publicationDate stringlengths 10 10 | title stringlengths 17 233 | abstract stringlengths 20 3.22k | id stringlengths 9 12 |
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2022-08-04 | Epitaxial growth, magnetoresistance, and electronic band structure of GdSb magnetic semimetal films | Motivated by observations of extreme magnetoresistance (XMR) in bulk crystals
of rare-earth monopnictide (RE-V) compounds and emerging applications in novel
spintronic and plasmonic devices based on thin-film semimetals, we have
investigated the electronic band structure and transport behavior of epitaxial
GdSb thin films grown on III-V semiconductor surfaces. The Gd3+ ion in GdSb has
a high spin S=7/2 and no orbital angular momentum, serving as a model system
for studying the effects of antiferromagnetic order and strong exchange
coupling on the resulting Fermi surface and magnetotransport properties of
RE-Vs. We present a surface and structural characterization study mapping the
optimal synthesis window of thin epitaxial GdSb films grown on III-V
lattice-matched buffer layers via molecular beam epitaxy. To determine the
factors limiting XMR in RE-V thin films and provide a benchmark for band
structure predictions of topological phases of RE-Vs, the electronic band
structure of GdSb thin films is studied, comparing carrier densities extracted
from magnetotransport, angle-resolved photoemission spectroscopy (ARPES), and
density functional theory (DFT) calculations. ARPES shows hole-carrier rich
topologically-trivial semi-metallic band structure close to complete
electron-hole compensation, with quantum confinement effects in the thin films
observed through the presence of quantum well states. DFT predicted Fermi
wavevectors are in excellent agreement with values obtained from quantum
oscillations observed in magnetic field-dependent resistivity measurements. An
electron-rich Hall coefficient is measured despite the higher hole carrier
density, attributed to the higher electron Hall mobility. The carrier
mobilities are limited by surface and interface scattering, resulting in lower
magnetoresistance than that measured for bulk crystals. | 2208.02648v2 |
2023-03-07 | Response to "On the giant deformation and ferroelectricity of guanidinium nitrate" by Marek Szafrański and Andrzej Katrusiak | Following a well-established practice of publishing commentaries to articles
of other authors who work on materials that were earlier studied by them (n.b.
six published comments[1-6]), Marek Szafra\'nski(MS) and Andrzej Katrusiak (AK)
have filed on the preprint server arXiv a manuscript entitled "On the giant
deformation and ferroelectricity of guanidinium nitrate"[7] with comments on
our article "Exceptionally high work density of a ferroelectric dynamic organic
crystal around room temperature" published in Nature Communications (2022, 13,
2823).[8] Both in the submitted comment as well as in the required (by the
journal) direct communication with us preceding its posting, MS and AK have
expressed dissatisfaction with the choice of literature references in our
article, for which they felt that their previous work on this material has not
been cited to a sufficient extent. In their comment, they summarize their other
remarks on our article as "the structural determinations of GN [guanidinium
nitrate] crystals, their phase transitions and associated giant deformation, as
well as its detailed structural mechanism, the molecular dynamics and
dielectric properties were reported before, while the semiconductivity,
ferroelectricity, and fatigue resistance of the GN [guanidinium nitrate]
crystals cannot be confirmed."[7] Apart from the sentiments of MS and AK on our
choice of cited literature, we find their comments on the scientific content of
our article to be strongly biased towards their own results and unfounded.
Below, we provide a detailed response to their comments. | 2303.04028v2 |
2023-05-12 | Automated Grain Boundary (GB) Segmentation and Microstructural Analysis in 347H Stainless Steel Using Deep Learning and Multimodal Microscopy | Austenitic 347H stainless steel offers superior mechanical properties and
corrosion resistance required for extreme operating conditions such as high
temperature. The change in microstructure due to composition and process
variations is expected to impact material properties. Identifying
microstructural features such as grain boundaries thus becomes an important
task in the process-microstructure-properties loop. Applying convolutional
neural network (CNN) based deep-learning models is a powerful technique to
detect features from material micrographs in an automated manner. Manual
labeling of the images for the segmentation task poses a major bottleneck for
generating training data and labels in a reliable and reproducible way within a
reasonable timeframe. In this study, we attempt to overcome such limitations by
utilizing multi-modal microscopy to generate labels directly instead of manual
labeling. We combine scanning electron microscopy (SEM) images of 347H
stainless steel as training data and electron backscatter diffraction (EBSD)
micrographs as pixel-wise labels for grain boundary detection as a semantic
segmentation task. We demonstrate that despite producing instrumentation drift
during data collection between two modes of microscopy, this method performs
comparably to similar segmentation tasks that used manual labeling.
Additionally, we find that na\"ive pixel-wise segmentation results in small
gaps and missing boundaries in the predicted grain boundary map. By
incorporating topological information during model training, the connectivity
of the grain boundary network and segmentation performance is improved.
Finally, our approach is validated by accurate computation on downstream tasks
of predicting the underlying grain morphology distributions which are the
ultimate quantities of interest for microstructural characterization. | 2305.07790v1 |
2011-05-22 | Optimal Three-Material Wheel Assemblage of Conducting and Elastic Composites | We describe a new type of three material microstructures which we call wheel
assemblages, that correspond to extremal conductivity and extremal bulk modulus
for a composite made of two materials and an ideal material. The exact lower
bounds for effective conductivity and matching laminates was found in
(Cherkaev, 2009) and for anisotropic composites, in (Cherkaev, Zhang, 2011).
Here, we show different optimal structures that generalize the classical
Hashin-Shtrikman coated spheres (circles). They consist of circular inclusions
which contain a solid central circle (hub) and radial spikes in a surrounding
annulus, and (for larger volume fractions of the best material) an annulus
filled with it. The same wheel assemblages are optimal for the pair of dual
problems of minimal conductivity (resistivity) of a composite made from two
materials and an ideal conductor (insulator), in the problem of maximal
effective bulk modulus of elastic composites made from two linear elastic
material and void, and the dual minimum problem. | 1105.4302v1 |
2015-10-10 | Intrusion in heterogeneous materials: Simple global rules from complex micro-mechanics | The interaction of intruding objects with deformable materials is a common
phenomenon, arising in impact and penetration problems, animal and vehicle
locomotion, and various geo-space applications. The dynamics of arbitrary
intruders can be simplified using Resistive Force Theory (RFT), an empirical
framework originally used for fluids but works surprisingly well, better in
fact, in granular materials. That such a simple model describes behavior in dry
grains, a complex nonlinear material, has invigorated a search to determine the
underlying mechanism of RFT. We have discovered that a straightforward
friction-based continuum model generates RFT, establishing a link between RFT
and local material behavior. Our theory reproduces experimental RFT data
without any parameter fitting and generates RFT's key simplifying assumption: a
geometry-independent local force formula. Analysis of the system explains why
RFT works better in grains than in viscous fluids, and leads to an analytical
criterion to predict RFT's in other materials. | 1510.02966v1 |
2017-06-05 | Dy$^{3+}$-doped Yttrium Complex Molecular Crystals for Two-color Thermometry in Heterogeneous Materials | We develop Dy$^{3+}$-doped yttrium complexes for use as two-color thermometry
(TCT) phosphor molecular crystals in heterogeneous materials. These complexes
include: Dy:Y(acac)$_3$(phen), Dy:Y(hfa)$_3$(DPEPO), Dy:Y(4-BBA)$_3$(TPPO),
Dy:Y(acac)$_3$, and Dy:Y(acac)$_3$(DPEPO), where the Dy/Y ratio is 1:9. We
characterize the materials' photoluminescence at different temperatures to
determine the TCT calibration parameters and the degree to which thermal
quenching influences the emission. From this data we observe a link between the
excited state lifetime at room temperature and the degree to which the material
is susceptible to thermal quenching (i.e. materials having long room
temperature lifetimes are more resistant to thermal quenching than materials
with short room temperature lifetimes). Of the five complexes tested we find
that Dy:Y(acac)$_3$(DPEPO) has the best thermal performance, with the most
likely source of improvement being DPEPO's compact rigid structure. This
rigidity helps with energy transfer to the Dy$^{3+}$ ion, suppresses
non-radiative loss modes, and reduces exciplex formation. | 1706.02658v1 |
1999-12-21 | Three-dimensional spontaneous magnetic reconnection in neutral current sheets | Magnetic reconnection in an antiparallel uniform Harris current sheet
equilibrium, which is initially perturbed by a region of enhanced resistivity
limited in all three dimensions, is investigated through compressible
magnetohydrodynamic simulations. Variable resistivity, coupled to the dynamics
of the plasma by an electron-ion drift velocity criterion, is used during the
evolution. A phase of magnetic reconnection amplifying with time and leading to
eruptive energy release is triggered only if the initial perturbation is
strongly elongated in the direction of current flow or if the threshold for the
onset of anomalous resistivity is significantly lower than in the corresponding
two-dimensional case. A Petschek-like configuration is then built up for \sim
100 Alfven times, but remains localized in the third dimension. Subsequently, a
change of topology to an O-line at the center of the system (``secondary
tearing'') occurs. This leads to enhanced and time-variable reconnection, to a
second pair of outflow jets directed along the O-line, and to expansion of the
reconnection process into the third dimension. High parallel current density
components are created mainly near the region of enhanced resistivity. | 9912443v1 |
2007-03-05 | MHD simulations of jet acceleration from Keplerian accretion disks: the effects of disk resistivity | Accretion disks and astrophysical jets are used to model many active
astrophysical objects, viz., young stars, relativistic stars, and active
galactic nuclei. In this paper we present self-consistent time-dependent
simulations of supersonic jets launched from magnetized accretion disks, using
high resolution numerical techniques. In particular we study the effects of the
disk magnetic resistivity, parametrized through an alpha-prescription, in
determining the properties of the inflow-outflow system. Moreover we analyze
under which conditions steady state solutions of the type proposed in the self
similar models of Blandford and Payne can be reached and maintained in a self
consistent nonlinear stage. We use the resistive MHD FLASH code with adaptive
mesh refinement, allowing us to follow the evolution of the structure for a
time scale long enough to reach steady state. A detailed analysis of the
initial configuration state is given. We obtain the expected solutions in the
axisymmetric (2.5D) limit. Assuming a magnetic field around equipartition with
the thermal pressure of the disk, we show how the characteristics of the disk
jet system, as the ejection efficiency and the energetics, are affected by the
anomalous resistivity acting inside the disk. | 0703064v1 |
1994-09-13 | Mesoscopic quantum transport: Resonant tunneling in the presence of strong Coulomb interaction | Coulomb blockade phenomena and quantum fluctuations are studied in mesoscopic
metallic tunnel junctions with high charging energies. If the resistance of the
barriers is large compared to the quantum resistance, transport can be
described by sequential tunneling. Here we study the influence of quantum
fluctuations. They are important when the resistance is small or the
temperature very low. A real-time approach is developed which allows the
diagrammatic classification of ``inelastic resonant tunneling'' processes where
different electrons tunnel coherently back and forth between the leads and the
metallic island. With the help of a nonperturbative resummation technique we
evaluate the spectral density which describes the charge excitations of the
system. From it physical quantities of interest like current and average charge
can be deduced. Our main conclusions are: An energy renormalization leads to a
logarithmic temperature dependence of the renormalized system parameters. A
finite lifetime broadening can change the classical picture drastically. It
gives rise to a strong flattening of the Coulomb oscillations for low
resistances, but in the Coulomb blockade regime inelastic electron cotunneling
persists. The temperature where these effects are important are accessible in
experiments. | 9409051v1 |
1994-12-22 | "Scaling of an anomalous metal/insulator transition in a 2D system in silicon at zero magnetic field" | We have studied the temperature dependence of resistivity, $\rho$, for a
two-dimensional electron system in silicon at low electron densities,
$n_s\sim10^{11}$ cm$^{-2}$, near the metal/insulator transition. The
resistivity was empirically found to scale with a single parameter, $T_0$,
which approaches zero at some critical electron density, $n_c$, and increases
as a power $T_0\propto|n_s-n_c|^\beta$ with $\beta=1.6\pm0.1$ both in metallic
($n_s>n_c$) and insulating ($n_s<n_c$) regions. This dependence was found to be
sample-independent. We have also studied the diagonal resistivity at Landau
level filling factor $\nu=3/2$ where the system is known to be in a metallic
state at high magnetic field and in an insulating state at low magnetic field.
