publicationDate stringlengths 10 10 | title stringlengths 17 233 | abstract stringlengths 20 3.22k | id stringlengths 9 12 |
|---|---|---|---|
2023-01-18 | Paper-based Flexible Supercapacitors with drawn van der Waals materials | Two-dimensional (2D) materials are widely used in various applications due to
their extraordinary properties. In particular, their electrochemical stability,
low electrical resistance, and huge specific surface area make them very
interesting active materials for supercapacitors. Herein, flexible,
biodegradable, and low-cost supercapacitors are introduced in a very simple way
based on hand-drawing pencil traces or -rubbing molybdenum disulfide (MoS2),
titanium trisulfide (TiS3) and franckeite traces on the paper. Results
demonstrate that pencil-drawn paper has higher capacitance performance (~6.39
F/g) among the suggested electrodes. Interestingly, the introduced MoS2/pencil,
TiS3/pencil, and franckeite/pencil drawn paper electrodes reveal dramatic
improvements with long cyclic life thanks to the occurrence of synergetic
effects and higher available active cites within the heterostructures.
Moreover, the assembled symmetric solid-state supercapacitors retain their
performance even under applied bending, indicating their excellent potential
for wearable/flexible applications. | 2301.07759v1 |
2023-02-18 | Magnetoresistance signature of two-dimensional electronic states in Co$_3$Sn$_2$S$_2$ | Two-dimensional (2D) Dirac bands and flat bands are characteristics of a
kagome lattice. However, experimental studies on their electrical transport are
few, because three-dimensional (3D) bulk bands of kagome materials, consisting
of stacked 2D kagome layers, dominate the transport. We report a
magnetoresistance (MR) study of a kagome material, Co$_3$Sn$_2$S$_2$. Based on
analysis of the temperature, magnetic field, and field angle dependence of the
resistivity, we obtain a complete anatomy of MR. Besides a magnon MR, a
chirality-dependent MR, and a chiral-anomaly-induced MR, the most intriguing
feature is an orbital MR that scales only with the out-of-plane field, which
strongly indicates its 2D nature. We attribute it to the Dirac band of the
kagome lattice. | 2302.09229v1 |
2023-03-01 | Thermodynamic determination of the equilibrium first-order phase-transition line hidden by hysteresis in a phase diagram | Phase diagrams form the basis for the study of material science, and the
profiles of phase-transition lines separating different thermodynamic phases
include comprehensive information about thermodynamic quantities, such as
latent heat. However, in some materials exhibiting field-induced first-order
transitions (FOTs), the equilibrium phase-transition line is hidden by the
hysteresis region associated with the FOT; thus, it cannot be directly
determined from measurements of resistivity, magnetization, etc. Here, we
demonstrate a thermodynamics-based method for determining the hidden
equilibrium FOT line. This method is verified for the FOT between
antiferromagnetic and ferrimagnetic states in magneto-electric compounds
(Fe$_{0.95}$Zn$_{0.05}$)$_{2}$Mo$_{3}$O$_{8}$. The equilibrium FOT line
determined based on the Clausius-Clapeyron equation exhibits a reasonable
profile in terms of the third law of thermodynamics, and it shows marked
differences from the midpoints of the hysteresis region. Our findings highlight
that care should be taken for referring to the hysteresis midpoint line when
discussing field-induced latent heat or magnetocaloric effects. | 2303.00327v1 |
2023-03-21 | Structure, physical properties, and magnetically tunable topological phases in topological semimetal EuCuBi | A single material achieving multiple topological phases can provide potential
application for topological spintronics, whereas the candidate materials are
very limited. Here, we report the structure, physical properties, and possible
emergence of multiple topological phases in the newly discovered, air-stable
EuCuBi single crystal. EuCuBi crystallizes in a hexagonal space group P63/mmc
(No. 194) in ZrBeSi-type structure with an antiferromagnetic (AFM) ground state
below TN = 11.2 K. There is a competition between AFM and ferromagnetic (FM)
interactions below TN revealed by electrical resistivity and magnetic
susceptibility measurements. With the increasing magnetic field, EuCuBi evolves
from the AFM ground state with a small amount of FM component, going through
two possible metamagnetic phases, finally reaches the field-induced FM phase.
Based on the first-principles calculations, we demonstrate that the Dirac,
Weyl, and possible mirror Chern insulator can be achieved in EuCuBi by tuning
the temperature and applying magnetic field, making EuCuBi a promising
candidate for exploring multiple topological phases. | 2303.11894v1 |
2023-04-20 | Magnetic behavior of cubic Dy4RhAl with respect to isostructural Dy4PtAl, revealing a novel 4f d-band interaction | We have investigated for the first time the magnetic behaviour of an
intermetallic compound, Dy4RhAl, crystallizing in Gd4RhIn type cubic structure
containing 3 sites for rare-earth (R), by several bulk measurements down to 1.8
K. This work is motivated by the fact that the isostructural Dy compound in the
R4PtAl family surprisingly orders ferromagnetically unlike other members of
this series, which order antiferromagnetically. The results reveal that the
title compound undergoes antiferromagnetic order at about 18 K, similar to
other heavy R members of R4RhAl family, unlike its Pt counterpart, indicating a
subtle difference in the role of conduction electrons to decide magnetism of
these compounds. Besides, spin-glass features coexisting with antiferromagnetic
order could be observed, which could mean cluster antiferromagnetism. The
electrical resistivity and magnetoresistance behaviours in the magnetically
ordered state are typical of magnetic materials exhibiting antiferromagnetic
gap. Features attributable to spin-reorientation as a function of temperature
and magnetic field can be seen in the magnetization data. | 2304.10122v1 |
2023-08-07 | Oxide layer formation prevents deteriorating ion migration in thermoelectric Cu$_2$Se during operation in air | Cu$_2$Se is a mixed ionic-electronic conductor with outstanding
thermoelectric performance originally envisioned for space missions.
Applications were discontinued due to material instability, where elemental Cu
grows at the electrode interfaces during operation in vacuum. Here, we show
that when Cu$_2$Se is operating in air, formation of an oxide surface layer
suppresses Cu$^+$ migration along the current direction. In operando X-ray
scattering and electrical resistivity measurements quantify Cu$^+$ migration
through refinement of atomic occupancies and phase composition analysis. Cu
deposition can be prevented during operation in air, irrespective of a critical
voltage, if the thermal gradient is applied along the current direction.
Maximum entropy electron density analysis provides experimental evidence that
Cu$^+$ migration pathways under thermal and electrical gradients differ
substantially from equilibrium diffusion. The study establishes new promise for
inexpensive sustainable Cu$_2$Se in thermoelectric applications, and it
underscores the importance of atomistic insight into materials during
thermoelectric operating conditions. | 2308.03559v1 |
2023-09-01 | Denture reinforcement via topology optimization | We present a computational design method that optimizes the reinforcement of
dental prostheses and increases the durability and fracture resistance of
dentures. Our approach optimally places reinforcement, which could be
implemented by modern multi-material, three-dimensional printers. The study
focuses on reducing deformation by identifying regions within the structure
that require reinforcement (E-glass material). Our method is applied to a
three-dimensional removable lower jaw dental prosthesis and aims to improve the
living quality of denture patients and pretend fracture of dental reinforcement
in clinical studies. To do this, we compare the deformation results of a
non-reinforced denture and a reinforced denture that has two materials. The
results indicate the maximum deformation is lower and node-based displacement
distribution demonstrates that the average displacement distribution is much
better in the reinforced denture. | 2309.00396v1 |
2023-09-06 | Magnetic order in the $S_{\mathrm{eff}}$ = 1/2 triangular-lattice compound NdCd$_3$P$_3$ | We present and characterize a new member of the $R$Cd$_3$P$_3$ ($R$= rare
earth) family of materials, NdCd$_3$P$_3$, which possesses Nd$^{3+}$ cations
arranged on well-separated triangular lattice layers. Magnetic susceptibility
and heat capacity measurements demonstrate a likely $S_{\mathrm{eff}}$ = 1/2
ground state, and also reveal the formation of long-range antiferromagnetic
order at $T_{N} = 0.34$ K. Via measurements of magnetization, heat capacity,
and electrical resistivity, we characterize the electronic properties of
NdCd$_3$P$_3$ and compare results to density functional theory calculations. | 2309.03332v1 |
2023-09-18 | Ferroelectric Schottky diodes of CuInP$_2$S$_6$ nanosheet | Ferroelectricity in van der Waals (vdW) layered material has attracted a
great deal of interest recently. CuInP$_2$S$_6$ (CIPS), the only vdW layered
material whose ferroelectricity in the bulk was demonstrated by direct
polarization measurements, was shown to remain ferroelectric down to a
thickness of a few nanometers. However, its ferroelectric properties have just
started to be explored in the context of potential device applications. We
report here the preparation and measurements of metal-ferroelectric
semiconductor-metal heterostructures using nanosheets of CIPS obtained by
mechanical exfoliation. Four bias voltage and polarization dependent resistive
states were observed in the current-voltage characteristics, which we attribute
to the formation of ferroelectric Schottky diode, along with switching
behavior. | 2309.10045v1 |
2023-10-25 | Super-resolution imaging reveals resistance to mass transfer in functionalized stationary phases | Chemical separations are costly in terms of energy, time, and money.
Separation methods are optimized with inefficient trial-and-error approaches
that lack insight into the molecular dynamics that lead to the success or
failure of a separation and, hence, ways to improve the process. We perform
super-resolution imaging of fluorescent analytes in four different commercial
liquid chromatography materials. Surprisingly, we observe that chemical
functionalization can block over fifty percent of the porous interior of the
material, rendering it inaccessible to small molecule analytes. Only in situ
imaging unveils the inaccessibility when compared to the industry-accepted ex
situ characterization methods. Selectively removing some of the
functionalization with solvent restores pore access without significantly
altering the single-molecule kinetics that underlie the separation and agree
with bulk chromatography measurements. Our molecular results determine that
commercial stationary phases, marketed as fully porous, are over-functionalized
and provide a new avenue to characterize and direct separation material design
from the bottom-up. | 2310.16266v1 |
2023-11-17 | Fabrication of damage-free and/or contamination-free sub-um electrodes using PMMA masks | Quality of the electrical contacts and interfaces in various
metal/semiconductor/insulator heterostructures is one of the pivotal aspects in
both applied and fundamental research areas. For instance, non-optimal contact
resistance can limit the overall efficiency of a certain developed technology
and thus considerably narrow the range or fully block its practical
application. On the other hand in fundamental research it is often the case
that the manifestation of targeted phenomenon crucially depends on the level of
contamination in the fabricated experimental samples. Here we offer a set of
recipes that are aimed at contamination-free and damage-free fabrication of the
devices, mostly developed for the two dimensional materials, but nevertheless
applicable for a wider range of the systems, where the quality of the
interfaces and/or non-invasiveness of the fabrication recipes are important.
Our recipes are based on the preparation of the flexible PMMA membranes, with
the help of which we can prepare residue-free or damage-free electrical
connections to the studied material. | 2311.10340v1 |
2023-11-20 | Spontaneous supercrystal formation during a strain-engineered metal-insulator transition | Mott metal-insulator transitions possess electronic, magnetic, and structural
degrees of freedom promising next generation energy-efficient electronics. We
report a previously unknown, hierarchically ordered state during a Mott
transition and demonstrate correlated switching of functional electronic
properties. We elucidate in-situ formation of an intrinsic supercrystal in a
Ca2RuO4 thin film. Machine learning-assisted X-ray nanodiffraction together
with electron microscopy reveal multi-scale periodic domain formation at and
below the film transition temperature (TFilm ~ 200-250 K) and a separate
anisotropic spatial structure at and above TFilm. Local resistivity
measurements imply an intrinsic coupling of the supercrystal orientation to the
material's anisotropic conductivity. Our findings add an additional degree of
complexity to the physical understanding of Mott transitions, opening
opportunities for designing materials with tunable electronic properties. | 2311.11842v1 |
2023-12-10 | Characterization of Semiconducting Materials Using the Van der Pauw Method | Semiconductors are currently an active topic of study due to the endless
range of applications in electronic hardware and computer engineering. In this
experiment, the material properties (i.e. resistivity $\rho$, Hall coefficient
$R_{H}$, and mobility $\mu$) of a doped GaAs sheet is described by utilizing
Hall Effect and the Van der Pauw method with varying temperature $T$ and
magnetic field values $B$. It is determined that the sample is an $n$-type
semiconductor using the sign of $R_H$, which is measured to be $R_H = -2.9
\times 10^{-12} \pm 0.1 \times 10^{-14} ~ \text{m}^{3} \text{C}^{-1}$, at $T =
303 ~\text{K}$ and $B = 3.3 ~\text{kGs}$. Furthermore, the rate of change for
the slope $R_H$ and $T$ is increasing along $B$ at the rate of $\Delta k/
\Delta B = \left(3.6 \pm 0.5 \right) \times 10^{-16} ~\text{m}^3 (\text{CK}
\cdot \text{kGs})^{-1}$, meaning the charge accumulation caused by the current
and Lorentz force is quadratic in $B$. It is also discovered that $\mu$, and
therefore the electron drift velocity is reduced proportionally at higher
$T$-values. This method provides a potential analogue in quantum scales with
the Quantum Hall Effect and characterisation of quantum dots. | 2312.05744v1 |
2023-12-15 | Smart sensing of the multifunctional properties of magnetron sputtered $MoS_2$ across the amorphous-crystalline transition | Molybdenum disulfide, $MoS_2$, is a next-generation semiconductor and is
frequently integrated into emergent optoelectronic technologies based on
two-dimensional materials. Here, we present a method that provides direct
optical feedback on the thickness and crystallinity of sputter-deposited
$MoS_2$ down to the few-layer regime. This smart sensing enables tracking the
material's functional properties, such as excitonic response, sheet resistance,
and hardness across the amorphous-crystalline transition. To illustrate the
potential of such feedback-controlled fabrication, we realized $MoS_2$-based
hyperbolic metamaterials (HMM) with controllable optical topological
transitions and hardness. | 2312.10180v2 |
2024-01-10 | A Universal Scaling Law for Intrinsic Fracture Energy of Networks | Networks of interconnected materials permeate throughout nature, biology, and
technology due to exceptional mechanical performance. Despite the importance of
failure resistance in network design and utility, no existing physical model
effectively links strand mechanics and connectivity to predict bulk fracture.
