellent quantum coherence and remarkable
versatility in a real, ambient environment. Taking advantage of these
strengths, we report on NV-based local sensing of the electrically driven
insulator-to-metal transition (IMT) in a proximal Mott insulator. We studied
the resistive switching properties of both pristine and ion-irradiated VO2 thin
film devices by performing optically detected NV electron spin resonance
measurements. These measurements probe the local temperature and magnetic field
in electrically biased VO2 devices, which are in agreement with the global
transport measurement results. In pristine devices, the electrically-driven IMT
proceeds through Joule heating up to the transition temperature while in
ion-irradiated devices, the transition occurs non-thermally, well below the
transition temperature. Our results provide the first direct evidence for
non-thermal electrically induced IMT in a Mott insulator, highlighting the
significant opportunities offered by NV quantum sensors in exploring nanoscale
thermal and electrical behaviors in Mott materials.",2009.02886v1
2020-09-09,Population Dynamics Model and Analysis for Bacteria Transformation and Conjugation,"We present a two-species population model in a well-mixed environment where
the dynamics involves, in addition to birth and death, changes due to
environmental factors and inter-species interactions. The novel dynamical
components are motivated by two common mechanisms for developing antibiotic
resistance in bacteria: plasmid {\it transformation}, where external genetic
material in the form of a plasmid is transferred inside a host cell; and {\it
conjugation} by which one cell transfers genetic material to another by direct
cell-to-cell contact. Through analytical and numerical methods, we identify the
effects of transformation and conjugation individually. With transformation
only, the two-species system will evolve towards one species' extinction, or a
stable co-existence in the long-time limit. With conjugation only, we discover
interesting oscillations for the system. Further, we quantify the combined
effects of transformation and conjugation, and chart the regimes of stable
co-existence, a result with ecological implications.",2009.04276v1
2020-09-28,Two-dimensional Janus van der Waals heterojunctions: a review of recent research progresses,"Two-dimensional Janus van der Waals (vdW) heterojunctions, referring to the
junction containing at least one Janus material, are found to exhibit tuneable
electronic structures, wide light adsorption spectra, controllable contact
resistance, and sufficient redox potential due to the intrinsic polarization
and unique interlayer coupling. These novel structures and properties are
promising for the potential applications in electronics and energy conversion
devices. To provide a comprehensive picture about the research progress and
guide the following investigations, here we summarize their fundamental
properties of different types of two-dimensional Janus vdW heterostructures
including electronic structure, interface contact and optical properties, and
discuss the potential applications in electronics and energy conversion
devices. The further challenges and possible research directions of the novel
heterojunctions are discussed at the end of this review.",2009.12985v1
2022-02-11,Unusual electrical and magnetic properties in layered EuZn2As2,"Eu-based compounds often exhibit unusual magnetism, which is critical for
nontrivial topological properties seen in materials such as EuCd2As2. We
investigate the structure and physical properties of EuZn2As2 through
measurements of the electrical resistivity, Hall effect, magnetization, and
neutron diffraction. Our data show that EuZn2As2 orders antiferromagnetically
with an A-type spin configuration below TN = 19 K. Surprisingly, there is
strong evidence for dominant ferromagnetic fluctuations above TN, as reflected
by positive Curie-Weiss temperature and extremely large negative
magnetoresistance (MR) between TN and Tfl {\guillemotright} 200 K. Furthermore,
the angle dependence of the MRab indicates field-induced spin reorientation
from the ab-plane to a direction approximately 45{\deg} from the ab plane.
Compared to EuCd2As2, the doubled TN and Tfl make EuZn2As2 a better platform
for exploring topological properties in both magnetic fluctuation (TN < T <
Tfl) and ordered (T < TN) regimes.",2202.05884v1
2022-02-16,Emergence of Intergranular Tunneling Dominated Negative Magnetoresistance in Helimagnetic Manganese Phosphide Nanorod Thin Films,"Helical magnets are emerging as a novel class of materials for spintronics
and sensor applications; however, research on their charge and spin transport
properties in a thin film form is less explored. Herein, we report the
temperature and magnetic field dependent charge transport properties of a
highly crystalline MnP nanorod thin film over a wide temperature range (2-350
K). The MnP nanorod films of 100 nm thickness were grown on Si substrates at
500 oC using molecular beam epitaxy. The temperature dependent resistivity data
exhibits a metallic behavior over the entire measured temperature range.
However, large negative magnetoresistance of up to 12% is observed below 50 K
at which the system enters a stable helical (screw) magnetic state. In this
temperature regime, the MR(H,T) dependence seems to show a magnetic field
manipulated phase coexistence. The observed magnetoresistance is dominantly
governed by the intergranular spin dependent tunneling mechanism. These
findings pinpoint a correlation between the transport and magnetism in this
helimagnetic system.",2202.07915v1
2014-01-30,Infrared luminescence in Bi-doped Ge-S and As-Ge-S chalcogenide glasses and fibers,"Experimental and theoretical studies of spectral properties of chalcogenide
Ge-S and As-Ge-S glasses and fibers are performed. A broad infrared (IR)
luminescence band which covers the 1.2-2.3~$\mu$m range with a lifetime about
6~$\mu$s is discovered. Similar luminescence is also present in optical fibers
drawn from these glasses. Arsenic addition to Ge-S glass significantly enhances
both its resistance to crystallization and the intensity of the luminescence.
Computer modeling of Bi-related centers shows that interstitial Bi$^+$ ions
adjacent to negatively charged S vacancies are most likely responsible for the
IR luminescence.",1401.7815v1
2016-03-02,Energy filtering enhancement of thermoelectric performance of nanocrystalline Cr-Si composites,"We report on thermoelectric properties of nanocrystalline Cr$_{\rm
1-x}$Si$_{\rm x}$ composite films. As-deposited amorphous films were
transformed into a nanocrystalline state with average grain size of 10--20~nm
by annealing during in-situ thermopower and electrical resistivity
measurements. The partially crystallized films, i.e. the films consisting of
crystalline grains dispersed in the amorphous matrix, are a new type of the
heterogeneous material where the nanocrystalline phase plays the role of
scattering centers giving rise to a large contribution to the thermopower. We
show that the thermopower enhancement is related to the energy dependent
scattering (energy filtering) of the charge carriers on the nanograin
interfaces.",1603.00626v4
2016-03-07,Tuning of thermoelectric properties with changing Se content in Sb2Te3,"Polycrystalline Sb 2 Te 3-x Se x (0.0 < x < 1.0) samples were synthesized by
the solid state reaction method. The structural analysis showed that up to the
maximal concentration of Se, the samples possess the Rhombohedral crystal
symmetry (space group R 3 m ). Increase of Se content increases the resistivity
of the samples. Variation of phonon frequencies, observed from Raman
spectroscopic study, depict anomalous behaviour around x = 0.2. The sample Sb 2
Te 2.8 Se 0.2 also shows maximum Seebeck coefficient, carrier concentration and
thermoelectric power factor. Nature of scattering mechanism controlling the
thermopower data has been explored. The thermoelectric properties of the
synthesized materials have been analyzed theoretically in the frame of
Boltzmann equation approach.",1603.01998v1
2016-03-28,Mechanism for the Large Conductance Modulation in Electrolyte-gated Thin Gold Films,"Electrolyte gating using ionic liquid electrolytes has recently generated
considerable interest as a method to achieve large carrier density modulations
in a variety of materials. In noble metal thin films, electrolyte gating
results in large changes in sheet resistance. The widely accepted mechanism for
these changes is the formation of an electric double layer with a charged layer
of ions in the liquid and accumulation or depletion of carriers in the thin
film. We report here a different mechanism. In particular, we show using x-ray
absorption near edge structure (XANES) that the previously reported large
conductance modulation in gold films is due to reversible oxidation and
reduction of the surface rather than the charging of an electric double layer.
We show that the double layer capacitance accounts for less than 10\% of the
observed change in transport properties. These results represent a significant
step towards understanding the mechanisms involved in electrolyte gating.",1603.08286v1
2017-04-05,Superconductivity at 33 - 37 K in $ALn_2$Fe$_4$As$_4$O$_2$ ($A$ = K and Cs; $Ln$ = Lanthanides),"We have synthesized 10 new iron oxyarsenides, K$Ln_2$Fe$_4$As$_4$O$_2$ ($Ln$
= Gd, Tb, Dy, and Ho) and Cs$Ln_2$Fe$_4$As$_4$O$_2$ ($Ln$ = Nd, Sm, Gd, Tb, Dy,
and Ho), with the aid of lattice-match [between $A$Fe$_2$As$_2$ ($A$ = K and
Cs) and $Ln$FeAsO] approach. The resultant compounds possess hole-doped
conducting double FeAs layers, [$A$Fe$_4$As$_4$]$^{2-}$, that are separated by
the insulating [$Ln_2$O$_2$]$^{2+}$ slabs. Measurements of electrical
resistivity and dc magnetic susceptibility demonstrate bulk superconductivity
at $T_\mathrm{c}$ = 33 - 37 K. We find that $T_\mathrm{c}$ correlates with the
axis ratio $c/a$ for all 12442-type superconductors discovered. Also,
$T_\mathrm{c}$ tends to increase with the lattice mismatch, implying a role of
lattice instability for the enhancement of superconductivity.",1704.01488v1
2017-04-09,Properties of In-Plane Graphene/MoS2 Heterojunctions,"The graphene/MoS2 heterojunction formed by joining the two components
laterally in a single plane promises to exhibit a low-resistance contact
according to the Schottky-Mott rule. Here we provide an atomic-scale
description of the structural, electronic, and magnetic properties of this type
of junction. We first identify the energetically favorable structures in which
the preference of forming C-S or C-Mo bonds at the boundary depends on the
chemical conditions. We find that significant charge transfer between graphene
and MoS2 is localized at the boundary. We show that the abundant 1D boundary
states substantially pin the Fermi level in the lateral contact between
graphene and MoS2, in close analogy to the effect of 2D interfacial states in
the contacts between 3D materials. Furthermore, we propose specific ways in
which these effects can be exploited to achieve spin-polarized currents.",1704.02669v1
2017-04-11,Neutron powder diffraction study on the iron-based nitride superconductor ThFeAsN,"We report neutron diffraction and transport results on the newly discovered
superconducting nitride ThFeAsN with $T_c=$ 30 K. No magnetic transition, but a
weak structural distortion around 160 K, is observed cooling from 300 K to 6 K.
Analysis on the resistivity, Hall transport and crystal structure suggests this
material behaves as an electron optimally doped pnictide superconductors due to
extra electrons from nitrogen deficiency or oxygen occupancy at the nitrogen
site, which together with the low arsenic height may enhance the electron
itinerancy and reduce the electron correlations, thus suppress the static
magnetic order.",1704.03119v1
2017-04-29,Infrared-transmittance tunable metal-insulator conversion device with thin-film-transistor-type structure on a glass substrate,"Infrared (IR) transmittance tunable metal-insulator conversion was
demonstrated on glass substrate by using thermochromic vanadium dioxide (VO2)
as the active layer in three-terminal thin-film-transistor-type device with
water-infiltrated glass as the gate insulator. Alternative positive/negative
gate-voltage applications induce the reversible protonation/deprotonation of
VO2 channel, and two-orders of magnitude modulation of sheet-resistance and 49%
modulation of IR-transmittance were simultaneously demonstrated at room
temperature by the metal-insulator phase conversion of VO2 in a non-volatile
manner. The present device is operable by the room-temperature protonation in
all-solid-state structure, and thus it will provide a new gateway to future
energy-saving technology as advanced smart window.",1705.00130v1
2017-05-02,Nodeless superconductivity and the peak effect in the quasi-skutterudites $\mathrm{Lu}_3\mathrm{Os}_4\mathrm{Ge}_{13}$ and $\mathrm{Y}_3\mathrm{Ru}_4\mathrm{Ge}_{13}$,"We report an investigation of the superconducting states of
$\mathrm{Lu}_3\mathrm{Os}_4\mathrm{Ge}_{13}$ and
$\mathrm{Y}_3\mathrm{Ru}_4\mathrm{Ge}_{13}$ single crystals by measurements of
the electrical resistivity, ac susceptibility and London penetration depth. The
analysis of the penetration depth and the derived superfluid density indicates
the presence of nodeless superconductivity and suggest that there are multiple
superconducting gaps in both materials. Furthermore, ac susceptibility
measurements of both compounds display the peak effect in the low temperature
region of the $H-T$ phase diagram. This anomalous increase of the critical
current with field gives an indication of a change of the arrangement of flux
lines in the mixed state, as found in some of the isostructural stannide
materials.",1705.00818v1
2017-05-15,Novel metal-insulator-transition at the SrTiO3/SmTiO3 interface,"We report on a metal-insulator transition (MIT) that is observed in an
electron system at the SmTiO3/SrTiO3 interface. This MIT is characterized by an
abrupt transition at a critical temperature, below which the resistance changes
by more than an order of magnitude. The temperature of the transition
systematically depends on the carrier density, which is tuned from ~ 1x10^14
cm^-2 to 3x10^14 cm^-2 by changing the SmTiO3 thickness. Analysis of the
transport properties shows non-Fermi liquid behavior and mass enhancement as
the carrier density is lowered. We compare the MIT characteristics with those
of known MITs in other materials systems and show that they are distinctly
different in several aspects. We tentatively conclude that both long range
Coulomb interactions and the fixed charge at the polar interface are likely to
play a role in this MIT. The strong dependence on the carrier density makes
this MIT of interest for field-tunable devices.",1705.05447v1
2017-07-11,Strain-dependent solid surface stress and the stiffness of soft contacts,"Surface stresses have recently emerged as a key player in the mechanics of
highly compliant solids. The classic theories of contact mechanics describe
adhesion with a compliant substrate as a competition between surface energies
driving deformation to establish contact and bulk elasticity resisting this.
However, it has recently been shown that surface stresses provide an additional
restoring force that can compete with and even dominate over elasticity in
highly compliant materials, especially when length scales are small compared to
the ratio of the surface stress to the elastic modulus, $\Upsilon/E$. Here, we
investigate experimentally the contribution of surface stresses to the force of
adhesion. We find that the elastic and capillary contributions to the adhesive
force are of similar magnitude, and that both are required to account for
measured adhesive forces between rigid silica spheres and compliant, silicone
gels. Notably, the strain-dependence of the solid surface stress contributes
significantly to the stiffness of soft solid contacts.",1707.03089v1
2017-08-02,Review on Modeling of Mechanical and Thermal Properties of Nano- and Micro-Composites,"This article deals with the prediction of thermomechanical properties of
fiber reinforced composites using several micromechanics models. These include
strength of material approach, Halpin-Tsai equations, multi-phase mechanics of
materials approaches, multi-phase Mori-Tanaka models, composite cylindrical
assemblage model, Voigt-Reuss models, modified mixture rule, Cox model,
effective medium approach and method of cells. Several composite systems
reinforced with short and long, aligned, random and wavy reinforcements were
considered. In addition, different aspects such as fiber-matrix interphase,
fiber-matrix interfacial thermal resistance, fiber geometry, and multiple types
of reinforcements were considered to model the composites systems. The current
study also presents some important preliminary concepts and application of
developed micromechanics models to advanced nanocomposites such as carbon
nanotube reinforced composite. Main contribution of the current work is the
investigation of several analytical micromechanical models, while most of the
existing studies on the subject deal with only one or two approaches
considering few aspects.",1708.00764v1
2017-08-10,Observation of two-dimensional Fermi surface and Dirac dispersion in YbMnSb$_2$,"We present the crystal structure, electronic structure, and transport
properties of the material YbMnSb$_2$, a candidate system for the investigation
of Dirac physics in the presence of magnetic order. Our measurements reveal
that this system is a low-carrier-density semimetal with a 2D Fermi surface
arising from a Dirac dispersion, consistent with the predictions of density
functional theory calculations of the antiferromagnetic system. The low
temperature resistivity is very large, suggesting scattering in this system is
highly efficient at dissipating momentum despite its Dirac-like nature.",1708.03308v1
2018-08-06,Short Note on Superconductivity at Ambient Temperature and Pressure in Silver Embedded Gold Nano-particles: A Goldsmith job ahead,"Very recent observation of superconductivity in both transport (resistance
versus temperature) and magnetization (Zero field cooled) at around 235 K has
obviously raised many eyebrows. The experimental fraternity in particular is
more thrilled. Although the results presented in the paper are clean and both
transport and magnetization measurements do approve the observation of
superconductivity to some extent (the shielding fraction is low), the problem
is to synthesize or fabricate the material. This I name a goldsmith job,
primarily because one has to deal with Gold and Silver nano particles
combination/amalgamation/alloying or even who knows the inter-facial new phase,
which could be superconducting. This short note is written in view to let the
spark continues and the interesting work of ) authors is reproduced
independently.",1808.01797v2
2018-08-12,"A Facile Approach to Prepare Self-Assembled, Nacre-Inspired Clay/Polymer Nano-Composites","Nature provides many paradigms for the design and fabrication of artificial
composite materials. Inspired by the relationship between the well-ordered
architecture and biopolymers found in natural nacre, we present a facile
strategy to construct large-scale organic/inorganic nacre-mimetics with
hierarchical structure via a water-evaporation self-assembly process. Through
hydrogen bonding, we connect Laponite-nanoclay platelets with each other using
naturally abundant cellulose creating thin, flexible films with a local
brick-and-mortar architecture. While the aqueous solution displays liquid
crystalline textures, the dried films show a pronounced Young's modulus (9.09
GPa) with a maximum strength of 298.02 MPa and toughness of 16.63 MJm-3. In
terms of functionalities, we report excellent glass-like transparency along
with exceptional shape-persistent flame shielding. We also demonstrate that
through metal ion-coordination we can further strengthen the interactions
between the polymers and the nanoclays. These ion-treated hybrid films exhibit
further enhanced mechanical, and thermal properties as well as resistance
against swelling and dissolution in aqueous environments. We believe that our
simple pathway to fabricate such versatile polymer/clay nanocomposites can open
avenues for inexpensive production of environmentally friendly, biomimetic
materials in aerospace, wearable electrical devices, artificial muscle, and
food packaging industry.",1808.03972v1
2019-03-16,Fundamental limits to radiative heat transfer: the limited role of nanostructuring in the near field,"In a complementary article, we exploited algebraic properties of Maxwell's
equations and fundamental principles such as electromagnetic reciprocity and
passivity, to derive fundamental limits to radiative heat transfer applicable
in near- through far-field regimes. The limits depend on the choice of material
susceptibilities and bounding surfaces enclosing arbitrarily shaped objects. In
this article, we apply these bounds to two different geometric configurations
of interest, namely dipolar particles or extended structures of infinite area
in the near field of one another, and compare these predictions to prior
limits. We find that while near-field radiative heat transfer between dipolar
particles can saturate purely geometric ""Landauer"" limits, bounds on extended
structures cannot, instead growing much more slowly with respect to a material
response figure of merit, an ""inverse resistivity"" for metals, due to the
deleterious effects of multiple scattering; nanostructuring is unable to
overcome these limits, which can be practically reached by planar media at the
surface polariton condition.",1903.07968v3
2019-04-17,Low temperature saturation of phase coherence length in topological insulators,"Implementing topological insulators as elementary units in quantum
technologies requires a comprehensive understanding of the dephasing mechanisms
governing the surface carriers in these materials, which impose a practical
limit to the applicability of these materials in such technologies requiring
phase coherent transport. To investigate this, we have performed
magneto-resistance (MR) and conductance fluctuations\ (CF) measurements in both
exfoliated and molecular beam epitaxy grown samples. The phase breaking length
($l_{\phi}$) obtained from MR shows a saturation below sample dependent
characteristic temperatures, consistent with that obtained from CF
measurements. We have systematically eliminated several factors that may lead
to such behavior of $l_{\phi}$ in the context of TIs, such as finite size
effect, thermalization, spin-orbit coupling length, spin-flip scattering, and
surface-bulk coupling. Our work indicates the need to identify an alternative
source of dephasing that dominates at low $T$ in topological insulators,
causing saturation in the phase breaking length and time.",1904.08517v1
2019-08-28,A Cantilever Torque Magnetometry Method for the Measurement of Hall Conductivity of Highly Resistive Samples,"We present the first measurements of Hall conductivity utilizing a new torque
magnetometry method designed for insulators. A Corbino disk exhibits a magnetic
dipole moment proportional to Hall conductivity when voltage is applied across
a test material. This magnetic dipole moment can be measured through torque
magnetometry. The symmetry of this contactless technique allows for the
measurement of Hall conductivity in previously inaccessible materials. Finally,
a low-temperature noise bound, the lack of systematic errors on dummy devices,
and a measurement of the Hall conductivity of sputtered indium tin oxide
demonstrate the efficacy of the technique.",1908.10857v3
2011-04-18,Manipulation of heat current by the interface between graphene and white graphene,"We investigate the heat current flowing across the interface between graphene
and hexagonal boron nitride (so-called white graphene) using both molecular
dynamics simulation and nonequilibrium Green's function approaches. These two
distinct methods discover the same phenomena that the heat current is reduced
linearly with increasing interface length, and the zigzag interface causes
stronger reduction of heat current than the armchair interface. These phenomena
are interpreted by both the lattice dynamics analysis and the transmission
function explanation, which both reveal that the localized phonon modes at
interfaces are responsible for the heat management. The room temperature
interface thermal resistance is about $7\times10^{-10}$m$^{2}$K/W in zigzag
interface and $3.5\times10^{-10}$m$^{2}$K/W in armchair interface, which
directly results in stronger heat reduction in zigzag interface. Our
theoretical results provide a specific route for experimentalists to control
the heat transport in the graphene and hexagonal boron nitride compound through
shaping the interface between these two materials.",1104.3371v2
2012-06-17,The efficiency and power of the martensite rotor heat engine. I,"The physical aspects - mechanics and thermodynamics - of operation of
martensite rotor heat engine (MRHE) on the basis of martensite-austenite
structural phase transition with the transition temperature in the region of
low-potential water temperatures have been studied. The engine converts the
thermal energy of low-potential water into the elastic energy of working body
(spring, ribbon or wire) made of the material with shape memory effect. At some
simplifying assumptions, the analytical expressions are obtained for the
thermal efficiency and the power of MRHE of different type. The registration of
head hydraulic resistance and heat conductivity of working body material is
made and the maximum value of power produced by the engine at the given
mechanical and heat conditions is calculated.
  The recommendations are given on the optimal choice of engine parameters. On
the basis of numerical estimations for nitinol, the possibility of application
of MRHE is shown for efficient and ecologically pure production of electric
energy both on local (geothermal waters, waste water of industrial enterprises,
etc.) and global (warm ocean stream) scales.",1206.3733v1
2012-06-29,Synthesis of a new alkali metal-organic solvent intercalated iron selenide superconductor with Tc{\approx}45K,"We report on a new iron selenide superconductor with a TC onset of 45K and
the nominal composition Lix(C5H5N)yFe2-zSe2, synthesized via intercalation of
dissolved alkaline metal in anhydrous pyridine at room temperature. This
superconductor exhibits a broad transition, reaching zero resistance at 10K.
Magnetization measurements reveal a superconducting shielding fraction of
approximately 30%. Analogous phases intercalated with Na, K and Rb were also
synthesized and characterized. The superconducting transition temperature of
Lix(C5H5N)yFe2-zSe2 is clearly enhanced in comparison to the known
superconductors FeSe0.98 (Tc ~ 8K) and AxFe2-ySe2 (TC ~ 27-32K) and is in close
agreement with critical temperatures recently reported for Lix(NH3)yFe2-zSe2.
Post-annealing of intercalated material (Lix(C5H5N)yFe2-zSe2) at elevated
temperatures drastically enlarges the c-parameter of the unit cell (~44%) and
increases the amount of superconducting shielding fraction to nearly 100%. Our
findings indicate a new synthesis road leading to possibly even higher critical
temperatures in this class of materials by intercalation of organic compounds
between Fe-Se layers.",1206.7022v1
2015-06-04,Thermal conductivity of bulk and nanoscaled Si/Ge alloys from the Kinetic Collective Model,"Several hitherto unexplained features of thermal conductivity in group IV
materials, such as the change in the slope as a function of sample size for
pure vs. alloyed samples and the fast decay in thermal conductivity for low
impurity concentration, are described in terms of a transition from a
collective to kinetic regime in phonon transport. We show that thermal
transport in pure bulk silicon samples is mainly collective, and that
impurity/alloy and boundary scattering are responsible for the destruction of
this regime with an associated strong reduction in thermal conductivity,
leaving kinetic transport as the only one allowed when those resistive
scattering mechanisms are dominant.",1506.01522v2
2015-07-01,Gas Sensing with h-BN Capped MoS2 Heterostructure Thin Film Transistors,"We have demonstrated selective gas sensing with molybdenum disulfide (MoS2)
thin films transistors capped with a thin layer of hexagonal boron nitride
(h-BN). The resistance change was used as a sensing parameter to detect
chemical vapors such as ethanol, acetonitrile, toluene, chloroform and
methanol. It was found that h-BN dielectric passivation layer does not prevent
gas detection via changes in the source-drain current in the active MoS2 thin
film channel. The use of h-BN cap layers (thickness H=10 nm) in the design of
MoS2 thin film gas sensors improves device stability and prevents device
degradation due to environmental and chemical exposure. The obtained results
are important for applications of van der Waals materials in chemical and
biological sensing.",1507.00308v1
2016-09-13,Gate voltage control of the $AlO_x$/$SrTiO_3$ interface electrical properties,"Electron-beam deposition of an insulating granular aluminium or of an
off-stoichiometric amorphous alumina layer on a $SrTiO_3$ surface is a simple
way to get a metallic interface from insulating materials. No heating nor
specific preparation of the $SrTiO_3$ surface are needed. In this paper, we
investigate how the electrical properties of this interface can be tuned by the
use of a back gate voltage (electrical field through the $SrTiO_3$ substrate).
We demonstrate that the slow field-effect observed at room temperature can be
used to tune reversibly and in a controlled way the low temperature electrical
properties of the interface. In particular, important parameters of a
transistor such as the amplitude of the resistance response to gate voltage
changes or the existence of an ""on"" or an ""off"" state at zero gate voltage and
at low temperature can be adjusted in a single sample. This method should be
applicable to any $SrTiO_3$-based interface in which oxygen vacancies are
involved and might provide a powerful way to study the metal or superconductor
insulator transition observed in such systems.",1609.03718v1
2018-07-04,Thermal and transport properties of U3Si2,"We have studied U_3Si_2 by means of the heat capacity, electrical
resistivity, Seebeck and Hall effects, and thermal conductivity in the
temperature range 2-300 K and in magnetic fields up to 9 T. All the results
obtained point to delocalized nature of 5f-electrons in this material. The low
temperature heat capacity is enhanced (gamma_el ~ 150 mJ/mol-K2) and shows an
upturn in Cp/T (T), characteristic of spin fluctuations. The thermal
conductivity of U3Si2 is ~8.5 W/m-K at room temperature and we show that the
electronic part dominates heat transport above 300 K as expected for a metallic
system, although the lattice contribution cannot be completely neglected.",1807.01757v1
2018-07-13,Laser-beam patterned topological insulating states on thin semiconducting MoS2,"Identifying the two-dimensional (2D) topological insulating (TI) state in new
materials and its control are crucial aspects towards the development of
voltage-controlled spintronic devices with low power dissipation. Members of
the 2D transition metal dichalcogenides (TMDCs) have been recently predicted
and experimentally reported as a new class of 2D TI materials, but in most
cases edge conduction seems fragile and limited to the monolayer phase
fabricated on specified substrates. Here, we realize the controlled patterning
of the 1T'-phase embedded into the 2H-phase of thin semiconducting
molybdenum-disulfide (MoS2) by laser beam irradiation. Integer fractions of the
quantum of resistance, the dependence on laser-irradiation conditions, magnetic
field, and temperature, as well as the bulk gap observation by scanning
tunneling spectroscopy and theoretical calculations indicate the presence of
the quantum spin Hall phase in our patterned 1T' phases.",1807.04914v3
2018-07-17,Electric Field Driven Memristive Behavior at the Schottky Interface of Nb doped SrTiO3,"Computing inspired by the human brain requires a massive parallel
architecture of low-power consuming elements of which the internal state can be
changed. SrTiO3 is a complex oxide that offers rich electronic properties; here
Schottky contacts on Nb-doped SrTiO3 are demonstrated as memristive elements
for neuromorphic computing. The electric field at the Schottky interface alters
the conductivity of these devices in an analog fashion, which is important for
mimicking synaptic plasticity. Promising power consumption and endurance
characteristics are observed. The resistance states are shown to emulate the
forgetting process of the brain. A charge trapping model is proposed to explain
the switching behavior.",1807.06274v1
2019-01-07,Non-topological Origin of the Planar Hall Effect in Type-II Dirac Semimetal NiTe2,"Dirac and Weyl semimetals are new discovered topological nontrivial materials
with the linear band dispersions around the Dirac/Weyl points. When applying
non-orthogonal electric current and magnetic field, an exotic phenomenon called
chiral anomaly arises and negative longitudinal resistance can be detected.
Recently, a new phenomenon named planer Hall effect (PHE) is considered to be
another indication of chiral anomaly which has been observed in many
topological semimetals. However, it still remains a question that is the PHE
only attributed to chiral anomaly? Here we demonstrate the PHE in a
new-discovered type-II Dirac semimetal NiTe2 by low temperature transport.
However, after detailed analysis, we conclude that the PHE results from the
trivial orbital magnetoresistance. This work reveals that PHE is not a
sufficient condition of chiral anomaly and one need to take special care of
other non-topological contribution in such studies.",1901.01749v1
2019-10-19,"Investigation of structural, electrical and electrochemical properties of La0.6Sr0.4Fe0.8Mn0.2O3-δ as an intermediate temperature solid oxide fuel cell cathode","La0.6Sr0.4Fe0.8Mn0.2O3 (LSFM) compound is synthesized by Sol-gel method and
evaluated as a cathode material for the intermediate temperature solid oxide
fuel cell (IT-SOFC). X-ray diffraction (XRD) indicates that the LSFM has a
Rhombohedral structure with R-3c space group symmetry. The XRD patterns reveal
very small amount of impurity phase in the LSFM and Y2O3-Stabilized ZrO2 (YSZ)
mixture powders sintered at 600, 700 and 800 C for a week. The maximum
electrical conductivity of LSFM is about 35.35 S.cm-1 at 783 C in the air. The
oxygen chemical diffusion coefficients, DChem, are increased from 1.39*10-6 up
to 7.66*10-6 .cm2. Besides, the oxygen surface exchange coefficients, kChem,
are obtained to lie between 2.9*10-3 and 8.7*10-3 cm.s-1 in a temperature range
of 600-800 C. The area-specific resistances (ASRs) of the LSFM symmetrical cell
are 7.53, 1.53, 1.13, 0.46 and 0.31 .cm2 at 600, 650, 700, 750 and 800 C
respectively, and related activation energy, Ea, is about 1.23 eV.",1910.08754v1
2019-10-21,Role of crystal lattice structure in predicting fracture toughness,"We examine the atomistic scale dependence of material's resistance-to-failure
by numerical simulations and analytical analysis in electrical analogs of
brittle crystals. We show that fracture toughness depends on the lattice
geometry in a way incompatible with Griffith's relationship between fracture
and free surface energy. Its value finds its origin in the matching between the
continuum displacement field at the engineering scale, and the discrete nature
of solids at the atomic scale. The generic asymptotic form taken by this field
near the crack tip provides a solution for this matching, and subsequently a
way to predict toughness from the atomistic parameters with application to
graphene.",1910.09343v2
2019-10-25,Macroscopic visualization of fast electrochemical reaction of SrCoOx oxygen sponge,"Strontium cobaltite (SrCoOx) is known as a material showing fast topotactic
electrochemical Redox reaction so-called oxygen sponge. Although atomic scale
phenomenon of the oxidation of SrCoO2.5 into SrCoO3 is known, the macroscopic
phenomenon has not been clarified yet thus far. Here, we visualize the
electrochemical oxidation of SrCoOx macroscopically. SrCoOx epitaxial films
with various oxidation states were prepared by the electrochemical oxidation of
SrCoO2.5 film into SrCoO3-d film. Steep decrease of both resistivity and the
absolute value of thermopower of electrochemically oxidized SrCoOx epitaxial
films indicated the columnar oxidation firstly occurred along with the surface
normal and then spread in the perpendicular to the normal. Further, we directly
visualized the phenomena using the conductive AFM. This macroscopic image of
the electrochemical oxidation would be useful to develop a functional device
utilizing the electrochemical redox reaction of SrCoOx.",1910.11465v1
2019-10-29,Improvement on corrosion resistance and biocompability of ZK60 magnesium alloy by carboxyl ion implantation,"Magnesium alloys have been considered to be potential biocompatible metallic
materials. Further improvement on the anti-corrosion is expected to make this
type of materials more suitable for biomedical applications in the fields of
orthopedics, cardiovascular surgery and others. In this paper, we introduce a
method of carboxyl ion (COOH+) implantation to reduce the degradation of ZK60
Mg alloy and improve its functionality in physiological environment. X-ray
photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) experiments
show the formation of a smooth layer containing carbaxylic group, carbonate,
metal oxides and hydroxides on the ion implanted alloy surface. Corrosion
experiments and in vitro cytotoxicity tests demonstrate that the ion
implantation treatment can both reduce the corrosion rate and improve the
biocompatibility of the alloy. The promising results indicate that organic
functional group ion implantation may be a practical method of improving the
biological and corrosion properties of magnesium alloys.",1910.13219v1
2019-11-21,Superconducting Contact and Quantum Interference Between Two-Dimensional van der Waals and Three-Dimensional Conventional Superconductors,"Two-dimensional (2D) transition-metal dichalcogenide superconductors have
unique and desirable properties for integration with conventional
superconducting circuits. However, fully superconducting contact must be made
between the 2D material and three-dimensional (3D) superconductors in order to
employ the standard microwave drive and readout of qubits in such circuits.
Here, we present a method for creating zero-resistance contacts between 2D
NbSe$_2$ and 3D aluminum that behave as Josephson junctions (JJs) with large
effective areas compared to 3D-3D JJs. We present a model for the supercurrent
flow in a 2D-3D superconducting structure by numerical solution of the
Ginzburg-Landau equations and find good agreement with experiment. These
results demonstrate a crucial step towards a new generation of hybrid
superconducting quantum circuits.",1911.09711v2
2020-01-07,Electrical transport properties of bulk tetragonal CuMnAs,"Temperature-dependent resistivity and magnetoresistance are measured in bulk
tetragonal phase of antiferromagnetic CuMnAs and the latter is found to be
anisotropic both due to structure and magnetic order. We compare these findings
to model calculations with chemical disorder and finite-temperature phenomena
included. The finite-temperature ab initio calculations are based on the alloy
analogy model implemented within the coherent potential approximation and the
results are in fair agreement with experimental data. Regarding the anisotropic
magnetoresistance (AMR) which reaches a modest magnitude of 0.12%, we
phenomenologically employ the Stoner-Wohlfarth model to identify
temperature-dependent magnetic anisotropy of our samples and conclude that the
field-dependence of AMR is more similar to that of antiferromagnets than
ferromagnets, suggesting that the origin of AMR is not related to isolated Mn
magnetic moments.",2001.01947v3
2020-01-18,Microscopic aspects of artificial ageing in Al-Mg-Si alloys,"Al-Mg-Si alloys with total solute contents ranging from 0.8 to 1.4 wt.% were
solutionised, quenched and then artificially aged (AA) at 180 {\deg}C, after
which positron annihilation lifetime spectroscopy was applied to obtain
information about precipitation and vacancy evolution during preceding ageing.
Hardness and electrical resistivity measurements were carried out to complement
these measurements. AA was carried out in four different heating media, which
allowed for varying the heating rate from 2.4 K/s to 170 K/s. The main result
of the study is that there is a competition between vacancy losses and
precipitation. Any precipitation taking place during quenching or during
heating to the AA temperature helps to prevent vacancies from going to sinks
and allows them to assist in solute clustering. Higher solute content, slower
heating to 180 {\deg}C and natural pre-ageing before AA were found to have a
comparable effect.",2001.06566v1
2020-01-27,"Metal to insulator transition, colossal Seebeck coefficient and ultralow thermal conductivity in solution-processed monodispersed nickel nanoparticles","We report here metal to insulator transition, colossal Seebeck coefficient
and ultralow thermal conductivity (0.0057th of its bulk value, significantly
smaller than many well-known thermoelectric materials and silicon, showing
potential applications in thermoelectrics, electronics and photonics for heat
dissipation) in monodispersed well characterized Ni nanoparticles. As a
consequence, thermoelectric power factor and figure of merit are significantly
enhanced compared to their bulk counterpart. Interestingly, a systematic
crossover from metallic to semiconducting to finally electrically insulating
behavior, large negative temperature coefficient of resistance and n-type
conduction to p-type conduction with decrease in particle size have been
observed. These results are mainly attributed to formation of metal/organic
interfaces, enhancement in local electronic density of sates and multiscale
electron and phonon scattering by various defects. Thus, this study will open a
new avenue to make better thermoelectrics through incorporation of such
nanoparticles in semiconducting hosts.",2001.09708v1
2020-05-21,Thermodynamic Origin of Reaction Non-Uniformity in Battery Porous Electrodes and its Mitigation,"The development of non-uniform reaction current distribution within porous
electrodes is a ubiquitous phenomenon during battery charging / discharging and
frequently controls the rate performance of battery cells. Reaction
inhomogeneity in porous electrodes is usually attributed to the kinetic
limitation of mass transport within the electrolyte and/or solid electrode
phase. In this work, however, we reveal that it is also strongly influenced by
the intrinsic thermodynamic behavior of electrode materials, specifically the
dependence of the equilibrium potential on the state of charge: electrode
reaction becomes increasingly non-uniform when the slope of the equilibrium
potential curve is reduced. We employ numerical simulation and equivalent
circuit model to elucidate such a correlation and show that the degree of
reaction inhomogeneity and the resultant discharge capacity can be predicted by
a dimensionless reaction uniformity number. For electrode materials that have
equilibrium potentials insensitive to the state of charge and exhibit
significant reaction non-uniformity, we demonstrate several approaches to
spatially homogenizing the reaction current inside porous electrodes, including
matching the electronic and ionic resistances, introducing graded electronic
conductivity and reducing the surface reaction kinetics.",2005.10916v1
2020-06-16,Ambient pressure Dirac electron system in quasi-two-dimensional molecular conductor $α$-(BETS)$_2$I$_3$,"We investigated the precise crystal structures and electronic states in a
quasi-two-dimensional molecular conductor ${\alpha}$-(BETS)$_2$I$_3$ at ambient
pressure. The electronic resistivity of this molecular solid shows
metal-to-insulator (MI) crossover at $T_{MI}$=50 K. Our x-ray diffraction and
$^{13}$C nuclear magnetic resonance experiments revealed that
${\alpha}$-(BETS)$_2$I$_3$ maintains the inversion symmetry below $T_{MI}$.
First-principles calculations found a pair of anisotropic Dirac cones at a
general k-point, with the degenerate contact points at the Fermi level. The
origin of the insulating state in this system is a small energy gap of ~2 meV
opened by the spin-orbit interaction. The Z$_2$ topological invariants indicate
that this system is a weak topological insulator. Our results suggest that
${\alpha}$-(BETS)$_2$I$_3$ is a promising material for studying the bulk Dirac
electron system in two dimensions.",2006.08978v2
2020-06-18,Dynamical vortex phase diagram of 2D superconductivity in gated MoS2,"Recent discoveries of two-dimensional (2D) superconductors have uncovered
various new aspects of physical properties including vortex matter. In this
paper, we report transport properties and a dynamical phase diagram at zero
magnetic field in ion-gated MoS2. In addition to the universal jump in the
current-voltage characteristic showing unambiguous evidence of the
Berezinskii-Kosterlitz-Thouless (BKT) transition, we observed multiple peaks in
the temperature- and current-derivative of the electrical resistance, based on
which a dynamical phase diagram in the current-temperature plane was
constructed. We found current-induced dynamical states of vortex-antivortex
pairs, containing that with the phase slip line. Also, we present a global
phase diagram of vortices in gated MoS2 which captures the nature of vortex
matter of clean 2D superconductors.",2006.10749v1
2020-07-03,From Weak Antilocalization to Kondo Scattering in a Magnetic Complex Oxide Interface,"Quantum corrections to electrical resistance can serve as sensitive probes of
the magnetic landscape of a material. For example, interference between
time-reversed electron paths gives rise to weak localization effects, which can
provide information about the coupling between spins and orbital motion, while
the Kondo effect is sensitive to the presence of spin impurities. Here we use
low-temperature magnetotransport measurements to reveal a transition from weak
antilocalization (WAL) to Kondo scattering in the quasi-two-dimensional
electron gas formed at the interface between SrTiO$_3$ and the Mott insulator
NdTiO$_3$. This transition occurs as the thickness of the NdTiO$_3$ layer is
increased. Analysis of the Kondo scattering and WAL points to the presence of
atomic-scale magnetic impurities coexisting with extended magnetic regions that
affect transport via a strong magnetic exchange interaction. This leads to
distinct magnetoresistance behaviors that can serve as a sensitive probe of
magnetic properties in two dimensions.",2007.01853v1
2020-08-02,Thermal stability for domain wall mediated magnetization reversal in perpendicular STT MRAM cells with W insertion layers,"We present an analytical model for calculating energy barrier for the
magnetic field-driven domain wall-mediated magnetization reversal of a
magneto-resistive random access memory (MRAM) cell and apply it to study
thermal stability factor $\Delta$ for various thicknesses of W layers inserted
into the free layer (FL) as a function of the cell size and temperature. We
find that, by increasing W thickness, the effective perpendicular magnetic
anisotropy (PMA) energy density of the FL film monotonically increases, but at
the same time, $\Delta$ of the cell mainly decreases. Our analysis shows that,
in addition to saturation magnetization $M_s$ and exchange stiffness constant
$A_\mathrm{ex}$ of the FL film, the parameter that quantifies the $\Delta$ of
the cell is its coercive field $H_c$, rather than the net PMA field $H_k$ of
the FL film comprising the cell.",2008.00412v2
2020-08-03,Intrinsic mechanism for anisotropic magnetoresistance and experimental confirmation in Co$_x$Fe$_{1-x}$ single-crystal films,"Using first-principles transport calculations, we predict that the
anisotropic magnetoresistance (AMR) of single-crystal Co$_x$Fe$_{1-x}$ alloys
is strongly dependent on the current orientation and alloy concentration. An
intrinsic mechanism for AMR is found to arise from the band crossing due to
magnetization-dependent symmetry protection. These special $k$-points can be
shifted towards or away from the Fermi energy by varying the alloy composition
and hence the exchange splitting, thus allowing AMR tunability. The prediction
is confirmed by delicate transport measurements, which further reveal a
reciprocal relationship of the longitudinal and transverse resistivities along
different crystal axes.",2008.00872v1
2020-08-12,Analysis of the influence of microstructural traps on hydrogen assisted fatigue,"We investigate the influence of microstructural traps on hydrogen diffusion
and embrittlement in the presence of cyclic loads. A mechanistic, multi-trap
model for hydrogen transport is developed, implemented into a finite element
framework, and used to capture the variation of crack tip lattice and trapped
hydrogen concentrations as a function of the loading frequency, the trap
binding energies and the trap densities. We show that the maximum value
attained by the lattice hydrogen concentration during the cyclic analysis
exhibits a notable sensitivity to the ratio between the loading frequency and
the effective diffusion coefficient. This is observed for both hydrogen
pre-charged samples (closed-systems) and samples exposed to a permanent source
of hydrogen (open-systems). Experiments are used to determine the critical
concentration for embrittlement, by mapping the range of frequencies where the
output is the same as testing in inert environments. We then quantitatively
investigate and discuss the implications of developing materials with higher
trap densities in mitigating embrittlement in the presence of cyclic loads. It
is shown that, unlike the static case, increasing the density of ""beneficial
traps"" is a viable strategy in designing alloys resistant to hydrogen assisted
fatigue for both closed- and open-systems.",2008.05452v1
2020-08-18,"Preparation of Isotopically enriched $^{112,116,120,124}$Sn targets at VECC","Resistive heating and mechanical rolling methods have been employed to
prepare isotopically enriched thin target foils of 116Sn (~380 \mu g/cm2),
124Sn(~400 \mu g/cm2) and thicker foils of 112Sn (1.7 mg/cm2),120Sn (1.6
mg/cm2),respectively. Preparation of enriched targets with small amount of
material, selection of releasing agent for thin targets and separation of
deposited material insolvent were among the several challenges while
fabrication of the thin targets. Uniformity of the targets has been measured
using 241Am {\alpha}-source. NaCl has been used as releasing agent in
preparation of the thin targets. These targets have been successfully used in
nuclear physics experiments at VECC.",2008.08081v2
2020-08-20,Polarization amplification by spin-doping in nanomagnetic/graphene hybrid systems,"The generation of non-equilibrium electron spin polarization, spin transport,
and spin detection are fundamental in many quantum devices. We demonstrate that
a lattice of magnetic nanodots enhances the electron spin polarization in
monolayer graphene via carrier exchange. We probed the spin polarization
through a resistively-detected variant of electron spin resonance (ESR) and
observed resonance amplification mediated by the presence of the nanodots. Each
nanodot locally injects a surplus of spin-polarized carriers into the graphene,
and the ensemble of all ""spin hot spots"" generates a non-equilibrium electron
spin polarization in the graphene layer at macroscopic lengths. This occurs
whenever the interdot distance is comparable or smaller than the spin diffusion
length.",2008.08813v2
2020-08-21,Fate of a soliton matter upon symmetry-breaking ferroelectric order,"In a one-dimensional (1D) system with degenerate ground states, their domain
boundaries, dubbed solitons, emerge as topological excitations often carrying
unconventional charges and spins; however, the soliton excitations are only
vital in the non-ordered 1D regime. Then a question arises; how do the solitons
conform to a 3D ordered state? Here, using a quasi-1D organic ferroelectric,
TTF-CA, with degenerate polar dimers, we pursue the fate of a spin-soliton
charge-soliton composite matter in a 1D polar-dimer liquid upon its transition
to a 3D ferroelectric order by resistivity, NMR and NQR measurements. We
demonstrate that the soliton matter undergoes neutral spin-spin soliton pairing
and spin-charge soliton pairing to form polarons, coping with the 3D order. The
former contributes to the magnetism through triplet excitations whereas the
latter carries electrical current. Our results reveal the whole picture of a
soliton matter that condenses into the 3D ordered state.",2008.09337v1
2020-10-09,Electronic and magnetic properties of $α$-FeGe$_2$ films embedded in vertical spin valve devices,"We studied metastable $\alpha$-FeGe$_2$, a novel layered tetragonal material,
embedded as a spacer layer in spin valve structures with ferromagnetic Fe$_3$Si
and Co$_2$FeSi electrodes. For both types of electrodes, spin valve operation
is demonstrated with a metallic transport behavior of the $\alpha$-FeGe$_2$
spacer layer. The spin valve signals are found to increase both with
temperature and spacer thickness, which is discussed in terms of a decreasing
magnetic coupling strength between the ferromagnetic bottom and top electrodes.
The temperature-dependent resistances of the spin valve structures exhibit
characteristic features, which are explained by ferromagnetic phase transitions
between 55 and 110~K. The metallic transport characteristics as well as the
low-temperature ferromagnetism are found to be consistent with the results of
first-principles calculations.",2010.04453v2
2020-10-16,Chirality induced Giant Unidirectional Magnetoresistance in Twisted Bilayer Graphene,"Twisted bilayer graphene (TBG) exhibits fascinating correlation-driven
phenomena like the superconductivity and Mott insulating state, with flat bands
and a chiral lattice structure. We find by quantum transport calculations that
the chirality leads to a giant unidirectional magnetoresistance (UMR) in TBG,
where the unidirectionality refers to the resistance change under the reversal
of the direction of the current or magnetic field. We point out that flat bands
significantly enhance this effect. The UMR increases quickly upon reducing the
twist angle and reaches about 20\% for an angle of 1.5$^\circ$ in a 10 T
in-plane magnetic field. We propose the band structure topology (asymmetry),
which leads to a direction-sensitive mean free path, as a useful way to
anticipate the UMR effect. The UMR provides a probe for chirality and band
flatness in the twisted bilayers.",2010.08385v2
2020-11-11,Electron doping of the iron-arsenide superconductor CeFeAsO controlled by hydrostatic pressure,"In the iron-pnictide material CeFeAsO not only the Fe moments, but also the
local 4f moments of the Ce order antiferromagnetically at low temperatures. We
elucidate on the peculiar role of the Ce on the emergence of superconductivity.
While application of pressure suppresses the iron SDW ordering temperature
monotonously up to 4 GPa, the Ce-4f magnetism is stabilized, until both types
of magnetic orders disappear abruptly and a narrow SC dome develops. With
further increasing pressure characteristics of a Kondo-lattice system become
more and more apparent in the electrical resistivity. This suggests a
connection of the emergence of superconductivity with the extinction of the
magnetic order and the onset of Kondo-screening of the Ce-4f moments.",2011.05665v1
2020-11-17,Dichotomy Between Orbital and Magnetic Nematic Instabilities in BaFe2S3,"Nematic orders emerge nearly universally in iron-based superconductors, but
elucidating their origins is challenging because of intimate couplings between
orbital and magnetic fluctuations. The iron-based ladder material BaFe2S3,
which superconducts under pressure, exhibits antiferromagnetic order below TN ~
117K and a weak resistivity anomaly at T* ~ 180K, whose nature remains elusive.
Here we report angle-resolved magnetoresistance (MR) and elastoresistance (ER)
measurements in BaFe2S3, which reveal distinct changes at T*. We find that MR
anisotropy and ER nematic response are both suppressed near T*, implying that
an orbital order promoting isotropic electronic states is stabilized at T*.
Such an isotropic state below T* competes with the antiferromagnetic order,
which is evidenced by the nonmonotonic temperature dependence of nematic
fluctuations. In contrast to the cooperative nematic orders in spin and orbital
channels in iron pnictides, the present competing orders can provide a new
platform to identify the separate roles of orbital and magnetic fluctuations.",2011.08600v1
2020-11-24,Evidence of interfacial asymmetric spin scattering at ferromagnet-Pt interfaces,"We measure the spin-charge interconversion by the spin Hall effect in
ferromagnetic/Pt nanodevices. The extracted effective spin Hall angles (SHAs)
of Pt evolve drastically with the ferromagnetic (FM) materials (CoFe, Co, and
NiFe), when assuming transparent interfaces and a bulk origin of the spin
injection/detection by the FM elements. By carefully measuring the interface
resistance, we show that it is quite large and cannot be neglected. We then
evidence that the spin injection/detection at the FM/Pt interfaces are
dominated by the spin polarization of the interfaces. We show that interfacial
asymmetric spin scattering becomes the driving mechanism of the spin injection
in our samples.",2011.12207v2
2020-11-25,Electron hydrodynamics of anomalous Hall materials,"We study two-dimensional electron systems in the hydrodynamic regime. We show
that a geometrical Berry curvature modifies the effective Navier-Stokes
equation for viscous electron flow in topological materials. For small electric
fields, the Hall current becomes negligible compared to the viscous
longitudinal current. In this regime, we highlight an unconventional Poiseuille
flow with an asymmetric profile and a deviation of the maximum of the current
from the center of the system. In a two-dimensional infinite geometry, the
Berry curvature leads to current whirlpools and an asymmetry of potential
profile. This phenomenon can be probed by measuring the asymmetric non-local
resistance profile.",2011.12590v1
2020-11-29,Pressure Dependent Electronic Structure in CeRh$_6$Ge$_4$,"Using the state-of-art dynamical mean-field theory combined with density
functional theory method, we have performed systematic study on the temperature
and pressure dependent electronic structure of ferromagnetic quantum critical
material candidate CeRh$_6$Ge$_4$. At -3.9 GPa and -8.3 GPa, the Ce-4$f$
occupation variation, the local magnetic susceptibility, and the low-frequency
electronic self-energy behaviors suggest the Ce-4$f$ electrons are in the
localized state; whereas at 6.5 GPa and 13.1 GPa, these quantities indicate the
Ce-4$f$ electrons are in the itinerant state. The characteristic temperatures
associated with the coherent Kondo screening is gradually suppressed to 0
around 0.8 GPa upon releasing external pressure, indicative of a local quantum
critical point. Interestingly, the momentum-resolved spectrum function shows
that even at the localized state side, highly anisotropic
$\mathbf{k}$-dependent hybridization between Ce-4$f$ and conduction electrons
is still present along $\Gamma$-A, causing hybridization gap in between. The
calculations predict 8 Fermi surface sheets at the local-moment side and 6
sheets at the Kondo coherent state. Finally, the self-energy at 0.8 GPa can be
well fitted by marginal Fermi-liquid form, giving rise to a linearly
temperature dependent resistivity.",2011.14256v1
2020-12-16,Superconductivity in the $\mathbb{Z}_2$ kagome metal KV$_3$Sb$_5$,"Here we report the observation of bulk superconductivity in single crystals
of the two-dimensional kagome metal KV$_3$Sb$_5$. Magnetic susceptibility,
resistivity, and heat capacity measurements reveal superconductivity below $T_c
= 0.93$K, and density functional theory (DFT) calculations further characterize
the normal state as a $\mathbb{Z}_2$ topological metal. Our results demonstrate
that the recent observation of superconductivity within the related kagome
metal CsV$_3$Sb$_5$ is likely a common feature across the AV$_3$Sb$_5$ (A: K,
Rb, Cs) family of compounds and establish them as a rich arena for studying the
interplay between bulk superconductivity, topological surface states, and
likely electronic density wave order in an exfoliable kagome lattice.",2012.09097v2
2020-12-25,3D Printing Autoclavable PPE on Low-Cost Consumer 3D Printers,"During the COVID-19 pandemic, medical facilities began using 3D printed PPE
sourced from their own print labs, makerspaces, universities, and individuals
with 3D printers to fill the gaps in supply as traditional manufacturing was
not widely enough distributed nor quick enough to scale to widespread spikes in
demand. However, to date this PPE has been limited to low-temperature, easy to
print thermoplastics which are not compatible with autoclave sterilization and
must be sterilized by hand washing methods. Herein, we present a method for 3D
printing a temperature resistant nylon copolymer on a common low-cost 3D
printer. We show that the resulting parts can be autoclaved without
deformation, and conduct uniaxial tensile testing showing that autoclaving the
material does not result in substantial degradation of material properties. As
a result, we demonstrate the capability to manufacture autoclavable PPE on
low-cost consumer 3D printers with only minor modification.",2012.13476v3
2021-02-01,"Electronic, magnetic and galvanomagnetic properties of Co-based Heusler alloys: possible states of a half-metallic ferromagnet and spin gapless semiconductor","Parameters of the energy gap and, consequently, electronic, magnetic and
galvanomagnetic properties in different X$_2$YZ Heusler alloys can vary quite
strongly. In particular, half-metallic ferromagnets (HMFs) and spin gapless
semiconductors (SGSs) with almost 100% spin polarization of charge carriers are
promising materials for spintronics. The changes in the electrical, magnetic
and galvanomagnetic properties of the Co$_2$YSi (Y = Ti, V, Cr, Mn, Fe) and
Co$_2$MnZ Heusler alloys (Z = Al, Si, Ga, Ge) in possible HMF and/or SGS states
were followed and their interconnection was established. Significant changes in
the values of the magnetization and residual resistivity were found. At the
same time, the correlations between the changes in these electronic and
magnetic characteristics depending on the number of valence electrons and spin
polarization are observed.",2102.00952v1
2021-02-14,PCM-trace: Scalable Synaptic Eligibility Traces with Resistivity Drift of Phase-Change Materials,"Dedicated hardware implementations of spiking neural networks that combine
the advantages of mixed-signal neuromorphic circuits with those of emerging
memory technologies have the potential of enabling ultra-low power pervasive
sensory processing. To endow these systems with additional flexibility and the
ability to learn to solve specific tasks, it is important to develop
appropriate on-chip learning mechanisms.Recently, a new class of three-factor
spike-based learning rules have been proposed that can solve the temporal
credit assignment problem and approximate the error back-propagation algorithm
on complex tasks. However, the efficient implementation of these rules on
hybrid CMOS/memristive architectures is still an open challenge. Here we
present a new neuromorphic building block,called PCM-trace, which exploits the
drift behavior of phase-change materials to implement long lasting eligibility
traces, a critical ingredient of three-factor learning rules. We demonstrate
how the proposed approach improves the area efficiency by >10X compared to
existing solutions and demonstrates a techno-logically plausible learning
algorithm supported by experimental data from device measurements",2102.07260v2
2021-03-01,Enhanced Superconductivity in the Se-substituted 1T-PdTe$_2$,"Two-dimensional transition metal dichalcogenide PdTe$_2$ recently attracts
much attention due to its phase coexistence of type-II Dirac semimetal and
type-I superconductivity. Here we report a 67 % enhancement of superconducting
transition temperature in the 1T-PdSeTe in comparison to that of PdTe2 through
partial substitution of Te atoms by Se. The superconductivity has been
unambiguously confirmed by the magnetization, resistivity and specific heat
measurements. 1T-PdSeTe shows type-II superconductivity with large anisotropy
and non-bulk superconductivity nature with volume fraction ~ 20 % estimated
from magnetic and heat capacity measurements. 1T-PdSeTe expands the family of
superconducting transition metal dichalcogenides and thus provides additional
insights for understanding superconductivity and topological physics in the
1T-PdTe$_2$ system",2103.00687v1
2021-03-02,Revealing atomic-scale vacancy-solute interaction in nickel,"Imaging individual vacancies in solids and revealing their interactions with
solute atoms remains one of the frontiers in microscopy and microanalysis. Here
we study a creep-deformed binary Ni-2 at.% Ta alloy. Atom probe tomography
reveals a random distribution of Ta. Field ion microscopy, with contrast
interpretation supported by density-functional theory and time-of-flight mass
spectrometry, evidences a positive correlation of tantalum with vacancies. Our
results support solute-vacancy binding, which explains improvement in creep
resistance of Ta-containing Ni-based superalloys and helps guide future
material design strategies.",2103.01639v3
2021-03-04,Strange electrical transport: Colossal magnetoresistance via avoiding fully polarized magnetization in ferrimagnetic insulator Mn3Si2Te6,"Colossal magnetoresistance is of great fundamental and technological
significance and exists mostly in the manganites and a few other materials.
Here we report colossal magnetoresistance that is starkly different from that
in all other materials. The stoichiometric Mn3Si2Te6 is an insulator featuring
a ferrimagnetic transition at 78 K. The resistivity drops by 7 orders of
magnitude with an applied magnetic field above 9 Tesla, leading to an
insulator-metal transition at up to 130 K. However, the colossal
magnetoresistance occurs only when the magnetic field is applied along the
magnetic hard axis and is surprisingly absent when the magnetic field is
applied along the magnetic easy axis where magnetization is fully saturated.
The anisotropy field separating the easy and hard axes is 13 Tesla, unexpected
for the Mn ions with nominally negligible orbital momentum and spin-orbit
interactions. Double exchange and Jahn-Teller distortions that drive the
hole-doped manganites do not exist in Mn3Si2Te6. The phenomena fit no existing
models, suggesting a unique, intriguing type of electrical transport.",2103.02764v1
2021-03-08,The Efficacy of the Method of Four Coefficients to Determine Charge Carrier Scattering,"The investigation of the electronic properties of semiconductors is
inherently challenging due to the ensemble averaging of fundamentals to
transport measurements (i.e., resistivity, Hall, and Seebeck coefficient
measurements). Here, we investigate the incorporation of a fourth measurement
of electronic transport, the Nernst coefficient, into the analysis, termed the
method of four-coefficients. This approach yields the Fermi level, effective
mass, scattering exponent, and relaxation time. We begin with a review of the
underlying mathematics and investigate the mapping between the four-dimensional
material property and transport coefficient spaces. We then investigate how the
traditional single parabolic band method yields a single, potentially incorrect
point on the solution sub-space. This uncertainty can be resolved through
Nernst coefficient measurements and we map the span of the ensuing sub-space.
We conclude with an investigation of how sensitive the analysis of transport
coefficients is to experimental error for different sample types.",2103.04569v1
2021-03-26,Electron-electron interactions and weak anti-localization in few-layer ZrTe5 devices,"Much effort has been devoted to the electronic properties of relatively thick
ZrTe5 crystals, focusing on their three-dimensional topological effects. Thin
ZrTe5 crystals, on the other hand, were much less explored experimentally. Here
we present detailed magnetotransport studies of few-layer ZrTe5 devices, in
which electron-electron interactions and weak anti-localization are observed.
The coexistence of the two effects manifests themselves in corroborating
evidence presented in the temperature and magnetic field dependence of the
resistance. Notably, the temperature-dependent phase coherence length extracted
from weak anti-localization agrees with strong electron-electron scattering in
the sample. Meanwhile, universal conductance fluctuations have temperature and
gate voltage dependence that is similar to that of the phase coherence length.
Lastly, all the transport properties in thin ZrTe5 crystals show strong
two-dimensional characteristics. Our results provide new insight into the
highly intricate properties of topological material ZrTe5.",2103.14329v1
2021-03-31,Deciphering water-solid reactions during hydrothermal corrosion of SiC,"Water solid interfacial reactions are critical to understanding corrosion.
More specifically, it is notoriously difficult to determine how water and solid
interact beyond the initial chemisorption to induce the surface dissolution.
Here, we report atomic-scale mechanisms of the elementary steps during SiC
hydrothermal corrosion, from the initial surface attack to surface dissolution.
We find that hydrogen scission reactions play a vital role in breaking Si-C
bonds, regardless of the surface orientations. Stable silica layer does not
form on the surface, but the newly identified chemical reactions on SiC are
analogous to those observed during the dissolution of silica. SiC is dissolved
directly into the water as soluble silicic acid. The rate of hydrothermal
corrosion determined based on the calculated reaction activation energies is
consistent with available experimental data. Our work sheds new light on
understanding and interpreting the experimental observations and it provides
foundation for design of materials that are resistant to corrosion in water.",2103.16738v1
2021-04-14,Low-Frequency Electronic Noise Spectroscopy of Quasi-2D van der Waals Antiferromagnetic Semiconductors,"We investigated low-frequency current fluctuations, i.e. noise, in the
quasi-two-dimensional (2D) van der Waals antiferromagnetic semiconductor FePS3
with the electronic bandgap of 1.5 eV. The electrical and noise characteristics
of the p-type, highly resistive, thin films of FePS3 were measured at different
temperatures. The noise spectral density was of the 1/f - type over most of the
examined temperature range but revealed well-defined Lorentzian bulges, and
increased strongly near the Neel temperature of 118 K (f is the frequency).
Intriguingly, the noise spectral density attained its minimum at temperature
T~200 K, which was attributed to an interplay of two opposite trends in noise
scaling - one for semiconductors and another for materials with the phase
transitions. The Lorentzian corner frequencies revealed unusual dependence on
temperature and bias voltage, suggesting that their origin is different from
the generation - recombination noise in conventional semiconductors. The
obtained results are important for proposed applications of antiferromagnetic
semiconductors in spintronic devices. They also attest to the power of the
noise spectroscopy for monitoring various phase transitions.",2104.06578v1
2020-12-26,The Main Role of Thermal Annealing in Controlling the Structural and Optical Properties of ITO Thin Film Layer,"Here we report on studying the electronic and optical material properties of
the technologically-relevant material indium tin oxide (ITO) as a function of
thermal annealing. In this work, ITO powder has been prepared utilizing
solid-state reaction methods. An electron beam gun technology has been used to
prepare a ITO film (325 nm). The ITO window layer has been investigated at
various temperatures. The effects of absolute temperature on the structural,
optical, and electrical properties of the prepared ITO thin film layer are
investigated. The energy band type corresponding to the orbital transitions has
been determined, and the energies of the orbital transitions have been
calculated in the Tauc region, HOMO/LUMO gap, and charge transfer gap. In
additions, the exciton and Urbach energies have been computed. It has been
found that these energies increase with increasing the annealing temperature,
except for Urbach's energies which behave differently. Thin-film quality
coefficient, surface resistance, and thermal emission in addition to the angle
of refraction as a function of wavelength, have been determined.",2104.07464v1
2021-04-16,Circuit-aware Device Modeling of Energy-efficient Monolayer WS$_2$ Trench-FinFETs,"The continuous scaling of semiconductor technology has pushed the footprint
of logic devices below 50 nm. Currently, logic standard cells with one single
fin are being investigated to increase the integration density, although such
options could severely limit the performance of individual devices. In this
letter, we present a novel Trench (T-) FinFET device, composed of a monolayer
two-dimensional (2D) channel material. The device characteristics of a
monolayer WS$_2$-based T-FinFET are studied by combining the first-principles
calculations and quantum transport (QT) simulations. These results serve as
inputs to a predictive analytical model. The latter allows to benchmark the
T-FinFET with strained (s)-Si FinFETs in both quasi-ballistic and diffusive
transport regimes. The circuit-level evaluation highlights that WS$_2$
T-FinFETs exhibit a competitive energy-delay performance compared to s-Si
FinFET and WS$_2$ double-gate transistors, assuming the same mobility and
contact resistivity at small footprints.",2104.07891v1
2021-04-19,Effect of wear particles and roughness on nanoscale friction,"Frictional contacts lead to the formation of a surface layer called the third
body, consisting of wear particles and structures resulting from their
agglomerates. Its behavior and properties at the nanoscale control the
macroscopic tribological performance. It is known that wear particles and
surface topography evolve with time and mutually influence one another.
However, the formation of the mature third body is largely uncharted territory
and the properties of its early stages are unknown. Here we show how a third
body initially consisting of particles acting as roller bearings transitions
into a shear-band-like state by forming adhesive bridges between the particles.
Using large-scale atomistic simulations on a brittle model material, we find
that this transition is controlled by the growth and increasing disorganization
of the particles with increasing sliding distance. Sliding resistance and wear
rate are at first controlled by the surface roughness, but upon agglomeration
wear stagnates and friction becomes solely dependent on the real contact area
in accordance with the plasticity theory of contact by Bowden and Tabor.",2104.09217v3
2021-05-01,Complementary electrochemical ICP-MS flow cell and in-situ AFM study of the anodic desorption of molecular adhesion promotors,"Molecular adhesion promoters are a central component of modern coating
systems for the corrosion protection of structural materials. They are
interface active and form ultrathin corrosion inhibiting and adhesion-promoting
layers. Here we utilize thiol-based self-assembled monolayers (SAMs) as model
system for demonstrating a comprehensive combinatorial approach to understand
molecular level corrosion protection mechanisms under anodic polarization.
Specifically, we compare hydrophilic 11-Mercapto-1-undecanol and hydrophobic
1-Undecanethiol SAMs and their gold-dissolution inhibiting properties. We can
show that the intermolecular forces (hydrophobic vs hydrophilic effects)
control how SAM layers perform under oxidative conditions. Specifically, using
\textit{in situ} electrochemical AFM and a scanning-flow cell coupled to an
ICP-MS a complementary view on both corrosion resistance, as well as on changes
in surface morphology/adhesion of the SAM is possible. Protection from
oxidative dissolution is higher with hydrophobic SAMs, which detach under
micelle formation, while the hydrophilic SAM exhibits lower protective effects
on gold dissolution rates, although it stays intact as highly mobile layer
under anodic polarization. The developed multi-technique approach will prove
useful for studying the interfacial activity and corrosion suppression
mechanism of inhibiting molecules on other metals and alloys.",2105.00280v1
2021-05-09,Planar topological Hall effect in a hexagonal ferromagnetic Fe5Sn3 single crystal,"The planar topological Hall effect (PTHE), appeared when the magnetic field
tended to be along the current, is believed to result from the real-space Berry
curvature of the spin spiral structure and has been experimentally observed in
skyrmion-hosting materials. In this paper, we report an experimental
observation of the PTHE in a hexagonal ferromagnetic Fe5Sn3 single crystal.
With a current along the c axis of Fe5Sn3, the transverse resistivity curves
exhibited obvious peaks near the saturation field as the magnetic field rotated
to the current and appeared more obvious with increasing temperature, which was
related to the noncoplanar spin structure in Fe5Sn3. This spin structure
induced nonzero scalar spin chirality, which acted as fictitious magnetic
fields to conduction electrons and contributed the additional transverse
signal. These findings deepen the understanding of the interaction between
conduction electrons and complex magnetic structures and are instructive for
the design of next-generation spintronic devices.",2105.03898v1
2021-06-02,Charge order dynamics in underdoped La$\mathbf{_{1.6-\textit{x}}}$Nd$\mathbf{_{0.4}}$Sr$\mathbf{_\textit{x}}$CuO$\mathbf{_{4}}$ revealed by electric pulses,"The dynamics of the charge-order domains has been investigated in
La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_{4}$, a prototypical stripe-ordered
cuprate, using pulsed current injection. We first identify the regime in which
nonthermal effects dominate over simple Joule heating, and then demonstrate
that, for small enough perturbation, pulsed current injection allows access to
nonthermally-induced resistive metastable states. The results are consistent
with pinning of the fluctuating charge order, with fluctuations being most
pronounced at the charge-order onset temperature. The nonequilibrium effects
are revealed only when the transition is approached from the charge-ordered
phase. Our experiment establishes pulsed current injection as a viable and
effective method for probing the charge-order dynamics in various other
materials.",2106.01469v1
2021-06-09,The heat equation for nanoconstrictions in 2D materials with Joule self-heating,"We consider the heat equation for monolayer two-dimensional materials in the
presence of heat flow into a substrate and Joule heating due to electrical
current. We compare devices including a nanowire of constant width and a bow
tie (or wedge) constriction of varying width, and we derive approximate
one-dimensional heat equations for them; a bow tie constriction is described by
the modified Bessel equation of zero order. We compare steady state analytic
solutions of the approximate equations with numerical results obtained by a
finite element method solution of the two-dimensional equation. Using these
solutions, we describe the role of thermal conductivity, thermal boundary
resistance with the substrate and device geometry. The temperature in a device
at fixed potential difference will remain finite as the width shrinks, but will
diverge for fixed current, logarithmically with width for the bow tie as
compared to an inverse square dependence in a nanowire.",2106.05129v2
2021-07-21,Bulk superconductivity and Pauli paramagnetism in nearly stoichiometric CuCo$_2$S$_4$,"It has long remained elusive whether CuCo$_{2}$S$_{4}$ thiospinel shows bulk
superconductivity. Here we clarify the issue by studying on the samples of
sulfur-deficient CuCo$_{2}$S$_{3.7}$ and sulfurized CuCo$_{2}$S$_{4}$. The
sample CuCo$_{2}$S$_{3.7}$ has a smaller lattice constant of $a=9.454$ {\AA},
and it is not superconducting down to 1.8 K. After a full sulfurization, the
$a$ axis of the thiospinel phase increases to 9.475 {\AA}, and the thiospinel
becomes nearly stoichiometric CuCo$_{2}$S$_{4}$, although a secondary phase of
slightly Cu-doped CoS$_2$ forms. Bulk superconductivity at 4.2 K and Pauli
paramagnetism have been demonstrated for the sulfurized CuCo$_{2}$S$_{4}$ by
the measurements of electrical resistivity, magnetic susceptibility, and
specific heat.",2107.09848v1
2021-09-16,Achieving adjustable elasticity with non-affine to affine transition,"For various engineering and industrial applications it is desirable to
realize mechanical systems with broadly adjustable elasticity to respond
flexibly to the external environment. Here we discover a topology-correlated
transition between affine and non-affine regimes in elasticity in both two- and
three-dimensional packing-derived networks. Based on this transition, we
numerically design and experimentally realize multifunctional systems with
adjustable elasticity. Within one system, we achieve solid-like affine
response, liquid-like non-affine response and a continuous tunability in
between. Moreover, the system also exhibits a broadly tunable Poisson's ratio
from positive to negative values, which is of practical interest for energy
absorption and for fracture-resistant materials. Our study reveals a
fundamental connection between elasticity and network topology, and
demonstrates its practical potential for designing mechanical systems and
metamaterials.",2109.07789v1
2021-09-22,Roller-Coaster in a Flatland: Magnetoresistivity in Eu-intercalated Graphite,"Novel phenomena in magnetically-intercalated graphite has been a subject of
much research, pioneered and promoted by M.~S. and G.~Dresselhaus and many
others in the 1980s. Among the most enigmatic findings of that era was a
dramatic, roller-coaster-like behavior of the magnetoresistivity in EuC$_6$
compound, in which magnetic Eu$^{2+}$ ions form a triangular lattice that is
commensurate to graphite honeycomb planes. In this study, we provide a
long-awaited {\it microscopic} explanation of this behavior, demonstrating that
the resistivity of EuC$_6$ is dominated by spin excitations in Eu-planes and
their highly nontrivial evolution with the magnetic field. Together with our
theoretical analysis, the present study showcases the power of the synthetic 2D
materials as a source of potentially significant insights into the nature of
exotic spin excitations.",2109.10916v3
2021-10-05,Experimental study of transport properties of Weyl semimetal LaAlGe thin films grown by molecular beam epitaxy,"Rare earth compounds display diverse electronic, magnetic, and
magneto-transport properties. Recently these compounds of the type RAlGe (R =
La, Ce, Pr) have been shown to exhibit Weyl semimetallic behavior. In this
work, we have investigated the crystal structure, electronic, and
magneto-transport properties of the Weyl semimetal LaAlGe thin films grown by
molecular beam epitaxy. The temperature dependence of longitudinal resistivity
at different magnetic fields is discussed. Observations of magnetoresistances
and Hall effect at different temperatures and their evolution with magnetic
field up to 6 T are also discussed with relevant mechanisms. We have observed
positive unsaturated magnetoresistances, with a small quadratic contribution at
low temperatures, which tends to saturate at higher fields. The Hall
measurements confirm the electron-dominated semimetallic conduction with an
average charge carrier density of ~ 9.68*10^21 cm^(-3) at room temperature.",2110.02322v1
2021-11-05,Externally controlled and switchable 2D electron gas at the Rashba interface between ferroelectrics and heavy $d$ metals,"Strong spin-orbit coupling in noncentrosymmetric materials and interfaces
results in remarkable physical phenomena, such as nontrivial spin textures,
which may exhibit Rashba, Dresselhaus, and other intricated configurations.
This provides a promising basis for nonvolatile spintronic devices and further
implications. Here, we simulate from first principles a two-dimensional
electron gas in ultrathin platinum and palladium layers grown on ferroelectric
PbTiO$_3$(001). The latter allows, in principle, to switch and control the
spin-to-charge conversion by the polarization reversal. We show how the band
structure and its Rashba splitting differ in the Pt and Pd overlayers and how
these electronic features change with increasing the overlayer thickness and
upon reversal of polarization. Besides, for both overlayers, we simulated their
current-voltage ($I-V$) characteristics, the resistance of which upon the
polarization reversal changes between 20% and several hundred percent. The
reported findings can be used to model directly the Rashba-Edelstein effect.",2111.03351v2
2021-11-12,Schwarzite and schwarzynes based load-bear resistant radial cellular griding-based 3D printed structures,"Nature-occurring structures exhibiting unique topological features such as
complex and gradient porosity has been the basis to create new materials and/or
structures. Most studies have been focused on complex periodic porous
structures but gradient porous ones have not been yet fully investigated for
stable structural designs. In this work, we have proposed and tested a new
approach to create cellular griding structures, in which the mass density
varies from the center to the borders, i.e, a radial gradient. To create these
new structures we exploited the topology of two carbon-based families with
different pore sizes, the schwarzites, and schwarzynes. We created fully
atomistic models that were translated into macroscale ones that were then 3D
printed. The mechanical behavior of the gradient structures was investigated by
molecular dynamics simulations and mechanical compression tests of the printed
models. Our results show that their mechanical response can be engineered (for
instance, in terms of energy absorption, ballistic performance, etc.) and can
outperform their corresponding density uniform structures.",2111.06641v1
2021-12-18,Enhanced Tunnel magnetoresistance in Fe/Mg4Al-Ox/Fe(001) Magnetic Tunnel Junctions,"Spinel MgAl2O4 and family oxides are emerging barrier materials useful for
magnetic tunnel junctions (MTJs). We report large tunnel magnetoresistance
(TMR) ratios up to 429% at room temperature (RT) and 1,034% at 10 K in a
Fe/MgAl2O4/Fe(001)-based MTJ prepared using electron-beam evaporation of
Mg4Al-Ox. Resistance oscillations with a MTJ barrier thickness of 0.3-nm were
significantly enhanced compared to those of a Fe/MgO/Fe(001) MTJ, resulting in
a large TMR oscillation peak-to-valley difference of 125% at RT. The
differential conductance spectra were symmetric with bias polarity, and the
spectrum in the parallel magnetization state at low temperature demonstrate
significant peaks within broad local minima at |0.2-0.6| V, indicating improved
barrier interfaces by the Mg4Al-Ox barrier. This study demonstrates that TMR
ratios in Fe(001)-MTJs can still be improved.",2112.09910v1
2022-01-20,Spin valve effect in two-dimensional VSe$_2$ system,"Vanadium based dichalcogenides, VSe$_2$, are two-dimensional materials in
which magnetic Vanadium atoms are arranged in a hexagonal lattice and are
coupled ferromagnetically within the plane. However, adjacent atomic planes are
coupled antiferromagnetically. This provides new and interesting opportunities
for application in spintronics and data storage and processing technologies. A
spin valve magnetoresistance may be achieved when magnetic moments of both
atomic planes are driven to parallel alignment by an external magnetic field.
The resistance change associated with the transition from antiparallel to the
parallel configuration is qualitatively similar to that observed in
artificially layered metallic magnetic structures. Detailed electronic
structure of VSe$_2$ was obtained from DFT calculations. Then, the ballistic
spin-valve magnetoresistance was determined within the Landauer formalism. In
addition, we also analyze thermal and thermoelectric properties. Both phases of
VSe$_2$, denoted as H and T, are considered.",2201.08420v1
2022-03-23,Dipolar Magnetic Interactions and A-type Antiferromagnetic Order in the Zintl Phase Insulator EuZn2P2,"Zintl phases, containing strongly covalently bonded frameworks with separate
ionically bonded ions, have emerged as a critical materials family in which to
couple magnetism and strong spin-orbit coupling to drive diverse topological
phases of matter. Here we report the single-crystal synthesis, magnetic,
thermodynamic, transport, and theoretical properties of the Zintl compound
EuZn2P2 that crystallizes in the anti-La2O3 P-3m1 structure, containing
triangular layers of Eu2+ ions. In-plane resistivity measurements reveal
insulating behavior with an estimated bandgap of Eg=0.11eV. Comparing Eu
magnetic ordering temperatures across trigonal EuM2X2 (M=divalent metal,
X=pnictide) shows that EuZn2P2 exhibits the highest ordering temperature, with
variations in TN correlating with changes in expected dipolar interaction
strengths within and between layers and independent of the magnitude of
electrical conductivity. These results provide experimental validation of the
cytochemical intuition that the cation Eu2+ layers and the anionic (M2X2)2-
framework can be treated as electronically distinct subunits, enabling further
predictive materials design.",2203.12739v1
2022-04-13,"Modeling crack propagation in heterogeneous materials: Griffith's law, intrinsic crack resistance and avalanches","Various kinds of heterogeneity in solids including atomistic discreteness
affect the fracture strength as well as the failure dynamics remarkably. Here
we study the effects of an initial crack in a discrete model for fracture in
heterogeneous materials, known as the fiber bundle model. We find three
distinct regimes for fracture dynamics depending on the initial crack size. If
the initial crack is smaller than a certain value, it does not affect the
rupture dynamics and the critical stress. While for a larger initial crack, the
growth of the crack leads to a breakdown of the entire system, and the critical
stress depends on the crack size in a power-law manner with a nontrivial
exponent. The exponent, as well as the limiting crack size, depend on the
strength of heterogeneity and the range of stress relaxation in the system.",2204.06334v1
2022-04-21,Computational Design of Kinesthetic Garments,"Kinesthetic garments provide physical feedback on body posture and motion
through tailored distributions of reinforced material. Their ability to
selectively stiffen a garment's response to specific motions makes them
appealing for rehabilitation, sports, robotics, and many other application
fields. However, finding designs that distribute a given amount of
reinforcement material to maximally stiffen the response to specified motions
is a challenging problem. In this work, we propose an optimization-driven
approach for automated design of reinforcement patterns for kinesthetic
garments. Our main contribution is to cast this design task as an on-body
topology optimization problem. Our method allows designers to explore a
continuous range of designs corresponding to various amounts of reinforcement
coverage. Our model captures both tight contact and lift-off separation between
cloth and body. We demonstrate our method on a variety of reinforcement design
problems for different body sites and motions. Optimal designs lead to a two-
to threefold improvement in performance in terms of energy density. A set of
manufactured designs were consistently rated as providing more resistance than
baselines in a comparative user study",2204.09996v1
2022-04-24,Large Hall electron mobilities in head-to-head BaTiO$_3$-domain walls,"Strongly charged head-to-head (H2H) domain walls (DWs) that are purposely
engineered along the [110] crystallographic orientation into ferroelectric
BaTiO$_3$ single crystals have been proposed as novel 2-dimensional electron
gases (2DEGs) due to their significant domain wall conductivity (DWC). Here, we
quantify these 2DEG properties through dedicated Hall-transport measurements in
van-der-Pauw 4-point geometry at room temperature, finding the electron
mobility to reach around 400~cm$^2$(Vs)$^{-1}$, while the 2-dimensional charge
density amounts to ~7$\times$10$^3$cm$^{-2}$. We underline the necessity to
take account of thermal and geometrical-misalignment offset voltages by
evaluating the Hall resistance under magnetic-field sweeps, since otherwise
dramatic errors of several hundred percent in the derived mobility and charge
density values can occur. Apart from the specific characterization of the
conducting BaTiO$_3$ DW, we propose the method as an easy and fast way to
quantitatively characterize ferroic conducting DWs, complementary to previously
proposed scanning-probe-based Hall-potential analyses.",2204.11265v1
2022-07-04,Interdependent Superconducting Networks,"Cascades are self-amplifying processes triggered by feedback mechanisms that
may cause a substantial part of a macroscopic system to change its phase in
response of a relatively small local event. The theoretical background for
these phenomena is rich and interdisciplinary with interdependent networks
providing a versatile ""two-interactions"" framework to study their multiscale
evolution. Yet, physics experiments aimed at validating this ever-growing
volume of predictions have remained elusive, hitherto hindered by the problem
of identifying possible physical mechanisms realizing interdependent couplings.
Here we develop and study the first experimental realization of an
interdependent system as a multilayer network of two disordered superconductors
separated by an insulating film. We show that Joule heating effects emerging at
sufficiently large driving currents act as dependency links between the
superconducting layers, igniting overheating cascades via adaptive back and
forth electro-thermal feedbacks. Through theory and experiments, we unveil a
rich phase diagram of mutual resistive transitions and cascading processes that
physically realize and generalize interdependent percolation. The present work
establishes the first physics laboratory bench for the manifestation of the
theory of interdependent systems, enabling experimental studies to control and
to further develop the multilayer phenomena of complex interdependent
materials.",2207.01669v1
2022-07-06,Ferroelastic domain walls in BiFeO$_3$ as memristive networks,"Electronic conduction along individual domain walls (DWs) has been reported
in BiFeO$_3$ (BFO) and other nominally insulating ferroelectrics. DWs in these
materials separate regions of differently oriented electrical polarization
(domains) and are just a few atoms wide, providing self-assembled nanometric
conduction paths. In this work, it is shown that electronic transport is
possible also from wall to wall through the dense network of as-grown DWs in
BFO thin films. Electric field cycling at different points of the network,
performed locally by conducting atomic force microscope (cAFM), induces
resistive switching selectively at the DWs, both for vertical (single wall) and
lateral (wall-to-wall) conduction. These findings are the first step towards
investigating DWs as memristive networks for information processing and
in-materio computing.",2207.02688v1
2022-07-07,Asymmetric Ground States in La$_{0.67}$Sr$_{0.33}$MnO$_3$/BaTiO$_3$ heterostructures Induced by Flexoelectric Bending,"Misfit strain delivered from single-crystal substrates typically modifies the
ground states of transition metal oxides, generating increasing interests in
designing modern transducers and sensors. Here, we demonstrate that
magnetotransport properties of La$_{0.67}$Sr$_{0.33}$MnO$_3$ (LSMO) films were
continuously tuned by uniaxial strain produced by a home-designed bending jig.