The temperature dependencies of resistivity at $B=0$ and at $\nu=3/2$ were
found to be identical. These behaviors suggest a true metal/insulator
transition in the two dimensional electron system in silicon at $B=0$, in
contrast with the well-known scaling theory. | 9412103v1 |
1995-01-19 | Resistivity as a function of temperature for models with hot spots on the Fermi surface. | We calculate the resistivity $\rho$ as a function of temperature $T$ for two
models currently discussed in connection with high temperature
superconductivity: nearly antiferromagnetic Fermi liquids and models with van
Hove singularities on the Fermi surface. The resistivity is calculated
semiclassicaly by making use of a Boltzmann equation which is formulated as a
variational problem. For the model of nearly antiferromagnetic Fermi liquids we
construct a better variational solution compared to the standard one and we
find a new energy scale for the crossover to the $\rho\propto T^2$ behavior at
low temperatures. This energy scale is finite even when the spin-fluctuations
are assumed to be critical. The effect of additional impurity scattering is
discussed. For the model with van Hove singularities a standard ansatz for the
Boltzmann equation is sufficient to show that although the quasiparticle
lifetime is anomalously short, the resistivity $\rho\propto T^2\ln(1/T)$. | 9501086v1 |
1996-06-05 | Transport and magnetic properties in ferromagnetic manganese-oxide thin films | The transport and magnetic properties in ferromagnetic manganese-oxide thin
films are studied based on the model of the coupling between the mobile
d-electrons and the core spins in Mn ions. The spontaneous magnetization and
the resistivity are obtained for various magnetic fields and temperature. The
resistivity in absence of magnetic field and the magnetoresistance exhibit
maxima near the Curie temperature, the applied magnetic field moves the
position of the resistivity peak to high temperature and suppresses the peak
value, which agree with the experimental results. The Hall resistivity is
predicted to exhibit maximum near the Curie point. The pressure effect of the
magnetoresistance can also be explained qualitatively in this mechanism. The
colossal magnetoresistance in ferromagnetic manganese-oxide thin films is
attributed to the spin-correlation fluctuation scattering and the low
dimensional effect. | 9606029v1 |
1997-04-14 | Temperature Dependent Resistivity of Single Wall Carbon Nanotubes | Nonchiral single wall carbon nanotubes with an "armchair" wrapping are
theoretically predicted to be conducting, and high purity samples consisting
predominantly of these tubes exhibit metallic behavior with an intrinsic
resistivity which increases approximately linearly with temperature over a wide
temperature range. Here we study the coupling of the conduction electrons to
long wavelength torsional shape fluctuations, or twistons. A one dimensional
theory of the scattering of electrons by twistons is presented which predicts
an intrinsic resistivity proportional to the absolute temperature. Experimental
measurements of the temperature dependence of the resistivity are reported and
compared with the predictions of the twiston theory. | 9704117v1 |
2002-05-24 | The quantized Hall effect in the presence of resistance fluctuations | We present an experimental study of mesoscopic, two-dimensional electronic
systems at high magnetic fields. Our samples, prepared from a low-mobility
InGaAs/InAlAs wafer, exhibit reproducible, sample specific, resistance
fluctuations. Focusing on the lowest Landau level we find that, while the
diagonal resistivity displays strong fluctuations, the Hall resistivity is free
of fluctuations and remains quantized at its $\nu=1$ value, $h/e^{2}$. This is
true also in the insulating phase that terminates the quantum Hall series.
These results extend the validity of the semicircle law of conductivity in the
quantum Hall effect to the mesoscopic regime. | 0205513v2 |
2003-07-01 | Effect of two bands on critical fields in MgB2 thin films with various resistivity values | Upper critical fields of four MgB2 thin films were measured up to 28 Tesla at
Grenoble High Magnetic Field Laboratory. The films were grown by Pulsed Laser
Deposition and showed critical temperatures ranging between 29.5 and 38.8 K and
resistivities at 40 K varying from 5 to 50 mWcm. The critical fields in the
perpendicular direction turned out to be in the 13-24 T range while they were
estimated to be in 42-57 T the range in ab-planes. In contrast to the
prediction of the BCS theory, we did not observe any saturation at low
temperatures: a linear temperature dependence is exhibited even at lowest
temperatures at which we made the measurements. Moreover, the critical field
values seemed not to depend on the normal state resistivity value. In this
paper, we analyze these data considering the multiband nature of
superconductivity in MgB2 We will show how the scattering mechanisms that
determine critical fields and resistivity can be different. | 0307013v2 |
2004-02-27 | Possible Pairing Mechanisms of PuCoGa$_5$ Superconductor | We examine possible pairing mechanisms of superconductivity in PuCoGa$_5$
based on spin-fluctuations or phonons as mediating bosons. We consider
experimental data of specific heat C(T) and resistivity $\rho(T)$ as input to
determine a consistent scattering boson with the superconducting transition
temperature of 18.5K in PuCoGa$_5$. Irrespective to the type of boson, the
characteristic boson frequency is found to be $\sim 150 K$ from the resistivity
fitting. The spin fluctuation model is most consistent with the experimental
resistivity, successfully explaining the anomalous temperature dependence
($\sim \frac{T^2}{150 K +T}$) at low temperatures as well as the saturation
behavior at high temperatures. Assuming that the pairing state is non s-wave,
the large residual resistivity $\rho_{imp} \sim 20 \mu \Omega cm \sim 120 K$
suggests that an ideally pure sample of PuCoGa$_5$ would have a maximum T$_c$
of 39 K. | 0402685v2 |
2004-04-28 | How normal is the "normal" state of superconducting cuprates? | High magnetic field studies of the cuprate superconductors revealed a non-BCS
temperature dependence of the upper critical field $H_{c2}(T)$ determined
resistively by several groups. These determinations caused some doubts on the
grounds of the contrasting effect of the magnetic field on the in-plane,
$\rho_{ab}$, and out-of-plane, $\rho_{c}$ resistances reported for large sample
of Bi2212. Here we present careful measurements of both $\rho_{ab}(B)$ and
$\rho_{c}(B)$ of tiny Bi2212 crystals in magnetic fields up to 50 Tesla. None
of our measurements revealed a situation when on field increase $\rho_c$
reaches its maximum while $\rho_{ab}$ remains very small if not zero. The
resistive $H_{c2}(T)$ estimated from $\rho_{ab}(B)$ and $\rho_{c}(B)$ are
approximately the same. We also present a simple explanation of the unusual
Nernst signal in superconducting cuprates as a normal state phenomenon. Our
results support any theory of cuprates, which describes the state above the
resistive phase transition as perfectly 'normal' with a zero off-diagonal order
parameter. | 0404678v1 |
2004-07-14 | Investigation of the Field-Tuned Quantum Critical Point in CeCoIn_5 | The main properties and the type of the field-tuned quantum critical point in
the heavy-fermion metal CeCoIn$_5$ arisen upon applying magnetic fields $B$ are
considered within the scenario based on the fermion condensation quantum phase
transition. We analyze the behavior of the effective mass, resistivity,
specific heat, charge and heat transport as functions of applied magnetic
fields $B$ and show that in the Landau Fermi liquid regime these quantities
demonstrate the critical behavior which is scaled by the critical behavior of
the effective mass. We show that in the high-field non-Fermi liquid regime, the
effective mass exhibits very specific behavior, $M^*\sim T^{-2/3}$, and the
resistivity demonstrates the $T^{2/3}$ dependence. Finally, at elevated
temperatures, it changes to $M^*\sim T^{-1/2}$, while the resistivity becomes
linear in $T$. In zero magnetic field, the effective mass is controlled by
temperature $T$, and the resistivity is also linear in $T$. The obtained
results are in good agreement with recent experimental facts. | 0407350v1 |
2005-04-02 | Non-Ohmic variable-range hopping transport in one-dimensional conductors | We investigate theoretically the effect of a finite electric field on the
resistivity of a disordered one-dimensional system in the variable-range
hopping regime. We find that at low fields the transport is inhibited by rare
fluctuations in the random distribution of localized states that create
high-resistance ``breaks'' in the hopping network. As the field increases, the
breaks become less resistive. In strong fields the breaks are overrun and the
electron distribution function is driven far from equilibrum. The logarithm of
the resistance initially shows a simple exponential drop with the field,
followed by a logarithmic dependence, and finally, by an inverse square-root
law. | 0504047v2 |
2006-06-15 | Crystalline-Electric-Field Effect on the Resistivity of Ce-based Heavy Fermion Systems | The behavior of the resistivity of Ce-based heavy fermion systems is studied
using a 1/$N$-expansion method a la Nagoya, where $N$ is the spin-orbital
degeneracy of f-electrons. The 1/$N$-expansion is performed in terms of the
auxiliary particles, and a strict requirement of the local constraints is
fulfilled for each order of 1/N. The physical quantities can be calculated over
the entire temperature range by solving the coupled Dyson equations for the
Green functions self-consistently at each temperature. This 1/N-expansion
method is known to provide asymptotically exact results for the behavior of
physical quantities in both low- and high-energy regions when it is applied to
a single orbital periodic Anderson model (PAM). On the basis of a generalized
PAM including crystalline-electric-field splitting with a single conduction
band, the pressure dependence of the resistivity is calculated by
parameterizing the effect of pressure as the variation of the hybridization
parameter between the conduction electrons and f-electrons. The main result of
the present study is that the double-peak structure of the $T$-dependence of
the resistivity is shown to merge into a single-peak structure with increasing
pressure. | 0606400v1 |
1996-10-07 | Toroidal Vortices in Resistive Magnetohydrodynamic Equilibria | Resistive steady states in toroidal magnetohydrodynamics (MHD), where Ohm's
law must be taken into account, differ considerably from ideal ones. Only for
special (and probably unphysical) resistivity profiles can the Lorentz force,
in the static force-balance equation, be expressed as the gradient of a scalar
and thus cancel the gradient of a scalar pressure. In general, the Lorentz
force has a curl directed so as to generate toroidal vorticity. Here, we
calculate, for a collisional, highly viscous magnetofluid, the flows that are
required for an axisymmetric toroidal steady state, assuming uniform scalar
resistivity and viscosity. The flows originate from paired toroidal vortices
(in what might be called a ``double smoke ring'' configuration), and are
thought likely to be ubiquitous in the interior of toroidally driven
magnetofluids of this type. The existence of such vortices is conjectured to
characterize magnetofluids beyond the high-viscosity limit in which they are
readily calculable. | 9610006v1 |
2006-09-14 | Comparison between resistive and collisionless double tearing modes for nearby resonant surfaces | The linear instability and nonlinear dynamics of collisional (resistive) and
collisionless (due to electron inertia) double tearing modes (DTMs) are
compared with the use of a reduced cylindrical model of a tokamak plasma. We
focus on cases where two q = 2 resonant surfaces are located a small distance
apart. It is found that regardless of the magnetic reconnection mechanism,
resistivity or electron inertia, the fastest growing linear eigenmodes may have
high poloidal mode numbers m ~ 10. The spectrum of unstable modes tends to be
broader in the collisionless case. In the nonlinear regime, it is shown that in
both cases fast growing high-m DTMs lead to an annular collapse involving small
magnetic island structures. In addition, collisionless DTMs exhibit multiple
reconnection cycles due to reversibility of collisionless reconnection and
strong ExB flows. Collisionless reconnection leads to a saturated stable state,
while in the collisional case resistive decay keeps the system weakly dynamic
by driving it back towards the unstable equilibrium maintained by a source
term. | 0609115v4 |
2006-12-08 | RPC with low-resistive phosphate glass electrodes as a candidate for the CBM TOF | Usage of electrodes made of glass with low bulk resistivity seems to be a
promising way to adapt the Resistive Plate Chambers (RPC) to the high-rate
environment of the upcoming CBM experiment. A pilot four-gap RPC sample with
electrodes made of phosphate glass, which has bulk resistivity in the order of
10^10 Ohm cm, has been studied with MIP beam for TOF applications. The tests
have yielded satisfactory results: the efficiency remains above 95% and the
time resolution stays within 120 ps up to the particle rate of 18 kHz/cm2. The
increase in rate from 2.25 to 18 kHz/cm2 leads to an increase of estimated
"tails" fraction in the time spectrum from 1.5% to 4%. | 0612083v1 |
2007-11-29 | Resistively Detected NMR in Quantum Hall States: Investigation of the anomalous lineshape near $ν=1$ | A study of the resistively detected nuclear magnetic resonance (RDNMR)
lineshape in the vicinity of $\nu=1$ was performed on a high-mobility 2D
electron gas formed in GaAs/AlGaAs. In higher Landau levels, application of an
RF field at the nuclear magnetic resonance frequency coincides with an observed