Here, we reveal a universal scaling law that bridges these levels to predict
the intrinsic fracture energy of diverse networks. Simulations and experiments
demonstrate its remarkable applicability to a breadth of strand constitutive
behaviors, topologies, dimensionalities, and length scales. We show that local
strand rupture and nonlocal energy release contribute synergistically to the
measured intrinsic fracture energy in networks. These effects coordinate such
that the intrinsic fracture energy scales independent of the energy to rupture
a strand; it instead depends on the strand rupture force, breaking length, and
connectivity. Our scaling law establishes a physical basis for understanding
network fracture and a framework for fabricating tough materials from networks
across multiple length scales. | 2401.05564v1 |
2024-01-23 | Berezinskii-Kosterlitz-Thouless transition in rhenium nitride films | The quest to manipulate and understand superconductivity demands exploring
diverse materials and unconventional behaviors. Here, we investigate the BKT
transition in synthesized ReN$_x$ thin films, demonstrating their emergence as
a compelling platform for studying this pivotal phenomenon. By systematically
varying synthesis parameters, we achieve ReN$_x$ films exhibiting a BKT
transition comparable or even surpassing the archetypal NbN$_x$ system.
Detailed current-voltage measurements unlock the intrinsic parameters of the
BKT transition, revealing the critical role of suppressed superconducting
volume in pushing ReN$_x$ towards the two-dimensional limit. Utilizing this
two-dimensional electron system, we employ Beasley-Mooij-Orlando (BMO) theory
to extract the vortex unbinding transition temperature and superelectron
density at the critical point. Further confirmation of the BKT transition is
obtained through temperature-dependent resistivity, current-voltage, and
magnetoresistance measurements. Our findings suggest that native disorder and
inhomogeneity within ReN$_x$ thin films act to suppress long-range coherence,
ultimately driving the system towards the BKT regime. This work establishes
ReN$_x$ as a promising material for exploring BKT physics and paves the way for
tailoring its properties for potential applications in superconducting devices. | 2401.12628v1 |
2024-02-11 | Cooperating Cracks in Two-Dimensional Crystals | The pattern development of multiple cracks in extremely anisotropic solids
such as bilayer or multilayer two-dimensional (2D) crystals contains rich
physics, which, however, remains largely unexplored. We studied crack
interaction across neighboring 2D layers by transmission electron microscopy
and molecular dynamics simulations. Parallel and anti-parallel ('En-Passant')
cracks attract and repel each other in bilayer 2D crystals, respectively, in
stark contrast to the behaviors of co-planar cracks. We show that the misfit
between in-plane displacement fields around the crack tips results in
non-uniform interlayer shear, which modifies the crack driving forces by
creating an antisymmetric component of the stress intensity factor. The
cross-layer interaction between cracks directly leads to material toughening,
the strength of which increases with the shear stiffness and decreases with the
crack spacings. Backed by the experimental findings and simulation results, a
theory that marries the theory of linear elastic fracture mechanics and the
shear-lag model is presented, which guides the unconventional approach to
engineer fracture patterns and enhance material resistance to cracking. | 2402.07088v1 |
2024-03-26 | Microscale Morphology Driven Thermal Transport in Fiber Reinforced Polymer Composites | Fiber-reinforced polymer composite (FRPC) materials are used extensively in
various industries, such as aerospace, automobiles, and electronics packaging,
due to their remarkable specific strength and desirable properties, such as
enhanced durability and corrosion resistance. The evolution of thermal
properties in FRPCs is crucial for advancing thermal management systems,
optimizing material performance, and enhancing energy efficiency across these
diverse sectors. Despite significant research efforts to develop new materials
with improved thermal properties and reduced thermal degradation, there is a
lack of understanding of the thermal transport phenomena considering the
influence of microscale reinforcement morphology in these composites. In the
current study, we performed experimental investigations complemented by
computations to determine the thermal transport properties and associated
phenomena in epoxy and carbon fiber-reinforced epoxy composites. The
experimental findings were utilized as input data for numerical analysis to
examine the impact of fiber morphology and volume fraction in thermal transport
phenomena. Our results revealed that composites incorporating non-circular
fibers manifested higher thermal conductivity than traditional circular fibers
in the transverse direction. This can be attributed to increased interconnected
heat flow pathways facilitated by the increased surface area of non-circular
fibers with the same cross-sectional areas, resulting in efficient heat
transfer. | 2403.17650v1 |
2024-04-24 | Synthesis of layered gold tellurides AuSbTe and Au$_2$Te$_3$ and their semiconducting and metallic behavior | Previous studies on natural samples of pampaloite (AuSbTe) revealed the
crystal structure of a potentially cleavable and/or exfoliable material, while
studies on natural and synthetic montbrayite (Sb-containing Au$_2$Te$_3$)
claimed various chemical compositions for this low symmetry compound. Few
investigations of synthetic samples have been reported for both materials,
leaving much of their chemical, thermal and electronic characteristics unknown.
Here, we investigate the stability, electronic properties and synthesis of the
gold antimony tellurides AuSbTe and Au$_{1.9}$Sb$_{0.46}$Te$_{2.64}$
(montbrayite). Differential thermal analysis and $\textit{in situ}$ powder
x-ray diffraction revealed that AuSbTe is incongruently melting, while
Au$_{1.9}$Sb$_{0.46}$Te$_{2.64}$ is congruently melting. Calculations of the
band structures and four-point resistivity measurements showed that AuSbTe is a
semiconductor and Au$_{1.9}$Sb$_{0.46}$Te$_{2.64}$ a metal. Various synthesis
attempts confirmed the limited stable chemical composition of
Au$_{1.9}$Sb$_{0.46}$Te$_{2.64}$, identified successful methods to synthesize
both compounds, and highlighted the challenges associated with single crystal
synthesis of AuSbTe. | 2404.16239v1 |
2024-05-03 | Piezoresistivity as an Order Parameter for Ferroaxial Transitions | Recent progress in the understanding of the collective behavior of electrons
and ions have revealed new types of ferroic orders beyond ferroelectricity and
ferromagnetism, such as the ferroaxial state. The latter retains only
rotational symmetry around a single axis and reflection symmetry with respect
to a single mirror plane, both of which are set by an emergent electric
toroidal dipole moment. Due to this unusual symmetry-breaking pattern, it has
been challenging to directly measure the ferroaxial order parameter, despite
the increasing attention this state has drawn. Here, we show that off-diagonal
components of the piezoresistivity tensor (i.e., the linear change in
resistivity under strain) transform the same way as the ferroaxial moments,
providing a direct probe of such order parameters. We identify two new proper
ferroaxial materials through a materials database search, and use
first-principles calculations to evaluate the piezoconductivity of the
double-perovskite CaSnF$_6$, revealing its connection to ferroaxial order and
to octahedral rotation modes. | 2405.02149v1 |
2004-11-16 | Upper Critical Fields up to 60T in Dirty Magnesium Diboride Thin Films | Upper critical fields of several magnesium diboride thin films were measured
up to 28 T at the Grenoble High Magnetic Field Laboratory (GHMFL) in Grenoble
and up to 60 T at the Laboratoire National des Champs Magnetiques Pulses
(LNCMP) in Toulouse. The samples were prepared both by pulsed laser deposition
(PLD) and hybrid physical chemical vapour deposition (HPCVD) technique; they
have critical temperatures between 29 and 39 K and normal state resistivities
between 5 and 250 μohmcm; one of them has been intentionally doped with
carbon. The measured critical fields were exceptionally high; we obtained the
record value of 52 T at 4.2 K in the parallel orientation. In contrast with the
BCS predictions, no saturation in Hc2 at low temperature was observed.
Furthermore, films with a wide range of resistivity values showed similar
critical fields, suggesting that in a two band system resistivity and Hc2 are
not trivially linked. The high Hc2 values seem to be related with the expanded
c-axis. The structure of one of the samples was carefully investigated with
X-ray diffraction at European Synchrotron Radiation Facility (ESRF) in
Grenoble. | 0411404v1 |
2008-07-22 | Microphysical dissipation, turbulence and magnetic fields in hyper-accreting discs | Hyper-accreting discs occur in compact-object mergers and collapsars, and may
power gamma-ray bursts (GRBs). We calculate the microscopic viscosity and
resistivity of plasma in these discs, and discuss the implications for their
global structure and evolution. In the neutrino-cooled innermost regions, the
viscosity is provided mainly by mildly degenerate electrons, while the
resistivity is modified from the Spitzer value due to the effects of both
relativity and degeneracy. The plasma behaves as an almost ideal MHD fluid.
Among the non-ideal MHD effects the Hall term is relatively the most important,
while the magnetic Prandtl number, Pr (the ratio of viscosity to resistivity),
is typically larger than unity: 10 < Pr < 6000. The outer radiatively
inefficient regions also display high Pr. Numerical simulations of the
magneto-rotational instability indicate that the saturation level and angular
momentum transport efficiency may be greatly enhanced at high Pr. If this
behaviour persists in the presence of a strong Hall effect we would expect that
hyper-accreting discs should be strongly magnetised and highly variable. The
expulsion of magnetic field that cannot be dissipated at small scales may also
favour a magnetic outflow. We note the similaries between the Prandtl number in
hyper-accreting discs and X-ray binary discs, which suggests that a comparison
between late-time activity in GRBs and X-ray binary accretion states may be
fruitful. Our results imply that the behavior of high Prandtl number MHD flows
needs to be considered in studies of hyper-accreting discs. | 0807.3547v2 |
2011-11-16 | Optical tuning and ultrafast dynamics of high-temperature superconducting terahertz metamaterials | Through the integration of semiconductors or complex oxides into metal
resonators, tunable metamaterials have been achieved by a change of environment
using an external stimulus. Metals provide high conductivity to realize a
strong resonant response in metamaterials; however, they contribute very little
to the tunability. The complex conductivity in high-temperature superconducting
films is highly sensitive to external perturbations, which provides new
opportunities in achieving tunable metamaterials resulting directly from the
resonant elements. Here we demonstrate ultrafast dynamical tuning of resonance
in the terahertz (THz) frequency range in YBa_2Cu_3O_7-\delta (YBCO) split-ring
resonator arrays excited by near-infrared femtosecond laser pulses. The
photoexcitation breaks the superconducting Cooper pairs to create the
quasiparticle state. This dramatically modifies the imaginary part of the
complex conductivity and consequently the metamaterial resonance in an
ultrafast timescale. We observed resonance switching accompanied with a wide
range frequency tuning as a function of photoexcitation fluence, which also
strongly depend on the nano-scale thickness of the superconducting films. All
of our experimental results are well reproduced through calculations using an
analytical model, which takes into account the SRR resistance and kinetic
inductance contributed from the complex conductivity of YBCO films. The
theoretical calculations reveal that the increasing SRR resistance upon
increasing photoexcitation fluence is responsible for the reduction of
resonance strength, and both the resistance and kinetic inductance contribute
to the tuning of resonance frequency. | 1111.3917v1 |
2012-05-14 | A fully covariant mean-field dynamo closure for numerical 3+1 resistive GRMHD | The powerful high-energy phenomena typically encountered in astrophysics
invariably involve physical engines, like neutron stars and black hole
accretion disks, characterized by a combination of highly magnetized plasmas,
strong gravitational fields, and relativistic motions. In recent years
numerical schemes for General Relativistic MHD (GRMHD) have been developed to
model the multidimensional dynamics of such systems, including the possibility
of an evolving spacetime. Such schemes have been also extended beyond the ideal
limit including the effects of resistivity, in an attempt to model dissipative
physical processes acting on small scales (sub-grid effects) over the global
dynamics. Along the same lines, magnetic fields could be amplified by the
presence of turbulent dynamo processes, as often invoked to explain the high
values of magnetization required in accretion disks and neutron stars. Here we
present, for the first time, a further extension to include the possibility of
a mean-field dynamo action within the framework of numerical 3+1 (resistive)
GRMHD. A fully covariant dynamo closure is proposed, in analogy with the
classical theory, assuming a simple alpha-effect in the comoving frame. Its
implementation into a finite-difference scheme for GRMHD in dynamical
spacetimes [the X-ECHO code: (Bucciantini and Del Zanna 2011)] is described,
and a set of numerical test is presented and compared with analytical solutions
wherever possible. | 1205.2951v3 |
2013-01-31 | An ageing study of resistive micromegas for the HL-LHC environment | Resistive-anode micromegas detectors are in development since several years,
in an effort to solve the problem of sparks when working at high flux and high
ionizing radiation like in the HL-LHC (up to ten times the luminosity of the
LHC). They have been chosen as one of the technologies that will be part of the
ATLAS New Small Wheel project (forward muon system). An ageing study is
mandatory to assess their capabilities to handle the HL-LHC environment on a
long-term period. A prototype has been exposed to several types of irradiation
(X-rays, cold neutrons, $^{60}$Co gammas and alphas) above the equivalent
charge produced at the detector in five HL-LHC running years without showing
any degradation of the performances in terms of gain and energy resolution.
