publicationDate stringlengths 10 10 | title stringlengths 17 233 | abstract stringlengths 20 3.22k | id stringlengths 9 12 |
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2017-06-23 | Fabrication of highly dense isotropic Nd-Fe-B bonded magnets via extrusion-based additive manufacturing | Isotropic bonded magnets with a high loading fraction of 70 vol.% Nd-Fe-B are
fabricated via an extrusion-based additive manufacturing, or 3D printing system
that enables rapid production of large parts for the first time. The density of
the printed magnet is 5.15 g/cm3. The room temperature magnetic properties are:
intrinsic coercivity Hci = 8.9 kOe (708.2 kA/m), remanence Br = 5.8 kG (0.58
Tesla), and energy product (BH)max = 7.3 MGOe (58.1 kJ/m3). The as-printed
magnets are then coated with two types of polymers, both of which improve the
thermal stability at 127 {\deg}C as revealed by flux aging loss measurements.
Tensile tests performed at 25 {\deg}C and 100 {\deg}C show that the ultimate
tensile stress (UTS) increases with increasing loading fraction of the magnet
powder, and decreases with increasing temperature. AC magnetic susceptibility
and resistivity measurements show that the 3D printed Nd-Fe-B bonded magnets
exhibit extremely low eddy current loss and high resistivity. Finally, we show
that through back electromotive force measurements that motors installed with
3D printed Nd-Fe-B magnets exhibit similar performance as compared to those
installed with sintered ferrites. | 1706.07792v1 |
2017-10-11 | Pressure Induced Superconductivity in the New Compound ScZrCo1-$δ$ | It is widely perceived that the correlation effect may play an important role
in several unconventional superconducting families, such as cuprate, iron-based
and heavy-fermion superconductors. The application of high pressure can tune
the ground state properties and balance the localization and itineracy of
electrons in correlated systems, which may trigger unconventional
superconductivity. Moreover, non-centrosymmetric structure may induce the spin
triplet pairing which is very rare in nature. Here, we report a new compound
ScZrCo1-${\delta}$ crystallizing in the Ti2Ni structure with the space group of
FD3-MS without a spatial inversion center. The resistivity of the material at
ambient pressure shows a bad metal and weak semiconducting behavior.
Furthermore, specific heat and magnetic susceptibility measurements yield a
rather large value of Wilson ratio ~4.47. Both suggest a ground state with
correlation effect. By applying pressure, the up-going behavior of resistivity
in lowering temperature at ambient pressure is suppressed and gradually it
becomes metallic. At a pressure of about 19.5 GPa superconductivity emerges. Up
to 36.05 GPa, a superconducting transition at about 3.6 K with a quite high
upper critical field is observed. Our discovery here provides a new platform
for investigating the relationship between correlation effect and
superconductivity. | 1710.04047v1 |
2019-05-07 | Nonsaturating magnetoresistance and nontrivial band topology of type-II Weyl semimetal NbIrTe4 | Weyl semimetals, characterized by nodal points in the bulk and Fermi arc
states on the surface, have recently attracted extensive attention due to the
potential application on low energy consumption electronic materials. In this
report, the thermodynamic and transport properties of a theoretically predicted
Weyl semimetal NbIrTe4 is measured in high magnetic fields up to 35 T and low
temperatures down to 0.4 K. Remarkably, NbIrTe4 exhibits a nonsaturating
transverse magnetoresistance which follows a power-law dependence in B.
Low-field Hall measurements reveal that hole-like carriers dominate the
transport for T $>$ 80 K, while the significant enhancement of electron
mobilities with lowering T results in a non-negligible contribution from
electron-like carriers which is responsible for the observed non-linear Hall
resistivity at low T. The Shubnikov-de Haas oscillations of the Hall
resistivity under high B give the light effective masses of charge carriers and
the nontrivial Berry phase associated with Weyl fermions. Further
first-principles calculations confirm the existence of 16 Weyl points located
at kz = 0, $\pm$0.02 and $\pm$0.2 planes in the Brillouin zone. | 1905.02455v1 |
2014-08-29 | Exotic Kondo crossover in a wide temperature region in the topological Kondo insulator SmB6 revealed by high-resolution ARPES | Temperature dependence of the electronic structure of SmB6 is studied by
high-resolution ARPES down to 1 K. We demonstrate that there is no essential
difference for the dispersions of the surface states below and above the
resistivity saturating anomaly (~ 3.5 K). Quantitative analyses of the surface
states indicate that the quasi-particle scattering rate increases linearly as a
function of temperature and binding energy, which differs from Fermi-Liquid
behavior. Most intriguingly, we observe that the hybridization between the d
and f states builds gradually over a wide temperature region (30 K < T < 110
K). The surface states appear when the hybridization starts to develop. Our
detailed temperature-dependence results give a complete interpretation of the
exotic resistivity result of SmB6, as well as the discrepancies among
experimental results concerning the temperature regions in which the
topological surface states emerge and the Kondo gap opens, and give new
insights into the exotic Kondo crossover and its relationship with the
topological surface states in the topological Kondo insulator SmB6. | 1408.7090v1 |
2018-10-08 | Correlation between scale-invariant normal state resistivity and superconductivity in an electron-doped cuprate | An understanding of the normal state in the high-temperature superconducting
cuprates is crucial to the ultimate understanding of the long-standing problem
of the origin of the superconductivity itself. This so-called strange metal
state is thought to be associated with a quantum critical point (QCP) hidden
beneath the superconductivity(1,2). In electron-doped cuprates in contrast to
hole-doped cuprates it is possible to access the normal state at very low
temperatures and low magnetic fields to study this putative QCP and to probe
the T~0 K state of these materials(3,4). We report measurements of the low
temperature normal state magnetoresistance (MR) of the n-type cuprate system
La2-xCexCuO4 (LCCO) and find that it is characterized by a linear-in-field
behavior, which follows a scaling relation with applied field and temperature,
for doping (x) above the putative QCP (x= 0.14)(5). This unconventional
behavior suggests that magnetic fields probe the same physics that gives rise
to the anomalous low-temperature linear-in-T resistivity(4). The magnitude of
the linear MR decreases as Tc decreases and goes to zero at the end of the
superconducting dome (x ~0.175) above which a conventional quadratic MR is
found. These results show that there is a strong correlation between the
quantum critical excitations of the strange metal state and the high-Tc
superconductivity. | 1810.03499v1 |
2017-04-12 | Fabrication of Simple Apparatus for Resistivity Measurement in High Temperature Range 300-620 K | A simple and low cost apparatus has been designed and built to measure the
electrical resistivity, ($\rho$), of metal and semiconductors in 300-620 K
temperature range. The present design is suitable to do measurement on
rectangular bar sample by using conventional four-probe dc method. A small
heater is made on the sample mounting copper block to achieve the desired
temperature. Heat loss from sample holder is minimize by using very low thermal
conductive insulator block. This unique design of heater and minimized heat
loss from sample platform provide uniform sample temperature and also have very
good thermal stability during the measurement. The electrical contacts of
current leads and potential probes on the sample are done by using very thin
(42 SWG) copper wires and high temperature silver paste. The use of limited
components and small heater design make present instrument very simple, light
weight, easy to sample mount, small in size, and low cost. To calibrate the
instrument pure nickel sample was used, and two other materials
La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) and LaCoO$_{3}$ (LCO) were also
characterized to demonstrate the accuracy of this set-up. $\rho$(T) behavior on
these samples were found to be in good agreement with the reported data. The
metal-insulator transition for LSMO (T$_{MI}$ = $\sim$358 K) and the
insulator-metal transition for LCO (T$_{IM}$ = $\sim$540 K) were clearly
observed and these transitions temperature were also consistent with those
reported in literature. | 1704.04122v1 |
2019-03-15 | Enhanced Tunnelling in a Hybrid of Single-Walled Carbon Nanotubes and Graphene | Transparent and conductive films (TCFs) are of great technological
importance. The high transmittance, electrical conductivity and mechanical
strength make single-walled carbon nanotubes (SWCNTs) a good candidate for
their raw material. Despite the ballistic transport in individual SWCNTs,
however, the electrical conductivity of their networks is limited by low
efficiency of charge tunneling between the tube elements. Here, we demonstrate
that the nanotube network sheet resistance at high optical transmittance is
decreased by more than 50% when fabricated on graphene and thus provides a
comparable improvement as widely adopted gold chloride ($\mathrm{AuCl_3}$)
doping. However, while Raman spectroscopy reveals substantial changes in
spectral features of doped nanotubes, no similar effect is observed in presence
of graphene. Instead, temperature dependent transport measurements indicate
that graphene substrate reduces the tunneling barrier heights while its
parallel conductivity contribution is almost negligible. Finally, we show that
combining the graphene substrate and $\mathrm{AuCl_3}$ doping, the SWCNT thin
films can exhibit sheet resistance as low as 36 $\Omega$/sq. at 90%
transmittance. | 1903.06449v1 |
2019-04-04 | Anomalous high-magnetic field electronic state of the nematic superconductors FeSe$_{1-x}$S$_x$ | Understanding superconductivity requires detailed knowledge of the normal
electronic state from which it emerges. A nematic electronic state that breaks
the rotational symmetry of the lattice can potentially promote unique
scattering relevant for superconductivity. Here, we investigate the normal
transport of superconducting FeSe$_{1-x}$S$_x$ across a nematic phase
transition using high magnetic fields up to 69 T to establish the temperature
and field-dependencies. We find that the nematic state is an anomalous
non-Fermi liquid, dominated by a linear resistivity at low temperatures that
can transform into a Fermi liquid, depending on the composition $x$ and the
impurity level. Near the nematic end point, we find an extended temperature
regime with $T^{1.5}$ resistivity. The transverse magnetoresistance inside the
nematic phase has as a $H^{1.55}$ dependence over a large magnetic field range
and it displays an unusual peak at low temperatures inside the nematic phase.