minimum in the longitudinal resistance, as predicted by the simple hyperfine
interaction picture. Near $\nu=1$ however, an anomalous dispersive lineshape is
observed where a resistance peak follows the usual minimum. In an effort to
understand the origin of this anomalous peak we have studied the resonance
under various RF and sample conditions. Interestingly, we show that the
lineshape can be completely inverted by simply applying a DC current. We
interpret this as evidence that the minima and maxima in the lineshape
originate from two distinct mechanisms. | 0711.4640v1 |
2008-09-06 | Doping dependence of upper critical field and Hall resistivity in LaFeAsO1-xFx | The electrical resistivity (Rxx) and Hall resistivity (Rxy) of LaFeAsO1-xFx
have been measured over a wide fluorine doping range 0 =< x =< 0.14 using 60 T
pulsed magnets. While the superconducting phase diagram (Tc, x) displays the
classic dome-shaped structure, we find that the resistive upper critical field
(Hc2) increases monotonically with decreasing fluorine concentration, with the
largest Hc2 >= 75 T for x = 0.05. This is reminiscent of the composition
dependence in high-Tc cuprates and might correlate with opening of a pseudo-gap
in the underdoped region. Further, the temperature dependence of Hc2(T) for
superconducting samples can be understood in terms of multi-band
superconductivity. Rxy data for non-superconducting samples show non-linear
field dependence, which is also consistent with a multi-carrier scenario. | 0809.1133v3 |
2008-10-21 | Nonlinear resistance of 2D electrons in crossed electric and magnetic fields | The longitudinal resistivity of two dimensional (2D) electrons placed in
strong magnetic field is significantly reduced by applied electric field, an
effect which is studied in a broad range of magnetic fields and temperatures in
GaAs quantum wells with high electron density. The data are found to be in good
agreement with theory, considering the strong nonlinearity of the resistivity
as result of non-uniform spectral diffusion of the 2D electrons. Inelastic
processes limit the diffusion. Comparison with the theory yields the inelastic
scattering time of the two dimensional electrons. In the temperature range
T=2-10(K) for overlapping Landau levels, the inelastic scattering rate is found
to be proportional to T^2, indicating a dominant contribution of the
electron-electron scattering to the inelastic relaxation. In a strong magnetic
field, the nonlinear resistivity demonstrates scaling behavior, indicating a
specific regime of electron heating of well-separated Landau levels. In this
regime the inelastic scattering rate is found to be proportional to T^3,
suggesting the electron-phonon scattering as the dominant mechanism of the
inelastic relaxation. | 0810.3713v2 |
2008-11-26 | Temperature Dependence of Interlayer Magnetoresistance in Anisotropic Layered Metals | Studies of interlayer transport in layered metals have generally made use of
zero temperature conductivity expressions to analyze angle-dependent
magnetoresistance oscillations (AMRO). However, recent high temperature AMRO
experiments have been performed in a regime where the inclusion of finite
temperature effects may be required for a quantitative description of the
resistivity. We calculate the interlayer conductivity in a layered metal with
anisotropic Fermi surface properties allowing for finite temperature effects.
We find that resistance maxima are modified by thermal effects much more
strongly than resistance minima. We also use our expressions to calculate the
interlayer resistivity appropriate to recent AMRO experiments in an overdoped
cuprate which led to the conclusion that there is an anisotropic, linear in
temperature contribution to the scattering rate and find that this conclusion
is robust. | 0811.4442v1 |
2009-03-04 | Resistivity Anisotropy of $AE$Fe$_2$As$_2$ ($AE$ =Ca, Sr, Ba): direct versus Montgomery technique measurements | The anisotropy of electrical resistivity was measured in parent compounds of
the iron-arsenic high temperature superconductors, AEFe2As2 with Alkali Earth
elements AE=Ca,Sr, Ba. Measurements were performed using both the Montgomery
technique and direct resistivity measurements on samples cut along principal
crystallographic directions. The anisotropy ratio \gamma_\rho=\rho_c/\rho_a is
well below 10 for all compounds in the whole temperature range studied (4 to
300 K), in notable contrast to previous reports. The anisotropy at room
temperature increases from about 2 in Ca, to about 4 in Sr and Ba. In all
compounds the resistivity ratio decreases on cooling through the
structural/antiferromagnetic transition temperature T_{SM}, with the change
mainly coming from stronger variation in \rho_a as compared with \rho_c. This
suggests that the transitions stronger affect the two-dimensional parts of the
Fermi surface. We compare our experimental observations with band structure
calculations, and find similar trend in the evolution of anisotropy with the
size of AE ion. Our results show that the electronic structure of the iron
pnictides has large contribution from three-dimensional areas of the Fermi
surface. | 0903.0820v1 |
2010-04-22 | Studies of resistance switching effects in metal/YBa2Cu3O7-x interface junctions | Current-voltage characteristics of planar junctions formed by an epitaxial
c-axis oriented YBa2Cu3O7-x thin film micro-bridge and Ag counter-electrode
were measured in the temperature range from 4.2 K to 300 K. A hysteretic
behavior related to switching of the junction resistance from a high-resistive
to a low-resistive state and vice-versa was observed and analyzed in terms of
the maximal current bias and temperature dependence. The same effects were
observed on a sub-micrometer scale YBa2Cu3O7-x thin film - PtIr point contact
junctions using Scanning Tunneling Microscope. These phenomena are discussed
within a diffusion model, describing an oxygen vacancy drift in YBa2Cu3O7-x
films in the nano-scale vicinity of the junction interface under applied
electrical fields. | 1004.3909v1 |
2010-06-11 | Mottness Collapse and T-linear Resistivity in Cuprate Superconductors | Central to the normal state of cuprate high-temperature superconductors is
the collapse of the pseudogap, briefly reviewed here, at a critical point and
the subsequent onset of the strange-metal characterized by a resistivity that
scales linearly with temperature. A possible clue to the resolution of this
problem is the inter-relation between two facts: 1) A robust theory of T-linear
resistivity resulting from quantum criticality requires an additional length
scale outside the standard 1-parameter scaling scenario and 2) breaking the
Landau correspondence between the Fermi gas and an interacting system with
short-range repulsions requires non-fermionic degrees. We show that a
low-energy theory of the Hubbard model which correctly incorporates dynamical
spectral weight transfer has the extra degrees of freedom needed to describe
this physics. The degrees of freedom that mix into the lower band as a result
of dynamical spectral weight transfer are shown to either decouple beyond a
critical doping, thereby signaling Mottness collapse or unbind above a critical
temperature yielding strange metal behaviour characterised by $T-$linear
resistivity. | 1006.2396v1 |
2011-01-04 | The effect of varying Fe-content on transport properties of K intercalated iron selenide KxFe2-ySe2 | We report the successful growth of high-quality single crystals of potassium
intercalated iron selenide KxFe2-ySe2 by Bridgeman method. The effect of iron
vacancies on transport properties was investigated by electrical resistivity
and magnetic susceptibility measurements. With varying iron content, the system
passes from semiconducting/insulating to superconducting state. Comparing with
superconductivity, the anomalous "hump" effect in the normal state resistivity
is much more sensitive to the iron deficiency. The electrical resistivity
exhibits a perfect metallic behavior (R300K/R35K=42) for the sample with little
iron vacancies. Our results suggest that the anomalous "hump" effect in the
normal state resistivity may be due to the ordering process of the cation
vacancies in this non-stoichiometric compound rather than magnetic/structure
transition. A trace of superconductivity extending up to near 44 K was also
detected in some crystals of KxFe2-ySe2, which has the highest Tc of the
reported iron selenides. | 1101.0789v1 |
2011-02-11 | Enhancement of edge channel transport by a low frequency irradiation | The magnetotransport properties of high mobility two dimensional electron gas
have recently attracted a significant interest due to the discovery of
microwave induced zero resistance states. Here we show experimentally that
microwave irradiation with a photon energy much smaller than the spacing
between Landau levels can induce a strong decrease in the four terminal
resistance. This effect is not predicted by the bulk transport models
introduced to explain zero resistance states, but can be naturally explained by
an edge transport model. This highlights the importance of edge channels for
zero resistance state physics that was proposed recently. | 1102.2314v2 |
2011-05-11 | Systematics of the temperature-dependent inter-plane resistivity in Ba(Fe$_{1-x}$T$_x$)$_2$As$_2$ with T= Rh, Ni, and Pd | Temperature-dependent inter-plane resistivity, $\rho_c(T)$, was measured
systematically as a function of transition metal substitution in the
iron-arsenide superconductors Ba(Fe$_{1-x}$T$_x$)$_2$As$_2$, $T$= Ni, Pd, Rh.
The data are compared with the behavior found in
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, revealing resistive signatures of pseudogap. In
all compounds we find resistivity crossover at a characteristic pseudogap
temperature $T^*$ from non-metallic to metallic temperature dependence on
cooling. Suppression of $T^*$ proceeds very similar in cases of Ni and Pd
doping and much faster than in similar cases of Co and Rh doping. In cases of
Co and Rh doping an additional minimum in the temperature-dependent $\rho_c$
emerges for high dopings, when superconductivity is completely suppressed.
These features are consistent with the existence of a charge gap covering part
of the Fermi surface. The part of the Fermi surface affected by this gap is
notably larger for Ni and Pd doped compositions than in Co and Rh doped
compounds. | 1105.2277v1 |
2011-09-08 | Group velocity and causality in standard relativistic resistive magnetohydrodynamics | Group velocity of electromagnetic waves in plasmas derived by standard
relativistic resistive MHD (resistive RMHD) equations is superluminal. If we
assume that the group velocity represents the propagation velocity of a signal,
we have to worry about the causality problem. That is, some acausal phenomena
may be induced, such that information transportation to the absolute past and
spontaneous decrease in the entropy. Here, we tried to find the acausal
phenomena using standard resistive RMHD numerical simulations in the suggested
situation of the acausal phenomena. The calculation results showed that even in
such situations no acausal effect happens. The numerical result with respect to
the velocity limit of the information transportation is consistent with a
linear theory of wave train propagation. Our results assure that we can use
these equations without problems of acausal phenomena. | 1109.1856v1 |
2012-04-03 | Resistive and magnetized accretion flows with convection | We considered the effects of convection on the radiatively inefficient
accretion flows (RIAF) in the presence of resistivity and toroidal magnetic
field. We discussed the effects of convection on transports of angular momentum
and energy. We established two cases for the resistive and magnetized RIAFs
with convection: assuming the convection parameter as a free parameter and
using mixing-length theory to calculate convection parameter. A self-similar
method was used to solve the integrated equations that govern the behavior of
the presented model. The solutions showed that the accretion and rotational
velocities decrease by adding the convection parameter, while the sound speed
increases. Moreover, by using mixing-length theory to calculate convection
parameter, we found that the convection can be important in RIAFs with magnetic
field and resistivity. | 1204.0743v1 |
2012-08-17 | Cooperative dynamics in charge-ordered state of alpha-(BEDT-TTF)2I3 | Electric-field-dependent pulse measurements are reported in the
charge-ordered state of alpha-(BEDT-TTF)2I3. At low electric fields up to about
50 V/cm only negligible deviations from Ohmic behavior can be identified with
no threshold field. At larger electric fields and up to about 100 V/cm a
reproducible negative differential resistance is observed with a significant
change in shape of the measured resistivity in time. These changes critically
depend whether constant voltage or constant current is applied to the single
crystal. At high enough electric fields the resistance displays a dramatic drop
down to metallic values and relaxes subsequently in a single-exponential manner
to its low-field steady-state value. We argue that such an electric-field
induced negative differential resistance and switching to transient states are
fingerprints of cooperative domain-wall dynamics inherent to two-dimensional
bond-charge density wave with ferroelectric-like nature. | 1208.3609v2 |
2012-11-05 | Metastable Resistivity States and Conductivity Fluctuations in Low-doped La$_{1-x}$Ca$_{x}$MnO$_3$ Manganite Single Crystals | Conductivity noise in dc current biased La_{0.82}Ca_{0.18}MnO_{3} single
crystals has been investigated in different metastable resistivity states
enforced by applying voltage pulses to the sample at low temperatures. Noise
measured in all investigated resistivity states is of 1/f-type and its
intensity at high temperatures and low dc bias scales as a square of the bias.