This study has been completed with the characterization of the tracking
performances in terms of efficiency and spatial resolution, verifying the
compatibility of results obtained with both resistive micromegas detectors,
irradiated and non-irradiated one. | 1301.7648v1 |
2014-03-20 | High Electron Mobility in Epitaxial Graphene on 4H-SiC(0001) via post-growth annealing under hydrogen | We investigate the magneto-transport properties of epitaxial graphene
single-layer on 4H-SiC(0001), grown by atmospheric pressure graphitization in
Ar, followed by H2 intercalation. We directly demonstrate the importance of
saturating the Si dangling bonds at the graphene/SiC(0001) interface to achieve
high carrier mobility. Upon successful Si dangling bonds elimination, carrier
mobility increases from 3 000 cm^2/Vs to > 11 000 cm^2/Vs at 0.3 K.
Additionally, graphene electron concentration tends to decrease from a few
10^12 cm^-2 to less than 10^12 cm^-2. For a typical large (30x280 um^2) Hall
bar, we report the observation of the integer quantum Hall states at 0.3 K with
well developed transversal resistance plateaus at Landau level fillings factors
of nu = 2, 6, 10, 14.. 42 and Shubnikov de Haas oscillation of the longitudinal
resistivity observed from about 1 T. In such a device, the Hall state
quantization at nu=2, at 19 T and 0.3 K, can be very robust: the dissipation in
electronic transport can stay very low, with the longitudinal resistivity lower
than 5 mOhm, for measurement currents as high as 250 uA. This is very promising
in the view of an application in metrology. | 1403.5059v1 |
2015-02-16 | (Li0.84Fe0.16)OHFe0.98Se superconductor: Ion-exchange synthesis of large single crystal and highly two-dimensional electron properties | A large and high-quality single crystal (Li0.84Fe0.16)OHFe0.98Se, the optimal
superconductor of newly reported (Li1-xFex)OHFe1-ySe system, has been
successfully synthesized via a hydrothermal ion-exchange technique. The
superconducting transition temperature (Tc) of 42 K is determined by magnetic
susceptibility and electric resistivity measurements, and the zero-temperature
upper critical magnetic fields are evaluated as 79 and 313 Tesla for the field
along the c-axis and the ab-plane, respectively. The ratio of out-of-plane to
in-plane electric resistivity,\r{ho}c/\r{ho}ab, is found to increases with
decreasing temperature and to reach a high value of 2500 at 50 K, with an
evident kink occurring at a characteristic temperature T*=120 K. The negative
in-plane Hall coefficient indicates that electron carriers dominate in the
charge transport, and the hole contribution is significantly reduced as the
temperature is lowered to approach T*. From T* down to Tc, we observe the
linear temperature dependences of the in-plane electric resistivity and the
magnetic susceptibility for the FeSe layers. Our findings thus reveal that the
normal state of (Li0.84Fe0.16)OHFe0.98Se becomes highly two-dimensional and
anomalous prior to the superconducting transition, providing a new insight into
the mechanism of high-Tc superconductivity. | 1502.04688v2 |
2015-09-29 | Design, development and performance study of six-gap glass MRPC detectors | The Multigap Resistive Plate Chambers (MRPCs) are gas ionization detectors
with multiple gas sub-gaps made of resistive electrodes. The high voltage (HV)
is applied on the outer surfaces of outermost resistive plates only, while the
interior plates are left electrically floating. The presence of multiple narrow
sub--gaps with high electric field results in faster signals on the outer
electrodes, thus improving the detector's time resolution. Due to their
excellent performance and relatively low cost, the MRPC detector has found
potential application in Time-of-Flight (TOF) systems. Here we present the
design, fabrication, optimization of the operating parameters such as the HV,
the gas mixture composition, and, performance of six--gap glass MRPC detectors
of area 27cm $\times$ 27 cm, which are developed in order to find application
as trigger detectors, in TOF measurement etc. The design has been optimized
with unique spacers and blockers to ensure a proper gas flow through the narrow
sub-gaps, which are 250 $\mu$m wide. The gas mixture consisting of R134A,
Isobutane and SF$_{6}$, and the fraction of each constituting gases has been
optimized after studying the MRPC performance for a set of different
concentrations. The counting efficiency of the MRPC is about 95% at $17.9$ kV.
At the same operating voltage, the time resolution, after correcting for the
walk effect, is found to be about $219$ ps. | 1509.08586v2 |
2017-02-21 | Pressure induced half-collapsed-tetragonal phase in CaKFe$_4$As$_4$ | We report the temperature-pressure phase diagram of CaKFe$_4$As$_4$
established using high pressure electrical resistivity, magnetization and high
energy x-ray diffraction measurements up to 6 GPa. With increasing pressure,
both resistivity and magnetization data show that the bulk superconducting
transition of CaKFe$_4$As$_4$ is suppressed and then disappears at $p$
$\gtrsim$ 4 GPa. High pressure x-ray data clearly indicate a phase transition
to a collapsed tetragonal phase in CaKFe$_4$As$_4$ under pressure that
coincides with the abrupt loss of bulk superconductivity near 4 GPa. The x-ray
data, combined with resistivity data, indicate that the collapsed tetragonal
transition line is essentially vertical, occuring at 4.0(5) GPa for
temperatures below 150 K. Band structure calculations also find a sudden
transition to a collapsed tetragonal state near 4 GPa, as As-As bonding takes
place across the Ca-layer. Bonding across the K-layer only occurs for $p$
$\geq$ 12 GPa. These findings demonstrate a new type of collapsed tetragonal
phase in CaKFe$_4$As$_4$: a half-collapsed-tetragonal phase. | 1702.06622v1 |
2016-06-30 | Identification of a possible superconducting transition above room temperature in natural graphite crystals | Measuring with high precision the electrical resistance of highly ordered
natural graphite samples from a Brazil mine, we have identified a transition at
$\sim$350~K with $\sim$40~K transition width. The step-like change in
temperature of the resistance, its magnetic irreversibility and time dependence
after a field change, consistent with trapped flux and flux creep, and the
partial magnetic flux expulsion obtained by magnetization measurements, suggest
the existence of granular superconductivity below 350~K. The zero-field virgin
state can only be reached again after zero field cooling the sample from above
the transition. Paradoxically, the extraordinarily high transition temperature
we found for this and several other graphite samples is the reason why this
transition remained undetected so far. The existence of well ordered
rhombohedral graphite phase in all measured samples has been proved by x-rays
diffraction measurements, suggesting its interfaces with the Bernal phase as a
possible origin for the high-temperature superconductivity, as theoretical
studies predicted. The localization of granular superconductivity at these two
dimensional interfaces prevents the observation of a zero resistance state or
of a full Meissner state. | 1606.09425v1 |
2022-02-04 | Fabrication of Surface Ion Traps with Integrated Current Carrying Wires enabling High Magnetic Field Gradients | A major challenge for quantum computers is the scalable simultaneous
execution of quantum gates. One approach to address this in trapped ion quantum
computers is the implementation of quantum gates based on static magnetic field
gradients and global microwave fields. In this paper, we present the
fabrication of surface ion traps with integrated copper current carrying wires
embedded inside the substrate below the ion trap electrodes, capable of
generating high magnetic field gradients. The copper layer's measured sheet
resistance of 1.12 m$\Omega$/sq at room temperature is sufficiently low to
incorporate complex designs, without excessive power dissipation at high
currents causing a thermal runaway. At a temperature of 40 K the sheet
resistance drops to 20.9 $\mu\Omega$/sq giving a lower limit for the residual
resistance ratio of 100. Continuous currents of 13 A can be applied, resulting
in a simulated magnetic field gradient of 144 T/m at the ion position, which is
125 $\mu$m from the trap surface for the particular anti-parallel wire pair in
our design. | 2202.02313v2 |
2019-03-15 | Hyper-Resistive Model of Ultra High Energy Cosmic Ray Acceleration by Magnetically Collimated Jets Created by Active Galactic Nuclei | This is the fourth in a series of companion papers showing that, when an
efficient dynamo can be maintained by accretion disks around supermassive black
holes in Active Galactic Nuclei (AGNs), it will lead to the formation of a
powerful, magnetically-collimated helix that could explain both the observed
jet/radiolobe structures on very large scales and ultimately the enormous power
inferred from the observed ultra high energy cosmic rays (UHECRs) with energies
> 10^19 eV. Many timescales are involved in this process. Our hyper-resistive
magnetohydrodynamic (MHD) model provides a bridge between General Relativistic
MHD simulations of dynamo formation, on the short accretion timescale, and
observational evidence of magnetic collimation of large-scale jets on
astrophysical timescales. Given the final magnetic structure, we apply
hyper-resistive kinetic theory to show how instability causes slowly-evolving
magnetically-collimated jets to become the most powerful relativistic
accelerators in the Universe. The model yields nine observables in reasonable
agreement with observations: the jet length, radiolobe radius and apparent
opening angle as observed by synchrotron radiation; the synchrotron total
power, synchrotron wavelengths and maximum electron energy (TeVs); and the
maximum UHECR energy, the cosmic ray energy spectrum and the cosmic ray
intensity on Earth. | 1903.06839v2 |
2019-01-23 | Josephson junctions and SQUIDs created by focused helium ion beam irradiation of YBa$_2$Cu$_3$O$_7$ | By scanning with a $30\, \mathrm{keV}$ focused He ion beam (He-FIB) across
YBa$_2$Cu$_3$O$_7$ (YBCO) thin film microbridges, we create Josephson barriers
with critical current density $j_\mathrm{c}$ adjustable by irradiation dose
$D$. The dependence $j_\mathrm{c} (D)$ yields an exponential decay. At $4.2\,
\mathrm{K}$, a transition from flux-flow to Josephson behavior occurs when
$j_\mathrm{c}$ decreases below $\approx 2\, \mathrm{MA/cm^2}$. The Josephson
junctions exhibit current-voltage characteristics (IVCs) that are well
described by the resistively and capacitively shunted junction model, without
excess current for characteristic voltages $V_\mathrm{c} \lesssim 1\,
\mathrm{mV}$. Devices on MgO and LSAT substrates show non-hysteretic IVCs,
while devices on SrTiO$_3$ show a small hysteresis. For all junctions an
approximate scaling $V_\mathrm{c} \propto j_\mathrm{c}^{1/2}$ is found. He-FIB
irradiation with high dose produces barriers with $j_\mathrm{c}=0$ and high
resistances of $10\, \mathrm{k\Omega} \ldots 1\, \mathrm{G\Omega}$. This
provides the possibility to write highly resistive walls or areas into YBCO
using a He-FIB. Transmission electron microscopy reveals an amorphous phase
within the walls, whereas for lower doses the YBCO stays crystalline. We have
also ``drawn'' superconducting quantum interference devices (SQUIDs) by using a
He-FIB for definition of the SQUID hole and the junctions. The SQUIDs show high
performance, with flux noise $< 500\, \mathrm{n \Phi_0/Hz^{1/2}}$ in the
thermal white noise limit for a device with $19\, \mathrm{pH}$ inductance. | 1901.08039v3 |
2023-02-14 | The current unbalance in stacked REBCO tapes -- simulations based on a circuit grid model | Unlike low temperature superconducting cables, there is so far no perfect
solution for REBCO coated conductors to form a fully transposed high current
cable. Every REBCO cable concept must import a stack of tapes to achieve an
operating current as high as tens of kiloamperes. The stacked REBCO tapes, no
matter whether they are twisted or not, however, have a nature of
non-transposing and therefore could result in current unbalance. In this
manuscript, the current unbalance and the related electrical characteristics of
a cable made of 40 stacked REBCO tapes are studied with an electrical circuit
simulation. The differences in splice resistances and tape inductances that are
both related to the non-transposed structure of a REBCO stack are considered.