The electrical conductivity and Curie temperature of LSMO films are enhanced by
bending stresses. The resistivity of a u-shape bended LSMO decays three times
faster than that of a n-shape bended LSMO as a response to the same magnitude
of strain. The asymmetric magnetic states in uniaxially strained LSMO are
attributed to the dual actions of Jahn-Teller distortion and strain gradient
mediated flexoelectric fields in an adjacent ferroelectric layer. These
findings of multi-field regulation in a single material provide a feasible
means for developing flexible electronic and spintronic devices.",2207.03297v1
2022-07-11,Thermoelectrics: from Longitudinal to Transverse,"In this article, we show fundamentals and recent advances on the transverse
thermoelectric generation, in which a thermopower is generated in the direction
perpendicular to an applied temperature gradient. Transverse thermoelectric
generation is one of the central topics in condensed matter physics, and can be
a breakthrough approach to solve long-standing technological problems with
contact resistances in thermoelectric generators. We review here the six
currently known driving mechanisms: the ordinary Nernst effect, the anomalous
Nernst effect, goniopolar materials, the spin Seebeck effect, Seebeck-driven
transverse thermoelectric generation, and ($p \times n$)-type multilayers. This
article summarizes the principles and functionalities of these transverse
thermoelectric effects and discusses their potential as ""Future energy"".",2207.05005v1
2022-07-13,Strong Spin-Orbit Torque Induced by the Intrinsic Spin Hall Effect in Cr1-xPtx,"We report on a spin-orbit torque study of the spin current generation in
Cr1-xPtx alloy, using the light 3d ferromagnetic Co as the spin current
detector. We find that the dampinglike spin-orbit torque of Cr1-xPtx/Co
bilayers can be enhanced by tuning the Cr concentration in the Cr1-xPtx layer,
with a maximal value of 0.31 at the optimal composition of Cr0.2Pt0.8. We find
that the spin current generation in the Cr1-xPtx alloy can be fully understood
by the characteristic trade-off between the intrinsic spin Hall conductivity of
Pt and the carrier lifetime in the dirty limit. We find no evidence for the
spin current generation by other mechanisms in this material, revealing that
the role of Cr is found to be simply the same as other metals and oxides in
previous studies. This work also establishes the low-resistivity Cr0.2Pt0.8 as
an energy-efficient spin-orbit torque provider for magnetic memory and
computing technologies.",2207.05992v2
2022-09-14,Revealing the band structure of ZrTe$_5$ using Multicarrier Transport,"The layered material ZrTe$_5$ appears to exhibit several exotic behaviors
which resulted in significant interest recently, although the exact properties
are still highly debated. Among these we find a Dirac/Weyl semimetallic
behavior, nontrivial spin textures revealed by low temperature transport, and a
potential weak or strong topological phase. The anomalous behavior of
resistivity has been recently elucidated as originating from band shifting in
the electronic structure. Our work examines magnetotransport behavior in
ZrTe$_5$ samples in the context of multicarrier transport. The results, in
conjunction with ab-initio band structure calculations, indicate that many of
the transport features of ZrTe$_5$ across the majority of the temperature range
can be adequately explained by the semiclassical multicarrier transport model
originating from a complex Fermi surface.",2209.06797v2
2022-09-29,Battery Testing Methods in Fuel Cell Research,"This report presents some of the key laboratory electrochemical battery
testing methods that are used in fuel cell research. Methods such as
voltammetry, chronoamperometry, chronopotentiometry, and electrochemical
impedance spectroscopy are of major importance. All the electrochemical
corrosion tests are performed through a tri-electrode polarization cell setup
containing a reference electrode, a counter electrode, and the working
electrode (metal sample of interest) in an electrolyte solution. All three
electrodes are connected to a potentiostat. Corrosion of metal occurs through
an oxidation-reduction (redox) reaction. All the above testing methods can be
performed by manipulating the current and voltage responses from the cell.
Potentiostatic experiments (voltammetry and chronoamperometry) are performed
using constant potential at the working electrode and recording the current
response while galvanostatic experiments (chronopotentiometry) and vice versa.
The measured data through all these experiments can provide very useful
information regarding reaction reversibility, diffusion coefficient, reduction
potential, rate of chemical reaction, durability, adsorption, voltage losses,
and effective resistance to the mass and charge transport offered by electrode
material.",2209.14541v1
2022-10-11,New Gd-based magnetic compound GdPt$_2$B with a chiral crystal structure,"Herein, we report the discovery of a novel Gd-based magnetic compound
GdPt$_2$B with a chiral crystal structure. X-ray diffraction and chemical
composition analyses reveal a CePt$_2$B-type crystal structure (space group:
$P6_422$) for GdPt$_2$B. Moreover, we successfully grew single crystals of
GdPt$_2$B using the Czochralski method. Magnetization measurements and the
Curie$-$Weiss analysis demonstrate that the ferromagnetic interaction is
dominant in GdPt$_2$B. A clear transition is observed in the temperature
dependence of electrical resistivity, magnetic susceptibility, and specific
heat at $T_{\rm O}$ = 87 K. The magnetic phase diagram of GdPt$_2$B, which
consists of a field-polarized ferromagnetic region and a magnetically ordered
region, resembles those of known chiral helimagnets. Furthermore, magnetic
susceptibility measurements reveal a possible spin reorientation within the
magnetically ordered phase in magnetic fields perpendicular to the screw axis.
The results demonstrate that GdPt$_2$B is a suitable platform for investigating
the competing effects of ferromagnetic and antisymmetric exchange interactions
in rare-earth-based chiral compounds.",2210.05099v1
2022-11-09,Coexistance of volatile and non-volatile memristive effects in phase-separated La$_{0.5}$Ca$_{0.5}$MnO$_{3}$-based devices,"In this work, we have investigated the coexistance of volatile and
non-volatile memristive effects in epitaxial phase-separated
La$_{\text{0.5}}$Ca$_{\text{0.5}}$MnO$_{3}$ thin films. At low temperatures (50
K), we observed volatile resistive changes arising from self-heating effects in
the vicinity of a metal-to-insulator transition. At higher temperatures (140 K
and 200 K) we measured a combination of volatile and non-volatile effects
arising from the synergy between self-heating effects and
ferromagnetic-metallic phase growth induced by an external electrical field.
The results reported here add phase separated manganites to the list of
materials which can electrically mimic, on the same device, the behavior of
both neurons and synapses, a feature that might be useful for the development
of neuromorphic computing hardware",2211.04955v1
2022-11-11,Quantum-Hall physics and three dimensions,"The discovery of the quantum Hall effect (QHE) in 1980 marked a turning point
in condensed matter physics: given appropriate experimental conditions, the
Hall conductivity {\sigma}_xy of a two-dimensional (2D) electron system is
exactly quantized. But what happens to the QHE in three dimensions (3D)?
Experiments over the past 40 years showed that some of the remarkable physics
of the QHE, in particular plateau-like Hall conductivities {\sigma}_xy
accompanied by minima in the longitudinal resistivity \r{ho}_xx, can also be
found in 3D materials. However, since typically \r{ho}_xx remains finite and a
quantitative relation between {\sigma}_xy and the conductance quantum e^2/h
could not be established, the role of quantum Hall physics in 3D remains
unsettled. Following a recent series of exciting experiments, the QHE in 3D has
now returned to the centre stage. Here, we summarize the leap in understanding
of 3D matter in magnetic fields emerging from these experiments.",2211.06248v1
2022-11-25,Microscopic parameters of the van der Waals CrSBr antiferromagnet from microwave absorption experiments,"Microwave absorption experiments employing a phase-sensitive external
resistive detection are performed for a topical van der Waals antiferromagnet
CrSBr. The field dependence of two resonance modes is measured in an applied
field parallel to the three principal crystallographic directions, revealing
anisotropies and magnetic transitions in this material. To account for the
observed results, we formulate a microscopic spin model with a bi-axial
single-ion anisotropy and inter-plane exchange. Theoretical calculations give
an excellent description of full magnon spectra enabling us to precisely
determine microscopic interaction parameters for CrSBr.",2211.14117v1
2022-11-30,Unification of Nonlinear Anomalous Hall Effect and Nonreciprocal Magnetoresistance in Metals by the Quantum Geometry,"The quantum geometry has significant consequences in determining transport
and optical properties in quantum materials. Here, we use a semiclassical
formalism coupled with perturbative corrections unifying the nonlinear
anomalous Hall effect (NLAHE) and nonreciprocal magnetoresistance (NMR,
longitudinal resistance) from the quantum geometry. In the dc limit, both
transverse and longitudinal nonlinear conductivities include a term due to the
normalized quantum metric dipole. The quantum metric contribution is intrinsic
and does not scale with the quasiparticle lifetime. We demonstrate the
coexistence of a NLAHE and NMR in films of the doped antiferromagentic
topological insulator MnBi$_2$Te$_4$. Our work indicates that both longitudinal
and transverse nonlinear transport provide a sensitive probe of the quantum
geometry in solids.",2211.17213v2
2022-12-15,Superconductivity by alloying the topological insulator SnBi2Te4,"Alloying indium into the topological insulator Sn1-xInxBi2Te4 induces bulk
superconductivity with critical temperatures Tc up to 1.85 K and upper critical
fields up to about 14 kOe. This is confirmed by electrical resistivity, heat
capacity, and magnetic susceptibility measurements. The heat capacity shows a
discontinuity at Tc and temperature dependence below Tc consistent with weak
coupling BCS theory, and suggests a superconducting gap near 0.25 meV. The
superconductivity is type-II and the topological surface states have been
verified by photoemission. A simple picture suggests analogies with the
isostructural magnetic topological insulator MnBi2Te4, in which a natural
heterostructure hosts complementary properties on different sublattices, and
motivates new interest in this large family of compounds. The existence of both
topological surface states and superconductivity in Sn1-xInxBi2Te4 identifies
these materials as promising candidates for the study of topological
superconductivity.",2212.08125v1
2022-12-04,Multiphase polarization in ion-intercalation nanofilms: general theory including various surface effects and memory applications,"Ion concentration polarization (CP, current-induced concentration gradient
adjacent to a charge-selective interface) has been well studied for
single-phase mixed conductors (e.g., liquid electrolyte), but multiphase CP has
been rarely addressed in literature. In our recent publication, we proposed
that CP above certain threshold currents can flip the phase distribution in
multiphase ion-intercalation nanofilms sandwiched by ion-blocking electrodes.
We call this phenomenon as multiphase polarization (MP). We then proposed that
MP can further lead to nonvolatile interfacial resistive switching (RS) for
asymmetric electrodes with ion-modulated electron transfer, which theory can
reproduce the experimental results of LTO memristors. In this work, we derive a
comprehensive 2D phase-field model for coupled ion-electron transport in
ion-intercalation materials, with surface effects including electron transfer
kinetics, non-neutral wetting, energy relaxation, and surface charge. Then we
use the model to study MP. We present time evolution of phase boundaries, and
analyze the switching time, current, energy, and cyclic voltammetry, for
various boundary conditions. We find that the switching performance can be
improved significantly by manipulating surface conditions and mean
concentration. Finally, we discuss the prospects of MP-based memories and
possible extensions of the current model.",2212.10404v1
2023-01-09,Memristive Memory Enhancement by Device Miniaturization for Neuromorphic Computing,"The areal footprint of memristors is a key consideration in material-based
neuromorophic computing and large-scale architecture integration. Electronic
transport in the most widely investigated memristive devices is mediated by
filaments, posing a challenge to their scalability in architecture
implementation. Here we present a compelling alternative memristive device and
demonstrate that areal downscaling leads to enhancement in memristive memory
window, while maintaining analogue behavior, contrary to expectations. Our
device designs directly integrated on semiconducting Nb-SrTiO$_3$ allows
leveraging electric field effects at edges, increasing the dynamic range in
smaller devices. Our findings are substantiated by studying the microscopic
nature of switching using scanning transmission electron microscopy, in
different resistive states, revealing an interfacial layer whose physical
extent is influenced by applied electric fields. The ability of Nb-SrTiO$_3$
memristors to satisfy hardware and software requirements with downscaling,
while significantly enhancing memristive functionalities, makes them strong
contenders for non-von Neumann computing, beyond CMOS.",2301.03352v1
2023-01-13,Multistep magnetization switching in orthogonally twisted ferromagnetic monolayers,"The advent of twist-engineering in two-dimensional (2D) crystals enables the
design of van der Waals (vdW) heterostructures exhibiting emergent properties.
In the case of magnets, this approach can afford artificial antiferromagnets
with tailored spin arrangements. Here, we fabricate an orthogonally-twisted
bilayer by twisting 90 degrees two CrSBr ferromagnetic monolayers with an
easy-axis in-plane anisotropy. The magneto-transport properties reveal
multistep magnetization switching with a magnetic hysteresis opening, that is
absent in the pristine case. By tuning the magnetic field, we modulate the
remanent state and coercivity and select between hysteretic and non-hysteretic
magneto-resistance scenarios. This complexity pinpoints spin anisotropy as a
key aspect in twisted magnetic superlattices. Our results highlight the control
over the magnetic properties in vdW heterostructures, leading to a variety of
field-induced phenomena and opening a fruitful playground for creating desired
magnetic symmetries and manipulating non-collinear magnetic configurations.",2301.05647v2
2023-01-17,A robust weak topological insulator in a bismuth halide Bi4Br2I2,"We apply a topological material design concept for selecting a bulk topology
of 3D crystals by different van-der-Waals stacking of 2D topological insulator
layers, and find a bismuth halide Bi4Br2I2 to be an ideal weak topological
insulator (WTI) with the largest band gap (~230 meV) among all the WTI
candidates, by means of angle-resolved photoemission spectroscopy (ARPES),
density functional theory (DFT) calculations, and resistivity measurements. Our
results vastly expand future opportunities for fundamental research and device
applications with a robust WTI.",2301.07158v1
2023-03-08,Fast offset corrected in-memory training,"In-memory computing with resistive crossbar arrays has been suggested to
accelerate deep-learning workloads in highly efficient manner. To unleash the
full potential of in-memory computing, it is desirable to accelerate the
training as well as inference for large deep neural networks (DNNs). In the
past, specialized in-memory training algorithms have been proposed that not
only accelerate the forward and backward passes, but also establish tricks to
update the weight in-memory and in parallel. However, the state-of-the-art
algorithm (Tiki-Taka version 2 (TTv2)) still requires near perfect offset
correction and suffers from potential biases that might occur due to
programming and estimation inaccuracies, as well as longer-term instabilities
of the device materials. Here we propose and describe two new and improved
algorithms for in-memory computing (Chopped-TTv2 (c-TTv2) and Analog Gradient
Accumulation with Dynamic reference (AGAD)), that retain the same runtime
complexity but correct for any remaining offsets using choppers. These
algorithms greatly relax the device requirements and thus expanding the scope
of possible materials potentially employed for such fast in-memory DNN
training.",2303.04721v1
2023-03-10,Conductivity of infinite-layer NdNiO$_{2}$ as a probe of spectator bands,"Using a density-functional theory plus dynamical mean-field theory
methodology, we compute the many-body electronic structure and optical
conductivity of NdNiO$_{2}$ under the influence of large scattering rates on
the Nd($5d$) bands and including dynamical interactions on the Nd($5d$)
orbitals with shifts of the Nd-Ni $d$-level energy difference. We find a robust
conducting pathway in the out-of-plane direction arising from strong
hybridization between the Ni-$d_{z^2}$ and Nd($5d$) orbitals. This pathway can
be ``short-circuited'' if this hybridization is suppressed through large
electronic scattering rates but is not reduced to zero even by very large
beyond-DFT shifts of the Nd-Ni $d$-level energy splitting. The computed
in-plane conductivity for NdNiO$_{2}$ predicts the material to be a ``good
metal'' in contrast to experiments indicating the material is a ``bad metal''
or ``weak insulator''. Our results motivate future experiments measuring the
$c$-axis resistivity as a proxy for the spectator bands and suggests the
essential difference between the infinite-layer nickelates and the cuprates is
dimensionality of their electronic structures.",2303.06046v1
2023-04-12,Exploring the interfacial coupling between graphene and the antiferromagnetic insulator MnPSe$_3$,"Interfacial coupling between graphene and other 2D materials can give rise to
intriguing physical phenomena. In particular, several theoretical studies
predict that the interplay between graphene and an antiferromagnetic insulator
could lead to the emergence of quantum anomalous Hall phases. However, such
phases have not been observed experimentally yet, and further experimental
studies are needed to reveal the interaction between graphene and
antiferromagnetic insulators. Here, we report the study in heterostructures
composed of graphene and the antiferromagnetic insulator MnPSe$_3$. It is found
that the MnPSe$_3$ has little impact on the quantum Hall phases apart from
doping graphene via interfacial charge transfer. However, the magnetic order
can contribute indirectly via process like Kondo effect, as evidenced by the
observed minimum in the temperature-resistance curve between 20-40 K, far below
the N\'eel temperature (70 K).",2304.05757v2
2023-04-27,Magnetism and exchange bias properties in Ba$_{2}$ScRuO$_{6}$,"This paper presents structural, detailed magnetic, and exchange bias studies
in polycrystalline Ba$_{2}$ScRuO$_{6}$ synthesized at ambient pressure. In
contrast to its strontium analogue, this material crystallizes in a 6L
hexagonal structure with the space group P$\overline{3}$m1. The Rietveld
refinement using the room-temperature powder X-ray diffraction pattern suggests
a Ru-Sc disorder in the structure. The temperature variation of the
dc-electrical resistivity highlights a semiconducting behaviour with the
electron conduction corresponding to the Mott 3D-VRH model. Detailed
magnetization measurements show that Ba$_{2}$ScRuO$_{6}$ develops
antiferromagnetic ordering at T$_{N}$ $\approx$ 9 K. Interestingly, below 9 K
(T$_{N}$), the field cooled (FC) magnetic field variation of the magnetization
curves highlights exchange bias effect in the sample. The exchange bias field
reaches a maximum value of 1.24 kOe at 2 K. The exchange bias effect below the
magnetic ordering temperature can be attributed to inhomogeneous magnetic
correlations owing to the disorder in the structure.",2304.13992v1
2023-05-10,On the origin of permeative flows in cholesteric liquid crystals,"Permeative flows, known for the explanation of the anomalous viscosity (10^5
Poise) in cholesterics at low shear rates, are still under debate due to the
difficulty of experiments. Here we use the Surface Force Balance, in which
uniform domains with regular circular defects are formed, to probe the forces
generated by compression in the direction of the helical axis. At the
quasi-static speed of the surface approach, the measured forces are shown to be
elastic (not dissipative), arising from the twist elastic deformation when the
planar anchoring at the walls is strong. A mechanism involving frictional
surface torque under strong planar surface anchoring will be proposed. The
results indicate that the strong resistance to flow observed, previously
interpreted as an enormous apparent viscosity, may in fact originate from the
intrinsic non-linear increase of elasticity when the molecules are rotated away
from equilibrium. The system is found to store energy (the force is
reversible), without dissipation, as long as the applied stress is below the
threshold for nucleating new defects. Our study underpins the importance of
boundary conditions that may dramatically change the rheology of other
viscoelastic materials and sheds light on the rational design of
strain-stiffening materials, nanomotors, and artificial muscles involving
helical architectures.",2305.06189v1
2023-05-20,Magnetic States of Graphene Proximitized Kitaev Materials,"Single layer $\alpha$-ruthenium trichloride ($\rm\alpha-RuCl_3$) has been
proposed as a potential quantum spin liquid. Graphene/$\rm RuCl_3$
heterobilayers have been extensively studied with a focus on the large
interlayer electron transfer that dopes both materials. Here we examine the
interplay between the competing magnetic state of $\rm RuCl_3$ layer and
graphene electronic properties. We perform self-consistent Hartree-Fock
calculations on a Hubbard-Kanamori model of the $4d^5$ $t_{2g}$ electrons of
$\rm\alpha-RuCl_3$ and confirm that out-of-plane ferromagnetic and zigzag
antiferromagnetic states are energetically competitive. We show that the
influence of hybridization between graphene and $\rm\alpha-RuCl_3$ bands is
strongly sensitive to the magnetic configuration of $\rm RuCl_3$ and the
relative orientations of the two layers. We argue that strong hybridization
leads to graphene magneto-resistance and that it may tilt the balance between
closely competing magnetic states. Our analysis can be applied to any van der
Waals heterobilayer system with weak interlayer hybridization and allows for
arbitrary lattice constant mismatch and relative orientation.",2305.12116v2
2023-05-31,Unravelling densification during sintering by multiscale modelling of grain motion,"The resulting microstructure after the sintering process determines many
materials properties of interest. In order to understand the microstructural
evolution, simulations are often employed. One such simulation method is the
phase-field method, which has garnered much interest in recent decades.
However, the method lacks a complete model for sintering, as previous works
could show unphysical effects and the inability to reach representative volume
elements. Thus the present paper aims to close this gap by employing molecular
dynamics and determining rules of motion which can be translated to a
phase-field model. The key realization is that vacancy absorption induced
motion of grains travels through a grain structure without resistance. Hence
the total displacement field of a green body is simply the superposition of all
grains reacting in isolation to local vacancy absorption events. The resulting
phase-field model is shown to be representative starting from particle counts
between 97 and 262 and contains the qualitative correct dependence of sintering
rate on particle size.",2305.19910v2
2023-06-08,Strain-stiffening elastomers fail from the edge,"The accurate measurement of fracture resistance in elastomers is essential
for predicting the mechanical limits of soft devices. Usually, this is achieved
by performing tearing or peeling experiments on thin-sheet samples. Here, we
show that these tests can be surprisingly thickness-dependent, with thicker
samples being significantly stronger than thinner ones. Even for a simple
geometry, direct imaging of the fracture surface shows that the fracture
process actually involves three distinct cracks: an inner crack, and two edge
cracks. Ultimately, samples fail when two edge cracks meet at the sample's
mid-plane. The opening angle of edge crack, $2 \theta$, determines how far the
sample has to be stretched before the edge cracks meet. Conveniently, $\theta$
is a material property that can be inferred from the elastomer's non-linear
elastic response. To yield thickness-independent fracture-test results, sample
thickness should be much smaller than the smallest lateral sample dimension
divided by $\tan \theta$. Our results have direct implications for
characterizing, understanding, and modelling fracture in soft elastomers.",2306.05575v1
2023-06-11,Elasto-viscoplastic Spreading: from Plastocapillarity to Elastocapillarity,"We study the spreading of elastoviscoplastic (EVP) droplets under surface
tension effects. The non- Newtonian material flows like a viscoelastic liquid
above the yield stress and behaves like a viscoelastic solid below it. Hence,
the droplet initially flows under surface tension forces but eventually reaches
a final equilibrium shape when the stress everywhere inside the droplet falls
below the resisting rheological stresses. We use numerical simulations and
combine Volume-of-Fluid (VOF) method and an EVP constitutive model to
systematically study the dynamics of spreading and the final shape of the
droplets. The spreading process examined in this study finds applications in
coating, droplet-based inkjet printing, and 3D printing, where complex fluids
such as paints, thermoplastic filaments, or bio-inks are deposited onto
surfaces. Additionally, the computational framework enables the study of a wide
range of multiphase interfacial phenomena, from elastocapillarity to
plastocapillarity.",2306.06640v1
2023-06-15,Long-Term Stability of Graphene/c-Si Schottky-Junction Solar Cells,"A long operational lifetime is required for the use of solar cells in
real-life photovoltaic applications. The optimization of operational lifetimes
is achieved through understanding the inherent degradation phenomena in solar
cells. In this study, graphene/Si Schottky-junction solar cells were produced,
utilizing liquid-phase-exfoliated graphene as an active surface. The
operational and interface stability of these solar cells over a period of 5
years in ambient conditions (following ISOS-D protocols: dark storage/shelf
life) was examined, and the origin of their degradation was reported. It was
found that the dominant degradation mechanism could be attributed to the
degradation of silver contacts. This was indicated by a decrease in shunt
resistance, an increase in the ideality factor (due to a higher carrier
recombination), and a constant defect density in graphene films for up to 4
years. Measurements across the solar cell's active area during the 5-year
period revealed neither significant spatial inhomogeneity, nor shunt channel
defects.",2306.09015v1
2023-06-17,Superconductivity of Ta-Hf and Ta-Zr alloys: Potential alloys for use in superconducting devices,"The electronic properties relevant to the superconductivity are reported for
bulk Ta-Hf and Ta-Zr body centered cubic alloys, in large part to determine
whether their properties are suitable for potential use in superconducting
qbits. The body centered cubic unit cell sizes increase with increasing
alloying. The results of magnetic susceptibility, electrical resistivity and
heat capacity characterization are reported. While elemental Ta is a type I
superconductor, the alloys are type II strong coupling superconductors.
Although decreasing the electron count per atom is expected to increase the
density of electronic states at the Fermi level and thus the superconducting
transition temperature (Tc) in these systems, we find that this is not
sufficient to explain the significant increases in the superconducting Tc's
observed.",2306.10438v1
2023-06-30,Role of defects on carrier dynamics and transport mechanism in Bi2Te3 single crystals,"Defects play an important role in determining the type of carriers as well as
on tuning the physical properties of layered materials. In this study, we have
demonstrated that by varying the growth kinetics one can control the defects
and can achieve electrons or holes dominated Bi2Te3 single crystals using
modified Bridgman method. The correlation between structural defects and the
type of dominant charge carriers in crystals are discussed using X-Ray
diffraction and Hall resistivity. Electrons are found to be originating from Te
vacancy type defects, while holes are manifested from predominant structural
defects viz. Bi_Te antisite defects or interstitial Te atoms. We observe that
the alteration of charger carriers from electrons to holes have enhanced
magnetoresistance (MR) from 103% to 224%. The enhancement in MR emerges from 2D
multichannel quantum coherent conduction mechanism.",2306.17487v1
2023-07-05,Mechanical Energy Absorption of Architecturally Interlocked Petal-Schwarzites,"We carried out fully atomistic reactive molecular dynamics simulations to
study the mechanical behavior of six newly proposed hybrid schwarzite-based
structures (interlocked petal-schwarzites). Schwarzites are carbon crystalline
nanostructures with negative Gaussian curvature created by mapping a TPMS
(Triply Periodic Minimal Surface) with carbon rings containing six to eight
atoms. Our simulations have shown that petal-schwarzite structures can
withstand uni-axial compressive stress up to the order of GPa and can be
compressed past 50 percent strain without structural collapse. Our most
resistant hierarchical structure has a calculated compressive strength of
260~GPa and specific energy absorption (SEA) of 45.95 MJ/kg, while possessing a
mass density of only 685 kg/m$^3$. These results show that these structures
could be excellent lightweight materials for applications that require
mechanical energy absorption.",2307.02660v1
2023-07-09,Optimal face-to-face coupling for fast self-folding kirigami,"Kirigami-inspired designs can enable self-folding three-dimensional materials
from flat, two-dimensional sheets. Hierarchical designs of connected levels
increase the diversity of possible target structures, yet they can lead to
longer folding times in the presence of fluctuations. Here, we study the effect
of rotational coupling between levels on the self-folding of two-level kirigami
designs driven by thermal noise in a fluid. Naturally present due to
hydrodynamic resistance, we find that optimization of this coupling as control
parameter can significantly improve a structure's self-folding rate and yield.",2307.04145v1
2023-07-19,Magneto-transport and electronic structures in MoSi$_2$ bulks and thin films with different orientations,"We report a comprehensive study of magneto-transport properties in MoSi$_2$
bulk and thin films. Textured MoSi$_2$ thin films of around 70 nm were
deposited on silicon substrates with different orientations. Giant
magnetoresistance of 1000% was observed in sintered bulk samples while MoSi$_2$
single crystals exhibit a magnetoresistance (MR) value of 800% at low
temperatures. At the low temperatures, the MR of the textured thin films show
weak anti-localization behaviour owing to the spin orbit coupling effects. Our
first principle calculation show the presence of surface states in this
material. The resistivity of all the MoSi$_2$ thin films is significantly low
and nearly independent of the temperature, which is important for electronic
devices.",2307.09802v1
2023-07-23,Ru doping induced spin frustration and enhancement of the room-temperature anomalous Hall effect in La2/3Sr1/3MnO3 films,"In transition-metal-oxide heterostructures, the anomalous Hall effect (AHE)
is a powerful tool for detecting the magnetic state and revealing intriguing
interfacial magnetic orderings. However, achieving a larger AHE at room
temperature in oxide heterostructures is still challenging due to the dilemma
of mutually strong spin-orbit coupling and magnetic exchange interactions.
Here, we exploit the Ru doping-enhanced AHE in LSMRO epitaxial films. As the
B-site Ru doping level increases up to 20 percent, the anomalous Hall
resistivity at room temperature can be enhanced from nOhmcm to uOhmcm scale. Ru
doping leads to strong competition between ferromagnetic double-exchange
interaction and antiferromagnetic super-exchange interaction. The resultant
spin frustration and spin-glass state facilitate a strong skew-scattering
process, thus significantly enhancing the extrinsic AHE. Our findings could
pave a feasible approach for boosting the controllability and reliability of
oxide-based spintronic devices.",2307.12253v1
2023-07-30,Superconductivity in amorphous and crystalline Re-Lu films,"We report on magnetron deposition and superconducting properties of a novel
superconducting material: rhenium-lutetium films on sapphire substrates.
Different compositions of Re$_{x}$Lu binary are explored from $x\approx 3.8$ to
close to pure Re stoichiometry. The highest critical temperature, up to
$T_{c}\approx $ 6.95 K, is obtained for $x\approx 10.5$. Depending on the
deposition conditions, polycrystalline or amorphous films are obtainable, both
of which are interesting for practice. Crystalline structure of polycrystalline
phase is identified using grazing incidence X-ray diffractometry as a
non-centrosymmetric superconductor. Superconducting properties were
characterized both resistively and magnetically. Demonstration of
superconductivity in this material justifies the point of view that Lu plays a
role of group 3 transition metal in period 6 of the Periodic table of elements.
In analogy with Re$_{0.82}$Nb$_{0.18}$, Re$_{6}$Ti, Re$_{6}$Hf and Re$_{6}$Zr,
one can expect that crystalline Re--Lu is also breaking the time-reversal
symmetry (this still waits confirmation). Magnetoresistivity and AC/DC
susceptibility measurements allowed us to determine H$_{c1}$ and H$_{c2}$ of
these films, as well as estimate coherence length $\xi (0)$ and magnetic
penetration depth $\lambda _{L}(0)$. We also provide information on surface
morphology of these films.",2307.16313v1
2023-08-01,Fatigue crack growth in anisotropic aluminium sheets -- phase-field modelling and experimental validation,"Fatigue crack growth is decisive for the design of thin-walled structures
such as fuselage shells of air planes. The cold rolling process, used to
produce the aluminium sheets this structure is made of, leads to anisotropic
mechanical properties. In this contribution, we simulate the fatigue crack
growth with a phase-field model due to its superior ability to model arbitrary
crack paths. A fatigue variable based on the Local Strain Approach describes
the progressive weakening of the crack resistance. Anisotropy regarding the
fracture toughness is included through a structural tensor in the crack surface
density. The model is parameterised for an aluminium AA2024-T351 sheet
material. Validation with a set of experiments shows that the fitted model can
reproduce key characteristics of a growing fatigue crack, including crack path
direction and growth rate, considering the rolling direction.",2308.00800v1
2023-08-11,Metallic Quantized Anomalous Hall Effect without Chiral Edge States,"The quantum anomalous Hall effect (QAHE) is a topological state of matter
with a quantized Hall resistance. It has been observed in some two-dimensional
insulating materials such as magnetic topological insulator films and twisted
bilayer graphene. These materials are insulating in the bulk, but possess
chiral edge states carrying the edge current around the systems. Here we
discover a metallic QAHE in a topological insulator film with magnetic sandwich
heterostructure, in which the Hall conductance is quantized to $e^{2}/h$, but
the longitudinal conductance remains finite. This effect is attributed to the
existence of a pair of massless Dirac cones of surface fermions, with each
contributing half of the Hall conductance due to quantum anomaly. It is not
characterized by a Chern number and not associated to any chiral edge states.
Our study offers novel insights into topological transport phenomena and
topological metallic states of matter.",2308.05963v1
2023-09-16,Investigation of the Anomalous and Topological Hall Effects in Layered Monoclinic Ferromagnet Cr$_{2.76}$Te$_4$,"We studied the electrical transport, Hall effect, and magnetic properties of
monoclinic layered ferromagnet Cr$_{2.76}$Te$_4$. Our studies demonstrate
Cr$_{2.76}$Te$_4$ to be a soft ferromagnet with strong magnetocrystalline
anisotropy. Below 50 K, the system shows an antiferromagnetic-like transition.
Interestingly, between 50 and 150 K, we observe fluctuating magnetic moments
between in-plane and out-of-plane orientations, leading to non-coplanar spin
structure. On the other hand, the electrical resistivity data suggest it to be
metallic throughout the measured temperature range, except a $kink$ at around
50 K due to AFM ordering. The Rhodes-Wohlfarth ratio
$\frac{\mu_{eff}}{\mu_{s}}=1.89 (>1)$ calculated from our magnetic studies
confirms that Cr$_{2.76}$Te$_4$ is an itinerant ferromagnet. Large anomalous
Hall effect has been observed due to the skew-scattering of impurities and the
topological Hall effect has been observed due to non-coplanar spin-structure in
the presence of strong magnetocrystalline anisotropy. We examined the mechanism
of anomalous Hall effect by employing the first principles calculations.",2309.08898v1
2023-10-10,Optical assembly of nanostructures mediated by surface roughness,"Rigorous understanding of the self-assembly of colloidal nanocrystals is
crucial to the development of tailored nanostructured materials. Despite
extensive studies, a mechanistic understanding of self-assembly under
non-equilibrium driven by an external field remains an ongoing challenge. We
demonstrate self-assembly by optical tweezers imposing an external attractive
field for cubic-phase sodium yttrium fluoride nanocrystals. We show that
surface roughness of the nanocrystals is a decisive factor for contact leading
to assembly between the nanocrystals, manifested by the roughness-dependent
hydrodynamic resistivity. This provides direct evidence that dynamics are
equally important to energetics in understanding self-assembly. These results
have implications in a wide variety of different fields, such as in
understanding the factors that mediate oriented attachment-based crystal growth
or in interpreting the structure of binding sites on viruses.",2310.06774v1
2023-10-20,Surface-symmetry-driven Dzyaloshinskii--Moriya interaction and canted ferrimagnetism in collinear magnetoelectric antiferromagnet Cr$_2$O$_3$,"Antiferromagnets are normally thought of as materials with compensated
magnetic sublattices. This adds to their technological advantages but
complicates readout of the antiferromagnetic state. We demonstrate
theoretically the existence of a Dzyaloshinskii-Moriya interaction (DMI) which
is determined by the magnetic symmetry classes of Cr$_2$O$_3$ surfaces with an
in-plane magnetic easy axis. The DMI explains a previously predicted
out-of-plane magnetization at the nominally compensated surfaces of chromia,
leading to a surface-localized canted ferrimagnetism. This is in agreement with
magnetotransport measurements and with density functional theory predictions
which further allow us to quantify the strength of DMI. The temperature
dependence of the transversal resistance for these planes shows distinct
behavior in comparison with that of the Cr$_2$O$_3$ $c$ plane, which we
attribute to the influence of DMI. Our work provides a framework to analyze
surface-driven phenomena in antiferromagnets, and motivates the use of
nominally compensated chromia surfaces for antiferomagnetic spintronics and
magnonics.",2310.13438v1
2023-10-27,Practical application of quantum neural network to materials informatics: prediction of the melting points of metal oxides,"Quantum neural network (QNN) models have received increasing attention owing
to their strong expressibility and resistance to overfitting. It is
particularly useful when the size of the training data is small, making it a
good fit for materials informatics (MI) problems. However, there are only a few
examples of the application of QNN to multivariate regression models, and
little is known about how these models are constructed. This study aims to
construct a QNN model to predict the melting points of metal oxides as an
example of a multivariate regression task for the MI problem. Different
architectures (encoding methods and entangler arrangements) are explored to
create an effective QNN model. Shallow-depth ansatzs could achieve sufficient
expressibility using sufficiently entangled circuits. The ""linear"" entangler
was adequate for providing the necessary entanglement. The expressibility of
the QNN model could be further improved by increasing the circuit width. The
generalization performance could also be improved, outperforming the classical
NN model. No overfitting was observed in the QNN models with a well-designed
encoder. These findings suggest that QNN can be a useful tool for MI.",2310.17935v1
2023-11-01,Giant anomalous Hall effect in epitaxial Mn$_{3.2}$Ge films with a cubic kagome structure,"We report on the first example of epitaxial Mn$_{3 + \delta}$Ge thin films
with a cubic $L1_2$ structure. The films are found to exhibit frustrated
ferromagnetism with an average magnetization corresponding to
0.98$~\pm~$0.06$~\mu_B$/Mn, far larger than the parasitic ferromagnetism in
hexagonal Mn$_3$Ge and the partially compensated ferrimagnetism in tetragonal
Mn$_3$Ge. The Hall conductivity is the largest reported for the kagome magnets
with a low temperature value of $\sigma_{xy} = 1587~$S/cm. Density functional
calculations predict that a chiral antiferromagnetic structure is lower in
energy than a ferromagnetic configuration in an ordered stoichiometric crystal.
However, chemical disorder driven by the excess Mn in our films explains why a
frustrated 120$^\circ$ spin structure is not observed. Comparisons between the
magnetization and the Hall resistivity indicate that a non-coplanar spin
structure contributes the Hall signal. Anisotropic magnetoresistance and planar
Hall effect with hysteresis up to 14 T provides further insights into this
material.",2311.00683v1
2023-11-06,Current-induced spin polarization in chiral Tellurium: a first-principles quantum transport study,"Te is a naturally p-doped semiconductor with a chiral structure, where an
electrical current causes the conduction electrons to become spin polarized
parallel to the transport direction. In this paper, we present a comprehensive
theoretical study of this effect by employing density functional theory (DFT)
combined with the non-equilibrium Green's functions (NEGF) technique for
quantum transport. We suggest that the spin polarization can quantitatively be
estimated in terms of two complementary quantities, namely the non-equilibrium
magnetic moments and the spin current density. The calculated magnetic moments
are directly compared with the values from previous theoretical studies
obtaining overall consistent results. On the other hand, the inspection of the
spin current density provides insights of the magnetotransport properties of
the material. Specifically, we predict that the resistance along a Te wire
changes when an external magnetic field is applied parallel or antiparallel to
the charge current direction. The computed magnetoresistance is however quite
small (~ 0.025%). Finally, we show that the description of the current-induced
spin polarization in terms of the spin current establishes a straightforward
connection with the phenomenon called chiral-induced spin selectivity, recently
observed in several nano-junctions.",2311.03219v2
2023-12-11,Superconductivity in Ternary Germanide ScPdGe and Silicide ScPdSi,"The electronic properties of ScPdGe and ScPdSi, crystallizing in the
hexagonal ZrNiAl and orthorhombic TiNiSi structures, respectively, are
investigated. ScPdGe and ScPdSi are found to show bulk superconductivity below
0.9 and 1.7 K, respectively, based on electrical resistivity and heat capacity
data measured using synthesized polycrystalline samples. First principles
calculations indicate the presence of large contributions of Sc 3d and Pd 4d
electrons at the Fermi energy in both materials. The electronic properties and
electronic states of these materials are discussed in comparison with those of
several superconductors containing scandium and a 4d transition metal element.",2312.06045v1
2024-01-12,Direction dependent switching of carrier-type enabled by Fermi surface geometry,"While charge carriers can typically be designated as either electron- or
hole- type, depending on the sign of the Hall coefficient, some materials defy
this straightforward classification. Here we find that LaRh$_6$Ge$_4$ goes
beyond this dichotomy, where the Hall resistivity is electron-like for magnetic
fields along the $c$-axis but hole-like in the basal plane. Together with
first-principles calculations, we show that this direction-dependent switching
of the carrier type arises within a single band, where the special geometry
leads to charge carriers on the same Fermi surface orbiting as electrons along
some directions, but holes along others. The relationship between the Fermi
surface geometry and occurrence of a Hall sign reversal is further generalized
by considering tight-binding model calculations, which show that this type of
Fermi surface corresponds to a more robust means of realizing this phenomenon,
suggesting an important route for tailoring direction dependent properties for
advanced electronic device applications.",2401.06333v1
2024-01-13,Synthesis of thin film infinite-layer nickelates by atomic hydrogen reduction: clarifying the role of the capping layer,"We present an integrated procedure for the synthesis of infinite-layer
nickelates using molecular-beam epitaxy with gas-phase reduction by atomic
hydrogen. We first discuss challenges in the growth and characterization of
perovskite NdNiO$_3$/SrTiO$_3$, arising from post growth crack formation in
stoichiometric films. We then detail a procedure for fully reducing NdNiO$_3$
films to the infinite-layer phase, NdNiO$_2$, using atomic hydrogen; the
resulting films display excellent structural quality, smooth surfaces, and
lower residual resistivities than films reduced by other methods. We utilize
the in situ nature of this technique to investigate of the role that SrTiO$_3$
capping layers play in the reduction process, illustrating their importance in
preventing the formation of secondary phases at the exposed nickelate surface.
A comparative bulk- and surface-sensitive study indicates formation of a
polycrystalline crust on the film surface serves to limit the reduction
process.",2401.07129v1
2024-02-01,A mechanism for electrostatically generated magnetoresistance in chiral systems without spin-dependent transport,"Significant attention has been drawn to electronic transport in chiral
materials coupled to ferromagnets in the chirality induced spin selectivity
(CISS) effect. A large magnetoresistance (MR) is usually observed which is
widely interpreted to originate from spin (dependent) transport. However, there
are severe discrepancies between the experimental results and theoretical
interpretations, most notably the apparent failure of the Onsager reciprocity
relation in the linear response regime. We provide an alternative explanation
for the mechanism of the two terminal MR in chiral systems coupled to a
ferromagnet. For this we point out that it was observed that the electrostatic
contact potential of chiral materials on a ferromagnet depends on the
magnetization direction and chirality. In our explanation this causes the
transport barrier to be modified by the magnetization direction, already in
equilibrium, in the absence of a bias current. This strongly alters the charge
transport through/over the barrier, not requiring spin transport. This provides
a mechanism that allows the linear response resistance to be sensitive to the
magnetization direction and also explains the failure of the Onsager
reciprocity relations. We propose experimental configurations to confirm our
alternative mechanism for MR.",2402.00472v1
2024-02-28,Optimizing Beer Glass Shapes to Minimize Heat Transfer During Consumption,"This paper addresses the problem of determining the optimum shape for a beer
glass that minimizes the heat transfer while the liquid is consumed, thereby
keeping it cold for as long as possible. The proposed solution avoids the use
of insulating materials. The glass is modelled as a body of revolution
generated by a smooth curve S, constructed from a material with negligible
thermal resistance at the revolution surface but insulated at the bottom. The
ordinary differential equation describing the problem is derived from the first
law of Thermodynamics applied to a control volume encompassing the liquid. This
is an inverse optimization problem, aiming to find the shape of the glass
(represented by curve S) that minimizes the heat transfer rate. In contrast,
the direct problem aims to determine the heat transfer rate for a given
geometry. The solution obtained is analytic, and the resulting expression for S
is in closed form, providing a family of optimal glass shapes that can be
manufactured using conventional methods.",2402.18544v1
2024-03-03,Defect-Induced Strain-Tunable Photoluminescence in AgScP$_2$S$_6$,"Metal thiophosphates (MTPs) are a large family of 2D materials that exhibit
large structural and chemical diversity. They also show promise for
applications in energy harvesting and photodetection. Strain and defect
engineering have previously been demonstrated as useful mechanisms to tune
several properties of MTPs such as resistivity, magnetic state, and electronic
band gap. However, the effect of these stimuli on engineering tunable light
emission in MTPs remains unexplored. Here, we show experimentally that
structural defects in metal thiophosphate AgScP$_2$S$_6$ are prominent in
exhibiting photoluminescence, which is likely driven by the
defect-state-to-conduction-band transitions and can be further tuned by
temperature-induced strain gradients.",2403.01581v1
2024-03-29,Gate-tunable quantum acoustoelectric transport in graphene,"Transport probes the motion of quasiparticles in response to external
excitations. Apart from the well-known electric and thermoelectric transport,
acoustoelectric transport induced by traveling acoustic waves has been rarely
explored. Here, by adopting a hybrid nanodevices integrated with piezoelectric
substrates, we establish a simple design of acoustoelectric transport with gate
tunability. We fabricate dual-gated acoustoelectric devices based on
BN-encapsuled graphene on LiNbO3. Longitudinal and transverse acoustoelectric
voltages are generated by launching pulsed surface acoustic wave. The gate
dependence of zero-field longitudinal acoustoelectric signal presents
strikingly similar profiles as that of Hall resistivity, providing a valid
approach for extracting carrier density without magnetic field. In magnetic
fields, acoustoelectric quantum oscillations appear due to Landau quantization,
which are more robust and pronounced than Shubnikov-de Haas oscillations. Our
work demonstrates a feasible acoustoelectric setup with gate tunability, which
can be extended to the broad scope of various Van der Waals materials.",2403.20248v1
2024-04-02,Accurate determination of thermoelectric figure of merit using ac Harman method with a four-probe configuration,"The ac Harman method has been used for the direct estimation of dimensionless
thermoelectric figure of merit (zT) through ac/dc resistance measurements.
However, accurate zT estimation with a four-probe configuration is difficult
owing to the occurrence of a thermal phase-delay in the heat flow with a low
frequency current. This study reports an exact solution for zT estimation by
solving the heat conduction equation. The analysis can explain the reverse heat
flow, which is the main source of the error in the four-probe configuration,
and the experimentally obtained behavior of the frequency dependence of zT of
(Bi,Sb)$_2$Te$_3$. Approximately 20 % of the error is caused by a thermal
phase-delay, unless an appropriate current frequency and voltage-terminal
position are chosen. Thus, an accurate zT evaluation using a four-probe
configuration at any voltage terminal position is achieved. These findings can
lead to interesting thermoelectric metrology and could serve as a powerful tool
to search for promising thermoelectric materials.",2404.01565v1
2024-04-02,From Seaweed to Security: The Emergence of Alginate in Compromising IoT Fingerprint Sensors,"The increasing integration of capacitive fingerprint recognition sensors in
IoT devices presents new challenges in digital forensics, particularly in the
context of advanced fingerprint spoofing. Previous research has highlighted the
effectiveness of materials such as latex and silicone in deceiving biometric
systems. In this study, we introduce Alginate, a biopolymer derived from brown
seaweed, as a novel material with the potential for spoofing IoT-specific
capacitive fingerprint sensors. Our research uses Alginate and cutting-edge
image recognition techniques to unveil a nuanced IoT vulnerability that raises
significant security and privacy concerns. Our proof-of-concept experiments
employed authentic fingerprint molds to create Alginate replicas, which
exhibited remarkable visual and tactile similarities to real fingerprints. The
conductivity and resistivity properties of Alginate, closely resembling human
skin, make it a subject of interest in the digital forensics field, especially
regarding its ability to spoof IoT device sensors. This study calls upon the
digital forensics community to develop advanced anti-spoofing strategies to
protect the evolving IoT infrastructure against such sophisticated threats.",2404.02150v1
2024-04-19,Perspective on descriptors of mechanical behavior of cubic transition-metal carbides and nitrides,"Cubic rocksalt structured transition-metal carbides, nitrides, and related
alloys (TMC/Ns) are attractive for a wide variety of applications, notably as
hard, wear-resistant material. To-date, valence electron concentration (VEC) is
used as a good indicator of stability and mechanical properties of these
refractory compounds. In this perspective, we argue for the need for electronic
descriptors beyond VEC to explain and predict the mechanical behavior of the
cubic TMC/Ns. As such, we point out that descriptors that highlight differences
between constituent have been underused, along with semi-empirical models of
mechanical properties. Additionally, it appears promising to partition VEC into
contribution to ionic, covalent, and metallic bonds and we suggest that such
partition could provide more insight into predicting mechanical properties in
the future.",2404.12853v2
2024-04-25,Anisotropic magnetoresistance in altermagnetic MnTe,"Recently, MnTe was established as an altermagnetic material that hosts
spin-polarized electronic bands as well as anomalous transport effects like the
anomalous Hall effect. In addition to these effects arising from
altermagnetism, MnTe also hosts other magnetoresistance effects. Here, we study
the manipulation of the magnetic order by an applied magnetic field and its
impact on the electrical resistivity. In particular, we establish which
components of anisotropic magnetoresistance are present when the magnetic order
is rotated within the hexagonal basal plane. Our experimental results, which
are in agreement with our symmetry analysis of the magnetotransport components,
showcase the existence of an anisotropic magnetoresistance linked to both the
relative orientation of current and magnetic order, as well as crystal and
magnetic order.",2404.16516v1
2024-05-26,Observation of in-plane anomalous Hall effect associated with orbital magnetization,"For over a century, the Hall effect, a transverse effect under out-of-plane
magnetic field or magnetization, has been a cornerstone for magnetotransport
studies and applications. Modern theoretical formulation based on the Berry
curvature has revealed the potential that even in-plane magnetic field can
induce anomalous Hall effect, but its experimental demonstration has remained
difficult due to its potentially small magnitude and strict symmetry
requirements. Here we report observation of the in-plane anomalous Hall effect
by measuring low-carrier density films of magnetic Weyl semimetal
EuCd$_2$Sb$_2$. Anomalous Hall resistance exhibits distinct three-fold
rotational symmetry for changes in the in-plane field component, and this can
be understood in terms of out-of-plane Weyl points splitting or orbital
magnetization induced by in-plane field, as also confirmed by model
calculation. Our findings demonstrate the importance of in-plane field to
control the Hall effect, accelerating materials development and further
exploration of various in-plane field induced phenomena.",2405.16722v1
2024-05-28,Exchange Splitting Mechanism of Negative Magnetoresistance in Layered Antiferromagnetic Semimetals,"Layered topologically non-trivial and trivial semimetals with AFM-type
ordering of magnetic sublattice are known to exhibit a negative
magnetoresistance that is well correlated with AFM magnetization changes in a
magnetic field. This effect is reported in several experimental studies with
EuFe$_2$As$_2$, EuSn$_2$As$_2$, EuSn$_2$P$_2$, etc., where the resistance
decreases quadratically with field by about $\delta\rho/\rho \sim 4-6\%$ up to
the spin-polarization field. Despite the fact that this effect is well
documented experimentally, its theoretical explanation is missing up to date.
In this paper we propose a novel theoretical mechanism describing the observed
magnetoresistance that does not imply either topological origin of the
materials, surface roughness, their potential defect structure, or
electron-magnon scattering. We believe, the proposed intrinsic mechanism of
magnetoresistance is applicable to a wide class of the layered AFM- ordered
semimetals. The theoretically calculated magnetoresistance is qualitatively
consistent with experimental data for crystals of various composition.",2405.18046v1
2005-04-07,Design of HIV-1-PR inhibitors which do not create resistance: blocking the folding of single monomers,"One of the main problems of drug design is that of optimizing the
drug--target interaction. In the case in which the target is a viral protein
displaying a high mutation rate, a second problem arises, namely the eventual
development of resistance. We wish to suggest a scheme for the design of
non--conventional drugs which do not face any of these problems and apply it to
the case of HIV--1 protease. It is based on the knowledge that the folding of
single--domain proteins, like e.g. each of the monomers forming the HIV--1--PR
homodimer, is controlled by local elementary structures (LES), stabilized by
local contacts among hydrophobic, strongly interacting and highly conserved
amino acids which play a central role in the folding process. Because LES have
evolved over myriads of generations to recognize and strongly interact with
each other so as to make the protein fold fast as well as to avoid aggregation
with other proteins, highly specific (and thus little toxic) as well as
effective folding--inhibitor drugs suggest themselves: short peptides (or
eventually their mimetic molecules), displaying the same amino acid sequence of
that of LES (p--LES). Aside from being specific and efficient, these inhibitors
are expected not to induce resistance: in fact, mutations which successfully
avoid their action imply the destabilization of one or more LES and thus should
lead to protein denaturation. Making use of Monte Carlo simulations within the
framework of a simple although not oversimplified model, which is able to
reproduce the main thermodynamic as well as dynamic properties of monoglobular
proteins, we first identify the LES of the HIV--1--PR and then show that the
corresponding p--LES peptides act as effective inhibitors of the folding of the
protease which do not create resistance.",0504011v1
2012-04-25,Rossby wave instability at dead zone boundaries in 3D resistive magnetohydrodynamical global models of protoplanetary disks,"It has been suggested that the transition between magnetorotationally active
and dead zones in protoplanetary disks should be prone to the excitation of
vortices via Rossby wave instability (RWI). However, the only numerical
evidence for this has come from alpha disk models, where the magnetic field
evolution is not followed, and the effect of turbulence is parametrized by
Laplacian viscosity. We aim to establish the phenomenology of the flow in the
transition in 3D resistive-magnetohydrodynamical models. We model the
transition by a sharp jump in resistivity, as expected in the inner dead zone
boundary, using the Pencil Code to simulate the flow. We find that vortices are
readily excited in the dead side of the transition. We measure the mass
accretion rate finding similar levels of Reynolds stress at the dead and active
zones, at the $\alpha\approx 10^{-2}$ level. The vortex sits in a pressure
maximum and does not migrate, surviving until the end of the simulation. A
pressure maximum in the active zone also triggers the RWI. The magnetized
vortex that results should be disrupted by parasitical magneto-elliptic
instabilities, yet it subsists in high resolution. This suggests that either
the parasitic modes are still numerically damped, or that the RWI supplies
vorticity faster than they can destroy it. We conclude that the resistive
transition between the active and dead zones in the inner regions of
protoplanetary disks, if sharp enough, can indeed excite vortices via RWI. Our
results lend credence to previous works that relied on the alpha-disk
approximation, and caution against the use of overly reduced azimuthal coverage
on modeling this transition.",1204.5711v2
2014-12-18,Field topologies in ideal and near ideal magnetohydrodynamics and vortex dynamics,"Magnetic field topology frozen in ideal magnetohydrodynamics (MHD) and its
breakage in near ideal MHD are reviewed in two parts. The first part gives a
physically complete description of the frozen in field topology, taking
magnetic flux conservation as fundamental and treating four topics, Eulerian
and Lagrangian descriptions of MHD, Chandrasekhar-Kendall and Euler-potential
field representations, magnetic helicity, and inviscid vortex dynamics in
comparison to ideal MHD. A corollary clarifies the challenge of achieving a
high degree of the frozen in condition in numerical MHD. The second part treats
field topology breakage centered on the Parker Magnetostatic Theorem on a
general incompatibility of a continuous magnetic field with the dual demand of
force free equilibrium and an arbitrarily prescribed, 3D field topology.
Preserving field topology as a global constraint readily results in formation
of tangential magnetic discontinuities, i.e., electric current sheets of zero
thickness. A similar incompatibility is present in the steady, force and
thermal balance of a heated radiating fluid subject to an anisotropic thermal
flux conducted strictly along the frozen in magnetic field in the low beta
limit. In a weakly resistive fluid the thinning of current sheets by these
incompatibilities inevitably results in sheet dissipation, resistive heating
and topological changes in the field despite the small resistivity. Faraday
induction drives but also macroscopically limits this mode of energy
dissipation, storing free energy in self organized, ideal MHD structures. This
property of MHD turbulence captured by the Taylor hypothesis is reviewed in
relation to the Sun's corona, calling for a basic quantitative description of
the breakdown of flux conservation in the low resistivity limit. A cylindrical,
initial boundary value problem provides specificity in the review.",1412.6158v1
2015-01-27,Unconventional Strong Spin-Fluctuation Effects around the Critical Pressure of the Itinerant Ising-Type Ferromagnet URhAl,"Resistivity measurements were performed for the itinerant Ising-type
ferromagnet URhAl at temperatures down to 40 mK under high pressure up to 7.5
GPa, using single crystals. We found that the critical pressure of the Curie
temperature exists at around $P_c$ ~ 5.2 GPa. Near $P_c$, the $A$-coefficient
of the $AT^{2}$ Fermi-liquid resistivity term below $T^*$ is largely enhanced
with a maximum around 5.2-5.5 GPa. Above $P_c$, the exponent of the resistivity
$\rho(T)$ deviates from 2. At $P_c$, it is close to $n = 5/3$, which is
expected by the theory of three-dimensional ferromagnetic spin fluctuations for
a 2nd-order quantum-critical point (QCP). However, $T_C(P)$ disappears as a
1st-order phase transition, and the critical behavior of resistivity in URhAl
cannot be explained by the theory of a 2nd-order QCP. The 1st-order nature of
the phase transition is weak, and the critical behavior is still dominated by
the spin fluctuation at low temperature. With increasing pressure, the
non-Fermi-liquid behavior is observed in higher fields. Magnetic field studies
point out a ferromagnetic wing structure with a tri-critical point (TCP) at ~
4.8-4.9 GPa in URhAl. One open possibility is that the switch from the
ferromagnetic to the paramagnetic states does not occur simply but an
intermediate state arises below the TCP as suggested theoretically recently.
Quite generally, if a drastic Fermi-surface change occurs through $P_c$, the
nature of the interaction itself may change and lead to the observed
unconventional behavior.",1501.06701v2
2015-02-06,General-relativistic resistive-magnetohydrodynamic simulations of binary neutron stars,"We have studied the dynamics of an equal-mass magnetized neutron-star binary
within a resistive magnetohydrodynamic (RMHD) approach in which the highly
conducting stellar interior is matched to an electrovacuum exterior. Because
our analysis is aimed at assessing the modifications introduced by resistive
effects on the dynamics of the binary after the merger and through to collapse,
we have carried out a close comparison with an equivalent simulation performed
within the traditional ideal magnetohydrodynamic approximation. We have found
that there are many similarities between the two evolutions but also one
important difference: the survival time of the hyper massive neutron star
increases in a RMHD simulation. This difference is due to a less efficient
magnetic-braking mechanism in the resistive regime, in which matter can move
across magnetic-field lines, thus reducing the outward transport of angular
momentum. Both the RMHD and the ideal magnetohydrodynamic simulations carried
here have been performed at higher resolutions and with a different grid
structure than those in previous work of ours [L. Rezzolla, B. Giacomazzo, L.
Baiotti, J. Granot, C. Kouveliotou, and M. A. Aloy, Astrophys. J. Letters 732,
L6 (2011)], but confirm the formation of a low-density funnel with an ordered
magnetic field produced by the black hole--torus system. In both regimes the
magnetic field is predominantly toroidal in the highly conducting torus and
predominantly poloidal in the nearly evacuated funnel. Reconnection processes
or neutrino annihilation occurring in the funnel, none of which we model, could
potentially increase the internal energy in the funnel and launch a
relativistic outflow, which, however, is not produced in these simulations.",1502.02021v2
2016-04-19,A chemical solver to compute molecule and grain abundances and non-ideal MHD resistivities in prestellar core collapse calculations,"We develop a detailed chemical network relevant to the conditions
characteristic of prestellar core collapse. We solve the system of
time-dependent differential equations to calculate the equilibrium abundances
of molecules and dust grains, with a size distribution given by size-bins for
these latter. These abundances are used to compute the different non-ideal
magneto-hydrodynamics resistivities (ambipolar, Ohmic and Hall), needed to
carry out simulations of protostellar collapse. For the first time in this
context, we take into account the evaporation of the grains, the thermal
ionisation of Potassium, Sodium and Hydrogen at high temperature, and the
thermionic emission of grains in the chemical network, and we explore the
impact of various cosmic ray ionisation rates. All these processes
significantly affect the non-ideal magneto-hydrodynamics resistivities, which
will modify the dynamics of the collapse. Ambipolar diffusion and Hall effect
dominate at low densities, up to n_H = 10^12 cm^-3, after which Ohmic diffusion
takes over. We find that the time-scale needed to reach chemical equilibrium is
always shorter than the typical dynamical (free fall) one. This allows us to
build a large, multi-dimensional multi-species equilibrium abundance table over
a large temperature, density and ionisation rate ranges. This table, which we
make accessible to the community, is used during first and second prestellar
core collapse calculations to compute the non-ideal magneto-hydrodynamics
resistivities, yielding a consistent dynamical-chemical description of this
process.",1604.05613v6
2017-03-06,Mutation supply and the repeatability of selection for antibiotic resistance,"Whether evolution can be predicted is a key question in evolutionary biology.
Here we set out to better understand the repeatability of evolution. We
explored experimentally the effect of mutation supply and the strength of
selective pressure on the repeatability of selection from standing genetic
variation. Different sizes of mutant libraries of an antibiotic resistance
gene, TEM-1 $\beta$-lactamase in Escherichia coli, were subjected to different
antibiotic concentrations. We determined whether populations went extinct or
survived, and sequenced the TEM gene of the surviving populations. The
distribution of mutations per allele in our mutant libraries- generated by
error-prone PCR- followed a Poisson distribution. Extinction patterns could be
explained by a simple stochastic model that assumed the sampling of beneficial
mutations was key for survival. In most surviving populations, alleles
containing at least one known large-effect beneficial mutation were present.
These genotype data also support a model which only invokes sampling effects to
describe the occurrence of alleles containing large-effect driver mutations.
Hence, evolution is largely predictable given cursory knowledge of mutational
fitness effects, the mutation rate and population size. There were no clear
trends in the repeatability of selected mutants when we considered all
mutations present. However, when only known large-effect mutations were
considered, the outcome of selection is less repeatable for large libraries, in
contrast to expectations. Furthermore, we show experimentally that alleles
carrying multiple mutations selected from large libraries confer higher
resistance levels relative to alleles with only a known large-effect mutation,
suggesting that the scarcity of high-resistance alleles carrying multiple
mutations may contribute to the decrease in repeatability at large library
sizes.",1703.01896v1
2020-03-16,Effect of cytosol viscosity on the flow behavior of red blood cell suspensions in microvessels,"The flow behavior of blood in microvessels is directly associated with tissue
perfusion and oxygen delivery. Current efforts on modeling blood flow have
primarily focused on the flow properties of blood with red blood cells (RBCs)
having a viscosity ratio $C$ of unity between the cytosol and suspending
medium, while under physiological conditions the cytosol viscosity is about
five times larger than the plasma viscosity (i.e., $C\approx 5$). The
importance of $C$ for the behavior of single RBCs in fluid flow has already
been demonstrated, while the effect of $C$ on blood flow has only been sparsely
studied. We employ mesoscopic hydrodynamic simulations to perform a systematic
investigation of flow properties of RBC suspensions with different cytosol
viscosities for various flow conditions in cylindrical microchannels. Our main
aim is to link macroscopic flow properties such as flow resistance to single
cell deformation and dynamics as a function of $C$. Starting from a dispersed
cell configuration, we find that the flow convergence and the development of a
RBC-free layer (RBC-FL) depend only weakly on $C$, and require a convergence
length in the range of $25D-50D$, where $D$ is the channel diameter. The flow
resistance for $C=5$ is nearly the same as that for $C=1$, which is facilitated
by a slightly larger RBC-FL thickness for $C=5$. This effect is due to the
suppression of membrane motion and dynamic shape deformations by a more viscous
cytosol for $C=5$, resulting in a more compact cellular core of the flow in
comparison to $C=1$. The weak effect of cytosol viscosity on the flow
resistance and RBC-FL explains why cells can have a high concentration of
hemoglobin for efficient oxygen delivery, without a pronounced increase in the
flow resistance.",2003.09217v1
2019-12-24,DC resistivity near a nematic quantum critical point: Effects of weak disorder and acoustic phonons,"We calculate the resistivity associated with an Ising-nematic quantum
critical point in the presence of disorder and acoustic phonons in the lattice
model. We use the memory-matrix transport theory, which has a crucial advantage
compared to other methods of not relying on the existence of well-defined
quasiparticles in the low-energy effective theory. As a result, we obtain that
by including an inevitable interaction between the nematic fluctuations and the
elastic degrees of freedom of the lattice (parametrized by the nemato-elastic
coupling $\kappa_{\text{latt}}$), the resistivity $\rho(T)$ of the system as a
function of temperature obeys a universal scaling form described by
$\rho(T)\sim T\ln (1/T)$ at high temperatures, reminiscent of the paradigmatic
strange metal regime observed in many strongly correlated compounds. For a
window of temperatures comparable with
$\kappa^{3/2}_{\text{latt}}\varepsilon_F$ (where $\varepsilon_F$ is the Fermi
energy of the microscopic model), the system displays another regime in which
the resistivity is consistent with a description in terms of $\rho(T)\sim
T^{\alpha}$, where the effective exponent roughly satisfies the inequality
$1\lesssim\alpha\lesssim 2$. However, in the low-temperature limit (i.e.,
$T\ll\kappa^{3/2}_{\text{latt}}\varepsilon_F$), the properties of the quantum
critical state change in an important way depending on the types of disorder
present in the system: It can either recover a conventional Fermi liquid
described by $\rho(T)\sim T^2$ or it could exhibit yet another non-Fermi liquid
regime characterized by the scaling form $\rho(T)-\rho_0\sim T^2\ln T$. Our
results emphasize the key role played by both phonon and disorder effects in
the scenario of nematic quantum criticality and might be fundamental for
addressing recent transport experiments in some iron-based superconductors.",1912.11558v3
2016-08-16,Universal Fragment Descriptors for Predicting Electronic Properties of Inorganic Crystals,"Historically, materials discovery has been driven by a laborious
trial-and-error process. The growth of materials databases and emerging
informatics approaches finally offer the opportunity to transform this practice
into data- and knowledge-driven rational design. By using data from the AFLOW
repository for high-throughput ab-initio calculations, we have generated
Quantitative Materials Structure-Property Relationship (QMSPR) models to
predict eight critical electronic and thermomechanical materials properties,
such as the metal/insulator classification, band gap energy, bulk and shear
moduli, Debye temperature, and heat capacity. The prediction accuracy obtained
with these QMSPR models approaches training data for virtually any
stoichiometric inorganic crystalline material. The success and universality of
these models is attributed to the construction of new materials
descriptors---referred to as the universal Property-Labeled Materials Fragments
(PLMF). The representation requires only minimal structural input and affords
straightforward model interpretation in terms of simple heuristic design rules
that guide rational materials design. This study demonstrates the power of
materials informatics to dramatically accelerate the search for new materials.",1608.04782v3
2019-05-30,Surface waves with negative phase velocity supported by temperature-dependent hyperbolic materials,"A numerical investigation was undertaken to elucidate the propagation of
electromagnetic surface waves guided by the planar interface of two
temperature-sensitive materials. One partnering material was chosen to be
isotropic and the other to be anisotropic. Both partnering materials were
engineered composite materials, based on the temperature-sensitive
semiconductor InSb. At low temperatures the anisotropic partnering material is
a non-hyperbolic uniaxial material; as the temperature is raised this material
becomes a hyperbolic uniaxial material. At low temperatures, a solitary
Dyakonov wave propagates along any specific direction in a range of directions
parallel to the planar interface. At high temperatures, up to three different
surface waves can propagate in certain directions parallel to the planar
interface; one of these surface waves propagates with negative phase velocity
(NPV). At a fixed temperature, the range of directions for NPV propagation
decreases uniformly in extent as the volume fraction of InSb in the isotropic
partnering material decreases. At a fixed volume fraction of InSb in the
isotropic partnering material, the angular range for NPV propagation varies
substantially as the temperature varies.",1905.13092v2
2015-06-13,Predicting Fracture Energies and Crack-Tip Fields of Soft Tough Materials,"Soft materials including elastomers and gels are pervasive in biological
systems and technological applications. Whereas it is known that intrinsic
fracture energies of soft materials are relatively low, how the intrinsic
fracture energy cooperates with mechanical dissipation in process zone to give
high fracture toughness of soft materials is not well understood. In addition,
it is still challenging to predict fracture energies and crack-tip strain
fields of soft tough materials. Here, we report a scaling theory that accounts
for synergistic effects of intrinsic fracture energies and dissipation on the
toughening of soft materials. We then develop a coupled cohesive-zone and
Mullins-effect model capable of quantitatively predicting fracture energies of
soft tough materials and strain fields around crack tips in soft materials
under large deformation. The theory and model are quantitatively validated by
experiments on fracture of soft tough materials under large deformations. We
further provide a general toughening diagram that can guide the design of new
soft tough materials.",1506.04271v1
2023-04-19,Towards a muon scattering tomography system for both low-Z and high-Z materials,"Muon scattering tomography (MST) is a non-destructive technique to image
various materials by utilizing cosmic ray muons as probes. A typical MST system
with a two-fold track detectors is particularly effective in detecting high-$Z$
materials (e.g. nuclear materials), but difficult to recognize low-$Z$
materials (e.g. explosive materials). In this work, we present a concept of MST
system to discriminate both low-$Z$ and high-$Z$ materials by extra measuring
momentum of low-energy muons with a Cherenkov detector. A toy Monte Carlo
simulation to describe detector responses and multiple scatterings of a muon
tracking through materials is developed for statistical tests. Based on
momentum-dependent track reconstruction and image reconstruction algorithm, we
evaluate separation powers of different materials in the system. The results
show that momentum measurement of low-energy muons and accurate track
reconstruction can improve separation power of low-$Z$ materials significantly.
This may enable the MST system to detect both low-$Z$ and high-$Z$ materials
with cosmic ray muons in the whole energy range.",2304.09489v2
2024-05-08,2D ferroelectrics and ferroelectrics with 2D: materials and device prospects,"Ferroelectric and two-dimensional materials are both heavily investigated
classes of electronic materials. This is unsurprising since they both have
superlative fundamental properties and high-value applications in computing,
sensing etc. In this Perspective, we investigate the research topics where 2D
semiconductors and ferroelectric materials both in 2D or 3D form come together.
2D semiconductors have unique attributes due to their van der Waals nature that
permits their facile integration with any other electronic or optical
materials. In addition, the emergence of ferroelectricity in 2D monolayers,
multilayers, and artificial structures offers further advantages since
traditionally ferroelectricity has been difficult to achieve in extremely
thickness scaled materials. In this perspective, we elaborate on the
applications of 2D materials + ferroelectricity in non-volatile memory devices
highlighting their potential for in-memory computing, neuromorphic computing,
optoelectronics, and spintronics. We also suggest the challenges posed by both
ferroelectrics and 2D materials, including material/device preparation, and
reliable characterizations to drive further investigations at the interface of
these important classes of electronic materials.",2405.05432v1
2019-08-14,Substrate effects on charged defects in two-dimensional materials,"Two-dimensional (2D) materials are strongly affected by the dielectric
environment including substrates, making it an important factor in designing
materials for quantum and electronic technologies. Yet, first-principles
evaluation of charged defect energetics in 2D materials typically do not
include substrates due to the high computational cost. We present a general
continuum model approach to incorporate substrate effects directly in
density-functional theory calculations of charged defects in the 2D material
alone. We show that this technique accurately predicts charge defect energies
compared to much more expensive explicit substrate calculations, but with the
computational expediency of calculating defects in free-standing 2D materials.
Using this technique, we rapidly predict the substantial modification of charge
transition levels of two defects in MoS$_2$ and ten defects promising for
quantum technologies in hBN, due to SiO$_2$ and diamond substrates. This
establishes a foundation for high-throughput computational screening of new
quantum defects in 2D materials that critically accounts for substrate effects.",1908.05208v1
2019-12-05,Do 2D material-based battery electrodes have inherently poor rate-performance?,"Two dimensional materials show great potential for use in battery electrodes
and are believed to be particularly promising for high-rate applications.
However, there does not seem to be much hard evidence for the superior
rate-performance of 2D materials compared to non-2D materials. To examine this
point, we have analyzed published rate-performance data for a wide range of 2D
materials as well as non-2D materials for comparison. For each capacity-rate
curve we extract parameters which quantify performance which can then be
analyzed using a simple mechanistic model. Contrary to expectations, by
comparing a previously-proposed figure of merit, we find 2D-based electrodes to
be on average ~40 times poorer in terms of rate performance than non-2D
materials. This is not due to differences in solid-state diffusion times which
were similarly distributed for 2D and non-2D materials. In fact, we found the
main difference between 2D and non-2D materials to be that ion mobility within
the electrolyte-filled pores of the electrodes to be significantly lower for 2D
materials, a situation which we attribute to their high aspect ratios.",1912.02482v1
2023-08-18,MATLABER: Material-Aware Text-to-3D via LAtent BRDF auto-EncodeR,"Based on powerful text-to-image diffusion models, text-to-3D generation has
made significant progress in generating compelling geometry and appearance.
However, existing methods still struggle to recover high-fidelity object
materials, either only considering Lambertian reflectance, or failing to
disentangle BRDF materials from the environment lights. In this work, we
propose Material-Aware Text-to-3D via LAtent BRDF auto-EncodeR
(\textbf{MATLABER}) that leverages a novel latent BRDF auto-encoder for
material generation. We train this auto-encoder with large-scale real-world
BRDF collections and ensure the smoothness of its latent space, which
implicitly acts as a natural distribution of materials. During appearance
modeling in text-to-3D generation, the latent BRDF embeddings, rather than BRDF
parameters, are predicted via a material network. Through exhaustive
experiments, our approach demonstrates the superiority over existing ones in
generating realistic and coherent object materials. Moreover, high-quality
materials naturally enable multiple downstream tasks such as relighting and
material editing. Code and model will be publicly available at
\url{https://sheldontsui.github.io/projects/Matlaber}.",2308.09278v1
2023-08-23,"Energy landscape and phase competition of CsV3Sb5-, CsV6Sb6-, and TbMn6Sn6-type Kagome materials","Finding viable Kagome lattices is vital for materializing novel phenomena in
quantum materials. In this work, we performed element substitutions on CsV3Sb5
with space group P6/mmm, TbMn6Sn6 with space group P6/mmm, and CsV6Sb6 with
space group R-3 m, respectively, as the parent compounds. A total of 4158
materials were obtained through element substitutions, and these materials were
then calculated via density function theory in high-throughput mode. Afterward,
48 materials were identified with high thermodynamic stability
(E_hull<5meV/atom). Furthermore, we compared the thermodynamic stability of
three different phases with the same elemental composition and predicted some
competing phases that may arise during material synthesis. Finally, by
calculating the electronic structures of these materials, we attempted to
identify patterns in the electronic structure variations as the elements
change. This work provides guidance for discovering promising AM3X5/AM6X6
Kagome materials from a vast phase space.",2308.11930v1
2019-11-26,A hunt for ultrahard materials,"Recent results on search (theoretical prediction, high-pressure synthesis,
etc.) for novel superhard and ultrahard materials are briefly reviewed.",1911.11731v1
2021-12-17,High-throughput Discovery and Intelligent Design of 2D Functional Materials for Various Applications,"Novel technologies and new materials are in high demand for future
energy-efficient electronic devices to overcome the fundamental limitations of
miniaturization of current silicon-based devices. Two-dimensional (2D)
materials show promising applications in the next generation devices because
they can be tailored on the specific property that a technology is based on,
and be compatible with other technologies, such as the silicon-based
(opto)electronics. Although the number of experimentally discovered 2D
materials is growing, the speed is very slow and only a few dozen 2D materials
have been synthesized or exfoliated since the discovery of graphene. Recently,
a novel computational technique, dubbed ""high-throughput computational
materials design"", becomes a burgeoning area of materials science, which is the
combination of the quantum-mechanical theory, materials genome, and database
construction with intelligent data mining. This new and powerful tool can
greatly accelerate the discovery, design and application of 2D materials by
creating database containing a large amount of 2D materials with calculated
fundamental properties, and then intelligently mining (via high-throughput
automation or machine learning) the database in the search of 2D materials with
the desired properties for particular applications, such as energy conversion,
electronics, spintronics, and optoelectronics.",2112.09347v1
2006-05-25,High-Pressure Synthesized Materials: a Chest of Treasure and Hints,"The present review covers the production of new materials under high
pressures. A primary limitation on the use of pressures higher than 1 GPa is a
small volume and mass of a produced material. Therefore, despite an extremely
wide range of new high-pressure synthesized substances with unique properties,
synthesis on an commercial scale is applied up to now only to obtain superhard
materials, this real treasure of today's industry. At the same time,
high-pressure experiments often give material scientists a hint at what new
intriguing substances can exist in principle. This is true for new superhard,
semiconducting, magnetic, superconducting and optical materials already
synthesized under pressure, and as well as for a large number of hypothetic new
polymers from low-Z elements. Many of new materials, including the above
polymers, may exist in the metastable form at normal pressure at sufficiently
high temperatures.",0605626v1
2020-02-13,First-principles discovery of stable two-dimensional materials with high-level piezoelectric response,"The rational design of two-dimensional piezoelectric materials has recently
garnered great interest due to their increasing use in technological
applications, including sensor technology, actuating devices, energy
harvesting, and medical applications. Several materials possessing high
piezoelectric response have been reported so far, but a high-throughput
first-principles approach to estimate the piezoelectric potential of layered
materials has not been performed yet. In this study, we systematically
investigated the piezoelectric ($e_{11}$, $d_{11}$) and elastic (C$_{11}$ and
C$_{12}$) properties of 128 thermodynamically stable two-dimensional (2D)
semiconductor materials by employing first-principle methods. Our
high-throughput approach demonstrates that the materials containing
Group-\textrm{V} elements produce significantly high piezoelectric strain
constants, $d_{11}$ $>$ 40 pmV$^{-1}$, and 49 of the materials considered have
the $e_{11}$ coefficient higher than MoS$_{2}$ insomuch as BrSSb has one of the
largest $d_{11}$ with a value of 373.0 pmV$^{-1}$. Moreover, we established a
simple empirical model in order to estimate the $d_{11}$ coefficients by
utilizing the relative ionic motion in the unit cell and the polarizability of
the individual elements in the compounds.",2002.05803v2
2022-03-08,Recent Progress of Heterostructures Based on Two Dimensional Materials and Wide Bandgap Semiconductors,"Recent progress in the synthesis and assembly of two-dimensional (2D)
materials has laid the foundation for various applications of atomically thin
layer films. These 2D materials possess rich and diverse properties such as
layer-dependent band gaps, interesting spin degrees of freedom, and variable
crystal structures. They exhibit broad application prospects in micro-nano
devices. In the meantime, the wide bandgap semiconductors (WBS) with an
elevated breakdown voltage, high mobility, and high thermal conductivity have
shown important applications in high-frequency microwave devices,
high-temperature and high-power electronic devices. Beyond the study on single
2D materials or WBS materials, the multi-functional 2D/WBS heterostructures can
promote the carrier transport at the interface, potentially providing novel
physical phenomena and applications, and improving the performance of
electronic and optoelectronic devices. In this review, we overview the
advantages of the heterostructures of 2D materials and WBS materials, and
introduce the construction methods of 2D/WBS heterostructures. Then, we present
the diversity and recent progress in the applications of 2D/WBS
heterostructures, including photodetectors, photocatalysis, sensors, and energy
related devices. Finally, we put forward the current challenges of 2D/WBS
heterostructures and propose the promising research directions in the future.",2203.03895v1
1998-11-17,"Stripes, Electron-Like and Polaron-Like Carriers, and High-T_c in the Cuprates","Both ""large-U"" and ""small-U"" orbitals are used to study the electronic
structure of the high-T_c cuprates. A striped structure with three types of
carriers are induced, polaron-like ""stripons"" which carry charge,
""quasielectrons"" which carry both charge and spin, and ""svivons"" which carry
spin and lattice distortion. Anomalous physical properties of the cuprates are
derived, and specifically the systematic behavior of the resistivity, Hall
constant, and thermoelectric power. Transitions between pair states of
quasielectrons and stripons drive high-temperature superconductivity.",9811261v1
1999-05-12,"Stripes, Carriers, and High Tc in the Cuprates","Considering both ""large-U"" and ""small-U"" orbitals it is found that the
high-Tc cuprates are characterized by a striped structure, and three types of
carriers: polaron-like ""stripons"" carrying charge, ""quasielectrons"" carrying
charge and spin, and ""svivons"" carrying spin and lattice distortion. It is
shown that this electronic structure leads to the anomalous physical properties
of the cuprates, and specifically the systematic behavior of the resistivity,
Hall constant, and thermoelectric power. High-Tc pairing results from
transitions between pair states of quasielectrons and stripons through the
exchange of svivons. A pseudogap phase occurs when pairing takes place above
the temperature where stripons become coherent, and this temperature determines
the Uemura limit.",9905172v1
1999-11-12,High-Field Electrical Transport in Single-Wall Carbon Nanotubes,"Using low-resistance electrical contacts, we have measured the intrinsic
high-field transport properties of metallic single-wall carbon nanotubes.
Individual nanotubes appear to be able to carry currents with a density
exceeding 10^9 A/cm^2. As the bias voltage is increased, the conductance drops
dramatically due to scattering of electrons. We show that the current-voltage
characteristics can be explained by considering optical or zone-boundary phonon
emission as the dominant scattering mechanism at high field.",9911186v1
2003-06-12,Magnetoresistance of Si(001) MOSFETs with high concentration of electrons,"We present an experimental study of electron transport in inversion layers of
high-mobility Si(001) samples with occupied excited subbands. The second series
of oscillations, observed in addition to the main series of Shubnikov-de Hass
oscillations, is tentatively attributed to the occupation of a subband
associated with the $E_{0'}$ level. Besides, a strong negative
magnetoresistance and nonlinear field dependence of the Hall resistance
accompany the novel oscillations at high carrier concentrations. The heating of
the 2D electron layers leads to suppression of the observed anomalies.",0306330v1
2005-02-18,High pressure synthesis of a new superconductor Sr2CuO2+xCl2-y induced by apical oxygen doping,"Using the apical oxygen doping mechanism, i.e. a partial substitution of
divalence O for the monovalence Cl, a p-type oxychloride cuprate
superconductor, Sr2CuO2+xCl2-y, was synthesized at high pressure high
temperature. The x-ray diffraction refinement suggests the superconductor
crystallizes into a 0201 structure with space group I4/mmm and lattice
parameters being a=3.92A, c=15.6 A. The magnetic susceptibility as well as
resistance measurements indicated that the bulk superconductivity with
transition temperature 30K was achieved in the sample.",0502449v1
2006-04-28,Evidence for Carrier-Induced High-Tc Ferromagnetism in Mn-doped GaN film,"A GaN film doped with 8.2 % Mn was grown by the molecular-beam-epitaxy
technique. Magnetization measurements show that this highly Mn-doped GaN film
exhibits ferromagnetism above room temperature. It is also revealed that the
high-temperature ferromagnetic state is significantly suppressed below 10 K,
accompanied by an increase of the electrical resistivity with decreasing
temperature. This observation clearly demonstrates a close relation between the
ferromagnetism with extremely high-Tc and the carrier transport in the Mn-doped
GaN film.",0604647v1
2006-10-05,Robust charge stripe order under high electric fields in Nd1.67Sr0.33NiO4,"The influence of high electric fields on the charge stripe order in
Nd1.67Sr0.33NiO4 was studied by means of simultaneous hard x-ray diffraction
and electrical transport experiments. Direct measurements of the charge stripe
satellite peaks in zero and high electric fields provide no evidence for a
deformation or a sliding of the stripe lattice, which contradicts previous
indications from non-linear conductance effects. By using the order parameter
of a structural phase transition for instant sample temperature measurements,
non-linear transport effects can be attributed to resistive heating.
Implications for the pinning of stripes in the nickelates are discussed.",0610132v1
2005-04-26,Flux profile scanners for scattered high-energy electrons,"The paper describes the design and performance of flux integrating Cherenkov
scanners with air-core reflecting light guides used in a high-energy, high-flux
electron scattering experiment at the Stanford Linear Accelerator Center. The
scanners were highly radiation resistant and provided a good signal to
background ratio leading to very good spatial resolution of the scattered
electron flux profile scans.",0504029v1
2001-06-05,Bell inequalities for arbitrarily high dimensional systems,"We develop a novel approach to Bell inequalities based on a constraint that
the correlations exhibited by local realistic theories must satisfy. This is
used to construct a family of Bell inequalities for bipartite quantum systems
of arbitrarily high dimensionality which are strongly resistant to noise. In
particular our work gives an analytic description of numerical results of D.
Kaszlikowski, P. Gnacinski, M. Zukowski, W. Miklaszewski, A. Zeilinger, Phys.
Rev. Lett. {\bf 85}, 4418 (2000) and T. Durt, D. Kaszlikowski, M. Zukowski,
quant-ph/0101084, and generalises them to arbitrarily high dimensionality.",0106024v2
2008-04-07,Hg-Based Superconducting Cuprates: High Tc and Pseudo Spin-Gap,"A brief review of microscopic studies of high-Tc superconductors HgBa2CuO4+d
and HgBa2CaCu2O6+d is presented. The topics concerned are the pseudo spin-gap,
the antiferromagnetic spin fluctuations near the quantum critical point, and
the mechanism of the high Tc via NMR. The crystal structure with the flat CuO2
plane, two-dimensional electrical resistivity, Cu NQR, NMR experimental results
are discussed.",0804.0911v2
2008-09-12,Effect of oxygen incorporation on normal and superconducting properties of MgB2 films,"Oxygen was systematically incorporated in MBE grown MgB2 films using in-situ
post-growth anneals in an oxygen environment. Connectivity analysis in
combination with measurements of the critical temperature and resistivity
indicate that oxygen is distributed both within and between the grains. High
values of critical current densities in field (~4x10^5 A/cm^2 at 8 T and 4.2
K), extrabolated critical fields (>45 T) and slopes of critical field versus
temperature (1.4 T/K) are observed. Our results suggest that low growth
temperatures (300oC) and oxygen doping (>0.65%) can produce MgB2 with high Jc
values in field and Hc2 for high-field magnet applications.",0809.2297v1
2009-07-20,Electrical Transport in High Quality Graphene pnp Junctions,"We fabricate and investigate high quality graphene devices with contactless,
suspended top gates, and demonstrate formation of graphene pnp junctions with
tunable polarity and doping levels. The device resistance displays distinct
oscillations in the npn regime, arising from the Fabry-Perot interference of
holes between the two pn interfaces. At high magnetic fields, we observe
well-defined quantum Hall plateaus, which can be satisfactorily fit to
theoretical calculations based on the aspect ratio of the device.",0907.3366v1
2009-11-11,Enhanced superconductivity of YBCO interfaces: origin of high critical temperature in layered superconductors,"Superconducting transition temperatures Tc of the YBCO film surface and of
the YBCO film/substrate interface were measured inductively. It was observed
that the interface- Tc is always higher then the surface - Tc. However
deposition of silver over-layer enhances the superconducting transition
temperatures. This observation was confirmed by four-point resistance
measurements. In the annealed YBCO/Ag bilayers magnetic properties of the
interface were observed. We believe that such phenomena are a common feature of
layered systems. This two dimensional structure reminds the layered
microstructure of the high-temperature superconductors and one can suppose that
covering of the superconducting layer by non-superconducting layer is a
condition for obtaining high critical temperatures in general.",0911.2107v1
2010-12-22,Transport properties of the new Fe-based superconductor KxFe2Se2 (Tc = 33 K),"We synthesized the new Fe-based superconductor K0.8Fe2Se2 single crystals.