Our study reveals anomalous transport inside the nematic phase, driven by the
subtle interplay between the changes in the electronic structure of a
multi-band system and the unusual scattering processes affected by large
magnetic fields and disorder | 1904.02522v1 |
2019-08-13 | Magnetization Current Simulation of High Temperature Bulk Superconductors Using A-V-A Formulation and Iterative Algorithm Method: Critical State Model and Flux Creep Model | In this work we will introduce the A-V-A formulation based iterative
algorithm method (IAM) for simulating the magnetization current of high
temperature superconductors. This new method embedded in ANSYS can simulate the
critical state model by forcing the trapped current density to the critical
current density Jc for all meshed superconducting elements after each iterative
load step, as well as simulate the flux creep model by updating the E-J power
law based resistivity values. The simulation results of a disk-shaped ReBCO
bulk during zero field cooling (ZFC) or field cooling (FC) magnetization agree
well with the simulation results from using the H-formulation in COMSOL. The
computation time is shortened by using the A-V formulation in superconductor
areas and the A-formulation in non-superconductor areas. This iterative method
is further proved friendly for adding ferromagnetic materials into the FEA
model or taking into account the magnetic field-dependent or mechanical
strain-related critical current density of the superconductors. The influence
factors for the magnetization simulation, including the specified iterative
load steps, the initial resistivity, the ramping time and the updating
coefficient, are discussed in detail. The A-V-A formulation based IAM,
implemented in ANSYS, shows its unique advantages in adjustable computation
time, multi-frame restart analysis and easy-convergence. | 1908.04640v2 |
2015-07-17 | Study of the Effects of High-Energy Proton Beams on Escherichia Coli | Antibiotic-resistant bacterial infection becomes one of the most serious
risks to public health care today. However, discouragingly, the development of
new antibiotics has been little progressed over the last decade. There is an
urgent need of the alternative approaches to treat the antibiotic-resistant
bacteria. The novel methods, which include photothermal therapy based on gold
nano-materials and ionizing radiation such as X-rays and gamma rays, have been
reported. Studies of the effects of high-energy proton radiation on bacteria
are mainly focused on Bacillus species and its spores. The effect of proton
beams on Escherichia coli (E. coli) has been limitedly reported. The
Escherichia coli is an important biological tool to obtain the metabolic and
genetic information and also a common model microorganism for studying toxicity
and antimicrobial activity. In addition, E. coli is a common bacterium in the
intestinal tract of mammals. Herein, the morphological and physiological
changes of E. coli after proton irradiation were investigated. The diluted
solutions of the cells were used for proton beam radiation. LB agar plates were
used to count the number of colonies formed. The growing profile of the cells
was monitored by optical density at 600 nm. The morphology of the irradiated
cells was analyzed with optical microscope. Microarray analysis was performed
to examine the gene expression changes between irradiated samples and control
samples without irradiation. | 1507.04863v1 |
2020-12-02 | Incoherent transport across the strange metal regime of highly overdoped cuprates | Strange metals possess highly unconventional transport characteristics, such
as a linear-in-temperature ($T$) resistivity, an inverse Hall angle that varies
as $T^2$ and a linear-in-field ($H$) magnetoresistance. Identifying the origin
of these collective anomalies has proved profoundly challenging, even in
materials such as the hole-doped cuprates that possess a simple band structure.
The prevailing dogma is that strange metallicity in the cuprates is tied to a
quantum critical point at a doping $p*$ inside the superconducting dome. Here,
we study the high-field in-plane magnetoresistance of two superconducting
cuprate families at doping levels beyond $p*$. At all dopings, the
magnetoresistance exhibits quadrature scaling and becomes linear at high $H/T$
ratios. Moreover, its magnitude is found to be much larger than predicted by
conventional theory and insensitive to both impurity scattering and magnetic
field orientation. These observations, coupled with analysis of the zero-field
and Hall resistivities, suggest that despite having a single band, the cuprate
strange metal phase hosts two charge sectors, one containing coherent
quasiparticles, the other scale-invariant `Planckian' dissipators. | 2012.01208v2 |
2021-11-16 | Orbital Selective Kondo Effect in Heavy Fermion Superconductor UTe$_{2}$ | It has been a great challenge to explore many-body effects in heavy fermion
systems with $ab$-$initio$ approaches. We computed the electronic structure of
UTe$_{2}$ without purposive judgements, such as intentional selection of
on-site Coulomb interaction and disregarding spin-orbit coupling. We show that
U-5$f$ electrons are highly localized in the paramagnetic normal state, giving
rise to the Kondo effect. It is also found that the hybridization between
U-5$f$ and U-6$d$ predominantly in the orthorhombic $ab$-plane is responsible
for the high-temperature Kondo effect. In contrast, the hybridization between
U-5$f$ and Te-5$p$ along the $c$-axis manifests the Kondo scattering at a much
lower temperature, which could be responsible for the low-temperature upturn of
the $c$-axis resistivity. Our results show that the electron correlation in
UTe$_2$ is orbital selective, which naturally elucidates the recent
experimental observations of anomalous temperature dependence of resistivity.
Furthermore, we suggest that the Kondo effect is suppressed at high pressure
owing to weak localization of magnetic moments, which results from enhanced
U-5$f$ electron hopping. | 2111.08800v4 |
2022-07-10 | Engineering underdoped CuO$_2$ nanoribbons in nm-thick $a$-axis YBa$_2$Cu$_3$O$_{7-δ}$ films | In underdoped cuprate high $T_{\mathrm{c}}$ superconductors, various local
orders and symmetry breaking states, in addition to superconductivity, reside
in the CuO$_2$ planes. The confinement of the CuO$_2$ planes can therefore play
a fundamental role in modifying the hierarchy between the various orders and
their intertwining with superconductivity. Here we present the growth of
$a$-axis oriented YBa$_2$Cu$_3$O$_{7-\delta}$ films, spanning the whole
underdoped side of the phase diagram. In these samples, the CuO$_2$ planes are
confined by the film thickness, effectively forming unit-cell-thick
nanoribbons. The unidirectional confinement at the nanoscale enhances the
in-plane anisotropy of the films. By X-ray diffraction and resistance vs
temperature measurements, we have discovered the suppression of the
orthorhombic-to-tetragonal transition at low dopings, and a very high
anisotropy of the normal state resistance in the $b$-$c$ plane, the latter
being connected to a weak coupling between adjacent CuO$_2$ nanoribbons. These
findings show that the samples we have grown represent a novel system,
different from the bulk, where future experiments can possibly shed light on
the rich and mysterious physics occurring within the CuO$_2$ planes. | 2207.04541v3 |
2022-12-11 | Strain induced variations in transport and optical properties of SrVO$_3$: a DFT+U study | First-principles calculations based on density functional theory + Hubbard U
(DFT+U) approach have been carried out to study the strain induced variations
in the optical and transport properties of the correlated perovskite SrVO$_3$.
By virtue of its conductivity, high carrier mobility and optical transparency,
SrVO$_3$ can be used as a potential replacement of indium tin oxide (ITO) as a
transparent conductor. As strain tuning is an effective way to tune the
electron-electron correlations in correlated oxides, the epitaxial strain
induced variations in V-3d bandwidth, band center shift and band splitting at
high symmetry points (${\Gamma}$, R) in SrVO$_3$ are investigated. The
alterations in resistivity, carrier concentration, Hall coefficient and plasma
frequency with applied strain are also elucidated. Our calculations revealed
that under tensile strain, the lifting of the threefold degeneracy of
3d-t$_{2g}$ orbital and d-band narrowing reinforces a relatively less
conducting state thus limiting the $\omega_P$ to lower frequencies. On the
contrary, in case of compressive strain the d-band widening predominates
leading to an increase in carrier concentration and decrease in resistivity
enhancing the metallic state. As a result, $\omega_P$ is increased to higher
frequencies which decreases the optical transparency window. Hence, our results
and findings clearly demonstrate the interdependence between the optical and
transport properties, and provides a detailed mechanism to tune the
optoelectronic properties of SrVO$_3$ for its applications as a transparent
conducting oxide. | 2212.05449v1 |
2022-12-19 | Optical Switching in Tb/Co-Multilayer Based Nanoscale Magnetic Tunnel Junctions | Magnetic tunnel junctions (MTJs) are elementary units of magnetic memory
devices. For high-speed and low-power data storage and processing applications,
fast reversal by an ultrashort laser pulse is extremely important. We
demonstrate optical switching of Tb/Comultilayer-based nanoscale MTJs by
combining optical writing and electrical read-out methods. A 90 fs-long laser
pulse switches the magnetization of the storage layer (SL). The change in
magnetoresistance between the SL and a reference layer (RL) is probed
electrically across the tunnel barrier. Single-shot switching is demonstrated
by varying the cell diameter from 300 nm to 20 nm. The anisotropy,
magnetostatic coupling, and switching probability exhibit cell-size dependence.
By suitable association of laser fluence and magnetic field, successive
commutation between high-resistance and low-resistance states is achieved. The
switching dynamics in a continuous film is probed with the magneto-optical Kerr
effect technique. Our experimental findings provide strong support for the
growing interest in ultrafast spintronic devices. | 2212.10361v1 |
2023-02-02 | Controlling the Skyrmion Density and Size for Quantized Convolutional Neural Networks | Skyrmion devices show energy efficient and high integration data storage and
computing capabilities. Herein, we present the results of experimental and
micromagnetic investigations of the creation and stability of magnetic
skyrmions in the Ta/IrMn/CoFeB/MgO thin film system. We investigate the
magnetic-field dependence of the skyrmion density and size using polar magneto
optical Kerr effect MOKE microscopy supported by a micromagnetic study. The
evolution of the topological charge with time under a magnetic field is
investigated, and the transformation dynamics are explained. Furthermore,
considering the voltage control of these skyrmion devices, we evaluate the
dependence of the skyrmion size and density on the Dzyaloshinskii Moriya
interaction and the magnetic anisotropy. We furthermore propose a skyrmion
based synaptic device based on the results of the MOKE and micromagnetic
investigations. We demonstrate the spin-orbit torque controlled discrete
topological resistance states with high linearity and uniformity in the device.
The discrete nature of the topological resistance makes it a good candidate to
realize hardware implementation of weight quantization in a quantized neural
network (QNN). The neural network is trained and tested on the CIFAR10 dataset,
where the devices act as synapses to achieve a recognition accuracy of 87%,
which is comparable to the result of ideal software-based methods. | 2302.01390v1 |
2023-03-04 | High pressure ferroelectric-like semi-metallic state in $Eu-$doped $BaTiO_3$ | We have conducted a detailed high-pressure (HP) investigation on $Eu-$doped
$BaTiO_3$ using angle-resolved x-ray diffraction, Raman spectroscopy,
dielectric permittivity and dc resistance measurements. The x-ray diffraction
data analysis shows a pressure-induced structural phase transition from the
ambient tetragonal to the mixed cubic and tetragonal phase above 1.4 GPa. The
tetragonality of the sample due to the internal deformation of the $TiO_6$
octahedra caused by charge difference from Eu doping cannot be lifted upon by
pressure. Softening, weakening, and disappearance of low-frequency Raman modes
indicate ferroelectric tetragonal to the paraelectric cubic phase transition.