At liquid nitrogen temperatures for under bias exceeding a threshold value, the
behavior of the noise deviates from above quasi- equilibrium modulation noise
and depends in a non monotonic way on applied bias. The bias range of
nonequilibrium 1/f noise coincides with the range at which the conductance
increases linearly with bias voltage. This feature is attributed to a broad
continuity of states enabling indirect inelastic tunneling across intrinsic
tunnel junctions. The nonequilibrium noise has been ascribed to indirect
intrinsic tunneling mechanism while resistivity changes in metastable states to
variations in the energy landscape for charge carriers introduced by
microcracks created by the pulse procedures employed | 1211.0838v1 |
2012-11-07 | Exchange Field-Mediated Magnetoresistance in the Correlated Insulator Phase of Be Films | We present a study of the proximity effect between a ferromagnet and a
paramagnetic metal of varying disorder. Thin beryllium films are deposited onto
a 5 nm-thick layer of the ferromagnetic insulator EuS. This bilayer arrangement
induces an exchange field, $H_{ex}$, of a few tesla in low resistance Be films
with sheet resistance $R\ll R_Q$, where $R_Q=h/e^2$ is the quantum resistance.
We show that $H_{ex}$ survives in very high resistance films and, in fact,
appears to be relatively insensitive to the Be disorder. We exploit this fact
to produce a giant low-field magnetoresistance in the correlated insulator
phase of Be films with $R\gg R_Q$. | 1211.1663v1 |
2013-04-30 | Mechanical resistance in unstructured proteins | Single-molecule pulling experiments on unstructured proteins linked to
neurodegenerative diseases have measured rupture forces comparable to those for
stable folded proteins. To investigate the structural mechanisms of this
unexpected force resistance, we perform pulling simulations of the amyloid
{\beta}-peptide (A{\beta}) and {\alpha}-synuclein ({\alpha}S), starting from
simulated conformational ensembles for the free monomers. For both proteins,
the simulations yield a set of rupture events that agree well with the
experimental data. By analyzing the conformations right before rupture in each
event, we find that the mechanically resistant structures share a common
architecture, with similarities to the folds adopted by A{\beta} and {\alpha}S
in amyloid fibrils. The disease-linked Arctic mutation of A{\beta} is found to
increase the occurrence of highly force-resistant structures. Our study
suggests that the high rupture forces observed in A{\beta} and {\alpha}S
pulling experiments are caused by structures that might have a key role in
amyloid formation. | 1304.7991v3 |
2013-06-11 | Effect of pressure cycling on Iron: Signatures of an electronic instability and unconventional superconductivity | High pressure electrical resistivity and x-ray diffraction experiments have
been performed on Fe single crystals. The crystallographic investigation
provides direct evidence that in the martensitic $bcc \rightarrow hcp$
transition at 14 GPa the $\lbrace 110\rbrace_{bcc}$ become the $\lbrace
002\rbrace_{hcp}$ directions. During a pressure cycle, resistivity shows a
broad hysteresis of 6.5 GPa, whereas superconductivity, observed between 13 and
31 GPa, remains unaffected. Upon increasing pressure an electronic instability,
probably a quantum critical point, is observed at around 19 GPa and, close to
this pressure, the superconducting $T_{c}$ and the isothermal resistivity
($0<T<300\,$K) attain maximum values. In the superconducting pressure domain,
the exponent $n = 5/3$ of the temperature power law of resistivity and its
prefactor, which mimics $T_{c}$, indicate that ferromagnetic fluctuations may
provide the glue for the Cooper pairs, yielding unconventional
superconductivity. | 1306.2587v1 |
2013-09-14 | Magnetic field tuned superconductor-to-insulator transition at the LaAlO$_3$ /SrTiO$_3$ interface | We present a study of the magnetic field tuned superconductor-to-insulator
transition (SIT) in the electron gas that forms at the LaAlO$_3$/SrTiO$_3$
interface. We find that the magnetic field induces a transition into a weakly
insulating state, as is observed for the electrostatically tuned SIT at this
interface. Finite size scaling of the magnetoresistance yields the critical
exponent product $z\nu \simeq$ 7/3, indicating that the transition is governed
by quantum percolation effects. While such critical exponents have been
reported previously for high resistance films, they have not been reported for
a low resistance system like ours, with a maximum sheet resistance of $\approx$
1.5 k$\Omega$, much less than the quantum of resistance $R_Q \equiv h/4e^2 =
6.45$ k$\Omega$. | 1309.3612v1 |
2013-11-11 | Holographic duality and the resistivity of strange metals | We present a strange metal, described by a holographic duality, which
reproduces the famous linear resistivity of the normal state of the copper
oxides, in addition to the linear specific heat. This holographic metal reveals
a simple and general mechanism for producing such a resistivity, which requires
only quenched disorder and a strongly interacting, locally quantum critical
state. The key is the minimal viscosity of the latter: unlike in a
Fermi-liquid, the viscosity is very small and therefore is important for the
electrical transport. This mechanism produces a resistivity proportional to the
electronic entropy. | 1311.2451v2 |
2015-03-09 | Effect of pressure on superconductivity in doped topological crystalline insulator Sn0.5In0.5Te | We report on the impact of hydrostatic pressure on the superconductivity of
optimally (Indium) doped SnTe which is established to be derived from a
topological crystalline insulating phase. Single crystals of Sn1-xInxTe were
synthesized by a modified Bridgman method that exhibited maximum
superconducting Tc of 4.4 K for x= 0.5. Hydrostatic pressure upto 2.5 GPa was
applied on the crystals of Sn0.5In0.5Te and electrical resistivity as a
function of temperature and pressure was measured. We observed decrease in
onset superconducting transition temperature from 4.4 K to 2.8 K on increasing
pressure from ambient to 2.5 GPa. The normal state resistivity also decreased
abruptly by an order of magnitude at 0.5 GPa but for higher pressures, the same
decreased marginally. From onset, offset and zero resistivity values, dTc/dP of
-0.6K/GPa was confirmed. The low temperature normal state resistivity followed
T^2 dependence suggesting Fermi liquid behaviour both for ambient and high
pressure data. This increase in metallic characteristics accompanied by normal
state Fermi liquid behaviour is in accordance with a dome structure for Tc
variation with varying carrier concentration. | 1503.02431v1 |
2015-03-24 | Anisotropic Electronic Mobilities in the Nematic State of the Parent Phase NaFeAs | Hall effect and magnetoresistance have been measured on single crystals of
the parent phase NaFeAs under a uniaxial pressure. Although significant
difference of the in-plane resistivity $\rho_{xx}(I\parallel a)$ and
$\rho_{xx}(I\parallel b)$ with the uniaxial pressure along $b$-axis was
observed, the transverse resistivity $\rho_{xy}$ shows a surprisingly isotropic
behavior. Detailed analysis reveals that the Hall coefficient $R_\mathrm{H}$
measured in the two orthogonal configurations ($I\parallel a$-axis and
$I\parallel b$-axis) coincide very well and exhibit a deviation from the high
temperature background at around the structural transition temperature
$T_{\mathrm{s}}$. Furthermore, the magnitude of $R_\mathrm{H}$ increases
remarkably below the structural transition temperature. This enhanced Hall
coefficient is accompanied by the non-linear transverse resistivity versus
magnetic field and enhanced magnetoresistance, which can be explained very well
by the two band model with anisotropic mobilities of each band. Our results
together with the two band model analysis clearly show that the anisotropic
in-plane resistivity in the nematic state is closely related to the distinct
quasiparticle mobilities when they are moving parallel or perpendicular to the
direction of the uniaxial pressure. | 1503.07090v1 |
2015-10-13 | Global solvability, non-resistive limit and magnetic boundary layer of the compressible heat-conductive MHD equations | In general, the resistivity is inversely proportional to the electrical
conductivity, and is usually taken to be zero when the conducting fluid is of
extremely high conductivity (e.g., ideal conductors). In this paper, we first
establish the global well-posedness of strong solution to an initial-boundary
value problem of the one-dimensional compressible, viscous, heat-conductive,
non-resistive MHD equations with general heat-conductivity coefficient and
large data. Then, the non-resistive limit is justified and the convergence
rates are obtained, provided the heat-conductivity satisfies some growth
condition. Finally, we discuss the thickness of the magnetic boundary layer,
which is particularly in consistent with the Stokes-Blasius law in the
classical theory of laminar boundary layer. | 1510.03529v2 |
2016-12-13 | Strongly temperature dependent resistance of meander-patterned graphene | We have studied the electronic properties of epitaxial graphene devices
patterned in a meander shape with the length up to a few centimeters and the
width of few tens of microns. These samples show a pronounced dependence of the
resistance on temperature. Accurate comparison with theory shows that this
temperature dependence originates from the weak localization effect observed
over a broad temperature range from 1.5 K up to 77 K. The comparison allows us
to estimate the characteristic times related to quantum interference. In
addition, a large resistance enhancement with temperature is observed at the
quantum Hall regime near the filling factor of 2. Record high resistance and
its strong temperature dependence are favorable for the construction of
bolometric photodetectors. | 1612.04222v1 |
2016-12-15 | Microscopic theory for radiation-induced Zero-Resistance States in 2D electron systems: Franck-Condon blockade | We present a microscopic model on radiation-induced zero resistance states
according to a novel approach: Franck-Condon physics and blockade. Zero
resistance states rise up from radiation-induced magnetoresistance oscillations
when the light intensity is strong enough. The theory starts off with the {\it
radiation-driven electron orbit model} that proposes an interplay of the
swinging nature of the radiation-driven Landau states and the presence of
charged impurity scattering. When the intensity of radiation is high enough it
turns out that the driven-Landau states (vibrational states) involved in the
scattering process are spatially far from each other and the corresponding
electron wave functions do not longer overlap. As a result, it takes place a
drastic suppression of the scattering probability and then current and
magnetoresistance exponentially drop. Finally zero resistance states rise up.
This is an application to magnetotransport in two dimensional electron systems
of the Franck-Condon blockade, based on the Franck-Condon physics which in turn
stems from molecular vibrational spectroscopy. | 1612.05247v1 |
2017-09-14 | Simultaneous drop in mean free path and carrier density at the pseudogap onset in high-$T_c$ cuprates | High-temperature superconducting cuprates are distinguished by an enigmatic
pseudogap which opens near optimal doping where the superconducting transition
temperature is highest. Key questions concern its origin and whether it is
essential in any way to superconductivity. Recent field-induced normal-state
transport experiments on hole-doped cuprates have measured abrupt changes in
the doping dependent Hall number and resistivity, consistent with a drop in
carrier density from $1+p$ to $p$ holes per copper atom, on entering the
pseudogap phase. In this work the change in resistivity is analyzed in terms of
an antiferromagnetic-order-induced Fermi surface reconstruction model that has
already successfully described the Hall number. In order for this model to
describe the resistivity we find that the zero-temperature mean free path must
also drop abruptly in proportion to the size of the Fermi surface. This
suggests that intrapocket scattering underlies the observed upturn in
resistivity in the pseudogap state. | 1709.04590v1 |
2018-03-02 | Robustness of the Insulating Bulk in the Topological Kondo Insulator SmB$_{6}$ | We used the inverted resistance method to extend the bulk resistivity of
SmB$_{6}$ to a regime where the surface conduction overwhelms the bulk.