The obtained single crystal exhibited a sharp superconducting transition, and
the onset and zero-resistivity temperature was estimated to be 33 and 31.8 K,
respectively. A high upper critical field of 192 T was obtained. Anisotropy of
superconductivity of K0.8Fe2Se2 was ~3.6. Both the high upper critical field
and comparably low anisotropy are advantageous for the application under high
magnetic field.",1012.4950v1
2011-12-13,High-frequency performance of graphene field effect transistors with saturating IV-characteristics,"High-frequency performance of graphene field-effect transistors (GFETs) with
boron-nitride gate dielectrics is investigated. Devices show saturating IV
characteristics and fmax values as high as 34 GHz at 600-nm channel length.
Bias dependence of fT and fmax and the effect of the ambipolar channel on
transconductance and output resistance are also examined.",1112.2777v1
2018-02-02,Ultra-high Q terahertz whispering-gallery modes in a silicon resonator,"We report on the first experimental demonstration of terahertz (THz)
whispering-gallery modes (WGMs) with an ultra high quality (Q) factor of $1.5
\times {10}^{4}$ at 0.62THz. The WGMs are observed in a high resistivity float
zone silicon (HRFZ-Si) spherical resonator coupled to a sub-wavelength silica
waveguide. A detailed analysis of the coherent continuous wave (CW) THz
spectroscopy measurements combined with a numerical model based on
Mie-Debye-Aden-Kerker (MDAK) theory allows to unambiguously identify the
observed higher order radial THz WGMs.",1802.00549v1
2022-06-09,Characterisation of a new RPC prototype using conventional gas mixture,"Resistive Plate Chamber (RPC) is a well-known gaseous detector in the field
of High Energy Physics (HEP) experiments for its good tracking capability, high
efficiency, good time resolution, and low cost of fabrication. The main issue
in RPC is its limitation in the rate handling capability. Several experimental
groups have developed sophisticated techniques to increase the particle rate
capability and reduce the noise rate of this detector. In this article, we
discussed a new method for linseed oil coating in case of bakelite RPC detector
to achieve good efficiency and the results obtained using a conventional gas
mixture.",2206.04259v1
2023-04-05,STRV -- A radiation hard RISC-V microprocessor for high-energy physics applications,"While microprocessors are used in various applications, they are precluded
from the use in high-energy physics applications due to the harsh radiation
present. To overcome this limitation a microprocessor design must withstand
high doses of radiation and mitigate radiation induced soft errors. A TMR
protection scheme is applied to protect a RISC-V microprocessor core against
these faults. The protection of the integrated SRAM by an independent scrubbing
algorithm is discussed. Initial irradiation results and power consumption
measurements of the radiation-resistant RISC-V microprocessor implemented in 65
nm CMOS technology are presented.",2304.02410v1
2023-05-02,Robust and Adaptive Functional Logistic Regression,"We introduce and study a family of robust estimators for the functional
logistic regression model whose robustness automatically adapts to the data
thereby leading to estimators with high efficiency in clean data and a high
degree of resistance towards atypical observations. The estimators are based on
the concept of density power divergence between densities and may be formed
with any combination of lower rank approximations and penalties, as the need
arises. For these estimators we prove uniform convergence and high rates of
convergence with respect to the commonly used prediction error under fairly
general assumptions. The highly competitive practical performance of our
proposal is illustrated on a simulation study and a real data example which
includes atypical observations.",2305.01350v1
2014-10-07,Decoding Spatial Complexity in Strongly Correlated Electronic Systems,"Inside the metals, semiconductors, and magnets of our everyday experience,
electrons are uniformly distributed throughout the material. By contrast,
electrons often form clumpy patterns inside of strongly correlated electronic
systems (SCES) such as colossal magnetoresistance materials and high
temperature superconductors. In copper-oxide based high temperature
superconductors, scanning tunneling microscopy (STM) has detected an electron
nematic on the surface of the material, in which the electrons form nanoscale
structures which break the rotational symmetry of the host crystal. These
structures may hold the key to unlocking the mystery of high temperature
superconductivity in these materials, but only if the nematic also exists
throughout the entire bulk of the material. Using newly developed methods for
decoding these surface structures, we find that the nematic indeed persists
throughout the bulk of the material. We furthermore find that the intricate
pattern formation is set by a delicate balance among disorder, interactions,
and material anisotropy, leading to a fractal nature of the cluster pattern.
The methods we have developed can be extended to many other surface probes and
materials, enabling surface probes to determine whether surface structures are
confined only to the surface, or whether they extend throughout the material.",1410.1787v1
2021-04-13,"Multiscale modeling of materials: Computing, data science,uncertainty and goal-oriented optimization","The recent decades have seen various attempts at accelerating the process of
developing materials targeted towards specific applications. The performance
required for a particular application leads to the choice of a particular
material system whose properties are optimized by manipulating its underlying
microstructure through processing. The specific configuration of the structure
is then designed by characterizing the material in detail, and using this
characterization along with physical principles in system level simulations and
optimization. These have been advanced by multiscale modeling of materials,
high-throughput experimentations, materials data-bases, topology optimization
and other ideas. Still, developing materials for extreme applications involving
large deformation, high strain rates and high temperatures remains a challenge.
This article reviews a number of recent methods that advance the goal of
designing materials targeted by specific applications.",2104.05918v1
2021-09-05,Discovery and Engineering of Low Work Function Perovskite Materials,"Materials with low work functions are critical for an array of applications
requiring the facile removal or efficient transport of electrons through a
device. Perovskite oxides are a promising class of materials for finding low
work functions, and here we target applications in thermionic and field
electron emission. Perovskites have highly malleable compositions which enable
tunable work function values over a wide range, robust stability at high
temperatures, and high electronic conductivities. In this work, we screened
over 2900 perovskite oxides in search of stable, conductive, low-work-function
materials using Density Functional Theory (DFT) methods. Our work provides
insight into the materials chemistry governing the work function value of a
perovskite, where materials with barely filled d bands possess the lowest work
functions. Our screening has resulted in a total of seven promising compounds,
such as BaMoO3 and SrNb0.75Co0.25O3 with work functions of 1.1 eV and 1.5 eV,
respectively. These promising materials and others presented in this study may
find use as low work function electron emitters in high power vacuum electronic
and thermionic energy conversion devices. Moreover, the database of calculated
work functions and materials chemistry trends governing the value of the work
function may aid in the engineering of perovskite heterojunction devices.",2109.02005v1
2003-05-20,Very high upper critical fields in MgB2 produced by selective tuning of impurity scattering,"We report a significant enhancement of the upper critical field $H_{c2}$ of
different $MgB_2$ samples alloyed with nonmagnetic impurities. By studying
films and bulk polycrystals with different resistivities $\rho$, we show a
clear trend of $H_{c2}$ increase as $\rho$ increases. One particular high
resistivity film had zero-temperature $H_{c2}(0)$ well above the $H_{c2}$
values of competing non-cuprate superconductors such as $Nb_3Sn$ and Nb-Ti. Our
high-field transport measurements give record values $H_{c2}^\perp (0) \approx
34T$ and $H_{c2}\|(0) \approx 49 T$ for high resistivity films and
$H_{c2}(0)\approx 29 T$ for untextured bulk polycrystals. The highest $H_{c2}$
film also exhibits a significant upward curvature of $H_{c2}(T)$, and
temperature dependence of the anisotropy parameter $\gamma(T) = H_{c2}\|/
H_{c2}^\perp$ opposite to that of single crystals: $\gamma(T)$ decreases as the
temperature decreases, from $\gamma(T_c) \approx 2$ to $\gamma(0) \approx 1.5$.
This remarkable $H_{c2}$ enhancement and its anomalous temperature dependence
are a consequence of the two-gap superconductivity in $MgB_2$, which offers
special opportunities for further $H_{c2}$ increase by tuning of the impurity
scattering by selective alloying on Mg and B sites. Our experimental results
can be explained by a theory of two-gap superconductivity in the dirty limit.
The very high values of $H_{c2}(T)$ observed suggest that $MgB_2$ can be made
into a versatile, competitive high-field superconductor.",0305474v2
2021-08-30,Machine Learning for Predicting Thermal Transport Properties of Solids,"Quantitative descriptions of the structure-thermal property correlation have
been a bottleneck in designing materials with superb thermal properties. In the
past decade, the first-principles phonon calculations using density functional
theory and the Boltzmann transport equation have become a common practice for
predicting the thermal conductivity of new materials. However, first-principles
calculations are too costly for high-throughput material screening and
multi-scale structural design. First-principles calculations also face several
fundamental challenges in modeling thermal transport properties, e.g., of
crystalline materials with defects, of amorphous materials, and for materials
at high temperatures. In the past five years, machine learning started to play
a role in solving these challenges. This review provides a comprehensive
summary and discussion on the state-of-the-art, future opportunities, and the
remaining challenges in implementing machine learning for studying thermal
conductivity. After an introduction to the working principles of machine
learning and descriptors of material structures, recent research using machine
learning to study thermal transport is discussed. Three major applications of
machine learning for predicting thermal properties are discussed. First,
machine learning is applied to solve the challenges in modeling phonon
transport of crystals with defects, in amorphous materials, and at high
temperatures. Machine learning is used to build high-fidelity interatomic
potentials to bridge the gap between first-principles calculations and
molecular dynamics simulations. Second, machine learning can be used to study
the correlation between thermal conductivity and other properties for
high-throughput materials screening. Finally, machine learning is a powerful
tool for structural design to achieve target thermal conductance or thermal
conductivity.",2108.12945v2
2020-12-02,An Improved Iterative Neural Network for High-Quality Image-Domain Material Decomposition in Dual-Energy CT,"Dual-energy computed tomography (DECT) has been widely used in many
applications that need material decomposition. Image-domain methods directly
decompose material images from high- and low-energy attenuation images, and
thus, are susceptible to noise and artifacts on attenuation images. The purpose
of this study is to develop an improved iterative neural network (INN) for
high-quality image-domain material decomposition in DECT, and to study its
properties. We propose a new INN architecture for DECT material decomposition.
The proposed INN architecture uses distinct cross-material convolutional neural
network (CNN) in image refining modules, and uses image decomposition physics
in image reconstruction modules. The distinct cross-material CNN refiners
incorporate distinct encoding-decoding filters and cross-material model that
captures correlations between different materials. We study the distinct
cross-material CNN refiner with patch-based reformulation and tight-frame
condition. Numerical experiments with extended cardiactorso (XCAT) phantom and
clinical data show that the proposed INN significantly improves the image
quality over several image-domain material decomposition methods, including a
conventional model-based image decomposition (MBID) method using an
edge-preserving regularizer, a recent MBID method using pre-learned
material-wise sparsifying transforms, and a noniterative deep CNN method. Our
study with patch-based reformulations reveals that learned filters of distinct
cross-material CNN refiners can approximately satisfy the tight-frame
condition.",2012.01986v4
2023-10-03,"Estimating viscoelastic, soft material properties using a modified Rayleigh cavitation bubble collapse time","Accurate determination of high strain rate (> 10^3 1/s) constitutive
properties of soft materials remains a formidable challenge. Albeit recent
advancements among experimental techniques, in particular inertial
microcavitation rheometry (IMR), the intrinsic requirement to visualize the
bubble cavitation dynamics has limited its application to nominally transparent
materials. Here, in an effort to address this challenge and to expand the
experimental capability of IMR to optically opaque materials, we investigated
whether one could use the acoustic signature of the time interval between
bubble nucleation and collapse, characterized as the bubble collapse time, to
infer the viscoelastic material properties without being able to image the
bubble directly in the tissue. By introducing a modified Rayleigh collapse time
for soft materials, which is strongly dependent on the stiffness of the
material at hand, we show that, in principle, one can obtain an order of
magnitude or better estimate of the viscoelastic material properties of the
soft material under investigation. Using a newly developed energy-based
theoretical framework, we show that for materials stiffer than 10 kPa the
bubble collapse time during a single bubble cavitation event can provide
quantitative and meaningful information about the constitutive properties of
the material at hand. For very soft materials (i.e., shear modulus less than 10
kPa) our theory shows that unless the collapse time measurement has very high
precision and low uncertainties, the material property estimates based on the
bubble collapse time only will not be accurate and require visual resolution of
the full cavitation kinematics.",2310.02475v1
2012-08-31,Ionization by bulk heating of electrons in capacitive radio frequency atmospheric pressure microplasmas,"Electron heating and ionization dynamics in capacitively coupled radio
frequency (RF) atmospheric pressure microplasmas operated in helium are
investigated by Particle in Cell simulations and semi-analytical modeling. A
strong heating of electrons and ionization in the plasma bulk due to high bulk
electric fields are observed at distinct times within the RF period. Based on
the model the electric field is identified to be a drift field caused by a low
electrical conductivity due to the high electron-neutral collision frequency at
atmospheric pressure. Thus, the ionization is mainly caused by ohmic heating in
this ""Omega-mode"". The phase of strongest bulk electric field and ionization is
affected by the driving voltage amplitude. At high amplitudes, the plasma
density is high, so that the sheath impedance is comparable to the bulk
resistance. Thus, voltage and current are about 45{\deg} out of phase and
maximum ionization is observed during sheath expansion with local maxima at the
sheath edges. At low driving voltages, the plasma density is low and the
discharge becomes more resistive resulting in a smaller phase shift of about
4{\deg}. Thus, maximum ionization occurs later within the RF period with a
maximum in the discharge center. Significant analogies to electronegative low
pressure macroscopic discharges operated in the Drift-Ambipolar mode are found,
where similar mechanisms induced by a high electronegativity instead of a high
collision frequency have been identified.",1208.6519v2
2022-01-13,High-temperature superconductivity in hydrides: experimental evidence and details,"Since the discovery of superconductivity at 200 K in H3S [1] similar or
higher transition temperatures, Tcs, have been reported for various
hydrogen-rich compounds under ultra-high pressures [2]. Superconductivity was
experimentally proved by different methods, including electrical resistance,
magnetic susceptibility, optical infrared, and nuclear resonant scattering
measurements. The crystal structures of superconducting phases were determined
by X-ray diffraction. Numerous electrical transport measurements demonstrate
the typical behaviour of a conventional phonon-mediated superconductor: zero
resistance below Tc, the shift of Tc to lower temperatures under external
magnetic fields, and pronounced isotope effect. Remarkably, the results are in
good agreement with the theoretical predictions, which describe
superconductivity in hydrides within the framework of the conventional BCS
theory. However, despite this acknowledgment, experimental evidence for the
superconducting state in these compounds has recently been treated with
criticism [3, 4], which apparently stems from misunderstanding and
misinterpretation of complicated experiments performed under very high
pressures. Here, we describe in greater detail the experiments revealing
high-temperature superconductivity in hydrides under high pressures. We show
that the arguments against superconductivity [3, 4] can be either refuted or
explained. The experiments on the high-temperature superconductivity in
hydrides clearly contradict the theory of hole superconductivity [4] and
eliminate it [3].",2201.05137v1
2024-01-15,High Frequency Response of Volatile Memristors,"In this theoretical study, we focus on the high-frequency response of the
electrothermal NbO2-Mott threshold switch, a real-world electronic device,
which has been proved to be relevant in several applications and is classified
as a volatile memristor. Memristors of this kind, have been shown to exhibit
distinctive non-linear behaviors crucial for cutting-edge neuromorphic
circuits. In accordance with well-established models for these devices, their
resistances depend on their body temperatures, which evolve over time following
Newton's Law of Cooling. Here, we demonstrate that HP's NbO2-Mott memristor can
manifest up to three distinct steady-state oscillatory behaviors under a
suitable high-frequency periodic voltage input, showcasing increased
versatility despite its volatile nature. Additionally, when subjected to a
high-frequency periodic voltage signal, the device body temperature oscillates
with a negligible peak-to-peak amplitude. Since, the temperature remains almost
constant over an input cycle, the devices under study behave as linear
resistors during each input cycle. Based on these insights, this paper presents
analytical equations characterizing the response of the NbO2-Mott memristor to
high-frequency voltage inputs, demarcating regions in the state space where
distinct initial conditions lead to various asymptotic oscillatory behaviors.
Importantly, the mathematical methods introduced in this manuscript are
applicable to any volatile electrothermal resistive switch. Additionally, this
paper presents analytical equations that accurately reproduce the temperature
time-waveform of the studied device during both its transient and steady-state
phases when subjected to a zero-mean sinusoidal voltage input oscillating in
the high-frequency limit.",2401.10924v1
2022-12-05,Unveiling the complex structure-property correlation of defects in 2D materials based on high throughput datasets,"Modification of physical properties of materials and design of materials with
on-demand characteristics is at the heart of modern technology. Rare
application relies on pure materials--most devices and technologies require
careful design of materials properties through alloying, creating
heterostructures of composites or controllable introduction of defects. At the
same time, such designer materials are notoriously difficult for modelling.
Thus, it is very tempting to apply machine learning methods for such systems.
Unfortunately, there is only a handful of machine learning-friendly material
databases available these days. We develop a platform for easy implementation
of machine learning techniques to materials design and populate it with
datasets on pristine and defected materials. Here we describe datasets of
defects in represented 2D materials such as MoS2, WSe2, hBN, GaSe, InSe, and
black phosphorous, calculated using DFT. Our study provides a data-driven
physical understanding of complex behaviors of defect properties in 2D
materials, holding promise for a guide to the development of efficient machine
learning models. In addition, with the increasing enrollment of datasets, our
database could provide a platform for designing of materials with predetermined
properties.",2212.02110v1
2023-02-16,GAASP: Genetic Algorithm Based Atomistic Sampling Protocol for High-Entropy Materials,"High-Entropy Materials are composed of multiple elements on comparatively
simpler lattices. Due to the multicomponent nature of such materials, the
atomic scale sampling is computationally expensive due to the combinatorial
complexity. We propose a genetic algorithm based methodology for sampling such
complex chemically-disordered materials. Genetic Algorithm based Atomistic
Sampling Protocol (GAASP) variants can generate low and well as high-energy
structures. GAASP low-energy variant in conjugation with metropolis criteria
avoids the premature convergence as well as ensures the detailed balance
condition. GAASP can be employed to generate the low-energy structures for
thermodynamic predictions as well as diverse structures can be generated for
machine learning applications.",2302.08101v1
2022-10-24,Quantifying the performance of machine learning models in materials discovery,"The predictive capabilities of machine learning (ML) models used in materials
discovery are typically measured using simple statistics such as the
root-mean-square error (RMSE) or the coefficient of determination ($r^2$)
between ML-predicted materials property values and their known values. A
tempting assumption is that models with low error should be effective at
guiding materials discovery, and conversely, models with high error should give
poor discovery performance. However, we observe that no clear connection exists
between a ""static"" quantity averaged across an entire training set, such as
RMSE, and an ML property model's ability to dynamically guide the iterative
(and often extrapolative) discovery of novel materials with targeted
properties. In this work, we simulate a sequential learning (SL)-guided
materials discovery process and demonstrate a decoupling between traditional
model error metrics and model performance in guiding materials discoveries. We
show that model performance in materials discovery depends strongly on (1) the
target range within the property distribution (e.g., whether a 1st or 10th
decile material is desired); (2) the incorporation of uncertainty estimates in
the SL acquisition function; (3) whether the scientist is interested in one
discovery or many targets; and (4) how many SL iterations are allowed. To
overcome the limitations of static metrics and robustly capture SL performance,
we recommend metrics such as Discovery Yield ($DY$), a measure of how many
high-performing materials were discovered during SL, and Discovery Probability
($DP$), a measure of likelihood of discovering high-performing materials at any
point in the SL process.",2210.13587v1
2024-05-14,An Interoperable Multi Objective Batch Bayesian Optimization Framework for High Throughput Materials Discovery,"In this study, we introduce a groundbreaking framework for materials
discovery, we efficiently navigate a vast phase space of material compositions
by leveraging Batch Bayesian statistics in order to achieve specific
performance objectives. This approach addresses the challenge of identifying
optimal materials from an untenably large array of possibilities in a
reasonable timeframe with high confidence. Crucially, our batchwise methods
align seamlessly with existing material processing infrastructure for
synthesizing and characterizing materials. By applying this framework to a
specific high entropy alloy system, we demonstrate its versatility and
robustness in optimizing properties like strain hardening, hardness, and strain
rate sensitivity. The fact that the Bayesian model is adept in refining and
expanding the property Pareto front highlights its broad applicability across
various materials, including steels, shape memory alloys, ceramics, and
composites. This study advances the field of materials science and sets a new
benchmark for material discovery methodologies. By proving the effectiveness of
Bayesian optimization, we showcase its potential to redefine the landscape of
materials discovery.",2405.08900v1
2023-02-19,Resistance Maintained in Digital Organisms despite Guanine/Cytosine-Based Fitness Cost and Extended De-Selection: Implications to Microbial Antibiotics Resistance,"Antibiotics resistance has caused much complication in the treatment of
diseases, where the pathogen is no longer susceptible to specific antibiotics
and the use of such antibiotics are no longer effective for treatment. A recent
study that utilizes digital organisms suggests that complete elimination of
specific antibiotic resistance is unlikely after the disuse of antibiotics,
assuming that there are no fitness costs for maintaining resistance once
resistance are established. Fitness cost are referred to as reaction to change
in environment, where organism improves its' abilities in one area at the
expense of the other. Our goal in this study is to use digital organisms to
examine the rate of gain and loss of resistance where fitness costs have
incurred in maintaining resistance. Our results showed that GC-content based
fitness cost during de-selection by removal of antibiotic-induced selective
pressure portrayed similar trends in resistance compared to that of no fitness
cost, at all stages of initial selection, repeated de-selection and
re-introduction of selective pressure. Paired t-test suggested that prolonged
stabilization of resistance after initial loss is not statistically significant
for its difference to that of no fitness cost. This suggests that complete
elimination of specific antibiotics resistance is unlikely after the disuse of
antibiotics despite presence of fitness cost in maintaining antibiotic
resistance during the disuse of antibiotics, once a resistant pool of
micro-organism has been established.",2302.13897v1
1998-04-16,Reconnection via the Tearing Instability,"We discuss the role of tearing instabilities in magnetic reconnection. In
three dimensions this instability leads to the formation of strong Alfvenic
waves that remove plasma efficiently from the reconnection layer. As a result
the instability proceeds at high rates while staying close to the linear
regime. Our calculations show that for a resistive fluid the reconnection speed
scales as the product of the Alfven speed V_A over the magnetic Reynolds number
to the power -0.3. In the limit of vanishing resistivity, tearing modes proceed
at a non-zero rate, driven by the electron inertia term, giving rise to a
reconnection speed V_A (c/\omega_p L_x)^{3/5}, where \omega_p is the plasma
frequency and L_x is the transverse scale of the reconnection layer. Formally
this solves the problem of fast reconnection, but in practice this reconnection
speed is small.",9804166v1
2006-06-15,Tearing instability in relativistic magnetically dominated plasmas,"Many astrophysical sources of high energy emission, such as black hole
magnetospheres, superstrongly magnetized neutron stars (magnetars), and
probably relativistic jets in Active Galactic Nuclei and Gamma Ray Bursts
involve relativistically magnetically dominated plasma. In such plasma the
energy density of magnetic field greatly exceeds the thermal and the rest mass
energy density of particles. Therefore the magnetic field is the main reservoir
of energy and its dissipation may power the bursting emission from these
sources, in close analogy to Solar flares. One of the principal dissipative
instabilities that may lead to release of magnetic energy is the tearing
instability. In this paper we study, both analytically and numerically, the
development of tearing instability in relativistically magnetically-dominated
plasma using the framework of resistive magnetodynamics. We confirm and
elucidate the previously obtained result on the growth rate of the tearing
mode: the shortest growth time is the same as in the case of classical
non-relativistic MHD, namely $\tau =\sqrt{\tau_a \tau_d}$ where $\tau_a$ is the
\Alfven crossing time and $\tau_d$ is the resistive time of a current layer.",0606375v2
1994-11-17,Hydrodynamic electron flow in high-mobility wires,"Hydrodynamic electron flow is experimentally observed in the differential
resistance of electrostatically defined wires in the two-dimensional electron
gas in (Al,Ga)As heterostructures. In these experiments current heating is used
to induce a controlled increase in the number of electron-electron collisions
in the wire. The interplay between the partly diffusive wire-boundary
scattering and the electron-electron scattering leads first to an increase and
then to a decrease of the resistance of the wire with increasing current. These
effects are the electronic analog of Knudsen and Poiseuille flow in gas
transport, respectively. The electron flow is studied theoretically through a
Boltzmann transport equation, which includes impurity, electron-electron, and
boundary scattering. A solution is obtained for arbitrary scattering
parameters. By calculation of flow profiles inside the wire it is demonstrated
how normal flow evolves into Poiseuille flow. The boundary-scattering
parameters for the gate-defined wires can be deduced from the magnitude of the
Knudsen effect. Good agreement between experiment and theory is obtained.",9411067v1
1995-12-15,Nonlocal conductivity in the vortex-liquid regime,"We investigate the nonlocal conductivity calculated from the time-dependent
Ginzburg-Landau equation. When the fluctuations of the vector potential are
negligible, the high-temperature (Gaussian) and low-temperature (flux-flow)
forms of the uniform conductivity withan an ab plane (sigma_yy) are essentially
identical. We find to what extent the nonlocal conductivity shares this
feature. The results suggest that for pure samples in theses regimes the length
scales of the nonlocal resistivity, rho_yy(y-y',z-z'), remain short-ranged in
the y and z directions in contrast to the assumptions made by the hydrodynamic
modelling of the multiterminal transport measurements. On the other hand, the
resistivity is seen to have a long length scale in the x direction
rho_yy(x-x'). The implications for the interpretation of recent experiments are
discussed.",9512121v1
1996-02-13,Giant Magneto-Resistance in Nd$_{0.7}$Sr$_{0.3}$MnO$_3$ at Optical Frequencies,"The optical properties of Nd$_{0.7}$Sr$_{0.3}$MnO$_3$ thin films have been
studied from 5 meV to 25 meV and from 0.25 eV to 3 eV, at temperatures from 15
K to 300 K and magnetic fields up to 8.9 T. A large transfer of spectral weight
from high energy to low energy occurs as the temperature is decreased below 180
K, where the dc resistivity peaks, or as the magnetic field is increased. The
optical data are found to be consistent with models that include both the
double exchange interaction and the dynamic Jahn-Teller effect on the Mn$^{3+}$
e$_g$ levels.",9602075v1
1997-09-01,Superconductor-Insulator Transitions and Insulators with Localized Pairs,"Two experiments are described which are related to the problem of localized
Cooper pairs. Magnetic-field-tuned superconductor-insulator transition was
studied in amorphous In--O films with onset of the superconducting transition
in zero field near 2 K. Experiments performed in the temperature range T>0.3 K
indicate that at the critical field, B=B_c, the first derivative of the
resistance dR/dT is non-zero at T=0 and hence the scaling relations should be
written in more general form. Study of the magnetotransport of high-resistance
metastable alloy Cd-Sb on the insulating side of the superconductor-insulator
transition revealed below 0.1 K a shunting condiction mechanism in addition to
usual one-particle hopping. Possibility of pair hopping is discussed.",9709017v1
1997-09-02,Spontaneous DC Current Generation in a Resistively Shunted Semiconductor Superlattice Driven by a TeraHertz Field,"We study a resistively shunted semiconductor superlattice subject to a
high-frequency electric field. Using a balance equation approach that
incorporates the influence of the electric circuit, we determine numerically a
range of amplitude and frequency of the ac field for which a dc bias and
current are generated spontaneously and show that this region is likely
accessible to current experiments. Our simulations reveal that the Bloch
frequency corresponding to the spontaneous dc bias is approximately an integer
multiple of the ac field frequency.",9709026v1
1997-10-15,Normal-State Hall Effect and the Insulating Resistivity of High-T_c Cuprates at Low Temperatures,"The normal-state Hall coefficient R_H and the in-plane resistivity \rho_{ab}
are measured in La-doped Bi_{2}Sr_{2}CuO_{y} (T_c \simeq 13 K) single crystals
and La_{2-x}Sr_{x}CuO_{4} thin films by suppressing superconductivity with 61-T
pulsed magnetic fields. In contrast to data above T_c, the R_H below \sim 10 K
shows little temperature dependence in all the samples measured, irrespective
of whether \rho_{ab} exhibits insulating or metallic behavior. Thus, whatever
physical mechanism gives rise to insulating behavior in the low-temperature
normal state, it leaves the Hall conductivity relatively unchanged.",9710155v1
1997-12-19,Nature of the Low Field Transition in the Mixed State of High Temperature Superconductors,"We have numerically studied the statics and dynamics of a model
three-dimensional vortex lattice at low magnetic fields. For the statics we use
a frustrated 3D XY model on a stacked triangular lattice. We model the dynamics
as a coupled network of overdamped resistively-shunted Josephson junctions with
Langevin noise. At low fields, there is a weakly first-order phase transition,
at which the vortex lattice melts into a line liquid. Phase coherence parallel
to the field persists until a sharp crossover, conceivably a phase transition,
near $T_{\ell} > T_m$ which develops at the same temperature as an infinite
vortex tangle. The calculated flux flow resistivity in various geometries near
$T=T_{\ell}$ closely resembles experiment. The local density of field induced
vortices increases sharply near $T_\ell$, corresponding to the experimentally
observed magnetization jump. We discuss the nature of a possible transition or
crossover at $T_\ell$(B) which is distinct from flux lattice melting.",9712246v2
1998-06-19,Resistance behavior near the magnetic-field-tuned quantum transition in superconducting amorphous In-O films,"We have studied the magnetic-field-tuned superconductivity destroying quantum
transition in amorphous In-O films with the onset of superconductivity in zero
field at about 2 K. At temperatures down to 30 mK the critical resistance
R_c=R(T,B_c) has been found to change approximately linearly with temperature,
which is in contradiction to a standard description where zero slope dR_c/dT =
0 is assumed near T=0. To make the data R(T,B) collapse in the vicinity of
transition against scaling variable (B-B_c)/T^{1/y}, one has either to allow
for the intrinsic temperature dependence of R_c or to postulate the critical
field B_c to be temperature-dependent B_c(T)-B_c(0)~T^{1+1/y}. We find that the
state on the high-field side of the transition can be both insulating and
metallic and we determine the critical index y=1.2.",9806244v2
1998-11-19,Nonlocal Effects on the Surface Resistance of High Temperature Superconductors with (100) and (110) Surfaces,"The low temperature surface resistance R_s of d-wave superconductors is
calculated as function of frequency assuming normal state quasiparticle mean
free paths l in excess of the penetration depth. Results depend strongly on the
geometric configuration. In the clean limit, two contributions to R_s with
different temperature dependencies are identified: photon absorption by
quasiparticles and pair breaking. The size of nonlocal corrections, which can
be positive or negative depending on frequency decreases for given l as the
scattering phase shift \delta_N is increased. However, except in the unitarity
limit \delta_N = 0.5 \pi, nonlocal effects should be observable.",9811291v2
1998-12-03,Residual resistivity ratio and its relation to the positive magnetoresistance behavior in natural multilayer LaMn2Ge2; relevance to artificial multilayer physics,"Results of low temperature magnetoresistance ($\Delta\rho/\rho$) and
isothermal magnetization (M) measurements on polycrystalline ferromagnetic (T_C
close to 300 K) natural multilayers, LaMn_{2+x}Ge_{2-y}Si_y, are reported. It
is found that the samples with large residual resistivity ratio,
$\rho(300K)/\rho(4.2K)$, exhibit large positive magnetoresistance at high
magnetic fields. The Kohler's rule is not obeyed in these alloys. In addition,
at 4.5 K, there is a tendency towards linear variation of $\Delta\rho/\rho$
with magnetic field with increasing $\rho(300K)/\rho(4.2K$); however, the field
dependence of $\Delta\rho/\rho$ does not track that of M, thereby suggesting
that the magnetoresistance originates from non-magnetic layers. It is
interesting that these experimental findings on bulk polycrystals are
qualitatively similar to what is seen in artificially grown multilayer systems
recently.",9812052v1
1998-12-21,"Non-Universal Power Law of the ""Hall Scattering Rate"" in a Single-Layer Cuprate Bi_{2}Sr_{2-x}La_{x}CuO_{6}","In-plane resistivity \rho_{ab}, Hall coefficient, and magnetoresistance (MR)
are measured in a series of high-quality Bi_{2}Sr_{2-x}La_{x}CuO_{6} crystals
with various carrier concentrations, from underdope to overdope. Our crystals
show the highest T_c (33 K) and the smallest residual resistivity ever reported
for Bi-2201 at optimum doping. It is found that the temperature dependence of
the Hall angle obeys a power law T^n with n systematically decreasing with
increasing doping, which questions the universality of the Fermi-liquid-like
T^2 dependence of the ""Hall scattering rate"". In particular, the Hall angle of
the optimally-doped sample changes as T^{1.7}, not as T^2, while \rho_{ab}
shows a good T-linear behavior. The systematics of the MR indicates an
increasing role of spin scattering in underdoped samples.",9812334v1
1999-08-30,From an antiferromagnet to a heavy-fermion system: CeCu5Au under pressure,"The electrical resistivity rho(T) of single crystalline CeCu_5Au under
pressure was measured in the temperature range 30mK<T<300K. Pressure suppresses
the antiferromagnetic order (T_N=2.35K at ambient pressure) and drives the
system into a non-magnetic heavy-fermion state above P_c=4.1(3)GPa. The
electrical resistivity shows a deviation from a T^2 dependence of a
Fermi-liquid in the pressure range 1.8GPa<=P<=5.15GPa. The rho(T)-curves can be
compared with those of CeCu_{6-x}Au_x at different Au concentrations. Just
before the long-range magnetic order vanishes, a possibly superconducting phase
(at T_c=0.1K and P=3.84GPa) occurs, pointing to a coexistence of
antiferromagnetic order and superconductivity. This new phase is only seen in a
narrow pressure interval Delta P=0.4GPa.",9908442v1
1999-09-01,Tunneling measurements of the coulomb pseudogap in a two-dimensional electron system in a quantizing magnetic field,"We study the Coulomb pseudogap for tunneling into the two-dimensional
electron system of high-mobility (Al,Ga)As/GaAs heterojunctions subjected to a
quantizing magnetic field at filling factor $\nu \leq 1$.
  Tunnel current-voltage characteristics show that for the double maximum
observed in the tunnel resistance at $\nu \approx 1$ the pseudogap is linear in
energy with a slope that depends on filling factor, magnetic field, and
temperature. We give a qualitative account of the filling factor dependence of
the pseudogap slope and we confirm the recently reported appearance of another
relaxation time for tunneling at $\nu \approx 1$. For the tunnel resistance
peaks at $\nu=1/3$ and 2/3 a completely different behaviour of the
current-voltage curves is found and interpreted as manifestation of the
fractional gap.",9909011v2
1999-09-02,Transport properties of strongly correlated metals:a dynamical mean-field approach,"The temperature dependence of the transport properties of the metallic phase
of a frustrated Hubbard model on the hypercubic lattice at half-filling are
calculated. Dynamical mean-field theory, which maps the Hubbard model onto a
single impurity Anderson model that is solved self-consistently, and becomes
exact in the limit of large dimensionality, is used. As the temperature
increases there is a smooth crossover from coherent Fermi liquid excitations at
low temperatures to incoherent excitations at high temperatures. This crossover
leads to a non-monotonic temperature dependence for the resistance,
thermopower, and Hall coefficient, unlike in conventional metals. The
resistance smoothly increases from a quadratic temperature dependence at low
temperatures to large values which can exceed the Mott-Ioffe-Regel value, hbar
a/e^2 (where ""a"" is a lattice constant) associated with mean-free paths less
than a lattice constant. Further signatures of the thermal destruction of
quasiparticle excitations are a peak in the thermopower and the absence of a
Drude peak in the optical conductivity. The results presented here are relevant
to a wide range of strongly correlated metals, including transition metal
oxides, strontium ruthenates, and organic metals.",9909041v1
1999-09-24,Weak Localization Effect in Superconductors by Radiation Damage,"Large reductions of the superconducting transition temperature $T_{c}$ and
the accompanying loss of the thermal electrical resistivity (electron-phonon
interaction) due to radiation damage have been observed for several A15
compounds, Chevrel phase and Ternary superconductors, and $\rm{NbSe_{2}}$ in
the high fluence regime. We examine these behaviors based on the recent theory
of weak localization effect in superconductors. We find a good fitting to the
experimental data. In particular, weak localization correction to the
phonon-mediated interaction is derived from the density correlation function.
It is shown that weak localization has a strong influence on both the
phonon-mediated interaction and the electron-phonon interaction, which leads to
the universal correlation of $T_{c}$ and resistance ratio.",9909358v1
2000-01-26,Antiferromagnetic Alignment and Relaxation Rate of Gd Spins in the High Temperature Superconductor GdBa_2Cu_3O_(7-delta),"The complex surface impedance of a number of GdBa$_2$Cu$_3$O$_{7-\delta}$
single crystals has been measured at 10, 15 and 21 GHz using a cavity
perturbation technique. At low temperatures a marked increase in the effective
penetration depth and surface resistance is observed associated with the
paramagnetic and antiferromagnetic alignment of the Gd spins. The effective
penetration depth has a sharp change in slope at the N\'eel temperature, $T_N$,
and the surface resistance peaks at a frequency dependent temperature below 3K.
The observed temperature and frequency dependence can be described by a model
which assumes a negligibly small interaction between the Gd spins and the
electrons in the superconducting state, with a frequency dependent magnetic
susceptibility and a Gd spin relaxation time $\tau_s $ being a strong function
of temperature. Above $T_N$, $\tau_s$ has a component varying as $1 / (T -
T_N)$, while below $T_N$ it increases $\sim T^{-5}$.",0001379v1
2000-11-20,Theory of the Hall Coefficient and the Resistivity on the Layered Organic Superconductors κ-(BEDT-TTF),"In the organic superconducting \kappa-(BEDT-TTF) compounds, various transport
phenomena exhibit striking non-Fermi liquid behaviors, which should be the
important clues to understanding the electronic state of this system.
Especially, the Hall coefficient ($R_H$) shows Curie-Weiss type temperature
dependence, which is similar to that of high-Tc cuprates. In this paper, we
study a Hubbard model on an anisotropic triangular lattice at half filling,
which is an effective model of \kappa-(BEDT-TTF) compounds. Based on the
fluctuation-exchange (FLEX) approximation, we calculate the resistivity
($\rho$) and $R_H$ by taking account of the vertex corrections for the current,
which is necessary for satisfying the conservation laws. Our theoretical
results of $R_H$ and $cot(\theta_H)$ explain the experimental behaviors well,
which are unable to be reproduced by the conventional Boltzmann transport
approximation. Moreover, we extend the standard Eliashberg's transport theory
and derive the more precise formula for the conductivity, which becomes
important at higher temperatures.",0011324v2
2000-12-07,Quantum Tunneling of the Order Parameter in Superconducting Nanowires,"Quantum tunneling of the superconducting order parameter gives rise to the
phase slippage process which controls the resistance of ultra-thin
superconducting wires at sufficiently low temperatures. If the quantum phase
slip rate is high, superconductivity is completely destroyed by quantum
fluctuations and the wire resistance never decreases below its normal state
value. We present a detailed microscopic theory of quantum phase slips in
homogeneous superconducting nanowires. Focusing our attention on relatively
short wires we evaluate the quantum tunneling rate for phase slips, both the
quasiclassical exponent and the pre-exponential factor. In very thin and dirty
metallic wires the effect is shown to be clearly observable even at $T \to 0$.
Our results are fully consistent with recent experimental findings [A.
Bezryadin, C.N. Lau, and M. Tinkham, Nature {\bf 404}, 971 (2000)] which
provide direct evidence for the effect of quantum phase slips.",0012104v1
2001-02-20,Unusual Properties of Anisotropic Hall Gas: Implication to Metrology of the Integer Quantum Hall Effect,"Physical properties of anisotropic compressible quantum Hall states and their
implications to integer quantum Hall effect are studied based on a mean field
theory on the von Neumann lattice. It is found that the Hall gas has unusual
thermodynamic properties such as negative pressure and negative compressibility
and unusual transport properties. Transport properties and density profile of
Hall gas states at half fillings agree with those of anisotropic states
discovered experimentally in higher Landau levels. Hall gas formed in the bulk
does not spread but shrinks, owing to negative pressure, and a strip of Hall
gas gives abnormal electric transport at finite temperature. Conductances at
finite temperature and finite injected current agree with recent experiments on
collapse and breakdown phenomena of the integer quantum Hall effect. As a
byproduct, existence of new quantum Hall regime, dissipative quantum Hall
regime, in which Hall resistance is quantized exactly even in the system of
small longitudinal resistance is derived.",0102347v3
2001-08-03,Electrical Resistivity Anisotropy from Self-Organized One-Dimensionality in High-Temperature Superconductors,"We investigate the manifestation of the stripes in the in-plane resistivity
anisotropy in untwinned single crystals of La_{2-x}Sr_{x}CuO_{4} (x = 0.02 -
0.04) and YBa_{2}Cu_{3}O_{y} (y = 6.35 - 7.0). It is found that both systems
show strongly temperature-dependent in-plane anisotropy in the lightly
hole-doped region and that the anisotropy in YBa_{2}Cu_{3}O_{y} grows with
decreasing y below about 6.60 despite the decreasing orthorhombicity, which
gives most direct evidence that electrons self-organize into a macroscopically
anisotropic state. The transport is found to be easier along the direction of
the spin stripes already reported, demonstrating that the stripes are
intrinsically conducting in cuprates.",0108053v2
2001-09-21,"Microwave Power, DC Magnetic Field, Frequency and Temperature Dependence of the Surface Resistance of MgB2","The microwave power, dc magnetic field, frequency and temperature dependence
of the surface resistance of MgB2 films and powder samples were studied. Sample
quality is relatively easy to identify by a number of characteristics, the most
clear being the breakdown in the omega squared law for poor quality samples.
Analysis of the experimental data suggests the most attractive procedure for
high quality film growth for technical applications.",0109397v1
2002-01-01,Memory Effects in Electron Transport in Si Inversion Layers in the Dilute Regime: Individuality versus Universality,"In order to separate the universal and sample-specific effects in the
conductivity of high-mobility Si inversion layers, we studied the electron
transport in the same device after cooling it down to 4K at different fixed
values of the gate voltage V^{cool}. Different V^{cool} did not modify
significantly either the momentum relaxation rate or the strength of
electron-electron interactions. However, the temperature dependences of the
resistance and the magnetoresistance in parallel magnetic fields, measured in
the vicinity of the metal-insulator transition in 2D, carry a strong imprint of
individuality of the quenched disorder determined by V^{cool}. This
demonstrates that the observed transition between ``metallic'' and insulating
regimes involves both, universal effects of electron-electron interaction and
sample-specific effects. Far away from the transition, at lower carrier
densities and lower resistivities < 0.1 h/e^2, the transport and
magnetotransport become nearly universal.",0201001v1
2002-02-08,Anisotropic Superconducting Properties of MgB2 Single Crystals,"In-plane electrical transport properties of MgB2 single crystals grown under
high pressure of 4-6 GPa and temperature of 1400-1700oC in Mg-B-N system have
been measured. For all specimens we found sharp superconducting transition
around 38.1-38.3K with transition width within 0.2-0.3K. Estimated resistivity
value at 40K is about 1 mkOhmcm and resistivity ratio R(273K)/R(40K) of about
4.9. Results of measurements in magnetic field up to 5.5T perpendicular to Mg
and B planes and up to 9T in parallel orientation show temperature dependent
anisotropy of the upper critical field with anisotropy ratio increasing from
2.2 close to Tc up to about 3 below 30K. Strong deviation of the angular
dependence of Hc2 from anisotropic mass model has been also found.",0202133v1
2002-03-27,"Transport critical current, anisotropy, irreversibility fields and exponential n factors in Fe sheathed MgB2 tapes","The influence of the initial MgB2 grain size on critical current density,
upper critical fields and irreversibility has been studied on Fe sheathed
monofilamentary MgB2 tapes prepared by the Powder-In-Tube technique. The effect
of the reduction of MgB2 grain size by ball milling was mainly to enhance both
the critical current density, jc, and the irreversibility field, while the
upper critical field remained unchanged. The anisotropy ratio of the upper
critical field between magnetic fields parallel and perpendicular the tape
surface was determined to 1.3, reflecting a deformation induced texture. A good
agreement has been found between resistive and inductive jc values, measured at
various temperatures. At 25K and 1 T, jc values close to 105 A/cm2 were
measured. The exponential n factor of the resistive transition was found to be
quite high at low fields, and decrease linearly from 60 at 4T to 10 at 8.5T.",0203551v1
2002-05-10,Universal Behavior of the Resistance Noise across the Metal-Insulator Transition in Silicon Inversion Layers,"Studies of low-frequency resistance noise show that the glassy freezing of
the two-dimensional (2D) electron system in the vicinity of the metal-insulator
transition occurs in all Si inversion layers. The size of the metallic glass
phase, which separates the 2D metal and the (glassy) insulator, depends
strongly on disorder, becoming extremely small in high-mobility samples. The
behavior of the second spectrum, an important fourth-order noise statistic,
indicates the presence of long-range correlations between fluctuators in the
glassy phase, consistent with the hierarchical picture of glassy dynamics.",0205226v2
2002-07-05,On the two-dimensional metallic state in silicon-on-insulator structures,"It is shown that the electronic conduction in silicon-on-insulator (SOI)
layers exhibits a metallic regime which is very similar to that in
high-mobility Si-metal oxide semiconductor structures (MOS). The peak in the
electron mobility versus density, the strong drop in resistivity and the
critical concentration for the metal-insulator transition are all consistent.
On the basis of our SOI data for the temperature and in-plane magnetic field
dependence of the resistivity, we discuss several models for the metallic state
in two dimensions. We find that the observed behavior can be well described by
the theory on the interaction corrections in the ballistic regime. For the
investigated regime, the temperature dependent screening of scattering
potentials gives also a good description of the data.",0207170v1
2003-01-21,Angular dependence of domain wall resistivity in SrRuO$_{\bf 3}$ films,"${\rm SrRuO_3}$ is a 4d itinerant ferromagnet (T$_{c}$ $\sim $150 K) with
stripe domain structure. Using high-quality thin films of SrRuO$_{3}$ we study
the resistivity induced by its very narrow ($\sim 3$ nm) Bloch domain walls,
$\rho_{DW}$ (DWR), at temperatures between 2 K and T$_{c}$ as a function of the
angle, $\theta $, between the electric current and the ferromagnetic domains
walls. We find that $\rho_{DW}(T,\theta)=\sin^2\theta
\rho_{DW}(T,90)+B(\theta)\rho_{DW}(T,0)$ which provides the first experimental
indication that the angular dependence of spin accumulation contribution to DWR
is $\sin^2\theta$. We expect magnetic multilayers to exhibit a similar
behavior.",0301400v2
2003-04-30,Radiation-induced magnetoresistance oscillation in a two-dimensional electron gas in Faraday geometry,"Microwave-radiation induced giant magnetoresistance oscillations recently
discovered in high-mobility two-dimensional electron systems in a magnetic
field, are analyzed theoretically. Multiphoton-assisted impurity scatterings
are shown to be the primary origin of the oscillation. Based on a model which
considers the interaction of electrons with the electromagnetic fields in
Faraday geometry, we are able not only to reproduce the correct period, phase
and the negative resistivity of the main oscillation, but also to obtain
secondary peaks and additional maxima and minima in the resistivity curve, some
of which were already observed in the experiments.",0304687v2
2003-06-03,Signatures of valence fluctuations in CeCu2Si2 under high pressure,"Simultaneous resistivity and a.c.-specific heat measurements have been
performed under pressure on single crystalline CeCu2Si2 to over 6 GPa in a
hydrostatic helium pressure medium. A series of anomalies were observed around
the pressure coinciding with a maximum in the superconducting critical
temperature, $T_c^{max}$. These anomalies can be linked with an abrupt change
of the Ce valence, and suggest a second quantum critical point at a pressure
$P_v \simeq 4.5$ GPa, where critical valence fluctuations provide the
superconducting pairing mechanism, as opposed to spin fluctuations at ambient
pressure. Such a valence instability, and associated superconductivity, is
predicted by an extended Anderson lattice model with Coulomb repulsion between
the conduction and f-electrons. We explain the T-linear resistivity found at
$P_v$ in this picture, while other anomalies found around $P_v$ can be
qualitatively understood using the same model.",0306054v1
2003-06-09,Thermal fluctuations in ultrasmall intrinsic Josephson junctions,"Current-voltage curves of small area hysteretic intrinsic Josephson
junctions, for which the Josephson energy $E_J=\hbar J_c/2e$ is of order of
thermal energy $kT$, are investigated. A non-monotonic temperature dependence
of the switching current is observed and explained by thermal phase
fluctuations. At low temperatures premature switching from the superconducting
into the resistive state is the most important effect of fluctuations. At high
temperatures only a single resistive branch is observed. At the cross-over
temperature a hysteretic phase-diffusion branch exists. It shows the importance
of a frequency-dependent impedance of an external circuit formed by the leads.",0306212v1
2003-11-25,Comparative study of in situ and ex situ MgB2 films deposited by pulsed laser deposition,"Two types of MgB2 films were prepared by pulsed laser deposition (PLD) with
in situ and ex situ annealing processes respectively. Significant differences
in properties between the two types of films were found. The ex situ MgB2 film
has a Tc of 38.1K, while the in situ film has a depressed Tc of 34.5K. The
resistivity at 40K for the in situ film is larger than that of the ex situ film
by a factor of 6. The residual resistivity ratios (RRR) are 1.1 and 2.1 for the
in situ and ex situ films respectively. The Jc-H curves of the in situ film
show a much weaker field dependence than those of the ex situ film,
attributable to stronger flux pinning in the in situ film. The small-grain
feature and high oxygen level may be critical for the significant improvement
of Jc in the in situ annealed MgB2 film.",0311556v1
2004-02-12,Self-localization of holes in a lightly doped Mott insulator,"We show that lightly doped holes will be self-trapped in an antiferromagnetic
spin background at low-temperatures, resulting in a spontaneous translational
symmetry breaking. The underlying Mott physics is responsible for such novel
self-localization of charge carriers. Interesting transport and dielectric
properties are found as the consequences, including large doping-dependent
thermopower and dielectric constant, low-temperature variable-range-hopping
resistivity, as well as high-temperature strange-metal-like resistivity, which
are consistent with experimental measurements in the high-T$_c$ cuprates.
Disorder and impurities only play a minor and assistant role here.",0402327v2
2004-03-09,Resistivity and Thermopower of Ni2.19Mn0.81Ga,"In this paper, we report results of the first studies on the thermoelectric
power (TEP) of the magnetic heusler alloy Ni$_{2.19}$Mn$_{0.81}$Ga. We explain
the observed temperature dependence of the TEP in terms of the crystal field
(CF) splitting and compare the observed behavior to that of the stoichiometric
system Ni$_2$MnGa. The resistivity as a function of temperature of the two
systems serves to define the structural transition temperature, T$_M$, which is
the transition from the high temperature austenitic phase to low temperatures
the martensitic phase. Occurrence of magnetic (Curie-Weiss) and the martensitic
transition at almost the same temperature in Ni$_{2.19}$Mn$_{0.81}$Ga has been
explained from TEP to be due to changes in the density of states (DOS) at the
Fermi level.",0403232v2
2004-07-21,YbNiSi3: a new antiferromagnetic Kondo lattice with strong exchange interaction,"We report on the structural, thermodynamic and transport properties of
high-quality single crystals of YbNiSi3 grown by the flux method. This compound
crystallizes in the SmNiGe3 layered structure type of the Cmmm space group. The
general physical behavior is that of a Kondo lattice showing an
antiferromagnetic ground state below T_N = 5.1 K. This is among the highest
ordering temperatures for a Yb-based intermetallic, indicating strong exchange
interaction between the Yb ions, which are close to +3 valency based on the
effective moment of 4.45 mu_B/f.u. The compound has moderately heavy-electron
behavior with Sommerfeld coefficient 190 mJ/mol K^2. Resistivity is highly
anisotropic and exhibits the signature logarithmic increase below a local
minimum, followed by a sharp decrease in the coherent/magnetically ordered
state, resulting in residual resistivity of 1.5 micro Ohm cm and RRR = 40.
Fermi-liquid behavior consistent with a ground-state doublet is clearly
observed below 1 K.",0407543v1
2004-09-05,Infrared study of giant dielectric constant in Li and Ti doped NiO,"We have measured optical reflectivity of Li and Ti doped NiO (LTNO) in the
infrared range at various temperatures. A Drude-like absorption is found at low
energy, $\omega <$ 100 cm$^{-1}$ and its spectral weight increases
substantially as temperature decreases. This observation and DC-resistivity
result show that LTNO has a conductive grain and resistive boundary. Such
composite structure provides evidence of the Maxwell-Wagner (MW) mechanism as
the origin of the high dielectric constant $\epsilon_{o}$. We propose a
three-phase granular structure and show that this extended MW model explains
the observed frequency and temperature dependence of the dielectric constant as
well as the giant value of $\epsilon_{o}$.",0409105v1
2004-09-09,Anomalous Pressure Dependence of Kadowaki-Woods ratio and Crystal Field Effects in Mixed-valence YbInCu4,"The mixed-valence (MV) compound YbInCu4 was investigated by electrical
resistivity and ac specific heat at low temperatures and high pressures. At
atmospheric pressure, its Kadowaki-Woods (KW) ratio, A/\gamma ^2, is 16 times
smaller than the universal value R_{KW}(=1.0 x 10^-5 \mu \Omega cm mol^2 K^2
mJ^-2), but sharply increases to 16.5R_{KW} at 27 kbar. The pressure-induced
change in the KW ratio and deviation from R_{KW} are analyzed in terms of the
change in f-orbital degeneracy N and carrier density n. This analysis is
further supported by a dramatic change in residual resistivity \rho_0 near 25
kbar, where \rho_0 jumps by a factor of 7.",0409243v2
2004-10-01,Inherent Relation between Nernst Signal and Nodal Quasiparticle Transport in Pseudogap Region of Underdoped High Temperature Superconductors,"In-plane Nernst signal and resistivity have been measured for three
$La_{2-x}Sr_xCuO_4$ single crystals (x=0.09, 0.11 and 0.145) with the magnetic
field parallel to c-axis. A quadratic temperature dependence of resistivity,
i.e., $\rho=\rho_0+aT^2$ is observed below a certain temperature $T_R$. It is
found that the upper boundary of the Nernst signal $T_n$ coincides with $T_R$,
which points to an inherent relation between the anomalous Nernst signal and
the nodal quasiparticle transport in the pseudogap region. Finally a phase
diagram together with the pseudogap temperature $T^*$ is presented, which
suggests a second energy scale in the pseudogap region.",0410013v2
2004-11-23,Magnetic field-tuned quantum critical point in CeAuSb_2,"Transport, magnetic and thermal properties at high magnetic fields (H) and
low temperatures (T) of the heavy fermion compound CeAuSb_2 are reported. At
H=0 this layered system exhibits antiferromagnetic order below T_N = 6 K.
Applying B along the inter-plane direction, leads to a continuous suppression
of T_N and a quantum critical point at H_c ~ 5.4 T. Although it exhibits Fermi
liquid behavior within the Neel phase, in the paramagnetic state the
fluctuations associated with H_c give rise to unconventional behavior in the
resistivity (sub-linear in T) and to a TlnT dependence in the magnetic
contribution to the specific heat. For H > H_c and low T the electrical
resistivity exhibits an unusual T^3-dependence.",0411588v2
2005-02-14,Superconductivity induced by spark erosion in ZrZn2,"We show that the superconductivity observed recently in the weak itinerant
ferromagnet ZrZn2 [C. Pfleiderer et al., Nature (London) 412, 58 (2001)] is due
to remnants of a superconducting layer induced by spark erosion. Results of
resistivity, susceptibility, specific heat and surface analysis measurements on
high-quality ZrZn2 crystals show that cutting by spark erosion leaves a
superconducting surface layer. The resistive superconducting transition is
destroyed by chemically etching a layer of 5 microns from the sample. No
signature of superconductivity is observed in rho(T) of etched samples at the
lowest current density measured, J=675 Am-2, and at T < 45 mK. EDX analysis
shows that spark-eroded surfaces are strongly Zn depleted. The simplest
explanation of our results is that the superconductivity results from an alloy
with higher Zr content than ZrZn2.",0502341v2
2005-04-05,Interaction and disorder in bilayer counterflow transport at filling factor one,"We study high mobility, interacting GaAs bilayer hole systems exhibiting
counterflow superfluid transport at total filling factor $\nu=1$. As the
density of the two layers is reduced, making the bilayer more interacting, the
counterflow Hall resistivity ($\rho_{xy}$) decreases at a given temperature,
while the counterflow longitudinal resistivity ($\rho_{xx}$), which is much
larger than $\rho_{xy}$, hardly depends on density. On the other hand, a small
imbalance in the layer densities can result in significant changes in
$\rho_{xx}$ at $\nu=1$, while $\rho_{xy}$ remains vanishingly small. Our data
suggest that the finite $\rho_{xx}$ at $\nu=1$ is a result of mobile vortices
in the superfluid created by the ubiquitous disorder in this system.",0504119v1
2005-05-19,On the problem of the Kondo-lattice model application to CeB6,"Precision measurements of charge transport parameters (resistivity, Hall and
Seebeck coefficients) have been carried out on high-quality single-crystals of
cerium hexaboride in a wide temperature range 1.8-300 K. It is shown that in
the temperature interval of 5 K < T < T* = 80 K the magnetic contribution in
resistivity obeys the power law rm = T -1/n, which corresponds to the regime of
weak localization of charge carriers with the critical index 1/n = 0.39 +-
0.02. In the same temperature interval an asymptotic behavior of thermopower S
= -lnT is found together with an essential decrease of the charge carriers
mobility in CeB6. A negative Hall coefficient anomaly has been detected at
liquid helium temperatures. The data obtained are compared with the results
predicted by the Kondo-lattice model and discussed also in terms of the theory
of excitonic ferromagnetism.",0505475v1
2005-06-15,"Resistivity study of the pseudogap phase for (Hg,Re) - 1223 superconductors","The pseudogap phase above the critical temperature of high $T_{c}$
superconductors (HTSC) presents different energy scales and it is currently a
matter of intense study. The complexity of the HTSC normal state requires very
accurate measurements with the purpose of distinguishing different types of
phenomena. Here we have performed systematically studies through electrical
resistivity ($\rho$) measurements by several different current densities in
order to obtain an optimal current for each sample. This approach allows to
determine reliable values of the pseudogap temperature $T^{*}(n)$, the layer
coupling temperature between the superconductor layers $T_{LD}(n)$, the
fluctuation temperature $T_{scf}(n)$ and the critical temperature $T_{c}(n)$ as
function of the doping $n$. The interpretation of these different temperature
scales allows to characterize possible scenarios for the (Hg,Re) - 1223 normal
state. This method, described in detail here, and used to derive the
(Hg,Re)-1223 phase diagram is general and can be applied to any HTSC.",0506387v2
2005-08-29,Universal Minimum Heat Leak on Low-Temperature Metallic Electrical Leads,"Low-temperature electronic systems require electrical leads which have low
electrical resistance to provide bias current I without excessive voltage drop
V. But proper cryogenic design also requires high thermal resistance to
maintain a minimum heat leak Q from the hot temperature T[hot] to the cold
temperature T[cold]. By the Wiedemann-Franz law, these requirements are in
direct conflict, and the optimal configuration takes a particularly simple
universal approximate form for the common case that T[cold] << T[hot]: Q/I = V
= 3.6 kT[hot]/e. This is applied here to the cryopackaging of RSFQ
superconducting circuits on a 4K cryocooler, but is equally applicable to other
cryogenic systems such as a superconducting sensor array at low and ultra-low
temperatures.",0508697v2
2005-09-01,"Comment on ""Magnetic quantum oscillations of the conductivity in layered conductors""","We discuss the recent theory of Gvozdikov [Phys. Rev. B 70, 085113 (2004)]
which aims at explaining the Shubnikov-de Haas oscillations of the longitudinal
resistivity \rho_zz observed in the quasi-two-dimensional organic compound
\beta''-(BEDT-TTF)_2SF_5CH_2CF_2SO_3.
  We point out that the self-consistent equations of the theory yielding the
longitudinal resistivity and the magnetic field dependence of the chemical
potential have been incorrectly solved. We show that the consideration of the
self-consistent Born approximation (which determines the relaxation rate in
Gvozdikov's paper) leads in fact to the complete absence of the longitudinal
conductivity \sigma_{zz} at leading order in high magnetic fields.",0509026v2
2005-10-14,Ferromagnetic Properties of ZrZn$_2$,"The low Curie temperature (T_C approx 28K) and small ordered moment (M_0
approx 0.17 mu_B f.u.^-1) of ZrZn2 make it one of the few examples of a weak
itinerant ferromagnet. We report results of susceptibility, magnetization,
resistivity and specific heat measurements made on high-quality single crystals
of ZrZn2. From magnetization scaling in the vicinity of T_C
(0.001<|T-T_C|/T_C<0.08), we obtain the critical exponents beta=0.52+/-0.05 and
delta=3.20+/-0.08, and T_C=27.50+/-0.05K. Low-temperature magnetization
measurements show that the easy axis is [111]. Resistivity measurements reveal
an anomaly at T_C and a non-Fermi liquid temperature dependence
rho(T)=rho_0+AT^n, where n=1.67+/-0.02, for 1<T<14K. The specific heat
measurements show a mean-field-like anomaly at T_C. We compare our results to
various theoretical models.",0510384v1
2005-12-23,Spin-charge gauge symmetry: A way to tackle HTS cuprates?,"We propose an explanation of several experimental features of transport
phenomena in the normal state of high Tc cuprates in terms of a spin-charge
gauge theory of the 2D t-J model. The calculated doping-temperature dependence
for a number of physical quantities is found in qualitative agreement with
data. In particular, we recover: in the ``pseudogap phase'' the metal-insulator
crossover of the in-plane resistivity and of the NMR ``relaxation time'' and
the insulating behavior of the out-of-plane resistivity; in the ``strange metal
phase'' (at higher temperature or doping) the linear in T behavior of the above
quantities; the appearance of maxima in the in-plane far-infrared conductivity
in strongly underdoped and overdoped samples.",0512607v1
2006-02-01,Coulomb blockade and transport in a chain of one-dimensional quantum dots,"A long one-dimensional wire with a finite density of strong random impurities
is modelled as a chain of weakly coupled quantum dots. At low temperature T and
applied voltage V its resistance is limited by ""breaks"": randomly occuring
clusters of quantum dots with a special length distribution pattern that
inhibits the transport. Due to the interplay of interaction and disorder
effects the resistance can exhibit T and V dependences that can be approximated
by power laws. The corresponding two exponents differ greatly from each other
and depend not only on the intrinsic electronic parameters but also on the
impurity distribution statistics.",0602008v3
2006-02-14,Intrinsic nonlinearity probed by intermodulation distortion microwave measurements on high quality MgB2 thin films,"The two tone intermodulation distortion arising in MgB2 thin films
synthesized by hybrid physical-chemical vapour deposition is studied in order
to probe the influence of the two bands on the nonlinear response of this
superconductor. The measurements are carried out by using a dielectrically
loaded copper cavity operating at 7 GHz. Microwave data on samples having
critical temperatures above 41 K, very low resistivity values, and residual
resistivity ratio larger than 10, are shown. The dependence of the nonlinear
surface losses and of the third order intermodulation products on the power
feeding the cavity and on the temperature is analyzed. At low power, the signal
arising from distortion versus temperature shows the intrinsic s-wave behavior
expected for this compound. Data are compared with measurements performed on Nb
and YBCO thin films using the same technique.",0602340v1
2006-02-21,Evidence of s-wave pairing symmetry in layered superconductor Li$_{0.68}$NbO$_2$ from the specific heat measurement,"A high quality superconducting Li$_{0.68}$NbO$_2$ polycrystalline sample was
synthesized by deintercalation of Li ions from Li$_{0.93}$NbO$_2$. The field
dependent resistivity and specific heat were measured down to 0.5 K. The upper
critical field $H_{c2} (T)$ is deduced from the resistivity data and
$H_{c2}(0)$ is estimated to be $\sim 2.98$ T. A notable specific heat jump is
observed at the superconducting transition temperature $T_c \sim 5.0$ K at zero
field. Below $T_c$, the electronic specific heat shows a thermal activated
behavior and agrees well with the theoretical result of the BCS s-wave
superconductors. It indicates that the superconducting pairing in
Li$_{0.68}$NbO$_2$ has s-wave symmetry.",0602476v1
2006-03-29,"Resistivity and Magneto-Optical Evidence for Variable and Incomplete Connectivity in Dense, High Critical Current Density C-alloyed Magnesium Diboride","Carbon-doped magnesium diboride was fabricated from pre-reacted pure MgB2 by
mechanical alloying. The sample set had excellent critical current densities
Jc(8T,4.2K) ranging from 15-60 kA/cm2, depending on composition.
Magneto-optical imaging detected regions up to 0.5 mm in size which were nearly
100% dense with Jc 2-6 times that of the matrix. Evaluation of resistivity
curves using the Rowell method predicts that only 10-50% of the cross sectional
area carries the normal state measurement current, suggesting that considerable
increases in Jc in these ~80% dense MgB2 samples would be possible with
complete grain and particle connectivity.",0603800v1
2006-06-08,Periodic Oscillations of Josephson-Vortex Flow Resistance in Oxygen-Deficient Y1Ba2Cu3Ox,"We measured the Josephson vortex flow resistance as a function of magnetic
field applied parallel to the ab-planes using annealed Y1Ba2Cu3Ox intrinsic
Josephson junctions having high anisotropy (around 40) by oxygen content
reduction. Periodic oscillations were observed in magnetic fields above 45-58
kOe, corresponding to dense-dilute boundary for Josephson vortex lattice. The
observed period of oscillations, agrees well with the increase of one fluxon
per two junctions ($H_{p}$\textit{=$\Phi $}$_{0}$\textit{/2Ls}), may correspond
to formation of a triangular lattice of Josephson vortices as has been reported
by Ooi et al. for highly anisotropic (larger than 200) Bi-2212 intrinsic
Josephson junctions.",0606202v2
2006-06-26,Flux-flow resistivity anisotropy in the instability regime in the a-b plane of epitaxial YBCO thin films,"Measurements of the nonlinear flux-flow resistivity $\rho$ and the critical
vortex velocity $\rm v^*_\phi$ at high voltage bias close to the instability
regime predicted by Larkin and Ovchinnikov \cite{LO} are reported along the
node and antinode directions of the d-wave order parameter in the \textit{a-b}
plane of epitaxial $YBa_2Cu_3O_{7-\delta}$ films. In this pinning-free regime,
$\rho$ and $\rm v^*_\phi$ are found to be anisotropic with values in the node
direction larger on average by 10% than in the antinode direction. The
anisotropy of $\rho$ is almost independent of temperature and field. We
attribute the observed results to the anisotropic quasiparticle distribution on
the Fermi surface of $YBa_2Cu_3O_{7-\delta}$.",0606667v1
2006-07-01,Nonlocal Effect of Local Nonmagnetic Impurity in High-Tc Superconductors: Induced Local Moment and Huge Residual Resistivity,"We study a Hubbard model with a strong onsite impurity potential based on an
improved fluctuation-exchange (FLEX) approximation, which we call the GVI-FLEX
method. We find that (i) both local and staggered susceptibilities are strongly
enhanced around the impurity. By this reason, (ii) the quasiparticle lifetime
as well as the local density of states (DOS) are strongly suppressed in a wide
area around the impurity (like a Swiss cheese hole), which causes the ``huge
residual resistivity'' beyond the s-wave unitary scattering value. These
results by the GVI method naturally explains the various impurity effects in
HTSC's in a unified way, which had been a long-standing theoretical problem.",0607011v1
2006-07-21,Vortex state microwave resistivity in Tl-2212 thin films,"We present measurements of the field induced changes in the 47 GHz complex
resistivity, $\Delta \tilde \rho(H,T)$, in Tl$_{2}$Ba$_{2}$CaCu$_{2}$O$_{8+x}$
(TBCCO) thin films with $T_{c}\simeq$ 105 K, prepared on CeO$_{2}$ buffered
sapphire substrates. At low fields ($\mu_{0}H<$10 mT) a very small irreversible
feature is present, suggesting a little role of intergranular phenomena. Above
that level $\Delta \tilde \rho(H,T)$ exhibits a superlinear dependence with the
field, as opposed to the expected (at high frequencies) quasilinear behaviour.
We observe a crossover between predominantly imaginary to predominantly real
(dissipative) response with increasing temperature and/or field. In addition,
we find the clear scaling property $\Delta \tilde \rho(H,T)=\Delta \tilde
\rho[H/H^{*}(T)]$, where the scaling field $H^{*}(T)$ maps closely the melting
field measured in single crystals. We discuss our microwave results in terms of
loss of flux lines rigidity.",0607552v1
2006-08-31,Magnetotransport in a two-dimensional electron system in dc electric fields,"We report on nonequilibrium transport measurements in a high-mobility
two-dimensional electron system subject to weak magnetic field and dc
excitation. Detailed study of dc-induced magneto-oscillations, first observed
by Yang {\em et al}., reveals a resonant condition that is qualitatively
different from that reported earlier. In addition, we observe dramatic
reduction of resistance induced by a weak dc field in the regime of separated
Landau levels. These results demonstrate similarity of transport phenomena in
dc-driven and microwave-driven systems and have important implications for
ongoing experimental search for predicted quenching of microwave-induced
zero-resistance states by a dc current.",0608727v3
2006-10-04,Quantum phase transition in the heavy-fermion compound YbIr$_2$Si$_2$,"We investigate the pressure-temperature phase diagram of YbIr$_2$Si$_2$ by
measuring the electrical resistivity $\rho(T)$. In contrast to the widely
investigated YbRh$_2$Si$_2$, YbIr$_2$Si$_2$ is a paramagnetic metal below
$p_c\simeq 8$ GPa. Interestingly, a first-order, presumably ferromagnetic,
transition develops at $p_c$. Similar magnetic properties were also observed in
YbRh$_2$Si$_2$ and YbCu$_2$Si$_2$ at sufficiently high pressures, suggesting a
uniform picture for these Yb compounds. The ground state of YbIr$_2$Si$_2$
under pressure can be described by Landau Fermi-liquid (LFL) theory, in
agreement with the nearly ferromagnetic Fermi-liquid (NFFL) model. Moreover,
evidence of a weak valence transition, characterized by a jump of the
Kadowaki-Woods (KW) ratio as well as an enhancement of the residual resistivity
$\rho_0$ and of the quasiparticle-quasiparticle scattering cross section, is
observed around 6 GPa.",0610126v1
2006-11-09,Small-angle interband scattering as the origin of the $T^{3/2}$ resistivity in MnSi,"A possible explanation is given for the anomalous $T^{3/2}$ temperature
dependence of the electrical resistivity of MnSi, which is observed in the
high-pressure paramagnetic state. The unusual Fermi surface of MnSi includes
large open sheets that intersect along the faces of the cubic Brillouin zone.
Close to these intersections, long-wavelength interband magnetic spin
fluctuations can scatter electrons from one sheet to the other. The current
relaxation rate due to such interband scattering events is not reduced by
vertex corrections as is that for scattering from intraband ferromagnetic
fluctuations. Consequently, current relaxation proceeds in a manner similar to
that occurring in nearly antiferromagnetic metals, in which low-temperature
$T^{3/2}$ behavior is well known. It is argued that this type of
non-Fermi-liquid behavior can, for a metal with ferromagnetic fluctuations near
Fermi sheet intersections, persist over a much wider temperature range than it
does in nearly antiferromagnetic metals.",0611236v1
2006-12-22,Transport through normal metal - graphene contacts,"Conductance of zigzag interfaces between graphene sheet and normal metal is
investigated in the tight-binding approximation. Boundary conditions, valid for
a variety of scattering problems, are constructed and applied to the normal
metal -- graphene -- normal metal (NGN) junctions. At the Dirac point, the
conductance is determined solely by the evanescent modes and is inversely
proportional to the length of the junction. It is also independent on the
interface resistance. Away from the Dirac point, the propagating modes'
contribution dominates. We also observe that even in the junctions with high
interface resistance, for certain modes, ideal transmission is possible via
Fabry-Perot like resonances.",0612577v3
2007-01-04,Anomalous Hall Resistance in Bilayer Quantum Hall Systems,"We present a microscopic theory of the Hall current in the bilayer quantum
Hall system on the basis of noncommutative geometry. By analyzing the
Heisenberg equation of motion and the continuity equation of charge, we
demonstrate the emergence of the phase current in a system where the interlayer
phase coherence develops spontaneously. The phase current arranges itself to
minimize the total energy of the system, as induces certain anomalous behaviors
in the Hall current in the counterflow geometry and also in the drag
experiment. They explain the recent experimental data for anomalous Hall
resistances due to Kellogg et al. [M. Kellogg, I.B. Spielman, J.P. Eisenstein,
L.N. Pfeiffer and K.W. West, Phys. Rev. Lett. \textbf{88} (2002) 126804; M.
Kellogg, J.P. Eisenstein, L.N. Pfeiffer and K.W. West, Phys. Rev. Lett.
\textbf{93} (2004) 036801] and Tutuc et al. [E. Tutuc, M. Shayegan and D.A.
Huse, Phys. Rev. Lett. \textbf{93} (2004) 036802] at $\nu =1$.",0701063v1
1995-12-08,The Complex Structure of 2D Surfaces,"The complex structure of a surface generated by the two-dimensional dynamical
triangulation(DT) is determined by measuring the resistivity of the surface. It
is found that surfaces coupled to matter fields have well-defined complex
structures for cases when the matter central charges are less than or equal to
one, while they become unstable beyond c=1. A natural conjecture that fine
planar random network of resistors behave as a continuous sheet of constant
resistivity is justified numerically for c<1.",9512014v1
2006-08-07,Random walk on the incipient infinite cluster for oriented percolation in high dimensions,"We consider simple random walk on the incipient infinite cluster for the
spread-out model of oriented percolation on $Z^d \times Z_+$. In dimensions
$d>6$, we obtain bounds on exit times, transition probabilities, and the range
of the random walk, which establish that the spectral dimension of the
incipient infinite cluster is 4/3, and thereby prove a version of the
Alexander--Orbach conjecture in this setting. The proof divides into two parts.
One part establishes general estimates for simple random walk on an arbitrary
infinite random graph, given suitable bounds on volume and effective resistance
for the random graph. A second part then provides these bounds on volume and
effective resistance for the incipient infinite cluster in dimensions $d>6$, by
extending results about critical oriented percolation obtained previously via
the lace expansion.",0608164v2
2003-02-21,New results from an extensive aging test on bakelite Resistive Plate Chambers,"We present recent results of an extensive aging test, performed at the CERN
Gamma Irradiation Facility on two single--gap RPC prototypes, developed for the
LHCb Muon System. With a method based on a model describing the behaviour of an
RPC under high particle flux conditions, we have periodically measured the
electrode resistance R of the two RPC prototypes over three years: we observe a
large spontaneous increase of R with time, from the initial value of about 2
MOhm to more than 250 MOhm. A corresponding degradation of the RPC rate
capabilities, from more than 3 kHz/cm2 to less than 0.15 kHz/cm2 is also found.",0302077v2
2004-03-09,Measuring the force ejecting DNA from phage,"We discuss how a balance can be established between the force acting to eject
DNA from viral capsids and the force resisting its entry into a colloidal
suspension which mimics the host cell cytoplasm. The ejection force arises from
the energy stored in the capsid as a consequence of the viral genome
(double-stranded DNA) being strongly bent and crowded on itself. The resisting
force is associated with the osmotic pressure exerted by the colloidal
particles in the host solution. Indeed, recent experimental work has
demonstrated that the extent of ejection can be progressively limited by
increasing the external osmotic pressure; at a sufficiently high pressure the
ejection is completely suppressed. We outline here a theoritical analysis that
allows a determination of the internal (capsid) pressure by examining the
different relations between force and pressure inside and outside the capsid,
using the experimentally measured position of the force balance.",0403057v1
2006-08-04,Design guide for electronics for resistive charge division in thermal neutron detection,"An amplifier has been designed for optimal use of position sensitive thermal
neutron detectors using the principle of resistive charge division. The
important points in this optimization are: high counting rates and good spatial
resolution. This amplifier is built as a hybrid circuit and is now used on
several new instruments at the ILL. It consists of a fast low noise current
pre-amplifier, a gaussian shaping circuit based on a 4th order active filter
and an essentially noiseless baseline reconstruction. In this paper, we present
a rather complete theoretical analysis of the problem that lead us to the
choices made above, and allows for an optimal adaptation to other situations.
An analysis of unwanted, secondary effects is also worked out.",0608046v1
2002-05-20,A Zoology of Bell inequalities resistant to detector inefficiency,"We derive both numerically and analytically Bell inequalities and quantum
measurements that present enhanced resistance to detector inefficiency. In
particular we describe several Bell inequalities which appear to be optimal
with respect to inefficient detectors for small dimensionality d=2,3,4 and 2 or
more measurement settings at each side. We also generalize the family of Bell
inequalities described in Collins et all (Phys. Rev. Lett. 88, 040404) to take
into account the inefficiency of detectors. In addition we consider the
possibility for pairs of entangled particles to be produced with probability
less than one. We show that when the pair production probability is small, one
must in general use different Bell inequalities than when the pair production
probability is high.",0205130v2
2007-05-17,Incoherent non-Fermi liquid scattering in a Kondo lattice,"One of the most notorious non-Fermi liquid properties of both archetypal
heavy-fermion systems [1-4] and the high-Tc copper oxide superconductors [5] is
an electrical resistivity that evolves linearly with temperature, T. In the
heavy-fermion superconductor CeCoIn5 [5], this linear behaviour was one of the
first indications of the presence of a zero-temperature instability, or quantum
critical point. Here, we report the observation of a unique control parameter
of T-linear scattering in CeCoIn5, found through systematic chemical
substitutions of both magnetic and non-magnetic rare-earth, R, ions into the Ce
sub-lattice. We find that the evolution of inelastic scattering in Ce1-xRxCoIn5
is strongly dependent on the f-electron configuration of the R ion, whereas two
other key properties -- Cooper-pair breaking and Kondo-lattice coherence -- are
not. Thus, T-linear resistivity in CeCoIn5 is intimately related to the nature
of incoherent scattering centers in the Kondo lattice, which provides insight
into the anomalous scattering rate synonymous with quantum criticality [7].",0705.2592v2
2007-07-22,Investigations of a THGEM-based imaging detector,"We present the results of our recent studies on a Thick Gas Electron
Multiplier (THGEM)-based imaging detector prototype. It consists of two 100x100
mm^2 THGEM electrodes in cascade, coupled to a resistive anode. The event
location is recorded with a 2D double-sided readout electrode equipped with
discrete delay-lines and dedicated electronics. The THGEM electrodes, produced
by standard printed-circuit board and mechanical drilling techniques, a 0.4 mm
thick with 0.5 mm diameter holes spaced by 1 mm. Localization resolutions of
about 0.7 mm (FWHM) were measured with soft x-rays, in a detector operated with
atmospheric-pressure Ar/CH4; good linearity and homogeneity were achieved. We
describe the imaging-detector layout, the resistive-anode 2D readout system and
the imaging properties. The THGEM has numerous potential applications that
require large-area imaging detectors, with high-rate capability,
single-electron sensitivity and moderate (sub-mm) localization resolution.",0707.3257v3
2007-08-13,Optimized minigaps for negative differential resistance creation in strongly delta-doped (1D) superlattices,"The ""atomic saw method"" uses the passage of dislocations in two-dimensional
(2D) quantum-well superlattices to create periodic slipping layers and
one-dimensional (1D) quantum wire superlattices. The effects of this space
structuring of the samples on the allowed energies are analysed in the case of
GaAs d-doped superlattices. If they are sufficiently large, the various
minigaps appearing in the 1D band structure could be responsible for the
presence of negative differential resistance (NDR) with high critical current
in these systems. The purpose is to determine the evolution of the minigaps in
terms of the sample parameters and to obtain the means to determine both the 2D
and 1D structural characteristics where NDR could appear.",0708.1673v1
2007-09-13,Influence of Mg Deficiency on the Superconductivity in MgB2 Thin Films Grown by using HPCVD,"The effects of Mg deficiency in MgB2 films grown by using hybrid
physical-chemical vapor deposition were investigated after vacuum annealing at
various temperatures. High-quality MgB2 films grown on c-cut Al2O3 substrates
with different superconducting transition temperatures (Tc) of 40.2 and 41 K
were used in this study. As the annealing temperature was increased from 200 to
800 C, the Mg contents in the MgB2 films systemically decreased, but the Tc's
did not change, within 0.12 K, until the annealing temperature reached 700 C.
For MgB2 films annealed at 800 C for 30 min, however, no superconductivity was
observed, and the temperature dependence of the resistivity showed a
semiconducting behavior. We also found that the residual resistivity ratio
decreased with increasing annealing temperature.",0709.1989v1
2007-12-20,The evolution of the Non-Fermi Liquid behavior of BaVS$_3$ under high pressure,"Temperature, pressure, and magnetic field dependencies of the resistivity of
BaVS$_3$ were measured above the critical pressure of $p_{cr}$=2 GPa, which is
associated with the zero temperature insulator-to-metal (MI) transition. The
resistivity exhibits the $T^n$ temperature dependence below $T_g\approx$15 K,
with $n$ of 1.5 at $p_{cr}$, which increases continuously with pressure towards
2. This is interpreted as a crossover from non-Fermi (NFL) to Fermi-liquid (FL)
behavior. Although the spin configuration of the $e_g$ electrons influences the
charge propagation, the NFL behavior is attributed to the pseudogap that
appears in the single particle spectrum of the $d_z^2$ electrons related to
large quasi-one dimensional (Q-1d) 2$k_F$-CDW fluctuations. The non-monotonic
magnetic field dependence of $\Delta$$\rho$/$\rho$ reveals a characteristic
field $B_0\approx$12 T attributed to the full suppression of the pseudogap.",0712.3393v1
2008-02-05,Verwey transition in Fe$_{3}$O$_{4}$ at high pressure: quantum critical behavior at the onset of metallization,"We provide evidence for the existence of a {\em quantum critical point} at
the metallization of magnetite Fe$_{3}$O$_{4}$ at an applied pressure of $p_{c}
\approx 8$ GPa. We show that the present ac magnetic susceptibility data
support earlier resistivity data. The Verwey temperature scales with pressure
$T_{V}\sim (1-p/p_{c})^{\nu}$, with $\nu\sim 1/3$. The resistivity data shows a
temperature dependence $\rho(T)=\rho_{0}+AT^{n}$, with $n\simeq 3$ above and
2.5 at the critical pressure, respectively. This difference in $n$ with
pressure is a sign of critical behavior at $p_{c}$. The magnetic susceptibility
is smooth near the critical pressure, both at the Verwey transition and near
the ferroelectric anomaly. A comparison with the critical behavior observed in
the Mott-Hubbard and related systems is made.",0802.0631v1
2008-02-20,Development of bakelite based Resistive Plate Chambers,"A Comparative study has been performed on Resistive Plate Chambers made of
different grades of bakelite paper laminates, produced and commercially
available in India. The chambers, operated in the streamer mode using argon :
tetrafluroethane : isobutane in 34:59:7 mixing ratio, are tested with cosmic
rays for the efficiency and the stability with cosmic rays. A particular grade
of bakelite (P-120, NEMA LI-1989 Grade XXX), used for high voltage insulation
in humid conditions, was found to give satisfactory performance with stable
efficiency of > 96% continuously for more than 110 days. A silicone treatment
of the inner surfaces of the bakelite RPC is found to be necessary for
operation of the detector.",0802.2766v1
2008-03-06,Graph Sparsification by Effective Resistances,"We present a nearly-linear time algorithm that produces high-quality
sparsifiers of weighted graphs. Given as input a weighted graph $G=(V,E,w)$ and
a parameter $\epsilon>0$, we produce a weighted subgraph
$H=(V,\tilde{E},\tilde{w})$ of $G$ such that $|\tilde{E}|=O(n\log
n/\epsilon^2)$ and for all vectors $x\in\R^V$ $(1-\epsilon)\sum_{uv\in
E}(x(u)-x(v))^2w_{uv}\le \sum_{uv\in\tilde{E}}(x(u)-x(v))^2\tilde{w}_{uv} \le
(1+\epsilon)\sum_{uv\in E}(x(u)-x(v))^2w_{uv}. (*)$
  This improves upon the sparsifiers constructed by Spielman and Teng, which
had $O(n\log^c n)$ edges for some large constant $c$, and upon those of
Bencz\'ur and Karger, which only satisfied (*) for $x\in\{0,1\}^V$.
  A key ingredient in our algorithm is a subroutine of independent interest: a
nearly-linear time algorithm that builds a data structure from which we can
query the approximate effective resistance between any two vertices in a graph
in $O(\log n)$ time.",0803.0929v4
2008-03-12,Bardeen-Stephen flux flow law disobeyed in the high-$T_c$ superconductor Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$,"Pulsed high current experiments in single crystals of the high-$T_{c}$
superconductor Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ in c-axis directed
magnetic field $H$ reveal that the $ab$-face resistance in the free flux flow
regime is a solely logarithmic function of H, devoid of any power law
component. Re-analysis of published data confirms this result and leads to
empirical analytic forms for the $ab$-plane and c-axis resistivities:
$\rho_{ab}\propto$ $H^{3/4}$, which does not obey the expected Bardeen-Stephen
result for free flux flow, and $\rho_{c} \propto H^{-3/4} \log^{2}H$.",0803.1804v1
2008-05-05,Fast dynamos in weakly ionized gases,"The turnover of interstellar gas on $\sim 10^9$yr timescales argues for the
continuous operation of a galactic dynamo. The conductivity of interstellar gas
is so high that the dynamo must be ""fast"" - i.e. the magnetic field must be
amplified at a rate nearly independent of the magnetic diffusivity. Yet, all
the fast dynamos so far known - and all direct numerical simulations of
interstellar dynamos - yield magnetic power spectra that peak at the resistive
scale, while galactic magnetic fields have substantial power on large scales.