But the pressure-induced increase in the intensity of [E(LO), A1(LO)] and the
octahedral breathing modes indicate the local structural inhomogeneity remains
in the crystal and is responsible for spontaneous polarization in the sample.
Low-frequency electronic scattering response suggests the pressure-induced
carrier delocalization, leading to a semi-metallic state in the system. Our HP
dielectric constant and dc resistance data can be explained by the presence of
pressure-induced localized clusters of microscopic ferroelectric ordering. Our
results suggest HP phase coexistence leads to a ferroelectric-like
semi-metallic state in $Eu-$doped $BaTiO_3$ under the extreme quantum limit. | 2303.02329v2 |
2023-09-21 | High-Conductance, Ohmic-like HfZrO$_4$ Ferroelectric Memristor | The persistent and switchable polarization of ferroelectric materials based
on HfO$_2$-based ferroelectric compounds, compatible with large-scale
integration, are attractive synaptic elements for neuromorphic computing. To
achieve a record current density of 0.01 A/cm$^2$ (at a read voltage of 80 mV)
as well as ideal memristive behavior (linear current-voltage relation and
analog resistive switching), devices based on an ultra-thin (2.7 nm thick),
polycrystalline HfZrO$_4$ ferroelectric layer are fabricated by Atomic Layer
Deposition. The use of a semiconducting oxide interlayer (WO$_{x<3}$) at one of
the interfaces, induces an asymmetric energy profile upon ferroelectric
polarization reversal and thus the long-term potentiation / depression
(conductance increase / decrease) of interest. Moreover, it favors the stable
retention of both the low and the high resistive states. Thanks to the low
operating voltage (<3.5 V), programming requires less than 10${^-12}$ J for 20
ns long pulses. Remarkably, the memristors show no wake-up or fatigue effect. | 2309.12070v1 |
2023-12-27 | Inkjet-Printed High-Yield, Reconfigurable, and Recyclable Memristors on Paper | Reconfigurable memristors featuring neural and synaptic functions hold great
potential for neuromorphic circuits by simplifying system architecture, cutting
power consumption, and boosting computational efficiency. Their additive
manufacturing on sustainable substrates offers unique advantages for future
electronics, including low environmental impact. Here, exploiting
structure-property relationship of MoS2 nanoflake-based resistive layer, we
present paper-based, inkjet-printed, reconfigurable memristors. With >90% yield
from a 16x65 device array, our memristors demonstrate robust resistive
switching, with $>10^5$ ON-OFF ratio and <0.5 V operation in non-volatile
state. Through modulation of compliance current, the devices transition into
volatile state, with only 50 pW switching power consumption, rivalling
state-of-the-art metal oxide-based counterparts. We show device recyclability
and stable, reconfigurable operation following disassembly, material collection
and re-fabrication. We further demonstrate synaptic plasticity and neuronal
leaky integrate-and-fire functionality, with disposable applications in smart
packaging and simulated medical image diagnostics. Our work shows a sustainable
pathway towards printable, high-yield, reconfigurable neuromorphic devices,
with minimal environmental footprint. | 2312.16501v1 |
2018-06-20 | Linear-$T$ resistivity at high temperature | The linear-$T$ resistivity is one of the characteristic and universal
properties of strange metals. There have been many progress in understanding it
from holographic perspective (gauge/gravity duality). In most holographic
models, the linear-$T$ resistivity is explained by the property of the infrared
geometry and valid at low temperature limit. On the other hand, experimentally,
the linear-$T$ resistivity is observed in a large range of temperatures, up to
room temperature. By using holographic models related to the Gubser-Rocha
model, we investigate how much the linear-$T$ resistivity is robust at higher
temperature above the superconducting phase transition temperature. We find
that strong momentum relaxation plays an important role to have a robust
linear-$T$ resistivity up to high temperature. | 1806.07739v2 |
2018-07-18 | Multi-band effects in in-plane resistivity anisotropy of strain-detwinned disordered Ba(Fe$_{1-x}$Ru$_{x}$)$_{2}$As$_{2}$ | In-plane resistivity anisotropy was measured in strain-detwinned as-grown and
partially annealed samples of isovalently-substituted
$\mathrm{Ba(Fe_{1-x}Ru_{x})_{2}As_{2}}$ ($0<x \leq 0.125$) and the results were
contrasted with previous reports on anneal samples with low residual
resistivity. In samples with high residual resistivity, detwinned with
application of strain, the difference of the two components of in-plane
resistivity in the orthorhombic phase, $\rho_a -\rho_b$, was found to obey
Matthiessen rule irrespective of sample composition, which is in stark contrast
with observations on annealed samples. Our findings are consistent with
two-band transport model in which contribution from high mobility carriers of
small pockets of the Fermi surface has negligible anisotropy of residual
resistivity and is eliminated by disorder. Our finding suggests that
magnetic/nematic order has dramatically different effect on different parts of
the Fermi surface. It predominantly affects inelastic scattering for small
pocket high mobility carriers and elastic impurity scattering for larger sheets
of the Fermi surface. | 1807.07130v1 |
2022-07-21 | Energy-scale competition in the Hall resistivity of a strange metal | Anomalous transport behavior -- both longitudinal and Hall -- is the defining
characteristic of the strange-metal state of High-Tc cuprates. The temperature,
frequency, and magnetic field dependence of the resistivity is understood
within strange metal phenomenology as resulting from energy-scale competition
to set the inelastic relaxation rate. The anomalously strong temperature
dependence of the Hall coefficient, however, is at odds with this
phenomenology. Here we report measurements of the Hall resistivity in the
strange metal state of cuprates over a broad range of magnetic fields and
temperatures. The observed field and temperature dependent Hall resistivity at
very high magnetic fields reveals a distinct high-field regime which is
controlled by energy-scale competition. This extends the strange metal
phenomenology in the cuprates to include the Hall resistivity and suggests, in
particular, that the direct effect of magnetic field on the relaxation dynamics
of quantum fluctuations may be at least partially responsible for the anomalous
Hall resistivity of the strange metal state. | 2207.10244v1 |
2022-04-26 | Flexibility of Fluorinated Graphene-Based Materials | The resistivity of different films and structures containing fluorinated
graphene (FG) flakes and chemical vapor deposition (CVD) grown graphene of
various fluorination degrees under tensile and compressive strains due to
bending deformations was studied. Graphene and multilayer graphene films grown
by means of the CVD method were transferred onto the flexible substrate by
laminating and were subjected to fluorination. They demonstrated a weak
fluorination degree (F/C lower 20%). Compressive strains led to a strong
(one-two orders of magnitude) decrease in the resistivity in both cases, which
was most likely connected with the formation of additional conductive paths
through fluorinated graphene. Tensile strain up to 3% caused by the bending of
both types of CVD-grown FG led to a constant value of the resistivity or to an
irreversible increase in the resistivity under repeated strain cycles. In the
case of the structures with the FG thin film printed on polyvinyl alcohol, a
stable bipolar resistive switching was observed up to 6.5% of the tensile
strain (bending radius was 2 mm). The excellent performance of the crossbar
memristor structures under tensile strain shows that the FG films and
structures created from suspension are especially promising for flexible
electronics. | 2204.12596v1 |
2021-03-18 | Topological Semimetals for Scaled Back-End-Of-Line Interconnect Beyond Cu | The resistance bottleneck in metal-interconnect scaling calls for new
interconnect materials. This paper explores topological semimetals as a
potential solution. After reviewing the desirable properties of topological
semimetals for back-end-of-line (BEOL) interconnects, we use CoSi as an example
to demonstrate the decreasing resistance-area product with scaling and provide
material-search guidelines. | 2103.10505v1 |
2021-08-31 | Magnetoresistance and Scaling Laws in Type-II Weyl Semimetal WP_2 | Topological materials with extremely large magnetoresistance exhibit a
prognostic feature of resistivity turn-on behaviour. This occurs when the
temperature dependence of resistivity changes from metallic to semiconducting
characteristics on application of external magnetic field above a threshold
value. Here, we study the magneto-transport properties of type-II Weyl
Semimetal WP2. We find that semi-classical theories of magnetoresistance are
consistent with our data without the need to invoke topological surface states.