Remarkably, the bulk resistivity shows an intrinsic thermally activated
behavior that changes ten orders of magnitude, suggesting that it is an ideal
insulator that is immune to disorder. Non-stoichiometrically-grown SmB$_{6}$
samples also show an almost identical thermally activated behavior. At low
temperatures, however, these samples show a mysterious high bulk resistivity
plateau, which may arise from extended defect conduction in a 3D TI. | 1803.00959v1 |
2018-04-10 | Purely electronic nanometallic ReRAM | Resistance switching random access memory (ReRAM), with the ability to
repeatedly modulate electrical resistance, has been highlighted as a feasible
high-density memory with the potential to replace negative-AND (NAND) flash
memory. Such resistance modulation usually involves ion migration and filament
formation, which usually lead to relatively low device reliability and yield.
Resistance switching can also come from an entirely electronic origin, as in
nanometallic memory, by electron trapping and detrapping. Recent research has
revealed additional merits of its mechanism, which entails smart, atomic-sized
floating gates that can be easily engineered in amorphous Si, oxides, and
nitrides. This article addresses the basic ideas of nanometallic ReRAM, which
may also be a contender for analogue computing and non-von Neumann-type
computation. | 1804.03302v1 |
2018-09-23 | Resistive cooling of highly charged ions in a Penning trap to a fluid-like state | We have performed a detailed experimental study of resistive cooling of large
ensembles of highly charged ions such as Ar$^{13+}$ in a cryogenic Penning
trap. Different from the measurements reported in [M. Vogel et al., Phys. Rev.
A, 043412 (2014)], we observe purely exponential cooling behavior when
conditions are chosen to allow collisional thermalization of the ions. We
provide evidence that in this situation, resistive cooling time constants and
final temperatures are independent of the initial ion energy, and that the
cooling time constant of a thermalized ion ensemble is identical to the
single-ion cooling time constant. For sufficiently high ion number densities,
our measurements show discontinuities in the spectra of motional resonances
which indicate a transition of the ion ensemble to a fluid-like state when
cooled to temperatures below approximately 14 K. With the final ion temperature
presently being 7.5 K, ions of the highest charge states are expected to form
ion crystals by mere resistive cooling, in particular not requiring the use of
laser cooling. | 1809.08606v1 |
2019-09-13 | Stabilizing effect of enhanced resistivity on peeling-ballooning instabilities on EAST | Previous stability analysis of NSTX equilibrium with lithium-conditioning
demonstrates that the enhanced resistivity due to the increased effective
charge number Zeff (i.e. increased impurity level) can provide a stabilizing
effect on low-n edge localized modes (Banerjee et al 2017 Nucl. Fusion 24
054501). This paper extends the resistivity stabilizing effect to the
intermediate-n peeling-ballooning (PB) instabilities with the linear stability
analysis of EAST high-confinement mode equilibria in NIMROD two-fluid
calculations. However, the resistivity stabilizing effect on PB instabilities
in the EAST tokamak appears weaker than that found in NSTX. This work may give
better insight into the physical mechanism behind the beneficial effects of
impurity on the pedestal stability. | 1909.06009v1 |
2020-03-10 | Resonance peak shift in the photo-current of ultrahigh-mobility two-dimensional electron systems | We report on a theoretical study on the rise of strong peaks at the harmonics
of the cyclotron resonance in the irradiated magnetoresistance in ultraclean
two-dimensional electron systems. The motivation is the experimental
observation of a totally unexpected strong resistance peak showing up at the
second harmonic. We extend the radiation-driven electron orbit model
(previously developed to study photocurrent oscillations and zero resistance
states) to a ultraclean scenario that implies longer scattering time and longer
mean free path. Thus, when the mean free path is equivalent, in terms of
energy, to twice the cyclotron energy ($2\hbar w_{c}$), the electron behaves as
under an effective magnetic field twice the one really applied. Then, at high
radiation power and/or low temperature, a resistance spike can be observed {\it
at the second harmonic}. For even cleaner samples the energy distance could
increase to three or four times the cyclotron energy giving rise to resistance
peaks at higher harmonics (third, fourth, etc.), i.e., a resonance peak shift
to lower magnetic fields as the quality of the sample increases. Thus, by
selecting the sample mobility one automatically would select the radiation
resonance response without altering the radiation frequency. | 2003.04869v1 |
2020-03-22 | Programmable quantum Hall bisector: towards a novel resistance standard for quantum metrology | We demonstrate a programmable quantum Hall circuit that implements a novel
iterative voltage bisection scheme and allows obtaining any binary fraction
$(k/2^n)$ of the fundamental resistance quantum $R_K/2=h/2e^2$. The circuit
requires a number $n$ of bisection stages that only scales logarithmically with
the precision of the fraction. The value of $k$ can be set to any integer
between 1 and $2^n$ by proper gate configuration. The architecture exploits
gate-controlled routing, mixing and equilibration of edge modes of robust
quantum Hall states. The device does not contain {\em any} internal ohmic
contact potentially leading to spurious voltage drops. Our scheme addresses key
critical aspects of quantum Hall arrays of resistance standards, which are
today widely studied and used to create custom calibration resistances. The
approach is demonstrated in a proof-of-principle two-stage bisection circuit
built on a high-mobility GaAs/AlGaAs heterostructure operating at a temperature
of $260\,{\rm mK}$ and a magnetic field of $4.1\,{\rm T}$. | 2003.10020v1 |
2014-08-27 | DC resistivity at the onset of spin density wave order in two-dimensional metals | The theory for the onset of spin density wave order in a metal in two
dimensions flows to strong coupling, with strong interactions not only at the
`hot spots', but on the entire Fermi surface. We advocate the computation of DC
transport in a regime where there is rapid relaxation to local equilibrium
around the Fermi surface by processes which conserve total momentum. The DC
resistivity is then controlled by weaker perturbations which do not conserve
momentum. We consider variations in the local position of the quantum critical
point, induced by long-wavelength disorder, and find a contribution to the
resistivity which is linear in temperature (up to logarithmic corrections) at
low temperature. Scattering of fermions between hot spots, by short-wavelength
disorder, leads to a residual resistivity and a correction which is linear in
temperature. | 1408.6549v2 |
2017-01-26 | Semi-analytical model of the contact resistance in two-dimensional semiconductors | Contact resistance is a severe performance bottleneck for electronic devices
based on two-dimensional layered (2D) semiconductors, whose contacts are
Schottky rather than Ohmic. Although there is general consensus that the
injection mechanism changes from thermionic to tunneling with gate biasing,
existing models tend to oversimplify the transport problem, by neglecting the
2D transport nature and the modulation of the Schottky barrier height, the
latter being of particular importance in back-gated devices. In this work, we
develop a semi-analytical model based on Bardeen's transfer Hamiltonian
approach to describe both effects. Remarkably, our model is able to reproduce
several experimental observations of a metallic behavior in the contact
resistance, i.e., a decreasing resistance with decreasing temperature,
occurring at high gate voltage. | 1701.07758v1 |
2018-10-05 | A Deep Learning Approach to the Inversion of Borehole Resistivity Measurements | We use borehole resistivity measurements to map the electrical properties of
the subsurface and to increase the productivity of a reservoir. When used for
geosteering purposes, it becomes essential to invert them in real time. In this
work, we explore the possibility of using Deep Neural Network (DNN) to perform
a rapid inversion of borehole resistivity measurements. Herein, we build a DNN
that approximates the following inverse problem: given a set of borehole
resistivity measurements, the DNN is designed to deliver a physically
meaningful and data-consistent piecewise one-dimensional layered model of the
surrounding subsurface. Once the DNN is built, we can perform the actual
inversion of the field measurements in real time. We illustrate the performance
of DNN of logging-while-drilling measurements acquired on high-angle wells via
synthetic data. | 1810.04522v2 |
2020-09-21 | A small-signal GFET equivalent circuit considering an explicit contribution of contact resistances | A small-signal equivalent circuit for graphene field-effect transistors is
proposed considering the explicit contribution of effects at the metal-graphene
interfaces by means of contact resistances. A methodology to separate the
contact resistances from intrinsic parameters, obtained by a de-embedding
process, and extrinsic parameters of the circuit is considered. The
experimental high-frequency performance of three devices from two different
GFET technologies is properly described by the proposed small-signal circuit.
Some model parameters scale with the device footprint. The correct detachment
of contact resistances from the internal transistor enables to assess their
impact on the intrinsic cutoff frequency of the studied devices. | 2009.09673v2 |
2014-01-30 | Scale-invariant hyperscaling-violating holographic theories and the resistivity of strange metals with random-field disorder | We compute the direct current resistivity of a scale-invariant,
$d$-dimensional strange metal with dynamic critical exponent $z$ and
hyperscaling-violating exponent $\theta$, weakly perturbed by a scalar operator
coupled to random-field disorder that locally breaks a $\mathbb{Z}_2$ symmetry.
Independent calculations via Einstein-Maxwell-Dilaton holography and memory
matrix methods lead to the same results. We show that random field disorder has
a strong effect on resistivity: charge carriers in the infrared are easily
depleted, as the relaxation time for momentum is surprisingly small. In the
course of our holographic calculation we use a non-trivial dilaton coupling to
the disordered scalar, allowing us to study a strongly-coupled scale invariant
theory with $\theta \ne 0$. Using holography, we are also able to determine the
disorder strength at which perturbation theory breaks down. Curiously, for
locally critical theories this breakdown occurs when the resistivity is
proportional to the entropy density, up to a possible logarithmic correction. | 1401.7993v3 |
2017-04-24 | Resistivity bound for hydrodynamic bad metals | We obtain a rigorous upper bound on the resistivity $\rho$ of an electron
fluid whose electronic mean free path is short compared to the scale of spatial
inhomogeneities. When such a hydrodynamic electron fluid supports a non-thermal
diffusion process -- such as an imbalance mode between different bands -- we
show that the resistivity bound becomes $\rho \lesssim A \, \Gamma$. The
coefficient $A$ is independent of temperature and inhomogeneity lengthscale,
and $\Gamma$ is a microscopic momentum-preserving scattering rate. In this way
we obtain a unified and novel mechanism -- without umklapp -- for $\rho \sim
T^2$ in a Fermi liquid and the crossover to $\rho \sim T$ in quantum critical
regimes. This behavior is widely observed in transition metal oxides, organic
metals, pnictides and heavy fermion compounds and has presented a longstanding
challenge to transport theory. Our hydrodynamic bound allows phonon
contributions to diffusion constants, including thermal diffusion, to directly
affect the electrical resistivity. | 1704.07384v1 |
2017-05-12 | Resistive switching in MoSe$_{2}$/BaTiO$_{3}$ hybrid structures | Here we study the resistive switching (RS) effect that emerges when
ferroelectric BaTiO$_{3}$ (BTO) and few-layers MoSe$_{2}$ are combined in one
single structure. The C-V loops reveal the ferroelectric nature of both
Al/Si/SiO$_{x}$/BTO/Au and Al/Si/SiO$_{x}$/MoSe$_{2}$/BTO/Au structures and the
high quality of the SiO$_{x}$/MoSe$_{2}$ interface in the
Al/Si/SiOx/MoSe$_{2}$/Au structure. Al/Si/SiO$_{x}$/MoSe$_{2}$/BTO/Au hybrid
structures show the electroforming free resistive switching that is explained
on the basis of the modulation of the potential distribution at the
MoSe$_{2}$/BTO interface via ferroelectric polarization flipping. This
structure shows promising resistive switching characteristics with switching
ratio of $\approx{}$10$^{2}$ and a stable memory window, which are highly
required for memory applications. | 1705.04475v1 |
2019-03-04 | On Resistive Memories: One Step Row Readout Technique and Sensing Circuitry | Transistor-based memories are rapidly approaching their maximum density per
unit area. Resistive crossbar arrays enable denser memory due to the small size
of switching devices. However, due to the resistive nature of these memories,
they suffer from current sneak paths complicating the readout procedure. In
this paper, we propose a row readout technique with circuitry that can be used
to read {selector-less} resistive crossbar based memories. High throughput
reading and writing techniques are needed to overcome the memory-wall
bottleneck problem and to enable near memory computing paradigm. The proposed
technique can read the entire row of dense crossbar arrays in one cycle, unlike
previously published techniques. The requirements for the readout circuitry are
discussed and satisfied in the proposed circuit. Additionally, an approximated
expression for the power consumed while reading the array is derived. A figure
of merit is defined and used to compare the proposed approach with existing
reading techniques. Finally, a quantitative analysis of the effect of biasing
mismatch on the array size is discussed. | 1903.01512v1 |
2011-04-22 | Symmetry breaking as the origin of zero-differential resistance states of a 2DEG in strong magnetic fields | Zero resistance differential states have been observed in two-dimensional
electron gases (2DEG) subject to a magnetic field and a strong dc current. In a
recent work we presented a model to describe the nonlinear transport regime of
this phenomenon. From the analysis of the differential resistivity and the
longitudinal voltage we predicted the formation of negative differential
resistivity states, although these states are known to be unstable. Based on
our model, we derive an analytical approximated expression for the
Voltage-Current characteristics, that captures the main elements of the
problem. The result allow us to construct an energy functional for the system.