In this paper we show that in weakly ionized gas the limiting scale may be the
ion-neutral decoupling scale, which although still small is many orders of
magnitude larger than the resistive scale.",0805.0412v1
2008-05-26,Negative differential resistance in molecular junctions: application to graphene ribbon junctions,"Using self-consistent calculations based on Non-Equilibrium Green's Function
(NEGF) formalism, the origin of negative differential resistance (NDR) in
molecular junctions and quantum wires is investigated. Coupling of the molecule
to electrodes becomes asymmetric at high bias due to asymmetry between its
highest occupied molecular orbital (HOMO) and lowest unoccupied molecular
orbital (LUMO) levels. This causes appearance of an asymmetric potential
profile due to a depletion of charge and reduction of screening near the source
electrode. With increasing bias, this sharp potential drop leads to an enhanced
localization of the HOMO and LUMO states in different parts of the system. The
reduction in overlap, caused by localization, results in a significant
reduction in the transmission coefficient and current with increasing bias. An
atomic chain connected to two Graphene ribbons was investigated to illustrate
these effects. For a chain substituting a molecule, an even-odd effect is also
observed in the NDR characteristics.",0805.3980v1
2008-06-10,Are Microwave Induced Zero Resistance States Necessarily Static?,"We study the effect of inhomogeneities in Hall conductivity on the nature of
the Zero Resistance States seen in the microwave irradiated two-dimensional
electron systems in weak perpendicular magnetic fields, and we show that
time-dependent domain patterns may emerge in some situations. For an annular
Corbino geometry, with an equilibrium charge density that varies linearly with
radius, we find a time-periodic non-equilibrium solution, which might be
detected by a charge sensor, such as an SET. For a model on a torus, in
addition to static domain patterns seen at high and low values of the
equilibrium charge inhomogeneity, we find that, in the intermediate regime, a
variety of nonstationary states can also exist. We catalog the possibilities we
have seen in our simulations. Within a particular phenomenological model, we
show that linearizing the nonlinear charge continuity equation about a
particularly simple domain wall configuration and analyzing the eigenmodes
allows us to estimate the periods of the solutions to the full nonlinear
equation.",0806.1562v1
2008-06-13,"Synthesis, crystal structure, microstructure, transport and magnetic properties of SmFeAsO and SmFeAs(O0.93F0.07)","SmFeAsO and the isostructural superconducting SmFeAs(O0.93F0.07) samples were
prepared. Characterization by means of Rietveld refinement of X-ray powder
diffraction data, scanning electron microscope observation, transmission
electron microscope analysis, resistivity and magnetization measurements were
carried out. Sintering treatment strongly improves the grain connectivity, but,
on the other hand, induces a competition between the thermodynamic stability of
the oxy-pnictide and Sm2O3, hence worsening the purity of the sample. In the
pristine sample both magnetization and resistivity measurements clearly
indicate that two different sources of magnetism are present: the former
related to Fe ordering at 140 K and the latter due to the Sm ions that orders
antiferromagnetically at low temperature. The feature at 140 K disappears in
the F-substituted sample and, at low temperatures a superconducting transition
appears. The magnetoresistivity curves of the F-substituted sample probably
indicates very high critical field values.",0806.2205v1
2008-07-17,Photosensitive Strip RETHGEM,"An innovative photosensitive gaseous detector, consisting of a GEM like
amplification structure with double layered electrodes (instead of commonly
used metallic ones) coated with a CsI reflective photocathode, is described. In
one of our latest designs, the inner electrode consists of a metallic grid and
the outer one is made of resistive strips; the latter are manufactured by a
screen printing technology on the top of the metallic strips grid The inner
metallic grid is used for 2D position measurements whereas the resistive layer
provides an efficient spark protected operation at high gains - close to the
breakdown limit. Detectors with active areas of 10cm x10cm and 10cm x20cm were
tested under various conditions including the operation in photosensitive gas
mixtures containing ethylferrocene or TMAE vapors. The new technique could have
many applications requiring robust and reliable large area detectors for UV
visualization, as for example, in Cherenkov imaging devices.",0807.2718v1
2008-07-21,Superconductivity at 34.7 K in the iron arsenide Eu0.7Na0.3Fe2As2,"EuFe2As2 is a member of the ternary iron arsenide family. Similar to BaFe2As2
and SrFe2As2, EuFe2As2 exhibits a clear anomaly in resistivity near 200 K. It
suggests that EuFe2As2 is another promising parent compound in which
superconductivity may be realized by appropriate doping. Here we report the
discovery of superconductivity in Eu0.7Na0.3Fe2As2 by partial substitution of
the europium site with sodium. ThCr2Si2 tetragonal structure, as expected for
EuFe2As2, is formed as the main phase for the composition Eu0.7Na0.3Fe2As2.
Resistivity measurement reveals a transition temperature as high as 34.7 K in
this compound, which is higher than the Tc of Eu0.5K0.5Fe2As2.",0807.3293v3
2008-08-03,Magnetic and Transport Studies on Electron-doped CeFeAsO1-xFx Superconductor,"The magnetic and transport behaviors of cerium substituted iron oxy-arsenide
superconductor with x = 0.1 to 0.4 fluoride (F) doping have been investigated
in this report. Temperature dependent susceptibility and resistivity
measurements showed the 0.1 F-doped sample (CeFeAsO0.9F0.1) has a
superconducting transition temperature (Tc) of around 30 K. With increasing
doping beyond x = 0.2 Tc saturates to around 40 K. Temperature dependent
susceptibility measured in different magnetic fields for the under-doped sample
showed Meissner effect in low field and the diamagnetism is still visible up to
1 Tesla, with an obvious magnetic transition below 5 K, perhaps originating
from magnetic ordering of the rare earth cerium. The corresponding field
dependent resistance versus temperature measurements indicated a broadening of
less than 3 K for Tc at mid-point by increasing the field to 5 Tesla indicating
rather low anisotropy. An estimated upper critical field of more than 48 Tesla
and accordingly an estimated maximum coherence length of 2.6 nm were obtained
confirming the high upper critical field with a short coherence length for this
superconductor.",0808.0296v1
2008-08-22,Correlation between extrinsic electroresistance and magnetoresistance in fine-grained La0.7Ca0.3MnO3,"We report our observation of a correlation between the extrinsic
electroresistance (EER) and magnetoresistance (EMR) via grain size in
fine-grained La0.7Ca0.3MnO3. The nature of dependence of EER and EMR on grain
size (~0.2-1.0 micron) indicates that for finer grains with low-resistive
boundaries both of them follow similar trend whereas they differ for coarser
grains with high-resistive boundaries. This could be due to a crossover in the
mechanism of charge transport across the grain boundaries - from spin-depedent
scattering process to spin-polarized tunneling one - as a function of grain
size.",0808.3043v2
2008-09-28,Scaling of 1/f noise in tunable break-junctions,"We have studied the $1/f$ voltage noise of gold nano-contacts in
electromigrated and mechanically controlled break-junctions having resistance
values $R$ that can be tuned from 10 $\Omega$ (many channels) to 10 k$\Omega$
(single atom contact). The noise is caused by resistance fluctuations as
evidenced by the $S_V\propto V^2$ dependence of the power spectral density
$S_V$ on the applied DC voltage $V$. As a function of $R$ the normalized noise
$S_V/V^2$ shows a pronounced cross-over from $\propto R^3$ for low-ohmic
junctions to $\propto R^{1.5}$ for high-ohmic ones. The measured powers of 3
and 1.5 are in agreement with $1/f$-noise generated in the bulk and reflect the
transition from diffusive to ballistic transport.",0809.4841v1
2008-10-20,Polaron relaxation and hopping conductivity in LaMn$_{1-x}$Fe$_{x}$O$_3$,"Dc and ac transport properties as well as electric modulus spectra have been
investigated for the samples LaMn$_{1-x}$Fe$_{x}$O$_3$ with compositions 0
$\leq x \leq$ 1.0. The bulk dc resistivity shows a temperature variation
consistent with the variable range hopping mechanism at low temperature and
Arrhenius mechanism at high temperatures. The ac conductivity has been found to
follow a power law behavior at a limited temperature and frequency region where
Anderson-localization plays a significant role in the transport mechanism for
all the compositions. At low temperatures large dc resistivities and dielectric
relaxation behavior for all the compositions are consistent with the polaronic
nature of the charge carriers. Scaling of the modulus spectra shows that the
charge transport dynamics is independent of temperature for a particular
composition but depends strongly on different compositions possibly due to
different charge carrier concentrations and structural properties.",0810.3502v1
2008-11-05,Superconductivity at 56 K in Samarium-doped SrFeAsF,"We synthesized the samples Sr$_{1-x}$Sm$_x$FFeAs with ZrCuSiAs-type
structure. These samples were characterized by resistivity and susceptibility.
It is found that substitution of rare earth metal for alkaline earth metal in
this system suppresses the anomaly in resistivity and induces
superconductivity. Superconductivity at 56 K in nominal composition
Sr$_{0.5}$Sm$_{0.5}$FFeAs is realized, indicating that the superconducting
transition temperatures in the iron arsenide fluorides can reach as high as
that in oxypnictides with the same structure.",0811.0761v3
2008-12-31,Cosmic-ray driven dynamo in galactic disks,"We present new developments on the Cosmic--Ray driven, galactic dynamo,
modeled by means of direct, resistive CR--MHD simulations, performed with ZEUS
and PIERNIK codes. The dynamo action, leading to the amplification of
large--scale galactic magnetic fields on galactic rotation timescales, appears
as a result of galactic differential rotation, buoyancy of the cosmic ray
component and resistive dissipation of small--scale turbulent magnetic fields.
Our new results include demonstration of the global--galactic dynamo action
driven by Cosmic Rays supplied in supernova remnants. An essential outcome of
the new series of global galactic dynamo models is the equipartition of the gas
turbulent energy with magnetic field energy and cosmic ray energy, in saturated
states of the dynamo on large galactic scales.",0901.0111v1
2009-01-13,Spin-Orbit Scattering and Quantum Metallicity in Ultra-Thin Be Films,"We compare and contrast the low temperature magnetotransport properties of
ultra-thin, insulating, Be films with and without spin-orbit scattering (SOS).
Beryllium films have very little intrinsic SOS, but by ""dusting"" them with
sub-monolayer coverages of Au, one can introduce a well controlled SOS rate.
Pure Be films with sheet resistance R >R_Q exhibit a low-temperature negative
magnetoresistance (MR) that saturates to the quantum resistance R_Q = h/e^2.
This high-field quantum metal phase is believed to represent a new ground state
of the system. In contrast, the corresponding negative MR in Be/Au films is
greatly diminished, suggesting that, in the presence of strong SOS, the quantum
metal phase can only be reached at field scales well beyond those typically
available in a low temperature laboratory.",0901.1873v1
2009-02-12,Two-Fluid Magnetohydrodynamic Simulations of Relativistic Magnetic Reconnection,"We investigate the large scale evolution of a relativistic magnetic
reconnection in an electron-positron pair plasma by a relativistic two-fluid
magnetohydrodynamic (MHD) code. We introduce an inter-species friction force as
an effective resistivity to dissipate magnetic fields. We demonstrate that
magnetic reconnection successfully occurs in our two-fluid system, and that it
involves Petschek-type bifurcated current layers in later stage. We further
observe a quasi-steady evolution thanks to an open boundary condition, and find
that the Petschek-type structure is stable over the long time period.
Simulation results and theoretical analyses exhibit that the Petschek outflow
channel becomes narrower when the reconnection inflow contains more magnetic
energy, as previously claimed. Meanwhile, we find that the reconnection rate
goes up to ~1 in extreme cases, which is faster than previously thought. The
role of the resistivity, implications for reconnection models in the
magnetically dominated limit, and relevance to kinetic reconnection works are
discussed.",0902.2074v2
2009-03-03,Insulating Phases Induced by Crossing of Partially Filled Landau Levels in a Si Quantum Well,"We study magnetotransport in a high mobility Si two-dimensional electron
system by in situ tilting of the sample relative to the magnetic field. A
pronounced dip in the longitudinal resistivity is observed during the Landau
level crossing process for noninteger filling factors. Together with a Hall
resistivity change which exhibits the particle-hole symmetry, this indicates
that electrons or holes in the relevant Landau levels become localized at the
coincidence where the pseudospin-unpolarized state is expected to be stable.",0903.0486v2
2009-03-22,The Turbulent Magnetic Prandtl Number of MHD Turbulence in Disks,"The magnetic Prandtl number Pr_M is the ratio of viscosity to resistivity. In
astrophysical disks the diffusion of angular momentum (viscosity) and magnetic
fields (resistivity) are controlled by turbulence. Phenomenological models of
the evolution of large scale poloidal magnetic fields in disks suggest that the
turbulent magnetic Prandtl number Pr_{M,T} controls the rate of escape of
vertical field from the disk; for Pr_{M,T} leq R/H vertical field diffuses
outward before it can be advected inward by accretion. Here we measure field
diffusion and angular momentum transport due to MHD turbulence in a shearing
box, and thus Pr_{M,T}, by studying the evolution of a sinusoidal perturbation
in the magnetic field that is injected into a turbulent background. We show
that the perturbation is always stable, decays approximately exponentially, has
decay rate proportional to k^2, and that the implied Pr_{M,T} ~ 1.",0903.3757v1
2009-04-08,Gate-controlled non-volatile graphene-ferroelectric memory,"In this letter, we demonstrate a non-volatile memory device in a graphene FET
structure using ferroelectric gating. The binary information, i.e. ""1"" and ""0"",
is represented by the high and low resistance states of the graphene working
channels and is switched by controlling the polarization of the ferroelectric
thin film using gate voltage sweep. A non-volatile resistance change exceeding
200% is achieved in our graphene-ferroelectric hybrid devices. The experimental
observations are explained by the electrostatic doping of graphene by electric
dipoles at the ferroelectric/graphene interface.",0904.1326v2
2009-04-13,Breakdown of the N=0 Quantum Hall State in graphene: two insulating regimes,"We studied the unusual Quantum Hall Effect (QHE) near the charge neutrality
point (CNP) in high-mobility graphene sample for magnetic fields up to 18 T. We
observe breakdown of the delocalized QHE transport and strong increase in
resistivities $\rho_{xx},|\rho_{xy}|$ with decreasing Landau level filling for
$\nu < 2$, where we identify two insulating regimes. For $1 \gtrsim |\nu|
\gtrsim 1/2$ we find an exponential increase of $\rho_{xx,xy} \sim
e^{a(H-H_c)}$ within the range up to several resistance quanta $R_K$, while the
Hall effect gradually disappears, consistent with the Hall insulator (HI) with
local transport. Then, at $\nu \approx 1/2$ a cusp in $\rho_{xx}(H)$ followed
by an onset of even faster growth indicates transition to a collective
insulator (CI) state. The likely candidate for this state is a pinned Wigner
crystal.",0904.1996v3
2009-08-03,The role of thermal conduction in magnetized viscous-resistive ADAFs,"Observations of the hot gas, which is surrounding Sgr A* and a few other
nearby galactic nuclei, imply that mean free paths of electron and proton are
comparable to gas capture radius. So, hot accretion flows likely proceed under
week collision conditions. As a result thermal conduction by ions has a
considerable contribution in transfer of the realized heat in accretion
mechanisms. We study a 2D advective accretion disk bathed in a poloidal
magnetic field of a central accretor in the presence of thermal conduction. We
find self-similar solutions for an axisymmetric, rotating, steady,
viscose-resistive, magnetized accretion flow. The dominant mechanism of energy
dissipation is assumed to be turbulence viscosity and magnetic diffusivity due
to magnetic field of the central accretor. We show that the global structure of
ADAFs are sensitive to viscosity, advection and thermal conduction parameters.
We discuss how radial flow, angular velocity and density of accretion flows may
vary with the advection, thermal conduction and viscous parameters.",0908.0325v1
2009-08-23,Direct Measurement of Thermal Fluctuation of High-Q Pendulum,"We achieved for the first time a direct measurement of the thermal
fluctuation of a pendulum in an off-resonant region using a laser
interferometric gravitational wave detector. These measurements have been well
identified for over one decade by an agreement with a theoretical prediction,
which was derived by a fluctuation-dissipation theorem. Thermal fluctuation is
dominated by the contribution of resistances in coil-magnet actuator circuits.
When we tuned these resistances, the noise spectrum also changed according to a
theoretical prediction. The measured thermal noise level corresponds to a high
quality factor on the order of 10^5 of the pendulum.",0908.3227v1
2009-08-25,Superconductivity in a single C60 transistor,"Single molecule transistors (SMTs) are currently attracting enormous
attention as possible quantum information processing devices. An intrinsic
limitation to the prospects of these however is associated to the presence of a
small number of quantized conductance channels, each channel having a high
access resistance of at best $R_{K}/2=h/2e^{2}$=12.9 k$\Omega$. When the
contacting leads become superconducting, these correlations can extend
throughout the whole system by the proximity effect. This not only lifts the
resistive limitation of normal state contacts, but further paves a new way to
probe electron transport through a single molecule. In this work, we
demonstrate the realization of superconducting SMTs involving a single C60
fullerene molecule. The last few years have seen gate-controlled Josephson
supercurrents induced in the family of low dimensional carbon structures such
as flakes of two-dimensional graphene and portions of one-dimensional carbon
nanotubes. The present study involving a full zero-dimensionnal fullerene
completes the picture.",0908.3638v1
2009-08-26,Observation of quantum-Hall effect in gated epitaxial graphene grown on SiC (0001),"Epitaxial graphene films were formed on the Si-face of semi-insulating 4H-SiC
substrates by a high temperature sublimation process. A high-k gate stack on
epitaxial graphene is realized by inserting a fully oxidized nanometer thin
aluminum film as a seeding layer followed by an atomic-layer deposition
process. The electrical properties of epitaxial graphene films are sustained
after gate stack formation without significant degradation. At low
temperatures, the quantum-Hall effect in Hall resistance is observed along with
pronounced Shubnikov-de Hass oscillations in diagonal magneto-resistance of
gated epitaxial graphene on SiC (0001).",0908.3822v3
2009-12-03,C-axis critical current of a PrFeAsO0.7 single crystal,"The c-axis transport properties of a high-pressure synthesized PrFeAsO0.7
single crystal are studied using s-shaped junctions. Resistivity anisotropy of
about 120 detected at 50 K shows the presence of strong anisotropy in the
electronic states. The obtained critical current density for the c-axis of
2.9*10^5 A/cm^2 is two orders of magnitude larger than that in
Bi2Sr1.6La0.4CuO6+d. The appearance of a hysteresis in the current-voltage
curve below T_c is the manifestation of the intrinsic Josephson effect similar
to that in cuprate superconductors. The suppression of the critical
current-normal resistance (I_cR_n) product is explained by an inspecular
transport in s_pm-wave pair potential.",0912.0598v1
2010-01-12,Resistive Magnetic Field Generation at Cosmic Dawn,"Relativistic charged particles (CR for cosmic-rays) produced by Supernova
explosion of the first generation of massive stars that are responsible for the
re-ionization of the universe escape into the intergalactic medium, carrying an
electric current. Charge imbalance and induction give rise to a return current,
$\vec j_t$, carried by the cold thermal plasma which tends to cancel the CR
current. The electric field, $\vec E=\eta \vec j_t$, required to draw the
collisional return current opposes the outflow of low energy cosmic rays and
ohmically heats the cold plasma. Owing to inhomogeneities in the resistivity,
$\eta(T)$, caused by structure in the temperature, $T$, of the intergalactic
plasma, the electric field possesses a rotational component which sustains
Faraday's induction. It is found that magnetic field is robustly generated
throughout intergalactic space at rate of 10$^{-17}-10^{-16}$ Gauss/Gyr, until
the temperature of the intergalactic medium is raised by cosmic reionization.
The magnetic field may seed the subsequent growth of magnetic fields in the
intergalactic environment.",1001.2011v2
2010-01-19,Theory of Normal State Pseudogap Behavior in FeSe(1-x)$Te(x),"The normal state of the recently discovered Iron Selenide (FeSe)-based
superconductors shows a range of inexplicable features. Along with bad-metallic
resistivity, characteristic pseudogap features and proximity to insulating
states, reminiscent of the underdoped high-Tc cuprates, mark these systems as
strongly correlated non-Fermi Liquid metals. Here, using the first-principles
LDA+DMFT method, we show how strong multi-orbital correlation-induced
orbital-selective Mott-like physics leads to an orthogonality catastrophe
underpinning these inexplicable incoherent features. Excellent agreement with a
range of resistivity and Seebeck data strongly support our proposal. We discuss
pseudogap regime microscopically, along with implications for the nature of the
instability at lower T, and propose that related systems could be of use in
thermoelectric devices.",1001.3273v1
2010-02-08,Indirect Magnetic-Field-Tuned Superconductor-Insulator Transitions and Weak Localization of Bosons of Quasi-Two Dimensional Metal Films,"Magnetic field and electrostatically tuned superconductor-insulator (SI)
transitions of ultrathin metal films with levels of disorder that place them
near the disorder-tuned SI transition appear to be direct, continuous quantum
phase transitions. When films with lower levels of disorder are subjected to a
perpendicular magnetic field, instead of a direct transition, a mixed
superconductor-nonsuperconductor regime emerges at the lowest temperatures. The
zero temperature limit of the resistance is either insulating or
superconducting, depending upon the value of the field, suggesting that the
behavior in this limit is governed by percolation physics. At high fields and
low temperatures, in the nominally insulating regime, the resistance rather
than the conductance is found to be a logarithmic function of temperature
corresponding to predicitons for the weak localization of bosons.",1002.1720v1
2010-02-16,Dynamic Nuclear Polarization and Nuclear Magnetic Resonance in the Simplest Pseudospin Quantum Hall Ferromagnet,"We present dynamic nuclear polarization (DNP) in the simplest pseudospin
quantum Hall ferromagnet (QHF) of an InSb two-dimensional electron gas with a
large g factor using tilted magnetic fields. The DNP-induced amplitude change
of a resistance spike of the QHF at large current enables observation of the
resistively detected nuclear magnetic resonance of the high nuclear spin
isotope 115In with nine quadrupole splittings. Our results demonstrate the
importance of domain structures in the DNP process. The nuclear spin relaxation
time T1 in this QHF was relatively short (~ 120 s), and almost temperature
independent.",1002.3087v3
2010-02-28,Microwave-induced magnetoresistance of two-dimensional electrons interacting with acoustic phonons,"The influence of electron-phonon interaction on magnetotransport in
two-dimensional electron systems under microwave irradiation is studied
theoretically. Apart from the phonon-induced resistance oscillations which
exist in the absence of microwaves, the magnetoresistance of irradiated samples
contains oscillating contributions due to electron scattering on both
impurities and acoustic phonons. The contributions due to electron-phonon
scattering are described as a result of the interference of phonon-induced and
microwave-induced resistance oscillations. In addition, microwave heating of
electrons leads to a special kind of phonon-induced oscillations. The relative
strength of different contributions and their dependence on parameters are
discussed. The interplay of numerous oscillating contributions suggests a
peculiar magnetoresistance picture in high-mobility layers at the temperatures
when electron-phonon scattering becomes important.",1003.0178v1
2010-03-19,Evidence for Anisotropic Vortex Dynamics and Pauli Limitation in the Upper Critical Field of FeSe1-xTex,"We have determined HC2(T) for FeSe1-xTex (x=0.52) single crystals using
resistivity measurements at high static and pulsed magnetic field, as well as
specific heat measurements up to 9T. We find that the significant anisotropy of
the initial slope of HC2(T) determined from resistivity measurements, is not
present when HC2 is determined from the specific heat results. This suggests
that the thermodynamic upper critical field is almost isotropic, and that
anisotropic vortex dynamics play a role. Further evidence of anisotropic vortex
dynamics is found in the behaviour in pulsed field. We also find that Pauli
limiting must be included in order to fit the temperature dependence of HC2,
indicating probably higher effective mass in FeSe1-xTex than in other Fe
superconductors.",1003.3812v1
2010-03-29,Three Dimensional Superconductivity in FeSe with Tczero Up to 10.9 K Induced by Internal Strain,"Polycrystalline sample FeSe was synthesized by a self-flux solution method
which shows a zero resistance temperature up to 10.9 K and a Tconset (90%
\rhon, \rhon: normal state resistivity) up to 13.3 K. The decrease of
superconducting transition temperature by heat treatment indicates that
internal crystallographic strain which plays the same effect as external
pressure is the origin of its high Tc. The fluctuation conductivity was studied
which could be well described by 3D Aslamazov-Larkin (AL) power law. The
estimated value of coherence length \xic=9.2 \AA is larger than the distance
between conducting layers (~6.0 \AA), indicating the three-dimensional nature
of superconductivity in this compound.",1003.5415v1
2010-06-01,"Synthesis, structural and physical properties of $δ'$-FeSe$_{1-x}$","We report on synthesis, structural characterization, resistivity, magnetic
and thermal expansion measurements on the as yet unexplored $\delta'$-phase of
FeSe$_{1-x}$, here synthesized under ambient- (AP) and high-pressure (HP)
conditions. We show that in contrast to $\beta$-FeSe$_{1-x}$, monophasic
superconducting $\delta'$-FeSe$_{1-x}$ can be obtained in off-stoichiometric
samples with excess Fe atoms preferentially residing in the van der Waals gap
between the FeSe layers. The AP $\delta'$-FeSe$_{1-x}$ sample studied here
($T_c$ $\simeq$ 8.5\,K) possesses an unprecedented residual resistivity ratio
RRR $\simeq$ 16. Thermal expansion data reveal a small feature around
$\sim$90\,K, which resembles the anomaly observed at the structural and
magnetic transitions for other Fe-based superconductors, suggesting that some
kind of ""magnetic state"" is formed also in FeSe. %indicative of a fluctuating
magnetic ordering. For HP samples (RRR $\simeq$ 3), the disorder within the
FeSe layers is enhanced through the introduction of vacancies, the saturated
magnetic moment of Fe is reduced and only spurious superconductivity is
observed.",1006.0073v2
2010-07-23,Phonon-induced resistance oscillations of two-dimensional electron systems drifting with supersonic velocities,"We present a theory of the phonon-assisted nonlinear dc transport of 2D
electrons in high Landau levels. The nonlinear dissipative resistivity displays
quantum magneto-oscillations governed by two parameters which are proportional
to the Hall drift velocity $v_H$ of electrons in electric field and the speed
of sound $s$. In the subsonic regime, $v_H<s$, the theory quantitatively
reproduces the oscillation pattern observed in recent experiments. We also find
the $\pi/2$ phase change of oscillations across the sound barrier $v_H=s$. In
the supersonic regime, $v_H>s$, the amplitude of oscillations saturates with
lowering temperature, while the subsonic region displays exponential
suppression of the phonon-assisted oscillations with temperature.",1007.4211v1
2010-07-26,Quantum phase transition of dynamical resistance in a mesoscopic capacitor,"We study theoretically dynamic response of a mesoscopic capacitor, which
consists of a quantum dot connected to an electron reservoir via a point
contact and capacitively coupled to a gate voltage. A quantum Hall edge state
with a filling factor nu is realized in a strong magnetic field applied
perpendicular to the two-dimensional electron gas. We discuss a noise-driven
quantum phase transition of the transport property of the edge state by taking
into account an ohmic bath connected to the gate voltage. Without the noise,
the charge relaxation for nu>1/2 is universally quantized at R_q=h/(2e^2),
while for nu<1/2, the system undergoes the Kosterlitz-Thouless transtion, which
drastically changes the nature of the dynamical resistance. The phase
transition is facilitated by the noisy gate voltage, and we see that it can
occur even for an integer quantum Hall edge at nu=1. When the dissipation by
the noise is sufficiently small, the quantized value of R_q is shifted by the
bath impedance.",1007.4404v1
2010-08-12,Single crystal growth and superconducting properties of LiFeAs,"We report the successful growth of high quality single crystals of LiFeAs
with lateral sizes up to 5 x 5 mm2 by the Sn-flux method. Electrical
resistivity studies reveal that the superconducting onset temperature is 18.2 K
with a transition width less than 1.1 K and the ratio of room temperature to
residual resistivity is about 24. Bulk superconductivity is supported by
perfect shielding in the magnetic susceptibility and a clear jump in the
specific heat Cp, resulting in deltaCp/T ~ 20.0 mJ/mol*K2. Upper critical field
slopes of dHc2c/dT ~ -1.39 and dHc2ab/dT ~ -2.99 T/K near Tc predict zero
temperature upper critical fields of Hc2c(0) ~ 17.2 and Hc2ab(0) ~ 36.9 T and
coherence lengths of Xi_ab = 4.4 and Xi_c = 2.0 nm in a single band model. This
result points to a modest superconducting anisotropy about 2.3 in LiFeAs.",1008.2050v1
2010-09-07,Mesoscopic transport in ultrathin films of La$_{0.67}$Ca$_{0.33}$MnO$_3$,"We investigate the electrical transport in mesoscopic structures of
La$_{0.67}$Ca$_{0.33}$MnO$_3$ in the regime of the metal-insulator transition
by fabricating microbridges from strained and unstrained thin films. We measure
current-voltage characteristics as function of temperature and in high magnetic
fields and with varying film thickness. For strained films, in warming from the
metallic to the insulating state, we find non-linear effects in the steep part
of the transition characterized by a differential resistance with a strong peak
around zero applied current, and saturating at higher currents after resistance
drops up to 60 %. We propose that this nonlinear behavior is associated with
melting of the insulating state by injecting charge carriers, signalling the
occurrence of an intervening phase which involves the formation of short range
polaron correlations.",1009.1386v1
2010-09-28,Influence of disorder on conductance in bilayer graphene under perpendicular electric field,"Electron transport in bilayer graphene placed under a perpendicular electric
field is revealed experimentally. Steep increase of the resistance is observed
under high electric field; however, the resistance does not diverge even at low
temperatures. The observed temperature dependence of the conductance consists
of two contributions: the thermally activated (TA) conduction and the variable
range hopping (VRH) conduction. We find that for the measured electric field
range (0 - 1.3 V/nm) the mobility gap extracted from the TA behavior agrees
well with the theoretical prediction for the band gap opening in bilayer
graphene, although the VRH conduction deteriorates the insulating state more
seriously in bilayer graphene with smaller mobility. These results show that
the improvement of the mobility is crucial for the successful operation of the
bilayer graphene field effect transistor.",1009.5467v1
2010-11-18,Vortex density waves and negative absolute resistance in patterned superconductors,"We study theoretically dynamical phases of vortices in superconducting films
with arrays of obstacles. By performing a series of molecular dynamics
simulations and analytical calculations, we demonstrate the existence of a
phase of soliton-like vortex-density waves appearing in a wide range of
parameters. These waves are formed by a self-assembled phase separation process
induced by strongly nonlinear density fluctuations of the moving vortex matter
above a certain critical driving current. At high vortex concentrations, the
waves move at an approximately current-independent speed resulting in a wide
plateau in the voltage-current characteristics. At stronger drives, the vortex
system enters into a fully jammed (zero-voltage) phase. By combining ac and dc
drives, the interplay between the vortex-density-wave and jammed phases leads
to the observation of negative absolute mobility of vortices, which induces the
superconducting film into a negative resistance state.",1011.4172v2
2010-12-03,Magnetic and electrical properties and carrier doping effects on the Fe-based host compound Sr4Sc2Fe2As2O6,"Additional charge carriers were introduced to the iron oxyarsenide
Sr4Sc2Fe2As2O6 under a high-pressure condition, followed by measurements of
electrical resistivity, Hall coefficient, and magnetic susceptibility. The host
compound Sr4Sc2Fe2As2O6 shows metallic conductivity down to ~200 K and turns to
show a semiconducting-like conductivity accompanied by a positive
magneto-resistance (22% at 70 kOe). Although the carrier density is comparable
at 300 K (5.9x1021 cm-3) with that of the other Fe-based superconductors, no
superconductivity appears down to 2 K. This is primarily because the net
carrier density decreases over 3 orders of magnitude on cooling and
additionally a possible magnetic order at ~120 K prevents carriers from
pairing. The properties were altered largely by introducing the additional
carriers.",1012.0616v1
2010-12-06,An analytical model of fractional overshooting,"We predict resistance anomalies to be observed at high mobility two
dimensional electron systems (2DESs) in the fractional quantized Hall regime,
where the narrow (L <10 ?m) Hall bar is defined by top gates. An analytic
calculation scheme is used to describe the formation of integral and fractional
incompressible strips. We incorporate the screening properties of the 2DES,
together with the effects of perpendicular magnetic field, to calculate the
effective widths of the current carrying channels. The many-body effects are
included to our calculation scheme through the energy gap obtained from the
well accepted formulation of the composite fermions. We show that, the
fractional incompressible strips at the edges, assuming different filling
factors, become evanescent and co-exist at certain magnetic field intervals
yielding an overshoot at the Hall resistance. Similar to that of the integral
quantized Hall effect. We also provide a mechanism to explain the absence of
1/3 state at the Fabry-Perot interference experiments. Yet, an un-investigated
sample design is proposed to observe and enhance the fragile effects like
interference and overshooting based on our analytical model.",1012.1294v1
2010-12-31,Beam test of signal cross-talk and transmission for LMPRC,"A new prototype of large area Multi-gap Resistive Plate Chamber (MRPC) with
long readout strips was built. This Long-strip Multi-gap Resistive Plate
Chamber (LMRPC) is double stacked and has ten 250 $\mu$m-thick gas gaps.
Signals are read out from two ends of strip with an active area of 50
cm$\times$2.5 cm in each. The detector was tested at FOPI in GSI, using the
secondary particles of proton beams ($E = 3.5 GeV$) colliding with a Pb target.
The results show that the LMRPC prototype has a time resolution of about
60$\sim$70 ps; the detecting efficiency is over 98% and the ratio of cross-talk
is lower than 2%. The detector also has a good spatial resolution of 0.36 cm
along the strip direction.",1101.0224v1
2011-02-10,Stimulated emission and absorption of photons in magnetic point contacts: toward metal-based spin-lasers,"Point contacts between high anisotropy ferromagnetic SmCo5 and normal metal
Cu are used to achieve a strong spin-population inversion in the contact core.
Subjected to microwave irradiation in resonance with the Zeeman splitting in
Cu, the inverted spin-population relaxes through stimulated spin-flip photon
emission, detected as peaks in the point contact resistance. Resonant spin-flip
photon absorption is detected as resistance minima, corresponding to sourcing
the photon field energy into the electrical circuit. These results demonstrate
fundamental mechanisms that are potentially useful for designing metallic
spin-based lasers.",1102.2167v1
2011-02-14,Edge effect on resistance scaling rules in graphene nanostructures,"We report an experimental investigation of the edge effect on the
room-temperature transport in graphene nanoribbon and graphene sheet (both
single-layer and bilayer). By measuring the resistance scaling behaviors at
both low and high carrier densities, we show that the transport of single-layer
nanoribbons lies in a strong localization regime, which can be attributed to an
edge effect. We find that this edge effect can be weakened by enlarging the
width, decreasing the carrier densities or adding an extra layer. From graphene
nanoribbon to graphene sheet, the data show a dimensional crossover of the
transport regimes possibly due to the drastic change of the edge effect.",1102.2681v1
2011-02-20,In situ TEM investigation of oxygen migration as a key mechanism for resistive switching in Pr0.7Ca0.3MnO3,"Low temperature growth Pr0.7Ca0.3MnO3 (PCMO) thin film showed high
performance in electric field induced resistance switching (RS). To understand
the micro-mechanism of RS in Metal/PCMO/Metal devices, structure evolution of
PCMO under external electric field monitored inside transmission electron
microscope (TEM) were performed. Evolution of the modulation stripe in as-grown
PCMO sample was investigated when applying electric field. The new-generated
modulation stripe gradually disappeared. These results indicate that oxygen ion
migration plays a key role in RS.",1102.4044v3
2011-05-19,Enhancement of the Superconducting Transition Temperature with Hydrostatic Pressure in Ca_{3}Ir_{4}Sn_{13} Single Crystals,"We report high pressure magnetic susceptibility and electrical resistivity
measurements on Ca_{3}Ir_{4}Sn_{13} single crystals up to 60 kbar. These
measurements allow us to follow the evolution of the superconducting critical
temperature T_c, the resistivity anomaly temperature T*, the superconducting
coherence length and the Fermi velocity under pressure. The
pressure-temperature phase diagram constructed for Ca_{3}Ir_{4}Sn_{13} shows a
dome-shaped pressure dependence of T_c. The initial rise in T_c, which is
accompanied by a decrease in T*, is consistent with a reduction in the partial
gapping of the Fermi surface under pressure.",1105.3941v1
2011-05-24,Low Bias Negative Differential Resistance in Graphene Nanoribbon Superlattices,"We theoretically investigate negative differential resistance (NDR) for
ballistic transport in semiconducting armchair graphene nanoribbon (aGNR)
superlattices (5 to 20 barriers) at low bias voltages V_SD < 500 mV. We combine
the graphene Dirac Hamiltonian with the Landauer-B\""uttiker formalism to
calculate the current I_SD through the system. We find three distinct transport
regimes in which NDR occurs: (i) a ""classical"" regime for wide layers, through
which the transport across band gaps is strongly suppressed, leading to
alternating regions of nearly unity and zero transmission probabilities as a
function of V_SD due to crossing of band gaps from different layers; (ii) a
quantum regime dominated by superlattice miniband conduction, with current
suppression arising from the misalignment of miniband states with increasing
V_SD; and (iii) a Wannier-Stark ladder regime with current peaks occurring at
the crossings of Wannier-Stark rungs from distinct ladders. We observe NDR at
voltage biases as low as 10 mV with a high current density, making the aGNR
superlattices attractive for device applications.",1105.4850v2
2011-10-22,Pressure Induced Metallization of BaMn2As2,"The temperature and pressure dependent electrical resistivity rho(T,P)
studies have been performed on BaMn2As2 single crystal in the 4.2 to 300 K
range upto of 8.2 GPa to investigate the evolution of its ground state
properties. The rho(T) shows a negative co-efficient of resistivity under
pressure upto 3.2 GPa. The occurrence of an insulator to metal transition (MIT)
in an external P ~4.5 GPa is indicated by a change in the temperature
co-efficient in the rho(T) data at ~36 K . However complete metallization in
entire temperature range is seen at a P~5.8 GPa. High pressure XRD studies
carried out at room temperature also shows an anomaly in the pressure versus
volume curve around P ~ 5 GPa, without a change in crystal structure,
indicative of an electronic transition. Further, a clear precipitous drop in
rho(T) at ~17 K is seen for P ~5.8 GPa which suggests the possibility of the
system going over to a superconducting ground state.",1110.4969v2
2011-10-24,Two coupled Josephson junctions: dc voltage controlled by biharmonic current,"We study transport properties of two Josephson junctions coupled by an
external shunt resistance. One of the junction (say, the first) is driven by an
unbiased ac current consisting of two harmonics. The device can rectify the ac
current yielding a dc voltage across the first junction. For some values of
coupling strength, controlled by an external shunt resistance, a dc voltage
across the second junction can be generated. By variation of system parameters
like the relative phase or frequency of two harmonics, one can conveniently
manipulate both voltages with high efficiency, e.g., changing the dc voltages
across the first and second junctions from positive to negative values and vice
versa.",1110.5287v3
2011-10-31,Resistivity saturation in a weakly interacting 2D Fermi liquid at intermediate temperatures,"We report a highly unusual temperature dependence in the magnetoresistance of
a weakly interacting high mobility 2D electron gas (2DEG) under a parallel
magnetic field and when the current is perpendicular to the field. While the
linear temperature dependence below 10 K and the exponential temperature
dependence above 40 K agree with existing theory of electron-phonon scattering,
a field induced resistivity saturation behaviour characterized by an almost
complete suppression of the temperature dependence is observed from
approximately 20 to 40 K, which is in sharp contrast to the phenomenology
observed when the current is parallel to the field. Possible origins of this
intriguing intermediate temperature phenomenon are discussed.",1111.0011v2
2011-11-14,Anomalous resistivity and the electron-polaron effect in the two-band Hubbard model with one narrow band,"We search for anomalous normal and superconductive behavior in the two-band
Hubbard model with one narrow band. We analyze the influence of
electron-polaron effect and Altshuler-Aronov effect on effective mass
enhancement and scattering times of heavy and light components in the clean
case. We find anomalous behavior of resistivity at high temperatures
$T>W_{h}^{*}$ both in 3D and 2D situation. The SC instability in the model is
governed by enhanced Kohn-Luttinger effect for p-wave pairing of heavy
electrons via polarization of light electrons.",1111.3135v1
2011-12-07,Low carrier concentration crystals of the topological insulator Bi$_2$Te$_2$Se,"We report the characterization of Bi$_2$Te$_2$Se crystals obtained by the
modified Bridgman and Bridgman-Stockbarger crystal growth techniques. X-ray
diffraction study confirms an ordered Se-Te distribution in the inner and outer
chalcogen layers, respectively, with a small amount of mixing. The crystals
displaying high resistivity ($> 1 \mathrm{\Omega cm}$) and low carrier
concentration ($\sim 5\times 10^{16}$/cm$^3$) at 4 K were found in the central
region of the long Bridgman-Stockbarger crystal, which we attribute to very
small differences in defect density along the length of the crystal rod.
Analysis of the temperature dependent resistivities and Hall coefficients
reveals the possible underlying origins of the donors and acceptors in this
phase.",1112.1648v1
2011-12-22,Field induced quantum-Hall ferromagnetism in suspended bilayer graphene,"We have measured the magneto-resistance of freely suspended high-mobility
bilayer graphene. For magnetic fields $B>1$ T we observe the opening of a field
induced gap at the charge neutrality point characterized by a diverging
resistance. For higher fields the eight-fold degenerated lowest Landau level
lifts completely. Both the sequence of this symmetry breaking and the strong
transition of the gap-size point to a ferromagnetic nature of the insulating
phase developing at the charge neutrality point.",1112.5368v2
2012-02-14,Precision comparison of the quantum Hall effect in graphene and gallium arsenide,"The half-integer quantum Hall effect in epitaxial graphene is compared with
high precision to the well known integer effect in a GaAs/AlGaAs
heterostructure. We find no difference between the quantised resistance values
within the relative standard uncertainty of our measurement of $8.7\times
10^{-11}$. The result places new tighter limits on any possible correction
terms to the simple relation $R_{\rm K}=h/e^2$, and also demonstrates that
epitaxial graphene samples are suitable for application as electrical
resistance standards of the highest metrological quality. We discuss the
characterisation of the graphene sample used in this experiment and present the
details of the cryogenic current comparator bridge and associated uncertainty
budget.",1202.2985v1
2012-02-14,Pressure suppression of unconventional charge-density-wave state in PrRu4P12 studied by optical conductivity,"Optical conductivity s(w) of PrRu4P12 has been studied under high pressure to
14 GPa, at low temperatures to 8 K, and at photon energies 12 meV-1.1 eV. The
energy gap in s(w) at ambient pressure, caused by a metal-insulator transition
due to an unconventional charge-density-wave formation at 63 K, is gradually
filled in with increasing pressure to 10 GPa. At 14 GPa and below 30 K, s(w)
exhibits a pronounced Drude-type component due to free carriers. This indicates
that the initial insulating ground state at zero pressure has been turned into
a metallic one at 14 GPa. This is consistent with a previous resistivity study
under pressure, where the resistivity rapidly decreased with cooling below 30 K
at 14 GPa. The evolution of electronic structure with pressure is discussed in
terms of the hybridization between the 4f and conduction electrons.",1202.3007v3
2012-02-16,Approximate strange metallic behavior in AdS,"We show for unit dynamical exponent, $z=1$, the appearance of the Fermi
liquid and non-Fermi liquid behavior as we tune the charge density and the
magnetic field in 3+1 dimensional field theory using the gauge-gravity duality.
There exists an upturn behavior of the resistivity only along the direction
perpendicular to the magnetic field. Also, there exists a universal behavior of
the resistivity, independent of the dimensionality of the spacetime, in a
specific corner of the parameter space, namely, in the large charge density and
small magnetic field limit: the longitudinal conductivity goes as $T^{-2/z}$,
whereas the Hall conductivity goes as $T^{-4/z}$. It means the Hall coefficient
goes as $T^{4/z}$. We compute the diffusion constant from the flow equation of
the conductivity.",1202.3555v1
2012-04-23,"Cyclopentadienyl-Benzene Based Sandwich Molecular Wires Showing Efficient Spin Filtering, Negative Differential Resistance, and Pressure Induced Electronic Transitions","Using density functional theory, we investigate TM-cyclopentadienyl-benzene
sandwich molecular wires (SMWs) which are composites of TM-cyclopentadienyl and
TM-benzene wires (TM = transition metal (V, Fe)). All the SMWs are found to be
highly stable ferromagnetic half-metals, showing spin switching behavior.
Transport calculations show that finite size clusters display spin filter
property when coupled with Au electrodes on either side. I-V characteristics of
all systems confirm the spin filter property, with Au-BzVCpVBz-Au displaying
exceptionally high performance. In addition to spin filtering, the
Au-BzFeCpFeBz-Au system also shows negative differential resistance (NDR).
Compression causes an abrupt reduction in magnetic moment and a transition to a
metallic phase, while stretching causes an increase in magnetic moment.
Half-metallicity is preserved for modest amounts of stretching and compression.",1204.5047v1
2012-05-17,Microwave heating-induced DC magnetic flux penetration in YBa$_{2}$Cu$_{3}$O$_{7-δ}$ superconducting thin films,"The magneto-optical imaging technique is used to visualize the penetration of
the magnetic induction in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin films during
surface resistance measurements. The in-situ surface resistance measurements
were performed at 7 GHz using the dielectric resonator method. When only the
microwave magnetic field $H_{rf}$ is applied to the superconductor, no
$H_{rf}$-induced vortex penetration is observed, even at high rf power. In
contrast, in the presence of a constant magnetic field superimposed on $H_{rf}$
we observe a progression of the flux front as $H_{rf}$ is increased. A local
thermometry method based on the measurement of the resonant frequency of the
dielectric resonator placed on the YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin film
shows that the $H_{rf}$--induced flux penetration is due to the increase of the
film temperature.",1205.3962v1
2012-07-04,Kondo-like behavior near the metal-to-insulator transition of nano-scale granular aluminum,"We show that the normal state transport properties of nano-scale granular
Aluminum films, near the metal to insulator transition, present striking
similarities with those of Kondo systems. Those include a negative
magneto-resistance, a minimum of resistance R at a temperature Tm in metallic
films, a logarithmic rise at low temperatures and a negative curvature of R(T)
at high temperatures. These normal state properties are interpreted in terms of
spin-flip scattering of conduction electrons by local magnetic moments,
possibly located at the metal/oxide interfaces. Their co-existence with the
enhanced superconductivity seen in these films is discussed.",1207.0970v3
2012-07-19,Simulation Studies of Charge Transport on Resistive Structures in Gaseous Ionization Detectors,"We developed a tool for the simulation of charge transport on a conducting
plate of finite dimensions. This tool is named Chani. Main motivation of
developing Chani was to provide a tool for the optimization of the dimensions
and resistivity of the anode electrodes in spark-protected Micropattern Gaseous
Detectors (MPGD). In this thesis, we start with the general description of the
LHC and the ATLAS Experiment. Then, we review the gaseous ionization detector
technologies and in particular, the micromegas technology. We then present the
working principles of Chani along with the example calculations. These examples
include comparisons with the analytically solvable problems which shows that
the simulation results are reasonable.",1207.4585v1
2012-07-20,Multi-Band Exotic Superconductivity in the New Superconductor Bi4O4S3,"Resistivity, Hall effect and magnetization have been investigated on the new
superconductor Bi4O4S3. A weak insulating behavior has been induced in the
normal state when the superconductivity is suppressed. Hall effect measurements
illustrate clearly a multiband feature dominated by electron charge carriers,
which is further supported by the magnetoresistance data. Interestingly, a kink
appears on the temperature dependence of resistivity at about 4 K at all high
magnetic fields when the bulk superconductivity is completely suppressed. This
kink can be well traced back to the upper critical field Hc2(T) in the low
field region, and is explained as the possible evidence of residual Cooper
pairs on the one dimensional chains.",1207.4955v1
2012-08-14,Superconductivity in Bismuth Oxysulfide Bi4O4S3,"Bismuth oxysulfide Bi4O4S3, which has recently been claimed to be an exotic
superconductor (Tc = 4.5 K), was investigated by magnetic susceptibility and
electrical resistivity measurements as well as by electron probe microanalysis.
Single-phase Bi4O4S3 was successfully prepared by a high-pressure method, and
its lattice parameters and normal-state resistivity, as well as the density of
states at the Fermi level, were found to be comparable to those determined
earlier. However, the observed superconductivity was most likely
impurity-driven, strictly contradictory to the observations in ongoing
experiments. The present results indicate that the superconductivity of Bi4O4S3
does not truly reflect the bulk nature of the BiS2 layered phase, regardless of
the manner in which Bi4O4S3 is synthesized. We discuss possible superconducting
impurities.",1208.2818v3
2012-08-15,Double negative differential thermal resistance induced by the nonlinear on-site potentials,"We study heat conduction through one-dimensional homogeneous lattices in the
presence of the nonlinear on-site potentials containing the bounded and
unbounded parts, and the harmonic interaction potential. We observe the
occurrence of double negative differential thermal resistance (NDTR), namely,
there exist two regions of temperature difference, where the heat flux
decreases as the applied temperature difference increases. The nonlinearity of
the bounded part contributes to NDTR at low temperatures and NDTR at high
temperatures is induced by the nonlinearity of the unbounded part. The
nonlinearity of the on-site potentials is necessary to obtain NDTR for the
harmonic interaction homogeneous lattices. However, for the anharmonic
homogeneous lattices, NDTR even occurs in the absence of the on-site
potentials, for example the rotator model.",1208.3008v1
2012-09-17,Hair of astrophysical black holes,"The ""no hair"" theorem is not applicable to black holes formed from collapse
of a rotating neutron star. Rotating neutron stars can self-produce particles
via vacuum breakdown forming a highly conducting plasma magnetosphere such that
magnetic field lines are effectively ""frozen-in"" the star both before and
during collapse. In the limit of no resistivity, this introduces a topological
constraint which prohibits the magnetic field from sliding off the newly-formed
event horizon. As a result, during collapse of a neutron star into a black
hole, the latter conserves the number of magnetic flux tubes N_B = e
\Phi_\infty /(\pi c \hbar), where \Phi_\infty is the initial magnetic flux
through the hemispheres of the progenitor and out to infinity. The black hole's
magnetosphere subsequently relaxes to the split monopole magnetic field
geometry with self-generated currents outside the event horizon. The
dissipation of the resulting equatorial current sheet leads to a slow loss of
the anchored flux tubes, a process that balds the black hole on long resistive
time scales rather than the short light-crossing time scales expected from the
vacuum ""no-hair"" theorem.",1209.3785v1
2012-09-24,Non-stationary Magnetic Microstructures in Stellar Thin Accretion Discs,"We examine the morphology of magnetic structures in thin plasma accretion
discs, generalizing a stationary ideal MHD model to the time-dependent
visco-resistive case. Our analysis deals with small scale perturbations to a
central dipole-like magnetic field, which give rise -- as in the ideal case --
to the periodic modulation of magnetic flux surfaces along the radial
direction, corresponding to the formation of a toroidal current channels
sequence. These microstructures suffer an exponential damping in time because
of the non-zero resistivity coefficient, allowing us to define a configuration
lifetime which mainly depends on the midplane temperature and on the length
scale of the structure itself. By means of this lifetime we show that the
microstructures can exist within the inner region of stellar discs in a precise
range of temperatures, and that their duration is consistent with local
transient processes (minutes to hours).",1209.5227v2
2012-09-29,Contact induced spin relaxation in Hanle spin precession measurements,"In the field of spintronics the ""conductivity mismatch"" problem remains an
important issue. Here the difference between the resistance of ferromagnetic
electrodes and a (high resistive) transport channel causes injected spins to be
backscattered into the leads and to lose their spin information. We study the
effect of the resulting contact induced spin relaxation on spin transport, in
particular on non-local Hanle precession measurements. As the Hanle line shape
is modified by the contact induced effects, the fits to Hanle curves can result
in incorrectly determined spin transport properties of the transport channel.
We quantify this effect that mimics a decrease of the spin relaxation time of
the channel reaching more than 4 orders of magnitude and a minor increase of
the diffusion coefficient by less than a factor of 2. Then we compare the
results to spin transport measurements on graphene from the literature. We
further point out guidelines for a Hanle precession fitting procedure that
allows to reliably extract spin transport properties from measurements.",1210.0093v1
2012-10-02,Magnetic structure of Coronal Mass Ejections,"We present several models of the magnetic structure of solar coronal mass
ejections (CMEs). First, we model CMEs as expanding force-free magnetic
structures. While keeping the internal magnetic field structure of the
stationary solutions, expansion leads to complicated internal velocities and
rotation, while the field structures remain force-free.
  Second, expansion of a CME can drive resistive dissipation within the CME
changing the ionization states of different ions. We fit in situ measurements
of ion charge states to the resistive spheromak solutions.
  Finally, we consider magnetic field structures of fully confined stable
magnetic clouds containing both toroidal and poloidal magnetic fields and
having no surface current sheets. Expansion of such clouds may lead to sudden
onset of reconnection events.",1210.0918v1
2012-10-25,The RPC-based proposal for the ATLAS forward muon trigger upgrade in view of super-LHC,"The innermost station of the present ATLAS forward muon detector needs to be
upgraded for the super-LHC. We present a proposal to replace it with a
sandwiched detector composed of several layers of small-radius Monitored Drift
Tube chambers (sMDT) for precision tracking measurement and two stations of
multi-gap Resistive Plate Chambers (mRPC) for triggering purpose. We describe
the layout of the upgraded detector and the trigger strategy. Several
modifications to the RPCs used in the ATLAS barrel region are needed to satisfy
the super-LHC requirements. Various studies with the proposed mRPC timing
resolution, spatial resolution and rate capability have been performed.",1210.6728v1
2012-12-06,The Reconstruction Algorithm Study of 2D Interpolating Resistive Readout Structure,"Systematic investigations including both simulation and prototype tests have
been done about the interpolating resistive readout structure with GEM (Gaseous
Electron Multiplier) detector. From the simulation, we have a good knowledge of
the process of charges diffusion on the surface of the readout plane and
develop several reconstruction methods to determine the hit position. The total
signal duration time of a typical event with the readout structure is about
several hundred nanoseconds, which implied an ideal count rate up to 106Hz. A
stable worked prototype was designed and fabricated after the simulation. Using
55Fe 5.9keV X-Ray, the image performance of the prototype is examined with flat
field image and some special geometry shapes, meanwhile, an energy resolution
of about 17% is obtained.",1212.1220v1
2012-12-12,Metal-insulator transition in holography,"We exhibit an interaction-driven metal-insulator quantum phase transition in
a holographic model. Use of a helical lattice enables us to break translation
invariance while preserving homogeneity. The metallic phase is characterized by
a sharp Drude peak and a d.c. resistivity that increases with temperature. In
the insulating phase the Drude spectral weight is transferred into a
`mid-infrared' peak and to energy scales of order the chemical potential. The
d.c. resistivity now decreases with temperature. In the metallic phase,
operators breaking translation invariance are irrelevant at low energy scales.
In the insulating phase, translation symmetry breaking effects are present at
low energies. We find the near horizon extremal geometry that captures the
insulating physics.",1212.2998v2
2013-01-06,Anomalous response to gate voltage application in mesoscopic LaAlO_3/SrTiO_3 devices,"We report on resistivity and Hall measurements performed on a series of
narrow mesa devices fabricated from LaAlO_3/SrTiO_3 single interface
heterostructure with a bridge width range of 1.5-10 microns. Upon applying
back-gate voltage of the order of a few Volts, a strong increase in the sample
resistance (up to factor of 35) is observed, suggesting a relatively large
capacitance between the Hall-bar and the gate. The high value of this
capacitance is due to the device geometry, and can be explained within an
electrostatic model using the Thomas Fermi approximation. The Hall coefficient
is sometimes a non-monotonic function of the gate voltage. This behavior is
inconsistent with a single conduction band model. We show that a theoretical
two-band model is consistent with this transport behavior, and indicates a
metal to insulator transition in at least one of these bands.",1301.1055v1
2013-04-22,Stochastic Memristive Devices for Computing and Neuromorphic Applications,"Nanoscale resistive switching devices (memristive devices or memristors) have
been studied for a number of applications ranging from non-volatile memory,
logic to neuromorphic systems. However a major challenge is to address the
potentially large variations in space and in time in these nanoscale devices.
Here we show that in metal-filament based memristive devices the switching can
be fully stochastic. While individual switching events are random, the
distribution and probability of switching can be well predicted and controlled.
Rather than trying to force high switching probabilities using excessive
voltage or time, the inherent stochastic nature of resistive switching allows
these binary devices to be used as building blocks for novel error-tolerant
computing schemes such as stochastic computing and provide a needed ""analog""
feature in neuromorphic applications. To verify such potential, we demonstrated
memristor-based stochastic bitstreams in both time and space domains, and show
that an array of binary memristors can act as a multi-level ""analog"" device for
neuromorphic applications.",1304.5993v1
2013-04-27,Attacks and Countermeasures in Fingerprint Based Biometric Cryptosystems,"We investigate implementations of biometric cryptosystems protecting
fingerprint templates (which are mostly based on the fuzzy vault scheme by
Juels and Sudan in 2002) with respect to the security they provide. We show
that attacks taking advantage of the system's false acceptance rate, i.e.
false-accept attacks, pose a very serious risk --- even if brute-force attacks
are impractical to perform. Our observations lead to the clear conclusion that
currently a single fingerprint is not sufficient to provide a secure biometric
cryptosystem. But there remain other problems that can not be resolved by
merely switching to multi-finger: Kholmatov and Yanikoglu in 2007 demonstrated
that it is possible to break two matching vault records at quite a high rate
via the correlation attack.
  We propose an implementation of a minutiae fuzzy vault that is inherently
resistant against cross-matching and the correlation attack. Surprisingly,
achieving cross-matching resistance is not at the cost of authentication
performance. In particular, we propose to use a randomized decoding procedure
and find that it is possible to achieve a GAR=91% at which no false accepts are
observed on a database generally used. Our ideas can be adopted into an
implementation of a multibiometric cryptosystem. All experiments described in
this paper can fully be reproduced using software available for download.",1304.7386v1
2013-06-19,Nematode Locomotion in Unconfined and Confined Fluids,"The millimeter-long soil-dwelling nematode {\it C. elegans} propels itself by
producing undulations that propagate along its body and turns by assuming
highly curved shapes. According to our recent study [PLoS ONE \textbf{7},
e40121 (2012)] all these postures can be accurately described by a
piecewise-harmonic-curvature (PHC) model. We combine this curvature-based
description with highly accurate hydrodynamic bead models to evaluate the
normalized velocity and turning angles for a worm swimming in an unconfined
fluid and in a parallel-wall cell. We find that the worm moves twice as fast
and navigates more effectively under a strong confinement, due to the large
transverse-to-longitudinal resistance-coefficient ratio resulting from the
wall-mediated far-field hydrodynamic coupling between body segments. We also
note that the optimal swimming gait is similar to the gait observed for
nematodes swimming in high-viscosity fluids. Our bead models allow us to
determine the effects of confinement and finite thickness of the body of the
nematode on its locomotion. These effects are not accounted for by the
classical resistive-force and slender-body theories.",1306.4423v1
2013-07-08,Effects of the non-uniform initial environment and the guide field on the plasmoid instability,"Effects of non-uniform initial mass density and temperature on the plasmoid
instability are studied via 2.5-dimensional resistive magnetohydrodynamic(MHD)
simulations. Our results indicate that the development of the plasmoid
instability is apparently prevented when the initial plasma density at the
center of the current sheet is higher than that in the upstream region. As a
result, the higher the plasma density at the center and the lower the plasma
$\beta$ in the upstream region, the higher the critical Lundquist number needed
for triggering secondary instabilities. When $\beta =0.2$, the critical
Lundquist number is higher than $10^4$. For the same Lundquist number, the
magnetic reconnection rate is lower for the lower plasma $\beta$ case.
Oppositely, when the initial mass density is uniform and the Lundquist number
is low, the magnetic reconnection rate turns out to be higher for the lower
plasma $\beta$ case. For the high Lundquist number case ($>10^4$) with uniform
initial mass density, the magnetic reconnection is not affected by the initial
plasma $\beta$ and the temperature distribution. Our results indicate that the
guide field has a limited impact on the plasmoid instability in resistive MHD.",1307.1963v1
2013-08-05,Explosive reconnection of double tearing modes in relativistic plasmas: application to the Crab flares,"Magnetic reconnection associated to the double tearing mode (DTM) is
investigated by means of resistive relativistic magnetohydrodynamic (RRMHD)
simulations. A linearly unstable double current sheet system in two dimensional
cartesian geometry is considered. For initial perturbations of large enough
longitudinal wavelengths, a fast reconnection event is triggered by a secondary
instability that is structurally driven by the nonlinear evolution of the
magnetic islands. The latter reconnection phase and time scale appear to weakly
depend on the plasma resistivity and magnetization parameter. We discuss the
possible role of such explosive reconnection dynamics to explain the MeV flares
observed in the Crab pulsar nebula. Indeed the time scale and the critical
minimum wavelength give constraints on the Lorentz factor of the striped wind
and on the location of the emission region respectively.",1308.0906v1
2014-02-05,Thermal-inertial effects on magnetic reconnection in relativistic pair plasmas,"The magnetic reconnection process is studied in relativistic pair plasmas
when the thermal and inertial properties of the magnetohydrodynamical fluid are
included. We find that in both Sweet-Parker and Petschek relativistic scenarios
there is an increase of the reconnection rate owing to the thermal-inertial
effects, both satisfying causality. To characterize the new effects we define a
thermal-inertial number which is independent of the relativistic Lundquist
number, implying that reconnection can be achieved even for vanishing
resistivity as a result of only thermal-inertial effects. The current model has
fundamental importance for relativistic collisionless reconnection, as it
constitutes the simplest way to get reconnection rates faster than those
accessible with the sole resistivity.",1402.1115v2
2014-02-14,Unification of the Pressure and Composition Dependence of Superconductivity in Ru substituted BaFe2As2,"Temperature dependent high pressure electrical resistivity studies has been
carried out on Ba(Fe_{1-x}Ru_{x})_{2}As_{2} single crystals with x = 0.12, 0.26
and 0.35, which correspond to under doped, optimally doped and over doped
composition regimes respectively. The evolution of structural/magnetic
(T_{S-M}) and superconducting transition (T_(c)) temperatures, with pressure
for various compositions have been obtained. The normal state resistivity has
been analyzed in terms of a model that incorporates both spin fluctuations and
the opening of the gap in the spin density wave (SDW)phase. It is shown that Tc
scales with the strength of the spin fluctuation, B, and T_{S-M} scales with
the SDW gap parameter, \Delta. This provides a prescription for the unification
of the composition and pressure induced superconductivity in BaFe2As2.",1402.3387v1
2014-03-24,Physics of Fully Depleted CCDs,"In this work we present simple, physics-based models for two effects that
have been noted in the fully depleted CCDs that are presently used in the Dark
Energy Survey Camera. The first effect is the observation that the point-spread
function increases slightly with the signal level. This is explained by
considering the effect on charge-carrier diffusion due to the reduction in the
magnitude of the channel potential as collected signal charge acts to partially
neutralize the fixed charge in the depleted channel. The resulting reduced
voltage drop across the carrier drift region decreases the vertical electric
field and increases the carrier transit time. The second effect is the
observation of low-level, concentric ring patterns seen in uniformly
illuminated images. This effect is shown to be most likely due to lateral
deflection of charge during the transit of the photogenerated carriers to the
potential wells as a result of lateral electric fields. The lateral fields are
a result of space charge in the fully depleted substrates arising from
resistivity variations inherent to the growth of the high-resistivity silicon
used to fabricate the CCDs.",1403.6185v1
2014-05-25,Negative differential resistance in graphene-based ballistic field effect transistor with oblique top gate,"Negative differential resistance (NDR) with room temperature
peak-valley-ratio of 8 has been observed in a ballistic field-effect-transistor
(FET) based on graphene, having an oblique top gate. Graphene FETs with a top
gate inclination angle of 45 degrees and a drain-source distance of 400 nm were
fabricated on a chip cut from a 4 inch graphene wafer grown by CVD. From the 60
measured devices, NDR was observed only in the regions where the CVD graphene
displays the Raman signature of defectless monolayers. In other specific
positions on the wafer, where graphene quality was not high enough and the
Raman signature indicated the presence of defects, the ballistic character of
transport is lost and the graphene FETs display nonlinear drain-voltage
dependences tuned by the top and back gate voltage.",1405.6407v1
2014-06-26,The value of monitoring to control evolving populations,"Populations can evolve in order to adapt to external changes. The capacity to
evolve and adapt makes successful treatment of infectious diseases and cancer
difficult. Indeed, therapy resistance has quickly become a key challenge for
global health. Therefore, ideas of how to control evolving populations in order
to overcome this threat are valuable. Here we use the mathematical concepts of
stochastic optimal control to study what is needed to control evolving
populations. Following established routes to calculate control strategies, we
first study how a polymorphism can be maintained in a finite population by
adaptively tuning selection. We then introduce a minimal model of drug
resistance in a stochastically evolving cancer cell population and compute
adaptive therapies, where decisions are based on monitoring the response of the
tumor, which can outperform established therapy paradigms. For both case
studies, we demonstrate the importance of high-resolution monitoring of the
target population in order to achieve a given control objective: to control one
must monitor.",1406.6957v1
2014-07-28,Critical point for the CAF-F phase transition at charge neutrality in bilayer graphene,"We report on magneto-transport measurements up to 30 T performed on a bilayer
graphene Hall bar, enclosed by two thin hexagonal boron nitride flakes. Our
high mobility sample exhibits an insulating state at neutrality point which
evolves into a metallic phase when a strong in-plane field is applied, as
expected for a transition from a canted antiferromagnetic to a ferromagnetic
spin ordered phase. For the first time we individuate a temperature-independent
crossing in the four-terminal resistance as a function of the total magnetic
field, corresponding to the critical point of the transition. We show that the
critical field scales linearly with the perpendicular component of the field,
as expected from the underlying competition between the Zeeman energy and
interaction-induced anisotropies. A clear scaling of the resistance is also
found and an universal behavior is proposed in the vicinity of the transition.",1407.7425v1
2014-11-28,The tearing mode instability of thin current sheets: the transition to fast reconnection in the presence of viscosity,"This paper studies the growth rate of reconnection instabilities in thin
current sheets in the presence of both resistivity and viscosity. In a previous
paper, Pucci and Velli (2014), it was argued that at sufficiently high
Lundquist number S it is impossible to form current sheets with aspect ratios
L/a which scale as $L/a\sim S^\alpha$ with $\alpha > 1/3$ because the growth
rate of the tearing mode would then diverge in the ideal limit
$S\rightarrow\infty$. Here we extend their analysis to include the effects of
viscosity, (always present in numerical simulations along with resistivity) and
which may play a role in the solar corona and other astrophysical environments.
A finite Prandtl number allows current sheets to reach larger aspect ratios
before becoming rapidly unstable in pile-up type regimes. Scalings with
Lundquist and Prandtl numbers are discussed as well as the transition to
kinetic reconnection",1412.0047v2
2014-12-02,Two-stage magnetic-field-tuned superconductor-insulator transition in underdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$,"In the underdoped pseudogap regime of cuprate superconductors, the normal
state is commonly probed by applying a magnetic field ($H$). However, the
nature of the $H$-induced resistive state has been the subject of a long-term
debate, and clear evidence for a zero-temperature ($T=0$) $H$-tuned
superconductor-insulator transition (SIT) has proved elusive. Here we report
magnetoresistance measurements in underdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$,
providing striking evidence for quantum critical behavior of the resistivity --
the signature of a $H$-driven SIT. The transition is not direct: it is
accompanied by the emergence of an intermediate state, which is a
superconductor only at $T=0$. Our finding of a two-stage $H$-driven SIT goes
beyond the conventional scenario in which a single quantum critical point
separates the superconductor and the insulator in the presence of a
perpendicular $H$. Similar two-stage $H$-driven SIT, in which both disorder and
quantum phase fluctuations play an important role, may also be expected in
other copper-oxide high-temperature superconductors.",1412.1134v1
2015-01-15,Non-ergodic metallic and insulating phases of Josephson junction chains,"Strictly speaking the laws of the conventional Statistical Physics, based on
the Equipartition Postulate and Ergodicity Hypothesis, apply only in the
presence of a heat bath. Until recently this restriction was not important for
real physical systems: a weak coupling with the bath was believed to be
sufficient. However, the progress in both quantum gases and solid state
coherent quantum devices demonstrates that the coupling to the bath can be
reduced dramatically. To describe such systems properly one should revisit the
very foundations of the Statistical Mechanics. We examine this general problem
for the case of the Josephson junction chain and show that it displays a novel
high temperature non-ergodic phase with finite resistance. With further
increase of the temperature the system undergoes a transition to the fully
localized state characterized by infinite resistance and exponentially long
relaxation.",1501.03853v1
2015-02-17,Variations of magnetic properties of UGa2 under pressure,"Electrical resistivity \rho(T) of the 5f ferromagnet UGa2 was investigated
for single-crystal samples as a function of pressure and magnetic field. The
Curie temperature monotonously increases from T$_{C}$ = 124 K under
quasi-hydrostatic pressure up to 154 K at p = 14.2 GPa, after which it turns
down steeply and reaches T$_{C}$ = 147 K at p = 15.2 GPa. At 20 GPa the
compound is already non-magnetic. This dramatic variation is compatible with
exchange interactions mediated by the 5f hybridization with the non-f states.
The external pressure first enhances the exchange coupling of the 5f moments,
but eventually suppresses the order by washing out the 5f moments. Such a
two-band model is adequate for the weakly delocalized 5f states. The
spin-disorder resistivity, which produces very high \rho-values (300
\mu\Omega.cm) is gradually suppressed by the pressure. In the paramagnetic
state, this leads to a crossover from initial negative to positive d\rho/dT.",1502.04948v1
2015-08-17,Suppression of Nonmagnetic Insulating State by Application of Pressure in Mineral Tetrahedrite Cu$_{12}$Sb$_{4}$S$_{13}$,"The mineral tetrahedrite Cu$_{12}$Sb$_{4}$S$_{13}$ exhibits a first-order
metal--insulator transition (MIT) at $T_{\rm MI}$ = 85 K and ambient pressure.
We measured the $^{63}$Cu-NMR at ambient pressure and the resistivity and
magnetic susceptibility at high pressures. $^{63}$Cu-NMR results indicate a
nonmagnetic insulating ground state in this compound. The MIT is monotonically
suppressed by pressure and disappears at $\sim1.0$ GPa. Two other anomalies are
observed in the resistivity measurements, and the pressure -- temperature phase
diagram of Cu$_{12}$Sb$_{4}$S$_{13}$ is constructed.",1508.03933v1
2015-09-25,Turbulent Reconnection in Relativistic Plasmas And Effects of Compressibility,"We report turbulence effects on magnetic reconnection in relativistic plasmas
using 3-dimensional relativistic resistive magnetohydrodynamics simulations. We
found reconnection rate became independent of the plasma resistivity due to
turbulence effects similarly to non-relativistic cases. We also found
compressible turbulence effects modified the turbulent reconnection rate
predicted in non-relativistic incompressible plasmas; The reconnection rate
saturates and even decays as the injected velocity approaches to the Alfv\'en
velocity. Our results indicate the compressibility cannot be neglected when
compressible component becomes about half of incompressible mode occurring when
the Alfv\'en Mach number reaches about $0.3$. The obtained maximum reconnection
rate is around $0.05$ to $0.1$, which will be able to reach around $0.1$ to
$0.2$ if injection scales are comparable to the sheet length.",1509.07703v2
2015-09-26,Destroying coherence in high temperature superconductors with current flow,"The loss of single-particle coherence going from the superconducting state to
the normal state in underdoped cuprates is a dramatic effect that has yet to be
understood. Here, we address this issue by performing angle resolved
photoemission spectroscopy (ARPES) measurements in the presence of a transport
current. We find that the loss of coherence is associated with the development
of an onset in the resistance, in that well before the midpoint of the
transition is reached, the sharp peaks in the ARPES spectra are completely
suppressed. Since the resistance onset is a signature of phase fluctuations,
this implies that the loss of single-particle coherence is connected with the
loss of long-range phase coherence.",1509.07937v3
2015-11-11,The Effect of Large Scale Magnetic Field on Outflow in ADAFs: an Odd Symmetry Configuration,"We construct self-similar inflow-outflow solutions for a hot
viscous-resistive accretion flow with large scale magnetic fields that have odd
symmetry with respect to the equatorial plane in $B_\theta$, and even symmetry
in $B_r$ and $B_\phi$. Following previous authors, we also assume that the
polar velocity $v_\theta$ is nonzero. We focus on four parameters:
$\beta_{r0}$, $\beta_{\phi0}$ (the plasma beta parameters for associated with
magnetic field components at the equatorial plane), the magnetic resistivity
$\eta_0$, and the density index $n=-d\ln\rho/d\ln r$. The resulting flow
solutions are divided into two parts consisting of an inflow region with a
negative radial velocity ($v_r<0$) and an outflow region with $v_r>0$. Our
results show that stronger outflows emerge for smaller $\beta_{r0}$
($\le10^{-2}$ for $n>1$) and larger values of $\beta_{\phi0}$, $\eta_0$ and
$n$.",1511.04366v1
2015-12-08,On hybrid circuits exploiting thermistive properties of slime mould,"Slime mould Physarum polycephalum is a single cell visible by unaided eye.
Let the slime mould span two electrodes with a single protoplasmic tube: if the
tube is heated to approximately 40{\deg}C, the electrical resistance of the
protoplasmic tube increases from 3 M{\Omega} to approximatively 10'000
M{\Omega}. The organism's resistance is not proportional nor correlated to the
temperature of its environment. Slime mould can therefore not be considered as
a thermistor but rather as a thermic switch. We employ the P. polycephalum
thermic switch to prototype hybrid electrical analog summator, NAND gates, and
cascade the gates into Flip-Flop latch. Computing operations performed on this
bio-hybrid computing circuitry feature high repeatability, reproducibility and
comparably low propagation delays",1512.02483v1
2015-12-11,Dynamical Decentralized Voltage Control of Multi-Terminal HVDC Grids,"High-voltage direct current (HVDC) is a commonly used technology for
long-distance electric power transmission, mainly due to its low resistive
losses. When connecting multiple HVDC lines into a multi-terminal HVDC (MTDC)
system, several challenges arise. To ensure safe and efficient operation of
MTDC systems, the voltage of all terminals need to be steered to within an
operational range. In this paper we study the commonly used decentralized
voltage droop controller, and show that it in general does not steer the
voltages to within the operational range. We propose a decentralized PI
controller with deadband, and show that it always steers the voltages to within
the operational range regardless of the loads. Additionally we show that the
proposed controller inherits the property of proportional power sharing from
the droop controller, provided that both the loads and the line resistances are
sufficiently low. The results are validated through simulation in MATLAB.",1512.03838v2
2016-01-06,Transfer Printing of CVD Graphene FETs on Patterned Substrates,"We describe a simple and scalable method for the transfer of CVD graphene for
the fabrication of field effect transistors. This is a dry process that uses a
modified RCA cleaning step to improve the surface quality. In contrast to
conventional fabrication routes where lithographic steps are performed after
the transfer, here graphene is transferred to a pre-patterned substrate. The
resulting FET devices display nearly zero Dirac voltage, and the contact
resistance between the graphene and metal contacts is on the order of 910 +-
340 Ohm-micrometer. This approach enables formation of conducting graphene
channel lengths up to one millimeter. The resist-free transfer process provides
a clean graphene surface that is promising for use in high sensitivity graphene
FET biosensors.",1601.01224v1
2016-01-25,A Perceptually Motivated Filter Bank with Perfect Reconstruction for Audio Signal Processing,"Many audio applications rely on filter banks (FBs) to analyze, process, and
re-synthesize sounds. To approximate the auditory frequency resolution in the
signal chain, some applications rely on perceptually motivated FBs, the
gammatone FB being a popular example. However, most perceptually motivated FBs
only allow partial signal reconstruction at high redundancies and/or do not
have good resistance to sub-channel processing. This paper introduces an
oversampled perceptually motivated FB enabling perfect reconstruction,
efficient FB design, and adaptable redundancy. The filters are directly
constructed in the frequency domain and linearly distributed on a perceptual
frequency scale (e.g. ERB, Bark, or Mel scale). The proposed design allows for
various filter shapes, uniform or non-uniform FB setting, and large
down-sampling factors. For redundancies $\geq$ 3 perfect reconstruction is
achieved by computing the canonical dual FB analytically. For lower
redundancies perfect reconstruction is achieved using an iterative method.
Experiments show performance improvements of the proposed approach when
compared to the gammatone FB in terms of reconstruction error and resistance to
sub-channel processing, especially at low redundancies.",1601.06652v1
2016-04-06,The Raspberry model for protein-like particles: ellipsoids and confinement in cylindrical pores,"The study of protein mass transport via atomistic simulation requires time
and length scales beyond the computational capabilities of modern computer
systems. The raspberry model for colloidal particles in combination with the
mesoscopic hydrodynamic method of lattice Boltzmann facilitates coarse-grained
simulations that are on the order of microseconds and hundreds of nanometers
for the study of diffusive transport of protein-like colloid particles. The
raspberry model reproduces linearity in resistance to motion versus particle
size and correct enhanced drag within cylindrical pores at off-center
coordinates for spherical particles. Owing to the high aspect ratio of many
proteins, ellipsoidal raspberry colloid particles were constructed and
reproduced the geometric resistance factors of Perrin and of Happel and Brenner
in the laboratory-frame and in the moving body-frame. Accurate body-frame
rotations during diffusive motion have been captured for the first time using
projections of displacements.",1604.01829v3
2016-04-29,Superconductivity and abnormal pressure effect in Sr0.5La0.5FBiSe2 superconductor,"Through the solid state reaction method, we synthesized a new BiSe2-based
superconductor Sr0:5La0:5FBiSe2 with superconducting transition temperature
Tc?3.8 K. A strong diamagnetic signal below Tc in susceptibility ?(T) is
observed indicating the bulk nature of superconductivity. Different to most
BiS2-based compounds where superconductivity develops from a
semiconducting-like normal state, the present compound exhibits a metallic
behavior down to Tc. Under weak magnetic field or pressure, however, a
remarkable crossover from metallic to insulating behaviors takes place around
Tmin where the resistivity picks up a local minimum. With increasing pressure,
Tc decreases monotonously and Tmin shifts to high temperatures, while the
absolute value of the normal state resistivity at low temperatures first
decreases and then increases with pressure up to 2.5 GPa. These results imply
that the electronic structure of Sr0:5La0:5FBiSe2 may be different to those in
the other BiS2-based systems.",1604.08686v1
2016-05-04,Eco-friendly gas mixtures for Resistive Plate Chambers based on Tetrafluoropropene and Helium,"Due to the recent restrictions deriving from the application of the Kyoto
protocol, the main components of the gas mixtures presently used in the
Resistive Plate Chambers systems of the LHC experiments will be most probably
phased out of production in the coming years. Identifying possible replacements
with the adequate characteristics requires an intense R&D, which was recently
started, also in collaborations across the various experiments. Possible
candidates have been proposed and are thoroughly investigated. Some tests on
one of the most promising candidate - HFO-1234ze, an allotropic form of
tetrafluoropropane- have already been reported. Here an innovative approach,
based on the use of Helium, to solve the problems related to the too elevate
operating voltage of HFO-1234ze based gas mixtures, is discussed and the
relative first results are shown.",1605.01691v1
2016-05-07,Numerical study on the effect of design parameters and spacers on RPC signal and timing properties,"Numerical calculations have been performed to understand the reason for the
observed non-uniform response of a Resistive Plate Chamber (RPC) in a few
critical regions such as near edge spacers and corners of the device. In this
context, the signal from a RPC due to the passage of muons through different
regions has been computed. Also, a simulation of RPC timing properties is
presented along with the effect of the applied field, gas mixture and
geometrical components.",1605.02154v3
2016-05-26,Preliminary results of Resistive Plate Chambers operated with eco-friendly gas mixtures for application in the CMS experiment,"The operations of Resistive Plate Chambers in LHC experiments require
Fluorine based (F-based) gases for optimal performance. Recent European
regulations demand the use of environmentally unfriendly F-based gases to be
limited or banned. In view of the CMS experiment upgrade, several tests are
ongoing to measure the performance of the detector with these new ecological
gas mixtures, in terms of efficiency, streamer probability, induced charge and
time resolution. Prototype chambers with readout pads and with the standard CMS
electronic setup are under test. In this paper preliminary results on
performance of RPCs operated with a potential eco-friendly gas candidate
1,3,3,3-Tetrafluoropropene, commercially known as HFO-1234ze, with CO2 and CF3I
based gas mixtures are presented and discussed for the possible application in
the CMS experiment.",1605.08172v1
2016-05-31,First results of CMS RPC performance at 13 TeV,"The muon spectrometer of the CMS (Compact Muon Solenoid) experiment at the
Large Hadron Collider (LHC) is equipped with a redundant system made of
Resistive Plate Chambers (RPCs) and Drift Tube (DT) chambers in the barrel, RPC
and Cathode Strip Chambers (CSCs) in the endcap region. In this paper, the
first results of the performance of the RPC system during 2015 with the LHC
running at 13 TeV is presented. The stability of the RPC performance, in terms
of efficiency, cluster size and noise, is reported.",1605.09521v3
2016-07-21,Magnetocapacitance oscillations and thermoelectric effect in two-dimensional electron gas irradiated by microwaves,"To study the influence of microwave irradiation on two-dimensional electrons,
we apply a method based on capacitance measurements in GaAs quantum well
samples where the gate covers a central part of the layer. We find that the
capacitance oscillations at high magnetic fields, caused by the oscillations of
thermodynamic density of states, are not essentially modified by microwaves.
However, in the region of fields below 1 Tesla, we observe another set of
oscillation, with the period and the phase identical to those of microwave
induced resistance oscillations. The phenomenon of microwave induced
capacitance oscillations is explained in terms of violation of the Einstein
relation between conductivity and the diffusion coefficient in the presence of
microwaves, which leads to a dependence of the capacitor charging on the
anomalous conductivity. We also observe microwave-induced oscillations in the
capacitive response to periodic variations of external heating. These
oscillations appear due to the thermoelectric effect and are in antiphase with
microwave induced resistance oscillations because of the Corbino-like geometry
of our experimental setup.",1607.06435v1
2016-08-01,TorBricks: Blocking-Resistant Tor Bridge Distribution,"Tor is currently the most popular network for anonymous Internet access. It
critically relies on volunteer nodes called bridges for relaying Internet
traffic when a user's ISP blocks connections to Tor. Unfortunately, current
methods for distributing bridges are vulnerable to malicious users who obtain
and block bridge addresses. In this paper, we propose TorBricks, a protocol for
distributing Tor bridges to n users, even when an unknown number t < n of these
users are controlled by a malicious adversary. TorBricks distributes O(tlog(n))
bridges and guarantees that all honest users can connect to Tor with high
probability after O(log(t)) rounds of communication with the distributor.
  We also extend our algorithm to perform privacy-preserving bridge
distribution when run among multiple untrusted distributors. This not only
prevents the distributors from learning bridge addresses and bridge assignment
information, but also provides resistance against malicious attacks from a m/3
fraction of the distributors, where m is the number of distributors.",1608.00509v1
2016-10-03,"Beyond ideal magnetohydrodynamics: Resistive, reactive and relativistic plasmas","We develop a new framework for the modelling of charged fluid dynamics in
general relativity. The model, which builds on a recently developed variational
multi-fluid model for dissipative fluids, accounts for relevant effects like
the inertia of both charge currents and heat and, for mature systems, the
decoupling of superfluid components. We discuss how the model compares to
standard relativistic magnetohydronamics and consider the connection between
the fluid dynamics, the microphysics and the underlying equation of state. As
illustrations of the formalism, we consider three distinct two-fluid models
describing i) an Ohm's law for resistive charged flows, ii) a relativistic heat
equation, and iii) an equation representing the momentum of a decoupled
superfluid component. As a more complex example, we also formulate a
three-fluid model which demonstrates the thermo-electric effect. This framework
allows us to model neutron stars (and related systems) at a hierarchy of
increasingly complex levels, and should enable us to make progress on a range
of exciting problems in astrophysics and cosmology.",1610.00449v1
2016-10-13,Straintronic magneto-tunneling-junction based ternary content addressable memory,"Straintronic magneto-tunneling junction (s-MTJ) switches, whose resistances
are controlled with voltage-generated strain in the magnetostrictive free layer
of the MTJ, are extremely energy-efficient switches that would dissipate a few
aJ of energy during switching. Unfortunately, they are also relatively
error-prone and have low resistance on/off ratio. This suggests that as
computing elements, they are best suited for non-Boolean architectures. Here,
we propose and analyze a ternary content addressable memory implemented with
s-MTJs and some transistors. It overcomes challenges encountered by traditional
all-transistor implementations, resulting in exceptionally high cell density.",1610.03902v2
2016-10-17,Topological quantum phase transition and superconductivity induced by pressure in the bismuth tellurohalide BiTeI,"A pressure-induced topological quantum phase transition has been
theoretically predicted for the semiconductor BiTeI with giant Rashba spin
splitting. In this work, the evolution of the electrical transport properties
in BiTeI and BiTeBr is investigated under high pressure. The pressure-dependent
resistivity in a wide temperature range passes through a minimum at around 3
GPa, indicating the predicted transition in BiTeI. Superconductivity is
observed in both BiTeI and BiTeBr while the resistivity at higher temperatures
still exhibits semiconducting behavior. Theoretical calculations suggest that
the superconductivity may develop from the multi-valley semiconductor phase.