Our findings in this work provides an alternative basis to understand the
temperature dependence of magnetoresistance in topological materials. | 2108.13981v1 |
2017-11-29 | Coexistence of superconductivity and charge-density wave in the quasi-one-dimensional material HfTe3 | We present the first experimental evidence for metallicity, superconductivity
(SC) and the co-existence of charge density waves (CDW) in the
quasi-one-dimensional material HfTe3. The existence of such phenomena is a
typical characteristic of the transition metal chalcogenides however, without
the application of hydrostatic pressure/chemical doping, it is rare for a
material to exhibit the co-existence of both states. Materials such as HfTe3
can therefore provide us with a unique insight into the relationship between
these multiple ordered states. By improving on the original synthesis
conditions, we have successfully synthesised single phase HfTe3 and confirmed
the resultant structure by performing Rietveld refinement. Using low
temperature resistivity measurements, we provide the first experimental
evidence of SC at ~1.4 K as well as a resistive anomaly indicative of a CDW
formation at ~82 K. By the application of hydrostatic-pressure, the resistivity
anomaly shifts to higher temperature. The results show that HfTe3 is a
promising new material to help study the relationship between SC and CDW. | 1711.10628v1 |
1995-03-08 | Model of C-Axis Resistivity of High-$\Tc$ Cuprates | We propose a simple model which accounts for the major features and
systematics of experiments on the $c$-axis resistivity, $\rho_c$, for $\lsco$,
$\ybco$ and $\bsco $. We argue that the $c$-axis resistivity can be separated
into contributions from in-plane dephasing and the $c$-axis ``barrier''
scattering processes, with the low temperature semiconductor-like behavior of
$\rho_c$ arising from the suppression of the in-plane density of states
measured by in-plane magnetic Knight shift experiments. We report on
predictions for $\rho_c$ in impurity-doped $\ybco$ materials. | 9503044v1 |
1998-09-29 | Point contact spectroscopy and temperature dependence of resistivity of metallic sodium tungsten bronzes -Role of optical phonons | In this paper we report the results of electrical resistivity (1.5K < T
<300K) and point contact spectroscopy (PCS) measurements on single crystals of
metallic sodium tungsten bronze with varying sodium content. We have shown that
the electron-phonon coupling function as measured through PCS can explain
quantitatively the large temperature dependence of resistivity $\rho$ seen in
these materials over the entire temperature range. The electron-phonon coupling
function shows predominatly large peaks for phonon frequency range of 30meV <
$\omega$ 100meV which match well with the calculated optical phonon modes for
WO$_6$ octahedra. The integrated electron-phonon coupling constant $\lambda$
from this data is $\approx$ 0.25-0.45. | 9809393v1 |
1998-11-24 | Ac transport studies in polymers by a resistor network and transfer matrix approaches: application to polyaniline | A statistical model of resistor network is proposed to describe a polymer
structure and to simulate the real and imaginary components of its ac
resistivity. It takes into account the polydispersiveness of the material as
well as intrachain and interchain charge transport processes. By the
application of a transfer matrix technique, it reproduces ac resistivity
measurements carried out with polyaniline films in different doping degrees and
at different temperatures. Our results indicate that interchain processes
govern the resistivity behavior in the low frequency region while, for higher
frequencies, intrachain mechanisms are dominant. | 9811335v1 |
1999-02-22 | La substitution induced linear temperature dependence of electrical resistivity and Kondo behavior in the alloys, Ce_{2-x}La_{x}CoSi_{3} | The results of electrical resistivity, heat capacity and magnetic
susceptibility behavior of new class of alloys, Ce_{2-x}La_{x}CoSi_{3}, are
reported. The x= 0.0 alloy is mixed valent and La substitution for Ce (x= 0.25)
induces linear temperature dependence of resistivity at low temperatures, an
observation of relevance to the topic of non-Fermi liquid behavior. The
modifications of Kondo effect for all the alloys are also presented. | 9902298v1 |
1999-04-06 | Conductance of Distorted Carbon Nanotubes | We have calculated the effects of structural distortions of armchair carbon
nanotubes on their electrical transport properties. We found that the bending
of the nanotubes decreases their transmission function in certain energy ranges
and leads to an increased electrical resistance. Electronic structure
calculations show that these energy ranges contain localized states with
significant $\sigma$-$\pi$ hybridization resulting from the increased curvature
produced by bending. Our calculations of the contact resistance show that the
large contact resistances observed for SWNTs are likely due to the weak
coupling of the NT to the metal in side bonded NT-metal configurations. | 9904083v1 |
1999-07-31 | Characterisation, Raman, Magnetic and Resistivity measurements in polycrystalline samples of LaMnO3 doped with Cd | We report a study of polycrystalline samples of the family La1-xCdxMnO3+dwith
different percentage of Mn4+ ions. X-rays diffraction, Iodometric titration,
Raman, Magnetic and Electrical Resistivity measurements provide a general
characterisation of the physical properties. Results are qualitatively similar
to the ones found in Ca doped manganese perovskites.
Key words: Cd, manganese perovskites, magnetoresistance, Raman, magnetic,
resistivity | 9908006v2 |
2000-05-19 | Interface resistance of disordered magnetic multilayers | We study the effect of interface disorder on the spin-dependent interface
resistances of Co/Cu, Fe/Cr and Au/Ag multilayers using a newly developed
method for calculating transmission matrices from first-principles. The
efficient implementation using tight-binding linear-muffin-tin orbitals allows
us to model interface disorder using large lateral supercells whereby specular
and diffuse scattering are treated on an equal footing. Without introducing any
free parameters, quantitative agreement with experiment is obtained. We predict
that disorder {\it reduces} the majority-spin interface resistance of
Fe/Cr(100) multilayers by a factor 3. | 0005314v1 |
2000-09-04 | Magnon scattering processes and low temperature resistivity in CMR manganites | Low temperature resistivity of CMR manganites is investigated. At the ground
state, conduction electrons are perfectly spin polarized, which is called
half-metallic. From one-magnon scattering processes, it is discussed that the
resistivity of a half metal as a function of temperature scales as rho(T) -
rho(0) propto T^3. We take (Nd,Tb,Sr)MnO_3 as an example to compare theory and
experiments. The result is in a good agreement. | 0009036v1 |
2000-10-26 | Magnetic-history-dependent nanostructural and resistivity changes in Pr0.5Ca0.5Mn0.98Cr0.02O3 | We show that nanostructure and resistivity of Pr0.5Ca0.5Mn0.98Cr0.02O3 are
sensitive to whether the sample is zero-field-cooled (ZFC) of field-cooled (FC)
either in the 'self magnetic field (H = 2 T)' of the electron microscope or
under the external magnetic field of 2 T. FC resistivity at H = 2 T is lower
than ZFC values below 140 K. The average value of the chare-orbital modulation
vector (q = 0.44) of the FC crystallites is lower than that of the ZFC
cystallites (q = 0.48) and the FC crystallites exhibit numerous defects like
discommensuration, dislocations and regios with loss of superstructures
compared to the ZFC crystallites. | 0010427v1 |
2000-10-30 | Theory of electrical spin injection: Tunnel contacts as a solution of the conductivity mismatch problem | Theory of electrical spin injection from a ferromagnetic (FM) metal into a
normal (N) conductor is presented. We show that tunnel contacts (T) can
dramatically increase spin injection and solve the problem of the mismatch in
the conductivities of a FM metal and a semiconductor microstructure. We also
present explicit expressions for the spin-valve resistance of FM-T-N- and
FM-T-N-T-FM-junctions with tunnel contacts at the interfaces and show that the
resistance includes both positive and negative contributions (Kapitza
resistance and injection conductivity, respectively). | 0010473v1 |
2001-11-09 | A common origin for the resistivity of Cd$_2$Re$_2$O$_7$, the cuprates, and Sr$_2$RuO$_4$? | We propose an explanation for the temperature dependence of the resistivity
of Cd$_2$Re$_2$O$_7$, including the regime above the structural phase
transition at $T$=200 $^o$K. The mechanism involved relies on the existence of
a strong van Hove singularity close to the Fermi surface, which is evidenced by
relevant band structure calculations. The same mechanism has successfully
described the $T$-linear resistivity of the cuprates and Sr$_2$RuO$_4$, and the
one-particle scattering rate in the former materials, as corroborated by recent
experiments. We describe a few predictions for Cd$_2$Re$_2$O$_7$ and
Cd$_2$Os$_2$O$_7$. | 0111166v1 |
2002-04-09 | Electrical transport properties of bulk MgB2 materials synthesized by the electrolysis on fused mixtures of MgCl2, NaCl, KCl and MgB2O4 | Electrolysis was carried out on fused mixtures of MgCl2, NaCl, KCl and MgB2O4
under an Ar flow at 600C. Electrical resistivity measurements for the grown
deposits show an onset of superconducting transition at 37 K in the absence of
applied magnetic field. The resistivity decreases down to zero below 32 K. From
an applied-field dependence of resistivity, an upper critical field and a
coherence length were calculated to be 9.7 T and 5.9 nm at 0 K, respectively. | 0204208v1 |
2002-05-22 | Scattering theory of interface resistance in magnetic multilayers | The scattering theory of transport has to be applied with care in a diffuse
environment. Here we discuss how the scattering matrices of heterointerfaces
can be used to compute interface resistances of dirty magnetic multilayers.
First principles calculations of these interface resistances agree well with
experiments in the CPP (current perpendicular to the interface plane)
configuration. | 0205452v1 |
2002-09-05 | Magnetoresistance and Hall Effect in the Ferromagnetic Semiconductor GaMnAs | The resistivity, temperature, and magnetic field dependence of the anomalous
Hall effect in a series of metallic Ga1-xMnxAs thin films with 0.015=<x=<0.08
is presented. A quadratic dependence of the anomalous Hall resistance on the
resistivity is observed, with a magnitude which is in agreement with Berry
phase theories of the anomalous Hall effect in dilute magnetic semiconductors. | 0209123v1 |
2003-04-06 | Microwave Residual Surface Resistance of Superconductors | Two distinct models account for the microwave residual surface resistance of
superconducting cavities with equally good agreement with the measured
temperature and frequency dependence. In presenting his phonon-generation
model, Passow claimed that Rabinowitz' fluxoid power-loss model of residual
resistance does not fit the experimental data, whereas his does. In fact, the
two models have essentially the same temperature and frequency dependence.
Furthermore, Passow's phonon-generation model cannot explain the observed
sensitivity to details of sample preparation and history, while the fluxoid
model can. | 0304139v1 |
2004-02-17 | Peculiarities of the resistive transition in fractal superconducting structures | The influence of fractal clusters of a normal phase on the current-voltage
characteristics of a percolation superconductor in the region of a resistive
transition has been studied. The clusters represent the aggregates of columnar
defects, which give rise to a correlated microscopic disorder in the system.
Dependencies of the static and dynamic resistance on the transport current are
obtained for an arbitrary fractal dimension of the cluster boundaries. It is
revealed that a mixed state of the vortex glass type is realized in the
superconducting system involved. | 0402437v2 |
2005-04-08 | Temperature dependent asymmetry of the nonlocal spin-injection resistance: evidence for spin non-conserving interface scattering | We report nonlocal spin injection and detection experiments on mesoscopic
Co-Al2O3-Cu spin valves. We have observed a temperature dependent asymmetry in
the nonlocal resistance between parallel and antiparallel configurations of the
magnetic injector and detector. This strongly supports the existence of a
nonequilibrium resistance that depends on the relative orientation of the
detector magnetization and the nonequilibrium magnetization in the normal metal
providing evidence for increasing interface spin scattering with temperature. | 0504201v2 |
2005-09-29 | Charge-transfer polaron induced negative differential resistance and giant magnetoresistance in organic spintronics: A Su-Schrieffer-Heeger model study | Combining the Su-Schrieffer-Heeger model and the non-equilibrium Green's
function formalism, we investigate the negative differential resistance effect
in organic spintronics at low temperature and interprete it with a self-doping
picture. A giant negative magnetoresistance exceeding 300% is theoretically
predicted as the results of the negative differential resistance effects. | 0509761v2 |
2005-12-30 | A Tunable Anomalous Hall Effect in a Non-Ferromagnetic System | We measure the low-field Hall resistivity of a magnetically-doped
two-dimensional electron gas as a function of temperature and
electrically-gated carrier density. Comparing these results with the carrier
density extracted from Shubnikov-de Haas oscillations reveals an excess Hall
resistivity that increases with decreasing temperature. This excess Hall
resistivity qualitatively tracks the paramagnetic polarization of the sample,
in analogy to the ferromagnetic anomalous Hall effect. The data are consistent
with skew-scattering of carriers by disorder near the crossover to
localization. | 0512730v1 |
2006-01-30 | Magnetic Moment Softening and Domain Wall Resistance in Ni Nanowires | Magnetic moments in atomic scale domain walls formed in nanoconstrictions and
nanowires are softened which affects dramatically the domain wall resistance.