Results show that for a 40 cm long termination, a proper method to keep the
contact resistivity between each tape and the copper termination around 1e-8
ohmm is crucial to totally avoid current unbalance lowering the cable
performance. Surprisingly, the inter-tape current transfer is found to be able
to further exacerbate local high current though it does make the overall
distribution more balanced. The inductance difference induced current unbalance
is only important if local defects exist at long REBCO tapes, which on the
other hand can be cured by good inter-tape current transfer. For a
fast-charging rate of 1 kA/s, the inter-tape contact resistivity should also be
low to a level of 1e-8 ohmm to ensure a short current transfer length of around
1 m. | 2302.06817v1 |
2024-04-25 | Conductivity of lattice bosons at high temperatures | Quantum simulations are quickly becoming an indispensable tool for studying
particle transport in correlated lattice models. One of the central topics in
the study of transport is the bad-metal behavior, characterized by the direct
current (dc) resistivity linear in temperature. In the fermionic Hubbard model,
optical conductivity has been studied extensively, and a recent optical lattice
experiment has demonstrated bad metal behavior in qualitative agreement with
theory. Far less is known about transport in the bosonic Hubbard model. We
investigate the conductivity in the Bose-Hubbard model, and focus on the regime
of strong interactions and high-temperatures. We use numerically exact
calculations for small lattice sizes. At weak tunneling, we find multiple peaks
in the optical conductivity that stem from the Hubbard bands present in the
many-body spectrum. This feature slowly washes out as the tunneling rate gets
stronger. At high temperature, we identify a regime of $T$-linear resistivity,
as expected. When the interactions are very strong, the leading
inverse-temperature coefficient in conductivity is proportional to the
tunneling amplitude. As the tunneling becomes stronger, this dependence takes
quadratic form. At very strong coupling and half filling, we identify a
separate linear resistivity regime at lower temperature, corresponding to the
hard-core boson regime. Additionally, we unexpectedly observe that at half
filling, in a big part of the phase diagram, conductivity is an increasing
function of the coupling constant before it saturates at the hard-core-boson
result. We explain this feature based on the analysis of the many-body energy
spectrum and the contributions to conductivity of individual eigenstates of the
system. | 2404.16559v1 |
2004-10-22 | Observation of double resistance anomalies and excessive resistance in mesoscopic superconducting Au$_{0.7}$In$_{0.3}$ rings with phase separation | We have measured mesoscopic superconducting Au$_{0.7}$In$_{0.3}$ rings
prepared by e-beam lithography and sequential deposition of Au and In at room
temperature followed by a standard lift-off procedure. In samples showing no
Little-Parks resistance oscillations, highly unusual double resistance
anomalies, two resistance peaks found near the onset of superconductivity, were
observed. Although resistance anomaly featuring a single resistance peak has
been seen in various mesoscopic superconducting samples, double resistance
anomalies have never been observed previously. The dynamical resistance
measurements suggest that there are two critical currents in these samples. In
addition, the two resistance peaks were found to be suppressed at different
magnetic fields. We attribute the observed double resistance anomalies to an
underlying phase separation in which In-rich grains of intermetallic compound
of AuIn precipitate in a uniform In-dilute matrix of Au$_{0.9}$In$_{0.1}$. The
intrinsic superconducting transition temperature of the In-rich grains is
substantially higher than that of the In-dilute matrix. The suppression of the
conventional Little-Parks resistance oscillation is explained in the same
picture by taking into consideration a strong variation in the $T_c$ of the
In-rich grains. We also report the observation of an unusual
magnetic-field-induced metallic state with its resistance higher than the
normal-state resistance, referred to here as excessive resistance, and an h/2e
resistance oscillation with the amplitude of oscillation depends extremely
weakly on temperature. | 0410567v2 |
2022-09-17 | Superfunctional materials by ultra-severe plastic deformation | Superfunctional materials are defined as materials with specific properties
being superior to the functions of engineering materials. Numerous studies
introduced severe plastic deformation (SPD) as an effective process to improve
the functional and mechanical properties of various metallic and non-metallic
materials. Moreover, the concept of ultra-SPD - introducing shear strains over
1000 to reduce the thickness of sheared phases to levels comparable to atomic
distances - was recently utilized to synthesize novel superfunctional
materials. In this article, the application of ultra-SPD for controlling atomic
diffusion and phase transformation and synthesizing new materials with
superfunctional properties is discussed. The main properties achieved by
ultra-SPD include: (i) high-temperature thermal stability in new immiscible
age-hardenable aluminum alloys; (ii) room-temperature superplasticity for the
first time in magnesium and aluminum alloys; (iii) high strength and high
plasticity in nanograined intermetallics; (iv) low elastic modulus and high
hardness in biocompatible binary and high-entropy alloys; (v) superconductivity
and high strength in the Nb-Ti alloys; (vi) room-temperature hydrogen storage
for the first time in magnesium alloys; and (vii) superior photocatalytic
hydrogen production, oxygen production, and carbon dioxide conversion on
high-entropy oxides and oxynitrides as a new family of photocatalysts. | 2209.08295v3 |
2020-06-08 | Data-driven topology design using a deep generative model | In this paper, we propose a sensitivity-free and multi-objective structural
design methodology called data-driven topology design. It is schemed to obtain
high-performance material distributions from initially given material
distributions in a given design domain. Its basic idea is to iterate the
following processes: (i) selecting material distributions from a dataset of
material distributions according to eliteness, (ii) generating new material
distributions using a deep generative model trained with the selected elite
material distributions, and (iii) merging the generated material distributions
with the dataset. Because of the nature of a deep generative model, the
generated material distributions are diverse and inherit features of the
training data, that is, the elite material distributions. Therefore, it is
expected that some of the generated material distributions are superior to the
current elite material distributions, and by merging the generated material
distributions with the dataset, the performances of the newly selected elite
material distributions are improved. The performances are further improved by
iterating the above processes. The usefulness of data-driven topology design is
demonstrated through numerical examples. | 2006.04559v3 |
2024-04-03 | Wenzhou TE: a first-principles calculated thermoelectric materials database | Since the implementation of the Materials Genome Project by the Obama
administration in the United States, the development of various computational
materials databases has fundamentally expanded the choices of industries such
as materials and energy. In the field of thermoelectric materials, the
thermoelectric figure of merit ZT quantifies the performance of the material.
From the viewpoint of calculations for vast materials, the ZT values are not
easily obtained due to their computational complexity. Here, we show how to
build a database of thermoelectric materials based on first-principles
calculations for the electronic and heat transport of materials. Firstly, the
initial structures are classified according to the values of bandgap and other
basic properties using the clustering algorithm K-means in machine learning,
and high-throughput first principles calculations are carried out for
narrow-bandgap semiconductors which exhibiting potential thermoelectric
application. The present framework of calculations mainly includes deformation
potential module, electrical transport performance module, mechanical and
thermodynamic properties module. We have also set up a search webpage for the
calculated database of thermoelectric materials, providing searching and
viewing the related physical properties of materials. Our work may inspire the
construction of more computational databases of first-principle thermoelectric
materials and accelerate research progress in the field of thermoelectrics. | 2404.02571v1 |
2023-12-13 | The Milky Way shines in high-energy neutrinos | The most energetic astrophysical sources in the Milky Way, cosmic
accelerators capable of producing high-energy cosmic rays, have resisted
discovery for over a century. Up to now, astrophysicists sought these sources
mainly by scouring the Galaxy for the gamma rays they are expected to emit. In
2023, the IceCube Neutrino Observatory discovered high-energy neutrinos from
the Milky Way, inaugurating a telltale stream of evidence of cosmic-ray
production and interaction in the Galaxy. | 2312.08102v1 |
1998-10-21 | Inverse Cascade of Primordial Magnetic Field in MHD Turbulence | The feature of the spectrum of primordial magnetic field is studied by using
renormalization group analysis in magnetohydrodynamics. Taking account of the
renormalized resistivity at the fixed point, we show that the scaling of the
typical scale with time obeys $L(t) \sim t^{2/5}$ for random initial condition. | 9810339v1 |
1999-06-10 | Luttinger liquid behavior in single wall nanotubes | Transport properties of metallic single-wall nanotubes are examined based on
the Luttinger liquid theory. Focusing on a nanotube transistor setup, the
linear conductance is computed from the Kubo formula using perturbation theory
in the lead-tube tunnel conductances. For sufficiently long nanotubes and high
temperature, phonon backscattering should lead to an anomalous temperature
dependence of the resistivity. | 9906150v1 |
2002-01-07 | Temperature-dependent $H_{c2}$ anisotropy in MgB$_2$ as inferred from measurements on polycrystals | We present data on temperature-dependent anisotropy of the upper critical
field of MgB$_2$ obtained from the analysis of measurements on high purity, low
resistivity polycrystals. The anisotropy decreases in a monotonic fashion with
increase of temperature. | 0201085v1 |
2003-05-29 | Imaging the charge transport in arrays of CdSe nanocrystals | A novel method to image charge is used to measure the diffusion coefficient
of electrons in films of CdSe nanocrystals at room temperature. This method
makes possible the study of charge transport in films exhibiting high
resistances or very small diffusion coefficients. | 0305684v1 |
2003-06-03 | Intrinsic tunneling or Joule heating? | It is shown that the `tunnelling spectra' reported by Yurgens et al. could be
reproduced qualitatively and quantitatively using the experimental out-of-plane
normal state resistance R(T) and assuming that the heating of the mesa, caused
by the Joule dissipation, is the only reason for effects observed at high bias. | 0306081v2 |
2004-10-09 | Comment on cond-mat/0409228 "Microwave photoresponse in the 2D electron system caused by intra-Landau level transitions" | We provide an article-extract which points out that a microwave-induced
modification in the resistance occurs at relatively "high" magnetic fields
where the radiation is incapable of producing inter-Landau level excitations
and, therefore, that the microwave radiation must be producing intra Landau
level excitations as well. | 0410227v1 |
2005-11-22 | Quantum phase slip junctions | In this paper we demonstrate that, if it exists, coherent quantum phase slip
is the exact dual to Josephson tunneling. We use the duality to predict kinetic
capacitance and a sharp resonance in narrow wires. Biased resistively and
driven at high frequency, quantum phase slip junctions should exhibit current
plateaus of interest for a fundamental standard. | 0511535v1 |
2003-04-13 | Comment on "Phase Transition-Like Behavior in a Low-Pass Filter" | This is a reminder that an infinite series can be defined other than as the
limit of a sequence of finite series. An example is provided in which a circuit
element comprised of an infinite series of resistors has negative resistance. | 0304051v1 |
2005-01-24 | Nonlocal Gate Of Quantum Network Via Cavity Quantum Electrodynamics | We propose an experimentally feasible scheme to realize the nonlocal gate
between two different quantum network nodes. With an entanglement-qubit (ebit)
acts as a quantum channel, our scheme is resistive to actual environment noise
and can get high fidelity in current cavity quantum electrodynamics (C-QED)
system. | 0501125v2 |
2008-03-16 | Asymmetric exclusion processes with constrained dynamics | Asymmetric exclusion processes with locally reversible kinetic constraints
are introduced to investigate the effect of non-conservative driving forces in
athermal systems. At high density they generally exhibit rheological-like
behavior, negative differential resistance, two-step structural relaxation,
dynamical heterogeneity and, possibly, a jamming transition driven by the
external field. | 0803.2287v2 |
2010-04-05 | Superconducting plasmonics and extraordinary transmission | Negative dielectric constant and dominant kinetic resistance make
superconductors an intriguing plasmonic media. Here we report on the first
study of one of the most important and disputed manifestations of plasmonics,
the effect of extraordinary transmission through an array of sub-wavelength
holes, using a perforated film of high-temperature superconductor. | 1004.0729v1 |
2010-05-03 | Construction of a Digital Hadron Calorimeter | The DHCAL collaboration is assembling a large scale prototype Digital Hadron
Calorimeter (DHCAL). The calorimeter utilizes Resistive Plate Chambers (RPCs)
as active medium and features of the order of 400,000 1 \times 1 cm2 pads with
binary (or digital) electronic readout. The purpose of the prototype is to
provide detailed measurements of hadronic showers and to prove the concept of a
DHCAL with RPCs as active elements. | 1005.0410v1 |
2010-07-16 | Indications of room-temperature superconductivity at a metal-PZT interface | We report the observation of an exceptionally large room-temperature
electrical conductivity in silver and aluminum layers deposited on a lead
zirconate titanate (PZT) substrate. The surface resistance of the silver-coated
samples also shows a sharp change near 313 K. The results are strongly
suggestive of a superconductive interfacial layer, and have been interpreted in
the framework of Bose-Einstein condensation of bipolarons as the suggested
mechanism for high-temperature superconductivity in cuprates. | 1007.2736v1 |
2010-07-18 | Test Beam Results Using an RPC Semi-Digital HCAL | We report on the development of an GRPCs (Glass Resistive Plate chambers)
Semi- Digital hadron calorimeter for the future International Linear Collider
(ILC).Two types of GRPCs (small and 1m2) were tested in PS beam at CERN.