The superconducting transition temperature Tc increases with applied pressure
and reaches a maximum value of 5.2 K at 23.5 GPa for BiTeI (4.8 K at 31.7 GPa
for BiTeBr), followed by a slow decrease. Our results demonstrate that BiTeX (X
= I, Br) compounds with non-trivial topology of electronic states display new
ground states upon compression.",1610.05364v1
2016-11-29,Sub 100nW volatile nano-metal-oxide memristor as synaptic-like encoder of neuronal spikes,"Advanced neural interfaces mediate a bio-electronic link between the nervous
system and microelectronic devices, bearing great potential as innovative
therapy for various diseases. Spikes from a large number of neurons are
recorded leading to creation of big data that require on-line processing under
most stringent conditions, such as minimal power dissipation and on-chip space
occupancy. Here, we present a new concept where the inherent volatile
properties of a nano-scale memristive device are used to detect and compress
information on neural spikes as recorded by a multi-electrode array.
Simultaneously, and similarly to a biological synapse, information on spike
amplitude and frequency is transduced in metastable resistive state transitions
of the device, which is inherently capable of self-resetting and of continuous
encoding of spiking activity. Furthermore, operating the memristor in a very
high resistive state range reduces its average in-operando power dissipation to
less than 100 nW, demonstrating the potential to build highly scalable, yet
energy-efficient on-node processors for advanced neural interfaces.",1611.09671v1
2016-12-21,Magnetotransport studies of Superconducting Pr$_4$Fe$_2$As$_2$Te$_{1-x}$O$_4$,"We report a detailed study of the electrical transport properties of single
crystals of Pr$_4$Fe$_2$As$_2$Te$_{1-x}$O$_4$, a recently discovered iron-based
superconductor. Resistivity, Hall effect and magnetoresistance are measured in
a broad temperature range revealing the role of electrons as dominant charge
carriers. The significant temperature dependence of the Hall coefficient and
the violation of Kohler's law indicate multiband effects in this compound. The
upper critical field and the magnetic anisotropy are investigated in fields up
to 16 T, applied parallel and perpendicular to the crystallographic c-axis.
Hydrostatic pressure up to 2 GPa linearly increases the critical temperature
and the resistivity residual ratio. A simple two-band model is used to describe
the transport and magnetic properties of Pr$_4$Fe$_2$As$_2$Te$_{1-x}$O$_4$. The
model can successfully explain the strongly temperature dependent negative Hall
coefficient and the high magnetic anisotropy assuming that the mobility of
electrons is higher than that of holes.",1612.07090v1
2016-12-23,Strained graphene Hall bar,"The effects of strain, induced by a Gaussian bump, on the magnetic field
dependent transport properties of a graphene Hall bar are investigated. The
numerical simulations are performed using both classical and quantum mechanical
transport theory and we found that both approaches exhibit similar
characteristic features. The effects of the Gaussian bump are manifested by a
decrease of the bend resistance, $R_B$, around zero-magnetic field and the
occurrence of side-peaks in $R_B$. These features are explained as a
consequence of bump-assisted scattering of electrons towards different
terminals of the Hall bar. Using these features we are able to give an estimate
of the size of the bump. Additional oscillations in $R_B$ are found in the
quantum description that are due to the population/depopulation of Landau
levels. The bump has a minor influence on the Hall resistance even for very
high values of the pseudo-magnetic field. When the bump is placed outside the
center of the Hall bar valley polarized electrons can be collected in the
leads.",1612.07995v1
2017-02-01,Superzone gap formation and low lying crystal electric field levels in PrPd$_2$Ge$_2$ single crystal,"The magnetocrystalline anisotropy exhibited in PrPd$_2$Ge$_2$ single crystal
has been investigated by measuring the magnetization, magnetic susceptibility,
electrical resistivity and heat capacity. PrPd$_2$Ge$_2$ crystallizes in the
well known ThCr$_2$Si$_2$\--type tetragonal structure. The antiferromagnetic
ordering is confirmed as 5.1~K with the [001]-axis as the easy axis of
magnetization. A superzone gap formation is observed from the electrical
resistivity measurement when the current is passed along the [001] direction.
The crystal electric field (CEF) analysis on the magnetic susceptibility,
magnetization and the heat capacity measurements confirms a doublet ground
state with a relatively low over all CEF level splitting. The CEF level
spacings and the Zeeman splitting at high fields become comparable and lead to
metamagnetic transition at 34~T due to the CEF level crossing.",1702.00220v1
2017-02-08,Giant microwave-induced $B$-periodic magnetoresistance oscillations in a two-dimensional electron gas with a bridged-gate tunnel point contact,"We have studied the magnetoresistance of the quantum point contact fabricated
on the high mobility two-dimensional electron gas (2DEG) exposed to microwave
irradiation. The resistance reveals giant $B$-periodic oscillations with the
relative amplitude $\Delta R/R$ of up to $700$\% resulting from the propagation
and interference of the edge magnetoplasmons (EMPs) in the sample. This giant
photoconductance is attributed to the considerably large local electron density
modulation in the vicinity of the point contact. We have also analyzed the
oscillation periods $\Delta B$ of the resistance oscillations and, comparing
the data with the EMP theory, extracted the EMP interference length $L$. We
have found that the length $L$ substantially exceeds the distance between the
contact leads but rather corresponds to the distance between metallic contact
pads measured along the edge of the 2DEG. This resolves existing controversy in
the literature and should help to properly design highly sensitive microwave
and terahertz spectrometers based on the discussed effect.",1702.02309v1
2017-05-31,An upper bound on transport,"The linear growth of operators in local quantum systems leads to an effective
lightcone even if the system is non-relativistic. We show that consistency of
diffusive transport with this lightcone places an upper bound on the
diffusivity: $D \lesssim v^2 \tau_\text{eq}$. The operator growth velocity $v$
defines the lightcone and $\tau_\text{eq}$ is the local equilibration
timescale, beyond which the dynamics of conserved densities is diffusive. We
verify that the bound is obeyed in various weakly and strongly interacting
theories. In holographic models this bound establishes a relation between the
hydrodynamic and leading non-hydrodynamic quasinormal modes of planar black
holes. Our bound relates transport data --- including the electrical
resistivity and the shear viscosity --- to the local equilibration time, even
in the absence of a quasiparticle description. In this way, the bound sheds
light on the observed $T$-linear resistivity of many unconventional metals, the
shear viscosity of the quark-gluon plasma and the spin transport of unitary
fermions.",1706.00019v2
2017-10-10,Transport coefficients from QCD Kondo effect,"We study the transport coefficients from the QCD Kondo effect in quark matter
which contains heavy quarks as impurity particles. We estimate the coupling
constant of the interaction between a light quark and a heavy quark at finite
density and temperature by using the renormalization group equation up to
two-loop order. We also estimate the coupling constant at zero temperature by
using the mean-field approximation as non-perturbative treatment. To calculate
the transport coefficients, we use the relativistic Boltzmann equation and
apply the relaxation time approximation. We calculate the electric resistivity
from the relativistic kinetic theory, and the viscosities from the relativistic
hydrodynamics. We find that the electric resistivity is enhanced and the shear
viscosity is suppressed due to the QCD Kondo effect at low temperature.",1710.03434v2
2017-10-17,Superconductivity of Cobalt in Thin Films,"Due to competing long range ferromagnetic order, the transition metals Fe, Co
and Ni are not superconductors at ambient pressure. While superconductivity was
observed in a non-magnetic phase of Fe, stabilized under pressure, it is yet to
be discovered in Co and Ni under any experimental conditions. Here, we report
emergence of superconductivity in the recently discovered high-density
nonmagnetic face centered cubic phase in Co thin films below a transition
temperature (Tc) of ~5.4 K, as revealed in experiments based on point-contact
spectroscopy and resistance, and four-probe measurements of resistance at
ambient pressure. We confirm the non-magnetic nature of the dense fcc phase of
Co within first-principles density functional theory, and show that its
superconductivity below 5 K originates from anomalous softening of
zone-boundary phonons and their enhanced coupling with electrons upon biaxial
strain.",1710.06114v1
2017-10-29,Gauge Topological Nature of the Superconductor-Insulator Transition,"It has long been believed that, at absolute zero, electrons can form only one
quantum coherent state, a superconductor. Yet, several two dimensional
superconducting systems were found to harbor the superinsulating state with
infinite resistance, a mirror image of superconductivity, and a metallic state
often referred to as Bose metal, characterized by finite longitudinal and
vanishing Hall resistances. The nature of these novel and mysterious quantum
coherent states is the subject of intense study.Here, we propose a topological
gauge description of the superconductor-insulator transition (SIT) that enables
us to identify the underlying mechanism of superinsulation as Polyakov's linear
confinement of Cooper pairs via instantons. We find a criterion defining
conditions for either a direct SIT or for the SIT via the intermediate Bose
metal and demonstrate that this Bose metal phase is a Mott topological
insulator in which the Cooper pair-vortex liquid is frozen by Aharonov-Bohm
interactions.",1710.10575v2
2018-01-09,Direct Detection of Ultralight Dark Matter via Astronomical Ephemeris,"A novel idea of the direct detection to search for a ultralight dark matter
based on the interaction between the dark matter and a nucleon is proposed.
Solar system bodies feel the dark matter wind and it acts as a resistant force
opposing their motions. The astronomical ephemeris of solar system bodies is so
precise that it has a strong capability to detect a dark matter whose mass is
much lighter than O(1) eV. We have estimated the resistant force based on the
calculation of the elastic scattering cross section between the dark matter and
the bodies beyond the Born approximation, and show that the astronomical
ephemeris indeed put a very strong constraint on the interaction between the
dark matter and a nucleon, depending on how smoothly the ultralight dark matter
is distributed at the scale smaller than the celestial bodies in our solar
system.",1801.02807v1
2018-01-09,Flare particle acceleration in the interaction of twisted coronal flux ropes,"The aim of this work is to investigate and characterise non-thermal particle
behaviour in a three-dimensional (3D) magnetohydrodynamical (MHD) model of
unstable multi-threaded flaring coronal loops. We have used a numerical scheme
which solves the relativistic guiding centre approximation to study the motion
of electrons and protons. The scheme uses snapshots from high resolution
numerical MHD simulations of coronal loops containing two threads, where a
single thread becomes unstable and (in one case) destabilises and merges with
an additional thread. The particle responses to the reconnection and
fragmentation in MHD simulations of two loop threads are examined in detail. We
illustrate the role played by uniform background resistivity and distinguish
this from the role of anomalous resistivity using orbits in an MHD simulation
where only one thread becomes unstable without destabilising further loop
threads. We examine the (scalable) orbit energy gains and final positions
recovered at different stages of a second MHD simulation wherein a secondary
loop thread is destabilised by (and merges with) the first thread. We compare
these results with other theoretical particle acceleration models in the
context of observed energetic particle populations during solar flares.",1801.02907v1
2018-02-12,First FBK Production of 50$μ$m Ultra-Fast Silicon Detectors,"Fondazione Bruno Kessler (FBK, Trento, Italy) has recently delivered its
first 50 $\mu$m thick production of Ultra-Fast Silicon Detectors (UFSD), based
on the Low-Gain Avalanche Diode design. These sensors use high resistivity
Si-on-Si substrates, and have a variety of gain layer doping profiles and
designs based on Boron, Gallium, Carbonated Boron and Carbonated Gallium to
obtain a controlled multiplication mechanism. Such variety of gain layers will
allow identifying the most radiation hard technology to be employed in the
production of UFSD, to extend their radiation resistance beyond the current
limit of $\phi \sim$ 10$^{15}$ n$_{eq}$/cm$^2$. In this paper, we present the
characterisation, the timing performances, and the results on radiation damage
tolerance of this new FBK production.",1802.03988v2
2018-02-12,"A candidate Theory for the ""Strange Metal"" phase at Finite Energy Window","We propose a lattice model for strongly interacting electrons with the
potential to explain the main phenomenology of the strange metal phase in the
cuprate high temperature superconductors. Our model is motivated by the
recently developed ""tetrahedron"" rank-3 tensor model that mimics much of the
physics of the better-known Sachdev-Ye-Kitaev (SYK) model. Our electron model
has the following advantageous properties: (1) it only needs one orbital per
site on the square lattice; (2) it does not require any quenched random
interaction; (3) it has local interactions and respects all the symmetries of
the system; (4) the soluble limit of this model has a longitudinal DC
resistivity that scales linearly with temperature within a finite temperature
window; (5) again the soluble limit of this model has a fermion pairing
instability in the infrared, which can lead to either superconductivity or a
""pseudogap"" phase. The linear$-T$ longitudinal resistivity and the pairing
instability originate from the generic scaling feature of the SYK model and the
tetrahedron tensor model.",1802.04293v2
2018-02-22,Negative differential resistance in Van der Waals heterostructures due to moiré-induced spectral reconstruction,"Formation of moir\'{e} superlattices is common in Van der Waals
heterostructures as a result of the mismatch between lattice constants and
misalignment of crystallographic directions of the constituent two-dimensional
crystals. We discuss theoretically electron transport in a Van der Waals
tunnelling transistor in which one of the electrodes is made of two crystals
forming a moir\'{e} superlattice at their interface. By investigating
structures containing either the aligned graphene/hexagonal boron nitride
heterostructure or twisted bilayer graphene, we show that negative differential
resistance is possible in such transistors as a consequence of the
superlattice-induced changes in the electronic density of states and without
the need of momentum conserving tunnelling present in high-quality exfoliated
devices.",1802.08100v3
2018-04-10,Development of Integration-Type Silicon-On-Insulator Monolithic Pixel Detectors by Using a Float Zone Silicon,"In this paper, we describe the development of monolithic pixel detectors by
using a Silicon-on-Insulator (SOI) technology for X-ray and charged particle
applications. The detectors are based on a 0.2 {\mu}m CMOS fully depleted SOI
process (Lapis Semiconductor Co., Ltd). The SOI wafer consists of a thick
high-resistivity substrate for sensing and a thin low resistivity Si layer for
CMOS circuits.
  We developed the integration-type SOI pixel detector, INTPIX4 mainly for
X-ray imaging; it is made of a Float Zone (FZ) or Czochralski (Cz) silicon
wafer. Since 2005, Cz SOI detectors were used initially. After 2011, FZ SOI
detectors were successfully fabricated. In this paper, we state recent
progresses and test results of the SOI monolithic pixel detector using a FZ
silicon and compare them with the results obtained using the Cz detector.",1804.03338v1
2018-05-07,Vacuum-dressed cavity magnetotransport of a 2D electron gas,"We present a theory predicting how the linear magnetotransport of a
two-dimensional electron gas is modified by a passive electromagnetic cavity
resonator where no real photons are injected nor created. For a cavity photon
mode with in-plane linear polarization, the dc bulk magnetoresistivity of the
2D electron gas is anisotropic. In the regime of high filling factors of the
Landau levels, the envelope of the Shubnikov-de Haas oscillations is profoundly
modified and the resistivity can be increased or reduced depending on the
system parameters. In the limit of low magnetic fields, the resistivity along
the cavity-mode polarization direction is enhanced in the ultrastrong
light-matter coupling regime. Our work shows the crucial role of virtual
polariton excitations in controlling the dc charge transport properties of
cavity-embedded systems.",1805.02623v2
2018-06-09,Streamer studies in Resistive Plate Chambers,"The present paper is meant as an update of the presentation given in a
previous Resistive Plate Chamber (RPC) workshop, aimed at finding an
eco-friendly gas mixture for streamer operation of RPCs. Indeed the streamer
working regime is still suitable for building large RPC systems dedicated to
low rate applications, such as cosmic ray and neutrino physics. In addition to
other studies about gas mixtures for streamer mode operation, in this paper the
replacement of R134a with CF4, a gas widely used in other gaseous detectors,
has been investigated. The effect of the gas gap thickness on the discharge
quenching has also been studied; this is an important check because thin gas
gaps of 1 mm, one half of the typical used value, have been introduced for high
rate applications. Finally preliminar results about the streamer formation
timing are also reported.",1806.03443v2
2018-09-04,Linear Wave Propagation for Resistive Relativistic Magnetohydrodynamics,"We present a linear mode analysis of the relativistic MHD equations in the
presence of finite electrical conductivity. Starting from the fully
relativistic covariant formulation, we derive the dispersion relation in the
limit of small linear perturbations. It is found that the system supports ten
wave modes which can be easily identified in the limits of small or large
conductivities. In the resistive limit, matter and electromagnetic fields
decouple and solution modes approach pairs of light and acoustic waves as well
as a number of purely damped (non-propagating) modes. In the opposite (ideal)
limit, the frozen-in condition applies and the modes of propagation coincide
with a pair of fast magnetosonic, a pair of slow and Alfv\'en modes, as
expected. In addition, the contact mode is always present and it is unaffected
by the conductivity. For finite values of the conductivity, the dispersion
relation gives rise to either pairs of opposite complex conjugate roots or
purely imaginary (damped) modes. In all cases, the system is dissipative and
also dispersive as the phase velocity depends nonlineary on the wavenumber.
Occasionally, the group velocity may exceed the speed of light although this
does not lead to superluminal signal propagation.",1809.01115v1
2018-09-16,Temperature-dependent transport measurements with Arduino,"The current performances of single-board microcontrollers render them
attractive not only for basic applications but also for more elaborate
projects, amongst which physics teaching or research. In this article, we show
how temperature-dependent transport measurements can be performed using an
Arduino microcontroller, from cryogenic temperatures up to room temperature or
above. We focus on two of the main issues for this type of experiments: the
determination of the sample temperature and the measurement of its resistance.
We also detail two student-led experiments: evidencing the magnetocaloric
effect in Gadolinium and measuring the resistive transition of a high critical
temperature superconductor.",1809.08075v1
2018-09-27,Impact of Integrated Circuit Packaging on Synaptic Dynamics of Memristive Devices,"The memristor can be used as non volatile memory (NVM) and for emulating
neuron behavior. It has the ability to switch between low resistance $R_{on}$
and high resistance values $R_{off}$, and exhibit the synaptic dynamic
behaviour such as potentiation and depression. This paper presents a study on
potentiation and depression of memristors in Quad Flat Pack. A comparison is
drawn between the memristors with and without the impact of parasitics of
packaging, using measured data and equivalent circuit models. The parameters in
memristor and packaging models for the SPICE simulations were determined using
measured data to reflect the memristor parasitics in Quad Flat Packs.",1809.10434v1
2019-09-30,Numerical simulation of magnetic reconnection around a black hole,"We performed numerical simulations of general relativistic
magnetohydrodynamics with uniform resistivity to investigatethe occurrence of
magnetic reconnection in a split-monopole magnetic field around a Schwarzschild
black hole. We found that magnetic reconnection happens near the black hole at
its equatorial plane. The magnetic reconnection has a point-like reconnection
region and slow shock waves, as in the Petschek reconnection model. The
magnetic reconnection rate decreases as the resistivity becomes smaller. When
the global magnetic Reynolds number is $10^4$ or larger, the magnetic
reconnection rate increases linearly with time from $2 \tau_{\rm S}$ to $\sim
10 \tau_{\rm S}$ ($\tau_{\rm S}=r_{\rm S}/c, r_{\rm S}$ is the Schwarzschild
radius and $c$ is the speed of light). The linear increase of the reconnection
rate agrees with the magnetic reconnection in the Rutherford regime of the
tearing mode instability.",1909.13414v1
2014-08-01,"The linear tearing instability in three dimensional, toroidal gyrokinetic simulations","Linear gyro-kinetic simulations of the classical tearing mode in
three-dimensional toroidal geometry were performed using the global gyro
kinetic turbulence code, GKW . The results were benchmarked against a
cylindrical ideal MHD and analytical theory calculations. The stability, growth
rate and frequency of the mode were investigated by varying the current
profile, collisionality and the pressure gradients. Both collision-less and
semi-collisional tearing modes were found with a smooth transition between the
two. A residual, finite, rotation frequency of the mode even in the absense of
a pressure gradient is observed which is attributed to toroidal finite
Larmor-radius effects. When a pressure gradient is present at low
collisionality, the mode rotates at the expected electron diamagnetic
frequency. However the island rotation reverses direction at high
collisionality. The growth rate is found to follow a $\eta^{1/7}$ scaling with
collisional resistivity in the semi-collisional regime, closely following the
semi-collisional scaling found by Fitzpatrick. The stability of the mode
closely follows the stability using resistive MHD theory, however a
modification due to toroidal coupling and pressure effects is seen.",1408.0112v1
2014-08-01,Development of Multi-gap Resistive Plate Chamber (MRPC) for medical imaging,"The low cost and high resolution Multi-gap Resistive Plate Chamber (MRPC)
opens up a new possibility to find an efficient alternative detector for the
Time of Flight (TOF) based Positron Emission Tomography, where the sensitivity
of the system depends largely on the time resolution of the detector. In a
layered structure, suitable converters can be used to increase the photon
detection efficiency. In this paper results of the cosmic ray test of a
four-gap bakelite-based prototype MRPC operated in streamer mode and six-gap
glass-based MRPC operated in avalanche mode are discussed.",1408.0280v1
2014-08-17,Quantum criticality in two dimensions and Marginal Fermi Liquid,"Kinetic properties of a two dimensional model of fermions interacting with
antiferromagnetic spin excitations near the quantum critical point (QCP) are
considered. The temperature or doping are assumed to be sufficiently high, such
that the pseudogap does not appear. In contrast to standard spin-fermion
models, it is assumed that there are intrinsic inhomogeneities in the system
suppressing space correlations of the antiferromagnetic excitations. It is
argued that the inhomogeneities in the spin excitations in the ""strange metal""
phase can be a consequence of existence of $\pi $-shifted domain walls in the
doped antiferromagnetic phase. Averaging over the inhomogeneities and
calculating physical quantities like resistivity and some others one can
explain unusual properties of cuprates unified under the name ""Marginal Fermi
Liquid"" (MFL). The dependence of the slope of the linear temperature dependence
of the resistivity on doping is compared with experimental data.",1408.3865v3
2017-03-29,Illumination effect by visible continuous-wave laser on bulk 40 K-superconductors,"Visible CW (continuous wave) -laser heating effects on the bulk
superconductors CeFeAsO0.65F0.35 and MgB2 with 1.5 mm thickness have been
investigated by measuring the temperature dependence of electrical resistivity.
Each compound shows a critical-temperature Tc reduction with increasing fluence
rate. At the normal state, a parallel circuit model based on the Fourier's law
can well reproduce the temperature dependence of electrical resistivity of
illuminated sample. On the other hand, the predicted temperature-rise due to
the laser heating in the superconducting state is much smaller than the
observed Tc-reduction. A temperature gradient of a few K across the sample
thickness easily triggers the destruction of bulk superconductivity.
Furthermore we have found a slight Tc-enhancement in CeFeAsO0.65F0.35 after a
rather high fluence-rate irradiation.",1703.10270v1
2004-06-12,Thermally-activated current transport in MgB_2 films,"Thermally-activated flux flow (TAFF) resistivity above the irreversibility
field is reported for two different c-axis textured MgB_2 superconducting
films. Transport measurements at different perpendicular magnetic fields 0 < B
< 9 T and temperatures from 5 to 40K reveal TAFF Ohmic resistivity described by
the Arrhenius law with the quadratic field dependence of the activation energy.
Our transport measurements on bulk MgB_2 ceramic samples also show the TAFF
behavior, but do not show the quadratic field dependence of U(T,B). We explain
our results in terms of thermally-activated drift of pre-existing quenched
dislocations in the vortex lattice. Our results indicate that thermal
fluctuations can be essential in determining the irreversibility field in MgB2
though to a much lesser extent than in high-temperature superconductors.",0406294v1
2011-07-05,Parametric oscillator based on non-linear vortex dynamics in low resistance magnetic tunnel junctions,"Radiofrequency vortex spin-transfer oscillators based on magnetic tunnel
junctions with very low resistance area product were investigated. A high power
of excitations has been obtained characterized by a power spectral density
containing a very sharp peak at the fundamental frequency and a series of
harmonics. The observed behaviour is ascribed to the combined effect of spin
transfer torque and Oersted-Amp\`ere field generated by the large applied
dc-current. We furthermore show that the synchronization of a vortex
oscillation by applying a ac bias current is mostly efficient when the external
frequency is twice the oscillator fundamental frequency. This result is
interpreted in terms of a parametric oscillator.",1107.0867v2
2013-12-02,Robust superconductivity with large upper critical field in Nb2PdS5,"We report synthesis, structural details and complete superconducting
characterization of very recently discovered Nb2PdS5 new superconductor. The
synthesized compound is crystallized in mono-clinic structure. Bulk
superconductivity is seen in both magnetic susceptibility and electrical
resistivity measurements with superconducting transition temperature (Tc) at
6K. The upper critical field (Hc2), being estimated from high field
magneto-transport measure-ments is above 240kOe. The estimated Hc2(0) is
clearly above the Pauli paramagnetic limit. Heat capacity measurements show
clear transition with well defined peak at Tc, but with lower jump than as
expected for a BCS type superconductor. The Sommerfield constant and Debye
temperature as determined from low temperature fitting of heat capacity data
are 32mJ/moleK2 and 263K respectively. Hall coefficients and resistivity in
conjugation with electronic heat capacity indicates multiple gap
superconductivity signatures in Nb2PdS5. We also studied the impact of
hydrostatic pressure on superconductivity of Nb2PdS5 and found nearly no change
in Tc for the given pressure range.",1312.0425v5
2013-12-12,Pressure-induced superconductivity in EuFe2As2 without a quantum critical point: magnetotransport and upper critical field measurements under high pressure,"Resistivity and Hall effect measurements of EuFe$_2$As$_2$ up to 3.2\,GPa
indicate no divergence of quasiparticle effective mass at the pressure
$P_\mathrm{c}$ where the magnetic and structural transition disappears. This is
corroborated by analysis of the temperature ($T$) dependence of the upper
critical field. $T$-linear resistivity is observed at pressures slightly above
$P_\mathrm{c}$. The scattering rates for both electrons and holes are shown to
be approximately $T$-linear. When a field is applied, a $T^2$ dependence is
recovered, indicating that the origin of the $T$-linear dependence is spin
fluctuations.",1312.3380v1
2013-12-25,"Ambipolar Transport and Magneto-resistance Crossover in a Mott Insulator, Sr$_{2}$IrO$_{4}$","Electric field effect (EFE) controlled magnetoelectric transport in thin
films of undoped and La-doped Sr$_{2}$IrO$_{4}$ (SIO) were investigated under
the action of ionic liquid gating. Despite large carrier density modulation,
the temperature dependent resistance measurements exhibit insulating behavior
in chemically and EFE doped samples with the band filling up to 10\%. The
ambipolar transport across the Mott gap is demonstrated by EFE tuning of the
activation energy. Further, we observe a crossover from a negative
magnetoresistance (MR) at high temperatures to positive MR at low temperatures.
The crossover temperature was around $\sim$80-90 K, irrespective of the
filling. This temperature and magnetic field dependent crossover is
qualitatively associated with a change in the conduction mechanism from Mott to
Coulomb gap mediated variable range hopping (VRH). This explains the origin of
robust insulating ground state of SIO in electrical transport studies and
highlights the importance of disorder and Coulombic interaction on electrical
properties of SIO.",1312.7015v2
2014-11-18,Tunneling transport in a few monolayer-thick WS2/graphene heterojunction,"This paper demonstrates the high-quality tunnel barrier characteristics and
layer number controlled tunnel resistance of a transition metal dichalcogenide
(TMD) measuring just a few monolayers in thickness. Investigation of vertical
transport in WS2 and MoS2 TMDs in graphene/TMD/metal heterostructures revealed
that WS2 exhibits tunnel barrier characteristics when its thickness is between
2 to 5 monolayers, whereas MoS2 experiences a transition from tunneling to
thermionic emission transport with increasing thickness within the same range.
Tunnel resistance in a graphene/WS2/metal heterostructure therefore increases
exponentially with the number of WS2 layers, revealing the tunnel barrier
height of WS2 to be 0.37 eV.",1411.4714v2
2016-06-01,Variation of transition temperatures and residual resistivity ratio in vapor-grown FeSe,"The study of the iron-based superconductor FeSe has blossomed with the
availability of high quality single crystals, obtained through
flux/vapor-transport growth techniques below the structural transformation
temperature of its tetragonal phase, T~450 C. Here, we report on the variation
of sample morphology and properties due to small modifications in the growth
conditions. A considerable variation of the superconducting transition
temperature Tc, from 8.8 K to 3 K, which cannot be correlated with the sample
composition, is observed. Instead, we point out a clear correlation between Tc
and disorder, as measured by the residual resistivity ratio. Notably, the
tetragonal-to-orthorhombic structural transition is also found to be quite
strongly disorder dependent (Ts =72 - 90 K), and linearly correlated with Tc.",1606.00500v1
2016-06-14,Effect of atomic disorder and Ce doping on superconductivity of Ca3Rh4Sn13: Electric transport properties under high pressure,"We report the observation of a superconducting state below 8K coexistent with
a spin-glass state caused by atomic disorder in Ce substituted Ca3Rh4Sn13.
Measurements of specific heat, resistivity, and magnetism reveal the existence
of inhomogeneous superconductivity in samples doped with Ce with
superconducting critical temperatures Tc higher than those observed in the
parent compound. For Ca3Rh4Sn13, the negative value of the change in
resistivity with pressure P, correlates well with the calculated decrease in
the density of states at the Fermi energy with P. Based on band structure
calculations performed under pressure, we demonstrate how the change in DOS
would affect Tc of Ca3Rh4Sn13 under negative lattice pressure in samples that
are strongly defected by quenching.",1606.04579v1
2017-01-19,Spin-filtering in superconducting junction with the manganite interlayer,"We report on the electronic transport and the impact of spin-filtering in
mesa-structures made of epitaxial thin films of cuprate superconductor
YBa2Cu3Ox(YBCO) and the manganite LaMnO3 (LMO) interlayer with the Au/Nb
counterelectrode. Ferromagnetic resonance measurements of heterostructure
Au/LMO/YBCO shows ferromagnetic state at temperatures below 150 K as in the
case of reference LMO film grown on the neodymium gallate substrate. The
heights of the tunneling barrier evaluated from resistive characteristics of
mesa-structures at different thickness of interlayer showed an exponential
decrease from 30 mV down to 5 mV with the increase of manganite interlayer
thickness. Temperature dependence of the conductivity of mesa-structures could
be described taking into account the d-wave superconductivity in YBCO and a
spin filtering of the electron transport. Spin filtering is supported also by
measurements of magneto-resistance and the high sensitivity of mesa-structure
conductivity to weak magnetic fields.",1701.05364v1
2017-01-27,Control of superconductivity with a single ferromagnetic layer in niobium/erbium bilayers,"Superconducting spintronics in hybrid superconductor/ferromagnet (S-F)
heterostructures provides an exciting potential new class of device. The
prototypical super-spintronic device is the superconducting spin-valve, where
the critical temperature, $T_c$, of the S-layer can be controlled by the
relative orientation of two (or more) F-layers. Here, we show that such control
is also possible in a simple S/F bilayer. Using field history to set the
remanent magnetic state of a thin Er layer, we demonstrate for a Nb/Er bilayer
a high level of control of both $T_c$ and the shape of the resistive
transition, R(T), to zero resistance. We are able to model the origin of the
remanent magnetization, treating it as an increase in the effective exchange
field of the ferromagnet and link this, using conventional S-F theory, to the
suppression of $T_c$. We observe stepped features in the R(T) which we argue is
due to a fundamental interaction of superconductivity with inhomogeneous
ferromagnetism, a phenomena currently lacking theoretical description.",1701.08065v2
2017-11-08,Mechanical characterization of disordered and anisotropic cellular monolayers,"We consider a cellular monolayer, described using a vertex-based model, for
which cells form a spatially disordered array of convex polygons that tile the
plane. Equilibrium cell configurations are assumed to minimize a global energy
defined in terms of cell areas and perimeters; energy is dissipated via dynamic
area and length changes, as well as cell neighbour exchanges. The model
captures our observations of an epithelium from a Xenopus embryo showing that
uniaxial stretching induces spatial ordering, with cells under net tension
(compression) tending to align with (against) the direction of stretch, but
with the stress remaining heterogeneous at the single-cell level. We use the
vertex model to derive the linearized relation between tissue-level stress,
strain and strain-rate about a deformed base state, which can be used to
characterize the tissue's anisotropic mechanical properties; expressions for
viscoelastic tissue moduli are given as direct sums over cells. When the base
state is isotropic, the model predicts that tissue properties can be tuned to a
regime with high elastic shear resistance but low resistance to area changes,
or vice versa.",1711.02909v2
2017-11-21,Strained graphene structures: from valleytronics to pressure sensing,"Due to its strong bonds graphene can stretch up to 25% of its original size
without breaking. Furthermore, mechanical deformations lead to the generation
of pseudo-magnetic fields (PMF) that can exceed 300 T. The generated PMF has
opposite direction for electrons originating from different valleys. We show
that valley-polarized currents can be generated by local straining of
multi-terminal graphene devices. The pseudo-magnetic field created by a
Gaussian-like deformation allows electrons from only one valley to transmit and
a current of electrons from a single valley is generated at the opposite side
of the locally strained region. Furthermore, applying a pressure difference
between the two sides of a graphene membrane causes it to bend/bulge resulting
in a resistance change. We find that the resistance changes linearly with
pressure for bubbles of small radius while the response becomes non-linear for
bubbles that stretch almost to the edges of the sample. This is explained as
due to the strong interference of propagating electronic modes inside the
bubble. Our calculations show that high gauge factors can be obtained in this
way which makes graphene a good candidate for pressure sensing.",1711.07904v1
2017-12-12,Dynamical Negative Differential Resistance in Antiferromagnetically Coupled Few-Atom Spin-Chains,"We present the appearance of negative differential resistance (NDR) in
spin-dependent electron transport through a few-atom spin-chain. A chain of
three antiferromagnetically coupled Fe atoms(Fe trimer) was positioned on a
Cu2N/Cu(100) surface and contacted with the spin-polarized tip of a scanning
tunneling microscope, thus coupling the Fe trimer to one non-magnetic and one
magnetic lead. Pronounced NDR appears at the low bias of 7 mV where inelastic
electron tunneling dynamically locks the atomic spin in a long-lived excited
state. This causes a rapid increase of the magnetoresistance between
spin-polarized tip and Fe trimer and quenches elastic tunneling. By varying the
coupling strength between tip and Fe trimer we find that in this transport
regime the dynamic locking of the Fe trimer competes with magnetic exchange
interaction, which statically forces the Fe trimer into the
high-magnetoresistance state and removes the NDR.",1712.04213v1
2017-12-12,Scaling Projections on Spin Transfer Torque Magnetic Tunnel Junctions,"We investigate scaling of technologically relevant magnetic tunnel junction
devices in the trilayer and pentalayer configurations by varying the
cross-sectional area along the transverse direction using the non-equilibrium
Green's function spin transport formalism. We study the geometry dependence by
considering square and circular cross-sections. As the transverse dimension in
each case reduces, we demonstrate that the transverse mode energy profile plays
a major role in the resistance-area product. Both types of devices show
constant tunnel magnetoresistance at larger cross-sectional areas but achieve
ultra-high magnetoresistance at small cross-sectional areas, while maintaining
low resistance-area products. We notice that although the critical switching
voltage for switching the magnetization of the free layer nanomagnet in the
trilayer case remains constant at larger areas, it needs more energy to switch
at smaller areas. In the pentalayer case, we observe an oscillatory behavior at
smaller areas as a result of double barrier tunneling. We also describe how
switching characteristics of both kinds of devices are affected by the scaling.",1712.04235v1
2017-12-14,Conductivity of anisotropic inhomogeneous superconductors above critical temperature,"We propose a model and derive analytical expressions for conductivity in
heterogeneous fully anisotropic conductors with ellipsoid superconducting
inclusions. This model and calculations are useful to analyze the observed
temperature dependence of conductivity anisotropy in various anisotropic
superconductors, where superconductivity onset happens inhomogeneously in the
form of isolated superconducting islands. The results are applied to explain
the experimental data on resistivity above the transition temperature $T_c$ in
the high-temperature superconductor $\mathrm{YBa_2Cu_4O_8}$ and in the organic
superconductor $\beta$-(BEDT-TTF)$_{2}$I$_{3}$. The comparison of resistivity
data and diamagnetic response in $\beta$-(BEDT-TTF)$_{2}$I$_{3}$ allows us to
estimate the size of superconducting inclusions as $d\sim 1\mu m$.",1712.05347v2
2017-12-16,Mitigating Asymmetric Nonlinear Weight Update Effects in Hardware Neural Network based on Analog Resistive Synapse,"Asymmetric nonlinear weight update is considered as one of the major
obstacles for realizing hardware neural networks based on analog resistive
synapses because it significantly compromises the online training capability.
This paper provides new solutions to this critical issue through
co-optimization with the hardware-applicable deep-learning algorithms. New
insights on engineering activation functions and a threshold weight update
scheme effectively suppress the undesirable training noise induced by
inaccurate weight update. We successfully trained a two-layer perceptron
network online and improved the classification accuracy of MNIST handwritten
digit dataset to 87.8/94.8% by using 6-bit/8-bit analog synapses, respectively,
with extremely high asymmetric nonlinearity.",1712.05895v1
2018-10-30,Whole genome single nucleotide polymorphism genotyping of Staphylococcus aureus,"Next-generation sequencing technology enables routine detection of bacterial
pathogens for clinical diagnostics and genetic research. Whole genome
sequencing has been of importance in the epidemiologic analysis of bacterial
pathogens. However, few whole genome sequencing-based genotyping pipelines are
available for practical applications. Here, we present the whole genome
sequencing-based single nucleotide polymorphism (SNP) genotyping method and
apply to the evolutionary analysis of methicillin-resistant Staphylococcus
aureus. The SNP genotyping method calls genome variants using next-generation
sequencing reads of whole genomes and calculates the pair-wise Jaccard
distances of the genome variants. The method may reveal the high-resolution
whole genome SNP profiles and the structural variants of different isolates of
methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus
(MSSA) strains. The phylogenetic analysis of whole genomes and particular
regions may monitor and track the evolution and the transmission dynamic of
bacterial pathogens. The computer programs of the whole genome sequencing-based
SNP genotyping method are available to the public at
https://github.com/cyinbox/NGS.",1810.13027v1
2018-11-02,Ladder-like optical conductivity in the spin-fermion model,"In the nested limit of the spin-fermion model for the cuprates,
one-dimensional physics in the form of half-filled two-leg ladders emerges. We
show that the renormalization group flow of the corresponding ladder is towards
the d-Mott phase, a gapped spin-liquid with short-ranged d-wave pairing
correlations, and reveals an intermediate SO(5)$\times$SO(3) symmetry. We use
the results of the renormalization group in combination with a memory-function
approach to calculate the optical conductivity of the spin-fermion model in the
high-frequency regime, where processes within the hot spot region dominate the
transport. We argue that umklapp processes play a major role. For finite
temperatures, we determine the resistivity in the zero-frequency (dc) limit.
Our results show an approximate linear temperature dependence of the
resistivity and a conductivity that follows a non-universal power law. A
comparison to experimental data supports our assumption that the conductivity
is dominated by the antinodal contribution above the pseudogap.",1811.01103v2
2018-11-13,Hydrodynamic and Solid Mechanics Analysis of Capillary Force-Induced Mold Deformation in Sub-10 nm UV Nanoimprint Lithography,"A model has been developed to study the dynamic filling process and to
investigate the capillary force-induced deformation of nanostructures on the
imprint mold during ultraviolet nanoimprint lithography (UV-NIL) down to sub-10
nm resolution. The dynamic behavior of resist filling with varied physical
parameters was investigated by a hydrodynamic model. The capillary
force-induced deformation of mold structures was modeled using beam bending
mechanics for both wetting and non-wetting mold structures. Theoretically
calculated results were cross-validated with finite-element simulations using
two-phase flow and solid mechanics methods. Based on the theoretical analysis,
a general parameter of critical aspect ratio for design of imprint mold for
UV-NIL is developed. The investigation of capillary force-induced deformation
in UV-NIL helps to deepen the understanding of dynamic mechanism of resist
filling and structural deformation at sub-10 nm scale and enable optimization
for high-fidelity UV-NIL.",1811.05103v2
2018-11-29,Magneto-immutable turbulence in weakly collisional plasmas,"We propose that pressure anisotropy causes weakly collisional turbulent
plasmas to self-organize so as to resist changes in magnetic-field strength. We
term this effect ""magneto-immutability"" by analogy with incompressibility
(resistance to changes in pressure). The effect is important when the pressure
anisotropy becomes comparable to the magnetic pressure, suggesting that in
collisionless, weakly magnetized (high-$\beta$) plasmas its dynamical relevance
is similar to that of incompressibility. Simulations of magnetized turbulence
using the weakly collisional Braginskii model show that magneto-immutable
turbulence is surprisingly similar, in most statistical measures, to critically
balanced MHD turbulence. However, in order to minimize magnetic-field
variation, the flow direction becomes more constrained than in MHD, and the
turbulence is more strongly dominated by magnetic energy (a nonzero ""residual
energy""). These effects represent key differences between pressure-anisotropic
and fluid turbulence, and should be observable in the $\beta\gtrsim1$ turbulent
solar wind.",1811.12421v2
2019-02-15,Electrodynamics of granular aluminum from superconductor to insulator: observation of collective superconducting modes,"We report on a detailed study of the optical response and $T_c-\rho$ phase
diagram ($T_c$ being the superconducting critical temperature and $\rho$ the
normal state resistivity of the film) of granular aluminum, combining transport
measurements and a high resolution optical spectroscopy technique. The
$T_c-\rho$ phase diagram is discussed as resulting from an interplay between
the phase stiffness, the Coulomb repulsion and the superconducting gap
$\Delta$. We provide a direct evidence for two different types of well resolved
sub-gap absorptions, at $\omega_1\simeq\Delta$ and at
$\Delta\lesssim\omega_2\lesssim2\Delta$ (decreasing with increasing
resistivity).",1902.05843v2
2019-02-27,Energy bandpass filtering in superlattice phase change memories,"We propose energy bandpass filtering employed using the idea of
anti-reflection heterostructures as a means to reduce the energy requirements
of a superlattice phase change memory based on GeTe and Sb$_{2}$Te$_{3}$
heterostructures. Different configurations of GeTe/Sb$_{2}$Te$_{3}$
superlattices are studied using the non-equilibrium Green's function approach.
Our electronic transport simulations calculate the coupling parameter for the
high resistance covalent state, to $97 \%$ that of the stable low resistance
resonant state, maintaining the ON/OFF ratio of 100 for a reliable read
operation. By examining various configurations of the superlattice structures
we conclude that the inclusion of anti-reflection units on both sides of the
superlattice increases the overall ON/OFF ratio by an order of magnitude which
can further help in scaling down of the memory device. It is also observed that
the device with such anti-reflection units exhibits 32$\%$ lesser RESET voltage
than the most common PCM superlattice configurations and 27$\%$ in the presence
of elastic dephasing. Moreover, we also find that the ON/OFF ratios in these
devices are also resilient to the variations in the periodicity of the
superlattice.",1902.10551v1
2019-05-15,Automatic Long-Term Deception Detection in Group Interaction Videos,"Most work on automated deception detection (ADD) in video has two
restrictions: (i) it focuses on a video of one person, and (ii) it focuses on a
single act of deception in a one or two minute video. In this paper, we propose
a new ADD framework which captures long term deception in a group setting. We
study deception in the well-known Resistance game (like Mafia and Werewolf)
which consists of 5-8 players of whom 2-3 are spies. Spies are deceptive
throughout the game (typically 30-65 minutes) to keep their identity hidden. We
develop an ensemble predictive model to identify spies in Resistance videos. We
show that features from low-level and high-level video analysis are
insufficient, but when combined with a new class of features that we call
LiarRank, produce the best results. We achieve AUCs of over 0.70 in a fully
automated setting. Our demo can be found at
http://home.cs.dartmouth.edu/~mbolonkin/scan/demo/",1905.08617v2
2019-05-28,The nature of the gravitational vacuum,"The vacuum must contain virtual fluctuations of black hole microstates for
each mass $M$. We observe that the expected suppression for $M\gg m_p$ is
counteracted by the large number $Exp[S_{bek}]$ of such states. From string
theory we learn that these microstates are extended objects that are resistant
to compression. We argue that recognizing this `virtual extended
compression-resistant' component of the gravitational vacuum is crucial for
understanding gravitational physics. Remarkably, such virtual excitations have
no significant effect for observable systems like stars, but they resolve two
important problems: (a) gravitational collapse is halted outside the horizon
radius, removing the information paradox; (b) spacetime acquires a `stiffness'
against the curving effects of vacuum energy; this ameliorates the cosmological
constant problem posed by the existence of a planck scale $\Lambda$.",1905.12004v1
2019-07-10,Finding Robust Periodic Timetables by Integrating Delay Management,"This paper defines and solves a mathematical model for finding robust
periodic timetables by proposing an extension of the Periodic Event Scheduling
Problem (PESP). In order to model delayed and not nominal travel times already
in the timetabling step, we integrate delay management into the periodic
timetabling problem. After revisiting both (PESP) and delay management
individually, we introduce a periodic delay management model capable of
evaluating periodic timetables with respect to delay resistance. Having
introduced periodic delay management, we define the Robust Periodic Timetabling
problem (RPT). Due to the high complexity of (RPT) we propose two different
simplifications of the problem and introduce solution algorithms for both of
them. These solution algorithms are tested against timetables found by standard
procedures for periodic timetabling with respect to their delay-resistance. The
computational results show that our algorithms yield timetables which can cope
better with occurring delays, even on large-scale datasets and with low
computational effort.",1907.04554v1
2020-02-07,Spin-dependent transport through a Weyl semimetal surface,"We experimentally compare two types of interface structures with magnetic and
non-magnetic Weyl semimetals. They are the junctions between a gold normal
layer and magnetic Weyl semimetal Ti$_2$MnAl, and a ferromagnetic nickel layer
and non-magnetic Weyl semimetal WTe$_2$, respectively. Due to the ferromagnetic
side of the junction, we investigate spin-polarized transport through the Weyl
semimetal surface. For both structures, we demonstrate similar current-voltage
characteristics, with hysteresis at low currents and sharp peaks in
differential resistance at high ones. Despite this behavior resembles the known
current-induced magnetization dynamics in ferromagnetic structures, evolution
of the resistance peaks with magnetic field is unusual. We connect the observed
effects with current-induced spin dynamics in Weyl topological surface states.",2002.02673v2
2020-03-02,A resistive ACHINOS multi-anode structure with DLC coating for spherical proportional counters,"The spherical proportional counter is a gaseous detector used in a variety of
applications, including direct dark matter and neutrino-less double beta decay
searches. The ACHINOS multianode structure is a read-out technology that
overcomes the limitations of single-anode read-out structures for large-size
detectors and operation under high pressure. A resistive ACHINOS is presented,
where the 3D printed central component is coated in a Diamond-Like Carbon (DLC)
layer. The production and testing of the structure, in terms of stability and
resolution, is described. Further applications in fundamental physics and
industry are also discussed.",2003.01068v2
2020-03-09,BitTensor: A Peer-to-Peer Intelligence Market,"As with other commodities, markets could help us efficiently produce machine
intelligence. We propose a market where intelligence is priced by other
intelligence systems peer-to-peer across the internet. Peers rank each other by
training neural networks which learn the value of their neighbors. Scores
accumulate on a digital ledger where high ranking peers are monetarily rewarded
with additional weight in the network. However, this form of peer-ranking is
not resistant to collusion, which could disrupt the accuracy of the mechanism.
The solution is a connectivity-based regularization which exponentially rewards
trusted peers, making the system resistant to collusion of up to 50 percent of
the network weight. The result is a collectively run intelligence market which
continual produces newly trained models and pays contributors who create
information theoretic value.",2003.03917v3
2020-04-20,Anomalous Magnetoresistance in Centrosymmetric Skyrmion-Lattice Magnet Gd2PdSi3,"We performed a systematic study of the temperature- and field-dependence of
magnetization and resistivity of Gd2PdSi3, which is a centrosymmetric skyrmion
crystal. While the magnetization behavior is consistent with the reported phase
diagram based on susceptibility, we show that a phase diagram can also be
constructed based on the anomalous magnetoresistance with one-to-one
correspondence among all the features. In addition, the crossover boundary into
the field-induced ferromagnetic state is also identified. Our results suggest
that the ferromagnetic spin fluctuations above the N\'eel temperature play a
key role in the high sensitivity of the resistivity anomalies to magnetic
field, pointing to the rich interplay of different magnetic correlations at
zero and finite wave vectors underlying the skyrmion lattice in this frustrated
itinerant magnet.",2004.09664v1
2020-04-29,Numerical study of space charge electric field inside Resistive Plate Chamber,"Resistive plate chamber (RPC) is one of the state-of-the-art particle
detection technology for the High Energy Physics (HEP) experiments. The basic
operating mechanism of an RPC involves ionization of gas due to the passage of
charged particles followed by electron transport , avalanche, and subsequent
electromagnetic induction on readout strips due to the movement of the
electrons and ions. Especially during streamer mode of operation, the electric
field applied to the RPC can get significantly modified due to the presence of
large number of electrons and ions. In this study, we have worked on dominant
issues related to the estimation of electric field due to the space charge
arising out of the presence of electrons, ions within an RPC. For this purpose
we have considered two approaches: representation of the space charge cloud as
(a) a collection of ring charges, and (b) as a collection of line charges. The
results from these different methods have been compared with results available
in the literature.",2004.13899v2
2020-09-22,Adversarial Attack Based Countermeasures against Deep Learning Side-Channel Attacks,"Numerous previous works have studied deep learning algorithms applied in the
context of side-channel attacks, which demonstrated the ability to perform
successful key recoveries. These studies show that modern cryptographic devices
are increasingly threatened by side-channel attacks with the help of deep
learning. However, the existing countermeasures are designed to resist
classical side-channel attacks, and cannot protect cryptographic devices from
deep learning based side-channel attacks. Thus, there arises a strong need for
countermeasures against deep learning based side-channel attacks. Although deep
learning has the high potential in solving complex problems, it is vulnerable
to adversarial attacks in the form of subtle perturbations to inputs that lead
a model to predict incorrectly.
  In this paper, we propose a kind of novel countermeasures based on
adversarial attacks that is specifically designed against deep learning based
side-channel attacks. We estimate several models commonly used in deep learning
based side-channel attacks to evaluate the proposed countermeasures. It shows
that our approach can effectively protect cryptographic devices from deep
learning based side-channel attacks in practice. In addition, our experiments
show that the new countermeasures can also resist classical side-channel
attacks.",2009.10568v1
2007-10-19,"Disorder, Metal-Insulator crossover and Phase diagram in high-Tc cuprates","We have studied the influence of disorder induced by electron irradiation on
the normal state resistivities $\rho(T)$ of optimally and underdoped YBa2CuOx
single crystals, using pulsed magnetic fields up to 60T to completely restore
the normal state. We evidence that point defect disorder induces low T upturns
of rho(T) which saturate in some cases at low T in large applied fields as
would be expected for a Kondo-like magnetic response. Moreover the magnitude of
the upturns is related to the residual resistivity, that is to the
concentration of defects and/or their nanoscale morphology. These upturns are
found quantitatively identical to those reported in lower Tc cuprates, which
establishes the importance of disorder in these supposedly pure compounds. We
therefore propose a realistic phase diagram of the cuprates, including
disorder, in which the superconducting state might reach the antiferromagnetic
phase in the clean limit.",0710.3737v2
2014-01-23,Crawling on directional surfaces,"In this paper we study crawling locomotion based on directional frictional
interactions, namely, frictional forces that are sensitive to the sign of the
sliding velocity. Surface interactions of this type are common in biology,
where they arise from the presence of inclined hairs or scales at the
crawler/substrate interface, leading to low resistance when sliding 'along the
grain', and high resistance when sliding 'against the grain'. This asymmetry
can be exploited for locomotion, in a way analogous to what is done in
cross-country skiing (classic style, diagonal stride). We focus on a model
system, namely, a continuous one-dimensional crawler and provide a detailed
study of the motion resulting from several strategies of shape change. In
particular, we provide explicit formulae for the displacements attainable with
reciprocal extensions and contractions (breathing), or through the propagation
of extension or contraction waves. We believe that our results will prove
particularly helpful for the study of biological crawling motility and for the
design of bio-mimetic crawling robots.",1401.5929v1
2016-03-14,Study of Performance of Bakelite Resistive Plate Chamber (RPC),"Resistive Plate Chamber (RPC) is a type of gaseous detector having excellent
time and position resolutions. VECC is involved in the R\&D of indigenously
developed bakelite RPCs. The largest size of bakelite RPC developed in India is
100 cm $\times$ 100 cm. We present here the test results of a bakelite sample
along with the cosmic ray test results of a bakelite RPC (30 cm $\times$ 30 cm
$\times$ 0.2cm) fabricated at VECC. The steps taken towards the development of
a large size (240 cm $\times$ 120 cm $\times$ 0.2 cm) bakelite RPC have also
been discussed.",1603.04875v1
2017-04-24,Electronic transport properties of intermediately coupled superconductors: PdTe2 and Cu0.04PdTe2,"We have investigated the electrical resistivity, Seebeck coefficient and
thermal conductivity of PdTe2 and 4% Cu intercalated PdTe2 compounds.
Electrical resistivity for the compounds shows Bloch-Gruneisen type linear
temperature (T) dependence for 100 K < T < 480 K, and Fermi liquid behavior (~
T^2) below 50 K. Seebeck coefficient data exhibit strong competition between
Normal (N) and Umklapp (U) scattering processes at low T. Though our results
indicate the transfer of charge carriers to PdTe2 upon Cu intercalation, it is
difficult to discern any change in the Fermi surface of the compound by
Nordheim-Gorter plots. The estimated Fermi energies of the compounds are quite
comparable to good metals Cu, Ag and Au. The low T, thermal conductivity (k) of
the compounds is strongly dominated by the electronic contribution, and
exhibits a rare linear T dependence below 10 K. However, high T, k(T) shows
usual 1/T dependence, dominated by U scattering process. The electron phonon
coupling parameters, estimated from the low T, specific heat data and first
principle electronic structure calculations suggest that PdTe2 and Cu0.04PdTe2
are intermediately coupled superconductors.",1704.07194v2
2017-05-01,Magnetic Skyrmions for Cache Memory,"Magnetic skyrmions (MS) are particle-like spin structures with whirling
configuration, which are promising candidates for spin-based memory. MS
contains alluring features including remarkably high stability, ultra low
driving current density, and compact size. Due to their higher stability and
lower drive current requirement for movement, skyrmions have great potential in
energy efficient spintronic device applications. We propose a skyrmion-based
cache memory where data can be stored in a long nanotrack as multiple bits.
Write operation (formation of skyrmion) can be achieved by injecting spin
polarized current in a magnetic nanotrack and subsequently shifting the MS in
either direction along the nanotrack using charge current through a spin-Hall
metal (SHM), underneath the magnetic layer. The presence of skyrmion can alter
the resistance of a magnetic tunneling junction (MTJ) at the read port.
Considering the read and write latency along the long nanotrack cache memory, a
strategy of multiple read and write operations is discussed. Besides, the size
of a skyrmion affects the packing density, current induced motion velocity, and
readability (change of resistance while sensing the existence of a skyrmion).
Design optimization to mitigate the above effects is also investigated.",1705.01095v1
2017-08-17,van der Waals Bonded Co/h-BN Contacts to Ultrathin Black Phosphorus Devices,"Due to the chemical inertness of 2D hexagonal-Boron Nitride (h-BN), few
atomic-layer h-BN is often used to encapsulate air-sensitive 2D crystals such
as Black Phosphorus (BP). However, the effects of h-BN on Schottky barrier
height, doping and contact resistance are not well known. Here, we investigate
these effects by fabricating h-BN encapsulated BP transistors with cobalt (Co)
contacts. In sharp contrast to directly Co contacted p-type BP devices, we
observe strong n-type conduction upon insertion of the h-BN at the Co/BP
interface. First principles calculations show that this difference arises from
the much larger interface dipole at the Co/h-BN interface compared to the Co/BP
interface, which reduces the work function of the Co/h-BN contact. The Co/h-BN
contacts exhibit low contact resistances (~ 4.5 k-ohm), and are Schottky
barrier free. This allows us to probe high electron mobilities (4,200 cm2/Vs)
and observe insulator-metal transitions even under two-terminal measurement
geometry.",1708.05162v1
2017-08-25,Pressure-induced magnetic collapse and metallization of $\mathrm{TlF}{\mathrm{e}}_{1.6}\mathrm{S}{\mathrm{e}}_{2}$,"The crystal structure, magnetic ordering, and electrical resistivity of
TlFe1.6Se2 were studied at high pressures. Below ~7 GPa, TlFe1.6Se2 is an
antiferromagnetically ordered semiconductor with a ThCr2Si2-type structure. The
insulator-to-metal transformation observed at a pressure of ~ 7 GPa is
accompanied by a loss of magnetic ordering and an isostructural phase
transition. In the pressure range ~ 7.5 - 11 GPa a remarkable downturn in
resistivity, which resembles a superconducting transition, is observed below 15
K. We discuss this feature as the possible onset of superconductivity
originating from a phase separation in a small fraction of the sample in the
vicinity of the magnetic transition.",1708.07702v1
2017-08-29,Physical and geometric constraints explain the labyrinth-like shape of the nasal cavity,"The nasal cavity is a vital component of the respiratory system that heats
and humidifies inhaled air in all vertebrates. Despite this common function,
the shapes of nasal cavities vary widely across animals. To understand this
variability, we here connect nasal geometry to its function by theoretically
studying the airflow and the associated scalar exchange that describes heating
and humidification. We find that optimal geometries, which have minimal
resistance for a given exchange efficiency, have a constant gap width between
their side walls, but their overall shape is restricted only by the geometry of
the head. Our theory explains the geometric variations of natural nasal
cavities quantitatively and we hypothesize that the trade-off between high
exchange efficiency and low resistance to airflow is the main driving force
shaping the nasal cavity. Our model further explains why humans, whose nasal
cavities evolved to be smaller than expected for their size, become obligate
oral breathers in aerobically challenging situations.",1708.08966v1
2018-08-29,Quantum phase transition in ultrahigh mobility SiGe/Si/SiGe two-dimensional electron system,"The metal-insulator transition (MIT) is an exceptional test bed for studying
strong electron correlations in two dimensions in the presence of disorder. In
the present study, it is found that in contrast to previous experiments on
lower-mobility samples, in ultra-high mobility SiGe/Si/SiGe quantum wells the
critical electron density, $n_{\text{c}}$, of the MIT becomes smaller than the
density, $n_{\text{m}}$, where the effective mass at the Fermi level tends to
diverge. Near the topological phase transition expected at $n_{\text{m}}$, the
metallic temperature dependence of the resistance should be strengthened, which
is consistent with the experimental observation of more than an order of
magnitude resistance drop with decreasing temperature below $\sim1$ K.",1808.10063v3
2019-03-14,A Two-Dimensional Resistor Network Model for Transition-Edge Sensors with Normal Metal Features,"Transition-edge sensors (TESs) can be used in high-resolution photon
detection, exploiting the steep slope of the resistance in the
superconducting-to-normal transition edge. Normal metal bars on the TES film
are commonly used to engineer its transition shape, namely the dependence of
resistance on temperature and current. This problem has been studied in one
dimension, however until now, there have been no predictive models of the
influence of two-dimensional (2-D) normal metal features on the TES transition
shape. In this work, we approach this problem by treating the TES as a 2-D
network of resistors, the values of which are based on the two-fluid model. We
present a study of the behavior of devices with different 2-D geometric
features. Our 2-D network model is capable of predicting how typical TES
geometry parameters, such as number of bars, bar spacing, and overall
dimensions, influence device behavior and thus is a powerful tool to guide the
engineering of new TES devices.",1903.06271v1
2019-04-01,Quantum and classical ratchet motions of vortices in a 2D trigonal superconductor,"Dynamical behavior of vortices plays central roles in the quantum phenomena
of two-dimensional (2D) superconductors. Quantum metallic state, for example,
showing an anomalous temperature-independent resistive state down to
low-temperatures, has been a common subject in recently developed 2D
crystalline superconductors, whose microscopic origin is still under debate.
Here, we unveil a new aspect of the vortex dynamics in a noncentrosymmetric 2D
crystalline superconductor of MoS$_{2}$ through the nonreciprocal transport
measurement. The second harmonic resistance $R^{2w}$ at low temperature with
high current indicates the classical vortex flow accompanying the ratchet
motion. Furthermore, we found that $R^{2w}$ is substantially suppressed in the
quantum metallic state with low current region, allowing identification of the
quantum and classical ratchet motions of vortices by the magnitude of the
second harmonic generation. This suggests that nonreciprocal transport
measurement can be a powerful tool to probe the vortex dynamics in
noncentrosymmetric 2D superconductors.",1904.00611v1
2019-04-03,Transport and chaos in lattice Sachdev-Ye-Kitaev models,"We compute the transport and chaos properties of lattices of quantum
Sachdev-Ye-Kitaev islands coupled by single fermion hopping, and with the
islands coupled to a large number of local, low energy phonons. We find two
distinct regimes of linear-in-temperature ($T$) resistivity, and describe the
crossover between them. When the electron-phonon coupling is weak, we obtain
the `incoherent metal' regime, where there is near-maximal chaos with front
propagation at a butterfly velocity $v_B$, and the associated diffusivity
$D_{\rm chaos} = v_B^2/(2 \pi T)$ closely tracks the energy diffusivity. On the
other hand, when the electron-phonon coupling is strong, and the linear
resistivity is largely due to near-elastic scattering of electrons off nearly
free phonons, we find that the chaos is far from maximal and spreads
diffusively. We also describe the crossovers to low $T$ regimes where the
electronic quasiparticles are well defined.",1904.02174v2
2019-12-10,Structural properties and magnetoresistance of La$_{1.952}$Sr$_{0.048}$CuO$_4$ thin films,"The evolution of the structural and transport properties of underdoped
La$_{1.952}$Sr$_{0.048}$CuO$_4$ thin films under compressive epitaxial strain
has been studied. The films of different thicknesses $d$ (from 26 nm to 120 nm)
were deposited using an insulating target. The onset of superconductivity in
the films is observed at temperatures as high as 26 K, while small residual
resistance persists at low temperatures, indicating that superconductivity is
inhomogeneous. The resistance measured under perpendicular magnetic field
saturates below about 0.65 K, suggesting a possible existence of
nonconventional metallic state. The magnetic-field-tuned
superconductor-insulator transition is observed at magnetic field of about 32
T.",1912.04594v2
2019-12-26,Inflationary routes to Gaussian curved topography,"Gaussian-curved shapes are obtained by inflating initially flat systems made
of two superimposed strong and light thermoplastic impregnated fabric sheets
heat-sealed together along a specific network of lines. The resulting inflated
structures are light and very strong because they (largely) resist deformation
by the intercession of stretch. Programmed patterns of channels vary either
discretely through boundaries, or continuously. The former give rise to
facetted structures that are in effect non-isometric origami and which cannot
unfold as in conventional folded structures, since they present localized angle
deficit or surplus. Continuous variation of channel direction in the form of
spirals is examined, giving rise to curved shells. We solve the inverse problem
consisting in finding a network of seam lines leading to a target axisymmetric
shape on inflation. They too have strength from the metric changes that have
been pneumatically driven, resistance to change being met with stretch and
hence high forces like typical shells .",1912.13425v3
2021-01-04,Holographic DC Conductivity for Backreacted NLED in Massive Gravity,"In this work a holographic model with the charge current dual to a general
nonlinear electrodynamics (NLED) is discussed in the framework of massive
gravity. Massive graviton can breaks the diffeomorphism invariance in the bulk
and generates momentum dissipation in the dual boundary theory. The expression
of DC conductivities in a finite magnetic field are obtained, with the
backreaction of NLED field on the background geometry. General transport
properties in various limits are presented, and then we turn to the three of
specific NLED models: the conventional Maxwell electrodynamics, the
Maxwell-Chern-Simons electrodynamics, and the Born-Infeld electrodynamics, to
study the parameter-dependence of in-plane resistivity. Two mechanisms leading
to the Mott-insulating behaviors and negative magneto-resistivity are revealed
at zero temperature, and the role played by the massive gravity coupling
parameters are discussed.",2101.00912v1
2021-01-06,Bose-Luttinger Liquids,"We study systems of bosons whose low-energy excitations are located along a
spherical submanifold of momentum space. We argue for the existence of gapless
phases which we dub ""Bose-Luttinger liquids"", which in some respects can be
regarded as bosonic versions of Fermi liquids, while in other respects exhibit
striking differences. These phases have bosonic analogues of Fermi surfaces,
and like Fermi liquids they possess a large number of emergent conservation
laws. Unlike Fermi liquids however these phases lack quasiparticles, possess
different RG flows, and have correlation functions controlled by a continuously
varying exponent $\eta$, which characterizes the anomalous dimension of the
bosonic field. We show that when $\eta>1$, these phases are stable with respect
to all symmetric perturbations. These theories may be of relevance to several
physical situations, including frustrated quantum magnets, rotons in superfluid
He, and superconductors with finite-momentum pairing. As a concrete
application, we show that coupling a Bose-Luttinger liquid to a conventional
Fermi liquid produces a resistivity scaling with temperature as $T^\eta$. We
argue that this may provide an explanation for the non-Fermi liquid resistivity
observed in the paramagnetic phase of MnSi.",2101.02197v2
2021-01-22,"Magnetic doping effects on the superconductivity of Y1-xMxBa2Cu3O7-d (M = Fe, Co, Ni)","The discovery of superconductivity in copper oxide compounds has attracted
considerable attention over the past three decades. The high transition
temperature in these compounds, exhibiting proximity to an antiferromagnetic
order in their phase diagrams, remains one of the main areas of research. The
present study attempts to introduce Fe, Co and Ni magnetic impurities into the
superconducting Y-123 with the aim of exploring the transition temperature
behavior. The solid-state synthesis is exploited to prepare fully oxygenated
Y1-xMxBa2Cu3O7 (M = Co, Fe, Ni) samples with low levels of doping (0< x <
0.03). Systematic measurements are then employed to assess the synthesized
samples using AC magnetic susceptibility, electrical resistivity and X-ray
diffraction. The measurements revealed an increase in Tc as a result of
magnetic substitution for Y. However, the study of non-magnetic dopings on the
fully oxygenated Y1-xM'xBa2Cu3O7 (M' = Ca, Sr) samples showed a decrease in Tc.
Quantitative XRD analysis further suggested that the internal pressure could
have minor effects on the increase in Tc. The normal state resistivity vs
temperature showed a linear profile, confirming that the samples are at an
optimal doping of the carrier concentration.",2101.09292v1
2011-04-01,Effective Field Theory of Fractional Quantized Hall Nematics,"We present a Landau-Ginzburg theory for a fractional quantized Hall nematic
state and the transition to it from an isotropic fractional quantum Hall state.
This justifies Lifshitz-Chern-Simons theory -- which is shown to be its dual --
on a more microscopic basis and enables us to compute a ground state wave
function in the symmetry-broken phase. In such a state of matter, the Hall
resistance remains quantized while the longitudinal DC resistivity due to
thermally-excited quasiparticles is anisotropic. We interpret recent
experiments at Landau level filling factor \nu =7/3 in terms of our theory.",1104.0256v2
2011-04-26,Degenerate versus semi-degenerate transport in a correlated 2D hole system,"It has been puzzling that the resistivity of high mobility
two-dimensional(2D) carrier systems in semiconductors with low carrier density
often exhibits a large increase followed by a decrease when the temperature
($T$) is raised above a characteristic temperature comparable with the Fermi
temperature ($T_F$). We find that the metallic 2D hole system (2DHS) in GaAs
quantum well (QW) has a linear density ($p$) dependent conductivity,
$\sigma\approx e\mu^*(p-p_0)$, in both the degenerate (T<<T_F) and
semi-degenerate (T T_F) regimes. The $T$-dependence of $\sigma(p)$ suggests
that the metallic conduction (d$\sigma$/d$T<$0) at low $T$ is associated with
the increase in $\mu^*$, the effective mobility of itinerant carriers. However,
the resistivity decrease in the semi-degenerate regime ($T>T_F$) is originated
from the reduced $p_0$, the density of immobile carriers in a two-phase
picture.",1104.4834v1
2012-06-13,LSFEM implementation of MHD numerical solver,"Many problems in physics are inherently of multi-scale nature. The issues of
MHD turbulence or magnetic reconnection, namely in the hot and sparse, almost
collision-less astrophysical plasmas, can stand as clear examples. The Finite
Element Method (FEM) with adaptive gridding appears to be the appropriate
numerical implementation for handling the broad range of scales contained in
such high Lundquist-number MHD problems. In spite the FEM is now routinely used
in engineering practice in solid-state and fluid dynamics, its usage for MHD
simulations has recently only begun and only few implementations exist so far.
In this paper we present our MHD solver based on the Least-Square FEM (LSFEM)
formulation. We describe the transformation of the MHD equations into form
required for finding the LSFEM functional and some practical issues in
implementation of the method. The algorithm was tested on selected problems of
ideal (non-resistive) and resistive MHD. The tests show the usability of LSFEM
for solving MHD equations.",1206.2730v1
2012-06-13,Implementation of low-loss superinductances for quantum circuits,"The simultaneous suppression of charge fluctuations and offsets is crucial
for preserving quantum coherence in devices exploiting large quantum
fluctuations of the superconducting phase. This requires an environment with
both extremely low DC and high RF impedance. Such an environment is provided by
a superinductance, defined as a zero DC resistance inductance whose impedance
exceeds the resistance quantum $R_Q = h/(2e)^2 \simeq 6.5\ \mathrm{k\Omega}$ at
frequencies of interest (1 - 10 GHz). In addition, the superinductance must
have as little dissipation as possible, and possess a self-resonant frequency
well above frequencies of interest. The kinetic inductance of an array of
Josephson junctions is an ideal candidate to implement the superinductance
provided its phase slip rate is sufficiently low. We successfully implemented
such an array using large Josephson junctions ($E_J >> E_C$), and measured
internal losses less than 20 ppm, self-resonant frequencies greater than 10
GHz, and phase slip rates less than 1 mHz.",1206.2964v1
2012-06-14,Universal transport near a quantum critical Mott transition in two dimensions,"We discuss the universal transport signatures near a zero-temperature
continuous Mott transition between a Fermi liquid (FL) and a quantum spin
liquid in two spatial dimensions. The correlation-driven transition occurs at
fixed filling and involves fractionalization of the electron: upon entering the
spin liquid, a Fermi surface of neutral spinons coupled to an internal gauge
field emerges. We present a controlled calculation of the value of the zero
temperature universal resistivity jump predicted to occur at the transition.
More generally, the behavior of the universal scaling function that collapses
the temperature and pressure dependent resistivity is derived, and is shown to
bear a strong imprint of the emergent gauge fluctuations. We further predict a
universal jump of the thermal conductivity across the Mott transition, which
derives from the breaking of conformal invariance by the damped gauge field,
and leads to a violation of the Wiedemann-Franz law in the quantum critical
region. A connection to organic salts is made, where such a transition might
occur. Finally, we present some transport results for the pure rotor O(N) CFT.",1206.3309v2
2012-06-22,Optically induced nuclear spin polarization in a single GaAs/AlGaAs quantum well probed by a resistance detection method in the fractional quantum Hall regime,"We study the optically pumped nuclear spin polarization in a single
GaAs/AlGaAs quantum well in the quantum Hall system. We apply resistive
detection via the contact hyperfine interaction, which provides high
sensitivity and selectivity, to probe a small amount of polarized nuclear spins
in a single well. The properties of the optical nuclear spin polarization are
clearly observed. We theoretically discuss the nuclear spin dynamics
accompanied with doped electrons to analyze the experimental data. The optical
nuclear polarization spectra exhibit electron-spin-resolved lowest Landau level
interband transitions. We find that the phonon emission process, which normally
assists the optical pumping process, influences the optical nuclear spin
polarization. We also discuss that the electron-electron interaction can play
an important role in the optical nuclear spin polarization.",1206.5227v3
2012-06-22,Inter-subband resistance oscillations in crossed electric and magnetic fields,"Quantum oscillations of nonlinear resistance are investigated in response to
electric current and magnetic field applied perpendicular to single GaAs
quantum wells with two populated subbands. At small magnetic fields
current-induced oscillations appear as Landau-Zener transitions between Landau
levels inside the lowest subband. Period of these oscillations is proportional
to the magnetic field. At high magnetic fields different kind of quantum
oscillations emerges with a period,which is independent of the magnetic field.
At a fixed current the oscillations are periodic in inverse magnetic field with
a period that is independent of the dc bias. The proposed model considers these
oscillations as a result of spatial variations of the energy separation between
two subbands induced by the electric current.",1206.5233v1
2012-06-28,"Trigonometrical sums connected with the chiral Potts model, Verlinde dimension formula, two-dimensional resistor network, and number theory","\ \ We have recently developed methods for obtaining exact two-point
resistance of the complete graph minus $N$ edges. We use these methods to
obtain closed formulas of certain trigonometrical sums that arise in connection
with one-dimensional lattice, in proving the Scott's conjecture on permanent of
Cauchy matrix, and in the perturbative chiral Potts model. The generalized
trigonometrical sums of the chiral Potts model are shown to satisfy recursion
formulas that are transparent and direct, and differ from those of Gervois and
Mehta. By making a change of variables in these recursion formulas, the
dimension of the space of conformal blocks of $SU(2)$ and $SO(3)$ WZW models
may be computed recursively. Our methods are then extended to compute the
corner-to-corner resistance, and the Kirchhoff index of the first non-trivial
two-dimensional resistor network, $2\times N$. Finally, we obtain new closed
formulas for variant of trigonometrical sums, some of which appear in
connection with number theory.",1206.6673v2
2015-06-12,Phase-coherent transport in catalyst-free vapor phase deposited Bi$_2$Se$_3$ crystals,"Free-standing Bi$_2$Se$_3$ single crystal flakes of variable thickness are
grown using a catalyst-free vapor-solid synthesis and are subsequently
transferred onto a clean Si$^{++}$/SiO$_2$ substrate where the flakes are
contacted in Hall bar geometry. Low temperature magneto-resistance measurements
are presented which show a linear magneto-resistance for high magnetic fields
and weak anti-localization (WAL) at low fields. Despite an overall strong
charge carrier tunability for thinner devices, we find that electron transport
is dominated by bulk contributions for all devices. Phase coherence lengths
$\l_\phi$ as extracted from WAL measurements increase linearly with increasing
electron density exceeding $1 \mu $m at 1.7 K. While $\l_\phi$ is in
qualitative agreement with electron electron interaction-induced dephasing, we
find that spin flip scattering processes limit $\l_\phi$ at low temperatures.",1506.04097v1
2015-06-24,C-axis electrical resistivity of PrO$_{1-a}$F$_a$BiS$_2$ single crystals,"The high anisotropy in RO1-aFaBiS2 (R denotes a rare-earth element)
superconductors demonstrates their potential use as intrinsic Josephson
junctions, considering the weak coupling among BiS2-PrO(F)-BiS2
(superconducting-normal-superconducting) layers along the c-axis. We grew
PrO1-aFaBiS2 single crystals using CsCl/KCl flux. The superconducting
anisotropies of the grown single crystals were estimated to be approximately
40-50 from the effective mass model. The c-axis transport properties were
characterized using single-crystal s-shaped intrinsic Josephson junctions with
a focused ion beam. Along the c-axis, the crystals showed zero resistivity at
2.7 K and a critical current density of 1.33*10^3 A/cm2 at 2.0 K. The
current-voltage curve along the c-axis displayed hysteresis. The c-axis
transport measurements under a magnetic field parallel to the ab-plane revealed
a ""lock-in"" state due to the Josephson vortex flow, indicating that BiS2
superconductors are promising candidates for intrinsic Josephson junctions.",1506.07231v1
2015-07-06,Switching Synchronization in One-Dimensional Memristive Networks,"We report on an astonishing switching synchronization phenomenon in
one-dimensional memristive networks, which occurs when several memristive
systems with different switching constants are switched from the high to low
resistance state. Our numerical simulations show that such a collective
behavior is especially pronounced when the applied voltage slightly exceeds the
combined threshold voltage of memristive systems. Moreover, a finite increase
in the network switching time is found compared to the average switching time
of individual systems. An analytical model is presented to explain our
observations. Using this model, we have derived asymptotic expressions for
memory resistances at short and long times, which are in excellent agreement
with our numerical calculations.",1507.01640v1
2018-07-09,Artificial Neural Networks-based Track Fitting of Cosmic Muons through Stacked Resistive Plate Chambers,"The India-based Neutrino Observatory (INO) collaboration, as part of its
detector R\&D program, has developed prototype stacks of resistive plate
chambers (RPCs) to study their performance. These stacks have also been used as
testbenches for the development of related hardware and software. A crucial
parameter in the characterisation of these detectors and other physics studies
is the detection efficiency, which is estimated from track fitting of cosmic
muons passing through the stack. So far, a simple straight line fit was used
for track fitting, which was sensitive to noise hits and led to rejection of
events. In this paper, we present our first results of using artificial neural
networks (ANN) for track fitting of cosmic muons traversing a stack of RPCs. We
present in detail, the simulation framework designed for this purpose and show
that ANN offers better track reconstruction efficiency than straight line
fitting. We also discuss the influence of noise and detection efficiency of
cosmic muons on the track reconstruction efficiency.",1807.04625v3
2018-12-01,A Flux-Balanced Fluid Model for Collisional Plasma Edge Turbulence: Numerical Simulations with Different Aspect Ratios,"We investigate the drift wave -- zonal flow dynamics in a shearless slab
geometry with the new flux-balanced Hasegawa-Wakatani model. As in previous
Hasegawa-Wakatani models, we observe a sharp transition from a turbulence
dominated regime to a zonal jet dominated regime as we decrease the plasma
resistivity. However, unlike previous models, zonal structures are always
present in the flux-balanced model, even for high resistivity, and strongly
reduce the level of particle and vorticity flux. The more robust zonal jets
also have a higher variability than in previous models, which is further
enhanced when the computational domain is chosen to be elongated in the radial
direction. In these cases, we observe complex multi-scale dynamics, with
multiple jets interacting with one another, and intermittent bursts. We present
a detailed statistical analysis which highlights how the changes in the aspect
ratio of the computational domain affect the third-order statistical moments,
and thus modify the turbulent dynamics.",1812.00131v1
2018-12-26,Deep learning electromagnetic inversion with convolutional neural networks,"Geophysical inversion attempts to estimate the distribution of physical
properties in the Earth's interior from observations collected at or above the
surface. Inverse problems are commonly posed as least-squares optimization
problems in high-dimensional parameter spaces. Existing approaches are largely
based on deterministic gradient-based methods, which are limited by
nonlinearity and nonuniqueness of the inverse problem. Probabilistic inversion
methods, despite their great potential in uncertainty quantification, still
remain a formidable computational task. In this paper, I explore the potential
of deep learning methods for electromagnetic inversion. This approach does not
require calculation of the gradient and provides results instantaneously. Deep
neural networks based on fully convolutional architecture are trained on large
synthetic datasets obtained by full 3-D simulations. The performance of the
method is demonstrated on models of strong practical relevance representing an
onshore controlled source electromagnetic CO2 monitoring scenario. The
pre-trained networks can reliably estimate the position and lateral dimensions
of the anomalies, as well as their resistivity properties. Several fully
convolutional network architectures are compared in terms of their accuracy,
generalization, and cost of training. Examples with different survey geometry
and noise levels confirm the feasibility of the deep learning inversion,
opening the possibility to estimate the subsurface resistivity distribution in
real time.",1812.10247v1
2019-01-24,Topological valley transport at the curved boundary of a folded bilayer graphene,"The development of valleytronics demands long-range electronic transport with
preserved valley index, a degree of freedom similar to electron spin. A
promising structure for this end is a topological one-dimensional (1D) channel
formed in bilayer graphene (BLG) under special electrostatic conditions or
specific stacking configuration, called domain wall (DW). In these 1D channels,
the valley-index defines the propagation direction of the charge carriers and
the chiral edge states (kink states) are robust over many kinds of disorder.
However, the fabrication of DWs is challenging, requiring the design of complex
multi-gate structures or have been producing on rough substrates, showing a
limited mean free path. Here, we report on a high-quality DW formed at the
curved boundary of folded bilayer graphene (folded-BLG). At such 1D conducting
channel we measured a two-terminal resistance close to the quantum resistance
$R = e^2/4h$ at zero magnetic field, a signature of kink states. Our
experiments reveal a long-range ballistic transport regime that occurs only at
the DW of the folded-BLG, while the other regions behave like semiconductors
with tunable band gap.",1901.08178v1
2019-06-12,Record-High Proximity-Induced Anomalous Hall Effect in (Bi$_x$Sb$_{1-x}$)2Te$_3$ Thin Film Grown on CrGeTe$_3$ Substrate,"Quantum anomalous Hall effect(QAHE) can only be realized at extremely low
temperatures in magnetically doped topological insulators(TIs) due to
limitations inherent with the doping precess. In an effort to boost the
quantization temperature of QAHE, magnetic proximity effect in magnetic
insulator/TI heterostructures has been extensively investigated. However, the
observed anomalous Hall resistance has never been more than several Ohms,
presumably owing to the interfacial disorders caused by the structural and
chemical mismatch. Here, we show that, by growing (BixSb1-x)2Te3(BST) thin
films on structurally and chemically well-matched, ferromagnetic-insulating
CeGeTe3(CGT) substrates, the proximity-induced anomalous Hall resistance can be
enhanced by more than an order of magnitude. This sheds light on the importance
of structural and chemical match for magnetic insulator/TI proximity systems.",1906.05245v1
2019-06-24,Mechanical characterization of cells and microspheres sorted by acoustophoresis with in-line resistive pulse sensing,"Resistive Pulse Sensing (RPS) is a key label-free technology to measure
particles and single-cell size distribution. As a growing corpus of evidence
supports that cancer cells exhibit distinct mechanical phenotypes from healthy
cells, expanding the method from size to mechanical sensing could represent a
pertinent and innovative tool for cancer research. In this paper, we infer the
cells compressibility by using acoustic radiation pressure to deflect flowing
cells in a microchannel, and use RPS to sense the subpopulations of cells and
particles at each acoustic power level. We develop and validate a linear model
to analyze experimental data from a large number of particles. This
high-precision linear model is complemented by a more robust (yet less
detailed) statistical model to analyze datasets with fewer particles. Compared
to current acoustic cell phenotyping apparatus based on video cameras, the
proposed approach is not limited by the optical diffraction, frame rate, data
storage or processing speed, and may ultimately constitute a step forward
towards point-of-care acousto-electrical phenotyping and acoustic phenotyping
of nanoscale objects such as exosomes and viruses.",1906.11944v1
2020-01-12,Interpretation of the modulus spectra of organic field-effect transistors with electrode overlap and peripheral regions: determination of the electronic properties of the gate insulator and organic semiconductor,"The modulus spectra of organic field-effect transistors (OFETs) with
electrode overlap and peripheral regions have been experimentally and
theoretically investigated. The complex impedance of regioregular
poly(3-hexylthiophene-2,5-diyl) (P3HT) OFETs with electrode overlap and
peripheral regions was measured with a frequency response analyzer. The complex
modulus was derived from an equivalent circuit of OFETs with overlap and
peripheral regions using a four-terminal matrix approach. The modulus spectra
of the P3HT OFETs were successfully fitted by those calculated using the
expression derived from the equivalent circuit. Three structures were found in
the modulus spectra of the P3HT OFETs owing to the dielectric properties of the
gate insulator, transport properties of the organic semiconductor, and contact
resistance from the low to high frequency ranges. The resistivity of the gate
insulators and the field-effect mobility of working OFETs were determined using
the values of the circuit components of the equivalent circuit obtained by
fitting.",2001.03957v1
2020-05-05,Resistance of Hall Sensors Based on Graphene to Neutron Radiation,"An in-situ study of Hall sensors based on single-layered graphene in neutron
fluxes of a nuclear reactor to the fluence of 1.5e20 n/sq,m was conducted. The
sensitivity of the sensors to the magnetic field remained stable throughout the
experiment, while the resistance changes correlated with the increase in sample
temperature due to radiation heating. The experiment confirmed the theoretical
expectations regarding the high stability of graphene sensors to neutron
irradiation. Necessary further improvement of sensor technology to optimize
their characteristics, as well as radiation testing to determine the maximum
permissible neutron fluence.",2005.01964v1
2020-05-12,Superradiant Cherenkov-Wakefield radiation as THz source for FEL facilities,"An electron beam passing through a tube which is lined on the inside with a
dielectric layer will radiate energy in the THz range due to the interaction
with the boundary. The resonant enhancement of certain frequencies is
conditioned by structure parameters as tube radius and permittivity of the
dielectric layer. In low loss structures narrow-band radiation is generated
which can be coupled out by suitable antennas. For higher frequencies the
coupling to the resistive outer metal layer becomes increasingly important. The
losses in the outer layer prohibit to reach high frequencies with narrow-band
conditions. Instead short broad-band pulses can be generated with still
attractive power levels. In the first section of the paper a general theory of
the impedance of a two-layer structure is presented and the coupling to the
outer resistive layer is discussed. Approximate relations for the radiated
energy, power and pulse length for a set of structure parameters are derived
and compared to numerical results in the following section. Finally first
numerical result of the out-coupling of the radiation by means of a Vlasov
antenna and estimates of the achieved beam quality are presented.",2005.05640v1
2020-05-18,Fmax = 270 GHz InAlN/GaN HEMT on Si with forming gas/nitrogen two-step annealing,"In this letter, N2 and forming gas (FG) were used during ohmic contact
annealing of InAlN/GaN HEMTs on Si. It is found that N2 annealing offers lower
ohmic contact resistance (RC) while FG annealing features lower sheet
resistance (Rsheet). Then FG/N2 two-step annealing was used to achieve a
subthreshold swing (SS) of 113 mV/dec, an on/off current (Ion/Ioff) ratio of ~
106, a transconductance (gm) peak of 415 mS/mm, a record low drain-inducing
barrier lowing (DIBL) of 65 mV/V, and a record high power gain cutoff frequency
(fmax) of 270 GHz on 50-nm InAlN/GaN HEMT on Si.",2005.08422v1
2020-05-18,Machine learning for the diagnosis of early stage diabetes using temporal glucose profiles,"Machine learning shows remarkable success for recognizing patterns in data.