In the zero temperature limit, the system presents a quantum phase transition,
with the control parameter given by the magnetic field. It is noted that above
a threshold value ($B>B_{th}$), the symmetry is spontaneously broken. At
sufficiently high magnetic field and low temperature the model predicts a phase
with a non-vanishing permanent current; this is a novel phase that has not been
observed so far. | 1104.4476v1 |
2012-03-08 | Precision quantization of Hall resistance in transferred graphene | We show that quantum resistance standards made of transferred graphene reach
the uncertainty of semiconductor devices, the current reference system in
metrology. A large graphene device (150 \times 30 \mum2), exfoliated and
transferred onto GaAs, revealed a quantization with a precision of (-5.1 \pm
6.3) \times 10-9 accompanied by a vanishing longitudinal resistance at current
levels exceeding 10 \muA. While such performance had previously only been
achieved with epitaxially grown graphene, our experiments demonstrate that
transfer steps, inevitable for exfoliated graphene or graphene grown by
chemical vapor deposition (CVD), are compatible with the requirements of high
quality quantum resistance standards. | 1203.1798v2 |
2012-03-23 | Pressure effects on the heavy-fermion antiferromagnet CeAuSb2 | The f-electron compound CeAuSb2, which crystallizes in the ZrCuSi2-type
tetragonal structure, orders antiferromagnetically between 5 and 6.8 K, where
the antiferromagnetic transition temperature T_N depends on the occupancy of
the Au site. Here we report the electrical resistivity and heat capacity of a
high-quality crystal CeAuSb2 with T_N of 6.8 K, the highest for this compound.
The magnetic transition temperature is initially suppressed with pressure, but
is intercepted by a new magnetic state above 2.1 GPa. The new phase shows a
dome shape with pressure and coexists with another phase at pressures higher
than 4.7 GPa. The electrical resistivity shows a T^2 Fermi liquids behavior in
the complex magnetic state, and the residual resistivity and the T^2
resistivity coefficient increases with pressure, suggesting the possibility of
a magnetic quantum critical point at a higher pressure. | 1203.5164v1 |
2015-06-03 | Electronic resistances of multilayered two-dimensional crystal junctions | We carry out a layer-by-layer investigation to understand electron transport
across metal-insulator-metal junctions. Interfacial structures of junctions
were studied and characterized using first-principles density functional theory
within the generalized gradient approximation. We found that as a function of
the number of crystal layers the calculated transmission coefficients of
multilayer silicene junctions decay much slower than for BN-based junctions We
revisited the semiclassical Boltzmann theory of electronic transport and
applied to multilayer silicene and BN-based junctions. The calculated
resistance in the high-transmission regime is smaller than that provided by the
Landauer formula. As the thickness of the barrier increases, results from the
Boltzmann and the Landauer formulae converge. We provide a upper limit in the
transmission coefficient below which, the Landauer method becomes valid.
Quantitatively, when the transmission coefficient is lower than $ \sim 0.05 $
per channel, the error introduced by the Landauer formula for calculating the
resistance is negligible. In addition, we found that the resistance of a
junction is not entirely determined by the averaged transmission, but also by
the distribution of the transmission over the first Brillouin zone. | 1506.01397v1 |
2019-01-28 | Quantifying Temperature-dependent Substrate Loss in GaN-on-Si RF Technology | Intrinsic limits to temperature-dependent substrate loss for GaN-on-Si
technology, due to the change in resistivity of the substrate with temperature,
are evaluated using an experimentally validated device simulation framework.
Effect of room temperature substrate resistivity on temperature-dependent CPW
line loss at various operating frequency bands are then presented. CPW lines
for GaN-on-high resistivity Si are shown to have a pronounced
temperature-dependence for temperatures above 150{\deg}C and have lower
substrate losses for frequencies above the X-band. On the other hand,
GaN-on-low resistivity Si is shown to be more temperature-insensitive and have
lower substrate losses than even HR-Si for lower operating frequencies. The
effect of various CPW geometries on substrate loss is also presented to
generalize the discussion. These results are expected to act as a benchmark for
temperature dependent substrate loss in GaN-on-Si RF technology. | 1901.09521v1 |
2019-01-29 | Simultaneous prediction of multiple outcomes using revised stacking algorithms | Motivation: HIV is difficult to treat because its virus mutates at a high
rate and mutated viruses easily develop resistance to existing drugs. If the
relationships between mutations and drug resistances can be determined from
historical data, patients can be provided personalized treatment according to
their own mutation information. The HIV Drug Resistance Database was built to
investigate the relationships. Our goal is to build a model using data in this
database, which simultaneously predicts the resistance of multiple drugs using
mutation information from sequences of viruses for any new patient.
Results: We propose two variations of a stacking algorithm which borrow
information among multiple prediction tasks to improve multivariate prediction
performance. The most attractive feature of our proposed methods is the
flexibility with which complex multivariate prediction models can be
constructed using any univariate prediction models. Using cross-validation
studies, we show that our proposed methods outperform other popular
multivariate prediction methods.
Availability: An R package will be made available. | 1901.10153v1 |
2019-06-07 | A resistive extension for ideal MHD | We present an extension to the special relativistic, ideal
magnetohydrodynamics (MHD) equations, designed to capture effects due to
resistivity. The extension takes the simple form of an additional source term
which, when implemented numerically, is shown to emulate the behaviour produced
by a fully resistive MHD description for a range of initial data. The extension
is developed from first principle arguments, and thus requires no fine tuning
of parameters, meaning it can be applied to a wide range of dynamical systems.
Furthermore, our extension does not suffer from the same stiffness issues
arising in resistive MHD, and thus can be evolved quickly using explicit
methods, with performance benefits of roughly an order of magnitude compared to
current methods. | 1906.03150v2 |
2019-06-19 | Phonon scattering induced carrier resistivity in twisted double bilayer graphene | In this work we carry out a theoretical study of the phonon-induced
resistivity in twisted double bilayer graphene (TDBG), in which two
Bernal-stacked bilayer graphene devices are rotated relative to each other by a
small angle $\theta$. We show that at small twist angles ($\theta\sim 1^\circ$)
the effective mass of the TDBG system is greatly enhanced, leading to a
drastically increased phonon-induced resistivity in the high-temperature limit
where phonon scattering leads to a linearly increasing resistivity with
increasing temperature. We also discuss possible implications of our theory on
superconductivity in such a system, and provide an order of magnitude
estimation of the superconducting transition temperature. | 1906.08224v2 |
2021-02-16 | Fast hierarchical inversion for borehole resistivity measurements in high-angle and horizontal wells using ADNN-AMLM | With the rapid development of deep learning, intelligent scheme is gradually
introduced to solve various nolinear inverse problems. In this paper, we
combine an efficient adaptive deep neural network (ADNN) framework with
adaptive modified Levenberg-Marquardt (AMLM) algorithm based on three-layer
inversion model to exact formation resistivity and invasion depth from array
laterolog resistivity measurements. ADNN presented in this paper can realize
the 2D/3D fast forward modeling of array laterolog. AMLM algorithm and
hierarchical inversion scheme are adopted to improve the anti-noise ability and
convergence in complex logging environments, which realizing the fast and
accurate reconstruction of longitudinal resistivity profile in HA/HZ wells. The
numerical simulation shows that the ADNN forward modeling only takes 0.021s for
each logging point, and the maximum relative error is less than 2%. Three-layer
inversion model can eliminate the effect of surrounding bed and improve the
inversion accuracy in thinly layered formation. The error between inverted
results and truth model is less than 3%. The AMLM inversion algorithm can
effectively suppress the influence of noise, and takes only 10 steps to achieve
convergence. | 2102.08038v1 |
2021-04-01 | Towards high-rate RPC-based thermal neutron detectors using low-resistivity electrodes | We present experimental results on the counting rate measurements for several
single-gap $^{10}$B lined resistive plate chambers ($^{10}$B-RPCs) with anodes
made from standard float glass, low resistivity glass and ceramic. The
measurements were performed at the V17 monochromatic neutron beamline (3.35
\.A) at the Helmholtz-Zentrum Berlin. For the $^{10}$B-RPCs with 0.28 mm thick
float glass a maximum counting rate density of about $8\times 10^{3}$
$Hz/cm^{2}$ was obtained. In the case of low resistivity glass and ceramic, the
counting rate density did not deviate from linear dependence on the neutron
flux up to the maximum flux available at this beamline and exceeded a value of
$3\times 10^{4}$ $Hz/cm^{2}$. | 2104.00695v1 |
2021-09-14 | Contactless Series Resistance Imaging of Perovskite Solar Cells via Inhomogeneous Illumination | A contactless effective series resistance imaging method for large area
perovskite solar cells that is based on photoluminescence imaging with
non-uniform illumination is introduced and demonstrated experimentally. The
proposed technique is applicable to partially and fully processed perovskite
solar cells if laterally conductive layers are present. The capability of the
proposed contactless method to detect features with high effective series
resistance is validated by comparison with various contacted mode luminescence
imaging techniques. The method can reliably provide information regarding the
severeness of the detected series resistance through photo-excitation pattern
manipulation. Application of the method to sub-cells in monolithic tandem
devices, without the need for electrical contacting the terminals, appears
feasible. | 2109.06971v1 |
2021-12-29 | Wide-range $T^2$ resistivity and umklapp scattering in moiré graphene | We argue that the unusually strong electron-electron interactions in the
narrow bands in moir\'e superlattices originate from compact Wannier orbitals.