We perform ab initio calculations of the electronic structure and conductance
of atomic-size Ni nanowires with domain walls only a few atomic lattice
constants wide. We show that the hybridization between noncollinear spin states
leads to a reduction of the magnetic moments in the domain wall. This magnetic
moment softening strongly enhances the domain wall resistance due to scattering
produced by the local perturbation of the electronic potential. | 0601662v1 |
2006-08-10 | Friedel oscillations, impurity scattering and temperature dependence of resistivity in graphene | We show that Friedel oscillations (FO) in grapehene are strongly affected by
the chirality of electrons in this material. In particular, the FO of the
charge density around an impurity show a faster, $1/r^3$, decay than in
conventional 2D electron systems and do not contribute to a linear
temperature-dependent correction to the resistivity. In contrast, the FO of the
exchange field which surrounds atomically sharp defects breaking the hexagonal
symmetry of the honeycomb lattice lead to a negative linear T dependence of the
resistivity. | 0608228v2 |
2006-10-19 | Magneto-resistive memory in ferromagnetic (Ga,Mn)As nanostructures | We show a novel magneto-resistive effect that appears in lithographically
shaped, three-arm nanostructure, fabricated from ferromagnetic (Ga,Mn)As
layers. The effect, related to a rearrangement of magnetic domain walls between
different pairs of arms in the structure, reveals as a dependence of zero-field
resistance on the direction of previously applied magnetic field. This effect
could allow designing devices with unique switching and memory properties. | 0610535v1 |
2006-11-06 | Unusual field and temperature dependence of Hall effect in graphene | We calculate the classic Hall conductivity and mobility of the undoped and
doped (or in the gate voltage) graphene as a function of temperature, magnetic
field, and carrier concentration. Carrier collisions with defects and acoustic
phonons are taken into account. The Hall resistivity varies almost linearly
with temperature. The magnetic field dependence of resistivity and mobility is
anomalous in weak magnetic fields. There is the square root contribution from
the field in the resistivity. The Hall mobility diverges logarithmically with
the field for low doping. | 0611147v2 |
2006-11-30 | Anisotropic magnetoresistance contribution to measured domain wall resistances of in-plane magnetised (Ga,Mn)As | We demonstrate the presence of an important anisotropic magnetoresistance
contribution to the domain wall resistance recently measured in thin-film
(Ga,Mn)As with in-plane magnetic anisotropy. Analytic results for simple domain
wall orientations supplemented by numerical results for more general cases show
this previously omitted contribution can largely explain the observed negative
resistance. | 0611780v1 |
2006-12-16 | Transmission Line Impedance of Carbon Nanotube Thin Films for Chemical Sensing | We measure the resistance and frequency-dependent gate capacitance of carbon
nanotube (CNT) thin films in ambient, vacuum, and under low-pressure (10E-6
torr) analyte environments. We model the CNT film as an RC transmission line
and show that changes in the measured capacitance as a function of gate bias
and analyte pressure are consistent with changes in the transmission line
impedance due to changes in the CNT film resistivity alone; the electrostatic
gate capacitance of the CNT film does not depend on gate voltage or chemical
analyte adsorption. However, the CNT film resistance is enormously sensitive to
low pressure analyte exposure. | 0612432v1 |
2007-03-01 | Bias-dependent Contact Resistance in Rubrene Single-Crystal Field-Effect Transistors | We report a systematic study of the bias-dependent contact resistance in
rubrene single-crystal field-effect transistors with Ni, Co, Cu, Au, and Pt
electrodes. We show that the reproducibility in the values of contact
resistance strongly depends on the metal, ranging from a factor of two for Ni
to more than three orders of magnitude for Au. Surprisingly, FETs with Ni, Co,
and Cu contacts exhibits an unexpected reproducibility of the bias-dependent
differential conductance of the contacts, once this has been normalized to the
value measured at zero bias. This reproducibility may enable the study of
microscopic carrier injection processes into organic semiconductors. | 0703029v1 |
2004-02-14 | Theory of resistor networks: The two-point resistance | The resistance between arbitrary two nodes in a resistor network is obtained
in terms of the eigenvalues and eigenfunctions of the Laplacian matrix
associated with the network. Explicit formulas for two-point resistances are
deduced for regular lattices in one, two, and three dimensions under various
boundary conditions including that of a Moebius strip and a Klein bottle. The
emphasis is on lattices of finite sizes. We also deduce summation and product
identities which can be used to analyze large-size expansions of two-and-higher
dimensional lattices. | 0402038v2 |
2004-12-17 | Introductory physics: The new scholasticism | Most introductory physics textbooks neglect air resistance in situations
where an astute student can observe that it dominates the dynamics. We give
examples from many books. Using dimensional analysis we discuss how to estimate
the relative importance of air resistance and gravity. The discussion can be
used to mitigate the baleful influence of these textbooks. Incorrectly
neglecting air resistance is one of their many unphysical teachings. Shouldn't
a physics textbook teach correct physics? | 0412107v2 |
2008-10-22 | Scaling behaviors of RESET voltages and currents in unipolar resistance switching | Unipolar switching phenomena have attracted a great deal of recent attention,
but the wide distributions of switching voltages still pose major obstacles for
scientific advancement and practical applications. Using NiO capacitors, we
investigated the distributions of the RESET voltage and current. We found that
they scaled with the resistance value Ro in the low resistance state, and that
the scaling exponents varied at Ro = 30 Ohm. We explain these intriguing
scaling behaviors and their crossovers by analogy with percolation theory. We
show that the connectivity of conducting filaments plays a crucial role in the
RESET process. | 0810.4043v1 |
2008-10-29 | FeTe as a candidate material for new iron-based superconductor | Tetragonal FeSe is a superconductor with a transition temperature Tc of 8 K
and shows a huge enhancement of Tc with applying pressure. Tetragonal FeTe has
a structure very analogous to superconducting FeSe, but does not show
superconducting transition. We investigated the pressure effect of resistivity
on FeTe. The resistivity at room temperature decreased with increasing
pressure. An anomaly in resistivity around 80 K shifted towards a lower
temperature with increasing pressure. | 0810.5191v1 |
2008-11-27 | Electrical resistance of Ni nanowires (diameter greater than or equal to 20 nm) near the Curie Temperatures | In this letter we report electrical transport measurements on nickel
nanowires of diameters down to 20 nm in the region close to its
paramagnetic-ferromagnetic transition temperature T_C (reduced temperature|t|
less than or equal to 0.001). The data analysis done in the frame work of
critical behavior of resistance near TC shows that the critical behavior
persists even down to the lowest diameter wire of 20 nm. However, there is a
suppression of the critical behavior of the resistivity as measured by the
critical exponents and the parameters quantifying the anomaly. The spin system
shows approach to a quasi one-dimensional spin system. | 0811.4544v1 |
2009-01-04 | Current Oscillations and Negative Resistances in Crossed Carbon Nanotubes Suspended Over a Dielectric Trench | An oscillatory dependence of the drain current on the drain voltage is found
in a nanostructure consisting of two crossing semiconductor carbon nanotubes
that are suspended over a dielectric trench, which is backed by a doped silicon
substrate that acts as a gate. Alternating positive and negative differential
resistance regions are generated as a function of the drain source values and
can be slightly shifted by the gate voltage. Moreover, the negative
differential resistance is retrieved in a large bandwidth, of up to 100 MHz,
when the structure is excited with ac signals. | 0901.0363v1 |
2009-01-05 | Contact resistance in graphene-based devices | We report a systematic study of the contact resistance present at the
interface between a metal (Ti) and graphene layers of different, known
thickness. By comparing devices fabricated on 11 graphene flakes we demonstrate
that the contact resistance is quantitatively the same for single-, bi-, and
tri-layer graphene ($\sim800 \pm 200 \Omega \mu m$), and is in all cases
independent of gate voltage and temperature. We argue that the observed
behavior is due to charge transfer from the metal, causing the Fermi level in
the graphene region under the contacts to shift far away from the charge
neutrality point. | 0901.0485v1 |
2009-03-09 | Predictability of reset switching voltages in unipolar resistance switching | In unipolar resistance switching of NiO capacitors, Joule heating in the
conducting channels should cause a strong nonlinearity in the low resistance
state current-voltage (I-V) curves. Due to the percolating nature of the
conducting channels, the reset current IR, can be scaled to the nonlinear
coefficient Bo of the I-V curves. This scaling relationship can be used to
predict reset voltages, independent of NiO capacitor size; it can also be
applied to TiO2 and FeOy capacitors. Using this relation, we developed an error
correction scheme to provide a clear window for separating reset and set
voltages in memory operations. | 0903.1490v1 |
2009-03-17 | Electronic transport in ferromagnetic conductors with inhomogeneous magnetic order parameter -- domain-wall resistance | We microscopically derive transport equations for the conduction electrons in
ferromagnetic materials with an inhomogeneous magnetization profile. Our
quantum kinetic approach includes elastic scattering and anisotropic spin-flip
scattering at magnetic impurities. In the diffusive limit, we calculate the
resistance through a domain wall and find that the domain-wall resistance can
be positive or negative. In the limit of long domain walls we derive analytical
expressions and compare them with existing works, which used less general
models or different theoretical frameworks. | 0903.3033v2 |
2009-06-02 | Effect of annealing on the magnetic and superconducting properties of single-crystalline UCoGe | Single-crystals of the new ferromagnetic superconductor UCoGe have been
grown. The quality of as-grown samples can be significantly improved by a
heat-treatment procedure, which increases the residual resistance ratio (RRR)
from ~5 to ~30. Magnetization and resistivity measurements show the annealed
samples have a sharp ferromagnetic transition with a Curie temperature T_C is
2.8 K. The ordered moment of 0.06 mu_B is directed along the orthorhombic
c-axis. Superconductivity is found below a resistive transition temperature T_s
= 0.65 K. | 0906.0497v1 |
2009-07-21 | Memristive switching of MgO based magnetic tunnel junctions | Here we demonstrate that both, tunnel magneto resistance (TMR) and resistive
switching (RS), can be observed simultaneously in nano-scale magnetic tunnel
junctions. The devices show bipolar RS of 6 % and TMR ratios of about 100 %.