Here we apply the machine learning (ML) for the diagnosis of early stage
diabetes, which is known as a challenging task in medicine. Blood glucose
levels are tightly regulated by two counter-regulatory hormones, insulin and
glucagon, and the failure of the glucose homeostasis leads to the common
metabolic disease, diabetes mellitus. It is a chronic disease that has a long
latent period the complicates detection of the disease at an early stage. The
vast majority of diabetics result from that diminished effectiveness of insulin
action. The insulin resistance must modify the temporal profile of blood
glucose. Thus we propose to use ML to detect the subtle change in the temporal
pattern of glucose concentration. Time series data of blood glucose with
sufficient resolution is currently unavailable, so we confirm the proposal
using synthetic data of glucose profiles produced by a biophysical model that
considers the glucose regulation and hormone action. Multi-layered perceptrons,
convolutional neural networks, and recurrent neural networks all identified the
degree of insulin resistance with high accuracy above $85\%$.",2005.08701v1
2020-05-28,Study of Streamer Development in Resistive Plate Chamber,"This work has been carried out to simulate a Resistive Plate Chamber and
corroborate it with experimental measurements in order to develop a numerical
tool for studying the performance of the device for any gas mixture. This will
allow us to explore the feasibility of operating these chambers in their
avalanche mode within the Iron Calorimeter setup at India-based Neutrino
Observatory with any eco-friendly substitute. The simulation has considered a
hydrodynamic model of charge transport to emulate the electronic and ionic
growths in the device as a function of the applied voltage which determines its
working mode as either of the avalanche or streamer. In order to validate, the
simulation result has been compared with compatible experimental data available
in the literature.",2005.13911v2
2020-06-20,In-Memory Resistive RAM Implementation of Binarized Neural Networks for Medical Applications,"The advent of deep learning has considerably accelerated machine learning
development. The deployment of deep neural networks at the edge is however
limited by their high memory and energy consumption requirements. With new
memory technology available, emerging Binarized Neural Networks (BNNs) are
promising to reduce the energy impact of the forthcoming machine learning
hardware generation, enabling machine learning on the edge devices and avoiding
data transfer over the network. In this work, after presenting our
implementation employing a hybrid CMOS - hafnium oxide resistive memory
technology, we suggest strategies to apply BNNs to biomedical signals such as
electrocardiography and electroencephalography, keeping accuracy level and
reducing memory requirements. We investigate the memory-accuracy trade-off when
binarizing whole network and binarizing solely the classifier part. We also
discuss how these results translate to the edge-oriented Mobilenet~V1 neural
network on the Imagenet task. The final goal of this research is to enable
smart autonomous healthcare devices.",2006.11595v1
2020-07-03,Surpassing the resistance quantum with a geometric superinductor,"The superconducting circuit community has recently discovered the promising
potential of superinductors. These circuit elements have a characteristic
impedance exceeding the resistance quantum $R_\text{Q} \approx
6.45~\text{k}\Omega$ which leads to a suppression of ground state charge
fluctuations. Applications include the realization of hardware protected qubits
for fault tolerant quantum computing, improved coupling to small dipole moment
objects and defining a new quantum metrology standard for the ampere. In this
work we refute the widespread notion that superinductors can only be
implemented based on kinetic inductance, i.e. using disordered superconductors
or Josephson junction arrays. We present modeling, fabrication and
characterization of 104 planar aluminum coil resonators with a characteristic
impedance up to 30.9 $\text{k}\Omega$ at 5.6 GHz and a capacitance down to
$\leq1$ fF, with low-loss and a power handling reaching $10^8$ intra-cavity
photons. Geometric superinductors are free of uncontrolled tunneling events and
offer high reproducibility, linearity and the ability to couple magnetically -
properties that significantly broaden the scope of future quantum circuits.",2007.01644v1
2020-07-17,Breaking the quantum PIN code of atomic synapses,"Atomic synapses represent a special class of memristors whose operation
relies on the formation of metallic nanofilaments bridging two electrodes
across an insulator. Due to the magnifying effect of this narrowest
cross-section on the device conductance, a nanometer scale displacement of a
few atoms grants access to various resistive states at ultimately low energy
costs, satisfying the fundamental requirements of neuromorphic computing
hardware. Yet, device engineering lacks the complete quantum characterization
of such filamentary conductance. Here we analyze multiple Andreev reflection
processes emerging at the filament terminals when superconducting electrodes
are utilized. Thereby the quantum PIN code, i.e. the transmission probabilities
of each individual conduction channel contributing to the conductance of the
nanojunctions is revealed. Our measurements on Nb$_2$O$_5$ resistive switching
junctions provide a profound experimental evidence that the onset of the high
conductance ON state is manifested via the formation of truly atomic-sized
metallic filaments.",2007.09215v1
2020-07-21,"Granular packings with sliding, rolling and twisting friction","Intuition tells us that a rolling or spinning sphere will eventually stop due
to the presence of friction and other dissipative interactions. The resistance
to rolling and spinning/twisting torque that stops a sphere also changes the
microstructure of a granular packing of frictional spheres by increasing the
number of constraints on the degrees of freedom of motion. We perform discrete
element modeling simulations to construct sphere packings implementing a range
of frictional constraints under a pressure-controlled protocol. Mechanically
stable packings are achievable at volume fractions and average coordination
numbers as low as 0.53 and 2.5, respectively, when the particles experience
high resistance to sliding, rolling and twisting. Only when the particle model
includes rolling and twisting friction, were experimental volume fractions
reproduced.",2007.10860v1
2020-07-27,Unconventional bulk superconductivity in YFe$_2$Ge$_2$ single crystals,"Using a new horizontal flux growth technique to produce high quality crystals
of the unconventional superconductor YFe$_2$Ge$_2$ has led to a seven-fold
reduction in disorder scattering, resulting in mm-sized crystals with residual
resistivities $\simeq \SI{0.45}{\micro\ohm\centi\meter}$, resistivity ratios
$\simeq 430$ and sharp superconducting heat capacity anomalies. This enables
searching multi-probe experiments investigating the normal and superconducting
states of YFe$_2$Ge$_2$. Low temperature heat capacity measurements suggest a
significant residual Sommerfeld coefficient, consistent with in-gap states
induced by residual disorder as predicted for a sign-changing order parameter.",2007.13584v1
2020-08-28,Superinsulators: a toy realization of QCD in condensed matter,"Superinsulators are dual superconductors, dissipationless magnetic monopole
condensates with infinite resistance. The long-distance field theory of such
states of matter is QED with dynamical matter coupled via a compact BF
topological interaction. We will quantize the 2D model in the functional
Schr\""odinger picture and show how strong entanglement of charges leads to a
phase which is a single-color, asymptotically free version of QCD in which the
infinite resistance is caused by the linear confinement of charges. This phase
has been experimentally detected in TiN, NbTiN and InO thin films, including
signatures of asymptotically free behaviour and of the dual, electric Meissner
effect. This makes superinsulators a ``toy realization"" of QCD with Cooper
pairs playing the role of quarks.",2008.12541v1
2020-11-03,Relativistic non-resistive viscous magnetohydrodynamics from the kinetic theory:a relaxation time approach,"We derive the relativistic non-resistive, viscous second-order
magnetohydrodynamic equations for the dissipative quantities using the
relaxation time approximation. The Boltzmann equation is solved for a system of
particles and antiparticles using Chapman-Enskog like gradient expansion of the
single-particle distribution function truncated at second order. In the first
order, the transport coefficients are independent of the magnetic field. In the
second-order, new transport coefficients that couple magnetic field and the
dissipative quantities appear which are different from those obtained in the
14-moment approximation \cite{Denicol:2018rbw} in the presence of a magnetic
field. However, in the limit of the weak magnetic field, the form of these
equations are identical to the 14-moment approximation albeit with a different
values of these coefficients. We also derive the anisotropic transport
coefficients in the Navier-Stokes limit.",2011.01606v1
2020-11-04,First application of machine learning algorithms to the position reconstruction in Resistive Silicon Detectors,"RSDs (Resistive AC-Coupled Silicon Detectors) are n-in-p silicon sensors
based on the LGAD (Low-Gain Avalanche Diode) technology, featuring a continuous
gain layer over the whole sensor area. The truly innovative feature of these
sensors is that the signal induced by an ionising particle is seen on several
pixels, allowing the use of reconstruction techniques that combine the
information from many read-out channels. In this contribution, the first
application of a machine learning technique to RSD devices is presented. The
spatial resolution of this technique is compared to that obtained with the
standard RSD reconstruction methods that use analytical descriptions of the
signal sharing mechanism. A Multi-Output regressor algorithm, trained with a
combination of simulated and real data, leads to a spatial resolution of less
than 2 $\mu m$ for a sensor with a 100 $\mu m$ pixel. The prospects of future
improvements are also discussed.",2011.02410v3
2020-11-15,Hidden Quantum Hall Stripes in Al$_{x}$Ga$_{1-x}$As/Al$_{0.24}$Ga$_{0.76}$As Quantum Wells,"We report on transport signatures of hidden quantum Hall stripe (hQHS) phases
in high ($N > 2$) half-filled Landau levels of
Al$_{x}$Ga$_{1-x}$As/Al$_{0.24}$Ga$_{0.76}$As quantum wells with varying Al
mole fraction $x < 10^{-3}$. Residing between the conventional stripe phases
(lower $N$) and the isotropic liquid phases (higher $N$), where resistivity
decreases as $1/N$, these hQHS phases exhibit isotropic and $N$-independent
resistivity. Using the experimental phase diagram we establish that the stripe
phases are more robust than theoretically predicted, calling for improved
theoretical treatment. We also show that, unlike conventional stripe phases,
the hQHS phases do not occur in ultrahigh mobility GaAs quantum wells, but are
likely to be found in other systems.",2011.07563v1
2020-11-26,Spin-Torsion effect on collapsing of first generation stars into neutron stars rather than black holes in Einstein-Cartan-Sciama-Kibble theory,"In this project, we try to find the correlation between the non-local
pressure inside the massive neutron stars resisting the gravitational collapse
of the core and ECSK dark energy led by the effect of spin-torsion coupling
between quark fields and the space-time at very high densities much larger than
the nuclear density. The injection of dark energy into the core of massive
neutron stars (MANs) and extra resistant nature of this dark energy to the
collapse of MANs by the anti-gravity give the possibility of existence of
neutron stars in the unobserved mass range of $[2.16M_{\odot},5M_{\odot}]$.
Obtaining the ECSK TOV equation gives the local pressure of the ambient medium
of MANs. Moreover, the negative pressure from the ECSK dark energy is obtained
from the Lagrangian again, from which we are able to investigate the
hydro-static equilibrium of the core and ambient medium of the MANs. If the
equilibrium state is satisfied for the unobserved mass gap for the MANs in ECSK
theory framework this will imply our model predicts this vast mass range of
unobserved spectrum of the MANs in astrophysical studies.",2012.01131v1
2020-12-07,Van der Waals Multiferroic Tunnel Junctions,"Multiferroic tunnel junctions (MFTJs) have aroused significant interest due
to their functional properties useful for non-volatile memory devices. So far,
however, all the existing MFTJs have been based on perovskite-oxide
heterostructures limited by a relatively high resistance-area (RA) product
unfavorable for practical applications. Here, using first-principles
calculations, we explore spin-dependent transport properties of van der Waals
(vdW) MFTJs which consist of two-dimensional (2D) ferromagnetic FenGeTe2 (n =
3, 4, 5) electrodes and 2D ferroelectric In2Se3 barrier layers. We demonstrate
that such FemGeTe2/In2Se3/FenGeTe2 (m, n = 3, 4, 5) MFTJs exhibit multiple
non-volatile resistance states associated with different polarization
orientation of the ferroelectric In2Se3 layer and magnetization alignment of
the two ferromagnetic FenGeTe2 layers. We find a remarkably low RA product
which makes the proposed vdW MFTJs superior to the conventional MFTJs in terms
of their promise for non-volatile memory applications.",2012.03546v1
2020-12-28,Excitation spectra of quantum matter without quasiparticles II: random $t$-$J$ models,"We present numerical solutions of the spectral functions of $t$-$J$ models
with random and all-to-all exchange and global SU($M$) spin rotation symmetry.
The solutions are obtained from the saddle-point equations of the large volume
limit, followed by the large $M$ limit. These saddle point equations involve
Green's functions for fractionalized spinons and holons carrying emergent U(1)
gauge charges, obeying relations similar to those of the Sachdev-Ye-Kitaev
(SYK) models. The low frequency spectral functions are compared with an
analytic analysis of the operator scaling dimensions, with good agreement. We
also compute the low frequency and temperature behavior of gauge-invariant
observables: the electron Green's function, the local spin susceptibility and
the optical conductivity; along with the temperature dependence of the d.c.
resistivity. The time reparameterization soft mode (equivalent to the boundary
graviton in holographically dual models of two-dimensional quantum gravity)
makes important contributions to all observables, and provides a
linear-in-temperature contribution to the d.c. resistivity.",2012.14449v1
2020-12-31,Linear-in-$T$ resistivity from semiholographic non-Fermi liquid models,"We construct a semiholographic effective theory in which the electron of a
two-dimensional band hybridizes with a fermionic operator of a critical
holographic sector, while also interacting with other bands that preserve
quasiparticle characteristics. Besides the scaling dimension $\nu$ of the
fermionic operator in the holographic sector, the effective theory has two
{dimensionless} couplings $\alpha$ and $\gamma$ determining the holographic and
Fermi-liquid-type contributions to the self-energy respectively. We find that
irrespective of the choice of the holographic critical sector, there exists a
ratio of the effective couplings for which we obtain linear-in-$T$ resistivity
for a wide range of temperatures. This scaling persists to arbitrarily low
temperatures when $\nu$ approaches unity in which limit we obtain a marginal
Fermi liquid with a specific temperature dependence of the self-energy.",2012.15679v3
2021-02-05,Cross-Code verification and sensitivity analysis to effectively model the electrothermal instability,"This manuscript presents verification cases that are developed to study the
electrothermal instability (ETI). Specific verification cases are included to
ensure that the unit physics components necessary to model the ETI are
accurate, providing a path for fluid-based codes to effectively simulate ETI in
the linear and nonlinear growth regimes. Two software frameworks with different
algorithmic approaches are compared for accuracy in their ability to simulate
diffusion of a magnetic field, linear growth of the ETI, and a fully nonlinear
ETI evolution. The nonlinear ETI simulations show early time agreement, with
some differences emerging, as noted in the wavenumber spectrum, late into the
nonlinear development of ETI. A sensitivity study explores the role of
equation-of-state (EOS), vacuum density, and vacuum resistivity. EOS and vacuum
resistivity are found to be the most critical factors in the modeling of
nonlinear ETI development.",2102.03378v1
2021-02-20,Deformation Mechanics of Self-expanding Venous Stents: Modelling and Experiments,"Deformation properties of venous stents based on braided design, chevron
design, Z design, and diamond design are compared using in vitro experiments
coupled with analytical and finite element modelling. Their suitability for
deployment in different clinical contexts is assessed based on their
deformation characteristics. Self-expanding stainless steel stents possess
superior collapse resistance compared to Nitinol stents. Consequently, they may
be more reliable to treat diseases like May-Thurner syndrome in which
resistance against a concentrated (pinching) force applied on the stent is
needed to prevent collapse. Braided design applies a larger radial pressure
particularly for vessels of diameter smaller than 75% of its nominal diameter,
making it suitable for a long lesion with high recoil. Z design has the least
foreshortening, which aids in accurate deployment. Nitinol stents are more
compliant than their stainless steel counterparts, which indicates their
suitability in veins. The semi-analytical method presented can aid in rapid
assessment of topology governed deformation characteristics of stents and their
design optimization",2102.10219v1
2021-03-09,Coulomb drag between two strange metals,"We study the Coulomb drag between two strange-metal layers using the
Einstein-Maxwell-Dilaton model from holography. We show that the
low-temperature dependence of the drag resistivity is $\rho_D \propto T^4$,
which strongly deviates from the quadratic dependence of Fermi liquids. We also
present numerical results at room temperature, using typical parameters of the
cuprates, to provide an estimate of the magnitude of this effect for future
experiments. We find that the drag resistivity is enhanced by the plasmons
characteristic of the two-layer system.",2103.05652v3
2021-03-29,Electrical conductivity of strongly magnetized dense quark matter -- possibility of quantum hall effect,"We have pointed out the possibility of quantum Hall effect or quantum
patterns of transportation in a degenerate strongly magnetized quark matter,
which might be expected inside a highly dense compact star. An anisotropic
pattern of electrical conductivity and resistivity tensor in classical and
quantum cases is explored by considering cyclotron motion and Landau
quantization respectively. With increasing magnetic field, classical to quantum
transitions are realized through enhanced/reduced resistivity/conductivity with
jumping pattern. Considering QCD relaxation time scale of 10 fm, $eB\approx
(1-4) m_\pi^2$ might be considered as strong magnetic field for massless and
degenerate quark matter with quark chemical potential $\mu\approx 0.2-0.4$ GeV.
Beyond these threshold ranges of magnetic field, perpendicular motion of quarks
might be stopped and 3 $\rightarrow$ 1 dimensionally reduced conduction picture
might be established.",2103.15364v1
2021-03-30,Noise-resistant Deep Metric Learning with Ranking-based Instance Selection,"The existence of noisy labels in real-world data negatively impacts the
performance of deep learning models. Although much research effort has been
devoted to improving robustness to noisy labels in classification tasks, the
problem of noisy labels in deep metric learning (DML) remains open. In this
paper, we propose a noise-resistant training technique for DML, which we name
Probabilistic Ranking-based Instance Selection with Memory (PRISM). PRISM
identifies noisy data in a minibatch using average similarity against image
features extracted by several previous versions of the neural network. These
features are stored in and retrieved from a memory bank. To alleviate the high
computational cost brought by the memory bank, we introduce an acceleration
method that replaces individual data points with the class centers. In
extensive comparisons with 12 existing approaches under both synthetic and
real-world label noise, PRISM demonstrates superior performance of up to 6.06%
in Precision@1.",2103.16047v2
2021-04-09,Piracy-Resistant DNN Watermarking by Block-Wise Image Transformation with Secret Key,"In this paper, we propose a novel DNN watermarking method that utilizes a
learnable image transformation method with a secret key. The proposed method
embeds a watermark pattern in a model by using learnable transformed images and
allows us to remotely verify the ownership of the model. As a result, it is
piracy-resistant, so the original watermark cannot be overwritten by a pirated
watermark, and adding a new watermark decreases the model accuracy unlike most
of the existing DNN watermarking methods. In addition, it does not require a
special pre-defined training set or trigger set. We empirically evaluated the
proposed method on the CIFAR-10 dataset. The results show that it was resilient
against fine-tuning and pruning attacks while maintaining a high
watermark-detection accuracy.",2104.04241v1
2021-04-19,Intermittent current interruption method for commercial lithium ion batteries aging characterization,"In this article, a pioneering study is presented where the intermittent
current interruption method is used to characterize the aging behavior of
commercial lithium ion batteries. With a very resource-efficient
implementation, this method can track the battery resistive and diffusive
behaviors over the entire state of charge range and be able to determine the
aging throughout the lifetime of the batteries. In addition, the incremental
capacity analysis can be carried out with the same data set. This method can
provide measurement results with a high repeatability and produce equivalent
information as the electrochemical impedance spectroscopy method. In this
study, both the resistive and diffusive parameters increase with the battery
capacity fading. This method does not require advanced test equipment and even
with a 0.1 Hz sampling frequency, it is possible to extract usable parameters
by prolonging the interruption length. Therefore, it has the potential to be
easily implemented in the charging sequence in electric vehicles or stationary
storage batteries for aging diagnostics.",2104.09260v3
2021-05-17,StRETcH: a Soft to Resistive Elastic Tactile Hand,"Soft optical tactile sensors enable robots to manipulate deformable objects
by capturing important features such as high-resolution contact geometry and
estimations of object compliance. This work presents a variable stiffness soft
tactile end-effector called StRETcH, a Soft to Resistive Elastic Tactile Hand,
that is easily manufactured and integrated with a robotic arm. An elastic
membrane is suspended between two robotic fingers, and a depth sensor capturing
the deformations of the elastic membrane enables sub-millimeter accurate
estimates of contact geometries. The parallel-jaw gripper varies the stiffness
of the membrane by uni-axially stretching it, which controllably modulates
StRETcH's effective modulus from approximately 4kPa to 9kPa. This work uses
StRETcH to reconstruct the contact geometry of rigid and deformable objects,
estimate the stiffness of four balloons filled with different substances, and
manipulate dough into a desired shape.",2105.08154v1
2021-05-26,Temperature Damping of Magneto-Intersubband Resistance Oscillations in Magnetically Entangled Subbands,"Magneto-intersubband resistance oscillations (MISO) of highly mobile 2D
electrons in symmetric GaAs quantum wells with two populated subbands are
studied in magnetic fields tilted from the normal to the 2D electron layer at
different temperatures $T$. Decrease of MISO amplitude with temperature
increase is observed. At moderate tilts the temperature decrease of MISO
amplitude is consistent with decrease of Dingle factor due to reduction of
quantum electron lifetime at high temperatures. At large tilts new regime of
strong MISO suppression with the temperature is observed. Proposed model
relates this suppression to magnetic entanglement between subbands, leading to
beating in oscillating density of states. The model yields corresponding
temperature damping factor: $A_{MISO}(T)=X/\sinh(X)$, where $X=2\pi^2kT\delta
f$ and $\delta f$ is difference frequency of oscillations of density of states
in two subbands. This factor is in agreement with experiment. Fermi liquid
enhancement of MISO amplitude is observed.",2105.12263v1
2021-06-12,RF surface resistance tuning of superconducting niobium via thermal diffusion of native oxide,"Recently, Nb superconducting radio frequency cavities vacuum heat treated
between 300-400 C for a few hours have exhibited very high quality factors
(~5x10^10 at 2.0 K). New secondary ion mass spectrometry measurements of O, N
and C show this enhancement in RF surface conductivity is primarily associated
with interstitial O alloying via dissolution and diffusion of the native oxide.
We use a theory of oxide decomposition and O diffusion to quantify previously
unknown parameters crucial in modeling this process. RF measurements of a
vacuum heat treated Nb superconducting radio frequency cavity confirm the
minimized surface resistance (higher Q0) previously expected only from 800 C
diffusive alloying with N.",2106.06647v2
2021-09-07,A Novel Manufacturing Process for Glass THGEMs and First Characterisation in an Optical Gaseous Argon TPC,"This paper details a novel, patent pending, abrasive machining manufacturing
process for the formation of sub-millimetre holes in THGEMs, with the intended
application in gaseous and dual-phase TPCs. Abrasive machining favours a
non-ductile substrate such as glasses or ceramics. This innovative
manufacturing process allows for unprecedented versatility in THGEM substrates,
electrodes, and hole geometry and pattern. Consequently, THGEMs produced via
abrasive machining can be tailored for specific properties, for example: high
stiffness, low total thickness variation, radiopurity, moisture
absorption/outgassing and/or carbonisation resistance. This paper specifically
focuses on three glass substrate THGEMs (G-THGEMs) made from Schott Borofloat
33 and Fused Silica. Circular and hexagonal hole shapes are also investigated.
The G-THGEM electrodes are made from Indium Tin Oxide (ITO), with a resistivity
of 150 $\Omega$/Sq. All G-THGEMs were characterised in an optical (EMCCD)
readout GArTPC, and compared to a traditionally manufactured FR4 THGEM, with
their charging and secondary scintillation (S2) light production behaviour
analysed.",2109.02910v2
2021-09-17,Less is more: more scattering leading to less resistance,"We study the breaking of integrability by a finite density of dilute
impurities, specifically the emerging diffusive transport. Provided the
distance between impurities (localized perturbations) is large, one would
expect that the scattering rates are additive, and therefore, the resistivity
is proportional to the number of impurities (the so-called Matthiessen's rule).
We show that this is, in general, not the case. If transport is anomalous in
the original integrable system without impurities, the diffusion constant in
the non-integrable system at low impurity density gets a nontrivial power-law
dependence on the impurity density, with the power being determined by the
dynamical scaling exponent of anomalous transport. We also find a regime at
high impurity density in which, counterintuitively, adding more impurities to
an already diffusive system increases transport rather than decreases it.",2109.08390v2
2021-09-17,Long-term evolution of neutron-star merger remnants in general relativistic resistive-magnetohydrodynamics with a mean-field dynamo term,"Long-term neutrino-radiation resistive-magnetohydrodynamics simulations in
full general relativity are performed for a system composed of a massive
neutron star and a torus formed as a remnant of binary neutron star mergers.
The simulation is performed in axial symmetry incorporating a mean-field dynamo
term for a hypothetical amplification of the magnetic-field strength. We first
calibrate the mean-field dynamo parameters by comparing the results for the
evolution of black hole-disk systems with viscous hydrodynamics results. We
then perform simulations for the system of a remnant massive neutron star and a
torus. As in the viscous hydrodynamics case, the mass ejection occurs primarily
from the torus surrounding the massive neutron star. The total ejecta mass and
electron fraction in the new simulation are similar to those in the viscous
hydrodynamics case. However, the velocity of the ejecta can be significantly
enhanced by magnetohydrodynamics effects caused by global magnetic fields.",2109.08732v1
2021-09-20,Fast Online Optimization for Terrain-Blind Bipedal Robot Walking with a Decoupled Actuated SLIP Model,"We present a highly reactive controller which enables bipedal robots to
blindly walk over various kinds of uneven terrains while resisting pushes. The
high level motion planner does fast online optimization for footstep locations
and Center of Mass (CoM) height using the decoupled actuated Spring Loaded
Inverted Pendulum (aSLIP) model. The decoupled aSLIP model simplifies the
original aSLIP with Linear Inverted Pendulum (LIP) dynamics in horizontal
states and spring dynamics in the vertical state. The motion planning can be
formulated as a discrete-time Model Predictive Control (MPC) and solved at a
frequency of 1k~HZ. The output of the motion planner using a reduced-order
model is fed into an inverse-dynamics based whole body controller for execution
on the robot. A key result of this controller is that the foot of the robot is
compliant, which further extends the robot's ability to be robust to unobserved
terrain changes. We evaluate our method in simulation with the bipedal robot
SLIDER. Results show the robot can blindly walk over various uneven terrains
including slopes, wave fields and stairs. It can also resist pushes while
walking on uneven terrain.",2109.09373v1
2021-11-15,Copper Large-scale Grain Growth by UV Nanosecond Pulsed Laser Annealing,"UV nanosecond pulsed laser annealing (UV NLA) enables both surface-localized
heating and short timescale high temperature processing, which can be
advantageous to reduce metal line resistance by enlarging metal grains in lines
or in thin films, while maintaining the integrity and performance of
surrounding structures. In this work UV NLA is applied on a typical Cu thin
film, demonstrating a mean grain size of over 1 {\mu}m and 400 nm in a melt and
sub-melt regime, respectively. Along with such grain enlargement, film
resistivity is also reduced.",2111.07580v1
2021-11-26,Absence versus Presence of Dissipative Quantum Phase Transition in Josephson Junctions,"Dissipative quantum phase transition has been widely believed to occur in a
Josephson junction coupled to a resistor despite a lack of concrete
experimental evidence. Here, on the basis of both numerical and analytical
nonperturbative renormalization group (RG) analyses, we reveal breakdown of
previous perturbative arguments and defy the common wisdom that the transition
always occurs at the quantum resistance $R_{Q} \!=\! h/(4e^2)$. We find that RG
flows in nonperturbative regimes induce nonmonotonic renormalization of the
charging energy and lead to a qualitatively different phase diagram, where the
insulator phase is strongly suppressed to the deep charge regime (Cooper pair
box), while the system is always superconducting in the transmon regime. We
identify a previously overlooked dangerously irrelevant term as an origin of
the failure of conventional understandings. Our predictions can be tested in
recent experiments realizing high-impedance long superconducting waveguides and
would provide a solution to the long-standing controversy about the fate of
dissipative quantum phase transition in the resistively shunted Josephson
junction.",2111.13710v3
2021-12-02,Effective model and Magnetic Properties of the Resistive Electron Quadrupling State,"Recent experiments [V.~Grinenko {\it et al.} {Nat. Phys. {\bf 17}, 1254
(2021)}; \url{http://doi.org/10.1038/s41567-021-01350-9}] reported the
observation of a condensate of four-fermion composites. This is a resistive
state that spontaneously breaks the time-reversal symmetry, leading to
unconventional magnetic properties, detected in muon spin rotation experiments
and by the appearance of a spontaneous Nernst effect. In this work, we derive
an effective model for the four-fermion order parameter that describes the
observed spontaneous magnetic fields in this state. We show that this model,
which is alike to the Faddeev-Skyrme model can host skyrmions:
magnetic-flux-carrying topological excitations.",2112.01286v2
2021-12-06,A stableness of resistance model for nonresponse adjustment with callback data,"Nonresponse arises frequently in surveys and follow-ups are routinely made to
increase the response rate. In order to monitor the follow-up process, callback
data have been used in social sciences and survey studies for decades. In
modern surveys, the availability of callback data is increasing because the
response rate is decreasing and follow-ups are essential to collect maximum
information. Although callback data are helpful to reduce the bias in surveys,
such data have not been widely used in statistical analysis until recently. We
propose a stableness of resistance assumption for nonresponse adjustment with
callback data. We establish the identification and the semiparametric
efficiency theory under this assumption, and propose a suite of semiparametric
estimation methods including a doubly robust one, which generalize existing
parametric approaches for callback data analysis. We apply the approach to a
Consumer Expenditure Survey dataset. The results suggest an association between
nonresponse and high housing expenditures.",2112.02822v3
2021-12-29,Geometric interference in a high-mobility graphene annulus p-n junction device,"The emergence of interference is observed in the resistance of a graphene
annulus pn junction device as a result of applying two separate gate voltages.
The observed resistance patterns are carefully inspected, and it is determined
that the position of the peaks resulting from those patterns are independent of
temperature and magnetic field. Furthermore, these patterns are not
attributable to Aharonov-Bohm oscillations, Fabry Perot interference at the
junction, or moir\'e potentials. The device data are compared with those of
another device fabricated with a traditional Hall bar geometry, as well as with
quantum transport simulation data. Since the two devices are of different
topological classes, the subtle differences observed in the corresponding
measured data indicate that the most likely source of the observed geometric
interference patterns is quantum scarring.",2112.14614v1
2022-03-26,A construction of exotic metallic states,"We discuss examples of two dimensional metallic states with charge
fractionalization, and we will demonstrate that the mechanism of charge
fractionalization leads to exotic metallic behaviors at low and intermediate
temperature. The simplest example of such state is constructed by fermionic
partons at finite density coupled to a $Z_N$ gauge field, whose properties can
be studied through rudimentary methods. This simple state has the following
exotic features: (1) at low temperature this state is a ""bad metal"" whose
resistivity can exceed the Mott-Ioffe-Regel limit; (2) while increasing
temperature $T$ the resistivity $\rho(T)$ is a nonmonotonic function, and it
crosses over from a bad metal at low $T$ to a good metal at relatively high
$T$; (3) the optical conductivity $\sigma(\omega)$ has a small Drude weight at
low $T$, and a larger Drude weight at intermediate $T$; (4) at low temperature
the metallic state has a large Lorenz number, which strongly violates the
Wiedemann-Franz law. A more complex example with fermionic partons at finite
density coupled to a SU(N) gauge field will also be constructed.",2203.14168v1
2022-04-07,Using electrical resistance asymmetries to infer the geometric shapes of foundry patterned nanophotonic structures,"While silicon photonics has leveraged the nanofabrication tools and
techniques from the microelectronics industry, it has also inherited the
metrological methods from the same. Photonics fabrication is inherently
different from microelectronics in its intrinsic sensitivity to 3D shape and
geometry, especially in a high-index contrast platform like
silicon-on-insulator. In this work, we show that electrical resistance
measurements can in principle be used to infer the geometry of such
nanophotonic structures and reconstruct the micro-loading curves of foundry
etch processes. We implement our ideas to infer 3D geometries from a standard
silicon photonics foundry and discuss some of the potential sources of error
that need to be calibrated out to improve the reconstruction accuracy.",2204.03591v1
2022-04-12,Biermann Battery Powered by Resistive Heating Induced by Cosmic Ray Streaming,"It is recently proposed that cosmic rays generate a seed magnetic field in
the early universe. In this paper, we propose another generation mechanism of
magnetic fields by cosmic rays, which is the Biermann battery driven by
resistive heating induced by the streaming of cosmic rays. This mechanism is
dominant in small-scale, low-temperature, and strongly-ionized regions,
compared with other previously proposed mechanisms. Because cosmic rays are
expected to be accelerated after the death of the first stars, this mechanism
can work during structure formation in the early universe. We show that it
makes the seed magnetic field with sufficient strength for the subsequent
dynamo to amplify it to the micro Gauss level in the current galaxies.",2204.05787v2
2022-06-15,Demonstration of high sensitivity of microwave-induced resistance oscillations to circular polarization,"We demonstrate that long-debated immunity of microwave-induced resistance
oscillations (MIRO) to the sense of circular polarization is not a generic
property of this phenomenon in solid-state two-dimensional electron systems.
Using a large-area GaAs-based heterostructure we detect up to 30 times larger
MIRO signal for the cyclotron resonance (CR) active helicity, fully consistent
with the concurrently measured transmission and the deduced CR shape of the
Drude absorption. We further elaborate conditions to avoid extrinsic factors
capable of producing an apparent immunity of the photoresponse.",2206.07600v2
2022-07-04,Granular Effect on Electron Conduction in Discontinuous Metal Films,"We reanalyze the seminal work by Dolan and Osheroff [Phys. Rev. Lett.
$\textbf{43}$, 721 (1979)] which reported anomalous low-temperature conduction
of high-resistivity thin-film metal strips. We argue that the observed
logarithmic increase of resistance with decreasing temperature in their
3-nm-thick Au-Pd strips be ascribed to the granularity effect on electron
conduction in discontinuous metal films. This reanalysis is further supported
by our measurements on conducting Pb$_x$(SiO$_2$)$_{1-x}$ nanogranular films,
where $x$ is the volume fraction of Pb.",2207.02304v2
2022-07-23,Bandwidth-Hard Functions from Random Permutations,"ASIC hash engines are specifically optimized for parallel computations of
cryptographic hashes and thus a natural environment for mounting brute-force
attacks on hash functions. Two fundamental advantages of ASICs over general
purpose computers are the area advantage and the energy efficiency. The
memory-hard functions approach the problem by reducing the area advantage of
ASICs compared to general-purpose computers. Traditionally, memory-hard
functions have been analyzed in the (parallel) random oracle model. However, as
the memory-hard security game is multi-stage, indifferentiability does not
apply and instantiating the random oracle becomes a non-trivial problem. Chen
and Tessaro (CRYPTO 2019) considered this issue and showed how random oracles
should be instantiated in the context of memory-hard functions. The
Bandwidth-Hard functions, introduced by Ren and Devadas (TCC 2017), aim to
provide ASIC resistance by reducing the energy advantage of ASICs. In
particular, bandwidth-hard functions provide ASIC resistance by guaranteeing
high run time energy cost if the available cache is not large enough.
Previously, bandwidth-hard functions have been analyzed in the parallel random
oracle model. In this work, we show how those random oracles can be
instantiated using random permutations in the context of bandwidth-hard
functions. Our results are generic and valid for any hard-to-pebble graphs.",2207.11519v1
2022-08-10,Spin and valley effects on the quantum phase transition in two dimensions,"Using several independent methods, we find that the metal-insulator
transition occurs in the strongly-interacting two-valley two-dimensional
electron system in ultra-high mobility SiGe/Si/SiGe quantum wells in zero
magnetic field. The transition survives in this system in parallel magnetic
fields strong enough to completely polarize the electrons' spins, thus making
the electron system ""spinless"". In both cases, the resistivity on the metallic
side near the transition increases with decreasing temperature, reaches a
maximum at a temperature $T_{\text{max}}$, and then decreases. The decrease
reaches more than an order of magnitude in zero magnetic field. The value of
$T_{\text{max}}$ in zero magnetic field is found to be close to the
renormalized Fermi temperature. However, rather than increasing along with the
Fermi temperature, the value $T_{\text{max}}$ decreases appreciably for
spinless electrons in spin-polarizing magnetic fields. The observed behavior of
$T_{\text{max}}$ cannot be described by existing theories. The results indicate
the spin-related origin of the effect. At the same time, the low-temperature
resistivity drop in both spin-unpolarized and spinless electron systems is
described quantitatively by the dynamical mean-field theory.",2208.05356v1
2022-09-19,Adaptive 3D Mesh Steganography Based on Feature-Preserving Distortion,"3D mesh steganographic algorithms based on geometric modification are
vulnerable to 3D steganalyzers. In this paper, we propose a highly adaptive 3D
mesh steganography based on feature-preserving distortion (FPD), which
guarantees high embedding capacity while effectively resisting 3D steganalysis.
Specifically, we first transform vertex coordinates into integers and derive
bitplanes from them to construct the embedding domain. To better measure the
mesh distortion caused by message embedding, we propose FPD based on the most
effective sub-features of the state-of-the-art steganalytic feature set. By
improving and minimizing FPD, we can efficiently calculate the optimal
vertex-changing distribution and simultaneously preserve mesh features, such as
steganalytic and geometric features, to a certain extent. By virtue of the
optimal distribution, we adopt the Q-layered syndrome trellis coding (STC) for
practical message embedding. However, when Q varies, calculating bit
modification probability (BMP) in each layer of Q-layered will be cumbersome.
Hence, we contrapuntally design a universal and automatic BMP calculation
approach. Extensive experimental results demonstrate that the proposed
algorithm outperforms most state-of-the-art 3D mesh steganographic algorithms
in terms of resisting 3D steganalysis.",2209.08884v1
2022-10-10,A general efficiency relation for molecular machines,"Living systems efficiently use chemical fuel to do work, process information,
and assemble patterns despite thermal noise. Whether high efficiency arises
from general principles or specific fine-tuning is unknown. Here, applying a
recent mapping from nonequilibrium systems to battery-resistor circuits, I
derive an analytic expression for the efficiency of any dissipative molecular
machine driven by one or a series of chemical potential differences. This
expression disentangles the chemical potential from the machine's details,
whose effect on the efficiency is fully specified by a constant called the load
resistance. The efficiency passes through a switch-like inflection point if the
balance between chemical potential and load resistance exceeds thermal noise.
Therefore, dissipative chemical engines qualitatively differ from heat engines,
which lack threshold behavior. This explains all-or-none dynein stepping with
increasing ATP concentration observed in single-molecule experiments. These
results indicate that biomolecular energy transduction is efficient not because
of idosyncratic optimization of the biomolecules themselves, but rather because
the concentration of chemical fuel is kept above a threshold level within
cells.",2210.04380v1
2022-10-18,A survey of open questions in adaptive therapy: bridging mathematics and clinical translation,"Adaptive therapy is a dynamic cancer treatment protocol that updates (or
""adapts"") treatment decisions in anticipation of evolving tumor dynamics. This
broad term encompasses many possible dynamic treatment protocols of
patient-specific dose modulation or dose timing. Adaptive therapy maintains
high levels of tumor burden to benefit from the competitive suppression of
treatment-sensitive subpopulations on treatment-resistant subpopulations. This
evolution-based approach to cancer treatment has been integrated into several
ongoing or planned clinical trials, including treatment of metastatic castrate
resistant prostate cancer, ovarian cancer, and BRAF-mutant melanoma. In the
previous few decades, experimental and clinical investigation of adaptive
therapy has progressed synergistically with mathematical and computational
modeling. In this work, we discuss 11 open questions in cancer adaptive therapy
mathematical modeling. The questions are split into three sections: 1) the
necessary components of mathematical models of adaptive therapy 2) design and
validation of dosing protocols, and 3) challenges and opportunities in clinical
translation.",2210.12062v1
2022-10-26,Access Service Records Based Trust Management Scheme for Internet of Things,"The distributed structure of the Internet of things has gradually replaced
the centralized structure because of its scalability, security, and single
point of failure. The huge scale of information recording of the Internet of
things brings challenges and opportunities to the trust management of the
Internet of things. Through the analysis of a variety of existing trust
management schemes, this paper proposes a unified data structure for
distributed access service records, TokenChain, in which triple DES data
encryption is used to ensure privacy and traceability, to achieve a unified
trust management scheme. Based on TokenChain, a three-tier trust management
architecture (TokenChain-Based Trust Management, TBTM) is implemented in the
data layer, computing layer, and control layer. Trust evaluation is affected by
four statistics and finally converges to a real value under certain conditions.
Based on TBTM, we carry out theoretical analysis, malicious attack resistance,
simulation, and performance evaluation in various complex scenarios. The
results show that TBTM satisfies service prediction, global trust analysis,
high security, and excellent performance in multi-domain complex scenarios.
Compared with the existing trust management schemes, TBTM realizes
cross-scenario interaction and two-way trust management, and simultaneously
meets the characteristics of traceability, tamper-proof, attack resistance, and
distribution. Finally, this paper is summarized.",2210.14566v1
2022-11-13,Negative differential thermal resistance of fluids induced by heat baths,"It has recently been shown that in one-dimensional hard-point gases, there is
a mechanism that induces negative differential thermal resistance (NDTR)
between heat baths. We examine this mechanism in more general higher
dimensional fluids described by multiparticle collision dynamics. We consider
fluids in a finite cuboid region of three-dimensional space with each end in
contact with a heat bath. Based on analytical results and numerical models, we
find that the mechanism underlying NDTR also works for high-dimensional fluidic
systems with weak interactions and is very robust to mixed fluids. Our results
significantly advance knowledge of NDTR induced by heat bath and illuminate new
directions to explore in fabricating fluid thermal transistors in micro- and
nanosystems.",2211.06872v1
2022-11-16,Coherent interlayer coupling in quasi-two-dimensional Dirac fermions in $α$-(BEDT-TTF)$_2$I$_3$,"Theoretical and experimental studies have supported that the electronic
structure of $\alpha$-(BEDT-TTF)$_2$I$_3$ under pressure is described by
two-dimensional Dirac fermions. When the interlayer tunneling is coherent, the
electronic structure of the system becomes three-dimensional, and we expect the
peak structure to appear in the interlayer resistivity under magnetic fields.
We theoretically and experimentally show that the peak appears in the
interlayer resistivity at low temperatures and high magnetic fields. From the
experiment, we estimate that the magnitude of the interlayer tunneling is $t_1
\sim 1$ meV. Our result opens the door to investigating the three-dimensional
electronic structure of $\alpha$-(BEDT-TTF)$_2$I$_3$.",2211.08730v2
2023-03-02,Random telegraph fluctuations in granular microwave resonators,"Microwave circuit electrodynamics of disordered superconductors is a very
active research topic spawning a wide range of experiments and applications.
For compact superconducting circuit elements, the transition to an insulating
state poses a limit to the maximum attainable kinetic inductance. It is
therefore vital to study the fundamental noise properties of thin films close
to this transition, particularly in situations where a good coherence and
temporal stability is required. In this paper, we present measurements on
superconducting granular aluminum microwave resonators with high normal state
resistances, where the influence of the superconductor to insulator phase
transition is visible. We trace fluctuations of the fundamental resonance
frequency and observe, in addition to a 1/f noise pattern, a distinct excess
noise, reminiscent of a random telegraph signal. The excess noise shows a
strong dependency on the resistivity of the films as well as the sample
temperature, but not on the applied microwave power.",2303.01079v1
2023-03-28,Anomalous superconducting diode effect in a polar superconductor,"A superconductor with broken time reversal and inversion symmetry may exhibit
nonreciprocal charge transport, including a nonreciprocal critical current,
also known as superconducting diode effect. We report an intrinsic
superconducting diode effect in a polar strontium titanate film. Differential
resistance measurements reveal a superconducting state whose depairing current
is polarity dependent. There is, however, no measurable deviation from Ohmic
behavior, implying that this state does not arise from a bulk magnetochiral
anisotropy. In the entire measurement range, the only deviation from linearity
in the differential resistance is on the edge of the superconducting transition
at high magnetic fields, likely due to the motion of flux vortices.
Furthermore, the magnitude of the effect is preserved even when the in-plane
magnetic field is oriented parallel to the current, indicating that this effect
truly does not originate from a bulk magnetochiral anisotropy.",2303.16238v1
2023-05-16,Gate-tunable multiband transport in ZrTe5 thin devices,"Interest in ZrTe5 has been reinvigorated in recent years owing to its
potential for hosting versatile topological electronic states and intriguing
experimental discoveries. However, the mechanism of many of its unusual
transport behaviors remains controversial, for example, the characteristic peak
in the temperature-dependent resistivity and the anomalous Hall effect. Here,
through employing a clean dry-transfer fabrication method under inert
environment, we successfully obtain high-quality ZrTe5 thin devices that
exhibit clear dual-gate tunability and ambipolar field effects. Such devices
allow us to systematically study the resistance peak as well as the Hall effect
at various doping densities and temperatures, revealing the contribution from
electron-hole asymmetry and multiple-carrier transport. By comparing with
theoretical calculations, we suggest a simplified semiclassical two-band model
to explain the experimental observations. Our work helps to resolve the
long-standing puzzles on ZrTe5 and could potentially pave the way for realizing
novel topological states in the two-dimensional limit.",2305.09119v1
2023-05-26,Room temperature quantum Hall effect in a gated ferroelectric-graphene heterostructure,"The quantum Hall effect is widely used for the investigation of fundamental
phenomena, ranging from topological phases to composite fermions. In
particular, the discovery of a room temperature resistance quantum in graphene
is significant for compact resistance standards that can operate above
cryogenic temperatures. However, this requires large magnetic fields that are
accessible only in a few high magnetic field facilities. Here, we report on the
quantum Hall effect in graphene encapsulated by the ferroelectric insulator
CuInP2S6. Electrostatic gating of the graphene channel enables the Fermi energy
to be tuned so that electrons in the localized states of the insulator are in
equilibrium with the current-carrying, delocalized states of graphene. Due to
the presence of strongly bound states in this hybrid system, a quantum Hall
plateau can be achieved at room temperature in relatively modest magnetic
fields. This phenomenon offers the prospect for the controlled manipulation of
the quantum Hall effect at room temperature.",2305.16825v1
2023-08-07,Hall Coefficient and Resistivity in the Doped Bilayer Hubbard Model,"Finding and understanding non-Fermi liquid transport behaviors are at the
core of condensed matter physics. Most of the existing studies were devoted to
the monolayer Hubbard model, which is the simplest model that captures
essential features of high-temperature superconductivity. Here we discover a
new type of non-Fermi liquid behavior emergent in the hole-doped bilayer
Hubbard model, using dynamical mean-field theory with a full consideration of
the short-range interlayer electron correlation. We find that at low
temperatures, the Hall coefficient has a strong nonmonotonic dependence on
temperature, leading to a double or quadruple reversal of its sign depending on
the doping level. At the same time, the resistivity exhibits two plateaus
rather than linearity in its temperature dependence. We show that these
intriguing transport behaviors stem from the formation of coherent interlayer
singlets, which scatter off gapped collective modes arising from short-range
interlayer antiferromagnetic fluctuations.",2308.03862v1
2023-11-17,Fate of the superconducting state in floating islands of hybrid nanowire devices,"We investigate the impact of transport current on the superconducting order
parameter in superconducting islands in full-shell epitaxial Al-InAs nanowires.
Depending on a device layout, the suppression of superconductivity occurs in
three fundamentally different ways -- by a critical current in the case of
superconducting reservoirs and by a critical voltage or by a critical Joule
power in the case of normal reservoirs. In the latter case, the collapse of the
superconducting state depends on the ratio of the dwell time and the
electron-phonon relaxation time of quasiparticles in the island. For low
resistive and high resistive coupling to the reservoirs, respectively, the
relaxation-free regime and the strong electron-phonon relaxation regime are
realized. Our results shed light on potential shortcomings of finite-bias
transport spectroscopy in floating islands.",2311.10676v2
2023-11-29,Dynamic Programming Algorithms for Discovery of Antibiotic Resistance in Microbial Genomes,"The translation of comparative genomics into clinical decision support tools
often depends on the quality of sequence alignments. However, currently used
methods of multiple sequence alignments suffer from significant biases and
problems with aligning diverged sequences. The objective of this study was to
develop and test a new multiple sequence alignment (MSA) algorithm suitable for
the high-throughput comparative analysis of different microbial genomes. This
algorithm employs an innovative tensor indexing method for partitioning the
dynamic programming hyper-cube space for parallel processing. We have used the
clinically relevant task of identifying regions that determine resistance to
antibiotics to test the new algorithm and to compare its performance with
existing MSA methods. The new method ""mmDst"" performed better than existing MSA
algorithms for more divergent sequences because it employs a simultaneous
alignment scoring recurrence, which effectively approximated the score for edge
missing cell scores that fall outside the scoring region.",2311.17538v1
2023-12-07,Energy dissipation in astrophysical simulations: results of the Orszag-Tang test problem,"The magnetic field through the magnetic reconnection process affects the
dynamics and structure of astrophysical systems. Numerical simulations are the
tools to study the evolution of these systems. However, the resolution,
dimensions, resistivity, and turbulence of the system are some important
parameters to take into account in the simulations. In this paper, we
investigate the evolution of magnetic energy in astrophysical simulations by
performing a standard test problem for MHD codes, Orszag-Tang. We estimate the
numerical dissipation in the simulations using state-of-the-art numerical
simulation code in astrophysics, PLUTO. The estimated numerical resistivity in
2D simulations corresponds to the Lundquist number $\approx 10^{4}$ in the
resolution of $512\times512$ grid cells. It is also shown that the plasmoid
unstable reconnection layer can be resolved with sufficient resolutions. Our
analysis demonstrates that in non-relativistic magnetohydrodynamics
simulations, magnetic and kinetic energies undergo conversion into internal
energy, resulting in plasma heating.",2312.06675v1
2024-01-10,Some aspects of resistive-to-normal state transition by direct and microwave currents in superconducting thin films with phase slip lines,"Based on analysis of current-voltage characteristics and imaging of the
resistive state of thin-film tin strips using the low-temperature laser
scanning microscopy (LTLSM), the process of destruction of superconductivity by
current and microwave irradiation with the formation and spatial rearrangement
of the order parameter phase slip lines, and their transformation into discrete
localized normal domains is shown. The prospects of LTLSM are considered form
the point of view of study of the high-frequency properties of superconducting
structures and spatial characteristics in the pre-critical state for
instrumental applications.",2401.05333v1
2024-02-24,A simple model of globally magnetized accretion discs,"We present an analytic, quasi-local dynamo model for accretion discs threaded
by net, vertical magnetic flux. In a simple slab geometry and ignoring
stochastic mean-field dynamo effects, we calculate the large-scale field
resulting from the balance between kinematic field amplification and turbulent
resistive diffusion. The ability of the disc to accumulate magnetic flux is
sensitive to a single parameter dependent on the ratio of the vertical
resistive diffusion time to the Alfv\'en crossing time, and we show how the
saturation levels of magnetorotational and other instabilities can govern disc
structure and evolution. Under wide-ranging conditions, inflow is governed by
large-scale magnetic stresses rather than internal viscous stress. We present
models of such ""magnetically boosted"" discs and show that they lack a radiation
pressure-dominated zone. Our model can account for ""magnetically elevated""
discs as well as instances of midplane outflow and field reversals with height
that have been seen in some global simulations. Using the time-dependent
features of our model, we find that the incorporation of dynamo effects into
disc structure can lead to steady or episodic ""magnetically arrested discs""
(MADs) that maximize the concentration of magnetic flux in their central
regions.",2402.15657v1
2024-02-28,Stability studies of sealed Resistive Plate Chambers,"The phase-out of hydro-fluorocarbons, owing to their high Global Warming
Power, affecting the main gas used in Resistive Plate Chambers (RPCs),
tetrafluoroethane C$_2$H$_2$F$_4$, has increased operational difficulties on
existing systems and imposes strong restrictions on its use in new systems.
  This has motivated a new line of R\&D on sealed RPCs: RPCs that do not
require a continuous gas flow for their operation and dispense the use of very
complex and expensive re-circulation and/or recycling gas systems. At the
moment it is not clear whether this solution can cover all fields of
application normally allocated to RPCs, but it seems that it could be
considered as a valid option for low particle flux triggering/tracking of
particles, e.g. in cosmic ray or rare event experiments.
  In this work, we demonstrate the feasibility of a small telescope for
atmospheric muon tracking consisting of four $300$~x~$300$~mm$^2$ sealed RPCs
with gas gap widths of $1$~mm, $1.5$~mm and $2$~mm. The results suggest that it
is possible to operate this type of detectors for extended periods of time
(more than five months) with its main characteristics, efficiency, average
charge and streamer probability, without apparent degradation and similar to a
RPC operated in continuous gas flow.",2402.18663v1
2024-03-06,Foot Shape-Dependent Resistive Force Model for Bipedal Walkers on Granular Terrains,"Legged robots have demonstrated high efficiency and effectiveness in
unstructured and dynamic environments. However, it is still challenging for
legged robots to achieve rapid and efficient locomotion on deformable, yielding
substrates, such as granular terrains. We present an enhanced resistive force
model for bipedal walkers on soft granular terrains by introducing effective
intrusion depth correction. The enhanced force model captures fundamental
kinetic results considering the robot foot shape, walking gait speed variation,
and energy expense. The model is validated by extensive foot intrusion
experiments with a bipedal robot. The results confirm the model accuracy on the
given type of granular terrains. The model can be further integrated with the
motion control of bipedal robotic walkers.",2403.03460v1
2024-03-13,Lithographically Defined Zerogap Strain Sensors,"Metal thin films on soft polymers provide a unique opportunity for
resistance-based strain sensors. A mechanical mismatch between the conductive
film and the flexible substrate causes cracks to open and close, changing the
electrical resistance as a function of strain. However, the very randomness of
the formation, shape, length, orientation, and distance between adjacent cracks
limits the sensing range as well as repeatability. Herein, we present a
breakthrough: the Zerogap Strain Sensor, whereby lithography eliminates
randomness and violent tearing process inherent in conventional crack sensors
and allows for short periodicity between gaps with gentle sidewall contacts,
critical in high strain sensing enabling operation over an unprecedently wide
range. Our sensor achieves a gauge factor of over 15,000 at {\epsilon}ext=18%,
the highest known value. With the uniform gaps of three-to-ten thousand
nanometer widths characterized by periodicity and strain, this approach has far
reaching implications for future strain sensors whose range is limited only by
that of the flexible substrate, with non-violent operations that always remain
below the tensile limit of the metal.",2403.08288v1
2024-03-19,Revisiting shear stress tensor evolution: Non-resistive magnetohydrodynamics with momentum-dependent relaxation time,"This study aims to develop second-order relativistic viscous
magnetohydrodynamics (MHD) derived from kinetic theory within an extended
relaxation time approximation (momentum/energy dependent) for the collision
kernel. The investigation involves a detailed examination of shear stress
tensor evolution equations and associated transport coefficients. The Boltzmann
equation is solved using a Chapman-Enskog-like gradient expansion for a
charge-conserved conformal system, incorporating a momentum-dependent
relaxation time. The derived relativistic non-resistive, viscous second-order
MHD equations for the shear stress tensor reveal significant modifications in
the coupling with dissipative charge current and magnetic field due to the
momentum dependence of the relaxation time. By utilizing a power law
parametrization to quantify the momentum dependence of the relaxation time, the
anisotropic magnetic field-dependent shear coefficients in the Navier-Stokes
limit have been investigated. The resulting viscous coefficients are seen to be
sensitive to the momentum dependence of the relaxation time.",2403.13160v2
2024-03-20,Experience gained about Resistive Plate Chambers ageing from the ALICE Muon TRigger/IDentifier detector,"The ALICE Muon IDentifier is composed of 72 single-gap bakelite Resistive
Plate Chambers, which have been operational since 2009 in maxi-avalanche mode
(discrimination threshold:7 mV without amplification) with a
Tetrafluoroethane/Isobutane/Sulfur Hexafluoride gas mixture, undergoing
counting rates of the order of tens of Hz/cm^2. In this talk, the long-term
performance and stability of the RPC system will be discussed, in terms of
efficiency, dark current and dark rate. An assessment of potential signs of
ageing observed on the detectors will be presented, together with a summary of
the most common hardware problems experienced.",2403.13618v1
2024-03-25,Improving Diffusion Models's Data-Corruption Resistance using Scheduled Pseudo-Huber Loss,"Diffusion models are known to be vulnerable to outliers in training data. In
this paper we study an alternative diffusion loss function, which can preserve
the high quality of generated data like the original squared $L_{2}$ loss while
at the same time being robust to outliers. We propose to use pseudo-Huber loss
function with a time-dependent parameter to allow for the trade-off between
robustness on the most vulnerable early reverse-diffusion steps and fine
details restoration on the final steps. We show that pseudo-Huber loss with the
time-dependent parameter exhibits better performance on corrupted datasets in
both image and audio domains. In addition, the loss function we propose can
potentially help diffusion models to resist dataset corruption while not
requiring data filtering or purification compared to conventional training
algorithms.",2403.16728v1
2024-04-01,Giant and negative magnetoresistances in conical magnets,"We study magnetotransport in conical helimagnet crystals. Spin dependent
magnetoresistance exhibits dramatic properties for high and low electron
concentrations at different temperatures. For spin up electrons we find
negative magnetoresistance despite only considering a single carrier type. For
spin down electrons we observe giant magnetoresistance due to depletion of spin
down electrons with an applied magnetic field. For spin up carriers, the
magnetoresistance is negative, due to the increase in charge carriers with a
magnetic field. In addition, we investigate spin dependent Hall effect. If a
magnetic field reaches some critical value for spin down electrons, giant Hall
resistance occurs, i.e., Hall current vanishes. This effect is explained by the
absence of spin down carriers. For spin up carriers, the Hall constant
dramatically decreases with field, due to the increase in spin up electron
density. Because of the giant spin dependent magnetoresistance and Hall
resistivity, conical helimagnets could be useful in spin switching devices.",2404.01401v1
2024-04-02,Integer and fractional quantum anomalous Hall effects in pentalayer graphene,"We critically analyze the recently reported observation of integer (IQAHE)
and fractional (FQAHE) quantum anomalous Hall effects at zero applied magnetic
field in pentalayer graphene. Our quantitative activation and variable range
hopping transport analysis of the experimental data reveals that the observed
IQAHE and FQAHE at different fillings all have similar excitation gaps of the
order of $5-10$ K. In addition, we also find that the observed FQAHE manifests
a large hidden background contact series resistance >10 k$\Omega$ of unknown
origin whereas this contact resistance is much smaller ~500 $\Omega$ in the
observed IQAHE. Both of these findings are surprising as well as inconsistent
with the well-established phenomenology of the corresponding high-field integer
and fractional quantum Hall effects in 2D semiconductor systems.",2404.02192v1
2024-05-06,Polynomial lower bound on the effective resistance for the one-dimensional critical long-range percolation,"In this work, we study the critical long-range percolation on $\mathbb{Z}$,
where an edge connects $i$ and $j$ independently with probability
$1-\exp\{-\beta |i-j|^{-2}\}$ for some fixed $\beta>0$. Viewing this as a
random electric network where each edge has a unit conductance, we show that
with high probability the effective resistances from the origin 0 to $[-N,
N]^c$ and from the interval $[-N,N]$ to $[-2N,2N]^c$ (conditioned on no edge
joining $[-N,N]$ and $[-2N,2N]^c$) both have a polynomial lower bound in $N$.
Our bound holds for all $\beta>0$ and thus rules out a potential phase
transition (around $\beta = 1$) which seemed to be a reasonable possibility.",2405.03460v1
2018-09-07,Mapping the depleted area of silicon diodes using a micro-focused X-ray beam,"For the Phase-II Upgrade of the ATLAS detector at CERN, the current ATLAS
Inner Detector will be replaced with the ATLAS Inner Tracker. The ATLAS Inner
Tracker will be an all-silicon detector, consisting of a pixel tracker and a
strip tracker. Sensors for the ITk strip tracker are required to have a low
leakage current up to bias voltages of -700 V to maintain a low noise and power
dissipation. In order to minimise sensor leakage currents, particularly in the
high-radiation environment inside the ATLAS detector, sensors are foreseen to
be operated at low temperatures and to be manufactured from wafers with a high
bulk resistivity of several k{\Omega} cm. Simulations showed the electric field
inside sensors with high bulk resistivity to extend towards the sensor edge,
which could lead to increased surface currents for narrow dicing edges. In
order to map the electric field inside biased silicon sensors with high bulk
resistivity, three diodes from ATLAS silicon strip sensor prototype wafers were
studied with a monochromatic, micro-focused X-ray beam at the Diamond Light
Source. For all devices under investigation, the electric field inside the
diode was mapped and its dependence on the applied bias voltage was studied.
The findings showed that the electric field in each diode under investigation
extended beyond its bias ring and reached the dicing edge.",1809.02667v2
2020-02-28,Accelerating and Stopping Resistance Drift in Phase Change Memory Cells via High Electric Field Stress,"We observed resistance drift in 125 K - 300 K temperature range in melt
quenched amorphous Ge2Sb2Te5 line-cells with length x width x thickness = ~500
nm x ~100 nm x ~ 50 nm. Drift coefficients measured using small voltage sweeps
appear to decrease from 0.12 +/- 0.029 at 300 K to 0.075 +/- 0.006 at 125 K.
The current-voltage characteristics of the amorphized cells measured in the 85
K - 300 K using high-voltage sweeps (0 to ~25 V) show a combination of a
linear, low-field exponential and high-field exponential conduction mechanisms,
all of which are strong functions of temperature. The very first high-voltage
sweep after amorphization (with electric fields up to ~70% of the breakdown
field) shows clear hysteresis in the current-voltage characteristics due to
accelerated drift, while the consecutive sweeps show stable characteristics.
Stabilization was achieved with 50 nA compliance current (current densities
~104 A/cm^2), preventing appreciable self-heating in the cells. The observed
acceleration and stoppage of the resistance drift with the application of high
electric fields is attributed to changes in the electrostatic potential profile
within amorphous Ge2Sb2Te5 due to trapped charges, reducing tunneling current.
Stable current-voltage characteristics are used to extract carrier activation
energies for the conduction mechanisms in 85 K - 300 K temperature range. The
carrier activation energy associated with linear current-voltage response is
extracted to be 331 +/- 5 meV in 200 - 300 K range, while carrier activation
energies of 233 +/- 2 meV and 109 +/- 5 meV are extracted in 85 K to 300 K
range for the mechanisms that give exponential current-voltage responses.",2002.12487v1
2021-10-18,Negative differential resistance state in the free-flux-flow regime of driven vortices in a single crystal of 2H-NbS$_2$,"Time series measurements in 2H-NbS$_2$ crystal had unravelled a drive induced
transition wherein the critical current (Ic) changes from a low to a high Ic
jammed vortex state, via a negative differential resistance (NDR) transition.
Here, using multiple current (I) - voltage (V) measurement cycles, we explore
the statistical nature of observing the NDR transition in the free-flux-flow
(FF) regime in a single crystal of 2H-NbS$_2$. The probability of observing the
NDR transition always remains finite for a vortex state created with either
fast or slow rate of magnetic field. The probability of observing the NDR
transition in the FF regime is found to systematically increase with magnetic
field (B) in weak collective pinning regime. In the strong pinning regime, the
said probability becomes B-independent. We show that the higher Ic state is
unique and cannot be accessed via any conventional route. While the I-V curves
do not distinguish between zero field cooled (ZFC) and field cooled (FC) modes
of preparing the vortex state, the probability for observing an NDR transition
has different B-dependences for the vortex matter prepared in the ZFC and FC
modes. We find that the NDR occurs in a high dissipation regime, where the flow
resistivity is well above the theoretical value expected in the FF regime. We
understand our results on the basis of a rapid drop in vortex viscosity at high
drives in 2H-NbS$_2$, which triggers a rapid increase in the vortex velocity
and reorganization in the moving vortex matter leading to a dynamical unstable
vortex flow. This dynamical instability leads to the NDR transition into a high
entropy vortex state with high Ic.",2110.09379v2
2020-11-28,Development of polar nematic fluids with giant-\k{appa} dielectric properties,"Super-high-\k{appa} materials that exhibit exceptionally high dielectric
permittivity are recognized as potential candidates for a wide range of
next-generation photonic and electronic devices. Generally, the high
dielectricity for achieving a high-\k{appa} state requires a low symmetry of
materials so that most of the discovered high-\k{appa} materials are
symmetry-broken crystals. There are scarce reports on fluidic high-\k{appa}
dielectrics. Here we demonstrate a rational molecular design, supported by
machine-learning analyses, that introduces high polarity to asymmetric
molecules, successfully realizing super-high-\k{appa} fluid materials
(dielectric permittivity, {\epsilon} > 104) and strong second harmonic
generation with macroscopic spontaneous polar ordering. The polar structures
are confirmed to be identical for all the synthesized materials. Our
experiments and computational calculation reveal the unique orientational
structures coupled with the emerging polarity. Furthermore, adopting this
strategy to high-molecular-weight systems additionally extends the novel
material category from monomer to polar polymer materials, creating polar soft
matters with spontaneous symmetry breaking.",2011.14099v1
2019-02-26,The Evidence of Cathodic Micro-discharges during Plasma Electrolytic Oxidation Process,"Plasma electrolytic oxidation (PEO) processing of EV 31 magnesium alloy has
been carried out in fluoride containing electrolyte under bipolar pulse current
regime. Unusual PEO cathodic micro-discharges have been observed and
investigated. It is shown that the cathodic micro-discharges exhibit a
collective intermittent behavior which is discussed in terms of charge
accumulations at the layer/electrolyte and layer/metal interfaces. Optical
emission spectroscopy is used to determine the electron density (typ. 10 15
cm-3) and the electron temperature (typ. 7500 K) while the role of F-anions on
the appearance of cathodic micro-discharges is pointed out. Plasma Electrolytic
Oxidation (PEO) is a promising plasma-assisted surface treatment of light
metallic alloys (e.g. Al, Mg, Ti). Although the PEO process makes it possible
to grow oxide coatings with interesting corrosion and wear resistant
properties, the physical mechanisms of coating growth are not yet completely
understood. Typically, the process consists in applying a high voltage
difference between a metallic piece and a counter-electrode which are both
immersed in an electrolyte bath. Compare to anodizing, the main differences
concern the electrolyte composition and the current and voltage ranges which
are at least one order of magnitude higher in PEO 1. These significant
differences in current and voltage imply the dielectric breakdown and
consequently the appearance of micro-discharges on the surface of the sample
under processing. Those micro-discharges are recognized as being the main
contributors to the formation of a dielectric porous crystalline oxide coating.
2 Nevertheless, the breakdown mechanism that governs the appearance of those
micro-discharges is still under investigation. Hussein et al. 3 proposed a
mechanism with three different plasma formation processes based on differences
in plasma chemical composition. The results of Jovovi{\'c} et al. 4,5
concerning physical properties of the plasma seem to corroborate this
mechanism, and also point out the importance of the substrate material in the
plasma composition. 6 Compared with DC conducted PEO process, using a bipolar
pulsed DC or AC current supply gives supplementary control latitude through the
current waveform parameters. The effect of these parameter on the
micro-discharges behavior has been investigated in several previous works.
2,3,7,8 One of the main results of these studies is the absence of
micro-discharge during the cathodic current half-period. 9-11 Even if the
cathodic half-period has an obvious effect on the efficiency of PEO as well as
on the coating growth and composition, the micro-plasmas appear only in anodic
half-period. Sah et al. 8 have observed the cathodic breakdown of an oxide
layer but at very high current density (10 kA.dm-${}^2$), and after several
steps of sample preparation. Several models of micro-discharges appearance in
AC current have already been proposed. 1,2,8,12,13 Though cathodic
micro-discharges have never been observed within usual process conditions, the
present study aims at defining suitable conditions to promote cathodic
micro-discharges and at studying the main characteristics of these
micro-plasmas.",1902.09828v1
2019-07-05,"Materials databases: the need for open, interoperable databases with standardized data and rich metadata","Driven by the recent rapid increase in the number of materials databases
published (open and commercial), I discuss here some perspectives on the
growing need for standardized, interoperable, open databases. The field of
computational materials discovery is quickly expanding, and recent advances in
data mining, high throughput screening, and machine learning highlight the
potential of open databases.",1907.02791v1
2016-01-07,"First principles search for $n$-type oxide, nitride, and sulfide thermoelectrics","Oxides have many potentially desirable characteristics for thermoelectric
applications, including low cost and stability at high temperatures, but thus
far there are few known high $zT$ $n$-type oxide thermoelectrics. In this work,
we use high-throughput first principles calculations to screen transition metal
oxides, nitrides, and sulfides for candidate materials with high power factors
and low thermal conductivity. We find a variety of promising materials, and we
investigate these materials in detail in order to understand the mechanisms
that cause them to have high power factors. These materials all combine a high
density of states near the Fermi level with dispersive bands, reducing the
trade-off between the Seebeck coefficient and the electrical conductivity, but
they do so for several different reasons. In addition, our calculations
indicate that many of our candidate materials have low thermal conductivity.",1601.01622v2
2014-09-03,Mechanics of freely-suspended ultrathin layered materials,"The study of atomically thin two-dimensional materials is a young and rapidly
growing field. In the past years, a great advance in the study of the
remarkable electrical and optical properties of 2D materials fabricated by
exfoliation of bulk layered materials has been achieved. Due to the
extraordinary mechanical properties of these atomically thin materials, they
also hold a great promise for future applications such as flexible electronics.
For example, this family of materials can sustain very large deformations
without breaking. Due to the combination of small dimensions, high Young's
modulus and high crystallinity of 2D materials, they have attracted the
attention of the field of nanomechanical systems as high frequency and high
quality factor resonators. In this article, we review experiments on static and
dynamic response of 2D materials. We provide an overview and comparison of the
mechanics of different materials, and highlight the unique properties of these
thin crystalline layers. We conclude with an outlook of the mechanics of 2D
materials and future research directions such as the coupling of the mechanical
deformation to their electronic structure.",1409.1173v2
2015-01-18,Ultra-high mechanical stretchability and controllable topological phase transitions in two-dimensional arsenic,"The mechanical stretchability is the magnitude of strain which a material can
suffer before it breaks. Materials with high mechanical stretchability, which
can reversibly withstand extreme mechanical deformation and cover arbitrary
surfaces and movable parts, are used for stretchable display devices, broadband
photonic tuning and aberration-free optical imaging. Strain can be utilised to
control the band structures of materials and can even be utilised to induce a
topological phase transition, driving the normal insulators to topological
non-trivial materials with non-zero Chern number or Z2 number. Here, we propose
a new two-dimensional topological material with ultra-high mechanical
stretchability - the ditch-like 2D arsenic. This new anisotropic material
possesses a large Poisson's ratio 1.049, which is larger than any other
reported inorganic materials and has a ultra-high stretchability 44% along the
armchair direction, which is unprecedent in inorganic materials as far as we
know. Its minimum bend radius of this material can be as low as 0.66 nm, which
is comparable to the radius of carbon-nanotube. Such mechanical properties make
this new material be a stretchable semiconductor which could be used to
construct flexible display devices and stretchable sensors. Axial strain will
make a conspicuous affect on the band structure of the system, and a proper
strain along the zigzag direction will drive the 2D arsenic into the
topological insulator in which the topological edge state can host
dissipation-less spin current and spin transfer toque, which are useful in
spintronics devices such as dissipation transistor, interconnect channels and
spin valve devices.",1501.04350v1
2022-04-02,Inventory of high-quality flat-band van der Waals materials,"More is left to do in the field of flat bands besides proposing theoretical
models. One unexplored area is the flat bands featured in the van der Waals
(vdW) materials. Exploring more flat-band material candidates and moving the
promising materials toward applications have been well recognized as the
cornerstones for the next-generation high-efficiency devices. Here, we utilize
a powerful high-throughput tool to screen desired vdW materials based on the
Inorganic Crystal Structure Database. Through layers of filtration, we obtained
861 potential monolayers from 4997 vdW materials. Significantly, it is the
first example to introduce flat-band electronic properties in the vdW materials
and propose three families of representative flat-band materials by mapping
two-dimensional (2D) flat-band lattice models. Unlike existing screening
schemes, a simple, universal rule, i.e., 2D flat-band score criterion, is first
proposed to efficiently identify 229 high-quality flat-band candidates, and
guidance is provided to diagnose the quality of 2D flat bands. All these
efforts to screen experimental available flat-band candidates will certainly
motivate continuing exploration towards the realization of this class of
special materials and their applications in material science.",2204.00810v1
2017-02-25,Electronic conduction properties of indium tin oxide: single-particle and many-body transport,"Indium tin oxide (Sn-doped In$_2$O$_{3-\delta}$ or ITO) is an interesting and
technologically important transparent conducting oxide. This class of material
has been extensively studied for decades, with research efforts focusing on the
application aspects. The fundamental issues of the electronic conduction
properties of ITO from 300 K down to low temperatures have rarely been
addressed. Studies of the electrical-transport properties over a wide range of
temperature are essential to unraveling the underlying electronic dynamics and
microscopic electronic parameters. We show that one can learn rich physics in
ITO material, including the semi-classical Boltzmann transport, the
quantum-interference electron transport, and the electron-electron interaction
effects in the presence of disorder and granularity. To reveal the
opportunities that the ITO material provides for fundamental research, we
demonstrate a variety of charge transport properties in different forms of ITO
structures, including homogeneous polycrystalline films, homogeneous
single-crystalline nanowires, and inhomogeneous ultrathin films. We not only
address new physics phenomena that arise in ITO but also illustrate the
versatility of the stable ITO material forms for potential applications. We
emphasize that, microscopically, the rich electronic conduction properties of
ITO originate from the inherited free-electron-like energy bandstructure and
low-carrier concentration (as compared with that in typical metals)
characteristics of this class of material. Furthermore, a low carrier
concentration leads to slow electron-phonon relaxation, which causes ($i$) a
small residual resistance ratio, ($ii$) a linear electron diffusion
thermoelectric power in a wide temperature range 1-300 K, and ($iii$) a weak
electron dephasing rate. We focus our discussion on the metallic-like ITO
material.",1702.07845v1
2018-06-11,Coincident Molecular Auxeticity and Negative Order Parameter in a Liquid Crystal Elastomer,"""Auxetic"" materials have the counter-intuitive property of expanding rather
than contracting perpendicular to an applied stretch, formally they have
negative Poisson's Ratios (PRs).[1,2] This results in properties such as
enhanced energy absorption and indentation resistance, which means that
auxetics have potential for applications in areas from aerospace to biomedical
industries.[3,4] Existing synthetic auxetics are all created by carefully
structuring porous geometries from positive PR materials. Crucially, their
geometry causes the auxeticity.[3,4] The necessary porosity weakens the
material compared to the bulk and the structure must be engineered, for
example, by using resource-intensive additive manufacturing processes.[1,5] A
longstanding goal for researchers has been the development of a synthetic
material that has intrinsic auxetic behaviour. Such ""molecular auxetics"" would
avoid porosity-weakening and their very existence implies chemical
tuneability.[1,4-9] However molecular auxeticity has never previously been
proven for a synthetic material.[6,7] Here we present a synthetic molecular
auxetic based on a monodomain liquid crystal elastomer (LCE). When stressed
perpendicular to the alignment direction, the LCE becomes auxetic at strains
greater than approximately 0.8 with a minimum PR of -0.8. The critical strain
for auxeticity coincides with the occurrence of a negative liquid crystal order
parameter (LCOP). We show the auxeticity agrees with theoretical predictions
derived from the Warner and Terentjev theory of LCEs.[10] This demonstration of
a synthetic molecular auxetic represents the origin of a new approach to
producing molecular auxetics with a range of physical properties and functional
behaviours. Further, it demonstrates a novel feature of LCEs and a route for
realisation of the molecular auxetic technologies that have been proposed over
the years.",1807.03608v1
2022-05-11,Effect of magnetic phase coexistence on spin-phonon coupling and magnetoelectric effect in polycrystalline Sm0.5Y0.5Fe0.58Mn0.42O3,"The polycrystalline co-doped samples of Sm0.5Y0.5Fe0.58Mn0.42O3 were prepared
by solid-state reaction route and its various physical properties with their
correlations have been investigated. The dc magnetization measurements on the
sample revealed a weak ferromagnetic (WFM) transition at TN=361 K that is
followed by an incomplete spin reorientation (SR) transition at TSR1= 348 K. A
first order magnetic transition (FOMT) around 292 K completes the spin
reorientation transition and the material enters into a nearly collinear
antiferromagnetic (AFM) state for T < 260 K. The compound exhibited
magnetization reversal below the compensation temperature (Tcomp) = 92 K at low
measured field of 100 Oe. At further low temperature below 71 K, the compound
also exhibited Zero-field cooled memory effects confirming a reentrant
spinglass state formation. Robust magnetodielectric (MD) magnetoelectric
coupling has been established in the present material through field dependent
dielectric and resistivity measurements. True ferroelectric transition with a
considerable value of saturation polarization (= 0.06 micro C/cm2 at 15 K) have
been found in the specimen below TFE= 108 K. We observed an intense spin-phonon
coupling (SPC) across TSR and TN from the temperature dependent Raman
spectroscopy and is responsible for the intrinsic magnetoelectric effect. This
SPC also stabilizes the ferroelectric state below TFE in the material. The
delicate interplay of the lattice (Phonons), charge and spins governs the
observed features in the investigated physical properties of the material that
makes the specimen a promising multifunctional material.",2205.05291v2
2023-08-18,"Magnon Diffusion Length and Longitudinal Spin Seebeck Effect in Vanadium Tetracyanoethylene (V[TCNE]$_x$, $x \sim 2$)","Spintronic, spin caloritronic, and magnonic phenomena arise from complex
interactions between charge, spin, and structural degrees of freedom that are
challenging to model and even more difficult to predict. This situation is
compounded by the relative scarcity of magnetically-ordered materials with
relevant functionality, leaving the field strongly constrained to work with a
handful of well-studied systems that do not encompass the full phase space of
phenomenology predicted by fundamental theory. Here we present an important
advance in this coupled theory-experiment challenge, wherein we extend existing
theories of the spin Seebeck effect (SSE) to explicitly include the
temperature-dependence of magnon non-conserving processes. This expanded theory
quantitatively describes the low-temperature behavior of SSE signals previously
measured in the mainstay material yttrium iron garnet (YIG) and predicts a new
regime for magnonic and spintronic materials that have low saturation
magnetization, $M_S$, and ultra-low damping. Finally, we validate this
prediction by directly observing the spin Seebeck resistance (SSR) in the
molecule-based ferrimagnetic semiconductor vanadium tetracyanoethylene
(V[TCNE]$_x$, $x \sim 2$). These results validate the expanded theory, yielding
SSR signals comparable in magnitude to YIG and extracted magnon diffusion
length ($\lambda_m>1$ $\mu$ m) and magnon lifetime for V[TCNE]$_x$
($\tau_{th}\approx 1-10$ $\mu$ s) exceeding YIG ($\tau_{th}\sim 10$ ns).
Surprisingly, these properties persist to room temperature despite relatively
low spin wave stiffness (exchange). This identification of a new regime for
highly efficient SSE-active materials opens the door to a new class of magnetic
materials for spintronic and magnonic applications.",2308.09752v1
1998-08-25,"Unconventional Transition from Metallic to Insulating Resistivity in the Spin-ladder Compound (Sr,Ca)$_{14}$Cu$_{24}$O$_{41}$","Spin-ladder compounds make interesting analogs of the high-temperature
superconductors, because they contain layers of nearly one-dimensional
""ladders"" consisting of a square array of copper and oxygen atoms. Increasing
the number of legs in the ladders provides a step-wise approach toward the
two-dimensional copper-oxygen plane, that structure believed to be a key to
high temperature superconductivity. Short-range spin correlations in ladders
have been predicted to lead to formation of hole pairs favorable for
superconductivity, once enough holes are introduced onto the ladders by doping.
Indeed, superconductivity has been discovered in the two-leg ladder compound
(Sr,Ca)$_{14}$Cu$_{24}$O$_{41}$ under high pressure. Here we show that charge
transport in the non-superconducting state of (Sr,Ca)$_{14}$Cu$_{24}$O$_{41}$
shares three distinct regimes in common with high-temperature superconductors,
including an unexplained insulating behavior at low temperatures in which the
resistivity increases as the logarithm of the temperature. These observations
suggest that the logarithmic divergence arises from a new localization
mechanism common to the ladder compounds and the high-temperature
superconductors, which may arise from nearly one-dimensional charge transport
in the presence of a spin gap.",9808284v2
2000-02-17,Effect of Magnetic field on the Pseudogap Phenomena in High-Tc Cuprates,"We theoretically investigate the effect of magnetic field on the pseudogap
phenomena in High-Tc cuprates.
  The obtained results well explain the experimental results including their
doping dependences.
  In our previous paper (J. Phys. Soc. Jpn. 68 (1999) 2999.), we have shown
that the pseudogap phenomena observed in High-Tc cuprates are naturally
understood as a precursor of the strong coupling superconductivity. On the
other hand, there is an interpretation for the recent high field NMR
measurements to be an evidence denying the pairing scenarios for the pseudogap.
In this paper, we investigate the magnetic field dependence of NMR $1/T_{1}T$
on the basis of our formalism and show the interpretation to be inappropriate.
  The results indicate that the value of the characteristic magnetic field
$B_{{\rm ch}}$ is remarkably large in case of the strong coupling
superconductivity, especially near the pseudogap onset temperature $T^{*}$.
Therefore, the magnetic field dependences can not be observed and $T^{*}$ does
not vary when the strong pseudogap anomaly is observed. On the other hand,
$B_{{\rm ch}}$ is small in the comparatively weak coupling case and $T^{*}$
varies when the weak pseudogap phenomena are observed.
  These results properly explain the high magnetic field NMR experiments
continuously from under-doped to over-doped cuprates.
  Moreover, we discuss the transport phenomena in the pseudogap phase. The
behaviors of the in-plane resistivity, the Hall coefficient and the c-axis
resistivity in the pseudogap phase are naturally understood by considering the
d-wave pseudogap.",0002274v1
2018-11-15,High Kinetic Inductance Microwave Resonators Made by He-Beam Assisted Deposition of Tungsten Nanowires,"We evaluate the performance of hybrid microwave resonators made by combining
sputtered Nb thin films with Tungsten nanowires grown with a He-beam induced
deposition technique. Depending on growth conditions the nanowires have a
typical width $w\in[35-75]$~nm and thickness $t\in[5-40]$~nm. We observe a high
normal state resistance $R_{sq}\in [65-150]$ $\Omega/sq$ which together with a
critical temperature $T_c\in[4-6]~K$ ensure a high kinetic inductance making
the resonator strongly nonlinear. Both lumped and coplanar waveguide resonators
were fabricated and measured at low temperature exhibiting internal quality
factors up to $3990$ at $4.5$~GHz in the few photon regime. Analyzing the wire
length, temperature and microwave power dependence we extracted a kinetic
inductance for the W nanowire of $L_K\approx15$ pH/sq, which is 250 times
higher than the geometrical inductance, and a Kerr non-linearity as high as
$K_{W,He}/2\pi=200 \pm 120$~Hz/photon at $4.5$~GHz. The nanowires made with the
helium focused ion beam are thus versatile objects to engineer compact, high
impedance, superconducting environments with a mask and resist free direct
write process.",1811.06496v2
2017-05-16,Scale-invariant magnetoresistance in a cuprate superconductor,"The anomalous metallic state in high-temperature superconducting cuprates is
masked by the onset of superconductivity near a quantum critical point. Use of
high magnetic fields to suppress superconductivity has enabled a detailed study
of the ground state in these systems. Yet, the direct effect of strong magnetic
fields on the metallic behavior at low temperatures is poorly understood,
especially near critical doping, $x=0.19$. Here we report a high-field
magnetoresistance study of thin films of \LSCO cuprates in close vicinity to
critical doping, $0.161\leq x\leq0.190$. We find that the metallic state
exposed by suppressing superconductivity is characterized by a
magnetoresistance that is linear in magnetic field up to the highest measured
fields of $80$T. The slope of the linear-in-field resistivity is
temperature-independent at very high fields. It mirrors the magnitude and
doping evolution of the linear-in-temperature resistivity that has been
ascribed to Planckian dissipation near a quantum critical point. This
establishes true scale-invariant conductivity as the signature of the strange
metal state in the high-temperature superconducting cuprates.",1705.05806v2
2022-11-22,Development of ultra-low mass and high-rate capable RPC based on Diamond-Like Carbon electrodes for MEG II experiment,"A new type of resistive plate chamber with thin-film electrodes based on
diamond-like carbon is under development for background identification in the
MEG II experiment. Installed in a low-momentum and high-intensity muon beam,
the detector is required to have extremely low mass and a high rate capability.