Enhanced overlaps of electronic wavefunctions, enabled by such orbitals, result
in a strong el-el superlattice umklapp scattering. We identify the umklapp
scattering processes as a source of the strong temperature-dependent
resistivity observed in these systems. In a simple model, the umklapp
scattering predicts a $T$-dependent resistivity that grows as $T^2$ and is
getting bigger as the Wannier orbital radius decreases. We quantify the
enhancement in el-el scattering by the Kadowaki-Woods (KW) ratio, a quantity
that is sensitive to umklapp scattering but, helpfully, insensitive to the
effects due to the high density of electronic states. Our analysis predicts
anomalously large KW ratio values that clearly indicate the importance of the
umklapp el-el processes and their impact on the $T$-dependent resistivity. | 2112.14745v2 |
2022-06-05 | Simplicial effective resistance and enumeration of spanning trees | A graph can be regarded as an electrical network in which each edge is a
resistor. This point of view relates combinatorial quantities, such as the
number of spanning trees, to electrical ones such as effective resistance. The
second and third authors have extended the combinatorics/electricity analogy to
higher dimension and expressed the simplicial analogue of effective resistance
as a ratio of weighted tree enumerators. In this paper, we first use that ratio
to prove a new enumeration formula for color-shifted complexes, confirming a
conjecture by Aalipour and the first author, and generalizing a result of
Ehrenborg and van Willigenburg on Ferrers graphs. We then use the same
technique to recover an enumeration formula for shifted complexes, first proved
by Klivans and the first and fourth authors. In each case, we add facets one at
a time, and give explicit expressions for simplicial effective resistances of
added facets by constructing high-dimensional analogues of currents and
voltages (respectively homological cycles and cohomological cocycles). | 2206.02182v2 |
2022-11-25 | Numerical study of SQUID array responses due to asymmetric junction parameters | Superconducting quantum interference device arrays have been extensively
studied for their high magnetic field sensitivity. The performance of these
devices strongly depends on the characteristic parameters of their Josephson
junctions, i.e. their critical currents and shunt resistances. Using a
resistively shunted junction model and including thermal noise, we perform a
numerical investigation of the effects of asymmetric Josephson junctions by
independently studying variations in the critical currents and junction
resistances. We compare the voltage response of a dc-SQUID with a 1D parallel
SQUID array and study the maximum transfer function dependence on the number of
junctions in parallel, the screening parameter and thermal noise strength. Our
results show that the maximum transfer function and linearity increase with the
number of junctions in parallel for arrays with different junction resistances,
in contrast to SQUID arrays with identical junctions or with spreads in the
critical currents. | 2211.13833v1 |
2023-01-08 | Resistive Read-out in Thin Silicon Sensors with Internal Gain | Two design innovations, low-gain avalanche (Low-Gain Avalance Diode, LGAD)
and resistive read-out (Resistive Silicon Detector, RSD), have brought strong
performance improvements to silicon sensors. Large signals, due to the added
gain mechanism, lead to improved temporal precision, while charge sharing,
introduced by resistive read-out, allows for achieving excellent spatial
resolution even with large pixels. LGAD- and RSD- based silicon sensors are now
adopted, or considered, in several future experiments and are the basis for
almost every next 4D-trackers. New results obtained with sensors belonging to
the second FBK production of RSD (RSD2) demonstrate how a combined resolution
of 30 ps and 30 \microns can be obtained with pixels as large as $1 \times 1 $
mm$^2$. | 2301.02968v1 |
2023-06-09 | Voltage-time dilemma and stochastic threshold voltage variation in pure silver atomic switches | The formation and dissolution of silver nanowires plays a fundamental role in
a broad range of resistive switching devices, fundamentally relying on the
electrochemical metallization phenomenon. It was shown, however, that resistive
switching may also appear in pure metallic nanowires lacking any
silver-ion-hosting embedding environment, but this pure atomic switching
mechanism fundamentally differs from the conventional
electrochemical-metallization-based resistive switching. To facilitate the
quantitative description of the former phenomenon, we investigate broad range
of Ag atomic junctions with a special focus on the frequency-dependence and the
fundamentally stochastic cycle-to-cycle variation of the switching threshold
voltage. These devices are established in an ultra-high purity environment
where electrochemical metallization can be excluded. The measured
characteristics are successfully described by a vibrational pumping model,
yielding consistent predictions for the weak frequency dependence and the large
variance of the switching threshold voltage. We also demonstrate that
electrochemical-metallization-based resistive switching and pure atomic
switching may appear in the same device structure, and therefore the proper
understanding of the pure atomic switching mechanism has a distinguished
importance in silver-based electrochemical metallization cells. | 2306.05736v1 |
2023-08-19 | Temperature, RF Field, and Frequency Dependence Performance Evaluation of Superconducting Niobium Half-Wave Cavity | Recent advancement in superconducting radio frequency cavity processing
techniques, with diffusion of impurities within the RF penetration depth,
resulted in high quality factor with increase in quality factor with increasing
accelerating gradient. The increase in quality factor is the result of a
decrease in the surface resistance as a result of nonmagnetic impurities doping
and change in electronic density of states. The fundamental understanding of
the dependence of surface resistance on frequency and surface preparation is
still an active area of research. Here, we present the result of RF
measurements of the TEM modes in a coaxial half wave niobium cavity resonating
at frequencies between 0.3-1.3 GHz. The temperature dependence of the surface
resistance was measured between 4.2 K and 1.6 K. The field dependence of the
surface resistance was measured at 2.0 K. The baseline measurements were made
after standard surface preparation by buffered chemical polishing. | 2308.09859v1 |
2023-12-16 | Negative differential resistance in Josephson junctions coupled to a cavity | Regions with negative differential resistance can arise in the IV curve of
Josephson junctions and this phenomenon plays an essential role for
applications, in particular for THz radiation emission. For the measurement of
high frequency radiation from Josephson junctions, a cavity - either internal
or external - is often used. A cavity may also induce a negative differential
resistance region at the lower side of the resonance frequency. We investigate
the dynamics of Josephson junctions with a negative differential resistance in
the quasi particle tunnel current, i.e. in the McCumber curve. We find that
very complicated and unexpected interactions take place. This may be useful for
the interpretation of experimental measurements of THz radiation from intrinsic
Josephson junctions. | 2312.14174v1 |
1995-01-26 | Superconductivity and Stoichiometry in the BSCCO-family Materials | We report on magnetization, c-axis and ab-plane resistivity, critical
current, electronic band structure and superconducting gap properties. Bulk
measurements and photoemission data were taken on similar samples. | 9501124v1 |
2002-06-14 | Electron scattering in multi-wall carbon-nanotubes | We analyze two scattering mechanisms that might cause intrinsic electronic
resistivity in multi-wall carbon nanotubes: scattering by dopant impurities,
and scattering by inter-tube electron-electron interaction. We find that for
typically doped multi-wall tubes backward scattering at dopants is by far the
dominating effect. | 0206264v1 |
2003-07-11 | Magnetic and transport percolation in diluted magnetic semiconductors | The ferromagnetic transition in a diluted magnetic semiconductor with
localized charge carriers is inevitably a percolation transition. In this work
we theoretically study the correlation between this magnetic percolation and
transport properties of the sample, including the possibility of a simultaneous
transport percolation. We find nontrivial signatures of the percolating
magnetic clusters in the transport properties of the system, including
interesting non-monotonic temperature dependence of the system resistivity. | 0307294v1 |
2003-09-26 | Vortex dynamics in dilute two dimensional Josephson junction arrays | We have investigated the dynamics of vortices in a dilute two dimensional
Josephson junction array where a fraction of the superconducting islands is
missing. We have used the multiple trapping model to calculate the mobility of
vortices and the frequency dependence of the resistance and inductance of the
array. | 0309620v1 |
2004-04-01 | Hall anomaly in mixed state of superconductors and vortex dynamics | The present author has long argued, with concrete predictions, that both
longitudinal and transverse (Hall) resistivities in the mixed state of
superconductors are dominated by vortex many-body effect. Hence there is no
need to introduce various ad hoc vortex dynamics theories. It is interesting to
note this point of view is now slowly creeping into the work of his most fierce
opponents. | 0404009v1 |
2010-01-29 | Cooper pairs under the action of disorder and strong magnetic field | The zero temperature phase diagram of Cooper pairs exposed to disorder and
magnetic field is found to exhibit four distinct phases: a Bose and a Fermi
insulating, a metallic and a superconducting phase, respectively. The results
explain the giant negative magneto-resistance found experimentally in In-O,
TiN, Bi and high-$T_c$ materials. | 1001.5431v2 |
2011-01-17 | Localized superconductive pairs | Different physical phenomena are discussed which should help to comprehend
and interpret the concept of localized superconductive pairs; these include
behavior of highly resistive granular materials with superconducting grains,
parity effect and the Berezinskii--Kosterlitz--Thouless transition.
Experimental arguments in support of localized pairs existence are presented
and conditions which promote their appearance are analyzed. | 1101.3203v2 |
2016-07-06 | Multilayer coating for higher accelerating fields in superconducting radio-frequency cavities: a review of theoretical aspects | Theory of the superconductor-insulator-superconductor (S-I-S) multilayer
structure in superconducting accelerating cavity application is reviewed. The
theoretical field limit, optimum layer thicknesses and material combination,
and surface resistance are discussed. Those for the S-S bilayer structure are
also reviewed. | 1607.01495v3 |
2023-05-25 | Structure and properties of the films based on ternary transition metal borides: theory and experiment | The review presents the results of theoretical and experimental studies of
the structure, bonding between atoms, mechanical properties, thermal stability,
and oxidation and corrosion resistance of films based on ternary transition
metal borides. | 2305.15854v1 |
2005-12-19 | Insulating transition in the flux-flow resistivity of a high temperature superconductor | Measurements of the DC resistivity of under-doped cuprate superconductors
have revealed a metal--insulator transition at low temperatures when
superconductivity is suppressed by a very large magnetic field, with the
resistivity growing logarithmically in the low temperature limit. This
insulating behaviour has been associated not only with the large magnetic
fields, but also with the under-doped composition and intrinsic sample
inhomogeneity, and it is important to establish whether these factors are
essential to it. Here we report high resolution microwave measurements of the
flux-flow resistivity of optimally doped YBa_(2)Cu_(3)O_(6+x) in the mixed
state at temperatures down to 1.2 K. We find that the effective resistivity of
the vortex cores exhibits a metal-insulator transition, with a minimum at 13 K
and a logarithmically growing form below 5 K. The transition is seen in samples
of the highest quality and in magnetic fields as low as 1 T. Our work is the
first report of a metal-insulator transition in optimally doped
YBa_(2)Cu_(3)O_(6+x), and the first such transition to be seen in a system in
which superconductivity has not been globally suppressed. | 0512459v1 |
2010-09-30 | Resistivity-driven State Changes in Vertically Stratified Accretion Disks | We investigate the effect of shear viscosity and Ohmic resistivity on the
magnetorotational instability (MRI) in vertically stratified accretion disks
through a series of local simulations with the Athena code. First, we use a
series of unstratified simulations to calibrate physical dissipation as a
function of resolution and background field strength; the effect of the
magnetic Prandtl number, Pm = viscosity/resistivity, on the turbulence is
captured by ~32 grid zones per disk scale height, H. In agreement with previous
results, our stratified disk calculations are characterized by a subthermal,
predominately toroidal magnetic field that produces MRI-driven turbulence for
|z| < 2 H. Above |z| = 2 H, magnetic pressure dominates and the field is
buoyantly unstable. Large scale radial and toroidal fields are also generated
near the mid-plane and subsequently rise through the disk. The polarity of this
mean field switches on a roughly 10 orbit period in a process that is
well-modeled by an alpha-omega dynamo. Turbulent stress increases with Pm but
with a shallower dependence compared to unstratified simulations. For
sufficiently large resistivity, on the order of cs H/1000, where cs is the
sound speed, MRI turbulence within 2 H of the mid-plane undergoes periods of
resistive decay followed by regrowth. This regrowth is caused by amplification
of toroidal field via the dynamo. This process results in large amplitude
variability in the stress on 10 to 100 orbital timescales, which may have
relevance for partially ionized disks that are observed to have high and low
accretion states. | 1010.0005v2 |
2011-11-30 | Self-Similar Solutions for Viscous and Resistive ADAF | In this paper, the self-similar solution of resistive advection dominated
accretion flows (ADAF) in the presence of a pure azimuthal magnetic field is
investigated. The mechanism of energy dissipation is assumed to be the
viscosity and the magnetic diffusivity due to turbulence in the accretion flow.