For each magnetic state, multiple resistive sates are created depending on the
bias history which provides a method for multi-bit data storage and logic. The
electronic transport measurements are discussed in the framework of a
memristive system. Differently prepared MgO barriers are compared to gain
insight into the switching mechanism. | 0907.3684v1 |
2010-03-03 | In-situ direct visualization of irradiated e-beam patterns on unprocessed resists using atomic force microscopy | We introduce an in-situ characterization method of resists used for e-beam
lithography. The technique is based on the application of an atomic force
microscope which is directly mounted below the cathode of an electron-beam
lithography system. We demonstrate that patterns irradiated by the e-beam can
be efficiently visualized and analyzed in surface topography directly after the
e-beam exposure. This in-situ analysis takes place without any development or
baking steps, and gives access to the chemical (or latent) image of the
irradiated resist. | 1003.0796v1 |
2010-06-06 | Spin Resistivity in Frustrated Antiferromagnets | In this paper we study the spin transport in frustrated antiferromagnetic FCC
films by Monte Carlo simulation. In the case of Ising spin model, we show that
the spin resistivity versus temperature exhibits a discontinuity at the phase
transition temperature: an upward jump or a downward fall, depending on how
many parallel and antiparallel localized spins interacting with a given
itinerant spin. The surface effects as well as the difference of two degenerate
states on the resistivity are analyzed. Comparison with non frustrated
antiferromagnets is shown to highlight the frustration effect. We also show and
discuss the results of the Heisenberg spin model on the same lattice. | 1006.1081v2 |
2010-07-20 | First-principles studies on electrical resistivity of iron under pressure | We investigate the temperature and pressure dependences of the electrical
resistivity for bcc and hcp Fe using the low-order variational approximation
and theoretical transport spectral functions calculated from first principles
linear response linear-muffin-tin-orbital method in the generalized-gradient
approximation. The calculated values are in close agreement with available
experimental data, and show strong increase with temperature and decrease with
pressure. We also discuss the behavior of the electrical resistivity for the
bcc -> hcp phase transition. | 1007.3423v1 |
2010-08-11 | Contact resistivity and current flow path at metal/graphene contact | The contact properties between metal and graphene were examined. The
electrical measurement on a multiprobe device with different contact areas
revealed that the current flow preferentially entered graphene at the edge of
the contact metal. The analysis using the cross-bridge Kelvin structure (CBK)
suggested that a transition from the edge conduction to area conduction
occurred for a contact length shorter than the transfer length of ~1 micron.
The contact resistivity for Ni was measured as ~5*10-6 Ohmcm2 using the CBK. A
simple calculation suggests that a contact resistivity less than 10-9 Ohmcm2 is
required for miniaturized graphene field effect transistors. | 1008.1826v1 |
2010-12-05 | Snake States in Graphene p-n Junctions | We investigate transport in locally-gated graphene devices, where carriers
are injected and collected along, rather than across, the gate edge. Tuning
densities into the p-n regime significantly reduces resistance along the p-n
interface, while resistance across the interface increases. This provides an
experimental signature of snake states, which zig-zag along the p-n interface
and remain stable as applied perpendicular magnetic field approaches zero.
Snake states appear as a peak in transverse resistance measured along the p-n
interface. The generic role of snake states disordered graphene is also
discussed. | 1012.0959v2 |
2011-08-18 | Non-volatile Complementary Resistive Switch-based Content Addressable Memory | This paper presents a novel resistive-only Binary and Ternary Content
Addressable Memory (B/TCAM) cell that consists of two Complementary Resistive
Switches (CRSs). The operation of such a cell relies on a logic$\rightarrow$ON
state transition that enables this novel CRS application. | 1108.3716v2 |
2012-11-16 | Universal scaling of resistivity in bilayer graphene | We report the temperature dependent electrical transport properties of gated
bilayer graphene devices. We see a clear evidence of insulating behavior due to
electron-hole charge puddles. The electrical resistivity increases while the
mobility decreases with decreasing temperature, a characteristic due to carrier
inhomogeneity in graphene. The theoretical fittings using an empirical formula
of single electron tunneling indicate that electrical resistivity follows a
universal curve with a scaling parameter. The scaling parameter is determined
to be a measure of the fluctuations in the electron-hole puddle distribution. | 1211.3807v1 |
2013-04-15 | Many Topological Insulators Fail the Surface Conduction Test | In this report, we scrutinize the thickness dependent resistivity data from
the recent literature on electrical transport measurements in topological
insulators. A linear increase in resistivity with increase in thickness is
expected in the case of these materials since they have an insulating bulk and
conducting surface. However, such a trend is not seen in the resistivity versus
thickness data for all the cases examined, except for some samples, where it
holds for a narrow range of thickness. | 1304.4037v2 |
2014-04-14 | Giant generic topological Hall resistivity of MnSi under pressure | We report detailed low temperature magnetotransport and magnetization
measurements in MnSi under pressures up to $\sim12\,{\rm kbar}$. Tracking the
role of sample quality, pressure transmitter, and field and temperature history
allows us to link the emergence of a giant topological Hall resistivity
$\sim50\,{\rm n\Omega cm}$ to the skyrmion lattice phase at ambient pressure.
We show that the remarkably large size of the topological Hall resistivity in
the zero-temperature limit must be generic. We discuss various mechanisms which
can lead to the much smaller signal at elevated temperatures observed at
ambient pressure. | 1404.3734v1 |
2015-01-27 | The Vacancy Effect on Thermal Interface Resistance between Aluminum and Silicon by Molecular Dynamics | Thermal transport across interfaces is an important issue for
microelectronics, photonics, and thermoelectric devices and has been studied
both experimentally and theoretically in the past. In this paper, thermal
interface resistance (1/G) between aluminum and silicon with nanoscale
vacancies was calculated using non-equilibrium molecular dynamics (NEMD). Both
phonon-phonon coupling and electron-phonon coupling are considered in
calculations. The results showed that thermal interface resistance increased
largely due to vacancies. The effect of both the size and the type of vacancies
is studied and compared. And an obvious difference is found for structures with
different type/size vacancies. | 1501.06666v1 |
2015-03-12 | Comment on "Correlation between Bulk Thermodynamic Measurements and the Low-Temperature-Resistance Plateau in SmB6" | Low-temperature-resistivity plateau observed in $\rm SmB_6$ single
crystal,which is due to surface, not bulk, conduction has been confirmed from
electrical transport measurements. Recently, the correlation between bulk
thermodynamic measurements and the low-temperature-resistance plateau in $\rm
SmB_6$ have been investigated and a change in Sm valence at the surface has
been obtained from x-ray absorption spectroscopy and x-ray magnetic circular
dichroism. Here we show that the statement of the report are not supported by
the results from x-ray absorption spectroscopy and x-ray magnetic circular
dichroism. | 1503.03901v1 |
2015-05-14 | On the vanishing resistivity limit and the magnetic boundary-layers for one-dimensional compressible magnetohydrodynamics | We consider an initial-boundary value problem for the one-dimensional
equations of compressible isentropic viscous and non-resistive
magnetohydrodynamic flows. The global well-posedness of strong solutions with
general large data is established. Moreover, the vanishing resistivity limit is
justified and the thickness of magnetic boundary layers is analyzed. The proofs
of these results are based on a full use of the so-called "effective viscous
flux", the material derivative and the structure of the equations. | 1505.03596v1 |
2017-02-06 | A thermodynamic theory of filamentary resistive switching | We present a phenomenological theory of filamentary resistive random access
memory (RRAM) describing the commonly observed features of their
current-voltage characteristics. Our approach follows the approach of
thermodynamic theory developed earlier for chalcogenide memory and threshold
switches and largely independent of their microscopic details. It explains,
without adjustable parameters, such features as the domains of filament
formation and switching, voltage independent current in SET and current
independent voltage in RESET regimes, the relation between the set and reset
voltages, filament resistance independent of its length, etc. Furthermore, it
expresses the observed features through the material and circuitry parameters
thus paving a way to device improvements. | 1702.01480v1 |
2017-10-02 | Electrical resistivity across the tricriticality in itinerant ferromagnet | We investigate the discontinuous ferromagnetic phase diagram near tricritical
point in UCo 1-x Ru x Al compounds by electrical resistivity measurements.
Separation of phases in UCo 0.995 Ru 0.005 Al at ambient pressure and in UCo
0.990 Ru 0.010 Al at pressure of 0.2 GPa and disappearance of ferromagnetism at
0.4 GPa is confirmed. The exponent of temperature dependence of electrical
resistivity implies change from Fermi liquid behavior to non-Fermi liquid at
0.2 GPa and reaches minimum at 0.4 GPa. Our results are compared to results
obtained on the pure UCoAl and explanation for different exponents is given. | 1710.00860v1 |
2017-10-04 | Towards Replacing Resistance Thermometry with Photonic Thermometry | Resistance thermometry provides a time-tested method for taking temperature
measurements that has been painstakingly developed over the last century.