Detector performances are presented here in terms of efficiency, pad
multiplicity, homogeneity and stability in time. | 1007.3009v3 |
2011-12-14 | Superconductivity in Single-Crystal YIn3 | We measure the superconducting transition of YIn$_3$ by resistivity,
susceptibility, and specific heat. Despite using high-quality single-crystal
samples, the transitions detected by the three techniques are shifted from each
other in temperature, suggesting a region of filamentary superconductivity. We
discuss the possible implications for filamentary superconductivity in
unconventional superconductors. | 1112.3083v1 |
2013-03-05 | Unusual suppression of superconductivity in YNi2B2C under neutron irradiation | The behavior of electrical resistivity rho(T), temperature of superconducting
transition Tc, and upper critical field Hc2(T) of polycrystalline YNi2B2C after
irradiation with thermal neutron and subsequent high-temperature isochronous
annealings in the temperature range Tann = 100 - 1000C has been studied. | 1303.0929v1 |
2015-01-11 | Resistance of a Rotating-Moving Brane with Background Fields Against Collapse | Using the boundary state formalism we investigate the effect of tachyon
condensation process on a rotating and moving D$p$-brane with various
background fields in the bosonic string theory. The rotation and motion are
inside the brane volume. We demonstrate that some specific rotations and/or
motions can preserve the brane from instability and collapse. | 1501.02453v1 |
2017-02-12 | Optimal doping of the diode current interrupters | An analytical solution to the problem of decreasing the energy losses
$\Omega$ in diode current interrupters during recovery of the blocking ability
by optimizing dopant distribution $N(x)$ over structure thickness has been
obtained. It was found the distribution $N(x)$ close to optimal one that
decreases $\Omega$ by 30-55% compared with standard interrupters with uniformly
doped high-resistivity layers. | 1702.03496v1 |
2016-03-24 | A note on "achieving security, robust cheating resistance, and high-efficiency for outsourcing large matrix multiplication computation to a malicious cloud" | We show that the Lei et al.'s scheme [Information Sciences, 280 (2014),
205-217] fails, because the verifying equation does not hold over the infinite
field R. For the field R, the computational errors should be considered
seriously. We also remark that the incurred communication cost in the scheme
could be overtake the computational gain, which makes it somewhat artificial. | 1603.07399v1 |
2020-06-07 | Asymmetric Jet launching | In resistive and viscous magnetohydrodynamical (MHD) simulations we obtain
axial jets launched from the innermost magnetosphere of a star-disk system. We
found that in a part of the parameter space continuous asymmetric jets, which
are propagating in opposite directions, are launched. We compare the speed of
propagation and rotation of obtained jets with recent observational results. | 2006.04083v1 |
2021-12-30 | Two Instances of Interpretable Neural Network for Universal Approximations | This paper proposes two bottom-up interpretable neural network (NN)
constructions for universal approximation, namely Triangularly-constructed NN
(TNN) and Semi-Quantized Activation NN (SQANN). Further notable properties are
(1) resistance to catastrophic forgetting (2) existence of proof for
arbitrarily high accuracies (3) the ability to identify samples that are
out-of-distribution through interpretable activation "fingerprints". | 2112.15026v2 |
2022-02-20 | High-throughput computational screening of nanoporous materials in targeted applications | Due to their chemical and structural diversity, nanoporous materials can be
used in a wide variety of applications, including fluid separation, gas
storage, heterogeneous catalysis, drug delivery, etc. Given the large and
rapidly increasing number of known nanoporous materials, and the even bigger
number of hypothetical structures, computational screening is an efficient
method to find the current best-performing materials and to guide the design of
future materials. This review highlights the potential of high-throughput
computational screenings in various applications. The achievements and the
challenges associated to the screening of several material properties are
discussed to give a broader perspective on the future of the field. | 2202.09886v2 |
2020-08-29 | High-throughput Design of Magnetic Materials | Materials design based on density functional theory (DFT) calculations is an
emergent field of great potential to accelerate the development and employment
of novel materials. Magnetic materials play an essential role in green energy
applications as they provide efficient ways of harvesting, converting, and
utilizing energy. In this review, after a brief introduction to the major
functionalities of magnetic materials, we demonstrated the fundamental
properties which can be tackled via high-throughput DFT calculations, with a
particular focus on the current challenges and feasible solutions. Successful
case studies are summarized on several classes of magnetic materials, followed
by bird-view perspectives for the future. | 2008.12907v1 |
2021-02-03 | High-throughput discovery of novel cubic crystal materials using deep generative neural networks | High-throughput screening has become one of the major strategies for the
discovery of novel functional materials. However, its effectiveness is severely
limited by the lack of quantity and diversity of known materials deposited in
the current materials repositories such as ICSD and OQMD. Recent progress in
machine learning and especially deep learning have enabled a generative
strategy that learns implicit chemical rules for creating chemically valid
hypothetical materials with new compositions and structures. However, current
materials generative models have difficulty in generating structurally diverse,
chemically valid, and stable materials. Here we propose CubicGAN, a generative
adversarial network (GAN) based deep neural network model for large scale
generation of novel cubic crystal structures. When trained on 375,749 ternary
crystal materials from the OQMD database, we show that our model is able to not
only rediscover most of the currently known cubic materials but also generate
hypothetical materials of new structure prototypes. A total of 506 such new
materials (all of them are either ternary or quarternary) have been verified by
DFT based phonon dispersion stability check, several of which have been found
to potentially have exceptional functional properties. Considering the
importance of cubic materials in wide applications such as solar cells and
lithium batteries, our GAN model provides a promising approach to significantly
expand the current repository of materials, enabling the discovery of new
functional materials via screening. The new crystal structures finally verified
by DFT are freely accessible at our Carolina Materials Database
http://www.carolinamatdb.org. | 2102.01880v2 |
2020-08-25 | Cathode Materials for Lithium Ion Batteries (LIBs): A Review on Materials related aspects towards High Energy Density LIBs | This article reviews the development of cathode materials for secondary
lithium ion batteries since its inception with the introduction of lithium
cobalt oxide in early 1980s. The time has passed and numerous cathode materials
are designed and developed to realize not only the enhanced capacity but also
the power density simultaneously. However, there are numerous challenges such
as the cyclic stability of cathode materials, their structural and thermal
stability, higher operating voltage together with high ionic and electronic
conductivity for efficient ion and charge transport during charging and
discharging. This article will cover the development of materials in
chronological order classifying as the lithium ion cathode materials in
different generations. The ternary oxides such as LiTMOx (TM=Transition Metal)
are considered as the first generation materials, whereas modified ternary and
quaternary oxide systems are considered as the second generation materials. The
current i.e. third generation includes complex oxide systems with higher
lithium content such as Li2TMSiO4 aiming for higher energy density. Further,
developments are heading towards lithium metal based batteries with a
possibility for very high energy densities. | 2008.10896v2 |
1999-11-15 | Comparison of the Transport Mechanism in Underdoped High Temperature Superconductors and in Spin Ladders | Recently, the normal state resistivity of high temperature superconductors
(in particular in La2-xSrxCuO4 single crystals) has been studied extensively in
the region below Tc by suppressing the superconducting state in high magnetic
fields. In the present work we report on the normal state resistance of
underdoped La2-xSrxCuO4 thin films under epitaxial strain, measured far below
Tc by applying pulsed fields up to 60 T. We will compare the transport
measurements on these high temperature superconductors with transport data
reported for the Sr2.5Ca11.5Cu24O41 spin ladder compound. This comparison leads
to an interpretation of the data in terms of the recently proposed 1D quantum
transport model and the charge-stripe models. | 9911217v1 |
2007-11-13 | High-resolution intracellular recordings using a real-time computational model of the electrode | Intracellular recordings of neuronal membrane potential are a central tool in
neurophysiology. In many situations, especially in vivo, the traditional
limitation of such recordings is the high electrode resistance, which may cause
significant measurement errors. We introduce a computer-aided technique, Active
Electrode Compensation (AEC), based on a digital model of the electrode
interfaced in real time with the electrophysiological setup. The
characteristics of this model are first estimated using white noise current
injection. The electrode and membrane contribution are digitally separated, and
the recording is then made by online subtraction of the electrode contribution.
Tests comparing AEC to other techniques demonstrate that it yields recordings
with improved accuracy. It enables high-frequency recordings in demanding
conditions, such as injection of conductance noise in dynamic-clamp mode, not
feasible with a single high resistance electrode until now. AEC should be
particularly useful to characterize fast phenomena in neurons, in vivo and in
vitro. | 0711.2075v1 |
2010-08-19 | Josephson Coupling and Fiske Dynamics in Ferromagnetic Tunnel Junctions | We report on the fabrication of Nb/AlO_x/Pd_{0.82}Ni_{0.18}/Nb
superconductor/insulator/ferromagnetic metal/superconductor (SIFS) Josephson
junctions with high critical current densities, large normal resistance times
area products, high quality factors, and very good spatial uniformity. For
these junctions a transition from 0- to \pi-coupling is observed for a
thickness d_F ~ 6 nm of the ferromagnetic Pd_{0.82}Ni_{0.18} interlayer. The
magnetic field dependence of the \pi-coupled junctions demonstrates good
spatial homogeneity of the tunneling barrier and ferromagnetic interlayer.
Magnetic characterization shows that the Pd_{0.82}Ni_{0.18} has an out-of-plane
anisotropy and large saturation magnetization, indicating negligible dead
layers at the interfaces. A careful analysis of Fiske modes provides
information on the junction quality factor and the relevant damping mechanisms
up to about 400 GHz. Whereas losses due to quasiparticle tunneling dominate at
low frequencies, the damping is dominated by the finite surface resistance of
the junction electrodes at high frequencies. High quality factors of up to 30
around 200 GHz have been achieved. Our analysis shows that the fabricated
junctions are promising for applications in superconducting quantum circuits or
quantum tunneling experiments. | 1008.3341v1 |
2010-09-02 | Superconducting and Structural Transitions in the β-Pyrochlore Oxide KOs2O6 under High Pressure | Rattling-induced superconductivity in the {\beta}-pyrochlore oxide KOs2O6 is
investigated under high pressure up to 5 GPa. Resistivity measurements in a
high-quality single crystal reveal a gradual decrease in the superconducting
transition temperature Tc from 9.7 K at 1.0 GPa to 6.5 K at 3.5 GPa, followed
by a sudden drop to 3.3 K at 3.6 GPa. Powder X-ray diffraction experiments show
a structural transition from cubic to monoclinic or triclinic at a similar
pressure. The sudden drop in Tc is ascribed to this structural tran-sition, by
which an enhancement in Tc due to a strong electron-rattler interaction present
in the low-pressure cubic phase is abrogated as the rattling of the K ion is
completely suppressed or weakened in the high-pressure phase of reduced
symmetry. In addition, we find two anomalies in the temperature dependence of
resistivity in the low-pressure phase, which may be due to subtle changes in
rattling vibration. | 1009.0355v1 |
2010-09-03 | Test beam studies for a highly granular GRPC Semi-Digital HCAL | The Particle Flow Analysis approach retained for the future ILC detectors
requires high granularity and compact particle energy deposition. A Glass
Resistive Plate Chamber based Semi-Digital calorimeter can offer both at a low
price for the hadronic section. This paper presents some recent developments
and results near test beam in the use of Glass Resistive Plate Chamber with
embedded front-end electronics to build a prototype based on this principle.