It is assumed that the magnetic diffusivity and the kinematic viscosity are not
constant and vary by position and $\alpha$-prescription is used for them. In
order to solve the integrated equations that govern the behavior of the
accretion flow, a self-similar method is used. The solutions show that the
structure of accretion flow depends on the magnetic field and the magnetic
diffusivity. As, the radial infall velocity and the temperature of the flow
increase, and the rotational velocity decreases. Also, the rotational velocity
for all selected values of magnetic diffusivity and magnetic field is
sub-Keplerian. The solutions show that there is a certain amount of magnetic
field that the rotational velocity of the flow becomes zero. This amount of the
magnetic field depends on the gas properties of the disc, such as adiabatic
index and viscosity, magnetic diffusivity, and advection parameters. The
solutions show the mass accretion rate increases by adding the magnetic
diffusivity and in high magnetic pressure case, the ratio of the mass accretion
rate to the Bondi accretion rate decreases as magnetic field increases. Also,
the study of Lundquist and magnetic Reynolds numbers based on resistivity
indicates that the linear growth of magnetorotational instability (MRI) of the
flow decreases by resistivity. This property is qualitatively consistent with
resistive magnetohydrodynamics (MHD) simulations. | 1111.7302v1 |
2016-11-09 | Numerical integral of resistance coefficients in diffusion | The resistance coefficients in screen Coulomb potential of stellar plasma are
evaluated in high accuracy. I have analyzed the possible singularities in the
integral of scattering angle. There are possible singularities in the case of
attractive potential. This may result in problem for numerical integral. In
order to avoid the problem, I have used a proper scheme, e.g., splitting into
many subintervals and the width of each subinterval is determined by the
variation of the integrand, to calculate the scattering angle. The collision
integrals are calculated by using Romberg's method therefore the accuracy is
high (i.e., $ \sim 10^{-12}$). The results of collision integrals and their
derivatives in $-12 \leq \psi \leq 5$ are listed. By using Hermite polynomial
interpolation from those data, the collision integrals can be obtained with an
accuracy of $10^{-10}$. For very weak coupled plasma ($\psi \geq 4.5$),
analytical fittings for collision integrals are available with an accuracy of
$10^{-11}$. I have compared the final results of resistance coefficients with
other works and found that, for repulsive potential, the results are basically
same to others, for attractive potential, the results in intermediate and
strong coupled case show significant differences. The resulting resistance
coefficients are tested in the solar model. Comparing with the widely used Cox
et al.(1989) and Thoul et al. (1994) models, the resistance coefficients in
screen Coulomb potential leads to a little weaker effect in solar model, which
is contrary to the expectation of attempts to solve the solar abundance
problem. | 1611.03115v1 |
2019-03-28 | Dynamic Streaming Spectral Sparsification in Nearly Linear Time and Space | In this paper we consider the problem of computing spectral approximations to
graphs in the single pass dynamic streaming model. We provide a linear
sketching based solution that given a stream of edge insertions and deletions
to a $n$-node undirected graph, uses $\tilde O(n)$ space, processes each update
in $\tilde O(1)$ time, and with high probability recovers a spectral sparsifier
in $\tilde O(n)$ time. Prior to our work, state of the art results either used
near optimal $\tilde O(n)$ space complexity, but brute-force $\Omega(n^2)$
recovery time [Kapralov et al.'14], or with subquadratic runtime, but
polynomially suboptimal space complexity [Ahn et al.'14, Kapralov et al.'19].
Our main technical contribution is a novel method for `bucketing' vertices of
the input graph into clusters that allows fast recovery of edges of
sufficiently large effective resistance. Our algorithm first buckets vertices
of the graph by performing ball-carving using (an approximation to) its
effective resistance metric, and then recovers the high effective resistance
edges from a sketched version of an electrical flow between vertices in a
bucket, taking nearly linear time in the number of vertices overall. This
process is performed at different geometric scales to recover a sample of edges
with probabilities proportional to effective resistances and obtain an actual
sparsifier of the input graph.
This work provides both the first efficient $\ell_2$-sparse recovery
algorithm for graphs and new primitives for manipulating the effective
resistance embedding of a graph, both of which we hope have further
applications. | 1903.12150v1 |
2019-06-20 | Substrate mediated nitridation of niobium into superconducting Nb2N thin films for phase slip study | Here we report a novel nitridation technique for transforming niobium into
hexagonal Nb2N which appears to be superconducting below 1K. The nitridation is
achieved by high temperature annealing of Nb films grown on Si3N4/Si (100)
substrate under high vacuum. The structural characterization directs the
formation of a majority Nb2N phase while the morphology shows granular nature
of the films. The temperature dependent resistance measurements reveal a wide
metal-to-superconductor transition featuring two distinct transition regions.
The region close to the normal state varies strongly with the film thickness,
whereas, the second region in the vicinity of the superconducting state remains
almost unaltered but exhibiting resistive tailing. The current-voltage
characteristics also display wide transition embedded with intermediate
resistive states originated by phase slip lines. The transition width in
current and the number of resistive steps depend on film thickness and they
both increase with decrease in thickness. The broadening in transition width is
explained by progressive establishment of superconductivity through proximity
coupled superconducting nano-grains while finite size effects and quantum
fluctuation may lead to the resistive tailing. Finally, by comparing with Nb
control samples, we emphasize that Nb2N offers unconventional superconductivity
with promises in the field of phase slip based device applications. | 1906.08692v1 |
2021-04-28 | Channel Models and Coding Solutions for 1S1R Crossbar Resistive Memory with High Line Resistance | Crossbar resistive memory with the 1 Selector 1 Resistor (1S1R) structure is
attractive for nonvolatile, high-density, and low-latency storage-class memory
applications. As technology scales down to the single-nm regime, the increasing
resistivity of wordline/bitline becomes a limiting factor to device
reliability. This paper presents write/read communication channels while
considering the line resistance and device variabilities by statistically
relating the degraded write/read margins and the channel parameters. Binary
asymmetric channel (BAC) models are proposed for the write/read operations.
Simulations based on these models suggest that the bit-error rate of devices
are highly non-uniform across the memory array. These models provide
quantitative tools for evaluating the trade-offs between memory reliability and
design parameters, such as array size, technology nodes, and aspect ratio, and
also for designing coding-theoretic solutions that would be most effective for
crossbar memory. Method for optimizing the read threshold is proposed to reduce
the raw bit-error rate (RBER). We propose two schemes for efficient channel
coding based on Bose-Chaudhuri-Hocquenghem (BCH) codes. An interleaved coding
scheme is proposed to mitigate the non-uniformity of reliability and a location
dependent coding framework is proposed to leverage this non-uniformity. Both of
our proposed coding schemes effectively reduce the undetected bit-error rate
(UBER). | 2104.14011v1 |
2022-05-13 | The Relationship Between Insulin Resistance Neutrophil to Lymphocyte Ratio | Aim: There is increasing interest in the role of chronic inflammation on
pathogenesis of various disease, and one of its markers, high NLR is associated
with various mortality and morbidity risk. Insulin resistance (IR) might be one
potential associate factors, as suggested in preclinical studies. However,
epidemiological studies are scarce which investigated the association between
NLR, and insulin resistance (IR) and they included only diabetes mellitus
patients, not the general population. This study aims to determine if there is
a direct correlation between NLR and IR in the US general population. Methods:
The sample consists of 3,307 from general population, provided by National
Health and Nutrition Examination Survey (NHANES). Homeostasis Model Assessment
of Insulin Resistance (HOMA-IR) value was calculated to evaluate insulin
resistance. We investigated the relationship between their NLR and HOMA-IR
values by bivariate and multivariate linear regression analyses. As insulin use
could results in inaccurate HOMA-IR estimation, we excluded them and ran the
analyses in subgroup analyses. Results: There was a relationship shown when
insulin users were included, having a beta coefficient value of 0.010 (95%
confidence interval [CI] of 0.003-0.017). However, when insulin users were
excluded, the beta value decreased to 0.004 (95% CI of -0.006-0.015). The
statistical significance was not reached when age, sex, and body mass index
were adjusted for in the multivariate analyses. Conclusion: There is no visible
relationship between IR and NLR in the general population. IR might not explain
the variation of NLR value in healthy people, and further studies are needed to
reveal the associated factor of high NLR. | 2205.08308v2 |
2019-12-08 | Multifilamentary character of anticorrelated capacitive and resistive switching in memristive structures based on (CoFeB)x(LiNbO3)100-x nanocomposite | Resistive and capacitive switching in capacitor metal/nanocomposite/metal
(M/NC/M) structures based on (CoFeB)x(LiNbO3)100-x NC fabricated by ion-beam
sputtering with metal content x $\approx$ 8-20 at. % is studied. The
peculiarity of the structure synthesis was the use of increased oxygen content
($\approx$ 2*10^-5 Torr) at the initial stage of the NC growth. The NC films,
along with metal nanogranules of 3-6 nm in size, contained a large number of
dispersed Co (Fe) atoms (up to ~10^22 cm^-3). Measurements were performed both
in DC and AC (frequency range 5-13 MHz) regimes. When switching structures from
high-resistance (Roff) to low-resistance (Ron) state, the effect of a strong
increase in their capacity was found, which reaches 8 times at x $\approx$ 15
at. % and the resistance ratio Roff/Ron $\approx$ 40. The effect is explained
by the synergetic combination of the multifilamentary character of resistive
switching (RS) and structural features of the samples associated, in
particular, with the formation of high-resistance and strongly polarizable
LiNbO3 layer near the bottom electrode of the structures. The proposed model is
confirmed by investigations of RS of two-layer nanoscale M/NC/LiNbO3/M
structures as well as by studies of the magnetization of M/NC/M structures in
the pristine state and after RS. | 1912.03726v3 |
2024-04-17 | Stress analysis of functionally graded hyperelastic variable thickness rotating annular thin disk: A semi-analytic approach | Functionally graded materials (FGMs) represent a promising class of advanced
materials designed with tailored microstructures to achieve optimized
mechanical, thermal, and functional properties across varying gradients. The
strategic integration of distinct materials within functionally graded
materials offers engineers unprecedented control over properties such as
strength, thermal conductivity, and corrosion resistance, enabling innovative
solutions for demanding applications in aerospace, automotive, and biomedical
industries. This study investigates a rotating annular thin disk with variable
thickness composed of incompressible hyperelastic material, made up of
functionally graded properties under large deformations. To elucidate these
phenomena, a power relation is employed to delineate the changes in
cross-sectional geometry m, the material property n, and the angular velocity w
of hyperelastic material. Constants used for hyperelastic material are obtained
from the experimental data. Equations are solved semi-analytically for
different values of m, n, and w, and the values of radial stresses, tangential
stresses, and elongation are calculated and compared for different conditions.
Results show that thickness and FG properties have a significant impact on the
behavior of disk, so that the expected behavior of the disk can be obtained by
an optimal selection of the disks geometry and material properties. By
selecting the optimum values for these variables, the location of maximum
stress can be controlled in large deformations, thereby furnishing significance
advantages in structural design and material selection. | 2404.11365v1 |
2023-05-03 | Universal sublinear resistivity in vanadium kagome materials hosting charge density waves | The recent discovery of a charge density (CDW) state in ScV$_6$Sn$_6$ at
$T_{\textrm{CDW}}$ = 91 K offers new opportunities to understand the origins of
electronic instabilities in topological kagome systems. By comparing to the
isostructural non-CDW compound LuV$_6$Sn$_6$, we unravel interesting electrical
transport properties in ScV$_6$Sn$_6$, above and below the charge ordering
temperature. We observed that by applying a magnetic field along the $a$ axis,
the temperature behavior of the longitudinal resistivity in ScV$_6$Sn$_6$
changes from metal-like to insulator-like above the CDW transition. We show
that in the charge ordered state ScV$_6$Sn$_6$ follows the Fermi liquid
behavior while above that, it transforms into a non-Fermi liquid phase in which
the resistivity varies sublinearly over a broad temperature range. The
sublinear resistivity, which scales by $T^{3/5}$ is a common feature among
other vanadium-containing kagome compounds exhibiting CDW states such as
KV$_3$Sb$_5$, RbV$_3$Sb$_5$, and CsV$_3$Sb$_5$. By contrast, the non-Fermi
liquid behavior does not occur in LuV$_6$Sn$_6$. We explain the $T^{3/5}$
universal scaling behavior from the Coulomb scattering between Dirac electrons
and Van Hove singularities; common features in the electronic structure of
kagome materials. Finally, we show anomalous Hall-like behavior in
ScV$_6$Sn$_6$ below $T_{\textrm{CDW}}$, which is absent in the Lu compound.
Comparing the transport properties of ScV$_6$Sn$_6$ and LuV$_6$Sn$_6$ is
valuable to highlight the impacts of the unusual CDW in the Sc compound. | 2305.02393v2 |
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