However, fundamental limits to resistance-based approaches along with a desire
to reduce the cost of sensor ownership and increase sensor stability has
produced considerable interest in developing photonic temperature sensors. Here
we demonstrate that silicon photonic crystal cavity-based thermometers can
measure temperature with uncertainities of 175 mK (k = 1), where uncertainties
are dominated by ageing effects originating from the hysteresis in the device
packaging materials. Our results, a 4-fold improvement over recent
developments, clearly demonstate the rapid progress of silicon photonic sensors
in replacing legacy devices. | 1710.01704v1 |
2018-09-28 | Thermal resistance of GaN/AlN graded interfaces | Compositionally graded interfaces in power electronic devices eliminate
dislocations, but they can also decrease thermal conduction, leading to
overheating. We quantify the thermal resistances of GaN/AlN graded interfaces
of varying thickness using ab initio Green's functions, and compare them with
the abrupt interface case. A non-trivial power dependence of the thermal
resistance versus interface thickness emerges from the interplay of alloy and
mismatch scattering mechanisms. We show that the overall behavior of such
graded interfaces is very similar to that of a thin-film of an effective alloy
in the length scales relevant to real interfaces. | 1809.11046v2 |
2017-03-08 | Resistive Switching in Memristive Electrochemical Metallization Devices | We report on resistive switching of memristive electrochemical metallization
devices using 3D kinetic Monte Carlo simulations describing the transport of
ions through a solid state electrolyte of an Ag/TiO$_{\text{x}}$/Pt thin layer
system. The ion transport model is consistently coupled with solvers for the
electric field and thermal diffusion. We show that the model is able to
describe not only the formation of conducting filaments but also its
dissolution. Furthermore, we calculate realistic current-voltage
characteristics and resistive switching kinetics. Finally, we discuss in detail
the influence of both the electric field and the local heat on the switching
processes of the device. | 1703.02946v2 |
2012-01-31 | Magnetoresistance, noise properties and the Koshino-Taylor effect in the quasi-1D oxide KRu_4O_8 | The low temperature electronic and galvanomagnetic transport properties of
the low dimensional oxide KRu_4O_8 are experimentally considered. A quadratic
temperature variation of the resistivity is observed to be proportional to the
residual resistivity. It shows the role of inelastic electron scattering
against impurities, i.e. a large Koshino-Taylor effect, rather than a
consequence of strong electronic correlations. In the same temperature range,
the Kohler rule is not fulfilled. The resistance noise increases also sharply,
possibly due to a strong coupling of carriers with lattice fluctuations in this
low dimensional compound. | 1201.6474v1 |
2022-07-12 | A Simple and Precise Way to Determine Electrical Resistivity of Isotropic Conductors: Simplifying the Four-Probe Method | COMSOL Multiphysics software is used to describe the behavior of the
electrical resistivity of several samples with rectangular shape typically used
in the Montgomery method. The simulation data obtained using four isotropic
conductors allowed us to understand in detail the behavior of the electric
potential and electric field of the samples. The results provide an analytical
method which can substitute the four-probe method with much more simplicity and
precision. | 2207.05863v1 |
2022-11-08 | Role of the annealing parameters on the resistance of indium tin oxide nanocrystalline films | The optical and electrical properties of films made of nanoparticles of
indium tin oxide (ITO) are widely studied because of the significance of this
material for transparent electrodes, smart windows, and nonlinear optics
components. In this work, a systematic study of the resistance in ITO
nanocrystalline films, as a function of post-fabrication parameters, such as
the temperature and time of annealing, has been performed. A tunability of the
resistance with the annealing parameters, in a range of three orders of
magnitude, has been demonstrated. | 2211.04144v2 |
2023-11-16 | Measuring the Kapitza Resistance between a Passivated Semiconductor and Liquid Helium | In this paper, we describe an experimental investigation into the effect of
passivation layer thickness on heat dissipation between a quartz substrate and
liquid helium. We have observed that by depositing SiN from 0 to 240 nm, the
Kapitza resistance increases by 0.0365 m^2.K/W per nanometer more than for an
unpassivated semiconductor. We hypothesize that this increase in Kapitza
resistance represents an additional barrier to the cooling of semiconductor
devices in liquid helium. | 2312.03713v1 |
2021-07-26 | Laser-equipped gas reaction chamber for probing environmentally sensitive materials at near atomic scale | Numerous metallurgical and materials science applications depend on
quantitative atomic-scale characterizations of environmentally-sensitive
materials and their transient states. Studying the effect upon materials
subjected to thermochemical treatments in specific gaseous atmospheres is of
central importance for specifically studying a material's resistance to certain
oxidative or hydrogen environments. It is also important for investigating
catalytic materials, direct reduction of an oxide, particular surface science
reactions or nanoparticle fabrication routes. This manuscript realizes such
experiments upon a thermochemical reaction chamber called the Reacthub and
allows for transferring treated materials under cryogenic & ultrahigh vacuum
workflow conditions for characterisation by either atom probe or scanning
Xe+/electron microscopies. Two examples are discussed in the present study. One
protocol was in the deuterium gas charging (25 kPa D2 at 200 {\deg}C) of a
high-manganese twinning-induced-plasticity steel and characterization of the
ingress and trapping of hydrogen at various features (grain boundaries in
particular) in efforts to relate this to the steel's hydrogen embrittlement
susceptibility. Deuterium was successfully detected after gas charging but most
contrast originated from the complex ion FeOD+ signal and the feature may be an
artefact. The second example considered the direct deuterium reduction (5 kPa
D2 at 700 {\deg}C) of a single crystal wuestite sample, demonstrating that
under a standard thermochemical treatment causes rapid reduction upon the
nanoscale. Further studies are required for complete confidence about these
phenomena, but these experiments successfully demonstrate that how an ex-situ
thermochemical treatment can be realised that captures
environmentally-sensitive transient states that can be analysed by atomic-scale
by atom probe microscope. | 2107.11987v2 |
2023-03-19 | 2D MXene Electrochemical Transistors | In the past two decades another transistor based on conducting polymers,
called the organic electrochemical transistor (ECT) was shown and largely
studied. The main difference between organic ECTs and FETs is the mode and
extent of channel doping: while in FETs the channel only has surface doping
through dipoles, the mixed ionic-electronic conductivity of the channel
material in Organic ECTs enables bulk electrochemical doping. As a result, the
organic ECT maximizes conductance modulation at the expense of speed. Until now
ECTs have been based on conducting polymers, but here we show that MXenes, a
class of 2D materials beyond graphene, have mixed ionic-electronic properties
that enable the realization of electrochemical transistors (ECTs). We show that
the formulas for organic ECTs can be applied to these 2D ECTs and used to
extract parameters like mobility. These MXene ECTs have high transconductance
values but low on-off ratios. We further show that conductance switching data
measured using ECT, in combination with other in-situ ex-situ electrochemical
measurements, is a powerful tool for correlating the change in conductance to
that of redox state: to our knowledge, this is the first report of this
important correlation for MXene films. Many future possibilities exist for
MXenes ECTs, and we think other 2D materials with bandgaps can also form ECTs
with single or heterostructured 2D materials. 2D ECTs can draw great
inspiration and theoretical tools from the field of organic ECTs and have the
potential to considerably extend the capabilities of transistors beyond that of
conducting polymer ECTs, with added properties such as extreme heat resistance,
tolerance for solvents, and higher conductivity for both electrons and ions
than conducting polymers. | 2303.10768v2 |
2016-02-10 | Electronic Evidence of Temperature-Induced Lifshitz Transition and Topological Nature in ZrTe5 | The topological materials have attracted much attention recently. While
three-dimensional topological insulators are becoming abundant, two-dimensional
topological insulators remain rare, particularly in natural materials. ZrTe5
has host a long-standing puzzle on its anomalous transport properties; its
underlying origin remains elusive. Lately, ZrTe5 has ignited renewed interest
because it is predicted that single-layer ZrTe5 is a two-dimensional
topological insulator and there is possibly a topological phase transition in
bulk ZrTe5. However, the topological nature of ZrTe5 is under debate as some
experiments point to its being a three-dimensional or quasi-two-dimensional
Dirac semimetal. Here we report high-resolution laser-based angle-resolved
photoemission measurements on ZrTe5. The electronic property of ZrTe5 is
dominated by two branches of nearly-linear-dispersion bands at the Brillouin
zone center. These two bands are separated by an energy gap that decreases with
decreasing temperature but persists down to the lowest temperature we measured
(~2 K). The overall electronic structure exhibits a dramatic temperature
dependence; it evolves from a p-type semimetal with a hole-like Fermi pocket at
high temperature, to a semiconductor around ~135 K where its resistivity
exhibits a peak, to an n-type semimetal with an electron-like Fermi pocket at
low temperature. These results indicate a clear electronic evidence of the
temperature-induced Lifshitz transition in ZrTe5. They provide a natural
understanding on the underlying origin of the resistivity anomaly at ~135 K and
its associated reversal of the charge carrier type. Our observations also
provide key information on deciphering the topological nature of ZrTe5 and
possible temperature-induced topological phase transition. | 1602.03576v1 |
2010-11-11 | Nonlinear Insulator in Complex Oxides | The insulating state is one of the most basic electronic phases in condensed
matter. This state is characterised by an energy gap for electronic excitations
that makes an insulator electrically inert at low energy. However, for complex
oxides, the very concept of an insulator must be re-examined. Complex oxides
behave differently from conventional insulators such as SiO2, on which the
entire semiconductor industry is based, because of the presence of multiple
defect levels within their band gap. As the semiconductor industry is moving to
such oxides for high-dielectric (high-k) materials, we need to truly understand
the insulating properties of these oxides under various electric field
excitations. Here we report a new class of material called nonlinear insulators
that exhibits a reversible electric-field-induced metal-insulator transition.
We demonstrate this behaviour for an insulating LaAlO3 thin film in a
metal/LaAlO3/Nb-SrTiO3 heterostructure. Reproducible transitions were observed
between a low-resistance metallic state and a high-resistance non-metallic
state when applying suitable voltages. Our experimental results exclude the
possibility that diffusion of the metal electrodes or oxygen vacancies into the
LaAlO3 layer is occurring. Instead, the phenomenon is attributed to the
formation of a quasi-conduction band (QCB) in the defect states of LaAlO3 that
forms a continuum state with the conduction band of the Nb-SrTiO3. Once this
continuum (metallic) state is formed, the state remains stable even when the
voltage bias is turned off. An opposing voltage is required to deplete the
charges from the defect states. Our ability to manipulate and control these
defect states and, thus, the nonlinear insulating properties of complex oxides
will open up a new path to develop novel devices. | 1011.2629v1 |
2022-08-31 | CeFe$_2$Al$_{10}$: a Correlated Metal with a Fermi Surface Exhibiting Nonmetallic Conduction | Metals can be defined as materials with a Fermi surface or as materials
exhibiting metallic conduction (i.e., $\mathrm{d} \rho / \mathrm{d}T > 0$).