A single-layer prototype detector with 2 cm $\times$ 2 cm size was constructed
and evaluated to have a high rate capability of 1 MHz/cm$^2$ low-momentum
muons. For a higher rate capability and scalability of the detector size, the
electrodes to supply high voltage were segmented at a 1 cm pitch by
implementing a conductive pattern on diamond-like carbon. Using the new
electrodes, a four-layer prototype detector was constructed and evaluated to
have a 46% detection efficiency with only a single layer active at a rate of
$\cal O$(10 kHz). The result with the new electrodes is promising to achieve
the required detection efficiency of 90% at a rate of 4 MHz/cm$^2$ with all the
layers active.",2211.12172v2
2010-05-05,Review of Best Practice Methods for Determining an Electrode Material's Performance for Ultracapacitors,"Ultracapacitors are rapidly being adopted for use for a wide range of
electrical energy storage applications. While ultracapacitors are able to
deliver high rates of charge and discharge, they are limited in the amount of
energy stored. The capacity of ultracapacitors is largely determined by the
electrode material and as a result, research to improve the performance of
electrode materials has dramatically increased. While test methods for packaged
ultracapacitors are well developed, it is often not feasible for the materials
scientist to assemble full sized, packaged cells to test electrode materials.
Methodology to reliably measure a material's performance for ultracapacitor
electrode use is not well standardized with the different techniques currently
being used yielding widely varying results. In this manuscript, we review the
best practice test methods that accurately predict a materials performance, yet
are flexible and quick enough to accommodate a wide range of material sample
types and amounts.",1005.0805v2
2016-07-22,How to Characterize Thermal Transport Capability of 2D Materials Fairly? - Sheet Thermal Conductance and the Choice of Thickness,"Ever since the discovery of the record-high thermal conductivity of single
layer graphene, thermal transport capability of monolayer 2D materials has been
under constant spotlight. Since thermal conductivity is an intensive property
for 3D materials and the thickness of 2D materials is not well defined,
different definitions of thickness in literature have led to ambiguity towards
predicting thermal conductivity values and thus in understanding the heat
transfer capability of different monolayer 2D materials. We argue that if
conventional definition of thermal conductivity should be used as the quantity
to compare the heat transfer capability of various monolayer 2D materials, then
the same thickness should be used. Alternatively, to circumvent the problem of
ambiguous thickness completely, we also suggest that a ""sheet thermal
conductance"" to be defined as an intensive 2D material property when
characterizing the heat transfer capability of 2D materials. When converting
literature thermal conductivity values of monolayer materials to this new
property, some new features that were not displayed when using different
thicknesses show up.",1607.06542v2
2018-02-05,Plasmonic physics of 2D crystalline materials,"Collective modes of doped two-dimensional crystalline materials, namely
graphene, MoS$_2$ and phosphorene, both monolayer and bilayer structures, are
explored using the density functional theory simulations together with the
random phase approximation. The many-body dielectric functions of the materials
are calculated using an {\it ab initio} based model involving
material-realistic physical properties. Having calculated the electron
energy-loss, we calculate the collective modes of each material considering the
in-phase and out-of-phase modes for bilayer structures. Furthermore, owing to
many band structures and intreband transitions, we also find high-energy
excitations in the systems. We explain that the material-specific dielectric
function considering the polarizability of the crystalline material such as
MoS$_2$ are needed to obtain realistic plasmon dispersions. For each material
studied here, we find different collective modes and describe their physical
origins.",1802.01291v1
2018-07-01,Correlated materials design: prospects and challenges,"The design of correlated materials challenges researchers to combine the
maturing, high throughput framework of DFT-based materials design with the
rapidly-developing first-principles theory for correlated electron systems. We
review the field of correlated materials, distinguishing two broad classes of
correlation effects, static and dynamics, and describe methodologies to take
them into account. We introduce a material design workflow, and illustrate it
via examples in several materials classes, including superconductors, charge
ordering materials and systems near an electronically driven metal to insulator
transition, highlighting the interplay between theory and experiment with a
view towards finding new materials. We review the statistical formulation of
the errors of currently available methods to estimate formation energies.
Correlation effects have to be considered in all the material design steps.
These include bridging between structure and property, obtaining the correct
structure and predicting material stability. We introduce a post-processing
strategy to take them into account.",1807.00398v2
2020-05-09,Learning Properties of Ordered and Disordered Materials from Multi-fidelity Data,"Predicting the properties of a material from the arrangement of its atoms is
a fundamental goal in materials science. While machine learning has emerged in
recent years as a new paradigm to provide rapid predictions of materials
properties, their practical utility is limited by the scarcity of high-fidelity
data. Here, we develop multi-fidelity graph networks as a universal approach to
achieve accurate predictions of materials properties with small data sizes. As
a proof of concept, we show that the inclusion of low-fidelity
Perdew-Burke-Ernzerhof band gaps greatly enhances the resolution of latent
structural features in materials graphs, leading to a 22-45\% decrease in the
mean absolute errors of experimental band gap predictions. We further
demonstrate that learned elemental embeddings in materials graph networks
provide a natural approach to model disorder in materials, addressing a
fundamental gap in the computational prediction of materials properties.",2005.04338v3
2020-08-24,Inverse Design of Composite Metal Oxide Optical Materials based on Deep Transfer Learning,"Optical materials with special optical properties are widely used in a broad
span of technologies, from computer displays to solar energy utilization
leading to large dataset accumulated from years of extensive materials
synthesis and optical characterization. Previously, machine learning models
have been developed to predict the optical absorption spectrum from a materials
characterization image or vice versa. Herein we propose TLOpt, a transfer
learning based inverse optical materials design algorithm for suggesting
material compositions with a desired target light absorption spectrum. Our
approach is based on the combination of a deep neural network model and global
optimization algorithms including a genetic algorithm and Bayesian
optimization. A transfer learning strategy is employed to solve the small
dataset issue in training the neural network predictor of optical absorption
spectrum using the Magpie materials composition descriptor. Our extensive
experiments show that our algorithm can inverse design the materials
composition with stoichiometry with high accuracy.",2008.10618v1
2022-04-04,Hole-doping induced ferromagnetism in 2D materials,"Two-dimensional (2D) ferromagnetic materials are considered as promising
candidates for the future generations of spintronic devices. Yet, 2D materials
with intrinsic ferromagnetism are scarce. High-throughput first-principles
simulations are performed in order to screen 2D materials that present a
non-magnetic to a ferromagnetic transition upon hole doping. A global
evolutionary search is subsequently performed, in order to identify alternative
possible atomic structures of the eligible candidates, and 122 materials
exhibiting a hole-doping induced ferromagnetism are identified. Their energetic
and dynamic stability, as well as their magnetic properties under hole doping
are investigated systematically. Half of these 2D materials are metal halides,
followed by chalcogenides, oxides and nitrides, some of them having predicted
Curie temperatures above 300 K. The exchange interactions responsible for the
ferromagnetic order in these 2D materials are also discussed. This work not
only provides theoretical insights into hole-doped 2D ferromagnetic materials,
but also enriches the family of 2D magnetic materials for possible spintronic
applications.",2204.01551v2
2023-03-29,A Comprehensive and Versatile Multimodal Deep Learning Approach for Predicting Diverse Properties of Advanced Materials,"We present a multimodal deep learning (MDL) framework for predicting physical
properties of a 10-dimensional acrylic polymer composite material by merging
physical attributes and chemical data. Our MDL model comprises four modules,
including three generative deep learning models for material structure
characterization and a fourth model for property prediction. Our approach
handles an 18-dimensional complexity, with 10 compositional inputs and 8
property outputs, successfully predicting 913,680 property data points across
114,210 composition conditions. This level of complexity is unprecedented in
computational materials science, particularly for materials with undefined
structures. We propose a framework to analyze the high-dimensional information
space for inverse material design, demonstrating flexibility and adaptability
to various materials and scales, provided sufficient data is available. This
study advances future research on different materials and the development of
more sophisticated models, drawing us closer to the ultimate goal of predicting
all properties of all materials.",2303.16412v1
2024-04-03,Construction of Functional Materials Knowledge Graph in Multidisciplinary Materials Science via Large Language Model,"The convergence of materials science and artificial intelligence has unlocked
new opportunities for gathering, analyzing, and generating novel materials
sourced from extensive scientific literature. Despite the potential benefits,
persistent challenges such as manual annotation, precise extraction, and
traceability issues remain. Large language models have emerged as promising
solutions to address these obstacles. This paper introduces Functional
Materials Knowledge Graph (FMKG), a multidisciplinary materials science
knowledge graph. Through the utilization of advanced natural language
processing techniques, extracting millions of entities to form triples from a
corpus comprising all high-quality research papers published in the last
decade. It organizes unstructured information into nine distinct labels,
covering Name, Formula, Acronym, Structure/Phase, Properties, Descriptor,
Synthesis, Characterization Method, Application, and Domain, seamlessly
integrating papers' Digital Object Identifiers. As the latest structured
database for functional materials, FMKG acts as a powerful catalyst for
expediting the development of functional materials and a fundation for building
a more comprehensive material knowledge graph using full paper text.
Furthermore, our research lays the groundwork for practical text-mining-based
knowledge management systems, not only in intricate materials systems but also
applicable to other specialized domains.",2404.03080v1
2024-04-09,Deep-Learning Database of Density Functional Theory Hamiltonians for Twisted Materials,"Moir\'e-twisted materials have garnered significant research interest due to
their distinctive properties and intriguing physics. However, conducting
first-principles studies on such materials faces challenges, notably the
formidable computational cost associated with simulating ultra-large twisted
structures. This obstacle impedes the construction of a twisted materials
database crucial for datadriven materials discovery. Here, by using
high-throughput calculations and state-of-the-art neural network methods, we
construct a Deep-learning Database of density functional theory (DFT)
Hamiltonians for Twisted materials named DDHT. The DDHT database comprises
trained neural-network models of over a hundred homo-bilayer and hetero-bilayer
moir\'e-twisted materials. These models enable accurate prediction of the DFT
Hamiltonian for these materials across arbitrary twist angles, with an averaged
mean absolute error of approximately 1.0 meV or lower. The database facilitates
the exploration of flat bands and correlated materials platforms within
ultra-large twisted structures.",2404.06449v1
2020-03-15,New quantum phases of matter: Topological Materials,"In this article, we provide an overview of the basic concepts of novel
topological materials. This new class of materials developed by combining the
Weyl/Dirac fermionic electron states and magnetism, provide a materials-science
platform to test predictions of the laws of topological physics. Owing to their
dissipationless transport, these materials hold high promises for technological
applications in quantum computing and spintronics devices.",2003.06835v1
2019-06-11,Towards Photoferroic Materials by Design: Recent Progresses and Perspective,"The use of photoferroic materials that combine ferroelectric and light
harvesting properties in a photovoltaic device is a promising route to
significantly improve the efficiency of solar cells. These materials do not
require the formation of a p-n junction and can produce photovoltages well
above the value of the band gap, because of the spontaneous intrinsic
polarization and the formation of domain walls. In this perspective, we discuss
the recent experimental progresses and challenges for the synthesis of these
materials and the theoretical discovery of novel photoferroic materials using a
high-throughput approach.",1906.04490v1
2023-11-06,Cross-Plane Thermal Transport in Layered Materials,"The cross-plane (across-layers) phonon thermal transport of five diverse,
layered semiconductors is investigated by accounting for higher-order
four-phonon scattering, phonon renormalization, and multi-channel thermal
transport. For materials having relatively large cross-plane thermal
conductivity (AlB6, MoS2, and MoSi2N4), phonons contributing to cross-plane
conductivity have an order of magnitude larger mean free path than that for the
basal-plane thermal transport, whereas the opposite effect is observed for
materials with low thermal conductivity (MoO3 and KCuSe). The contribution from
the wave-like coherent transport channel is less than 5% in all considered
materials. Our work unravels the contrasting role of nano-structuring on the
basal- vs. cross-plane thermal conductivity of low and high thermal
conductivity layered materials.",2311.03144v1
2024-03-15,MADAS -- A Python framework for assessing similarity in materials-science data,"Computational materials science produces large quantities of data, both in
terms of high-throughput calculations and individual studies. Extracting
knowledge from this large and heterogeneous pool of data is challenging due to
the wide variety of computational methods and approximations, resulting in
significant veracity in the sheer amount of available data. Here, we present
MADAS, a Python framework for computing similarity relations between material
properties. It can be used to automate the download of data from various
sources, compute descriptors and similarities between materials, analyze the
relationship between materials through their properties, and can incorporate a
variety of existing machine learning methods. We explain the design of the
package and demonstrate its power with representative examples.",2403.10470v1
2017-02-18,Tunable Hyperbolic Dispersion and Negative Refraction in Natural Electride Materials,"Hyperbolic (or indefinite) materials have attracted significant attention due
to their unique capabilities for engineering electromagnetic space and
controlling light propagation. A current challenge is to find a hyperbolic
material with wide working frequency window, low energy loss, and easy
controllability. Here, we propose that naturally existing electride materials
could serve as high-performance hyperbolic medium. Taking the electride Ca$_2$N
as a concrete example and using first-principles calculations, we show that the
material is hyperbolic over a wide frequency window from short-wavelength to
near infrared. More importantly, it is almost lossless in the window. We
clarify the physical origin of these remarkable properties, and show its
all-angle negative refraction effect. Moreover, we find that the optical
properties can be effectively tuned by strain. With moderate strain, the
material can even be switched between elliptic and hyperbolic for a particular
frequency. Our result points out a new route toward high-performance natural
hyperbolic materials, and it offers realistic materials and novel methods to
achieve controllable hyperbolic dispersion with great potential for
applications.",1702.05602v1
2018-04-23,Gaussian Material Synthesis,"We present a learning-based system for rapid mass-scale material synthesis
that is useful for novice and expert users alike. The user preferences are
learned via Gaussian Process Regression and can be easily sampled for new
recommendations. Typically, each recommendation takes 40-60 seconds to render
with global illumination, which makes this process impracticable for real-world
workflows. Our neural network eliminates this bottleneck by providing
high-quality image predictions in real time, after which it is possible to pick
the desired materials from a gallery and assign them to a scene in an intuitive
manner. Workflow timings against Disney's ""principled"" shader reveal that our
system scales well with the number of sought materials, thus empowering even
novice users to generate hundreds of high-quality material models without any
expertise in material modeling. Similarly, expert users experience a
significant decrease in the total modeling time when populating a scene with
materials. Furthermore, our proposed solution also offers controllable
recommendations and a novel latent space variant generation step to enable the
real-time fine-tuning of materials without requiring any domain expertise.",1804.08369v1
2022-02-10,Topogivity: A Machine-Learned Chemical Rule for Discovering Topological Materials,"Topological materials present unconventional electronic properties that make
them attractive for both basic science and next-generation technological
applications. The majority of currently known topological materials have been
discovered using methods that involve symmetry-based analysis of the quantum
wavefunction. Here we use machine learning to develop a simple-to-use heuristic
chemical rule that diagnoses with a high accuracy whether a material is
topological using only its chemical formula. This heuristic rule is based on a
notion that we term topogivity, a machine-learned numerical value for each
element that loosely captures its tendency to form topological materials. We
next implement a high-throughput procedure for discovering topological
materials based on the heuristic topogivity-rule prediction followed by ab
initio validation. This way, we discover new topological materials that are not
diagnosable using symmetry indicators, including several that may be promising
for experimental observation.",2202.05255v3
2021-09-11,"Highly Accurate, Reliable and Non-Contaminating Two-Dimensional Material Transfer System","The exotic properties of two-dimensional (2D) materials and 2D
heterostructures, built by forming heterogeneous multi-layered stacks, have
been widely explored across a number of subject matters following the goal to
invent, design, and improve applications enabled by 2D materials. To
successfully harvest these unique properties effectively and increase the yield
of manufacturing 2D material-based devices for achieving reliable and
repeatable results is the current challenge. The scientific community has
introduced various experimental transfer systems explained in detail for
exfoliated 2D materials, however, the field lacks statistical analysis and the
capability of producing a transfer technique enabling; i) high transfer
precision and yield, ii) cross-contamination free transfer, iii)
multi-substrate transfer, and iv) rapid prototyping without wet chemistry. Here
we introduce a novel 2D material deterministic transfer system and
experimentally show its high accuracy, reliability, repeatability, and
non-contaminating transfer features by demonstrating fabrication of 2D
material-based optoelectronic devices featuring novel device physics and unique
functionality. Such rapid and material-near prototyping capability can
accelerate not only layered material science in discovery but also engineering
innovations.",2109.05158v2
2021-11-10,Piezoelectric modulus prediction using machine learning and graph neural networks,"Piezoelectric materials are widely used in all kinds of industries such as
electric cigarette lighters, diesel engines and x-ray shutters. However,
discovering high-performance and environmentally friendly (e.g. lead-free)
piezoelectric materials is a difficult problem due to the sophisticated
relationships from materials' composition/structures to the piezoelectric
effect. Compared to other material properties such as formation energy, band
gap, and bulk modulus, it is much more challenging to predict piezoelectric
coefficients. Here, we propose a comprehensive study on designing and
evaluating advanced machine learning models for predicting the piezoelectric
modulus from materials' composition and/or structures. We train the prediction
models based on extensive feature engineering combined with machine learning
models (Random Forest and Support Vector Machines) and automated feature
learning based on deep graph neural networks. Our SVM model with crystal
structure feature outperform other methods. We also use this model to predict
the piezoelectric coefficients for 12,680 materials from the Materials Project
database and report the top 20 potential high performance piezoelectric
materials.",2111.05557v1
2023-06-25,Discovering two-dimensional magnetic topological insulators by machine learning,"Topological materials with unconventional electronic properties have been
investigated intensively for both fundamental and practical interests.
Thousands of topological materials have been identified by symmetry-based
analysis and ab initio calculations. However, the predicted magnetic
topological insulators with genuine full band gaps are rare. Here we employ
this database and supervisedly train neural networks to develop a heuristic
chemical rule for electronic topology diagnosis. The learned rule is
interpretable and diagnoses with a high accuracy whether a material is
topological using only its chemical formula and Hubbard $U$ parameter. We next
evaluate the model performance in several different regimes of materials.
Finally, we integrate machine-learned rule with ab initio calculations to
high-throughput screen for magnetic topological insulators in 2D material
database. We discover 6 new classes (15 materials) of Chern insulators, among
which 4 classes (7 materials) have full band gaps and may motivate for
experimental observation. We anticipate the machine-learned rule here can be
used as a guiding principle for inverse design and discovery of new topological
materials.",2306.14155v2
2023-10-21,Advances in Complex Oxide Quantum Materials Through New Approaches to Molecular Beam Epitaxy,"Molecular beam epitaxy (MBE), a workhorse of the semiconductor industry, has
progressed rapidly in the last few decades in the development of novel
materials. Recent developments in condensed matter and materials physics have
seen the rise of many novel quantum materials that require ultra-clean and
high-quality samples for fundamental studies and applications. Novel
oxide-based quantum materials synthesized using MBE have advanced the
development of the field and materials. In this review, we discuss the recent
progress in new MBE techniques that have enabled synthesis of complex oxides
that exhibit ""quantum"" phenomena, including superconductivity and topological
electronic states. We show how these techniques have produced breakthroughs in
the synthesis of 4d and 5d oxide films and heterostructures that are of
particular interest as quantum materials. These new techniques in MBE offer a
bright future for the synthesis of ultra-high quality oxide quantum materials.",2310.13902v1
2002-05-31,"Structure and Superconductivity in Zr-Stabilized, Nonstoichiometric Molybdenum Diboride","The structure and physical properties of the Zr-stabilized, nonstoichiometric
molybdenum diboride superconductor are reported. Good quality material of the
diboride structure type can only be obtained by partial substitution of Zr for
Mo, and the quenching of melts. The phase is best made with boron in excess of
the ideal 2:1 boron to metal ratio. Powder neutron diffraction measurements
show that the non-stoichiometry is accommodated by atom deficiency in the metal
layers. The diboride structure type exists for (Mo.96Zr.04)xB2 for x between
0.85 and 1.0. Electron diffraction shows that the stoichiometric material, x=1,
has a significant number of stacking faults. Tc increases from 5.9 to 8.2K with
the introduction of metal vacancies. Resistivity measurements indicate that
(Mo.96Zr.04).88B2 is a bad metal, and specific heat measurements show that
gamma= 4.4 mJ/mol K2, and that deltaC/gammaTc = 1.19. Preliminary boron isotope
effect measurements indicate an exponent 0.11(5). Analysis of the data in terms
of the electronic structure is reported, allowing an estimate of the
electron-phonon coupling constant, lamda = 0.1-0.3, making these weak-coupling
superconductors. Preliminary characterizations of the superconductivity in the
related phases NbxB2 and (Mo.96X.04).85B2 for X=Ti, and Hf are reported.",0206006v1
2003-07-31,The break up of heavy electrons at a quantum critical point,"The point at absolute zero where matter becomes unstable to new forms of
order is called a quantum critical point (QCP). The quantum fluctuations
between order and disorder that develop at this point induce profound
transformations in the finite temperature electronic properties of the
material. Magnetic fields are ideal for tuning a material as close as possible
to a QCP, where the most intense effects of criticality can be studied. A
previous study on theheavy-electron material $YbRh_2Si_2$ found that near a
field-induced quantum critical point electrons move ever more slowly and
scatter off one-another with ever increasing probability, as indicated by a
divergence to infinity of the electron effective mass and cross-section. These
studies could not shed light on whether these properties were an artifact of
the applied field, or a more general feature of field-free QCPs. Here we report
that when Germanium-doped $YbRh_2Si_2$ is tuned away from a chemically induced
quantum critical point by magnetic fields there is a universal behavior in the
temperature dependence of the specific heat and resistivity: the characteristic
kinetic energy of electrons is directly proportional to the strength of the
applied field. We infer that all ballistic motion of electrons vanishes at a
QCP, forming a new class of conductor in which individual electrons decay into
collective current carrying motions of the electron fluid.",0308001v1
2006-06-16,Multiferroic tunnel junctions,"Multiferroics are singular materials that can display simultaneously electric
and magnetic orders. Some of them can be ferroelectric and ferromagnetic and,
for example, provide the unique opportunity of encoding information
independently in electric polarization and magnetization to obtain four
different logic states. However, schemes allowing a simple electrical readout
of these different states have not been demonstrated so far. In this article,
we show that this can be achieved if a multiferroic material is used as the
tunnel barrier in a magnetic tunnel junction. We demonstrate that thin films of
ferromagnetic-ferroelectric La0.1Bi0.9MnO3 (LBMO) retain both ferroic
properties down to a thickness of only 2 nm. We have used such films as
spin-filtering tunnel barriers the magnetization and electric polarization of
which can be switched independently. In that case, the tunnel current across
the structure is controlled by both the magnetic and ferroelectric
configuration of the barrier, which gives rise to four distinct resistance
states. This can be explained by the combination of spin filtering by the
ferromagnetic LBMO barrier and the partial charge screening of electrical
charges at the barrier/electrode interfaces due to ferroelectricity. We
anticipate our results to be a starting point for more studies on the interplay
between ferroelectricity and spin-dependent tunneling, and for the use of
nanometric multiferroic elements in prototype devices. On a wider perspective,
they may open the way towards novel reconfigurable logic spintronics
architectures and to electrically controlled readout in quantum computing
schemes using the spin-filter effect.",0606444v1
2006-10-29,Detection of Individual Gas Molecules Absorbed on Graphene,"The ultimate aspiration of any detection method is to achieve such a level of
sensitivity that individual quanta of a measured value can be resolved. In the
case of chemical sensors, the quantum is one atom or molecule. Such resolution
has so far been beyond the reach of any detection technique, including
solid-state gas sensors hailed for their exceptional sensitivity. The
fundamental reason limiting the resolution of such sensors is fluctuations due
to thermal motion of charges and defects which lead to intrinsic noise
exceeding the sought-after signal from individual molecules, usually by many
orders of magnitude. Here we show that micrometre-size sensors made from
graphene are capable of detecting individual events when a gas molecule
attaches to or detaches from graphenes surface. The adsorbed molecules change
the local carrier concentration in graphene one by one electron, which leads to
step-like changes in resistance. The achieved sensitivity is due to the fact
that graphene is an exceptionally low-noise material electronically, which
makes it a promising candidate not only for chemical detectors but also for
other applications where local probes sensitive to external charge, magnetic
field or mechanical strain are required.",0610809v2
2007-11-26,Experimental investigation on the microscopic structure of intrinsic paramagnetic point defects in amorphous silicon dioxide,"In the present Ph.D. Thesis we report an experimental investigation on the
effects of gamma- and beta-ray irradiation and of subsequent thermal treatment
on many types of a-SiO2 materials, differing in the production methods, OH- and
Al-content, and oxygen deficiencies. Our main objective is to gain further
insight on the microscopic structures of the E'_gamma, E'_delta, E'_alpha and
triplet paramagnetic centers, which are among the most important and studied
class of radiation induced intrinsic point defects in a-SiO2. To pursue this
objective, we use prevalently the EPR spectroscopy. In particular, our work is
focused on the properties of the unpaired electrons wave functions involved in
the defects, and this aspect is mainly investigated through the study of the
EPR signals originating from the interaction of the unpaired electrons with
29Si magnetic nuclei (with nuclear spin I=1/2 and natural abundance 4.7 %). In
addition, in some cases of interest, OA measurements are also performed with
the aim to further characterize the electronic properties of the defects.
Furthermore, due to its relevance for electronics application, the charge state
of the defects is investigated by looking at the processes responsible for the
generation of the defects of interest. Once these information were gained, the
possible sites that can serve as precursors for defects formation are deduced,
with the definitive purpose to obtain in the future more radiation resistant
a-SiO2 materials in which the deleterious effects connected with the point
defects are significantly reduced.",0711.4029v1
2011-06-16,The Memory-Conservation Theory of Memristance,"The memristor, the recently discovered fundamental circuit element, is of
great interest for neuromorphic computing, nonlinear electronics and computer
memory. It is usually modelled either using Chua's equations, which lack
material device properties, or using Strukov's phenomenological model (or
models derived from it), which deviates from Chua's definitions due to the lack
of a magnetic flux term. It is shown that by modelling the magnetostatics of
the memory-holding ionic current (oxygen vacancies in the Strukov memristor),
the memristor's magnetic flux can be identified as the flux arising from the
ions. This leads to a novel theory of memristance consisting of two components:
1. A memory function which describes how the memristance, as felt by the ions,
affects the conducting electrons located in the `on' part of the device; 2. A
conservation function which describes the time-varying resistance in the `off'
part of the device. This model allows for a straight-forward incorporation of
the ions within the electronic theory and relates Chua's constitutive
definition of a memristor with device material properties for the first time.",1106.3170v3
2012-04-18,Controlling bulk conductivity in topological insulators: Key role of anti-site defects,"The binary Bi-chalchogenides, Bi2Ch3, are widely regarded as model examples
of a recently discovered new form of quantum matter, the three-dimensional
topological insulator (TI) [1-4]. These compounds host a single spin-helical
surface state which is guaranteed to be metallic due to time reversal symmetry,
and should be ideal materials with which to realize spintronic and quantum
computing applications of TIs [5]. However, the vast majority of such compounds
synthesized to date are not insulators at all, but rather have detrimental
metallic bulk conductivity [2, 3]. This is generally accepted to result from
unintentional doping by defects, although the nature of the defects responsible
across different compounds, as well as strategies to minimize their detrimental
role, are surprisingly poorly understood. Here, we present a comprehensive
survey of the defect landscape of Bi-chalchogenide TIs from first-principles
calculations. We find that fundamental differences in the energetics of native
defect formation in Te- and Se-containing TIs enables precise control of the
conductivity across the ternary Bi-Te-Se alloy system. From a systematic
angle-resolved photoemission (ARPES) investigation of such ternary alloys,
combined with bulk transport measurements, we demonstrate that this method can
be utilized to achieve true topological insulators, with only a single Dirac
cone surface state intersecting the chemical potential. Our microscopic
calculations reveal the key role of anti-site defects for achieving this, and
predict optimal growth conditions to realize maximally-resistive ternary TIs.",1204.4063v1
2013-09-12,Theoretical Field Limits for Multi-Layer Superconductors,"The SIS structure---a thin superconducting film on a bulk superconductor
separated by a thin insulating film---was propsed as a method to protect
alternative SRF materials from flux penetration by enhancing the first critical
field $B_{c1}$. In this work, we show that in fact $B_{c1}$ = 0 for a SIS
structure. We calculate the superheating field $B_{sh}$, and we show that it
can be enhanced slightly using the SIS structure, but only for a small range of
film thicknesses and only if the film and the bulk are different materials. We
also show that using a multilayer instead of a single thick layer is
detrimental, as this decreases $B_{sh}$ of the film. We calculate the
dissipation due to vortex penetration above the $B_{sh}$ of the film, and find
that it is unmanageable for SRF applications. However, we find that if a
gradient in the phase of the order parameter is introduced, SIS structures may
be able to shield large DC and low frequency fields. We argue that the SIS
structure is not beneficial for SRF cavities, but due to recent experiments
showing low-surface-resistance performance above $B_{c1}$ in cavities made of
superconductors with small coherence lengths, we argue that enhancement of
$B_{c1}$ is not necessary, and that bulk films of alternative materials show
great promise.",1309.3239v2
2014-07-08,Competing magnetic phases and field-induced dynamics in DyRuAsO,"Analysis of neutron diffraction, dc magnetization, ac magnetic
susceptibility, heat capacity, and electrical resistivity for DyRuAsO in an
applied magnetic field are presented at temperatures near and below those at
which the structural distortion (T_S = 25 K) and subsequent magnetic ordering
(T_N = 10.5 K) take place. Powder neutron diffraction is used to determine the
antiferromagnetic order of Dy moments of magnitude 7.6(1) mu_B in the absence
of a magnetic field, and demonstrate the reorientation of the moments into a
ferromagnetic configuration upon application of a magnetic field. Dy magnetism
is identified as the driving force for the structural distortion. The magnetic
structure of analogous TbRuAsO is also reported. Competition between the two
magnetically ordered states in DyRuAsO is found to produce unusual physical
properties in applied magnetic fields at low temperature. An additional phase
transition near T* = 3 K is observed in heat capacity and other properties in
fields greater than about 3 T. Magnetic fields of this magnitude also induce
spin-glass-like behavior including thermal and magnetic hysteresis, divergence
of zero-field-cooled and field-cooled magnetization, frequency dependent
anomalies in ac magnetic susceptibility, and slow relaxation of the
magnetization. This is remarkable since DyRuAsO is a stoichiometric material
with no disorder detected by neutron diffraction, and suggests analogies with
spin-ice compounds and related materials with strong geometric frustration.",1407.2184v1
2014-07-13,Gate-tunable Phase Transitions in 1T-TaS$_2$,"The ability to tune material properties using gate electric field is at the
heart of modern electronic technology. It is also a driving force behind recent
advances in two-dimensional systems, such as gate-electric-field induced
superconductivity and metal-insulator transition. Here we describe an ionic
field-effect transistor (termed ""iFET""), which uses gate-controlled lithium ion
intercalation to modulate the material property of layered atomic crystal
1T-TaS$_2$. The extreme charge doping induced by the tunable ion intercalation
alters the energetics of various charge-ordered states in 1T-TaS$_2$, and
produces a series of phase transitions in thin-flake samples with reduced
dimensionality. We find that the charge-density-wave states in 1T-TaS$_2$ are
three-dimensional in nature, and completely collapse in the two-dimensional
limit defined by their critical thicknesses. Meanwhile the ionic gating induces
multiple phase transitions from Mott-insulator to metal in 1T-TaS$_2$ thin
flakes at low temperatures, with 5 orders of magnitude modulation in their
resistance. Superconductivity emerges in a textured charge-density-wave state
induced by ionic gating. Our method of gate-controlled intercalation of 2D
atomic crystals in the bulk limit opens up new possibilities in searching for
novel states of matter in the extreme charge-carrier-concentration limit.",1407.3480v1
2014-12-16,Characterization of 3 mm Glass Electrodes and Development of RPC Detectors for $INO-ICAL$ Experiment,"India-based Neutrino Observatory (INO) is a multi-institutional facility,
planned to be built up in South India. The INO facility will host a 51 kton
magnetized Iron CALorimeter (ICAL) detector to study atmospheric muon
neutrinos. Iron plates have been chosen as the target material whereas
Resistive Plate Chambers (RPCs) have been chosen as the active detector element
for the ICAL experiment. Due to the large number of RPCs needed ($\sim$ 28,000
of $2~m \times 2~m$ in size) for ICAL experiment and for the long lifetime of
the experiment, it is necessary to perform a detailed $R\&D$ such that each and
every parameter of the detector performance can be optimized to improve the
physics output. In this paper, we report on the detailed material and
electrical properties studies for various types of glass electrodes available
locally. We also report on the performance studies carried out on the RPCs made
with these electrodes as well as the effect of gas composition and
environmental temperature on the detector performance. We also lay emphasis on
the usage of materials for RPC electrodes and the suitable enviormental
conditions applicable for operating the RPC detector for optimal physics output
at INO-ICAL experiment.",1412.4998v1
2015-12-07,Insulating phase in Sr$_2$IrO$_4$: An investigation using critical analysis and magnetocaloric effect,"The nature of insulating phase in 5$d$ based Sr$_2$IrO$_4$ is quite debated
as the theoretical as well as experimental investigations have put forward
evidences in favor of both magnetically driven Slater-type and interaction
driven Mott-type insulator. To understand this insulating behavior, we have
investigated the nature of magnetic state in Sr$_2$IrO$_4$ through studying
critical exponents, low temperature thermal demagnetization and magnetocaloric
effect. The estimated critical exponents do not exactly match with any
universality class, however, the values obey the scaling behavior. The exponent
values suggest that spin interaction in present material is close to mean-field
model. The analysis of low temperature thermal demagnetization data, however,
shows dual presence of localized- and itinerant-type of magnetic interaction.
Moreover, field dependent change in magnetic entropy indicates magnetic
interaction is close to mean-field type. While this material shows an
insulating behavior across the magnetic transition, yet a distinct change in
slope in resistivity is observed around $T_c$. We infer that though the
insulating phase in Sr$_2$IrO$_4$ more close to be Slater-type but the
simultaneous presence of both Slater- and Mott-type is the likely scenario for
this material.",1512.02041v1
2016-02-04,Picosecond electric-field-induced threshold switching in phase-change materials,"Many chalcogenide glasses undergo a breakdown in electronic resistance above
a critical field strength. Known as threshold switching, this mechanism enables
field-induced crystallization in emerging phase-change memory. Purely
electronic as well as crystal nucleation assisted models have been employed to
explain the electronic breakdown. Here, picosecond electric pulses are used to
excite amorphous Ag$_4$In$_3$Sb$_{67}$Te$_{26}$. Field-dependent reversible
changes in conductivity and pulse-driven crystallization are observed. The
present results show that threshold switching can take place within the
electric pulse on sub-picosecond time-scales - faster than crystals can
nucleate. This supports purely electronic models of threshold switching and
reveals potential applications as an ultrafast electronic switch.",1602.01885v2
2016-10-17,"Structural, magnetic, electric, dielectric, and thermodynamic properties of multiferroic GeV4S8","The lacunar spinel GeV4S8 undergoes orbital and ferroelectric ordering at the
Jahn-Teller transition around 30 K and exhibits antiferromagnetic order below
about 14 K. In addition to this orbitally driven ferroelectricity, lacunar
spinels are an interesting material class, as the vanadium ions form V4
clusters representing stable molecular entities with a common electron
distribution and a well-defined level scheme of molecular states resulting in a
unique spin state per V4 molecule. Here we report detailed x-ray, magnetic
susceptibility, electrical resistivity, heat capacity, thermal expansion, and
dielectric results to characterize the structural, electric, dielectric,
magnetic, and thermodynamic properties of this interesting material, which also
exhibits strong electronic correlations. From the magnetic susceptibility, we
determine a negative Curie-Weiss temperature, indicative for antiferromagnetic
exchange and a paramagnetic moment close to a spin S = 1 of the V4 molecular
clusters. The low-temperature heat capacity provides experimental evidence for
gapped magnon excitations. From the entropy release, we conclude about strong
correlations between magnetic order and lattice distortions. In addition, the
observed anomalies at the phase transitions also indicate strong coupling
between structural and electronic degrees of freedom. Utilizing dielectric
spectroscopy, we find the onset of significant dispersion effects at the polar
Jahn-Teller transition. The dispersion becomes fully suppressed again with the
onset of spin order. In addition, the temperature dependencies of dielectric
constant and specific heat possibly indicate a sequential appearance of orbital
and polar order.",1610.05244v1
2017-02-15,Negative Differential Resistance in Graphene Boron Nitride Heterostructure Controlled by Twist and Phonon-Scattering,"Two-dimensional (2D) crystals, such as graphene, hexagonal boron nitride and
transitional metal dichalcogenides, have attracted tremendous amount of
attention over the past decade due to their extraordinary thermal, electrical
and optical properties, making them promising nano-materials for the
next-generation electronic systems. A large number of heterostructures have
been fabricated by stacking of various 2D materials to achieve different
functionalities. In this work, we simulate the electron transport properties of
a three-terminal multilayer heterostructure made from graphene nanoribbons
vertically sandwiching a boron nitride tunneling barrier. To investigate the
effects of the unavoidable misalignment in experiments, we introduce a tunable
angular misorientation between 2D layers to the modeled system. Current-Voltage
(I-V) characteristics of the device exhibit multiple NDR peaks originating from
distinct mechanisms. A unique NDR mechanism arising from the lattice mismatch
is captured and it depends on both the twisting angle and voltage bias.
Analytical expressions for the positions of the resonant peaks observed in I-V
characteristic are developed. To capture the slight degradation of PVR ratios
observed in experiments when temperature increases from 2K to 300K,
electron-photon scattering decoherence has been added to the simulation,
indicating a good agreement with experiment works as well as a robust
preservation of resonant tunneling feature.",1702.04435v1
2017-09-12,Electric field induced semiconductor-to-metal phase transition in vertical MoTe2 and Mo1-xWxTe2 devices,"Over the past years, transition metal dichalcogenides (TMDs) have attracted
attention as potential building blocks for various electronic applications due
to their atomically thin nature. An exciting development is the recent success
in 'engineering' crystal phases of TMD compounds during the growth due to their
polymorphic character. Here, we report an electric field induced reversible
engineered phase transition in vertical 2H-MoTe2 devices, a crucial
experimental finding that enables electrical phase switching for these
ultra-thin layered materials. Scanning tunneling microscopy (STM) was utilized
to analyze the TMD crystalline structure after applying an electric field, and
scanning tunneling spectroscopy (STS) was employed to map a
semiconductor-to-metal phase transition on the nanoscale. In addition, direct
confirmation of a phase transition from 2H semiconductor to a distorted 2H'
metallic phase was obtained by scanning transmission electron microscopy
(STEM). MoTe2 and Mo1-xWxTe2 alloy based vertical resistive random access
memory (RRAM) cells were fabricated to demonstrate clear reproducible and
controlled switching with programming voltages that are tunable by the layer
thickness and that show a distinctly different trend for the binary compound if
compared to the ternary materials.",1709.03835v1
2018-01-05,Writing on Nanocrystals: Patterning Colloidal Inorganic Nanocrystal Films through Irradiation-Induced Chemical Transformations of Surface Ligands,"In the past couple of decades, colloidal inorganic nanocrystals and, more
specifically, semiconductor quantum dots have emerged as crucial materials for
the development of nanoscience and nanotechnology, with applications in very
diverse areas such as optoelectronics and biotechnology. Films made of
inorganic NCs deposited on a substrate can be patterned by e-beam lithography,
altering the structure of their capping ligands and thus allowing exposed areas
to remain on the substrate while non-exposed areas are redispersed in a
solvent, as in a standard lift-off process. This methodology can be described
as a direct lithography process, since the exposure is performed directly on
the material of interest, in contrast with conventional lithography which uses
a polymeric resist as a mask for subsequent material deposition or etching. A
few reports from the late 1990 and early 2000 used such direct lithography to
fabricate electrical wires from metallic NCs. However, the poor conductivity
obtained through this process hindered the widespread use of the technique. In
the early 2010, the same method was used to define fluorescent patterns on QD
films, allowing for further applications in biosensing. For the past 2 ,3
years, direct lithography on NC films with e-beams and X rays has gone through
an important development as it has been demonstrated that it can tune further
transformations on the NCs, leading to more complex patternings and opening a
whole new set of possible applications.",1801.01756v1
2018-04-09,Pressure effects on the structural and superconducting transitions in La3Co4Sn13,"La3Co4Sn13 is a superconducting material with transition temperature at Tc =
2.70 K, which presents a superlattice structural transition at T* ~ 150 K, a
common feature for this class of compounds. However, for this material, it is
not clear that at T* the lattice distortions arise from a charge density wave
(CDW) or from a distinct microscopic origin. Interestingly, it has been
suggested in isostructural non-magnetic intermetallic compounds that T* can be
suppressed to zero temperature, by combining chemical and external pressure,
and a quantum critical point is argued to be observed near these critical
doping/pressure. Our study shows that application of pressure on
single-crystalline La3Co4Sn13 enhances Tc and decreases T*. We observe thermal
hysteresis loops for cooling/heating cycles around T* for P > 0.6 GPa, in
electrical resistivity measurements, which are not seen in x-ray diffraction
data. The hysteresis in electrical measurements may be due to the pinning of
the CDW phase to impurities/defects, while the superlattice structural
transition maintains its ambient pressure second-order transition nature under
pressure. From our experiments we estimate that T* vanishes at around 5.5 GPa,
though no quantum critical behavior is observed up to 2.53 GPa.",1804.03215v2
2018-06-14,Tunneling spin valves based on Fe$_3$GeTe$_2$/hBN/Fe$_3$GeTe$_2$ van der Waals heterostructures,"Thin van der Waals (vdW) layered magnetic materials disclose the possibility
to realize vdW heterostructures with new functionalities. Here we report on the
realization and investigation of tunneling spin valves based on van der Waals
heterostructures consisting of an atomically thin hBN layer acting as tunnel
barrier and two exfoliated Fe3GeTe2 crystals acting as ferromagnetic
electrodes. Low-temperature anomalous Hall effect measurements show that thin
Fe3GeTe2 crystals are metallic ferromagnets with an easy axis perpendicular to
the layers, and a very sharp magnetization switching at magnetic field values
that depend slightly on their geometry. In Fe3GeTe2/hBN/Fe3GeTe2
heterostructures, we observe a textbook behavior of the tunneling resistance,
which is minimum (maximum) when the magnetization in the two electrodes is
parallel (antiparallel) to each other. The magnetoresistance is 160% at low
temperature, from which we determine the spin polarization of Fe3GeTe2 to be
0.66, corresponding to 83% and 17% of majority and minority carriers,
respectively. The measurements also show that, with increasing temperature, the
evolution of the spin polarization extracted from the tunneling
magnetoresistance is proportional to the temperature dependence of the
magnetization extracted from the analysis of the anomalous Hall conductivity.
This suggests that the magnetic properties of the surface are representative of
those of the bulk, as it may be expected for vdW materials.",1806.05411v1
2018-06-18,Mott transition and collective charge pinning in electron doped Sr2IrO4,"We studied the in-plane dynamic and static charge conductivity of electron
doped Sr2IrO4 using optical spectroscopy and DC transport measurements. The
optical conductivity indicates that the pristine material is an indirect
semiconductor with a direct Mott-gap of 0.55 eV. Upon substitution of 2% La per
formula unit the Mott-gap is suppressed except in a small fraction of the
material (15%) where the gap survives, and overall the material remains
insulating. Instead of a zero energy mode (or Drude peak) we observe a soft
collective mode (SCM) with a broad maximum at 40 meV. Doping to 10% increases
the strength of the SCM, and a zero-energy mode occurs together with metallic
DC conductivity. Further increase of the La substitution doesn't change the
spectral weight integral up to 3 eV. It does however result in a transfer of
the SCM spectral weight to the zero-energy mode, with a corresponding reduction
of the DC resistivity for all temperatures from 4 to 300 K. The presence of a
zero-energy mode signals that at least part of the Fermi surface remains
ungapped at low temperatures, whereas the SCM appears to be caused by pinning a
collective frozen state involving part of the doped electrons.",1806.06937v1
2018-06-22,Disorder control in crystalline GeSb2Te4 and its impact on characteristic length scales,"Crystalline GeSb2Te4 (GST) is remarkable material, as it allows to
continuously tune the electrical resistance by orders of magnitude without
involving a phase transition or stoichiometric changes, just by altering the
short-range order. While well-ordered specimen are metallic, increasing amounts
of disorder can eventually lead to an insulating state with vanishing
conductivity in the 0K limit, but a similar number of charge carriers. These
observations make disordered GST one of the most promising candidates for the
realization of a true Anderson insulator. While so far the low-temperature
properties have mostly been studied in films of small grain size, here a
sputter-deposition process is employed that enables preparation of a large
variety of these GST states including metallic and truly insulating ones. By
growing films of GST on mica substrates, biaxially textured samples with huge
grain sizes are obtained. A series of these samples is employed for transport
measurements, as their electron mean free path can be altered by a factor of
20. Yet, the mean free path always remains more than an order of magnitude
smaller than the lateral grain size. This proves unequivocally that grain
boundaries play a negligible role for electron scattering, while intragrain
scattering, presumably by disordered vacancies, dominates. Most importantly,
these findings underline that the Anderson insulating state as well as the
system's evolution towards metallic conductivity are indeed intrinsic
properties of the material.",1806.08636v1
2019-09-26,Large-area implementation and critical evaluation of the material and fabrication aspects of a thin-film thermoelectric generator based on aluminum-doped zinc oxide,"A large-area thermoelectric generator (TEG) utilizing a folded thin-film
concept is implemented and the performance evaluated for near room temperature
applications having modest temperature gradients (< 50 K). The TEGs with the
area of ~0.33 m^2 are shown capable of powering a wireless sensor node of
multiple sensors suitable e.g. for monitoring environmental variables in
buildings. The TEGs are based on a transparent, non-toxic and abundant
thermoelectric material, i.e. aluminium-doped zinc oxide (AZO), deposited on
flexible substrates. After folding, both the electrical current and heat flux
are in the plane of the thermoelectric thin-film. Heat leakage in the folded
TEG is shown to be minimal (close to that of air), enabling sufficient
temperature gradients without efficient heat sinks, contrary to the
conventional TEGs having the thermal flux and electrical current perpendicular
to the plane of the thermoelectric films. The long-term stability studies
reveal that there are no significant changes in the electrical or
thermoelectric properties of AZO over several months, while the contact
resistance between AZO and silver ink is an issue exhibiting a continuous
increase over time. The performance of the TEGs and technological implications
in relation to a state-of-the-art thermoelectric material are further assessed
via a computational study.",1909.12042v2
2019-09-26,"Quantum effects in graphitic materials: Colossal magnetoresistance, Andreev reflections, Little-Parks effect, ferromagnetism, and granular superconductivity","Unlike the more common local conductance spectroscopy, nonlocal conductance
can differentiate between nontopological zero-energy modes localized around
inhomogeneities, and true Majorana edge modes in the topological phase. In
particular, negative nonlocal conductance is dominated by the crossed Andreev
reflection. In graphene, the Andreev reflection and the inter-band Klein
tunneling couple electron-like and hole-like states through the action of
either a superconducting (SC) pair potential or an electrostatic potential. We
are here probing quantum phenomena in modified graphitic samples. Four-point
contact transport measurements at cryogenic to room temperatures were conducted
using a Quantum Design Physical Property Measurement System. The observed
negative nonlocal differential conductance Gdiff probes the Andreev reflection
at the walls of the SC grains coupled by Josephson effect through the
semiconducting matrix. In addition, Gdiff shows the butterfly shape that is
characteristic to resistive random-access memory devices. In a magnetic field,
the Andreev reflection counters the effect of the otherwise lowered conduction.
At low temperatures, the magnetoresistance shows irreversible yet strong
colossal oscillations that are known to be quantum in nature. In addition, we
have found evidence for seemingly granular SC as well as ferromagnetism.
Moreover, the Little-Parks effect is revealed in both the classical
small-amplitude and the phase-slip driven large-amplitude oscillations in the
magnetoresistance. Thus, graphitic materials show potential for quantum
electronics applications, including rectification and topological states.",1909.12145v1
2015-05-18,Photoemission System with Polarized Hard X-rays for Probing Ground State Symmetry of Strongly Correlated Materials,"We have developed a polarized hard X-ray photoemission (HAXPES) system to
study the ground-state symmetry of strongly correlated materials. The linear
polarization of the incoming X-ray beam is switched by the transmission-type
phase retarder composed of two diamond (100) crystals. The best degree of the
linear polarization $P_L$ is $-0.96$, containing the vertical polarization
component of 98%. A newly developed low temperature two-axis manipulator
enables easy polar and azimuthal rotations to select the detection direction of
photoelectrons. The lowest temperature achieved is 9 K, offering us a chance to
access the ground state even for the strongly correlated electron systems in
cubic symmetry. The co-axial sample monitoring system with the
long-working-distance microscope enables us to keep measuring the same region
on the sample surface before and after rotation procedures. Combining this
sample monitoring system with a micro-focused X-ray beam by means of an
ellipsoidal Kirkpatrick-Baez mirror (25 $\mu$m $\times$ 25 $\mu$m (FWHM)), we
have demonstrated the polarized valence-band HAXPES on NiO for voltage
application as resistive random access memories to reveal the origin of the
metallic spectral weight near the Fermi level.",1505.04591v1
2017-01-02,Thermoelectric power factor enhancement by spin-polarized currents - a nanowire case study,"Thermoelectric (TE) measurements have been performed on the workhorses of
today's data storage devices, exhibiting either the giant or the anisotropic
magnetoresistance effect (GMR and AMR). The temperature-dependent (50-300 K)
and magnetic field-dependent (up to 1 T) TE power factor (PF) has been
determined for several Co-Ni alloy nanowires with varying Co:Ni ratios as well
as for Co-Ni/Cu multilayered nanowires with various Cu layer thicknesses, which
were all synthesized via a template-assisted electrodeposition process. A
systematic investigation of the resistivity, as well as the Seebeck
coefficient, is performed for Co-Ni alloy nanowires and Co-Ni/Cu multilayered
nanowires. At room temperature, measured values of TE PFs up to 3.6 mWK-2m-1
for AMR samples and 2.0 mWK-2m-1 for GMR nanowires are obtained. Furthermore,
the TE PF is found to increase by up to 13.1 % for AMR Co-Ni alloy nanowires
and by up to 52 % for GMR Co-Ni/Cu samples in an external applied magnetic
field. The magnetic nanowires exhibit TE PFs that are of the same order of
magnitude as TE PFs of Bi-Sb-Se-Te based thermoelectric materials and,
additionally, give the opportunity to adjust the TE power output to changing
loads and hotspots through external magnetic fields.",1701.00404v1
2018-11-20,Towards integrated metatronics: a holistic approach on precise optical and electrical properties of Indium Tin Oxide,"The class of transparent conductive oxides includes the material indium tin
oxide (ITO) and has become a widely used material of modern every-day life such
as in touch screens of smart phones and watches, but also used as an optically
transparent low electrically-resistive contract in the photovoltaics industry.
More recently ITO has shown epsilon-near-zero (ENZ) behavior in the
telecommunication frequency band enabling both strong index modulation and
other optically-exotic applications such as metatronics. However the ability to
precisely obtain targeted electrical and optical material properties in ITO is
still challenging due to complex intrinsic effects in ITO and as such no
integrated metatronic platform has been demonstrated to-date. Here we deliver
an extensive and accurate description process parameters of RF-sputtering,
showing a holistic control of the quality of ITO thin films in the visible and
particularly near-infrared spectral region. We further are able to
custom-engineer the ENZ point across the telecommunication band by explicitly
controlling the sputtering process conditions. Exploiting this control we
design a functional sub-wavelength-scale filter based on lumped
circuit-elements, towards the realization of integrated metatronic devices and
circuits.",1811.08344v4
2018-11-30,Thermal Transport Across Graphene Step Junctions,"Step junctions are often present in layered materials, i.e. where
single-layer regions meet multi-layer regions, yet their effect on thermal
transport is not understood to date. Here, we measure heat flow across graphene
junctions (GJs) from monolayer to bilayer graphene, as well as bilayer to
four-layer graphene for the first time, in both heat flow directions. The
thermal conductance of the monolayer-bilayer GJ device ranges from ~0.5 to
9.1x10^8 Wm-2K-1 between 50 K to 300 K. Atomistic simulations of such GJ device
reveal that graphene layers are relatively decoupled, and the low thermal
conductance of the device is determined by the resistance between the two
dis-tinct graphene layers. In these conditions the junction plays a negligible
effect. To prove that the decoupling between layers controls thermal transport
in the junction, the heat flow in both directions was measured, showing no
evidence of thermal asymmetry or rectification (within experimental error
bars). For large-area graphene applications, this signifies that small bilayer
(or multilayer) islands have little or no contribution to overall thermal
transport.",1811.12622v1
2019-05-29,Physical mechanisms involved in the formation and operation of memory devices based on a monolayer of gold nanoparticles-polythiophene hybrid materials,"Understanding the physical and chemical mechanisms occurring during the
forming process and operation of an organic resistive memory device is a major
issue for better performances. Various mechanisms were suggested in vertically
stacked memory structures, but the analysis remains indirect and needs
destructive characterization (e.g. cross-section to access the organic layers
sandwiched between electrodes). Here, we report a study on a planar, monolayer
thick, hybrid nanoparticle/molecule device (10 nm gold nanoparticles embedded
in an electro-generated poly(2-thienyl-3,4-(ethylenedioxy)thiophene) layer),
combining, in situ, on the same device, physical (scanning electron microscope,
physico-chemical (thermogravimetry and mass spectroscopy, Raman spectroscopy)
and electrical (temperature dependent current-voltage) characterizations. We
demonstrate that the forming process causes an increase in the gold particle
size, almost 4 times larger than the starting nanoparticles, and that the
organic layer undergoes a significant chemical rearrangement from a sp3 to sp2
amorphous carbon material. Temperature dependent electrical characterizations
of this nonvolatile memory confirm that the charge transport mechanism in the
device is consistent with a trap-filled space charge limited current in the off
state, the sp2 amorphous carbon material containing many electrically active
defects.",1905.12719v1
2020-03-25,Synergistically creating sulfur vacancies in semimetal-supported amorphous MoS2 for efficient hydrogen evolution,"The presence of elemental vacancies in materials is inevitable according to
statistical thermodynamics, which will decide the chemical and physical
properties of the investigated system. However, the controlled manipulation of
vacancies for specific applications is a challenge. Here we report a facile
method for creating large concentrations of S vacancies in the inert basal
plane of MoS2 supported on semimetal CoMoP2. With a small applied potential, S
atoms can be removed in the form of H2S due to the optimized free energy of
formation. The existence of vacancies favors electron injection from the
electrode to the active site by decreasing the contact resistance. As a
consequence, the activity is increased by 221 % with the vacancy-rich MoS2 as
electrocatalyst for hydrogen evolution reaction (HER). A small overpotential of
75 mV is needed to deliver a current density of 10 mA cm-2, which is considered
among the best values achieved for MoS2. It is envisaged that this work may
provide a new strategy for utilizing the semimetal phase for structuring MoS2
into a multi-functional material.",2003.11436v1
2020-04-01,Physical properties and thermal stability of Fe5GeTe2 single crystals,"The magnetic and transport properties of Fe-deficient Fe5GeTe2 single
crystals (Fe5-xGeTe2 with x~0.3) were studied and the impact of thermal
processing was explored. Quenching crystals from the growth temperature has
been previously shown to produce a metastable state that undergoes a strongly
hysteretic first-order transition upon cooling below ~100K. The first-order
transition impacts the magnetic properties, yielding an enhancement in the
Curie temperature T_C from 270 to 310K. In the present work, T_HT ~550K has
been identified as the temperature above which metastable crystals are obtained
via quenching. Diffraction experiments reveal a structural change at this
temperature, and significant stacking disorder occurs when samples are slowly
cooled through this temperature range. The transport properties are
demonstrated to be similar regardless of the crystal's thermal history. The
scattering of charge carriers appears to be dominated by moments fluctuating on
the Fe(1) sublattice, which remain dynamic down to 100-120K. Maxima in the
magnetoresistance and anomalous Hall resistance are observed near 120K. The
Hall and Seebeck coefficients are also impacted by magnetic ordering on the
Fe(1) sublattice. The data suggest that both electrons and holes contribute to
conduction above 120K, but that electrons dominate at lower temperature when
all of the Fe sublattices are magnetically ordered. This study demonstrates a
strong coupling of the magnetism and transport properties in Fe5-xGeTe2 and
complements the previous results that demonstrated strong magnetoelastic
coupling as the Fe(1) moments order. The published version of this manuscript
is DOI:10.1103/PhysRevMaterials.3.104401 (2019)",2004.00494v1
2020-04-14,Photoanodes Based on TiO$_2$ and $α$-Fe$_2$O$_3$ for Solar Water Splitting Superior Role of 1D Nanoarchitectures and of Combined Heterostructures,"Solar driven photoelectrochemical water splitting (PEC-WS) using
semiconductor photoelectrodes represents a promising approach for a sustainable
and environmentally friendly production of renewable energy vectors and fuel
sources, such as dihydrogen (H2). In this context, titanium dioxide (TiO$_2$)
and iron oxide (hematite, $\alpha$-Fe$_2$O$_3$) are among the most investigated
candidates as photoanode materials, mainly owing to their resistance to
photocorrosion, non-toxicity, natural abundance, and low production cost. Major
drawbacks are, however, an inherently low electrical conductivity and a limited
hole diffusion length that significantly affect the performance of TiO$_2$ and
$\alpha$-Fe$_2$O$_3$ in PEC devices. To this regard, one-dimensional (1D)
nanostructuring is typically applied as it provides several superior features
such as a significant enlargement of the material surface area, extended
contact between the semiconductor and the electrolyte and, most remarkably,
preferential electrical transport that overall suppress charge carrier
recombination and improve TiO$_2$ and $\alpha$-Fe$_2$O$_3$
photo-electrocatalytic properties. The present review describes various
synthetic methods, properties and PEC applications of 1D-photoanodes
(nanotubes, nanorods, nanofibers, nanowires) based on titania, hematite, and on
$\alpha$-Fe$_2$O$_3$/TiO$_2$ heterostructures. Various routes towards
modification and enhancement of PEC activity of 1D photoanodes are also
discussed including doping, decoration with co-catalysts and heterojunction
engineering. Finally, the challenges related to the optimization of charge
transfer kinetics in both oxides are highlighted.",2004.12844v1
2007-10-08,Colossal dielectric constants in single-crystalline and ceramic CaCu3Ti4O12 investigated by broadband dielectric spectroscopy,"In the present work the authors report results of broadband dielectric
spectroscopy on various samples of CaCu3Ti4O12, including so far only rarely
investigated single crystalline material. The measurements extend up to 1.3
GHz, covering more than nine frequency decades. We address the question of the
origin of the colossal dielectric constants and of the relaxational behavior in
this material, including the second relaxation reported in several recent
works. For this purpose, the dependence of the temperature- and
frequency-dependent dielectric properties on different tempering and surface
treatments of the samples and on ac-field amplitude are investigated. Broadband
spectra of a single crystal are analyzed by an equivalent circuit description,
assuming two highly resistive layers in series to the bulk. Good fits could be
achieved, including the second relaxation, which also shows up in single
crystals. The temperature- and frequency-dependent intrinsic conductivity of
CCTO is consistent with the Variable Range Hopping model. The second relaxation
is sensitive to surface treatment and, in contrast to the main relaxation, also
is strongly affected by the applied ac voltage. Concerning the origin of the
two insulating layers, we discuss a completely surface-related mechanism
assuming the formation of a metal-insulator diode and a combination of surface
and internal barriers.",0710.1610v1
2017-04-13,Extreme Magnetoresistance in Magnetic Rare Earth Monopnictides,"The acute sensitivity of the electrical resistance of certain systems to
magnetic fields known as extreme magnetoresistance (XMR) has recently been
explored in a new materials context with topological semimetals. Exemplified by
WTe$_{2}$ and rare earth monopnictide La(Sb,Bi), these systems tend to be
non-magnetic, nearly compensated semimetals and represent a platform for large
magnetoresistance driven by intrinsic electronic structure. Here we explore
electronic transport in magnetic members of the latter family of semimetals and
find that XMR is strongly modulated by magnetic order. In particular, CeSb
exhibits XMR in excess of $1.6 \times 10^{6}$ % at fields of 9 T while the
magnetoresistance itself is non-monotonic across the various magnetic phases
and shows a transition from negative magnetoresistance to XMR with field above
magnetic ordering temperature $T_{N}$. The magnitude of the XMR is larger than
in other rare earth monopnictides including the non-magnetic members and
follows an non-saturating power law to fields above 30 T. We show that the
overall response can be understood as the modulation of conductivity by the Ce
orbital state and for intermediate temperatures can be characterized by an
effective medium model. Comparison to the orbitally quenched compound GdBi
supports the correlation of XMR with the onset of magnetic ordering and
compensation and highlights the unique combination of orbital inversion and
type-I magnetic ordering in CeSb in determining its large response. These
findings suggest a paradigm for magneto-orbital control of XMR and are relevant
to the understanding of rare earth-based correlated topological materials.",1704.04226v1
2018-08-28,Mott metal-insulator transitions in pressurized layered trichalcogenides,"Transition metal phosphorous trichalcogenides, $M{\rm P}X_3$ ($M$ and $X$
being transition metal and chalcogen elements respectively), have been the
focus of substantial interest recently because of their possible magnetism in
the two-dimensional limit. Here we investigate material properties of the
compounds with $M$ = Mn and Ni employing $\textit{ab-initio}$ density
functional and dynamical mean-field calculations, especially their electronic
behavior under external pressure in the paramagnetic phase. Mott
metal-insulator transitions (MIT) are found to be a common feature for both
compounds, but their lattice structures show drastically different behaviors
depending on the relevant orbital degrees of freedom, i.e. $t_{\rm 2g}$ or
$e_{g}$. MnPS$_3$ undergoes an isosymmetric structural transition by forming
Mn-Mn dimers due to the strong direct overlap between the neighboring $t_{\rm
2g}$ orbitals, accompanied by a significant volume collapse and a spin-state
transition. In contrast, NiPS$_3$ and NiPSe$_3$, with their active $e_g$
orbital degrees of freedom, do not show a structural change at the MIT pressure
or deep in the metallic phase. Hence NiPS$_3$ and NiPSe$_3$ become rare
examples of materials hosting electronic bandwidth-controlled Mott MITs, thus
showing promise for ultrafast resistivity switching behavior.",1808.09263v2
2019-03-01,Unraveling Bulk and Grain Boundary Electrical Properties in La0.8Sr0.2Mn1-yO3 Thin Films,"Grain boundaries in Sr-doped LaMnO3 thin films have been shown to strongly
influence the electronic and oxygen mass transport properties, being able to
profoundly modify the nature of the material. The unique behaviour of the grain
boundaries can be correlated with substantial modifications of the cation
concentration at the interfaces, which can be tuned by changing the overall
cationic ratio in the films. In this work, we study the electronic properties
of La0.8Sr0.2Mn1-yO3 thin films with variable Mn content. The influence of the
cationic composition on the grain boundary and grain bulk electronic properties
is elucidated by studying the manganese valence state evolution using
spectroscopy techniques and by confronting the electronic properties of
epitaxial and polycrystalline films. Substantial differences in the electronic
conduction mechanism are found in the presence of grain boundaries and
depending on the manganese content. Moreover, the unique defect chemistry of
the nanomaterial is elucidated by measuring the electrical resistance of the
thin films as a function of oxygen partial pressure, disclosing the importance
of the cationic local non-stoichiometry on the thin films behavior.",1903.00235v1
2019-04-12,Spin-dependent transport in van der Waals magnetic tunnel junctions with Fe3GeTe2 electrodes,"Van der Waals (vdW) heterostructures, stacking different two-dimensional
materials, have opened up unprecedented opportunities to explore new physics
and device concepts. Especially interesting are recently discovered
two-dimensional magnetic vdW materials, providing new paradigms for spintronic
applications. Here, using density functional theory (DFT) calculations, we
investigate the spin-dependent electronic transport across vdW magnetic tunnel
junctions (MTJs) composed of Fe3GeTe2 ferromagnetic electrodes and a graphene
or hexagonal boron nitride (h-BN) spacer layer. For both types of junctions, we
find that the junction resistance changes by thousands of percent when the
magnetization of the electrodes is switched from parallel to antiparallel. Such
a giant tunneling magnetoresistance (TMR) effect is driven by dissimilar
electronic structure of the two spin-conducting channels in Fe3GeTe2, resulting
in a mismatch between the incoming and outgoing Bloch states in the electrodes
and thus suppressed transmission for an antiparallel-aligned MTJ. The vdW
bounding between electrodes and a spacer layer makes this result virtually
independent of the type of the spacer layer, making the predicted giant TMR
effect robust with respect to strain, lattice mismatch, interface distance and
other parameters which may vary in the experiment. We hope that our results
will further stimulate experimental studies of vdW MTJs and pave the way for
their applications in spintronics.",1904.06098v1
2019-12-13,Shallow impurity band in ZrNiSn,"ZrNiSn and related half Heusler compounds are candidate materials for
efficient thermoelectric energy conversion with a reported thermoelectric
figure-of-merit of n-type ZrNiSn exceeding unity. Progress on p-type materials
has been more limited, which has been attributed to the presence of an impurity
band, possibly related to the presence of Ni interstitials in nominally vacant
4d position. The specific energetic position of this band, however, has not
been resolved. Here, we report results of a concerted theory-experiment
investigation for a nominally undoped ZrNiSn, based on measurements of
electrical resistivity, Hall coefficient, Seebeck coefficient and Nernst
coefficient, measured in a temperature range from 80 to 420 K. The results are
analyzed with a semi-analytical model combining a density functional theory
(DFT) description for ideal ZrNiSn, with a simple analytical correction for the
impurity band. The model provides a good quantitative agreement with
experiment, describing all salient features in the full temperature span for
the Hall, conductivity, and Seebeck measurements, while also reproducing key
trends in the Nernst results. This comparison pinpoints the impurity band edge
to 40 meV below the conduction band edge, which agrees well with a separate DFT
study of a supercell containing Ni interstitials. Moreover, we corroborate our
result with a separate study of ZrNiSn0.9Pb0.1 sample showing similar agreement
with an impurity band edge shifted to 32 meV below the conduction band.",1912.06539v1
2020-12-23,A general theory for anisotropic Kirchhoff-Love shells with in-plane bending of embedded fibers,"This work presents a generalized Kirchhoff-Love shell theory that can
explicitly capture fiber-induced anisotropy not only in stretching and
out-of-plane bending, but also in in-plane bending. This setup is particularly
suitable for heterogeneous and fibrous materials such as textiles,
biomaterials, composites and pantographic structures. The presented theory is a
direct extension of classical Kirchhoff-Love shell theory to incorporate the
in-plane bending resistance of fibers. It also extends existing second-gradient
Kirchhoff-Love shell theory for initially straight fibers to initially curved
fibers. To describe the additional kinematics of multiple fiber families, a
so-called in-plane curvature tensor -- which is symmetric and of second order
-- is proposed. The effective stress tensor and the in-plane and out-of-plane
moment tensors are then identified from the mechanical power balance. These
tensors are all second order and symmetric in general. Constitutive equations
for hyperelastic materials are derived from different expressions of the
mechanical power balance. The weak form is also presented as it is required for
computational shell formulations based on rotation-free finite element
discretizations.",2101.03122v3
2012-03-06,Discrete modelling of capillary mechanisms in multi-phase granular media,"A numerical study of multi-phase granular materials based upon
micro-mechanical modelling is proposed. Discrete element simulations are used
to investigate capillary induced effects on the friction properties of a
granular assembly in the pendular regime. Capillary forces are described at the
local scale through the Young-Laplace equation and are superimposed to the
standard dry particle interaction usually well simulated through an
elastic-plastic relationship. Both effects of the pressure difference between
liquid and gas phases and of the surface tension at the interface are
integrated into the interaction model. Hydraulic hysteresis is accounted for
based on the possible mechanism of formation and breakage of capillary menisci
at contacts. In order to upscale the interparticular model, triaxial loading
paths are simulated on a granular assembly and the results interpreted through
the Mohr-Coulomb criterion. The micro-mechanical approach is validated with a
capillary cohesion induced at the macroscopic scale. It is shown that
interparticular menisci contribute to the soil resistance by increasing normal
forces at contacts. In addition, more than the capillary pressure level or the
degree of saturation, our findings highlight the importance of the density
number of liquid bonds on the overall behaviour of the material.",1203.1234v1
2015-06-12,Current-limiting challenges for all-spin logic devices,"All-spin logic device (ASLD) has attracted increasing interests as one of the
most promising post-CMOS device candidates, thanks to its low power,
non-volatility and logic-in-memory structure. Here we investigate the key
current-limiting factors and develop a physics-based model of ASLD through
nano-magnet switching, the spin transport properties and the breakdown
characteristic of channel. First, ASLD with perpendicular magnetic anisotropy
(PMA) nano-magnet is proposed to reduce the critical current (Ic0). Most
important, the spin transport efficiency can be enhanced by analyzing the
device structure, dimension, contact resistance as well as material parameters.
Furthermore, breakdown current density (JBR) of spin channel is studied for the
upper current limitation. As a result, we can deduce current-limiting
conditions and estimate energy dissipation. Based on the model, we demonstrate
ASLD with different structures and channel materials (graphene and copper).
Asymmetric structure is found to be the optimal option for current limitations.
Copper channel outperforms graphene in term of energy but seriously suffers
from breakdown current limit. By exploring the current limit and performance
tradeoffs, the optimization of ASLD is also discussed. This benchmarking model
of ASLD opens up new prospects for design and implementation of future
spintronics applications.",1506.03946v2
2019-01-15,Phenomenal magneto-elastoresistance of WTe$_{2}$: strain engineering of electronic and quantum transport properties,"Elastoresistance describes the relative change of a material's resistance
when strained. It has two major contributions: strain induced geometric and
electronic changes. If the geometric factor dominates, like in ordinary metals
such as copper, the elastoresistance is positive and rather small, i.e.
typically of order 1. In a few materials, however, changes in electronic
structure dominate, which gives rise to larger and even negative values, such
as (-11) for Bi. Here, we report that the transition metal dichalcogenide
(TMDC) WTe$_{2}$ is a member of the second group, exhibiting a large and
non-monotonic elastoresistance that is about (-20) near 100 K and changes sign
at low temperatures. We discover that an applied magnetic field has a dramatic
effect on the elastoresistance in WTe$_{2}$: in the quantum regime at low
temperatures, it leads to quantum oscillations of the elastoresistance, that
ranges between (-80) to 120 within a field range of only half a Tesla. In the
semiclassical regime at intermediate temperatures, we find that the
elastoresistance rapidly increases and changes sign in a magnetic field. We
provide a semi-quantitative understanding of our experimental results using a
combination of first-principle and analytical low-energy model calculations.
Understanding bulk properties of TMDCs under uniaxial strain is an important
stepping stone toward strain engineering of 2D TMDCs.",1901.05090v1
2019-10-26,Magic continuum in twisted bilayer WSe2,"Emergent quantum phases driven by electronic interactions can manifest in
materials with narrowly dispersing, i.e. ""flat"", energy bands. Recently, flat
bands have been realized in a variety of graphene-based heterostructures using
the tuning parameters of twist angle, layer stacking and pressure, and
resulting in correlated insulator and superconducting states. Here we report
the experimental observation of similar correlated phenomena in twisted bilayer
tungsten diselenide (tWSe2), a semiconducting transition metal dichalcogenide
(TMD). Unlike twisted bilayer graphene where the flat band appears only within
a narrow range around a ""magic angle"", we observe correlated states over a
continuum of angles, spanning 4 degree to 5.1 degree. A Mott-like insulator
appears at half band filling that can be sensitively tuned with displacement
field. Hall measurements supported by ab initio calculations suggest that the
strength of the insulator is driven by the density of states at half filling,
consistent with a 2D Hubbard model in a regime of moderate interactions. At 5.1
degree twist, we observe evidence of superconductivity upon doping away from
half filling, reaching zero resistivity around 3 K. Our results establish
twisted bilayer TMDs as a model system to study interaction-driven phenomena in
flat bands with dynamically tunable interactions.",1910.12147v1
2020-06-26,YBCO-based non-volatile ReRAM tested in Low Earth Orbit,"An YBCO-based test structure corresponding to the family of ReRAM devices
associated with the valence change mechanism is presented. We have
characterized its electrical response previous to its lift-off to a Low Earth
Orbit (LEO) using standard electronics and also with the dedicated LabOSat-01
controller. Similar results were obtained in both cases. After about 200 days
at LEO on board a small satellite, electrical tests started on the memory
device using the LabOSat-01 controller. We discuss the results of the first 150
tests, performed along a 433-day time interval in space. The memory device
remained operational despite the hostile conditions that involved launching,
lift-off vibrations, permanent thermal cycling and exposure to ionizing
radiation, with doses 3 orders of magnitude greater than the usual ones on
Earth. The device showed resistive switching and IV characteristics similar to
those measured on Earth, although with changes that follow a smooth drift in
time. A detailed study of the electrical transport mechanisms, based on
previous models that indicate the existence of various conducting mechanisms
through the metal-YBCO interface showed that the observed drift can be
associated with a local temperature drift at the LabOSat controller, with no
clear evidence that allows determining changes in the underlying microscopic
factors. These results show the reliability of complex-oxide non-volatile
ReRAM-based devices in order to operate under all the hostile conditions
encountered in space-borne applications.",2006.15062v1
2020-07-22,Machine Learning Potential for Hexagonal Boron Nitride Applied to Thermally and Mechanically Induced Rippling,"We introduce an interatomic potential for hexagonal boron nitride (hBN) based
on the Gaussian approximation potential (GAP) machine learning methodology. The
potential is based on a training set of configurations collected from density
functional theory (DFT) simulations and is capable of treating bulk and
multilayer hBN as well as nanotubes of arbitrary chirality. The developed force
field faithfully reproduces the potential energy surface predicted by DFT while
improving the efficiency by several orders of magnitude. We test our potential
by comparing formation energies, geometrical properties, phonon dispersion
spectra and mechanical properties with respect to benchmark DFT calculations
and experiments. In addition, we use our model and a recently developed
graphene-GAP to analyse and compare thermally and mechanically induced rippling
in large scale two-dimensional (2D) hBN and graphene. Both materials show
almost identical scaling behaviour with an exponent of $\eta \approx 0.85$ for
the height fluctuations agreeing well with the theory of flexible membranes.
Based on its lower resistance to bending, however, hBN experiences slightly
larger out-of-plane deviations both at zero and finite applied external strain.
Upon compression a phase transition from incoherent ripple motion to
soliton-ripples is observed for both materials. Our potential is freely
available online at [http://www.libatoms.org].",2007.11448v3
2020-07-24,"Determination of the spin Hall angle, spin mixing conductance and spin diffusion length in Ir/CoFeB for spin-orbitronic devices","Iridium is a very promising material for spintronic applications due to its
interesting magnetic properties such as large RKKY exchange coupling as well as
its large spin-orbit coupling value. Ir is for instance used as a spacer layer
for perpendicular synthetic antiferromagnetic or ferrimagnet systems. However,
only a few studies of the spintronic parameters of this material have been
reported. In this paper, we present inverse spin Hall effect - spin pumping
ferromagnetic resonance measurements on CoFeB/Ir based bilayers to estimate the
values of the effective spin Hall angle, the spin diffusion length within
iridium, and the spin mixing conductance in the CoFeB/Ir bilayer. In order to
have reliable results, we performed the same experiments on CoFeB/Pt bilayers,
which behavior is well known due to numerous reported studies. Our experimental
results show that the spin diffusion length within iridium is 1.3 nm for
resistivity of 250 n$\Omega$.m, the spin mixing conductance $g_{eff}^{\uparrow
\downarrow}$ of the CoFeB/Ir interface is 30 nm$^{-2}$, and the spin Hall angle
of iridium has the same sign than the one of platinum and is evaluated at 26%
of the one of platinum. The value of the spin Hall angle found is 7.7% for Pt
and 2% for Ir. These relevant parameters shall be useful to consider Ir in new
concepts and devices combining spin-orbit torque and spin-transfer torque.",2007.12413v1
2020-10-06,Conductance Model for Single-Crystalline/Compact Metal Oxide Gas Sensing Layers in the Non-Degenerate Limit: Example of Epitaxial SnO$_2$(101),"Semiconducting metal oxide (SMOX)-based gas sensors are indispensable for
safety and health applications, e.g. explosive, toxic gas alarms, controls for
intake into car cabins and monitor for industrial processes. In the past, the
sensor community has been studying polycrystalline materials as sensors where
the porous and random microstructure of the SMOX does not allow a separation of
the phenomena involved in the sensing process. This lead to conduction models
that can model and predict the behavior of the overall response, but they were
not capable of giving fundamental information regarding the basic mechanisms
taking place. The study of epitaxial layers is the definite prove to clarify
the different aspects and contributions of the sensing mechanisms that are not
possible to do by studying a polycrystalline sample. A detailed analytical
model for n and p-type single-crystalline/compact metal oxide gas sensors was
developed that directly relates the conductance of the sample with changes in
the surface electrostatic potential. Combined DC resistance and work function
measurements were used in a compact SnO2 (101) layer in operando conditions
that allowed us to check the validity of our model in the region where
Boltzmann approximation holds to determine surface and bulk properties of the
material.",2010.02962v1
2020-11-16,Ferroelectric tunnel junctions,"My research is dedicated to the electronic properties of functional oxides.
My activity specifically focuses on ferroelectric tunnel junctions in which an
ultrathin layer of ferroelectric material is intercalated between two metallic
electrodes. In these devices, polarization reversal induces large modifications
of the tunnel resistance, leading to a non-destructive readout of the
information. After a demonstration of the concept with scanning probe
microscopy techniques, I have been exploring the properties of ferroelectric
tunnel junctions with various ferroelectric materials (BaTiO3, BiFeO3, and
PVDF). I showed that these devices possess attractive properties for
applications as non-volatile binary memories. In addition, exploring the fact
that polarization usually reverses by the nucleation and propagation of
domains, I demonstrated a memristive behavior in the junctions associated to
non-uniform configurations of ferroelectric domains. Such ferroelectric
memristors can be used as artificial synapses in neuromorphic architectures.
Coupled to magnetic electrodes, the resulting multiferroic tunnel junctions
enable a non-volatile control of magnetism at the ferroelectric/electrode
interface and of the spin-polarized current associated. Besides this main
activity on tunnel devices, I explored the influence of ferroelectricity on
magnetic orders and on the properties of functional oxides.",2011.07864v1
2021-02-09,Quasi-quantized Hall response in bulk InAs,"The quasi-quantized Hall effect (QQHE) is the three-dimensional (3D)
counterpart of the integer quantum Hall effect (QHE),exhibited only by
two-dimensional (2D) electron systems. It has recently been observed in layered
materials, consisting of stacks of weakly coupled 2D platelets that are yet
characterized by a 3D anisotropic Fermi surface. However, it is predicted that
the quasi-quantized 3D version of the 2D QHE should occur in a much broader
class of bulk materials, regardless of the underlying crystal structure. Here,
we compare the observation of quasi-quantized plateau-like features in the Hall
conductivity of then-type bulk semiconductor InAs with the predictions for the
3D QQHE in presence of parabolic electron bands. InAs takes form of a cubic
crystal without any low-dimensional substructure. The onset of the plateau-like
feature in the Hall conductivity scales with $\sqrt{2/3}k_{F}^{z}/\pi$ in units
of the conductance quantum and is accompanied by a Shubnikov-de Haas minimum in
the longitudinal resistivity, consistent wit the results of calculations. This
confirms the suggestion that the 3D QQHE may be a generic effect directly
observable in materials with small Fermi surfaces, placed in sufficiently
strong magnetic fields",2102.04928v3
2021-03-18,Giant spin Hall angle in the Heusler alloy Weyl ferromagnet Co$_2$MnGa,"Weyl semimetals are playing a major role in condensed matter physics due to
exotic topological properties, and their coexistence with ferromagnetism may
lead to enhanced spin-related phenomena. Here, the inverse spin Hall effect
(ISHE) in the ferromagnetic Weyl-semimetal Heusler alloy Co$_2$MnGa was
investigated at room temperature by means of electrical spin injection in
lateral spin valve structures. Spin transport properties such as spin
polarization and spin diffusion length in this material were precisely
extracted in order to estimate the spin Hall angle $\theta_{\textrm{SH}}$,
which was found to be $-0.19\pm0.04$ and is among the highest reported for a
ferromagnet. Although this value is on the same order of magnitude of known
heavy metals, the significantly higher resistivity of Co$_2$MnGa implies an
improvement on the magnitude of detection voltages, while its ferromagnetic
nature allows controlling the intensity of SHE through the magnetization
direction. It was also shown that Onsager's reciprocity does not hold for this
system, which is in part attributable to a different spin-dependent Hall
conductivity for spin-up and spin-down carriers.",2103.10188v1
2021-04-06,Relationship between the TC of smart meta-superconductor Bi(Pb)SrCaCuO and inhomogeneous phase content,"A smart meta-superconductor Bi(Pb)SrCaCuO (B(P)SCCO) may increase the
critical transition temperature (TC) of B(P)SCCO by electroluminescence (EL)
energy injection of inhomogeneous phases. However, the increase amplitude
{\Delta}TC ({\Delta}TC=TC-T(C,pure)) of TC is relatively small. In this study,
a smart meta-superconductor B(P)SCCO with different matrix sizes was designed.
Three kinds of raw materials with different particle sizes were used, and
different series of Y2O3:Sm3+, Y2O3, Y2O3:Eu3+, and Y2O3:Eu3++Ag doped samples
and pure B(P)SCCO were prepared. Results indicated that the TC of the Y2O3 or
Y2O3:Sm3+ non-luminescent dopant doping sample is lower than that of pure
B(P)SCCO. However, the TC of the Y2O3:Eu3++Ag or Y2O3:Eu3+ luminescent
inhomogeneous phase doping sample is higher than that of pure B(P)SCCO. With
the decrease of the raw material particle size from 30 to 5 {\mu}m, the
particle size of the B(P)SCCO superconducting matrix in the prepared samples
decreases, and the doping content of the Y2O3:Eu3++Ag or Y2O3:Eu3+ increases
from 0.2% to 0.4%. Meanwhile, the increase of the inhomogeneous phase content
enhances the {\Delta}TC. When the particle size of raw material is 5 {\mu}m,
the doping concentration of the luminescent inhomogeneous phase can be
increased to 0.4%. At this time, the zero-resistance temperature and onset
transition temperature of the Y2O3:Eu3++Ag doped sample are 4 and 6.3 K higher
than those of pure B(P)SCCO, respectively.",2104.02229v1
2021-05-12,Superconducting diode effect via conformal-mapped nanoholes,"A superconducting diode is an electronic device that conducts supercurrent
and exhibits zero resistance primarily for one direction of applied current.
Such a dissipationless diode is a desirable unit for constructing electronic
circuits with ultralow power consumption. However, realizing a superconducting
diode is fundamentally and technologically challenging, as it usually requires
a material structure without a centre of inversion, which is scarce among
superconducting materials. Here, we demonstrate a superconducting diode
achieved in a conventional superconducting film patterned with a conformal
array of nanoscale holes, which breaks the spatial inversion symmetry. We
showcase the superconducting diode effect through switchable and reversible
rectification signals, which can be three orders of magnitude larger than that
from a flux-quantum diode. The introduction of conformal potential landscapes
for creating a superconducting diode is thereby proven as a convenient,
tunable, yet vastly advantageous tool for superconducting electronics. This
could be readily applicable to any superconducting materials, including
cuprates and iron-based superconductors that have higher transition
temperatures and are desirable in device applications.",2105.05456v1
2021-07-01,Dopant-segregation to grain boundaries controls electrical conductivity of n-type NbCo(Pt)Sn half-Heusler alloy mediating thermoelectric performance,"Science-driven design of future thermoelectric materials requires a deep
understanding of the fundamental relationships between microstructure and
transport properties. Grain boundaries in polycrystalline materials influence
the thermoelectric performance through the scattering of phonons or the
trapping of electrons due to space-charge effects. Yet, the current lack of
careful investigations on grain boundary-associated features hinders further
optimization of properties. Here, we study n-type NbCo1-xPtxSn half-Heusler
alloys, which were synthesized by ball milling and spark plasma sintering
(SPS). Post-SPS annealing was performed on one sample, leading to improved
low-temperature electrical conductivity. The microstructure of both samples was
examined by electron microscopy and atom probe tomography. The grain size
increases from ~230 nm to ~2.38 {\mu}m upon annealing. Pt is found within
grains and at grain boundaries, where it locally reduces the resistivity, as
assessed by in situ four-point-probe electrical conductivity measurement. Our
work showcases the correlation between microstructure and electrical
conductivity, providing opportunities for future microstructural optimization
by tuning the chemical composition at grain boundaries.",2107.00326v1
2021-07-10,Effect of characteristic size on the collective phonon transport in crystalline GeTe,"We study the effect of characteristic size variation on the phonon thermal
transport in crystalline GeTe for a wide range of temperatures using the
first-principles density-functional method coupled with the kinetic collective
model approach. The characteristic size dependence of phonon thermal transport
reveals an intriguing collective phonon transport regime, located in between
the ballistic and the diffusive transport regimes. Therefore, systematic
investigations have been carried out to describe the signatures of phonon
hydrodynamics via the competitive effects between grain size and temperature. A
characteristic nonlocal length associated with phonon hydrodynamics and a heat
wave propagation length has been extracted. The connections between phonon
hydrodynamics and these length scales are discussed in terms of the Knudsen
number. Further, the scaling relation of thermal conductivity as a function of
characteristic size in the intermediate size range emerges as a crucial
indicator of the strength of the hydrodynamic behavior. A ratio concerning
normal and resistive scattering rates has been employed to understand these
different scaling relations, which seems to control the strength and prominent
visibility of the collective phonon transport in GeTe. This systematic
investigation emphasizes the importance of the competitive effects between
temperature and characteristic size on phonon hydrodynamics in GeTe, which can
lead to a better understanding of the generic behavior and consequences of the
phonon hydrodynamics and its controlling parameters in low-thermal conductivity
materials.",2107.04731v1
2021-07-23,Few-layer antimonene electrical properties,"Antimonene -- a single layer of antimony atoms -- and its few layer forms are
among the latest additions to the 2D mono-elemental materials family. Numerous
predictions and experimental evidence of its remarkable properties including
(opto)electronic, energetic or biomedical, among others, together with its
robustness under ambient conditions, have attracted the attention of the
scientific community. However, experimental evidence of its electrical
properties is still lacking. Here, we characterized the electronic properties
of mechanically exfoliated flakes of few-layer (FL) antimonene of different
thicknesses (~ 2-40 nm) through photoemission electron microscopy, kelvin probe
force microscopy and transport measurements, which allows us to estimate a
sheet resistance of ~ 1200 $\Omega$sq$^{-1}$ and a mobility of ~ 150
cm$^2$V$^{-1}$s$^{-1}$ in ambient conditions, independent of the flake
thickness. Alternatively, our theoretical calculations indicate that
topologically protected surface states (TPSS) should play a key role in the
electronic properties of FL antimonene, which supports our experimental
findings. We anticipate our work will trigger further experimental studies on
TPSS in FL antimonene thanks to its simple structure and significant stability
in ambient environments.",2107.11218v1
2021-07-26,Pressure-driven electronic and structural phase transition in intrinsic magnetic topological insulator MnSb2Te4,"Intrinsic magnetic topological insulators provide an ideal platform to
achieve various exciting physical phenomena. However, this kind of materials
and related research are still very rare. In this work, we reported the
electronic and structural phase transitions in intrinsic magnetic topological
insulator MnSb2Te4 driven by hydrostatic pressure. Electric transport results
revealed that temperature dependent resistance showed a minimum value near
short-range antiferromagnetic (AFM) ordering temperature TN', the TN' values
decline with pressure, and the AFM ordering was strongly suppressed near 10 GPa
and was not visible above 11.5 GPa. The intensity of three Raman vibration
modes in MnSb2Te4 declined quickly starting from 7.5 GPa and these modes become
undetectable above 9 GPa, suggesting possible insulator-metal transition, which
is further confirmed by theoretical calculation. In situ x-ray diffraction
(XRD) demonstrated that an extra diffraction peak appears near 9.1 GPa and
MnSb2Te4 started to enter an amorphous-like state above 16.6 GPa, suggesting
the structural origin of suppressed AFM ordering and metallization. This work
has demonstrated the correlation among interlayer interaction, magnetic
ordering, and electric behavior, which could be benefit for the understanding
of the fundamental properties of this kind of materials and devices.",2107.12071v1
2021-07-26,Nitrogen-doped graphene based triboelectric nanogenerators,"Harvesting all sources of available clean energy is an essential strategy to
contribute to healing current dependence on non-sustainable energy sources.