All the critical parameters such as the spatial and angular uniformity of the
response as well as the noise level have been measured on small chambers and
found to be appropriate. Small semi-conductive chambers allowing for high rates
and a large chamber have also been tested. | 1009.0719v1 |
2016-10-19 | Gossamer bulk high-temperature superconductivity in FeSe | The cuprates and iron-based high-temperature superconductors share many
common features: layered strongly anisotropic crystal structure, strong
electronic correlations, interplay between different types of electronic
ordering, the intrinsic spatial inhomogeneity due to doping. The understanding
of complex interplay between these factors is crucial for a directed search of
new high-temperature superconductors. Here we show the appearance of
inhomogeneous gossamer superconductivity in bulk FeSe compound at ambient
pressure and at temperature 5 times higher than its zero-resistance $T_c$. This
discovery helps to understand numerous remarkable superconducting properties of
FeSe. We also find and prove a general property: if inhomogeneous
superconductivity in a anisotropic conductor first appears in the form of
isolated superconducting islands, it reduces electric resistivity
anisotropically with maximal effect along the least conducting axis. This gives
a simple and very general tool to detect inhomogeneous superconductivity in
anisotropic compounds, which is critically important to study the onset of
high-temperature superconductivity. | 1610.06117v1 |
2016-12-09 | Graphenic Carbon-Silicon Contacts for Reliability Improvement of Metal-Silicon Junctions | Contact resistance and thermal degradation of metal-silicon contacts are
challenges in nanoscale CMOS as well as in power device applications. Titanium
silicide (TiSi) contacts are commonly used metal-silicon contacts, but are
known to diffuse into the active region under high current stress. In this
paper we show that a graphenic carbon (C) contact deposited on n-type silicon
(C-Si) by CVD, has the same low Schottky barrier height of 0.45 eV as TiSi, but
a much improved reliability against high current stress. The C-Si contact is
over 100 million times more stable against high current stress pulses than the
conventionally used TiSi junction. The C-Si contact properties even show
promise to establish an ultra-low, high temperature stable contact resistance.
The finding has important consequences for the enhancement of reliability in
power devices as well as in Schottky-diodes and electrical contacts to silicon
in general. | 1612.06362v1 |
2018-10-05 | Superconducting proximity effect in epitaxial Al-InAs heterostructures | Semiconductor-based Josephson junctions provide a platform for studying
proximity effect due to the possibility of tuning junction properties by gate
voltage and large-scale fabrication of complex Josephson circuits. Recently
Josephson junctions using InAs weak link with epitaxial aluminum contact have
improved the product of normal resistance and critical current, $I_cR_N$, in
addition to fabrication process reliability. Here we study similar devices with
epitaxial contact and find large supercurrent and substantial product of
$I_cR_N$ in our junctions. However we find a striking difference when we
compare these samples with higher mobility samples in terms of product of
excess current and normal resistance, $I_{ex}R_N$. The excess current is
negligible in lower mobility devices while it is substantial and independent of
gate voltage and junction length in high mobility samples. This indicates that
even though both sample types have epitaxial contacts only the high-mobility
one has a high transparency interface. In the high mobility short junctions, we
observe values of $I_cR_N/\Delta \sim 2.2$ and $I_{ex}R_N/\Delta \sim 1.5$ in
semiconductor weak links. | 1810.02514v4 |
2019-07-23 | High-Chern-Number and High-Temperature Quantum Hall Effect without Landau Levels | The quantum Hall effect (QHE) with quantized Hall resistance of h/{\nu}e2
starts the research on topological quantum states and lays the foundation of
topology in physics. Afterwards, Haldane proposed the QHE without Landau
levels, showing nonzero Chern number |C|=1, which has been experimentally
observed at relatively low temperatures. For emerging physics and
low-power-consumption electronics, the key issues are how to increase the
working temperature and realize high Chern numbers (C>1). Here, we report the
experimental discovery of high-Chern-number QHE (C=2) without Landau levels and
C=1 Chern insulator state displaying nearly quantized Hall resistance plateau
above the N\'eel temperature in MnBi2Te4 devices. Our observations provide a
new perspective on topological matter and open new avenues for exploration of
exotic topological quantum states and topological phase transitions at higher
temperatures. | 1907.09947v4 |
2021-01-08 | Superconductivity at ~70 K in Tin Hydride SnHx under High Pressure | Various tin hydrides SnHx (x = 4, 8, 12, 14) have been theoretically
predicted to be stable at high pressures and to show high-critical-temperature
superconductivity with Tc ranging from about 70 to 100 K. However, experimental
verifications for any of these phases are still lacking to date. Here, we
report on the in-situ synthesis, electrical resistance, and synchrotron x-ray
diffraction measurements of SnHx at ~ 200 GPa. The main phase of the obtained
sample can be indexed with the monoclinic C2/m SnH12 via comparison with the
theoretical structural modes. A sudden drop of resistance and the systematic
downward shift under external magnetic fields signals the occurrence of
superconductivity in SnHx at Tc = ~ 70 K with an upper critical field u0Hc2(0)
= ~ 11.2 T, which is relatively low in comparison with other reported high-Tc
superhydrides. Various characteristic superconducting parameters are estimated
based on the BCS theory. | 2101.02846v1 |
2021-07-20 | Performance of a fast timing micro-pattern gaseous detector for future collider experiments | The fast timing MPGD is a micro-pattern gaseous detector conceived for
achieving sub-nanosecond time resolution while maintaining the ability to
instrument large areas in high-rate environments; applications of such
technology are perspected in high-energy physics experiments at future
colliders and medical diagnostics with time-of-flight methods. This work shows
the systematic studies carried on an FTM prototype on the performance of GEM
foils coated with resistive DLC films, whose development is essential for the
FTM operation. The resistive foil performance has been tested with several gas
mixtures and compared with the results obtained on conductive foils. The
results show that the performance of the FTM is presently limited by the
technology of manufacturing of DLC-coated GEM foils, with high gains reachable
exclusively in isobuthane-based mixtures. | 2107.09439v1 |
2021-10-27 | Robust genuine high-dimensional steering with many measurements | Quantum systems of high dimensions are attracting a lot of attention because
they feature interesting properties when it comes to observing entanglement or
other forms of correlations. In particular, their improved resistance to noise
is favourable for experiments in quantum communication or quantum cryptography.
However, witnessing this high-dimensional nature remains challenging,
especially when the assumptions on the parties involved are weak, typically
when one of them is considered as a black box. In this context, the concept of
genuine high-dimensional steering has been recently introduced and
experimentally demonstrated [Phys. Rev. Lett. 126, 200404 (2021)]; it allows
for a one-sided device-independent certification of the dimension of a
bipartite shared state by only using two measurements. Here I overcome this
limitation by developing, for more than two measurements, universal bounds on
the incompatibility robustness, turned into meaningful dimension certificates.
Interestingly, even though the resulting bounds are quite loose, they still
often offer an increased resistance to noise and could then be advantageously
employed in experiments. | 2110.14435v2 |
2022-03-10 | Large output voltage to magnetic flux change in nanoSQUIDs based on direct-write Focused Ion Beam Induced Deposition technique | NanoSQUIDs are quantum sensors that excel in detecting a small change in
magnetic flux with high sensitivity and high spatial resolution. Here, we
employ resist-free direct-write Ga+ Focused Ion Beam Induced Deposition (FIBID)
techniques to grow W-C nanoSQUIDs, and we investigate their electrical response
to changes in the magnetic flux. Remarkably, FIBID allows the fast
($3~\mathrm{nm}$) growth of $700~\mathrm{nm}\times 300~\mathrm{nm}$
Dayem-bridge nanoSQUIDs based on narrow nanowires ($50~\mathrm{nm}$ wide) that
act as Josephson junctions. The observed transfer coefficient (output voltage
to magnetic flux change) is very high (up to $1301~\mathrm{\mu V/\Phi_0}$),
which correlates with the high resistivity of W-C in the normal state. We
discuss here the potential of this approach to reduce the active area of the
nanoSQUIDs to gain spatial resolution as well as their integration on
cantilevers for scanning-SQUID applications. | 2203.05278v1 |
2008-08-07 | Thermal strain-induced enhancement of electromagnetic properties in SiC-MgB2 composites | Strain engineering has been used to modify materials properties in
ferroelectric, superconducting, and ferromagnetic thin films. The advantage of
strain engineering is that it can achieve unexpected enhancement in certain
properties, such as an increase in ferroelectric critical temperature, Tc, by
300 to 500K, with a minimum detrimental effect on the intrinsic properties of
the material. The strain engineering has been largely applied to the materials
in thin film form, where the strain is generated as a result of lattice
mismatch between the substrate and component film or between layers in
multilayer structures. Here, we report the observation of residual thermal
stress/strain in dense SiC-MgB2 superconductor composites prepared by a
diffusion method. We demonstrate that the thermal strain caused by the
different thermal expansion coefficients between the MgB2 and SiC phases is
responsible for the significant improvement in the critical current density,
Jc, the irreversibility field, Hirr, and the upper critical field, Hc2, in the
SiC-MgB2 composite where the carbon substitution level is low. In contrast to
the common practice of improving the Jc and Hc2 of MgB2 through chemical
substitution, by taking advantage of residual thermal strains we are able to
design a composite, which shows only a small drop in Tc and little increase in
resistivity, but a significant improvement over the Jc and Hc2 of MgB2. The
present findings open up a new direction for manipulation of materials
properties through strain engineering for materials in various forms. | 0808.1136v1 |
2008-08-26 | Thermoelectric Effects in Anisotropic Systems: Measurement and Applications | The Harman method for measuring the thermal conductivity of a sample using
the Peltier effect, may also be used to determine the dimensionless figure of
merit from just two electrical resistance measurements. We consider a modified
version of the Harman method where the current contacts are much smaller than
the contact faces of the sample. We calculate the voltage and temperature
distributions in a rectangular sample of a material having anisotropy in all of
its transport coefficients. The thermoelectric anisotropy has important
consequences in the form of thermoelectric eddy currents and the Bridgman
effect. We prove that in the limit of a very thin sample of arbitrary shape,
there exist van der Pauw formulae relating particular linear combinations of
the potential and temperature differences between points on the edges of the
sample. We show that the Harman figure of merit can be radically different from
the intrinsic figures of merit of the material, and can often be substantially
enhanced. By defining an effective figure of merit in terms of the rate of
entropy production, we show that the increase in the Harman figure of merit
does indicate an improvement in the thermoelectric performance of an
anisotropic sample having small current contacts. However, we also prove that
in the case of a material with tetragonal symmetry, the effective figure of
merit is always bounded from above by the largest intrinsic figure of merit of
the material. | 0808.3526v1 |
2015-02-27 | Electrically Tunable Band Gap in Antiferromagnetic Mott Insulator Sr2IrO4 | The electronic band gap in conventional semiconductor materials, such as
silicon, is fixed by the material's crystal structure and chemical composition.
The gap defines the material's transport and optical properties and is of great
importance for performance of semiconductor devices like diodes, transistors
and lasers. The ability to tune its value would allow enhanced functionality
and flexibility of future electronic and optical devices. Recently, an
electrically tunable band gap was realized in a 2D material - electronically
gated bilayer graphene [1-3]. Here we demonstrate the realization of an
electrically tunable band gap in a 3D antiferromagnetic Mott insulator Sr2IrO4.
Using nano-scale contacts between a sharpened Cu tip and a single crystal of
Sr2IrO4, we apply a variable external electric field up to a few MV/m and
demonstrate a continuous reduction in the band gap of Sr2IrO4 by as much as
16%. We further demonstrate the feasibility of reversible resistive switching
and electrically tunable anisotropic magnetoresistance,which provide evidence
of correlations between electronic transport, magnetic order, and orbital
states in this 5d oxide. Our findings suggest a promising path towards band gap
engineering in 5d transition-metal oxides that could potentially lead to
appealing technical solutions for next-generation electronic devices. | 1502.07982v1 |
2016-11-28 | Synthesis of low-moment CrVTiAl: a potential room temperature spin filter | The efficient production of spin-polarized currents at room temperature is
fundamental to the advancement of spintronics. Spin-filter materials ---
semiconductors with unequal band gaps for each spin channel --- can generate
spin-polarized current without the need for spin-polarized contacts. In
addition, a spin-filter material with zero magnetic moment would have the
advantage of not producing strong fringing fields that would interfere with
neighboring electronic components and limit the volume density of devices. The
quaternary Heusler compound CrVTiAl has been predicted to be a zero-moment
spin-filter material with a Curie temperature in excess of 1000 K. In this
work, CrVTiAl has been synthesized with a lattice constant of $a = 6.15 \AA$.