Usually, these definitions both hold at low temperatures, such as liquid-helium
temperatures, as the Fermi energy is sufficiently larger than the thermal
energy. However, they may not both hold in correlated electron systems where
the Fermi energy is reduced by renormalization. In this paper, we demonstrate
that although the resistivity of CeFe$_2$Al$_{10}$ increases with decreasing
temperature below $\sim20$ K, CeFe$_2$Al$_{10}$ is a metal with a Fermi
surface. This assertion is based on the observation of Shubnikov--de Haas
oscillations and a Hall resistivity that changes sign with the magnetic field,
which requires the coexistence of electron and hole carriers. Our analysis of
Shubnikov--de Haas and magnetotransport data indicates that the Fermi energies
are as small as $\sim$30 K and that, despite the increasing carrier mobility
with decreasing temperature as in conventional metals, the loss of thermally
excited carriers leads to nonmetallic conduction ($\mathrm{d} \rho /
\mathrm{d}T < 0$) below $\sim20$ K. Furthermore, we investigate how this
anomalous metal transforms to a more conventional metal with metallic
conduction by the application of high pressure and a high magnetic field. This
study illustrates the subtle distinction between semimetals and semiconductors
in correlated electron systems. This distinction is relevant to investigations
of correlated topological insulators and semimetals. | 2208.14630v4 |
2011-08-08 | KEK effort for high field magnets | KEK has emphasized efforts to develop the RHQNb3Al superconductor and a
sub-scale magnet reaching 13 T towards the HL-LHC upgrade in last years. In
addition, relevant R&D regarding radiation resistance has been carried out. For
higher field magnets beyond 15 T, HTS in combination with A15 superconductors
should be one of baseline materials. However, all these superconductors are
very sensitive to stress and strain and thorough understanding of behaviour is
truly desired for realization of high field magnets. KEK has launched a new
research subject on stress/strain sensitivity of HTS and A15 superconductors in
collaboration with the neutron diffraction facility at J-PARC and High Field
Laboratory in Tohoku University. Present activity for high field magnets at KEK
is reported. | 1108.1626v1 |
2013-10-29 | Fabrication of single-walled carbon nanotube/Si heterojunction solar cell with high photovoltaic conversion efficiency and stability | The photovoltaic properties of carbon nanotube/Si heterojunction solar cells
were investigated using network films of high quality single-walled carbon
nanotubes (SWNTs) grown by atmospheric-pressure floating-catalyst chemical
vapor deposition. Because of the optimization of the device window size and the
utilization of SWNT thin films with both low resistivity and high transparency,
a high photovoltaic conversion efficiency of greater than 12% was achieved for
SWNTs/Si heterojunction solar cells without any post processing, such as
carrier doping treatment. In addition, the high stability and reproducibility
of the photovoltaic performance of these devices in air was demonstrated. | 1310.7783v2 |
2021-02-15 | Fermi-surface reconstruction at the metamagnetic high-field transition in uranium mononitride | We report on the electronic and thermodynamic properties of the
antiferromagnetic metal uranium mononitride with a N\'eel temperature
$T_N\approx 53\,$K. The fabrication of microstructures from single crystals
enables us to study the low-temperature metamagnetic transition at
approximately $58\,$T by high-precision magnetotransport, Hall-effect, and
magnetic-torque measurements. We confirm the evolution of the high-field
transition from a broad and complex behavior to a sharp first-order-like step,
associated with a spin flop at low temperature. In the high-field state, the
magnetic contribution to the temperature dependence of the resistivity is
suppressed completely. It evolves into an almost quadratic dependence at low
temperatures indicative of a metallic character. Our detailed investigation of
the Hall effect provides evidence for a prominent Fermi-surface reconstruction
as the system is pushed into the high-field state. | 2102.07512v2 |
2020-06-17 | Electrical transport measurements for superconducting sulfur hydrides using boron-doped diamond electrodes on beveled diamond anvil | A diamond anvil cell (DAC) which can generate extremely high pressure of
multi-megabar is promising tool to develop a further physics such a
high-transition temperature superconductivity. However, electrical transport
measurements, which is one of the most important properties of such functional
materials, using the DAC is quite difficult because the sample space is very
small and a deformation of electrodes under extreme condition. In this study,
we fabricated a boron-doped diamond micro-electrode and an undoped diamond
insulation on a beveled culet surface of the diamond anvil. By using the
developed DAC, we demonstrated the electrical transport measurements for sulfur
hydride H$_2$S which known as a pressure-induced high-transition temperature
superconducting H$_3$S at high pressure. The measurements were successfully
conducted under high pressure up to 192 GPa, and then a multi-step
superconducting transition composed from pure sulfur and some kinds of surfer
hydrides, which is possible HS$_2$, was observed with zero resistance. | 2006.09671v1 |
2023-10-02 | Thermoelectric properties of high-entropy wolframite oxide: (CoCuNiFeZn)$_{1-x}$Ga$_x$WO$_4$ | In this report, the synthesis of high-entropy wolframite oxide
(CoCuNiFeZn)$_{1-x}$Ga$_x$WO$_4$ through standard solid-state route followed by
spark plasma sintering (SPS) and their structural, microstructural, and
thermoelectric properties are investigated. X-ray diffraction pattern followed
by pattern matching refinement shows monoclinic structure with volume of the
unit cell decreasing with increasing Ga content. The optical band gap for these
oxides shows a cocktail effect in high entropy configuration. The Seebeck
coefficient indicates electrons as dominating charge carriers with a
non-degenerate behavior. The electrical resistivity decreases with increasing
temperature depicting a semiconducting nature. Thermal conductivity in
high-entropy samples ($\kappa\sim$2.1 W/mK @ 300\,K) is significantly lower as
compared to MgWO$_4$ ($\kappa\sim$11.5 W/mK @ 300\,K), which can be explained
by the strong phonon scattering due to large lattice disorder in high entropy
configuration. The thermoelectric figure of merit zT increases with Ga doping
via modifying all three thermoelectric parameters positively. | 2310.00930v1 |
1999-03-01 | Anisotropic resistivity of the antiferromagnetic insulator Bi_2Sr_2ErCu_2O_8 | Anisotropic resistivities of Bi_2Sr_2Ca_{1-x}Er_xCu_2O_8 single crystals were
measured and analyzed from 4.2 to 500 K with special interest in the parent
antiferromagnetic insulator of x=1.0. Although the resistivity is
semiconducting along both the in- and out-of-plane directions, the temperature
dependence is found to be significantly different. As a result, the resistivity
ratio for x=1.0 takes a broad maximum near room temperature. The electric
conduction in parent antiferromagnetic insulators is different from other
semiconductors, and is as unconventional as that in high-temperature
superconductors. | 9903023v2 |
2002-11-18 | Transverse voltages and reciprocity theorem in magnetic fields for high T_c superconductors | We have tested four-point methods of the Hall effect measurement on BiSrCaCuO
(2223) polycrystal and also the validity of the magnetic field form of the
reciprocity theorem. We found that different types of determination of the Hall
resistance using various combination of measured resistances provide different
value of it. We have separated two parts of the resistance combinations, which
are even and odd in magnetic field, respectively. The odd part, which is
equivalent to the Hall effect, is equal for all formulae used. The even part of
transverse resistance varies in different formulae. The magnetic field form of
the reciprocity theorem is not valid. Models for explanation of this violation
are also discussed. | 0211370v1 |
2003-06-03 | Anomalous Flux Flow Resistivity in Two Gap Superconductor MgB_2 | The flux flow resistivity associated with purely viscous motion of vortices
in high-quality MgB_2 was measured by microwave surface impedance. Flux flow
resistivity exhibits unusual field dependence with strong enhancement at low
field, which is markedly different to conventional s-wave superconductors. A
crossover field which separates two distinct flux flow regimes having different
flux flow resistivity slopes was clearly observed in H//ab-plane. The unusual
H-dependence indicates that two very differently sized superconducting gaps in
MgB_2 manifest in the vortex dynamics and almost equally contribute to energy
dissipation. The carrier scattering rate in two different bands is also
discussed with the present results, compared to heat capacity and thermal
conductivity results. | 0306057v1 |
2005-09-30 | Valence fluctuation mediated superconductivity in CeCu2Si2 | It has been proposed that there are two types of superconductivity in
CeCu2Si2, mediated by spin fluctuations at ambient pressure, and by critical
valence fluctuations around a charge instability at a pressure P_v \simeq 4.5
GPa. We present in detail some of the unusual features of this novel type of
superconducting state, including the coexistence of superconductivity and huge
residual resistivity of the order of the Ioffe-Regel limit, large and pressure
dependent resistive transition widths in a single crystal measured under
hydrostatic conditions, asymmetric pressure dependence of the specific heat
jump shape, unrelated to the resistivity width, and negative temperature
dependence of the normal state resistivity below 10 K at very high pressure. | 0509787v1 |
2007-06-05 | Hall magnetoresistivity response under Microwave excitation revisited | We theoretically analyzed the microwave-induced modification of the Hall
magnetoresistivity in high mobility two-dimensional electron systems. These
systems present diagonal magnetoresistivity oscillations and zero-resistance
states when are subjected to microwave radiation. The most surprising
modification of the Hall magnetoresistivity is a periodic reduction which
correlates with a periodic increase in the diagonal resistivity. We present a
model that explains the experimental results considering that radiation affects
directly only the diagonal resistivity and the observed Hall resistivity
changes are coming from the tensor relationship between both of them. | 0706.0588v1 |
2009-06-22 | Temperature dependent electrical resistivity of a single strand of ferromagnetic single crystalline nanowire | We have measured the electrical resistivity of a single strand of a
ferromagnetic Ni nanowire of diameter 55 nm using a 4-probe method in the
temperature range 3 K-300 K. The wire used is chemically pure and is a high
quality oriented single crystalline sample in which the temperature independent
residual resistivity is determined predominantly by surface scattering. Precise
evaluation of the temperature dependent resistivity ($\rho$) allowed us to
identify quantitatively the electron-phonon contribution (characterized by a
Debye temperature $\theta_R$) as well as the spin-wave contribution which is
significantly suppressed upon size reduction. | 0906.3903v1 |
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