Recently, triboelectric nanogenerators (TENGs) have gained visibility as new
mechanical energy harvester offering a valid alternative to batteries, being
particularly suitable for portable devices. Here, the increased capacitance of
a few-layer graphene-based electrode is obtained by incorporating
nitrogen-doped graphene (N_graphene), enabling a 3_fold enhancement in TENGs
power output. The dependence of TENGs performance on the electronic properties
of different N_graphene types, varying in the doping concentration and in the
relative content of N-pyridinic and N-graphitic sites is investigated. These
sites have different electron affinities, and synergistically contribute to the
variation of the capacitive and resistive properties of N-graphene and
consequently, TENG performance. It is demonstrated that the power enhancement
of the TENG occurs when the N_graphene, an n-semiconductor, is interfaced
between the positive triboelectric material and the electrode, while a
deterioration of the electrical performance is observed when it is placed at
the interface with the negative triboelectric material. This behavior is
explained in terms of the dependence of N_graphene quantum capacitance on the
electrode chemical potential which shifts according to the opposite
polarization induced at the two electrodes upon triboelectrification.",2107.12114v1
2021-09-19,"Float, borosilicate and tellurites as cover glasses in Si photovoltaics: optical properties and performances under sunlight","One of the most significant materials in a solar panel is the glass, which
provides transparency, UV protection as well as mechanical and chemical
resistance. In this work, we describe the production of prototypes of four
solar modules made using borosilicate, zinc-tellurite, Pr$^{3+}$ doped
zinc-tellurite, and float glass as cover materials. The performance of these
prototypes was evaluated under a solar simulator, and a device was developed to
monitor all prototypes under real conditions. A comparison between indoor and
outdoor measurements shows that outdoor results are fundamental to evaluate the
performance of modified solar modules as the ones considered in this study. In
addition, we demonstrate the fundamental role played by the refractive index of
cover glasses in the performance of the prototypes, and discuss how this
feature could be explored to achieve enhanced devices, as well as other
benefits that may arise from this field of research.",2109.09116v3
2021-09-29,"Mechanical Properties and Nanostructure of Monolithic Zeolitic Imidazolate Frameworks: A Nanoindentation, Nanospectroscopy and Finite-Element Study","The synthesis of metal-organic frameworks (MOFs) in a monolithic morphology
is a promising way to achieve the transition of this class of materials from
academia to industrial applications. The sol-gel process has been widely
employed to produce MOF monoliths. It is relatively cheap and simple compared
to other techniques (e.g., mechanical densification) and moreover it allows to
produce ""pure"" monoliths, i.e., without the need of using binders or templates
that could affect the functional properties of the MOF. Understanding the
mechanical properties of these monoliths is crucial for their transit to
practical applications. We studied the mechanical behavior of two zeolitic
imidazolate frameworks (ZIF-8 and ZIF-71) by means of instrumented
nanoindentation and atomic force microscopy (AFM). Tip Force Microscopy (TFM),
an extension of AFM, was used to reveal the surface nanostructure of the
monoliths. We employed finite-element (FE) simulations alongside the
experiments, to establish a suitable constitutive model and determine an
improved estimate of the yield stress of ZIF monoliths. NanoFTIR was
subsequently used to pinpoint local structural alteration of the framework in
the contact area. The combination of TFM, FE simulations, and nanoFTIR enabled
us to identify the mechanical deformation mechanisms in monolithic ZIF
materials: grain boundaries sliding is dominating at low stresses, then
breakage of chemical bonds and a partial failure of the framework occurs,
eventually leading to a densification of porous framework at the contact zone.
Finally, we measured the fracture toughness using a cube corner indenter to
study the resistance of monoliths against cracking failure.",2109.14670v1
2021-09-30,Electronic and Thermal Properties of $\text{GeTe/Sb}_{2}\text{Te}_{3}$ Superlattices by ab-initio Approach: Impact of Van der Waals Gaps on Vertical Lattice Thermal Conductivity,"In the last decade, several works have focused on exploring the material and
electrical properties of $\text{GeTe/Sb}_{2}\text{Te}_{3}$ superlattices (SLs)
in particular because of some first device implementations demonstrating
interesting performances such as fast switching speed, low energy consumption,
and non-volatility. However, the switching mechanism in such SL-based devices
remains under debate. In this work, we investigate the prototype
$\text{GeTe/Sb}_{2}\text{Te}_{3}$ SLs, to analyze fundamentally their
electronic and thermal properties by ab initio methods. We find that the
resistive contrast is small among the different phases of
$\text{GeTe/Sb}_{2}\text{Te}_{3}$ because of a small electronic gap (about 0.1
eV) and a consequent semi-metallic-like behavior. At the same time the
out-of-plane lattice thermal conductivity is rather small, while varying up to
four times among the different phases, from 0.11 to 0.45 W/m$^{-1}$K$^{-1}$,
intimately related to the number of Van der Waals (VdW) gaps in a unit block.
Such findings confirm the importance of the thermal improvement achievable in
$\text{GeTe/Sb}_{2}\text{Te}_{3}$ super-lattices devices, highlighting the
impact of the material stacking and the role of VdW gaps on the thermal
engineering of the Phase-Change Memory cell.",2109.15168v2
2021-10-01,A general isogeometric finite element formulation for rotation-free shells with in-plane bending of embedded fibers,"This paper presents a general, nonlinear isogeometric finite element
formulation for rotation-free shells with embedded fibers that captures
anisotropy in stretching, shearing, twisting and bending -- both in-plane and
out-of-plane. These capabilities allow for the simulation of large sheets of
heterogeneous and fibrous materials either with or without matrix, such as
textiles, composites, and pantographic structures. The work is a computational
extension of our earlier theoretical work [1] that extends existing
Kirchhoff-Love shell theory to incorporate the in-plane bending resistance of
initially straight or curved fibers. The formulation requires only displacement
degrees-of-freedom to capture all mentioned modes of deformation. To this end,
isogeometric shape functions are used in order to satisfy the required
$C^1$-continuity for bending across element boundaries. The proposed
formulation can admit a wide range of material models, such as surface
hyperelasticity that does not require any explicit thickness integration. To
deal with possible material instability due to fiber compression, a
stabilization scheme is added. Several benchmark examples are used to
demonstrate the robustness and accuracy of the proposed computational
formulation.",2110.00460v3
2021-10-15,Ground state of Ce$_{3}$Bi$_{4}$Pd$_{3}$ unraveled by hydrostatic pressure,"Noncentrosymmetric Ce$_{3}$Bi$_{4}$Pd$_{3}$ has attracted a lot of attention
as a candidate for strongly correlated topological material, yet its
experimental ground state remains a matter of contention. Two conflicting
scenarios have emerged from a comparison to prototypical Kondo insulator
Ce$_{3}$Bi$_{4}$Pt$_{3}$: either Ce$_{3}$Bi$_{4}$Pd$_{3}$ is a
spin-orbit-driven topological semimetal or a Kondo insulator with smaller Kondo
coupling than its Pt counterpart. Here we determine the ground state of
Ce$_{3}$Bi$_{4}$Pd$_{3}$ via electrical resistivity measurements under
hydrostatic pressure, which is a clean symmetry-preserving tuning parameter
that increases hybridization but virtually preserves spin-orbit coupling.
Ce$_{3}$Bi$_{4}$Pd$_{3}$ becomes more insulating under pressure, which is a
signature of Ce-based Kondo insulating materials. Its small zero-pressure gap
increases quadratically with pressure, similar to the behavior observed in the
series Ce$_{3}$Bi$_{4}$(Pt$_{1-x}$Pd$_{x}$)$_{3}$, which indicates that Pt
substitution and applied pressure have a similar effect. Our result not only
demonstrates that Kondo coupling, rather than spin-orbit coupling, is the main
tuning parameter in this class of materials, but it also establishes that
Ce$_{3}$Bi$_{4}$Pd$_{3}$ has a narrow-gap Kondo insulating ground state.",2110.08230v1
2021-11-16,Interpreting Angle Dependent Magnetoresistance in Layered Materials: Application to Cuprates,"The evolution of the low temperature electronic structure of the cuprate
metals from the overdoped to the underdoped side has recently been addressed
through Angle-Dependant Magneto-Resistance (ADMR) experiments in
La$_{1.6-x}$Nd$_{0.4}$Sr$_x$CuO$_4$. The results show a striking difference
between hole dopings $p = 0.24$ and $p = 0.21$ which lie on either side of a
putative quantum critical point at intermediate $p$. Motivated by this, we here
study the theory of ADMR in correlated layered materials, paying special
attention to the role of angle dependent quasiparticle weights
$Z_{\mathbf{k}}$. Such a $Z_{\mathbf{k}}$ is expected to characterize a number
of popular models of the cuprate materials, particularly when underdoped.
Further, in the limit of weak interlayer hopping the quasiparticle weight will
affect the $c$-axis transport measured in ADMR experiments. We show that proper
inclusion of the quasiparticle weight does not support an interpretation of the
data in terms of a $(\pi, \pi)$ spin density wave ordered state, in agreement
with the lack of direct evidence for such order. We show that a simple model of
Fermi surface reconfiguring across a van Hove point captures many of the
striking differences seen between $p = 0.21$ and $p = 0.24$. We comment on why
such a model may be appropriate for interpreting the ADMR data, despite having
a large Fermi surface at $p = 0.21$, seemingly in contradiction with other
evidence for a small Fermi surafce at that doping level.",2111.08740v2
2022-01-06,Optical properties of Au-Hf thin films,"The optical properties of thin films of intermetallic Au$_{3}$Hf were
experimentally investigated for the first time, which display clear plasmonic
properties in the optical and near infrared region with negative permittivity.
In contrast to similar alloys, such as films of Au$_{3}$Zr, the films express
more negative $\epsilon'$ values and lower $\epsilon''$ values across most of
the wavelengths (370-1570 nm) investigated. The Au$_{3}$Hf films were
fabricated by DC magnetron sputtering at a range of deposition temperatures,
from room temperature to 415$^{o}$C, and annealed at different vacuum levels.
The films mostly formed as a combination of Au$_{3}$Hf, Au$_{2}$Hf and
Au$_{4}$Hf phases when deposited below 400$^{o}$C, and exclusively Au$_{3}$Hf
phase at above 400$^{o}$C, indicating key conditions for isolating this phase.
The films were stable when annealed at 10$^{-8}$ Torr, but when annealed again
at 10$^{-6}$ Torr the films oxidised and changed into a mix of Au- Hf phases,
suggesting resistance to oxidization may be an issue for un-encapsulated
applications at elevated temperatures.",2201.02163v1
2022-03-31,Thermally enhanced photoluminescence and temperature sensing properties of Sc$_2$W$_3$O$_{12}$:Eu$^{3+}$ phosphors,"Currently,lanthanide ions doped luminescence materials applying as optical
thermometers have arose much concern. Basing on the different responses of two
emissions to temperature, the fluorescence intensity ratio (FIR) technique can
be executed and further estimate the sensitivities to assess the optical
thermometry performances. In this study, we introduce different doping
concentrations of Eu$^{3+}$ ions into negative expansion material
Sc$_2$W$_3$O$_{12}$:Eu$^{3+}$, accessing to the thermal enhanced luminescence
from 373 to 548 K, and investigate the temperature sensing properties in
detail. All samples exhibit good thermally enhanced luminescence behavior. The
emission intensity of Sc$_2$W$_3$O$_{12}$: 6 mol% Eu$^{3+}$ phosphors reaches
at 147.81% of initial intensity at 473 K. As the Eu doping concentration
increases, the resistance of the samples to thermal quenching decreases. The
FIR technique based on the transitions 5D0-7F1 (592 nm) and 5D0-7F2 (613 nm) of
Eu$^{3+}$ ions demonstrate a maximum relative temperature sensitivity of 3.063%
K-1 at 298 K for Sc$_2$W$_3$O$_{12}$:Eu$^{3+}$: 6 mol% Eu$^{3+}$ phosphors. The
sensitivity of sample decreases with the increase of Eu$^{3+}$ concentration.
Benefiting from the thermal enhanced luminescence performance and good
temperature sensing properties, the Sc$_2$W$_3$O$_{12}$:Eu$^{3+}$: Eu$^{3+}$
phosphors can be applies as optical thermometers.",2203.16888v1
2022-04-19,Cell barrier characterization in transwell inserts by electrical impedance spectroscopy,"We describe an impedance-based method for cell barrier integrity testing. A
four-electrode electrical impedance spectroscopy (EIS) setup can be realized by
simply connecting a commercial chopstick-like electrode (STX-1) to a
potentiostat allowing monitoring cell barriers cultivated in transwell inserts.
Subsequent electric circuit modeling of the electrical impedance results the
capacitive properties of the barrier next to the well-known transepithelial
electrical resistance (TEER). The versatility of the new method was analyzed by
the EIS analysis of a Caco-2 monolayer in response to (a) different membrane
coating materials, (b) two different permeability enhancers ethylene
glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) and saponin,
and (c) sonoporation. For the different membrane coating materials, the TEERs
of the standard and new protocol coincide and increase during cultivation,
while the capacitance shows a distinct maximum for three different surface
materials (no coating, Matrigel, and collagen I). The permeability enhancers
cause a decline in the TEER value, but only saponin alters the capacitance of
the cell layer by two orders of magnitude. Hence, cell layer capacitance and
TEER represent two independent properties characterizing the monolayer. The use
of commercial chopstick-like electrodes to access the impedance of a barrier
cultivated in transwell inserts enables remarkable insight into the behavior of
the cellular barrier with no extra work for the researcher. This simple method
could evolve into a standard protocol used in cell barrier research.",2204.08886v1
2022-04-25,Substrate-Dependence of Monolayer MoS$_2$ Thermal Conductivity and Thermal Boundary Conductance,"The thermal properties of two-dimensional (2D) materials, like MoS$_2$, are
known to be affected by interactions with their environment, but this has
primarily been studied only with SiO$_2$ substrates. Here, we compare the
thermal conductivity (TC) and thermal boundary conductance (TBC) of monolayer
MoS$_2$ on amorphous (a-) and crystalline (c-) SiO$_2$, AlN, Al$_2$O$_3$, and
$\textit{h}$-BN monolayers using molecular dynamics. The room temperature TC of
MoS$_2$ is ~38 Wm$^{-1}$K$^{-1}$ on amorphous substrates and up to ~68
Wm$^{-1}$K$^{-1}$ on crystalline substrates, with most of the difference due to
substrate interactions with long-wavelength MoS$_2$ phonons (< 2 THz). An
$\textit{h}$-BN monolayer used as a buffer between MoS$_2$ and the substrate
causes the MoS$_2$ TC to increase by up to 50%. Length-dependent calculations
reveal TC size effects below ~2 $\mu$m and show that the MoS$_2$ TC is size-
but not substrate-limited below ~100 nm. We also find that the TBC of MoS$_2$
with c-Al$_2$O$_3$ is over twice that with c-AlN despite a similar MoS$_2$ TC
on both, indicating that the TC and TBC could be tuned independently. Finally,
we compare the thermal resistance of MoS$_2$ transistors on all substrates to
show that MoS$_2$ TBC is the most important parameter for heat removal for
long-channel (> 150 nm) devices, while TBC and TC are equally important for
short channels. This work provides important insights for electro-thermal
applications of 2D materials on various substrates.",2204.11381v1
2022-05-23,Spatial stress correlations in strong colloidal gel,"In this work, we systematically investigate for the first time the nature of
stress correlations in soft colloidal gel materials which support tensile and
compressive forces as well as finite rolling torque, as a function of system
pressure. Similar to previous studies on frictional granular matter with only
compressive forces and without any rolling torque, the full stress
autocorrelation matrix is dictated by the pressure and torque autocorrelations
due to mechanical balance and material isotropy constraints. Surprisingly, it
is observed that the gel materials do not behave as a normal elastic solid
close to the gel point as assumed loosely in the literature because the real
space pressure fluctuations decay slower than the normal. We also demonstrate
that at low pressure the fractal like structural correlation determines the
pressure fluctuations and this is manifested in the real space in terms of
inhomogeneous and anisotropic force networks formed due to large voids. Far
away from the gel point, as the voids collapse under compression, the force
chain network becomes homogeneous and isotropic and the pressure fluctuations
become normal leading to normal elastic decay at long range, behaving similar
to frictionless granular matter and glass. We also observe that the torque
autocorrelation is not hyperuniform in the presence of rolling resistance close
to the gel point. Furthermore, we link the abnormal pressure fluctuations to
the non-hyperuniform behaviour of the system with respect to the local packing
fraction fluctuations, thus relating the deviations from the normal elastic
behaviour across various non-equilibrium systems under a common framework.",2205.11575v1
2022-07-06,Elastoresistivity in the incommensurate charge density wave phase of BaNi$_{\textrm{2}}$(As$_{\textrm{1-x}}$P$_{\textrm{x}}$)$_{\textrm{2}}$,"Electronic nematicity, the breaking of the crystal lattice rotational
symmetry by the electronic fluid, is a fascinating quantum state of matter.
Recently, BaNi$_2$As$_2$ has emerged as a promising candidate for a novel type
of nematicity triggered by charge fluctuations. In this work, we scrutinize the
electronic nematicity of BaNi$_2$(As$_{1-x}$P$_x$)$_2$ with $0 \leq x \leq
0.10$ using electronic transport measurements under strain. We report a large
$B_{1g}$ elastoresistance coefficient that is maximized at a temperature
slightly higher than the first-order triclinic transition, and that corresponds
to the recently discovered tetragonal-to-orthorhombic transition. The reported
elastoresistance does not follow the typical Curie-Weiss form observed in
iron-based superconductors but has a much sharper temperature dependence with a
finite elastoresistance onsetting only together with a strong enhancement of
the incommensurate charge density wave of the material. Consequently, the
$B_{1g}$ elastoresistance and the associated orthorhombic distortion appears
here as a property of this incommensurate charge density wave. Finally, we
report and track the hysteretic behavior seen in the resistance versus strain
sweeps and interpret its origin as the pinning of orthorhombic domains. Our
results revise the understanding of the interplay between nematicity, charge
density waves and structural distortions in this material.",2207.02462v2
2022-07-13,Multi-state data storage in a two-dimensional stripy antiferromagnet implemented by magnetoelectric effect,"A promising approach to the next generation of low-power, functional, and
energy-efficient electronics relies on novel materials with coupled magnetic
and electric degrees of freedom. In particular, stripy antiferromagnets often
exhibit broken crystal and magnetic symmetries, which may bring about the
magnetoelectric (ME) effect and enable the manipulation of intriguing
properties and functionalities by electrical means. The demand for expanding
the boundaries of data storage and processing technologies has led to the
development of spintronics toward two-dimensional (2D) platforms. This work
reports the ME effect in the 2D stripy antiferromagnetic insulator CrOCl down
to a single layer. By measuring the tunneling resistance of CrOCl on the
parameter space of temperature, magnetic field, and applied voltage, we
verified the ME coupling down to the 2D limit and unraveled its mechanism.
Utilizing the multi-stable states and ME coupling at magnetic phase
transitions, we realize multi-state data storage in the tunneling devices. Our
work not only advances the fundamental understanding of spin-charge coupling
but also demonstrates the great potential of 2D antiferromagnetic materials to
deliver devices and circuits beyond the traditional binary operations.",2207.05954v1
2022-08-09,Discovery of Superconductivity in Nb$_4$SiSb$_2$ with a V$_4$SiSb$_2$-Type Structure and Implications of Interstitial Doping on its Physical Properties,"We report on the discovery, structural analysis, and the physical properties
of Nb$_4$SiSb$_2$ -- a hitherto unknown compound crystallizing in the
V$_4$SiSb$_2$-type structure with the tetragonal space group $I4/mcm$ and unit
cell parameters $a$ = 10.3638(2) $\mathring{\mathrm{A}}$ and $c$ = 4.9151(2)
$\mathring{\mathrm{A}}$. We find Nb$_4$SiSb$_2$ to be a metal undergoing a
transition to a superconducting state at a critical temperature of $T_{\rm c}
\approx$ 1.6 K. The bulk nature of the superconductivity in this material is
confirmed by the observation of a well defined discontinuity in specific heat
with a normalized specific heat jump of $\Delta C(T_{\rm c})/\gamma T_{\rm c} =
1.33\, {\rm mJ}\, {\rm mol}^{-1}\, {\rm K}^{-2}$. We find that for
Nb$_4$SiSb$_2$, the unoccupied sites on the $4b$ Wyckoff position can be
partially occupied with Cu, Pd, or Pt. Low-temperature resistivity measurements
show transitions to superconductivity for all three compounds at $T_{\rm c}
\approx\, 1.2\, {\rm K}$ for Nb$_4$Cu$_{0.2}$SiSb$_2$, and $T_{\rm c} \approx\,
0.8\, {\rm K}$ for Nb$_4$Pd$_{0.2}$SiSb$_2$ as well as for
Nb$_4$Pt$_{0.14}$SiSb$_2$. The addition of electron-donor atoms into these void
positions, henceforth, lowers the superconducting transition temperature in
comparison to the parent compound.",2208.04834v1
2022-09-07,Ultrahigh breakdown current density of van der Waals One Dimensional $\mathrm{PdBr_2}$,"One-dimensional (1D) van der Waals (vdW) materials offer nearly defect-free
strands as channel material in the field-effect transistor (FET) devices and
probably, a better interconnect than conventional copper with higher current
density and resistance to electro-migration with sustainable down-scaling. We
report a new halide based ""truly"" 1D few-chain atomic thread, PdBr$_2$,
isolable from its bulk which crystallizes in a monoclinic space group C2/c.
Liquid phase exfoliated nanowires with mean length (20$\pm$1)$\mu$m transferred
onto SiO$_2$/Si wafer with a maximum aspect ratio of 5000 confirms the lower
cleavage energy perpendicular to chain direction. Moreover, an isolated
nanowire can also sustain current density of 200 MA/cm$^\mathrm{2}$ which is
atleast one-order higher than typical copper interconnects. However, local
transport measurement via conducting atomic force microscopy (CAFM) tip along
the cross direction of the single chain records a much lower current density
due to the anisotropic electronic band structure. While 1D nature of the
nanoobject can be linked with non-trivial collective quantum behavior, vdW
nature could be beneficial for the new pathways in interconnect fabrication
strategy with better control of placement in an integrated circuit (IC).",2209.03296v6
2023-01-27,A ferromagnetic Eu-Pt surface compound grown below hexagonal boron nitride,"One of the fundamental applications for monolayer-thick 2D materials is their
use as protective layers of metal surfaces and in-situ intercalated reactive
materials in ambient conditions. Here we investigate the structural,
electronic, and magnetic properties, as well as the chemical stability in air
of a very reactive metal, Europium, after intercalation between a hexagonal
boron nitride (hBN) layer and a Pt substrate. We demonstrate that Eu
intercalation leads to a hBN-covered ferromagnetic EuPt$_2$ surface alloy with
divalent Eu$^{2+}$ atoms at the interface. We expose the system to ambient
conditions and find a partial conservation of the di-valent signal and hence
the Eu-Pt interface. The use of a curved Pt substrate allows us to explore the
changes in the Eu valence state and the ambient pressure protection at
different substrate planes. The interfacial EuPt$_2$ surface alloy formation
remains the same, but the resistance of the protecting hBN layer to ambient
conditions is reduced, likely due to a rougher surface and a more discontinuous
hBN coating.",2301.11837v2
2023-01-31,Elastic solids with strain-gradient elastic boundary surfaces,"Recent works have shown that in contrast to classical linear elastic fracture
mechanics, endowing crack fronts in a brittle solid with Steigmann-Ogden
surface elasticity yields a model that predicts bounded strains at the crack
tips for plane-strain problems. However, a logarithmic singularity is still
present in general for anti-plane shear (mode-III fracture) even when
Steigmann-Ogden surface elasticity is incorporated. Motivated by obtaining a
model of brittle fracture capable of predicting bounded strains for all modes
of loading, we formulate an exact general theory of a bulk solid containing a
boundary surface with strain-gradient surface elasticity. For planar reference
surfaces, the form of surface elasticity reduces to that introduced by Hilgers
and Pipkin, and when the surface energy is independent of the surface gradient
of the stretching, the theory reduces to that of Steigmann and Ogden. We give a
full discussion of material symmetry using Murdoch and Cohen's extension of
Noll's theory. We present a model quadratic surface energy that incorporates
resistance to geodesic distortion, satisfies strong ellipticity, and requires
the same material constants found in the Steigmann-Ogden theory. Finally, we
derive and apply the linearized theory to mode-III fracture in an infinite
plate. We prove that there always exists a unique classical solution to the
governing integro-differential equation, and in contrast to using
Steigmann-Ogden surface elasticity, our model is consistent with the
linearization assumption in predicting finite strains at the crack tips.",2301.13744v2
2023-02-10,Cryogenic Characteristics of Graphene Composites -- Evolution from Thermal Conductors to Thermal Insulators,"The development of cryogenic semiconductor electronics and superconducting
quantum computing requires composite materials that can provide both thermal
conduction and thermal insulation. We demonstrated that at cryogenic
temperatures, the thermal conductivity of graphene composites can be both
higher and lower than that of the reference pristine epoxy, depending on the
graphene filler loading and temperature. There exists a well-defined cross-over
temperature - above it, the thermal conductivity of composites increases with
the addition of graphene; below it, the thermal conductivity decreases with the
addition of graphene. The counter-intuitive trend was explained by the
specificity of heat conduction at low temperatures: graphene fillers can serve
as, both, the scattering centers for phonons in the matrix material and as the
conduits of heat. We offer a physical model that explains the experimental
trends by the increasing effect of the thermal boundary resistance at cryogenic
temperatures and the anomalous thermal percolation threshold, which becomes
temperature dependent. The obtained results suggest the possibility of using
graphene composites for, both, removing the heat and thermally insulating
components at cryogenic temperatures - a capability important for quantum
computing and cryogenically cooled conventional electronics.",2302.05524v1
2023-02-23,The influence of crystalline electric field on the magnetic properties of CeCd3X3 (X = P and As),"CeCd$_3$P$_3$ and CeCd$_3$As$_3$ compounds adopt the hexagonal
ScAl$_3$C$_3$-type structure, where magnetic Ce ions on a triangular lattice
order antiferromagnetically below $T_\text{N} \sim$0.42~K. Their crystalline
electric field (CEF) level scheme has been determined by fitting magnetic
susceptibility curves, magnetization isotherms, and Schottky anomalies in
specific heat. The calculated results, incorporating the CEF excitation, Zeeman
splitting, and molecular field, are in good agreement with the experimental
data. The CEF model, with Ce$^{3+}$ ions in a trigonal symmetry, explains the
strong easy-plane magnetic anisotropy that has been observed in this family of
materials. A detailed examination of the CEF parameters suggests that the
fourth order CEF parameter $B_{4}^{3}$ is responsible for the strong CEF
induced magnetocrystalline anisotropy, with a large $ab$-plane moment and a
small $c$-axis moment. The reliability of our CEF analysis is assessed by
comparing the current study with earlier reports of CeCd$_{3}$As$_{3}$. For
both CeCd$_{3}X_{3}$ ($X$ = P and As) compounds, less than 40 \% of $R\ln(2)$
magnetic entropy is recovered by $T_\text{N}$ and full $R\ln(2)$ entropy is
achieved at the Weiss temperature $\theta_{p}$. Although the observed magnetic
entropy is reminiscent of delocalized 4$f$-electron magnetism with significant
Kondo screening, the electrical resistivity of these compounds follows a
typical metallic behavior. Measurements of thermoelectric power further
validate the absence of Kondo contribution in CeCd$_{3}X_{3}$.",2302.11714v1
2023-03-08,Spin-valve nature and giant coercivity of a ferrimagnetic spin semimetal Mn$_2$IrGa,"Spin semimetals are amongst the most recently discovered new class of
spintronic materials, which exhibit a band gap in one spin channel and
semimetallic feature in the other, thus facilitating tunable spin transport.
Here, we report Mn$_2$IrGa to be a candidate material for spin semimetal along
with giant coercivity and spin-valve characteristics using a combined
experimental and theoretical study. The alloy crystallizes in an inverse
Heusler structure (without any martensitic transition) with a para- to
ferri-magnetic transition at $T_\mathrm{C} \sim$ 243 K. It shows a giant
coercive field of about 8.5 kOe (at 2 K). The negative temperature coefficient,
relatively low magnitude and weak temperture dependance of electrical
resistivity suggest the semimetallic character of the alloy. This is further
supported by our specific heat measurement. Magnetoresistance (MR) confirms an
irreversible nature (with its magnitude $\sim$1\%) along with a change of sign
across the magnetic transition indicating the potentiality of Mn$_2$IrGa in
magnetic switching applications. In addition, asymmetric nature of MR in the
positive and negative field cycles is indicative of spin-valve characteristics.
Our ab-initio calculations confirm the inverse Heusler structure with
ferrimagnetic ordering to be the lowest energy state, with a saturation
magnetization of 2 $\mu_\mathrm{B}$. $<100>$ is found to be the easy magnetic
axis with considerable magneto-crystalline anisotropy energy. A large positive
Berry flux at/around $\Gamma$ point gives rise to an appreciable anomalous Hall
conductivity ($\sim$-180 S/cm).",2303.04649v2
2023-03-31,"Chiral anomaly and positive longitudinal magnetoresistance in the type-II Dirac semimetals $\it{A}_x$PdTe$_2$ (\textit{A} = Cu, Ag)","The Planar Hall effect (PHE) in topological materials has been a subject of
great interest in recent years. Generally, it is understood to originate from
the chiral-anomaly (CA) induced charge pumping between doubly degenerate Weyl
nodes. However, the occurrence of PHE in the materials with positive and
anisotropic orbital magnetoresistance has raised questions about CA being the
sole origin of this effect. Here, we report the PHE, magnetoresistance, and
thermal transport properties (Seebeck and Nernst coefficients) on the Ag
intercalated PdTe$_2$. We observe positive longitudinal magnetoresistance, the
linear field dependence of the amplitude of PHE, and a prolate pattern in the
parametric plots. The planar Hall resistivity and anisotropic magnetoresitance
fits well with theoretical study of CA being the origin of PHE. So, our
observations are consistent with Weyl physics dominating the PHE in PdTe$_2$,
Cu$_{0.05}$PdTe$_2$, and Ag$_{0.05}$PdTe$_2$. We further support our data with
a theoretical model that reproduces the qualitative experimental features. In
addition, we have calculated the Seebeck ($\it{S}$) and Nernst ($\nu$)
coefficients for PdTe$_2$ and Cu and Ag intercalated compounds. The estimated
values of Fermi energy for the Cu and Ag intercalated compounds are
respectively two times and three times larger than that of PdTe$_2$.",2303.18075v2
2023-07-11,Microstructure of a spark-plasma-sintered Fe2VAl-type Heusler alloy for thermoelectric application,"The influence of microstructure on thermoelectricity is increasingly
recognized. Approaches for microstructural engineering can hence be exploited
to enhance thermoelectric performance, particularly through manipulating
crystalline defects, their structure, and composition. Here, we focus on a
full-Heusler Fe2VAl-based compound that is one of the most promising
thermoelectric materials containing only Earth-abundant, non-toxic elements. A
Fe2VTa0.05Al0.95 cast alloy was atomized under a nitrogen-rich atmosphere to
induce nitride precipitation. Nanometer- to micrometer-scale microstructural
investigations by advanced scanning electron microscopy and atom probe
tomography (APT) are performed on the powder first and then on the material
consolidated by spark-plasma sintering for an increasing time. APT reveals an
unexpected pick-up of additional impurities from atomization, namely W and Mo.
The microstructure is then correlated with local and global measurements of the
thermoelectric properties. At grain boundaries, segregation and precipitation
locally reduce the electrical resistivity, as evidenced by in-situ four-point
probe measurements. The final microstructure contains a hierarchy of structural
defects, including individual point defects, dislocations, grain boundaries,
and precipitates, that allow for a strong decrease in thermal conductivity. In
combination, these effects provide an appreciable increase in thermoelectric
performance.",2307.05051v1
2023-08-15,Phases and magnetism at the microscale in compounds containing nominal Pb10-xCux(PO4)6O,"Achieving superconductivity at room temperature could lead to substantial
advancements in industry and technology. Recently, a compound known as Cu-doped
lead-apatite, Pb10-xCux(PO4)6O (0.9 < x < 1.1), referred to as ""LK-99"", has
been reported to exhibit unusual electrical and magnetic behaviors that appear
to resemble a superconducting transition above room temperature. In this work
we collected multiphase samples containing the nominal Pb10-xCux(PO4)6O phase
(no superconductivity observed in our measured samples), synthesized by three
independent groups, and studied their chemical, magnetic, and electrical
properties at the microscale to overcome difficulties in bulk measurements.
Through the utilization of optical, scanning electron, atomic force, and
scanning diamond nitrogen-vacancy microscopy techniques, we are able to
establish a link between local magnetic properties and specific microscale
chemical phases. Our findings indicate that while the Pb10-xCux(PO4)6O phase
seems to have a mixed magnetism contribution, a significant fraction of the
diamagnetic response can be attributed to Cu-rich regions (e.g., Cu2S derived
from a reagent used in the synthesis). Additionally, our electrical
measurements reveal the phenomenon of current path switch and a change in
resistance states of Cu2S. This provides a potential explanation for the
electrical behavior observed in compounds related to Pb10-xCux(PO4)6O.",2308.07800v3
2023-08-17,Ferromagnetic and insulating behavior in both half magnetic levitation and non-levitation LK-99 like samples,"Finding materials exhibiting superconductivity at room temperature has long
been one of the ultimate goals in physics and material science. Recently,
room-temperature superconducting properties have been claimed in a copper
substituted lead phosphate apatite (Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O, or called
LK-99) [1-3]. Using a similar approach, we have prepared LK-99 like samples and
confirmed the half-levitation behaviors in some small specimens under the
influence of a magnet at room temperature. To examine the magnetic properties
of our samples, we have performed systematic magnetization measurements on the
as-grown LK-99-like samples, including the half-levitated and non-levitated
samples. The magnetization measurements show the coexistence of
soft-ferromagnetic and diamagnetic signals in both half-levitated and
non-levitated samples. The electrical transport measurements on the as-grown
LK-99-like samples including both half-levitated and non-levitated samples show
an insulating behavior characterized by the increasing resistivity with the
decreasing temperature.",2308.11768v2
2023-08-26,Complex Antiferromagnetic Order in the Metallic Triangular Lattice Compound SmAuAl$_4$Ge$_2$,"The compounds $Ln$AuAl$_4$Ge$_2$ ($Ln$ $=$ lanthanide) form in a structure
that features two-dimensional triangular lattices of $Ln$ ions that are stacked
along the crystalline $c$ axis. Together with crystal electric field effects,
magnetic anisotropy, and electron-mediated spin exchange interactions, this
sets the stage for the emergence of strongly correlated spin and electron
phenomena. Here we investigate SmAuAl$_4$Ge$_2$, which exhibits weak
paramagnetism that strongly deviates from conventional Curie-Weiss behavior.
Complex antiferromagnetic ordering emerges at $T_{\rm{N1}}$ $=$ 13.2 K and
$T_{\rm{N2}}$ $=$ 7.4 K, where heat capacity measurements show that these
transitions are first and second order, respectively. These measurements also
reveal that the Sommerfeld coefficient is not enhanced compared to the
nonmagnetic analog YAuAl$_4$Ge$_2$, consistent with the charge carrier
quasiparticles exhibiting typical Fermi liquid behavior. The
temperature-dependent electrical resistivity follows standard metallic
behavior, but linear magnetoresistance unexpectedly appears within the ordered
state. We compare these results to other $Ln$AuAl$_4$Ge$_2$ materials, which
have already been established as localized $f$-electron magnets that are hosts
for interesting magnetic and electronic phases. From this, SmAuAl$_4$Ge$_2$
emerges as a complex quantum spin metal, inviting further investigations into
its properties and the broader family of related materials.",2308.13945v2
2023-09-23,Radiation Hardness and Defects Activity in PEA2PbBr4 Single Crystals,"Metal halide perovskites (MHPs) are low-temperature processable hybrid
semiconductor materials with exceptional performances that are revolutionizing
the field of optoelectronic devices. Despite their great potential, commercial
deployment is hindered by MHPs lack of stability and durability, mainly
attributed to ions migration and chemical interactions with the device
electrodes. To address these issues, 2D layered MHPs have been investigated as
possible device interlayers or active material substitutes to reduce ion
migration and improve stability. Here we consider the 2D perovskite PEA2PbBr4
that was recently discussed as very promising candidate for X-ray direct
detection. While the increased resilience of PEA2PbBr4 detectors have already
been reported, the physical mechanisms responsible for such improvement
compared to the standard ""3D"" perovskites are not still fully understood. To
unravel the charge transport process in PEA2PbBr4 crystals thought to underly
the device better performance, we adapted an investigation technique previously
used on highly resistive inorganic semiconductors, called photo induced current
transient spectroscopy (PICTS). We demonstrate that PICTS can detect three
distinct trap states (T1, T2, and T3) with different activation energies, and
that the trap states evolution upon X-ray exposure can explain PEA2PbBr4
superior radiation tolerance and reduced aging effects. Overall, our results
provide essential insights into the stability and electrical characteristics of
2D perovskites and their potential application as reliable and direct X-ray
detectors.",2309.13355v1
2023-09-28,Extraordinary physical properties of superconducting YBa$_{1.4}$Sr$_{0.6}$Cu$_3$O$_6$Se$_{0.51}$ in a multiphase ceramic material,"We report on a novel material obtained by modifying pristine YBCO
superconductor in solid phase synthesis via simultaneous partial substitution
of Ba by Sr and O by Se. Simultaneous application of EDX and EBSD confirmed
that Se atoms indeed enter the crystalline lattice cell. The detailed XRD
analysis further confirmed this conclusion and revealed that the obtained
polycrystalline material contains 5 phases, with the major phase ($>$30\%)
being a cuprate YBa$_{1.4}$Sr$_{0.6}$Cu$_{3}$O$_{6}$Se$% _{0.51}$. The obtained
superconductor demonstrates unique properties, including i) two superconducting
transitions with $T_{c1}\approx$ 35 K (granular surface phase) and
$T_{c2}\approx$ 13 K (bulk granular phase) - this granular phase arrangement
naturally yields the Wohlleben effect; ii) reentrant diamagnetism and resistive
state; iii) strong paramagnetism with Curie-Weiss behavior (% $\theta_{CW}
\approx$ 4 K) and the ferromagnetic phase overruled by superconductivity; iv)
Schottky anomaly visible in the heat capacity data and most likely delivered by
small clusters of magnetic moments. Thorough analysis of the heat capacity data
reveals a strong-coupling $d-$wave pairing in its bulk phase (with $2\Delta
/T_{c}\approx 5$), and, most importantly, a very unusual anomaly in this
cuprate. There are reasons to associate this anomaly with the quantum
criticality observed in traditional cuprate superconductors at much higher
fields (achievable only in certain laboratories). In our case, the fields
leading to quantum criticality are much weaker ($\sim $7-9 T) thus opening
avenues for exploration of the interplay between superconductivity and pair
density waves by the wider research community.",2309.16814v1
2023-12-06,Nonlinear magnetotransport in MoTe${}_2$,"The shape of the Fermi surface influences many physical phenomena in
materials and a growing interest in how the spin-dependent properties are
related to the fermiology of crystals has surged. Recently, a novel
current-dependent nonlinear magnetoresistance effect, known as bilinear
magnetoelectric resistance (BMR), has been shown to be not only sensitive to
the spin-texture in spin-polarized non-magnetic materials, but also dependent
on the convexity of the Fermi surface in topological semimetals. In this paper,
we show that the temperature dependence of the BMR signal strongly depends on
the crystal axis of the semimetallic MoTe${}_2$. For the a-axis, the amplitude
of the signal remains fairly constant, while for the b-axis it reverses sign at
about 100 K. We calculate the BMR efficiencies at 10 K to be $\chi^{J}_{A} =
(100\pm3)$ nm${}^2$T${}^{-1}$A${}^{-1}$ and $\chi^{J}_{B} = (-364\pm13)$
nm${}^2$T${}^{-1}$A${}^{-1}$ for the a- and b-axis, respectively, and we find
that they are comparable to the efficiencies measured for WTe${}_2$. We use
density functional theory calculations to compute the Fermi surfaces of both
phases at different energy levels and we observe a change in convexity of the
outer-most electron pocket as a function of the Fermi energy. Our results
suggest that the BMR signal is mostly dominated by the change in the Fermi
surface convexity.",2312.03405v2
2024-01-09,Coexistence of large anomalous Nernst effect and large coercive force in amorphous ferrimagnetic TbCo alloy films,"The Anomalous Nernst Effect (ANE) has garnered significant interest for
practical applications, particularly in energy harvesting and heat flux
sensing. For these applications, it is crucial for the module to operate
without an external magnetic field, necessitating a combination of a large ANE
and a substantial coercive force. However, most materials exhibiting a large
ANE typically have a relatively small coercive force. In our research, we have
explored the ANE in amorphous ferrimagnetic TbCo alloy films, noting that the
coercive force peaks at the magnetization compensation point (MCP). We observed
that transverse Seebeck coefficients are amplified with Tb doping, reaching
more than 1.0 uV/K over a wide composition range near the MCP, which is three
times greater than that of pure Co. Our findings indicate that this enhancement
is primarily due to direct conversion, a product of the transverse
thermoelectric component and electrical resistivity. TbCo films present several
significant advantages for practical use: a large ANE, the capability to
exhibit both positive and negative ANE, the flexibility to be deposited on any
substrate due to their amorphous nature, a low thermal conductivity, and a
large coercive force. These attributes make TbCo films a promising material for
advancing ANE-based technologies.",2401.04445v1
2024-02-27,Percolating Superconductivity in Air-Stable Organic-Ion Intercalated MoS2,"When doped into a certain range of charge carrier concentrations, MoS2
departs from its pristine semiconducting character to become a strongly
correlated material characterized by exotic phenomena such as charge density
waves or superconductivity. However, the required doping levels are typically
achieved using ionic-liquid gating or air-sensitive alkali-ion intercalation,
which are not compatible with standard device fabrication processes. Here, we
report on the emergence of superconductivity and a charge density wave phase in
air-stable organic cation intercalated MoS2 crystals. By selecting two
different molecular guests, we show that these correlated electronic phases
depend dramatically on the intercalated cation, demonstrating the potential of
organic ion intercalation to finely tune the properties of 2D materials.
Moreover, we find that a fully developed zero-resistance state is not reached
in few-nm-thick flakes, indicating the presence of three-dimensional
superconductive paths which are severed by the mechanical exfoliation. We
ascribe this behavior to an inhomogeneous charge carrier distribution, which we
probe at the nanoscale using scanning near-field optical microscopy. Our
results establish organic-ion intercalated MoS2 as a platform to study the
emergence and modulation of correlated electronic phases.",2402.17328v1
2024-03-28,"MaterialsMap: A CALPHAD-Based Tool to Design Composition Pathways through feasibility map for Desired Dissimilar Materials, demonstrated with RSW Joining of Ag-Al-Cu","Assembly of dissimilar metals can be achieved by different methods, for
example, casting, welding, and additive manufacturing (AM). However, undesired
phases formed in liquid-phase assembling processes due to solute segregation
during solidification diminish mechanical and other properties of the processed
parts. In the present work, an open-source software named MaterialsMap, has
been developed based on the CALculation of Phase Diagrams (CALPHAD) approach.
The primary objective of MaterialsMap is to facilitate the design of an optimal
composition pathway for assembling dissimilar alloys with liquid-phases based
on the formation of desired and undesired phases along the pathway. In
MaterialsMap, equilibrium thermodynamic calculations are used to predict
equilibrium phases formed at slow cooling rate, while Scheil-Gulliver
simulations are employed to predict non-equilibrium phases formed during rapid
cooling. By combining these two simulations, MaterialsMap offers a thorough
guide for understanding phase formation in various manufacturing processes,
assisting users in making informed decisions during material selection and
production. As a demonstration of this approach, a compositional pathway was
designed from pure Al to pure Cu through Ag using MaterialsMap. The design was
experimentally verified using resistance spot welding (RSW).",2403.19084v1
2024-04-14,Role of stress/strain in tailoring the magnetic and transport properties of magnetic thin films and multilayers,"Magnetic anisotropy is a fundamental property of magnetic materials that
determines the alignment of the spins along the preferential direction, called
the easy axis of magnetization. Magnetic polycrystalline thin films offer
several advantages over magnetic epitaxial thin films because of fabrication
flexibility, higher coercivity and improved magnetic stability, higher
magnetoresistance (useful in magneto-resistive devices such as magnetic field
sensors and MRAM cells), cost-effectiveness and thermal stability, etc. In the
case of polycrystalline thin films or multilayers, Magneto-crystalline
anisotropy (MCA) is not expected due to the random orientation of grains.
Therefore, understanding the origin of uniaxial magnetic anisotropy (UMA) is
generally difficult and can't be understood in terms of crystal orientation.
The origin of UMA in polycrystalline films is often related to the preparation
conditions and substrate properties. In the present thesis, we have provided
direct in-situ real-time evidence of the stress dependence of magnetic
anisotropy through the multibeam optical stress sensor (MOSS) technique. Also,
we have tuned the magnetic anisotropy in strength and direction using
externally applied stress. To further increase the strength of the magnetic
anisotropy, we have developed a new technique that creates a multilayer using a
single magnetic material through sequential oblique and normal depositions.
This oblique angle deposition technique also helps reduce the penetration of
the top ferromagnetic layer inside the organic semiconductor layer in organic
spin valve structures. We confirm our results through various in-situ (in UHV
and HV) and ex-situ temperature-dependent conventional and unconventional
structural, morphological, and magnetic measurements (both lab-based and
synchrotron-based) that include MOKE, KERR, GIXRD, AFM, RHEED, and GISAXS, etc.
measurements.",2405.00049v1
2024-05-22,Nuclear quantum effects in structural and elastic properties of cubic silicon carbide,"Silicon carbide, a semiconducting material, has gained importance in the
fields of ceramics, electronics, and renewable energy due to its remarkable
hardness and resistance. In this study, we delve into the impact of nuclear
quantum motion, or vibrational mode quantization, on the structural and elastic
properties of 3C-SiC. This aspect, elusive in conventional {\it ab-initio}
calculations, is explored through path-integral molecular dynamics (PIMD)
simulations using an efficient tight-binding (TB) Hamiltonian. This
investigation spans a wide range of temperatures and pressures, including
tensile stress, adeptly addressing the quantization and anharmonicity inherent
in solid-state vibrational modes. The accuracy of the TB model has been checked
by comparison with density-functional-theory calculations at zero temperature.
The magnitude of quantum effects is assessed by comparing PIMD outcomes with
results obtained from classical molecular dynamics simulations. Our
investigation uncovers notable reductions of 5%, 10%, and 4% in the elastic
constants $C_{11}$, $C_{12}$, and $C_{44}$, respectively, attributed to atomic
zero-point oscillations. Consequently, the bulk modulus and Poisson's ratio of
3C-SiC exhibit reduced values by 7% and 5% at low temperature. The persistence
of these quantum effects in the material's structural and elastic attributes
beyond room temperature underscores the necessity of incorporating nuclear
quantum motion for an accurate description of these fundamental properties of
SiC.",2405.13733v1
1999-04-27,The ARGO-YBJ Detector and high energy GRBs,"ARGO-YBJ ia a detector optimized to study small size air showers. It consists
of a layer of Resistive Plate counters (RPCs) covering an area of about 6500
m^2 and will be located in the Yangbajing Laboratory (Tibet, China) at 4300 m
above the sea level. ARGO-YBJ will be devoted to a wide range of fundamental
issues in cosmic rays and astroparticle physics, including in particular
gamma-ray astronomy and gamma-ray bursts physics in the range 10 GeV-500 TeV.
The sensitivity of ARGO-YBJ to detect high energy GRBs is presented.",9904373v1
1995-12-12,Mechanism of thermally activated c-axis dissipation in layered High-T$_c$ superconductors at high fields,"We propose a simple model which explains experimental behavior of $c$-axis
resistivity in layered High-T$_c$ superconductors at high fields in a limited
temperature range. It is generally accepted that the in-plane dissipation at
low temperatures is caused by small concentration of mobile pancake vortices
whose diffusive motion is thermally activated. We demonstrate that in such
situation a finite conductivity appears also in $c$-direction due to the phase
slips between the planes caused by the mobile pancakes. The model gives
universal relation between the components of conductivity which is in good
agreement with experimental data.",9512097v3
1998-03-24,Magnetic Penetration Depth and Surface Resistance in YBa_2Cu_3O_{7-delta}: New Results for Ultra High Purity Crystals,"We have succeeded in growing very high purity (99.995%) YBa_2Cu_3O_{7-delta}
crystals in BaZrO_3 crucibles and have measured Delta-lambda(T) and R_s(T) at 1
GHz in crystals with various oxygen treatments. For an oxygen vacancy level of
delta=0.007, Delta-lambda and R_s essentially reproduce our previous results
and show no sign of the existence of the two order parameter components as
recently reported by Srikanth et al. on BaZrO_3-grown crystals. For other
oxygen concentrations, we have in some cases observed deviations from the
linear low T dependence of Delta-lambda, but never any sign of a second
transition.",9803292v1
2000-02-24,Search for Magnetic Field Induced Gap in a High-Tc Superconductor,"Break junctions made of the optimally doped high temperature superconductor
Bi2Sr2Ca2CuO8 with Tc of 90 K has been investigated in magnetic fields up to 12
T, at temperatures from 4.2 K to Tc. The junction resistance varied between
1kOhm and 300kOhm. The differential conductance at low biases did not exhibit a
significant magnetic field dependence, indicating that a magnetic-field-induced
gap (Krishana et al., Science 277 83 (1997)), if exists, must be smaller than
0.25 meV.",0002376v1
2001-06-11,Microwave absorption by the Josephson-junction network in a low field: A realistic model for ceramic high-temperature superconductor,"We discuss the applied magnetic field dependence of the absorption of
microwaves by a 3-dimensional array up to 30x30x30 Josephson junctions with
random parameters including the resistivity, capacity and inductance of each
junction. The numerical simulation results for the networks show characteristic
microwave absorption anomalies observed in the ceramic samples of high
temperature superconductor YBa2Cu3O(7-x). We also provide a discussion of the
absorption in simple analytical terms of Josephson loop instabilities.",0106188v2
2002-03-15,High quality MgB2 thin films in-situ grown by dc magnetron sputtering,"Thin films of the recently discovered magnesium diboride (MgB2) intermetalic
superconducting compound have been grown using a magnetron sputtering
deposition technique followed by in-situ annealing at 830 C. High quality films
were obtained on both sapphire and MgO substrates. The best films showed
maximum Tc = 35 K (onset), a transition width of 0.5 K, a residual resistivity
ratio up to 1.6, a low temperature critical current density Jc > 1 MA/cm2 and
anisotropic critical field with gamma = 2.5 close to the values obtained for
single crystals. The preparation technique can be easily scaled to produce
large area in-situ films.",0203322v1
2002-10-09,Effects of In-Plane Impurity Substitution in Sr2RuO4,"We report comparative substitution effects of nonmagnetic Ti^(4+) and
magnetic Ir^(4+) impurities for Ru^(4+) in the spin-triplet superconductor
Sr2RuO4. We found that both impurities suppress the superconductivity
completely at a concentration of approximately 0.15%, reflecting the high
sensitivity to translational symmetry breaking in Sr2RuO4. In addition, a rapid
enhancement of residual resistivity is in quantitative agreement with
unitarity-limit scattering. Our result suggests that both nonmagnetic and
magnetic impurities in Sr2RuO4 act as strong potential scatterers, similar to
the nonmagnetic Zn^(2+) impurity in the high-Tc cuprates.",0210190v1
2003-02-01,Higher cumulants of voltage fluctuations in current-biased diffusive contacts,"The third and fourth cumulants of voltage in a current-biased diffusive metal
contact of resistance $R$ are calculated for arbitrary temperatures and
voltages using the semiclassical cascade approach. The third cumulant equals
$e^2R^3I/3$ at high temperatures and $4e^2R^3I/15$ at low temperatures, whereas
the fourth cumulant equals $2e^2R^3T/3$ at high temperatures and
$(34/105)e^3R^4I$ at low temperatures.",0302008v3
2003-05-20,High performance temperature controller: application to the excess noise measurements of YBCO thermometers in the transition region,"Dedicated read-out electronics was developed for low impedance resistive
thermometers. Using this high performance temperature controller, the
temperature dependence of the excess noise of a YBa2Cu307-d (YBCO) sample in
the superconducting transition was monitored as a function of the current bias.
The noise could reach 3.10-8 K Hz-1/2 at 1 Hz, 5 mA bias and 90 K.",0305469v2
2003-08-31,Paramagnetic Meissner effect and related dynamical phenomena,"The present review is given on the paramagnetic Meissner effect observed in
conventional and ceramic high-Tc superconductors. We discuss two mechanisms
leading to this phenomenon: the d-wave and the flux compensation. It is shown
that the chiral glass phase may occur in granular superconductors possessing
d-wave pairing symmetry. Dynamical phenomena such as AC susceptibility,
compensation effect, anomalous microwave absorption, aging effect, AC
resistivity and enhancement of critical current due to the external electric
field are considered.",0309020v1
2003-12-15,Bulk antiferromagnetism in $\bf Na_{0.82}CoO_2$ single crystals,"Susceptibility, specific heat, and muon spin rotation measurements on
high-quality single crystals of $\rm Na_{0.82}CoO_2$ have revealed bulk
antiferromagnetism with N\'{e}el temperature $\rm T_N = 19.8 \pm 0.1$ K and an
ordered moment perpendicular to the $\rm CoO_2$ layers. The magnetic order
encompasses nearly 100% of the crystal volume. The susceptibility exhibits a
broad peak around 30 K, characteristic of two-dimensional antiferromagnetic
fluctuations. The in-plane resistivity is metallic at high temperatures and
exhibits a minimum at $\rm T_N$.",0312376v2
2004-12-31,Numerical evaluation of the dipole-scattering model for the metal-insulator transition in gated high mobility Silicon inversion layers,"The dipole trap model is able to explain the main properties of the apparent
metal-to-insulator transition in gated high mobility Si-inversion layers. Our
numerical calculations are compared with previous analytical ones and the
assumptions of the model are discussed carefully. In general we find a similar
behavior but include further details in the calculation. The calculated strong
density dependence of the resistivity is not yet in full agreement with the
experiment.",0412762v1
2006-07-27,Microwave photoresistance of a high-mobility two-dimensional electron gas in a triangular antidot lattice,"The microwave (MW) photoresistance has been measured on a high-mobility
two-dimensional electron gas patterned with a shallow triangular antidot
lattice, where both the MW-induced resistance oscillations (MIRO) and
magnetoplasmon (MP) resonance are observed superposing on sharp commensurate
geometrical resonance (GR). Analysis shows that the MIRO, MP, and GR are
decoupled from each other in these experiments.",0607740v1
2006-08-30,Magnetoresistance oscillations in two-dimensional electron systems under monochromatic and bichromatic radiations,"The magnetoresistance oscillations in high-mobility two-dimensional electron
systems induced by two radiation fields of frequencies 31 GHz and 47 GHz, are
analyzed in a wide magnetic-field range down to 100 G, using the
balance-equation approach to magnetotransport for high-carrier-density systems.
The frequency mixing processes are shown to be important. The predicted peak
positions, relative heights, radiation-intensity dependence and their relation
with monochromatic resistivities are in good agreement with recent experimental
finding [M. A. Zudov {\it et al.} Phys. Rev. Lett. 96, 236804 (2006)].",0608655v2
1995-01-30,CHIRAL SYMMETRY RESTORATION AS THE GEORGI VECTOR LIMIT,"I discuss recent work done with Gerry Brown on chiral phase transition at
high temperature and/or density described in terms of Georgi's vector limit.
The notion of ``mended symmetry"" is suggested to play an important role in
understanding the properties of hadrons in dense and/or hot matter before
reaching the phase transition. It is shown that while the QCD vacuum in
baryon-free space is resistant to ``melting"" up to the critical temperature,
baryon-rich medium can induce the vacuum to become softer in temperature: the
hadron masses drop faster in temperature when baryon matter is present.",9501403v1
1998-07-22,Carbon Coated Gas Electron Multipliers,"Gas electron multipliers (GEMs) have been overcoated with a high resistivity
10e14 - 10e15 Ohms / square amorphous carbon layer. The coating avoids charging
up of the holes and provides a constant gain immediately after switching on
independent of the rate. The gain uniformity across the GEM is improved.
Coating opens the possibility to produce thick GEMs of very high gain.",9807039v1
2007-04-26,Quantum Darwinism in quantum Brownian motion: the vacuum as a witness,"We study quantum Darwinism -- the redundant recording of information about a
decohering system by its environment -- in zero-temperature quantum Brownian
motion. An initially nonlocal quantum state leaves a record whose redundancy
increases rapidly with its spatial extent. Significant delocalization (e.g., a
Schroedinger's Cat state) causes high redundancy: many observers can measure
the system's position without perturbing it. This explains the objective (i.e.
classical) existence of einselected, decoherence-resistant pointer states of
macroscopic objects.",0704.3615v1
2007-06-12,High-quality all-oxide Schottky junctions fabricated on heavily Nb-doped SrTiO3 substrates,"We present a detailed investigation of the electrical properties of epitaxial
La0.7Sr0.3MnO3/SrTi0.98Nb0.02O3 Schottky junctions. A fabrication process that
allows reduction of the junction dimensions to current electronic device size
has been employed. A heavily doped semiconductor has been used as a substrate
in order to suppress its series resistance. We show that, unlike standard
semiconductors, high-quality oxide-based Schottky junctions maintain a highly
rectifying behavior for doping concentration of the semiconductor larger than
10^20 cm^(-3). Moreover, the junctions show hysteretic current-voltage
characteristics.",0706.1620v2
2007-07-09,High-temperature PbTe diodes,"We describe the preparation of high-temperature PbTe diodes. Satisfactory
rectification was observed up to 180-200 K. Two types of diodes, based on a
p-PbTe single crystal, were prepared: (1) by In ion-implantation, and (2) by
thermodiffusion of In. Measurements were carried-out from ~ 10 K to ~ 200 K.
The ion-implanted diodes exhibit a satisfactorily low saturation current up to
a reverse bias of ~ 400 mV, and the thermally diffused junctions up to ~ 1 V.
The junctions are linearly graded. The current-voltage characteristics have
been fitted using the Shockley model. Photosensor parameters:
zero-bias-resistance x area product, the R0C time constant and the detectivity
D* are presented.",0707.1213v1
2008-02-20,Prospects for a direct dark matter search using high resistivity CCD detectors,"The possibility of using CCD detectors in a low threshold direct detection
dark matter search experiment is discussed. We present the main features of the
DECam detectors that make them a good alternative for such an experiment,
namely their low noise and their large depleted volume. The performance of the
DECam CCDs for the detection of nuclear recoils is discussed, and a measurement
of the ionization efficiency for these events is presented. Finally the plans
and expected reach for the CCD Experiment at Low Background (CELB) are
discussed.",0802.2872v3
2008-08-14,Synthesis and superconducting properties of the iron oxyarsenide TbFeAsO0.85,"The iron oxyarsenide TbFeAsO0.85 was synthesized by a high-pressure method. A
high-quality polycrystalline sample was obtained and characterized by
measurements of magnetic susceptibility and electrical resistivity. Bulk
superconductivity with Tc of 42 K was clearly established without an F doping
usually conducted to tune on superconductivity in the iron oxypnictide.",0808.1948v1
2008-09-08,Pressure Study of Superconducting Oxypnictide LaFePO,"Electrical resistivity and magnetic susceptibility measurements under high
pressure were performed on an iron-based superconductor LaFePO. A steep
increase in superconducting transition temperature (Tc) of LaFePO with dTc/dP >
4 K/GPa to a maximum of 8.8 K for P = 0.8 GPa was observed. These results are
similar to isocrystalline LaFeAsO1-xFx system reported previously. X-ray
diffraction measurements were also performed under high pressure up to 10 GPa,
where linear compressibility ka and kc are presented.",0809.1239v1
2008-09-29,High-quality quantum point contact in two-dimensional GaAs (311)A hole system,"We studied ballistic transport across a quantum point contact (QPC) defined
in a high-quality, GaAs (311)A two-dimensional (2D) hole system using shallow
etching and top-gating. The QPC conductance exhibits up to 11 quantized
plateaus. The ballistic one-dimensional subbands are tuned by changing the
lateral confinement and the Fermi energy of the holes in the QPC. We
demonstrate that the positions of the plateaus (in gate-voltage), the
source-drain data, and the negative magneto-resistance data can be understood
in a simple model that takes into account the variation, with gate bias, of the
hole density and the width of the QPC conducting channel.",0809.5047v1
2008-10-07,Superconductivity under high pressure in LaFeAsO,"Electrical resistivity measurements under high pressures up to 29 GPa were
performed for oxypnictide compound LaFeAsO. We found a pressure-induced
superconductivity in LaFeAsO. The maximum value of Tc is 21 K at ~12 GPa. The
pressure dependence of the Tc is similar to those of LaFeAsO1-xFx series
reported previously.",0810.1153v1
2009-01-06,Fantastic Behavior of High-TC Superconductor Junctions: Tunable Superconductivity,"Carrier injection performed in oxygen-deficient YBa2Cu3O7(YBCO)
hetero-structure junctions exhibited tunable resistance that was entirely
different with behaviors of semiconductor devices. Tunable superconductivity in
YBCO junctions, increasing over 20 K in transition temperature, has achieved by
using electric processes. To our knowledge, this is the first observation that
intrinsic property of high TC superconductors superconductivity can be adjusted
as tunable functional parameters of devices. The fantastic phenomenon caused by
carrier injection was discussed based on a proposed charge carrier
self-trapping model and BCS theory.",0901.0594v1
2009-10-15,ATLAS Muon Detector Commissioning,"The ATLAS muon spectrometer consists of several major components: Monitored
Drift Tubes (MDTs) for precision measurements in the bending plane of the
muons, supplemented by Cathode Strip Chambers (CSC) in the high eta region;
Resistive Plate Chambers (RPCs) and Thin Gap Chambers (TGCs) for trigger and
second coordinate measurement in the barrel and endcap regions, respectively;
an optical alignment system to track the relative positions of all chambers;
and, finally, the world's largest air-core magnetic toroid system. We will
describe the status and commissioning of the muon system with cosmic rays and
plans for commissioning with early beams.",0910.2767v1
2010-01-30,High yield fabrication of chemically reduced graphene oxide field effect transistors by dielectrophoresis,"We demonstrate high yield fabrication of field effect transistors (FET) using
chemically reduced graphene oxide (RGO) sheets suspended in water assembled via
dielectrophoresis. The two terminal resistances of the devices were improved by
an order of magnitude upon mild annealing at 200 0C in Ar/H2 environment for 1
hour. With the application of a backgate voltage, all of the devices showed FET
behavior with maximum hole and electron mobilities of 4.0 and 1.5 cm2/Vs
respectively. This study shows promise for scaled up fabrication of graphene
based nanoelectronic devices.",1002.0086v2
2010-02-28,Theory of acoustic-phonon assisted magnetotransport in 2D electron systems at large filling factors,"A microscopic theory of the phonon-induced resistance oscillations in weak
perpendicular magnetic fields is presented. The calculations are based on the
consideration of interaction of two-dimensional electrons with
three-dimensional (bulk) acoustic phonons and take into account anisotropy of
the phonon spectrum in cubic crystals. The magnetoresistance is calculated for
[001]-grown GaAs quantum wells. The results are in agreement with available
experimental data. Apart from the numerical results, analytical expressions for
the oscillating part of magnetoresistance are obtained. These expressions are
valid in the region of high-order magnetophonon resonances and describe the
oscillating magnetoresistance determined by several groups of phonons polarized
along certain high-symmetry directions.",1003.0176v1
2011-01-19,Hidden Fermi Liquid: Self-Consistent Theory for the Normal State of High-Tc Superconductors,"Hidden Fermi liquid theory explicitly accounts for the effects of Gutzwiller
projection in the t-J Hamiltonian, widely believed to contain the essential
physics of the high-Tc superconductors. We derive expressions for the entire
""strange metal"", normal state relating angle-resolved photoemission,
resistivity, Hall angle, and by generalizing the formalism to include the Fermi
surface topology - angle-dependent magnetoresistance. We show this theory to be
the first self-consistent description for the normal state of the cuprates
based on transparent, fundamental assumptions. Our well-defined formalism also
serves as a guide for further experimental confirmation.",1101.3609v1
2011-03-28,Superconducting properties of FeSe wires and tapes prepared by gas diffusion technique,"Superconducting FeSe in the form of wires and tapes were successfully
fabricated using a novel gas diffusion procedure. Structural analysis by mean
of x-ray diffraction shows that themain phase of tetragonal PbO-type FeSe was
obtained by this synthesis method. The zero resistivity transition temperature
of the FeSe was confirmed to be 9.3 K. The critical current density as high as
137 A/cm^2 (4 K, self field) has been observed. The results suggest that the
diffusion procedure is promising in preparing high-quality FeSe wires and
tapes.",1103.5304v1
2011-06-13,Resistant estimates for high dimensional and functional data based on random projections,"We herein propose a new robust estimation method based on random projections
that is adaptive and, automatically produces a robust estimate, while enabling
easy computations for high or infinite dimensional data. Under some restricted
contamination models, the procedure is robust and attains full efficiency. We
tested the method using both simulated and real data.",1106.2442v3
2011-12-01,Superconductivity in the doped topological insulator Cu$_x$Bi$_2$Se$_3$ under high pressure,"We report a high-pressure single crystal study of the topological
superconductor Cu$_x$Bi$_2$Se$_3$. Resistivity measurements under pressure show
superconductivity is depressed smoothly. At the same time the metallic behavior
is gradually lost. The upper critical field data $B_{c2}(T)$ under pressure
collapse onto a universal curve. The absence of Pauli limiting and the
comparison of $B_{c2}(T)$ to a polar state function point to spin-triplet
superconductivity, but an anisotropic spin-singlet state cannot be discarded
completely.",1112.0102v1
2011-12-16,Pseudogap and local pairs in high-Tc cuprate superconductors,"Analysis of the resistivity data recently reported by Kondo et al. [1] for
(Bi,Pb)2(Sr,La)2CuO{6-delta} (Bi2201) single-crystals has been performed within
our model developed to study pseudogap (PG) in high-Tc superconductors (HTS's).
The model is based on an assumption of the existence of local pairs in HTS's at
temperatures well above Tc. Comparative analysis of our results and results of
ARPES experiments reported by Kondo et al. suggests the local pairs to be one
of the possible reason of the PG formation.",1112.3812v1
2012-02-08,A proposal to solve some puzzles in semileptonic B decays,"Some long-standing problems in the experimental data for semileptonic b -> c
l nu decay rates have resisted attempts to resolve them, despite substantial
efforts. We summarize the issues, and propose a possible resolution, which may
alleviate several of these tensions simultaneously, including the ""1/2 vs. 3/2
puzzle"" and the composition of the inclusive decay rate in terms of exclusive
channels.",1202.1834v3
2012-02-24,The 1m3 Semidigital Hadronic Prototype,"A high granularity hadronic 1 m3 calorimeter prototype with semi-digital
readout has been designed and built. This calorimeter has been made using
stainless steel as absorber and Glass Resistive Plates Chambers (GRPC) as
active medium, and read out through 1x1 cm2 pads. This prototype aims to
demonstrate that this technology fulfills the physics requirements for future
linear collider experiments, and also to test the feasibility of building a
realistic detector, taking into account design aspects as for instance a fully
embedded front-end electronics based on power pulsing system, a compact and
self-supporting mechanical structure, one-side services...",1202.5567v1
2012-04-13,Studies of Vertex Tracking with SOI Pixel Sensors for Future Lepton Colliders,"This paper presents a study of vertex tracking with a beam hodoscope
consisting of three layers of monolithic pixel sensors in SOI technology on
high-resistivity substrate. We study the track extrapolation accuracy,
two-track separation and vertex reconstruction accuracy in pion-Cu interactions
with 150 and 300 GeV/c pions at the CERN SPS. Results are discussed in the
context of vertex tracking at future lepton colliders.",1204.2910v1
2012-05-02,High-field magnetoresistance revealing scattering mechanisms in graphene,"We show that the type of charge carrier scattering significantly affects the
high-field magnetoresistance of graphene nanoribbons. This effect has potential
to be used in identifying the scattering mechanisms in graphene. The results
also provide an explanation for the experimentally found, intriguing
differences in the behavior of the magnetoresistance of graphene Hall bars
placed on different substrates. Additionally, our simulations indicate that the
peaks in the longitudinal resistance tend to become pinned to fractionally
quantized values, as different transport modes have very different scattering
properties.",1205.0492v2
2012-05-13,Modeling high impedance connecting links and cables below 1 Hz,"High impedance connecting links and cables are modeled at low frequency in
terms of their impedance to ground and to neigbouring connecting links. The
impedance is usually considered to be the parallel combination of a resistance
and a capacitance. While this model is adequate at moderate and low frequency,
it proved to be not satisfactory at very low frequency, in the fractions of Hz
range. Deep characterization was carried out on some samples down to 10 uHz,
showing that an additional contribution to capacitance can emerge. A model was
developed to explain and account for this additional contribution.",1205.2848v1
2012-07-24,Van Kampen modes for bunch longitudinal motion,"Conditions for existence, uniqueness and stability of bunch steady states are
considered. For the existence uniqueness problem, simple algebraic equations
are derived, showing the result both for the action and Hamiltonian domain
distributions. For the stability problem, van Kampen theory is used. Emerging
of discrete van Kampen modes show either loss of Landau damping, or
instability. This method can be applied for an arbitrary impedance, RF shape
and beam distribution function Available areas on intensity-emittance plane are
shown for resistive wall wake and single harmonic, bunch shortening and bunch
lengthening RF configurations.",1207.5826v1
2012-11-28,Homogeneous superconducting phase in TiN film : a complex impedance study,"The low frequency complex impedance of a high resistivity 92 {\mu}{\Omega} cm
and 100 nm thick TiN superconducting film has been measured via the
transmission of several high sensitivity GHz microresonators, down to Tc/50.
The temperature dependence of the kinetic inductance follows closely BCS local
electrodynamics, with one well defined superconducting gap. This evidences the
recovery of an homogeneous superconducting phase in TiN far from the disorder
and composition driven transitions. Additionally, we observe a linearity
between resonator quality factor and frequency temperature changes, which can
be described by a two fluid model.",1211.6678v2
2013-05-08,Evidence for effective mass reduction in GaAs/AlGaAs quantum wells,"We have performed microwave photoresistance measurements in high mobility
GaAs/AlGaAs quantum wells and investigated the value of the effective mass.
Surprisingly, the effective mass, obtained from the period of microwave-induced
resistance oscillations, is found to be about 12% lower than the band mass in
GaAs, $\mb$. This finding provides strong evidence for electron-electron
interactions which can be probed by microwave photoresistance in very high
Landau levels. In contrast, the measured magnetoplasmon dispersion revealed an
effective mass which is close to $\mb$, in accord with previous studies.",1305.1814v1
2014-06-23,Control of MTDC Transmission Systems under Local Information,"High-voltage direct current (HVDC) is a commonly used technology for
long-distance electric power transmission, mainly due to its low resistive
losses. In this paper a distributed controller for multi-terminal high-voltage
direct current (MTDC) transmission systems is considered. Sufficient conditions
for when the proposed controller renders the closed-loop system asymptotically
stable are provided. Provided that the closed loop system is asymptotically
stable, it is shown that in steady-state a weighted average of the deviations
from the nominal voltages is zero. Furthermore, a quadratic cost of the current
injections is minimized asymptotically.",1406.5839v2
2014-06-27,Energy measurement with the SDHCAL prototype,"The SDHCAL prototype that was completed in 2012 was exposed to beams of
pions, electrons of different energies at the SPS of CERN for a total time
period of 5 weeks. The data are being analyzed within the CALICE Collaboration.
However preliminary results indicate that a highly granular hadronic
calorimeter conceived for PFA application is also a powerful tool to separate
pions from electrons. The SDHCAL provides also a very good resolution of
hadronic showers energy measurement. A new calibration method that takes into
account the degradation of the Glass Resistive Plate Chambers (GRPC) response
for runs with rather high particle beam rate is presented.",1406.7111v1
2014-06-29,CMS RPC muon detector performance with 2010-2012 LHC data,"The muon spectrometer of the CMS (Compact Muon Solenoid) experiment at the
Large Hadron Collider (LHC) is equipped with a redundant system made of
Resistive Plate Chambers and Drift Tube in barrel and RPC and Cathode Strip
Chamber in endcap region. In this paper, the operations and performance of the
RPC system during the first three years of LHC activity will be reported. The
stability of RPC performance, such as efficiency, cluster size and noise, will
be reported. Finally, the radiation background levels on the RPC system have
been measured as a function of the LHC luminosity. Extrapolations to the LHC
and High Luminosity LHC conditions are also discussed.",1406.7543v1
2014-12-08,Anomalous specific heat behaviour in the quadrupolar Kondo system PrV2Al20,"We have measured the specific heat of PrV$_2$Al$_{20}$ at very low
temperatures, using high quality single crystals with the residual resistivity
ratio ~ 20. The high-quality single crystals exhibit clear double transitions
at $T_{\rm Q} =$ 0.75 K and $T^* =$ 0.65 K. These transitions are clearer and
shift to higher temperature in higher quality single crystals. Besides, there
was no hysteresis in those transitions in warming and cooling process of the
heat capacity measurements. In the ordered state below $T^*$, the specific heat
shows a $T^4$ dependence, indicating the gapless mode associated with the
quadrupole and/or octupole ordering.",1412.2583v1
2016-02-25,The quantum phase slip phenomenon in superconducting nanowires with high-impedance environment,"Quantum phase slip (QPS) is the particular manifestation of quantum
fluctuations of the order parameter of a current-biased quasi-1D
superconductor. The QPS event(s) can be considered a dynamic equivalent of
tunneling through conventional Josephson junction containing static in space
and time weak link(s). At low temperatures T<<Tc the QPS effect leads to finite
resistivity of narrow superconducting channels and suppresses persistent
currents in tiny nanorings. Here we demonstrate that the quantum tunneling of
phase may result in Coulomb blockade: superconducting nanowire, imbedded in
high-Ohmic environment, below a certain bias voltage behaves as an insulator.",1602.07935v1
2016-05-07,Monte-Carlo study of the MRPC prototype for the upgrade of BESIII,"A GEANT4-based simulation is developed for the endcap time of flight (ETOF)
upgrade based on multi-gap resistive plate chambers (MRPC) for the BESIII
experiment. The MRPC prototype and the simulation method are described. Using a
full Monte-Carlo simulation, the influence of high voltage and threshold on
time resolution and detection efficiency are investigated. The preliminary
results from simulation are presented and are compared with the experimental
data taken with the prototype MRPC modules.",1605.02155v1
2016-10-24,Compact sorting of optical vortices by means of diffractive transformation optics,"The orbital angular momentum (OAM) of light has recently attracted a growing
interest as a new degree of freedom in order to increase the information
capacity of today optical networks both for free-space and optical fiber
transmission. Here we present our work of design, fabrication and optical
characterization of diffractive optical elements for compact OAM-mode division
demultiplexing based on optical transformations. Samples have been fabricated
with 3D high-resolution electron beam lithography on polymethylmethacrylate
(PMMA) resist layer spun over a glass substrate. Their high compactness and
efficiency make these optical devices promising for integration into
next-generation platforms for OAM-modes processing in telecom applications.",1610.07443v1
2017-02-22,Interfacing of High Temperature Z-meter Setup Using Python,"In this work, we interface high temperature Z-meter setup to automize the
whole measurement process. A program is built on open source programming
language Python which convert the manual measurement process into fully
automated process without any cost addition. Using this program, simultaneous
measurement of Seebeck coefficient, thermal conductivity and electrical
resistivity are performed and using all three, figure-of-merit (ZT) is
calculated. Developed program is verified by performing measurement over p-type
Bi0.36Sb1.45Te3 sample and the data obtained are found to be in good agreement
with the reported data.",1702.06691v1
2017-06-01,Nonlinear transport by vortex tangles in cuprate high-temperature superconductors,"A unified model of vortex tangles is proposed to describe unconventional
transport in cuprate high-temperature superconductors, which not only captures
the fast vortices scenario at low density, but also predicts a novel mechanism
of core-core collisions in dense vortex fluid regime. The theory clarifies the
nature of vortex fluctuations being the quantum fluctuations of holes and then
resolves a discrepancy of two orders of magnitude of Anderson's damping model
$\hbar n_v$, with right prediction of the nonlinear field dependence of the
resistivity $\rho=\rho_n(B+B_T)/(B_0+B+B_T)$ and the Nernst effect, validated
by data of several samples. Consequently, Anderson's vortex tangles concept and
phase fluctuation scenario of pseudogap are verified quantitatively.",1706.00228v1
2017-06-20,Saturation of Strong Electron-Electron Umklapp Scattering at High Temperature,"We consider clean metals, at finite temperature, in which the inelastic rate,
$\hbar/ \tau_{ee}$, can become of the order of, or larger, than the band
splitting energy. We show that in suchsystems, contrary to the common
knowledge, the umklapp scattering rate becomes independent of both $\tau_{ee}$
and the temperature $T,$ in three dimensional systems. We discuss the relation
of this phenomenon to the saturation of resistivity at high temperature.",1706.06256v2
2018-02-05,High Kinetic Inductance NbN Nanowire Superinductors,"We demonstrate that a high kinetic inductance disordered superconductor can
realize a low microwave loss, non-dissipative circuit element with an impedance
greater than the quantum resistance ($R_Q = h/4e^2 \simeq 6.5k\Omega$). This
element, known as a superinductor, can produce a quantum circuit where charge
fluctuations are suppressed. The superinductor consists of a 40 nm wide niobium
nitride nanowire and exhibits a single photon quality factor of $2.5 \times
10^4$. Furthermore, by examining loss rates, we demonstrate that the
dissipation of our nanowire devices can be fully understood in the framework of
two-level system loss.",1802.01723v1
2011-07-05,Deep sub electron noise readout in CCD systems using digital filtering techniques,"Scientific CCDs designed in thick high resistivity silicon (Si) are excellent
detectors for astronomy, high energy and nuclear physics, and instrumentation.
Many applications can benefit from CCDs ultra low noise readout systems. The
present work shows how sub electron noise CCD images can be achieved using
digital signal processing techniques. These techniques allow readout bandwidths
of up to 10 K pixels per second and keep the full CCD spatial resolution and
signal dynamic range.",1107.0925v1
2013-12-13,Recent DHCAL Developments,"This talk reports on recent progress concerning the development of a Digital
Hadron Calorimeter with Resistive Plate Chambers as active elements. After the
successful testing of a Digital Hadron Calorimeter prototype, the DHCAL, in the
Fermilab and CERN test beams, the DHCAL group is now tackling some of the
remaining technical issues which were not addressed specifically with the
prototype. The talk reports on developments related to the RPC chamber design,
to improvements in the RPC rate capabilities, the high voltage distribution
system, and a gas recirculation system.",1312.3868v1
2015-05-14,High-pressure and doping studies of the superconducting antiperovskite SrPt3P,"We report the results of our investigation of SrPt3P, a recently discovered
strong-coupling superconductor with Tc = 8.4 K, by application of high physical
pressure and by chemical doping. We study hole-doped SrPt3P, which was
theoretically predicted to have a higher Tc, resistively, magnetically, and
calorimetrically. Here we present the results of these studies and discuss
their implications.",1505.03849v1
2016-12-18,Power nano- and picosecond optoelectronic switches based on high-voltage silicon structures with p-n-junctions. II. Energy efficiency,"Energy efficiency of optoelectronic switches based on high-voltage silicon
photodiodes, phototransistors or photothyristors and triggered-on by picosecond
laser pulses has been studied for the first time. For given values of resistive
load, amplitude and duration $t_R$ of voltage pulses it is shown that there
exist optimal sets of values for the device area, energy and absorption
coefficient for triggering illumination, which provide the maximal general
efficiency of the switch about 0.92. All three types of switches have almost
identical efficiencies at short $t_R$, and in case of long $t_R$
photothyristors possess a noticeable advantage among them.",1701.03412v1
2017-01-28,Point-contact studies of high-temperature superconductor $\rm YBa_2Cu_3O_{7-δ}$,"Point-contacts formed by the high-temperature superconductor $\rm
YBa_2Cu_3O_{7-\delta}$ prepared by cryochemical technique, and a noble metal Ag
or Cu) are investigated. The maximum value of the energy gap $\Delta\simeq
40~meV$ and the ratio $2\Delta/kT_c\simeq 12$ are obtained. It is found that
along certain crystallographic axes of the superconductor under investigation,
the electrical resistivity $\lesssim 10^{-5} \Omega\cdot cm$.",1701.08293v1
2019-04-23,Spatio-temporal crop classification of low-resolution satellite imagery with capsule layers and distributed attention,"Land use classification of low resolution spatial imagery is one of the most
extensively researched fields in remote sensing. Despite significant
advancements in satellite technology, high resolution imagery lacks global
coverage and can be prohibitively expensive to procure for extended time
periods. Accurately classifying land use change without high resolution imagery
offers the potential to monitor vital aspects of global development agenda
including climate smart agriculture, drought resistant crops, and sustainable
land management. Utilizing a combination of capsule layers and long-short term
memory layers with distributed attention, the present paper achieves
state-of-the-art accuracy on temporal crop type classification at a 30x30m
resolution with Sentinel 2 imagery.",1904.10130v1
2019-01-06,Enhanced magnetic ordering in Sm metal under extreme pressure,"The dependence of the magnetic ordering temperature To of Sm metal was
determined through four-point electrical resistivity measurements to pressures
as high as 150 GPa. A strong increase in To with pressure is observed above 85
GPa. In this pressure range Sm ions alloyed in dilute concentration with
superconducting Y exhibit giant Kondo pair breaking. Taken together, these
results suggest that for pressures above 85 GPa Sm is in a highly correlated
electron state, like a Kondo lattice, with an unusually high value of To. A
detailed comparison is made with similar results obtained earlier on Nd, Tb and
Dy and their dilute magnetic alloys with superconducting Y.",1901.01563v1
2021-03-19,Low differentially uniform permutations from Dobbertin APN function over $\mathbb{F}_{2^n}$,"Block ciphers use S-boxes to create confusion in the cryptosystems. Such
S-boxes are functions over $\mathbb{F}_{2^{n}}$. These functions should have
low differential uniformity, high nonlinearity, and high algebraic degree in
order to resist differential attacks, linear attacks, and higher order
differential attacks, respectively. In this paper, we construct new classes of
differentially $4$ and $6$-uniform permutations by modifying the image of the
Dobbertin APN function $x^{d}$ with $d=2^{4k}+2^{3k}+2^{2k}+2^{k}-1$ over a
subfield of $\mathbb{F}_{2^{n}}$. Furthermore, the algebraic degree and the
lower bound of the nonlinearity of the constructed functions are given.",2103.10687v1