Magnetization measurements reveal an exceptionally low moment of $\mu = 2.3
\times 10^{-3} \mu_B/f.u.$ at a field of $\mu_0 H = 2 T$, that is independent
of temperature between T = 10 K and 400 K, consistent with the predicted
zero-moment ferrimagnetism. Transport measurements reveal a combination of
metallic and semiconducting components to the resistivity. Combining a
zero-moment spin-filter material with nonmagnetic electrodes would lead to an
essentially nonmagnetic spin injector. These results suggest that CrVTiAl is a
promising candidate for further research in the field of spintronics. | 1611.09307v3 |
2016-10-19 | Lattice of infinite bending-resistant fibers | This article present the double-periodical lattice made of infinite elastic
fibers that withstand bending and tension. The model describes the elastic
properties of flat periodic structure. With this model the behavior of a
two-dimensional array of infinite fibers is simulated. The material that
contains a row of broken fibers is considered. These broken fibers form the
failure in the material that shapes like a long straight crack. The lattice is
tensioned in the direction, which is orthogonal to the direction of straight
crack. The conditions of fracture of this lattice are investigated. The closed
form expression for the stress in the first unbroken fiber and the expression
for fracture toughness are given. These values are the functions of mechanical
parameters of lattice and tensions in both families of fibers. The closed form
solution demonstrates a notable behavior of the material. Namely, the fracture
behavior of two-dimensional lattice is cardinally depends upon the pre-stress
in the material in the direction, parallel to crack direction. If the tension
in fibers that parallel to the crack direction exists, it stabilizes the crack
growth and makes the load distribution in the unbroken fibers more even. The
two-dimensional lattice behaves in the presence of tension in both directions
similarly to the plane elastic media. The finite length crack assumes the shape
of the elongated elliptic split. Another behavior of lattice occurs if the
fibers, parallel to crack direction, are unstressed. The character of stress
concentration near the crack differs. The load distribution at the crack tip
varies considerably. The first unbroken fiber carries higher load. The crack is
lens-shaped and the crack borders form at the tip the finite angle. | 1612.00274v1 |
2017-06-20 | Coulomb drag in topological materials | Dirac fermions are at the forefront of modern condensed matter physics
research. They are known to occur in materials as diverse as graphene,
topological insulators, and transition metal dichalcogenides, while closely
related Weyl fermions have been discovered in other materials. They have been
predicted to lend themselves to a variety of technological applications, while
the recent prediction and discovery of the quantized anomalous Hall effect of
massive Dirac fermions is regarded as a potential gateway towards low-energy
electronics. Some materials hosting Dirac fermions are natural platforms for
interlayer coherence effects such as Coulomb drag and exciton condensation. The
top and bottom surfaces of a thin topological insulator film provide such a
prototype system. Here we describe recent insights into Coulomb drag between
two layers of Dirac fermions relying primarily on topological insulator films
as a minimal model. We consider both non-magnetic topological insulators,
hosting massless Dirac fermions, and magnetic topological insulators, in which
the fermions are massive. We discuss in general terms the dynamics of the
thin-film spin density matrix, outlining numerical results and approximate
analytical expressions where appropriate for the drag resistivity \r{ho}D at
low temperatures and low electron densities. In magnetic topological insulators
with out-of-plane magnetizations in both the active and passive layers we
analyze the role of the anomalous Hall effect in Coulomb drag. | 1706.07291v2 |
2019-02-11 | Large area photoelectrodes based on hybrids of CNT fibres and ALD grown TiO2 | Hybridisation is a powerful strategy towards the next generation of
multifunctional materials for environmental and sustainable energy
applications. Here, we report a new inorganic nanocarbon hybrid material
prepared with atomically controlled deposition of a monocrystalline TiO2 layer
that conformally coats a macroscopic carbon nanotube (CNT) fiber. Through X-ray
diffraction, Raman spectroscopy and photoemission spectroscopy we detect the
formation of a covalent Ti-O-C bond at the TiO2/CNT interface and a residual
strain of approximately 0.7-2 \%, which is tensile in TiO2 and compressive in
the CNT. It arises after deposition of the amorphous oxide onto the CNT surface
previously functionalized by the oxygen plasma used in ALD. These features are
observed in samples of different TiO2 thickness, in the range from 10 to 80 nm.
Ultraviolet photoemission spectroscopy on a 20 nm-thick TiO2 coated sample
gives a work function of 4.27 eV, between that of TiO2 (4.23 eV) and the CNT
fiber (4.41 eV), and the presence of new interband gap states that shift the
valence band maximum to 1.05 eV below the Fermi level. Photoelectrochemical
measurements demonstrate electron transfer from TiO2 to the CNT fiber network
under UV irradiation. Electrochemical impedance spectroscopy measurements
reveal a low resistance for charge transfer and transport, as well as a large
capacitance. Our results point to the fact that these hybrids, in which each
phase has nanometric thickness and the current collector is integrated into the
material, are very different from conventional electrodes and can provide a
number of superior properties. | 1902.04137v1 |
2020-09-15 | Correlated electron metal properties of the honeycomb ruthenate Na$_2$RuO$_3$ | We report the synthesis and characterisation of polycrystalline
Na$_2$RuO$_3$, a layered material in which the Ru$^{4+}$ ($4d^4$ configuration)
form a honeycomb lattice. The optimal synthesis condition was found to produce
a nearly ordered Na$_2$RuO$_3$ ($C2/c$ phase), as assessed from the refinement
of the time-of-flight neutron powder diffraction. Magnetic susceptibility
measurements reveal a large temperature-independent Pauli paramagnetism
($\chi_0 \sim 1.42(2)\times10^{-3}$ emu/mol Oe) with no evidence of magnetic
ordering down to 1.5 K, and with an absence of dynamic magnetic correlations,
as evidenced by neutron scattering spectroscopy. The intrinsic susceptibility
($\chi_0$) together with the Sommerfeld coeficient of $\gamma=11.7(2)$ mJ/Ru
mol K$^2$ estimated from heat capacity measurements, gives an enhanced Wilson
ratio of $R_W\approx8.9(1)$, suggesting that magnetic correlations may be
present in this material. While transport measurements on pressed pellets show
nonmetallic behaviour, photoemission spectrocopy indicate a small but finite
density of states at the Fermi energy, suggesting that the bulk material is
metallic. Except for resistivity measurements, which may have been compromised
by near surface and interface effects, all other probes indicate that
Na$_2$RuO$_3$ is a moderately correlated electron metal. Our results thus stand
in contrast to earlier reports that Na$_2$RuO$_3$ is an antiferromagnetic
insulator at low temperatures. | 2009.07105v1 |
2019-04-08 | Ideal isotropic auxetic networks from random networks | Auxetic materials are characterized by a negative Poisson's ratio,
$\mathrm{\nu}$. As the Poisson's ratio becomes negative and approaches the
lower isotropic mechanical limit of $\mathrm{\nu = -1}$, materials show
enhanced resistance to impact and shear, making them suitable for applications
ranging from robotics to impact mitigation. Past experimental efforts aimed at
reaching the $\mathrm{\nu = -1}$ limit have resulted in highly anisotropic
materials, which show a negative Poisson's ratio only when subjected to
deformations along specific directions. Isotropic designs have only attained
moderately auxetic behavior, or have led to structures that cannot be
manufactured in 3D. Here, we present a design strategy to create isotropic
structures from disordered networks that leads to Poisson's ratios as low as
$\mathrm{\nu = -0.98}$. The materials conceived through this approach are
successfully fabricated in the laboratory and behave as predicted. The
Poisson's ratio $\mathrm{\nu}$ is found to depend on network structure and bond
strengths; this sheds light on the structural motifs that lead to auxetic
behavior. The ideas introduced here can be generalized to 3D, a wide range of
materials, and a spectrum of length scales, thereby providing a general
platform that could impact technology. | 1904.04359v1 |
2019-08-22 | Size dependent yield hardness induced by surface energy | Size dependent hardness has long been reported in nanosized indentations,
however the corresponding explanation is still in exploration. In this paper,
we examine the influence of surface energy on the hardness of materials under
spherical indentation. To evaluate the ability of materials to resist
indentation, a yield hardness is defined here as the contact pressure at the
inception of material yield. It is found that this defined hardness is an
intrinsic material property depending only on the yield strength and Poisson
ratio in conventional continuum mechanics. Then, the impact of surface energy
on the yield hardness is analyzed through finite element simulations. By using
the dimensional analysis, the dependences of the yield hardness and critical
indent depth at yield initiation on surface energy have been achieved. When the
yield strength is comparable to the ratio of surface energy density to indenter
radius, surface energy will alter the yield hardness and the critical indent
depth. As the size of indenter decreases to nanoscale, both the yield hardness
and the indent depth will increase significantly. This study provides a
possible clarification to the size dependence of hardness and a potential
approach to measure the yield strength and surface energy of solids through
nanosized indentations. | 1908.08175v1 |
2020-07-25 | Industrial manufacturing and characterization of multiscale CFRP laminates made from prepregs containing graphene-related materials | The introduction of graphene-related materials (GRMs) in carbon
fibre-reinforced polymers (CFRP) has been proved to enhance their mechanical
and electrical properties. However, methodologies to produce the 3-phase
materials (multiscale composites) at an industrial scale and in an efficient
manner are still lacking. In this paper, multiscale CFRP composites containing
different GRMs have been manufactured following standard procedures currently
used in the aerospace industry with the aim to evaluate its potential
application. Graphite nanoplateletelets (GNPs), in situ exfoliated graphene
oxide (GO) and reduced graphene oxide (rGO) have been dispersed into an epoxy
resin to subsequently impregnate aeronautical grade carbon fibre tape. The
resulting prepregs have been used for manufacturing laminates by hand lay-up
and autoclave curing at 180 {\deg}C. Abroad characterization campaign has been
carried out to understand the behaviour of the different multiscale laminates
manufactured. The degree of cure, glass transition temperature and degradation
temperature have been evaluated by thermal evolution techniques. Similarly,
their mechanical properties (tensile, flexural, in-plane shear, interlaminar
shear and mode I interlaminar fracture toughness) have been analysed together
with their electrical conductivity. The manufacturing process resulted
appropriated for producing three-phase laminates and their quality was as good
as in conventional CFRPs. The addition ofGOand rGO resulted in an enhancement
of the in-plane shear properties and delamination resistance while the addition
ofGNPimproved the electrical conductivity. | 2007.12902v1 |
2021-04-06 | Phase Change Memory by GeSbTe Electrodeposition in Crossbar Arrays | Phase change memories (PCM) is an emerging type of non-volatile memory that
has shown a strong presence in the data-storage market. This technology has
recently attracted significant research interest in the development of non-Von
Neumann computing architectures such as in-memory and neuromorphic computing.
Research in these areas has been primarily motivated by the scalability
potential of phase change materials and their compatibility with industrial
nanofabrication processes. In this work, we are presenting our development of
crossbar phase change memory arrays through the electrodeposition of GeSbTe
(GST). We show that GST can be electrodeposited in microfabricated TiN crossbar
arrays using a scalable process. Our phase switching test of the
electrodeposited materials have shown that a SET/RESET resistance ratio of 2-3
orders of magnitude is achievable with a switching endurance of around 80
cycles. These results represent the first phase switching of electrodeposited
GeSbTe in microfabricated crossbar arrays. Our work paves the way towards
developing large memory arrays involving electrodeposited materials for passive
selectors and phase switching devices. It also opens opportunities for
developing a variety of different electronic devices using electrodeposited
materials. | 2104.02340v2 |
2021-07-29 | Magnetic frustration in a van der Waals metal CeSiI | The realization of magnetic frustration in a metallic van der Waals (vdW)
coupled material has been sought as a promising platform to explore novel
phenomena both in bulk matter and in exfoliated devices. However, a suitable
material platform has been lacking so far. Here, we demonstrate that CeSiI
hosts itinerant electrons coexisting with exotic magnetism. In CeSiI, the
magnetic cerium atoms form a triangular bilayer structure sandwiched by van der
Waals stacked iodine layers. From resistivity and magnetometry measurements, we
confirm the coexistence of itinerant electrons with magnetism with dominant
antiferromagnetic exchange between the strongly Ising-like Ce moments below 7
K. Neutron diffraction directly confirms magnetic order with an incommensurate
propagation vector k ~ (0.28, 0, 0.19) at 1.6 K, which points to the importance
of further neighbor magnetic interactions in this system. The presence of a
two-step magnetic-field-induced phase transition along c axis further suggests
magnetic frustration in the ground state. Our findings provide a novel material
platform hosting a coexistence of itinerant electron and frustrated magnetism
in a vdW system, where exotic phenomena arising from rich interplay between
spin, charge and lattice in low dimension can be explored. | 2107.13810v1 |
2022-03-31 | Catapulting of topological defects through elasticity bands in active nematics | Active materials are those in which individual, uncoordinated local stresses
drive the material out of equilibrium on a global scale. Examples of such
assemblies can be seen across scales from schools of fish to the cellular
cytoskeleton and underpin many important biological processes. Synthetic
experiments that recapitulate the essential features of such active systems
have been the object of study for decades as their simple rules allow us to
elucidate the physical underpinnings of collective motion. One system of
particular interest has been active nematic liquid crystals (LCs). Because of
their well understood passive physics, LCs provide a rich platform to
interrogate the effects of active stress. The flows and steady state structures
that emerge in an active LCs have been understood to result from a competition
between nematic elasticity and the local activity. However most investigations
of such phenomena consider only the magnitude of the elastic resistance and not
its peculiarities. Here we investigate a nematic liquid crystal and selectively
change the ratio of the material's splay and bend elasticities. We show that
increases in the nematic's bend elasticity specifically drives the material
into an exotic steady state where elongated regions of acute bend distortion or
"elasticity bands" dominate the structure and dynamics. We show that these
bands strongly influence defect dynamics, including the rapid motion or
"catapulting" along the disintegration of one of these bands thus converting
bend distortion into defect transport. Thus, we report a novel dynamical state
resultant from the competition between nematic elasticity and active stress. | 2204.00113v1 |
2023-09-15 | Emergence of partially disordered antiferromagnetism and isothermal magnetization plateau due to geometrical frustration in a metallic compound, Er2RhSi3 | Partially disordered antiferro (PDA) magnetism (in which one of the three
magnetic ions in a triangular network remains magnetically disordered), has
been known commonly among geometrically frustrated insulating materials. The
one-third plateau in isothermal magnetization (M) of such materials has been of
great theoretical interest. Here, we report these properties in a
AlB2-structure derived metallic material, Er2RhSi3 in which Er sublattice has
triangular networks. The presence of a well-defined lamda anomaly in the
temperature (T) dependence of heat capacity and its magnetic-field (H)
dependence, and the loss of spin-disorder contribution in electrical
resistivity (rho) confirm antiferromagnetic order below (TN=) 5 K. On the other
hand, the separation of zero-field-cooled and field-cooled dc magnetic
susceptibility (chi) curves, decay of isothermal remnant magnetization and the
frequency dependence of real and imaginary components of ac chi suggest the
onset of spin-glass freezing concomitant with the antiferromagnetic order. In
addition, interestingly, we observe one-third plateau in M(H) below 20 kOe for
T less than TN. The change in rho as a function of H at a given temperature
well below TN is also revealing, with this compound exhibiting a plateau below
20 kOe, with complexities at higher fields. Therefore, this compound serves as
a prototype for theoretical understanding of transport behavior across
one-third plateau due to PDA magnetism in a metal without any interference from
the 4f delocalization phenomena. | 2309.08176v1 |
2023-10-18 | Moire synaptic transistor for homogeneous-architecture reservoir computing | Reservoir computing has been considered as a promising intelligent computing
paradigm for effectively processing complex temporal information. Exploiting
tunable and reproducible dynamics in the single electronic device have been
desired to implement the reservoir and the readout layer of reservoir computing
system. Two-dimensional moire material, with an artificial lattice constant
many times larger than the atomic length scale, is one type of most studied
artificial quantum materials in community of material science and
condensed-matter physics over the past years. These materials are featured with
gate-tunable periodic potential and electronic correlation, thus varying the
electric field allows the electrons in the moire potential per unit cell to
exhibit distinct and reproducible dynamics, showing great promise in robust
reservoir computing. Here, we report that a moire synaptic transistor can be
used to implement the reservoir computing system with a homogeneous
reservoir-readout architecture. The synaptic transistor is fabricated based on
a h-BN/bilayer graphene/h-BN moire heterostructure, exhibiting
ferroelectricity-like hysteretic gate voltage dependence of resistance. Varying
the magnitude of the gate voltage enables the moire transistor to be switched
between long-term memory and short-term memory with nonlinear dynamics. By
employing the short- and long-term memory as the reservoir nodes and weights of
the readout layer, respectively, we construct a full-moire physical neural
network and demonstrate that the classification accuracy of 90.8% can be
achieved for the MNIST handwritten digit database. Our work would pave the way
towards the development of neuromorphic computing based on the moire materials. | 2310.11743v1 |
2024-05-06 | Band structure engineering using a moiré polar substrate | Applying long wavelength periodic potentials on quantum materials has
recently been demonstrated to be a promising pathway for engineering novel
quantum phases of matter. Here, we utilize twisted bilayer boron nitride (BN)
as a moir\'e substrate for band structure engineering. Small-angle-twisted
bilayer BN is endowed with periodically arranged up and down polar domains,
which imprints a periodic electrostatic potential on a target two-dimensional
(2D) material placed on top. As a proof of concept, we use Bernal bilayer
graphene as the target material. The resulting modulation of the band structure
appears as superlattice resistance peaks, tunable by varying the twist angle,
and Hofstadter butterfly physics under a magnetic field. Additionally, we
demonstrate the tunability of the moir\'e potential by altering the dielectric
thickness underneath the twisted BN. Finally, we find that
near-60{\deg}-twisted bilayer BN provides a unique platform for studying the
moir\'e structural effect without the contribution from electrostatic moir\'e
potentials. Tunable moir\'e polar substrates may serve as versatile platforms
to engineer the electronic, optical, and mechanical properties of 2D materials
and van der Waals heterostructures. | 2405.03761v1 |
2001-11-01 | To the problem of electron-phonon interaction and "d-wave pairing" in high-Tc oxides | It is supported a recent proposal by Maksimov that electron-phonon
interaction (EPI) (Gruneisen-Bloch formulae) determines the linearity of
temperature dependence of resistivity for both HTSC-cuprates and most of metals
at T near above 0.2 of their characteristic Debye temperature (normal state for
HTSC). However, it is emphasized here that in this T-region the resistivity is
not proportional to T but is only linear in T. This fact indicates to
T-independent contribution to normal-state resistivity in HTSC-cuprates
(magnetic contribution, in our treatment) which behavior, in its turn,
indicates to possible magnetic (SDW-like) phase transition before SC transition
in HTSC-system. SDW-gap (measured as pseudogap with d-wave symmetry, in our
treatment) is formed at the symmetrical parts of the Fermi surface above Tc and
persists in SC state. The magnitude of SDW-gap is essentially larger than that
for SC-gap. So, SDW formed can mimic d-wave symmetry of the order parameter
measured below Tc (which is now attributed to d-wave pairing). On the other
hand, since the Gruneisen-Bloch curve appears to be (in approach used) a
geometric locus for the Tc(onset)(H) (as in LTSC) this fact evidents about
EPI-nature (BCS) of SC transition (s-wave) in high-Tc oxides. The proposal to
increase Tc using above (SDW/CDW/SC) model (and possible realization) is
presented. | 0111015v1 |
2004-05-31 | Transport Properties in the "Strange Metal Phase" of High Tc Cuprates: Spin-Charge Gauge Theory Versus Experiments | The SU(2)xU(1) Chern-Simons spin-charge gauge approach developed earlier to
describe the transport properties of the cuprate superconductors in the
``pseudogap'' regime, in particular, the metal-insulator crossover of the
in-plane resistivity, is generalized to the ``strange metal'' phase at higher
temperature/doping. The short-range antiferromagnetic order and the gauge field
fluctuations, which were the key ingredients in the theory for the pseudogap
phase, also play an important role in the present case. The main difference
between these two phases is caused by the existence of an underlying
statistical $\pi$-flux lattice for charge carriers in the former case, whereas
the background flux is absent in the latter case. The Fermi surface then
changes from small ``arcs'' in the pseudogap to a rather large closed line in
the strange metal phase. As a consequence the celebrated linear in T dependence
of the in-plane and out-of-plane resistivity is shown explicitly to recover.
The doping concentration and temperature dependence of theoretically calculated
in-plane and out-of-plane resistivity, spin-relaxation rate and AC conductivity
are compared with experimental data, showing good agreement. | 0405704v2 |
2007-05-03 | Mean-Field Magnetohydrodynamics of Accretion Disks | We consider the accretion process in a disk with magnetic fields that are
dragged in from the interstellar medium by gravitational collapse. Two
diffusive processes are at work in the system: (1) "viscous" torques exerted by
turbulent and magnetic stresses, and (2) "resistive" redistribution of mass
with respect to the magnetic flux arising from the imperfect conduction of
current. In steady state, self-consistency between the two rates of drift
requires that a relationship exists between the coefficients of turbulent
viscosity and turbulent resistivity. Ignoring any interactions with a stellar
magnetosphere, we solve the steady-state equations for a magnetized disk under
the gravitational attraction of a mass point and threaded by an amount of
magnetic flux consistent with calculations of magnetized gravitational collapse
in star formation. Our model mean-field equations have an exact analytical
solution that corresponds to magnetically diluted Keplerian rotation about the
central mass point. The solution yields the strength of the magnetic field and
the surface density as functions of radial position in the disk and their
connection with the departure from pure Keplerian rotation in representative
cases. We compare the predictions of the theory with the available observations
concerning T Tauri stars, FU Orionis stars, and low- and high-mass protostars.
Finally, we speculate on the physical causes for high and low states of the
accretion disks that surround young stellar objects. One of the more important
results of this study is the physical derivation of analytic expressions for
the turbulent viscosity and turbulent resistivity. | 0705.0421v1 |
2008-08-27 | The quantum critical point in CeRhIn_5: a resistivity study | The pressure--temperature phase diagram of CeRhIn_5 has been studied under
high magnetic field by resistivity measurements. Clear signatures of a quantum
critical point has been found at a critical pressure of p_c = 2.5 GPa. The
field induced magnetic state in the superconducting state is stable up to the
highest field. At p_c the antiferromagnetic ground-state under high magnetic
field collapses very rapidly. Clear signatures of p_c are the strong
enhancement of the resistivity in the normal state and of the inelastic
scattering term. No clear T2 temperature dependence could be found for
pressures above T_c. From the analysis of the upper critical field within a
strong coupling model we present the pressure dependence of the coupling
parameter lambda and the gyromagnetic ratio g. No signatures of a spatially
modulated order parameter could be evidenced. A detailed comparison with the
magnetic field--temperature phase diagram of CeCoIn_5 is given. The comparison
between CeRhIn_5 and CeCoIn_5 points out the importance to take into account
the field dependence of the effective mass in the calculation of the
superconducting upper critical field H_c2. It suggests also that when the
magnetic critical field H_(0) becomes lower than H_c2 (0)$, the persistence of
a superconducting pseudo-gap may stick the antiferromagnetism to H_c2 (0). | 0808.3687v1 |
2009-07-13 | Enhanced Critical parameters of nano-Carbon doped MgB2 Superconductor | The high field magnetization and magneto transport measurements are carried
out to determine the critical superconducting parameters of MgB2-xCx system.
The synthesized samples are pure phase and the lattice parameters evaluation is
carried out using the Rietveld refinement. The R-T(H) measurements are done up
to a field of 140 kOe. The upper critical field values, Hc2 are obtained from
this data based upon the criterion of 90% of normal resistivity i.e. Hc2=H at
which Rho=90%Rho; where RhoN is the normal resistivity i.e., resistivity at
about 40 K in our case. The Werthamer-Helfand-Hohenberg (WHH) prediction of
Hc(0) underestimates the critical field value even below than the field up to
which measurement is carried out. After this the model, the Ginzburg Landau
theory (GL equation) is applied to the R-T(H) data which not only calculates
the Hc2(0) value but also determines the dependence of Hc2 on temperature in
the low temperature high field region. The estimated Hc(0)=157.2 kOe for pure
MgB2 is profoundly enhanced to 297.5 kOe for the x=0.15 sample in MgB2-xCx
series. Magnetization measurements are done up to 120 kOe at different
temperatures and the other parameters like irreversibility field, Hirr and
critical current density Jc(H) are also calculated. The nano carbon doping
results in substantial enhancement of critical parameters like Hc2, Hirr and
Jc(H) in comparison to the pure MgB2 sample. | 0907.2129v2 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.